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389022Metropolitan St. Louis Sewer District 2350 Market Street St. Louis, MO 63103-2555 (314) 768-6200 Apri18, 2011 Jeff Clarke Hydro -Kinetics Corp. 5741 Manchester Ave. St. Louis, MO 63110 RE: Hydrovex VHV Vortex Flow Regulator Provisional Use Level (PUL) Approval within the District Dear Jeff, The Metropolitan St. Louis Sewer District (MSD) has reviewed your application regarding the Hydrovex VHV Vortex Flow Regulator for use as a stormwater flow control device. MSD is pleased to provide Provisional Use Level (PUL) approval for the Hydrovex VHW Flow Regulator for use as a stormwater flow control device, subject to the following conditions. • The VHV Vortex Flow Regulator device may be used in flood protection (Qp) and channel protection (Cp) detention basin outlet structures. When used for Cp, routing must show that the 24-hour extended detention is provided. The 24 hour extended detention is defined providing a 24 hour lag time (T) for the one year 24 hour rain event. "T" is defined as the interval of time between the centroid of the inflow and the centroid of the outflow hydropgraph. • Project specific design calculations and maintenance plans furnished by Hydro -Kinetics Corp. must be included within the project's "Stormwater Management Facilities Report" prepared by the consulting engineer. All applicable elements for the design shall comply with the "VHV Vortex Flow Regulator Submittal to Metropolitan St. Louis Sewer District December 7, 2010. • Proper access shall be provided to each location to ensure proper maintenance and inspection of the flow control valve. The minimum size access hole is 30 inches in diameter. All proprietary lids and covers should be captive components. • The manufacturer shall guarantee the Hydrovex VHV Vortex Flow Regulator to be free from defects in materials and workmanship for a period of twelve months following MSD construction approval. • Flow regulators shall be protected from sediment build-up during and after construction. A trash rack will be required for orifices 8 inches and smaller. • The initial installation of the Hydrovex VHV Vortex Flow Regulator in the MSD shall include the following: 1) A manufacturer's or vendor's representative must be onsite during the installation to ensure the product's installation requirements are met. 2) Shop drawings indicating elevations of flowlines, pipe inverts, etc. will be required prior to installation. 3) The manufacturer or vendor must arrange for an as -built survey of the proprietary device to be performed by a Missouri -registered Professional Land Surveyor once the device has been installed, and prior to any testing or monitoring. 4) The manufacturer or vendor must perform quarterly inspections of the proprietary device 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. 5) Formal 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, and outfall conditions, etc. The reports shall also evaluate the performance of the owner's adherence to the approved maintenance program, and offer suggestions for any areas of improvement. 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, Jason Peterein, PE Civil Engineer (BMP Committee Chairman) Engineering Department / Planning Division Metropolitan St. Louis Sewer District pc: Jeremy Langburt - John Meunier Inc.