Reso PC15-01 PC Reso (3051 ) to Adopt Initial Study-Mitigated Negative Declaration - La Palma

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3.0 Environmental Impact Checklist include minimizing impervious surfaces,implementing the use of permeable pavers,leading rooftop drain downspouts to bio-retention basins,and using landscape swales, area drains, and a stormwater detention system on the project site. Mitigation Measure HYD-3 would be implemented to ensure preparation of an adequate SWCP such that its implementation would reduce water quality impacts to less than significant levels. Mitigation Measure HYD-3:A Stormwater Control Plan(SWCP) shall be prepared to detail the permanent stormwater management facilities that shall be incorporated into the project to treat stormwater runoff and to control runoff rates and volumes after the construction process. The facilities shall, at a minimum, incorporate the following features and techniques:minimizing impervious surfaces,implementing the use of permeable pavers, leading drain rooftops downspouts to bio-retention basins,and using landscape swales, area drains,and a stormwater detention system on the project site. The SWCP shall be submitted for review and approval by Planning Services and Engineering and Transportation Services prior to the issuance of Grading and Building Permits. b) Substantially deplete groundwater supplies or interfere substantially with groundwater recharge such that there would be a net deficit in aquifer volume or a lowering of the local groundwater table level? No Impact.Water for dust control during project construction(see Mitigation Measure AIR-1) would utilize the existing municipal water service on-site. Project construction would not use groundwater and there would be no impact to groundwater supplies or recharge. The long-term occupancy of the homes does not require groundwater withdrawal. The existing residential uses on the project site currently receive domestic water services from the City. Likewise,the City would continue to provide domestic water to the project site. Groundwater quality and overall infiltration are not expected to be affected by project development; therefore, there would be no impact to groundwater. c) Substantially alter the existing drainage pattern of the site or area,including through the alteration of the course of a stream or river,in a manner that would result in substantial erosion or siltation on or off site? Less-than-Significant Impact with Mitigation Incorporated.Project construction would involve ground disturbing activities such as excavations and grading. However,these activities would not substantially alter the existing topography of the project site,which is relatively flat. The project would be required to comply with the City's NPDES(stormwater control) requirements and SWRCB's General Construction Permit for erosion and sedimentation control during the construction period. As such, with implementation of Mitigation Measures HYD-1 and HYD-2, the project is not likely to contribute substantial amounts of erosion or siltation on- or off-site due to construction. Post-construction, the project would not result in substantial erosion or siltation because there would be no exposed native soils and the topography of the project site would remain flat. Construction-related impacts would be less than significant with implementation of mitigation. La Palma Subdivision Project Final Initial Study/Mitigated Negative Declaration 43