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k" KLEINFELDER 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 120 to 190 feet below ground surface. FIELD EXPLORATIONS AND TESTING The subsurface conditions at the home site were explored on November 27, 2001, by drilling one boring to a depth of approximately 8 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 and 4.5 feet below site grade. The location of the boring and percolation tests is approximately 120 feet northwest of the tree on the knoll where the residence is to be Iocated and approximately 75 feet southwest of the nearest tree in the draw north of the knoll. There are no other readily available permanent landmarks in the vicinity of the proposed construction. The approximate boring (arid percolation tests) location is presented as B-1 on the attached plate. Based on our findings, the subsurface soils encountered consisted of silty fine-grained sands to a depth of about 6.5 feet, underlain by cobbles and coarse-grained gravel. A log of boring that describes the subsurface conditions encountered is attached. We also attempted to drill seven percolation holes in possible leach field areas for a proposed barn on the plateau south of the proposed residence. The approximate Iocations probed are indicated as B-2 through B-8 on the attached plate. At each of these locations; up to 1 foot of silty sand or sandy silt was underlain by cobbles and coarse-grained gravel. At depths of approximately 1.5 to 2.5 feet, these soils were underlain by a moderately weathered rock folpation that we were unable to drill t roug ccor mg to e , eac le s cannot be installed in roc ccor ingly,no perco ation tests were installed or performed. The percolation tests installed near the home site 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. The hole is then pre-soaked with water at least 24 hours a prior to performing the test. The test is performed by first adding about 6 inches of water per 3 ifoot 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 Department (SJGPHD), 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 for test numbers P-1,and P-2 is attached. Test NnmUer' D th ft. Percolation Rate niin./high P-I 3 11.4 P-2 4.5 4.5 20-4683-01.G01/201 I R1533 December 12,2001 ©2001 Kleinfelder, Inc. Page 2 of 4 i I i