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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 of a 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. � I l�an rates will be assumed based on soil type as listed below, unless v�siie infiltration tests are completed that indicate otherwise. Hydrologic Infiltration Soil Group Rate Soil Textures A • """"""' sand, loamy sand, or sandy �flam B silt Iva�nn or loam C �� i3�,�. sandy clay loam D �.€�� m.�i.r i clay loam, silty clay loam, silty clay, or clay Source: U�ban Hyd�ology fo� Small Wate�sheds, SCS, June 1986. � Developments must incorporate effective non-point source pollution reduction �3�'s to achieve 90% solid removal for the NUR�.' 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 developmentswill 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, f❑al size; two sets, reduced to maximum size of 1�"x17." .(a) Property lines and delineation of lands 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 e�sting stormwater facilities' location, alignment and elevation. •(d) Delineation of existing on-site wetland, marshes, shoreland andlQr floodplain areas. CRWD D�aft Rules - 45 Day Review Ve�sion Octobe� 6, 2005 Page 7 of 14