ML14238A384

Quad Cities Units 1 & 2, Response to Request for Additional Information Regarding Fukushima Lessons Learned - Flood Hazard Reevaluation Report

ML14238A384
Person / Time
Site:	Quad Cities
Issue date:	07/03/2014
From:	Kaegi G T Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
Shared Package
ML14238A446	List: RS-14-173, Response to Request for Additional Information Regarding Fukushima Lessons Learned - Flood Hazard Reevaluation Report
References
RS-14-173
Download: ML14238A384 (62)

Text

Exelon Generation, Security-Related Information

-Withhold Under 10 CFR 2.39010 CFR 50.54(f)RS-14-173 July 3, 2014U.S. Nuclear Regulatory Commission ATTN: Document Control DeskWashington, DC 20555-0001 Quad Cities Nuclear Power Station, Units 1 and 2Renewed Facility Operating License Nos. DPR-29 and DPR-30NRC Docket Nos. 50-254 and 50-265

Subject:

Response to Request for Additional Information Regarding Fukushima LessonsLearned -Flood Hazard Reevaluation Report

References:

1. Exelon Generation

Company, LLC Letter to USNRC, Response to March 12, 2012Request for Information Enclosure 2, Recommendation 2.1, Flooding, RequiredResponse 2, Flooding Hazard Reevaluation Report, dated March 12, 2013 (RS-13-047)

2. NRC Letter, Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f)

Regarding Recommendations 2.1, 2.3, and 9.3 of the Near-Term Task Force Reviewof Insights from the Fukushima Dai-ichi

Accident, dated March 12, 20123. NRC Letter, Request for Additional Information Regarding Fukushima Lessons Learned-Flood Hazard Reevaluation Report, dated June 25, 2014In Reference 1, Exelon Generation

Company, LLC (EGC) provided the Quad Cities NuclearPower Station, Units 1 and 2, Flooding Hazard Reevaluation Report in response to the March 12,2012 Request for Information Enclosure 2, Recommendation 2.1, Flooding, Required Response2, (Reference 2).The purpose of this letter is to provide the response to the NRC request for additional information (RAI) (Reference

3) regarding the Quad Cities Nuclear Power Station, Units 1 and 2 FloodingHazard Reevaluation Report. Enclosure 1 provides the response to each NRC RAI. Enclosures 2 and 3 provide the electronic information files requested by the respective RAIs.Enclosure 2 to this letter contains Sensitive Unclassified Non-Safeguards Information (SUNSI)and the information should be withheld from public disclosure in accordance with therequirements of 10 CFR 2.390. Enclosure 2 has been marked accordingly with the notation"Security-Related Information

-Withhold Under 10 CFR 2.390."Security-Related Information

-Withhold Under 10 CFR 2.390Enclosure 2 contains Sensitive Unclassified Non-Safeguards Information (SUNSI);

uponseparation this letter is decontrolled.

U.S. Nuclear Regulatory Commission Response to Request for Additional Information (Flooding Hazard Reevaluation Report)July 3, 2014Page 2Security-Related Information

-Withhold Under 10 CFR 2.390This letter contains no new regulatory commitments.

If you have any questions regarding thisreport, please contact Ron Gaston at (630) 657-3359.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on the 3rd dayof July 2014.Respectfully submitted, Glen T. KaegiDirector

-Licensing

& Regulatory AffairsExelon Generation

Company, LLC

Enclosures:

1. Quad Cities Nuclear Power Station, Units 1 and 2 -Response to Request for Additional Information Regarding Fukushima Lessons Learned -Flood Hazard Reevaluation Report2. DVD # 1 of RS-14-173 for RAI Response No. 4 -Regarding Fukushima LessonsLearned-Flood Hazard Reevaluation Report3. DVD # 2A of RS-1 4-173 for RAI Response No. 11, 12, 13, 15, 17, 20, 22, and 23-Regarding Fukushima Lessons Learned-Flood Hazard Reevaluation ReportDVD # 2B of RS-1 4-173 for RAI Response No. 15- Regarding Fukushima LessonsLearned-Flood Hazard Reevaluation ReportDVD # 2C of RS-14-173 for RAI Response No. 15- Regarding Fukushima LessonsLearned-Flood Hazard Reevaluation ReportDVD # 2D of RS-14-173 for RAI Response No. 15- Regarding Fukushima LessonsLearned-Flood Hazard Reevaluation ReportDVD # 2E of RS-14-173 for RAI Response No. 15- Regarding Fukushima LessonsLearned-Flood Hazard Reevaluation ReportDVD # 2F of RS-14-173 for RAI Response No. 15- Regarding Fukushima LessonsLearned-Flood Hazard Reevaluation ReportSecurity-Related Information

-Withhold Under 10 CFR 2.390Enclosure 2 contains Sensitive Unclassified Non-Safeguards Information (SUNSI);

uponseparation this letter is decontrolled.

U.S. Nuclear Regulatory Commission Response to Request for Additional Information (Flooding Hazard Reevaluation Report)July 3, 2014Page 3Security-Related Information

-Withhold Under 10 CFR 2.390cc: Director, Office of Nuclear Reactor Regulation NRC Regional Administrator

-Region IIINRC Senior Resident Inspector

-Quad Cities Nuclear Power Station, Units 1 and 2 (w/oEnclosures 2 and 3)NRC Project Manager, NRR -Quad Cities Nuclear Power Station, Units 1 and 2 (w/oEnclosures 2 and 3)Mr. Robert J. Fretz, Jr, NRRIJLD/PMB, NRC (w/o Enclosures 2 and 3)Mr. Robert L. Dennig, NRRIDSS/SCVB, NRC (w/o Enclosures 2 and 3)Mr. Blake Purrnell, NRR/DORL/LPL3-2 Illinois Emergency Management Agency -Division of Nuclear Safety (w/o Enclosures 2 and3)Security-Related Information

-Withhold Under 10 CFR 2.390Enclosure 2 contains Sensitive Unclassified Non-Safeguards Information (SUNSI);

uponseparation this letter is decontrolled.

U.S. Nuclear Regulatory Commission Response to Request for Additional Information (Flooding Hazard Reevaluation Report)July 3, 2014Page 4Security-Related Information

-Withhold Under 10 CFR 2.390bcc: Site Vice President

-Quad Cities Nuclear Power Station, Units 1 and 2 (w/o Enclosures 2and 3)Vice President Operations Support (w/o Enclosures 2 and 3)Site Engineering Director

-Quad Cities Nuclear Power Station, Units 1 and 2 (w/oEnclosures 2 and 3)Regulatory Affairs Manager (w/o Enclosures 2 and 3)Regulatory Assurance Manager -Quad Cities Nuclear Power Station, Units 1 and 2 (w/oEnclosures 2 and 3)Severe Accident Management Director (w/o Enclosures 2 and 3)Site Operations Director

-Quad Cities Nuclear Power Station, Units 1 and 2 (w/oEnclosures 2 and 3)Corporate Licensing Manager -West (w/o Enclosures 2 and 3)Corporate Licensing Director

-West (w/o Enclosures 2 and 3)Exelon Records Management (w/o Enclosures 2 and 3)Vinod Aggarwal (w/o Enclosures 2 and 3)Joseph Bellini (w/o Enclosures 2 and 3)Dustin Damhoff (w/o Enclosures 2 and 3)Security-Related Information

-Withhold Under 10 CFR 2.390Enclosure 2 contains Sensitive Unclassified Non-Safeguards Information (SUNSI);

uponseparation this letter is decontrolled.

Enclosure 1Quad Cities Nuclear Power Station, Units 1 and 2Response to Request for Additional Information Regarding Fukushima Lessons Learned -Flood Hazard Reevaluation Report(55 pages)

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 1 of 55RAI 1: Hazard Input for the Integrated Assessment

-Flood Event Duration Parameters

Background:

Enclosure 2 of the 50.54(f) letter requests the licensee to perform an integrated assessment of the plant's response to the reevaluated hazard if the reevaluated flood hazard isnot bounded by the current design basis. Flood scenario parameters from the flood hazardreevaluation serve as the input to the integrated assessment.

To support efficient and effective evaluations under the integrated assessment, NRC staff will review flood scenario parameters as part of the flood hazard reevaluation and document results of the review as part of the NRCstaff assessment of the flood hazard reevaluation.

Request:

Provide the applicable flood event duration parameters (see definition and Figure 6 ofthe NRC interim staff guidance document JLD-ISG-2012-05, "Guidance for Performing anIntegrated Assessment,"

November 2012 (ADAMS Accession No. ML1 2311 A214), associated with mechanisms that trigger an integrated assessment using the results of the flood hazardreevaluation.

This includes (as applicable) the warning time the site will have to prepare for theevent (e.g., the time between notification of an impending flood event and arrival of floodwaters on site) and the period of time the site is inundated for the mechanisms that are not bounded bythe current design basis. The licensee is also requested to provide the basis or source ofinformation for the flood event duration, which may include a description of relevant forecasting methods (e.g., products from local, regional, or national weather forecasting centers) and/ortiming information derived from the hazard analysis.

Response

The flood event duration parameters shown in Figure 1.1 are determined for the critical floodcausing mechanism in terms of maximum water surface elevation and fastest arrival time. Forthe Quad Cities Nuclear Power Station (QCNPS),

the flooding scenarios with coincident damfailures (i.e., Probable Maximum Flood (PMF) + hydrologic dam failure) bound the floodingscenarios without dam failures both for critical timing and maximum water surface elevation.

After evaluating the US Army Corps of Engineers, Hydrologic Engineering Center, RiverineAnalysis System (HEC-RAS) results for all the storm centers that flood the QCNPS (i.e., floodelevation greater than an elevation of 595.0 feet MSL 1912), the controlling PMF in terms ofmaximum water surface elevation and the fastest arrival time is the cool-season PMP centeredover the McGregor sub-watershed, snowmelt from an antecedent 100-year

snowpack, andhydrologic dam failure.Flood event durations are calculated as the temporal difference between the end of theProbable Maximum Precipitation (PMP) and arrival time of flood water at QCNPS for variousflood causing mechanisms and critical flood elevations.

Flood event duration parameters are based on the HEC-RAS model developed to support theflood hazard analysis of the QCNPS. The PMF flood hydrograph for the flood event durationparameters calculation was obtained at HEC-RAS cross section 506.9 (Mississippi River, Reach#13), which crosses the northern portion of QCNPS.The controlling PMF stillwater elevation (PMF+ hydrologic dam failure) is 600.9 feet MSL 1912.QCNPS enters flood emergency procedure immediately when the river level exceeds 586 feetor when the river level is predicted to be greater than 594.0 feet MSL 1912 in less than 96hours.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 2 of 55Flood event duration parameters for the controlling flooding mechanism for elevations above595.0 feet MSL 1912 are calculated based on the shape of the PMF hydrograph.

Flood eventduration parameters for the controlling flood causing mechanism (PMF+ hydrologic dam failure)are summarized as follows:1. The flood duration from the end of the PMP to elevation 595.0 feet MSL 1912 is 172 hour0.00199 days <br />0.0478 hours <br />2.843915e-4 weeks <br />6.5446e-5 months <br />saccording to the HEC-RAS output time series table for the controlling PMF simulation (PMF+ hydrologic dam failure).

2. The duration of inundation above elevation 595.0 feet MSL 1912 is 240 hours0.00278 days <br />0.0667 hours <br />3.968254e-4 weeks <br />9.132e-5 months <br /> according tothe HEC-RAS output time series table for the controlling PMF simulation (PMF + hydrologic dam failure).

As identified by JLD-ISG-2012-05, the critical warning time, inundation time, and recession timefor the controlling flooding mechanism (PMF+ hydrologic dam failure) are provided in Figure 1.1and Table 1.1. Timing parameters for other analyzed flood causing mechanisms aresummarized in Table 1.1 as well.Flood Event Duration---------------------------------- -0-h40 uourPeriod ofInundation t _ _ _ _ _ _172 hours I4ursEnd of Rarall Arrival of flood Water begins towaters on plant recede from plantWSE = 595A Bt WSE <S9S.0 ftFigure 1.1 -Flood Event Duration Parameters (Elevations in MSL 1912)

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 3 of 55Table 1.1 -Timing Parameters for Various Flood Mechanisms (Elevations in MSL 1912)Critical Flood CriteriaCorresponding Conservative FloodScenarioParameter Value1 Flooding in Streams and Rivers (HEC-RAS Modeling)

Time to reach elevation 595.0 feet from the 173 hour0.002 days <br />0.0481 hours <br />2.86045e-4 weeks <br />6.58265e-5 months <br />sla enote Pend of the PMP Cool-season PMP centered over theMcGregor sub-watershed, with1 b Time to reach the highest water surface snowmelt from an antecedent 100-year 256 hour0.00296 days <br />0.0711 hours <br />4.232804e-4 weeks <br />9.7408e-5 months <br />selevation at the plant of 600.5 feet snowpackDuration of inundation above elevation oflc 55fet238 hours595.0 feet2 PMF with Hydrologic Dam Failures (HEC-RAS Modeling)

Time to reach elevation 595.0 feet from the 172 hour0.00199 days <br />0.0478 hours <br />2.843915e-4 weeks <br />6.5446e-5 months <br />send of the PMPTime to reach the highest water surface 250 hour0.00289 days <br />0.0694 hours <br />4.133598e-4 weeks <br />9.5125e-5 months <br />selevation at the plant of 600.9 feetDuration of inundation above elevation of2c 59. et240 hours31- 595.0 feet3 Seismic Dam Failure (HEC-RAS Modeling) 3aTime to reach the highest water surfaceelevation at the plant of 589.6 feet256 hours3bTime to reach elevation 595.0 feet from theend of the PMPN/A** Elevation of 595.0 feet is not reached due to seismic dam failureRAI 2: Hazard Input for the Integrated Assessment

-Flood Height and Associated Effects

Background:

Enclosure 2 of the 50.54(f) letter requests the licensee to perform an integrated assessment of the plant's response to the reevaluated hazard if the flood hazard is not boundedby the current design basis. Flood scenario parameters from the flood hazard reevaluation serve as the input to the integrated assessment.

To support efficient and effective evaluations under the integrated assessment, NRC staff will review flood scenario parameters as part of theflood hazard reevaluation and document results of the review as part of the staff assessment ofthe flood hazard reevaluation.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 4 of 55Request:

Provide the flood height and associated effects (as defined in Section 9 of JLD-ISG-2012-05) that are not described in the flood hazard reevaluation report for mechanisms thattrigger an integrated assessment.

This includes the following quantified information for eachmechanism (as applicable):

• Hydrodynamic

loading, including debris;" Effects caused by sediment deposition and erosion (e.g., flow velocities, scour);" Concurrent site conditions, including adverse weather; and" Groundwater ingress.Response:

a. Flood HeightThe maximum flood elevation for the local intense precipitation (LIP) event, as reported inthe March 12, 2103 submittal, ranges between 593.74 and 597.81 feet NAVD-88.

The LIPanalysis was conducted using a two dimensional model. Therefore, maximum floodelevations vary throughout the plant. More details on the results are provided with the March12, 2013 submittal.

The maximum (stillwater) flood elevation for the Combined Effects river flood (including upstream dam failure),

as reported in the March 12, 2103 submittal, is 600.9 feet MSL 1912.b. Wind Wave and Runup EffectsConsideration of wind-wave action for the LIP event is not explicitly required by NUREG/CR-7046 and is judged to be a negligible associated effect because of limited fetch lengths andflow depths.The maximum wind-wave runup elevation for the Combined Effects river flood, as reportedin the March 12, 2103 submittal, is 605.0 feet MSL 1912.c. Hydrodynamic/debris loadingThe LIP analysis resulted in hydrodynamic loads ranging between 0.01 and 271.83 lbs/footwidth. The LIP analysis was conducted using a two dimensional model. Therefore, hydrodynamic loads vary throughout the plant. More details on the results are provided withthe March 12, 2013 submittal.

The debris load for the LIP event is negligible due to lowvelocities and depths, which results in a lack of power to transport heavy debris.During the Combined Effects river flood, Quad Cities Station allows flood waters to enter andfill up the plant to equalize the associated hydrostatic loading.

Therefore, during the riverflood, the structural loading to consider is limited to the hydrodynamic and debris loading.Hydrodynamic and debris impact loading during the governing probable maximum flood(PMF) scenario were evaluated in Calculation QDC-0085-S-2034.

The hydrodynamic forcesfor low velocity flow (less than 10 feet per second) are converted into an equivalent hydrostatic force. Section 7.3.1 of Calculation QDC-0085-S-2034 reports a hydrodynamic load of 3.6 lbs/ft width, equivalent static force corresponding to the PMF at elevation 598 feetMSL 1912 for Approach 1 and 4.1 lbs/ft acting at elevation 598.9 feet MSL 1912 for Approach Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 5 of 552. (See below for description of two dam failure approaches.)

Debris impact loading wasanalyzed using the guidelines described in FEMA P-259 and by considering debris weightrecommended in ASCE/SEI-7-10 (1000 Ibs). Section 7.3.2 of Calculation QDC-0085-S-2034 reports a debris impact load of 480 lbs.Please note that two approaches were considered to evaluate flooding from upstream damfailure.

Approach 1 considered failure of a subset of the upstream dams to develop aconservative but representative upstream dam failure scenario based on ANSI/ANS 2.8guidance, which states that some dams can be eliminated from dam failure analysis basedon "low head differential, small volume, distance from plant site, and major intervening natural or reservoir detention capacity."

Smaller and more remote dams, judged to beunlikely to significantly contribute to flooding at the site, were excluded in Approach 1.Approach 2 was applied for sensitivity purposes only and introduced additional conservatisms by evaluating failure of all 1,558 upstream dams within the watershed, represented in the hydrologic model as hypothetical dams. The NRC Dam Failure InterimStaff Guidance (July 31, 2013) was released after Quad Cities Flood Hazard Reevaluation Report was submitted and, therefore, was not applicable to the reevaluation.

The approachwas developed based on ongoing discussions, at the time the reevaluation was beingconducted, of dam failure methodology between the NRC and the Nuclear Energy Institute (NEI). The information provided in response to this Request for Information is based onresults from Dam Failure Approach 1.The Mississippi River is a navigable water body and, therefore, the potential for a barge toimpact critical structures during the PMF event was assessed.

As shown in Table 2.1,velocities in the main channel are much higher than overbank velocities at the site. Also, asshown in Figure 2.1, the plant is located in the left (looking downstream) overbank and innercurve of bend in the river channel.

The velocity differential and configuration of the river atthe site indicates that inertia alone would keep floating barges in the main channel, makingany direct or indirect strike on critical structures not credible.

Furthermore, topographic features between the site and river would protect the plant from barge impacts.Table 2.1: Summary of Channel and Overbank Velocities (for PMF + Dam Failure Approach 1)Average Velocity-LeftRiver (looking downstream)

Average ChannelRiver Reach # Station Overbank (fps) Velocity (fps)Mississippi 13 506.9 0.55 4.94Mississippi 13 506.0 0.07 3.55 Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 6 of 55Figure 2.1: HEC-RAS Cross-Section Locations (Calculation

1. QDC-0085-S-1991, Attachment 1, Figure 15)Id. Effects of sediment deposition and erosionThe sediment supply is expected to limit the amount of deposition that could occur during aLIP event. Velocities around the plant during the LIP event range between 0.19 and 6.29feet per second (fps). The maximum velocity is well below permissible velocities for paved Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 7 of 55surfaces, which is the dominant surface in the power block area, of 12 to 30 fps (U.S. ArmyCorps of Engineers (USACE),

Engineer Manual EM 1110-3-136, Drainage and ErosionControl Mobilization Construction, April 1984) so erosion and localized scour is also notexpected to be a significant effect of LIP flooding.

A detailed sediment transport analysis was not performed as part of the flood hazardreevaluation for the PMF river flood. However, a qualitative evaluation was conducted toassess the potential impacts of sediment deposition and erosion on flooding and at plantstructures.

Table 2.1 shows a reduction in the left overbank velocity from the upstream todownstream side of the plant, indicating that some deposition of sediment may occur duringthe flood. However, the magnitude of the left overbank velocities are low and expected toonly transport very fine particle sizes (e.g. clay) with very low settling velocities.

Therefore, deposition is expected to be minimal and would not affect flood levels at the site. The lowoverbank velocities, shown in Table 2.1, also indicate that scour and erosion is notexpected, even where localized eddies form around plant structures.

The site is largelycovered with asphalt and concrete

pavement, which is able to withstand velocities between12 and 30 fps (USACE 1984). Even the most erodible bare soil can withstand velocities upto 2 fps or more (USACE 1984), which is still much greater than the applied velocities.

e. Concurrent site conditions The meteorological events that could potentially result in significant rainfall of the LIP andprobable maximum precipitation (PMP) magnitude are squall lines, thunderstorms withcapping inversion, and mesoscale convective systems.

These meteorological events aretypically accompanied by hail, strong winds, and even tornadoes.

The flood hazardreevaluation calculations indicate that the site is also subject to flooding from a rain-on-snow event in the watershed, which can produce concurrent high winds, ice, and snow conditions on the site. The riverine PMF can be accompanied with debris loads, which may impact siteaccessibility once the flood waters recede.f. Groundwater ingressDuring a LIP event, impervious cover immediately around the power block buildings and theshort-duration (1-hour precipitation) will keep infiltration of precipitation and groundwater seepage to a minimum.

Therefore, groundwater level changes are not expected to occurduring a LIP flood.The river flood may cause groundwater levels to surcharge at the plant. The impact of thissurcharge on the plant's ability to protect against the ingress from surcharged groundwater levels will be evaluated in the Integrated Assessment, which will consider groundwater levels to rise with the river flood up to plant grade.RAI 3: Site Information

Background:

The March 12, 2013, letter (Section c) and FHRR (Sections 2.a and 4) state thatthe current design-basis flood elevation is 603 feet mean sea level (MSL, 1912 datum) and thatthis corresponds to the probable maximum flood (PMF) elevation (FHRR, Section 4, Table 1).However, Section 4.a of the flooding walkdown report for QCNPS (ADAMS Accession No.ML12332A307) states that the original design-basis flood elevation is 589 ft MSL, which was Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 8 of 55based on the 200-year flood that was considered to be the PMF at the time of the plant design.The flooding walkdown report further states that floods in excess of the 200-year event areplausible and notes that the updated final safety analysis report provides a stage discharge curve indicating that PMF is estimated to reach an elevation of 601 feet MSL. The walkdownreport (Section 4.a) discusses the 603 feet MSL elevation in the context of an elevation to whichthe plant can mitigate flood effects, but does not identify 603 feet MSL as the design-basis floodelevation.

The comparison between the design basis and the reevaluated hazard is key for determining which hazards, if any, should be evaluated in the integrated assessment report.Request:

Provide clarification regarding the apparent discrepancy between the FHRR and theflooding walkdown report with respect to the design-basis PMF elevation.

Response

The 200-year flood corresponding to an elevation of 589 feet was considered to be the ProbableMaximum Flood in the original FSAR. Ensuing discussions between ComEd and the AEC duringoriginal approval

-documented in FSAR Amendments 13, 16, 18 and 23, expanded thediscussion on Probable Maximum Flood to encompass a flood up to elevation 603 feet based onlower probability scenarios.

The Safety Evaluation Report (August 25, 1971) that approved the Operating License for theplant reviews the data discussed above and includes discussion that the plant selected the 200-year flood as the Probable Maximum Flood but also provides additional discussion that "Morerecently for construction permit reviews, we have used the larger "Probable Maximum Flood"(PMF), as defined by the U.S. Corps of Engineers, as a basis for establishing the maximum floodlevel for which a facility should be designed.

Using this criterion, the applicant's flood analysispredicted that the highest level that would be reached by a PMF would reach about 8 feet aboveplant site grade. The applicant has described emergency measures that can be taken underthese circumstances to protect the plant against the effects of flooding, and to achieve andmaintain a safe shutdown condition without resulting in any structural damage or release ofradioactivity from the reactor system."

A PMF of 8 feet above plant grade corresponds to anelevation of 603 feet. Therefore, the design basis PMF from the original SER for Quad Cities is603 feet.RAI 4: Local Intense Precipitation

-Supporting Analysis and Electronic Files

Background:

The information provided in the LIP evaluation report does not adequately describemodeling assumptions and key features of the modeling implementation such as therepresentation of topography and land cover, model input parameters, and model outputaccuracy.

The NRC staff audit found that some of this information is described in Calculation Package LIP-QDC-001, Rev. 3, "Quad Cities Local Intense Precipitation Evaluation."

Request:

Provide the following information:

1) The body of the supporting analysis (LI P-QDC-001, Rev 3, pages 1-19)2) Appendix A (Figures) of the supporting analysis (LIP-QDC-001, Rev 3, pages 20-65)3) Electronic versions of input and output files for the LIP analysis, including:

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 9 of 55a. Digital Elevation Model (DEM) or other x-y-z data files used to produce the groundsurface elevation map (Figure A-01 in Calculation Package LIP-QDC-001, Rev. 3).b. An electronic version of the ground surface elevation map (Figure A-01 in Calculation Package LIP-QDC-001, Rev. 3)c. An electronic version of the map showing land cover and Manning's n roughness coefficients (Figure A-02 in LIP-QDC-001, Rev. 3)d. Electronic versions of all FLO-2D flood routing model input files (including modelexecution and numerical solution control files) used for surface flow modeling of theLIP probable maximum precipitation (PMP) event described in LIP-QDC-001, Rev. 3,and all FLO-2D output files listed in Appendix D of Calculation Package LIP-QDC-001, Rev. 3.Response:

1) The body of the supporting analysis (LI P-QDC-001, Rev 3, pages 1-19) -See Enclosure 2, DVD #1 under file labeled "1 -LIP-QDC-001_Rev 3_Narrative.pdf"

2) Appendix A (Figures) of the supporting analysis (LIP-QDC-001, Rev 3, pages 20-65) -See Enclosure 2, DVD #1 under file labeled "2 -LIP-QDC-001

_Rev 3_Appendix A.pdf"3) Electronic versions of input and output files for the LIP analysis, including:

a. Digital Elevation Model (DEM) or other x-y-z data files used to produce theground surface elevation map (Figure A-01 in Calculation Package LIP-QDC-001, Rev. 3) -See Enclosure 2, DVD #1 under folder labeled "3 -LIP AnalysisInput and Output Files", subfolder labeled "a -Digital Elevation Model".b. An electronic version of the ground surface elevation map (Figure A-01 inCalculation Package LIP-QDC-001, Rev. 3) -See Enclosure 2, DVD #1 underfolder labeled "3 -LIP Analysis Input and Output Files", subfolder labeled "b -Ground Surface Elevation Map".c. An electronic version of the map showing land cover and Manning's n roughness coefficients (Figure A-02 in LIP-QDC-001, Rev. 3) -See Enclosure 2, DVD #1under folder labeled "3 -LIP Analysis Input and Output Files", subfolder labeled"c -Land Cover and Manning's n Roughness Map".d. Electronic versions of all FLO-2D flood routing model input files (including modelexecution and numerical solution control files) used for surface flow modeling ofthe LIP probable maximum precipitation (PMP) event described in LIP-QDC-001, Rev. 3, and all FLO-2D output files listed in Appendix D of Calculation PackageLIP-QDC-001, Rev. 3 -See Enclosure 2, DVD #1 under folder labeled "3 -LIPAnalysis Input and Output Files", subfolder labeled "d -FLO-2D Input-Output Files".

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 10 of 55RAI 5: Local Intense Precipitation

-Storm Analysis Basis for Design Storm

Background:

The LIP analysis relied on the storm analyses performed by National WeatherService in developing Hydrometeorology Reports (HMRs) 51 and 52. However, the licenseeconducted a site-specific PMP study to support the PMF analysis in the FHRR. The site-specific PMP study included storms not considered in HMRs 51 and 52.Request:

Justify using one set of storms as a basis for the LIP estimates and a different set ofstorms as the basis for the PMF analysis.

Response

The local intense precipitation event (LIP) was analyzed for the 1-hour/I-square-mile PMP, asdefined in HMR-52. (The depth-area-duration data in HMR-51 does not include the 1-hour/1

-square-mile PMP. The storm with the shortest duration and smallest area in HMR-51 is the 6-hour/10-square-mile PMP.) HMR-51 is frequently used for riverine watershed studies but islimited to a watershed size of approximately 20,000 square miles. The watershed size for theMississippi River at Quad Cities (88,000 square miles), which is far larger than the sizelimitation in HMR-51, was the primary driver for performing a watershed-wide site-specific study.Because of its short duration and small area, a site-specific study for the 1 -hour/1 -square-mile PMP would have involved an additional analysis of storms, different than those included in thewatershed-wide study. Industry's experience, including Exelon's more recent experience inIllinois, is that site-specific studies for the 1-hour/I-square-mile PMP consistently results in lowerrainfall values than in HMR-52, particularly in inland areas. In this submittal, Exelon chose toaccept a more conservative value in HMR-52 for the 1 -hour/I-square-mile PMP.RAI 6: Local Intense Precipitation

-Design Storm Duration and Temporal Distribution

Background:

Although the basic approach for developing the design storm is outlined in HMR52, several key details are left to the discretion of the analyst.

Among these are the duration ofthe design storm (e.g., in relation to watershed characteristics such as the time of concentration) and the temporal distribution of the rainfall within the selected duration.

Request:

Describe the rational, including any sensitivity

analysis, that indicates whether the 1-hrPMP scenario used in the LIP analyses (Figure 3-2) bounds the effects of LIP in comparison with alternative duration PMP scenarios (e.g. 6-hr, 12-hr, 48-hr, or 72-hr PMP scenarios).

Thelicensee is requested to evaluate the bounding LIP scenarios in terms of the severity of floodlevel as well as inundation duration.

The licensee is also requested to describe the rationale forevaluating LIP using a temporal rainfall distribution in which the peak rainfall intensity occurs atthe beginning of the PMP event and declines thereafter (e.g., in comparison with anothertemporal distribution, such as a centered distribution).

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 11 of 55Response:

Per NUREG/CR-7046 Section 3.2 (Reference 1): "Local intense precipitation is a measure ofthe extreme precipitation at a given location.

The duration of the event and the support areaare needed to qualify an extreme precipitation event fully. Generally, the amount of extremeprecipitation decreases with increasing duration and increasing area. The PMP values for areasof the United States east of the 105th meridian are presented in HMRs 51 (Schreiner and Riedel1978) and 52 (Hansen et al. 1982). The 1-hr, 2.56-km2 (1--mi) PMP was derived using single-station observations of extreme precipitation, coupled with theoretical methods for moisturemaximization, transposition, and envelopment.

HMR 52 recommended that no increase in PMPvalues for areas smaller than 2.56 km2 (1 mf) should be considered over the 1-hr, 2.56-km2 (1-min) PMP. The local intense precipitation is, therefore, deemed equivalent to the 1-hr,2.56-km2 (1-mi2) PMP at the location of the site."Since the 1-hr, 1-mi2 LIP event would fully encompass the contributing drainage area of theQuad Cities Nuclear Station, the evaluation of a longer duration and larger storm event (6-hr,10-mi2) was not warranted.

This approach is in accordance with the definition of the LIP eventper NUREG/CR-7046, as described above. In addition, because of the rainfall intensity duringthe first hour of the storm event, the amount of precipitable water available for a longer durationstorm event would be minimal compared to the first hour. Therefore, any increase in maximumflood levels due to a longer duration storm event is unlikely.

The 1-hr PMP event temporal distribution was developed in accordance with HMR 52(Reference 2), which provides a set of multiplication factors for the 5-, 15-, and 30-minute timeintervals relative to the 1 -hr, 1-mi2 PMP depths. While HMR 52 does not specifically state thetime intervals be arranged in this particular order, with the typical west-east flow across NorthAmerica, the type of storm set-up that would provide an LIP would likely be a mesoscale convective system (such as a squall line for example).

Using the conceptual model of this typeof system (Reference

3) the initial precipitation is associated with the mature cells and a zone ofconvergence and as such will be very intense.

The storm motion and nature of the systemwould then see a decrease in the precipitation after the initial burst as the rear trailing stratiform region with the cold pool moves over the area. This type of meteorological system fits with thefront loaded distribution.

References:

1. United States Nuclear Regulatory Commission (2011) NUREG/CR-7046, "Design-Basis Flood Estimation for Site Characterization at Nuclear Power Plants in the United Statesof America."

2. NOAA Hydrometeorological Report No. 52 (HMR-52)

(1982), Application of ProbableMaximum Precipitation Estimates

-United States East of the 105th Meridian, U.S.Department of Commerce, National Oceanic and Atmospheric Administration, and U.S.Department of the Army Corps of Engineers.

3. Houze, Robert A., Jr. (2004), "Mesoscale Convective Systems."

Review of Geophysics, 42, RG4003/2004.

Paper number 2004RG0001

50.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 12 of 55RAI 7: Local Intense Precipitation

-Precipitation onto Buildings

Background:

The LIP evaluation report does not describe how precipitation onto building roofswas modeled.

The NRC staff audit found that some of this information is described in LIP-QDC-001, Rev. 3.Request:

Provide a detailed description of how rainfall onto buildings is modeled in the LIPanalysis, including a description of how water draining from roofs is routed and how this isimplemented in the FLO-2D model. Provide justification for any assumptions regarding waterstorage by buildings.

Response

To represent the buildings in the FLO-2D model, FLO-2D Area Reduction Factors (ARFs) andWidth Reduction Factors (WRFs) functions were utilized.

ARFs and WRFs are coefficients thatmodify the individual grid element surface area storage and flow width, respectively.

ARFs canbe used to reduce the flood volume storage on grid elements due to buildings and enhance theaccuracy of the flood simulation.

ARFs are specified as a percentage of the total grid elementsurface area (less than or equal to 100%). WRFs are specified as a percentage of the gridelement side (less than or equal to 100%). In the FLO-2D model version used for the analysis, when an element's ARF is set from 0.95 to 1.0, any rainfall volume is assumed to go into thestorm drain system and will not route through the model.In the Quad Cities LIP FLO-2D model, the elements requiring ARF and WRF values wereselected using a shapefile created in ArcGIS software representing the outline of the buildings.

The ARF value for buildings was set to 0.94 to ensure that stormwater falling on top of roofbuildings is accounted for in the model and not removed from the model domain. A WRF valueof 1.0 was set for grids adjacent to the buildings in the four critical directions to prevent inflowsfrom the surrounding elements and to ensure that the building elements do not provide storagefor floodwaters from the surrounding elements.

Water was allowed to pond on building roofs dueto roof parapets, which assumes any roof drains are completely blocked.

The justification forthis assumption was based on the existence of roof parapets on the Turbine Building and theReactor Building.

The height of roof parapets on the Reactor Building is 17 inches on the eastside and 29 inches on the west side (Reference 1), with the roof sloped towards the west. Theheight of roof parapets on the Turbine Building is 17 inches with additional storage providedtowards the center of the roof where the height between the top of the parapet and the roof is 24inches (Reference 2). The blockage of roof drains is consistent with Case 3 scenario.

References:

1. Exelon Drawing B-764, Quad Cities Nuclear Station, "Reactor Building Roof Plan."2. Exelon Drawings B-716 and B-717, Quad Cities Nuclear Station, "Turbine Building RoofPlan."

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 13 of 55RAI 8: Local Intense Precipitation

-Modeling Approach for Spray Canal

Background:

The LIP evaluation report indicates that the spray canal is included within the FLO-2D modeling domain. However, no discussion of the modeling approach used for the spraycanal is provided.

A Manning's n roughness coefficient for the canal water surface is providedinstead of a Manning's n roughness coefficient based on the canal sides and bottom, whichimplies that the canal is not treated a flow element.Request:

Provide clarification regarding the modeling approach used for the spray canal.Response:

The spray canal geometry is included in the FLO-2D model as part of the gridded digitalelevation model (DEM) surface based on publically available LiDAR survey data (Reference 1).The LiDAR survey coverage of the spray canal reflects the side slopes and water surfaceelevation in the canal at the time of the LiDAR survey. The LiDAR survey did not penetrate thewater surface in the spray canal to capture bathymetry and, therefore, the spray canal bottomelevation in the DEM is represented by the water surface elevation at the time of the LiDARsurvey. This method of depicting the spray canal is conservative since it does not treat the spraycanal as a flow element and reflects the NUREG/CR-7046 Case 3 scenario for the LIP analysis(all drainage canals blocked).

The Manning's n roughness coefficient for water surface (0.02)was assigned to the elements representing the spray canal bottom since the elevation of thegrid element reflects water surface.

The Manning's n roughness coefficient for grass (0.32) wasassigned to the grassed-lined canal side slopes. It should be noted that the inner and outerberms around the canal provide topographic relief and, therefore, the selection of the Manning's n roughness coefficient is not critical in the LIP evaluation.

Runoff from adjacent drainage areaswould flow away from the site and would not contribute to higher flood levels in the power block.In addition, with the culverts modeled as completely

blocked, the spray canal would providestorage for runoff flowing directly into the canal without causing a backwater condition on thepower block.

References:

1. Aero-Metric Photogrammetry and Geospatial Data Solutions (2010). Vertical AccuracyReport for State of Illinois Department of Transportation Rock Island County Illinois.

Available at http://www.isgs.uiuc.edu/nsdihome/webdocs/ilhmp/county/rockisland.html (accessed on June 6, 2012).RAI 9: Local Intense Precipitation

-Modeling of Concrete Security Barriers

Background:

The LIP evaluation report does not describe how flow over (or around) concretesecurity barriers is modeled.

The NRC staff audit found that some of this information isdescribed in LIP-QDC-001, Rev. 3. The staff is aware that FLO-2D treats flow over structures such as levees as flow over a broad-crested weir, with a fixed weir coefficient of 2.85. A weircoefficient of 2.85 is within the range found in several hydrology text books. However, weircoefficients provided in standard hydrology and hydraulics texts are for flow measurement weirs. The concrete security barriers are not flow measurement devices.

In addition, the weircoefficient is a function of the weir breadth and the head upstream of the weir.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 14 of 55Request:

Provide justification for modeling the flow over concrete security barriers using theFLO-2D levee function (i.e., as flow over a broad-crested weir with a fixed weir coefficient of2.85), including a discussion of any physical characteristics which prompt such a selection andany sensitivity analysis that was performed.

Response

The levee feature was used to represent the concrete jersey barriers and concrete blocks in theFLO-2D model to account for the security barrier's effects on local drainage patterns.

The use ofthe levee feature allowed for modeling of the gaps between the security barriers to accurately represent potential flow paths around and over the structures.

Weir flow will occur until thetailwater depth is 85% of the headwater depth, and at that point the model will calculate theexchange across the levee using the difference in water surface elevation.

This modelingapproach allows for better representation of the security barrier compared to changing theground elevation of each individual grid element to reflect the top elevation of the securitybarrier.

Furthermore, the breadth of the security barrier (concrete block width and jersey barrierconfiguration) is more representative of a broad crested weir and justifies the use of the broadcrested weir coefficient for estimating overtopping flow in this analysis.

In addition, only a limitedsegment of the security barriers is overtopped during the LIP event, as shown in Figure 1.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 15 of 55Figure 1 -Overtopped Security Barriers during FLO-2D LIP Model Run!1LegendOvertopped BarriersNon-Overtopped BarriersSecurity BarriersMax Velocity (ff.s)0.00- 1.00100 -250250 -500500- 10,0010.00 -15 75WI 'BaNW+ES0 100 200 300i ea ,.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 16 of 55RAI 10: Consistent Vertical Datums

Background:

The submittals do not use a consistent vertical datum. The LIP evaluation reportprovides elevations with respect to the North American Vertical Datum of 1988 (NAVD88).

Analyses for other flooding phenomena in the FHRR report elevations with respect to the legacyGeneral Adjustment of 1912 (MSL 1912) datum. Furthermore, the submittals do not provide aconversion between the two datums. The NRC staff audit found that datum conversions areprovided in Calculation Package QDC-0085-S-1 991, "Calculation of Probable Maximum Flood(PMF) Water Surface Elevation:

Evaluation of Riverine Hydraulics for the Upper Mississippi River at QCNGS."Request:

Provide a consistent set of vertical datum for the submittals or provide a conversion between the various datums used. In particular, describe what relationships were used toconvert between modern datums such as NAVD88 and legacy datums such as MSL 1912.Response:

The LIP evaluation was performed utilizing NAVD88 because current surrounding planttopographical information was available in NAVD88 at the time of the evaluation.

The floodingdepths as provided in the LIP evaluation are the water surface depths corresponding totopographical information in NAVD88.Subsequent to the completion of the LIP evaluation, an elevation survey was performed tocorrelate NAVD88 to the plant grade elevation.

The elevation survey was performed by aProfessional Land Surveyor licensed in the State of Illinois.

Door sill elevations were capturedand the elevations ranged from 594.51 feet to 594.61 feet (NAVD88).

Therefore, plant grade elevation of 595.0 feet, corresponds to a plant grade elevation of 594.55(NAVD88).

Thus, an equation to convert the datum shift for NAVD88 at Quad Cities Station isconcluded to be:Plant Grade -NAVD88 (feet) = 0.45 feetQDC-0085-S-1 991, Rev. 0, Attachment 2E (Datum Conversion between MSL 1912 and NAVD88Equation Sheet and Results) indicates the datum shift (MSL 1912 -NAVD88) to be 0.70 feet atthe River Mile 506.9 (corresponding to Quad Cities Station).

This indicates that the Plant Gradeis 0.25 feet above MSL 1912 (0.70 feet -0.45 feet). Thus an equation to convert the datum shiftfor MSL 1912 at Quad Cities Station is concluded to be:Plant Grade -MSL 1912 (feet) = 0.25 feetRAI 11: Probable Maximum Precipitation Analysis

Background:

The discussion of the PMP analysis in FHRR Section 3.1 does not adequately describe the overall logic, key assumptions,

methods, inputs, and results.

The NRC staff auditfound that this information is documented, in part, in Calculation Package QDC-0085-S-1989, Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 17 of 55"Probable Maximum Precipitation (PMP) for the Upper Mississippi River Watershed Contributory to QCNGS."Request:

Provide the following portions of QDC-0085-S-1 989:* Main text (Pages 1-36)* Attachment 1, Figures* Attachment 2, Section 10 (Storm Dimensions)

• Attachment 2, Section 13 (Recommendations for Applications)

• Attachment 2, Appendix E (SPAS System Description)

Also provide electronic editable files for the following portions of QDC-0085-S-1989:

• Depth-Area Duration Tables (Attachment 7)* Percentage of 6-hr PMP Increment tables (Attachment 8)* Average 6-hr Incremental PMP Spreadsheets (Attachment 9)* All Season and cool season hyetographs (Attachment 10)* 100-year snowpack calculation spreadsheet (Attachment 11)* Meteorological Time Series Data for Snowmelt (Attachment 13)* Snowmelt Spreadsheet (Attachment 14)Response:

The requested excerpts from Calculation QDC-0085-S-1989 and electronic editable files areincluded in Enclosure 3 DVD #2A under folder labeled "RAI 11". Note that NDCD Stations14923 and 479304 conservatively reported the March statistics in the PMP calculation.

TheMarch statistics for these two gages are included in Enclosure 3 DVD #2A.RAI 12: Site-Specific PMP Estimates

Background:

FHRR Section 3.1 states that a site-specific PMP analysis was performed tocalculate PMP values specific to the 88,000 square-mile (mi2) contributory watershed of theMississippi River upstream of the QCNPS site because HMR 51 does not provide PMPestimates for areas in excess of 20,000 mi2. The FHRR further states that the site-specific PMPanalysis used techniques and databases that differ from those used in HMR 51. However, theFHRR does not provide adequate detail to evaluate the differences in techniques and dataused. The NRC staff audit found that some of this information is documented in QDC-0085-S-1989.Request:

Provide the following information:

• A detailed description of the techniques and databases used, including storm selection.

Describe any difference between techniques and databases used in the current analysisand those used in HMR 51.* A detailed comparison between PMP results in HMR 51 and the FHRR analysis for thoseareas and duration common to both analyses.

Include an explanation for differences thatmay exist.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 18 of 55* A detailed description of the alternate dewpoint climatology used, including data sources,methods, and resulting maps or databases.

An existing report that includes thisinformation would suffice.* Electronic versions of the storm analysis spreadsheets developed for the site-specific PMP study (QDC-0085-S-1989, Attachment 2, Appendix F)* Electronic versions of the spreadsheets used to perform the depth-area and depth-duration envelopments

• Electronic versions of the final all-season and cool-season PMP maps (QDC-0085-S-1989, Attachment 2, Appendices A and B)Response:

, A detailed description of the techniques and databases used, including storm selection.

Describe any difference between techniques and databases used in the current analysis andthose used in HMR 51.The storm selection process employed during the analysis of the Quad Cities Nuclear PowerStation (QCNPS) PMP work included analysis of several databases and previous storm listsderived during previous and ongoing PMP work in the region considered transpositionable toany point within the overall watershed.

Applied Weather Associates (AWA) has completed numerous PMP studies in the region where storms were considered transpositionable to theQCNPS watershed.

This region covers most of the Midwest below 3,000 feet east through theinitial upslope region of the Appalachians and within about 60 latitudinal extent. Stormscomprising these storm lists were queried from National Climatic Data Center (NCDC) hourlyand daily datasets, US Army Corps of Engineers (USACE) storm studies, National WeatherService Hydrometeorological Reports (HMRs), United State Geological Survey (USGS) floodreports, journal articles, various government and private mesonets, weather books, and othersources.

All data have been quality controlled to verify the accuracy of the given rainfallreport(s).

Storms which comprised the initial list of storms had to have been at least equivalent to orgreater than the 100-year precipitation frequency value for the given duration and given locationand/or have resulted in major flooding at given location.

This resulted in hundreds of potential rainfall events. This list then needed to be analyzed further to produce a manageable list ofstorms which would then be fully analyzed to derive the PMP values. This final list is known asthe short storm list.The final short storm list used to determine the PMP values for QCNPS basin was derived usingthe results of previous PMP studies in regions similar to this basin. These include the EPRIMichigan/Wisconsin Regional PMP study (accepted by FERC), the Nebraska Statewide PMPstudy (accepted by FERC and Nebraska dam safety),

the Ohio Statewide PMP study (accepted by FERC and Ohio dam safety),

Tarrant Regional Water District PMP (accepted by Texas damsafety),

and the Wyoming Statewide PMP study (in progress).

During this process, the final short storm lists used in each of these studies was combined andevaluated.

The first set of parameters used to delineate the storms was whether they weretranspositionable to any grid point used to derive the PMP values for the QCNPS basin.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 19 of 55Factors such as elevation differences of more than +/- 1,000 feet and/or distances of more than+/- 60 latitude were considered.

Next, the storm type was evaluated.

Storm types which wouldnot result in a PMP/PMF scenario for the large QCNPS watershed were not considered.

Thisincluded storms which were individual thunderstorms, Mesoscale Convective Systems (MCS)and storms which were directly associated with remnant tropical systems.This storm search and storm selection process and methods were generally the same as thoseused and described in HMR 51. However, no notes or working papers are available from HMR51, so explicit comparisons are not possible.

However, all storms used in HMR 51 whichoccurred within the region considered transpositionable were included.

Differences includeupdating the storm database to include all storms through 2013 (adding more than 40 years ofstorm record to the previous design basis). In addition, more databases were queried andutilized because several did not exist when the original analysis was completed.

Finally, the transpositioning of storms to each of the grid points was an area where potential differences between this study and HMR 51 exist. AWA has the original copy of alltransposition limits maps produced by the NWS. In addition, maps of transposition limits forspecific storms are provided in various HMRs (e.g. HMR 52 Figure 26) and included for severalstorms in HMR 53 Table 2.1. AWA utilized this information along with our updated analysis todetermine explicit transposition limits for each storm considering the QCNPS watershed characteristics.

AWA's analysis included the guidance provided in HMR 51 Section 2.4.2 andupdated understanding of storm dynamics, available moisture

sources, variations in dew pointclimatologies by season, interactions with topography, and differences by storm type.These analyses and engineering judgments were applied to each storm considering each gridpoint, with specific meteorological and topographical characteristics considered.

This generalanalysis process is similar to that described in HMR 51. However, the major difference is AWAdoes not allow implicit transpositioning to occur as was done in HMR 51. This occurs in HMR51 during the smoothing and regionalization process employed to produce consistent PMPisolines across the entire region covered by HMR 51. In order to envelope all data across theentire region covered by HMR 51 and avoid bulls-eyes or inconsistent PMP isolines, HMR 51had to allow storms to influence PMP values far beyond their intended explicit transposition limits. It was not within HMR 51 scope to consider explicit characteristics of individual basins,but instead they were required to provide a generalized PMP estimate across the entire region.This updated site-specific analysis was not constrained by this consideration and was able toexplicitly consider the unique meteorological and topographic characteristics of the basin andapply updated understanding to the study not available to HMR 51.A specific example of the implicit transpositioning that effects HMR 51 PMP values across theentire domain is demonstrated by the maximized values of the Smethport, PA July 1942 stormand how those values were enveloped.

The NWS explicitly states that this storm should only betranspositioned east to the crest of the Appalachians, south to 350N, north to 430N and westalong the first upslopes of the Appalachians (Figure 1). However, the PMP isolines across theentire region covered by HMR 51 envelope the data from this storm, thereby allowing a stormwhich is not transpositionable to much of the domain to control PMP values inappropriately.

This is evidenced by comparing all storms used in HMR 51 to the PMP values over the regionswhere they are transpositionable and noting that no storm data supports the values providedexcept the maximized Smethport storm.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 20 of 55, )T 1 9

• _ .* .11 .'DkP'AR17d

,`OrOFCOW4M WEArHER BUREUMSN, 4,4 -../.... .1.!..... .*, A ,...... .'" r. .. , ..-" !Figure 1 -Smethport, PA July 1942 INWMS transposition limits with notes detailing constraints

Response

• A detailed comparison between PMP results in HMR 51 and the FHRR analysis for thoseareas and duration common to both analyses.

Include an explanation for differences that mayexist.A direct comparison to HMVR 51 PMVP values for duration from 24- through 72-hours and areasizes from 1000- through 20,000-square miles is provided at each grid point analyzed during thestudy in Table 12.1-12.3.

In the tables, values greater than zero represent reductions from theHMVR 51 values and values less than zero represent increases from the HMVR 51 values. Figure12.1 displays the grid point locations used in this study and referenced in the Tables 12.1-12.3.

Comparisons are only directly valid at these area sizes and durations because the storms usedin this study to compute PMVP values were of the storm type relevant for producing PMVF overlarge area sizes and long durations.

Therefore, short duration, high intensity storms (MCCs andthunderstorms) were not included in the analysis.

This is because those storms types areunique and would not co-occur with large scale, long duration storms. Therefore, there shouldnot be a comingling of storm types that would result in a PMVP design storm which is notphysically

possible, as this would violate the HMR definition of PMVP. Comparisons for cool-season PMVP values are not possible because no explicit cool-season PMVP values exist in HMVR51. HMVR 52 does provide seasonality adjustments which can be applied to HMVR 51 all-season PMP values. However, these data do not result in true cool-season PM-,P, as they are a result of Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 21 of 55ratio applied to all-season type storm events which are different than cool-season rain-on-snow events.Quad Cities Nuclear Generating StationGrid Point Locations

" p aw V iWý Wým'O'o'w ! I !ut-t~t190North, aoloo 16South Dakota144x0n4-4 ~-4&3Quad Cities NuclearGenerating StationbraskaýopyrioItVM)ESRI M550 U Vit I tI ll 1 1 I I *4-.j11-e~o'6q WWO5O "C -F;-5WCW6n 10.0.40000 Oin'0100 200 300 400 500Figure 12.1 -Grid points used in the study with QCNPS watershed and sub-basins delineated for reference Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 22 of 55Table 12.1 -Percent difference between the all-season PMP values at each grid point andthe basin centroid at the 24-hour duration vs HMR 51 PMP values. Positive valuesrepresent reductions from HMR 51.GRIDPOINT LAT ION I lO0miZ 5"00miZ 1OO0mi 2 20,000miZ 41.50 -91.50 13% 11% 10% 8%41.72 -90.32 12% 10% 7% 8%42.00 -89.00 11% 10% 7% 6%42.50 -93.00 14% 10% 10% 9%43.00 -95.00 15% 11% 10% 10%43.50 -91.00 11% 8% 8% 7%43.50 -88.50 7% 6% 6% 4%44.00 -97.00 13% 11% 9% 14%44.50 -94.00 8% 5% 3% 4%45.50 -98.00 10% 6% 4% 8%45.50 -95.50 10% 7% 6% 6%45.50 -93.00 7% 4% 4% 4%45.50 -90.50 8% 7% 7% 5%45.50 -88.00 2% 2% 3% 0%46.50 -94.50 9% 7% 6% 9%47.00 -97.00 8% 4% 3% 8%47.00 -91.00 1% 3% 3% -1%47.00 -89.00 0% 2% 2% -1%48.00 -95.50 10% 7% 7% 11%48.00 -93.00 8% 7% 7% 5%44.89 -92.69 10% 8% 7% 5%

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 23 of 55Table 12.2 -Percent difference between the all-season PMP values at each grid point andthe basin centroid at the 48-hour duration vs HMR 51 PMP values. Positive valuesrepresent reductions from HMR 51.GRIDMON LAT ILON I1,000m12 54)O))p~j 10,000M12 20,OO0mil 241.50 -91.50 11% 3% -2% 1%41.72 -90.32 10% 0% -5% -3%42.00 -89.00 9% -1% -5% -3%42.50 -93.00 13% 5% -1% 1%43.00 -95.00 14% 8% 3% 2%43.50 -91.00 8% -1% -4% -2%43.50 -88.50 5% -3% -7% -5%44.00 -97.00 15% 10% 12% 10%44.50 -94.00 7% 0% -6% -5%45.50 -98.00 13% 10% 8% 7%45.50 -95.50 11% 5% -1% 2%45.50 -93.00 6% 0% -6% -5%45.50 -90.50 7% 0% -5% -4%45.50 -88.00 3% -5% -11% -11%46.50 -94.50 10% 5% 0% -1%47.00 -97.00 11% 8% 7% 6%47.00 -91.00 3% -4% -10% -11%47.00 -89.00 1% -5% -11% -13%48.00 -95.50 11% 10% 10% 10%48.00 -93.00 5% 0% -4% -4%44.89 -92.69 8% 1% -4% -2%

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 24 of 55Table 12.3 -Percent difference between the all-season PMP values at each grid point andthe basin centroid at the 72-hour duration vs HMR 51 PMP values. Positive valuesrepresent reductions from HMR 51.Because no working papers or notes exists for HMR 51, explicit comparisons are not possiblefor many of the components.

However, comparisons can be made for some of the data andgeneral comparisons and reasons for differences are discussed.

The following areas weretreated differently and/or updated in this study versus the HMRs:1. HMR 51 provides generalized and smoothed PMP values over a large geographic domain covering the United States east of the 105'h meridian.

Specific characteristics unique to individual basins, such as QCNPS, were not addressed.

This study considered characteristics specific to the basin, and produced PMP values explicitly considering thetopography of the basin and the meteorology of the PMP storm type which would resultsin the PMF for the basin.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 25 of 552. Each storm's inflow vector was re-evaluated and combined with an updated set of dewpoint climatology data and when necessary, updated storm representative dew pointvalues were used for the in-place maximization and computation of the total adjustment factors.

The HYSPLIT trajectory model was used to evaluate and verify moisture inflowvectors for storms on the short storm list. Trajectory models were not available inprevious HMR studies.

The use of HYSPLIT allowed for a high degree of confidence when evaluating moisture inflow vectors and storm representative dew points.3. Several new storms have been analyzed and included in this site-specific PMP study thatwere not included in HMR 51. This provided a higher level of confidence in the final site-specific PMP values. Further, this allowed for a refined set of values that better represent the PMP values for both the all-season and cool-season PMP scenarios, as the data setused to derive PMP has been expanded to include a larger set of more recent storms.4. The site-specific PMP study provided adjustments for storm elevation to the nearest 100feet of elevation, whereas HMR 51 made no explicit adjustment for elevation for PMPvalue over the basin. This adjustment depends on the elevation of the historic storm'smaximum rainfall location and therefore varies from storm to storm. Further, the averagebasin elevation for each grid point was evaluated in this study using GIS, providing amuch more accurate representation and calculation to account for loss of available moisture up to that elevation.

5. SPAS was used in conjunction with NEXRAD data (when available) to evaluate thespatial and temporal distribution of rainfall.

Use of NEXRAD data generally producedhigher point rainfall amounts than were observed using only rain gauge observations andprovides objective spatial distributions of storm rainfall for locations among rain gauges.SPAS results provided storm depth area durations (DADs), total storm precipitation

patterns, and mass curves for the newly analyzed storms. Using these technologies, significant improvements of the storm rainfall analyses were achieved.

6. Previously analyzed storm events that occurred prior to 1948 that used 12-hour persisting dew points were adjusted using storm representative dew point adjustments of 20F forsynoptic type storm events and 70F for MCS type storm events. This was done to adjustfor using average dew point values for varying durations vs. 12-hour persisting dew pointvalues. Recent evaluations of 12-hour persisting storm representative dew points showthose used in HMR 51 underestimated the storm representative values. An updated setof maximum dew point climatology maps were produced.

These maps have highermaximum dew point values than those used in HMR studies and therefore compensate for the higher storm representative dew points.7. Interpolation of PMP values at each duration between each of the 20 grid point displayed in Figure 1 was completed using GIS and manual engineering judgment.

This resulted ina consistent and meteorologically reasonable spatial and temporal distribution of PMPvalues across the entire domain analyzed.

HMR 51 employed a similar process wherePMP isolines were contoured across a much larger domain (which also encompassed theQCNPS watershed) using engineering judgment.

Computer technologies, such a GISinterpolation, were not available in HMR 51. Therefore, more refined analysis in thisstudy specific to the site, increased understanding of meteorology and topography in theregion, and use of computer interpolation technologies resulted in PMP distributions thatare specific to the QCNGS watershed that were not available in HMR 51.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 26 of 55Response:

• A detailed description of the alternate dew point climatology used, including data sources,methods, and resulting maps or databases.

An existing report that includes this information would suffice.The dew point climatology used for site-specific PMP analysis is provided in detail in Attachment 2 of Calculation QDC-0085-S-1 989. Appropriate excerpts from Calculation QDC-0085-S-1 989are included in Enclosure 3 DVD #2A under folder labeled "RAI 12".Response:

• Electronic versions of the storm analysis spreadsheets developed for the site-specific PMPstudy (QDC-0085-S-1989, Attachment 2, Appendix F)The requested electronic versions of the storm analysis spreadsheets for the site-specific PMPare included in Enclosure 3 DVD #2A under folder labeled "RAI 12".Response:

• Electronic versions of the spreadsheets used to perform the depth-area and depth-duration envelopments The requested electronic versions of the spreadsheets used to perform the depth-area anddepth-duration envelopments are included in Enclosure 3 DVD #2A under folder labeled "RAI12".Response:

• Electronic versions of the final all-season and cool-season PMP maps (QDC-0085-S-1989, Attachment 2, Appendices A and B)The requested electronic versions of the final all-season and cool-season PMP maps (QDC-0085-S-1989, Attachment 2, Appendices A and B) are included in Enclosure 3 DVD #2A underfolder labeled "RAI 12".RAI 13: Probable Maximum Flood Analysis

Background:

The discussion of the PMF analysis in FHRR Section 3.1 does not adequately describe the overall logic, key assumptions,

methods, inputs, and results.

The NRC staff auditfound that this information is documented, in part, in Calculation Package QDC-0085-S-1 990,"Probable Maximum Flood (PMF) for the Upper Mississippi River Watershed Contributory toQCNGS."Request:

Provide the following portions of QDC-0085-S-1990:

" Main text (Pages 1-73)" Attachment 1, Figures" Attachment 6, Nonlinearity Adjustment

" Attachment 8, Muskingum-K Estimates Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 27 of 55Also provide electronic editable files for the following:

" NRCS Soil Data (QDC-0085-S-1 990, Attachment 4)* USGS Monthly Flow Data (QDC-0085-S-1990, Attachment 5)* Input and Output files for the HEC-HMS hydrologic model calibration andverification runs* Input and Output files for the HEC-HMS hydrologic all-season PMF and cool-season PMF simulations

Response

The requested excerpts from Calculation QDC-0085-S-1 990 and electronic editable files areincluded in Enclosure 3 DVD #2A under folder labeled "RAI 13". The computer model namescorresponding to the critical scenarios are specified in Table 13.1.Table 13.1 -Computer Models Corresponding to Probable Maximum Flood -Hydrology AnalysisComputerSoftwareComputer Model Name1. Calibration HEC-HMSHEC-HMSHEC-HMSHEC-HMSHEC-HMSHEC-HMSHEC-HMSHEC-HMSHEC-HMSRAI Response\RAI 13\HEC-HMS\Calibration\Upper-Mississippi-Aug95-Calibration\Upper-Mississippi-Aug95-Cal RAI Response\RAI 1 3\HEC-HMS\Ca-ibrati-n\UpperMississippi-July2 ca Cibration\Upper-Mississippi-July1

-Ca.RAI Response\RAI 13\HEC-HMS\Calibration\UpperMississippiJune04_Calibration\UpperMississippi Jun04_Cal RAI Response\RA113\HEC-HMS\Calibration\UpperMississippiJune08_Calibration\Upper Mississippi_June08_Cal RAI Response\RAI 13\HEC-HMS\Calibration\UpperMississippiJune2002_calibration\Upper MississippiJun02_Cal RAI Response\RA.113\HEC-HMS\Calibration\UpperMississippiMay99_Calibration RAI Response\RAI 13\HEC-HMS\Calibration\Upper Mississippi May2002-Calibration\Upper Mississippi-May2002 CalRAI Response\RA 1 3\HEc-HMS\Ca-ibrati-n\Upper-MississippiO-ct02-Ca-ibration\Upper-Mississippi-ct 2-Ca-lRAI Response\RAI 13\HEC-HMS\Calibration\Upper-Mississippi-Jept94-Calibration\Upper-Mississippi-Sept94Cal HEC-HMSHEC-HMSHEC-HMSHEC-HMSHEC-HMSHEC-HMSHEC-HMSHEC-HMS2. Verification RAI Response\RAI 13\HEC-HMS\Verification\UpperMississippiAug09 Verification\Upper Mississippi-Aug09 VeRAI Response\RAI 1 3\HEC-HM\Verificatin\Upper

-Mississippi-Juy97- Verificatin\Upper-Mississippi

-Juy97 -VeRAI Response\RAI 13\HEC-HMS\Verification\Upper Mississippi July98Verification\Upper Mississippi July98_Ver RAI Response\RA.113\HEC-HMS\Verification\UpperMississippiJune00_Verification\UpperMississippi June00_Ver RAI Response\RAI 13\HEC-HMS\Verification\Upper-Mississippi-May03-Verification\Upper-Mississippi-uMay3-Ver RAI Response\RAI 1 3\HEC-HMSVeri-catin\Upper

-Mississippi-ct0 .-erifiCati.n\Upper Mississippi Oct05_Ver RAI Response\RAI 13\HEC-HMs\Verification\Upper-Mississippi-Oct07-Verification\Upper-Mississippi-uct7 VerRAI Response\RAI 13\HEC-HMs\Verification\Upper-Mississippi-Oct95-Venfication\Upper-Mississippi-Oct95-Ver Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 28 of 55Table 13.1 -Computer Models Corresponding to Probable Maximum Flood -Hydrology Analysis (Continued)

Computer Computer Model NameSoftware3. PMFHEC-HMS RAI Response\RAI 13\HEC-HMS\PMF\AIlSeasonatWClinton HEC-HMS RAI Response\RAI 13\HEC-HMS\PMF\AIISeasonPMF at AnokaHEC-HMS RAI Response\RAI 13\HEC-HMS\PMF\CooI_Season_PMF atAcreoka HEC-HMS RAI Response\RAI 13\HEC-HMS\PMF\CooI_Season_PMF atClitonhe HEC-HMS RAI Response\RAI 13\HEC-HMS\PMF\ACooSeasonPMF-atWMcGregor HEC-HMS RAI Response\RAI 13\HEC-HMS\PMF\CooI_SeasonPMF at Watershed REC-HMS RAI Response\RAI 13\HEC-HMS\PMF\oAII_Season_PMF_avtWinona HEC-HMS RAI Response\RAI 13\HEC-HMS\PMF\CooI_SeasonPMF-at-Anoka HEC-HMS RAI Response\RAI 13\HEC-HMS\PMF\CooliSeasonPMFHat-Clinton HEC-HMS RAI Response\RAI 13\HEC-HMS\PMF\CooISeasonPMF-at Watershed HC-RMS RAI Response\RAI 13\HEC-HMS\PMF\CoolSeasonPMF at-Winona

---HEC---f H_ M S_-- -- -- RAI -R-e-s-p-ons-e"\,R-,Ai13-\"H-EC--H-M-S,\,PM,"C"ooI_'Sea-sonPM'F_"M-oving HEC-HMS RAI Response\RAI 13\HEC-HMS\PMF\Nonlinear_UH RAI 14: Flooding on Streams and Rivers -Cool-Season Baseflow

Background:

FHRR Section 3.1 states that streamflow data for March was used to estimate thecool-season mean monthly basef low. Stream data for April was not used. The stated rational foromitting the April data was to avoid double-accounting for April snow melt.Reauest:

Provide justification for the inclusion of baseflow values for March instead of April, withconsideration of the likelihood that streamflows for both months result from a combination ofsnowmelt and rainfall.

Response

The March basef low was conservatively used to reflect the river condition prior to the onset ofthe combined cool season probable maximum precipitation (PMP)/April snowmelt event. Basedon review of historical streamf low data, the April basef low is significantly larger than winter(December through March) baseflow, likely indicating the additional influence of snowmelt.

Theclimate conditions necessary to accumulate and preserve a 100-year snowpack for an AprilPMP across the entirety of the Quad Cities Nuclear Power Station (QOCNPS) watershed wouldnot be the conditions necessary to simultaneously melt the same snowpack prior to the PMPthat lead to a typically high April baseflow.

These conditions would likely involve an abundance of snowfall combined with the necessary cold to preserve/avoid losing snowpack to snow melt inmonths prior to April. The objective of the cool season probable maximum flood (PMF) analysiswas to preserve a ripe 100-year snowpack that would melt rapidly due to the cool season PMP(i.e., rain-on-snow).

April baseflow was therefore excluded specifically so as to not doublecount snowmelt.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 29 of 55Consideration was given to exclude both March and April to avoid double-counting snowmelteffects.

However, excluding both March and April flows from the calculation for the cool seasonbasef low would result in a reduction of approximately 70 percent, compared to a baseflowcalculated to include both March and April. Therefore, the baseflow from March was allowed toremain as a conservative approach.

RAI 15: Probable Maximum Flood Water Surface Calculations

Background:

The discussion of the PMF water surface calculation in FHRR Section 3.1 does notadequately describe the overall logic, key assumptions,

methods, inputs, and results.

The NRCstaff audit found that this information is documented, in part, in Calculation Package QDC-0085-S-1 991, "Calculation of Probable Maximum Flood (PMF) Water Surface Elevation:

Evaluation ofRiverine Hydraulics for the Upper Mississippi River at QCNGS."Request:

Provide the following portions of QDC-0085-S-1 991:* Main text (Pages 1-32)" Attachment 1, Figures" Attachment 2, Data Conversions

" Attachment 5, Bridge PlansAlso provide electronic editable files for the following:

" Bridge Spreadsheets (QDC-0085-S-1991, Attachment 6)" Stream Flow Data (QDC-0085-S-1991, Attachment 7)" USACE Observed Historical Profiles (QDC-0085-S-1991, Attachment 8)" HEC-RAS hydraulic model input and output files for the calibration floods (QDC-0085-S-1 991, Attachment 9)* HEC-RAS hydraulic model input and output files used for water level simulation resulting from the PMF event reported in FHRR Section 3.1, including those in QDC-0085-S-1991, Attachments 10-14Response:

The requested excerpts from Calculation QDC-0085-S-1 991 and electronic editable files, listedbelow, are included in Enclosure 3 DVD #2A.* Main text (Pages 1-32)* Attachment 1, Figures* Attachment 2, Data Conversions

• Attachment 5, Bridge Plans* Bridge Spreadsheets (QDC-0085-S-1 991, Attachment 6)* Stream Flow Data (QDC-0085-S-1 991, Attachment 7)* USACE Observed Historical Profiles (QDC-0085-S-1 991, Attachment 8)* HEC-RAS hydraulic model calibration profiles (QDC-0085-S-1 991, Attachment

9)

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 30 of 55The requested HEC-RAS input-output files, listed below, are split on 5 DVDs #2B through #2Fdue to file size. The computer model names corresponding to the critical scenarios are specified in Table 15.1. In order for HEC-RAS Calibration model to run, all files from folders labeled"HEC-RAS-Calibration" from DVDs #2B through #2F need to be copied in the same folder." HEC-RAS hydraulic model input and output files for the calibration floods (QDC-0085-S-1991, Attachment 9)* HEC-RAS hydraulic model input and output files used for water level simulation resulting from the PMF event reported in FHRR Section 3.1, including those in QDC-0085-S-1991, Attachments 10-14Additionally, the USACE Observed Historical Profiles (QDC-0085-S-1 991, Attachment

8) aregraphics which are obtained through the USACE River Gages website(http://rivergaqes.mvr.usace.army.mil/WaterControl/new/layout.cfm) and are not available aselectronic editable files. Therefore, Attachment 8 is included in Enclosure 3 DVD #2A in pdfformat under folder labeled "RAI 15".

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 31 of 55Table 15.1 -Computer Models Corresponding to Probable Maximum Flood -Hydrology AnalysisComputer Software Computer Model NameCalibration

-1965 FloodHEC-RAS HEC-RAS -Calibration Project Quad Cities-Mississippi RiverPlan 1965 Flood Calibration

(.p66)Geometry file Calc QCNGS Geometry

(.g09)Unsteady Flow File 1965 Flood (.u30)Output QuadCities-Mississ.dss Calibration

-2001 FloodHEC-RAS HEC-RAS -Calibration Project Quad Cities-Mississippi RiverPlan 2001 Flood Calibration

(.p67)Geometry file Calc QCNGS Geometry

(.g09)Unsteady Flow File 2001 Flood (.u31)Output QuadCities-Mississ.dss Calibration

-1993 FloodHEC-RAS HEC-RAS -Calibration Project Quad Cities-Mississippi RiverPlan 1993 Flood Calibration

(.p68)Geometry file Calc QCNGS Geometry

(.g09)Unsteady Flow File 1993 Flood (.u32)Output QuadCities-Mississ.dss Calibration

-1969 FloodHEC-RAS HEC-RAS -Calibration Project Quad Cities-Mississippi RiverPlan 1969 Flood Calibration

(.p69)Geometry file Calc QCNGS Geometry

(.g09)Unsteady Flow File 1969 Flood (.u33)Output QuadCities-Mississ.dss Calibration

-1997 FloodHEC-RAS HEC-RAS -Calibration Project Quad Cities-Mississippi RiverPlan 1997 Flood Calibration

(.p70)Geometry file Calc QCNGS Geometry

(.g09)Unsteady Flow File 1997 Flood (.u34)Output QuadCities-Mississ.dss Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 32 of 55Table 15.1 -Computer Models Corresponding to Probable Maximum Flood -Hydrology Analysis (Continued)

Computer Software Computer Model NameAll Season PMF -Watershed CentroidHEC-RAS HEC-RAS -PMFProject Quad Cities-Mississippi RiverPlan PMF-AII Season-Watershed Centroid at 291 (.p01)Geometry file Final QCNGS Geometry

(.g 14)Unsteady Flow File PMF-AII Season-Watershed Centroid at 291 (.uOl)Output QCNGS.dss All Season PMF -Clinton Subwatershed CentroidHEC-RAS HEC-RAS -PMFProject Quad Cities-Mississippi RiverPlan PMF-AII Season Clinton Centroid

(.p02)Geometry file Final QCNGS Geometry

(.g14)Unsteady Flow File PMF-AII Season Clinton Centroid

(.u02)Output QCNGS.dss All Season PMF -McGregor Subwatershed CentroidHEC-RAS HEC-RAS -PMFProject Quad Cities-Mississippi RiverPlan PMF-AII Season-McGregor Centroid

(.p03)Geometry file Final QCNGS Geometry

(.g14)Unsteady Flow File PMF-AII Season-McGregor Centroid

(.u03)Output QCNGS.dss All Season PMF -Winona Subwatershed CentroidHEC-RAS HEC-RAS -PMFProject Quad Cities-Mississippi RiverPlan PMF-AII Season-Winona Centroid

(.p04)Geometry file Final QCNGS Geometry

(.g14)Unsteady Flow File PMF-All Season-Winona Centroid

(.u04)Output QCNGS.dss All Season PMF -Anoka Subwatershed CentroidHEC-RAS HEC-RAS -PMFProject Quad Cities-Mississippi RiverPlan PMF-AII Season-Anoka Centroid

(.p05)Geometry file Final QCNGS Geometry

(.g14)Unsteady Flow File PMF-AII Season-Anoka Centroid

(.u05)Output QCNGS.dss Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 33 of 55Table 15.1 -Computer Models Corresponding to Probable Maximum Flood -Hydrology Analysis (Continued)

Computer Software Computer Model NameAll Season PMF -Watershed Centroid Alternative 2HEC-RAS HEC-RAS -PMFProject Quad Cities-Mississippi RiverPlan PMF-AII Season-Watershed Centroid at 254 (.p09)Geometry file Final QCNGS Geometry

(.g14)Unsteady Flow File PMF-AII Season-Watershed Centroid at 254 (.u06)Output QCNGS.dss All Season PMF -Nonlinear HEC-RAS HEC-RAS -PMFProject Quad Cities-Mississippi RiverPlan PMF-All Season-Nonlinear

(.pl0)Geometry file Final QCNGS Geometry

(.g14)Unsteady Flow File PMF-AII Season-Nonlinear

(.u07)Output QCNGS.dss All Season PMF -Moving StormHEC-RAS HEC-RAS -PMFProject Quad Cities-Mississippi RiverPlan PMF-AII Season-Moving Storm (.p52)Geometry file Final QCNGS Geometry

(.g14)Unsteady Flow File PMF-AII Season-Moving Storm (.u35)Output QCNGS.dss Cool Season PMF -Moving StormHEC-RAS HEC-RAS -PMFProject Quad Cities-Mississippi RiverPlan PMF-Cool Season-Moving

(.p56)Geometry file Final QCNGS Geometry

(.g14)Unsteady Flow File PMF-Cool Season-Moving

(.u38)Output QCNGS.dss Cool Season PMF -Watershed CentroidHEC-RAS HEC-RAS -PMFProject Quad Cities-Mississippi RiverPlan PMF-Cool Season Centroid

(.p57)Geometry file Final QCNGS Geometry

(.g14)Unsteady Flow File PMF-Cool Season Centroid

(.u39)Output QCNGS.dss Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 34 of 55Table 15.1 -Computer Models Corresponding to Probable Maximum Flood -Hydrology Analysis (Continued)

Computer Software Computer Model NameCool Season PMF -Nonlinear HEC-RAS HEC-RAS -PMFProject Quad Cities-Mississippi RiverPlan PMF-Cool Season-Nonlinear-McGregor

(.p58)Geometry file Final QCNGS Geometry

(.g14)Unsteady Flow File PMF-Cool Season-Nonlinear-McGregor

(.u40)Output QCNGS.dss Cool Season PMF -Winona Subwatershed CentroidHEC-RAS HEC-RAS -PMFProject Quad Cities-Mississippi RiverPlan PMF-Cool Season-Winona Centroid

(.p59)Geometry file Final QCNGS Geometry

(.g14)Unsteady Flow File PMF-Cool Season-Winona Centroid

(.u41)Output QCNGS.dss Cool Season PMF -Anoka Subwatershed CentroidHEC-RAS HEC-RAS -PMFProject Quad Cities-Mississippi RiverPlan PMF-Cool Season-Anoka Centroid

(.p60)Geometry file Final QCNGS Geometry

(.g14)Unsteady Flow File PMF-Cool Season-Anoka Centroid

(.u42)Output QCNGS.dss Cool Season PMF -Clinton Subwatershed CentroidHEC-RAS HEC-RAS -PMFProject Quad Cities-Mississippi RiverPlan PMF-Cool Season-Clinton Centroid

(.p61)Geometry file Final QCNGS Geometry

(.g14)Unsteady Flow File PMF-Cool Season-Clinton Centroid

(.u43)Output QCNGS.dss Cool Season PMF -McGregor Subwatershed CentroidHEC-RAS HEC-RAS -PMFProject Quad Cities-Mississippi RiverPlan PMF-Cool Season-McGregor Centroid

(.p61)Geometry file Final QCNGS Geometry

(.g14)Unsteady Flow File PMF-Cool Season-McGregor Centroid

(.u43)Output QCNGS.dss Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 35 of 55RAI 16: Flooding on Streams and Rivers -Manning's n Roughness Coefficient

Background:

The description of the PMF analysis in FHRR Section 3.1 states that theManning's n roughness coefficient was the main parameter adjusted during HEC-RAS hydraulic model calibrations.

However, the FHRR does not adequately describe how this adjustment wasperformed or discuss the adequacy of the final coefficient values.Request:

Provide additional details on the initial and final values of Manning's n roughness coefficient, and describe how those values compare with recommended values in standardreferences for site conditions existing in the watershed.

For example, provide a table similar toTable 1 in the LIP evaluation report, which includes the type of surface coverage and the extentof coverage.

Response

Initial Manning's Roughness Coefficients for the Mississippi River, Apple River, Wapsipinicon River, and Rock River originated from the UNET model included as part of the U.S. Army Corpsof Engineers (USACE) Upper Mississippi River System Flow Frequency Study and were verifiedusing published guidance for selection of Manning's Roughness Coefficients based on Chow,1959 (Reference 1). The Manning's Roughness Coefficient was used as a calibration parameter.

Initial and final values (calibrated) of Manning's Roughness Coefficients betweenLock & Dam No. 13 (cross section 522.5) and Lock & Dam No. 14 (cross section 493.4) aretabulated in Table 16.1. Quad Cities Nuclear Power Station (QCNPS) is located at section 506.9(Mississippi River, Reach #11), which crosses the northern portion of QCNPS. Manning's Roughness Coefficients set as follows:1. Cap Manning's Roughness Coefficients values to 0.10 for the developed areas (i.e.,residential, commercial and industrial areas)2. Use Manning's Roughness Coefficient with 0.08 for forest areas. Chow, 1959recommend Manning's Roughness Coefficients in the range of 0.080 to 0.120 for forestareas.3. Use Manning's Roughness Coefficient values within 0.03 for agriculture areas. Chow,1959 recommends Manning's Roughness Coefficients in the range of 0.030 to 0.050 foragricultural areas.As discussed above, for some cross sections the lower end of Manning's roughness coefficients from Chow, 1959 were used. However, for calibration

purposes, the Manning roughness coefficients were adjusted to better match computed profiles to observed historical watersurface elevations.

The results of the QCNPS HEC-RAS model calibration (Table 16.2) showthat four of the simulated calibration floods (1965, 2001, 1993, and 1969) generated a peakwater surface elevation at QCNPS within 0.5 foot of the observed elevations, and onecalibration flood (1997) slightly exceeded the target elevation difference by 0.2 foot (i.e., +0.7foot difference between simulated and observed).

Based on the calibration

results, theQCNPS model is judged to be acceptably calibrated.

Using the higher end values would bemore conservative, but the results would deviate from observed elevation and would not beconsidered sound calibration.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 36 of 55Based on a visual examination of aerial photographs of the QCNPS watershed, mainlyresidential, commercial, industrial, and forested areas exist (see Figures 16.1 through 16.4). Incoomparison to published values in Chow, 1959, the calibrated Manning's roughness coefficients are representative of the site conditions existing in the QCNPS watershed.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 37 of 55Table 16.1 Comparison of UNET and Calibrated Manning's Roughness Coefficients Final (Calibrated Manning's Roughness Initial Manning's Roughness Coefficients Coefficients)

(USACE UNETLeft Right RightRiver River Station Overbank Channel Overbank Left Overbank Channel Overbank522.5 L&D 13 TAILMISSISSIPPI

-RM 0.03 0.0275 0.08 0.04 0.025 0.08MISSISSIPPI 522.4 0.03 0.0275 0.077 0.04 0.025 0.07MISSISSIPPI 522.3 0.03 0.0275 0.077 0.04 0.025 0.07MISSISSIPPI 522.2 0.03 0.0275 0.077 0.04 0.025 0.07MISSISSIPPI 521.7 0.03 0.0275 0.1 0.04 0.025 0.1MISSISSIPPI 521.2 0.1 0.0275 0.1 0.1 0.025 0.12MISSISSIPPI 521 0.1 0.0275 0.1 0.04 0.025 0.12MISSISSIPPI 520.6 0.1 0.0275 0.1 0.04 0.025 0.12MISSISSIPPI 520.4 0.1 0.0275 0.1 0.04 0.025 0.12MISSISSIPPI 520 0.03 0.0275 0.1 0.04 0.025 0.12MISSISSIPPI 519.95 0.03 0.0275 0.1 0.04 0.025 0.12MISSISSIPPI 519.9 0.03 0.0275 0.1 0.04 0.025 0.12MISSISSIPPI 519.75* 0.03 0.0275 0.08 0.04 0.025 0.12MISSISSIPPI 519.6 0.03 0.0275 0.1 0.04 0.025 0.12MISSISSIPPI 519.1 0.03 0.0275 0.1 0.04 0.025 0.12MISSISSIPPI 518.4 0.03 0.0275 0.1 0.04 0.025 0.12MISSISSIPPI 518.15 0.03 0.0275 0.1 0.04 0.025 0.12MISSISSIPPI 518.1 0.055 0.0275 0.1 0.05 0.025 0.12MISSISSIPPI 518.05 0.055 0.0275 0.1 0.04 0.025 0.12518 CLINTON -MISSISSIPPI RM 518 0.03 0.0275 0.1 0.04 0.025 0.12MISSISSIPPI 517.95 0.03 0.0275 0.1 0.04 0.025 0.12MISSISSIPPI 517.7 0.077 0.0275 0.1 0.07 0.025 0.12MISSISSIPPI 517 0.03 0.0275 0.1 0.04 0.025 0.12MISSISSIPPI 516.6 0.03 0.0275 0.1 0.04 0.025 0.12MISSISSIPPI 516 0.055 0.0275 0.1 0.12 0.025 0.12MISSISSIPPI 515.5 0.055 0.0275 0.1 0.05 0.025 0.12MISSISSIPPI 515 0.066 0.0275 0.1 0.06 0.025 0.12MISSISSIPPI 514.4 0.066 0.0275 0.1 0.06 0.025 0.12MISSISSIPPI 514 0.03 0.0275 0.1 0.06 0.025 0.04MISSISSIPPI 513 0.1 0.0275 0.03 0.04 0.025 0.04MISSISSIPPI 512.7 0.03 0.0275 0.03 0.04 0.025 0.04512 CAMANCHEMISSISSIPPI DS -RM 0.03 0.0275 0.03 0.04 0.025 0.04 Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 38 of 55Table 16.1 Comparison of UNET and Calibrated Manning's Roughness Coefficients (Continued)

Final (Calibrated Manning's Roughness Initial Manning's Roughness Coefficients Coefficients)

(USACE UNETLeft Right RightRiver River Station Overbank Channel Overbank Left Overbank Channel Overbank511.6 CAMANCHEMISSISSIPPI

-FLOW 0.03 0.0275 0.03 0.04 0.025 0.04MISSISSIPPI 511 0.03 0.0275 0.03 0.04 0.025 0.04MISSISSIPPI 510.1 0.03 0.0275 0.066 0.04 0.025 0.06MISSISSIPPI 509.3 0.03 0.0275 0.03 0.04 0.025 0.06MISSISSIPPI 509 0.03 0.0275 0.03 0.04 0.025 0.06MISSISSIPPI 508.6 0.03 0.0275 0.03 0.04 0.025 0.04MISSISSIPPI 507.9 0.03 0.0275 0.03 0.04 0.025 0.05MISSISSIPPI 507.4 0.03 0.0275 0.03 0.04 0.025 0.06MISSISSIPPI 506.9 (QCNPS) 0.03 0.0275 0.08 0.09 0.025 0.08MISSISSIPPI 506 0.99 0.0275 0.03 0.09 0.025 0.08MISSISSIPPI 505.5 0.066 0.0275 0.03 0.06 0.025 0.04MISSISSIPPI 505 0.03 0.0275 0.03 0.04 0.025 0.04MISSISSIPPI 504 0.03 0.0275 0.03 0.04 0.025 0.04MISSISSIPPI 503.3 0.03 0.0275 0.03 0.04 0.025 0.04MISSISSIPPI 503.1 0.03 0.0275 0.03 0.04 0.025 0.05MISSISSIPPI 502.9 0.03 0.0275 0.03 0.04 0.025 0.04MISSISSIPPI 502.5 0.099 0.0275 0.1 0.09 0.025 0.12502 PRINCETON MISSISSIPPI

-RM 5 0.1 0.0275 0.1 0.12 0.025 0.12MISSISSIPPI 501.74 0.08 0.0275 0.1 0.08 0.025 0.12MISSISSIPPI 501.5 0.055 0.0275 0.1 0.05 0.025 0.12MISSISSIPPI 501 0.08 0.0275 0.1 0.08 0.025 0.11MISSISSIPPI 500.5 0.1 0.0275 0.055 0.12 0.025 0.05MISSISSIPPI 500 0.1 0.0275 0.1 0.1 0.025 0.12MISSISSIPPI 499.5 0.1 0.0275 0.1 0.1 0.025 0.12MISSISSIPPI 499 0.1 0.0275 0.1 0.12 0.025 0.12MISSISSIPPI 498.5 0.1 0.0275 0.055 0.12 0.025 0.05MISSISSIPPI 498 0.1 0.0275 0.1 0.12 0.025 0.12497.1 LECLAIRE

-MISSISSIPPI RM 49 0.1 0.0275 0.1 0.12 0.025 0.12MISSISSIPPI 496.8 0.1 0.0275 0.1 0.12 0.025 0.12MISSISSIPPI 496.5 0.1 0.0275 0.1 0.12 0.025 0.12MISSISSIPPI 496 0.1 0.0275 0.1 0.12 0.025 0.12 Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 39 of 55Table 16.1 Comparison of UNET and Calibrated Manning's Roughness Coefficients (Continued)

Final (Calibrated Manning's Roughness Initial Manning's Roughness Coefficients Coefficients)

(USACE UNETLeft Right RightRiver River Station Overbank Channel Overbank Left Overbank Channel OverbankMISSISSIPPI 495.3 0.1 0.0275 0.1 0.12 0.025 0.12MISSISSIPPI 495 0.1 0.0275 0.1 0.12 0.025 0.12MISSISSIPPI 494.6 0.1 0.0275 0.1 0.12 0.025 0.12MISSISSIPPI 494 0.1 0.0275 0.1 0.1 0.025 0.12493.4 L&D 14MISSISSIPPI POOL 0.1 0.0275 0.1 0.11 0.025 0.12Table 16.2: Observed versus Predicted Water Surface Comparison Flood Elevation, ft (MSL 1912) Difference Modeled_._ Observed X-Section 506.9 (feet)1965 586.0 586.2 0.22001 584.9 584.4 -0.51993 584.2 584.1 -0.11969 583.0 583.0 0.01997 582.5 583.2 0.7 Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 40 of 55Figure 16.1: HEC-RAS Cross Sections Locations on Top Of Topographic Map (CrossSection 522.5 to 512.7)

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 41 of 55LegendGZA HEC-RAS Cross Sections-- GZA Cross Sections Verticaly ExtendedImported Cross Sections from UNET ModelIIINCH = 1 MILE0-5 1SOURCE: This rma contains the ESRI ArcG4S Online USA TooMaps service, revised June 15. 2012 by ESIRI ARCIMS Services-The service includes seamless.

scanned images of United StatesFigure 16.2: HEC-RAS Cross Sections Locations on Top Of Topographic Map (CrossSection 512.7 to 506)

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 42 of 55Figure 16.3: HEC-RAS Cross Sections Locations on Top Of Topographic Map (CrossSection 512 to 498)

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 43 of 55I1 INCH!=MIE 0.5 1 r2M.ies'ISOURCE: This map contains the ESR1 ArcGIS Online USA Topo10Maps service.

revised June 15,2012 by ESR1 ARCIMS ServicesThe swvce includes seamless.

scanned knages of United StatesGeological Survey (USGS) paper topographic mnaps.I WL I I I I ý Wý ý I ý_I.L GZA H-EC-RA Cross SectionsSGZA Cross Sections Vertically ExtendedImported Cross Sections from UNET ModelFigure 16.4: HEC-RAS Cross Sections Locations on Top Of Topographic Map (CrossSection 498 to 488)

References:

1. Open-Channel Hydraulics, Ven Te Chow, Reprint of the 1959 Edition, McGraw Hill BookCompany.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 44 of 55RAI 17: Dam Failure -Supporting Analysis and Electronic Files

Background:

The discussion of the upstream dam failure flood analysis in FHRR Section 3.2does not adequately describe the key assumptions,

methods, and results.

The NRC staff auditfound that this information is documented, in part, in Calculation Package QDC-0085-S-2032, "Upstream Dam Failure Flood Evaluations at QCNGS."Request:

Provide the following portions of QDC-0085-S-2032:

• Main text (Pages 1-49)* Attachment 1, Figures* Attachment 3, Dams Information

• Attachment 4, Datum Conversions

• Attachment 5, Reservoir Storage Information

• Attachment 7, Muskingum-Cunge Parameters Also provide electronic editable files for the following:

• QDC-0085-S-2032, Attachment 2, Major Dams in Watershed

• QDC-0085-S-2032, Attachment 10A, NID Subwatershed Dams* HEC-RAS hydrologic model and HEC-RAS hydraulic model input and output filesused for surface flow modeling of the individual and cascading dam failure eventsdiscussed in FHHR Enclosure 2, Section 3.2* HEC-RAS hydrologic model input and output files used for the screening analysis forfailure of all dams in the upstream watershed (i.e., Approach

2) discussed in FHHRSection 3.2Response:

The requested excerpts from Calculation QDC-0085-S-2032 and electronic editable files areincluded in Enclosure 3 DVD #2A under folder labeled "RAI 17". The computer model namescorresponding to the critical scenarios are specified in Table 17.1.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 45 of 55Table 17.1 -Computer Models Corresponding to Dam Failure AnalysisC om puterC o p t r M d l N mSoftware IoptrMdlNm Approach 1 -Hydrologic HEC-HMS HEC-HMS Approach 1\QCNGSDamFailures HEC-RAS HEC-RAS Approach 1 \Dam FailureModel-Delivered_5-27-14 Project QCNGS-Dam FailurePlan Hydrologic (PMF) Dam Failure (.p08)Geometry file Final QCNGS Geometry

(.g14)Unsteady FlowFile Hydrologic (PMF) Dam Failure (.u78)Approach 1 -SeismicHEC-HMS HEC-HMS Approach 1\QCNGSDamFailures HEC-RAS HEC-RAS Approach 1 \Dam FailureModel-Delivered_5-27-14 Project QCNGS-Dam FailurePlan Seismic Day-Dambreak Dam 13 (.p22)Geometry file Final QCNGS Geometry

(.g14)Unsteady FlowFile Seismic Dam Failure (.u79)Approach 1 -Sunny DayHEC-HMS HEC-HMS Approach 1\QCNGSDamFailures HEC-RAS HEC-RAS Approach 1 \DamFailureModel-Delivered_5-27-14 Project QCNGS-Dam FailurePlan Sunny Day-Dam Failure (.p17)Geometry file Final QCNGS Geometry

(.g14)Unsteady Flow Sunny Day Dam Failure (.u77)File Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 46 of 55Table 17.1 -Computer Models Corresponding to Dam Failure Analysis (Continued)

Computer lComputer Model NameSoftware IApproach 2 -Hydrologic HEC-HMS HEC-HMS Approach 2\HypotheticalDamPMF HEC-RAS HEC-RAS Approach 2Project QCNGS Dam Failure CombinedPlan PMF Dambreak Dam Combined

(.p14)Geometry file Final QCNGS Geometry

(.g14)Unsteady Flow PMF-Cool Season-McGregor Centroid

(.u82)FileApproach 2 -SeismicHEC-HMS HEC-HMS Approach 2\HypotheticalDamSeismic HEC-RAS HEC-RAS Approach 2Project QCNGS Dam Failure CombinedPlan Seismic Dam Failure (.p15)Geometry file Final QCNGS Geometry

(.g14)Unsteady Flow Seismic Dam Failure(.u83)

FileRAI 18: Dam Failure -Large Dam Criteria

Background:

Many dam safety agencies consider dams over 50 ft in height as "large dams."However, the dam failure flood analysis reported in FHRR Section 3.2 limited consideration todams over 60 feet in height (labeled "significant" dams). The limitation to dams over 60 feet inheight may potentially exclude some dams that could have a significant impact on estimated flood levels due to dam failure.Request:

Provide justification for limiting consideration to dams over 60 feet in height in the damfailure flood analysis.

Response

There are approximately 236 major dams in the watershed contributory to Quad Cities NuclearPower Station (QCNPS),

based on the criteria used in National Atlas database.

National Atlascriteria for major dams is -"Major dams include dams 50 feet or more in height, dams with anormal storage capacity of 5,000 acre-feet or more, and dams with a maximum storage capacityof 25,000 acre-feet or more."The criterion for major dams described in the National Atlas was used in selection of damswithin 100 miles. All dams within a 100 mile radius of QCNPS that meet the major dam criteriawere included in the dam failure analysis.

Only two dams within the 100 miles radius have a Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 47 of 55height between 50 feet and 60 feet with normal storage capacity of 163 acre-feet and 670 acre-feet, and with maximum storage capacity of 325 acre-feet and 2,130 acre-feet respectively.

Thenormal and maximum storage capacities for these two dams are well below the major damcriteria described in the National Atlas.Therefore, there are no dams within the 100 mile radius, between 50 feet to 60 feet heightrange, which meets the major dam criteria described in the National Atlas for normal andmaximum storage.

The minimum dam height in the QCNPS watershed that meets the NationalAtlas criteria for major dams is 60 feet, therefore, 60 feet was listed as the limiting criteria for theQCNPS watershed in the FHRR.In summary, the major dams criteria described in National Atlas was considered in selecting individual dams for the dam failure analysis.

Based on the database in National Inventory of Dams and the National Atlas, most dams in thewatershed are relatively low-head or low-storage due to the limited topographic relief in thewatershed.

Dams located more than 100 miles upstream were determined to not significantly contribute topeak flooding at QCNPS. This is because dam failure flood waves attenuate as they traveldownstream, and the flood-carrying capacity of the Mississippi River and its 88,000 square-miles drainage area at QCNPS is able to accommodate significant flow below site gradeelevation (Calculation No. QDC-0085-S-1992).

Eau Galle Reservoir is the largest dam in the QCNPS watershed lies within 250 miles ofQCNPS. Based on a combination of height and storage, Eau Galle Reservoir Dam wasincorporated into the dam failure analysis.

The 127-foot high Eau Galle Reservoir Dam is thelone dam in the watershed with a height of over 100 feet.Additionally, Lock & Dams 11, 12, and 13 were included in the dam failure analysis becausethey are on the Mississippi River within 100 miles of QCNPS. The locks and dams are low-head structures that might be submerged during flood conditions, which would result in relatively minor dam breach flood flows. A domino failure of the three lock dams plus the dam breachflows (plus flood flows, as applicable) from other upstream dams on tributaries to the Mississippi River was used in the dam failure analysis.

RAI 19: Dam Failure -Failure of All Upstream Dams

Background:

FHHR Section 3.2 describes a screening method that considers all upstream damsby lumping them into several hypothetical dams (referred to as Approach 2). However, theFHRR does not adequately describe the modeling decisions made when lumping upstreamdams into hypothetical dams.Request:

Describe how dams were lumped, including justification of any adjustments made tostorage volumes during the lumping process.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 48 of 55Response:

This screening analysis was developed before the publication of the Nuclear Regulatory Commission's (NRC's) Guidance for Assessment of Flooding Hazard Due to Dam Failure, JLD-ISG-2013-01, Revision 0; dated July 29, 2013 was published.

However, this analysisincorporates conservative concepts discussed in JLD-ISG-2013-01.

Two approaches were considered to evaluate flooding from upstream dam failure (Calculation QDC-0085-S-2032).

Approach 1 considered failure of a subset of the upstream dams todevelop a conservative but representative upstream dam failure scenario based on ANSI/ANS2.8 guidance, which states that some dams can be eliminated from dam failure analysis basedon "low head differential, small volume, distance from plant site, and major intervening natural orreservoir detention capacity."

Smaller and more remote dams were excluded in Approach 1 perthe ANSI/ANS 2.8 guidance.

Approach 2 was applied for sensitivity purpose only and introduced additional conservatism by evaluating failure of all 1,558 upstream dams within the watershed, represented in the hydrologic model as hypothetical dams. The NRC Dam Failure Interim StaffGuidance (July, 2013) was released after Quad Cities Flood Hazard Reevaluation report wassubmitted and, therefore, was not applicable to the reevaluation.

The approach was developed based on ongoing discussions, at the time the reevaluation was being conducted, of dam failuremethodology between the NRC and the Nuclear Energy Institute (NEI). The information provided in response to the Request for Information is based on results from Dam FailureApproach

1. Approach 2 was performed only as a sensitivity study and final results are basedon Approach 1.A screening level conservative dam failure analysis was performed for the dams listed in theNational Inventory of Dams (NID) database within the contributory watershed to Quad CitiesNuclear Power Station (QCNPS).

Representative hypothetical dams were created in each ofthe ten sub-watersheds.

Dams that were modeled individually as part of Approach 1, were notincluded in the hypothetical reservoirs/dams.

The Approach 1 dams were failed individually inApproach 2.The geometry and characteristics of the hypothetical dam structures were based on the NIDdatabase, developed and maintained by the U.S. Army Corps of Engineers (USACE).

Thedams were then grouped by sub-watershed.

A single hypothetical reservoir was created foreach sub-watershed and inserted into the HEC-HMS rainfall-runoff model at the outlet of eachrespective sub-watershed.

Each single hypothetical reservoir contains 50 percent of the sum of the NID storage for all theNID dams in a given sub-watershed (excluding the individually modeled dams discussed inApproach 1). The use of 50 percent of the NID storage was selected to account for floodplain

storage, flood control dams within the watershed and the fact that the probable maximumprecipitation (PMP) does not cover the entirety of the large QCNPS watershed at any given time(due to meteorological limitations of the size of the storm). Typically, flood control dams areoperated at a minimum below the maximum storage capacity or empty: in this caseapproximately 20 percent of all the dams located within the QCNPS watershed are flood controlstructures.

It is also noted that a portion of these dams are likely to be designed to withstand flooding such as that experienced during the probable maximum flood (PMF) at QCNPS,particularly since the storm that produces the PMF would not typically produce a dam-specific PMF. However, this was conservatively not considered directly in this evaluation.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 49 of 55The storage represents each reservoir's maximum pool volume or normal pool volume, in theabsence of maximum pool information.

The hypothetical reservoir was represented in HEC-HMS using an elevation versus volume data table. The table included two points: a zero pointat the toe of the dam and 50 percent of the total NID storage volume (in acre-feet) at the top ofthe dam.The top of dam elevation was assigned based on the NID storage-weighted dam height of thedams in a given sub-watershed.

The weighted dam height was calculated as follows:Sum (NID Swroa~e X Dani lleiglht)

Hypothetical Dam Height = (NSr- X Dan Height)(Sum of Total Storajqe)

The toe (i.e., bottom) elevation of the hypothetical dam was set to 0 feet. The top of damelevation was set to be equal to toe of dam elevation plus the hypothetical dam height.The dam breach width and side slope input parameters used for the sub-watershed hypothetical dams were based on published guidance and engineering judgment to represent the disparate locations of the dams within a given sub-watershed.

The average breach width was selected as2.5 times the hypothetical dam height for each dam and the time to failure selected as equal tothe time of concentration for the corresponding sub-watershed.

This represents the travel timeand a portion of the attenuation of the dam break flood wave as it travels from its actual locationto the outlet of the sub-watershed where the hypothetical dam in HEC-HMS is located.

Theaverage breach width was selected to represent the average breach widths of concrete andearthen embankment dams included in the hypothetical dam.RAI 20: Ice Jam Flooding

-Supporting Information

Background:

The ice jam flooding analysis described in FHRR Section 3.6 does not adequately describe key assumptions,

methods, and results.

The NRC staff audit found that this information is documented, in part, in Calculation Package QDC-0085-S-2033, "Ice-Induced FloodingEvaluation at QCNGS."Request:

Provide the following portions of QDC-0085-S-2033:

• Main text (Pages 1-12)* Attachment 1, Figures* Attachment 3, Stage Flow Rating Curve, including the source for the curveAlso provide electronic editable files for the following:

• USACE Ice Jam Query Results (QDC-0085-S-2033, Attachment 2)* HEC-RAS hydraulic model input and output files for the calculation of water surfaceelevations for the historic,

upstream, and downstream ice jams discussed in FHRRSection 3.6 Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 50 of 55Response:

The requested excerpts from Calculation QDC-0085-S-2033 and electronic editable files areincluded in Enclosure 3 DVD #2A under folder labeled "RAI 20". The computer model namescorresponding to the critical scenarios are specified in Table 20.1. The stage flow rating curvefrom Attachment 3 of Calculation QDC-0085-S-2033 is provided as Figure 20.1. The stage flowrating curve was developed using the USGS stream gage data and the HEC-RAS modeldeveloped as part of the Calculation QDC-0085-S-1 991. Information on the rating curve inFigure 20.1 below beyond the theoretical maximum stillwater flood elevation of 600.9 MSL 1912is not valid and should not be used. Meteorological and hydrological data does not support aflood of greater magnitude.

Note also that the recurrence interval estimates shown on Figure20.1 were developed in Calculation QDC-0085-S-1992 based on a simplified extrapolation of aLog-Pearson Type III probability distribution function.

The methods used in this calculation follow guidance in USGS Bulletin 17B (Reference

1) but did not involve a rigorous andcomprehensive probabilistic flood hazard assessment.

605600595~5900C585580575I L 150,000,000-Year I...--- -'-_.. .. 100,000,000-Year

_ iii + 1___ _ ._ _ _____________

-I

-..Q.7- '> ' '-T-- .10 ,000,0-Y-reL

__1- ___1_F _ I I__I___7 100 ,000-Yea 1 -K -S10,0 00Year.itJillFiiiI O Eear~ iL LLIL1 -A--H-____ý __Hfl !.IKII+V2 -Year L jj5ii9 LI zr-100,000 200,000300,000 400,000 500,000Flow at QCNGS (cfs)600,000 700,000800,000900,000Figure 20.1 -Stage Flow Rating Curve for QCNPS Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 51 of 55Table 20.1 -Computer Models Corresponding to Upstream Ice Jam Failure AnalysisSofptwaer T Computer Model NameIce Jam FailureHEC-RAS RAI Response\RAI 20\HEC-RAS Project QDCNGSUppstream-lce JamPlan Constant37000

(.p09)Geometry file Final QCNGS Geometry-UpstreamlCEJAM

(.g02)Unsteady Flow File Constant37000

(.u05)Output QDCNGSUpstream-lce.dss

References:

1. U.S. Department of the Interior Geological Survey, "Guidelines for Determining FloodFlow Frequency Bulletin

1. 17B", September 1981RAI 21: Ice Jam Flooding

-Ice Jam Locations

Background:

NUREG/CR-7046, "Design-Basis Flood Estimation for Site Characterization atNuclear Power Plants in the United States of America,"

November 2011 (ADAMS Accession No.ML1 1321A1 95), recommends that the size and location of the jam or dam and its breachparameters should be postulated conservatively to maximize the flood caused by release ofimpounded water. In part, this should include an examination of locations that may besusceptible to ice jam formation.

The most common location for ice jam formation is a reachwhere the river slope decreases significantly.

Other common locations include river bends andareas of obstructions, such as a bridge or dam piers. Confluences of tributary streams withlarger rivers or confluences of rivers with lakes or reservoirs are also prone to ice jam formation.

However, FHRR Section 3.6 identifies the first upstream and downstream bridge with no rationalgiven for choosing these locations.

Request:

Provide the rational for choosing to locate the ice jams at the first upstream anddownstream bridges giving consideration to the common ice jam formation locations discussed above.Response:

The Mississippi River near Quad Cities Nuclear Power Station (QCNPS) is regulated fornavigational purposes and is not prone to significant hydraulic changes.

QCNPS is locatedadjacent to Pool 14 of the Mississippi River, at river mile 506.9. Pool 14 spans 29.2 miles fromupstream Lock & Dam 13 located at river mile 522.5 to Lock & Dam 14 located at river mile493.3. From river mile 522.5 to 497 the slope of the Mississippi River is 0.13 feet per mile andfrom river mile 497 to 493.3 the slope is 1.5 feet per mile (Reference 1). Therefore, there is nosignificant decrease in slope within Pool 14.

Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 52 of 55There are two bends in the river within Pool 14, at approximately river mile 516 and 497:a. The upstream bend (river mile 516) is located 2.1 miles downstream from the US 30bridge (the upstream bridge where the ice jam was assumed to form). The results fromthe upstream ice jam failure at the US 30 bridge resulted in a flood elevation of 573.7feet at QCNPS, 21.3 feet below site grade. The formation of the historic ice jam 2.1miles further downstream would not result in an appreciable increase in the floodelevation at QCNPS. In addition, the bridge would more likely be the location for thebuild-up of ice rather than the bend in the natural river section due to obstructions fromthe bridge in the river.b. The normal pool at the downstream bend (river mile 497) is equal to the normal pool atthe US 80 bridge (the downstream bridge where the ice jam was assumed to form atriver mile 495.4). The peak water surface elevation was calculated as the normal pool atQCNPS combined with the depth of the backwater resulting from the downstream icejam. The depth of the backwater from a downstream ice jam was equal to the height ofthe ice jam. Therefore, the depth of backwater and the resulting water surface elevation would be equal regardless of the location of the downstream ice jam (either at thedownstream bend or at the US 80 bridge).The confluence of the Wapsipinicon River is located at river mile 506.9, on the opposite bankfrom QCNPS. The normal pool at river mile 506.9 is equal to the normal pool at the US 80Bridge (the downstream bridge where the ice jam was assumed to form at river mile 495.4).The peak water surface elevation was calculated as the normal pool at QCNPS combined withthe depth of the backwater resulting from the downstream ice jam. The depth of the backwater from a downstream ice jam was equal to the height of the ice jam. Therefore, the depth ofbackwater and the resulting water surface elevation would be equal regardless of the location ofthe downstream ice jam (either at the confluence of the Wapsipinicon River or at the US 80bridge).

References:

1. Lock and Dam No. 14 Master Water Control Manual -Mississippi River Nine-Foot Channel Navigation Project-Appendix 14, U.S. Army Corps of Engineers, October 2002.RAI 22: Combined Effects -Supporting Information

Background:

The discussion of the combined effect flood analysis in FHRR Section 3.8 does notadequately describe the key assumptions,

methods, and results.

The NRC staff audit found thatthis information is documented, in part, in Calculation Package QDC-0085-S-2034, "Combined Events Flood Assessment at QCNGS."Request:

Provide the following portions of QDC-0085-S-2034:

• Main text (Pages 1-28)* Attachment 1, Figures* Attachment 3, 2-Minute Wind Speed Calculation and Formulas Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 53 of 55Response:

The requested excerpts from Calculation QDC-0085-S-2034 are included Enclosure 3 DVD #2Aunder folder labeled "RAI 22".RAI 23: Combined Effects -Waves

Background:

The discussion of the combined effect flood analysis in FHRR Section 3.8 statesthat the licensee used engineering judgment and information on topography and bathymetry ofthe Mississippi River bottom to determine that waves will not break at or near the QCNPS site,thus eliminating the need to calculate the wave set up.Request:

Provide the topography and bathymetry of the Mississippi River in the vicinity ofQCNPS site associated with this conclusion in FHRR Section 3.8.Response:

Topographic and bathymetric input data for the wind-wave calculation were derived from theQuad Cities Nuclear Power Station (QCNPS) probable maximum flood (PMF) HEC-RAS model.Two cross sections from the PMF HEC-RAS model intersect QCNPS: cross sections at rivermile 506.9 and 506.0. The HEC-RAS model was initiated by importing the geometry file fromthe UNET hydraulic model, developed as part of the Upper Mississippi River System FlowFrequency Study by the U.S. Army Corps of Engineers (USACE).

The UNET model wasobtained from the Rock Island District of the USACE. The cross section information from theUNET model was converted to HEC-RAS format. The imported UNET cross section elevation data was validated through visual comparison of elevations with USGS quadrangle topographic mapping data (Reference

1) and USACE hydrographic data (Reference 2).The requested topography and bathymetry files along with UNET input files are included inEnclosure 3 DVD #2A under folder labeled "RAI 23".References

1. Quadrangle Topographic Maps 7.5 Minute Series, U.S. Geological Survey. The mapimages were downloaded from three sources:* Illinois Natural Resources Geospatial Data Clearinghouse.

(http://crystal.isgs.uiuc.edu/nsdihome/webdocs/drgs/drgorder24bymap.html).

" Iowa Natural Resources Geographic Information Systems Library.(http://www.igsb.uiowa.edu/nraislibx/).

" Wisconsin Department of Natural Resources Geographic Information Systems.(http://dnr.wi.gov/maps/gis/datadrq.html#data)

2. Hydrographic Surveys of the Mississippi River, USACE Rock Island District.

http://www2.mvr.usace.army.mil/odrsurvey/default.cfm Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 54 of 55RAI 24: Combined Effects -Clarification of Scenarios

Background:

In the combined effects flood analysis (FHRR Section 8) the licensee brieflydescribes three alternatives with respect to floods caused by precipitation events and twoalternatives with respect to floods caused by seismic dam failure and states that the alternatives are "described in detail earlier".

However, it is not clear where the alternatives are described inearlier sections of the document.

Further, the discussion in this section did not provide a clearrational for why the described alternatives were selected and why others were excluded.

Request:

Clarify how the alternatives discussed in this section relate to scenarios, alternatives and approaches described in earlier sections of the document.

Provide a clear and detaileddescription of how the alternatives used in the combined event analysis were selected.

Response

Quad Cities Nuclear Power Station (QCNPS) is located on the eastern bank of the Mississippi River approximately 506.8 miles upstream of the confluence of the Ohio River with theMississippi River. Topographic relief at the site is low and relatively flat, with a mean stationelevation of about 595 feet, mean sea level (MSL) 1912. The site is located approximately equidistant between Lock & Dam Nos. 13 and 14, which are owned and operated by the U.S.Army Corps of Engineers (USACE).NUREG/CR-7046 Design-Basis Flood Estimation for Site Characterization at Nuclear PowerPlants in the United States of America (NUREG/CR-7046) recommends various scenarios (Appendices H.1 through H.5) for analyzing combined effect floods.The flood hazard at QCNPS is due to the Mississippi River, therefore all alternatives from thecombined events listed in NUREG/CR-7046 Appendix H.1 and H.2 are considered for QCNPS.The QCNPS is not located along an open or semi-enclosed body or enclosed body of water.Therefore, the combinations listed in NUREG/CR-7046 Appendices H.3 and H.4 are notapplicable to QCNPS. Analysis of flooding along the shores of an open, semi-enclosed, orenclosed body of water was not performed.

Similarly, QCNPS is not located along a coast.Therefore, the combinations listed in NUREG/CR-7046 Appendix H.5 are not applicable toQCNPS. Analysis of flooding caused by tsunamis was not performed as tsunami flooding is notan applicable hazard.Section 1 .c of the Flood Hazard Reevaluation Report (FHRR) provides the methodology, approach and results from the three alternatives (All-Season PMF, Probable MaximumSnowpack and 100-Year Cool-Season

Rainfall, and 100-Year Snowpack and Cool-Season PMP) listed in NUREG/CR-7046 Appendix H.1, without hydrologic dam failure and addedeffects of wind-wave.

As discussed in Section 1 .d of the FHRR, Alternative 3 of Combination H.1 provides the controlling PMF still water surface elevation.

Alternatives listed in Combination H.1 are evaluated in Calculations QDC-0085-S-1990 and QDC-0085-S-1991, without the effectsof dam failure and wind-wave activity.

Hydrologic dam failure in combination with Alternative 3 of Combination H.1 provides thecontrolling still water surface elevation of all dam failure scenarios.

Section 2 of the FHRRprovides the methodology, approach and results from the hydrologic dam failure scenario.

Dam Response to Request for Additional Information (Flood Hazard Reevaluation Report)Enclosure 1Page 55 of 55failure scenarios are evaluated in Calculation QDC-0085-S-2032, without the effects of wind-wave activity.

Section 7 of the FHRR provides the methodology, approach and results for wind-wave activitycoincident with the controlling

scenario, Alternative 3 of Combination H.1 with hydrologic damfailure.

Wind-wave effects are evaluated in Calculation QDC-0085-S-2034.

The seismic dam failure scenarios are evaluated due to requirements in the Combined-Effect Flood evaluation discussed in NUREG/CR-7046, Appendix H.2 with the potential for floodingabove site grade and shorter response time than may be available under PMF conditions.

Theanalysis indicates that the seismically-induced dam failure scenario does not produce a floodthat reaches plant grade.The Sunny Day scenario evaluated in this dam failure analysis is conservatively assumed tocorrespond to "Alternative 1" of the NUREG/CR-7046, Appendix H.1 -Floods Caused byPrecipitation Events. Section 2 of the FHRR provides the methodology, approach and resultsfrom these dam failure scenarios.

Dam failure scenarios are evaluated in Calculation QDC-0085-S-2032, without the effects wind-wave activity.

Enclosure 2Quad Cities Nuclear Power Station, Units 1 and 2DVD #1 of RS-14-173 for RAI Response No. 4Regarding Fukushima Lessons Learned -Flood Hazard Reevaluation ReportThe contents of Enclosure 2 areSecurity-Related Information

-Withhold Under 10 CFR 2.390 Enclosure 3Quad Cities Nuclear Power Station, Units 1 and 2DVD #2A of RS-14-173 for RAI Response Nos. 11, 12, 13,15,17, 20, 22, and 23DVD #2B of RS-14-173 for RAI Response No. 15DVD #2C of RS-14-173 for RAI Response No. 15DVD #2D of RS-14-173 for RAI Response No. 15DVD #2E of RS-14-173 for RAI Response No. 15DVD #2F of RS-14-173 for RAI Response No. 15Regarding Fukushima Lessons Learned -Flood Hazard Reevaluation Report