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Verizon Communications-Stormwater Site Plan Everett,WA <br /> ECH <br /> ittno. ire Size and Cost Estimate <br /> SfORMWATER <br /> S•++� OLUTIONrjiNc. <br /> Prepared by Joe Reidy on February 12,25W <br /> LBA Verizon—Stormwater Treatment System Rev 1 <br /> Everett,WA <br /> Information provided: <br /> • Structure ID= Conversion <br /> • Total Area(acre)= 9.12 <br /> • Percent Impervious= 80 <br /> • Water Quality Flow,WQF(cfs)= 0.65 <br /> • Peak Flow,Q100(cfs)= Offline <br /> • Height of cartridge(inches) 27 <br /> • Cartridge flow rate(gpm) 11.25 <br /> • Drop required from inlet to outlet 3.0 <br /> (feet) <br /> Assumptions: <br /> • Media=ZPG cartridges <br /> • Presiding agency=City of Everett <br /> Size and cost estimates: <br /> The StormFilter is a flow-based system,and therefore,is sized by calculating the water quality flow rate associated <br /> with the design storm.The water quality flow rate was calculated by the design engineer using the SBUH method <br /> and provided to CONTECH Construction,Inc. <br /> Structure water Approximate No.of Estimated <br /> ID Quality Depth Cartridges System Size Cost <br /> Flow <br /> Conversion 0.65 6' 26 8'x16' $68,350 <br /> The estimated costs are for complete systems delivered to the job site. This estimate assumes that the vault is 6 <br /> feet deep. The final system cost will depend on the actual depth of the units and whether extras like doors rather <br /> than castings are specified, The contractor is responsible for setting the StormFilter systems and all external <br /> plumbing. <br /> Typically the precast StormFilters have internal bypass capacities of 1.8 cfs. If the peak discharge off the site is <br /> expected to exceed this rate, we recommend placing a high-flow bypass upstream of the StormFilter system. <br /> CONTECH Stormwater Solutions could provide our high-flow bypass,the StormGate,which provides a combination <br /> weir-orifice control structure to limit the flow to the StormFilter. The estimated cost of this structure is$4,500. The <br /> final cost would depend on the actual depth and size of the unit. <br /> 02006 CONTECH Stormwater Solutions 120214B NE Airport way.Portland OR 97220 Page 1 of 1 <br /> contechstormwater.com Toll-free:800.548.4667 Fax:800.561.1271 TS-P027 <br /> A presettling chamber will also be installed as part of the water quality system, upstream of <br /> the StormFilter Vault. Per the DOE Manual requirements, Chapter 6 Pretreatment states <br /> that the treatment volume to be used for sizing a presettling basin shall be at least 30010 of <br /> the total volume of runoff from the 6-month, 24-hour storm event. The volume of this <br /> storm event was calculated using StormShed software. As shown above, the volume of the <br /> water quality storm event is 28,629 CF. The r volume to be used for sizing the presettling <br /> chamber was calculated as follows: <br /> PACLAN D Job#50183001 Page 23 <br />