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Page 1: Chapter 1 Introduction€¦ · Chapter 1 Introduction ... 1 2

Chapter 1Introduction

Page 2: Chapter 1 Introduction€¦ · Chapter 1 Introduction ... 1 2

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor StationDraft Environmental Impact Report 

1‐1 August 2012

ICF 00122.11

 

Chapter 1 1

Introduction 2

1.1 Overview 3

TheCaliforniaRegionalWaterQualityControlBoard,LahontanRegion(WaterBoard),isthe4

CaliforniaEnvironmentalQualityAct(CEQA)leadagencyfortheenvironmentalinvestigationand5

chromiumgroundwatercleanupatPacificGasandElectricCompany’s(PG&E’s)HinkleyCompressor6

Station.TheCompressorStationislocatedabout3milessoutheastofthetownofHinkleyin7

SanBernardinoCounty,California.8

TheCompressorStationfacilityisusedtotransportnaturalgasalongpipelinesfromTexasto9

California.Between1952and1964,coolingtowerwaterwastreatedwithacompoundcontaining10

chromiumtopreventcorrosion,andthewaterwasthendischargedtounlinedpondswhichresulted11

incontaminationofthesoilandgroundwaterbeneaththesitewithtotalandhexavalentchromium12

(Cr[T]andCr[VI]1,respectively).Asof2008,thiscontaminationcreatedaplumeofchromiumin13

groundwaterextendingabouttwomilestothenorthoftheCompressorStationandabout1.3miles14

wide(LahontanRegionalWaterQualityControlBoard2008).Asoflate2011,theplumewasmuch15

largerthanin2008andwasapproximately5.4milesinlengthandupto2.4mileswideatitswidest16

point.TheWaterBoardhasrequiredPG&Etotakeremedialactions2tocleanupthechromium17

contamination,andtoslowandstoptheplumefromspreading(alsoreferredtoascontainingthe18

plume).Theseremedialactionstodatehaveconsistedofthefollowingcleanuptechnologies:19

Groundwaterextraction:contaminatedgroundwaterispumpedfromthesubsurface(alsocalled20

theaquifer)tocontainthecontaminationplume.21

Agriculturalre‐use(alsocalledagriculturaltreatment,landtreatmentoragriculturalunits):22

extractedgroundwaterisusedtoirrigateforagecropsforlivestock.Hexavalentchromiuminthe23

extractedgroundwaterisconvertedtotrivalentchromium(Cr[III])bycontactwithorganic24

matterinthesoilasitinfiltratesthroughthesoil.Hexavalentchromiumisthetoxicformof25

chromium;trivalentchromiumhasverylowtoxicity(OEHHA2011).26

Subsurfacetreatment(alsocalledin‐situtreatmentorin‐situreactivezones):carbonsubstancesare27

injectedintothegroundwateraquifertoturnthehexavalentchromiumintotrivalentchromium.28

Subsurfacefreshwaterinjection:freshwaterisinjectedwithintheaquiferalongthewesternside29

oftheplumetopreventthespreadofcontaminatedgroundwatertotheHinkleySchooland30

residentialareas.31

1Inthecontextofthedescriptionofcontaminationingeneral,theterm“chromium”(Cr)isusedinplaceoftheseparateterms“totalchromium”(Cr[T])or“hexavalentchromium”(Cr[VI]).Hexavalentchromiumisacomponentoftotalchromium.Whenthereisreferencetoonlyhexavalentchromium,thenitisidentifiedassuch.2Varioustermsareusedinterchangeablythroughoutthisdocumenttoreferto“remedialactions.”Theseinclude“remedialoptions,”“technologies,”“remediationactivities,”and/or“treatmentapproaches.”Additionally,theproposedalternativesaredefinedasthevariouscombinationsofthenewremedialoptionsthatarebeingevaluatedinthisEIR.ThesealternativesaredescribedinChapter2,ProjectDescription.

Page 3: Chapter 1 Introduction€¦ · Chapter 1 Introduction ... 1 2

California Regional Water Quality Control Board, Lahontan Region  Introduction

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

1‐2 August 2012

ICF 00122.11

 

TheWaterBoardadoptedCleanupandAbatementOrder(CAO)No.R6V‐2008‐0002in2008,which1

requiredsite‐wideremediationofthecontaminatedgroundwater,andadoptedWasteDischarge2

Requirements(WDRs3)(OrderNo.R6V‐2008‐0014),alsoknownastheGeneralPermit,forthe3

implementationofplumecontainmentactions,in‐situremediation,andabove‐groundtreatment.4

Althoughabove‐groundtreatmentwasanapprovedactionundertheGeneralPermit,thisremedial5

methodhasnotbeenusedtodate.PriortoadoptionoftheGeneralPermit,PG&Ewasimplementing6

plumecontainment,in‐situtreatment,andlandtreatmentactionspursuanttopriorWaterBoard7

ordersandtheassociatedWDRsonalimitedbasis.ThemainWDRsthatexpandedonthemore8

limitedremediationactivitiesbefore2008include:9

AgriculturalreuseattheDesertViewDairyunderindividualWDRsforthePG&EInterimPlume10

ContainmentandHexavalentChromiumTreatmentProject(WaterBoardOrderNo.R6V‐2004‐11

0034)in2004;12

Extended‐scalein‐situremediationatthesourcearea(WaterBoardOrderNo.R6V‐2006‐0054),13

locatedonPG&E’sHinkleyCompressorStationpropertyin2006;14

Extended‐scaleinsituremediationintheCentralArea(WaterBoardOrderNo.R6V‐2007‐15

0032),locatedalongandnorthofFrontierRoad,in2007;and16

ExpandedpumpingfrompropertiesoutsidetheDesertViewDairywithdischargestotheDesert17

ViewDairy(WaterBoardOrderNo.RCV‐2004‐0034A1)in2007.18

AnadditionalWDRamendmentwasadoptedin2010toallowgroundwaterextractionfrom19

propertiesnorthandeastoftheDesertViewDairywithdischargestotheDesertViewDairyanda20

50percentincreaseintheallowablecombinedextractionrate(WaterBoardOrderNo.R6V‐2004‐21

0034A2).422

PriortoadoptionoftheWDRsandpursuanttoCEQA,theWaterBoardconductedenvironmental23

analysestoaddresstheimpactsofimplementingtheWDRsbypreparingandcertifyingrespective24

mitigatednegativedeclarations(MNDs)in2004,2006,and2007.In2008,aMNDwasalsoprepared25

toevaluateenvironmentalimpactsofimplementingtheGeneralPermitpriortoitsadoption.The26

WaterBoardadoptedaresolutionapprovingtheMNDpreparedfortheGeneralPermit(State27

ClearinghouseNo.2008011097)in2008.Anamendmenttothe2007MNDwaspreparedin2010to28

addressadditionalimpactsresultingfromexpandingremediationactivitiesattheDesertView29

Dairy.30

TheWaterBoardisnowpreparingtoissueanewCAOwhichwillsetspecificcleanuprequirements31

includingthecleanuplevelsandthetimeperiodsbywhichthoselevelsmustbemet.Anewsite‐32

wideGeneralPermitwillbeadopted,specifyingtheoperating,dischargeandmonitoring33

requirementsforcomprehensivecleanupofchromiumingroundwatertomeettherequirementsset34

bytheCAO.AlthoughtheWaterBoardisrestrictedbyWaterCodesection13360fromspecifying35

themethodandmannerofPG&E’scompliancewiththecleanupandabatementorder,thecleanup36

levelswilldrivewhatremedialactionsaretaken,wheretheyaretaken,andatwhatintensity.37

3WDRsarethepermitsthatsetoperating,dischargeandmonitoringrequirementsforPG&Etoconductremediationactivities.WDRsarealsoreferredtobytheirWaterBoardOrdernumber.4AlistofthecurrentCAOsandWDRsbeingimplementedcanbeaccessedontheWaterBoard’sprojectwebsiteathttp://www.waterboards.ca.gov/rwqcb6/water_issues/projects/pge/index.shtml#wbo.

Page 4: Chapter 1 Introduction€¦ · Chapter 1 Introduction ... 1 2

California Regional Water Quality Control Board, Lahontan Region  Introduction

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

1‐3 August 2012

ICF 00122.11

 

Manyofthesametechnologiesthatarecurrentlybeingimplemented(agricultural/landtreatment,1

in‐situtreatment,plumecontainment,freshwaterinjection/extraction)underexistingindividual2

WDRsandtheGeneralPermitwillcontinuetobeimplementedunderthenewGeneralPermit;3

however,theremaybenewpotentiallysignificantenvironmentalimpactssincethevarious4

combinationsofthesetechnologieswillbeexpandedsubstantiallyoverthosethatwereanalyzedin5

priorMNDs.Therefore,theWaterBoardhasdeterminedthatpreparationofanEIRisnecessaryto6

disclosepotentiallysignificantimpactsofadoptingthenewGeneralPermitandimplementing7

cleanuprequirementsprescribedintheCAO.TheEIRwillincludethefollowingcontentspursuantto8

therequirementsofCEQA:9

Newprojectalternativesdevelopedforcomprehensiveremediationofthechromium10

contamination.11

Newinformationrelatedtochangesinphysicalconditionswhereremedialactionshavebeen12

implemented,includingchangesinthecontaminatedareathathaveoccurredsincetheprevious13

CEQAMNDswereadopted(between2004and2010)(LahontanRegionalWaterQualityControl14

Board2008).15

Potentialsignificantdirectandindirectenvironmentalimpactsresultingfromimplementation16

oftheprojectalternatives,including:17

Groundwaterdrawdowneffectsonregionalandlocalwatersupplies,18

Impairmentofwaterqualityfromremedialactions,19

Lossordisturbanceofendangeredspecieshabitat,20

Increasednoiseandtraffic,21

Permanentlossofresidencesthroughpropertybuyouts,and22

Constructionimpacts.23

Mitigationmeasuresproposedtoreduceoravoidpotentialsignificantenvironmentalimpacts24

resultingfromimplementationoftheprojectalternatives.25

Cumulativeandgrowth‐inducingimpacts.26

1.2 Water Board Outreach Activities 27

AspartoftheCEQAprocess,theWaterBoardhasengagedthepublicinanexpansiveprocessto28

keeptheminvolvedandinformedoftheproject’sdevelopmentandtheEIRdevelopment.TheWater29

Boardissuedpublicnoticesrequestingcommentsonthevariousremediationfeasibilitystudiesand30

CAOsandconductedseveralcommunitymeetings.Thisprocesshasbeenongoingsinceinitiationof31

theCEQAscopingperiodinNovember2010.DuringthescopingperiodforthisEIR,whichwas32

concurrentwiththecommentperiodforthe2010FeasibilityStudypreparedbyPG&E,theWater33

BoardreceivedcommentsrelativetotheCEQAanalysis,theoveralltreatmentapproach,andother34

issuesrelatedtoPG&E’sactivitiesintheHinkleyarea(someofwhichareoutsidethepurviewofthe35

WaterBoard).Thekeymilestonesinthepublicoutreachprocesstodate,andasummaryof36

commentsandissuesraisedareprovidedbelow.Foreachissueraised,asummaryoftheissueanda37

discussionofwhetheritiswithinthepurviewofthisEIRisprovided,includingadescriptionof38

whetherandhowtheissueisaddressedinthisEIR.39

Page 5: Chapter 1 Introduction€¦ · Chapter 1 Introduction ... 1 2

California Regional Water Quality Control Board, Lahontan Region  Introduction

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

1‐4 August 2012

ICF 00122.11

 

1.2.1 Timeline of Activities 1

November24,2010:ANoticeofPreparation(NOP)waspublishedtonotifythepublicofthe2

WaterBoard’sintentforpreparinganEIRtoevaluatepotentialenvironmentalimpactsofthe3

project.TheNOPincludedinformationontheproposedcomprehensivecleanupstrategy4

proposedbyPG&EandtheCEQAprocess.TheWaterBoardrequestedpubliccommentsonthe5

NOP.ThedeadlineforpubliccommentswasDecember31,2010.6

December1,2010:AspartoftheCEQAscopingprocess,apublicscoping/feasibilitystudy7

informationalmeetingwasheldinHinkley.TheWaterBoardstaffaskedforinputonissuesto8

evaluateintheEIRandalsoaskedforpublicinputonthealternativesanalyzedintheSeptember9

2010FeasibilityStudy.10

December10,2010:RequestforpubliccommentsonfinalsitecleanupatthePG&E11

CompressorStation.TheWaterBoardrequestedpubliccommentsonPG&E’sfeasibilitystudy12

forfinalcleanup.ThedeadlineforpubliccommentswasJanuary10,2011.13

January26and27,2011:TheWaterBoardhostedtwoinformationmeetingsatHinkley14

ElementarySchoolaboutcleanupactivitiesatPG&E’sHinkleysite.Themeetingsincludedmaps15

showingcurrentboundariesofthechromiumplumeingroundwater,summariesofcomments16

theWaterBoardreceivedonPG&E’sSeptemberfeasibilitystudyonachievingfinalsitecleanup,17

andinformationonthescopeandcontentoftheEIRtheWaterBoardisdevelopingtoevaluate18

theenvironmentalimpactsofcleanupalternatives.19

March9and10,2011:TheWaterBoardhostedapublicmeetinginBarstowtoprovideastatus20

reportonPG&E’scontainmentandremediationactivitiesforthecleanup.Discussionwas21

providedontheneedandprocessfordevelopingtheEIR,thecleanupstandard,cleanuptimes22

andtechnologies,andpotentialenvironmentalimpactsofthecleanupactivities.Hinkley23

residentsexpressedconcernsaboutPG&E’s2007chromiumbackgroundstudyandhowthe24

backgroundchromiumconcentrationsingroundwaterweredetermined.Inresponsetothose25

concerns,WaterBoardmembersdirectedstafftohavePG&E’s2007GroundwaterBackground26

StudyReport(the2007BackgroundStudyReport)reviewedbyindependentscientific27

reviewers(seethesummaryofpubliccommentsonthisissueunderSection1.2.2below).28

October14,2011:TheWaterBoardpostedtheresultsofthethreeindependentpeerreviews29

ofthebackgroundchromiumstudyonitswebsite.Thereviewswereconductedandsubmitted30

byProfessorYoramRubin,Ph.D.,oftheUniversityofCaliforniaatBerkeleyDepartmentofCivil31

andEnvironmentalEngineering;JamesJacobs,PG,fromClearwaterGroupEnvironmental32

Services;andDr.StuartNagourneyoftheCollegeofNewJersey,DepartmentofChemistry.The33

WaterBoardalsoadoptedCAONo.R6V‐2011‐0005A1concerningwholehousewater34

replacement.35

December8,2011:TheWaterBoardheldapublicinformationmeetingatHinkleyElementary36

School.MeetingtopicsincludedCAONo.R6V‐2011‐0005A1issuedinOctober2011,resultsofthefall37

2011groundwatermonitoringforchromium,EIRdevelopmentupdate,andasummaryofpeer38

reviewcommentsonthe2007BackgroundStudyReport.39

March15and16,2012:AtaWaterBoardMeetinginBarstow,theBoardadoptedastipulated40

orderandsettlementagreementimposingatotalliabilityamountof$3.6millionagainstPG&E41

forfailuretocomplywitharequirementofCAONo.R6V‐2008‐0002.One‐halfoftheliability42

wouldbepaidtotheStateandtheotherhalfwouldbeusedtoimplementaprojecttoeliminate43

Page 6: Chapter 1 Introduction€¦ · Chapter 1 Introduction ... 1 2

California Regional Water Quality Control Board, Lahontan Region  Introduction

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

1‐5 August 2012

ICF 00122.11

 

groundwaterpumpingattheHinkleySchoolandsupplywaterfromalocationupgradientofthe1

CompressorStation.TheSettlementalsoincludesaprovisionwherebytheWaterBoard2

amendedtheplumecontainmentrequirementsintheexistingAmendedCAONo.R6V‐2008‐3

0002A1issuedonApril7,2009,allowingcertainlateralspreadingofthechromiumplume4

associatedwithremediationactivities.Atthismeeting,theBoardalsoheardasummaryand5

discussionofthe2011PeerReviewofPG&E’s2007BackgroundStudyReportfromWaterBoard6

staff.Supportingmaterialsincluded:1)aWaterBoardstaffreportdiscussingthepeer7

reviewers’comments;2)apubliccommentletter;and3)PG&E’sFebruary2012proposedwork8

planforevaluationofbackgroundchromiumintheupperaquiferoftheHinkleyValley.9

October2011toJune2012:InOctober2011,theWaterBoardissuedCAONo.R6V‐2011‐10

0005A1toPG&E.TheOrderrequired,inpart,thatPG&Eprovideinterimandwholehouse11

replacementwaterservicetothoseservedbydomesticorcommunitywellsthatarewithinthe12

affectedareaanddeterminedtobeimpactedbyitsdischarge.TheOrderdefinedimpactedwells13

asalldomesticorcommunitywellsintheaffectedareathatareabove3.1partsperbillion(ppb)14

hexavalentchromiumor3.2ppbtotalchromiumplumeboundaries,baseduponmonitoringwell15

datadrawninthemostcurrentquarterlysite‐widegroundwatermonitoringreportsubmitted16

byPG&E.TheOrderalsodefinedimpactedwellsasthosedomesticorcommunitywellsinthe17

affectedareathatcontainhexavalentchromiuminconcentrationsgreaterthan0.02ppbthat18

weretheresultofPG&E’sdischargeattheFacility.PG&Ewasrequiredtodevelopamethodto19

determineifawellwithintheaffectedarea,thatcontaineddetectablelevelsofhexavalent20

chromiumbelow3.1ppbortotalchromiumbelow3.2ppb,wasimpactedbyitsdischarge.21

InlettersdatedNovember23,2011,andDecember22,2011,PG&Eprovideditspositionthat22

thereiscurrentlynocrediblemethodtodeterminethesourceofhexavalentchromiumin23

domesticwellswithdetectionsbelowthecurrentbackgroundvalues(3.1ppbhexavalent24

chromiumor3.2ppbtotalchromium).Instead,PG&EofferedtoimplementaVoluntaryWhole25

HouseReplacementWaterProgram(Program).26

OnJune6,2012,PG&Esubmittedaletterwithits“RevisedReplacementWaterSupply27

FeasibilityReport,”(FeasibilityStudy)supplementinginformationregardingtheProgram.28

TheProgramwillprovideinterim(untilthewholehousereplacementwaterisimplemented)or29

wholehousereplacementwaterservicefordrinkingwaterpurposesthatmeetsallCalifornia30

primaryandsecondarydrinkingwaterstandardsandhexavalentchromiumlevelsoflessthan31

0.02ppborthefinalMCL,oncethatstandardisadoptedbyCDPH,toallthoseservedby32

domesticorcommunitywellsintheaffectedareawhenanalyticalmonitoringresultsfromthose33

wellsindicatedetectablelevelsofhexavalentchromiumatanytimeduringthemostrecentfour34

consecutivequarters.Propertyownerswouldbegiventheoptionofanionexchangeunitsfor35

thetreatmentofallwaterplusandundersinkreverseosmosisunitforadditionaltreatmentof36

allwaterusedfordrinkingwaterpurposesorinstallationofdeeperwells,wherefeasiblebased37

onPG&E’sassessmentofexistingwaterqualityandhydrogeology.38

Inresponsetothatproposal,theWaterBoardsuspendedseveralprovisionsofOrderR6V‐2011‐39

0005A1,includingtherequirementtodevelopamethodtodetermineifawellwithinthe40

affectedareathatcontaineddetectablelevelsofhexavalentchromiumbelow3.1ppbortotal41

chromiumbelow3.2ppbwasimpactedbyitsdischarge,aslongasPG&Econtinuedto42

implementitsvoluntaryprogram(CAOR6V‐2011‐0005A2).43

Page 7: Chapter 1 Introduction€¦ · Chapter 1 Introduction ... 1 2

California Regional Water Quality Control Board, Lahontan Region  Introduction

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

1‐6 August 2012

ICF 00122.11

 

1.2.2 Public Comments 1

1.2.2.1 Cleanup Levels and the Definition of Background 2

Thecommentsbelowweremadeduringthescoping/feasibilitystudycommentperiodregardingthe3

definitionof“background”andtheextenttowhichtheWaterBoardshouldrequirePG&Etoclean4

upthechromiumcontaminationintheHinkleyaquifer.5

TheWaterBoardshouldrequirecleanuptoresultinconcentrationsthatarelessthanthe6

maximumbackground(3.1ppb)identifiedinthebackgroundstudy(forbothhexavalentchromium7

(Cr[VI])andtotalchromium(Cr[T])).8

TheWaterBoardshouldrequirecleanuptoresultinconcentrationsthatarelessthantheaverage9

backgroundlevel(1.2ppb)identifiedinthebackgroundstudy.10

TheWaterBoardshouldconsiderOEHHA’sadoptedPublicHealthGoal(0.02ppb)asthe11

backgroundandstandardforCr[VI]cleanup.12

TheWaterBoardshouldrevisitthebackgroundstudy(PacificGasandElectric2007[submittedto13

theWaterBoardin2007andacceptedbytheWaterBoardin2008])inlightoftheplume14

spreadingtothenorthandeastin2010.15

In2011,theWaterBoardinitiatedapeerreviewofthe2007BackgroundStudyReportandpeer16

reviewcommentsidentifiedspecificconcernsregardingthewellsutilized,analyticalprocedures,17

statisticalanalysis,andotherissues.TheWaterBoardstaff,asdirectedbytheWaterBoardinits18

March2012meeting,isretainingtheexistingbackgroundvaluesadoptedinamendedCAOR6V‐19

2011‐005A1whilereviewingPG&E’sproposednewbackgroundstudyandconsideringtheneedfor20

peerreviewand/orconsultationwithotherexperts,suchastheUSGeologicalSurvey,toensurethat21

anynewstudywillyieldavalid,credibleanddefensibleresult.ForthepurposeofthisDraftEIR,the22

WaterBoardisusingthevaluesderivedfromthe2007BackgroundStudyReporttodefinethe23

chromiumplumeandasinterimcleanuplevelspendingcompletionofanewbackgroundstudy.24

StateWaterResourcesControlBoardResolution92‐49requiresdischargerstocleanupandabate25

theeffectsofdischargesinamannerthatpromotesattainmentofeitherbackgroundwaterquality,26

orthebestwaterqualitywhichisreasonableifbackgroundlevelsofwaterqualitycannotbe27

restored.Insettingcleanuplevels,allcurrentandexpecteddemandsonthosewatersmustbe28

considered,includingbeneficial,detrimental,economic,social,tangible,andintangiblevalues.29

TheWaterBoardcannotrequirePG&EtocleanupnaturallyoccurringCr[VI].Totheextentthatthe30

proposedPublicHealthGoalislessthannaturallyoccurringbackgroundlevels,theWaterBoard31

doesnothavetheauthoritytorequirecleanuptotheproposedPublicHealthGoal.Asnotedabove,32

theWaterBoardisrevisitingthebackgroundstudyandmayadoptrevisedbackgroundlevelsif33

warrantedbasedontheresultsofanewbackgroundstudy.Ifnewbackgroundlevelsareadopted,34

theWaterBoardmayberequiredtoamendthenewGeneralPermitandCAO,andsubsequent35

environmentalanalysismayberequirediftheamendmentswouldrequireanyactionsthatgo36

beyondthescopeofthisEIRanalysis.Section3.1,WaterResourcesandWaterQuality,describesthe37

regulatorybackgroundrelatedtoestablishmentandrevisionofbackgroundcontaminationlevels.38

1.2.2.2 Project Alternatives and Time Period to Complete Cleanup 39

Thecommentsbelowweremadeduringthescopingperiodregardingthetimeitwilltaketo40

completethecleanupofthesiteunderthevariousproposedalternatives:41

Page 8: Chapter 1 Introduction€¦ · Chapter 1 Introduction ... 1 2

California Regional Water Quality Control Board, Lahontan Region  Introduction

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

1‐7 August 2012

ICF 00122.11

 

Allofthe2010FeasibilityStudyalternativestaketoolongtocleanupthesite.1

Theloweraquiferplumeareashouldbedelineated.2

SoilcontaminationattheCompressorStationshouldbeaddressed.3

TheeffectsofCr[III]remaininginthesoilafterproposedin‐situtreatmentshouldbeaddressed.4

ThepotentialforCr[VI]andothercontaminantstospreadshouldbeaddressed.5

Additionaltechnologiesbeyondthoseproposedinthefeasibilitystudyshouldbeconsidered.6

TheimpactofPG&E’spropertybuyoutprogramshouldbeanalyzed.7

TheWaterBoard’sgoalinsettingcleanupobjectivesistorequirePG&Etocleanuptheportionof8

theHinkleygroundwateraquiferthatitcontaminatedtobackgroundlevelsofCr[VI]aspossiblein9

theminimumamountoftimefeasible,whilelimitingormitigatingenvironmentalimpacts10

associatedwiththecleanupactivities.Tothatend,theWaterBoardhasrequiredPG&Etoconsider11

additionalalternativesthatwouldresultinshortercleanuptimeframesthanthoseoriginally12

proposedinthe2010FeasibilityStudy.Accordingly,threeaddendaandadditionalevaluationshave13

beenpreparedbyPG&Etoevaluatemethodstoachievecleanupgoalsmorerapidly(seeChapter2,14

ProjectDescription,foradescriptionofthealternativesanalyzedindetailinthisEIRaswellasthe15

alternativesconsideredanddismissedfromfurtherconsideration).16

PG&EcompleteddelineationofthecontaminationintheloweraquiferinFebruary2011.17

Informationfromthatinvestigationisusedinthisdocument.Theapprovedcomprehensivecleanup18

strategywillincludecleanupofloweraquifercontaminationtobackgroundconcentrationsorthe19

cleanupgoalstobesetbytheWaterBoardspecificallyfortheloweraquifer.20

TheWaterBoardcanrequirecleanupofsoilswheretheyposeathreattogroundwaterorother21

watercontamination.PriorsoilremovalactionsoccurredattheCompressorStation.Thecurrent22

remedialactionisfocusedongroundwatercleanup.23

ThisEIR(seeSection3.1,WaterResourcesandWaterQuality)addressesthepotentialforand24

impactsofconversionofCr[III]backtoCr[VI],potentialchangesintheplumeasaresultof25

remediationactivities,thepotentialforincreasesinothercontaminantsattributabletoremediation,26

andotherpotentialeffectsonwaterqualityasaresultofimplementingremediation.27

AsdescribedinChapter2,ProjectDescription,theproposedalternativesweredevelopedandbased28

onthe2010FeasibilityStudyanditsfirst,second,andthirdaddendaandotherinformation.The29

suiteoftechnologiesevaluatedinthefeasibilitystudy/addenda(andinaprior2002feasibility30

study)isextensiveandbasedondatasupportingtheeffectivenessofeachtechnology.31

PG&E’spropertyacquisitionprogramisanongoingactivitythatPG&Ehasbeenimplementingatits32

owninitiativeovertime.However,theremedialalternativesconsideredinthisEIRwillmostlikely33

requireacquisitionofcertainparcelsofland(andpossiblyresidences)toimplementremediation34

fully.Whereitisreasonablyforeseeablethatimplementationofremediationwillrequireproperty35

acquisition,theenvironmentalimpactofthatacquisitionwillbeanalyzedinthisEIRinrelationto36

impactstolanduse,housing,population,andsocioeconomics(seeSection3.2,LandUse,Agriculture,37

Population,andHousing).38

Page 9: Chapter 1 Introduction€¦ · Chapter 1 Introduction ... 1 2

California Regional Water Quality Control Board, Lahontan Region  Introduction

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

1‐8 August 2012

ICF 00122.11

 

1.2.2.3 Water Supply 1

Theprimaryconcernraisedinthescopingcommentsrelatedtowatersupplywasthepossibilityof2

reducedavailabilityofpotable/domesticwaterasaresultofcontinuedcontamination.Inaddition,3

residentsraisedconcernaboutwaterfordomesticanimals(includinghorses)andvegetableplanting.4

Thepotentialeffectsofremediationongroundwaterlevels,supply,andqualityareevaluatedinthis5

EIR(seeSection3.1,WaterResourcesandWaterQuality).6

1.2.2.4 Data Collection and Information 7

Thecommentsbelowconcerningdatacollectionandinformationwerereceived.8

PG&EshouldbeinvolvedonlyinfundingtheWaterBoard’scollectionofdataanddevelopmentof9

alternatives,notproducingit.10

Anindependentcostanalysisshouldbeprepared.11

Plumemapsneedtohavebetterreferencepoints,suchasroads,andbelabeledmoreclearly.12

Thetypeandamountoftracersbeinginjectedintheaquifershouldbeidentified.13

ItisPG&E’sresponsibilitytocollectdatanecessarytodevelopfeasiblealternativestomeetWater14

Boardcleanuprequirements(WaterCodeSection13307;StateWaterResourcesControlBoard15

Resolution92‐49).Ininvestigatingthesiteanddevelopingcleanupalternatives,PG&Eisrequiredto16

usecertifiedmethods,labs,andprofessionals.17

PG&Eisresponsibleforthecostsofremediation.ThosecostsarenotaprimaryfactorintheWater18

Board’sdeterminationofcleanupobjectives,excepttotheextentthatitisonefactorofseveralthat19

theWaterBoardmustconsiderindecidingwhethertorequirecleanuptobackgroundlevelsorto20

thebestwaterqualitywhichisreasonableifbackgroundlevelsofwaterqualitycannotberestored.21

(StateWaterResourcesControlBoard,Resolution92‐49.)Anindependentcostanalysisisnot22

required,anditisnotclearwhatbenefitsuchananalysiswouldprovide.Thecostsprovidedby23

PG&Einitsfeasibilitystudyandaddendaareusedprimarilyforcomparingrelativecostsofeach24

alternativeanalyzed.25

ThisEIRincludesmapsanddiagramsdesignedtohelpthereaderunderstandthelocationsof26

componentsoftheproposedremediationactivitiesandhowtheyrelatetoexistingfeatures.Tothe27

extentpossible,mapsincluderoadnamesandotherlabels.28

ThisEIRdescribesallowedtracers,allowablelimits,andhowtheleveloftraceelementsmaychange29

withimplementationoftheremediationactivities(Section3.1,WaterResourcesandWaterQuality).30

TheWaterBoardwillrequirereportingandtrackingoftracersandotheradditives/chemicalsas31

partoffuturepermitsororders.TheexistingGeneralPermitrequiresidentification,tracking/32

monitoring,andreportingofanytracersoradditivesused(injectedintothegroundwater).33

1.2.2.5 Health and Safety 34

Thecommunityalsoexpressedconcernsaboutthesafetyofwellwaterfordrinking,cooking,35

bathing,swimming,laundry,petconsumption,anduseinswampcoolers.Additionally,therewere36

questionsabouthowlawnsandotheroutdoorareasirrigatedwithwellwatercouldaffectthose37

playingonormowingthelawns.38

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Thepotentialhealtheffectsofchromium(bothCr[III]andCr[VI])andotherconstituentsare1

discussedinSection3.1,WaterResourcesandWaterQuality,includingrisksassociatedwithpotable2

useandnon‐potableuses.3

ContaminatedgroundwaterisanexistingconditionattributabletothepriorreleaseofCrfromthe4

CompressorStation.Assuch,priororcurrenthealthimpactsrelatedtoCrcontaminationarea5

componentoftheproject’senvironmentalbaselineandattributabletothepriorreleasesandnot6

totheproposedproject(i.e.,thecomprehensivecleanupstrategy).Thecomprehensivecleanup7

strategyisintendedtolowertheCr[VI]concentrationsingroundwatertobackgroundlevelsand8

assuchwouldreducehealthimpactsrelatedtoCrcontaminationcomparedwithexisting9

conditions(late2011).Therefore,theimpactsidentifiedinthisEIRarethoseassociatedwiththe10

remediationactivities,nottheexistingcontamination.However,thereisthepotentialforcertain11

remedialactionstoresultinincreasedconcentrationsofotherconstituents(suchasarsenic,iron,12

manganese,nitrate,ortotaldissolvedsolids)asaresultofremedialactivity.Shouldthisoccur,13

remedialactivitycouldincreasepublichealthriskscomparedwithexisting,conditions.Sections14

3.1,WaterResourcesandWaterQuality,and3.3,HazardsandHazardousMaterials,analyzethis15

possibility.16

Itshouldalsobenotedthatin2011,theWaterBoardorderedPG&Etoprovidewholehouse17

replacementwatertoanyresidencesaffectedbythecontaminatedplume.Furthermore,PG&Ewas18

orderedtosubmitaplantoprovidepermanentreplacementwaterforallindoordomesticuses19

(referredtoas“wholehousewater”)forallwellsimpactedbyPG&E’sdischargewithinthe“affected20

area”(definedastheareawithin1miledowngradientorcrossgradientfromtheplume).PG&E21

conductedapilotstudytoevaluatewatertreatmenttechnologiesforpurposesofprovidingwhole22

housewaterreplacementtoaffectedresidences.Basedonconclusionsofthatstudy,foranyone23

withintheaffectedareawithdetectablelevelsofhexavalentchromiumintheirwell,PG&Edecided24

toofferthechoiceofeither1)anionexchangeunitforthetreatmentofallwaterplusanundersink25

reverseosmosisunitforadditionaltreatmentofallwaterusedfordrinkingwaterpurposes,or2)26

installationofadeeperwell,wherefeasiblebasedonPG&E’sassessmentofexistingwaterquality27

andhydrogeology.28

1.3 Other Permits and Approvals 29

Asdescribedabove,PG&Eiscurrentlyimplementingprojectremedialactivitiesincompliancewith30

priorandexistingCAOsandWDRs.Implementationoftheactionalternativeswillrequirethe31

LahontanWaterBoardtoadoptnewWDRsandaCAOthatwilladdressbothexistingandexpanded32

remedialactivities.ToimplementtheremediationactivitiesanalyzedinthisEIR,PG&Ewillalso33

needtoobtainthepermitsandapprovalsfoundinTable1‐1.34

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Table 1‐1. Other Required Permits and Approvals 1

Permit PermittingAgency Trigger

Incidentaltakepermit(perthefederalEndangeredSpeciesAct(ESA)undereitherSection7orSection10oftheAct)

U.S.FishandWildlifeService(USFWS)

Potentialtakeofdeserttortoiseduetoremedialactivities.DeserttortoiseislistedasthreatenedunderthefederalESA.TakeisdefinedunderfederalESAas“harass,harm,pursue,hunt,shoot,wound,kill,trap,capture,orcollect,ortoattempttoengageinanysuchconduct.”

Encroachmentpermit U.S.BureauofLandManagement(BLM)

Encroachmentduetoconstructionactivitiesonfederalland

CleanWaterAct(CWA)Section404

U.S.ArmyCorpsofEngineers PotentialpermitforfillthatmayoccurindrainagestotheMojaveRiver.

NewWDRs;CWASection401and402;PorterCologneWaterQualityAct

CaliforniaRegionalWaterQualityControlBoard,LahontanRegion(WaterBoard)

RemediationofchromiumplumeDischargeofpollutantsduringconstruction

Incidentaltakeauthorization(perSection2081oftheCaliforniaFishandGameCode)

CaliforniaDepartmentofFishandGame(CDFG)

PotentialtakeofMohavegroundsquirrelduetoremedialactivities.MohavegroundsquirrelislistedasthreatenedundertheCaliforniaEndangeredSpeciesAct(CESA).TakeisdefinedunderCESAas“hunt,pursue,catch,capture,orkill,orattempttohunt,pursue,catch,capture,orkill.”

Encroachmentpermit CaliforniaDepartmentofTransportation(Caltrans)

Encroachmentinstatehighwayrightofway(ifneeded)

Emissionreductioncreditlease

MojaveDesertAirQualityManagementDistrict(MDAQMD)

Particulateandexhaustemissionimpactsbeyondestablishedthresholds(ifneeded)

Encroachment,drilling,grading,andbuildingpermits

SanBernardinoCounty Drilling,grading,and/orotherconstructionactivitiesandnewbuildings(suchasabove‐groundtreatmentfacilities)inareasunderCountyjurisdiction.

1.4 Intent of the EIR 2

ThisDraftEIRhasbeenpreparedinaccordancewithCEQA,whichrequiresallstateandlocal3

governmentagenciestoconsidertheenvironmentalconsequencesofprojectsoverwhichtheyhave4

discretionaryauthoritybeforetakingactiononthoseprojects(CaliforniaPublicResourcesCode5

Section21000etseq.).6

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TheintentofthisDraftEIRisto:1

Identifypotentialdirect,indirect,andcumulativeenvironmentalimpactsassociatedwiththe2

project.3

Describefeasiblemitigationmeasuresintendedtolessenoravoidpotentiallysignificantproject4

impactsorreducethemtoaless‐than‐significantlevel.5

Disclosepotentialprojectimpactsandproposedmitigationmeasuresforpublicreviewand6

comment.7

Discussprojectalternativesthatavoidorreduceidentifiedsignificantprojectimpacts.8

ThisEIRevaluatessixalternativestoachievethefinalgroundwatercleanup.Allofthealternatives9

involvedifferentcombinationsofseveraltypesofremediationtechnologies,includinggroundwater10

extractionandagriculturalreuse;cleanwaterinjection;groundwaterextraction,aboveground11

treatment,anddischarge;andin‐situtreatment.Thedifferentcombinationsoftheseremediation12

technologiesnotonlyresultincleanuptimesto3.1ppbofCr[VI])rangingfrom29to40years,but13

theyalsoresultindifferingkindsandseverityofimpacts.Thescopeofthealternativeschosentobe14

analyzedinthisEIRwasintendedinparttodemonstratethetradeoffsbetweencleanuptimeand15

environmentalimpactsfromtheremedialactivities.Asremediationactivitiesarerampedupin16

ordertoachievecleanupmorequickly,theseverityoftheenvironmentalimpactspotentiallyalso17

increases.18

Ratherthanselectingoneremediationalternativeastheproposedprojectandprovidingaless19

detailedevaluationofotheralternatives(asCEQAallows),thisEIRprovidesadetailedanalysisofall20

ofthealternatives.TheWaterBoardwillusethisEIRtosupportitsadoptionofWDRsforPG&Eto21

implementthevariousremediationtechnologiesthroughouttheprojectareaandduration,andto22

supportitsadoptionofanewCAO.ThenewCAOwillestablishspecificcleanupobjectivesand23

timelinesbasedontheanalysiscontainedintheEIRandwillrequirePG&Etotakeactionswithinthe24

prescribedtimelinestomeetthecleanupobjectives.AlthoughtheWaterBoardmaydecideto25

identifyinitsnewCAOoneofthealternativesanalyzedintheEIRasthebestmethodtoachievethe26

prescribedobjectivesandtimelines,theWaterBoardmayonlyfocusitsOrderonwaterquality27

outcomesbasedonimplementationofoneormoreoftheremediationtechnologiesanalyzedinthis28

EIR.29

1.5 EIR Organization 30

ThisEIRisorganizedasoutlinedbelow.31

ExecutiveSummary:Providesasummaryoftheprojectandproposedalternativesand32

environmentalimpactsandmitigationmeasures.33

Chapter1,Introduction:Providesanoverviewoftheproject,pastenvironmentalanalysisof34

elementsoftheprojectonwhichthisEIRisbased,anddescribestheWaterBoard’spublic35

outreachactivities,includingsummarizingconcernsraisedduringthepublicscopingmeeting,36

andhowthoseconcernswillbeaddressed,andidentifiesadditionalrequiredpermitsand37

approvals.38

Chapter2,ProjectDescription:Identifiestheprojectlocationandprojectarea,describes39

developmentoftheproposedalternativesandeachofalternativestobeevaluated,disclosesthe40

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alternativesconsideredandwithdrawnfromfurtheranalysis,andidentifiesmitigation1

measuresthatwillbeimplementedaspartoftheproject.2

Chapter3,ExistingConditionsandImpacts:Describestheenvironmentalsettingandpresents3

theimpactanalysisassociatedwithimplementationoftheproposedalternativesforthe4

followingresources:5

3.1,WaterResourcesandWaterQuality6

3.2,LandUse,Agriculture,PopulationandHousing7

3.3,HazardsandHazardousMaterials8

3.4,GeologyandSoils9

3.5,AirQualityandClimateChange10

3.6,Noise11

3.7,BiologicalResources12

3.8,CulturalResources13

3.9,UtilitiesandPublicServices14

3.10,TransportationandTraffic15

3.11,Aesthetics16

3.12,Socioeconomics17

Chapter4,OtherCEQAAnalyses:Presentsthepotentialgrowth‐inducingandcumulativeeffects18

resultingfromimplementationoftheprojectforeachresourcearealistedabove,andidentifies19

theenvironmentallysuperioralternative,significantandunavoidableenvironmentalimpactsof20

theproject,andsignificantirreversibleenvironmentalchangesthatwouldbecausedbythe21

project.22

Chapter5,References23

Chapter6,ListofPreparers24

AppendixA,GroundwaterandRemediationSupportingDocumentation25

AppendixB,AdditionalDataonAlternatives26

AppendixC,BiologicalResourcesReport27

AppendixD,AirQualityandClimateChangeBackgroundInformationandCalculations28

AppendixE,NoticeofPreparationandScopingComments29

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Chapter 2Project Description

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Chapter 2 1

Project Description 2

2.1 Introduction 3

Thischapterdescribestheprojectlocation,definestheprojectarea,establishestheexisting4conditions,identifiesprojectgoalsandobjectives,discussesthecontextforhowtheproject5alternativesweredeveloped,anddescribesthealternativesevaluatedintheEIR.6

PursuanttoexistingWaterBoardorders,PG&Ehasimplementedremediationactivitiestocleanthe7groundwaterimpactedbyhistoricalchromiumdischargesfromPG&E’sHinkleyCompressorStation8(refertoSection1.1,Overview,inChapter1).Theproposedprojectconsistsofexpanded9remediationactivities.ThisEIRevaluatessixalternativeswithdifferenttypesandcombinationsof10additionalremediationactivities,includingplumecontainment,in‐situtreatment,landtreatment,11andabove‐groundtreatment.RefertoSection2.8,ProjectAlternatives,belowforadetailed12descriptionofeach.13

Ratherthanselectingonealternativeastheproposedprojectandprovidingalessdetailed14evaluationoftheotheralternatives(asCEQAallows),theWaterBoardhaselectedtoevaluateeach15alternativewithanequallevelofdetailtoprovidemoredetailedinformationanddisclosureof16impacts.17

2.2 Project Location 18

TheproposedprojectislocatedinSanBernardinoCountyinthetownofHinkley,California.The19PG&EHinkleyCompressorStationislocatedintheMojaveDesertapproximately6mileswestofthe20cityofBarstow,California,andabout1milenorthoftheMojaveRiver.Figure2‐1showstheproject21locationandvicinity.AllChapter2figuresareincludedattheendofthischapter.22

2.3 Project Area 23

AttheinitiationofthisCEQAprocessinlate2010,theprojectareawasdelineatedasthehexavalent24chromiumCr[VI]contamination(orplume)areacontainingmorethan3.1partsperbillion(ppb)of25Cr[VI],includingimmediatelyadjacentareas.Sincelate2010,thedefinedplumeareacontaining26morethan3.1ppbofCr[VI]hasbeendeterminedtobesubstantiallylarger,likelyduetosome27combinationofmovementofthechromiumwithgroundwater(alsocalledplumemigration),more28comprehensivesamplingofadditionalareassurroundingthepriorplumeboundaries,andimproved29understandingofwherethechromiumoccursindifferentlayersoftheaquiferandhowtosampleto30obtainmaximumconcentrations.Inaddition,groundwatermodelinganalysisofprojectalternatives31hasindicatedthatremediationactivitiesmayresultinpotentialgroundwaterdrawdowninareasfar32outsideofthedefinedplumearea.Theprojectarea,therefore,hadtobeexpandedtobeableto33analyzethesepotentialimpactsoftheremediationactivities.34

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Consequently,thecurrentprojectareafortheEIRanalysisencompassestheplumeareaasofthe1fourthquarterof2011(Q42011),adjacentareastothenorth,eastandwestwheretheplumemay2bedefinedinthefuture(duetomigrationandadditionalinvestigation)andwheremonitoring3activitiesmayoccur,aswellasareasofpotentialeffectsduetogroundwaterpumpingfromthe4remediationalternatives.Thisprojectareathatcouldbedirectlyorindirectlyaffectedbytheproject5isapproximately33squaremiles(21,093acres)insizeandextendsapproximately6milesnorth6and3milessouthofStateRoute58(SR58)atitslongestpoint.Itisapproximately6mileseastto7westatitswidestpoint,andgenerallyboundedbyHinkleyRoadonthewest,MountGeneralonthe8northeast,andtheMojaveRiveronthesoutheast.9

ForthepurposesofEIRanalysis,theprojectareaisalsodiscussedintermsofsub‐areas,which10includethefollowing:11

Plumearea,whichisthegeographicallimitsofknowngroundwatercontaminationasofQ4122011;13

Areasinwhichgroundwatercontaminationmaymigrateorbedetectedasaresultofexpanding14themonitoringwellnetwork;15

Operableunits(OUs),whichareareaswherespecificremedialactivitieswouldcontinueorbe16expandedundertheproject;and17

Potentialareasofdirectandindirecteffectsfromtheremedialactivities,suchasbutnotlimited18togroundwaterdrawdown,impairmentofwaterquality,reductionindomesticwatersupplies,19visualeffects,increasednoiseandtraffic,socioeconomiceffects,lossordisturbanceof20endangeredspecieshabitat;monitoringactivities,constructionofsupportinginfrastructureto21implementremediation(suchaspiping,buildings,ethanol,andequipmentstorage),and22constructionofnewwellstoprovidewatersupplies(forfreshwaterinjection,replacement23water,andextractionandinjectionforcleanup).24

Theprojectareaisalsogenerallydiscussedashavingsouth,central,andnorthsectionsrelativeto25thegeographicportionsoftheplume.ThesouthareaextendsfromRiverviewAvenuenorthto26CommunityBoulevardandcontainsthePG&EHinkleyCompressorStation;thecentralareaextends27fromCommunityBoulevardnorthtoSR58;andthenorthareaextendsfromSR58northtothe28northernlimitoftheprojectarea.29

TheEIRprojectarea,includingthesub–areas,isshowninFigure2‐2a.Detaileddescriptionsofthe30plumeareaandOUsareprovidedbelow.31

2.3.1 Plume Area 32

AsdescribedinChapter1,Introduction,theWaterBoardrequiresPG&Etomonitorandreporton33theconcentrationsoftotalchromium(Cr[T])andCr[VI]presenttoestablishtheextentofwaste34chromiumingroundwater.PG&EhassampledforCr[T]andCr[VI]contaminationlevelsformany35yearsbyinstallingmonitoringwellsthroughouttheprojectarea.Monitoringactivitiesconsistof36samplingofgroundwaterandsoils(i.e.,collectionofgroundwaterandsoilsfortesting)andwater37levelreadings.Datacollectedduringsamplingisusedtodeterminethegeographicalvariancein38contaminationlevelsthatisthenusedtodevelopboundariestorepresentthepresenceofCr[T]and39Cr[VI]contamination.Themaximumextentoftheseboundariesischaracterizedastheplumearea40andthegroundwatercontoursfordifferentlevelsofcontaminationaredepictedonplumemaps.At41present,theplumemapsdepictcontoursrepresentingCr[VI]concentrationsof3.1partsperbillion42

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(ppb,essentiallyequivalenttomicrogramsperliter)(Figure2‐2b),10ppb(Figure2‐2c),and50ppb1(Figure2‐2d).Theseconcentrationsweremappedforthefollowingreasons:2

3.1ppbforCr[VI]–Thiscontourtracestheouterboundaryofwhatisdefinedasthechromium3plumeingroundwaterasoftheFourthQuarter2011.The3.1ppbvalueforCr[VI]was4determinedbasedona2007BackgroundStudyReportconductedbyPG&Ethatevaluated5backgroundlevelsofCr[T]andCr[VI]inareasthatwerethenoutsidetherecognizedplume6area.Theresultsofthatstudyestimatedthatmaximumbackgroundlevelswere3.1ppbfor7Cr[VI]and3.2ppbforCr[T]andtheaveragebackgroundlevelswere1.2ppbforCr[VI]and1.58ppbforCr[T](PacificGasandElectric2007).TheWaterBoardwillusethesevaluesascleanup9targetsfortheremediationunlessanduntilnewevidenceisdevelopedthatbackgroundlevels10aredifferentthanthesecleanuptargets1orPG&Edemonstratesthatbackgroundlevelsofwater11qualitycannotberestored,atwhichtimetheWaterBoardwillidentifythebestwaterquality12achievable,consistentwiththeproceduressetforthinStateWaterResourcesControlBoard13Resolution92‐49(describedindetailinSection2.5below).14

10ppbforCr[VI]–Thiscontourdefinestheportionoftheplumewheremedium‐level15concentrationsoccur.The10ppblevelisnottiedtoaregulatorylevelorabackgroundlevel.16

50ppbforCr[T]orCr[VI]–ThiscontourdefinestheportionoftheplumewhereinCr[T]or17Cr[VI]concentrationsareatorabovetheCaliforniaMaximumContaminantLevel(MCL)of5018ppbforCr[T],whichincludesCr[VI].TheMCListhecurrentdrinkingwaterstandardandisonly19specifiedfortotalchromium,nothexavalentchromium.20

Sinceinitiatingmonitoringactivities,PG&Ehaspreparedquarterlygroundwatermonitoringreports21(GMP)inaccordancewithWaterBoardordersthathavebeenusedtotracktheareaof22contamination.GMPsarealsousedasameanstodetermineeffectivenessofremediationactivities23beingimplementedaswellastheirabilitytomeetinterimremedialtargets.Insamplingfrom24monitoringwellsconductedbetween2006throughthesecondquarterof2010(Q22010),alevelof254.0partsperbillion(ppb)wasusedtodelineatetheextentoftheplumearea.Subsequently,the263.1ppbCr[VI]andCr[T]levelshavebeenusedtodelineatetheextentoftheplumearea.27

Figures2‐2bthrough2‐2dillustratetheprogressionoftheplumeareaboundariesfrom200828throughtheendof2011.29

2.3.2 Operable Units 30

ThreeOUs(OU1,OU2,andOU3)weredefinedtogenerallyrepresentareasinwhichdifferenttypes31ofremedialactivitieswouldbeimplementedinrelationtothevariousgroundwatercontamination32levelsrepresentedbytheplumearea(seeFigures2‐2ato2‐2d).TheOUlocationsandtheir33boundariesaredescribedbelow.Adetaileddescriptionofthetypesofremedialactivitiestobe34implementedwithineachOUisprovidedinSection2.9,Construction,Operation,andMaintenance.35

OU1extendsfromthesourceareainthesouthtotheapproximatenorthernextentofthe50ppb36groundwatercontouroftheplume.TheOU1areaencompassesapproximately1,378acresand37istheareawiththehighestlevelsofchromiumcontamination.Remedialactivities(in‐situ,land38

1AsdescribedinSections1.2.1and3.1,WaterResourcesandWaterQuality,theWaterBoardinitiatedapeerreviewin2011ofthe2007BackgroundStudyReportandisevaluatingthepotentialreevaluationofthe2007dataand/orconductinganewbackgroundstudy.Theseeffortsmayresultinidentificationofdifferentbackgroundlevelsthanthe2007study.

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treatment,andabove‐groundex‐situtreatment)aimedattreatingthehighestconcentration1portionsoftheplumewouldlikelybelocatedwithinOU1.Existingin‐situremediationzones2(IRZs)arelocatedwithinOU1.3

OU2extendsfromthenorthernboundaryofOU1northtoSalinasRoadandcontainsmostofthe410ppbgroundwatercontouroftheplumearea(thatisoutsidethe50ppbcontour).TheOU25areaencompassesapproximately1,715acres.Thisareacontainstheexistingagricultural/land6treatmentunits2,includingtheDesertViewDairylandtreatmentunit,theformerGormanand7Cottrellpropertyagriculturalunits,andtheRanchagriculturalunit.8

OU3encompassestheportionoftheprojectareathatisoutsideofandadjacenttoOU1andOU2.9Thisincludesareaswheretheplumemaymigrate,andfutureremedialactions,monitoring10activitiesanddirectandindirecteffectsofremedialactions(suchasthoseasdescribedabove)11mayoccur.Itispossiblethatthemaximumextentoftheplumeareamaychangecomparedto12thelate2011plumeareaandthatremedialactionsmayultimatelybenecessarybeyondtheOU313boundaryandpossiblyoutsideoftheoverallEIRprojectareaasshowninFigure2‐2a.The14currentOU3areaencompassesapproximately16,765acres.15

Forthepurposesofthisanalysis,remedialactionsareassumedtopotentiallyoccurwithinany16portionofOU3.However,therearepracticalconstraintswithincertainareasincludedinOU3that17mayinfluencewhereremedialactionsaremostlikelytooccur.Forexample,OU3containsareasof18steeplyslopinggroundtothewestandeastoftheHinkleyValley.Itisunlikelythatabove‐groundex‐19situtreatmentfacilitiesoragriculturalunitswouldbeplacedinsuchareas.Similarly,OU3contains20residentialareasnorthoftheHinkleySchoolwheremonitoringwellsmightbeplaced,butitwould21notbefeasibleordesirabletoplaceagriculturalunitsintheseresidentialareas.Themostlikely22areasofremedialactioninOU3arewithintheboundariesoftheplumeasknowninlate2011,23depictedinFigure2‐2a.24

2.4 Existing Conditions 25

AsdiscussedinChapter1,Introduction,theWaterBoardpreviouslyissuedCAOsrequiringactions26topreventplumemigrationandactionstocleanuptheaffectedgroundwater.TheWaterBoard27preparedCEQAdocumentationforallWDRsissuedtoimplementremedialactivities,suchasin‐situ28remediation,agriculturallandtreatment,andfreshwaterinjection.IftheWaterBoardtakesno29furtheractiononthecleanup,PG&EwillstillbeobligatedtofulfillthepriorCAOrequirementsand30canimplementremedialactivitiescurrentlyallowedunderexistingWDRswhosepotential31environmentalimpactswerepreviouslyevaluatedunderCEQA.TheseCEQAdocuments,all32mitigatednegativedeclarations,encompasstheareafromtheCompressorStationto1,000ftnorth33oftheDesertViewDairyonMountainViewRoad,whichisabout3milesinlength.34

SincetheNoticeofPreparation(NOP)oftheEIRwaspublishedinlate2010,theprojectareaandthe35amountofexistingremedialactionshavebothexpanded.Thesechangesneedtobeaccountedfor36whendescribingtheexistingconditionsagainstwhichpotentialenvironmentalimpactswillbe37

2Landtreatmentisperformedbyirrigatinglandwithchromium‐ladenwaterresultingintransformationofdissolvedCr[VI]tosolidCr[III]throughmicrobialactionandchemicalreactionsinsoil.Landtreatmentunitsinvolvedispersingwateronsoilwithorwithoutcrops,whereasagriculturalunitsincludegrowingcrops.TherearemoreagriculturalunitsthanlandtreatmentunitsatpresentandinthealternativesconsideredinthisEIR;theterm“agriculturalunit”issometimesusedtorefertoboth.

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analyzed.Therefore,forthepurposesofthisEIRanalysis,theexistingconditionsaredefinedasthe1physicalconditionsonthegroundasoflate2011.Inordertofullydiscloseproject‐relatedimpacts,2impactsofallprojectalternativeswillbecomparedtotheexistingconditions(late2011)insteadof3physicalconditionsthatwerepresentwhentheNOPwaspublishedinlate2010.4

Table2‐1summarizesandFigure2‐2eshowsthecharacteristicsofexistingremediationactivities5andtheremediationinfrastructurecurrentlyinplaceandoperatingintheprojectarea.Remediation6activitiesforchromiumcontaminationarecurrentlybeingimplementedwherepastandongoing7remediationpilottestingandexperiencehasshowntreatmenttobeeffective.Thecurrenttreatment8approachesandtechnologiesbeingimplementedwithintheprojectareainclude:9

In‐situtreatmentofthehigher‐concentrationplumeintheIRZareaswithinthesouthandcentral10sectionsofOU1.TheIRZareasaregenerallydividedintotheSourceAreaIRZ,theSouthCentral11ReinjectionAreaIRZ,andtheCentralAreaIRZ.Groundwaterextractedwithintheseareasis12carbon‐amended(e.g.,ethanolorlactate)andinjectedineitherarecirculationloop13configurationorasspotinjections(alsoreferredtoasdosed‐injectioninTable2‐1below).14

Plumecontainmentandlandtreatmentusingwaterextractedfromthelow‐concentration15northernandfringeportionsoftheplume.Fiveagriculturalunitsarecurrentlybeingoperated16(2Gorman,1Cottrell,1Ranch,andtheDesertViewDairylandtreatmentunit).Extractionwells17areoperatedtoaugmentcontainmentpumpingandforapplicationofwatertotheagricultural18unitsthroughaconveyancesystemofpiping.19

Plumecontainment(orhydrauliccontrol)usingfreshwaterinjectiontofivewellslocatedinthe20northarea,directlyadjacenttothewesternboundariesofOU1andOU2.Freshwaterisextracted21fromthreesupplywells(PGE‐14,FW‐01,andFW‐02)locatedsouthoftheCompressorStation22property.ThewaterfromwellPGE‐14isfilteredforarsenicandcombinedwiththewaterfrom23theothertwowells,whichhavelowarsenicconcentrations;andthatwaterisconveyedthrough24apipelinetothenorthernfreshwaterreinjectionwells.Theresultinggroundwatermound25createsahydraulicbarrierandpreventsfurtherplumemigrationtothewest.26

Monitoring.Inadditiontothecontainment,landtreatment,andin‐situactivities,PG&Eoversees27anextensivenetworkofmonitoringwells,whicharelocatedthroughouttheprojectarea.28Monitoringwellsareconstructedwithscreensacrossvariousdepthsoftheupperaquiferandin29theloweraquifer.Monitoringactivitiesincludegroundwatersamplingandwaterlevelreadings.30Groundwatersamplingfrequencyrangesfromquarterlytosemi‐annuallyorannually,although31PG&Emaysometimessamplemorefrequentlywhenanewmonitoringwellisinstalled.Water32levelreadingsareconductedconcurrentwiththegroundwatersamplingactivities.Themajority33ofaccessroadstowellsandtheagriculturalunitsarefromsecondarydirtroadsor,where34feasible,frompublicstreets.Existingpublicstreetsarealsousedasthemainpointofaccessto35dirtroads.36

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Table 2‐1. Summary of Remedial Components under Existing Conditions 1

AgriculturalLandApplicationAgriculturalUnits 182acaAgriculturalUnitExtractionWells 29Trenches(maycontainmultiplepipelines) 24,499linearfeet(lf)AgriculturalUnitExtractionflowb,c 1,100gpmIn‐SituRemediation(IRZ)

ExtractionWells 12InjectionWells 58Pipelines 14,985lfCarbon‐amendedIRZflow(SouthCentralAreaIRZ,SourceAreaIRZ)c

190gpm

IRZrecirculationflow(CentralAreaIRZ,SourceAreaIRZ)c

83gpm

NorthwestFreshwaterReinjectionExtractionWells 3InjectionWells 5Pipelines 31,886lfFreshwaterinjectionflowc 80gpmMonitoringWellsandOtherInfrastructureMonitoringWells 434WellsandSupportinginfrastructured 36acresAccessroads 1acreNotes:a AgriculturalUnitsincludetheDesertViewDairy+4pivots[Gorman(2),Cottrell,Ranch])b Flows(gpm)forDesertViewDairylandtreatmentunitareincludedinagriculturalunittreatmentflowsforallalternatives.

c Allflowsareaverageannualpumpingrates.d Includesareaforagriculturalunits,IRZ,andnorthwestreinjectionwellsaswellasmonitoringwells.

2.5 Whole‐House Replacement Water 2

AsdescribedinSection1.2.1,TimelineofActivities,inChapter1,Introduction,PG&Eisrequiredto3provideinterimandwholehousereplacementwaterservicetothoseservedbydomesticor4communitywellsthatarewithintheaffectedareaofthechromiumplumeanddeterminedtobe5impactedbythePG&Echromiumdischargeforallindooruses,includingdrinking,cooking,bathing,6andhygiene(CAONo.R6V‐2011‐0005A1andR6V‐2011‐0005A2).Thisorderappliestoalldomestic7supplywellsaffectedbyPG&E’swastedischargeofchromiumwithin1miledowngradientorcross8gradientfromthemostrecentplumeboundary,definedbythemaximumbackgroundchromium9concentrations,currently3.1ppbCr[VI]/3.2ppbCr[T].10

2.5.1 Affected Wells Eligible for Replacement Water 11

CaliforniaWaterCodesection13304(a)allowstheWaterBoardtorequirereplacementwaterfor12wells“affected”byadischargeofwaste.“Affectedwells”arethosethatdonotmeetfederal,state13

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andlocaldrinkingwaterstandards.Wherenofederal,state,orlocalstandardyetexists,asisthe1situationforhexavalentchromium,theStateWaterBoardWaterhasconcludedthat“itis2appropriatetousegoalsdevelopedbyagencieswithexpertiseforpublichealthdeterminationsin3decidingwhetherreplacementdrinkingwaterisnecessary”(WaterQualityOrder2005‐007,the4“OlinOrder”).5

BecausenoMCLforhexavalentchromiumhasbeenset,theWaterBoardisrelyingonthePublic6HealthGoalof0.02ppbhexavalentchromiumtodetermine“affectedwells”requiringreplacement7waterpursuanttoCAOR6V‐2011‐0005A2.Duetothecurrentlimitationsoflaboratoriestodetect8hexavalentchromiumdowntothePublicHealthGoalof0.02ppb,affectedwellsarethosethat9containanyhexavalentchromiumabovethecurrentlaboratorydetectionlimit,whichis0.06ppb.10

2.5.2 Replacement Water Provision before an MCL is Adopted 11

CAOR6V‐2011‐0005A2addressesimpactstowatersupplywellsfromtheexistingchromiumplume,12whicharenotconsideredimpactsunderCEQAbecausetheywerenotcausedbytheimplementation13oftheproject(remedialactivities).Thechromiumplumeingroundwaterispartofthebaselineor14existingconditionsoftheprojectareacausedbypastactionsofPG&Ewhenwastechromiumwas15dischargedtogroundwaterinthe1950sand1960s.Thatdischargeofwasteissubjecttoregulatory16andenforcementactionsbytheWaterBoard,suchasCAOR6V‐2011‐0005A2,butisnotanimpact17oftheprojectunderCEQAbecauseitisnotcausedbytheproject(where,ashere,theprojecthereis18tocleanuptheplume).19

ThereplacementwatersupplyprogramrequiredbyR6V‐2011‐0005A2willcontinue,ataminimum,20untilafinalMCL(ordrinkingwaterstandard)forhexavalentchromiumisadoptedbytheCalifornia21DepartmentofPublicHealth(CDPH).22

AsdiscussedinSection3.1,WaterResourcesandWaterQuality,ifremedialactivitiessignificantly23affectwaterqualityconditionsforwatersupplywells,replacementwaterwillalsoberequiredas24mitigationforremedialimpacts.25

2.5.3 Replacement Water Provisions after an MCL is Adopted 26

AfterCDPHadoptsanMCLforhexavalentchromium,requirementspertainingtoprovidingwhole‐27housereplacementwatertoaffectedwellswillonlyapplytolocationswithwellscontaining28hexavalentchromiumatlevelsabovetheMCLlevelestablishedbyCDPH.Atthattime,PG&E’s29obligationunderCAOR6V‐2011‐0005A2toprovidewholehousereplacementwaterceasesfor30thoselocationswithfourconsecutivequartersofhexavalentchromiumdetectionswhichdonot31exceedtheMCL.32

AsdiscussedinSection3.1,WaterResourcesandWaterQuality,ifremedialactivitiessignificantly33affectwaterqualityconditionsforwatersupplywells,replacementwaterwillalsoberequiredas34mitigationforremedialimpacts.35

2.6 Project Goal and Objectives 36

Thefollowingprovidesabriefcontextforthediscussionoftheprojectgoalandobjectives.37

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The2008CAONo.R6V‐2008‐0002requiredPG&EtosubmitafeasibilitystudybySeptember1,12010(the2010FeasibilityStudyisdescribedinmoredetailinSection2.6below)thatassessed2remediationstrategiesforchromiumandproposedafinalgroundwaterremediationproposalto3achievecompliancewithStateWaterResourcesControlBoard(SWRCB)Resolution92‐49,“Policies4andProceduresforInvestigationandCleanupandAbatementofDischargesUnderWaterCode5Section13304”(Resolution92‐49).6

Resolution92‐49requiresadischargerto:7

Developacleanupplanthatevaluatesmultipleremediesandweighsthemagainstnumerous8factorssuchas:9

Abilitytoachievebackgroundlevels;310

Timeframetoachievebackgroundlevels;and11

Potentiallysignificantimpacts.12

Proposeacleanupplanthateithertargetsgroundwatercleanuptobackgroundlevelsor13providestheappropriatejustificationforahigherstandard;and14

Considerwhatisreasonablewhenevaluatingacleanupgoal,takingintoaccountthetechnical15andeconomicfeasibilityofattainingbackgroundconditions,theprojectedtimeframetoachieve16backgroundconditions,andthemaximumbeneficialuseoftheresourcebeingprotected.17

2.6.1 Project Goal 18

Thegoaloftheprojectistorestoregroundwaterqualitytobackgroundlevelsofchromiuminthe19minimumamountoftimepracticable,whilelimitingormitigatingenvironmentalimpactsassociated20withthecleanupactivities.21

TheWaterBoardhastheauthoritytorequirecleanupofanygroundwateraffectedbychromium22dischargedfromPG&E’sHinkleyCompressorStation.Groundwaterisconsideredtobeaffectedby23PG&E’sdischargeifthelevelsofchromiumareabovenaturallyoccurringbackgroundlevelsasa24resultofCompressorStationoperations.25

ForthisEIR,theanalysislooksatcleanuptothechromiumbackgroundlevelssetinCAONo.R6V‐262008‐002A1because,inpart,PG&E’sfeasibilitystudyandaddendahaveconsideredcleanupto27thoselevelsandthatanalysishasgenerallyshownthatitispossibletomeetthoselevels.Inthe28future,theWaterBoardmayidentifyadifferentbackgroundlevelandmaysetcleanuplevelsto29meetthatnewbackgroundlevel.IfPG&Eisabletoshowthatitisnotfeasibletorestorewater30qualitytobackgroundlevels,theWaterBoardmayrequirecleanuptothebestwaterquality31reasonablyachievable,afterconsideringanumberoffactorsidentifiedinStateWaterResources32ControlBoardResolution92‐49,subsectionG.Aslongastheremedialactivitiesthatwouldbe33necessarytomeetanynewcleanupobjectivesaresimilartothoseanalyzedinthisEIRandany34associatedenvironmentalimpactsdonotexceedwhathadbeenanalyzedinthisEIR,theWater35Board’sconsiderationoftherevisedcleanupobjectivesandapprovalofneworamendedWDRscan36relyuponforCEQAcompliancetheevaluationinthisdocument.37

3Theterm“backgroundlevel”referstothewaterqualitythatexistedbeforethedischarge.

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2.6.2 Project Objectives 1

Thespecificprojectobjectivesareto:2

Containthecontaminatedgroundwaterplumehorizontallyandverticallyimmediatelyand3continuouslyintheareadescribedintheamendedCAONoR6V‐2008‐0002A3.4

Containthecontaminatedgroundwaterplumeoverall.5

Reducemaximumgroundwaterconcentrationsto3.2ppbCr[T]and3.1ppbCr[VI]asdescribed6inCAONo.R6V‐2008‐0002A1.7

Reduceaveragegroundwaterconcentrationsto1.2ppbCr[VI]and1.5ppbCr[T],asdescribedin8CAONo.R6V‐2008‐0002A1.9

Restorebeneficialusesofthegroundwaterbyachievingthecleanuplevelsnotedaboveinthe10minimumtimefeasible.11

Limitormitigateenvironmentalimpactsassociatedwiththecleanupactivities.12

Overall,theseobjectivesareintendedtoreducechromiumconcentrationsingroundwatertothe13cleanuptargetsandcontainthegroundwaterplume.4Developmentoftheseobjectivestakesinto14considerationtheavailabletechnologies,recoveryofbeneficialuses,short‐termeffectiveness,long‐15termeffectiveness,andcommunityconcerns.Together,theseobjectivesareintendedtorestore16beneficialuses5tothegroundwateraquifer.17

2.7 Development of Project Alternatives 18

DevelopmentoftheprojectalternativesbytheWaterBoardwasprimarilybasedontheWater19Board’sindependentreviewofinformationcontainedinthe2010FeasibilityStudy6andits20Addendum1and2,theinputandsuggestionsofthepublic(asdescribedinChapter1,Introduction),21independentreviewofthefeasibilitystudyandaddendabytheU.S.EnvironmentalProtection22AgencyandtheCaliforniaDepartmentofToxicSubstancesControl,aswellasinformationbasedon23previousandexistingPG&EremedialpilotprojectsinHinkley.Thefeasibilitystudyanditsaddenda24provideextensivedetailregardingthepotentialtechnologies,theireffectivenessatmeetingcleanup25objectives,andlogistical,technological,andeconomicfeasibility.26

The2010FeasibilityStudyinitiallyscreened36chromiumcleanuptechnologies/approaches(also27referredtoasremediationoptionsortreatmentapproaches)withpotentialtobefeasibleand28

4Minorexpansionofthechromiumplume,incidentaltotheremediation,suchaslimited“bulging”duetoinjectionofwaterassociatedwithremediationactivitieswouldbeconsistentwiththeseobjectivessimilartotheminorexpansion(upto1,000feet)allowedbyAmendedCAONo.R6V‐2008‐0002A2providedthatchromiumwillbecapturedbythegroundwaterextractionsysteminthedowngradientflowdirection.5DesignatedbeneficialusesfortheHinkleyaquiferintheBasinPlan(seediscussioninSection3.1)include:municipalanddomesticsupply;agriculturalsupply;industrialservicesupply;freshwaterreplenishment;andaquaculture.6Apriorfeasibilitystudywascompletedin2002andwasalsoconsideredbyWaterBoardstaff,butthe2010feasibilitystudy(anditsaddenda)isamorecomprehensiveevaluationofpotentialremedialapproachesfrom2002through2010andistheprimarysourceofinformationusedtohelpdefineprojectalternatives.The2002feasibilitystudyisavailablefromtheWaterBoarduponrequest.

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effectiveforcontainmentandcleanupoftheplume(PacificGasandElectric2010).These361technologiescangenerallybecategorizedintothefollowingremedialapproaches:2

PlumeContainmentthroughGroundwaterExtraction:Extractingcontaminated3groundwaterattheouteredgeoftheplumetopreventfurtherspreadingoftheplume.4

PlumeContainmentthroughCleanWaterInjection:Injectingclean(non‐contaminated5water)attheouteredgeoftheplumetocreateahydraulicbarriertopreventfurtherspreading6oftheplume.7

GroundwaterExtractionandLandTreatment(withAgriculturalReuse):Extracting8contaminatedgroundwaterandapplyingittolandwheresoilmicrobialactionwillreduce79dissolvedCr[VI]tosolidCr[III].10

Plume‐wideIn‐SituTreatment:Throughouttheplume,injectingbiologicalandchemical11reductants(food‐gradecarbonsourcessuchasethanolorlactate)directlyintothe12contaminatedgroundwatertopromotemicrobialreductionofCr[VI]toCr[III]withinthe13aquifer.Cr[III]hasverylowtoxicityandisanessentialdietarynutrient.Itistypically14immobilizedinsoilsandtendsnottodissolveeasilyingroundwater.15

Plume‐core8OnlyIn‐SituTreatment:Onlyinthesourcearea(i.e.,OU1),injectingbiological16andchemicalreductantsdirectlyintothecontaminatedgroundwatertopromotemicrobial17reductionofCr[VI]toCr[III]withintheaquifer.18

Ex‐SituTreatment(i.e.,above‐ground)andDischargetoLand:Extractingcontaminated19groundwaterandphysicallyseparatingCr[VI]fromthewater,disposingoftheprecipitated20Cr[VI]offsite,anddischargingthetreatedwatertoland.Alternatively,ex‐situtreatmentcould21usebiologicalandchemicalreductantstoreduceCr[VI]toCr[III]incontaminatedwaterand22thendischargethetreatedwatertoland.23

Ex‐SituTreatmentandInjectiontoGroundwater:Extractingcontaminatedgroundwaterand24physicallyseparatingCr[VI]fromthewater,disposingoftheprecipitatedCr[VI]offsite,and25injectingthetreatedwaterdirectlyintotheaquifer.Alternatively,ex‐situtreatmentcoulduse26biologicalandchemicalreductantstoreduceCr[VI]toCr[III]incontaminatedwaterandthen27injectthetreatedwaterdirectlyintotheaquifer.28

Manyofthetechnologiesstudiedinthefeasibilitystudyandaddendawereincludedinoneormore29ofthealternativesevaluatedinthefeasibilitystudyand/orincludedintheprojectalternatives30evaluatedinthisEIR.Someoftheapproacheswerenotadvancedfurtherandarenotconsideredin31detailinthisEIR.Section2.10belowdiscussesthereasonswhycertaintechnologies/approaches32werenotstudiedfurther.33

7“Reduce”inthiscontextreferstoachemicalreactionthataddselectronstoachemicalspecies.Chromiumhas24protonsand24electronsinitsneutralstate.Cr[VI]has24protons,butonly18electronsandanoxidationstateof+6.Cr[III]has24protonsand21electronsandanoxidationstateof+3.Inthiscase,reductionofCr[VI]toCr[III]meansthatthechemicalreactionadds3electronstoeachCr[VI]moleculewhichreducesitsoxidationstatefrom+6to+3,therebyconvertinghexavalentchromiumtotrivalentchromium.8Theterm“plume‐core”isonlyusedtorefertothetechnologiesconsistentwiththeterminologyusedinthefeasibilitystudy.

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2.7.1 2010 Feasibility Study (September 2010) 1

Inthe2010FeasibilityStudy,theselectedtechnologieswerecombinedtoformfivealternativesto2addressthechromiumcleanupgoalsspecifiedintheprojectobjectives.Thesefivealternativeswere3asfollows:4

FeasibilityStudyAlternative1.Nofuturepumpingorgroundwatertreatment;cleanup5achievedthroughnaturalattenuation.Estimatedtimetocleanupto3.1ppbCr[VI]:>1,000years6

FeasibilityStudyAlternative2.Containmentbyinjectingfreshwateratthetoeoftheplume7andlandtreatment.Estimatedtimetocleanupto3.1ppbCr[VI]:260years8

FeasibilityStudyAlternative3.Plume‐widein‐situtreatmentusingexistingandnew9proposedinjectionwells.Estimatedtimetocleanupto3.1ppbCr[VI]:110years10

FeasibilityStudyAlternative4.In‐situtreatmentinOU1andlandtreatmentusingoneexisting11andonenewagriculturalunit.Estimatedtimetocleanupto3.1ppbCr[VI]:150years12

FeasibilityStudyAlternative5.Plume‐widepumpandtreatex‐situ,usingexistingandnew13injectionandextractionwellsandnewabove‐groundtreatmentfacilities.Estimatedtimeto14cleanupto3.1ppbCr[VI]:140years15

BasedontheWaterBoardstaff’sindependentreviewofthe2010FeasibilityStudy,itwas16determinedthatnoneofthefiveprimaryalternativesdescribedabovemettheprojectgoaland17objectivesforthefollowingreasons:theproposedtimeframesforcleanupandbeneficialuses18restorationachievedbythefiveoriginalalternativesweretooslow;thealternativesdidnotappear19tocleanupcontaminationintheminimumtimefeasible;andduetoalargerplumeareainlate202011/early2012thanin2010,noneofthefiveoriginalalternativeswerespecificallydesignedto21containthelargerplume.22

TheWaterBoardstaffrequestedPG&Etodevelopadditionalalternativesthatincludedplume23containment,ex‐situtreatment,in‐situtreatment,andlandtreatmentthatcouldachievecleanup24fasterandcontrolplumemigrationbetterthanthefive2010FeasibilityStudyalternatives.25

2.7.2 2010 Feasibility Study Addendum 1 and Addendum 2 26

(January/March 2011) 27

BasedonWaterBoarddirection,PG&Edevelopedtwoadditionalalternativestoaccelerate28groundwatercleanupandtoprovidemorecomprehensiveplumecontainment,whichwerethebasis29ofFeasibilityStudyAddendum1(PacificGasandElectric2011a).30

Alternative4A:Hydrauliccontainmentofthechromiumplumethroughgroundwater31extractionandinjection,in‐situtreatmentusingIRZchromiumconversionfromCr[VI]toCr[III],32andtreatmentofaportionoftheextractedgroundwaterinagriculturalfields.Alternative4Ais33enlargedinscaleoverthe2010FeasibilityStudyAlternative4byanincreaseintheCentralArea34IRZ,expansionofagriculturalunits,increasedIRZoperationsby15years,andincreased35volumesofgroundwaterextractionforapplicationtoexpandedagriculturalunits.Estimated36timetocleanupto3.1ppbCr[VI]:75years37

CombinedAlternative:Hydrauliccontainmentofthechromiumplumethroughgroundwater38extractionandinjection,corein‐situtreatment,above‐groundtreatmentofthehigh39concentrationportionoftheplume,groundwaterextractionandlandtreatmentofthelow40

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concentrationportionoftheplumethroughexpandedagriculturalunitstoachievetheproject1objectives.Estimatedtimetocleanupto3.1ppbCr[VI]:90years2

Uponreviewoftheeffectivenessofthesealternatives,theWaterBoardrequestedthatPG&E3investigateoptionstousetechnologiesemployedinAlternative4Atofurtherreducethetime4necessarytomeettheprojectobjectivesandtoprovideformorecomprehensiveplumecontrol.Asa5result,PG&EissuedaFeasibilityStudyAddendum2(PacificGasandElectric2011b)thatdescribed6Alternative4B.7

Alternative4B.ThisalternativeusesthesameapproachasAlternative4A,butitincludes8additionalextractionwellsforagriculturallandtreatmentandotherfacilitiesthatmore9effectivelyremovetheCr[VI]contaminationthanAlternative4Aandsignificantlyaccelerates10cleanuptimes.Estimatedtimetocleanupto3.1ppbCr[VI]:40years11

2.7.3 2010 Feasibility Study Addendum 3 (September 2011) 12

FollowingreviewofFeasibilityStudyAddendum2,theWaterBoardsolicitedinputfromthe13CaliforniaDepartmentofToxicSubstancesControl(DTSC)andtheU.S.EPAonthe2010Feasibility14Study,FeasibilityStudyAddendum1,andFeasibilityStudyAddendum2.Basedonthisinputand15review,theWaterBoardrequestedPG&Etodevelopfurtheroptionstoimplementaprogramthat16maintainedmaximumyear‐roundpumpingandplumecontainment,evaluatedtheneedforand17effectivenessofvaryingpumpingschedules,furtherevaluatedthepotentialforadditionalcleanup18time‐framereductionfromthatestimatedunderAlternative4B,developedmilestonesforcleanup19ofdifferentparts(or“operableunits”)oftheplume,developedoptimizationperiodstofacilitate20adaptivemanagementoftheremedialactivities,andestablishedacontingencyplantomaintain21year‐roundplumecapture.Optimizationreferstochangesthatwouldbemadeintheremediation22systemconfiguration(e.g.,changeextractionwelllocations)tomaximizeremediationasplume23cleanupprogressesandtheplumeshapechanges.24

InresponsetotheWaterBoard’srequest,PG&Edevelopedfouradditionalalternativesaspartof25FeasibilityStudyAddendum3(PacificGasandElectric2011c)thatusedthesamegeneral26remediationtechnologiesasthepreviouslystudiedAlternative4Bwiththeadditionof27extraction/treatmentfeaturesandincreasestoextractionflowrates,continuousyear‐round28pumpingforenhancedyear‐roundhydrauliccontrol,winter‐cropagriculturalunitoperation,and29theconsiderationofwinterwatertreatmentbyanex‐situ(above‐ground)treatmentplant.The30purposeoftheex‐situtreatmentapproachistomaintainfixedrate,year‐roundextractionrates31sincetheagriculturalunitshaveareducedcapacitytotreatwateronaper‐acrebasisduringwinter32monthswhenlesswatercanbeabsorbed.Theadditionalalternativeswere:33

Alternative4C‐1.In‐situandenhancedagriculturaltreatment,includingadditionalextraction34wellsandagriculturalunitsandassociatedinfrastructurewithhigherextractionrates.Onlyone35cropwouldbeusedforeachagriculturaltreatmentunit,resultinginseasonalfluctuationsin36flowrates.Estimatedtimetocleanupto3.1ppbCr[VI]:40years37

Alternative4C‐2.Samein‐situandenhancedagriculturaltreatmentasAlternative4C‐1,except38awintercropwouldbeaddedtoincreaseextractionratesinwinterrelativetoAlternative4C‐2.39Estimatedtimetocleanupto3.1ppbCr[VI]:39years40

Alternative4C‐3.Samein‐situandenhancedagriculturaltreatmentasAlternative4C‐2with41operationsduringsummerandwinterandtheadditionofex‐situtreatmentwithadditional42

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injectionwellstoaccommodatetheexcessflowfromtheagriculturalunitsinthewinterinorder1tomaintainacontinuousextractionflowyear‐round.Estimatedtimetocleanupto3.1ppbCr[VI]:236years3

Alternative4C‐4.Samein‐situasAlternative4C‐2withsubstantiallyexpandedagriculture4operationsoccurringduringsummerandwinter,withadditionofnewagriculturalunitsfor5winter‐onlyoperationsinlieuofex‐situtreatmentinordertomaintaincontinuousextraction6flowyear‐round.Estimatedtimetocleanupto3.1ppbCr[VI]:29years7

AfterreviewofFeasibilityStudyAddendum3,theWaterBoardrecommendeddevelopmentofa8moreaggressivecombinedalternativethatapproximatelymatchedthecleanuptimeframeof9Alternatives4C‐1through4C‐4whileprovidingforremovalofchromiumfromtheaquiferinthe10highconcentrationportionoftheplume.PG&Edevelopedanew“Alternative4C‐5”inMarch2012to11respondtotheWaterBoard’srecommendation.12

Alternative4C‐5.Thisalternativecombinesthein‐situandlandtreatmentapproaches13proposedunderAlternative4C‐2withex‐situapproachesproposedundertheprevious14CombinedAlternativetoremovechromiumfromtheoverallsitefromthehighconcentration15portionoftheplume.Estimatedtimetocleanupto3.1ppbCr[VI]:50years16

2.8 Scaling Approach to Address Recent Plume 17

Changes 18

Thefeasibilitystudyevaluations(andaddenda)werebasedonthecontaminatedplumeasitwas19definedatthetimeoftheevaluation.ThecurrentchromiumplumeasofQ42011isapproximately202,949acres,whichismuchlargerthantheplumethatwasstudiedinthefeasibilitystudyas21describedbelow:22

Alternative4B.FeasibilityStudyAddendum2usedtheQ12010plumeasitsbaseconditionfor23studyforAlternative4B.TheQ12010plume(definedbythe3.1ppbCr[VI]contour)was24approximately1,225acresinsize.25

Alternative4C‐1toAlternative4C‐5.Asnotedabove,FeasibilityStudyAddendum3studied26boththeQ12010plumeandtheQ12011plume.Addendum3(andsubsequentdataprovided27byPG&E)presentedanidentificationofinfrastructureneededtoaddresstheQ12011plume.28TheQ12011plume(definedbythe3.1ppbCr[VI]contour)wasapproximately1,788acresin29size.30

Thefullextentoftheplumeareacannotbedefinedatthistimebecausetheplumeboundarymaybe31largerthantheQ42011delineatedboundaryasaresultoffurtherinvestigationand/orplume32migration.Therefore,forthisEIR,ithasbeenassumedthatthecontaminatedplumemaybelarger33byupto15%fromtheQ42011plume,whichwouldresultinatotalplumeareaof3,391acres.This34plumeareaisapproximately190%largerthantheQ12011plumeand277%largerthantheQ1352010plume.36

Toprovideanestimateofthepotentialexpandedamountofremedialactivitythatmaybenecessary37toaddressafutureplumethatissubstantiallylargerthanthatusedasthebaseconditionfor38identificationofremedialactivitiesproposedinthefeasibilitystudy(andaddenda),thefeasibility39studyestimatesofremedialactivitywerescaledasfollows:40

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California Regional Water Quality Control Board, Lahontan Region  Project Description 

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

2‐14 August 2012

ICF 00122.11

 

NoProjectAlternative.TheNoProjectAlternativewasnotscaledupasitispresumedthat1remedialactivitywillbelimitedtotheareaoftheplumeasidentifiedbetween2008and2010.2

AgriculturalLandTreatment.Agriculturalunitacreages,piping,wells,andextractionflows3werescaledupbyincreasingthefeasibilitystudyamountstoincludeadditionalagriculturalunit4acreage,infrastructure,andflowstotreattherevisedplumearea.5

In‐SituRemediation.In‐situremediationisprimarilyproposedtoaddressthehigh6concentrationpartoftheplume(>50ppb)andsomeofthemediumconcentrationpartofthe7plume(>10ppb).The50ppbplumeboundaryhasbeenmostlystableinrecentyearsdueto8remedialactions.The10ppbplumeboundaryhasexpandedbutnottothesamedegreeasthe93.1ppbplumeboundary.Asaresult,scalingforin‐situremediationwells,piping,andflows10utilizeda25%factorinsteadofscalingbasedonplumesize.11

Ex‐SituRemediation.Ex‐situremediationisproposedinAlternative4C‐3tomaintainyear‐12roundpumpingratesandwinterhydrauliccontrolandtreatment,andthusex‐situremediation13activityforAlternative4C‐3wasscaledusingthesamemethodsasforagriculturalland14treatment.Ex‐situtreatmentisproposedinAlternative4C‐5fortreatmentofthehigh15concentrationplume(>50ppb)area.Sincethehighconcentrationplumeareahasbeenmoreor16lessstableduetocurrentremedialactions,noscalingwasappliedforex‐situtreatmentin17Alternative4C‐5,butascalingfactorof25%wasincludedforthepurposesofEIRanalysisinthe18eventthathigherpumpingratesmaybeneededtosupportremedialgoals.19

FreshwaterInjection.Todate,freshwaterinjectiononthenorthwestsideoftheplumehas20beeneffectiveatcontrollingfurtherwestwardmigrationoftheplumeanddeflectingits21movementnorthward.Thus,itwasassumedthatasimilaramountoffreshwaterinjectionwould22beusedinallalternativesinthefuture.Ascalingfactorof15%wasusedinordertocover23potentialexpansion,shoulditbeneeded,totheexistingamountsforEIRanalysis.24

MonitoringWells.Astheplumehasexpanded,thenumberofmonitoringwellshasalso25expanded.PG&Eoriginallyincludedanadditional12monitoringwellsaboveexistingwells.In26ordertocoverpotentialmonitoringwellneedstoaddressanexpandingplume,ascalingfactor27of25%wasaddedtotheexistingandprojectednumberofmonitoringwellsfortheEIRanalysis.28

Inthealternativedescriptionsbelow,referencetoagriculturalacreages,wells,pipinglengths,and29flowsaretothescaledtotals,nottheoriginalfeasibilitystudytotal.Tablesthatsummarizethe30originalfeasibilitystudytotalsforeachalternativeandshowthespecificscalingadjustmentsto31accountfortheexpandedplumearepresentedinAppendixB.32

2.9 Project Alternatives 33

Basedonthereviewofthefeasibilitystudy(andaddenda),inputfromEPAandDTSC,public34commentandreviewofremediationexperiencesofpriorpilottestsandremediationactivitiesatthe35sitetodate,theWaterBoardselectedthemostpromisingfiveprojectalternativestoanalyzeinthis36EIR,inadditiontotheCEQArequiredanalysisoftheNoProjectAlternative.Table2‐2identifiesthe37keyfeaturesoftheanalyzedalternatives.Eachalternativeisfurtherdescribedbelow.38

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Table 2‐2. PG&E Hinkley Groundwater Remediation Alternatives Analyzed in the EIR 1

Alternatives NoProjecta 4B 4C‐2 4C‐3 4C‐4 4C‐5SourceofInformation FSAddendum3 FSAddendum2 FSAddendum3 FSAddendum3 FSAddendum3 FSAddendum4PlumeFSanalysisbasedon Q1/2011 Q1/2010 Q1/2011 Q1/2011 Q1/2011 Q1/2011OU1–RemedialMethodforHighConcentrationPlume

In‐Situ In‐Situ In‐Situ In‐Situ In‐Situ Above‐ground/In‐situ

Timeto50ppb 6b 6 6 4 3 20Timeto80%Cr[VI]MassConversiontoCr[III]orRemoval

13b 10 7 6 6 15

OU1/2/3–Remedialmethodforlowconcentrationplume

IRZ/AUsc

IRZfor20yearsAUsfor95years

IRZfor20yearsAUsfor90years

IRZfor20yearsAUsfor85years

IRZfor20yearsAUsfor75years

IRZfor32yearsAUsfor95years

Timeto3.1ppbcleanup NAc 40 39 36 29 50Timeto1.2ppbcleanup NAc 95 90 85 75 95FateofCr3+inthesoil Leaves Leaves Leaves Leaves Leaves Removesfromhigh

concentrationareaAUPumpingRatesc 1,100gpm(FS) 1,270gpm(FS)

2,395gpm(total)2,042gpm(FS)3,167gpm(total)

2,829gpm(FS)4,388gpm(total)

2,829gpm(FS)4,388gpm(total)

2,042gpm(FS)3,167gpm(total)

AUsd,e 182acres 222acres(FS)/446acres(total)

351acres(FS)/575acres(total)

351acres(FS)/575acres(total)

895acres(FS)/1,394acres(total)

351acres(FS)/575acres(total)

FSEstimatedCosts(NPV)f N/A $84.9M $118M $276M $173M $171MKeyFeature RequiredbyCEQA Lessgroundwater

pumping,AUacreageandlowercost.

Yearroundpumpingforplumecontrol(winterCrop).

Yearroundpumpingforplumecontrol(winterabove‐groundtreatment).

Yearroundpumpingforplumecontrol.Fastestcleanupofallalternative.

Removalofchromiumfromthehighconcentrationplumearea.

Notes:a NoProjectAlternativedefinedbasedontheNoProjectdetailsprovidedforAlternative4C‐2inFSAddendumNo.3.b BasedonFSAlternativeNo.4cleanuptimesbecauseFSAddendumNo.3didnotidentifycleanuptimesforNoProjectconditions.c NoProjectAlternativelimitedtoaddressingthe2008–2010plume.Thus,nodurationforcleanupofentireplumeisidentified.d Twopumpingratesshownforactionalternatives.FirstishighestpumpingrateintheFS/Addendamarkedwitha(FS).SecondisscaleduptoaccountforexpandedplumebeyondthatatthetimeoftheFS/Addenda.

e Twoacreagesshownforagriculturalunitsforactionalternatives.FirstisfromtheFS/Addendamarkedwitha(FS).SecondisscaleduptoaccountforexpandedplumebeyondthatatthetimeoftheFS/Addenda.

f CostsarebasedonFS/Addendacoststoremediateto1.2ppbCr[VI]levelandonlyincludetheinfrastructuredescribedintheFS/Addendaanddonotaccountfortheadditionalcostfortheinfrastructureandactivitiestoaddresstheexpandedplume.

AU = AgriculturalUnitsFS = FeasibilityStudygpm = gallonsperminuteIRZ = In‐SituRemediationNPV = Netpresentvalueppb = partsperbillion

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California Regional Water Quality Control Board, Lahontan Region  Project Description 

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

2‐15 August 2012

ICF 00122.11

 

Thedescriptionofremedialactionsundereachalternativeisidentifiedbyphases,includingtheyear1thatanactionwouldbeinitiatedandtheperiodoftimeitwouldbeimplementeduntilcleanupis2achieved.Forallalternatives,theoverallphasesare:3

InitialBuildout(0–5years)4

Years5to105

Years10to206

BeyondYear207

2.9.1 No Project Alternative 8

UndertheNoProjectAlternative,theWaterBoardwouldnotadoptanewCAO(andassociatedsite‐9wideWDRs)andthepriorauthorizationswouldcontinuetobeusedforcleanupactivities.Thecurrent10remediationactivitiesthatwouldcontinuetobeimplementedundertheNoProjectAlternativeare11describedbelow.Table2‐3summarizestheremedialactionsfortheNoProjectAlternative,and12Figure2‐3showsthelocationsofwhereremediationactivitieswouldbeimplemented.13

PlumeContainment.Plumecontainmentwouldcontinueviafreshwaterreinjectionand14northernlandtreatment.FreshwaterwouldbepumpedfromthethreeexistingPG&Esupply15wellslocatedsouthoftheCompressorStationandpipedtothefivereinjectionwellslocated16northwestoftheplumeatthecurrentlyauthorizedvolumesandrates(80gpm).Landtreatment17viatheDesertViewDairyandfouragriculturalunits(describedbelow)wouldcontinueasunder18existingconditions.19

LandTreatmentattheDesertViewDairyandFourAdjacentParcels.Extractionoflow20concentrationCr[VI]groundwaterandlandapplicationattheDesertViewDairyandthefour21agriculturalunits(ontheGorman[northandsouth],Cottrell,andRanchproperties)within22OU1/OU2wouldcontinueatthecurrentvolumesandrates(1,100gpm).23

In‐SituTreatment.In‐situtreatmentwithintheSource,Central,andSouthCentralIRZareas24usinginjectionofreductantsintothecontaminatedaquifertoconvertdissolvedCr[VI]tosolid25Cr[III]wouldcontinue.In‐situoperationswouldcontinueviapumpinggroundwaterfrom26extractionwells,mixinggroundwaterandreagentsinmixingtanks,andinjectionofthemixture27intoinjectionwells.Biological(i.e.,carbon‐amended)andchemicalreductantsareinjectedby28manualorsemi‐automatedrecirculationsystems,ormanuallyusingtemporarywellpointson29directinjectionmethods.TherearecurrentlytwoIRZcompoundsthatincludeequipment,tanks,30andwells,withfootprintofnomorethan100by200feetinareaand20feetinheight31surroundedbyfencesupto12feethigh.Additionally,therearealmost30smallerabove‐ground32compounds(withapproximately20by20feetfootprint)forextractionwells,and5similar33smallcompoundsforinjectionwellsdealingwiththewesternbulge.Allcompoundshave34approximately12‐foothighfenceswithbrown‐coloredslats.Alsoincludedareconveyance35pipelinesforin‐situtreatment.36

Authorizedchemicalreductantsusedforin‐situtreatmentandgroundwaterinjectionforabove‐37groundtreatmentincludecalciumpolysulfide,ferrouschloride,ferroussulfate,sodium38dithionite,andzero‐valentiron.Biologicalreductantsincludeemulsifiedvegetableoil,ethanol,39lactate,whey,molasses,cornsyrup,acetate,glucose,andmethanol.Onlysomeofthese40biologicalreductantshavebeenusedtodate.Authorizedoperationandmaintenance(O&M)41activitiesincludedischargesoftracercompounds,well‐rehabilitationcompounds,process42

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California Regional Water Quality Control Board, Lahontan Region  Project Description 

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

2‐16 August 2012

ICF 00122.11

 

chemicals,andnutrientsintogroundwater.Tracersareinjectedintogroundwaterto1characterizeflowconditionswithinthetreatmentareas.Tracersmayincludebromide,2fluorescein,eosine,andadditionalfluorescenttracers.Wellrehabilitationcompoundsareused3toremovemicrobialorgeochemicalfoulingthatmayhavedevelopedinthewell.Well4rehabilitationcompoundsauthorizedforuseareaceticacid,citricacid,hydrochloricacid,5hydrogenperoxide,andsodiumhydroxide.Additionally,theWaterBoardhasapprovedtheuse6ofseveralcommercialwellrehabilitationcompoundsthatarecertifiedundertheCalifornia7WaterworksStandardsforcommonlyusedrehabilitationofdrinkingwaterwells(LiquidAcid8Descaler,Aqua‐ClearAE,Aqua‐ClearMGA,BETZMPH500,NuWell120LiquidAcid,NuWell3109BioacidDispersant,andNuWell400Non‐IonicSurfactant).Processchemicalsauthorizedfor10remediationactivitiesincludealuminumsulfate,anti‐sealants,calciumhydroxide,calciumoxide,11hydrochloricacid,phosphoricacid,polymericflocculants,sodiumhydroxide,andsulfuricacid.12Potentialdischargesofnutrientsduringoperationincludeammonium,nitrate,phosphate,13vitamins,andyeastextract.14

MonitoringActivities.Monitoringwellsandsamplingofchromiumandby‐product15concentrationswouldcontinuetooccurasunderexistingconditions;theseactivitieswouldnot16belimitedtoaspecificOUareaandcouldbeimplementedthroughouttheprojectarea.17

ThephasedimplementationoftheremedialactionsundertheNoProjectAlternativewouldoccuras18follows:19

InitialBuildout:InstallnewextractionwellsintheOU1IRZareasandadjacenttotheCottrell20pivot9andtheDesertViewDairylandtreatmentunitinOU2.Installnewinjectionwellsinthe21OU1IRZareas.Constructassociatedadditionalpipelineconnections.Additionalmonitoring22wellswouldbeinstalledthroughouttheprojectarea.ContinuelandtreatmentandIRZ23treatment,includingIRZby‐productmanagement.24

Year5to10:Constructanadditional600linearfeet(lf)oftrenchingforpipelinesto25accommodateagriculturalunitwelloperations.Allotheroperationswouldcontinueasinthe26previousphase.27

Year10to20:Installthreenewextractionwells(inOU2forpumpingtoIRZarea)andthree28newinjectionwells(inSourceAreaIRZandSouthCentralAreaIRZ)forIRZtreatmentofhighest29remainingCr[VI].Allotheroperationswouldcontinueasinthepreviousphases.30

Allextractionandinjectionflowrateswouldbemaintainedthroughouteachphaseascurrently31beingoperatedunderexistingconditions.32

AsnotedinTable2‐2,theestimatedtimeperiodsforcleanupforthisalternativeareexpectedtobe33asfollows:34

Estimatedtimeto50ppb:6years35

Estimatedtimetoachieveconversionof80%ofCr[VI]masstoCr[III]inhighconcentrationarea:3613years37

9Center“pivot”irrigationisaformofirrigationconsistingofseveralsegmentsofpipe(usuallygalvanizedsteeloraluminum)joinedtogetherandsupportedbytrusses,mountedonwheeledtowerswithsprinklersordriplinespositionedalongitslength.Thesystemmovesinacircularpatternandisfedwithwaterfromthepivotpointatthecenterofthearc.DriplineswouldbeusedtoeliminatethepotentialforairbornemistscontainingCr[VI].

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Table 2‐3. Summary of Components under No Project Alternativea 1

OptimizationPeriodInitialBuildout(0–5years)

Year5(5–10years)

Year10(10–20years)

Year20(20+years)

AgriculturalLandApplicationAgriculturalUnits(AUs) 182acresbAUExtractionWells 29Pipelines 24,499lfAUExtractionFlowc 1,100gpmIn‐SituRemediationZone(IRZ)ExtractionWells 17 17 20 20InjectionWells 86 86 89 89Pipelines 31,392lf 31,992lf 33,892lf 33,892lfCarbonamendedIRZflow(SCRIA,SAIRZ)c,d 190gpm(110gpm–SCRIA;80gpm–SAIRZ)IRZRecirculationflow(CAIRZ)c,d 83gpmNorthwestAreaFreshwaterInjectionExtractionWells 5InjectionWells 3Pipelines 31,886lfNorthwestFreshwaterReinjectionFlowc 80gpmMonitoringWellsMonitoringWells 446WellsandSupportinginfrastructureacreagee 39 39 39 39Accessroads 1 1 1 1Notes:a Alltotalsincludeexistinginfrastructure(seeTable2‐1)b AgriculturalUnits=DVD,Gorman,Cottrell,andRanch(allexisting).c Allflowsarebasedonaverageannualrates.d SCRIAreferstotheSouthCentralReinjectionArea.SAIRZreferstotheSourceAreaIn‐SituRemediationZone.CAIRZreferstotheCentralAreaIn‐SituRemediationZone.

e Includesacreageforallwells,includingAgriculturalUnits,In‐SituRemediation,NorthwestFreshwaterReinjection,andmonitoringwells.lf=linearfeetgpm=gallonsperminute

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California Regional Water Quality Control Board, Lahontan Region  Project Description 

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

2‐17 August 2012

ICF 00122.11

 

Estimatedtimetointerimmaximumcleanuplevelof3.1ppbCr[VI]/3.2ppbCr[T]:150years1(butonlyfortheQ12010plume)2

Estimatedtimetointerimaveragecleanuplevelsof1.2ppbCr[VI]/1.5ppbCr[T]:220years3(butonlyfortheQ12010plume)4

Asdescribedabove,theNoProjectAlternativedoesnotincluderemedialactionstoaddressthe5expandedplumeandthuswouldnotactivelyremediatealloftheexisting(orpotentialfuture6expanded)plume.Asaresult,thetimetoremediatechromiumcontaminationwithintheentireplume7wouldbecloserto1,000yearsforareasoutsidetheQ12010plume(similartofeasibilitystudy8Alternative1).TheNoProjectAlternativealsodoesnotincludeacontingencyplanintheeventthat9agriculturalunitscannotbeoperatedduetocropdisease,extendedstorms,orotherevents.10

2.9.2 Alternative 4B 11

2.9.2.1 Overview 12

Alternative4Bexpandsthearea,intensity,anddurationofremediationactivitiesoverexisting13authorizedandoperatingactivitiesproposedundertheNoProjectAlternative.Theproposed14treatmentapproachunderthisalternativewouldbesimilartothegeneralapproachthatPG&Eis15currentlyoperatingintheprojectareabutonagreaterscale.16

Treatmentmethodsforthisalternativeincludein‐situtreatmentbyextraction,carbonamendment17ofgroundwaterandreinjectionintheIRZareasinOU1(asdescribedinthedescriptionoftheNo18ProjectAlternative),agriculturalapplicationwithinandadjacenttothenortherndiffuseportionof19theplumeinOU2,andfreshwaterinjectioninthenorthwestareaoftheplumeadjacenttothe20westernboundariesofOU1andOU2.Therewouldbemorein‐situcarboninjection/extractionwells21andthusmoreabove‐groundIRZwellcompounds(approximately20by20feetfootprint)22comparedtotheNoProjectAlternative.Thisalternativealsoincludesexpansionofagriculturalland23treatmentandgroundwaterpumpingasnecessarytoaddresstherevisedplumearea,includinginto24OU3.Forexample,thisalternativecouldincludeupto446acresofagriculturalunitsandupto2,39525gpmofextractionforlandtreatment(comparedto182acresofagriculturalunitsand1,100gpmof26extractionpumpingforlandtreatmentwiththeNoProjectAlternative).27

Implementationofthisalternativeislikelytorequiretheacquisitionofpropertiesand/or28easementswithintheprojectareaforinstallationandmaintenanceofsupportinginfrastructurefor29implementingremediationactivities.Thisalternativealsowouldrequireacquisitionofwaterrights30becauseitincludesagriculturalwaterusethatwouldexceedPG&E’scurrentwaterallocation.31

Table2‐4summarizesthemaincomponentsofAlternative4B,andFigure2‐4showstheproposed32remediationactivitiesthatwouldbeimplemented.Thephasedimplementationoftheremedial33actionsunderAlternative4Bwouldoccurasfollows:34

InitialBuildout:AgriculturalunitsandassociatedwellsandpipelineswouldbeinstalledinOU235forexpandedlandtreatment(andinOU3asnecessary);flowrateswouldbeincreasedover36existingconditionsforplumecontainment,landapplication,andIRZtreatment.IRZtreatment37wouldbecontinuouslyoperated.Additionalmonitoringwellsalsowouldbeinstalledwithinthe38projectarea.39

Year5:SeveralSouthCentralAreainjectionwellsintheIRZareaswouldbeturnedoffand40northernareaextractionflowswouldberedirectedtotheremainingSouthCentralAreaand41

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California Regional Water Quality Control Board, Lahontan Region  Project Description 

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

2‐18 August 2012

ICF 00122.11

 

SourceAreainjectionwellsforshareddosedinjection;therewouldbeareductionintheSouth1CentralArea/SourceAreaflowrate.SouthernSourceAreaextractionwellswouldbeturnedoff2andconvertedtoinjectionwells;allotheroperationswouldcontinueasinthepreviousphases.3

Year10:Newextractionwellsandpipelinesforagriculturalunittreatmentwouldbeinstalled4inthenorthwestandnorthernareasinOU2(andinotherareasasnecessary);IRZflowratesin5theSourceAreaandSouthCentralAreawouldbeincreased.Allotheroperationswould6continueasinpreviousphases.7

Year20:IRZflowratesintheSourceArea/SouthCentralAreawouldbereducedandeastern8SouthCentralAreawellswouldbeturnedoff.TheCentralAreaflowswouldbeshutdown.IRZ9treatmentinSouthCentralAreawouldbemodifiedfromcontinuousoperationtolong‐term10intermittentcarbonamendedtreatmentoflowconcentrationareasinselectSouthCentral11Area/SourceAreainjectionwellsthatmayneedtooperatebeyond20years.Carbondosagein12theSourceAreawouldbereduced.Allotheroperationswouldcontinueasinpreviousphases.13

AsnotedinTable2‐2,theestimatedtimeperiodsforcleanupforthisalternativeareexpectedtobe14asfollows:15

Estimatedtimeto50ppb:6years16

Estimatedtimetoachieveconversionof80%ofCr[VI]masstoCr[III]inhighconcentrationarea:1710years18

Estimatedtimetointerimmaximumcleanuplevelof3.1ppbCr[VI]/3.2ppbCr[T]:40years19

Estimatedtimetointerimaveragecleanuplevelsof1.2ppbCr[VI]/1.5ppbCr[T]:95years20

Overall,incomparisontotheotherprojectalternatives,Alternative4Bwould:21

HaveasmallerlandtreatmentoperationthanAlternatives4C‐2,4C‐3,4C‐4,and4C‐5;22

Havenowinteragriculturaloperations/extraction;23

Havesimilarcleanuptimeframesasotherprojectalternatives;24

Havethesamefreshwaterinjectionoperationstomaintainhydrauliccontroloftheplumeasall25projectalternatives;and26

Costlessthanallotherprojectalternatives.27

2.9.2.2 Implementation Details 28

Plume Containment and Land Treatment 29

UnderAlternative4B,anewagriculturalunitwouldbeinstalledintheOU2areareferredtoasthe30Yangpivotandadditionalagriculturalunitswouldbeinstalledasnecessarytoaddresstheexpanded31plume.TheYangpivotislocatedadjacenttotheeasternareaoftheDesertViewDairyland32treatmentunit.Thespecificlocationofadditionalagriculturalunitshavenotyetbeenidentifiedbut33arelikelytobeinthenorthernoreasternportionsofOU2orinOU3basedonthecurrent34configurationofthechromiumplume.Agriculturalapplicationwouldinvolveextractionofwater35fromextractionwellsconstructedtosupportlandtreatment.Thewaterwouldbepipedtoexisting36ornewagriculturalunitsforapplicationbyfloodordripirrigation(drag‐driporsubsurface).37OperationoftheDesertViewDairylandtreatmentunitwouldcontinueasitdoesunderexisting38conditions.Landtreatmentwouldbeseasonalandwouldnotoccurduringwintermonths.39

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Table 2‐4. Summary of Components under Alternative 4Ba 1

OptimizationPeriodInitialBuildout(0–5years)

Year5(5–10years)

Year10(10–20years)

Year20(20+years)

AgriculturalLandApplicationAgriculturalUnits(AUs)b 446 acresAUExtractionWells 65 65 90 90AUPipeline 59,049 lf 59,049 lf 78,419 lf 78,419 lfAUExtractionFlowc 2,395 gpmIn‐SituRemediationZone(IRZ)ExtractionWells 21 21 21 25InjectionWells 108 108 111 111Pipelines 39,240 lf 39,990 lf 42,365 lf 42,365 lfCarbon‐amendedIRZflow(SCRIA/SAIRZ)c,d 431 gpm 244 gpm 319 gpm 213 gpmIRZRecirculationflow(CAIRZ)c,d 279 gpmNorthwestAreaFreshwaterInjectionExtractionWells 5InjectionWells 4Pipelines 36,669lfNorthwestFreshwaterReinjectionFlowc 92 gpmMonitoringWells/SupportingInfrastructureMonitoringWells 558WellsandSupportingInfrastructure(acres)e 51 51 53 53Accessroads(acres) 3 3 5 5Notes:a Alltotalsincludeexistinginfrastructure.AllestimateshavebeenscaledupfromthedatafromtheFeasibilityStudyandAddendatoaccountforalargerplumethanusedinthefeasibilitystudy.Seediscussionintext.

b DesertViewDairy,Gorman,Cottrell,Ranch,plusadditionalAgriculturalUnits.c Allflowsarebasedonaverageannualrates.d SCRIAreferstotheSouthCentralReinjectionArea;SAIRZreferstotheSourceAreaIn‐SituRemediationZone;CAIRZreferstotheCentralAreaIn‐SituRemediationZone.

e Includesacreageforallwells,includingAgriculturalUnits,In‐SituRemediation,NorthwestFreshwaterReinjection,andmonitoringwells.lf=linearfeetgpm=gallonsperminute

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California Regional Water Quality Control Board, Lahontan Region  Project Description 

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

2‐19 August 2012

ICF 00122.11

 

Containmentofthechromiumplumewouldalsobeachievedascurrentlyoperatedthrough1freshwaterextractionfromfreshwaterwellsinthesouthernIRZareaandinjectiontowellslocated2atthenorthwesternboundaryoftheplumeadjacenttoOU1andOU2.Freshwaterextractionand3injectionisestimatedtobeuptoapproximately92gpm(including15%contingencyovercurrent4levels).5

In‐Situ Treatment 6

IRZtreatmentwouldoccurthroughoutOU1.TheinjectionswithinOU1wouldtargetthehighest7Cr[VI]concentrationswithintheplume.GroundwaterrecirculationintheareaoftheCentralArea8IRZandSourceAreaIRZandinjectionintheSouthCentralAreaIRZwouldprovideadditional9treatmenttotheSourceAreainOU1.10

In‐situtreatmentwouldinclude:11

ContinuousSouthCentralAreaIRZ/SourceAreaIRZoperationsupto431gpmduringinitial12buildout.13

ContinuousSourceAreaIRZoperationsupto188gpmduringinitialbuildout.14

ContinuousCentralAreaIRZrecirculationoperationfor20yearsatupto279gpm.15

Duringthesecondphase(5–10years),selectSouthCentralAreawellswouldbeturnedoffwith16flowsredistributedtobothSouthCentralAreaandSourceAreainjectionwellsforsharedflow17fordosed‐injection(operatedatupto244gpmbetweenyear5and10andthenupto319gpm18foryears10through20).19

After20years,easternSouthCentralAreawellswouldbeturnedoffandcontinuous,20intermittentlow‐dosagecarbonamendmentwouldbeappliedtoselectSouthCentral21Area/SourceAreainjectionwellsafter20years(upto213gpm)withreductionindosagefrom22125mg/Lto25mg/L.CentralAreaIRZflowswouldbeturnedoff.23

Monitoring Activities 24

Monitoringactivitieswouldbethesameasthosebeingimplementedforexistingoperations25throughouttheprojectarea(describedunderSection2.4above).26

Contingency Plan for Agricultural Unit Operations 27

Alternative4Bincludesacontingencyplanintheeventthatagricultural/landtreatmentcannotbe28implementedduetosevereandextendedstormactivitythatwouldprecludeinfiltration,crop29disease,orotherunforeseeneventsthatwouldprecludeagriculturalunitoperationsforany30substantialdurationoftime.10Basedonareviewofstormrecordsandincludinga200percent31contingency,thepotentialdurationofasignificantstormeventwouldbe18days.Thisgapin32agriculturalunitextractionpumpingisnotexpectedtoresultinanymeaningfulplumemovementor33lossofcaptureandevena90‐daygapisnotexpectedtoresultinfullreversalofhydraulicgradients34(PacificGasandElectric2011c).Thus,thelikelihoodofhavingtoimplementthecontingencyplan35duetoinclementweatherislow.However,theremaybeotherunforeseeneventsthatcouldresultin36aprolongedimpairmentofagriculturalunitoperationsthatimpairsplumecontrolandtreatment;in37suchacasethecontingencyplanwouldbeputintoeffect.38

10Alternatives4C‐2,4C‐3,and4C‐4alsoincludecontingencymeasuresasdescribedbelow.

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ThecontingencyplanisdescribedintheSeptember2011FeasibilityStudyAddendum3and1includesthefollowingphases:2

RoutineAgriculturalUnitOperations–Flowratesincludedinthisalternativewouldbe3maintainedbyadjustingthenumberofagriculturalunitsbeingoperated.4

TierIContingencyAgriculturalUnitOperation–Intheeventofsevereweatherorother5impedimentstotemporaryagriculturalunitoperations,agriculturalunitflowratescanbe6temporarilyreducedforaperiodoftimewithouthamperingplumehydrauliccontrol.However,7iftheimpairmentislengthier,thenPG&Ewouldbringadditionalagriculturalunitsonlineby8constructingadditionalagriculturalunitsorrestartingidleagriculturalunits.Flowrateswould9bereducedtoupto90days(asnecessary)whileadditionalagriculturalunitswerebroughton10line.11

TierIIContingencyAlternativeOperations–Ifadditionalagriculturalunitsarenotfeasible,then12alternativecontrolandtreatmentmethodswillneedtobeemployed.Thecontingencyplan13identifiespotentialuseofinfiltrationgalleriesand/orex‐situtreatment11.Giventhattheamount14oflandrequired(200acrestomaintainflowratesof1,200gpm)forinfiltrationgalleriesismuch15smallerthantheamountoflandrequiredforagriculturalunitsforagivenflowandthatthe16natureofimpacts(suchasgrounddisturbance)areverysimilartoagriculturalunits,infiltration17galleriesarenotseparatelyanalyzedinthisEIR.Theimpactsofex‐situtreatmentareas18describedbelowfortheex‐situelementsincludedinAlternatives4C‐3and4C‐5.19

2.9.3 Alternative 4C‐2 20

2.9.3.1 Overview 21

Alternative4C‐2usesmuchofthesamegeneralinfrastructureandoptimizationasthatproposed22underAlternative4BinrelationtoplumecontainmentandIRZtreatment.Alternative4C‐2differs23fromAlternative4Bbyincludingmoreintensivegroundwaterextractionforlandtreatmentwiththe24additionofwintercrops(winterryeorasimilarcrop)atselectagriculturalunits.Thisexpansionis25proposedtoachieveandmaintainyear‐roundextraction/hydrauliccontroloftheplumemovement26tofosterfastercleanupperiodscomparedtoAlternative4B.27

Thisalternativealsoincludesexpansionofagriculturallandtreatmentandgroundwaterpumpingas28necessarytoaddresstherevisedplumearea,includingintoOU3;forexamplethisalternativecould29includeupto575acresofagriculturalunitsandupto3,167gpmofextractionforlandtreatment30(comparedto182acresofagriculturalunitsand1,100gpmofextractionpumpingforland31treatmentwiththeNoProjectAlternative).32

Implementationofthisalternativeislikelytorequiretheacquisitionofpropertiesand/or33easementswithintheprojectareaforinstallationandmaintenanceofsupportinginfrastructureto34implementremediationactivities.Thisalternativealsowouldrequireacquisitionofwaterrights35becauseitincludesagriculturalwaterusethatwouldexceedPG&E’scurrentwaterallocation.36

11Aninfiltrationgalleryisanundergroundstructurewithperforatedpipeswhereextractedgroundwateristreatedandrechargedtothevadosezoneandwatertable.WatertreatmentisaccomplishedthroughtheadditionofamendmentstoreduceCr[VI]toCr[III]similartotheIRZprocess.

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Table2‐5summarizesthemaincomponentsofAlternative4C‐2,andFigure2‐5showstheproposed1remediationactivitiesthatwouldbeimplemented.Thephasedimplementationoftheremedial2actionsunderAlternative4C‐2wouldoccurasfollows:3

InitialBuildout:Agriculturalunitpivotsandassociatedextractionwellsandpipelineswouldbe4constructedinOU1andOU2areas;allflowratesforcontainment,landapplication,andIRZ5treatmentwouldincreasefromexistingconditions.Additionalpivotsnecessarytoaddress6plumeexpansionwouldbelocatedinOU2andOU3.IRZtreatmentwouldbecontinuous.7Additionalmonitoringwellsalsowouldbeinstalledwithintheprojectarea.8

Year5:SeveralSouthCentralAreainjectionwellsintheIRZareaswouldbeturnedoffand9northernareaextractionflowswouldberedirectedtoremainingSouthCentralAreaandSource10Areainjectionwellsforshareddosedinjection;therewouldbeareductionintheSouthCentral11Area/SourceAreaflowrate.SouthernSourceAreaextractionwellswouldbeturnedoffand12convertedtoinjectionwells;allotheroperationswouldcontinueasinthepreviousphases.13

Year10:Additionalextractionwellsandpipelineswouldbeconstructedinthenorthwestand14northernareasinOU2toexpandagriculturalunittreatment;IRZflowratesintheSourceArea15andSouthCentralAreawouldbeincreased.Allotheroperationswouldcontinueasinprevious16phases.17

Year20:Severalagriculturalpivotsmaybeturnedoff(dependingonremedialprogressatthe18time)andflowsfromnorthernagriculturalunitextractionwellsinstalledinYear10couldbe19shiftedtoIRZtreatment;CentralAreaIRZrecirculationflowswouldbeturnedoff.EasternSouth20CentralAreawellswouldbeturnedoff;IRZtreatmentinSouthCentralAreawouldbemodified21fromcontinuousoperationtolong‐termintermittentcarbonamendedtreatmentoflow22concentrationareasinselectSouthCentralArea/SourceAreainjectionwellsbeyond20years.23CarbondosageintheSourceAreawouldbereduced.24

AsnotedinTable2‐2,theestimatedtimeperiodsforcleanupforthisalternativeareexpectedtobe25asfollows:26

Estimatedtimeto50ppb:6years27

Estimatedtimetoachieveconversionof80%ofCr[VI]masstoCr[III]inhighconcentrationarea:287years29

Estimatedtimetointerimmaximumcleanuplevelof3.1ppbCr[VI]/3.2ppbCr[T]:39years30

Estimatedtimetointerimaveragecleanuplevelsof1.2ppbCr[VI]/1.5ppbCr[T]:90years31

Overall,incomparisontotheotherprojectalternatives,Alternative4C‐2would:32

Haveamoreextensivelandtreatmentapproach(includingwinteroperations)thantheNo33ProjectAlternativeandAlternative4B;34

Havethesamefreshwaterinjectionoperationstomaintainhydrauliccontrolasallproject35alternatives;and36

HaveashorterperiodforachievingcleanuptoaverageandmaximumCr[T]andCr[VI]interim37cleanuplevelsovertheNoProjectAlternativeandAlternative4Bonly.38

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2.9.3.2 Implementation Details 1

Plume Containment and Land Treatment 2

ThisalternativesupportsmoreagriculturaltreatmentthanAlternative4Btoaccommodate3additionalagriculturalextraction.Theadditionalagriculturalunitswouldinclude:4

OnepivotlocatedjustsouthoftheDesertViewDairylandtreatmentunit;5

OnepivotlocatedeastoftheDesertViewDairy;6

TwopivotslocatedinthecentralareaoftheplumeonorneartheformerBellproperty;7

OnepivotlocatedinthesouthernportionoftheSouthCentralArea,southeastoftheBellpivots8andnorthofthesourceareawithinOU1;and9

Additionalpivotsnecessarytoaddresstheexpandedplumeareatotheeastandthenorth10(infuturelocationsasyetundetermined).11

UnderAlternative4C‐2themaximumflowratesforextractionofgroundwaterfromnorthernlow‐12concentrationareaswouldbeincreasedandusedforyear‐roundcontinuousoperationof13agriculturaltreatmentonselectagriculturalunitstosupportwintercrops.Agriculturalunitflows14maybedecreasedatYear20dependingonthetreatmentachievementsatthattime.Freshwater15injectionwouldremainthesame,withestimatedflowsofupto92gpm(15%contingencyover16existinglevels)forthedurationoftreatment.Otherthanthesechanges,allotheractivitieswouldbe17similartoAlternative4B.18

In‐Situ Treatment 19

In‐situtreatmentunderAlternative4C‐2wouldbethesameasin‐situtreatmentdescribedunder20Alternative4B.21

Monitoring Activities 22

Monitoringactivitieswouldbethesameasthosebeingimplementedforexistingoperations23throughouttheprojectarea(asdescribedunderSection2.4above).24

Contingency Plan for Agricultural Unit Operations 25

Alternative4C‐2wouldincludeacontingencyplanasdescribedforAlternative4Babove.26

2.9.4 Alternative 4C‐3 27

2.9.4.1 Overview 28

Alternative4C‐3usesmuchofthesamegeneralinfrastructureandoptimizationasthatproposed29underAlternatives4Band4C‐2inrelationtoplumecontainment,landtreatmentviaagricultural30treatment,andIRZtreatment.Alternative4C‐3addsex‐situtreatmentplantstoprovideyear‐round31continuouspumpingtotreatexcesswinterwaterthatcannotbetreatedbyproposedagricultural32unitsinwinter.Theproposedex‐situtechnologyisextraction,treatmentthroughchemical33reduction/precipitation,andreinjectionoftreatedwaterintothegroundwater.Thistechnologywas34selectedbasedonsimilaroperationsthathavebeenimplementedbyPG&EatitsTopocksitewhere35

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Table 2‐5. Summary of Components under Alternative 4C‐2a 1

OptimizationPeriodInitialBuildout(0–5years)

Year5(5–10years)

Year10(10–20years)

Year20(20+years)

AgriculturalLandApplicationAgriculturalUnits(AUs)b 575 acresAUExtractionWells 80 80 102 102AUPipeline 68,489 lf 68,489 lf 83,374 lf 83,374 lfAUExtractionFlowc 3,167 gpmIn‐SituRemediationZone(IRZ)ExtractionWells 21 21 25 25InjectionWells 108 108 111 111Pipelines 39,240 lf 39,990 lf 42,365 lf 42,365 lfCarbon‐amendedIRZflow(SCRIA/SAIRZ)c,d 431 gpm 244 gpm 319 gpm 213 gpmIRZRecirculationflow(CAIRZ)c,d 279 gpmNorthwestAreaFreshwaterInjectionExtractionWells 5InjectionWells 4Pipelines 36,669 lfNorthwestFreshwaterReinjectionFlowc 92 gpmMonitoringWells/SupportingInfrastructureMonitoringWells 558WellsandSupportingInfrastructureAcreagee 52 52 54 54Accessroads(acres) 4 4 5 5Notes:a Alltotalsincludeexistinginfrastructure.AllestimateshavebeenscaledupfromthedatafromtheFeasibilityStudyandAddendatoaccountforalargerplumethanusedinthefeasibilitystudy.Seediscussionintext.

b DesertViewDairy,Gorman,Cottrell,Ranch,plusadditionalAgriculturalUnits.c Allflowsarebasedonaverageannualrates.d SCRIAreferstotheSouthCentralReinjectionArea.SAIRZreferstotheSourceAreaIn‐SituRemediationZone.CAIRZreferstotheCentralAreaIn‐SituRemediationZone.

e Includesacreageforallwells,includingAgriculturalUnits,In‐SituRemediation,NorthwestFreshwaterReinjection,andmonitoringwells.lf=linearfeetgpm=gallonsperminute

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thetechnologyhasbeeneffectiveinthecleanupofwatercontaminatedbyCr[VI].Therewouldbeup1toatotaloftwoabove‐groundtreatmentfacilities.Onetreatmentfacilitywouldbelocatedgenerally2neartheCompressorStationadjacenttothesouthernboundaryoftheSourceAreaIRZinOU1,and3onetreatmentfacilitywouldbelocatedgenerallyneartheDesertViewDairyadjacenttothe4northwesternboundaryofOU2.5

Thisalternativealsoincludesadditionalagriculturallandtreatmentandgroundwaterpumpingas6necessarytoaddresstherevisedplumeareaincludingintoOU3;forexamplethisalternativecould7includeupto575acresofagriculturalunitsandupto4,388gpmofextraction(annualaverage)for8landtreatment(comparedto182acresofagriculturalunitsand1,100gpmofextractionpumping9forlandtreatmentwiththeNoProjectAlternative).10

Implementationofthisalternativeislikelytorequiretheacquisitionofpropertiesand/or11easementswithintheprojectareafortheinstallationandmaintenanceofinfrastructurethat12supportstheimplementationofremediationactivities.Thisalternativealsowouldrequire13acquisitionofwaterrightsbecauseitincludesagriculturalwaterusethatwouldexceedPG&E’s14currentwaterallocation.15

Table2‐6summarizesthemaincomponentsofAlternative4C‐3,andFigure2‐6showstheproposed16remediationactivitiesthatwouldbeimplemented.Thephasedimplementationoftheremedial17actionsunderAlternative4C‐3wouldoccurasfollows:18

InitialBuildout:Newagriculturalunitpivotsandassociatedextractionwellsandpipelines19wouldbeconstructedinOU1andOU2areas;allflowratesforcontainment,landapplicationand20IRZtreatmentwouldincrease.Additionalpivotsnecessarytoaddressplumeexpansionwould21belocatedinOU2andOU3.Northandsouthex‐situtreatmentplants,includingsupporting22facilities,wouldbeconstructed;newex‐situinjectionwellsassociatedwitheachtreatmentplant23wouldbeinstalled,withadditionalconveyancepipingandsupportinginfrastructure;operation24ofex‐situtreatmentwouldbeinitiated.Additionalmonitoringwellswouldalsobeinstalled25withintheprojectarea.26

Year5:SeveralSouthCentralAreainjectionwellsintheIRZareaswouldbeturnedoffand27northernareaextractionflowswouldberedirectedtoremainingSouthCentralAreaandSource28Areainjectionwellsforshareddosedinjection;therewouldbeareductionintheSouthCentral29Area/SourceAreaflowrate.SouthernSourceAreaextractionwellswouldbeturnedoffand30convertedtoinjectionwells.31

Year10:Additionalextractionwellsandpipelineswouldbeconstructedinthenorthwestand32northernareasinOU2toexpandagriculturalunittreatment;IRZflowratesintheSourceArea33andSouthCentralAreawouldbeincreased.Allotheroperationswouldcontinueasinprevious34phases.35

Year20:Severalagriculturalunitpivotsmaybeturnedoff(dependingoncleanupachievements36byyear20)andflowsfromnorthernagriculturalunitextractionwellsinstalledinYear1037wouldbeshiftedtoIRZtreatment.CentralAreaIRZrecirculationflowswouldbeturnedoff.38EasternSouthCentralAreawellswouldbeturnedoff;IRZtreatmentinSouthCentralArea39wouldbemodifiedfromcontinuousoperationtolong‐termintermittentcarbonamended40treatmentoflowconcentrationareasinselectSouthCentralArea/SourceAreainjectionwells41beyond20years.CarbondosageintheSourceAreaIRZwouldbereduced.42

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AsnotedinTable2‐2,theestimatedtimeperiodsforcleanupforthisalternativeareexpectedtobe1asfollows:2

Estimatedtimeto50ppb:4years3

Estimatedtimetoachieveconversionof80%ofCr[VI]masstoCr[III]inhighconcentrationarea:46years5

Estimatedtimetointerimmaximumcleanuplevelof3.1ppbCr[VI]/3.2ppbCr[T]:36years6

Estimatedtimetointerimaveragecleanuplevelsof1.2ppbCr[VI]/1.5ppbCr[T]:85years7

Overall,incomparisontotheotherprojectalternatives,Alternative4C‐3would:8

HaveashortertimeperiodtoachievecleanuptoaverageandmaximumCr[T]andCr[VI]interim9cleanuplevelsthanallotheralternativesexceptAlternative4C‐4;10

Removechromiummassfromtheaquiferduetotheuseofwinterex‐situtreatment12;11

Requiremoreexpansiveconstructionassociatedwiththeex‐situtreatmentplantsand12supportinginfrastructure;13

Haveagreateramountoftrucktrafficasrequiredbytheoperationoftheex‐situtreatment14plants;15

Havethesamefreshwaterinjectionoperationstomaintainhydrauliccontrolasallproject16alternatives;and17

Havethehighestcostforimplementationofallalternatives.18

2.9.4.2 Implementation Details 19

Plume Containment and Land Treatment 20

ThisalternativewouldsupportasimilarlevelofagriculturallandtreatmentandunitsasAlternative214C‐2.UnderAlternative4C‐3,themaximumflowratesforextractionofgroundwaterfromnorthern22low‐concentrationareasforagriculturallandtreatmentwouldbethehighestofallproject23alternatives,exceptforAlternative4C‐4,whichwouldhavethesameflowrate.Agriculturalunit24flowswouldbedecreasedatYear20,dependingontheeffectivenessofremediationinreducing25contaminationlevelsbythattime.Freshwaterinjectionwouldremainthesamewithestimated26flowsofupto92gpm(15%morethanexisting)forthedurationoftreatment.Otherthanthese27changes,allotheractivitieswouldbethesameasthosedescribedforAlternative4C‐2.28

In‐Situ Treatment 29

In‐situtreatmentunderAlternative4C‐3wouldbethesameastreatmentdescribedunder30Alternatives4Band4C‐2.31

12Alternatives4B,4C‐2,and4C‐4wouldnotremovechromiumfromtheaquiferbutinsteadconvertthehighlytoxicCr[VI]ingroundwatertolowtoxicitysolidCr[III].Alternative4C‐5wouldremovechromiuminthesourceareausingex‐situabove‐groundtreatment.

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Table 2‐6. Summary of Components under Alternative 4C‐3 1

OptimizationPeriodInitialBuildout(0–5years)

Year5(5–10years)

Year10(10–20years)

Year20(20+years)

AgriculturalLandApplicationAgriculturalUnits(AUs)a 575acresAUExtractionWells 80 80 102 103AUPipeline 72,751lf 72,751lf 83,374lf 83,374lfAUExtractionFlow 4,388gpm 4,388gpm 4,388gpm 3,606gpmIn‐SituRemediationZone(IRZ)ExtractionWells 22 22 25 25InjectionWells 108 108 111 111Pipelines 39,240lf 39,990lf 42,365lf 42,365lfCarbon‐amendedIRZflow(SCRIA/SAIRZ)b,c 431gpm 244gpm 319gpm 213gpmIRZRecirculationflow(CAIRZ)b,c 279gpmEx‐SituTreatmentExtractionWells 31Pipelines 41,816 lfExtractionFlow(annual) 1,222 gpmNorthwestAreaFreshwaterInjectionExtraction/InjectionWells 5/4Pipelines 36,669lfNorthwestFreshwaterReinjectionFlowb 92 gpmMonitoringWells/SupportingInfrastructureMonitoringWells 558WellsandSupportingInfrastructureacreaged 54 54 56 56Accessroads(acres) 7 9 12 15Notes:a DesertViewDairy,Gorman,Cottrell,Ranch,plusadditionalAgriculturalUnits.b Allflowsarebasedonaverageannualrates.c SCRIAreferstotheSouthCentralReinjectionArea.SAIRZreferstotheSourceAreaIn‐SituRemediationZone.CAIRZreferstotheCentralAreaIn‐SituRemediationZone.

d Includesacreageforallwells,includingAgriculturalUnits,In‐SituRemediation,NorthwestFreshwaterReinjection,andmonitoringwells.lf=linearfeetgpm=gallonsperminute

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Ex‐Situ Treatment  1

Asdescribedabove,underAlternative4C‐3,uptoatotaloftwoex‐situtreatmentplantswouldbe2constructedtotreatexcesswinterflowsthatwouldnotbesupportedbytheagriculturalunit3operations.Asshownintheconceptuallayout(Figures2‐6),asouthplantandassociatedinjection4wellswouldbelocatednearthesourceareaattheCompressorStationinOU1andanorthplant5wouldbelocatedadjacenttotheDesertViewDairyinOU2.Twotreatmentplantsareassumed6underthisalternative,onewithatreatmentcapacityofapproximately1,200gpmfromflowsnorth7ofSR58,whichwouldgenerallytreatcontaminationinOU2,andasecondplantwithatreatment8capacityofapproximately450gpmsouthofSR58,whichwouldgenerallytreatcontaminationin9OU1.Ex‐situtreatmentaverageannualflowswouldbe1,222gpm.Ex‐situtreatmentincludes10extractionofchromiumcontaminatedgroundwaterfromthehighestconcentrationareasandlow‐11concentrationareas,treatingitatthenearbyabove‐groundfacilityusingchemicalprecipitationand12filtrationprocesses,andreinjectingthecleanwaterintoassociatedinjectionwells.Thesolidby‐13productresiduegeneratedduringtreatmentwouldbemanagedanddisposedofatClassIlandfill14disposalfacilities,suchastheWasteManagementKettlemanHillsFacility,thatarepermittedto15accepthazardouswastesasauthorizedunderTitle27oftheCaliforniaCodeofRegulations.16

Monitoring Activities 17

Monitoringactivitieswouldbethesameasthosebeingimplementedunderexistingoperations18throughouttheprojectarea(asdescribedunderSection2.4).19

Contingency Plan for Agricultural Unit Operations 20

Alternative4C‐3wouldincludeacontingencyplanasdescribedforAlternative4Babove,exceptthat21thetwoabove‐groundtreatmentplantsincludedinthisalternativealreadyprovidecontingency22optionsintheeventthatagriculturalunittreatmentisimpairedforashortperiodoftime.The23above‐groundtreatmentplantsarebeingdesignedwithmorecapacitythanneededforexpected24averageflows,whichcreatessomebuilt‐incontingency.Also,sinceAlternative4C‐3alreadyrelies25onabove‐groundtreatmentinwinter,ithasabuilt‐incontingencyintheeventofimpairmentof26agriculturalunitsduetowinterstorms.27

2.9.5 Alternative 4C‐4 28

2.9.5.1 Overview 29

Alternative4C‐4usesmuchofthesameinfrastructureandoptimizationasproposedunder30Alternatives4B,4C‐2,and4C‐3butsignificantlyexpandsthenumberofagriculturalunitsforland31treatmentviaoperationofwinteragriculturalunitpivotsusingcontinuouspumpinginlieuofanex‐32situtreatmentplantasproposedunderAlternative4C‐3.33

Thisalternativealsoexpandsagriculturallandtreatmentandgroundwaterpumpingasnecessaryto34addresstherevisedplumearea,includingintoOU3;forexamplethisalternativecouldincludeupto351,394acresofagriculturalunitsandanannualextractionrateofupto4,388gpmforlandtreatment36(comparedto182acresofagriculturalunitsand1,100gpmofextractionpumpingforland37treatmentwiththeNoProjectAlternative).38

Implementationofthisalternativeislikelytorequiretheacquisitionofpropertiesand/or39easementswithintheprojectareaforinstallationandmaintenanceofsupportinginfrastructurefor40

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implementingremediationactivities.Thisalternativealsowouldrequireacquisitionofwaterrights1becauseitincludesagriculturalwaterusethatwouldexceedPG&E’scurrentwaterallocation.2

Table2‐7summarizesthemaincomponentsofAlternative4C‐4,andFigure2‐7showstheproposed3remediationtechnologiesthatwouldbeimplemented.Thephasedimplementationoftheremedial4actionsunderAlternative4C‐4wouldoccurasfollows:5

InitialBuildout:Atleastsixteennewagriculturalunitpivotsandassociatedextractionwells6andpipelineswouldbeconstructedinOU1andOU2areas;allflowratesforcontainment,land7application,andIRZtreatmentwouldincrease.Additionalagriculturalunitpivotswouldbe8necessarytoaddresstheexpandedplumeandwouldlikelybelocatedinOU2andOU3.9Additionalmonitoringwellsalsowouldbeinstalledwithintheprojectarea.10

Year5:SeveralSouthCentralAreainjectionwellsintheIRZareaswouldbeturnedoffand11northernareaextractionflowswouldberedirectedtoremainingSouthCentralAreaandSource12Areainjectionwellsforshareddosedinjection;therewouldbeareductionintheSouthCentral13Area/SourceAreaflowrate.SouthernSourceAreaextractionwellswouldbeturnedoffand14convertedtoinjectionwells.15

Year10:Additionalextractionwellsandpipelineswouldbeconstructedinthenorthwestand16northernareasinOU2toexpandagriculturalunittreatment;IRZflowratesintheSourceArea17andSouthCentralAreawouldbeincreased.Allotheroperationswouldcontinueasinprevious18phases.19

Year20:Severalagriculturalunitpivotsmaybeturnedoff(dependingoneffectivenessof20remediationbyYear20)andflowsfromnorthernagriculturalunitextractionwellsinstalledin21Year10wouldbeshiftedtoIRZtreatment;CentralAreaIRZrecirculationflowswouldbeturned22off;EasternSouthCentralAreawellswouldbeturnedoff;IRZtreatmentinSouthCentralArea23wouldbemodifiedfromcontinuousoperationtolong‐termintermittentcarbonamended24treatmentoflowconcentrationareasinselectSouthCentralArea/SourceAreainjectionwells25beyond20years.CarbondosageintheSourceAreawouldbereduced.Allotheroperations26wouldcontinueasinpreviousphases.27

AsnotedinTable2‐2,theestimatedtimeperiodsforcleanupforthisalternativeareexpectedtobe28asfollows:29

Estimatedtimeto50ppb:3years30

Estimatedtimetoachieveconversionof80%ofCr[VI]masstoCr[III]inhighconcentrationarea:316years32

Estimatedtimetointerimmaximumcleanuplevelof3.1ppbCr[VI]/3.2ppbCr[T]:29years33

Estimatedtimetointerimaveragecleanuplevelsof1.2ppbCr[VI]/1.5ppbCr[T]:75years34

Overall,incomparisontotheotherprojectalternatives,Alternative4C‐4would:35

HavethefastesttimeframestoachieveaverageandmaximumCr[T]andCr[VI]interimcleanup36levelsoverallprojectalternatives;37

Requireconstructionofthelargestareaofagriculturalunitsandassociatedpipelineconveyance38systemsofallprojectalternatives;andhavethesamefreshwaterinjectionoperationsto39maintainhydrauliccontrolasallalternatives;and40

Havethesecondhighestcostofallalternatives.41

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Table 2‐7. Summary of Components under Alternative 4C‐4 1

OptimizationPeriodInitialBuildout(0–5years)

Year5(5–10years)

Year10(10–20years)

Year20(20+years)

AgriculturalLandApplicationAgriculturalUnits(AUs)a 1,394acresAUExtractionWells 149 149 190 190AUPipeline 132,875lf 132,875lf 147,374lf 147,374lfAUExtractionFlow 4,388gpmIn‐SituRemediationZone(IRZ)ExtractionWells 22 22 25 25InjectionWells 108 108 111 111Pipelines 39,240lf 39,990lf 42,365lf 42,365lfCarbon‐amendedIRZflow(SCRIA/SAIRZ)b,c 431gpm 244gpm 319gpm 213gpmIRZRecirculationflow(CAIRZ)b,c 279gpmNorthwestAreaFreshwaterInjectionExtractionWells 5InjectionWells 4Pipelines 36,669lfNorthwestFreshwaterReinjectionFlowb 92gpmMonitoringWells/SupportingInfrastructureMonitoringWells 558WellsandSupportingInfrastructureacreaged 56 56 59 59Accessroads(acres) 8 8 9 9Notes:a DesertViewDairy,Gorman,Cottrell,Ranch,plusadditionalAgriculturalUnits.b Allflowsarebasedaverageannualrates.c SCRIAreferstotheSouthCentralReinjectionArea.SAIRZreferstotheSourceAreaIn‐SituRemediationZone.CAIRZreferstotheCentralAreaIn‐SituRemediationZone.

d Includesacreageforallwells,includingAgriculturalUnits,In‐SituRemediation,NorthwestFreshwaterReinjection,andmonitoringwells.lf=linearfeetgpm=gallonsperminute

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California Regional Water Quality Control Board, Lahontan Region  Project Description 

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

2‐27 August 2012

ICF 00122.11

 

2.9.5.2 Implementation Details 1

Containment and Land Treatment 2

Thisalternativeincludesalargeincreaseinagriculturalpivotsovertheexistingcondition.3Theincreaseinagriculturalpivotsforthisalternativeisgreaterthanallotheralternatives,with4additionalagriculturalunitstobeaddedforwinter‐onlyoperations.UnderAlternative4C‐4,5themaximumflowratesforextractionofgroundwaterfromnorthernlow‐concentrationareasfor6agriculturallandtreatmentwouldbethehighestofallalternatives,exceptforAlternative4C‐3,7whichwouldhavethesameflowrates.AgriculturalunitflowsmaybedecreasedatYear208dependingoneffectivenessofremediationbythattime.Theoveralllandtreatmentflowratesare9higherthanAlternatives4Band4C‐2becausethetreatmentapproachismoreaggressive.10Freshwaterinjectionwouldremainthesamewithestimatedflowsofupto92gpm(existingflow11levelplus15%contingency)forthedurationoftreatment.12

In‐Situ Treatment 13

In‐situtreatmentunderAlternative4C‐4wouldbethesameasin‐situtreatmentproposedunderthe14otherdescribedalternatives.15

Monitoring Activities 16

Monitoringactivitieswouldbethesameasthoseproposedundertheotherdescribedalternatives.17

Contingency Plan for Agricultural Unit Operations 18

Alternative4C‐4wouldincludeacontingencyplanasdescribedforAlternative4Babove.19

2.9.6 Alternative 4C‐5 20

2.9.6.1 Overview 21

Alternative4C‐5isacombinationofthreeremedialstrategies:agriculturallandtreatment,in‐situ22remediation,andex‐situ(above‐ground)chemicaltreatment.Liketheotheractionalternatives,23implementationofthisalternativeislikelytorequiretheacquisitionofpropertiesand/or24easementswithintheprojectareaforinstallationandmaintenanceofsupportinginfrastructurefor25implementingremediationactivities.Thisalternativealsowouldrequireacquisitionofwaterrights26becauseitincludesagriculturalwaterusethatwouldexceedPG&E’scurrentwaterallocation.27

Table2‐8summarizesthemaincomponentsofAlternative4C‐5,andFigure2‐8showstheproposed28remediationactivitiesthatwouldbeimplemented.29

TheprimarydifferenceintheconfigurationsofAlternative4C‐5andAlternative4C‐2isthat30Alternative4C‐5focusesin‐situtreatmentintheSouthCentralAreaandCentralAreaandincludes31above‐groundtreatmentintheSourceAreainsteadofthein‐situtreatmentproposedfortheSource32AreaunderAlternative4C‐2.Therefore,comparedtotheNoProjectAlternativeandtheotheraction33alternatives,therewouldfewerin‐situcarboninjection/extractionwellsandthuslessabove‐ground34IRZwellcompounds(approximately20by20feetfootprint).Theprimarydifferencebetweenthe35configurationsofAlternative4C‐5andAlternative4C‐3isthatAlternative4C‐5usesonlyoneabove‐36groundtreatmentplantforyear‐roundex‐situtreatmentofthehighconcentrationplume,whereas37

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Alternative4C‐3usestwoabove‐groundtreatmentplantsforwinterplumecontrolonly.Theabove‐1groundtreatmentplantwouldbelocatedgenerallyneartheCompressorStationadjacenttothe2southernboundaryoftheSourceAreaIRZinOU1.Thisalternativealsoexpandsagriculturalland3treatmentandgroundwaterpumpingasnecessarytoaddresstherevisedplumearea,includinginto4OU3;forexample,thisalternativecouldincludeupto575acresofagriculturalunitsandupto3,1675gpm(annualaverage)ofextractionforlandtreatment(comparedto182acresofagriculturalunits6and1,100gpmofextractionpumpingforlandtreatmentwiththeNoProjectAlternative).7

Implementationofthisalternativeislikelytorequiretheacquisitionofpropertiesand/or8easementswithintheprojectarea.Theseacquisitionswouldbeforinstallationandmaintenanceof9supportinginfrastructureforimplementingremediationactivities.10

ThephasedimplementationoftheremedialactionsunderAlternative4C‐5wouldoccurasfollows:11

InitialBuildout:Newagriculturalunitpivotsandassociatedextractionwellsandpipelines12wouldbeconstructedinOU1andOU2areas;allflowratesforcontainment,landapplicationand13IRZtreatmentwouldincrease.Theex‐situtreatmentplantandassociatedsupporting14infrastructurewouldbeconstructed.Newex‐situinjectionwellswouldbeinstalledinthe15SourceAreawithassociatedpipelines.16

Year5:SeveralSouthCentralAreainjectionwellsintheIRZareaswouldbeturnedoffand17northernareaextractionflowswouldberedirectedtoremainingSouthCentralArea;there18wouldbeareductionintheSouthCentralAreaflowrate.Allotheroperationswouldcontinueas19inpreviousphases.20

Year10:Additionalextractionwellsandpipelineswouldbeconstructedinthenorthwestand21northernareasinOU2toexpandagriculturalunittreatment;IRZflowratesintheSourceArea22andSouthCentralAreawouldbeincreased.Allotheroperationswouldcontinueasinprevious23phases.24

Year15:SourceAreaex‐situtreatedwaterinjectionwouldbeshiftednorth;additionalinjection25wellsinstalledandconveyancepipingandsupportinginfrastructurewouldbeconstructed;26severalextractionwellswouldbeturnedoff.27

Year20:Severalagriculturalunitpivotswouldbeturnedoff(dependingoneffectivenessof28remediationbythattime)andflowsfromnorthernagriculturalunitextractionwellsinstalledin29Year10wouldbeshiftedtoIRZtreatment;CentralAreaIRZrecirculationflowswouldbeturned30off;IRZtreatmentinSouthCentralAreawouldbemodifiedfromcontinuousoperationtolong‐31termintermittentcarbonamendedtreatmentoflowconcentrationareasinselectSouthCentral32Areainjectionwellsbeyond20years.CarbondosageintheSourceAreawouldbereduced.All33otheroperationswouldcontinueasinpreviousphases.34

Year32:SourceAreaextractionwellswouldbeconvertedtocarbon‐amendedinjectionwells35suppliedbySouthCentralAreaextractionflows.36

AsnotedinTable2‐2,theestimatedtimeperiodsforcleanupforthisalternativeareexpectedtobe37asfollows:38

Estimatedtimeto50ppb:20years39

Estimatedtimetoachieveremovalof80%ofCr[VI]massinhighconcentrationarea:15years40

Estimatedtimetointerimmaximumcleanuplevelof3.1ppbCr[VI]/3.2ppbCr[T]:50years41

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Table 2‐8. Summary of Components under Alternative 4C‐5 1

OptimizationPeriodInitialBuildout(0–5years)

Year5(5–10years)

Year10(10–20years)

Year20(20+years)

AgriculturalLandApplicationAgriculturalUnits(AUs)a 575 acresAUExtractionWells 80 80 102 102AUPipeline 68,489 lf 68,489 lf 83,374 lf 83,374 lfAUExtractionFlowb 3,167gpm 3,167gpm 3,167gpm 2,618gpmIn‐SituRemediationZone(IRZ)ExtractionWells 19 19 23 23InjectionWells 90 90 91 91Pipelines 33,940lf 34,690lf 36,340 lf 36,340 lfCarbon‐amendedIRZflow(SCRIA/SAIRZ)b,c 244 gpm 244gpm 319gpm 213gpmIRZRecirculationflow(CAIRZ)b,c 279gpmEx‐SituTreatmentExtractionWells 20 20 24 24Pipelines 7,719lf 7,719lf 8,594lf 8,589lfExtractionFlow(annual) 250gpm 250gpm 250gpm 0gpmNorthwestAreaFreshwaterInjectionExtraction/InjectionWells 5/4Pipelines 36,669lfNorthwestFreshwaterReinjectionFlowb 92gpmMonitoringWells/SupportingInfrastructureMonitoringWells 558WellsandSupportingInfrastructure(acres)d 52 52 54 54Accessroads(acres) 4 4 5 5Notes:a DesertViewDairy,Gorman,Cottrell,Ranch,plusadditionalAgriculturalUnits.b Allflowsarebasedonaverageannualrates.c SCRIAreferstotheSouthCentralReinjectionArea.

SAIRZreferstotheSourceAreaIn‐SituRemediationZone.CAIRZreferstotheCentralAreaIn‐SituRemediationZone.

d Includesacreageforallwells,includingAgriculturalUnits,In‐SituRemediation,NorthwestFreshwaterReinjection,andmonitoringwells.lf=linearfeetgpm=gallonsperminute

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California Regional Water Quality Control Board, Lahontan Region  Project Description 

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

2‐29 August 2012

ICF 00122.11

 

Estimatedtimetointerimaveragecleanuplevelsof1.2ppbCr[VI]/1.5ppbCr[T]:95years1

Overall,incomparisontotheotherprojectalternatives,Alternative4C‐5would:2

TakelongertoachieveinterimcleanuplevelstomeetthedrinkingwaterMCLforCr[T](below350ppb)thantheotherdescribedalternatives;4

TakelongertoachieveaverageandmaximumCr[T]andCr[VI]interimcleanuplevelscompared5tootheralternatives;6

Useabove‐groundpumpandtreatintheSourceAreaIRZinsteadofin‐situtreatmentresulting7inremovalofchromiumfromthefromtheoverallsiteinsteadofconversionfromCr[VI]to8Cr[III]thusresultinginthelargestremovalofchromiummassofallalternatives;and9

Havethesamefreshwaterinjectionoperationstomaintainhydrauliccontrolasallother10describedalternatives.11

2.9.6.2 Implementation Details 12

Containment and Land Treatment 13

ThiscomponentofAlternative4C‐5wouldbethesameasthatdescribedforAlternative4C‐2;14howeverthetotalmaximumgroundwaterextractionflowsforlandtreatmentwouldbeslightly15higher.16

In‐Situ Treatment 17

In‐situtreatmentunderAlternative4C‐5wouldbesimilartoin‐situtreatmentdescribedfor18Alternative4C‐2.However,Alternative4C‐5doesnotincludein‐situtreatmentintheSourceArea19IRZ;asaresult,theoverallin‐situtreatmentimplementedunderAlternative4C‐5wouldbeless20thanthatoftheotherdescribedalternatives.21

Ex‐Situ Treatment 22

AsshowninFigure2‐8,theconceptualapproachforex‐situtreatmentactivitiesunderAlternative234C‐5includesextractingapproximately200gpmofchromiumcontaminatedgroundwaterfromthe24highestconcentrationareasintheSourceAreaIRZ,treatingitatthenearbyabove‐groundfacility25usingchemicalprecipitationandfiltrationprocesses,andreinjectingthecleanwaterintothesouth26endoftheSourceAreaIRZ.Thesolidby‐productresiduewouldbemanagedanddisposedoffsitein27thesamemannerasthatdescribedunderAlternative4C‐3.28

Monitoring Activities 29

Monitoringactivitieswouldbethesameasthosebeingimplementedunderexistingoperations30throughouttheprojectarea(asdescribedunderSection2.4above).31

Contingency Plan for Agricultural Unit Operations 32

Alternative4C‐5wouldincludeacontingencyplanasdescribedforAlternative4Babove.33

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California Regional Water Quality Control Board, Lahontan Region  Project Description 

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

2‐30 August 2012

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2.10 Construction, Operation, and Maintenance 1

2.10.1 Description of Remediation Activities in Operable Units 2

AspartofAddendum3,PG&EdelineatedthreeOUs(Figure2‐2a).TheOUdelineationwasgenerally3basedonareasthatcontaindifferentplumecharacteristicsandthereforedifferentremedial4emphasis.ThespecificactivitiesthatwouldoccurwithineachOUaregenerallyasfollows:5

OU1.TheremediationemphasisinOU1istreatmentofthehighconcentrationplumethrough6eitherin‐situchromiumreductionfromCr[VI]toCr[III](allalternativesexcept4C‐5)orremoval7throughex‐situtreatment(Alternative4C‐5).In‐situtreatment(Alternatives4B,4C‐2,‐3,and‐84)inOU1willuseIRZtechnology(i.e.,treatmentbybiologicalorchemicalreductants)andwill9focusonaccomplishingtheMCLfordrinkingwater(50ppb)attheboundaryofOU1andOU2.10In‐situreductionbyproducts(e.g.,manganese,iron,arsenic)willbegeneratedthroughtheIRZ11processandprimarilymanagedwithinOU1.Duetotheaggressivenatureoftreatmentproposed12inOU1,thefringesofthe3.1ppbplumecouldtemporarilyfluctuateovertimeinresponseto13injectionandextractionactivities.Tominimizetheseeffects,hydrauliccontrolandinward14gradients(i.e.,plumecontainment)willbemaintainedaslongasnecessarytopreventCr[VI]15andbyproduct(e.g.,manganese)migration.TheagriculturalunitswithinOU1willbeusedfor16watertreatmentasappropriatetoassistwithinwardhydraulicgradientsandplumewater17balance.Alternative4C‐5wouldaddex‐situtreatmentinOU1toremoveCr[VI]fromtheaquifer18insteadofreducingittoCr[III].19

OU2.OU2isalowerconcentrationareawhereagriculturaltreatmentwouldbefocusedinall20alternatives.Theremediationemphasiswillbeongroundwaterextractionandtreatmentvia21agriculturalunits.Chromiumplumecontainmentisaccomplishedthroughthemaintenanceof22seasonaloryear‐roundinwardhydraulicgradientsproducedbynumerousgroundwater23extractionwellsandlimitedfreshwaterinjection.Watersupplypumpingintheloweraquifer1324willbeminimizedtomitigatefurtherCr[VI]impactsontheloweraquifer.Aggressivepumping25intheupperaquifer14overtheloweraquifercombinedwithminimizingloweraquiferpumping26isalsoplannedtoneutralizeorreversedownwardgradientsandmitigateCr[VI]impacts27occurringviadownwardmigration.Limitedremedialpumpingintheloweraquifermayalsobe28consideredinthefuturetoaddressthelimitedareaofcontaminationintheloweraquiferat29present.In‐situremediation,asdescribedabove,maybeappliedtoOU2toaddresshigher30concentrationsoftheplumeifand/orwhereitispresentinOU2.Anabove‐groundtreatment31plantwouldbeincludedinOU2inAlternative4C‐3toprovideforwintergroundwater32extractionandtreatment.33

OU3.AsofDecember2011,theexpandedplumeincludedover900acresinOU3.Assuch,34agriculturallandtreatmentmaybeappliedtotreattheplumeinOU3,similartothatdescribed35aboveforOU2.Groundwatermonitoringandassessmentactivitiesarecurrentlyongoinginthe36northernsectionofOU3incoordinationwiththeWaterBoard.ItispossiblethattheOU3area37(andsubsequentlytheplumeareaboundary)couldchangeintheeventmonitoringand38assessmentactivitiesshowcontinuedmigrationofchromiumcontaminationlevels.Monitoring39

13Theloweraquiferistheportionoftheaquiferlocatedbelowtheclayconfininglayer(i.e.,theblueclay)whichseparatestheupperandloweraquifer.14Theupperaquiferistheportionoftheaquiferlocatedabovetheblueclaywhichseparatestheupperandloweraquifer.

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California Regional Water Quality Control Board, Lahontan Region  Project Description 

 

Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

2‐31 August 2012

ICF 00122.11

 

andremedialpumpingandconveyance(toagriculturalunittreatmentunits)aretheprimary1activitiesanticipatedforthisarea.Elevatedtotaldissolvedsolids(TDS)andnitrate2concentrationsareobservedinsomeofthenorthernportionsofOU3asaresultofhistorical3agriculturaloperations.AlthoughnoremediationiscurrentlyshownforOU3inthefeasibility4studyandaddenda,itisexpectedthatnewagriculturalunitunitsmaybeplacedinOU3starting5intheareasnorthofThompsonRoadwithgroundwaterextractionwithlocalizedagricultural6unittreatment.Ex‐situtreatment(asproposedinAlternative4C‐3)couldalsobeimplemented7inOU3incombinationwithabove‐groundtreatment,ifrequired.AdjustmentofthefinalOU38boundarymaybenecessarytoaddressanymigrationofthechromiumcontaminationlevels.9

2.10.2 Construction Equipment 10

Constructionequipmentwillbeneededfortheinstallationofwellsandsupportinginfrastructure,to11developagriculturalunitsandconstructconveyancepipelinesandnewfacilitiesassociatedwith12above‐groundtreatmentplants.Thisequipmentwouldbesimilarforallalternatives.The13constructionequipmentandanticipateddurationofconstructionactivitiesaresummarizedbyeach14alternativeinTables2‐9and2‐10below.Constructionactivitiesareexpectedtooccurbetweenthe15hoursof7a.m.and7p.m.Uponcompletionofconstruction,allconstructionequipmentwillbe16removedandsiteswillbereturnedtopre‐projectconditionstotheextentpossible.17

Table 2‐9. Required Construction Equipment and Infrastructure. 18Alternative ConstructionActivity EquipmentAllAlternatives

Pipelineinstallation ExcavatorBackhoeFront‐endloaderMotorgraderWatertruckUtilitypotholingmachineUtility/support/weldingtruck

Jumpingjackcompactor(aroundvaults)VibratoryplatecompactorTrenchrollercompactorGeneratorCompressorHDPEweldingmachine

Wellinstallationanddevelopment

DrillrigAuxiliarycompressorConcretewellvault480‐voltpowerdropandmotorcontrolpanelHDPEgroundwaterconveyancepipingSSsubmersiblegroundwaterextractionpump120‐voltpowerconduit

SupporttruckForkliftPVCandSSwellcasing120‐voltcontrolpanelwithradiocommunicationsSteelwellheadpipingSecurityfencingActuatedvalvesandswitches

Alternatives4C‐3and4C‐5only

Above‐GroundTreatmentFacilityGrading/excavation Motorgrader

BackhoeUtility/support/weldingtruck

RubbertireddozerFrontendloaderWatertruck

Paving/concrete Cement/mortarmakerRollerMotorgraderChopsawforsteelreinforcementVibratoryplatecompactorUtility/support/weldingtruck

PaverFront‐endloaderwithforksWatertruckConcretesawGenerators

Buildingconstruction

CraneTractor/loader/backhoeCutoffsawordemolitionsawVibratoryplatecompactorUtility/support/weldingtruck

ForkliftFront‐endloaderwithforksConcretesaw

Source:PacificGasandElectric2011d,2012Notes:HDPE=High‐densitypolyethylene,PVC=Polyvinylchloride,SS=Stainlesssteel

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Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

2‐32 August 2012

ICF 00122.11

 

Table 2‐10. Typical Timeframes by Alternative 1

AlternativePipelineaInstallation

WellInstallationandDevelopmenta

TreatmentFacility—GradingandExcavation

TreatmentFacility—PavingandConcrete

TreatmentFacility—BuildingConstructiona

NoProject 5months 16months n/a n/a n/a

Alternative4B 3months 6months n/a n/a n/a

Alternative4C‐2 4months 11months n/a n/a n/a

Alternative4C‐3 6months 16months 1month 2months 12months

Alternative4C‐4 7months 11months n/a n/a n/a

Alternative4C‐5 4months 11months 1month 2months 12monthsa ThedurationassumesfullbuildoutasdefinedintheFeasibilityStudyandAddenda.DurationsforactionsrelativetothelargerplumeareassumedtobethesameasdescribedinFeasibilityStudyandAddendaindicatinghigherintensityofactivitywithhigherinfrastructureconstruction.

2.10.3 Construction Activities 2

2.10.3.1 Wells and Agricultural Units 3

Constructionofnewwellswouldinvolveaminimalamountoflandclearing,welldrillingandwell4casingplacement,installationofwellpadsandmounts,installationofsupportingequipment5(e.g.,pumps)andmixingtanks(forwellsusedinin‐situtreatment),installationofconveyance6piping,andinstallingexclusionaryfencingaroundthewelloperationalarea.7

Constructionofnewagriculturalunitswouldinvolvelandclearing,plantingofcrops,installationof8irrigationsystems,andinstallationofconveyancepipingtocarrywaterpumpedfromextraction9wellsforlandapplication.Newaccessroadsmayberequiredtoreachwellsandagriculturalunits10withtheirassociatedsupportinginfrastructureinareasthatwerepreviouslyundisturbed.These11accessroadswouldprimarilybeunpavedandconsistoflandclearedtoaccommodatethelargest12pieceofequipment(abouta10‐footwidelane).Itisestimatedthatapproximately3–6workersper13daywouldberequiredforinstallationanddevelopmentofawellandapproximately15workersper14daywouldberequiredforpipelineinstallation.15

2.10.3.2 Ex‐Situ Treatment Facilities 16

Constructionoftheex‐situ(above‐ground)facilitieswouldinvolvesitepreparationthroughgrading17andexcavation,pavingandconcretepouringforbuildingfoundations,andconstructionofthe18treatmentfacilitybuildingandotherstructures.Newutilitiesincludingpowerconnections19(includingbackupdieselgenerators),septicsystems(fornon‐processandnon‐labwastewater),and20telecommunicationsconnectionsalsowouldbeinstalled.Anewpavedroadwouldbeconstructedto21provideaccesstothetreatmentfacilityfromtheneareststreet.Therewouldbeapproximately5–1922workersonsiteperdayduringconstructionactivities.Uponcompletionofconstruction,all23constructionequipmentwouldberemovedandsiteswouldbereturnedtopre‐projectconditionsto24theextentpossible.Thesizeoftheabove‐groundfacilityisdescribedunderEx‐SituTreatment25Facilitiesbelow.26

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2.10.4 Operations and Maintenance Activities 1

Operationsandmaintenance(O&M)activitieswouldbesimilartocurrent,ongoingactivitiesand2wouldbesimilaracrossallalternativesforeachtypeoftreatmentbeingimplemented.Thescaleof3activitywouldincreasefromexistinglevelsandwouldvaryinscalefordifferentprojectalternatives.4

2.10.4.1 Wells 5

Operatingcharacteristicsforfutureextractionandinjectionwellswouldbesimilartotheoperating6characteristicsofexistingwells.Extractionwellssupplyingwatertoagriculturalunitswould7operatemostlyatnight,andthelevelofpumpingactivitycouldvaryoverthecourseoftheyear.8(Operationsandmaintenanceactivitiesassociatedwithagriculturalunitsaredescribedbelow.)IRZ9extractionandinjectionwellswouldlikelyoperatecontinuously,andflowcouldvarybasedonthe10relativeoptimizationyear.SourceAreaIRZwellsandthefreshwatersupplywellPG&E#14are11connectedtotheHinkleyCompressorStation’selectricalsupply.Itisexpectedthatpowertonew12IRZwells(notwithintheSourceAreaIRZ)wouldcomefromtie‐instotheexistinginfrastructure13andwouldbepoweredbytheelectricgrid.Itisexpectedthat2to4additionalworkerswouldbe14neededtooperateandmaintainnewwellandassociatedfacilities.15

ThemainoperationsandmaintenanceactivitiesatIRZwellswouldinclude:16

Dailysystemchecks(e.g.,onsitesysteminspections);17

Collectionofoperatingdataatwellandotherfacilitysites(e.g.,water‐levelmeasurements,tank18readings);19

Adjustmentofpumpoperations;20

CompletingCentralArea,SourceArea,andSouthCentralAreainjections;21

Periodiccleaning,includinghandlingofbackwashwater;22

Periodictroubleshooting,repairs,andreplacementofcomponents;23

Collectionofwaterqualitysamplesforlaboratoryanalysis;24

Periodiccleaningormaintenanceofpipelines,tanks,andappurtenances;25

Removalandcleaningormaintenanceofdownholeequipmentsuchaspumps,pipes,andvalves;26and27

As‐neededmanualcarbonsubstrateaddition.28

Freshwatersupplywellswouldcontinuetobeoperatedasunderexistingconditions.Thesame29generalO&MactivitieswouldoccuratthesewellsasundertheIRZwells.Inaddition,O&Mactivities30atthesewellswouldrequireadjustmentofflowratesinextractionwellsandinindividual31freshwaterinjectionwellstooptimizehydraulicmounding.32

Desert View Dairy Land Treatment Unit 33

OperationsandmaintenanceactivitiesassociatedwiththeDesertViewDairylandtreatmentunit34wouldcontinueasexistingconditionsandinclude:35

Performingdailysystemchecksforleaks,potentialtroubleshootingandrepair,andgeneral36maintenanceneeds;37

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Comprehensive Groundwater Cleanup Strategy for Historical Chromium Discharges from PG&E’s Hinkley Compressor Station Draft Environmental Impact Report 

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ICF 00122.11

 

Collectingsystemflow,pressure,andtotalizerreadingsinextractionwellsandboosterpump1andperformingvisualinspectionofinstrumentationandequipment;2

Adjustingflowratesinindividualextractionwellstooptimizeirrigationratesand/orhydraulic3capture;4

Collectingwaterdepthmeasurementsatextractionwellsandsamplesfromlysimetersand5monitoringwellsforlaboratoryanalyses;6

Planting,coordinatingharvestscheduling,andevaluatingcrophealth;7

Periodictroubleshooting,maintenance,andrepairofpumpsandothersystems;8

Periodicwellrehabilitationandredevelopment;9

Periodiccleaningormaintenanceofpipelinesandappurtenancesviasurgingorchemical10injection;11

Removalandcleaningormaintenanceofdownholeequipmentsuchaspumps,pipes,andvalves;12and13

Replacementofequipmentoverthecourseofoperations.14

Agricultural Units 15

Operationsandmaintenanceactivitiesassociatedwithlandtreatmentviaagriculturalunitswould16besimilartoexistingagriculturalunitoperations,whicharealsosimilartotheDesertViewDairy17landtreatmentunitoperations.O&Mactivitiesatnewagriculturalunitswouldinclude:18

Checkingwaterapplicationratestoevaluategroundwaterextractionforhydrauliccontrol;19

Routineinspectionandmonitoringofextractionwellperformance;20

Routineinspection,repair,andmaintenanceoffiltersandsystemparts;21

Planting,coordinatingharvestscheduling,andevaluatingcrophealth;22

Periodicwellrehabilitationandredevelopment;23

Periodiccleaningormaintenanceofpipelinesandappurtenances;24

Periodicpumptroubleshootingandrepair;25

Removalandcleaningormaintenanceofdownholeequipment–pumps,pipes,andvalves;and26

Replacementofequipmentoverthecourseofoperations.27

Itisexpectedthat1to3additionalworkerswouldbeneededtooperateandmaintainthenew28agriculturalunits.29

Ex‐Situ Treatment Facilities 30

Asdescribedabove,therewouldbetwoex‐situ(above‐ground)treatmentfacilitiesunder31Alternative4C‐3andonetreatmentfacilityunderAlternative4C‐5.Figures2‐6and2‐8,32respectively,showtheapproximatelocationsoftheex‐situtreatmentfacilities.Eachoftheproposed33above‐groundtreatmentfacilitieswouldbelocatedinacompoundapproximately40,500square34

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feetinsize.15ForAlternative4C‐3,onefacilitywouldtreatwaterfrommostlynorthofSR58andone1wouldtreatwaterfrommostlysouthofSR58.ForAlternative4C‐5,thefacilitywouldonlytreat2waterintheSourceAreasouthofSR58.Eachtreatmentfacilitywouldincludetreatmentwells,3conveyancesystemoperations,a35‐foottallprocessbuildingandanoffice/laboratory,and12‐foot4highsecurityfencingwithbrownslats.Theprocessbuildingswouldhousepumps,pipes,reactors16,5filters,andotherequipmenttotreatthecontaminatedwater.Theoffice/laboratorieswouldinclude6officespaces,acontrolroom,restrooms,andalaboratory.Theareawithinthecompoundwouldbe7paved,wouldincludeaconcreteloadingdockforoutgoingwasteandincomingmaterials,andwould8includeexteriorfloodlighting.Watertanksandotherappurtenantstructuresmaybehousedinthe9compoundareas.Operationsofnewfacilitieswouldbepoweredbytheexistingelectricgrid.Waste10residuefromex‐situwatertreatmentwouldbetransportedanddisposedoff‐siteattheWaste11ManagementKettlemanHillsFacilityorasimilarClassIlandfillpermittedtoaccepthazardous12wastesasauthorizedunderTitle27oftheCaliforniaCodeofRegulations.Operationsand13maintenanceactivitiesassociatedwithex‐situtreatmentfacilitieswouldprimarilyinclude:14

Monitoringandmaintenanceofex‐situtreatmentwellsandconveyancesystemoperations;15

Collectingandanalyzingmid‐treatmentsamplesattheon‐sitelab;16

Measuring,tracking,andchangingoperationalandprocessparametersasneeded;17

Schedulingtrashandlabwastepickupandtransportationtoalandfill;18

Schedulingmaterialsdelivery;19

Mechanicalmaintenanceofallequipment;and20

Inspectionandmaintenanceofallsupportingstructures.21

Onetothreeworkerswouldbepresentatalltimes(24‐hoursaday)ateachtreatmentfacilitythat22maybeconstructed,workingin2–3shiftsperdaytoconductallO&Mactivities.23

2.11 Other Alternatives Considered but Dismissed 24

from Further Analysis 25

CEQArequiresthattheleadagencyconsideralternativesthatwouldavoidorreduceoneormoreof26thesignificantimpactsidentifiedfortheprojectinanEIR.TheCEQAGuidelines(Title14ofthe27CaliforniaCodeofRegulations)statethattherangeofalternativesrequiredtobeevaluatedinanEIR28isgovernedbythe“ruleofreason”;theEIRneedstodescribeandevaluateonlythosealternatives29necessarytoallowareasonablechoiceandtofosterinformeddecision‐makingandinformedpublic30participation(CEQAGuidelinessection15126.6[a][f]).Detailedconsiderationofalternativesfocuses31onthosethatcaneithereliminatesignificantadverseenvironmentalimpactsorreducethemtoless‐32than‐significantlevels;alternativesconsideredinthiscontextmayincludethosethataremore33costlyandthosethatcouldimpedetosomedegreetheattainmentofalltheprojectobjectives(CEQA34Guidelinessection15126.6[b][f]).CEQAdoesnotrequirethealternativestobeevaluatedinthesame35levelofdetailastheproposedproject.36

15Theprecisesizeofthetreatmentfacilitydependsonthealternative.16Thisisavat(i.e.,vatreactor)wherethecontaminatedwaterisplacedtoreactwithsubstances.

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Aspartofthealternativesdevelopmentprocess,arangeofreasonablechromiumcleanup1alternativeswasevaluatedinthe2002and2010feasibilitystudiesandthethreeaddendatothe22010FeasibilityStudy.Thesealternativesincludesuggestionsbymembersofthepublicduringthe3EIRscopingprocess.4

Outofthesealternatives,fiveprojectalternatives(4B,4C‐2,4C‐3,4C‐4,and4C‐5,asdescribed5above)wereselectedfordetailedanalysisinthisEIR.6

Theotheralternatives,alldescribedbelow,eitherdonotmeettheprojectgoalandmostofthe7objectives,orhavefeasibilityoreffectivenessconcernsthatprecludedthemfromfurther8consideration.Thealternativesaredescribedbrieflybelow,andthereasonstheyweredismissed9fromfurtherconsiderationareidentified.10

2.11.1 2010 Feasibility Study Alternative 1—Natural 11

Attenuation 12

Thisalternativeassumesnofuturepumpingorgroundwatertreatment;thus,currentcontainment13pumping,agriculturalwatertreatment,andin‐situchromiumtreatmentoperationswouldbe14discontinued.Thisalternativewouldtakemorethan1,000yearstoreduceCr[VI]concentrationsto153.1ppb.Thisalternativedoesnotmeetthefundamentalprojectobjectivesbecauseitdoesnotclean16upchromiuminthegroundwaterwithinameaningfulperiodoftime.17

2.11.2 2010 Feasibility Study Alternative 2—Containment Only 18

Themainoperationalfeaturesofthisalternativeincludeplumecontainment/hydrauliccontrol19throughgroundwaterextractionfollowedbytreatmentanduseofextractedgroundwaterfor20agriculturalapplication.AlloperationswouldoccurnorthofSR58.Thisalternativewouldtake21approximately120yearstoreduceCr[VI]concentrationsthroughouttheplumeto50ppb,260years22toreduceCr[VI]concentrationsto3.1ppb,and320yearstoreduceCr[VI]concentrationsto1.2ppb.23Thisalternativedoesnotmeetthefundamentalprojectobjectivesbecauseitdoesnotcleanupthe24groundwaterwithinameaningfulperiodoftime.25

2.11.3 2010 Feasibility Study Alternative 3—Plume‐Wide In‐Situ 26

Treatment 27

TheconceptualapproachforAlternative3istoutilizeextractionwellsatthepointoftheplume28farthestawayfromthesourcetoprovidehydrauliccontainment,addcarbonamendmenttothe29extractedwater,andinjectthecarbon‐amendedwaterintowellstocreateIRZs.Thisalternative30wouldtakeapproximately8yearstoreduceCr[VI]concentrationsthroughouttheplumeto50ppb,31approximately110yearstoreduceCr[VI]levelsto3.1ppb,and180yearstoreduceCr[VI]32concentrationsto1.2ppb.Thisalternativedoesnotmeetthefundamentalprojectobjectives33becauseitdoesnotcleanupchromiumingroundwaterwithinameaningfulperiodoftime.34

2.11.4 2010 Feasibility Study Alternative 4—In‐Situ Remediation 35

and Land Treatment 36

Thisalternativewouldbesimilartothegeneralcombinedtreatmentapproachpresentlyoperating37intheprojectarea(in‐situremediationandagriculturallandtreatment)andthatproposedin38

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Alternatives4Band4C‐2.Asoriginallyproposedinthe2010FeasibilityStudy,thisalternativewas1onlydesignedtoaddresstheextentofthechromiumplumethatwasknownasofFebruary2010,2whichisfarsmallerthantheplumenowknowntoexistasoflate2011andwouldhaveagricultural3unitsandpumpingsimilartowhatisalreadyoccurring,butwouldhaveincreasedIRZtreatment.4Thisalternativewouldtakeapproximately6yearstoreduceCr[VI]concentrationsthroughoutthe5plumeto50ppb,approximately150yearstoreduceCr[VI]concentrationsto3.1ppb,and220years6toreduceCr[VI]concentrationsto1.2ppb.Thisalternativedoesnotmeetthefundamentalproject7objectivesbecauseitdoesnotcleanupchromiumingroundwaterwithinameaningfulperiodof8time.9

2.11.5 2010 Feasibility Study Alternative 5—Plume‐Wide Pump 10

and Treat 11

Thisalternativewouldfocusonplumecontainmentandex‐situtreatmenttoreduceCr[VI]12contaminantmasswhileprovidingsupplementalcontainmentthroughrechargingthetreated13groundwatertotheperipheryoftheplume.Thisalternativeprovidesalevelofhydraulic14containmentsimilartoAlternative2,althoughwithadifferentgroundwaterwithdrawal15configuration.Thisalternativewouldtakeapproximately50yearstoreduceCr[VI]concentrations16throughouttheplumeto50ppb,approximately140yearstoreduceCr[VI]concentrationsto3.117ppb,and210yearstoreduceCr[VI]concentrationsto1.2ppb.Thisalternativedoesnotmeetthe18fundamentalprojectobjectivesbecauseitdoesnotcleanupchromiumingroundwaterwithina19meaningfulperiodoftime.20

2.11.6 2010 Feasibility Study (Addendum 1) Alternative 4A—21

Aggressive In‐Situ Treatment with Beneficial Agricultural 22

Use 23

Alternative4Awasdevelopedtofurtheraccelerateclean‐upperiodstomeettheprojectobjectiveof24timelycleanup.Alternative4AwasenlargedinscaleoverfeasibilitystudyAlternative4byan25increaseintheCentralAreaIRZ,expansionofagriculturalunits,increasingIRZoperationsby1526years,andincreasingthevolumeofgroundwaterextractionforapplicationtoexpandedagricultural27units.Alternative4AwouldcleanupCr[VI]contaminationtothemaximuminterimcleanuptarget28levelof3.1ppbin75yearsandtotheaverageinterimcleanuptargetlevelof1.2ppbin130years.29Thesetimeperiodswouldnotadequatelymeettheobjectivesoftheproject.30

2.11.7 2010 Feasibility Study (Addendum 1)—Combined 31

Alternative 32

TheCombinedAlternativewasdevelopedasanalternativemethodforacceleratingremovalof33Cr[VI]fromthehighconcentrationareaoftheplumethroughadditionofex‐situtreatmentatan34above‐groundfacility.TheCombinedAlternativewouldcleanupCr[VI]contaminationtothe35maximuminterimcleanuptargetlevelof3.1ppbin90yearsandtotheaverageinterimcleanup36targetlevelof1.2ppbin130years.37

ThisalternativewouldbeslowerthanAlternative4B,anyofthealternativesdevelopedunder38Addendum3,andAlternative4C‐5,whichincludesabove‐groundtreatment(includedinthe39

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detailedanalysisintheEIR).Thisalternativedoesnotachievetheprojectobjectiveoftimely1cleanupand,therefore,doesnotmeaningfullyexpandtherangeofalternativesforanalysis.2

2.11.8 2010 Feasibility Study (Addendum 3) Alternative 4C‐1—3

In‐Situ and Enhanced Agricultural Treatment (1 crop) 4

Alternative4C‐1wasdevelopedtofurtherexpandonthein‐situandagriculturaltreatment5approachesdevelopedunderAlternative4B.Themaingoalsofdevelopingthisalternativewereto6optimizeandincreaseextractionrelatedtoplumecapture,mitigateplumemigrationtotheeast,7reducetheincidenceoftheuntreatedareasintheIRZ,reduceformationofmanganeseasaby‐8productofin‐situreduction,andattempttofurtherreducetheoverallremediationtimeframe.This9alternativedoesnotacceleratecleanuptimeperiodsorprovideadditionalbenefitbeyondthat10providedbyAlternatives4B,4C‐2,4C‐3,4C‐4,or4C‐5,andthusdoesnotmeaningfullyexpandthe11rangeofalternativesforanalysis.12

2.11.9 Other Alternative Technologies Considered in the 13

2010 Feasibility Study 14

Thefollowinglistdescribestherangeofotheralternativetechnologiesforchromiumcleanup15consideredinthe2010FeasibilityStudythatweredismissedfrommoredetailedanalysisor16considerationintheEIR.Thesealternativeswerescreenedoutbecauseeither(1)theydonotmeet17theprojectgoalandmostoftheobjectivesor(2)feasibilityoreffectivenessconcernsprecluded18themfromfurtherconsideration.Thesealternativesarebrieflydescribedbelow,andthereasons19theyweredismissedfromfurtherconsiderationareidentified.20

AlternativeWaterSupply:Developaplantosupplyalternativewatertolocalresidentsanda21monitoringprogramtolimituseofcurrentlyaffecteddomesticgroundwaterwells.Thiswould22requireagroundwaterpipinginfrastructurefromthenewwell(s).Thisalternativealonewould23notresultinremediationofthecontaminatedaquiferandwouldnotreturnittobeneficialuse.24Asdescribedabove,the2011CAO(No.RV6‐2011‐005)requiresPG&Etoprovideinterimand25wholehousereplacementwaterservicetothoseservedbydomesticorcommunitywellsthat26arewithintheaffectedareaanddeterminedtobeimpactedbyitsdischarge.TheOrderdefined27impactedwellsasalldomesticorcommunitywellsintheaffectedareathatareabove3.1ppb28hexavalentchromiumor3.2ppbtotalchromiumplumeboundaries,baseduponmonitoringwell29datadrawninthemostcurrentquarterlysite‐widegroundwatermonitoringreportsubmitted30byPG&E.TheOrderalsodefinedimpactedwellsasthosedomesticorcommunitywellsinthe31affectedareathatcontainhexavalentchromiuminconcentrationsgreaterthan0.02ppbthat32weretheresultofPG&E’sdischargeattheFacility.Asaresult,thisremedialactionisalready33requiredandneednotbeconsideredasanalternative.34

Containment—Capping:Coveraffectedareaswithanimpermeablecap(i.e.,engineered,native35soils,orimportedsoilcaps)tomitigateinfiltrationandaidingroundwatertransport36retardation.Thisalternativewasnotretainedbecauseitisconsiderednottobeeffectivedueto37limitedrainfallintheregion,influencesofareaagriculturalpumping,andthedepthof38contaminatedgroundwater.Thisalternativealsowouldnotrestorebeneficialusestothe39aquifer.40

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Containment—PhysicalBarriers:Installaverticalorhorizontalphysicalbarrierthatlimits1themigrationoftheaffectedgroundwater.Thislikelywouldbeincorporatedinconjunction2withagroundwaterextractionsystem.Thisalternativeiseffectiveinlocalizedareas,butitwas3notretainedbecausetheextent(5.4milesby2.4miles)andmobilityoftheplumealongwiththe4requireddepths(>100feet)wouldmakeitinfeasibletoeffectivelycontroltheplumeusingthis5method.6

In‐SituBiologicalTreatment—AerobicBioremediation:Addanoxidativesubstratetothe7subsurfacetoaerobicallydegradeCr[VI].Thisalternativewasnotretainedbecauseitisnot8applicabletoCr[VI]asthismaterialisalreadyinanoxidizedstateandneedstobereduced9ratherthanoxidized.10

In‐SituBiologicalTreatment—Phytoremediation:Useplantsandtheirassociated11rhizosphericmicroorganismstoremove,degrade,orcontaincontaminantsingroundwater.This12alternativewasnotretainedbecausetheextentofgroundwatercontaminationistoodeepfor13thisdirectapplicationtobeeffective.However,theagriculturallandtreatmentincludedinall14projectalternativesoperatesonthesameprincipalsasthisalternative,butusesagricultural15cropsandtheirmicroorganisms.Thereforethisalternativeisincorporatedinitsgeneral16approachintotheprojectalternatives.17

In‐SituPhysical/ChemicalTreatment—AirSparging:Injectairintothesubsurfaceto18volatilizethecontaminantandenhanceaerobicconditionstoaccelerateaerobicbiological19remediationofplume.Thisalternativewasnotretainedbecauseairspargingisnotapplicable20forCr[VI],whichisnotvolatileandalreadyexistsinanoxidizedstate.21

In‐SituPhysical/ChemicalTreatment—ElectrokineticTreatment:Createelectricalfieldsby22applicationoflow‐voltagepowertosubsurfaceelectrodestoalterredoxstateandtoimmobilize23certainconstituentsin‐situ.Althoughthisalternativeiseffective,itwasnotretainedbecauseit24iscost‐prohibitiveduetothelargesizeoftheplume.Inaddition,thistechnologyisonlyeffective25inareasofhighcontaminantconcentrations,butnotforrelativelylowCr[VI]concentrationsand26highaquiferpermeabilitycharacteristicoftheplume.27

In‐SituPhysical/ChemicalTreatment—DualPhaseExtraction:Applyahigh‐powered28vacuumsystemtosimultaneouslyremovesoilvapors,groundwater,andotherliquid(i.e.,29nonaqueous‐phaseliquid)fromlow‐permeabilityorheterogeneoussubsurfaceenvironments.30ThisalternativewasnotretainedbecauseCr[VI]isnotvolatile,andthistechnologyhasnotbeen31proventoreduceCr[VI]concentrations.32

In‐SituPhysical/ChemicalTreatment—PermeableReactiveBarriers(PRBs):Install33permeabletreatmentwalls(i.e.,zero‐valentironPRBs)usingtrenches,fracturing,boreholes,or34othermeanstocreateabarrierwallacrosstheflowpathofacontaminantplume.As35groundwatermovesthroughthetreatmentwall,contaminantsarepassivelyremovedinthe36treatmentzonesbyphysicaland/orchemicalprocesses.Althoughthisalternativeiseffective,it37wasnotretainedbecauseitisnotfeasibleduetothedepthofcontamination,whichisatthehigh38endoftraditionaltrenchapplicationtechnologylimits.39

In‐SituPhysical/ChemicalTreatment—In‐SituAirStripping:Injectairintothesubsurface40(throughcirculatingcells,vacuumvaporextraction,etc.)atahighratetostripCr[VI]outofthe41groundwater;theprocessalsooxidizesthetreatmentarea.Thisalternativewasnotretained42becauseairstrippingisnotapplicableforCr[VI],whichisnotvolatileandalreadyexistsinan43oxidizedstate.44

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In‐SituPhysical/ChemicalTreatment—In‐SituChemicalOxidation:Injectanoxidantsuch1ashydrogenperoxideorpotassiumpermanganatetooxidizetheaffectedareas.Thisalternative2wasnotretainedbecausechemicaloxidationhasnotbeenproventoreduceCr[VI]3concentrationsbecauseCr[VI]alreadyexistsinanoxidizedstate.4

In‐SituThermalTreatment—SteamInjection,6‐PhaseHeating,ElectricalResistance:Use5heattovolatilize,oxidize,ormobilizeCr[VI].Thisalternativewasnotretainedbecauseitisnot6applicableforreducingCr[VI]concentrationsasCr[VI]alreadyexistsinanoxidizedstate,isnot7volatile,andneedstobereduced.8

Ex‐SituBiologicalTreatment—AerobicBioremediation:Addanoxidativesubstratetoa9bioreactortoaerobicallydegradeCr[VI].Thisalternativewasnotretainedbecauseitisnot10applicableforreducingCr[VI]concentrationsasCr[VI]alreadyexistsinanoxidatedstateand11needstobereduced.12

Ex‐SituPhysical/ChemicalTreatment—ChemicalOxidation:Extractgroundwaterfromthe13subsurfaceandaddanoxidantsuchashydrogenperoxideorpotassiumpermanganatetothe14flowtooxidizetheaffectedgroundwater.Thisalternativewasnotretainedbecauseitisnot15applicableforreducingCr[VI]concentrationsasCr[VI]isalreadyinanoxidatedstateandneeds16tobereduced.17

Ex‐SituPhysical/ChemicalTreatment—AirStripping:Extractwaterandpassitthroughan18airstrippertostripCr[VI]fromthegroundwatertotheair.Thisalternativewasnotretained19becauseitwouldnotbeeffectiveasCr[VI]isnotvolatileandthereforewillnotstripoutof20water;inadditionthetechnologyhasnotbeenproventoworkforremovingCr[VI]fromwater.21

Ex‐SituPhysical/ChemicalTreatment—ElectrocoagulationProcess:Useelectricitypassed22throughironplatestogenerateferrousirontoreducethechromiumandprecipitateitfrom23solution.Theresultingsludgeissettledinaclarifierandthendisposed.Thisalternativecanbe24effectivebutwasnotretainedbecauseitisnotfeasibleatthesiteduetohighcapitalandO&M25costs,andbecausethesizeoftheexistingdiffuseplumeandtreatmentflows.26

Ex‐SituPhysical/ChemicalTreatment—Liquid‐PhaseCarbonAdsorption:Pump27groundwaterthroughaseriesofcanistersorcolumnscontainingactivatedcarbontowhich28dissolvedorganiccontaminantsareadsorbed.Periodicreplacementorregenerationof29saturatedcarbonisrequired.Thisalternativewasnotretainedbecauseitisgenerallynot30applicabletoCr[VI]treatment,andbecauseCr[VI]doesnotabsorbtocarbonmediaasorganic31carboncontaminantsdo.32

Discharge/Injection—Off‐SiteManagementatPermittedFacility:Pumpgroundwaterfrom33theplumeandpipeorshipittoanoff‐sitetreatmentfacility.Thisalternativewasnotretained34becausetheprojectareaislocatedinaremoteareaandnotreatmentfacilityislocatedwithina35suitabledistanceforthisoption,especiallyinlightoftheamountofcontaminatedwaterthat36wouldhavetobepipedorshippedconsideringtheplumeextentandextractionflows.In37additiontothepotentialnegativeenvironmentalimpactsofextensiveshipping,offsitedisposal38wouldreducegroundwateravailabletosurroundingagriculturaloperations.39

Discharge/Injection—DischargetoSurfaceWater:Treatgroundwaterusingex‐situ40remediationbyanapprovedtreatmentmethodandthendischargetreatedwatertosurface41receivingstreams.Althoughthisalternativeiseffective,itwasnotretainedbecausethe42preferenceistokeepwaterwithinprojectboundariesandreturnittotheaquiferifpossible,43andtherealsoarenoreceivingsurfacewaterstreamswithactiveflowinthearea.44

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Discharge/Injection—DischargetoEvaporationPonds:Usesurfaceimpoundmentsto1containtreatedoruntreatedgroundwateruntilitevaporates.Evaporationpondsfortemporary2storageofextractedwaterwereevaluatedasacontingencytoinjectionoragricultural3application.Evaporationpondswouldbedesignedwithimpermeablelinerstoprevent4infiltrationofstoredwater,aleakdetectionsystem,andaccesscontrolstopreventaccesstothe5pondsbyunauthorizedpersonnelorwildlife.Thepondswouldpossiblyrequireclassificationas6permittedWasteManagementUnitsbasedonthequalityofthestoredwater.Pondswould7requirelargesurfaceareastocompletelyevaporatestoredwaterinareasonabletime.A8minimumofapproximately330acresofstoragepondswouldberequiredtoevaporate9extractedwaterwithinoneyear.Theconcentrationofdissolvedconstituentswouldincreaseas10storedwaterevaporates,possiblyrequiringfurthertreatmentoroff‐sitedisposalofremaining11concentratedwaterorsludge.Evaporatedwaterwouldnotbeputtobeneficialuses,suchasfor12agriculture,orinjectedtoenhanceplumecontrol.Itismorefeasibletotreat,irrigate,or13otherwiseactivelymanageextractedwateratthetimeofextractionratherthantostoreiton‐14sitebecauseon‐sitestoragewouldrequiresomuchlandandalsomayrequirefurtheron‐siteof15off‐sitetreatment.Thisalternativewasnotretainedbecausespacerequirements,potential16environmentalimpacts(e.g.,theconversionofagriculturallandtoponds),andreduced17groundwateravailabilityforagriculturerenderthealternativeunattractive.18

Thefollowinglistdescribesotheralternativesconsideredforchromiumcleanupinthe201019FeasibilityStudythatinitiallywereretainedduringthealternativesscreeningandwerepilot‐tested20orresearchedforapplicationatthesite.Althoughthesealternativeswereinitiallyretained,they21ultimatelywerenotincludedascoreelementsoftheremedialalternativesbecausethereareother22technologiesincludedinthefiveactionalternativesanalyzedinthisEIR(agriculturalland23treatment,in‐situremediation,andex‐situremediation)thathavebeenfoundtobemoresuitedfor24usebasedonpastsiteexperienceorotherconsiderations.Thesetechnologyalternativesmayplaya25roleinthefutureassubstitutesforthecoreelements(forexample,anionexchangesystemcouldbe26substitutedforachemicalreduction/precipitationsystemforuseinanex‐situtreatmentplant).27Thesealternativesarebrieflydescribedbelowandthereasonstheywerenotselectedasthecurrent28primarytechnologyatthistimeareidentified.29

Direct‐PushTechnology(DPT):Directlyinjectreducingagentsatvariousgroundwaterdepths30ineachoftheDPTinjectionpoints.TracerstudyresultsindicatedDPTisnoteffectiveforfull‐31scaleimplementationbecausethedistributionofinjectedamendmentintargetareaswas32unpredictableandwouldrequireverycloseinjectionspacing(PacificGasandElectricCompany332010).34

InfiltrationGalleriesforIn‐SituCr[VI]ReductionintheVadoseZone:Divertcontaminated35groundwaterthroughasubsurfaceinfiltrationgallery(gravel)andamendtheinfiltratedwater36withethanolandthetracerdyeeosine.PilotStudyresultsindicatedinfiltrationgalleriescanbe37effective,buttheycouldgenerateby‐productssuchasiron,manganese,andarsenic(similarto38IRZoperations),theydonotprovideforanybeneficialuseofgroundwater(e.g.,forcrop39production),andfull‐scaleinfiltrationgallerieshavenotbeentestedorprovenatthesite.40

Ex‐SituTreatmentUsingIonExchangeUnits:RemoveCr[VI]inextractedgroundwaterusing41ionexchangetechnology.Althoughthistechnologywasnotrecommendedforuseintheex‐situ42treatmentplantspresentedinthefeasibilitystudy,thetechnologymaybebeneficialinspecific43circumstancesthatariseastheprojectevolves.Giventhesimilaritiesofenvironmentalimpacts44expectedforionexchangetochemicalreduction/precipitation,theanalysesinthisEIRforex‐45

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situchemicalreductionwouldbeapplicabletoion‐exchangeaswell.Intheionexchange1process,theCr[VI]isremovedbyexchangewithanotherinertion.Ion‐exchangecanbedone2througheitheraStrong‐BaseAnion(SBA)ExchangeoraWeak‐BaseAnion(WBA)Exchange.3BothwerereviewedforpotentialapplicationatHinkleyasdiscussedbelow.4

TheSBAexchangeprocessisgreatlyinfluencedbysulfateconcentrations.TheSBAresins5haveahigherselectivityforsulfatecomparedtootheranions.Hinkleygroundwaterhas6highconcentrationsofsulfate(relativetocomingledCr[VI]concentrations)thatseverely7affecttheperformanceandfeasibilityofSBAexchangeprocesses.TheLawrenceLivermore8NationalLaboratory(LLNL)evaluatedtheuseofSBAresinstoremoveCr[VI]from9groundwater.AttheLLNLSite,theaverageCr[VI]andsulfateconcentrationswere10respectively34ppband38ppm(LLNL1997).FortheLLNLstudy,thebreakthroughfor11Cr[VI]occurredatlessthan6,000bedvolumes,whichtranslatetoapproximately10daysof12runtimeat2.5minutescontacttime.TheCityofGlendaleevaluatedseveralSBAresinsfor13treatinggroundwaterwithCr[VI]andsulfateconcentrationsof100ppband87ppm,14respectively(WRFReport2007).Thenumberofbedvolumesforbreakthroughwas400to151,700,whichtranslatetoapproximately1to3daysofruntime.AttheHinkleySite,Cr[VI]16concentrationsinthediffusedowngradientareaoftheplumecanrangeaslowas17approximately2.5to4.5ppbwithsulfateconcentrationsintherangeof186to700ppm.18SulfateconcentrationsareseveralordersofmagnitudehigherthanCr[VI]concentrations19throughoutthediffusedowngradientplume.Underthesegroundwaterconditions,20anticipatedruntimebeforebreakthroughforSBAresinsislessthanoneday.Rigorouspilot21testingandcontinuousmonitoringandoperationofSBAvesselsinserieswouldbe22necessarytoavoidsubstandardperformancedueto“chromatographicpeaking,”whichisa23phenomenainwhichlesspreferentiallyabsorbedionsappearintheeffluentathigher24concentrationsthantheyappearintheinfluentastheyarereleasedfromionexchangeresin25whenmorestronglyheldionsareadsorbed.Duetointerferencefromhighlevelsofsulfate26insomeareasandexpectedshorttimetobreakthrough,theSBAexchangeprocessisnot27recommendedforfurtherconsiderationforlarge‐scaleremediationatHinkley17(PacificGas28andElectric2011c).29

TheWBAexchangeprocessislesssensitivetoco‐occurringions.However,thepotential30feasibilityofWBAexchangeprocessforCr[VI]removalfromHinkleygroundwaterhasnot31beenevaluatedatbenchorpilot‐scalelevel.BeforeWBAexchangecanbeconsideredasan32alternative,extensivepilottestingoftheWBAexchangeprocesswouldneedtooccurto33evaluatetechnicaleffectivenessandtheimplementabilityfactorsdescribedbelow(Pacific34GasandElectric2011c).35

TheperformanceoftheWBAresinsisstronglyinfluencedbyfactorssuchastheinfluent36waterpH.RecentstudiesindicatetheoptimumpHforCr[VI]removalisapproximately375.5to6.0.TestingisnecessarytoconfirmandoptimizethepHrangeforHinkley38groundwater.39

IntheWBAexchangeprocess,theCr[VI]canberemovedbytwomechanisms:ion40exchangeprocessandreductiontotrivalentchromium(Cr[III]).Themechanismof41

17IonexchangewithSBAisbeingconsideredasoneapproachforprovidingwhole‐housewaterforaffectedresidences.However,theuseforanindividualhouseisonaverysmallscalebycomparisonwiththeefforttocleantheentirecontaminatedplume.Theoperationalconcernsnotedaboveforlarge‐scaleapplicationarenotthesameforasingleresidence‐scaletreatmentsystem.

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removalfortheHinkleygroundwaterwillneedtobedeterminedtodesignatreatment1systemthatcanreliablylowertheCr[VI]concentrationstotherequiredtarget2concentrations.3

RecentstudiesonWBAresinsbytheCityofGlendaleindicatedpotentialleachingof4harmfulbyproductssuchasformaldehydeandN‐nitrosodimethylamine(NDMA)or5nitrosamines.TheEPAisplanningtoregulateNDMAindrinkingwaterinthenear6future.7

TheWBAresinscouldalsoaccumulateotherionssuchasradionuclides(uraniumwas8recentlydetectedatoneoftheexistingagriculturalunits),whichwouldrequirespecial9handlinganddisposalofthespentresin.10

RigorouspilottestingthataddressesthetechnicalissuesofWBAresinswouldneedto11beconductedpriortofull‐scaleimplementation.Pendingpilottestresultsthatprovide12datarequiredtofullyevaluatethetechnicaleffectivenessandabilitytoimplement,WBA13exchangemaybefeasiblefortheContingencyPlanduetothesimplicityof14implementationandalsomaybeconsideredatafuturedate.15

MembraneBiofilmReactors(MBfRs):ReduceCr[VI]andnitrateinextractedgroundwater16withamembrane‐basedbiologicaltreatment.Bench‐scaletestresultsindicatethatMBfR17technologycantreatgroundwaterwithCr[VI]concentrationsintherangeof50µg/L,butitis18ineffectivefortreatinggroundwaterwiththehighCr[VI]concentrationspresentintheplume19coreandhasnotbeendemonstratedfortreatmenttotheinterimcleanuplevelsforthisproject.20Thefollowingisasummaryofreasonswhythisalternativewasdismissedfromfurther21considerationatthistime(PacificGasandElectric2011c).22

Asdescribedinthefeasibilitystudy,MBfRisapotentiallyviabletechnologyfortreating23relativelylow(i.e.,≤50ppb)Cr[VI]concentrationsingroundwater.MBfRwasretainedasan24ex‐situtreatmentprocessoptionduringtheinitialtechnologyscreeninginthefeasibility25study,butwasnotselectedasthepreferredprocessoptionforremediationalternativesthat26wouldincludeex‐situtreatment.27

Bench‐scaletestingconductedbyPG&Ein2009showedproof‐of‐conceptoftheprocess’s28technicaleffectivenessforremovingCr[VI]ingroundwater.However,MBfRhasnotyetbeen29fullyimplementedataremediationsitetotreatCr[VI].Asofthelastreviewofthe30technology,MBfRwasbeingpilottestedforremovalofdissolvedperchlorateandnitratein31groundwateronly.Thetechnologyiscurrentlycommerciallyavailableonlyasanitrate32removalprocessinthewastewatertreatmentindustry.Asaresult,thetechnologycannotbe33fullyevaluatedfortechnicaleffectiveness.Ataminimum,thefollowingfactorswouldneed34tobebetterunderstoodbeforeitcouldbeadoptedasaremedialoption.35

Treatmenttodischargelimits:MBfRhasnotbeenproventoremoveCr[VI]tomeet36projectobjectivesofCr[VI]levelsof3.1ppbmaximumand1.2ppbaverageatfullscale.37

Reliability:Thistechnologyhasnotbeenimplementedatascalesimilartothescale38neededinHinkley.Itisnotknownwhetherthisprocesscouldoperatereliablyforthe39extendedperiodoftimeneeded.40

Hydrogenstorageandmanagement:MBfRusesdiffusedhydrogengasastheelectron41donor.Hydrogenwouldhavetobedeliveredandstoredorgeneratedon‐site.AsMBfR42hasneverbeenimplementedatthescalerequiredattheHinkleySite,itiscurrently43

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infeasibletofullyevaluatetheimplementabilityconstraintsofeffectivelyandsafely1delivering,storing,orgeneratingtherequiredquantityofhydrogengas.2

Post‐MBfRsecondarytreatmentforinjection:MBfRgeneratesbiomassaspartofthe3process.Thisexcessbiomassisusuallysloughedintothewaterstream.Astreatedwater4wouldbereturnedtogroundwaterviainjectionwells,thesuspendedbiomasswould5likelyhavetoberemovedtopreventbiofoulingininjectionwells.Withoutextensive6pilottesting,biomassgenerationcannotbeestimatedandtheappropriatesecondary7treatmentprocessrequiredtomitigatebiomassgenerationcannotbeevaluated.8

Thetechnologyrequiresextensivepilottestingtoevaluatetechnicaleffectivenessand9implementabilityfactorsdescribedabove.Withoutthisinformation,MBfRisnot10recommendedasapreferredex‐situtreatmentprocess(forAlternative4C‐3orAlternative114C‐5)relativetootherprocesses.12

In‐SituChemicalReductants:Useseveraldifferentchemicalreductantsforin‐situremediation13insteadoforganiccompounds.Thefollowingisasummaryofthereasonschemicalreductants14werenotincludedintheactionalternativesaspartofin‐situremediationapproaches(PacificGas15andElectric2011c).Althoughthesereagentsarenotrecommendedforgeneraluseinthein‐situ16recirculationsystemspresentedinthefeasibilitystudy,theymaybebeneficialinspecific17circumstancesthatariseastheprojectevolves.18

Thisalternativewasconsideredinthebenchtestingphaseoftheproject,priortopilotstudy19implementationandfeasibilitystudypreparation.Calciumpolysulfidewasscreenedout20priortobenchscaletestingduetopotentialproblemswithprecipitationin‐well,uncertainty21ofnitratetreatment,andpotentialincreasedsulfurcontentoftheaquifer.Zero‐valentiron22(ZVI)wasscreenedoutduetocostandin‐situdeliverychallenges.Thebenchtestingresults23indicatethattheorganiccarbonsubstrates(e.g.,emulsifiedvegetableoil,lactate,and24ethanol)andsodiumdithioniteareeffectivereagentsforthetreatmentofCr[VI]in25groundwater.Theorganiccarbonsubstrateswereretainedforpilottestingoversodium26dithionitebasedonsafety,easeofhandling,materialproperties,abilitytodelivertothe27aquifer,permitting,andnitrateremovalconsiderations.28

Oneofthemostchallengingaspectsofin‐situtreatmentisreagentdeliverywithinthe29aquifer,particularlyatthespatialscalesofthein‐situareasforthisproject.Reagentswhich30areveryreactivewillbeconsumedmorequicklyinthesubsurfaceandaremoredifficultto31distributethanlessreactivereagentsthataremoreslowlyconsumed.Chemicalreductants,32includingcalciumpolysulfide,sodiumdithionite,andferrousiron,areveryreactiveinthe33subsurface.Forexample,dithioniteconsumptionisonthetimescaleofminutescomparedto34organiccarbonconsumptionrateswhichareonthetimescaleofdays.Theslower35consumptionratesoftheorganiccarbonsubstratesallowthemtopersistinthesubsurface36andbedistributedtogreaterdistancesfrominjectionlocations.Asecondconsiderationfor37reagentdistributionisthepotentialforcloggingtheaquiferformation,whichlimitsthe38abilitytoinjectanddistributereductants.Sulfide‐andferrousiron‐basedreagentsmay39oxidizetoelementalsulfurandferricironprecipitates,whichcanlimitinjectabilitymuch40morerapidlythanthegradualbuild‐upoffoulingmaterialswithorganiccarbonsubstrates.41Nanoscalezerovalentiron(nZVI)distributionislimitedbytheagglomerationofnZVI42particlesandincorporationintoaquifersolids;thismakesitdifficulttodistributenZVIvia43injectionsforin‐situtreatment.44

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TreatmentEffectiveness.Organiccarbonsubstratesarejustaseffectiveandaggressiveas1chemicalreductantsintreatinghighCr[VI]concentrationsinsourceareas.Forexample,in2theSourceArea,Cr[VI]concentrationswerereducedfromgreaterthan1,000ppbtoless3than0.2ppbatonelocationwithinapproximatelyonemonthofthestartupofin‐situ4injectionsofsodiumlactateinonesourcearea(seediscussioninSection3.1,Water5ResourcesandWaterQuality).Similarly,inapilottestconductedatthePG&ETopock6CompressorStationinNeedles,California,Cr[VI]concentrationsofupto8,000ppbwere7rapidlytreatedtolessthan0.2ppbinapilottestusingethanol.Organiccarbonsubstrates8arealsoaseffectiveaschemicalreductantsfortreatmentofCr[VI]thatmaybepresentin9immobileporespaceinsourceareas.10

GenerationofBy‐products.Forbothorganiccarbonsubstratesandsolublechemical11reductants,reductionofaquifermineralsandassociateddissolutionofiron,manganese,and12arsenicwilloccurwithin‐situtreatmentimplementation.Duetothehighlyreactivenature13ofchemicalreductants,concentrationsofmetalsgeneratedmaybecomparabletoorgreater14withchemicalreductantsthanwiththeuseoforganiccarbonsubstrates,asindicatedinEPA15commentsonthefeasibilitystudy.Forexample,injectionofsodiumdithioniteissometimes16followedbyanextractionphasewhereseveraltimestheinjectedvolumeofreagentis17extractedduetotheproductionofelevatedconcentrationsofby‐productsaswellasreagent18reactionby‐products.Inadditiontodissolutionofmetals,somechemicalreductantsmay19alsoincreaseconcentrationsofotherconstituentsthatcontributetototaldissolvedsolids.20Thereactionproductsofsodiumdithioniteincludesulfite,thiosulfate,andsulfate.Ferrous21ironisoftenprovidedasferroussulfate,therebyincreasingtheconcentrationofsulfate22throughinjections.23

MonitoredNaturalAttenuation:Dilute,diffuse,and/orreduceCr[VI]toCr[III]underthe24geochemicalconditionsthatexistingroundwaterinthenortherndiffuseportionoftheplume.25Resultsofan8‐weekPilotStudyindicatedthatportionsoftheupperaquiferhavesome26reductivecapacity,whichcanreducelowlevelsofCr[VI]ingroundwater,butthemagnitudeof27thisreductivecapacityisnotsufficientforuseasaprimarycomponentofaplume‐wideremedy.28

2.11.10 Other Alternatives Considered in the 2002 Feasibility 29

Study 30

Thefollowinglistdescribestherangeofotheralternativesconsideredinthe2002FeasibilityStudy31thatweredismissedfromfurtherconsideration.Thesealternativeswerescreenedoutbecausethey32donotmeettheprojectgoalandmostoftheobjectivesorhavefeasibilityoreffectivenessconcerns33thatprecludedthemfromfurtherconsideration.Thesealternativesarebrieflydescribedbelow,and34thereasonstheyweredismissedfromfurtherconsiderationareidentified.Alternativesthatwere35consideredinthe2002FeasibilityStudyandpreviouslylistedasconsiderationsinthe201036FeasibilityStudy,suchasmonitorednaturalattenuation,ex‐situtreatment—ionexchange,ex‐situ37treatment—coagulation,andmicrofiltrationwerediscussedaboveunderthediscussionofthe201038FeasibilityStudyandarenotdiscussedfurtherhere.39

Ex‐SituTreatment—ElectrochemicalPrecipitation:Useelectricalcurrentandreactive40electrodestoreduceCr[VI]andprecipitatechromiumasCr[III].Thisalternativewasnot41retainedbecauseofuncertaintyofeffectivenessandveryhighO&Mcostsfromtheproductionof42wasterequiringtransportanddisposal.43

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Ex‐SituTreatment—ReverseOsmosis:UsemembranestoremoveCr[VI]fromwater.This1alternativewasnotretainedbecauseofveryhighO&Mcostsfromtheproductionofwaste2requiringtransportanddisposal.3

Ex‐SituTreatment—BiologicalReduction/Precipitation:BiologicallyreduceCr[VI]toless4solubleCr[III]inabioreactor.Althoughthisalternativecanbeeffective,itwasnotretained5becauseitrequirescontinualoperatoroversight,whichmakesitdifficulttoimplement.6

WaterReuse/Disposal—FloodIrrigation:Useoverlandflow(floodirrigation)todistribute7water.Althoughthisalternativeisconsideredtobepotentiallyeffectiveasareuseoption,its8effectivenessdependsonspecificsoilconditionsatproposedlocations(i.e.,infiltrationability),9themethodrequiresadditionaloperationalcontrolstocontainalloverlandflowfromentering10adjacentareas,andthemethodrequiresfencingtoprecludehumanentryintotheirrigatedarea11toavoidexposure.Further,thisapproachwouldresultinmuchhigherevaporationthandrip12irrigationincludedintheprojectalternativesandthereforelacksthegreaterbeneficialuseof13treatedwaterthatresultsfromdripirrigation.14

WaterReuse/Disposal—ReuseatCompressorStation:Reusetreatedwaterattheplantfor15variouspurposes,suchasprocessandcoolingwater.Thisalternativewasnotretainedbecause16itiseffectiveonlyiftheCompressorStationcanuseallthewaterandthusitmaybe17incompatiblewithCompressorStationoperations.Additionally,itisnotfeasiblebecauseof18pipelinelengthsandextensivepermittingandapprovalrequiredforrailway/roadwaycrossings,19wouldnotmeetthefundamentalobjectiveofremediatingthecontaminatedgroundwaterwithin20ameaningfulperiodoftime.21

WaterReuse/Disposal—Reinjection:Injecttreatedgroundwaterintosubsurfaceusingwells,22infiltrationgalleries,orrechargebasins.Thisalternativeiseffectiveifasubsurfaceaquifercan23accommodatewaterquantitiesandthusitisretainedonlyasabackuptodripirrigationsystems24includedinagriculturaltreatmentapproachesincludedinthefiveprojectalternatives.25

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kley

State Highway 58

Santa Fe Railway

M O J A V E

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Figure 2-2eExisting Remedial Activities±0 0.5 10.25

Miles

HinkleyElementary

School

PG&E HinkleyCompressorStationPG&E-14

NORT

H AR

EA

Sources: Haley-Aldrich 2011. CH2MHill, 2011.

CENT

RAL A

REA

SOUT

H AR

EA

Ranch

Gorman N.

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Cottrell

NOTE: All well locations are approximated.

FW-01FW-02

!. Existing Injection Wells

!C Existing Extraction Wells

"/ Northwest Freshwater Injection Wells

!C Existing Freshwater Extraction Wells

LegendProject Study Area

IRZ Area

OU1

OU2

OU3

Desert View Dairy LTU

Existing Agricultural Units

Approximate limit of saturated alluvial aquifer

Bedrock exposed at ground surface

Roads

Santa Fe Railway

Page 82: Chapter 1 Introduction€¦ · Chapter 1 Introduction ... 1 2

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Santa Fe Railway

State Highway 58

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Figure 2-3No Project Alternative Conceptual Layout

(Initial Buildout to Year 20)±0 0.5 10.25

Miles

HinkleyElementary

School

PG&E HinkleyCompressorStation

PG&E-14

NORT

H AR

EA

Sources: Haley-Aldrich 2011. CH2MHill, 2011.

CENT

RAL A

REA

SOUT

H AR

EA

Ranch

Gorman N.

Gorman S.

Cottrell

NOTE: New infrastructure layouts are slightlyexaggerated and locations are approximatedfor graphical display.

FW-01FW-02

LegendProject Study Area

IRZ Area

OU1

OU2

OU3

Desert View Dairy LTU

Existing Agricultural Units

Approximate limit of saturated alluvial aquifer

Bedrock exposed at ground surface

Roads

Santa Fe Railway

!C Existing Freshwater Extraction Wells

! ! New Infrastructure

Page 83: Chapter 1 Introduction€¦ · Chapter 1 Introduction ... 1 2

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ra

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Santa Fe Railway

State Highway 58

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ngst

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Hin

kley

State Highway 58

Santa Fe Railway

M O J A V E

R I V

E R

Note 1: New infrastructure layouts are slightlyexaggerated and locations are approximatedfor graphical display.Note 2: Number of new wells shown on thisfigure are according to FS/Addenda estimates.It is expected additional infrastructure will benecessary to address the expanded plume.See discussions in text.

PotentialFuture

RemedialActivity Area

PotentialFuture

RemedialActivity Area

PotentialFuture

RemedialActivity Area

±0 0.5 10.25

Miles

!C Existing Freshwater Extraction Wells

New Infrastructure (wells and pipelines)! !

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Figure 2-4Alternative 4B Conceptual Layout

(Initial Buildout to Year 20)

HinkleyElementary

School

PG&E HinkleyCompressorStation

NORT

H AR

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NTRA

L ARE

ASO

UTH

AREA

Ranch

Gorman N.Gorman S.

Cottrell

FW-01FW-02

Legend

Project Study Area

IRZ Area

OU1

OU2

OU3

Desert View Dairy LTU

Existing Agricultural Units

New Agricultural Units

Approximate limit of saturated alluvial aquifer

Bedrock exposed at ground surface

Roads

Santa Fe Railway

Yang

PG&E-14

Page 84: Chapter 1 Introduction€¦ · Chapter 1 Introduction ... 1 2

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ra

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in V

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ie

Santa Fe Railway

State Highway 58

Livi

ngst

on

Hin

kley

State Highway 58

Santa Fe Railway

M O J A V E

R I V E R

Note 1: New infrastructure layouts are slightlyexaggerated and locations are approximatedfor graphical display.Note 2: Number of new wells shown on thisfigure are according to FS/Addenda estimates.It is expected additional infrastructure will benecessary to address the expanded plume.See discussions in text.

PotentialFuture

RemedialActivity Area

PotentialFuture

RemedialActivity Area

PotentialFuture

RemedialActivity Area

±0 0.5 10.25

Miles

!C Existing Freshwater Extraction Wells

New Infrastructure (wells and pipelines)! !

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Figure 2-5Alternative 4C-2 Conceptual Layout

(Initial Buildout to Year 20)

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School

PG&E HinkleyCompressorStationPG&E-14

NORT

H AR

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NTRA

L ARE

ASO

UTH

AREA

Ranch

Gorman N.Gorman S.

Cottrell

FW-01FW-02

Legend

Project Study Area

IRZ Area

OU1

OU2

OU3

Desert View Dairy LTU

Existing Agricultural Units

New Agricultural Units

Approximate limit of saturated alluvial aquifer

Bedrock exposed at ground surface

Roads

Santa Fe Railway

Bell N.

Yang

West

Bell S.

South

Page 85: Chapter 1 Introduction€¦ · Chapter 1 Introduction ... 1 2

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ngst

on

Hin

kley

State Highway 58

Santa Fe Railway

M O J A V E

R I V

E R

Note 1: New infrastructure layouts are slightlyexaggerated and locations are approximatedfor graphical display.Note 2: Number of new wells shown on thisfigure are according to FS/Addenda estimates.It is expected additional infrastructure will benecessary to address the expanded plume.See discussions in text.

PotentialFuture

RemedialActivity Area

PotentialFuture

RemedialActivity Area

PotentialFuture

RemedialActivity Area

±0 0.5 10.25

Miles

!C Existing Freshwater Extraction Wells

New Infrastructure (wells and pipelines)! !

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Figure 2-6Alternative 4C-3 Conceptual Layout

(Initial Buildout to Year 20)

HinkleyElementary

School

PG&E HinkleyCompressorStation

PG&E-14

NORT

H AR

EACE

NTRA

L ARE

ASO

UTH

AREA

Ranch

Gorman N.Gorman S.

Cottrell

FW-01FW-02

Legend

Project Study Area

IRZ Area

OU1

OU2

OU3

Desert View Dairy LTU

Existing Agricultural Units

New Agricultural Units

Approximate limit of saturated alluvial aquifer

Bedrock exposed at ground surface

Roads

Santa Fe Railway

Bell N.

Yang

West

Bell S.

South

Above GroundTreatment Plant

Above GroundTreatment Plant

Page 86: Chapter 1 Introduction€¦ · Chapter 1 Introduction ... 1 2

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Livi

ngst

on

Hin

kley

State Highway 58

Santa Fe Railway

M O J A V E

R I V

E R

Note 1: New infrastructure layouts are slightlyexaggerated and locations are approximatedfor graphical display.Note 2: Number of new wells shown on thisfigure are according to FS/Addenda estimates.It is expected additional infrastructure will benecessary to address the expanded plume.See discussions in text.

PotentialFuture

RemedialActivity Area

PotentialFuture

RemedialActivity Area

PotentialFuture

RemedialActivity Area

±0 0.5 10.25

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Figure 2-7Alternative 4C-4 Conceptual Layout

(Initial Buildout to Year 20)

HinkleyElementary

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PG&E HinkleyCompressorStation

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ASO

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Ranch

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Legend

Project Study Area

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OU2

OU3

Desert View Dairy LTU

Existing Agricultural Units

New Agricultural Units

Approximate limit of saturated alluvial aquifer

Bedrock exposed at ground surface

Roads

Santa Fe Railway

!C Existing Freshwater Extraction Wells

New Infrastructure (wells and pipelines)! !

Page 87: Chapter 1 Introduction€¦ · Chapter 1 Introduction ... 1 2

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Figure 2-8Alternative 4C-5 Conceptual Layout

(Initial Buildout to Year 20)

HinkleyElementary

School

PG&E HinkleyCompressorStation

PG&E-14

NORT

H AR

EACE

NTRA

L ARE

ASO

UTH

AREA

Ranch

Gorman N.Gorman S.

Cottrell

FW-01FW-02

Legend

Project Study Area

IRZ Area

OU1

OU2

OU3

Desert View Dairy LTU

Existing Agricultural Units

New Agricultural Units

Approximate limit of saturated alluvial aquifer

Bedrock exposed at ground surface

Roads

Santa Fe Railway

Bell N.

Yang

West

Bell S.

South

Above GroundTreatment Plant

Note 1: New infrastructure layouts are slightlyexaggerated and locations are approximatedfor graphical display.Note 2: Number of new wells shown on thisfigure are according to FS/Addenda estimates.It is expected additional infrastructure will benecessary to address the expanded plume.See discussions in text.

!C Existing Freshwater Extraction Wells

New Infrastructure (wells and pipelines)! !

PotentialFuture

RemedialActivity Area

PotentialFuture

RemedialActivity Area

PotentialFuture

RemedialActivity Area

±0 0.5 10.25

Miles