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{{#Wiki_filter:OapsEA-12- | {{#Wiki_filter:OapsEA-12-049 10 CFR 50.54(f)DWIGHT C. MIMSSenior Vice President, NuclearRegulatory | ||
& Oversight Palo VerdeNuclear Generating StationP.O. Box 52034Phoenix, AZ 85072Mail Station 7605Tel 623 393 5403102-06967-DCM/TNW December 12, 2014ATTN: Document Control DeskU.S. Nuclear Regulatory Commission Washington, DC 20555-0001 | |||
==References:== | ==References:== | ||
: 1. NRC Letter, Request for Information Pursuant to Title 10 of theCode of Federal Regulations 50.54(f) Regarding | : 1. NRC Letter, Request for Information Pursuant to Title 10 of theCode of Federal Regulations 50.54(f) | ||
Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insightsfrom the Fukushima Dai-ichi | |||
: Accident, dated March 12, 20122. NRC Letter, Palo Verde Nuclear Generating | |||
: Station, Units 1, 2, and 3-Relaxation of Response Due Dates Regarding Flooding HazardReevaluations for Recommendation 2.1 of the Near-Term Task ForceReview of the Insights from the Fukushima Dai-ichi | |||
: Accident, datedJuly 29, 2014 | |||
==Dear Sirs:== | ==Dear Sirs:== | ||
==Subject:== | ==Subject:== | ||
Palo Verde Nuclear Generating Station (PVNGS)Units 1, 2, and 3Docket Nos. STN 50-528/529/ | |||
Palo Verde Nuclear Generating Station (PVNGS)Units 1, 2, and 3Docket Nos. STN 50-528/529/530 Flood Hazard Reevaluation ReportIn accordance with the NRC request for information documented in Reference 1,enclosed please find the Flood Hazard Reevaluation Report for Palo Verde NuclearGenerating Station Units 1, 2, and 3.Subsequent to the issuance of the request for information, the NRC issued aprioritization of the due dates for the submittal of the flood hazard reevaluation report for all sites. The NRC set the reevaluation due date for PVNGS as March 12,2014. The initial flood hazard reevaluation report for PVNGS concluded that thefollowing events and corresponding results were found to be comparable with thecurrent licensing basis:0S0Probable maximum flood (PMF) for Winters WashSitewide inundation as a result of local intense precipitation (LIP)Dam failureHowever, the flood levels predicted by the initial flood hazard reevaluation weresomewhat greater than expected for the following: | |||
* Areas adjacent to the powerblock structures due to LIP* East Wash embankment due to PMFA member of the STARS (Strategic Teaming and Resource Sharing) | |||
AllianceCallaway | |||
* Comanche Peak | * Comanche Peak | ||
* Diablo Canyon | * Diablo Canyon | ||
* Palo Verde | * Palo Verde | ||
* Wolf Creeklk I Dvaq-'ýL 102-06967-DCM/ | * Wolf Creeklk I Dvaq-'ýL 102-06967-DCM/TNW ATTN: Document Control DeskU.S. Nuclear Regulatory Commission Flood Hazard Reevaluation ReportPage 2As a result, Arizona Public Service Company (APS) requested and received approvalfor an extension of the reevaluation report due date to December 12, 2014, inReference | ||
: 2. The purpose of the extension was to complete a reanalysis by anindependent contractor using refined analysis techniques and a room-by-room internal flooding analysis by APS.The enclosure to this letter contains the results from the initial and refined floodhazard reevaluation, as well as the room-by-room internal flooding analysiscompleted by APS during the extension period.No operator or mitigation actions are needed to ensure safe shutdown capability as aresult of the flood hazard reevaluation. | |||
As no additional actions to protect against thereevaluated flood hazards are needed and the results are comparable to the licensing basis, APS believes that an integrated assessment is not needed or warranted. | |||
No new commitments are being made to the NRC by this letter. Should you needfurther information regarding this submittal, please contact Thomas N. Weber,Licensing Department Leader, at (623) 393-5764. | |||
I declare under penalty of perjury that the foregoing is true and correct.Executed on,tDate)Sincerely, DCM/TNW | |||
==Enclosure:== | ==Enclosure:== | ||
Flood Hazard Reevaluation Report for Palo Verde Nuclear Generating StationUnits 1, 2, and 3cc: M. L. Dapas NRC Region IV Regional | |||
Flood Hazard Reevaluation Report for Palo Verde Nuclear Generating StationUnits 1, 2, and 3cc: M. L. Dapas NRC Region IV Regional Administrator B. K. Singal NRC NRR Project Manager for PVNGSM. M. Watford NRC NRR Project ManagerD. R. Reinert NRC Acting Senior Resident Inspector for PVNGS FLOOD HAZARDREEVALUATION REPORTforPALO VERDE NUCLEAR GENERATING STATIONUNITS 1, 2, AND 3REVISION 0DECEMBER 12, 2014I.0 Flood Hazard Reevaluation ReportTABLE OF CONTENTS | |||
==1.0 INTRODUCTION== | ==1.0 INTRODUCTION== | ||
................................................................................... | |||
31.1 PURPOSE AND SCOPE ............................................................................. | |||
31.2 HYDROLOGIC DESCRIPTION OF STUDY AREA ........................................ | |||
41.3 SITE FLOOD HAZARD BACKGROUND AND HISTORY .............................. | |||
51.4 DESIGN BASIS OF THE PLANT .................................................................. | |||
61.5 BASIC APPROACH OF THE FLOOD HAZARD REEVALUATION | |||
.................. | |||
61.6 PROBABLE MAXIMUM FLOOD REEVALUATION | |||
........................................ | |||
82.0 FLOOD HAZARDS AT THE SITE ......................................................... | |||
112.1 DETAILED SITE INFORMATION | |||
................................................................ | |||
112.2 CURRENT DESIGN BASIS FLOOD ELEVATIONS | |||
.................................... | |||
132.3 FLOOD-RELATED CHANGES TO THE LICENSING BASIS ......................... | |||
172.4 CHANGES TO THE WATERSHEDS AND LOCAL SITE AREA ..................... | |||
182.5 CURRENT LICENSING BASIS FLOOD PROTECTION AND PERTINENT FLOOD MITIGATION FEATURES | |||
.............................................................. | |||
192.6 ADDITIONAL SITE DETAILS .................................................................... | |||
203.0 FLOOD HAZARD REEVALUATION ANALYSIS | |||
................................. | |||
213.1 SOFTWARE USED .................................................................................. | |||
213.2 FLOOD-CAUSING MECHANISMS | |||
............................................................ | |||
213.3 COMBINED EFFECTS FLOODING | |||
........................................................... | |||
373.4 DAM BREACHES AND FAILURES | |||
............................................................ | |||
423.5 STORM SURGE ....................................................................................... | |||
423 .6 S EIC HE ................................................................................................... | |||
433 .7 T SU NA M I ................................................................................................. | |||
443.8 ICE-INDUCED FLOODING | |||
....................................................................... | |||
44 Flood Hazard Reevaluation Report3.9 FLOODING RESULTING FROM CHANNEL MIGRATION OR DIVERSION | |||
........ | |||
444.0 COMPARISON OF CURRENT AND REEVALUATED PREDICTED FLOOD LEVELS ............................................................ | |||
454.1 COMPARISON OF CURRENT AND REEVALUATED FLOOD-CAUSING M ECHANISM S ......................................................................................... | |||
454.2 ASSESSMENT OF DIFFERENCES BETWEEN CURRENT DESIGNBASIS AND REEVALUATED FLOOD ELEVATIONS AND EFFECTS ........ | |||
454.3 SUPPORTING DOCUMENTATION | |||
............................................................ | |||
494.4 C ONCLUSIONS | |||
....................................................................................... | |||
505.0 INTERIM EVALUATION AND ACTIONS ............................................ | |||
526.0 ADDITIONAL ACTIONS .................................................................... | |||
5 | |||
==37.0 REFERENCES== | ==37.0 REFERENCES== | ||
...................................................................................... | |||
54Appendix A -TablesAppendix B -FiguresAppendix C -Probable Maximum Precipitation in ArizonaAppendix D -Software Used in Flood Hazard Reevaluation ii Flood Hazard Reevaluation ReportLIST OF TABLES IN APPENDIX ATable 2-1 Existing Design Parameters Table 2-2 Current Design Basis Flood Elevations due to all FloodMechanisms Table 3-1 Characteristics of Winters Wash Sub-Basins and HEC-HMS ModelResultsTable 3-2 Summary of FLO-2D Simulations for Winters Wash FloodingTable 3-3 Floodplain Cross-Section PMF Results (100-ft Grid Element Model)Table 3-4 Floodplain Cross-Section PMF Results (25-ft Grid Element Model)Table 3-5 Comparison of PMF LevelsTable 3-6 Fetch DataTable 3-7 Wave Run-up and Freeboard Table 3-8 Summary of FLO-2D Simulation Cases for Combined Effects FloodingTable 4-1 Comparison of Modeling Approaches for CLB and Reevaluation Table 4-2 Comparison of Analytical Inputs for CLB and Reevaluation Table 4-3 Comparison of Flood Levels for CLB and Reevaluation Table 4-4 Comparison of Flooding for CLB and Reevaluation Table 4-5 List of Supporting Documents iii Flood HazardFigure 1-1Figure 1-2Figure 1-3Figure 2-1Figure 2-2Figure 2-3Figure 2-4Figure 3-1Figure 3-2Figure 3-3Figure 3-4Figure 3-5Figure 3-6Figure 3-7Figure 3-8Figure 3-9Figure 3-10Figure 3-11Figure 3-12Figure 3-13Figure 3-14Reevaluation ReportLIST OF FIGURES IN APPENDIX BGeographic Location of Palo Verde Nuclear Generating StationGeneral Location Map of the SiteFlood Hazard Reevaluation Flowchart Site Layout Topography Powerblock Arrangement Aerial View of Site LayoutEast Wash & Winters Wash Watershed HHA Diagram for Local Intense Precipitation Flooding AnalysisLocal Intense Precipitation Hyetographs FLO-2D Inundation Map for Local Intense Precipitation Fetch Locations for Wind-Wave Activity Coincident With LIPFloodingHHA Diagram for Analysis of Flooding in Rivers and StreamsPMP Hyetographs for Winters Wash and East Wash Watersheds Winters Wash and East Wash Sub-Basins Initial Analysis HEC-HMS Model for East Wash and Winters WashWatersheds Fetch Locations for Flooding in Winters WashEast Wash Location Map and Model ExtentEast Wash Floodplain Cross-Section Hydrographs | |||
-Refined PMF(100-ft Grid Element Model)East Wash Flow Depths -Refined PMF (100-ft Grid ElementModel)East Wash Flow Velocities | |||
-Refined PMF (100-ft Grid ElementModel)East Wash Floodplain Cross-Sections iv Flood Hazard Reevaluation ReportFigure 3-15Figure 3-16Figure 3-17Figure 3-18Figure 3-19Figure 3-20Figure 3-21Figure 3-22Figure 3-23Figure 3-24Figure 3-25Figure 3-26Figure 3-27LIST OF FIGURES IN APPENDIX B (CONTINUED) | |||
East Wash Watershed Inflow Hydrographs (Refined Analysis) | |||
East Wash Water Depths -Refined PMF (25-ft Grid ElementModel)East Wash Potential Fetches (Refined Analysis) | |||
North and East Embankment FetchesNorth Embankment Fetch Selection East Wash (Refined Analysis) | |||
East Embankment Fetch Selection East Wash (Refined Analysis) | |||
HHA Diagram for Combined Effects Flooding AnalysisFLO-2D Model Domains for Combined Effects AnalysisMaximum Combined Effects Flood Depth (ft) for Case 3Duration of Combined Effects Flooding (hours) for Case 3ISG-2013-01 Diagram for Determining Levels of Analysis for DamBreak Evaluation ISG-2013-01 Diagram for Analysis of Dam Breaches and FailuresUsing the Volume MethodLocations of Dams Near the SiteV Flood Hazard Reevaluation ReportACRONYMSADWRAGSANSANSIAPSAWACAPCEFCEMCFRCLBDADESPESRIEWFCDMCFEMAHEC-HMSHEC-RASHHAHMRLIPmslMSWNCDCArizona Department of Water Resources Arizona Geological SurveyAmerican Nuclear SocietyAmerican National Standards Institute Arizona Public Service CompanyApplied Weather Associates Corrective Action Programcombined effects floodingCoastal Engineering ManualCode of Federal Regulations current licensing basisdepth-a rea-d u rationessential spray pondEnvironmental Systems Research Institute East WashFlood Control District of Maricopa CountyFederal Emergency Management AgencyHydrologic Engineering Center-Hydrologic Modeling SystemHydrologic Engineering Center-River Analysis Systemhierarchical hazard assessment Hydrometerological Reportlocal intense precipitation mean sea levelmaximum sustained windNational Climatic Data Centervi Flood Hazard Reevaluation ReportACRONYMS (CONTINUED) | |||
NEXRAD next generation radarNGVD National Geodetic Vertical DatumNRC Nuclear Regulatory Commission NRCS National Resource and Conservation ServiceNWS National Weather ServicePMF probable maximum floodPMP probable maximum precipitation PVNGS Palo Verde Nuclear Generation StationREI Riada Engineering, Inc.RG Regulatory GuideSCS U. S. Soil Conservation ServiceSOCA Security Owner Controlled AreaSSC structures, | |||
: systems, and components UFSAR Update Final Safety Analysis ReportUSACE United States Army Corps of Engineers USBR United States Bureau of Reclamation USDA United States Department of Agriculture USGS United States Geological SurveyVBS vehicle barrier systemWW Winters Washvii Flood Hazard Reevaluation ReportEXECUTIVE SUMMARYThis report provides a reevaluation of potential flood causing mechanisms at Palo VerdeNuclear Generating | |||
: Station, (PVNGS) Units 1, 2, and 3, with consideration of thepresent-day regulatory guidance and methodologies being used for combined licensereviews, including current techniques, | |||
: software, and methods used in present-day standard engineering practice. | |||
The flood hazards considered include local intenseprecipitation, flooding from the nearby washes, and potential dam failure flooding. | |||
Otherflood causing mechanisms, such as tsunami, storm surge, seiche, ice-induced | |||
: flooding, and channel diversion | |||
: effects, were excluded as not being applicable based on thecharacteristics of the site.Subsequent to the issuance of the Nuclear Regulatory Commission (NRC) request forinformation on March 12, 2012, (NRC, 2012a) pursuant to Title 10 of the Code ofFederal Regulations (CFR), Section 50.54(f), | |||
the NRC issued a prioritization of the duedates for the submittal of the flood hazard reevaluation report for all sites. The NRC setthe reevaluation due date for PVNGS as March 12, 2014. The initial flood hazardreevaluation report was performed by Paul C. Rizzo Associates, Inc. under asubcontract with Westinghouse Electric Company.The initial flood hazard reevaluation report concluded that the following events andcorresponding results were found to be comparable with the current licensing basis:* Probable maximum flood (PMF) for Winters Wash* Sitewide inundation as a result of local intense precipitation (LIP)" Dam failureHowever, the flood levels predicted by the initial flood hazard reevaluation weresomewhat greater than expected for the following plant locations: | |||
* Areas adjacent to the powerblock structures due to LIP0 East Wash embankment due to PMFAs a result, Arizona Public Service Company (APS) requested and received approvalfor an extension of the reevaluation report due date to December 12, 2014, to completea reanalysis by an independent contractor using refined analysis techniques and aroom-by-room internal flooding analysis by APS.This report contains the results from the initial and refined flood hazard reevaluation, aswell as the room-by-room internal flooding analysis completed by APS during theextension period.1J Flood Hazard Reevaluation ReportThe analyses completed during the extension period included the following specificareas:" Utilized FLO-2D software to model the impacts on the site caused by a PMF inEast Wash* Updated the combined effects analysis in this report to reflect the refined analysisof East Wash* Performed a room-by-room internal flooding analysis of the potential impact onsafe shutdown equipment due to water intrusion from a LIP event. Subsequent refined analysis of LIP in the powerblock validated that the depth and duration ofwater accumulation (hydrographs) used in the room-by-room internal floodinganalysis were conservative. | |||
The results of the refined PMF analysis of East Wash showed flood levels comparable to the current licensing bases with adequate freeboard to contain the PMF including wave runup. The combined effects analysis of the PMF event in Winters Wash and EastWash was bounded by the individual PMF event in each individual wash. The room-by-room internal flooding analysis conservatively utilized the results from the initial LIPanalysis and concluded there was no impact to safe shutdown equipment. | |||
No operator or mitigation actions are needed to ensure safe shutdown capability as aresult of the flood hazard reevaluation. | |||
As no additional actions to protect against thereevaluated flood hazards are needed and the results are comparable to the licensing basis, APS believes that an integrated assessment is not needed or warranted. | |||
Flood Hazard Reevaluation Report | Flood Hazard Reevaluation Report | ||
==1.0 INTRODUCTION== | ==1.0 INTRODUCTION== | ||
1.1 Purpose and ScopeThe Nuclear Regulatory Commission (NRC) issued a request for information on March12, 2012, (NRC, 2012a) pursuant to Title 10 of the Code of Federal Regulations (CFR),Section 50.54(f), | |||
related to the implementation of Recommendations 2.1, 2.3, and 9.3from the Near Term Task Force, a portion of which calls for performing flood hazardreevaluations at all nuclear power plants in the United States. This Flood HazardReevaluation Report for the Palo Verde Nuclear Generating Station (PVNGS) Units 1,2, and 3 provides the information required to address NRC Recommendation 2.1 withconsideration of the present-day regulatory guidance and methodologies being used forcombined license reviews, including current techniques, | |||
: software, and methods used inpresent-day standard engineering practice. | |||
The site (geographic location shown in Figure 1-1 is licensed for the operation of threeCombustion Engineering System 80 pressurized water reactor nuclear generating units.The original operating licenses for Units 1, 2, and 3 were issued June 1, 1985, April 24,1986, and November 25, 1987, respectively. | |||
The operating licenses for all three unitswere renewed on April 21, 2011, and will expire June 1, 2045, April 24, 2046, andNovember 25, 2047, respectively. | |||
Revision 17 to the Updated Final Safety Analysis Report (APS, 2013) for PVNGS Units1, 2, and 3 was issued to the NRC in June 2013.1.1.1 Flood Hazard Reevaluation Extension Subsequent to the issuance of the NRC request for information, the NRC issued aprioritization of the due dates for the submittal of the flood hazard reevaluation report forall sites. The NRC set the reevaluation due date for PVNGS as March 12, 2014.The initial flood hazard reevaluation report concluded that the following events andcorresponding results were found to be comparable with the current | |||
==7.0 REFERENCES== | ==7.0 REFERENCES== | ||
: 1. (ADOT, 1969), State of Arizona, State Highway Department, "As-Built | |||
: Drawings, 1-10-2(13), | |||
Ehrenberg Highway -Phoenix Highway, Tonopah East & West,Maricopa County," | |||
November 4, 1969.2. (ADWR, 2014),"http://www.azwater.qov/AzDWR/PubliclnformationOfficer/MissionAndGoals.htm, accessed 2014.3. (AGS, 2000), Arizona Geological Survey, "Earthquake Hazard in Arizona," | |||
Vol.30, No. 1, Spring 2000.4. (ANS, 1992), American Nuclear Society, 1992, "Determining Design BasisFlooding at | |||
==REFERENCE:== | ==REFERENCE:== | ||
Background Image: ESRI, 2013a, Environmental Systems Research Institute (ESRI),"World Street Map"Website:http://goto.arcgisonline.com/maps/ | |||
Background Image: ESRI, 2013a, Environmental Systems Research Institute (ESRI),"World Street Map"Website:http://goto.arcgisonline.com/maps/WorldStreetMap Date Accessed: | |||
January 14, 2014FIGURE 1-1GEOGRAPHIC LOCATION OFPALO VERDE NUCLEAR GENERATING STATIONPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT The Winters Wash1 Miles The East WashCross-sections 010.5II IILegend* Site Center Point~ Watershed Boundaries | |||
, USGS Gauge StationsRivers and Streams | |||
==REFERENCE:== | ==REFERENCE:== | ||
Background Image: ESRI, 2013a, Environmental Systems Research Institute (ESRI), "WCStreet Map"Website:http://goto.arcgisonline.com/maps/ | |||
-VOTl"rFIGURE 2-1SITE LAYOUT | Background Image: ESRI, 2013a, Environmental Systems Research Institute (ESRI), "WCStreet Map"Website:http://goto.arcgisonline.com/maps/Wodd_StreetMap Date Accessed: | ||
January 14, 2013USGS, 2013c, United States Geological Survey (USGS)"USGS Water Data for the Nation,' | |||
Website <http://waterdata.usgs.gov/nwis>, | |||
Date Accessed: | |||
October 9, 2013FIGURE 1-2odd GENERAL LOCATIONMAP OF THE SITEPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT INITIALANALYSISREFINEDANALYSISI --- ----------------- | |||
* NOT IN DESIGN BASISFIGURE 1-3FLOOD HAZARD REEVALUATION FLOWCHART PALO VERDE NUCLAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT | |||
-VOTl"rFIGURE 2-1SITE LAYOUT TOPOGRAPHY SPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT LEGEND:1. AUXILIARY BUILDING2. CONDENSATE STORAGE TANK3. CONTROL BUILDING4. DIESEL GENERATOR BUILDING5. EMERGENCY FUEL OIL TANKS6. FUEL BUILDING7. CONTAINMENT BUILDING8. ESSENTIAL SPRAY POND9. MAIN STEAM SUPPORT STRUCTURE | |||
: 10. REFUELING WATER TANKNOTE:BACKGROUND IMAGE MODIFIED FROM: GOOGLEEARTH, 2014FIGURE 2-2POWERBLOCK ARRANGEMENT PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT Legend-SOCA Perimeter Coordinate Systemr: | |||
I NA D 1983 StatePlaneArizowaCentral_FI PS_0202-_Feet Projection:Transvers_Mercator 0 0.25 0.5 100 M =MilesContour LinesRF: 1:30,000---Buildings | |||
-Embankment | |||
-Fence Line Surrounding Powerblock Area | |||
==Reference:== | ==Reference:== | ||
Background Source: ESRI, 2013b, Environmental Systems ResearchInstitute (ESRI), 'World Imagery"Website:http:l/goto.arcgisonline.com/mapsl~ | |||
Background Source: ESRI, 2013b, Environmental Systems ResearchInstitute (ESRI), 'World Imagery"Website:http:l/goto.arcgisonline.com/mapsl~orld_lmagery Date Accessed: | |||
January 14, 2014FIGURE 2-3AERIAL VIEW OF SITE LAYOUTPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORTLýlilil- | |||
,IAMMON-maffilW FIGURE 2-4EAST WASH & WINTERS WASH WATERSHED PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT NOTE:1. INCLUDES LIMITED SENSITIVITY ANALYSISUs sit -seic data ~ torfn h Uoaines prcptto flodn *.* 0So .Saet f h.S~de osrtdNoA* YesNoL mosI .efoI YesFIGURE 3-1HHA DIAGRAM FOR LOCAL INTENSEPRECIPITATION FLOODING ANALYSISPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT 3.0012.502. 0012 1.50.2.1 1.00.13LJs 0.500.000 60 120 180 240Time (minutes) 300 360INCREMENTAL RAINFALL DISTRIBUTION FOR THE6-HR DURATION LIP FOR REEVALUATION ANALYSIS141210 8364 ..--AWAPMPEvaluation Toolo. ii~V0I0 1 2 3 4 5 6Time (hoaur)CUMULATIVE REEVALUATION LIP HYETOG RAPHSFIGURE 3-2LOCAL INTENSEPRECIPITATION HYETOGRAPHS PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORTK lii | |||
-- FLO-2D Model DomainFLO-2D Model FeaturesNA0 0.250.5 MilesI I I IFlood DOpM ffwt0.01 -0.200.21 -OAOC 041 -OAOI0.01 | -- FLO-2D Model DomainFLO-2D Model FeaturesNA0 0.250.5 MilesI I I IFlood DOpM ffwt0.01 -0.200.21 -OAOC 041 -OAOI0.01 | ||
* 0.810S0,0 -1.001.01 -120121 -140II1.41 | * 0.810S0,0 -1.001.01 -120121 -140II1.41 | ||
* 1460S1.61 -t.801h 18-2A0=I2.01 -220W 2.21 -2,40M2A41 -2.402.61 -2.802Jm -3.00S3.01 3203.21 2 340341 0 3.603,61 -803,81 -4004.01-4. | * 1460S1.61 -t.801h 18-2A0=I2.01 -220W 2.21 -2,40M2A41 -2.402.61 -2.802Jm -3.00S3.01 3203.21 2 340341 0 3.603,61 -803,81 -4004.01-4.20 4321 3 4,404.41 -34.81 -4.00514.0t -0.4,.31 440I 61 4.00-m -8 N-FIGURE 3-3FLO-2D INUNDATION MAP FORLOCAL INTENSE PRECIPITATION PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT | ||
-Fetch length-Path for screening inside SOCA1600 800 0 1M00 FeetFIGURE 3-4FETCH LOCATIONS FOR WIND- | -Fetch length-Path for screening inside SOCA1600 800 0 1M00 FeetFIGURE 3-4FETCH LOCATIONS FOR WIND-WAVE ACTIVITY COINCIDENT WITHLIP FLOODINGPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORTNOTE:FETCH LENGTHS ARE APPROXIMATE Jaft' NOTES:1. INCLUDES MULTIPLE CASES IN SUPPORT OFPOTENTIAL HHA CASES TO FOLLOW.2. INCLUDES LIMITED SENSITIVITY ANALYSIS. | ||
m*NoJse site-soec | |||
-ic cat-= -creire aralys-s. | |||
II YesStoo. Jse the mo.5tre4',)ed case ýcrccmoai.zcn tc the des grLasis,womYesNoFIGURE 3-5HHA DIAGRAM FOR ANALYSIS OF FLOODINGIN RIVERS AND STREAMSJ \iiPALO VERDE NUCLEAR GENERATING STATION& ý FLOOD HAZARD REEVALUATION REPORT 4.504.003.502.00-zsoj2,001.000,506 12 19 24 30 36 42 49 54 60 66 72Time (bern)2.520.5012110j 8a6420aTnWh" W4l12j10Ioa 200 10 20 30 40 so 60 70 80Time (hours)WINTERS WASH PMP DISCRETE ANDCUMULATIVE HYETOGRAPHS 0 1 2 3 4 5 6 7Time(hours) | |||
EAST WASH PMP DISCRETE ANDCUMULATIVE HYETOGRAPHS FIGURE 3-6PMP HYETOGRAPHS FOR WINTERS WASH ANDEAST WASH WATERSHEDS U/i"wommimumw PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT NOTE:WW = WINTERS WASHEW = EAST WASHFIGURE 3-7WINTERS WASH AND EAST WASH SUB-BASINS PALO VERDE NUCLEAR GENERATING STATION-FLOOD HAZARD REEVALUATION REPORT RUPIIoLEGEND:SUBBASINJUNCTIONIEWUPI10 STORAGE1i4 spidl FLOW SPLITo10in SINK%SinkREACHPVNGS SITENOT TO SCALEFIGURE 3-8INITIAL ANALYSISHEC -HMS MODEL FOR EAST WASHAND WINTERS WASH WATERSHEDS PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT 1kWinters Wash Fetch LengthWater Depth >= 0.5 ft0-71.4MiIftFIGURE 3-9 | |||
==REFERENCE:== | ==REFERENCE:== | ||
Background Image: ESRI, 2013c, Environmental Systems Research Institute (ESRI),-ARCGIS IMAGERY,-WEBSITE: <http://www.arcgis.com/homef/item. | |||
Background Image: ESRI, 2013c, Environmental Systems Research Institute (ESRI),-ARCGIS IMAGERY,- | |||
WEBSITE: | |||
<http://www.arcgis.com/homef/item.htm Date of publication: | |||
January 16, 2012, date accessed: | |||
June 21, 2013FETCH LOCATIONS FOR FLOODING INWINTERS WASHPALO VERDE NUCLEAR GENERATING STATIONIFLOOD HAZARD REEVALUATION REPORT FIGURE 3-10EAST WASH LOCATION MAP ANDMODEL EXTENT | |||
==REFERENCE:== | ==REFERENCE:== | ||
Model Boundary is based on the East Wash Watershed delineation.Image Source: 2013 U.S. Department of Agricultural, National | |||
Model Boundary is based on the East Wash Watershed delineation. | |||
Image Source: 2013 U.S. Department of Agricultural, National Agricultural Inventory Project.1/PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT 14000112000- I-XS2-XS310000 -XS.. .... -XS4-- XS5-8000V' 60004000_,200000 2 4 6 8 10 12 14 16 18 20Time (hours)FIGURE 3-11EAST WASH FLOODPLAIN CROSS-SECTION HYDROGRAPHS | |||
-REFINED PMF (100-FT GRIDELEMENT MODEL)SPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT FIGURE 3-12 | |||
==REFERENCE:== | ==REFERENCE:== | ||
Flow depths in power block area are a result of direct rainfall only.Image Source: 2013 U.S. Department of Agricultural, National | |||
Flow depths in power block area are a result of direct rainfall only.Image Source: 2013 U.S. Department of Agricultural, National Agricultural Inventory Project.EAST WASH FLOW DEPTHS -REFINED PMF(100-FT GRID ELEMENT MODEL)PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT'7: | |||
IIFIGURE 3-13 | IIFIGURE 3-13 | ||
==REFERENCE:== | ==REFERENCE:== | ||
Flow velocities in powerblock area are a result of direct rainfall onlyImage Source: 2013 U.S. Department of Agricultural, National | |||
Flow velocities in powerblock area are a result of direct rainfall onlyImage Source: 2013 U.S. Department of Agricultural, National Agricultural Inventory Project.EAST WASH FLOW VELOCITIES-REFINED PMF(100-FT GRID ELEMENT MODEL)PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT FIGURE 3-14EAST WASH FLOODPLAIN CROSS SECTIONS | |||
==REFERENCE:== | ==REFERENCE:== | ||
Image Source: 2013 U.S. Department of Agricultural,National Agricultural Inventory Project.PALO VERDE NUCLEAR GENERATING STATIONi FLOOD HAZARD REEVALUATION REPORT 120001000080006000U40002000-XS4 -XS500 2 4 6 8 10 12 14 16 18 20Time (hours)FIGURE 3-15EAST WASH WATERSHED INFLOWHYDROGRAPHS (REFINED ANALYSIS)U-PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT FIGURE 3-16 | |||
Image Source: 2013 U.S. Department of Agricultural, National Agricultural Inventory Project.PALO VERDE NUCLEAR GENERATING STATIONi FLOOD HAZARD REEVALUATION REPORT 120001000080006000U40002000-XS4 -XS500 2 4 6 8 10 12 14 16 18 20Time (hours)FIGURE 3-15EAST WASH WATERSHED INFLOWHYDROGRAPHS (REFINED ANALYSIS) | |||
U-PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT FIGURE 3-16 | |||
==REFERENCE:== | ==REFERENCE:== | ||
Image Source 2013 U.S. Department of Agriculture, National | |||
Image Source 2013 U.S. Department of Agriculture, National Agricultural Inventory Project | |||
* Maximum water surface elevation does not includeeffects from wind-wave action.EAST WASH WATER DEPTHS -REFINED PMF(25-FT GRID ELEMENT MODEL)PALO VERDE NUCLEAR GENERATING STATIONIFLOOD HAZARD REEVALUATION REPORT FIGURE 3-17EAST WASH POTENTIAL FETCHES(REFINED ANALYSIS) | * Maximum water surface elevation does not includeeffects from wind-wave action.EAST WASH WATER DEPTHS -REFINED PMF(25-FT GRID ELEMENT MODEL)PALO VERDE NUCLEAR GENERATING STATIONIFLOOD HAZARD REEVALUATION REPORT FIGURE 3-17EAST WASH POTENTIAL FETCHES(REFINED ANALYSIS) | ||
==REFERENCE:== | ==REFERENCE:== | ||
Image Source: 2013 U.S. Department of Agricultural,National Agricultural Inventory Project.'I'PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT FIGURE 3-18NORTH AND EASTEMBANKMENT FETCHES | |||
Image Source: 2013 U.S. Department of Agricultural, National Agricultural Inventory Project.'I'PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT FIGURE 3-18NORTH AND EASTEMBANKMENT FETCHES | |||
==REFERENCE:== | ==REFERENCE:== | ||
Image Source: 2013 U.S. Department of Agricultural,National Agricultural Inventory Project.PALO VERDE NUCLEAR GENERATING STATIONJFLOOD HAZARD REEVALUATION REPORT 10051000995990Chz998598097597096501000 2000 3000 4000 5000 6000Cross Section Length (kt)7000FIGURE 3-19NORTH EMBANKMENT FETCH | |||
Image Source: 2013 U.S. Department of Agricultural, National Agricultural Inventory Project.PALO VERDE NUCLEAR GENERATING STATIONJFLOOD HAZARD REEVALUATION REPORT 10051000995990Chz998598097597096501000 2000 3000 4000 5000 6000Cross Section Length (kt)7000FIGURE 3-19NORTH EMBANKMENT FETCH SELECTION EAST WASH (REFINED ANALYSIS) | |||
PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT 10051000 r995990 Fi Lehighi V= feet975970-Maximum Water Surface9_5__________ | |||
nrtedent Watre vet~974-.9-ft | |||
_______ _____________ | |||
9600 1000 2000 3000 4000 5000 6000 7000Cross Section Length (ft)FIGURE 3-20EAST EMBANKMENT FETCH SELECTION EAST WASH (REFINED ANALYSIS) | |||
SPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT NOTE:1. INCLUDES LIMITED SENSITIVITY ANALYSIS&Eli.SoNoIUs sit -seic dattorfn0nlss 1r YesSto. Us th mosrefie 1as oYesNo_vIFIGURE 3-21HHA DIAGRAM FORCOMBINED EFFECTS FLOODING ANALYSISPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT l I lFIGURE 3-22FLO-2D MODEL DOMAINS FORCOMBINED EFFECTS ANALYSISPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT Water Depth (ft)-0.50 -1.00-1.01 -2.00-2.01 -3.003.01 -4.004.01 -5.00-5.01 -6.00-6.01 -7.00-7.01 -8.008.01 -9.00-9.01 -10.0010.01 .11.00-11.01 -12.0012.01 -13.0013.01 -14.0014.01 15.00m15.01 -16.00-16.01 -17.00-17,01 -18,00-18.01 -19.00-19.00-PVNGS Siruclures N0 0,25 0.5 MilesI I IFIGURE 3-23NOTES:THE WATER DEPTHS INDICATED IN IMPOUNDED WATER BODIES DO NOTINCLUDE THE INITIAL WATER DEPTHS. THE ILLUSTRATED FLOOD DEPTHS ATTHE POWERBLOCK ARE DUE TO PMP AT THE PVNGS SITE, NOT DUE TOFLOODWATER FROM THE WASHESMAXIMUM COMBINED EFFECTS FLOODDEPTH (FT) FOR CASE 3% PALO VERDE NUCLEAR GENERATING STATION.lM ~ FLOOD HAZARD REEVALUATION REPORT Duration of Inundation (hr)1.00 -3.003.01 -7.007.01 -9.009.01 -11.00-11.01 -13.00-13.01 -15.00-15.01 -17.00-17.01 -19.00I 19.01 -21 .0021.01 -23.00-23.01 -25.002501 -27.0027.01 -29.0029.01 -31.00-31.01 -33.0033.01 -35.00PVNGS Structures NA0 0.25 0.5 MilesFIGURE 3-24DURATION OF COMBINED EFFECTSFLOODING (HOURS) FOR CASE 3ii- PALO VERDE NUCLEAR GENERATING STATIONOW ý FLOOD HAZARD REEVALUATION REPORT cl-DminzInconsequential' DamsLEGEND:ISG -INTERIM STAFF GUIDANCE | |||
==REFERENCE:== | ==REFERENCE:== | ||
Background Image: ESRI, 2013e, United States Nuclear Regulatory Commission (NRC),"GUIDNCE FOR ASSESSMENT OF FLOODING HAZARDS DUE TO DAM FAILURE,- JLD-ISG-2013-01,NRC INTERIM STAFF GUIDANCE (ML13151A153), WASHINTON, DC, REVISION 0, JULY 29, 2013.FIGURE 3-25ISG-2013-01 DIAGRAM FORDETERMINING LEVELS OF ANALYSIS FOR DAMBREAK | |||
Background Image: ESRI, 2013e, United States Nuclear Regulatory Commission (NRC),"GUIDNCE FOR ASSESSMENT OF FLOODING HAZARDS DUE TO DAM FAILURE,- | |||
JLD-ISG-2013-01, NRC INTERIM STAFF GUIDANCE (ML13151A153), | |||
WASHINTON, DC, REVISION 0, JULY 29, 2013.FIGURE 3-25ISG-2013-01 DIAGRAM FORDETERMINING LEVELS OF ANALYSIS FOR DAMBREAK EVALUATION PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORTI-, | |||
FIGURE 3-26ISG-2013-01 DIAGRAM FORANALYSIS OF DAM BREACHES AND FAILURESUSING THE VOLUME METHODPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT | FIGURE 3-26ISG-2013-01 DIAGRAM FORANALYSIS OF DAM BREACHES AND FAILURESUSING THE VOLUME METHODPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT | ||
==REFERENCE:== | ==REFERENCE:== | ||
Background Image: ESRI, 2013e, United States Nuclear Regulatory Commission (NRC),"GUIDNCE FOR ASSESSMENT OF FLOODING HAZARDS DUE TO DAM FAILURE," JLD-ISG-2013-01,NRC INTERIM STAFF GUIDANCE (ML13151A153), WASHINTON, DC, REVISION 0, JULY 29, 2013."1-64ýr HUC Wau'hedsSan Carlos RiverSalt RiverLower Gila RiverSUpper Gila River-Z Gila River Downstream of PVNGS-~-~ As., | |||
Background Image: ESRI, 2013e, United States Nuclear Regulatory Commission (NRC),"GUIDNCE FOR ASSESSMENT OF FLOODING HAZARDS DUE TO DAM FAILURE," | |||
JLD-ISG-2013-01, NRC INTERIM STAFF GUIDANCE (ML13151A153), | |||
WASHINTON, DC, REVISION 0, JULY 29, 2013."1-64ýr HUC Wau'hedsSan Carlos RiverSalt RiverLower Gila RiverSUpper Gila River-Z Gila River Downstream of PVNGS-~-~ As., | |||
==REFERENCES:== | ==REFERENCES:== | ||
: 1. ESR, 201c, ENVIRONMENTAL SYSTEM RESEARCH INSTITUTE (ESRI), "ARCGIS IMAGERY," WEBSITE<http://arcgis.com/home/item.htm, DATE OF PUBLICATION: JANUARY 16, 2012, DATE ACCESSED: JUNE 21, 2013.2. USGS, 2013b, UNITED STATES GEOLOGIGAL SURVEY (USGS), "USGS WATER DATA FOR THE NATION," WEBSITE:<http://waterdata.usgs.gov/nwis>, DATE ACCESSED: OCTOBER 9,2013.3. USGS, 2013, UNITED STATES ARMY CORPS OF ENGINEERS (USACE), "NATIONAL INVENTORY OF DAMS," WEBSITE:<http://geo.usace.army.mil/pgis/>, DATE ACCESSED: JUNE 11, 2013FIGURE 3-27LOCATION OF DAMS NEAR THE SITEPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT Flood Hazard Reevaluation ReportAPPENDIX CPROBABLE MAXIMUM PRECIPITATION IN ARIZONASlik Flood Hazard Reevaluation ReportAPPENDIX CPROBABLE MAXIMUM PRECIPITATION IN ARIZONAThe intent of this document is to justify the use of the Probable Maximum Precipitation(PMP) values used to calculate the Local Intense Precipitation at the Palo VerdeNuclear Generating Station (PVNGS) in response to the Nuclear | : 1. ESR, 201c, ENVIRONMENTAL SYSTEM RESEARCH INSTITUTE (ESRI), "ARCGIS IMAGERY," | ||
WEBSITE<http://arcgis.com/home/item.htm, DATE OF PUBLICATION: | |||
JANUARY 16, 2012, DATE ACCESSED: | |||
JUNE 21, 2013.2. USGS, 2013b, UNITED STATES GEOLOGIGAL SURVEY (USGS), "USGS WATER DATA FOR THE NATION," | |||
WEBSITE:<http://waterdata.usgs.gov/nwis>, | |||
DATE ACCESSED: | |||
OCTOBER 9,2013.3. USGS, 2013, UNITED STATES ARMY CORPS OF ENGINEERS (USACE), | |||
"NATIONAL INVENTORY OF DAMS," WEBSITE:<http://geo.usace.army.mil/pgis/>, | |||
DATE ACCESSED: | |||
JUNE 11, 2013FIGURE 3-27LOCATION OF DAMS NEAR THE SITEPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT Flood Hazard Reevaluation ReportAPPENDIX CPROBABLE MAXIMUM PRECIPITATION IN ARIZONASlik Flood Hazard Reevaluation ReportAPPENDIX CPROBABLE MAXIMUM PRECIPITATION IN ARIZONAThe intent of this document is to justify the use of the Probable Maximum Precipitation (PMP) values used to calculate the Local Intense Precipitation at the Palo VerdeNuclear Generating Station (PVNGS) in response to the Nuclear Regulatory Commission (NRC) letter requesting information Pursuant to Title 10 of the Code ofFederal Regulations 50.54(f) | |||
(NRC, 2012) and conformance with NUREG/CR-7046 (NRC, 2011). The updated Arizona 6-hour and 72-hour PMP values and distributions are also utilized in calculating the potential flood hazards from East Wash and WintersWash, respectively. | |||
The potential flood hazard impacts of two washes are evaluated indetail because the site is located in both washes watersheds. | |||
The methodology used in Arizona for estimating the PMP for the design of dams wasupdated by the state through the Arizona Department of Water Resources (ADWR). Anupdate was necessary because the previous methodology utilized the procedures described in Hydrological Report No. 49 (HMR 49) prepared by the National WeatherService (NWS) for the US Army Corps of Engineers (NWS, 1977). At the time, HMR 49was prepared to estimate the PMP for locations in the Colorado River and Great BasinDrainages (part or all of Arizona, Utah, New Mexico, Colorado, Nevada, and Wyoming)as well as all of California. | |||
The methodology was used to calculate the PMP for areasup to 5,000 sq mi and durations up to 72-hours. | |||
HMR 49 is an outdated publication andmany of the locations are already covered by other HMRs. Presently, the PMPcalculations for California have been updated by HMR 59 in 1999 and there is a state-wide PMP update for Utah. The updates occurred as a result of additional storminformation and procedures that are physically based. The updates include a narrowerdomain pertaining to location, similar orographic, topographic, and meteorologic characteristics. | |||
The report Probable Maximum Precipitation Study for Arizona (AWA, 2013) is thesuccessor document to HMR 49 for the State of Arizona. | |||
The most relevant reason forthe update is increasing the period of the data base originally used in HMR 49 and thedocument is old. Only a few storms were evaluated in preparing HMR 49. Over the pastforty years more storms have occurred and the state-of-the practice in evaluating extreme storm events has changed making the new analysis more appropriate and up-to-date (AWA, 2008).Applied Weather Associates (AWA) completed the statewide PMP study for Arizona in2013. The study was funded by the ADWR with financial support from the Flood ControlDistrict of Maricopa County, Arizona Game and Fish Department, and USDA NaturalResources Conservation Service. | |||
These agencies also provided technical input on thedocument. | |||
An independent Peer Review Committee (PRC) reviewed and providedfeedback on the methodology at critical milestones and the final document. | |||
The PRCwas comprised of Dr. Keim a climatologist and professor at Louisiana State University, C-1 Flood Hazard Reevaluation ReportDr. Sabol a Principal and water resources engineer with Stantec in Phoenix, and Dr.Selover a climatologist and research professor at Arizona State University. | |||
The PRCpublished a final report in August 2013 (PRC, 2013).The statewide study is being implemented to calculate the PMP events used in thehydrologic analysis of dams in Arizona. | |||
Maricopa County is applying the PMP tool inpreparing new PMF hydrology in support of Emergency Action Plans for the following structures: | |||
* Wickenburg Structures, Arizona* Powerline, | |||
: Vineyard, and Rittenhouse Structures, Arizona* McMicken Dam, Arizona* Guadalupe Flood Retarding Structure, ArizonaAWA is presently preparing a similar study for the State of Wyoming, where the USACEis on the technical review committee. | |||
They have utilized the methodology for use inevaluating dams in other states for the Federal Energy Regulatory Commission (FERC);other state dam programs, and PMP estimates at Nuclear Power Plant sites.Individual storm events were not evaluated in HMR 49 providing a direct correlation between depth-area and area-duration (DAD envelope). | |||
Instead general ratios wereused when evaluating both the area (area reduction) and duration of PMP storms basedon the overall study area. The widely varying climatology and topography of the regionis not conducive to using a general approach. | |||
HMR 49 uses the persisting (lowest) 12-hour dewpoint in developing the PMP. Newer studies use the average dewpoint that fitswith predicting extreme rainfall events.The procedures used in the Arizona update are required by the state for dams andrecommended for other projects because the study has updated the data since 1977 toinclude many more rainfall events. The method evaluated 51 extreme valueprecipitation storm events and 91 storm centers using the Storm Precipitation andAnalysis System (SPAS) in characterizing magnitude, | |||
: temporal, and spatial data (DADvalues, mass curves, and total storm isohyets). | |||
The use of NEXt generation RADar(NEXRAD) data (mid 1990's) has contributed significantly to the quality of the stormdata being used. The procedure considers climate zone, topography and othervariables. | |||
Updated dewpoint data was used to maximize the effects of moisture that isassociated with the rainfall events. The study was done to develop a consistent procedure using a consistent data base for the entire state. However, the PMP tool(AWA, 2013) applies the data base to calculate site specific PMP values. The input datato the PMP tool is a shapefile of the study area. The tool then determines PMP valuesusing a 2.5 sq mi grid to calculate the PMP for each grid in the study area. The gridvalues are calculated from the storm data base that are similar to the site. It then uses aweighting process to calculate the average PMP value for the specific study. The tool isused for analyzing local storms where durations analyzed vary from 1 to 6 hours.C-2 Flood Hazard Reevaluation ReportTropical and general storms are analyzed for durations of 6, 12, 18, 24, 48, and 72hours.The PMP values developed by the state of Arizona (AWA, 2013) that update HMR 49and are consistent with the storms of record and state-of-the-practice technology. | |||
TheAPS contractor used the PMP tool (AWA, 2013) and values as the foundation forevaluating extreme event flood hazards at the Palo Verde Nuclear Generating Stationsite.References AWA, Evaluation of the Reliability of Generalized PMP Values Provided by HMR 49 forArizona, Alternative Approaches that can be Used on a Statewide Basis for PMPDetermination, Applied Weather Associates, LLC, September 2008.AWA, Probable Maximum Precipitation Study in Arizona, Applied Weather Associates, LLC, July 2013b.NOAA, Hydrometeorological Report No. 49, Probable Maximum Precipitation Estimates, Colorado River and Great Basin Drainages, NOAA, National Weather Service,Septmenber 1977.NRC, United States Nuclear Regulatory Commission (NRC), Design-Basis FloodEstimation for Site Characterization at Nuclear Power Plants in the United States ofAmerica, NUREG/CR-7046. | |||
PNNL-20091, NRC Job Code N6575, Washington, D.C.,November 2011.NRC, United States Nuclear Regulatory Commission (NRC), 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 Force Review of Insights fromthe Fukushima Dai-ichi | |||
: Accident, Washington, D.C., March 12, 2012.PRC, Peer Review Committee Final Report for the Probable Maximum Precipitation Study for Arizona by Applied Weather Associates' Peer Review Committee, August 2013.C-3 Flood Hazard Reevaluation ReportAPPENDIX DSOFTWARE USED IN FLOOD HAZARD REEVALUATION | |||
&-*ýw Flood Hazard Reevaluation ReportAPPENDIX DSOFTWARE USED IN FLOOD HAZARD REEVALUATION The following software was used to perform the flood hazard reevaluation analyses: | |||
* FLO-2D Pro (FLO-2D, 2012)* FLO-2D Pro Release 14.03.07 (FLO-2D, 2014a)* FLO-2D Pro Release 14.03.07.URS (FLO-2D, 2104d)* ArcGIS 9.3.1 (ESRI, 2009)* ArcGIS 10.1 (ESRI, 2012)* ArcHydro 10.1 (ESRI, 2011)* United States Army Corps of Engineers HEC-HMS 3.5 (USACE, 2010a)* USACE HEC-GeoHMS (USACE, 2009)* USACE HEC-RAS 4.1 (USACE, 2010b).The FLO-2D Pro software is a volume conservation model that routes fluid flow inone-dimensional channel flow, two-dimensional overland flow, or an interaction between the two model components. | |||
The FLO-2D Pro software is an effective tool for delineating flood hazards or designing flood mitigation. | |||
The software isalso available in a Basis configuration with fewer capabilities. | |||
The Basic modelhas been approved by the Federal Emergency Management Agency (FEMA) foruse in Flood Insurance Studies. | |||
The Pro model, though not specifically approvedby FEMA, includes all the features of the Basic model, along with someadditional features (e.g., storm drain interface with surface water using the EPASWMM program, parallel processing capabilities, and expanded capabilities forsimulating sediment transport (FLO-2D, 2012).FLO-2D Pro Release 14.03.07.URS utilized a modified version of the FLO-2Dmodel that specifically accounted for roof detention, parapet walls, scupper inlets,scupper outlets locations, | |||
: leaders, and downspouts. | |||
The flow to the ground forthe LIP event was attenuated on the roof and discharged to specific locations, inlieu, of directing runoff directly to the ground. This enhancement to the FLO-2Dprogram was developed by the FLO-2D developers specifically for this project.HEC-GeoHMS and ArcHydro are tools that function within the ArcGIS interface. | |||
At the time of the writing of this report, hydrologic and hydraulic simulation models developed, described, and maintained by the USACE Hydrologic Engineering Center (HEC) are acceptable to the NRC (NRC, 2011).D-1 Flood Hazard Reevaluation ReportHEC-HMS is designed to simulate the precipitation-runoff processes of drainagebasin networks. | |||
It is applicable in a wide range of geographic areas, including large and small urban and natural watersheds. | |||
HEC-HMS is capable ofrepresenting many different watershed sizes and land coverage conditions (USACE, 2010a).HEC-GeoHMS (USACE, 2009) and ArcHydro (ESRI, 2011), which are run withinthe ArcGIS framework (ESRI, 2012), were used in the pre-processing ofwatershed data to develop input data files for the HEC-HMS model.HEC-RAS (USACE, 2010b) is designed to perform one-dimensional hydraulic calculations for a full network of natural and constructed channels. | |||
It was used toprovide rating curves for modeling the flow through culverts under Highway 1-10in the East Wash. These rating curves were then used in the HEC-HMS modeldeveloped to support the reevaluation of the river flooding hazard due to thePMP event.All software used to perform the flood hazard reevaluation analyses has beenverified and validated, and commercially dedicated in accordance with a qualityassurance program that meets the requirements of 10 CFR 50 Appendix Bthrough compliance with the Basic and Supplementary Requirements established in Part I of American Society of Mechanical Engineers (ASME) NQA-1-2008 andNQA-la-2009 Addenda2 (ASME, 2009), as well as the following Subparts thatapply to the previously identified software: | |||
" Subpart 2.7, "Quality Assurance Requirements for Computer Software forNuclear Facility Applications." | |||
* Subpart 2.14, "Quality Assurance Requirements for Commercial GradeItems and Services." | |||
2 ASME NQA-1-2008 and NQA-la-2009 Addenda documents cannot be reproduced electronically or viahardcopy without the written consent of ASME.D-2}} |
Revision as of 07:45, 1 July 2018
ML14350A466 | |
Person / Time | |
---|---|
Site: | Palo Verde ![]() |
Issue date: | 12/12/2014 |
From: | Mims D C Arizona Public Service Co |
To: | Document Control Desk, Office of Nuclear Reactor Regulation |
References | |
102-06967-DCM/TNW, EA-12-049 | |
Download: ML14350A466 (128) | |
Text
OapsEA-12-049 10 CFR 50.54(f)DWIGHT C. MIMSSenior Vice President, NuclearRegulatory
& Oversight Palo VerdeNuclear Generating StationP.O. Box 52034Phoenix, AZ 85072Mail Station 7605Tel 623 393 5403102-06967-DCM/TNW December 12, 2014ATTN: Document Control DeskU.S. Nuclear Regulatory Commission Washington, DC 20555-0001
References:
- 1. NRC Letter, Request for Information Pursuant to Title 10 of theCode of Federal Regulations 50.54(f)
Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insightsfrom the Fukushima Dai-ichi
- Accident, dated March 12, 20122. NRC Letter, Palo Verde Nuclear Generating
- Station, Units 1, 2, and 3-Relaxation of Response Due Dates Regarding Flooding HazardReevaluations for Recommendation 2.1 of the Near-Term Task ForceReview of the Insights from the Fukushima Dai-ichi
- Accident, datedJuly 29, 2014
Dear Sirs:
Subject:
Palo Verde Nuclear Generating Station (PVNGS)Units 1, 2, and 3Docket Nos. STN 50-528/529/530 Flood Hazard Reevaluation ReportIn accordance with the NRC request for information documented in Reference 1,enclosed please find the Flood Hazard Reevaluation Report for Palo Verde NuclearGenerating Station Units 1, 2, and 3.Subsequent to the issuance of the request for information, the NRC issued aprioritization of the due dates for the submittal of the flood hazard reevaluation report for all sites. The NRC set the reevaluation due date for PVNGS as March 12,2014. The initial flood hazard reevaluation report for PVNGS concluded that thefollowing events and corresponding results were found to be comparable with thecurrent licensing basis:0S0Probable maximum flood (PMF) for Winters WashSitewide inundation as a result of local intense precipitation (LIP)Dam failureHowever, the flood levels predicted by the initial flood hazard reevaluation weresomewhat greater than expected for the following:
- Areas adjacent to the powerblock structures due to LIP* East Wash embankment due to PMFA member of the STARS (Strategic Teaming and Resource Sharing)
AllianceCallaway
- Comanche Peak
- Diablo Canyon
- Palo Verde
- Wolf Creeklk I Dvaq-'ýL 102-06967-DCM/TNW ATTN: Document Control DeskU.S. Nuclear Regulatory Commission Flood Hazard Reevaluation ReportPage 2As a result, Arizona Public Service Company (APS) requested and received approvalfor an extension of the reevaluation report due date to December 12, 2014, inReference
- 2. The purpose of the extension was to complete a reanalysis by anindependent contractor using refined analysis techniques and a room-by-room internal flooding analysis by APS.The enclosure to this letter contains the results from the initial and refined floodhazard reevaluation, as well as the room-by-room internal flooding analysiscompleted by APS during the extension period.No operator or mitigation actions are needed to ensure safe shutdown capability as aresult of the flood hazard reevaluation.
As no additional actions to protect against thereevaluated flood hazards are needed and the results are comparable to the licensing basis, APS believes that an integrated assessment is not needed or warranted.
No new commitments are being made to the NRC by this letter. Should you needfurther information regarding this submittal, please contact Thomas N. Weber,Licensing Department Leader, at (623) 393-5764.
I declare under penalty of perjury that the foregoing is true and correct.Executed on,tDate)Sincerely, DCM/TNW
Enclosure:
Flood Hazard Reevaluation Report for Palo Verde Nuclear Generating StationUnits 1, 2, and 3cc: M. L. Dapas NRC Region IV Regional Administrator B. K. Singal NRC NRR Project Manager for PVNGSM. M. Watford NRC NRR Project ManagerD. R. Reinert NRC Acting Senior Resident Inspector for PVNGS FLOOD HAZARDREEVALUATION REPORTforPALO VERDE NUCLEAR GENERATING STATIONUNITS 1, 2, AND 3REVISION 0DECEMBER 12, 2014I.0 Flood Hazard Reevaluation ReportTABLE OF CONTENTS
1.0 INTRODUCTION
...................................................................................
31.1 PURPOSE AND SCOPE .............................................................................
31.2 HYDROLOGIC DESCRIPTION OF STUDY AREA ........................................
41.3 SITE FLOOD HAZARD BACKGROUND AND HISTORY ..............................
51.4 DESIGN BASIS OF THE PLANT ..................................................................
61.5 BASIC APPROACH OF THE FLOOD HAZARD REEVALUATION
..................
61.6 PROBABLE MAXIMUM FLOOD REEVALUATION
........................................
82.0 FLOOD HAZARDS AT THE SITE .........................................................
112.1 DETAILED SITE INFORMATION
................................................................
112.2 CURRENT DESIGN BASIS FLOOD ELEVATIONS
....................................
132.3 FLOOD-RELATED CHANGES TO THE LICENSING BASIS .........................
172.4 CHANGES TO THE WATERSHEDS AND LOCAL SITE AREA .....................
182.5 CURRENT LICENSING BASIS FLOOD PROTECTION AND PERTINENT FLOOD MITIGATION FEATURES
..............................................................
192.6 ADDITIONAL SITE DETAILS ....................................................................
203.0 FLOOD HAZARD REEVALUATION ANALYSIS
.................................
213.1 SOFTWARE USED ..................................................................................
213.2 FLOOD-CAUSING MECHANISMS
............................................................
213.3 COMBINED EFFECTS FLOODING
...........................................................
373.4 DAM BREACHES AND FAILURES
............................................................
423.5 STORM SURGE .......................................................................................
423 .6 S EIC HE ...................................................................................................
433 .7 T SU NA M I .................................................................................................
443.8 ICE-INDUCED FLOODING
.......................................................................
44 Flood Hazard Reevaluation Report3.9 FLOODING RESULTING FROM CHANNEL MIGRATION OR DIVERSION
........
444.0 COMPARISON OF CURRENT AND REEVALUATED PREDICTED FLOOD LEVELS ............................................................
454.1 COMPARISON OF CURRENT AND REEVALUATED FLOOD-CAUSING M ECHANISM S .........................................................................................
454.2 ASSESSMENT OF DIFFERENCES BETWEEN CURRENT DESIGNBASIS AND REEVALUATED FLOOD ELEVATIONS AND EFFECTS ........
454.3 SUPPORTING DOCUMENTATION
............................................................
494.4 C ONCLUSIONS
.......................................................................................
505.0 INTERIM EVALUATION AND ACTIONS ............................................
526.0 ADDITIONAL ACTIONS ....................................................................
5
37.0 REFERENCES
......................................................................................
54Appendix A -TablesAppendix B -FiguresAppendix C -Probable Maximum Precipitation in ArizonaAppendix D -Software Used in Flood Hazard Reevaluation ii Flood Hazard Reevaluation ReportLIST OF TABLES IN APPENDIX ATable 2-1 Existing Design Parameters Table 2-2 Current Design Basis Flood Elevations due to all FloodMechanisms Table 3-1 Characteristics of Winters Wash Sub-Basins and HEC-HMS ModelResultsTable 3-2 Summary of FLO-2D Simulations for Winters Wash FloodingTable 3-3 Floodplain Cross-Section PMF Results (100-ft Grid Element Model)Table 3-4 Floodplain Cross-Section PMF Results (25-ft Grid Element Model)Table 3-5 Comparison of PMF LevelsTable 3-6 Fetch DataTable 3-7 Wave Run-up and Freeboard Table 3-8 Summary of FLO-2D Simulation Cases for Combined Effects FloodingTable 4-1 Comparison of Modeling Approaches for CLB and Reevaluation Table 4-2 Comparison of Analytical Inputs for CLB and Reevaluation Table 4-3 Comparison of Flood Levels for CLB and Reevaluation Table 4-4 Comparison of Flooding for CLB and Reevaluation Table 4-5 List of Supporting Documents iii Flood HazardFigure 1-1Figure 1-2Figure 1-3Figure 2-1Figure 2-2Figure 2-3Figure 2-4Figure 3-1Figure 3-2Figure 3-3Figure 3-4Figure 3-5Figure 3-6Figure 3-7Figure 3-8Figure 3-9Figure 3-10Figure 3-11Figure 3-12Figure 3-13Figure 3-14Reevaluation ReportLIST OF FIGURES IN APPENDIX BGeographic Location of Palo Verde Nuclear Generating StationGeneral Location Map of the SiteFlood Hazard Reevaluation Flowchart Site Layout Topography Powerblock Arrangement Aerial View of Site LayoutEast Wash & Winters Wash Watershed HHA Diagram for Local Intense Precipitation Flooding AnalysisLocal Intense Precipitation Hyetographs FLO-2D Inundation Map for Local Intense Precipitation Fetch Locations for Wind-Wave Activity Coincident With LIPFloodingHHA Diagram for Analysis of Flooding in Rivers and StreamsPMP Hyetographs for Winters Wash and East Wash Watersheds Winters Wash and East Wash Sub-Basins Initial Analysis HEC-HMS Model for East Wash and Winters WashWatersheds Fetch Locations for Flooding in Winters WashEast Wash Location Map and Model ExtentEast Wash Floodplain Cross-Section Hydrographs
-Refined PMF(100-ft Grid Element Model)East Wash Flow Depths -Refined PMF (100-ft Grid ElementModel)East Wash Flow Velocities
-Refined PMF (100-ft Grid ElementModel)East Wash Floodplain Cross-Sections iv Flood Hazard Reevaluation ReportFigure 3-15Figure 3-16Figure 3-17Figure 3-18Figure 3-19Figure 3-20Figure 3-21Figure 3-22Figure 3-23Figure 3-24Figure 3-25Figure 3-26Figure 3-27LIST OF FIGURES IN APPENDIX B (CONTINUED)
East Wash Watershed Inflow Hydrographs (Refined Analysis)
East Wash Water Depths -Refined PMF (25-ft Grid ElementModel)East Wash Potential Fetches (Refined Analysis)
North and East Embankment FetchesNorth Embankment Fetch Selection East Wash (Refined Analysis)
East Embankment Fetch Selection East Wash (Refined Analysis)
HHA Diagram for Combined Effects Flooding AnalysisFLO-2D Model Domains for Combined Effects AnalysisMaximum Combined Effects Flood Depth (ft) for Case 3Duration of Combined Effects Flooding (hours) for Case 3ISG-2013-01 Diagram for Determining Levels of Analysis for DamBreak Evaluation ISG-2013-01 Diagram for Analysis of Dam Breaches and FailuresUsing the Volume MethodLocations of Dams Near the SiteV Flood Hazard Reevaluation ReportACRONYMSADWRAGSANSANSIAPSAWACAPCEFCEMCFRCLBDADESPESRIEWFCDMCFEMAHEC-HMSHEC-RASHHAHMRLIPmslMSWNCDCArizona Department of Water Resources Arizona Geological SurveyAmerican Nuclear SocietyAmerican National Standards Institute Arizona Public Service CompanyApplied Weather Associates Corrective Action Programcombined effects floodingCoastal Engineering ManualCode of Federal Regulations current licensing basisdepth-a rea-d u rationessential spray pondEnvironmental Systems Research Institute East WashFlood Control District of Maricopa CountyFederal Emergency Management AgencyHydrologic Engineering Center-Hydrologic Modeling SystemHydrologic Engineering Center-River Analysis Systemhierarchical hazard assessment Hydrometerological Reportlocal intense precipitation mean sea levelmaximum sustained windNational Climatic Data Centervi Flood Hazard Reevaluation ReportACRONYMS (CONTINUED)
NEXRAD next generation radarNGVD National Geodetic Vertical DatumNRC Nuclear Regulatory Commission NRCS National Resource and Conservation ServiceNWS National Weather ServicePMF probable maximum floodPMP probable maximum precipitation PVNGS Palo Verde Nuclear Generation StationREI Riada Engineering, Inc.RG Regulatory GuideSCS U. S. Soil Conservation ServiceSOCA Security Owner Controlled AreaSSC structures,
- systems, and components UFSAR Update Final Safety Analysis ReportUSACE United States Army Corps of Engineers USBR United States Bureau of Reclamation USDA United States Department of Agriculture USGS United States Geological SurveyVBS vehicle barrier systemWW Winters Washvii Flood Hazard Reevaluation ReportEXECUTIVE SUMMARYThis report provides a reevaluation of potential flood causing mechanisms at Palo VerdeNuclear Generating
- Station, (PVNGS) Units 1, 2, and 3, with consideration of thepresent-day regulatory guidance and methodologies being used for combined licensereviews, including current techniques,
- software, and methods used in present-day standard engineering practice.
The flood hazards considered include local intenseprecipitation, flooding from the nearby washes, and potential dam failure flooding.
Otherflood causing mechanisms, such as tsunami, storm surge, seiche, ice-induced
- flooding, and channel diversion
- effects, were excluded as not being applicable based on thecharacteristics of the site.Subsequent to the issuance of the Nuclear Regulatory Commission (NRC) request forinformation on March 12, 2012, (NRC, 2012a) pursuant to Title 10 of the Code ofFederal Regulations (CFR), Section 50.54(f),
the NRC issued a prioritization of the duedates for the submittal of the flood hazard reevaluation report for all sites. The NRC setthe reevaluation due date for PVNGS as March 12, 2014. The initial flood hazardreevaluation report was performed by Paul C. Rizzo Associates, Inc. under asubcontract with Westinghouse Electric Company.The initial flood hazard reevaluation report concluded that the following events andcorresponding results were found to be comparable with the current licensing basis:* Probable maximum flood (PMF) for Winters Wash* Sitewide inundation as a result of local intense precipitation (LIP)" Dam failureHowever, the flood levels predicted by the initial flood hazard reevaluation weresomewhat greater than expected for the following plant locations:
- Areas adjacent to the powerblock structures due to LIP0 East Wash embankment due to PMFAs a result, Arizona Public Service Company (APS) requested and received approvalfor an extension of the reevaluation report due date to December 12, 2014, to completea reanalysis by an independent contractor using refined analysis techniques and aroom-by-room internal flooding analysis by APS.This report contains the results from the initial and refined flood hazard reevaluation, aswell as the room-by-room internal flooding analysis completed by APS during theextension period.1J Flood Hazard Reevaluation ReportThe analyses completed during the extension period included the following specificareas:" Utilized FLO-2D software to model the impacts on the site caused by a PMF inEast Wash* Updated the combined effects analysis in this report to reflect the refined analysisof East Wash* Performed a room-by-room internal flooding analysis of the potential impact onsafe shutdown equipment due to water intrusion from a LIP event. Subsequent refined analysis of LIP in the powerblock validated that the depth and duration ofwater accumulation (hydrographs) used in the room-by-room internal floodinganalysis were conservative.
The results of the refined PMF analysis of East Wash showed flood levels comparable to the current licensing bases with adequate freeboard to contain the PMF including wave runup. The combined effects analysis of the PMF event in Winters Wash and EastWash was bounded by the individual PMF event in each individual wash. The room-by-room internal flooding analysis conservatively utilized the results from the initial LIPanalysis and concluded there was no impact to safe shutdown equipment.
No operator or mitigation actions are needed to ensure safe shutdown capability as aresult of the flood hazard reevaluation.
As no additional actions to protect against thereevaluated flood hazards are needed and the results are comparable to the licensing basis, APS believes that an integrated assessment is not needed or warranted.
Flood Hazard Reevaluation Report
1.0 INTRODUCTION
1.1 Purpose and ScopeThe Nuclear Regulatory Commission (NRC) issued a request for information on March12, 2012, (NRC, 2012a) pursuant to Title 10 of the Code of Federal Regulations (CFR),Section 50.54(f),
related to the implementation of Recommendations 2.1, 2.3, and 9.3from the Near Term Task Force, a portion of which calls for performing flood hazardreevaluations at all nuclear power plants in the United States. This Flood HazardReevaluation Report for the Palo Verde Nuclear Generating Station (PVNGS) Units 1,2, and 3 provides the information required to address NRC Recommendation 2.1 withconsideration of the present-day regulatory guidance and methodologies being used forcombined license reviews, including current techniques,
- software, and methods used inpresent-day standard engineering practice.
The site (geographic location shown in Figure 1-1 is licensed for the operation of threeCombustion Engineering System 80 pressurized water reactor nuclear generating units.The original operating licenses for Units 1, 2, and 3 were issued June 1, 1985, April 24,1986, and November 25, 1987, respectively.
The operating licenses for all three unitswere renewed on April 21, 2011, and will expire June 1, 2045, April 24, 2046, andNovember 25, 2047, respectively.
Revision 17 to the Updated Final Safety Analysis Report (APS, 2013) for PVNGS Units1, 2, and 3 was issued to the NRC in June 2013.1.1.1 Flood Hazard Reevaluation Extension Subsequent to the issuance of the NRC request for information, the NRC issued aprioritization of the due dates for the submittal of the flood hazard reevaluation report forall sites. The NRC set the reevaluation due date for PVNGS as March 12, 2014.The initial flood hazard reevaluation report concluded that the following events andcorresponding results were found to be comparable with the current licensing basis:" PMF for Winters Wash* Sitewide inundation as a result of LIP* Dam failureHowever, the flood levels predicted by the initial flood hazard reevaluation weresomewhat greater than expected for the following plant locations:
0 Areas adjacent to the powerblock structures due to LIP0 East Wash embankment due to PMFAs a result, Arizona Public Service Company (APS) requested and received approvalfor an extension of the reevaluation report due date to December 12, 2014, to complete3 I*b Flood Hazard Reevaluation Reporta reanalysis by an independent contractor using refined analysis techniques and aroom-by-room internal flooding analysis by APSThis report contains the results from the initial and refined flood hazard reevaluation, aswell as the room-by-room internal flooding analysis completed by APS during theextension period.The analyses completed during the extension period included the following specificareas:" Utilized FLO-2D software to model the impacts on the site caused by a PMF inEast Wash* Updated the combined effects analysis in this report to reflect the refined analysisof East Wash* Performed a room-by-room internal flooding analysis of the potential impact onsafe shutdown equipment due to water intrusion from a LIP event. Subsequent refined analysis of LIP in the powerblock validated that the depth and duration ofwater accumulation (hydrographs) used in the room-by-room internal floodinganalysis were conservative.
1.2 Hydrologic Description of Study AreaThe site is located in Maricopa County, AZ at approximately 33023' North latitude and112052' West longitude.
The site is isolated from maritime bodies of water and isapproximately 46 miles west of the center of Phoenix (Figure 1-1). Two desert streams,Winters Wash and East Wash, are located to the west and east of the site, respectively, as shown in Figure 1-2.The site is located in a dry, desert region adjacent to the Palo Verde Hills. The terrainhas very little topographic relief and slopes gently southward.
Palo Verde is considered a "dry site" in accordance with the definition contained in Regulatory Guide (RG) 1.102,Revision 1 (NRC, 1976). As defined in the RG, a dry site is a site where the plant is builtabove the Design Basis Flooding Level, and therefore safety-related structures, systems and components (SSCs) are not affected by external flooding.
The gradeelevations
[mean sea level (msl)] of Seismic Category I structures are 957.5 ft for Unit 1,954.5 ft for Unit 2, and 951.5 ft for Unit 3 (UFSAR Figure 2.4-4).The vertical datum used in the UFSAR is msl. At the site, the msl datum is equated withthe National Geodetic Vertical Datum of 1929 (NGVD29),
which, prior to 1973, wasreferred to as the Sea Level Datum of 1929 (USGS, 2013a). Equivalency between themsl datum and NGVD29 is apparent in a 1962 USGS map (USGS, 1962) covering thesite area. In this Flood Hazard Reevaluation Report, all elevations are provided inNGVD29, unless stated otherwise.
Additional dry rivers and washes in the vicinity of the site include the Gila River and twoof its tributaries, the Hassayampa River and the Centennial Wash. The Gila River'snearest approach is approximately six miles southeast of the site. The Hassayampa 4 J Flood Hazard Reevaluation ReportRiver and Centennial Wash are located approximately five miles east and five milessouth of the site, respectively.
Luke Wash is further east than East Wash and thedischarge from its watershed is conservatively combined in this study with theHassayampa River.1.3 Site Flood Hazard Background and HistoryEast Wash and Winters Wash discharge to Centennial Wash (UFSAR Figure 2.4-1),which discharges into the Gila River upstream of the Gillespie Dam. The Hassayampa River also discharges into the Gila River. Although there is no stream gage on EastWash, a study of the available United States Geological Survey (USGS) stream gagedata for the other four watercourses found no published information to indicate thatflooding on any of these conveyances has resulted in water depths that would constitute a flood hazard at the site.Additional details concerning historic flooding along these rivers and washes areprovided in the following discussion.
The stream gage and discharge rate information isprovided through the USGS (USGS, 2013b).Gila River FloodingThe Gillespie Dam is approximately 12 miles southeast of the site. The Gila Riverwatershed upstream of the Gillespie Dam has an area of approximately 50,000 squaremiles (sq mi) (USGS, 2013b), including watersheds of East Wash, Winters Wash,Centennial Wash, and the Hassayampa River.Systematic reporting of estimated discharges on the Gila River upstream of theGillespie Dam began in 1888 (USACE, 1957). The largest flood of record is for February1891 with an estimated discharge of 250,000 cubic feet per second (cfs) at the site ofGillespie Dam. Peak annual flood flows for this gage (USGS gage 09519000) through1977 are reported in UFSAR Table 2.4-5. Significant flood events reported since 1977and the discharge rates include the following:
- 1979 125,000 cfs* 1984 95,200 cfs* 1989 178,000 cfs* 1993 130,000 cfsA second gage along the Gila River is USGS Gage 09514100 for the Gila River atEstrella
- Parkway, near Goodyear, AZ. This gage is approximately 30 miles upstream ofthe Gillespie Dam along the Gila River and five miles downstream of inflows along theSalt River. The period of record is from 1993 to 2013, with the two highest flowsrecorded as 162,000 cfs in 1993 and 74,900 cfs in 1995.5 lk Flood Hazard Reevaluation ReportHassayampa River FloodingThe Hassayampa River discharges to the Gila River at a location approximately 9 mileseast of the site. USGS Gage 09517000 for the Hassayampa River near Arlington, AZ islocated approximately 1.8 miles upstream of the confluence with the Gila River. Theperiod of record for this gage is 1961 through 2012. The two largest annual peak floodsfor this period are 39,000 cfs in 1970 and 22,000 cfs in 2001.Peak flows for USGS Gage 09516500 for the Hassayampa River near Morristown, AZare reported in UFSAR Table 2.4-4. The peak flow rate for this location of 47,500 cfs onSeptember 5, 1970, remains the largest flood recorded at the gage station.Centennial Wash FloodingThe Centennial Wash discharges to the Gila River just upstream of the Gillespie Dam,approximately six miles south of the site. USGS Gage 09517490 is located on this washat the Southern Pacific Railroad Bridge near Arlington, AZ, providing flow records from1983 to the present.
The two largest annual peak floods recorded at this gage are15,600 cfs in 1984 and 9,210 cfs in 1993.A second gage along the Centennial Wash (USGS Gage 09517500) near Arlington, AZhas flow records for the period of 1961 through 1978. The largest flood for this gage is14,500 cfs occurring in 1961. The next largest flood for this gage is 11,900 cfs in 1970.This gage was the source for the flows reported in UFSAR Table 2.4-2.Winters Wash FloodinqUSGS Gage 09517400 on Winters Wash near Tonopah, AZ is located approximately 8miles northwest of the site. The two largest annual peak floods of record for this gageare 3,640 cfs in 1976 and 2,100 cfs in 1972. This gage was used for the flows reportedin UFSAR Table 2.4-3.1.4 Design Basis of the PlantThe onsite drainage system is designed such that runoff due to probable maximumprecipitation (PMP) will not inundate safety-related structures, equipment, and access tothose facilities.
Areas adjacent to the powerblock are sloped away at 0.5% to 1%,resulting in a minimum drop of 5 to 7 feet at the peripheral drainage system. The designbasis calculated maximum water surface elevations due to local PMP storm are 955.5ft, 952.5 ft, and 949.5 ft at Units 1, 2, and 3, respectively.
These maximum floodelevations are 2.0 feet below the grade elevations at the respective units (UFSARSection 2.4.2.3).
1.5 Basic Approach of the Flood Hazard Reevaluation As stated earlier in this report, the initial flood hazard reevaluation report was conducted by Rizzo, a subcontractor to Westinghouse Electric Corporation.
The scope of this initial6 91 d-.
Flood Hazard Reevaluation Reportreevaluation is shown in Figure 1-3 and includes the following analyses that wereperformed in accordance with NUREG/CR-7046 (NRC, 2011):* PMF for both Winters Wash and East Wash" Sitewide inundation as result of LIP* Dam failure" Combined effectsIn this report, the first reevaluation done by Rizzo is referred to as the "initial floodhazard reevaluation."
The initial flood hazard reevaluation predicted flood levels for aLIP that were somewhat greater than expected for areas adjacent to the powerblock structures and also for PMF flood levels for East Wash. APS requested an extension from the NRC in order to have additional analyses done using specific refinements.
Oneof the elements of the refined analysis was to use FLO_2D software (FLO-2D, 2012) tomodel the impact on the site caused by a PMF in East Wash.Another element of the refined analysis was to utilize a modified version of the FLO-2Dsoftware model that specifically accounted for roof detention (parapet walls), scupperinlets, scupper outlets, and downspouts.
This enhancement to the FLO-2D program wasdone by the FLO-2D developers specifically for this project.
The flow to the ground forthe LIP event is attenuated on the roof and discharged to specific locations, in lieu ofdirecting runoff directly to the ground. This was intended to address the unexpected results for the higher flood levels for areas adjacent to the powerblock structures.
The final action was for APS to perform a room-by-room internal flooding analysis.
Dueto the time constraints of having to complete the flood hazard revaluation by December12, 2014, the room-by-room internal flooding analysis had to be performed beforecompletion of the refined analyses.
Therefore, the results from the second element ofthe refined analysis (LIP) were not available to use as an input to the room-by-room internal flooding analysis.
The lower flood levels obtained for the second refinement were used to validate margin for the depth and duration of water accumulation in theareas adjacent to the powerblock structures.
1.5.1 Probable Maximum Precipitation The original design basis PMP was used to determine the PMF levels in thewatercourses near the site that might contribute to flooding of the site, specifically Winters Wash and East Wash. The design basis PMP for Winters Wash was calculated using the Hershfield method based on the statistics of extreme events (UFSAR Section2.4.3.1.1),
while the PMP for East Wash was obtained using extreme summerthunderstorm rainfall for the southwest (USFAR Section 2.4.3.1.2).
7 -.t Flood Hazard Reevaluation ReportThe LIP1 was calculated for the current design basis using the 1972 Preliminary Probable Maximum Thunderstorm Precipitation Estimates Southwest States Report(NWS, 1972) by the National Weather Service (NWS) (UFSAR Table 2.4-6).For the initial and refined flood hazard reevaluation, the most up-to-date PMPestimation methodology for the state of Arizona was applied to develop the LIPhyetograph using a PMP evaluation tool developed by Applied Weather Associates (AWA) for the Arizona Department of Water Resources (ADWR) (AWA, 2013).1.6 Probable Maximum Flood Reevaluation The design basis 24-hour PMP produced the most severe design basis PMF for WintersWash, while the design basis 6-hour thunderstorm produced the most severe designbasis PMF for East Wash (UFSAR Section 2.4.3.1).
For the initial and refinedreevaluation
- analyses, PMP hyetographs were developed and applied over theircorresponding watersheds to characterize the design basis PMF within the two desertwatersheds adjacent to the site. The hyetographs were determined using the AWA tool,which provides PMP values for three different storm types: local storms (i.e.,thunderstorms),
general winter storms, and tropical storms.Winters Wash and East Wash Reevaluation For East Wash, the depth and duration of flooding, maximum flood velocities, andhydraulic forces associated with flooding at the site were determined in the initialanalysis using the FLO-2D flood routing program (FLO-2D, 2012).Inputs to the model included the flood hydrographs for each wash using the Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS) and rainfall based on thePMP hyetograph for each watershed.
The initial analysis calculations were refined to include additional detailed data andmethodology in accordance with the hierarchical hazard assessment (HHA) approach inNUREG/CR-7046 (NRC, 2011) utilizing a two-dimensional hydraulic model (FLO-2D,2014a) to calculate the impacts on the site caused by PMF in East Wash. A two-dimensional model simulates the flow of water more accurately than a one-dimensional model such as HEC-HMS (USACE, 2010a) in combination with the Hydrologic Engineering Center-River Analysis System (HEC-RAS)
(USACE, 201 Ob). It had beendetermined that flooding in Winters Wash does not affect the site, so the analysis forWinters Wash was not refined.1 The NRC defines LIP as a 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, 1 sq mi PMP event located at the site. The UFSAR uses the term"local intense precipitation,"
but not the abbreviation "LIP." The UFSAR also uses the term point-value PMP when referring to the rainfall associated with the LIP (UFSAR 2.4.3.2).
8 1*
Flood Hazard Reevaluation Report1.6.1 Local Intense Precipitation in the Powerblock The most up-to-date PMP estimation methodology for the state of Arizona was appliedto develop the LIP hyetograph for the powerblock using the PMP evaluation tooldeveloped by AWA. The hyetograph was developed for the Security Owner Controlled Area (SOCA), which is approximately 1 sq mi and encompasses safety-related SSCs atthe site. It was assumed to rain evenly over the FLO-2D model domain (approximately four sq mi). The resulting cumulative 6-hour rainfall depth was 12.80 inches following the methodology of the AWA tool. The maximum rainfall in one hour within the LIPhyetograph was 10.73 inches.1.6.2 Effects of LIP on Safety-Related SSCs in the Powerblock UFSAR Section 2.4.2.3 states that areas adjacent to the powerblock are sloped away at0.5 to 1%. This results in a minimum drop of 5 to 7 feet at the peripheral drainagesystem, as compared to the grade elevation at each unit. Computer and handcalculation methodologies used during initial design did not have the capability topredict minor accumulation adjacent to the entrances of buildings.
Therefore, thelicensing bases did not provide a specific value for the transient water accumulation phenomenon.
- However, the design of powerblock structures did include sufficient capability to mitigate internal flooding resulting from high and moderate energy linebreaks, which was implicitly assumed to bound the effects of external flooding fromlocalized transient water accumulation during the LIP event. These design featuresinclude independent four-inch drain headers, pedestals, curbs, check valves and roomtrain separation, and a large holdup capacity at the lower elevations of each building.
These passive design features provide an inherently safe design for localized transient water accumulation during a LIP event and the corresponding internal flooding ofbuildings, as further discussed in Section 3.2.1.6.Today, numerical models and software such as FLO-2D can predict a conservative estimate of local transient water accumulation adjacent to the powerblock structures.
Appendix B to NUREG/CR-7046 utilizes a one-dimensional flow model and does notprovide a method to predict the accumulation of water within the powerblock complex.The initial flood hazard reevaluation for LIP was performed using FLO-2D. A byproduct of the analysis was hydrographs for the perimeters of each powerblock building.
Acomprehensive room-by-room internal flooding analysis of water infiltration from LIPwas performed using the hydrographs and existing design features for internal flooding.
The analysis concluded that infiltrating water from LIP does not impact safe shutdownequipment within these buildings due to the various plant features such as curbs,pedestals, train separation, drains, stairwells, and trenches that redirect or limit waterflow into the critical areas of the plant.Additionally, to understand the margin of the room-by-room internal flooding
- analysis, arefined model of each powerblock was developed using modified FLO-2D (FLO-2D,2014b) software that included roof, gutters and downspouts.
The refinement provided amore accurate representation of the flow characteristics of roof runoff and consequential 9 *4 Flood Hazard Reevaluation Reporttransient water accumulation adjacent to structures.
This refined LIP for the powerblock provided additional insight to the complex nature of sheet flows surrounding powerblock structures and confirmed that additional margin can be realized by more complexmodeling.
10 .
Flood Hazard Reevaluation Report2.0 FLOOD HAZARDS AT THE SITESection 2.0 has been prepared in response to Item 1.a. of NRC Recommendation 2.1,Enclosure 2 of the 10 CFR 50.54(f) letter. This section documents current design basisresults, as well as pertinent site information related to the applicable flood hazards.The current flood hazards are identical to the flood hazards that existed during the initiallicensing phase and documented in UFSAR Sections 2.4.2 through 2.4.7, except for theaddition of combined effects flooding (CEF) as required by the NRC.2.1 Detailed Site Information Section 2.1 has been prepared in response to Item 1.a.i. of NRC Recommendation 2.1,Enclosure 2 of the 10 CFR 50.54(f) letter. Relevant site data presented for consideration include the present-day site layout, elevation of pertinent SSCs important to safety, sitetopography, as well as pertinent spatial and temporal data sets.2.1.1 Design Site Information Design site information describes characteristics considered for the original licensing basis of the site. Changes to the site layout and SSCs related to flooding protection were discussed and evaluated as part of the Flooding Walkdown Report (APS, 2012).These changes were evaluated as part of this hazard reevaluation report with respect tothe new guidance and methodologies.
The topographic mapping and site layout are provided in Figure 2-1 and supplemented by aerial photography (Figures 2-2 and 2-3). The powerblock arrangement is shown inFigure 2-2.Site Topography Ground surface elevations range from 890 ft at the southern site boundary to nearly1,030 ft at the northern site boundary (UFSAR Section 2.1.1.2).
Protection of safety-related facilities from inundation by offsite flood sources is achieved by the location ofthe facilities beyond the extent of flooding (UFSAR Section 2.4.2.2.1).
The onsitedrainage system is designed so that runoff due to PMP will not inundate the safety-related structures, equipment, and access to these facilities (UFSAR Section 2.4.2.3).
The existing flooding design bases found in the UFSAR, the structure elevations, andthe flood levels are presented in Table 2-1. Plant grades for Units 1, 2, and 3 are all 951ft or above (UFSAR Section 2.4.2.2.2).
East Wash was realigned from its natural course to a location east of the site during sitegrading and construction activities (UFSAR Section 2.4.10).
Flood calculations documented in the UFSAR were based upon the realigned position of East Wash.11 Flood Hazard Reevaluation ReportSafety-Related SSCsThe locations of the safety-related structures are shown in Figure 2-2. A list of theexisting flooding elevations found in the UFSAR is presented in Table 2-1.Ultimate Heat SinkThe ultimate heat sink for each unit consists of two independent Seismic Category Iessential spray ponds (ESPs) (UFSAR Section 9.2.5) located adjacent to the unit(Figure 2-2). The ESPs for each unit are rectangular reinforced concrete structures ableto remain functional following any external event as required by 10 CFR 50 Appendix A,General Design Criterion 2 (UFSAR Section 9.2.5.2).
2.1.2 Present-Day Site Information Site ToDocraphy Changes to site and surrounding topography since licensing have been identified anddocumented.
The site topography was confirmed by aerial mapping as part of the floodhazard reevaluation and recent surrounding topography information was obtained fromgovernmental agencies for use in the PMF reevaluation.
Present-day topographic mapping for the site includes the detailed APS 2013 aerialtopographic mapping and digital topographic maps provided by the Flood ControlDistrict of Maricopa County (FCDMC).
The 2013 site aerial topographic mapping wasused to obtain ground and pond surface elevations for the area within the site. Theaerial data were supplemented with GPS survey data where shadows causedinaccuracies in the aerial data. The map data obtained from the FCDMC includes:
- Palo Verde mapping (2-foot vertical contours from June 2007)* Luke Wash and Arlington mapping (2-foot vertical contours from September andDecember 2005)* Countywide mapping (10-foot vertical contours from December 2000)The two-foot vertical contour mapping provided by the FCDMC was used for delineation of the watersheds adjacent to the site for the flood hazard reevaluation.
The verticaldatum for the topographic contour data is the North American Vertical Datum of 1988(NAVD88),
which was converted to NGVD29. The FCDMC topographic data providessufficient detail to support the simulation of floods in East Wash and Winters Wash. Thetopographic data reflects the bottom of the stream beds, not a water surface, becausethe data was collected when the stream beds were dry.The topographic data for the on-site ponds and reservoirs reflects the water levels at thetime of the 2013 site aerial topographic mapping.
The starting water surface elevations used in the flooding analyses were higher than the water levels recorded in thetopographic data. Therefore, detailed bathymetric data for these impounded waterbodies was not required to conduct the flooding analyses described in Sections 3.2. 112 .1 Mw Flood Hazard Reevaluation Reportand 3.2.2. The topographic data for the areas around the impounded water bodies wassufficient for evaluating potential flooding at the site.The rivers and washes in the vicinity of the site are the Hassayampa River, Gila River,Winters Wash, Centennial Wash, and East Wash, as shown in Figure 2-4.Safety-Related SSCsChanges to the site layout and SSCs related to flooding protection were noted as part ofthe Flooding Walkdown Report. Based on field observations, the alterations to thetopography by the modifications do not adversely affect the runoff assumed in thecurrent licensing basis (CLB) to the point where it could affect Seismic Category Istructures.
The external flooding walkdowns identified some conditions related to features thatprotect Seismic Category I structures from the effects of PMP and PMF as well asgroundwater intrusion.
These items were entered into the Corrective Action Program(CAP) and actions are being taken to correct the conditions.
The conditions have beenaddressed to ensure the affected SSCs continue to be functional or operable, asapplicable.
Ultimate Heat SinkThe design and design criteria for the ESPs have not changed and were verified by thewalkdowns performed in support of NTTF 2.3 as reported in the Flooding WalkdownReport.2.2 Current Design Basis Flood Elevations Section 2.2 has been prepared in response to Item 1 .a.ii. of NRC Recommendation 2.1,Enclosure 2 of the 10 CFR 50.54(f) letter. Relevant site data to be considered includesthe current design basis flood elevations for all flood-causing mechanisms.
2.2.1 Point-Value Probable Maximum Precipitation For the current design basis, the point-value PMP (equivalent to the new NRC definition of LIP) was calculated using National Weather Service data (NWS, 1972), which waseventually issued as Hydrometeorological Report No. 49 (HMR 49) (NOAA, 1977). Therainfall depth was computed to be 11.8 inches for a duration of 1-hour and 15.53 inchesfor a duration of six hours (UFSAR Table 2.4-6).The current design basis point-value PMP calculations assumed zero infiltration lossesand complete blockage of the drainage culverts.
The occurrence of snow and iceaccumulation coincident with the point-value PMP was not considered to be a probableevent. The maximum local flooding water surface elevations due to the point-value PMPevent were 955.5 ft, 952.5 ft, and 949.5 ft at Units 1, 2, and 3, respectively, which aretwo feet below the floor elevations of the respective units (UFSAR Section 2.4.2.3).
13&*i Flood Hazard Reevaluation Report2.2.2 Probable Maximum Flood on Rivers and StreamsPMP hyetographs were developed and applied over the corresponding watersheds tocharacterize the design basis PMF within the two desert watersheds adjacent to thesite, Winters Wash and East Wash (UFSAR Figure 2.4-1).Winters WashThe PMP for the Winters Wash watershed was calculated using the Hershfield method.The PMP that produces the most severe PMF for the Winters Wash watershed was the24-hour PMP, which has a cumulative rainfall of 14.6 inches. (UFSARSection 2.4.3.1.1).
The current design basis PMF flow rate calculated for Winters Washis 172,400 cfs at cross-section D (UFSAR Table 2.4-16).
The maximum water surfaceelevations for the PMF on Winters Wash at cross-sections near the site (UFSARFigure 2.4-2) range from 929.5 ft at cross-section D to 956.4 ft at cross-section AA,including wind-wave run-up. These flood levels do not adversely affect the site asimportant to safety SSCs are not inundated by the PMF in Winters Wash (UFSARSection 2.4.3).The current design basis combined wind setup and run-up heights are provided inTable 2-2.East WashThe UFSAR states that flood protection will be achieved by site grading such that allSeismic Category I facilities will be located beyond the extent of PMF (UFSARSection 2.4.10).
It further states that:East Wash has been realigned along the eastern edge of the site tomaximize use of the site for other facilities and to limit the extent of the PMF.The normal channel of East Wash has been blocked by an embankment between the two hills on the northern edge of the site. This embankment forces flood flows around the small hill in the northeast corner of the site andcuts off any flow through the old channel.
An additional embankment hasbeen constructed along the eastern edge of the site to prevent flooding of thesite proper.The PMP for the East Wash watershed was calculated using National Weather Servicedata (NWS, 1972). The 6-hour PMP with a cumulative rainfall of 14.44 inches causedthe most severe PMF for East Wash. The current design basis PMF flow rate calculated for East Wash is 16,600 cfs (UFSAR Table 2.4-7). The water surface elevations due toPMF on East Wash at cross-sections near the site range from 926.6 ft at cross-section F to 978.8 ft at cross-section G2 (UFSAR Figure 2.4-2, and UFSAR Table 2.4-16).These flood levels do not adversely affect the site at the associated cross-sections.
Accordingly, the UFSAR concluded that all Category I facilities are safe from inundation by the PMF on (or from) East Wash (UFSAR Section 2.4.3).14 Flood Hazard Reevaluation ReportThe maximum flood elevation for the current design basis combined wind setup andrun-up heights is provided in Tables 2-2, 4-3 and 4-4.Hassayampa River, Gila River, and Centennial WashA topographic ridge between the plant site and the Hassayampa River, five miles eastof the plant site, provides a natural barrier against site flooding that is approximately 33 ft above the river's PMF level. The nearest approach of the Gila River to the sitesix miles to the southeast, where the PMF stage is 175 ft below the lowest plant gradeelevation of 951 ft at Unit 3. Centennial Wash is approximately five miles south ofUnit 3, with a PMF level approximately 63 ft below the lowest plant grade (UFSARSection 2.4.2.2.1).
An evaluation of the PMF similar to that of East and WintersWashes determined that flood events on these watercourses do not reach the site(UFSAR Section 2.4.3).2.2.3 Potential Dam Failures (Seismically Induced)According to the UFSAR, the floodwater surface elevation due to dam failure does notadversely affect the plant. Using the cross-section data and inundation maps of the Salt,Verde and Agua Fria river systems, a floodwater surface elevation of 900 ft wouldaccommodate a peak discharge of 7.6 million cfs at the selected point in the Gila River,51 ft lower than the plant grade for Unit 3. Accordingly, a peak discharge of 7.6 millioncfs resulting from domino-type failure of dams in the Gila River system upstream fromthe site with timing such that the peaks from each river arrive simultaneously at thepoint in the Gila River nearest to the plant site during a standard project flood has beendetermined to not impact the site. Wind-waves superimposed upon these water surfaceelevations will also not affect the site (UFSAR Section 2.4.4.3).
2.2.4 Probable Maximum Surge and Seiche Flooding, Probable MaximumTsunami Flooding, and Ice EffectsStorm surge and seiche flooding, tsunami flooding, and ice effects were screened outas potential flooding mechanisms in the UFSAR:" Probable maximum surge and seiche flooding (UFSAR Section 2.4.5)" Probable maximum tsunami flooding (UFSAR Section 2.4.6)* Ice effects (UFSAR Section 2.4.7)2.2.5 Channel Diversion The source of cooling water for PVNGS, including a source of makeup for the ESPs, istreated sewage effluent primarily from the city of Phoenix.
The effluent is conveyed tothe site through approximately 35 miles of pipeline and treated in the onsite waterreclamation facility to meet plant water quality requirements.
Onsite storage reservoirs provide for a continuous water supply in the event of scheduled or unscheduled interruptions or reductions in the normal water source (UFSAR Section 2.4.9).is&5-A Flood Hazard Reevaluation ReportSince the conveyance line, water reclamation plant, and reservoirs are not specifically designed against failure under extreme environmental conditions, the normal watersource is subject to possible interruption.
- However, the ESPs are designed to providestorage of safety-related water necessary for safe shutdown, and the ponds will not besubject to loss of function due to any interruptions in the water source (UFSARSection 2.4.9).Therefore, channel diversion is not applicable in the current design basis from theperspective of interruption of cooling water supply.2.2.6 Operating Water Surface Elevations There are two cooling water makeup reservoirs at the site (Figure 2-3). These reservoirs are called the "45-Acre Reservoir" and the "85-Acre Reservoir" because at the normaloperating capacity (water surface elevation at 951 ft), the associated surface areas areapproximately 45 acres and 85 acres for the two reservoirs, respectively.
The pumps in the intake structure of each reservoir require a minimum water surfaceelevation of 922.5 ft for operation.
The normal operating level in both reservoirs is 951 ftwith a maximum operating level in both reservoirs of 952.5 ft to accommodate emergencies and power plant outages.
Operational procedures provide for the controlof water levels in the ponds so that they are only raised above 951 ft when there is nolarge storm in the weather forecast.
A freeboard of 1.5 ft (between 951 ft and 952.5 ft) isprovided to contain the 6-hour PMP and to accommodate occasional excess flows fromthe reclamation plant in emergencies.
An additional minimum 2.5 ft of freeboard isprovided to accommodate waves and run-up (UFSAR Section 2.4.8.2.2) so theminimum embankment elevation is 955 ft.There are currently three evaporation ponds in service near the site southern boundary(Figure 2-3). Pond No. 1, with a surface area of approximately 250 acres, wasconstructed initially to provide sufficient capacity for approximately four years from thestartup of Unit 1. Pond No. 2, with a surface area of approximately 235 acres, wasconstructed in 1988, along the east side of Pond No. 1. Pond No. 2 was eventually divided with internal embankments into three segments; Pond 2A (117 acres), Pond 2B(87 acres) and Pond 2C (30 acres). In 2009, Pond No. 3, with a surface area ofapproximately 180 acres, was constructed as an earth embankment structure to thesouth of Pond No. 1, and is divided into two near-equal halves.The maximum operating water surface elevation for all of the evaporation ponds is937 ft. The maximum operating elevation provides 1.5 ft of freeboard above the normaloperating level of 935.5 ft to allow for the 6-hour PMP and occasional plant wastewater discharge during startup.
An additional minimum 5 ft of freeboard is provided toaccommodate waves and run-up (UFSAR Section 2.4.8.2.3) such that the minimumembankment elevation is 942 ft for all three ponds.The ESPs are operated with a maximum static water level of 1.1 ft below the top of thevertical walls, which is maintained by an overflow weir (UFSAR Figure 9.2-1). This16 9, Flood Hazard Reevaluation Reportarrangement provides adequate freeboard for high wind conditions i.e., wavesgenerated within the ESPs could not spill out. The ESP walls are rated for full capacity(water levels up to the top of each wall), which accounts for hydrostatic loads and waverun-up for flood events.2.3 Flood-Related Changes to the Licensing BasisSection 2.3 has been prepared in response to Item 1.a.iii of NRC Recommendation 2.1,Enclosure 2 of the 10 CFR 50.54(f) letter. Relevant site data to be considered includeflood-related changes to the licensing basis and any flood protection changes (including mitigation) since license issuance.
2.3.1 Description of Hydrological Changes and Flood Elevations Hydrologic changes since the initial license issuance with a potential to impact floodelevations at the site include changes in the rainfall-runoff response of the WintersWash and East Wash watersheds due to natural geomorphologic processes andanthropogenic (i.e., man-made) changes.Natural geomorphologic processes with the potential to change the rainfall-runoff response of the watersheds include severe erosion and channel down-cutting andmigration.
There has been no report of processes of this nature that would impact floodelevations at the site.Anthropogenic forces with the potential to change the rainfall-runoff response of thewatersheds include urbanization, road construction, and channelization.
There has beenno report of urban development with an aerial extent sufficient to change runoff in theWinters or East Wash watersheds.
- However, the construction of the Interstate 10 (1-10)embankment and associated drainage ditches and culverts more than six milesupstream of the site has potentially impacted drainage patterns and peak discharges associated with rainfall events. The flood hazard reevaluation includes the effects of1-10 (Section 2.4.2).Channelization and realignment of East Wash associated with the construction ofPVNGS had a beneficial impact on flood elevations at the site. These changes wereincorporated in the hydrologic studies and flooding calculations associated with theoriginal license application.
The design basis flood elevations for the flood-causing mechanisms that are applicable to the site are summarized in Table 2-2. A description of changes to flood-related protection implemented since license issuance is provided in Sections 2.3.2 and 2.4.2.Up-to-date information and data regarding topography, buildings, structures, andhydrologic controls were utilized in the flood hazard reevaluation analysis.
2.3.2 Description of Flood Protection Changes (Including Mitigation)
The flood protection system described in the UFSAR and observed and documented inthe Flooding Walkdown Report, is specifically relevant to the flood hazard reevaluation 17 M Flood Hazard Reevaluation Reportanalyses.
Changes to the site layout and SSCs related to flood protection were noted aspart of Recommendation 2.3, Flooding Walkdown.
Changes to flood protection related to site layout are discussed further in Section 2.4.2.Safety-related SSCs that are credited in the CLB with protection of the plant fromexternal flood hazards were identified, inspected, and evaluated.
Observations ofnonconforming conditions were entered into the CAP.2.4 Changes to the Watersheds and Local Site AreaSection 2.4 has been prepared in response to Item 1.a.iv of NRC Recommendation 2.1,Enclosure 2 of the 10 CFR 50.54(f) letter. Relevant site data to be considered includeschanges to the watershed and local area since license issuance.
Descriptions of thewatersheds at the time of license issuance and pertinent changes to the watersheds since license issuance are presented in the following two subsections.
2.4.1 Description of the Watersheds and Local Area at the Time of LicenseIssuanceThe site is located within a broad valley or basin surrounded by a series of low hills witha maximum relief of less than 250 ft. The average elevation of the basin floor isapproximately 950 ft and the adjacent hills rise to about 1,200 ft elevation.
The basinfloor slopes to the south with a gradient of about 28 ft per mile and is dissected by anumber of stream channels that converge and flow toward the Gila River, about 10miles to the south. Figure 2-4 provides an aerial view with the various rivers andwatersheds annotated.
The site is bordered by Winters Wash on the west and East Wash on the east. BuckeyeSalome Road is north of the site and runs in a northwest-southeast direction.
A pavedcounty road, Wintersburg Road, runs north-south along the west edge of the site, andElliot Road (also referred to as Ward Road) runs east-west along the southern boundaryof the site (UFSAR Figure 1.2-2).A Union Pacific railroad line runs on a southwest-northeast alignment approximately twomiles south of Elliot Road. A spur from that rail line heads north across Elliot Road andforms a peripheral ring around most of the site; thereby, providing rail access at anumber of points within the powerblock, near the cooling towers, and other areas of thesite.2.4.2 Description of Changes to the Watersheds and Local Area since LicenseIssuanceChanges at the site since the development of the original design basis include theaddition of the 45-Acre Reservoir, construction of a vehicle barrier system (VBS)creating a SOCA boundary (Figure 2-3), and non-safety-related building expansion outside the Protected Area. In addition, Evaporation Ponds No. 2 and No. 3 wereconstructed in 1988 and 2009, respectively.
These changes were accounted for in theflood hazard reevaluation.
18 A m Flood Hazard Reevaluation ReportExcavated soils from the 45-Acre Reservoir were initially placed in East Wash, east ofthe embankment.
Later, this spoils pile was removed from East Wash and was placed inseveral locations around the 45-Acre and 85-Acre Reservoirs, where it would not affectflow of water in East Wash. The impact of this earthwork activity on site topography wasaccounted for in the flood hazard reevaluation.
A section of 1-10 was constructed across Winters Wash and East Wash watersheds north of the site (Figure 2-4). The impact of the embankment and associated drainageditches and culverts on flow patterns within the watersheds were accounted for inhydrologic modeling associated with the flood hazard reevaluation.
The flood hazardreevaluation uses newer and higher resolution topographic data than the floodingevaluation documented in the UFSAR. The analysis in the UFSAR was based on USGSquadrangle maps which, due to the date of the survey and/or the low resolution, maynot account for the presence of 1-10. The higher resolution data used in the flood hazardreevaluation leads to a more detailed delineation of watershed boundaries.
In the caseof the East Wash watershed, the updated delineation indicates a larger watershed thanwas delineated for the UFSAR analysis (UFSAR Section 2.4.3).South of the site, Elliot Road was paved to accommodate new industrial development south of the road. There have been some minor developments north of the site with aninsignificant impact on watershed runoff or site drainage.
Changes in the Gila River watershed include replacement (i.e., submergence) of theWaddell Dam by construction of the New Waddell Dam, which was completed in 1994(USBR, 2011 a). Additionally, the Theodore Roosevelt Dam and the Bartlett Damstorages have been augmented since license issuance.
The increased storage volumewas accounted for in the screening of dam failure for the flood hazard reevaluation.
The impact of the changes on regional and site drainage have been taken into accountin the hydrologic and hydraulic analysis performed in support of this flood hazardreevaluation report, as described in Section 3.0.2.5 Current Licensing Basis Flood Protection and Pertinent Flood Mitigation FeaturesSection 2.5 has been prepared in response to Item 1.a.v of NRC Recommendation 2.1,Enclosure 2 of the 10 CFR 50.54(f) letter. Relevant site data to be considered includeCLB flood protection and pertinent flood mitigation features at the site.The flood protection features credited in the CLB were identified in the FloodingWalkdown Report and include the East Wash embankment, the East Wash riprap, theWinters Wash embankment, Seismic Category I building exterior walls, basemats, roofdrainage
- systems, the 45-Acre and 85-Acre Reservoir berms, drainage ditches,compacted fill near cooling towers, vaults, and site grading.
Two embankment structures were designed to realign East Wash around the site. The north-facing embankment was constructed between two hills on the northern edge of the site, andcompletely diverts flood flows of East Wash from its old channel to the east to prevent19&*a Flood Hazard Reevaluation Reportflooding of the site proper. The eastern embankment extends south toward a pointabout even with the edge of the powerblock area and continues to divert the water inEast Wash away from the site. Both embankments were included in the original sitedesign to provide protection from the design-basis PMF flood with two feet of freeboard.
The ground elevation along the west side of the site was raised to limit the extent ofPMF on the site. Approximately 10 feet of compacted fill was placed in the cooling towerareas, such that ground between the peripheral road and the powerblock areas is abovethe PMF levels (UFSAR Section 2.4.10).2.6 Additional Site DetailsSection 2.6 has been prepared in response to Item 1.a.vi of NRC Recommendation 2.1,Enclosure 2 of the 10 CFR 50.54(f) letter. Relevant site data to be considered includesadditional site details necessary to assess relevant flood hazards (i.e., bathymetry, walkdown
- results, etc.).2.6.1 Bathymetry Storage of floodwater in the Winters Wash and East Wash channels and floodplains hasa significant impact on peak discharges and flood levels adjacent to the site. Detailedbathymetric data (i.e., channel topography) was obtained from recent topographic
- mapping, as discussed in Section 2. 1.2, for hydrologic and hydraulic modeling executedin support of the flood hazard reevaluation.
2.6.2 Recommendation 2.3 Walkdown ResultsFlood protection features that are credited in the CLB to protect the plant from externalflood hazards were identified, inspected, and evaluated as reported in the FloodingWalkdown Report. The results of the walkdown observations were reviewed using siteprocesses in accordance with NRC Inspection Manual Chapter 326 (NRC, 2014) andentered into the CAP.Topographic mapping with aerial photography taken in 2013 captured the conditions ofthe site for incorporation in the flood hazard reevaluation.
2.6.3 Site VisitsReevaluation team representatives have investigated the area outside the PVNGSproperty, including:
hydraulic controls at some bridges and roads; the site layout; theEast Wash embankment; and hydraulic structures along the entrance road. Additionally, photographs of flood mitigation features were taken and reviewed during thedevelopment of the flood hazard reevaluation analyses.
2094 Flood Hazard Reevaluation Report3.0 FLOOD HAZARD REEVALUATION ANALYSISSection 3.0 has been prepared in response to Item 1.b of NRC Recommendation 2.1,Enclosure 2 of the 10 CFR 50.54(f) letter and provides the results of the flood hazardreevaluation for the site, addressing each applicable flood-causing mechanism basedon present-day methodologies and regulatory guidance.
The flood-causing mechanisms potentially impacting the site include local intense precipitation and site drainage, flooding in rivers and streams (including combined effects flooding (CEF) scenarios),
dam breaches and failures, and channel migration or diversion.
Storm surge andseiche, tsunami, and ice-induced flooding were screened out as credible sources offlooding at the site. The site-specific LIP and the PMP on the washes use the AWAstudy in lieu of HMR 49 for rainfall distribution.
Appendix C provides the basis for usingthe AWA study for the flood hazard reevaluation.
3.1 Software UsedThe following software was used to perform the flood hazard reevaluation analyses.
Thedescriptions and capabilities of the software are provided in Appendix D." FLO-2D Pro 2012 (FLO-2D, 2012)" FLO-2D Pro Release 14.03.07 (FLO-2D, 2014a)" FLO-2D Pro Release 14.03.07.URS (FLO-2D, 2014b)" ArcGIS 9.3.1 (ESRI, 2009)" ArcGIS 10.1 (ESRI, 2012)* ArcHydro 10.1 (ESRI, 2011)* United States Army Corps of Engineers (USACE) HEC-HMS 3.5(USACE, 2010a)" USACE HEC-GeoHMS (USACE, 2009)* USACE HEC-RAS 4.1 (USACE, 2010b)* AWA PMP Evaluation Tool (AWA, 2013)3.2 Flood-Causing Mechanisms NUREG/CR-7046 recommends using an HHA method for evaluating the safety ofSSCs. The HHA method is a progressively
- refined, stepwise estimation of site-specific hazards that starts with the most conservative plausible assumptions consistent withavailable data. The HHA process is used for each flood-causing mechanism to bereanalyzed.
This method can be summarized as follows:1. Develop a conservative estimate of the hydrologically relevant site-related parameters using simplifying assumptions for the flood-causing mechanism andestimate new flood elevations using the appropriate modeling approach.
21 LAA Flood Hazard Reevaluation Report2. Compare the reevaluated flood hazard elevation (from step 1) with the originaldesign flood elevation for the selected flood-causing mechanism.
If the newlycalculated flood elevation is lower, it is used for comparison against the currentdesign basis for the reevaluation of this causal mechanism.
3, If not lower, determine if the parameterization of site hydrology can be furtherrefined.
If yes, perform reevaluation (repeat steps 1, 2). If not, use the floodelevation from the previous step for this causal mechanism for comparison ofreevaluation against the current design basis.4, If all flood-causing mechanisms have not been addressed, select another flood-causing mechanism and proceed to step 1.For each flood-causing mechanism, the final flood elevations from the hazardreevaluation were compared with the current design basis flood elevations to determine whether the current design basis flood bounds each reevaluated hazard.The methodology described above was used to reevaluate the potential flooding effectsresulting from each potential flood-causing mechanism relevant to the site usingpresent-day methodologies and regulatory guidance.
Details regarding theconsiderations and results of the analyses regarding each flood-causing mechanism arepresented in the following subsections of this report.3.2.1 Local Intense Precipitation Sections 3.2.1.1 through 3.2.1.3 address the effects of LIP at the site. A flow chart of theHHA screening methodology for the site overall LIP flooding
- analysis, based onguidance developed in NUREG/CR-7046, is presented in Figure 3-1.3.2.1.1 Local Intense Precipitation Hyetograph A LIP hyetograph (graphical representation of rainfall over time) was developed as partof the flood hazard reevaluation to support analysis of the flooding effects associated with intense rainfall on the overall site drainage system. The most up-to-date PMPestimation methodology for the state of Arizona was applied to develop the LIPhyetograph.
This methodology utilizes a PMP evaluation tool developed by AWA underthe direction/funding of the ADWR, Arizona Game & Fish Department, FCDMC, NavajoCounty Flood Control District, National Resource and Conservation Service (NRCS),and the Federal Emergency Management Agency (FEMA). Refer to Appendix C forinformation about the AWA PMP evaluation tool for determining rainfall in Arizona.The LIP hyetograph was developed for the SOCA (approximately 1 sq mi), whichencompasses all safety-related SSCs at the site. The resulting cumulative 6-hourrainfall depth was 12.80 inches. This rainfall was distributed in 10-minute increments over a 6-hour period, following the methodology of the AWA PMP Evaluation Tool. Themaximum rainfall in one hour within the LIP hyetograph was 10.73 inches. Theincremental and cumulative distributions of the 6-hour PMP are shown in Figure 3-2.22 *8i Flood Hazard Reevaluation Report3.2.1.2 Effects of LIPIn accordance with the guidance presented in NUREG/CR-7046, the considerations addressed in the analysis of site overall flooding resulting from the LIP were:" Depth of flooding* Duration of flooding* Maximum velocities
" Hydrodynamic and hydrostatic loads" Sedimentation
- Debris loadingEach of these considerations was evaluated based on the results of two-dimensional flow modeling in FLO-2D to simulate runoff from the site. The output of the FLO-2Dmodel includes water surface elevations, water depths, maximum water velocities, andthe duration of flooding.
FLO-2D also computes the hydrostatic and hydrodynamic forces that the floodwater could exert on obstacles (e.g., buildings) within flooded areas.These results from FLO-2D directly address requirements of NUREG/CR-7046.
Thepotential for sedimentation and debris loading was qualitatively evaluated, based on theinterpretation of FLO-2D output of depths, maximum velocities, and flow directions.
The FLO-2D model boundaries were established away from the powerblock area andsafety-related SSCs in order to ensure the stability of the model. The domain of theFLO-2D model was developed to represent site conditions reflected in 2013 site aerialtopographic mapping.
The boundaries of the FLO-2D domain were primarily established along drainage divides (e.g., roads, berms, and embankments).
The FLO-2D domain forthe LIP analysis is shown in Figure 3-3.Consistent with established FLO-2D methodology, boundary conditions includemechanisms through which water enters or leaves the model domain. Thesemechanisms include lateral outflow through the model boundaries, rainfall applieddirectly to the FLO-2D grid cells, and infiltration that removes water from the modeldomain. Lateral outflow conditions along all boundaries allow runoff to drain from theFLO-2D domain in a natural manner. The rainfall hyetograph discussed in Section3.2.1.1 was applied as direct rainfall in FLO-2D, and infiltration was characterized in themore refined cases for pervious areas surrounding the powerblock using the Green-Ampt method (FLO-2D, 2012). Site-specific soil properties and land use classifications were also used.The FLO-2D model characterized topographic and man-made features that affect runofffrom the site, including the VBS. As a modeling assumption, spaces between VBSblocks were assumed to be closed (i.e., water was not allowed to flow between adjacentblocks).
This effect is intended to simulate obstruction by potential debris carried awayfrom the powerblock due to runoff during the LIP simulation.
Thus, any backwater effects of debris jams during the LIP event are accounted for in the FLO-2D model.23&1 Flood Hazard Reevaluation ReportAdditionally, buildings, tanks, and other structures were characterized within FLO-2D asflow obstructions.
The HHA methodology for evaluating LIP flooding is shown in Figure 3-1. It consists ofiterative calculations starting with conservative modeling assumptions and progressively refining the inputs and assumptions.
Four basic cases were developed for the wholesite, and an additional simulation was conducted for sensitivity analysis.
These casesare summarized as follows:* Case 1 was a steady state simulation (i.e., constant rainfall intensity) with 25x25ft grid cells, and assumed high Manning's roughness coefficients and noinfiltration losses." Case 2 included infiltration losses and a time-varying LIP distribution wasapplied." Case 3 reflected the same characteristics as Case 2, but had a finer grid cell sizeof 15x15 ft.* Case 4 included the 15x1 5 ft grid resolution and lower, more representative Manning's roughness coefficients.
Also, the roof slopes were simulated withinFLO-2D to more closely reflect the plant configuration.
- Case 5 was a sensitivity analysis to demonstrate the effect of varying the rainfalldistribution.
A sensitivity study was performed to determine the effects of lower Manning's roughness coefficients.
It was found that lowering the Manning's roughness coefficients below those used in Case 4 had negligible impact on the maximum transient wateraccumulation depths. Cases 1 through 4 applied the rainfall distribution recommended by the AWA PMP evaluation tool.Case 4 was considered the most representative for the LIP event because of the refinedgrid size, Manning's roughness coefficients, and roof slopes and was used for thedevelopment of the flood hazard reevaluation.
An inundation map developed with theoutput from Case 4 is provided in Figure 3-3.3.2.1.3 Sedimentation and Debris Loading Coincident with LIPSedimentation and debris loading during a LIP event were screened out qualitatively ashazards at the site based on the results of the LIP analysis.
This screening was basedon flow depths, flow velocities, and flow directions predicted by the FLO-2D model forthe powerblock area. Flow depths and velocities near safety-related structures weregenerally small and did not constitute a credible hazard for erosion, sedimentation, ordebris loading.
Additionally, predicted flow directions were away from safety-related SSCs, which are surrounded by predominantly paved areas, precluding any impact onthe SSCs from sedimentation or debris loading.
While it is not expected that debriscould impact safety-related structures, potential debris blockage is accounted for in themodel by assuming the spaces between VBS blocks are closed.24 o Flood Hazard Reevaluation Report3.2.1.4 Wind-waves and Run-up Coincident with LIPWave run-up is a process whereby wind-generated waves impinge on a structure orembankment and cause intermittent flow of water up the side of the structure orembankment.
In general, the impact of wave action increases with the speed of thewind, the depth of the water over which it acts, and the length over which the windblows (i.e., the "fetch").
The two-year, 10-minute overland MSW speed used at the site was calculated to be39.35 mph. The sustained overland wind speed was converted to an overwater windspeed of 47.28 mph using procedures outlined in the USACE CEM (USACE, 2008).Wave action coincident with the LIP analysis was evaluated for the various water bodiesat the site as follows (Figure 3-4):" 45-Acre and 85-Acre Reservoirs
- Evaporation ponds" ESPsThe results of the wave run-up analysis indicated a maximum water level of 955.08 ftwithin the 45-Acre Reservoir due to run-up from wind-waves.
This run-up level cannotcause spillover toward the powerblock area because the 45-Acre Reservoir is separated from the powerblock area by a ridge that has a minimum elevation of 961.0 ft. The waverun-up level computed for the 85-Acre Reservoir was 953.97 ft, which is 1.03 ft lowerthan the minimum reservoir embankment elevation of 955.0 ft. Consequently, wave run-up in the 85-Acre Reservoir during the LIP event does not affect water levels in thepowerblock area.The maximum run-up level computed for the evaporation ponds was 938.76 ft. Thiselevation is below the top of the surrounding berms (942 ft). Consequently, run-up in theevaporation ponds does not affect water levels in the powerblock.
Wave run-up was not computed for the ESPs. Any waves generated by wind wouldresult in water spilling out from the ESPs onto the powerblock area. However, anypotential spill of water from the ESPs during a LIP event was screened out as a hazardbecause site grading will direct the flow away from safety-related SSCs, as confirmed by the maximum LIP water depths modeled in FLO-2D.Water levels within the SOCA were too shallow for significant wave development andthere were many obstructions that disrupt fetches over the standing water. A fetch wasdeveloped for this area, but wave effects were screened out due to the short length ofthe fetch and the intervening obstructions.
The longest potential fetch was defined foreach water body listed above as shown in Figure 3-4.The growth of wind-waves on the transient LIP runoff in the powerblock area wasscreened out as a flood hazard because of the relatively shallow depth of transient 25 g~t Flood Hazard Reevaluation Reportwater accumulation and the limits on fetch lengths resulting from the number of tallstructures inside the SOCA. All potential wave paths approaching safety-related SSCswere blocked by shallow water or transverse flows in drainage ditches.
Consequently, wave action on the maximum water surface elevations experienced at safety-related SSCs has no effect.3.2.1.5 LIP Accumulation at Safety-Related SSCsOn-site LIP accumulation depths (Case 4) at entrances to safety-related structures werecalculated and were found to be higher than the inlet elevations of some doors andhatches for limited durations.
Potential pathways for water intrusion intobuildings/structures through gaps in doors and hatches were evaluated for each unit.APS conducted an evaluation of the effects of these flood depths in the room-by-room internal flooding analysis described in the next section.3.2.1.6 Effects of LIP on Safety-Related SSCsA room-by-room internal flooding analysis of the critical areas of the plant wasperformed to assess the potential impact to safe shutdown equipment when water froma LIP event enters buildings through door thresholds and gaps in hatches (pathways).
These transient flood evaluations were performed utilizing methodology in the DesignBasis Flooding Calculations per the Standard Review Plan, NUREG-0800, Section 3.6.1(NRC, 1981).Protection of essential equipment against the postulated water inflow through gaps indoors and hatches, and corresponding internal room flood levels is provided by plantdesign features such as compartmentalized train separation, curbs, pedestals, checkvalves, level sensors and drainage systems.
There are typically two drain headers atthe ground floor elevation of each building which discharge the inflow water to the sumpin the lowest elevation of the building.
Additional drainage for the ground floor elevation is provided by stairwells that communicate to the lower floors of the building andtrenches or seismic gap cavities between adjacent buildings.
Based on the existing passive plant features and the room-by-room internal floodinganalysis, it has been determined that there is no effect on safe shutdown equipment.
Methodology The path water would take once it entered the buildings through gaps in doors andhatches was investigated by review of plant layout drawings, design basis internalflooding calculations and walk downs. These activities helped determine the water flowcharacteristics and the configuration of passive plant features, such as walls, curbs,doors, door transoms, equipment pedestals, penetrations, drains and check valves, thatlimit the effects of internal flooding.
All of these compartment features that redirect orlimit water flow are used to generate various simulations to determine the boundingwater levels in the compartments where safe shutdown equipment is located.26 1Ak Flood Hazard Reevaluation ReportThe analyses of the internal flooding within the safety related structures of thepowerblock were subdivided into the following sections to determine the water heightsin the critical areas of the following buildings:
- Diesel Generator Building* Control Building* Auxiliary Building* Fuel Building" Main Steam Support System Building* Essential Pipe Density Tunnel* Condensate Storage Tank Tunnel" Internal Flooding at the Perimeter Yard Areas and HatchesThe internal flooding design basis was initially prepared in 1979 and then furtherupdated to demonstrate compliance with the GDC 2 requirements as well as the BTPASB 3-1 requirements for pipe breaks outside containment.
The major assumptions of the internal flooding transient analysis consist of thefollowing:
- 1. The amount of localized transient water accumulation around the powerblock buildings, due to a LIP (or PMP) event is based on the analysis as described inSection 3.2.1.2.2. The FLO-2D computer program provides conservative results (flood time histories, hydrographs) because it does not credit the roofs, parapet walls, scuppers andgutters that hold up water and distribute it to specific locations, which has a laggingeffect as well as inventory reduction, in the calculation of water accumulation in theareas adjacent to building pathways.
- 3. Inflow of water from outside into the building pathways through gaps in doors isassumed to not occur when the predicted depth of transient water accumulation isequal to or less than 0.6 inch. This criterion is based on plant operating experience where normal rain storm runoff typically results in no flooding at the ground level ofthe buildings.
- 4. Accumulation of water around the buildings in the powerblock starts approximately one to two hours after the beginning of the LIP event based on the hydrographs.
Thus, the flood evaluations start one hour into the LIP event, considered as timezero in the simulation.
- 5. The water height inside the buildings was determined using optimal time steps toaccurately model the hydrographs.
For instance, the flood height inside thebuildings is determined in small time increments of one or two minutes during the27 AA Flood Hazard Reevaluation Reportincreased initial inflow rate of the outdoor water accumulation and larger timeintervals thereafter for the duration of the 6-hr LIP event. The inflow rate can beinput as a constant rate in the source room or a combined variable rate fromvarious pathways at discreet time steps into the event.6. Since the outflow of water through drains, floors, and doors is dependent on theflood height in the room, the flood height for the previous time period was used todetermine the outflow for the current time step.7. Proper visualization of the water flow path is critical in establishing appropriate boundary conditions between compartments to provide a bounding flood depth foreach critical compartment.
Walkdowns of the modeled flooded areas wereperformed to confirm the water flow characteristics, and the configuration of passiveplant features, such as walls, curbs, doors, door transoms, equipment pedestals, penetrations, drains and check valves, that limit the effects of internal flooding wereproperly accounted for in the model.8. The drain systems were assumed to function at a reduced capacity of 75% toaccount for debris or blockage in the pipe.9. The amount of drainage flow allowed was based on the amount of hydraulic headprovided by water accumulation on the floor, the number of drains, and the capacityof the header serving the area and/or multiple floors in the building.
- 10. The flow through the drains was determined using Darcy's Formula taking intoaccount the head and the total resistance coefficient of the drain pipe and fittings upto the discharge location at the sump.11. The flow through the floor openings and door gaps was determined using theequation for a rectangular weir with a discharge flow coefficient (Cd) value of 0.6:Q = (E)Cd(L)(G)\/2,h This equation provides equivalent results to that of a sluice gate model when takinginto account the free flow and submerged conditions of the hydraulic jump waveexperienced across the rectangular opening of the door as the room is flooded.
Thislimits the amount of flow into the room. For conservatism, the inflow of waterthrough the door gaps was determined without considering the differential headacross the door as the room was being flooded.12. Where applicable and for conservatism, the transoms at the bottom of doors arecredited to restrict flow out of the source room to maximize the water depth in thesource room.13. Where applicable, the seals and gaskets were credited in precluding ingression ofwater during a LIP event.28914 Flood Hazard Reevaluation ReportMargin Evaluation The room-by-room internal flooding analysis provided a conservative and reasonable internal water level for each unit. A refined FLO-2D PRO (FLO-2D, 2014b) model wasdeveloped that accounts for roof rain inventory distribution and localized grade aroundthe access doors. Use of this model yielded lower time duration of water accumulation and lower water levels, resulting in a significant reduction of the inflow into the SSCsbased on the APS simulations (URS, 2014). The lower values for duration of wateraccumulation and for water level were used to show the existence of margin and werenot used as input for the room-by-room internal flooding analysis.
Conclusion Localized accumulation of water, adjacent to structures in the powerblock as a result ofa LIP event does not impact safe shutdown equipment.
No operator action is requiredas a result of the LIP event.3.2.2 Flooding in Rivers and StreamsRiver flooding hazards at the site were evaluated using the HHA method presented inNUREG/CR-7046, which is shown schematically in Figure 3-5. The initial flood hazardreevaluation identified the following watercourses near the site for evaluation of floodhazards due to river flooding:
the Hassayampa and Gila Rivers, and Centennial, East,and Winter Washes (Figure 2-4).3.2.2.1 Screening Out Watersheds, Rivers, and WashersFlooding due to the PMF on Centennial Wash, Hassayampa River, and Gila River wasevaluated using steady state HEC-RAS models. Each of these watercourses wasevaluated to determine whether the PMF could cross watershed divides and reach thesite.Sufficient historic stream flow datasets from the USGS or any other source were notavailable for estimating PMF discharge rates for these streams with a sufficient level ofconfidence for screening purposes.
Consequently, the PMF flow rates for the screening analysis were estimated from a regression equation relating PMF discharge towatershed area for locations in this region. The regression equation was developed based on data in USACE and United States Bureau of Reclamation (USBR) reports(USACE, 1957; USBR, 2011a, 2011b, 2012).Maximum water surface elevations were obtained for each watercourse using steadystate HEC-RAS models. These models indicated that the site was not susceptible toflooding associated with PMF along Centennial Wash, and the Hassayampa and GilaRivers.Luke Wash lies between East Wash and the main branch of the Hassayampa River(Figure 2-4) and was treated as part of the Hassayampa River watershed for this29 10 w Flood Hazard Reevaluation Reportevaluation.
This is a conservative approach that results in higher estimates of peakflows nearer to the East Wash watershed.
3.2.2.2 PMP for East Wash and Winters Wash Watersheds The PMP hyetographs for the East Wash and the Winters Wash watersheds weredetermined in the initial analysis using the AWA PMP Evaluation Tool, which providesPMP values for three different storm types: local storms (i.e., a thunderstorm),
generalwinter storms, and tropical storms. The AWA PMP Evaluation Tool limits theapplicability of local storms to relatively small areas (approximately 50 sq mi or less).The tropical storm PMP event was identified as the PMP event with the most intensepotential rainfall for Winters Wash. The duration of the PMP on Winters Wash was72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, with a cumulative rainfall of 11.21 inches. The peak rainfall intensity was 4.16inches in six hours, occurring 42 hours4.861111e-4 days <br />0.0117 hours <br />6.944444e-5 weeks <br />1.5981e-5 months <br /> after the start of the rainfall event.A local storm PMP was identified as the critical PMP for the East Wash watershed.
TheEast Wash PMP has a six-hour
- duration, with a cumulative depth of 10.09 inches. Thepeak rainfall intensity was 2.11 inches in 10 minutes, occurring three hours after thestart of the rainfall event. The hyetographs for the East and Winters Wash watershed PMPs are illustrated in Figure 3-6.3.2.2.3 PMF for Winters Wash Watershed A hydrologic response model (HEC-HMS) was developed to determine the runoff ratesfor the PMP events in the Winters Wash watershed.
The Winters Wash watershed wasdivided into thirteen sub-basins for the river flooding analysis (Figure 3-7).A schematic of the HEC-HMS model is illustrated in Figure 3-8. The runoff rate outputsfrom the HEC-HMS model were used as input to the FLO-2D model used to computethe PMF flood levels at the site.PMF hydrographs were calculated for the Winters Wash watershed using HEC-HMSmodels following the HHA process.
Following the guidance in (FCDMC, 2011), S-graphunit hydrographs developed for watersheds of similar characteristics to Winters Washwere used to transform excess rainfall to runoff.Rainfall losses were calculated using the Green-Ampt method, as recommended by theFCDMC. Varying levels of soil moisture conditions were also evaluated.
Table 3-1provides the key hydrologic input parameters and the peak discharges for each modelsub-basin.
The nonlinearity effects of the unit hydrograph process were reviewed using a 33%reduction in the lag time and a 5% increase in the peak of the unit hydrographs.
Asstated in NUREG/CR-7046, the recommended adjustments are a 5% to 20% increasefor the peak discharge and a 33% reduction in the lag time.30 16 4 Flood Hazard Reevaluation ReportThe paper by Pilgrim and Cordery referenced in NUREG/CR-7046 indicates that thechannel morphology will have an impact on the extent of non-linearity (P & C, 1993):... drainage basins where the design flow is retained within channels that areformed or have small floodplains are likely to respond in a highly nonlinear manner. In drainage basins with large floodplains and vegetation or otherobstructions within high banks and on overbank areas, average velocities arelikely to remain fairly constant or even to decrease to some extent as flow ratesincrease.
In other words, the peak discharge of the PMF for a watershed with large floodplains willtend to be less than the peak from a watershed with flow contained within well-defined channels.
As indicated by modeling results for the flood hazard reevaluation, the PMFevent within the Winters Wash watershed would not be contained within channel banksand the majority of runoff would flow in the floodplain area, which is vegetated withdesert brush. Therefore, following Pilgrim and Cordery, the nonlinear effects wereexpected to be small, so a 5% increase in peak discharge was applied.Effects of PMF on Winters Wash Watershed The following considerations were addressed for the watershed PMF analysis per theguidance of NUREG/CR-7046:
- Depth of flooding* Duration of flooding* Maximum flood velocities
- Hydrodynamic and hydrostatic loads associated with flooding* Sedimentation associated with flooding* Debris loading associated with floodingThe depth and duration of flooding, maximum flood velocities, and hydraulic forcesassociated with the flooding at the site were determined for the flood hazardreevaluation using the FLO-2D flood routing program (FLO-2D, 2012). The modeldomain used for the PMF evaluation of Winters Wash is shown in Figure 3-8.A diagram of the HHA approach for the analysis of flooding from rivers and streams isprovided in Figure 3-5. It consists of iterative model runs starting with conservative assumptions and progressively refining the inputs and assumptions.
A series of simulations with increasingly refined inputs and a verification run withhydrographs from UFSAR Figure 2.4-11, were run to evaluate the effects of PMFflooding on the site. The FLO-2D cases considered are summarized in Table 3-2. Case2 is the most representative simulation of the PMF in the Winters Wash. Flooding fromWinters Wash was screened out as a flood hazard due to differences in topographic grade and the significant conveyance capacity of the Winters Wash floodplain.
31 #Ak Flood Hazard Reevaluation ReportWind-waves and Run-up Coincident with PMFThe potential for flooding due to wind-wave run-up coincident with the PMF wasanalyzed for Winters Wash, the ESPs, the evaporation ponds, the 45-Acre and 85-AcreReservoirs, and the powerblock area. The run-up was calculated by identifying criticalfetches within areas of floodwater on the site and calculating wave run-up using theprocedures described in the USACE CEM. The two-year MSW (overwater) of 47.28mph was used for the wind-wave action coincident with the PMF.The critical fetch length used for Winters Wash is shown in Figure 3-9. The run-up onWinters Wash was 0.37 ft. As indicated in the figure, the floodwaters from Winters Washdid not reach the powerblock area. The run-up was computed for Winters Wash at apoint closest to the powerblock area (cross-section B). The final flood elevation forWinters Wash including run-up was 940.4 ft (FLO-2D Case 2), which does not reach theminimum grade elevation of the powerblock, which is 951.0 ft.The effects of wave run-up in the ESPs and the evaporation ponds were bounded bythe wind-wave effects considered in the LIP analysis (Section 3.2. 1.4) because theprecipitation depths and corresponding water levels were higher in the LIP analysis.
Thedesign of the 45-Acre and 85-Acre Reservoirs accommodates wave run-up. Run-up onthe transient flows on the powerblock area was screened out as a flood hazard becauseof the numerous obstacles that prevent formation of substantial waves. Additionally, water levels in the powerblock area were lower for the river flooding analysis than forthe LIP analysis because of lower precipitation rates. Consequently, any small wavesthat could form were bounded by the waves associated with the LIP analysis.
3.2.2.4 PMF for East Wash Watershed The initial flood hazard reevaluation hydrologic response model using HEC-HMS(USACE, 2010a) was developed to determine the runoff rates for the PMP events in theEast Wash watershed.
The East Wash watershed was divided into five sub-basins forthe river flooding analysis (Figure 3-7). The HEC-HMS model was set up and calibrated to represent the East Wash watershed, including a relatively detailed representation of1-10 within the East Wash watershed.
Refined AnalysisA refined flood hazard reevaluation, in conformance with the HHA, was subsequently performed to evaluate the two-dimensional flow characteristic associated with the EastWash watershed.
The analysis modeled predominant flow direction along thewatercourse.
A description of the data, assumptions, methodology, and results for eachportion of the refined analysis from the calculations is discussed in the following sections.
The initial analysis included a number of calculations to reevaluate the PMP event. Thefirst task in refining the flood hazard reevaluation at the site was to develop a strategic process for modifying the initial analysis.
The refinements are in conformance with32 94C Flood Hazard Reevaluation ReportNUREG/CR-7046 and the HHA process, which allows for progressively refining themethods that increasingly use site-specific data to demonstrate whether the plant SSCsimportant to safety are adequately protected from the adverse effects of severe floods.General areas considered for refinement were:* Precipitation amount and distribution
- Topography
- Site characteristics
- Site-specific hydrologic and hydraulic analysis* Contributing watershed hydrology and hydraulics
- Existing site protection
- Wind-wave actionAPS and contract subject matter experts met with or spoke to the following agenciesand firms as part of the assessment of these areas for refinement:
" Flood Control District of Maricopa County -FCDMC is involved in identifying, regulating, and remediating regional flood hazards.
As such, they havedeveloped or supported the development of comprehensive tools fordetermining flood hazards.
Their support of the development of the refinedmethodologies for calculating site specific PMP events in Arizona and usingtwo-dimensional flow models (FLO-2D) for evaluating arid watershed floodsare considered important to this study. The FCDMC also recently sponsored a floodplain delineation study of East Wash where the 100-year hydrology was accepted by the FEMA.* Arizona Department of Water Resources
-Meetings were held with ADWR todiscuss the use of extreme rainfall events. In 1980, the ADWR was created tosecure long- term dependable water supplies for Arizona communities (ADWR, 2014). One function they perform to support this mission isregulating dam safety. In 2013, AWA prepared the report Probable MaximumPrecipitation Study for Arizona (AWA, 2013) that developed a procedure forcalculating PMP storms throughout the state. The results of the study weredeveloped to replace the historical results from HMR 49." Applied Weather Associates
-Meetings were held with AWA to discuss theapplicability of using Arizona site specific PMP information.
The refined 100-foot grid element analysis is an enhancement to the HEC-HMS modelbecause it more accurately defines the hydrologic and hydraulic performance of theEast Wash watershed during the PMP event. The entire East Wash, from the northernboundary approximately seven miles north of 1-10 to the evaporation ponds at cross-section XS7 (Figure 3-10), was included in the 100-foot grid element analysis.
The FLO-2D 100-foot grid element hydrograph (Figure 3-15) has two flow paths. Thedischarges at cross-sections XS4 and XS5 (Figure 3-10 were used as inflows in the 25-33 9*rl Flood Hazard Reevaluation Reportfoot grid element model, which extended in East Wash from cross-sections XS4 andXS5 down to XS7 (area shown in Figure 3-14). High points along the east embankment are modeled as levees to reflect the highest height in the 25-foot grid element indetermining overtopping.
Topography Considerations for the East Wash refined model include:* The crown of the roadways at 1-10 was included in the refined analysis in the100-foot grid element FLO-2D model to simulate the potential overtopping elevation during the PMP in the East Wash. The data was obtained from theArizona Department of Transportation As-Built plans for the specific section of1-10 (ADOT, 1969)." High resolution contour mapping data were obtained from the FCDMC fordelineating the East Wash watershed.
The datasets used were the PaloVerde Mapping, 2-ft contours from June 2007, and Luke Wash and Arlington
- Mapping, 2-ft contours from September 2005 (FCDMC, 2011)." Aerial mapping flown for APS on March 25, 2009, was used in the refinedanalysis (URS, 2013). The topographic survey information was only usedwhere ground elevations and other sources of data were not available.
Watershed Characteristics The HEC-HMS unit hydrograph rainfall runoff approach developed for the initial analysisof East Wash PMF divided the watershed into only five sub-basins.
To account for theunit hydrograph
- approach, nonlinearity was accounted for by reducing lag time andincreasing the peak discharge as required in Appendix I of NUREG/CR-7046.
The HEC-HMS model has some inherent issues when modeling a watershed's hydrologic response in Maricopa County. Presently, the FCDMC has coordinated with the USACEto modify the program for use in Maricopa County. The USACE is modifying HEC-HMSfor Maricopa County in the following areas:* Point-area rainfall area reduction (similar to HEC-1 JD cards)* Green-Ampt method with GIS (land use and soil shape file)* Clark unit hydrograph (FCDMC time of concentration method)* Normal depth channel routing* Efficient handling and management of large models with hundreds of sub-basinsFCDMC uses either HEC-1 or FLO-2D to model both rural and urban watersheds.
Selection of the model being used depends on the detail needed for the analysis andthe project budget. FLO-2D is a more accurate model for simulating overland flowpatterns in areas such as East Wash because the washes in the upper watershed, including the area north of 1-10, are small and intermittent.
34 Flood Hazard Reevaluation ReportFor the refined flood hazard reevaluation of East Wash, a significant portion of the flowoccurs in the floodplain adjacent to the wash, especially for less frequent flood eventsincluding the PMF. When Entellus prepared a flood delineation study of East Wash, theFLO-2D model was still being tested by the FCDMC and HEC-1 was the model selectedfor the study. Since then the FCDMC has worked with Riada Engineering, Inc. (REI) inupdating the FLO-2D model. The FCDMC has used the model on many of their recentwatershed studies.Use of a two-dimensional flow model (100-ft grid elements) provides a morerepresentative simulation of hydrologic and hydraulic parameters for predicting peakdischarges and water surface elevations in the watershed for severe rainfall events thana one-dimensional model such as HEC-HMS or HEC-1. No adjustments are needed fornonlinearity because FLO-2D is a physically based two-dimensional rainfall runoffmodel that explicitly accounts for the hydrologic effects that contribute to surface runoffgeneration.
The refined analysis of East Wash utilizes a 100-ft grid element forbenchmarking with the FEMA-accepted 100-year flood, a 100-ft grid element PMPmodel and, near the site, a 25-ft grid element to refine the analysis when estimating thewater surface elevation at the east embankment.
Floodplain Cross-Sections Floodplain cross-sections were added to the East Wash FLO-2D model to determine the peak flow rates at several locations.
Five locations were chosen along thewatershed:
- XS1 -north of 1-10* X$2 -south of 1-10* XS3 -north of PVNGS, at upper boundary of the initial model, and at thesame location as HEC-HMS junction EJ16* XS6 -at Water Reclamation Access Road, and at the same location as theinitial HEC-HMS junction EJ11* XS7 -south boundary of model* Two more cross-sections, XS4 and XS5, were added at the XS3 location toquantify the flow going across the two primary flow paths in the East Wash atthat point. Figure 3-10 shows the locations of the seven floodplain cross-sections.
The discharges at cross-sections XS4 and XS5 were used as the East Wash inflows inthe 25-ft grid element model.Results for PMF in East Wash Without Wind EffectsThe hydrographs for floodplain cross-sections XS1 through XS5 are shown in Figure 3-11. The results of the model show that the floodwaters from the PMP storm do notbreach the East Wash or the north-facing embankments around the site. Figures 3-1235 XMMM Flood Hazard Reevaluation Reportand 3-16 show the flow depths near the site, and Figure 3-13 shows velocity vectorsrepresenting the flow velocities and directions.
Floodwaters shown inside the site arethe result of direct rainfall onto the site only, since no floodwaters breach theembankments.
Table 3-3 summarizes the results at the floodplain cross-sections.
There were six hydraulic cross-sections evaluated as shown on Figure 3-14. Floodplain cross-sections Xl, X2, and X3 correspond to locations defined in the initial analysis, andAl, B, and C are locations from the UFSAR. Placing floodplain cross-sections at theselocations provides discharges and flood elevations that are easily extracted from themodel. The model results for the six hydraulic cross-sections are shown in Table 3-4,along with the embankment elevations and calculated embankment freeboard.
Wind-Wave Action Coincident with PMFThe fetch lengths were re-calculated for the refined PMF analysis to determine thechange in fetch length and wave height. The critical 2-year wave heights werecalculated using the information from the initial analysis and the reduced fetch length forthe lower water surface elevations.
The results show that when the predicted waveheights are added to the PMF water surface elevation, the north and east embankments are not overtopped.
Fetch Selection The refined analysis analyzed eight potential
- fetches, five at the north embankment andthree at the east embankment, to select the worst case scenario fetches for this wind-wave analysis.
The potential fetches were selected where deep water is adjacent to theembankments and at multiple directions that follow the deepest backwaters.
They areshown in Figure 3-17.The maximum water depth is used in the fetch selection process and will yield aconservative selection of the fetches used in the analysis.
Potential fetches N-2, N-3,N-4, and E-1 were not selected because their extents reach into flow channels atlengths that do not accurately capture the backwater effect that contributes to thewind-wave generation and propagation as can be visually verified on Figure 3-17.Sections were taken at potential fetches N-I, N-5, E-2, and E-3 and the maximum waterdepths were tabulated in spreadsheets to determine the fetch lengths contributing towind-wave propagation based upon the same assumption as in the initial analysis, i.e.,areas with water depth less than 0.5 foot are not considered while computing fetchlengths.
Fetch N-5, referred to as north embankment fetch henceforth, and E-2, referredto as east embankment fetch are selected as the worst case scenario wind-wave propagating fetches for analysis.
Figure 3-18 shows the north fetch and east fetch inplan view, and Figures 3-19 and 3-20 show the sectional views for the north and eastfetches, respectively.
36 Flood Hazard Reevaluation ReportWind-wave AnalysisThe procedures used to determine the impacts of wind-wave actions and wave run-upon the embankments are similar to the procedures in the CEM. A 2-year return periodMSW speed and maximum over water fetch is used to calculate the maximum waveheight, and the same wind speed is used to calculate run-up at the embankments thatcould cause spillover.
Refined Flood Hazard Reevaluation Results for East WashTables 3-6 and 3-7 summarize the results of the calculation.
The refined analysisdetermined that the static freeboard available at the north embankment is approximately 3.60 ft and at the east embankment is approximately 3.10 ft. The refined analysis alsoshows that the wave run-up freeboard available at the north embankment isapproximately 2.09 ft and at the east embankment is approximately 1.72 ft. Neitherembankment is overtopped by wave run-up during the PMF event.3.3 Combined Effects FloodingThis section has been prepared in response to the Request for Information Item 1 .b ofNRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a).NUREG/CR-7046 provides guidance for the CEF analysis.
This type of analysis was notconsidered or required during the initial licensing of PVNGS.The CEF analyses are based on the initial flood hazard reevaluation.
The East Washevaluation also considered the refined analysis to establish that the embankment is notovertopped when subjected to the PMF in combination with wind wave action.Both American Nuclear Society (ANS), ANSI/ANS-2.8-1992 (ANS, 1992), andNUREG/CR-7046 indicate that isolated flood-causing events are not adequate as adesign basis for power reactors.
Consequently, it is appropriate to postulate criticalcombinations of flood-causing events when reevaluating the flood hazard at the site.Characteristics of the combined effects addressed for this flood hazard reevaluation include:* Depth of flooding* Duration of flooding* Maximum flood velocities
- Hydrodynamic and hydrostatic loads associated with flooding* Sedimentation associated with flooding* Debris loading associated with floodingIn accordance with NUREG/CR-7046 and ANSI/ANS-2.8-1992, combined effectsflooding alternatives for the site included floods caused by precipitation events andfloods caused by seismic dam failures.
A schematic diagram of the HHA methodology 37 9*4 Flood Hazard Reevaluation Reportfor CEF is provided in Figure 3-21. The CEF alternatives considered for the site were asfollows:Alternative IAlternative IIAlternative IIIPrecipitation FloodsMean monthly (base)flowMean monthly (base)flowMean monthly (base)flowMedian soil moisture Probable maximum 100-yr snowpacksnowpackAntecedent (or Coincident 100-yr Coincident snowsubsequent) 40% of snow season rain season PMPPMP or 500-yr rain,whichever is less2-yr wind speed in the 2-yr wind speed in the 2-yr wind speed in thecritical direction critical direction critical direction PMPN/AN/ASeismic Dam 25-yr flood 50% of PMP or 500-yr N/AFailures flood, whichever islessDam failure caused by Dam failure caused N/ASSE coincident with by OBE coincident peak of flood with peak of flood2-yr wind speed in the 2-yr wind speed in the N/Acritical direction critical direction The effect of snow as part of the CEF analysis was screened out for this desertrangeland area. Additionally, the proposed dam failure scenarios were screened out asless conservative than the dam failure analysis completed in Section 3.4.3.3.1 Characterization of Combined Effects FloodingThe remaining precipitation flood alternative that required investigation for the combinedeffects flooding analysis was Alternative I proposed for precipitation floods inANSI/ANS-2.8-1992.
Each of the effects listed for Alternative was addressed as follows:Mean monthly base flow -base flow was screened out as not applicable, sinceEast Wash and Winters Wash are intermittent streams and their base flows areequal to zero.Median soil moisture
-the soil moisture classification of "dry" was used as themedian soil moisture as defined by the FCDMC in the Drainage Design Manualfor Maricopa County (FCDMC, 2011).This classification was appropriate for thearid desert lands surrounding the site.Antecedent or subsequent rainfall
-the 500-year return period rainfall eventswere computed for both the East Wash and the Winters Wash watersheds.
- However, for both watersheds, the 40% PMP was selected over the 500-year38 9*0 Flood Hazard Reevaluation Reportrainfall depth. Consequently, 40% of the PMP was used as the antecedent stormfor both the East Wash and the Winters Wash watersheds.
Consistent with theguidance in ANSI/ANS-2.8-1992, the storms in Winters Wash were spaced withthree days between peak rainfall intensities, and the storms in East Wash werespaced with one day (24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) between peak rainfall intensities.
PMP -the PMP hyetographs for the East Wash and the Winters Washwatersheds were developed as part of the PMF analysis (Section 3.2.2.2, Figure3-6). The PMP rainfall along with antecedent rainfall was used as input for theFLO-2D model. The CEF simulations with the FLO-2D models included the PMPdistribution both on the powerblock and the washes concurrently to account forthe contribution to runoff from each source.Wind-waves
-the effect of wind-waves was included in the CEF usingprocedures similar to those described in Section 3.2.2.4.
Note that for the EastWash credit is taken for the refined analysis as described in Section 3.2.2.4which results in lower wind wave action heights.To simulate the CEF at the site, separate FLO-2D models were developed for fourdifferent watershed regions surrounding the site (Figure 3-22). Two domains were usedto simulate runoff from the East Wash (EW) watershed and two were used to simulatethe Winters Wash (WW) watershed, as follows:EW-North
-this domain characterized runoff from East Wash upstream of thesite. Runoff from this domain was used as an inflow boundary condition forsimulations on the EW-South domain.EW-South
-this domain characterized the flood levels near the site on EastWash.WW-North
-this domain characterized runoff from Winters Wash upstream of thesite. Runoff from this domain was used as an inflow boundary condition forsimulations on the WW-South domain.WW-South
-this domain characterized the flood levels near the site on WintersWash.A total of 12 FLO-2D simulations (Table 3-8) were developed for the CEF analysis.
Sixsimulations (W1 through W3 and El through E3) were conducted on the northernwatershed domains (EW-North and WW-North; Figure 3-22). Simulations W1 throughW3 evaluated runoff from the Winters Wash watershed.
Each simulation applieddifferent Manning's roughness coefficients as a sensitivity analysis.
Similarly, thesimulations El through E3 evaluated runoff from the East Wash watershed, with arange of Manning's roughness coefficients.
Simulations El through E3 included arepresentation of 1-10 in East Wash to account for the flow through the large boxculverts and over the highway as a weir.Six FLO-2D simulations (Cases 1 through 6; Table 3-8) were also conducted on thesouthern watershed domains (EW-South and WW-South; Figure 3-22). Case 1 appliedan inflow hydrograph from the WW-North domain to simulate flooding in Winters Wash.39914 Flood Hazard Reevaluation ReportCases 2 through 6 evaluated flooding in East Wash near the site using a finer grid cellsize of 25x25 ft. Cases 2 through 4 apply a range of Manning's roughness coefficients as a sensitivity analysis.
Of Cases 2 through 4, Case 3 was the most representative ofthe site. Case 5 accounted for failure of the East Wash embankment and removal of theVBS, a simulation developed because wind-waves associated with Case 3 withoutembankment failure indicated overtopping of the East Wash embankment.
Case 6 wasa sensitivity simulation to demonstrate the effect of completely blocking the culvertsunder the Water Reclamation Access Road. Given the results of the refined analysiswhere it is shown that the embankments are not overtopped, Case 5 is not applicable but is included for completeness.
3.3.2 Combined Effects Flooding ResultsThe modeling for the CEF analysis, which utilizes a two-dimensional model of the entirewatersheds in lieu of the hybrid one-dimensional and two-dimensional models (Rizzo,2014), was a continuation (per the HHA approach) of the river flooding analysis.
Winters Wash -CEF modeling for Winters Wash (Case 2) indicated that flood levelswere bounded by, but were similar to, the flood levels for the reevaluated PMF riverflood model (Section 3.2.2.3).
The slightly reduced water levels are the result of a morerefined modeling approach (i.e., applying FLO-2D to simulate runoff from thewatersheds instead of HEC-HMS).
East Wash -the results from Case 3 (Table 3-8) indicated that the freeboard betweenthe maximum still water level and the East Wash embankment crest at a pointimmediately north of the Water Reclamation Facility Access Road is 1.48 ft. Thetransient water accumulation observed in the powerblock shown in Figure 3-23 resultsfrom rainfall directly on the powerblock, not from river flooding.
The effects reported forthe powerblock area, including the water depth, duration of flooding (Figure 3-24),maximum velocities, as well as hydrostatic and hydrodynamic forces, were bounded bythe levels reported in the reevaluated LIP analysis (Section 3.2.1).In the initial analysis, water levels were analyzed in the ESPs, 45-Acre and 85-AcreReservoirs, and evaporation ponds, with the following results:" The ESPs filled and overflowed due to the rainfall associated with the CEFconsidered.
- The 45-Acre and 85-Acre Reservoirs were submerged by floodwater for theEast Wash embankment failure scenario.
Consequently, water levels werenot computed for these impoundments.
" The water level in the evaporation ponds due to the CEF was approximately 937.0 ft. This water elevation does not overtop the berms of the evaporation ponds at elevation 942 ftThe Case 6 sensitivity simulation that evaluated the effect of completely blocking theculverts under the Water Reclamation Access Road indicated a negligible effect onwater surface elevations within East Wash.40 Flood Hazard Reevaluation ReportThe CEF analysis determined that the static water level for Case 3 did not overtop theEast Wash embankment.
- However, the initial flood hazard reevaluation of wind-wave effects showed potential embankment overtopping at cross-section C, south of Unit 3(Figure 3-14) and cross-section X2 at the Water Reclamation Facility road.The refined flood hazard reevaluation determined that the PMF levels in the East Washwere lower than those calculated in the initial analysis and critical wind-wave run-upwas 1.38 ft at cross-section X2 rather than 2.0 ft. The refined analysis determined thatthe PMF level plus wind-wave effects allowed a freeboard of 1.72 ft at X2 (Figure 3-16)and no overtopping was postulated along the East Wash embankment.
Based on the above discussion, it is appropriate to use the results of CEF Case 3 andthen add the wind wave action from the refined flood hazard reevaluation.
Using the above approach, the available static freeboard from CEF Case 3 at cross-section X2 is 1.48 ft and, when subtracting the wind wave height of 1.38 ft from therefined model, this demonstrates that the embankment is not overtopped.
Also at cross-section C (Figure 3-16) the available static freeboard is 1.04 ft. The fetchat this location in East Wash south of the Unit 3 ESPs is significantly shorter (less than0.25 mile) than at the north boundary.
This results in a wind-wave height that is smallerthan the available freeboard, thus no overtopping of the embankment occurs. Ifovertopping at cross-section C were to occur, there would be no detrimental effect onthe powerblocks given its location along the very southern edge of Unit 3.3.3.3 Wind waves and Run-up coincident with Combined Effects FloodingWind-waves were evaluated for the following locations:
" Evaporation Ponds -the final run-up level was 939.06 ft, which is below theberm elevation of 942 ft.* ESPs -the ESPs were filled completely so any waves would cause spill-over from the ESPs, which would drain away from the ESPs and not affect waterlevels near other safety-related SSCs." Powerblock area -wind-wave effects on the powerblock area were screenedout due to the shallow water and intervening obstacles that reduced potential fetches and prevented waves from reaching safety-related SSCs.Additionally, water levels in the powerblock area were lower for the CEFanalysis than for the LIP analysis because of lower precipitation rates.Consequently, any small waves that could form were bounded by the wavesassociated with the LIP analysis (Section 3.2.1.4).
" Winters Wash -the final run-up level for Winters Wash was 940.4 ft, which didnot approach the powerblock.
" East Wash -the East Wash wind-wave effects for CEF are considered to beequivalent to the wind-wave effects described for PMF in Section 3.2.2.4.41 91A6 Flood Hazard Reevaluation Report3.4 Dam Breaches and FailuresThe potential flooding of the site due to dam breaches and failures was evaluated usingthe method outlined in ISG-2013-01 (NRC, 2013a). A flowchart of the method isprovided in Figure 3-25.The Volume Method, which is shown schematically in Figure 3-26, consists ofcalculating the theoretical flood elevation that would be obtained by combining thepredicted flood elevation from the failure of all upstream dams with the 500-year floodon the main watercourse starting from a cross-section located as close to the site aspossible.
This is a conservative assessment and represents a condition with allupstream dams breached simultaneously and translated to a point near the site withoutattenuation.
The dam break hazard can be screened out if the results of the VolumeMethod show that the flood level does not reach the site grade.The locations and storage volumes for each dam upstream of the site were obtainedfrom the USAGE National Inventory of Dams (USAGE, 2013). The locations of thesedams are shown in Figure 3-27. In addition to the dams in the inventory, the volumes ofthe on-site reservoirs were considered.
The total storage volume for all of the off-sitedams and the Evaporation Ponds is 7,897,049 acre-ft.
The addition of 3,928 acre-ft toaccount for the combined storage of the 45-Acre and 85-Acre Reservoirs gives a totalvolume of 7,900,977 acre-ft of water to be superimposed on top of the antecedent watersurface elevation based on a 500-year flood.The antecedent water surface profile was derived in HEC-RAS for a PMF discharge of730,000 cfs (USAGE, 1957), which bounds the 500-year flood discharge rate. Based onan analysis of digital topographic data in ArcGIS, it was determined that the floodelevation associated with the 7,900,977 acre-ft storage volume superimposed on theantecedent water surface profile did not rise above elevation 935 ft. Because this is 16 ftbelow the minimum site grade elevation of 951 ft, the dam-break mechanism, including aspects related to potential debris and sediment loads, was screened out as a floodhazard.Based on the approximately 16-ft difference in elevation between the maximum watersurface derived from the Volume Method and the minimum site grade elevation, it wasconcluded that wind-waves associated with the two-year return period wind speed couldnot reach the site because maximum wave heights were no greater than three feet.3.5 Storm SurgeThe site lies more than 1,000 miles from both the Atlantic Ocean and Gulf of Mexicoand is located approximately 258 miles inland from the Pacific coast (Figure 1-1).Therefore, the site is located a sufficient distance inland from these water bodies toscreen hurricane storm surge out as a potential flooding hazard so that the moredetailed considerations contained in NUREG/CR-7134 (NRC, 2012b) were notapplicable.
42 &*a Flood Hazard Reevaluation ReportThe site is also approximately 134 miles inland from the Gulf of California (Figure 1-1).While Pacific hurricane surges can be transmitted up into the gulf to some degree (ANS,1992), and spring tides as high as 10 meters (approximately 33 ft) have been reported(Filloux, 1973), the potential for flooding due to hurricane surge from the Gulf ofCalifornia was screened out because of the significant topographic barriers between theshore and the site, which is located approximately 920 ft above the highest high tideelevation at the head of the Gulf of California.
Because safety-related SSCs at the site were not affected from storm surge flood levelsfrom any water body, the evaluations of hydrostatic and hydrodynamic forces, debris,and water-borne projectiles, and the effects of sediment erosion or deposition due tostorm surge laid out in JLD-ISG-2012-06 (NRC, 2013b) were not necessary.
3.6 SeicheA seiche is defined as an oscillation of the water surface in an enclosed or semi-enclosed body of water initiated by an external cause in NUREG/CR-7046.
Where theamplitude of seiche action is sufficiently large, the areas adjacent to the effected waterbodies are at risk of flooding.
Following NRC guidelines detailed in NUREG/CR-7046, the risk of flooding at the sitedue to seiche-motion was evaluated for seismic effects, free oscillation of the waterbody due to meteorological
- effects, and landslides.
The site is not located near any coastlines or large bodies of water from which floodingdue to seiches can occur. Water bodies with a theoretical potential for seiche-induced flooding at the site include the reservoirs, evaporation ponds and ESPs.The Arizona Geological Survey (AGS, 2000) indicates that the site is located in an areaof low seismic hazards, so there is a minimal risk of seismic activity.
- However, if seismicmotion, barometric
- effects, or landslides along the embankments adjacent to thereservoirs were to cause a seiche large enough to displace water from the 45-AcreReservoir or the 85-Acre Reservoir, an evaluation of the 2013 aerial topographic mapping of the site indicates that any water spilling from the reservoirs would flow southand away from the powerblock area, following the natural topography and site grading.Thus, seiche action in the reservoirs was screened out as a potential source of floodingto the SSCs.Due to the small fetch across the ESPs, any induced surge and waves would berelatively minor. However, any water originating from the ESPs would drain away fromthe powerblock following site gradients.
The evaporation ponds are south and downstream of the powerblock.
Any water leavingthe evaporation ponds would be conveyed to the Gila River and away from thepowerblock.
Based on the evaluation of topography summarized above, potential seiches on thereservoirs, evaporation ponds, and ESPs at the site due to meteorological effects,43 l Flood Hazard Reevaluation Reportseismic effects, or landslides were screened out as a potential source of flooding toSSCs.3.7 TsunamiA review of historic tsunamis impacting the west coast of the United States and Mexicowas undertaken following the guidance of NUREG/CR-6966 (NRC, 2008). Themaximum water level due to historic tsunami run-up recorded along the west coast ofthe United States and/or Mexico was 39.4 ft at Newport Beach, California, in 1934(NOAA, 2013), approximately 292 miles from the site. Based on the distance, intervening topographic features and differences in elevation (the minimum grade levelof safety related SSCs is 951 ft, over 910 ft above the maximum recorded tsunami run-up elevation),
it was concluded that tsunami run-up from Pacific coast events cannotreach the site and, therefore, tsunami flooding at the site was screened out.3.8 Ice-Induced FloodingThe risk of ice-induced flooding which could adversely impact safety-related structures at the site was assessed in accordance with the applicable guidelines of the NRC. Ice-induced flooding analysis for the site included an assessment of ice jams, frazil ice, andice thickness.
According to guidance in NUREG CR-7046, ice-induced flooding wasonly considered in the context of whether a collapse of an ice jam can cause water topropagate to the site and whether an ice jam can cause flooding via backwater effects.The analysis screened out ice-induced flooding at the site based on historical ice jamrecords and meteorological data.3.9 Flooding Resulting from Channel Migration or Diversion The reevaluation of flood hazards at the site included an evaluation of the potential forsite flooding resulting from channel migration or diversion upstream and downstream ofthe site. The rivers and washes in the vicinity of the site are the Hassayampa and GilaRiver, and Winters, Centennial, and East Washes, as shown in Figure 2-4. A qualitative assessment of these watercourses, based on an evaluation of local and regionaltopography, current and future land use, and seismic, geological, and thermal (e.g.,volcanic) processes in the region, determined that the possibility of channel migration causing a flood hazard to safety-related SSCs at the site was negligible.
44 *2r Flood Hazard Reevaluation Report4.0 COMPARISON OF CURRENT AND REEVALUATED PREDICTED FLOOD LEVELSSection 4.0 has been prepared in response to Item 1.c. of NRC Recommendation 2.1,Enclosure 2 of the 10 CFR 50.54(f) letter. Item 1 .c. requires a comparison of currentand reevaluated flood causing mechanisms at the site, an assessment of the currentdesign basis flood elevation to the reevaluated flood elevation for each flood causingmechanism, and how the findings from Enclosure 4 of the letter (i.e., Recommendation 2.3 flooding walkdowns) support this determination.
If the current design basis floodbounds the reevaluated hazard for all flood causing mechanisms, justification should beincluded for how this finding was determined.
4.1 Comparison of Current and Reevaluated Flood-causing Mechanisms The flood-causing mechanisms evaluated under the current design basis were:* Effects of local intense precipitation (UFSAR Section 2.4.2.3)" PMF on rivers and streams (UFSAR Section 2.4.3) including coincident wind-wave activity (UFSAR Section 2.4.3.6)" Potential dam failures (seismically induced)
(UFSAR Section 2.4.4)" Probable maximum surge and seiche flooding (UFSAR Section 2.4.5)* Probable maximum tsunami flooding (UFSAR Section 2.4.6)" Ice effects (UFSAR Section 2.4.7)" Channel diversions (UFSAR Section 2.4.9).The flood hazard reevaluation includes the same flooding mechanisms as presented inthe current design basis with some differences between the terminology in current NRCguidance and the UFSAR. Additionally, CEF has been evaluated as part of thereevaluated flood hazard.The conditions for which the flooding analyses were performed and the methods usedto perform the analyses varied between CLB analyses and the reevaluation analyses.
The differences are summarized in Tables 4-1 and 4-2.4.2 Assessment of Differences between Current Design Basis and Reevaluated Flood Elevations and EffectsA comparison of CLB and reevaluated flood levels and effects at the site for each floodmechanism is provided in the following subsections of this report. A summarycomparison is provided in Tables 4-3 and 4-4.4.2.1 Local Intense Precipitation FloodingFor the current design basis, the maximum calculated water levels near the safety-related structures due to the LIP event are two feet below the plant floor elevations at45. AWk Flood Hazard Reevaluation Reporteach unit. As a result, the current design basis does not include hydrostatic orhydrodynamic forces associated with flooding at safety-related SSCs.The initial flood hazard reevaluation for sitewide inundation determined that wateraround the powerblock runs off during the LIP to the peripheral drainage system withsome accumulation in localized areas approximately 1.0 to 1.75 ft. below the plant floorelevation at each unit (Tables 4-3 and 4-4). The areas of water accumulation are limitedin size and depth and are primarily due to localized grade depressions as depicted inFigures 3-3, 3-23 and 3-24.The 1-hour, 1 sq mi LIP depth is 11.8 inches, with a cumulative 6-hour rainfall of15.53 inches. The cumulative 6-hour rainfall depth for the LIP reevaluation analysisobtained using the AWA PMP evaluation tool was 12.80 inches, with a 1-hour rainfalldepth of 10.73 inches.The current licensing bases presented in the UFSAR recognizes that some transient water accumulation could occur. The onsite drainage system is designed such thatrunoff due to PMP will not inundate safety-related structures, equipment, and access tothose facilities.
Areas adjacent to the powerblock are sloped away at 0.5% to 1%,resulting in a minimum drop of 5 to 7 feet at the peripheral drainage system (UFSARSection 2.4.2.3).
The initial flood hazard reevaluation for LIP identified transient localized wateraccumulation adjacent to the powerblock structures, which could result in water ingressinto the structures.
This was addressed by the room-by-room internal flooding
- analysis, which determined that there was no impact to safe shutdown equipment.
No operatoraction is required as a result of the LIP event.The room-by-room internal flooding analysis provided a conservative and reasonable internal water level for each unit. A refined FLO-2D PRO (FLO-2D, 2014b) model wasdeveloped to account for roof rain inventory distribution and localized grade around theaccess doors was developed.
Use of this model yielded lower time duration of wateraccumulation and lower water levels resulting in a significant reduction of the inflow intothe SSCs based on APS simulations (URS, 2014).The potential for sedimentation and debris loading on safety-related SSCs due to LIPwas screened out qualitatively in the reevaluation analysis because of the low flood flowvelocities.
In addition, the flood flows were not in directions that would carry sedimentfrom any potential sediment source into the powerblock area. Similarly, debris loadingwas screened out as a potential hazard for the site, because flows were shallow andcould not carry larger debris into the powerblock area.The effect of wave action on the maximum water surface elevations experienced atsafety-related SSCs during the reevaluation LIP event was determined to be negligible.
46 &1iA Flood Hazard Reevaluation Report4.2.2 Flooding in Rivers and StreamsFloodwater elevations were analyzed in terms of the impact of backwater from riverineflooding (i.e., "stillwater" or "static" flood levels) and the superposition of wave action asdiscussed below.PMP Distributions The current design basis PMP for the Winters Wash watershed was the 24-hour PMP of14.6 inches (UFSAR Table 2.4-10) with a peak rainfall intensity of 5.20 inches in1.15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br />. The reevaluated PMP for the Winters Wash watershed was determined using the AWA PMP evaluation tool. The PMP for the Winters Wash watershed was a72-hour tropical storm PMP of 11.21 inches with an associated peak rainfall intensity of4.16 inches in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.For the East Wash watershed, the current design basis 6-hour PMP of 14.44 inches(UFSAR Table 2.4-11) with a peak rainfall intensity of 6.65 inches in 0.32 hours3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br /> causedthe most severe PMF. Using AWA, a local storm PMP was identified as the critical PMPfor the East Wash watershed, with a 6-hour cumulative depth of 10.09 in. and anassociated peak rainfall of 2.11 inches in 10 minutes.PMF Discharqes The current design basis peak discharge from the Winters Wash watershed of172,400 cfs occurs approximately 5 hr and 45 min after the start of the PMP (UFSARTable 2.4-7). The reevaluated peak discharge determined by using the HEC-HMS is33,260 cfs.The current design basis peak discharge from the East Wash watershed of 16,600 cfsoccurs approximately 2 hr and 10 min after the start of the PMP (UFSAR Table 2.4-7).The refined flood hazard reevaluation results are shown in Table 3-4. The maximumPMF discharge rate of 12,830 cfs occurs at cross-section X3 (Figure 3-16) in East Washjust south of the north embankment.
Stillwater LevelsThe current design basis PMF water level along Winters Wash for the watershed PMPis 944.7 ft at cross-section B (UFSAR Table 2.4-16).
The flood hazard reevaluation determined the peak flood elevation along Winters Wash would be 940.0 ft. usingFLO-2D.The current design basis PMF water levels for East Wash are 962.8 ft, 954.7 ft, and944.0 ft for cross-sections Al, B, and C, respectively (UFSAR Figure 2.4-2,UFSAR Table 2.4-16).
The refined flood hazard reevaluation results for the six hydraulic cross-sections are shown in Table 3-4, along with the embankment elevations andcalculated embankment freeboard.
The locations of these six floodplain cross-sections are shown in Figure 3-14. The analysis determined that East Wash PMF flows do not47 9.mi Flood Hazard Reevaluation Reportbreach the north or east embankments at any point in the simulation.
Figure 3-16 showsthe maximum water depths determined by the model.Wind-waves and Run-up Coincident with PMFThe design basis wave run-up and set-up height in Winters Wash (at cross-section B) is5.6 ft, (i.e., run-up 4.8 ft + set-up 0.8 ft. height)(UFSAR Table 2.4-16).
The flood hazardreevaluation wave run-up on Winters Wash was 0.37 ft at the same location (Figure 3-9). The maximum flood elevation for the current design basis was obtained by summingthe PMF water surface elevation, the wind setup, and the wave run-up height, whichwas evaluated for waves associated with a sustained overland wind velocity of 40 mph.The current design basis water level along Winters Wash for the watershed PMP is950.3 ft at cross-section B (UFSAR Table 2.4-16).
The flood hazard reevaluation maximum water surface elevation at this location, including run-up, was determined tobe 940.4 ft, which does not reach the minimum elevation of the powerblock.
Table 4-3summarizes these results.The design basis maximum water levels, including wind-waves, for East Wash are964.6 ft, 956.5 ft, and 945.8 ft for cross-sections Al, B, and C, respectively (UFSARTable 2.4-16).
The refined flood hazard reevaluation (Table 3-5) determined the waterlevels at these locations to be 964.78 ft., 956.58 ft., and 947.58 ft, respectively.
Both thedesign bases and the refined flood hazard reevaluation show sufficient freeboard.
The design basis wave run-up and set-up height for the East Wash embankment atcross section X2 is 1.8 ft (UFSAR Table 2.4-16),
which results in a freeboard of 1.75 ft.The run-up and setup for the north embankment is 4.0 ft (UFSAR Table 2.4-16),
whichresults in a freeboard of 3.0 ft at UFSAR cross-section GI, which is equivalent to crosssection Xl in the refined flood hazard reevaluation report (Table 3-5). At the criticalfetch length cross-sections (Figure 3-18), the refined flood hazard evaluation wave run-up freeboard is 2.09 ft for the north embankment (at Xl) and 1.72 ft for the eastembankment (at X2) (Table 3-7). These values are comparable to the design basis.Thus, the East Wash east and north embankments that realign the PMF flood aroundthe site have sufficient freeboard to contain the PMF coincident with a wave heightinduced by a 2-year wind event. East Wash PMF flows do not overtop the north or eastwash embankments at any point.4.2.3 Combined Effects FloodingNo CEF analysis is documented in the current design basis.As described in Section 3.3, the CEF for Winters and East Wash concluded that thePMF event is contained within the washes and the embankments are not overtopped.
48 J Flood Hazard Reevaluation Report4.2.4 Dam Breaches and FailuresThe current design basis states that the site is not exposed to flooding due to damfailure using a domino failure analysis method and that peak flood levels only reachelevation 900 ft, which is below the plant grade elevations (UFSAR Section 2.4.4.3).
The reevaluation analysis for dam breaches and failures used the more conservative Volume Method screening analysis of ISG-2013-01, which utilizes 100% of the damcapacity and does not account for attenuation of flood waves. The reevaluation determined that peak flood levels did not exceed 935 ft as compared to the lowestgrade elevation at the powerblock of 951 ft, which screened out dam failure at the site.4.2.5 Storm Surge and Seiche, Tsunami, and Ice-Induced FloodingStorm surge and seiche, tsunami, and ice-induced flooding were screened out aspotential flooding events in the current design basis in the UFSAR and in the initial floodhazard reevaluation report.4.2.6 Channel Diversion The UFSAR confirmed that the plant and essential water supplies will not be adversely affected by natural stream channel diversion or, that in such an event, alternate watersupplies are available for safety-related equipment.
The flood hazard reevaluation identified potential inflows from the Jackrabbit Wash intothe Winters Wash watershed, but also determined that flood waters in Winters Wash didnot impact the site. The reevaluation analysis excluded potential diversion acrosswatershed divides into East Wash based on a series of simplified HEC-RASsimulations.
Therefore, channel diversion was screened out at the site in the initial floodhazard reevaluation analysis.
4.3 Supporting Documentation The reevaluated flood levels presented in this report are based on detailed calculations developed in support of the flood hazard reevaluation at the site. The calculations wereprepared and reviewed by the responsible organizations and a client review wasperformed by APS. The critical calculations were also peer reviewed by an independent organization (Table 4-5). The Flooding Walkdown Report provides additional information regarding the current design basis flood hazard levels, as well as floodingprotection and mitigation features.
APS determined through the flooding walkdowns thatthe flood protection features were capable of providing the level of protection credited inthe licensing basis. Nonconforming conditions discovered during the walkdowns wereentered into the CAP.4.3.1 Technical Justification of the Flood Hazard AnalysisThe flood hazard reevaluation analyses described in this report utilized techniques,
- software, and methods used in present-day standard engineering practice.
The49 j t Flood Hazard Reevaluation Reporttechnical basis for the various scenarios modeled under the HHA method and the keyassumptions utilized in determination of the reevaluated flooding levels for each flood-causing mechanism are discussed individually in Section 3.0 and are summarized inTables 4-1 through 4-4.4.3.2 Technical Justification by the Recommendation 2.3 Walkdown ResultsThe results from the Flooding Walkdown Report were taken into consideration duringthe implementation of the flood hazard reevaluation and when drawing conclusions fromthe analyses.
Specifically, it was found that site modifications have not adversely affected the ability of safe shutdown equipment to perform their safety function.
4.4 Conclusions
No operator or mitigation actions are needed to ensure safe shutdown capability as aresult of the flood hazard reevaluation.
As no additional actions to protect against thereevaluated flood hazards are needed and the results are comparable to the licensing basis, APS believes that an integrated assessment is not needed or warranted.
4.4.1 Effects of LIPThe current licensing basis flood elevations for LIP are two feet below plant grade at theperiphery of the powerblock.
As described in Section 2.2.1, the current analysis used amethodology that accounted for water levels in ditches, but not transient wateraccumulation and sheet flow adjacent to buildings.
Specific values for transient wateraccumulation adjacent to powerblock structures were not stated in the LIP licensing basis.Using present-day regulatory guidance and methodologies, including currenttechniques,
- software, and methods used in present-day standard engineering
- practice, the flood hazard revaluation quantified localized water accumulations adjacent to safety-related SSCs. Specifically, these accumulations from LIP were determined to be oflimited duration, although possibly reaching peak accumulations of 1 to 7 inches. Theseprojected levels would exceed entrance elevations of a limited number of safety-related SSCs (i.e., doors or hatches).
APS has determined in a room-by-room internal floodinganalysis that localized accumulation of water adjacent to structures in the powerblock does not require operator action and does not impact safe shutdown equipment.
Sincethe LIP flood levels for the current licensing bases do not require operator action, just asthe reevaluated LIP flood levels do not require operator action to ensure the capability for safe shutdown, APS believes that no further action is required to address LIP.4.4.2 PMF in Nearby Watercourses The reevaluated PMF static flood levels in Winters Wash were approximately 5 ft lowerthan the static flood levels computed in the current licensing basis. Therefore, thelicensing basis bounds the PMF static water levels and wave run-up height computed inthe reevaluation analysis for Winters Wash.50 Flood Hazard Reevaluation ReportThe refined analysis determined that PMF flood levels in East Wash were comparable to the flood levels computed in the current design basis. The refined analysisdetermined that both the north embankment and east embankment of East Wash werenot overtopped by wave run-up during the PMF event, which is consistent with thecurrent licensing basis.No CEF analysis is documented in the current licensing basis. As described inSection 3.3, the CEF for Winters and East Wash concluded that the PMF event iscontained within the washes and there is no impact to safe shutdown equipment.
The reevaluated PMF flood levels were found to be comparable to current licensing basis flood levels. The results showed that there is no impact to the site from WintersWash, the East Wash embankments are not overtopped, there is no new operatoraction required, and there is no impact to safe shutdown equipment.
Therefore, APSbelieves that no further action is required to address PMF.4.4.3 Remaining Flood-Causing Mechanisms Both the current licensing basis and the reevaluation analysis dismiss flooding as aresult of storm surge and seiche, tsunami, and ice-induced flooding.
Both the current licensing basis and the reevaluation analysis concluded that channeldiversion is not a hazard for the site.Both the current licensing basis and the reevaluation analysis screened out dam failureas a potential hazard to the site.Based upon the reevaluation results for storm surge, seiche, tsunami, ice-induced
- flooding, channel diversion, and dam failure, no further action is required.
51 *4 Flood Hazard Reevaluation Report5.0 INTERIM EVALUATION AND ACTIONSSection 5.0 has been prepared in response to Item 1.d. of NRC Recommendation 2.1,Enclosure 2 of the 10 CFR 50.54(f) letter: "Provide an interim evaluation and actionstaken or planned to address any higher flooding hazards relative to the design basis,prior to completion of the integrated assessment."
At this time, there are no additional actions which are planned to address floodinghazards at the site.52 *4 Flood Hazard Reevaluation Report6.0 ADDITIONAL ACTIONSSection 6.0 has been prepared in response to Item 1.e. of NRC Recommendation 2.1,Enclosure 2 of the 10 CFR 50.54(f) letter: "Provide additional actions beyond Requestfor Information item 1 .d taken or planned to address flooding
- hazards, if any."At this time, there are no additional actions beyond Item 1 .d. of NRC Recommendation 2.1 (Section 5.0) to address flooding hazards at the site.53 Flood Hazard Reevaluation Report
7.0 REFERENCES
- 1. (ADOT, 1969), State of Arizona, State Highway Department, "As-Built
- Drawings, 1-10-2(13),
Ehrenberg Highway -Phoenix Highway, Tonopah East & West,Maricopa County,"
November 4, 1969.2. (ADWR, 2014),"http://www.azwater.qov/AzDWR/PubliclnformationOfficer/MissionAndGoals.htm, accessed 2014.3. (AGS, 2000), Arizona Geological Survey, "Earthquake Hazard in Arizona,"
Vol.30, No. 1, Spring 2000.4. (ANS, 1992), American Nuclear Society, 1992, "Determining Design BasisFlooding at Power Reactor Sites," ANSI/ANS-2.8-1992.
102-06627 (ML12334A416),
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August 12, 2013.57 9 w Flood Hazard Reevaluation ReportAPPENDIX ATABLES&,A*
Flood Hazard Reevaluation ReportTable 2-1: Existing Design Parameters Parameter Value UFSARLIP due to thunderstorm PMP 11.8" (1 hr) Table 2.4-615.53" (6 hr)Maximum ponding depth on roof < 6" during 6-hr Section 2.4.2.3thunderstorm PMPMaximized Storm PMP for the Winters 14.6" (24.15 hr) Table 2.4-10Wash watershed Maximized Storm PMP for the East 14.44" (6.06 hr) Table 2.4-11Wash watershed East Wash flow velocity during PMP 6 fps (estimated)
Section 2.4.10East Wash embankment maximum local 0.8 psf Section 2.4.10boundary shear for PMPMaximum run-up levelWinters Wash 4.8 ft Tables 2.4-19East Wash north embankment 3.8 ft through 2.4-21East Wash east embankment 1.7 ftProtection of safety-related facilities from Structure elevation inundation by offsite flood sources is Unit 1 -957.5 ft Section 2.4.2.2.1 achieved by the location of the facilities Unit 2 -954.5 ft Figure 2.4-4beyond the extent of flooding Unit 3 -951.5 ftTables 2.4-19Wind speed for wave run-up (over land) 40 mph through 2.4-21Freeboard in the Essential Spray Ponds 4.0 ft Design basiscalculation Maximum surfaceThe onsite drainage system is designed waterso that runoff due to PMP will not Unt9Sinundate the safety-relates structures, Unit 2 -952.5 ftequipment, and access to these facilities Unit 3 -949.5 ftUnit 3 -949.5 ft&JA*__
Flood Hazard Reevaluation ReportTable 2-2: Current Design Basis Flood Elevations Due to All Flood Mechanisms Parameters Value UFSARUnit 1 -957.5 ftLowest Exterior Entrance Elevation for Unit 2 -954.5 ft Section 2.4.2.3any Safety-Related Building Unit 3 -951.5 ftUnit 1 -955.5 ftPoint-Value PMP (LIP) Flooding Level Unit 2 -952.5 ft Section 2.4.2.3at the Periphery of the Powerblock Unit 3 -949.5 ftPMF levels on East Wash 926.6 ft at "F" Section 2.4.3978.8 ft at "G2" Table 2.4-16 Sh 1East Wash Run-up + Wind Setup:North Facing Embankment 4.0 ft Table 2.4-16East Facing Embankment 1.8 ft929.5 ft at "D" Section 2.4.3956.4 ft at "AA" Table 2.4-16 Sh 1Winters Wash Run-up + Wind Setup 5.6 ft Table 2.4-16Maximum Water Level with Upstream 900 ft Section 2.4.4.3Dam FailureStorm Surge and Seiche Flooding N/A Section 2.4.5Tsunami Flooding N/A Section 2.4.6Ice Flooding N/A Section 2.4.7Channel Diversion Flooding N/A Section 2.4.9&A*4 Flood Hazard Reevaluation ReportTable 3-1: Characteristics of Winters Wash Sub-Basins and HEC-HMS Model Results 1Sub-Basin Green-AmptImAea Lag Time4 PMP PMP Peak Time toDrainage SbArea GreenAp Area (hr) Depth Duration Discharge PeakSub-Basin (sq mi) Parameters 3 (%) (in.) (hr) (cfs) Discharge WW-1 35.628 0.13 0.36 5.47 0.36 11.1 2.54 11.21 72 6,819 42:25WW-2 29.399 0.13 0.38 5.22 0.37 11.6 1.77 11.21 72 5,767 42:00WW-3 49.722 0.13 0.37 5.44 0.34 10.7 2.37 11.21 72 10,155 42:00WW-4 14.265 0.11 0.36 5.06 0.39 3.1 1.45 11.21 72 2,332 42:00WW-5 49.200 0.10 0.35 4.67 0.48 14.2 2.09 11.21 72 6,902 42:00WW-6 15.169 0.11 0.36 4.89 0.43 2.9 1.24 11.21 72 2,076 42:00WW-7 15.903 0.10 0.35 4.75 0.48 3.5 1.52 11.21 72 1,664 42:00WW-8 19.419 0.12 0.36 5.00 0.41 5.4 0.99 11.21 72 3,101 42:00WW-9 13.415 0.10 0.35 4.38 0.54 18.1 1.79 11.21 72 1,637 42:00WW-10 8.557 0.11 0.35 5.08 0.39 13.1 1.42 11.21 72 1,654 42:00WW-11 1.982 0.10 0.35 4.94 0.41 18.2 0.89 11.21 72 392 42:00WW-12 11.547 0.11 0.35 5.05 0.39 4.0 1.38 11.21 72 1,933 42:00WW-13 17.278 0.11 0.36 4.71 0.48 12.8 1.05 11.21 72 2,402 42:00Notes:1 Results presented are for the transient most refined case (Case W8). which included normal soil conditions, rainfall losses, and reach routing2 Refer to Figure 3-7 for a wash sub-basin map.3 Values from left to right are: initial soil moisture as a % volume, saturated soil moisture as a % volume, suction in inches, and soil vertical hydraulic conductivity (inches/hour) 4 Lag time is reduced by 33% and the peak of unit hydrographs were increased by 5% to account for non-linearity effects (NUREG/CR-7046).
NA*__0WU=Zxr Flood Hazard Reevaluation ReportTable 3-2: Summary of FLO-2D Simulations for Winters Wash FloodingWith VBSDomain and Simulated 1 FLO-2D Manning's Sedimentation and WashlPedCase PMF Hydrograph Domain Grid Size Roughness 2 Evaluation East Wash Period(ft) Embank (hr)RemovedConstant at Peak PMF1 from downstream of Large 50 x 50 Higher No No 11PVNGS2 Downstream hydrograph Large 50 x 50 Higher No No 96applied upstream3 Downstream hydrograph Large 50 x 50 Higher Yes No 96applied upstream9 Time-Varying PMF fromUFSAR (PVNGS, 2013) Large 50 x 50 LowerNotes:1 Hydrographs are from HEC-HMS simulations for the most refined cases Case W8 for the Winters Wash.2 Manning's roughness coefficients are for the higher and lower ends of the recommended rangesfiAi Flood Hazard Reevaluation ReportTable 3-3: Floodplain Cross-Section PMF Results (100-ft Grid Element Model)FLO-2D Peak Flowrate (cfs) Time to Peak (hr) Total Discharge (acre-ft)
XS1 10,630 4.2 2,470XS2 10,090 4.4 2,500XS3 12,070 3.9 4,280XS4* 1,400 3.2 120XS5* 11,700 4.0 4,170Note:* XS4 and XS5 discharges were used as the hydrologic inputs into the 25-ft grid element model to represent flowsfrom the East Wash watershed.
Table 3-4: Floodplain Cross-Section PMF Results(25-ft Grid Element Model)MaximumFloodplain Peak Time to Water Embankment Embankment Cross- Flowrate Peak Surface Elevation Freeboard Section * (cfs) (hr) Elevation**
(ft) (ft)(ft)Xl 11,770 4.53 979.5 983.0 3.5X2 12,530 4.79 974.9 978.0 3.1X3 12,830 4.85 969.2 973.1 3.9Al 12,280 4.95 963.4 967.5 4.1B 11,040 5.13 955.2 961.6 6.4C 10,860 5.30 946.2 948.4 2.2Notes:* Cross-sections Xl, X2, and X3 are locations defined incross-sections from the UFSAR report.Figures 3-14 and 3-16, and cross-sections Al, B, and C are** Maximum water surface elevation does not include effects from wind-wave action.914k Flood Hazard Reevaluation ReportTable 3-5: Comparison of PMF LevelsFloodplain Cross-Section Xl (G1) Al B CEmbankment elevation (ft) 983.1 967.5 961.6 948.4UFSAR static flood level / (freeboard)
(ft) 976.1 (7.0) 962.8 (4.7) 954.7 (6.9) 944.0 (4.4)Wave run-up + set-up (ft) 4.0 1.8 1.8 1.8Wind-wave flood level / (freeboard)
(ft) 980.1 (3.0) 964.6 (2.9) 956.5 (5.1) 945.8 (2.6)Refined static flood level / (freeboard)
(ft) 979.5 (3.6) 963.4 (4.1) 955.2 (6.4) 946.2 (2.2)Wave run-up + set-up (ft) 1.51 1.38 1.38 1.38Wind-wave flood level / (freeboard)
(ft) 981.01 (2.09) 964.78 (2.72) 956.58 (5.02) 947.58 (0.82)Note:Cross-sections Al, B, and C are cross-sections from UFSAR Figure 2.4-2. Cross-section Xl is defined in Figures 3-14 and 3-16. Cross-section G1 is equivalent tocross-section Xl as shown in UFSAR Figure 2.4-2. The crest elevations of the embankments are based on survey data taken as part of the refined flood hazardreevaluation.
Flood Hazard Reevaluation ReportTable 3-6: Fetch DataFetch Fetch FetchFetch Deth Length Length Length(m) (ft) (mi) (ft) (m)North Embankment 2.68 8.78 1.02 5,400 1,646East Embankment 3.14 10.29 0.87 4,600 1,402Table 3-7: Wave Run-Up and Freeboard Fetch North EastEmbankment Embankment Surf Similarity,
ýo 1.14 1.13Wave Run-up, R2% (ft) 1.51 1.38Antecedent Static Water Level 9 974.9(NGVD29)Final Run-up Water Level (NGVD29) 981.01 976.28Embankment Crest (NGVD29) 983.1 978.0Static Freeboard (ft) 3.60 3.10Run-up Freeboard (ft) 2.09 1.72&*ffkV Flood Hazard Reevaluation ReportTable 3-8: Summary of FLO-2D Simulation Cases forCombined Effects FloodingGrid Culverts Reference EastCell Manning's Detailed Under Simulation WashSimulation Size Roughness Representation WRF From Embank(ft) Coefficients of 1-10 Access FLO-2DRoad PMF RemovedW1 200 x 0.09 No N/A N/A N/A200W21 200 x 0.06 No N/A N/A N/A200W31 200 x 0.04 No N/A N/A N/A200E1 2 50 x 0.09 Yes N/A N/A N/A50E2 2 50 x 0.06 Yes N/A N/A N/A50E3 2 50 x 0.04 Yes N/A N/A N/A50Case 1 3 50 x 0.094 No N/A Case 2 No___ ___ ___ 50 _ _ _ _ _Case 2 5 25 x 0.09 Yes Partially Case 4 No25 Unblocked Case 3 5 25 x 0.06 Yes Partially Case 5 No25 Unblocked 5 25 x Partially Manning's Case 4 25 0.04 Yes Unblocked roughness Nosensitivity Case 5 5 25 x 0.06 Yes Partially Case 7 Yes25 Unblocked Case 6 5 25 x 0.06 Yes Blocked N/A No25Notes:1 This is a model of the north domain of the Winters Wash watershed.
2 This is a model of the north domain of the East Wash watershed.
3 This is a model of the south domain of the Winters Wash watershed.
4 These Manning's roughness coefficients correspond to the desert rangeland areas within theFLO-2D model. Appropriate coefficients were used for other land cover types near the site.5 This is a model of the south domain of the East Wash watershed.
Flood Hazard Reevaluation ReportTable 4-1: Comparison of Modeling Approaches for CLB and Reevaluation Modeling Approach Reevaluated Hazards Current Licensing BasisStation used for Wind Phoenix Sky Harbor Phoenix Sky Harbor International Analysis International Airport AirportLocal Intense Precipitation AWA PMP Evaluation Tool Calculated based on(LIP) (NWS, 1972)1The powerblock areas were dividedinto small tributary areas, andA 2D flood routing model runoff rates were computed forLIP Flooding (FLO-2D) is used to each area. These rates wereCharacterization simulate runoff from the supplied to periphery ofpowerblock and powerblock.
Flood elevations weresurrounding areas. computed using elevation-volume relationships developed for eachtributary area.Calculated based on Hershfield PMP Calculation (River AWA PMP Evaluation Tool Method for Winters Wash; PMPFlooding)
Estimates for East Wash 2PMP Rainfall Hyetograph Time period of 6 hrs with Time period of 6.06-hr PMP, withEast Wash Watershed 10-min increments 19.2-minute increments (UFSARTable 2.4-11)Time period of 24.15 hrs withPMP Rainfall Hyetograph Time period of 72 hrs with 1.15-hr increments FAtaWinters Wash Watershed 6-hr increments 2.4-10)2.4-10)HEC-HMS was not used for theRainfall-Runoff Model USACE HEC-HMS2 UFSAR analysis; PMF wascomputed based on SCS method.Transformation Method Maricopa County S-graph 3 SCS Type II Unit Hydrograph PMF loss, and routing Green-Ampt Method SCS Curve Number MethodCross-sectional data was used toRiver Hydraulic Model FLO-2D cmuetePFwtrlvl compute the PMF water level.Volume Method used to Seismically induced domino failureDam Break Flooding determine water surface with an antecedent 500-yr floodelevation eventCombined effects flooding analysisFlooding NUREG/CR-7046 and was not required and is notCombined Effects ANS, 1992 methods documented in the current designI basis&-&U, Flood Hazard Reevaluation ReportTable 4-1: Comparison of Modeling Approaches for CLB and Reevaluation (Continued)
Notes:1 The local intense precipitation analysis in the UFSAR is based on a point value PMP distribution at the site (UFSAR Section 2.4.3.2).
2 HEC-HMS is only used for modeling discharge upstream of the site for the River and StreamsPMF analysis, but not the CEF analysis.
3 Rainfall is directly applied to the FLO-2D models for the LIP, PMF, and CEF analysis.
Flood Hazard Reevaluation ReportTable 4-2: Comparison of Analytical Inputs for CLB and Reevaluation Analytical Input Reevaluated Hazards Current Licensing BasisLocal Intense 10.73" (1 hr) 11.8" (1 hr)Precipitation 112.80" (6 hrs) 15.53" (6 hrs)(UFSAR Table 2.4-6)A 72-hour PMP was notPMP for Winters Wash 11.21" computed.
The 24.15-hr PMPwatershed (72-hr PMP) is 14.60"(UFSAR Table 2.4-10)PMP for East Wash 10.09" 14.44" (6.06-hr PMP) 2watershed (6-hr value) (UFSAR Table 2.4-11)12,830 cfs 16,600 cfs (East Wash)PMF Model, peak flow (East Wash, cross-section X3 (UFSAR Table 2.4-7)rate north of the site from172,400 cfs (Winters Wash)33,260 cfs (Winters Wash) 3 (UFSAR Table 2.4-7)CEF model, peak flow 15,842 cfs (East Wash)rates north of the site 29,585 cfs (Winters Wash)4 CEF not requiredMaximum Sustained 40 mphOverland 10-min, 2-yr 39.35 mph (UFSAR Section 2.4.3m6)Wind SpeedMaximum Sustained 48.8, 43.2, and 46.8 mph 5Overwater 10-min, 2-yr 47.28 mph (UFSAR Tables 2.4-19Wind Speed through 2.4-21)Notes:1 The local intense precipitation analysis in UFSAR Section 2.4.3.2 is based on a point value PMPdistribution at the site.2 The value of 14.44 inches is obtained from summing the incremental rainfall values presented in UFSARTable 2.4-11. The area reduction for the 6-hour PMP is reported as 93% (UFSAR Section 2.4.3.1.2),
whichreduces 15.53 inches to 14.44 inches.3 The listed flows are from the HEC-HMS simulations.
4 The listed flows are from the FLO-2D simulations; the CEF analysis is more detailed than the HEC-HMSsimulations.
5 Values presented are for Winters Wash, East Wash east-facing embankment, and East Wash north-facing embankment, respectively.
Flood Hazard Reevaluation ReportTable 4-3: Comparison of Flood Levels for CLB and Reevaluation Mechanism Reevaluated Water Current Licensing BasisLevel (ft) Water Level (ft)0.19 to 0.63 (transient Did not specify 2water accumulation) 1Maximum Transient WaterAccumulation Depths at Safety- 1.0 to 1.75 ft below 2 ft below plant gradeRelated Structures for the LIP plant grade at localized at each unit4sections near the (UFSAR Section 2.4.2.3)powerblock 3979.5 at "X1" 5 976.1 at "G1" River Flooding:
East Wash 963.4 at "Al" 962.8 at "Al"(Stillwater) 955.2 at "B" 954.7 at "B"'946.2 at "C" 944.0 at "C"(Refined model) (UFSAR Table 2.4-16)River Flooding:
Winters Wash 940.0 at "B" 944.7 at "B"(Stillwater)
(UFSAR Table 2.4-16)1.51 4.0Oat "G1"River Flooding East Wash1.140a"G" River Fongup Esetup: Wah Cross-section (UFSAR Table 2.4-16)Wave Run-up + setup: North Xl (Refined model)Facing Embankment River Flooding East Wash 1.38 1.8Waver Rcnsl Easetu: East (Refined model) (UFSAR Table 2.4-16)Wave Run-up + setup: East Cross-sections All, BFacing Embankment and CRiver Flooding Wave Run-up + 0.37 5.6setup: Winters Wash (UFSAR Table 2.4-16)981.01 at "X1" 980.1 at "GI"964.78 at "Al" 964.6 at "Al"River Flooding Flood Elevations 96.58 at "B" 96.5 at "B"with Wave Run-up, East Wash 947.58 at "C" 95.8 at "C"947.58 at "C" 945.8 at "C"(Refined model) (UFSAR Table 2.4-16)2.09 at "Xl" 3.0 at "GI"2.72 at "Al" 2.9 at "Al"RvrFodFebad5.02 at "B" 5.1 at "B"Wave Run-up + setup, East Wash 02 at "C" 2.6 at "C"0.82 at "C" 2.6 at "C"(Refined model)6 (UFSAR Table 2.4-16)S...4k Flood Hazard Reevaluation ReportTable 4-3: Comparison of Flood Levels for CLB and Reevaluation (Continued)
Reevaluated Water Current Licensing BasisLevel (ft) Water Level (ft)River Flood Elevations with Wave 940.4 950.3Run-up, Winters Wash (UFSAR Table 2.4-16)River Flood Freeboard Wave Run-up + setup, 10.6 7 0.7 7Winters WashDam Failure Flooding Screened Out Screened OutStorm Surge & Seiche Flooding Screened Out Screened OutTsunami Flooding Screened Out Screened OutIce Flooding Screened Out Screened OutChannel Diversion Flooding Screened Out Screened OutNotes:1APS room-by-room internal flood analysis evaluated the localized transient water accumulation adjacent tostructures and determined that there was no impact to safe shutdown equipment.
2 The licensing bases did not provide a specific value for the transient water accumulation phenomenon.
- However, the design of powerblock structures did include sufficient capability to mitigate internal floodingresulting from high- and moderate-energy line breaks which was implicitly assumed to bound the effects ofexternal flooding from the localized transient water accumulation during the LIP event.3 The initial flood hazard reevaluation for sitewide inundation determined that water around the powerblock runs off during the LIP to the peripheral drainage system with some accumulation in localized areasapproximately 1.0 to 1.75 ft below the plant floor elevation at each unit. The areas of water accumulation arelimited in size and depth and are primarily due to localized grade depressions as depicted in Figures 3-3, 3-23 and 3-24.4CLB values from UFSAR Section 2.4.2.3.
The levels reported in the current design basis refer to watersurface elevations at the periphery of the powerblock and do not account for sheet flow and transient wateraccumulation adjacent to buildings.
5 Cross-section X1 in the refined model is equivalent to G1 from UFSAR Figure 2.4-2.6 The crest elevations of the embankment are based on survey data taken as part of the refined FloodHazard Reevaluation Report.7 Freeboard for Winters Wash with wave-runup was calculated with respect to the lowest plant gradeelevation (951 ft) (UFSAR 2.4.2.2.2).
Flood Hazard Reevaluation ReportTable 4-4: Comparison of Flooding for CLB and Reevaluation Flood Condition Reevaluated Flood Hazard Current Licensing BasisLocal Intense Precipitation 0.19 to 0.63 (transient wateraccumulation) 1 Did not specify 2Flood Depth (ft) 1.0 to 1.75 ft below plant 2 ft below plant gradegrade at localized sections at each unit4near the powerblock 3 (UFSAR Section 2.4.2.3)Flood Duration (hr) 2 to 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> 5 Did not specify 6Maximum Flow Velocity 1.7 7 Did not specify(ft/sec) 1.7___Didnotspecify__
Maximum Hydrostatic Loading (lb/ft) 10.2 8 Did not specify 9Maximum Hydrodynamic Loading (lb/ft) 3.2 8 Did not specify 6Flood Elevation with Debris Screened Out1o Did not specify 6EffectsFlood Elevation with Screened Out" Did not specify 6Sedimentation Effects94L Flood Hazard Reevaluation ReportTable 4-4: Comparison of Flooding for CLB and Reevaluation (Continued)
Flood Condition Reevaluated Flood Hazard Current Licensing BasisFlooding in Rivers and Streams12981.01 at "Xl" 980.1 at "G1"Flood Elevation along East 964.78 at "Al" 964.6 at "Al"Wash with wind-wave 956.58 at "B" 956.5 at "B"effects (ft) 947.58 at "C" 945.8 at "C"(Refined model) (UFSAR Table 2.4-16)Flood Elevation alongWinters Wash with wind- 940.4 950.3wave effects (ft) (UFSAR Table 2.4-16)Duration of PMF is 13hours 6Flood Duration (hr) for Footnote 14 (UFSAR Figure 2-4-13 andPMF (Refined model) Figure 2.4-14)Maximum Flow Velocity in 3 to 7 13 6 6, 13East Wash (ft/sec)
(Refined model) (UFSAR Section 2.4.10)Debris Effects Screened Out N/AScour due to sedimentSedimentation Effects Screened Out transport during riverflooding was evaluated.
(UFSAR Section 2.4.10)Aa*_
Flood Hazard Reevaluation ReportTable 4-4: Comparison of Flooding for CLB and Reevaluation (Continued)
Notes:1 APS room-by-room internal flooding analysis evaluated the localized transient water accumulation adjacentto structures and determined that there was no impact to safe shutdown equipment.
2 The licensing bases did not provide a specific value for the transient water accumulation phenomenon.
- However, the design of powerblock structures did include sufficient capability to mitigate internal floodingresulting from high- and moderate-energy line breaks, which was implicitly assumed to bound the effects ofexternal flooding from the localized transient water accumulation during the LIP event.3 The initial flood hazard reevaluation for sitewide inundation determined that water around the powerblock runs off during the LIP to the peripheral drainage system with some accumulation in localized areasapproximately 1.0 to 1.75 ft below the plant floor elevation at each unit. The areas of water accumulation arelimited in size and depth and are primarily due to localized grade depressions as depicted in Figures 3-3, 3-23 and 3-24.4 CLB values from UFSAR Section 2.4.2.3.
The levels reported in the current design basis refer to watersurface elevations at the periphery of the powerblock and do not account for sheet flow and transient wateraccumulation adjacent to buildings.
5 Flood duration transient, where water enters the building, lasts on average two to three hours and amaximum of five hours depending on the door and adjacent grade and curb features.
6 Flooding does not reach safety-related SSCs.7 Maximum flood velocity near doors within powerblock.
8 Maximum load at safety-related structures.
Hydrostatic Loading -Detailed structural analysis regarding the effects of these forces is not requiredbecause the flow vectors that are computed in this analysis indicate that the flows are away from SeismicCategory I structures.
Hydrodynamic Forces- act in the direction of flow velocity.
Consequently, the reported hydrodynamic forcesshould be interpreted as a conservative estimate.
In cases where flow velocity is directed away from orparallel to the door, the hydrodynamic force acting on the door is zero.9 Flooding does not reach safety-related SSCs. Hydrostatic loads due to groundwater were considered forthe current design basis, but not in the reevaluation study.1o Simulated water levels were too shallow, velocities were too low, and flow directions were not towardbuildings.
" Simulated low velocities at the powerblock were too low and flow directions were not toward buildings.
12 Includes the CEF analysis as the most refined cases. CEF was not considered in the design basesbecause it was not required at the time of license issuance.
13 Maximum hydrodynamic and hydrostatic loads associated with river flooding were computed for allinundated areas with the FLO-2D model domain in the CEF evaluation.
Forces associated with flooding onthe powerblock during river flooding were bounded by the forces associated with the LIP flooding.
Using a velocity of 6 fps, 10 ft maximum water depth, and an average stone diameter of 12 inches, the valueof local boundary shear is 0.8 psf. Since the range of velocity in the wash is 3 to 7 fps, then thecorresponding loading on the embankment is less than the design values of 3.6 and 3.1 psf (UFSAR 2.4.10).14 Flood durations in East Wash and Winters Wash are not provided since the PMFs in the washes do notresult in overtopping the embankment or inundating the site.
Flood Hazard Reevaluation ReportTable 4-5: List of Supporting Documents Document Title Originating Peer ReviewOrganization Organization Local Intense Precipitation Westinghouse Electric URS Corporation Company/
Paul C. RizzoAssociates Effects of Local Intense Westinghouse Electric URS Corporation Precipitation Using FLO-2D Company/
Paul C. RizzoAssociates Wind-Wave Activity Coincident Westinghouse Electric Deemedwith the LIP Company/
Paul C. Rizzo Unnecessary Associates Watershed Delineation for East Westinghouse Electric URS Corporation Wash and Winters Wash Company/
Paul C. RizzoAssociates PMP Estimation for the East Wash Westinghouse Electric URS Corporation and Winters Wash Watershed Company/
Paul C. RizzoAssociates Probable Maximum Flood in Rivers Westinghouse Electric URS Corporation Company/
Paul C. RizzoAssociates Water Level Estimation Due to Westinghouse Electric URS Corporation PMF Using FLO-2D Company/
Paul C. RizzoAssociates Potential Dam Breaches and Westinghouse Electric DeemedFailures Company/
Paul C. Rizzo Unnecessary Associates Screening of Coastal Flooding Westinghouse Electric DeemedCompany/
Paul C. Rizzo Unnecessary Associates Channel Diversion Flooding Westinghouse Electric DeemedCompany/
Paul C. Rizzo Unnecessary Associates Wind-Wave Activity Coincident Westinghouse Electric Deemedwith the PMF Company/
Paul C. Rizzo Unnecessary Associates
&A*
Flood Hazard Reevaluation ReportTable 4-5: List of Supporting Documents (Continued)
Document Title Originating Peer ReviewOrganization Organization Low Water Considerations Westinghouse Electric DeemedCompany/
Paul C. Rizzo Unnecessary Associates Ice Flooding Westinghouse Electric DeemedCompany/
Paul C. Rizzo Unnecessary Associates Combined Effects Westinghouse Electric URS Corporation Company/
Paul C. RizzoAssociates Transmittal of Palo Verde Nuclear Westinghouse Electric URS Corporation Generating Station Flood Hazard Company/
Paul C. RizzoReevaluation Closeout Associates Documentation
& Third PartyReviewPalo Verde Nuclear Generating Westinghouse Electric DeemedStation -Procedure for Aerial Company Unnecessary Photography of the OwnerControlled Area (OCA) as a basisof Topographical MappingAeroTech Aerial Photographic AeroTech Mapping DeemedCoverage Report Unnecessary URS Review of Palo Verde Westinghouse Electric URS Corporation Nuclear Generating Station Flood Company/
Paul C. RizzoHazard Reevaluation Calculation Associates Evaluation of Internal Flooding in APS Sargent & LundySafety Related Structures as aResult of Localized Ponding at thePower Block During a LIP Event insupport of NRC 50.54(f) letter andthe PVNGS Flood HazardReevaluation Report Flood Hazard Reevaluation ReportAPPENDIX BFIGURESIj-k TucsorXTEXASsanoAi'P10--PacificOcean" emiMfLegend* Site Center Point-Shortest Distance from Water Body to SiteCoordinate System: ONAD 1983_StatePlane_ArizonaCentralFI PS_0202_Feet Projecton:
TransverseMercator 160 80 0 160 320MilesRF: 1:8,320,000
REFERENCE:
Background Image: ESRI, 2013a, Environmental Systems Research Institute (ESRI),"World Street Map"Website:http://goto.arcgisonline.com/maps/WorldStreetMap Date Accessed:
January 14, 2014FIGURE 1-1GEOGRAPHIC LOCATION OFPALO VERDE NUCLEAR GENERATING STATIONPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT The Winters Wash1 Miles The East WashCross-sections 010.5II IILegend* Site Center Point~ Watershed Boundaries
, USGS Gauge StationsRivers and Streams
REFERENCE:
Background Image: ESRI, 2013a, Environmental Systems Research Institute (ESRI), "WCStreet Map"Website:http://goto.arcgisonline.com/maps/Wodd_StreetMap Date Accessed:
January 14, 2013USGS, 2013c, United States Geological Survey (USGS)"USGS Water Data for the Nation,'
Website <http://waterdata.usgs.gov/nwis>,
Date Accessed:
October 9, 2013FIGURE 1-2odd GENERAL LOCATIONMAP OF THE SITEPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT INITIALANALYSISREFINEDANALYSISI --- -----------------
- NOT IN DESIGN BASISFIGURE 1-3FLOOD HAZARD REEVALUATION FLOWCHART PALO VERDE NUCLAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT
-VOTl"rFIGURE 2-1SITE LAYOUT TOPOGRAPHY SPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT LEGEND:1. AUXILIARY BUILDING2. CONDENSATE STORAGE TANK3. CONTROL BUILDING4. DIESEL GENERATOR BUILDING5. EMERGENCY FUEL OIL TANKS6. FUEL BUILDING7. CONTAINMENT BUILDING8. ESSENTIAL SPRAY POND9. MAIN STEAM SUPPORT STRUCTURE
- 10. REFUELING WATER TANKNOTE:BACKGROUND IMAGE MODIFIED FROM: GOOGLEEARTH, 2014FIGURE 2-2POWERBLOCK ARRANGEMENT PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT Legend-SOCA Perimeter Coordinate Systemr:
I NA D 1983 StatePlaneArizowaCentral_FI PS_0202-_Feet Projection:Transvers_Mercator 0 0.25 0.5 100 M =MilesContour LinesRF: 1:30,000---Buildings
-Embankment
-Fence Line Surrounding Powerblock Area
Reference:
Background Source: ESRI, 2013b, Environmental Systems ResearchInstitute (ESRI), 'World Imagery"Website:http:l/goto.arcgisonline.com/mapsl~orld_lmagery Date Accessed:
January 14, 2014FIGURE 2-3AERIAL VIEW OF SITE LAYOUTPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORTLýlilil-
,IAMMON-maffilW FIGURE 2-4EAST WASH & WINTERS WASH WATERSHED PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT NOTE:1. INCLUDES LIMITED SENSITIVITY ANALYSISUs sit -seic data ~ torfn h Uoaines prcptto flodn *.* 0So .Saet f h.S~de osrtdNoA* YesNoL mosI .efoI YesFIGURE 3-1HHA DIAGRAM FOR LOCAL INTENSEPRECIPITATION FLOODING ANALYSISPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT 3.0012.502. 0012 1.50.2.1 1.00.13LJs 0.500.000 60 120 180 240Time (minutes) 300 360INCREMENTAL RAINFALL DISTRIBUTION FOR THE6-HR DURATION LIP FOR REEVALUATION ANALYSIS141210 8364 ..--AWAPMPEvaluation Toolo. ii~V0I0 1 2 3 4 5 6Time (hoaur)CUMULATIVE REEVALUATION LIP HYETOG RAPHSFIGURE 3-2LOCAL INTENSEPRECIPITATION HYETOGRAPHS PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORTK lii
-- FLO-2D Model DomainFLO-2D Model FeaturesNA0 0.250.5 MilesI I I IFlood DOpM ffwt0.01 -0.200.21 -OAOC 041 -OAOI0.01
- 0.810S0,0 -1.001.01 -120121 -140II1.41
- 1460S1.61 -t.801h 18-2A0=I2.01 -220W 2.21 -2,40M2A41 -2.402.61 -2.802Jm -3.00S3.01 3203.21 2 340341 0 3.603,61 -803,81 -4004.01-4.20 4321 3 4,404.41 -34.81 -4.00514.0t -0.4,.31 440I 61 4.00-m -8 N-FIGURE 3-3FLO-2D INUNDATION MAP FORLOCAL INTENSE PRECIPITATION PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT
-Fetch length-Path for screening inside SOCA1600 800 0 1M00 FeetFIGURE 3-4FETCH LOCATIONS FOR WIND-WAVE ACTIVITY COINCIDENT WITHLIP FLOODINGPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORTNOTE:FETCH LENGTHS ARE APPROXIMATE Jaft' NOTES:1. INCLUDES MULTIPLE CASES IN SUPPORT OFPOTENTIAL HHA CASES TO FOLLOW.2. INCLUDES LIMITED SENSITIVITY ANALYSIS.
m*NoJse site-soec
-ic cat-= -creire aralys-s.
II YesStoo. Jse the mo.5tre4',)ed case ýcrccmoai.zcn tc the des grLasis,womYesNoFIGURE 3-5HHA DIAGRAM FOR ANALYSIS OF FLOODINGIN RIVERS AND STREAMSJ \iiPALO VERDE NUCLEAR GENERATING STATION& ý FLOOD HAZARD REEVALUATION REPORT 4.504.003.502.00-zsoj2,001.000,506 12 19 24 30 36 42 49 54 60 66 72Time (bern)2.520.5012110j 8a6420aTnWh" W4l12j10Ioa 200 10 20 30 40 so 60 70 80Time (hours)WINTERS WASH PMP DISCRETE ANDCUMULATIVE HYETOGRAPHS 0 1 2 3 4 5 6 7Time(hours)
EAST WASH PMP DISCRETE ANDCUMULATIVE HYETOGRAPHS FIGURE 3-6PMP HYETOGRAPHS FOR WINTERS WASH ANDEAST WASH WATERSHEDS U/i"wommimumw PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT NOTE:WW = WINTERS WASHEW = EAST WASHFIGURE 3-7WINTERS WASH AND EAST WASH SUB-BASINS PALO VERDE NUCLEAR GENERATING STATION-FLOOD HAZARD REEVALUATION REPORT RUPIIoLEGEND:SUBBASINJUNCTIONIEWUPI10 STORAGE1i4 spidl FLOW SPLITo10in SINK%SinkREACHPVNGS SITENOT TO SCALEFIGURE 3-8INITIAL ANALYSISHEC -HMS MODEL FOR EAST WASHAND WINTERS WASH WATERSHEDS PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT 1kWinters Wash Fetch LengthWater Depth >= 0.5 ft0-71.4MiIftFIGURE 3-9
REFERENCE:
Background Image: ESRI, 2013c, Environmental Systems Research Institute (ESRI),-ARCGIS IMAGERY,-
WEBSITE:
<http://www.arcgis.com/homef/item.htm Date of publication:
January 16, 2012, date accessed:
June 21, 2013FETCH LOCATIONS FOR FLOODING INWINTERS WASHPALO VERDE NUCLEAR GENERATING STATIONIFLOOD HAZARD REEVALUATION REPORT FIGURE 3-10EAST WASH LOCATION MAP ANDMODEL EXTENT
REFERENCE:
Model Boundary is based on the East Wash Watershed delineation.
Image Source: 2013 U.S. Department of Agricultural, National Agricultural Inventory Project.1/PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT 14000112000- I-XS2-XS310000 -XS.. .... -XS4-- XS5-8000V' 60004000_,200000 2 4 6 8 10 12 14 16 18 20Time (hours)FIGURE 3-11EAST WASH FLOODPLAIN CROSS-SECTION HYDROGRAPHS
-REFINED PMF (100-FT GRIDELEMENT MODEL)SPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT FIGURE 3-12
REFERENCE:
Flow depths in power block area are a result of direct rainfall only.Image Source: 2013 U.S. Department of Agricultural, National Agricultural Inventory Project.EAST WASH FLOW DEPTHS -REFINED PMF(100-FT GRID ELEMENT MODEL)PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT'7:
IIFIGURE 3-13
REFERENCE:
Flow velocities in powerblock area are a result of direct rainfall onlyImage Source: 2013 U.S. Department of Agricultural, National Agricultural Inventory Project.EAST WASH FLOW VELOCITIES-REFINED PMF(100-FT GRID ELEMENT MODEL)PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT FIGURE 3-14EAST WASH FLOODPLAIN CROSS SECTIONS
REFERENCE:
Image Source: 2013 U.S. Department of Agricultural, National Agricultural Inventory Project.PALO VERDE NUCLEAR GENERATING STATIONi FLOOD HAZARD REEVALUATION REPORT 120001000080006000U40002000-XS4 -XS500 2 4 6 8 10 12 14 16 18 20Time (hours)FIGURE 3-15EAST WASH WATERSHED INFLOWHYDROGRAPHS (REFINED ANALYSIS)
U-PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT FIGURE 3-16
REFERENCE:
Image Source 2013 U.S. Department of Agriculture, National Agricultural Inventory Project
- Maximum water surface elevation does not includeeffects from wind-wave action.EAST WASH WATER DEPTHS -REFINED PMF(25-FT GRID ELEMENT MODEL)PALO VERDE NUCLEAR GENERATING STATIONIFLOOD HAZARD REEVALUATION REPORT FIGURE 3-17EAST WASH POTENTIAL FETCHES(REFINED ANALYSIS)
REFERENCE:
Image Source: 2013 U.S. Department of Agricultural, National Agricultural Inventory Project.'I'PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT FIGURE 3-18NORTH AND EASTEMBANKMENT FETCHES
REFERENCE:
Image Source: 2013 U.S. Department of Agricultural, National Agricultural Inventory Project.PALO VERDE NUCLEAR GENERATING STATIONJFLOOD HAZARD REEVALUATION REPORT 10051000995990Chz998598097597096501000 2000 3000 4000 5000 6000Cross Section Length (kt)7000FIGURE 3-19NORTH EMBANKMENT FETCH SELECTION EAST WASH (REFINED ANALYSIS)
PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT 10051000 r995990 Fi Lehighi V= feet975970-Maximum Water Surface9_5__________
nrtedent Watre vet~974-.9-ft
_______ _____________
9600 1000 2000 3000 4000 5000 6000 7000Cross Section Length (ft)FIGURE 3-20EAST EMBANKMENT FETCH SELECTION EAST WASH (REFINED ANALYSIS)
SPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT NOTE:1. INCLUDES LIMITED SENSITIVITY ANALYSIS&Eli.SoNoIUs sit -seic dattorfn0nlss 1r YesSto. Us th mosrefie 1as oYesNo_vIFIGURE 3-21HHA DIAGRAM FORCOMBINED EFFECTS FLOODING ANALYSISPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT l I lFIGURE 3-22FLO-2D MODEL DOMAINS FORCOMBINED EFFECTS ANALYSISPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT Water Depth (ft)-0.50 -1.00-1.01 -2.00-2.01 -3.003.01 -4.004.01 -5.00-5.01 -6.00-6.01 -7.00-7.01 -8.008.01 -9.00-9.01 -10.0010.01 .11.00-11.01 -12.0012.01 -13.0013.01 -14.0014.01 15.00m15.01 -16.00-16.01 -17.00-17,01 -18,00-18.01 -19.00-19.00-PVNGS Siruclures N0 0,25 0.5 MilesI I IFIGURE 3-23NOTES:THE WATER DEPTHS INDICATED IN IMPOUNDED WATER BODIES DO NOTINCLUDE THE INITIAL WATER DEPTHS. THE ILLUSTRATED FLOOD DEPTHS ATTHE POWERBLOCK ARE DUE TO PMP AT THE PVNGS SITE, NOT DUE TOFLOODWATER FROM THE WASHESMAXIMUM COMBINED EFFECTS FLOODDEPTH (FT) FOR CASE 3% PALO VERDE NUCLEAR GENERATING STATION.lM ~ FLOOD HAZARD REEVALUATION REPORT Duration of Inundation (hr)1.00 -3.003.01 -7.007.01 -9.009.01 -11.00-11.01 -13.00-13.01 -15.00-15.01 -17.00-17.01 -19.00I 19.01 -21 .0021.01 -23.00-23.01 -25.002501 -27.0027.01 -29.0029.01 -31.00-31.01 -33.0033.01 -35.00PVNGS Structures NA0 0.25 0.5 MilesFIGURE 3-24DURATION OF COMBINED EFFECTSFLOODING (HOURS) FOR CASE 3ii- PALO VERDE NUCLEAR GENERATING STATIONOW ý FLOOD HAZARD REEVALUATION REPORT cl-DminzInconsequential' DamsLEGEND:ISG -INTERIM STAFF GUIDANCE
REFERENCE:
Background Image: ESRI, 2013e, United States Nuclear Regulatory Commission (NRC),"GUIDNCE FOR ASSESSMENT OF FLOODING HAZARDS DUE TO DAM FAILURE,-
JLD-ISG-2013-01, NRC INTERIM STAFF GUIDANCE (ML13151A153),
WASHINTON, DC, REVISION 0, JULY 29, 2013.FIGURE 3-25ISG-2013-01 DIAGRAM FORDETERMINING LEVELS OF ANALYSIS FOR DAMBREAK EVALUATION PALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORTI-,
FIGURE 3-26ISG-2013-01 DIAGRAM FORANALYSIS OF DAM BREACHES AND FAILURESUSING THE VOLUME METHODPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT
REFERENCE:
Background Image: ESRI, 2013e, United States Nuclear Regulatory Commission (NRC),"GUIDNCE FOR ASSESSMENT OF FLOODING HAZARDS DUE TO DAM FAILURE,"
JLD-ISG-2013-01, NRC INTERIM STAFF GUIDANCE (ML13151A153),
WASHINTON, DC, REVISION 0, JULY 29, 2013."1-64ýr HUC Wau'hedsSan Carlos RiverSalt RiverLower Gila RiverSUpper Gila River-Z Gila River Downstream of PVNGS-~-~ As.,
REFERENCES:
- 1. ESR, 201c, ENVIRONMENTAL SYSTEM RESEARCH INSTITUTE (ESRI), "ARCGIS IMAGERY,"
WEBSITE<http://arcgis.com/home/item.htm, DATE OF PUBLICATION:
JANUARY 16, 2012, DATE ACCESSED:
JUNE 21, 2013.2. USGS, 2013b, UNITED STATES GEOLOGIGAL SURVEY (USGS), "USGS WATER DATA FOR THE NATION,"
WEBSITE:<http://waterdata.usgs.gov/nwis>,
DATE ACCESSED:
OCTOBER 9,2013.3. USGS, 2013, UNITED STATES ARMY CORPS OF ENGINEERS (USACE),
"NATIONAL INVENTORY OF DAMS," WEBSITE:<http://geo.usace.army.mil/pgis/>,
DATE ACCESSED:
JUNE 11, 2013FIGURE 3-27LOCATION OF DAMS NEAR THE SITEPALO VERDE NUCLEAR GENERATING STATIONFLOOD HAZARD REEVALUATION REPORT Flood Hazard Reevaluation ReportAPPENDIX CPROBABLE MAXIMUM PRECIPITATION IN ARIZONASlik Flood Hazard Reevaluation ReportAPPENDIX CPROBABLE MAXIMUM PRECIPITATION IN ARIZONAThe intent of this document is to justify the use of the Probable Maximum Precipitation (PMP) values used to calculate the Local Intense Precipitation at the Palo VerdeNuclear Generating Station (PVNGS) in response to the Nuclear Regulatory Commission (NRC) letter requesting information Pursuant to Title 10 of the Code ofFederal Regulations 50.54(f)
(NRC, 2012) and conformance with NUREG/CR-7046 (NRC, 2011). The updated Arizona 6-hour and 72-hour PMP values and distributions are also utilized in calculating the potential flood hazards from East Wash and WintersWash, respectively.
The potential flood hazard impacts of two washes are evaluated indetail because the site is located in both washes watersheds.
The methodology used in Arizona for estimating the PMP for the design of dams wasupdated by the state through the Arizona Department of Water Resources (ADWR). Anupdate was necessary because the previous methodology utilized the procedures described in Hydrological Report No. 49 (HMR 49) prepared by the National WeatherService (NWS) for the US Army Corps of Engineers (NWS, 1977). At the time, HMR 49was prepared to estimate the PMP for locations in the Colorado River and Great BasinDrainages (part or all of Arizona, Utah, New Mexico, Colorado, Nevada, and Wyoming)as well as all of California.
The methodology was used to calculate the PMP for areasup to 5,000 sq mi and durations up to 72-hours.
HMR 49 is an outdated publication andmany of the locations are already covered by other HMRs. Presently, the PMPcalculations for California have been updated by HMR 59 in 1999 and there is a state-wide PMP update for Utah. The updates occurred as a result of additional storminformation and procedures that are physically based. The updates include a narrowerdomain pertaining to location, similar orographic, topographic, and meteorologic characteristics.
The report Probable Maximum Precipitation Study for Arizona (AWA, 2013) is thesuccessor document to HMR 49 for the State of Arizona.
The most relevant reason forthe update is increasing the period of the data base originally used in HMR 49 and thedocument is old. Only a few storms were evaluated in preparing HMR 49. Over the pastforty years more storms have occurred and the state-of-the practice in evaluating extreme storm events has changed making the new analysis more appropriate and up-to-date (AWA, 2008).Applied Weather Associates (AWA) completed the statewide PMP study for Arizona in2013. The study was funded by the ADWR with financial support from the Flood ControlDistrict of Maricopa County, Arizona Game and Fish Department, and USDA NaturalResources Conservation Service.
These agencies also provided technical input on thedocument.
An independent Peer Review Committee (PRC) reviewed and providedfeedback on the methodology at critical milestones and the final document.
The PRCwas comprised of Dr. Keim a climatologist and professor at Louisiana State University, C-1 Flood Hazard Reevaluation ReportDr. Sabol a Principal and water resources engineer with Stantec in Phoenix, and Dr.Selover a climatologist and research professor at Arizona State University.
The PRCpublished a final report in August 2013 (PRC, 2013).The statewide study is being implemented to calculate the PMP events used in thehydrologic analysis of dams in Arizona.
Maricopa County is applying the PMP tool inpreparing new PMF hydrology in support of Emergency Action Plans for the following structures:
- Wickenburg Structures, Arizona* Powerline,
- Vineyard, and Rittenhouse Structures, Arizona* McMicken Dam, Arizona* Guadalupe Flood Retarding Structure, ArizonaAWA is presently preparing a similar study for the State of Wyoming, where the USACEis on the technical review committee.
They have utilized the methodology for use inevaluating dams in other states for the Federal Energy Regulatory Commission (FERC);other state dam programs, and PMP estimates at Nuclear Power Plant sites.Individual storm events were not evaluated in HMR 49 providing a direct correlation between depth-area and area-duration (DAD envelope).
Instead general ratios wereused when evaluating both the area (area reduction) and duration of PMP storms basedon the overall study area. The widely varying climatology and topography of the regionis not conducive to using a general approach.
HMR 49 uses the persisting (lowest) 12-hour dewpoint in developing the PMP. Newer studies use the average dewpoint that fitswith predicting extreme rainfall events.The procedures used in the Arizona update are required by the state for dams andrecommended for other projects because the study has updated the data since 1977 toinclude many more rainfall events. The method evaluated 51 extreme valueprecipitation storm events and 91 storm centers using the Storm Precipitation andAnalysis System (SPAS) in characterizing magnitude,
- temporal, and spatial data (DADvalues, mass curves, and total storm isohyets).
The use of NEXt generation RADar(NEXRAD) data (mid 1990's) has contributed significantly to the quality of the stormdata being used. The procedure considers climate zone, topography and othervariables.
Updated dewpoint data was used to maximize the effects of moisture that isassociated with the rainfall events. The study was done to develop a consistent procedure using a consistent data base for the entire state. However, the PMP tool(AWA, 2013) applies the data base to calculate site specific PMP values. The input datato the PMP tool is a shapefile of the study area. The tool then determines PMP valuesusing a 2.5 sq mi grid to calculate the PMP for each grid in the study area. The gridvalues are calculated from the storm data base that are similar to the site. It then uses aweighting process to calculate the average PMP value for the specific study. The tool isused for analyzing local storms where durations analyzed vary from 1 to 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.C-2 Flood Hazard Reevaluation ReportTropical and general storms are analyzed for durations of 6, 12, 18, 24, 48, and 72hours.The PMP values developed by the state of Arizona (AWA, 2013) that update HMR 49and are consistent with the storms of record and state-of-the-practice technology.
TheAPS contractor used the PMP tool (AWA, 2013) and values as the foundation forevaluating extreme event flood hazards at the Palo Verde Nuclear Generating Stationsite.References AWA, Evaluation of the Reliability of Generalized PMP Values Provided by HMR 49 forArizona, Alternative Approaches that can be Used on a Statewide Basis for PMPDetermination, Applied Weather Associates, LLC, September 2008.AWA, Probable Maximum Precipitation Study in Arizona, Applied Weather Associates, LLC, July 2013b.NOAA, Hydrometeorological Report No. 49, Probable Maximum Precipitation Estimates, Colorado River and Great Basin Drainages, NOAA, National Weather Service,Septmenber 1977.NRC, United States Nuclear Regulatory Commission (NRC), Design-Basis FloodEstimation for Site Characterization at Nuclear Power Plants in the United States ofAmerica, NUREG/CR-7046.
PNNL-20091, NRC Job Code N6575, Washington, D.C.,November 2011.NRC, United States Nuclear Regulatory Commission (NRC), 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 Force Review of Insights fromthe Fukushima Dai-ichi
- Accident, Washington, D.C., March 12, 2012.PRC, Peer Review Committee Final Report for the Probable Maximum Precipitation Study for Arizona by Applied Weather Associates' Peer Review Committee, August 2013.C-3 Flood Hazard Reevaluation ReportAPPENDIX DSOFTWARE USED IN FLOOD HAZARD REEVALUATION
&-*ýw Flood Hazard Reevaluation ReportAPPENDIX DSOFTWARE USED IN FLOOD HAZARD REEVALUATION The following software was used to perform the flood hazard reevaluation analyses:
- FLO-2D Pro (FLO-2D, 2012)* FLO-2D Pro Release 14.03.07 (FLO-2D, 2014a)* FLO-2D Pro Release 14.03.07.URS (FLO-2D, 2104d)* ArcGIS 9.3.1 (ESRI, 2009)* ArcGIS 10.1 (ESRI, 2012)* ArcHydro 10.1 (ESRI, 2011)* United States Army Corps of Engineers HEC-HMS 3.5 (USACE, 2010a)* USACE HEC-GeoHMS (USACE, 2009)* USACE HEC-RAS 4.1 (USACE, 2010b).The FLO-2D Pro software is a volume conservation model that routes fluid flow inone-dimensional channel flow, two-dimensional overland flow, or an interaction between the two model components.
The FLO-2D Pro software is an effective tool for delineating flood hazards or designing flood mitigation.
The software isalso available in a Basis configuration with fewer capabilities.
The Basic modelhas been approved by the Federal Emergency Management Agency (FEMA) foruse in Flood Insurance Studies.
The Pro model, though not specifically approvedby FEMA, includes all the features of the Basic model, along with someadditional features (e.g., storm drain interface with surface water using the EPASWMM program, parallel processing capabilities, and expanded capabilities forsimulating sediment transport (FLO-2D, 2012).FLO-2D Pro Release 14.03.07.URS utilized a modified version of the FLO-2Dmodel that specifically accounted for roof detention, parapet walls, scupper inlets,scupper outlets locations,
- leaders, and downspouts.
The flow to the ground forthe LIP event was attenuated on the roof and discharged to specific locations, inlieu, of directing runoff directly to the ground. This enhancement to the FLO-2Dprogram was developed by the FLO-2D developers specifically for this project.HEC-GeoHMS and ArcHydro are tools that function within the ArcGIS interface.
At the time of the writing of this report, hydrologic and hydraulic simulation models developed, described, and maintained by the USACE Hydrologic Engineering Center (HEC) are acceptable to the NRC (NRC, 2011).D-1 Flood Hazard Reevaluation ReportHEC-HMS is designed to simulate the precipitation-runoff processes of drainagebasin networks.
It is applicable in a wide range of geographic areas, including large and small urban and natural watersheds.
HEC-HMS is capable ofrepresenting many different watershed sizes and land coverage conditions (USACE, 2010a).HEC-GeoHMS (USACE, 2009) and ArcHydro (ESRI, 2011), which are run withinthe ArcGIS framework (ESRI, 2012), were used in the pre-processing ofwatershed data to develop input data files for the HEC-HMS model.HEC-RAS (USACE, 2010b) is designed to perform one-dimensional hydraulic calculations for a full network of natural and constructed channels.
It was used toprovide rating curves for modeling the flow through culverts under Highway 1-10in the East Wash. These rating curves were then used in the HEC-HMS modeldeveloped to support the reevaluation of the river flooding hazard due to thePMP event.All software used to perform the flood hazard reevaluation analyses has beenverified and validated, and commercially dedicated in accordance with a qualityassurance program that meets the requirements of 10 CFR 50 Appendix Bthrough compliance with the Basic and Supplementary Requirements established in Part I of American Society of Mechanical Engineers (ASME) NQA-1-2008 andNQA-la-2009 Addenda2 (ASME, 2009), as well as the following Subparts thatapply to the previously identified software:
" Subpart 2.7, "Quality Assurance Requirements for Computer Software forNuclear Facility Applications."
- Subpart 2.14, "Quality Assurance Requirements for Commercial GradeItems and Services."
2 ASME NQA-1-2008 and NQA-la-2009 Addenda documents cannot be reproduced electronically or viahardcopy without the written consent of ASME.D-2