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KLEINFELDER no knowledge of whether any of these are present along these particular tracks. Seasonal fertilization of agricultural crops and residential lawn fertilization, as well as septic waste disposal, are probably the largest on- and off-site contributors of nitrogen to groundwater in the 6. project vicinity. On October 21, 2003, a representative with our firm obtained samples of groundwater using ,,f.3 ✓ 6' clean procedures from a faucet on the westernmost residence on the subject property. The samples were immediately placed in a chilled cooler, transported to our office, and stored in a (q.5) refrigerator until they were picked up ame day by Sequoia Analytical using chain-of- custody procedures for DBCP and nisting. The results of the tests and a copy of the �f1f ✓ chain-of-custody are attached. 5. SOIL PROFILE The subsurface conditions at the site were explored at about 8:00 am on October 16, 2003, by drilling one boring to a depth of approximately 20 feet below existing grade at location P-1. Due to percolation rates at location P-1 not meeting SJCEHD criteria for passing percolation tests, an additional boring was performed at location P-2 before 9:00 am on October 20 to a maximum depth of about 21 fed below existing site grade. The borings were drilled using a Simco 2400 truck-mounted drill rig equipped with 6-inch O.D. solid-stem auger. The approximate boring / percolation test locations and approximate dimensions from reference points are presented on the (S.1) site plan. Based on our findings, the subsurface soils encountered consisted predominately of silty and sandy clay and clayey and sandy silt to the maximum depths explored, with silty and relatively "clean" sand encountered at location P-2 between depths of about 11 %2 and 15 feet below existing site grade. The soil conditions at location P-3 were similar to those at location P-2. More detailed descriptions of the subsurface conditions. encountered during our field investigation are presented on the attached Logs of Borings. Based on our prior experience, the low permeable, near-surface clay in the project area yields percolation tests not passing SJCEHD percolation requirements. &.y> 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 Jacktone clay and Vignolo silty clay loam soil series (Map Symbols 180 and 271, respectively). The soils are described as having severe percolation characteristics due to a cemented pan. Other attributes are given in the table below: Map Available Water Organic Content, Symbol Soil Name Capacity, inches/inch PH percent 180 Jacktone 0.13 to 0.17 7.9 to 9 2 to 5 271 Vignolo 0.17 to 0.21 7.4 to 1 to 2 L 7.8 L36012.G01/ST03R1749 November 20,2003 ©2003 Mcinfelder,Inc. Page 3 of 5 L