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KLEINFELDER GROUNDWATER DEPTH During the time of our investigation, groundwater was encountered at a depth of approximately 16.2 feet below existing site grade at the proposed septic system location. FIELD EXPLORATIONS AND TESTING The subsurface conditions at the site were explored on September 4, 2002, by drilling one boring ` to a depth of approximately 10 feet below existing grade. The boring was drilled using a Simco 2400 truck-mounted drill rig equipped with 4-inch O.D. solid-stem auger. During the same time period, percolation borings were drilled to depths of about 3.5, 8.0, and 11.5 feet below site r grade. The approximate percolation test locations are presented as P-1, P-2 and P-3 on the attached plate. V. Based on our findings, the subsurface soils encountered at the proposed septic system site consisted of brown clayey silty sand that extended to a depth of approximately 2 feet below the ground surface. The surface soils were underlain by sandy silt that extended to a depth of 7.5 6. feet. Below this depth interbedded layers of silty sand, sandy silt and sandy and silty clay extended to the depth explored. 6. The percolation tests were performed on October 22, 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 bore hole. 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 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 l_ 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 23 ` P-2 8.0 3 P-3 11.5 25 L Following our percolation testing, a staff engineer with our firm obtained a sample of groundwater using clean procedures from a nearby residence. The residence was located to the west of the parcel's northwest comer on the north side of Klo Road. The same day, the water sample was submitted to Sequoia Analytical using chain-of-custody procedures for DBCP and nitrate testing. The results of our tests and a copy of the chain-of-custody are attached. L 20670.G01/ST02R679 October 25,2002 ©2002 Kleinfelder,Inc. Page 2 of 4