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Modeling PCB Loadings Reduction Scenarios to the
Lake Washington Watershed: Final Report
March 2014
Alternate Formats Available
Modeling PCB Loadings Reduction Scenarios to the Lake Washington Watershed: Final Report
Prepared for: US EPA Region 10
Submitted by: Richard Jack, Jenée Colton, Curtis DeGasperi, and Carly Greyell King County Water and Land Resources Division Department of Natural Resources and Parks
Funded by the United States Environmental Protection Agency Grant PC-J28501-1
Disclaimer: This project has been funded wholly or in part by the United States Environmental Protection Agency under assistance agreement PC-00J285-01 to King County. The contents of this document do not necessarily reflect the views and policies of the Environmental Protection Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.
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Acknowledgements Afantasticgroupofpeoplehavemadethisprojectpossibleandcontributedtoitssuccess.ColinElliottoftheKingCountyEnvironmentalLaboratoryprovidedlaboratoryprojectmanagementservicesthroughoutthefieldstudy.ManythanksgotoBenBudka,MarcPatten,DavidRobinson,BobKruger,JimDevereaux,andStephanieHess,wholedtheyear‐longfieldsamplingprogram.TheknowledgeablestaffatAXYSAnalyticalServicesprovidedhighqualityadviceandanalyticalservices.ArchieAllenandKirkTullaroftheWashingtonDepartmentofTransportationprovidedcriticalassistanceduringsitingandsamplingofthehighwaybridgerunofflocation.JohnWilliamsonoftheWashingtonDepartmentofEcologygraciouslyallowedusaccessandsharedspaceattheBeaconHillairstation.LauraReedandvariousstaffatSeattlePublicUtilitiessupportedusinsiteselectionandsetupofmultipleSeattlesamplinglocations.SpecialthanksgotoJonathanFrodge,JennyGaus,RonStraka,andPatrickYamashitafortakingextratimetomeetwithusandprovideinformationduringsiteselection.GinnaGrepo‐GroveofEPARegion10assistedwithdatavalidationruleinterpretation.
ThanksalsogototheTechnicalAdvisoryPanelmemberswhoprovidedfeedbackatourinitialresultsandloadingestimatepresentation.SpecialthankstopanelmembersJonathanFrodgeandHeatherTrimwhocontributedsubstantiallytothetributaryflowandcontaminantloadingextrapolationapproachpresentedintheloadingsreport.
WethankalloftheLakeWashingtonLoadingsprojectadvisorypanelmembersforreviewingthedraftprojectdocumentsandtheirconstructivecriticismsthroughout.
TechnicalAdvisoryPanelMembers(inalphabeticalorder)were:
FredBergdolt,WADept.ofTransportation BetsyCooper,KingCountyWastewaterTreatmentDivision JonathanFrodge,SeattlePublicUtilities JennyGaus,CityofKirkland JoanHardy,WADept.ofHealth RachelMcCrea,WADept.ofEcology DougNavetski,KingCountyWaterandLandResourcesDivision AndyRheaume,CityofRedmond RonaldStraka,CityofRenton BruceTiffany,KingCountyWastewaterTreatmentDivision HeatherTrim,PeopleforPugetSound/FutureWise PatrickYamashita,CityofMercerIsland
ValuableadviceandfeedbackontechnicalaspectsofbothfateandbioaccumulationmodelswereprovidedbyGregPelletieroftheWashingtonStateDepartmentofEcology(Ecology).WeacknowledgeDebLesterandJimSimmondswhoprovidedmanysuggestionsthroughoutthatresultedinimprovementstotheprojectoverallandtothecomponentreports.
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Citation KingCounty.2014.ModelingPCBLoadingReductionstotheLakeWashingtonWatershed:
FinalReport.PreparedbyRichardJack,JenéeColton,CurtisDeGasperiandCarly
Greyell,WaterandLandResourcesDivision.Seattle,Washington.
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Table of Contents ExecutiveSummary.................................................................................................................................................v
1.0. Introduction.................................................................................................................................................1
2.0. ProjectFindings..........................................................................................................................................3
2.1 FieldStudy...............................................................................................................................................3
2.2 tPCBLoadingsEstimates...................................................................................................................7
2.3 tPBDELoadingsEstimates.............................................................................................................10
2.4 LakeWashingtonPCBFatemodel..............................................................................................11
2.5 LakeWashingtonPCBBioaccumulationmodel....................................................................12
2.6 LoadReductionTissueRecoveryScenarios...........................................................................13
3.0. NextStepsandRecommendedActions.........................................................................................18
3.1 UpdatetheConceptualModelofPCBsintheLocalEnvironment................................19
3.2 SourceControl‐DevelopaPCBInventory.............................................................................19
3.2.1 PerformRegionalSourceTracingUsingCongenerData.............................................20
3.3 ConductOutreachandEducationtoDecision‐makersandPublic...............................20
3.4 EvaluateEffectivenessofStormwaterTreatmentandLIDMethods..........................21
3.5 DevelopAirshed&WashoffModels..........................................................................................22
4.0. Conclusions................................................................................................................................................24
5.0. References..................................................................................................................................................26
Figures Figure1. Fieldstudysamplingstations......................................................................................................4
Figure2. tPCBaverageandstandarddeviationconcentrationsinmajorwaterpathways.6
Figure3. tPBDEaverageandstandarddeviationconcentrationsinmajorwaterpathways..............................................................................................................................................7
Figure4. PredictedwholefishtissueconcentrationswithPCBloadreductions..................14
Figure5. PredictedresponseofwatercolumntPCBconcentrationsto10,25,50,and85percenttPCBloadreductions...................................................................................................15
Figure6. PredictedresponseoftPCBsedimentconcentrationsto10,25,50,and85percenttPCBloadreductions...................................................................................................15
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Figure7. PredictedfilletconcentrationsoftPCBsunder10,25,50,80,and90percentloadingreductionscenarioscomparedtoWADOHhumanhealthfilletscreeningconcentrations................................................................................................................................17
Tables Table1. Average,25thand75thpercentiletPCBloadingratesforpathwaystoLake
Washington,LakeUnion/ShipCanal,andtoPugetSound(g/yr)............................10
Table2. Average,25thand75thpercentiletPBDEloadingratesforpathwaystoLakeWashington,LakeUnion/ShipCanal,andtoPugetSound(g/yr)............................11
Table3. PredictedsteadystatetPCBconcentrationsinLakeWashingtonwaterandsedimentunderselectedloadreductionscenarios........................................................14
Table4. WADOHfilletscreeningconcentrationsfortPCBs..........................................................16
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EXECUTIVE SUMMARY WashingtonDepartmentofHealth(WADOH)issuedafishconsumptionadvisoryonLakeWashingtonnorthernpikeminnow,cutthroattroutandyellowperchin2006becauseofhumanhealthrisksfromPCBcontamination(WADOH2004).Givenconcernsabouthowtoaddresstheadvisory,in2010,KingCountywasawardedaU.S.EnvironmentalProtectionAgency(USEPA)PugetSoundScientificStudiesandTechnicalInvestigationsAssistanceGranttoestimateloadingoftotalpolychlorinatedbiphenyls(tPCBs)andtotalpolybrominateddiphenylethers(tPBDEs)toLakeWashington,LakeUnion,andPugetSound.ThegrantalsosupportedmodelingthepotentialdecreaseinLakeWashingtonresidentfishtissueconcentrationsassociatedwithselectPCBloadingreductionscenarios.Thisreportisthefinalproductofthegrantproject,whichsynthesizes:
a) Thefieldstudycomponents(KingCounty2013a),
b) EstimatesoftPCBloadingstoLakesWashingtonandUnion,andthesubsequentloadexportedtoPugetSoundbytheShipCanal(KingCounty2013b),
c) ModelingeffortstodescribefateoftPCBloadsinthelakeandtPCBbioaccumulationinfish(KingCounty2013c),and
d) Loadreductionscenariooutcomes.
Theprojectelementsweredevelopedinconjunctionwiththeproject’sadvisorypanel.Thefindingsincludetheircollectiverecommendationsforfurthertechnicalandmanagementactions.ThisreportalsopresentsrecommendationsfornextstepstobetterunderstandPCBsources,pathways,andbioaccumulationinLakesWashingtonandUnion,andsubsequentinputstoPugetSound.
Theproject’sfieldstudycomponentcollectedandanalyzed146samplesforPCBsandPBDEsfrom:
1) AmbientLakeWashingtonwaters
2) AmbientLakeUnionandShipCanalwaters
Andalsofromthefollowingsixinputpathways:
3) Threecreeksduringbothbaseflowandstormconditions,
4) TheCedarandSammamishRivers,
5) Threecombinedseweroverflow(CSO)dischargelocations,
6) Sixmunicipalstormwaterdischargelocations,
7) Twocombinedwetanddryatmosphericdepositionlocations,and
8) Onehighwaybridgestormwaterdischarge.
Themajorfindingsareasfollows.tPCBloadingstoLakeWashingtonwereestimatedat672g/yrwhichismorethantheestimated140g/yrloadexportedfromthelakeoutletattheMontlakeCut.Therefore,LakeWashingtonservesasapartialsink(repository)forPCBs,primarilyduetosedimentaccumulationandburial.LakeWashingtonPCBsareexportedtoLakeUnionandtheShipCanalandtheyalsovolatilizefromthelakesurface.Of
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theestimated2,023g/yrtPBDEloadtothelake,only800g/yrexitsattheMontlakeCuttoLakeUnionandtheShipCanal,thusLakeWashingtonactsasasinkforPBDEsaswell.
LakeUnionandShipCanaltPCBandtPBDEloadsincreasefromtheoutletofLakeWashingtonattheMontlakeCuttoPugetSound,partiallyduetoloadsfromthecombinedsewer/stormwatersysteminSeattle.CSOdischargesareestimatedtocontributemoretPCBsandtPBDEstoLakeUnionandtheShipCanalthantoLakeWashington.AveragetPCBloadingfromtheShipCanal’sHiramM.ChittendenLockstoPugetSoundwasestimatedat360g/yr.Normalizedtowatershedarea,360g/yrequals6.27x10‐4g/km2/daywhichiscomparabletootherpublishedurbanwatershedrates,buthigherthanruralPugetSoundwatershedrates.AveragetPBDEloadingfromtheShipCanal’sHiramM.ChittendenLockstoPugetSoundwasestimatedat990g/yrtPBDEs.BasedonfatemodelingofinstantaneoustPCBloadreductions,thelargestchangesinLakeWashingtonsedimentandwaterconcentrationswouldoccurwithin20years;upto40yearsisrequiredtoreachequilibrium.While20to40yearsisalongtime,intheabsenceofsubstantialwatershed‐wideeffortstoreducetPCBloads,theexistingfishconsumptionadvisoryisprojectedtoremainindefinitely.
DespiteabanontheproductionandmanyusesofPCBsinthelate1970s,foodwebbioaccumulationmodelingpredictsthatapproximatelyanadditional85percentreductionintPCBloadingisrequiredtoreduceLakeWashingtonfishtissueconcentrationsandremovetheexistingWADOHfishconsumptionadvisory.Toprogresstowardreductionsofthismagnitudewerecommend:
TraceandidentifyongoingPCBsourcesincurrentandhistoricallyusedmaterials.
Developingastate‐wideand/orregionalPCBinventorytoenabletargetedsourcecontrolactions,
Conductoutreachandengagedecision‐makersandthecommunityindiscussionaboutthewidespreadsourcesofPCBs,andthefinancialandregulatorychallengesinherentincontrollingsuchsources,
EvaluatetheeffectivenessoftreatmenttechnologiesandbestmanagementpracticesforPCBremoval,and
Developbulkdeposition/washoffmodelstodeterminecontributionofatmosphericPCBdepositiontostormwaterrunoff.
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1.0. INTRODUCTION WashingtonDepartmentofHealthissuedafishconsumptionadvisoryonnorthernpikeminnow,cutthroattroutandyellowperchin2006becauseofhumanhealthrisksfromPCBcontamination(WADOH2004).Inaddition,asimilarlypersistentandmoremodernchemical,polybrominateddiphenylethers(PBDEs)isalsobioaccumulatinginLakeWashingtonfish(KingCountyunpublisheddata).ElevatedconcentrationsofPCBsandPBDEsarenotuniquetoLakeWashington,asevidencedbychemicalconcentrationsmeasuredinmarinemammalandfishtissuefromPugetSound(Rossetal.2000,Rossetal.2004,Krahnetal.2007,Westetal.2008,Sloanetal.2010,Cullonetal.2005).However,todatetherehavenotbeenanystudiesfocusedonhowthesechemicalsaregettingintoLakeWashingtonfishorthequantityofthesechemicalsenteringLakeWashington,LakeUnionandtheShipCanal(LakeUnion),andPugetSoundfromthiswatershed.Therefore,primarygoalsofthisprojectaretohelpfillPCBandPBDEdatagapsfortheLakeWashingtonwatershedandPugetSoundbasinandprovideinformationandtoolsneededtodirectmanagementofPCBsandreducehealthrisksassociatedwithLakeWashingtonfishconsumption.
In2010,KingCountywasawardedaU.S.EnvironmentalProtectionAgency(USEPA)PugetSoundScientificStudiesandTechnicalInvestigationsAssistanceGrantto(1)estimateloadingoftotalpolychlorinatedbiphenyls(tPCBs)andtotalpolybrominateddiphenylethers(tPBDEs)toLakeWashington,LakeUnionandPugetSound,and(2)modelthepotentialdecreaseinLakeWashingtonfishtissueconcentrationsassociatedwithselectPCBloadingreductionscenarios.tPCBswerethefocusofthemodelingbecauseLakeWashington’scarpandnorthernpikeminnowarecurrentlyunsafetoeatinanyamountandcutthroattroutorlargeyellowperchareonlysafeinlimitedamounts(WADOH2004).WhilesmallmouthbassarenotpartoftheWashingtonDepartmentofHealth(WADOH)advisory(2004),theyhavesincebeenfound(KingCounty2013e)tohavesimilartPCBconcentrationstothoseinnorthernpikeminnow.
UnderstandingtherootcausesofthehighPCBlevelsinfishiscriticaltoattainingsafetissueconcentrations.tPCBswerenotmodeledinLakeUnionduetoalackofresidentfishtissuedataforLakeUnion.tPBDEswerealsonotmodeledbecausetheyarenotpartoftheexistingLakeWashingtonfishconsumptionadvisoryandinformationabouttheirconcentrationsininvertebratesandpreyfishwaslacking.
Tofocusthefieldandmodelingefforts,threemanagementquestionsweredeveloped:
1) WhichtypesofimportpathwaysarethehighestprioritiesfortPCB/tPBDEloadingreduction?
2) HowwillpotentialloadingreductionsfromthesepathwaysreducethemagnitudeofresidentfishtissuePCBconcentrationsandtheneedforafishconsumptionadvisoryonLakeWashington?
3) HowlongmightthesystemtaketorespondtothesehypotheticaltPCBloadingreductions?
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Thisreportisthefinalproductofthegrantprojectwhichsynthesizes:
a) Thefieldstudycomponents(KingCounty2013a),
b) LoadingestimatestoLakesWashingtonandUnion,andtheloadexportedtoPugetSoundbytheShipCanal(KingCounty2013b),
c) ModelingeffortsdescribingthefateofPCBloadsinthelakeandPCBbioaccumulationinresidentLakeWashingtonfish(KingCounty2013c),and
d) Loadreductionscenariooutcomes,Section2.5ofthisreport.
Theprojectelementsweredevelopedinconjunctionwiththeproject’sadvisorypanel.Thefindingsincludetheircollectiverecommendationsforfurthertechnicalandmanagementactions.
ThisprojectcollectedthefirstextensivemeasurementsoflowleveltPCBandtPBDEconcentrationsinwholewaterfromLakeWashingtonandtheShipCanal,aswellasinavarietyofotherwaterinputpathways(KingCounty2013a).Thepathwaysincludedwetanddrybulkatmosphericdeposition(dustandrainfall)becausePCBsandPBDEsaresemi‐volatilecompoundswhichmayseasonallycyclebetweensoils,water,andtheatmosphere(Hornbuckleetal.1994,Kayaetal.2012).ThetPCBandtPBDEwateranddepositiondatawerethenusedtoestimatecontaminantloadingstoLakesWashingtonandUnionandsubsequentlyfromthemajorityofthe(WRIA8)watershedtoPugetSoundviatheHiramM.ChittendenLocks.Loadingsestimatesarepresentedinaseparatereport(KingCounty2013b)thataddressedthefirstmanagementquestionabove.
HistoricalandprojectPCBdata(KingCounty2013a)werethenusedtodevelopfateandbioaccumulationmodelsforLakeWashington(KingCounty2013c).Incombinationwiththeloadingsinformation,thesemodelswereusedtoinformpriorityloadingreductionpathwaysandestimatethelengthoftimetheLakeWashingtonecosystemmighttaketorespondtochangesintPCBloadings.
Thisfinalreportconcludeswithadescriptionofthemagnitudeofloadingreductionsneededtoachievesafefishtissuelevels.SuggestionsandrecommendationsarealsoprovidedfornextstepstobetterunderstandPCBsources,pathways,andbioaccumulationinLakesWashingtonandUnion,andsubsequentinputstoPugetSound.TheseincludeactionsthatmaybeusedtoreducePCBloadstoLakeWashingtonfromthewatershed.
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2.0. PROJECT FINDINGS Theprojectconsistedoffourcomponents:afieldstudy,loadingsanalysis,fateandbioaccumulationmodeling,andloadreductiontissuerecoveryscenarios.Detailsofthefirstthreecomponentsareprovidedinpriorreports(KingCounty2013a,b,c)andaresummarizedbelow.Adetaileddescriptionofthescenariosexaminedtoreducefishtissueconcentrationsisalsopresentedinthissection.
2.1 Field Study ThisprojectcollectedandanalyzedsamplesfromlakereceivingwatersandsixdifferentlakeinputpathwaytypestosupportdevelopmentofmassloadingsestimatesoftPCBsandtPBDEstoLakesWashingtonandUnion,andsubsequentlytoPugetSoundfromthemajorityofthegreaterCedar‐SammamishLakeWashingtonWaterResourceInventoryArea(WRIA8).Thereceivingwatersevaluatedincluded:(1)LakeWashingtonand(2)LakeUnionandtheShipCanal.Theinputpathwaysincluded:(1)threecreeksinthewatershed;sampleswerecollectedduringbothbaseflowandstormconditions;(2)theCedarandSammamishRivers;(3)threecombinedseweroverflow(CSO)locations;(4)sixstormwaterdischargelocations;(5)highwaybridgerunoff;and(6)combinedwetanddryatmosphericdeposition.Atotalof146sampleswerecollectedandanalyzedforPCBandPBDEcongenersandselectconventionalparameters.Wholewatersamples(whichincludedbulkairdeposition)weresuccessfullycollectedaccordingtothestudydesignspecifiedintheQualityAssuranceProjectPlan(QAPP)(KingCounty2011a)withafewmodifications(KingCounty2013a).AnoverviewofthesamplinglocationsbytypeisprovidedinFigure1.
SomeoftheanticipateddataqualityobjectivesofprecisionforPCBandPBDEcongeners1werenotmetasoutlinedintheQAPP.Particularlylowreproducibilityoccurredinambientlakeandriverwaters:LakeWashington,theShipCanal,andtheCedarandSammamishrivers.ThisstudywasunabletoreliablymeasuretheselowtomoderatetPBDEconcentrationsinregionalambientlakeandriversamplesbecauseofbackgroundlaboratorycontaminationandtheoverallubiquityofPBDEs.
1Thereare209uniquePCBand209uniquePBDEcongeners.Eachhasslightlydifferentchemicalpropertiesbasedontheirspecificformulaandshape.ThisprojectanalyzedallPCBcongeners,butresultsareexpressedasasum(total).TheprojectonlyanalyzedthemostcommonninePBDEcongenersandreportedtheirtotals.
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Figure 1. Field study sampling stations.
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tPCBandtPBDEconcentrationsdetectedinLakeWashingtonandriversampleswerethelowestofallsamplesmeasured.Thiswasexpectedgiventhatparticle‐associatedcontaminantslikePCBsandPBDEsareprovidedalongsettlingtimeinthelakeandthelargesurfaceareaofthelakeprovidesanadditionallosspathwayforthesecontaminantsthroughvolatilization.Thus,detectedtPCBconcentrationsinLakeWashingtonrangedfrom36to415pg/Landfrom32to1,572pg/LfortPBDEs.WhendatacollectedfromLakeWashingtonandthetwoShipCanalstationsarecompared,thehighestdetectedtPCBconcentrationswereattheBallardLocksstation(upto583pg/L)indicatinginputsintoLakeUnion/ShipCanalrepresentasubstantialcontributionoftPCBs.tPBDEconcentrationsinLakesWashingtonandUnionandtheShipCanalwereoftentooclosetomethodblankconcentrationstoreliablymeasure(i.e.,theywerenotdetected);however,thethreehighestmeasurementswerealsodetectedattheBallardLocksandMontlakeCutlocations(upto2,148pg/L).Comparedtootherinputpathwaysandthelakeitself,tPCBandtPBDEconcentrationsintheCedarandSammamishRiverswerebothrelativelylow.ThetPCBsintheCedarandSammamishriversrangedfrom10to267pg/L,whiletPBDEsrangedfrom3to3,150pg/L.TheselevelsaresimilartotPCBandtPBDEconcentrationsmeasuredbyHerreraEnvironmentalConsultants(2011a)inforested,agricultural,andresidentialtributariestotheSnohomishandPuyallupRivers,whicharealsoinWesternWashington.Comparedtothecurrentstudy,tPCBswerehigherduringstormeventsinthecommercial/industrialtributariessampledbyHerrera(2011a);however,thiswasnotthecasefortPBDEs.
tPCBandtPBDEconcentrationsmeasuredinmajorcreeksdifferedbylocation,withThorntonCreekexhibitingthehighestconcentrations,upto10,527pg/LtPCBsand20,910pg/LtPBDEsduringstorms.Asexpected,tPCBandtPBDEconcentrationswerelowerincreeksduringbaseflowconditions(minimaof105and59pg/L,respectively).tPCBandtPBDEconcentrationsvariedwidelyinstormwaterandhighwayrunoff.ThehighesttPCBconcentrationwasobservedintheFremontstormwater(165,685pg/L),whilethesecondhighestconcentrationwasdetectedinthehighwaybridgerunoff(16,133pg/L).tPBDEconcentrationsinstormwaterrunoffweresimilarbetweenSeattledischarges(Madrona,SewardParkandFremontDrainages),whilesmallercitydischarges(Kirkland,MercerIslandandRenton)exhibitedmorevariability,butweregenerallylowerthanthoseinSeattle.
ThehighesttPCBandtPBDEconcentrationsdetectedatCSOlocationswerealwaysobservedattheDexterCSO(upto565,108and212,174pg/L,respectively).ForbothtPCBsandtPBDEs,theSewardParkCSOhadthelowestreportedconcentrations(minimaof2,301and6,703pg/LfortPCBsandtPBDEs,respectively),whileconcentrationsattheBallard150CSOwereintermediate.TheaveragetPBDEconcentrationforallCSOswas82,898pg/L(N=8),whiletheaverageCSOtPCBconcentration(101,426pg/L,N=8)wasanorderofmagnitudehigherthantheaveragetPCBconcentrationofanyotheraqueousinputpathway.ThehighvariabilityofCSOtPCBconcentrationsgeneratedsignificantuncertaintyaroundthisarithmeticaverageconcentration.BecauseanarithmeticaverageCSOtPCBconcentrationwasrequiredformodelingandloadingsestimates,additionaldata(45samples)collectedfromCSOsintheLowerDuwamishRiverBasinWaterwaywereincludedtoenhancethereliabilityoftheestimatedconcentration.The53samplecombined
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datasethadamorereliablearithmeticaverageof70,543pg/L,lowerthanthisproject’sCSOaverage,butstillmuchhigherthananyothermeasuredinputpathway’saverageconcentration.Figures2and3belowsummarizetheaveragetPCBandtPBDEwaterconcentrationsfoundinthefieldcomponentoftheproject.
PCBs pg/L
0
2.0x
104
4.0x
104
6.0x
104
8.0x
104
105
3.0x
105
AmbientStormwaterCSOs
Streams Baseflow
Rivers
Streams Storms
CSO
Stormwater Bridges
Stormwater All
Stormwater Seattle
Stormwater Small Cities
n=8n=4
n=25
n=10
n=11
n=3
n=16
n=9
Figure 2. tPCB average and standard deviation concentrations in major water pathways. Stormwater All is the average and standard deviation of Seattle, small city, and bridge runoff measurements.
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Figure 3. tPBDE average and standard deviation concentrations in major water pathways. Stormwater All is the average and standard deviation of Seattle, small city and bridge runoff measurements.
Ofthetwoairdepositionsamplinglocations,airdepositionratesforBeaconHillwereconsistentlyhigherthanSandPoint.However,thedifferenceintPCBdepositionratesbetweensitesisgenerallywithinafactoroftwo.tPBDEdepositionrateswereaboutfourtimeshigheratBeaconHillthanSandPoint.AveragetPCBdepositionrateswere3.4ng/m2/d,whileaveragetPBDEdepositionrateswere18.1ng/m2/d.
Thisproject’sdataprovidethefirstextensivemeasurementsoflow‐leveltPCBandtPBDEconcentrationsinwholewaterfromLakeWashingtonandtheLakeUnion/ShipCanal,aswellasfromtheriver,creek,stormwater,bulkdeposition,CSO,andhighwayrunoffpathwaystoLakeWashington.Thesedatawereusedintheloadingsanalysisandmodelingphasesoftheproject(KingCounty2013b,c),whicharesummarizedbelow.
2.2 tPCB Loadings Estimates Followingcompletionofthefieldstudy,contaminantloadingpathwaystoLakesWashingtonandUnionweredevelopedbycombiningcontaminantconcentrationdatawithlong‐termflowestimates.tPCBandtPBDEmassloadingestimatestoLakeWashingtonandLakeUnion/ShipCanalaswellasthecontaminantexporttoPugetSoundweredeveloped.DetailsofthetPCBandtPBDEloadingcalculationapproachandresultingestimatesarepresentedinapreviousreport(KingCounty2013b).tPCBfindingsarehighlightedbelowastheprojectusedtheseloadingestimatestodevelopfateandbioaccumulationmodels.
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Approximately70percentofthetPCBloadtoLakeWashingtoncomesfromlocaltributarywatershedsaroundthelakeandtheirstormwaterrunoff.Thethreesampledcreeks(Thornton,JuanitaandMay)representarangeinthetypeandintensityofdevelopmentandlanduse.Amongthesecreeks,theThorntonCreek’sbasinhadthehighestamountofcommercial/industrialdevelopmentthatoccurredpriortothebanonPCBmanufactureanduselimitationsinthelate1970s.ThisbasinhadthehighestestimatedtPCBmeanloadingof56g/yr(2.0g/km2/yr).TheMayCreekbasinhadthelowestamountofpre‐1979commercial/industrialdevelopmentandalsothelowestestimatedtPCBmeanloadingof23g/yr(0.66g/km2/yr).TheJuanitaCreekbasinhadanintermediateamountofpre‐1979commercial/industrialdevelopmentandanestimatedtPCBmeanloadingof17g/yr(0.93g/km2/yr),whichfallsbetweenthearealestimatesforThorntonandMaycreeks.Theseloadingestimatesandadditionalcorrelationanalyses(KingCounty2013b)suggestthatthepredominantsourceoftPCBstoLakeWashingtonisstormwaterrunofffromdevelopedareas–possiblylinkedtopre‐1979commercial/industrialdevelopment.TheseresultsareconsistentwiththeconceptualmodeloftPCBsourcesandpathwaysemergingfromotherstudies(Beltonetal.2007,Diamondetal.2010,RodenburgandMeng2013)thatsuggestPCBsourcesareconcentratedinurbancenterscontainingoldercommercialandindustrialbuildingswheretransformers,lightballasts,paints,caulks,andsealantswereused.Therefore,extrapolationofthesampleddrainagestotributarieswithoutconcentrationorflowmonitoringwasdonebasedontheirpercentageofpre‐1979industrial/commerciallanduseandrainfall.Thisproducedanestimatedtotallocaldrainageloadof450g/yr(1.2g/km2/yr)(KingCounty2013b).
LoadingestimatesforthetwomajorriverstoLakeWashington(CedarandSammamish)suggesttPCBloadsof56and41g/yr,respectively(97g/yrcombined).Thesearesomewhatlowerthanthetributaryload,althoughthereisahighdegreeofuncertaintyintheseestimatesduetothelowreportedtPCBconcentrationsinrivers;concentrationswereclosetothosedetectedinmethodblanks.ThecontributionofatmosphericdepositiontothesurfaceofLakeWashingtonwasalsoestimatedtoberelativelysignificantfortPCBs(110g/yr)representing14percentofthetotalloadtothelake.
Despitehavingthehighestmeasuredconcentrations,CSOsandhighwaybridgerunoffcontributedrelativelylittletotheoveralltPCBloadstoLakeWashington,12and2.9g/yrrespectively.Togetherthesepathwayscontributeapproximately2.2percentofthetPCBannualloadtoLakeWashington(14.9g/yr).Theseloadingswererelativelysmall,despitetheirhighconcentrations,duetotheirsmallcontributingvolumes.
EstimatedaveragetPCBloadingof672g/yrtoLakeWashingtonisgreaterthantheestimatedloadexportedfromthelakeoutlet(140g/yr).ThisisbecausethelakeactsasapartialsinkforPCBs,primarilyastheresultofsedimentaccumulationandburial.PCBsarealsolostfromthelakesurfacebyvolatilizationbackintotheatmosphere.
tPCBconcentrations,andhenceloading,increasefromtheoutletofLakeWashingtontotheoutletofLakeUnion/ShipCanaltoPugetSound.ThisispartiallyduetoCSOswhichdischargealargermassofPCBstoLakeUnionandtheShipCanal(58g/yr)thantoLakeWashington(12g/yr).TheaveragetPCBloadingestimatefromLakeUnionandtheShipCanaltoPugetSoundwas360g/yr.
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The360g/yrloadingratefromtheShipCanal’sHiramM.ChittendenLockstoPugetSoundrepresentsabout4.5percentofthemediantotalloadofPCBstotheentirePugetSoundassummarizedbyNortonetal.(2011).GriesandSloan(2009)estimatedtPCBloadstotheDuwamishRiverfromtheGreenRiverusingsevensuspendedparticulatesamples.Theyestimatedthat0.6to1.21g/daytPCBsentertheDuwamishRiverfromtheGreenRiver(attheconfluencewiththeBlackRiverinTukwila).Theirflowratinganalysissuggeststhiswouldresultinthedischargeof153.3to2,263g/yrtPCBsfromtheGreenRiverintotheDuwamishWaterway.Theseloadingsarewithinasimilarrangeandboundthoseestimatedinthisstudy.However,GriesandSloan’s(2009)studymayunderestimateloadingsbyexcludingthedissolvedfractionofPCBs.Incomparison,theLakeWashingtonprojectbasedloadingsestimatesonwholewaterresultsattheHiramM.ChittendenLocks.Aswithmanyfieldefforts,loadingestimatesfrombothstudiesarenotdirectlycomparable(e.g.,differentmethodsofestimatingannualflow)andhavesubstantialassociateduncertaintiessuchaslimitedsamplesizes.
Onanareabasis,theGreaterLakeWashington(Cedar‐Sammamish)watershedis1,572km2;therefore,the360g/yrloadingratetoPugetSoundequalsanarea‐normalizedloadingrateof6.27x10‐7kg/km2/day.Thisarealoadingrateisnearlyanorderofmagnitudehigherthanthe7.39x10‐8kg/km2/daymaximumratecalculatedbyGriesandOsterberg(2011)fromfiveotherPugetSoundwatersheds:theSkagit,Snohomish,Nooksack,Stillaguamish,andPuyallup.However,thesewatershedshaverelativelylesspre‐1979development,havelessurbanareaoverall,andhavemoreagriculturalandforestlandthantheGreaterLakeWashingtonwatershed.Approximately600,000peopleliveintheGreaterLakeWashingtonwatershed(USCensus2010),andPCBsourcesarepartoftheoverallolderinfrastructuresupportingthesepeople‐nearly10percentofthestatewidepopulation.Therefore,whiletheestimatedloadingratefromtheLakeWashingtonwatershedisthehighestofthesixwatersheds,thisisplausible.
ThetPCBloadingestimatesdocumentedinKingCounty’sloadingsreport(2013b)werethefirstestimatesofPCBloadingsinthismajormetropolitanwatershed.Asummaryofthemeanloadsbypathway,alongwiththeir25thand75thpercentilevalues,isprovidedinTable1.TheseestimateswereusedinthefateandbioaccumulationmodelsdiscussedbelowtosimulatetheresponseofLakeWashingtonfishtissueconcentrationstoreductionsintPCBloading.
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Table 1. Average, 25th and 75th percentile tPCB loading rates for pathways to Lake Washington, Lake Union/Ship Canal, and to Puget Sound (g/yr).
Pathway 25th
Percentile Mean
75th Percentile
Local drainages and rivers to Lake Washington 190 450 620
Highway runoff to Lake Washington 1.7 2.9 4.1
CSOs to Lake Washington 4.9 12 12
Direct atmospheric deposition to Lake Washington 84a 110 140a
Totals to Lake Washington 333 672 889
Lake Washington to Lake Union/Ship Canal 73 140 140
Local drainages to Lake Union/Ship Canal 22 40 53
Highway runoff to Lake Union/Ship Canal 0.52 0.87 1.2
CSOs to Lake Union/Ship Canal 23 58 59
Direct atmospheric deposition to Lake Union/Ship Canal 3.6a 4.8 6.0a
Lake Union/Ship Canal to Puget Sound 190 360 540
aMinimumandmaximumreportedbecauseonly2locationsweresampled.
2.3 tPBDE Loadings Estimates SimilartothetPCBloadsdescribedabove,tPBDEmassloadingestimatestoLakeWashingtonandLakeUnion/ShipCanalweredevelopedaswellastheloadexportedtoPugetSound.tPBDEloadingswere,ingeneral,moreuncertainthantPCBloadingestimates.ThiswasduetotheanalyticalchallengesinmeasuringlowlevelPBDEsinriversandLakeWashington.Theestimatesarelikelybiasedlow,becauseonlynineofthemostcommonPBDEswerequantifiedbythechosenmethod.Despitetheanalyticalchallengesandthemorelimitedanalytelist,overallPBDEloadingstoLakeWashingtonweremorethandoubletPCBloadings.Table2illustratesthatthe25thto75thpercentilerangesofPBDEloadingestimatesspananorderofmagnitudeformostpathways,whereasfortPCBs(Table1)the25thand75thpercentileloadingsspannedlessanorderofmagnitudeforallpathways.
AswithtPCBs,localdrainagescomprisedthemajorityofthetPBDEloadtoLakeWashington(820g/yr).Atmosphericdepositiontothelakesurfacealsocontributedarelativelylargemass.AsisthecasefortPCBs,aportionofthetPBDEloadingsaresequesteredinsedimentsorvolatilizefromthesurfaceofLakeWashington.Ofthe2,023g/yrtPBDEloadtothelake,only800g/yrexitsattheMontlakeCuttoLakeUnionandtheShipCanal.ThisisaugmentedbyCSOs,localdrainagesandatmosphericdepositionto990g/yrtPBDEsthatareexportedtoPugetSoundviatheHiramH.ChittendenLocks.
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Table 2. Average, 25th and 75th percentile tPBDE loading rates for pathways to Lake Washington, Lake Union/Ship Canal, and to Puget Sound (g/yr).
Pathway 25th
Percentile Mean
75th Percentile
Local drainages and rivers to Lake Washington 200 820 1,200
Highway runoff to Lake Washington 1.3 19 19
CSOs to Lake Washington 3.3 14 26
Direct atmospheric deposition to Lake Washington 190a 590 980a
Totals to Lake Washington 416 2,023 2,755
Lake Washington to Lake Union/Ship Canal 330 800 940
Local drainages to Lake Union/Ship Canal 28 69 95
Highway runoff to Lake Union/Ship Canal 0.39 5.6 5.8
CSOs to Lake Union/Ship Canal 16 68 120
Direct atmospheric deposition to Lake Union/Ship Canal 8.3a 25 42a
Lake Union/Ship Canal to Puget Sound 280 990 1,400
aMinimumandmaximumreportedbecauseonly2locationsweresampled.
2.4 Lake Washington PCB Fate model ThefatemodelwasoriginallydevelopedbyGobasetal.(1995)andhasbeenappliedtoLakeOntario,SanFranciscoBayandPugetSound(Gobasetal.1995,Davis2004,PelletierandMohamedali2009).Itincorporatesmultipleprocessesincludingpartitioningtoparticulatesandorganiccarbon,LakeWashington‐specificsedimentationrates,andvolatilizationfromthelakesurface.Boththefateandbioaccumulationmodelsusethephysical/chemicalparametersofPCB‐118asasurrogatefortherangeofPCBchemicalpropertiesacrossallcongeners.ThechemicalcharacteristicsofothercongenerswithintherangeofthePCBsmostcommonlyfoundinLakeWashingtonfishtissuewereexaminedinthesensitivitysectionsofthefatemodel(KingCounty2013c).
ThefateandbioaccumulationmodelsforLakeWashingtonweredevelopedtoreliablyforecasttherecoveryoffishfromPCBcontaminationunderhypotheticalmanagementscenarios.Thefirstmodelingobjectivewastodevelopaquantitativeunderstandingofthelong‐termfateofPCBsinLakeWashington.Thesecondobjectivewastoprovidequantitativeestimatesofthetimeandmagnitudeoftheresponseoflakewater,sedimentandfishtissuetoreductionsinPCBloading.Thesetwomodelingobjectivesaddressoverallprojectstudyquestions2and3describedinSection1.0above.
Althoughthefatemodelisasimple,two‐compartmentboxmodel,itperformedwellwhentestedagainstobservedwaterandsedimentconcentrations.Thepredictedequilibrium
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watertPCBconcentration(95pg/L)closelymatchesthe92pg/Lvolume‐weightedbestestimateofcurrentconcentrationsinLakeWashington.ThepredictedequilibriumsedimenttPCBconcentration(18µg/kgdry)wasapproximatelyone‐thirdthemeanobservedconcentrationbasedonobserveddata(55µg/kgdry,N=69).However,themeanobservedsedimenttPCBconcentrationissuspectedtobebiasedhighduetonon‐randomstudydesigns(KingCounty2013c).Manysedimentsampleswerecollectedfromgreaterthan3cmdeep(e.g.,0‐10cmgrabs),whichreflectolder,morecontaminatedsedimentasdescribedinUSGSandEcology(Ecology2010)sedimentcores.Thus,themodel‐predictedsedimentconcentrationmaybeclosertothetruemeansedimentconcentrationthanindicatedbycomparisonstoavailabledata.Thefatemodelestimatesabout98percentofthetotaltPCBmassresidesinthesurfacesedimentcompartment;examiningallcompartments,biotaareasmall(~4percent)reservoirforPCBs(KingCounty2013c).
TheLakeWashingtonimportandexportloadingsestimatesindicatethatLakeWashingtonisapartialsinkforPCBs;theexportloadissmallerthanthetotalimportload.Thefatemodeldemonstratedthatsedimentburial(44%)isthedominantlosspathwayofPCBsfromLakeWashington,followedbyvolatilization(24%).Lossbyoutflow(16%)anddegradation(9%)arelessimportantpathways.TheremainingsevenpercentoftPCBmassremainsinLakeWashington’swater.
Accordingtomodeltesting,theresponsetimeforLakeWashingtonsedimentandwaterconcentrationstoreachequilibriumunderaconstantloadingisapproximately40years;however,themostrapidchangesoccurforwaterandwithinthefirst20years.Sensitivityanalysisofthefatemodelfoundittobeverysensitivetothelogarithmoftheoctanol‐waterpartitioncoefficient(logKow)2andPCBloads.Whentheseinputswerevariedintheuncertaintyanalysisindependentlyandtogether,itwasdeterminedthattPCBloadingestimatescontributedmuchmoreuncertaintythanlogKow.However,fatemodeluncertaintyremainedwithintherangeofestimateduncertaintyinobservedwaterandsedimentconcentrations.Therefore,uncertaintyinthefatemodel‐predictedwaterandsedimentconcentrationsislessthanuncertaintyassociatedwithobservedwaterandsedimentdata.
2.5 Lake Washington PCB Bioaccumulation model Thebioaccumulationmodel(KingCounty2013c)wasoriginallydevelopedbyGobasetal.(1995),ArnotandGobas(2004),andadaptedforuseinSanFranciscoBay(GobasandArnot2005),andtheStraitofGeorgia(Condon2007).FurtheradaptationsallowedmodelingcontaminantbioaccumulationinselectPugetSoundbiota(PelletierandMohamedali2009).BoththefateandbioaccumulationmodelsselectedforLakeWashingtonhavedemonstratedhistoriesofutilityandsuccess.
BioaccumulationmodeltestingusedbestestimatesofwaterandsedimenttPCBconcentrationsfromobserveddataaswellasthewaterandsedimentconcentrationswhichweregeneratedbythefatemodelwith672g/yrtPCBloadtoLakeWashington.
2Theoctanol‐waterpartitioningcoefficientisaunitlessmeasureofachemical’shydrophobicity.
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Bioaccumulationmodeloutputtissueconcentrationswerethencomparedtoobservedtissueconcentrations.Thebioaccumulationmodel‐predictedtissueconcentrationsmatchedobservedconcentrationsbetterwhenthefatemodeloutputsedimentconcentrationwasusedasaninput(18µg/Kgdry)ratherthanobservedsedimentdata(55µg/Kgdry).
TestingindicatedthemodelperformedadequatelyandsimilarlytoapplicationsofthismodelinPugetSound,GeorgiaBasinandSanFranciscoBay(GobasandArnot2005,Condon2007,PelletierandMohamedali2009)withabias3of1.2,i.e.,themodelover‐predictsLakeWashingtontissueconcentrationsby20percent(KingCounty2013c).Similartothefatemodel,thebioaccumulationmodelishighlysensitivetologKow.ThismeansthatthefishtissueconcentrationspredictedbythebioaccumulationmodelcanchangesignificantlywiththevalueselectedforthelogKow.However,uncertaintyanalysisindicatedthatvariabilityintheobservedtissuedatawasgreaterthanmodeluncertaintyforseveralfishspeciesincludingsmallmouthbass,cutthroattroutandnorthernpikeminnow.Theseuncertaintyresultsindicatethereismoreuncertaintyintheobservedfishtissuedatathanthemodel‐predictedtissueconcentrationsforthesespecies.Forlargeyellowperch,uncertaintyinthemodel‐predictedconcentrationswasgreaterthantheobservedtissuedata.
Althoughsedimentconcentrationsareordersofmagnitudehigherthanwaterconcentrations,lowertrophiclevelbiotaassociatedwithwater(e.g.,daphnia,copepods)playanimportantroleinthebioaccumulationofPCBsinuppertrophiclevelfishofLakeWashington.Themodeledspeciesbestmatchingobservedtissuedatawerenorthernpikeminnowandsmallmouthbass,twospeciesofhighconcernintheWADOH(2004)consumptionadvisory.Modeledlargeyellowperchconcentrationstendedtooverestimatetheobservedtissuedata.Thecauseofthisdifferenceisunknown;however,yellowperchdietsshift,becomingmorepiscivorouswithage.ToestimateyellowperchfishbodyburdenmoreaccuratelywouldrequireadditionaldataonLakeWashingtonyellowperchdietsthroughouttheirdevelopmentandseasonally.
2.6 Load Reduction Tissue Recovery Scenarios Inthefinalprojectphase,thefateandbioaccumulationmodelswerecoupledtotesttPCBloadingreductionscenariosandinformwaterqualitymanagers,stakeholdersandothersofthemagnitudeofchangeneededtoreachPCBfishfilletconcentrationsthataresafeforhumanconsumption(definedastheWADOHunrestrictedconsumptionscreeninglevelforPCBs).Theloadreductionscenariosdidnotincludeactivecleanupsofexistingcontaminatedsediments(e.g.,dredging,capping)ortheexclusivereductionofanyparticularpathway/source.
Themethodsandresultsofthesescenariomodelrunsarepresentedbelow.TohelpunderstandhowpotentialloadingreductionswillreducefishtissuetPCBconcentrationsin
3Modelbiasisthegeometricmeanofthedifferencesbetweenobservedandpredictedtissueconcentrationsforeachmodeledspeciesortaxon.Modelbiasabove1.0indicatesthemodelover‐predictstissueconcentrations,whilebiasbelow1.0indicatesunder‐prediction.
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LakeWashingtonresidentfish,thecurrentestimatedtPCBloadof672g/yrwasreducedby10,25and50percentandeachreducedtotalloadwasusedasinputtorunthefatemodel.Theresultingpredictedsteady‐statesedimentandwaterconcentrations(Table1)werethenusedasinputstothebioaccumulationmodel.ThepredictedwholefishtissueconcentrationswereapproximatelyproportionaltothecorrespondingpercentreductionintotaltPCBload(Figure2).
Table 3. Predicted steady state tPCB concentrations in Lake Washington water and sediment under selected load reduction scenarios.
tPCB Loading Reduction Scenario
Water Sediment
(pg/L) (µg/kg dw)
Base case (load = 0.672 kg yr-1/logKow = 6.65) 95 18
10% tPCB load reduction 85 17
25% tPCB load reduction 71 14
50% tPCB load reduction 47 9
Observed 25th and 75th-percentile concentrations 51 - 118 11 - 53
Figure 4. Predicted whole fish tissue concentrations with PCB load reductions.
Thefatemodel‐predictedresponsetimetochangesinthetotaltPCBloadscenarios,suggeststhattheresponseofwaterconcentrationsisrelativelyquick,perhapsayearortwo(Figure5).However,theoverallsystemresponseislimitedbythesediments,which
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requireabout20yearsforthemajorityofchangetooccurandabout40yearstoreachsteady‐stateequilibriumwiththereducedtPCBload(Figure6).Relativetosediment,thetypicalresponsetimeoforganismstochangesinPCBloadsisveryshort(days)(GobasandArnot2010).
Figure 5. Predicted response of water column tPCB concentrations to 10, 25, 50, and 85
percent tPCB load reductions.
Figure 6. Predicted response of tPCB sediment concentrations to 10, 25, 50, and 85 percent
tPCB load reductions.
ToestimatethemagnitudeofchangeneededtoreachsafetPCBlevelsinfish,thewaterandsedimentconcentrationsusedinthebioaccumulationmodelweredecreasedby10,25,50,80and90percent,andtheresultingpredictedwholebodytissueconcentrationswere
0
20
40
60
80
100
120
140
0 20 40 60 80 100
tPCB (pg/L)
Time (years)
10% reduction
25% reduction
50% reduction
85% reduction
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0 20 40 60 80 100
tPCB µg/kg dw)
Time (years)
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convertedtofilletconcentrationsforspeciesincludedinthecurrentLakeWashingtonfishconsumptionadvisory:cutthroattrout,largeyellowperch,northernpikeminnowaswellassmallmouthbass.FilletconcentrationswerethencomparedtoWADOHhumanhealthscreeningconcentrations(McBrideunpublishedmemorandum).WADOHdevelopedfillettPCBscreeningconcentrationstoevaluatefishtissuedataforpossiblerestrictionsonhumanconsumption.ThesescreeningconcentrationsaccountforlossofPCBsbycookingandarebasedonmeanconcentrationsinskin‐onfillets(Table3).Thepredictedtissueconcentrationsfromthebioaccumulationmodelarebasedonwholefish.Thus,species‐specificwhole‐to‐filletratiosbasedonDOH(2004)wereusedtoconvertthepredictedwholetissuetofillettissueconcentrations.4
Table 4. WADOH fillet screening concentrations for tPCBs.
Consumption Restriction Screening PCB Concentrations in
Fillet (ug/kg wet)
No Restriction (“safe”) <46
Possible Restriction 46-380
Do Not Eat >380
ThecomparisonofpredictedfillettissueconcentrationswithWADOHscreeninglevelsindicatesthatsubstantial(approximately85%)reductionsinsedimentandwaterconcentrationsarerequiredtobringtheaveragefishfilletconcentrationsofallfourspeciestothe“NoRestriction”level(<46ug/kgww,Figure7).ThepredictedtissueconcentrationinFigure7isbasedonthefatemodel‐predictedsedimentandwaterconcentrationsunderazeroreductionassumption.Errorbarswereaddedontheobservedandpredictedmeanforcomparisonandshowvariabilitycanexistforsomespeciesinbothactualtissuedataandthatpredictedbythebioaccumulationmodel.Forexample,thestandarddeviationonthemeannorthernpikeminnowfilletconcentrationisordersofmagnitudelargerthantheerroronthepredictedmeanconcentration(tissueconcentrationsbasedonlowor25thpercentileandhighor75thpercentileestimatesoftPCBloads,seenoteinFigure5).
Itshouldbenotedthatthisanalysisisonlyusefulasageneralindicationoftherequiredmagnitudeofsedimentandwaterconcentrationsreductionsnecessary,becauseinadditiontouncertaintiesassociatedwiththebioaccumulationmodelandobservedtissuedata,therearealsouncertaintiesinthewhole‐to‐filletratiosandWADOHfishtissuescreeninglevels.Thereisadditionaluncertaintyassociatedwithpredictedconcentrationsinlargeyellowperchduetotheiroverallpoorermodelfit,althoughtheircurrenttPCBconcentrationsarenotashighasotherspecies.Nevertheless,thisanalysisdemonstratesthatverylargereductionsintPCBloadsareneededtobringLakeWashingtoncutthroattrout,northernpikeminnowandsmallmouthbasstissueconcentrationsdowntolevelsthataresafeforhumanconsumption.
4Whole‐to‐filletratiosof0.5wereusedforsmallmouthbass,yellowperchandnorthernpikeminnowand0.68forcutthroattrout.
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Figure 7. Predicted fillet concentrations of tPCBs under 10, 25, 50, 80, and 90 percent loading
reduction scenarios compared to WADOH human health fillet screening concentrations.
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3.0. NEXT STEPS AND RECOMMENDED ACTIONS
Attheoutsetofthisproject,anadvisorypanelconsistingofrepresentativesfromseveraljurisdictionsandagencieswasestablishedtoprovideinputonprojectdesignandexecution,aswellasbrainstormfutureactionsandrecommendations.Panelmemberswere:
FredBergdolt,WADepartmentofTransportation
BetsyCooper,KingCountyWastewaterTreatmentDivision
JonathanFrodge,SeattlePublicUtilities
JennyGaus,CityofKirkland
JoanHardy,WADepartmentofHealth
RachelMcCrea,WADepartmentofEcology
DougNavetski,KingCountyWaterandLandResources
AndyRheaume,CityofRedmond
RonaldStraka,CityofRenton
HeatherTrim,PeopleforPugetSound/FutureWise
BruceTiffany,KingCountyWastewaterTreatmentDivision
PatrickYamashita,CityofMercerIsland
Throughoutthethree‐yearproject,advisorypanelmembersreviewedandcritiquedthefieldstudydesign,modelingframeworkandassumptions,andallprojectdeliverables.Projectteamandadvisorypanelmembersalsodiscussedthescenarioresultsdescribingthe~85percentreductionintPCBloadingsrequiredtoachievefishtissueconcentrationsthatarebelowtheWADOH“No‐Restriction”screeninglevel.Aspartofthisdiscussion,theadvisorypanelprovidedrecommendationsfornextstepsandactions,focusingontPCBs.Thefollowingsectionsdescribethecollectiverecommendationsofthepanel.ManyoftheseideasaddresssomeformofPCBsourcecontrol,althoughtheymaynotmeetthedefinitionsofsourcecontrolusedinpotentiallyapplicablelawsandregulationssuchastheModelToxicsControlAct(Chapter70.105DRCW).SourcecontrolisseenastheultimatesolutiontoreducingPCBloadingstoLakeWashington.However,sourcecontrolisaslowprocess;therefore,additionalactionsarerecommendedthatcanalsoreducePCBloadingstotheLake.Advisorypanelmembers,otherjurisdictions,businesses,andgovernmentalandnon‐governmentalorganizationsareencouragedtoconsiderimplementingoneormoreofthesenextstepsthroughouttheregion.
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3.1 Update the Conceptual Model of PCBs in the Local Environment
PerhapsoneofthemostfundamentalfindingsofthisstudyisthepervasiveandactivenatureofPCBsourcesthroughoutthewatershed.Localtributariestothelakeareresponsibleforapproximately70percentoftheestimated672gannualloadingtothelake(333to889g/yrestimatedrange).InurbanareaslikeSeattleandthesurroundingmetropolitanarea,PCBsarenotjustlegacycontaminantspresentinsediment.TheemergingconceptualmodelforLakeWashingtonissimilartothosedevelopinginotherurbanareassuchasSanFranciscoBay(Tsaietal.2002),Camden,NJ(Beltonetal.2007),Chicago(RodenburgandMeng2013)andToronto,Canada(Robsonetal.2010).Thesemodelspostulate,investigate,anddescribeanurbanplumeordomeofPCBsinandaroundcities;conceptuallysimilartothepollutionplumesatmosphericscientistshavedescribedforheat,carbondioxide,particulates,andotherairpollutants(HuddartandStott2010).Urbanareasarelongknowntotrapheat,CO2andparticulatesbeneathaninversionlayerwhichmayelongatedownwinddependingonprevailingwinds(Munn1976).PCBsalsoformanurbanplumeofairpollutionastheyvolatilizefromcaulks(Robson,etal.2010),paints,andolderlightballasts,particularlythoseballastswhichfail(Guoetal.2011).ThesegaseousPCBscanthenprecipitateontoparticulatesorsurfacefilmsandgetpickedupinstormwaterrunoffordissolvedirectlyintorainorwaterbodies.PCBscanalsowashdirectlyintowaterbodiesfromflakingpaintorfromabradedjointcaulksusedinconcretesurfaces(Ecology2011,CityofTacoma2013).PCBs,whileubiquitousintheurbanenvironmentappeartobeconcentratedinolder(e.g.,pre‐1979)buildingsandinfrastructure.Previousstudiessuggestthatresidentialbuildingsandstructuresolderthan1945andnewerthan1980arelesscommonlyassociatedwithPCB‐containingbuildingmaterials(Robsonetal.2010,Ecology2011).
AlloftheseprocessesarepartoftheemergingunderstandingthatPCBsarenotsimplyhistoricalcontaminants,butinsteadhavenumerouson‐going,diffuseurbansources(Diamondetal.2010).ThesizeofthegreaterLakeWashingtonPCBplumeisunknown,butBrandenbergeretal.(2010)foundthaturbanPugetSoundPCBdepositionwasmorethanthreetimeshigherthaninruralareas.
Thisconceptualmodelofdiffusesourcesthroughoutthewatershed,asopposedtodistinctreleasesandpointemissions,isconsistentwithfindingsofpreviousattemptstoidentifyhotspotsofPCBcontaminationinLakeWashingtonsurfacesediments(Era‐Milleretal.2010).Todate,noPCBsurfacesedimenthotspotshavebeenfound.ThisprojectfocusedonPCBtransportpathways;futureinvestigationswillneedtoinvestigatethesepathwaystotraceandidentifyPCBsourcesincurrentandhistoricallyusedmaterials.
3.2 Source Control - Develop a PCB Inventory Thefirststepinsourcecontrolisidentifyingwheresourcesarelocated.Therefore,werecommendconductinganurbaninventoryofPCBstocks.Developingalistofcurrentlyusedproductsandin‐situsourcessuchaspaints,caulks,ballasts,andcontaminatedsiteswithhistoricalreleasestosoil,sedimentsand/orgroundwaterwouldemphasizeand
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reinforcethecross‐basincollaborationnecessarybyregionalpartnerstoidentifythematerialscontributingPCBstotheregion’senvironmentalmedia.
Aspartofaninventory,arankingoftherelativemassandcontributionsfromdifferentsourcesisrecommended.Forinstance,Robsonetal.(2010)estimatedthat13metrictonsofPCBsremaininbuildingsealantsinToronto,acitywithapopulationof2.6million.TheGreaterSeattlemetropolitanareahas3.5millionresidents.WhilethisprojectisunabletoaccountfordifferencesinbuildingagebetweenTorontoandSeattle,scalingforpopulationsuggeststhattheSeattleregioncouldhave17+metrictonsofPCBsincurrentuseassealantsandcaulksalone.Ecology(2011)estimated850g(0.00085metrictons)ofPCBswerecurrentlyinpaintaloneon2,286buildingsconstructedbetween1950and1977intheDiagonalAvenueSouthsub‐basinoftheDuwamishWaterway–anareaofabout9,000acreswithatotalof27,000buildings.
WhileconductingsourcetracingactivitiesintheLowerDuwamishWaterwayarea,Ecology(2011)developedapartialinventoryofPCB‐containingbuildingmaterials.However,gettingpropertyaccessandpermissiontosamplewaschallenging;only32ofthe92contactedpropertyownersagreedtocompositesamplecollection(materialscombinedfrommultiplebuildings).Ecology’s(2011)inventoryusedcompositesamplingtoallowindividualpropertyownerstoremainanonymous.ItislikelythatliabilityconcernsandthegenerallackofawarenessregardingthewidespreadnatureofPCBsourcesaresignificantbarrierstocreatingalocal,actionableinventory.Nevertheless,
3.2.1 Perform Regional Source Tracing Using Congener Data Narrowingthelistofbuildings,sites,andproductscontainingPCBstoasub‐basinlevelwouldalsoallowfordevelopmentandtestingofpilotprojectsinsomeofthemostcontaminatedareasand/oronthemorecontaminatedrunoff.Thisproject’sdatasetpresentsarichopportunityforresearcherstoanalyzePCBcongenerpatternsandpotentiallymatchthemtourbansources.EcologyrecentlyfundedaSpokaneRiverToxicsTaskForceprojecttoanalyzeforPCBsincommonlyusedmunicipalproducts,suchaspaints,caulksandsealants,andresultsofthiseffortmaybecombinedwitheffortstolinksourcestoloadsintheGreaterLakeWashingtonwaterandairsheds.EffortstobetterunderstandandidentifyPCBsourcesintheLakeWashingtonwaterandairshedswouldformthebasisforfuturesourcecontrolactions.
3.3 Conduct Outreach and Education InadditiontoupdatingtheconceptualmodelanddevelopinganactionableinventoryofPCBsources,anoutreachandeducationstrategyisneededtoengagedecision‐makersandthecommunityatlargeinadiscussionofthefinancialandregulatorychallengesfacingeffortstoreducePCBloadingstoLakeWashingtonandotherwaterbodies.ThesediscussionshavebegunintheLowerDuwamishandSpokaneRiverwatersheds,buttodatehaveyettooccurwithintheLakeWashingtonwatershed.
PCBspresentinbuildingmaterials,whetherassociatedwithcaulk,paints,orfromspillsoftransformersorcapacitors,areregulatedbyEPAandEcology(EPA2005,WAC173‐303‐9904).Thefederalregulatorythresholdformostproductsandwastesis50mg/kg;
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transformerandcapacitorwaste(evenwhendrainedofPCBoils)isregulatedabove2mg/kgbyEcology(ModelToxicsControlActdangerouswastecodeWPCB,WAC173‐303‐9904).TheselevelsareordersofmagnitudehigherthanPCBlevelsofconcernintheenvironment.LakeWashingtonjurisdictionsareencouragedtosupporteffortstoreformfederalregulationsforPCB‐containingmaterialsremaininginuse.
Thedegreetowhichsuspectpaintorcaulksaretestedpriortobuildingdemolitionorrenovationisunknown.Paints,caulksorspilledPCB‐containingoilscanalsocontaminateunderlying/adjacentplaster,wood,masonry,andconcrete.EPA(undated)hasissuedguidanceforcontractors;however,thisisanemergingareaofwastemanagement.Knowledgeoftheserequirementsforbothprotectionofwaterqualityandworkerhealthisunknown.EnhancedscreeningofbuildingspotentiallycontainingPCB‐ladencaulksorpaintsisonestrategytofurtherlimitreleasesofPCBsfromthesematerials.GiventhereluctanceofLowerDuwamishareapropertyownerstoconsenttosamplingtheirbuildings’paintsandcaulks(Ecology2011),financialorregulatoryincentivestofacilitatetestingandsafePCBremovalduringdemolitionorrenovationsof1950‐1980eraindustrial,commercialandinstitutionalbuildingsandinfrastructuremayencouragewidertestingandsourcecontrol.Forinstance,buildingownersthatvoluntarilytesttheirbuildingmaterialsforinventorypurposescouldreceiveanin‐usegraceperiodtoallowthemtograduallyremovethepaint,caulk,etc.whilesuchmaterialsdiscoveredthroughotherinvestigations(e.g.,cityorcountystormwatersourcecontrolstudies)wouldrequiremoreurgentremoval.Thesetypesofregulatorychangesandapproachesrequirebroadercommunityandlegislativeeducationanddiscussions.
WhilethetimeframenecessaryforLakeWashingtonfishtissueconcentrationstosubstantivelydeclineundera“noaction”scenarioiscurrentlyunknown,underanyloadreductionscenarios,atleast20to40yearsarerequiredtoreachnewequilibrium.LakeWashingtonsurfacesedimentconcentrationshavedeclinedsubstantiallysincetheirpeakinthe1970s(Era‐Milleretal.2010)buttherateofdeclineasevidencedbysedimentcores,hasslowedoverthepast2decades.Basedontherelativelyconstantsurfacesedimentconcentrationsoverthepasttwodecades,currentsedimentandwaterconcentrationsarelikelyinroughequilibriumwithcurrentloadings.ThisplateauofsedimentconcentrationsindicatesthatthecurrentrateofPCBsourceremovalsuchasbuildingrenovationandtransformerreplacementresultsinaslowtonodeclineinoverallPCBloading.Continuingthestatusquowillresultinthecurrentfishadvisorypotentiallyremainingindefinitely.
Ecology’s“ChemicalActionPlan”(Ecology2013)forPCBsiscurrentlyinpreparationandpresentsanidealopportunitytodevelopaneducationandoutreachstrategyaimedatovercomingthefinancialandregulatorychallengesfacingeffortstoreducePCBloadings.
3.4 Evaluate Effectiveness of Stormwater Treatment and LID Methods
Todate,literaturereviewshavenotfoundanystudiestestingtheeffectivenessofvarioustechnologiesfortreatingPCB‐contaminatedstormwaterrunoff(Herrera2011b).SeveralpromisingtechnologieshavebeenandcontinuetobetestedintheLowerDuwamisharea(Kalmar2010,Schmoyer2012).Electro‐coagulationandchitosan‐enhancedsandfiltration
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aretwoofthesemoreintensivestormwatertreatmenttechnologies.Theseexpensivetreatmenttechnologiesaretypicallyusedindiscretewastewaterandconstructionstormwatersettingstoaddressspecific,contaminatedsourcesordischarges.FundingsuchtechnologiesonthescalenecessarytoreduceLakeWashingtonPCBloadings~85percentwouldbeextremelychallengingandtodateitisunknowniftheyareeffectiveatreducingmodest(ng/Lorless)PCBconcentrationsinwater.ThecostofstormwaterrunofftreatmentneedstobeevaluatedatthebasinscaletoestimatethecostpermassofPCBsremoved.ThisinformationshouldthenbecomparedtotheeffectivenessofotherPCBremovaloptions(e.g.,paintremoval,conveyancepipecleaning,etc.)toidentifythebestoptionstomaximizetheenvironmentalbenefitoflimitedpublicfunds.
Highefficiency‐streetsweepingtocapturesmallerparticulatesisabasicsourcecontroltechniquethathasthepotentialtoreduceloadingsfromimpervioussurfaces.Similarly,catchbasinandstormwaterconveyancepipecleaningareotherpossibletools,whichmayreducestormwaterrunoffloadings,particularlyfromhistoricsources.BothrelyonbulksolidsremovaltopotentiallyremovePCBsthathaveadheredtosolidspresentonthestreetsurfaceandwithintheconveyancesystem.Theefficacyandcost‐benefitofthesestrategieshasalsoyettobedemonstratedforwidespreaduseinwesternWashingtonurbanwatershedsorforPCBs.Moreextensiveuseofrapidandrelativelylowcost(<$100/sample)immunoassayanalyticalmethods(EPA1996)toscreenPCB‐contaminatedmaterialsincludingstreetdirt/solidsisencouraged.
EPA,Ecology,andotherregulatoryagenciesaremovingtowardlowimpactdevelopment(LID)asapreferredstormwatermanagementtool(EPAetal.2007,EPA2013).However,recentreviewsofLIDtechnologies(Herrera2011b,TaylorandCardno2013)havebeenunabletodocumenttheeffectivenessofLIDinreducingPCBloads.Forinstance,eventhoughtechnologieslikepermeablepavementsmayreducestormwaterflowsthroughinfiltration,theirPCBcontaminantloadsmayremaintrappedonsurfaceparticulateswithsomeportionre‐volatilizinglaterintotheurbanatmosphereanddepositingelsewhere.AdditionalLIDdesignconsiderationssuchasincorporationofspecificsoilamendmentslikebiochar(charcoal)mayenhancePCBretentioninswales,bioretentionfacilitieslikeraingardens,orgreenroofs.Unfortunately,theefficacyofanyspecificamendmentordesignelementiscurrentlyunknown,asLIDstormwatermanagementpracticeshavenotbeenevaluatedforimpactsonurbanPCBcycling.GiventhesubstantialinterestinLIDtechnologyforstormwaterflowcontrol,volumereduction,andothercontaminantremoval(e.g.,dissolvedcopper),understandingtheefficacyanddesignrequirementsforPCBremovalisnecessaryandtimely.
3.5 Develop Airshed & Washoff Models Thecurrentdatasuggestthatbulk(wetanddryforms)aerialdepositionisasignificantcontributortostormwaterloads;however,thedegreetowhichbulkaerialdepositioncontributestoPCBstormwaterloadsfromdifferentlandsurfacessuchasgrass,pavement,orroofingisunknown.Furthermore,therelativecontributiontoLakeWashingtonairdepositionfromtheLowerDuwamishValley,anidentifiedregionalPCBhotspot,isunknown.WindpatternsarelikelytocarryPCBsvolatilizedfromtheLowerDuwamishwater,sediments,anduplandstowardsLakeWashington’swatershedandmaycontribute
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totheregionalairdepositionthatinfluenceswatershedloadings.TheregionaleffectsoffuturecleanupsintheLowerDuwamishorelsewherehavenotbeenestimatednorquantified.
MostPCBcontrolstudieshavefocusedontracingprominentPCBsources(Beltonetal.2007,Bottsetal.2007,Cargill2008,KCIWandSPU2005,Schmoyer2007,KingCounty,2011).Thesetypesofinvestigationshavefocusedonin‐pipestormwatersystemsamplingandanalysistotraceandidentifyPCBcontributionsfromcommercialorindustrialsources.Ifonecanbedeveloped,aregionalrunofforwashoffmodelcouldbeusedtoprioritizelandusesorsub‐basinsformorerigoroussourcetracingsamplingandanalysiseffortssuchasthese.
Awashoffmodelwouldsimulatetherelationshipsbetweenbulkaerialdepositionandrunofffromdifferentsurfacesandlanduses.Awashoffmodelisnecessarytodefinetheroleofaerialdepositioninstormwatercontaminationandextendthepredictivecapabilityofthebulkdepositiondatatodifferentlandsurfacesordevelopmenttypes,whichwouldhelpfocussourcecontrolstudies.Forexample,stormwatersamplesexceedingexpectedconcentrationsfrombulkdepositionalonecouldbethefocusofadditionalsourcetracingefforts.Suchanair‐land‐watermodel,whetherstatisticalormechanistic,wouldbemultivariateasmultiplefactorssuchasparticulates,temperature,rainfallandwindspeedallcorrelatewithbulkdepositiondata(KingCounty2013d).FurtherunderstandingofPCBvolatilizationandcyclingfromurbansurfacesinWesternWashingtonorasimilarclimatewouldbenecessarytodevelopauseful,predictivewashoffmodel.Thedevelopmentofsimplerelationshipsbetweenbulkdepositionandstormwaterconcentrationssimilartotherelationshipstestedintheregionaldrainageextrapolations(KingCounty2013b)wouldbeagoodfirststeptowarddevelopingawashoffmodel.
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4.0. CONCLUSIONS ThisprojectevaluatedsixmajorPCBandPBDEcontaminantpathwaystoLakesWashington,UnionandtheShipCanalinSeattle,Washingtontoestimateloadings.TheloadingswerelinkedwithafatemodelandabioaccumulationmodeltofurtherunderstandhowchangesinloadingsaffectfishtissueconcentrationsofPCBs.
ThemostsignificantloadtoLakeWashingtonwasfromlocaldrainagestormwaters(stormwaterdischargesandcreekstormflows),whichcontributeapproximately67percentoftheannualtPCBload.Directatmosphericdepositionandriverscontributeapproximately14percentoftheannualtPCBload.Despitehavingthehighestaveragemeasuredconcentrationsbyatleastanorderofmagnitude,theoverallloadsfromCSOsandhighwaybridgerunoffcombinedwerelessthanthreepercentoftheestimatedtotaltPCBloading.Combined,thesixpathwaysareestimatedtocontributeapproximately672g/yrofPCBsonaveragetoLakeWashington(25thpercentile‐333g/yr,75thpercentile‐889g/yr).LakeWashingtonout‐flowaccountsfor140g/yrofPCBsenteringLakeUnionwhereitisaugmentedto360g/yrbyCSOs,localstormwaterdrainages,andatmosphericdepositionbeforedischargingtoPugetSound.MuchoftheremainingloadisburiedinLakeWashingtonsedimentsorvolatilizedthroughthelakesurface.Thus,LakeWashingtonactsasbothasourceandasinkforPCBs.EstimatesoftPBDEloadingstoLakesWashington,UnionandPugetSoundwerecompleted,butconsideredmoreuncertainduetothechallengesposedbymeasuringPBDEsinambientwatersatlevelsclosetothoseinmethodblanks.TheaveragetotaltPBDEloadfromallassessedpathwaystoLakeWashingtonisestimatedtobe2,023g/yr(25thpercentile–416g/yr,75thpercentile–2,755g/yr).
LakeWashingtonbiotabioaccumulatePCBsresultinginthecurrentfishtissueconcentrationswhicharesomeofthemostcontaminatedinthestate(WADOH2004,JackandColton2011).Thebioaccumulationmodelindicatesthatasubstantialreduction(~85%)incurrentPCBloadsisnecessarytoreducePCBbodyburdensinresidentfishtosafelevels(belowpublichealthfishconsumptionadvisorylimits)andeliminatethecurrentfishconsumptionadvisory(WADOH2004).Thefateandbioaccumulationmodelsdevelopedforthisprojectpredictalarge~80‐85percentreductioninPCBloadingsisnecessarytoremovethecurrentfishconsumptionadvisoryfornorthernpikeminnow,cutthroattrout,andyellowperch.Althoughnotcurrentlysubjecttotheconsumptionadvisory,an85percentreductionshouldalsoreducePCBconcentrationsinsmallmouthbasstobelowWADOHscreeninglevels.Carpwerenotincludedinthemodelingeffort;additionaldatawouldbenecessarytodetermineifan85percentPCBloadreductionwouldresultintissueconcentrationssufficienttoremovethecarpconsumptionadvisory.Lakesedimentandwaterconcentrationswoulddeclinesubstantiallywithin20yearsofreducedloadings.However,steady‐stateconditionsbetweenloadings,water,andsedimentconcentrationswilltheoreticallytakeapproximately40yearstoachieve.While20to40yearsisalongtime,intheabsenceofsubstantialwatershed‐wideeffortstoreducetPCBloads,theexistingfishconsumptionadvisoryisprojectedtoremainindefinitely.
Theproject’sadvisorypaneldiscussedanumberofpotentialstrategiestohelptargetandeventuallyreduceoverallPCBloadings.SupportingWashingtonStateandregionalpartnersindevelopinganurbaninventoryofpotentialPCBsourcesisoneoftheproject’s
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toprecommendations.Asecondrecommendationistodevelopanoutreachstrategywhichengagesdecisionmakerswhileactivelyeducatingthecommunity‐at‐largeaboutthefinancialandregulatorychallengesfacingeffortstoreducePCBloadingstoLakeWashingtonandotherwaterbodies.Also,anumberofjurisdictionsandstormwatermanagersarealreadyactivelypursuingLIDtechnologiestotreatormanagestormwatervolumes,nutrients,metals,andsuspendedsediment.Sincestormwater,asdirectdischargeorstormflowsincreeks,isthemostsignificantloadingpathway(estimatedtobeabout70percentofthetotalloadingtoLakeWashington),studyingandunderstandingtheefficacyofLIDtechnologiesandensuringtheyareeffectiveatPCBremovalisanimportantnextstep.Lastly,furtherinvestigationofPCBairdeposition,volatilization,cycling,andwashoffinWesternWashingtonurbanareasisrecommended,sincewetanddrydepositionarebothsuspectedtobeimportantcontributorstooverallstormwaterloads.
Inconclusion,acombinationofaggressivesourceidentification,removal,andstormwatertreatmentarerecommendedtoworktowardsachievingtheestimated~85percentloadreductionnecessarytolowerLakeWashingtonfishtissueconcentrationstosafelevels.
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