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k4 KLEINFELDER 5. SOIL PROFILE The subsurface conditions at the site were explored on January 25 and 26, 2005, by drilling a boring in each proposed lot to a depth ranging from about 10 to 25 feet below existing grade. The borings were drilled using a Simco 2400 truck-mounted drill rig equipped with 4%-inch O.D. solid-stem auger. The approximate location of the test boring and dimensions from a reference point are presented on the Plate 2. The soils observed were visually classified according to the Unified Soil Classification System (see Plate 4). Based on our findings, the subsurface soils encountered in our borings varied considerably across the site. The soils observed in our borings consisted of highly interbedded and discontinuous strata of low to moderately plastic sandy to silty clay, sandy silt, silty to clayey sand, and relatively "clean" sand to the maximum depths explored. A key to the Logs of Borings is presented on Plate 5. Detailed descriptions of the subsurface conditions encountered during our field investigation are presented on the Logs of Borings, Plates 6 through 22. 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 soil within the project area as belonging to the San Joaquin soil series (Map Symbols 238 and 240). These soils are described as having "severe" percolation characteristics. Other attributes are given in the table below: Map Available I Water Capacity, Organic Symbol Soil Name inches/inch H Content, percent 238 San Joaquin 0.04- 0.16 5.6 - 7.8 0.5 — 1 240 San Joaquin ; 0.04- 0.17 5.6 — 7.8 0.5 — 1 6. PERCOLATION TESTING Shallow and deep percolation test holes were installed in each of the proposed leach field areas with the same drill rig used for the soil profile boring, only equipped with a 6-inch diameter auger. The approximate percolation test locations are presented on Plate 2. Following drilling, the sides of the holes were scored, and significant loose material was removed from the bottom of the holes. The holes were drilled and prepared on January 25 and 26, 2005, in accordance with SJCEHD criteria. Approximately 2 inches of fine gravel was placed at the bottom of each test hole. The percolation tests were run on January 26, 27, and 28, 2005, in accordance with accepted guidelines using clear potable water. The tests holes were presoaked with at least 12 inches of water at least 24 hours prior to testing. During the three days of testing the skies were overcast, the temperatures were cool, and there were periods of rainfall. The approximate depth of each percolation test below existing site grade is shown on the -following table. The holes did not exhibit sloughing or caving. From a fixed reference point, a marked location on the side of 52709.GOI/ST05R550 May 9,2005 © 2005 Kleinfelder, Inc, Page 3 of 7