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5. GROUNDWATER Groundwater was not encountered in the borings drilled for this investigation. Lines of Equal Depth to Groundwater contour maps published in groundwater reports by the San Joaquin County Flood Control and Water Conservation District (1982 to 1999) show groundwater levels in the project area ranging from about 160 to 180 feet below ground surface. Based on Lines of Equal Elevation of Groundwater contour maps, the groundwater gradient in the project area is generally from east to west. Local gradient variations may occur due to well usage. At the time of our field investigation, two agricultural wells were located along the west side of parcel 009-170-04. These wells were out of service at the time of our investigation. No new wells are planned to be constructed within the project area. The results of the groundwater analysis to determine the concentrations of nitrate (N) in the water sampled from the off-site well indicated a concentration of 0.75 mg/l. This nitrate concentration is below the state drinking water standard of 45 mg/I. DBCP was not present in detectable amounts. Copies of the test results and the chain-of-custody are presented on Plate 18 We do not know of groundwater contamination issues at the project site at this time. No underground storage tanks are known to exist on the site and no gas stations or dairies are located adjacent to the site. The potential sources of nitrate in the project area include the grazing of cattle and horses; existing septic systems for single-family housing located in the project area; and any fertilizers, pesticides, and herbicides that may be used for agricultural purposes in the area. After the parcels are split, we anticipate that the on-site sources of nitrate will be limited to the use of pesticides on the planned vineyards. 6. SOIL PROFILE The subsurface soil encountered in our soil profile borings consisted of sandy silt to sandy clay to a depth of approximately 2 to 9 feet below existing site grade underlain by discontinuous and interbedded layers of cemented clayey sand, gravelly sand, and silty sand to sandy silt to the depths explored. 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 Corning-Redding complex soil series (Map Symbol 135 and 138). Redding Gravelly Loam soil series (Map Symbol 220), and the Yellowlark Gravelly Loam soil series (Map Symbol 280). These soils are all described as being "well drained" and having "severe" pf,.rcolation characteristics for Septic tank 57556.G01/ST05RG87R August 25,2005 ..'+2005 Kloinfolder, Inc. Page!of 5