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333136Metropolitan St. Louis Sewer District 2350 Market Street St. Louis, MO 63103-2555 (314) 768-6200 October 5, 2009 Mr. Alex Weisz Regulatory Compliance Coordinator BaySaver Technologies, Inc. 1302 Rising Ridge Road Mount Airy, MD 21771 RE: Baysaver Technologies BayFilter System: St. Louis MSD Submission Redevelopment Use Level (RUL) + Provisional Use Level (PUL) Approval within District Dear Sir: The Metropolitan St. Louis Sewer District (MSD) has reviewed your application regarding the BayFilter for use as a Best Management Practice for stoiniwater management. MSD is pleased to provide Redevelopment Use Level (RUL) + Provisional Use Level (PUL) approval for use of the BayFilter as a stand-alone water quality BMP, subject to the following provisions. • The BayFilter is approved for use on 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 Stoiniwater Management Program (Rev. Jan. 2009). Proprietary devices should be treated a?supplementary (rather thana primary) means of meeting small MS 4 requirements. • Proposed uses and designs of the device must be in general confotniance with the infoiniation and methodologies provided in BayFilter's application dated January 18, 2009. • The use of buried filters shall be avoided on residential type projects. • The BayFilter 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 (WQv). Procedures for calculating WQ„ are provided in Volume I of the Maryland Stoiniwater Design Manual (2000). All units shall be installed with adequate storage to treat 75% of the WQv. • The peak inflow is limited to 30 gallons per minute (gpm) for each BayFilter cartridge. • The BayFilter cartridge shall have an annual sediment removal of no more than 150 pounds (lbs) at 30 gpm or 300 lbs at 15 gpm. Cartridges shall be designed to operate at 34 inches of head above the outlet and use a sand perlite media mix. • BayFilter systems must provide a minimum of 7 square feet of settling area for every BayFilter cartridge. • 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 include BaySeparator unit. No reduction in the number of filter cartridges shall be made for the installation of pretreatment. The BaySeparator shall be sized to remove 50% of the TSS (ok 110 PSD) at the water quality flowrate (WQf). • All units shall include at least one (1) drain down cartridge with a flow capacity of 0.5 gpm. • 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 BaySaver must be included within the project's "Stoiiiiwater Management Facilities Report" prepared by the consulting engineer. The devices maintenance plan shall be consistent with the plans presented in the June 4, 2009 revised BayFilter Technical and Design Manual. • The initial installation of the BaySeparator in the MSD shall include the following: 1) A manufacturer's or vendor's representative must be onsite during the proprietary BMP installation to ensure the product's installation requirements are met. 2) Shop drawings indicating elevations of flowlines, weirs, pipe inverts, etc. will be required prior to installation. 3) The manufacturer or vendor must arrange for an as -built survey of the proprietary BMP to be perfoinied by a Missouri -registered Professional Land Surveyor once the device has been installed, and prior to any testing or monitoring. 4) Upon construction approval of the initial installation of this device the manufacturer shall prepare and submit a QAPP (Quality Assurance Performance Plan) to the BMP committee for review. At a minimum the QAPP shall address: include 4a and 4b as bullets. 4a)The manufacturer or vendor must perfoini quarterly inspections of the proprietary BMP during its' first year of operation, which will include visual inspections and quantitative analysis of the service's sediment removal efficiency, especially as compared to its design efficiency. MSD requests to be invited to these inspections to further enhance familiarity and understanding of the device. 4b)Foriiial reports shall be submitted to MSD, including as-builts and at each quarterly inspection. The reports shall include summaries, quantitative analysis mentioned in item 4, photographs of the structure, inlet, internal conditions of the structure, the filters, and outfall conditions, etc. The reports shall also evaluate the perfoiniance of the owner's adherence to the approved maintenance program, and offer suggestions for any areas of improvement. 5) Upon approval of the QAPP, the manufacturer shall carry out the plan. 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, Michael T. Buechter, P.E. Principal Engineer (BMP Committee Chairman) Engineering/Design Metropolitan St. Louis Sewer District