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l � <br /> Geotrchnical Gngincering Rcport <br /> Proposed Ahn Warehouse <br /> May I l, 2001 <br /> CG File No. I 121 <br /> Page 10 <br /> dense, or better nahvc soils. The CDF is then placed in the excavation to planned footing <br /> subgrade elevation. Conventional shallow spread fbundauons may then be placed on the CDP <br /> hench. <br /> The hench sidewalls need to stay open for the CDF method to be successful. Severe caving of <br /> the test pit sidewalls was encountered during our explorations, after the test pits were deeper than <br /> about S feet. It would be best to excavate the CDF trenches just prior to or during the placement <br /> of the CDF, as the trenches are not expected?o stay open for an extended period of time. <br /> Design Values for Conventional Shallow Foundations: Footings should extend at least 18 <br /> inches below the lowest adjacent finished ground surface for frost protection and beanng capacity <br /> considerations. Minirrum foundation widths of 16 and 24 inches should be used for continuous <br /> and isolated spread footings,respectively. Standing water should not be allowed to accumulate in <br /> footing trenches. All loose or disturbed soil should be removed from the foundation excavation <br /> prior to placing concmte. <br /> For foundations conswcted as outlined above, we recommend an allowable design bearing <br /> pressure of 2,500 pounds per square foot (ps�be used for the footing design. Ilnifonn Building <br /> Code (UBC) guidelines should be followed when considering short-term transitory wind or <br /> seismic loads. Potential foundat�on settlement using the recommended allowable bearing <br /> pressure is es[imated [o be less than 1-inch total and 1/2-inch differentia] between footings or <br /> across a distance of about 20 feet. Higher soil bearing values may be appropriate for footings <br /> founded on the unweathered very dense till, and with wider footings. These higher values can be <br /> determined after a review of a specific design. <br /> Seismic Design: '1'he site is located within Zonc 3 of the Seismic Zone Map shown as Figure 16- <br /> 2 of the 1997 Uniform Building Code (UI3C). 7'his corresponds to a Seismic Zone Factor, Z, of <br /> 030. This, in tum, corresponds to a honzontal acceleration of P.3 g. SSte conditions best fit the <br /> lII3C description for Soil ProSie"fype Sp("Stiff Soil Prnfile"). <br /> Cornerstone Geotechnical, Inc. ( l �I a� <br />