2011 018 Ordinance - Laserfiche WebLink

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* The WQv shall completely infiltrate within 48 hours so there is no standing or residual water pool. ** Sized to pass a hydrograph with a volume equal to the WQv, a duration of 2 hours, peak rainfall intensity of 1 inch/hour at a depth of no more than 3 inches and have a minimum hydraulic residence time of 5 minutes. The use of this criterion is limited to sites where the total area disturbed is 5 acres or less. Prior approval from the Village Engineer is necessary to use this practice. For sites greater than five (5) acres or less than five (5) acres but part of a larger common plan of development or sale which will disturb five (5) or more acres, prior written approval is required from the Ohio EPA. ** The use of a forebay and micropool is required on all extended dry detention basins. Each is to be sized at a minimum 10% of the WQv. +Provide both a permanent pool and an extended detention volume above the permanent pool, each sized with at least 0.75*WQv. ^Pocket wetland must have a wet pool equal to the WQv, with 25% of the WQv in a pool and 75% in marshes. The EDV above the permanent pool must be equal to the WQv. d. Each practice shall be designed to facilitate sediment removal, vegetation management, debris control, and other maintenance activities defined in the Inspection and Maintenance Agreement for the site. Additional criteria ap~lying to infiltration facilities. A. Infiltration facilities shall only be allowed if the soils of the facility fall within hydrologic soil groups A or B, if the seasonal high water table is at least three (3) feet below the final grade elevation, and any underlying bedrock is at least six feet below the final grade elevation. B. All runoff directed into an infiltration basin must first flow through a pretreatment practice such as a grass channel or filter strip to remove coarser sediments that could cause a loss of infiltration capacity. C. During construction, all runoff from disturbed areas of the site shall be diverted away from the proposed infiltration basin site. No construction equipment shall be allowed within the infiltration basin site to avoid soil compaction. 4. Additional criteria applying to extended conveyance facilities. a. Facilities shall be lined with fine turf-forming, flood tolerant grasses. b. Facilities designed according to the extended conveyance detention design drain time shall: (I) Not be located in areas where the depth to bedrock and/or seasonal high water table is less than 3 feet below the final grade elevation. (2) Only be allowed where the underlying soil consists of hydrologic soil least equivalent to group (HSG) A or B, unless the underlying soil is replaced by at a 2.5 foot deep layer of soil amendment with a permeability a HSG A or B soil and an underdrain system is provided. c. Facilities designed according to the flow through design drain time shall: