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A .IuTC'AVs <br /> STORMWATER ' <br /> SOLUTIONS INC. <br /> Prepared by Joe Reidy on May 1,2008 <br /> Ron Riach <br /> JRR Engineering <br /> RE: Review of StormFilter""Design for Bank of Washington project. <br /> This is to document for the City of Everett our review of the plans and the proposed application of the <br /> StormFitter at this site as you have requested. <br /> CONTECH Stormwater Solutions, Inc. has reviewed the StormFilter design for the Bank of Washington site. <br /> The storm drainage system for this project was designed by JRR Engineering of Lynnwood,WA. We believe <br /> the StormFilter T""is an appropriate water quality solution for this site. <br /> The water quality flow rate was determined by JRR Engineering, using the Santa Barbara Urban Hydrograph <br /> method.The water quality design precipitation of 1.08"/24-hour was utilized in the basin model: Using the <br /> conversion from SBUH to WWHM by the Washington DOE GULD of the StormFitter in an online configuration, <br /> the design water quality flow rate was determined to be 0.13 cfs.The 96"manhole StormFilter with (8) 18" <br /> cartridges will treat up to 0.1336 cfs. Thus,the StormFilter is correctly sized for our standard flow rate of 7.5 <br /> gpm (0.0167 cfs) per cartridge. Since the 96"manhole StormFilter does not have an inlet bay,the hydraulic <br /> drop from inlet invert to outlet invert can be reduced to 2.0'for the 18"cartridge without creating backwater in <br /> the inlet pipe. Our systems require periodic maintenance to operate properly. Given typical rooftop/parking lot <br /> pollutant loading rates, CONTECH Stormwater Solutions, Inc. recommends maintenance on an annual basis. <br /> The configuration of the StormFilter inlet and outlet pipes is acceptable. The system appears to be <br /> constructible and is located in order to facilitate maintenance activities. In summary,this filter is expected to <br /> operate in accordance with CONTECH Stormwater Solutions, Inc.'s design intent. However, CONTECH <br /> Stormwater Solutions, Inc. has not reviewed the hydraulics of the collection system upstream or downstream of <br /> the filter. <br /> Either you or the City's reviewer may contact me if you have any questions. <br /> Sincerely, <br /> /liffJoe Re' y <br /> Project Designer <br /> ©2006 CONTECH Stormwater Solutions 12021-B NE Airport Way,Portland OR 97220 Page 1 of 1 <br /> contechstormwater.com Toll-free:800.548.4667 Fax 800.561.1271 TS-P052 <br /> 5 <br />