Laserfiche WebLink
8.A. - Page 56 <br />General Construction Activities Storm Water Permit Requirements established by <br />the CWA. <br />The applicant can obtain coverage under the General Permit by filing a Notice of <br />Intent (NOI) with the State Water Resource Control Board's (SWRCB) Division <br />of Water Quality. The filing shall describe erosion control and stormwater <br />treatment measures to be implemented during and following construction and <br />provide a schedule for monitoring performance. These BMPs shall serve to <br />control point and non -point source pollutants in stormwater and constitute the <br />project's Stormwater Pollution Prevention Plan (SWPPP) for construction <br />activities. While the SWPPP will include several of the same components of the <br />ECP, the SWPPP shall also include Best Management Practices (BMPs) for <br />preventing the discharge of other non -point source pollutants besides sediment <br />(such as paint, concrete, etc.) to downstream waters. <br />Mitigation Measure Hydrology -6: The applicant shall conduct hydrological <br />calculations for pre -development and post -development peak discharge at <br />downstream drainage facilities. The calculations shall use the Rational Method to <br />calculate peak discharge for the 2 -year, 10 -year, and 100 -year storm events. A <br />change in peak flow of 5% or greater would require implementation of mitigation <br />measure Hydrology -7. <br />Mitigation Measure Hydrology -7: Prior to recordation of the Final Map, the <br />applicant shall submit to the City Engineer of Redwood City for review and <br />approval a plan to mitigate increases in peak discharge such that post -construction <br />peak discharge does not exceed preconstruction discharge by more than 5%. All <br />drainage improvements shall be constructed in accordance with Redwood City's <br />Storm Drain Design Criteria (Engineering Standards Volume 3, Part V). The <br />applicant shall confer with the City Engineer prior to the preparation of the plan <br />for the purpose of receiving specific direction on the plan and what would be <br />acceptable to the City. The applicant shall implement the approved plan to <br />mitigate increases in peak discharge. -Design elements in the plan could include: <br />a) Reconfiguration and/or redesign of bioretention swales; <br />b) Reconfiguration and/or redesign of detention pipelines or basins; and <br />c) Addition of detention tanks. <br />Finding: Implementation of Mitigation Measures Hydrology -1, Hydrology -2, Hydrology -6, <br />and Hydrology -7 would reduce impacts from increased off-site erosion or <br />flooding (that could be caused by increased peak discharge at downstream <br />drainage facilities) to a less than significant level. <br />Facts in Support of Finding: Implementation of Mitigation Measure Hydrology -1 would <br />reduce impacts from off-site erosion and flooding by requiring preparation and <br />submittal of a detailed Erosion Control Plan to the Director of Public Works of <br />Redwood City for review and approval prior to issuance of a grading permit. The <br />Erosion Control Plan will specify how erosion will be controlled during <br />construction. Implementation of Mitigation Measure Hydrology -2 would reduce <br />40 <br />