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�..1 KLEINFELDER Joaquin County Flood Control and Water Conservation District show groundwater levels in the project area ranging from about 55 to 90 feet below ground surface from Spring 1981 to Spring 1999. FIELD EXPLORATIONS AND TESTING The subsurface conditions at the site were explored on July 2, 2002, by drilling one boring to a depth of approximately 25 feet below existing grade. The boring was drilled using a Simco 2400 truck-mounted drill rig equipped with 6-inch O.D. solid-stem auger. During the same time period, percolation borings were drilled to depths of about 3.5, 15 and 25 feet below site grade. The location of the percolation tests is approximately 35 feet north and between 100 to 170 feet west of the southeastern property corner. The tests were spread out due to the presence of parked trailers at the planned septic field area. Additional percolation holes were drilled on July 15, 2002, for the replacement area. These tests were located approximately 20 feet north and 175 to 190 feet east of the southwest property corner. The approximate percolation test locations are presented as P-1 through P-5 on the attached plate. Based on our findings, the subsurface soils encountered consisted of light brown to gray/brown sandy clays to a depth of about 23.5 to24 feet below site grade, underlain by orange-brown to light brown clayey and silty sand to the depth explored. The percolation tests were performed on July 3 and 16, 2002, 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 borehole. The hole is then pre-soaked with water at least 24 hours prior to performing the test. The test is performed by first adding about 6 inches of water per 3 foot of percolation test depth above the gravel to the hole. From a fixed reference point, the drop in water level is measured in approximately 30-minute intervals for four hours, refilling as necessary to maintain the prescribed amount of water over the gravel. Under the observation of a sanitarian from the San Joaquin County Public Health Services, Environmental Health Division (SJCPHS/EHD), the last 30-minute reading of the four hour period is recorded and used to calculate the percolation rate in minutes per inch. The estimated percolation rates are summarized below. A copy of our field percolation test results signed by a representative from SJCPHS/EHD is attached. Test Number Depth, ft. Percolation Rate min./inch P-1 3.5 250 P-2 15 125 P-3 25 36 P-4 3.5 Did not percolate P-5 25 16 We have included the results of water testing performed for Viking Freight in June 2001. The testing included tests for Nitrate as N and DBCP. The results of the tests and a copy of the chain-of-custody are attached. 18492.GOI/ST02R254 July 18,2002 ©2002 Kleinfelder,Inc. Page 2 of 4