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File No. 20-3668-01 K L E I N F E L D E R January 7, 1993 of underground utilities or any other buried objects should be overexcavated and backfilled with Engineered Fill placed as recommended below. In areas where old, buried landfill debris is located beneath structures or paved areas, we recommend that all debris be excavated and replaced with Engineered Fill, as described in the following sections. Removal of debris should extend at least 5 feet beyond all structures. Excavation sidewalls should be sloped to at least 2:1 (horizontal to vertical) if not flatter. In our opinion, it is not necessary to remove debris from landscape areas for structural reasons. However, consideration of the effects of the debris with the desired landscaping should be evaluated. After stripping and removal of vegetation and debris, excavation to provide for Engineered Fill beneath foundations, if planned, and before placement of any Engineered Fill, the exposed surface soil within and to a minimum of 5 feet beyond the building area should be scarified and recompacted to a minimum depth of 6 inches. The recommended minimum degree of compaction is 90 percent of the maximum dry density as determined by the ASTM D-1557 test procedure, at a moisture content near optimum. Any extremely loose pockets of soil encountered during this process should be overexcavated and recompacted. Engineered Fill placed beneath foundations or any fill required to bring the site to finished grade should consist of on-site soils or imported granular nonexpansive soil having a maximum percentage 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 backfills 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. Pavement Sections We performed two R-Value tests on samples of the near-surface soils. The test results indicate R-Values of 77 and 79 at an exudation pressure of 300 pounds per square inch. We have used a design R-Value of 50 in design. Based on the design method presented in Topic 608 of the Cal Highway Design Manual, along with assumed traffic indices and traffic indices provided by your firm, we recommend the following pavement sections: Copyright 1993 Kleinfelder, Inc. Page 7 of 11