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KLEINFELDER ` SOIL CONDITIONS AND PERCOLATION TESTING The subsurface conditions at the site were explored in mornings July 7, 10, and 21, 2003. The ` site was initially explored by drilling two 6-inch-diameter soil borings to depths of approximately 20 feet below existing site grade to observe the subsurface conditions at the site. The locations of these borings (B-1 and B-2) are presented on the attached site map, and logs of borings are attached. One shallow, 6-inch-diameter percolation boring was drilled at each of the proposed nine lots and in the remaining lot to depths ranging from about 3 to 3%z feet below the existing site grade. Due to the clayey nature of the near-surface soils, a second 6-inch-diameter ` percolation boring was drilled in each lot adjacent to the first shallow boring to depths ranging from about 8 to 17 feet. The percolation holes were drilled using a Simco 2400 track-mounted drill rig equipped with 6-inch O.D. solid-stem auger, the sides of each hole were scored, and `, loose material was removed manually. The depth of each test hole is indicated on Table 1. The approximate location of each set of percolation tests is shown on the attached map, and dimensions for each test location are shown on the attached field percolation result sheets. L Based on our borings and percolation test holes, the subsurface soils encountered consisted generally of silty to sandy clay to depths ranging from about 8 to 14 feet below the existing site i.. grade, underlain by silty to clayey sand. However, the near surface soils at the test locations in Lots 1, 8, and 26 consisted of clayey sand. Our deeper exploratory borings, Borings B-1 and B- 2, encountered sandy clay underlying the sandy soils at depths of about 15 and 18% feet below L the existing site grade. The Soil Survey of San Joaquin County, California published by the US Department of �- Agriculture, Soil Conservation Service (1992) refers to the near-surface soils within the project area as belonging to the Hollenbeck soil series (Map Symbol 173). The soils are described as having severe percolation characteristics, an available water capacity of 0.14 to 0.20 inches per inch, a pH ranging from 6.6 to 8.4, and an organic content of 1 to 2 percent. i The percolation tests were performed on July 8, 16, and 24, 2003, 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 was then pre-soaked with a minimum of 1 foot of water at least 24 hours prior to performing the test. The shallow tests were performed by adding about 6 inches of water above the gravel in the hole. The deeper tests were performed by adding up to about 1 foot of water above the gravel. From a fixed reference point, a marked location on the side of plastic pipe inserted into the hole, the drop in water level was measured in approximate 30-minute intervals for four hours, refilling as necessary to maintain the prescribed amount of water over the gravel (SJCEHD procedure 2). Under the observation of an Environmental Health Specialist from the SJCEHD, the last 30-minute reading of the four-hour period was recorded and used to calculate the percolation rate in minutes per inch (min/inch). The estimated percolation rates are summarized in Table 1. A copy of our field percolation test Lresults signed by a representative from SJCEHD is attached. At the time of testing the weather conditions were sunny and hot with a gentle breeze, and each hole was still in tact. Details of each test can be found on the individual result sheets. r L32585.G01/ST03R1168 November 26,2003 O 2003 Kleinfelder,Inc. Page 3 of 6 L