Draft Environmental Impact Report Appendix L · SEPTEMBER 2016 Draft Environmental Impact Report...
Transcript of Draft Environmental Impact Report Appendix L · SEPTEMBER 2016 Draft Environmental Impact Report...
SEPTEMBER 2016
Draft Environmental Impact Report(DRAFT EIR)
[STATE CLEARINGHOUSE NO. 2015021014]
City of Los AngelesLos Angeles World Airports
for Los Angeles International Airport (LAX)Landside Access Modernization Program
Appendix L
Hyddrology
y and WWater QQuality
A
y Techn
Append
nical Re
dix L
eport
i
LAWAEA TechnEIR for
Pr
Environ
nical A LAMP
repared fo
nmental a
ppendP Deve
or:
and Land
dix to telopme
Use Plan
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theent
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repared
pril 15, 201
d by:
16
i
Table of Contents
Acronyms List ....................................................................................................................... v
Section 1 Introduction and Project Overview ..................................................................... 1‐11.1Purpose.........................................................................................................................................................................1‐11.2ProjectOverview.......................................................................................................................................................1‐11.3GeographicScopeofAnalysis..............................................................................................................................1‐41.4AnalysisFramework................................................................................................................................................1‐5
1.4.1Drainage..........................................................................................................................................................1‐51.4.2WaterQuality................................................................................................................................................1‐5
1.1 DocumentOrganization.........................................................................................................................1‐10
Section 2 Regulatory Framework ....................................................................................... 2‐12.1DrainageRegulationsandStandards...............................................................................................................2‐1
2.1.1Federal.............................................................................................................................................................2‐1FederalAviationAdministration...........................................................................................................2‐1
2.1.2Regional...........................................................................................................................................................2‐1CityofLosAngeles.......................................................................................................................................2‐1LosAngelesCountyFloodControlDistrict.......................................................................................2‐2
2.1.3SummaryofDrainageRequirementsatLAX...................................................................................2‐32.2WaterQualityRegulations....................................................................................................................................2‐3
2.2.1Federal.............................................................................................................................................................2‐3CleanWaterAct............................................................................................................................................2‐3NationalPollutantDischargeEliminationSystemProgram......................................................2‐4
2.2.2State..................................................................................................................................................................2‐4Porter‐CologneWaterQualityAct........................................................................................................2‐4WaterQualityControlPlanfortheCoastalWatershedsofLosAngelesandVentura
Counties............................................................................................................................................................2‐5NPDESConstructionGeneralPermit...................................................................................................2‐6NPDESIndustrialGeneralPermit.........................................................................................................2‐6
2.2.3Regional...........................................................................................................................................................2‐7NPDESMunicipalSeparateStormSewer(MS4)Permit.............................................................2‐7TotalMaximumDailyLoadProgram...................................................................................................2‐9
2.2.4Local................................................................................................................................................................2‐11LowImpactDevelopmentOrdinance................................................................................................2‐11StandardUrbanStormwaterMitigationPlan................................................................................2‐13
Section 3 Existing Conditions ........................................................................................ 3‐13.1DominguezNorthFloodZones...........................................................................................................................3‐13.2StormwaterDrainage..............................................................................................................................................3‐1
3.2.1ExistingInfrastructure..............................................................................................................................3‐33.2.2ExistingDrainageDeficiencies..............................................................................................................3‐3
3.3RunoffWaterQuality..............................................................................................................................................3‐43.3.1PollutantsofConcern................................................................................................................................3‐43.3.2ExistingWaterQualityConditions......................................................................................................3‐5
Table of Contents
ii
3.3.3PotentialSourceAreas..............................................................................................................................3‐5
Section 4 Methodology ...................................................................................................... 4‐14.1Hydrology.....................................................................................................................................................................4‐1
4.1.1ThresholdsofSignificance.......................................................................................................................4‐14.1.2ImpactAnalysisMethodology................................................................................................................4‐1
4.2WaterQuality..............................................................................................................................................................4‐24.2.1ThresholdsofSignificance.......................................................................................................................4‐24.2.2WaterQualityImpactAnalysisMethodology..................................................................................4‐2
Section 5 Potential Project Impacts and Project Design Features .................................. 5‐15.1Drainage........................................................................................................................................................................5‐1
5.1.1PotentialProjectImpacts.........................................................................................................................5‐15.1.2ProjectDesignFeatures............................................................................................................................5‐4
5.2WaterQuality..............................................................................................................................................................5‐65.2.1WetWeatherRunoff...................................................................................................................................5‐6
5.2.1.1PotentialProjectImpacts...........................................................................................................5‐65.2.1.2ProjectDesignFeatures...........................................................................................................5‐10
5.2.2StormwaterFlows....................................................................................................................................5‐105.2.3DryWeatherFlows..................................................................................................................................5‐105.2.4ConstructionRunoff................................................................................................................................5‐10
Section 6 Mitigation Measures and Design Features ..................................................... 6‐16.1DrainageMitigationMeasures............................................................................................................................6‐1
6.1.1 Detain/ReduceProject‐RelatedStormwaterFlows............................................................6‐16.1.2 RerouteStormwaterFlows............................................................................................................6‐26.1.3 ConstructImprovementstoExistingStormwaterDrainageSystem...........................6‐2
6.2WaterQualityDesignFeatures...........................................................................................................................6‐36.3SummaryofVolumeRequirementsforOn‐SiteMitigation....................................................................6‐2
Section 7 References ..................................................................................................... 7‐3
Table of Contents
iii
List of Figures
Figure1‐1:LAMPComponentFootprint.....................................................................................................................1‐7Figure1‐2:DrainageAreaSubbasins............................................................................................................................1‐8Figure1‐3:DominguezDrainageArea.........................................................................................................................1‐9Figure3‐1:PrimaryStormDrainsinDominguezChannelArea.......................................................................3‐2Figure3‐2:Exisiting(Pre‐Project)ImperviousnessValuesintheDominguezNorthSubBasin.........3‐7Figure5‐1:DrainageAreasforLAMPComponents................................................................................................5‐2Figure5‐2:ProposedCisternsforConRAC.................................................................................................................5‐5
List of Tables
Table1‐1:LAMPProjectComponents..........................................................................................................................1‐2Table2‐1:BeneficialUsesofStateWatersintheDominguezChannelBasinandSantaMonicaBay2‐5Table2‐2:MS4PermitDefinedCategories.................................................................................................................2‐8Table2‐3:MS4CategoriesforPotentialDominguezChannelConstituents.................................................2‐9Table2‐4:TMDLsforReceivingWaterBodies.......................................................................................................2‐10Table2‐5:FutureTMDLCompletionScheduleforDominguezChannel(EstuarytoVermontAvenue)......................................................................................................................................................................................................2‐10Table2‐6.SUSMPProjectTypes....................................................................................................................................2‐13Table3‐1:ExistingCharacteristicsDominguezChannelNorthSub‐Area.....................................................3‐3Table3‐2:PollutantsofConcern.....................................................................................................................................3‐4Table4‐1:EMCValues.........................................................................................................................................................4‐3Table5‐1:CompositePercentImperviousValues...................................................................................................5‐3Table5‐2:10‐yearstormPeakDepths.........................................................................................................................5‐3Table5‐4:LandUseAreasandTypes...........................................................................................................................5‐6Table5‐5:PollutantRunoffConcentrations(lb/yr)orMostProbableNumber(MPN).........................5‐8Table5‐6:RunoffVolumeforthe85thPercentileStorm......................................................................................5‐9Table6‐1:10‐yearStormMitigationVolumes..........................................................................................................6‐1Table6‐2:PotentialDrainageImprovementOptions............................................................................................6‐3Table6‐3:TypicalPollutantRemovalforBMPs(percent)..................................................................................6‐5Table6‐4VolumeRequirementsforOn‐siteAlternatives...................................................................................6‐1Table6‐5VolumeRequirementsforOn‐siteAlternatives...................................................................................6‐3
Table of Contents
iv
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v
Acronyms List
APM AutomatedPeopleMoverBMP BestManagementPracticesCEQA CaliforniaEnvironmentalQualityActcfs cubicfeetpersecondCIMIS CaliforniaIrrigationManagementInformationSystemCIP capitalimprovementprojectsConRAC ConsolidatedRentalCarFacilityCTA CentralTerminalAreaCWA CleanWaterActEIR EnvironmentalImpactReviewEPA EnvironmentalProtectionAgencyESA EnvironmentallySensitiveAreasHTP HyperionWastewaterTreatmentPlantIGP IndustrialGeneralPermitITF IntermodalTransportationFacilityLAMP LandsideAccessModernizationProgramLASAN LosAngelesDepartmentofPublicWorksBureauofSanitationLACDPW LosAngelesCountyDepartmentofPublicWorksLAR‐IAC LosAngelesRegionImageryAcquisitionConsortiumLARWQCB LosAngelesRegionalWaterQualityControlBoardLAWA LosAngelesDepartmentofAirportsLAX LosAngelesInternationalAirportLID LowImpactDevelopmentNAD NationalAmericanDatumNAVD NorthAmericanVerticalDatum1988NEPA NationalEnvironmentalPolicyActNCOS NorthCentralOutfallSystemNDPES NationalPollutantDischargeEliminationSystemSWMM StormwaterManagementModelSMP StormwaterManagementPlanSWPPP StormwaterPollutionPreventionPlanSWRCB StateWaterResourcesControlBoardTMDL TotalMaximumDailyLoad
Acronyms List
vi
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1‐1
Section 1
Introduction and Project Overview
1.1 Purpose ThisappendixpresentsthehydrologyandwaterqualitytechnicalanalysisinsupportoftheDraftEnvironmentalImpactReport(DEIR)fortheLandsideAccessModernizationProgram(proposedProject)tobeundertakenbyLosAngelesWorldAirports(LAWA)atLosAngelesInternationalAirport(LAX).ThisProjectwillhelprelievetrafficcongestion,improveaccessoptionstotheairportandprovideaconnectionfromLAXtotheLosAngelesCountyMetropolitanTransportationAgency(Metro)railsystem.
InadditiontosupportingthepreparationoftheDEIR,thetechnicalanalysiscompletedfortheProjectwillalsobeusedinconjunctionwithalargerhydrologyandwaterqualityplanningprogramforLAX.LAWAhasinitiateddevelopmentofacampusairport‐wideStormwaterManagementPlan(SMP)forLAXinordertosupportongoingandfuturecapitalimprovementprojects,suchastheLandsideAccessModernizationProgram.ThehydrologyandwaterqualityanalysispresentedhereinwillbeincorporatedintothatSMP.
1.2 Project Overview TheproposedProjectareaislocatedontheeastsideofLAXandisboundedbytheTomBradleyInternationalTerminal(TBIT)onthewest,I‐405ontheeast,WestchesterParkwayandWestArborVitaeStreetonthenorth,andI‐105onthesouth.TheproposedProjectwouldconnecttheCentralTerminalArea(CTA)ofLAXwithaproposedconsolidatedrentalcarfacilityandintermodaltransportationfacilities.Table1‐1describeseachcomponentoftheproposedProjectandindicatestheapproximatesizeofeachcomponent’sfootprint.Thisanalysisusestheproposedbuildingareaandadjacentassociatedlandtoevaluatewaterqualityimpacts.Theapproximatesizeofthedrainageareaforeachcomponent,whichisusedinthisanalysistoevaluatehydrologyimpacts,isalsoshowninTable1‐1.Figure1‐1illustratestheproposedProjectareaanddelineatesthelocationsoftheindividualcomponentsdescribedinTable1‐1.
TheproposedProjectalsoincludespotentialfuturerelateddevelopment.TheEIRevaluateshydrologyandwaterqualityimpactsoffuturerelateddevelopmentataprogrammaticlevel.Thisappendixdoesnotprovideadditionalinformationonthoseimpacts.
Section 1 Introduction and Project Overview
1‐2
Tabl
e 1-
1: L
AM
P Pr
ojec
t Co
mpo
nent
s
Project Component
Description
Location
Build
ing Area (acres)
Drainage
Area (acres)
Automated
Peo
ple M
over
(APM) system
An elevated guidew
ay connecting the
CTA
to proposed ground transportation
facilities. Six stations would be located
along the alignmen
t at designated
facilities and are included
in the water
quality analysis for the guidew
ay
discussed
in this appen
dix.
The alignmen
t generally extends from the western
end of the CTA
along World W
ay to Sep
ulved
a Boulevard and then
onto Cen
tury Boulevard. A
t Vicksburg Avenue the guidew
ay turns north and
then
east along West 96th until it term
inates east
of Aviation Boulevard.
19.8
APM M
aintenance and
Storage Facility
Supports the operations and
maintenance of the APM operating
system
.
The southeast corner of West Arbor Vitae
Street
and Airport Boulevard.
2.18
20
Passenger Walkw
ay system
Connects the APM stations to passenger
term
inals, parking garages, and ground
transportation facilities.
Along the APM track.
N/A
(included
in track
footprint)
Modifications to existing
term
inals
Support the APM walkw
ay system.
In the CTA
. N/A
West Interm
odal
Transportation Facility
(ITF)
Provide parking and pick‐up/drop‐off
areas outside the CTA
. Bounded
by West 98th street to the south, A
irport
Boulevard to the east, W
estchester Parkw
ay to the
north, and extends just past Jenny Avenue to the
west.
14
71
East Interm
odal
Transportation Facility
(ITF)
Provide parking and pick‐up/drop‐off
areas outside the CTA
. Situated
east of Aviation Boulevard between W
est
96th and W
est 98th Streets.
11.71 (21 with
adjacent land)
32
Consolidated
Rental Car
Facility (ConRAC)
A facility designed
to m
eet the needs of
future car ren
tal operations. Facility
users would access the CTA
via the APM.
The facility would gen
erally be located west of I‐
405, north of Cen
tury Boulevard., south of West
Arbor Vitae
Street, and east of Aviation Boulevard.
36.73 (67 with
adjacent land)
75
Roadway Im
provemen
ts
Improve access to the proposed facilities
and the CTA
. A series of roadway im
provemen
ts would occur
generally in
the areas of:
S. Sep
ulved
a Boulevard and W
. Cen
tury
Boulevard, just east of the CTA
;
East of the CTA
, bound generally by W.
Cen
tury Boulevard to the south, S.
Sepulved
a Boulevard to the west, the I‐405
to the east and W
estchester Parkw
ay/W
. Arbor Vitae
Street to the north; and
South of W. Century Boulevard along
Aviation Boulevard south to I‐105 as well as
areas along 111th Street between Aviation
N/A
(May include space
within the CONRAC
and ITF areas)
1S 1‐3 Project Compon
Utilities infrastruc
Source:Nam
e,descrnent
cture
Both ne
ription,location,and
Description
ew and m
odified to
proposed projec
dsizeofLAMPcomp
support the
ct. ponents‐Ricondoa
L
Boulevard and A
andAssociatesInc.,2
Location
S. La Cienega Boule
s needed
2015;Drainagearea
Section 1 Int
Build
evard.
(Ma
with a
asizes–CDMSmithro
dcution and Proj
ding Area (acres)
N/A
ay include space
hin the CONRAC
nd ITF areas)
h,2015
ject Overview
Drainage
Area (acres)
Section 1 Introduction and Project Overview
1‐4
1.3 Geographic Scope of Analysis Figure1‐2delineatesthegeographicrelationshipbetweentheproposedProjectareaandthedrainagewatershedsatandaroundLAX.Asshown,theProjectareaislocatedmostlywithintheNorthDominguezChannelwatershed.AsmallportionoftheProjectareaissituatedtothewestoftheDominguezChannelwatershed,extendingintotheArgowatershedandtheImperialwatershed.ThetechnicalanalysispresentedhereinfocusesontheProject’spotentialdrainageandwaterqualityimpactsoccurringwithintheDominguezChannelwatershed,asthatistheonlywatershedthatwouldbemateriallyaffectedbyimplementationoftheProject.
AsfurtherdescribedinSection4,impactstohydrologyareprimarilyafunctionofproject‐relatedchangeswithrespecttoexistingperviousandimperviousareas;changesinsurfaceflowpatterns;andchangestothestormdrainsystem.Impactstowaterqualityareprimarilyafunctionofchangesinexistinglandusetypes.Whilethosetypesofproject‐relatedchangeswouldoccurwithintheNorthDominguezChannelwatershed,asdescribedindetailinSection5,suchchangeswouldnotoccurwithintheArgoandImperialwatershedswithrespecttoimplementationandoperationoftheproposedProject.AsshowninFigure1‐2,theProjectcomponentsoccurringoutsidetheNorthDominguezChannelwatershedwouldincludetheelevatedAPMalignmentthatcrossesaboveSepulvedaBoulevardintotheCTAandassociatedAPMstationsandpedestrianwalkways.Withtheexceptionoflimitedareasofornamentallandscaping,theproject‐relatedimprovementareaswithintheArgoandImperialwatershedsare100percentimpervioussurfaces,withstormwaterdrainingintotheexistingstormdrainsysteminandneartheCTA.ThedevelopmentoftheelevatedAPMsystemandassociatedimprovementswouldnotsubstantiallyaffecttheexistingsurfacecharacteristicsordrainagesystem(i.e.,wouldnotimpactexistinghydrology)withintheArgoandImperialwatersheds.Fromawaterqualityperspective,developmentoftheAPMsystemandassociatedimprovementswouldnotchangetheexistingtypesoflandusesinorneartheCTA;therefore,nosignificantchangeinexistingwaterqualitypollutantloadsassociatedwithspecificlandusetypeswouldoccurwithintheArgoandImperialwatershedsasaresultoftheproposedProject.However,constructionoftheProjectcomponentswithintheArgoandImperialwatershedsmaycausetemporaryconstruction‐relatedimpactstowaterquality:theseimpactsareaddressedinSection5.Basedonthediscussionabove,thehydrologyandwaterqualityanalysesincludedhereinarefocusedonimpactstotheNorthDominguezChannelwatershed.
TheproposedProjectfacilitiesconstituteasmallfraction(<1%)oftheDominguezChannelsubarea.TheentireDominguezChanneldrainageareaoccupiesapproximately133squaremilesinthesouthernportionofLosAngelesCounty.TheDominguezChanneldrainageareaisfurtherdividedintoseveralwatersheds,including:theDominguezChannelwatershed(consistingofapproximately58squaremiles,44%oftheentiredrainagearea);theMachadoLakewatershed;theWilmingtonDrainwatershed;andtheLosAngeles/LongBeachHarborwatersheds,asshowninFigure1‐3.TheDominguezChannelitselfbeginsapproximatelytwomileseastofLAXandextendssouthto,andthrough,theDominguezEstuary,whereitdrainstotheLosAngeles(SanPedro)Harbor.TheChannelcarriesdryandwetweatherurbanrunofffromapproximately72squaremilesofurbanareawithinLosAngelesCounty.Theuppermost6.7milesoftheChannelisconcrete‐linedandtravelsfromWest116thstreetnearI‐105toVermontAvenuenearI‐110.TheproposedProjectwouldnotphysicallyimpactoraltertheDominguezChannel.
1‐5
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Section 1 Introduction and Project Overview
1‐6
proposedfacilities.TheLIDPlanand/orSUSMPwouldidentifyanyincreaseincontaminantloadsandproposeBMPstomitigatetheseimpacts.BMPswouldbeestablishedwiththegoalofreducingcontaminantloadingtosurfacewaterbodiesandcomplyingwiththeLIDOrdinanceandNationalPollutantDischargeEliminationSystem(NPDES)permit.LIDBMPsincludeawiderangeofBMPsthatpromoteinfiltration,reuse,orbioretention.BMPswouldbesizedinaccordancewiththeLIDManualandmayinclude:
Oil/waterseparators
Clarifiers,mediafiltration
Catchbasininsertsandscreens
Continuousflowdeflectivesystems
Detentionbasins
Manufacturedtreatmentunits
Hydrodynamicdevices
InadditiontostructuralBMPs,non‐structuralandsourcecontrolBMPscanhelptomitigatepollutantrunoff.Newnon‐structuralandsourcecontrolBMPswouldbeincorporatedintotheLAXStormWaterPollutionPreventionPlan(SWPPP)atacquisitionareaswhereindustrialactivitieswouldpotentiallyimpactwaterquality.
1F 1‐7
Figure 1‐1: LA
MP Component Foot print
Section 1 Introduction and Proeejct Overview
Section 1 Introduction and Project Overview
1‐8
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Figure 1‐2: Drainage Area Subbasins
1F 1‐9
Figure 1‐3: Dominnguez Drainage Arrea
Section 1 Introduction and Proe
ejct Overview
Section 1
1‐10
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2‐1
Section 2
Regulatory Framework
StormwatermanagementatLAXissubjecttomanyfederal,state,andlocalregulationsanddesignstandardswiththepurposeofprovidingfloodprotectionandmitigatingwaterqualityimpactsbeforebeingdischargedintodownstreamfloodcontrolfacilitiesandreceivingwaters,suchasDominguezChannel.Thissectionsummarizestherelevantfederal,regional,andlocalregulationsregardingfloodcontrolandstormwaterquality,includingcurrentFederalAviationAdministration(FAA)drainagedesigncriteriaandNPDESgeneralindustrial,municipal,andconstructionpermitrequirements.
2.1 Drainage Regulations and Standards DrainagesystemswithinLAXareownedandmaintainedbyLAWA;thesesystemsdischargetofacilitiesownedandoperatedbytheCityofLosAngelesandLosAngelesCountyFloodControlDistrict(LACFCD).Eachagencyhasitsowndrainageregulationsanddesignstandards,whicharesummarizedinthefollowingsections.Inaddition,drainagefacilitiesatLAXmustbedesignedandconstructedinaccordancetoguidelinesissuedbytheFAA.Theregulationsandguidanceestablishedbyeachagencyaresummarizedbelow.
2.1.1 Federal
Federal Aviation Administration
TheFAAAdvisoryCircular(AC)150/5320‐5Destablishesguidanceforengineers,airportmanagersandthepublicinthedesignandmaintenanceofairportsurfacedrainagesystemsandsubsurfacedrainagesystemsforpavedrunways,taxiways,andaprons.TheFAAguidanceincludesminimumdesignstormfrequenciesforthreecategories:
1. 2‐yearstormeventforDepartmentofDefense(DOD)airfieldsandheliports
2. 5‐yearstormeventforFAAfacilities
3. 10‐yearstormeventforareasotherthanairfields
However,thedesignfrequencymaybehighertoprotectimportantfacilities.TheACstatesthat,“thedegreeofprotectiontobeprovidedbythedrainsystemdependslargelyontheimportanceofthefacilityasdeterminedbythetypeandvolumeoftraffictobeaccommodated,thenecessityforuninterruptedservice,andsimilarfactors.”Inaddition,theACrequiressurfacerunofftobedisposedofproperlytoavoiddamagingfacilities,saturatingthesubsoil,andinterruptingtraffic.
2.1.2 Regional
City of Los Angeles
PertheCityofLosAngelesBureauofEngineeringStormDrainDesignManual‐PartG(1973),designfrequenciesareasfollows:
Section 2 Regulatory Framework
2‐2
10‐yearstormfrequencyforareaswithoutsumps.
50‐yearstormfrequencyforsumpareas.
10‐yearstormfrequencyforclosedconduitsinnaturalwatercoursesifthewatercourseismaintainedinplace.Thecombinedcapacityofwatercourseandconduitmustcontainastormof50‐yearfrequency.
10‐yearstormfrequencyforopenchannelsinnaturalwatercourseswithfreeboardtocontainastormof50‐yearfrequency.
50‐yearstormfrequencyforanystormdraininanaturalwatercourseifthewatercourseiseliminated.
Thesumpconditionreferstoinletsthatarelocatedatalowpointandtowhichwaterentersfrombothdirections.Sumpconditionsexistattheseinletswheneverwaterponds.WithinLAX,theonlyareathathasasumpconditionistheareawestoftheTomBradleyInternationalTerminal;howeverthissumpconditionwouldberemoveduponconstructionofthenewMidfieldSatelliteConcourseandisnotaddressedinfurtherdiscussionoftheproposedProjectfacilities.
Regardingoutfallcapacitylimits,designfrequenciesmaybemodifiedifthereceivingsystem’scapacityislimited.Newdrainsdischargingintoexistingdrainagesystemsmusthaveaproposedcapacitythatmeetsthereceivingdrainagesystem’scapacity.However,iftheexistingdrainagesystemisplannedtobereplacedtoaccommodatethecapacityofthenewdrain,thenewdrainshouldbesizedtotheappropriatecapacityperthedesignfrequenciesindicatedabove.Undercircumstanceswherelevelofprotectionstandardsmaybechanged,theCityofLosAngelesBureauofEngineeringshouldbeconsulted.
Los Angeles County Flood Control District
TheLosAngelesCountyDepartmentofPublicWorks(LACDPW)establishedtheirpolicyonlevelsoffloodprotectionforusewithintheCountyofLosAngelesinamemorandumdatedMarch31,1986titledGeneralFilesNo.2‐15.3621;thismemorandumwasincorporatedintothe2006LosAngelesCountyDepartmentofPublicWorksHydrologyManual(Manual).ThethreelevelsofprotectionincludedintheManualarecapitalfloodprotection,urbanfloodprotection,andprobablemaximumfloodprotection.ThefirsttwopoliciesmaybeapplicabletotheLosAngelesFloodControlDistrict(LACFCD)‐ownedormaintainedstormdrainsinthevicinityofLAX.Probablemaximumfloodprotectionisnotapplicablefortheproposedfacilities,asfloodprotectionisonlyrequiredfor“damsanddebrisbasinsthathold1,000acre‐feet,are50feetorhigher,wouldrequireatleast1,000peopletobeevacuated,andhaveadamagepotentialof$25,000,000ormore.”LAXdoesnotincludeanydamsordebrisbasins.
Capitalfloodprotectionappliestonaturalwatercourses,whichincludechannelsandclosedconduits,floodways,naturaldepressionsorsumps,culvertsundermajorandsecondaryhighways,andtributaryareassubjecttoburning.Thecapitalfloodprotectionlevelrequiresthatdrainagesystemshavethecapacitytoconveyrunofffroma50‐yearstormfrequency.ThiscriterionappliestoaportionoftheLACFCD‐ownedDominguezChannel,whichbeginsoffsiteofLAXpropertyandisthewaterbodytowhichtheproposedProjectfacilitiesdrain.
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Urbanfloodprotectionappliestoalldevelopedareasnotcoveredunderthecapitalfloodprotectionlevel.However,sinceallon‐siteareasanddrainagesystemswithintheboundariesofLAXarealsowithintheCityofLosAngeles,theCity’sdesignstandardsapply.
SimilartotheCityofLosAngelesguidelinesonoutfalls,LosAngelesCountyoutfallsmaybemodifiedduetooutletconditions.Iftheexistingoutfallcannothandlethecapacityfromtheproposeddrain,theDesignDivisionofLACDPWshouldbeconsultedtodetermineacompatiblelevelofprotection,ortheLACFCDwillmakeplanstoprovidefuturerelieftotheexistingdrainagesystem.
2.1.3 Summary of Drainage Requirements at LAX Basedontherequirementsofthethreeagenciesdescribedabove,LAXstormdraindesignintheProjectdrainageareamustmeetthefollowrequirements:
On‐sitestormdrainfacilitiesshallbesizedtoaminimum10‐yearstormeventpertheCityofLosAngelescriteria,whichisstricterthantheFAAdesigncriteria.
OutfallstoCityofLosAngelesdrainagesystemsandLosAngelesCountydrainagesystemsmustcomplywiththeagency’scriteriaregardingcumulativecapacityimpactsontheexistingCityorCountyofLosAngelesdrain.Ifanexistingdraindoesnothavethecapacitytoreceivetheflowfromaproposeddrain,theappropriatejurisdictionwoulddecideiftheexistingdrainwillbereplacedorrelieved.Iftheexistingdrainwillnotbechanged,acompatiblelevelofdrainage/floodingprotectioncouldbedeterminedinconsultationandcoordinationwiththeagencyhavingjurisdictionoverthesubjectdrain.
2.2 Water Quality Regulations LAXissubjecttomanyfederal,state,andregionalwaterqualityregulationstomaintainadequatewaterqualitytodownstreamwaterbodiesthatreceiveairportsurfacestormwaterdischarges.Themainobjectiveoftheseprogramsistoprotectwaterbodiesandmitigatewaterqualityimpactsfromdevelopmentandmodernizationtakingplaceattheairport,aswellastomeetwaterqualitystandardsandwastedischargerequirements.
2.2.1 Federal
Clean Water Act
TheCleanWaterAct(CWA)of1972istheprincipalstatutethatgovernswaterqualityintheU.S.;itprovideslegalframeworktoseveralstateandlocalregulations.Theobjectiveofthisactistoprotectandrestorethenation’swaterbymonitoringthewaterqualityandcontrollingdischargefrompointsources.ThisactdesignatedtheU.S.EnvironmentalProtectionAgency(EPA)astheagencytoestablishfederalguidelines,objectives,andlimits.TheCWAisadministeredatthestatelevelbytheStateWaterResourcesControlBoard(SWRCB),andenforcedatthelocallevelbynineRegionalWaterQualityControlBoards(RWQCB).
ThroughtheirdelegatedauthorityundertheCWA,theSWRCBandtheRWQCBinLosAngeles(LARWQCB)haveadoptedandenforcedvariouspermitsandotherregulatoryactionsthataffectlocalpermittedentities,includingtheCityofLosAngelesandLAWA.
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National Pollutant Discharge Elimination System Program
TheCWAprohibitsthedischargeofanypollutantfromapointsourceintowatersoftheUnitedStates,unlessthedischargeisincompliancewithaNationalPollutantDischargeEliminationSystem(NDPES)permit.Pointsourcesaredefinedasdiscreteconveyancessuchaspipesorman‐madeditches.IndustrialandmunicipalfacilitiesthatdischargedirectlytosurfacewatersmustalsoobtainNPDESpermits.
Tocomplywithsection402(p)oftheCWA,theEPAdevelopedatwophaseNPDESstormwaterprogramtoaddressstormwaterdischargesfromindustrialsourcesandmunicipalities.PhaseIbeganin1990andwasappliedtolargeandmediummunicipalstormsewersystems(MS4).MS4saredescribedasstormdrainsystemsandincludestreets,gutters,conduits,naturalorartificialdrains,channelsandwatercourses,orotherfacilitiesthatareowned,operated,maintained,orcontrolledbypermittees(citiesandcounties)forthepurposeofcollecting,storing,transporting,ordisposingstormwater.TheCWArequiresthatpermitsforstormdrainsystems:(i)beissuedonasystemorjurisdictionwidebasis,(ii)includearequirementtoeffectivelyprohibitnon‐stormwaterdischargesintothestormsewers,(iii)requirecontrolstoreducethedischargeofpollutantstothemaximumextentpractical(MEP),includingmanagementpractices,controltechniquesandsystem,design,andengineeringmethods.
TheEPAPhaseIstormwaterregulationsweredirectedatMS4sservingapopulationof100,000ormore,andconstructionprojectsthatdisturbanareaoffiveacresormore.TheLosAngelesmetropolitanareaandLAXarecurrentlyregulatedunderPhaseIoftheNPDESStormWaterProgram.SmallersourcescameunderregulationunderPhaseIIoftheprogram.PhaseIIautomaticallyregulatedallownersandoperatorsofsmallMS4andconstructionactivitiesthatarelessthanfiveacres,butequaltoorgreaterthanone.TheNDPESpermitsystemformunicipal,industrial,andconstructionactivitiesisdiscussedfurtherinSections2.2.2and2.2.3.
2.2.2 State
Porter‐Cologne Water Quality Act
ThePorter‐CologneWaterQualityAct(Act)istheprimarylawfortheregulationofwaterqualityinCalifornia.TheActappliestosurfacewaters,wetlands,andgroundwater,andtobothpointandnonpointsourcesofpollution.TheActcontainsprovisionsthatprotectwaterqualityanddesignatedbeneficialusesofwater,includingimplementationoftheNPDESprogram,dredgeandfillprograms,andcivilandadministrativepenalties.TheActrequiresprojectsthatcouldaffectthequalityoftheState’swaterthroughdischargetofileaReportofWasteDischarge(ROWD)withtheSWRCBortheappropriateRWQCBtoreceiveWasteDischargeRequirements(WDR).WhenaprojectdischargestoadesignatedwatersoftheU.S.,suchasSantaMonicaBay,DominguezChannelandtheLosAngelesHarbor,ajointNPDESPermitandROWDisissued,whichincorporatesrequirementsconsistentwithboththeCWAandthisAct.
AlsounderthisAct,theSWRCBisauthorizedtoestablishstatewidepoliciesandregulationsfortheimplementationofwaterqualitycontrolprograms,whiletheRWQCBimplementsuchpolicyprograms,developregionalbasinplans,andissueNPDESpermits.Together,theSWRCBandthenineRWQCBprotectwaterqualityandallocatesurfacewaterrights.
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Water Quality Control Plan for the Coastal Watersheds of Los Angeles and Ventura Counties
UnderthePorter‐CologneWaterQualityAct,theStateofCaliforniaisdividedintonineregionalwaterqualitycontrolboardsforindividualpermitting,inspection,andenforcementactions.EachRWQCBisrequiredtoprepareandperiodicallyupdateaWaterQualityControlPlan(BasinPlan)thatidentifiesexistingandpotentialbeneficialusesforspecificwaterbodies.BasinPlansarethemasterpolicydocumentsthatcontaindescriptionsofthelegal,technical,andprogrammaticbasisforwaterqualityregulationineachregion.
WhiletheoriginalWaterQualityControlPlanfortheCoastalWatershedsofLosAngelesandVentura(whichincludestheCityofLosAngelesandLAX)waspreparedandadoptedbytheLARWQCB(Region4)in1976,anewplanwasadoptedonFebruary23,1995.Sincethattime,theLARWQCBBasinPlanhasbeenamendednumeroustimes.
TheLARWQCBBasinPlangivesdirectiononthebeneficialusesofStatewaters(bothsurfacewatersandgroundwater),provideswaterqualityobjectivesandpolicies,andincludesimplementationplansandmonitoringprogramstocontrolnonpointandpointsourcesofpollutantstotheState’swaters.AlldiscretionaryprojectsrequiringpermitsfromtheRWQCB(i.e.,wastedischargerequirementsandNPDESpermits)mustimplementBasinPlanrequirements(i.e.,waterqualitystandards),takingintoconsiderationthebeneficialusestobeprotected.TheLARWQCBhasdevelopedtheWaterQualityControlPlanfortheLosAngelesRegionwhichidentifiesthebeneficialusesofDominguezChannelandSantaMonicaBay(Table2‐1).
Table 2-1: Beneficial Uses of State Waters in the Dominguez Channel Basin and Santa Monica Bay
Beneficial Use Abbreviation Dominguez Channel Santa Monica Bay
Industrial Service Supply IND N/A Existing
Navigation NAV N/A Existing
Municipal and Domestic Supply MUN Existing N/A
Contact Recreation REC‐1 Potential Existing
Non‐Contact Recreation Rec‐2 Existing Existing
Commercial and Sport Fishing COMM N/A Existing
Marine Habitat MAR N/A Existing
Warm Freshwater Habitat WARM Potential N/A
Wildlife Habitat Wild Existing Existing
Preservation of Biological Habitat BIOL N/A Existing
Rare, Threatened or Endanger Species RARE Existing Existing
Migration of Aquatic Organisms MIGR N/A Existing
Spawning, Reproduction, and/or Early Development
SPWN N/A Existing
Shellfish Harvesting SHELL N/A Existing
Source:CaliforniaRegionalWaterQualityControlBoardBasinPlanfortheCoastalWatershedsofLosAngelesandVenturaCounties(1994)
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NPDES Construction General Permit
PursuanttotheCWA,theSWRCBissuedastatewideGeneralConstructionActivityPermit1(ConstructionGeneralPermit)forstormwaterdischargesassociatedwithconstructionactivities(NPDESNo.CAS000002).Underthispermit,constructionactivitiesthatresultinsoildisturbancesofatleastoneacrearerequiredtoobtainanindividualNPDESpermitorbecoveredbyaConstructionGeneralPermit.Thisrequirementappliestobothprivateandpublicagencyconstructionprojects,includingprojectsundertakenatLAX.
CoveragebytheConstructionGeneralPermitisaccomplishedbyfilingaPermitRegistrationDocument(PRD)onlinewiththeSWRCB.PRDsconsistof:
a. NoticeofIntent
b. RiskAssessment
c. SiteMap
d. StormWaterPollutionPreventionPlan
e. AnnualFee
f. SignedCertificationStatement
PRDsincludespecificinformationonthetypesofconstructionactivitiesthatwouldoccuratconstructionsites(i.e.,grounddisturbance).Inaddition,thePRDsmustincludeasite‐specificplancalledtheStormWaterPollutionPreventionPlan(SWPPP)tohelpminimizepollutionfromconstructionactivities.TheSWPPPincludesBMPstoeliminateorreducestormwaterpollutantsfromleavingtheconstructionsite.TheConstructionGeneralPermitcontainsreceivingwaterlimitstopreventviolationsofwaterqualitystandards.Thepermitalsorequiresimplementationofprogramsforvisualinspectionsandsamplingforspecifiedconstituents(e.g.,non‐visiblepollutants).
NPDES Industrial General Permit
PursuanttoCWA,theSWRCBre‐issuedastatewideIndustrialStormwaterGeneralPermit(IndustrialGeneralPermitorIGP)(SWRCBOrderNo.2014‐057‐DWQ)in2014,whichbecameeffectiveonJuly1,2015.TheIGPregulatesthedischargeof10categoriesofindustrialactivity,includingtransportationfacilities,whichdenoteportionsofLAX.Industrialactivityatatransportationfacility,asdefinedbythefederalregulations,consistsof“thoseportionsofthefacilitythatareeitherinvolvedinvehiclemaintenance(includingvehiclerehabilitation,mechanicalrepairs,painting,fueling,andlubrication),equipmentcleaningoperations,airportdeicingoperations,orwhichareotherwiseidentifiedintheregulations.”
CertainfacilitiesproposedaspartoftheProjectwouldbesubjecttotheNPDESIndustrialGeneralPermit.TheAPMmaintenancefacility,aswellasvehiclerepairandrefuelingareaswithintheConRAC,requirecoverageundertheindustrialpermitbecauseactivitiesfromthesefacilities
1SWRCBOrderNo.2009‐0009‐DWQwasadoptedin2009andbecameeffectiveJuly1,2010;amendedthereafterby2010‐0014‐DWQand2012‐0006‐DWQ.
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contributetothedischargeofindustrialpollutants(EPA,2014).Dependingontheuseofthevariousproposedparkingareas,theIndustrialGeneralPermitmayapply.UndertheIGP,employeeparkinglotsareconsiderednon‐industrialareas;however,ifstormwaterrunofffromthisareacommingleswithrunofffromaregulatedindustrialarea,thecombineddischargewouldrequirepermitcoverage.Inaddition,parkinglotsusedtostorevehiclesawaitingmaintenancealsorequirepermitcoverage(NPDES,1993).
TheIndustrialGeneralPermitrequirestheimplementationoftheBestAvailableTechnologyEconomicallyAchievable(BAT),theBestConventionalPollutionControlTechnology(BCT),andthedevelopmentofanIndustrialSWPPPandmonitoringplan.ThroughtheIndustrialSWPPP,sourcesofpollutantsaretobeidentifiedandthemeanstomanagethesourcesinordertoreducestormwaterpollutionaredescribed.TheIndustrialGeneralPermitalsorequiresimplementationofminimumcontrolmeasuresinsevencategories,listedbelow.
GoodHousekeeping
PreventativeMaintenance
SpillandLeakPreventionResponse
MaterialHandlingandWasteManagement
ErosionandSedimentControl
EmployeeTrainingProgram
QualityAssuranceandRecordKeeping
TheIGPalsoincludesarequirementforadvancedstructuralBMPs(i.e.,relatedtoexposureminimization,stormwaterreductionanddischargereduction,andtreatmentcontrol)ifNumericActionLevels(NALs)areexceeded.NALsareconcentrationsforanumberofconstituentsestablishedintheIGP.AfterJuly1,2015,ifstormwatermonitoringresultsduringtherainyseasonshowanexceedanceofoneormoreNALs,theDischargerentersaLevel1statusrequiringanevaluation,implementationaction,andreportingonmeasurestakentoavoidfutureexceedances.Ifanexceedanceofthesameparameter(s)occursinasubsequentyear,theDischargerentersLevel2statusrequiringadditionalevaluation,BMPimplementation,andreporting.
2.2.3 Regional
NPDES Municipal Separate Storm Sewer (MS4) Permit
Since1990,operatorsoflargemunicipalseparatestormsewersystems(MS4s)havebeenregulatedunderNPDESpermits.MS4Permitsrequireeachregulatedentitytodevelopastormwatermanagementprogramdesignedtopreventharmfulpollutantsfromimpactingwaterqualityviastormwaterrunoff.ThestormsewersystemsregulatedunderMS4sincludecurbsandgutters,man‐madechannels,catchbasins,andstormdrainsthroughouttheLosAngelesregion.ThepurposeoftheMS4PermitistoensurePermitteesarenotcausingorcontributingtoexceedancesofwaterqualityobjectivesorimpairmentsofbeneficialusesinthereceivingwatersoftheLosAngelesregion.TheLACFCD,theCountyofLosAngeles,and85incorporatedcities
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therein,includingtheCityofLosAngeles,(collectivelyreferredtoasPermittees)arejointlycoveredunderasingleMS4Permit(OrderNo.R4‐2012‐0175;NPDESPermitNo.CAS004001)forthedischargeofurbanrunofftowatersoftheU.S.
TheMS4Permitestablishesthewastedischargerequirementforstormwaterandnon‐stormwaterdischargeswithinthewatershedsofLosAngelesCounty.TheMS4Permitidentifiesconditions,requirements,andprogramsthatmunicipalitiesmustcomplywithtoprotectregionalwaterresourcesfromadverseimpactsassociatedwithpollutantsinstormwaterandurbanrunoff.UndertheMS4Permit,permitteesarerequiredtoreducepollutantsinstormwaterdischargestothemaximumextentpracticable(MEP).TheMS4Permitcontainseffluentlimitations,waterquality‐basedeffluentlimitations(WQBELS),receivingwaterlimits(RWLs),MinimumControlMeasures(MCMs),TMDLprovisions,aswellasthreecategoriesthatclassifywaterbodypollutantpriorities(Table2‐2).
Table 2-2: MS4 Permit Defined Categories
Category 1 Highest Priority
Water body‐pollutant combinations for which TMDLs are established in Attachment N of the MS4 Permit.
Category 2 High Priority
Pollutants for which data indicate water quality impairment in the receiving water according to the State’s Water Quality Control Policy for Developing California’s CWA Section 303(d) List (State Listing Policy) and for which MS4 discharges could potentially be contributing to the impairment.
Category 3 Medium Priority
Pollutants for which there are insufficient data to indicate water quality impairment in the receiving water according to the State’s Listing Policy, but which have exceeded applicable receiving water limitations contained in the MS4 Permit and for which MS4 discharges could potentially be contributing to the exceedance.
TheMS4PermitalsoincludesprovisionsthatallowPermitteestovoluntarilyimplementanEnhancedWatershedManagementProgram(EWMP)toachievepermitcompliancewithRWLs.TheintentoftheEWMPistocomprehensivelyevaluateopportunities,withintheparticipatingPermittees’collectivejurisdictionalboundaries,forcollaborationamongPermitteesandotherpartnersonmulti‐benefitregionalprojectsthat,whereverfeasible,retainnon‐stormwaterrunoffandalsoaddressfloodcontroland/orwatersupply.TwelveEWMPgroupshaveformedtoimplementacollaborativeapproachtomeettherequirementsoftheMS4Permit.LAXandsurroundingportionsoftheCityofLosAngelesarepartoftheSantaMonicaBayJurisdictions2and3WatershedManagementGroup.
TheEnhancedWaterManagementProgramfortheDominguezChannelWatershedManagementArea(EWMP,2015)wasdevelopedbytheDominguezChannelWaterManagementAreaGroup(DCWMG)toconformtorequirementsissuedbytheNPDESregardingtheMS4.TheEWMPaddressestheregulatoryrequirementsenforcedbytheMS4permitaswellasexistingcontaminantconditionsintheDominguezChannelwatershed.ThedatafrompriorreportsallowedtheEWMPtosortthecontaminantsintooneofthreeMS4permitcategories(Table2‐3).
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Table 2-3: MS4 Categories for Potential Dominguez Channel Constituents
Waterway Category 1 (TMDL)
Category 2
(303(d) List)
Category 3
(Other)
Dominguez Channel (lined portion above Vermont Avenue)
Copper, Lead, Zinc, Toxicity
Indicator Bacteria, Ammonia, Diazonin
Cadmium, Chromium, Mercury, Thallium, Bis (2‐Ethylhexl) phthalate, pH, Dissolved
Oxygen
Permitteesmustimplementminimumcontrolmeasuresthatidentifypotentialmodificationsthataddresswatershedpriorities,including:(i)DevelopmentConstructionProgram,(ii)Industrial/CommercialFacilitiesProgram,(iii)IllicitConnectionandIllicitDischargesDetectionandEliminationProgram,(iv)PublicAgencyActivitiesProgram,and(v)PublicInformationandParticipationProgram.RunofffromtheproposedProjectfacilitieswouldbetreatedon‐site,andasaresult,thebenchmarkpollutantvaluesdevelopedforprojectsapprovedforoffsitemitigationdonotapply.
Total Maximum Daily Load Program
PursuanttotheCWA,statesarerequiredtoidentifythewaterbodiesthatdonotmeetwaterqualitystandardsdespitecontrolofpointsourcedischargesunderNPDESpermits(33U.S.C.§1313).The303(d)listindicateswhichpollutantsandstressorsareprioritiesforeachwater‐qualitylimitedor“impaired”waterbody.Priorities(i.e.,high,medium,low)wereestablishedbytheSWRCBbasedonacombinationoffactorsthatincludedthedegreeofnonattainment/complexityoftheproblemandtherelativeimportanceofthewatershed.
Forthesewaterbodies,statesarerequiredtodevelopappropriateTotalMaximumDailyLoads(TMDLs)forthepollutantsorflowscausingtheimpairment.TMDLsarethesumoftheindividualwasteloadallocations(WLAs)forpointsources,nonpointsources,andnaturalbackgroundconditions,withanappropriatemarginofsafetyforadesignatedwaterbody(40CFR130.2).ATMDLrepresentsanamountofpollutionthatcanbereleasedintoaspecificwaterbodywithoutcausingadeclineinwaterqualityandimpairmentofbeneficialuses.TMDLsareestablishedbasedonaquantitativeassessmentofwaterqualityproblems,thecontributingsources,andloadreductionsorcontrolactionsneededtorestoreandprotectanindividualwaterbody.AsopposedtotheNPDESprograms,whichfocusesonreducingoreliminatingnon‐stormwaterdischargesandreducingthedischargeofpollutantstothemaximumextentpracticable,TMDLsprovideananalyticalbasisforplanningandimplementingpollutioncontrols,landmanagementpractices,andrestorationprojectsneededtoprotectwaterquality.Onceestablished,theTMDLallocatesthepollutantloadsamongcurrentandfuturepollutantsourcestothewaterbody.Ingeneral,theimplementationofandcompliancewiththeTMDLrequirementsisnecessarywhereurbanrunoffisidentifiedasasignificantsourceofpollutantscausingimpairments.
TMDLshavenowbeenadoptedforallofthemajorimpairmentsidentifiedforDominguezChannelabovetheestuary,andtheLosAngelesHarbor,towhichtheDominguezChannelistributary,andareshowninTable2‐4.
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Table 2-4: TMDLs for Receiving Water Bodies
Waterway Pollutant Effective Date
Dominguez Channel Nutrients July 31, 2013
Dominguez Channel Toxics March 21, 2012
Dominguez Channel Metals August 31, 2011
Dominguez Channel Trash March 18, 2008
Los Angeles Harbor Bacteria March 10, 2005
Source:StateofCalifornia,StateWaterResourcesControlBoard,October29,2015.
Table2‐5liststheTMDLconstituentsunderreviewandtheirestimatedcompletiondate,whichindicatesthedatethatTMDLsmustbeestablishedforeachpollutant. Table 2-5: Future TMDL Completion Schedule for Dominguez Channel (Estuary to Vermont Avenue)
Pollutant/Stressor Expected Completion
Ammonia 01/01/2019
Benthic Community Effects 01/01/2019
Benzo[a]pyrene (3,4‐Benzopyrene ‐7‐d) 01/01/2019
Benzo[a]anthracene 01/01/2019
Chlordane (tissue) 01/01/2019
Chrysene (C1‐C4) 01/01/2019
Coliform Bacteria 01/01/2019
DDT (tissue and sediment) 01/01/2019
Dieldrin (tissue) 01/01/2019
Lead (tissue) 01/01/2019
PCBs 01/01/2019
Phenanthrene 01/01/2019
Pyrene 01/01/2019
Sediment Toxicity 01/01/2019
Zinc (sediment) 01/01/2019
Source: StateofCalifornia,StateWaterResourcesControlBoard,July19,2009.
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2.2.4 Local
Low Impact Development Ordinance
In2011,theCityofLosAngelesBoardofPublicWorksapprovedtheStormwaterLIDOrdinance(Ordinance)toimposerainwaterLIDstrategiesonprojectsrequiringbuildingpermits.2Unliketraditionalstormwatermanagement,whichcollectsandconveysstormwaterrunoffthroughstormdrains,pipes,orotherconveyancestoacentralizedstormwaterfacility,LIDusessitedesignandstormwaterBMPstomaintainthesite’spre‐developmentrunoffratesandvolumes.ThefollowingOrdinancecategoriesmaybeapplicabletotheProjectArea:
Industrial/Commercialdevelopmentswithoneacreormoreofimpervioussurfacearea
Automotiveservicefacilities
Parkinglotsof5,000squarefeetormoreofsurfaceareaorwith25ormoreparkingspaces
TheStormwaterLIDOrdinancecallsfordevelopmentandredevelopmentprojectstomitigaterunoffthroughrainwatercapturemethodsandBMPs(e.g.,rainbarrels,permeablepavements,rainwaterstoragetanks,orinfiltrationswales).TheStormwaterLIDOrdinancerequires100percentofrainwaterfromathree‐quarterinchrainstormtobecompletelycaptured,infiltrated,and/orusedonsite.IfsiteconstraintsdonotallowforLIDstrategiestobeimplemented,off‐sitemitigationorfeepaymentforoff‐sitemitigationisallowed.CompliancewiththisordinancesatisfiesthePlanningandLandDevelopmentrequirementsoftheMS4Permit.
TheCity’sDevelopmentBestManagementPracticesHandbook3(Handbook),andtheLowImpactDevelopmentStandardsManual4weredevelopedtoassistdevelopers,aswellasCitydepartmentsforpublicworksprojectssuchasthoseatLAX,incomplyingwiththeOrdinance.TheHandbookprovidesthenecessarystepsrequiredfortheprojectreviewandpermittingprocessforobtainingapprovalofaLIDPlanincompliancewiththeOrdinance.
ProjectsmustmeetoneormorecriteriabeforetherequirementsoftheOrdinancearesatisfied.AlldevelopmentandredevelopmentprojectsthatfallintooneoftheapplicableprojectcategorieswouldberequiredtocomplywiththeOrdinanceandtheHandbook.However,theextentofcomplianceisgovernedbythefollowing:
Ifdevelopmentorredevelopmentresultsinanalterationofatleast50%ormoreofimpervioussurfacesonanexistingdevelopedsite,thentheentiresitemustcomply;
Ifdevelopmentorredevelopmentresultsinanalterationoflessthan50%oftheimpervioussurfacesofanexistingdevelopedsite,thenonlytheincrementaldevelopmentsurfacesofthesitemustcomply;and
2CityofLosAngeles,CityofLosAngelesMunicipalCode,ChapterIVArticle4.4Section64.70.01andSection64.72asamendedbyOrdinanceNo.181899,2011.Accessibleonlineat:www.lastormwater.org/wpcontent/files_mf/finallidordinance181899.pdf.3CityofLosAngeles,DevelopmentBestManagementPracticesHandbook,LowImpactDevelopmentManual,PartB,4thEdition,June2011.4CountyofLosAngeles,DepartmentofPublicWorks,LowImpactDevelopmentStandardsManual,February2014.
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Ifdevelopmentorredevelopmentofanysizethatwouldcreate2,500squarefeetormoreofimpervioussurfaceareaandislocatedwhollyorpartlyinanenvironmentallysensitivearea,thentheentiresitemustcomply.
TheCity’sOrdinancestipulatesthevolumeofstormwaterrunoffthatmustbetreatedfordevelopmentprojects.Onsitestormwatermanagementmeasuresmustbesizedtopreventanystormwaterrunofffromleavingthesitebasedonthefollowingtypesofevents:
85thpercentile24‐hourrunoffeventdeterminedasthemaximizedcapturestormwatervolumefortheareausinga48‐to72‐hourdrawdowntimebasedontheformularecommendedinUrbanRunoffQualityManagement5;or
VolumeofannualrunoffbasedonaunitbasinstoragewaterqualityvolumebythemethodrecommendedintheCaliforniaStormwaterBestManagementPracticesHandbook–Industrial/Commercial6;or
Volumeofrunofffroma0.75‐inchstormevent.
TheOrdinanceandHandbookspecifythatstormwatermanagementtechniquesbeimplementedinthefollowingorderofpriority:
1. Infiltrationsystems
2. Evapotranspiration
3. Captureanduse
4. Treatmentthroughhighremovalefficiencybiofiltration/biotreatment
TheHandbookprovidesspecificperformancestandardsandrequirementsforhighremovalefficiencybiofiltration/biotreatmentsystems.Anywaterleavingthesitefromhighremovalefficiencybiofiltration/biotreatmentsystemsisallowableastheyaredeemedincompliancewiththerequirementthatthefulldesigncapturevolumeberetainedonsite.
LIDPlansarerequiredtobecompletedandsubmittedforapprovalforallprojectsthatfallintothecategoriescoveredbytheOrdinance.TheseplansmustdemonstratehowcompliancewiththeOrdinanceandHandbookwouldbeachieved.IfimplementationofLIDrequirementsisdeemedtechnicallyinfeasible,theninfeasibilitymustbedemonstratedintheLIDPlans.However,allSUSMPrequirementsmustbemetandforanyrunoffthatcannotbemanagedonsite,offsitemitigationmustbeimplementedwithinthesamewatershed(e.g.Dominguez,SantaMonicaBay)onpublicorprivateland.ThereareanumberofconditionsorcircumstancesthatmayresultintheinfeasibilityofinstallationofLIDstormwatermanagementtechniques.Examplesinclude:
5UrbanRunoffQualityManagement,WEFManualofPracticeNo.23/ASCEManualofPracticeNo.87,19986CaliforniaStormwaterQualityAssociation,IndustrialandCommercialBestManagementPracticesOnlineHandbook,September2014.
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Locationswhereseasonalgroundwaterisbelow5feetofthesurfacegrade;
Siteswithsoiland/orgroundwatercontamination;
Locationswithin100feetofagroundwaterdrinkingwell;
Sitesonbrownfieldsorlocationswherepollutantmobilizationisadocumentedconcern;
Locationswithpotentialgeotechnicalhazards;and
Locationswithimpermeablesoiltypesasindicatedinapplicablesoilsandgeotechnicalreports.
TheHandbookshouldbeconsultedfordetailsregardingallofthepotentialconditionsthatmayresultinafindingofinfeasibilityforvarioustypesofLIDBMPs.
Standard Urban Stormwater Mitigation Plan
OfparticularimportancetoLAWAaretherequirementsoftheSUSMPPlanningandLandDevelopmentProgramforallnewdevelopmentandredevelopmentprojectswithintheMS4Permit.AnyprojectthatcannotcomplywiththeLIDrequirementsmust,atminimum,fulfilltheSUSMPcriteria.SUSMPisapplicabletoprojectsincludingsingle‐familyhillsideresidences,100,000‐squarefootcommercialdevelopments,automotiverepairshops,restaurants,andhomesubdivisionswith10ormorehousingunits.AdditionaltypesofprojectsthataresubjecttoSUSMPrequirementsarelistedinTable2‐6.TheSUSMPrequiresthatredevelopmentprojectsthatcreate,add,orreplace5,000squarefeetormoreofimperviousareaonanalreadydevelopedsitearesubjectedtothesameconditionsasnewdevelopmentprojects.
Table 2-6. SUSMP Project Types
Development Project Area of disturbed area
All development projects 1 acre or greater and adding more than 10,000 square feet of impervious surface area
Retail gasoline outlets 5,000 square feet or more of surface area
Parking lots 5,000 square feet or more of impervious surface area or with 25 or more parking spaces
Street and road construction 10,000 square feet or more of
impervious surface area
Automotive service facilities 5,000 square feet or more of surface area
Projects located in or directly adjacent to, or discharging directly to a Significant Ecological Area where the development would discharge stormwater runoff that is likely to impact a
sensitive biological species or habitat
2,500 square feet or more of impervious surface area
Source:StandardUrbanStormWaterMitigationPlanforLosAngelesCountyandCitiesinLosAngelesCounty(2000.)
DevelopmentprojectswithinthelistedcategoriesarerequiredtoincorporatethefollowingSUSMPrequirementsintotheirdesignplans:
1.Controlpeakstormwaterrunoffdischargerates
2.Conservenaturalareas
Section 2 Regulatory Framework
2‐14
3.Minimizestormwaterpollutantsofconcern
4.Protectslopesandchannels
5.Providestormdrainsystemstencilingandsignage
6.Properlydesignoutdoormaterialsstorageareas
7.Properlydesigntrashstorageareas
8.ProvideproofofongoingBMPmaintenance
9.DesignstandardsforstructuralandtreatmentcontrolBMPs
RelevanttoLAWA,theSUSMPincludesspecificrequirementsforprojectcategoriessuchascommercialdevelopment,retailgasolineoutlets,andautomotiverepairshopsthataddressstormwaterissues,suchastheproperdesignofparkinglotstolimitoilcontaminationandeasilyperformmaintenance.
SimilartotheLIDrequirementsdescribedabove,SUSMPBMPdesigncriteriarequirearetentionvolumeequaltothe0.75‐inch,24‐hourraineventorthe85thpercentile,24‐hourrainevent.ToassistwiththeselectionanddesignofBMPs,theSUSMPprovidesalistofexampleBMPsthatcanbeusedtoreducepollutantsgeneratedfromsiterunofftothestormwaterconveyancesystems.Sincestormwaterhasthepotentialtocontaminategroundwater,infiltrationBMPsarenotrecommendedforindustrialareasorareassubjecttohighvehiculartrafficunlessproperpretreatmentisprovided.RetentionandinfiltrationBMPscanbeimplementedforcontrollingrunofffromimpervioussurfaces.
3‐1
Section 3
Existing Conditions
ExistingconditionsintheDominguezChannelNorthdrainageareawereassessedastheypertaintopotentialfloodzones,stormwaterdraincapacityrestrictions,andexistingwaterqualityimpacts.Asdiscussedbelow,theDominguezChannelareaisnotlocatedwithinaFederalEmergencyManagementAgency(FEMA)floodzone.ExistingdrainagepatternsarediscussedbasedonpriorreportsfortheDominguezChannelarearelativetothe10‐yearstormconveyancerequirementforconduitsandthe50‐yearstormcapacityforfloodevaluationinDominguezChannel.Descriptionsofcurrentlanduseandwaterqualityconditionsarealsodescribed.ThesedescriptionsprovideabasiswithwhichtoassesstheimpactsoftheproposedProjectatLAX.
3.1 Dominguez North Flood Zones The100‐yearfloodplainistheareanearawaterwaydefinedbya1percentchanceofannualflood,whilethe500‐yearfloodplainexperiencesa0.2percentchanceofflood.TheBestAvailableMapsfromtheCaliforniaDepartmentofWaterResources(DWR,2015)indicatesthattheDominguezNorthstudyareaisnotlocatedina100‐yearfloodplain.TheFEMAFloodMapServiceCenter(MSC)wasaccessedtoviewavailableinformationonfloodplainsinthestudyarea,whichindicatethatthestudyareaisalsolocatedoutsidethe500‐yearfloodplain.
3.2 Stormwater Drainage TwoseparatedrainagesystemsconveywaterfromtheeastsideoftheLAXpropertytoDominguezChannel(ParsonsBrinckerhoff,2002andLAWA,2005);thesestructuresincludethe“ProjectNo.13”stormdrainandtheDominguezChannelConcreteConduit,whichdividetheProjectAreaintonorthernandsoutherndrainageareas,respectively.SomeoftheproposedProjectfacilitiesintheDominguezChannelNorthSubbasinwouldbelocatedneartheProjectNo.13stormdrain,whichisshowningreeninFigure3‐1.TheProjectNo.13stormdraincapturesrunofffromthenorthernportionsoftheDominguezChanneldrainagebasin,andconveystherunoffparalleltotheconcreteconduitunder116thStreetuntilthetwostormdrainsintersect(andProjectNo.13ends)atInglewood.TheDominguezChannelConcreteConduitcontinueseasttoKornblumAvenuewhereitflowsintoanopenchannel.
DrainagesystemsegmentswithflowrestrictionsupstreamofandalongtheProjectNo.13stormdrainareidentifiedintheredboxesdepictedinFigure3‐1,andarediscussedinSection3.2.2.
Section 3 Existing Conditions
3‐2
Figure 3‐1: Primary Storm
Drains in Dominguez Chan
nel Area
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Section 3 Existing Conditions
3‐3
3.2.1 Existing Infrastructure TheProjectNo.13stormdraincollectsrunofffromthenorthernsubbasinina10’x11’6”reinforcedconcretebox(RCB)thatbeginsattheintersectionofCenturyandAviationBoulevards.ThestormdrainflowsalongCenturyBoulevard,changesdimensionsto11’6”x10’andthenturnssouthonLaCienegawhereitstartsatdimensions11’9”x10’andgraduallyreaches13’x11’.AtLaCienegaand116thStreet,thestormdraindimensionschangeto13’6”x10’6”;thesedimensionsincreaseto14’9”x14’astheProjectNo.13stormdrainflowstoajunctionwiththeDominguezChannelconcreteconduitatInglewoodAvenueon116thstreet.Theoriginaldesigncalculatedwatersurfaceprofilesfortheupstreamportionofthe10’x11’6”RCBresultedinadesignflowcapacityof730cubicfeetpersecond(cfs)whilethe14’9”x14’ReinforcedConcretePipe(RCP)outletatInglewoodAvenueprovideddesignflowcapacityof1,230cfs.Norecordswerefoundthatidentifythedesignstormforwhichtheseconduitsweresized(ParsonsBrinckerhoff,2002).Table3‐1summarizestheProjectNo.13stormdraincontributingareadesignflow.
Table 3-1: Existing Characteristics Dominguez Channel North Sub-Area
Parameter Description
Drainage Area 1,100 acres
Drainage Boundaries Manchester Boulevard to midway between Airport and Aviation, cross‐country to Arbor Vitae Street, easterly to La Cienega Boulevard, South to I‐105, west to Aviation Boulevard, north to Aviation Boulevard/Century
Boulevard intersection, west to Century Boulevard/Sepulveda Boulevard Intersection, north to Manchester Boulevard/La Tijera Boulevard
intersection.
Drainage Pattern East and South
Outfall Dominguez Channel (Los Angeles Harbor)
Existing Capacities Century Boulevard: 730 cfs
South of 104th Street (under La Cienega between 104th and 111th): 1080 cfs
Outlet at Inglewood Avenue into Dominguez Channel: 1230 cfs
Downstream Control 14’‐9”Wx14’H RCB outlet into Dominguez Channel Concrete Conduit at Inglewood Avenue
Source:LAXMasterPlanDraftEIR,2005
DrainagedeficienciesupstreamofandalongtheProjectNo.13stormdrainarediscussedinthefollowingsub‐sectionastheypertaintothefutureproposedfacilities.
3.2.2 Existing Drainage Deficiencies DrainagedownstreamofthefutureProjectfacilitiesmusthaveampleconveyanceforthe10‐yearstormevent.The10‐yearstormiscurrentlyconstrainedbystormdrainsthatdrainweston96thstreet,southonAirportBoulevard,andwestonCenturyBoulevard(LAWA,2015andPB,2002).
SeveralstudiesacknowledgethatthesectionoftheProjectNo.13stormdrainalongLaCienegaBoulevardbetween104thstreetand111thstreetisinadequatelysizedtoconveytheLADPW50‐yeardesignstorm.
Capitalfloodprotectionforthe50‐yeareventforDominguezChanneliscurrentlybeinginvestigatedbytheUSArmyCorpsofEngineers(2015).Additionally,LAWAeffortsmayhelpreducefloodrisksforthe50‐yeareventalongDominguezChannel,asfurtherdiscussedinSection5.
Section 3 Existing Conditions
3‐4
3.3 Runoff Water Quality ThissectionaddressespollutantsofconcernthataregeneratedintheDominguezChannelsubarea,aswellaswaterqualityconcernsobservedinthedownstreamreceivingwaters.
3.3.1 Pollutants of Concern TMDLsfortoxics,metals,nutrients,PCBs,pesticides,andtrashhavebeendevelopedforDominguezChannel(CASWRCB).TwentyfivepollutantsthathaveshownrecentexceedancesinDominguezChannelanditstributaries,orthatareclassifiedinthe2015EWMPasWaterBody‐PollutantCombinations(WBPCs)arepresentedinTable3‐2.SeveraloftheseconstituentshaveareasonablelikelihoodtobepresentinstormwaterrunofffromtheproposedProjectfacilities.BecauseproposedrentalcarandAPMcarmaintenanceareaswouldbelocatedwithintheDominguezChannelsub‐basin,oilandgreasemaybepresentinrunoffenteringthestormwaterconveyancesystemfromLAWAproperties(CampDresser&McKeeInc.,2001).
Table 3-2: Pollutants of Concern
Pollutant of Concern Description Reasonable Likelihood to be Present
Ammonia Fertilizer Component
Arsenic Used in pesticides,
herbicides, and insecticides
Bis (2‐Ethylhexl) phthalate
Plasticizer
Cadmium Heavy metal
Chlordane Insecticide, banned in 1988
Chromium Heavy metal
Coliform Bacteria Plastic Component
Copper Heavy metal
Yes. Weathered soils, atmospheric deposition, automobile emissions and residuals (brake pad and tire wear), applied
chemicals, and industrial and other sources can contribute to this contaminant
Cyanide Used in processes such as
rubber and plastic production
Dichloro‐diphenyl‐trichloroethane (DDT)
Pesticide, not been manufactured since 1985
Diazinon Insecticide
Dieldrin Insecticide
Dissolved Oxygen Oxygen dissolved/carried in
water
E. coli Bacteria
Fecal Coliform Bacteria
Indicator Bacteria Disease‐causing organisms
Lead Heavy metal
Yes. Weathered soils, atmospheric deposition, automobile emissions and residuals (brake pad and tire wear), applied
chemicals, and industrial and other sources can contribute to this contaminant
Mercury Used for manufacture of
chemicals
Section 3 Existing Conditions
3‐5
Nickel Metal plating material
Polycyclic Aromatic Hydrocarbon (PAHs)
Component of fossil fuels
Polychlorinated Biphenyl (PCBs)
Component of coolants, banned since 1976
Selenium Refining element for heavy
metals
Silver Heavy metal
Thallium Byproduct of metal refining
Zinc Heavy metal
Yes. Weathered soils, atmospheric deposition, automobile emissions and residuals (brake pad and tire wear), applied
chemicals, and industrial and other sources can contribute to this contaminant
Source: Pollutants of Concern from 2015 EWMP, likelihood to be present from Camp Dresser & McKee Inc., 2001 (EIS‐EIR Tech Report 6)
BestmanagementpracticesrecommendedfortheproposedProjectfacilitiesinordertoaddressthepollutantsofconcernthatmaybepresentinstormwaterrunoffaredescribedinSection5.
3.3.2 Existing Water Quality Conditions WaterqualityintheDominguezChannelisaffectedbyseveralpointandnonpointsourcesofcontamination.Waterqualitydatacollectedfrom1993to2013intheDominguezChannel(CDMSmith,2015)showthataluminum,zinc,andcopperconcentrationswerefoundtobeapproximately25timestheannualaverageNumericActionLevel(NAL)intheIGP(asintroducedinSection2).Thiscorrespondsto0.75mg/lforaluminum,0.16mg/lforzincand0.0189mg/lforcopper(CAWaterBoard).Maximumtotalcoliformandfecalcoliformconcentrationswereabout15timestheTMDLtargets,whereasmaximumenterococcusconcentrationsweremorethan50timestheTMDLtargets.Themaximumobservedconcentrationsofoilandgrease,BOD,andCODalsoexceededNALsandmaybeapollutantofconcernincertainyears.
AfinalreportbytheEnhancedWatershedManagementProgramfortheDominguezChannelWatershedGroupalsoreportedexceedancesindissolvedmetalsfromwaterqualityassessmentsduringtheperiodof2002to2013.TheEWMPreportalsonotedexceedancesindissolvedmetalshardness‐adjustedCaliforniaToxicsRule(CTR)criteriaforcopper,lead,andzincinwetweathersamples.HighlevelsofbacteriaconcentrationsandpHvaluesabovetheBasinPlanobjectiveswerealsoobserved.TheestuarineportionofDominguezChannelshowedadverseimpactstobenthiccommunitieswith3of5stationsclassifiedasbeinginpoorcondition.
3.3.3 Potential Source Areas ExistingactivitiesatLAXandsurroundingareasgeneratepollutantsthatrunofftoDominguezChannel,whichcancontributetoexceedancesinwaterqualitystandards.Itshouldbenoted,however,thatnotalloftheseactivitiesoccurwithintheProjectArea.Runoffischaracterizedintotwomajorsourcesofwater,dryweatherflowsorwetweatherflows.Dryweatherflowsattheairportlikelyoriginatefromoutdoormaintenanceofaircraftsandvehicles,buildingandgroundsmaintenance,aircraftandgroundvehiclefueling,painting,stripping,washing,andchemicalandfueltransportandstorage.Wetweatherflowsattheairportoccurswhenthereisprecipitationthatflowsacrossthegroundbeforeandafterarainevent.
Section 3 Existing Conditions
3‐6
Inadditiontobeingcomponentsofdryweatherflows,heavymetals,suchascopper,zinc,andleadmayexistinwetweatherflowsthatdraintoDominguezChannel.Constructionactivitiesattheairportmayalsogeneratepollutantsourcesthatadverselyaffectwaterquality,includingerosion‐inducedsediments,nutrients,tracemetals,toxicchemicals,andconstructionwaste.
Existing(pre‐projectconditions)imperviousandperviousareaswereidentifiedbasedonaerialphotographstakeninOctober2015fortheregionandareshowninFigure3‐2.Streets,parkinglots,andbuildingsareconsidered100percentimperviouswhilestreetmediansandareasofgrassorvegetationareconsideredpervious.LowdensityhousingislocatedinthenorthwestcorneroftheDominguezNorthDrainageAreaandtheManchesterSquarearea;ManchesterSquarereferstotheareaboundedbyW.CenturyBlvdtothesouth,AviationBlvd.tothewest,W.ArborVitaeSt.tothenorth,andS.LaCienegaBlvd.totheeast.Lowdensityresidentialareasareassumedtohaveanexistingimperviousvalueof25percent.ResidentialcommunitiesonlyaccountforasmallpercentageoflanduseinManchesterSquareandmostoftheexistinglanduseintheareaiscategorizedasopenspace,leadingtoexistingrunoffconditionscomprisedmainlyoftotalsuspendedsolids(TSS)suchasdirtandgravelassociatedwithopenspace.
Section 3 Existing Conditions
3‐7
Figure 3‐2: Exisiting (Pre‐Project) Im
perviousness Values in the Dominguez North SubBasin
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4‐1
Section 4
Methodology
ThissectiondescribesthemethodologyusedtoassesspotentiallysignificanthydrologicandwaterqualityimpactsfortheproposedProject.Theimpactanalysesarebasedonavailableinformation.
4.1 Hydrology 4.1.1 Thresholds of Significance Impactstodrainageandhydrologyareevaluatedforsignificancerelativetoidentifiedsignificancethresholds.ThisappendixpresentsthresholdsusedinpreviousLAXreportstoassessthesignificanceofhydrologyimpactsthatarerelevanttothisanalysis.AsignificanthydrologyimpactwouldoccuroftheProjectwouldeither:
Increaserunoffthatwouldcauseorexacerbatefloodingwiththepotentialtoharmpeople,damageproperty,damagesensitivebiologicalresources,orwouldexceedthecapacityofexistingorplannedstormwaterdrainagesystems
Causesubstantialalterationoftheexistingdrainagepatternofthesiteinamannerwhichwouldresultinsubstantialerosionorsiltationon‐oroff‐site.
TheimpactanalysispresentedinthistechnicalappendixutilizesthequantitativeclassificationofasignificanthydrologicimpactasdescribedinSection4.1.2below(i.e.,floodprotectionfora10‐yeardesignstormandfora50‐yeardesignstorm).Specificdesignstormsareanalyzedforpre‐andpost‐developmentconditionsforpotentialexceedanceofexistingdrainagesystemcapacity.
4.1.2 Impact Analysis Methodology AsdescribedinSection2,stormsizesareusedbyagenciesandengineersasstandardstodictateconveyancedesignstoattenuatefloodingandhydrologicimpacts.TheFAA,LACDPW,andtheCityofLosAngelesdesigncriteriastatethatthedesignandimprovementsofstormdrainsshouldprovidefloodprotectioncapacityforaminimumofa10‐yearstormevent.ForopenchannelsandotherregionalfacilitiessuchasDominguezChannel,theLACDPWHydrologyManualrequiresprotectionfromtheCapitalFloodwhichisdefinedasthe50‐yeardesignstorm.Asaresult,thesignificanceofincreasesinrunoffduetodevelopmentoftheproposedProjectisevaluatedfortheimpactonstormdrainsfroma10‐yeardesignstorm,andonDominguezChannelfromthe50‐yeardesignstorm.Existingsiterunoffratesandvolumeswerecomparedtositerunoffunderdevelopedconditions.Peakrunoffflowratesfromthedevelopedconditionsthatwouldexceeddrainagesystemcapacityforeitherofthesedesignstorms,dependinguponthedesignstormfrequencyforspecificdrainagefacilities,isconsideredasignificantimpactasitmaycauseupstreamsurfaceflooding.Stormdrainagesystemsthatcannotachieve10‐yearcapacityareconsidereddeficient.
Section 4 Methodology
4‐2
TheLosAngelesCountyHydrologyManual(2006)definesthe50‐year,24hourdesignstormdepthoverthearea,andtheappropriatecoefficientsbywhichtomultiplythisdepthtodownscaletothe10‐yearstormintensity.Ahyetograph(i.e.,graphindicatingdistributionofrainfalleventsovertime)fortheVeniceBeachareaindicatesthattheManchesterSquareandDominguezChannelareashavea50‐year,24‐hourdesignstormvaluebetween5.0and5.2inches(LosAngelesCountyDepartmentofPublicWorksHydrologyManual,2006).Anaverage50‐yearrainfallof5.1inchesisutilizedforthisanalysis.Amultiplicativecoefficientof0.714yieldsthe10‐yearstorm,asspecifiedintheLosAngelesCountyHydrologyManual.
Toassessthepotentialoffloodingandhydrologyimpact,thepeakflowratefortheproposedProjectareawascalculatedandcomparedtothedesigncapacityoftheexistingdrainagesystemusinganEPASWMMmodeltoassessanypotentialincreasesindownstreamstormdrainwatersurfaceelevations.Thisapproachcomparestwodrainageareasbasedontheamountofimperviousareaandassociatedlanduse.Achangeinlandusewithallotherparametersheldconstantwouldproduceachangeintheamountofimperviousareaandacorrespondingchangeinstormwaterpeakflowrates.Theincreaseinpeakflowrunoffratefromtheincreaseinpercentageofimperviousareamayexceedthedesigncapacityforthedrainagestructure,andthus,increasethelikelihoodofflooding.
4.2 Water Quality 4.2.1 Thresholds of Significance SurfacewaterflowsthataregeneratedwithintheProjectAreaboundariesultimatelydraintotheDominguezchannel.Thequalityoftherunoffcanimpactthewaterqualityofthereceivingwaterbodies.TheL.A.CEQAThresholdsGuide(2006)defineasignificantwaterqualityimpactasdirectandindirectchangestotheenvironmentthatmaybecausedbytheProject.Morespecifically,theProjectwouldcauseasignificantimpactifdischargesassociatedwiththeProjectwouldcreatepollution,contamination,ornuisanceasdefinedinSection13050oftheCleanWaterCode(CWC)orthatcauseregulatorystandardstobeviolated,asdefinedintheapplicableNPDESstormwaterpermitorWaterQualityControlplanforthereceivingwaterbody.TheimpactanalysisinthistechnicalappendixrecognizesNPDESLIDspecificationsastheapplicableregulatorystandardbywhichtodeterminesignificantwaterqualityimpacts(i.e.,wouldtheprojectprovideforwaterqualityBMPssufficienttocaptureandtreatrunofffromthe85thpercentiledesignstorm).
4.2.2 Water Quality Impact Analysis Methodology Theeventmeanconcentration(EMC)isusedtoestimateProjectpollutantloadings.Sincelandusecanbequantifiedbyamountandtype,theEMCshavebeenusedtocharacterizepollutantconcentrationsinurbanrunoff.TheEMCrepresentstheaverageconcentrationofapollutantduringastormevent.Itdoesnot,however,considerfluctuationsofloadswithinstormevents.LocalEMCdataforlandusecategorieshavebeencompiledbytheseveralmunicipalitiesthatparticipatedinanextensivestormwatermonitoringprogramtosupportstormwaterqualitymanagementinLosAngelesCounty.EMCsforallthelandusecategories,withtheexceptionofairportoperationsandairportopenspace,isbasedondatacollectedbetween1994and2000bytheLosAngelesCountyDepartmentofPublicWorks,asshowninTable4‐1.
Section 4 Methodology
4‐3
Table 4-1: EMC Values
Pollutant EMC for Industrial (mg/l)
EMC for Commercial
(mg/l)
EMC for Open Space
(mg/l)
EMC for Mixed
Residential (mg/l)
EMC for Transportation
(mg/l)
Total Suspended Solids (TSS) 240 66 186 63 78
Total Phosphorus 0.41 0.39 0.16 0.26 0.44
Total Kjeldahl Nitrogen (TKN)
3.00 3.40 0.79 2.50 1.90
Total Copper 0.03 0.04 0.02 0.02 0.06
Total Lead 0.02 0.02 0 0.01 0.01
Total Zinc 0.64 0.24 0.05 0.20 0.29
Oil and Grease 1.70 3.30 0 0 3.10
Biological Oxygen Demand (BOD)
20 27 12 18 21
Chemical Oxygen Demand (COD)
80 98 17 64 50
Ammonia 0.59 1.26 0.13 0.67 0.29
Fecal Coliform (MPN/100ml) 338,220 528,750 1,397 100 328,750
Fecal Enterococcus (MPN/100ml)
98,200 86,250 679 0 32,000
Source: LACDPW (http://ladpw.org/wmd/npdes/9400_wq_tbl/Table_4‐12.pdf)
Developmentorredevelopmentprojectsthat,asrequiredbytheSUSMP,create,add,orreplace5,000squarefeetormoreofimperviousareaonanalreadydevelopedsite,shallprepareanLIDplantoreducestormwaterandpollutantrunofffrom100percentofthesitearea.BasedontheLIDplan,BMPsshouldbeadoptedtoinfiltrate,evapotranspirate,capture,andtreatstormwaterrunoff.Thevolumeofrunoffproducedfromthe85thpercentile,24‐hourstormeventcanbeusedtospecifythedesignofvolumetric‐basedstormwaterqualityBMPs.
Themodifiedrationalmethod(CityofLA,2011)wasusedtodeterminethevolumerequiredfortreatment.Thismethodrequiresthataunithyetographforthedesignstormbeestablishedbeforerunoffcomputationscantakeplace.AssumptionsregardingthehyetographtimingandhighestintensityweremadeinaccordancewiththeLosAngelesCountyHydrologymanual.ThemaximumintensityforaspecifieddurationwasfoundusingtheLosAngelesCountyspecifiedIntensity‐Duration‐Frequency(IDF)equationthatrelatesthestormintensity,duration,andfrequency(Equation4‐3).Thetotalstormvolumeiscomputedasthesumoftherunoffvolumeunderthehydrographgeneratedfromthedesignhyetograph.
Equation4‐1wasimplementedateachtimestepandsummedtodeterminetherunoffvolume.Thedesignstormintensity(It)ismultipliedbyadevelopedrunoffcoefficient(Cd)andthesubbasinarea(A)toyieldapeakflow(Q,incfs)thatmustbemitigatedduetodevelopment(CityofLAAppendixF,2011).
Equation 4-1:
Section 4 Methodology
4‐4
ThevariableCdisthedevelopedrunoffcoefficientforthebasinandrepresentstheratioofrunoffratetorainfallintensityperEquation4‐2.
Equation 4-2: 0.9 1.0
Thepercentoftheimperviousarea,Imp,isspecifiedas0to1andCu,theundevelopedrunoffcoefficient,isafunctionofsoiltypeandrainfallintensity.Soiltype20,andtherelatedCuasafunctionofrainfallintensityfromLosAngelesCounty,wasusedfortheManchesterSquarearea.
Therainfallintensityforthesub‐areainEquation4‐1iscomputedinEquation4‐3.
Equation 4-3: .
Thevariabletrepresentsthedurationinminutes;thisisspecifiedasthetimeofconcentrationforasub‐basin.Therainfallintensityfortheduration(ininchesperhour),It,isdividedbythe24‐hourrainfallintensityI1440toyieldadimensionlessratio.ThetimeofconcentrationsubstitutedfortinthisequationiscomputedforasshowninEquation4‐4.
Equation 4-4: . .
. .
ThelongestflowpathlengthfromthewatershedboundarytotheoutletisgivenasL,theslopeofthisflowpathisS,andItrepresentstherainfallintensityasexpressedinEquation4‐3.NotethataninitialapproximationforthetimeofconcentrationmustbegiveninEquation4‐3inordertodeterminearainfallintensitythatisusedinEquation4‐4.ThetimeofconcentrationfortheseareasintheDominguezChannelNorthSubbasinwascalculatedbypartitioningdevelopmentintosubareastoyieldanexistinganddevelopedpercentimperviousnesscausedbyeachProjectcomponent.Theslopewasdeterminedbysubtractingtheelevationofthemostremotepointinthesubareatothesubareaoutletanddividingtheresultbythelengthbetweenthetwopoints.
TherunoffcoefficientinEquation4‐2wasdevelopedassumingthateachProjectcomponentwouldaddanareathatis100%impervioustothesite.Themostconservativewaytoensurethe85thpercentilerequirementisaddressedwastoaddresstheflowfromthe100%imperviousnewfootprint,assumingnorunofffrompre‐developedconditions.Thisanalysisprovidesconservativehighpeakflowratecalculations.
5‐1
Section 5
Potential Project Impacts and Project Design
Features
PotentialimpactsoftheproposedProjectrelativetoexistingconditionswereaddressedaschangesinpeakflowratesfordrainage,andchangesinthedischargeofpollutantsofconcernforwaterquality.HydrologicimpactswereassessedbycombiningProjectelementswithneighboringroadwaysandAPMGuideway.Hydrologicimpactsforthefollowingdrainageareasaredescribedinthissection.
ConRACandadjacentroadwaysandAPMGuideway
ITFEastandadjacentroadwaysandAPMGuideway
APMStorageandMaintenanceFacilityandadjacentroadwaysandAPMGuideway
ITFWestandadjacentroadwaysandAPMGuideway
Approximately1.7acresofproposedroadwayneartheintersectionof111thSt.andAviationBlvd.
WaterqualityimpactswereassessedfortheseparatefootprintofeachProjectcomponent.Methodsusedtoexaminehydrologyandwaterqualitywerediscussedintheprevioussection;thischapterpresentsdetailsforandtheresultsoftheanalysis.
5.1 Drainage 5.1.1 Potential Project Impacts Drainageimpactsweredeterminedbasedonchangesinlanduseandsitegradingasopposedtobuildingfootprint;drainagebasinsweredefinedforeachProjectcomponentasshowninFigure5‐1.AnEPASWMMmodelwasusedtoassessanypotentialincreasesindownstreamstormdrainwatersurfaceelevationsthatwouldresultfromdevelopment.
S F Section 5 Potent
Figure 5‐1: Drainaia
l Project Im
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age Areas for LA
Ms and Project Desig
MP Components
n Features
5‐2
Section 5 Potential Project Impacts and Project Design Features
5‐3
ThechangeinimpervioussurfacesareshowninTable5‐1fordrainageareasdefinedinFigure5‐1.Section4indicatesthatperviousareasareassignedtheundevelopedlanduserunoffcoefficientbasedonareasoiltype.ThePre‐ProjectConditionsrowsinthetableconstitutesthedrainageareaswithvaryingpercentimperviousnessbeforetheproposedProjectdevelopment.
Table 5-1: Composite Percent Impervious Values
Project Component
Project Condition
Total Drainage Area
(Acres)
Area 100% Impervious (Acres)
Area 25% Impervious (Acres)
Area Pervious (Acres)
Composite Percent
Impervious1
ConRAC
Pre‐Project 75 22 3 50 30%
Proposed Project
75 72 0 3 96%
East ITF
Pre‐Project 32 14 4 14 47%
Proposed Project
32 27 0 5 84%
West ITF
Pre‐Project 71 69 0 2 97%
Proposed Project
71 70 0 1 99%
APM Maintenance
Facility
Pre‐Project 20 7 0 13 35%
Proposed Project
20 11 0 9 55%
Roadways near South Airfield
Pre‐Project 34 5 0 29 15%
Proposed Project
34 7 0 27 20%
1Composite Percent imperviousness = % . % %
ParkinglotscurrentlycovertheWestITFdevelopmentarea,andadditionofanewstructurewouldhaveminimalimpactonthepercentofimpervioussurface.TheAPMmaintenancefacilitywouldbeconstructedonamostlyemptylotwithmulti‐familyandcommerciallanduseinthenorthwestcorner.Existing(pre‐project)conditionsinManchesterSquareincludeopenspace,roads,andexistinglowdensityresidentialdevelopment.
Table5‐2delineates,foreachoftheProject’smaincomponents:
Theexisting(i.e.,pre‐project)downstreamdrainagesystempeakdepthsforthe10‐yeardesignstorm,thefuturedownstreampeakdepthsthatwouldoccurwithimplementationoftheproposedProject(i.e.,estimatedincreaseindownstreamflowsresultingfromtheProject)
Theestimatedvolumeofstormwaterdetentionthatwouldberequiredforeachprojectcomponentinordertomaintaintheexisting/pre‐projectdownstreampeakdepthsforthe10‐yeardesignstorm.
Table 5-2: 10-year storm Peak Depths
Component Existing Downstream Peak
Depth (ft) Future Downstream Peak
Depth (ft) Detention Volume Required (ft3)
ConRAC 4.44 (to the north) 6.28 (to the north) 571,000
Section 5 Potential Project Impacts and Project Design Features
5‐4
12.81 (to the south) 15.13 (to the south)
East ITF 9.57 12.04 200,000
West ITF 12.41 (to the south)
12.45 (to the east)
12.80 (to the south)
12.87 (to the east) 94,000
APM Maintenance
Facility 5.21 7.67 23,000
Roadways near South Airfield
1.39 1.39 0
ItshouldbenotedthatalthoughtheWestITFisbeingconstructedonanexistingparkingareasandtherewouldbeanegligibleincreaseinimpervioussurfaceareaandassociatedrunoffassociatedwiththatcomponentoftheProject,rerouteddrainagepatternsintheareawouldrequiredetentionvolumeabovethatwhichiscurrentlyavailable.
ItshouldalsobenotedthattheincreasedstormwaterflowattributabletotheproposedProjectwouldaddtoanalreadysurchargedcondition(i.e.,theexistingdrainagedeficienciesdescribedaboveinSection3.3.3),whichistheresultofbothLAWAexistingflows(i.e.,runofffromLAWAproperties)andnon‐LAWAexistingflows(runofffrompropertiesowned/controlledbyothers)reachingthedownstreamdrainagesystem.Assuch,theproposedProjectmaybeonlypartiallyresponsibleforfuturedrainagesystemimprovementsnecessarytoaddresssuchdrainagedeficiencies,asfurtherdescribedbelow.
5.1.2 Project Design Features Undergroundcisternswithatotalvolumeof500,000ft3areincludedintheproposedProjectdesignforstormwatercapturebeneaththeConRACfacilityasshowninFigure5‐2.Althoughthecisternsareproposedandsizedprimarilytoaddresspotentialwaterqualityimpacts,asfurtherdiscussedinSection5.2below,theirfunctioninstoring/retainingstormwaterwouldalsoservetoreducehydrologyimpacts,specificallyasrelatedtoreducingProject‐relatedpeakflows.
Section 5
Figure 5
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TheothWhilerdetailedmainlymeasurresultithatharunoffwsystemproposdamagehydrolo
5 Potential P
5‐2: Proposed
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rrentlypropeswouldlikethosefacilitiLIDrequiremned.Implemmpactsbycaeficiencies.Tedthecapaciesignificant.orexacerbatedressespoten
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ninFigure5‐ortion,whilenthenorthertentionvolumimately88%eareainordestreampeak
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ecifieddetencorporatedinmeasuresfoSection5.2beascurrentlyowswithinauldcreateordstormwaterbesignificanntialtoharmstoaddress
ly25%ofthee,theplanneacility,andwch,thisprojetionvolumeojectdownstorm.
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5‐5
edwouldct
tream
es.eC,
wouldstem
e
Section 5 Potential Project Impacts and Project Design Features
5‐6
5.2 Water Quality AssessmentofpollutantrunoffutilizesthedrainageareasandimperviousvaluesdiscussedinSection5.1;thewaterqualityimpactforthe85thpercentilestormisconservativelycalculatedassumingtheProjectcomponentfootprintsare100%impervious;potentialsmallperviousareasincludingcourtyards,grassbetweensidewalks,andplantersareignored
5.2.1 Wet Weather Runoff
5.2.1.1 Potential Project Impacts
WetweatherrunofffromtheproposeddevelopmentareaswouldresultinsomeincreasedpollutantloadsthatwouldbedischargedtotheDominguezChannelNorthsubbasinandeventuallytotheDominguezChannelanddownstreamreceivingwaters.Eventmeanconcentrations,listedinTable4‐1,togetherwithtotalrunoffvolumeswereusedtocalculatepre‐andpost‐Projectpollutantloadsintheabsenceofanyproject‐specificmeasurestoreduceloads.FivetypesoflanduseforwhichEMCvaluesareavailablewereassumedtorepresentdifferentportionsofexistingand/orfuturelandusesintheProjectArea:industrial,commercial,openspace,transportation,andmixedresidential.
Changestothelandcoverasaresultofthedevelopment(proposedProjectconditions)oftheConRACandEastITFfacilitieswouldreduceopenspaceareaby56acresandreducemixedresidentialby7acres.Thefacilitieswouldincreasecommercialareaby27acresandincreaselanddevotedtotransportationby36acres.ThereductioninopenspacelandusewouldresultinanetincreaseinimperviousareaandanassociateddecreaseininfiltrationvolumewithintheManchesterSquarearea.Thischangeintotalimpervioussurfaceareawouldincreasecontaminantloadinsurfacewaterrunoff.TheannualtotalpollutantloadinstormwaterrunofftoDominguezChannelforbacteria,oilandgrease,totallead,andammoniawouldincreaseduetoadditionalimpervioussurfacessuchasroadsandparkingfacilities.
Similarly,conversionofopenspaceareatotransportationareaforthedevelopmentoftheWestITFandAPMfacilitieswouldincreaseimpervioussurfacesanddecreaseinfiltrationintheprojectarea.TheconversionofopenspacetotransportationlanduseforthedevelopmentoftheWestITFwouldincreasecontaminantloadsforallconstituentsexceptfortotalsuspendedsolids(TSS)comparedtoexistingconditions.DevelopmentoftheAPMmaintenancefacilitywouldalsoconvertopenspacetoindustrialandtransportationlanduse,impactingsurfacerunoffandwaterquality.Greaterestimatedloadsarepredictedforbacteria,lead,zinc,andoilandgreaseasaresultofincreasedimpervioussurfaces.
Table5‐4categorizesthelandusetypesforpre‐andproposedprojectconditionsbasedonthedrainageareasdepictedinFigure5‐1.Table5‐4areaswereusedtoassesscontaminantvolumesinrunoff,percentimperviousisderivedfromtheselandusetypesbydenotingopenspaceas0%impervious,mixedresidentialas25%impervious,andallotherlandusetypesas100%impervious.Thetotalpercentimperviousisacompositedpercentimperviousforthetotalprojectcomponentdrainagearea.
Table 5-4: Land Use Areas and Types
Project Land Use Pre‐Project Conditions Proposed Project Conditions
Section 5 Potential Project Impacts and Project Design Features
5‐7
Component Area (Acre)
Percent of Total Area
Area (Acre) Percent of Total
Area
ConRAC
commercial 1 1% 37 49%
transportation 21 28% 35 47%
mixed residential 3 4% 0 0%
open space 50 67% 3 4%
total 75 30% 75 96%
ITF East
commercial 9 28% 0 0%
transportation 5 16% 27 84%
mixed residential 4 13% 0 0%
open space 14 44% 5 16%
total 32 47% 32 84%
APM
Maintenan
ce
and Storage
Facility
commercial 3 15% 0 0%
transportation 4 20% 8 40%
open space 13 65% 9 45%
industrial 0 0% 3 15%
total 20 35% 20 55%
ITF West
commercial 0 0% 0 0%
transportation 69 97% 70.2 99%
open space 2 3% 0.8 1%
industrial 0 0% 0 0%
total 71 97% 71 99%
Source:RicondofacilitymapandArcGISaerialimagery(accessed2015)
UndertheproposedProject,theestimatedannualtotalpollutantloadgeneratedwithintheprojectareawouldincreaseforallconstituentsevaluatedcomparedtoexistingpre‐projectconditions.TheAPMmaintenancefacilityisconsideredanindustrialbuildingbeingplacedonopenspace;withacommercialareaadjacenttotheproposedfacility.TheConRACandEastITF,tobedevelopedintheManchesterSquarearea,wereconsideredtobeconstructedonopenspacewithaportionofmixedresidentialandtransportationlandusestodeterminethemaximumloadvolume.DevelopmentoftheManchesterSquareareawouldincreasetheoverallpercentofimpervioussurfacesbyconvertingopenspaceandresidentiallandusetopredominantlycommercialandtransportationlanduses.PortionsoftheAPMMaintenanceandStorageFacilityandConRACmaybecoveredbyaroof,andanypotentialindustrialactivitieswithinthesefacilitieswouldbeunlikelytocontributetothisincreaseduetoroofrunoffcontrol.
PollutantloadsdischargedtoDominguezChannelbysurfacewaterrunoffwouldincreaseintheabsenceofanycontrolmeasures.ThelargestpercentileincreasesduetoProjectconstructionareforoilandgrease,lead,zinc,andammoniaasshowninTable5‐5.
Section 5 Potential Project Im
pacts and Project Design Features
5‐8
Tabl
e 5-
5: P
ollu
tant
Run
off
Conc
entr
atio
ns (l
b/yr
) or
Mos
t Pr
obab
le N
umbe
r (M
PN)
Drainage Area
TSS
Total
Phosphorus
TKN
Total
Copper
Total
Lead
To
tal
Zinc
Oil an
d
Grease
BOD
COD
Ammonia
Fecal Coliform
(M
PN)
Fecal Enterococcus
(MPN)
ConRAC
Pre‐Project
9,503
16
77
1.94
0.22
8
58
953
1,859
13
2.90E+13
3.06E+12
Proposed Project
12,025
64
409
7
2.29
40
484
3,715
11,388
120
2.96E+14
4.11E+13
Percent Change
from Pre‐Project
26.5%
306.9%
432.9%
279.2%
934.6%
401.8%
733.3%
289.9%
512.7%
791.0%
923.7%
1245.8%
ITF East
Pre‐Project
4,469
10
71
1
0
6
53
685
1,892
20
3.40E+13
5.00E+12
Proposed Project
5,700
24
104
3
1
15
157
1,177
2,694
16
7.58E+13
7.40E+12
Percent Change
from Pre‐Project
27.5%
127.6%
45.7%
161.3%
57.0%
154.9%
198.7%
71.9%
42.4%
‐20.9%
123.1%
47.9%
APM M
aintenance Facility
Pre‐Project
2,746
5
26
1
0
2
21
301
670
6
1.24E+13
1.69E+12
Proposed Project
3,979
8
41
1
0
6
39
443
1,045
7
2.19E+13
3.34E+12
Percent Change
from Pre‐Project
44.9%
73.7%
56.8%
67.1%
96.2%
160.5%
88.5%
47.1%
55.9%
11.5%
76.1%
97.8%
ITF West
Pre‐Project
12,205
65
281
8
1
43
454
3,124
7,389
43
2.19E+14
2.13E+13
Proposed Project
12,111
67
289
9
1
44
469
3,195
7,587
44
2.26E+14
2.20E+13
Percent Change
from Pre‐Project
‐0.8%
2.6%
2.5%
2.6%
3.3%
3.0%
3.3%
2.3%
2.7%
2.5%
3.3%
3.2%
All Drainage Facilities
Pre‐Project
28,923
96
456
12
2
59
585
5,063
11,810
83
2.94E+14
3.10E+13
Proposed Project
33,815
162
842
20
4
106
1,149
8,530
22,714
187
6.20E+14
7.39E+13
Percent Change
from Pre‐Project
16.9%
69.4%
84.8%
65.9%
114.7%
78.8%
96.3%
68.5%
92.3%
125.7%
110.8%
137.9%
Section 6 Potential Project Impacts and Project Design Features
5‐9
InTable5‐5,thespecificlandusetypesfactorintotheEMCcalculationsastherunoffvolumeofeachcontaminantisweightedpertheappropriateboundariesofeachlanduseinthedrainagearea.ThetotalannualrainfallintheLAXareaisrecordedbytheWesternRegionalClimateCenter(WRCC,2015).Theaveragerainfallbetweentheyears1936to2015is12.02inches;thisvaluewasmultipliedbytheProjectareaandEMCvaluestodeterminepollutantloading.Multiplyingtheannualrainfallbythemeanconcentrationsyieldsacontaminantrunoffvolume.
Increasesinestimatedloadswouldrangefrom96percentforoilandgreaseto17percentforTSS.AlthoughEMCvaluesforTSSundertransportationlandusearelessthanopenspace,conversionfromopenspacetotransportationwouldresultingreaterestimatedTSSloadsasaresultofincreasesinimperviousarea,whichwouldgeneratelargerrunoffcoefficientsandmoreaverageannualrunoffs.Similarly,changestolandusewiththeadditionofanAPMmaintenancefacility,WestITF,andotherProjectcomponentsarepredictedtoproducegreaterestimatedloadsforallconstituents.TSS,however,isreducedasaresultoftheproposedWestITFdevelopment.ThisdevelopmentwoulddecreaseTSSby0.8percent.SincemodernizationinthewesternportionsoftheProjectareawouldbeonpreviouslyexistingimpervioussurface,developmentinthisregionwouldresultinsmallerincreasesinthepercentofimpervioussurfaces.
Overall,theproposedProjectwouldincreasepollutantloadingduetotheeffectsoflanduseintensificationandchangesinimperviousarea,andrelativeincreasesandpercentagechangesincontaminantloading.
BMPstoaddressstormwaterquantityandqualityassociatedwithdevelopmentoftheproposedProjectwouldbedefinedinconjunctionwithmeetingLIDOrdinancerequirements.TheoverallBMPprogramfortheProjectwouldbesizedtomeettheLIDspecificationsrelativetoaddressingrunoffvolumesforthe85thpercentilestormevent,whichisapproximately1‐inchin24‐hours.Table5‐6delineatestherunoffvolumeassociatedwiththe85thpercentilestormeventthatwouldneedtobeaddressedintheBMPprogramforeachProjectcomponent.AsnotedaboveinSection2.2.4,theSUSMPrequiresthatredevelopmentprojectsthatcreate,add,orreplace5,000squarefeetormoreofimperviousareaonanalreadydevelopedsitearesubjecttothesameconditionsasnewdevelopmentprojects.Assuch,thewaterqualityvolumespresentedinTable5‐6aredeterminedbyassumingallnewdevelopmentis100%imperviousandtheentirefootprintmustbeaccountedfor;newroadwaysandAPMguidewayareasarebrokenoutfromaggregateddrainageareasandincludedseparatelyinthiscalculation.
Table 5-6: Runoff Volume for the 85th Percentile Storm
Project Component Total Area (acres) Volume to be Mitigated (ft3)
ConRAC 67 220,000
ITF East 21 70,000
ITF West 14 45,000
APM Maintenance and Storage Facility
2.2 7,000
Roads 39 130,000
APM Guideway 16.5 54,000
Roads near South Airfield 1.7 5,600
Section 5 Potential Project Impacts and Project Design Features
5‐10
5.2.1.2 Project Design Features
TheproposedundergroundcisternsbeneaththeConRACfacility,introducedinSection5.1.2,aresizedtohold500,000ft3,avolumemorethantwicetheamountneededtoaddressthewaterqualitytreatmentvolumeof220,000ft3associatedwiththatProjectcomponent.Cisternwaterwouldbetreatedandusedforcarwashingon‐site;suchreuseofstormwaterisconsistentwithgoodwaterqualitymanagementpracticesandwouldmeetLIDrequirements.
5.2.2 Stormwater Flows AsdescribedaboveinSection5.2.1,implementationoftheproposedProjectwouldresultinincreasedpollutantflowsinstormwaterrunoff.ThedesignoftheproposedConRACfacilityincludestheuseofundergroundcisternsthatcollect,store,andsupporton‐sitereuseofstormwater,whichwouldmeetLIDrequirementsandfullyaddressthestormwaterqualityimpactsassociatedwiththatProjectcomponent.ThewaterqualityimpactsoftheConRACwouldbelessthansignificantbecausepollution,contaminationornuisanceasdefinedinSection13050oftheCWCorviolationofregulatorystandardsasdefinedintheapplicableNPDESstormwaterpermitorWaterQualityControlPlanforreceivingwaterbodywouldbeminimized..
SpecificwaterqualityBMPswouldbeidentifiedduringmoredetailedprojectplanninganddesignfortheothercomponents,inconjunctionwithmeetingLIDrequirements;however,inthecurrentabsenceofsuchdesignfeaturesforthoseothercomponents,thestormwaterqualityimpactsassociatedwiththoseaspectsoftheProjectareconsideredtobesignificant.Section6belowidentifiesmitigationmeasuresforthoseimpacts.
5.2.3 Dry Weather Flows ProjectedsourcesofdryweatherflowswithintheProjectareaareassociatedwithactivitiesthatincludeoutdoorcleaningandmaintenanceofrentalvehicles;maintenanceoftheAPMsystemandequipment;andbuildingandgroundsmaintenance.TheseactivitiescouldpotentiallyresultinreleaseofspillsandleaksofhazardousmaterialstotheDominguezChannelwatersheds.Compliancewithexistingregulationsandairportprocedures,particularlytheLAXSWPPPwhichwouldbeupdatedtoincludethenewfacilities,wouldreducethelikelihoodofanydryweatherdischargesandthepotentialimpactsassociatedwithhazardousmaterialsspills.Withsuchcontinuedcompliance,thepollutantloadgeneratedfromdryweatherflowswouldnotincreaseandtheassociatedimpactswouldbelessthansignificantbecausepollution,contaminationornuisanceasdefinedinSection13050oftheCWCorviolationofregulatorystandardsasdefinedintheapplicableNPDESstormwaterpermitorWaterQualityControlPlanforreceivingwaterbodywouldbeminimized..
5.2.4 Construction Runoff ConstructionoftheproposedProjectfacilitiesmaygeneratepollutantsourcesthatadverselyaffectwaterquality,includingerosion‐inducedsediments,nutrients,tracemetals,toxicchemicals,andconstructionwaste.BecauseimprovementsundertheproposedProjectwouldaffectanareagreaterthanone‐acre,LAWA'sexistingconstructionpolicywouldrequirethedevelopmentofproject‐specificconstructionSWPPPsincompliancewiththeState'sGeneralConstructionPermit.TemporaryconstructionBMPsthatwouldlikelybeconsideredandincorporatedintoeachproject‐specificSWPPP,asappropriate,wouldinclude:
Section 6 Potential Project Impacts and Project Design Features
5‐11
Soilstabilization(erosioncontrol)techniquessuchasseedingandplanting,mulching,andcheckdams
Sedimentcontrolmethodssuchasdetentionbasins,siltfences,anddustcontrol
Contractortrainingprograms
Materialtransferpractices
Wastemanagementpracticessuchasprovidingdesignatedstorageareasandcontainersforspecificwasteforregularcollection
Roadwaycleaning/trackingcontrolpractices
Vehicleandequipmentcleaningandmaintenancepractices
Fuelingpractices
ByfollowingtheproceduresoutlinedintheSWPPPandemployingtheappropriateBMPsfromthelistaboveandanyadditionalBMPsrequiredinproject‐specificconstructionSWPPPs,impactstowaterqualityassociatedwithconstructionactivitieswouldbelessthansignificantbecausepollution,contaminationornuisanceasdefinedinSection13050oftheCWCorviolationofregulatorystandardsasdefinedintheapplicableNPDESstormwaterpermitorWaterQualityControlPlanforreceivingwaterbodywouldbeminimized..
Section 5 Potential Project Impacts and Project Design Features
5‐12
Thispageintentionallyleftblank.
Section 6 Mitigation Measures
6‐1
Section 6
Mitigation Measures and Design Features
ProjectimpactsandproposeddesignfeatureswerediscussedinSection5.Designfeatureshavenotbeenproposedforallprojectelements,andmitigationmeasuresdiscussedinthissectionprovideabasisforreducingthehydrologyimpactstolevelsthatarelessthansignificant.
6.1 Drainage Mitigation Measures Potentialdrainage(flooding)impactsduringthe10‐yearstormthatresultfromtheproposedProjectwouldbemitigatedinoneoffollowingthreeways,orsomecombinationthereof:
1. DetainorreduceonsiteProject‐relatedflowsinordertomaintainexisting(pre‐Project)downstreampeakdepths;
2. Re‐routeflowsthroughabypassdrain,orconnectanewstormdraintothelargerstormdrain;or
3. Constructimprovementstotheexistingstormwaterdrainagesystemsegments/facilitieswheredeficienciesexist.
Thefollowingidentifiespotentialoptionsforeachofthesethreewaystoreduceimpacts,recognizingthattheselectionandrefinementofaparticularoptionforimplementationwouldbedeterminedinconjunctionwiththemoredetailedplanning,design,andpermittingofeachProjectcomponent.
6.1.1 Detain/Reduce Project‐Related Stormwater Flows Thestoragevolumesneededtomaintainpre‐projectdownstreampeakdepthsforthe10‐yearstormareportrayedinTable6‐1.Projectdesignfeaturevolumesassociatedwitheachfacilityareshown,andTable6‐1indicatesthattheConRACcisternsreducetheamountofremaining10‐yearstormvolumetobemitigated.
Table 6-1: 10-year Storm Mitigation Volumes
Component Detention Volume Required (ft3)
Project Design Feature Volume (ft3)
Remaining Volume to be Mitigated (ft3)
Manchester Square 571,000 500,000 71,000
East ITF 200,000 0 200,000
West ITF 94,000 0 94,000
APM Maintenance Facility 23,000 0 23,000
Roads near South Airfield 0 0 0
Atotalvolumeof571,000ft3isrequiredtofullymitigateimpactsforthe10‐yearstormfortheConRAC.The500,000ft3cisternstorageincorporatedintothefacilitydesignalleviatessomeof
Section 6 Mitigation Measures
6‐2
theimpacts,butanadditional40,000ft3ofdetentioninthenorthand31,000ft3inthesouthisneeded.
Inadditiontotheoptionofon‐sitedetentionofstormwater,above‐grademeasurestoreducedrainageimpactsincludedecreasingtheimperviousareaofadevelopmentand/ordivertingrunoffwatertoperviousareas.AsfurtherdescribedbelowinSection6.2,potentialoptionsforwaterqualityBMPsinclude,butarenotlimitedto,biofiltration,infiltration,evapotransporation,andvariouswaterqualitystructuraltreatmentsystems,allofwhichcanalsoservicetoreducepeakflowsfromtheProjectandmitigatedrainage/floodingimpacts.
6.1.2 Reroute Stormwater Flows InconjunctionwithmoredetailedengineeringanddesignofdrainageinfrastructureimprovementsassociatedwiththeProjectcomponents,moredetailedevaluationsoftherunoffcharacteristicsofeachcomponentrelativetothereceivingstormdrainlinescanbeconductedtoassessthepotentialforreroutingflows,eitherbymodifyingexistingorproposedsurfaceelevationsanddirectionsoffloworbyinstallationofnewstormdrainlinesonsitetocarryrunofftoexistingstormdrainthathavesufficientdownstreamcapacity.
6.1.3 Construct Improvements to Existing Stormwater Drainage System Aspartofthedetailedplanninganddesignoftheproposedfacilities,LAWAwouldevaluateandidentifyimprovementstosegmentsoflocalstormdrainsystemshavingexistingorfuturepeakflowsthatexceedthedesigncapacityofthefacilities.AsapartoftheproposedProject,LAWAwouldconstruct,orsupportonafair‐sharebasis,improvementsneededtoaddressexistingorfuturedeficienciesandaccommodatestormwaterattributabletotheProject.
InaddressingtheexistingdownstreamdrainagedeficienciesattheDominguezChanneloutlet,whichisaCountyregionalfacility,LAWAwouldworkincoordinationwiththeCountyandotheraffectedjurisdictionsinthedevelopmentofacomprehensivesolutiontothatdeficiency,understandingthatLAWA’sparticipationinimplementingsuchasolutionwouldneedtobeonafair‐sharebasisinlightoftheProject’scontributiontoincreasedflows.Table6‐2outlinesmeasuresthatLAWAcouldimplementtomitigatethesignificantimpactsoftheproposedProjectonexistingdrainagedeficienciesidentifiedinSection3.3.3.
Section 6 Mitigation Measures
6‐1
Table 6-2: Potential Drainage Improvement Options
Capacity Restriction
Design Storm for which Restriction Occurs
Proposed Solution
Section along 96th street and Airport Boulevard, and
Century Boulevard storm drain1
10‐yr Approximately 6,100 LF of replacement storm drains would be coordinated with roadway improvements for the proposed Project facilities. These upgraded storm drains are recommended along Westchester Pkwy., Airport Blvd., and 96th Street.
La Cienega between 104th and 111th street for the Project 13
conduit2
50‐yr FAA, LACDPW, and City of Los Angeles design criteria require that storm
drains provide flood protection capacity for the 10‐year storm event.
Table 5‐2 lists the volume of stormwater detention that would be
required in order to maintain the pre‐project downstream peak depths
for the 10‐year design storm. By installing these detention volumes on‐
site, the proposed Project components are not expected to increase
flooding along the Project 13 Conduit.
The capital flood protection level requires that Dominguez Channel has
the capacity to convey runoff from a 50‐year storm frequency, proposed
Project facilities are not expected to increase peak flows in to Dominguez
Channel. However, LAWA would support any additional detention or
additional storm drain installation on a fair‐share basis.
Source: 1CDP, 2005; 2PB, 2002
ThroughimplementationofoneormoreoftheaboveoptionsforaddressingincreasedflowsassociatedwiththeproposedProject,withtheresultbeingtoavoidanincreaseinrunoffthatwouldcauseorexacerbatefloodingwiththepotentialtoharmpeople,damageproperty,orexceedthecapacityofexistingorplannedstormwaterdrainagesystems,thehydrologyimpactsoftheprojectwouldbereducedtolessthansignificant.
6.2 Water Quality Design Features AspartoftheproposedProjectduringtheplanninganddesignoftheproposedProjectfacilities,LAWAwouldselectandsizewaterqualityprotectionfeaturesthatmeettherequirementsoftheLIDOrdinanceandtheNPDESPermit.PrioritywillbegiventoLIDBMPs.TheLosAngelesLIDManualprovidesrequirementsandguidancefortheselectionandsizingofBMP’sforagivenstormvolumegivenuserinputparameterssuchassoilporosity,depthofinfiltrationallowed,andthepondingtime.ThesesizingmethodsarecombinedwithresearchdonetoestablishthepollutantremovalefficacyofmanyBMPtypes.Overthepast10years,lowimpactdevelopmentBMPshavebeenimplementedforstormwatermanagementandwaterpollutioncontrol.LIDconsistsofbestmanagementpracticesthataimtoreducetheimpactsofincreasesinstormwaterrunoffthroughtheuseofnaturalandstructuralsystemsforinfiltration,evapotranspiration,andretention.SeveralBMPsarelistedinTable6‐3alongwithpollutantremovalefficienciesbasedonscientificreportsfromfederalandlocalagencies(EWMP,2015).Infiltration‐basedBMPsandevapotranspiration(orotherreuse)BMPs,foraneventequivalenttothe85thpercentilestorm,wouldremove100percentofallpollutantsinthefractionofrunoffdetained.ForotherLID‐basedBMPsandotherBMPs,lessthan100percentofpollutantsareremoved.However,thevaluesin
Section 6 Mitigation Measures
6‐2
Table6‐3showthatovertimeforavarietyofstormevents,thepercentremovedcanfallbelow100percent.
Section 6 M
itigation M
easures
6‐3
Tabl
e 6-
3: T
ypic
al P
ollu
tant
Rem
oval
for
BM
Ps (p
erce
nt)
BMP Category
BMP Type
Total Suspen
ded
Solid
s Nitrogen
Phosphorus
Total Cu
Total Zn
Total
PB
Oil an
d
Grease
Source of Data1
A
B
A
B
A
B
A
B
A
B
A
A
LID Biofiltration
BMPs
Biosw
ales
49
30
‐106
63
77
68
Biofiltration Strip
69
‐10
‐46
85
72
88
Bioretention
59
46
5
81
79
Wetlands
72
24
48
47
42
LID Infiltration
BMPs
Infiltration
89
42
65
86
66
Surface Sand Filters
81‐90
9‐32
39‐44
50‐66
80‐92
85‐87
LID
Evapotranspiration
BMPs
Extended
Detention
Basins (Unlined
) 72
14
39
58
73
72
Extended
Detention
Basins (Lined
) 40
14
15
27
54
30
Wet Basin Storm
(Wet
Weather)
94
51
5
89
91
98
Wet Basin Base Flow
(Wet Weather)
21
43
49
54
62
62
Wet Pond
80
31
52
57
64
Dry Pond
49
24
20
29
29
Other BMPs
Multi‐Cham
bered
Treatm
ent Train
75
0
18
35
75
74
Inlet Insert
3‐14
0‐2
1‐2
1‐7
Continuous Deflective
Separators (CDS)
0
5
15
8
17
11
Oil Water Sep
arator
49
2
2
7
89
1 DatasourceAwasextractedfrom
theCaltransBMPRetrofitPilotProgram
;Breferstodatafrom
theCenterforWatershedProtection
Source:EWMP(2015).
7‐1
TheselectionanddesignofBMPswoulddeterminethepercentpollutantremoval,whichinturnaffectsthepollutantloaddischargedtothereceivingwaterbodies.VariousstudieshaveproposeddifferenttypesofBMP’sfortheproposedProjectarea.HighconcentrationsofzincareaffiliatedwithstormwaterrunoffintheDominguezChannelarea,andgreenstreetswereproposed,inthe2015EWMP,inthegeneralareaoftheproposedProjectfacilities.Inaddition,theConceptualDesignPlan(CDP;LAWA,2005)preparedforLAWAtosupporttheoriginalMasterPlanidentifiedseveralBMPoptionsfortheDominguezChannelNorthdrainageareabasedonsite‐specificwatershedcharacteristicsincludingvegetatedswalesandbioretentionforareaparkinglotsandITFareas.
Table6‐4presentsthewaterqualityvolumerequirements.. ForallProjectcomponents,LIDBMPsofadequatesize,orcaptureandreusealternatives,wouldbeincorporatedtoaddressthevolumesshowninTable6‐4.
Table 6-4 Volume Requirements for On-site Alternatives
LAMP Component Water Quality
Requirement (ft3) Project Design Feature
Volume (ft3) Remaining Volume (ft3)
CONRAC 220,000 500,000 0
ITF East 70,000 0 70,000
ITF West 45,000 0 45,000
APM Maintenance Facility 7,000 0 7,000
APM Track (entire length) 54,000 0 54,000
New Roadways 130,000 0 130,000
APMtrackandproposedroadwaysarebeingdesignedwithnewstorm‐drainstosufficientlyattenuateflowsinordertomaintainpeakflowdepthsfurtherdownstream.However,boththetrackandroadswouldalsoincludewaterqualitymeasuresaslistedinTable6‐4.
Tocaptureandinfiltrate,reuseorbiotreattheremainingvolumefortheManchesterSquarearea,additionalLIDBMPswouldberequired.ForallotherProjectcomponents,LIDBMPswouldbeincorporatedofsufficientsizetoaddressthevolumesshowninTable6‐4.BMPswouldbeevaluatedandselectedfromthoseidentifiedintheLIDManualorotherequivalentBMPs.ThelistofBMPsmayinclude:
Infiltrationbasins
Infiltrationtrenches
Permeablepavementswithanunderdrain
Permeablepavementswithoutanunderdrain
Bioretention
Bioretentionwithunderdrain
Drywells
Section 7 References
7‐2
Planterboxes
Bioinfiltration
Vegetatedswalesandstrips
Wetponds
Constructedwetlands
Sandfilters
Extendeddetentionbasins
ImplementingBMPsassetforthintheLIDOrdinance,withthespecificsoftheBMPsassociatedwitheachProjectcomponenttobedefinedinconjunctionwiththedetailedplanning,design,engineering,andpermitting,particularlytheLID/SUSMPcomplianceprocess,wouldassurethepotentialwaterqualityimpactsassociatedwithdevelopmentofproposedProjectwouldbelessthansignificantbecausepollution,contaminationornuisanceasdefinedinSection13050oftheCWCorviolationofregulatorystandardsasdefinedintheapplicableNPDESstormwaterpermitorWaterQualityControlPlanforreceivingwaterbodywouldbeminimized.
ItshouldbenotedthatwhiletheabovediscussionpertainstothemitigationneedsandpotentialoptionsassociatedwiththeproposedLAMPfacilities,asmayoccurinconjunctionwithdevelopmentofeachofthosefacilities,LAWAhasinitiateddevelopmentofacampus‐wide(i.e.,LAXandassociatedLAWA‐ownedproperties)StormwaterManagementPlan,asindicatedaboveinSection1.1.ThatStormwaterManagementPlanwilltakeintoaccounttheproposedLAMPProjectfacilitiesandinfrastructure.WhilecertainBMPsareconceptuallyidentifiedintheframeworkofthecampus‐wideStormwaterManagementPlan,theyarenotformallylocatedordefinedyet,asamoredetailedanalysiswillbecompletedduringfacilityplanninganddesigninconcertwiththedevelopmentofthecampus‐wideStormwaterManagementPlan.Assuch,otherpotentialoptionsforaddressingthehydrologyandwaterqualityimpactsassociatedwiththeLAMPProjectmaybeidentifiedaspartofalarger,morecomprehensivedrainageandwaterqualitymanagementprogram,beyondthosepresentedabove.
6.3 Summary of Volume Requirements for On‐Site Mitigation
Table6‐5summarizesthevolumeofstormwaterthatwouldrequiremanagementinordertomeetthewaterqualitytreatmentrequirementforeachLAMPfacility,aswellastheadditionalon‐siterunoffstorage/detentionthatwouldbeneededasamitigationmeasureinordertofullymitigatepeakrunoffdepthdownstreamforthe10‐yearstormevent.AsdescribedaboveinSection6.1,itisalsopossiblethatmitigationofhydrologyimpactscanoccurthroughotheroptionsthatmayoccuroffsite.
"Click here to type section #" "Click here to type title of section"
G‐3
Table 6-5 Volume Requirements for On-site Alternatives
LAMP Component Water Quality Requirement
Additional Drainage Requirement
Total
CONRAC 220,000 ft3 351,000 ft3 571,000 ft3
ITF East 70,000 ft3 130,000 ft3 200,000 ft3
ITF West 45,000 ft3 49,000 ft3 94,000 ft3
APM Maintenance Facility 7,000 ft3 16,000 ft3 23,000 ft3
APM Track (entire length) 54,000 ft3 New Storm Drains 54,000 ft3
New Roadways 130,000 ft3 New Storm Drains 130,000 ft3
LAWAcouldcompleteacampus‐wideStormwaterManagementPlanthatincorporatestheproposedProjectfacilitiesandinfrastructure.WhilecertainBMPsareconceptuallyidentifiedinthisdocument,theyarenotformallylocatedasamoredetailedanalysiswillbecompletedduringfacilityplanninganddesigninconcertwiththedevelopmentofthecampus‐wideSMP.
Section 7
References
CaliforniaDepartmentofWaterResources.DWR.2015.BestAvailableMaps.http://gis.bam.water.ca.gov/bam/
CaliforniaRegionalWaterQualityControlBoard.(1994).WaterQualityControlPlanLosAngelesRegion:BasinPlanfortheCoastalWatershedsofLosAngelesandVenturaCounties.Availableat:http://www.waterboards.ca.gov/losangeles/water_issues/programs/basin_plan/basin_plan_documentation.shtml
CampDresser&McKeeInc.2001.HydrologyandWaterQualityTechnicalReport,LAXMasterPlanEIS/EIR.
CDMSmithinassociationwithVCAEngineers,Inc.,2015.LAXStormwaterManagementPlanExistingConditionsAssessment.
CityofLosAngeles.2006.L.A.CEQAThresholdGuide:YourResourceforPreparingCEQAAnalysesinLosAngeles.Availableat:<http://www.environmentla.org/programs/Thresholds/Complete%20Threshold%20Guide%202006.pdf>
CityofLosAngeles.2011.DevelopmentBestManagementPracticesHandbook,LowImpactDevelopmentManual,PartB.
CityofLosAngeles.2013.FinalLAXSpecificPlanAmendmentStudyReportforLosAngelesInternationalAirport(LAX)SpecificPlanAmendmentStudy.Availableat:
Section 7 References
7‐4
<http://www.lawa.org/uploadedFiles/SPAS/PDF/LAX%20SPAS%20Final%20SPAS%20Report%20Document%20Final%20CD‐Web%20Version%2001%2030%202013.pdf>
CityofLosAngeles,LosAngelesWorldAirports,LAXLandsideAccessModernizationProgramDraftEIRNoticeofPreparation/InitialStudy.February5,2015.Available:http://connectinglax.com/files/LAX.LAMP.Initial.Study_2015.pdf
CityofLosAngelesBureauofEngineering.1973.StormDrainDesignManual‐PartG.Availableat:<http://eng.lacity.org/techdocs/stormdr/Index.htm>[Dateaccessed:October28,2015]
CountyofLosAngelesDepartmentofPublicWorks.2014.LowImpactDevelopmentStandardsManual.Availableat:<https://dpw.lacounty.gov/ldd/lib/fp/Hydrology/Low%20Impact%20Development%20Standards%20Manual.pdf>
CTC&AssociatesLLC.2007.GrassSwales:GaugingTheirAbilitytoRemovePollutantsfromHighwayStormwaterRunoff.WisconsinDepartmentofTransportation.
DominguezChannelWatershedManagementAreaGroup.2015.EnhancedWatershedManagementProgram.
LosAngelesDepartmentofPublicWorks(LADPW).2014.GuidelinesforDesign,Investigation,andReportingLowImpactDevelopmentStormwaterInfiltration.Availableat:<http://ladpw.org/gmed/permits/docs/policies/GS200.1.pdf>
LosAngelesWorldAirports(LAWA).1996.HydrologyandWaterQuality.Availableat:<http://www.lawa.org/uploadedFiles/OurLAX/Past_Projects_and_Studies/Past_Publications/FEIS_EIR_Part1‐17_0407_HydrologyandWaterQuality.pdf>
LosAngelesInternationalAirport(LAWA).2005.SouthAirfieldImprovementProjectDraftEnvironmentalImpactReport(DraftEIR).
LosAngelesInternationalAirport(LAWA).SPASDraftEIR,Section4.8HydrologyandWaterQuality.Availableat:<http://www.lawa.org/uploadedfiles/spas/pdf/SPAS%20DRAFT%20EIR/LAX%20SPAS%20DEIR%2004.08%20Hydrology%20Water%20Quality.pdf>[Dateaccessed:October28,2015]
LosAngelesCountyDepartmentofPublicWorksHydrologyManual.2006.Availableat:<http://dpw.lacounty.gov/wrd/publication/engineering/2006_Hydrology_Manual/2006%20Hydrology%20Manual‐Divided.pdf>
NPDESStormWaterProgram.1993.(http://www3.epa.gov/npdes/pubs/owm0250.pdf)
ParsonsBrinckerhoffQuadeDouglas,Inc.2002.FinalOn‐siteHydrologyReportforLosAngelesInternationalAirport.
StateWaterResourcesBoardofCalifornia(2000).StandardUrbanStormWaterMitigationPlanforLosAngelesCountyandCitiesinLosAngelesCounty(SUSMP).Availableat:
"Click here to type section #" "Click here to type title of section"
G‐5
http://www.swrcb.ca.gov/losangeles/water_issues/programs/stormwater/susmp/susmp_rbfinal.pdf
TMDLsfromUSEPA:
http://iaspub.epa.gov/tmdl_waters10/attains_waterbody.control?p_list_id=CAE4051200020050203154519&p_cycle=9999&p_report_type=#tmdls
http://iaspub.epa.gov/tmdl_waters10/attains_waterbody.control?p_list_id=CAR4051200019980918161017&p_cycle=2012&p_report_type=#tmdls