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k� KLEINFELDER <br /> File No. 20-2182-24 <br /> February 20, 1990 <br /> Pavement Sections <br /> We have assumed, based on numerous previous tests, that the near <br /> surface clayey soils encountered at this site have an R-Value of <br /> 5 or less . The Caltrans method of design for flexible pavements <br /> permits the use of a minimum R-Value of 5 in design. Based on this <br /> design R-Value and on assumed traffic indices, we recommend the <br /> following pavement sections : <br /> Minimum <br /> Minimum Thickness <br /> Assumed Thickness of Class II <br /> Traffic of Asphalt Aggregate <br /> Index Concrete Base <br /> 4 . 0 2" 9" <br /> 5 . 5 2" 14" <br /> 6 . 0 2-1/2 " 15" <br /> The subgrade soils over which the asphalt concrete paving materials <br /> are to be placed should be compacted to a minimum depth of 6 inches <br /> to a minimum of 95 percent of the ASTM D-1557 maximum dry density <br /> at a moisture content near optimum. In addition, it is recommended <br /> that all pavements conform to the following criteria: <br /> 1 . All trench backfills, including utility and sprinkler <br /> lines, should be properly placed and adequately <br /> compacted to provide a stable subgrade. <br /> 2 . An adequate drainage system should be provided to <br /> prevent surface water or subsurface seepage from <br /> saturating the subgrade soil . <br /> 12 <br />