Appendix E - Geology and Soils Geotechnical Supporting Information COMBINED

LESTER-SHRINER PROPERTY 132-8-2 Page 18 6.11 PERMANENT EROSION CONTROL MEASURES Hillside grading will require periodic maintenance after construction to reduce the potential for erosion and sloughing. At a minimum all slopes should be vegetated by hydroseeding or other landscape ground cover. The establishment of vegetation will help reduce runoff velocities, allow some infiltration and transpiration, trap sediment within runoff, and protect the soil from raindrop impact. Depending on the exposed material type and the slope inclination, more aggressive erosion control measures may be needed to protect slopes for one or more winter seasons while vegetation is establishing. For slopes with inclinations of 2:1 (horizontal:vertical), erosion control may consist of jute netting, straw matting, or erosion control blankets used in combination with hydroseeding. Both construction and post-construction Storm Water Pollution Prevention Plans (SWPPPs) should be prepared for the project-specific requirements. SECTION 7: FOUNDATIONS 7.1 SUMMARY OF RECOMMENDATIONS On a preliminary basis, the proposed single-family residential structures may be supported on shallow foundations provided the recommendations in the “Earthwork” section and the sections below are considered in the preliminary design. Additional exploration and analysis should be performed during the design-level investigation to confirm the foundation type and design parameters. 7.2 SEISMIC DESIGN CRITERIA We assume that the project structural design will be based on the 2019 California Building Code (CBC), which provides criteria for the seismic design of buildings in Chapter 16. The “Seismic Coefficients” used to design buildings are established based on a series of tables and figures addressing different site factors, including the soil profile in the upper 100 feet below grade and mapped spectral acceleration parameters based on distance to the controlling seismic source/fault system. Based on our review of previous exploration and the local geology, the site is underlain by shallow bedrock with estimated shear wave velocities ranging on the order of 1,300 to 8,900 feet per second. Therefore, the site will likely be classified as Site Classification B or C for rock or soft rock conditions. The site classification should be further evaluated during the design-level geotechnical investigation. 7.3 BUILDING SETBACKS Since the proposed residential structures would likely be supported on mat foundations, we recommend that minimum building setbacks be maintained from the bottom edge of foundations to the face of fill slopes to reduce the potential for seismic slope deformation and/or slope creep from impacting the structures. Preliminary building setbacks for varying slope heights are presented in Table 2 below; final slope setbacks should be further evaluated during the design- level investigation. Ii! CORNERSTONE EARTH GROUP