2016 024 Ordinance - Laserfiche WebLink

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J CHIkGRtE~ ~.. r~ F:lG~E4~ \'L~~TER~N+EB • ~ " E~~~iTP~E[~S ~_. events as defined in Table 2. moray 2016 e. Sites within watersheds of Coldwater habitat streams shall include SCMs to infiltrate the water quality volume or reduce the temperature of discharged runoff. SCMs that reduce the temperature of discharged runoff include bioretention, permeable pavement, underground detention, and incorporation of shading and infiltration in parking lot design. f. Each practice shall be designed to facilitate sediment removal, vegetation management, debris control, and other maintenance activities defined in the Inspection Plan and Maintenance Agreement for the site. Table 2: Draw Down Times for Stormwater Control Measures Stormwater Control Measure Drain Time of WQv Infiltration Basin or Trench' 48 hours Permeable Pavement -Infiltration' 48 hours Permeable Pavement -Extended Detention 24 hours Extended Detention Facilities ^ Dry Extended Detention Basing 48 hours ^ Wet Extended Detention Basin 3 24 hours ^ Constructed Wetlands (above permanent pool) a 24 hours ^ Bioretention Area/Cells,6 24 hours ^ Sand and other Media Filtrations 24 hours ^ Pocket Wetland' 24 hours ~ Practices designed to fully infiltrate the WQ~ shall empty within 48 hours to provide storage for subsequent storm events. z The use of a forebay and micropool is required on al] dry extended detention basins. Each is to be sized at a ~niniinum ] 0% of the WQ~. 3Provide both a permanent pool and an extended detention volume above the permanent pool, each sized with at least 0.75*WQv . 4Extended detention shall be provided for the WQv above the permanent water pool. s The surface ponding area shall completely empty within 24 hours so that there is no standing water. Shorter drawdown times are acceptable as long as design criteria in Rainwater and Land Development have been met. 6 This includes grassed linear bioretention, which was previously titled enhanced water quality swale. Pocket wetlands must have a wet pool equal to the WQ~, with 25% of the WQ~ in a pool and 75% in marshes. The EDP, above the permanent pool must be equal to the WQ,.. Additional criteria apple to infiltration facilities. a. Infiltration facilities should be designed to meet all criteria in Rainwater and Land Development. 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. 22