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625 Cypress Avenue <br />Geotechnical Investigation <br /> <br />Project No. W1895-88-01 - 23 - April 23, 2024 <br />and concrete to verify that the excavations and exposed soil conditions are consistent with <br />those anticipated. If unanticipated soil conditions are encountered, foundation modifications <br />may be required. <br />7.6.13 This office should be provided with a copy of the final construction plans so that the <br />excavation recommendations presented herein could be properly reviewed and revised if <br />necessary. <br />7.7 Lateral Design <br />7.7.1 Resistance to lateral loading may be provided by friction acting at the base of foundations, <br />slabs and by passive earth pressure. An allowable coefficient of friction of 0.3 may be used <br />with the dead load forces in the newly placed engineered fill or undisturbed alluvial soils. <br />7.7.2 Passive earth pressure for the sides of foundations and slabs poured against newly placed <br />engineered fill or undisturbed alluvial soils may be computed as an equivalent <br />fluid having a density of 200 pounds per cubic foot (pcf) with a maximum earth pressure of <br />2,000 psf. When combining passive and friction for lateral resistance, the passive component <br />should be reduced by one-third. A one-third increase in the passive value may be used for <br />wind or seismic loads. <br />7.8 Concrete Slabs-on-Grade <br />7.8.1 Exterior concrete slabs-on-grade subject to vehicle loading should be designed in accordance <br />with the recommendations in the Preliminary Pavement Recommendations section of this <br />report (Section 7.9). <br />7.8.2 Unless specifically evaluated and designed by a qualified structural engineer, concrete slabs- <br />on-grade for structures, not subject to vehicle loading, should be a minimum of 4 inches thick <br />and minimum slab reinforcement should consist of No. 3 steel reinforcing bars placed 18 <br />inches on center in both horizontal directions. Steel reinforcing should be positioned <br />vertically near the slab midpoint. It is recommended that any soils disturbed during <br />construction activities be properly compacted for slab support. The finished subgrade must <br />observed and be approved in writing prior to placement of a vapor retarder, reinforcing steel, <br />or concrete. <br />7.8.3 Slabs-on-grade at the ground surface that may receive moisture-sensitive floor coverings or <br />may be used to store moisture-sensitive materials should be underlain by a vapor retarder <br />placed directly beneath the slab. The vapor retarder and acceptable permeance should be