2600 FEDERAL AVE 2021 PORT OF EVERETT 2025-09-29

wlm� WA SH IN GT0N STATE EECA4 LE' C GY April 2017 GENERAL USE LEVEL DESIGNATION FOR BASIC (TSS) TREATMENT For CONTECH Engineered Solutions Stormwater Management StormFilter® With ZPG Media at 1 gpm/sq ft media surface area Ecology's Decision: Based on the CONTECH Engineered Solutions' (CONTECH) application submissions,Ecology hereby issues a General Use Level Designation (GULD) for the Stormwater Management StormFilter® (StormFilter): 1. As a basic stormwater treatment practice for total suspended solids (TSS) removal, • Using ZPGTM media (zeolite/perlite/granular activated carbon),with the size distribution described below, • Sized at a hydraulic loading rate of 1 gpm/ft2 of media surface area, per Table 1, and • Internal bypassing needs to be consistent with the design guidelines in CONTECH's current product design manual. Table 1. StormFilter Design Flow Rates per Cartridge Effective Cartridge Height (inches) 12 18 27 Cartridge Flow Rate ( pm/cartrid e) 5 7.5 11.3 2. Ecology approves StormFilter systems containing ZPGTM media for treatment at the hydraulic loading rates shown in Table 1, and sized based on the water quality design flow rate for an off-line system. Contech designs their StormFilter systems to maintain treatment of the water quality design flow while routing excess flows around the treatment chamber during periods of peak bypass. The water quality design flow rates are calculated 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 latest version of the Western Washington Hydrology Model or other Ecology-approved continuous runoff model. CONTECH-StormFilter®GULD Maintenance Update(November 2012) Page 11