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r./ k'g KLEINFELDER PRESENT USE OF THE SITE At the time of our field exploration, the project site was an active cucumber field. Topographically, the site was essentially level. HISTORICAL GROUNDWATER DEPTH In accordance with groundwater reports published by the San Joaquin County Flood Control and Water Conservation District (Spring 1972 to Spring 1999), high groundwater in the project area has been recorded at depths in the range of about 90 to 100 feet below ground surface. FIELD EXPLORATIONS AND TESTING The subsurface conditions at the site were initially explored on September 12 and 13, 2001, by drilling eight borings to depths of about 16.5 to 25.8 feet below existing grade. At this time, two percolation tests were performed on the west side of the facility within the proposed leach field area. The borings were drilled using a Simco 2400 truck-mounted drill rig equipped with 4.5- inch O.D. solid-stem auger. Due to relocation of the proposed leach field area to the east side of the proposed facility, two additional percolation tests were performed on January 31, 2002, ranging from about 3.5 to 8 feet below existing site grade. The approximate percolation test locations are shown on the attached plate. Based on our findings, the subsurface soils encountered consisted predominately of stiff to hard, moderately-plastic silty to sandy clays to depths ranging from about 2.5 to 11 feet below site grade. These soils were underlain by loose to very-dense silty to clayey sands, stiff to hard silty to sandy clays, and very-stiff to hard sandy silts to the maximum depths explored. The percolation tests were performed in accordance with accepted guidelines using clear potable water. The procedure calls for first placing about 2 inches of fine gravel at the bottom of the bore hole, installing a perforated PVC casing, and then placing additional gravel. The holes were then pre-soaked with water at least 24 hours prior to performing the tests. The tests are performed by first adding about 6 inches of water above the gravel. From a fixed reference point, the drop in water level was measured in approximate 10-minute intervals, refilling as necessary to maintain the original head of water over the gravel. Under the observation of a sanitarian from the San Joaquin County Public Health Department, the last 10 minute reading of the monitoring period was recorded and used to calculate the percolation rate in minutes per inch and gallons per square foot per day(gfd). Test Number Approximate Depth, ft. Percolation Rate min./inch P-1 3.5 26.3 P-2 8 7.7 A soil percolation rate of 60 minutes per inch or faster is generally required within the upper 3.5 feet of subgrade for county approval. At deeper depths, a soil percolation rate of 30 minutes per inch or faster is required. Based on our findings, the upper soils yielded an acceptable percolation rate. The sandy soils encountered in our test borings beneath the near-surface soils 20-2080-19.GOI/2002R083 February 4,2002 ©2002 Kleinfelder,Inc. Page 2 of 4