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1) awetpond <br />2) a constructed wetland <br />3) a SMI StormFilter (see additional criteria below)(SEPA Earth and Water Policies) <br />4. All storm water facilities shall be designed in accordance with City standards. (SEPA Earth and <br />Water Policies) <br />5. SMI StormFilter: The City will allow the use of a Stormwater Management, Inc. (SMI) StormFilter <br />to meet the City's Stormwater treatment standards, provided the design and construction of the SMI <br />StormFilter meet the following criteria: <br />1) The StormFilter must be preceded by a pretreatment wetvault/tank containing at least 30% of <br />the 6-month, 24-hour sto.,n runoff volume from the contributing, developed drainage area. <br />2) The StonnFilter must treat at least the 6-month, 24-hour storm. <br />3) The StonnFilter cartridges shall be designed with a maximum flow rate of 7.5 gpm per <br />cartridge. Flows exceeding 7.5 gpm shall be bypassed around the system, but should generally <br />pass through the pretreatment wetvault/tank. <br />4) The StormFilter media shall target dissolved pollutants and nutrients, in addition to total <br />suspended solids. As more effective media become available in the future, the StonmFilter shall <br />be upgraded, during routine cartridge replacement, to utilize these improved media. <br />5) The StonnFilter shall be designed with a minimum of 2.3 feet of head differential between the <br />inverts of the inlet and outlet of the filter. Downstream hydraulic calculations will be performed <br />to demonstrate that downstream conditions will not reduce the hydraulic potential across the <br />filter due to backwater effects. <br />6) Routine maintenance of the StormFilter is required. A detailed operation and maintenance plan <br />for the system must be prepared for approval by the City. A certificate of system maintenance <br />must be submitted to the City annually. <br />7) Maintenance and operation of the StormFilter on this site shall be adapted, in the future, to <br />reflect the current knowledge regarding this emerging technology. <br />8) All other applicable, and non -conflicting criteria in the current edition of SMI's Product Design <br />Manual shall be followed in the design, construction, and maintenance of the SMI StormFilter <br />on this site. <br />9) For StormFilters located downstream of detention systems, the SMI mass loading design <br />procedure, with the following assumptions, shall be utilized: <br />a. TSS removal required = 80% <br />b. Vb = the volume of dead storage plus the 7-day average live storage volume from the <br />routing of the 6 month, 24-hour storm through the detention system (if a 7-day routing <br />is not available, use Vb = volume of dead storage) <br />c. Vr = the runoff volume from the mean annual storm (use precipitation volume of 0.48 <br />inches) <br />d. Depth of water in basin, H = depth of Vb <br />e. Mean annual rainfall = 37 inches <br />f. Percent runoff capture = 90% <br />g. Event Mean Concentration (EMC) = I00mg/L <br />h. Allowable cartridge flow rate = 7.5 gpm <br />i. Mass load per cartridge = 36 lbs <br />