2005-10-25_PWETC_AgendaPacket - Laserfiche WebLink

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. Reduce the total volume of stormwater to protect surface water quality and provide recharge to groundwater. . Remove sediment, pollutants, and nutrients from stormwater to protect surface water quality. 2. Regulation. A permit and stormwater management plan are required under this rule for development ofa site. 3. Design Criteria For Stormwater Management Plans. Stormwater management plans must comply with the following criteria: . Peak discharge rates for developments must be at or below existing rates for the 2, 10, and 100 year storm events. . Developments must reduce runoff volumes in the amount equivalent to an inch of runoff from the impervious areas of the site. Stormwater must be pretreated to remove solids before discharging to infiltration areas to maintain the long-term viability of the infiltration area. . Infiltration rates will be assumed based on soil type as listed below, unless onsite infiltration tests are completed that indicate otherwise. Hydrologic Infiltration Soil Group IRate IISoil Textures A 10.50 in/hr Ilsand, loamy sand, or sandy loam B 10.25 in/hr Ilsilt loam or loam C 10.1 0 inlhr Ilsandy clay loam D 10.03 inlhr Ilclay loam, silty clay loam, silty clay, or clay Source: Urban Hydrology for Small Watersheds, SCS, June 1986. . Developments must incorporate effective non-point source pollution reduction BMPs to achieve 90% solid removal for the NURP water quality storm (2.5" rainfall). For the 90% removal calculation volume reduction will be considered. . Where stormwater management facilities are proposed, a maintenance agreement must be submitted and approved by the District. The agreement shall specifY the methods, schedule, and responsible parties for maintenance. The executed agreement must be submitted for recording with the County within 10 days of the issuance date of the permit. Public developments will require a maintenance agreement in the form of a Memorandum of Agreement or an approved Local Water Management Plan that details the methods, schedule and responsible parties for maintenance of stormwater management facilities for permitted development. 4. Required Exhibits. The following exhibits must accompany the permit application. One set, full size; two sets, reduced to maximum size of 11 "x 17." . (a) Property lines and delineation oflands under ownership of the applicant. . (b) Delineation of the subwatershed contributing runoff from off-site, proposed and existing subwatersheds on-site, emergency overflows, and drainageways. . (c) Proposed and existing stormwater facilities' location, alignment and elevation. . (d) Delineation of existing on-site wetland, marshes, shoreland and/or floodplain areas. CRWD Draft Rules - 45 Day Review Version October 6, 2005 Page 70fl4