14 ATTACHMENT 6 - Appendix A - E

City of Pleasanton–Spotorno Ranch Reduced Development Project Initial Study/Consistency Checklist Environmental Checklist FirstCarbon Solutions 99 https://adecinnovations.sharepoint.com/sites/PublicationsSite/Shared Documents/Publications/Client (PN-JN)/2148/21480021/Consistency Checklist/21480021 Spotorno Ranch Consistency Checklist ScreenCheck.docx b) Erosion Would the project: Result in substantial soil erosion or the loss of topsoil? The 1998 HVSP FEIR determined that within the HVSP planning area, erosion hazards on hilltops are severe to very severe where runoff is rapid, and that the erosion hazard is slight to moderate on the valley floor. However, t his question was not included in the 1998 HVSP FEIR; therefore, no determination was made regarding the level of significance related to soil erosion or the loss of topsoil on the project site. The proposed project would involve grading, building construction, paving, and utility installation activities that could result in erosion and sedimentation. Left unabated, the accumulation of sediment in downstream waterways could result in the blockage of flows, potentially causing increased localized ponding or flooding. However, as discussed in Section 4.11, Hydrology and Water Quality of the 2018 Draft Recirculated EIR, the developer would be required to obtain a National Pollutant Discharge Elimination System (NPDES) permit issued by the RWQCB. Under the NPDES permitting program, the preparation and implementation of Storm Water Pollution Prevention Plans (SWPPPs) are required for construction activities more than 1 acre in size. The SWPPP must identify potential sources of erosion or sedimentation that may be reasonably expected to affect the quality of stormwater discharges as well as identify BMPs that ensure the reduction of these pollutants during stormwater discharges. Typical BMPs used for erosion control include sandbags, detention basins, silt fencing, landscaping, hydroseeding, storm drain inlet protection, street sweeping, and monitoring of water bodies. Prior to construction grading, the project applicant would file a Notice of Intent to comply with the General NPDES Permit issued by the RWQCB and prepare the SWPPP, which addresses the measures that would be included in the project to minimize and control construction and post-construction runoff to the “maximum extent practicable.” In addition, development of the proposed project would be required to comply with the Municipal Code requirements pertaining to grading and excavation. Site grading within the project site would include cuts varying in depth to 15 feet, with fills varying up to 25 feet deep. Retaining walls are also included in the site plan development. Furthermore, the landscaping plans would implement strategies to reduce soil loss during the operational lifetime of the proposed project. In addition, a 2015 Geotechnical Report recommends that pavement areas be sloped at a minimum of 1 percent toward drop inlets and other surface drainage facilities, that roof downspouts be discharged into closed conduits and directed away from buildings to appropriate drainage devices, and that finished grade be sloped away from building exteriors at a minimum of 5 percent for a distance of at least 10 feet. The 2015 report recommended that prior to halting grading activities tops of fill or cut slopes be graded in such a way as to prevent water from flowing freely down slopes. Implementation of the geotechnical report recommendations would be consistent with MM H1, MM H4, MM H5, and MM H7 which require a soils study, slope stability study, grading recommendations, and a final geotechnical report for grading to be prepared for proposed development.