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� J KLEINFELDER All soft or disturbed soils encountered in the site stripping or recompaction process should be overexcavated to stable soil and recompacted, free of debris. We recommend that our representative be allowed to observe any areas of soft or disturbed soils encountered in order to determine the required depth of overexcavation. Engineered Fill placed on building pads can consist of on-site soils, free of debris, or imported nonexpansive soils. If imported granular nonexpansive soil is used beneath floor slabs, we recommend that the soil have a maximum percentage passing the No. 200 Sieve of 40; a maximum Plasticity Index of 8, and a minimum Resistance-Value of 40. We recommend that samples of any proposed imported fill soils be submitted to the geotechnical 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 method, at near optimum moisture content. All Engineered Fill within 12 inches of finished subgrade beneath proposed pavement areas should be compacted to a minimum of 95 percent of the above maximum dry density. WARNING: Should site grading be performed during or subsequent to wet weather or shortly after irrigation, we anticipate that the near surface site soils may be significantly above optimum moisture content. This condition could hamper equipment maneuverability and the contractor's efforts to compact site soils to the recommended compaction criteria. Disking to aerate, chemical treatment, and/or other methods may be required to reduce excessive soil moisture. Additionally, care should be exercised when moisture conditioning on-site fine-grained soils. These materials are moisture sensitive, and excess moisture may cause an unstable or "pumping" condition. We recommend that structural and trench backfill be placed in the same manner as Engineered Fill. In our opinion, trench backfill outside structure 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. Any backfill adjacent to structure foundations should be clean of all construction debris,properly compacted, and sloped to drain away from the structures. Because of the expansive nature of the clay soils, positive drainage away from the foundations is very important. In addition, since interior concrete slab-on-grade floors will be used for the structures, we recommend that existing clayey soils be used for backfill within the structure areas and 10 feet beyond for utility lines extending outside the structure perimeters. This should create a plug to prohibit rapid lateral migration of water beneath the structures through utility lines. Beyond the 10 foot distance from the structures, existing or imported soils may be used for trench backfill. We suggest that compaction of the backfill within the structure areas and 10 feet beyond be by mechanical methods only. In addition, we recommend that landscaping be graded in order to prevent surface water from ponding against the structures. 20-4280-01.Gol/2019RI50 Page 7 of 12 Copyright 1999 Kleinfelder,Inc. April 14, 1999