ML17309A179

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Ginna Station Design Basic Flooding Study for Rochester Gas & Electric Co.
ML17309A179
Person / Time
Site: Ginna Constellation icon.png
Issue date: 08/31/1981
From:
NUS CORP.
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ML17258B184 List:
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NUDOCS 8108240057
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GINNASTATIONDESIGNBASISFLOODINGSTUDYFORROCHESTERGASANDELECTRICCORPORATIONAugust1981NUSCorporation4ResearchPlaceRockville,Maryland2085081082400S7810818PDRADOCK05000244PPDR~

I-8llI TABLEOFCONTENTSParcaeSUMMARYANDRESULTSDEERCREEKWATERSHEDRAINFALLFLOODDISCHARGEFLOODELEVATIONCONCLUSIONREFERENCES10LISTOFTABLESTable1HydrologicSoilGroupsinDeerCreekWatershedTable224-HourPointPrecipitationTable3TimeDistributionof24-HourPrecipitationTable4DeerCreekWatershedUnitHydrograph(24Hr,1"Storm)Table5SpecialBridgeParameters12131415LISTOFFIGURESFigure1DeerCreekWatershedLocationMapFigure2DeerCreekWatershednearGinnaStationFigure3ReturnPeriodsfor24-HourPrecipitations1718Figure4Figure5UnitHydrographforDeerCreek(24Hr,1"Storm)DeerCreekFloodHydrograph(24Hr,10"Storm)1920Figure6StreamCrossSectionsLocationMapFigure7DeerCreekCrossSectionData21~22

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SUMMARYANDRESULTSThepurposeofthisstudywastodeterminethefloodelevationsinDeerCreekneartheGinnaGeneratingStationforstormsvaryinginseverityfromthe100-yearprecipitationtotheProbableMaximumPrecipitation(PMP).Thepeakdischargeswereestimatedusingtherainfall-runoffmodeldevelopedbytheSoilConservationService.ThecalculationsweremadewiththeHEC-1FloodHdrorahPackaecomputerprogram.ThewatersurfaceelevationswereestimatedwiththeHEC-2WaterSurfaceProfilescomputerprogram.BothcomputerprogramsweredevelopedbytheU.S.ArmyCorpsofEngineers.Theresultsofthecalculationsareasfollows:ReturnPeriod(Years)Precipitation(Inches)FloodDischarge~cfsFloodElevationatCulvertBridgenearGinnaStation-MSL1005001,000-15)000*-350,000*<<]07*PMF4.85.96.38.010.012.023.85,970"6i9747,63310,10912,07613,67932,486264.1265.0265.6267.4268.7269.7277.1Basedonstraight-lineextrapolationonGumbelprobabilitypapertoprovideorder-of-magnitudeapproximation.Theconclusionsofthestudyare:oThe12"storm(abouta107-yearevent)andthe10"storm(abouta350,000-yearevent)arecalculatedtoproducefloodelevationsof269.7ftand268.7ft(msl),respectively,neartheGinnaStation.Theplantgradeelevationisat270ft(msl).oTheDeerCreekPMFwillflowovertheplantyardoftheGinnaStation.oTheeliminationorimprovementoftheculvertbridgeforminimizingthebridgebackwatereffectwillnotsolvetheGinnaStationfloodingresultingfromaDeerCreekPMFevent.

III>II)gI DEERCREEKWATERSHEDFieldreconnaissanceoftheDeerCreekwatershedwasconductedonJune3,1981toestimatethehydrauliccharacteristicsofthewatershed,particularlythechannelandoverbankareas.ThewatershedwaswalkedfromitsmouthinLakeOntariototheconfluenceofDeerandMillCreeks.LocationmapsshowingtheDeerCreekwatershedinrelationtotheGinnaStationarepresentedinFigures1and2.AsdeterminedfromtheU.S.GeologicalSurvey7.5minutequadrangles,(1)theDeerCreekwatershedhasadrainageareaof13.9squaremiles,achannellengthof11.5miles,andadifferenceinelevationbetweenitsheadandmouthof405feet.Therearetwobridges(Figure2)overDeerCreekthatcaninfluencethebackwaterelevationsneartheGinnaStation:(a)Thelowerbridgeislocatedabout880feetupstreamofthemouth.Ithasatrapezoidalbridgeopening.(b)Theupperbridgeislocatedabout2300feetupstreamofthemouthandabout320feetdownstreamofitsconfluencewithMillCreek.ItistheroadtotheStationentrance.Thebridgeopeningconsistsoffivecircularculverts,each5feetindiameter.ThesoilmappingunitsinDeerCreekwatershedweredeterminedfromtheSoilConservationServicesoilsurveyforWayneCounty.(2)Thesoilmappingunitsandthecorrespondinghydrologicsoilgroups(3)areshowninTable1.Themajorportionofthewatershedconsistsofthesoilmappingunitsthatcorrespondtohydrologicsoilgroup"C".Thisgroupisdefinedas:Soilshavingslowinfiltrationrateswhenthoroughlywettedandconsistingchieflyofsoilswithalayerthatimpedesdownwardmovementofwater,orsoilswithmoderatelyfinetofinetexture.Thesesoilshaveaslowrateofwatertransmission.(3)

I-I58I BasedontheUSGStopographicmapsandthefieldreconnaissanceinformation,themajorlanduseandtreatmentinthewatershedwasestimatedasrowcropsingoodhydrologiccondition.(3)ThechannelofDeerCreekisgenerallywelldefinedwithatypicalchannelwidthofabout40feet.However,thehydrauliccharacteristicsofthechannelandoverbankareasdiffersignificantlyfromthelowertoupperreaches.TheManning'sresistancecoefficientswereestimatedusingcriteriadescribedbyChow.(4)Thecharacteristicsofthelower,middleandupperreachesareasfollows:(a)LowerReach(frommouthtothecrosssectionnearthevisitorcenter,about1820feetupstreamofmouth):Thechannelisgenerallycleanandwindingwithsomeshallowpools,stonesandweeds.Theoverbankareasaregenerallycoveredwithmediumtodensebrushandtrees.TheManningresistancecoefficientforthechannelandoverbankareaswasestimatedas0.045and0.05,respectively.(b)MiddleReach(fromcrosssectionnearthevisitorcentertotheconfluenceofDeerandMillCreeks,about2620feetupstreamofmouth):Thechanneliscleanandstraight.Theoverbankareasaregenerallycoveredwithshortgrass.TheManningresistancecoefficientforthechannelandoverbankareaswasestimatedas0.02and0.03,respectively.isveryweedywithheavystandsofunderbrush.Theoverbankareasaregenerallycoveredwithdensebrushandtrees.TheManningresistancecoefficientforthechannelandoverbankareaswasestimatedas0.10and0.06,respectively.

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RAINFALLTherainfallusedinthisstudyrangesfromthe100-yearprecipitationtotheProbableMaximumPrecipitation(PMP).The24-hourpointprecipitationsfortheDeerCreekwatershedforreturnperiodsof1to100yearswereestimatedfromgeneralizedchartsoftheUnitedStates.(Thesedata,showninTable2,wereplottedonGumbelextremeprobabilitygraphpaper(6)toobtainestimatesoftheprecipitationwithreturnperiodsof500yearsandgreater(Figure3).The500-and1000-yearprecipitationswereestimatedas5.9and6.3inches,respectively.Rainfallsof8.0,10,and12inches,allwithanestimatedreturnperiodgreaterthan10,000years,werealsousedinthisstudyforcomparisonpurposes.TheProbableMaximumPrecipitation(PMP)fortheDeerCreekwatershedwasestimatedfromageneralizedchartoftheUnitedStateseastofthe105thmeridian.(3)The6-hour,10-squaremilePMPis24.5inches.ThePMPsfor12,24and48hours,asdeterminedfromdepth-area-durationcurves,(3)are26.5,29.4and31.4inches,respectively.

II~IIIIII~I FLOODDISCHARGEThepeakdischargesatthemouthofDeerCreekfortheselectedprecipitationswereestimatedwiththerainfall-runoffmodeldevelopedbytheSoilConservationServiceforsmallungagedwatersheds.(3)ThecalculationsweremadewiththeHEC-1FloodHdrorahPackaecomputerprogramdevelopedbytheU.S.ArmyCorpsofEngineers.(7).TheinputstoHEC-1aredescribedbelow.ThetimedistributionofrainfalldevelopedbytheU.S.CorpsofEngineers()fortheStandardProjectFlood(SPF)andProbableMaximumFlood(PMF)wasusedinthisstudy.Sincethewatershedisonly13.9squaremilesinarea,thearealreductionfactorwasnotappliedtotheprecipitationotherthanthePMP.Forthelattercase,a24-hourPMPof23.8incheswascalculatedusinganarealreductionfactorof0.81asdeterminedbytheHEC-1PMPoption.ThetimeprecipitationdistributionsoftheselectedprecipitationsareshowninTable3.Thewatershedtimeofconcentration,Tc,isgivenby:(Tc0.38511.9L3where:L=channellengthinmilesH=elevationdifferenceinfeet.ThetimeofconcentrationfortheDeerCreekwatershedis4.3hours.Thebasinlagisapproximately0.6Tc,or2.6hours.Theamountofrainfallinaperiodof5to30daysprecedingaparticularstormisreferredtoasantecedentrainfall.Theresultingconditionofthewatershedinregardtopotentialrunoffisreferredtoasanantecedentmoisturecondition.Ingeneral,theheaviertheantecedentrainfall,thegreaterthedirectrunoffthat

-III occursfromagivenstorm.TheantecedentmoistureconditionAMC-II,usedinthisstudy,isdefinedas:"Theaveragecaseforannualfloods,thatis,anaverageoftheconditionswhichhaveprecededtheoccurrenceofthemaximumannualfloodonnumerouswatersheds."(3)Precipitationlosseswereestimatedusingthedirectrunoffcurvenumber,CN,whichisafunctionofthehydrologicsoilgroup,thelanduseandcover,andtheantecedentmoisturecondition.Forahydrologicsoilgroup"C",landusecharacterizedasrowcropsingoodhydrologiccondition,andanantecedentmoistureconditionofAMC-II,thecurvenumberfortheDeerCreekwatershedwasestimatedasCN=85.(3)ThecalculatedunithydrographfortheDeerCreekwatershedisshowninTable4andFigure4.Forillustrationpurposes,thehydrographfortheflooddischargeof12,076cfsisshowninFigure5.Theestimatedpeakdischargesandprecipitationlossesfortheselectedprecipitationsareasfollows:EstimatedReturnPeriod(Years)PrecipitationInches)PrecipitationLosses~InchesPeakDischargecfs1005001,000-15~000*-350,000*~]07*PMF4.85.96.38.010.0'2.023.81.621.69l.71l.791.841.891.995,9706,9747,63310,10912,07613,67932,486*Basedonstraight-lineextrapolationonGumbelprobabilitypapertoprovideorder-of-magnitudeapproximation.

5IlII~b'IIrI FLOODELEVATIONThewatersurfaceprofilesforthepeakflooddischargeswerecalculatedusingtheHEC-2HaterSurfaceProfilescomputerprogramdevelopedbytheU.S.ArmyCorpsof'Engineers.(9)ThecalculationalprocedureusedinHEC-2isthestandardstepmethodforcalculatingbackwatercurves.TheinputstoHEC-2aredescribedbelow.Boundarygeometryfortheanalysisofthefl'ooddischargeswasspecifiedintermsofgroundsurfaceprofiles(crosssections)andthedistancesbetweenthem(reachlengths).Crosssections,asshowninFigure6,werelocatedatintervalsalongDeerCreektocharacterizetheflowcarryingcapabilityofthechannelandoverbankareas.Elevenofthecrosssectionsweresurveyedforthisstudy.SelectedcrosssectionsforDeerCreekareshowninFigure7togiveindicationofchannelgeometry.SeveraltypesoflosscoefficientswereselectedforuseinHEC-2toevaluateheadlosses
(a)Manningresistancecoefficientforfrictionlosses(b)Contractionandexpansioncoefficientstoevaluatetransitionlossesbetweencrosssections(c)Bridgelosscoefficientstoevaluatelossesrelatedtoweirshape,pierconfiguration,andpressureflow.Thehydrauliccharacteristicsofthechannelandoverbankareasdeterminethecrosssectionconveyance.TheManning'scoefficientsusedinthisstudyareasfollows:Reach(feetabovemouth)ChannelMannin'sCoefficientOverbank0-18201820-262026200.0450.020.10.050.030.06 II;IIII.a Thecontractionandexpansioncoefficientsareusedtoestimatelossesassociatedwithchangesintheshapeofcrosssections.TransitionsthroughchannelsectionsinDeerCreekaregradual.Consequently,O.land0.3wereusedforthecontractionandexpansioncoefficients,respectively.Thecorrespondingcoefficientsforthebridgesectionswere0.3and0.5.(9)TheHEC-2specialbridgemethodwasusedtomodelthe'ridges.Theculvertbridgewasapproximatedasanequivalentarearectangularbridgeopening.ThespecialbridgecoefficientsusedinthecalculationsareshowninTable5.(9)Znordertoexaminethebackwatereffectoftheculvertbridge,calculationswerealsomadetodeterminethewaterelevationsassumingthattheculvertbridgeisnotinexistence.TheestimatedwatersurfaceelevationsattheculvertbridgelocationneartheGinnaStationareasfollows:EstimatedReturnPeriod(Years)WithCulvertBrideWithoutCulvertBrideWaterSurfaceElevations(ft)attheCulvertBrideLocationnearGinnaStation100500lI000-15(000*-350,000*~]07*PMF264.1265.0265.6267.4268.7269'277.1263.7264.6265.2267.1268.1269.0276.0*Basedonstraight-lineextrapolationonGumbelprobabilitypapertoprovideorder-of-magnitudeapproximation.Asshown,thebackwatereffectduetotheculvertbridgewillraisethePMFelevationtoaboutonefootabovethenaturalfloodlevelcondition(i.e.,withoutthebridge).Fortheotherfloodsconsideredinthisstudy,thewaterlevelraisedbythebridgebackwatereffectislessthanonefoot.ThelowerbridgeneartheDeerCreekmouthhasarelativelylargebridgeopeningandisnotconsideredasapotentiallocationtocausesignificantbackwatereffectonthevariousfloodlevels.

IIIIIIIIIIIilIILI CONCLUSIONThefollowingconclusionscanbedrawnfromtheforegoingstudyresults:a)The12"stormeventwithareturnperiodapproximating107yearsiscalculatedtoproduceafloodpeakof13,679cfsandafloodelevationof269.7ft(msl)attheculvertbridgeneartheGinnaStation.Theplantgradeelevationisat270ft(msl).b)The-10"stormeventwithareturnperiodapproximating350,000yearsiscalculatedtoproduceafloodpeakof268.7ft(msl)attheculvertbridgeneartheGinnaStation.c)ThewaterlevelproducedbyaProbableMaximumFloodof32,486cfsonDeerCreeknearthestationiscalculatedtobe277.1ft(msl).Sincetheplantgradeis270.0ft(msl),theDeerCreekPMFwillflowovertheplantyardoftheGinnaStation.AsimilarfloodstudypreviouslyconductedbytheU.S.NuclearRegulatoryCommission(0)hascalculatedaDeerCreekPMFof37,500cfswithafloodelevationofabout275ft(msl).Thedifferencesbetweenthesetwostudyresultsareprobablycausedbytheuseofdifferentlyassumedmodelinputparameters,suchastherunoffcurvenumberinHEC-1andtheroughnessandtransitionlosscoefficientsinHEC-2.Itistobenotedthatthisstudyhasusedfieldsurveyedcrosssectionswhichprovidemorereliablechannelgeometrydata.d)ThebackwatereffectduetotheculvertbridgewillraisethePMFelevationbyaboutonefootabovethenaturalfloodlevelcondition.SincethepredictedPMFlevelismorethanonefoothigherthantheplantgrade,theeliminationorimprovementoftheculvertbridgeforminimizingthebackwatereffectwillnotsolvetheGinnaStationfloodingresultingfromaDeerCreekPMFevent.

(-I-.I'llI:II REFERENCES1.74Minuteuadranles:FurnacevilleN.Y.Photorevised1969;NinemilePointN.Y.1971;Webster,N.Y.(Photorevised1978);Ontario,N.Y.(Photorevised1978),U.S.DepartmentoftheInterior,GeologicalSurvey.2.SoilSurveofWaneCount,NewYork,U.S.DepartmentofAgriculture,SoilConservationService(October1978).3.DesinofSmallDams,U.S.DepartmentoftheInterior,BureauofReclamation(1977).4.VenTeChow,0en-ChannelHdraulics,McGraw-HillBookCo.,NewYork(1959).5.RainfallFreuencAtlasoftheUnitedStatesforDurationsfrom30Minutesto24HoursandReturnPeriodsfrom1to100Years,TechnicalPaperNo.40,U.S.DepartmentofCommerce,WeatherBureau(May1961).6.ProbabilitTablesfortheAnalsisofExtreme-ValueData,AppliedMathematicsSeries22,NationalBureauofStandards,U.S.DepartmentofCommerce(July1953).7.HEC-1FloodHdrorahPackae(Feb.1981version),UserManual,U.S.DepartmentoftheArmy,CorpsofEngineers,HydrologicEngineeringCenter(July1981).8.StandardPro'ectFloodDeterminations,EM-1110-2-1411,U.S.DepartmentoftheArmy,OfficeoftheChiefofEngineers(March25,1952).9.HEC-2WaterSurfaceProfiles(Airl1980version,UserManual,U.S.DepartmentoftheArmy,CorpsofEngineers,HydrologicEngineeringCenter(January1981).10.EvaluationofSEPToicsII-3.A,II-3.B,andII-3.CHdrolo,FloodinandUltimateHeatSink-R.E.GinnaNuclearPlant,U.S.NuclearRegulatoryCommission,OperatingReactorsBranch05,DivisionofLicensing(December12,1980).

-II(IlilII-I~~ig I,goalTABLE1HYDROLOGICSOILGROUPSINDEERCREEKWATERSHEDSoilMainUnitHdroloicSoilGrouIIljAlluvialLandAltonGravellySandyLoamCanadaiguaSiltLoamCazenoviaGravellySiltLoamCollamerSiltLoamElnoraLoamyFineSandHiltonGravellyLoamNiagaraSiltLoamOvidSiltLoamRhinebeckSiltyClayLoamSodusGravellyFineSandyLoamWilliamsonSiltLoam

IIIIIl,lIIII TABLE224-HOURPOINTPRECIPITATIONReturnPeriod(YearsPrecipitationInches1025501002.12.43.03.54.04.54.8 f,gIII~<'l TABLE3TIMEDISTRIBUTIONOF24-HOURPRECIPITATIONTimeDistributionforIndicated24-HourPreciitation(Inches)Duration~Hours0-64.80.059.90.066.30.068.00.0810~00.3212.00.6423.810.936-120.380.470.500.641.101.661.6212-1818-244.180.195.130.245.480.256.960.327'20.668.701.0019.861.41Note:Thetimedistributionofthemaximum6-hourprecipitationexpressedasapercentageofthemaximum6-hourprecipitationisasfollows:Duration(Hours)PercentofMaximum6-HourPreciitation0-11-22-33-44-55-6101215381411 II:IIIII.I TABLE4DEERCREEKWATERSHEDUNITHYDROGRAPH(24HRF1STORM)'ime(Hours)0.51.01.52.02.53.03.54.04.55.05.56.06.57.0Discharge~CFS)1955911,2251,9362,2992F3432F144lF8291,378994772569430320Time~HQSFS)7.58'8.59.09.510.010.511.011.512.012.513.013.514~014.5Discharge~CFS24118013410277584433252010-14-"

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TABLE5SPECIALBRIDGEPARAMETERSCoefficientPiershapecoefficientforuseinYarnell'senergyequationLowerBridcreOe9Upper~Beidel.25TotallosscoefficientforuseinorificeflowequationCoefficientofdischargeforuseinweirflowequation1.63.01.83.0 i'IjlII~lIIII.I NEWYORKSTATE10864201000FEET10\/I'i)tFigure1-DeerCreekWatershedLocationHao(Source:USGSHaps)(1)

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~i~~~ufoV'jClNHgtttt~j~~II~oI~II+~gIII~~II~~~c+~~vt.'i~asctgt~~WERBRtDGE~IIIIIIg'IUPPf'gNIDCiE(cggygt7allDGQ)III~~~IIJ/W543210o00ICIIII0100FEETFigure2-DeerCreek01atershednearGinnaStation(Source:RGSEDr,awingNo.SK447-93)

IIl 1210510501010310RETURNPERIOD-YEARS1010'I23453789fofff2f3HISREDUCEDVARIATE-YF'iguve3-ReturnPeviodsfoe2I1-HouvPrecipitations liiIl 250020001500H-10005004810,12TIME(HOURS)1416Figure4-UnitHydrographforDeerCreek(24Hr.,1"Storm)

IlIII,l 20000150001000050001015TIME(HOURS)202530Figure5-DeerCreekFloodHydrograph(29Hr.,l0"Storm)

I)iLllI/"II.l gf:fl'Ž:If."Iot0>>I>>(eoi.',I:FIICK/Q/OCINNRSpaI~~J/'rg,)Wr.ONP~~I~~I~LON(tRSRIDCL-~II~tt'~iI:2(00~IVPPLRII(IDGE(CULVIRTP2(IDGL1I120280IIIjl:g/g'I(20tlretIrrnHouthtoScutlan0~SrcticnSetaI(cntt(po(trpa2620J~2200I>>>>ct(rnen(Io>>c>>rn(Poo~SI'ctlcII>>(r((Ir(SectlcnDatalrneSurvey543210100FEETFigure6-StreamCrossSectionsLocationMap(Source:RGSEDrawingNo.SK447-93)

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SECZICN100GEVATIOI(FEEDINSINQXIRN4SONONTNSCOSNIIXSIINIZW1&8DISTANCE<FEEDSECTST200ELECTIONIFEEDINSINDSISCN4NONOCQTNICCISNINSIININCISNOISThlCEIFKEDFigure7-DeerCreekCrossSectionData(LookingDownstream)

IlQIIgIII'IigI~J SECTICN470GXVATIIVISEEDINEINZS$$4SIWIWTNSN161IIWIINIENleDIETAtCESEEDSECTICET580GXVATINIFEEDISIINOIETAICEtFEEDIKQIINIRN13CSFIGURE7-Continued "IIIIIIIII

~',ISI11lP~,I:'llll'IS (ICg(Iii SECTICN900E1EVATINOTXDIN3IN2N3IS4S3NNOTNSSCMII3SIINI2NISODISTANCEOEED~m920ELEVATOR<FEED-IN3FN2IS3M4NENSQTN8NIXSINIINI2NI3NDISTAKX0%EDFIGURE7-Continued iJ)II SKTIaT1120ELEVhTI(8(FEETIIWIINENRS4WQSIWTWOWONIIV'IWIEWIKSOISTllCEtFEXTISECZICR1420GEVhTITIIITTETIIWOINZN%SINSSCWTNOWOWINSIIWICOSIIOWDIOTPICEITEETIFIGURE7-Continued

'IIIIII SKTICN1820EILYATII3ISTEEDINIIIN2NI3N4NN3IXeTIO8%II33IIN3IINI2NI3NOISTAICEITXEDSECZI(Ã22B0ELWATIIII(FEED"IN3IN3N4NSS8%ITNSNONIIENIINI2Nl3NDISTAICEINDEEDFIGURE7-Continued

SECTICN2300ELEVATICH<FEEDIMIIMEMSSAMEMOWTMMlQSIÃ0IIMISSI3OIDISTNCEOXEPSKTICN2320GLVATIW(FEEDIM1IMIMXOAMEMCMFM8%IOMIIESIIMMSIÃNOIETANXOXENFIGURE7-Continued

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