09-11-08 Planning Comm. Agenda - Laserfiche WebLink

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2. Water Quality -Developments must incorporate effective non-point source pollution reduction BMPs to achieve 90% and/or 40% total suspended solids removal from the runoff generated by a NURP water quality storm (2.5" rainfall). Runoff volume reduction requirement may be considered and included in the calculations showing compliance with achieving the 90% TSS and/or 40% TSS removal requirement. Water quality calculations, documentation and/or water quality modeling shall be submitted to verify compliance with the standard. 3. Runoff rate control -hydrologic calculations - A hydrograph method based on sound hydrologic theory shall be used to analyze runoff for the design or analysis of flows and water levels.. 4. Runoff rate control -design standards -Runoff rates for the proposed activity shall not exceed existing runoff rates for the 2-year, 10-year, and 100-year critical storm events, and runoff rates may be restricted to less than the existing rates when the capacity of downstream conveyance systems is limited. 5. Outlets -Discharges from new construction sites must have a stable outlet capable of carrying designed flow at anon-erosive velocity. Outlet design must consider flow capacity and flow duration. This requirement applies to both the site outlet and the ultimate outlet to stormwater conveyance or waterbody. 6. Pond Requirements -For all projects creating more than one acre of impervious surface, ponding shall be required. At a minimum all pond design specif cations shall conform to the current City and NPDES construction permit requirements. In addition the following are required: a. A bench shall be provided starting at the normal water level and ending 1 foot below normal water level with side slopes no less than 10 feet horizontal to 1 foot vertical (10:1) for safety considerations. Pond side slopes shall not exceed 4 feet horizontal to 1 foot vertical (4:1) without approval of the City. b. All public and private owned stormwater management facilities shall provide an unobstructed access path (minimum of 10 feet) capable of supporting light truck traffic during normal weather for the purpose of conducting inspections of the facility and maintenance thereof. No private stormwater facility may be approved unless an easement is provided to the City allowing access for maintenance and inspection. Maintenance agreements before, during, and after development are also required. a To provide proper protection for adjacent property within the first tier from the pond, the design storm interval for the ponding area is stormwater Ordinance 928- 9