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KLEINFELDER Based on our Findings, the subsurface soils encountered consisted predominately of about 3%2 feet of silty clay underlain by silt to a depth of about 8%2 feet below existing site grade. At this depth, sandy clay and clayey sand were encountered to the maximum depths explored. More detailed descriptions of the subsurface conditions encountered during our field investigation are presented on the Log of Boring, Plate A-3. The Soil Survey of San Joaquin County, California published by the U.S. Department of Agriculture, Soil Conservation Service (1992) refers to the near-surface soils within the project area as belonging to the Capay-Urban soil series (Map Symbol 122). The soils are described as having severe percolation characteristics due to clayey soil. Other attributes are given in the a e e ow: gym' Map s� ,'s , ;; q `Ava>tlable WaterE€ ' E drgan>ic Content, S >><ubol , ° Soil %Ca�:aci ,�ncheslinch� =� � `. _ H `; ,. :Percent ..,;�.o .' 122 Ca ay-Urban j 0.14-0.16 6.6-8.4 1-2 F. 6. PERCOLATION TESTING Two 6-inch diameter percolation holes were drilled with the same equipment as the soil profile Fboring. The approximate percolation test location is presented on Plate 1. The holes had scored v sides and no significant loose material in the bottom of the hole. The holes were drilled and prepared before 9:00 am on November 13, 2003 in accordance with SJCEHD criteria. The preparation procedure calls for first placing about 2 inches of fine gravel at the bottom of the borehole. The hole is then pre-soaked with a minimum of 12 inches of water-at least 24 hours F1 prior to performing the test. The percolation tests were started at noon under sunny and warm T weather on Novemberl4, 2003, in accordance with accepted guidelines using clear potable water. The approximate depth of each percolation test below existing site grade is shown on the following table. None of the holes exhibited sloughing or caving. At the time of testing, no standing water from the presoaking remained in the hole. The holes were dry prior to testing. From a fixed reference point, a marked location on the side of PVC pipe inserted into the hole, the drop in water level was measured in approximately 30-minute intervals for four hours, refilling as necessary to maintain the prescribed amount of water over the gravel (SJCEHD Procedure 12). Under the observation of a representative from the SJCEHD, the last 30-minute reading of the four-hour period was recorded and was 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 SJCEHD is attached. Details of each test can be found on the percolation test sheet. l _Test Number:' �` .�Perforimed�Deptli (feet) . APercolation'Rat�'(mifianch},, P-1 3.1 9.3 3.5 62.5 38058.GOI/ST04R650 May 14,2004 ©2004 Kleinfelder,Inc. Page 3 of 6