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c I L] i I C G C I I P L U M t46M116101 51111 6 t.111v11r f6 ECOLOGY November 19, 2003 (Updated May 2006) GENERAL USE LEVEL DESIGNATION FOR PRETREATMENT (TSS) For CONTECH Stormwater Solutions Inc. Vortechs® System Ecology's Decision: Based on the CONTECH Stormwater Solutions Inc. (CONTECH) application submissions for the Vortechs System® and recommendations by the Technical Review Committee (TRC), Ecology hereby issues the following use designations for the Vortechs technology: 1. General Use Level Designation (GULD) for pretreatment use, as defined in the Ecology Manual Volume I, (a) ahead of infiltration treatment, or (b) to protect and extend the maintenance cycle of a Basic or Enhanced Treatment device (e.g., sand or media filter). This GULD applies to Vortechs units sized at an operating rate of no more than 35 gpm/sf of grit chamber area at the Water Quality design flow rate as determined using the Western Washington Hydrology Model (WWHM). The following table shows flow rates associated with various grit chamber sizes: Washington State Vortechs System Sizing Vortechs System Grit Chamber Diameter 35 gpm/ft2 Flow Rate Model ID ft cfs 1000 3 0.55 2000 4 1.0 3000 5 1.5 4000 6 2.2 5000 7 3.0 7000 8 3.9 9000 9 5.0 11000 10 6.1 16000 12 8.8 2. Properly designed and operated Vortechs systems may also have applicability in other situations (example: low -head situations such as bridges or ferry docks), for TSS and oil/grease removal where, on a case -by -case basis, it is found to be infeasible or impracticable to use any other approwA practice. Local jurisdictions should follow established variance or exception procedures in approving such applications. E 144