iv.g hydrology and water quality - la city planning€¦ · iv.g surface water hydrology, surface...

CityofLosAngeles IV.G‐1 BarlowHospitalReplacementandMasterPlanProjectENV2009‐2519‐EIR DraftEIR. April2012

IV.G SURFACE WATER HYDROLOGY, SURFACE WATER QUALITY, AND GROUNDWATER

1. INTRODUCTION

This section describes the potential impacts of the proposed Barlow Replacement Hospital and

Master Plan Project on surface hydrology and water quality on the Project site and in the

surroundingarea.ThissectionincorporatesandsummarizesinformationcontainedintheBarlow

Replacement Hospital & Master Plan Hydrology technical report prepared by KPFF Consulting

Engineers(December2010).AcopyofthereportisprovidedinAppendixIV.GofthisDraftEIR.

2. REGULATORY SETTING

a. Federal Regulations

i. Clean Water Act

TheCleanWaterAct,formerlyknownastheFederalWaterPollutionControlAct,wasestablished

in1948andamendedinthe1960s,1970s,andthe1980s.TheActistheprimaryregulationatthe

national level for the management of water quality, and its chief goal is the restoration and

maintenanceofthechemical,physical,andbiologicalintegrityofthenation’swaters.Accordingly,

the Act sets forth objectives for themanagement ofwater quality that include the regulation of

pollutants and toxic pollutants discharges; ensuring water quality that protects and fosters the

propagationoffish,shellfish,andwildlife;developingwastetreatmentmanagementprograms;and

developingandimplementingprogramsforthecontrolofnon‐pointsourcesofpollution.

Amendments to theAct in1972established theNationalPollutantDischargeEliminationSystem

(NPDES)permitprogram,whichprohibitsdischargeofpollutantsintothenation’swaterswithout

procurement of a NPDES permit from the U.S. Environmental Protection Agency (U.S. EPA).

Although federallymandated, the NPDES permit program is generally administered at the State

level. As discussed below under the Porter CologneWater Quality Control Act, in California, the

State delegates authority for implementation of the NPDES permit program to its nine Regional

Water Quality Control Boards (RWQCBs). With the 1977 amendment requiring State‐level

developmentofBestManagementPractice(BMP)programs,theActbecamecommonlyknownas

theCleanWaterAct(CWA).

TheWaterQualityActof1987addedSection402(p) to theCWA,whichdirected theU.S.EPA to

establish requirements for stormwater discharges from municipal and industrial sources. In

IV.G Surface Water Hydrology, Surface Water Quality, and Groundwater


responsetothe1987amendment,PhaseIoftheU.S.EPA’sNPDESProgramrequirespermitsforthe

following:

1. Municipalseparatestormsewersystemsgenerallyserving,orlocatedin,incorporatedcities

with100,000ormorepeople(referredtoasMS4permits);

2. Elevenspecificcategoriesofindustrialactivity(includinglandfills);and

3. Constructionactivitythatdisturbs5acresormoreofland.

InMarch2003,PhaseIIoftheNPDESProgramextendedrequirementsforpermitstothefollowing:

1. Numeroussmallmunicipalseparatestormsewersystems;

2. Constructionsitesbetween1and5acres;and

3. Industrial facilitiesownedoroperatedbysmallmunicipal separatestormsewersystems,

whichwerepreviouslyexemptedfromstormwaterpermitting.

Section 402 (p) of the CleanWater Act mandates that Municipal Separate Storm Sewer System

(MS4)permitsmust (1) effectivelyprohibit thedischargesof non‐stormwater to the stormwater

system, except under certain circumstances; and (2) require controls to reduce pollutants in

discharges from the stormwater system to the maximum extent practicable, including best

managementpractices,controltechniques,andsystem,design,andengineeringmethods.Although

mandated at the federal level, the permits are issued byRWQCBs tomunicipalities or groups of

municipalitiesencompassinglargemetropolitanareas,andpermitrequirementsareimplemented

locallybythosemunicipalities.

ii. National Flood Insurance Act

TheNationalFloodInsuranceActestablishedtheNationalFloodInsuranceProgram,whichisbased

ontheminimalrequirementsforfloodplainmanagementandisdesignedtominimizeflooddamage

withinSpecialFloodHazardAreas.AccordingtotheFederalEmergencyManagementAgencyFlood

InsuranceRateMap, theentireProject site is inanareaofminimal flooding (FloodZoneC), and

thereforedoesnotrequirefloodinsurance.



b. State Regulations

i. Porter‐Cologne Water Quality Control Act (California Water Code)

ThePorter‐CologneWaterQualityControlActof1969establishedtheprincipalStateprogramfor

waterqualitymanagementandauthorizestheSWRCBtoimplementtheprovisionsoftheFederal

CleanWaterAct.ThePorter‐CologneActdividedthestateintonineRegionalWaterQualityControl

Board(RWQCB)areasoperatingundertheCaliforniaEnvironmentalProtectionAgency(CalEPA).

EachRWQCBimplementsandenforcesprovisionsof thePorter‐CologneActandtheCleanWater

Act subject topolicy guidanceand reviewby theSWRCB.TheProject site is located inRegion4,

whichisgovernedbytheLosAngelesRegionalWaterQualityControlBoard(LARWQCB).

Section13050ofthePorter‐CologneWaterQualityControlActdefinespollution,contamination,or

nuisance. Pollution is defined as alteration ofwater quality such that it unreasonably affects the

water’sbeneficialuses;contaminationisdefinedasimpairmentofwaterqualitytothedegreethat

itcreatesahazardtopublichealth;andanuisanceisdefinedasanythingthatisinjurioustohealth,

offensivetothesenses,anobstructiontopropertyuse,andwhichaffectsaconsiderablenumberof

people.

c. Local Regulations

i. County of Los Angeles Hydrology Manual

Drainage and flood control in the City of LosAngeles are subject to review and approval by the

BureauofEngineeringoftheCityofLosAngelesDepartmentofPublicWorks(BOE).Stormdrains

withintheCityareconstructedbyboththeCityandtheLosAngelesCountyFloodControlDistrict.

TheCounty’sFloodControlDistrictconstructsandhasjurisdictionoverregional facilitiessuchas

majorstormdrainsandopenfloodcontrolchannels,whiletheCityconstructsandisresponsiblefor

localinterconnectingtributarydrains.TheCountyDepartmentofPublicWorks’HydrologyManual

requiresthatstormdrainsbedesignedfor25‐yearstormevents,andcombinedstormdrain/street

flowsystemsbedesignedfor5‐yearstormevents.Propertiesrequiringsumpstodischargerunoff

arerequiredtobedesignedfora50‐yearstormevent.

DrainageandfloodcontrolstructuresandimprovementswithintheCityaresubjecttoreviewand

approvalbytheCity’sDepartmentofPublicWorks(DPW)andDepartmentofBuildingandSafety

(LADBS). As required by the Department of Public Works, all public storm facilities must be

designedinconformitywiththestandardssetforthbyLosAngelesCounty.TheCity’sDepartment

of Public Works reviews and approves storm drain plans prior to construction. Any proposed



increasesindischargedirectlyintoCountyfacilities,orproposedimprovementstoCountyfacilities,

requireapproval fromtheCounty’sFloodControlDistrictdepartment toensurecompliancewith

theCounty’sMunicipalNPDESPermitrequirements.

ii. National Pollutant Discharge Elimination System (NPDES) Permit

Although federallymandated, responsibility for implementing theNPDESpermitprogramwithin

California is delegated to the State’s nine Regional Water Quality Control Boards (RWQCBs).

Administrationofthepermitprogramisdiscussedbelow.

Construction: Storm Water Pollution Prevention Plan (SWPPP)

The SWRCB adopted a General Permit for StormWater Discharges from Construction Activities

(ConstructionGeneral Permit) in 2004.1 The ConstructionGeneral Permit regulates construction

activityincludingclearing,grading,andexcavationofareas1acreormoreinsizeandprohibitsthe

discharge of materials other than stormwater, authorized non‐stormwater discharges, and all

dischargesthatcontainahazardoussubstance, unlessaseparateNPDESpermithasbeenissued

for thosedischarges. TheConstructionGeneral Permit requires that developers complywith the

followingrequirements:

1. Eliminateorreducenon‐stormwaterdischargestostormdrainsystemsandotherwatersof

theU.S.;

2. Developand implement aSWPPP that specifies theBMPs intended to reducepollution in

stormwater discharges in compliance with Best Available Technology Economically

Achievable/BestConventionalPollutantControlTechnologystandards;and

3. PerforminspectionsandmaintenanceofallBMPs.

ASWPPPismeanttoidentifypotentialsourcesandtypesofpollutantsassociatedwithconstruction

activityandlistBMPsthatwouldprohibitpollutantsfrombeingdischargedfromtheconstruction

siteintothepublicstormdrainsystem.BMPstypicallyaddressstabilizationofconstructionareas,

minimization of erosion during construction, sediment control, control of pollutants from

constructionmaterials, andpost‐construction stormwatermanagement (e.g., theminimization of

impervioussurfacesortreatmentofstormwaterrunoff).TheSWPPPisalsorequiredto includea

discussionoftheproposedprogramtoinspectandmaintainallBMPs.

1 StateWaterResourcesControlBoard,NationalPollutantDischargeEliminationSystem (NPDES)GeneralPermit for

StormWaterDischargesAssociatedwithConstructionActivity(NPDESNo.CAS000002).2004.



ToobtaincoverageundertheConstructionGeneralPermit,adeveloperisrequiredtofileaNotice

ofIntent(NOI)withtheappropriateRWQCBandprovideproofoftheNOIpriortoapplyingfora

grading or building permit from the local jurisdiction, and must prepare a State SWPPP that

incorporatestheminimumBMPsrequiredunderthepermitaswellasappropriateproject‐specific

BMPs.TheSWPPPmustbecompletedandcertifiedbythedeveloperandBMPsimplementedprior

to the commencement of construction, andmay requiremodification by a developer during the

courseofconstructionasconditionswarrant.Whenprojectconstructioniscomplete,adeveloperis

requiredtofileaNoticeofTermination(NOT)withtheRWQCBcertifyingthatalltheconditionsof

theConstructionGeneralpermit,includingconditionsnecessaryfortermination,havebeenmet.

Operation: Standard Urban Storm Water Mitigation Plan (SUSMP)

A Municipal NPDES Permit was issued in December 2001 to Los Angeles County and 84

incorporatedpermitteecitieswithintheCounty.ThepermitdefinestheminimumrequiredBMPs

thatmustbeadoptedbythepermitteemunicipalitiesandincludedbydeveloperswithinplansfor

facility operations. To obtain coverage under this permit, a developermust obtain approval of a

project‐specificSUSMPfromtheappropriatepermitteemunicipality.

A SUSMP addresses the discharge of pollutants within stormwater generated following new

constructionorredevelopment.UnderrecentregulationsadoptedbytheLARWQCB,projectsare

requiredtoimplementaSUSMPduringtheoperationallifeofaprojecttoensurethatstormwater

quantity and quality is addressed by incorporating BMPS into project design. This plan defines

water quality design standards to ensure that stormwater runoff is managed for water quality

concerns and to ensure that pollutants carried by stormwater are confined and not delivered to

receivingwaters. ApplicantsarerequiredtoabidebysourcecontrolandtreatmentcontrolBMPs

from the list approved by the LA RWQCB and included in the SUSMP. These measures include

infiltrationofstormwaterintothegroundaswellasfilteringrunoffbeforeitleavesasite.Thiscan

beaccomplishedthroughvariousmeans,includingtheuseofinfiltrationpits,flow‐throughplanter

boxes,hydrodynamicseparators,andcatchbasinfilters.

In combination, these treatment control BMPsmust be sufficiently designed and constructed to

treatorfilterthefirstthree‐quartersofaninchofstormwaterrunofffroma24‐hourstormevent,

andpost‐developmentpeakrunoffratesandvolumescannotexceedpeakrunoffratesandvolumes

ofpre–developmentconditions.

Tomeetpermitrequirements,municipalitiesarerequired to implement theStormWaterQuality

Management Program prepared for the Report of Waste Discharge filed as part of Los Angeles



County’s Municipal NPDES Permit approval process. Pursuant to this program, municipalities

includingtheCityofLosAngelesarerequiredtoconductavarietyofactivities including,butnot

limitedto,thefollowing:

1. Control discharges at commercial/industrial facilities through tracking, inspecting, and

ensuringcomplianceatfacilitiesthatarecriticalsourcesofpollutants;

2. Implementadevelopmentplanningprogramforspecifieddevelopmentprojects;

3. Implement a program to control construction runoff from construction activity at all

constructionsiteswithinitsjurisdiction;and

4. Implementapublicagencyactivitiesprogram.

TheproposedprojectissubjecttoSUSMPrequirementssinceitproposesahousingdevelopmentof

10unitsormoreandaparkinglotof5,000squarefeetormoreofsurfaceareaorwith25ormore

parkingspaces.

iii. City of Los Angeles Stormwater Program

The Watershed Protection Division of the City of Los Angeles Department of Public Works is

responsible for stormwater pollution control throughout the City in compliance with the Los

AngelesCountyMunicipalNPDESPermit.TheWatershedProtectionDivisionadministerstheCity’s

StormwaterProgram,whichhas twomajorcomponents:PollutionAbatementandFloodControl.

The Watershed Protection Division publishes a two‐part handbook that provides guidance to

developersforcompliancewiththeCounty’sMunicipalNPDESpermitthroughtheincorporationof

water quality management into development planning. The Development Best Management

PracticesHandbook, Part A: Construction Activities (3rd edition) reiterates the policies contained

within the Construction General Permit, provides specific minimum BMPs for all construction

activities,andrequiresthepreparationofaSWPPPandthefilingofanNOItocomplywiththeState

NPDES General Construction Permit requirements with the LA RWQCB. TheDevelopmentBest

Management Practices Handbook, Part B: Planning Activities (3rd edition, June 2004) provides

guidance to developers to ensure the post‐construction operation of newly developed and

redeveloped facilities comply with the County’s Municipal Stormwater Permit. The Handbook

assistsdeveloperswiththeselection,design,andincorporationofstormwatersourcecontroland

treatment control BMPs into project design plans, and provides an overview of the City’s plan

reviewandapprovalprocess.



The stormwater pollution controls contained in the Handbook are codified in the LAMC as

OrdinanceNo.173,494.CityapprovalofSUSMPBMPsisrequiredpriortotheissuanceofgrading

andbuildingpermitsbytheDepartmentofBuildingandSafety,andtherequirementtoincorporate

stormwater BMPs into the SUSMP is implemented through the City’s plan review and approval

process.Duringthereviewprocess,projectplansandspecificationsarereviewedbyBOSand,ifthe

project is subject to SUSMP requirements (i.e., falls within a SUSMP project category) or site‐

specific stormwater mitigation measures are necessary because of the potential for generating

pollutants, the Watershed Protection Division of the Bureau of Sanitation (BOS) of the City’s

DepartmentofPublicWorksforcompliancewiththeCity’sGeneralPlans,zoningordinances,and

otherapplicablelocalordinancesandcodes,includingstormwatermanagementrequirements.

TheCity’spreferredSUSMP improvement is infiltrationofstormwateron theprojectsitesince it

allowsforgroundwaterrechargeandreducesthevolumeofstormwaterenteringmunicipaldrains.

If project site conditions are not suitable for infiltration, the City requires one of the following

systems to be implemented, in order of City preference: bio‐filtration/retention systems,

stormwatercaptureandreuse,mechanical/hydrodynamicunits,oracombinationthereof.

iv. Water Quality Compliance Master Plan for Urban Runoff

TheWaterQualityComplianceMasterPlan forUrbanRunoff (MasterPlan)wasdevelopedby the

WatershedProtectionDivisionoftheBOS,incollaborationwithstakeholders,inresponsetoa2007

CityCouncilmotionforthedevelopmentofawaterqualitymasterplanaddressingpollutionfrom

urbanrunoffwithintheCity.TheMasterPlanwasadoptedinApril2009.

TheMasterPlanaddresses planning, budgeting, and funding for achieving clean stormwater and

urban runoff. Within its eight chapters, it presents an overview of the status of urban runoff

managementwithin the City. TheMasterPlan identifies the City’s four watersheds; summarizes

water quality conditions in the City’s receiving waters as well as known sources of pollutants;

summarizes regulatory requirements forwater quality; describes BMPs required by the City for

stormwater quality management; and discusses related plans for water quality that are

implemented within the Los Angeles region, particularly TMDL Implementation Plans and

WatershedManagementPlansinLosAngeles.TheWaterQualityComplianceMasterPlanforUrban

Runoffprovidesanimplementationstrategythatincludesthefollowingthreeinitiatives:

• WaterQualityManagementInitiative‐discussesthevarioustechnicalcomponentsthatgo

into developing projects for the Water Quality Management Plans to comply with

stormwaterregulations;



• Citywide Collaboration Initiative – discusses what is needed to revise and develop City

policies,ordinances,andguidelinesforurbandevelopmentandredevelopmenttofocuson

green solutions, Low Impact Development (LID), and stormwater use while increasing

coordinationCitywide;

• OutreachInitiative–discusseshowtheCitywillenhanceoutreachactivitiestoreachtarget

audiences, andestablishmethods toquantify thewaterqualitybenefits achieved through

outreachactivities.

Thefinalchaptersofthereportaddressthecostsandpossiblefundingsourcesforimplementation

oftheseinitiatives.

v. Los Angeles Municipal Code (LAMC)

LAMC Sections 12.40–12.43, Landscape Ordinance

In 1996, Ordinance No. 170,978 amended LAMC Sections 12.40–12.43 to establish consistent

landscape requirements for new projects within the City. Section 12.40 contains general

requirements, including a point system for specific project features and techniques in order to

determine compliance with the ordinance, and defines exemptions from the ordinance. Section

12.41setsminimumstandardsforwaterdeliverysystems(irrigation)tolandscapes.Section12.43

defines the practices addressed by the ordinance, of which two are applicable to stormwater

management. The Heat and Glare Reduction practice states among its purposes the design of

vehicularuseareasthatreducestormwaterrunoffandincreasegroundwaterrecharge;andtheSoil

andWatershedConservationpracticeisintended,amongotherpurposes,toincreasethe“residence

time of precipitation” within a given watershed. Implementation guidelines developed for the

ordinance provide specific features and techniques for incorporation into projects, and include

WaterManagementguidelinesaddressingrunoff,infiltration,andgroundwaterrecharge.

LAMC Section 62.105, Construction “Class B” Permit

Anyproposeddrainageimprovementswithinaroadwayright‐of‐wayorotherpropertyforwhich

theCity is responsible, including theconstructionofnewconnectionsbetweenaproject siteand

theCity’sstormdrainsystem,requirestheapprovalofa“BPermit”(Section62.105,LAMC).Under

theBPermitprocess,plansforstormdrainconstructionormodificationsaresubjecttoreviewand

approvalbytheBureauofEngineeringoftheCityofLosAngelesDepartmentofPublicWorks.



LAMC Section 64.70.01, Stormwater and Urban Runoff Pollution Control Ordinance

LAMCSection64.70.01,theStormwaterandUrbanRunoffPollutionControlOrdinance,wasadded

byOrdinanceNo. 172,176 in1998andprohibits thedischargeof unauthorizedpollutants in the

CityofLosAngeles.Theordinanceappliestoalldischargersandplacesofdischargethatdischarge

stormwater or non‐stormwater into any storm drain system or receiving waters. While this

practice is prohibited under the County’s Municipal NPDES Permit, adoption of the ordinance

allowsenforcementbytheDepartmentofPublicWorksaswellasthe levyof fines forviolations.

Theordinanceprohibitsthedischargeofpollutantsbypersonsoperatingorperformingindustrial

orcommercialactivitiesintothestormdrainsystemandreceivingwaters,exceptasauthorizedby

ageneralor separateNPDESpermit;defines illicit, exempt,andconditionallyexemptdischarges;

prohibits the placement or discharge of trash, sewage, hazardousmaterials, and other waste in

stormdrains or receivingwaters, or the accumulation, storage, or disposal of thesematerials in

such away as to contaminate runoff discharged to these facilities; requires control of pollutants

from parking lots; prohibits the creation or use of illicit connections to municipal storm drain

facilities.

LAMC Section 64.72, Stormwater Pollution Control Measures For Development Planning

and Construction Activities

LAMC Section 64.72, Stormwater Pollution Control Measures For Development Planning and

ConstructionActivities,wasaddedbyOrdinance173,494in2000andsetsforthrequirementsfor

construction activities and facility operations of development and redevelopment projects to

complywiththerequirementsof theNPDESpermitSUSMPrequirements,asdefined intheCity’s

DevelopmentBestManagementPracticesHandbook,PartsAandB(ThirdEdition,2004),adoptedby

theBoardofPublicWorks.

vi. City of Los Angeles Low Impact Development Ordinance

InNovember 2011, the City of Los Angeles adopted a City‐wide Low ImpactDevelopment (LID)

ordinancethatamendstheCity’sexistingStormwaterOrdinance(LAMCSectionNos.64.70.01and

64.72, discussed above). In contrast to conventional stormwater management practices, which

focus on conveying runoff off‐site and into storm drains as efficiently as possible and providing

treatmentatawastewatercollectionendpoint,LIDpracticesrequiretheretentionandinfiltration

ofstormwateratthegenerationsourcetopromotenaturalfilteringofwaterbornepollutants.LID

primarily refers tonatural structuralBMPssuchasvegetatedswales, retentionponds,andgreen

roofs,asopposedtomechanicalstructuralBMPssuchaswatertreatmentfacilities.



The Citywide LID strategy addresses land development planning as well as storm drain

infrastructure. Toward this end, LID is implemented throughBMPs that fall into four categories:

site planning BMPs, landscape BMPs, building BMPs, and street and alley BMPs. While the LID

ordinance andBMPs contained thereinare compliantwithLosAngelesCountyMunicipalNPDES

Permitrequirementsforstormwatermanagement,thoserequirementsapplyonlytoproposednew

development and redevelopment of a certain size, primarily address stormwater pollution

preventionasopposedtogroundwaterrecharge,andvaryovertimeasthepermitisreissuedevery

fiveyears.TheLIDordinanceprovidesaconsistentsetofBMPsthatareintendedtobeinclusiveof,

and potentially exceed, SUSMP standards, apply to existing as well as new development, and

emphasizenaturaldrainagefeaturesandgroundwaterrechargeinadditiontopollutionprevention

inreceivingwaters.Theordinancerequiresthecaptureandmanagementofthefirstthree‐quarters

of an inchof runoff flowduring stormeventsdefined in theCity’s SUSMPBMPs, throughoneor

more of the City’s preferred SUSMP improvements: on‐site infiltration, capture and reuse,

evapotranspiration,orbiofiltration/biotreatmentBMPs,tothemaximumextentfeasible.

3. EXISTING CONDITIONS

a. Surface Water Hydrology

i. Project Site Drainage and Storm Drain Infrastructure

TheProjectsiteislocatedintheLosAngelesRiverWatershedManagementArea(WMA),oneofthe

largestsuchareasinthecountry,asshowninFigureIV.G‐1,LosAngelesRiverWatershedMap.The

LosAngelesRiveris51mileslonganddrainsawatershedof834squaremiles.

Project sites

Eastern Parcel

TheeasternProjectsiteisapproximately10.6acresandisrelativelyflatwhereithasbeengraded

and developed along StadiumWay,with an elevation differential of approximately 20 feet from

north to south and approximately 85 feet between Stadium Way and the eastern property

boundaryadjacent toDodgerStadium.ElevationsontheeasternProjectsiterange from435 feet

abovemeansealevel(msl)to515feetabovemsl.

TheeasternProject site is currentlydevelopedwith29buildings, including theexistinghospital,

surface parking lots, pedestrianwalkways, and gardens,which are generally concentrated in the

Figure IV.G-1 Los Angeles River Watershed Map

Source: KPFF Consulting Engineers, Barlow Replacement Hospital & Master Plan: Hydrology Technical Report, December 2010.

Not to Scale

N



areas closest to StadiumWay.Most of the on‐site buildings and infrastructurewere constructed

before1930.

The eastern Project site is divided into two drainage subareas, DA1‐2 and DA2‐3, as shown in

Figure IV.G‐2, Project Site: Existing Drainage Subareas. Subarea DA2‐3 encompasses a 6.0‐acre

portionof theeasternProjectsitenear the intersectionofStadiumWayandScottAvenue.There

arenoconstructedstormwaterconveyancesystemsordrainagestructureswithinthissubareaand

all runoff is conveyeddownslopevia surface (sheet) flow followingexisting topographyand into

thegutterwithinStadiumWay.Flowsareconveyedsouthbytheguttertothelowestpointwithin

StadiumWay, justwestoftheon‐sitelibrary,wheretheyentertheundergroundmunicipalstorm

drain via 36‐foot‐wide and 38‐foot‐wide curb inlets leading to underground catch basins. These

catchbasinsrepresenttheProjectsite’sinitial“infallpoint”tothemunicipalstormdrain,a60‐inch

reinforcedclaypipe(RCP)beneathStadiumWaythatbeginsmidwaybetweenBoylstonStreetand

Scott Avenue. The Project site is Subarea DA2‐3 encompasses the remaining 9.3 acres on the

easternProject site. In addition to runoff generatedby rainfall directlyonto theProject site, this

subareareceives“run‐on”–surfaceflowfromoff‐site–froma19.8‐acreareanorthofScottAvenue,

showninFigureIV.G‐3,ProjectSite:ExistingStormDrainInfrastructure,assubareaDA1‐1.Subarea

DA1‐1 encompasses theBoylston Street residential neighborhoodaswell as aportionofElysian

Park (MontecillodeLeoPolitiPark).Stormwater flowsgeneratedby thisoff‐site subareaentera

storm drain culvert that passes beneath Scott Avenue and are discharged onto the Project site

througha24‐inch“outfall”indicatedbyaheadwallnearthenorthern‐centralpropertyline.Run‐on

from this off‐site subarea, togetherwith runoff generated on theProject site’s subareaDA1‐2, is

conveyeddownslopeandsouthviasurfaceflowuntilenteringtheon‐sitestormdrainsysteminthe

southernendoftheeasternProjectsite.Surfaceflowsareinterceptedbyfouron‐sitecatchbasins

located near Building No. 6 (Shipping and Receiving), just south of Building 19 (former patient

cottage),andwithinthehospital’ssouthernparkinglot.AllrunofffromsubareasDA1‐2andoff‐site

subareaDA1‐2 is eventually collectedwithin a 48‐foot catchment basin/sumpnear the southern

endoftheeasternProjectsite, justnorthofthe intersectionofStadiumWayandBoylstonStreet.

Runoff is then conveyed from the sump/catch basin via a 54‐inchRCP stormdrain to a 75‐inch

segmentoftheRCPmunicipalstormdrainbeneathStadiumWay.

AscanbeseeninthemapcontoursinFigureIV.G‐3,previouslyreferenced,overtimethevolume

andvelocityof stormwater flowsacross subareaDA2‐3have resulted in the creationof a broad,

curvingswalethatextendsfromtheheadwalloutfallwhereoff‐siterun‐onenterstheProjectsite,

nearScottAvenue,allthewaytothe48‐footcatchbasin/sumpatthesouthernendoftheeastern

Projectsite.Theswalehasbeencreatedbytheerosionofsoilaswellasunderlyingbedrock.



Western Parcel

ThewesternProjectsite,approximately14.2acres,slopessteeplyupfromStadiumWaytoElysian

ParkDrive,withelevationsrangingfromapproximately435feetabovemslto572feetabovemsl.It

contains10buildings, includingeightcottagesat thebottomof theslopealongStadiumWayand

two single‐family residences at the top of the slope on Elysian Park Drive. The majority of the

westernProjectsiteisundevelopedandvegetationconsistsofnonnativegrasses(regularlydisked

forfirepreventionpurposes),shrubs,andmaturetrees.

ThewesternProjectsiteisdividedintotwodrainagesubareas,DA4‐1andDA3‐4.SubareaDA4‐1

comprises4.2acresatthesouthernendofthewesternProjectsiteandsubareaDA3‐4comprises

theremainderof theProject site, approximately11.6acres.SubareaDA3‐4receives run‐on from

1.4 acres of off‐site land to the north, subarea DA3‐3; these flows enter the Project site at its

northwestcorner.

Unlike the eastern Project site, there are no constructed runoff conveyance systems or drainage

structuresonthewesternProjectsite.Allrunoffisconveyeddownslopeviasheetflowtothegutter

inStadiumWay.RunofffromsubareaDA4‐1isconveyedsouthtoa36‐footcurbinletcatchbasinon

thewest sideof StadiumWay, at its lowestpoint, across from the36‐foot curb inlet catchbasin

servingtheeasternProjectsite.RunofffromsubareaDA3‐4drainstoa40‐footcurbinletandcatch

basininStadiumWay,about200feetnorthofthedrainagestructureservingsubareaDA4‐1.

ii. Project Site Hydrological Conditions

Table IV.G‐1, Summary of Existing Hydrologic Analysis Results, provides a summary of runoff

volumesfor1)Projectsitedrainagesubareas,2)off‐sitedrainagesubareasthatcontributerun‐on

totheProjectsite,and3)off‐sitedrainagesubareasthatcontributerunofftothemunicipalstorm

drain system beneath Stadium Way. Runoff volumes were calculated based on the City of Los

AngelesDepartmentofPublicWorksPeakRateMethod.Thecalculationsperformedforthistable

indicate that the majority of stormwater runoff from the Project and surrounding drainage

subareas is conveyed as runoff into the municipal storm drain system, with the remainder, a

relatively small proportion of the overall runoff volumes, percolating into the ground. The

municipalstormdrainsystemservingtheProjectsite,includinginfall/outfallstructuresandstorm

waterconveyancepipes,areadequatelysizedtoconveythepeakrunoffratesgeneratedbyupto

50‐year design storm events, and are therefore considered adequate to prevent flooding during

stormsofthisfrequency.

Figure IV.G-2Project Site: Existing Drainage Subareas


LEGEND

0 300 600

Scale (Feet)

N

Figure IV.G-3 Project Site: Existing Storm Drain Infrastructure


LEGEND

0 100 200

Scale (Feet)

N



Table IV.G‐1

Summary of Existing Hydrologic Analysis Results

Drainage Subarea

Acres Peak Discharge by Storm Return Frequency (cfs)a

100‐YEAR 50‐YEAR 10‐YEAR 5‐YEARDA1‐1 19.8 20.5 18.3 13 7.1

DA1‐2 9.3 13.6 12.1 8.6 4.7

DA2‐1 6.8 7 6.1 4.4 2.4

DA2‐2 12.9 19 17 12.1 6.6

DA2‐3 6.0 9.1 8.2 5.8 3.2

DA3‐1 27.7 28.5 25.5 18.1 9.9

DA3‐2 5.2 6.6 5.9 4.2 2.3

DA3‐3 1.4 2.1 1.8 1.3 0.7

DA3‐4 11.6 15.8 14.1 10.0 5.4

DA4 4.2 5.8 5.2 3.7 2.0

POA 104.9 128 114.2 81.2 44.3 Note:acfs=cubicfeetpersecond

Source:KPFFConsultingEngineers,BarlowReplacementHospitalandMasterPlan:Hydrology,(2010).

According to the Federal EmergencyManagement Agency Flood Insurance RateMap, the entire

Projectsiteisinanareaofminimalflooding(FloodZoneC).

iii. Off‐Site Storm Drain System

OntheeasternProjectsite,a38‐foot‐wideeasementnearthesouthernendoftheparcelcontains

the54‐inchRCPstormdrainthatdischargestheon‐sitecatchbasin/sumptothemunicipalstorm

drainbeneathStadiumWay.A38‐foot‐wideeasementonStadiumWaycontains the38‐footcurb

inlet towhichsubareaDA2‐3drains (thenorthwesternportionof theeasternProjectsite).A36‐

foot‐wide easement across StadiumWay onto both parcels; it contains the two 36‐foot catch

basinsoneithersideofStadiumWayatitslowestpoint.TheeasternProjectsitealsocontainsa20‐

footeasementthatcontainstheculvertandinfall/outfallstructuresforoff‐siterun‐onthatenters

theProjectsiteatthenorthernpropertylineonScottAvenue.



ThewesternProjectsitecontainsthe36‐footeasementandcurbinlet/catchbasinattheStadium

Waylowpointaswellasa40‐footeasementonStadiumWaycontainingthecurbinletandcatch

basintowhichsubareaDA4‐1drains(thesouthernendofthewesternProjectsite).

ThemunicipalstormdrainbeneathStadiumWayadjacenttotheProjectsiteisinitially60inchesin

width,to75inchesasitapproachesBoylstonStreet;itcontinuessouthbeneathStadiumWayand

other roadway alignments, gradually increasing in size to a 120‐inch arch elliptical pipe that

dischargesintotheLosAngelesRiveratCesarChavezAvenue,approximately1.95milesfromthe

Project site. Figure IV.G‐4, Project Vicinity StormDrain System, and Figure IV.G‐5, ProjectArea

StormDrainSystem,showthemunicipalstormdrainsystemontheimmediateProjectvicinityand

largerProjectarea.

b. Surface Water Quality

i. Potential Sources of Erosion, Sedimentation, and Pollution

Erosion and Sedimentation

The potential for erosion and sedimentation (waterborne sediment) existwhere steep slopes or

undevelopedandunvegetatedlandaresubjecttouncontrolledsheetorchannelstormwaterflows

duringevents.

Aspreviouslydiscussed,theeasternProjectsitecontainsabroadswalecreatedbytheheavy of

runoffthatflowsoverlandbetweentheoutfall/headwallneartheScottAvenuepropertyboundary

andthecatchbasin/sumpatthesouthernendofthisparcel.Thisrunoffincludesstormwaterthat

flowsontotheProjectsitefromtheoff‐sitedrainageareatothenorth.Althoughsomestormwater

is intercepted by on‐site drainage structures in low‐lying areas, and the remaining runoff is

directed into the 48‐foot catch basin/sump at the southern end of the parcel, the volume and

velocityofflows erodedawaysoilaswellasunderlyingbedrockalongthepathoftravelacross

the eastern Project site, especially near the outfall/headwall. Slope gradients on the eastern and

northernedgesoftheeasternProjectsiterangefromamoderate5:1upto2:1,whichexacerbates

thepeakrunoffvolumesinthispartoftheProjectsite.

The lessdevelopedwesternProject site is steeplysloped,withgradients ranging from7:1 to2:1

and steeper slopesup to1.5:1.Although theundevelopedportionsof thisparcel are generally

vegetated,theslopesareregularlydiskedforwildfirecontrolpurposes,reducingopportunitiesfor

runoff percolation on‐site. Since all runoff generated on the western Project site is conveyed

downslope to Stadium Way via uncontrolled sheet flow, some potential exists for erosion and

Figure IV.G-4Project Vicinity Storm Drain System


N

Not to Scale

Figure IV.G-5Project Area Storm Drain System

LEGEND


N

Not to Scale



sedimentation,particularlyifchannelflowsdevelopinareaswhererunoff is locallyconcentrated.

Atpresent,however,thereisnoevidenceoferosionorsedimentationonthewesternProjectsite.

Pollution

TheProjectsitecontainsapproximately18.8acresofundevelopedandunpavedperviousarea(75

percentoftheProjectsite),muchofwhichislandscapedwithgrasslands,lawn,shrubs,tree,grass

and/ormiscellaneousvegetation.Theseareasmayusepesticidesand/orfertilizers,whichcanbea

sourceofpollutionifcarriedoff‐sitebystormwaterrunoff.

The remainder of the Project site, approximate 6.2 acres, is impervious. Nearly all of this

impervious area is on the eastern Project site and includes areas developed with buildings,

roadways and driveways, parking lots, and hardscape such aswalkways. All impervious surface

areascollectdustandparticulatematterthatareconveyedtothestormwaterdrainagefacilitiesby

stormwaterrunoff.Inaddition,drivewaysandparkinglotareascollectoilandgreasedepositsand

brakedustfromautomobiles,whichcanbewashedoffanddepositedintotheexistingcatchbasins.

ii. Measures to Control Erosion, Sedimentation and Pollution

Sump

MostofthestormwaterrunofffromthemajorityoftheeasternProjectsite,inthe9.3‐acredrainage

subareaDA1‐2, is collected in thecatchbasin/sumpat thesouthernendof theparcel.Thesump

allows sediment and pollutants to settle out prior to stormwater conveyance off‐site into the

municipal stormdrain system. There are also four catchment basins at low spots in the eastern

Projectsitethatinterceptsurfaceflows;thesehavedraingratestopreventtrashfromenteringthe

catchbasins.Thison‐sitesystemisdesignedtohandleupto50‐yeardesignstormflows.

StormwaterelsewhereontheProjectsiteisconveyeddownslopeviasurfaceflowanddischarged

offsite, into gutters lining StadiumWay that, in turn, convey flows to themunicipal stormdrain

system.

c. Groundwater

AsstatedinSectionIV.E,GeologicHazards,ofthisDraftEIR,theProjectsiteoccupiesthelowpoint

of a small north‐south trending valley infilled with permeable alluvial deposits underlain by

bedrock.ElevationsontheProjectsiterising from435feetabovemslalongStadiumWayto515

feetabovemslat theeasternpropertyboundarynearDodgerStadiumand572 feetabovemslat



the western property boundary along Elysian Park Drive. According to the Seismic Hazard

Evaluation of the Los Angeles 7.5 Minute Quadrangle, the Project site is not located within a

groundwaterbasin.

Boringsencounteredgroundwaterwithinthealluvialdepositsinlow‐lyingportionsoftheeastern

Project site, between5 and39 feet below the surface.This is considered to represent aperched

(confined)groundwatercondition,nothydrologicallyconnectedtoaregionalgroundwatersource.

Groundwater is continually recharged by an influx of groundwater and runoff from surrounding

hillsideareas,and therefore thedepth togroundwatervarieswith topographyacross theProject

site,annualprecipitation,andtheresultingmigrationofgroundwaterthroughthealluvialdeposits.

GroundwaterwasnotencounteredatthehigherelevationsalongtheeasternandwesternProject

sites,whichareunderlainbyshallowbedrock;bedrockisconsiderednon‐waterbearingbecauseof

its impermeability. Groundwater would not normally be expected in these areas unless it is

generatedbyrunoffandseepage;however,groundwaterlevelsandflowratesvaryseasonallyand

perchedgroundwatermaydevelopwherenonepreviouslyexisted,especiallyinimpermeablefine‐

grainedsoilsorbedrockfollowingheavyirrigationorrainfall.

4. ENVIRONMENTAL IMPACT ANALYSIS

a. Methodology

ThisanalysiswaspreparedbasedonthetechnicalreportpreparedfortheproposedProject,titled

BarlowHospitalandMasterPlan:Hydrology(December2010)byKPFFConsultingEngineers,which

is provided inAppendix IV.G of this Draft EIR. The technical report includes all calculations

performedtodeterminepre‐andpost‐developmentrunoffvolumes,duringa50‐yearstormevent,

in order to determine potential impacts on conveyance systems and drainage structure on the

ProjectsiteandinthemunicipalstormdrainsystemservingtheProjectsite.

b. Significance Thresholds

i. Surface Water Hydrology

The City of Los Angeles CEQA Thresholds Guide states that a project would normally have a

significantimpactonsurfacewaterhydrologyifitwould:

• Cause floodingduring the projected 50‐year developed stormevent,whichwouldhave

thepotentialtoharmpeopleordamagepropertyorsensitivebiologicalresources;



• Substantiallyreduceorincreasetheamountofsurfacewaterinawaterbody;or

• Result in a permanent, adverse change to themovement of surface water sufficient to

produceasubstantialchangeinthecurrentordirectionofwaterflow.

ii. Surface Water Quality


significantimpactonsurfacewaterqualityif:

DischargesassociatedwiththeProposedProjectwouldcreate“pollution,”“contamination”

or“nuisances”asdefinedinSection13050oftheCaliforniaWaterCode.

Pollutionmeans an alterationof the quality of thewaters of the state to adegree,which

unreasonably affects either of the following: (1) the waters for beneficial uses;2 or (2)

facilitieswhichservethesebeneficialuses.PollutionmayincludeContamination.

Contaminationmeansanimpairmentofthequalityofthewatersofthestatebywastetoa

degreewhichcreatesahazardtothepublichealththroughpoisoningorthroughthespread

of disease.3 Contamination includes any equivalent effect resulting from the disposal of

waste,whetherornotwatersofthestateareaffected.

Nuisancemeansanythingwhichmeetsallofthefollowingrequirements:(1)isinjuriousto

health,orisindecentoroffensivetothesensesoranobstructiontothefreeuseofproperty,

soastointerferewiththecomfortableenjoymentoflifeorproperty;(2)affectsatthesame

time an entire community of neighborhood, or any considerable number of persons,

althoughtheextentoftheannoyanceordamageinflicteduponindividualsmaybeunequal;

and(3)occursduring,orasaresultofthetreatmentordisposalofwastes.

The proposed Projectwould cause regulatory standards to be violated, as defined in the

applicable National Pollutant Discharge Elimination System stormwater permit orWater

QualityControlPlanforthereceivingwaterbody.

2 Section13050oftheCaliforniaWaterCodeprovidesthatthefollowingdefinitionforbeneficialuses:“Beneficialuses’

ofthewatersofthestatethatmaybeprotectedagainstqualitydegradationinclude,butarenotlimitedto,domestic,municipal, agricultural and industrial supply; power generation; recreation; aesthetic enjoyment; navigation; andpreservationandenhancementoffish,wildlife,andotheraquaticresourcesorpreserves.”

3 Section13050oftheCaliforniaWaterCodeprovidesthefollowingdefinitionforwaste:“’Waste’includessewageandany and all otherwaste substances, liquid, solid, gaseous, or radioactive, associatedwith humanhabitation, or ofhuman or animal origin, or from any producing, manufacturing, or processing operation, including waste placedwithincontainersofwhatevernaturepriorto,andforpurposesof,disposal.



iii. Groundwater Quality

Groundwater Level


significantimpactongroundwaterlevelif:

Theprojectwouldchangepotablewaterlevelssufficientlyto:

Reducetheabilityofawaterutilitytousethegroundwaterbasinforpublicwatersupplies,

conjunctive use purposes, storage of imported water, summer/winter peaking, or to

respondtoemergenciesanddrought;

Reduceyieldsofadjacentwellsorwellfields(publicorprivate);or

Adverselychangetherateordirectionofflowofgroundwater.

Theprojectwouldresultindemonstrableandsustainedreductionofgroundwaterrecharge

capacity.

Groundwater Quality


significantimpactongroundwaterqualityif:

The project would affect the rate, or change the direction, of movement of existing

contaminants;

Theprojectwouldexpandtheareaaffectedbycontaminants;

Theprojectwouldresultinanincreasedlevelofgroundwatercontamination(includingthat

fromdirectpercolation,injectionorsaltwaterintrusion);or

Theprojectwouldcauseregulatorywaterqualitystandardsinanexistingproductionwell

tobeviolated,asdefinedintheCaliforniaCodeofRegulations,Title22,Division4,Chapter

15,andintheSafeDrinkingWaterAct.



AppendixG of the StateCEQAGuidelinesprovides samplequestions foruse in an initial study to

determine a project’s potential for environmental impacts. According to the sample questions4

included inAppendixGunderSection IX,HydrologyandWaterQuality, andSectionXVI,Utilities

andServiceSystems,aprojectwouldhaveapotentiallysignificantimpactifitwould:

IX.a) Violateanywaterqualitystandardsorwastedischargerequirements;

IX.b) Substantially deplete groundwater supplies or interferewith groundwater recharge

such that therewould be a net deficit in aquifer volume or a lowering of the local

groundwater table level (e.g., theproductionrateofpreexistingnearbywellswould

droptoa levelwhichwouldnotsupportexisting landusesorplannedlanduses for

whichpermitshavebeengranted);

IX.c) Substantiallyaltertheexistingdrainagepatternofthesiteorarea,includingthrough

thealterationof thecourseof a streamor river, inamannerwhichwouldresult in

substantialerosionorsiltationonoroffsite;

IX.d) Substantiallyaltertheexistingdrainagepatternofthesiteorarea,includingthrough

thealterationofthecourseofastreamorriver,orsubstantiallyincreasetherateor

amountofsurfacerunoffinamannerwhichwouldresultinfloodingonoroffsite;

IX.e) Create or contribute runoff water which would exceed the capacity of existing or

planned stormwater drainage systems or provide substantial additional sources of

pollutedrunoff;

IX.f) Otherwisesubstantiallydegradewaterquality;

IX.g) Place housing within a 100‐year flood hazard area as mapped on a federal Flood

HazardBoundaryorFloodInsuranceRatemaporotherfloodhazarddelineationmap;

IX.h) Placewithina100‐yearfloodhazardareastructureswhichwouldimpedeorredirect

floodflows;

IX.i) Expose people or structures to a significant risk of loss, inquiry or death involving

flooding,includingfloodingasaresultofthefailureofaleveeordam;

4 The remainder of the Appendix G Utilities and Service Systems sample questions (XVI.a, ‐b, and –d through ‐g)

pertain towater supply,wastewater, and solidwaste and are addressed inSections IV.L.1,WaterSupply, IV.L.2,Wastewater,andIV.L.3,SolidWaste,respectively.



IX.j) Inundationbyseiche,tsunami,ormudflow;or

XVI.c) Require or result in the construction of new storm water drainage facilities or

expansion of existing facilities, the construction of which could cause significant

environmentaleffects.

TheInitialStudypreparedfortheproposedProjectdeterminedthatitwouldhavenoimpactwith

regardtosamplequestionsVIII.gand‐hofAppendixGoftheStateCEQAGuidelines.Theresponses

tothesequestionsarediscussedinSectionVII,EffectsFoundNottobeSignificant.TheInitialStudy

isprovidedinAppendixIofthisDraftEIR.

The thresholds used in the City of Los Angeles CEQA Thresholds Guide to determine significant

impacts on surfacewater hydrology, surfacewater quality, and groundwater quality incorporate

the more general checklist questions contained in AppendixG of the State CEQA Guidelines.

Therefore, based on the more specific City of Los Angeles CEQA Thresholds Guide, the proposed

Projectwouldhaveasignificantsurfacewaterhydrologyimpactif:

HWQ‐1 TheProjectwouldcausefloodingduringtheprojected50‐yeardevelopedstormevent,

which would have the potential to harm people or damage property or sensitive

biologicalresources;

HWQ‐2 TheProjectwouldsubstantiallyreduceor increasetheamountofsurfacewater ina

waterbody;or

HWQ‐3 TheProjectwouldresultinapermanent,adversechangetothemovementofsurface

watersufficienttoproduceasubstantialchange inthecurrentordirectionofwater

flow.

HWQ‐4 Dischargesassociatedwith theProjectwould create “pollution,” “contamination”or

“nuisances”asdefinedinSection13050oftheCaliforniaWaterCode.

HWQ‐5 The Project would cause regulatory standards to be violated, as defined in the

applicable National Pollutant Discharge Elimination System stormwater permit or

WaterQualityControlPlanforthereceivingwaterbody.

HWQ‐6 TheProjectwouldchangepotablewaterlevelssufficientlyto:



Reducetheabilityofawaterutilitytousethegroundwaterbasinforpublicwatersupplies, conjunctive use purposes, storage of imported water, summer/winterpeaking,ortorespondtoemergenciesanddrought;

Reduceyieldsofadjacentwellsorwellfields(publicorprivate);or

Adverselychangetherateordirectionofflowofgroundwater.

HWQ‐7 The Projectwould result in demonstrable and sustained reduction of groundwater

rechargecapacity;

HWQ‐8 TheProjectwouldaffect the rate, or change thedirection, ofmovement of existing

contaminants;

HWQ‐9 TheProjectwouldexpandtheareaaffectedbycontaminants;

HWQ‐10 The Project would result in an increased level of groundwater contamination

(includingthatfromdirectpercolation,injectionorsaltwaterintrusion);or

HWQ‐11 TheProjectwouldcauseregulatorywaterqualitystandardsinanexistingproduction

welltobeviolated,asdefinedintheCaliforniaCodeofRegulations,Title22,Division4,

Chapter15,andintheSafeDrinkingWaterAct.

HWQ‐12 TheProjectwouldrequireorresult intheconstructionofnewstormwaterdrainage

facilities or expansion of existing facilities, the construction of which could cause

significantenvironmentaleffects.

c. Project Design Features

Project implementation would develop the Project site with buildings, subterranean parking,

retaining walls along slopes, paved roadways and walkways, hardscape, and landscaped areas.

Project implementation would increase on‐site impervious area from approximately 6.2 acres,

which is approximately 25 percent of the site, to approximately 12.7 acres or approximately 51

percentoftheProjectsite.Thisisanincreaseofapproximately6.5acresoverexistingconditions.

Project implementation would alter on‐site stormwater drainage patterns and the direction of

flows.IncompliancewithLIDrequirements,theProjectsitewouldbedesignedtomanagerunoff

produced from the stormeventsdefined in the LIDordinance , and runoffwould accordinglybe

designedtoinfiltratethesite,orwouldbetreatedon‐sitepriortodischarge.Oncethisrequirement

ismet,runoffgeneratedontheeasternProjectsitewouldcontinuetobeconveyeddownslopevia



surface flow to the 48‐foot catch basin/sump at the southern end of the Project site. However,

future surface flows would be controlled and directed, and the existing swale created by the

concentrationof runoff fromtheProjectsiteandoff‐sitedrainagesubarea to thenorthwouldbe

regradedtoaccommodateProjectdevelopment.Surfaceflowswouldbemanagedsoastoprevent

futureerosionandsedimentationontheeasternProjectsite.RunoffontheProjectsite’swestern

Project site would be conveyed downslope via a combination of surface sheet flow and

underground conveyance systems.Runoffwould continue to be discharged into the gutter along

StadiumWayandthenintothemunicipalstormdrainviatheexistingcurbinletsandcatchbasins

onthewestsideofStadiumWay.

With respect to groundwater, if active seepage is constructed during construction, temporary

dewateringortheconstructionofFrenchdrainstocollectandcontrolwaterwouldbeconstructed.

Subterranean structures such as parking structures or basements would be waterproofed and

properly drained, or designed for the hydrostatic pressure that results from lack of drainage in

saturatedsoils.

Site‐specificBMPsfortheproposedProjecthavenotyetbeendefined,sincebuildingsitingandthe

locationofallProjectsitehardscapeandlandscapefeatureshavenotyetbeenfinalized.Moreover,

site‐specificconstraints including,butnot limitedto, finalizedparkingneeds,undergroundutility

clearance requirements for Project upgrades, and compliance with American Disability Act

requirements will influence the stormwater management features that are incorporated into

Projectdesign.However,a site‐specificSWPPPwouldbepreparedand implementedprior to the

commencement of each separate Project construction phase. BMPs would include, but not be

limitedto,erosioncontrol,sedimentcontrol,andthemanagementoftrash,debris,andothernon‐

stormwaterdischarges.

FinaldesignforeachconstructionphasewouldincorporateLID‐compliantfeaturesandpracticesto

beimplementedduringtheoperationallifeoftheProjectphase.TheLIDPlanwouldmeetorexceed

allapplicableCountyMunicipalNPDESPermitSUSMPrequirements,includingBMPsforsourceand

treatment controls. Treatment control BMPs to be implemented include increased retention of

stormwater runoff on the Project site for infiltration into the soil and groundwater recharge, in

compliancewiththepost‐developmentpeakstormwaterrunoffdischargeraterequirementsinthe

SUSMPstructuralBMP.

TreatmentcontrolBMPswouldalsobe implementedduring theoperational lifeof theProject, in

compliance with LID Plan SUSMP requirements. Treatment controls (to treat, infiltrate, or filter



stormwaterrunoff)wouldbeeitherflow‐basedBMPsorvolume‐basedBMPs,asdiscussedabovein

Subsection2.a.ii,CityofLosAngelesStormwaterProgram.

d. Project Impacts

i. Surface Water Hydrology

HWQ‐1 Would the Project cause flooding during the projected 50‐year developed

storm event, which would have the potential to harm people or damage

propertyorsensitivebiologicalresources?

HWQ‐2 Would the Project substantially reduce or increase the amount of surface

waterinawaterbody?

HWQ‐3 Would the Proposed Project result in a permanent, adverse change to the

movementofsurfacewatersufficienttoproduceasubstantialchangeinthe

currentordirectionofwaterflow?

Construction

ConstructionoftheproposedProjectwouldoccurinphasesoverthecourseof10yearsandwould

require the removal of existing buildings and hardscape; clearing, grading and excavation; and

constructionofnewbuildings,subterraneanparking,andhardscapeandlandscapedareas.Project

implementationwouldnecessitatetheconstructionofnewon‐sitestormdrainfacilitiesandother

underground and aboveground utility infrastructure. As stated in Subsection C, Project Design

Features, a LID Plan would be prepared and implemented prior to the commencement of each

Projectconstructionphase.Constructionwouldhavealessthansignificantimpactwithrespectto

flooding during a 50‐year design storm event, a substantial increase/decrease of the amount of

waterinreceivingwaters,orchangesinthecurrentordirectionofsurfacewaterflows.

Operation

The increase in impervious cover, grading, and new construction, as indicated inFigure IV.G.6,

ExistingConditions: ImperviousArea,andFigure IV.G.7,ProposedProject: ImperviousArea,would

alter existing drainage patterns on the Project site’s eastern and western Project sites, which

presently rely entirely on surface (sheet flow) to convey runoff off‐site. As discussed in under

ProjectDesignFeatures,futurestormwatermanagementontheProjectsitewillcontinuetorelyon

acombinationofsurface(sheetflow)andundergroundstormdrainsystemstoconveyrunofftothe



local municipal storm system beneath Stadium Way. Project implementation is anticipated to

increasethevolumeofrunoffgeneratedontheProjectsitebecauseoftheincreasein impervious

area.However,finalProjectdesignwillberequiredtodemonstratecompliancewithLIDordinance

requirements through the preparation of a LID Plan, which requires runoff to be managed or

capturedon‐siteinoneofseveralways,asprioritizedintheLIDordinance.

All proposed subterranean structures will be waterproofed and properly drained, or will be

designedforhydrostaticpressureresultingfromthepresenceofgroundwater.Ifactiveseepageis

encounteredduringexcavation,atemporarydewateringsystemconsistingofwellsand/orFrench

drainswouldbeconstructedtocollectandcontrolthewater.

Therefore, the proposed Project would not cause, or be subject to, flooding during a 50‐year

developed storm event, which could harm people, damage property, or sensitive biological

resources. Impacts related to flooding,a substantial increase/decreaseof theamountofwater in

receivingwaters,orchangesinthecurrentordirectionofsurfacewaterflowswouldbelessthan

significant.

ii. Surface Water Quality

HWQ‐4 Would the Project create “pollution,” “contamination”, or “nuisances” as

definedinSection13050oftheCaliforniaWaterCode?

HWQ‐5 Would theProject cause regulatory standards tobeviolated, asdefined in

theapplicableNationalPollutantDischargeEliminationSystemstormwater

permitorWaterQualityControlPlanforthereceivingwaterbody?

Construction

ThethreeprimarysourcesofpotentialstormwaterpollutionassociatedwithProjectconstruction

are:(1)thehandling,storage,anddisposalofconstructionmaterialscontainingpollutants,(2)the

maintenanceandoperationofconstructionequipment,and(3)earthmovingactivitieswhich,when

notcontrolled,maygeneratesoilerosionandsedimentationviastormrunoff,wind,ormechanical

equipment.

Thestorage,handling,anduseofchemicalsusedinconstruction,suchasfuels,paints,solvents,and

petroleum products, associatedwith construction activities could causewater quality impacts if

spilled or released in the path of stormwater runoff. Miscellaneous wastes include wash from

concretemixers, solidwasteresulting fromvegetationremovedduring landclearance,woodand

Figure IV.G-6Existing Conditions: Impervious Area

LEGEND

0 200 400

Scale (Feet)


N

Figure IV.G-7Proposed Project: Impervious Area

LEGEND

0 200 400

Scale (Feet)


N



papermaterialsfrombuildingproductspackaging,foodcontainers,andsanitarywastes.Concrete

washwater can be toxic and requires proper control. The discharge of thesewastes can lead to

polluted waterways. The unnecessary or improper application of herbicides, insecticides, and

rodenticidesat constructionsitesmayalsoresult in receivingwatercontaminationandpollution

through drift, or transport of soil particles by wind and rain fall. Generally, routine safety

precautions (“good housekeeping procedures”) for handling and storing construction materials

mayeffectivelyreducethepotentialforpollutionofstormwaterrunoffbythesematerials.

Siteclearanceofvegetationandbuildingdebrisandgradingandexcavationactivities,includingsoil

stockpiling,canalsogreatlyincreaseerosionprocessesandleadtosedimentloadingofstormwater

runoffandsubsequent impactsonstormdrains.Constructionequipmentcantrackmudanddust

off‐siteandintoarearoadways,whereitisabletoenterthemunicipalstormdrainsystem.

Finally,poorly‐maintainedvehiclesandheavyequipmentleakingfuel,oil,antifreeze,orotherfluids

onconstructionsitescanbecommonsourcesofstormwaterpollutionandsoilcontamination.

AsdiscussedinSubsectionc,ProjectDesignFeatures,oneormoreSWPPPswouldbepreparedin

compliancewith applicable local and State regulatory requirements for the Project construction,

includingindividualphasedProjectcomponents.BMPstobeimplementedontheProjectsitewould

beidentifiedindetailintheSWPPP.WithadherencetotheCity’sLIDordinanceandLIDandSWPPP

requirements,constructionisanticipatedtohavealessthansignificantimpactwithrespecttothe

creationofpollution, contamination,ornuisancesasdefined in theCaliforniaWaterCode,or the

violationofregulatorystandardscontainedintheLosAngelesCountyMunicipalNPDESPermit.

Operation

Surface water quality is generally affected by the length of time since the last rainfall, rainfall

intensity,urbanusesofthearea,andquantityoftransportedsediment.Typicalurbanwaterquality

pollutants usually result from motor vehicle operations, oil/grease residues, fertilizer/pesticide

uses,human/animallittering,carelessmaterialstorage/handling,andpoorpropertymanagement.

Themajorityofpollutantloadsareusuallywashedawayduringthefirstflushofastormoccurring

afterthedry‐seasonperiod.

Street and parking lot/garage‐generated pollutants typically contain atmospheric pollution, tire‐

wear residues, petroleum products, oil, and grease, fertilizer and pesticide wash‐offs, chemical

spills,aswellasanimaldroppingsandlittertypesofwastes.Thepollutantsarewashedfromstreet

surfacesbyarainfalladequatetoproducerunoff.Theamountofpollutantswashedoff thestreet



surfaceisafunctionoftheamountofpollutantsthathaveaccumulatedonstreetsurfacesandthe

frequency and amount of surface water flow flushing the pollutants from storm and non‐storm

events(suchashosingdownofwalkwaysandparkinggaragesurfaces).Thesepollutantshavethe

potentialtodegradewaterqualityandmayresultinsignificantimpacts.

The current building standards for parking structures require the installation of oil and grease

traps and other mechanisms to treat water before being sent to the storm drain system. The

proposed Project would replace most of the existing surface lot parking (which do not have

mechanisms in place to treat runoff) with subterranean parking grade. The unnecessary or

improper application of herbicides, insecticides and rodenticides may result in receiving water

contaminationandpollutionthroughdrift,ortransportofsoilparticlesbywindandrainfall.Also,

pesticidesmay inadvertentlybe released to the environment if notproperly labeled, handled, or

stored. Barlow Hospital maintains on‐site storage of all such materials in accordance with

requirementsoftheCaliforniaDepartmentofPesticideRegulation.

Fewmechanisms are in currently inplace to reduce runoff volumesdischarged to themunicipal

stormdrainsystemortotreatrunoffon‐sitebeforedischargeoff‐site,withtheexceptionofthe48‐

footcatchbasin/sumpatthesouthernendoftheeasternProjectsite,whichreceivesmostrunoff

generated on the eastern Project site. As discussed inSubsectionc,ProjectDesignFeatures, the

proposed developer is required to develop a LID Plan and SUSMP in accordance with the Los

AngelesCountyMunicipalNPDESPermitrequirements,whichwouldincludesourceandtreatment

control BMPs. With adherence to the City’s LID and SWPPP requirements, Project operation is

anticipated to have a less than significant impact with respect to the creation of pollution,

contamination,ornuisancesasdefinedintheCaliforniaWaterCode,ortheviolationofregulatory

standardscontainedintheLosAngelesCountyMunicipalNPDESPermit.

iii. Groundwater

HWQ‐6 WouldtheProjectchangepotablewaterlevelssufficientlyto:

• Reduce the ability of a water utility to use the groundwater basin for

public water supplies, conjunctive use purposes, storage of imported

water, summer/winter peaking, or to respond to emergencies and

drought;

• Reduceyieldsofadjacentwellsorwellfields(publicorprivate);or



• Adverselychangetherateordirectionofflowofgroundwater?

HWQ‐7 Would the Project result in demonstrable and sustained reduction of

groundwaterrechargecapacity?

HWQ‐8 Would theProject affect the rate, or change thedirection, ofmovementof

existingcontaminants?

HWQ‐9 WouldtheProjectexpandtheareaaffectedbycontaminants?

HWQ‐10 WouldtheProjectresultinanincreasedlevelofgroundwatercontamination

(includingthatfromdirectpercolation,injectionorsaltwaterintrusion)?

HWQ‐11 Would the Project cause regulatorywater quality standards in an existing

production well to be violated, as defined in the California Code of

Regulations,Title22,Division4,Chapter15,andintheSafeDrinkingWater

Act?

HWQ‐12 WouldtheProjectrequireorresultintheconstructionofnewstormwater

drainage facilities or expansion of existing facilities, the construction of

whichcouldcausesignificantenvironmentaleffects?

e. Mitigation Measures

Themitigationmeasureswouldaddressimpactstosurfacewaterhydrologyandwaterqualityand

ensurethatimpactsremainlessthansignificant.

MM‐HWQ‐1 Prior to thestartof soil‐disturbingactivitieson theProject site, aNoticeof Intent

(NOI) and StormWater Pollution Prevention Plan (SWPPP) shall be prepared in

accordancewith,andinordertopartiallyfulfill,theCaliforniaSWRCBOrderNo.99‐

08‐DWQ, National Pollutant Discharge Elimination System General Permit No.

CAS000002 (GeneralConstructionPermit).The StormWaterPollutionPrevention

PlanshallmeettheapplicableprovisionsofSections301and402oftheCleanWater

ActandChapter6Article4.4,StormWaterandUrbanRunoffPollutionControlfrom

theCityofLosAngelesMunicipalCodebyrequiringcontrolsofpollutantdischarges

thatutilizebestavailabletechnologyeconomicallyachievableandbestconventional

pollutantcontroltechnologytoreducetherateandquantityofstormwaterrunoff.



MM‐HWQ‐2 TheProjectsiteshallbedesignedtomanageandcapturestormwaterrunoff,tothe

maximumextentfeasible,inpriorityorder:infiltration,evapotranspiration,capture

anduse,treatedthroughhighremovalefficiencybiofiltration/biotreatmentsystem

of all of the runoff on site. High removal efficiency biofiltration/biotreatment

systemsshallcomplywiththestandardsandrequirementsoftheDevelopmentBest

ManagementPracticesHandbook.ALIDPlanshallbepreparedtocomplywiththe

following:

Stormwater runoff shall be infiltrated, evapotranspired, captured and used,

treated through high removal efficiency Best Management Practices, onsite,

throughstormwatermanagementtechniquesthatcomplywiththeprovisionsof

the Development Best Management Practices Handbook. To the maximum

extent feasible, on‐site stormwater management techniques shall be properly

sized, at aminimum, to infiltrate, evapotranspire, store for use, treat through

high removal efficiency biofiltration/biotreatment system, without any storm

water runoff leaving theSite forat least thevolumeofwaterproducedby the

qualitydesignstormeventthatresultsfrom:

The85thpercentile24‐hourrunoffeventdeterminedas themaximized

capture stormwater volume for the area using a 48 to 72‐hour draw

down time, from the formula recommended in Urban Runoff Quality

Management,WEFManualofPracticeNo.23/ASCEManualofPractice

No.87,(1998);or

Thevolumeofannualrunoffbasedonunitbasinstoragewaterquality

volume,toachieve80percentormorevolumetreatmentbythemethod

recommendedintheCaliforniaStormwaterBestManagementPractices

Handbook‐Industrial/Commercial,(2003);or

Thevolumeofrunoffproducedfroma0.75inchstormevent.

Forpurposesofcompliancewith theLIDrequirements,andwithoutchanging

thepriorityorderofdesignpreferencesidentifiedinthisSection,allrunofffrom

the water quality design storm event, as identified in Paragraph (a) of this

Subdivision, that has been treated through an onsite high removal efficiency

biofiltration/biotreatment system shall be deemed to have achieved 100%

infiltrationregardlessoftherunoffleavingtheSitefromanonsitehighremoval



efficiency biofiltration/biotreatment system, and thus any runoff volume shall

notbesubjecttotheoffsitemitigationrequirementofthisArticle.

Pollutants shall be prevented from leaving the Site for awater quality design

stormeventasdefined inParagraph (a)of thisSubdivisionunless ithasbeen

treated through an onsite high removal efficiency biofiltration/biotreatment

system.

Hydromodification impacts shall beminimized to natural drainage systems as

definedintheMS4Permit.

When, as determined by the Director, the onsite LID requirements are

technically infeasible, partially or fully, as defined in the Development Best

ManagementHandbook,theinfeasibilityshallbedemonstratedinthesubmitted

LIDPlan,shallbeconsistentwithotherCityrequirements,andshallbereviewed

inconsultationwiththeDepartmentofBuildingandSafety.

Ifpartialorcompleteonsitecomplianceofanytypeistechnicallyinfeasible,the

project Site and LID Plan shall be required to comply with all applicable

StandardUrbanStormwaterMitigationPlan(SUSMP)requirementsinorderto

maximizeon‐sitecompliance. Fortheremainingrunoffthatcannotfeasiblybe

managedonsite,theprojectshallimplementoffsitemitigationonpublicand/or

privatelandwithinthesamesub‐watershed.Thisshallincludeconstructionand

perpetualmaintenance of projects thatwill achieve at least the same level of

runoffretention,infiltrationand/oruse,andwaterquality.AllCityDepartments

willassistthedeveloper,whenandwherefeasible,inthedesign,permittingand

implementation of LID BMP projects within the public right of way, with a

preference for utilizing the public right of way immediately adjacent to the

subjectdevelopment.

AMulti‐PhasedProjectmaycomplywiththestandardsandrequirementsofthis

Sectionforallofitsphasesby:(a)designingasystemacceptabletotheBureau

of Sanitation to satisfy these standards and requirements for the entire Site

duringthefirstphase,and(b)implementingthesestandardsandrequirements

for each phase of Development or Redevelopment of the Site during the first

phaseorpriortocommencementofconstructionofalaterphase,totheextent

necessarytotreatthestormwater fromsuch laterphase. Forpurposesof this



Section,"Multi‐PhasedProject"shallmeananyDevelopmentorRedevelopment

implementedovermorethanonephaseandtheSiteofaMulti‐PhasedProject

shall include any land and water area designed and used to store, treat or

manage stormwater runoff in connection with the Development or

Redevelopment.

f. Level of Significance After Mitigation

All Project‐specific construction and operational impacts would be less than significant and no

mitigation is required. Nonetheless, mitigation measures MM‐HWQ‐1 and MM‐HWQ‐2 are

recommendedtoensurecompliancewithpertainingtoconstructionandoperationalimpactson

surfacewaterquality.

g. Cumulative Impacts

Thegeographiccontext forevaluationofcumulative impactsonsurfacewaterhydrology, surface

waterqualitystemdownstreamoftheProjectsite.AsdiscussedinSectionIII,GeneralDescription

of Environmental Setting, several related projects are proposed and/or planned in the Project

vicinity.AlltheprojectsarelocateddownstreamoftheproposedProject,and,consideredtogether

withtheproposedProject,havethepotentialtocontributetocumulativelysignificant impactson

surfacewaterhydrologyandsurfacewaterquality.Themajorityoftheseprojects,however,willbe

requiredtoimplementSWPPandSUSMPprogramsincompliancewithCityandStateregulations,

which would result in a cumulative decrease in stormwater runoff rate and volume and,

consequently,adecreaseintheamountofpollutantscarriedbystormwaterrunoff.

The Project site is the most upstream point of direct connection to the municipal storm drain

system that serves it and themunicipal system isadequately sized toaccommodateexistingand

post‐Project runoff volumes. With compliance with SUSMP volumetric or flow‐based treatment

controlBMPsthatregulatethevolumeofrunoffdischargedoff‐site,post‐Projectdischargevolumes

wouldremainunchanged,andmaydecrease,during50‐yeardesignstormevents.Withcompliance

with other SWPPP and SUSMP requirements, the potential for conveyance of pollutants off‐site

wouldalsobelessthansignificant.Projectimpactsonsurfacewaterhydrologyandsurfacewater

qualitywouldbelessthansignificant,andtheProjectisnotanticipatedtoresultinaconsiderable

contribution to cumulatively significant impacts related to surface water hydrology or surface

waterquality.



TheProjectisunderlainbyaperchedgroundwatertable,oraquifer,thatfluctuatesindepthwith

seasonalrainfallandother factors. Itdoesnotoverlieorproposewithdrawals fromaproduction

wellandwouldnotaffect thewaterquality inawell.TheproposedProjectwouldnotresult ina

considerablecontributiontocumulativelysignificantimpactsongroundwaterlevelsorquality.

iv.g hydrology and water quality - la city planning€¦ · iv.g surface water hydrology, surface...

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