RegulatoryguidesareissuedtodescribeandmakeavailabletothepublicsuchinformationasmethodsacceptabletotheNRCstaffforimplementingspecificpartsoftheNRC’sregulations,techniquesusedbythestaffinevaluatingspecificproblemsorpostulatedaccidents,anddataneededbytheNRCstaffinitsreviewofapplicationsforpermitsandlicenses.Regulatoryguidesarenotsubstitutesforregulations,andcompliancewiththemisnotrequired.MethodsandsolutionsdifferentfromthosesetoutintheguideswillbeacceptableiftheyprovideabasisforthefindingsrequisitetotheissuanceorcontinuanceofapermitorlicensebytheCommission.Thisguidewasissuedafterconsiderationofcommentsreceivedfromthepublic.Commentsandsuggestionsforimprovementsintheseguidesareencouragedatalltimes,andguideswillberevised,asappropriate,toaccommodatecommentsandtoreflectnewinformationorexperience.WrittencommentsmaybesubmittedtotheRulesandDirectivesBranch,ADM,U.S.NuclearRegulatoryCommission,Washington,DC20555-0001.Regulatoryguidesareissuedintenbroaddivisions:1,PowerReactors;2,ResearchandTestReactors;3,FuelsandMaterialsFacilities;4,EnvironmentalandSiting;5,MaterialsandPlantProtection;6,Products;7,Transportation;8,OccupationalHealth;9,AntitrustandFinancialReview;and10,General.Singlecopiesofregulatoryguides(whichmaybereproduced)maybeobtainedfreeofchargebywritingtheDistributionServicesSection,U.S.NuclearRegulatoryCommission,Washington,DC20555-0001,orbyfaxto(301)415-2289,orbyemailtoDISTRIBUTION@NRC.GOV.ElectroniccopiesofthisguideandotherrecentlyissuedguidesareavailableatNRC’shomepageat(DraftwasissuedasDG-1105)PROCEDURESANDCRITERIAFORASSESSINGSEISMICSOILLIQUEFACTIONATNUCLEARPOWERPLANTSITESA.INTRODUCTIONThisregulatoryguidehasbeendevelopedtoprovideguidancetolicenseapplicantsonacceptablemethodsforevaluatingthepotentialforearthquake-inducedinstabilityofsoilsresultingfromliquefactionandstrengthdegradation.Itdiscussesconditionsunderwhichthepotentialforsuchresponseshouldbeaddressedinsafetyanalysisreports.Theguidanceincludesproceduresandcriteriacurrentlyappliedtoassesstheliquefactionpotentialofsoilsrangingfromgraveltoclays.In10CFRPart100,“ReactorSiteCriteria,”§100.23,“GeologicandSeismicSitingCriteria,”setsforththeprincipalgeologicandseismicconsiderationsthatguidetheNRCinitsevaluationofthesuitabilityofaproposedsite.Inaddition,10CFR100.23(d)(4)discussesseveralsitingfactorsthatmustbeevaluatedandrequiresthatthepotentialforsoilliquefactionbeevaluatedinadditiontoseveralothergeologicandseismicfactors.Safety-relatedsitecharacteristics,includingthoserelatedtotheresponseofsoilstoearthquakes,areidentifiedinRegulatoryGuide1.70,“StandardFormatandContentofSafetyAnalysisReportsforNuclearPowerPlants(LWREdition).”RegulatoryGuide4.7,“GeneralSiteSuitabilityCriteriaforNuclearPowerStations,”discussesmajorsitecharacteristicsthataffectsitesuitability.ProceduresandmethodsofsiteinvestigationsaredescribedinRegulatoryGuide1.132,“SiteInvestigationsforFoundationsofNuclearPowerPlants.”GuidelinesforlaboratorytestingaregiveninRegulatoryGuide1.138,“LaboratoryInvestigationsofSoilsforEngineeringAnalysisandDesignofNuclearPowerPlants.”1.198-2RegulatoryGuide1.165,“IdentificationandCharacterizationofSeismicSourcesandDeterminationofSafeShutdownEarthquakeGroundMotion,”definesinvestigationsrelatedtoseismicity,faults,andvibratorygroundmotion.Thescopeofthisguideislimitedtoevaluationofthebehaviorofsoilssubjectedtoearthquakeshaking.Itspecificallyexcludesnonseismicfailureofsensitiveclays,failureunderstaticloads(suchasflowslidesinloosepointbardeposits),andsoilresponsetomachinevibrationsandblasting.Theselectionorsynthesisofappropriategroundmotionrecordstouseforaresponseanalysisisnotincluded.ThetechnicalbasisforthisregulatoryguideiscontainedinNUREG/CR-5741(1999).NUREG/CR-5741wasdevelopedtocompilecurrentandstate-of-the-arttechniquesforevaluatingearthquake-inducedliquefaction.Itsummarizestheprocessofacquiringandusinggeological,geophysical,geotechnical,andotherkindsofrelevantinformationthatsupportdesignconsiderationswithrespecttotheliquefactionpotentialofsoils.Areportfromthe1996NCEERand1998NCEER/NSFworkshopssummarizedevaluationproceduresforliquefactionsusceptibilityinthepast30yearsandrecommendedstate-of-the-artevaluationpractices(Youdetal.,2001).Theinformationcollectionscontainedinthisdraftregulatoryguidearecoveredbytherequirementsof10CFRParts50and100,whichwereapprovedbytheOfficeofManagementandBudget(OMB),approvalnumbers3150-0011and3150-0093.TheNRCmaynotconductorsponsor,andapersonisnotrequiredtorespondto,arequestforinformationoraninformationcollectionrequirementunlesstherequestingdocumentdisplaysacurrentlyvalidOMBcontrolnumber.B.DISCUSSIONGENERALEverysiteandplantfacilityisunique,andthereforerequirementsforanalysisandinvestigationsvary.Itisnotpossibletoprovideevaluationproceduresforseismicsoilliquefactionpotentialtodealwitheverycontingency.Incircumstancesthatarenotspecificallyaddressedinthisguide,pruden