2008 005 Ordinance - Laserfiche WebLink

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Direct runoff to a BMP: The site shall be designed to direct runoff to one or more of the following storm water management practices. These practices are listed in Table 2 of this regulation and shall be designed to meet the following general performance standards: a. Extended conveyance facilities that slow the rate of storm water runoff; filter and biodegrade pollutants in storm water; promote infiltration and evapotranspiration of storm water; and discharge the controlled runoff to a water resource. b. Extended detention facilities that detain storm water; settle or filter particulate pollutants; and release the controlled storm water to a water resource. c. Infiltration facilities that retain storm water; promote settling, filtering, and biodegradation of pollutants; and infiltrate captured storm water into the ground. The Mayfield Village Engineer may require a soil engineering report to be prepared for the site to demonstrate that any proposed infiltration facilities meet these performance standards. d. The Mayfield Village Engineer may approve other BMPs if the applicant demonstrates to the Mayfield Village Engineer's satisfaction that these BMPs meet the objectives of this regulation as stated in Section 1129.09.C.6. 2. Criteria applyin~ to all storm water mana e~~ment practices. Practices chosen must be sized to treat the water quality volume (WQv) and to ensure compliance with Ohio Water Quality Standards (OAC Chapter 3745-1). a. The WQv shall be equal to the volume of runoff from a 0.75 inch rainfall event and shall be determined according to one of the following methods: (1) Through a site hydrologic study approved by the Mayfield Village Engineer that uses continuous hydrologic simulation; site-specific hydrologic parameters, including impervious area, soil infiltration characteristics, slope, and surface routing characteristics; proposed best management practices controlling the amount and/or timing of runoff from the site; and local long-term hourly records, or (2) Using the following equation: WQv where terms h WQv C P A = C*P*A/12 ave the following meanings: = water quality volume in acre-feet =runoff coefficient appropriate for storms less than 1 in. = 0.75 inch precipitation depth = area draining into the storm water practice, in acres. Runoff coefficients required by the Ohio Environmental Protection Agency (Ohio EPA) for use in determining the water quality volume are listed in Table 1. Alternatively, the Mayfield Village Engineer may consider use of the following equation to calculate the runoff coefficient if the applicant can demonstrate that appropriate controls are in place to limit the proposed impervious area of the development: