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El Dorado Apartments April 19, 2002 File No. 1754-006 Page 3 GROUNDWATER Although no free groundwater was encountered in our explorations, we would expect the free groundwater level to be 20 to 25 feet below site grades. Based on our experience in the area, we conclude that the permanent groundwater table should not be a factor in the design and construction of the proposed improvements,although very deep trenches for sewers could engage groundwater during the rainy season. The uppermost native soils exhibit very low permeabilities. Saturated fill conditions will likely occur during and shortly following the rainy season. The potential for saturated surficial fills should be considered in scheduling of earthwork construction. RECOMMENDATIONS EARTHWORK General site clearance should include the removal of surface vegetation,unwanted trees and associated root system elements greater than two inches in maximum dimension, rubble, rubbish, and any other existing construction or debris. Any underground pipes within two feet of original or final grade(whichever is lower) should be removed. Any excavations required for the removal of the above items should be cleaned of loose, saturated,or soft materials so that firm undisturbed soils are exposed. Building pads and the area five feet beyond should be over-excavated to a depth of two feet relative to existing grades. The exposed subgrades should be proof rolled;the proof rolling should be observed by our representative. Areas deemed unacceptable by our representative should be further over-excavated as directed. The earthwork contractor also should be prepared to pothole, under our direction as necessary to identify buried construction. Any other loose or unstable soil deposits or buried construction debris identified by our representative should be removed completely in order to expose firm, undisturbed soils. Deep excavations required for the removal of any of the above items should be sloped back to a dish-shaped configuration allowing through passage of compaction equipment. Earthwork contractors should provide unit prices for remedial earthwork as may be directed in the field. Following site clearance and any required excavation to final grades,the building pads should be observed by our representative to determine if highly expansive clays are present. Any highly expansive clays identified by our representative should be overexcavated to either remove the clays entirely or to a depth of 12 inches, whichever requires less excavation. Grades may then be restored with leaner clays or other site soils placed and compacted as recommended below. Building pads and pavement areas designated to receive engineered fill or which are left at existing grade should be scarified to a depth of eight inches and brought to a uniform near-optimum moisture condition. In the case of clays,moisture conditioning to a minimum two percent over optimum state will be required. Then the soil should be recompacted in place to at least 90 percent of the maximum dry density determined by the ASTM D 1557-00 test procedure. Engineered fill should be placed in lifts not exceeding six inches in compacted thickness,brought to a uniform near-optimum or over optimum moisture condition as recommended above, and compacted to at least 90 percent of the ASTM D1557-00 maximum dry density. Building pad fills placed at depths of more than three