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File No. 20-3514-01 k%J KLEINFELDER September 11, 1991 passing the No. 200 Sieve of 40, a maximum Plasticity Index of 8, and a minimum R-Value of 40. Such imported fill should be compacted at a moisture content at or near optimum. We recommend that samples of any proposed imported fill soil be submitted to the soils engineer for approval prior to being taken to the site. Engineered Fill should be placed in horizontal layers a maximum of 8 inches in loose thickness and be compacted to a minimum of 90 percent of the maximum dry density as determined by the ASTM D- 1557 test procedure, at a moisture content near optimum. We recommend that structural and trench backfill be placed in the same manner as Engineered Fill . In our opinion, trench backfill y outside building areas may be jetted. However, if jetting is performed, sufficient time should be set aside to allow consolidation to occur. In addition, density tests should be taken to confirm the recommended compaction is achieved. In areas to receive asphaltic concrete, we recommend that the subgrade soils to a depth of at least 6 inches for existing soils and 12 inches for Engineered Fill be compacted at or near optimum moisture content, to a minimum of 95 percent of the referenced test procedure. Due to the reported standing surface water during heavy rains, we stress the importance of raising the building pads to above the anticipated high water level and of grading the pads to slope away from the buildings. In addition, especially on the south portion of the site, if floor slabs are used or there is any chance that standing water could develop beneath raised floors, we recommend ' that french drain systems be constructed to minimize the flow of water beneath the structures. The drains should extend to the silt soils encountered approximately 3-1/2 to 4 feet below existing ground surface. F. Pavement Sections We performed one R-Value test on a sample of the near-surface soil obtained from the approximate location shown on Plate A-1 of the appendix. The test results indicate an R-Value of 78 at an exudation pressure of 300 pounds per square inch. The detailed R- Value test result is presented on Plate A-8 of the appendix. The Caltrans method of design for flexible pavements permits the use of a maximum R-Value of 50 in design. However, the City of Manteca allows the use of a higher R-Value in design. Therefore, due to the high R-Value obtained, the city-allowed minimum pavement sections may apply. Copyright 1991 Kleinfelder, Inc. Page 7 of 13