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366309M5CI Metropolitan St. Louis Sewer District 2350 Market Street St. Louis, MO 63103-2555 (314) 768-6200 August 3, 2010 Mr. Josh Dickinson CONTECH Stormwater Solutions 6413 Lloyd Ave. St. Louis, MO 63139 RE: CONTECH Stormwater Solutions - StormFilter: St. Louis MSD Submission General Use Level (GUL) Approval within District Dear Sir: The Metropolitan St. Louis Sewer District (MSD) has reviewed your application regarding the StormFilter for use as a Best Management Practice for stormwater management. MSD is pleased to provide General Use Level (GUL) approval for use of the StoiinFilter as a stand-alone water quality BMP, subject to the following provisions. • The StonnFilter is approved for use on new development and redevelopment sites of any size. This approval is based on compliance with requirements listed in MSD's Proprietary Water Quality Products and the MSD's Stormwater Management Program (Rev. Jan. 2009). Proprietary devices should be treated as a supplementary (rather than a primary) means of meeting small MS 4 requirements. • Proposed uses and designs of the device must be in general conformance with the information and methodologies provided in StormFilter's application dated July 2007. • The use of buried filters shall be avoided on residential type projects. • The StormFilter must be sized to capture all floatable trash and free oil, and remove 80% of the total suspended solids for the site Water Quality Volume (WQ,,). Procedures for calculating WQ,, are provided in Volume I of the Maryland Stormwater Design Manual (2000). All units shall be installed with adequate storage to treat 75% of the WQ,,. • The StormFilter cartridges shall be designed in accordance with the following parameters: Cartridge Height 12 inches 18 inches 27 inches Cartridge Flow Rate at 1 gpm/ft2 (gpm/cart) 5 7.5 11.3 Mass Loading Capacity at 1 gpm/ft(lb) 24 36 54 Cartridge Flow Rate at 2 gpm/ft2 (gpm/cart) 10 15 22.6 Mass Loading Capacity at 2 gpm/ft2 (lb) 15 22.5 32.75 • The device must be configured so that the filter vault is closed off from the outfall. All units including pretreatment, should be configured in an off-line layout. • Adequate pretreatment shall be provided in all site designs. In this case this will likely consist of a Vortsentry HS or approved Hydrodynamic Separator (HDS) unit (Vortsentry or Vortechs). No reduction in the number of filter cartridges shall be made for the installation of pretreatment. The HDS shall be sized to remove 50% of the TSS (OK 110 PSD) at the water quality flowrate (WQf). • All proprietary lids and covers should be captive components. At least one "oversized" access shall be proved on the filter vault and storage chamber (each). The Neenah MH 1741-F1, cover, or equivalent, MSD approved cover is required. • Project specific design calculations and maintenance plans furnished by CONTECH must be included within the project's "Stormwater Management Facilities Report" prepared by the consulting engineer. The device's maintenance plan shall be consistent with the plans presented in StormFilter's July 2007 application. • CONTECH will provide local field testing and observations in accordance with the July 7, 2009 QAPP for the Edward Jones North Campus Project for the StormFilter. MSD reserves the ability to withdraw or modify this approval based on subsequent information, including information indicating that this BMP does not satisfy MSD rules, requirements, or construction specifications. Sincerely, muAw,V T u,t,ca Michael T. Buechter, P.E. Principal Engineer (BMP Committee Chairman) Engineering/Design Metropolitan St. Louis Sewer District pc: Jim Lenhart, CONTECH Construction Products, Inc