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Home My WebLink AboutC_ADS Stormchamber System Adjustment Approval_170714.pdfDenisLawMayorCommunity&EconomicDevelopmentC.E.“Chip”Vincent,AdministratorJuly13,2017LauriePfarr,PELPDEngineering,Inc.1932;stAvenue,Suite201Seattle,WA98101RE:SunsetCourtApartments(U16006459)—ADSStormTechChamberSystem-Adjustment2017-05(LUA16-000068)DearMs.Pfarr:TheCityofRentonhascompletedthereviewoftheenclosedadjustmentrequestsfortheabovereferencedprojectinaccordancewithCityadopted2009KingCountySurfaceWaterDesignManual(KCSWDM)andCityAmendmentstothe2009KCSWDMtowhichtheprojectisvestedtoinaccordanceRMC4-1-045.Astheapplicant’sengineer,youarerequestinganadjustmentfromthe2009KingCountySurfaceWaterDesignManualtosection5.3,DetentionFacilitiesandaccessroadrequirements.TheadjustmentrequestproposestouseStormTechSC-740ChamberSystemasadetentionfacility.TheADSStormTechSC-740ChamberSystemisnotincludedintheCity’sadopted2009KCSWDMasaflowcontrolfacility,butjurisdictionslikeKingCounty,Bothell,Seattle,andtheCityofRentonhaveapprovedtheuseofthesefacilitiesthroughanadjustment/varianceprocess.Findings:1.Theprojectsiteislocatedat1144-1158HarringtonAveNE.Flowcontrolstandardapplicabletotheprojectisthepeakflowcontrolstandardmatchingexistingconditions.2.Proposedprojectwillultimatelyconstructamulti-familydevelopmentwithparkingareathatwillresultinapproximately1.27acresofimperviousand0.73acresofpervious.3.Thesurfacewaterfromtheproposeddevelopmentroofrun-offwillbecollectedthenroutedthroughtwostormdrainagestructures,eachwithtwofootsumps,priortoenteringtheStormTechSC-740ChamberSystempriortodischargeintothepublicstormdrainageconveyancesysteminHarringtonAvenueNE.4.TheADSStormTechSC-740ChamberSystemandotheron-sitedrainagefacilitieswillbeprivatelyownedandmaintained.TheADSStormTechSC-740ChamberSystemisnotapprovedfortheuseofCity(Publicly)ownedandmaintainedstormsystemswithoutanadjustmentrequest.1055SouthGradyWay,Renton,WA98057.rentonwa.gov Ms.LauriePfart,PEPage2of4July13,20175.AmaintenanceaccessroadtothefacilitywillnotbeprovidedinaccordancewiththedesignstandardsoutlinedinSection5.3.2.1and5.3.3.1.Theapplicanthasprovideddocumentationfromtheproposedmaintenanceoperatorofthefacilitythatthefacilitycanbemaintainedwiththeuseofa300-fthosewithparkingintheparkingstallsonthesouthsideoftheproposeddevelopment.Basedontheinformationprovidedintheenclosedadjustmentrequest,theADSStormTechSC-740ChamberSystemforflowcontrolisapprovedfortheproposeddevelopmentlocatedattheSunsetCourtApartmentswiththefollowingconditions:Conditions:1.TheADSStormTechSC-740ChamberSystemshallbedesignedpersection5.4.6ofthe2009KCSWDMforalternateinfiltrationsystems.TheADSStormTechSC-740ChamberSystemmaybesubstitutedfortherequiredlengthofperforatedpipeandwashedrockfilledtrenchintheSWDMdesigns.2.ThemanifoldsystemfortheinlettotheADSStormTechSC-740ChamberSystemshallbeabletovisuallybeinspectedfromtheinletmanholewiththeoverflowweir.Theweirshallberemovablesuchthatthevisualinspectionisfeasible.3.An8”inspectionportshallbelocatedateachendofeachisolatorrowoftheADSStormTechSC-740ChamberSystem.4.MaintenancestandardsspecifictotheADSStormlechSC-740ChamberSystemsshallbeincludedintheTechnicalInformationReport.5.Theconstructionbondamount(foronsiteimprovements)willneedtoincludetheadditionalcostofinstallingallrequiredflowcontrolandwaterqualityfacilities.6.TheADSStormTechSC-740ChamberSystemmustbeinstalledinanareathatisaccessibletomaintenanceequipment.ThemaintenanceoftheADSStormTechSC-740ChamberSystemrequiresavacuumtruck.Themanholecovers,and/oraccesshatchesoftheSystemsmustbeplacedinlocationsthatcanbeeasilyreachedbysuchavehicle.10.InstallationoftheADSStormTechSC-740ChamberSystemshallfollowthemanufacturer’srecommendedinstallationandmaintenanceprocedures.11.TheADSStormTechSC-740ChamberSystemshallbeinstalledinaccordancewiththeCityapprovedconstructionplans.As-builtconstructionplansshallbeprovidedpriortoissuanceoftheFinalCertificateofOccupancy.12.TheADSStormTechSC-740ChamberSystemwillbeprivatelyownedandmaintainedbythepropertyowner.13.IfitisdeterminedthatthePropertyOwnerisunabletoproperlymaintainthesystemasdesigned,thePropertyOwnerwillberesponsibleforexploringotheravenuestomaintainthesystemandobtainingconcurrencewiththeManufacturerthattherevisedmaintenanceoption(s)is/areanacceptablemethodofperformingmaintenancetotheADSStormlechSC-740ChamberSystem.1055SouthGradyWay,Renton,WA98057rentonwa.gov Ms.LauriePfarr,PEPage3of4July13,201714.Facilityinspection,maintenance,andreportingarerequiredbytheCityofRentonSurfaceWaterUtilityforthePropertyOwnermaintainedADSStormTechSC-740ChamberSysteminperpetuity.Thefacilityinspection,maintenanceandreportingisrequiredpertheEcologyNationalPollutantDischargeEliminationSystemPhaseIIMunicipalStormwaterPermit(SectionS5.C.4.c.iii).Facilityownersareresponsibleforensuringthatstormwaterfacilitiesareproperlymaintainedandfunctioningasdesignedandpermitted.15.TheADSStormTechSC-740ChamberSystemshallbeinspectedandmaintainedinaccordancewithmanufacturerrecommendationsand,inaddition,beinspectedandmaintainedasdetailedbelow:a.Forthefirsttwoyearsafterconstruction,theADSStormTechSC-740ChamberSystemshallbeinspectedeverysixmonthstoassureproperperformance.Inspectionreportswillbeusedtodeterminefuturesite-specificmaintenanceschedulesandrequirements.b.Followingthefirstyearofoperation,thefacilityowner(s)shallannuallyhavetheADSStormlechSC-740ChamberSysteminspectedandmaintainedpertheproceduresinthemostrecentversionoftheADSStormTechSC-740ChamberSystemOperationandMaintenanceManuals.AllwrittenrecordsoftheinspectionandmaintenanceshallbesubmittedtotheCityofRentonSurfaceWaterUtility,totheattentionofSurfaceWaterUtilityPrivateStormwaterFacilityInspectionProgram.IfmorefrequentinspectionandmaintenanceoftheADSStormlechSC-740ChamberSystemisrequiredbythemanufacturerorisneededtoensureperformanceofthefacility,thentheadditionalinspectionandmaintenancereportscompletedwithintheyearshallbeprovidedwiththeannualreport.c.Uponcompletionofthetwo-yearinspectionperiodafterconstructionoftheADSStormTechSC-740ChamberSystem,theCitywillreviewtheinspectionreportandfacilitymaintenancelogtore-evaluatefutureinspectionsfrequencyofthesystem.Theinformationwillbeusedtodetermineiftheminimuminspectionfrequencyofonceayearcanbeallowed.d.Maintenanceactivities,toassureproperperformanceoftheADSStormTechSC-740ChamberSystemsshallbeasneeded,orasdeterminedintheannualinspection,tocomplywiththerequirementsinthe2009KingCountySurfaceWaterDesignManualformaintenanceofdrainagefacilities.Inaddition,maintenanceproceduresshouldfollowthosegiveninthemostrecentversionoftheADSStormTechSC-740ChamberSystemOperationandMaintenanceManual.16.TheapplicantwillneedtosubmitaDrainageFacilityCovenantfortheSunsetCourtApartmentsProjecttoallowtheCityaccesstothefacilityforinspectionoftheprivateADSStormTechSC-740ChamberSystemthatwillbeprivatelymaintained.TheDrainageFacilityCovenantmustbeapprovedforrecordingpriortotheCity’sCivilConstruction1055SouthGradyWay,Renton,WA98057rentonwa.gov Ms.LauriePfarr,PEPage4of4July13,2017permitbeingissuedfortheconstructionofthefacilities.TheDrainageFacilityCovenantcanbefoundinReferenceJoftheCityofRentonAmendmentstothe2009KingCountySurfaceWaterDesignManual.AsiteplanshowingthelocationofthetreatmentfacilitymustbeincludedasExhibitAwiththedeclarationofcovenant.17.Theapprovalofthisadjustmentdoesnotrelievetheapplicantfromothercity,state,orfederalrequirements.18.TheapprovalofthisadjustmenttousetheADSStormTechSC-740ChamberSystemsforthisprojectdoesnotauthorizetheuseoftheADSStormTechSC-740ChamberSystemsonfutureprojectswithoutpriorapprovalfromtheCityofRenton.Ifyouhaveanyquestionsaboutthisadjustment,pleasecontactBrianneBannwarth,DevelopmentEngineeringManager,at(425)430-7299orRonStraka,SurfaceWaterUtilityEngineeringManager,at(425)430-7248.RonaldJ.Straka,P.E.SurfaceWaterUtilityEngineeringManagerH:\FileSys\SWP-SurfaceWaterProjects\SWP-27-SurfaceWaterProjects(CIP)\27-3129RentonStormwaterManual\ADJUSTMENTS\2016\2016-13956NE24thStreet-ADAStormTechChamberSystem.docSincerely,/BrianneBannwart,P.E.DevelopmentEngineeringManagercc:LysHornsby,P.E.,UtilitySystemsDirectorGaryFink,CivilEngineerIllAnnFowler,PlanReviewerMattHerrera,SeniorPlanner1055SouthGradyWay,Renton,WA98057rentonwa.gov