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f KLEINFELDER We anticipate that waste disposal for the residence will be provided by an individual on-site sewage disposal system consisting of a septic tank/leach trench sewage disposal system with seepage pits. HISTORICAL GROUNDWATER DEPTH According to groundwater reports published by the San Joaquin County Flood Control and Water Conservation District (Spring 1993 to Spring 1999), high groundwater in the project area has been recorded at depths in the range of about 70 to 100 feet below ground surface. FIELD EXPLORATIONS AND TESTING The subsurface conditions at the proposed leach field Iocation were explored on December 6, 2001, by drilling one boring to a depth of approximately 15 feet below existing grade, which was used for a percolation test. The boring was drilled using a Simco 2400 truck-mounted drill rig f equipped with 6-inch O.D. solid-stem auger. During the same time period, percolation borings were drilled to depths of about 3.5 and 9 feet below site grade. When the testing on these.',three borings was performed on December 7, 2001, all the tests failed to adequately percolate. Via a telephone call with our field representative, Mr. Rodney Estrada of San Joaquin County Environmental Health Division (SJCEHD) stated that due to failing results, the percolation testing an these borings could be terminated without SJCEHD inspection. On December 10, additional percolation tests were installed in the same potential leachfield area at depths of approximately 19 and 25 feet. These tests were performed on December 11, 2001. The location of these tests was approximately 50 feet north and 50 feet west of the southeast corner of the property. The approximate boring (an percolation tests) location is presented as P-1 on the attached plate. As requested by SJCEHD, the initial failing tests were reinstalled on October 9, 2002 and performed with SJCEHD inspection on October 21. Percolation tests were simultaneously installed and run on the adjacent parcel, 10834 Copperopolis Road, at this time. These tests were located approximately 16 feet south and 16 feet west of the northeast property corner and are presented as P-2 on the attached plate. Based on our findings, the subsurface soils encountered at location P-1 consisted of approximately 4.5 feet of sandy clays over approximately I1 feet of sandy and clayey silts, underlain by approximately 6.5 feet of silty sands. Beneath the silty sands existed sandy clay soils to the maximum depth explored of approximately 25 feet. A Iog of boring that describes the subsurface conditions encountered is attached. 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 borehole. The hole is then pre-soaked with water at least 24 hours prior to performing the test. The 3.5-foot deep test was performed by adding about 6 inches of water above the gravel iwthe hole. The deeper tests were performed by adding up to about 12 inches of water above the gravel. From a fixed reference point, the drop in water level is measured at approximate 30- minute intervals for four hours, refilling as necessary to maintain the prescribed amount of water 20-4684-01.GO 1/S T02R731 November 5,2002 ©2002 Kleinfelder,Inc. Page 2-',of 5