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1 <br />that does not create additional impervious surface. <br />3. DESIGN CRITERIA FOR STORMWATER MANAGEMENT PLANS. - Stormwater <br />(a) Modeling. <br />PLAN REQUIREMENTS. <br />(ap A hydrograph method based sn--sound-hydroldgis-tnedryor <br />computer program based on Natural Resources Conservation Service <br />Technical Release #20 (TR-20) and subsequent guidance must be used <br />to analyze stormwater runoff for the design or analysis of flows and water <br />levels within and off the project site. Composite Curve Numbers shall not <br />include directly connected impervious surfaces. <br />Stormwater runoff rates for the proposed project must not exceed pre <br />• 1111 le Of f g 111111111 <br />1 <br />construction limits is to be shifted down one classification to account for <br />compaction and soil smearing. <br />(d) Analysis(iii) The 100-year critical event analysis of flood <br />levels, storage volumes, and flow rates for waterbodies and detention <br />fnelt--dufatiens <br />which — produces the critical (highest) flood levels- and <br />discharges.stormwater management basins must include both the 24- <br />hour rainfall and the 10-day snowmelt events. <br />Detenti-eh-besins must be designed to provide: <br />(1) An outlet structure to control the 1 year or 2 year -8g <br />(2) <br />11 <br />cites. <br />■ 3: <br />: . . . • Z <br />storm event. <br />(3) Access for futurc maintenance. <br />(p) Standards. <br />(i)Management Plan Framework, <br />(a) When a stormwater basin is necessary, regional siting is <br />preferred when regional management would not divert supply <br />awayfroma local recharge area __.girgundwater-Aellendent <br />natural resource. In evaluating the appropriateness of peak flow <br />and water • ualit management in an existing regional basin the <br />District will consider whether it previously approved the basin and <br />whether the basin was designed for build-out of the site to the <br />DRAFT DOCUMENT <br />13 <br />