EvaluationoftheLandfillOdorProblemattheSunshineCanyonLandfill

Preparedby:YazdaniConsulting

RaminYazdani,Ph.D.,P.E.1800BirchLaneDavis,CA95616(530)574‐1499

Preparedfor:SouthCoastAirQualityManagementDistrict

21865CopleyDriveDiamondBar,CA91765

August15,2015

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Table of Contents 

PURPOSE.....................................................................................................................................................3

LANDFILLS..................................................................................................................................................4

SITEBACKGROUNDANDHISTORY....................................................................................................4

STUDIESCONDUCTEDATSCLTOMITIGATELANDFILLODOR...............................................6

METHODSFORESTIMATIONOFLANDFILLGASGENERATIONRATE...................................8

IMPACTOFBAROMETRICPRESSURECHANGEONLANDFILLMETHANEEMISSIONANDAUTOMATEDLANDFILLGASWELLADJUSTMENT....................................................................11

LANDFILLGASCOLLECTIONEFFICIENCYMEASUREMENTUSINGGASTRACERS..........15

BETTERLANDFILLGASCOLLECTIONSYSTEMDESIGNTOMITIGATEEMISSIONSANDAIRINTRUSIONINLANDFILL...........................................................................................................17

SATURATEDWASTECONDITIONANDGASCOLLECTIONEFFICIENCY..............................19

HYDROGENSULFIDEPRODUCTIONINLANDFILLSANDTHEUSEOFSOILASDAILYCOVER.......................................................................................................................................................20

CONTROLOFEMISSIONSATTHEACTIVEFILLINGAREA.......................................................21

IMPACTOFDAILYCOVERSOILUSEONLANDFILLGASTRANSPORTANDEMISSION..21

MEASUREMENTOFWHOLE‐LANDFILLGASEMISSIONS.........................................................24

SUMMARYOFRECOMMENDATIONS:.............................................................................................25

APPENDIXA............................................................................................................................................28

LIMITATIONS.........................................................................................................................................32

LISTOFREFERENCES..........................................................................................................................33

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YazdaniConsultingRaminYazdani,Ph.D.,P.E.

1800BirchLaneDavis,CA95618

Tel(530)574‐1499Email:ryazdani@sbcglobal.net

August15,2015Mr.NicholasA.SanchezSeniorDeputyDistrictCounselSouthCoastAirQualityManagementDistrict21865CopleyDriveDiamondBar,CA91765Subject: EvaluationofLandfillOdorProblemattheSunshineCanyon

LandfillDearMr.Sanchez:Atyourrequest,YazdaniConsultinghasreviewedtheavailabledataforSunshineCanyonLandfill(SCL)andhasidentifiedpotentialimprovementsinthedesignandoperationofthelandfillgas(LFG)collectionsystemtoreducegasemissionsandodors.Thepurposeofthispreliminaryevaluationwastoprovideasummaryofknownsiteconditions,andproposefurtherinvestigationandpotentialsolutionstobettermanageLFGcollectionandcontrolodornuisance.Theresultsareprovidedbelow.

Purpose YazdaniConsultingwasretainedbySouthCoastAirQualityManagementDistrict(SCAQMD)toprovideconsultingservicestoSCAQMDandtoassistHydroGeoChem,Inc.(HGC)intheplanning,testingandevaluationoftheSCLgascollectionsystemusingbaro‐pneumatictestingandcomputermodeling.Inaddition,provideideasforfurtherinvestigationthatwouldyieldbettermanagementofthelandfillgascollectionsystemandcontrollandfillodornuisance.

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Landfills  Whensolidwastecontainingorganicmaterialsisdisposedinlandfills,thewastedecomposesanaerobically,resultingingenerationoflandfillgasconsistingmainlyofCH4(50%)andCO2(50%).Thegasgenerationdependsontheamountandageofwasteinthelandfill,thewastecomposition,nutrients,presenceofinhibitorycompounds,andthelandfillconditionssuchastemperature,wastemoisture,wastepH,wastecompaction,andlandfillcoverdesign.Thelandfillgasbuildsuppressureinsidethelandfillandthepressure,togetherwithdiffusion,causesgasescapefromthelandfill.AsillustratedinFigure1,thefugitiveemissionandodorfromalandfilloccursthroughmanydifferentescaperoutesandmeasuringtheindividualortotalemissionratefromtheseroutesischallenging.Thegeneratedgascanberecoveredbyengineeredgascollectionandremovalsystemsandutilizedforenergyproduction,whichreducestheoverallemissions.TheCH4emissionsthroughthesoilcoverandcrackscanbemitigatedthroughtheuseofbiocoversystemwheremethaneisoxidized.However,reliablemeasurementsforquantificationofLFGcollectionefficiencyandmethaneoxidationinbiocoversarenecessary.

Figure1‐Methaneproduction,transport,andemissionfromalandfill.1

Site Background and History  SunshineCanyonLandfill(ClassIIIlandfill)operatesunderSolidWasteFacilityPermit19‐AA‐2000issuedbyCalRecyclelocatedinSylmar,California.ThesiteisownedandoperatedbyBrowningFerrisIndustriesofCalifornia,Inc./RepublicServices,Inc.The“CountyLandfill”DisposalPhasesIthroughVarelocatednorthoftheCity‐Countyboundary,andwereconstructedwithacompositelinerandleachatecollectionandremovalsystem.The“CityLandfill”includesUnit1andUnit2wastedisposalareasthataresouthoftheCity‐Countyboundary.CityLandfillUnit1isaclosed,unlinedClassIIIMSWdisposalunitthatoperatedbetween1958and

Gas well

CHrecovered

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Anaerobic methane production:methanogens in waste

Lateral migration

CO2

CH4

Methanestorage

CH emission throughcover and cracks4

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1993.CityLandfillUnit2iscurrentlyactive,ClassIIIMSWdisposalunitthatwasconstructedwithacompositelinersystemandislocatedgenerallybetweenCityLandfillUnit1andtheCountydisposalphases.CellAofCityLandfillUnit2beganoperationsduringthethirdquarterof2005,withsubsequentdisposaloperationsexpandingintoCellsCC‐1andCC‐2.RefuseiscurrentlybeingdisposedofinCellCC‐3A(SeeAppendixA,FigureA1‐SCLProposedPhasingPlan).Themaximumweeklytonnagereceivedatthefacilityis66,000tonsofmunicipalsolidwaste(MSW)fordisposaland6,600tonsofmaterialreceivedforbeneficialreuseandrecycling,whichtogethertotal72,600tonsperweekforallmaterial.Currentlythelandfillreceives8,300tonsofMSWperday.Thepermittedmaximumelevationofthewasteis1,904ft.(MSL)onportionswithinthe“CountyLandfill”boundaryand2,004ft.(MSL)onportionswithinthe“CityLandfill”.Thetotalpermittedareaforwastedisposalis363acreswithdesigncapacityof140,900,000cubicyardsofMSW.Thesiteisestimatedtocloseby2037.Since2009,themembersofcommunitiessurroundingtheSunshineCanyonLandfill(SCL)havereportedsmellingodorstoSCAQMDandSCL(SeeFigure2).Inresponsetothecomplaints,SCAQMDstaffsoughtanOrderforAbatementfromitsautonomousHearingBoard.TheHearingBoardissuedanOrderforAbatementthatrequiresanumberofactivitiesdesignedtoreducepotentialodorsfromthelandfill,suchasinstallationofadditionalgaswellsandflares;limitinglandfillingundercertainwindconditionsatcertaintimesofday;implementingnewrestrictionsattheworkingface;enhancingodorpatrols;reroutingtransfertrucksonMondaymornings;andreplantinglostvegetationthatmayhelpwiththedispersionofodors.TodateRepublicServiceshasengagedinavarietyofstudiesaimedatbetterunderstandingthesourcesofpotentialodorsfromtheSCL,thepossibletransportofodorsfromSCLtothecommunity,andpotentialodor‐reductionmeasures.RepublicServiceshasimplementednumerousodorcontrolmeasuresandhashiredconsultantstoevaluatetheimmediateandfutureneedsofLFGcollectionanddisposalsystemstoaccommodatethecaptureanddestructionofallgasexpectedtobegeneratedatthelandfillusingverticallandfillgaswells,horizontalcollectors,linercollectors,trenchcollectors,andflares.InMarch2010,theSCAQMDissuedastipulatedorderforAbatementfollowedbythreestipulatedAmendedordersforAbatementthatimposedaseriesofconditionsincludingmakingenhancementstotheLFGcollectionsystemtoaddressodornuisance.Inaddition,theCountyofLosAngeles,PublicWorksDepartmentrequiredcorrectivemeasuresbeimplementedbyRepublicServicestoreduceodors.RepublicServiceswasrequiredtocoverdisposedsolidwastewithaminimumof9‐inchesofcompactedsoilattheendofeachoperatingdayinlieuofusingtarporotheralternativedailycover.RepublicServiceswasalsorequiredtodiscontinueremovalofthedailycoveratthebeginningofthenextoperatingday.Inspiteoftheseoperationalchangesthathavetakenplaceduringthepastfouryears,odorcomplaintscontinuebutthenumberofcomplaintshasdecreaserecently.DataonthenumberofcomplaintsreportedtoSCAQMDbetween1995and2015isshowninFigure2.

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InOctober22,2014,theCountyofLosAnglesPublicWorksDepartmentrequiredRepublicServicestoimplementadditionalcorrectivemeasurestomitigatetheodornuisanceresultingfromactivitiesrelatedtotheoperationoftheSCL.TheLFGmanagementrequirementswereasfollows:a)newlycompletedcellsshallhavethreeverticalgasextractionwellsperacreandhorizontalcollectorsareeveryotherlift.Forcellsthatwillbeinactiveformorethantwodayshorizontalgascollectorsmustbeinstalledwithinthetoplift;b)Ataminimumforeachexistingandfuturedevelopmentcellcalculatethein‐placedensityoffillmaterialtakingintoaccountthedailysoilcover,andcalculatetheradiusofinfluenceaswellasspacingforverticalgasextractionwellsandhorizontalgascollectorsbasedonthatdensity.Areaswithdifferentsitecharacteristicsmayrequireseparatecalculationsofin‐placedensities.ThesecalculationsandwellspacingmustbesubmittedtoPublicWorksforapprovalwithcopiestoSCAQMDandSCLLocalEnforcementAgency(LEA).

Figure2‐TotalnumberofcomplaintsreportedtotheSCAQMDbetween1995to2015(FigureprovidebySCAQMD).

Studies Conducted at SCL to Mitigate Landfill Odor  Addressingvariousoperationsanddesignissuescanreducelandfillodorinthesurroundingareaofalandfill(Figure3).Theseissuesare:a)reducingtheworking

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faceofthelandfillandapplicationofdailycovermaterial;b)timelyapplicationoffinalcoverandvegetationlayer;c)properlysizedLFGcollectionandcontrolsystem;d)odor‐neutralizingchemicalsprayedalongtheborder;e)propermaintenanceofleachateandLFGcontrolequipmentcomponents;f)surfacewatermanagementandpropergradingofthelandfillsurfacetoreducewaterinfiltration;g)usingthegasasafueltoreduceodorsandprovideelectricity.

Figure3‐Typicallandfillwithvarioussystemstocontrolodor.2StudiesthathavebeenconductedatSCLtobetteridentifythecauseandtobettermanageodorattheSCLlandfillarelistedbelow.Someoftherecommendationsidentifiedinthesestudieshavealreadybeenimplemented.In2011astudywasconductedbyENVIRONInternationalCorporation3toevaluatetheimpactoflandfillworkingfacesizeandrateofwastedepositedonodor.Basedonthedatacollecteditappearedthatodorsourcestrengthattheworkingfacedidnotcorrelatewithworkingfacesize.Also,thechemicalmeasurementsaswellasolfactoryobservationsdidnotindicateanyapparenttrendswhencomparedtoworkingfacesizeandodorcomplainsreceivedfromthehotlines.In2011TetraTechBAS(BAS)4evaluatedtheexistinglandfillgascollectionandcontrolsystemandrecommendedchangestoincreasethecurrentlandfillgascollectionefficiency.BASusedtheOctober4,2010LFGgenerationanalysispreparedbyCornerstoneEnvironmentalGroup,LLCastheprimaryreferenceforanindependentanalysis.Cornerstone’sreportreferencedseveralwastecompositionstudiesperformedfortheSCL.InFebruary2015,TetraTech,Inc.andEcoTelesisInternational5performedamorerecentwastecharacterizationstudyperformedtodevelopbetterparametersforthelandfillgasmodelsusedattheSCL.Accordingto

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thisstudythetotalreadilydegradablewetfractionoforganicwaste(foodwaste)wasdeterminedtobebeween23%to30%.In2011,landfillgascollectionimprovementrecommendationsbyBASwere:a)installationofadditional70verticalgaswellsintheareaswiththemostsurfaceemissions;b)installationofatemporaryflarewitha3,000SCFMcapacity;c)replacementofflare#8withalargercapacityflare;d)evaluationforimprovementofflarestation#1and#3;e)replacementoftheundersizedgascollectionandcontrolsystempiping.ManyoftheserecommendationshavealreadybeenimplementedattheSCL.In2012,awhitepaperwaspreparedbyBlueRidgeServices6toevaluateanddeterminethemosteffectivemeanstopreventoff‐siteodorfromtheactivefaceofthelandfill.BlueRidgeServicesevaluatedtheeffectivenessoftherequirednine(9)inchesofdailysoilcoverasamitigationmeasureforreductionofoff‐siteodorsascomparedtotheregulatorystandardsix(6)inchesof`soil.Othersiteconditionsthathavehistoricallycontributedtotheoff‐siteodorproblemwerealsoevaluated.Therecommendationofthisstudywastodiscontinueplacementofnine(9)inchesofdailycoversoilandinsteaduseAlternativeDailyCover(ADC).Additionally,itwaspointedoutthattheuseofnine(9)inchesofdailycoversoilcouldimpedetheverticalmovementofleachateandlandfillgasandcauselateralmigration.SeeAppendixA,FigureA2,fortheboundaryofthenine(9)inchesofdailysoilcoverandthelocationofverticalgaswellswithdedicatedpumpsfordewateringgaswells.

Methods for Estimation of Landfill Gas Generation Rate  ThereareseveralmethodstoestimateLFGgenerationrate:a)afirst‐orderkineticgasgenerationmodelsuchastheLandfillGasEmissionModel(LandGEM)(USEPA20057);b)combinationofpneumaticwelltestdatawithassumptionsaboutwellrecoverytoestimateLFGgeneration(EMCON19808);c)andbiokineticmodelsdescribingstagesofwastedecomposition(El‐Fadeletal.19969).ThesemethodshavesignificantlimitationswhenestimatingtheactualLFGgeneration.ThedefaultCH4generationpotential,L0,andfirst‐orderwastedecayrate,k,recommendedinLandGEMmodelaredependentonsiteconditions(ScharffandJacobs200610)andevenwhensitespecificL0areusederrorscansignificantlyaffectestimatesofk(Tolaymatetal.201011).Additionally,estimatesrequireassumptionsabouttheLFGcollectionefficiency,whicharealsounknown.Inanotherrecentstudy12,theobservedmethanecollectiondatafrom11U.S.landfillsandestimatesofgascollectionefficienciesdevelopedfromsite‐specificgaswellinstallationdatawereincludedinareformulatedLandGEMequation.TheresultsdemonstratedthatthecurrentLandGEMmodel(AP‐42)defaultdecayrateusedbyindustryistoolow.Thisissignificantbecauseahigherdecayratewillresultinpredictionsofmoremethanegenerationintheearlyyearsafterwasteburialwhengascollectionefficienciestendtobelower.Thushigherdecayrateswillresult

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inhigherestimatesofuncollectedmethane.ThisresearchalsosuggeststhatitismisleadingtorefertoL0asthemethaneproductionpotentialbecausethevalueofL0inLandGEMincludesunmodeledparametersthatinfluencemethanegeneration.Furtherworkisrequiredtoidentifythecontrollingunmodeledparameters,explorereformulationsofLandGEMthatmightincludeaslowandrapidlydecomposingwastefraction,quantifyuncertainty,andexpandobservationaldatasets.Thebaro‐pneumaticmethod(Bentleyetal.200313)usedbyHGCinthemostrecentstudyattheSCLquantifiedLFGgenerationratesandestimatedthefieldgaspermeabilitywithinthelandfillusingsimultaneousmeasurementofgaspressureatthesurfaceandatvariouslandfilldepths.Themathematicalanalysesofpressurechangesintherefuseinresponsetovariationinatmosphericpressure,LFGgeneration,andpumpageatLFGextractionwellwereusedtomaketheestimate.Thebaro‐pneumaticmethodusessite‐specificdatathatreduceuncertaintiesinestimatedofLFGgenerationrates.ThismethoddoesnotassumethattheLFGgenerationrateisequaltotheflowrateofagasextractionwellwithinitszoneofinfluence,anassumptionthatistechnicallyflawed(Walter200314)andthereforethebaro‐pneumaticmethodisabettermethodtoquantifyLFGgenerationrates.

Photo1‐Shallowanddeepvapormonitoringwellswithpressuretransducersinstalled.In2014,SCAQMDhiredHydroGeoChem,Inc.(HGC)15toperformfieldtestsandcollectatmosphericandsubsurfacepressuredatawithinthelandfillandanalyzethecollecteddatabothqualitativelyandquantitativelytomakerecommendationforpotentialsolutionstocontrolodorfromthelandfill.Threelocationswereselectedforthisfieldstudy.TwolocationswereselectedinthenewerportionofthelandfillnearcollectorwellCGW740S/DandCGW575andthethirdlocationintheolderportionoftheCitylandfillnearthecollectorwellGW7024(SeeAppendixA,FigureA3).Afterthewellmonitoringinstallation,HGCinstalledaseriesofpressure

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transducersformonitoringpressureswithinthelandfillatthesethreelocations(Photo1).AtlocationCGW740S/Dresultsdemonstratethatcovermaterial(approximately1.5feetthickatthislocation)providesonlyaslightbarriertopneumaticcommunicationbetweentheatmosphereandthesubsurface,consistentwithitsthinnessandamoderatelyhighverticalpermeability.Theresultsalsosuggestthattheverticalpermeabilityofatleasttheshallowestrefuse(between1.5feetand8feetindepth)isrelativelyhigh.Theapparentpoorcommunicationofdeeprefusewiththeatmospheresuggeststhatthedeeprefusehasalowgaspermeabilityorthatpartialpneumaticbarriersexistintherefuseatdepthsgreaterthanapproximately35feetbls,possiblytheresultoflayershavinghighwatercontentsandlowgasporosity.Overall,theLFGcollectionsystemappearstobeeffectiveatthislocationexceptinthedeeprefusewherepressuresaregreaterthanatmosphericandatdistancesgreaterthan75feetfromCGW740S/DwhereLFGcontrolsysteminducedvacuumswereslight.AtlocationCGW575,thecovermaterialisapproximately6feetthickandprovidesabarriertopneumaticcommunicationbetweentheatmosphereandthesubsurface.Theapparentpoorcommunicationofdeeperrefuse(>95ft.bls)withtheatmospheresuggeststhatatleastpartialpneumaticbarriersexistintherefuse.AtlocationGW7024,thecovermaterialthicknessisapproximately10feetthickandthedatasuggestthatcoversoilhashighereffectivegaspermeabilitythancoveratCGW575.Theresultsaboveindicatethatthecoversoilpermeabilitymaybetoohighorsoilmaynotbecompactedenough,allowinggasemission.Comparingthiswiththepublishedsoilsurvey16fortheSCL(Figure4andFigure5),themajorityofthesoilsattheSCLareratedtohaveamoderatelyhigh‐saturatedhydraulicconductivity.Thereisnotaclearproportionalitybetweenhigh‐saturatedhydraulicconductivityandporosity.However,typicallysandysoilwithhighporositywillhaveahighhydraulicconductivity(moreopenareasforflowofwaterorgas),butthisrelationshipismorecomplicatedinsoilswithclay.Werecommendthecollectionofin‐tactcoresamplesofcoversoilatvariouslocationsattheSCLforlaboratorytesting.ThesesampleswillbesenttotheUniversityofDelawarelaboratorieswheredensity,totalporosityandgastransportpropertieswillbemeasured.Whiletheinitialwatercontentofthesampleswillberecorded,theeffectofmoistureongastransportwillbeevaluatedbyvaryingthewatercontentsystematicallyineachsampleinthelaboratory.Wecanprovideadetailproposalforfurtherstudyatalaterdate.

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Figure4‐MapofstandardclassesofsoilatSCL.16

Figure5‐SaturatedhydraulicconductivityofsoilsatSCL.16

Impact of Barometric Pressure Change on Landfill Methane Emission and Automated Landfill Gas Well Adjustment  Inanumberofstudiestheinfluencesofatmosphericpressureonlandfillmethaneemissionshavebeenevaluated.ThediurnalmeasurementduringadropinbarometricpressureshowthatLFGfluxescanchangedramaticallywithinavery

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shorttime(Czpieletal.,200317;Gianietal.,200218;Christophersen,etal.,200119;Xuetal.,201420).Forexample,inonestudybyCzepiel,etal.200321conductedattheNashua,NewHampshiremunicipallandfill,withanactiveverticalandhorizontalgascollectionsystem,foundsurfacemethanefluxesincreased300%duetodecreasesinbarometricpressureof10millibars,whichoccurredduringpassageoflowpressureweatherfrontsoverananaerobiclandfill(Figure6).Inanotherlandfillstudywithpassivegascollectionsystema35‐foldvariationinday‐to‐daymethaneemissionswasobservedduetochangesinbarometricpressure(Figure6).Risingbarometricpressuresuppressedtheemission,whilefallingbarometricpressureenhancedtheemission,aphenomenoncalledbarometricpumping(Xuetal.,201420).Generallyspeaking,highpressure(usuallydryair)isassociatedwithcalm,sunnyweatherandlowpressure(generallymoistair)occursoncloudy,rainydays.

Figure6‐Resultsfromtwostudiesshowingincreaseinmethaneemissionsoverashorttimeasbarometricpressuredrops17,20.AsdemonstratedinFigure7andFigure8,theatmosphericpressureattheSCLchangesonadailyorevenhourlybasis,aswellasseasonally.Thisisduetonormaldayandnightcycleofsolarradiation,andalsoduetolocalweatherpatterns.SCAQMDRule1150.1requiresquarterlylandfillemissionsmonitoringbywalkingthesurfaceofthelandfillandscanningformethaneemissions(atthissitemonthlyemissionsmonitoringisperformed).Typicallysurfaceemissionmonitoringisnotperformedduringfallingbarometricpressure(badweathersuchaswindgreaterthan5mphand/orrainyweather)whenthesurfaceemissionscouldbehigher.Landfillsurfacescanningisnormallyperformedduringthedaywhentheweatheriscalmandthebarometricpressureishigh.Thiscouldunderestimatetheactualaveragedailyemissionmeasuredbysurfacescanningmethod.Ifthebarometricpressuredropsduringthenight,emissionfluxandodorfromthelandfillincrease.CurrentairemissionregulationsignorethebarometricpressureimpactsandassumethatsurfaceemissionisconstantunderhighorlowatmosphericpressureinlandfillswithactiveorpassiveLFGcollectionsystem.Inordertopreventexcessemissionandodorfromthelandfilleachwellheadmustbeundercontinuousmonitoringandautomaticallyadjustedasthebarometricpressurechanges.Thisisnottypicallydoneandisnotevenrequiredbyregulations;however,thistypeof

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landfillgasoperationmayreduceemissionsandthereforeodorfromthelandfill.Suchasystemwasdesigned,testedandsuccessfullyoperatedattheYoloCountyCentrallandfillaspartofaresearchprojectfortheCaliforniaEnergyCommission22.AcommercialversionofsuchsystemhasrecentlybeendevelopedbyLociControls23andinthesummerof2014wastestedattheCrapoHillLandfillinDartmouth,Massachusetts.UsingautomationtocontroleachgaswellheadincreasedthepoweroutputfromtheLFGtoenergyfacilityby26%atthislandfillsite,andthereforereducedtheoveralllandfillgassurfaceemissions.Photos2and3showthetypicalcontrolsoftwarescreenusedforautomaticadjustmentofthegaswellheadandthewellheadconstructionatthelandfill,respectively.WerecommendedthatsuchasystembetestedattheSCLonamainheaderlinewhereseriesofLFGwellsareconnectedtogetherandononeLFGwell.Automaticadjustmentofindividualgaswellsisidealbutautomaticadjustingofthemainheaderlinewithseriesofgaswellsconnectedtogethercouldalsoimprovefugitivegasemissions.Gascollectionsystemshouldbetestedundervariousoperatingparameterssuchaswellheadsuctionandgascompositiontodeterminetheeffectivenessofsystemandreductionoffugitivegasemissionsandairintrusion.Wecanprovideadetailproposalforfurtherstudyatalaterdate.

Figure7‐BarometricpressureatSunshineCanyonLandfillduringpneumatictest(datafromHGCpneumaticfieldtest‐June27‐July1,2015).

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Photo2‐LociControlsWellWatchermonitoringsoftwareusedtoautomaticallymonitoreachgaswell.

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Photo3‐LociControlsWellWatchermonitoring&controlsystemusedtoautomaticallyadjustandmonitoreachlandfillgaswell.

Landfill Gas Collection Efficiency Measurement Using Gas Tracers WhendesigningaLFGcollectionsystem,anassessmentoftheregionofinfluence(ROI)ofeachwellinrequired.AsimplewaytoassesstheROIofapumpingwellistomeasurethegaspressuredistributionintherefusewiththewellonandoff.Ifthereisameasurabledifferenceingaspressureatanysamplingpointbetweentheon/offconditions,thenthispointisimpactedbythewell.TheROIisaffectedbytheLFGgenerationrate,whichcanvaryinspaceandtime;wastecompactionandmoisturecontent;theextractionrateatindividualwells;thelocationsofwellsinthelandfill;andthedegreetowhichgascanpermeatethelandfillboundaries.UnderstandingwhereLFGcollectionis“good”andwhereitis“poor”isthefirststeptodevelopingimproveddesignsforgascollectionsystems.CurrentlyweareonlyawareofonestudywheredirectmeasurementsLFGcollectionefficiencywasmadeusinganin‐situgastracermethod(Yazdanietal.,201524).ThegastracermethodwasusedtoquantifygascollectionefficienciesatvariouspointsinatestlandfillwellandresultswerecomparedwiththeROIasdeterminedfrompressuremeasurements.Whileanassessmentofawell’sROImightresultinspecifiedsteady‐statesuctionsappliedatwell‐headstoachieveoptimalcollectionefficiency,transientLFGflowresultsfrombarometricpressurevariationscansignificantlyimpactcollectionefficiency.Asdiscussedearlier,publishedliteratureindicatesthatbarometricpressurechangesresultinundesired

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“pulses”ofLFGemissionstotheatmospheresimilartowhathasbeenobservedattheSCLduringearlymorningandlateafternoonasindicatedbytheBlueRidgeServices6reportandotherstudies(KjeldsenandFischer199525;BorjessonandSvensson199726;Christophersen,Kjeldsenetal.200127;Czepiel,Shorteretal.200328).Inaddition,over‐pressureLFGbuildingwithinisolatedareasofthelandfillcouldalsocausereleaseofLFG.Thus,aLFGcollectionsystemthatismanuallyadjustedonaweeklyormonthlybasiswithoutconsiderationofatmosphericpressurechangesorinternalpressurewithinthelandfillmayresultinappreciablefugitivemethaneemissionsaswellasairintrusion.Imhoffetal.,201224performedcomputersimulationsandhaveconductedlarge‐scalefieldteststhatsupportsthisobservation.AsillustratedinFigure9(a),twovariationsinatmosphericpressureareshown:amoderatecase,where24‐houraveragebarometricpressuredatafromSacramento,Californiacollectedforaone‐monthperiodwereused;andastrongcase,wherevariationsinatmosphericpressuresmeasuredattheSkellingstedLandfill,Denmark(Poulsen,Christophersenetal.200329)wereselected.TheresultingLFGemissionspredictedfromthisLFGmodel(Jung,Imhoffetal.200930)areshowninFigure9(b).Fortwocases:onewithapermeablelayerinstallednearthelandfillsurfacetoenhanceLFGcaptureandonewithout.Inbothcases,thegascollectionwellwasoperatingsuchthataconstantmassfluxofLFGwasextractedfromthelandfill.Whiletheexistenceofanear‐surfacepermeablelayerdecreasedbaselinemethaneemissionsfrom22to15%ofthemethanegeneratedinthelandfill,barometricpressurechangesstillresultedinemissionspikes.Itisimportanttonotethatthesesimulationshadno“cracks”inthelandfillcoverandthesoiltypewasnothighlypermeable:crackingandpermeablecoversoilwouldallowsignificantlygreaterfugitiveemissionsinresponsetobarometricchanges,witheffectsapproachingthosecitedinCzepiel’sstudy(Czepieletal.,200328).Assuggestedearlier,werecommendthatanautomatedwellheadadjustmentbeusedtomitigatetheinfluenceofatmosphericpressurechangesontheoperationofLFGcollectionsystemsandemissions.Thistypeofoperationwillresultinreducedemissions,increasedcollectionefficiency,andthecostsassociatedwithsuchasystemmaybeoffsetbytheincreasedrevenuepotentialfromtheadditionalLFGcollectedandenergyproducedattheexistingLFGtoenergyfacility.Werecommendthatthein‐situgastracermethoddevelopedbyYazdanietal.,201524beusedtodeterminetheverticalgaswellcollectionefficiencyandtoassessalternativegascollectionstrategiesandlandfillcoversystem(intermediateandfinalcover)tomitigatetheeffectsofbarometricpressurechangesandvariouscoversystemdesignsusedtocontrolLFGemissions.

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Figure9‐Variationsinmethaneemissionsassociatedwithatmosphericpressurechangesovera24‐hourperiod(Jung,Imhoffetal.200930).Resultsareshownforalandfillwithorwithoutahorizontalpermeablelayerinstalledatthetopofthelandfill.(a)Variationsinatmosphericpressure;(b)variationsinmethaneemissions,expressedas%oftotalmethanegeneratedinrefuse.

Better Landfill Gas Collection System Design to Mitigate Emissions and Air Intrusion in Landfill  TypicallyvacuumisappliedtoLFGcollectionwellstopullgasoutofthewasteinlandfillviaverticalextractionwellsorhorizontalextractiontrenches.Figure10(a)illustratesthedirectionandmagnitudeoftheexpectedgasflowswitharrowsdrawn.Pumpingoftheverticalgascollectionwellsmaycauseunequalmethaneemissionsandairintrusionatthelandfillsurface.ToaddressthisproblemanalternativeLFGcollectionsystemdesignisproposedfortheSCLasshowninFigure10(b)(Augensteinetal.,U.S.PatentNo.7,198,433(2007)31,Jung,etal.201132).Inthisnewlandfillgascollectionsystemdesign,ahigh‐permeabilitylayerisinstallednearthelandfillsurfaceandLFGiscollectedatdeeppumpingwells(notfromthehigh‐permeablelayernearthesurface).Thisenablesessentiallyuniformpressureacrosstheentiretyoftheconductiveorpermeablelayer,andcanenableauniformverticalpressuregradientthroughthesurfacelayersofthelandfillandgreatlyreduceirregularitiesinverticalgasflowatthelandfillsurface.Inotherwords,itwillgreatlyreducetheairentrainmentnearverticalwells,andfugitiveemissionfarfromverticalwells,asshowninFigure11.Theexpectationisbetterefficiencyofgascollectionbecauseahighpermeabilitylayerequalizesdifferencesingaspressurenearthelandfillsurfaceresultingin:1)reducedmethaneemissionsthroughcovermaterialsand;2)moreuniformflowofLFGthroughlandfillcovers;and3)reductionintheextentofairintrusion.

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Figure10‐Typicalcross‐sectionofgascollectionsystem:(a)conventionalverticallandfillgascollectionwell;(b)landfillgascollectionwellwithpermeablelayer.

Figure11‐Oxygenprofiles(%bymass)forconventionalverticallandfillgascollectionwell(left)andlandfillgascollectionwellwithpermeablelayer(right).Thistypeofdesignisalsoapplicablewhereforareaswithintermediatecoverandwastehasnotreachedthefinalelevationandadditionalwastewillbeplacedontopofexistingwastelift(Figure12).Permeablelayercanbeconstructedfromwastematerialthatisthreetofiveordersofmagnitudemorepermeablethanthesurroundingwastesuchasshreddedtires(usedonlyinareaswherewasteoxidizationisnotaconcern),gravel,andC&Dwaste.However,theintermediatecoversoilmaterialmustbelesspermeablethanthewastebelow.Thisdesignwillalsominimizeatmosphericairintrusionintolandfillgascollectionsystem,aproblemthatiscurrentlyseenintheSCLgassystem.Figure13showslandfillgasbalanceandoxygendataforalloftheverticalgaswells(notincludingCity‐Southarea)attheSCL(between2/4/2014to7/24/2015)forthepasttwoyears(12,487recordedverticalgaswellheadcompositiondatacollected).Duringthistime,368verticalgaswellsoutof410(89.8%oftheverticalgaswells)hadLFGbalancecontent(nitrogengas)equaltoorgreaterthanof20%(v/v),and95verticalgaswellsoutof410(23.2%oftheverticalgaswells)hadoxygencontentequaltoorgreaterthan5%(v/v).Thisindicatesthatmanyofthelandfillgaswellsarepullingairintothelandfill.Thiscreatesanoxidizingenvironmentinthelandfillthatleadstoconsumptionofmethanebyoxidationandcouldincreasetheriskoflandfillfire.

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WealsorecommendthatgassamplesfromthemainLFGcollectionsystemintheseareasbetestedforcarbonmonoxide(CO)levelsusinglaboratoryinstrument(gaschromatography)andnotmeasuredusingfieldinstrumentbecauseofinterferencewithothergasespresent.WealsorecommendtheproposedpermeablelayerLFGcollectionsystemdesignbetestedinasectionofthelandfill(intermediateorfinalfillarea)todeterminehowitmightbeimplementedtoreducegasemissionsattheSCL.Furtherassistanceinthedesignandtestingofsuchsystemcanbeprovided.Wecanprovideadetailproposalforfurtherstudyatalaterdate.

Figure12‐Landfillgascollectionwellwithpermeablelayerinstalledaswastefillingadvances.

Figure13‐SCLverticallandfillgaswelldatabetween2/4/2014to7/24/2015.

Saturated Waste Condition and Gas Collection Efficiency  Wastethatissaturatedwithwatercangreatlyreducegaspermeability(Jainetal.,200533;Reinhartetal.,200234).Liquidmovementandchangeinwatersaturationmayalsobeaffectedbyrefuseheterogeneity(McCreanorandReinhart,200035).InalandfillsimulationstudybyJung,etal.,201132themeangaspermeabilityofwaste

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wasreducedbyafactoroffivewhileallotherparametersremainedthesame.Modelingresultsshowedthatwithoutthenear‐surfacepermeablelayertheconventionallandfillgasdesignhademissionsthatwere25%ofthetotalCH4generated.ThisindicatesthatconventionalLFGcollectionsystemsarenotefficientwheregaspermeabilitiesarereducedbecauseofelevatedmoistureconditions(Jainetal.,200533),conditionsthatappeartoexistinthelowerlayersofwasteattheSCL.Afterinstallationofdewateringwellsandtrenches,thenear‐surfacepermeablelayerdesignextendsthezoneofinfluenceofthepumpingwellandcausesamoreuniformverticalLFGflowabovethepermeablelayerandresultsinnearconstantcollectionefficienciesofbiogasregardlessofvariationsinheterogeneouslandfillconditions,includingvariationsingaspermeability(Jungetal.,201132).Werecommendthatdewateringtrenchesbeinstalledandthenewlandfillgascollectiondesignbetestedinasectionofthelandfillwithsaturatedconditionwithintermediatecovertodeterminehowitmaybeimplementedtoreducegasemissionsandimprovegascollectionefficiency.Furtherassistanceinthedesignandtestingofsuchsystemcanbeprovidedatalaterdate.Wecanprovideadetailproposalforfurtherstudy.

Hydrogen Sulfide Production in Landfills and the Use of Soil as Daily Cover  Inlandfillenvironmentswherethereisanabsenceofoxygen(anaerobiccondition),microbesdegradeorganicwasteandproducecarbondioxide(CO2)andmethane(CH4),typicallyproducedinequalquantities(Eq.1).Whensulfurispresent,itisconvertedbyanaerobicbacteriatoH2S.Typicallysulfurispresentintheformofsulfate(SO4)butalsointheformofelementalsulfur(S)andsulfite(SO3).

Organicmatter(e.g.municipalwaste)+H2OCO2+CH4 Eq.(1)

Organicmatter(e.g.municipalwaste)+SO4+H2OH2S+CO2Eq.(2)

InorderforH2Stobeproducedinlandfillenvironment,asshowninEq.2above,twoingredientsareneeded,asourceoforganicmatterandsourceofsulfur(S).Organicmatterispresentintheformofmunicipalorcommercialwaste,biosolidsorleachateinliquidform.Thesulfur(S)canbepresentinconstructionanddemolition(C&D)waste(wallboard),thewallboardfinesfromamaterialrecoverfacility(MRF)thatprocessesC&Dwaste,flyashorotherindustrialwastecontainingsulfur.Also,sulfurcouldbepresentinthesoilusedasdailycoveratthelandfillsite.In2011,soilsamplesfromseveralsoilstockpilesattheSCLweretestedforvariouschemicalproperties.LaboratoryresultswerereportedinthegeologicalandgeotechnicalinvestigationreportpreparedbyAMEC,201136.BasedonthetestresultsbyAMECtheaveragesulfatecontentofsoilusedasdailycoverwas1,424mg/kg.Eachyearabout700,000to1,000,000cubicyardsofsoilisusedasdailyandintermediatecoversoilattheSCL.Calculationbasedontheaveragesulfatecontentofthecoversoilindicatesthataround1,500to2,100tonsofsulfateisaddedtothelandfillannually.Thishasthepotentialof

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producingover500to750tonsofH2S.Theuseofdailyandintermediatecoversoilwithhighlevelsofsulfatecouldincreasethepotentialforodors.Werecommendthatsamplesofthesoilusedfordailyandintermediatecoverbetestedforsulfurcontent.Samplesshouldalsobetestedforbiochemicalsulfurpotential(BSP)inananaerobicenvironmenttodeterminethepotentialofsoilproducingH2S.TheNorthCarolinaStateUniversitylaboratoryistheonlyoneweareawareofthatisqualifiedtoperformBSPtestsonsoilsamples.AproposalcanbeprovidedforlaboratorytestingofsoiltodeterminethesulfurcontentandtheBSP.

Control of Emissions at the Active Filling Area  Inadditiontotherecommendationsmadeforalternativedailycover(ADC)tocontrolemissionsattheactivefillingareabyHGC15,otherADCmaterialsuchascompost37andshreddedgreenwaste38haveshowntobeaneffectivemeansofcontrollingLFGemissionsandshouldbeconsideredforfurthertestingattheSCLinsteadofnine(9)inchesofcoversoil.TheuseofgreenwasteasADCmaybelimitedduetolocalCityand/orCountypolicyofdivertinggreenwastefromthelandfillaswellasmandatorywastediversionassemblybill(AB1826andAB341).Otherstudieshavealsoinvestigatedbio‐tarp39asanalternativecovertoreduceemissionthatmaybeconsideredinstead.InadditiontorecommendationsmadebyHGCtousesprayonproductsasdailycover,werecommendinvestigatingthepossibilityofobtainingshreddedgreenwasteorcompostthatcouldalsobeusedasADC.Wealsosuggestinvestigatingtheuseofbio‐tarpasanalternativecovertoreduceemission.

Impact of Daily Cover Soil Use on Landfill Gas Transport and Emission Inordertobetterassesstheimpactofnine(9)inchesofdailycoveronlandfillgastransportandemission,analysisoftheeffectsofdailycoverongastransportpropertiesandwaterretentionisneeded.Werecommendtwomethodstofurthergatherdata.Inthefirstmethod,weproposethecollectionofin‐tactwastecoresamplesatvariousdepthsattheSCLusingsonicdrillingtechnique(Figure14)inconjunctionwithfreezingofsamples(tomaintainporestructure).Theeight(8)inchdiametersamplesthatarecontinuouslylinedwithplastictubeswillbeusedtocollectwastesamplesatdepthsandinlocationswithlittleornosignificantdailycover.ThesesampleswillbesenttotheUniversityofDelawarelaboratorieswheredensity,totalporosityandgastransportpropertieswillbemeasured.Whiletheinitialwatercontentofthesampleswillberecorded,theeffectofmoistureongastransportwillbeevaluatedbyvaryingthewatercontentsystematicallyineachsampleinthelaboratory.TheUniversityofDelawarehasconductedsimilarmeasurementsonotherwastesamples(Hanetal.,2011)40.Thisinformationwillquantifytheeffectofdailycoveronwaterretentionandgastransportproperties,informationthatmaybeusedinnumericalmodelingoflandfillgastransportandemissionsintheSCL.Inthesecondmethod,weproposetousein‐situcone

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penetrationtest(CPT)andpiezoconepenetrationtest(PCPT)(Figure15).Thisisafast,economicalmethodthatprovidescontinuousprofilingofwastetodeterminevariousconditionssuchas:locationofcompactedwasteandcoversoillayers,liquidandgaspressures,identifyzonesofvacuum,determinedensityofwasteasafunctionofdepth(Figure16).Werecommendthatastudybeconductedtogetabetterunderstandofhowthesoillayersusedasdailycoverimpactsgasandwatermovementinlandfill.Wecanprovideadetailedproposalforfurtherstudyatalaterdate.

Figure14‐WastesamplingusingaSonicdrillingunit

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Figure15‐ConePenetrationTest(CPT)procedureandsetup41.

Figure16‐TypicalPiezoconeConePenetration(PCPT)testresults41.

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Measurement of Whole‐Landfill Gas Emissions InSouthernCalifornia,themainanthropogenicemissionsourcesofCH4arelandfills(Table1)42.ThereareseveralfieldmethodstomeasurelandfillCH4emissionssuchasstaticanddynamicfluxchambermethodsatgroundlevel,subsurfaceconcentrationandpressuregradientmethods,andabovegroundmicrometeorologicalandtracermethods(Scheutzetal.,2009)43.Entirelandfillemissionscouldbemeasured(dynamicorstationary)usingatracer‐dilutionmethod,wheredownwindconcentrationofemissionmixedwiththereferencegastracerreleased(Figure17)ismeasured(Galleetal.,200144;Czepieletal.,199645;Tregouresetal.,199946).Suchmethodshaverecentlybeentestedandevaluatedforlandfillemissionquantification(Babilotte,201147;Goldsmithetal.,201248;Greenetal.,201049;Peischletal.,201350).CaliforniaAirResourcesBoard(ARB)ownsamobilemeasurementplatform(MMP)withequipmenttomeasuregreenhousegasemissions(e.g.,nitrousoxide(N2O,)‐tracergas,methane(CH4),andcarbondioxide(CO2))andiscurrentlyinuseintheLosAngelesarea.Werecommendthatanentirelandfillemissionmeasurement(dynamicorstationary)usingatracer‐dilutionmethodbeconducted.Werecognizethatapplyingthismethodtothissitecouldbechallengingbutitwillprovidemoreinsighttobetterunderstandthesourceofodors.WeproposetocoordinatewithARBinordertoconductwholelandfillemissionstestingusingthetracer‐dilutionmethod.IfARBisunabletoassistthenweproposetocoordinatewitheitherLosGatosResearch(LGR)locatedinMountainView,CaliforniaorPicarroinSantaClara,California.PicarroconductedsimilarpreliminarytestsofsuchmobilesetupattheYoloCountyCentralLandfill.BothcompanieshavedevelopedportableinstrumentstomeasureGHGwithlowdetectionlimitsneededforsuchemissionsstudy.Table1‐CARBYear2004statewideandSouthCoastAirBasin(SoCAB)portionofLACountyCH4inventories.42

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Figure17‐Schematicviewofdynamicdispersionmethodappliedatalandfill.1

Summary of Recommendations: InadditiontotherecommendationsintheHGCreport15werecommendthefollowing:1) Intermediate Cover Soil Testing‐Werecommendthecollectionofin‐tactcore

samplesofcoversoilatvariouslocations(topandsideslopes)attheSCLtobetterunderstandthepropertiesoftheon‐sitesoil.ThesesampleswillbesenttotheUniversityofDelawarelaboratorieswheredensity,totalporosityandgastransportpropertieswillbemeasured.Whiletheinitialwatercontentofthesampleswillberecorded,theeffectofmoistureongastransportwillbeevaluatedbyvaryingthewatercontentsystematicallyineachsampleinthelaboratory.TheseparameterscandirectlyimpacttheamountofLFGreleasedtotheatmospherethroughthecoversoilandthereforeincreasethepotentialodorattheSCL.

2) Daily Cover Soil‐Thefollowingtestsrelatedtotheuseofdailycoversoilarerecommended:a) Werecommendthatrepresentativesamplesofdailycoversoilstockpilebe

collectedandtestedforsulfurcontent.Samplesshouldalsobetestedforbiochemicalsulfurpotential(BSP)underanaerobicenvironmenttodetermineitspotentialforproductionofH2S.ThesetestswillbesenttoNorthCarolinaStateUniversityforlaboratorytesting.

b) Samplesofthelandfillleachatefromvariousleachatecollectionareasofthelandfillshouldalsobetestedforsulfate.

c) Landfillgassamplesfromvariouslocations(gaswellsandgasheaderlines)shouldbecollectedforH2Slaboratorytesting.

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d) Wealsorecommendtwotypesoffieldstudiestogatherdataandbetterunderstandhowthedailycoversoillayersimpactgasandwatermovementinlandfillandtheimpactithasongascollectionefficiencyandemissions.i) Inthefirststudy,weproposethecollectionofin‐tactcoresamplesof

wasteatvariousdepthsusingsonicdrillingtechniqueinconjunctionwithfreezingofsamples(tomaintainporestructure).ThesesampleswillbesenttotheUniversityofDelawarelaboratorieswheredensity,totalporosity,andgastransportpropertieswillbemeasured.Whiletheinitialwatercontentofthesampleswillberecorded,theeffectofmoistureongastransportwillbeevaluatedbyvaryingthewatercontentsystematicallyineachsampleinthelaboratory.Thisinformationwillquantifytheeffectofdailycoveronwaterretentionandgastransportproperties,informationthatmaybeusedinnumericalmodelingoflandfillgastransportandemissionsintheSCL.

ii) Inthesecondstudy,weproposetousein‐situconepenetrationtest(CPT)andpiezoconepenetrationtest(PCPT).Thisisafast,economicalmethodthatprovidescontinuousprofilingofwastetodeterminevariousconditionssuchas:locationofcompactedwasteandcoversoillayers,liquidandgaspressures,identifyzonesofvacuum,anddeterminedensityofwasteasafunctionofdepth.

3) Alternative Daily Cover (ADC)‐AssuggestedbyHGC15othertypesofADC

(sprayonproducts)shouldbeusedinsteadoftheon‐sitesoil,particularlybecauseofhighsulfatecontentofsoilthatcouldreactwithleachategenerated.Inadditiontosprayonproducts,werecommendinvestigatingthepossibilityofobtainingshreddedgreenwasteorcompostthatcouldbeusedasADC.TheuseofgreenwasteasADCmaybelimitedduetolocalCityand/orCountypolicyofdivertinggreenwastefromthelandfillaswellasmandatorywastediversionassemblybills(AB1826andAB341).Wealsosuggestinvestigatingtheuseofbio‐tarp51asADCtoreduceemission.

4) Estimation of LFG Generation Rate and LFG Collection Adjustment‐

a) Werecommendusingthebaro‐pneumaticmethodtoestimatingLFGgenerationbecauseitreducesuncertaintiesinestimationofLFGgenerationrates.

b) ThecurrentmethodofLFGwellheadadjustmententrainsairintothelandfillanddoesnottakeintoaccountthediurnalbarometricpressurechanges.Werecommendthatatleastonemainheaderlinewithseveralgaswellsandonegaswellintheareawherebaro‐pneumatictestswereperformedbyHGCbemodifiedwithanautomaticwellheadadjustmentsystem(LociControls23).Todeterminetheeffectivenessofreducinglandfillgasemissionswerecommendgastracermethod24beusedtomeasuretheactualgascollectionefficiencywithandwithouttheautomaticwellheadadjustmentsystem.

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5) Saturated Waste Condition and Gas Collection Efficiency‐Werecommendthatthenear‐surfacepermeablelayer31bedesigned,constructed,andtestedinanareawherewasteissaturatedandsurfaceemissionsareknowntobeaproblem.Thegascollectionefficiencywillbemeasuredbeforeandafterinstallationofthispermeablelayerusingthegastracermethod24.

6) Whole‐Landfill Gas Emissions‐Werecommendusingthetracer‐dilution

method(dynamicorstationary)toconductseveralweeksoffieldstudytodeterminetheentirelandfillemissionsunderdifferentatmosphericconditions.ResultswillbeusedtoidentifythelocationofgasemissionswithintheSCLsite.

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Appendix A 

FigureA1‐SCLJointTechnicalDocument(JTD)2007,Proposed

PhasingPlan

FigureA2‐SCLLocationofVerticalGasWellswithDedicatedPumpandBoundaryofnine(9)inchDailySoilCover

FigureA3‐HydroGeoChem,Inc.FieldTestLocationattheSCL

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Limitations NoinvestigationisthoroughenoughtoguaranteethefutureeliminationofodorattheSCLsite.WhilethisreportprovidesreasonablerecommendationsandsuggestsfurtherstudiestoimproveodorcontrolatSCL,itshouldnotbeconstruedasaguaranteethatthesuggestedideaswouldaccuratelyforecasttheeliminationofodorattheSCLsite.Theservicesdescribedinthisreportwereperformedconsistentwithgenerallyacceptedprofessionalconsultingprinciplesandpractices.Nootherwarranty,expressorimplied,ismade.Theseserviceswereperformedconsistentwithouragreementwithyou,ourclient.Thisreportissolelyfortheuseandinformationofourclientunlessotherwisenoted.Anyrelianceonthisreportbyathirdpartyisatsuchparty’ssolerisk.Opinionandrecommendationscontainedinthisreportapplytoconditionsexistingwhenserviceswereperformedandareintendedonlyfortheclient,purposes,locations,timeframesandprojectparametersindicated.Wearenotresponsiblefortheimpactstoanychangesinenvironmentalstandards,practices,orregulationssubsequenttoperformanceofservices.Wedonotwarranttheaccuracyofinformationsuppliedbyothers,ortheuseofsegregatedportionsofthisreport.

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13Bentley,H.W.,Smith,S.J.,Tang,J.,Walter,G.R.“Amethodforestimatingtherateoflandfillgasgenerationbymeasurementandanalysisofbarometricpressurewaves.”In:Proceedingsofthe18thInternationalConferenceonSolidWasteTechnologyandManagement,Philadelphia,PA(2003).14Walter,G.R.“Fatalflawsinmeasuringlandfillgasgenerationratesbyempiricalwelltesting.”J.AirWasteManag.Assoc.53,461–468(2003).15“PneumaticTestingandRecommendedChangesattheSunshineCanyonLandfill”,HydroGeoChem,Inc.,March11,2015.16http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/ref/?cid=nrcs142p2_05357317Czepiel,P.M.,Shorter,J.H.,Mosher,B.,Allwine,E.,McManus,J.B.,Harriss,R.C.,Kolb,C.E.,Lamb.B.K.(2003).“Theinfluenceofatmosphericpressureonlandfillmethaneemissions.”WaterManagement23(7):593‐598.18Giani,L.,J.Bredenkamp,etal.(2002).“TemporalandspatialvariabilityoftheCH4dynamicsoflandfillcoversoils.”J.PlantNutr.SoilSci.,165,205–210.19Christophersen,M.,Kjeldsen,P.,Holst,H.,Chanton,J.(2001).“Lateralgastransportinsoiladjacenttoanoldlandfill:factorsgoverningemissionsandmethaneoxidiation.”WasteManag.Res.19(6):595‐612.20Xu,L.,Lin,X.,etal.(2014).“Impactofchangesinbarometricpressureonlandfillmethaneemission.”GlobalBiogeochemicalCycles28(7):679–695.21Czepiel,P.M.,J.H.Shorter,etal.(2003)."Theinfluenceofatmosphericpressureonlandfillmethaneemissions."WasteManagement23(7):593‐598.22Yazdani,R.,D.Augenstein,P.Imhoff,M.Barlaz.(2008),“DemonstrationofLandfillTechnologyforPeakingPowerPotentialatYoloCountyCentralLandfill.”CaliforniaEnergyCommission,PIEREnergy‐RelatedEnvironmentalResearchProgram.CEC‐500‐00‐034.23http://locicontrols.com24Yazdani,R.,Imhoff,P.T.,Han,B.,Mei,C.,Augenstein,D.(2015).“QuantifyingCaptureEfficiencyofGasCollectionWellswithGasTracers”,WasteManagement,43:319‐327.25Kjeldsen,P.andE.V.Fischer(1995)."LandfillGasMigration‐FieldInvestigationsatSkellingstedLandfill,Denmark."WasteManagement&Research13(5):467‐484.

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