ML13273A324

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

ML13273A324
Person / Time
Site:	Fort Calhoun
Issue date:	09/19/2013
From:	Office of Information Services
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References
FOIA/PA-2012-0235
Download: ML13273A324 (249)

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Section 5.12 Underground Cable Trench teL.J Priority 1 Structures Page 5.12-1 Underground Cable Trench Rev. 2 5.12 Underground Cable Trench 5.12.1 Summary of Underground Cable Trench Baseline information for the Underground Cable Trench (Trenwa, Inc.) is provided in Section 2.0, Site History, Description, and Baseline Condition.

The Trenwa is the trench system that contains the security system cablin CS he Trenwa is a precast concrete cable trench that follows the PA perimeter.

Th -a een 5 and 7 ft wide and is between approximately 1.8 and 3.2 ft deep, depen locati holes are interspersed along the Trenwa alignment.

The Trenwa is cove ith pr traffic crossings, specialized lids are in place to allow vehicular traffic renwrenwa section is modified for these locations, including a thicker base an t inserts S.Trenwa bedding at typical road crossings was specified to be co de and b minimum 95 percent of maximum dry density per ASTM D1557. -Trenwa bedding is compacted subgrade soil. Per the dr , enginee ing was not specified except at certain locations.

The design pl tare the "Soil compaction under the trench brackets should be eq the und averae so il compaction must equal 4000# per square ft or 28# per square ' Pedes IS and dra pipe crossings included a minimum bedding of 3 in. of crushed nderlaith fabric. Drawings 88-185-1 and 9364-C-0012, files 47643 646 ,ilud r d details for Trenwa bedding and subgrade.The Trenwa system is located insi ility perimete ws the fence alignment around the site. The T enwa is cons s long, straig along most sides of the facility except at the s f the sit e it jogs around ecurity Building and the Condensate Storage T ," 20 orth anc ides of the Intake Structure.

The Trenwa section ends ap ely 200 ft no Intake re. Underground cabling continues beyond the Tren , uipment connected abling e original northern section of the Trenwa w d where the north face o ew W is located. The Trenwa system ends at a point th onds to the north face th Warehouse, but security system cabling with handhole acces has-been extended aroun ISFSI facility, the New Warehouse, and the security perimet ortheast corer oft See drawings listed in Table 5.12-1 for location and 5.12.2 lnputs/R Ices -Is gu n the Analysis Table 5.12-1 lists refe- " We ided by OPPD and other documents used to support HDR's analysis.Table5.12-1

-References for Underground Cable Trench Document Title OPPD Document Date Page Number Number(s)(if applicable)

Cable Trench Layout 88-185-1 (#47643) 6/30/1988 Cable Trench Layout 88-185-2 (#47644) 6/30/1988 Cable Trench Layout 88-185-3, Rev.1 (#47645) 7/1/1988 Cable Trench Details 88-185-4 (#47646) 7/1/1988 Cable Trench Layout 89-67-1 (#49669) 3/17/1989 Priority 1 Structures Underground Cable Trench Page 5.12-2 Rev. 2 Table 5.12-1 -References for Underaround Cable Trench Pag512-2 Document Title OPPD Document Date Page Number Number(s)(if applicable)

Cable Trench Layout 89-67-2 (#49670) 3/17/1989 Cable Trench Details 89-67-5 (#49717) 3/17/1989 Cable Trench Layout 89-132-1 (#49750) 5/19/1989 Cable Trench Layout 89-132-2 (#49751) 5/&_ _ 89 Cable Trench Layout 89-132-3 (#49752) 5 5Nj Cable Trench Details 89-132-4 (#497533)

A. 5/10 M W Cable Trench Details 89-132-5 (#49754)=.

5/10__Precast Concrete 9364-C-0106, Sht.Cable Trench Layout Rev. 2 (#47449) o .n Security System Duct Bank 9364-C-00012, Sht. 1 .Sections and Cable Trench Details Rev. 0 (#46463) !g," Independent Spent Fuel Storage Installation 59058-EE-6A, R .Ur" ISFSI Cable Trench and Raceway (#60753). ___Independent Spent Fuel Storage Installation 59058-. Unknow'ISFSI Cable Trench Section & 6 wi W Cable Trench Layout 04-8W3' (#608 19 WV09~1004

_______Naval Facilities Engineering Command, __ __ _All Dsg Manual 7.01, Si ehnc Detailed site observations-field re eld notes, and ctio ists-for the Undergrofind Cable Trench are provided in Atta ,, ",., 411 Observed per` e d data are as fol ows: The covers appea ht and ; l tong the north, west, and south sides, which were arte during site inspect differential settlement wa -d where t renwa section varied due to connectivity to es, changes in alignment, vehice crossing points. Because the Trenwa base is set ab 6 dard frost depth for this. ', some minor differences in the top elevation of the system are tcted.* The rive.t.&section of the Tre nd the section at the northeast corner of the site were not inspecte d avy depos t in some areas and inundation by floodwaters at the northeast corner of the sIit ern fied 4'ections were being made.* Soils along the T i '.rnn ent were normally stable and firm. Isolated locations of soft soil were encountered.

'¶ t soil locations were observed where the soil showed signs of being saturated or moist and 4 heir lowest strength condition.

It is anticipated that the soils will dry and re-stabilize in the future.5.12.3 Assessment Methods and Procedures 5.12.3.1 Assessment Procedures Accomplished Assessments were made by walking the Trenwa alignment and observing surface features of the system (manholes), the precast concrete cover, and the ground surface adjacent to the Trenwa cover. The surface assessment included using a 4-ft-long, 0.5-in.-diameter, steel-tipped Priority 1 Structures Underground Cable Trench Page 5.12-3 Rev. 2 K f.fiberglass T-handle soil probe to hand probe the ground surface to judge the relative soil strength.

The assessment focused on identifying conditions indicative of potential flood-related impacts or damage to the utility, as follows:* Ground surface conditions immediately adjacent to the utility including scour, subsidence.or settlement, lateral spreading, piping, and heave* Soft ground surface areas (native soil, engineered fill, and limestone gravel surfacing), as determined by probing* Water accumulations and flows in subsurface system c, o es and concrete cable encasement pipes)* Damage to at-grade or above-grade system feature equip* Variance from normal installation conditions inclu I d system features and equipment* Operation of the system and appurtenant equipment (i. stem oper d operating as intended?)

Additional investigations were performed to furt.including areas where conditions indicative of observed.

These included the following nor investigations:

te g 0 GPR. (Test reports were not a)evisi(5.12.3.2 Assessment Pr Cor Assessments of the Trenwa not complel wing: 0 1 wa),served except for visual observations that were n joints in the Trenwa cover. It is not expected that Snrior observatioff

'gat only sediment dep No excavation to inspect hwas not deemed necessar rease -dence in the conclusion because it is anticipal n the Tre uld be observed.,ground s 'ems and conditions was performed because it Chis structure.-river that will provide an indication of slope movement.ted iometer readings alo 5.12.4 A Identified PFMs w%% 1ll "ed as discussed in Section 3.0. The review considered the preliminary informa ja ~irom OPPD data files and from initial walk-down observations.

Eleven PFMs

....e different Triggering Mechanisms were determined to be"non-credible" for all I1 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 5.12.4.1.

The CPFMs carried forward for detailed assessment are discussed in Section 5.12.4.2.

Priority 1 Structures Underground Cable Trench Page 5.12-4 Rev. 2 I 5.12.4.1 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 Trenwa system survey was not completed due ndati-of inspection.

Although this PFM is not considered d on completed, it has the potential to occur in flooded area e not bet However, due to silt deposited between the PA fencin istence armoring, this PFM was judged to be unlikely for the 9bs -eas z* Some localized and limited surface erosion was n ted at the sit , sidewalls of the Trenwa. According to the Trenwa below the ground surface. Undermining e was not-because it is well below the depths of s erosion d in the fi perimeter fence includes a 4-ft-tall Ne, sey Ba -:the bott section. The New Jersey Barrier is mi -d to a ete continuous around the site, pr t fl and sit Blockage of direct flows on e reduces elihood t surface the Trenwa. , -P).".y at the time ner'vatlons n d.ng adjacent o the is at least 1.8 ft red credible , l e site om reinforced barrier is te and Trenwa.erosion will affect The Trenwa system obs'~ on was n 3 tM pleted due to inundation of the facility at theof inspection.

Altho SI-his PFM is not considered credible based on present field bbservations, it has the poA... to occur in flooded areas that are unobserved.

Little or no lifce erosion was obser iong the Trenwa, and silt deposits that were observed across 11 he. entire Trenwa,7indicate flow velocity rates that were too low to initiate scoWwduced failure. )4oii,1nws through the northeast site were observed at the time of field 5 ing and other structures observed from a distance appeared to be intact q the flood. This PFM was judged to be unlikely for the unobserved areas. _* The Trenwa isaIlgned for some displacement and flexibility, and cabling inside the Trenwa is a flexible system. The system will tolerate some movement without loss of functionality or damage to enclosed utilities." According to the drawings, the Trenwa bottom is at least 1.8 ft below the ground surface.Undermining of the Trenwa base was not considered credible because it is below the depths of surface erosion observed in the field.

Priority 1 Structures Underground Cable Trench Page 5.12-5 Rev. 2 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 Reason for ruling out:* Soil supporting and surrounding a majority of the Tren wetted. The peak flood elevation prior to 2011 was Triggering Mechanism 10- Machine!dVibration-nd CPFM I Oa -Cracked slab, differential settlement o support CPFM 1Ob -Displaced structure/broken connections CPFM 1Oc -Additional lateral force on below-grade v Reasons for ruling out:* Machine vibrations from the facility (tu and van occurred, and no indications of these s are ev* Pumps used on site during the 2011 fl ere ground or structure vibrations

1. 'tia li No structure movements in f soil liq ion observed; no structure cr settlements, ral ,previously.Ted in 1993.tt,.structural is) have rally tqo b on.and mol size to cause Itant settlement were nts were observed.Trigger SeepaA 11-Soil Sti Liquefaction or Upward of shallow foundation, loss of structural.Ik suppo.&PFM Ib- Displac CPFM 1 c -Additiona ture/bro mnectionsýl force on o'w-grade walls for ruling out: 0 S to be not been obserN'.oil/piping feal)served in the missile room was determined to be too shallow Triggering Me' 12 -Rapid Drawdown CPFM 12a -t-"' bank slope failure and undermining surrounding structures CPFM 12b -Lateral spreading Reasons for ruling out:* The structures did not have evident signs of distress identified during the field assessments." Slope failure was not observed at the site.* River stage level has receded and stabilized as of October 4, 2011.

Priority I Structures Page 5.12-6 Underground Cable Trench Rev. 2-As of October 11, 2011, groundwater elevations had already had one week to stabilize to at least a partial degree.The river bank is armored and has historically protected and stabilized the existing river bank.Triggering Mechanism 13 -Submergence CPFM 13a -Corrosion of underground utilities Reasons for ruling out:* Groundwater elevations controlled by Missouri Ri er elev d percolation of storm precipitation, including winter snowmelt, wo ex underground improvements including constructed steel and concr ement .ch, steel and concrete site improvements are assumed to be designe .standthe co environment of groundwater and wetted soil.* Conditions have not been changed due to the 2011 floo 5.12.4.2 Detailed Assessment of Credible ileilur Mo The following CPFMs are the only CPFMs ed forwa etailed ass t for the Trenwa as a result of the 2011 flood. Thi ailed ass vided be ow.Triggering Mechanism 3 -Subs, ce on CPFM 3a -Undermining an en -of sh foundat sla /surfaces (due to pumping)CPFM 3c -Undermin utilities (due The T r ism and ,could occur as o ows: multiple potentially connected see h soil ba t the site, including soil backfill in utility trenches, tench beddi re-exis cts/voids under pavement.

The paths are exposed e locations to the odwate en areas outside the Aqua Dam perimeter or e hole in the pavement no e Secu uilding).

This network of seepage paths is ected to pumping source e site: the Trenwa beside the Security Building and insidebarrier, and the n us pumps inside the perimeter of the Aqua Dam and the SIbbarer.

The pumps W,-- cerated for an extended period, maintaining a head de pn the seepage pa h orks. Gradient was sufficient to begin erosion of surrounhIN",l leepageAA ered and erosion continues unarrested.

Erosion extends out, interceptile ketwor ii lity trenches, including the Trenwa. Voids are created under and along the Utl ., utilities, structures, and pavements.

The potential damage includes settle Trenwa. Significant settlement might cause a loss of electrical connectivity.

Below are field observations and data that.support the likelihood of these CPFMs: " Trenwa trenches beside the Security Building were pumped for the duration of flooding to remove water coming in from outside Trenwa locations.

This created a head differential." Site drainage pumps inside the perimeter of the Aqua Dam and HESCO barriers pumped from numerous sources around the perimeter of the facility.

The Aqua Dam was located in proximity to the Trenwa along, the west, south, and east sides of the PA. The HESCO barriers that were used to protect the Security Building crossed the Trenwa.

Priority 1 Undergro< -Structures und Cable Trench Page 5.12-7 Rev. 2 A hole in the pavement with a void area beneath the concrete slab was observed just north of the Security Building and east-southeast of MH-5. The hole and void area could be the result of piping and subsurface erosion. The hole and void area are located in proximity to the Trenwa.Based on a conversation with the OPPD operations employee testing FP-3E on September 13, 2011, fire hydrant FP-3C, located northeast of the Security Building, was tested on September 13, 2011, and failed. According to the OPPD operations employee, when opening the valve to test the hydrant, the base cracked and le and the valve had to be closed. The access cabinet was tagged-out for repair t hydrant that failed is located in proximity to the Trenwa.Concrete areas in the Paved Access Area and pede areas b river and Servic Building north of where the ductbank crosses the P cc ea. ibited distress including cracking, slab settlement, and unde s evidenc llow-sounding pavement areas).An area of apparent pavement settlement, located in t a Area we of the Intake Structure overhead door, is located near the no water ali Below are field observ* The observed hole developed by outfli Temporary surface the Aqua Dam. On observations.

Con observed hole.* Most areas along ti ie extent of the s1 4GPR data (awaitinl IRfollowing table de e the nntentinl I-d distress indicators and other data that would increase or associated with these CPFMs for the Trenwa.

Priority 1 Structures

_Underground Cable Trench Conclusion Significance Potential for Degradat Indicators for these CP failure north of the Sec subsurface erosion exti the potential for degraw Implication The occurrence of the, is flexible and will tol exposed utilities.

The low.Confidence There are multiple ele]2011 flood, the hole in section in the Paved A However, even thouglg pavement, the extent c Available data are not Page 5.12-8 Rev. 2 tion/Direct Floodwater Impact'FMs have been observed.

The pavement void area and fire cabinet test:urity Building are in the proximity of the T wa. It is possible that ends below the Trenwa northeast of the Se Bu' g. Therefore, dation due to these CPFMs is judg e se CPFMs could cause the collapse enwa. Ho e Trenwa ,rate movement without loss of refore, the implication of the po ments to these CPF e inflc the pavement nort he Seci.ccess Area beeen ervioc-the confi hi n -that ifthese v s not known.the , Structure.

the corridor erosion, fhto a conclusion that subsurface in the assessment is low, which CPFMs 3a and 3c, as above, tlfpotential for degradation is high because the ,ement void area and fire c30t test failure north of the Security Building are in the imity of the Trenwa. Thi4 could have caused enough erosion to impact the ir intended functionA it structure.

The combined consideration of the potential for r Ohmand the implicathif that degradation to a structure of this type puts it in the "not iifickdi1?bAtegory.

Thca4currently collected are not sufficient to rule out these CPFMs.Io -e ,.. ... de e above assessment is low, which means more data or continued nri~~t N.M.i might be necessary to draw a conclusion.

The mor Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3d -Undermining and settlement of shallow foundation/slab (due to river drawdown)CPFM 3f- Undermined buried utilities (due to river drawdown)These CPFMs are similar to and in addition to CPFM 3a and 3c, but instead of pumping, the gradient is created by rapidly receding river level.

Priority 1 Structures Page 5.12-9 Underground Cable Trench Rev. 2 The Triggering Mechanism and CPFM could then occur as follows: river level drops faster than pore water pressure in the soil foundation can dissipate.

A gradient is created that moves soil into existing defects and enlarges voids under or along the Trenwa walls or utility lines.Depending on the extent of the voids created, impacts can include the following:

trench subsidence, unsupported Trenwa sections, Trenwa failures, unsupported pipe sections, pipe deflections, pipe failure, and possible impacts on adjacent improvements or utilities.

Field observations and data that support the likelihood of these C Is are as follows:* Subsurface erosion is known to exist beneath buildin sl ow unknown whether these erosion and piping features xtend the Trenwa.Areas of soft soils were observed in localized areas ent to, idewalls.The east segment of the Trenwa structure is relative river herefore susceptible to subsurface piping associated with draw e river.Field observations and data or site conditions that indicat s are unlike follows: 0 The Trenwa has been subjected to floodin ast, and e of erosion and piping or impacts have not been recorde ** The east segment of the Trenwa is nea yiver. H majori e Trenwa is well away from the river. Increased d 'ce from vd educes the likelihood of subsurface erosion/piping related-to th r dra, ,v- 'The following are data-gaps (da quired to these C* Geophysical investigati

_ o address adja areas* Inclin§,.,trzpgta to addre ed concerns .R .ai measur in existing piezometers/monitoring wells table b s indicators and other data that would increase or o5wing d pbsers i ease the potential for -ation with these CPFMs for the Trenwa.

fdoodwater Favorable (Degradation/Direct Imact More L ike .Floodwater Impact Less Likely) at a high level exist or an USACE suspended the river drawdown eKtaAperiod of time that co#*llow between August 27 and September 18, 2011.surrou- oils to become p ed. This gap in the scheduled reduction of dam release rates was provided to allow groundwater elevations to equalize with river N, t flow elevations.

Riverbank is armored and protects against creation of a weakened flow path.Indications of these CPFMs have not been exhibited or reported for previous floods.Data Gaps:* Field observations after river drawdown* Geophysical investigation data to address adjacent pavement slabs* Inclinometer data to address observed concerns Priority 1 Structures Page 5.12-10 Underground Cable Trench Rev. 2* / Conclusion Sianificant Potential for Degradation/Direct Floodwater Impact None of the indicators for the CPFMs has been observed at the Trenwa. However, voids due to rapid drawdown might not have been evident at the time of the fi assessments.

Additionally, the extent of voids created by rapid drawdown could be insi. ifi e tential that degradation due to this CPFM has occurred is low.Implication The occurrence of these CPFMs could cause the collapse nwa. Ho e Trenwa is flexible and will tolerate movement without loss of fun r detrimen s exposed utilities.

Therefore, the implication of the potent e n for these low.Confidence The data at hand are not sufficient to rule ese CPF d to a con sion that subsurface erosion would undermine the a. Th e, idence in the assessment is low, which means more data are n ,ess dra n s Summary For CPFMs 3d and 3f, as di bove, the pot dation is low. This degradat' ve to occ large scale to 1 e integrity or intended function of the T consi of the potential for degradation and the implications of adation ure of i puts it in the "not significant" category.

The dataaencollectediare cient to these CPFMs. Therefore, the confidence in the e ' mons o- 1ntu monitoring and inspections might be necessary to draw a o cl s Tri;gog.alMechanism st Effects CPF'A a,- Heav g fng, or displacement Heave associ( " penetration below the Trenwa could occur.The Triggering nism and CPFM could occur as follows: the trigger for frost penetration to occur is no different than in previous years. However, higher subsurface water level and increased moisture content of near-surface soils could increase the magnitude of frost movement over the upcoming winter season.Field observations and data that support the likelihood of this CPFM are as follows:* Wet soil conditions were observed near the Trenwa structure, especially near the northeast corner of the site.

Priority 1 Structures Underground Cable Trench Page 5.12-11 Rev. 2 Field observations and data or site conditions that indicate this CPFM is unlikely are as follows:* Conditions required to trigger this CPFM have typically occurred every year since construction.

• The majority of the Trenwa, except the east segment, is well away from the river and potential subsurface water associated with the river.The following are data gaps (data yet required to assess this" Geophysical investigation data to address observed I* No Condition Reports are available to review to ad heave have created problems in the past. However, needed for increasing the confidence in the conclusion CPFM typically happen on a yearly basis.The following table describes observed distress indicators ai decrease the potential for degradation associatedwA( C of frost/I/Adverse (DegradationlDirect Floodwal Impact More Likely)Wet soil conditions currently exist.F The Ty npac (for.jone of the indicators for;ing temperatures II due to this CPFMi observed along the structure.

However, since the 2011 flood. The potential that is low.The :Qf this !~'elow the Trenwa would likely not affect the performance of the Trenwa ly subjected to frost conditions.

Therefore, the implication of the potential the CPFMs is low.Confidence The potential impact on the structure from this CPFM is not known due to unknown supporting/surrounding soil saturation levels. River and groundwater levels at this time are such that this CPFM might occur.The data at hand are not sufficient to rule out this CPFM or to lead to a conclusion that frost effects would negatively affect the Trenwa. Therefore, the confidence in the assessment is low, which means more data are necessary to draw a conclusion.

Priority 1 Structures Underground Cable Trench Page 5.12-12 Rev. 2 (Summary For CPFM 14a, as discussed above, the potential for degradation is low. 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 not sufficient to rule out these CPFMs. 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.

&5.12.5 Results and Conclusions The CPFMs evaluated for the Trenwa are presented in the foll the estimated significance and the level of confidence in the eN 5.12.6 RecommebnlAc.ti4l Further forensic investiga and physical modifications are recommended to address CPFMs 3a, 3c, 3d, and 3f for the Trenwa. CPFMs 3a and 3c are associated with the distress in and near the Paved Access Area between the Service Building and the Intake Structure (Key Distress Indicator

1. 2). These recommendations are described in detail in Section 4.2.5.Also, monitoring of groundwater well data and a review of the geophysical data, when available, should be done. The results of this monitoring will be used increase the confidence in the assessment results. 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 Priority 1 Structures Page 5.12-13 Underground Cable Trench Rev. 2 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.

5.12.7 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 monit g for most of the Priority 1 Structures was not completed by the submittal date. Thi vi ffi' sessment Report includes the results of additional forensic investigation and mo to s structure as described beloW.5.12.7.1 Additional Data Available The following additional data were available for the Und hable Trench Revisions 1 and 2 of this Assessment Report: o Results of KDI #2 forensic investigation (se 2)Additional groundwater monitoring well --el -data D.* Field observations of the river bank (see .ion 5.25* Results of geophysical investigation b otechnol G. Attachment 6).*Results of geotechnical investigation

-iele G. In .chment 6).* Data obtained from inclinom by G I nc (s Results of continued survey, p Rynear d Assoc (see Attachment 6).* Field assessment of the in areas that acces- prior to Revision 0 of the report and a visual inspe interior sectiom a where the system had been 5. ddition K sis Revision 0, additional data have become ailable which has clarifie gnificance nd confidence for these CPFMs. The following

, nts the previously identi PFMs and the new interpretation of their significance and Zae oiom nd river stage level data from OPPD.Data at th d groundwater have returned to nominal normal levels.Field !river bank No significance distress from the 2011 Flood was observed.Results of geophysical investigation report 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 Underground Cable Trench Page 5.12-14 Rev. 2 Proiy -tucue 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 1 .. ... ...+-...-loss or uiuv~remi.

All of the SPT and CPT test results conducted for to similar data from numerous other geotechnical i on the FCS site in previous years. This comparisor, the soil strength and stiffness over that time period. .1 performed in the top 10 feet to protect existing utilities.

Data from inclinometers to date, compared to the origir exceeded the accuracy range of the inclinometers e)locations since the installation of the instru itions T test* Results of continued survey by Lamp Survey data to date compared to the o accuracy range of the survey uip locations, since the survey b. l te)tth Lwere compared been conducted a*a changes to erenot ini n at the monitoredthe te monitored sment Report to, or to Revision 0 to the areas that-d where the top m of the trench.cted that interior anticipated that to river sd the river level as'out 2 ft above the r level by about Additional visual inspectio ompleted sin f., i J @F this Assess assess possib hanges due ed river levels. -not visited pri were v" umente "ion of the Trenwa was found similar wer Interio ' tions of the Trenwa were complete n removed. r areas ed had soil deposits in the botto sive areas of the Tre .ere be opened. It was notexpec sw cnfidence e conclusion because it was would be observed.irface Erosion/Piping ,ettlement of shallow foundation/slab (due utilities (due to river drawdown)The groundw ! a-t .a measured in the monitoring wells closely followe the floodwater re' I The data indicate that groundwater elevation was ab river level near the beginning of October 2011 and receded to match the rive October 14, 2011. Therefore the differential head created by the river drawd insufficient to facilitate subsurface erosion.ownV wvas Triggering Mechanism 14 -Frost Effects CPFM 14a -Heaving, crushing, or displacement The foundation for the Trenwa is not below frost depth and is therefore subjected to frost effects during prolonged periods of cold weather. Areas of the Trenwa that were not inspected PrioritýUnder!1 1 Structures ground Cable Trench Page 5.12-15 Rev. 2 due to inundation for Revision 0 of the report have now been visited. Though there were a few soft spots, soils in the areas visited were generally firm. In addition, the groundwater elevation measured in the monitoring wells closely followed the river level as the floodwater receded.The data indicate that groundwater elevation was about 2 ft above the river level near the beginning of October 2011 and receded to the river level by about October 14, 2011. Since current groundwater levels are not different than normal seasonal levels and prolonged cold weather has not yet occurred, the effects of frost heave on the Trenwa are no longer applicable.

5.12.7.3 Revised Re suits.The CPFMs evaluated for the Underground Cable Tre which shows the rating for the estimated significance evaluation.

CPFMs 3d, 3f, and 14a for the Undergroun Key Distress Indicators.

Inspections of the Trenwa not vi inspections of the inside of the Trenwa have been compleq level data were reviewed.

The results of the additional for CPFMs are ruled out. Therefore, these CPFMs are yed representing "No Further Action Recommende for the Underground Cable Trench are assoc..presents the results of additional forensic .gation th*these CPFMs could be ruled out. The res f the ad i these CPFMs are ruled out. Therefore, thd PFMs representing "No Further Action .m Red R ..- j t rcn are ! ciatec with to Revisio visual d groundw ation showthe matrix CPFMs 3a and 3c di .Section 4.2 ducted t rtain whether Sic investigation show that.jlq..adrant of the matrix Priority 1 Structures Page 5.12-16 Underground Cable Trench Rev. 2 5.12.7.4 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 modificati o remove them from the list for any particular structure.

Because all CPFMs for th d d e Trench other than CPFMs 3a, 3c, 3d, 3f, and 14a had been ruled out p Rev cause CPFMs 3d, 3f, and 14a have been ruled out as a result of the Revis* fnding use CPFMs 3a and 3c have been ruled out using the results of the KD d in Section 4.2, no Triggering Mechanisms and their associa ,cor theemain Underground Cable Trench. Therefore, HDR has conclude e 2011 Mis ver od did not impact the geotechnical and structural integrity of ound Cable because the potential for failure of this structure due to the o jgnificant.

Section 5.10 Turbine Building South Switchyard

~-'-< ~e K Priority 1 Structures Turbine Building South Switchyard Page 5.10-1 Rev. 2 5.10 Turbine Building South Switchyard 5.10.1 Summary of Turbine Building South Switchyard Baseline information for the Turbine Building South Switchyard is provided in Section 2.0, Site History, Description, and Baseline Condition.

5.10.2 Inputs/References Supporting the Analysis Table 5.10-1 lists references provided by OPPD and other doc oundation for Transformer T-,a 1.5-ft-thiSf pile cap supported on ten 10BP42 steel piles.05-S-412).

Top-of-conc evation for this foundation is 1005.5 ft.* The tion for Transformers

• A1 and TI -A2 is a 1.5-ft-thick pile cap supported on four 1OBP ~ iles (see 11405-S- Top-of-concrete elevation for this foundation is 1005.5 ft.* The foun' r Transforme k-3 and TI-A4 is a 1.5-ft-thick pile cap supported on four IOBP42st ssee 11420-2 ). Top-of-concrete elevation for this foundation is 1005.5 ft." The foundation.

s 'Il C-3B is an approximately 0.7-ft-thick pile cap supported on four 8-in.-diamete a, "piles with tip elevation of 997 ft (see 11405-S-412).

Top-of-concrete elevation for this foi n is approximately 1004.8 ft. The piles are reinforced with a single #7 bar centered in the pile,'with the bar having a straight development into the slab.* The foundation for the small switchgear located on the southwest comer of the west cable trench is an approximately 0.7-ft-thick slab-on-grade foundation." The Dead End/161 Structure is a two-column frame, approximately 27 ft in height, with interconnecting cross beams. There are separate foundations for each octagonal column. The piers are 5 ft by 5 ft by 3 ft in height. Top-of-pier elevation is 1004.5 ft. Top-of-concrete elevation for the pile cap is 1001.5 ft. Each cap is 4 ft thick, 7 ft by 20 ft in plan dimensions, supported by six 12-in.-diameter auger cast piles with tip elevation of 940 ft (see 11405-S-414).

The piles are Priority 1 Structures Page 5.10-2 Turbine Building South Switchyard Rev. 2 reinforced with a single # 11 bar centered in the pile, with the bar having a straight development into the slab." The driving criteria, tip elevation, and capacities of the 10BP42 piles are unknown. However, the tops of the piles are capped with a plate and anchor rods for a positive shear and uplift connection (see 11405-S-412).

• The capacities of the 8-in.- and 12-in.-diameter auger cast piles are unknown." A continuous cable trench is adjacent to each transformer (see 11405- -411). This conduit trench is a cast-in-place concrete trench with intermittent drain holes in the The trench also has a vertical drain pipe penetrating the west end of the trench e oted as heading west "to storm sewer manhole." The trench backfill below a and he walls is free-draining granular material (see 11405-S-412).

• An approximately 0.7-ft-thick concrete block separation w lnc twe sformer TI and T1 -A2. This wall is constructed on a continuous, cast-in'" crete gra spanning to isolated footings.

The wall is laterally braced via anchor s j WF31 piles ( 5-S 414).* The structures were originally contained within a cast-in-place retain that projecte approximately 6 in. above the surrounding grade. 0 .ately Jun II, OPPD built an additional approximately 0.7-ft-thick cast-in-plac.

n insulate te forms (ICF)on top of the existing wall. This additional wal 3.3 ft tall, laced the top of concrete at about 1008.3 ft.* Condition report summaries were not availabl r these Ur1." The structures were protected from flodiWate he of th od by an Aqua Dam;however. the Aqua Dam failed for erio oft e to bei amaged, allowing floodwater to enter the area insid ua Dam per !r." These structures were located -Aqua Dam p -ere also protected by the cast-in-place ed wall fo°,b" The areas-nsform' -e filled with small riprap. Small depressions were dug out in tre , spot w able pumps were placed to remove water around the fou I~* Val, there were no sign' ial nd these structures with the exception of aon the southwest come IIhe west ca etrench. This soft spot resulted in differential nt of the switch pad to the trench.Po mps were removing gr water from the cable trenches, and there appeared to be a layer ment on the cable tra conduit, and on the bottom of the trench." Assessm a isurvey elevations i¶ 1te shows no movement of the structure.

5.10.3 Assessm Procedures 5.10.3.1 .rocedures Accomplished Assessments of the Turbine Building South Switchyard included the following:

• Visual inspection of the exterior of the structures where accessible.

Observations were made from outside the ICF concrete wall due to "Danger -High Voltage" warning tape and signs." Assessment of collected survey data to date for indications of trends in the movement of the structure.

• Review of previously referenced documents listed in Table 5.10-1.

Priority 1 Structures Turbine Building South Switchyard Page 5.10-3 Rev. 2* Identification of relative surface soil densities (native soil, engineered fill, and limestone gravel pavement) as determined by hand probing." Observations and documentation of water accumulations and flows in subsurface system components (manholes and concrete trenches).

Additional investigations were performed.

These included the following non-invasive geophysical and invasive geotechnical investigations:

&" Seismic surveys (seismic refraction and refraction mi available at the time of Revision 0.)* Geotechnical investigations including test borings A laboratory tests. Note that OPPD required vacuum test holes to avoid utility conflicts.

Therefore, test rel in the upper 10 ft of site and locations where shallow available at the time of Revision 0.)* Inclinometers had not been installed at the time of Re available.

Inclinometer data is not required to supplement the other data used to reach th 5.10.3.2 Assessment Procedures Not l:eted Assessments of the Turbine Buildin Souk itchy following:

• The interior of the cable as not obse 6ci possible from outside cause they w Voltaaz".were not observations that were d "Danger -High systems and conditions was performed because the kth the equipment in the switchyard.

within the ICF wall at the time of Revision 0 L3 Voltage." 5.Identified Etwere initially reviewz, discussed in Section 3.0. The review considered the preliminary 14#"NOtion available fro.@PPD data files and from initial walk-down observations.

Eleven PFMs a f,-d with fiv ent Triggering Mechanisms were determined to be non-credible" fo6' rity tures, as discussed in Section 3.6. The remaining PFMs were carried forward asc ..er the design review for the structure, the structure observations, and the results of available ical, geophysical, and survey data were analyzed, a number of CPFMs were ruled out as discussed ifi Section 5.10.4.1.

The CPFMs carried forward for detailed assessment are discussed in Section 5.10.4.2.5.10.4.1 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.

Priority 1 Structures Turbine Building South Switchyard Page 5.10-4 Rev. 2 Triggering Mechanism 2 -Surface Erosion CPFM 2a -Undermining shallow foundation/slab/surfaces CPFM 2b -Loss of lateral support for pile foundation CPFM 2c -Undermined buried utilities Reasons for ruling out:* The Turbine Building South Switchyard is located a si riverbank and was within the Aqua Dam perimeter, an surface erosion.* Surface erosion was not identified in or around the during the field assessments.

Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3d -Undermining and settlement of shallow fq drawdown)Reason for ruling out:* The Turbine Building South Switchyar

'cated a s riverbank and was therefore not subje o Triggering Mechanism 3 -Subs f'ce ] ionfP CPFM 3e -Loss of lateral s or pile fo ion Reason for ruling out: away from the&subiected to rfrom the drawdown.'drawdown) is locatedTM cient distance away from the d to subsurface erosion due to river drawdown.0 itchyard is located a sufficient distance away from the subjected to subsurface erosion due to river drawdown.

AVHdoy-i'ydrodyl CPFM CPFM5b CPFM 5c -

in flexure CPFM 5d -Wall failure in shear CPFM 5e -Damage by debris CPFM 5f- Excess deflection mic Loading Reasons for ruling out:* 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 the Aqua Dam perimeter.

Priority I Structures Turbine Building South Switchyard Page 5.10-5 Rev. 2* Visual observation did not identify distress to the structure that can be attributed to these CPFMs.Triggering Mechanism 6 -Buoyancy, Uplift Forces on Structures CPFM 6a -Fail tension piles Reason for ruling out:* The equipment foundations within the Turbine Buildin out h that have eith(steel or concrete piles have pile caps near the ground. e a -t subjected to n buoyancy uplift forces.Triggering Mechanism 6 -Buoyancy, Uplift Forces s CPFM 6b -Cracked slab, loss of structural support Reasons for ruling out:* The equipment foundations within the steel or concrete piles have pile caps n(buoyancy uplift forces.* The cable trench was designed with drn drain system complete with free-drainH Therefore, the trench was not s , cte Triggering Mechanism 6 -B cy, U CPFM 6c -Displaced s ' roker walls and-a foundation Mbelow the slab."ms withi ,pprbine Building South Switchyard that have eithor .... concrete p e caps ý. e ground surface and were not subject to net buoyancy uplift forces.The cable trench was des with drain holes within the trench walls and a foundation

%1raine system complete wit e-draining backfill on the walls and below the slab.fflibKfore, the trench was z#5~subjected to buoyancy forces.er 7 se (first time wetting)settlement of shallow foundation, loss of structural CPFM 7b -CPFM 7c -CPFM 7d -Dite structure/broken connections i-1 site settlement buckling from down drag Reason for ruling out:* 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. Elevations in the South Turbine Switchyard are such that the area would not be subjected to first time wetting.

Priority 1 Structures Turbine Building South Switchyard Page 5.10-6 Rev. 2 Triggering Mechanism 10 -MachineNibration-Induced Liquefaction CPFM I Oa -Cracked slab, differential settlement of shallow foundation, loss of structural support Reasons for ruling out:* There is no permanent equipment within the Turbine Building South Switchyard that has the capacity to produce significant dynamic forces due to vibr i&n.0 Temporary pumping equipment located on the ground ithin u perimeter was small and therefore deemed to. have inconsequential 0 Liquefaction was not observed near the Turbine B " South rd.Triggering Mechanism 10- Machine/Vibration-Indu, CPFM 1 Ob -Displaced structure/broken connections Reasons for ruling out:* There is no permanent equipment within the the capacity to produce significant

• Temporary pumping equipment locate he grounA small and therefore deemed to have in equential* No broken structural connections or s ral di* Liquefaction was not observe-4.

the rin.rb.n Triggering Mechanism 10 ine/Vibratiown-gu(CPFM 1 Od -Pile/pile bility A was te Turbine Building South Switchyard that has lynoitaforces due to vibration.

ated-Ae ground within the Aqua Dam perimeter was inconsequential effect.the Turbine Building South Switchyard.

of Soil Strength due to Static Liquefaction or Upward differential settlement of shallow foundation, loss of structural

• Visual observations and survey measurements indicate no structure movement.

Therefore, differential settlement and loss of structural support did not occur at the observed structures.

Priority 1 Structures.Turbine Building South Switchyard Page 5.10-7 Rev. 2 Triggering Mechanism 11 -Loss of Soil Strength due to Static Liquefaction or Upward Seepage CPFM I1 b -Displaced structure/broken connections Reasons for ruling out:* Visual observations and survey measurements indicate no structure movement.

Therefore, degradation that can be attributed to this CPFM did not occur r the Turbine Building South Switchyard.

0 a No instances of broken connections were observed.Triggering Mechanism 11 -Loss of Soil Strength di Seepage CPFM l1 d -Pile/pile group instability Reason for ruling out:* Visual observations and survey measureme degradation that can be attributed to this South Switchyard.

Triggering Mechanism 12 -Rapid Dra n A CPFM 12a -River bank slope re de CPFM 12b -Lateral spread'Reason for ruling out: I or Upward ino ent. Therefore, uur near th e Building g surr ctures istance away from the riverbank failure or lateral spreading because of is a suffi i)ank slope drawdown.iggering Mechanism 13'CPFM 13a -Corrosion EIPFM 13b -Corrosion elements TheNU .eBu that wJk c floodwate failed due to I Dam perimeter.'

0 Switchyard has not been subjected to corrosive circumstances Yeyond the normal conditions.

The structure was protected from Dam except during a short period of time when the Aqua Dam iaged, which allowed floodwater to enter the area inside the Aqua Triggering Mechanism 14 -Frost Effects CPFM 14a -Heaving, crushing, or displacement Reasons for ruling out: The equipment foundations within the Turbine Building South Switchyard have either steel or concrete piles with pile caps near the ground surface. The piles have an anchor plate with anchor rods developed into the pile cap, indicating a positive tension connection.

In Priority 1 Structures Turbine Building South Switchyard Page 5.10-8 Rev. 2 addition, the frost uplift on the pile caps will not be different than the condition prior to the flood.The cable trench was designed with drain holes within the trench walls and a foundation drain system complete with free-draining backfill on the walls and below the slab.Therefore, the trench is not subjected to frost effects.5.10.4.2 Detailed Assessment of Credible Potential Failure Modes The following CPFMs are the only CPFMs carried forw Turbine Building South Switchyard as a result of the 20'provided below.Triggering Mechanism 3 -Subsurface Erosion/Pipii CPFM 3a -Undermining and settlement of shallow: pumping)The nearby Turbine Building has a documented histo groundwater drainage to broken floor and condeq associated with the 2011 flood have increase pipes in the floor drain system. The sump " urbin continually pumped, maintaining the hydr gradien pipes in the system.The Triggering Mechanism and ou the r begins erosion or increases e s 6 surroundin continues unarrested.

Eros*'. ds out beneat and extend ard the T ding South S ment for the d assessment is and and broken as foll t, fe hydraulic gradient Seep <;s unfiltered and erosion ilding or from Manhole MH-oids form under utilities and jacent to the Turbine Building South and utilities occurs and causes distress th Switchyard orstructures dation slab located on the southwest corner of ling on the east side adjacent to the conduit trench,-d distress indicators and other data that would increase or associated with this CPFM for the Turbine Building South Priority 1 Structures Page 5.10-9 Turbine Building South Switchyard Rev. 2 Adverse (Degradation/Direct Floodwater Favorable (Degradation/Direct Impact More Likely) Floodwater Impact Less Likely)Documented void under the foundation slab of There have been no observed signs of structural the adjacent Turbine Building.

distress in the CMU screen wall.Differential settlement has occurred on the Sinkholes and other piping features were not switch foundation located on the southwest observed during site inspections in the Turbine comer of the west cable trench. Building Switchyard or adjacent areas, except for the settlement notes ear the switch foundation, and the san oil/ fea observed in the missile r fth uilding.Pavement failures were observed east of the Turbine Building.Data Gaps:* Survey data to track trends in vertical movement of the C n wall and ca h.* Visual inspection of the cable trench was not possible be nch is located was not accessible due to safety tape. Where the trench was acc emporary p drawing water from the bottom of the trench, and the inside was co sediment.c Existence, size, and location of voids..* Seismic refraction data are not yet availableA Conclusion.;

Potential for Degradation/Diret bdater ,I m Many indicators for the C .been observe remove water from the Turbin MH- 11, ugh a system of broken pipes and grau `%pro ,he system for this CPFM. Known voids exist under the urbin Bu Settlemneftý'

adi s' q have been observed in the Paved Access Area the. Service Buthe I cture. Settlement of the switch foundation near the sout ora the west trench has already occurred due t6 this CPFM.erefore, the potential that n ation this CPFM is occurring due to the 2011 flood is Settlem he switch faion slab near the southwest comer of the west cable trench has already o6 due toJV S.PFM. The CMU wall is supported on shallow foundations.

This CPFM could -:% .Ilow foundation systems. The CMU wall could show signs of distress, and wal i could damage adjacent facilities or equipment.

Therefore, the implication of the p6fential degradation for this CPFM is high due to the nature of the adjacent structure.

Confidence Observations have shown that settlement has occurred on the switch foundation slab.Subsurface erosion is believed to have occurred under the adjacent Turbine Building foundation and at some nearby areas of pavement.

Priority 1 Structures Page 5.10-10 Turbine Building South Switchyard Rev. 2 Therefore, the confidence in the above assessment is high, indicating that repairs and more data are necessary.

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 type puts it in the "significant" category.

There is high confidence that there has been significant adation to the soil surrounding the Turbine Building South Switchyard.

Repairs an er itoring are needed.Triggering Mechanism 3 -Subsurface Erosion-Piping CPFM 3b -Loss of lateral support for pile foundation mping)The nearby Turbine Building has a documented history of a void l e foundation and groundwater drainage to broken floor and conde _ ,s. The fib elevations associated with the 2011 flood have feedit ad fed o the broken pipes in the floor drain system. The sump i urbine g and Ma H-5 were continually pumped, maintaining the hydrr gradient, aturated so' and broken pipes in the system.co he follo h dalcgain The Triggering Mechanism and cou then rasfollo The ydraulic gradient begins erosion or increases eros surroundina

.s. Seep s unfiltered and erosion continues unarrested.

Eros* ds out beneath urj" ilding or Manhole MH-5 and extends toward the Turbine South Switch ' form under utilities and structu e Buildi Switchyard or' aint to the Turbine Building South Snon-pi: rrted structures and utilities occurs and causes distress ae of flities, following table descried dis .s hdicators and other data that would increase or Rcrease the potential for de on associated with this CPFM for the Turbine Building S.o, Switchyard.

'A (Degradation.Dir..I.

loodwater Favorable (Degradation/Direct JV. Impact More WINE) Floodwater Impact Less Likely) under slab of Review of survey data indicates that there have th "d ae , .1 # 'pf,,i the e Buid been no observed signs of movement of the pile foundations.

Data Gaps: " Existence, location of voids.* Seismic refraction data are not yet available.

Priority 1 Structures Turbine Building South Switchyard Page 5.10-11 Rev. 2 Conclusion Significance Potential for Degradation/Direct Floodwater Impact Many indicators for the CPFM have been observed.

Pumping to remove water from the Turbine Building sump and from Manhole MH-5 carried through stem of broken pipes and granular trench backfill.

This provides the system for this CPF wn 'ds exist under the adjacent Turbine Building.

Settlement issues have been ed Access Area between the Service Building and the Intake Structure. -efore, t ial that degradation due to this CPFM is occurring due to the 2t iJ Implication Loss of lateral support for the pile supported foundations t instability of the foundations for the transformers.

Therefore, the degradation for this CPFM is high.Confidence Subsurface erosion is believed to have oc d under,. i foundation and at some nearby areasef pa 'ent. er, th existence, size and location of v Wete eine er this C, location.A.al to causeý'iation of the r iufficient data on the or will occur at this Therefore, the confidence ird to draw Aoz, I means more data are necessary tPFM 3b, as discusseg(!e, the coi ii&i consideration of the potential for degradation the implications of that d§graation to the&strcture puts it in the "significant" category.re is low confidence that iNahas been significant degradation to the soil surrounding theý,Je Building South Switc due to the lack of test data available at thistime.

More monitoring 4Wspections are needed.Triggering

-i.[244 Subsurface Erosion/Piping CPFM 3c '".ned buried utilities (due to pumping)The nearby Turbine Building has a documented history of a void below the foundation slab with a potential for increased erosion with greater external water head (see Section 5.8).The Triggering Mechanism.

and CPFM could then occur as follows: there is a potential for the previously documented void to erode larger voids under the Turbine Building and out to the surrounding structures.

Buried utilities within the Turbine Building South Switchyard include cable trenches, ductbanks, underdrains, and storm drain pipes. Three fire protection pipes are routed beneath the Turbine Building South Switchyard, just west of Transformer T1. The Aqua Dam was placed over the fire lines near where they are routed into the Turbine Building.

This Priority 1 Structures Page 5.10-12 Turbine Building South Switchyard Rev. 2 provides a possible flow path directed toward the Turbine Building.

Connectivity is possible to flow paths feeding the broken floor and condensate drain pipes in the basement.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 Turbine Building South Switchyard.

Adverse (DegradationlDirect Floodwater Favorabl egradation/Direct Impact More Likely) Flooowat a.tac ss Likely)Documented void under the foundation slab of There h no ýgns of structural the adjacent Turbine Building.

distresle s.Differential settlement has occurred on the switch foundation located on the southwest comer of the west cable trench.Data Gaps: e Visual inspection of the cable trench was not possible becme t Js located in t was not accessl e to safety tape. Where he tto remaorary pumps were drawing water from the bottom of the trench, ws cbc e thr over m oediment." Existence, size, and location of voids. te mft C 0 Seismic refraction data are not yet availab u e. Tn Conclusion Si--nlificance "1 Potential for Degradation/

oo~°dwater I Many inegati At4e grF or observed.

f to remove water from the TurbineMR N~ fhardo T herefo caret ed implicatio systemnof broken the ad tiCFM is ,i MT Confienc sse S ubsurfaceeorovis foi know to have ocure under the aCent T ne Buildsig fundetin.. .. -rf. _- ý, I e e the systent Turbine Bunial leaed h inave been observed in the Paved Access Area subsurfacthe Sersion e T i e B n cture.h wTchyrd , ad en potential Bidn H owever, the re t insuPFfcit dcurring tuo th e exite 2011 flood is high.grdeterionde whthe this CPFM ha2o1 il3 ccr A of utilities a4%kiied under the Turbine Building South Switchyard, which is adjacen .guetd s~ in the Turbine Building.

The occurrence of this CPFM could nega paIny or intended function of a number of buried utilities near the Turbine Buil itchyard.

Therefore, the implication of the potential degradation for this CPFM is h" Confidence Subsurface erosion is known to have occurred under the adjacent Turbine Building foundation.

With the increased head pressure due to the 2011 flood, the amount of water moving through the system has potentially increased, which in turn increases the likelihood of instigating subsurface erosion in the Turbine Building South Switchyard adjacent to the Turbine Building.However, there are insufficient data on the existence, size and location of possible voids to determine whether this CPFM has or will occur.

Priority 1 Structures Turbine Building South Switchyard Page 5.10-13 Rev. 2 Therefore, the confidence in the above assessment is low, which means more data are necessary Therefore, the confidence in the above assessment is low, which means more data are necessary to draw a conclusion.

Summary For CPFM 3c, as discussed above, the combined consideration of the potential for degradation and the implications of that degradation to a structure of this type puts it in the "significant" category.

There is low confidence that there has been significant Agwadation to the soil surrounding the Turbine Building South Switchyard due to ee laIS available at this time. More data or continued monitoring and inspectio ed 5.10.5 Results and Conclusions The CPFMs evaluated for the Turbine Building South Switchvar matrix, which shows the rating for the significance and the level Low Confidence H (Insufficient Data)CPFM 3b CPFM 3c 5N q .xmThe following actions are recommended for the Turbine Building South Switchyard.

The settlement of the switch foundation slab located on the southwest comer of the west cable trench should be corrected as soon as possible.The CMU wall should be observed by OPPD on a regular basis for signs of distress such as cracking or tipping.

Priority 1 Structures Page 5.10-14 Turbine Building South Switchyard Rev. 2 Given the Low Confidence rating for CPFMs 3b and 3c, 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 will be used to 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, 201 ppropriate HDR personnel should be notified immediately to determine whether a nor assessment should be conducted.

Observation of new distress indicators m ult in ication of the recommendations for this structure.

Further forensic investigations and physical modifications are r to ad Ms 3a, 3b, and 3c for the Turbine Building South Switchyard.

CPFM 3a, 3b, ware associ nfiltered flow of groundwater into the Turbine Building basement drain pig (ey Dise#1). These recommendations are described in detail in Section 4.1 3 C is associate distress in and near the Paved Access Area between the mt .ructure an rvice Building (Key Distress Indicator

1. 2). These recommendations are de ail in Secti_ 5.5.10.7 Updates Since Revision 0 Revision 0 of this Assessment Report was submi OPP cto 0 11. Revision 0 presented the results of preliminary asses ets f Sh P Stru ese assessments were incomplete in Revision 0 because the f d/or mo for most of the Priority 1 Structures was not completed he submittal

' This r n of this Assessment Report includes the results of additional f vestigation.

an date for this structure as described below.5.1 kvailat ollowing additional ere avai the Turbine Building South Switchyard for evisions I and 2 of this A ent Rep.. " Sesults of KDI #1 forensi ! stigation (see Section 4.1)ts of KDI #2 forensic (see Section 4.2).essment teams from I on site for continued monitoring of the Key Distress tnheQa.Nave visual ected the cable trenches and CMU wall where visible outside the are" d "D ell,- High Voltage" and the settlement of the switch foundation slab near the s e of the west cable trench.* Additional f '&ter monitoring well and river stage level data from OPPD.* Results of falling weight deflectometer investigation by American Engineering Testing, Inc.(see Attachment 6).* Results of geophysical investigation by Geotechnology, Inc. (see Attachment 6).* Results of continued survey by Lamp Rynearson and Associates (see Attachment 6).

Priority 1 Structures Page 5.10-15 Turbine Building South Switchyard Rev. 2 5.10.7.2 Additional Analysis The following analysis of additional data was conducted for the Turbine Building South Switchyard: " Groundwater monitoring well and river stage level data from OPPD.Data shows that the river and groundwater have returned to noiinal normal levels.* Results of falling weight deflectometer investigation eri' ering Testing, Inc..P .g .pe.rf. Pnr, Access Falling Weight Deflectometer and associated GPR g perfoP Area identified anomalies such as soft clay and bro ."Ad' .d ground truthing of the investigation results were performedas e KDIa- #2 nal investigations.

• Results of geophysical investigation by Geotechnology, Inc. ,'Seismic Refraction and Seismic ReMi tests i.Qund the o emeter ofe power block as part of KDI #2 identified pan maiT could be V sfcly loose sand, or possibly voids.Results of geotechnical investiý*ton b ele Q ccwh Six test borings were drilled Jcontinuous Aling of tl&oil encountered, to ground truth the Geotechnolog Rl.' ismic investi resul4spart of the KDI #2 forensic"d anomalie identified in the investigation.

Test bore re located to anomaliesi f n ses f- ion The ng data dinoffhiWany piping voids or very soft/very 1qthmvs ight be i ve of subsurface erosion/piping or related material or movenent-

..CAll of the SPT and C n tad for this Assessment Report were compared:o ...o t e S T a d e s u lts c o nic , -to similar data from num i'js~other geot&'hnical investigations that have been conducted ,. the FCS site in I Mars. This comparison did not identify substantial changes to k'..°soil strength and stiffnelis§Lier that time period. SPT and CPT test results were not-eripmed in the top 10 fe protect existing utilities.

0 Resulso nnnueds' yby Lamp Rynearson and Associates.

Survey deftto , , mpared to the original baseline surveys have not exceeded the accuracy rangp,'fThe surveying equipment.

Therefore, deformation at the monitored locations, since the survey baseline was shot, has not occurred.Follow-up inspections since Revision 0 of the report have noted that the standing water and sediment has been removed from the cable trenches around the switchyard..

The bottom of the cable trench was able to be viewed beyond the area labeled "Danger -High Voltage" but no additional information regarding the trenches was obtained from this observation.

The observation also noted no visible distress or cracking of the CMU wall.

Priority 1 Structures Page 5.10-16 Turbine Building South Switchyard Rev. 2 Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3a -Undermining and settlement of shallow foundation/slab/surfaces (due to pumping)CPFM 3a for the Turbine Building South Switchyard as it relates to the settlement of the switch foundation slab near the southwest comer of the west cable trench is not associated with Key Distress Indicators.

Additional inspection since Revision 0 indicates that the switch foundation slab was not remediated as recommended.

The results of the add*_ al forensic investigation show that this CPFM is not ruled out; therefore, the recoi da ..rowision 0 has not changed. Therefore, assuming that OPPD implements th m isical modification and assuming that no further concerns are identified fo M 3a a to Key Distress Indicator

1. 1 and #2 (see Sections 4.1 and 4.2) or throu mo i for the Turbine Building South Switchyard (discussed in Sectio continn til December 31, 2011), this CPFM is moved to the quadrant atrix repres o Further Action Recommended Related to the 2011 Flood I..Triggering Mechanism 3 -Subsurface Eros CPFM 3b -Loss of lateral support for pile CPFM 3c -Undermined buried utilities CPFMs 3b and 3c for the Turbine Buildin Indicator

1. 1. Section 4.1 presents the resti" conducted to ascertain whether t h PF forensic investigations show th ecomr are implemented that this CP led out.identified through the moni ogram for (discusse Un5.10.6 a uing ur to thegVa .1 e x repre". "No to punociated with Key Distress W ore stigation that was u out. slults of the additional ins for ph modifications in KDI #1 re, assui that no further concerns are ng South Switchyard 2011), these CPFMs are moved Action Recommended Related to the Priority 1 Structures Turbine Building South Switchyard Page 5.10-17 Rev. 2 5.10.7.1 Revised Results The CPFMs evaluated for the Turbine Building South Switchyard are presented in the following matrix, which shows the rating for the significance and the level of confidence in the evaluation.

Note that the placement of CPFM 3a in the "No Further Action Recommended Related to the 2011 Flood" is dependant on the remediation of the switch foundation slab located near the southwest comer of the west cable trench.In the ass'esrs-it of the@ Sltructures, the first step was to develop a list of all Triggering Mechanismrig's could have occurred due to the prolonged inundation of the FCS site during the U. ,sbouri River flood and could have negatively impacted these structures.

The next step was* se 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 modifications to remove them from the list for any particular structure.

Because all CPFMs for the Turbine Building South Switchyard other than CPFMs 3a, 3b, and 3c had been ruled out prior to Revision 1, because CPFM 3a will be ruled out upon completion of the remediation to the switch foundation slab described above, and because CPFMs 3b and 3c will be ruled out when the physical modifications recommended for KDI #1 in Section 4.1, no Triggering Mechanisms and their associated PFMs will remain credible for the Turbine Building South Switchyard.

HDR has concluded that the geotechnical and structural impacts of the 2011 Missouri River flood will be mitigated by the Priority 1 Structures Turbine Building South Switchyard Page 5.10-18 Rev. 2 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 5.11 Condensate Storage Tank'V..j v Priority 1 Structures Condensate Storage Tank Page 5.11-1 Rev. 2 5.11 Condensate Storage Tank 5.11.1 Summary of Condensate Storage Tank Baseline information for the Condensate Storage Tank is provided in Section 2.0, Site History, Description, and Baseline Condition.

The 150,000-gallon welded steel plate Condensate Storage Tank is power block and south of the Intake Structure.

The tank shell is .4 The tank foundation is a 2-ft-minimum-thickness concrete ma----driven to bedrock at approximate el. 934 ft. The top-of-concre<

slab is approximately 41 ft in diameter, resulting in a walkway ar;within a steel sheet pile system that is driven into the riverbank tog approximately 10 ft above bedrock.5.11.2 Inputs/References Supporting the Analysis Table 5.11-1 lists references provided by OPPD an d ocu Table 5.11 References, Document Title -i background data are as follows:* The Condensate Stora' Jeank is a welded steel storage tank designed to the American Water Works Association (AWWA) D100-65 (see 002391).* The tank is a flat-bottom storage tank without anchor bolts.* Construction of the foundation is a cylindrical sheet pile wall driven through the riverbank.

The inside of the sheet pile wall was backfilled to the bottom of the slab elevation.

Steel piles were then driven within the contained sheet piles and capped with a structural cast-in-place slab (see tank foundation drawing 11405-S-418).

• The adjacent bank is such that the eastern half of the sheet pile wall is exposed to the river from the bottom-of-concrete slab el. 1003.5 ft to bank grade of approximately 994.4 ft, with the normal river water elevation of 992 ft (see tank foundation drawing 11405-S-418).

Priority 1 Structures Page 5.11-2 Condensate Storage Tank Rev. 2" The exposed side of the sheet pile wall was painted with rust-inhibiting paint and constructed with five 3-in.-diameter weep holes at approximately 7 ft on center. These weeps are located at approximate el. 997.5 ft." The steel piles are I 0BP42 driven to bedrock and capped with a welded steel plate and anchor rods providing positive shear and tension connection to the base slab. This pile size and anchor details are the same as those shown for the transformer foundations in the Turbine Building South Switchyard." The driving criteria, tip elevation, and capacities of the 10BP42 piles .However, the top of the piles are capped with a plate and anchor rods for a ve sion connection (see 11405-S-412).

• The Condensate Storage Tank was outside the Aqua Dam eter an ore unprotected from the hydrostatic flood load and hydrodynamic forces ow." In accordance with tank levels provided by OPPD, the Cond,'- a ge Tank intained at a minimum of 72 percent full for the duration of the flood eve* At the time of inspection, the river level had dropped below u g grade. Ob were made around the western half of the Condensate Storage Tank. was noO a through the security gate onto the walkway on the rii bsevatio e sheet pile wall and the surrounding riverbank were not feasible v" There was a thick layer of river sediment alon oncrete iion and su ng grade." The Trenwa was covered with river sediment indicati ent h into the trench via gaps in the removable covers. .....ed* Small localized areas of erosion and r wer serv on south sides of the Condensate Stora No eros r scour w bserved at the tank structure.

• The tank shell, nozzle necks, ans below the fl owed signs of surface corrosion thro s in tstem. No pi gnificant loss of plate thickness was obse c .'ece adequately seen because of the deposit of river sedim-%-, The ell appears to b tard w cnt of inflection at about the painted horizontal another point ofinfl h just lo aagnitude ofthis deviation the r shape cann ,eterined visual observations, and therefore, it is not Xf it meets normal AWW 0 tolerances for tank construction.

It is unknown whether this, i deformation is a result o initial construction or whether it was directly or indirectly cause 2011 flood.* Because level at the the field assessment, it was not possible to get a good view of the east ", side of the tank. Observations from just north of the Securit eii out-of-tolerance shape might be limited to all sides of the Condensate pt the east side.* Survey data points on the north, south, and west quadrants of the tank. Assessment of current survey data for'fiese points indicates no vertical movement.

Priority 1 Structures Condensate Storage Tank Page 5.11-3 Rev. 2 5.11.3 Assessment Methods and Procedures 5.11.3.1 Assessment Procedures Accomplished Assessments of the Condensate Storage Tank included the following:

• V isual inspection ox me exterior ox me structure, w" An assessment of collected survey data to date for the structure.

• A review of previously referenced documents listec* A relative surface soil density test via probing was crushed rock surface below the sediment, it was no subgrade.Additional investigations were performed.

These inclu geophysical and invasive geotechnical investigations: " Seismic surveys (seismic refraction and refr (Test reports were not available at the time* GPR in the protected area. (Test repo e not* Geotechnical test borings in the protec rea. Nc excavation for the first 10 ft of propos st hol s reports will not show soil co s in upp were not available at the tim 'evision 0.) -5.11.3.2 AssessmentP, s Not Comp here accessible..

indications trends in the movement of pted. ecause of the'b~~ e rod into the ing non-i: tected area.time Wvision 0.)vacuum ts. Therefore, test (Test reports that were not completed include the following: "Rection of the of the -ate Storage Tank was not accomplished due to Firrent river levels. I river e s, the remainder of the structure will need to be inspected.

Inspection of the riverban he north and south sides of the Condensate Storage Tank not accomplished rrent river levels. Once the river level drops, the remainder structure will need ;nspected.

l -on of the tank a l dation interface was not accomplished due to the large 0 adjacent to the tank. Once the sediment is removed, the 0 rilt6e inspected.

flong the river that will provide an indication of slope movement.been installed; therefore, readings were not available at the time of Inclinomete Revision 0.5.11.4 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 I 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 Priority 1 Structures Page 5.11-4 Condensate Storage Tank Rev. 2 CPFMs were ruled out as discussed in Section 5.11.4.1.

The CPFMs carried forward for detailed assessment are discussed in Section 5.11.4.2.5.11.4.1 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 2c -Undermined buried utilities Reasons for ruling out: Observed surface erosion in the Condensate Storage s limited t localized areas along the security fence south of the s r dition, only and limited surface erosion was observed on the ground surfac ss the facility.Triggering Mechanism 3 -Subsurface Ero CPFM 3b -Loss of lateral support forp ndatio pumpmg -Reason for ruling out: The nearby Turbine Buildin e oc ente 0 ofa ow the foundation slab with a potential for increase ion with gr external r head. For further information see Sectio more detailed '. Distress Indicator is presented in Section 4.1. is a potential sly documented condition to ero nder the e Building a o the surrounding structures., Cor ,Storage Tank are protected by a sheet pile wall to approxim , above and are therefore not subjected to loss of pile Oport due to pump iggering Mechanism 4 static La eral Loading (water loading on structures)

PFM 4a -Overturning M 4b- Sliding C Ac -Wall failure in ure C ~.- Wall failure aear CPF xcess n Reasons for* At the 2011 pea flood elevation of approximately 1006.9 ft, the Condensate Storage Tank shell had a maximum of 1.5 ft of external water head on the tank shell." Overturning and sliding stability conditions are not credible because the external water force is balanced around the circumference of the tank.* There were no field observations or indications of tank shell deformations due to flexure or shear." OPPD records indicate that the Condensate Storage Tank was maintained at a minimum of 72 percent full during the 2011 flood.

Priority 1 Structures Page 5.11-5 Condensate Storage Tank 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 rulin2 out: " At the 2011 peak flood elevation of approximately

.9 ft, the ate Storage Tank shell had a maximum of 1.5 ft of external water he he t 0 OPPD records indicate that the tank was maintained m of 7 t full during the 2011 flood.* Overturning and sliding stability conditions are not c se there wa Q internal liquid head resisting structure movement that waser than e e hydrodynamic load.* There were no field observations or indicat. ell defo _ ue to flexure or shear.* There were no field observations of de ound th 1, and ther as no observed damage to the tank shell and nozzles flexur. e Triggering Mechanism 6 -Bu , U Fo n Struc CPFM 6ae- Fail tension pile o CPFM 6b -Cracked sla f structural su CPFM 6c -Displaced s rokenc W' he 2011 peakff Cell had a maxi um OPPD records indicate A q2 percent full during the'ause of the internal w4 re no field obso field imately 1006.9 ft, the Condensate Storage Tanký,er head on the tank shell.Storage Tank was maintained at a minimum of there was no condition where the piling was subjected 0 0 that would indicate uplift on the tank structure.

of broken structural connections.

Priority 1 Structures Page 5.11-6 Condensate Storage Tank Rev. 2 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 CPFM 7d -Piles buckling from down drag Reasons for ruling out:* The peak flood elevation prior to 2011 was 1003.3 0- i oc 993. The ground surface outside the tank is about el. 1005 ft. There 0.1 e soils reviously saturated.

• The Condensate Storage Tank structure has a pile-su dation, erefore, loss of structural support for shallow foundations is not cre* No broken structural connections or structural displa bserved.* No site settlement around the Condensate Storage Tank was o n Triggering Mechanism 10 -MachineNibra.

Liquefac CPFM 1Oa -Cracked slab, differential s nt o foundati4of structural support Reasons for ruling out: " No permanent equipment in densate S e Tank h e capacity to produce significant dynamic forc o vibration." Liquefaction was not o Trigg 10-M ibration-Induced Liquefaction b -Ctrut~4 n connections as"ns for ruling out: 4No permanent equipment

... Condensate Storage Tank area has the capacity to produce ificant dynamic forcesd vibration.

• structural conJ HiMs or structural displacement was observed.* ~~action wasntote anis .achineNibration-Induced Liquefaction.CPFM l -i, up instability Reasons for rlin~* No permanent equipment within the Condensate Storage Tank area has the capacity to produce significant dynamic forces due to vibration." Liquefaction was not observed.

Priority 1 Structures Condensate Storage Tank Page 5.11-7 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 1 lb -Displaced structure/broken connections CPFM I1 c -Additional lateral force on below-grade walls CPFM l1 d -Pile/pile group instability Reasons for ruling out:* Liquefaction was not observed at the Condensate S" Visual observations and survey measurements indic differential settlement and loss of support (CPFM 1 structures.

.No broken structural connections or structural displ Triggering Mechanism 12 -Rapid Drawdown CPFM 12a -River bank slope failure and u CPFM 12b -Lateral spreading Reasons for ruling out:* The structures did not have ev sil -disti,* Slope failure was not observ _-- e site.a River stage level has d stabilized a* As of October 11, 2011, ater elevatio 0 The rarmored historically tro Therefore, field assessments.

qhad one week to stabilize.

stabilized the existing river a the surrounding utilities have not been subjected to be considered beyond the normal conditions.

g- Frost Effects crushing, or displacement

• The Condensate Storage Tank is on a deep pile foundation system that is not frost susceptible.

5.11.4.2 Detailed Assessment of Credible Potential Failure Modes The following CPFMs are the only CPFMs carried forward for detailed assessment for the Condensate Storage Tank as a result of the 2011 flood. This detailed assessment is provided below.

Priority 1 Structures Condensate Storage Tank Page 5.11-8 Rev. 2 Triggering Mechanism 2 -Surface Erosion CPFM 2b -Loss of lateral support for pile foundation Observable signs of surface erosion were limited to very small localized areas at the security fence. No large-scale surface erosion was observed around the Condensate Storage Tank or the tank foundation.

However, at the time of the inspection, the site was covered with a thick layer of river sediment; therefore, an adequate assessment could not be completed to determine whether areas had experienced erosion. Hand probing of the surrd, ing soil at the top of the riverbank was not possible due to the presence of a layer o f'gs T" a surface.The following table describes observed distress indica decrease the potential for degradation associated with Tank.The ste Storage T efindation is protected by a sheet pile skirt wall extending from the 1e tank to F 0 feet above the bedrock. The skirt wall would protect the tank pile erosion. The surface erosion around the skirt wall was not deep enough t "02 wall. Therefore, the potential for degradation is low.R ~f ;-j &U"&5t" LI.v ýU "'The occurrence of this CPFM would negatively impact the capacity of the piling supporting the Condensate Storage Tank. This could lead to excessive foundation movement and negatively impact the integrity or intended function of the Condensate Storage Tank. Therefore, the implication of the potential degradation for this CPFM is high.

Priority 1 Structures Page 5.11-9 Condensate Storage Tank Rev. 2 Confidence Indicators for this CPFM have not been observed; however, inspection of the east side of the tank and the ground surface around the tank was not possible.

Survey data to date have indicated no trends in structure movement.

The available data are not sufficient to rule out this CPFM or lead to a conclusion that surface erosion has occurred under the Condensate Storage Tank. Therefore, the confidence in the above assessment is low, which means more data are necessary to draw a conclusion.

Summary For CPFM 2b, as discussed above, the combined consi on of or degradation and the implications of that degradation to a structure o it in significant" category.

The data currently collected are not sufficient toMthis CPF the 2011 flood. Therefore, the confidence in the above assessment ch means m continued monitoring and inspections might be necessary dra clusion.Triggering Mechanism 3 -Subsurfacne E iping CPFM 3c -Undermined buried utiliti e to pu Buried utilities in the area of the CQjalens orag mclu .Force Water (FW)from the Condensate Storage T Tr a, th Water , and the ductbank west of the Raw Water Piping with v s utilities.

The Triggering Mechanism M could occu Futility lines can act as possible seepage eepage , uld connect to S pumping sources such as the Tur Distres "ator # 1 in Section 4.1), Manhole MH-5, and a number s that were if n the A m perimeter.

The pumps were operated for an ed period (the pum Turlbi ding sump will continue to operate until the reas in the drain pipes ar main a head differential on the seepage path o°rks Some gradients by the heardifferential may have been sufficient to begin on of surrounding soil. I age is unfiltered and erosion continues unarrested, erosion-ends out intercepting t jetork of utility trenches, including the 1 0-in. FW from the Co fn s Storage Tank. T damage includes settlement of pipe or thrust blocks.overstress e that is corroded, could cause a pipe to break, or could cause the displ fat of a th ck, which in turn could cause failure of a pipe operating under pressure.The following ta scribes observed distress indicators and other data that would increase or decrease the potential for degradation associated with this CPFM for the Condensate Storage Tank.Adverse (Degradation/Direct Floodwater Favorable (DegradationlDirect Impact More Likely) Floodwater Impact Less Likely)A documented void exists under the foundation There have been no observed indications of site slab of the Turbine Building with a known settlement in the area directly surrounding the hydraulic connection between groundwater Condensate Storage Tank.elevation and flows into the building sump. A more detailed discussion of this Key Distress Priority 1 Structures Page 5.11-10 Condensate Storage Tank Rev. 2 Adverse (Degradation/Direct Floodwater Favorable (Degradation/Direct Impact More Likely) Floodwater Impact Less Likely)Indicator is presented in Section 4.1.MH-5 on the dry side of the Aqua Dam was pumped continually.

Pumping within the Aqua Dam perimeter.

Data Gaps: Observation of the ground surface around the tank will be perforce the deposited sediment is removed. i cet Additional data whll be acquired feom GPR, seismi oe T iet boruigs in the Paved Access Area. U #,1 Conclusion dre

-" Potentialfor DegradationhDirect Floodwater Impi h The CPFM has not been observed at the struc ods ceogroundwater pumping at MH-5 might not have been evid t e imfield asses" Additionally, the extent of voids due to ffg of gro4 Turbine Building sumps has not been determined.

Indicators for t PFM h een ithin the paved area between the Service Building and te e ak osidct h poenia tatderaatonha oue othis is hig ae potential for fuirther degradation will remain unti ing drain pi the T Building are sealed.Implication Tan he ground sa oe a Icould cause pipe settlement, thrust block andd to act ther ality of the Condensate Water Tank FW. The Tank of the pote onude n~i a i CPFM is judged to be low.Ion f he teti daio nfidence Fo rs for this CPFM u ave, e observed; however, inspection of the east side of the tant`*e i ground surface ati the tank was not possible and geotechnical and geophysical i n fo 4 S orn the Pave ..45%ss Area was not complete.

Survey data to date haveincae catrego. Thre is Lt. The availabl t rehas not sufficient to rule out this CPFM, or lead to a coMI&I'D t urace erosion will negatively impact the Condensate Storage Tank F. ThM confidence in the abv sesetis low, which means more data are necessary to dMiconclusion.*

Summary For CPFM 3 c, as discussed above, 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.

There is Low Confidence that there has been significant degradation to soil beneath the Condensate Storage Tank FW due to the 2011 flood.

Priority 1 Structures Condensate Storage Tank Page 5.11-11 Rev. 2 Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3e -Loss of lateral support for pile foundation (due to river drawdown)The sheet pile wall enclosing the pile foundation has weep holes on the east face to allow water to drain from the inside of the wall back to the river when the river elevation is below el. 997 ft 6 in. As the river level drops, there will be a hydrostatic head pushing water out of the weep holes, which has the potential to erode the soils surrounding the piles from within the wall, if not properly filtered at the weep holes. Al The Triggering Mechanism and CPFM could then occursa to a level that saturates the soil surrounding the piles w'level drops below the weep holes, there is a differentia, i the water drains, there is a potential for the soil to erode,'system. If the erosion were to continue, the voids couldg lateral support for the piling. 4 The following table describes observed distress indicators and othe decrease the potential for degradation associated PFM for Tank.Adverse (Degradation/Direct Floodw F(Degrada" Direct Impact More Likely) d Q pact Less Likely)Open weep holes in the sheet pile wa ave S ta c indicate no potential to allow free movement .'ent of re.tent of th `-ep holes is to drain the sheet ils and constructed uld not degrade the soil fill with et pile wall.Da e pieations of wver) sied ,e 'Condensate Storage Tank foundation including the e eet willbe petile pw~i~ ;oc t he riw, as receded.Observation of the gro" ace arouni will be performed once the deposited sediment is removed.

of the weep h s not considered necessary based on the current collected data.Siani In ce'Potential for .....irect Floodwater Impact The structure has ergone wetting cycles previously.

It is reasonable to assume that the foundation system and weep hole drainage system were designed to account for flooding over the top of the weep holes. Therefore, the potential that the 2011 flood caused further degradation for this CPFM is low.

Priority 1 Structures Condensate Storage Tank Page 5.11-12 Rev. 2 Implication The occurrence of this CPFM is not expected to negatively impact the capacity of the piling supporting the Condensate Storage Tank, since the distance from the weep holes to the bottom of the tank floor is about 5 feet. A 5 feet void at the top of the piles is not expected to cause the piles to buckle. Therefore, the implication of the potential degradation for this CPFM is low.Confidence Indicators for this CPFM have not been observed; howev'tank, the ground surface around the tank, and sheet pilep Survey data to date have indicated no trends in structurw sufficient to rule out this CPFM or lead to a conclusioni, under the Condensate Storage Tank support slab. Theref assessment is low, which means more data are necessary Summary For CPFM 3e, as discussed above, the combi _ 0 and the implications of that degradation to t category.

The data currently collected are , ufficientO, flood. Therefore, the confidence in the a ssess's continued monitoring and inspecti.i g nece4: side of the data are not Soccurred ifidence.'Al br degradation

ýiot significant" ue to the 2011 iore data or?M is simila river level i is created by rapidly Triggering Mechanism er than pore water pressi ,E-des the soil. Depem trench subsidenc 31 b acts on adiacen M could~fien occur as follows: if the river level drops foundation soil can dissipate, a gradient could be created te extent of the voids created, impacts could include the iorted pipe sections, pipe deflections, pipe failure, and ements or utilities.

The follow'm decrease the Tank.observed distress indicators and other data that would increase or radation associated with this CPFM for the Condensate Storage Adverse (Degradation/Direct Floodwater Favorable (Degradation/Direct Impact More Likely) Floodwater Impact Less Likely)Condensate Storage Tank and utilities are located No signs of distress have been observed.on the riverbank.

The 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.

Priority 1 Structures Condensate Storage Tank Page 5.11-13 Rev. 2 Data Gaps: " Observations of the east (river) side of the Condensate Storage Tank foundation including the sheet pile will be performed once the river has receded." Observation of the ground surface around the tank will be performed once the deposited sediment is removed." Additional data will be acquired from GPR, seismic survey, and geotechnical test borings in the Paved Access Area.Conclusion Significance Potential for Degradation/Direct Floodwater Impact The potential degradation from this CPFM may not have have likely not receded to a nominal normal level.None of the indicators for the CPFM has been ol to rapid drawdown might not have been Additionally, the extent of voids created by , degradation has occurred due to this CPF Implication The occurrence of this CPFM c egatively i could lead to pipe or thrust ttlement and intended functionality of th sate Storage ,aw w.the oper ' of the structure.

This negat mpact the integrity or stem. The implication of the-this ot been o however, inspection of the east side of the the tank s not possible and geotechnical and geophysical fts Area was not complete.

Survey data to date have indicated 3the available data are not sufficient to rule out this CPFM or erosion will negatively impact the Condensate Storage he confidence in the above assessment is low, which means a conclusion.

more Summary For CPFM 3f, as MOrussed above, 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.

There is Low Confidence that there will be significant degradation to soil beneath the Condensate Storage Tank piping system due to the 2011 flood.

Priority 1 Structures Condensate Storage Tank Page 5.11-14 Rev. 2 5.11.5 Results and Conclusions The CPFMs evaluated for the Condensate Storage Tank are presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

Low Confidence (Insufficient Data)I CPFM 3c CPFM 3e CPFM 3f 5.1 the Condensate Storage Tank: S 0 S In-dj~Visual Further fore (Key Distre:

map with results and recommendations.

%".e tank and the ground surface around the tank Sphysical modifications are recommended to address CPFM 3a recommendations are described in detail in Section 4.1.3.While inspection of thi necessary at this time.in the sheet pile wall would be beneficial, it is not deemed Continued monitoring is recommended to include a continuation of the elevation surveys of the previously identified targets on this structure and surrounding site. In addition, a review of the ongoing geophysical investigations and monitoring of inclinometer readings is recommended.

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. 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 Priority 1 Structures Page 5.11-15 Condensate Storage Tank Rev. 2 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.

5.11.7 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 Strucire.

These assessments were incomplete in Revision 0 because the forensic investigation and/or ni 0 or t of the Priority 1 Structures was not completed by the submittal date. This revi this ent Report includes the results of additional forensic investigation and m g tod structure as described below.5.11.7.1 Additional Data Available The following additional data were available for the Con Tank fori1 and 2 of this Assessment Report: " Results of KDI #1 forensic investigation

• Results of KDI #2 forensic investigatio.

Section (s* Additional groundwater monitoring w d river s from OPPD.* Field observations of the river bank (s i ection* Results of falling weight defi eter esti by Am gineering Testing, Inc.(see Attachment 6).* Results of geophysical infts 'tion by Geote ogy, In. ee Attachment 6)." Results of geotechnical ion by Thiel (see Attachment 6).* Data om inclino .y Thiele Geo (see Attachment 6).* R~ ~ isrvey b , Rynearson and Associates (see Attachment 6).assesse an on interface.

e: OPPD requested in m. ion from n firms that specialize in in-depth tank surveys assist them in a stigation fotpossible shell distortion of the tank. HDR has ded this information to g.5.l if dditional5' The fol1 haalysis of ona data was conducted for the Condensate Storage Tank: " Groundw well and river stage level data from OPPD.Data shows t r e river and groundwater have returned to nominal normal levels." Field observations of river bank No significance distress from the 2011 Flood was observed.

Priority I Structures Condensate Storage Tank Page 5.11-16 Rev. 2* Results of falling weight deflectometer investigation by American Engineering Testing, Inc.Falling Weight Deflectometer and associated GPR testing performed in the Paved Access Area identified anomalies 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 performe power block as part of KDI #2 identified deep ano tha loose sand, or possibly voids." Results of geotechnical investigation by Thiele Geoteed Six test borings were drilled, with continuous samplin t truth the Geotechnology, Inc. seismic investigation results a investigation.

Test bore holes were located the seismic investigation.

The test boring da loose conditions that might be indicative bsurfac loss or movement.All of the SPT and CPT test re co ed fB Asses to similar data from numero geo echn vestigati on the FCS site in previous .This comp did no the soil strength and sti _. er that time p of the material ,M_ ort were compared athave been conducted Fy substantial changes to test results were not to the original baseline measurements, have not meters. Therefore, deformation at the monitored mentation has not occurred.and Associates.

the original baseline surveys have not exceeded the equipment.

Therefore, deformation at the monitored ine was shot, has not occurred.Triggering CPFM iurface Erosion I support for pile foundation Field observations oTthe Condensate Storage Tank, after OPPD removed the deposited sediment, identified that the surrounding grades were predominately surfaced in gravel.Observations of the grades did not determine that surface erosion had occurred.

Observations of the sheet pile skirt wall identified the visible portions of the wall to be in good condition.

Priority 1 Structures Condensate Storage Tank Page 5.11-17 Rev. 2 Significance Potentialfor Degradation/Direct Floodwater Impact The Condensate Storage Tank foundation is protected by a sheet pile skirt wall extending from the bottom of the tank to about 10 feet above the bedrock. The skirt wall protected the foundations from surface erosion. Therefore, the potential that the 2011 flood caused further degradation for this CPFM is low.Implication The occurrence of this CPFM would negatively impac Condensate Storage Tank. This could lead to excessive, impact the integrity or intended function of the Condensa implication of the potential degradation for this CPFM is Confidence The extent of surface erosion and its potential Revision 0 due to the river sediment that hadfiMeen deposr and visibility.

Subsequent field inspectionsaa reviev/movement.

Since the structure has been and&n detected, the confidence in the assessmentg , gra"Sin further structure monitoring reve~ frte iss Ne CPFM becomes high. 311 t supporting the 4 negatively M the ctlng access no structure Rhas increased.

If the assessment for this Summary For above tential for degradation is low because the tank 6nsapro", #a sheet 4 wall. It is unlikely this degradation would have to edtcause impac integriM o ended function of the structure.

The combined deration of the potenti degradati0nld the implications of that degradation to a:ure of this type puts it significant" category.

The data collected since Revision.sufficient to rule out assuming the previously recommended monitoring L1Ae is continued.

Theref c :reMe confidence in the above assessment is high, which means onal data and inspect 1s~are necessary to draw a conclusion.etchanism 3'Subsurface Erosion/Piping PFM'3M -oss al:,ra. support for pile foundation (due to river drawdown)Field observations6ý,e Condensate Storage Tank after OPPD removed the deposited sediment did not idtifWy distress to the tank foundation.

Observations of the sheet pile skirt wall identified the visible portions of the wall to be in good condition.

Sianificance Potential for Degradation/Direct Floodwater Impact The structure has undergone wetting cycles previously.

It is reasonable to assume that the foundation system and weep hole drainage system were designed to account for flooding over Priority 1 Structures Page 5.11-18 Condensate Storage Tank Rev. 2 the top of the weep holes. Therefore, the potential that the 2011 flood caused further degradation for this CPFM is low.Implication The occurrence of this CPFM would negatively impact the capacity of the piling supporting the Condensate Storage Tank. This could lead to excessive foundation movement and negatively impact the integrity or intended function of the Condensate Storag ank. Therefore, the implication of the potential degradation for this CPFM is h Confidence The extent of subsurface erosion and its potential impa as n at the time of Revision 0 due to the river sediment that had been deptn und the access and visibility and not having inspected the weep h roundwater measured in the monitoring wells closely followed the iv dev floodwater the differential head created by the river drawdown was insufficie itate subsu e erosion. Subsequent field inspections and a revi yed data no structure movement-and an observation of the weep h ed neces nce the structure has been monitored and no signs ement n detecte nfidence in the assessment of degradation for this CP as er strucre monitoring reveals no further issues, the confidence o assess i or t becomes high.Summary For CPFM 3e, as discusse he potential rad low because it is reasonable to assume that the foundation and weep ho , stem were designed to account for flof the les. It is unlike is degradation would have occurred to c ty or led function of the structure.

The combined c. a tion of the p or degr and the implications of that degradation to a re of this type put e "not + cant" category.

The data collected since Revisionsufficient to rule ou &edsufeiscontined Trule hi het t assu tnfhe previously recommended monitoring ule is continued.

There. he confidence in the above assessment is high, which means'Additional data and inspecti.

re necessary to draw a conclusion.

T rig v Mechanism 3- rface Erosion/Piping

-Undermine d utilities (due to river drawdown)Significa n, Potential for Deg a on/Direct Floodwater Impact The groundwater elevation measured in the monitoring wells closely followed the river level as the floodwater receded. The data indicate that groundwater elevation was about 2 ft above the river level near the beginning of October 2011 and receded to the river level by about October 14, 2011. Therefore the differential head created by the river drawdown was insufficient to facilitate subsurface erosion. The potential that degradation has occurred due to this CPFM is low.

Priority 1 Structures Page 5.11-19 Condensate Storage Tank Rev. 2 Implication The occurrence of this CPFM could negatively impact the operation of the structure.

This could lead to pipe or thrust block settlement and could negatively impact the integrity or intended functionality of the Condensate Storage Tank piping system. The implication of the potential degradation for this CPFM is considered high.Confidence The extent of subsurface erosion and its potential impact pi was not known at the time of Revision 0 due to the river sediment that een dep ound the tank restricting access and visibility.

Subsequent field insp s and rveyed data indicate no structure movement.

Since the structure has ed anof movement have been detected, the confidence in the asses degradatio s CPFM has increased.

If further structure monitoring reveals no s, the confi assessment for this CPFM becomes high.Summary For CPFM 3f, as discussed above, the pote r degra low beca differential head created by the river drawdown was i icient to urface er sion. It is unlikely this degradation would have occ ,to cu act tegrity or intended fun--ction of the structure.

The comtile pot rt degradation and the implications of that degradation cteoft pe puts he not significant" category.

The data collectedsi evision 0 are icient to out this CPFM assuming the previously recommended g schedule is ,fore, the confidence in the above assess. e t is high, win s no addition ~inspections are necessary to 5 R , Ciiac egfore Tank are presented in the following matrix, ich shows the rating for tH cce and the level of confidence in the evaluation.

Ms 2b, 3e, and 3f for the densate Storage Tank are not associated with Key Distress s. The results of the aijdonal forensic investigation show that these CPFMs are ruled o e ,fore, assuming that¶ rther concerns are identified through the monitoring proghe Condensat ige Tank (discussed in Section 5.11.6 and continuing until D ecembeI"'

l 1), ther Ms are moved to the quadrant of the matrix representing "No Further AcAR com ec- d Related to the 2011 Flood." CPFM 3c for the Condensate Storage Tank i s i with Key Distress Indicators

1. 1 and #2. Sections 4.1 and 4.2 present the ditional forensic investigation that was conducted to ascertain whether the CPFM could be ruled out. The results of the additional forensic investigations show that if the recommendations for physical modifications in KDI #1 are implemented that this CPFM is ruled out. Therefore, assuming that no further concerns are identified through the monitoring program for the Condensate Storage Tank (discussed in Section 5.11.6 and continuing until December 31, 2011), and the physical modifications recommended for KDI #1 are implemented, the CPFM is moved to the quadrant of the matrix representing "No Further Action Recommended Related to the 2011 Flood.

Priority 1 Structures Condensate Storage Tank Page 5.11-20 Rev. 2 In th. CS S4 the first step was to develop a list of all Triggering MWoI s an A ould h urred due to the prolonged inundation of the FCS 9the 201 M *ver fib could have negatively impacted these structures.

ext step was to use variou -sigations, including systematic observation of structures over time, eithi ; liminate t Triggering Mechanisms and PFMs from the list fto recommend further inve on and/or physical modifications to remove them from the mr- any particular structure ecause all CPFMs for the Condensate Storage Tank other thass 2b, 3c, 3e, and 3 ;been ruled out prior to Revision 1, because CPFMs 2b, 3e, andy been ruled out tult of the Revision 1 findings, and because CPFM 3c will be ruled 0 he physici recommended for KDI #1 in Section 4.1 are implemen Tr gg echanisms and their associated PFMs will remain credible for the Condensa_

a nk. HDR has concluded that the geotechnical and structural impacts of the 2011 ' er flood will be mitigated by the implementation of the physical modifications recom ended 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 5.13 C,÷., J Priority 1 Structures Page 5.13-1 Circulating Water System Rev.2 5.13 Circulating Water System 5.13.1 Summary of Circulating Water System Baseline information for the Circulating Water System is provided in Section 2.0, Site History, Description,.ancd.Baseline Condition The Circulating Water System is composed of two cast-in-place concret ittnrel cqjponents that Provide -latr , o r -,,, the intake, S ..tructur to the Tur." A Aý "A An Building to the river. The tunnel structures intersect and stack, e.iner of the intake structure and remain stacked under the Service Building.

The tuels rota U they T I14N s(own sde where the extend under the Turbine Building.

The discharge tunnel 1est Intake Structure then turns 600 east to the outlet located at the riverbanki the Intake S.e and the Condensate Storage Tank. The bottom of the tunnel is generally The top oft-h -.at el. 997 ft where thetunnels are stacked and el. 986 ft where the'Mne psde-by-side.

inTdestm is founded on 12-in.-diameter Class B steel pipe piles that are driven to bdif.ommt, ind concrete filL-Some Class B piles are designated as tension piles and eainforcing d o' provid positive tension connection to the foundation mat.__ Z_The Intake Structure, Service Building,-and Turbri i.jdIng ai_.-p de- Itfidationswith bottom floor elevations of 966 ft, 1007.5 ft, and 9 ree The raw water discharge pipe and the Tur- .Buil'1ing su, umppi 'discarge into the Circulating Water Discharge Tunnel.5.13.2 Inputs/References Suppoi te Analysis Table 5.13- by .to support HDR's analysis.A Table 5.13J%..

Water System ,,.EP Document TitlI ',VOPPD Document Date Pag Number Number(s)(if applicable)

PiliP ubme Room & Service B, ng 16506 1/17/1975 1 1405-S-274 Piling P1 tke Structure 16507 1/20/1975 11405-S-275 Circu.atm.in...nnelsPlans

.16522 1/22/1975 11405-S-299 Circulating W w u Inels Sectio.r&

eetails 16523 1/22/1975 11405-S-300 Intake Structure I F o.i ;itfon Plan & 16531 1/23/1975 11405-S-311 Details Intake Structure

& Tunq ctions & Details 16537 1/9/1975 114.05-S-317 Intake Structure

& Tunnel Miscellaneous Details 16540 1/29/1975 11405-S-320 Incident Report Summary *.>

• CR 2011-5369 6/5/2011 '* All- ...Incident Report Summary CR 2011-5254 6/1/2061 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 Priority 1 Structures Page 5.13-2 Circultinig Water System ReVr 2 Table 5.13-1 -References for Circulating Water System Document Title OPPD Document Date Page Number Number(s)(if applicable)

Incident Report Summary CR 2011-5737 6/22/2011 All Incident Report Summary CR 2011-5805 6/26/2011 All Incident Report Summary CR 2011-5932 7/1/2011 All Turbine Building 6" and 10" Floor Drain Pipe (Summary of bnknown All Breaks i' R Summary Report of Broken Floor Drain Pipes All tt~~p'za .. .-91,

• Sz Detailed site observations-field reports, field notes, and insp, he q1ih2 Circulating Water System are provided in Attachment 8.Observed performance and pertinent background data are as follo I On* No utilities are known to cross under the Circulating Wate System ,* The Trenwa, Main Underground Cable Bank ,betw=izefflnd M-5) .-e., Raw Water Piping, and a group of 7 pipes encased in concr -e 0L'now '. ss over thl' o the Circulating Water Tunnels.* Concrete pavement in the corridor that extend be-ween t fri lding and the Intake Structure exhibits conditions that indicate distres ,inclu dackih ettlemen, and undermining.

Pavement slab settlin bse ed noýWest of theraknZ tructure and east of the abandoned acid tank. A aveme a wa m W-Ied east of the Service Building truck dock. Pavement g was evident thein paeenonakn A4'4 the pavement cracking could be, conditionffge and use of the facility.*King Tut b thousand ptids each) located djaent to the PA fence at the north end of the corr-ia aQ e tena 4 ding, were loaded onto trucks and removed from this area od.ý,,, 'Ember 14, 20'ljr' he observed and photographed this operation.

No-displacement or n~wa 'I" !. 1. ""N-dduring the lifting or removal of these blocks.pa wise toe l* 40Mqua Dam surrounding th Nbc I Circulating Water Tunnel.* B piles consist of pip , outside diameter and 0.25-in. wall thickness, which g, STM. a 25 Grad e 2 .becA252 Gfilled (Fwih, p SI). The piles were driven closed-ended to refusal on bedT ki filled with 4000 psi c-.igrtee(e LB-S5)cbtA~te (see PLDBD-CS-54).

SBelow report of braloor drai pipes with reference to CR2009-1365:

-CR.0019was created~fiff rch 24, 2009.-There are VW-0rain line. u, n parallel to each other; the 6-in. floor drain and the 10-in.waterbox dra.' s brought in to visually inspect the drain lines because undocumented

-1. observed draining into the sump pit from both lines. They found a break in the I -imi'n at the branch tee from the VD-193 drain valve. They could not inspect the 6-in. floor drain because the line does not have a cleanout connection in this area and accessibility through floor drains is restricted by,4hedfain trap at each location...:

-. .-Review of system files shows that a break in the waterbox drain line has been known for quite some time. In 1997, a repair was attempted by core drilling holes in the vicinity the break and pressure grouting to seal the pipe. Per the "Water Systems Report Card for Report Period April 1 Through June 30, 1997" (memo PED/EOS SYE 97-123): Repair of the Turbine Building Basement Drain line header was attempted during this period. The repair procedure consisted of core drilling holes in the vicinity of the leak and pressure grouting to seal the leak. Approximately 10 holes were Priority 1 Structures Page 5.13-3 Circilating Water System -Rev. 2 drilled and it was estimated that a void of approximately 10 by 8 by 1 ft existed under the concrete slab. The void was filled with cement grout but the leak could not be stopped. Boroscope inspection of the pipe exterior performed through the core drills showed considerable pipe damage, in more than one location.

The extent of the damage and concern over collapsing the line were determining factors in terminating the pressure grouting operation.

FC ECN 97-213 was originated to request that a new drain header be.installed.

01* The river bank is armored and has historically protected and stabilized",e existing river bank.* USACE reduced Missouri River Mainstem System releases t DO0q ,sr 2, 2011.River levels corresponding to the 40,000 cfs release rate staW i at F t_ ober 4, 2011, at about el. 995 ft. P 5.13.3 Assessment Methods and Procedures 5.13.3.1 Assessment Procedures Accomplished 1,X M Assessments were made by walking the corridor between uSildig and the structures located at the riverbank and observingof, eeatures ofthenm and the paved surface overlying the Circulating Water Tun 40. 3e is located 1lthe corridor paving, limiting visual observation to surfacgia-vement nM nt, settlem d distress.The surface assessment included using a 4 g 0l5-ong 1 -tippedi fiberglass the~ ~ ~ ~ ' grs;rfc. iljc ateel deteribe rglassv T-handle soil probe to hand probe the gronftf' eRbjaceWake o determine relative soil strength.

Soil probing was limifd to arpas bey, -hhe fuFa~paiVng and paving joints

%n aigjit* hie: as ( --- N t cused o n iyn g c n i ion s that would accommodate the prbs, Off c g ntifying conditions indicative of potential flood- a !impacts or to t u ao , i pa to the as follows:* Ground eaconditions"9 0ing and immedi-A --cent to the structure-engnere Seas (nafi .,engineered fill, and/or limestone gravel pavement) as by ir~bEgE(where pop .dup- e amage to at-grade .features and equipmentto a-graaeowe-gradeiy

1. O Variance from normal i lH7l.ation conMi including settled, tilted, or heaved pavements in Operation of the system ipurtenantequpment (i.e., is the system operational?)

iLcdonal investigations wererformed to further characterize the subsurface at the facility, 4.areas where conditio .mindicative of potential flood-related impacts or damage was included thollBowing non-invasive geophysical and geotechnical investig~tibl

• GPR alon tvement between the Intake Structure and the Service Building. (Test reports were'no f, ilable at the time of Revision 0.)* Seismic survey- seismic refraction and refraction micro-tremor) in the protected area.(Test reports were not available at the time.-of Revision 0.) ...Geotechnical test borings in the PA. Note th`at 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.)

Priority 1 Structures

_Circulating Water System Page 5.13-4 Revi.- 2-11 5.13.3.2 Assessment Procedures Not Completed Assessments of the Circulating Water System that were not completed include the following: " Video inspection of tunnels to determine the current condition. (TV inspections are not currently planned to be performed)." Visual inspection of:.the tunnel outfall structure at the river was not possible due to the current river elevation. (Visual inspection of the outfall is not urrently planned because the river level is not expected to drop below the Discharge Tui5 o9ojp 5.13.4 Analysis Identified PFMs were initially reviewed as discussed in Section .,i preliminary information available from OPPD data files and from Eleven PFMs associated with five different Triggering Mechanis" &credible" for all Priority 1 Structures, as discussed in Section 3.672 forward as "credible." After the design review for each structure, the preliminary results of available geotechnical, geophysic 1rey CPFMs were ruled out as discussed in Section 5.13.assessment are discussed in Section 5.13.4.2.5.13.4.1 Potential Failure Modes Rule ut Priort the Assessment a number of of the Detailed Th wil Tr e ruled-out CPFMs reside in tfiNN-ot Significarnj 4h Confld category and for clarity not be shown in the Pot v1or Failure 9101 eCn -mat"f igge ARM ism 2 -

supMA:f Pile foundation for ruling oUt: Bathymetric survey did n -Adqntify scourat the discharge tunnel.S!ur.face erosion was not o' led in the area of the tunnels-during the-field assessments.

gifbiig Mechanism 3 -S i.i.rface Erosion/Piping CP0'e- Loss of latepport for pile foundation (due to river drawdown)CPFMR j.},ndermriinbiried utilities (due to river drawdown)* The tunnels are"a-sufficient depth below the ground surface to be outside the zone of influence of these CPFMs.

Priority 1 Structures..,...

Circulating Water System Page 5.13-5 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- Excessdeflection Reason for ruling out: The portion of this system that is subjected to hydrodi The Discharge Tunnel is located on the south side riverbank is protected by revetment above and upstre Triggering Mechanism 7 -Soil Collapse (first time w4 CPFM 7a -Cracked slab, differential settlement of sl support Q CPFM 7b -Displaced structure/broken connefs CPFM 7c -General site settlement CPFM 7d -Piles buckling from down di Reason for ruling out: X11 The Circulating Water SysteaUR,4cated adjac1o " surrounding the structure

1. piMuning the subgr ha saturated condition. , 'L:.Tunnel.he Missjiri River. The soil past or is normally in a wed Liquefaction walls to Static Liquefaction or Upward Trigj CPFM 11 N CPFM I Id -onal lateral force on below-grade walls le group instability Reason for ruling out:* This phenomenon was not observed at the site.

Priority 1 Structures Page 5.13-6 Circulating WaterSystem Rev. 2 Triggering Mechanism 12 -Rapid Drawdown CPFM 12a -River bank slope failure and undermining surrounding structures CPFM 12b -Lateral spreading Reasons for ruling out:-Slope failure was not observed at the site.* River stage level has receded and stabilized at a level correspo d.ng to the nominal normal river level at 40,000 cfs as of October 4, 2011. '.CPFM 13b -Corrosion of structural elements Reasons for ruline out: The soil surrounding the structure, including the subgr y in a saturate!condition." Conditions have not changed due to flood conq4f'i" i Triggering Mechanism 14 -Frost Effects "--CPFM 14a -Heaving, crushing, or dis .met Reasons for ruling out: " The Circulating Water Syst founded bel ost level.* Conditions have not cha l4ul. he to flood con,'34ssessme, ible Poten i1Failure Modes Tee owing CPFn o carried forward for detailed assessment for the ating Water Syste flood. This detailed assessment is provided-'i ggering Mechanism 3 -

Erosion/Piping"M 3b -Loss of for pile foundation (due to pumping)The YITime Building has ad vi-ented history of a void below the foundation dating back to 1997. T ..Ye of into the Turbine Building sump through breaks in the drainage pipes is 0n e _ejrress Indicators discussed in Section 4.The Triggerin ism and CPFM could then occur as follows: the seepage condition will remain until the br'a s in the drainage pipes are repaired, which means the potential for further ero0sion continues unarrested..

Erosion could extend out, creating voids under the Circulating Watertunnel.

-. --- -- --- " 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 Circulating Water System.

Priority 1 Structures Circulating Water-System Page 5.13-7"'Rev. 2 Adverse (DegradationlDirect Floodwater Favorable (DegradationlDirect Impact More Likely) Floodwater Impact Less Likely)Previously documented void under the The bottom of the tunnels is more than 5 ft below foundation in the Turbine Building.

the broken pipe locations.

Documented breaks in the drain piping below the foundation in the Turbine Building.Documented continual groundwater flow from the broken drain piping into the sump in the Turbine Building.

g The soil around the piling was not compacted to :0&the same requirements as the material under the Class I structures (vibroflotation effort).Pavement distress was observed between the Intake Structure and the Service Building.

_, Data Gaps: The size and location of voids below the Turbine Building foundatio d.,whi below the tunnels Conclusion Significance Potential for Degradation/Dire(Indicators for this CPFM have bl" observed in tfirurbine 1J.ng. A void below the mat foundation in the Turbine BEi~is known to e? NdA.g -dwater is constantly flowing into the sunmfrn the five drakides.

Because ti N2 O d caused increased groundwater flow thrri piMea-,era, pipe e,,potential that the 2011 flood caused further and more r iation dit Ciii C %&`h. However, it is unlikely that these voids extend iel.'large scale could negatively impact the capacity of the piling-,stem. This is not expected to occur to the extent that would i,.intended function of the Circulating Water Tunnels.potential degradation to the Circulating Water Tunnels for this The data at hand are'not sufficient to rule out this CPFM or to conclude that physical modificationato ensure that the.pilings that support this building have loQs$,tcapaqity-ybecause of.,..;;, this CPFM. Therefore, the confidence in the above assessment is low, which means more data are needed to draw a conclusion.

Priority 1 Structures Circulating Water'System Page 5.13-8 Rev. 2 Summary For CPFM 3b. as discussed above, the potential for degradation is low because it is unlikely the voids extend downward and below the Circulating Water Tunnel. 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 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 necess.a.

to draw a conclusion.

r A d~ r fl I~-~ ti The CPFMs evaluated for the Circulating Water System are pri shows the rating for the estimated significance and the level of 5.13.6 Recommended:Actions:,ý The following actions are"T.ecommended for the Circulating Water System: Review.the .geotechnical and geophy..sical data and assess.the impact.on-the Circulating Water .System.Further forensic investigations and.physical modifications are recommended to address CPFM 3b associated with the Turbine Building basement drain piping system (Key Distress Indicator

1. 1). These recommendations are described in detail in Section 4.1.3.

Priority 1 Structures Circulating Water System Page 5.13-9 Riev. 2 5.1.3.7 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 monitoring for most of the Priority I 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. J111_.5.13.7.1 Additional Data Available The following additional data were available for the Ciidt and 2" of this Assessment Report:* Results of KDI #1 forensic investigation (see Section" Re silts of KDI #2 forensic investigation (see Section* Additional groundwater monitoring well and river-sta" Field observations of the river bank (see Sectibfr5S25.

• Results of falling weight deflectorneter 1 (see Attachment 6)." Results.of geophysical investigation by.}.Gdotechno LWJ" Results of geotechnical investigation i Geot,"" Data obtained, from inclinome&si!by TlViele Ge.t eh." Results of continued survey_ amp "y_.and. d Revisions 1 Inc.1ttfahment 6).(see Attachment 6).5.13.7.2 Additional Anal The level data from OPPD.levels.0 No`the 2011 Flood was observed.0 Results deflectometer investigation by American Engineering Testing, Inc.Falling Weigh]-iDIlectometer and associated GPR testing performed in the Paved Access Area identified anomalies such as soft clay and broken pavement.

Additional ground truthing of the investigation-results wereperformed-as-part:

of-the KDI.#2 additional investigations.

a Results of geophysical investigation report 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 513-10.Circulating Water System .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.I su' CU. U~rvr' L. C ' s -' .e.tI-ij 01 LI1 Or I ani d .. C 1F tes~ ut z i ~ U~~ ItsI Liiiuc e niiJ.i.J,ý Piv to similar data from numerous other geotechnical iJn' gtions t-.been conducted on the FCS site in previous years. This comparisorl 1:tfinot identi.st .s.tati al changes to the soil strength and stiffness over that time period.

• a CPT test ry ere not performed in the top 10 feet to protect existing utilities",---

Data from inclinometers to date, compared to the origina n "t exceeded the accuracy range of the inclinometers.

herefore.

dei ation at the moiitored locations since the installation of the not )ccureq4`1-Results of continued survey by Lamp R-r° and AN :iates. 4V Survey data to date compared to the o I exceeded the accuracy range of the survey ingqui e iprfi. Th.eif5ire, defomiitroiit the monitored locations, since the survey base:e§H&wasshot, h0--Not occurred';.

Triggering Mechanism 3 +.1ii 4 Susrface ErosionwPping

-.XR CPFM 3b -Loss of lfiei!support for pile ue to pumping)CPF61 ter tem is associated with Key Distress Indicator

1. 1 and Key.Dstress Indicatod

.#'Sections 4 4.2 present the results of additional forensic Sumii:eshgation that was conite.ted to asceA0i-,Whether this CPFM could be ruled out. The.results of the additional that if the recommendations for physical e:NJ,-,odifications in KDI #1 are implemented that this CPFM is ruled out. Therefore, assuming thatno further concerns are iddii-fied through the monitoring program for the Circulating W'! er &System (discussed in Se6hn 5 13. 6 and continuing until December 31, 2011), thisved to the quadrant f the matrix representing "No Further Action Recommended 0 Flood 21.1 Prio.rity 1 Structures Circulating Water System .Page 5.13-11 Rev. 2 5.13.7.1 Revised Results The CPFMs evaluated for the Circulating Water System are presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

n,, Ye assessment of the FCS the first step was to develop a list of all -Triggering NNWRclanisms and PFMs that co]tiLhave occurred due to the prolonged inundation of the FCS site diningthe 2011 Missouri-N er flood and could have negatively impacted these structures.

The nextsl's ,_was to use data4friom various investigations, including systematic observation of the struct 6`h.des:6'Ver time,. -ieer to eliminate the Triggering Mechanisms and PFMs from the list or to recommr .,tit estigation and/or physical modifications to remove them from the list for any partliuffI, iticture.

Because all CPFMs for the Circulating Water System other than CPFM 3b had-6ieen ruled out prior to Revision 1, and because CPFM 3b will be ruled out when the physical modifications recommended for KDI #1 in Section 4.1 are implemented, no"TiggeringMeChan:isms and th~eifassociated PFMs will remain credible.for theGrculating Water System. 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.

r Section 5.14 Deminera ized Water Tank, Pump .House, a-gfnd RO Un Priority 1 Structures Page 5.14-1 Demineralized Water Tank, Pump House, and RO Unit Rev. 2 5.14 Demineralized Water Tank, Pump House, and RO Unit 5.14.1 Summary of Demineralized Water Tank, Pump House, and RO Unit Baseline information for the Demineralized Water Tank, Pump House, and RO Unit is provided in Section 2.0, Site History, Description, and Baseline Condition.

The Demineralized Water Tank is a 33-ft-inside-diameter storage tank ah-n.nd- proximately 31 ft above grade. The tank is fabricated of stainless steel to meet the F irem, 'API Standard 650. The tank is supported around its perimeter on a continuo..s a ct te ring wall that is about 1.2 ft wide by 2 ft tall. The interior of the tank bears on -er of s n a geotextile filter fabric, which in turn is on top of a free-draining crushed IMF tý rgate rushed limestone aggregate is drained by three 1.5-in.-diameter founda6, spaced equaround thoe concrete ring wall.The Pump House is a small pre-engineered metal building supported on a .-i. kab.The entire tank footprint, including the concrete ring ftsneerior crus along with the Pump House slab, is supported on a rammed aggrega pe sol ementsys The RO Unit resides in the northern section ofthe., i Ware dW arehouse is a pre-engineered metal building supported onja~cas lace dr-am wall on continuous footings that extend below frost depth. a 5.14.2 Inputs/References Supp, fil' e Analysis Table 5.14-1 lists .,,rovided and other ds used to support HDR's analysis.Tablig.01

-1 Ref r-ffier tor Demi'n iiAzed Water Tank, Pump House, and RO Unit Document .T.. OPPD Document Date Page Number Number(s)( if applicable)

Suei At4 8/28/2009 1 of 2 8/28/2009 2 of 2 Geopiert cation System 4/20/2010 GEO-1 &P09-PMN-0e(%)

9i GEO-2 Naval Facilitieýs@gieering Cornfij, 9/1986 All Design Manual 7 .0 e s Detailed site d reports, field notes, and inspection checklists-for the Demineralized Water Tank, Pump House, and RO Unit are provided in Attachment 8.Observed performance and pertinent background data are as follows:* The soils below the Demineralized Water Tank and Pump House were improved by installation of fifty 30-in.-diameter-by-18-ft-minimum-depth rammed aggregate piers (see Geo-1 and Geo-2)." A total of 41 rammed aggregate piers were installed below the tank footprint, and 9 were installed under the Pump House slab.

Priority 1 Structures Page 5.14-2 Demineralized Water Tank, Pump House, and RO Unit Rev. 2* The tank foundation system, including crushed rock interior, is shown on the site plan and detail sheets by LRA in table 5.14-1.* Structural drawings for the Old Warehouse are not available, so descriptions of the foundations are assumed based on normal standard practice for foundation construction for a pre-engineered metal building." The Aqua Dam surrounding the Demineralized Water Tank and Pump House failed for an unknown amount of time, allowing floodwater to enter the area inside.the Aqua Dam perimeter.

Based on observed water marks on the Demineralized Water Tank and mp ouse, water levels reached approximately 2.5 ft above grade. 4* The interiors of the Pump House and Old Warehouse showegl. pgs of up eepage at slab-on-grade joints. Other HDR employees observed up ' eepage in the slab during previous inspections.

• Site soils were saturated at the times of inspection." Small channels of water flow were observed as water dissipated.t.

o e vicinity o an Pump House.* Neither the Demineralized Water Tank nor the Pump House has a fou n that extends w frost depth.* Foundation drains for the tank were found to be diment at th f inspection.

• Areas of relatively soft soils were observed bydRg a soil pr e generalii

• t of the tank and Pump House, but these areas are out of the e of inflenn-e rfoundation systems." Probed areas around the Pump House are softwrie up An pe, ne spot near the southwest comer of the Pump Houseu a hr soils 6be could be pushed in to a depth of2 ft.* In an area between the Deminerliz&

_*ater Tank an, np Hous pproximately 10 ft from the east side of the structures, the p, 7 I b p 1f pth of the probe. The soils were not unifor gelayers werse6 and others stif ft4s distance the soft soils are out of the zone -

fo1o.e6ftems

• A void Eaedeto -be i ,to2 ft deep was observed below a transformer pad at tph Reast comrer of t W W a arehosu tis area was pumped with a small pump for the d.jTien of the 2011 flood.* rOea directly east of the Old',, arehouse between the rock road and the building was dug out Wedhd as a water collection trollg \These areas had multiple small portable pumps removing watefýthe trench.5.14.3 As.sesment Methods and' rocedures 5.14.3.1 , $mn' W dures Accomplished Assessments 0e Dmineralized Water Tank, Pump House, and RO Unit included the following:

V* Visual inspection of the interior and exterior of the north side of the Old Warehouse at the water treatment facility and also the exterior of the tank and Pump House" An assessment of collected survey data to date for indications of trends in the movement of the structures

• Probe of surrounding grades to determine stiffness and consistency of soils* A review of previously referenced documents listed in Table 5.14-1 Priority 1 Structures Demineralized Water Tank, Pump House, and RO Unit Page 5.14-3 Rev. 2 Additional investigations were performed.

These included the following non-invasive geophysical and invasive geotechnical investigations:

• 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.) 1 5.14.3.2 Assessment Procedures Not Completed Assessments of the Demineralized Water Tank, Pump completed include the following:

• Review of as-built construction drawings for the Old treatment area, was not completed because at the timt available.

5.14.4 Analysis Identified PFMs were initially reviewed as discussedm ection: preliminary information available from OPPD dat s and frot Eleven PFMs associated with five different Trigg Mechai, credible" for all Priority 1 Structures, as diseassed ecti forward as "credible." After the detaile, T g review fairea h and the results of available geotechnica physical, an e, 'CPFMs were ruled out as discussed.

.... ion 5.14.4.1.

T assessment are discused in Section 5QVQMVQ 5.14.4 ltVR rntiaA t i Eie Mod~sl R, led Out Prior tc were not observations, forward for detailed the Detailed Assessr ruled-out CPFMs category and for clarity 11 not be shown in the Potdf4or Failure/Confidence matrix.2 -uiiie Erosion ningsihbow foundation/slab/surfaces inedAied utilities d after floodwaters had begun to recede from the area. No signs of seen that could contribute to undermining of the foundations or slabs* The site was OB ser surface erosion wen for these structures.

Priority 1 Structures Page 5.14-4 Demineralized Water Tank, Pump House, and RO Unit 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:* In accordance with conversations with OPPD personnel, the Drn ineralized Water Tank was kept full during the 2011 flood, resulting in no net fere. allmessures.

• The Pump House was inundated at the time of the A mi- fijfa M eIting in no net differential wall pressures." Water surrounded the Pump House and Demineralize R ater o .es, creating equal hydrostatic pressure.* The water treatment area of the Old Warehouse was isoj dktfrpm n n Dam.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: -Overlgdmflo elocity at s 4ation was very ing very minimal forces due to hy, i og. s ouring in this location was isolated to areas where the fil ea was and the Vreas (i.e., the King Tut blocks). In general, theýReka naad area had se.~dmen wo' ~jf4ate low flow velocity.;+loodwaters have sinc giein torecee& o the site, and no signs of distress that could be attributed to hydrodynamic,"Iading have'be observed.T-ring Mechanism 6 -B uyiancy, Uplift Forces on Structures "73 w 6b -Cracked slab structural support C-P, '416c -Displaced strauRt dfe/broken connections Reasons for rdh"Z out* In accordande_'"onversations with OPPD personnel, the Demineralized Water Tank was kept full diftiiiig the 2011 flood, resulting in no net buoyancy effects.* The Pump House was inundated at the time of the Aqua Dam failure, resulting in no net differential wall pressures.

• Although a net uplift force from floodwaters might have occurred on the Old Warehouse floor slabs, cracking or loss of structural support of the slabs was not observed at the time of the inspection.

Priority 1 Structures Demineralized Water Tank, Pump House, and RO Unit Page 5.14-5 Rev. 2 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 Reason for ruling out:* Soil collapse due to first time wetting occurs immedie Degradation related to this CPFM would have been a!Triggering Mechanism 10 -Machine/Vibration-Indu, CPFM I Oa -Cracked slab, differential settlement ofE support CPFM 1 Ob -Displaced structure/broken connections Reasons for ruling out:* Vibrations from equipment in the Pump HuOse create minimal localized vibrations thaJ not cau No signs of liquefaction were observed ring the inA Triggering Mechanism 11 -LossbfSoipSifngt dU Seepage W and CPFM 11 a- Cracked slabsiýJ.-rential settle f shallow undation, loss of structural support tr roe .-CPFM *,-,Displaced stru jeboe onci CPMrknconned

", Reasoifolin'

&ebit.!, Visual observations. ,rniey measr s show no structure movement.

Therefore, degradation that can be "ib, ted to this M did not occur.1Br4ggering Mechanism 12 -Rapid Drawdown 12a -River bank s§Be ailure and undermining surrounding structures OPUBMN 2b -Lateral spreading Reaso n firtfii -out: The structiikep ted outside of the PA and are a sufficient distance away from the riverbank to be'ouiside the zone of influence of a bank slope failure.Trggrig ecans 1 -Sumegec Triggering Mechanism 13 -Submergence CPFM 13b -Corrosion of structural elements Reasons for ruling out:* The Demineralized Water Tank and connected piping are stainless steel and have not been subjected to corrosive circumstances that would be considered beyond the normal conditions.

Priority 1 Structures Demineralized Water Tank, Pump House, and RO Unit Page 5.14-6 Rev. 2" The Pump House was inundated at the time of the Aqua Dam failure. However, this inundation duration was short, and no abnormal corrosion on the building was observed.* The water treatment area of the Old Warehouse was isolated from floodwater by the Aqua Dam.5.14.4.2 Detailed Assessment of Credible Potential Failure Modes The following CPFMs are the only CPFMs carried forward for d Demineralized Water Tank, Pump House, and RO Unit as a esu detailed assessment is provided below.Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3a -Undermining and settlement of shallow f"-m" pumping)Subsurface erosion was observed at the northeast corner o e pumping of floodwaters occurred.

The approximately 4-ft-diam caused some undermining of the transformer fa the p conduit. Observations made by HDR in June an...urs s 1 Nl joints in the floor slab.No pumping occurred in the vicinity of thQ nlnerat ae therefore, these structures would ne._be suWj4ted PFM.ssment for the flood. This ias due to some buried through the Pump House;The following table describe decrease the potential for dq Tank, Pump Itp._se, and RO data that would increase or r the Demineralized Water Favorable (Degradation/Direct Floodwater Impact Less Likely)."-'Sble subsurface erosi'o`Ve pumpinr Was X oserved under a transfornerýPad1on the ext northeast comer of the Old Wai-4 otse building"" d~warehouse floor.Erosion observed did not appear to extend deep'ýenough to reach the foundations of the Old Warehouse.the vicinity were found of varying desiigwhich could include liw soils that are mor~e tiJble to erosion dtu !,ipumping.

Soils where pumping occurred seemed to be a gravel/structural fill with relatively high density, which is less susceptible to erosion.Observitih.j une andJ A, & dicated water infiltration o he K@ ttiiit buildingslab joints.Data Gaps: "" The presence oýfubsurface erosion under the RO Unit in the Old Warehouse slab due to pumping is not known to exist." Geotechnical borings and CPT soundings in the vicinity of the structures to determine current soil conditions and capacities have not been conducted.

Priority 1 Structures Page 5.14-7 Demineralized Water Tank, Pump House, and RO Unit Rev. 2 Conclusion Significance Potential for Degradation/Direct Floodwater Impact Indicators for the CPFM have been observed, although they seem to be isolated to one area below a transformer pad on the northeast comer outside of the 01 Warehouse and in the center of the Warehouse floor. The void below the transformer pads wnto eJ-st and the extent of the void can easily be observed.

The void does not appe te foundation.

Because there are observed signs of flow he floo own void adjacent to the Old Warehouse building, it is possible t, is voi 'r n s er the building and possibly undermines the foundation, although obsei xm'o t indic is to be the case. The potential is low that this CPFM will occur under b i'ding in the ar, using the RO Unit.implication The occurrence of this CPFM could negativel

1. t acity of t.lieii-d arehouse building foundation.

This could lead to grad oundati in ment but s 01not negatively impact the integrity or intended4tion of t fbefore remedial action can lmpllca th" " R, poo be implemented.

Therefore, the implicati he u ion for this CPFM is low.Confidence The extent of subsurface eresoy 44 its potential .Pat on ldWarehouse building is not known due to the lack of daA r-tied on " s. Because there is not enough informati c~ bnl-lons at this time, he pumping occurred directly adjacent.

....intahat could caused subsurface erosion under the building, the cor dece for this PF-Mis- obw.Tiinmmar,`FiiCPFM 3a, as discussed a81', the potential for degradation is low because the extent of"erps- ccurring is visible and, s not extend below the building foundation.

The combined c ,nsidetation of the potentialf and the implications of that degradation to a struct$W-F." 4this type puts in- ot significant" category.

The data currently collected are not sufficief0tle out this :of Therefore, the confidence in the above assessment is low, which means Ainue is necessary to draw a conclusion.

Triggering Mechanism 14 -Frost Effects CPFM 14a -Heaving, crushing, or displacement The foundations for the Demineralized Water Tank and Pump House are not below frost depths and are therefore subjected to frost effects.The Triggering Mechanism and CPFM could then occur as follows: soils may be saturated when the ground freezes, which would increase the potential for excessive frost heave. Drains below the tank appear to be clogged, not allowing water under the tank to drain before it freezes, which would not be the design intent of the tank.

Priority 1 Structures Demineralized Water Tank, Pump House, and RO Unit Page 5.14-8 Rev. 2 The Old Warehouse is on footings that extend below frost and is not susceptible to this CPFM.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 Demineralized Water Tank, Pump House, and RO Unit.Potential for Degradation/Direct The potential for this CPFM exifW6ii the DemineVMied Waterzffi.lk and Pump House due to the foundation systems use tse structures a d o rains below the tank. Due to the saturated soils and the tir Wear, it is possibl *11will freeze before the water levels inith e hi. a chance "1reduce to norma lev ,St'using excessive soil expansion.

Due. 4.e a td, the tank and pump house have been subjected to ir.fe sY putp cycles althjiptentially not to this extent and not with the drains'b1he tank clogged I tential that this CPFM will affect the Demineralized

ý4uter Tank and Pump Hotisl-ce the incfe. .s in effect due to the clogged drains and high'roundwater levels is minmal effect.Th'pliea ionm The ,cdm-rence of this CPFMcaid potentially cause some movement in the Tank and Pump House esysteis ver, because the foundations have always been subjected to freeze-thawtqs, th 5onal movement under current conditions is not expected to cause an excessive l se : ovement. Therefore, the implication of the potential degradation for Confidence At this time, it is not known whether the ground will freeze before soil water levels are able to lower to a normal condition.

In addition, the foundation drains were completely plugged with sediment, which does not allow the crushed rock bedding to drain and could cause adverse effects on the bottom of the tank if the ground were to freeze in this condition.

Therefore, the data at hand are not sufficient to rule out this CPFM. As a result, the confidence in the assessment is low, which means more data are necessary to draw a conclusion.

Priority 1 Structures Page 5.14-9 Demineralized Water Tank, Pump House, and RO Unit Rev. 2 Summary For CPFM 14a, as discussed above, the potential for degradation is low because the effects due to frost heave are expected to cause minimal effects on the structures.

The combined consideration of the potential for degradation and the implications of that degradation to the structures of this type puts it in the "not significant" category.

The data currently collected are not sufficient to rule out this CPFM. Therefore, the confidence in the above assessment is low, which means continued monitoring is necessary to draw a conclus..5.14.5 Results and Conclusions The CPFMs evaluated for the Demineralized Water Tank, Puni the following matrix, which shows the rating for the estimated in the evaluation.

Low Confidence (Insufficient Data)-"- -0)5.14.6 Recommendg iSe.e presented inýqf confidence Continued monitoring is recommended to include a continuation of the elevation surveys of the previously identified targets on this structures and surrounding site. The purpose is to monitor for signs of structure distress and movement or changes in soil conditions around the structures.

The results of this monitoring will be used to 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 Priority 1 Structures Page 5.14-10 Demineralized Water Tank, Pump House, and RO Unit Rev. 2 an immediate inspection or assessment should be conducted.

Observation of new distress indicators might result in a modification of the recommendations for these structures.

5.14.7 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 monitobrg for most of the Priority 1 Structures was not completed by the submittal date. Thi§ývisMoth' Vssessment Report includes the results of additional forensic investigation and monilo g to s s structure as described below.5.14.7.1 Additional Data Available The following additional data were available for the Deminel& e Water Tank, p and RO Unit for Revisions 1 and 2 of this Assessment Re'"i 'N* Additional groundwater monitoring well and. s e level da PPD.* Results of geophysical investigation by G e C. (see A t 6).* Results of geotechnical investigation by 3 e Geote ..see Atta.h.. 6).* Results of continued survey by Lamp parson and Ass. Attadhment 6).* Review of as-built construction drawi ~. o.r the aeý s cuding the water Review ot e-bul e ofhe treatment area, was not compalo A becasat the tcn e o re',ein. he drawings were not available.

5.14.7.2 Additional Anal 4 s The fow4 gjanalysis of additio .dta was conducteilfor the Deminerahzed Water Tank,'anR..i roundwater monitoring ll and riV &isge level data from OPPD.w Data shows that the river a roundwater have returned to nominal normal levels.Results of geophysical invelstiation by Geotechnology, Inc.S andySisic ReMi tests performed around the outside perimeter of the power6.c16ckas J #2 identified deep anomalies that could be gravel, soft clay, loose sall soi~ ds.Results of geý, ehical 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.

Priority 1 Structures Demineralized Water Tank, Pump House, and RO Unit Page 5.14-11 Rev. 2 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.

• Results of continued survey by Lamp Rynearson and Survey data to date compared to the original baseline range of the surveying equipment.

However, the devg concern for structures of this type.Several CPFMs were identified in Revision 0. Since Revýavailable which has clarified the significance and confide presents each of the previously identified CPFMs and the, significance and confidence based upon the new data.Triggering Mechanism 3 -Subsurface ErosionIIiping CPFM 3a -Undermining and settlementsh n pumping)the accuracy-not of a khave become Subsurface erosion was observed at the pumping of floodwaters occurred..

4 Te caused some undermining of th conduit. Observations made by iWkR in joints in the floor slab.house where localized'5-ft-deep void has o--Texposing some buried coming up through the No rater Tank or Pump House;for Degradation/l"d'ipors for the CPFM have MY observed, although they seem to be isolated to one area be6i tansformer pad on the'e$theast corner outside of the Old Warehouse.

The void below the tr~iifisfM-er pad is known.t.eist, and the extent of the void can easily be observed.

The d o ppear to e&fi elow the building foundation.

Because there is a known void adjacent building, it is possible that this void extends under the building and possibly UNiQnse 1 the foundation, although observations do not indicate this to be the case. The potenti4lis 6low that this CPFM will occur under the building in the area housing the RO Unit.Implication The occurrence of this CPFM could negatively impact the capacity of the Old Warehouse building foundation.

This could lead to gradual foundation movement but should not negatively impact the integrity or intended function of the building before remedial action can be implemented.

Therefore, the implication of the potential degradation for this CPFM is low.

Priority 1 Structures Page 5.14-12 Demineralized Water Tank, Pump House, and RO Unit Rev. 2 Confidence The extent of subsurface erosion and its potential impact on the building was not known due to the lack of data gathered on subsurface conditions.

Subsequent field inspections and a review of surveyed data indicate no significant structure movement.

Since the structure has been monitored and no signs of movement have been detected, the confidence for this CPFM is high.Summar, For CPFM 3a, as discussed above, the potential for degr ad n is 1ow._ ause signs of distress were not observed.

It is unlikely this degradation woul ve cause erosion to impact the integrity or intended function of the structure.

The bned C -V f the potential for degradation and the implications of that e of thi e t"not significant" category.

The data collected since Revisi, ne sufficient out this CPFM assuming the previously recommended monltormg6 continuedor, the confidence in the above assessment is high, which means naU ieonal data and .sons are necessary to draw a conclusion.

The data previo y thought t required to rule ou this CPFM, which includes a geotechnical investigai eview of a '45. drawings, are no longer required.Triggering Mechanism 14 -Frost Effec CPFM 14a -Heaving, crushing, or diAi aement The foundations for the Deminerf ~ie. Wat6r T Pump H-tf e are not below frost depths and are therefore subjected to~froef.ects.

Soils Were thoug ao ave a potential of being saturated when the groundRt eeating a poten re frost heave. Drains below sauae hnthe grunankoe the t ap eared to be cloggedý f e time of the ini e ion, not allowing water under the tan would nidelfet the design onten r the tank. The Old Warehouse is on low frst M.4s ......o g--blwrot susceptible to this CPFM.

P. .Pqtentialfor Degradation/D in loodwater Impact T* .undwater elevation measurded in the monitoring wells closely followed the river level as reded.h The dicate that groundwater elevation was about 2 ft above the river 1thebeginning4October 2011 and receded to the river level by about October 14, 2011'. lý4 ore, sat ,7!8soil conditions beyond normal are no longer an issue and the potential foj .ti i his CPFM is low.Implication

'The occurrence of this CPFM could cause some movement in the tank and Pump House foundation systems; however, because the foundations have always been subjected to freeze-thaw cycles, the additional movement under current conditions is not expected to cause an excessive increase in movement.

Therefore, the implication of the potential degradation for this CPFM is low.

Priority 1 Structures Page 5.14-13 Demineralized Water Tank, Pump House, and RO Unit Rev. 2 Confidence At this time, it is known that the ground will not freeze before soil water levels are able to lower to a normal condition because water levels have been determined to be at normal conditions at the time of Revision 1 and the ground has not frozen. Therefore, the data at hand are sufficient to rule out this CPFM. As a result, the confidence in the assessment is high, which means no other data are necessary to draw a conclusion.

Summary For CPFM 14a, as discussed above, the potential for de, adtion is l ause the effects due to frost heave are not applicable due to lowered groun leve l ned consideration of the potential for degradation and the ir 1ior tat on to the structures of this type put it in the "not significant" -ata currentEvy coected are sufficient to rule out this CPFM. Therefore, the confiden ove assessmen i§which means no additional data and inspections are necessary t ,a s previously thought to be required to rule out this CPF which inc O e geotechnica information, are no longer required.

-

Priority 1 Structures Demineralized Water Tank, Pump House, and RO Unit Page 5.14-14 Rev. 2 5.14.7.1 Revised Results and Recommendations The CPFMs evaluated for the Demineralized Water Tank, Pump House, and RO Unit are presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

CPFMs 3a and 14a for the Demineralized Water Tank, Pump House, and RO Unit are not associated with Key Distress Indicators.

Results of survey data, ground well monitoring data, and field inspections do not indicate signs of significant structure movement or other adverse effects that could be attribute..

o these CPFMs.Therefore, assuming that no further concerns are identified oug rn ring program for the Demineralized Water Tank, Pump House, and RO Ut ion 5.14.6 and continuing until December 31, 2011), these CPFMs wi, f moved to rant of the matrix representing "No Further Action Recommended Relate ete 29 Low Confidence (Insufficient Data)CPFM 14a 5.14.7.2 Concli 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 modifications to remove them from the list for any particular structure.

Because all CPFMs for the Demineralized Water Tank, Pump House, and RO Unit other than CPFMs 3a and 14a had been ruled out prior to Revision 1, and Priority 1 Structures Page 5.14-15 Demineralized Water Tank, Pump House, and RO Unit Rev. 2 because CPFMs 3a and 14a have been ruled out as a result of the Revision I findings, no Triggering Mechanisms and their associated PFMs will remain credible for the Demineralized Water Tank, Pump House, and RO Unit. Therefore, HDR has concluded that the 2011 Missouri River flood did not impact the geotechnical and structural integrity of the Demineralized Water Tank, Pump House, and RO Unit because the potential for failure of this structure due to the flood is not significant.

r Section 5.15 Raw Water Piping Priority 1 Structures Page 5.15-1 Raw Water Piping Rev. 2 5.15 Raw Water Piping 5.15.1 Summary of Raw Water Piping Baseline information for the Raw Water Piping is provided in Section 2.0, Site History, Description, and Baseline Condition.

The Raw Water Piping is a once-through cooling water system thatjzem at the component cooling water system. The Raw Water Piping also provides direct , "h the component cooling water piping to selected safety-related co ts in th at the component cooling water system is unavailable.

The Raw Water Piping serves as a conduit for discharging water r from v rces.The system is composed of four motor-driven pumps, two strain sets, valves, instrumentation, and controls.Two 20-in. raw water pipes are routed between the In n the so er of the Auxiliary Building.

Alignments of the given pipes own on awings no able 5.15-1.Raw water pipes are carbon steel pipe (Attachmemi.,1l8, OPPD -W-101).The first raw water lineis routed out the ýsid the ctu oint where it clears the the Discharge Tunnel and other Intake re utility li re it b -900 and runs about 88.8 ft toward the Service Building.

It the another 90 nd is to the south, parallel to the Service Building.

The alignment i the Service Bed to avoid Fuel Oil Tank 10 and the Undergr 'D.! ank. A ing the Unde ' able Bank north of MH-5, the r wtI' eei i een the ie Building and the Turbine Building South Switchya r clearing of the Building, it is routed to the south side of the Auxiliahr..

ding at the south ier.T d 20-in. raw water line exils south side f the Intake Structure adjacent to and east of oth ting utilities.

The raw wa ne and adjacent utilities are concrete-encased together and routed ýsouth. Once the utilities

ý the Discharge Tunnel (see 11405-M-312 and 314), they make a 45 o the southwest andrew a path that passes the southeast comer of MH-5. Once beyond the 1 atsi JvlI-5, the enca tility lines are routed to. the west, and the raw water line continues alongeint to t hwest. When the raw water line reaches a point south of the Turbine Building itc --it makes a 45' bend and is routed to the west, parallel to the south face of the Service Bu *l a outside of the limits of Turbine Building South Switchyard.

At a point 18.5 ft west ofth n of where the first raw water line enters the Auxiliary Building, it makes a 900 bend to the noifh and extends to the Auxiliary Building and penetrates into the building at el. 996 ft.

Priority 1 Structures Raw Water Piping Page 5.15-2 Rev. 2 5.15.2 Inputs/References Supporting the Analysis Table 5.15-1 lists references provided by OPPD and other documents used to support HDR's analysis.Table 5.15-1 -References for Raw Water Piping Document Title OPPD Document Date Drawing No./Number Page (if applicable)

Number(s)Yard Piping Sheet 1 10752 .1 ....405-M-312 Yard Piping 10753 'U405-M-313 Yard Piping Sheet 3 10754 4, T -M-314 Yard Piping 10755_ wn-1 Design Basis Document SDBD-AC-RW-101 06 Naval Facilities Engineering Command, Design Manual 7.01, Soil Mechanics 1%1114, All ýýI Detailed site observations-field reports, field notes Piping are provided in Attachment

8. A Observed performance and pertinent background

• Groundwater was observed flowing bast condensate drain pipes not designed ercept history dating back to 1997. Tmine Build Intake Structure and the Service I g.* Settlement f .~rnrnrsin,.the Main Builc heckli -eaw Water are as'ient pf of the'ruter. Thi EFmBuilding from floor and ndition has a recorded dor and utilities between the MNUM-e Turbine Building, has been Building are west of the corridor and 0 S 0 S R Dam surrounding fility cro : .Mr alignment of the Raw Water Piping.ua Dam failed for a sh od of to being damaged, allowing floodwater to ente inside the Auai r. Surfac above the Raw Water Piping were inundated ter when the facility failed.af&e the perimeter of th, Nae men macement Aqua Dam were inundated for an extended period.igj~kin the corridor (p4' i.arlve and pedestrian areas between the river and the Service r Building) h~~~'- hibited distre~i ludng' cracking, slab settlement, and undermining.

However, most of the pam t crza. o ýo the other conditions could be pre-existing conditions due the age and use of tlrfaeg -There is a hole in ti_ ent and void area beneath the concrete slab north of the Security Building and east-southst of MH-5. The hole and void area are outside 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 approximated as a 4-ft-diameter-by-0.8-ft-deep void as measured by a tape measure through the hole. The void could be attributed to subsurface erosion.

Priority 1 Structures Page 5.15-3 Raw Water Piping Rev. 2* The hole in the pavement is near the observed discharge point of a pump operated prior to the removal of the Aqua Dam. The void could be attributed to scour created by the discharge of the pipe operating for an extended period in one place.0 Fire Protection Cabinet FP-3C north of the Security Building and east-southeast of MiH-5 is located in proximity to the pavement failure and void area. The fire hydrant was tested September 13, 2011 (reportedly), and failed. According to OPPD operations personnel testing FP-3E during site inspections, the base of FP-3C cracked when the valve was opened. e fire hydrant was shut down, and the access cabinet was tagged out. The cause of failure w o at the time field observations were made.* Pavement slab settling was observed northwest of the Intak -ture of the abandoned acid tank.* A hollow-sounding pavement area was noticed east of the g tr .k" The fire hydrant located in FP-3E was being tested on Septe .011, duri investigations.

No operational problems were observed dunin -on site.* OPPD operations personnel testing the fire hydrant at FP-3E e 13, 2011, questioned about other fire hydrant tests. The OPPD employee questi ted that no p a ems were observed for the fire hydrant at FP-3D during te e informa' he problem at FP-3C, noted previously, was gathered at this tim 5.15.3 Assessment Methods and Procedures 5.15.3.1 Assessment Procedur c ish Assessments were made by wal! e Raw Wa ping syst.. lignment and observing the ground surface overlying t ound piping ace.asseesass t included using a 4-ft-long, 0.5-in.-dia 0 eel-tipped fib, tle soil probe to hand probe the ground q tlihe utili ents and adjac teas to determine relative soil stree[ ocusei tifying conditions indicative of potential flood-related in 16 or dam utility s :-Ground surface conditI rlying ediately adjacent to the utility and its backfilled trench includi .,, subsidence or settlement, lateral spreading, piping, and soil, engineered fill, and/or limestone gravel pavement) as 0 in subsurface system components (manholes and concrete 0 Elove-grade system features and equipment* Variance fi~m fiiffil installation conditions including settled, tilted, or heaved syst features and eqqjipment

• Operation of the system and appurtenant equipment (i.e., is the system operational?)

em Priority 1 Structures Raw Water Piping Page 5.15-4 Rev. 2 Additional investigations were performed to further characterize the subsurface at the facility including areas where conditions indicative of potential flood-related impacts or damage were observed.

These included the following non-invasive geophysical and invasive geotechnical investigations.

• GPR. (Test reports were not available at the time of Revision 0.)* Seismic surveys (seismic refraction and refraction micro-tremor) available at the time of Revision 0.)Geotechnical investigations including test borings witt4 id laboratory tests. Note that OPPD required vacuum ion test holes to avoid utility conflicts.

Therefore, test s will R the upper 10 ft of test boring logs. (Test reports we ava Revision 0.)5.15.3.2 Assessment Procedures Not Completed Assessments of the Raw Water Piping that were not.., leted inc* No excavation to inspect underground sY nsw* No video inspection of the system was leted." Inclinometer readings along the river will prov 5.15.4 Analysis Identified PFMs were initially revie iscussed in n 3.0. n preliminary information available D data files a:. wa Eleven PFMs associat-d~awth five di riherina Mec ere dc.(Test reports were not itial review considered the lk-down observations.

etermined to be ussed in Section 3.6. The remaining PFMs were riew for each structure, the structure observations,& and available survey data were analyzed, a ftWin 5.15.4.1.

The CPFMs carried forward for Ruled Out Prior to the Completion of the Detailed The ruli will not",.he Not Significant/High Confidence category and for clarity fial for Failure/Confidence matrix.Triggering Mai -Surface Erosion CPFM 2a -Ui@Ermining shallow foundation/slab/surfaces CPFM 2c -Undermined buried utilities Reason for ruling out: No surface erosion was observed along the surface overlying the raw water alignment.

In addition, only localized and limited surface erosion was observed on the ground surface across the facility.

The raw water system is constructed below frost depth, and sufficiently below potential scour depths indicated by erosion features observed in other areas.

Priority 1 Structures Page 5.15-5 Raw Water Piping Rev. 2 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 Reasons for ruling out: " Soil supporting and surrounding the raw water lines ha, een us etted. The peak flood elevation prior to 2011 was 1003.3 ft, which o l in und elevations above the raw water alignments are in the range of -to 1004 w water lines were installed as part of the original plant construc the ith the exception of possible trench backfill above repair are back e the raw water lines has been saturated or wetted over the cours e ost 40 years." The climate of the region includes times of snow accrring therwin seasonal wet periods (springtime rain events), which can be s nt and exten a period of days. Site soils are subjected to saturi luring sno eriods and during extended rainstorm events. Most trenches e ckfill exhi of subsidence within I or 2 years. After an almost 40- erio b ill o6 aw water lines has been wetted and saturated nu s times.Triggering Mechanism 10 -MachineVi on- Li CPFM I 0a- Cracked slab, di- tial em allow fion, loss of structural support" CPFM lOb -Displaced OR e/broken co s vi r the fa rbines in the Turbine Building, pumps in the Intake cture, or other cc .f equiprm ave historically occurred, and no indications of eeCPFMs areevi are ev ' ".Pumps used on site during floo d not cause ground or structure vibrations ufficient to initiate soil li"I ction. Visible indications of liquefaction were not observed Xmt und the areas where the ps were operating, and no occurrences of liquefaction wereto HDR.Nre movements..

t:.'ktive of soil liquefaction and resultant settlement were obs ..... o structurN 4 I.ing or lateral movements were observed.Triggering .sn~ .-Loss of Soil Strength due to Static Liquefaction or Upward Seepage CPFM I la -CIcaked slab, differential settlement of shallow foundation, loss of structural support CPFM 1 lb -Displaced structure/broken connections Reasons for ruling out:* The structures did not have evident signs of distress identified during the field assessments." Liquefaction was not observed at the site.

Priority 1 Structures Raw Water Piping Page 5.15-6 Rev. 2 Triggering Mechanism 12 -Rapid Drawdown CPFM 12a -River bank slope failure and undermining surrounding structures CPFM 12b -Lateral spreading Reasons for ruling out:* The structures did not have evident signs of distress identified during the field assessments.

• Slope failure was not observed at the site.* River stage level had receded and stabilized as of Octo,.- 4, 0 As of October 11,2011, groundwater elevations ha , e we ilize to at least a partial degree.The river bank is armored and has historically prot d e sting river bank.Triggering Mechanism 13 -Submergence CPFM 13a -Corrosion of underground utilities CPFM 13b -Corrosion of structural elements Reasons for ruling out: " There are no flood-induced changes to Unatur," The raw water piping system is below ilesigi Groundwater elevations con by qsour*precipitation, and winter sn would be i appurtenant improveme h uned ele withstand the e ondwater anhr*Accni kh the rsaw water pipe system.wte facility.p, 1 s, 1 percolation of storm Sct the piping system and designed and installed to MdEv", vett-.m nrp ne-mmpri tn inrlnrl.-

Apý'bends in the system. Thrust blocks are normally where groundwater and wetted soil is expected."lbd in confiJ gradation ofthe'"i'The raw water system corrosive soil conditio structural backfill, and corrosion due to ing Mechanism 14 -S14a -Heaving, cn, Effects or displacement

• The Raw"WR 4 R' "is installed below the depth of frost penetration.

• Conditions

• h,'-'changed due to flood conditions.

5.154.2 Detailed Assessment of Credible Potential Failure Modes The following CPFMs are the only CPFMs carried forward for detailed assessment for the Raw Water Piping system as a result of the 2011 flood. This detailed assessment is provided below.

Priority I Structures Page 5.15-7 Raw Water Piping Rev. 2 Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3a -Undermining and settlement of shallow foundation/slab/surfaces (due to pumping)CPFM 3c -Undermined buried utilities (due to pumping)This Triggering Mechanism and CPFM could occur as follows: multiple potentially connected seepage paths existed in the soil backfill at the site, including soil backfill in utility trenches, granular trench bedding, building floor drains with open/broken j , and pre-existing defects/voids under pavement.

The paths are exposed at so lo ver floodwaters (e.g., a hole in the ground north of the Security Buildin A ne .eepage paths is connected to several pumping sources: the sump pit in rbine anhole MH-5, and a series of surface pumps along the interior perime the p a pumps were operated for an extended period, maintaining a head di e seep networks.Gradient was sufficient to begin erosion of surrounding soi ge is unfilt" erosn continues unarrested.

Erosion extends out, intercepting t ¶ of utility tren including the Raw Water Piping System. Voids are create de .vement and utility trench walls or pipes. The potential damage inal es settleme %Pe or thrust blocks.Settlement can overstress a pipe that is corrode ia pipe to ',can cause the displacement of a thrust block, which, in tu ca rare of a pip ting under pressure.Below are field observations and data tha port th looPFM:* The raw water alignments e.ustallatio

• MH-5, located within the 10 Sam Permet l s r the duration of flooding.This created a head di Raw water lii close proximity to MH-5 and also under ound cable b .cnnected to SThe,-4) nto MH-d 3 k i .bserved on mul ip field visits. Sources of the water* area inside he'pf -ter of te a Dam was pumped dry, which created a hydrostaff betwee ide and outside of the Aqua Dam perimeter.

The area within the peri of the am was pumped from several locations, creating points toward w derground piping and subsurface flows would tend to flow."idaesadptni l p tocation were observed beneath the concrete slab just northSecurity Building (etA-utheast of MH-5) and directly west of the Security Ba! conversati~l

¶hh the OPPD operations employee testing FP-3E on September 13,2 located northeast of the Security Building, was tested that day and faile .... the OPPD operations employee, when opening the valve to test the 1 hydrantthe cked and leaked, and the valve had to be closed. The access cabinet was tagged out lr repair at that time.* Fire hydrant FP-3D has also been marked with an impairment tag according to October 7, 2011, field observations.

The tag states that there was extensive leakage when the isolation valve was opened.* Concrete areas in the corridor (paved drive and pedestrian areas between the east fence line and the Service Building) have exhibited pavement distress including cracking, slab settlement, and undermining (as evidenced by hollow-sounding pavement areas).* The Turbine Building sump pit was pumped continually during the 2011 flood. The five pipes connected to this sump pit are floor drain and condensate system flush drain pipes.

Priority 1 Structures Page 5.15-8 Raw Water Piping Rev. 2 Since this is a floor drain system, no infiltration of ground water should occur in the system.The infiltration of groundwater into the system indicates an open flow path of some sort. A record of this drainage issue dates back to 1997.An area of apparent pavement settlement, located in the driveway corridor west-northwest of the Intake Structure overhead door, is near the northern raw water alignment.

Below are field observations and data that indicate these CPFMs are unlikely:* Sediment accumulations and small fish were observed at the of~uanhole MIH-5 at the time MH-5 was being emptied (on September 14, ane associa with this CPFM. The manhole was uncovered when qua Da and the area was flooded. Sediment and fish could have entered the ole wit rs as a result of the Aqua Dam failure. Thus, MH-5 might not be a i ermm oint of subsoil piping.* Alternatively, the observed hole in the pavement no urity Buildi been developed by outflow from the surface pumps a.i& n iated with t Temporary surface pumps were pumping water back into the n C hoses place ver the Aqua Dam. One of the discharge points observe 4ee photos).Concentrated discharge flow might have eand create bserved hole.The following table describes observed di indicato data that uld increase or decrease the potential for degradation ass d with ,Ra Water system.eRa ae ytm Adverse (Degradation/Direc-i lwar -Favora radation/Direct Impact More Lik FloodwA-,-

Impact Less Likely)Electrical MH-5 was pumpep lly during "i the flood event and created a p -uce for u nd e rga59-fi z _& 0 Aw to0wa Pae" ý 1MRl at mufkl'7 ations betweun e Stru d rvice Building.

Th e is loca 10e same narrow corridor.

_AF-lectrical MH-5 was pumpedfififually durime'flood. Fire protection the electrical , N banks that connect to the m! le.,T4 0-hine Building sump pit),W history of g d inflows. Flood cd6i ifins increased the h0 k ead of waterAx,$0ig to the sump. __Fire Hydr 3C an .have both failed during testtection system subsequent to .'fi cs.,e of floodwaters from the site. The fire H ts noted are located to the north and south of tie Intake Structure.

Data Gaps:* The extent of the subsurface erosion is not well known at this time.* Geophysical investigation reports to evaluate data related to the raw water system.* Seismic Survey (refraction/tomography and refraction microtremor).

Priority 1 Structures Raw Water Piping Page 5.15-9 Rev. 2 Conclusion Significance Potential for Degradation/Direct Floodwater Impact The field observations indicate that the trigger to these CPFMs might have initiated in close proximity to the Raw Water lines. Multiple indications of subsure distress are located along the corridor between the Service Building and the Intake Structur vement slab settlement, undermining (as evidenced by a hollow-sounding pavem 'a), n the pavement with visible undermining were observed in the field. F water in and impacts are likely causes for the distress and failures observed in t d.Fire hydrants to the north and south of the Intake Structur'subsequent to the subsidence of floodwaters from the site.to the north and south sides of the Intake Structure and arn hydrants.The raw water line also runs in close proximi Building.

Subsurface erosion due to the Tu uildinm Refer to the discussion of Key Distress In #1 in So With indications of distress throug t the the Implication The occurrence of these Ca large scale c exists.IO'd areas that would induce pipe Therefore, the implication of the hfiere are multiple elements seCPFM'Rhcluding the inflow of water into MH-5 during R3&,201 1 flood, the hole in the ment north of the Security Building, and the settled ent section in the corrid Te hydrant failures, and groundwater drainage to the Turbine B ý*sump. However, ev. the confidence is high that there are multiple distress e extent and to Io i

of these CPFMs on the raw water system is not fully The data at h' i~~~Ciiff cent to rule out these CPFMs or to lead to a conclusion that subsurface erost6Za§n"hs[&hdermined the Raw Water Piping system. Additional geophysical data are needed to help ermine the possible occurrence of these CPFMs and whether they could impact the Raw Water Piping system.Therefore, the confidence in the above assessment is low, which means more data are necessary to draw a conclusion.

Summary For CPFMs 3a and 3c, as discussed above, the potential for degradation is high because distress indicators exist in close proximity to the system. This degradation in the region could have Priority I Structures Page 5.15-10 Raw Water Piping Rev. 2 caused erosion that impacts the integrity or intended function of the structure.

The combined consideration of the potential for degradation and the implications of that degradation to the system puts it in the "significant" category.

The data currently collected are not sufficient to rule out these CPFMs. Therefore, the confidence in the above assessment is low, which means more data or continued monitoring and inspections might be necessary to draw a conclusion.

Triggering Mechanism 3 -Subsurface Erosion/Piping A CPFM 3d -Undermining and settlement of shallow fw tio o river drawdown)CPFM 3f- Undermined buried utilities (due to riv ,do These CPFMs are similar to CPFMs 3b and 3c, but instea t ping, the gr

• s created by rapidly receding river level...... .r e e -r p ---r The Triggering Mechanism and CPFM could then occur as follows leelii s than pore water pressure in the soil can dissipateen t is create noves soil into existing defects and enlarges voids under al ench wal ility pipes.Dependent on the extent of the voids create g 'acts mi- ude the fofll : trench subsidence, unsupported pipe sections, lections 'and even-possible impacts on adjacent improvements or utilities Below are field observations and dt at suppo I ikelihood thmse CPFMs:* The Raw Water Piping j d close to the ouri ank.Below are lia-,-. ations a taor site conditio ridicate these CPFMs are unlikely:*',system t from the River Bank. This offset from the river reduces the k d that rap wdown and related bank failure will impact the A stem.4-7 Soils in the area of the MEWater PipinqRr stem and to the east are backfill materials that were placed and compactIN m ing construction of site improvements and therefore would expected to be less susc fle to rapid drawdown impacts. (Structural fill materials areto be homogenousaind of a structural nature. Compacted in. place, they shouldomogenous soil ri1 ith no expected weak planes or layers conducive to form S aths through.otl.

f this 'eVPFM were not observed during the most recent site inspection on Oct .o .....1Uer 7, 2011.SThe River B a ored and protected.

The following table describes observed distress indicators and other data that would increase or decrease the potential for degradation associated with these CPFMs for the Raw Water Piping system.

Priority 1 Structures Page 5.15-11 Raw Water Piping Rev. 2 Adverse (DegradationlDirect Favorable (DegradationlDirect Floodwater Floodwater Impact More Likely) Impact Less Likely)Floodwaters were at a high level for an USACE reduced Missouri River Mainstem System extended period, which allowed surrounding releases to 40,000 cfs on October 2, 2011. River soils to become saturated.

levels corresponding to the 40,000 cfs release rate stabilized at FCS on October 4, 2011.River bank is armored and has been protected in previous floods. i Data Gaps: ., 0 Observations of the riverbank following drawdown to nqmver 0 Geophysical investigation data to address observed coppprri 4 Conclusion Significance Potential for Degradation/Direct Floodwater Impact The potential for degradation exists since rive dequate se CPFMs to occur. However, USACE reduced Missouri _fMant stem releas 0,000 cfs on October 2, 2011. River levels correspondi' o the 40,O 0 ase rate sti-lized at FCS on October 4, 2011. Groundwater levels hav. s started.tab'z tween the termination of drawdown and the time of Revisio Teu erosion due to river drawdown decreas me ue to trization " ngoundwater elevations and river elevations.

The poten or degradatio I decreas.1th time.Implication The w lkely only affect the utility installations near the river.ve aw fafi.. syseegzated away from the zone of influence of thesewith the excepti ].f e supply #.,tat connect to the Intake Structure.

Thus, the most important rPonents of are at the point of greatest risk from these WAIfbundwater ver elevations stabilize, the potential head differential between thaffP¶,l decrease, and the pass ity of subsurface erosion will also decrease.

In addition, the stabifiiý5 er embankmen

-' ifes the likelihood of these CPFMs.The implic0 othe. s affecting the Raw Water Piping system is considered low.Confidence The data at hand are not sufficient to rule out these CPFMs or to lead to a conclusion that subsurface erosion has undermined the Raw Water Piping system. Therefore, the confidence in the above assessment is low, which means more data are necessary to draw a conclusion.

Summary For CPFMs 3d and 3f, as discussed above, the potential for degradation is considered low. The combined consideration of the potential for degradation and the implications of that degradation to the structure puts it in the "not significant" category.

The data currently Priority 1 Structures Raw Water Piping Page 5.15-12 Rev. 2 collected are not sufficient to rule out these CPFMs. Therefore, the confidence in the above assessment is low, which means more data or continued monitoring and inspections are necessary to make a final assessment.

5.15.5 Results and Conclusions The CPFMs evaluated for the Raw Water Piping are presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in th aluation.* Further forens sti gati d'physical modifications are recommended to address CPFMs 3a, 3c, 3d, and 3 ffM NR AM'weWir Piping. CPFMs 3a and 3c are associated with unfiltered flow of groundwater into t 4 oIoqp- Building basement drain piping system (Key Distress Indicator

1. 1).These recommendatioire described in detail in Section 4.1.3. CPFMs 3a, 3c, 3d, and 3f are associated with the distress in and near the Paved Access Area between the Service Building and the Intake Structure (Key Distress Indicator

1. 2). These recommendations are described in detail in Section 4.2.5.* Monitoring of groundwater well data and a review of the geophysical data when available should be done. The results of these reviews will be used to increase the confidence in the assessment results. 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.

Priority 1 Structures Raw Water Piping Page 5.15-13 Rev. 2 Observation of new distress indicators might result in a modification of the recommendations for this structure.

Continued monitoring is recommended to include a continuation of the elevation surveys of the previously identified targets on this utility 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 will be used to 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 the writing of this version of the Report, groundwater A s had not yet stabilized to nominal normal levels. Therefore, it is possible that new distr rndi -c0 ,,still develop. If new distress indicators are observed before December31, 29 prop .'R personnel should be notified immediately to determine whether an immedia ection ...ndcaor sa r ent should be conducted.

Observation of new distress indicators might re ;a icatF I h e recommendations for this structure.

Review geophysical and geotechnical reports to evaluate the d. .e pertain to WV atur System. Y" Make additional river bank inspections to evaluate whether signs of fa, 3c, 3d, or"eA* Install inclinometers to monitor the river bank." Perform a detailed analysis of the pavement subgta' lignment avement in the corridor between the Intake Structure and the S e Buildi , _ laced.5.15.7 Updates Since Revision 0 Revision 0 of this Assessment Report presented the results of preliminary as incomplete in Revision 0 because th, Priority 1 Structures was not complI includes the resuk-WO aM-anal foren described bel A1 DI 1Fn Octob1.eO

11. Revision 0 ti rrity 1 StrM re. These assessments were iGO d/or m,4 ring for most of the I d R, vision of this Assessment Report Lnd mormonng to date for this structure as the Raw Water Piping System for Revisions I'.1 Additional following additional 2 of this Assessment 0 0 0 of KDI #1 forensi}i-ifestigation (see Section 4.1)ofKDI #2 forensition (see Section 4.2)g,.roundwqt.

.-onitoring well and river stage level data from OPPD.S 0 0 Field obb2 ionsf,& e 'iiver bank (see Section 5.25).Results offdiik deflectometer investigation by American Engineering Testii (see Attachl ,16 Results of geop ysical investigation by Geotechnology, Inc. (see Attachment 6).Results of geotechnical investigation by Thiele Geotech, Inc. (see Attachment 6).Data obtained from inclinometers by Thiele Geotech, Inc. (see Attachment 6).Results of continued survey by Lamp Rynearson and Associates (see Attachment 6).ng, Inc.5.15.7.2 Additional Analysis The following analysis of additional data was conducted for the Raw Water Piping System:

,Priority 1 Structures Page 5.15-14 Raw Water Piping Rev. 2" Groundwater monitoring well and river stage level data from OPPD.Data shows that the river and groundwater have returned to nominal normal levels.* Field observations of river bank No significance distress from the 2011 Flood was observed." Results of failing weight deflectometer investigation byte n ring Testing, Inc.Falling Weight Deflectometer and associated GPR _ag perfo e Paved Access Area identified anomalies such as soft clay and bro F1 agroun truthing of the investigation results were performed KDI .nal investigations." Results of geophysical investigation by Geotechnolog nc.Seismic Refraction and Seismic ReMi tests p. .round the perimeter of the power block as part of KDI #2 identified dn s hat cold 1, soft clay, loose sand, or possibly voids.Results of geotechnical investigation iel e Gex IInI Six test borings were drilled contimous ing of th soi encountered, to ground truth the Geotechnology, In mic investi results a.:rt of the KDI #2 forensic investigation.

Test Nwere located to' ate ýep anomalies identified in the seismic investigation.

T boring data did A piping voids or very soft/very loosji,at 1 iative of subsu eosion/piping or related material' of the SPT and Pa t results OEbted for this Assessment Report were compared to similar data from nu is other ge j nical investigations that have been conducted on the FCS site in prevo rs. S This comparison did not identify substantial changes to the soil strength and stiffn oEi er that time period. SPT and CPT test results were not i ormed in the top 10 fe SOprotect existing utilities.

D~"- tt ...Inclinometersae cor Mtafm. a ...... " " -, compared to the original baseline measurements, have not exCOMheaccurae.,_a

.of the inclinometers.

Therefore, deformation at the monitored location of the instrumentation has not occurred.* Results of cohffmd 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, deformation at the monitored locations, since the survey baseline was shot, has not occurred.Updates to assessment procedures not completed are outlined in Section 5.15.3.2.

Excavation to inspect underground systems is included with the KDI#2 investigation.

Video inspection of the system was not completed and is not planned due to the expected low value of data produced with respect to addressing these CPFMs.

Priority 1 Structures Page 5.15-15 Raw Water Piping Rev. 2 Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3a -Undermining and settlement of shallow foundation/slab/surfaces (due to pumping)CPFM 3c -Undermined buried utilities (due to pumping)CPFMs 3a and 3c for the Raw Water Piping System are associated with Key Distress Indicator

1. 1. Section 4.1 presents the results of additional forensic investigation that was conducted to ascertain whether these CPFMs could be ruled o The results of the additional forensic investigation show that, assuming t ,mp -tat of the physical modifications recommended for KDI #1, these CPF led refore, assuming that no further concerns are identified through the pthe Raw Water Piping System (discussed in Section 5.15.6 and co u e 1, 2011), these CPFMs are moved to the quadrant of the matrix repr o Recommended Related to the 2011 Flood." -Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3d -Undermining and settlement of shal f, drawdown)CPFM 3f- Undermined buried utilities I v CPFMs 3d and 3f for the Raw Water Pipi stem arIR#2. Section 4.2 presents the results of ad al foret-'ascertain whether these CPFMs c -e out.investigation show that these C e ru ed ou0 ere concerns are identified throu onitoring pret fc (discussed in Section 5.15. tinuing until to the qua ft e matrix rep ting "No Furth to river N-vith Key D-istress Indicator-that was conducted to i".l litional forensic Mining that no further Water Piping System 1 1), these CPFMs are moved ,ommended Related to the Priority 1 Structures Raw Water Piping Page 5.15-16 Rev. 2 5.15.7.1 Revised Results and Recommendations The CPFMs evaluated for the Raw Water Piping System are presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

,&,,assessment of the FCS OiMciures, the first step was to develop a list of all Triggering NI 41ms and PFMs that c02111have occurred due to the prolonged inundation of the FCS site e 2011 Missouri.jV.ir flood and could have negatively impacted these structures.

The ne...~,p)was to use datag-,or various investigations, including systematic observation of The nestructrt a, to use ..the struc vser time , er' to eliminate the Triggering Mechanisms and PFMs from the list or to recomi rin.vestigation and/or physical modifications to remove them from the list for any par ucture. Because all CPFMs for the Raw Water Piping System other than CPFMs 3a, c, and 3f had been ruled out prior to Revision 1, because CPFMs 3d and 3f were ruled out using the results of the KDI #2 investigation presented in Section 4.2, and because CPFMs 3a and 3c will be ruled out when the physical modifications recommended for KDI # I in Section 4.1 are implemented, no Triggering Mechanisms and their associated PFMs will remain credible for the Raw Water Piping System. 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 5.16 Fire Protection System Piping..77 Priority 1 Structures Page 5.16-1 Fire Protection System Piping Rev. 2 5.16 Fire Protection System Piping 5.16.1 Summary of Fire Protection System Piping Baseline information for the Fire Protection System Piping is provided in Section 2.0, Site History, Description, and Baseline Condition.

The Fire Protection System Piping has two vertical turbine-type fire u ched for 2000 gpm at 125 pounds per square inch gauge (psig). One fire pump is drive er" and the other fire pump is driven by a diesel engine. Both pumps deliver scr and stra souri River water to the underground water-distribution system, which, in turn, s s the ter fire suppression systems, the interior hose stations, and the fire hyd -rd.During normal operation, the system is pressurized to 125 to 135 , eld at that p small pressure maintenance pump (jockey pump). The primary p ospump frequent operation of the main fire pumps. The pressure maintenance pumn omatically s and stopped based on system pressure.

The water distri b,,.:stem consist erground piping that delivers water to the following: " Yard hose and hydrant houses" Wet pipe sprinkler systems ...., ,* Dry pipe sprinkler systems" Preaction sprinlder systems* Deluge/water spray systems .-The undergroundy

-main sys rovided with p -type sectionalizing valves and underground a,2 es withe ;,I boxes (curb v es) to facilitate the isolation of portions o£t~fne or ithout interrupting the supply to the remaining system.,4E

$Rater suppresslb st is pr 'ith an outside screw and yoke (OS&Y) gate val h connects ntemal p. Each 6-in. lateral connecting the hydrant to tikna loop has a valve instailtfo allo is on of individual hydrants for maintenance pu4% ydrants are placed at 300-ft intervals around the yard main loop andni1 50 ft from buildings.

X;ng of the fire water distribution system is prevented by burying fh,"Je. V~g below the frost linevtaid by routing indoor piping through heated areas. The.dergr a main loop is tcted of 12-in. and 10-in. transite (asbestos cement) pipe and cast (ductile iRt fwlth g 5.16.2 Inputs/Refe irting the Analysis Table 5.16-1 lists referen , rovided by OPPD and other documents used to support HDR's analysis.Table 5.16-1 -References for Fire Protection System PiDing Document Title OPPD Document Date Drawing Number Number/(if applicable)

Page Number(s)Underground Piping Extension 44740 8/23/1990 FC-UG-1A Underground Fire Loop 41428 Unknown E-4182 Fire Protection SDBD-FP-!

15 3/9/2011 All Priority 1 Structures Page 5.16-2 Fire Protection System Piping Rev. 2 Table 5.16-1 -References for Fire Protection System Piping Document Title OPPD Document Date Drawing Number Number/(if applicable)

Page Number(s)Naval Facilities Engineering Command, 9/1986 All Design Manual 7.01, Soil Mechanics I I I _I Detailed site observations-field reports, field notes, and inspection chec ists-for the Fire Protection System Piping are provided in Attachment 8.Observed performance and pertinent background data are as foll : _" The fire protection loop and lateral system crosses multiple ines a' he facility.* Groundwater was observed flowing into the basement sump o ine BuildihR n floor and condensate drain pipes not designed to intercept mdition has a R history dating back to 1997. The Turbine Building is west.----

con---. utilities

.&a between the Intake Structure and the Service Building.* Settlement of a column in the Maintenance Buildin e Turbine g, has been documented.

The Turbine Building and the Mai are west orridor and associated utility alignments within the corrido " The Aqua Dam surrounding the facility cross, e alignm protection piping at multiple locations, including the following:

-Fire supply lines from the Intake lre ing 'rd mam* gstem.-The fire supply line feeding FP- '-The fire supply lateral feedinat r_g- re hydran no ast of Warehouse.

-The building fire supply lin e ew Warehou-The fire s- .that is rou L, .g the west si 6ew Warehouse and to FP-31 and-Th ire loo.... .fire su .* extends to the west toward the Welding Fab Shop."

to the so the w e .f the facility, the Aqua Dam crosses the main j.' loop line northwest o , Rad Wast ..i..ng.ong the west side of the : it appears hat the Aqua Dam was located over the top of a ,4a gitudinal alignment of a s :line that was routed to FP-3K.-Warehouse fire suppl i.-ain loop where th leg extends to the south toward the site perimeter/security fenc-~~3-The yarr" i.1oop crossft1, location of the Aqua Dam where the line runs north of the Security B .2,,* The Aqua Dam fa. leh rt period of time due to being damaged, allowing floodwater to enter the area inside the perimeter.

All surfaces above the fire protection piping were inundated when the fact ity Aqua Dam failed.* Areas outside the perimeter of the replacement Aqua Dam were inundated for an extended period." Concrete areas in the corridor (paved drive and pedestrian areas between the river and Service Building) have exhibited distress including cracking, slab settlement, and undermining.

Some of these conditions are reported to be new, although pavement spalling and cracking is likely to have existed prior to the flooding." A hole in the pavement and void area beneath the concrete slab is north of the Security Building and east-southeast of MH-5. The hole and void area are outside the perimeter of the Aqua Dam that surrounded the facility.

The pavement failure occurred at the intersection point of pavement Priority 1 Structures Page 5.16-3 Fire Protection System Piping Rev. 2 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 approximated as a 4-ft-diameter-by-10-in.-deep void as measured by a tape measure through the hole. The void might be attributable to subsurface erosion." The hole in the pavement is near the observed discharge point of a pump operated prior to the removal of the Aqua Dam. The void might be attributable to scour created by the discharge of the pipe operating for an extended period in one place." The fire hydrant located in FP-3E was tested on September 13,2011, g site investigations.

No operational problems were observed during the time on si* Fire Protection Cabinet FP-3C north of the Security Buildi east-s of MH-5 is located in proximity to the pavement failure and void area. The rant w September 13, 2011 (reportedly), and failed. According to OPPD operatio so st during site inspections, the base of FP-3C cracked when the valve was o e fire hy as shut down, and the access cabinet was tagged out. The cause of fa unknownn at fi observations were made. I" OPPD operations personnel testing the fire hydrant at FP-3E on Septe -3, 2011, wer questioned about other fire hydrant tests. The OPPDQ questione d that no problems were observed for the fire hydrant at FP-3D durinn iigformatio e problem at FP-3C, noted previously, was gathered at this* Fire hydrant FP-3D has also been marked withS "n e.i ardingto.c ber 7, 2011, field observations.

The tag states that there A tensive dage e isolation valve was opened.Pavement slab settling was observe est of the e Struc n" east of the abandoned acid tank.* A hollow-sounding pavement noticed east o lding truck dock.5.16.3 Asses 1, sandPP udes 5 pshed were madeng firektection system alignment and observing surface atures of the system, post i tor valves, fire cabinets, and the ground surface overlying the g~er~ground pipe. The surfac assessment included using a 4-ft-long, 0.5-in.-diameter, 9l~~-~ipped fiberglass T-hand~fi1 probe to hand probe the ground surface along the utility and adjacent areas leltermine relative soil strength.

The assessment focused on identi nditions indicd, iof potential flood-related impacts or damage to the utility as follows:* Ground df ns overlying and immediately adjacent to the utility and its backfilled treii haficluding scour, subsidence or settlement, lateral spreading, piping, and heave* Soft ground surface areas (native soil, engineered fill, or limestone gravel pavement) as determined by probing* Water accumulations and flows in subsurface system components (manholes and concrete cable encasement pipes)* Damage to at-grade or above-grade system features and equipment" Variance from normal installation conditions including settled, tilted, or heaved system features and equipment" Operation of the system and appurtenant equipment (i.e., is the system operational?)

Priority 1 Structures Fire Protection System Piping Page 5.16-4 Rev. 2 Additional investigations were performed to further characterize the subsurface at the facility, including areas where conditions indicative of potential flood-related impacts or damage were observed.

These included the following non-invasive geophysical and geotechnical investigations." GPR. (Test reports were not available at the time of Revision 0.)" Seismic surveys (seismic refraction and refraction microtremor). (Test reports were not available at the time of Revision 0.)* Geotechnical investigations including test borings with d CPT) and laboratory tests. Note that OPPD required vacuum ion __ st 10 ft of proposed test holes to avoid utility conflicts.

Test reports wi not ad -conditions in the upper 10 ft of site and locations where shallow utili ' r ere not available at the time of Revision 0.)* Paved areas were evaluated with GPR and dynamic de ethods (i.e., ,eig deflectometer). (Test reports were not available at th e, ision 0.) " t 5.16.3.2 Assessment Procedures Not C Assessments of the Fire Protection System P following:

the* Assessment of subgrade condi replacement in the Paved Acc1, Structure.

Work in the area o the time of pavement and the Intake 5.16.4 Analysis Identified viewe ~si, ussed in Section-.O.

The review considered the..... '. .. ..... O ..!files and from initial walk-down observations.

Eleven E!tTsssocaianggeiNing Mechanisms were determined to be nong-. le" for all Priority I St es, as I e in Section 3.6. The remaining PFMs were c dgrward as "credible." edgn rev for each structure, the structure observations, and Its of available geotechnl1eophysical, and available survey data were analyzed, a n were ruled out as di sed in Section 5.16.4.1.

The CPFMs carried forward for detailed aRlmssemhent are discussed in Sdffin 5.16.4.2.5.16.4 i" oientiaI Failu des Ruled Out Prior to the Completion of the Detailed

, The ruled-out in the Not Significant/High Confidence category and for clarity will not be Potential for Failure/Confidence matrix., Triggering Mechanism 2 -Surface Erosion CPFM 2a -Undermining shallow foundation/slab/surfaces CPFM 2c -Undermined buried utilities Reasons for ruling out:* Minor surface erosion was observed south of the Auxiliary Building adjacent to and extending through the inside perimeter fence. This observed surface erosion is attributed to Priority 1 Structures Page 5.16-5 Fire Protection System Piping Rev. 2 multiple pump discharge lines that were pumped over the Aqua Dam. Discharge lines were tied to the fence, which held them continually in place over one general area. The location of the scour is in close proximity to where the yard fire loop is routed. The scour is approximately 0.5 ft deep and did not appear to affect anything beyond the immediate points of pump discharge.

'In addition, only localized and limited surface erosion was observed on the ground surface across the entire facility.

This PFM was discredited due to thedepth that fire protection piping is installed compared to the minor scouring that was o0 ed on the site.Triggering Mechanism 7 -Soil Collapse (first time w " CPFM 7a -Cracked slab, differential settlement ofiga 'ow fou s of structural support CPFM 7b -Displaced structure/broken connections

, CPFM 7c -General site settlement Reasons for ruling out:* Soil supporting and surrounding the Fire Pr ttem has bee ously wetted.The peak flood elevation prior to 2011 w .occurre i ." However, isolated cases of soil collaps d be app £#4recent wate~Jie replacements have been made. OPPD dition R s Id be required to check for isolated cases that might exist.w Triggering Mechanism 10 -

uced Li action CPFM 1 Oa -Cracked slab erential settle f shall undation, loss of structural support I r CPF is aced st"q .roken conned Rea~dfl& ru in.vibrations f6,b facility i( ig and various pumps) have historically occurred, and no these P are evident.-".,,Pumps used on site during.i011 flood were too small to cause ground or structure sufficient to initiekoil liquefaction.

Visible indications of liquefaction were ,w"abi.observed around the ara here the pumps were operating, and no occurrences of" se.-tion were reporte D R.No 9-r-ictae movemeat dIcative of soil liquefaction and resultant settlement were observ _ stuc q.king or lateral movements were observed.Triggering Mee 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 1 lb -Displaced structure/broken connections Reasons for ruling out: " The structures did not have evident signs of distress identified during the field assessments.

• Liquefaction was not observed at the site.

Priority 1 Structures Fire Protection Systema Piping Page 5.16-6 Rev. 2 Triggering Mechanism 13 -Submergence CPFM 1 3a -Corrosion of underground utilities Reason for ruling out: Underground utilities and structures are located below the design flood elevation for the facility.

Groundwater elevations controlled by Missouri River water elevations, percolation of storm precipitation, and winter snow melt would be expecte 0o contact underground improvements including constructed steel and concrete fncili e s such, steel and concrete site improvements are assumed to be desi , ith 'orrosive environment of groundwater and wetted soil. 04 A Triggering Mechanism 13 -Submergence CPFM 13b -Corrosion of structural elements Reason for ruling out:* The only structural elements of the system are pipe bends and pipe connection points.normally affect buried concrete thrust b -Triggering Mechanism 14 -Frost Effec CPFM 14a -Heaving, crushin disr, s em, Reasons for ruling out:* The fire protection pipin Iled below t1* com. re above are designe* C- cd,"n oht' ig A 911 installed at conditions that I-'st d to aecommod I flood.conditioi penetration.

The system ate freeze/thaw cycles.Arl 1-4.2 Detailed Ass§ ent of CF l 5[Potential Failure Modes following CPFMs are th,_i CPFMs carried forward for detailed assessment for the Fire ection System Piping as a~na st of the 2011 flood. This detailed assessment is provided;urface Erosion/Piping settlement of shallow foundation/slab/surfaces (due to CPFM 34 buried utilities (due to pumping)The Triggering Mecihanism and CPFM could occur as follows: multiple potentially connected seepage paths existed in the soil backfill at the site, including soil backfill in utility trenches, granular trench bedding, building floor drains with open/broken joints, and pre-existing defects/voids under pavement.

The paths are exposed at some locations to the river floodwaters (e.g., a hole in the ground north of the Security building).

This network of seepage paths is connected to three pumping sources: the sump pit in the Turbine Building, Manhole MH-5, and a series of surface pumps along the interior of the Aqua Dam perimeter.

The pumps were operated for an extended period, maintaining a head differential on the seepage path networks.Gradient was sufficient to begin erosion of surrounding soil. Seepage is unfiltered, and erosion Priority 1 Structures Page 5.16-7 Fire Protection System Piping Rev. 2 continues unarrested.

Erosion extends out, intercepting the network of utility trenches, including the Fire Protection System. Voids are created under the pavement and along the utility trench walls. The potential damage includes settlement of pipe(s) causing joints to open, overstressing the pipe, causing the pipe to break, or undermining thrust blocks.Below are field observations and data that support the likelihood of these CPFMs: The fire protection loop crosses multiple other utility lines anrckovers the entire perimeter of the facility.

Interconnectivity between crossing pipe trenc eates ossible piping routes for subsurface water flow.* MH-5 was pumped for the duration of flooding to r water into the manhole.Known water sources included ducts from MH-31 a ucts run uxiliary Building.

This created a head differential.

The flow of water into MH-5 was observed on multip 1 sits. Wate 5ocumented to be entering through two conduits on the south wall ole. It was conclusively demonstrated that this was the only route wd , Sediment deposits (and fish) were observed in the bottom of th when it was emptied on September 14, 2011. The sediment coul of p

• and subsurface erosion.* The area inside the perimeter of the Aq ,l..am was p e ,ry. which ed a hydrostatic head condition between the .a inside utside the~Aqua Dam. The area inside the perimeter of the Aqua was pumfr 0llocations, creating points toward which undergro 'pipidid sU b ace fib end to flow.* Void areas and potential pip m ation were ' ed ben the concrete slab just north of the Security Buildin utheast of 4a"d direMwest of the Security Building.Base PD oerat oyee testing FP-3E on September 1 , .d northeast of the Security Building, was tested that fg to the R U operations employee, when opening the valve to the hydrant, e cked a ked, and the valve had to be closed. The access cabinet wastagged ou ir.air at thiat.e"'9 Fire hydrant FP-3D has en markedwith an impairment tag according to October 7, m011, field observations.

ig states that there was extensive leakage when the isolation Atlve was opened." N-nment distress was obsld along the paved access area between the Intake Structure and'- &','Service Building lie area north of where the fire protection piping crosses the corriT oludes obs 'lab settlement and undermining (as evidenced by hollow -'ain'MR t ht areas)." The pit was pumped continually during the 2011 flood. The five pipes connec4 e ihs sump pit are floor drain and condensate system flush drain pipes.Since this is a fibor drain system, no infiltration of groundwater should occur in the system.The infiltration of groundwater into the system indicates an open flow path of some sort.Below are field observations and data that indicate these CPFMs are unlikely:* Sediment and fish were observed in the bottom of MH-5 when it was emptied on September 14, 2011. Sediment accumulations and small fish at the bottom of MH-5 might not be associated with these CPFMs. The manhole was uncovered when the Aqua Dam Priority 1 Structures Page 5.16-8 Fire Protection System Piping Rev. 2 failed and the area was inundated.

Sediment and fish could have been transported into the manhole with floodwaters.

• The observed hole in the pavement, north of the Security Building, could have been developed by outflow from the surface pumps and might not be associated with these CPFMs. Temporary surface pumps were pumping water back into the river with hoses placed over the Aqua Dam* One of the discharge points was near the observed hole (See site photos). Concentrated discharge flow could have eroded pavement and created the o ed hole.* Fire hydrants that are part of the yard loop system havy n oodwaters have receded from the facility.

The system is pressurize , perati lated cases of failure can be assessed as CRs are produced and re are ma* Observed subsurface damage indicators or known 5 acorridor are not located immediately adjacent to the Fire Protectio iping.Yard fire loop alignments were walked and soils were pr pipe alignm either side of the pipe alignments.

Soils on site were generally fi. table. Site .at were visibly wet or moist were the only areas wh robing sh o degree of penetration.

Only a couple of locations along oop on the est, and south sides of the facility were observed to be wet ist. Ting table e. s observed distress indicators and other data that wou. rease or a e potentiaiS'r degradation associated with this CPFM for the Fire Pro(! ion Sys p Adverse (Degradation/Direct I wats F ble (De ..n/Direct Floodwater Impact More likel Im; Less Likely)FP-3C failed during system t .F as te September 13,2011 and FP-3D t an imp ag that fire hydrants marked with stat eendistr a impairment tags, the system is operational.Stru rbtie Building i a_ histre 44 unwaer inflows. FloM ions lireased the hydraulic head aowi M_%-ment distress was noted at M Vle Rh the crridor betwee !Ij.nlet Stit01,d the Service The fire line is k .*ý p the same gWcorridor.

Electrical...

Sas pu i ntinually during the flood. F t es cross the electrical duct n connect to the manhole.Data Gaps:* Ground Penetrating Radar data are not available at the time of this draft report to assist in determining possible void areas at the facility." The extent of the subsurface erosion is not well-known at this time.* Seismic Survey (refraction/tomography and refraction microtremor)." OPPD CRs related to fire main repairs required as part of ongoing yard system testing.

Priority 1 Structures Page 5.16-9 Fire Protection System Piping Rev. 2 Conclusion Significance Potentialfor Degradation/Direct Floodwater Impact Field observations indicate that this CPFM might have initiated in close proximity to the Fire Protection yard piping system. Multiple indications of subsurfacedistress are located along the paved access area between the Service Building and the Intake S re. Pavement slab settlement, undermining (as evidenced by a hollow-soundq, av and a hole in the pavement with visible undermining was observed in the .Floo nundation and impacts are likely causes for the distress and failures o ed in th In addition, fire hydrant FP-3C failed during testing on , 201 l Wse of the fire hydrant cracked when opening the valve for testing. F ant FP-3D been marked with an impairment tag according to October 7, 2bservations.

that there was extensive leakage when the isolation valve s These condi 1y indicate a degraded condition due to floodwater inundation.

Th e l t failres incte some form of impairment on lines that are onil -) and south Is*,f the Intake Structure.

This places known failures on thef b th supply in the Intake Structure.

Implication The occurrence of this CPFM cq act sectiod .sthe fire po in yard piping system and adjacent utilities or The fire prot pipe s -m loops the entire facility and it is located in close proxim iany other utilie Ws. Since the fire protection system is ressurized H of the system sirn, impact adjacent structures oreslml M: ; ... ut spipe d pressurzed water erodes soils around the point of/j jFire Protection Syste" ooped s. includes isolation valves at lateral pipe s tees and on th pop on eaol one of the lateral connection.

Thus, the system conne g ii n%sdesigned to be shut down i ions for repair purposes with continued supply to fire supply 9)ine'on both sides of potentia An operative fire protection system is required at on the site. The Fire ir3'ction System has been tested since floodwaters have rec~ePd it is an operativ nstm, but has a minimum of two known impairments that have shut ý" d atoera t ivie- f shut d6*1MV aterai fire hydraia1ies.

Therefore, the implication of the potential degradation for these CPFWsihigh.

Confidence The fire protection system is an extensive system that circles the entire FCS facility.

Therefore problems could exist in some areas of the site that are not indicative of problems systemwide.

Indications of possible degradation exist within the paved access area between the Intake Structure and the Service Building.

The lateral and vertical extent of subsurface erosion on the site is not known and ground penetrating radar report data have not yet been received to address this issue in detail. Therefore, confidence with the assessment is low.

Priority 1 Structures Fire Protection System Piping Summary Page 5.16-10 Rev. 2 For CPFMs 3a and 3c, as discussed above, the potential for degradation is high because distress indicators exist in close proximity to the system and two connected fire hydrants have failed during testing since floodwaters have subsided.

This degradation in the region could have caused enough erosion to impact the integrity or intended function of the structure.

The combined consideration of the potential for degradation and the imaplications of that degradation to the system put it in the "significant" category.

Theata currently collected are not sufficient to rule out this CPFM. Therefore, the confidpce o ,sessment is low, which means more data or continued monitoring and in ns c%& _ýI Zcssary to draw a conclusion.

~c esr oda Triggering Mechanism 3 -Subsurface Erosion/Pipin CPFM 3d -Undermining and settlement of shallow drawdown)CPFM 3f- Undermined buried utilities (due These CPFMs is similar to CPFMs 3a and instea rapidly receding river level.is created by The Triggering Mechanism and C]than pore water pressure in the s water and soil into existingde system and through the soi w extent of the.d.ps created, i 'a'Q -r level drops faster A diient is created that moves r 4,.cent to the fire protection networks.

Dependent on the Wg effects: trench subsidence, possible impacts on adjacent Vdrobservations and d'.' L, .suppor lihood of these CPFMs: Field observation data h t been gatheed along the river bank and nearest utilityýinstallations on a schedul regular basis to inspect for developing conditions or distress Windicators.

_ations and data conditions that indicate these CPFMs are unlikely: Fii* USA'GEW ced Mis!9i'Wiver Mainstem System releases to 40,000 cfs on October 2, 2011. l to the 40,000 cfs release rate stabilized at the FCS on October 4,70*31N* Indications of:isV e of CPFM were not observed during the most recent site inspections on October 4, 7, and October 27 2011.The Fire Protection System Piping is offset from the river bank which reduces the likelihood-that rapid drawdown and related subsurface piping to the river bank will impact the Fire Protection System Piping.Soils in the area of the Fire Protection System Piping and to the east are backfill materials that were placed and compacted during construction of site improvements and, therefore, would be expected to be less susceptible to rapid drawdown impacts.

Priority 1 Structures Fire Protection System Piping Page 5.16-11 Rev. 2 The following table describes observed distress indicators and other data that would increase or decrease the potential for degradation associated with these CPFMs for the Fire Protection System Piping." Inspection of the riverbank following drawdown to" Geophysical investigation data to address any obser Potential for Degradation/Direct Fl dw~ lmpac c ";Indications that subsurface erost"4i" t exist wi Ahe corri etween the Intake Structure*ii exs wi t e th Itaetrctr and the Service Building is 'J from paven -stress ors and fire service line failures nearest the river. st installations tection system to the river bank are , t0n points NP orth and south the Intake Structure.

The fire protejo ms7ire sin the Intake Structure..

Subsurface erosion along the fac g.ME intake R6i44 r betweef&i1.WY trenches or lines and the nearest point of the river eas the ctiniglf , etwsaon tS~ ~ t theff , es that connect to the Intake Structure.

failure of fire hydrant FR7Wand FP-3i5lMdicate that potential problems already exist in system. Complications ing'aed by CPFMs 3d and 3f could compound problems that L exis t.re is armored a historically protected and stabilized the existing river bank.potd4ft rdegradat."i ieduced due to these improvements.

USACE redf Asg, i;iiver Mainstem System releases to 40,000 cfs on October 2, 2011.River levels cow Awhg to the 40,000 cfs release rate stabilized at the FCS on October 4, 2011. Groundwat&tAevels have thus started to stabilize between the termination of drawdown reduction and the time of this report. The potential for development of subsurface erosion due to river drawdown decreases with the time due to stabilization between groundwater elevations and river elevations.

Implication The occurrence of these CPFMs would likely only affect the utility installations nearest the river. Most of the fire protection system is located well away from the zone of influence from these CPFMs with the exception of the supply lines that connect to the Intake Structure.

Thus, Priority 1 Structures Page 5.16-12 Fire Protection System Piping Rev. 2 the two most important supply components of the system are located at the point of greatest potential for degradation from these CPFMs.As groundwater elevations and river elevations stabilize, the head potential between the two conditions will decrease and the possibility of subsurface erosion will also decrease correspondingly.

In addition, the stabilized river embankment reduces the likelihood of these CPFMs.The implication of the CPFMs affecting the fire protection Hhste sr ed low.Confidence Data are not available to make a determination on subs r er r due t 4 rawdown.Time between the termination of the steady reduction of se rates an, time without indications of subsurface erosion does not ase the likel damage is not present. Thus, confidence with the assessmM 1 .Summary For CPFMs 3d and 3f, as discussed above, t ential dation iso ered low because the potential for highly elevated wa' waee rsus river eAevations is unlikely due to stabilized river levels, stru I -soil b Il o and the protected nature of the existing bank. The combine sider of the -or degradation and the implications of that degradatif thes_ sctur s it in the category.The data currently collected are uao"ufficient to ut this C Therefore, the confidence in the above assessment is ch means more ed monitoring and inspections could be necessa e a final assessim gring Mechanism .apid :')CPFM 12a-_ River failure surrounding structures-CPFM 12b -Lateral spreig Tji iggering Mechanism an FMs could occur as follows: the river level drops faster the-'xwater pressure in thlF~di can dissipate.

The saturated soil is elevated above the droppngier level. The a' 5bank of the river provides no lateral pressure support for the saturate&ýbif-At some p. j ere is insufficient support on the river side to support the saturated so haC, the soils experience slope movements or even failure. Generally, slope failures rapid drawdown are relatively localized and shallow in nature;however, deeperi iis can occur.The 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. At the time of the writing of this version of the Report the groundwater levels had not yet stabilized to nominal normal levels. Therefore, it is possible that new distress indicators could still develop. Field observation of the river bank area has not been performed since the river level has dropped.The following table describes observed distress indicators and other data that would increase or decrease the potential for degradation associated with these CPFMs for the Fire Protection System Piping.

Priority 1 Structures Fire Protection System Piping Page 5.16-13____ ___ ___ ____ ___ ___Rev. 2 Adverse (DegradationlDirect Floodwater Favorabl Impact More Likely) FloodwatE The Main Fire Protection System Piping is in No distress was ol close proximity to the river, inspections.

Elevated saturated soils and elevated flood levels provided a water source.Data Gaps:* Observations of the riverbank following drawdown to nominal no* Geophysical investigation data to address any observed co?.* Inclinometer readings which that will monitor for possibd&e n e (Degradation/Direct er Impact Less Likely)bserved at the time of site I Conclusion Significance Potential for Degradation/Direct Floodwater Impact The river stage level has receded and stabilized river level at 40,000 cfs as of October 4, 201 OE continued river drawdown is not expected t r at Since it is believed that a potential for degA,., ion of CPFMs are considered low.Implication The occurrence of these CP a large scale system. No distress has bee d during ourY the poteae. wion for tlh& lVEMs is low.nominal normal trolled and Skse CPFMs.likely, these but he integrity of the the implication of the river bank has not been inspected for signs confidence for these CPFMs is low.as di'ised above, the combined consideration of the potential for%b, s of that degradation to a structure of this type puts it in the "not 1uver bank has not been inspected for signs of degradation and slope ilt rule out these CPFMs and the confidence is low, which means inspections could be necessary to draw a conclusion.

failure. T1, continued Priority 1 Structures Fire Protection System Piping Page 5.16-14 Rev. 2 5.16.5 Results and Conclusions The CPFMs evaluated for the Fire Protection System Piping are presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

sic investigations and plhyZcl modifications are recommended to address CPFMs 3a, 3c,Fire Protection SystCPFMs 3a and 3c are associated with unfiltered flow of i~thie Turbine Buildin~u

_sement drain piping system (Key Distress Indicator

1. 1).are describ6dti detail in Section 4.1. CPFMs 3a, 3c, 3d, and 3f are associated iss m ani ear the -AM ccess Area between the Service Building and the Intake y Disr1 ,Of,#2). These recommendations are described in detail in Section 4.2.he geophysii'ahd geotechnical reports as they pertain to the Fire Protection System A review of th should be done when available.

OPPD should initiate a procedure to monitor for problems during cable pulling operations.

Problems associated with cable pulling operations to and from MH-5 might be indicative of problems that could affect the Fire Protection System.A detailed analysis of the pavement subgrade and trench alignments should be performed if the pavement in the paved access area between the Intake Structure, around gate one, and the Service Building is replaced.

Priority 1 Structures Fire Protection System Piping Page 5.16-15 Rev. 2 The results of proceeding recommendations will be used to increase the confidence in the assessment results.At the time of the writing of this version of the Report, 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 modi ation of the recommendations for this structure.

.. A.5.16.7 Updates Since Revision 0.Revision 0 of this Assessment Report was submitted to OPPD presented the results of preliminary assessments for each Priori incomplete in Revision 0 because the forensic investigation anc Priority 1 Structures was not completed by the submittal date.includes the results of additional forensic investigation and moi described below.5.16.7.1 Additional Data Available.

The following additional data were availa or the F Revisions 1 and 2 of this Assessmq4,V gepR" Results of KDI #1 forensic igation (see o* Results of KDI #2 fore stigation (see* Addition oundwater i g well and ri* Fi , fth riv see Section 5.2*ni pivit..h dflpe4T inp.ictn ion 0 Piping for n el data from OPPD.nk.. .A~mprJr-n t1nAn n Tfc'na Tn 0Attachment 6)Results of geophysical Results of geotechnical ,ata obtained from inc~esults of continued su m J;tigation b technology, Inc. (see Attachment 6).Geotech, Inc. (see Attachment 6).by Thiele Geotech, Inc. (see Attachment 6).rvey ,Lamp Rynearson and Associates (see Attachment 6).tional data was conducted for the Fire Protection System Piping: ig well and river stage level data from OPPD.litional The 0 Grouni Data shows that the river and groundwater have returned to nominal normal levels.* Field observations of river bank No significance distress from the 2011 Flood was observed.

Priority 1 Structures Page 5.16-16 Fire Protection System Piping Rev. 2" Results of falling weight deflectometer investigation by American Engineering Testing, Inc.Falling Weight Deflectometer and associated GPR testing performed in the Paved Access Area identified anomalies 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 perform &,nd t perimeter of the power block as part of KDI #2 identified deep ano that co el, soft clay, loose sand, or possibly voids.* Results of geotechnical investigation by Thiele Geotec Six test borings were drilled, with continuous samplin 't nuntered.truth the Geotechnology,.

Inc. seismic investigation results as p 5: e KDI #2 frensic*investigation.

Test bore holes were located the deep a es identified in the seismic investigation.

The test boring da pverys y piping ire veyoft/very loose conditions that might be indicativ N 4-sbsurfac l/piping d material loss or movement.

O All of the SPT and CPT test resitft co ted f .I Asses, ed to similar data from numero, r gechni , tht have been conducted on the FCS site in previous ,ds This comp Hn did not. 4 tify substantial changes to the soil stre'ijth and sti -er that time p .CPT test results were not perform he top 10 .ect existing s to dateoared to the original baseline measurements, have not Meds e the accu in e of nometers.

Therefore, deformation at the monitored Uosince the in n of the Ml entation has not occurred.*

of continued surv Lamp Rynearson and Associates..ey data to date comp the original baseline surveys have not exceeded the"acy range of the survim equipment.

Therefore, deformation at the monitored locltiý , since the sury e line was shot, has not occurred.Triggering Mechim 3 -Subsurface Erosion/Piping CPFM 3a -Undermining and settlement of shallow foundation/slab/surfaces (due to pumping)CPFM 3c -Undermined buried utilities (due to pumping)Significance Potential for Degradation/Direct Floodwater Impact Except for Turbine Building sump, conditions which could cause subsurface erosion no longer exist due to present site and flood conditions.

Site pumping sources have been removed and Priority 1 Structures Page 5.16-17 Fire Protection System Piping Rev. 2 high groundwater conditions no longer exist. The, potential for this CPFM to occur presently only exists in conjunction with KDI# 1. Recommended actions in conjunction with KDI#2 address a majority of the areas in question as part of the "Paved Access Area." Therefore, with known issues being addressed and further investigated by OPPD, the potential degradation due to this CPFM is low.Implication The occurrence of this CPFM could impact sections of the fm pr@ n piping system and adjacent utilities or structures.

The fire protection etem ntire facility and it is located in close proximity to many other utilities a ctures. e fire protection system is highly pressurized, failure of the system coul Mtun, -t structures or utilities significantly if a pipe breaks and pressurized wails aro oint of failure.The Fire Protection System is a looped system and include Sol alvesat latera-connection tees and on the main loop on each side of the lateral co n Thus, the sytem is designed to be shut down in sections for repa .' swith conIidpply to fire supply lines on both sides of potential line breaks. A rprotection s required at all times on the site. The Fire Protection S has bee ijce floo have receded and it is an operative system, but tls.a minimu 1wn impairments that have shut down lateral fire hydrant lines. There me- the imlt ion tential degradation for these CPFMs is high.Confidence With investigations and repai" t iated with KD 'andling known issues, and contingh dng in s and repairs as' neded and directed by geotechnical inspetd, dressde es associated with this CPFM is high.041rensic Nsresuts e tei test results ceived the issuance of the Rev 0 report have narrowed and definedtable areas impact i'FM. Recommended actions associated with the results of tiiensic reports and site in ons will address known problem areas and allow the dir 4tof the expansion offi~osed investigations and repairs as necessary to address the condigsX, eated by this The combined consideration of the potential for degradatfrdna the Hiis to that structure or system puts it in the "not-significant" category.Triggering ec 9i' 3 -Subsurface Erosion/Piping CPFM 3d -Undermining and settlement of shallow foundation/slab (due to river drawdown)CPFM 3f- Undermined buried utilities (due to river drawdown)Significance Potentialfor Degradation/Direct Floodwater Impact Based on groundwater monitoring data taken in conjunction with river drawdown and on a continuing weekly basis, groundwater levels have been dropping at a rate that follows the river Priority 1 Structures Fire Protection System Piping Page 5.16-18 Rev. 2 drawdown rate. Thus, the differential head necessary to create subsurface erosion due to river drawdown is no longer present. The area most conducive to create this CPFM is nearest the river. River bank inspections made since the issuance of the Rev 0 report show no indications of this CPFM. The "Paved Access Area" between the Intake Structure and the Service Building is the developed area nearest the river bank and includes most of the utility services that are critical to the operation of the facility.

Recommended actions in association with KDI#2 will repair and address issues that are identified in the area. This will include instances of subsoil*erosion that could have been induced by river drawdown.

The pd~tial for degradation for this CPFM to occur is considered low. & 4&Implication The occurrence of these CPFMs would likely only affecl, river. Most of the fire protection system is located well a, these CPFMs with the exception of the supply lines that cq the two most important supply components of the system potential for degradation from these CPFMs.As groundwater elevations and river elevatio conditions will decrease and the possibility," surface: the corres CPFM The in Confi With of rec pondingly.

In addition, the stabilize .er emban__dies the like1ihood of these dplication of the CPFMs af&ge, r t p i ion systeým..s considered low.lence Sindicat igh head con i no longer exist and the instigation ft pjated wit, nl.#2, confidence in the assessment associated with this Whigh." on these discussion itens'. e combined consideration of the potential for degradation eimplications to that or system puts it in the "not-significant category" in the meFt matrix.erlf echanism J2 'pid Drawdown rf mpkslope failure and undermining surrounding structures CPFM 1L Significance Potential for Degradation/Direct Floodwater Impact The river stage level has been stabilized at a level corresponding to the nominal "normal" river level at 40,000 cfs since October 4, 2011. Rapid drawdown was controlled by the release rate schedule set by the USACE and continued river drawdown is not expected to occur at a rate that would initiate this CPFM. Groundwater monitoring well measurements have been taken since floodwaters have receded from the site. Groundwater readings based on the weekly records show the groundwater levels dropped at a rate that closely followed the river level drop Priority 1 Structures Fire Protection System Piping Page 5.16-19 Rev. 2 rate. With groundwater levels dropping in conjunction with river levels there is little chance of highly.elevated groundwater levels in comparison to river levels. The river bank is armored and has historically protected and stabilized the existing river bank. In addition, no indications of this type of failure were noted on the most recent riverbank inspection completed as of October 27, 2011. Due to updated data and observations, the potential for degradation due to this CPFM is considered low.Implication The occurrence of this CPFM on a large scale could neg system. No distress has been observed during our insp the potential degradation for this CPFM is low.Confidence Based on recent data and observations, this CPFM was no eati conditions associated with the Missouri River flood of 2011 and associated with this CPFM is high.Summary Based on these discussion items, the com consid. n and the implications to that structurir sy~ puts e not assessment matrix.5.16.7.1 Results and R -ndations The CPF,,ý ,d for the .W tection System are of the of for degradation category" in the significance anc presented in the following l the level of confidence in the12a and 12b for tV m Piping are not associated with Key Distress Indicators.

The results of thS i*tional forensic investigation show that these CPFMs are ruled u,,Therefore, assuming thatu2od rther concerns are identified through the monitoring Sfor the Fire Protectioily,'em Piping (discussed in Section 5.16.6 and continuing until Dxert, ,2011), these CHI! are moved to the quadrant of the matrix representing "No FurthlW&iion Recommend Rli.1ated to the 2011 Flood."3&or th6.fi&rprotection system are associated with Key Distress Indicator

1. 1.Section 4.1 sfsen ieesults of additional forensic investigation that was conducted to ascertain whethdif 5es5 CPFMs could be ruled out. The results of the additional forensic investigation assuming the recommendations for physical modifications for KDI #1 are implemented, these CPFMs are ruled out. Therefore, assuming that no further concerns are identified through the monitoring program for the fire protection system (discussed in Section 5.16.6 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." CPFMs 3a, 3c, 3d and 3f for the fire protection system are associated with Key Distress Indicator

1. 2. Section 4.2 presents the results of additional forensic investigation that was conducted to ascertain whether these CPFMs could be ruled out. The results of the additional forensic investigation show that these CPFMs are ruled out. Therefore, assuming that no Priority 1 Structures Fire Protection System Piping Page 5.16-20 Rev. 2 further concerns are identified through the monitoring program for the fire protection system (discussed in Section 5.16.6 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." IFthe assessment of the FCG ctures therest step was to develop a list of all Triggering and PFMs that have occurred due to the prolonged inundation of the FCS sit d~uring the 2011 Missouri RiWr flood and could have negatively impacted these structures.

T n44tltep was to use data 'various investigations, including systematic observation of the sWWtkes over time, eith&eý h eliminate the Triggering Mechanisms and PFMs from the list further. .or to reeofed further ýl gation and/or physical modifications to remove them from the hst for anyearhwlar sttrefe. Because all CPFMs for the Fire Protection System Piping other than CPFMs3, 12a, and 12b had been ruled out prior to Revision 1, because CPFMs 12a andA-I~a&ve been ruled out as a result of the Revision 1 findings, because CPFMs 3d and 3f were rulEd"ut using the results of the KDI #2 investigation presented in Section 4.2, and because CPFMs 3a and 3c will be ruled out when the physical modifications recommended for KDI # 1 in Section 4.1 are implemented, no Triggering Mechanisms and their associated PFMs will remain credible for the Fire Protection System Piping. 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 5.17 Waste Disposal Piping i Q01-9 Priority 1 Structures Page 5.17-1 Waste Disposal Piping Rev. 2 5.17 Waste Disposal Piping 5.17.1 Summary of Waste Disposal Piping Baseline information for the Waste Disposal Piping is provided in Section 2.0, Site History, Description, and Baseline Condition.

Waste Disposal Piping is a 2-in.-diameter stainless steel pipeline e ase ncr with several other pipe systems. The encased utility bank is routed from the south th -ulding to the south end of the Intake Structure.

The utility bank begins adja .Trans R 1 and is routed south of the Underground Cable Bank and MH-5. From the s est co -the encased utility bank (including the Waste Disposal Piping) is routed to o a po h of the discharge tunnel. At that point, it turns to the north, crosses the unnel an ates at the south side of the Intake Structure.

The concrete-encased utility b .fire protec sanitary sewer lines, storm drain lines, demineralized water lines,.d t -rground Ca (Trenwa) as it is routed across the site.-T he as-asymsed-to -co -llect;-store;- , a d contrsl -f ...ra-diOtiewaste.'

The Waste Disposal Piping is u release te once it np to within acceptable levels.5.17.2 Inputs/References Supporting tb na, Table 5.17-1 lists references provided PD and othe uments to support HDR's analysis.;, Table 5.17-%M.Mfiences for Piping Plan(nt Title# 3 OPPD Do, t Drawing No/Number Page(If applicable)

Number(s)Yard I t 0--1 Unknown-. ig I 11M'-M-313 Unknown(# 10753)Yard `1r'heet 3 11405-M-314 8/3/1973 (#10754)Waste DispC temr SDBD-WD-144 7/28/11 All Rev._28 .Z_______

_ _, Naval Facilities En mg m'jedd 9/1986 All Design Manual 7.01 ,M"11 equiics Detailed site observations-field reports, field notes, and inspection checklists-for the Waste Disposal Piping are provided in Attachment

8.

Priority 1 Structures Page 5.17-2 Waste Disposal Piping Rev. 2 Observed performance and pertinent background data are as follows: Groundwater was observed flowing into the basement sump of the Turbine Building from floor and condensate drain pipes not designed to intercept groundwater.

This condition has a recorded history dating back to 1997. The Turbine Building is west of the corridor and utilities, between the Intake Structure and the Service Building.Settlement of a column in the Maintenance Building, north of the Turbine Building, has been documented.

The Turbine Building and the Maintenance Building ar st of the corridor and associated utility alignments within the corridor.The Aqua Dam surrounding the facility crossed the alignm e* The Aqua Dam failed for a short period of time due to bei aged, odwater to enter the area inside the Aqua Dam perimeter.

Surfaces above t te osalere inundated when the facility Aqua Dam failed.* Areas outside the perimeter of the facility Aqua Dam were mu ith water fo nd period of time.* Concrete areas in the corridor (paved drive and pedestrian areas betw iver and Se Building) have exhibited distress, including crackin lement, an ining. However, most of the pavement cracking or other conditionsii isting con due the age and use of the facility.

.I* A hole in the pavement and void area beneath oncrete of the Sec rity Building and east-southeast of MH-5. The hole and vo ea are I d o .. perimeter of the Aqua Dam that surrounded the facility.

The .emr ilur ed at ection point of pavement jointing.

The hole in the ntis irreg shape a P more than 1 ft wide both in the north-south and east-westjdi ons. The voi beneat 1 hole was approximately 4 ft wide by 0.8 ft deep; it was meas a tape measu le. The void can be attributed to subsu face erosion.,__ MW. ~islcae The holei located observed disc arge point of a pump operated prior to the am d can be attributed to scour created by the discharge of th iotperatmg for ed pei place.F Fjratection Cabinet FP-3 .of the uilding and east-southeast of MH-5 is located 4 aximity to the pavement fa d void a ' It was reported that the fire hydrant was tested Rhiber 13, 2011, and failed. gording to OPPD operations personnel testing FP-3E during si g!s*ections, the base of FP-3qý. ked when the valve was opened. The fire hydrant was shut downr~-be access cabinet was jed out. The cause of failure was unknown at the time field observatt rmde n .re m a de ,:;* Pavement M ing was obso' northwest of the Intake Structure and east of the abandoned acid tank. .* A was noticed east of the Service Building truck dock.* The fire .hydrant loc P-3E was tested on September 13, 2011, during site investigations.

No operational proble I were observed during the time on site.* OPPD operations personnel testing the fire hydrant at FP-3E on September 13, 2011, were questioned about other fire hydrant tests. An OPPD employee who was questioned noted that no problems were observed for the fire hydrant at FP-3D during testing. The information on the problem at FP-3C, noted previously, was gathered at this time.

Priority 1 Structures Waste Disposal Piping Page 5.17-3 Rev. 2 5.17.3 Assessment Methods and Procedures 5.17.3.1 Assessment Procedures Accomplished Assessments were made by walking the Waste Disposal Piping alignment and observing the ground surface overlying the underground pipe system. The surface assessment included using a 4-ft-long, 0.5-in.-diameter, steel-tipped fiberglass T-handle soil probe to hand probe the ground surface along the utility alignments and adjacent areas to dctermine relative soil strength.

The assessment focused on identifying conditions~indi f tial flood-related impacts or damage to the utility as follows:* Ground surface conditions overlying and immediat ace and its backfilled trench including scour, subsidence or sett I spre ping, and heave.* Soft ground surface areas (native soil, engineered fill, determined by probing.* Water accumulations and flows in subsurface s ,m cable encasement pipes).* Damage to at-grade or above-grade syste res* Variance from normal installation conc s includi features and equipment.

• Operation of the system and apputen uip _1 gravel pa pcompon Dles and concrete it.system operational).

Additional investigations were including areas where condififi observed.

These were compni subsurface at the facility 1 impacts or damages were)hvsical and invasive ions: the time of Revision 0.)micro-tremor). (Test reports were not uding boifihgs in the vicinity of the utility to determine cities. Note that OPPD required vacuum excavation for the to avoid utility conflicts.

Test reports will thus not show t of test boring logs. (Test reports were not available at the'with GPR and dynamic deflection methods (i.e., drop weight ts were not available at the time of Revision 0.)the river that provide an indication of slope movement.IncH 5.17.3.2 Procedures Not Completed Assessments of the Waste Disposal Piping that were not completed include the following:

The interior of underground cable bank manholes and connecting concrete-encased cable pipes in the Protected Area were not inspected except for visual observations that were possible from above and behind temporary safety railings.

Manholes are a confined space as defined by OSHA regulations.

In accordance with these regulations and OPPD FCS safety procedures, manhole entry is a permit-required confined space entry and can only be Priority 1 Structures Waste Disposal Piping Page 5.17-4 Rev. 2 performed by appropriately trained OPPD personnel.

The underground cable bank and the Waste Disposal Piping system follow a similar route, and surface indicators for the cable bank can also be indicators for the disposal piping.* No excavation to inspect underground systems and conditions was performed.

• No video inspection of the system was completed.

5.17.4 Analysis Identified PFMs were initially reviewed as discussed in Section 3.preliminary information available from OPPD data files and frol Eleven PFMs associated with five different Triggering MechaEM"non-credible" for all Priority 1 Structures, as discussed in Sec 7 carried forward as "credible." After the design review for each q and the results of available geotechnical, geophysical, and survey CPFMs were ruled out as discussed in Section 5.17.4.1.

The CPI assessment are discussed in Section 5.17.4.2.5.17.4.1 Potential Failure Modes Ruled Out Assessment The ruled-out CPFMs reside in the Not Si.1r will not be shown in the Potential for onfideIg Triggering Mechanism 2 -Su oslon CPFM 2a -Underminin shat foundatio CPFM 2c -UnderminLE utilities considered the were Detailed e "ýcategory'nd for clarity Sare category anWiignment.

In additioiT ground surface across below pot(a e surface overlying the Waste Disposal Piping lize ffiffimited surface erosion was observed on the Th&%!e Disposal Piping system is constructed depths indicated by erosion features observed in other lapse (first time wetting)itial settlement of shallow foundation, loss of structural roken connections settlement Soil supporting and surrounding the Waste Disposal Piping system has been previously wetted. The peak flood elevation prior to 2011 was 1003.3 ft, which occurred in 1993.

Priority 1 Structures Waste Disposal Piping Page 5.17-5 Rev. 2 Triggering Mechanism 10 -Machine/Vibration-Induced Liquefaction CPFM 10a -Cracked slab, differential settlement of shallow foundation, loss of structural support CPFM 10b -Displaced structure/broken connections Reasons for ruling out:* Machine vibrations from the facility (turbine and various and no indications of these CPFMs were evident." Pumps used on site during the flood event were insu vibrations sufficient to initiate soil liquefaction.

Vii not observed around the areas where the pumps we liquefaction .were reported to HDR.* No structure movements indicative of soil liquefaction i observed; no structure cracking or lateral movements Triggering Mechanism 11 -Loss of Soil Strengt u to Seepage CPFM 11 a -Cracked slab, differential s n CPM1 b-support117 CPFM 11 b -Displaced structure/brok onnectlo Y Reasons for ruling out: !N* Liquefaction was not ob ea along the corri r acro:* Visual observations and- MUMNe easurements 4 or structure faction were rences of ire movement.

Therefore, (CPFMs I la and lIb) did#g-i ng Mechanisio t PFM 12a -River b.CPFM 12b -Lateralctures. did not ha gident signs of distress identified during the field assessments.

• Slopqhaiure was not cýWs..ed at the site." River " ewel hag:5'eeled and stabilized as of October 4, 2011.* As of daat h NU t report, October 11, 2011, groundwater elevations have already had one week to e to at least a partial degree.* The river bank-Is-armored and has historically protected and stabilized the existing river bank.Triggering Mechanism 13 -Submergence CPFM 13a -Corrosion of underground utilities Reasons for ruling out:* There are no flood-induced changes to the nature of the buried Waste Disposal Piping system.

Priority 1 Structures Page 5.17-6 Waste Disposal Piping Rev. 2 The Waste Disposal Piping system is located below the design flood elevation for the facility.

Groundwater elevations controlled by Missouri River water elevations, percolation of storm precipitation, and winter snow melt would be expected to contact underground improvements, including constructed steel and concrete facility elements.

As such, steel and concrete site improvements are assumed to be designed to withstand the corrosive environment of groundwater and wetted soil.* The Waste Disposal Piping system is stainless-steel pipe that is encased in concrete and installed in an area of structural backfill.

Therefore, corrosio to flood-induced site changes is not expected.Triggering Mechanism 14 -Frost Effects CPFM 14a -Heaving, crushing, or displacement Reasons for ruling out: " The Waste Disposal Piping system is installed below t dep .. st penetrati* Conditions have not changed due to flood cond", 0 i-y, ti 5.17.4.2 Detailed Assessment of Cre re Modes _The following CPFMs are the only CPFMsried fo

• led assessment for the Waste Disposal Piping system as a result .201 T d assessment is provided below.Triggering Mechanism 3 -Sy I..face Erosion" ng CPFM 3a -Undermini ttlement of .f Ia s/surfaces (due to umping)Cilned bun ,ities (due to pumping)$.,ggering

.c MA d CPFMt&`7M occur as follows: multiple potentially connected 4 age paths existed in' backfl ste including soil backfill in utility trenches,'.zranular trench bedding, bdk' gLfloor drasvifikith open/broken joints, and pre-existing efects/voids under pavemen z.g, paths are exposed at some locations to the river'waters (e.g., a hole in theýg`uind north of the Security Building).

This network of seepage pi onnected to several pjbiiiJJing sources: the sump pit in the Turbine Building, Manhole series of sur ps located along the interior of the. Aqua Dam perimeter.

The pu .S.%pre operatedAf 4ran, extended period of time, maintaining a head differential on the seepage r iorks Qent was sufficient to begin erosion of surrounding soil. Seepage is unfiltered osnues unimpeded.

Erosion extends out, intercepting the network of utility trench' j 'ing the Underground Cable Bank. Voids are created under the pavement an alo e utility trench walls. The potential damage includes settlement of the Underground Cable Bank and manholes causing a loss of electrical connectivity.

Below are field observations and data that support the likelihood of these CPFMs: " MH-5 was pumped for the duration of flooding to remove water entering into the manhole.Known water sources included ducts from MH-3 1 and ducts running to the Auxiliary Building.

This created a head differential." The flow of water into MH-5 was observed on multiple field visits. Sources of the water could not be determined.

Priority 1 Structures Page 5.17-7 Waste Disposal Piping Rev. 2" Sediment deposits (and fish) were observed in the bottom of the MH-5 when it was emptied on September 14, 2011. The sediment could be an indication of piping and subsurface erosion." The area inside the Aqua Dam perimeter was pumped dry and created a hydrostatic head condition between the area inside and the area outside of the Aqua Dam perimeter.

The inside the Aqua Dam perimeter was pumped from several locations creating points where underground piping and subsurface flows would tend to flow." Avoid area and potential piping location were observed benea e concrete slab just north of the Security Building and east-southeast of MH-5.* Based, on a conversation with an OPPD operations e ee tes E on September 13, 2011, fire hydrant FP-3C, located northeast of t "curity s tested on September 13, 2011, and failed. According to the e o e ns em , when opening the valve to test the hydrant, the base cracke ed and the .ad to be closed. The access cabinet was tagged out for repair a. e.* Pavement distress was observed along the driveway c o en the Intake and the Service Building.

The area north of where the duct b ses the corri r-'includes observed slab settlement and unde evidence ow-sounding pavement areas).* The Turbine Building sump pit was pu continuahe o five pipes connected to this sump pit are flo rain and .. system fli udrain pipes.2 .... ...i ...Since this is a floor drain system, no i ~sation o ndwa ou the system.The infiltration of groundwater o fth em -es s open flow path.Below are field observations anda a that indicat se CPF M e unlikely:* Sediment and fish were 'in the bottom it was emptied on Septembe -011. Sedii acumulations an -.:fish at the bottom of MH-5 might no: -a M 'a ,ath these §,The manhole was uncovered when the Aqua Dam AL int J s 2anunI-t ...Ziunater.

Sediment and fish could have been ansported into th iq le with 0l", Mters."'_.ýThe wbserved hole' tM fithI he Security Building, could have beeni~~e observed hole in te vm nt nol aebe developed by outflow fri'e surface pdmfips and might not be associated with these-CPFMs. Temporary surfa-h'p mps were pumping water back into the river with hoses nlaced over the Aqua Dam ...... of the discharge points was near the observed hole Yeffence figure/photo ordy report). Concentrated discharge flow could have eroded paden.ht and created Berved hole.Data Gaps R .Attill re to assess these CPFMs):* The extent ubsurface erosion is not known at this time.* GPR data. (Tes reports were not available'at the time of Revision 0.)* Seismic Survey -refraction/tomography and refraction microtremor. (Test reports were not available at the time of Revision 0.)The following table describes observed distress indicators and other data that would increase or decrease the potential for degradation associated with these CPFMs for the Waste Disposal Piping system.

Priority 1 Structures Waste Disposal Piping Page 5.17-8 Rev. 2 Adverse (DegradationlDirect Floodwater Impact More Likely)Favorable (Degradation/Direct Floodwater Impact Less Likely)I I r i A hole in the pavement with a void space beneath was observed north of the Security Building and east of MH-5. This location was outside the Aqua Dam perimeter and could be a sinkhole that developed due to subsurface erosion.Alternatively, the observed hole could have been developed by outflow from the surface pumps and not be associated with this CPFM.Temporary surface pumps were pumping water back over the Aqua Dam. One of the pump discharge points was near the observed hole.Concentrated dis e flo ould have created the obse .Data Gaps:* Geophysical investigation data to address observed c* Geotechnical investigation data to address observed* Existence, size, and location of voids Conclusion Significance Potentialfor Degradation/Direct Indicators for these CPFMs have been ob Piping in multiple locations during field i failures in the vicinity, the potent4a d is of subsurface high.Implication The settl impi-scale coifflýý id areas that would induce pipe could lead to excessive movement and negatively ff the Waste Disposal Piping system. Therefore, the`5ese CPFMs is high.431:e ii. are multiple elements to ie CPFMs. The inflow of water into MH-5 during the flood evne hole in the pavemenji h of the Security Building, and the settled pavement section in thtt i'idor. However, ev "iugh the confidence is high that there are some voids under the the t of these voids is not known.tecf5M.ri.. th,,,1-1f o e The data at e no cient to rule out these CPFMs, or lead to a conclusion that subsurface erogi dermined the Waste Disposal Piping system. Therefore, the confidence in the assessment is low, which means more data are necessary to draw a conclusion.

Summary For CPFMs 3a and 3c, as discussed above, the potential for degradation is high because indicators for these CPFMs have been observed.

This degradation could have caused erosion that impacts the integrity or intended function of the structure.

The combined consideration of the potential for degradation and the implications of that degradation to a structure of this type puts it in the "significant" category.

That data currently collected are not sufficient to rule out Priority 1 Structures Waste Disposal Piping Page 5.17-9 Rev. 2 these CPFMs. Therefore, the confidence in the above assessment is low, which means more data or continued monitoring and inspections are necessary to draw a conclusion.

Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3d -Undermining and settlement of shallow foundation/slab (due: to river drawdown)CPFM 3f- Undermined buried utilities (due to river dr do These CPFMs are similar to CPFMs 3a and 3c. but ins adient by rapidly receding river level.The Triggering Mechanism and CPFMs could then occur s: river le than pore water pressure in the soil can dissipate.

A grad -ated that mov soil into existing defects. The flow enlarges voids along t-ti ch as it mov the soil toward the river via piping features or networks.

Other con es include to adjacent structures, including fire protection rground c nk, raw piping, and the Underground Cable Trench.Field observations and data that support t elihood Conditions required to trigger the e C had curr e of Revi, Therefore, field observations ta sup e likel" ese CPFM be made.is created faster sion 0.s could not* The river was still be, conditions could initi.Future river drawdown Fi that indicate these CPFMs are unlikely: at a level corresponding to the nominal normal Mier level at 40,000Ho9k Octobe r -1. Field observations that indicate that these CPFMs are unlikely ha-' been mad V The Waste Disposal Pipintskffset from the river bank. This offset from the river bank the likelihood thatv 1 drawdown and related subsurface piping to the river bank IIIpact Waste 'V Piping System.w[ pact the vist iS a the area of the Wi t'-Disposal Piping System and to the east are backfill materials thafert1 aced and c ied during construction of site improvements and therefore W Wod9xpected,,, ss susceptible to rapid drawdown impacts.0* Void spa to cause surface erosion would have to be significant to create conditions system to fail.Data Gaps (data has yet to be acquired to assess these CPFMs):* Observations of the riverbank following drawdown to normal river elevations." Geophysical investigation data to address observed concerns.* Geotechnical investigation data to address observed concerns.The following table describes observed distress indicators and other data that would increase or decrease the potential for degradation associated with these CPFMs for the Waste Disposal Piping system.

Priority 1 Structures Page 5.17-10 Waste Disposal Piping Rev. 2 Adverse (DegradationlDirect Favorable (DegradationlDirect Floodwater Impact More Likely) Floodwater Impact Less Likely)Flood waters were at a high level for an USACE suspended the river drawdown extended period of time which allowed between August 27, 2011 and September 18, surrounding soils to become saturated.

2011. This gap period in the scheduled reduction of dam release rates was provided to allow groundwater elevations to equalize with river flow The river bank s and tects against the creatio e th.Indicatio ese CP not been exhibited ported.,N-....

us floods."Observations of the riverbank following drawdown to noelevations.t. ;Significance.

Potentialfor Degradation/Direct to The potential for degradation aitsince ground levels not yet reached a nominal normal level. Sincitsbea at a potential f graKenwill affect the structure, these ccurrence of these -could n impact the operation of the structure.

This ud lead to pipe settlemea t egative ct the integrity or intended functionality of the aste Disposal Piping systeMMI erefore, the implication of the potential degradation for these CPFMsrcs is high.0o ~ence The act c tture from these CPFMs is not known due to unknown future river drawdath es. 'd*idwater levels are such that these CPFMs could still occur.The data at hand%&ý"pt sufficient to rule out these CPFMs, or lead to a conclusion that subsurface erosion'as undermined the Waste Disposal Piping system. Therefore, the confidence in the above assessment is low, which means more data are necessary to draw a conclusion.

Summary For CPFMs 3d and 3f, as discussed above, the potential for degradation is high because groundwater levels have not yet reached nominal normal levels. This degradation could cause erosion that impacts the integrity or intended function of the structure.

The combined consideration of the potential for degradation and the implications of that degradation to a Priority 1 Structures Waste Disposal Piping Page 5.17-11 Rev. 2 structure of this type puts it in the "significant" category.

The data currently collected are not sufficient to rule out these CPFMs. Therefore, the confidence in the above assessment is low, which means more data or continued monitoring and inspections is be necessary to draw a conclusion.

5.17.5 Results and Conclusions The CPFMs evaluated for the Waste Disposal Piping are presented in the shows the rating for the estimated significance and the level of coja~enq* Review geophy 4 g-4ýnidgitqenical reports to evaluate the data as they pertain to the Waste Disposal Piping. " Inspect the interior ofP .-5. Inspect walls, floor, cover, joints, and duct bank penetrations.

Obtain a photographic record of conditions." Perform a detailed analysis of the pavement subgrade and trench alignments, if the pavement in the corridor between the Intake Structure and the Service Building is replaced.5.17.7 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 Waste Disposal Piping Page 5.17-12 Rev. 2 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.5.17.7.1 Additional Data Available The following additional data were available for the Waste Disposal Piping for Revisions 1 and 2 of this Assessment Report: ,,L* Results of KDI #1 forensic investigation (see Sectio* Results of KDI #2 forensic investigation (see Secti* Additional groundwater monitoring well and river s* Field observations of the river bank (see Section " Results of falling weight deflectometer investigation byý(see Attachment 6).* Results of geophysical investigation by Geotechnology,.Results of geotechnical investigation by Thiel .h* Data obtained from inclinometers by Thiel -* Results of continued survey by Lamp R on an 5.17.7.2 Additional Analysis The following analysis of additio ýta w ond -for Groundwater monitorin d river stage data Data shawpstatthe river a ndwater have r* A~d~hervat Il ir hank'l~6).Piping: nominal normal levels.lo significance was observed.,Results of falling weight diflebtometer investigation by American Engineering Testing, Inc.FAllig Weight Deflectom aslnd associated GPR testing performed in the Paved Access anomahies h as soft clay and broken pavement.

Additional ground trui i"Mthe ivestig# esults were performed as part of the KDI #2 additional in,* Reultsof iZI investigation report 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." 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 Priority 1 Structures Page 5.17-13 Waste Disposal Piping Rev. 2 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 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 test results were not performed in the top 10 feet to protect existing utilities.:.

4ýData from inclinometers to date, compared to the 6 1 baseliii' ements, have not exceeded the accuracy range of the inclinometers.

fore, the monitored locations since the installation of the istrumentatio , -urred.* Results of continued survey by Lamp Rynearson and Survey data to date compared to the original baseline surveys I exceeded t e accuracy range of the surveying equipment-deformati monitored locations, since the survey baseline was sh ed. 0 Updates to assessment procedures not comp-k d are ou tion .17. Excavation to inspect underground systems is include fth the K 2 in on. Video inspection of the system was not completed andsot pl du anti ow value of data oin Js o e mA s were ompleted and are no longer deemed necessary.

Triggering Mechanism 3- ace Erosion CPf 1 ent of shallow o ndation/slab/surfaces (due to 3c- PeObhuried u u to pumping)" 1¢PFMs 3a and 3c for thet ta"psposal Pig System are associated with Key Distress lnh-dicator

1. 1. Section 4.1 pres&&tsthe results of additional forensic investigation that was to ascertain CPFMs could be ruled out. The results of the additional sice, mvestigation show th at, ssu" ,vs h ssuming the recommendations for physical modifications forthe-7PFMs are ruled out. Therefore, assuming that no further concerns,-M identlfied throM ithe. monitoring program for the Waste Disposal Piping System (discusse 1 bS~ction continuing until December 31, 2011), these CPFMs are moved to the quad heicxrepresenting "No Further Action Recommended Related to the 2011 Flood." `fte 'bseivation recommended in Section 5.17.6 regarding the interior inspection of NMl +/-54isýno longer needed because CPFMs 3a and 3c will be ruled out when the physical modifications recommended for KDI # 1 in Section 4.0 are implemented.

Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3d -Undermining and settlement of shallow foundation/slab (due to river drawdown)CPFM 3f- Undermined buried utilities (due to river drawdown)CPFMs 3d and 3f for the Waste Disposal Piping System are associated with Key Distress Indicator

1. 2. Section 4.2 presents the results of additional forensic investigation that was Priority 1 Structures Page 5.17-14 Waste Disposal Piping Rev. 2 conducted to ascertain whether these CPFMs could be ruled out. The results of the additional forensic investigation show that these CPFMs are ruled out. Therefore, assuming that no further concerns are identified through the monitoring program for the Waste Disposal Piping System (discussed in Section 5.17.6 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." 5.17.7.1 Revised Results The CPFMs evaluated for the Waste Disposal Piping matrix, which shows the rating for the estimated signi evaluation.

In the assessmentf0tlie 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 modifications to remove them from the list for any particular structure.

Because all CPFMs for the Waste Disposal Piping other than CPFMs 3a, 3c, 3d, and 3f had been ruled out prior to Revision 1, because CPFMs 3d and 3f were ruled out using the results of the KDI #2 investigation presented in Section 4.2, and because CPFMs 3a and 3c will be ruled out when the physical modifications recommended for Priority 1 Structures Page 5.17-15 Waste Disposal Piping Rev. 2 KDI # 1 in Section 4.1 are implemented, no Triggering Mechanisms and their associated PFMs will remain credible for the Waste Disposal Piping. 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 5.18 Fuel Oil Storage Tanks and Piping AA A J B Priority 1 Structures Page 5.18-1 Fuel Oil Storage Tanks and Piping Rev. 2 5.18 Fuel Oil Storage Tanks and Piping 5.18.1 Summary of Fuel Oil Storage Tanks and Piping Baseline information for the Fuel Oil Storage Tanks and Piping is provided in Section 2.0, Site History, Description, and Baseline Condition.

The Fuel Oil Storage Tanks and Piping consist of three fuel tanks as d s ly piping located inside the protected area. The purpose of these tanks is to provi oi emergency diesel generators and diesel water pumps. Fuel tank FO- 1 is an 18,0 on stee ound tank founded on a pile-supported concrete slablocated south of the iary tank FO-10 is an 18,000-gallon steel underground tank founded on a pile-sup e sla outside the east wall of the Service Building.

Tanks FO-1 and FO-10 supply e diesel-p generators.

Fuel tank FO-27 is a 500-gallon, concrete, abovegro cated outsi of the Intake Structure.

Fuel tank FO-27 is supported by a concre laart of thes supported Intake Structure This tank supplies fuel for the diesel-powered mp inside the ntake Structure." 5.18.2 Inputs/References Supporting the Anal Table 5.18-1 lists references provided by OPPD ther do ts upport HDR's analysis.*Table 6.18-1 -Refere rr F Il OWAN g Wan &'ýr'Piping Document Title -- OPP rmen t Date Page* x "(i a r Number(s)Yard Piping S ____11405-M-31_

)_Unknown Yard Pipj 1405-M-313

(# 10753) Unknown Yard ý eet3 05-M-314 (#10754) 8/3/1973 T ., ations 'qW r -4 1 8 (#16588) Unknown 1'T1 -412 (#16583) 1/29/1973 SDBD-DG-112 1/19/2011 All SDBD-STRUCT-503 6/22/2010 All 9/1986 All Detailed site obse --fi s, field notes, and inspection checklists-for the Fuel Oil Storage Tanks and ided in Attachment 8.Observations and pertine ckground data are as follows:* Utility lines run in close proximity to tanks FO-1 and FO-10." Tank FO- 1 is surrounded by a perimeter security fence and could only be inspected from outside the fence.* A sand boil/piping feature was observed (originally reported in CR 2011-7265) near the southwest comer of the Missile Shield Room. This room is on the outside of the south wall of the Auxiliary Building and has an unfinished, pea-gravel floor surface. Tank FO-1 is south of this Missile Shield Room and fuel oil piping enters this room below floor elevation very near the observed boil/piping Priority 1 Structures Fuel Oil Storage Tanks and Piping Page 5.18-2 Rev. 2 feature. The Main Underground Cable Bank (MH-1 to the Auxiliary Building portion) runs through the subsurface, in proximity to the location of the boil/piping feature." A hollow-sounding pavement area was noticed east of the Service Building truck dock; this area is in proximity to underground fuel tank FO-10." Groundwater was observed flowing into the basement sump of the Turbine Building from floor and condensate drain pipes not designed to intercept groundwater.

This condition has a recorded history dating back to 1997. The Turbine Building is west of the corrior and utilities are located between the Intake Structure and the Service Building." Settlement of a column in the Maintenance Building, north o T, has been documented." Water inflow into MH-5 occurred during the flood event s obse site visits and photographed.

• The Aqua Dam surrounding the facility crossed the alignmen e protect water piping, the underground utility bank, the underground cable b e circulatio tunnels.* The Aqua Dam failed for a short period of time due to being damage , g floodwate enter the. area inside the Aqua Dam perimeter.

Surfaces a te utilities undated when the facility Aqua Dam failed." Areas outside the facility Aqua Dam were inun or an e eriod o" Concrete areas in the corridor (paved drive an estrian the river .nd Service Building) have exhibited distress including cr .g, sla me dermining.

However, most of the pavement cracking or the co ons -e, pre- -onditions due the age and use of the facility." There is a hole in the pavement .d area beneat concret north of the Security Building and east-southeast of he hole and -side the perimeter of the Aqua Dam that surr e facility.

ement failure the intersection point of pavement*.

the t is irregular in shape and is more than 1 ft wide both in the an t direct e void area beneath the hole is approximately 4 ft wid ft deep; it was d bya asure through the hole.* e in the pavement is n observe rge point of a pump operated prior to the al of the Aqua Dam. The an be a ted to scour created by the discharge of the pipe.for an extended period -e in one place.SFir' tion Cabinet FP-3C no i the Security Building and east-southeast of MH-5 is located in pro o the pavement fail ..d void area. It was reported that the fire hydrant was tested Septem 011 and failed. rding to OPPD operations personnel testing FP-3E during site inspections, e of FP-3 ed when opening the valve. The fire hydrant was shut down and the access a was out. The cause of failure was unknown at the time field observations were* Pavement slab settli observed northwest of the Intake Structure and east of the abandoned acid tank." The fire hydrant located in FP-3E was being tested on September 13, 2011, during site investigations.

No operational problems were observed during the time on site." OPPD operation personnel testing the fire hydrant at FP-3E on September 13, 2011, were questioned about other fire hydrant tests. The OPPD employee questioned noted that no problems were observed for the fire hydrant at FP-3D during testing. The information on the problem at FP-3C, noted previously, was gathered at this time.

Priority 1 Structures Page 5.18-3 Fuel Oil Storage Tanks and Piping Rev. 2* The enclosure for fuel tank FO-27, outside the Intake Structure, is designed to withstand an external hydrostatic load due to flooding of the Missouri River to el. 1014.5 ft (see SDBD-STRUC-503)." The concrete support slabs for fuel tanks FO-1 and FO-10 are 15 ft wide by 25 ft long by 3 ft thick and are founded on four 10BP42 steel-bearing piles. The top of the support slab for tank FO-I is at el. 989 ft and the top of the support slab for tank FO-10 is at el. 990 ft." The driving criteria, tip elevation, and capacities of the 10BP42 piles e unknown. However, the top of the piles are capped with a plate and anchor rods for a positive and plift connection (see 1 1405-S-412)." The piles are anchored to the support slab through a welde ap pl -in. diameter bent rods that protrude into the slab." The tank is attached to the slab by two hold-down straps an t supp with 1.5-in.-diameter bent rods." The river bank is armored and has historically protected and s e existing* USACE reduced Missouri River Mainstem System releases to ,O n October 2 River levels corresponding to the 40,000 cfs release rate stabilized at t on October , 11, at about el. 995 ft.5.18.3 Assessment Methods and Procedures 5.18.3.1 Assessment Procedures Ac lished Assessments were made by obse u fe fthesy cess points and vent/fill pipes) and the ground surface o ng the unde r nd fuel s e tanks. The surface assessment included using g, 0.5-in.-dia stee d fiberglass t-handle soil probe to hand probe the gro ce along the ts and adjacent areas to determ ' strengt. sessmet focu identifying conditions indicative of poti acts or to the utility as follows: inc und i fare con verlyindmediately adjacent to the utility and backfill.o ater accumulations an t in subsuo ace system components (manholes and concrete g ble encasement pipes)go .SGPaR e to at-grade or abowr n 'ade system features and equipment.

S~e from normal inc ion conditions, including settled, tilted, or heaved system fe a equiPme R Additional

"' re performed to further characterize the subsurface at the facility icuigare .... it... io.... ns indicative of potential flood-related impacts or damage were observed.

These composed of the following non-invasive geophysical and invasive geotechnical investigations." GPR. (Test reports were not available at the time of Revision 0.)" Seismic surveys (seismic refraction and refraction micro-tremor). (Test reports were not available at the time. of Revision 0.)" Geotechnical investigations including borings in the vicinity of the utility to determine current soil conditions and capacities.

Note that OPPD required vacuum excavation for the first 10 ft of proposed test holes to avoid utility conflicts.

Test reports will thus not show Priority 1 Structures Fuel Oil Storage Tanks and Piping Page 5.18-4 Rev. 2 soil conditions in the upper 10 ft of test boring logs. (Test reports were not available at the time of Revision 0.)Paved areas were evaluated with GPR and dynamic deflection methods (i.e., drop weight deflectometer). (Test reports were not available at the time of Revision 0.)5.18.3.2 Assessment Procedures Not Completed Assessments ofthe-Fuel-Oil Storage Tanks and Piping that were following:

a No excavation to inspect underground, systems and tior 5.18.4 Analysis pleted include the Identified PFMs were initially reviewed as discussed in Section 34 preliminary information available from OPPD data files and from Eleven PFMs associated with five different Triggering Mechanisir"non-credible" for Priority 1 Structures, as discussed in forward as "credible." After the design review for e results of available geotechnical, geophysical, and data w were ruled out as discussed in Section 5.18.4.1.

PFMs c are discussed in Section 5.18.4.2.

-s were d 5. There own obse -'uned to be FMs were carried ions, and the nu f CPFMs deta. ed assessment zed, a td for 5.18.4.1 Potential Failure M(Assessment the C n of the Detailed The ruled-out CPFMs reside'will not,1 ý ý Pote category and for clarity.ix.Ffg -M FM 2b -Loss of FM 2c -Undermin for ruling out: 0erosion was c ng. In

• ce acros:2iýd along the surface overlying the Fuel Oil Storage Tanks localized and limited surface erosion was observed on the cility. Therefore surface erosion-induced failure is discounted le to this system.grou as a Triggering Mec , 4 -Hydrostatic Lateral Loading (water loading on structures)

CPFM 4c -Wa failure in flexure CPFM 4d -Wall failure in shear CPFM 4e -Excess deflection Reasons for ruling out:* Underground storage tanks and buried piping are designed to be below the groundwater surface." The tanks were nearly full during the 2011 flood.

Priority 1 Structures Page 5.18-5 Fuel Oil Storage Tanks and Piping 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 Reason for ruling out: Fuel storage tanks FO-1 and FO-10 are located bel ound an -usceptible to hydrodynamic loading. Fill and vent pipes for thes we o oving water following the failure of the Aqua Dam and until it w e ucture fuel storage and pipelines (FO-27) are above ground. Fuel s components ible t this loading show no observable signs of movement Triggering Mechyad suou tncy, Uplift Forae Ten Structue i CPFM 6b -Cracked slab, loss of structural CPFM 6c -Displaced structure/broken c Reasons for ruling out: " Undergrmund storage tanks ant flod evet w u ndged of the groundwater orstrfactue.

vbainoiiitesiiufcin SThVisibe indicaion nearly fuea the 2011 fl wTerg erin anism n -apse (first ti C d stru, en connections 7d -Piles from do asons for ruling out: l dsupporting and surroui Fuel Oil Storage Tanks and Piping has been previously d..Th peak flood el nprior to 2011 was 1003.3 ft. which occurred in 1993.Nuiiation of soil sett. utwas observed during site inspections pertaining to these etanks. ".Triggering Liquefaction CPFM 10 d-...... structureibrokencontis CPFM 10d -le group instability Reasons for ruling out: " Machine vibrations from the facility (turbine and various pumps) have historically occurred and no indications of these CPFMs are evident." Pumps used on site during the flood event were judged of insufficient size to* cause ground or structure vibrations to initiate soil liquefaction." Visible indications of liquefaction were not observed around the areas where the pumps were operating and no occurrences of liquefaction were reported to HDR.

Priority 1 Structures Fuel Oil Storage Tanks and Piping Page 5.18-6 Rev. 2* No structure movements indicative of soil liquefaction and resultant settlement were observed; no structure cracking or lateral movements were observed.Triggering Mechanism 11 -Loss of Soil Strength due to Static Liquefaction or Upward Seepage CPFM I1 b -Displaced structure/broken connections CPFM 11 c -Additional lateral force on below-grade walls CPFM 1 d -Pile/pile group instability Reason for ruling out:* This has not been observed on site.Triggering Mechanism 12 -Rapid Drawdown n4 n s CPFM 12a -River bank slope failure and undermini ng structure CPFM 12b -Lateral spreading Reasons for ruling out:* The structures did not have evident si" Slope failure was not observed at the" River stage level has receded and stat river level at 40,000 cfs as of el a The river bank is armored is bank.Triggerinrg T e _Mn anism 13 -rgei CP aon of X1 at a 11. A to the nominal normal cted and~bilIzed the existing river for ruling out: Underground fuel tanks at otective coating and cor N' , corrosive nature of 1 ing are resistant to corrosion by design, through the use of Sallowance in design. There are no flood-induced changes vironment.

FO-27, is a ConVault fuel oil storage tank. This tank is a e tank. The exterior surfaces of the concrete encasement is omponents for this tank are located at the top of the tank and not 6 eground store ficased steel col #Afexposed Priority 1 Structures Page 5.18-7 Fuel Oil Storage Tanks and Piping Rev. 2 Triggering Mechanism 14 -Frost Effects CPFM 14a -Heaving, crushing, or displacement Reasons for ruling out: a Fuel oil storage tanks FO-1 and FO-10 are pile-supported with the pile caps located well below frost depth, thus not subject to frost heave.* Fuel storage tank FO-27 is supported by the Intake Structure, *ch is pile-supported and not susceptible to frost effects. Piping for this tank is b1 I ccommodate some movement.* Conditions have not been changed due to the flood 5.18.4.2 Detailed Assessment of Credible Potenti des The following CPFMs are the only CPFMs carried forwa ed assessme Oil Storage Tanks and Piping as a result of the 2011 flood. es s are only to tanks FO-1 and FO-10 and associated piping beca Tank FO- orted on the ntke Structure.

The detailed assessment is provided Triggering Mechanism 3 -Subsurface E fPipin CPFM 3b -Loss of lateral support for foundati imping)CPFM 3c -Undermined buried utiliti e to g)Subsurface structures in the gen ni of th oil tanks , ing that were pumped during the flood due to gro infiltration i ed Ma -5 and the Turbine Building sump pit.This T ism an could occur as ows: multiple potentially connected see , sh' soil ba the site, including soil backfill in utility trenches, tench beddi _. n flo with open/broken joints, and pre-existing"s/voids under pave epot age includes settlement of pipe. Settlement overstress a pipe that is ' sed and c use a pipe or its connections to break, which cause failure of the pip stem.g are field observatioms

'd data that support the likelihood of these CPFMs: Building was pumped continually during the flood event. The five pipesd to t p pit are floor drain and condensate system flush drain pipes.Since o tn system, no infiltration of groundwater should occur in the system.The infiltr iundwater into the system indicates an open flow path." MR-5 was pur" for the duration of flooding to remove water entering into the manhole.Known water sources included ducts from MH-31 and ducts running to the Auxiliary Building.

Pumping created a head differential.

• The flow of water into MH-5 was observed on multiple field visits. Sediment deposits (and fish) were observed in the bottom the MH-5 when it was emptied on September 14, 2011.The sediment could be an indication of piping and, subsurface erosion.* A void area was observed beneath the concrete slab just north of the Security Building and east-southeast of MH-5.* Based on a conversation with the OPPD operations employee testing fire hydrant FP-3E on September 13, 2011, fire hydrant FP-3C, located northeast of the Security Building, was Priority 1 Structures Fuel Oil Storage Tanks and Piping Page 5.18-8 Rev. 2 tested on September 13, 2011, and failed, According to the OPPD operations employee, when opening the valve to test the hydrant, the base cracked and leaked and the valve had to be closed. The access cabinet was tagged out for repair at that time.0 Pavement distress was observed along the driveway corridor between the Intake Structure and the Service Building.

Distress indicators include observed slab settlement and undermining (as evidenced by hollow-sounding pavement area).Following are field observations and data that indicate these C* No indications of soil subsidence or piping were obs ar piping system for tanks FO-1 and FO-10.* Site soils above and around tank FO-10 and around and stable. Soil probing indicated no soft spots at th* Sediment and fish were observed in the bottom of M-H September 14, 2011. Sediment accumulations and s not be associated with this failure mode. The manhole was -failed and the area was inundated with water. nt and fis transported into the manhole with floodwa a The observed hole in the pavement, no e Sec ild developed by outflow from the surface .ps and failure modes. Temporary surface p ere Pu hoses placed over the Aqua I D On e di ge po (verify and reference a figur eld port) centrate eroded pavement and create 5 observed ho 0 Observed subsurface d -* dicators or kn ntt-locatedimmediately

!to the fuel st enl ig, co " ., been associate ith these into the river with r the observed hole ge flow might have damage in the corridor are Dat ed to!se CPFMs):&PR data and reportm Seismic Survey (refrac I(bee"q ed for assessment of subsurface conditions.)graph efraction microtremor).

served distress indicators and other data that would increase ation associated with these CPFMs for the Fuel Oil Storage Ilowing table summan2 rase the potential for d iping system.1b, Adveiifta Water was p Turbine BuilNdi*n Slab settlement wa 27.Idatioi Floodwater 0ly)Favorable (Degradation/Direct Floodwater Impact Less Likely)M ly pumped from the and MH-5 Soils were firm and stable surrounding tanks FO- 1 and FO-10.)ted northwest of tank FO-No soil subsidence was noted above or adjacent to tanks FO-1 and FO-10.Data Gaps:* Geophysical investigation data to address observed concerns.* Geotechnical investigation data to address observed concerns.* Existence, size, and location of voids Priority 1 Structures Page 5.18-9 Fuel Oil Storage Tanks and Piping Rev. 2 Conclusion Significant Potentialfor Degradation/Direct Floodwater Impact None of the indicators for these CPFMs have been observed at the structures.

However, voids due to pumping of MH-5 might not have been evident at the time the field assessments.

Additionally, the extent of voids due pumping of groundw in rb uiding sump has not been determined.

Field observations indicate th tial ation has occurred due to these CPFMs is low.Implication Depending on the location and extent of the subsurface er CPF pipe movement or tilted foundations negatively impacting or intended the Fuel Oil Storage Tanks and Piping. Therefore, the implication otential de tion for these CPFMs are high.Confidence The data at hand are not sufficient to rule ese C o a conclusion that the Fuel Oil Storage Tanks and Piping aror bec erm se of these CPFMs.Therefore, the confidence in the asse sment ,which a more data are necessary to draw a conclusion.

Summary For discuss P, the combined consideration of the potential for de n and the ons of adation to a structure of this type put it in the "not"category.

current1 l cted are not sufficient to rule out these CPFMs.,erefore, the confidence above t is "low," which means more data or ntinued monitoring and in ns are necessary to draw a conclusion.

Trigg echanism 3 -.surface Erosion/Piping CP -Loss of IA,. upport for pile foundation (due to river drawdown)CPF der turied utilities (due to river drawdown)The Trigge.the river is affums'm and CPFM could then occur as follows: the drop in elevation of eooccur at a higher rate than the drop in elevation of the groundwater.

an increased groundwater gradient.

This increase could allow for subsurface erosion to occur.

Priority 1 Structures Page 5.18-10 Fuel Oil Storage Tanks and Piping. Rev. 2 Following are field observations and data that support the likelihood of these CPFMs:* Flood waters were at a high level for an extended period of time and saturated soils under and adjacent to facility site improvements." The observed void area beneath the concrete slab north of the Security Building and the pavement distress observed along the driveway corridor between the Intake Structure and the Service Building, support the likelihood that subsurface pi ing features/networks from within the site to the river exist.Following are field observations and data or site conditi in CPFMs are unlikely:* Tank FO-1 is located south of the Auxiliary Buildin fro t bank. Tank FO- 10 is offset from the river bank, outside the east wa Service Bu The offset from the river bank reduces the likelihood that own and rel subsurface piping to the river bank will impact these compon oid spaces c subsurface erosion would have to be significant eate conditi ause the Fuel Oil Storage Tank system to fail.R Data Gaps (data still required to assess the FMs):* Gauge report data for the fuel oil ta g, reco fuel es in the tanks and observations by OPPD emplo ke part er reuirements).

The following table describe ed distress or and r data that would increase or decrease the potential for d n associated s for the Fuel Oil Storage P ote i a Favorable (DegradationfDirect dpýwate rl mhk .h Floodwater Impact Less Likely)Noe aftheidctrs fore a t hee aP haveobeen obssperved a the sructures.

Howevrnod ended period d ofntmight d soils b een tween August 27, 2011 and September 18,and adjacent to facility 2011. This gap period in the scheduled vments. reduction of dam release rates was provided to"allow groundwater elevations to equalize with river fow elvatons' is armored; bank has beenprotected in previous floods.Data Gap 0 Obserr 9 H rbank following drawdown to normal river elevations.

0 Geophysical i~ ation data to address observed concerns.Geotechnical investigation data to address observed concerns.Conclusion Sig-nificance Potential for Degradation!Direct Floodwater Impact None of the indicators for theses CPFMs have been observed at the structures.

However, voids due to rapid drawdown might not have been evident at the time of the field assessments.

Priority 1 Structures Page 5.18-11 Fuel Oil Storage Tanks and Piping Rev. 2 Additionally, the extent of voids created by rapid drawdown could be insignificant.

The potential that degradation due to these CPFMs has occurred is low.Implication Depending on the location and extent of the subsurface erosion, these CPFMs could manifest as pipe movement or tilted foundations which could negatively impact the integrity or intended function of the Fuel Oil Storage Tanks and Piping. Therefore, the Aplications of the potential degradation for these CPFMs are high.Confidence The data at hand are not sufficient to rule out these CP a c thatthe Fuel Oil Storage Tanks and Piping are or could become u d because CPFMs.Therefore, the confidence in the above assessment is low, ns more da to draw a conclusion.

Summary For CPFMs 3e and 3f, as discussed above, bine ration of ntial for degradation and the implications of that d tion to f this typ t it in the "not significant" category.

The data currently cted ar u i rule out these CPFMs.Therefore, the confidence in the ab ass nti whi more data or continued monitoring and inspe enecess Iraw a c u n.

Priority 1 Structures Fuel Oil Storage Tanks and Piping Page 5.18-12 Rev. 2 5.18.5 Results and Conclusions The CPFMs evaluated for the Fuel Oil Storage Tanks and Piping are presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

Confidence fficient Data)High Confidence (Sufficient Data)I CPFM 3c CPFM 3e CPFM 3f 5.18.6 ended and 3f. N Indicator condensate si building (Ke 4.2 and 4.3.g actions are recomm dfor the FSf Storage Tanks and Piping: Review the and geophysical dataa ess the impct on the Fuel Oil Storage Tanks and Piping.Lsic investigations and p I modifications are recommended to address CPFMs 3b, 3e, PFMs are associated urbine Building basement drain piping system (Key Distress,avement failure ai ole in and near the access area southwest of the nk (Key Dist "Iicator #2), and Column settlement in the Maintenance Shop y 13i ndicato ese recommendations are described in detail in Sections 4.1, CPFM 3c for fuel tank V3 1I be addressed under separate investigation due to the following:

1. The observed sand-boil/piping feature in the Auxiliary Building missile shield room is not associated with or addressed in the KDI investigations.

2. The distance from fuel tank FO-1 to the access corridor, reduces the likelihood that results from the KDI investigations could be used to rule out CPFM 3c for fuel tank FO-l.Also, inventory control and leak detection results should continue to be monitored and compared to the results of inventory control and leak detection prior to the 2011 flood.

Priority 1 Structures Page 5.18-13 Fuel Oil Storage Tanks and Piping Rev. 2 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.

5.18.7 Updates Since Revision 0 Revision 0 of this Assessment Report was submitted to OPPD on ob 0 evision 0 presented the results of preliminary assessments for each Priori c assessments were incomplete in Revision 0 because the forensic investigation an onito st of the Priority 1 Structures was not completed by the submittal date. evis t essment Report includes the results of additional forensic investigation and mon e for Rpr: a described below.5.18.7.1 Additional Data Available The following additional data were available for e .il Storage sad Piping for Revisions 1 and 2 of this Assessment Report:* Results of KDI #1 forensic investigati eae SectioET SResults of KDI #2 forensic investigati ee Sec In.2" Results of KDI #3 forensic in ati e S 4.3)* Additional groundwater mo well and stge 1ev j afrom OPPD.* Field observations of the n(see Secti '25)." Results of falling weigh I meter investi erican Engineering Testing, Inc.invsti ~y Geotechnology, Inc. (see Attachment 6).s of geote ' vestiga Thiele Geotech, Inc. (see Attachment 6).'ata obtained from eters b e. Geotech, Inc. (see Attachment 6).sults of continued s Lamp son and Associates (see Attachment 6).,.7.2 Additional Analys'S FMs were identifi

0. Additional analysis related to CPFMs 3b, 3e, and 3 ussed in Secti $ifor KDI #1, Section 4.2 for KDI #2, and Section 4.3 for KDI#3. In a to analysis ciated with the KDIs, analysis of the additional data listed above has clarifi i d confidence for these CPFMs. The following analysis of additional da ted for the Fuel Oil Storage Tanks and Piping: " Groundwater Monitoring well and river stage level data from OPPD.Data shows that the river and groundwater have returned to nominal normal levels.* Field observations of river bank No significance distress from the 2011 Flood was observed.

Priority 1 Structures Page 5.18-14 Fuel Oil Storage Tanks and Piping Rev. 2* Results of falling weight deflectometer investigation by American Engineering Testing, Inc.Falling Weight Deflectometer and associated GPR testing performed in the Paved Access Area identified anomalies 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 report by Geotechnology Seismic Refraction and Seismic ReMi tests perform nd perimeter of the power block as part of KDI #2 identified deep ano that co el, soft clay, loose sand, or possibly voids." Results of geotechnical investigation by Thiele Geotec Six test borings were drilled, with continuous sampli t countered, truth the Geotechnology, Inc. seismic investigation results as p e KDI #2 fore .sc investigation.

Test bore holes were located the deep es identified in the seismic investigation.

The test boring da y piping very soft/very loose conditions that might be indicativ ubsurac piping o d material loss or movement.All of the SPT and CPT test re co .ed feAsses _ ort were compared to similar data from numero geo echn vestigati t have been conducted on the FCS site in previo .This comp, n did no rtify substantial changes to the soil strength and sti er that time p CPT test results were not perform he top 10 f6 tect existing.r~sto dat : ared to the original baseline measurements, have not Seded the accu e oft ometers. Therefore, deformation at the monitored* cations since the in n of the entation has not occurred.Results of continued s urve Rynearson and Associates.

eydata to date cop h rgnlbaseline sreshav~e not exceeded the cy range of the su Ug equipment.

Therefore, deformation at the monitored 10 since the s ." seline was shot, has not occurred.Updates to e ures not completed are outlined in Section 5.18.3.2.The following pr, he previously identified CPFM 3c for fuel tank FO-1 which is not associated with I and the new interpretation of the significance and confidence based on the new data.Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3c -Undermined buried utilities (due to pumping)A sand boil/piping feature was observed in the Auxiliary Building, missile shield room. This feature is an indication of subsurface erosion near fuel tank FO- 1, more specifically, the fuel tank piping into the Auxiliary Building.

Priority 1 Structures Page 5.18-15 Fuel Oil Storage Tanks and Piping Rev. 2 Significance Potential for Degradation/Direct Floodwater Impact Indication of this CPFM has been observed.

This appears to be isolated to an area inside the missile shield room. From feature documentation and plant construction plans, the observed feature coincides with the fuel tank piping route into the Auxiliary Building.

The potential is high that this CPFM has occurred with respect to the fuel tank pip system.Implication The occurrence of this CPFM could negatively impact nction el tank FO-1 piping system. Subsurface erosion occurring over a far lead t ettlement, or broken pipes or connections, negatively impacting the int tended f the fuel piping system. Except for the boil/piping feature, no othe bsidence or observed inside or outside the missile shield room. There e, jication of th.degradation for this CPFM is considered low.Confidence The extent of subsurface erosion and the p ial impa ctures w ot known due to the lack of data gathered on subsurface itions. eqa inspections and a review of surveyed data indicate n c *ove n site. tures have been monitored and no signs of move ye en d .d. The I e of this CPFM could be inadequate to initiate mov d associate age oft u rrounding structure and piping system. Therefore, dence for this 'al mode is high.the p for degradation and the implications of that ation to a structu type p e "significant" category.

The confidence in the've assessment is "high, means p Imdfcto sncsay Revised Results a cmedain T .s evaluated for the Oil Storage Tanks and Piping are presented in the following mat shows the ratWg the estimated significance and the level of confidence in the evaluati.

M 3c for Oil Storage Tanks and Piping (tank FO-1) is not associated with the ess rs. The recommendations for physical modifications to remediate im ed with this CPFM are as follows: excavate the sand boil/piping feature in the mis ield room to determine the extent of potential undermining; then backfill the pipe tre ah as necessary with compacted granular material.

Following the implementation of this recommended physical modification, and assuming that no further concerns are identified through the monitoring program for the Fuel Oil Storage Tanks and Piping (discussed in Section 5.18.6 and continuing until December 31, 2011), this CPFM is moved to the quadrant of the matrix representing "No Further Action Recommended Related to the 2011 Flood." CPFMs 3b, 3e, and 3f for the Fuel Oil Storage Tanks and Piping are associated with Key Distress Indicator KDI #1, KDI #2, and KDI #3. Section 4.1, Section 4.2, and Section 4.3 present the results of additional forensic investigation that was conducted to ascertain whether these CPFMs could be ruled out. The results of the additional forensic Priority 1 Structures Fuel Oil Storage Tanks and Piping Page 5.18-16 Rev. 2 investigations show that if the recommendations for physical modifications in KDI #1 and KDI#3 are implemented that these CPFMs are ruled out. Therefore, assuming that no further concerns are identified through the monitoring program for the Fuel Oil Storage Tanks and Piping (discussed in Section 5.18.6 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." Low Confidence (Insufficient Data)e~pce.I 8.7.2 Conclusions A.eassessment of the FCS Mr yes, the first step was to develop a list of all Triggering mi.e, isms and PFMs that c Iave occurred due to the prolonged inundation of the FCS sit he 2011 MissourIi r flood and could have negatively impacted these structures.

The n %was to use da various investigations, including systematic observation of the struc. r time o eliminate the Triggering Mechanisms and PFMs from the list or to recoin e , estigation and/or physical modifications to remove them from the list for any par cture. Because all CPFMs for the Fuel Oil Storage Tanks and Piping other than CPFM .c, 3e, and 3f have been ruled out prior to Revision 1, because CPFM 3c has been ruled out assuming the implementation of the recommended physical modifications presented in the paragraph above, and because CPFMs 3b, 3e, and 3f will be ruled out when the physical modifications recommended for KDIs #land #3 in Sections 4.1 and 4.3 are implemented, no Triggering Mechanisms and their associated PFMs will remain credible for the Fuel Oil Storage Tanks and Piping. 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 5.19 Main Underground Cable Bank, Auxit Auxiliary Building to Inta Structure* ..... ..... .. .. .. .. .

....; ."== = : ' : :. .=..; :.-=- = 2 ..:i;." ;" .?i=, ?-:" : .: I S" Priority 1 Structures Page 5.19-1 Main Underground Cable Bank, Auxiliary Building to Intake Structure Rev. 2 5.19 Main Underground Cable Bank, Auxiliary Building to Intake Structure 5.19.1 Summary of Main Underground Cable Bank, Auxiliary Building to Intake Structure Baseline information for the Main Underground Cable Bank from the Auxiliary Building to the Intake Structure is provided in Section 2.0, Site History, Description, -and Baseline Condition.

The portion of the Main Underground Cable Bank system covered der ect' extends from the Auxiliary Building to MH-3 1, which is adjacent to the southwes r o -Structure.

There are two duct banks that begin at the south face of the Auxiliary ing. ucts turn 90' and combine into one 7-ft-wide, 3-ft, 2.5-in.-deep, concrete-encas t-ba runs east to MH-5 in a corridor between the outside face of the Turbine Bu SotWUaru.

At MH-5 the ducts are split into two separate duct banks before pen manhole. cts then turn 900 to the north and run parallel to the east face of the Servi Southeast of Fuel Oil Tank 10, the duct bank turns to the northeast and angl o Intake Struc Adjacent to the southwest corner of the Intake Structure, the duct bank ma al bend tot east and terminates at MH-3 1. The duct bank configuration etween d MH-3 1. The size of the duct bank entering MH-31 is 4 ft 9 in wid. ep per re plan data.The conduits from MH-31 feed into the west side ntake S From fie rvations, MH-31 is partially filled with insulation installed

'e north aIs of the structure and which reduces the open space of the manhole to a narr rea.5.19.2 Inputs/References Supportin.

a , Table 5.19-1 lists references provid PPD and othe e d to support HDR's analysis.Re -r ain Und ound Cable Bank,o. ME f ri ...,d un: Sxilia to Intake Structure cu "~mn~titlNF Document Date Drawing mnmber No./Aif 14a (i licable Page Number(s)Ui und Duct System 60184 12/13/2002 CE-79-3 Site 1qbnderground Ducts -ManholesL 12582 Unknown 11405-E-319 Outdoof ".%.g -Fence Grounding P Undergrou' i ..& Manholes 12583 Unknown Sections & DU ,',,..Underground anholes 12584 Unknown 1 1405-E-321 Sections & Details sf Underground Ducts & 12585 Unknown 11405-E-322 SH.3 Sections & Details Electrical Underground Duct Bank -Site 16581 Unknown 11405-S-410 Plan Foundation-Plan Transformer Yard Unknown 11405-S-411 Naval Facilities Engineering Command, 9/1986 All Design Manual 7.01, Soil Mechanics Detailed site observations-field reports, field notes, and inspection checklists-for the Main Underground Cable Bank from the Auxiliary Building to the Intake Structure are provided in Attachment

8.

Priority 1 Structures Page 5.19-2 Main Underground Cable Bank, Auxiliary Building to Intake Structure Rev. 2 Observed performance and pertinent background data are as follows:* OPPD assistance is required for inspection of the electrical duct bank manholes and appurtenant system components.

Access and egress into the manholes will be required by OPPD personnel to assist in the evaluation of the system." Water levels in the system require that manholes and appurtenant ducts be pumped dry before the interior of manholes can be inspected.

• MH-5 was opened by OPPD employees and then emptied by Thiele N technical employees using a "Jet-Vac" on Wednesday, September 14, 2011. The water 1e p .g of vacuuming activities measured 8.8 ft from the rim of the manhole. Due size uum storage tank, multiple trips were made to empty the manhole." After MI--5 was emptied, observations were made to dete if in f uld be observed.

No drainage into the manhole was observed durn 15 min er the manhole was emptied. Approximately I hour and 10 minutes 1 a ditional accumulation was observed when rechecking the manhole.* The Aqua Dam surrounding the facility crossed the Undergro d Ca k.* The Aqua Dam failed for a short period of time due to damaged, floodwater to enter the area inside the Aqua Dam perimeter.

All surfa Undergro le Bank were inundated when the facility Aqua Dam failed.* Equipment outside the perimeter of the replac Aqua D undated f extended period of time. A hole in the pavement and v '?rea ben e e slab is north of the Security Building and east-southeast of MH- e hol oid a btside the perimeter of the Aqua Dam that surrounded the faJ r Th iave ailre t at the intersection point of pavement jointing.

The hole in t ement is ' atr-shape is more than I ft wide both in the north-south and east , f ections. en hole was approximated as a 4-t-imee-b-I -i-ee o .asured by a tap ugh the hole.* The holen t is near t ed discharge a pump operated prior to the remova 'd eatibuted to scour created by the discharge of the pump gfo n .eriod a n one place or to subsurface erosion.* Fir ction Cabinet FP- of the Building and east-southeast of MH-5 is located mity to the pavement d void scussed above. The fire hydrant was tested on mber 13, 2011 (reportedly ailed. Accrdn to OPPD operations personnel testing FP-si te inspections, the ba cracked when opening the valve. The fire hydrant.. wn and the access cb astagdo." Concr e corridor that exte etween the Service Building and the Intake Structure exhibits s that indicat ss including cracking, slab settlement, and undermining.

Pavement s g was d northwest of the Intake Structure and east of the abandoned acid tank. A "ct vement area was noticed east of the Service Building truck dock.And pavement cr -evident throughout the entire area, although most of the pavement cracking could be pret .N.mg conditions due the age and use of the facility.* Flow into the basemenrt ump of the Turbine Building from the building floor drain system is occurring and has a recorded history dating back to 1997.* Settlement of a column in the Maintenance Building, north of the Turbine Building, has been documented.

The Turbine Building and the Maintenance Building are west of the corridor and associated utility alignments within the corridor.* The fire hydrant located in FP-3E was being tested on September 13, 2011, during site investigations.

No operational problems were observed during the time on site.

Priority 1 Structures Main Underground Cable Bank, Auxiliary Building to Intake Structure Page 5.19-3 Rev. 2 OPPD operation personnel, testing the fire hydrant at FP-3E, were questioned about other fire hydrant tests. The OPPD employee questioned noted that no problems were observed for the fire hydrant at FP-3D during testing. The information on the problem at FP-3C, noted previously, was gathered at this time.5.19.3 Assessment Methods and Procedures 5.19.3.1 Assessment Procedures Accomplished Assessments were made by walking the cable bank alignm the system (manholes) and the ground surface overlying surface assessment included using a 4-ft-long, 0.5-in.-d soil probe to hand probe the ground surface along the ud determine relative soil strength.

The assessment focused potential flood-related impacts or damage to the utility as irface features of bank. The r.glass T-handle t areas to tý icative of ying con(* Ground surface conditions overlying and immediate backfilled trench including scour, subsidenc_

heave.* Soft ground surface areas (native soil, e ered fi determined by probing." Water accumulations and flows in sub ce sy cable encasement pipes). A& A.y adjacei tility and its""'ng, piping, and tone gra, ement) as IMp iholes and concrete 0 0 Damage to at-grade or a Variance from normal ir features and equipment.

and eqi ina sel9.nt.tilted, or heaved system 0 s the system operational).

characterize the subsurface at the facility itial flood-related impacts or damage were sive geophysical and geotechnical(Test reports were n " ilable at the time of Revision 0.)A r c surveys (seismic tion and refraction micro-tremor). (Test reports were not a t at the time of n 0.)Geo 1 investig" including test borings with field tests (SPT and CPT) and laborat Ss. N OPPD required vacuum excavation for the first 10 ft of proposed test holes' ' conflicts.

Test reports will, therefore, not address soil conditions in the upper site and locations where shallow utilities exist. (Test reports were not available at thel.me of Revision 0.)5.19.3.2 Assessment Procedures Not Completed Assessments of the Underground Cable Bank, Auxiliary Building to Intake Structure, that were not completed include the following:

• The interior of underground cable bank manholes and connecting concrete-encased cable pipes in the Protected Area were not inspected except for visual observations that were possible from above and behind temporary safety railings.

Manholes are a confined space Priority 1 Structures Main Underground Cable Bank, Auxiliary Building to Intake Structure Page 5.19-4 Rev. 2 as defined by OSHA regulations.

In accordance with these regulations and OPPD FCS safety procedures, manhole entry is a permit-required confined space entry and can only be performed by appropriately trained OPPD personnel.

No excavation to inspect underground systems and conditions was performed.

No camera inspection of the system was completed.

0 0 5.19.4 Analysis Identified PFMs were initially reviewed as discussed in Section 3.preliminary information available from OPPD data files and fro-Eleven PFMs associated with five different Triggering MechaAi"non-credible" for all Priority I Structures, as discussed in Sec 'carried forward as "credible." After the design review for eachj and the results of available geotechnical, geophysical, and survey CPFMs were ruled out as discussed in Section 5.19.4.1.

The CPFN assessment are discussed in Section 5.19.4.2.5.19.4.1 Potential Failure Modes Ruled Assessment All of the ruled-out CPFMs reside in the ignifica clarity will not be shown in the Potential t the were and for Triggering Mechanism 2 -Sui CPFM 2a -Underminin gsh CPFM 2c -Undermined urfae erososerved e ground surface overlying the alignment of the ain Underground

k. In aa , only localized and limited surface erosion was observed on the ground ' e across t cility. The Main Underground Cable Bank system is constructed at ranging from about 5 to 11 ft below existing ground surface sd sufficiently below pot scour depths indicated by erosion features observed in areas.se (first time wetting)settlement of shallow foundation, loss of structural CPFM 7b 'N"jivl structure/broken connections CPFM 7c -G( I site settlement Reason for ruling out:* Soil supporting and surrounding the Main Underground Cable Bank system has been previously wetted. The peak flood elevation prior to 2011 was 1003.3 ft, which occurred in 1993.

Priority 1 Structures Page 5.19-5 Main Underground Cable Bank, Auxiliary Building to Intake Structure Rev. 2 Triggering Mechanism 10 -Machine/Vibration-Induced Liquefaction CPFM 10a -Cracked slab, differential settlement of shallow foundation, loss of structural support CPFM lOb -Displaced structure/broken connections CPFM 10c -Additional lateral force on below-grade walls Reasons for ruling out:* Machine vibrations from the facility (turbine and vario u Nipul eAA~storically occurred and no indications of these CPFMs are evident.* Pumps used on site during the flood event were ins ent to d or structure vibrations sufficient to initiate soil liquefaction.

Vis ndici -o tie'action were not observed around the areas where the pumps wer nd no o ces of liquefaction were reported to HDR.No structure movements indicative of soil liquefactio

• t settleme observed; no structure cracking, or lateral movements, ered.Triggering Mechanism 11 -Loss of Soil Stre Static Liq n or Upward Seepage CPFM I Ia -Cracked slab, differential ment ofs undation, of structural support CPFM 1 lb -Displaced structure/broke nnect'CPFM 1 ic -Additional later .e eo owi walls Reasons for ruling out:* Thes s ~ owed nos, distress at t[ ,'ld assessments.

1. Mechanir PM1a- Corrosio degue ason for rulingot.ground utilities and res are located below the design flood elevation for the Groundwater el ns controlled by Missouri River water elevations, percolation nter snow melt would be expected to contact underground impro incltu f nstructed steel and concrete facility elements.

As such, steel and nts are designed to withstand the corrosive environment of groundwate d soil.Triggering Mechanism 14 -Frost Effects CPFM 14a -Heaving, crushing, or displacement Reasons for ruling out:* Utility not adversely affected due to frost heave as long as joints remain tight.* Manholes are founded below frost level and should not heave." Conditions have not been changed due to flood conditions.

Priority 1 Structures Page 5.19-6 Main Underground Cable Bank, Auxiliary Building to Intake Structure Rev. 2 5.19.4.2 Detailed Assessment of Credible Potential Failure Modes The following CPFMs are the only CPFMs carried forward for detailed assessment for the Underground Cable Bank Inside the PA as a result of the 2011 flood. This detailed assessment is provided below.Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3a -Undermining and settlement of shallow foundatio ab/surfaces (due to pumping)CPFM 3c -Undermined buried utilities (due to pumr The Triggering Mechanism and CPFMs could occur a ws: III ially connected seepage paths existed in the soil backfill at the site, incl kfill. i trenches, granular trench bedding, building floor drains with open/binsmts, and 9g defects/voids under pavement.

The paths are exposed at s-, ns to the riv (e.g., a hole in the ground north of the Security building).is

n. of seepage pa connected to several pumping sources: the sump pit the Turbine g, Manhole M-5, and a series of surface pumps along the interior Dam per e pumps were operated for an extended period of time, maii fferential o epage path networks.

Gradientwas sufficient to begin e n of su soil. Se s unfiltered and erosion continues unarrested.

Erosion nds out, e networ of utility trenches, including the Underground Cabl k. Vo e cr er the pavement and along the utility trench walls. The tia ag des se f cable bank and manholes causing a loss of elec ectivity Following are field observ data that sup od of these CPFMs:* MH- for the of flooding t e water entering into the manhole.nclude om MH-31 and ducts running to the Auxiliary-m.This c end di .1.e flow of water inc was o n multiple field visits. Sources of the water were not Sediment deposits (and i ere observed in the bottom the MH-5 when it was emptied September 14, 2011. T diment could be an indication of piping and subsurface on.* inside the Aqua perimeter was pumped dry and created a hydrostatic headeen the side and the area outside of the Aqua Dam. The area inside te peri as pumped from several locations creating points toward which undergro " &subsurface flows would tend to flow.SA void arential piping location was observed beneath the concrete slab just north of the Securi llding and east-southeast of MH-5.* Based on a conversation with the OPPD operations employee testing FP-3E on September 13, 2011, fire hydrant FP-3C, located northeast of the Security Building, was tested that day and failed. According to the OPPD operations employee, when opening the valve to test the hydrant, the base cracked and leaked and the valve had to be closed. The access cabinet was tagged out for repair at that time.* Pavement distress was observed along the driveway corridor between the Intake Structure and the Service Building.

The area north of where the duct bank crosses the corridor includes observed slab settlement and undermining (as evidenced by hollow-sounding pavement areas).

Priority 1 Structures Page 5.19-7 Main Underground Cable Bank, Auxiliary Building to Intake Structure Rev. 2 The Turbine Building sump pit was pumped continually during the flood event. The five pipes connected to this sump pit are floor drain and condensate system flush drain pipes.Since this is a floor drain system, no infiltration of groundwater should occur in the system.The infiltration of groundwater into the system indicates an open flow path of some sort.Below are field observations and data that indicate these CPFMs are unlikely:* Sediment and fish were observed in the bottom of MH-5 whe, *was emptied on September 14, 2011. Sediment accumulations and smallfish

_ bottanm of M1H-5 might not be associated with these CPFMs. The manholesw ov Q e Aqua Dam failed and the area was inundated.

Sediment and fis w d have ,. rted into the manhole with floodwaters.

• The observed hole in the pavement, north of the Se been developed by outflow from the surface pumps and mi "e associate, ese CPFMs. Temporary surface pumps were pumping w to the river placed over the Aqua Dam. One of the discharge poin as e eed Concentrated discharge flow might have eroded avement and the observe e.* Subsurface erosion paths are limited betwee Structur e Service Building.The top of the Circulation Tunnel extend Paveme in the area are in the range of+/-1004 ft. Thus, for a lar tion of idor bee- Intake Structure and Service Building, the on, ssible s iiicrpath is rectly beneath the pavement slab." Any void spaces created by s ace' ion ave to cant to create conditions to cause the duct I fail.* Observed subsurface da,, dicators or kn' nstanc damage in the corridor are not located immediatel t to the Main em uct Bank.Data 'tired to hese CPFMs): Daask c d, await rts). The occurrence and extent of subsurface rosion is not known ime.Seismic Survey -refrac 0mography refraction microtremo.

Ilowing table describes ed distress indicators and factors that would increase the n a m-iated with these CPF M tnd factors that would make these CPFMs less likely.-grada Ict Favorable (DegradationlDirect Floodwater Impact Less Likely)pact p , -,"Ikely)A hole in the space underneath was 0h of the Security Building an I of MH-5. This location was outside the Aqua Dam perimeter and might be a void developed due to subsurface erosion.MH-5 was pumped continually during the time the site was flooded.Alternatively, the observed hole could have been developed by outflow from the surface pumps and might not be associated with these CPFMs. Temporary surface pumps were pumping water back over the Aqua Dam. One of the pump discharge points was near the observed hole (see photo). Concentrated discharge flow could have created the observed hole.-i Priority 1 Structures Page 5.19-8 Main Underground Cable Bank, Auxiliary Building to Intake Structure Rev. 2 Adverse (Degradation/Direct Favorable (Degradation/Direct Floodwater Floodwater Impact More Likely) Impact Less Likely)Monitoring well data seems to indicate a cone of influence around the facility that might be attributable to the subsurface drainage flowing to the Turbine Building sump Data Gaps:* Ground Penetrating Radar data are not available at the time of.Revi .in determining possible void areas at the facility % w Conclusion Significance Potentialfor Degradation/Direct Floodwater Impact MH-5 was continually pumped during the flood ev created a f head differential that created a potential direct path along the e]- %ank for su erosion. In addition, areas of pavement distress were ob in t or betwee ke Structure and the Service Building that might be tie -5 pu -s, a direc .ential source for subsurface erosion is linked to the sys .nd pote of subsurface erosion are* located in the region of the duct ban lii t.The Turbine Building sump, ref , ey Distr dicator 4 Iso creates a potential subsurface erosion path flect the elec bank it is located closest to the facility.

Groundwater momn ell readings seW .that there is a zone of influenc ttribute d.,wdown from a -, rce such as the Turbine Building sumwater, -s, high head conditions created the potential for m-nubsurfu to poin o pressure (i.e., pumped locations) during the 2011 voentia.fr.i e ptetil ordegradatio sdr H ationW The ound cable ban tructural entity. The cables in the duct bank are flexible and some ection c rated. Small signs of distress due to this CPFM might be noticeable )D employees who work installing cables. A large-scale failure vfoid -- ductg of the cables would likely only be possible in' the case of a very large *gound voids usually present surface indications of underground distress.

Therefoi "e* implication of degradation for these CPFMs is low.Confidence Information on the duct bank is limited to inspection information gathered from observations made along the duct bank alignment and visual observations made through the top of MH-5 and MH-3 1. Detailed information was not available from an inside inspection of the manholes or from information provided by OPPD employees.

Therefore, the confidence in the above assessment is low. "Low Confidence" indicates that additional information and studies are required to increase the confidence in the above findings.

Priority 1 Structures Page 5.19-9 Main Underground Cable Bank, Auxiliary Building to Intake Structure Rev. 2 Summary For CPFMs 3a and 3c, as discussed above, the combined consideration of the potential for degradation and the implications of that degradation to the system puts it in the "significant" category.

As discussed, the potential for degradation is composed of two parts. The potential for subsurface erosion appears to be high based on flood-induced conditions and data regarding the Turbine Building sump and MH-5. However, the potential for subsurface erosion impacting the underground duct bank to a point of failure without- ible signs of distress prior to failure of the system appear to be low. The data current oil e ufficient to rule out this CPFM. Therefore, the confidence in the above a ment ich means more data or inspections might be necessary to draw a cclnch Triggering Mechanism 3 -Subsurface Erosion/Pipin_ CPFM 3d -Undermining and settlement of shallow fd`datm due to rive drawdown)CPFM 3f- Undermined buried utilities (due wdown)This CPFM is similar to CPFMs 3a and 3c,, stead og, the gra' created by rapidly receding river level.The Triggering Mechanism and CQ s cc_. hen as fr level drops faster than pore water pressure in the s. dation c lpate. At ie ttis created that moves water and soil into existing defe- nd enlarges along t le bank and through the soil toward the river via piping , .or networks.

ces include damage to adjacent struc es such as f evtion piping, ra png, and the Trenwa.Fiel that su e likelihood of these CPFMs are as follows: d observation o er bank been completed since the river release rate abilzed at 40,000 c on Oct 2011. The nearest utility installations have notbeen observed on a r to ipect for developing conditions or distress dicators.rvations and data or conditions that indicate this CPFM is unlikely are as folldo ,* US ced Mis ver Mainstem System releases to 40,000 cfs on October 2, 2011. esponding to the 40,000 cfs release rate stabilized at the FCS on October 0 The Main Un round Cable Bank is offset from the river bank. This offset reduces the likelihood that rapid drawdown and related subsurface piping to the river bank will impact the Main Underground Cable Bank.* Soils in the area of the Main Underground Cable Bank and to the east are backfill materials that were placed and compacted during construction of site improvements and, therefore, would be expected to be less susceptible to rapid drawdown impacts.* Void spaces created by subsurface erosion would have to be significant to create conditions to cause the duct bank to fail.

Priority 1 Structures Main Underground Cable Bank, Auxiliary Building to Intake Structure Page 5.19-10 Rev. 2 Data Gaps (data have yet to be acquired to assess these CPFMs):* Inspection of the riverbank following drawdown to normal river elevations.

• Geophysical surveys (GPR, seismic refraction and refraction micro-tremor) in the protected area. (Test reports were not available at the time of Revision 0.)* 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 A*Pig logs. (Test reports were not, available at the time of Revision 0.)The following table describes observed distress mdi, risk associated with these CPFMs and factors that w increase the likely.Adverse (DegradationlDirect Floodwater Impact More Likely)Floodwaters inundated the site for an extended period of time and totally saturated site soils.'for nearest installation ofth " ' Underground Cable Bank system to the river bank is MH-ated at the southwest co f the Intake Structure.

The structure is located on the west.e structure and a dire nection from the manhole to the river bank is not possible.The is armored historically protected and stabilized the existing river bank.The pote degra reduced due to these improvements.

USACE reduc River Mainstem System releases to 40,000 cfs on October 2, 2011.River levels corre ing to the 40,000 cfs release rate stabilized at the FCS on October 4, 2011. Groundwater levels had thus started to stabilize between the termination of drawdown reduction and the time of Revision 0. The potential for development of subsurface erosion due to river drawdown decreases with the time due to stabilization between groundwater elevations and river elevations.

The potential for this CPFM thus decreases with time as long as subsurface erosion has not instigated and created a flow path that will be subject to future impacts.

Priority 1 Structures Main Underground Cable Bank, Auxiliary Building to Intake Structure Page 5.19-11 Rev. 2 As groundwater elevations and river elevations stabilize, the head potential between the two conditions will decrease and the possibility of subsurface erosion will also decrease correspondingly.

In addition, the stabilized river embankment reduces the likelihood of these CPFMs.Overall, the potential for degradation is considered low for these CPFMs.Implication The underground cable bank is a structural entity. The r.some minor deflection can be tolerated.

Small signs of 4 noticeable to experienced OPPD employees who work of the duct bank and shearing of the cables would likelyM large void. Large underground voids usually present surf distress.

Therefore, the implication of degradation for tht Confidence Data are not available to make a determinatioN Time between the termination of the steady tion of time without indications of subsurface erol does not not present. Thus, confidence with the as., ent is b0 Summary For CPFMs 3d and 3f, as di above, the co d degradation and the implicati1 4hat degradatio categor 4 the pot tifor degradation I for hU.i .wate s versus river e.due: are flexible and FM might be ge-scale failure e of a very 6096und WItMtions of u low.rates drawdown.a most current at damage is 0 ation of the potential for Wiem put it in the "not significant" sidered low because the potential levations is unlikely due to stabilized)tected nature of the existing bank.this CPFM. Therefore, the confidence r continued monitoring and ie, and the prc rule out1data o inal assessmer (water loading on structures)

CPFM 4V The Triggering MdWanism and CPFMs could occur as follows: water level rises and imposes additional unbalanced lateral pressure on manhole walls exceeding shear or flexure capacity of the wall and/or causing excessive deflection or failure. Alternatively, the wall transfers load to supporting elements, overloading them. The supporting elements fail allowing below-grade walls to fail. These CPFMs are credible only for possible degradation to manhole MH-5. The remainder of the system is non-structural (a poured concrete encasement with no walls, floors, or roof structures) or was not exposed to hydrostatic loading beyond design standards (MH-31 was flooded and therefore balanced as regards hydrostatic loading).

Priority 1 Structures Page 5.19-12 Main Underground Cable Bank, Auxiliary Building to Intake Structure Rev. 2 Following are field observations and data that support the likelihood of these CPFMs: MH-5 was pumped for the duration of flooding to remove water coming in from duct banks extending between the Auxiliary Building and MH-3 1. Floodwaters outside the Aqua Dam perimeter were above grade and possibly created a hydraulic head condition greater than the design standard for underground structures (i.e., hydraulic loading to the ground surface).Following are field observations and data that indicate these" No movement or distress of MH-5 concrete cover w" After pumping MH-5 dry on September 14, 2011, ni" 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 10 minute time period.Following are observations and data still required to assess* Visual inspection and photographs of the inside of MH-" Visual inspection of the inside of MH-31 was de.manhole prevents access and visual inspect'* Basis of design/design assumptions fort 0 e The following table describes observed di s indic risk associated with these CPFMs and fac at w a]noted over a Adverse (Degra Floodwater Impa MH-5 was continually Manho I 5-bur lnderground utilities are designed water conditions and forces.No leakage was noted after observing MH-5 get pumped hdry with high groundwater conditions still existing.Floodwater Impact Indicators fori> CPFMs 4c, 4d, and 4e on only the MH-5 element of the Main Underground Ca k have been observed.

These include continual pumping from manhole MH-5 and oodwater elevations above the ground surface outside the Aqua Dam perimeter, resulting in hydraulic head conditions greater than the design standard for MH-5.However, MH-5 is designed for high groundwater conditions and forces. The possible additional forces related to about 3 ft of additional head from floodwaters outside the Aqua Dam perimeter are not believed to be sufficient to cause degradation of MH-5 due to these CPFMs. In addition, following pumping MH-5 dry on September 14, 2011, no visible water inflow was noted over a 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 10 minute time period. Therefore, the potential for degradation to the Main Underground Cable Bank system due to CPFMs 4c, 4d, and 4e is low.

Priority 1 Structures Main Underground Cable Bank, Auxiliary Building to Intake Structure Page 5.19-13 Rev. 2 Implication As stated, a couple of CPFM 4c, 4d, and 4e indicators have been observed supporting low (or unlikely) potential for degradation to the MH-5 element of the Main Underground Cable Bank system. The occurrence of CPFMs 4c, 4d, and 4e on a large scale could result in degradation of MH-5 including wall failure in flexure, shear, or deflection.

For degradation from these CPFMs to impact service (i.e., damage that renders electrical cables carried by the system inoperable), degradation would need to result in complete failure elements of MH-5 and this is not deemed likely. Therefore, the implic n : for these CPFMs is low.Confidence Currently, evidence supporting possible degradation of, Underground Cable Bank system is based on possible f observations of physical site conditions as discussed ab(information obtained through geophysical surveys co [element of the Main Underground Cable Bank s Revision 0. Therefore, the confidence in the indicates that additional information and s are reqi above findings.

X Summary For CPFMs 4c, 4d, and 4e, degradation and the implic significant"at, .The these -.dat as sed above, t bined deration of the potential for' that degradati puts it in the "not d tly collected cient to rule out or confirm a or d monitoring an inspections might be necessary to-t~ncy, Uplift Forces on Structures ab, f structural support connections PFMs could occur as follows! water level rises and water is uplift force. This uplift force exceeds the weight of the abs to crack and buckle. Additional damage could include broken utility connections.

g Mechanism 6 6b -Cracked sl 6c -Displaced structure, structure Following are and data that support the likelihood of these CPFMs:* MH-5 was pumped for the duration of flooding to remove water coming in from duct banks extending between the Auxiliary Building and MH-3 1 and possible other sources. This created a head differential.

• Water levels outside the Aqua Dam perimeter created hydrostatic uplift forces on MH-5 while it was being pumped that were potentially greater than the hydrostatic forces that the manhole was designed to resist.

Priority 1 Structures Page 5.19-14 Main Underground Cable Bank, Auxiliary Building to Intake Structure Rev. 2 Following are field observations and data that indicate these CPFMs are unlikely:* No movement or distress of MH-5 concrete cover was observed.* After MH-5 was emptied, observations were made to determine if inflow of water could be observed.

No drainage into the manhole was observed during the initial 15 minutes after the manhole was emptied. Approximately 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> later, no additional water accumulation was observed.Following are observations and data still required to assess these* Visual inspection and photographs of the inside MEL" Visual inspection of the inside of MH-31 was not a annot sides of the manhole prevents access and visual ins* Basis of design data for the system are unknown.The following table describes observed distress indicators a!i risk associated with these CPFMs and factors that would make th on the annole access's-around the manhole top of the structure that buoyancy on the Impact MH-5 --ated inside t fiia Dam perimeter and was pumped continually during the flood eve wtexisted outside the Aqua Dam perimeter, creating a hydraulic head conditi e corridor within the Aqua Dam perimeter created a barrier that prevented the , om equalizing on the inside of the Aqua Dam. The confined water potentially uplift forces to structures in the area inside of the Aqua Dam perimeter including MH-5 which was pumped during the same time as the high hydrostatic forces. The potential for degradation due to flood conditions was increased above design norms. The potential for buoyancy forces and chances of degradation was offset by the weight of sandbags and other materials on top of the manhole. Overall, the potential for degradation is considered low for these CPFMs.

Priority 1 Structures Main Underground Cable Bank, Auxiliary Building to Intake Structure Page 5.19-15 Rev. 2 Implication Underground structures are normally designed for groundwater conditions and will experience buoyancy forces. In addition, sandbag installation on top of MH-5and a pipe extension connected to the manhole opening that extended above the hydrostatic head conditions helped weigh down the structure and offset buoyancy induced by flood conditions.

No indications of movement or distress were noted from surface observations.

Since groundwater, levels have dropped with river drawdown, the implication of degradation relaftAto these CPFMs occurring is considered low. AI Confidence As discussed, the potential for degradation is considere due to buoyancy is no longer a factor. Since no apparent expected due to the groundwater elevations at the presentq results is high.Summary For CPFMs 6b and 6c, as discussed above, mbine degradation and the implications of that d ation to tli significant" category.

As discussed, the p tial f M potential for buoyancy impacts fro°1od gmritio above assessment is high. WA impacts is in for red low because the confidence in the 12b -'Triggering Mechanisn PFMs c' ,cur as follows: the river level drops faster pore water pressure in t 1 can dissipate.

The saturated soil is elevated above the ing river level. The slo nk of the river provides no lateral pressure support for thed soil. At some point ,e,,is insufficient support on the river side to support the sa ils. At that point, p oils experience slope movements or even failure. Generally, slope ' associated w d drawdown are relatively localized and shallow in nature;however, failures cur.The river stag ceded and stabilized at a level corresponding to the nominal normal river level at 40," as of October 4, 2011. At the time of Revision 0, the groundwater levels had not yet st ilized to nominal normal levels. Therefore, it is possible that new distress indicators could still develop. Field observation of the river bank area has not been performed since the river level has dropped.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 Underground Cable Bank, Auxiliary Building to Intake Structure.

Priority 1 Structures Main Underground Cable Bank, Auxiliary Building to Intake Structure Page 5.19-16 Rev. 2 Adverse (Degradation/Direct Floodwater Favorable (DegradationlDirect Impact More Likely) Floodwater Impact Less Likely)The Main Underground Cable Bank is in close No distress was observed at the time of HDR's proximity to the river, site inspection.

Elevated saturated soils and elevated flood levels provided a water source.Data Gaps:* Observations of the riverbank following drawdown to nominal no]* Geophysical investigation data to address any observed con ns.i* Inclinometer readings which that will provide an indica4,J.

lo Conclusion Significance Potential for Degradation/Direct Floodwater Impact The river stage level has receded and stabilized river level at 40,000 cfs as of October 4, 201 continued river drawdown is not expected t potential for degradation for this CPFM is.Implication The occurrence of this CPFM o& ge scale c cables in the trench. No di been obser Therefore, the implication 0 ntial dear, ir at a ered 1(01 ativel, act the integrity of the ections, however.M is low.the river bank has not been inspected for signs`confidence for this CPFM is low.above, the combined consideration of the potential for Efthat degradation to a structure of this type puts it in the "not tbank has not been inspected for signs of degradation and slope out this CPFM and the confidence is low, which means ctions might be necessary to draw a conclusion.

failure, thi continued Priority 1 Structures Main Underground Cable Bank, Auxiliary Building to Intake Structure Page 5.19-17 Rev. 2 5.19.5 Results and Conclusions The CPFMs evaluated for the Main Underground Cable Bank, Auxiliary Building to Intake Structure are presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

ain Underground Cable Bank, Auxiliary Building to 4d, 4e, 6a, and 6b. These actions are discussed, separately

• Further nd physical modifications are recommended to address CPFMs 3a and 3c for the Ma round Cable Bank. These CPFMs are associated with unfiltered flow of groundwater into t',l- rbine Building basement drain piping system (Key Distress Indicator#1). These recommendations are described in detail in Section 4.1.* CPFM 3a, 3c, 3d, and 3f are associated with the distress in and near the Paved Access Area between the Service Building and the Intake Structure (Key Distress Indicator

1. 2). These recommendations are described in detail in Section 4.2.Actions to address CPFMs listed:* Continued monitoring is recommended to include a continuation of the elevation surveys of the previously identified targets on this structure and surrounding the site. The purpose is to monitor Priority 1 Structures Page 5.19-18 Main Underground Cable Bank, Auxiliary Building to Intake Structure Rev. 2 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.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 .e recommendations for this structure.

• Inspect the interior of MH-5, including walls, floor, cover,ji nd penetrations.

Obtain photographic record of conditions.

• Inspect the interior of MH-31 as practical." Have OPPD initiate a procedure to monitor for problems du ullinu olin Unusual/non-typical conditions encountered or noted during c, ing operatio d b documented, reported, and evaluated for additional investiga e (i.resistance is encountered during cable pulling, then consider vii o ca spectin of problem and adjacent ducts.)* Perform a detailed analysis of the pavement subgra aignmen pavement in the corridor between the Intake Structure and the SeI* Perform detailed geophysical analysis (GPR seismic the systeubgrade and trench alignments if failure is suspected or if -. ent/ne ements indicate failure due to subsurface erosion or piping." Review geophysical and geotechnic s t valu data as rtain to the Underground Cable Bank." Observe the river bank for signsi adation and s ilur 5.19.7 Update, s ision 0m Revision ' ssess wass" d to OPPD on October 14, 2011. Revision 0 presentof preeimmin essmen ch Priority 1 Structure.

These assessments were inco in Revision 0 because ensic n ion and/or monitoring for most of the Pr Structures was not compl the submiItal date. This revision of this Assessment Report inc i results of additional fore avestigation and monitoring to date for this structure as describ w.5.19 1dditional Data ble The follo iti 'were available for the Main Underground Cable Bank for Revisions 1 s , *sessment Report: " Results of forensic investigation (see Section 4.1)* Results of KDI #2 forensic investigation (see Section 4.2)" Additional groundwater monitoring well and river stage level data from OPPD.* Field observations of the river bank (see Section 5.25).* Results of falling weight deflectometer investigation by American Engineering Testing, Inc.(see Attachment 6).* Results of geophysical investigation by Geotechnology, Inc. (see Attachment 6).* Results of geotechnical investigation by Thiele Geotech, Inc. (see Attachment 6).* Data obtained from inclinometers by Thiele Geotech, Inc. (see Attachment 6).

Priority 1 Structures Main Underground Cable Bank, Auxiliary Building to Intake Structure Page 5.19-19 Rev. 2* Results of continued survey by Lamp Rynearson and Associates (see Attachment 6).* Inspection reports for MH-5 and MH-3 1.5.19.7.2 Additional Analysis The following analysis of additional data was conducted for the Main Underground Cable Bank: " Groundwater monitoring well and river stage level data.Data shows that the river and groundwater have ret 1* Field observations of river bank No significance distress from the 2011 Flood was obs 4" Results of falling weight deflectometer investigation by Falling Weight Deflectometer and associa -.Area identified anomalies such as soft cl.b broke truthing of the investigation results we 'ormed investigations.

• Results of geophysical invesf repo by chn Seismic Refraction and ReMi tests p ed a power block as part of entified deep a.loos , ... "Jbly voi .levels.Inc.Access fthe outside perimeter of the could be gravel, soft clay, I.',.Il %, V'Ut u'%',l, 11%l'..th conýfiW sampling of the soil encountered, to ground ismic investigation results as part of the KDI #2 forensic ,ere located to penetrate the deep anomalies identified in the)oring data did not show any piping voids or very soft/very idicative of subsurface erosion/piping or related material All of an T&-rst results conducted for this Assessment Report were compared to similar merous other geotechnical investigations that have been conducted ont s evious years. This comparison did not identify substantial changes to the soil strengthiand 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.0 Results of continued survey by Lamp Rynearson and Associates.

Priority 1 Structures Page 5.19-20 Main Underground Cable Bank, Auxiliary Building to Intake Structure Rev. 2 Survey data to date 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." Results of Inspection report by OPPD for MH-5: The results of the inspection indicate no apparent damages caused by 2011 flooding.* Results of Inspection report by OPPD for MH-31 (OPP, CR 4 Pictures of exposed concrete surfaces did not show. a ions o cracks or damage to the concrete walls and floor. Steel cond N port I ers were extremely corroded.

The corrosion damage was ge an t related to the 2011 flood.Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3a -Undermining and settlement of shallow foundatio rfaces (due f pumping)CPFM 3c -Undermined buried utilities (d Significance Potential for Degradation/Direct dw a Except for Turbine Building su -onditions in ,e to sub ce erosion no longer exist due to present site floo ons. Site pu sour ve been removed and high groundwater conditions no ist. The pote PFM to occur only exists in conjunc 1. Som ons produced surface erosion might still exist fronL Areas ed by forensic investigations with indications of s .evsubsurface g -aye bee sed for further investigation and repair asRecommen e s i co 0 n with KDI#2 address a majority of the areas in stion as part of the "Pa =e ea..0 erefore, with known issues being addressed further investigated by the implication of the potential degradation due to this Ais low.The un able NA structural entity. The cables in the duct bank are flexible and some mino tion tolerated.

Small signs of distress due to this CPFM might be noticeable to W, PPD employees who work installing cables. A large-scale failure of the duct bank earing of the cables would likely only be possible in the case of a very large void. Large un' erground voids usually present surface indications of underground distress.

Therefore, the implication is low.Confidence With investigations and repairs associated with KDI #1 and #2 handling known issues, and contingencies for expanding investigations and repairs as needed and directed by geotechnical inspectors, confidence in addressing issues associated with this CPFM is high.

Priority 1 Structures Page 5.19-21 Main Underground Cable Bank, Auxiliary Building to Intake Structure Rev. 2 Summary Forensic test results received since the issuance of the Rev 0 report have narrowed and defined probable areas impacted by this CPFM. Recommended actions associated with the results of the forensic reports and site inspections will address known problem areas and allow the direction and expansion of proposed investigations or repairs as necessary.

The combined consideration of the potential for degradation and the implications to that structure or system puts it in the "not-significant" category.Triggering Mechanism 3 -Subsurface Erosion/Pipin CPFM 3d -Undermining and settlement of shallo dation/si to river drawdown)CPFM 3f- Undermined buried utilities (due to river.,.Significance Potentialfor Degradation/Direct Floodwater Impact Based on groundwater monitoring data taken ith rivern and on a continuing weekly basis, groundwater level been at a rate t ely follows the river drawdown rate. Thus, the differe head nec eate subs' ce erosion due to river drawdown has not occurred.

The a most c ive this CPFM is nearest the river. River bank inspections massing._

iss af o, show no indications of this CPFM. The -cce s Arv een the, k Structure and the Service Building" is the deve rea nearest t eb n cludes most of the utility services that are critical to tion of the fa 0 nded actions in association with KDI #2 1 address issu -are encountere, This will include instances of subsoiL d have duced (however un kely) by river drawdown.

The pot e this occur is considered low.underground cable bank' ity. The cables in the duct bank are flexible anddeflection can* be Small signs of distress due to this CPFM might be n- .l experienced OPshaig who work installing cables. A large-scale failurevr o f" ý bank and shai e cables would likely only be possible in the case of a vr large ., ge undergrq aids usually present surface indications of underground distress. ,l ifore, the tion is low.Confidence With groundwater ci ta indicating the absence of a high head condition and the instigation of recommendations associated with KDI#2, confidence in the assessment associated with this CPFM is high.Summary Based on the above discussion items, the combined consideration of the potential for degradation and the implications to that structure or system puts it in the "not-significant category" in the assessment matrix.

Priority 1 Structures Main Underground Cable Bank, Auxiliary Building to Intake Structure Page 5.19-22 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 Significance Potentialfor Degradation/Direct Floodwater Impact Based on groundwater monitoring data taken in conjunct continuing weekly basis, groundwater levels have been, the river drawdown rate. Thus, hydrostatic loading corm, and the structures are designed for normal groundwaterl susceptible to this CPFM would have been MH-5. From manhole, no indications of this CPFM were apparent.

T1 CPFM of having occurred is low since hydrostatic loads conditions were limited. The manhole is intact, ap e rs signs of leakage at the time of previous inspecti.and on a longer exist reveal significant degradation due this CPFM is considered low.Implication As stated, a couple of CPFM unlikely) potential for degrad;system. The occurrence of: of MH-5 includ4in' wall failui CFM ..ce (i.e,* to the 201 otential -.dation due to 4e' dic e bee ed supporting low (or the MI-5 e 0t oftheASX Underground Cable Bank 4c, 4d, and 4e could result in degradationshear, or ee For degradation from these d..hat renders elec cal cables carried by the system e Iult in complete failure of supporting elements of y. re, the implication of degradation for these ftt monitoring well readings are now down to an elevation Eonfidence is high that no additional impacts due to flooding'undwater elevations and on inspections of MH-5 that indicate Summary For CPFMs 4c through 4e, based on these discussion items, the combined consideration of the potential for degradation and the implications to that structure or system puts it in the "not-significant category" in the assessment matrix.Triggering Mechanism 12 -Rapid Drawdown CPFM 12a -River bank slope failure and undermining surrounding structures CPFM 12b -Lateral spreading The groundwater monitoring well data and river level data indicate that excess pore pressures due to river drawdown had generally dissipated by about October 14, 2011. Field observations Priority 1 Structures Page 5.19-23 Main Underground Cable Bank, Auxiliary Building to Intake Structure Rev. 2 of the River Bank on October 20, 2011, did not identify deformation of the River Bank that could be attributed to slope failure or lateral spreading.

Therefore, neither slope failure nor lateral spreading occurred due to the 2011 flood.5.19.7.3 Revised Results and Recommendations The CPFMs evaluated for the Main Underground Cable Bank from the Auxiliary Building to the Intake Structure are presented in the following matrix, which 9ws the rating for the estimated significance and the level of confidence in the ev atic -CPFMs 3a and 3c for the Main Underground Cable Ba m the Building to the Intake Structure are associated with Key Distress Indic 1. S ents the results of additional forensic investigation that was conducted ,etr PFMs could be ruled out. The results of the additional forensic invest :i ow that i recommendations for physical modifications in KDI #1 nted that ruled out. Therefore, assuming that no further concerns ar denh them program for the Main Underground Cable Bank from the Auxiliarn g to the IntakeE Structure (discussed in Section 5.19.6 and conti ecember 1J), these CPFMs are moved to the quadrant of the matrix repr ee nAction mended Related to the 2011 Flood." CPFMs 3d and 3f for the Main Undergro able B om e.liary Building to the Intake Structure are associated wi y s r #2. .2 presents the results of additional forensic was cond t scert ether these CPFMs could be ruled out. The results of e t ional forensi estigati ow that these CPFMs are ruled out. Therefore, assum r nofurther cort i t ified through the monitoring program for ain Underg .able Bank fro -iary Building to the Intake Struc ection .d continuing ut December 31, 2011), these CPFMs are e them ' resenting "No Further Action Recommended Sto the PFMs 4c, 4d, and 4e for t Underg idCable Bank from the Auxiliary Building to Intake Structure are not a ted with Key Distress Indicators.

Groundwater monitoring a 4ve been gathered since evision 0 report and indicate groundwater levels have e elow a level that ca ostatically load the system and create these CPFMs.Imp to the effects of ing and high hydrostatic head conditions were assessed by interna tion of MU A internal assessment of MH-5 found no indications of flood damage a esults -dditional forensic investigation show that these CPFMs are ruled out based on-' .-Lditions.

Therefore these CPFMs move to the quadrant of the matrix urther Action Recommended Related to the 2011 Flood." CPFMs 12a and 12b for the Main Underground Cable Bank from the Auxiliary Building to the Intake Structure are not associated with Key Distress Indicators.

River bank inspections have been made and groundwater monitoring data have been gathered since the Revision 0 report.The results of the additional forensic investigation show that these CPFMs are ruled out.Therefore, assuming that no further concerns are identified through the monitoring program for the Main Underground Cable Bank from the Auxiliary Building to the Intake Structure (discussed in Section 5.19.6 and continuing until December 31, 2011), these CPFMs will be moved to the quadrant of the matrix representing "No Further Action Recommended Related to the 2011 Flood."

Priority 1 Structures Main Underground Cable Bank, Auxiiiary Building to Page 5.19-24 Rev. 2 Intake Structure{ Low Confidence High Confidence (Insufficient Data) (Sufficient Data)0 CL U-0.4-.(U U)75 0 a-,2 U-.U).4.6 0 z sessment oftt tructur t step was to develop a list of all Triggering anisms and PFMs d have d due to the prolonged inundation of the FCS e during the 2011 Missou r flood ould have negatively impacted these structures.

next step was to use data various investigations, including systematic observation of ctures over time, eithe iminate the Triggering Mechanisms and PFMs from the list o mend further inves on and/or physical modifications to remove them from the list articular struc cause all CPFMs for the Main Underground Cable Bank from th ary Build* e Intake Structure other than CPFMs 3a, 3c, 3d, 3f, 4c, 4d, 4e, 6b, 6c, 12b hai ruled out prior to Revision 1, because CPFMs 4c, 4d, 4e, 6b, 6c, 12a, and 12b d out as a result of the Revision 1 findings, because CPFMs 3d and 3f were ruled 0o results of the KDI #2 investigations, and because CPFMs 3a and 3c will be ruled out w the physical modifications recommended for KDI #1 in Section 4.1 are implemented, no Triggering Mechanisms and their associated PFMs will remain credible for the Main Underground Cable Bank from the Auxiliary Building to the Intake Structure.

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 5.20 Meteorological Tower and Miscellaneous Structures

--- 4 .4:0, j rI Priority 1 Structures Page 5.20-1 Meteorological Tower and Miscellaneous Structures Rev. 2 5.20 Meteorological Tower and Miscellaneous Structures 5.20.1 Summary of Meteorological Tower and Miscellaneous Structures Baseline information for the Meteorological Tower and Miscellaneous Structures is provided in Section 2.0, Site History, Description, and Baseline Condition.

The Meteorological Tower is located to the far north of the owner-cnr op The tower is a three-post truss tower extending 360 ft above grade. The base o we ed at a single center point that is pinned to a 7-ft by 7-ft by 4-ft, 6-in.-deep s .oting nds 4 ft below grade. Guy wires are used to support the tower against lateral The orted by multiple wires in three directions at 1200 intervals.

The tower seve 1 points by wires in each of the three directions.

The top four wires extend to an 290 ft base of the tower. The bottom three wires extend to a smaller deadman the base of larger deadman is 8 ft by 6 ft by 4 ft deep and is located 4 ft belo a smaller dea by 4 ft by 3-ft-deep and is located 4 ft below grade.There is a weather tower Instrumentation Shelter loc the Meteo 1 Tower. The building is about 11.3 ft by 11.3 ft and is construct a 6-in. c slab with thickened edge. The walls are constructed with approximat

.7-ft mas 5.20.2 Inputs/References Supporting

1. t n nu W Table 5.20-1 lists references provide D and othe uments .'to support HDR's analysis.Table 5.20 References MM'.-ftorological Trn.

Structures nt Title Date Page Al Document Number(s)" .. alrmlicable)

A n or 100 Meter Weather To E-1 1 16957 Unknown F-4000Weather Tower Electrical inmunication 16958 Unknown F-4001 Mod7 WE34keries Section "20ft" 22775 8/9/1971 C-036-020-012 Model T-Aý'% .n 2. 2774 8/24/1973 C-036-020-

________014 1Oft Boom Moun ea ..i 22776 3/26/1976 C-100-145-

______k_ 7603 26 Base and Anchor Details..

22784 2/26/1976 D-100-036-

___760218-1 360ft T-36 Tower 22785 2/18/1976 D-100-036-760218 Plan & Details of Weather Tower Instrumentation Shelter 41304 Unknown D-4685 Naval Facilities Engineering Command, Design Manual 9/1986 All 7.01, Soil Mechanics I I I Detailed site observations-field reports, field notes, and inspection checklists-for the Meteorological Tower and Miscellaneous Structures are provided in Attachment

8.

Priority 1 Strucures Page 5.20-2 Meteorologica'ower and Miscellaneous Structures Rev. 2 Observed performance and pertinent background data are as follows:* Soils aroind the Meteorological Tower were found to be soft when probed with a fiberglass T-probe. It was possible to plunge the probe into the ground up to handle depth with little force.* There is i large area n6rth and west of the Meteorological Tower that is lower in elevation than the surrounding area and it still had standing water during observation.

• Several of the guy wire anchors are covered by a significant number o vines growing up the wires, or have small trees growing around the anchor locations.

Vegetation ared to have been present prior to flooding.

The vines growing up the guy wires are we b trees that are growing are large, indicating that they have been growing f ral y There is a seveal-inch-thick layer of sediment covering th ess roa eorological Tower and Insrumentation Shelter; however, there was no e ge ad." The maximun surveyed flood elevation for the Meteorologi s not kno ever, observation ihdicates the maximum depth was approximately ve existing th.Meteorologi~al Tower. The maximum flood elevation at the on Shelter approximately 2,5 ft above finish floor." Observatici inside the Instrumentation Shelter was ue to larg es of mold growing itside, visible through a window in the s of stru ess were noted." Design dawings show the tops of the deadm hors to of fill. g the visual inspectin, the grade was probed at the locati f the d d one of the anchors was fotnd to be only 2 ft under the so' er e no of ero area. Areas that were observed nearby have several f d osite iment.There is fencing around the Met cal Tower s e, excl the guy anchor locations, and tie Instrumentation Shelte ation on the ce is not available.

However, based on observ it is appro 8 ft tall with of barbed wire at the top.Minimal d d arou e of the fencing.5 .2 .3e n t M t or c.3.1 Assessment P res Acc shed: sments of the Meteorolo Tower and Miscellaneous Structures include the following:

terological mertinl Shelter, and surrounding grades were visually in r signs of distress.csA re -built geotechnical reports to determine possible weak points in the constr affected by the flood.Probe of s grade to determine softness and consistency of soils near the s r ctures.5.20.3.2 Assessment Procedures Not Completed Assessments of the Meteorological Tower and Miscellaneous Structures that were not completed in6lude the following:

• A review of survey data to-date for indications of trends in the movement of structures.

Requested survey information for the Meteorological Tower is not yet available.

Priority 5 Structures Meteorological Tower and Miscellaneous Structures Page 5.20-3 Rev. 2 5.20.4 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 wekalyzed, a number of CPFMs were ruled out as discussed in Section 5.20.4.1.

The CPF Al i& r detailed assessment is discussed in Section 5.20.4.2.

it 5.20.4.1 Potential Failure Modes Ruled Out PriorS Assessment The ruled-out CPFMs are in the Not Significant/High Co not be shown in the Potential for Failure/Confidence mat Triggering Mechanism 2 -Surface Erosion CPFM 2a -Undermining shallow foun Reason for ruling out:* No surface erosion was visible g spe were observed in surroundiný , , f deposited sediment Triggering Mechanism 3 ;CPFM 3a -Underrinir)n/slab/surfaces (due to dynamic Loading Flows and velocities in the area observed were small, which is supported by the lack of scouring.

Sediment deposits several inches thick were observed on top of the pavement surrounding the Meteorological Tower and the Instrumentation Shelter. No damage from debris was observed.

The Meteorological Tower, excluding the guy anchor locations, and the Instrumentation Shelter are surrounded by fencing that protected them from moving objects. A minimal amount of debris was observed around the fencing.

Priority 1 Structures Meteorological Tower and Miscellaneous Structures Page 5.20-4 Rev. 2* The Meteorological Tower and Instrumentation Shelter are no longer inundated and no signs of distress have been observed.Triggering Mechanism 10 -Machine/Vibration-Induced Liquefaction CPFM 10a -Cracked slab, differential settlement of shallow foundation, loss of structural support Reason for ruling out: Permanent equipment or temporary equipment that ha dynamic forces due to vibration was not operated n Instrumentation Shelter during a saturated conditio used was not observed to cause liquefaction.

Triggering Mechanism 10- Machine/Vibration-Induc CPFM IOb- Displaced structure/broken connections Reason for ruling out: Permanent equipment or temporary equ t that hi dynamic forces due to vibration was n erated n Instrumentation Shelter during a satur- conditi used was not observed to caus e Triggering Mechanism 11 f Soil Stren ue Seepage CPFM 11 a -Cracked sla ential settleme rt Mete duce significant Tower or_vehicle being tion significant Fower or foundation, loss of structural'Visual observations shg attributed to this CPFM hnent. Therefore, degradation that can be the Meteorological Tower.ing Mechanism 12 -,k12a -River bank, I Drawdown ailure and undermining surrounding structures Reason out:* Both str CPFM.sufficient distance away from the river to not be influenced by this Triggering Mechanism 12 -Rapid Drawdown CPFM 12b -Lateral spreading Reason for ruling out:* Power and signal cables used by the structures are at a sufficient distance away from the river to not be influenced by this CPFM.

Priority 1 Structures Meteorological Tower andMiscellaneous Structures Page 5.20-5 Rev. 2 Triggering Mechanism 13 -Submergence CPFM 13b -Corrosion of structural elements Reason for ruling out: The structures have not been subjected to a corrosive environment that would be considered beyond normal conditions.

The structure has been in operation for more than 30 years and has been exposed to environmental conditions over this time.Triggering Mechanism 14 -Frost Effects CPFM 14a -Heaving, crushing, or displacement Reasons for ruling out: " The Meteorological Tower foundation is below frost* The Instrumentation Shelter is on a 6-in. concrete slab conditions.

However, the conditions the Instrumentati different than what would have occurred bef.5.20.4.2 Detailed Assessment of Credi .tentia The following CPFMs are the only CPF ed fo Meteorological Tower as a result e 20 od.below.'d i0 She to heave frN&e subject to hot Modes is provided Triggering Mechanism 7 CPFM 7c -General site The occur as follows: the soils become saturated, passive pressure resistance.

The overall capacity J*sgn capacity.Rower wereTound to be soft when probed with a fiberglass T-Be probe into the ground up to handle depth with little force.Wining the capacity of the deadman anchors against the 3 passive soil pressures in conjunction with the self weight of The soft soils found around the site could reduce'the soils due to loss of shear strength, resulting in a reduction n anchors.the dT the passI in overall This PFM does to the Instrumentation Shelter.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 Meteorological Tower.

Priority 1 Structures Meteorological Tower and Miscellaneous Structures Page 5.20-6 Rev. 2 Adverse (Degradation/Direct Floodwater Favorable (Degradation/Direct Impact More Likely) Floodwater Impact Less Likely)Soft soils around the deadman anchors.The Meteorological Tower design is a failure-critical structure.

-_I Data Gaps:* Design assumptions used for the passive pressure resistance for ti unknown due to detailed design information not being rew" Information on the soils from past geotechnical reports discussed in the baseline information.

iman anchors are e except as Conclusion Significance Potential for Degradation/Direct Floodwater Impact Soft soil conditions were observed near the pressure resistance of the soils and, in turn, , the soils around the deadman anchors were-CPFM is high. I could re lassive Rchors. Since n due to this Implication The occurrence of this This could lead to functio, for t ** of the deadman anchors.the integrity or intended of the potential degradation assumptions for the hand are not sufficient cation must be done to H= as intended.)uld not bg6ompared with existing conditions; therefore, the le out this CPFM, or lead to a conclusion that physical ie that the support for the Meteorological Tower is Summa For CPFM 7,e above, the combined consideration of the potential for degradation and the implicaf hat degradation to the structure puts it in the "significant" category.The data currently ilected are 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 could be necessary to draw a conclusion.

Priority 1 Structures Meteorological Tower and Miscellaneous Structures Page 5.20-7 Rev. 2 5.20.5 Results and Conclusions The CPFMs evaluated for the Meteorological Tower and Miscellaneous Structures are presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

the Meteorological Tower and Miscellaneous Structures:

Given t0j-'. onfidence Rating fofi CPFM, continued monitoring is recommended to include elevations"".

on this structure.

g prpose is to monitor for signs of structure distress and movement or, in soil condit around the building.

The results of this monitoring will be used to increase (dencekl.

ssessment results. Elevation surveys should be performed weekly for 4 week til December 31, 2011. At the time of Revision 0, groundwater levels had not yet stabi minal levels. Therefore, it is possible that new distress indicators could still develop. If ne tress 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 could result in a modification of the recommendations for this structure.

In addition, OPPD should provide information on how the deadmen for the Meteorological Tower were designed (i.e., was passive pressure used or just the dead load of the anchor?).

If the tower was designed using just the dead load of the anchor, then the potential for degradation does not remain significant indicating that the recommended survey schedule can be ceased.

Priority 1 Structures Page 5.20-8 Meteorological Tower and Miscellaneous Structures Rev. 2 5.20.7 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.5.20.7.1 Additional Data Available The following additional data were available for the M logic evisions 1 and 2 of this Assessment Report:* Additional groundwater monitoring well and river sta from OP* Results of continued survey by Lamp Rynearson and oci e Attachme" An Assessment Team from HDR visited the Met ological To ctober 27, 21 1, to document current conditions in that area.5.20.7.2 Additional Analysis Analysis of the additional data listed abo clarif i ce and confidence of the assessment.

The following analysa Add 1 d cond e Fuel Oil Storage Tanks and Piping: Groundwater monitori nd river stage t )PPD.Dat, river an dwater have re to nominal normal levels.* ts of conti , y by earson and Associates.

Survey data to date co to the o baseline surveys have exceeded the accuracy range of the surveying e ' nt. The significance of this fact is discussed below.ing Mechanism 7 -S ollapse (first time wetting)7c -General site s tent The folk ssessmen evision 1 of this Assessment Report indicated that the soils were soft in., but there were stiffer soils below this layer that required a substantial e t he probe rod to its full depth. These soils are within expected stiffness levels f ted field in an alluvial setting and indicate that the soils are less saturated than whe 'ihey were inspected for Revision 0 of the report.The data available for the survey points that have been established are outside of the accepted range; however, there is no constant trend that has formed. Visual inspection of the survey points on the guy wires noted that the points were located on the turnbuckles of the wires. The wires are easily affected by wind movement.

It was also noted that standing on a vine next to the south guy wires pulled on the wire lowering the survey point. Either of these observations could account for the movement outside the accepted tolerance.

Three of the four locations being surveyed do not show movement outside of the accepted tolerance when reviewing the Priority 1 Structures Page 5.20-9 Meteorological Tower and Miscellaneous Structures Rev. 2 first and last measurement taken; indicating any additional movement outside the tolerance should not be expected.

The groundwater elevation measured in monitoring wells closely followed the river level as the floodwater receded. The data indicate that groundwater elevation was about 2 ft above the river level near the beginning of October 2011 and receded to the river level by about October 14, 2011. Therefore the differential head created by the river drawdown was insufficient to facilitate subsurface erosion.Siganificance Potential for Degradation/Direct Floodwater Impact The initial field assessment noted that soft soils were p arou anchors.This was accomplished by probing surrounding soils to t with little or no resistance.

The follow-up assessment for Revision 1 o sessment R icated that, though the soils could still be considered soft, subs was needed probe rod to its full depth. Due to the soils becoming less a firmer the p or degradation due to this CPFM is low.Implication The occurrence of this CPFM could negat impact f the dea an anchors.This could lead to movement of the anch 'd neg imý integrity or intended function of the Meteorological To re, t licati potential degradation for this CPFM are high.

Tent for 1 of this Asse Report indicates that soils are bec r bd firme ey data available for this revision are outside of the a rngewbut aing a t tend. The analysis of the survey data indicates movemnen e of the d tolerance is not expected.

Overall,.the data liable suggest that soil ns haw e ved. Therefore, the confidence for this CPFM ih.Foras discussed the combined consideration of the potential for degradation and the t i ofn t rdation to the structure put it in the "not significant" category.The data c im Sion 0 are sufficient to rule out this CPFM. Therefore, the confidence in 'sessment is high.CPFM 7c for the Meorological Tower is not associated with Key DistressIndicators.

The follow-up assessment for Revision 1 of the Assessment Report indicates that the soils at the Meteorological Tower are less saturated and firmer. Passive pressure capacity of the deadmen is no longer reduced as much as it would have been when the soils were more saturated.

The results of the additional forensic investigation as of this revision show that this CPFM is ruled out. However, the monitoring program discussed in Section 5.20.6 should continue.Therefore, assuming that no further concerns are identified through the monitoring program for the Meteorological Tower (discussed in Section 5.20.6 and continuing until December 31, 2011), this CPFM is moved to the quadrant of the matrix representing "No Further Action Priority 1 Structures Meteorological Tower and Miscellaneous Structures Page 5.20-10 Rev. 2 Recommended Related to the 2011 Flood." In addition, the information requested in Section 5.20.6 regarding the design capacity of the deadman anchors and a review of any geotechnical data will no longer be needed.5.20.7.1 Revised Results The CPFM evaluated for the Meteorological Tower is presented in the following matrix, which shows the rating for the estimated significance and the level of co ence in the evaluation.

Low Confidence (Insufficient Data)Du 2 I-=a N---N NPI Conclusions In the nt of the FG "ctures, the first step was to develop a list of all Triggering Mechani uld have occurred due to the prolonged inundation of the FCS site during t ..1.. .. ...River flood and could have negatively impacted these structures.

The next step &ata from various investigations, including systematic observation of the ucres ove either to eliminate the Triggering Mechanisms and PFMs from the list or to recommend further investigation and/or physical modifications to remove them from the list for any particular structure.

Because all CPFMs for the Meteorological Tower other than CPFM 7c had been ruled out prior to Revision 1, and because CPFM 7c has been ruled out as a result of the Revision 1 findings, no Triggering Mechanisms and their associated PFMs remain credible for the Meteorological Tower. Therefore, HDR has concluded that the 2011 Missouri River flood did not impact the geotechnical and structural integrity of the Meteorological Tower because the potential for failure of this structure due to the flood is not significant.

Section 5.21 Original Steam Generator Storage Building (OSGS)'A g I L i7 2 Priority 1 Structures Page 5.21-1 Original Steam Generator Storage Building Rev. 2 5.21 Original Steam Generator Storage Building 5.21.1 Summary of Original Steam Generator Storage Building Baseline information for the Original Steam Generator Storage Building (OSGS) is provided in Section 2.0, Site History, Description, and Baseline Condition.

5.21.2 Inputs/References Supporting the Analysis Table 5.21-1 lists references provided by OPPD and other doc sued t IDR's analysis.Table 6.21 References for Original Steam G o geg .DocumentrTitle OPrD d notsan! ' .... ...-?,:?iii.Number,-(Ofapplicable k-provdediAtc Original Steam Generator Storage Facility Sheet 4 as7 ' /2005 fols-053 Original Steare Generator Storage Facility R eug s on a c250o6-Cd021 Grade _ft Naval Facilities Engineering Command, 2o 1 9 All Design Manual 7.01, Soil Detailed site observations"-fieldr I notes, a klistsfor the OSGS are provided in Atta st uh Obser e nt ce S t back ata are as follows: GS is a reinforced-co tructure ts on a concrete mat foundation.

No ction documents exist e survey .cdtare; efore,a"b iinformation about its srauction was derived uShere.nstruction repair for the mat foundation and visual"Tpevation for the OS 022 ft." The pe~a .= levation in 201 approximately 1006.9 ft."The OSGS stt, hest st od} m the Missouri River." The OSGS is e elevation from the river.5.21.3 Assessment a nd Procedures 5.21.3.1 Assessment Procedures Accomplished Assessments of the OSGS include the followingr: " Visual inspection of the exterior of the'structure." Assessment of collected survey data t~o-date for indications of trends in the movement of the structure.

7:-?. :...

Priority 1 Structures Page 5.21-2 Original Steam Generator Storage Building Rev. 2 5.21.3.2 Assessment Procedures Not Completed Assessments of the OSGS that were not completed include the following:

Visual inspection of the interior of the structure was not completed because access to the structure is not possible.

However, inspection of the interior of the structure is not necessary to reach a confident final conclusion.

.5.21.4 Analysis Identified PFMs were initially reviewed as discussed in Sectio The re sidered the preliminary information available from OPPD data files and itial ervations.

Eleven PFMs associated with five different Triggering Mechano ermin"non-credible" for all Priority 1 Structures, as discussed in Sectio e remaini were determined to be "not applicable" to the OSGS; therefore, none w rward fo assessment.

5.21.5 Results and Conclusions Due to the OSGS' relative proximity to the Missou r, its e relative t oodwaters, and type of construction, there is no PFM related e 2011 fl hat is appl le to the OSGS.5.21.6 Recommended Actions In the assessment of the FCS Stru first step w velo t of all Triggering Mechanisms and PFMs that could urred due to th undation 0f the FCS site during the 201 1 r flood d have negativ acted these structures.

The next step was to vesti including systematic observation of the structures over to eliminat " gering aaisms and PFMs from the list or to recommend frthe~ igation and/or phy odificat emove them from the list for any particular str ere were no applicab s e rthe OSGS. Therefore, HDR has concluded th -11 Missouri River flood -impact the geotechnical and structural integrity of the OSGS beca otential for failure oft cture due to the flood is not significant.

Section 5.22 Switchyard 4'1'L j S Priority 1 Structures Page 5.22-1 Switchyard Rev. 2 5.22 Switchyard 5.22.1 Summary of Switchyard Baseline information for the Switchyard is provided in Section 2.0, Site History, Description, and Baseline Condition.

The Switchyard is located west of the Old Warehouse Building between drainageways to its east and west. The drainage is channeled flowing north into culverts dr in h k. Ground surface elevations within the Switchyard vary from approximat 2 rainage swales to a crown ridgeline of 1007 ft. A temporary levee with an appro top at ft was constructed around most of the Switchyard to protect it from the floodwat Sw* e discussed in four categories:

the 161-kilovolt (kV) Switchyard, the 345-kV e Sou hyard, and general site surfacing/security fencing.The 161-kV Switchyard is in the western section outside the temp ry ee Figure 5.161-kV Building is located in the southwest corner of the yard. A tempor hen berm wi a 12-ft accessible top width surrounds the 161-kV Building co o the leve 1n-kdg has a finished floor elevation of 1005.6 ft. The eart construct econd sandbag berm constructed closer to the structure.

The sand xn was oodwater on and was covered with plastic to reduce infiltration.

Farthe h, a tra ce (T4) ada temporary sandbag berm around it, enclosed by the levee. nts o cot berm comprised of rock reside inside the sandbags.

The san be as a oodwa ion and was covered with plastic to reduce infiltration.

Over itch Tow. d Trans ison Towers outside the levee were subjected to floodwaters ground utiliti ten t ctures were subjected to percolating floodwaters.

Storm dr carrying flow nside the containment berm were plugged due J .tion ofth .ipes. Parts o intake were observed at the southwest co , odwate into the protective sandbag berms at the 161 -kV Building aEtran cture olled by numerous sump pumps.The B itchyard is in the s portion te (see Figure 5.22-1). All facilities in the So itchyard are inside the te *. levee. "insformer structure (TI) is located in the so 9.comer. A pre-existing oil ' inment berm comprised of rock surrounds the transformer.

Storm 1 es carrying flow from aea inside the containment berm were plugged due to inundatid outlet pipes. Parts a storm observed at the southwest containment area. A se structu, )is located in the southeast corner. An oil containment berm comprised of r ounds the fier. Storm drain pipes carrying flow from the area inside the.j-, -containment berm lugged.% inundation of the outlet pipes. An erosion channel in the west bank of the drainage .# ...t.was observed as possibly the outlet for the storm outlet pipe. Parts of the storm intake wer ed at the northeast containment area. The South Switchyard area has overhead Switch Towers af Transmission Towers that were subjected to saturated subgrades.

Underground utilities between the structures were subjected to percolating floodwaters.

A manhole structure southwest of T2 had the lid removed and was being pumped at the time of the inspection.

A precast trench heads west from the manhole to another vault in the southwest corner of the Switchyard.

The lids from the precast trench have been removed and are adjacent to the trench. The precast trench opening into the manhole is open. The trench is nearly full of sediment the farther the distance from the manhole, with water up to the top surface at the west end. The visual appearance of the sediment in the trench suggests that the manhole pump pulled in the sediment from around the trench until the pump was turned off and the water drained out, leaving the sediment.

Low areas inside the levee on the south and east end have ponded water up to a few inches deep.

0 04 U, U)* Power Pole* Light Pole# Sandbag Levee X- Fence Utilities Power Transformer Ea 345 Ckt Brkr=- 161 Ckt Brkr r-lArea Boundaries Structures No Priority Assigned Priority i Priority 2 Utilities No Priority Assigned-Priority I Priority 2 135 270 I S"M IFeet IlOmaha Public Power Disbict Switch Yard Detail Fort Calhoun Station Plant and Facility Geotechnical and Structural Assessment DATE Oct 2011 FIGURE 5.22-1 HRx& a &

Priority 1 Structures Switchyard Page 5.22-3 Rev. 2 The 345-kV area of the Switchyard is the largest area. All facilities in the 345-kV Switchyard are inside the temporary levee. In the southwest section of the Switchyard is the 345-kV West Building.To the east of this building is the 345-kV East Building.

The 345-kV West Building has a finished floor elevation of 1005.75 ft. The 345kV East Building has a finished floor elevation of 1007.5 ft.Sandbag berms were constructed around the 345-kV East Building and the 345-kV West Building even though they are inside the levee. A 161-kV transformer and towers are situated slightly east of 345-kV East Building.

An oil containment berm comprised of rock surrounds the transformer.

Parts of a storm intake were observed at the southeast containment area. A Shunt tor is situated in the northeast corner of the 345-ky area. An oil containment berm co ~se unds the Shunt Reactor. Storm drain pipes carrying flow from the area inside tai were plugged due to inundation of outlet pipes. A crushed corrugated metal ayligh drainageway to the east was observed after water levels subsided.

Parts of the in re d at the southeast containment area. The 345-kV Switchyard area has o tch To Transmission Towers that were subjected to saturated subgrades.

ound utilitie e t structures were subjected to percolating floodwaters.

Because o provision drainage, low areas inside the levee on the east end have ponded water up dep ow inside the levee on the western edge had shallow pondedNmero sumps were utilized inside the berms and the levee to remove infiltration.

No drawings are available to determine if the r, prior to placement.

It could not be determined fabric. The Switchyards (161-kV, 345-kV, c fencing had been reworked due to flood i Switchyard was removed to construct p after the construction of the tempor e.of the Switchyard starting nearcthe n c levee was const orary fe permanent .g. ost att accumula is inclu i oles, comin _ e site. Some of ic was cing has improveiWhscompleted 1rushed r a laced on a geotextile i) are s dfencing.

Parts of the e g fencin outheast comer of the leve tempora ate and fence were placedwas ed along the entire north end f the, hyard where the temporary constru ide the levee from the 161 -kV comer of the Switchyard.

The temporary fence hes, wooden pallets, and trash from floodwaters dby sump pump piping strung over the top of the pumped floodvm 5 ..2 Table 5.: ,/References Suppo e Analysis references proATat AQnf TKifl TPD and other documents used to support HDR's analysis.I -References for Switchyard OPPD Document Date Page NumberN--(if applicable)

Date Page.Number(s)Site Plan Topography Sitei IlnTpgah nnw 45S21 45711 Unknown 11405-S-251, Sheets 2.3 Switchyard Area Grading Plan 8/23/1968 11405-S-279 Plan General Site Grading 8/23/1968 11405-S-283 Naval Facilities Engineering Command, 9/1986 All Design Manual 7.01, Soil Mechanics Detailed site observations-field reports, field notes, and inspection checklists-for the Switchyard are provided in Attachment

8.

Priority 1 Structures Page 5.22-4 Switchyard Rev. 2 Observed performance and pertinent background data are as follows:* For the duration of the 2011 flood event, the 161-kV Switchyard area was inundated by floodwaters.

The temporary levee construction access blocked water from flowing across the Switchyard.

The 161-kV Building and transformer structure had sandbag berms constructed to protect these structures from inundation.

Sump pumps continually pumped seepage water back over the berms." For the duration of the 2011 flood event, the 345-kV and South Swit rd areas were protected by the temporary levee. Security fencing along the northern edg e as reworked due to flooding.

Some of the permanent fencing was removed t ct .Temporary security fencing along this perimeter collected floating de the fib oming in to the site.* The Shunt Reactor, TI through T4 Transformers, and the sp ansform unded on augered cast-in-place piles supporting a mat foundation.

• The other Switchyard structures are supported by 2- to 5-ft-d d piers 5 to* The buildings are supported by shallow continuous spread footings e to frost dep a grade-supported slab.5.22,3 Assessment Methods and Procedures 5.22.3.1 Assessment Procedures Ac fished Assessments of the Switchyard

i. d th o low" A visual inspection of general to o smkh d soft subgrade areas.* A visual inspection oft .r of the build" A vis n of the of the buildin ctures.ected su ta to-date for indications of trends in the movement of lcture. .eview of previou mente 'on reports, as-built building plans, and geotechnical reports to poss ak points in the buildings' construction that could be affected by the ]i investigations wer ormed. These included the following non-invasive gI and invasive geo cal investigations; Geo I investi cuding test borings with field tests (SPT and CPT) and w pleted near the Switchyard.

Note that OPPD required vacuum excavatior Jten feet of proposed test holes to avoid utility conflicts.

Test reports will thus not' soil conditions in the upper ten feet of site and locations where shallow utilitiesexist. (Test reports were not available at the time of Revision 0.)

Priority 1 Structures Switchyard Page 5.22-5 Rev. 2 5.22.3.2 Assessment Procedures Not Completed Assessments of the Switchyard that were not completed include the following: " Pump water out of underground utilities for further investigation.

Floodwater elevations are not sufficiently below grade to allow pumping utilities dry without continued infiltration.

Priority of staff is pumping Protected Area utilities.

• Geophysical testing such as GPR or seismic refraction was no nsidered necessary for the Switchyard.A" k, &5.22.4 Analysis Identified PFMs were initially reviewed as discussed in Secti preliminary information available from OPPD data files and Eleven PFMs associated with five different Triggering Mech"non-credible" for all Priority 1 Structures, as discussed in S carried forward as "credible." After the detailed design revi inspections, and the results of available geotechnical,g number of CPFMs were ruled out as discussed in Se detailed assessment are discussed in Section 5.22.4 5.22.4.1 Potential Failure Modes Ruld ut Pric Assessment A I the Mons.a the Detailed The ruled-out CPFMs reside d will not be shown in the PoM category and for clarity 2 -Si rosion S ndation/slab/surfaces ppo e foundation

d was protected by the temporary levee or sandbag berms.l-kV Switchyard was inundated, but there was no flow over was observed during the field assessments.

• No Triggering -Subsurface Erosion/Piping CPFM 3e -LU. lq l ateral support for pile foundation (due to river drawdown)Reason for ruling out:* The Switchyard is a sufficient distance from the river to be outside the zone of influence of the CPFM.

Priority I Structures Switchyard Page 5.22-6.Rev. 2 Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3f- Undermined buried utilities (due to river drawdown)Reason for ruling out:* The Switchyard is a sufficient distance from the river to be outside the zone of influence of the CPFM.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 i Reason for ruling out:* The majority of the Switchyard was prol The northwest corner of the 161-kV S the site.Triggering Mechanism 7 -Soil ps CPFM 7a -Cracked slab, di is support CPFM 7b -Displaced roken CPFM 7c -General sitet CP -.n ckling d ad was tI lenit shallo)&idhIion, loss of structural connl rag ruling There was potential forI no settlement was obser me wi some of the fills above el. 1003.3; however, ng Mechanism 10 -lOa -Cracked sla]support DisplaA, hine/Vibration-Induced Liquefaction erential settlement of shallow foundation, loss of structural CPF1X CPFI 4 mcture/broken connections up instability Reason for* The Switchyard has not been subjected to machine vibrations, and no liquefaction was observed on site. Therefore, machine/vibration-induced liquefaction failures are not credible.

Priority 1 Structures Switchvard Page 5.22-7 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 1 lb -Displaced structure/broken connections CPFM lId -Pile/pile group instability Reason for ruling out: 0 Liquefaction was not observed at the site.Triggering Mechanism 12 -Rapid Drawdown CPFM 12a -River bank slope failure and und CPFM 12b -Lateral spreading Reason for ruling out: sti* The Switchyard is located a sufficient dista outside the zone of influence of a bank sl, Triggering Mechanism 13 -Submergen I CPFM 13a -Corrosion of I CPFM 13b -Corrosion of stru I el Reason for ruling out: n the therefore is.ts 0 The Switchyard has not jected to corr Wances that would be considered or , ement ation systems are below frost level. Therefore, frost effects and foundation conditions.

The structures have always rature with moist to saturated soils.ment of Credible Potential Failure Modes The following CPP s are the only CPFMs carried forward for detailed assessment for the Switchyard as a result of the 2011 flood. This detailed assessment is provided below.

Priority 1 Structures Switchyard Page 5.22-8 Rev. 2 Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3a -Undermining and settlement of shallow foundation/slab/surfaces (due to pumping)CPFM 3b -Loss of lateral support for pile foundation (due to pumping)CPFM 3c -Undermined buried utilities (due to pumping)The Triggering Mechanism and CPFMs could occur as follows: the site soils are erodible, and some of the gradients may be sufficient to facilitate erosion. If se ge is unfiltered and infiltration continues unarrested, voids could develop. Du th -jknown pumping points throughout the site, voids that develop could resu de °'ndations.

The following table describes observed distress indicat d otlt uld increase or decrease the potential for degradation associated with the S)Adverse (DegradationlDirect Floodwater Impact More Likely)A substantial amount of sand was observed inside electrical trenches that were connected to a manhole that was being pumped. A legradatiorce 6act Lessl_K'&ard structures ofvth'e)v an ear Voids at conduit locations around the 161 -kV Building were observed in the general vicini pump locations.

i Voids were observed around the transformer pad.Data Gaps: a Site grade=nstruction is n'As have been observed.

The sand in the trench after m the soils surrounding the trench, therefore, the CPFMs has occurred due to the 2011 flood is high.The occurrence CPFMs on a large enough scale could negatively impact the trench structure.

This cou id lead to excessive trench unit movement and negatively impact the integrity of the utility. Therefore, the implication of the potential degradation for these CPFMs is high Confidence The extent of subsurface erosion and its potential impact to the utilities in the Switchyard is not known due to the lack of data gathered on subsurface conditions.

Since there is not enough information on the subsurface conditions at this time and the pumping on site could have caused undermining and/or settlement, the confidence for these CPFMs is low.

Priority 1 Structures Switchyard Page 5.22-9 Rev. 2 Summary For CPFMs 3a through 3c, as discussed above, the combined consideration of the potential for degradation and the implications of that degradation to a structure of this type puts it in the"significant" category.

There is low confidence that there has been significant degradation to the soil surrounding the Switchyard due to the lack of test data available at this time. More data or continued monitoring and inspections are needed.5.22.5 Results and Conclusions The CPFMs evaluated for the Switchyard are presented in the rating for the estimated significance and the level of confidenc Low Confidence (Insufficient Data)CPFM 3a CPFM 3b CPFM 3c U-0 Z 5.22.6 Rpcomn ~ ctioA rig m;h shows the mce The following actionw iended for the Switchyard:

Given the Low Confidence'kRating for these CPFMs, continued monitoring is recommended to continue elevation surveys on this structure.

The purpose is to monitor for signs of structure distress and movement or changes in soil conditions around the building.

The results of this monitoring will be used to increase the confidence in the assessment results. tlIevation surveys should be performed weekly for four weeks and biweekly until December 31, 2011. At the time of Revision 0, groundwater levels had not yet stabilized to nominal 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 and/or Priority 1 Structures Page 5.22-10 Switchyard Rev. 2 assessment should be conducted.

Observation of new distress indicators may result in a modification of the recommendations for this structure.

5.22.7 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 monit p g for most of the Priority 1 Structures was not completed by the submittal date. Thi evi th* ssessment Report includes the results of additional forensic investigation and moni to s structure as described below.5.22.7.1 Additional Data Available The following additional data were available for the Swit evisions 1 Assessment Report: " Additional groundwater monitoring well and e level da PPD.* Results of geotechnical investigation by (see A t 6).* Results of continued survey by Lamp on and es (see A ent 6).5.22.7.2 Additional Analysis The following analysis of additi was con for the ar* Groundwater monitor' d river sPPD.Dat river a dwater have re to nominal normal levels.s of geotu daatigai ele Geotech, Inc.ra1ge of the g equiCP mesnt. T for this Assessment Report were compared to similar data from nuh inother R eotvhnical investigations that have been conducted n the FCS site cin previof s. This comparison did fotheentify substantial changes to oil strength and stiffni e er that tithe period. SPT and CPT test results were not cniec based in the top 10 f protect existing utilities.

• Res. tinued ."y Lamp Rynearson and Associates.

SurveyN " pared to the original baseline surveys have exceeded the accuracy range of the' ,g equipment.

The significance of this fact is discussed below.Three CPFMs were identified in Revision 0. Since Revision 0, additional data have become available which has clarified the significance and confidence for these CPFMs. The following presents the previously identified CPFMs and the new interpretation of its significance and confidence based upon the new data.*

Priority 1 Structures Page 5.22-11 Switchyard Rev. 2 Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3a -Undermining and settlement of shallow foundation/slab/surfaces (due to pumping)CPFM 3b -Loss of lateral support for pile foundation (due to pumping)CPFM 3c -Undermined buried utilities (due to pumping)The data available for survey points have shown no movement outside the accepted tolerance levels except the following point: TW 29. TW 29 is a 161-kV p the southeastern comer of the Switchyard.

The data for TW29 show that there wa el c e between the first and second survey. Data have held steady since. inal ey data point was taken when the area around the pole was flooded. Bas the con follow-on data point elevations in non-flooded conditions, we believe e baeb elevation does not correlate with later data and is an error.SPT and CPT test results did not identify substantial ch, SPT and CPT test results were not performed in the top The groundwater elevation measured in the mo the floodwater receded. The data indicate th river level near the beginning of October 20 d rece October 14, 2011.CPFMs 3a through 3c for the Swit d t as Results of survey data, nearby g ical ata, inspections do not indicate s* tructure mo t attributed to these CPFMs. Its of the add CPFMs ..ut.

uming that no strength A; existing L Feet the river level as 1 ft above the bout vit tress Indicators.

'r n ormg, and nearby field h verse effects that could be-investigation show that these cems are identified through the 5.22.6 and continuing until t of the matrix representing "No I Flood."

Priority 1 Structures Switchyard Page 5.22-12 Rev. 2 5.22.7.1 Revised Results The CPFMs evaluated for the Switchyard are presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

Low Confidence (Insufficient Data)High Confidence (Sufficien Data).M 0 'a C LL 0 z CPf CPf.7.2 Conclusions e assessment of the FCS i~tures, the first step was to develop a list of all Triggering isms and PFMs that c ave occurred due to the prolonged inundation of the FCS g the 2011 Missouri flood and could have negatively impacted these structures.

The was to use dat -various investigations, including systematic observation of the s ver time, e .i eliminate the Triggering Mechanisms and PFMs from the list or to recon rthr igation and/or physical modifications to remove them from the list for any MDtýre. Because all CPFMs for the Switchyard other than CPFMs 3a, 3b, and 3c had out prior to Revision 1, and because CPFMs 3a, 3b, and 3c have been ruled out as a resul the Revision 1 findings, no Triggering Mechanisms and their associated PFMs remain credible for the Switchyard.

Therefore, HDR has concluded that the 2011 Missouri River flood did not impact the geotechnical and structural integrity of the Switchyard because the potential for failure of this structure due to the flood is not significant.

r Section 5.23 Transmission To wers KK..P 7ý.7:A Priority 1 Structures Page 5.23-1 Transmission Towers Rev. 2 5.23 Transmission Towers 5.23.1 Summary of Transmission Towers Baseline information for the Transmission Towers is provided in Section 2.0, Site History, Description, and Baseline Condition.

The following three types of transmission towers reside on the pro 345kV Lattice Transmission Towers There are four 345 kV lattice transmission towers labeled U n rty. The superstructure is constructed of a tapered steel truss frame t o an un eight due to the lack of available drawings.

The trusses are supported o t each of the l The piers are founded on pile caps below grade which are su ing pile arrangements.

Piles are 12 in. in diameter and the pile material/

pecity are u Pile depths below the pile cap range from 20 to 69 f. for the onsincaen uplift piling option that may be implemented on cof the to eexact pile group type and uplift piling location forracho 0 161kV Single Pier Transmission Towers There are numerous single column tr e"s tHe proper superstructures are oge- galvanized steel colut e xsend t nknownsa ue to lack of available drawings.

Th e supolrd by ah e bed appicaion f thetwo o Turbine Building South Switchyard and the Switchyar orted on a sise dhat ;Q advanced to depths varying from 2 55 ft. a ve vertical al I reinforcing for the full depth.5.3.r2d design snformation for the 16 1 kV transmb le s5 .2d l he st d edad othe r north of the site is unknown.Q ost Wood Transmi2 ers 6al dul-omnwooden er existn the property.

No drawings are available for n n the standard installation of these towers, they are pr be supported by a bed application of the wood pole in soil. Bottom portions of the , ole are encased in al sleeve.5.2.2 the Analysis Table 5.23-1 lists re , ted by OPPD and other documents used to support HDR's analysis.TM6 5.23-1 -References for Transmission Towers Document Title OPPD Document Date Page Number Number(s)(if applicable) 161 kV Transmission Line Anchor Bolt C-8140-1 5/26/2004 Foundations Transmission Plan & Profile Lines 70 & 76 2/3/2011 N/A Circuit I 345kV Foundations for Lattice Towers E-4600 6/17/1968 Priority 1 Structures Page 5.23-2 Transmission Towers Rev. 2 Table 5.23-1 -References for Transmission Towers Document Title OPPD Document Date Page Number Number(s)(if ap licable)345kV Foundations for Lattice Towers Pile E-4602 6/17/1968 Foundation Table Naval Facilities Engineering Command, 9/1986 All dDesign Manual 7.01, Soil Mechanics Figure 5.23-1 10=20141'&

AN/A Detailed site observations-nfield reports, field notes, and anspe hepsi the Transmission Towers are provided in Attachment 8.Observed performance and pertinent background follows beloe.Aseset f ernmsinTwesicue h following* The to wers ae inundated with water for the duration of the the ember, o Figure 5.23-1, Sheets I through 3): 201e mforksgs of dis toeor pess. vg s r-TowerST #70 8-, which had woate r o nn n the sot h ntr buto shoed novlent water marks on the tower or pier an ege I'l IS prest-e Some towers were still inundated wml aa e reach inicservation during the site inspection (see Figue 5.23-1t S 1 through 3 0 The posts of the double wood R smisslon Toa 9 08 appeared saturated extending svrlfeet above gra* Soils arou " the ex of those in payee areas and those that were not in inundat. soft od with a fiberglass probe. The probe was i, S the towers are supp gydn he towers with guy acoswr bevdt S ead man anchor except #122, S # 13,. STS # 14, and STS #25 which have=,anchor foundations.

dsge ' :ce erosion was noted ill bserve areas. Most areas had deposited sediments. r ! ,egne 5.23.3 Ass;s ethos fed ures 5.23.3.1 Accomplished Assessments .rof t nsmission Towers included the following: " The towers and surrounding grades were visually inspected in August and September of 2011 lfor signs of distress.* An assessment was made of collected survey data to-date for indications of trends in the movement of the structures.

r Section 5.24 iam Underground Cable Bank.A.7- t Au. ar..... ..;N. */.9v Priority 1 Structures Page 5.24-1 Main Underground Cable Bank, MH-1 to the Auxiliary Building Rev. 2 5.24 Main Underground Cable Bank, MH-1 to Auxiliary Building 5.24.1 Summary of Main Underground Cable Bank, MH-1 to Auxiliary Building Baseline information for the Main Underground Cable Bank from MH-I to the Auxiliary Building is provided in Section 2.0, Site History, Description, and Baseline Condition.

The portion of the Main Underground Cable Bank system covered under ecti t:extends from MH-1 to the Auxiliary Building.

M-I is located near the me itchyard.

A duct bank from the switchyard connects to the north wall of MH-1.'l. is loca. ., aofMH-I1 and west of the old warehouse.

The duct bank between MH-1 and MH-aoouted eeaa 'e rthwest comer of the new Maintenance Garage and King Tut Wall. From I s edas nds to MH-3, which is located inside the Rad Waste Building.

Between -L-3, the croses beneath the old warehouse addition, the site perimeter and securi nd the "Tren trench. From MH-3 the duct bank is routed to the south and out o e Waste Buildi MH-4. At MH-4, the cabling turns east 900 and extends east to the point heturns 90a terminates outside of the Auxiliary Building.

Outside o R Buildi duct bank turns vertically upward and terminates above grade in a pul.. AN f the duct rminate in the pull box adjacent to the Auxiliary Building are set a, .005.0 k aringto dra'jgnl 1405-E-320.

The duct bank between MH-4 and the Auxiliary Building runs daacefi e face of ie Auxiliary Building.

A "Missile Shield Room" addition to t Iadn4lt subsequent to construction of the duct bank and is locat rect ]S er the in Und V~able Bank.5.24.2 Inputs/References Supporting the Analysis , Table 5.24-1 lists references provide' PD and other d'l. , used to support HDR's analysis.Table

~s~for Main UiarIground Cable Bank, MH-1 to Auxiliary Building DocumehtT

' OPPD Date Page Document Number(s)(if applicable)

Un gud Duct System 60184 12/13/2002 CE-79-3 Desel'Ghrator Enclosure Plan & Detk H-s'SH- 1 24002 Unknown 13007.18-EC-1-8A-,1 Site Plan UnZt !qnd Ducts -Manl_ eý utdoor 12582 Unknown 11405-E-319 Lighting-Fence Gr}tdig Underground Duc-M hI ons & Details, SH 12583 Unknown Underground Ducts & osr ations-fiectlons

& Details, SH 12i584 Unknown 11405-E-321, 2 ClB SH. 2 Underground Ducts & Manhole Sections & Details 12585 Unknown 11405-E-322, SH. 3 Naval Facilities Engineering Command, Design Manual 9/1986 All 7.01, Soil MechanicsIIII Detailed site observations--field reports, field notes, and inspection checklists--for the Main Underground Cable Bank from MH-1I to the Auxiliary Building, are provided in Attachment

8.

Priority 1 Structures Main Underground Cable Bank, MH-1 to the Auxiliary Building Page 5.24-2 Rev. 2 Observed performance and pertinent background data are as follows:* Groundwater was observed flowing into the basement sump of the Turbine Building from floor and condensate drain pipes not designed to intercept groundwater.

This condition has a recorded history dating back to 1997. For further information see Section 5.8. A more detailed discussion of this Key Distress Indicator is presented in Section 4.1.* Settlement of a column in the Maintenance Building, north of the Turbine Building, was documented by OPPD and HDR personnel.

A CR describing the eve, ondition, and related issues was created by OPPD and is on record. The Turbine Building enance Building are located east of the Auxiliary Building.

A more detailed dis.ision o ' y Distress Indicator is presented in Section 4.3 The Main Underground Cable Bank (MH-4 to the Auxiliary'.4dig, ýn er the Auxiliary Building Missile Shield Room.* The Main Underground Cable Bank alignment, where it passes ea the Missil i o is located adjacent to fuel oil tank 1 (FO-1) and the associate e iping." A sand boil/piping feature was observed (originally reported in CR 2' 65) near the so est comer of the Auxiliary Building, in the Missile Shie -This roo ii ated along the south wall of the Auxiliary Building and has an unfinish 21 fi oor surf a 'el oil storage tank FO-1 is located outside the Missile Shield Ream, with elep iping ent-m, einthe room below floor elevation near the observed boil/iping fe~kilfe.* The Aqua Dam surrounding the facility crossed .Ke Main n"rgr6, d@-able Bank.* The Aqua Dam failed for a short period. f time'duie to beiig damag iatl.No ,ing floodwater to enter the area inside the Aqua Dam perimef.urfaces ab4 ] e Main Un rgrcound Cable Bank were inundated with water when the A qu ILm failed. King tut blocks (20 to 25 thousanfitl&odnds per block) I o ae a, t to the Protected Area fence at the northeast epd of the site wefhed onto trucks sper load) and removed from this area on,,';, ' W 4 2011.

team observed and photographed this operation.

Pavemerx~di'j m6l ein dlection during the lifting or removal of these blocksaA'_ditionally, defTc 6n of as not observed where loaded trucks crossed varoi ility alignments wlhySiting the*1 "was opened and pumpedot~i y OPPD enci6yees on Wednesday, September 7, 2011. The'IIvel prior to beginning pufiping activities was level to the bottom of the manhole concrete cov~er ording to OPPD employ.:suestioned while observing pumping operations.

• MH- ~aslso opened and pumpgb, t by OPPD employees on Monday, September 13, 2011. An OPPD e, pl5y.ee entered MH-1 aI 4ý4gotographed the interior walls once the manhole was emptied.The emplO no~ted that craqks:djcent to the cable duct openings were a pre-existing condition that existed pfiSo6t-he 20,14406W event.MH-1 pump dischfar.S ituted to a large swale located along the east side of the switchyard.

The water level wassgific'Wantly lower than the rim and cover of the manhole at the time of initial pumping. Water level ii the swale had dropped an additional 1 ft or 2 ft lower at the time of the second pumping.* Pumping operations to empty the manhole required emptying the connecting duct banks and adjoining manholes to the level of the connecting ducts.* OPPD employees pumping MH-I the first day stated that MH-2 had been pumped dry the day prior." Manhole pumping operations were performed after flood waters had receded to the point where the manholes were accessible.

Priority 1 Structures Page 5.24-3 Main Underground Cable Bank, MH-1 to the Auxiliary Building Rev. 2* A swale crosses the duct bank east of MH-2. Minor localized surface erosion was observed along the banks of the swale north of the Maintenance Garage and where it crosses the duct bank.* On September 13, 2011, Thiele Geotechnical Services was hydro-excavating for soil borings south of the new, six-bay, Maintenance Garage. At the time of field observations, vacuum excavations had proceeded to a 2-ft depth and exposed a reinforced gravel road section composed of Geo-grid installed in 6-in. layers. Four layers of Geo-grid were visible at the time of field observations.

The lateral extents of the Geo-grid reinforcement in the gravel surfaced areas are not known at this time.5.24.3 Assessment Methods and Procedures 5.24.3.1 Assessment Procedures Accomplished Assessments were made by walking the cable bank alignmrMdn4observing s'r`e eatures of the system (manholes) and the ground surface overlying th84dpgkound cable ba surface assessment included using a 4-ft-long, 0.25-in.-diafheteir,, Ipped T-handle soil probe to hand probe the ground surfacealong the a*,.,; ents and ad acent areas to determine relative soil strength.

The cused on i. Amng conditions indicative of potential flood-related impacts o ge Me utility as foi..* Ground surface conditions overlying an, , mediatel jac1to the utility and its backfilled trench including scour, subs, iece or sr nent,!, sreading piping, and heave.* Soft ground surface areas (n i enginee and/or".l, estone gravel pavement) as determined by probing.* Water accumulations subsurface systM"q onents (manholes and concrete cable encasement pipes).* D &gXf6t-rd M a above--, sstem features and equipment.

• 1 ce fro nora tallation co'j tions, including settled, tilted, or heaved systemand equipmr ms"Operation of the systemland appurtena ipment (i.e., is the system operational).

.#,dditional investigations wer6pefrformed to further characterize the subsurface at the facility~iu g areas where conditidWitdicative of potential flood-related impacts or damage was observkThese included the.4'f6iwing:

• wer hot available at the time of Revision 0.)Paved aresvere emlffd- with GPR and dynamic deflection methods (i.e., drop weight deflectome Wtsr i eports were not available at the time of Revision 0.)5.24.3.2 Assessment Procedures Not Completed Assessments of the Main Underground Cable Bank from MH-1 to the Auxiliary Building that were not completed include the following:

The interior of underground cable bank manholes and connecting concrete-encased cable ducts were not inspected except for visual observations that were possible from above and behind temporary safety railings.

Manholes are a confined space as defined by Occupational Safety and Health Administration (OSHA) regulations.

In accordance with these regulations and OPPD Fort Calhoun Station (FCS) safety procedures, manhole entry Priority 1 Structures Page 5.24-4 Main Underground Cable Bank, MH-1 to the Auxiliary Building Rev. 2 is requires a confined space entry permit and can only be performed by appropriately trained OPPD personnel.

No excavation to inspect underground systems and conditions was performed.

Unless field conditions are observed that might indicate problems, this assessment is not warranted.

5.24.4 Analysis Identified PFMs were initially reviewed as discussed in Section 3.0. Theileview considered the preliminary information available from OPPD data files and from ,intial ido bservations.

Eleven PFMs associated with five different Triggering Mechanismsre dKfm 6d to be"non-credible" for all Priority 1 Structures, as discussed in Sec ]pi6 The e ig PFMs were carried forward as "credible." After the design review for each sc.icture s Feobservations, and the results of available geotechnical, geophysical, and surv i T re analy zeber of CPFMs were ruled out as discussed in Section 5.24.4.1.

The CPFi]Is ed forward 0 iled assessment are discussed in Section 5.24.4.2.5.24.4.1 Potential Failure Modes Ruled Out Prioro the Corn i of the DetaHed Assessment The ruled-out CPFMs reside in the Not Sigg,"an tigh I nce catego for clarity will not be shown in the Potential for Fail"-ut onfidence ai.Triggering Mechanism 2 -Surfac,-Eros4on t CPFM 2a -Undermining sha 0Abundation/I RZsurfaces CPFM 2c- Undermined burA!Mltilities.

Reasons for ruling out: TNsj u e- eevrsinnwasbwas, observeh ...t.. Main Underground Cable Bank manholes or on the enc a eeont.."" al"ia f this system's underground concrete cableprncasements. , 4

• Only localized and limifets&&face erosi Zias observed on the ground surface across the'Jacility.

The Main Cable Bank system is constructed at depths sufficiently

"belw. potential scour depthsinicated by surface erosion features observed in other areas.TriHeU`gg Mechanism 4 -#,$y ostatic Lateral Loading (water loading on structures)

CP p c_~e~ Wall xure CPFTVf~dWall failute'iimshear CPFM 4Eea.,e Reasons for rulinriut:

• This segment of the Main Underground Cable Bank system was not pumped while the site was inundated with water. Manholes in this segment (MH-1, MH-2, and MH-4) were not pumped until flood waters had receded to below ground surface elevations and the manholes were vehicle accessible.

Prior to pumping, the system was flooded and not susceptible to hydrostatic loads.* Underground structures are designed for hydrostatic pressures as a standard practice.* According to OPPD staff, this system was pumped on numerous occasions in the past due to high groundwater conditions.

Priority 1 Structures Main Underground Cable Bank, MH-1 to the Auxiliary Building Page 5.24-5 Rev. 2 Triggering Mechanism 6 -Buoyancy, Uplift Forces on Structures CPFM 6b -Cracked slab, loss of structural support CPFM 6c -Displaced structure/broken connections Reason for ruling out: This segment of the cable bank was not pumped while the site was inundated by flood water. Manholes in this segment (MH-1, MH-2, and MH-4) ' not pumped until the water level had receded. Prior to pumping, the system was flo d refore it was not susceptible to uplift forces.Triggering Mechanism 7 -Soil Collapse (first time t CPFM 7a -Cracked slab, differential settlement ofs support CPFM 7b -Displaced structure/broken connections CPFM 7c -General site settlement Reason for ruling out:* Soil supporting and surrounding the Main X ergroi previously wetted. The peak flood ele n prior to 1993.Triggering Mechanism 10 -Ma.cin./Vii ratio u CPFM 16a -Cracked slab, derential settler n ,of been occurred in loss of structural support 4 CPFM Ob -Displaced CPRO ýTý--itional vibrations froh ief'acility (ttiibhze and various pumps) have historically occun and no indications of the '4 PFMs are evident.usd n-i e d w,,mps used on-site duringefood event were too small to cause ground or structure vi tions sufficient to initiate soil liquefaction.

Visible indications of liquefaction were Iolooberved around the a#ia Xwhere the pumps were operating, and no evidence of liefaAti'on was reportedl-toýHDR.

ed a licative of soil liquefaction and resultant settlement were tintz or lateral movements were observed.

Priority 1 Structures Main Underground Cable Bank, MH-1 to the Auxiliary Building Page 5.24-6 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 1 lb -Displaced structure/broken connections CPFM 1 Ic -Additional lateral force on below-grade walls Reason for ruling out: 0 Static liquefaction results from a relatively small di, condition that allows a liquefaction failure to occur!Indications of liquefaction have not been observed Triggering Mechanism 12 -Rapid Drawdown CPFM 12a -River bank slope failure and undermin CPFM 12b -Lateral spreading Reason for ruling out:* This condition pertains to slope instabili gociate level. Since this segment of the Main Hn erground the river, the potential for these CPFM. remot-4, an unstable f the river away from Triggering Mechanism 13 -CPFM 13a -Corrosion of Ud~o [iei d stru? lgare located below the design flood elevation for theGrounJ ledtero"ed by Missouri River water elevations, percolation

!_fstorm precipitati0o 4intersnow would be expected to contact underground improvements, includifn structed st"'ahd concrete facility elements.

As such, steel and concrete site improvemelts are assumed to be designed to withstand the corrosive environment of groundwa 'd wetted soil.ggening Mechanism 14 is Effects PON 4a -Heaving, qrush-ing, or displacement

• Utility cablix glisWit! rigid and not subject to major damage due to frost-induced displacement. -r" Manholes and the bottom of the duct banks are founded below frost level." Saturated soil conditions have occurred in the past Conditions have not been ch iaflQ'ed due to flood conditions.

Priority 1 Structures Page 5.24-7 Main Underground Cable Bank, MH-1 to the Auxiliary Building Rev. 2 5.24.4.2 Detailed Assessment of Credible Potential Failure Modes The following CPFMs are the only CPFMs carried forward for detailed assessment for the Main Underground Cable Bank from MH-1 to the Auxiliary Building as a result of the 2011 flood. This detailed assessment is provided below.Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3a -Undermining and settlement of shallow foundatioAXslab/surfaces (due to pumping)CPFM 3c -Undermined buried utilities (due to pum_;Y The Triggering Mechanism and CPFMs could occur as.f. ws: M P. nially connected seepage paths exist in the soil backfill at the site, includm Ja ii in nches, granular trench bedding, broken building floor and condensater , ains pipes, pr e ing defects/voids under pavement, etc. The paths may be Mse a s e locations R.-A flood waters (e.g., open ground along areas outside the Aqua Dpath en'= c eeter). This hf seepage paths is connected to several pumping source the sump pit *Ml e Turbine Bui ing, I.U... h Au Dam Manhole MH-5, and a series of surface pumps 1Italo g the AquaDa perimeter.

The pumps were operated for an Jg time, manlt%216fg a head differential on the seepage path networks.

,'dent was suffident to begin n of surrounding soil. The potential damage inQ. es settleinl ain Underground Cable Bank and manholes causing a loss of eleciica -..Pumping of MH- 1, MH-2, and ý4Asfter floodwataeis receded &6 ated'temporary and minor drawdown effects. The temperrawdown woi~dl~ause a hE differential on the seepage path networks already creat h , higherhead c ios, causing additional increment o c ical damag. ,.Belo. 'oe ob i s and ddtadha&,,support the likelihood of these CPFMs: '.6undwater flows weren w bserved ig into the basement sump of the Turbine Building from foor ad cone~~i~~aintipes

'no digned to intercept groundwater.

This condition has a recordedWiij'i;, dating býaffk to 1997. The Main Underground Cable Bank S terminates at the southeastt4i!iier of the Auxiliary Building, which is directly adjacent to theTurbine Building.a"l a inside the Aqua lDi1was pumped dry and created a hydrostatic head between the outside the Aqu.avPDam perimeter.

The inside the Aqua Dam perimeter was pumfidrom severalAcMOns, creating locations where suction increased the potential head differential be~tWiw area inside and the area outside the Aqua Dam perimeter.

A sand gcondition was observed within the exposed floor of the auxiliary building.

"* Manholes were pumped to remove water that accumulated due to the flood event. This created a head differential.

Below are field observations and data that indicate these CPFMs are unlikely:* Trench settlement along the alignment of the duct banks was not observed.* Soil probing along the duct bank alignments indicated soils were generally firm and stable.

Priority 1 Structures Page 5.24-8 Main Underground Cable Bank, MH-1 to the Auxiliary Building Rev. 2 Data Gaps (data yet required to assess these CPFMs):* GPR data and reports have not been delivered for assessment of subsurface conditions.

The following table describes observed distress indicators and other data that would increase or decrease the potential for degradation associated with these CPFMs for the Main Underground Cable Bank from MH-1 to the Auxiliary Building.Adverse (Degradation/Direct Floodwater Favorable (0 atJp4"/Direct Impact More likely) Floodater Im¶a-tlL.es Likely)The southwest comer of the Turbine Building is N A located adjacent to the termination point of the duct bank. __Water was pumped from several manholes.

Manholeswe

• dIl ated during7qJ' od event and Nverelpt umped until fldo waters hadrece the manholese accessible Th7e m esre only pumpe fora-sqha-t duration OfM ,i .The area inside the Aqua Dam perimeter was -" AN pumped from several locations.

Sand boil/piping feature observed in Auxiliar * .Building Missile Shield Room.____

____ ____Data Gaps: ., s " Ap* GPR data were not available att Kl*e of evisio 1 assis n e psb areas or paths at the facility.Conclusion Poentigfor 6vaber Impact catosfor this CPFM h' en observ, !'I he Turbine Building and Auxiliary Building hyl~ich is directly adjacent to Underground Cable Bank. The voids below the base ,'-slalibin the Turbine Building aeiekn'own to exist with heavy flows of water being pumped from t'....i. Since the 2011 flood aused increased flow through the broken drain pipes, the potentW1 that the 2011 flood caus6ed further and more rapid degradation due to these CPFMs is high.4; The occurrence ofAthese CPFMs could potentially cause the collapse of the Main Underground Cable Bank. HoweVer, the integrity of system of cables in the trench may not be impacted due to the flexibility of the cables. Therefore, the implication of the potential degradation for this CPFM is low.Confidence The extent of subsurface erosion and its potential impact to the Main Underground Cable Bank is not known due to the lack of data gathered on subsurface conditions.

Since there is not enough information on the subsurface conditions at this time and the pumping in the Turbine Building could have caused subsurface erosion, the confidence for these CPFMs is low.

Priority 1 Structures Main Underground Cable Bank, MH-1 to the Auxiliary Building Page 5.24-9 Rev. 2 Summary For CPFMs 3a and 3c, as discussed above, the potential for degradation is high because the pumping in the Turbine Building and the sand boil/piping feature in the Auxiliary Building.This degradation could have caused enough erosion to impact the integrity or intended function of the structure.

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 not sufficient to rule ou these CPFMs. Therefore, the confidence in the above assessment is low, which mea or a r inued monitoring and inspections may be necessary to draw a conclusion.

Q 5.24.5 Results and Conclusions The CPFMs evaluated for the Main Underground Cable Bank are presented in the following matrix, which shows the rating level of confidence in the evaluation.

Low Confidence (Insufficient Data) _=._ 2".b 5.24.6 Recommended Further forensic investigations and physical modifications are recommended to address CPFM 3a and 3c for the Main Underground Cable Bank. CPFM 3a and 3c are associated with unfiltered flow of groundwater into the Turbine Building basement drain piping system (Key Distress Indicator

1. 1).These recommendations are described in detail in Section 4.1.Also, a review of the geophysical data when available should be done. The results of this review will be used increase the confidence in the assessment results. At the time of Revision 0, groundwater levels had not yet stabilized to nominal normal levels. Therefore, it is possible that new distress Priority 1 Structures Main Underground Cable Bank, MH-1 to the Auxiliary Building Page 5.24-10 Rev. 2 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 and/or assessment should be conducted.

Observation of new distress indicators may result in a modification of the recommendations for this structure.

5.24.1 Updates Since Revision 0 Revision 0 of this Assessment Report was submitted to OPPD on 0(presented the results of preliminary assessments for each Priority 14 incomplete in Revision 0 because the forensic investigation and/,rii Priority 1 Structures was not completed by the submittal date.includes the results of additional forensic investigation and described below.5.24.1.1 Additional Data Available The following additional data were available for the Main U: MH-1 to the Auxiliary Building for Revisions1 a Ehi,* Results of KDI #1 forensic investigatio , Section*;41

• Additional groundwater monitoring well; and river A,* Results of geophysical investigation by ,Neotech* Results of geotechnical investigdibf]n by)1-iele eiietch 5.24.1.2 Additional Analysis The following..analysis of was condu4.e 0 from M10 t .&&uxtiliarv Bull Ali 2011. Revision 0 were Main Underground Cable Bank level data from OPPD.ive returned to nominal normal levels.report by Geotechnology, Inc.c ReMi tests performed around the outside perimeter of the identified deep anomalies that could be gravel, soft clay, Results of~g6tcJfihcl 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 5.24-11 Main Underground Cable Bank, MH-1 to the Auxiliary 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.

Triggering Mechanism 3 -Subsurface Erosion/Piping CPFM 3a -Undermining and settlement of shallow foundation/slab/surfaces (due to pumping)CPFM 3c -Undermined buried utilities (due to pumping)Significance Potentialfor Degradation/Direct Floodwater Impact Indicators for this CPFM have been observed in the Turbn BMuIling and Au uilding, which is directly adjacent to the Main Underground Cablee voids bel base" slab in the Turbine Building are known to exist with heavy flows- tr be ig pump M'the sump. Since the 2011 flood caused increased flow through the No drain pipes, potential that the 2011 flood caused further and mar irapd.leg ada i rN/de this CPFM is gd eradar high. The Turbine Building Sump drainage i a e al OW1I as parto eport lowd recommendations to address this issue made and implemented d$ition, a sand boil/piping feature in the Auxiliary Buildidiissile Shil mo s A" sno ted during post flood inspections.

Based on implementation and pair of isue6associa,,with KDI#1 and.. .. ssie 6, the potential for instigation of assessment and necesat' repis in t ssie n~ qi,thpoeiafr degradation of this system is lo,1 Implication The occur eli"; ibis CPFM cou~dhicuse the collaps e Main Underground Cable Bank.HoweeN~;intg V.ystem n od .esithe trench might not be impacted due to the flte AMiN of the cablZOs sNRefore, thf'imp Kcation of the potential degradation for this CPFM eonfidence 1-h gioundwater elevations ha dropped to a level where they no longer can impact the sy9tEt , Based omainten repair activities planned in conjunction with KDI#1 and in the NVIiitShield room, co-"4,n~ce is high that problems associated with these CPFMs will be address p0 PPD. Sum m ary , i .7'::;.: As discussed, the potential for degradation is low because the pumping in the Turbine Building and the sand boil/piping feature in the Auxiliary Building are being addressed based on the recommendations for each. 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 this CPFM. Therefore, the confidence in the above assessment is high.

Priority 1 Structures Main Underground Cable Bank, MH-1 to the Auxiliary Building Page 5.24-12 Rev. 2 5.24.1.1 Revised Results and Recommendations The CPFMs evaluated for the Main Underground Cable Bank from MH- 1 to the Auxiliary Building are presented in the following matrix, which shows the rating for the estimated significance and the level of confidence in the evaluation.

CPFMs 3a and 3c for the Main Underground Cable Bank from MH- 1 to the Auxiliary Building are associated with Key Distress Indicator

1. 1. Section 4.1 presents the results of additional forensic investigation that was conducted to ascertain whether these CPFMs could be ruled The results of the additional forensic investigations show that if the recommendatioI scal modifications in KDI #1 are implemented that this CPFM is ruled out. efore, s that no further concerns are identified through the monitoring progran :*Z e Maij' egound Cable Bank from MH-1 to the Auxiliary Building (discussed in Se avr 24.6gifi to 5M.g until December 31, 2011), these CPFMs are moved to the qua** .3n tmatrx' ning "No Further Action Recommended Related to the 2011 Flood." r Low Confidence (Insufficient Data)CPFM 3c 5.24.1.2 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 modifications to remove them from the list for any particular structure.

Because all CPFMs for the Main Underground Cable Bank from MH-1 to the Auxiliary Building other than CPFMs 3a and 3c have been ruled out, and Priority 1 Structures Page 5.24-13 Main Underground Cable Bank, MH-1 to the Auxiliary Building Rev. 2 because CPFMs 3a and 3c will be ruled out when the physical modifications recommended for KDI #1 in Section 4.1 are implemented, no Triggering Mechanisms and their associated PFMs will remain credible for the Main Underground Cable Bank from MH-1 to the Auxiliary Building.

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.

&I SECTION 7.0.f- .2-A .... .' o.... .... ...............

AA Irk~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~~a

....

..... .... .... ...... ....f .. .

.. ..h.... .

Page 7-1 Summary and:Conclusiofis

-"'- --Rev. 2 7.0

SUMMARY

AND CONCLUSIONS 7.1 Scope and Purpose The FCS Plant and Facility Geotechnical and Structural Assessment hasbeen completed to identify and describe the effects of the 2011 flood on Structures at the site. Specifically, the objective of this Assessment Report is to present HDR's assessment of changes to the soil," rock that supports the structures at FCS that may have negatively impacted those Revision 0 of this Assessment Report was submitted to OPPD .6°icber I Revision 0 presented the results of preliminary assessments for each Prio tructu f-4 I of this Assessment Report was submitted to OPPD on November 28, 721dn ided ud- enfor"ation related to Priority I Structures.

These assessments were incompl t~iner 'ds on 0 a I{ 3 because the forensic investigations and/or monitoring for most oftij y .I completed by the submittal date. Revision 2 of this Assessment

'ort 'des updated ri, Priority I Structures to include additional monitoring data and the results 3196ional forensic investigations for the Key Distress Indicators.

Revisio re ents the e the assessments for each of the Priority 2 structures.

This section of the report provides a brief summa the proce. se 2 onduct thesructure assessments.

Conclusions and recommendations hen presented reg Fito the geotechnical conditions at the FCS site, the Key Distres~sr§ and A1iority i , 2 brity 2 structures.

7.2 Summary of the Assessmentf 6cess The Flood of 2011 inundated portio 9a FCS site for ;r'k" onths. Peak flood depths across the site a- ý,Wffpaed betWeeNand 4 feet, and fl....elocities over the site were generally

~ ~con T ts of this flooding were assessed by frst conducting a systemnaihd thorough VIsMa hervation eh structure to identify any outward signs of distress cause 1h.. '6 flood. After the i bservatio, &a on the 2011 flood, including the areal extent,* water velocities, an ...fect on gro;11 ater at the FCS site, were compiled.

Baseline Wdd 'e geology, geomorpholog .technical, and design conditions prior to the 2011 flood were also :Ted. A list of flood-induce mechanisms (Triggering Mechanisms) was identifi~einggering Mechanisms co [have caused degradation to the soil and/or rock that supports the FCS s RUN .and/or caused dir ipacts to structures due to the force of the floodwaters (Triggering Meelfa-sms).

Exam "

Mechanisms include settlement, erosion, stability, hydraulic actionlM-ost actiosi ing the list of potential Triggering Mechanisms, a list of PFMs was developed.

PF gyet4 y "in which a structure might fail. Failures are any errors or defects, and can be potential o amples of PFMs include undermining and settlement of shallow foundation/slab, undermI turied utilities, and loss of lateral support for pile foundations.

A detailed list of Triggering Mechanisms and PFMs is presented in Table 7-1.

Summary andl onclusions, Page 7-2 ReV. 2 Table 7-1 -Tri gering Mechanisms and Potential Failure Modes Triggering Triggering PFM Mechanism echanism No. Potential Failure Mode No.]a Undermining shallow foundation/slab River Bank lb Loss of lateral support for pile foundation Erosion/Scour Ic Undermined buried utilities pipes/cables I d Additional lateral force on piles 2a Undermining shallow foundap.nrslal

..Surface Erosion 2b Loss of lateral support for,$e &ndatioM " 2c Undermined buried utieh iAf 3a Undermining and settlerintishallo,,Mf~ndaaJVo (due to pumping)3b Loss of lateral support for PRO Iaton (due to pujg.)3c Undermined buried utilities .tpeitmping)

Subsurface Undermining and settlementý'

shai, undatin/slab Mo(mayeA.-

Erosion/Piping 3d drawdown)

M, 3e Loss of lateral supp- 0 ._ pile foundationi , r'iver drawdown)3f Undermined b.W N ýe to river dra I-,______ 3g Sinkhoe d rment due jbp. g into karst 4a Overturn "It" Hydrostatic Lateral 4b Sliding ., Loading (water 4c W fil loading on a- structures) 4d in sheqW.___ _. e~1..xcess deflectionil

'%4 JDverturning

'AT4 rh M.":&, .VA,'55"1 ".10 ing 5cýt!W.lfnfailure in flexure AI z"r- :"-i L -.-r,-l A.06ading-*'I`"Vitiffire in shear wný5 d in shear T I I Dam~Qi~tieris

---l. I Excess dR Buoyancy, Uplift L. ., Forces on ..slab, loss of structural support 6c b .isplaced structure/broken connections

". R Cracked slab, differential settlement of shallow foundation, loss of*, structural support"SI@,lapse (first 7-.i , p ( tl Displaced structure/broken connections l7c General site settlement

<_ _ 7d Piles buckling from down drag 8 Soil 8a Not applicable 9a Cracked slab, differential heave of shallow foundation, loss of structural support 9 Swelling of 9b Displaced structure/broken connections Expansive Soils 9c Fail tension piles 9d Additional lateral force on below-grade walls

....Page 7-3 Sufnmary and Coniclusions..

-_-LRv. 2.Table 7-1 -Triqgerinq Mechanisms and Potential Failure Modes Triggering Triggering PFM Mechanism Mechanism No. Potential Failure Mode No.Cracked slab, differential settlement of shallow foundation, loss of Machine/Vibration-

-tructural support 10. Induced l0b Displaced structure/broken connections Liquefaction W c Additional lateral force on below-grajowalls 10d Pile/pile group instability

• ,0.. A4&. , Cracked slab, differential sOMIffienknt of j-,y ndation, loss of Loss of Soil structural support Sr due to* I b Displaced nectiqM0 Static Liquefaction Ic Ada lal c or Upward Seepage Ile Additional lateral frce onO.OVr waus "'W lid Pile/pile group instability

.12a River bank slope failure ane.peO surrounding srU-1u0dip 1 2 Rapid Drawdown I ;1 -12b Lateral spreading tj 13a Corrosion of undergp.u.4.t.

utilities

'13 Submergence 1b Corrosion of r,%14 Frost Effects 14a Not applica&d

...Karst Foundation 15 ClapsF 15a Piles punc g, through ON-h.ub°to additional loading-Triggering Mechanism 5 applies to only the Missguri RRQ, ihere ...wnW velocsuover the FCS site.Using the knowledge compiled for ...i"b e on each s r dure's standard (for example, shallow or deep founded building of, eutility), a list :140--l PFMs was compiled for each structure.

These V.- screened .rmine if they wvTr&27dible" (CPFMs), which means a particular PF .ed or Go .eAn progress due to the changes caused by the 2011 flood. Th. aled detei-m Aon of wh Triggering Mechanisms for the CPFMs could have b. were actually inith i the fi0 t ntial for degradation/direct floodwater impact).As some PFMs were deter d to be noW ible. For example, PFMs arising from riveri.on were eliminated becausqi-.evidence orbank erosion was observed.

A detailed list of PFM ted from detailed in Section 3.6.During defci. ssessment, when add al data was available including the results of the systematic visual obser' a secondary sc -g took place to rule out more of the CPFMs. This might have resulted in the er idtaonof all, CPFMs initially identified for a particular structure, or there could be remaining-."4M re discussed in detail in this Assessment Report. Also, the PFMs screened out as non-c , n initial screening described above were reviewed again in light of the additional availab le -WAdetermine if they should be added back to the list of CPFMs. The remaining CPFMs were ev -uated 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 201 1flood and~then .the implications of that degradation to a structure of that particular design type. The combina ion o:f the potential for degradation/direct floodwater impact and the implications of that degradation/impact is termed the "potential for failure" and is then categorized as "significant" or "not significant." The final step in the analysis was to evaluate the "confidence" in the potential-for-failure significance determination as either "low" or "high."

..S-Tm a rY aand C Con-clusio.sn I-:: Page 7-4..2 7.3 Principal Findings of the Comparative Geotechnical Analysis Comparison of geotechnical data for pre-flood and current investigations indicates 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 by the prolonged inundation caused by the 2011 flood. Comparison of seismic refraction data from the pre-flood and current investigations reveals similarrma2nitude of seismic wave velocities over the full depth of the overburden soils..and.no observable differences between pre- and post-flood conditions were identiffi from this work.Based on these findings and evaluations, the overall geotechnica significantly altered due to the sustained high water. The obseEN with the relatively wide range of strength and stiffness and encountered in the alluvial soils within the Missouri River valle at the FCS site, and data from these SPTs willbe incorporated in However, these findings are considered applicable only to those at the site. The upper 10 feet were hydro-excavated to avoid dar layer may have been disturbed from underseepage beneath the-te of utility backfill during drawdown of the river level an.-7.4 Key Distress Indicators K,.During the site visual assessments, three problemreas were 6.b.the 2011 flood had changed the site's geotecrhnicaie phs .J areas, referred to as Key Distress Indica kD ar ]c le have not been ints is consistent ypically gggs-.are planned nent ially indicated that observed problem 1. Increased groundwater flow in-2. Pavement failure and sinkhole Building 3. Co umnera Intake Structure and Service The Yure8V E, ach of the observed KDIs was evaluated using.gge n Igchanism, to identify the CPFMs, to identify same PFM, and to recommend remedial measures d condition.

inm 7.4.1 Tuif 7.4.1.1 Is The Turbine B1 ih'Mt ',Iment floor drilling and subgrade testing identified both a number of significant voids ,,.,sfpots as well as zones of competent soil. Table 4-2 provides the drill-hole number (see Figure¶-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..th... .e aiaila(.able d- However, somezonies such as the voids encounterEd -in DCP 2-6, DCP""I.-.

,, DCP 1-5 and DCP 2-8 are both significant enough and close enough in lateral distance that we conclude that these voids are part of a connected void system. All of these voids are close to where both the 10-inch and 6-inch drain lines run adjacent to each other and have multiple bends where joints may be more susceptible to cracking or separation in the pipe.. In this scenario, significant groundwater inflow into the drainage system is likely. There also are, however, zones where there is little to no evidence of voids or subgrade deterioration such as in

.:.Page 7-5 Summary and-Conclusions

__ Rev. 2 testing locations 2-10, 2-11, 2-12, 1-8, 2-14, and 2-18. Overall the data support the following conclusions:

• The Triggering Mechanism of subsurface piping of soil material due to the sump operation and seepage/flow into the drainage system pipes is occurring." Voids are significant and interconnected." The foundation subgrade is not affected uniformlyby this Triggering Mechanism.

Regarding CPFM 3b -Loss of lateral pile support due to sulhsurfr siAad piping (due to pumping) for the Turbine Building.

As discussed in Secti. 78, t s of the void and the potential effects on lateral pile support were consideW The mn id thickness is 6.54 feet in DCP test location 2-8 and the elevation of mom i's 80.63 ft. The deepest void in DCP test location 1-6 is 3.79 feet thick wrom a e, V 97654.For the worst case in the collected data, pile support could b " limited areas: evatioi 976.54. The maximum length of loss of lateral piling sup otto void, calcu bottom of the pile cap at elevation 983.5 to the lowest voidboto ion at 976 7 feet. There are a total of 10 locations were zero unt zones at elevation greater than three feet below the bottom of slab elevati ...mately of pile cap elevation 984). Of these 10 zero blow greater sn blow per tha drill-horelOt esshavan 1 foot. The remainder of the drill-hole localshave co r greater blow per two inch material to within 3 feet of the botto .the n atthe bottom of the pile cap elevation (el. 984).Based on the available informatr-, without a itative ysis we find that the loss of lateral piling support shown t llected data. th Tipe Building, over the limited areas suggested by the coll& a does not in e A icant risk of piling failure is present" in .nditions dul resence ofthe__ voids. Therefore, we have ruled out C bine Bui t should be noted that the subsurface erosion piping Tri W echani ...going a ateral pile support could be compromised in the void thickness tconf.u ,%increase.

Seismic considerations have not been ssed for this report an' not a bconclusion with respect to the effect of voids V lateral pile support durin' V ic loadin , 'ata from the Turbine BuiIH sub-slab investigations cannot be used to rule out b. for other pile-suppoii1structures in the vicinity of the Turbine Building, including:Building, AuxikhlilBuilding, Service Building, Circulating Water System, Turbi Uffli g South S yard, and the Fuel Oil Storage Tanks and Piping.Two other CPRM' ssCe ed with KDI #1 and Triggering Mechanism

1. 3 have not been ruled out by the Turb q "gin sub-slab investigations and have the potential to continue to affect structures other th~iiThe Turbine Building.

They are:: " CPFM 3a -Undermining and setti aces (diuteto pumping)0 CPFM 3c -Undermined buried utilities (due to pumping)Structures potentially affected include: Technical Support Center, Fire Protection System, Raw Water Line, Security BBRE's, Maintenance Shop, Underground Cable Trench (Trenwa), Waste Disposal Piping, Main Underground Cable Bank, Blair Water System, Demineralized Water System, Turbine Building South Switchyard, Fuel Oil Tanks and Piping, PA Page 7-6 Summary and Conclusions Rev. 2 Paving/Sidewalks/Outdoor Drives, Sanitary Sewer System, and Condensate Storage Tank* (buried utilities portion of system). For this Triggering Mechanism to affect these structures, a void would have had to progress beyond the Turbine Building Basement foundation and extend under the Structures listed above. The fact that the flow into the broken pipes has been occurring for many years makes the hypothesis that the voids could have extended beyond the Turbine Building foundation and under the Structures listed above more plausible.

The collected data showing that voids were found'at the perimeter of th~e Turbine Building basement between the pile caps at II locations also suggests that piping of raterial from beyond the Turbine Building Basement subgrade may have occurred.

..The Triggering Mechanism of subsurface erosion/pipin oil fro r n te pin h ys~ah nthe Turbein Building basement and perhaps beyond continues as lo ,the d remains unrepaired.

Voids, soft zones, and associated groundwa art' .mg flow l continue to enlarge and extend out from the drainage and sump systd yr time unless of e water into the sump system is stopped. Therefore, CPFM-!.W 3c for the listed above cannot be ruled out and remain credible until the foiT-cl, oremedial " recommendations are implemented to stop the Trigger.mg MechanisgN 7.4.1.2 Recommendations OPPD should perform remedial work to sY10 e uncontr.iied mage of the 6roundwater into the broken Turbine Building basement dr J.ge syste .ing ..,khe voids beneath the basement floor slab. The first prigis toW the ge of ter into the drainage st ae P " T !echanism.i he quickest and easiest way system as quickly as possible to ,IN. Triggrr'to stop the flow of groundwatear the sump is tU ck the dippge system pipes at their termination points into the alternative t 10 ; e i:{he existing drainage system is to abandonp*-i, s ting system y, and replace .above-structural-floor-slab sysplm ernative would be to construct a new system that isb that ýM§,J 'Jtpilize pump(s) to remove water from the existing en base M .o j 41 fl and the ins. A tion would be to trench cut the 7 inch concrete¢~ing on the structural rib llow spa6 -installation of new drain pipes. Both theset ions would facilitate morn. ing and acc~eto the system should repairs be necessary.

~lition to drainage systemtn lir, the voids created by the subsurface erosion/piping shouldThese voids were a einty caused by groundwater flow through the broken drain',agstem pipes. Becai1he extent of the voids cannot be defined beyond the perimeter of the T Ii .Buiding, the 7,.me of the material required to fill the voids should be m s e ie ay fthe extent of the voids.measured'.

'g.,de aQW.N.The repair/r pl the drainage system and filling of the voids to return the foundation soils and subgrad V,:pre-pipe break condition will allow us to rule out CPFMs 3a, 3b, and 3c for the Structures listed in Section 4.1.3. To fill the voids and determine the volume of the voids a grouting program should be The grouting program design should include:* Specifications for a grout mix that has the proper rheologic and chemical properties to ensure a balanced, stable mix that will maximize penetration and long-term performance.

• Specifications for a grout mix that can displace very soft disturbed zones and that can provide long term support for the piles, footing, and slabs.

Page 7-7 Summary and Cbnrdlusions Rev. 2* Identification of the grout pressure(s) necessary to provide for maximum grout penetration into voids, and soft zones within the subgrade soil material.* Identification of the maximum grouting pressure allowable to avoid damage to any structures and utilities.

Particular attention should be given to the under-slab drain pipes in the event that they are repaired and re-used.* A plan for real-time, full-time, monitoring and recording of:.-Grout volufmies and pressures under the direction of a qualified engineer at the time of the grouting.-Any movement of key Structures during grouting cDrati oft me ;rn B asem- -'n n after the-Groundwater elevations outside of the Turbine B Bae" %ring anda grouting operation.

hK ,0" A sequence/logic tree for grout program progressio

.... ..,.* A plan for the drilling of verification holes to includep (;aI ty tests to as ess the affect of the grouting program on the subgrade soils. AV '* A grouting acceptance protocol by the Engineer.

-* A system to report all of the grouting and monitoring data on a fdbasis to the er." A final report including all data, results and .d e dveIop e grouting-es tOt grout tak contractor.

This should include data on g o each location, verification holes and results, and moni g and data that w6 pport the conclusion that the subsurface voids h een fille.As mentioned previously, OPPD sId c er ab the , drainage pipes that are in place below the Turbine B* basement slab. A -?gnp ing to grout the voids after the existing drainage pines been 11 likelye crush the pipes Aps e be 11 likly -ageor evencrsthpie and complicate the grouting., to th dr ..l remediation.

This spe9011i5. -f groutinq-" tion is necessa to properly treat the subsurface voids..provide cation and documentation that the program was a suA 9s'l ,We recomme :. electio°%

ecialty grouting contractor experienced in ,i 'erng this type ofSi I re-bid sef ih criteria should be developed and potential lers should be pre-quaii

' ased on t c r , time of the writing oft ort, it--was not certain that a grouting contractor could be K x -at could implement a gam that would yield the data necessary to rule out the rerng:,PFMs described

-Discussions with specialty grouting contractors will be schedlibi-4dsoon as possi? .e future to ascertain if they have the capability to provide the data rule out remaining CPFMs.7.4.2 Paved a 7.4.2.1 Summar of Analysis Forensic investigations w'vere pe-rored wiere observed pavement distress was most -prominent, at locations coincident with shallow underground structures and utilities, and where recent seismic surveys identified low velocity features (locations where potential for degradation related to the Triggering Mechanisms and CPFMs associated with KDI #2 was identified).

Page 7-8 Summary and-Conclusions-Rev. -Excavation and subgrade testing identified no evidence of piping erosion, voids, or subsidence of site fills. Field SCP testing of the exposed subgrade indicated that stiff to very stiff soils were generally encountered in the upper 3 feet below the ground surface or pavement.

Based on the observations 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 monitoring indicates that movement of oqijte subsurface soils or structures has not occurred.Possible Triggering Mechanisms and related CPFMs id'if ied for A1 d the PAA include:* Subsurface Erosion and Piping (due to pumping).

CPF and 3c.* Subsurface Erosion and Piping (due to rapid river draAb ýFMs 3d, 3e, -fqZ,.Based on the observations and test results, the individual distress in that comprise KDI#2 are not attributed to the possible Triggering N WJidentified 42: Subsurface Erosion and Piping (due to pumping);

and, S,7uface E andPipi V to rapid river drawdown).

FAN Our investigation for KDI #2 also indicate t the T-..ggring P imof Subsurface Erosion and Piping (due to rapid rFdraw n) wa ot initia fI 2011 flood and that the CPFMs related to this Triggtgegmg echanismAhxEuding CP 3d, 3e, and 3f, are not credible.

ý01i However, Mec.....nof Subsurfac sn a Piping (due to pumping) and ts74rigger calenasm, incuing CPFM 'a, 3b, and 3c cannot be rule --'." associatea lthe PAA. Even though this Triggering Mechanism d6" t appear to have, C, 'd the distr bserved in the PAA, their root cause (damaged r. me uilding sub-flo pipes and p i as identified by investigations in.1~e Turbine Building ontinues.

timber of other Priority I and Priority 2 have been assigned ",Ms that are related to this remaining credible Triggering T nism and its related CPt, These other structures differ from KDI #2 and the PAA in t trong evidence of dist as beidentified or documented through assessment obse~f~.~ins or ongoing sur ;onitoring.

Priority VSfructures in h egory include: " Security BB* Turbine Building' South Switchyard" Condensate Storage Tank* Underground (TRENWA) Cable Trench" Circulation Water System* Demineralized Water System (line)* Raw Water Piping* Fire Protection System Piping* Waste Disposal Piping* Fuel Oil Storage Tanks and Piping Page 7-9 Rev. 2 Su'mmary and Conclusions 0 S 0 Main Underground Cable Bank, Auxiliary Building to Intake Structure Blair Water System River Bank Priority 2 Structures in this category include: " Service Building" Sanitary Sewer System The potential for impact to the above Priority I and Prioj Mechanism of Subsurface Erosion and Piping (due to to this Triggering Mechanism remain credible until theT4 presented below are implemented and completed.

Conti'structures will be required after these recommendations evaluate if the recommended actions were effective and deemed credible.HDR concluded that the Subsurface Erosion/Pip giT k most-likely did not extend outside the perim_,_, the power block. This conclusion suports- ou to pumping) CPFMs associated with this

• Security Building -" Intake Structure A 1135"ON* River Bank the Triggering CPFMs related Z4d to KDI #I as 7.4.2.2 Thi o~ f thsK~N. orensic i$gatlon have ruled out potential Triggering harisms andi assoclHPF ls thnatfirld have been the cause of the observed distress.vever, it could not be'.A-i entirely reDtIht CPFMs associated with KDI #1, which is ciated with the uncontrol rainage of"le groundwater into the broken Turbine Buildin ement drainage system pipmW4 2:These CPFMs will only be ruled out when the physical Rl!cations presented for K4 , as presented in Section 4.1 of this Assessment Report, are 7.4.3 Mai 7.4.3.1 Ilysis Forensic investig~fi consisting of concrete floor slab drilling and field and laboratory subgrade testing was completed in the Maintenance Shop to evaluate subsurface conditions near Key:IDistress Indicator.-(KDI)

1. 3. This Key Distrtss Indicator consists.

of--.di.'fferentil;,.....

settlement of Building Column MG-I15, presumed differential settlement of the nearby floor slab, and cracked nearby masonry partition walls. These building distresses were observed at the southwest comer of the building immediately adjacent to the north side of the Turbine Building during facility assessments.

Page 7-10 Summary and Conclusions Rev. 2 Possible TriggeringMechanisms identified for KDI #3 include: " Subsurface Erosion and Piping (due to pumping);

and" Soil Collapse (due to first time wetting).Observations of the conditions underlying the floor slab in the vicinity of Column MG-15 confirm that the subgrade has subsided and a void space has.developed.

The void space ranges from about none to 8.5 inches in depth below the bottom of the floslab and extends about 15 feet to the north, east and west-northwest of Column MG-1l. Th I..,1 nt of void beneath the floor slab to the south, southeast and a not ed by this investigation.

Field testing including SCP and DCP tests on the subgr 06 '0W the did not identify the presence of voids or soft soils below the top of ddrae at tested i 0i nbs. Field observations and laboratory testing from this investigatiowma

._e, -.the previous RB I investigation are in general agreement and indicate that tne-igen ame`Joess derive~dlt fiJtihe vicinity of Column MG-15 consists of medium stiff totiff, low plIst I.silt that has allowable bearing pressure of 2,000 psf or gr te.fiel d obseb norfield and laboratory testing performed, for this investigt 1ihaepor fl plac 6 1 pr conditions that would result in subgrade or column se,i,7. entof the ag'[$ .ude observe.Based on these observations and field and ratory s ubsdence and resultant void identified below the floor slab, nd ...tor.resu l re ..t. relate Settement vol ~And thdimn" urensettemen cracking expressed in nearby mqa'srfalls is nt to- eTriggering Mechanism of Soil Collapse (due to first time., l ng). As such .CPFMs 0 ciated with this Triggering Mechanism; 7a -Cracked S- I. erential SettleW fh SheIAUk Foundation, and Loss of Structural S 7.b -Displa r ucture/Broken8-n ns; and 7c -General Site the M nance Shop.1 in to the dis mal Mainteian

.Shop, cracks have recently been observed and Uk'imented in the TecnmS1 pr areas located south, southwest, and west of Maintenance Shop distre' a (area ofsNgrade void, settled column, and wall cracking).

V10 e results of the assessment'rlhe Technical Support Center (see Section 5.5) indicate that istress s associated with'Y #3. Therefore, the Triggering Mechanism ofSoil Collapse ahifl Mlssociated CPFMs listef.labove are also ruled out for the Technical Support Center.The re KDI #3 forenbsic investigation show that the Triggering Mechanism of"ubsurfaalli..n'ng (due to pumping) is likely responsible for the subsidence and related voi d ..tt1 distress in the Maintenance Shop and the distress (cracked walls) in the Technical]

tr.nter. Voids, material loss, and material movements have been identified by vef tions in the Turbine Building Basement (KDI #1) including along the north wall of the Turbine Building which is a shared/adjoining wall with theMaintenance Shop. Theievoids/subgrade settlement and distress oliserved.inthe.MaintenanceShop are.believed to be directly related to deep subsurface piping erosion and soil losses occurring at and radiating out from damaged subfloor drain pipes in the Turbine Building subgrade.Based on the KDI #1 investigation, it appears that material has been removed below the Turbine Building north wall through piping as a result of the hydraulic gradient created by the breaks in the subfloor drain pipes. Piping has been evidenced by depressed groundwater levels, measured voids below the Turbine Building basement floor slab, and sediment accumulated in Summary and Conclusions.Page 7-11 Rev. 2 the Turbine Building sump pit. The depressed groundwater-levels and void conditions are more prominent near the northwest portion of the Turbine Building adjacent to the observed KDI #3 structural distresses.

We presume that the piping and void conditions extend north beyond the extents of the Turbine Building basement floor slab and below portions of the Maintenance Shop (and Technical Support Center). The soil column above the presumed piping and void condition is thought to be subsiding as a block unit, or column and translating to the ground surface resulting in-the void space observed below the floor slab. It should be noted that our investigation was not exhaustive.

Subgrade void sp*g was not delineated to the south, southeast, or southwest (see Figure 4-1 1), which are.;t ard&h cJpns of observed/measured groundwater flow, groundwater lows;.aný oidsi6ljo~lfe Turbine Building basement.

It should also be noted that wall cracriig expreseAg-

.,$1ie Maintenance Shop masonry walls of the Men's restroom appears to bE -.'andmgferaclC, pEhure appears larger than previously noted during structure observation -ih 7.4.3.2 Recommendations V, IL Z v, The results of the KDI #3 forensic investigations havefound that thl'the Maintenance Shop (failed column) and the 1ec TTl Support (cra associated with the Triggering Mechanism 7.Sol CoSllapse (ue to fi Therefore the CPFMs associated with this ]7.jggermg Mechanm (7a forensic investigation.

The results show thAi4he distres a -ofltf:e Technical Support Center are connected #1, w, liieis ass~bi drainage of the groundwater into th okek rIurbn6nBiiddng b piping. KDI #1 is associated Id-hanism of.-1lbs (due to pumping) and the CRVC hlicable to the ntenan, -' op Center is 3a -Undermining "a1n7.'.e-,ement of shall". slab CPFM wilLon .b.,,ruled out wlh.hfile physical modi1ic .fios present prese#f [ ' S ,U this Asqse ent Report, are implemented.

.3tr..ess observed in both dwalls) are not rst -7c) out by this 4aintenance Shop and the'dwith the uncontrolled t'drainage system urface Erosion/Piping and Technical Support (due to pumping).

This ed for KDI # 1, as L.11s110ecommended that iei ,,..]mplemeiyMsical modifications to remediate the distress in the Mvfiitenance Shop as plann dhelical eia g). This may or may not affect adjacent tmasonry walls exhibiting sefilhment crackin'g-However, this does nothing to mitigate the Ikey cause of the observed ]t,&tenance Shop distresses, Subsurface Erosion and Piping. Nor-d.W'.r ensure that further distres will not be realized in other structural components of the buiiidlAimin nearby areas that mi4railso be affected by Subsurface Erosion and Piping but not yet expressfhngany observable distfess.

Future distress could include other building support columns7UA'djacent elevatorishaft, and other nearby masonry walls (load bearing or not). It should be noter6,that ourna`vefilggation did not determine the extent of settlement or voids to the south, rsouth.est of settled Column MG-15.No further investigations are recommended for the purposes of this Assessment Report.However, further investigations could be undertaken by the owner as part of the design for the remedial work to repaifiihe Maiiitenaince Shibp -and Supj5&rtCe etei'-distress.

This could include investigation of the subgrade below the floor slab in the Maintenance Shop to the south, southeast, and southwest of Column MG-1 5 to include drilling, coring, SCP and DCP tests, soil sampling, and laboratory testing as appropriate to delineate the area of subsiding subgrade and identify other structural building elements at risk. It is further recommended that the physical modifications outlined in the KDI #1 forensic investigations be competed before the physical modifications to remediate the distress in the Maintenance Shop and Technical Support Center are implemented.

This is to ensure that the subsurface erosion/piping Page 7-12 Summary and Conclusions Rev. 2 associated with the broken pipes under the Turbine Building basement slab is halted.Continued subsurface erosion/piping would most likely reduce the efficacy of any physical modifications designed to remediate the distress in the Maintenance Shop and the Technical Support Center.7.5 Status of Priority 1 Structural Assessments In the assessment of the FCS Structures, the first step was to develop a lisftf all Triggering Mechanisms and PFMs that could have occurred due to the prolonged inufiAfpn offthe FCS site during the 2011 Mivissouri River flood and couid have negativelyimp~ated uaes The next step was to use data from various investigations, including systematic observs iOf the structures over time. either to eliminate the Triggering Mechanisms and froms -6st further investigation and/or physical modifications to remove them list for-any.particular structure.

The results of the Assessment are detailed for each o therit I Structures inthe paragraphs below.7.5.1 Intake Structure Because all CPFMs for the Intake Structure other thaniCPFs.

1."t2aa..2aad 12b hadbeIenruled out prior to Revision 1,.and because CPFMs 12a and 12b havebe6n' ruled ouAsýisresult ofthe Rision I findings, no Triggering Mechanisms and their associated PEMs:remain cr iBflh.:.Itrlhe Intake Sfructure.

Therefore, I-DR has concluded that the 2011 Missah River flobd did n-U@@npact the geotechnical and structural integrity of the Intake Structurebgauseqih&"otentriailfor failu ldki 'structure due to the flood Is not significant.

"..7.5.2 Auxiliary BuildingF Because all CPA 7.gg uxiliary B ing. other than CPFX,4M3b' had been ruled out prior to Revision adb,60-Mu'eU -b. will bel -i: diout when the physical modifications recommended for KDI #1 i Secft6ion 4.1 are impleem"nted, no Trig-geing Mechanisms and their associated PFMs will remain;r.d.ble for the Auxiliary-,Bulding.

HIDRijasd§cioncluded that the geotechnical and structural impd f the 2011 Missouri River' f..od will be tlaed by the implementation of the physical m:bMod lions recommended in this Assessment Report. Therefore.

after the implementation of the recomNiq`,4qO physical modifications'Ahe potential for failure of this structure due-to--the flood will not be signitfi anft 7.5.3 ContaildIff~i-jht Because all C C ri.ment other than CPFM 3b had been ruled out prior to Revision 1, and because CPFM t T out when the physical modifications recommended for KDI #1 in Section 4.1 are im pleme o 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.

7.5.4 Rad Waste Building Because all CPFMs for the Rad Waste Building other than CPFMs 7b and 7d had been ruled out prior to Revision 1. and because CPFMs 7b and 7d have been ruled out as a result of the Revision I Page 7-13 Summary and Conclusions

-Rev. 2 findings, no Triggering Mechanisms and their associated PFMs remain credible for the Rad Waste Building.

Therefore, HDR has concluded that the 2011 Missouri River flood did not impact the geotechnical and structural integrity of the Rad Waste Building because the potential for failure of this structure due to the flood is not significant.

7.5.5 Technical Support Center Because all CPFMs for the Technical Support Center other than CPFMs 6c, 7a, 7b, and 7c had been ruled out prior to Revision 1, because CPFMs 6b, 6c. 7a, 7b and 7cidheenrtuled out as a result of the Revision i findings, and because CPFM 3a wiil be ruled'" oQt.f en tnepys-a...

modifeations recommended for KD1s #1 and #3 in Section 4.1 and 4.3 are ill Dented, noTriggering Mechansms and their associated PFMs remain credible for the Technical Siffift Center ¶DRNhas concluded that MA oll be that the geotechnical and structural impacts of the 2011 Missouri Ri ' be mifij...by the implementation of the physical modifications recommended in t.i ..ent Report -JN1refore,..

after the implementation of the recommended physical modificati6n,', ;k.6ptential for fa?1..e:,4s--

structure due to the flood will not be significant.

7.5.6 Independent Spent Fuel Storage Installation Because all CPFMs for the ISFSI have been ruled otU.nb Trigge fg-t echanisms and eir associated PFMs remain credible for the JSFSI. Therefore, HIR has cone]Ithe I Missouri River flood did not impact the geotechnical and structurahntegnty' ofhe ISlSbeai se the potential for failure of this structure due to the flood istos ioniPn t .7.5.7 Security Building .Because all CPFMs for the Security -BANdi h other than CPF 3O, 12a, and 12b had been ruled out prior to Revisii6iýaor fid because CPFMs3a 3d, 12a and e21iiave been ruled out as a result of the Revision I fi.dis.notngggerng Mechanism's 4and their associated PFMs remain credible for the Security BIiMrng* Thereforei{NThRN.as conclUded..that the 2011 Missouri River flood did not impact the geofptnica1 and structural lntfery of the SeouiityBulding because the potential for failure of.thi~: s7',ture due to the flood is nolSl:g cant.7.5.8 Tub ine Building Because a1UG].-FMs for.the Turbine B. uiiing other than CPFM 3b had been ruled out prior to Revision 1, and becauseGPM 3b has been r lg'd;6ut by the additional forensics investigations for KDJ #1 (see Section 4. 1), novft'gring Mechaffms and their associated PFMs will remain credible for the Turbine Building.

HIDRLhas cdinclded that the geotechnical and structural impacts of the 2011 Missouri River flood by the implementation of the physical modifications recommended in this Ass i 'nt 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.

7.5.9 Security Barricaded Ballistic Resistant Enclosures Because all CPFMs for the Security BBREs other than CPFMs 3a and 3d had been ruled out prior to Revision 1, and because CPFMs 3a and 3d will be ruled out when the physical modifications recommended for KDI #1 in Section 4.1 are implemented, no Triggering Mechanisms and their associated PFMs will remain credible for the Security BBREs. HDR has concluded that the geotechnical and structural impacts of the 201 1 Missouri River flood will be mitigated by the Page 7-14 Summary and Conclusions

-Rev. 2 implementation of the physical modifications recommended in this Assessment Report. Therefore, after the implementation of therecommended physical modifications, the potential for failure of this structure due to the flood will not be significant.

7.5.10 Turbine Building South Switchyard Because all CPFMs for the Turbine Building South Switchyard other than CPFMs.3a, 3b, and 3c had been ruled out prior to Revision 1, because CPFM 3a will be ruled out upon completion of the remediation to the switch foundation slab described in Section 5.10,%and b."Eause CPFMs 3b and 3c will be ruled out when the physical modifications recommended Ao Di I ection 4. no Triggering Mechanisms and their associated PFMs will remainwredible for theiTurbine Building South Switchyard.

HDR has concluded that the geotechnical and strucal impactsof the6 201 I Missouri River flood will be mitigated by the implementation of the physib o dffications rdeoimmended in this Assessment Report. Therefore.

after the implementation of the re& .ii-ended physicalro.ifications, the potential for failure of this structure due to the flood will not be.ifilat.

-7.5.11 Condensate Storage Tank Because all CPFMs for the Condensate Storage Tank othan I., s 2b, 3c 3e and 3f had been ruled out prior to Revision I, because CPFMs 2b. _&.arid 3f have-,`en5 led out asý aresult of the Revision I findings, and because CPFM 3c will bemiii'ed out whe}h:piscal modifications recommended for KDI #1 in Section 4.1 are implemdnted, n oTriggeringfZlhan isms and their associated PFMs will remain credible for thdeCondrt ate Sfto~oK Tank concluded that the geotechnical and structural impacts of Missouri }j['er flood wiiUbe mitigated by the:;,j implementation of the physical modifricirids recommen dým this Asse sment Report. Therefore, after the implementation of the rec.i.ftiinded physical potential for failure of this s gtructure due to the flood.will not be Sig-'mIcant.

7.5.12 U n desgtou ch... *'PF' fo the 4 Becaus&allCPFMs forthe Under#.6erid Cable Trenth (Trenwa) other than CPFMs 3a. 3c, 3d, 3f, and l4a¢1YaZgbeen ruled out prior to RevIsiRn1J because- Q,@FMs 3d, 3f, and 14a have been ruled out as a reMi0,Y-the Revision I findinas, andcfl2cause CPFMs 3a and 3c have been ruled out using the results of thF4KDf`#2 investigation presentedinfSection 4.2, no Triggering Mechanisms and their associated PFMs remiain"redible for the Undergroui Cable Trench. Therefore, HDR has concluded that the 2011 ,er flood did not imqtý the geotechnical and structural integrity of the Underground Cable Trench because the potentialforfIilure of this structure due to the flood is not significant.

7.5.13 Circulating -ater- Syste'n.Because all CPFMs for tFh'dirculating Water System other than CPFM 3b had been ruled out prior to Revision 1, and because CPFM 3b will be ruled out when the physical modifications recommended for*_-KDI#.I in..Section 4.4. are implemented noTriggering-Mechanisms and .their.assbciated.tFMs~wi.ll remain credible for the Circulating Water System. T-DR 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.

Page 7-15 Summary and Conclusions

-.ReV.' 2 7.5.14 Demineralized Water Tank, Pump House, and RO Unit Because all CPFMs for the Demineralized Water Tank, Pump House, and RO Unit other than CPFMs 3a and 14a had been ruled out prior to Revision 1, and because.CPFMs 3a and 14a have been ruled out as a result of the Revision 1 findings, no Triggering Mechanisms and. their associated PFMs will remain credible for the Demineralized Water Tank, Pump House, and RO Unit. Therefore, HDR has._ concluded that the 2011 Missouri River flood~did~not impact the geotechnical and structural integrity 0 ; of the Demineralized Water Tank, Pump House, and RO Unit because the<ý.tential for failure of this structure due to the flood is not significant.

7.5.15 Raw Water Piping...Because all CPFMs for the Raw Water Piping System other thaini-CPEM' 3 3c 3d`iid 3f had been ruled out prior to Revision 1, because CPFMs 3d and 3f were ruled'out using the result-s fthe KDI #2 investigation presented in Section 4.2. and because CPFT\ls 'a and3c i. be ruled out wheiie..physical modifications recommended for KDI # 1 in Section 4.1 arierimp"lemeted, no Trigg-enn

Mechanisms and their associated PFMs will remain credible for the Raw Va -P#,ping System7.-HDR has concluded that the geotechnical and structural impactgbf the 2011 MissounaRIver flood will be mitigated by the implementation of the physical modif"l 6nmended in th ."ssesssment Report. Therefore, after the implementation of thes8ecommendedpPysical modificat;ijO the potential for failure of this structure due to the flood will-notd s >ig can , '-, 7.5.16 Fire Protection System Piping* .( ..., , 2 i ,' : Because all CPFMs for the Fire Protecti-System Pipinmwfter than C0EM's 3a, 3c, 3d. 3f, 12a. and 12b had been ruled out prior to Revdsiqul4,-

d because CPFMNffi2a andil12-.b have been ruled out as a result of the Revision 1 findings, becausG6PFMs 3d and 3f -; ee out using the results of the KDI#2 investigation,,-p

?$---s~'ý,tý--XiýSection 4 211 and~because CP~-3ana;d 3c will be ruled out when the be~~niillgated by the implementationi 4 fie recommended in this Assessment be~~ ~~ 21," * :.5ý-I.ý -.

.1 .-...27...herefore, after the impleme- ttion of the recommended physical modifications, the potential for fail se-$,d this structure due to tMse flgbd will not be significant.

.. p Piping*Because all ftor, the waste-Dip oal Piping other than CPFMs 3a, 3c, 3d, and 3fRhad been ruled out prior to Revisi05iThbecause GP.FMs 3d and 3f were ruled out using the results of the KDI #2*

presentedti Sectioni 4.2, and because CPFMs 3a and 3c will be ruled out when the physical modifications recomm"iended for KDI # 1 in Section 4.1 are implemented, no Triggering Mechanisms and their associated PFMs will remain credible for the Waste Disposal Piping. HDR has.:..concluded that the geotechnical and strutctural impacts of the 2011 Missouri.Riversfiood .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.

/P 7..7W/" ~ ~ sosIPpn//t J7./lPpn te hnCFs3, c d n fhdbe ue Page 7-16 Summary and Conclusions RevI 2 7.5.18 Fuel Oil Storage Tanks and Piping Because all CPFMs for the Fuel Oil Storage Tanks and Piping other than CPFMs 3b, 3c, 3e, and 3f have been ruled out prior to Revision 1, because CPFM 3c has been ruled out assuming the implementation of the recommended physical modifications presented in Section 5.18, and because CPFMs 3b, 3e, and 3f will be ruled out when the physical modifications recommended for KDIs #1 and#3 in Sections 4.1 and 4.3 are implemented, no Triggering Mechanisms and their associated PFMs will remain credible for the Fuel Oil Storage Tanks and Piping. HDR has concluded that the geotechnical and structural impacts of the 2011 Missouri River flood will be mitigate&db:ý2,e implementation of the physical modifications recommended in this Assessment R epoa1--1eiretiaer,,ne impiementation of the recommended physical modifications, the potential for fMTA of this siirf e.,due to-the flood will not be significant.

7.5.19 Main Underground Cable Bank, Auxiliary Building to n takerStructure,.

Because all CPFMs for the Main Underground Cable Bank from the Auxiliary Building to Structure other than CPFMs 3a, 3c, 3d, 3f. 4c, 4d, 4e, 6b, 6c, 12a. and 12bhadbeen ruled out prior to Revision 1, because CPFMs 4c, 4d, 4e, 6b, 6c, 122a. andJo-I2W1taRV~e been ruled ouis~a result of the Revision 1 findings, because CPFMs 3d and 3f wereIdiitt-y.-t-tejesults of th :-DI #2 investigations, and because CPFMs 3a and 3c will bie$iuiled out when the Physical m'odifications recommended for KDI #1 in Section 4.1 are implein'tited, no Ti' :g-ige echanisms and their associated PFMs will remain credible for the Maifik...Ldergro-uid Cablý!kB, from the Auxiliary Building to the Intake Structure.

IDR has irgeotechnical afid structural impacts of the 2011 Missouri River flood will be m.'fte'd by the im~pIeentation oihe physical modifications recommended in this Assessment afte'ie implementation of the recommended physical modifications, the potentihl'f~

u of th i s str ciuetOe flood will not be significant.

....... _4 7.5.20 Meteqoro',oVi k rand Mi-6laineous Structures Because adll-CPFMs for the Mb p1o~gical T6oer.6ther than CPFM 7c had been ruled out prior to Revision;ij,ýi:and because CPFM 7, li.been ruled ij@kas a result of the Revision 1 findings, no TIrg'permgo Mechanisms and their aEcahted PFMs reffain credible for the Meteorological Tower.Th'fref ,IHDR has concluded that tlE2.01 I Missouri River flood did not impact the geotechnical and structbi tegrity of the Meteorologib1 Tower because the potential for failure of this structure due to the flood -i nificant.

S.7.5.2 1 Orii am Generator ge Building*. .g9. ._-.' ..... .There were no sdentified for the OSGS. Therefore, HDR has concluded that the 2011 Missouri River nonC~ddada-ot impact the geotechnical and structural integrity of the OSGS because the potential foCr ire of this structure due to the flood is not significant.

-7.5.22 Switchyard

,.Because all CPFMs for the Switchyard other than CPFMs 3a, 3b, and 3c had been ruled out prior to Revision 1. and because CPFMs 3a, 3b, and 3c have been ruled out as a result of the Revision I findings, no Triggering Mechanisms and their associated PFMs remain credible for the Switchyard.

Therefore, HDRfhas concluded that the 2011 Missouri River flood did not impact the geotechnical and structural integrity, of the Switchyard because the potential for failure of this structure due to the flood is not significant.

Page 7-17 Summary and Conclusions Rev: 2 7.5.23 Transmission Towers Because all CPFMs for the Transmission Towers other than CPFM 7c had been ruled out prior to Revision 1, and because CPFM 7c has been ruled out as a result of the Revision I findings, no Triggering Mechanisms and their associated PFMs remain credible for the Transmission Towers..i"Therefore, HDR has concluded that the 2011 Missouri River flood did not impact the geotechnical and structural integrity of the Transmission Towers because the potential for failure of this structure due to t,'he flood is not significant.

7.5.24 Main Underground Cable Bank, MH-i to Auxiiiary , Because all CPFMs for the Main Underground Cable Bank fromw- -1 to~t1iu Buiding other than CPFMs 3a and 3c have been ruled out, and because CPFM:"nd 'Z ill be when the physical modifications recommended for KDI #1 in Section 4.] af'"x.p"t kmented, no Tiggering Mechanisms and their associated PFMs will remain credible for t nderground Cb21&,Bank]i->i from MH-I- to the Auxiliary Building.

HDR has concluded that t-ageoi al. and structA of the 2011 Missouri River flood will be mitigated by the implementation 4¶ie physical modif"dations recommended in this Assessment Report. Therefore, ib ementation of£the recommended physical modifications, the potential for failure of this -' 1 the flood " it be significant.

/. : 7.5.25 River Bank ISO, Because all CPFMs for the River Bank othevahan'PFMs 30.!37d, 12a, a M5i~hd been ruled out prior to Revision I and because CPFMs 3a, 3td-l021a1'and 12b hameybeen ruled tA< 0a result of the Revision 1 findings, no Triggering Mechanisms an._'heir associatdc' s rem -redible for the River Bank.Therefore, HDR has concluded that.th' I Missouri Ri, food.dI~ot impact the geotech1ca1 and structural integrity bfthe River Bank%:e ause the potential fi' fairof this structure due to the flood is not si~~4 7. 5.26 BlajW:ater Systemrn , Becauise&'f CPFMs for the Blair othi4tfn CPFMs 3a. 3c, 7a, 7b, and 7c have been CPFMs 7a, 7b, ',Will be ruled out as a result of the Revision I findings and the impliemenianlhtion of the physical modificot'ns-recommended in Section 5.26. and because CPFMs ')a and 3 c il0gribuled out when the physitl Imodifications recommended for KDIs #1 and #3' in Section 4.1& and 4.4-ame.-nplemented no Trg.eiig Mechanisms and their associated PFMs will remain credible for theaiia.Water System H:DR has concluded that the geotechnical and structural impacts of the 2011 MisseuriRiver mitigated by the implementation of the physical modifications recommended in Therefore, after the implementation of the recommended physical modifications,"thpotential for failure of this structure due to the flood will not be significant.

7.5.27 Demineralized Water System Because all CPFMs for'the Deemineralized Water System other than CPFM 3c had been ruled out prior to Revision 1, and because CPFM 3c will be ruled out when the physical modifications recommended for KDIs #1 and #3 in Section 4.1 and 4.3 are implemented, no Triggering Mechanisms and their associated PFMs will remain credible for the Demineralized Water System. 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, Page 7-18 Summary and Conclusions Rev. 2 after the implementation of the recommended physical modifications, the potential for failure of this structure due to the flood will not be significant.

7.5.28 Camera Towers and High Mast Lighting Because all CPFMs for the Camera Towers and High Mast Lighting other than CPFMs 3a. 3d, 12a, and 12b had been ruled. out prior to Revision 1, and because CPFMs 3a, 3d, 12a, and 12b hav'e.been:

ruled out as a result of the Revision I findings, no Triggering Mechanismsand their associated PFMs remain credible for the Camera Towers and High Mast Lighting.

Theref6fjV concluded that the 20 11 Missouri River flood did not impact the geotechnicai ana.structur a tegry of the Camera Towers and High Mast Lighting because the potential for failure6ofthis strucliine&due to the flood is not significant."......................

..-...%..4.. .: ).'.......

7.6 Status of Priority 2 Structure Assessments " " , In the assessment of the FCS Structures.

the first step was to develop6 a lisoýfria]

TggerinýA' Mechanisms and PFMs that could have occurred due to the prolonged inundattn..of the FCS site j during the 2011 Missouri River flood and could have the'.- ctures. The next step was to use data from various investigations, observatioffthe structures over time, either to eliminate the Triggering Mechasisi" and PF~g.fom the list or11.Iircommend further investigation and/or physical them6iiomthe list for ani particular structure.

The results of the Assessment are detaile&tfor Pritg'-y,.Structures in the paragraphs below. -,.7.6.1 New Warehouse

-, Because all CPFMs for the New Wai'e'h-bGsehave been po Tiggering Mechanisms and their associated PFM.sz for ' w. ....,Warehouse.

Thýeif6ire, HDR has concluded that the 2011 MissourTi rg&ff4'g V 6d64 ne iompact flRig oltechnical and structural integrity of the New Ware k because the poteitial for faihiieof this structure due to the flood is not significant.

7.6..2S. Svice Building Becatigeu.1.&tlCPFMs._for the Service Bufdiag other than CPFM 3b had been ruled out prior to Revision 2. an d 3b will be ruledMutwhen the physical modifications recommended for KDI #1 in Section "ý.Idr.pimplemented.

no Triggring Mechanisms and their associated PFMs will remain credible for th&eiva'.ice Building.

1-RW has concluded that the geotechnical and structural impacts of the 2011 Missouai i-Riier flood will, ,be .mitigated by the implementation of the physical modifications recommended in tt As-essment

!Report. Therefore, after the implementation of the recommended physical modifications`e-p'Otential for failure of this structure due to the flood will not be significant.

7.6.3 Chemistry/Radiation Protection Building Because all CPFMs f6r the CARP Building have been ruled out, no Triggering Mechanisms and their associated PFMs remain credible for the CARP Building.

Therefore, HDR has concluded that the 201 1 Missouri River flood did not impact the geotechnical and structural integrity of the CARP Building because the potential for failure of this structure due to the flood is not significant.

Page 7-19 Summary and Conclusions R Rev. 2 7.6.4 Maintenance Shop Because all CPFMs for the Maintenance Shop other than CPFM 3a have been ruled out, and because CPFM 3a will be ruled out when the physical modifications recommended for KDIs #1 and #3 in Section 4.1 and 4.3 are implemented, no Triggering Mechanisms and their associated PFMs will remain credible for the Maintenance Shop. HDR has concluded that the geotechnical and structural impacts of the 2011 Missouri River flood will be mitigated by theimplementation of the physical modifications recommended in this Assessment Report. Therefore, after fte. implementation of the recommended physical modifications, the potential for failure of thjisstruX flood will not be significant.

,.N .., 4.7.6.5 Maintenance Fabrication Shop Because all CPFMs for the Maintenance Fabrication Shop have bde4,3-i '1d out. no Trigg g Mechanisms and their associated PFMs remain credible for the M-h"gig ce

, Therefore, HDR has concluded that the 2011 Missouri River flood".id no'tixipact the geote- iand structural integrity of the Maintenance Fabrication Shop because the poteAfor-ailure of thi.structure due to the flood is not significant.

7.6.6 PA Paving, PA Sidewalks, and ,*Because all CPFMs for the PA Paving, PA Sidewa.ks and u1:r Dties ,other than CPFMs 2a, 3a, 7a, 7b, and 7c have been ruled out, and because CE 2.s 3a .ru le "dhi the physical modifications recommended for KDI #1i: cton i,. $ arei;nplemented

aId because CPFMs 2a, 7a.7b, and 7c will be ruled out when OPPD petesther itn work, no Triggering

&'fipee ter menrsrainwoknoTigig Mechanisms and their associated PEsRMW lI remain credieffori t eVAOIPaving, PA Sidewalks, and Outdoor Drives. HDR has concluded e geotechnicai-fad icral impacts of the 2011 Mssour River flood will , týhe , imp I§htation of the physi-al modifications recommended in this rpr o Nf q recommended physical modifications the potential for failu r .his structure d ueMph ~lood w41-06b significant.

7. Potable Water Piping .

for the Potable W.Vbi-Piping other than CPFM 7c have been ruled out. and because 4,7c will be ruled out as-a'eRpult of placing engineered fill in locations where soil subsidenceý,,.. (detailed 6.7), no Triggering Mechanisms and their associated PFMs will reminarnedible for the -t4abe Water Piping. Therefore, HDR has concluded that the 2011 Missouri River flb'beNdid not im-ad e geotechnical and structural integrity of the Potable Water Piping because the p~titial f of this structure due to the flood is not significant.

7.6.8 Sanitary Sewei-.Because-all.

CPFMs for the Sanitary Sewer Systemother than CPFMs 3a and 3c have been ruled. out, and because CPFNTs 3a and 3c will be ruled out when the physical modificatiinsrecomrmendedTor KDI #1 in Section 4.1, and the physical modifications to MH-t I(detailed in Section 6.8)are implemented, no Triggering Mechanisms and their associated PFMs will remain credible for the Sanitary Sewer System. HDR has concluded that the geotechnical and structural impacts of the 20 11 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.

Page 7-20 Summary and Conclusions Rev. 2 7.6.9 Maintenance Storage Building Because all CPFMs for the Maintenance Storage Building have been ruled out, no Triggering Mechanisms and their associated PFMs remain credible for the Maintenance Storage Building.Therefore, HDR has concluded that the 2011 Missouri.

River flood did not impact the geotechnical and structural integrity of the Maintenance Storage Building because the potential for failure of this structure due to the flood is not significant.

7.6.10 Old Warehouse Because all CPFMs for the Old Warehouse have been ruled out -oTriggerig Mnhanisms and their associated PFMs remain credible for the Old Warehouse.

Theiefqr e, that the 2011 Missouri River flood did not impact the geotechnical and sructw. of the OldQf'arehouse because the potential for failure of this structure due to the flood isnt,' significant.

7.6.11 Training Center -> "-Because all CPFMs for the Training Center have been Triggering.Mchanisms and their associated PFMs remain credible for the Traininp Center,:;~Therefore, HDR has that the 2011 Missouri River flood did not impact the geotechiii'al and -suMemI,"h integrity vf1t1iieTraining Center because the potential for failure of this structuke due to thiffho.d' jisot sicnificant 7.6.12 Administration Building 41.,M-7 Because all CPFMs for the Administrati onBuilding have,:been ruled out`Io Triggering Mechanisms and their associated PFMs remain crf.ib1e:for the Administation Buicing. Therefore, HDR has concluded that the 2011 Missouri RiN& flood did not impacd.-te7tgeoteEhinical and structural integrity of the because th&e otential for failu'e r ohis structure due to the flood is not significant.~

7.6.11 H5azardous Material Sior,;g@e .Buildng>KK Bebaise.--all CPFMs for the Hazardoug.,.

'Material Storage Building have been ruled out, no Triggering Me(hNa.tI s and their associated PF~sremain credible for the Hazardous Material Storage Building.Theref i'.ý fR has concluded that th 01Q I Missouri River flood did not impact the geotechnical and structuralmritguty of the Hazardous M -ial Storage Building because the potential for failure of this structure due 7t t ood is not signfiTnt.

7.6.14 Maintenance Garage,-Because all CPFMs for Garage have been ruled out, no Triggering Mechanisms and their associated PFMs remain credible for the Maintenance Garage. Therefore, HDR has concluded that the 2011 Missouri River flood did not impact the geotechnical and structural integrity of the Mainten-iiance Garage b'cadse the potential for failiuire.bf this structure:

due to-the-floodis

'not significant.

7.6.15 Tertiary Building Because all CPFMs for the Tertiary Building (Boat Storage) have been ruled out. no Triggering Mechanisms and their associated PFMs remain credible for the Tertiary Building (Boat Storage).Therefore.

HDR has concluded that the 2011 Missouri River flood did not impact the geotechnical and Page 7-21-Rev. 2 Summary and Conclusions structural integrity of the Tertiary Building (Boat Storage) because the potential for failure of this structure due to the flood is not significant.

7.6.16 Spare Transformer Pads Because all CPFMs for the Spare Transformer Pads have been ruled out, no Triggering Mechanisms.and.their-associated PFMs remain credible for the Spare Transformer Pads. The!refore, HDR has concluded that the 2011 Missouri River flood did not impact the geotechniical and structural integrity of the Spare Transformer Pads because the potential for failure of this strf"!Le duelo the flood is not significant.

, 7.6.17 Shooting Range Because all CPFMs for the Shooting Range other than CPFM 2a hael61ee CPFM 2a will be ruled out when the physical modifications recommien implemented, no Triggering Mechanisms and theirassociated PFMfswTh Shooting Range. HDR has concluded that the geotechnical and structuralf Missouri River flood will be mitigated by the implementat16ii-the physi recommended in this report. Therefore, after the l ihdetn6i%,kb"the re modifications the potential for failure of this structuiue to the fo!w.1:ause 7.6.18 Gravel Parking Lots Because all CPFMs for the Gravel Par]their associated PFMs remain credible that the 2011 Missouri River flooddiN Gravel Parking Lots because the poteii 7.6.19 Sewa.d.e.:.Laaoons,..iffring Mechanisms andýýIore, HDR has concluded ructural integrity of the to the flood is not significant.

BecauseI 'ECPFMs for the Sewaef ýagoons otlhft1an CPFMs 6c, 7b, and 7c have been ruled out, and becatffsCPFMs 6c, 7b, and 7c wiliR$E; rled out wrAdeMe physical modifications recommended in Se&Uio6. 19 are implemented, no Tfiggering Mechanisms and their associated PFMs will remain credAie for.the Sewage Lagoons. 16Di As concluded that the geotechnical and structural impacts of the 20f1" k.isuri River flood will be mitigated by the implementation of the physical modifications recommended in this report. Therefor.eafter the implementation of the recommended physical modifications ,i.hbotential for faiyi.r this structure due to the flood will not be significant.

Iv r SECTION 9.0 AUA CHMENTC 7,'41/4~'.. .. .... .,c 4 A~-~"'i II A,-Th ;-~~.m A A 4I I 4 ,4h '~4' 4~-.A-' '~.4-h S...7: 4'. , -'4: N i Page 9-1 Attachments Rev. 2 9.0 ATTACHMENTS 9.1 Attachment 1 -Deaggregation Plots 9.2 Attachment 2 -Structural Baseline References 9.3 Attachment 3 -FCS Site Inspection Checklists 9.4 Attachment 4 -Triggering Mechanisms and Potential Failure Modes by Structure 9.5 Attachment 5 -Supporting Data for Comparative Evaluation of Geotechnical Analyses 9.6 Attachment 6 -Geotechnical Data from Subconsultants and OPPD 9.7 Attachment 7 -Photo Documentation 9.8 Attachment 8 -Field Reports, Field Notes, and inspection Checklists