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ENGEO <br /> INCORPORATED <br /> <br /> <br />5150.100.101 <br />May 2, 2008 Page 25 <br />9.4 FOUNDATIONS <br /> <br />Retaining walls may be supported on continuous footings designed in accordance with <br />recommendations presented in Section 5.2, except the minimum embedment depth should be <br />increased to 24 inches below lowest adjacent soil grade. <br /> <br />10. PAVEMENT DESIGN <br /> <br />10.1 FLEXIBLE PAVEMENTS <br /> <br />Based on soil observed during our field exploration, an R-value of 25, was judged to be <br />appropriate for design. Using estimated traffic indices for various pavement loading <br />requirements, we developed the following recommended pavement sections using Procedure 608 <br />of the Caltrans Highway Design Manual (including the asphalt factor of safety), presented in <br />Table 1 below. <br /> <br />Table 1 <br />Recommended Asphalt Concrete Pavement Sections <br /> Section <br />Traffic Index Asphalt Concrete (in.) Class 2 Aggregate Base (in.) <br />5 3 7 <br />6 3 10 <br /> <br />If soil, such as clay, with an R-value less than 25 is encountered during subgrade preparation, the <br />subgrade should be excavated a depth of 18 inches and backfilled with soil or aggregate base <br />with an R-value of at least 25. The civil engineer should determine the appropriate traffic <br />indices based on the estimated traffic loads and frequencies. <br />