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Mr. Marty Hartzell <br /> February 16, 2001 <br /> Page 2 of 8 <br /> i 2.0 BACKGROUND INFORMATION <br />' 2.1 Site Description Hydrogeologic Setting <br /> ' Garner Constriction of Oakdale, California removed three USTs (one 10,000-gallon diesel, one <br /> 1,000-gallon gasoline and one 500-gallon diesel) from the.subject site on March 31, 1988. One soil <br /> sample was collected from beneath each of the USTs to determine if soil had been impacted. <br /> The samples were submitted to State-Certified California Water Labs, Inc. for analysis. Analysis <br /> consisted of total petroleum hydrocarbons as gasoline (TPHg), total petroleum hydrocarbons as <br /> ' kerosene (TPHk), and total petroleum hydrocarbons as motor oil (TPHmo), Ethylene dibromide <br /> (EDB) and total lead. <br /> ' Analytical results indicated that elevated levels of petroleum hydrocarbons were present in the soil <br /> beneath the 1,000-gallon gasoline UST. Total petroleum hydrocarbons as diesel (TPHd) was <br /> detected in the sample collected beneath the 500-gallon diesel UST at a concentration of 66 parts <br /> ' per million (ppm), but no benzene, toluene, ethylbenzene, or total xylenes (BTEX) constituents <br /> were detected. No target analytes were detected in the sample collected beneath the 10,000-gallon <br /> diesel UST.' Analytical results of soil samples collected beneath the USTs are summarized in Table <br /> 1. The locations of the former USTs are shown on the site plan, Figure 2. <br /> 2.2 Hydrogeologic Setting <br /> The site is situated in central Escaion in Section 4 of Township 2 South, Range 9 East, San <br /> Joaquin County, California. The property is located in the San Joaquin Valley physiographic <br /> province. The valley is a topographic and structural basin bounded on the east by the Sierra <br /> Nevada and on the west by the Coast Ranges. The local topography slopes gently toward the <br /> southwest. <br /> ' The near surface geology typical of the San Joaquin Valley is comprised of unconsolidated <br /> alluvial deposits of Pleistocene to Holocene age. These deposits, sometimes referred to as "older <br /> ' alluvium", consist of intercalated beds of gravel, sand, silt and clay. The thickness of the older <br /> alluvium in the Escalon area averages approximately 450 feet. Underlying the older alluvium <br /> are Plio/Pleistocene continental deposits of similar derivation and lithology. The older alluvium <br /> ' functions as the most important aquifer in the site area (USGS Professional Paper 1401-C, 1986). <br /> Soils developed on the alluvium are generally well drained, differing from the parent material <br /> only in the increased volume of organic matter(DWR Bulletin No. 146, 1967). <br /> ' The important bodies of surface water in proximity to the site are the Stanislaus Tuolumne and <br /> p P Y , <br /> San Joaquin Rivers. The Stanislaus and Tuolumne Rivers are located approximately 2 t/2 and 10 <br /> ' z/2 miles south of the site, respectively. These two rivers flow in a westerly direction and are <br /> tributaries to the San Joaquin River, located approximately 14 miles west of the site. The <br /> ' northerly flowing San Joaquin River drains the San Joaquin Valley. Existing and potential <br /> beneficial uses of these surface water bodies include domestic water supply, irrigation, industrial <br /> supply, groundwater recharge, freshwater replenishment, hydroelectric power, recreation, <br /> ' datalgrou=z gonza es�sumrpt doe <br />