The URL can be used to link to this page

Home My WebLink AboutAproved Stormwater Adjustment of Vortechs for presettling for Sunset's Edge Townhomes PUD.pdfDenisLawMayor0Community&EconomicDevelopmentC.E.“Chip”Vincent,AdministratorAugust29,2017HaroldDuncanson,PEDuncansonCompany,Inc.1455Wl5SStreet,Suite102Seattle,Washington98166RE:Sunset’sEdgeTownhomesPUD(C17002053)—UseofVortechs(Contech)hydrodynamicseparatordevicetoprovidepresettlingupstreamof$tormfilter—Adjustment2017-06DearMr.Duncanson:TheCityofRentonhascompletedreviewoftheadjustmentrequestforSunset’sEdgeTownhomes(C17002053)inaccordancewiththeCityadopted2009KingCountySurfaceWaterDesignManual(KCSWDM)andassociatedCityAmendments.Astheapplicant’sengineer,youarerequestinganadjustmentfromthe2009KCSWDMtouseVortechs(Contech)hydrodynamicseparatordevicetoprovidepresettlingupstreamofaStormfiltermediafilterfacilityasneededforBasicWaterQualitytreatment.Findings:1.Theprojectisazerolotline15unitmulti-familyPUDprojectandislocatedat701SunsetBlvdNE.2.Thestormfacilitiesfortheprojectwillbeprivatelymaintained.3.TheprojectisvestedtotheCityadopted2009KingCountySurfaceWaterDesignManual(KCSWDM)andassociated2009CityAmendments4.Atthetimeofadoptionofthe2009SurfaceWaterManual,theVortechsdevicedidnotyethaveEcologyGULDapprovalandsowasnotanapprovedpresettlingfacility.TheVortechshassincereceivedGULDapproval.5.DepartmentofEcology’srecommendationwasthattheVortechssystem,sizedat35GPM/sfshouldprovide,ataminimum,equivalentperformancetoapresettlingbasinasdefinedintheStormwaterManagementManualforWesternWashington.6.Thecurrent2017CityofRentonSurfaceWaterManualacceptstheuseofVortechsforpre-treatmentforprivatelymaintainedfacilities.Basedontheinformationprovidedintheenclosedadjustmentrequest,theuseofVortechs(Contech)hydrodynamicseparatordevicetoprovidepresettlingupstreamofStormfllterisapprovedfortheSunset’sEdgeTownhomesPUDwiththefollowingconditionsofusethatarerequiredbytheDepartmentofEcology(GULDapproval).1055SouthGradyWay,Renton,WA98057rentonwa.gov Design,assemble,install,operate,andmaintainVortechsSystemsinaccordancewithapplicableCONTECHProductDesignManualVersion4.1(April2006)ormostcurrentversions,andtheEcologyDecision.2.DischargesfromtheVortechsSystemshallnotcauseorcontributetowaterqualitystandardsviolationsinreceivingwaters.Ifyouhaveanyquestionsaboutthisadjustment,pleasecontactBrianneBannwarth,DevelopmentEngineeringManager,at(425)430-7299orRonStraka,SurfaceWaterUtilityEngineeringManager,at(425)430-7248.RonaldJ.Straka,P.E.SurfaceWaterUtilityEngineeringManagerPage2of2August29,2017Conditions:1.Sincerely,BrianneBannwarth,RE.DevelopmentEngineeringManagercc:LysHornsby,PB.,UtilitySystemsDirectorGaryFink,civilEngineer1WRohiniNair,PlanReviewerMaltHerrera,SeniorPlanner1055SouthGradyWay,Renton,WAp8057rentonwa.gov