14 ATTACHMENT 6 - Appendix A - E

City of Pleasanton–Spotorno Ranch Reduced Development Project Initial Study/Consistency Checklist Environmental Checklist FirstCarbon Solutions 119 https://adecinnovations.sharepoint.com/sites/PublicationsSite/Shared Documents/Publications/Client (PN-JN)/2148/21480021/Consistency Checklist/21480021 Spotorno Ranch Consistency Checklist ScreenCheck.docx c) Drainage Would the project: Substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of a stream or river or through the addition of impervious surfaces, in a manner which would: i) result in substantial erosion or siltation on- or off-site; The 1998 HVSP FEIR determined that erosion and sedimentation could occur during the construction period as a result of grading and excavation activities. The 1998 HVSP FEIR included measures to control erosion associated with the Golf Course; however, no conclusion was made regarding erosion or siltation on the project site. According to the 1998 HVSP FEIR, compliance with the Construction General Permit and preparation of a SWPPP that includes BMPs would prevent impacts related to water quality and erosion. The BMPs would be required to include erosion and sediment control measures, such as soil stabilization controls, watering for dust control, perimeter silt fences, placement of hay bales, and sediment basins. According to the 1998 HVSP FEIR, implementation of BMPs required in the SWPPP would reduce impacts to less than significant. The majority of the project site would be left undeveloped, and existing drainage would not be modified. No impervious surfaces would be constructed outside the Residential Development Area and drainage would continue to be directed to existing natural drainages. The landscape would be substantially altered on the 31-acre portion of the project site that would be developed, which may affect the existing natural drainage pattern on the project site. Compliance with the General Construction permit conditions and the applicable provisions of the Municipal Code would ensure that the project implementation does not result in substantial erosion or siltation on- or off-site. The proposed project would require the installation of new on-site storm drainage infrastructure. The on-site storm drainage system would consist of a network of street gutters, inlets, basins, and underground piping that would ultimately convey runoff to five different detention basins. The proposed project’s landscaping plans feature groundcover, DMAs, bioretention, and self-retaining areas to increase infiltration rates and reduce runoff volumes and erosion and sedimentation. As described previously, the project would be required to comply with Chapter 9.14 Stormwater Management and Discharge Control of the City of Pleasanton Municipal Code. Chapter 9.14, also known as the City of Pleasanton Stormwater Management and Discharge Control Ordinance, requires implementation of BMPs and compliance with general permits. The provision of the on-site stormwater infrastructure would ensure that the project would not result in substantial erosion. The proposed project would not create or contribute runoff water that would exceed the capacity of the drainage system. Adherence to all applicable regulations from the Alameda County Clean Water Program, City of Pleasanton Municipal Code, and California State Water Resources Control Board (State Water Board) would ensure that the proposed project does not result in substantial erosion or siltation.