14 ATTACHMENT 6 - Appendix A - E

City of Pleasanton–Spotorno Ranch Reduced Development Project Environmental Checklist Initial Study/Consistency Checklist 98 FirstCarbon Solutions https://adecinnovations.sharepoint.com/sites/PublicationsSite/Shared Documents/Publications/Client (PN-JN)/2148/21480021/Consistency Checklist/21480021 Spotorno Ranch Consistency Checklist ScreenCheck.docx A 2015 Geotechnical Feasibility Report (Appendix E) concluded that, based on existing subsurface information and experience in the project site and vicinity, the potential for liquefaction for the project site is likely to be low with proposed improvements to differential settlement. Furthermore, the United States Geological Survey (USGS) and the Association of Bay Area Governments (ABAG) Resilience Program has mapped the area to have low susceptibility for liquefaction. Structures and constructed slopes would be required to implement the most recent UBC and would implement MM H1, MM H2, and MM H3. Therefore, impacts associated with liquefaction is likely to be low. The proposed project would not result in any peculiar effects and would not result in new or more severe impacts related to ground failure beyond what was previously analyzed in the 1998 HVSP FEIR. iv) Landslides The 1998 HVSP FEIR determined that steep slopes of the upland areas of the project site present the potential for landslides, including shallow rotational landslides and debris flows, that could adversely affect development within those areas. According to the 1998 HVSP FEIR, the area along the south side of Happy Valley Road may be affected by slope stability problems. Residential development or roadway construction would be subject to requirements to include a slope stability analysis in the geotechnical report for areas with slopes steeper than 20 percent or within or adjacent to existing landslides, consistent with MM H4. The 1998 HVSP FEIR concluded that impacts related to landslides and slope stability would be less than significant with mitigation incorporated. The project site includes the Greater Happy Valley Semi-Rural Density Residential Subarea and a portion of the Agriculture/Open Space Subarea.. As shown in Exhibit 6, there are slopes steeper than 20 percent adjacent to the eastern side of the project site. The 2015 Geotechnical Report indicates that numerous landslides have been mapped within or immediately adjacent to the project site. Seismic ground shaking can trigger deformation of high graded slopes or unstable natural hillsides. All housing units and structures would be located below the 25 percent slope line, and all grading for the purposes of constructing the residential structure would also occur below the 25 percent slope line. Home sites would be constructed in areas with slopes of less than 10 percent. Portions of residential lots would extend into areas of 10–20 percent slope along the eastern portion of the project site; however, structures would not be located in these areas. Measure PP limits the placement of housing units and structures on slopes of 25 percent or greater. The site is also affected by the presence of the Verona Fault, which crosses the site adjacent to the 25 percent slope limit, and an associated Building Restriction Zone that extends to 50 feet on both sides of the Verona Fault. As a result, no residential structures would be located on slopes of 25 percent, and the project would be consistent with Measure PP requirements. Because numerous landslides have been mapped within or immediately adjacent to the project site, the proposed project would comply with the preparation of a slope stability analysis, consistent with MM H4. Therefore, the proposed project would not result in any peculiar effects and would not result in new or more severe impacts related to landslides beyond what was previously analyzed in the 1998 HVSP FEIR.