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LOWRY & ASSOCIATES <br /> Page 8 <br /> { August 18, 1990 <br /> L & a No. 90-190 <br /> 1 ake Permeability <br /> Observation of soil samples recovered from the borings and laboratory test results <br /> indicate that on-site soils at the proposed excavation depth for the Tracy Lakes are <br /> clayey organic silts which, when compacted will provide a relatively low permeability rate <br /> on the order of 1 to 5 x 10-' centimeters per second. Permeability rates of this <br /> magnitude are considered acceptable for retaining water and will result in a minimal <br /> water loss through the base of the lakes. <br /> Pavement Dgsien <br /> Pavement design analysis for this project was based upon the results of Resistance <br /> value tests conducted upon selected samples of the anticipated subgrade soils. These test <br /> i results in conjunction with the Caltrans "Design Methods for Flexible Pavements" and <br /> ' assumed traffic indices ('T.I."), which are indications of anticipated wheel load frequency <br /> and intensity, have been used to design the recommended pavement sections. <br /> The Asphalt Institute typically recommends that T.I. = 4.5 be used by streets subject to <br /> light automobile traffic. T.I. = 5.5 is recommended for through-going streets. Final <br /> pavement section selection should conform with the County of San Joaquin requirements <br /> where applicable. <br /> l Our recommended pavement sections follow: <br /> 1 <br /> RECOMMENDED PAVEMENT SECTION - inches <br /> Traffic Asphalt Aggregate <br /> Index Concrete Base <br /> (Type B) (Class II) <br /> I 4.5 2.5 7 <br /> l 5.0 2.5 8 <br /> J 5.5 3.0 8 <br /> 6.0 3.0 10 <br />