ML13273A323

FOIA/PA-2012-0235 - Resp 1 - Partial. Group a, Records Being Released in Their Entirety. Part 20 of 21

ML13273A323
Person / Time
Site:	Fort Calhoun
Issue date:	09/19/2013
From:	Office of Information Services
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FOIA/PA-2012-0235
Download: ML13273A323 (241)

Text

Hair, Christopher From: Wilkins, Lynnea Sent: Friday, January 06, 2012 11:02 AM To: Hair, Christopher

Subject:

Fort Calhoun And Cooper Acknowledgement Letter and FRN Attachments: ML1200300270.doc; ML1200300223.docx

Chris, As discussed, Kristy is logging these in now (letter -ML1200300223, FRN - ML1200300270)

Thanks Again!

Lynnea Lynnea Wiffins, Project Manager Fort Calhoun Station, Unit 1 Cooper Nuclear Station Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation US Nuclear Regulatory Commission Phone: 301-415-1377 1 cjg

Mr. Thomas Saporito Senior Consulting Associate Saprodani Associates P.O. Box 8413 Jupiter, FL 33468-8413

Dear Mr. Saporito:

On behalf of the U.S. Nuclear Regulatory Commission (NRC), I am responding to your petitions by letters dated June 26 and July 3, 2011 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML11182B029 and ML11192A285, respectively), in which you requested escalated enforcement action against Fort Calhoun Station (FCS) and Cooper Nuclear Station (Cooper), respectively, regarding flood protection. Specifically, you asked the NRC to take action to suspend or revoke the NRC license(s) granted for the operation of these nuclear power reactors and issue a notice of violation with a proposed civil penalty against the collectively named and each singularly named licensee in the matters, in the amount of

$500,000 for FCS and $1,000,000 for Cooper.

In your letter dated June 26, 2011, you also requested that the NRC issue a confirmatory order to Omaha Public Power District, the licensee for FCS, prohibiting the licensee from restarting FCS until such time as (1) the floodwaters subside to an appreciably lower level or to sea level, (2) the licensee upgrades its flood protection plan, (3) the licensee repairs and enhances its current flood protection berms, and (4) the licensee upgrades its station blackout procedures to meet a challenging extended loss-of-offsite power as a result of floodwaters and other natural disasters or terrorist attacks.

In your letter dated July 3, 2011, you requested that the NRC issue a confirmatory order to Nebraska Public Power District, the licensee for Cooper, requiring the licensee to bring Cooper to a cold-shutdown mode of operation until such time as (1) the floodwaters subside to an appreciably lower level or to sea level, (2) the licensee upgrades its flood protection plan, (3) the licensee repairs and enhances its current flood protection berms, and (4) the licensee upgrades its station blackout procedures to meet a challenging extended loss-of-offsite power as a result of floodwaters and other natural disasters or terrorist attacks.

As the basis of the request related to FCS, you stated the following:

On June 26, 2011, a 2,000-foot berm at the Ft. Calhoun Nuclear Plant collapsed from the forces of flood waters surrounding the nuclear plant. The berm was constructed 16-feet wide at the base and 8-feet tall to provide flood protection for the nuclear plant's power-block. The licensee transferred the nuclear plant's off-site power to on-site diesel generators because of water leaking around the concrete berm surrounding the main transformers. In addition, flood-waters also surrounded auxiliary and containment buildings - designed to handle water up to 1,014-feet above sea level. NRC officials issued a statement to the media that -

T. Saporito the licensee has an earthen berm to protect the electrical switch-yard and a concrete barrier surrounding electrical transformers.

Petitioner contends here that (1) the licensee's installed flood-protection measures and systems and barriers at the Ft. Calhoun Nuclear Power Plant are not sufficient to adequately protect the nuclear reactor from a full-meltdown scenario like that currently unfolding in Japan; and (2) the licensee's station blackout procedures are not sufficient to meet a challenging extended loss of off-site power due to flood-waters and other natural disasters or terrorist attacks.

As the basis of the request related to Cooper, you stated the following:

On June 19, 2011, the licensee notified the U.S. Nuclear Regulatory Commission (NRC) of an Unusual Event Declared at the Cooper Nuclear Station - in connection with the Missouri River flooding its banks. The NRC documented the licensee's notification as Event Number: 46969 indicating an Event Time of 04:02 CDT; and a Notification Time of 05:27 ET. During the context of the Unusual Event, the licensee maintain[ed] the nuclear reactor power at 100%.

The licensee further communicated to the NRC that, "The Missouri River is expected to crest at 899.5 feet within the next couple of days. It is expected that the elevation of the MissouriRiver will remain above 899 feet for most of the summer.....

Petitioner contends here that (1) the licensee's installed flood-protection measures and systems and barriers at the Cooper Nuclear Station are not sufficient to adequately protect the nuclear reactor from a full-meltdown scenario like that currently unfolding in Japan; (2) the licensee's station blackout procedures are not sufficient to meet a challenging extended loss of off-site power due to flood-waters and other natural disasters or terrorist attacks; (3) the licensee failed to timely notify the NRC of the Declaration of an Unusual Event within a one-hour period; and (4) the license continues to jeopardize public health and safety by failing to bring the Cooper Nuclear Station to a "cold-shutdown" mode of operation.

In accordance with Management Directive 8.11, "Review Process for 10 CFR 2.206 Petitions,"

dated October 25, 2000, the NRC has processed your letters under Title 10 of the Code of Federal Regulations (10 CFR) 2.206, "Requests for Action under this Subpart," and assigned these petitions to the NRC's Office of Nuclear Reactor Regulation.

On July 7 and 12, 2011, the NRC petition manager, Ms. Lynnea Wilkins, acknowledged receipt of your petitions, and you asked to address the Petition Review Board (PRB) before its meeting to make the initial recommendation to accept or reject your petitions for review. On August 29, 2011, you addressed the PRB during a teleconference to provide additional information in support of your petitions. During the teleconference, you asked the PRB to

T. Saporito I consider the information you provided as a supplement to your petitions. A copy of the transcript-from the teleconference is available under ADAMS Accession No. ML11256A036.

On September 12 and October 13, 2011, the PRB met internally to discuss your petitions, as supplemented by the transcript. During both meetings, the PRB determined that it needed additional informatknjfromr other internal resources before making its initial recommendation and a decision on the requests for immediate action. On November 28, 2011, the PRB again met internally to discuss your petitions. During this meeting, the PRB reached an initial recommendation that your petitions meet the criteria for review. The PRB also determined that there is no immediate safety concern that would warrant an immediate action by the NRC to prevent the restart of FCS or to bring Cooper to cold shutdown, as you requested. Therefore, the PRB has denied your request for immediate action.

Additionally, the PRB identified that your petitions raise several issues that are currently undergoing NRC evaluation as part of the agency's Near-Term Task Force review of insights from the Fukushima Dai-ichi accident in Japan, as documented in "Recommendations for Enhancing Reactor Safety in the 2 1st Century," dated July 12, 2011 (ADAMS Accession No. ML112510264), and in the associated staff requirements memorandum for SECY-1 1-0137, "Prioritization of Recommended Actions to be Taken in Response to Fukushima Lessons Learned," dated December 15, 2011 (ADAMS Accession No. ML113490055).

The PRB intends to use the results of the above review to inform its final decision on whether to implement the actions requested in your petition. In an e-mail dated December 13, 2011, the petitioner manager conveyed the PRB's decision to deny your requests for immediate action and the PRB's initial recommendation to accept the petitions for review. The petition manager also offered you a second opportunity to address the PRB by teleconference; however, you declined this opportunity.

Because you did not request to address the PRB upon receipt of this initial recommendation, the PRB's initial recommendation to accept your petitions for review has become the PRB's final recommendation.

As required by 10 CFR 2.206, the NRC will act on your petitions within a reasonable time. The petition manager, Ms. Lynnea Wilkins, can be reached at (301) 415-1377.

T. Saporito I have enclosed for your information a copy of the notice that the NRC is filing with the Office of the Federal Register for publication. I have also enclosed for your information a copy of Management Directive 8.11 and the associated brochure NUREG/BR-0200, "Public Petition Process," Revision 5, issued February 2003, prepared by the NRC Office of Public Affairs.

Sincerely, Eric J. Leeds, Director Office of Nuclear Reactor Regulation

Enclosures:

1. Federal Register Notice

2. Management Directive 8.11

3. NUREG/BR-0200 cc: Listserv

Package ML113530557; Incoming ML11182B029 and ML11192A285; Letter ML120030022: FR Notice ML120030027; NUREG/BR-0200 ML050900248 *via email OFFICE NRR/DORL/LPL4/PM NRR/DORL/LPL4/LA QTE NRR/DPR NAME LWilkins JBurkhardt KKribbs* TMensah*

DATE 1/4/12 1/4/12 1/5/12 1/5/12 OFFICE RIVIDRS/OB/BC NRR/DE/EICB/BC RES/DD OGC NAME MHaire GWilson BHolian (A)*

DATE 1/5/12 OFFICE NRR/DORL/LPL4/BC NRR/DORUD NRR/D NAME MMarkley MEvans ELeeds DATE ENCLOSURE 1 FEDERAL REGISTER NOTICE

[7590-01-P]

NUCLEAR REGULATORY COMMISSION Docket No. 50-285, License No. DPR-40; Docket No. 50-298, License No. DPR-46; NRC-2012-XXXX Request for Action against Omaha Public Power District and Nebraska Public Power District Notice is hereby given that by petitions dated June 26 and July 3, 2011, respectively, Thomas Saporito (the petitioner) has requested that the U.S. Nuclear Regulatory Commission (NRC or the Commission) take escalated enforcement actions against Omaha Public Power District, the licensee for Fort Calhoun Station, Unit 1 (FCS), and Nebraska Public Power District, the licensee for Cooper Nuclear Station (Cooper). The petitions dated June 26 and July 3, 2011, are publicly available in the NRC's Agencywide Documents Access and Management System (ADAMS) under Accession Nos. ML11182B029 and ML11192A285, respectively.

The petitioner has requested that NRC take action to suspend or revoke the NRC license(s) granted for the operation of nuclear power reactors and issue a notice of violation with a proposed civil penalty against the collectively named and each singularly named licensee in this matter - in the amount of $500,000 for Fort Calhoun Station and $1,000,000 for Cooper.

Additionally, the petitioner requested that the NRC issue confirmatory orders to prohibit restart at FCS and to bring Cooper to a "cold shutdown" mode of operation until such time as (1) the flood-waters subside to an appreciable lower level or sea-level; (2) the licensee upgrades its flood-protection plan; (3) the licensee repairs and enhances its current flood-protection berms; and (4) the licensee upgrades its station blackout procedures to meet a challenging extended loss of off-site power due to flood-waters and other natural disasters or terrorist attacks.

As the basis for these requests, the petitioner stated that (1) the licensees' installed flood-protection measures and systems and barriers at FCS and Cooper are not sufficient to adequately protect the nuclear reactor from a full-meltdown scenario like that currently unfolding in Japan; and (2) the licensees' station blackout procedures are not sufficient to meet a challenging extended loss of off-site power due to flood-waters and other natural disasters or terrorist attacks.

The requests are being treated pursuant to Title 10 of the Code of FederalRegulations Section 2.206 of the Commission's regulations. The requests have been referred to the Director of the Office of Nuclear Reactor Regulation. As provided by Section 2.206, appropriate action will be taken on these petitions within a reasonable time. The petitioner requested an opportunity to address the Petition Review Board (PRB). The PRB held a recorded teleconference with the petitioner on August 29, 2011, during which the petitioner supplemented and clarified the petitions. The results of those discussions were considered in the PRB's determination regarding the petitioner's requests. As a result, the PRB acknowledged the petitioner's concerns regarding flood protection, including station blackout procedures, at FCS and Cooper. By letter dated January ,2012 (ADAMS Accession No. ML120030022), the Director of the NRC's Office of Nuclear Reactor Regulation denied the petitioner's requests for immediate action. Additionally, the PRB noted that (1) natural disasters such as earthquakes and flooding and (2) station blackout regulations are undergoing NRC review as part of the lessons-learned from the Fukushima event. The PRB intends to use the results of the Fukushima review to inform its final decision on whether to implement the requested actions.

Copies of the petitions dated June 26 and July 3, 2011, are available for inspection at the NRC's Public Document Room (PDR), located at One White Flint North, Public File Area 01 F21, 11555 Rockville Pike (first floor), Rockville, Maryland 20852. Publicly available

documents created or received at the NRC are accessible electronically through ADAMS in the NRC Library at http://www.nrc.-qov/readinq-rm/adams.html. Persons who do not have access to ADAMS or who encounter problems in accessing the documents located in ADAMS should contact the NRC's PDR Reference staff by telephone at 1-800-397-4209 or 301-415-4737, or by e-mail to PDR.Resource(*,nrc.qov.

Dated at Rockville, Maryland, this _ day of January 2012.

FOR THE NUCLEAR REGULATORY COMMISSION.

Eric J. Leeds, Director, Office of Nuclear Reactor Regulation.

ENCLOSURE 2 MANAGEMENT DIRECTIVE 8.11

ENCLOSURE 3 NUREG/BR-0200

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Omaha Public Power Oistrict Fort Calhou.n Statio Flood Recovery Action Plan 4.1 Plant and Facility Geo4tecimical and Strueiu'al-Asse'ssm-ent, De~cem ber 28, 2011

'KRevision 2 Prepared for: Prepared by:

O..a Public Power District.

Fort Calhoun Station 8404 Indian Hills Drive 9610 Power Lane Omaha, NE 68114 Blair, NE 68008 J

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Page ES-1 EXECUTIVE

SUMMARY

Introduction Omaha Public Power District's (OPPD's) Fort Calhoun Station (FCS) is a 484-megawatt nuclear power plant (OPPD, September 25, 201]). FCS is located on the west bank of the Missouri River in northeastern Washington County, Nebraska. FCS is approximately 4 milessoutheast of Blair, Nebraska, and approximately 19 miles north of Omaha, Nebraska.

The flooding of the Missouri River during the summer of 2011 has "significantly,:challenged" the operation of FCS (OPPD, August 10, 2011). In response to this event, OPPL prepbaed a Flooding Recovery Action Plan that documented the actions necessary for the-repair and restoration of FCS operations. This Fort Calhoun Station Plant and Facility Geotechnica! 4i.d' Structural Assessment Report (Assessment Report) has been prepared in response to FCSFloodingg Recovery Action Plan 4.1,

,Plant and Facility Geotechnical and Structural Assessment.

Scope and Purpose The FCS Plant and Facility Geotechnical and Structural Assessment has been completed to identify and describe the effects of the 2011 flood on 28 Priority 1 Structures and 19 Priority 2 structures at the site. Specifically, the objective of this Assessment Report is to present HDR's assessment of changes to the soil or rock that supports the structures at FCS-that may have negatively impacted those structures.

Revision 0 of this Assessment Report was submitted to OPPD on October 14, 2011. Revision 0 presented the results of preliminary assessments for each Priority I Structure. These assessments were incomplete in Rev'iSi0_n-Vbecause the forensic investigation and/or monitoring for most of the Priority I Strqetufbsswa1s.hot completed by the submittal date.

Revision I of this Assessment Report was submitted to. OPPD on November 28, 2011. Revision I presented the partial and preliminary results of additiorial forensic investigation and monitoring to date for the Key Distress Indicators and the: draft final assessment results for Priority I Structures.

Revision 2,of-this Assessment Report presents the following:

" Corfiplete and final results of~thieilKey Distress Indicators forensic investigations

• Final assessrient results for the Priority 1 Structures

• Final assessmerit:results for the Priority 2 Structures

• Final results of.the Comparative Geotechnical Analysis Principal Findings of the Comparative Geotechnical Analysis

... Com-pausof.geotechnica] data for pre-flood and,.current investigations indicatestha,.t,.here .was no.

observable difference in the overall geotechnical conditions at the site and that the foundation materials have not been disturbed or significantly weakened by the prolonged inundation caused by the 2011 flood. Comparison of seismic refraction data from the pre-flood and current investigations reveals similar magnitude of seismic wave velocities over the full depth of the overburden soils, and no observable differences between pre- and post-flood conditions were identified from this work.

Page ES-2

'ExecuitiV'Su Sm ary -R Based on these findings and evaluations, the overall geotechnical conditions at the site have not been significantly altered due to the sustained high water. The observed scatter of data points is consistent with the relatively wide range of strength and stiffness and corresponding blow counts typically encountered in the alluvial soils within the Missouri River valley. However, these findings are considered applicable only to those soils present below a depth of 10 feet at the site. The upper 10 feet were hydro excavated to avoid damaging buried utilities. This upper layer may have been disturbed from-underseepage beneath the temporary levees or from the settlement of utility backfill during drawdown of the river level and groundwater.

Detailed Forensic Investigations at Key Distress Indicators Each structure was systematically observed for obvious signs of structural damage or distress caused by the 201 1 flood. These inspections revealed three significant'indicatotS:of distress:'

1. Increased groundwater flow into the Turbine Building sump

2. Pavement failure and sinkhole development in the paved access area between the Intake Structure and Service Building

3. Column settlement in the Maintenance Shop.

Since publication of Revision 0, work has been ongoing to investigate subsurface conditions at each of the three Key Distress Indicators, as discussed below:

In the basement of the Turbine Building, 26 one-inch.diameter~test holeswere drilled through the floor slab to reach the subgrade. This work found that the Triggerinhg Mechanism of subsurface piping of soil material due to the sump operation and seepage/flow -in0to the drainage system pipes is occurring, and that the voids are significant and .interconnected. Alth&ughitowas-also found that the foundation

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i. wa.. o: fon tha th subgrade was not affected uniformly by tlie Triggenng Mechanism,:subsurface erosion/piping of soil from beneath the..: . iIilldingbaseenýit-and perhaps beyond will continue as long as the drain system piping remainans unirepaiied. Voids, ýso6ft'zones, and associated groundwater and piping flow paths will continue to enlarge and,.extend out f6om-.the drainage and sump system over time unless the flow Qýfate6r into the sump system"iAs*stopped.

Inth*e Paved Access Area, 40 one-inch-diameter test holes were drilled-through the concrete paving slab, and six continuous SPT borings were completed. This work found no evidence of piping erosion, voids, or subsidence of site fills. Field testing of the subgrade exposed after concrete panel removal indicated that stiff to very stiff soils were generally encountered in the upper 3 feet below the ground surface or pavement. Based on the 6bservations made and tests results obtained, the fill soils in the locations exposed and tested are compact, cohesive soils that are not susceptible to piping erosion.

SPT borings did not identify. voids. or very soft/very loose conditions that might indicate piping or related material loss nor did they identify changes in soil relative density following the 2011 flood.

Inclinometer and survey moinitoring in the Paved Access Area indicates that movement of on-site subsurface soils or structures has not occurred.

nte4*ainteriance. Shob-5ý; 6 ýon:tiindh-diarheter test holes were drilled followed by'.4vseicidcset-of.6 one-inch-diameter test holes to investigate the settled column. The results of the KDI #3 forensic investigations have found that the distress observed in both the Maintenance Shop (failed column) and the Technical Support (cracked walls) are not associated with the Triggering Mechanism 7 - Soil Collapse (due to first time wetting). Therefore the CPFMs associated with this Triggering Mechanism (7a-7c) have been ruled out by this forensic investigation. The results show that.the distress in both the Maintenance Shop and the Technical Support Center are connected to KDI #1, which is associated

Page ES-3 with the uncontrolled drainage of the groundwater into the broken Turbine Building basement drainage system piping. KDI #Uisag"ociated with the Triggering Mechanism of Subsurface Erosion/Piping (due to pumping) and the CPFM applicable to the Maintenance Shop and Technical Support Center is 3a - Undermining and settlement of shallow foundation/slab (due to pumping). This CPFM will only be ruled out when the physical modifications presented for KDI #1, as presented in Section 4.1 of this Assessment Report, are implemented.

Recommendations Turbine Building Sump

• OPPD should perform remedial work to stop the uncontrolled: drainage of the groundwater into the broken Turbine Building basement drainage system piping and fill the voids beneath the basement floor slab.

" In addition to drainage system repair, the voids created by the subsurface erosion/ piping.should be filled.

" A grouting program should be implemented to fill the voids and determine the volume of the voids.

Paved Access Area

• OPPD should complete their pavement restoration work.

Maintenance Shop

• Physical modifications to remediate the distress in the&Maintenance Shop should be implemented as planned.

• Further investigations could be undertaken by OPPD as part.of the design for the remedial work to repair the Maintenancer:.Shop and Technical Support Center distress.

Physical modifications outlined in the KDI #1 forensic investigations should be competed before the physical modifications toiTemediate the distress in the Maintenance Shop and Technical Support'Center are implemented.'.

Priority 1 and Priority 2 Structural Assessments The Geotechnical and Structural Assessments have been completed for each of the Priority 1 and Priority 2 Structures. In general, it has been determined that the 2011 Missouri River flood did not impact the geotechnical and structural integrity of the structures. However, in addition to the recommendations associated with the KDI investigations as described above, there are specific recommendations for remediationI of 2011 flood impacts for seven structures as presented in each of their respective Section 5 andiSection 6 assessments. Therefore, this determination is conditional upon implementation of those specific recommendations for the structures listed below:

Table E Priority 1 and Priority 2 Structures Havinq Specific Remediation Recommendations P io ity .-St...

........ t S...... P-i rity2 'Structures -

Auxiliary Building Service Building Containment Maintenance Shop Technical Support Center PA Paving, PA Sidewalks, and Outdoor Drives Turbine Building Potable Water Piping Security Barricaded Ballistic Resistant Enclosures Sanitary Sewer System (BBREs)

Page ES-4 Executive Summary -..Rev. 2 Table E Priority 1 and Priority 2 Structures Having Specific Remediation Recommendations Priority I Structures Priority 2 Structures Turbine Building South Switchyard Shooting Range Condensate Storage Tank Circulating Water System Raw Water Piping Fire Protection System Piping Waste Disposal Piping Fuel Oil Storage Tanks and Piping Main Underground Cable Bank, Auxiliary Building to.

Intake Structure Main Underground Cable Bank, MH-I to Auxiliary Building _ _.__ .__ .".

Blair Water System Demineralized Water.System HDR has concluded that the 2011 Missouri River flood.did not impact the geotechnical and structural integrity of the following structures because the potential for failure of this structure due to the flood is not significant.

Table E Priority 1 and Priority 2 Structures NotImpacted by.2011 Flood Priority 1 Structures 'PrioritV 2: Str-uctures Intake Structure New Warehouse Rad Waste Building Chemristry/Radiation:Protection (CARP) Building Independent Spent Fuel Storage Installation (ISFSI) - Maintenance Fabrication Shop Security"Building Maintenance Storage Building Underground:ýCable:Trench:,(Trenwa) Old Warehouse Demineralized Water Tank, Pump-House, and Training Center Reverse Osmosis (RO)>.Unit Meteorological Tower and Miscellaneous Structures Administration Building Original Steam Generator Storage Building (OSGS) Hazardous Material Storage Building Switchyard Maintenance Garage Transmission Towers Tertiary Building (Boat Storage)

River Bank Spare Transformer Pads Camera Towersand High Mast Lighting Gravel Parking Lots Sewage Lagoons

Page i Tabl~e fcrtent~' "... ...... Rev22 Table of Contents 1.0 Intro d uctio n ................................................................................................................ 1-1 1.1 S cope a nd P urpose ......................................................................................... 1-1 1.2 Assessment Report Organization, Content, and Revision History .................. 1-3 1.2 .1 D ocum ent Organization .................................................................................. 1-3 1.2 .2 Docum e nt C ontent .......................................................................................... 1-3 1.2 .3 Re visio n Histo ry .............................................................................................. 1-4 1.3 Ba c kg ro u nd ...................................................................................................... 1 -+

1.4 A ssessm ent P rocess ....................................................................................... 1-6 1.5 Q uality A ssurance and C ontrol .......................................................... 1-7 2.0 Site History, Description, and Baseline Condition ........ ...... ............. 2-1 2.1 G eologic Setting ........................... 2-1 2.1.1 Historical S eism icity ....................................................................... ..... 2-1 2.1.2 Regional Seism icity and Faulting .......... ". ................................................. 2-2 2.1.3 Seism ic Hazard ............................................. 2-2 2.1.4 Site Geologic Hazards .................... ....................... 2-3 2.2 Geomorphology and Physiographic Setting .................................................... 2-7 2 .2 .1 S ite S o ils ........................................................................................ ................. 2 -9 2.2.2 Geomorphic Features.......................................... 2-9 2.3 Hydrologic Baseline ................ . .'........................................... 2-9 2.3.1 Historic Missouri River Flooding ................................. 2-11 2.3.2 2011 Missouri R iver Basin Flood ................................... ................................ 2-13 2.3.3 Missouri River Flood.. rnp08act at FCS ............................. 2-15 2.3.4 Potential Flood Damagesat FCS... ........................................................... 2-26 2.34 G eote enti cal l odB iase if e!*. a,,...... ....................... ........................................... 2-26 2.4 Geotechnical Baselines:.............................................................. 2-27 2.4 .1 In-S itu Soil Characteristics ... ...................... .. .................................... 2-27 2.4.2 R ock Mass C haracteristics ........................................................................... 2-29 2 .4 .3 G roundw ater " . . ..... .................................................................. 2-30 2.4.4 G round Improvem ent Methods ...................................................................... 2-31

2.4.5 Excavation and Backfill .......................... ................................. 2-32 2 i5 .. S tructural Baseline ... ............................................. ....................................... 2-32 2.5.1 -Intake S tructure .......... ' .. ........-........................................................... . 2-34 2 .5 .2; A uxilia ry B uild ing .................................................................. ....................... 2-35 2 .5 .3 "C o nta inm e nt .............".,.-................................................................................. . 2 -36 2 .5 .4 Rad Waste Buildihg : ................................................................................... 2-37 2.5.5 Techniical :Supprft Center ................. .................... 2-37 2.5.6 Independent,:S.pent Fuel Storage Installation ....................... 2-38 2.5.7 Security Bulilding.................................................................... 2-39 2 .5 .8 T u rbine Bu ild ing ............................................................................................ 2-4 0 2.5.9 Security Barricaded Ballistic Resistant Enclosures ....................................... 2-41

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2.5.11 C ondensate S torage Tank ............................................................................ 2-43 2.5.12 Demineralized Water Tank, Pump House, and RO Unit ............................... 2-44 2 .5 .13 Meteorolog ical T ow er .................................................................................... 2-45 2.5.14 Original Steam Generator Storage Building ........................ 2-46 2.5.15 Switchyard .............................................................................. 2-47 2 .5 .16 T ra nsm issio n T owers .................................................................................... 2 -5 1

Page ii Table -ofContents . . ,......... ...- ReV. 2 -.

2.5 .17 N ew W are house ............ ............................................................................... 2-52 2.5.18 Service Building .......................................... 2-53 2.5.19 CARP Building .............................................. 2-53 2.5.2.0 M aintenance Shop ........................................................................................ 2-54 2.5.21 M aintenance Fabrication Shop ..................................................................... 2-55 2.5.22 M aintenance Storage Building ...................................................................... 2-55 2.5.23_OId W arehouse ................................................................... .......... 2-56 2 .5 .24 T raining C e nter ............................................................. ................................ 2-56 2.5.25 Administration Building ........................................................... 2-57 2.5.26 Hazardous Material Storage Building ........... 2-58 2.5.27 Maintenance Garage.................................. ......... 2-58 2.5.28 Tertiary Building ................ ......... ..................... 2-59 2.5.29 Spare Transformer Pads ...................................... 2-60 2.5.30 Shooting Range ......................................................................... 2-60 2.6 Civil Baseline .............................................. 2-61 2.6.1 Underground Piping Utilities..................................... 2-61 2.6.2 Underground Electrical Utilities ........................................................ ..... 2-65 2.6.3 Underground Structures .......................... ............ 2-68 2.6.4 Aboveground Structures ...................................... 2-69 3.0 Assessment Process, Procedures, and Methods .......................... 3-1 3.1 Assessment Process ......... .............. ................... 3-1 3.2 Assessm ent Process Steps ........... .............................. .... .......................... 3-2 3.3 Field Observations ... .................................. ...... 3-6 3.4 Identified Potential Failure Modes ........................... :. ................. 3-7 3.5 Initial Screening of Potential Failure Modes ............. .... ............. 3-9 3.6 Potential Failure Modes)Deemed Non-Credible -for All Structures .................. 3-9 3.7 A ssessm ent M ethods ... . ......................... . ........................................ 3-11 4.0 Key Dist'r~essndica

• . ... 'I"*.. .:

• ors .... .......... ,.............. .. ......................

.. .. . .. .. . .. .. . .. .. . 4-1 4.1- Increased Groundwater Flow into the Turbine Building Sump ......................... 4-1 4A.:1. Physical Observations... .........................

• .............. ... 4-1 4..1.2 T riggering M echanism ,.................. . .................... ......................................... 4-3 4.1.3 Structures and CPFMs Associated'with Triggering Mechanism ........... 4-4 4A.,4 Assessment Methods4 and Procedures ............................................................ 4-5 41.5. KDI #1 Forensic Investigation-,:......................... ................................. 4-8 4.2 Pavement Failure and Sinkhole in Paved Access Area Between Intake Structure and Service Building ............................................ 4-23 4 .2.1 P hysical O bservations ................................................................................... 4-23 4 .2.2 T riggering Mechanism s ................................................................................. 4-23 4.2.3 Structures and CPFMs Associated with Triggering Mechanisms .................. 4-25 4.2.4 Assessment, M ethods and Procedures .......................................................... 4-28 4 .2.5 R ecom m ended A ctions ................................................................................. 4-28 .

4.2.6 K DI #2 Forensic Investigation ....................................................................... 4-29

-4.3.  :*=,, 4 3 :,: Cmer~*,

u n:,Se~tl Column.:,ettleme~nt o JniwMa nte~a~ e Shop n-A/l intenxc Shop n._.......................... -,..: ... . .- *-4z:40,,.*-: . 4-Q40.,  :- ..

4 .3.1 P hysical O bserv atio ns .................................................................................. 4-4 0 4 .3 .2 T riggering M echanism s ................................................................................. 4-4 0 4.3.3 Structures and CPFMs Associated with Triggering Mechanisms .................. 4-41 4.3.4 Assessment M ethods and Procedures .......................................................... 4-42 4.3.5 Previous Investigations and Baseline Information .......................................... 4-42 4 .3.6 R ecom m ended A ctions ................................................................................. 4-43

Page iii Table of Conte"t-s . - - .................- ,Rev. 2:

4.3.7 KD I #3 Forensic Investigation ....................................................................... 4-44 4.4 Comparative Evaluation of Geotechnical Analyses....................... 4-56 4 .4 .1 S ite C o nditio ns ............................................................................................. 4 -57 4.4.2 Pre-Flood Investigations ...................................... 4-57 4 .4 .3 C urrent Investigation ..................................................................................... 4-58 4.4.4 Interpretation of Penetration Resistance Data ................... ... 4-60 4.4.5 Preliminary Findings and.Conclusions .......................................................... 4-60 4 .4 .6 Lim ita tio n s .....................................................................................................

.. . .. .. .. . 44 -6 6 1 4.4.7 Test Standards ................................................ ...... ............. 4-61 5.0 Priority 1 Structures .............................................. 5.1-1

.5.1 Intake S tructu re ................................... ..................................... 5 .1.-1 5.1.1 Summary of Intake Structure ...................... ............ 5.1-1 5.1.2 Inputs/References Supporting the Analysis ............................. 5.1-1 5.1.3 Assessment Methods and Procedures ............................................... .......... 5.1-3 5 .1 .4 An a ly s is ........................................................................................................ 5 .1 -3 5.1.5 R esults and C onclusions ............................................................................ 5.1-10 5 .1.6 R ecom m ended A ctions .............................. .................................................. 5.1-10 5.1.7 U pdates Since Revision 0 .............. .. 5 1...-.1.....................

.................. 5.1-11 5.2 Auxiliary Building ............................................. .............. 5.2-1 5.2.1 Sum m ary of A uxiliary Building...... ........................ ................... .............. 5.2-1 5.2.2 Inputs/References Supporting the:Analysis.............................................. 5.2-2 5.2.3 Assessment Methods and Procedures ...... ... ... ... ....

5.2-3 5.2.4 Analysis ..................... ....... 5.2-4 5.2.5 R esults and C onclusions ..................... ................................................... 5..

5.2-9 5.2.6 Recom m ended Actions' ... .....................

,. 5.....

5.2-10 5.2.7 Updates Since Revision, 0............................................ 5.2-10 5 .3 C o nta inme n t ....................................... .............. ...................................... 5 .3-1 5.3.1 Sunmary'of y ....

Containment ..... ........ .... ......... ...................

.... ... 5.3-1 5.3.2 Inputs/References Supportingthe Analysis ................................................. 5.3-1 5.3.3 Assessment Methods and Procedures ........................................................ 5.3-2

5 .3 .4 A n a ly s is .............. .............. .............................................................. 5 .3-3 5.3.5 R esults and C onclusions ........... ...................... ..................................... 5.3-9 5.3.6 R ecom m ended A ctions ................................................................................. 5.3-9 5.3 _7 U pdates-S ince R evision 0.................................

0 ..... ................................... 5.3-10 5 .4 R ad W aste B uild ing ...................................................................................... 5 .4-1 5.4.1 Sum m ary of Rad W aste Building ................................................................. 5.4-1 5.4.2 Inputs/References Supporting the Analysis ................................................ 5.4-1 5.4.3 Assessment Methods and Procedures ........................................................ 5.4-2 5 .4 .4 A n a lysis. .. ............................................................................................ 5 .4 -2 5.4 .5 R esults and C onclusions .............................................................................. 5.4-7 5.4.6 Recommended Actions ...................................... 5.4-7 5.4 .7 Updates S ince R evision 0 ........................................................................... 5 .4-7 S5:5 Technical Support. Center, . ... . .. ....... V ..................... 5.5-1 5.5.1 Summary qf Technical Support Center ........................................................ 5.5-1 5.5.2 Inputs/References Supporting the Analysis .............................................. 5.5-1 5.5.3 Assessment Methods and Procedures ............. ....................................... 5.5-2 5 .5 .4 A n a ly s is ........................................................................................................ 5 .5 -2 5.5.5 R esults and C onclusions ............................................................................ 5.5-10 5.5.6 R ecom m ended A ctions .............................................................................. 5.5-10

Page iv Table of Contents --. .....-. Rev. 2 5.5.7 Updates S ince Revision 0 .......................................................................... 5.5-11 5.6 Independent Spent Fuel Storage Installation ......... .............. 5.6-1 5.6.1 Summary of Independent Spent Fuel Storage Installation ........................... 5.6-1 5.6.2 Inputs/References Supporting the Analysis ................................................. 5.6-2 5.6.3 Assessment Methods and Procedures ......................................................... 5.6-2 5 .6 .4 A n a ly s is ........................................................................................................ 5 .6 -3 5.6.5 Results and Conclusions ..................................... 5.6-5 5.6.6 Recommended Actions .................. ..................... 5.6-5 5.6.7 Updates Since Revision 0 ..................................... 5.6-5 5 .7 S e cu rity B u ild ing ............................................................................................ 5 .7-I 5.7.1 Sum m ary of Security Building ........................................ ............................ 5.7-1 5.7.2 Inputs/References Supporting the Analysis ....., ......... ..... 5.7-2 5.7.3 Assessment Methods and Procedures .......... ...................................... 5.7-3 5 .7 .4 A na lysis ........................................................... ....... 5 .7-3 5.7.5 Results and Conclusions 5..7.-11 5.7.6 R ecom m ended A ctions .............................................. ........................... 5.7-11 5.7.7 Updates Since Revision 0 .................................... 5.7-12 5.8 Turbine Building ........................................... 5.8-1 5.8.1 Summary of Turbine Building .................. 5.8-1 5.8.2 Inputs/References Supporting the Analysis ....... ...................................... 5.8-1 5.8.3 Assessment Methods and Procedures ................................. 5.8-3 5 .8 .4 A n a ly s is ..................................... ....... .. .................................................. 5 .8-4 5.8.5 Results and Conclusions'................................. 5.8-10 5.8.6 Recommended Actions ......................................... 5.8-10 5.8.7 Updates Since Revision 0..... ................... .. ............................. 5.8-11 5.9 Security Barricaded'6Balistic Resistant Enclosurýes .................................... 5.9-1 5.9.1 Summary pf. Security Barricaded Ballistic Resistant Enclosures ............ .... 5.9-1 5.9.2 :.Inputs/References Sup portihg the Analysis ................... ................... 5.9-1 5..9.3 Assessment, Methods and Procedures ......................................................... 5.9-4 5.59 4 A nalysis ............ ..A. ............-.. . . ..... ...... ........................................ 5.9-4

... 5 Results and Conc i ns .... .... ................................................... . 5.9-10 5.9.6 R ecom m ended A ctioniý ............... ....................... ...................................... 5.9-10

..5.9.7 Updates S ince R evision 0 .......................................................................... 5.9-11 1 0-: Turbine Building South*-,Sw itchyard ............................................................ 5.10-1 5.10 .1:'Summary of Turbinel Building South Switchyard ........................................ 5.10-1 5.10.2 Inputs/References Supporting the Analysis ............................................... 5.10-1 5.10.3 Assessment Methods and Procedures ....................................................... 5.10-2 5.10.4 Analysis.......................................... ....... 5.10-3 5.10.5 R esulgS and :C onclusions .......................................................................... 5.10-13 5.10.6 R ecom m ended A ctions ............................................................................ 5.10-13 5.10.7 Updates S ince R evision 0 ........................................................................ 5.10-14 5.11 C ondensate Storage Tank ......................................................................... 5.11-1

--5A-1.-i Sumnmary:of Condensate Storage-Tank-.... . ... . ......

5.11.2 Inputs/References Supporting the Analysis ............................................... 5.11-1 5.11.3 Assessm ent M ethods and Procedures ....................................................... 5.11-3 5 .1 1 .4 A n a ly s is ..................................................................................................... 5 .1 1-3 5.11.5 R esults and C onclusions .......................................................................... 5.11-14 5.11.6 R ecom m ended A ctions ............................................................ .............. 5.11-14 5.11.7 U pdates S ince R evision 0 ........................................................................ 5.11-15

Page v TaLIteof Contents , Rev.2 5.12 Underground Cable Trench ........................... ....... 5.12-1 5.12.1 Summary of Underground Cable Trench ............................ ..... 5.12-1 5.12.2 Inputs/References Supporting the Analysis ........................ .......... 5.12-1 5.12.3 Assessment Methods and Procedures ................................. ........ 5.12-2 5 .12.4 A nalysis ....................................................................................... 5 .12-3 5.12.5 R esults and C onclusions .......................................................................... 5.12-12

5. 12_6 Recommended Actions ................................................................. . 12-12 5.12.7 Updates Since Revision 0 " 5.12-13 5.13 C irculating W ater System ........... . ........................... .;'....................

..... 5.13-1 5.13.1 Summary of Circulating VVater Syster . . ........ ................... 5.13-I.

5.13.2 Inputs/References Supporting the Analysis .......................... . ............. 5.13-1 5.13.3 Assessment Methods and Procedures ........... ............... 5.13-3 5 .13.4 A nalysis ............................ .... e .................... 5 .13-4 5 .13.5 R esults and C onclusions ............................................................................ 5 .13-8 5.13.6 R ecom m ended A ctions ............................................................................... 5.13-8 5.13.7 Updates Since Revision 0 .................................. * . 5.13-9 5.14 Demineralized Water Tank, Pump House, and RO Unit-......... ................... 5.14-1 5.14.1 Summary of Demineralized Water Tank, Pump House, anndt O . ....

U .... ... .... ... . .. ............

and RO Unit.........................................5.1-1 *  :...................... i.i~.-....

............ 5 .14 -

5.14.2 Inputs/References Supporting the Analysis .............................. 5.14-1 5.14.3 Assessment Methods and Procedures ..................... .. .......................... 5.14-2 5.14.4 Analysis ......... ........................... 5.14-3 5.14.5 Results and Conclusions .................................... 5.14-9 5.14.6 Recommended Actions .................... ..... 5.14-9 5.14.7 U pdates Since Revision 0 ...................................... .............................. 5.14-10 5.15 Raw Water Piping ......................................... 5.15-1 5.15.1 Sum m aryof R aw W ater Piping ............................ ................... ....... 5.15-1 5.15.2Iln*uts/References Supporting the Analysis ............ I.......... .................. 5.15-2 5.1,5*.i3- Assessment"M ethods and Procedures ........................................................ 5.15-3 5 .1:5'.4 A n a lysis .. . ........ ............... ................................................ 5 .15-4 5.15.5 Results and Conclusions................................... 5.15-12 5.15.6 Recommended Actions .................................... 5.15-12 5.15.7 U pdates S ince R evision 0 ........................................................................ 5.15-13 5.16 Fire Protection System Piping..................................516-1 5.16.1.Summ ary of Fire Protection System Piping ............................ ;.................. 5.16-1 5.16.2 :Inputs/References Supporting the Analysis .............................................. 5.16-1 5.16.3 Assessm ent Methods and Procedures ....................................................... 5.16-3 5 .16.4 A nalysis ...... .................................... ......................................... . .5.16-4 5.16.5 R esults:.and :ýC obnclusions .......................................................................... 5.16-14 5.16.6 R ecom m ended A ctions ............................................................................ 5.16-14 5.16.7 Updates S ince Revision 0 ........................................................................ 5.16-15 5 .17 W aste D isposal P iping .............................................................................. 5 .17-1 1 ..1 Sum mar.y*fZf asteD sposa: ping ....................................

.5;. . . , . t,:*.-,*,....,

i.,&:Ji!-::*.".:

5.17.2 Inputs/References Supporting the Analysis ............................................... 5.17-1 5.17.3 Assessm ent Methods and Procedures ....................................................... 5.17-3 5 .1 7 .4 A n a ly s is ...................................................................................................... 5 .17 -4 5.17.5 Results and Conclusions ............................. 5.17-11 5.17.6 R ecom m ended A ctions ............................................................................ 5.1 7-11 5.17.7 U pdates S ince R evision 0 ....................................................................... 5.17-11

Page vi Table of Contents' -. Rev: 2 5.18 Fuel O il Storage Tanks and Piping ............................................................... 5.18-1 5.18.1 Summary of Fuel Oil Storage Tanks anid Piping ........................................ 5.18-1 5.18.2 Inputs/References Supporting the Analysis ............................................... 5.18-1 5.18.3 Assessment Methods and Procedures ....................................................... 5.18-3 5 .1 8 .4 A n a ly sis ...................................................................................................... 5 .18 -4 5.18.5 R esults and Conclusions .......................................................................... 5.18-12 5.18.6 R ecom m ended A ctions ............................................................................. 5.18-12. .

5.18.7 Updates Since Revision 0 .................... ....... ..... 5.18-13 5.19 Main Underground Cable Bank, Auxiliary Building to intake Structure ........................................... 5.19-1 5.19.1 Summary of Main Underground Cable Bank,.:Auxiliary Building to Intake Structure ........ .......... ................. 5.19-1 5.19.2 Inputs/References Supporting the Analysis ....................... 5.19-1 5.19.3 Assessment M ethods and Procedures ........................................................ 5.19-3 5.19.4 Analysis....................... ........ ................. 5.1.9-4 5.19.5 Results and C onclusions ......................................................................... 5.1:9-17 5.19.6 Recommended Actions ...................................... 5.19-17 5.19.7 Updates-Since R evision 0 .............................. .. ................................... 5.19-18 5.20 Meteorological Tower and Miscellaneous Structures ................................ 5.20-1 5.20.1 Summary of Meteorological Tower and Miscellaneous Structures ........... 5.20-1 5.20.2 Inputs/References Supporting the Analysis,...: .......................................... 5.20-1 5.20.3 Assessment Methods and Procedures... ...................... 5.20-2 5.20.4 Analysis ............................................ ..... 5.20-3 5.20.5 R esults and C onclusions ............................................................................ 5.20-7 5.20.6 Recom m ended A ctions .......................... .............................................. 5.20-7 5.20.7 Updates Since Revision: 0 ...................... ........................ .......... 5.20-8 5.20.-8.....

5.21 Original.Steam Generator Storage Building.',v;.: ......... ............. ............... 5.21-1 5.21.,1Surmary, of Original SteamrGenerator Storage Building ........................... 5.21-1 5.2:1.':2 Inputs/References.. Supporting :the Analysis ....................... 5.21-1 5.24.3 Assessment Methods and Procedures ...................................................... 5.21-1

-:5.2 1.4 A n a lysis ............ .................... . ..... ................................................. 5 .2 1-2

5.2 1.5 R esults and C onclusions ........................................................................... 5.21-2 5.2 1.6 R ecom m ended A ctions ............................................................................. 5.21-2 5.2 2 S w itchya rd ................................................................................................ 5 .2 2-1 5.22.1 S um m ary of Sw itchyard ............................................................................. 5.22-1 5.22.2 Inputs/References Supporting the Analysis ............................................... 5.22-3 5.22.3 Assessment Methods and Procedures ....................................................... 5.22-4 5.22.4 Analysis.. ...................................... ............ 5.22-5 5.22.5 R esults and C onclusions ............................................................................ 5.22-9 5.22.6 R ecom m ended A ctions .............................................................................. 5.22-9 5.22.7 Updates Since R evision 0 ........................................................................ 5.22-10 5 .23 T ransm ission T ow ers ................................................................................. 5.23-1 5.23.1 Summa-ryof Transmission Towers.*.., ...... :.. .................... 523::- ..

5.23.2 Inputs/References Supporting the Analysis ............................................... 5.23-1 5.23.3 Assessment Methods and Procedures. .......................... 5.23-2 5 .2 3 .4 A n a ly s is ................................................................. .................................... 5 .2 3 -6 5.23.5 R esults and C onclusions .......................................................................... 5.23-11 5.23.6 Recommended Actions ............. .................... ... 5.23-11 5.23.7 Updates S ince R evision 0 ....................................................................... 5.23-11

Page vii Tl-alble of Contents 2Rev.2 5.24 Main Underground Cable Bank, MH-1 to Auxiliary Building .......... ............ 5.24-1 5.-24.1 Summary of Main Underground Cable Bank, MH-1 to A uxilia ry Bu ild ing ....................................................................................... 5 .24 -1 5.24.2 Inputs/References Supporting the Analysis ............................................... 5.24-1 5.24.3 Assessment Methods and Procedures ....................................................... 5.24-3 5.24.4 Analysis ......................... I ...................................... .... 5.24-4 5.24.5 R esults and C onclusions .......................................... .................................... 5.24-9 5.24.6 Recommended Actions ........ .............................. 5.24-9 5.24.7 Updates Since R evision 0 ........................................................................ 5.24-10 5 .2 5 Rive r Ba n k ................................................................................................. 5 .2 5 -i 5.25.1 Sum m ary of R iver B ank ............................................................................. 5.25-1 5.25.2 Inputs/References Supporting the Analysis ....................... 5.25-1 5.25.3 Assessment Methods and Procedures ....................................................... 5.25-2 5.25.4 Analysis .............................................................. ... 5.25-3 5.25.5 R esults and C onclusions ............................................................................. 5.25-9 5.25.6 Recom m ended Actions ........................................... 5.25-9......................

. 5.2 -9 5.25.7 Updates Since Revision 0 ............................ 5.25-10 5.26 Blair Water System ........................ .. 5.26-1 5.26.1 Summary of Blair Water System .........

.................................. 5.26-1 5.26.2 Inputs/References Supporting the Analysis............................................ 5.26-1 5.26.3 Assessment Methods and Procedures ............. .... ............................... 5.26-3 5.26.4 Analysis .................. ................................... 5.26-4 5.26.5 Results and Conclusions ...................................... 5.26-12 5.26.6 Recommended Actions .................................... 5.26-12 5.26.7 Updates 5.27 eSince in ralim ed w te*!Si~i 0........

Revision:0 tem ..........................

i...:

a ............ .............. 5.26-13 5.27-1 5.27 Demnineralized Water,-.System 5.27......-1 5.27.1 Summary of Demineralized Water System 5.27-1 5.27.2Inputs/References Supporting the Analysis. ....................... 5.27-2 5.27*3Assessment Methods and Procedures ....................................................... 5.27-3 5 .2 7.4 A n a lys is ...................................................................................................... 5 .2 7-3

-.5.27.5 Results and Conclusions .............. ..................... 5.27-9 5..27.6 Recommended Actions .............................. 5.27-9

.5,.?27.7 Updates Since R evision 0 ........................................................................ 5.27-10 5.28_ -Camera Towers and High Mast Lighting .................................................... 5.28-1 5.28.1 Summary of Camera Towers and High Mast Lighting ................................ 5.28-1 5.28.2 Inputs/References Supporting the Analysis ............................................... 5.28-1 5.28.3 Assessment Methods and Procedures ....................................................... 5.28-2 5.28.4 Analysis................................................. 5.28-2 5.28.5 R esults and C onclusions ............................................................................ 5.28-9 5.28.6 R ecom m ended A ctions ............................................................................ 5.28-10 5.28.7 Updates S ince R evision 0 ........................................................................ 5.28-10 6 .0 P rio rity 2 S tru ctu re s ................................................................................................ 6 .1-1 6.&A :'N~ew Warehouse ........... "*.... ...... . . .. Q$6_1 i -~

6.1.1 Sum m ary of New W arehouse ...................................................................... 6.1-1 6.1.2 Inputs/References Supporting the Analysis ................................................. 6.1-1 6.1.3 Assessm ent Methods and Procedures ......................................................... 6.1-3 6 .1.4 A n a ly s is ........................................................................................................ 6 .1-3 6 .1.5 R esults and C onclusions .............................................................................. 6 .1-5 6 .2 S e rv ic e Bu ild ing ............................................................... ........................... 6 .2-1

Page viii Table ,of Contents~ - . Rev. 2 6.2.1 Sum m ary of Service Building ....................................................................... 6.2-1 6.2.2 Inputs/References Supporting the Analysis ................................................. 6..2-1 6.2.3 Assessment M ethods and Procedures ......................................................... 6.2-3 6.2.4 Analysis .................. " ............. ......... ...... 6.2-4 6.2.5 Results .......................................... ........ 6.2-9 6.2.6 Conclusions ............................. 6.2-10 6.3 Chemistry/Radiation Protection Building: ...... .................... 6.3-1 6.3.1 Summary of Chemistry/Radiation Protection Building .................................. 6.3-1 6.3.2 Inputs/References Supporting the Analysis ................ ................... 6.3-1 6.3.3 Assessment Methods and Procedures ..... ...................... 6.3-2 6.3.4 Analysis.............. ......................... .. ..... ... 6.3-2 6.3.5 Results and Conclusions .............. ....... 6.3-5 6.4 Maintenance Shop ............................... .. ......... 6.4-1 6.4.1 Sum m ary of Maintenance Shop .................................................................. 6.4-1 6.4.2 Inputs/References Supporting the Analysis ........................ 6.4-2 6.4.3 Assessment Methods and Procedures .................... ........ ....................... 6,4-3 6.4.4 A nalysis .............................................. ............................... 6.4-4 6 .4 .5 R e s u lts .............................................................................................. 6 .4 -9 6 .4 .6 C o n c lu sio n s ................................................. ............................ .................. 6 .4 -9 6.5 Maintenance Fabrication Shop .. " ............................... ..... 6.5-1 6.5.1 Sum mary of Maintenance Fabrication Shop ................................................. 6.5-1 6.5.2 Inputs/References Supporting the Analysis, ................................................. 6,5-1 6.5.3 Assessment Methods and Procedures........................... 6.5-2 6.5.4 Analysis ............... ................... ...... ......... 6.5-2 6.5.5 Results and Conclusions............ ...... .................. 6.5-4 6.6 PA Paving, PA Sidewalks, and OutdoorDriv"es...................... 6:6-1 6.6.1 Summ.ary.of -PA Paving6,.PASidewalks, and'.;Outdoor Drives ....................... 6.6-1 6.6.2 Iiputs/References Supporting.the Analysis .................................................. 6.6-1 6.6.3. Assessment Methods and Procedures .................................................... 6,6-3 6 .6 .4 A n a ly s is ... ........ .................. ................................................................ 6 .6-3 6.6.5 Results and Recommendations ............................... 6.6-11 6 .6 .6 C o n clu sio n s ............................................................................................... 6 .6 -12 6 .7 P otable W ate r P iping ................................................................................... 6 .7-1 6.7.1 Sum m ary of Potable W ater Piping ............................................................... 6.7-1 6.7.2 Inputs/References Supporting the Analysis ................................................. 6.7-1 6.7.3 Assessm ent Methods and Procedures ......................................................... 6.7-2 6 .7.4 Ana lys is .......... 0 ..................................................................................... 6.7 -3 6.7.5 Results~and Recommendations. ................................ 6.7-8 6.7.6 Conclusions ............................................... 6.7-8 6 .8 S anitary S ew er S ystem ................................................................................ 6 .8-1 6.8.1 Sum m ary of Sanitary Sewer System ............................................................ 6.8-1 6.8.2 Inputs/References Supporting the Analysis .................... . .................. 6.8-2 6..8.3. Assessment Methods..and Procedures:...-_ - -3 ~

8 6 .8 .4 A n a ly s is ........................................................................................................ 6 .8 -4 6.8.5 Results and Recom m endations ................................................................... 6.8-9 6 .8 .6 C o n c lu sio n s ............................................................................................... 6 .8 -10 6.9 Maintenance Storage Building ..................................................................... 6.9-1 6.9.1 Summary of Maintenance Storage Building ............. 6.9-1 6.9.2 Inputs/References Supporting the Analysis .................................................. 6.9-1

Page ix "Table of Contents.,. -ReV. 2 6.9.3 Assessment Methods and Procedures ......................................................... 6.9-2 6 .9 .4 A n a ly s is ........................................................................................................ 6 .9-2 6.9.5 Results and Conclusions...................................... 6.9-4 6 .10 O ld W a rehouse ............................................................................................ 6 .9-1 6.10.1 Sum m ary of O ld W arehouse ........................................................................ 6.9-1 6.10.2 Inputs/References Supporting the Analysis ................................................. 6.9-1 6.10.3 Assessment Methods and Procedures ......................................................... 6.9-2, 6 .10 .4 A n a ly s is ................................................................................................. ..... 6 .9-2 6.10.5 R esults and C onclusions .............................................................................. 6.9-5 6 .1 1 T ra in in g C e n te r .......................................................................................... 6 .1 1-1 6.11.1 Summary of Training Center .................................. 6.11-1 6.11.2 Inputs/References Supporting the Analysis ............................................ 6.11-1 6.11.3 Assessment Methods and Procedures ................. .................. ............ 6.11-2 6.11.4 Analysis ................................................ 6.11-2 6.11.5 Results and Conclusions .................................... 6.11-4 6.12 Administration Building ...................................... 6.12-1 6.12.1 Summary of Administration Building ............ "'................................ 6.12-1 6.12.2 Inputs/References Supporting the Analysis....................... 6.12-1 6.12.3 Assessment Methods and Procedures ...................................................... 6,12-2 6 .1 2 .4 A n a ly s is ........................................................................................... ............ 6 .12 -2 6.12.5 R esults and C onclusions ............. ' . .. .......................................... 6.12-4 6.13 Hazardous Material Storage Building ................................... 6.13-1 6.13.1 Summary of Hazardous MaterialiStorage:,1Building. ....... ............ 6.13-1 6.13.2 Inputs/References Supporting the Analysis ............. ................................... 6.13-1 6.13.3 Assessment Methods and Procedures............. .................................... 6.13-2 6 .13.4 A nalysis ................... . ......... ........ .. ..................... 6 .13-2 6.13.5 R esUlts:and C onclusions .. ......................... ... . ...................................... 6.13-4 6.14 M aintenance G arage ................................................................................. 6.14-1 6.14.1 Sum m ary of M aintenance Garage ................ .......... ............................. 6.14-1 6.14.2 Inputs/References Supporting the Analysis ............................................... 6.14-1 6.14.3 Assessment Methods and Procedures ....................................................... 6.14-2 6 .14 .4 A n a lys is ................................................................................. 6 .14 -2 6.14 .5 R esults and C onclusions ............................................................................ 6.14-4 6 ,:15 T e rtia ry B u ild ing ........................................... ........................................... 6 .15-1 6.15..1 S um m ary of Tertiary:Building ..................................................................... 6.15-1 6.15.2Inhputs/

References:

Supporting the Analysis ....................... 6.15-1 6.15.3 Assessment Methods and Procedures ....................................................... 6.15-2 6.15.4 Analysis.... ........................................ ..... 6.15-2 6 .15.5 R esults.and C onclusions ............................................................................ 6.15-4 6.16 S pare T ransform er P ads ............................................................................. 6.16-1 6.16.1 Sum m ary of Spare Transform er Pads ........................................................ 6.16-1 6.16.2 Inputs/References Supporting the Analysis ............................................... 6.16-1 6.16.3 Assessment Methods and. Proced:ures,...:;.... .............. :6.6:2 2..

6 .1 6 .4 A n a ly s is ...................................................................................................... 6 .1 6 -2 6 .16.5 R esults and C onclusions ............................................................................ 6.16-5 6 .17 S h oo tin g R a n g e ......................................................................................... 6 .17 -1 6.17.1 Sum m ary of Shooting Range ..................................................................... 6.17-1 6.17.2 Inputs/References Supporting the Analysis ............................................... 6.17-1 6.17.3 Assessm ent Methods and Procedures ....................................................... 6.17-2

Page x Table of Conten-ts .Rev. 2 6.17.4 Analysis ................... ..................... 6.17-2 6.17.5 Results and Recommendations ............................... 6.17-6 6 .17 .6 C o nclusio n s ............................................................................................... 6 .17-6 6 .18 G rave l P arking Lots .................................................................................... 6 .18-1 6.18.1 Sum m ary of G ravel Parking Lots ............................................................... 6.18-1 6.18.2 Inputs/References Supporting the Analysis ................................................ 6.18-1 6.18.3 Assessment Methods and Procedures ....................................................... 6.18-2 6.18.4 Analysis ........ . ..................  ; ..................... 6.18-2 6.18.5 Results and C onclusions ..... ........................ 6.18-4 6. 8-.......................

6.19 Sewage Lagoons ....................... ..................

6.19.1 Sum m ary of Sewage Lagoons ......................... .............. .. ................ 6.19-1 6.19.2 Inputs/References Supporting the Analysis ...................... ........... 6.19-1 6.19.3 Assessment Methods and Procedures ........................................... 6.19-3 6 .19 .4 A n a lysis ... ................................ 66.19-3....................

.19-3 6.19.5 Results and Recom m endations ...................... ...b ............................... 6.19 9 6 .19.6 C o nclusions 6.1-........................

6 19-9 7.0 Summary and Conclusions .......................................... 7-1 7 .1 -Scope and P urpose ... ..................... . ............................. ....................... 7-1 7.2 Summary of the Assessment Process ... .... . ...................... 7-1 7.3 Principal Findings of the Comparative Geotechnical Analysis ............ 7-4 7.4 Key D istress Indicators ............. ..................... .. ................................. 7-4 7.4.1 T urbine Building S um p ........ ......................  : .................................. 7-4 7.4.2 Paved Access Area .......................................... 7-7 7.4.3 Maintenance Shop ................................ 7-9 7.5 Status of Priority 1 Structural Assessments ................................................... 7-12" 7.5.1 Intake Structure ........................................... ................. 7-12 7 .5 .2 A uxilia ry Build ing ........... ....................... ........................................... 7-12 7.5.3 Containment ....... ...................................... 7-12 7.5.4 Rad Waste Building .................................... 7-12 7.5.5 Technical Support Center......................................... 7-13

.7.5.6 Independent Spent Fuel Storage :Installation ................................................ 7-13 7 .5 .7 S e cu rity Bu ild in g ............................................................................................ 7-13 7 .5.8 T u rb in e Bu ild in g ............................................... ............................................ 7 -13 7.5..9.:- Security Barricaded BallisticResistant-Enclosures ....................................... 7-13 7.5. 10 Turbine Building South Sw itchyard ............................................................... 7-14 7.5.11 Condensate Storage. Tank ............................................................................ 7-14 7.5.12 Underground C able T rench ........................................................................... 7-14 7.5.13 C irculating W ater System .............................................................................. 7-14 7.5.14 Deminerialized Water Tank, Pump House, and RO Unit ............................... 7-15 7 .5 .15 Raw W ater P iping ........................ ................ ............................................ 7-15 7.5.16 Fire P rotection S ystem P iping ....................................................................... 7-15 7 .5 .17 W a ste D isposal P iping .................................................................................. 7-15 7.5.18 Fuel Oil StorageTanks and Piping.... ....... .. I..:. ..... .............. 7-16 7.5.19 Main Underground Cable Bank, Auxiliary Building to Inta ke S tru ctu re ............................................................................................. 7-16 7.5.20 Meteorological Tower and Miscellaneous Structures .................................... 7-16 7.5.21 Original Steam Generator Storage Building .................................................. 7-16 7 .5 .2 2 S w itc h ya rd .................................................................................................... 7 -16 7 .5.23 T ransm ission T ow ers .................................................................................... 7-17

Page xi Table of Con'tents -----"-

- Rev. 2 7.5.24 Main Underground Cable Bank, MH-1 to Auxiliary Building .......................... 7-17 7 .5 .25 R iver B ank .................................................................................................... ..7-17 7 .5 .26 B lair W ater S yste m ....................................................................................... 7-17 7.5.27 Dem ineralized W ater System ........................................................................ 7-17 7.5.28 Camera Towers and High M ast Lighting ....................................................... 7-18 7.6 Status of Priority 2 Structure Assessments. ......................... 7-18 7 .6 .1 N ew W a rehouse ..................................................... ..................................... 7-18 7 .6 .2 S e rvice B uild ing ............................................................................................ 7-18 7.6.3 Chem istry/Radiation Protection Building................................ ....................... 7-18 7.6.4 Mvaintenance Shop. ........................................... 7-19 7.6.4 Maintenance Fa rc.................................

S hop to , .* ......................... *.................. 7-19 7.6.5 Maintenance Fabrication Shop................. .......... 7-19 7.6.6 PA Paving, PA Sidewalks, and Outdoor Drives ........................ 7-19 7.6.7 Potable Water Piping ............... ......................... 7-19 7.6.8 Sanitary Sewer System ........................................................ ..... 7-19 7.6.9 M aintenance Storage Building ......................................................... .......... 7-20 7.6.10 O ld W arehouse ........................................................................................ 7-20 7 .6 .11 T ra ining C e nte r ......................................................... ............................... 7-20 7.6.12 Administration Building ....................................... 7-20 7.6.13 Hazardous Material Storage Building ........................................................ 7-20 7 .6 .14 Maintenance G arage .................................................................................... 7-20 7 .6 .15 T e rtia ry Bu ild ing ............................................. ............................................ 7-20 7.6.16 Spare Transform er Pads ..................................................................... 7-21 7.6.17 Shooting Range ............................................ 7-21 7.6.18 Gravel Parking Lots ......................................... 7-21 7 .6 .19 S ew age Lagoons ............................... * ........................................... 7-2 1 8.0 References ........................ .............................. ........ 8-1 9.0 Attachments ................................................. 9-1 9.1 Attachm ent 1 - Deaggregation Plots ............................................................... 9-1 9.2 Attachment 2 -:Structural Baseline References ............................................... 9-1 9.3 Attachment 3 - FCS Site Inspection Checklists .............................................. 9-1 9.4 Attachment 4 - Triggering Mechanisms and Potential Failure Modes by Structure.......................................... 9-1 9.5 Attachment 5 - Supporting Data for Comparative Evaluation of G eotechnical A nalyses ............................................................................... 9-1 9.6.. Attachment 6 - Geotechnical Data from Subconsultants

a Pd P ............

and OPPD . .. .. .. .i~~i !:. :*. .. ............................................................................

....... .................... 9-9-1 9.7 Attachm ent 7 - Photo Docum entation ............................................................. 9-1 9.8 Attachment 8 - Field Reports, Field Notes, and Inspection C h e ck lists ........................................................................................................ 9- 1 List of Tables Table 1-1 - Priority 1 Structures (Must Be Assessed Prior to Plant Restart) ........................ 1-2 Table 1-2 - Priority 2 Structures (Do Not Directly Support Plant Operations) ...................... 1-3 Table 1-3 - Assessm ent Report Revision History ................................................................ 1-4 Table 1-4 - Summary of Flood Protection Measures Taken for P rio rity 1 Stru c tu re s ........................................................................................... 1-5

Page xii Tabl-e of Contents Rev. 2 Table 1 Summary of Flood Protection Measures Taken for Priority 2 Structures .............................................................. 1-6 Table 2 Historical Seismicity Within 100 Miles of Fort Calhoun Station .......................... 2-1 Table 2 Peak Ground Acceleration as Percentage for Various R e tu rn P e rio d s ................................................................................................... 2-3 Table 2 Missouri River Flood Recurrence Intervals at RM 646 (FCS) .......................... 2-11 Table 2 Historic Flood Events on the Missouri River at Fort Calhoun S tatio n , R M 64 6 ................ ............................ ............................................. 2-12 Table 2 Groundwater and River Level Elevations ........................... 2-30 Table 2 Underground Piping Utilities ............................................................................ 2-62 Table 2 Underground Electrical Utilities ................................... .................................. 2-66 Table 3 Potential for Failure/Confidence Matrix and Associated R eco m m ended A ctions ....................................... ...... s....................................... 3-6 Table 3 Triggering Mechanisms and Potential Failure Modes .......................... 3-7 Table 3 Potential Failure Modes Determined to be Non-Credible for Priority 1 Structures ....................................... ....................... . 3-9 Table 3 Potential Failure Modes Determined to beNon-Credible for Prio rity 2 S tructures .................... .......... ,......... ........................................ 3-10 Table 3 Potential Methods and Procedures for Addressing Identified Potential Failure Modes................................ 3-12 Table 4 Turbine Building Basement Subgrade Investigation Observations .................. 4-11 Table 4 Turbine Building Basement Subgrade Investigation DCP:Results .................. 4-19 Table 4 Maintenance Shop Forensic lnvestigation70bservations. ............... 4-46 Table 4 Maintenance Shop SCP Test Results ......... .... .. .............................. 4-52 Table 5.1 References for Intake Structure ........... ................ 5.1-1 Table 5.2 References for Auxiiliary'Building... i ....  ;................ ......... 5.2-2 Table 5.3 References for Containm ent ............... .......... .................................. 5.3-1 Table 5.4 References for Rad Waste Building ............................................................. 5.4-1 Table 5.5 References for Technical Support Center .................................................... 5.5-1 Table 5.6 R eferences for IS FSI ................................................................................... 5.6-2 Table 5.7 References for Security Building ................................................................. 5.7-2 Table 5.8 References for Turbine:Building .................................................................. 5.8-1 Table 5.:9-..1 - References for Security:BBR Es ................................................................... 5.9-1 Table 57*1 O -: References for Turbine Building South Switchyard ................................. 5.10-1 Table 5.11-1 -:References for Condensate Storage Tank .............................................. 5.11-1 Table 5.12 References for Underground Cable Trench ............................................. 5.12-1 Table 5.13-1 -. References forCirculating Water System ................................................ 5.13-1 Table 5.14 References for Demineralized Water Tank, Pump House, a n d R O Un it ................................ ........... ............................................. 5 .14 -1 Table 5.15 References for Raw Water Piping ........................................................... 5.15-2 Table 5.16 References for Fire Protection System Piping ......................................... 5.16-1 Table 5.17 References for Waste Disposal Piping .................................................... 5.17-1 Table 5.1t8-,-References-for Fuel Oil StorageTariks and.Piping......... .*....n.:-.5.18-.1 -

Table 5.19 References for Main Underground Cable Bank, A uxiliary Building to Intake Structure ....................................................... 5.19-1 Table 5.20 References for Meteorological Tower and Miscellaneous S tructures ......................................................................... 5.20-1 Table 5.21 References for Original Steam Generator Storage Building ................... 5.21-1 Table 5.22 References for Sw itchyard ...................................................................... 5.22-3

Page xiii

...Table of Confents - -  :-:--Rev. 2 Table 5.23 References for Transmission Towers ...................................................... 5.23-2 Table 5.24 References for Main Underground Cable Bank, MH-1 to Auxiliary Building ...................................................................... 5 .24-1 Table 5.25 References for River Bank ...................... 5.25-1 Table 5.26 References for Blair W ater System ......................................................... 5.26-1 Table 5.27 References for Demineralized Water System .......................................... 5.27-2 Table 5.28 1 - References for Camera Towers and High Mast Lighting ......................... 5.28-1 Table 6.1 References for New W arehouse .................................................................. 6.1-1 Table 6.2 References for Service Building ................................ 6.2-1 Table 6.3-1 - References for CARP Building .................................. ........................... 6.3-1 Table 6.4 References for Maintenance Shop ......................................... 6.4-2 Table 6.6 References for PA Paving, PA Sidewalks, and Outdoor Drives ................. 6.6-1 Table 6.7 References for Potable W ater Piping ................. ................ ...................... 6.7-1 Table 6.8 References for Sanitary Sewer System ....................................................... 6.8-2 Table 6.10 References for Old Warehouse. .............................. 6.10-1 Table 6.11-1 -References for Training Center. .............................. 6.11-1 Table 6.12 References for Adm inistration Building ..................................................... 6.12-1 Table 6.13 References for Hazardous'Material Storage Building .............................. 6.13-1 Table 6.14 References for Maintenance Garage .................................................... 6.14-1 Table 6.15-1 - References for Tertiary Building:..............................6.15-1 Table 6.16 References for Spare Transformer Pads................ ....................... 6.16-1 Table 6.19 References for Sewage Lagoons .................................... *............................ 6.19-1 Table 7 Triggering Mechanisms and Potential Failure Modes ........................................ 7-2

.- List of Figures Figure 2-1 -,Geotechnical:Areas and Cross-Section Locations ........................................... 2-4 Figure 2-2.- S e ctio n A-A . . .. .... .................................................................... 2-5 Figure 2 -3 : S e ctio n B-B ........ .................. .... ..................................................................... 2-6 Figure..2 Physiographic Setting of FCS Region . ............................................................ 2-8 Figure 2 Location of FCS along..-M issouri River ............................................................ 2-10 Figure 2-6...- Missouri R iver Basin.. 1.-6 ................................................................................ 2-14 Figure 2-7 Flow and-Water Surface.Elevations (June through August) for Fort Calhoun Statio :in, RM 646 .................................................................. 2-15 Figure 2-8 '-Comparison of Discharges on the Missouri River at Omaha in Years when Flooding Occurred (1928 to 2011) .......................................... 2-16 Figure 2 Hydraulic Cross-Section Locations ................................................................. 2-17 Figure 2 Comparison of Cross Sections at Stations 4+10 and 6+65 .......................... 2-18 Figure 2 Comparison of Cross Sections at Stations 9+05 and 11+38 ........................ 2-19 Figure 2 Comparison of Cross Sections at Stations 14+00 and 16+48 ...................... 2-20 Figure 2 Comparison of Cross Sections at Stations 18+91 and 21+44 ...................... 2-21 Figure 2 Flow Paths atFC.-S:on:July 12,:2011......... ..................... 2-24 Figure 2 S urveyed High W ater Line .................................................  ;......................... 2-25 Figure 2 Soil Boring and Monitoring Well Locations ................................................... 2-28 Figure 2 S ite P lan O verview ....................................................................................... 2-33 Figure 2 T ransm ission Tow ers ................................................................................... 2-70 Figure 3-1 - Plant and Facility Geotechnical and Structural Assessment P ro c e s s ............................................................................................................ 3 -3

Page xiv Table of Contents: ....... -Rev; 2 Figure 4 Distress Indicators ............................................................. ........... ..... 4-2 Figure 4 Turbine Building Drilling Locations, October 2011 ............................................ 4-6 Figure 4 Turbine Building Drilling Locations, December 2011 ...................................... 4-10 Figure 4 Comprehensive Groundwater Gradient Map .................................................. 4-14 Figure 4 Turbine Building Groundwater Gradient Map ................................................. 4-15 Figure 4 Top of Subgrade Topographic Map Based on Probe Me asu re m e nts ................................................... ............................................. 4 -16 Figure 4 Top of Subgrade Topographic Map Based on Dynamic C one P enetrom eter T ests .............................................................................. 4-17 Figure 4 Pavement -Excavationand Subgrade Testing Areas .................. 4-1 Figure 4 GTI Seismic Investigation Lines and SPT Boring Locations ......................... 4-36 Figure 4 Maintenance Shop Drilling Locations, Cross Section Location Plan ...... ...... ....................................... 4-48 Figure 4 Maintenance Shop Drilling Locations, Cross Section A-A ............................ 4-49 Figure 4 Maintenance Shop Drilling Locations, Cross Section B-.B ............................. 4-50 Figure 4 Maintenance Shop Drilling Locations, Cross Section CC........................... 4-51 Figure 5.9 Security BBR E Overview ...................... ..... .............. ...................... 5.9-2 Figure 5.22 Sw itch Yard Detail  :..-.....,2........................ 5.22........................

. ......... ....... 5.22-2 Figure 5.23 Transmission Towers Visited (9/14J1/2011) ..................... 5.23-4 Figure 5.23 Transmission.Towers Visited (.11/15/2011) ...................................... 5.23-13

Page xv Abcronyms and-Abbreviations ...... 'Rev. 2 Acronyms and Abbreviations ANSS Advanced National Seismic System BB RE Barricaded Ballistic Resistant Enclosure CARP Chemistry/Radiation Protection Building CEUS Central and Eastern United States cfs cubic feet per second CHDPE corrugated high density polyethylene CMP corrugated metal pipe CMU concrete masonry unit CPFM credible PFM CPT cone penetration test

.CQE Critical Quality Element EAR Engineering Assistance Request el. elevation FAA Fedei-*a-Aviation Administration FCS Fort Calhoun Station FMEA Failure Modes anid tEffects Analysis fps " feet per second 7 L FRP fiberglass reinforced plastic ft feet g acceleration due to gravity ..........

gpm gallon per minute

-GPR -ground-penetrating radar HD high density HDR HDR Engineering, Inc.

Page xvi Acronyms and-Abbreviations . "-"RbeV. 2-HVAC heating, ventilation, and air conditioning in. inches.

ICF insulated concrete forms ISFSI Independent Spent Fuel Storage Installation ISO International Organization for Standardization kV kilovolt LOCA loss of coolant accident MAF million acre-feet MCE maximum credible earthquake Met Meterological MH Manhole MSL mean sea-level N value blows per foot NAVD 88 North American Vertical Datum of 1988:

NEI Nuclear:Energy Institute NGVD 29 National Geodetic Vertical Datum of 1929 NOUE Notification of Unusual Event NQA-1 Nuclear Quality Assurance OPPD Omaha Public Power-District OSGS Original Steam Generator Storage Building P&ID piping and instrumentation diagrams PA Protected Area PBD Program Basis Document PFM potential failure mode PGA peak ground acceleration PSF pounds per square foot

Page x.vii AC ronyms and'Abbreviations -Rev 2 psi pounds per square inch PV,C polyvinyl chloride QA Quality Assurance QC Quality Control QC P Quality Control Plan RC P reinforced concrete pipe RM River Mile RQ D rock quality designation SP poorly graded sand SP' F standard penetralion test U.S United States us ACE U.S. Army Corps of Engineers us DA-NRCS U.S. Department of Agriculture, Natural Resource Conservation Service us GS U.S. Geolocial Survey VC P vitrified ýclay pipe

Page xviii Definitions Rev. 2 Definitions Class I Class I indicates a system, structure, or component, including instruments and controls, whose failure might cause or increase the severity of an accident that could result in an uncontrolled release of radioactivity. This classification also includes components and structures vital to safe shutdown and isolation of the reactor.

Confidence Confidence is an opinion regarding the need for additional information.

Credible PFMs CPFMs were those that were significantenough to demand further investigation (CPFMs) and evaluation or studies that would increase the confidence in the findings or change the conclusion.

Critical Quality CQEs are structures, systems, components, or items whose satisfactory Element (CQE) performance is required to prevent or mitigate the consequences of postulated accidents that could cause undue risktothe :health and safet. of the public.

Degradation Degradation is a negative chafige to the soil or rock that suppoi6t0 a structure, caused by the sustained inundation of the FCS site during the summer of 2011, which could materially and;negatively impact theiitegrity or intended function of the structure.

Key DiStress A Key Distress Indicator is an obserVed problem: aea that potentially indicated Indicator that the 2011 flood had changed the:site's geotechnical and physical character.

Non-credible PFMs Non-credible PFMs are those that were clearly so remote that they were considered negligible risk contributors.

Potential Failure PFMs are the ways in whicha.structure might fail. Failures are any errors or Mode (PFM) defects, and can be potential0:-oractual.

Potential for a determination. Of whether the Triggering Mechanisms for the CPFMs could degradationldirect have been or were actually initiated by theflood.

floodwater impact Priority I Structures Priority I Structures are those structures and systems that directly support plant operations:

Priority 2 Structures Prioiity 2 Structures are those structures and systems that do not directly support plant operations.

Significance Significance isdetermined by the combined consideration of two elements. The first element is the potential for degradation as described above. The second is the implications of that degradation to a structure built to its specific design standard.

Page xix Definitibns Rev. 2 Triggering Triggering Mechanisms are flood-induced triggering mechanisms that could Mechanism have caused degradation of the soil and/or rock that supports the FCS structures and/or could have caused direct impacts on structures due to the force of the floodwater. Triggering Mechanisms could lead to a potential failure mode (PFM).

Page xx Report Contributors ;-: R6\v'2 Report Contributors Name Project Role Education and Experience Project Management M.S. Industrial/Manufacturing Engineering David Rohan, PE Project Manager B.S. Mechanical Engineering 17 years of experience Lawrence Cieslik, PE Project Principal B.S. CivilEngineering 36 years of experien.ce M.S. Civil Engineering Tom Sanders, PE Project Principal B.S. Civil lEngiheering 33 years .f experience Michael Siedschlag, PE Project Principal B.S. Civil Engieering 37 years of experience,.

Barry Butterfield Quality Assurance/Quality M.SI BS .Civil Engineering ii Engineering niern B ryB tefedControl B.S. Civil .

Control

. 37 years.,df experience B.S. Civil Engineering Quality Assurance/Quality. B.S...ConservatibhiRenewable Natural Craig Osbom, PE Control Resources 36-years of experience Baseline Condition B.S.Civil Engineering Michael Butterfield, PE Civil Engineer 9 years of experience M.S. Geological and Related Sciences M.B.A. Business Administration Engineering Geologist B.A. History John Charlton B.A. History 19 years of experience M.B.A. Business Administration Charles .H.okham, PE Structural Engineer B.S. Civil Engineering 31 years experience Ph.D. Civil Engineering M.S. Civil Engineering Andrew McCoy, PhD, PE Water Resources Engineer B.S. Civil Engineering 12 years of experience M.S. Structural Engineering Christopher Miller, PE Structural Engineer B.S. Civil-Engineering B.Arch. Architecture

..33 years of experience National Technical Advisor M.S. Mechanical Engineering Elena Sossenkina, PE for Dams, Levees, and Hydraulic15 years of experience

Page xxi Report -Contributors - .R*ev. 2 Name Project Role Education and Experience Civil Engineering B.S. Civil Engineering Civil Engineering Team Lead 39 years ofieerinc Richard Niedergeses, PE 39 years of experience B.C.E. Civil Engineering Anna Grimes, PE Civil Engineer 26 years of experience B.S. Civil Engineering Brian ricardHindley, Madsnde, PEPE Engineer6yerofxprnc Civil Engineer B.S. Civil 26years of Engineering experience HughardGrady, PE Civil Engineer B.S. Civil Engineefin g 23 years of experieince B.E. Civil Engineering Hugh O'Grady, PE Civil Engineer 26 years of experience B.S. Civil Engt ineering John Smith Civil Engineering Geotechnical EngineeringGE John eam Lad 2 years of experience MS.

Civi Engineerin SenGeotechnical EngineeringIn B.S. Civil Engineering Roln d Borisseh, PE Team Lead 23 years ofexperience M.S. Civil Engineering Justin Anderson Geotechnical Engineer B.S. Civil Engineering 5 years of expe~riencee M.S. Geotechnical Engineering Rolland Boehm, PE Senior Geoteihnical Engineer B.S. Civil Engineering 24 years of experience Bryan Kumm, PE Geotechnical Engineer B.S. Civil Engineering 26years of experience SB.S. Environmental Technology B.C.E.: Civil Engineering Gregg MitchMell, PG Engineering Geologist A.A. Liberal Arts/Sciences

... ,.* .. 23 years of experience Steve Olson, PE Senior Geoterhnical Engineer B.C.E. Civil Engineering 28 years of experience

....  := .*..-': ....cM .E. Geotechnical Engineering M.S. Geotechnical Engineering Patrick Po nsweihPE Geotecrut icralEngineer B.S. Citul Engineering 27 years of experience Structural Engineerinig*

M.S. Civil Engineering Keith Kirchner, PE StructuralLead Engineer 17 years 32 yas of eering of experience 7:: .... M.S. Architectural Erigineering Camneron Collingsworth Structural Engineer B.S. Architectural Engineering 3 years of Experience B.S. Civil Engineering Keith Froscheiser, PE Structural Engineer 17 years of experience

Page xxii

.- Report Contributors ,:".*,.-..

.: . ..... .-'.... . .. . Re v .2 Name Project Role Education and Experience I "M.S. Civil Engineering Nick Lampe, PE Structural Engineer B.S. Civil Engineering 13 years of experience Engineering Support Joshua Miller oshuaMillerSurvey

_7 B.S. Mechanical Engineering

_years Monitor of expenrence Senior Review Team National Practice Leader for M.S. Civil Engineering Keith Ferguson, PE Dams, Levees, and Hydraulic B.S. Civil Engineering Structures 33 years.of experience Ph.D. Civil Engineering Senior Water Resources M.S. Civil Engineering Technical Advisor B.S. Civil Engineering

.36years of experience T M.S. Structural Engineering Eniner B.S. il..Engineering Christopher M iller, PE Senior Structural Engineer B.S rCivil'... i nietur B.Arch. Architecture 33 y6ars of experience Document Support B.S. Political Science Louise Baxter Technical Editor

• ... 1

.'.!0.iyears of.!experience M -,Engiisglh Composition and Rhetoric Kimberly Gust 'Technical Editor. B.SýE."English 14 years of experience Klayton;.Ia,-Sperbauer Copy..Editor  :*.'.. B.A. English (expected May 2012) ayt peau.CpELess than 1 year of experience A.S. Geographic Information Systems Amy.Sorensen GIS Analyst: A.S. Education 7 years of experience

SECTION

1.0 INTRODUCTION

I/

Page 1-1 Introduction Rev.

1.0 INTRODUCTION

Omaha Public Power District's (OPPD's) Fort Calhoun Station (FCS) is a 484-megawatt nuclear power plant (OPPD, September 25, 2011). FCS is located on the west bank of the Missouri River in northeastern Washington County, Nebraska. FCS is located approximately 4 miles southeast of Blair, Nebraska, and approximately 19 miles north of Omaha, Nebraska.

Massive flooding in the Missouri River basin occurred in 2011, as describ~ed in Section 1.3, Background. Because FCS is located along the Missouri River, flodwatfe 'tcroa-hbed on the FCS site. In June 2011 OPPD contracted HDR Engineering, Rn(eT.R)T*e*pr.fe tBoding s

• ierAfcsional,.

engineering services in support of OPPD's Fort Calhoun Stato*O A*ti oPlan

?ttinjboding wRo-egcinPln HDR provided specialized engineering services for the assessm , f5c-structural ge changes caused by the 2011 Missouri River flood. N, T The flooding of the Missouri River during the summer of 2011 hasl,-,,ii a challey'. .

operation of FCS (OPPD, August 10, 2011). In response to this event, OF.D prepared a F 0 Recovery Action Plan that documented the actions necessary for the repair-ard'.restoration of FCS operations. This Fort Calhoun Station Plant and Faci*it :e* aI Report (Assessment Report) has been prepared in resp.aonse,ýto- -F§, oding Recot` ction Plan 4.1, Plant and Facility Geotechnical and Structural Asse , Mnt

1. i -Cope and Purpose The FCS Plant and Facility Geotechni( rctfural Aýffsment has.l:en completed to identify and describe the geotechnical and stri( cts of the'O I flood ow,28 Priority I Structures and 1 9 Priority 2 Structures at the site. Mi 1 Structuriss*. ethosf&stiuctures and systems that directly support pla*1£perations. TV es are listehfi JIF-1. Priority 2 Structures are those structures *e at do nc support plant operations. These structures are listed in Table 1-2. i1 6c 1-id h*iTii*se %smentReport is to present HDRs assessment of changes t4 9`soil or rock thi*j*3I1 e.*es at FCS due to the 2011 Missouri River flood and/or. irect, impacts of floo; i'= 1le~negatively impacted those structures.

Page 1-2

,-,.*: .. , ... .. ....," 'b &... -:,'.'.;..... .. .... ...

Introduction - . - .. "- ..... t-Oev 2-Table 1 Priority 1 Structures (Must Be Assessed Prior to Plant Restart)

Class I (Seismic) Structures Non-Class I Structures Outside Protected Area Intake Structure Original Steam Generator Storage Building (OSGS)

Auxiliary Building Switchyard Containment Transmission Towers Rad Waste Building . .Meteorological Tower Technical Support Center Demineralized Watefi-Tank PuMp House, and Reverse Oswl}s (]OQJiti "

Non-Class I Structures Inside Protected Area Undergrqoi&f lities Independent Spent Fuel Storage Installation (ISFSI) Blair at-Systemr..4"'

Security Building Main p% jgromCaB-I Turbine Building Auxiliaryi@ig (M -1, t3, MH-4)

Security Barricaded Ballistic Resistant Enclosures River Bank**y%.'.

(BBREs) ,

Turbine Building South Switchyard Condei-sate Storage Tank ____ __ ___. __,

Underground Utilities Underground Cable Trench (Security Trenwa) i. , -

Circulating Water System .

• Demineralized Water System .. *,.. '

Raw Water Piping Fire Protection System Piping .

Waste Disposal Piping ,,

Fuel Oil StorageJ .and Piping 'k,.6 WE "

(only FO- I Lo:& *i"Th In~ontake

'ul Structure (M~~e [MH]-5, M-i-1 _____________________

Camg13-owers and High Mast Lightli'gQ-. __

SotZ&,.OTPPD. August 10, 2011. Floo*1 d'Reco eAction Plan, Revision 0. Document number LIC- l I-0 0. A4 k A..

4:.

.* i***{+

Page 1-3 Introduction - - Rev. 2 I

Assessment Report Orgý 1.2.1 Document Organization This Assessment, -eport.s,*rganzed

• Se ph10, Introduction

" S*6n'-i2.0, Site History, Desc~dd

" ,Sbion 3.0, Assessment Process'

• Sction4 0, Key Distress Indicati SecdW5[C0* Priority 1 Structures

• Sectio 2 Structures-

,ý,0Caiority included in a future revision of the Assessment Report)

• Section 7.0'O!S: mary and Cond

• Section 8.0, ReMTences ,-....

• Section 9.0, At'ta ts.

This report presents the findings, conclusions, and recommendations for the geotechnical, structural, and civil aspects of HDR's inspection completed at the FCS site. It has been prepared .inaccordai "ce".

with generally accepted engineering practice and in a manner consistent with the level of care and skill required for this type of project within this geographical area. No warranty, expressed or implied, is made.

The findings, conclusions, and recommendations presented herein are based on systematic and thorough visual observations and reconnaissance, review of available design and construction

Page 1-4 Introduction .ReV:2 information provided by otbers, the results of field exploration and laboratory materials testing, the results of engineering evaluations, and HDR's experience and engineering judgment.

Geotechnical engineering and the geologic sciences are characterized by uncertainty. Professional judgments presented herein are based partly on HDR's understanding of the past construction at the FCS site, information gathered during the inspection, HDR's general experience, and the state of the practice at the time of this writing.

For structures that were or potentially could still be impacted by the.:201 lidation of the FCS site, this Assessment Report presents recommendations for 1) additiona*ldetailMe n investigations,

2) additional monitoring, or 3) physical modifications. This Asse-ssment Re ot intended to

.mi' modify the accepted design basis of each structure, or to modify any"accepted'eMýgd'cy action plan for FCS.

1.2.3 Revision History Revision 0 of this Assessment Report was submitted to OPPD on October 4 I Revision 0 presented the results of preliminary assessments for each;ei4-a I Structurt additional surveys and site monitoring activities were conducte hv ed the a! ;itnt results for some structures, and are included in this Revision 1-3 s -h1.le of this

izes the re* 4.history document.

Table 1 AssessmenTebport,19Reision Hsto**i,.

Revision Date of Issuance Chan Number Changes 0 October 14, 20)) .

,Koporates results of {*e'.TAIi :ng:

'6k6technical G. summary, including the majority of the data from a~,N~irib~t 7 8 WV ut0chncsmysultants Geote6a. comparative analysis 1ý1"

_ZX ',!41*:*"* Additionwi montorig ecme"8b brporates rltNs of the following:

( December 28, ý'4"-':."orensics F2011 investigations for Key Distress Indicators

._k _ _4___._ *.7Assessment of Priority 2 Structures 1.3 Backgroun.i FCS shut down on for a scheduled maintenance and refueling outage. The refueling and maintenance activities po:did until a combination of above-normal snowpack in the plains in the Northern United States (US'), above-normal snowpack in the mountains above Fort Peck DamI on the Missouri River, and excessive upstream spring rains in eastern Montana and North and South Dakota resulted in massive flooding in the Missouri River basin. The U.S. Army Corps of Engineers (USACE)began releasing record discharges from Gavins Point D amr2 in late May 201 1. The hydrologic background of this Missouri River flood event is explained in Section 2.3 of this Assessment Report.

Fort Peck Dam is the uppermost in a series of six mainstem dams on the Missouri River.

2 Gavins Point Dam is the lowermost of six mainstem dams on the Missouri River.

Page 1-5 Introduction Rev. 2 The plant was in cold shutdown when, on June 6, 201l, FCS entered Notification of Unusual Event (NOUE) status as floodwater on the site exceeded an elevation of 1004.,feet:(ft).3 After this declaration, the Missouri River continued to rise as increasing amounts of water were released from upstream dams. Floodwater covered much of the FCS site, reaching a maximum elevation of approximately 1006.9 ft. The average elevation of the site surrounding the Containment, Turbine Building, and Auxiliary Building is approximately 1004 ft. A variety of steps were taken to prevent floodwater from entering any critical buildings.on site. The measures taken to protect the Priority I and Priority 2 structures are listed in Tables 1-4 and 1-5, respectively.  :,

Table 1-4 - Summary of Flood Protection Measures Teifr~ ~&c~rcue Priority 1 Structure . Methodrpf, J .dProtection Intake Structure tS"iural f 0op'To walkway access

`k"::i" Auxiliary Building AqX4 n. ,.

Containment Aqua: -,

Rad Waste Building Aquaa-Technical Support Center Aqua Dam ." .

Independent Spent Fuel Storage Installation (ISFSI)  ;[ ,.audbag levee" ,

Security Building .... b rrierB Turbine Building "' . A .iaq,D.am Security Barricaded Ballistic Resistant Enclosures (.BBREs) .Vaes (*egelow)

BBRE F-I Aqua .

BBRE F-2 '".- *il- ".. Aqua .

BBRE F-3 .,. None.(#kway access)

BBRE F-4 6;

. NoN*i lkway access)

BBRE F-5 . , (wa lkway access)

BBRE F-6 ,;. . one (walkway access)

Turbine Buimnikg .gSo "..f. S- Aqua Dam CondenfsaR 'torage Tank . .'- '." None DeMO.,r.a zed Water Tank and Pumplaouse ".. Aqua Dam

'.flogical(Met) Tower and Mi..ceI..eous Str-uc..e4s None Or, Steam Generator Storage Buiing (OSGS) None Switcn~hy.*rd:Temporary earthen--berm/sandbag levee Transmissd' owers None An Aqua a"ian engineered wAlarner used to contain, divert, and control the flow of water. It consists of tW6o ~ethylene llner, s~ontained by a single woven geo-tech outer tube. When the two inner tubes are filled w.twhater, jhe',rsulting pressure and mass create a stable, non-rolling wall of water (Layfield Environr -tkSy0t~fs, 2008).

A HESCO barrier is a`"ll-psible container used to block and control floodwater and debris. Composed of wire-mesh with heavy.duty polypropylene geotextile liner, HESCO barriers are filled with aggregate and placed as temporary dikes or flood defense walls.

All elevations are expressed in National Geodetic Vertical Datum of 1929 (NGVD 29), also known as the Sea Level Datum of 1929.

Page 1-6 Introduction Rev. 2 Table 1 Priority Summary of Flood Protection Measures Taken for Priority 2 Structures 2 Structure Method of Flood Protection New Warehouse None Service Building Aqua DamA Chemistry/Radiation Protection (CARP) Building Aqua Dam Maintenance Shop Aqua Dam Maintenance Fabrication Shop None Maintenance Storage Building (Maintenance Shed) None .. .......

Old Warehouse AquafNi] aro%'f.bm , r-n portion of Training Center Aqoga am .'n Administrative Building Acuaq_

e6 ,

Hazardous Material Storage Building (Hazmat Shed) Unkn'6.

Maintenance Garage None,:i." '

Tertiary Building (Boat Storage) None Spare Transformer Pads . j.j..es (see beloI;.c%

TI Spare Transformer Pad berm ccveredt,'with cnushed cru-'IE:i*hen rock Spare pad located west of the TI Spare Transformeia" qg,'levee ,.:

Shooting Range Ber..

- An Aqua Dam is an engineered water barrier use .tt,;contain .7,ert anxff,-1 the flow of water. It consists of two polyethylene liners cont aad1 by le w)-engeo-tech a,ad msF{t N'§ue *4e*.*ýT a stble*,,,5,,.in-rolhng . When wall ofthewater two inner tubes are filled with water, the resultingj ure an.d ma a sta (Layfield Environmental Systems, 200* *. A1,0'_i The peak reiea§ o . ,1?bint Dan . .60,000cubic feet per second (cfs), which was reached onoJumne* on Junej and ,releas~~este esim and011 ned at t untilI..mid-August. USACE's forecast on

-le{,el Novee -20 11 estimated t 'a I, ruI . the Missouri River above Sioux City would be e.,!illion acre-feet (MAF) .h.sis the iount of runoff since 1898, eclipsing the preyioi-s.high runoff of 49 MA. B6giffing Augst 19, 2011, USACE began reducing releases dail~ii '5000 cfs increments, and waiflevels began to decline. FCS remained in emergency status until Aug -t*t,29, 2011, when floodwatel 1l below elevation (el.) 1004 ft. The site was in an emergency lcnIton for 84 days.

Since then, OPPD4iasbeen activef.ln;gaged i cleaning up deposited sediment from the parking lots and roadways, removn.mgflood~*eris, repairing obvious flood damage, and conducting the plant activities necessary toresux eration. Preparation of this Assessment Report is part of these activities.

1.4 Assessment Process The post-flooding assessment of FCS structures was completed by first conducting a systematic and thorough visual observation of each structure to identify any outward signs of distress caused by the flood. After the visual observations, data on the 2011 flood, including the areal extent, water depths, water velocities, and the effect on groundwater at the FCS site, were compiled. Baseline data for the geology, geomorphology, geotechnical,. and design conditions prior to the 2011 flood were also compiled. A list of flood-induced triggering mechanisms that could have caused degradation to the

Page 1-7 Introduction Rev. :2 soil and/or rock that supports the FCS structures and/or could have caused direct impacts on structures due to the force of the floodwater (Triggering Mechanisms) was then developed. Examples of Triggering Mechanisms include settlement, erosion, stability, hydraulic actions, and frost actions.

Using the list of potential Triggering Mechanisms, a comprehensive list of potential failure modes (PFMs) was developed. PFMs are the ways in which a structure might fail. Failures are any errors or defects, and can be potential or actual. Examples of PFMs include undermining and settlement of shallow foundation/slab, undermined buried utilities, and loss of lateral support for pile foundations.

Using the knowledge compiled for the baseline on each structure's desi ndard .(for example, shallow or deep founded building or buried utility), a list of corre di s compiled for each structure from the comprehensive list of PFMs. A more d k, disc i.the assessment process is provided in Section 3.0 of this Assessment Report. 01 1.5 Quality Assurance and Control HDR has developed a Quality Control Plan (QCP), which suppI Assurance/Quality Control, (QA/QC) Program Manua_, to provmidebjdfiii evaluations of assessment activities. HDR's program is basedon Internal Standardization (ISO) 9000 principles. HDR's QA/QCMOQ ot cer Assurance (NQA-1) program. The Project QCP ens' 1itQAi.Q and performed in accordance with written procedueor checis .

SECTION 3.0 ASSESSMENT PROCESS, PROCEDURES, AND METH DS I/

Page 3-1 Assessment Process, Procedures, and Methods Rev. 2 3.0 ASSESSMENT PROCESS, PROCEDURES, AND METHODS The purpose of the assessment process is to qualitatively detenmine the significance of the potential for failure of each FCS structure due to the effects of the 2011 Missouri River flood. This section of the Assessment Report presents detail on the steps in the assessment process, a description of the methods used during the field observations, a list of all of the potential failure modes (PFMs) that were identified, a list of the PFMs determined to be "non-credible" in the initialscreening (prior to the detailed assessments), and the reasons for their elimination. This spctionalýsQ'presents information on the assessment methods used to determine the significance of the'potential fo* f.ilure'due to the 2011 Missouri River flood. . --' i.

3.1 Assessment Process As discussed in Section 1.1, the purpose of this Assessment Report is.to-present HDR's assesesment.of changes to the soil or rock that supports the structures at FCS dueWt6he.!,20j4.1Missouri Rix'lAod:.'.

and/or any direct impacts of floodwater that may have negatively impacted th..se structures. Stfrictures to be assessed were selected and prioritized by OPPD (se .'.bjj!.e 1) and includebuildings, process structures, equipment foundations, tank foundations, 4 nae16ctheat'i.towers, all of.whliihare referred to as structures in this Assessment Report.

The post-flooding assessment of FCS structures was complete.,. ýb-..jy first.bn~diucting a systematic and thorough visual observation of each structure .to identify anyiofvard si~g:hof.di'tress caused by the flood. After the visual observations, dat iY.ci the 2011 flood ;Thcluding th arela extent, water depths, water velocities, and the effect on groundiawý,ater at the FCSiste, were compiled. Baseline data for the geology, geomorphology, geotechnial, iand design cond2tif..ktriort6'ihe 2011 flood were also compiled. A list of flood-induced trig .gmechanisms that,-c6ul*',have caused degradation to the soil and/or rock thatl'isE}pof Ahe FCS sftrctues and/or could ihg caused direct impacts on structures f

due to the force: F--' &'116"6d6wr(Triggering Mechanisms) was then developed. Examples of TriggeringýMechanisms include-'settlement erosio~nstability, hydraulic actions, and frost actions.

Usingthe; -list of potential Triggering Mechanisms,.,'a :comprehensive list of PFMs was developed.

PFM1-afe the ways in which a structurenight fail. Failures are any errors or defects, and can be poten&'i-l -or actual. Examples of PFN4sn-,clude undermining and settlement of shallow foundaiibii1ab, undermined buried utiliies, and loss of lateral support for-pile foundations. Using the knowledgte.orpimled for the baseline on,'e~ach structure's design standard (for example, shallow or deep founded bu idi *:or buried utility), aisýit:6Of corresponding PFMs was compiled for each structure fiom the comprehensi"velist of PFMs. A detailed list of Triggering Mechanisms and PFMs is presented in Section 3.4.

Once the list of PFMs was compiled foi each structure, these PFMs were screened to determine if they were "credible" (CPFMss), .vhich means a particular PFM could have occurred or could be in progress due to the changes caused by the 2011 flood. This included a determination of whether the Triggering Mechanisms..for the:.CPFMs could have been or were.actually initiated by the flood (potentia! for degradation/direct floodwater impact). As a result, so-me PFMs were determined to be non-credible.

For example, PFMs arising from river bank erosion were eliminated because no evidence of bank erosion was observed. A detailed list of PFMs eliminated from detailed study is presented in Section 3.6.

Page 3-2 Assessment Process, Procedures, and Methods Rev. 2 During detailed assessment, when additional data were available including the results of the systematic visual observations, a secondary screening took place to rule out additional CPFMs. This might have resulted in the elimination of all of the CPFMs initially identified for a particular structure, or there could be remaining CPFMs, which are discussed in detail in this Assessment Report. Also, the PFMs screened out as non-credible in the initial screening described above were reviewed again in light of the additional available data to determine if they should be added back to the list of CPFMs. The remaining CPFMs were evaluated to determine first the potential for degradation to the soil or rock that supports the structure and/or the direct floodwater impacts due to the'20.]I flood and then the implications of that, degradation to a structure of that particular design typ*eibiatin of the potential for degradation/direct floodwater impact and of the implications 6fhaidegradation/impact is termed the "potential for failure" and is then categorized as "sightfji'cant" or.t¢ sirnificant." The final step in the analysis was to evaluate the "confidence" in the pot;n-fi'a1-forl-faiir ddtii ation as either "low" or "high."

3.2 Assessment Process Steps The purpose of the assessment process is to qualitatively detennine the significance of the potential for failure of each FCS structure due to the effects of the 20..:.fl6d". The assessMrri t:process involved eight steps, as shown in Figure 3-1. In addition, the assessment process has severaldfeedback loops to allow for incorporation, of new information as it be3om{es availabie*and revision of them:ubsequent steps as appropriate.

Step 1. Site Description and Baseline Co~ifiifon/Hi~tory - Review story construction documents, as-built drawings, previous.a.eports, and pl*.erformand.eýN to determine the pre-flood conditions at:lhVite. This step isýinecessary.to allow a comparison of the pre-flood and post-flo' structurs..,.wa j ~ ditions.data cop'B**clude Baseleidinfomait*ion e;n tle.geogy. geomorphology, and for the FCS sitegeotechnical, structures iwas compi Iedticuedt on t>i d" . .igcditions prIorY-46te 2011 flood. In addition, data on the 2011 flood itself,

- extent water edpths, water velocities, and the effect on groundwater at the FCS site w,'ere compiled. The6baseline condition and history as it pertains to the various structures at the site is provi:lhin Section 2.0 of this Assessment Report.

Step*{2... Potential Failure Mod-e.s. Using the compiled data on the 2011 flood in Step 1, develop a list of Trger.*fi: Mechanisms. Using the list of potential Triggering

,.Mechanisms, develop qý&.O.fnprehensive list of PFMs. Using the knowledge compiled

,-for'the baseline on eacli fructure' s design standard, select the corresponding PFMs for each structure from.hie comprehensive list. The list of identified PFMs is presented in Section3.4.

Page 3-3 Assessment Process, Procedures, and Methods Rev. 2 Site Description & .Potential for Failure An.alyi Addtinal Baseline Condition J ... 'A...*...Dat History Potetia ... r , ;.:ra* * *:* 'AdtOn Necpfn&Ptnil[rF

. .i..n-h b * '-

~ ~~

Nistory~ ~ ~ ~~~~~~Dt Gahe". .1ih ,..: -O..nagrgi  :!k!,4**.p.*

UBnptedi Long Term Monitoring Assessmren t Detailed Forensics Fiel Exporaton &Physical Modification Sit Viua tis Key Doe ... =t_.res.s, .......- .

- r.ed.ible. .... , ... "* .

Assessmentso e<

/I :" I Dete min p tion':*-*

IndC:_tredbs c be=

L::-: 6 .:*...."

i1 '":::/:*i;.

s.es/" .'  :..

-1 Non-Credible REPORT FiguWre3-1 - Plant and Facility Gbotechnical 'and Structural Assessment Process

S..Page 3-4 Assessment Process, Procedures, and Methods Rev. 2 Step 3. Credible/Applicable Determination - Conduct initial screening of Triggering Mechanisms and PFMs to determine if a specific PFM is applicable, credible, or non-credible for a particular structure. The initial screening is based on general review of background information, prior knowledge of the site, and observations from the initial site inspection(s). In this step, PFMs are categorized as one of following:

" Not Applicable - PFMs that are not applicable to that type.Of structure (For example, "loss of lateral support for pile foundation" would not apply to a structure that does not have a pile foundation.) ,

0 Credible - PFMs that are 1) physically possib--an' 2) sig.ifiicnt enough to be further evaluated 2) siican enough to be

• Non-credible - PFMs (or their associated Trigg-img Mec*`*ianismsi),ffor which the chance of their existence is judged to be so smA'I

• _ e'1,on the avafl able information, that they are considered negligibleo0 butors to the p6tential for .

failure Develop methods and procedures for evaluating CPFMs, includiig.the scope and

.objectives for various field exploration activities-Adistress indicatoist*4.look for in the field, and a list of baseline data required~fr the e!*ton of a paiff,4iuarCPFM.

Step 4. Field Exploration and Data Gathering - Conduct fi'l4Visits, geophysical and geotechnical testing, laboratory testing structu:rýcondiilj assessment, civil inspections, field survey, andpother field data .gathering. IThisstep also includes additional research of existing OPPD documents to .idenYbasis of design, construction details,and,',:formance histoqy of a strunfe~ or system in question.

Step 5. Credible Reassess. ech CPFM identified in Sptqp3 ,sing the additional data and

• an,a ys.is-oI-determine if any-Of the CPFMs should be "ruled out"prior to detailed assessment. it-.addition, reviewthe PFMs screened out as non-credible i the initial screening described.above in light of the additional available data to determine if they should be added back .o.thelist of CPFMs. This could result in the elimination of all of the CPFMs initially identified for a particular structure, or there might be remaining

' . ... CPFMs that will be caifedi forward for detailed assessment.

Step 6. 'Detailed Assessment -4 Conduct a detailed assessment of each remaining CPFM for e'ach, structure to ider!ifhanges from the baseline conditions. Determine whether the ng Mechan'm or the CPFMs were actually initiated by the flood (potential for .*l idation/difect floodwater impact).

Step 7. Potentialfor F.ijlure Analysis - Given the potential for degradation/direct floodwater impact as identified in Step 6,..determine the significance of the potential for failure.

The significance of the potential for failure is determined by the combined.

consideration of two-elements.: the first element is the. potential for..degradation/direct floodwater impact, and the second is the implications of that degradation/direct floodwater impact to a structure built to its specific design standard.

Page 3-5 Assessment Process, Procedures, and Methods Rev. 2 The rationale for the potential-for-failure significance determination, including a description of the role each element played in that determination, is provided in.

Sections 5.0 and 6.0 of this Assessment Report for Priority ! and Priority 2 Structures, respectively:

Not Significant/High Confidence - "Not Significant" indicates that the potential for failure (the combined consideration of the potential.for degradation/direct floodwater impact and the implications of that degradation/direct floodwater impact to a structure built to its specific design standarld)ihas been:quali,tatvely evaluated as "low."

• w . A description

.. of the reason

.. why a C.., *;',

- - O r anypa 2rit a structure structur was was placed in this category, including a descriptroiT the role ead-i element played in the significance determination, is provided in Sections , fOAnd&.0::fthis Assessment Report for Priority I and Priorty) 72 O`Moes respect' ly. "High Confidence" indicates that additional informati'onat*d tudies are not*.l!.y. to increase the confidence in the findings or change..theconclusions.

.enitioin!.;*,lBy of the non-credible PFMs (see Tables 3-3 and 3 4) and"-.',uled out CPFMs1-l-ntio this category. There are no recommended. actions identified.for:. any CPFMs listed in this category.

Not Significant/Low Confidence,' '.Not sigmiant indicates.thatibe potential for failure (the combined consideration of the potenti -al for degradation/direct floodwater impact and the implications of that degra"Aaion/direct floodwater impact to a structure built to its specific design standard) has beceDqualitatively evaluated as "low." A descnrptionwoftl& reason whya:' GPFM for an.y particular structure was placed in this categor ncludng a desI~ion of th..[6ible each element played i the significance d&-teirnination, is provid*d*ein Secti'pa 5.0 and 6.0 of this Assessment Repoitffoi..riority I and Ph :.,tY.i-22.. .. actures, respectively, "Low

-:Cofidence" idia*Silat addional ont'and studies are required to increaseconfidence infhe."idings. The CPFMs included in this category are those for which additfiional data are fequired to confirm that there are "no further recommended actions."

Significant/Low: Confidence -"Significant" diates that the potentil for faile (the combined co~nsisi'eration of the potentia for degradation/direct floodwater impact and the imri tat.ions

.. of that degradation/direct floodwater impact to a structure built to its5 specific design standard) has been qualitatively evaluated as

-high'" A descriptio, of the reason why a CPFM for any particular structure was placed in this cate"ory, including a description of the role each element played in ths-.*.i2gni ficanced termn1atIon, is provided in Sections 5.0 and 6.0 of this A glsesment]Report for Priority I and Priority 2 Structures, respectively. "Low Confidende'?.indicates that additional information and studies are required to increas&flth`6 confidence in the findings. The CPFMs included in this category are those for which additional data are required to determine whether physical modification wil] be recommended.

Significant/High Con'fidence - "Significant" in icates that the potential for failure (the combined consideration of the potential for degradation/direct floodwater impact andthe implications of that degradation/direct floodwater impact to a structure built to its specific design standard) has been qualitatively evaluated as "high." A description of the reason why a CPFM for any particular structure was placed in this category, including a description of the role each element played in the significance determination, is provided in Sections 5.0 and 6.0 of this

Page 3-6 Assessment Process, Procedures, and Methods Rev. 2 Assessment Report for Priority I and Priority 2 Structures, respectively. "High Confidence" indicates that additional information and studies are not likely to increase the confidence in the findings or change the conclusions. The CPFMs included in this category are those for which physical modifications are recommended. Any additional data are required only to facilitate the implementation of those physical modifications.

Document the results using a four-quadrant matrix. This matrix, provided as Table 3-1, shows the rating for the estimated total potential forailurea:.ing thiý.vertical axis and the level of confidence along the horizontal axis.

Table 3 Potential for Failure/Confide6ce Matrix-a nd Associated Recommended Afiisns.

Low Confidence HigdhConfidence (Insufficient Data) (D.6ficibit-Bata)

Recommend additional detailed Recommend detai:e**"-rensic forensic investigations and/or iny.est.gations leadingtdij3'. sical

" monitoring leading to a decision .hmodification to a structur&e.

_ . on physical modification to a " ... . .*.

W F6 structure

- LL -

Recommend c'ntinued ý,.Nofurther recommended actions

• monitormgwtonfirm no further related to the20:1Ol flood

- recommended'actions "

• 0 Z

Step 8. '-'4Report - Following the potenti al -for- fai1lure assessment, determine whether additional

~1.aare needed. Sumnmarize the results of the assessment, and document specific

. ommended

.. actiots.;:.

3.3 Field Observatilbns The 2011 flood event coveted nearly 80 percent of the FCS site. Some of the Priority I Structures were protected by engineering measures (such as sandbags, temporary berms, and other flood-proofing measures), many, of the Priority I Structures, including a number of buried infrastructure systemns,

.were not. .Asbutfloodwater receded. -v.Sis zbsevatih r6ns ofeah as structure wetr, coanducted to identify any obvious signs of distress or to identify Triggering Mechanisms that could lead to distress. The inspecti ons were completed by three-person teams consisting of senior HDR professionals experienced in structural, civil, and geotechnical engineering. The overall FCS site was also visited by a variety of other professionals for purposes of generally assessing the flood damages and site conditions.

Page 3-7 Assessment Process, Procedures, and Methods Rev. 2

• Prior to conducting the site inspections, each discipline lead developed a -checklist of specific structural and utility system concerns or issues thai might have resulted from prolonged exposure to the floodwater. Copies of each checklist (structural, civil, and geotechnical) are included in Attachment 3 of this Assessment Report. Examples of the concerns and issues include the following:

" Is there evidence of distress from flood forces on the structure caused by foundation uplift, foundation undermining, or other actions?

" Is there evidence of surface erosion or observable scour?

• Is the existing revetment protection undamaged?

" Is there evidence of moisture damage to concrete or metallic.,urfaces?

" Are there any signs of tilting or cracking of concrete slabs?9-V

• Is there observable ground subsidence?

" Is there observable pavement subsidence?

• Is there observable piping (sand boils, sinkholes)?

3.4 Identified Potential Failure Modes The assessment teams identified 15 Triggering Mechani*$e.!eiafiveto the 201 Vlflod and FCS site inundation that could materially and negatively impadi f.tr uctur*.-: Once the Trigg"hi..,gi:Mechanisms were identified, PFMs that could develop as a resultiifthose mechlaisnism were identified. A list of identified Triggering Mechanisms and associated -*WMs is prQyoiled in :Talhe 3-2.

Table 3 TriggerincrMecihanisms anfd)Pbtential Failure Modes Triggering Triggering PF.M .

MMechanism echanism .N .; Potential Failure Mode N o. _____"___._.___-______.--"_________-"-____.______Y_,____

Ia i lUndermining shallow\*founfioitn/slab River Bank?.,. lb "Loss of lateral support for pile foundation

.:Erosion/Scour .. . Underriined. buried utilities pipes/cables

.. ___________ _____ _ ",d*.r . Additi6 id i'jajral force on piles 2a. .*ai,.. Unden-niniin-gshallow foundation/slab 2 - Surface Erosion 2b Loss of lateral support for pile foundation 2c :Undermined

., buried utilities

- 3a,`,*. Undermining and settlement of shallow foundation/slab (due to pumping) 3:b, Loss of lateral support for pile foundation (due to purnping) 3c Undennined buried utilities (due to pumping)

Subsurface,','. Undennining and settlement of shallow foundation/slab (due to river Eros on/Piln. 3d drawdown) 3e Loss of lateral support for pile foundation (due to river drawdown) 3f Undennined buried utilities (due to river drawdown)

_3g Sinkhole deveiopmenit due to piping into karst voids 4a Overturning Hydrostatic Lateral 4b Sliding Loading (water 4c Wall failure in flexure loading on structures) 4d Wall failure in shear 4e Excess deflection

Page 3-8 Assessment Process, Procedures, and Methods Rev. 2 Table 3 Triggering Mechanisms and Potential Failure Modes Triggering T PFM Mechanism riggering P, Potential Failure Mode No. Mechanism No.

5a Overturning 5b Sliding 5-Hydrodynamic 5c Wall failure in flexure Loadinge 5d Wall failure in shear 5e Damage by debris . - ,2' 5f Excess deflection Buoyancy, Uplift 6a Fail tension piles 6 Forces on 6b Cracked slab, loss of stucturalsupport Structures 6c Displaced structure/broken c6niiections Cracked slab, differential setlieement.of:shd*.ow foundation,8ls:o f 7a structural support 7timne Soil Collapse wetting) (first 7b Displaced structuf..e..brken connections "

7c General site, .ementi.

7d Piles buckG.ii.from down dr ..-

• 8 Soil Solutioning 8a Not applic .ble

,iQcked sM '-differeftift1,heave of shaltloifoundation, loss of structural PPS,ort 9 Swelling of 9b kMDisplaced structuieY1f"ken connectio.ns 9Expansive Soils ,

Expansive Soils*-T-ail *:,:*...

9c tension piles . . . :*:.:

9d -' Additional lateral force sonb'bl ow-grade walls 1Craced slab, differential settlement of shallow foundation, loss of

.. "a' strUct support 4Machine/Vibration.-

1- " inducedacib Displaced sti*cture/broken connections L e i0 Additional, force on below-grade walls IOd-d*Pile/pile group instability

Cracked slab, differential settlement of shallow foundation, loss of Loss of Soil :structural support 11 Strength due to 1lb.. Displaced structure/broken connections StaticLiquefact or 'U Ward Seepageion

-111-c Additional lateral force on below-grade walls

'I d Pile/pile group instability 12 a River bank slope failure and undennining surrounding structures 12 Rapid Drawdowi

• 2b Lateral spreading 13a Corrosion of underground utilities 13 .... Submergen 13b Corrosion of~stniictural elements 14 Frost Effects 14a Not applicable 15 Karst Foundation 15a Piles punching through karst voids due to additional loading

_________Collapse I___ ________________________________

Page 3-9 Assessment Process, Procedures, and Methods Rev. 2 3.5 Initial Screening of Potential Failure Modes A summary of Triggering Mechanisms and associated PFMs by structure is presented in Attachment 4.

Structures to be assessed were selected and prioritized by OPPD and included buildings, process structures, equipment foundations, tank foundations, and electrical towers (structures). In Attachment 4, the structures are grouped into three categories:

• Class I structures

" Non-class 1 structures inside the Protected Area

" Non-class I structures outside the Protected Area PFMs judged by the assessment teams to be credible based on inntial screeriiifi rq[reled "C" in Attachment.4. Failure modes deemed non-credible are labeled NC-ihn"Aahiment  :!.,fa ilure modes that do not apply to a particular structure are labeled NA in Attachment 4..

Attachment 4. presents the results of initial screening. As more informafibn:'becomes available,2each PFM will be reevaluated and rerated as appropriate. The results of the PFM analysis for each structure and system are presented in Section 5.0 of this Assessmeit-'R-port.'..

.3.6 Potential Failure Modes Deemed Non-Cdidible for All Structures The results of the field observations combined with re.view of>FCS designidbcuments indicated that some of the PFMs listed in Table 3-2 were.not possb1e. For-'example, siteblnv.estigations revealed no evidence of bank scour along the east boundary of the site":'hBerefore, failure modes associated with river scour/bank erosion were non-credibie.- The failure modes describ-din Table 3-3 were judged to be non-credible for all Priority I Stf6te's evaluated. Thel*&ji!ure"t6.des described in Table 3-4 were judged to be non-credible for all Prioi:ii.S 2Structures evaluated.

Table 3-3-*.otential-failure'.Modes DOi~g*-mined to be Non-Credible for Priority 1 Structures ldentifie&r.,: Potenfial F,,filure ModeWi'." Rationale for Elimination TriggeI echanism I - River BaniW* ,o.i.n/Scour P Undermining shallow r Aon/slab . Bathymetric survey of the river channel and banks PFMlb~* p¢*!illi~!!i:.:

Los Loss oof laera lateral supor fo.?p.!e*oudaton support for*pilecfundation signs of bank indicated erosion. sloughing, scouring, or other no observable PFM - . .

,c Undermined buried ulilities ppes/cables sVisual observations of the river bank indicated no PFM Id Additional lateral force on piles sloughing, scouring, or other signs of bank erosion.

. Bank stabilization features installed by USACE are robust, and there is no known major bank failure as a result of 2011 flooding.

Triggering Mechanism 3"- SubsurWface Erosion/Piping 3

PFM g Sinkhole dev'elopment (due to piping into Karsi voids are filled with water. There is no head karst voids) differential (gradient) to initiate this type of soil erosion.

Triggering Mechanism 8 - Soil Solutioning PFM 8a Various Mineralogy of local soils is'ndt susceptible to solutioning.

Page 3-10 Assessment Process, Procedures, and Methods - Rev. 2 Table 3 Potential Failure Modes Determined to be Non-Credible for Priority I Structures Identifier 7 Potential Failure Mode Rationale for Elimination Triggering Mechanism 9- Swelling of Expansive Soils PFM 9a Cracked slab, differential heave of ° Highly expansive soils are not present at the FCS site.*

shallow foundation, loss of structural Structures are founded either on non-expansive select support fill or on non-expansive native granular soils (pile-PFM 9b Displaced structure/broken connections supported stnictures).

P With respect to soil saturation of expansive soils, the 2011 flood event waq ugntusual because similar soil PFM 9d Additional lateral force on below-grade wetting occIlrd dunug ,severairji6st floods for the walls majority.ofthel site .

Triggering Mechanism 15 - Karst Foundation Collapse ______________' ______________________.

PFM 15a Piles punching through karst voids due to Piles were drivenmor drilled to an el6atiiohbelow the additional loading deepest karst/terbsmiiia.!feature. Exploratilond, for the design/construction-extended into bedrock.-'N'o voids exist below thIepileý tips. Additional verticloaVb due to, soil downdrag is minia Icompared to the "basie:ine" vertical load.

Table 3 Potential Failure Modes Determined:.to be NonlCriedible for Priority 2 Structures Identifier T Potential Failure Mode Ratibo.....for Elimination Triggering Mechanism I - River Bank Erosion/Scour PPM Ia Undermining shallow foundatioi ab Rivei isback to nominal"normal levels, and the Triggering PFM Ib Loss of lateral support for pia ... i~r was notlsev d wandations:not os.:-ved PFM Ic Undermined buried utiljpii"'esi/cables " ': '

PFMI1 d Additional lateral force oniil.es.  :. 5.

Triggering Mecba£isnm--3 Susface. Erosiooliping9 F PFM 3d dermining'ritelment of s'il1 River is back to nominal normal levels and the PFMs foundation/slab (dWt.,.gver drawdo  ;.)..were not observed.

PPM-,3e Loss of lateral support;i...jpke foundation,

_____________- (due to river drawdownYXIP PFM *3', Undermined buried utilitmsii`ue to river drawdown) V_'__._ _ _ _ _ _

deelpmn (du3e topiping

• S8nkhole development PPM 3g "t : "Snkol ppig into nt Karst voids are filled with water. There is no head "a.kg*stvoids) . }:: differential (gradient) to initiate this type of soil erosion.

Triggering Mechari%8.;S Soil Solutio* _.__ _ _

PFM Sa various , .

, Mineralogy oflocal soils is not susceptible to solutioning.

Triggering Mechanism 10;-Macýhne/Vibration Induced Liquefaction PFM 10a Crack Slab, differential settlement of Groundwater is back to nominal nonrnal levels, andthe shallow foundation, loss.of structural PFMs were not observed.

support PFM I Ob Displaced structure/broken connections PFM IOc Additional lateral force on below-grade walls PFM I 0d Pile/pile group instability

Page 3-11 Assessment Process, Procedures, and Methods - Rev. 2 Table 3 Potential Failure Modes Determined to be Non-Credible for Priority 2 Structures Identifier Potential Failure Mode Rationale for Elimination Triggering Mechanism 12 - Rapid Drawdown PFM I 2a River bank slope failure and underniining Groundwater is back to nominal normal levels, and the surrounding structures PFMs were not observed.

PFM 12b Lateral spreading Triggering Mechanism 13 - Submergence PFM 13a Corrosion of underground utilities The structures were not!t.1ected to. a corrosive environment thAtwoualdbe:*considered bevond normal PFM 13b Corrosion of structural elements cond.io.n Triggering Mechanism 14 - Frost Effects PFM 4a Various Prior to groun d..eezrýg the groundwater returned to nominal normal level's..

Triggering Mechanism 15 - Karst Foundation Collapse PPM 15a Piles punching through karst voids due to Piles were.:*,iven or drilled toan:elevation below the additional loading k deepest kars'tlerosional feature. Expllorations for the

.design/constrne-ibnmextended into bedrock. No voids exisl below.tielets. Additional vertical load due to soil downdrdag-is miniia-.compared to the "baseline" vertical Id d.. .

3.7 Assessment Methods .:.

Table 3-5 lists the various methods thaI.:..mikght be used to deterniine the significance of the potential of failure for any.,dfohe(*ef:.tuies. The mthods'.,included visual observations of the structures and civil works, field..:&-s eys and geqphySical and geote*_hncal ivestigatins Field teams composed of structurali,'V]*, and geotechnic*icýengkineering plof6ssionals examined the structures as floodwater recedd&t,"ese investigations wer.e.bed on detait68i16hecklists, as noted in Section 3.3. The results of th-ejisua observations were supp e nted with elevation surveys and geophysical and geotechnical investigations. V

Page 3-12 Assessment Process, Procedures, and Methods Rev. 2 Table 3 Potential Methods and Procedures for Addressina ldentifiedt Potential Failure Modes Potential Failure Mode (PFM) Investigation Mblthod,;

Triggering Background Data Subsurface MechanismPFM M n*i e h Description Research Reea c Field Observations.... Structure Assessment

.... ... :..nvestigations Snbstrgacn

1. River Bank a. Unden-nining shallow These PFMs were detennined to be non-credible.

Erosion/Scour foundation/slab

b. Loss of lateral support for pile foundation

c. Undennined buried utilities pipes/cables

d. Additional lateral force on piles

2. Surface a! Undermining shallow [Note: these actions were Observe'*su*ace con itinu* Look for se itel"fnt of slab, Erosion foundation/slab taken for each PFM.] for erosi6n* broken cracks in fourindain and Interview OPPD staff. pavemint depressionsj, )alls, tilt, or se'"leient of Review plans and gullies, and other signs of f tndation.

specifications to identify , distress.. nd hand.pr'obe pertinent design and . area adjacent to structures.

construction details needed to define pre-floo-'-,i:

conditions. _ ...

RleviewOPPD Condit'ion.. .

...Repprts to determne r-m s ....'J nod.:..'.ifications since construcits .1 .

Review flood dat~anluding observed flow conhditins depths, and velocitis,§:,I.,-.I'

b. Loss of late*al"support Observe soil conditions Observe pile-sUpported. slab for pile founda-tion aiound structure for for cracking or excessive settlement. deflection.

Page 3-13 Assessment Process, Procedures, and Methods Rev. 2 Table 3 Potential Methods and Procedures for Addressina Identified Potential Failure Modes Potential Failure Mode (PFM) Investigation M1thod Triggering Background Trigeringm PFM Description Backgron Data Field Observations ..

- StrtdctureiAssessmnent

• ";:'-..:*'.Subsurface Mtec han ismin Research K' Investigations

2. Surface c:. Undermined buried Observe surface condition.

Erosion utilities for erosion, broken t'-

(continued) pavement, depressions,-

gullies, and other signs of distress, and hand probel .

area adjacent to structures .. .

TV open conduits and pipe in soil if accessible or as possible.  :

3. Subsurface a. Undermining Er s.,P>.n etle e t f and h ll w,:".! Observe.suface .: condition -','  ; "*Observe setiemnqt.of slabs, Test for voids using Erosion/'Piping .settlelent of shallow arounabldildings for  : racks in found*i*n, or ground penetrating radar foundation/slab (due to anornaimes, and hand.p6obe 'seftlement of foundation. (GPR).

pumping) alighDnt! or area adjacent Hydro-excavate:suspect S to struCtures. , areas where feasible.

Survey/monitor elevation of designated pointsoni' foundations or slabs.

b. Loss of lateral support Observe soil cotditibns Obevesi Sample areas adjacent to nifo.,:.

.. .:.:? *.

for pile foundation (due. around structure f  ::structures using standard to pumping) .. ettlerent. penetration test (SPT) or cone penetration test (CPT) methods as

______-______ _:_appropri ate.

c. Unden-nified buried Observe surface condition Observe soil conditions at Test for voids using utilities ,(due"to for anomalies, and hand utilities for settlement or GPR.

pumping) probe alignment or area lost soil material. Hydro-excavate suspect adcjacent to structures. areas where feasible.

TV open conduits and pipe Open test pit where in soil if accessible or as feasible.

-. , " . possible. Inspect utility manholes (MHs) if

- ~ ~ possible. Identify MH penetrations that leak: look for sediment in MH bottom and in pumped water.

Page 3-14 Assessment Process, Procedures, and Methods Rev. 2 Table 3 Potential Methods and Procedures for Addressing Identified Potential Failure Modes Potential Failure Mode (PFM) Investigation Mbthod Triggering Background Data Subsurface PFM Description Field Observations.... StSucure. Assessinent M.ec.... Research Investigations

3. Subsurface d. Undennining and Observe surface condition Observesoil c"Onditions Test for voids using Erosion/Piping settlement of shallow for anomalies, and had:. arouid strcture:.for GPR.

(continued) foundation/slab (due to probe alignment or area, 1fitement of s1%;-4..tacks ill Hydro-excavate suspect

'river drawdown) adjacent to structures. ' foundation, or seftkr6ent of areas where feasible.

Survey/monitor elevation'Ooffindation.

designated points on" foundations.

e. Loss of lateral support Observe surface condition Observe soil conditions Sample areas adjacent to for pile foundation (due for anomalie, and hai*nd around strctre for structures using SPT or to river drawdown) probe alignmrient -or area settlement. ." CPT methods as adjacenitto structures. . appropriate.

f. Undennined buried Observe surface condition ýt.-Observe soil conditions at Test for voids using utilities (due to river for an6riialies, aud hand utilities for settlement or GPR.

drawdown) probe aiignment, o area iost*oil:nilaterial. Hydro-excavate suspect aadjacent to strntutes. i areas where feasible.

TV open conduits and pipe Open test pit where i lnsoil ifaccessible or as. feasible.

possible.

inspect utility MHs if possible. Identify MH

. -.epletrations that leak; look f6r-sediment in MH bottom and in umrnped water.

g..ik .dib.,d eve;: pme..  : :.

g. Sinkhol.; l opment This PFM was detenifined to be non-credible.

(due to pipin.*into karst volds).

4. Hydrostatic a..-Overtu.nin, Survey/monitor elevation of Observe structures for signs Lateral ý . ...v.e..-.-n,.

Lateral:"" 2,,; .. " designated points on ofm Loading .;, foundations.

(water (water bb.::.:l.,..d.i.,n Sidn .;i.a,+ - .,**.

v:. Survey/monitor elevation of Observe structures for signs loading oil loadingiues "";:.

"designated ',:... points on of movement.

struc'tures) *"foundations.

Page 3-15 Assessment Process, Procedures, and Methods Rev. 2 Table 3 Potential Methods and Procedures for Addressing Identified, Potential Failure Modes Potential Failure Mode (PFM) Investigation Method TrigerngPFM Description Triggering Background Data Field Fd Observations-:.,

e t . 'Sfr~c`ýUrctu

t. .....,Awssessent* Subsurface Mechanism Research . Investigations

4. Hydrostatic c.:Wall failure in flexure Survey/monitor elevatiox of Ob.0sevperi.,eter walls Lateral designated points oni a*.nii'dlow-,r:ade.walls for Loading foundations. ... . isign§ of crackii:,*ter (water loading . * ' . l:eakageo

'.::.** e, or excessl2i?.:...

e" I'S'i " '

o ilstructu res) *.:.* , gir( s ble) deflection. -':' * ': *

(continued) d. Wall failure in shear Survey/monitor elevatinof (sb e pe) metertion ., .

designated points on and b'e1.w-grade walls for '

foundations. ,-.,... signs"- king water leakage fex~essive

e. Exes delcto k ge;'dtvX.e.ess (visible) deflection.

e. Excess deflection Surxeym~onitor elevation .cif, Observe perimetdirwalls designated points on . -' andibelow-grade walls for foundtions ....... s-i f.&cacking, water

.e-*agej-:r excessive

(.isible) deflection.

5. -lydrodynamic a. Overturning Survey/monit6.o ejevation of. ý,bserve structures for signs Loading'designated po 0tson oýf high water exposure or

,1. foundations.  : structure movement.

b. Sliding " Survey/mnonitor elevation of Observe structures for signs

.....des'ignated points on of high water exposure or

• foundations. structure movement.

c. Failure in flexure..eObserve exposed stricture for signs of high water.

Observe exposed structural elements for signs of cracking, water leakage, or excessive (visible) deflection.

-7

Page 3-16 Assessment Process, Procedures, and Methods Rev. 2 Table 3 Potential Methods and Procedures for Addressina Identified Potentiil F~1ihlmrp Mndl*

Potential Failure Mode (PFM) Investigation Method Triggering PFM Description Background Data Field .. ... Subsurface Mechanisnm Research Field Observation S t..cturSe Assessment.Investigations

5. Hydrodynamic d. Failure in shear ObseFe!*,,**N-e structure Loading . for si s ofh*.lg .ater.

(continued) O:bserve expdgd9tctural efements for sig's;i._-

-.cracking, water lealager.

" e"":*"essive (visible) "

, deflection.

e:'"Damage by debris .Obeve exposed structure for signs of high water o,

' impact abrasi6bis/damage from debris.

f. Excess deflection  ?: berve exposed structure f...

o. .. s-of high water.

Ob..&v.eexposed structural

,-lpl lents for signs of cracking, water leakage, or

-excessive (visible)

. ,deflection.

6. Buoyancy, a, Failed tension piles .. .a 'i:'" . Observe pile-supported Uplift Forces slabs for cracking, upward on Structures . deflection.

b.,Cracked slab, .... loss'o f bse.r::}V 6perimn eter grade Observe pile supported Hydro-excavate suspect structuralsupport cond.hion for anomalies, slabs for cracking or areas.

and hahi probe aligiunent upward deflection.

or area adjacent to structures.

c. Displaced Observe perimeter grade Observe structures for structure/bciokens condition for anom,,alies, cracking, broken members, connections. and hand probe alignment or other signs of structural or area adjacent to distress.

structures.

Page 3-17 Assessment Process, Procedures, and Methods Rev. 2 Table 3 Potential Methods and Procedures-for Addressing Identified Potential Failure Modes Potential Failure Mode (PFM) Investigation Method Triggering Background Data dObt Subsurface Research Field ,:ý. .. en "StrunsessmentS Investigations Mechanism PFM Description

7. Soil Collapse a. Cracked slab, Observe surface condition Observeisoil cojditions Hydro-excavate suspect (first time wetting) differential settlement of shadlow foundation, for anoalg *alies,and .i..... ar.u.d strdbiufor areas.

ne to "'..... " ".. krbi;i*!:":i.

eting)nprobe alignment o area sen Obtain undisturbed loss of structural adjacent to structures. foundation or t samples, and test density support Survey/imonitor elevatiofi;; iwater cotent.

designated points on.

foundations.

b. Displaced Observe surface conaition Observe structures for Hydro-excavate suspect structure/broken for anomalieskand hand' cracking, *rokei*members, areas.

connections probe aig*nment or area of- other signs Of:*rural -bed adjacistress. oftuc

- a Obtai aples,undsure and test density Sur tiinonitor elevation of and water content.

desintd peo ints .ni '-

.foundalons ..,_ ___._;.__._._

c. General site settlement AeW-' 'Observe surfaý,ciondition Hydro-excavate suspect for anomalies na6d hand areas.

probe alignindtor,-rea . Obtain undisturbed adjacent to structes.:" samples, and test density.

Survey/monitor elevation of and water content.

d.signated points on f*ýundations.

d.Piles buckling f.romi.. Observe pile-supported Hydro-excavate suspect down drag"::," slabs for cracking or areas.

downward deflection. Obtain undisturbed samples, and test density and water content.

8. Soil a., Not applicable This PFM was determine to be non-credible.

Solutioning -Thi s *. .

'I

Page 3-18 Assessment Process, Procedures, and Methods Rev. 2 Table 3 Potential Methods and Procedures for Addressing Identified Potential Failure Modes Potential Failure Mode (PFM) Investigatio Method Mnis ech Triggering Desseartio PFM Description Background Data F ield O bservation s';;:,* . ' uct, r.",l ssm.. Subsurface M..echi Research Investigations

9. Swelling of a. Cracked slab, These PFMs were detennined to be non-credible.

Expansive differential heave of Soils shallow foundation, loss of structural support

b. Displaced

• structure/brokeni connections c..Fail tension piles

d. Additional lateral force . . . .

on below-grade walls 7: .

10. Machine! a. Cracked slab, Obsere surface condition Observe foundations for Sample areas adjacent to Vibration- differential settlement for anomalies and hfilt -cracking and/or deflection structures using SPT or Induced of shallow foundation, probeiaignment or area fr6omi swelling. CPT methods as Liquefaction " loss of structural ladjacei to struetues.

q.- appropriate.

su p p ort,..*<:; , *., ... .

oSurvey/monitor elevation of Hydro-excavate suspect designated points 1on areas.

foundations. Conduct seismic

.. :refraction surveys.

b. Displaced ..- es- f b...Displaced..... ; -::-, ',v ,Observe surface condition Observe structures for Sample areas adjacent to structure/broken t&f anomalies, and hand cracking, broken members, structures using SPT or connections f;tb.b.rigrunent or area or other signs of structural CPT methods as adjacetto structures.; distress. appropriate.

..  :** Survey.ihitor elevation of Hydro-excavate suspect designated points on areas.

foundations. Conduct seismic refraction surveys.

cAdtolaera loc.. Observe perimeter walls Sample areas adjacent to on below-grade walls,. and below-grade walls for structures using SPT or

signs of cracking, water CPT methods as leakage. or excessive appropriate.

.(visible) deflection. Hydro-excavate suspect areas.

Conduct, seismic refraction surveys.

Page 3-19 Assessment Process, Procedures, and Methods Rev. 2 Table 3 Potential Methods and Procedures for Addressing Identified Potential Failure Modes Potential Failure Mode (PFM) Investigation Method Triggering Background Data Subsurface Mhi Descrsearch Field Observations  : 'Sucfiici.*Asessment e Mechanism PFMDe nResearchFd- Investigations 10.Machine/ & :Pi le/pi le group O.bs*?:. **** .,; p Observe ptsbported Sample areas adjacent to Vibration- instability sl~obs .*for craq .j_ gi,, structures using SPT or tutrsuigSTO Induced '.  : ..-. :, 'd* ward de ti .Test CPT methods as Liquefaction f6r voids using GPR-. appropriate.

(continued) .iydro-excavate suspect areas.

LssofSol CraConduct . seismic

..._._._-_.._ ." ",_efaction surveys.

11. Loss of Soil a. Cracked Observe.surf ace codifioi.. Observe fuifi*ditions for Sample areas adjacent to Strength due slab/differential for anoiiiis, and hand Qi:-, cracking and/or~deflection structures using SPT or to Static settlement of shallow probe!i unent oi area *";:-'K' seln. CPT.me.hods as Liquefaction foundation/loss of adjabe6kt-o structures. SUV-ey/rnonitor elevation of appropriate.

or Upward structural support Surv65i/reonitor elevation of  : points on M dgated Hydro-excavate suspect Seepage ..." *n;.- J o'*:* s.

S adesignated points.'.oi . areas.

foundations. Conduct seismic

• " refraction surveys.

b.*Displaced*Observe surfaie clditionv.Observe structures for Sanple areas adjacent to st*icture/broken.for anomalies, aiii"hi-.. cracking, broken members, structures using SPT or connections . -probe alignment or area or other signs of structural CPT methods as a.jacent to structures. distress. appropriate.

-Sdiiy/monitor elevation of Hydro-excavate suspect des.tated points on areas.

foun'aif~ Conduct seismic refraction surveys.

Add itionalWiteral force Observe perimeter walls Sample areas adjacent to on below-g.ade... :ls and below-grade walls for structures using SPT or signs of cracking, water CPT methods as leakage, or excessive aippropriate.

(visible) deflection. Hydro-excavate suspect areas.

Conduct seissic refraction surveys.

=I;

Page 3-20

.,, trocess, Procedures, and Methods Rev. 2 Table 3 Potential Methods and Procedures for Addressing Identified Potential Failure Modes Pnfanfind F~nil~ra Menda (PF:M1 Invo~i~nefrfirn f*t&%hnrl I **L,.

't'1 -. -iI i  % *.SIt* .LItfI i IlS*I ISJ.A TriggeringBackground Data . .. .. ubsurfa Triggering PFM Description B Field Observations, Sucture*Assessment Subsurface Mechanism Research - Investigations II. Loss of Soil &',.Pile/pile group * . ~~~~~Obsee*iýVq lp~ported S ple areas adjacent to Sampeaesadaett Strength due instabilityrcl structures using SPT or to Static d "d6iward CPT methods as Liquefaction approp~late.

or Upward...i . ;..;." *, .r.- "

or"Upward"  ;..'Hdro-excavate suspect Seepage  ;.-eas' (continued) ' (continued...'Conduct

,: .. *,.':, seismic refraction surveys.

12. Rapid e. River bank slope Observe. surf*6c condition Observe sowldcodcitions Install and monitor Drawdovn failure and for anonialijes, and haid..., around structure,"for eroded incliniometers.

undermining probeialignment or arn . o,r lost matenalsettlement Hydro-excavate suspect surrounding structures adjaCeritto structures. . .. ofslab cracks in areas.

Surxey/onitor elev~ton of .fd atjon, or settlement of desigfdtgd po'i~ns on on.di foundations.

f. Lateral spreading Observe surfa6 etondition Observe site soils Install and monitor for anomaliesý-nd iihahand . 'conditions for signs of soil inclinometers.

probe alignmefinnor area movements or spreading.

.. adjacent to structure:'.ý

13. Submergence a. Corrosion of .;:2:.

underground utiliis! " "_"__'.._.'...-...__""

b. Corrosion of structural Observe exposed structural elements: " elements for signs of rust, degraded material, or other signs of corrosion.

14. Frost Effects a. Not applicable Test soil properties.

15. Karst a. Piles punching'tbtough, This PFM was deterniAt to be non-credible.

Foundation karstvolids due.to. .:

Collapse additional loading

SECTION 4.0 KEY DISTRESS INDICATORS

Page 4-1 Key Distress Indicators Rev. 2 4.0 KEY DISTRESS INDICATORS During the site visual assessments, three problem areas were observed that potentially indicated that the 2011 flood had changed the site's geotechnical and physical character. These observed problem areas, referred to as Key Distress Indicators (KDIs), are the following:

I. Increased groundwater flow into the Turbine Building sump

2. Pavement failure and sinkhole in the paved access area betwec and Service Building

3. Column settlement in the Maintenance Shop The locations of these KDIs are shown in Figure 4-1. Each of d4" PFM analysis to determine the associated Triggering Mechanism, other structures that could be affected by the same PFM, and to ro intended to restore the KDIs to their pre-flood condition.

4.1 Increased Groundwater Flow into the KDI #1 is the increased flow of groundwater (ab Turbine Building sump. PFM analysis determin( with increased flow in the Turbine Building sump is S associated with this Triggering Mechanis]NW tt

• CPFM 3a- Undermining and se to pumping)

• CPFM 3b - Loss of lateral supg

• CPFM 3c - Undermined buried historý7y id below the foundation mat dating back to houndation nd slabs and camera recordings of t r slab. Conversations with OPPD personnel indicate that a tes through these broken pipes into the sump from that time Vi', e sump is directly attributed to the hydraulic head of the te .. increased as the floodwater elevation increased across the "gned as a closed system; therefore, the pipes are not s to preclude the transportation of soils from under the slab. It groundwater moves below the foundation and into the broken has occurred.

The increased flow is origiiiating from breaks in the pipes that are designed to carry water from the floor drains in the basement of the Turbine Building. These drains are also used to drain equipment in the Turbine Building. The structures potentially affected by the CPFMs associated with the Triggering Mechanism (Subsurface Erosion/Piping) for Key Distress Indicator #I are presented in Section 4.1.1.

A complete description of each structure is presented in its respective subsection of Section 5.0.

I JJ' New

).,War-ehou~se 1 Jj 1 I ;I . . ... . . J,-

ort 3r I Ja J3

.1

~Mainit I-,

Th~r~

iL ntake ructu n

-a

1. 2 - Pw S11fF k~tctsd Area 4- -. oý

................ Power"'.................

M, Security'Lot Distress Indicators

-Fence Sep 2011 K>jArea of Concern

_p Fort Calhoun mahha Public P*o r District Pl~rI t n*An IP (rlt-'n r hninl and Structural Assessment FMl

Page 4-3 Key Distress Indicators Rev. 2 The following information was taken from a summary report prepared by OPPD dated March 24, 2009, regarding broken floor drain pipes:

" There are two drain lines that run parallel to each other: the 6-in. floor drain and the 10-in waterbox drain. The drain lines are not cross-connected, so both lines must have a piping break if the 10-in.

line is causing the floor drains to back up.

• A vendor was brought in to visually inspect the drain lines. The vend found a break in the 10-in.

drain at the branch tee from the VD- 193 drain valve but could not ins* the 6-in. floor drain because the line does not have a cleanout connection in this ar . i through floor drains is restricted by a drain trap at each location.

• A review of system files shows that a break in the waterbo n line own about for quite some time. In 1997, a repair was attempted by core ho h ofthe leak and pressure grouting to seal the leak. Per the "Water Syste ar r eriod April 1 Through June 30, 1997" (memo PED/EOS SYE 97-I 2* , d .

Repair of the Turbine Building Basement Drain line r" tempted d period. The repair procedure consisted of core drillingles i inity of thi and pressure grouting to seal the leak. Apro 10 holes )led and it was estimated that a void of approximately isted und oncrete slab. The void was filled with cement t Id not be Boroscope inspection of the pipe exteri rformed e core dri owed considerable pipe damage, in more th je locati f the damage and concern over collapsing the linS ere ¢ in ors in g the pressure grouting operation. FC E wa origi So reque

. new drain header be installed. 0ili 9 The grout was injected in the ar ,f f. V D-193 (FM A*out box tail valve). At some time later, the Turbine Building s w s cleaned out hardened grout was found in the sump, c he gr out *wed through th n system into the sump. A recent inspecti vealec 'derable amount of grout in the floor drain south of the FW- nsate Coole . ain loo almost fully restricted. This grout most likely ca the 1997 effort, i g that . were broken at that time too.

4 f "ggeringMechanism As dist 4 ..reviously, the Triggeri-4 *echanism for increased flow into the Turbine Building sump is Subsuur ison/Piping. Multi 6tentially connected seepage paths could exist in the soil backfill at t 014, cluding soil b fin utility trenches, granular trench bedding, and building floor drains witn roken joi he paths could be exposed at some locations to the river floodwater and h *'is network of seepage paths could be connected to the sump in the Turbine Building". : .in the piping have been documented for an extended period of time (dating back to at least I aintaining a head differential on the potential seepage path networks.

The gradient during 20 flood increased, which could have led to higher flows through the seepage path networks. The unfiltered scepage condition will continue until the breaks in the piping system are repaired, which means the potential for further erosion remains. Erosion could extend out, creating voids under other structures.

Review of video from the sump and visual observations indicate groundwater flowing from all five drains. Drain lines are located below the mat foundation slab. OPPD personnel indicated that the drain lines were cleaned in 2011.

Page 4-4 Key Distress Indicators Rev. 2 Three soil borings (Boring B22, B-24, and B70) were completed within the Turbine Building footprint as part of the Dames & Moore 1968 report, "Foundation Studies." Excavation for the Turbine Building foundation extended to el. 985 ft, so material logged in these three borings from el. 985 to 975 ft is of most importance to the Key Distress Indicator. Boring 24 (B-24) logged fine sand with clayey silt and silty clay lenses and SPT N-values of 7 and 11; B-22 logged fine sand with some medium sand and SPT N-values of II and 7; and B-70 logged fine sand with some medium sand and SPT N-values of 26 and 15. The fine sand is susceptible to piping if water velocity is sufficient. The zones of silty clay and clayey silt encountered in B-24 are the materials susceptible to piping.

Excavation beneath the Turbine Building footprint is shown in the w c"on and Grading Cross Sections" to extend to an approximate elevation of 984 ation. Elevations of 979.2 ft were reached for the Sump Pit. Soil density tests r ,d by N sting in 1968 during foundation preparation show density test elevation for t bin- er as low as el. 977 to 980.2 ft and ranging from 97 to 100 percent of modifi tions re  %

modified) using the American Association of State Highway and lton Offici ,SH test method T-147-54 for the Turbine Generator Mat. Material as brown s elevations below the excavation level of 984 ft likely indicate a zone e piles overex l due to the presence of loose material.

The portion of the drain pipe located below the for The material placed around the pipe is assumed to backfill around the drain pipes are available.

This review of the data associated with t a~binI the Triggering Mechanism Subsurface n/Pi plausible scenario.

Loss of lateral support for pile foundation (due to Undermining and settlement of shallow Technical SUl%`ný /Piterping.-

- CPFM 3a - Su~tl'". .s on/ ping. Undermining and settlement of shallow foundation/slab upmg ).

in(,,

" Turbine Building ,

- CPFM 3b - Subsurface Erosion/Piping. Loss of lateral support for pile foundation (due to pumping).

" BBREs

- CPFM 3a - Subsurface Erosion/Piping. Undermining and settlement of shallow foundation/slab (due to pumping).

" Turbine Building South Switchyard

- CPFM 3a - Subsurface Erosion/Piping. Undermining and settlement of shallow foundation/slab (due to pumping).

Page 4-5 Key Distress Indicators Rev. 2 Main Underground Cable Bank (Inside and Outside the PA)

- CPFM 3a - Subsurface Erosion/Piping. Undermining and settlement of shallow foundation/slab (due to pumping).

- CPFM 3c - Subsurface Erosion/Piping. Undermined buried utilities (due to purr aping).

• Circulating Water System

- CPFM 3b - Subsurface Erosion/Piping. Loss of lateral support for pile foundati4on (due to pumping).

Demineralized Water System

- CPFM 3a - Subsurface Erosion/Piping. Undermining an *. e .

foundation/slab (due to pumping).

• Raw Water Piping

- CPFM 3a - Subsurface Erosion/Piping. Undermining le fs foundation/slab (due to pumping).

- CPFM 3c - Subsurface Erosion/Piping. Undermined burii (due topu*

' Fire Protection System Piping

- CPFM 3a - Subsurface Erosion/Piping. Undermining and setIhallow foundation/slab (due to pumping).

- CPFM 3c - Subsurface Erosion/Piping. Und,~ik.tlltes(

• Service Building ..

- CPFM 3a - Subsurface Erosion/Piping. U foundation/slab (due to pumping).

" Maintenance Shop Ar. -

ning a**

t of shallt v

- CPFM 3a - Subsurface Erosion - Unaermi nd settl het of shallow foundation/slab (due to pump.VA....

The influence of ht be som  ?,ftntidiJ by the fact that vibroflotation of subsoils wa, the Auxiliary 6ilding and Containment. However, subsurface., etely ,.Jbecause that Triggering Mechanism could extend to the Con and the A

4. sessn nent Methods -edui The ac tions are recommen Key Distress Indicator #1 (increased flow into the Turbine Buildin' 7 ), and Triggering Med (Subsurface Erosion/Piping due to pumping).

4.1.1 icrete Drillii Sub-grade Testing Program To determi* i&d vertical extents of potential voids within the slab subsurface, a procedure to tilling of selective holes in the Turbine Building basement floor is proposed.

Preliminary locations for the proposed drill holes are shown in Figure 4-2. Eight holes were located in areas of anomalies as identified during Ground Penetrating Radar (GPR) testing and analysis. Nineteen holes were distributed around the Turbine Building basement perimeter to further explore for voids and determine their connection with surrounding structures. The locations shown in Figure 4-2 are preliminary and approximate. A detailed drilling plan will be developed based on a site examination with the appropriate OPPD personnel to determine locations that minimize impacts on the.structure, underground piping, and equipment.

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1. Drilling locations 1-x are located .a*waliesas identified in GPR ana

2. Drilling locations 2-x are spread alorrngl- ment perimeter for void e tion.

3. Drilling location 1-7 has been removed .f" uipmen

• conflicts.

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m DATE Turbine Building Drilling Locations Oct 2011 Fort Calhoun Station 07M ha Z b.I M %0-1 711.1C'1FIGURE Plant and Facility Geotechnical"- 4-2 and Structural Assessment 11L¶,

Page 4-7 Key Distress Indicators Rev. 2 Anticipated requirements for the drilling and testing program include the following:

I. Establish concrete thickness during core tests for future reference.

2. Observe water flowing out of drill hole.

3. Determine vertical dimensions of any voids found immediately below the slab.

4. Conduct miniature cone or other penetration tests for up to 10 ft below the bottom of the slab to determine soil density.

5. Obtain and test soil samples.

6. Insert a borescope through the drill hole if a void is dietd Recommended Drilling and Inspection Procedure using a rebar locator to adjust drilling location as needi conflicts with the drainage system below the floor slab. ' system from recent inspections should be used.

A carbide-tipped hammer drill should be used~to drill a I locations specified in the detailed drilling plan. The goi to be 2 ft 7 in. thick. A means and method of temp from groundwater shall be proposed by the d11*

HDR staff prior to initiation of the drilling iions. C mat could be required in order to achieve top- 9Q sing elev water into the Turbine Building due to art* pressutq A miniature cone designed to re jti*ip resistanc blc iito the foundation soil material 10 ft beneath the fo d n mat in order,: cc ristance. Depths of voids and soft zones encountered will; mined and do .t addition to the use of a miniatureaterproo *

• e with lighti available to investigate further and de*f£ anv oi ountered.

will be refilled with non-shrink grout having a

ý,,[si. Repair of holes shall meet QPPD criteria

ýýgrilling and inspection work, OPPD and HDR staff will 0n of additional drilling locations, possibly to include adj d e the extent of any voids encountered. Approval by OPPD staff, inning any additional drilling operation.

4.1.4.1 is Related to Other Key Distress Indicators Additional foren estigations associated with Key Distress Indicators #2 (Pavement failure.

and sinkhole in the raved area between the Intake Structure and Service Building) and #3 (Settled Column in Maintenance Shop) could increase the confidence in the determination of the significance of the potential for degradation associated with this Triggering Mechanism (Subsurface Erosion/Piping due to pumping). See Sections 4.2 and 4.3 for details on the recommendations for additional forensic investigations associated with KDIs #2 and #3, respectively.

Page 4-8 Key Distress Indicators Rev. 2 4.1.4.2 Recommended Physical Modifications Repair Drainage Pipes - Repair of the drainage pipes to stop the groundwater flow into the sump pit from the breaks in the drain piping is critical. This could be accomplished by repairing the breaks in the existing pipes or by plugging the existing pipes and constructing a new drain system.

Treatment of Voids Beneath the Turbine Building Foundationrt, If voids are encountered during the concrete drilling and sub-grade testing program, ,groll.. ro should be designed and completed to fill the voids and restore the yo de. Breaks in the drainage pipes must be repaired prior to initiation of th _5 ting pr Depending on the size and extent of the voids, a grout ng pr must be developed in order to maximize the stability and effective e grouting - . The grout mix must be designed to allow maximum migratio t past the v into the sandy backfill material. This would reduce seepa pt any future and will most effectively repair the foundation. The outing proc be design e o consider the maximum grouting pressure allowArength. umes and grouting pressure must be monitored in real t,* tect the ., pipes and any other structures that could be affected by t uting pro Monitoring and documentation of the gro .proce§#us, h evaluate the success of the void trQent .

4.1.4.3 Continued Monitorir%,Program Continued monitoring is recaiWs W'ded to include 4I* ions of the structure and Ocont .1- *irveys f the elevation of the previously identified targ surou fte. The purpose is to monitor for signs of structure nd ovme

• ges nd movem' g in in ssj " dition ions...

s around the structures listed in n 4.1.1. The resul g 4,0s monito ill be used to increase the confidence in the A essment results. Elevatffi"_`- eys and -"I*ainspections should be performed weekly for

• v#eeks and biweekly until ber 31, 2011. If any new distress indicators are observed X1. en inspection intervals o - r December 31, 2011, appropriate personnel should be 11,_ immediately to dete lhether an immediate inspection or assessment should be 4.1.5 KDI#1 , Inve A forensic investigati consisting of concrete floor slab drilling and subgrade testing was completed in the Turbine ing basement to evaluate subsurface conditions for K.DI #1. KDI #1 consists of the increased vo ume of water pumped from the Turbine Building Sump that has entered the drain pipes through existing breaks in those pipes. The Triggering Mechanism associated with this distress indicator is #3 - Subsurface Erosion Piping and the related CPFMs are 3a, 3b, and 3c, which are all "due to pumping." The flow into the broken drain pipes has caused a cone-of-depression in the groundwater similar to what would have occurred due to the pumping of groundwater from a well (see Figure 4-4). The resulting flow through the subsurface soils into the broken pipes and then into the sump resulted in the piping of soil material out from under the floor slab in the basement of the Turbine Building, and possibly from the subsurface below adjacent Structures. The voids under the Turbine Building Basement floor slab were first observed in 1997 and remedial actions were taken by

Page 4-9 Key Distress Indicators Rev. 2 QPPD to grout the voids, but were unsuccessful in that the entrance of significant amounts of groundwater into the drainage pipes was not arrested. The purpose of this investigation was to confirm piping and erosion of foundation materials and to estimate the location and possible extent of the void or subgrade disturbance beneath the floor slab and to ascertain their significance related to the CPFMs identified for the Turbine Building itself, and other structures that may be affected by the voids.

4.1.5.1 Scope of Work This phase of the forensic investigation of the Turbine Buil g t grade began on November 11, 2011, A total of 27 floor slab locations w,.igniling and subsequent underlying subgrade evaluation (see Figure or drill- tions). One of the locations, 1-7, was not drilled due to OPPD Plant Safe cern igation of the Turbine Building Basement subgrade and potential pipi ugust ith estimates of flow into the sump, GPR surveys performed by Geotec Inc. of the on slab and subgrade, and drainage pipe video investigation by E jE Inc. The noted some anomalous zones of seemingly lower density ten e drainage noted two breaks in the 10" diameter drainage pipIe. '1-hole loc ; I through I- as presented in Figure 4-3 were located to investi wer density d pipe break locations. Drill-hole locations 2-1 through 2 e. data as possible near the edges of the foundation s U order to e extent of possible soft zones or voids away from the drainage pi ad sump I e Geot c no logy Inc.

report and Elite Pipeline report are presen Atta t 6.'

Drilling was accomplished by 0 oncrete S and Lu Construction Company under contract to OPPD usia er drill to ce 1-in. eter holes in the floor slab through which subgrade ev w:-iere perforrr les were covered immediately followin d before subgrade eva Tsing temporary plastic caps that were riunding ce.

ee evaIuati ed obst)jt of conditions immediately below the floor slab aenbyHRfield testieg rade mat' t each drilled location. Observations were by HDR and Thiele cade i , In geotechnical engineering and testing firm based aha, NE. Subgrade fiel ing was performed by Thiele as a subcontractor to HDR

' DR representatives pre Inv& .n of the subgrade , the floor slab included the following:

• Direc 'observIf't1rough the open holes with the aid of a flashlight

• Direct vi* 4 s using a lighted, water-proof bore scope lowered througl the open drill-holes

• Estimation of *R' to water in each borehole using a T-rod probe

" Measurement of the floor slab thickness

• Depth to subgrade using a tape measure (to determine thickness of existing voids)

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FIGURE Plant and FacilIty Geotechnical 4-3 and Structural Assessment

Page 4-11 Key Distress Indicators Rev. 2 Subgrade testing consisted of dynamic cone penetrometer tests (DCP) at each drilled location.

Thiele used a Humboldt Model H-4219 Heavy Duty Dual Mass Dynamic Cone Penetrometer to perform the DCP test in accordance with ASTM D6951/D695 IM, Standard Method for Use of the Dynamic Cone Penetrometer in Shallow Pavement Applications. The preferred methods of estimating density of non-cohesive soils is the use of the Standard Penetration Test (SPT) and the Cone Penetrometer Test (CPT). Employment of the SPT and CPT was not possible in this case due to access and space constraints in the Turbine Building basement. The data obtained from the DCP can be used to identify zones of relatively low den* r softness compared to the surrounding subgrade as stated in Note I of the Stand det.-- ti such zones is relevant to developing a comprehensive model of subgr e.eor to pumping and material piping.

4.1.5.2 Results t Investigation results are summarized below. The Thiele testing and DCP logs are presented in Attachment 6.

4.1.5.2.1 Drill-hole Results 1' Visual observations and measurements wer e as de, at each drill-hole are summarized below in Table 4 These d surface presented graphically in Figures 4 d 4-7.

hole Thickness Depth to Number I (inches) Subgrade

Page 4-12 Key Distress Indicators Rev. 2 Table 4 Turbine Building Basement Subgrade Investic ation Observations Drill- Floor Slab Initial Depth to Initial DCP DCP Comments hole Thickness Depth to Subgrade Potential Depth Elevation Number (inches) Subgrade (inches) at Void Tested Tested (inches) DCP Space below (ft.)

Testing Depth floor (ft.)

(inches) (inches) upon penetrating slab,odor of fuel, water bubbled to vis*'*!surface

' sec. for up to 60 2-4 30 37 30.5 7 IAN -. Wte tr25"below =

2-5 32.25 34.75 32.25 2.5! 977 below 2-6 35 38 37 3 7 s.g....,

_ _ __ _ *, zone/voi 2-7 31.75 , 33.5 33.5* 1.75 07 water 27.5" below

• ,-floor, some air g:.**.*sed when slab 2-8 34.5 36 977tral 2-9 31.75 33 33.25%250 water 6" below 2-10 31.75 35 5 3.25 13 977 2-11 1 32.75 35 I -1 13 977 2-12 NK 33 "980  ?*

2-13 307 ,3 275 973 OW 2" below floor 2-14 * *. .". 2.75 10 980 pressurized air, then water to 10 inches below floor AIA, hmi' Iminutes later 32.25 2.75 1 10 980 GW extruded onto q., floor intermitantly for 60 sec, then

. *, GW 17.25" below

_

• _AM floor 2-16 "*.o -"," 36 & !0,k7 1.75 13 977 2-17 32.5 330. 75 2.25 10 980 GW 17.5" below

_ _ _floor 2-18 30.5 , 31.25 2 10 980 2-19 28 4 10 980 GW 17.5" below floor As indicated by the measurement data above, floor slab thickness at the locations drilled ranged from 27 to 38 inches. Construction drawings show the floor slab thickness as 31 inches. These differences from the drawings may be attributed to variations during construction. Upon penetration of the slab, the hammer drill often punched through the bottom of the slab and penetrated the subgrade before the drill operator could stop the drill. For this reason, voids between the bottom of the slab and the subgrade were assumed to have developed if the difference between the bottom of the slab and the surface of the subgrade was greater than or

Page 4-13 Key Distress Indicators Rev. 2 equal to 2inches. Void thickness greater than or equal to 2 inches was detected below the floor slab at 16 drilled locations. Overall, void thickness ranged from 2 to 11 inches. Voids were measured immediately after the hammer drill was extracted from the drill-hole.

The void space immediately below the slab was also measured by Thiele immediately prior to DCP testing. In many cases, the void space measured at that time was significantly less than that measured by HDR immediately following foundation slab drilling. The explanation for this discrepancy is that the Thiele measurements were taken hour even days after the initial drilling occurred, allowing the fine grained silty sand to flo ,-nto. i ce. Pressurized air was noted flowing from the drill holes at a number of ati pressure under the foundation slab was released, the groundwater wit ,grained was able to flow into the void space as groundwater was no longer held

• y ai the foundation slab. In no case did we encounter evidence of silty sand hilt thees.

Figure 4-6 shows the estimated top of subgrade beneath t based on P Measurements taken on 12/09/1 1 by HDR personnel. Figu e 4- esents the e top of subgrade beneath the floor slab based on the ired depth ade data at t e time of DCP testing.

4.1.5.2.2 Groundwater Levels Groundwater was measured in 11 of the b s imrn ly a 'ng and ranged from 2.0 to 27.5 inches below the floor ele 0 m ely afte ion slab drilling.

Water elevations were not meas, the remai 6 drill-h octions due to either dry curate water tion du ater level fluctuation, or drill cuttings mixed with w 0 ie drill-hole 1ong the T-rod probe and 0,'

preventin curate meas In the case ofl 1-6 and 2-15 water flowed from

• thenr"fora

• ately one minute then flow ceased. These are the only tw K ater re e foundation floor surface. At no time did any water fe or any d period of time. Figure 4-5, Turbine Building ndwater Gradient Ms grou *,contours based on water level data obtained December 9, 2011. Fig ,,shows a consistent groundwater level with the S4.eption of the hhigher pto orfashe gradi ighrs4i*;so

• the south wall. Figure 4-4, Comprehensive Groundwater gradietdopninlvaonowr rudaer a Pt Map shows the grou er gradient in the vicinity of the Turbine Building and a reas. Figures 4-4 show groundwater gradient dropping in elevation toward the , t comer of the e Building near drill locations 1-3, 1-4, and 2-6. This is consist the prese gnificant void space in this area and with previous reports (Elite Pip The combin ort) ntify drainage pipe breaks and high flow rates in this vicinity.

.' depressed groundwater elevations and evidence of voids is subjective evid subgrade piping due to pumping is occurring in this area.

Groundwater cont were generated using MicroStation GeoPak DTM Tools to triangulate between the groundwater elevation points and develop a groundwater elevation surface. From this surface the contours were generated from elevations along the triangulation lines in MicroStation. This function is within standard practices for ground surface and groundwater surface contouring.

Comprehensive Groundwater Gradient Map - Contours based on data from 12/09111 Turbine Building Drilling & Site Monitoring Wells Fort Calhoun Station Plant and Facility Geotechnical and Structural Assessment

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987.5 ... MajorGroundwater contour 4& Drilling Locations . -- '," v;, Turbine Building Ground Water Gradient Map Dec 2011

-..... Minor Groundwater Contour XX ,*.,* Fort Calhoun Station Note: Groundwater elevations were recorded on 12-9-2011. - , -

Turbine Basement slab elevation is 990.0. omaha Puhlic Po"er Oistlicl Drilling and Testrng Program 4-5

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• -Drilling Locations Top of Subgrade Topographic Map ATE Dec 2011 x DxrillingLocatios .... *" Based on Dynamic Cone Penetrometer

- 9870 ... Major Subgrade Contour (1) j Tests - 11116111 through 12/0211 Minor Subgrade Contour (.5) ZaIa P',,*P'M' Y,, Fort Calhoun Station FIGURE Note: Subgrade elevations represent DCP Test subgrade elev tions. Plant and Facility Geotechnical 4-7 Only shallow voids shown. and Structural Assessment

Page 4-18 Key Distress Indicators Rev. 2 4.1.5.2.3 DCP Test Results DCP testing began on November 16, 2011 and was completed on December 2, 2011. Thiele performed the DCP with a 10.1 pound hammer recording blow counts for every 2 inches of cone penetration, or as close to each 2 inch penetration interval as possible. The data and related calculated bearing capacity in pounds per square foot (psf) and pounds per square inch (psi) is presented in Attachment 6 - DCP Field Test Data.

The DCP test is useful in indentifying zones that are soft or ose lo w counts) relative to the surrounding fill as noted in ASTM D695 1 1 M, fny zone that drove with the weight of the hammer without a drop of ammer w cou, and/or with only one blow is considered a very loose zo at ha- with flowing sand. In addition, any zone that drove more than 2 inche, 2 blow sidered soft and likely altered by some process of material loss but is s dered soil. C2s density test of fill in the vicinity of the Turbine Building during co c range from  :

percent compaction and N values of in situ soil under the 6týbin T 'ng from preconstruction borings yielded SPT N values of no jw~er than 2 b foot and commonly 4 to 11 blows per foot in the upper soil zone. All cases of f rod material in original borings. As noted previously there i d"reteion of D Ttests, but it is our engineering opinion that material th) ws a tip rough so' er weight of rods or weight of rods and hammer provi d idence r ft material that does not reflect conditions at the time of constructi( *hese and do not include the void space between the foundatioaz Jb an t1 top d in Table 4-1 since the DCP tests began at the top of subp"l .

A number of zero blow cod and soft zonei "dl using the DCP. Twenty-one of the 26 - eshowed s within the z' r id soil. Fifteen of the 26 DCP holes e as a 1he upper portion of the subgrade. Vgids at the upper o sud in th from 0.1 to 6.4 feet. The most notable voids at the

) subgrade C - are 0 8

• 3*:2-8 * (6. Nt CP 2-15 (3.89 ft.), DCP 1-4 (3.08 ft.), DCP 2-4 f.,DCP 2- 81 P 1-5 (0( if and DCP 2-1 (0.71 ft.). Figure 4-7, Top of

• 'bgrade Topographic Map t 11Dynanfic Cone Penetrometer Tests, provides the drill-locations an contour of 9p of competent (greater than 1 blow per 2 inches) subgrade n DCP testing. Sevent,0 oids were identified that exist at some depth within the su These voids range i cness from 0. 12 ft. to 5.99 ft. The most notable voids in this are n DCP 2 61ef*9 ft.), DCP 1-6 (3.79 ft.), and DCP 2-13 (1.94 ft.). The deepestfW14 0.23 ft. 2( 2-13 that occurs between 16.06 and 16.29 ft. below the Turbine B ase. oor (Elevations 973.94 to 973.71).

Eleven of the v , at or below the bottom elevation of the pile caps (983.5). These voids range in thi "ss from 0.15 to 6.54 feet. A summary of the voids encountered during the DCP investigation is presented in Table 4-2.

Page 4-19 Key Distress Indicators Rev. 2 Table 4 Turbine Building Basement Subgrade Investigation DCP Results Drill- Depth to Depth to Elevation Elevation Zero blow Depth to Depth to hole top of Bottom Top of Bottom of count /soft top of Bottom of Number Void of Void Void (ft.) Void (ft.) zone Void from Void from from from Thickness (ft.) Floor (ft.) Floor (ft.)

TOS (ft.) TOS (ft.)

1-1 0.00 0.20 987.42 987.22 0.20 2.58 2.78 1-3 0.00 0.10 987.06 986.96 0.10 2.ý4 3.04 1-4 0.00 3.08 986.58 983.50 - _ 6.50 1-5 0.00 0.78 987.19 986.40  ? 3.60 1-6 6.58 10.38 980.33 976.54 79 13.46 2-1 0.00 0.72 987.44 986,72 2.~ 3.28 2-2 2.54 3.00 985.06 984.60 4.94 5.40 2-3 0.00 0.81 987.44 986.63 , 2.56 .

2-3 3.35 3.70 984.09 983.74 5 5. 9 2-4 0.00 1.07 987.46 986.39 1.07 .* 54 2-5 0,00 0.33 987.31 986.9. !33 ,_3.02 2-6 0.00 -0.35 986.92 98 2-6 1.32 1.50 985.60 4.58 2-6 2.64 8.63 984.28 . .. 5.73 2-7 1.64 1.82 985.57 # 9 0. 18 4.43 4.61 2-7 2.96 3.18 4'803 ' 022 5 2-8 0.00 6.54 98 98063 6.54 2.83 9.38 2-8 7.07 7.51 -AN 979.66 - , 0,4,.,. 9.90 10.34 2-8 12.26 12.54 974.63 *' " 15.09 15.38 2-9 984.98 *'.74 4.28 5.02 2-10.., 987.2)f 986.72 , 0,55 2.73 3.28 2-11, O W7 Q. 4 ... 64 0.12 ---- ,,--3.55 3.66 2.46Jý 2."-3"3*' " 0.18 5.27- 5.45 0.00 0.20 M44 0.20 2.56 2.76 7.27 9.21 ,! 978.21 1.94 9.85 11,79

,1 1973".71 0,23 16.06 16.29 2- ",5

[-.O0 3.89 983.38 3.89 2,73 6.62 2-15 7.14 980.13 0.15 9,72 9.87 2-16 ~ 'I 0.69 A 10 986.41 0.69 2.90 3.59 2-17 1. 1.9- 985.45 0.64 3.91 4.55 2-19 0.00 N 987.67 987.48 0.18 2.33 2.52 2-19 2,62 985.05 984.88 0.17 4.95 5.12 TSTpof Subgrade

Page 4-20 Key Distress Indicators Rev. 2 4.1.5.3 Discussion/Conclusions The Turbine Building basement floor drilling and subgrade testing identified both a number of significant voids/soft spots as well as zones of competent soil. Table 4-2 provides the drill-hole number (see Figure 4-3 for drill-hole locations), depth to void and thickness of soft zone (per DCP). The lateral extent and interconnectedness of identified voids can only be inferred from the available data. However, some zones such as the voids encountered in DCP 2-6, DCP 1-4, DCP 1-5 and DCP 2-8 are both significant enough and close eno *n lateral distance that we conclude that these voids are part of a connected void syst A s *ds are close to where both the 10-inch and 6-inch drain lines run adjac-, Q ach ave multiple bends where joints may be more susceptible to crackin . eparatio .pe. In this scenario, significant groundwater inflow into the drain te e also are, however, zones where there is little to no evidence of vo ade det n such as in testing locations 2-10, 2-11, 2-12, 1-8, 2-14, and 2-18. Ov datsuppo, How

• The Triggering Mechanism of subsurface piping of soi ate to the sump Un and seepage/flow into the drainage system pipe curring.

• Voids are significant and interconnected.

• The foundation subgrade is not affected y riggering ism, Regarding CPFM 3b - Loss of lateral pile or, due s rosion and piping (due to pumping) for the Turbine Building. As di ed in n5 thickness of the void and the potential effects on later, sup wer sidered.. ximum void thickness is 6.54 feet in DCP test location d the eleva 'of the bott'* of this void is 980.63 ft.

The deepest void in DCP te n 1-6 is 3.79'" hick w e bottom at elevation 976.54.

For the worst case in the col ta, pile supp in limited areas to elevation 976.54b let of lateral pil due to a void, calculated from the

.olevatio to the lowest void bottom elevation at 976.54, is 7 . ere are a * . locat re zero blow count zones exist at elevation greater ree feet below to sla on of approximately 987 (bottom of pile cap ation 984). Of these ~ blow co es, only five are greater in thickness than foot. The remainder of th hole locati s have competent or greater than I blow per two material

,ation to 984). 3 feet (el.within bottom of the foundation slab or at the bottom of the pile Base available info , and without a quantitative analysis we find that the loss of lateral port sho - le collected data under the Turbine Building, over the limited areas sugth 4e data, does not infer that a significant risk of piling failure is present in sta due to the presence of the existing voids. Therefore, we have ruled out CPFM 3b b 'rbine Building. It should be noted that the subsurface erosion piping Triggering Mechan m is ongoing and that lateral pile support could be compromised in the future if void thickness and extent continues to increase. Seismic considerations have not been assessed for this report and we do not make any conclusion with respect to the effect of voids on lateral pile support during seismic loading.

The data from the Turbine Building sub-slab investigations cannot be used to rule out CPFM 3b for other pile-supported structures in the vicinity of the Turbine Building, including:

Containment Building, Auxiliary Building, Service Building, Circulating Water System, Turbine Building South Switchyard, and the Fuel Oil Storage Tanks and Piping.

Page 4-21 Key Distress Indicators Rev. 2 Two other CPFMs associated with KDI #1 and Triggering Mechanism #3 have not been ruled out by the Turbine Building sub-slab investigations and have the potential to continue to affect structures other than the Turbine Building. They are:

CPFM 3a - Undermining and settlement of shallow foundation/slab/surfaces (due to pumping)

CPFM 3c - Undermined buried utilities (due to pumping)

Structures potentially affected include: Technical Support QIterg r on System, Raw Water Line, Security BBRE's, Maintenance Shop, Und ,d Ch (Trenwa), Waste Disposal Piping, Main Underground Cable Bank, laim r Syste eralized Water System, Turbine Building South Switchyard, Fuel Oil and Paving/Sidewalks/Outdoor Drives, Sanitary Sewer Systd ensate Tank (buried utilities portion of system). For this Triggering Me to affect tl cture a void would have had to progress beyond the Turbine Bui ent foundati under the Structures listed above. The fact that the flow in the ipes has be occurring for many years makes the hypothesis tha .oids coul tended beyond the Turbine Building foundation and under the S N.bove mor0. 'ble. The collected data showing that voids were foun PC f the ur ding basement between the pile caps at 11 locations also s ts that aterial fr eyond the Turbine Building Basement subgrade may] e occurr The Triggering Mechanism of su' ce on/ of soil eath the Turbine Building basement and perhaps continues ng as the* in system piping remains unrepaired. Voids, soft zon!9 ssociated gro ater a ing flow paths will continue to enlarge and extend out & ' .rainageand si. er time unless the flow of into.~-~m~~,system waterwater ,noQis

.he' . Therefore, e ( 3b and 3c for the structures listede out a in credible until the following remedial re ONati~onsiented "the to Triggering Mechanism,

.4 Recommend recommends that OPPI rm remedial work to stop the uncontrolled drainage of the water into the broken e Building basement drainage system piping and fill the v eath the basement fl ab. The first priority is to stop the drainage of groundwater into system asasage as possible to stop the subgrade erosion process. The quicke iest wa he flow of groundwater into the sump is to block the drainage system pi eir te n points into the sump. An alternative to the repair of the existing dra*0 to abandon the existing system entirely, and replace it with an above-structura . ab system. One option to implement this alternative would be to construct a new s .inthat is entirely above basement floor that would utilize pump(s) to remove water from the existing floor drains and the turbine drains. Another option would be to trench cut the 7 inch concrete topping on the structural slab to allow space for installation of new drain pipes. Both these options would facilitate monitoring and access to the system should repairs be necessary.

in addition to drainage system repair, we recommend the voids created by the subsurface erosion/piping caused by the groundwater flow through the broken drainage system pipes be grouted to reestablish the foundation subgrade integrity. This program is for the purpose of preventing further subgrade deterioration that could potentially affect pile lateral support over

Page 4-22 Key Distress Indicators Rev. 2 time and extend beyond the Turbine Building over time. Since the extent of the voids cannot be defined beyond the perimeter of the Turbine Building, we further recommend that the volume of the material it takes to fill the voids be measured to provide a proof of the extent of the voids.

The repair/replacement of the drainage system and filling of the voids to return the foundation soils and subgrade to pre-pipe break condition will allow us to rule out CPFMs 3a, 3b, and 3c for the Structures listed in Section 4.1.3 above. To fill the voids determine the volume of the voids/zero blow count zones a grouting program shoulh i" t ,r)d.p The grouting program design should include:

" Specifications for a grout mix that has the proper rh emic rties to ensure a balanced, stable mix that will maximize penet d long-te .rance.

• If pipes are abandoned, a monitoring program to esta water condi '"

the drain pipe and sump operation should be develope in in order to characterize conditions that must be addressed d grouting,

" Specifications for a grout mix that can disp disturbe d that can provide long term support for the piles, an

" Identification of the grout pressure(s) n ary to pr, xmaximm, t penetration into voids, and soft zones within the s 'de soil, 'a

" Identification of the maximum 9utin$g*'ssure4., any structures and utilities. Parti tten shQ e given der-slab drain pipes in the event that te r ea e d

" A plan for real-time, fu onitoring an Tdin Grout volumes and p under the dir .... alified engineer at the time of ey St uring grouting operations.

'oundwate' s outsi e Turbine Building Basement during and after the

• ¢*!* grouting operati` ..

'vY Asequence/logic tree t progratression.

A plan for the drilling of cation holes to include permeability tests to assess the affect the grouting program o ,Lsubgradesoils.

uting acceptance crit' y the Engineer.

to report all outing and monitoring data on a daily basis to the Engineer.

A ort includin

• ta, results and conclusions developed by the grouting contr is sh, ilude data on grouting locations, grout takes for each location, verificat sults, and monitoring and any other data that would support the conclusion I bsurface voids have been filled.

As mentioned previously, we recommend that OPPD consider abandoning the existing drainage pipes that are in place below the Turbine Building basement floor slab. Attempting to grout the voids after the existing drainage pipes have been repaired will likely damage or even crush the pipes and complicate the grouting process to the detriment of the-overall remediation, In conclusion, this specialized type of grouting operation is necessary both to properly treat the subsurface voids and soft zones and to provide verification/documentation that the program was a success. We recommend the selection of a specialty grouting contractor experienced in

Page 4-23 Key Distress Indicators Rev. 2 performing this type of work. Pre-bid selection criteria should be developed and potential bidders should be pre-qualified based on the selection criteria.

At the time of the writing of this report, it was not certain that a grouting contractor could be found that could implement a program that would yield the data necessary to rule out the remaining CPFMs described above. Discussions with specialty grouting contractors will be scheduled as soon as possible in the future to ascertain if they have the capability to provide the data necessary to rule out the remaining CPFMs.

4.2 Pavement Failure and Sinkhole in Paved Access A tw Structure and Service Building Key Distress Indicator #2 is the failure of paving and developm . ole b e roadway paving a few feet west of the Condensate Storage Tank. This roa L , art of a U- ý,area of paved surface that wraps around the northeast, east, and southeat of the conti Ah.i-Block buildings (Paved Access Area). The inside of the U-shaped v eSS is north exterior face of the Maintenance Shop on the north, the east exterior <Jthe MaintenancIe Shop and the Service Building on the east, and the sout*. :faces of the iI 4 e and Service Buildings on the south. The outside.of the U shape i or face of Warehouse on the north, the Trenwa Cable Trench along the Misq iver on nd the nI terior face of the Security Building and the Trenwa Cable Tren om the S ing west to the end of the pavement on the south, which is generally aligne the s ast c h Turbine Building South Switchyard.

The Paved Access Area overlies a nU e f structures ed utiliti 4 R-etweenthe Power Block and the Intake Structure. The base bel ea was excav 4 during construction. Current top-of-paved-surfa

• ation is app '< -,ely 1004.5 ft. avement slabs at the surface are underlain by a * * ,a*e 6 This *ent section over ies structural fill down to el. 973 ft with the except' e area *e Cir Water Tunnels, where fill is placed above the structur has a top ele .vt997 ft.

4.29` ysical Observations A"4..,,,physica ,m observats uring the facility assessments have been grouped under Key Anumitb'r~f~pnysicaI observations rd' Distres'si**adj" tor #2 Softeneds * ,bg'e

" Pavement joi$rts . .i

" Voids under pa 4

• Water hydrant failur 1""j

• Water seepage at BBgkF-2, MH-5, Intake Structure, and Security Building 4.2.2 Triggering Mechanisms Seven possible Triggering Mechanisms that might be the root cause of this Key Distress Indicator are as follows:

" Subsurface ex.osion and piping (due to pumping)

" Subsurface erosion and piping.(due to rapid river drawdown)

• Rapid river drawdown, river bank slope failure/spreading

Page 4-24 Key Distress Indicators Rev. 2

• Soil collapse

• Frost effects

" Hydrostatic lateral loading

• Buoyancy 4.2.2.1 Subsurface Erosion and Piping (Due to Pumping)

Multiple connected seepage paths have the potential to exist in th soil backfill at the site. The paths could be exposed at some locations to the river floo* er pr h&in the ground north of the Security building). This potential network *age pahs ,uld be connected to several pumping sources: the sump in the Turbine Buil -5nd aManhoe a series of surface pumps inside the perimeter of the Aqua Dam.

• ewat8in p i-snside the Aqua Dams were operated for an extended period, maintaining`ý eafferential -op potential seepage path networks. Gradient may have been sufficient erosion of surrdungnsoil.

Unfiltered seepage into the Turbine Building sump continu'e's, soI tlýe,'.ei*sion has the pnt 04i to continue until that seepage is stopped. The potential.subsurface erosbiiYpping caused by the Turbine Building sump pumping could extend u h&ePaived Access,+/-e.Voids could be created under the pavement and along the util tiyj4tencn w-*ltlor pipes. Thicpoential damage includes settlement of pipe or thrust blocksl $tlemenl A W.vestress a pi can cause a pipe to break, or can cause the displacement of kst block, ich;turn, could cause failure of a pipe operating under pressure.

4.2.2.2 Subsurface Erosion ani**-Piping (dueto-Rapid Riv"eri Drawdown)

This Triggering MechanisrR, suibsurface erosioný .ipi, Mfed T1~~asm*,rrtdbgrvrd...awown by river drawdown.

Instead of pumping causing a7§signficant groundwacrdi', the groundwater gradient is Sp rpid receding river leve\River level drops faster than pore water pressure in the 6 Ad s s*na 6. h4r'iiItinggretcould be sufficient to begin erosion of the soil along so Ii~~n" eO'bs~epage path.

4, 2.2.3 Rapid Drawdowr, River Bank'Stoipe Failure/Lateral Spreading

[he Triggering Mechanism of slop'e failure or spreading could occur when the river level drops faýtti.han pore water pressure; m-the soil can dissipate. The saturated soil is elevated above the dropping *irver level. The open bank of the river provides no lateral support for the saturated soil anrdth*Oiesult is an imp6ndifig slope failure. If the soil's shear strength is exceeded, the slope wiiF'l*Ta~l long the, *of least resistance. Generally slope failures associated with rapid drawdown are*reiat.eive.16clized and shallow in nature.

4.2.2.4 Soil Col ipse (first time wetting)

The Triggering Mechanism of soil collapse due to first time wetting occurs when loose soil (spoils with high void ratios and corresponding low dry densities) is saturated for the first time.

Saturation of the soils lubricates the soil particles and increases the pore pressure in the soil, An Aqua Dam is an engineered water barrier used to contain, divert, and control the flow of water. It consists of two polyethylene liners contained by a single woven geo-tech outer tube. When the two inner tubes are filled with water, the resulting pressure and mass create a stable, non-rolling wall of water (Layfield Environmental Systems, 2008).

Page 4-25 Key Distress Indicators Rev. 2 loosening the bond between the soil particles. This allows the soil particles to shift into a more compact alignment as the pore water pressure dissipates. The result is a decrease in the soil's void ratio and an increase in dry density. This change in volume is observed as settlement at the ground surface.

4.2.2.5 Frost Effects The Triggering Mechanism of Frost Effects occurs as soil freezes,4F ost effects occur as both frost penetration and uplift, and as frost heave. Completely ,aturted o.i] slow frost to penetrate more deeply. Frost penetration and uplift occurg` 4 he wa -60et'*Ined in the soil void spaces freezes and expands. Frost heave occurs asJ e f M from capillary water movement. The change in volume as the- ar freeesa U asthe ice loses form, causes heave at the ground surface. ,

4.2.2.6 Hydrostatic Lateral Loading j  : ;'

The Triggering Mechanism of Hydrostatic Loading occurs when w.at. vels rise, imposing additional lateral pressure on structures.

4.2.2.7 Buoyancy .

NV The Triggering Mechanism of Buoyancy &c'qrs due toor. groundwater elevaion*Uplif elevation. Uplift forces occur whenfores *Nfeth ess than a tthe weight 4the weij of th&bred struqctL I of the water or groundwater it disices. In'ciease9a4ter or groldaWater levels increase the

• buoyancy uplift force on the lhu4~eW ructure.

4.2.3 Structures and CPFMs As'oiebdai with Triggeoiag }ýfia6nisms

- Nk The TriggerinM-edh smnisis'iiti*ined couliý I to the following structures and CPFMs:

"lntAke:-Str~cture ,X '

_/CPFM 12a - Rapid Drawdown, ~Riverbaý'ik.;s16ýe failure and undermining surrounding structures.

- PFM 12b - Rapid DrawdowhiR iteral spreading.

SSei ur t, ilding )r*,t

- CPFI3 :'4,- Subsurface Erosion/Piping. Undermining and settlement of shallow foundctidin/lab (due to pumpiing).

- CPFM 3d*&>Subsurface ErosiolilPiping. Undermining and settlement of shallow foundation/Z a* (due to*rerd'rawdown).

- CPFM 12a an*2: pid Drawdown. River bank slope failure/lateral spreading.

• Security BBRs

- CPFM 3a - Subsurface Erosion/Piping. Undermining and settlement of shallow foundation/slab (due to pumping).

- CPFM 3d - Subsurface Erosion/Piping. Undermining and settlement of shallow foundation/slab (due to river drawdown).

- CPFM 12a and 12b - Rapid Drawdown. River Bank slope failure/lateral spreading.

- CPFM14a - Frost Effects.

Page 4-26 Key Distress Indicators Rev. 2

• Turbine Building South Switchyard

- CPFM 3a - Subsurface Erosion/Piping. Undermining and settlement of shallow foundation/slab (due to pumping).

- CPFM 3b - Subsurface Erosion/Piping. Loss of lateral support for pile foundation (due to

. pumping).

- CPFM 3c - Subsurface Erosion/Piping. Undermined buried utilities (due to pumping).

" Condensate Storage Tank

- CPFM 3c - Subsurface Erosion/Piping. Undermined buried utii (due to pumping).

- CPFM 3f- Subsurface Erosion/Piping. Undermined buried*i*tilties(du ver drawdown).

- CPFM 12a and 12b - Rapid Drawdown. River bank slq aie/ht sr ading

• Underground Cable Trench (TRENWA) X

- CPFM 3a - Subsurface Erosion/Piping. Undermining apJttlem& t6of sha....

foundation/slab (due to pumping).

- CPFM 3c - Subsurface Erosion/Piping. Undermined buried dnilkties (due to pumpring)i -

- CPFM 3d - Subsurface Erosion/Piping. Undermining ana*ttie jiertkof shallow - ,

foundation/slab (due to river drawdown). "i':mr*'I CPFM 3f- Subsurface Erosion/Piping. Undermined16uried utilitieSŽ(dii"o,river drawdown).

- CPFM 14a - Frost. Effects. . .

• Circulating Water System

- CPFM 3b - Subsurface Erosion/Piping. Loss; of lateral sujpiort f6rpile foundation (due to pumping).

CPFM 12a and 12b - Rapid Drawdown. Rifpr bariklqpe failure lJal:tespreadmg

" Demineralized Water System A .

- CPFM 3c - Subsurface Erosini*,ifpng. Undermie buried utifies (due to pumping).

- CPFM 3f- Subsurface Erosgm'Ijpng. Undermiedlluriedttiuiities (due to river drawdown).

Raw Water Piping N .

CPFM 3,-; Subsur-Lce.Erosion/Pipmg.. Undermining-ang settlement of shallow fou ndatioh/lstab "(due;.to!ppimping).

- C.PIFM3c - SubsurfacE"gerson/Pipin.ii,Undermined buried utilities (due to pumping).

3d- Subsurface ErosioPiping. Urndermining and settlement of shallow f ndation/slab (due to river:*awdown). \

,s.<.P;FM 3f- Subsurface Erosi6iilPiping. Undermined buried utilities (due to river drawdown).

F "ie'Proltection System Piping

- G41Z 'a- Subsurface Erosion/Piping. Undermining and settlement of shallow fou (due to pumping.

sdatib/slab

- -CPFMO CPFM3.ýSubsurface 3d, .Sutbsurfc.rschP Ero'ý1iofPiping. Undermined buried utilities (due to pumping).

- CPFM.... ri ping. Undermining and settlement of shallow foundation/sl( ,n*aue4tiverdrawdown).

- CPFM 3f- SubsurfaceErosion/Piping. Undermined buried utilities (due to river drawdown).

Waste Disposal Pipingiý"

- CPFM 3a - Subsurface Erosion/Piping. Undermining and settlement of shallow foundation/slab (due to pumping).

- CPFM 3c - Subsurface Erosion/Piping. Undermined buried utilities (due to pumping).

- CPFM 3d - Subsurface Erosion/Piping. Undermining and settlement of shallow foundation/slab (due to river drawdown).

- PFM 3f- Subsurface Erosion/Piping. Undermined buried utilities (due to river drawdown).

- CPFM 12a and 12b - Rapid Drawdown. River bank slope failure/lateral spreading.

Page 4-27 Key Distress Indicators Rev. 2 Fuel Oil Storage Tanks and Piping

- CPFM 3a- Subsurface Erosion/Piping. Undermining and settlement of shallow foundation/slab (due to pumping).

- CPFM 3b - Subsurface Erosion/Piping. Loss of lateral support for pile foundation (due to pumping).

- CPFM 3c - Subsurface Erosion/Piping. Undermined buried utilities (due to pumping).

- CPFM 3d - Subsurface Erosion/Piping. Undermining and settlement of shallow foundation/slab (due to river drawdown).

- CPFM 3f- Subsurface Erosion/Piping. Undermined buriedguilifiti 6d( e t friver drawdown).

- CPFM 4c - Hydrostatic Lateral Loading (water loading ,ns io cturdQ failure in flexure.

lW11

- CPFM 4d - Hydrostatic Lateral Loading (water loadinQ'§n tructure W4f1,failure in shear.

- CPFM 4e - Hydrostatic Lateral Loading (water loadingX deflection.

- CPFM 6a - Buoyancy, Uplift Forces on Structures. Fail&ten.siodfi ies.

- CPFM 6b - Buoyancy, Uplift Forces on Structures. Cracke , loss of struc asupport-.

,s CPFM 6c - Buoyancy, Uplift Forces on Structures. Dispiae ItiWure/broken conlietionOON.

- CPFM 12a and 12b - Rapid Drawdown. River bank slope failure/ ateradspreading. J Main Underground Cable Bank, Auxiliary Building toSQtake tructure *.

- CPFM 3a - Subsurface Erosion/Piping. Undern*iinig-an settlement o6f6haIibw foundation/slab (due to pumping).

CPFM 3c - Subsurface Erosion/Piping. Uiilernined buried*..ut1ifes (due to ing).

- CPFM 3d - Subsurface Erosion/Piping. U-ndermining~and;settlenmerftof shallow foundation/slab (due to river drawdown).

CPFM 3f~1 Subsurface Erosion/Pjn*mg\ Unde rmib*l biSiried utilitiu6e to river drawdown).

CPFM 4c - Hydrostatic Lateral tocing (water loadig on structuýes). Wall failure in flexure.

CPFM 4d - Hydrostatic LateralL oading (water loA, g on stimctures). Wall failure in shear.

- CPFM 4e - Hydrostatic Lateir:,4121 Ading (water loadingVo tructures). Excess deflection.

- CPFM6b*!Buaicy, Uplift Forcos.son Structures. YieMlra slabs, loss of structural support.

- C PF06c 'BuacyanP,.,ihf For*t s onStructures. Displaced structure/broken connections.

- 121l -'Piý2aand idDrawdon.4 Fer bank slope failure/lateral spreading.

• Blair Wafer System

PFM3a - Subsurface Er6onJiiping. Uidermining and settlement of shallow ifoundation/slab (due to pumpfig).\

'-,CPFM 3c - Subsurface Erosinping. Undermined buried utilities (due to pumping).

" Camera Towers and High Mast Lighti*g

- CPFM] 3 Subsurface Erosi6iiPip'ing. Undermining and settlement of shallow foundatioi slab (due to pumping).

- CPFM 3d Subsurface.rosin/Piping. Undermining and settlement of shallow foundation/isli,,l,,

t eo- er drawdown).

- CPFM 12a andl2b IRapid Drawdown. River bank slope failure/lateral spreading.

" Service Building (Prioiqty 2 Structure)

- CPFM 3a - Subsurface Erosion/Piping. Undermining and settlement of shallow foundation/slab (due to pumping).

• Maintenance Shop (Priority 2 Structure)

- CPFM 3a - Subsurface Erosion/Piping. Undermining and settlement of shallow foundation/slab (due to pumping).

Page 4-28 Key Distress Indicators Rev. 2 4.2.4 Assessment Methods and Procedures Assessments were made by walking the Paved Access Area and observing surface features of the system (manholes) and the ground surface. The surface assessment included using a 4-fl-long, 0.5-in.-

diameter, steel-tipped fiberglass T-handle soil probe to hand probe the adjacent ground surface along the utility alignments and areas to determine relative soil strength. The assessment focused on identifying conditions indicative of potential flood-related impacts on or damage to the utility as follows:

• Ground surface conditions overlying and immediately adjacebotfheia! ýA*e_*

ess Area

• Soft ground surface areas as determined by probing

" Water accumulations and flows in subsurface system comppnents (mj'n lýes U)klc'Oincrete cable encasement pipes)*

• Damage to at-grade or above-grade system features

• Variance from normal installation conditions including settled, eaved syste'rre'ftars and equipment ina ys

" Operation of the system and appurtenant equipment (i.e~iS,19he system operahbnal?)

Additional investi gations were performed to furtherclharacterize th'e:,subsurface at theifacility including areas where conditions indicative of potential flood'related impacts' or4danage were bserved. These included the following non-invasive geophysical andl invasive,,eotechmci*mInvestigations. Results of these tests are described in Section 4.4 of this Assessmlent. ,,'X.

• GPR

• Seismic surveys (seismic refractqiin,,d

" I*,;*,.

- A, . refraction

.- min r,emor /

• Geotechnical investigations tst borings wiel tncelu PT and cone penetration test

[CPT]) and la~b§rýý `tests.,ORPD Note required v cavation for the first 10 ft of proposee V d,, co.i Therefore test reports will not show soil conditions in theu~p6rf 0 ft of testib- g logs. ' ".

" Pa~v 6eldaes were evaluated wfitGPR and dynamic deflection methods (i.e., drop weight Aeflctometer). "

4.2.5, Recommended Actions The following '*tions are recommend6 f6r this Key Distress Indicator/Triggering Mechanism.

4.2.5. 1 Detailed Forensic Investigations Review of GPRRand-se!smic refraction surveys indicates zones of relatively lower density material- In additidndro&p weight deflectometer tests reveal additional potentially degraded zones. A plan andprofile view of the Paved Access Area should be developed showing the suspected zones of lower density material. These zones should be geo-referenced so that they can be located and marked on the ground surface.

Selected sections of pavement will be removed from the paved access area between the Intake Structure and Service Building. All lower density zones identified within 5 ft of the ground surface by the aforementioned assessment methods should be investigated with test pits. Test pits should be carefully excavated with a backhoe or hand excavation to the extent possible in order to prevent damage to any existing utilities. Soil samples should be collected and tested to establish material characteristics such as Atterberg Limits, particle gradation, and moisture-

Page 4-29 Key Distress Indicators Rev. 2 density relationships. The bottom of each trench should be probed with a rod to establish the general limit of the soft material.

Excavation to greater depths could be considered if OPPD and HDR are confident that no potential damage to any utilities exists.

All excavated trenches will be backfilled according to existing pavement subgrade specifications.

The rationale for this trenching and testing program is to'uai the d of the subgrade of the paved access area between the Intake Structure a rvice Bu iii'to the extent feasible and to provide analysis and recommendations oreextent t*.dethod of necessary subgrade repair.

4.2.5.2 Physical Modifications Damaged pavement in the paved access area should be removed. ,-it emoval,t should be inspected for voids and soft soils. The sa should the Xslabilized, and new

• grade pavement should be installed. The extent of ýga iiations req ii-e or the paved access area between the Intake Structure and.heKervi*ce"ul g cannott b efed at this point. Based on observations, it is reasonabse t*ose /:he "Ien improvements

• to the phyica subgrade will be necessary. HDR will defln:the natureand ed e of$required physical modifications based on the findingsf.,the'*:ý" Forensics

• iled ' ny*es atiribn.

4.2.5.3 Continued Monitarin ,'rogram .

Continued monitoring of the4ac -access area be6AW6-jn thcAItake Structure and Service Buildingp AT e comnaended to in*A hisual inspections:,ofpavement slabs, structures, and surrodiidi~gg oi'asiad lrecommend, is the continuation of the elevation surveys of the pne vidgly identifiedtagetý-.4n the Sture and surrounding site. The purpose is to monitor

'foirstgns of structure distress and movementiýor~changes in soil conditions around the structures A1hsted in Section 4.2.3.

Th6,results of this monitoring\wiltlbe used to increase the confidence in the assessment results.

El.*.

. in surveys and visual inspections should be performed weekly for 4 weeks and e until December 31, i*1i. If any new distress indicators are observed between inspection 1ntervals by OPRP) '40ff the proper personnel should be notified immediately to determiiieif ,arniimmediat.itispection or assessment should be conducted.

4.2.6 KDI #2 Forensic slIn 'tigation Forensic investigation to addr'ess KDI #2 consisted of field observation and testing of subsurface soils exposed through excavation of trenches and removal of concrete pavement at selected locations, test borings and field and laboratory tests, and evaluation of inclinometer and survey monitoring data.

KDI #2 consists of a number individual distress indicators observed within the PAA including softened subgrade, pavement settlement, a void beneath the pavement in one location, water hydrant failure, and water seepage at BBRE-F2, MH 5, and the Intake Structure and Security Building.

Page 4-30 Key Distress Indicators Rev. 2 Possible Triggering Mechanisms identified for KDI #2 include:

• Subsurface erosion and piping (due to pumping)

• Subsurface erosion and piping (due to rapid river drawdown)

These Triggering Mechanisms and related Structures/CPFMs are discussed in detail in Sections 4.2.2 and 4.2.3. Conclusions related to these are discussed below in Section 4.2.6.3.

The purpose of this investigation was to determine the presence andexteifitw~fpoteiitial voids and soft zones in the subsurface, lateral or vertical movement in the subsif  ; and1if(te'oiwhich of the Triggering Mechanisms and associated CPFMs identified for A# if anyj,*1*ppar to be responsible for the observed distresses.

4.2.6.1 Scope of Work Trench excavations and concrete removals and associatedi$asso Ose.ation and tesl, ia ciffbrt*onan tsurvey Standard Penetration Test (SPT) borings and field tests, and inclin.ori.ter.and survey monitoring were performed between August 201116aC ary 201 lq 'activities are

,ee described below. ,.>~K 4.2.6.1.1 Excavation and Subgrade Tst!i.ng Trenching and concrete removals and,.ass"ciated field',,6bservatio, and ttsting were completed November 28 through Decembe{rv'2-1011. 'renchdesWere excav'acd1and the exposed excavation floor soils tested in t*voocations, both wi he el surfaced area located adjacent to, and extending tp.4.1ie6Trth of, Manho I e was removed, generally in full-panel sections, and subgra test~ing performedaL.iour ocalions across the main corridor of the sout-,. wriorth, the Void arnres Area, South Panels Area, Panel 16 Area%,` !*aiid.-orth anels.,Area. Th*es tt.areas are illustrated in Figure 4-9, Pavement R,4 Vation and SubKrde'Tcsting Are~i'ý,,,,.

E'V~aliuation of the trenches Rid Txposed pavemenht subgrade included observation of soil 4"conditions and in-situ field t sthiAg Observatio'ns of exposed subgrade were made by HDR and

• 'Thiele. Subgrade field testingawsiperformed solely by Thiele as directed by HDR.

O15"'6erNvdion included continua visgual observations of the subsurface soils and pavement subgr'a~'rahat were exposed~as excavations and concrete pavement removals progressed and followin'ge.r:iicompletipn:H.."DR also evaluated the exposed materials using a pointed, metal tipped T-haiidleprobe (commonlyreferred to as a foundation probe) where the probe was pushed into the6ip-sed-surface by hand to qualitatively evaluate relative consistency/firmness and depth of deteclddsoft areas.

MAINTENANCE SHOP SERVICE BUILDING BACK OF ~~

4. N .1 ~

22 v~ <------ 1----

INTAKE STRUCTURE UTILITY LEGEND RAW WATER WASTE DISPOSAL 5,,_13 PROPOSED BORING FIRE PROTECTION LOCATION (SEE FIGURE 1-2)

ELECTRICAL CABLE BANK BLAIR / DEMIN WATER (UTILITY LOCATIONS ARE APPROXIMATE) 3 DEEP TEST TRENCH -

GRAVEL LOCATION 0D 15' 30' PLANT NOTE: CROSS PANEL TEST TRENCHES WILL BE NORTH LOCATED AS DIRECTED BYTHE ENGINEER Pavement Excavation and Subgrade Dec 2011 Testing Areas Fort Calhoun Station Oriaha PubhCPower DtitrCt P Paved Access Area Field Inveatrgation Program 1-iR

Page 4-32 Key Distress Indicators Rev. 2 In-situ field tests on exposed trench floor soil and pavement subgrade consisted of static cone penetrometer (SCP) tests. Thiele used a Humboldt Model H-4210A Portable Static Cone Penetrometer to perform the SCP tests. This device consists of a direct-read penetrometer that measures the amount of penetration resistance as the device is pushed into soil materials. The cone penetrometer was advanced into the soil by hand in continuous six-inch vertical intervals until refusal or the maximum vertical reach of the device (3.0 feet) was reached, whichever occurred first. Resistance readings were observed and recorded for each 6-inch interval.

Measurements of the depth into the subgrade at each location testAed'were made using gradation markings on the cone penetrometer shaft. A4.

SCP tests were performed at a frequency of about 1 tes ,erI atofposed soil (trench excavation floor or exposed concrete pavement subgrae).d weregenre*r ,completed at 3-foot horizontal intervals. Exceptions to this included two areais of.*.,xposedoc6ncrte pavement subgrade, one made inaccessible by a soil stockpile and one ,aIje that was not pa*"f'he originally planned investigation, as described below. <"U.,  : .

The trench excavations were identified as Trench TE;7,.and Trench 2Ž,Both trenches were excavated to depths of about three feet below eei tv surface "*ii h Bobcat 325 track excavator using a 2-foot wide bucket. Trenchgt* mA*,eabout 2 dfe.

by 30 feet long. Trench TE-2 measured about 2 feet w~h R'y5 feet 6log. Concrete wasteeountered during excavation of Trench T-2 at the noAi3h.loor of thebxcaýLatinoat a depth of about 3 feet below existing ground surface at which ti Fne achin 8' 6vatite d. Further hand excavation exposed the top and so ;loeast s"'e' of the 'in Unde r 1dund' Cable Bank.

The Void Panels Area included removal of one cor ete concr eteu pavement panel and a small (about 3-foot) diagonal cut~pi'o r iof the adjoining ane o henorth (at the small void) located just-nol*h..of the Secut 3'lding, adjacent t:*.**e.ener-most security fence, west-south esf 4Ath6R'th1densate Stor'r }.Tank. This area was investigated to address a subgrade voidKbeow i (out one tsofka:eross) of broken concrete at the expansion joint between two concrete panes, The area bf d*oncrete removal and exposed subgrade testing 7-,mmeasured about 12 feet by4L2.feet (about square feet or 16 square yards). A total of 16 SCP tests were completed in the subgrade at the Void Panels Area.

' Activities

-. in the South Panels Area included removal of 7 complete concrete pavement panels a.I-wasl0ocated along the eastsi,,,de of the PAA main corridor beginning just west of the southwest.omrner of the Intaký:'Stricture. It included the 4 panels originally planned for removatand's.ubgrade mvestigation, plus 3 additional panels removed at the direction of OPPD.

This area w~qa._estg*gted to address possible piping and voids below the concrete pavement or along near-sui.r:6cctittes and structures. The area of exposed subgrade and testing extended north to south f6ioahou.t.60 feet, with the southern roughly 47 feet (of the 60 feet - 6 pavement panels) measuring about 26 feet east to west and the northern roughly 13 feet (of the 60 feet -

one pavement panel) measuring about 14.5 feet east to west (roughly 1,410 square feet or 156 square yards). A total of 112 SCP tests were completed in the subgrade at the South Panels Area. Prior to testing, the subgrade exposed in the northeastern-most portion of the South Panels Area (not part of the originally planned investigation but where concrete was removed at OPPD's direction) was covered by a stockpile of RCC fill and was not SCP tested.

The Panel 16 Area included removal of one concrete pavement panel (field marked by OPPD as Panel 16) located in the central portion of PAA main corridor west of the rollup door to the Intake Structure. This area was investigated to address possible piping and voids below the

Page 4-33 Key Distress Indicators Rev. 2 concrete pavement and/or near-surface utilities and structures. The area of exposed subgrade and testing measured about 4.5 feet north to south and 12 feet east to west (roughly 54 square feet or 6 square yards). A total of 6 SCP tests were completed in the subgrade at the Panel 16 Area.

The North Panels Area included removal of 7 complete panels and one diagonally cut half-panel and was located along the east side of the PAA main corridor beginning just northwest of the northwest corner of the Intake Structure and included 3 of the ,panels originally planned for removal and subgrade investigation, plus 4.5 additional aelsUdovedit`the direction of OPPD. The southeastern-most pavement panel of planpe stigation area panels was not removed at the request of OPPD as it w~ssiu very go I".on and to avoid possible impacts/damage to the immediately adjacent slp, ty fence a.n. a.....drant. This area was investigated to address possible piping and vo~ir o" concre ,'ement and/or near-surface utilities and structures. The area of exposed si:6qe and testing'e d north for about 89 feet, with the northern-most 15 feet including 'kest*ý92-Itata-aE cu atthe t n n e 0ro-; - KNfie mer and pan-handle feature extending about 12 to 13 feet to the west. tal area ofti Panels Area was roughly 1,322 square feet (147 squa e-vards) and inc uded about 466 square feet (52 square yards) of originally planned inveshgationarea and 856' sare.eet.(95 square yards) of additional area exposed at the directi'o J P( ¶,tltotal of 49TN ests were completed in the subgrade of the originallyjd"i

,ptan e,ýd imvesfi-gioi,)ýi.'.,area with i Tk10l1" stscocompleted pe d in the additional exposed subgrade. A relatfivly reducL g was performed in the additional area due to time constraints iof0iinmpendngg:;rain andtoa1ýOw*for full-frequency testing in the originally planned inves igatio°n'rea

, ,;, ' I -. I:

Geotechnology, Inc. Seismic,.Anril*tsis Geotechn.9 4ogy, .c.,(GTI) condiiu5&tseismic evaluatio*"n along 5 lines utilizing two different metho~ls e~a** *eifaction a1.Rdfraction Microtremor (ReMi). The seismic investigation lines$ae snown -Roenl-homete &.1*kpeort dated October 24, 2011 and is presented in Attachment6* The folI.oW. s takenfimfhe GTI Report.

?i; 3".1 Seismic Methods 'j'.;:

Refraction. The seismic refracti**h method involves generating compressional seismic waves.

( vs) at the ground surfac eing an impact source. The seismic waves travel from the sour'cetthrr6ugh the subsurface alo.ng a variety of paths including refracting along interfaces between ~ts1ŽPnd rock layer i-aing different seismic velocities. The seismic waves return to the groun ce wherIthy* are recorded at various distances from the source using geophones an aseismrogaph. Seismic velocity calculations are made by analyzing the differences in e&14,sedt;iie from the source to each geophone. The resulting profile is a representation of p'-,Wve velocities of the soil and bedrock directly beneath the survey line.

Refraction Microtremor (ReMi). The ReMi method is used to develop shear wave velocity profiles. ReMi surveys are conducted by passively recording background surface waves (microtremors) that are generated by passing vehicles, equipment, airplanes, etc. The surface seismic energy produced by the noise sources travels across the ground surface and is received by geophones placed in a linear array. The seismic energy detected at the geophones is recorded using a seismograph and is transformed into a phase velocity spectrum for analysis.

Shear wave velocity profiles are constructed by analyzing surface wave phase velocities and frequencies, and performing inversion modeling.

Page 4-34 Key Distress Indicators Rev. 2 3.4 Seismic Results. The seismic data were interpreted by comparing the velocity profiles to nearby Borings B-4, B-7, -8, and -9, which were used to establish the types of geologic materials corresponding to the profiled velocities. The stratigraphy at the site is generally comprised of approximately 70 feet of alluvial deposits over limestone bedrock. Weathered shale bedrock was observed in a boring immediately north of the subject survey area. The alluvial deposits are comprised of alternating layers of loose and dense silty sand to sand with silt and occasional layers of clay up to 14 feet thick. Sand and clay each exhibit a wide range of velocities depending on a number of physical parameters such ,,"oisture content, porosity, sorting, and particle packing. Based on the seismic refraction data !allvuat the subject site exhibits velocities ranging between approximately 1;50 "t i e TO feet of material and increasing with depth to approximately 5,000 ft/s n . t e top dk. Published P-wave velocities for sands range between 1,300 and 6,5{64 s las Age between.

approximately 3,500 and 8,200 ft/s. Top of bedrock wa ITrT1eted to generaly*¢oincide with the 5,000 foot/second (ft/s) contour on the refraction data as ,sl on ,n Plates lhikvui6gh 134-\

Top of bedrock undulated across the site. The shallowest*>dr.ock imaged appeared toibea a depth of approximately 56 feet at the east end of Line 5 andthe dqpest ,bedrock imagdj.' 7 appeared to be at a depth of approximately 78 feet atthe-west end oftLiine"5 The circulation structure located between thenKfding and the-kssruri River was thexawlaongt*ujdiganxhlted isoi* R oivrwse not imaged in Lines 2 and 3. The data colly=_ along t `eseA1_'exhibited sigthcant noise from facility activities and exhibited high,'. 1city sha enei*fy°m the surface pavement, which masked w our ability to pick the arivalo lated shallo wcrclation structure.

Zones of low velocity were obs&'r, in the refract'ioniand ReMi data above and below the top of bedrock as indicated on Plateý`s 9through 18. Ae&4 *low velo t zones indicate locations at which material is softer andicor les' dense and throu iIi seismic wave travels slower compared topsuwouding mateni ?hese velocity co :atre gradational and illustrate velocitNy*lalngesebe.e*een extremne, values. These values do not necessarily represent the actual se speuoc es, but rather, illustreateth) eneral trends of velocity changes across the profiles Anlh'general locations-aijrndelative di-ffer'nces of the extreme high and low velocities.

'.Low velocity features within miestone bedrock.could be due to the presence of:

".karst features such as voids" clay or water filled cavities or solution-widened

• !:!..:jolnts/fra cture s. r : :.-.:

%*s"Oesof weathered or otherwie weak rock compared to surrounding more competent rock.

Low velocity features within thealluvium could be related to:

zones ofgoose~sandf'as observed in nearby borings.

voids, if "'*ffi6e****iverlying cohesive material is present for bridging."

SPT borings were used to ground-truth the findings of the GTI Seismic Investigation as described in the following paragraphs.

Page 4-35 Key Distress Indicators Rev. 2 4.2.6.1.2 SPT Borings Thiele completed six SPT borings (identified as Borings B- 10 through B- 15, inclusive)

November 9 through 17, 2011. The location of the SPT borings and their relationship to the GTI Seismic investigation lines is presented in Figure 4-10. These 6 borings were drilled to ground-truth subsurface anomalies identified as "low velocity features" in the GTI Report One of the SPT borings, B-10, was intended to be a baseline boring and was drilled in an area that did not evidence low velocity features. The other 5 borings were rilled at locations of reported low velocity features. These borings were drilled bedrok I anp e continuously sampled so that the low velocity features could be evalu sing es esult data. Of these 6 borings, 3 were completed in the PAA (Boring -

7 B-13, 134 '. Boring logs and test results from Borings B-12, B-13, and B-14 we e lu, *vuate& ddre s.*I#2.

The borings were continuously sampled from 10 feet belovj*,dseing ground ,,mrf!eto the maximum depth investigated. The upper-most 10 feet of soil ai eC-:boring was 'hdro-, ...

excavated to clear possible underground utilities. Continuous sphisp*oon SPTs (ASTM..Y/

1586-08a) were performed and soil samples collected-during drilling exc t occasionally7where undisturbed Shelby tube samples were collectedb;y duIeti push Where Sl§9lby tube samples were collected, laboratory dry density test res,ats.wvereused tor our evaluati6 ni-,All borings were advanced to auger refusal and terminated on the top o imestone be6dock formation Lithe underlying the site. ,

A summary of the test borings andsier, smic

• J iall/ 7'"/

ressed ]b1 eacls as follows:

" Boring B intercepteda'single anomaly rere as existing from about 32 to 58 feet below ground surface (rfrtoGTI report, Plate 11 ) ...

• Boring.B.1 31-iptercepted two reported anomalies",_onexisting from about 3 to 20 feet ace and one exis.hng from about 41 to 70 feet below ground surface (refer beldo ioý!grioud,'s'g.

2rep Bofing B interpe*d .two rep,., te-nomalies, one existing from about 6 to 28 feet A >below ground surface anemone existinfofmrabout 38 to 53 feet below ground surface (refer to GTI report, Plate 9). ".

4,2*6A.3 Inclinometer Moni ioring Thiele6peformed weekly monitoring of inclinometers (installed into bedrock for this assessffiint), which begani N,*lat'ovember, 2011 and will run through late January, 2012. A total of 5 inicmometers,,(Iclinometers I-1 through 1-5, inclusive) were installed and monitored to evaluate if any'laterf,.mdvement was occurring at the site related to the 2011 flood.

Monitoring results frbimi'the inclinometers were reviewed for this KDI #2 forensic investigation to evaluate movement in the PAA possibly related to KDI #2.

~&r**

GTI Siesmic Investigation Lines and SPT Boring Dec 2011 Locations Fort Calhoun Station r Omaha Public Power District Paved Access Area Field Investigation Program M 4-10

Page 4-37 Key Distress Indicators Rev. 2 4.2.6.1.4 Survey Monitoring LRA provided weekly survey monitoring under contract to OPPD from late August through late December, 2011. 264 survey points associated with 40 structures and site features across the FCS are included in this weekly monitoring. Of these, 49 survey points associated with 9 structures/site features were reviewed for this KDI #2 forensic investigation to evaluate movement in the PAA Structures. These Structures included the Auxiliary Building, BBRE-F2, Condensate Storage Tank, Intake Structure, Maintenance SholSecurity Building, Service building, Turbine Building South Switchyard, and MH-25.

4.2.6.2 Results Forensic investigation results including field observati 1,t results, and inclinometer and survey monitoring results are sumari&z&eblow Test repnby Thiele and .LRA survey monitoring results are included in AttacJ*[t6-:

4.2.6.2.1 Excavation and Subgrade Testing No piping voids or ground subsidence were i* __ifii' t '.h visual ob"si*qA, T-handle probing, or SCP tests in any of the locationsýex'posed throu R~ench excavations or concrete pavement removals. Field SCP testing idi,'dt~d that sti~tVQiff clayey silt to silty clay fill soils were generally encountered in the uper 3 feet jeiow the ground surface or pavement.

Occasionally, soft to medium stiff sois pil weencounr, weg.*.ncu er,' at the "34ýf' ot'Žepth. Some very soft 6s7 appeared to soft soilassociated wih relativeliN was encountered * **~l6the upper*.ost 6 to 122ice andkisqgenerdllytu limitedtio inches andn ivhigh moisture cotent soils (ve*ry moist to wet) associated with concrete pavement exl nst'-ipoints (joints b 6en djent panels) and surface run-on from adj acentpavements reltdtprecipitation (ra p R) that occurred during the work.

The t*-ja'id sutheast, si of the mqplilthic concrete Main Underground Cable Bank were ecpsep d and observe8-iTrench T*- 2 `Th*top of the structural concrete Circulation Water Z/" 'exposdstructure Tunneýl Ih was exposed#ate. a few Sot'Pnls Thelocations fill 6:!*by hand excavations completed in the subgrade exposedin the South PanelAaTe eped at both of these concrete features was compact fine-grained cohesive- material and showed no evidence of piping erosion or excessive

"*.:moisture.

4.2.6.,2'-2;SPT Borings ,Yj Material'erkountered in the siubsurface at Borings B-12, B-13, and B-14 generally consisted of alluvium lneluding.poora~ded, fine- to coarse-grained sand (SP) and to a lesser extent silty sand (SP-SM);a id cl[y ei:sands (SC). Silt and lean clay zones were encountered in Borings B-13 and B-14 in tlhe'4p",pr 10 to 20 feet; these soils were logged as fill and documented as such in various historical 'geotechnical reports and as-built drawings provided by OPPD.

No voids or very soft/very loose conditions that might be indicative of piping or related material loss or movement were identified through drilling and continuous sampling of the test borings. N-values (uncorrected) indicated that the encountered alluvium ranges from loose to medium dense and that soil conditions were similar between anomalous zones (low velocity features reported by GTI) and non-anomalous zones. The reported low velocity zones are attributed to the inherent variability in the relative density of the granular alluvium that underlies the site. SPT results were compared to similar data from numerous other

Page 4-38 Key Distress Indicators Rev. 2 geotechnical investigations that have been conducted on the FCS site in previous years and for this assessment at other locations across the site. This comparison did not identify apparent differences from soils encountered at other on-site test boring locations nor did it identify changes in soil relative density following the 2011 flood.

4.2.6.2.3 Inclinometer Monitoring Data from inclinometers to date, compared to the original baseline'%measurements, have not exceeded the accuracy range of the inclinometers. Therefore, defo' t hen,&he monitored locations since the installation of the inclinometers has n V 4.2.6.2.4 Survey Monitoring //

Survey data points to date (in the PAA) compared to the oig-i*a1 baseline suveys have not exceeded the accuracy range of the surveying equipment. <1efoe,deformatioia'. thf.e

• monitored locations, since the survey baseline was shot, hasnot 0 ,re 4.2.6.3 Discussion and Conclusions Forensic investigation as described above was:*peormeý,W-ie observed pVeifient distress was most prominent, at locations coincident with shallo ndeground struc*tht's and utilities, and where recent seismic surveys identifi Nw veloc" leatu*r*F (s.cations where potential for degradation related to the Triggenig~1ec -smsa*P FMs aso dwi K w identified).

Excavation and subgrade tesfNiigdentified no evillnhe of pipingerosion, voids, or subsidence of site fills. Field SCP testing,ofthe exposed subgdq iimi cted that stiff to very stiff soils were genefa1lyrfie&nuntered in the :upper 3 feet below the-round surface or pavement. Based on thek 6b] fi ha:1eand tests leMuts obtained, the fill soils in the locations exposed and testeudare- compact, 6ohesivesoils that &e'not susceptible to piping erosion. SPT borings did A-n&'6dentify voids or veryfft/very looseco ions that might indicate piping or related

, Kiii;aterial loss nor did they 'idpitif changesi isoil relative density following the 2011 flood.

"inclinometer and survey monitoring ind*icate that movement of on-site subsurface soils or

\,, siirutures has not occurred. ,

Possi.ble:Triggering Mechanismsand related CPFMs identified for KDI #2 and the PAA include

" Subsurface. Etrosiodan4nPiping (due to pumping), CPFMs 3a, 3b, and 3c.

" Subsurfac&4Eigi6iiaifd Piping (due to rapid river drawdown), CPFMs 3d, 3e, and 3f.

Based on the obseraions and test results, the individual distress indicators that comprise KDI

1. 2 are not attributed to the possible Triggering Mechanisms identified for KDI #2: Subsurface Erosion and Piping (due to pumping); and, Subsurface Erosion and Piping (due to rapid river drawdown).

Our investigation for KDI #2 also indicates that the Triggering Mechanism of Subsurface Erosion and Piping (due to rapid river drawdown) was not initiated by the 2011 flood and that the CPFMs related to this Triggering Mechanism, including CPFM 3d, 3e, and 3f, are not credible.

Page 4-39 Key Distress Indicators Rev. 2 However, the Triggering Mechanism of Subsurface Erosion and Piping (due to pumping) and the CPFMs related to this Triggering Mechanism, including CPFM 3a, 3b, and 3c cannot be ruled out for all structures associated with the PAA. Even though this Triggering Mechanism does not appear to have caused the distresses observed in the PAA, their root cause (damaged Turbine Building sub-floor drain pipes and sump pumping) as identified by investigations in the Turbine Building basement continues. A number of other Priority I and Priority 2 structures have been assigned CPFMs that are related to this remaining credible Triggering Mechanism and its related CPFMs. These other structures differ ftbm KDI #2 and the PAA in that no strong evidence of distress has been identified or doe mntedtýrotg assessment observations or ongoing survey monitoring. /

Priority I Structures in this category include:

• Security BBREs

• Turbine Building South Switchyard

" Condensate Storage Tank .<. *A"

• Underground (TRENWA) Cable Trench

" Circulation Water System >-

i Demineralized Water System (line) /

• Raw Water Piping '"

" Fire Protection System Piping / .' .

" Waste Disposal Piping

" Fuel Oil Storage Tanks and igw-

" Main Underground Cabl,¢eB r Auxiliary BuM'1ig to Inta1&Structure

• Blair Water System

" River Bank--- NK i, Priotri'2Struictures' iithis category include:

7. S~ervice Building ,.

. Sanitary Sewer System

.The ential for impact to the A6Ve Priority 1 and Priority 2 Structures from the Triggering

• ll*.hnsm of Subsurface Ero*ibn~land Piping (due to pumping) exists and the CPFMs related to thpreiigering Mechanisdrem ain credible until the recommendations related to KDI #1 as presente~&$eeh.w are implelmented and completed. Continued monitoring of the above structureswi'l, erequirei, afIe these recommendations are implemented and completed to evaluate if thierco1 e Mic-ed actions were effective and the CPFMs are therefore no longer deemed credible. ,

However, it can be concluded that the Subsurface Erosion/Piping Triggering Mechanism (due to pumping) most-likely did not extend outside the perimeter of the Seismic investigation lines taken around the power block. This conclusion supports the ruling out of the Subsurface Erosion/Piping (due to pumping) CPFMs associated with this Triggering Mechanism for the following Structures:

• Security Building

" Intake Structure

• River Bank

Page 4-40 Key Distress Indicators Rev. 2 4.2.6.4 Recommendations The results of this KDI #2 forensic investigation have ruled out potential Triggering Mechanisms and associated CPFMs that could have been the cause of the observed distress.

However, it could not be used to entirely rule out CPFMs associated with KDI #1, which is associated with the uncontrolled drainage of the groundwater into the broken Turbine Building basement drainage system piping. These CPFMs will only be ruled out when the physical modifications presented for KDI #1, as presented in Section 4.1 o~this Assessment Report, are implemented.

4.3 Column Settlement in Maintenance Shop Key Distress Indicator #3 is the settlement of column TE-15 in a *intnnce c. SIa e column is on the first floor of the Maintenance Shop outside the men's restro *aj to the side of the Turbine Building. OPPD staff has indicated that the column tthng lib"3*

priOk 62,-0*tl Flood, and that the settlement had increased during the flood. As 'f c oe-,,2011, the counnas settled 2.2 in. In addition to the. settled column, there are cracks in the wall iimerest the beam adj*acent to the men's restroom, and the doors on the restroom no.lo-nger-oerate properly-..,

4.3.1 Physical Observations /-

A number of physical observations made during te fa'cility as"sesents ýhaVebeen grouped under this Key Distress Indicator: . , .

Significant settlement of a building colum (2.2 in.) iI.'

• Significant settlement of floor sla!i'b",

" Cracking of maso.nrypartition xw,5s1inthe southwest c e..rAYms building immediately adjacent to the Turbeifllhdfflfl 4.3.2 Txigg,-ing Mechanisms \

Twdip~ssible triggering mechanisms'thl. might b6elroot cause of this Key Distress Indicator are discusssed.,as follows.

4.3.2.1.\ Subsurface Erosion ahiad Piping (Due to Pumping)

Multi~le.chnnected seepage..aths have the potential to exist in the soil backfill at the site. This potentialnetW*rk of seepagep~aths could be connected to several pumping sources: the sump in the Turbinme.&Buldinag,.Manhole MH-5, and a series of surface pumps inside the perimeter of the Aqua Dam. The dew .ering pumps inside the Aqua Dams were operated for an extended period, maintainingý.ahiiad differential on any potential seepage path networks. Gradient might have been sufficien'tio begin erosion of surrounding soil.

Unfiltered seepage into the Turbine Building sump continues, so the erosion has the potential to continue until that seepage is stopped. The potential subsurface erosion/piping caused by the Turbine Building sump pumping could extend underneath the Maintenance Shop.

Page 4-41 Key Distress Indicators Rev. 2 4.3.2.2 Soil Collapse (first time wetting)

The most recent flood elevation prior to the 2011 flood was 1003.3 ft, which occurred in 1993.

The maximum flood elevation in 2011 was approximately 1006.9 ft. The foundation of the maintenance shop has footings at el. 1000.5 ft and subgrade below the flooring slab of approximately el. 1006 ft. Therefore, it is possible that up to 3 ft. of soil were saturated for the first time as a result of the 2011 flood. This alone could not cause settlement of the foundation footings due to first time wetting because the footing elevation of 10.5 ft had likely experienced first time wetting in 1993. ,

4.3.3 Structures and CPFMs Associated with Trigger The Triggering Mechanisms outlined could apply to the fol

" Security Building ~x ,~

- CPFM 3a - Subsurface Erosion/Piping.

foundation/slab (due to pumping).

" Security BBREs

- CPFM 3a - Subsurface Erosion/Piping.

foundation/slab (due to pumping).

• Turbine Building South Switchyard

- CPFM 3a - Subsurface Erosion/Piping. enf'of shallow foundation/slab (due to pumping),.<g

- CPFM 3c - Subsurface Erosion/-Pipi*i"g* es (due to pumping).

- CPFM 7a through 7c - Soil (olf'i*e (fi slab, differential settlement of shallow foundation, loss fI'stiural re/broken connections; and general sitessettlement.

" CondensatepgeT

-C '-Subsu**ace srion/Pigpfin UndOei,-,grund Cable Trencl\ , "

(I*FM 3a - Subsurface EFfiin/iping. UInrd~erining and settlement of shallow

• .i:':f~undationislab (due to pum pi"'g)**::i',,

GPFM 3c - Subsurface Erosion/Pýiping. Undermined buried utilities (due to pumping).

" Deminer.alized Water System ,

- CPFM'*T3,- Subsurface Erosion/Piping. Undermined buried utilities (due to pumping).

• aw Wafe*ip'_Ih¶

- CPFM 3a. -"Subsurface Ero.*EonsPiping. Undermining and settlement of shallow foundatiornab'.(ue toý,uipipg).

- CPFM 3c - SukaLicrosion/Piping. Undermined buried utilities (due to pumping).

• Fire Protection SystemPip'ing

- CPFM 3a - Subsurface Erosion/Piping. Undermining and settlement of shallow foundation/slab (due to pumping).

- CPFM 3c - Subsurface Erosion/Piping. Undermined buried utilities (due to pumping).

• Waste Disposal Piping

- CPFM 3a - Subsurface Erosion/Piping. Undermining and settlement of shallow foundation/slab (due to pumping).

- CPFM 3c - Subsurface Erosion/Piping. Undermined buried utilities (due to pumping).

Page 4-42 Key Distress Indicators Rev. 2

" Fuel Oil Storage Tanks and Piping

- CPFM 3a - Subsurface Erosion/Piping. Undermining and settlement of shallow foundation/slab (due to pumping).

- CPFM 3c - Subsurface Erosion/Piping. Undermined buried utilities (due to pumping).

• Main Underground Cable Bank, Auxiliary Building to Intake Structure

- CPFM 3a - Subsurface Erosion/Piping. Undermining and settlement of shallow foundation/slab (due to pumping).

- CPFM 3c - Subsurface Erosion/Piping. Undermined buried utiliti' ,.(due to pumping).

" Blair Water System .

- CPFM 3a - Subsurface Erosion/Piping. Undermining and seittlementiof shallow foundation/slab (due to pumping). pumping).

- CPFM 3c -. Subsurface Erosion/Piping. Undermined buried utilitieS.(due toPurnping).

" Camera Towers and High Mast Lighting CPFM 3a - Subsurface Erosion/Piping. Undermining andseitlement of shallow.

foundation/slab (due to pumping).

" Service Building

- CPFM 3a - Subsurface Erosion/Piping. Underminiinagdn, settlement.of shallow foundation/slab (due to pumping). -* ,

4.3.4 Assessment Methods and Procedures. 4-Initial assessments were made by OPPD staff andare. described in OPPD rlorts:.

An additional investigation was performed on August 2, 2001, to further characterize the subsurface at the areas where conditions indicatiye ofpotential flood-related, impacts or damage were observed. A subsurface survey using GPR was performed by Ground Penetrating Radar Systems, Inc. (GPRS). The report is titled "Ground Penetrating Radar (GPR) survey to locatee sub surface voids at the Ft. Calhoun Nuclear Facjlity* *.in 14,ir NE." The GPR survey identified potential voids in the soil beneath the column and aldongthe length -ofthe corridor fiýom 8 to 12 in. below the surface. The voids are referred to as "small in thickness in most areas" and slightly :thicker nearest the settled colunm.

4.3.5 Previous Investigations and Baseline Information 4-*

Prior to .cii*struction of the Maintenance Shop addition, Geotechnical Services, Inc., performed an investigation titled "Report of Subsoil Investigation for Proposed Maintenance Shop Addition" in 1977. Four Ibrings were completed :to.,assess soil conditions. The borings recorded 7 to 9.5 ft of fill material consistfingOf clayey siltodntl~esouth side of the proposed structure area and fine sand on the north side of the proposed structure area. SPT N-values of the fill material range from 9 to 20.

Elevations of the borings ~were n onrecorded.

Maintenance Shop drawings indicate that the floor elevation is 1007.5 ft, and the elevation of the bottom of the foundation footings is 1000.5 ft. Therefore, based on the depth of fill material below existing grade established in the previously mentioned report, the foundation footings are placed on fill material.

Page 4-43 Key Distress Indicators Rev. 2 4.3.6 Recommended Actions The following actions are recommended for this Key Distress Indicator/Triggering Mechanism:

4.3.6.1 Detailed Forensic Investigations Review of GPR and seismic refraction surveys reveals voids or zones of relatively lower-density material. One-in.-diameter borings through the flodr slab should be drilled at the surey ;IN*gned~to, record tip locations where GPR surveys were conducted. A miniature conedti resistance should be pushed into the foundation soil mate 1 a s deepas #ssbskle beneath the floor slab in order to record tip resistance. Depths of Vo 'nd soft Wo eencountered will be determined and documented. In addition to the use of iature wat roof bore scope with lighting should be available to investigate fu rmin e tent of any voids encountered.

Upon completion, the floor holes would be refilled with non-shn rout with a mi \rnf4um Q 28-day compressive strength of 2000 psi. Repair of holes shall metq PD criteria and be approved by OPPD staff..

Upon completion of the proposed drilling aapfinspectinw OPPD and staff will discuss the necessity and location for additional drilling locatoinslto further defi ne the extent of any voids encountered. Approval by OPP s*aff willeirequired ibr to beginning any additional drilling. . ."

The results of this subsurfacenvostigation would*kfb*used to d~fermine the existence of voids and low density zones that c be related to the ýstet d col umn' 4.3.6.2,-7% ýhijcsaIModificatio ...

Once.the ieotechnica evaluation is complete, an engineered .design for foundation restoration

/§hoqj Ibe developed. PoNssilýeremeddia1bfif6fts include foundation jacking and underpinning.

...i.6. d improvement can in mde easure:siici as compaction grouting to increase the density 5 6f o? the subsurface soils. ,

-V 3 Continued MonitorohýigdProgram 3 '3.,

Contt*ued monitoring in thefaMitenance Shop is recommended to include visual inspections of the aeae-wiihere observedft Iement has occurred; also recommended is a continuation of the elevation surveysof preyi*o*sly identified targets on the structure and surrounding site prior to remediation ofte M-ainfeinance Shop foundation and structure.

The results of this im6nitoring would be used to increase the confidence in the assessment results. Elevation surveys and visual inspections should be performed weekly until remediation is complete. Once remediation is complete, specific survey monitoring points should be installed in the remediated area of the Maintenance Shop. These points should be monitored weekly for 2 months after remediation, then once every 3 months for a period of I year in order to assess the overall effectiveness of the repair.

Page 4-44 Key Distress Indicators Rev. 2 4.3.7 KDI #3 Forensic Investigation Forensic investigation consisting of concrete floor slab drilling and field and laboratory subgrade testing was completed in the Maintenance Shop to evaluate subsurface conditions near Key Distress Indicator (KDI) #3. This Key Distress Indicator consists of differential settlement of Building Column MG-15, presumed differential settlement of the nearby floor slab, and cracked nearby masonry partition walls. These building distresses were observed at the southwest corner of the building immediately adjacent to the north side of the Turbine Building during faci,,*ity assessments.

Possible Triggering Mechanisms identified for KDI #3 include:

• Subsurface Erosion and Piping (due to pumping); and

" Soil Collapse (due to first time wetting).

These Triggering Mechanisms and related Structures/CPFMs are di *es-ss" d in detail in Scis 4.3.2 and 4.3.3. Conclusions related to these are discussed below in SeGtion 43*3 7,"3.

The purpose of this investigation was to determine the presence-and extentsof ,tentia voids and soft zones beneath the floor slab and evaluate which of the,"n.g gerin~gMechanism§s idei'tified for KDI #3 are responsible for the observed building distresses. -i *'

4.3.7.1 Scope of Work ,

Forensic investigation of the Maint*iance Sho wa ciwducted fomNv'ember 9 through December 2,.2011. A total of 24f locati ns were drille d`a1d the underlying subgrade "orslab evaluated by the investigation. Th included 1-inc diameter l s at 16 locations as originally planned (drill-hol41"1through 1-16). dUti~i*l4 1-inch diameter holes were drilled and.,'mesb gated to the easCt bthe original invtgation area (drill-holes EW- I through EW-4),and-l, tvltheoftof the ot'llinvestigation area (drill-holes NS-1 and NS-2). Shelby tube.sýiplng in 2 te"t borings was also. added to the original scope of work.

je, Drilling of the concrete fo.the.2-2, 1-inch'diameter holes was accomplished by Lueder Snsrcto C yu tract to O using a hammer drill. All of the I-inch Construction Company under cnrc o ' sn Jameter drill-holes were prote'*id immediately following drilling and before and after evaluations using teitiporary plastic caps that were flush with the surrounding floor stira Concrete drilling forlhlit test borings was accomplished by Omaha Concrete Sawing C..

undei- contract to Lueder Consciiietion using a 4-inch diameter core bit and a hammer drill. The 4-inchb diumý4* drill-holes.w'ere protected after subgrade evaluations using temporary expanding,..,, ,

Subgrade evalua.tion;included observation of conditions below the floor slab, in-situ field testing at each drilled" Iocation, and laboratory testing on Shelby tube samples of the subgrade material at the 2 test boring locations. Observations were made by HDR and Thiele Geotech, Inc. (Thiele). Subgrade field and laboratory testing was performed solely by Thiele as directed by HDR.

Observation of the subgrade below the floor slab included direct visual observation through the open holes with the aid of a flashlight, close-up visual observations using a lighted, water-proof borescope lowered through the open drill-holes, and measurement of the floor slab thickness and depth to subgrade using a hooked probe made from #9 tie wire.

Page 4-45 Key Distress Indicators Rev. 2 In-situ field tests on the subgrade consisted of static cone penetrometer (SCP) tests at each drilled location and a dynamic cone penetrometer (DCP) test performed at one drill-hole (1-12).

Laboratory tests included moisture content and unit weight (wet and dry).

Thiele used a Humboldt Model H-42 1OA Portable Static Cone Penetrometer to perform the SCP tests. This device consists of a direct-read penetrometer that measures the amount of penetration resistance as the device is pushed into soil materials. The cone penetrometer was advanced into the subgrade by hand in continuous six-inch vertic~rintervals until refusal or the maximum vertical reach of the device was reached, which*er oN d.d fird, Resistance readings were observed and recorded for each 6-inchin L MeaL-em*n*s of the depth to subgrade at each location tested were also made using gmiion marlngsonthe cone penetrometer.

Thiele used a Humboldt Model H-4219 Heavy Duty Dual s namic ConeIPAromet r to perform the DCP test in accordance with ASTM D695 1/D69$14M "Standard Me %r So f the Dynamic Cone Penetrometer in Shallow Pavement Applicat si iothough no* ert applicable to determining density of non-cohesive soils1as would be~tfe "andard Penetration Test (SPT), the DCP was used due to limited acc~ wd ispace of the Ma*ifntenance Shop hallway. The data obtained can be used to idextif-zn~o ot'elatively f lowdoensity or consistency compared to the surrounding su$gr de *a* as stated ta~e iN-*lNote 1o I of the h 4STM ;' Standard.

tnad

• 'leus n,m - -wmd'Sthelbtubes at two test Laboratory test samples were collected byI i'le us ipn walt w boring locations; one advanced abo1t2it 3 fee.tWestb Ifilding C31i M (identified as Boring No. ST-1) and one advantýd Abut 2.3 feet east of Building Column MG-15 (identified as Boring No. ST-2). Borings!w 4 ere initiated usin d'3-inch diaimter hand auger to advance through about 6 inches of gr ei:o,.mprising the upp*i s18on of the floor slab subgrade.

Below the giave~layer, continuousShelby be samrijo1eie .rcollectedto depths of about 4 feetlbel'oW .f subgrade whe.ei'e.sal was encountered on coarse gravel.

investigation mu~r also i1ue review, fprevious geotechnical investigation report prepared

,,nj*support of design of the o MaiiiarfceShop structure (Geotechnical Services, Inc.

Mginal N-72 MResult Forensichibvestigation results ncluding field observations, SCP and DCP test results, laboratory t6est results, andprivious geotechnical investigation results are summarized below.

Test reports-bThiele and .iheiprevious geotechnical investigation report are included in Ata c hmenft*E.!,*:.:!*:.* i*:.,.I:

4.3.7.2.1 Observation Results Visual observations and measurements were made as described above. Data obtained at each drill-hole are summarized below in Table 4-3.

Page 4-46 Key Distress Indicators Rev. 2 Table 4 Maintenance Shop Forensic Investigation Observations Depth to Straight-Line Cardinal Floor Slab Subgrade Void Distance from Direction Drill-hole Thickness(') from To Space Column Relative to Comments Number (inches) of Slabf) Depth(" MG-1 5(2) Column MG-(inches) (inches) (feet) 15 (based on (inches)_ (feet)_plant north) 1-1 5.0 7.0 2.0 18.0 W__ _, upper 6" granular fill 1 3

• • % ,*Cuppýer granularfll3 6" granular fill'3) 1-2 5.3 6.0 0.8 18.0 '-W * , r 6" 3

1-3 5.0 8.0 3.0 12.0 , WSW r 6" granular fi"11 )

1-4 5.0 8.5 3.5 11.5 W IT' -grained fill 1-5 5.5 7.5 2.0 9.5S, ,W;. " granular fill(3) 1-6 5.0 9.5 4.5 7.5 nuiar 1-7 5.5 8.0 2.5 5.5 *1 , uppe g*raular fiu 1-8 4.3 12.5 8.3 5.5 upper 6' gý ii-f 1-9 5.0 11.5 6.5 2.0 NNW upper 6" gr ',flld3) 1-10 5.5 10.0 4.5 4.5 - S . upper 6" granular fill1) 1-11 1 5.0 13.5 8.5 5 N ipper 6"granular fill 3) 1-12 5.5 9.0 3.5 2/8' "2*'2I SE u*p"6,' granular fill 3) 1-13 5.0 9.5 4.5 :5.5 , SE upjýi'&6" granular fill 3 )

1-14 5.5 10.0 4.5 6.5 R( * : *ESE*. upper 6" granular fill13) 1-15 6.0 8.5 5

• 1.5

• upper 6" granular fill3) 1-16 5.5 7.0 1.5 lo

16. V upper 6" granular fill(3)

EW-I 6.0 7.0 0 19.p 1E1&.7 upper 6" granular fill 3)

EW-2 5.0 6.0 * ' .O 45.6 , , iN _NE upper 6" granular fill(3)

Eu p r 6""ga t3 ua fill(3)

EW-3 5.0 5.0 -. .....0.0I, u-.

65. 0 *; , * "ENE upper granularfi 1(

EW-4 _._,______._ ' 5.8 \P0.3 83.0 ENE upper 6" granular fill*3 )

NS-l1, 506

. **2 33.0 NNW upper 6" granular fillP3)

NS-2 5.0 `-5,_,3 0.3 "

• 47.0 NNW upper 6" granular fill(3 )

Notes z;.:".  : *. .

(4**tpproximate value, rounded to the nerest-,it 0-inch, bas*eon probe measurements using a tape measure.

(2")Zproximate value, rounded to the nea+s-.4foot, based on scaled plan drawings; not field measured.

(3) Subjectiveapparent material encountered. based on CPT probe action during advancement through subgrade is believed-, onsist of fine-grained fill.

N north, S ýb ýE = east, W = west V

• :; *'*"*?:

" "*:; . .1*i :::!.'

Page 4-47 Key Distress Indicators Rev. 2 As indicated by the data above, floor slab thickness at the locations drilled ranged from about 5 to 6 inches at the testing locations. Drilling completed to access the floor slab subgrade resulted in penetration slightly below the slab. Observations during drilling indicated that the drill usually advanced beyond the slab bottom about an inch. Measured void space of less than about an inch was not considered significant or representative of a void space.

Significant void space (greater than about 1 inch) was detected below the floor slab at all but one of the 16 locations drilled in the open area surrounding Colu G- 15. Away from the settled column in the adjacent hallways, no significant vdeoied_ below the floor slab in any of the locations drilled (drill-holes EW-1 throd W4 and NS-2).

Overall, void depths ranged from zero to about 8.5 inc testp*d averaf*g ab6*3.0 inches. In the area surrounding the settled column, void depths v*'re teýf4nging roaout 0.8 to 8.5 inches and averaging about 3.9 inches.

The data also indicates that void space below the floor nearer to the settled column as shown below.

• Within about 3.5 feet of the settled colurn d

• Within about 4.5 feet of the settled colu. nvoid sl

• Within about 5.5 feet of the settled coltmn, void si

" Within about 7.5 feet of the settled coluuni, void s

" Beyond about 7.5 feet from thV mtled c,01" 'mn, e A1.4 inches

• Beyond about 18 feet from t ed column;\oPK 0.5 inches The above statements relategdiyoNdO*d space are illutnil is sections A-A', B-B', and C-C' presentedpasifiguyes 4-12,4 3,4*"nd 4-14. The ions are shown in Figure 4-11.

/ vi

/

2,,

\k' V

/

7

.~1~~...~~

i li'qi!/ PLANT NORTH CV~L~~

S 10'

-SThS-L3V' F;Ok i

.L EW 3-J-'~

4"SA 1%_ _ _ _ __ _ _ _ _ _

1 I l Note: Background is OPPD Drawing #16892 Maintenance Shop Drilling L(

Cross Section Location Plan 14- Drilled Test Holes Sections A-A, B-B, C-C Drilled Test Holes with Shelby Tube Sampling Fort Calhoun Station OrnIiaa Public Power Distnrt Plant and Facility Geotechnical and Structural Assessment i Sections - See Figures 2-4 HiR

Column MG-15 WNW ESE 1-2 (2.0' N.)

0 I r 0 Min. Significant

- Void Depth (1")

2 VD = 1.0" 2 4 4 Inches 6 6 8 8 10 10 40 A'

LEGEND VD = 1.0" Measured Void DepthPoint Deptl k 1-2 Drilled Hole Identification (Off:

(2.0' N.)

- U U DATE NOTES Maintenance Shop Drilling Locations Dec 2011 Nominal floor slab thickness is 5.5". Cross Section A-A Vertical Scale is 1" = 5".

Horizontal Scale is 1" = 5'.

Fort Calhoun Station FIGURE DwN Public Powl Disti1a Plant and Facility Geotechnical 4-12 and Structural Assessment H-N

Column MG-15 NNW SSE NS-1 1-12 1-10 1-13 (6.5' W.) (1.0' E.) (2.0' W.) (1.5- E.)

Concrete Floor Slab 0 __, 0 Min. Significant VD = / Void Depth (1")

2 2 4 4 Inches VD = 4.5"

• ; ....IIIL

\," L,,....L.y ...

<;fSubgrade,; '.*:*-*

\  ;:*:. **

6 ~j,,

11 MC FJ~ftt:U 6 S1it-t,**: ClayeyiSilt (ML) Fill Silt / Clayey Silt Ji"t/ (ML) Fill 8

VD =8.5" 1010 5 .!£;:  :***"  : 10

• 20 25 30 35 40 B B'

",F..- -

LEGEND Measured Point DethI VD = 1.0" Void Depth 1-2 , t)

Drilled Hole Identification (Oe .. .j (2.0' N.)

? Extent of Void Unknown /

" ,*t;;*.* {... .:,?*;  ;** '/DATE NOTES Maintenance Shop Drilling Locations Dec 2011 Nominal floor slab thickness is 5.5". Cross Section B-B Vertical Scale is 1" = 5".' Station FortSttionFIGUREalhon Horizontal Scale is 1" = 5'. Omaha Public Powvet Distiict Plant and Facility Geotechnical 4-13 and Structural Assessment 4-13

Column MG-15 (1.5' Offset N.)

WSW ENE 1-1 1-3 1-6 1-8 1-12 1-14 EW V11 (0') (0.5 N.) (1.0' S.) (2.5' S.) (0 0 Min Significant 0 ? VD _ 2.._ ...

__ _ _ _ _._._...... Void Depth (1")

7~ .0 VD 3.0 VD 1.0 2 4 ......... ..... ... ..1, ........ ...........

. ITop 4

Inches Silt / ClayeySilt (ML) Fill 6 IFill 6

8 VD 8.5" 10 -'

10 0 5 25 30 35 40 C .- C' LEGEND Measured Point DOpth VD = 1.0" Void Depth

-L-4 Drilled Hole Identification n ffot)n (2.0' N.)

Extent of V o id Unknow n * ':/ :. :

DATE NOTES Maintenance Shop Drilling Locations De 2011 Nominal floor slab thickness is 5.5". ..- , ..- Cross Section C-C Vertical Scale is 1" = 5". Fort Calhoun Omah Pubic Station DW*.ID~st~ctFIGURE Horizontal Scale is 1" = 5'. P o DiFIGURE Plant and Facility Geotechnical 4-14 and Structural Assessment

Page 4-52 Key Distress Indicators Rev. 2 4.3.7.2.2 SCP Test Results SCP tests were performed as described above. Data obtained at each drill-hole are summarized below in Table 4-4.

Approx.

Correlated N-value Comments refusal 36" BTOS refusal 6" 8

BTOS

Page 4-53 Key Distress Indicators Rev. 2 1-16 0.0-0.5 9 2 very soft 16.5 ESE refusal 8.5" 0.5-1.0 54 14 stiff BTOS EW- 1 0.0-0.5 39 10 stiff 19.0 ENE refusal 7" 0.5-1.0 55 14 stiff BTOS stiff refusal 6" EW-2 0.0-0.5 58 15 45.0 ENE refs BTOS EW-3 0.0-0.5 59 15 stiff 65.0 P, ENE refusal 5"

~BTOS stiff *i'dL*S0 .....**** E.'. ':

a...., fusal 5" reul EW-4 0.0-0.5 56 14stf

.. 4*:i*: *, <:Y :**,;* BTOS stiff *- refusal 5 NS-! 0.0-0.5 52 13 stiff 3 0re.f.sl.

0.0-0.5 50 13 stiffW"=-west NS-2 0.5-1.0 32 8mred. stiff *'.0* NNW * *faa 45 1.0-1.5 46 12 stiff  ::"* *<": * " ":'*¢ *

• Notes:. . . ,

(1) Approximate values based on scaled investigation plan dIrawlngs), not-field measured'*

BTOS = below top of subgrade.* .. t: 'i;r" .",,

N = north, S = south, E = east, W = west \_,j>

No voids were detected below the top o a the settled

,ugiadeat die est 1t'~f Auroudin h ete

,orlte*df*, ert building column. Based on N-va-ITsuncorected) cone index results, medium stiff to stiff fine-grainei1swere encountered at all tef'lcations. Very soft to soft soils were sometimes encouner, the upper 6 "e of subgi e.

The Humboldt, anufacturer) uiser 7,s~manual for the SOP test device provides a coefficient of 0.25 fo"&ti Adrect readvale Wof cone index (Qj)in kilograms per square centimeter to N'I:Vlue. The Humboldti Manual stat6ýkthat the correlation was determined through extensive

,fleldj-sevainrequired but is not abs'oljte, in the* ýd should lie-Verified for local soil types. Because of the hydro-

'46ipjb X r ed i pe10 feet of :dEftst borings completed during the geotechnical investigation, direct correlatiQ.i. Mth on-site sdi'ls was not possible. As such, the N-values jprovided 3.V,in the data table abce ,Cdllde not based on correlations with site soils, and were used

,oiiiyfor qualitative comparisoind evaluation in this investigation.

4. 3".ý-3,D.CP Test Results,7 DCP testing*x*s perforiee'n& t drill-hole 1-12. The DCP test was performed from about 4.3 feet to 24.2 feet lhelovto f subgrade. No voids or very soft to soft soil zones were detected by the DCP tes'yNiconei6mdex correlated California Bearing Ratio (CBR) values ranged from about 6.5 to 50. Cýone index correlated bearing capacity ranged from about 2,000 to 7,000 pounds per square foot. Anomalously high CBR and bearing capacity values were obtained for soil at about 60 inches below the top of subgrade; these values are related to unusually high blow counts believed to be the result of the cone tip encountering a particle of gravel and are not included in the CBR and bearing capacity ranges mentioned above.

4.3.7.2.4 Shelby Tube Samples and Laboratory Test Results Soils encountered during Shelby tube sampling were generally logged as silt. At one 12-inch interval (1.0 to 2.0 feet below top of subgrade) the material encountered was logged as lean

Page 4-54 Key Distress Indicators Rev. 2 clay. Shelby tube advancement/recovery ranged from 8 to 18 inches. Refusal was encountered at both test borings at about 4 feet below top of subgrade on coarse gravel (crushed limestone) believed to be at the previous plant grade and placed during original plant construction to stabilize the ground surface for heavy equipment traffic.

Moisture contents of the sampled soils ranged from 17.2 to 24.8 percent and averaged 20.6 percent. Void ratio (based on an assumed specific gravity of 2.7) ranged from 0.591 to 0.731 and averaged 0.600. Percent saturation (based on an assumed sp eýfc gravity of 2.7) ranged from 78 to 96 and averaged 86.

Wet unit weight ranged from 118.8 to 125.9 pcf and avwarged 123.6.cf. Dry unit weight ranged from 97.3 to 105.9 pcf and averaged 102.5 pcf. aibed on aiassumed'Standard Proctor dry density of 104 pcf, estimated relative compaction ranged 4 to 1Oercont and averaged 99 percent.

4.3.7.2.5 Previous Geotechnical Investigation Report1-In 1977, a geotechnical investigation and repote by Geo hical Services, Inc.

(GSI) to support the foundation design of the jMainnane chop buildingc fiie.nvestigation included 4 test borings (one of which was adv'anced in th&eAixiidiate vicinity Building Column MG-15), field SPTs, collection of subsurface soils usig.4hm-walled Shelby tube and standard split-spoon samplers, and laboratofrytesting. ATenvesi*.t n indicated that the southern portions of the planned buiRing fo~oprint (metudding rls~l onwhic Building Column MG-15 is founded) consiso'dbf 7 to 9 feet6f1,oess derikd fill that classified as medium stiff, low plasticity glt (ML). Fin slaiy fill wa.....countered along northern portions of the planned buil4  %..6tprint. Below*h!fi.r 1 1. iu~ dense to dense stratified alluvium incuiding sandy siltjcaiys, Fine sands, anID'clyeams were encountered. The report1edihei e following:

• J ;ebuilding could*Oe supported o 4shallow foundations.

SExisting site fills are sultabte.

" .Cohesive soils would proVl&a safe neikESr=3) allowable bearing pressure of 2,000 psf.

settlement of3/ to 1'ffilkwould be expected.

" S'ettlement would be rapid'dýr! .settlements lfferental, would not be a problem.

4. " and d.&onclusions Observatio4s &si the condi,.tions' underlying the floor slab in the vicinity of Column MG-15 confirm tha e subgre h......as subsided and a void space has developed. The void space ranges from about noneto in depth below the bottom of the floor slab and extends about 15 feet to the north, ea. and west-northwest of Column MG-15. The lateral extent of void beneath the floor slab to the south, southeast and southwest was not determined by this investigation.

Field testing including SCP and DCP tests on the subgrade soil below the floor slab did not identify the presence of voids or soft soils below the top of subgrade at tested locations. Field observations and laboratory testing from this investigation and from the previous GSI investigation are in general agreement and indicate that the fine grained loess derived fill in the vicinity of Column MG-15 consists of medium stiff to stiff, low plasticity silt that has allowable bearing pressure of 2,000 psf or greater. Neither field observations nor field and

Page 4-55 Key Distress Indicators Rev. 2 laboratory testing performed for this investigation indicated poor fill placement or conditions that would result in subgrade or column settlement of the magnitude observed.

Based on these observations and field and laboratory test results, the subsidence and resultant void identified below the floor slab and the column settlement and apparently related settlement cracking expressed in nearby masonry walls is not attributed to the Triggering Mechanism of Soil Collapse (due to first time wetting). As such, the CPFMs associated with this Triggering Mechanism; 7a - Cracked Slab, Differential Settlement of ShallowT'oundation, and Loss of Structural Support; 7b - Displaced Structure/Broken Conneepons.,ild't7c -'General Site Settlement, are ruled out for the Maintenance Shop.

In addition to the distress in the Maintenance Shop, cr

• ave r ceily 1e6eserved and documented in the Technical Support Building in areas cdt ith, southfwestand west of the Maintenance Shop distress area (area of subgrade void a.e.*,edcolumn, andx[MI Iracking).

The results of the assessment for the Technical Support C* 'Section5.5) 5 in}dicie.-tlhaf' this. distress is associated with KDI #3. Therefore, the Tiring** Mechanismof se and its associated CPFMs listed above are also ruledco-tfor the Technichal,,Support Center.

The results of this KDI #3 forensic investigationl h 'wfhaiatfie Tnggerigi echanism of Subsuirface Erosion and Piping (due to punjg- is likely tfsensible for tht:Ub~idence and related void and settlement distress in the *Tlntenance Sip he distress (&acked walls) in the Technical Support Center. Voids, mate-a1lloss, and material...yer.ents have been identified by investigations in the&r.Tin e T Mfinludi'g along the

,*0 . "s .AncuiMen, north wall of the Turbine Building*which O isdistre.

andiien a ,sharef t adjoining WAI,vý with the ain ten anMaintenance ce S o r Shop. The voids/subgrade squent and Shop are believed to be directly relat* *p subsurface p*p g er-n asiind soil losses occurring at and radiating QUt fromuamaged subfio drain pipes in the.1, AineBuilding subgrade.

ot-fod a,ýd appes p...d,...w.,- "*0, t.. It` es that material has been removed below the Turbine. Building north"Wli1through pip*i*rigs a result of the hydraulic gradient created by the breaks in the subfloor dreaii*.s. Pipin sbeen evidenced by depressed groundwater levels,

• measured voids below the Tiubine Building asement floor slab, and sediment accumulated in the Turbine Building sump pit4*le depressed groundwater levels and void conditions are 40.Ieprominent near the northWest portion of the Turbine Building adjacent to the observed kDF.#3 structural distresses. W`e..,presume that the piping and void conditions extend north beyý'dfe'ýq extents of the TurineBquilding basement floor slab and below portions of the Maintený**e,ý,Shop (and Te*fiical Support Center). The soil column above the presumed piping andQViid condit 'ioirsistliought to be subsiding as a block unit, or column and translating to the groun' ,'resulting in the void space observed below the floor slab. It should be noted that our investigation was not exhaustive. Subgrade void space was not delineated to the south, southeast, 6r.southwest (see Figure 4-11), which are toward the locations of observed/measured groundwater flow, groundwater lows, and voids below the Turbine Building basement. It should also be noted that wall cracking expressed in the Maintenance Shop masonry walls of the Men's restroom appears to be expanding (crack aperture appears larger than previously noted during structure observations in August/September 2011).

Page 4-56 Key Distress Indicators Rev. 2 4.3.7.4 Recommendations HDR's recommendations are listed below.

The results of the KDI #3 forensic investigations have found that the distress observed in both the Maintenance Shop (failed column) and the Technical Support (cracked walls) are not associated with the Triggering Mechanism 7 - Soil Collapse (due to first time wetting).

Therefore the CPFMs associated with this Triggering Mechan,, (7a-7c) have been ruled out by this forensic investigation. The results show that~he ds s.i the Maintenance Shop and the Technical Support Center re conne te fI #1, which is associated with the uncontrolled drainage of the gruqiidwater inoti b" ken Turbine Building basement drainage system piping. KDI #1 i*ý41;0:'% ssoat,........

d it"he11.riggering

,td!he dpplcbetth Mechanism of Subsurface Erosion/Piping (due to pump an), CPFýMi to the

" -licable Maintenance Shop and Technical Support Center is 3a -Jlndemiining and "settilentof shallow foundation/slab (due to pumping). This CPFM i iyv.be ruled ouiilhe',j;<Ž-

physical modifications presented for KDI #1, as presen{ted inS*ection 4.1 of this A9Ssihnt Report, are implemented. , ,..

It is recommended that OPPD implement wgidasemo ,ns tof,*mdiate the distress in the Maintenance Shop as planned (helica.. and This ma di>.my not affect veri" adjacent masonry walls exhibiting settlemt cracking cWevr, this d6$ipothing to mitigate the likely cause of the observea,. aintena h aistresses Subsurface Erosion and Piping. Nor does it ensure that e distres'sý,iil not -uealized in other structural components of the -yebuilding imiby ie a that'i, istress,,Yn distres also be a.ffected by Subsurface Erosion and Piping but notyet expressgany observal'istress. Ftre distress could include other building support colbnr"s. the adjacent dlexrator shaft".an'd other nearby masonry walls (load Ibn noted that d not determine the extent of settlenifYfiorwoids to thieout,<<* "Nh,southeast, or sAb'otfwes of settled Column MG- 15.

4N1, eR et.iktions

ý are recommiended for the purposes of this Assessment Report.

• wver, o furthernvert.1gations co undertaken by the owner as part of the design for

ý1'bremedial work to p -Aihe Maintdiaii"e Shop and Technical Support Center distress.

/This could include inveati on of the si:ade below the floor slab in the Maintenance

. Shop to the south, southat.2and southwes~i of Column MG- 15 to include drilling, coring, SCP and DCP tests, soil s4pling, and laboratory testing as appropriate to delineate the

• area of subsiding subgrade andridentify other structural building elements at risk. It is

\fui-t*r.recommended that'fthei hysical modifications outlined in the KDI #1 forensic investigations be competed.before the physical modifications to remediate the distress in the Mdihite.nance Shop0,,pdTechnical Support Center are implemented. This is to ensure that the ssu siaceeroskin/piping associated with the broken pipes under the Turbine Building iiasement slab is halted. Continued subsurface erosion/piping would most likely reduce the effiacyof any physical modifications designed to remediate the distress in the Maintenance Shop and the Technical Support Center.

4.4 Comparative Evaluation of Geotechnical Analyses The purpose of this comparative evaluation is to assess the potential impacts of the 2011 flood on the overall geotechnical conditions at the FCS site. This assessment included a comparative evaluation of new and existing geotechnical data in an attempt to assess whether the foundation soils have been disturbed or weakened from the sustained high water.

Page 4-57 Key Distress Indicators Rev. 2 The primary basis of comparison for this evaluation was provided by 1) the penetration resistance data recorded during drive sampling and seismic refraction surveys completed as a part of the pre-flood investigations, and 2) the subsurface investigations conducted for this assessment. The penetration resistance data from these investigations provide an indirect but useful indication of the relative strength and stiffness of the subsurface soils and bedrock at the FCS site. The seismic refraction surveys provide an estimation of the p-wave (compression) wave velocity, which can be an additional indication of the relative strength and stiffness of these materials.

4.4.1 Site Conditions Site grades before construction at the FCS site generally ranged frin abou 1000 ft. At the boring locations for the current investigations, the site grades taried from.r] 5 ft.

For reference, the generalized subsurface profile at the FCS site consistscf 1 iAg sitata in descending order:

• A 1- to 10-foot-thick layer of existing earth fill, most of which was plaD ime of the original construction

" An intermittent layer of soft to firm, fine alluviur s-'s that lickness from 0 to 20 feet *.a Xthat

" A 50- to 60-foot-thick layer of loose to dense, r granu a11u.,u silty to poorly graded sands with some clay seams) -,

• Limestone/shale bedrock at depth of aout, 75 f . !esent gradp.§ it about el. 930 ft.

The granular alluvium at the FCS sit *i.ense layer of recent alluvium extending to about el. 960, luvium extending to the top of rock. r _

Groundwatej1leovels at'ihe-'times.6of the pre-flood and current investigations varied in elevation from about 98.61 "Jo 001 ft. River leVe-sAL'dbring the 2Q.JJ4flood reached a high water elevation of apprpimaately 1006.9 ft.

Addli iofiial discussions of the geologa1ic-and geotechnical conditions at the FCS site are provided by Dames{&:Moore (1967, 1968) and HDR` (2011).

4.4.2 Pre'F .octnvestigations 4.1.1.1 - Dames & Moo~ireDrive Sampling The majority o*ftheegetechnical data obtained from the pre-flood investigations was derived from the subsurfeiic vestigation completed by Dames & Moore (D&M, 1967, 1968) of New York, NY. This investigation consisted of advancing 73 test bonings in the area of the main facility using 3.25-inch diameter hollow stem augers and drive sampling at 5-foot intervals in the overburden soils and BX-size rock coring in the bedrock. The depths of the borings ranged from 50 to 150 feet below grade.

The Dames & Moore "Type U" sampler and the Standard Penetration Test (SPT) sampler were used to collect samples and measure driving resistance as the number of hammer blows per foot of sampler penetration. The D&M sampler retrieved 2.42-inch diameter drive samples using a 300 to 350-pound weight falling a vertical distance of 24 inches (energy = 600 to 680 foot-

Page 4-58 Key Distress Indicators Rev. 2 pounds). The SPT sampler retrieved 1.375-inch diameter drive samples using a 140-pound weight falling from a vertical distance of 30 inches (energy = 350 foot-pounds).

4.4.2.1 Dames & Moore Seismic Refraction Surveys Three deep and one shallow seismic refraction surveys were also conducted as a part of the 1967 D&M investigation. The deep seismic surveys, which ranged in length from 600 to 1000 feet, were conducted to investigate the depth to rock at the site, as,.Well as to estimate the p-wave velocities of the overburden soil and underlying bedrock. TI 150sallo I survey was 60 feet in length and was conducted to investigate an anomaly idW Iedi -ie -dsurveys that was determined to be a group of timber piles.

The results of the seismic refraction surveys from the DY&M invCation are presented in Attachment 5A. A summary of the estimated p-wave velocities are presentedin .Attachment 5A, D&M Plate 1I C- 1. The estimated p-wave velocities ,Wver6'ifou to vary from 10Q*Q* 200 feet/second between depths of 0 to 46 feet (or from about 61 g. 95 to 960 feetj,j 61 ..

feet/second between the depths of 46 to 70 feet (from out elevati'Ioii,3.Jeet). The p-wave velocity in the bedrock was estimated to be 15,30 05&ond.

4.4.2.2 Other Pre-Flood Investigations ,ý The results of other pre-flood investigations conducte4at the F('10 wev also used in this evaluation, including the following.,studies:

The 1987 investigation by W6o*ward-Clyde ý*91*ltans I( AC, "nsult.nts ........ 1987), consisting of 21 borings at the site of the aining Center. .

• The 1989 investigation b- ooddyard-Clyde C6 isitantsVWCC, 1989), consisting of 14 bon"lisif**of the Administration Building.

.el0.,.,

23 vestgatlon-completed_by.ŽShaw Stoneo& & Webster (SS&W, 2003), consisting 9 b and el'*v*(11) CPTs atithe'site of ISFSI.

4;4.2.3 Boring Location' 'Plans and Los" SThe-logs of the borings from the pre-flood investigations are not included as a part of this

>echnibal memorandum. How'vqr* a tabular summary of the pertinent penetration data from thee'iefod investigations aieowvided in Attachment 5B. A Boring Location Plan for all of the pre-floodinvestigationsisýro6vided in Attachment 5B, Figure 1.

4.4.3 Current Investigation, 4.1.1.1 General The current subsurface investigation was completed by Thiele Geotech of Omaha, NE, in September of 2011. This investigation consisted of advancing 9 test borings and 12 cone penetration tests (CPTs) across the entire site. The locations of the borings and CPTs for the current investigation are shown in Attachment 5B, Figure 1.

Page 4-59 Key Distress Indicators Rev. 2 Prior to commencing each boring and CPT, OPPD required that the upper 10 feet of soil be hydro-excavated (soil removed by jetting and vacuuming) due to the potential for encountering shallow utilities across the site. As a result, no soil samples or geotechnical data were retrieved from the present ground surface to a depth of 10 feet at these locations.

Detailed discussions of the current investigation are provided in HDR (2011).

4.4.3.1 SPT Sampling The test borings were advanced to depths of 46 to 76 feeAtit.s a .. b ow grade.

Sampling of the overburden soils was completed using3,g25inch dia.hrnte'ollow stem augers and drive sampling using the SPT sampler (ASTM D lf48a S, i ph.e borehole was maintained during drilling with the use of bentonite sluiy!*

Prior to drilling and sampling, the SPT hammer systems on' 9.i'aiildr1rigs to be used in-this..

investigation were energy calibrated by Foundation TestirigandaC-onslting of Ove ridPark, l

KS. The calibration was performed to determine the actual efficiency,*m.transferring the--energy of the hammer blow to the drive sampler. The restilsM'this ca ibratioA'indicated that the efficiency of the SPT hammers used in the curr*n(1 ivýesgation ranged fri' 77% to 83%

(FTC, 2011).

4.4.3.2 Cone Penetration Testing The CPTs completed by Thiele Greote ;sic piezocone rig manufactured by Geoprobe Systefs.. ' ere performed in accordance with ASTM D 508%0. TI pths of 16 to 47 feet below existing grade. Some of the*P`Ts reac1 ion in the dense alluvium at aboute6;v &960 feet. "Xi "T~he c-urrent investigation also mcluded several geophysical testing methods conducted by Ge.otew'qology, Inc. of St. Lo,*'s, MO. These methods included five seismic refraction lines and a se'es-o,. ground pene r.ifi g radar and spontaneous resistivity grids. The purpose of the geophysical.Vtesting, includi. gtNie seismic refraction surveys, was to investigate the overburden soils in an. i..to

't identifthe presence of soft or loose zones of soil or voids that may have developed at tlhýiit&yoinhe flooding.

Locations of the seisfi"ic refraction surveys are provided in Attachment 5B, Figure 2. A full version of the report is provided in Geotechnology (2011).

The graphical results of the seismic refraction surveys from Geotechnology are provided in Attachment 5C and consist of plots of p-wave (compression) wave velocity versus depth along each of the seismic lines. The plots display contours of the p-wave velocities that range from about 1000 feet/second near the surface to about 6000 feet/second at the base of the alluvium.

In general, the magnitude of the p-wave velocities were found to increase with depth, except some isolated zones of lower velocity material were encountered at depths of 40 to 75 feet below existing grade.

Page 4-60 Key Distress Indicators Rev. 2 4.4.4 Interpretation of Penetration Resistance Data Because the drive sampling in the pre-flood and current investigations were completed under variable site conditions and with different equipment and technology, the penetration resistance values (in number of sampler blows per foot of penetration) had to be adjusted for these differences to allow a reasonable basis for comparison. Correction factors were applied to the field blowcount values to account for these differing conditions in accordance with ASTM D 6066-96. These factors included corrections for:

• Overburden pressure at the time of drive sampling, since th? of. hiC was raised about 10 feet since the 1967 D&M investigation, and that groundwaf'evation a esilting effective stress condition varied at the time of each investigation;

• Hammer energy, since drive sampling with the D&M sampl e *iaqpp1*g.reater ajtriou of energy than the SPT procedure (600-680 foot-pounds versus 350 foot-_,.orihS);

• Borehole diameter; since sampling in larger diameter holes is'WS ht.y..ess i efficient in'*afnsff`.i-is g the energy to the sampler than in smaller holes;

" Drill rod length; since drive samples taken with shorterilengths of drill 5.lare more efficient than sampling with longer sections; and Whether thin-walled liners were utilized in the sm withou g p'**c A9 -Ai: ce teueflesis the usofii.ners is les less efficient than sampling without liners.

As described above, each of these variables affectAihnagnitude the iel measured blowcount value recorded at the time of the investigtidn.,"g'WFollowing a e , *eft "' *)This oerecionafctorsie i normalized value is normalized resistance value is developef-. hammer e ncy of 6 .i referred to as N1 60 . An efficiency of"6Q!'ovas selected f6fto-e.. norm value since the commonly used safety hammer with a rope-catjihw ihas an efficiency-,.tbut ' In addition, many of the published correlatiQon.sfS-PZ values AWN properties have een, eveloped using blowcount data from this ham-mnerýsytemýNeer equip m*tat utilizes an automatic trip hammer typically has a higher effifiency 7*0 to 800oj rope-eath,'60 system. Donut-type hammers typically have a rfte lower eJffciency that range fro,a 1 0 to 5-/o Cat* lations of the N160 values and background infom ation for the correction factors are provided in Rtiment5B. Plots of the N1 60 vales. versus elevation of the recorded blowcount for the pre-flood and cu'fr:tiiiwestigations are presented: in. Attachment 5B, Figure A-3. Using the correlations and procedur6s&recomnended by Robertson et a[,(ti986).,,and Lunneeetdbi(l997), estimates of N160 were derived from the CPT data and these data points'have'den incl-ided*in these plots.

As depicted in Attachment 513B'Figure A-3, the N1 60 values from the pre-flood and current investigations show a simriar pattern and scatter of blowcounts that range from 2 to 60 blows/foot along the full depth of the subsurface profile. The mean and standard deviation for the pre-flood and current N 160 values are plotted in Attachment 5B, Figures A-3 and A-4 along the full depth of the profile. These plots also display a similar range and scatter of values.

4.4.5 Preliminary Findings and Conclusions Comparison of the computed N1 60 values for the pre-flood and current investigations indicate that there was no observable difference in the overall geotechnical conditions at the site and that the foundation materials have not been disturbed or significantly weakened from the flood inundation. In

Page 4-61 Key Distress Indicators Rev. 2 addition, comparison of the seismic refraction data from the pre-food and current investigations reveals similar magnitudes of p-wave velocities over the full depth of the overburden soils, and no observable differences were identified from this work. The presence of loose to medium dense zones with lower p-wave velocities interbedded within denser materials confirm the inherent variation in the resistance data retrieved in the pre-flood and current investigations.

Based on these findings and evaluations, it appears that the overall geotechnical conditions at the site have not been significantly altered due to the sustained high water. The o~srved scatter of data points in both plots is consistent with the relatively wide range of strengt rand Aul&Eess Aworresponding blowcounts typically encountered in the alluvial soils within theA lsun r aey, It should be noted that the findings and conclusions from the S !P:oimparativeaioy jt are considered applicable only to those existing soils below a depth of 10 feet a. 'ot *l' tlon of about 995 feet, since these soils were hydro-excavated to avoid daihigfig buried utilities.. The uppe"w 10 feet of soil may have been disturbed from underseepage and hfighkejie, ,adients nts bene'*a,,*

b"e ,

temporary levees during high water. Additionally, disturbance toe, sil coildhave beenVrestetf t from the settlement of utility backfill during drawdown of the-river level an4Fgi&undwater.

It should also be noted that additional test borings a ... e s"te and the m this SPT sampling will be incorporated into this study whenavait'able.

Additionally, it should be noted that these findingl 'ad conclusi' 4s are*p'e applicable to the potential impacts that may have occurred due to the*irpisen *%W'the H43 h pipingeflow wsthfOcret of*.oug lgrofstations.wint into the Turbine Building Sump since the tir e ofourr, site visits current i~v~stigations.

Limitations " .( "

4.4.6 This Assessmenreportkpesents the pieh mmnary findings and conclusions for an engineering evaluation o of the 20Ql,VFlood on the geotechnical conditions at the FCS site. It has beer ared in accordlina'&ihgener)lia't-epted engineering practice and in a manner consistGt With the level of care an,kil for thils of project within this geographical area. No wanty;, expressed or implied, is' 4;le.

Geot'ee al.........

engineering and the geoigi sciences are characterized by uncertainty. The professional judg t psented herein are based or review of available design and construction information provided t rsheresults of field explkbirion and laboratory materials testing by others, the results of engineering evaluaUiions, our general experience and the state-of-the-practice at the time of this writing.

4.4.7 Test Standards

" ASTM D 1586-08a, ,.Statdard Test Method for Penetration Test (SPT) and Split-Barrel Sampling of Soils."

" ASTM D 5778-07, "Standard Test Method for Electronic Friction Cone and Piezocone Penetration Testing of Soils."

• ASTM D 6066-96, "Standard Practice for Determining the Normalized Penetration Resistance of Sands for Evaluation of Liquefaction Potential."

SECTION 5.0 PRIORITY I STRUCTURES

/

\

1<* ~

J

Section 5.1 Intake Structure

.. iz . =: * .~~* -*... .+ :.

/ k . / !.i.:,..!.!.<. **..* . ..<: > .. .? :

/. ..

L

Priority 1 Structures Page 5.1-1 Intake Structure Rev. 2 5.1 Intake Structure 5.1.1 Summary of Intake Structure Baseline information for the Intake Structure is provided in Section 2.0, Site History, Description, and Baseline Condition.

The Intake Structure is located at the extreme east side of the PA and is o*sructed'directly into the riverbank. This structure is subjected to unbalanced soil loads frme*ast the basement walls backfilled on the west and subjected to the river on the e ace. .a-'e The Intake Structure is a multi-floored Class I structure below o .ei1ating 6'bxsel. 410A From foundation mat at approximately el. 960.8 ft to el. 1014.5 ft, the stW;tLu__Sis cast-in-p uQeemeinforced o de The basemql.',

concrete with integral pilasters that align with the steel columns braced by vertical concrete walls and horizontal floor slabs. The mat fbo dfion is on 20-11 irn. metr steel pipe piles driven to bedrock. From el. 1014.5 ft to the roof at approkimately el. 1035.6 ftfh'e structure is a braced rigid steel frame clad with Ar-lite precastconcrete sandwi.ch.panels. The roof is a multi-layer built-up roof supported by metal decking, m ing-'etween open-we sýe.joists. The roof structure is seismically braced independent of the m'& lteck. i..

Y The Intake Structure houses major systems and components, bo.thCQE',and*,non-CQE, in designated rooms. The major function of the Intake S turestpro Missouri River that is required for component cooling and firelting aFort al inprovide the structural support and environmental protection recessary to ensure the, functiownf integrity of the CQE systems and components under operationalfcV1 evaronmental coniiti osn 5.1.2 Inputs/Ref6ren-Ce Supporting thkeAnalysis Table prererencesrpTidedby OPPD'aii-other documents used to support HDR's analysis.

Table*5wl,'54,-, Referencsfor Intake Structure Document Title ' OPPD Do""ment Date Page Number(s)

• !:* Number (if applicable)

System esi,gBasis Document i 'SDBD-STRUC-503 6/22/2010 46, 57-61

__ __ __ *Rev. 10 2009 Structural I 'specion of the Intale., SE-PM-AE-1002 7/16/2009 All Building and Misc.`,\<reas\ / 7, _____________

Incident Report Summary,~ Y CR 2011-56 6/5/2011 All Incident Report Summary CR 2011-521 6/1/2011 All Incident Report Summary CR 2011-5321 6/3/2011 All Incident Report Summary CR 2011-5323 6/3/2011 All Incident Report Summary CR 2011-5377 6/5/2011 All Incident Report Summary CR 2011-5384 6/6/2011 All Incident Report Summary CR 2011-5473 6/10/2011 All Incident Report Summary CR 2011-5737 6/22/2011 All Incident Report Summary CR 2011-5805 6/1/2/011 All Incident Report Summary CR 201 1-5932 7/1/2011 All

Priority 1 Structures Page 5.1-2 Intake Structure Rev. 2 Table 5.1-1 - References for Intake Structure Document Title OPPD Document Date Page Number(s)

Number (if applicable)

Summary of Vibroflotation 1/27/1972 All Naval Facilities Engineering Command, 9/1986 All Design Manual 7.01, Soil Mechanics I Detailed site observations-field reports, field notes, and inspection checd s-it--fof'the Intake Structure are provided in Attachment 8.

Observed performance and pertinent background data are as :o

• The foundation slab is cast with the pipe piles embedded with' ,ee2gncretebma s piivide a "fixed head" condition for the pile design (see SDBD-STRUGC503,)

• The piles consist of 20-in.-outside-diameter pipe with 1.031 -inX.."'alit*iigness, which mi American Petroleum Institute (API) standard 5L GradeB .minimum yied ss [Fy = 35 kips per squareinch [ksi]). The piles were driven open-ended' 6 od. bedrock am*- ad tested for compression, tension, and lateral loads. The pile ,desriallobWedfor .0625-1nu$. consion of the wall thickness and was considered to be an additiona1,1eve. of co &ctfsm due to the1cýhodic protection system (see USAR-5.7). A 2

• The coefficient of lateral subgrade modulus is. based on laterA loadflestmgof test piles in the in situ soil condition, which is conservative Jecause t6granuldrsoils w er&subseqiently compacted.

The in situ granular soils were compact* d via vibrofio itn to m ize the possibility of seismic liquefaction (see Summary of Vibfldration).** n* -

" For the majority of the flood e*7 structure was s'aandbag wall along the entire west face comrbin&wdih, interior lbs and portable p*iWp located at the exterior doors on the east and wetwalls&,

T he"rew

• The surroundiing "co.

rivpbaiian ca~bhle sureonch fiir*jd, the structure~i oected by revetment and slopes downward at 3H: IV.

• Thelir*enwa cable trench coru'ects~to the n south sides of the structure.

Cb* ¢ie-encased service line*iuding the Raw Water return line, connect to the south side of

~th&estructure.

The.. aw. Water supply line and tw'ýYo Fire Protection lines connect to the north side of the building.

• Incidi'entt"trport summaries listed in ýTale 5. 1-1 document many areas of the structure where groundwateir.has infiltrated the bu'ildin*g through previously monitored cracks in the concrete, through wa.ll;enetrations, and tough conduit.

• The Intake St-icet.,is deslgfie..4,to withstand an external hydrostatic load due to flooding of the Missouri Riverto t i.10 4o,,. e SDBD-STRUC-503).

• Without special provisioiis>the Intake Structure can accommodate flood levels of up to 1004.5 ft without water enterin'gOfite' structure. For higher flood levels, protection can be provided by steel flood barriers equipped with seals (up to el. 1009.5 ft) and sandbags and other methods to el. 1014 ft (see SDBD-STRUC-503).

" The building was located outside the Aqua Dam perimeter and was protected by the steel flood barriers and sandbags, with small portable pumps to remove light water infiltration.

• A layer of dried river sediment was present on the north and south grades adjacent to the structure.

• Small localized areas directly at the soil and exterior wall interface had signs of subsidence and scour. However, globally there were no signs of large-scale soil movement.

• Visual observation was not made to the river (east) side of the structure due to high water levels in the Missouri River at the time of the field inspection.

Priority 1 Structures Page 5.1-3 Intake Structure Rev. 2 General observations of the interior of the structure indicated minor concrete cracking with both current water infiltration (damp to slight running water) and-dty walls with signs of water infiltration that occurred at an earlier time. The observed cracking appears to be a condition previously recorded and monitored.

5.1.3 Assessment Methods and Procedures 5.1.3.1 Assessment Procedures Accomplished Assessments of the Intake Structure included the follow . .. _

e Visual inspection of the interior of the structure wi r exceX *circulation tunnel, the north stairwell, and the operating floor a

• Visual inspection of the exterior of the structure where .*sabIle. Inspec e river (east) side of the structure was not possible due to hig P* is at the tim e inspection.

• An assessment of collected survey data to-date cat od 'ehds in the movement of the structure.

• A review of previously referenced docum _, -K.es-e5.1 - 1.

Additional investigations were performed bse inclu wing non-invasive geophysical and invasive geotechnical in gationsg

• Seismic surveys (seismic re refrac icro-tre e )and in the protected area.

(Test reports were not av t the time of ision 0.

• Geotechnical test born pro ected area PD required vacuum excavatieo#f ie first 10 *oposed test ho ~utility conflicts. Therefore, test res t.iavl ,us sieoi soil ccon* in the upper 10 ft of test bor-ing logs. (Test reports inometer ereno read te ri I provide an indication of slope movement installed at th of R r S 2 Assessment Prot " res Not Completed Ft 4, onal assessment pro ,-*es have been identified for this structure.

5.1.4 Anal'yis~i****. ,.

7);

N~ ~ I ~ A, Identified PFMs w ter aiiUw 1 iwed as discussed in Section 3.0. The review considered the preliminary informatio ne,. from OPPD data files and from initial walk-down observations.

Nil be fro osratos Eleven PFMs associated itlft'ive different Triggering Mechanisms were determined to be "non-credible" for all Priority 1 Structures, as discussed in Section 3.6. The remaining PFMs were carried forward as "credible." After the design review for each structure, the structure observations, and the results of available geotechnical, geophysical, and survey data were analyzed, a number of CPFMs were ruled out as discussed in Section 5.1.4.1. The CPFMs carried forward for detailed assessment are discussed in Section 5.1.4.2.

Priority 1 Structures: Page 5.1-4 Intake Structure Rev. 2 5.1.4.1 Potential Failure Modes Ruled Out Prior to the Completion of the Detailed Assessment The ruled-out CPFMs reside in the Not Significant/High Confidence category and for clarity will not be shown in the Potential for Failure/Confidence matrix.

Triggering Mechanism 2 - Surface Erosion I*

CPFM 2b - Loss of lateral support for pile foundation Reasons for ruling out:

" The pile foundation is located below basement elev4 74.7 ft, while grade is at approximate el. 1004.0 ft. Field observai :e erosic *,ve been*

edge.

isolated to a fencepost at the river's

" The bathymetric survey did not indicate significant n at the was under water.

Triggering Mechanism 3 - Subsurface Erosio CPFM 3b - Loss of lateral support forr pil d Reasons for ruling out:

• There is no condition at this stjie ,epu in differential head, thus resulting in loss on.f.l support fo-t e

• The small portable pumps, thl ere used in t e which would not create subsur rosion or viping."

• The pile foundation is Ao e below basy"ment elevation of approximately 974.7 ft, which.

As well below designated nUo I or low river levels.. Therefore, the pile foundation is below

-*,.river level regardless oEAUrate of drawdow n. Soil material around the piles will not be

'd,"nwupward as the rive i subsides.

Triggering hanism.4-ý#,Ydrostatic Lateral Loading (water loading on structures) .:

CPFM ' l fW]. &in flexure CPFM 4d i e in shear CPFM 4e Esdeflection 3-.8 Reasons for ruling out:

• The Intake Structure is designed to withstand an external water load due to flooding of the Missouri River to el. 1014 ft (see SDBD-STRUC-503). The peak flood elevation in 2011 was approximately 1006.9 ft, which is less than the structural design basis.

Priority 1 Structures Page 5.1-5 Intake Structure Rev. 2 9 The structure cannot slide or overturn due to hydrostatic lateral loads because these loads are approximately equal on all sides of the structure.

0 Visual observations did not identify distress to the structure that can be attributed to this PFM.

Triggering Mechanism 5 - Hydrodynamic Loading CPFM 5a - Overturning CPFM 5b - Sliding CPFM 5c - Wall failure in flexure CPFM 5d - Wall failure in shear CPFM 5e - Damage by debris CPFM 5f- Excess deflection Reasons for ruling out:

" The Intake Structure is designed to withstand an extern wat .due to floodi.1% e Missouri River to el. 1014 ft (see SDBD-STRU 503). The pe ,d elevation in 2011 was approximately 1006.9 ft, which is lessh 'ctural design-.a,

" The reinforced concrete walls of the Inta k ctur e riginally dosged to withstand blast forces, making the likelihood of daiage from 'debris small'.,

" Visual observations did not identify d s tote the,5 tire at can be attributed to these CPFMs.

• Triggering Mechanism 6 - BuoanCy, Uplift F s on Stru res CPFM 6a - Fail tension ples CPFM 6b - Cracked sla fes structural su CPF 6c-Nisplaced StrU L.LNbroken connections.

Reas'onsf rulingý ut

5The T Intake Structure R 3esined to wilst an external hydrostatic load due to flooding of the Missouri River to el. `24.1-ft (see SDlI4-STRUC-503). The peak flood elevation in

"-N,2011 was approximately l OO!9 ft, which is less than the structural design basis.

,~ Vsual observations and surv measurements indicate no structure movement. Therefore, failed .tension piles (CPFM ki)and displaced structure and damage (CPFM 6c) did not Triggerin, ech Soil Collapse (first time wetting)

CPFM 7 "Isple.0dstructure/broken connections CPFM 7c-NerA ite settlement CPFM 7d - Pilf buckling from down drag Reason for ruling out:

• The Intake Structure is directly adjacent to the Missouri River. The soil surrounding the structure, including the subgrade under buried utilities leading to the structure, is normally in a saturated condition.

Priority 1 Structures Page 5.1-6 Intake Structure Rev. 2 Triggering Mechanism 10 - Machine/Vibration-Induced Liquefaction CPFM IOb - Displaced structure/broken connections Reasons for ruling out:

" Permanent equipment that has the capacity to produce significant dynamic forces due to vibration is mounted on the base mat foundation slab of the structure. This structure is below the river level regardless of the flood elevation. 6ý§

• Temporary pumping equipment located on the ground :itbm bequaJDam perimeter produced minimal localized vibrations, which were Wose e re and therefore deemed to have inconsequential effect. disp ii"nt No broken structural connections or structural d ent wsp seI,ýed.*,

" This is not a changed condition due to the flood. ThtAfl¶vibehaýbt tkc-ture Wsr nnsevc 38 years under similar saturated soils and machine viba

• The in situ granular soils were compacted via vibrofl t~io t , imize the po6 sjfll t F liquefaction.

Triggering Mechanism 10 - Machine/Vibratidii-i i*ced Liquefactio.i CPFM 1Oc - Additional lateral force on b raib 'atf§ Reasons for ruling out:

• Permanent equipment that ha l capacity to prk-d signiforces due to vibration is mounted on the bale ,ý`t foundaoftn lab of the structure. This structure is below the river level regatdl ss of the flood e o

• Temporary pumping equipmexhocated on the O, i -n the Aqua Dam perimeter producedý.mjmnmal localizeda tons, which we*effsrf efrom the structure and therefore d4eefeh',ane, nconsequentid-fWfect.

• TihiJsi not a chAýege'condition diue tothe flood. The Intake Structure has been in service 3.8" years under similar saturated soils.,and4machine vibration.

,4:ý ,Iihein situ granular soils*were compa&tedWia vibroflotation to minimize the possibility of

-'*" liquefaction.

r lgering Mechanism 10 - ]laý?inne/Vibration-lnduced Liquefaction CPM* 10d -dPile/pile gro. pinstability Reasons fo:44i'ng out*:

• Permaeniit menlathat has the capacity to produce significant dynamic forces due to vibration is ni,*.onted on the base mat foundation slab of the structure. This structure is below the riv ei level regardless of the flood elevation.

• Temporary pumping equipment located on the ground within the Aqua Dam perimeter produced minimal localized vibrations, which were offset from the structure and therefore deemed to have inconsequential effect.

• This is not a changed condition due to the flood. The Intake Structure has been in service 38 years under similar saturated soils and machine vibration. Reviewed condition survey reports do not indicate signs of distress that would be attributed to pile instability.

• The in situ granular soils were compacted via vibroflotation to minimize the possibility of liquefaction.

Priority 1 Structures Page 5.1-7 Intake Structure Rev. 2 Triggering Mechanism 11 - Loss of Soil Strength due to Static Liquefaction or Upward Seepage CPFM 1l b - Displaced structure/broken connections CPFM 1l c - Additional lateral force on below-grade walls CPFM 11 d - Pile/pile group instability Reasons for ruling out:

" The Intake Structure is located outside the Aqua Dam .ubjected to floodwater and is therefore not subjected to static liqi

• This is not a changed condition due to the flood. T*f*. been in service 38 years under similar saturated soils.

Triggering Mechanism 13 - Submergence CPFM 13b - Corrosion of structural elements Reasons for ruling out:

" The Intake Structure is directly adjacent to t1Te D structure, including the subgrade under. 1* ed utilities is normally in a saturated condition.

" This is not a changed condition due toj.Al ood. i. been in service 38 years under similar saturated(oils. Riewe4*. do not indicate signs of distress that would b*.atnbuted to co iswon c Triggering Mechanism 14'-ý,tEr Effects CPFM !,a,-=Heaving, crusI* i h4 r displacement and susceptible connecting utilities are

,of Credible Potential Failure Modes iy CPFMs carried forward for detailed assessment for the I'201 1 flood. This detailed assessment is provided below.

Triggering i *imnisffi

- Rapid Drawdown CPFM 12aJ-R:verbafk slope failure and undermining surrounding structures CPFM 12b - tLa ectra- spreading The Triggering Mechanism and CPFMs could occur as follows: the river level drops faster than pore water pressure in the soil can dissipate. The saturated soil is elevated above the dropping river level. The sloped bank of the river provides no lateral pressure support for the saturated soil. At some point, there is insufficient support on the river side to support the saturated soils. At that point, the soils experience slope movements or even failure. Generally, slope failures associated with rapid drawdown are relatively localized and shallow in nature; however, deeper failures can occur.

Priority 1 Structures Page 5.1-8 Intake Structure Rev. 2 Floodwater elevations, at the time of HDR's inspection, were above finished floor elevations, and river levels were being lowered at a relatively slow pace. River elevations were still well above normal levels. The drop in elevation of the river is expected to occur at a higher rate than the drop in elevation of the groundwater. This will result in an increased groundwater gradient. This increase could cause localized riverbank slope failure and/or lateral spreading.

At the time of Revision 0, the river level had dropped to a nominal normal level (roughly el.

994 ft). Field observation of the river bank area has not been perdirmed since the river level dropped. 116 Adverse (Degradation/Direct Floodwater *l,*_?rFe (Vgr °nFDirect" Impact More Likely) Floodwater-Mpc s Likely)

The Intake Structure is in close proximity to the DrawddWT1iinmrdions requirt 4zogger this river. CPFM had,1b1 o rred at the tii eofthe field report. Th&&efield observationsýadata.ý>,l.

that discre-idithisC=PM, could not boe* i'Wj' Utilities provide many potential flow paths to Soils in the area of'*t$Wn Undergroun'ttble and around the structure. foafpithoo atni the east a l materials that

,Ni W "e*leacnd compac dding construction

/ ]f site ul m ents and tnI Rewould be expecte sssusceptible to apid drawd vnimodqlts;

i1 .1with rip p Elevated saturated soils and elevated floodwAt`er i3 The,'riverbank sou"th offe Intake Structure is levels provide a water source. A potential pat x" p.b.tee*,"d w thri'ap'- ,,

for water and soil migration can exten under the structure to the river, causing*4verse effects attributed to river drawdown. ,4", '.

, The riverbank to the north of the Intake

.. Structure is protected by sheet piling.

.... Review of survey data to date indicates no trends

.'* , in structure movement.

Piles support the Intake Structure, reducing the

@ K.-"-',risk that the structure will be affected by shallow

... undermining.

- {Survey data to date does not identify movement of the building.

Data Gap: 4

" Obse %,,aLaioof the eroank following drawdown to normal river elevations

• GeophysiMainvestigatin data to address observed concerns S-I. . .I-Inclinome' gjLý w l pprovide aan indication of slope movement l,-tat will

• • t*r:."

Conclusion Significance Potentialfor Degradation/DirectFloodwaterImpact River stage level has receded and stabilized at a level corresponding to the nominal "normal" river level at 40,000 cfs as of October 4, 2011. The potential for degradation from drawdown is low because it has not been observed as of October 4, 2011. Rapid drawdown has been controlled, and continued river drawdown is not expected to occur at a rate that would initiate

Priority 1 Structures Page 5.1-9 Intake Structure Rev. 2 this Triggering Mechanism. Because it is believed that a potential for degradation of the foundation exists but is not likely, the potential for degradation is considered low for this Triggering Mechanism and associated CPFMs 12a and 12b.

Implication The occurrence of these CPFMs could lead to excessive movement and negatively impact the integrity or intended function of the structures and systems surroukding the Intake Structure.

Therefore, the implication of the potential for degradation i ;hi<bh" Confidence At the time of the field report, conditions required to ii the 'Tgering* echanism associated with CPFMs 12a and 12b had not yet occurred. jeldý.6'servationlýd *e.`.er investigation data required to evaluate these CPFMs hav e ;-: n ade; therefi h ,,

evaluation cannot be made.

The data available at the time of Revision 0 are io su.Ff.ibent to rule 61t t ese CPFMs or lead to a recommendation for a physical modificatiob*toiensurethat river baf, sm, failure and lateral spreading will not occur. Therefore, bie-Obnfidenc ",In.h above assessient at this time is low.

Summary '*" / *,,

For CPFMs 12a and 12b, as dis{tssed above, the pýot'ential for degradation to the river bank surrounding the Intake Struc s jow because th aLk is pfleted. In the unlikely event that these CPFMs were to occurt ilication of this tqegifinto the structures and systems

........ut e .hgThe combined*consideration of the potential for degraannte iffijlmlcations of hatNdegradation to this structure put it in the "not sig1ifiqant" categorS

• dta curreiitlyeollected are not sufficient to rule out these CPFMs.

Tieefore, the confidenr ineihe above assessment is low, which means that more data or

°,4Zcontinued t nn indspecons are nreqssary to draw a conclusion. These data will be

,* ,ailable insubsequent revisions-f this Assessment Report.

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Priority 1 Structures Page 5.1-10 Intake Structure Rev. 2 5.1.5 Results and Conclusions The CPFMs evaluated for the Intake Structure are presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

5.1 .6 ,Riýwmended Actiobrký Coniucd monitoring is recommended to include a on-tinuation of the elevation surveys of the p e ous'lidentified targets on this situlre and surrounding site. In addition, a review of the ongoing~geoysical investigations and monitoring of inclinometer readings is recommended. The purpose iss wtonitor

• for signs of stru*2i distress and movement or changes in soil conditions around the structure' Th&-results of this monitoring will be used to increase the confidence in the assessment results. Elevation-'viseys shouldbeer*eformed weekly for 4 weeks and biweekly until December 31, 2011. At the time-of Revision 0 groundwater levels had not yet stabilized to nominal normal levels.

Therefore, it is possibil&th'atne ".di stress indicators could still develop. If new distress indicators are observed before December312.011, appropriate HDR personnel should be notified immediately to determine if an immediateimspection or assessment should be conducted. Observation of new distress indicators might result in a modification of the recommendations for this structure.

Priority 1 Structures Page 5.1-11 Intake Structure Rev. 2 5.1.7 Updates Since Revision 0 Revision 0 of this Assessment Report was submitted to OPPD on October 14, 2011. Revision 0 presented the results of preliminary assessments for each Priority 1 Structure. These assessments were incomplete in Revision 0 because the forensic investigation and/or monitoring for most of the Priority 1 Structures was not completed by the submittal date. This revision of this Assessment Report includes the results of additional forensic investigation and monitoring to date for this structure as described below.

5.1.7.1 Additional Data Available Tb e following additional data were available for the In isions liStrucrfir 1 and 2 of this Assessment Report:

0 Additional groundwater monitoring well and river stag* fl -id'atafrom OPPD,:.

6 Field observations of the river bank (see Section 5.25).' "

0 Results of geophysical investigation by Geotechnology, Inc. (seeAttA4i*ment 6).

0 Results of geotechnical investigation by Thje1Get Inc. (see Atment 6).

S Data obtained from inclinometers by Thieqle Wieot-ýj~' (see Attach iit6).

S Results of continued survey by Lamp 45Ai rson andj4ssoij1es (see Afttiament 6).

5.1.7.2 Additional Analysis The following analysis of additic Structure:

Groundwater monitorinklW 1 frdmiOPPD.

d to nominal normal levels.

ýAý,Fi 1 observation§- iver-bank No significance distressbom the 2011 Flo6d was observed.

" . ':Results of geophysical investigation report by Geotechnology, Inc.

$,5ibismic Refraction and Seismic ReMi tests performed around the outside perimeter of the power blo.ck identified deep anomalies that could be gravel, soft clay, loose sand, or pos4siblyv,oids.

Results of'geo!echnica] investigation by Thiele Geotech, Inc.

Six test borings were drilled, with continuous sampling of the soil encountered, to ground truth the Geotechnology, Inc. seismic investigation results as part of the KDI #2 forensic investigation. Test bore holes were located to penetrate the deep anomalies identified in the seismic investigation. The test boring data did not show any piping voids or very soft/very loose conditions that might be indicative of subsurface erosion/piping or related material loss or movement.

All of the SPT and CPT test results conducted for this Assessment Report were compared to similar data from numerous other geotechnical investigations that have been conducted

Priority 1 Structures Page 5.1-12 Intake Structure Rev. 2 on the FCS site in previous years. This comparison did not identify substantial changes to the soil strength and stiffness over that time period. SPT and CPT test results were not performed in the top 10 feet to protect existing utilities.

Data from inclinometers to date, compared to the original baseline measurements, have not exceeded the accuracy range of the inclinometers. Therefore, deformation at the monitored locations since the installation of the instrumentation has not occurred.

• Results of continued survey by Lamp Rynearson and Associates* L Survey data to date compared to the original baseliiies.surveys hav,eot exceeded the accuracy range of the surveying equipment. There ef aina emonitored locations, since the survey baseline was shot, has not Occurred "

The CPFMs that could not be ruled out in Revision 0 are aobased on t fhe additional data available for Revisions I and 2 of this AssessmentReport.

Triggering Mechanism 12 - Rapid Drawdown-:],....

CPFM 12a - River bank slope failure ande-inr 1 nm!iisurrounding structures CPFM 12b - Lateral spreading The Triggering Mechanism and CPFMs coi occur a~d,1i ows'"The.-iver level drops faster than pore water pressure in the soi,[ di4ss 'i*ea e dropping river level.. The sloped f thie riverpo. 'ides no .tI

& ,ressure support for the saturated soil. At some point therls insufficient*su ol onrt Ver side to support the saturated soils. At that poiit,1 )ils experience .- m eints or even failure. Generally, slope failures associated withtrij.l rawdown are rel,, riocalized and shallow in nature; however Ri es can oce&f.

SDdnificance ./..

,.otentialfor Degradation/DirectFloodwater.Impact ii 'groundwater monitoring weldata and river level data indicate that excess pore pressures drawdown had generally gaofTiverdissipated by about October 14, 2011. Field observations o iver af Bank on Octobern.O 2011, did not identify deformation of the river bank that couldWjat*iributed

• ,-L. * ,.

to slopefai;6

• i._:'

or lateral

. spreading. Therefore, it can be concluded that neither sope*,raiure nor ]aterasfpreading occurred due to the 2011 flood.

Because it is b5leve&that a potential for degradation of the structure exists but is not likely, the potential for degra~doin is considered low for this Triggering Mechanism and associated CPFMs 12a and Ib; Implication The occurrence of this potential degradation could lead to excessive movement and negatively impact the integrity or intended function of the structures and systems surrounding the Intake Structure. Therefore, the implication of the potential degradation for the Intake Structure is high.

Priority 1 Structures Page 5.1-13 Intake Structure Rev. 2 Confidence Field observations of the river bank and review of the groundwater data indicates that neither slope failure nor lateral spreading occurred due to the 2011 flood. Therefore, confidence in the results of this assessment for these CPFMs is high.

Summary For CPFMs 12a and 12b, as discussed above, the potential for de altionto~the river bank surrounding the Intake Structure is low because of field ol ',,ation flujaa'T~sis of groundwater data. In the unlikely event that these CPFM]s Vere to owur, 4e implication of this degradation to the structures and systems surrounding 4he itake sgh. The combined consideration of the potential for degradation d'- ~

dfiurteA

• e~~icationo**8s 0 tiat degradation to this structure places it in the "not significan gory. The da oUlected since Revision 0 is sufficient to rule out these CPFMs assumin e. vi'ously recomm"dZ pY monitoring schedule is continued. Therefore, the confide 'cdine ie A1*ove assessment-.high, which means no additional data and inspections are necessary to dria a6onclusion. Assuming that no further concerns are identified through theino -tormg programf6r, the Intake Structure (discussed in Section 5.1.6 and continuing unti1fIeemberr'ti2011),

3c thes&C'!Evis are moved to the quadrant of the matrix representing "14Fufitherlc Action commend[e'-, "dated to the 2011 Flood."  :

5.1.7.3 Revised Results The CPFMs evaluated for the.Inrike Structure are Apsented inAhe following matrix, which shows the rating for the est~i.edAignificance and tf ifidence in the evaluation.

'.- Low Confidence Higdh Confidence

.(1nsufficibentData) (Sufficient Data)

Jd

'N.

U_

CPFMV 12a CPFM 12b 0

z

Priority 1 Structures Page 5.1-14 Intake Structure Rev. 2 5.1.7.4 Conclusions In the assessment of the FCS Structures, the first step was to develop a list of all Triggering Mechanisms and PFMs that could have occurred due to the prolonged inundation of the FCS site during the 2011 Missouri River flood and could have negatively impacted these structures.

The next step was to use data from various investigations, including systematic observation of the structures over time, either to eliminate the Triggering Mechanisms and PFMs from the list or to recommend further investigation and/or physical modificatios to remove them from the list for any particular structure. Because all CPFMs for the Intaka.*. cturel$her than CPFMs 12a and 12b had been ruled out prior to Revisio ad beu 12a and 12b have been ruled out as a result of the Revision 1 findin Trigge and their associated PFMs remain credible for the Intake Structure ,lere Or DRjhas concluded that the 2011 Missouri River flood did not impact the geotec li d s ructura 'gnty of the Intake Structure because the potential for failure of this structuredue to the floWisiot significant. >

Ile ( * 'X: :7 i,:?

. '.*:,i

. ;5 " .'.:*.

st:;

.- " :"% ':7; 4:'i: =.*:.,

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Section 5.2 Auxiliary Building J

Priority 1 Structures Page 5.2-1 Auxiliary Building Rev. 2 5.2 Auxiliary Building 5.2.1 Summary of Auxiliary Building Baseline information for the Auxiliary Building is provided in Section 2.0, Site History, Description, and Baseline Condition.

The Auxiliary Building is located in the center of the PA. It is attached t' heTurbine Building, Technical Support Building, CARP Building, and Rad Waste B g on ,14itheast, northwest, and west, respectively. The Auxiliary Building surrounds a maviyof the C 6namenit, which is located at its center.

The Auxiliary Building is a multi-story reinforced concrete Class uitue essential t pMnt operation. The building houses major systems and components, bdtli&QE-and non-CQOn, .? .

81 designated rooms. The major function of the building is to provide th, .sfctural supportand environmental protection necessary to ensure the functional integrity of tlhe*CQE systems and components under all operational and environmental condfi insiiThe buildin I.&s:*,-provides radiation shielding and mitigates radiological releases to the enviirojnment. '

The Auxiliary Building basement floor elevation itp4roximatehy*,ýsime elevatio*s the basement slab for the Turbine Building (990 ft). The adjoi*m Th* pportBuilding, CARP Building, adjim~echrip~

M- aM hegr*iii*2 lab ogl and Rad Waste Buildings are shallow-foundation tt res grou slabs.rou matching the ground level elevation of t15:uxiiliary. Buildiii *(1007 ft) 6fi 'easement floor elevation where it adjoins with the Technical SuppoiBuildmg an4CAP BuildingIs 989.00 ft. The basement floor elevation where it adjoins witfth6ikad Waste Bui ini ange 971 to 989 ft. The grade-supported structures adjacent toJie;,fundation walls aýircharge onto the foundation walls of the Auxilitiry BUlding.

The Auxiliary Building is a reoiiidieed concrete-sltrcture with a multitude of vertical concrete shear walls SUl*P, ia4concrete floor diaphrag" Von 20-in.-diameter at providIr support to the building. The building is opennd*[:: steel pi~e;I~tending into sound bedrock. Where solution ca~itibsre located below the piles, e-pi-les are underreamed and extended past the solution cavities.

Te The pes filled*. filled wi-4Q ifrteThe with pls are sand cap ` m ol*

up to'l . the bottom of the mat, and the remainder of the piles are filled w The piles are cappe'dwith a 2-in.-thick ASTM A36 steel cap plate that is 22 in. by 0itoncrete.,**

22 in. Th6'piles are spaced at approxiately 9 ft on center. The pile-supported mat foundation varies in thickness from .12 ft to 1.5 ft, depending on the room use. The exterior walls are a minimum of 2.5-ft-thick reinf6i&e&&oncrete.,-The~r'of Is cast-in-place reinforced concrete supported on concrete beams cast monolitfically.ywiltthe'oof. Interior floors and walls are cast-in-place reinforced concrete.

Thicknesses vary per roeomuse and floor span.

The Containment, which resides at the center of the Auxiliary Building, is supported on 20-in.-

diameter open-ended steel piling extending into sound bedrock. Where solution cavities are located below the piles, the piles are underreamed and extend past the solution cavities. The piles are filled with sand up to 1 ft from grade, and the remainder of the piles are filled with concrete. The piles are capped with a 2-in.-thick ASTM A36 steel cap plate that is 22 in. by 22 in. The number of piles in each circle is constant, with each pile circle 5 ft closer to.the center. Therefore, the piling density increases as you reach the center of the Containment. The top of the foundation adjacent to the Auxiliary Building is at el. 991 ft. The top-of-foundation elevations for the Auxiliary Building, where it adjoins the Containment, range from 971 to 1002 ft.

Priority 1 Structures Page 5.2-2 Auxiliary Building Rev. 2 5.2.2 Inputs/References Supporting the Analysis Table 5.2-1 lists references provided by OPPD and other documents used to support HDR's analysis.

Table 5.2 References for Auxiliary Building Document Title OPPD Document Date Page Number(s)

Number (if applicable)

Incident Report Summary CR 2011-5490 6/10/2011 e'.

A.ll Incident Report Summary CR 2011-5560 6A4/2Q, 1 1< 1ll Incident Report Summary CR 2011-5605 b 2011 ll Incident Report Summary CR 2011-5609 /6* 011. i;A"*-

Incident Report Summary CR 2011-5670 ANOW 1

• Incident Report Summary CR 2011-5837 6/28$1,2#1 . Alf-'"

Incident Report Summary CR 2011-5853 6/28*01*l* ,1-.' All ,

Incident Report Summary CR 2011-5961 7/4/2011 . All Incident Report Summary CR 2011-5977 -<"77/6/2011 - *All Incident Report Summary CR 2011-5978 .. */*6.2"., I Incident Report Summary CR 2011-6051...... 7/0/I'-l .

Incident Report Summary CR 201 1-605 l*.j2 /7/9........ \ All System Design Basis Document SDBD-AUX-5f..0Rev 18A W1; i* ,

Foundation Studies . . W' <t/19/196', All Soils Exploration Report

• 2/2/1967:.All Auxiliary Building Structural ....

5,/ 22/..*,1 All Inspection °' ,,- \. . _,______,_,__,,______..

Naval Facilities Engineerng',n` - -.. . '.:....

'91986 All Command, Desgi* auat 70,l4Soi.

Mechanic,.,~

Detailed site observations-field reJotS field nots and inspection checklists-for the Auxiliary BdAltlg,are provided in Attachment 8."

Observpd~peieformance and pertinent 1 ,round data are as follows:

A sand b6il/p'ping feature was obsered (originally reported in CR 2011-7265) near the southwest comer of the'. Missile Shield R6o.m./ This room is located on the outside of the south wall of the Auxiliary Building(commob N .. :: -........ wall to both spaces) and has an unfinished, pea gravel floor surface.

Ingress/egress can onlmybeimade from Door 45 located outside of the Auxiliary Building (there is no connecting door'ay`rbeteen the Missile Shield Room and the adjacent Auxiliary Building).

This feature was measuired using a hand tape measure and vertically probed using a 4-ft-long, 0.5-in.-diameter, steel-tipped fiberglass T-handle soil probe (commonly referred to as a foundation probe). Field measurements showed the feature was about 3.5 ft in diameter and 1 ft deep. A high-water line was observed on the interior walls approximately 0.8 ft above the floor. Various utility conduits extend vertically into the ground along the outside wall at the southwest comer (a few feet west of the alignment of the boil/piping feature). The Main Underground Cable Bank, MH- I to the Auxiliary Building, passes through the subsurface, extending east to west below the location of the boil/piping feature.

Priority 1 Structures Page 5.2-3 Auxiliary Building Rev. 2

• General observations of the interior of the structure showed minor concrete cracking in several walls and ceilings throughout the building. These hairline cracks could be associated with concrete shrinkage that is typically seen in concrete construction. The below-grade walls were dry at the time of inspection although there was evidence of past water infiltration. The observed cracks appear to be those previously recorded and monitored based on incident report summaries from OPPD listed in Table 5.2.1.

• The structure was protected from floodwaters for the majority of the 2 11 flood by an Aqua Dam; however, the Aqua Dam failed for a short period of time due to bein aged allowing floodwater to enter the area inside the Aqua Dam's perimeter. 4 is i-t Ted in the flooding of the truck dock room along the south elevation. FIlUdwatersachc approximately 2 ft in the dock room and infiltrated room 24A directly below the-41tsck rooth6:qxisting cracks in both the floor and walls.

• Voids were found below the slab in the Turbine Building, whiheis aciljacent to andWe sof the Auxiliary Building. These voids were documented in 1997 to*q*p'fo.ximately I dee,.-h&ý,-

extent of the voids is unknown, but they have been located app.oximately> 15 ft from tbe;vall K>

shared with the Auxiliary Building. A constant flow of water throughlie 'voids at variouates since 1997 is believed to have occurred due to the cons*t-np pump 6,erfitop in the Turbine Building. For further information see Section 5.8. -'2Aijded *tidled discussioi obf this Key Distress Indicator is presented in Section 4. 1.

• The Maintenance Shop to the northeast has docunmented settlefekt issues. One b'iiding column footing had settled approximately 3 in. at the 4.iic of Revisi. O A secion of floor slab on grade is settling. A more detailed discussionof thik oDistressl'ndicator 7*res nted in Section 4.3.

5.2.3 Assessment Methods and Prdc6dures /

5.2.3.1 Assessment ProGodures Accomplisfird Assess montEsofthAue "iary Buiding included the following:

,.,visual inspection6,the interior ofitestructure's lowest levels

• 2, A visual inspection oflthe exterior of the.,structure where accessible

A visual inspection of su...ps.. the Auxili'a'ry Building for the presence of water, water

ý"Ievel, and the presence of s~diment in water AAnassessment of collectedsiiurvey data to date for indications of trends in the movement of

\'t, 's~ucture A revieW of previously docu0 ented condition reports, as-built building plans and geotechnicdLreportst~dt*rimine possible weak points in the building's construction that could bietadee kheflood Additional investigations were performed. These included the following non-invasive geophysical and invaisive geotechnical investigations:

• Seismic surveys (seismic refraction and refraction micro-tremor) in the PA. (Test reports were not available at the time of Revision 0.)

Priority 1 Structures Page 5.2-4 Auxiliary Building Rev. 2

" Geotechnical test borings in the protected area. Note that OPPD required vacuum excavation for the first 10 ft of proposed test holes to avoid utility conflicts. Therefore, test reports will not show soil conditions in the upper 10 ft of test boring logs. (Test reports were not available at the time of Revision 0.)

• Four inclinometers were installed on site to determine the condition of the riverbank by detecting lateral movement of the soils. (Inclinometers were not installed and thus no data were available at the time of Revision 0.)

5.2.3.2 Assessment Procedures Not Completed , ,

No additional assessment procedures have been identi this SteCUrt.ure 5.2.4 Analysis Identified PFMs were initially reviewed as discussed in Section Nhj..1. e consider1,e

" .yiew preliminary information available from OPPD data files and from :fitiaN1V-own observatios, Eleven PFMs associated with five different Triggering Mechanisms were Zd'%ined to be "non-credible" for all Priority 1 Structures, as discussed htin,3.6. The rimnaining PFMs were carried forward as "credible." After the design revie ach the h si -, b servations, and the results of available geotechnical, geophysical,Iad surve dath here analyze umber of CPFMs were ruled out as discussed in Section 5.2.4.. The CPb af:vriedoforward fOr detailed assessment are discussed in Section 5.2.4.2.

AIt 0u Al~ WC*m o 5.2.4.1 Potential Failure Mo 6,tRuled ut ior to the on of the Detailed Assessment .

The ruled-out CPFMs reside in th&,Not Significant/"ighi6Cnfidence category and for clarity will notbestohwn:,in the PotentWa :foiFailure/Confidence matrix.

,gering Mechanism[2-Surface-osion

ý- PFM 2b - Loss of ll'a 1rsupport f6ojfil&'-foundation

• K~:1sReason for ruling out:

• It ' as evident from HDR's ite observations that no surface erosion occurred in the vicinity th'Auxiliary Building ..

Triggering Yfechanism,.. .3-Subsurface Erosion/Piping CPFM i3:e,.POss oftlr~1 support for pile foundation (due to river drawdown)

":* .;:.*',v".

-.. .:-*:,),

Reason for ruling out:./

• The structure is a sufficient distance from the river to be outside the zone of influence of the CPFM.

Priority 1 Structures Page 5.2-5 Auxiliary Building Rev. 2 Triggering Mechanism 4 - Hydrostatic Lateral Loading (water loading on structures)

CPFM 4c - Wall failure in flexure CPFM 4d - Wall failure in shear CPFM 4e - Excess deflection Reasons for ruling out:

• The Auxiliary Building is designed to withstand an external witer load due to flooding of the Missouri River to el. 1014 ft (see SDBD-AUX-502, Aev ae flood elevation p*he in 2011 was approximately 1006.9 fi, which is less t sib

• Visual observations did not identify distress to the s ture that ributed to this CPFM.

Triggering Mechanism 5 - Hydrodynamic Loading '>

CPFM 5a - Overturning <;i;!. ." ,.

CPFM 5b - Sliding ,- *. ..

CPFM 5c - Wall failure in flexure CPFM 5d - Wall failure in shear CPFM 5e - Damage by debris CPFM 5f- Excess deflection /

Reasons for ruling out:

• The structure was protected 46onmAflbodwater b Aqua Daýenexcept during a short period of time when the Aqua Damrn:failed due to beirA4d a'maged hich allowed floodwater to enter the area inside theAquaDam perimeter. .

The Auxihl Bilding is'nesigied to withstand anxetnal water load due to flooding of the-p[isso'i4lybrito el. 10 1t*'*(*see SDBD-AUX-502, Rev 18). The peak flood elevation 14i0 6AQft'which is less than the structural design basis.

• yjsua1 observationf it identify distress to the structure that can be attributed to this iCPFM.

-. ggering Mechanism 6 - Bu.oyancy, Uplift Forces on Structures N`:,,P*FM 6a - Fail tension pltesi CFMN 6b - Cracked slab,,16ss'6f structural support C"PMK6c"- Displaced sty.c.,tifre/broken connections Reasons f6rriing out The Auxiliary Building is designed to withstand an external water load due to flooding of the Missouri Riier to el. .1014 ft (see SDBD-AUX-502, Rev 18). The peak flood elevation in 2011 was approximately 1006.9 ft, which is less than the structural design basis.

• Visual observations and survey measurements show no structure movement. Therefore, it is unlikely that the tension piles failed (CPFM 6a) or that the structure was displaced or damaged (CPFM 6c) due to buoyancy effects.

Priority 1 Structures Page 5.2-6 Auxiliary Building Rev. 2 Triggering Mechanism 7 - Soil Collapse (first time wetting)

CPFM 7b - Displaced structure/broken connections CPFM 7c - General site settlement CPFM 7d - Piles buckling from down drag Reasons for ruling out:

The pile foundations are located below el. 971.0 ft. while the d"mal river level is at.

approximate el. 992.0 ft. It is therefore logical to assumerthatthe,_is býe~ow the mat foundation were previously wetted. docum.. - .

The peak flood elevation prior to 2011 was docume. 1993 as0 which would show that the soils below and surrounding the buil . ere sgturatedl$aý t time.

Triggering Mechanism 10 - Machine/Vibration-Induce kf uefaction CPFM lOb- Displaced structure/broken connections ,

CPFM 1Oc - Additional lateral force on below-grade w.i , ,-

CPFM IOd - Pile/pile group instability Reasons for ruling out: , ..

• The underlying soils were improved wjith*vibroflot4t,ýP "ontto.ec'e the risk 'f liquefaction.

" Temporary pumping equipment locatebtonthe g: from te.Aua Dam perimeter produced minimal localized vigaftion &was f~t'f hst i tre and therefore is deemed to have an inconseqtieala effect.

• Machine/vibration-indu Zkliuefaction was ....

serve e site.

This is not a changed cOlIiodue to the flooiTs ABa s ervice ers under si -saturated soils admine vibration conditions.

Tr-ggeng )e,-Is Loss filtrength due to Static Liquefaction or Upward nee fg

, ý.-CPFM 1l b - Displacedi.ltricture/brokleiftocinections CPFM 11 c- Additional laterl. force on btoiw-grade walls

,,CPFM 1 d - Pile/pile group instability Keasoýfor ruling out: ,

• Vis Servations and suiwey measurements show no structure movement. Therefore, de gradaionihat canbc attributed to this PFM did not occur.

" Sandboi/pipp.feaitir observed in the missile room was determined to be too shallow to be significantii...

• The underlying sgoils were improved with vibroflotation to reduce the risk of liquefaction.

Triggering Mechanism 12 - Rapid Drawdown CPFM 12a - River bank slope failure and undermining surrounding structures CPFM 12b - Lateral spreading Reason for ruling out:

• The Auxiliary Building is located a sufficient distance away from the river bank and therefore is outside the zone of influence of a bank slope failure.

Priority 1 Structures Page 5.2-7 Auxiliary Building Rev. 2 Triggering Mechanism 13 - Submergence CPFM 13b - Corrosion of structural elements Reasons for ruling out:

" The Auxiliary Building has not been subjected to corrosive circumstances that would be considered beyond the normal conditions. The structure was protected from floodwater by an Aqua Dam except during a short period of time when the Aqua Dam failed due to being damaged, which allowed floodwater to enter the area inside tli-beAua Dim perimeter..

Therefore, structural elements being wetted by the 201fl"od cofrciaered in the original design of the facility.

" This is not a changed condition due to the flood. The uxilia ml i 4s been in service for 38 years under similar saturated soils con tionfs iewed'eO.tiiion survey reports have not indicated signs of distress to the structur'ethat would be atw'butd* to corrosion due to submergence.

Triggering CPFM 14a Mechanism

- Heaving,14crushing,

- Frost Effects or displace*-*'"*":"****

Reason for ruling out:

The Auxiliary Building foundation is apfxima 2 q de and therefore not frost susceptible. In addition,,fir9t-sus PTIblejconectmg ub116MNi; below the frost level.

5.2.4.2 Detailed Assess66, Asosm itf Cr l Credible tial Fail"re/Md*

.ittaFailueodes d The following CPFMs are the oil,)CPFMs carried 10nmiftr -r detailed assessment for the Auxiliuary ildii 'as a result ofth6 20.11 flood. This detailed assessment is provided below.

T4ggeAing Mechansm 3 - Subsurface*Eýrosion/Piping C?*9PFM 3b - Loss of latera1support f6rvp 16 foundation (due to pumping)

'K,*

he Turbine Building, which\sconnected to the Auxiliary Building on its east, has a Sd,6oumented history of a void below the foundation slab dating back to 1997. This void was cofefirm d via cored holes in tle6foundation slabs and camera recordings of broken drain piping thaaties Under the floor slab. Conversations with OPPD personnel indicate that groundwater has b"en.flowing i\tes' at varying- through these broken pipes into the sump from that time to the preseintda\ The rate ýof flow into the sump is directly related to the hydraulic head of the groundwai,,she flok.dter increased in elevation across the site, observed flow rates increased. Thefoliw61fgrdundwater into this drain piping system through the breaks in the pipes is one of th&d4cey' Distress Indicators discussed in Section 4. This drain pipe system was designed as a closed system therefore, the pipes are not surrounded by appropriate filter systems to preclude the transportation of soils from the surrounding area under the slab. It is logical to assume that because the groundwater moves below the foundation and into the broken piping, some movement of the soil has occurred. If these voids were to continue under the Auxiliary Building, they could become large enough to create a loss of lateral support for the piling.

Priority 1 Structures Page 5.2-8 Auxiliary Building Rev. 2 The Triggering Mechanism and CPFM could then occur as follows: multiple potentially connected seepage paths could exist in the soil backfill at the site, including soil backfill in utility trenches, granular trench bedding, and building floor drains with open/broken joints. The paths could be exposed at some locations to the river floodwaters and high groundwater. This network of seepage paths could be connected to the sump pit in the Turbine Building. The breaks in the piping have been documented for an extended period (dating back to at least 1997), thus creating a continuous head differential on the potential seepage path networks.

Gradient has been sufficient to begin erosion of surrounding soil. se.gradient during the 2011 flood was increased, which could have led to higher flows -oug h. is:e a p t The unfiltered seepage condition will continue until the s in th-*ipf ystem are repaired, which means the potential for further erosion midns. Er di create large voids under the Turbine Building base slab and pei der g foundations, including the Auxiliary Building. The potential damage iA` e-" ss of soi po1around piles leading to pile buckling, decreased pile capacity, and fdjnidation failure. "

The following table describes observed distress indicators 'nd otiihqrdta that would inrease or decrease the potential for degradation associated withthlis CPFM f;*,41,iuxillary Building.

Adverse (Degradation/Direct Floodwater Fble (Degra da ji6nIDirect Impact More Likely) Flo.tdTer Im lact Likel A documented void exists under the foundat ciii 'The in pn*acnde filaterial aroeunir d the piling slab of the Turbine Building with a known hydraulic connection between grouaiter >

. was ,,'Jac te X q Classi ctures,(vilrtaion). This higher t

elevation and flows into the buildi?#'tisnip. d. granuiariblaterina is less susceptible to 4A~i~re ,v'efbeetnno observed signs of structural diis floor slab under the current X ~loadinig conditions.

Survey data to date does not identify movement

'- of the building.

Elta Gaps:

The size and location o evoids below the undation slab

.6oiblcusion Si*n *ficance 7 Potential-fgfr Degradationi/DirectFloodwaterImpact Indicators for thiisGPFM have been observed in the Turbine Building, which is adjacent to the Auxiliary Buildiig.**The voids below the base slab in the Turbine Building are known to exist with heavy flows of water being pumped from the sump. Because the 2011 flood caused increased flow through the broken drain pipes, the potential that it caused further and more rapid degradation due to this CPFM is high. It is possible that these voids extend under the Auxiliary Building although the potential is low due to the vibro-compacted soils below the Auxiliary Building.

Priority 1 Structures Page 5.2-9 Auxiliary Building Rev. 2 Implication The occurrence of this CPFM on a large scale could negatively impact the capacity of the piling supporting the building. This could lead to excessive foundation movement and negatively impact the integrity or intended function of the Auxiliary Building. Therefore, the implication of the potential degradation for this CPFM is high.

Confidence The extent of subsurface erosion and its potential impac*n'"......h* known due to the lack of data gathered on subsurface conditions. Be a*usehe ;h information on the subsurface conditions at this time, and the pumpin the Ti zcould have caused subsurface erosion, the confidence for this CPF vtsow Summary For CPFM 3b, as discussed, the potential for degradation is low vibrocompacted soils below the Auxiliary BuildingsThi'sdegra, enough erosion to impact the integrity or inten dtdi!Wnt'iw- th consideration of the potential for degradati* 'te impjhcaio:

structure of this type puts it in the "signifi n t categoryT,-

c oj d are not sufficient to rule out this CPFM. Therefor e confide.iwe in d which means more data or continued'-onit andoýinspecti to draw a conclusion. .-.

V I

WI

Priority 1 Structures Page 5.2-10 Auxiliary Building Rev. 2 5.2.5 Results and Conclusions The CPFM evaluated for the Auxiliary Building is presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

Low Confidence High Confidence (Insufficient Data) (Sufficient Data)

CPFM 3b Q -

a- N I,...-. *t.' ,. .

CI

• ,-'* :i,* . . .. .

.r...v.'

LL7 M 04 0/

5.2.6 R.ecernended Actions  :

Furtr.eorensic investigations andx'psi Ical modificatibns are recommended to address CPFM 3b for th&A ixi4iajry Building. CPFM 3b isasskiated with unfiltered flow of groundwater into the Turbine Building!',basement drain piping system-,(Key Distress Indicator #1). These recommendations are described1in:detail in Section 4.1.

Continued mo6nioring is recommendeto include a continuation of the elevation surveys of the previously identifie'dtargets on,t.hýs structure and surrounding site. The purpose is to monitor for signs of structure distress 'Move"'t d or changes in soil conditions around the structure. The results of this monitoring will biseto2icrease the confidence in the assessment results. Elevation surveys should be performed week for 4 weeks and biweekly until December 31, 2011. At the time of Revision 0, groundwater levels had not yet stabilized to nominal normal levels. Therefore, it is possible that new distress indicators could still develop. If new distress indicators are observed before December 31, 2011, appropriate HDR personnel should be notified immediately to determine whether an immediate inspection or assessment should be conducted. Observation of new distress indicators might result in a modification of the recommendations for this structure.

Priority 1 Structures Page 5.2-11 Auxiliary Building Rev. 2 5.2.7 Updates Since Revision 0 Revision 0 of this Assessment Report was submitted to OPPD on October 14, 2011. Revision 0 presented the results of preliminary assessments for each Priority 1 Structure. These assessments were incomplete in Revision 0 because the forensic investigation and/or monitoring for most of the Priority 1 Structures was not completed by the submittal date. This revision of this Assessment Report includes the results of additional forensic investigation and monitoring to date for this structure as described below.

5.2.7.1 Additional Data Available The following additional data were available for the Ali q r'evisions I and 2 Buildag f*o*

of this Assessment Report:

• Results of KDI #1 forensic investigation (see Section4: le &dataom

• - OPPD."'

Additional groundwater monitoring well and river sta~g v l ,o ,P<*,

• Results of geophysical investigation by Geotechnolo, Inc. (se: Atachment 6).

• Results of geotechnical investigation by Theleetec ,' , Inc. (see A &, ent 6).

• Data obtained from inclinometers by Thie I esee Attachue)t 6).

• Results of continued survey by Lamp R arson and A es (see Attchjent 6).

5.2.7.2 Additional Analysis ,

The following analysis of additiu was condued for the uxiliary Building:

• Groundwater monitonng ad n!, river stage 1 dio OPPD Data:ý-i istatthe river anfg,rdumdwater have returned to nominal normal levels.

Results of geophyst¢)wimývestigati6nre port by Geotechnology, Inc.

, Seismic Refraction and"Seinmic ReMi Pis{performed around the outside perimeter of the o;:> block identified deepanomalies that could be gravel, soft clay, loose sand, or power

\ .ossibly voids.

" Rkesults- of geotechnical investigation by Thiele Geotech, Inc.

NSix testboings werdil'ld, with continuous sampling of the soil encountered, to ground truth th*eGetechn6luoo Inc. seismic investigation results as part of the KDI #2 forensic investigation. Tfestbore holes were located to penetrate the deep anomalies identified in the seismic investigaln. The test boring data did not show any piping voids or very soft/very loose conditions that might be indicative of subsurface erosion/piping or related material loss or movement.

All of the SPT and CPT test results conducted for this Assessment Report were compared to similar data from numerous other geotechnical investigations that have been conducted on the FCS site in previous years. This comparison did not identify substantial changes to the soil strength and stiffness over that time period. SPT and CPT test results were not performed in the top 10 feet to protect existing utilities.

Priority 1 Structures Page 5.2-12 Auxiliary Building Rev. 2 Data from inclinometers to date, compared to the original baseline measurements, have not exceeded the accuracy range of the inclinometers. Therefore, deformation at the monitored locations since the installation of the instrumentation has not occurred.

Results of continued survey by Lamp Rynearson and Associates.

Survey data to date compared to the original baseline surveys have not exceeded the accuracy range of the surveying equipment. Therefore, defo ,ation at the monitored locations, since the survey baseline was shot, has not op rre

• The CPFMs that could not be ruled out in Revision it on the additional data available for Revisions 1 and 2 of tl ý,

Triggering Mechanism 3 - Subsurface Erosion/Piping CPFM 3b - Loss of lateral support for pile foundation.I CPFM 3b for the Auxiliary Building is associated with Kc presents the results of the additional forensic invesii whether this CPFM could be ruled out. Theres',f1-5e show that if the recommendations for physidal modificat-j that this CPFM is ruled out. Therefore, assuming that no fu~tlh monitoring program for the Auxiliary Buildig (discus§ until December 31,2011), this CPFM isp-vedWN~he quiddkni' senting "No Further Action Recommended Relatii&tto the 201 Vlood.

I~ A.

"14

Priority 1 Structures Page 5.2-13 Auxiliary Building Rev. 2 5.2.7.3 Revised Results The CPFM evaluated for the Auxiliary Building is presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

Low Confidence High Confidence (Insufficient Data) (Sufficient.Data)

C., --

0

'Nk CPFMP -R .3b.*

/ '74Conclusions ,*,****.*;

Inb* assessment of the FCS Stru*tures, the first step was to develop a list of all Triggering

• nthe

"*: M*echanisms and PFMs that coudtidhave occurred dlue to the prolonged inundation of the FCS site dunng the 2011 Missouri Pive flood and could have negatively impacted these structures.

The'*e~tste~p was to use data'fr.Iifi various investigations, including systematic observation of the stru~ueg *over time, eitlher,:to eliminate the Triggering Mechanisms and PFMs from the list orto reome .furth n*er~iainand/or s physical modifications to remove them from the list for any pacui~yir 4s.e, ire. Because all CPFMs for the Auxiliary Building other than CPFM3b hd b legil out prior to Revision 1, and because CPFM 3b will be ruled out when the physical mod~iafi~f~ons recommended for KDI #1 in Section 4.1l are implemented, no Triggering Mechanisms and their associated PFMs will remain credible for the Auxiliary Building. HDR has concluded that the geotechnical and structural impacts of the 2011l Missouri River flood will be mitigated by~the implementation of the physical modifications recommended in this Assessment Report. Therefore, after the implementation of the recommended physical modifications, the potential for failure of this structure due to the flood will not be significant.

Section 5.3 Containment

Priority 1 Structures Page 5.3-1 Containment Rev. 2 5.3 Containment 5.3.1 Summary of Containment Baseline information for the Containment is provided in Section 2.0, Site History; Description, and Baseline Condition.

The Containment is surrounded by the Auxiliary Building on the north easL,, d w.est sides, and on a portion of the south side. The Containment basement top-of-slab .leation4i'SO%5 below the reactor and 991 ft along the perimeter. A tunnel is located around the eeter bel wAHe-,lab to access the post-tension cables (stressing gallery). The floor elevation of eE essing ibout 969 ft. The basement floor elevation of the Auxiliary Building where the C4pnt a~joins es"from el.

971 to 1004 ft. The outside grade is approximately at el. 1004 ft.

The Containment is supported on 20-in.-diameter open-ended ste p gs,,iliWiih 1.031 extending into sound bedrock. Where solution cavities were located below thedpiles, they wer underreamed and extended past the cavities. The piles a , ;Vo.1 h sandZ from grade, and the remainder is filled with concrete. To provide a so1 b5 s ffce, the pil1s arecapped with a 2-in.-thick ASTM A36 steel cap plate that is 22 in 22. Th mr of piles; %Neh circle is constant, with each pile circle 5 ft closer to the ce ",Therefoe, *h p.ei" gig density increases toward the center of the building. The stressing gallery tunnil is not sup orted-. ir s.

The mat foundation is a 10- to 12-ft-thic A_ boIiced rrete with ,mro layers of mild reinforcing.

The exterior walls are approximately.3.9 f thick post-tenrsi6i.ed reinforeAA concrete. A steel liner is located on the interior of the wall. 4hie`,toof is a 55-ft-radiiis concre4-dome monolithically integrated into the exterior walls, Interior floors. ndwalls are cast-i lakeeiihiforced concrete. Thicknesses vary per room useandfor span. .

5.3.2 Ir0tsl/References'S4po'rting the."A,4:.s TablF5.31 lists references proviat*ed vOl and othei documents used to support HDR's analysis.

Table .54jIJ-References for Containment 0966ment Title 1,9OPD Document Date Page Number(s)

. Number

________________________________ 'ifapplicable) __________________________

Condition Report,,>,. ,, R2011-5761 6/23/2011 All y CR......2011-5763 CdiRo 6/23/2011 All Condition Report .- .' CR 2011-5792 6/24/2011 All Condition Report " CR 2011-7265 9/9/2011 All System Design Basis Document SDBD-CONT-501, Rev 32 9/30/2010 Piling Plan Containment & 11405-S-1 (#16380) 5/6/1968 Auxiliary Building Structure Inspection SE-PM-AE- 1004 7/16/2009 All Naval Facilities Engineering 9/1986 All Command, Design Manual 7.01, Soil Mechanics

Priority 1 Structures Page 5.3-2 Containment Rev. 2 Detailed site observations-field reports, field notes, and inspection checklists-for the Containment are provided in Attachment 8.

Observed performance and pertinent background data are as follows:

A sand boil/piping feature was observed (originally reported in CR 2011-7265) near the southwest corner of the Missile Shield Room. This room is located on the outside of the south wall of the Auxiliary Building (common wall to both spaces) and has an unfinish pea gravel floor surface.

Ingress/egress can be gained only from Door 45, located outsidegthe I'M

' T eMkihiaryAnilding

-0a B id (there ng . Tis ino connecting doorway between the Missile Shield Room and tl A Building) This feature was measured using a hand tape measure and vertic 4 =:Fobed us4q,*a,4-ft-long, 0.5-in.-

diameter, steel-tipped fiberglass T-handle soil probe (commog referre-Niof ,dation probe).

Field measurements indicated that the feature is about 3.5 ftt*i an I , .

high-water line was observed on the interior walls about 0.8 ft *Qthe floor. aVeU9 .... t conduits extend vertically into the ground along the outside I uthwest com fe 01.

west of the alignment of the boil/piping feature). The Main Un ergr'om Cble Bank, to e Auxiliary Building, runs through the subsurface, extending east to westý1be ,wthe location of the boil/piping feature. 6t

• Voids were found below the slab in the Turbine li hi'_is adjacent to tnc4est of the Auxiliary Building. These voids were documei*: in 1997 todb'apjoroximately I ý-I'deep. The extent of the voids is unknown, but they have §eenh located, proki.ft&nity 15 ft from the wall shared by the Auxiliary Building and the Turbine`Building*,'7 consfantfl6w of water through the voids at various rates since 1997 is belfeved tohave occurred due to ,n sump operation in the Turbine Building. L.or-'firther information see Sectitnup5.8.

" The stressing gallery is a tunnel o,cated below the maitflor., 6r.slab of,:t Containment. The gallery has one entrance in and out from, 1.o22 of the AuxifiaiyBufifdig. The gallery provides access to the Conta4pin.1..ost-tensido strands and runihe enre perimeter of the Containment.

The stressing und to cntalarge amount of water in low level areas of the floor near th o sump pits. Nat overed app-iqimately half of the floor area at the time of HDR's s ton Water was approxnmately 4 in dep*t the sump pit locations and decreased in depth awayý-rom the pits due to floorfsN1bslope. Thesuirck of the water was not apparent from the

<i.mslection. Previous testing of the water by OPPiD discovered that the water contained Cesium-N14 \3ery little sediment was

• • "°*":*.benremoved see'nxmthe water.

fromth*i:!

• Pumpsý.adeen rhdsumps m in the stressing gallery prior to HDR's inspection.

• The trusic-lrewas protected frommfloodwater for the majority of the 2011 flood by an Aqua Dam; however, tli&-qua Dam failede. oQrashort period of time due to being damaged, allowing floodwater t6Vtb,,e area 'idNthe Aqua Dam perimeter.

5.3.3 Assessment nvefi and Procedures 5.3.3.1 Assessment Procedures Accomplished Assessments of the Containment included the following:

• Visual inspection of the interior of the Containment's lowest levels (perimeter rooms only).

Visual inspection of other interior rooms is not necessary to provide report results.

• Visual inspection of the exposed, above-grade exterior of the structure.

" Visual inspection of sumps in the stressing gallery for the presence of water, the water level, and the presence of sediment in the water.

Priority 1 Structures Page 5.3-3 Containment Rev. 2

" An assessment of collected survey data to date for indications of trends in the movement of the structure.

" A review of previously documented condition reports, as-built building plans, and geotechnical reports to determine possible weak points in the Containment's construction that could be affected by the 2011 flood.

Additional investigations were performed. These included the following non-invasive geophysical and invasive geotechnical investigations:

• Seismic surveys (seismic refraction and refraction mi,* m'emor) (Test reports were not available at the time of Revision 0.) 4,

" Geotechnical test borings in the PA. Note that OP1tequire qd uurn.k.c ation for the first 10 ft of proposed test holes to avoid utility con li'!s.. ,,fore,test* will not show soil conditions in the upper 10 ft of test boring lo s st reports w at the time of Revision 0.)

5.3.3.2 Assessment Procedures Not Comple e No additional assessment procedures have bee en is structure,.

5.3.4 Analysis / V Identified PFMs were initially reviewed as,.discussedi ýVtiles Section3.0.

analk-down Te revi-ew considered the preliminary information available from filesdatfm initia 1"k-own observations.

Eleven PFMs associated with five diffeip Triggering NMeeainisms w~iadetermnined to be "non-credible" for all Priority 1 Strieusi6 as discussed i 1,Syytion9.6.4The remaining PFMs were carried forward as redible." After fi: es~gn review for eaqljs7,.tbire,the structure observations, and the resulpsysi***hca, and survey data were analyzed, a number of CPFMs were Lufed outlwasd sd in Secho' 3.4. 1. The CPFMs carried forward for detailed asses sme ar* ,t iscussed in S. .3.4.2. ...

//5 4 1 Potential Failur6 Modes Rule~d-9ut Prior to the Completion of the Detailed

, ,", Assessment Theruled-out CPFMs reside ii.,,theiNot Significant/High Confidence category and for clarity wi-b i1tshown in the ....lfor Failure/Confidence matrix.

TriggerinVrJechanisme2&-ýSurface Erosion CPFM 2b. Jss offtieral support for pile foundation Reason for rulin.'Out:

• It was evident from the site inspection that no surface erosion occurred in the vicinity of the Containment.

Priority 1 Structures Page 5.3-4 Containment Rev. 2 Triggering Mechanism 3 - Subsurface Erosion/Piping CPFM 3e - Loss of lateral support for pile foundation (due to river drawdown)

Reason for ruling out:

• The structure is a sufficient distance from the river to be outside the zone of influence of the CPFM.

Triggering Mechanism 4 - Hydrostatic Lateral Loading*(ateI structures)

CPFM 4c -Wall failure in flexure A-,

CPFM 4d - Wall failure in shear U.

CPFM 4e - Excess deflection Reasons for ruling out:

" The Containment is designed to withstand an externarNw)ater*l)

Missouri River to el. 1014 ft (see SDBD-CONT-501, Rev 32). in 2011 was approximately 1006.9 ft, Which is les-IF the struct

" Visual observations did not identify distro4tot e QOln,',men to this CPFM.

Triggering Mechanism 5 - Hydrodynanu cLoadin( ";'

CPFM 5a - Overturning ,' / '

CPFM 5b - Sliding ..

CPFM 5c - Wall failure in flexu're CPFM 5d - Wall failurejin~ ar2 CPFM 5e*_D.amagte by debri*s> ,.

'The structure was proteat 'rom floodateifby an Aqua Dam except during a short period

,,of time when the Aqua Dqafailed due to being damaged, which allowed floodwater to

<ýenter the area inside the Aqu4 Daam perimeter..

TIe Containment is design"qto withstand an external water load due to flooding of the issoiri River to el. 10.14'ft.(gee SDBD-CONT-501, Rev 32). The peak flood elevation in 206ý: .wkapproximatelIf,006.9 ft, which is less than the structural design basis.

• Visua~l~bservations,di*d ot identify distress to the structure that can be attributed to this CPFM. ., .

Triggering Mechanism 6 - Buoyancy, Uplift Forces on Structures CPFM 6a - Fail tension piles CPFM 6b - Cracked slab, loss of structural support CPFM 6c - Displaced structure/broken connections Reasons for ruling out:

• The Containment is designed to withstand an external water load due to flooding of the Missouri River to el. 1014 ft (see SDBD-CONT-501, Rev 32). The peak flood elevation in 2011 was approximately 1006.9 ft, which is less than the structural design basis.

Priority 1 Structures Page 5.3-5 Containment Rev. 2

• Visual observations and survey measurements indicate no structure movement. Therefore, it is unlikely that the tension piles failed (CPFM 6a) or that the structure was displaced or damaged (CPFM 6c) due to buoyancy effects.

Triggering Mechanism 7 - Soil Collapse (first time wetting)

CPFM 7b - Displaced structure/broken connections CPFM 7c - General site settlement CPFM 7d - Piles buckling from down drag Reasons for ruling out:

• The pile foundations are located below el. 979.0 ft i te01 iral 4level is at approximate el. 992.0 ft. Therefore it is logical to as.suifefitat *e, soils betow2the mat foundation have been previously wetted. N,

" The peak flood elevation prior to 2011 was document¢e'*d-,a033 ft, which w'6ilId indiCtAW the soils below and surrounding the Containment had been saz'.tdrad at this time... "',

Triggering Mechanism 10 - MachineNibrato ce Liquefactipn CPFM lOb - Displaced structure/broken C 'cotonS CPFM 1Oc - Additional lateral force onAew-gradewals CPFM I Od - Pile/pile group instability-Reasons"underlying forThe ruling out:

soilsdwwith ,\ ' ,;.

vibrlttt The underlying soils were impr tion to educe the risk of liquefaction.

• Machine/vibration-indut4f This isn~oua-ch 1I iefaction was n,,se.t'we~dvthe 6uetoth site.

Thisinged condi de to the floo tainment has been in service for 3 61ailslf saturatedsoil.s and machine vibration.

,_sinii'lar

• ,,mporary pumpFg qpmenticatbd on the ground within the Aqua Dam perimeter duced miniml'u( *d**ed vibrations an-d was offset from the structure and therefore is

'Aemdto have inconse*'ioteilial effectik, 7Triggering Mechanism 11 -L69S of Soil Strength due to Static Liquefaction or Upward 1:eej age

-'ý<PFM 11 b - Displaced strucfure/broken connections F.,M 1Ic - Additional t1rai force on below-grade walls CPF*I l id.-*., Pile/pile

... ,; *'..... /

p:'instability Reasons for rh;ngiout. <-

" The underlying soils were improved with vibroflotation to reduce the risk of liquefaction.

• The sandboillpiping feature observed in the missile room of the Auxiliary Building was determined to be too shallow to be significant.

• Visual observations and survey measurements indicate no structure movement. Therefore, degradation that can be attributed to this PFM did not occur.

Priority 1 Structures Page 5.3-6 Containment Rev. 2 Triggering Mechanism 12 - Rapid Drawdown CPFM 12a - River bank slope failure and undermining surrounding structures CPFM 12b - Lateral spreading Reason for ruling out:

• The Containment is located a sufficient distance away from the riverbank and therefore is outside the zone of influence of a bank slope failure.

Triggering Mechanism 13 - Submergence ,

CPFM 13b - Corrosion of structural elements ý,V Reasons for ruling out:

The Containment has not been subjected to corrosive *cumstances that woulNe,-ý,*

considered beyond the normal conditions. The structurewas rot7Icted from fldoolatefby an Aqua Dam except during a short period of time when the Aqia*Dam failed due to being damaged, which allowed floodwater to enter e aXainsde the Aq1fV am perimeter Therefore, any structural elements being 1Ieflood was considered in the original, design of the facility. N ..

This is not a changed condition due to ood. Th ^60fihent has been in service for 38 years under similar saturated soils. B iition sxezeports have not indicated signs of distress thatVUWld b di-týibutcorrosienidue to submergence.

22*

Triggering Mechanism 14 oEffects CPFM 14a - Heaving, crushing' or displacement*t

"..incty .

Reason.f->

o/*The *Containmentfoudation is a minimum of 25 ft below grade and is therefore not

..su'ceptible to frost. frIn:

ost-, sdeptible connecting utilities are also below frost level.

`5.3&4.2 Detailed Assessme 'of Credible Potential Failure Modes Ttief_.llo*ing CPFMs are theo CPFMs carried forward for detailed assessment for the J * .*. ; .,

1, '. I*

.*!:,.; rIY ....

Contnm~ent.,as a result of th.2.04 1 flood. This detailed assessment is provided below.

Triggerin">y'Tc4hinismý .6-Su bsurface Erosion/Piping CPFM 3b ' ss`ý....teral T, support for pile foundation (due to pumping)

The Turbine Building, which is adjacent to the Containment, has a documented history of a void below the foundation slab dating back to 1997. This void was confirmed via cored holes in the foundation slabs and camera recordings of broken drain piping that lies under the floor slab. Conversations with OPPD personnel indicate that groundwater has been flowing at varying rates through these broken pipes into the sump from that time to the present day. The rate of flow into the sump is directly related to thehydraulic head of the groundwater. As the floodwater increased in elevation across the facility, observed flow rates increased. The flow of groundwater into this drain piping system through the breaks in the pipes is one of the Key Distress Indicators discussed in Section 4. This drain pipe system was designed as a closed

Priority 1 Structures Page 5.3-7 Containment Rev. 2 system; therefore, the pipes are not surrounded by appropriate filter systems to preclude the transportation of soils from the surrounding area under the slab. It is possible to assume that because the groundwater moves below the foundation and into the broken piping, some movement of the soil has occurred. If these voids were to continue under the Containment, they could become large enough to create a loss of lateral support for the piling.

The Triggering Mechanism and CPFM could then occur as follows: multiple potentially connected seepage paths could exist in the soil backfill at the site.'ficluding soil backfill in utility trenches, granular trench bedding, and building floor-drais opeiroken joints. The paths could be exposed at some locations to the river flo~dwafbrs an *lhifgroundwater. This network of seepage paths could be connected to the sunp3;pit in the ToKiiieBuilding. The breaks in the piping have been documented for an exteidd1. ej~bat kto at least 1997), thus creating a continuous head differential on tl'oI 1

,ý'..e

ýIýseep e pa ttworks.I i....... s Gradient was potentially sufficient to begin erosion of surrounding Sol. he gr t during.the 2011 flood was increased, which could have led to higher4 101s' iugh the seepage .thw.

networks. The unfiltered seepage condition will remain un il the* i the pipin y.

are repaired, which means the potential for further erpsion remains."E-sip* could extend out, creating large voids under the. Turbine Buildingjibs*abýind potentiafy,ffi-der the Containment. The potential damage include1 SO] ,I rt around p14i1s-,tading to pile buckling, decreased pile capacity, and foundaion failure,,

The following table describes observed distres indic sand oher d- that would increase or decrease the potential for degradati kasso ted wif'his CPFMl fo- ieContainment.

Adverse (Degradation/D Favorablea 6e("

(DegradationlDirect *

(D!g. ra ai n-r,9e Adverse b d a e *" ' .....

Impact More 14R19,)a - Fiopdwater Impact Less Likely)

A documented void exists under' ,fundation The HiE andfill material around the piling was slab 9~of?,uwdin ding wilth a.: n compacted to the requirements under the Class I to~n he!.e-au~ and andeflows n flcows intre"*'l 24M."*.een grounmpat dNg ...... structures (vibroflotation). This higher density

'41llio asump..granular material is less susceptible to erosion.

, ... There have been no observed signs of structural

- ,distress in the floor slab under the current X .loading conditions.

Surveyed elevations for the foundations show no

.. .significant signs of movement.

\ .  :.The

, bottom of the mat foundation is about 10 ft

. ./ lower in elevation than the bottom of the Turbine

. / Building mat foundation, making it unlikely that voids migrated below the Containment foundation.

Data Gaps: \*}

• The presence, size, and location of the voids below the foundation slab

Priority 1 Structures Page 5.3-8 Containment Rev. 2 Conclusion Significance Potentialfor Degradation/DirectFloodwaterImpact Indicators for this CPFM have been observed in the Turbine Building, which is near the Containment. The voids below the base slab in the Turbine Building are known to exist with heavy flows of water being pumped from the sump. Becausethe iflffloqodýcaused increased flow through the broken drain pipes, the potential that thep2iU flo6 e6,further and more rapid degradation due to this CPFM is high. It is possib16"`4iut not like'jy at_ these voids extend under the Auxiliary Building and to the Contairknient mat

• 3 'idia h potential for degradation is low due to the distance between the Turbin il-Bu I nd. th6,Gontainment and the presence of vibrocompacted soils under both the Auxir-V-J30 ,ding and iffntainment.

Implication The occurrence of this CPFM on a large scale could gaHtively imps c*apacity of the piling supporting the building. This could lead to exq ss fi d5tion movernenfta'd negatively impact the integrity or intended function ofp4c1ion tainm nt. Because the 4gsystem is robust, and voids of this size are not likelyhe* implicati6f potental deTr dation for this CPFM is low. /4 "

Confidence 7 .

The extent of subsurface erosion and its potential ýinact onthebuilding is not known due to the lack of data gathered on Vsiilsurace conditions. B*ecause tbare is not enough information on the subsufýf'cb.oiditions at this tieand the pumping-miite Turbine Building could have caused sibuabce;*rosn,,ion the confidence for this CPFM is low.

Wffiffiarv

,,*>*,.r CPFM 3b, as discussed aove. the potential for degradation is low because the pumping in

• ,<A Turbine Building is unlikel ,-o;have caused enough erosion to impact the integrity or Kinten1ed function of the structure:.Although large amounts of erosion are not likely, large de'pihso4,erosion and degradatffe could impact the integrity or intended function of the struct46reThe combined cons deration of the potential for degradation and the implications of that degr4a'tion to a structiureIof this type puts it in the "not significant" category. The data currently coe'ted are nofsufficient to rule out this CPFM. Therefore, the confidence in the above assessmentlstlow§iwhich means more data and/or continued monitoring and ispectons are necessaryv to dLw* a 'conclusion.

Priority 1 Structures Page 5.3-9 Containment Rev. 2 5.3.5 Results and Conclusions The CPFM evaluated for the Containment is presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

Low Confidence High Confidence (Insufficient Data) (SufficientData) t a- ,

'0 5.3.6 R&ecMrmended Actions: 7 N ,

Furtherf.orensic investigations and physIcal modifications are recommended to address CPFM 3b for the"ontainment. CPFM 3b is associat**dwith unfiltered flow of groundwater into the Turbine Buildcingjb aserment drain piping system'iýi(Key Distress Indicator #1). These recommendations are describe* deail in Section 4. 1.

• ,.*-**.,. :.,*.4.  ;},!:p, Water observd;,ii the, pre stressinggallry cannot be attributed to a specific source at this time. To determine the wate srsource, it i,,*sugiested that the water be removed and a procedure developed and implemented to detewieiiný,esthsoukce of the water. Once a source is determined, the proper personnel should be notified andth arjnspected to determine whether further analysis or corrections are necessary.

Continued monitoring is recommended to include a continuation of the elevation surveys of the previously identified targets on this structure and surrounding site. The purpose is to monitor for signs of structure distress and movement or changes in soil conditions around the structure. The results of this monitoring increase the confidence in the assessment results. Elevation surveys should be performed weekly for 4 weeks and biweekly until December 31, 2011. At the time of Revision 0, groundwater levels had not yet stabilized to nominal normal levels, Therefore, it is possible that new distress indicators could still develop. If any new distress indicators are observed before December 31, 2011, appropriate HDR personnel should be notified immediately to determine whether an immediate

Priority 1 Structures Page 5.3-10 Containment Rev. 2 inspection or assessment should be conducted. Observation of any new distress indicators might result in a modification of the recommendations for this structure.

5.3.7 Updates Since Revision 0 Revision 0 of this Assessment Report was submitted to OPPD on October 14, 2011. Revision 0 presented the results of preliminary assessments for each Priority I Structure. These assessments were incomplete in Revision 0 because the forensic investigation and/or moniting for most of the Priority 1 Structures was not completed by the submittal date. Thistrsessment Report includes the results of additional forensic investigation and monaioging to dateaer Tis structure as described below.

5.3.7,1 Additional Data Available ' \*" \

The following additional data were available for the Conta, itfor Revisions .* 2- of2fftis*?

Assessment Report: "-V,.

Results of KDI #1 forensic investigation (see t4 1)

Results of geophysical investigation by .yG 'inIt (see A

.,,*c(se Af 6).

• ax*h*en Results of geotechnical investigation by te Geotejhc. see Attad eiih 6).

Data obtained from inclinometers by Thi~le Geote .c,. 'seettachment 6).

• Results of continued survey by Lamp Rvt'arson an 6Associ te& e Attachment 6).

5.3.7,2 Additional Analysis The following analysis of addi~hnal data was condiwt.d-forýt1t ontaament 0 Resulff ý:46geopscal investigation report by Geoftc&inology, Inc.

isfiic Refract'in ei~ R~itests performed around the outside perimeter of the esmic 4V*ower block identifie p, anomalitO *tcould be gravel, soft clay, loose sand, or

~~;/ possibly voids.

Results R', of geotechnical inv,.estigation by Thiele Geotech, Inc.

\Sxi.test borings were drille,:with continuous sampling of the soil encountered, to ground tiýthi&hi*Geotechnology ,:'seismic investigation results as part of the KDI #2 forensic invesýtigtion. Test boreýetoles were located to penetrate the deep anomalies identified in the seismi"Jiýestigatiad>n'he test boring data did not show any piping voids or very soft/very loose conditi:6nns~thaiiight be indicative of subsurface erosion/piping or related material

• loss or moverffi""

All of the SPT and CPT test results conducted for this Assessment Report were compared to similar data from numerous other geotechnical investigations that have been conducted on the FCS site in previous years. This comparison did not identify substantial changes to the soil strength and stiffness over that time period. SPT and CPT test results were not performed in the top 10 feet to protect existing utilities.

Priority 1 Structures Page 5.3-11 Containment Rev. 2 Data from inclinometers to date, compared to the original baseline measurements, have not exceeded the accuracy range of the inclinometers. Therefore, deformation at the monitored locations since the installation of the instrumentation has not occurred.

• Results of continued survey by Lamp Rynearson and Associates.

Survey data to date compared to the original baseline surveys have not exceeded the accuracy range of the surveying equipment. Therefore, deforkation at the monitored locations, since the survey baseline was shot, has not o urre The CPFMs that could not be ruled out in Revision 0 a tyzed b Nb*'sed on the additional data available for Revisions 1 and 2 of this fi-ik men! *4u ..

Triggering Mechanism 3 - Subsurface Erosion/Piping\ ,."

CPFM 3b - Loss of lateral support for pile foundation,.(dup: Pinpmg)

CPFM 3b for the Containment is associated with Key Distress In 1. Section 41 presents the presentsni results of additional forensic investigati& "a, was conduked -o ascertain whether ivspgainss this CPFM could be ruled out. The results of .oeladiti asow that if the recommendations for physical modifications in KDI -a-plemente$rPthis CPFM is ruled out. Therefore, assuming that no ftui-ir"e m r idetfied througlte monitoring program for the Containment (discussed i3c n d continuin until December3 1, 2011), this CPFM is moved to the -tfidrantBo.the represqiqg b Further Action Recommended Related to the 2011l .'F, o1od. ,.

...)]

Priority 1 Structures Page 5.3-12 Containment Rev. 2 5.3.7.1 Revised Results The CPFM evaluated for the Containment is presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

5..'37.2 Conclusions :.,

In the assessment of the FCS'Sticetures, the first step was to develop a list of all Triggering KlNMechanisms and PFMs that coiuld have occurred due to the prolonged inundation of the FCS stUng the 2011 Missouri ,River flood and could have negatively impacted these structures.

Thexi .p was to use data4fem various investigations, including systematic observation of the struetaes!,over time, ei.r er[to eliminate the Triggering Mechanisms and PFMs from the list or to recoin d,.furtherimvesligation and/or physical modifications to remove them from the list for any paIeIIlar'steture. Because all CPFMs for the Containment other than CPFM 3b had been ruled dut! or,to Revision 1, and because CPFM 3b will be ruled out when the physical modificai on's recommended for KDI #1 in Section 4.1 are implemented, no Triggering Mechanisms and their associated PFMs will remain credible for the Containment.

HDR has concluded that the geotechnical and structural impacts of the 2011 Missouri River flood will be mitigated by the implementation of the physical modifications recommended in this Assessment Report. Therefore, after the implementation of the recommended physical modifications, the potential for failure of this structure due to the flood will not be significant.

Section 5.4 Rad Waste Building

"... .I .: : .,' ,.:'):".* ii,

"*&i.i,'* ..... 14......*.,

• *.,, 4,.*NV, , ~I

/ ~ ':;, ",'*!ih ,  :;* "* ,:,,  :::,*

": 7.<'"L ,.,:H **,,,,, .**;**.,," .

A',.. '. ...*' '-:'.,:'!k  :, ' .i i, *,

! .? w':'.;'*" * '.;" :: @ "* :"*.*', ..'.:'

K,,*:,.::p

" ,** ,,, ,*:,,,: , * ,

• i:i :*,

Priority 1 Structures Page 5.4-1 Rad Waste Building Rev. 2 5.4 Rad Waste Building 5.4.1 Summary of Rad Waste Building Baseline information for the Rad Waste Building is provided in Section 2.0, Site History, Description, and Baseline Condition.

The Rad Waste Building is a single-story, rectangular-shaped building w plan ,th dimensions of about 73 by 175 ft. The building was added onto the south side of theA*,.i,'ar 4R AVThe roof is supported by a steel moment frame that transfers the load to a .ucttural mat oun tion. Exterior walls consist of precast panels, and interior walls consist of m*o*ny block.' RoTpof the mat foundation ranges from about el. 1002 to 1007 ft and is tk mrposed`ý,g'e where it extends to 4 ft below exterior grades (up to 7 ft thick). The baseme fR elevation Auxiliary Building where the Rad Waste Building abuts is 987 ft. fcornhe Auxiliary B *1dg  !*k have extended to about el. 983.5 ft. Site grades prior to the originl evelpment ranged fr*i*aboii el. 1002 to 1004 ft. This would suggest placement of about 20 ft of backffMbion* the Auxilia*.

Building wall and minimal placement of additional fill. I design gra ds -Excavations as deep as about 4 ft would have been necessary where the to p oe a 0dation isestabtished at 1002 ft.

5.4.2 Inputs/References Supporting the Analysis Table 5.4-1 lists references provided by OPD andbfier do/p"ýents use dlt6u:port HDR's analysis.

Table 5.4 References for R d..Waste Buiiling Document Title , \v OPPD Doc6fibin I <,Date

-i Page Number(s)

Nuberj (ifapplicable)-i_ _ _

Foundation P.anfNortii a X"ý7753-03-A-12 10/03/1988

_____ _____ _____ _____ (#46694) _ _ _ _ _ _ _ _

Foundat no'?Plan South Area - 7753*,3A 13 10/03/1988 S (#46694)ký (Sie,*i0.) *Unknown Bath *ie.cjWS.urvey K.v Unknown Survey PImilevations A __________Unknown Naval FaciifftErgineering

1. Comman' 9/1986 All Design Manual ,74.,0**.oil Mechanics,<Ksr __,_ _ _ __";_ _

Detailed site obsercatioens- field:reports, field notes, and inspection checklists-for the Rad Waste Building are provided h -A*trtakbIient 8 Observed performance an*13ertinent background data are as follows:

• Vibrofloation was not documented to have been performed below the structure.

• The electrical ductbank located inside the Rad Waste Building was present prior to construction.

• The sump in the truck bay did not have groundwater infiltration at the time of the field assessment.

" The structure was protected from floodwater for the majority of the 2011 flood by an Aqua Dam; however, the Aqua Dam failed for a short period of time due to being damaged, allowing floodwater to enter the area inside the Aqua Dam perimeter. This incident resulted in the flooding of the truck bay. Floodwater flowed into the sump until the temporary flood barrier was installed.

Priority 1 Structures Page 5.4-2 Rad Waste Building Rev. 2

• Water that is pumped from the sumps is documented and stored.

" Hairline and stair-step cracking was observed in the masonry walls at various locations. It is unclear whether these cracks were present prior to the 2011 flood.

" The structure is designated as a Class I (seismic) structure in accordance with OPPD.

• No incident report summaries or inspection records are available for this structure.

" No design basis summary document is available for this structure.

• General observations of the interior of the structure were limited by the accessibility in certain rooms.

5.4.3 Assessment Methods and Procedures 5.4.3.1 Assessment Procedures Accomplished Assessments of the Rad Waste Building included the fllowlng

" Visual inspection of the accessible areas of the interior of the *etiuire

" Visual inspection of the accessible exterior ofthe structure

" An assessment of collected survey data to d1 fo Wications of itrnrsFihith e movement of the structure

. Review of previously documented condition reports,,aisbuiltRplans, site topography, and geotechnical reports to identify possibl&.,, 6 nditions.l4iat cot.b ,. affected by the 2011 flood Additional investigations were pef~rrfaed. 'ilse iic4-ded thelfd611vmig non-invasive geophysical and invasive geotednil investigati Y," .

• Seismic surveys (seismi* x(ffaition and seismi 'tRh h.e protected area. (Test reports were _n lable at the timen f Revision 0.)

• ..... chiaf boings In thcprotected area. Note that OPPD required vacuum e'xcaxvation for thelti,rst -Q ft of proos. test holes to avoid utility conflicts. Therefore, test conditiOnsi eupper 10 ft of test boring logs. (Test reports willnotshow-soil*

were not available at t~eiin of ."

Procu'ies .Assessment Not Completed Ad*'t."itoa  :*

NbdklUi~onal assessment procedures have been identified for this structure.

5.4.4 Analyis*bK Identified PFMs we'rnit aly'reve.wed as discussed in Section 3.0. The review considered the preliminary information ivdiabife from OPPD data files and from initial walk-down observations.

Eleven PFMs associated with' five different Triggering Mechanisms were determined to be "non-credible" for all Priority 1 Structures, as discussed in Section 3.6. The remaining PFMs were carried forward as "credible." After the design review for each structure, the structure observations, and the results of available geotechnical, geophysical, and survey data were analyzed, a number of CPFMs were ruled out as discussed in Section 5.4.4.1. The CPFMs carried forward for detailed assessment are discussed in Section 5.4.4.2.

Priority 1 Structures Page 5.4-3 Rad Waste Building Rev. 2 5.4.4.1 Potential Failure Modes Ruled Out Prior to the Completion of the Detailed Assessment The ruled-out CPFMs reside in the Not Significant/High Confidence category and for clarity will not be shown in the Potential for Failure/Confidence matrix.

Triggering Mechanism 2 - Surface Erosion CPFM 2a - Undermining shallow foundation/slab/surfaces Reasons for ruling out:

" The structure was protected from the floodwater by ý a short period of time when the Aqua Dam failed due to bel floodwater to enter the area inside the Aqua Dam perimeter.

• Surface erosion was not identified near the structure Triggering Mechanism 3 - Subsurface Erosion/Pipin, CPFM 3a - Undermining and settlement of sha'lI.v, (due to pumping)

Reason for ruling out:

• The structure is a sufficient the zone of influence of the CPI Triggering Mechanism 3 7 CPFM 3d - Underminij (due to river JI .*ddodwn)

Redsdn for rulinsouft

-0,vThe structure is a suffibi~eiii-di stance "ithI river to be outside the. zone of influence of the rPN1. *'""V geeing Mechanism 4- H-. ,bstatic Lateral Loading (water loading on structures)

CP1M, 4a - Overturning CR1M4j- Sliding  !:I2>

CPFM- 4&,'Wall failui&fm flexure CPFM 4d Wall faffie in shear CPFM 4e `T'xgessdeflection Reasons for rulingoi ut:

" The Rad Waste Building is designed to withstand an external water load due to flooding of the Missouri River to el. 1007 ft. The peak flood elevation in 2011 was approximately 1006.9 ft.

• Visual observation did not identify distress to the structure that can be attributed to this CPFM.

Priority 1 Structures Page 5.4-4 Rad Waste Building Rev. 2 Triggering Mechanism 5 - Hydrodynamic Loading CPFM 5a - Overturning CPFM 5b - Sliding CPFM 5c - Wall failure in flexure CPFM 5d - Wall failure in shear CPFM 5e - Damage by debris CPFM 5f- Excess deflection Reasons for ruling Out:

• Sufficient high floodwater velocities were not idenl near the t°r ue*,I e*.

" The structure was protected from the floodwater b an ua Dam ex 14dring a short period of time when the Aqua Dam failed due to be-- g~imcig which k floodwater to enter the area inside the Aqua Dam perimeter.

Visual observation did not identify distress to the st be attribut li.

CPFM.

Triggering Mechanism 6 - Buoyancy, Uplift lFres on Structures',,  :

CPFM 6b - Cracked slab, loss of structura-s4 pport 6..

CPFM 6c - Displaced structure/broken..iections ..

Reason for ruling out:

The Rad Waste Building is to withstan n externwater load due to flooding of the Missouri River to el. I00'7ft The peak fl od. levation~h 2011 was approximately 1006.9 ft.

TriggegYfýeb m 7 - Soil C6llapse (first time wetting)

,* *7 -settlemen "

asons for ruling out:

". Site settlement was not oblse'r.ed near the Rad Waste Building during the field assessments.

'"ZIthe peak flood elevation pnOTorto 2011 was documented in 1993 at 1003.3 ft, which would "undicate the soils below an iirounding the building have been saturated.

Trigge!,inggAlechanism 10' Machine/Vibration-Induced Liquefaction CPFM1.0a,.Cracked'sl differential settlement of shallow foundation, loss of structural CPFM I0b\-Displaced structure/broken connections CPFM 1Oc - Additional lateral force on below-grade walls Reason for ruling out:

0 Machine/vibration-induced liquefaction was not observed to have occurred at the site.

Priority 1 Structures Page 5.4-5 Rad Waste Building Rev. 2 Triggering Mechanism 11 - Loss of Soil Strength due to Static Liquefaction or Upward Seepage CPFM 11 a - Cracked slab, differential settlement of shallow foundation, loss of structural support CPFM 1l b - Displaced structure/broken connections CPFM 11 c - Additional lateral force on below-grade walls Reason for ruling out:

0 Machine/vibration-induced liquefaction was not ol at the site.

Triggering Mechanism 12 - Rapid Drawdown CPFM 12a - River bank slope failure and undermi CPFM 12b - Lateral spreading Reason for ruling out:

• The Rad Waste Building is a sufficient distanceOmlthe river to be ouiitde the zone of influence of the CPFM.

Triggering Mechanism 14- Frost Effect". ,

CPFM 14a - Heaving, crushing, or disV ement-Reason for ruling out: -.

The Rad Waste /lamne-s',undation system el, and the interior of th(e IMI eKl'ow building is a heated structur, T*he building wil[ iected to freeze/thaw cycles.

Floodi-nLhfiiotichange thefrosft;and foundation cob'ditions.

le Potential Failure Modes The' following CPFMs are eli4,0l y CPFM-ar iied forward for detailed assessment for the IRad Waste Building as a resfdltq'f the 2011 fl od. This detailed assessment is provided below.

ing Mechanism 7 - Soil. ollapse (first time wetting)

\'*FM 7a - Cracked slab differential settlement of shallow foundation, loss of structural

, support ,-

CPFM,ýb t-Di splaced.&fs cture/broken connections Portions of thleRa&dW;asteBuilding are supported on a differential thickness of backfill and new fill.placed Mfg','the Auxiliary Building exterior wall. The thickness of a portion of this fill could be up to aMut 20 ft thick.

This Triggering Mechanism and CPFM could then occur as follows: the rise of the groundwater elevation associated with the flooding, in addition to the flooding that occurred when the Aqua Dam failed due to being damaged, could have resulted in the first time wetting of a portion of this backfill. When sandy soils are wetted, the water acts like a lubricant, allowing the sand particles to rearrange. When clayey soils are wetted, the water reacts with the clay, causing it to slake. When cemented soils are wetted, the water dissolves the cement, allowing the particles to rearrange.

Priority 1 Structures Page 5.4-6 Rad Waste Building Rev. 2 Previous floods since backfilling of the Auxiliary Building wall have been as high as about el. 1004 ft. Rise in groundwater elevations during previous floods could have previously wetted portions .of the backfill.

The following table describes observed distress indicators and other data that would increase or decrease the potential for degradation associated with this CPFM for the Rad Waste Building.

Adverse (DegradationlDirect Favorable (Degradation/Direct Floodwater Floodwater Impact More Likely) Impactjg s. Likegly)

Hairline and stair-step cracking of the Previous floods Mbhav`e a NTited a majority of masonry walls was observed, the fill.

The site soils aor',ot ceme n,'t.i ,,

Survey data to , does n6o entif- rable movement.

Data Gaps: Z..

Subsurface conditions and how they may facilitate the CPWs are well understoo.,,,.

7 Additional data will be acquired from GPR, seismic survey, and ged'ý cal tborms Conclusion Significance-Potentialfor Degradation/DirectFlpoodwater mpact The presence of thick fills belotheRad Waste Building may increase the potential that degradation due to these CPEMs' has occurred pri~r-to'or due to4~he 2011 flood. Because the 2011 flood was approxima6ey.!3 fthigher than previousflods -and occurred for a longer duration, thelvotential that the'2011 flood caused futefdgradation due to these CPFMs is

,m4lzcation 6*h*?he Rad Waste Building is SIPpprted on a mat toundation that can tolerate moderate si.isttlement. Additionally, theIbikness of fill that potentially was wetted from the 2011 flood is

\]tily.ely small. The occurrenee of this CPFM is not expected to negatively impact the performance of the mat foundation'. Therefore, the implication of the potential degradation for this C-VJPFs low. '

Confidence',

The available dtifa,di not sufficient to rule out these CPFMs or lead to a conclusion that the Rad Waste BuildiNf6undations might have been impacted because of the CPFMs. Therefore, the confidence in the above assessment is low, which means more data are necessary to draw a conclusion.

Summary For CPFMs 7a and 7b, as discussed above, the potential for degradation is high. However, this degradation is expected to be relatively small due to previous wetting. Therefore, the combined consideration of the potential for degradation and the implications of that degradation to a structure of this type puts it in the "not significant" category. The data currently collected are

Priority 1 Structures Page 5.4-7 Rad Waste Building Rev. 2 not sufficient to rule out this CPFM. Therefore, the confidence in the above assessment is "low," which means more data or continued monitoring and inspections might be necessary to draw a final conclusion.

5.4.5 Results and Conclusions The CPFMs evaluated for the Rad Waste Building are presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in theyaluation.

5.4.6 *Recommended Actions Continued ýmontorjng is recommende'to "include a continuation of elevation surveys of the prewously identified targetsonthi4s structure afid surrounding site. The purpose is to monitor for signs of structure distress andn&omovement oir changes in soil conditions around the structure. The results of this monitoring will be u6s9cdo mereas the confidence in the assessment results. Elevation surveys should be performed weekly fo 4 xweel*s and biweekly until December 31, 2011. At the time of Revision 0, groundwater levels had not,,yet stabilized to nominal normal levels. Therefore, it is possible that new distress indicators could still develop. If new distress indicators are observed before December 3 1, 2011, appropriate HDR personnel should be notified immediately to determine whether an immediate inspection or assessment should be conducted. Observation of new distress indicators might result in a modification of the recommendations for this structure.

5.4.7 Updates Since Revision 0 Revision 0 of this Assessment Report was submitted to OPPD on October 14, 2011. Revision 0 presented the results of preliminary assessments for each Priority 1 Structure. These assessments were

Priority 1 Structures Page 5.4-8 Rad Waste Building Rev. 2 incomplete in Revision 0 because the forensic investigation and/or monitoring for most of the Priority 1 Structures was not completed by the submittal date. This revision of this Assessment Report includes the results of additional forensic investigation and monitoring to date for this structure as described below.

5.4.7.1 Additional Data Available The following additional data were available for the Rad Waste BAi:ding for Revisions 1 and 2 of this Assessment Report: . . *4b te~aee

ýy<*" I

• Foundation drawings that show the Rad Waste mat founlation smoportLby step-tapered driven pile. These drawings are 7753-03-A-l10 and 3 3-ý-,rAý-..

• Results of geophysical investigation by Geotechnology cei.se Attachit).

Results of geotechnical investigation by Thiele Geotec (see Attachmfentf.) .

" Data obtained from inclinometers by Thiele Geotech,4ci (*s*ttacment6%-A4"

" Results of continued survey by Lamp Rynearson and ASCi (e. Attachmen'l*fr, 5.4.7.2 Potential Failure Modes Ruled Outtl-i lohe Compl tbeorf the Detailed Assessment The CPFMs ruled out in Section 5.4.4.1 wlerbased on th..*n'derstanding that the Rad Waste Building was supported by a grade-suppoi e4iat foundation Nelwinformation available for Revision 1 shows the mat foundationfto be'pile suppor.led. Theparagraphs below provide the ruled-out CPFMs based on the afliti*if~al informatiopi available *o*rRevisions 1 and 2 of this Assessment Report and reeva,,hApi0 of each CPF MN ,4 As previouslystated, the rulel-out 6PFMs reside inth' nificant/High Confidence cate'la -will not in the Potential for Failure/Confidence matrix.

'Ifiggering Mechanism ZwSurface rs!,6n 2 ACPFM 2b - Loss of l'aterasupport forY1Ieil foundation

• &iReasons for ruling out  :

hstructure was protected/from the floodwater by an Aqua Dam except during a short bPthd of time instde iu am failed due to being damaged, which allowed floodwater to 6`iffie area insidthe qua Dam perimeter.

Surfa¢c jesn was not&identified near the structure during the field assessments.

Triggering Mein[amism, Subsurface Erosion/Piping CPFM 3b - Lbossdif lateral support for pile foundation (due to pumping)

Reason for ruling out:

• The structure is a sufficient distance from the known pumping locations to be outside the zone of influence of the PFM.

Priority 1 Structures Page 5.4-9 Rad Waste Building Rev. 2 Triggering Mechanism 3 - Subsurface Erosion/Piping CPFM 3e - Loss of lateral support for pile foundation (due to river drawdown)

Reason for ruling out:

• The structure is a sufficient distance from the river to be outside the zone of influence of the PFM.

Triggering Mechanism 6 - Buoyancy, Uplift Forces on Structures-,',

CPFM 6a - Fail tension piles Reason for ruling out: <<.

• Distress was not observed at the structure that can be a ttr.buted to the PFM: ./>

Triggering Mechanism 10 - MachineVibration-InducetPLijuefaction '-

CPFM 1Od - Pile/pile group instability . , ,

Reason for ruling out:

0 Machine/vibration-induced liquefaction' as not obse eto:'aye occurredPai the site.

Triggering Mechanism 11 - Lossof 4 Soil Nength. e ic i lq4faction or Upward CPFM lId - Pile/pile group:i i bility K Reason for ruling out: ' /

liqu*efaction was not observed to have occurred at the site.

.MachinIb*.iation-i-duced 547,3 Additional A,1Wys\s

..,The following analysis of addti.-nal data was' onducted for the Rad Waste Building:

ltes o g op y ica ..........

onv*

sults of geophysical inveis..gation report by Geotechnology, Inc.

S'eIsmic Refraction and Sei6si'c ReMi tests performed around the outside perimeter of the powr bil'ock identified *dcep.

anomalies that could be gravel, soft clay, loose sand, or possiblyivoids y Results of geotei*c'al investigation by Thiele Geotech, Inc.

Six test borings were drilled, with continuous sampling of the soil encountered, to ground truth the Geotechnology, Inc. seismic investigation results as part of the KDI #2 forensic investigation. Test bore holes were located to penetrate the deep anomalies identified in the seismic investigation. The test boring data did not show any piping voids or very soft/very loose conditions that might be indicative of subsurface erosion/piping or related material loss or movement.

All of the SPT and CPT test results conducted for this Assessment Report were compared to similar data from numerous other geotechnical investigations that have been conducted

Priority 1 Structures Page 5.4-10 Rad Waste Building Rev. 2 on the FCS site in previous years. This comparison did not identify substantial changes to the soil strength and stiffness over that time period. SPT and CPT test results were not performed in the top 10 feet to protect existing utilities.

Data from inclinometers to date, compared to the original baseline measurements, have not exceeded the accuracy range of the inclinometers. Therefore, deformation at the monitored locations since the installation of the instrumentation has not occurred.

• Results of continued survey by Lamp Rynearson and Associate 'S Survey data to date compared to the original baselin urveys haveainlt exceeded the accuracy range of the surveying equipment. Theretoýe~eform9 u onitored locations, since the survey baseline was shot, has noterCý a,,a.

The CPFMs that could not be ruled out in Revision 0 are arial1 elow based o th.ie- .

additional data available for Revisions 1 and 2 of this As men k-ort.

Triggering Mechanism 7 - Soil Collapse (first, rigting)

CPFM 7b - Displaced structure/broken cone ions Portions of the Rad Waste Building are supported on a d*thickness obackfill and new fill placed along the Auxiliary Builditig extenror Wd1l'ý The aickhess of a portion of this fill could be up to about 20 ft thick._-The niseuo-f thegr.oundwaterfelevauýon associated with the flooding, in addition to the floodinggthat occurred When the AquA: Dam failed due to being damaged, could have resulted in 'tfirst time wetuggof a portioi'of this backfill. When sandy soils are wetted, the water actsdlikiea lubricant, allbo =9gthe~sndi particles to rearrange. When clayey soils are wetted, the water reacts with the cliy\ itausmgWtto slake. When cemented soils are wetted.' Watrissolves iheement allowing the particles to rearrange.

PN, floods since-eae!ling of the Auxiliary Building wall have been as high as about

,,el*1004 ft. Rise in groun.+,water elevationss during previous floods could have previously

/iKeited

• portions of the backT /ýii

'Slnificance 7.

Poteqnt afor Degradation/DirectFloodwaterImpact The presncý&eo6f thick fillsA6e1ow the Rad Waste Building could increase the potential that degradationd jeo.these'OEFMs has occurred prior to or due to the 2011 flood. Because the 2011 flood wgpr tely 3 ft higher than previous floods and occurred for a longer duration, the potentia*lthat the 2011 flood caused further degradation due to the CPFM is high.

Implication The structures supported on the grade would settle while structures supported by piles would not. This could result in a "pinch-point at the interface of the non-pile supported and pile supported structures. Depending on the flexibility of the interface connection and the magnitude of settlement, the occurrence of the CPFM could impact the performance of the structure negatively. The amount of settlement due to collapse of the upper 3 ft of fill is negligible. Therefore, the implication of the potential degradation for the CPFM is low.

Priority 1 Structures Page 5.4-11 Rad Waste Building Rev. 2 Confidence The available data lead to a conclusion that the Rad Waste Building was not impacted by the CPFM. Therefore, the confidence in the above assessment is high.

Summary For CPFM 7b as discussed above, the potential for degradation is high. However, this degradation is expected to be relatively small due to previous wefti, Ther*fore, the combined consideration of the potential for degradation and the imphdaons o)-'*hai'egradation to a structure of this type put it in the "not significant" categip'Then datad'Wintly collected are sufficient to rule out these CPFMs. Therefore, the con nace inth 4,]ovisessment is "high."

Triggering Mechanism 7 - Soil Collapse (first time wetting) K.

CPFM 7d - Piles buckling from down drag N Portions of the Rad Waste Building are supporte. 0.n A ferential i* sof backfill and new fill placed along the Auxiliary Building extderikw e thickness-ýp aportion of this fill could be up to about 20 ft thick. The ris o he roNdwter elevation aýsociated with the flooding, in addition to the flooding that oaUrre.d when e Iji am failed die to being damaged, could have resulted in the first t pettnin6 his backfill. When sandy soils are wetted, the water acts hkeo.t::tubrie*;: alloNiihe I sanlti:t i to rearrange. When clayey soils are wetted, the wate,. eacts with the cla,,*,*qusingit, kslake. When cemented soils are wetted, the water dissolves the cement allowingthe particles otrearrange.

Previous floods since backfilling:,ofthe Auxiliary Bb'mgdiD li have been as high as about el.1iq1~eatons during prew'vidtfloods could have previously.

wetted it6ionsofithebaikfill .

Asii-,ficance .V

< *_'J`otentialfor Degradation/DEct.,iFloodwate>mpact ce,1preosence of thick fills belo, ithe Rad Waste Building could increase the potential that degradadion due to the CPFMtih oa*bccurred prior to or due to the 2011 flood. Because the 2011 floodwas approximately 3 ýfl hier than previous floods and occurred for a longer duration, the potenihl týat the 201',. flodcaused further degradation due to the CPFM is high.

Implication The amount of down drag force that would be applied to the piles due to collapse of the upper 3 ft of fill is negligible. The occurrence of the CPFM is not expected to impact the performance of the mat foundation negatively. Therefore, the implication of the potential degradation for the CPFM is low.

Confidence The available data lead to a conclusion that the Rad Waste Building foundation was not impacted by the CPFM. Therefore, the confidence in the above assessment is high.

Priority 1 Structures Page 5.4-12 Rad Waste Building Rev. 2 Summary For CPFM 7d, as discussed above, the potential for degradation is high. However, this degradation is expected to be relatively small due to previous wetting. Therefore, the combined consideration of the potential for degradation and the implications of that degradation to a structure of this type put it in the "not significant" category. The data currently collected are sufficient to rule out the CPFM. Therefore, the confidence in the above assessment is "high."

5.4.7.1 Revised Results The CPFM evaluated for the Rad Waste Building is prese shows the rating for the estimated significance and the *1'e*

CPFMs 7b and 7d for the Rad Waste Building are not a844 The results of the additional forensic investigation show ti Therefore, assuming that no further concerns are identifie the Rad Waste Building (discussed in Section 5.4.6 and c(

these CPFMs are placed in the quadrant of the matrix epi Recommended Related to the 2011 Flood."

Priority 1 Structures Page 5.4-13 Rad Waste Building Rev. 2 5.4.7.2 Conclusions In the assessment of the FCS Structures, the first step was to develop a list of all Triggering Mechanisms and PFMs that could have occurred due to the prolonged inundation of the FCS site during the 2011 Missouri River flood and could have negatively impacted these structures.

The next step was to use data from various investigations, including systematic observation of the structures over time, either to eliminate the Triggering Mechanisms and PFMs from the list or to recommend further investigation and/or physical modificatioAsgto remove them from the list for any particular structure. Because all CPFMs for the Rad A-"d Buifd',g other than CPFMs 7b and 7d had been ruled out prior to Revision slec Ms 7b and 7d have been ruled out as a result of the Revision I findings, nolfig'gering ,,hanisms and their associated PFMs remain credible for the Rad Waste Bt31-b*ght" lg. They.

" )fr ."jhas concluded t'u*aliintegrity of that the 2011 Missouri River flood did not impact the ge)*al~ and str , e o the Rad Waste Building because the potential for failure of-S tSucture due to~he Vs1ot hood significant.

Section 5.5 Technical Support Center

Priority 1 Structures Page 5.5-1 Technical Support Center Rev. 2 5.5 Technical Support Center 5.5.1 Summary of Technical Support Center Baseline information for the Technical Support Center is provided in Section 2.0, Site History, Description, and Baseline Condition.

5.5.2 Inputs/References Supporting the Analysis ,,

Table 5.5-1 lists references provided by OPPD and other documnised to o HDR's analysis.

Table 5.5-I - References for Technical tpooknoiter' Document Title OPPD Documerift* **," Date Page Number Wber.

(if applicable) l Mat-Plan Sections and Details 4778-293-404-001 2/1 84 ,

(#31553) _ _ _ _

Foundation Walls el. 1005 ft 4778-2 a' 2/16/1984' Sections and Details -V00 i2 1980

(#31**

lawmJ Naval Facilities Engineering Command, M 9/ All Design Manual 7.01, Soil Mechanics ,,._ __ _ _

Detailed site observations-field rq t eld notes, and ctionn* lists-for the Technical Support Center are provided inA Observed peV ent ac a'ddata are as follows:

is re s surounded*n* *ides by~tl iliary Building, the CARP, and the inance r92 Shop. The C ' aintena op have shallow foundations similar to the 3"2 expansion of the Techni, Support Cen r. The Auxiliary Building, located to the south,

• ..'rs ted by a deep foundatiorns4fem with a basement.

• Th , re is designated as a CILS4 (seismic) structure in accordance with OPPD.

• The fb -----

for Phase 1 consi!.. *a 2.0-ft minimum thickness rigid structural mat slab with top-of-corz levation of 1OQ1 (see drawing 4778-293-404-001). Finished floor elevation is 1005.0 f, w T. *zachieveddti the use of an architectural false floor or concrete fill, depending on

" The foundation fo' nsists of simple wall footings and stem walls and a slab-on-grade with top-of-concrete

• ion of 100.5.0 ft (see drawing 4778-293-405-002).

• The superstructure for Phase I consists of cast-in-place concrete walls and roof slab. The roof system is a membrane roof with tapered insulation (see drawing 4778-293-108-001).

" The superstructure for Phase 2 consists of concrete masonry walls. The roof is an open-webbed joist system with concrete slab on metal deck. The roof system is the same as for Phase 1 (see drawing 4778-293-108-001).

" The drawings indicate a 1-in. -wide expansion joint at the floor and roof elevations (see drawing 4778-293-108-001).

" This structure, along with the surrounding buildings, was protected from the 2011 flood by an Aqua Dam. It is possible that the foundations for this structure were subjected to high groundwater

Priority 1 Structures Page 5.5-2 Technical Support Center Rev. 2 pressure equal to the flood elevation. The maximum flood elevation at the Aqua Dam near the Technical Support Center was approximately el. 1007 ft. No incident report summaries or inspection records are available for this structure.

• No design basis summary document is available for this structure.

• General observations of the interior of the structure were limited by the accessibility of certain rooms. In addition, many areas have architectural walls and ceilings that limit visual observations.

• Where the concrete slab was accessible, there were no signs of cracki , movement, or water infiltration at the time of this inspection.

Indications of structural distress in many areas were limited t ob dicators within the architectural treatments such as gypsum board walls an gs tors were found within the architectural systems.

" Sandbags were stacked within the corridor outside the mec c d1 oms. There was no sign of water infiltration through slab joints at the tim ction.

" Voids were found below the slab in the Turbine Building, wh' ed to the so Technical Support Center. For further information, see Secti e detailed d-ie this Key Distress Indicator is presented in Section 4.1.

" The Maintenance Shop to the northeast has docume .. ent issues. uilding column footing and a section of floor slab had settled at t - on 0. A n* itled discussion of this Key Distress Indicator is presented in Se .3.

5.5.3 Assessment Methods and Procedure 5.5.3.1 Assessment Procedr ccorplis Assessments of the Technic . ort Center inc e ng:

" Vis mof access s of the interi structure

• e**M**eference ments listed in Table 5.5-1 AssesmenI urespleted ssessments of the Technic ort Cente hat were not completed included the following:

eline survey with perio .eview indicating trends in the top of concrete. This was not a eted t because o survey,.the st ý e is surrounded by other structures and was not directly SGeo al borings icinity of the Technical Support Center to determine current soil cohA-, n. I t ies.

5.5.4 Analysis Identified PFMs were initially reviewed as discussed in Section 3.0. The review considered the preliminary information available from OPPD data files and from initial walk-down observations.

Eleven PFMs associated with five different Triggering Mechanisms were determined to be "non-credible" for all Priority 1 Structures, as discussed in Section 3.6. The remaining PFMs were carried forward as "credible." After the design review for each structure, the structure observations, and the results of available geotechnical, geophysical, and survey data were analyzed, a number of CPFMs were ruled out as discussed in Section 5.5.4.1. The CPFMs carried forward for detailed assessment are discussed in Section 5.5.4.2.

Priority 1 Structures Page 5.5-3 Technical Support Center Rev. 2 5.5.4.1 Potential Failure Modes Ruled Out Prior to the Completion of the Detailed Assessment The ruled-out CPFMs reside in the Not Significant/High Confidence category and for clarity will not be shown in the Potential for Failure/Confidence matrix.

Triggering Mechanism 2 - Surface Erosion CPFM 2a - Undermining shallow foundation/slab/surfaces Reason for ruling out:

The Technical Support Center is completely surroun by oth )'C:-"esand is therefore not subjected to surface erosion. V.

Triggering Mechanism 3 - Subsurface Erosion/Pipings" ,i;\

'CPFM 3d - Undermining and settlement of shallow fo ii61ab (due to riveri'. 7 Reason for ruling out:

• The Technical Support Center is not ne ,b *Ksurroun dlw other structures and is therefore not subjecte . - draw n Triggering Mechanism 10 - Machine/Vii *on- ed Li tC CPFM 1Oa - Cracked slab, diffe#6fitial' lem ' shallow i'puination, loss of structural support . ,

CPFM lOb - Displace

• tde/broken conn'::) s CPFM 1Oc - Additional a afrce on b w Reas st o Y.

ca e does e permanent equipment capable of providing enough energy to resut ration indue dliquefaction.

ering Mechanism 11 s of Soil Strength due to Static Liquefaction or Upward

`&e_1ge 11 a - Cracked slab ifferential settlement of shallow foundation, loss of structural

" \ support ig-T-CPF*.st 41 Displacedq& s tureibroken connections CAddi 'tateralforce on below-grade walls Reason for rulin'o

• Static liquefaction was not observed on site in the vicinity of the Technical Support Center and surrounding structures.

Triggering Mechanism 12 - Rapid Drawdown CPFM 12a - River bank slope failure and undermining surrounding structures CPFM 12b - Lateral spreading Reason for ruling out:

Priority 1 Structures Page 5.5-4 Technical Support Center Rev. 2

• The Technical Support Center is located a sufficient distance away from the river bank and therefore is outside the zone of influence of a bank slope failure or lateral spreading.

Triggering Mechanism 14 - Frost Effects CPFM 14a - Heaving, crushing, or displacement Reasons for ruling out:

• The Technical Support Center foundation system is belo. fr e, aed the interior of the building is a heated structure. The building will not b ect* tha cycles.

Therefore, frost effects have been discounted.

5.5.4.2 Detailed Assessment of Credible Potenti aMuha des The following CPFMs are the only CPFMs carried forwa i ed assessme h Technical Support Center as a result of the 2011 flood. Tis assessment is below.

Triggering Mechanism 3 - Subsurface Eros, '

CPFM 3a - Undermining and settlemen e allowI n/slab/s A (due to pumping)

The Turbine Building, which is locted to outh f'the T c Support Center, has documented history of a void be1l@*e fo uhidatio 'asff dating b*ki6d1997. This void was confirmed via cored holes in th dation slabs '~camera rcrdings of broken drain piping under the floor slab. ConvertT"iii"with OPPD p I'iI that groundwater has been flowing at v ingrates thro e broken ipe s'p from that time to the present day. Theravinto the* 'directly related e hydraulic head of the groundwater.

As in ele On, cross the site, observed flow rates increased. The fo oundwater"fI'll -1Irain p tm through the breaks in the pipes is one of the

• istress Indicators dis&m~d in Seci* This drain pipe system was designed as a sed system; therefore, t1 are not ~unded by appropriate filter systems to preclude transportation of soils fro 1 surrounding area under the slab. It is logical to assume that the groundwater move ow the foundation and into the broken piping, some nt of the soil has occ CO. If these voids were to continue under the Technical Supp .,. ter they could belA enough to undermine the shallow foundations or slab on grade. *-*

The Triggeri, W.,And CPFM could then occur as follows: the unfiltered seepage condition will '1the breaks in the piping system are repaired, which means the potential for sion remains. Erosion could extend out, creating large voids under the Turbine Building mat foundation and ultimately under the Technical Support Center Foundation.

The following table describes observed distress indicators and other data that would increase or decrease the potential for degradation associated with this CPFM for the Technical Support Center.

Adverse (Degradation/Direct Floodwater Favorable (Degradation/Direct Impact More Likely) Floodwater Impact Less Likely)

Priority 1 Structures Page 5.5-5 Technical Support Center Rev. 2 A documented void exists under the foundation There have been no observed signs of structural slab of the Turbine Building with a known distress in the floor slab or indicators of hydraulic connection between groundwater structural distress in the architectural coverings elevation and flows into the building sump. A at the current loading conditions.

more detailed discussion of this Key Distress Indicator is presented in Section 4.1.

Unknown soil compaction density below the structure.

Varying foundation systems within the same structure (mat vs. spread footing) have the potential for differential settlement.

The Maintenance Shop, to the east, has documented settlement issues. One building column footing and a section of floor slab had settled at the time of Revision 0. A more detailed discussion of this Key Distress Indicator is presented in Section 4.3.

Data Gaps:

• Previous areas that were not accessible will b4

• Continued observation of structure as the flip Conclusion Significance PotentialforDegradation/I oodwaterI'ma Indicatos.M have served in the uilding, which is located to the sout . e* Suppo . Voids below the base slab in the Turbine Building ar to exist flows Z6o dwater are being pumped from the sump. Because 1 flood cause~d Iaflow ti the broken drain pipes, the potential that the

,fod caused further and nTi6irpid dr due to this CPFM is high. It is possible that fese voids extend under the"e16inical Support Center.

The o ce of this CPFUV` FId cause settlement of the shallow foundations or slab on grade e potenti use cracking of the walls, cracking of the slabs, or distress to the archite* - ve*. owever, the Phase 1 portion, which is designated Class I, is founded on a n and has much more redundancy. If degradation occurred it would be slower to de would allow time to respond with corrective action. Minor amounts of settlement wou]dibe considered a serviceability problem, not a strength or safety issue.

Therefore, this implication of the potential degradation for this CPFM is low.

Priority 1 Structures Page 5.5-6 Technical Support Center Rev. 2 Confidence The available data are not sufficient to rule out this CPFM. Therefore, the confidence in the above assessment is low, which means more data are necessary to draw a conclusion.

Summary For CPFM 3a, as discussed above, the combined consideration of the potential for degradation and the implications of that degradation to a structure of this typeti't inme "not significant" category. It is possible that voids extend under the Technii-'Sup*pen although the potential is low due to the distance from the Technical Ct .sump in the Turbine Building. The data currently collected are not ient to M s CPFM.

Therefore, the confidence in the above assessment is ,owI ca S mor or continued monitoring and inspections might be necessary to draw a I on.

Triggering Mechanism 6 - Buoyancy, Uplift Forces on pu

• Y CPFM 6b - Cracked slab, loss of structural support CPFM 6c - Displaced structure/broken connecr The peak flood elevation prior to 2011 was l ,W urred in 1 .1e peak flood elevation in 2011 was approximately 1006. ,

The Triggering Mechanism and CPFMs cl occur s orows:, ietvel rises in areas around the Technical Support e Wa s pu from in ro rea, causing an uplift force. This uplift forc ced by th loss be n the flooded areas and the area under the building. Th. force exceed self we' f the structure, causing structure slabs to crack au., dditional d ude structure displacement and broken1* p itc Theff g es obs *r ress indicators and other data that would increase or the potential d4 aor dation aq ted with these CPFMs for the Technical Support ter. * '

Xr dverse (Degradation/Diiloodwater Favorable (DegradationlDirect A Impact More L Floodwater Impact Less Likely)

... as in the corridor adjacen4ftiWhe There have been no observed signs of structural res1+/-i- ýindicate that water in" in into the distress in the floor slab or indicators of

%tu stu happening at siogme during the structural distress in the architectural coverings 2011 flodx water c t401 oming up at the current loading conditions.

through floor drain sy** bfifiiý,

sla or b p through the floor:Floodwater dain levels are receding. The structure "V has already experienced the maximum buoyant uplift pressures. Therefore, the possibility of failure from buoyancy is reduced.

Data Gaps:

• Previous areas that were not accessible due to security issues will be inspected.

0 Visual observation of structural elements that were not accessible.

• Continued observation of structure as the flood waters recede will be performed.

Priority 1 Structures Page 5.5-7 Technical Support Center Rev. 2 Conclusion Significance Potentialfor Degradation/DirectFloodwaterImpact The degradation associated with these CPFMs would include vertical movement of subgrade soils through the slab joints within the structure. There have been~o observed signs of structural distress in the floor slab or indicators of structura dis*r the hitectural coverings at the current loading conditions. Sandbags iin M

-ie to the restrooms could indicate that water intrusion into the structure w ening ... me during the 2011 flood. This water could be coming up through slb j ts or... ough the floor drain system. Since there were not signs of structure dis" n, al adation low.

Implication A.."

The occurrence of these CPFMs could cause vert ement of the* iN'ation or slab on grade and has the potential to cause distress t 'cht fý , as as d "r .-th als cracking of the slabs, or distress to the archi" al cov addition, .e upward pressure can cause water infiltration into t cture .. tion is con'sdered a serviceability problem, not a strength or s issue . for lication of the potential degradation for these CP iss lI' Confidence Indicators for this CPFM haen observed, ual observation was limited to a few acce. ,dor. d the The aval ata are not sufficient to rule out this l e confi ,ttheabove assessment is low, which means more data

/~~rnmmar" CPF0 s 6b and 6c, as discnsse above, the combined consideration of the potential for e ation and the implicatio. that degradation to a structure of this type puts it in the "not sig"i ta category. The st e has already experienced the maximum buoyant uplift press , observed signs of structural distress in the floor slab or indicato" ctural di e In the architectural coverings at these loading conditions. The data curren t. cte' ot sufficient to rule out this CPFM. Therefore, the confidence in the above asses. en 4', which means more data or continued monitoring and inspections might be necessai aw a conclusion.

Triggering Mechanism 7 - Soil Collapse (first time wetting)

CPFM 7a - Cracked slab, differential settlement of shallow foundation, loss of structural support CPFM 7b - Displaced structure/broken connections CPFM 7c - General site settlement The Triggering Mechanism and CPFMs could occur as follows: soil material under the structure is poorly compacted backfill or uncompacted native subgrade. Groundwater elevation rises to a level that saturates these soils. Soil undergoes excessive settlement, termed "collapse

Priority 1 Structures Page 5.5-8 Technical Support Center Rev. 2 settlement," due to first time wetting. The potential damage includes settlement of floor slabs and foundations, cracks in walls, and deflections in floors and roofs.

The peak flood elevation prior to 2011 was 1003.3 ft, which occurred in 1993. The peak flood

.elevation in 2011 was approximately 1006.9 ft. The bottom of foundation elevation for the Phase 1 rigid mat is 1000 to 1002, which is below the previously documented flood elevation.

The bottom of the Phase 2 slab on grade is approximately 1004.33 ft, which is above the previously documented high-water level but within the flood elev4.fkn of the current year.

Therefore, there is. approximately 1 ft of sub-grade directly,lhelow* .ab ýgrade that has the

• potential to be subjected to first time wetting.

The following table describes observed distress dicat

• d other Jfa. uld increase or decrease the potential for degradation associated with tlbUR*for 0 the"'1LQical Support Center.

Adverse (Degradation/Direct Floodwater Fa;i~ab*!*,.e-.*radation/Di*,-

Impact More Likely) Floodwaterf et Less Likeily)r Unknown backfill compaction density below the .e ,,been no ose" of structural structure. . floor slab o NTaors of str cturin the arA e covengs

__ at the c u* g conditionsýV Sandbags in the corridor indicate that water hsz T " "ood ' prior to 2011 was potentially moved through the floor drain pipuk 15"i which m'hla6 fl.* Rlevation iii-ZO ~I 1993. The peak I-as approximately through piping trenches, or upward h slab c>1,,vaton ,,ikas 0i apxme 1.13,19 ft Soil N1 w this structure were p iilly w.o'during earlier flooding events.

The Maintenance Shop to the ndV'm- has.

documt

• eitOssues. One b-iding col on of floor I #ad s0a the tire A m' ,

Ogg d discussion of thi istress .n *a..

4ripresented in Section 4.3. ý"

• ,,Pata Gaps:

Survey data to track trends ip ical movement of the structure.

• iji-sual observation of structe~1 dlements that were not accessible.

ous areas that were ng Ecssible will be inspected.

observation of/cture as the flood waters recede will be performed.

Conclus n.,..

Sigznificance Potentialfor Degradation/DirectFloodwaterImpact Indicators for these CPFMs have not been observed in the Technical Support Center. However, survey data has not been obtained to verify that vertical movement has not occurred. The peak flood elevation prior to 2011 was 1003.3 ft, which occurred in 1993. The peak flood elevation in 2011 was approximately 1006.9 ft. Soils below this structure were potentially wetted during earlier flooding events. The potential for degradation is considered to be low.

Priority 1 Structures Page 5.5-9 Technical Support Center Rev. 2 Implication The occurrence of this CPFM could cause settlement of the shallow foundations or slab on grade and has the potential to cause issues with the structure such as cracking of the walls, cracking of the slabs, or distress to the architectural coverings. However, the Phase 1 portion, which is designated Class I, is founded on a mat foundation and has much more redundancy. If degradation occurred it would be slower to develop and would allow time to respond with corrective action. Minor amounts of settlement would be considered a serviceability problem, not a strength or safety issue. The layers of subgrade not pre.,uous'11wttedi. e likely thin, reducing the effects of first time wetting. Therefore, the iati'Lpiotenti al degradation for these CPFMs is low.-,"

Confidence Indicators for this CPFM have not been observed; h few accessible rooms and the main corridor. The ai this CPFM. Therefore, the confidence in the above are necessary to draw a conclusion.

Summary For CPFMs 7a through 7c, as discussed abU the lion of the potential for degradation and the implications o at de 4tior. tpe puts it in the "not significant" category. The data y co ected rule out these CPFMs.

Therefore, the confidence in e v assessmer more data or continued monitoring and inspection , e necessary to%

Priority 1 Structures Page 5.5-10 Technical Support Center Rev. 2 5.5.5 Results and Conclusions The CPFMs evaluated for the Technical Support Center are presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

Low Confidence High Confidence (Insufficient Data) (Sufficient,.Data)

CPFM 6b the Technical Support Center:

0 accessible areas.

0 ,ysical modifications are recommended to address CPFM 3a, 7a thoughi #1 and #3). These recommendations are described in detail in Section 4.1.

Continued monitoring mis igmeended to consist of visual inspection of the Technical Support Center.

The purpose is to monitor for signs of structure distress and movement or changes in soil conditions around the structure. The results of this monitoring will be used to increase the confidence in the assessment results. The visual inspections should be performed weekly for 4 weeks and biweekly until December 31,2011.

At the time of Revision 0, groundwater levels had not yet stabilized to nominal normal levels.

Therefore, it is possible that new distress indicators could still develop. If new distress indicators are observed before December 31, 2011, appropriate HDR personnel should be notified immediately to determine if an immediate inspection or assessment should be conducted. Observation of new distress indicators might result in a modification of the recommendations for this structure.

Priority 1 Structures Page 5.5-11 Technical Support Center Rev. 2 5.5.7 Updates Since Revision 0 Revision 0 of this Assessment Report was submitted to OPPD on October 14, 2011. Revision 0 presented the results of preliminary assessments for each Priority I Structure. These assessments were incomplete in Revision 0 because the forensic investigation and/or monitoring for most of the Priority 1 Structures was not completed by the submittal date. This revision of this Assessment Report includes the results of additional forensic investigation and monitoring to date for this structure as described below.

5.5.7.1 Additional Data Available '4 The following additional data were available for the T Revisions 1 and 2 of this Assessment Report:

" Results of KDI #1 forensic investigation (see Section.4,

" Results of KDI #3 forensic investigation (see Section 4"

" Additional groundwater monitoring well and river stagc Results of geotechnical investigation by Thi-e1 g edlj

• Results of continued survey by Lamp RVY...ian 6).

• Results of continued monitoring and assortMents ina

• Field assessments of the areas of the Telical Supgp

• Results of crack monitor observations' ,om L 5.5.7.2 Additional Analysisiop The following analysis of addNOtW data was con r4iTechnical Support Center:

• Gr 4 nrn well.and- ver stage level data from OPPD.

shows that have returne d to nominal normal levels.

Results of geotechnical i ele Geotect i, Inc.

of the SPT and CPT teifkj'ults conducted for this Assessment Report were compared imilar data from numersiipther geotechnical investigations that have been conducted

,MI~heCS site in previou*.yers. This comparison did not identify substantial changes to f-sor16s&ength and stifffi over that time period. SPT and CPT test results were not foih44$* e ,h toP*tol1 pefet to protect existing utilities.

• Results of, by Lamp Rynearson and Associates.

Survey data to diate compared to the original baseline surveys have not exceeded the accuracy range of the surveying equipment. Therefore, deformation at the monitored locations, since the survey baseline was shot, has not occurred.

Several CPFMs were identified in Revision 0. Since Revision 0, additional data have become available that have clarified the significance and confidence for these CPFMs. The following presents each of the previously identified CPFMs and the new interpretation of their significance and confidence based on the new data.

Priority 1 Structures Page 5.5-12 Technical Support Center Rev. 2 Field observations of the Technical Support rooms (not previously visited due to security issues) identified a horizontal crack along the east wall of Room 127. This CMU wall is along the east expansion joint line with the adjacent Maintenance Shop. The horizontal crack in the east wall was within a horizontal mortar joint and was approximately 15 ft long and up to about 1/8 in. wide. The crack could be caused by localized settlement of the foundation below the wall or flexural cracking of the wall due to out-of-plane forces. The crack appears to be new since there is paint that bridges across the crack and there does not appear .tO be an accumulation of dust within the opening. There is no evidence o 4t-Of-plane movement of the wall or other signs of structural distress at this location.,& %W0 Field observations of the Technical Support rooms (nod to security issues) identified cracking along the east wall of the cra krom 127. This CMU wall is along the east expansion joint line with the .Shei and the south expansion joint line with the Auxiliary Building.

basement with pile foundation for the Auxiliary Buildinq grade for the Technical Support Center. As the shallow adjacent structures the settlement caused a point load, cracking.

These detailed observations indicate that s undati( JIG ement has occurred along the expansion joints betwe e Techn'i ~idhe adjacent buildings. However, no out-of-plane mo t of t"M signs of structural distress have been observed at th W .ktio Triggering Mechanism 3 u r face Erosio in CPFM 3a - Undermininm,- lettlement of sh' sab/surfaces (due to for icators for this CPFM havxel.5Jon observed in the Turbine Building, Maintenance Shop, and hsonry wall of the Tech rt Center shared with the Maintenance Shop. Voids below Sin the Turbine Buildir d the Maintenance Shop are known to exist and might d 'mw the foundationsi;trhe masonry walls causing it to settle. The crack in the sonry*'_and settlemeW ought to be related to KDIs I and 3. The potential for is high.

Implication The occurrence of this CPFM could cause settlement of the shallow foundations or slab on grade and has the potential to cause cracking of the walls, cracking of the slabs, or distress to the architectural coverings. However, the Phase 1 portion, which is designated Class i, is founded on a mat foundation and has much more redundancy. If degradation occurred it would be slower to develop and would allow time to respond with corrective action. Minor amounts of settlement would be considered a serviceability problem, not a strength or safety issue.

Therefore, this implication of the potential degradation for this CPFM is low.

Priority 1 Structures Page 5.5-13 Technical Support Center Rev. 2 Confidence The occurrence of damage due to subsurface erosion was not known at the time of Revision 0 due to lack of access to some of the structure. Subsequent field inspections indicate structure movement that is thought to be associated with this CPFM and directly related to KDIs l and 3.

If repairs are conducted relating to KDIs 1 and 3 then the confidence of the assessment for this CPFM becomes high. I Summary For CPFM 3a, as discussed above, the future potential distress were observed. The combined consideration o1l and the implications of that degradation to the structure put iti data collected since Revision 0 are sufficient to rule out tlH KDIs 1 and 3 are conducted. Therefore, the confidence in, means no additional data and inspections are necessary to Triggering Mechanism 6 - Buoyancy, Uplift F CPFM 6b - Cracked slab, loss of structuralVgi CPFM 6c - Displaced structure/broken q- ctions Significance PotentialforDegradation/Direc 1,'wawr Impal The re have been no observed~i. of structural d es in thel r slab or indicators of strutctural distress in the archt-e11 coverings at*" a \u tVading conditions that would be editedotj &e-r;GPFMs. Si i1"re were no signs inc ture distress in these areas, the

[WON'jgiadkiiiiii-is low. W peation " N occurrence of these CP ould cause-vertical movement of the foundation or slab on le and has the potential to use distress to the structure such as cracking of the walls, king of the slabs, or distre the architectural coverings. In addition, positive upward ui'.an cause water infil '*'.* into the structure. The degradation is considered a 4 Vrl-

.jissue, not a lif~iy issue. Therefore, the implication of the potential Confidence "4 Since Revision leted, areas that were not previously accessible in the Tech Support Center have been observed. Although some signs of distress have been observed in these areas, it is not believed that it could be related to these CPFMs because the wall footings and slab on grade did not show signs of distress related to buoyancy or uplift forces. Since all areas of the Tech Support Center have now been observed and no signs of distress relating to these CPFMs have been found, the confidence of the assessment for these CPFMs is high.

Priority 1 Structures Page 5.5-14 Technical Support Center Rev. 2 Summary For CPFMs 6b and 6c, as discussed above, the potential for degradation is low because the implications of these types of CPFMs would most likely be serviceability issues rather than life safety issues and would be apparent at this time. The combined consideration of the potential for degradation and the implications of that degradation to a structure of this type puts it in the "not significant" category. The data collected since Revision 0 are sufficient to rule out this CPFM. Therefore, the confidence in the assessment is high. whic eans no additional data and inspections are necessary to draw a conclusion.

Triggering Mechanism 7 - Soil Collapse (first time , g)

CPFM 7a - Cracked slab, differential settlement ofis,.. w fa. tio ,i ss.,of structural support CPFM 7b - Displaced structure/broken connections CPFM 7c - General site settlement Significance Potentialfor Degradation/DirectFloodwater Indicators for these CPFMs may have bee eda Suppor;enter in Room 127 where the horizontal masonry exists Ms ugh 7c as they pertain to the Technical Support Center are f *ssed er a K.DK# on 4.3 and were determined degradation to to not be the occur likely at this tii c W.theobserv

" aistress. re, the potential for Impl ication

• r"P M s The FMs ause settlement of the shallow foundations or slab on

, ia has the po cause i th the structure such as cracking of the walls, Sng of the sAbs, or to the a &tural coverings. However, the Phase 1 portion, ich is designated Class sf nded on foundation and has much more redundancy. If egradation occurred it would lower to develop and would allow time to respond with

,W~iective action. Minor amo- of settlement would be considered a serviceability problem, Iýen gth or safety issue. ~~yers of subgrade not previously wetted are likely thin, redcgh effects of first timrayetting. Therefore, the implication of the potential degra-for these CPFrr Iw.

Confidence .

The occurrence o ge due to soil collapse was not known at the time of Revision 0 due to lack of access to some of the structure. Subsequent field inspections indicate structure movement that can be associated with these CPFMs. The investigation of KDI #3 identified the distress as being the result of subsurface erosion due groundwater flowing into the broken drain pipes below the Turbine Building floor. Therefore, the distress is not believed to be the result of soil collapse due to first time wetting. The confidence of the assessment for these CPFMs becomes high.

Priority 1 Structures Page 5.5-15 Technical Support Center Rev. 2 Summary Since Revision 1, KDI #3 was investigated and concluded that the distress in the Technical Support Center is most likely the result of subsurface erosion due groundwater flowing into the broken drain pipes below the Turbine Building floor.

For CPFMs 7a through 7c, as discussed above, our confidence is high that the future potential for degradation is low because soil collapse due to first time wetti&Pgis not believed to have caused the distress. The data collected since Revision 0 aresuffid" rl ut these, which means no additional data and inspections are necessaryt a,c O P.

5.5.7.1 Revised Results 1012ig" The CPFMs evaluated for the Technical Support Center arpggsened in the matrix, which shows the rating for estimated significance and the J ence in aii" CPFMs 6b and 6c for the Technical Support Center arenoith Key Diss Indicators. The results of the additional monitoring show that thess s are ruled 0 The results of the KDI #3 investigations show that C,- b, and 7c associated with Key Distress Indicators and can be ruled out..,; ha er concerns are identified through the monitoring program fi* Techni ort Cente ussed in Section 5.5.6 and continuing until Decem 2011 ),s e sare mov dto the quadrant of the matrix representing "No Ft' r Actii com* -Related to the 2011 Flood." CPFM 3a is associated w y s to#cn present the results of additional i investiga at was cffnaucced to ascertain whether these CPFMs could be ruled out*fe results oft ditionalf'6 sic investigations show that if the recommendations for 1,rU-1 modification n 10, KDI #3 are implemented that this CPFMj1d out. Ther*ti:o*asumlng that n8 ncerns are identified through the pport Center (discussed in Section 5.5.6 and se CPFMs are moved to the quadrant of the matrix

.ded Related to the 2011 Flood."

Priority 1 Structures Page 5.5-16 Technical Support Center Rev. 2 Low Confidence High Confidence (Insufficient Data) (Sufficient Data) 5.5.7.2 In thea, ei .l"yCS Str .the first step was to develop a list of all Triggering M eý ms and *hcoula na"ud-urred due to the prolonged inundation of the FCS gthe 2011 M H iuver floedf .ould have negatively impacted these structures.

enext step was to use dfAn variou N igations, including systematic observation of structures over time, eitirq ehminate tim'riggering Mechanisms and PFMs from the list recommend further inve ion and/or physical modifications to remove them from the

'7..rany particular structure*," Bdause all CPFMs for the Technical Support Center other th'J~s 3, b. c,~~,, 7 ay d1 7c had been ruled out prior to Revision 1, and because CPFMý ,1R c, 7a, 7b and 7a.jl"been ruled out as a result of the Revision I findings, and because*M _;-* 3a will beA out when the physical modifications recommended for KDIs #1 and #3 in iIa~A're 1 implemented, no Triggering Mechanisms and their associated PFMs remair %q Technical Support Center. HDR has concluded that the geotechnical and&iRral impacts of the 2011 Missouri River flood will be mitigated by the implementation of The physical modifications recommended in this Assessment Report.

Therefore, after the implementation of the recommended physical modifications, the potential for failure of this structure due to the flood will not be significant.

f Section 5.6 Indpenen Spn tod n s a a "o.n 5 FS I

f

Priority 1 Structures Page 5.6-1 Independent Spent Fuel Storage Installation Rev. 2 5.6 Independent Spent Fuel Storage Installation 5.6.1 Summary of Independent Spent Fuel Storage Installation Baseline information for the Independent Spent Fuel Storage Installation (ISFSI) is provided in Section 2.0, Site History, Description, and Baseline Condition.

The ISFSI consists of spent fuel modules placed inside 3-ft-thick reinfor A.rncreg shield walls and

. f onC eXe basemat.

ceiling. The modules and shield walls are supported on a 2-ft-thickm0eein orb m Approach slabs are located on the plan north, south, and east siderthe base The approach slabs consist of approximately 0.7-ft-thick reinforced concrete. A h oad*eeX ,ortheast corner of the approach slabs and turns ninety degrees to exit towiW W erdies*: At the6eFhdof the radius, the concrete pavement ends and gravel surfacing begins.

The basemat is elevated relative to the surrounding grades to prowite p'ote6n from flood* "Ile elevation at the surface of the basemat is about 1009.5 ft. The approach sl ]* e downwaria from the basemat to provide drainage. The haul road slope nward to thM*,nding grade,*

which is at about el. 1004 ft. Side slopes along the pegmet6-th. vearea from erosion with large-diameter riprap. The riprap extend-frtom theqdLge.0fthe pavere mwni to the toe of the slope.

An Electrical Equipment Building is locateo of theS*FSI. A eab16;Wxf'ch extends from the Electrical Equipment Building to the exi*stiNew Warehodlse and fromnkhe PErctrical Equipment Building to the spent fuel modules. The.T rnch follows apo. from the..E1lctrical Equipment Building plan west along the plan south edgqfObtl eapproach slab 4a4teA tu sthlan north along the plan west edge of the approach slab, where it enm.r tihe shield walls.

Two high mt, cated n6 ANlISFSI. One is near the toe of the side slope along the plan southisidpfthe ISFSI, sonearth-sieof the slope between the ISFSI and the haul road.

Thn~asia*. t and approach slabs ade supporte S`4te preparation prior to placement of the Va's~ovd approach slabs included r-excavation of the existing fill. The structural backfill and strutlrhfi Cconsisted of crushed limestoe compacted to 95 percent of the material's maximum density'i determmed by the modifiedl4 ?rý,octor test (ASTM D 1557) at a water content between 3 percent befimvand 3 percent above a&lpiinum water content.

The ISFSI-inclu týmg:;.e haul rdar.o4fip, the Electrical Equipment Building, and two high mast light towers-is surrounfd P*,y anin dent security fence.

Priority 1 Structures Page 5.6-2 Independent Spent Fuel Storage Installation Rev. 2 5.6.2 Inputs/References Supporting the Analysis Table 5.6-1 lists references provided by OPPD and other documents used to support HDR's analysis.

OPPD

)ocume ntl Number A applicableef-1 Geotechnical Report Independent Spent Fuel Storage Installation Fort Calhoun Station Fort Calhoun Station ISFSI, Basemat Evaluation Naval Facilities Engineering Command. Design Manual 7.01, Soil Mechanics Detailed site observations-field reports, field notes, and i provided in Attachment 8.

Observed performance and pertinent background

• Floodwaters extended about half-way up the

• The Electrical Equipment Building wasprote with sandbags, and a pump appeared to have been us a

" Water stains on the Electrical Eq JPrnent Bui structure being inundated by floodwater.

" The river bank is arMored and halhist.icall' cteTd, 96bil~zed the existing river bank.

• USACE red*Ut'-df ver MaITmS release1*o40,000 cfs on October 2, 2011.

River le.dd Mt e 40,OOtc rate stabilized at FCS on October 4, 2011, at feet.

5. -Assessment Methods an**rcedures 5*.6-3.1 Assessment Proced.res Accomplished Assessmeints of the ISFSI inchiddc the following:

• A visuadiispection o,,tb,*egkade-supported slabs and surrounding grades

• Probing*6Tiflio. grado ound the perimeter of the structure for changes in consistency

• An assessr e~ti6tfllected survey data to date for indications of trends in the movement of the structure **,Z7N

• A review of building plans and the geotechnical report to identify possible subsurface features that might be susceptible to the PFMs 5.6.3.2 Assessment Procedures Not Completed Assessments of the ISFSI that were not completed include the following:

• Geophysical surveys using GPR and seismic refraction to find voids (currently not planned.

Other data and observations are sufficient to reach a confident conclusion.)

Priority 1 Structures Page 5.6-3 Independent Spent Fuel Storage Installation Rev. 2

" Visual inspection of a portion of the precast cable trench and the grades adjacent to the Electrical Equipment Building where the sandbag temporary berm was still in place (to be completed)

• Inclinometers installed along the river bank to identify lateral movement (inclinometers are planned to be installed- Other data and observations are sufficient to reach a confident conclusion)

" Geotechnical borings to determine current soil conditions and capacities (currently not planned- Other data and observations are sufficient to reach a.cifident conclusion) 5.6.4 Analysis ..ci..Z Identified PFMs were initially reviewed as discussed in Sectio Thereview ensi ered the preliminary information available from OPPD data files and from. in... ak-dowi... "ations Eleven PFMs associated with five different Triggering Mechaniss re.determined t "non-credible" for all Priority 1 Structures, as discussed in SectioiI, r emin S carried forward as "credible." After the design review for each structurekt tcture obseiljow and the results of available geotechnical, geophysical, and..suryw. data were ed, a number of CPFMs were ruled out as discussed in Section 5.6.4.1. ,TP1ClP carried ,o r detailed assessment are discussed in Section 5.6.4.2. Y 5.6.4.1 Potential Failure Modes Rul*e'g 5ut PriorotheC of the Daid Assessment The ruled-out CPFMs reside in to wtf Significan!iTgh Confidence category and for clarity will not be shown in the Poteiati4or Failure/Conince matrifyi TriggeringM.ecbanism 2 - S9f1uceErosion CRM3 -,jaexinn sha II wýftýundation/slab/surfaces Reasorts for rulin2 out:

4jSlabs were never inundatqd, i"th floodwater.

' ,:*Surface erosion near the rsESI was not observed during the field assessment.

Triiggeriing Mechanism 2 - Surf*ce Erosion

.,.F...,fM2c - Undermined lv 'ued utilities Reason for iuliig out: /

• Surface ersio he ISFSI was not observed during the field assessment.

Triggering Mechanism 3 - Subsurface Erosion/Piping CPFM 3a - Undermining and settlement of shallow foundation/slab/surfaces (due to pumping)

Reason for ruling out:

• The basemat and slabs are supported on 10 ft of crushed limestone, which would require higher water velocities to erode than inflow due to pumping can produce.

Priority 1 Structures Page 5.6-4 Independent Spent Fuel Storage Installation Rev. 2 Triggering Mechanism 3 - Subsurface Erosion/Piping CPFM 3c - Undermined buried utilities (due to pumping)

Reason for ruling out:

• Distress that can be attributed to the CPFM was not observed during the field assessments.

Triggering Mechanism 3 - Subsurface Erosion/Piping CPFM 3d - Undermining and settlement of shallow foundatid6ýHIb (dt.Ato river drawdown)

Reason for ruling out:

The ISFSI is a sufficient distance from the river to be ifsik *he zone of iiiNece for this CPFM.

Triggering Mechanism 3 - Subsurface Erosion/Piping "

CPFM 3f- Undermined buried utilities (due ,,trve*rdrawdown)

Reason for ruling out:

The ISFSI is a sufficient distance fromwtbc-river to t*b*eot id o of influence for this CPFM. e ne Triggering Mechanism 7- Soil oapse (first tiewetting)

CPFM 7a - Cracked slati*rential settlemMXfshallo.* fundation, loss of structural CPF"4.M7Fh--Mplaced structe roken connections CRF , neva,:s;ie settlement*\

RAeW7asons for ruling out:

assessments did not identify settlement of the site during the observations durig..the*Visual

• field assessment.

• • " bmpacted crushed limest"..i&ýelow the basemat, approach slabs, and haul road does not cco'1Pse when wetted.

SinO iwere previous1N\eOtted. The peak flood elevation prior to 2011 was documented in 19'3* ,wftwh would indicate that the soils below and surrounding the buildingaatbbe~enisatur~at, d at this time.

Triggering Mechianfism 10 - Machine/Vibration-Induced Liquefaction CPFM IOa - Cracked slab, differential settlement of shallow foundation, loss of structural support CPFM lOb - Displaced structure/broken connections Reasons for ruling out:

• ISFSI is not subjected to machines or vibrations that could induce liquefaction.

• Liquefaction was not observed at the site during the field assessment.

Priority 1 Structures Page 5.6-5 Independent Spent Fuel Storage Installation Rev. 2 Triggering Mechanism 11 - Loss of Soil Strength due to Static Liquefaction or Upward Seepage CPFM 1 a - Cracked slab, differential settlement of shallow foundation, loss of structural support CPFM 1 lb - Displaced structure/broken connections Reason for ruling out:

• Liquefaction was not observed at the site during the Triggering Mechanism 12 - Rapid Drawdown CPFM 12a - River bank slope failure and undermirn CPFM 12b - Lateral spreading Reasons for ruling out:

• The ISFSI is a sufficient distance from the river to b PFM.

• Slope failure was not observed at the site...

" River stage level has receded and stabili "as of Oc 5.6.5 Results and Conclusions 4 Possible CPFMs for the ISFSI have Ino CPFMs related to the 2011 flood event that are applic, 5.6.6 Recommended Actions No further ai.fiei' . . o.md..

5.6.7 -AJfdtes Since Revisioni'.0 Re-',i son 0 of this Assessment Repo'4T s submitted&-F OPPD on October 14, 2011. Revision 0 prese--ted the results of preliminary assessments for each Priority I Structure. These assessments were incomptleie iiievision 0 because the forepsic investigation and/or monitoring for most of the Priority .. es was not complet4dY"the submittal date. This revision of this Assessment Report includes the ruii *"of additional

" fQo psiinvestigation and monitoring to date for this structure as described below.

5.6.7.1 The following additi data were available for the ISFSI for Revisions I and 2 of this Assessment Report:

• Results of continued survey by Lamp Rynearson and Associates (see Attachment 6).

• A visual inspection of the cable trench at the grades adjacent to the Electrical Equipment building was observed with no signs of distress.

Priority 1 Structures Page 5.6-6 Independent Spent Fuel Storage Installation Rev. 2 5.6.7.2 Additional Analysis The following analysis of additional data was conducted for the ISFSI:

Results of continued survey by Lamp Rynearson and Associates.

Survey data to date compared to the original baseline surveys have not exceeded the accuracy range of the surveying equipment. Therefore, deforniation at the monitored locations, since the survey baseline was shot, has not ocourredW,*

5.6.7.3 Conclusions In the assessment of the FCS Structures, the first step was4 dee a listf'y riggering Mechanisms and PFMs that could have occurred due to th r ed inund Iat' i hF site during the 2011 Missouri River flood and could have *na1yi mpacted th*e*se sructures',

The next step was to use data from various investigations,*l. tematlc the structures over time, either to eliminate the Triggering Mechanl ad PFMs frorifte list or to recommend further investigation and/or phy fiifications Vteo"ve them from the list for any particular structure. Because all CPSFIhave remaT~eIble or the !ed TS out, no Terefore, Triggering Mechanisms and their associate s eedile fot [

HDR has concluded that the 2011 Missouia'River flood.di m~act the geotechnical and structural integrity of the ISFSI because tl.#.6tential fflE ure,:ti&structure due to the flood is not significant. ,

r Section 5.8

.. .,.7 .  ::. .. .. .".."... "7' ,*;,,,i

• '** "* "*S '*i7*

- :7 ... ~ . .*. . ... ---- -. .  :. * ..

.. .:. . .i -- i_,'.- **

Priority 1 Structures Page 5.8-1 Turbine Building Rev. 2 5.8 Turbine Building 5.8.1 Summary of Turbine Building Baseline information for the Turbine Building is provided in Section 2.0, Site History, Description, and Baseline Condition.

The Turbine Building is located within the PA. directly adjacent to the AIry Biilding to the west, the Maintenance Shop to the north, and the Turbine Building Soutf tcniýe south. The Service Building to the east was built integrally with the Turbidflieilding. `,c

.. r.lation Water System extends under the Service Building and ties into the bof~of theJuin4'idlng foundation. The Turbine Building basement floor elevation is esbishedht 990 f ftom of floor el. 987.5 ft), while the Service Building floor is established at an of 1007.5 f Service i'onoa10er , c Building is supported by deep foundations. The bottom of the CireIlgnbWater Systenrsg-Ya elevation of 969 ft and is supported by deep foundations. The Aux, 'ari*,1_u ng basemenrtit'kQ elevation adjacent to the Turbine. Building is established at 989 ft (bottomnf I'~lel.

983.5 ft), df--f it also is supported by deep foundations. The Turbine Buil*.d .".i Switchy i;d4sconstructed at a grade of about 1004.5 ft, and the structures are suppode" n ations. Th&Maintenance Shop floor is established at an elevation of 1007.5 ft andAs-u-pported oni tLlow foundati#Ro The Turbine Building is a multi-floored structure From the top of'the fbiddtion mat at el. 990 ft to el. 1007.5 ft, the structure is cast-in-placereemforcejd cobncret*yth inte,,ýL lsters that align with the steel columns above grade. From el. 10075:ft to the roofelevation. the:structure consists of braced.

rigid steel frames clad with precast concrete sandwich panels- The mat"T~,tndation is supported on a combination of 0-in.-diameter Class steel pipe piles unde1&the-Wgýuie generator mat foundation and 12-in.-diameter Clas&B concrete-filled ste.e1 pipe piles unde*tthe buidging mat foundation. all of which are driven to bed'6 ..-Seie..Xlass B pfle.ar5e4designated as tension piles and include reinforcing dowels to 1roVIi'D;*lt'ivir&.teisisOnýconnection.to-he foundation mat (see Table 5.8-1 ).

5.8 .2_Th4l"ts/References Supoobrifrg the Arraly:,is.\

Ta4_Si i*-,1sts references providedýhy PD and other documents used to support HDR's analysis.

Table 5.8-4"References for Turbine Building 4 " Document Title OPPD Date Page Document Number(s)

Number 2010 Turbine-(if applicable) 2010 Turbine Butldnnspection SE-PM-AE-1003 7/16/2009 All.

Turbine Building 6" and i'VE~loor Drain Pipe Breaks (Summary of Unknown All

" "CR2009-1365)

Design Basis Document - Geotechnical PLDBD-CS-54 Unknown All Summary Report of Broken Floor Drain Pipes NA 3/24/2009 All Design Basis Document - External Flooding PLDBD-CS-56 Unknown All Work Order Package - 00350972 01 2010 Structural Reference to Unknown All Inspection of the Turbine Building Procedure SE-PM-AE- 1003 Naval Facilities Engineering Command, 9/1986 All Design Manual 7.01, Soil Mechanics

Priority 1 Structures Page 5.8-2 Turbine Building Rev. 2 Detailed site observations-field reports, field notes, and inspection checklists-for the Turbine Building are provided in Attachment 8.

Observed performance and pertinent background data are as follows:

• The Turbine Building is a Class II structure and is designed to withstand an external hydrostatic load due to flooding of the Missouri River to el. 1007 ft (see PLDBD-CS-56).

• The below-grade structure is independent of the Auxiliary Building, Wfth a 1-ft-9-in. void (expansion joint) between the basement walls. The void is fill~vlth san*belopgrade and covered with a metal closure plate at ground elevation (see 127 H 12195).

• The Class A piles consist of pipe with 20-in. outside diamete7*d 1.03L-.,,nwa~thickness, which meets API Standard 5L Grade B (Fy = 35 KSI). The piles wire-'adrivea ' ,1'-end-ed- Io refusal on bedrock. An exploratory boring was drilled through the pipe;i2Pht5fthe bedrockl-- Ma void was encountered, the pile was underreamed and the pile advanced thr6*u he void.

4, pils n-f The Class A pile capacities were developed by load testing ndodoc, i.n piles for co4,r!so,,

tension, and lateral loads (see PLDBD-CS-54).

• The Class B piles consist of pipe with 12.57-in. outside.djameter and 0.2Tfig`walI thickness, which meets ASTM A252 Grade 2 (Fy = 35 KSI). The piiesWere driven closede6 refusal on bedrock and filled with 4000-psi concrete (see PEDBD-CS '5) ,

• The soils below the structure were not densified h/Zvibroflotahn \i

" The structure was protected from floodwaters rorthe majontyof the 2,0141, flood by an Aqua Dam, combined with sand bags and portable p.umps datfthe exterioroverheaa' dor on the south building face adjacent to the Turbine Buildincr -South Switchvarcd-'-. 'towever, th,,iAqua Dam failed for a short period of time due to being da.aed. allowing floodwater to enter the area inside the Aqua Dam perimeter. Approximate r.,,_,elevation during ti, period o,,he breach was 1006 ft.

• Condition report summaries listed,.in,-Xý.document many'areasgof..'-the structure where groundwater has infiltrated I .through hg* pre. iusly monitored &iiKls in the concrete, wall penetrations.

and cdocu 'd groundwater infiltration areas did not identify areas of structuralconcerni.

• Generakobservations of the interio-of the stiikt*erIndicated minor concrete cracking with both

, :*cuent water infiltration (damp to"s light runnig 'vater) and dry walls with signs of water NM.tration that has occurred at aIeartier time. The observed cracking has been previously re-orde.,and monitored. There we.re.msrall isolated areas of standing static water in low spots.

HoWV&ik'he source of this static Wter was not found because no water movement was detected.

• Typical"W dtcracking observed conlmsted of vertical shrinkage cracks at the horizontal mid-span between plaster These are classic,'concrete shrinkage cracks between the very stiff pilaster elements that eee:inklurig the initial concrete curing period.

• The majority of the.w,&Il,&p~nes encompassed between the pilasters have vertical shrinkage cracks that were either daim-to2 shghtly running or show signs of previous water infiltration.

• There is a vertical crack that is full wall height on the north basement wall, approximately 1 ft west of column pilaster TC-9. During additional investigation, it was determined that the crack width at the top of the wall is approximately 0.0625 in. and extends through the thickness of the wall. The crack and the surrounding concrete at the top of the wall were dry with packed dirt/dust within the crack, indicating that the crack had existed long before the flood event.

• The 2010 structural inspection of the Turbine Building (see Reference to Procedure SE-PM-AE-1003) indicated that there was no evidence of significant structural deterioration and that previously installed crack monitors showed no signs of movement.

Priority 1 Structures Page 5.8-3 Turbine Building Rev. 2

• The south exterior of the building adjacent to the Turbine Building South Switchyard was visually inspected, and no indications of soil subsidence were observed.

• A column footing in the Maintenance Shop in the first row of footings adjacent to the Turbine Building (Column MG-15) has settled. about 2 in., and cracks in the nearby masonry partition walls indicate settlement of the floor slab.

" Below is a summary report of broken floor drain pipes with reference to CR2009-1365:

- CR2009-1365 was created on March 24, 2009.

- Two drain lines run parallel to each other: the 6-in. floor drain andfffe 10-in. waterbox drain. A vendor visually inspected the drain lines because undocume:r ed &w.,s*bserveddraining into the sump pit from both lines. They found a break inilf-W, 0-in. d te branch tee from the VD-193 drain valve. They could not inspect the 6-tf'floor drainibeausethe line does not have a cleanout connection in this area and acce il g e 'r i estricted by the drain trap at each location.

Review of system files shows that a break in the waterbox dain4fie has been kibGQnýor _. quite some time. In 1997, a repair wasattempted by core drillihn 5le "thevicinity oF10 b and by pressure grouting to seal the pipe, according to the "Water'SPteps Report Cafu~or Report Period April 1 Through June 30. 1997" (me iP/ED/EOS SY9,1\13):

"Repair of the Turbine Building Basemen ýiajih llribheader was at-ropted during this period. The repair procedutý2on stel- f6re drilling ffo Ies the vicinitv of the leak and pressure grot.tam to seal th&Te*klApproximate1Wy 10 holes 10 by 8 by 1 ft were drilled and it was estimated t6ata void of,aroximately existed under the concrete slab. The voId was *filled with cement - grout but the leak could not be stopped Boroscope inspection of the pip5eexterior performed through the core drills shtiytd considerablNepipe damagae i, more than one location. The extentlQf th*d*amage and concerm overco*lapsing the line were determinini factors intermimating

~~~~~~~~~~...*

':................ ****'..** the pressureg.routmg

. operation. FC ECN 97-

• • .,;.:'.*.-.".:..p2-2.-1"5a.s'*rgi~ated to reqiithat a new drain edder be installed."

• The grout-was ,an'et-ithe'area by theý;,W)!j 93_ (FW- 1A south return box tail valve). At some time tater flfe Turbine Bui4' :sump wasZfreeaned out, and a slab of hardened grout was found in thexsuip, confirming the orouthad>flowed tIrouip.,the drain system into the sump. A recent

.jftspection of the floor drains notde aonsiderabte-iamount of grout in the floor drain south of the

'HEW--Condensate Cooler. The drainltooks to be almost fully restricted. It seems certain that this groutcame from the 1997 effort, ihindicting that both lines were also broken at that time.

• Revie*,vd* *Video taken from the suhnp:bn July 22, 2011, and subsequent visual observations indicate groufdwater flowing into"7fi sump from all five drain lines.

• OPPD persne~indscated that(cring an outage, the drain lines that discharge into the sump do not receive flow frbNA~tle systeim yL

• A majoritv of thei J.1 s,are located below the mat foundation slab.

" OPPD personnel indf1i*d that the drain lines were cleaned in 2011.

5.8.3 Assessment Methods and Procedures 5.8.3.1 Assessment Procedures Accomplished Assessments of the Turbine Building included the following:

" Visual inspection of the accessible areas of the interior of the structure from the ground elevation of 1007.5 ft down to the basement floor elevation of 990 ft

" Visual inspection of the exterior of the structure, where accessible

Priority 1 Structures Page 5.8-4 Turbine Building Rev. 2

• An assessment of collected survey data to date for indications of trends in the movement of the structure

• A review of previously referenced documents listed in Table 5.8-1.

Additional investigations were performed. These included the following noninvasive geophysical and invasive geotechnical investigations:

GPR along portions of the basement floor. (Test reports were 16t available at the time of Revision 0.)

Seismic surveys (seismic refraction and refraction n -remorflpepemprtected area.

(Test reports were not available at the time of Revisinnto.)

• TV inspection of the drain pipes below the basementf foor (Testn rep6t:p6 ere not available at the time of Revision 0.) ,

• Geotechnical test borings in the protected area. Note th". req uired v?*m.

excavation for the first 10 ft of proposed test holes to aconflicts.. :*...°*L.* THISr.e _Me;te reports will not show soil conditions in the upper 10 ft of test '&rlin ogs. (Test repts-were not available at the time of Revision 0. -

5.8.3.2 Assessment Procedures Not C~otplReed Assessments of the Turbine Building that -iý not compledinclude the following:

Core holes through the basemeFefloor toimeasu 'he size of _i',dpresent 5.8.4 Analysis Identified PFMs werpe-imbally reviewed asiý.iscussed in SectdnF,34l>The revew considered the preliminary info§. Atfable from BRi,.data files and from initial walk-down observations.

Eleven PFMS : associte Vie' differen* igering Mechanisms were determined to be "non-credible3,£f&rl1 Priority 1 Structures.as discusse'dihSection 3.6. The remaining PFMs were taken into h.detailed assessment as c6r.edi`.h!e." After"t-i-*dUZsjign review for each structure, the structure

.obseiations and preliminary results*ofs~me of the geotechnical, geophysical, and survey data were anal,. .'and a number of CPFMs wereruled out as discussed in Section 5.8.4.1. The CPFMs carried forwar*ifor detailed assessment are dfse-assed in Section 5.8.4.2.

5.8.`4, ,Ptential FailureJY4es Ruled Out Prior to the Completion of the Detailed 4,,_,Assessment ..

The ruled-ouiG.P sr, side in the Not Significant/High Confidence category and for clarity will not be show.1ii3UHPotential for Failure/Confidence matrix.

Triggering Mechanism 2 - Surface Erosion CPFM 2b - Loss of lateral support for pile foundation Reason for ruling out:

• Surface erosion was not identified near the Turbine Building during the field assessments.

Priority 1 Structures Page 5.8-5 Turbine Building Rev. 2 Triggering Mechanism 3 - Subsurface Erosion/Piping CPFM 3e - Loss of lateral support for pile foundation (due to-river drawdown)

Reason for ruling out:

0 The Turbine Building is at sufficient distance from the river and sufficient depth below the ground surface to be outside the zone of influence of the CPFM.

Triggering Mechanism 4 - Hydrostatic Lateral Loading (wat~wtadingon structures)

CPFM 4c - Wall failure in flexure ,. ..

CPFM 4d - Wall failure in shear ,

CPFM 4e - Excess deflection / .

Reasons for ruling out:

" The Turbine Building is designed to withstand an external wAte#l~ad due to flo64i f hý Missouri River to el. 1007 ft (see PLDBD-CS-56). The peak flood._6eation in 201T"was approximately 1006.9 ft, which is less than the -sbr a desig'n bas'sL's

• No signs of structural distress due to lateraL a6 mI'h" below-grade Wals't were observed.

Triggering Mechanism 5 - Hydrodynamicý oading .. ,

CPFM 5a - Overturning CPFM 5b - Slidin CPFM 5c - Wall failure in flexr.--

CPFM 5d - Wall failure in siear CPFM 5e - Damage byvýd*hius- ".A,*,-

CPFM 5f._=Excess deflectior:,... *,.

ReasonSI'Iff6fhoiddt T.*

he Turbine Buildin isAj6Scated witliiiA and was not subjected to high-velocity river

.A,:J4/or overland flows capabl&ofAproducing sicient hydrodynamic forces.

No damage from floating~d -nis was observed.

'::T* he Turbine Building is slielt ed from high velocity by the Maintenance Building on the dfrth (upstream) side, the Sefyice Building on the east (river) side, and the Auxiliary B Aii g on the west side:,-

TriggeringzhMqanism 6' -. Buoyancv, Uplift Forces on Structures CPFM 6-i4, E-t. tensib'4kpiles CPFM 6b Ci*a6kedslab, loss of structural support CPFM 6c - DTlfpfl:ced structure/broken connections Reasons for ruling out:

• The Turbine Building is designed to withstand an external water load due to flooding of the Missouri River to el. 1007 ft (see PLDBD-CS-56). The peak flood elevation in 2011 was approximately 1006.9 ft, which is less than the structural design basis.

• No signs of structural distress due to buoyancy were observed.

Priority 1 Structures Page 5.8-6 Turbine Building Rev. 2 Triggering Mechanism 7 - Soil Collapse (first time wetting)

CPFM 7b - Displaced structure/broken connections.

CPFM 7c - General site settlement CPFM 7d - Piles buckling from down drag Reason for ruling out:

The building basement elevation of 990 ft is below the normaliiwixer elevation of approximately 992 ft. Therefore, the building foundationpyste-m p$:yi-ally below normal groundwater elevations.

Triggering Mechanism 10 - MachineVibration-Indiiced L i4quefi CPFM 10b - Displaced structure/broken connectionsý;.

Reasons for ruling out:

" Permanent equipment that has the capacity to produce signific'ardynamcic forces db&me vibration is mounted on the base mat foundatiowsUab f the structure*.This structure is alwavs below the river level regardless ofr el~dt'ation

" The turbine was not operated during the flo"o event..,-

• This is not a changed condition due to theflood. The4Zur-mibi uilding has been operating under similar saturated soil conditions,ýad'nachin'e.ibrationS,s.

" No broken structural connection!sý.,or strPg&firal displ&acement W.'6rd. 6eerved.

" Liquefaction was not observed:'to,,have occurredOat the site.

Triggering Mechanism 10-4lVMahine/Vibration*n-dducedýriNquefaction CPFM IW7-7Additional lateral*f*orce on below- da l1

-.-Permanent equipmenetb*.6has the capcdioto produce significant dynamic forces due to

• vibration is mounted on'the base mat fondaiion slab of the structure. This structure is

.. always below the river lev'el regardless of the flood elevation.

':,Ithe turbine was not operatedduring the flood event.

" 314h,-is not a changed condit*ion due to the flood. The Turbine Building has been operating unf&s~imilar saturated soi1londitions and machine vibrations.

• Liquiifaction was not oabse.ed to have occurred at the site.

Triggering eeanism If- Machine/Vibration-Induced Liquefaction CPFM 10d Ple/.pT ie group instability Reasons for ruling out:

• Permanent equipment that has the capacity to produce significant dynamic forces due to vibration is mounted on the base mat foundation slab of the structure. This structure is always below the river level regardless of the flood elevation.

• The turbine was not operated during the flood event.

• This is not a changed condition due to the flood. The Turbine Building has been operating under similar saturated soil conditions and machine vibrations.

" Liquefaction was not observed to have occurred at the site.

Priority 1 Structures Page 5.8-7 Turbine Building Rev. 2 Triggering Mechanism 11 - Loss of Soil Strength due to Static Liquefaction or Upward Seepage CPFM 1 lb - Displaced structure/broken connections CPFM I Ic - Additional lateral force on below-grade walls CPFM lId - Pile/pile group instability Reason for ruling out:

• Liquefaction was not observed to have occurred at the site.

Triggering Mechanism 12 - Rapid Drawdown CPFM 12a - River bank slope failure and undermnig surroundrngs stliudiiues CPFM 12b - Lateral spreading Reason for ruling out:

The Turbine Building is at sufficient distance from the river anL'ufficlent depth be lorw the ground surface to be outside the zone of influmet & e CPFM.-',-.

Triggering Mechanism 13 - Submergence'.

CPFM 13b - Corrosion of structural eLements :j!>.,,.'. ,i >

Reason for ruling out:

• The Turbine Building is desf d to withstand4 fexternal w*'ar load due to flooding of the Missouri River to el. lIOq7i(siee PLDBD-CS;6) T*he peakfAlood elevation in 2011 was approximately 1006.9 f less than the struC:tu*r.deswn basis. Therefore, structural elem 6gr,-,,Wetlted by the, Lflood were congre6d in the original design of the

,4iggering Mechanism' 14-ýFrost Effectsl-,ý

," CPFM 14a - Heaving, cushing, or dis l~acement

,.e-aon for rulin2 out:

• 31heA*Turbine Building foundation is approximately 20 ft below grade and therefore not frost s ofi*]i~b~e. In addition. f',A-susceptible connecting utilities are also below frost level.

5.8.4.2 0'etaled Assessment of Credible Potential Failure Modes The following CPFMisare the only CPFMs carried forward for detailed assessment for the Turbine Building ds*;a result of the 2011 flood. This detailed assessment is provided below.

Triggering Mechanism 3 - Subsurface Erosion/Piping CPFM 3b - Loss of lateral support for pile foundation (due to pumping)

The flow of groundwater into this drain piping system through the breaks in the pipes is one of the Key Distress Indicators discussed in Section 4.

The Turbine Building has a documented history of a void below the foundation dating back to 1997. Conversations with OPPD personnel indicate that groundwater has been flowing at

Priority 1 Structures Page 5.8-8 Turbine Building Rev. 2 varying rates through these broken pipes into the sump from that time to the present day. The rate of flow into the sump is directly attributable to the hydraulic head of the groundwater because the observed flow rates have increased as the floodwater elevation increased. This drain pipe system was designed as a closed system; therefore, the pipes are not surrounded by appropriate filter systems to preclude the transportation of soils from the surrounding area under the slab. It is logical to assume that as the groundwater flows into the broken piping, the gradient is sufficient to erode the soil.

The Triggering Mechanism and CPFM could then occur a:

condition will remain until the breaks in the piping systemn potential for further erosion continues unarrested. Erosfion voids under the Turbine Building mat foundation.

The following table describes observed distress indicators decrease the potential for degradation associated with thisi Adverse (Degradation/Direct Floodwater T Impact More Likely)

Codclusion Sianificarhce~i PotentialforDeg adtrong/DirectFloodwaterImpact Indicators for this CPFM have been observed. A void below the mat foundation in the Turbine Building is known to exist, and groundwater is constantly flowing into the sump from all five drain lines. Because the 2011 flood caused increased groundwater flow through the broken drain pipes, the potential that the 2011 flood caused further and more rapid degradation due to this CPFM is high. It is possible that these voids extend beyond the Turbine Building.

Priority 1 Structures Page 5.8-9 Turbine Building Rev. 2 Implication The occurrence of this CPFM would have to be large to negatively impact the capacity of the piling supporting the building. Therefore, the implication of the potential degradation to the Turbine Building for this CPFM is low.

Confidence This CPFM has two elements: 1) the breaks in the drain pipes all o'.ggroimdwater to flow into the sump pit and 2) the potential for voids to developi*nd thepg! ystem. The flow of groundwater through breaks in the drain pipes has been ,documented, ToHwever the extent of the associated voids is unknown. The data at hand are ,ufficient-ittb.-lut this PFM or to

- -i...... g have p rttthildin conclude that physical modification to ensure that the pifigs thasipport gsýýý#Vsa av lost capacity because of this CPFM. Therefore, the confidence-JiJthe above asse-ssent is low, which means more data are needed to draw a conclusion. -

Summary For CPFM 3b, as discussed above, the potentia.t, 'AiMion is high lecAke of the flow of groundwater through the drain pipes. This degradation wbtntd-have to be lagi6,impact the integrity or intended function of the structure NThe combi*ied.'onideration of the potential for degradation and the implications of that de&'.datin to.a.sftuctui.egd týhis type puts it in the stiMificant" category. The data curenttv-o.llected not suffiiemt 7-tohue out this CPFM.

Therefore. the confidence in the above-assessment islow which.means more data or continued monitormin and inspections midhtebe necessary to:draw a concisdin.

Priority 1 Structures Page 5.8-10 Turbine Building Rev. 2 5.8.5 Results and Conclusions The CPFMs evaluated for the Turbine Building are presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

Low Confidence High Confidence (Insufficient Data) (Sufficient Data)

CPFM 3b

.24 0~

.~'-5

... *O. .,;

5.8.6 Rc rhmmended Actidos-Thef&fUbwing actions are recommed&for the Tu rin Building.

Revie t*he .GPRdata and TV inspectok--ideo to assess the impact on the piling system. Further forensic 'ivestigations and physical modifications are recommended to address CPFM 3b (Key Distress Ind1catoi"#1). These recommpteniaons are described in detail in Section 4. 1.3.

Continued monitoerm.gýis recomn1ihded to include a continuation of the elevation surveys of the previously identifieAt Ages ofmtis, structure and surrounding site. The purpose is to monitor for signs of structure distress an*i o',*ement and changes in soil conditions around the structure. The results of this monitoring will be use'dt6 increase the confidence in the assessment results. Elevation surveys should be performed weekly for 4 weeks and biweekly until December 31, 2011. At the time of Revision 0, groundwater levels had not yet stabilized to nominal normal levels. Therefore, it is possible that new distress indicators could still develop. If new distress indicators are observed before December 31, 2011, appropriate HDR personnel should be notified immediately to determine whether an immediate inspection or assessment should be conducted. Observation of new distress indicators might result in a modification of the recommendations for this structure.

Priority 1 Structures Page 5.8-11 Turbine Building Rev. 2 5.8.7 Updates Since Revision 0 Revision 0 of this Assessment Report was submitted to OPPD on October 14, 2011. Revision 0 presented the results of preliminary assessments for each Priority 1 Structure. These assessments were incomplete in Revision 0 because the forensic investigation and/or monitoring for most of the Priority 1 Structures was not completed by the submittal date. This revision of this Assessment Report includes the results of additional forensic investigation and monitoring to date for this structure as described below.

5.8.7.1 Additional Data Available . - .

The following additional data were available for the Tuibne Building*Aor Revisions 1 and 2 of this Assessment Report:

" Results of KDI #1 forensic investigation (see Section .4611)k-

• Results of the TV inspection report by Elite Pipeline S* ices'.7,(see,'Attachment 6,'"-,..

" Results of geophysical investigation by Geotechnol.Qgy, Inc. (sedAttchment 6).

• Results of geotechnical investigation by Thiet:l;i&;G edh, Inc. (see A ,ffa Itent 6).

• Results of continued survey by Lamp Rynearson anW'As'ociates (see dAft*hment 6).

5.8.7.2 Additional Analysiss. . ,

The following analysis of additionaldlata wa§sconduted' for the TrtbieBAuildinz:

• Results of the TV inspectiorr.eqport by Elite Pipethe Servicesil TV inspections performed.d(uihedrain pipes confmnedJbreaks in the pipes are allowing groundWteF4i.ifif~itrate the "'p'ebs-,,Additionally. sediment could be observed suspended in

.thef nnspec,-on.up to about 3 ft of sand was found in the sump pit.

Results of geophysical figvestiation by.Geotechnology, Inc.

. : GPR tests performed on the-Turbine Building floor identified anomalies which could be

JK1Cgavel, soft clay, or possibty*..vids. Additional ground truthing of the investigation results

-was performed as part of tliK* DI #1 forensic investigation.

• Reýsu*l£f geotechnical nv4e:sfigation by Thiele Geotech, Inc.

All of the'SST.,,and ,CTest results conducted for this Assessment Report were compared to similar datA o1.tm merous other geotechnical investigations that have been conducted on the FCS sTeh-previous years. This comparison did not identify substantial changes to the soil strength'and stiffness over that time period. SPT and CPT test results were not performed in the top 10 feet to protect existing utilities.

• Results of continued survey by Lamp Rynearson and Associates.

Measurements to date compared to the original baseline measurements have not exceeded the accuracy range of the surveying equipment. Therefore continued deformation at the monitored locations due to the 2011 flood has not occurred.

Priority 1 Structures Page 5.8-12 Turbine Building Rev. 2 Additional analysis related to CPFM 3b is discussed in Section 4.1 for KDI # 1.

The CPFMs that could not be. ruled out in Revision 0 are analyzed below based on the additional data available .for Revisions 1 and 2 of this Assessment Report.

Triggering Mechanism 3 - Subsurface Erosion/Piping CPFM 3b - Loss of lateral support for pile foundation (due to pumping)

CPFM 3b for the Turbine Building is associated with Key Distresg°!adicato9#l. Section 4.1 presents the results of additional forensic investigation thaas conidu0cte6tascertain whether the CPFM could be ruled out. The results of the addition *11frensic iAvestigations show that this CPFM is ruled out. Therefore, assuming that no ',,concers re:,ih ieied through the monitoring program for the Turbine Building (discussed4&Sbect*o.t :-8.6a i uing until December 31, 2011), the CPFM is moved to the quadrant o;;ihematrix represenimIgNo Further Action Recommended Related to the 2011 Flood 5.8.7.1 Revised Results The CPFM evaluated for the Turbine Building,.aire'*re's ent4din the follow,,Agrmkatrix which shows the rating for the significance and the:;i ofconfggien'edn the eval'ak Low Confidence)ý" ~H'Oh Cfhfide'nce Dat,. -_"_,(Insufficient .eS-:."ufficient b

• ::,.-*.,,.{.:*{*,*{ax,o . .... .

No,..a........;

.

s**,<

-L:,..*1*

Lg. '

2 **:'> *:-'  ;>%*:.

Priority 1 Structures Page 5.8-13 Turbine Building Rev. 2 5.8.7.2 Conclusions In the assessment of the FCS Structures, the first step was to develop a list of all Triggering Mechanisms and PFMs that could have occurred due to the prolonged inundation of the FCS site during the 2011 Missouri River flood and could have negatively impacted these structures.

The next step was to use data from various investigations, including systematic observation of the structures over time, either to eliminate the Triggering Mechanisms and PFMs from the list or to recommend further investigation and/or physical modificationt.4o remove them from the list for any particular structure. Because all CPFMs for the*Turbii _*'**l.didither than CPFM 3b had been ruled out prior to Revision 1, and betis- CPFNW3If-ihas 'een ruled out by the additional forensic investigations for KDI #1 (see S.edti&h 4.1), noz__ viering Mechanisms and their associated PFMs will remain credible for the *MEe BuidmýRr'g -as concluded that the geotechnical and structural impacts of the 2011 INssour5tker flood43'jibe mitigated by the implementation of the physical modifications recommrA-hed in this Ass6§96iat Report.

Therefore, after the implementation of the recommended..p .,w, edificatlons, thej6te for failure of this structure due to the flood will not be sinflncan,

r Section 5.9 Security Barricaded BamIstic Palsktant-Endos reps B

_J

Priority 1 Structures Page 5.9-1 Security Barricaded Ballistic Resistant Enclosures Rev. 2 5.9 Security Barricaded Ballistic Resistant Enclosures 5.9.1 Summary of Security Barricaded Ballistic Resistant Enclosures Baseline information for the Security Barricaded Ballistic Resistant Enclosures (BBREs) is provided in Section 2.0, Site History, Description, and Baseline Condition.

Six BBREs are located at the site, as indicated in Figure 5.9-1.

manufactured steel enclosure supported on an elevated reinforc by a 36-in.-diameter reinforced concrete column and a 16-ft-sq spread footing. Based on the readily available construction dr, assumed to be identical), the foundations were sized based on i 1500 psf.

Prior to the original site development, grades in the area of the B'S--

to 1004 ft. Final site grades, in the area of the BBREs, are established at aT 1005 ft. This-would suggest the placement of up to abo ew fill i assumed to consist of a combination of sand, silt, an _31 Iat the 5.9.2 Inputs/References Supporting the Ani Table 5.9-1 lists references provided by 0 , ai ort HDR's analysis.

Table 5.9 erences Document Title Page W-D (ifDocument applicab Number(s)

- I l I I m Buried Utilities * *7 -008, Rev. 0 Yard Pip ý% e3O 11405 Sht. 3, Rev. 9 8/13/1973 W( #10754)) ._ _

Exc nd Grading Building ArA k, 4 05-S-272 i504) 1/18/1975 Siff~ gopography * *i 05-S-251 Unknown BBR*

• eff-Details W 12 (#62425) 09/06/2007 (BBRE) <on, Column, 552-SS-S5000 (#62163) 08/04/2006 Platform, Ph'I*,N _t., & Detai ls ..

• Summary of Pr'e T Lissouri River: Unknown All Summary of Prewious'! '-. ** 'w Unknown All Elevations *r **

Bathymetric Survey __ _ _ Unknown All Survey Point Elevations Unknown All Naval Facilities Engineering 9/1986 All Command, Design Manual 7.01, Soil Mechanics Detailed site observations-field reports, field notes, and inspection checklists-for the BBREs are provided in Attachment 8.

Priority 1 Structures Page 5.9-3 Security Barricaded Ballistic Resistant Enclosures Rev. 2 Observed performance and pertinent background data are as follows:

" F-I was constructed with the top of its spread footing flush with the surrounding pavement and is assumed to reside on the pre-existing soils.

• F-2 was constructed with the top of its spread footing ranging from about 1 to 10 in. above the surrounding sloped pavement and is assumed to reside on the pre-existing soils.

• F-3 and F-6 were constructed on top of the pre-existing pavement with reinforcing bars doweled into the pavement.

" F-4 and F-5 were constructed on top of the pre-existing soils.

• Estimated fill placement above original grade at each BBol

- 10 ft at F-I, F-2, and F-3

- I ft at F-4, F-5, and F-6

• Some site utilities might cross under the BBREs. The Raw g, with elevation of about 995 ft, has been identified as crossing near or under t tion for F-1.

• Groundwater was observed flowing into the basement sump e Building d condensate drain pipes not designed to intercept groundwater. This c has a recor history dating back to 1997.

Settlement of a column in the Maintenance Shop bine Buil s been documented.

• F-i and F-2 were protected by an Aqua Dam ee majori 1 flood; h wever, the Aqua Dam failed for a short period of time due to b damag water to enter the area inside the Aqua Dam perimeter. Flood er or pe oundat 1'1 and F-2 during this period. Maximum depth of inundati, ng th Aq m failureas aproximately 2 ft with an approximate river elevation of 1 0 BBREs F-3 through F-6 are lo side the perim Dam, which resulted in the foundations be' erged for n of the flood. depth of flooding was approxim *,.oundin es. with an approx mate river elevation of 1006.9 ft.

• Water .....v of the tween the pavement and the southern face of BBRE F-2' .- ation. Estimat rate of age appeared to be less than 1 gallon per minute August 25, 2011staff had andbags in front of the seeping area. Water

• *redS"mer*- clear 13, with 2011.*no lndicati sediment tsport. Seepage flow was no longer occurring on

• Av offset of about 1 in. wa. ! tified along the southern side of BBRE F-i 's foundation and t  % the surrounding pax rt,with the pavement being higher in elevation. The offset could be .xisting conditio* !i

• MH-5 is lot ia F-i and the perimeter of the Aqua Dam. An inflow of water was observed to be Rg th o conduits near the top of the southern wall of the manhole.

These conduits ct-.o a manhole outside the perimeter of the Aqua Dam. Observations indicated that up to Th ps had been used, ranging in size from 2 to 4 in.

" Concrete areas in the corridor (paved drive and pedestrian areas between the river and Service Building) have exhibited distress including cracking, settlement, and undermining. Portions of the pavement distress could be pre-existing conditions.

" There is a hole in the pavement and void area beneath the pavement north of the Security Building and east-southeast of MH-5. The hole and void area are outside of the perimeter of the Aqua Dam that surrounded the facility. The pavement failure occurred at the intersection point of pavement jointing. The hole in the pavement is irregular-shaped and is more than 1 ft wide both in the north-south and east-west directions. The void area beneath the hole was approximately 4 ft in diameter by 0.8 ft deep, as measured with a tape measure through the hole.

AY 6I 4 3 DATE Security BBRE Overview Oct 2011 Fort Calhoun Station FIGURE Omaha Public Power District Plant and Facility Geotechnical 5.9-1 IN I411 and Structural Assessment IM U a

Priority 1 Structures Page 5.9-4 Security Barricaded Ballistic Resistant Enclosures Rev. 2 0 The river bank is armored and has historically protected and stabilized the existing river bank.

0 USACE reduced Missouri River Mainstem System releases to 40,000 cfs on October 2, 2011.

River levels corresponding to the 40,000 cfs release rate stabilized at FCS on October 4, 2011, at about el. 995 ft.

5.9.3 Assessment Methods and Procedures 5.9.3.1 Assessment Procedures Accomplished Assessments of the BBREs included the following:

• Visually observed the grade around the perimeter and sinkholes

• Visually observed the grade in the vicinity of the s RckingN 6ement

• Probed the grades around the perimeter of the stru ctur~e ;es in con

• Visually observed the structure for indications of

" Established survey points on each foundation and penI red

• Assessed survey data to determine whether io R iý occur

" Reviewed previously documented conditio  : graphy, and geotechnical reports to identify possible ion! ý,he flood Additional investigations were performed rther cl at the facility including areas where conditions ind'. ati ~~otenti1 observed. These included the fo no gnvas*1 investigations.

" GPR in the PA. (Test r re not availa Ymf Revision 0.)

• Seis " eismic r and refractio emor) in the protected area.

avail time of Rev ision 0.)

a Q~hi~ W- in lhp, area N ote that OPPD required vacuum op Aflest holes to avoid utility conflicts. Therefore, test

)fl5 X ~iper E I0 ft of test boring logs. (Test reports Not Completed were not completed include the following:

0 the river bank to identify lateral movement. (Inclinometers are p, 5.9.4 Analysis Identified PFMs were initially reviewed as discussed in Section 3.0. The review considered the preliminary information available from OPPD data files and from initial walk-down observations.

Eleven PFMs associated with five different Triggering Mechanisms were determined to be "non-credible" for all Priority 1 Structures, as discussed in Section 3.6. The remaining PFMs were carried forward as "credible." After the design review for each structure, the structure observations, and the results of available geotechnical, geophysical, and survey data were analyzed, a number of CPFMs were ruled out as discussed in Section 5.9.4.1. The CPFMs carried forward for detailed assessment are discussed in Section 5.9.4.2.

Priority 1 Structures Page 5.9-5 Security Barricaded Ballistic Resistant Enclosures Rev. 2 5.9.4.1 Potential Failure Modes Ruled Out Prior to the Completion of the Detailed Assessment The ruled-out CPFMs reside in the Not Significant/High Confidence category and for clarity

.1 will not be shown in the Potential for Failure/Confidence matrix.

Triggering Mechanism 2 - Surface Erosion CPFM 2a - Undermining shallow foundationlslab/surfaces Reason for ruling out:

• Surface erosion was not identified near the BBREs _g t Triggering Mechanism 5 - Hydrodynamic Loading CPFM 5a - Overturning CPFM 5b - Sliding CPFM 5e - Damage by debris CPFM 5f- Excess deflection Reasons for ruling out:

• Sufficient high velocities of the flood r were ent 0 The structures did not have evit si-* dis tentifi he field assessments.

Triiggering Mechanism 7 - So' apse (first wetting CPFM 7a - Cracked sla . ential settlem hal undation, loss of structural support CP I ed struc ken connectio, settle s for ruline out u'*

The peak flood elevation& .,'to12011 wlas 1003.3 ft, which occurred in 1993. The peak M ood elevation in 2011 wk 'iroximately 1006.9 ft. The soils had been previously i4mrated, and soil conditi* ere not altered during construction of the BBREs.

0

=utctures did not hayelfga"dent signs of distress identified during the field assessments.

Ti ggerii,

• hanismachine/Vibrat s n-Induced Liquefaction r

FM k ?CP, ,differential settlement of shallow foundation, loss of structural CPFM l0b-1 aiced structure/broken connections CPFM 1Od - ile group instability Reasons for ruling out:

• The structures did not have evident signs of distress identified during the field assessments.

" Machines that induce vibrations are not located near the structures.

" Liquefaction was not observed at the site.

Priority 1 Structures Page 5.9-6 Security Barricaded Ballistic Resistant Enclosures Rev. 2 I. Triggering Mechanism 11 - Loss of Soil Strength due to Static Liquefaction or Upward Seepage CPFM 11 a - Cracked slab, differential settlement of shallow foundation, loss of structural support CPFM I1b - Displaced structure/broken connections Reasons for ruling out:

• The structures did not have evident signs of distress id

• Liquefaction was not observed at the site.

Triggering Mechanism 12 - Rapid Drawdown CPFM 12a - River bank slope failure and undermini CPFM 12b - Lateral spreading Reasons for ruling out:

• The structures did not have evident signs of assessments.

• Slope failure was not observed at the site-

• River stage level has receded and stabili' t a to tinal normal river level at 40,000 cfs as of October 11.

Triggering Mechanism 14- Fr fec ".

CPFM 14a - Heaving, crus

• isp acem Reason for ruling out: RA AS TRimRuhiectedi to dinrincr winter months are not different

.2 Detailed Ass`,*,nt of Cripotential Failure Modes following CPFMs are th~i, CPFMs carried forward for detailed assessment for the

.REs as a result of the 201 1 yd. This detailed assessment is provided below.

,j~fi-Ag Mechanism 3 - Sn rface Erosion/Piping CAIV&2a - UnderminT°inigOsettlement of shallow foundation/slab/surfaces (due to Subsurface e general vicinity of the BBREs that were pumped during the flood due to grot tion included the following:

• Manhole MH-5

• Manhole MH-24

• The Turbine Building sump pit

• The Trenwa near the Security Building

• Turbine Building South Switchyard cable trenches

Priority 1 Structures Page 5.9-7 Security Barricaded Ballistic Resistant Enclosures Rev. 2 This CPFM is only considered applicable to F- I and F-2 because F-3 through F-6 are a substantial distance from the known groundwater pumping locations and would not be in the CPFM's zone of influence.

The Triggering Mechanism and CPFM could then occur as follows: soil deposits could have been carried with the water flow, causing subsurface erosion. If enough soil was removed from these areas, it is possible that portions of the building's foundation and slabs could be undermined.

The following table describes observed distress indicat(

decrease the potential for degradation associated with ti The CPFM has not Yeen observed at the structures. However, voids created due to groundwater pumping at MIH-5 and MH-24 might not have been evident at the time of the field assessments. Additionally, the extent of voids due to pumping of groundwater in the Turbine Building sump has not been determined. Observations of the BBREs indicate the potential that degradation has occurred due to this CPFM is low.

Priority 1 Structures Page 5.9-8 Security Barricaded Ballistic Resistant Enclosures Rev. 2 Implication The occurrence of this CPFM would have to be large to negatively impact the performance of the BBRE foundation. Depending on the location and extent, this would manifest as foundation movement, which could negatively impact the integrity or intended function of the BBREs. Therefore, the implications of the potential degradation for this CPFM is high.

Confidence The data at hand are not sufficient to rule out this CPFM re tet to lead to a conclusion that the BBRE foundations are or could bec** ndermi ause of this CPFM Therefore, the confidence in the above assessment is I ich ta are necessai to draw a conclusion.

Summary For CPFM 3a, as discussed above, the potential for degradation is- is degradafi uld have to be large to impact the integrity or intend of the - The combined consideration of the potential for degradation ions of anon to a structure of this type puts it in the "not sign categ e data cu ollected are not sufficient to rule out this CPFM. Ther e, the co e above asessment is "low," which means more data or continu onitori 7 in- ,'* s could be necessary to draw a final conclusion.

Triggering Mechanism 3 - ace Erosion CP ining ment of shallo tndation/slab (due to river ggering Mechan a, CPFM en occur as follows: the drop in elevation of

.river is expected to occ higher ra the drop in elevation of the groundwater.

result in an increas undwater gradient. This increase could allow for subsurface pe-.n to occur.

TMh,,* M is only considere . 5 icable to F-I through F-3, because F-4 through F-6 are a subst listance from th ier and would not be in the CPFM's zone of influence.

The .... des besobserved distress indicators and other data that would increase or decrease th egradation associated with this CPFM for the BBREs.

Adverse (DegradationlDirect Floodwater Favorable (Degradation/Direct Floodwater Impact More Likely) Impact Less Likely)

The structures do not show signs of movement.

Survey data to date do not identify measurable movement.

Data Gaps:

e Additional data will be acquired from GPR. seismic survey, and geotechnical test borings.

Priority 1 Structures Page 5.9-9 Security Barricaded Ballistic Resistant Enclosures Rev. 2 Conclusion

.j:.

Significance PotentialforDegradation/DirectFloodwaterImpact None of the indicators for the CPFM has been observed at the structures. However, voids due to rapid drawdown might not have been evident at the time of the &d assessments.

Additionally, the extent of voids created by rapid drawdown-cou s cant. The potential that degradation has occurred due to this CFA .

Implication The occurrence of this CPFM below a BBRE foundation 7 impact the performance of the BBRE foundations. Depen would manifest as foundation movement, which could ne e intended function of the BBREs. Therefore, the implication of this CPFM is high. 60 b Confidence The data at hand are not sufficient to rule is CPF, ficient to lead to a conclusion that the BBRE foundati are ight ýb4 un Decause of this CPFM.

Therefore, the confidence in the .S! iore data are necessary to draw a conclusion.

Summary For 51. 01s ed abov > O1 ential for degradation is low. This degradation would Wtended function of the structures. The combined eration of the po &=t*and the implications of that degradation to a icture of this type puts t category. The data currently collected are sufficient to rule out tl efore, the confidence in the above assessment is

, which means more :d monitoring and inspections might be necessary to 1final conclusion.

Priority 1 Structures Page 5.9-10 Security Barricaded Ballistic Resistant Enclosures Rev. 2 5.9.5 Results and Conclusions The CPFMs evaluated for the BBREs are presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

.I a, and assess the impact on the BBREs. Further forensic recommended to address CPFM 3a and 3d (Key Distress Ls are described in detail in Section 4.1.3.

Continued monffr s recomrn ir"to include a continuation of elevation surveys of the previously

.identified target d the surrounding site. The purpose is to monitor for signs of structure distress and R r changes in soil conditions around the structure. The results of this monitoring will be used bcease the confidence in the assessment results. Elevation surveys should be performed weekly for 4\-,eeks and biweekly until December 31, 2011. At the time of Revision 0, groundwater levels had not yet stabilized to nominal normal levels. Therefore, it is possible that new distress indicators could still develop. If new distress indicators are observed before December 31, 2011, appropriate HDR personnel should be notified immediately to determine whether an immediate inspection or assessment should be conducted. Observation of new distress indicators might result in a modification of the recommendations for this structure.

Priority 1 Structures Page 5.9-11 Security Barricaded Ballistic Resistant Enclosures Rev. 2 5.9.7 Updates Since Revision 0 Revision 0 of this Assessment Report was submitted to OPPD on October 14, 2011. Revision 0 presented the results of preliminary assessments for each Priority 1 Structure. These assessments were incomplete in Revision 0 because the forensic investigation and/or monitoring for most of the Priority 1 Structures was not completed by the submittal date. This revision of this Assessment Report includes the results of additional forensic investigation and monitoring to date for this structure as described below.

5.9.7.1 Additional Data Available The following additional data were available for the B for R 2 of this Assessment Report:

e Results of KDI #1 forensic investigation (see Section

• Results of KDI #2 forensic investigation (see Section 0 Additional groundwater monitoring well and rive tage level OPPD.

I Field observations of the river bank (see Se 0 Results of falling weight deflectometeri io erican En g Testing, Inc.

(see Attachment 6).

0 Results of geophysical investigation b .otechno ttachment 6).

• Results of geotechnical investigation ele h, In chment 6).

• Data obtained from inclinom eG , Inc. (s ent 6).

• Results of continued surveyf amp Rynear d Assoc' s (see Attachment 6).

5.9.7.2 Additional Anal 1 TefadditioTe 'was conducted for the Security BBtREs:

undwater mot ell and age level data from OPPD.

Data shows that the riv .3 -groundwa ave returned to nominal normal levels.

Ij,!d observations of river h

...... ficance distress f *lWe 2011 Flood was observed.

• Resul 'l~ing:5 g Te.

flectometer investigation by American Engineering Testing, Inc.

Fli We t4,ctometer and associated GPR testing performed in the Paved Access Area identifie malies such as soft clay and broken pavement. Additional ground truthing of the investigation results were performed as part of the KDI #2 additional investigations.

• Results of geophysical investigation by Geotechnology, Inc.

Seismic Refraction and Seismic ReMi tests performed around the outside perimeter of the power block as part of KDI #2 identified deep anomalies that could be gravel, soft clay, loose sand, or possibly voids.

Priority 1 Structures Page 5.9-12 Security Barricaded Ballistic Resistant Enclosures Rev. 2 Results of geotechnical investigation by Thiele Geotech, Inc.

Six test borings were drilled, with continuous sampling of the soil encountered, to ground truth the Geotechnology, Inc. seismic investigation results as part of the KDI #2 forensic investigation. Test bore holes were located to penetrate the deep anomalies identified in the seismic investigation. The test boring data did not show any piping voids or very soft/very loose conditions that might be indicative of subsurface erosion/piping or related material loss or movement.

All of the SPT and CPT test results condu ct o t"_

th ss enconducted r compared to similar data from numerous other geotechnical* g been conducted on the FCS site in previous years.. This compariso ot i aIschanges to the soil strength and stiffness over that time period. test r ere not performed in the top 10 feet to protect existing utilities.

Data from inclinometers to date, compared to the origi ba easurement t exceeded the accuracy range of the inclinometer erefore on at the monitored locations since the installation of the instru not occu Results of continued survey by Lamp son and es.

Survey data to date compared to the o I base rve ot exceeded the accuracy range of the surveyi uip .e, defo i.tthe monitored locations, since the survey b ' as shot, t occurr t Additional analysis related ***3ais discuss s for KDI # 1,and additional analysis relat to CPFM 3d *sed in Section. #2.

brue be kRevision 0 are analyzed below based on the a data availa evision 2 of this Assessment Report.

ggering Mechanism 3- surface 11iping 3a - Underminin etCPFM shallow foundation/slab/surfaces (due to ettlementof pumping) 3d-Uettlement

- of shallow foundation/slab (due to river drawdown)

CPFMs .... d for th s are associated with Key Distress Indicators #1 and #2.

Section 4..1 2e results of additional forensic investigation that was conducted to ascertain whe*e e*e*FMs could be ruled out. The results of the additional forensic investigations si ait if the recommendations for physical modifications in KDI #1 are implemented that these CPFMs are ruled out. Therefore, assuming that no further concerns for the BBREs are identified through the monitoring program (discussed in Section 5.9.6 and continuing until December 31, 2011), these CPFMs are moved to the quadrant of the matrix representing "No Further Action Recommended Related to the 2011 Flood."

Priority 1 Structures Page 5.9-13 Security Barricaded Ballistic Resistant Enclosures Rev. 2

.r 5.9.7.1 Revised Results The CPFMs evaluated for the BBREs are presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

the assessment of the FCS ctures, the'fs-t step was to develop a list of all Triggering

• chanisms and PFMs that c, Whave occurred due to the prolonged inundation oftheFCS

• mg the 2011 Missouri Raw flood and could have negatively impacted these structures.

tep s to use data J., "various investigations, including systematic observation of the - es over time, eith 1liminate the Triggering Mechanisms and PFMs from the list or to re nd further ation and/or physical modifications to remove them from the list r ar s Because all CPFMs for the Security BBREs other than C a e.n ruled out prior to Revision 1, and because CPFMs 3a and 3d will be ruled out wt hysical modifications recommended for KDI #1 in Section 4.1 are implemented, no T-ggering Mechanisms and their associated PFMs will remain credible for /

the Security BBREs. HDR has concluded that the geotechnical and structural impacts of the 2011 Missouri River flood will be mitigated by the implementation of the physical modifications recommended in this Assessment Report. Therefore, after the implementation of the recommended physical modifications, the potential for failure of this structure due to the flood will not be significant.