Appendix E - Geology and Soils Geotechnical Supporting Information COMBINED

LESTER-SHRINER PROPERTY 132-8-2 Page 19 Table 2: Preliminary Building Setbacks Slope Height (H)1 (feet) Foundation Type Minimum Building Setback2 (feet) H < 30 PT Mat 10 30<H<>50 PT Mat 15 >50 PT Mat 20 1H = vertical distance between toe and crest of slope 2 Applies to rear or side yard setback adjacent to crest of slope; if setbacks are not feasible, then supplemental foundation criteria may be required. 7.4 POST-TENSIONED MAT FOUNDATIONS The planned residential structures can likely be supported on post-tensioned (PT) concrete mat foundations, which should be designed in accordance with the procedures developed by the Post-Tensioning Institute (latest edition) and the 2019 California Building Code. To reduce potential differential movement, on a preliminary basis, mats should be designed for a maximum average areal bearing pressure of 500 psf for dead plus live loads; at column or wall loading, the maximum localized allowable bearing pressure should be limited to about 2,000 to 3,000 psf. When evaluating wind and seismic conditions, allowable bearing pressures may be increased by one-third. Additional reinforcing steel may be required to help span irregularities and differential settlement. Provided that cut/fill transitions are mitigated during site grading, we estimate that differential settlements due to combined static and seismic loading will be on the order of ½ to ¾ inch or less across a typical mat foundation area unless located in a deep fill area. Structures located in fill areas greater than 20 feet deep could experience long-term total settlement on the order of 1 to 2 inches over the life of the project. Differential settlement in these deep fill areas will likely be on the order of 1 inch or less provided differential fill thicknesses are adequately mitigated during grading. As discussed in Section 7.3, if minimum building setbacks cannot be maintained, mat foundation edges could potentially be deepened to increase the setback distance to face of slope. If considered, this would need to be evaluated on a lot-by-lot basis during the design- level investigation and final grading plan review. SECTION 8: CONCRETE SLABS AND PEDESTRIAN PAVEMENTS 8.1 EXTERIOR FLATWORK Exterior concrete flatwork subject to pedestrian and/or occasional light pick up loading should be at least 4 inches thick and supported on 4 to 6 inches of non-expansive fill overlying prepared subgrade. If expansive colluvial soils are adequately buried in deeper fills, concrete 15! CORNERSTONE EARTH GROUP