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05 September 2002 AGE-NC Project No. 01-0887 Page 2 of 9 The northern and southern portions of the Great Valley Province have been designated the Sacramento and San Joaquin Valleys, respectively. Based on the General Soil Map from the San Joaquin County Soil Survey, published by the United States Department of Agriculture Soil Conservation Service in 1992, the site area is within the Jackson-Hallenbeck-Stockton (JHS) association. The JHS soils are located within basins, and generally consist of moderate to poorly drained fine textured soils. The soils are generally derived from both marine and non-marine sediment, and are generally formed in alluvium derived from mixed rock sources. The Modesto, Riverbank, Turlock Lake Formations and overlying recent alluvium are the principal sources of domestic ground water inthe 13,500-square-mile San Joaquin Valley Ground Water Basin (Basin 5-22). This basin is drained primarily by the San Joaquin River. The nearest surface water feature in the vicinity of the property is the Old River, approximately 2.5 miles west of the property. 2.2. UNDERGROUND STORAGE TANK REMOVAL On 07 December 1992, one 10,000-gallon gasoline UST and approximately 100 feet of associated piping were removed from the site by Western Meter Service,Inc. and was transported to Cal Coast Manufacturing Co. for disposal. An Unauthorized Release Report (UAR) was issued by the EHD on 31 December 1992. The UAR was issued after laboratory analysis of soil samples collected during the UST and piping removal detected volatile aromatic compounds benzene, toluene, ethylbenzene and total xylenes (BTEX) at concentrations as high as 0.026 milligrams per kilogram (mg/kg). 0.007 mg/kg, 0.009 mg/kg and 0.01 mg/kg, respectively. Total petroleum hydrocarbons quantified as gasoline (TPH-g) and BTEX were detected at concentrations of as high as 8.3 mg/kg and 15.9 mg/kg, respectively, in soil samples collected from below the product piping (approximately 4 feet bsg). Analytical results of soil samples collected during removal of the USTs are summarized in Table 1. 2.3. PREVIOUS INVESTIGATIONS In May 2002, a preliminary site assessment was conducted at the site. The assessment consisted of the advancement of three probe borings(P-1 through P-3)for the collection of soil and groundwater samples. Probe borings are illustrated in Figure 2. TPH-g was detected in the soil samples at concentrations of 1,000 mg/kg (P1-4.5), 2,800 mg/kg (P2-5) and 190 mg/kg(P3-5). BTEX compounds were detected in each of the analyzed soil samples Advanced GeoEnvironmental,Inc.