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k r� <br /> Basic Treatmen <br /> The filter media cartridges are sized based on an approved flowrate capacity per canister,as est%:blished <br /> by ihe WSDOE and Ihe manufacturer's recommendations. A treatment capaciry of 7.5 gpm is used to <br /> meet the WSDOE's General Use I_evel Designation of allowing 1 gpm/square foot of�nedia treaiment and <br /> applying i[to the 18-inch standard filter that is provided by Contech S[ormwatPr Solutions. <br /> LVater Quality Flowrate = 15.3 gpm <br /> T�eatment Capacity - � gpm/cartridge <br /> Required No. o(Cartridges = 2.0 cartridges <br /> Ba=ed on this calculation, two carVidges will bP provided. <br /> 2300 Kasc� Park Road Property <br /> EXISTING CONDITIONS <br /> The existing Community Transit Kasch Pari<Operating Base is being used as a bus maintenance and <br /> storage base. <br /> A mWti-phased Master Planning exercise that toelc place in 1993-1994 included development of a <br /> storm drainage runoff control system to menage a full operatin�base build out. The entire parcel <br /> cons�sts of 20 acres. 7he Master Plan accounted for a full build-out of 13.9 acres of impervious area <br /> and 5 acres of pervious,and the remainder as wetlands and wetland bu(fer. The stormwater system <br /> includes catchbasins and conveyance pipe,which collect site runoff and direct it to a flow splitter <br /> leading to an oil/water separetor or directly to the detention v�ulL The detention vault has been sized <br /> for Ihe 13.12cres of impervious surface and 5 acres of pervious. From the outlet of the flow control <br /> for the detention system,the full rivo-year release rate is pumped up to a bioswale to provide water <br /> yuality treaUnent. The ouUet to the bioswale and the remaining detention system disr.harge to a <br /> �.�.dvert in[he far south east corner of the site. The stormwater controls were sized and built for t4a <br /> ireas listed above. Currently,the site consists of only 12 acres of im�ervious surface. rathc� than the <br /> �.�.�II 13.1 acres of impervious surface for which the system was designed. <br /> r:EDEVELOPED CONDITIONS <br /> ;ae redevelepment a[the exlsting Operating Base consis[s nt regrading and paving of an existing <br /> ;��,�rking IoL The existing parking lot is currenily asphalt paved and includes stormwater catchbasins <br /> ;nd conveyance piping that connect this area to the ornsite stormwater runoff controls mentioned <br /> above. The parking area is currenUy sloped up to 10 parcent,and Communiq�7ransit desires to <br /> I re-grade it to approximately 2 percent sfope and pave it in concrete to allow buses to be parked there. <br /> The area impacted is approxim�:�ly 0.45 acres and is 100 percent impervious. In addition to the <br /> parking area,there will be minor grading to the area surrounding the nr.w bw wash building. This will <br /> iequire removal of approximately 2,5E5 square feet of existing ccncrete pavement to accommodate <br /> regrading and �.;idity trenching pnor to repaving with concrete. <br /> ���-- <br /> Community Translt 3 <br /> I<nsch Park Operaling Baso <br />