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WA SN INGION SIAIE OEPARE 'E NI OF E C O L O G Y November 2016 GENERAL USE LEVEL DESIGNATION FOR BASIC (TSS), ENHANCED, PHOSPHORUS & OIL TREATMENT For Americast Filterrag Ecology's Decision: Based on Americast's submissions, including the Final Technical Evaluation Reports, dated March 27, 2014 and December 2009, and additional information provided to Ecology dated October 9, 2009, Ecology hereby issues the following use level designations: A General Use Level Designation for Basic, Enhanced, Phosphorus, and Oil Treatment at the following water quality design hydraulic loading rates: Treatment Hydraulic Conductivity* (in/hr) for use in Western Washington Sizing Infiltration Rate (in/hr) for use in eastern Washington Sizing Basic 70.92 100 Phosphorus 70.92 100 Oil 35.46 50 Enhanced 24.82 35 *calculated based on listed infiltration rate and a hydraulic gradient of 1.41 inch/inch (2.55 ft head with 1.80 ft media). 2. The Filterra(A' unit is not appropriate for oil spill -control purposes. 3. Ecology approves the Filterra�R' units for treatment at the hydraulic loading rates listed above, to achieve the maximum water quality design flow rate. Calculate the water quality design flow rates using the following procedures: Western Washington: for treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using the sand filter module in the latest version of the Western Washington Hydrology Model or other Ecology -approved continuous runoff model. The model must indicate the unit is capable of processing 91 percent of the influent runoff file. Eastern Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using one of the three flow rate based methods described in Chapter 2.2.5 of the Stormwater Management Manual for Eastern Washington (SWMMEW) or local manual.