2016 024 Ordinance - Laserfiche WebLink

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i~iVEC? l~1~~"EF~Si~ED ~~. Pt-1RTfiirRS May 2016 the 10-year, 24-hour stormwater runoff from upstream contributory areas. Open drainages stems: Open drainage systems shall be preferred on all new development sites to convey stormwater where feasible. Storm sewer systems shall be allowed only when the site cannot be developed at densities allowed under Village of Mayfield zoning or where the use of an open drainage system affects public health or safety, all as determined by the Village Engineer. The following criteria shall be used to design storm sewer systems when necessary: a. Storm sewers shall be designed such that they do not surcharge from runoff caused by the 10-year, 24-hour storm, and that the hydraulic grade line of the storm sewer stays below the gutter flow line of the overlying roadway, or below the top of drainage structures outside the roadway during a 25-year, 24-hour storm. The system shall be designed to meet these requirements when conveying the flows from the contributing drainage area within the proposed development and existing flows from offsite areas that are upstream from the development. b. The minimum inside diameter of pipe to be used in public storm sewer systems is 12 inches. Smaller pipe sizes maybe used in private systems, subject to the approval of the Village Engineer. c. All storm sewer systems shall be designed taking into consideration the tailwater of the receiving facility or water resource. The tailwater elevation used shall be based on the design storm frequency. The hydraulic grade line for the storm sewer system shall be computed with consideration for the energy losses associated with entrance into and exit from the system, friction through the system, and turbulence in the individual manholes, catch basins, and junctions within the system. d. The inverts of all curb inlets, manholes, yard inlets, and other structures shall be formed and channelized to minimize the incidence of quiescent standing water where mosquitoes may breed. e. Headwalls shall be required at all storm sewer inlets or outlets to and from open channels or lakes. Water Resource Crossings. The following criteria shall be used to design structures that cross a water resource in the Village of Mayfield: a. Water resource crossings other than bridges shall be designed to convey the stream's flow for the minimum 25-year, 24-hour storm; however a 50-year or 100-year 24-hour storm design may be required by-the Village Engineer. b. Bridges, open bottom arch or spans are the preferred crossing technique and shall be considered in the planning phase of the development. Bridges and open spans should be considered for all State Scenic Rivers, Coldwater habitat, exceptional warmwater habitat, seasonal salmonid habitat streams, and Class III headwater streams. The footers or piers for these bridges and open spans shall not be 18