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15 September 1999 AGE-NTC Project No. 97-0369 Page 2 of 9 ranging as high as 0.07 mg/kg. Analytical results of soil samples collected during the tank removals are summarized in Table 1. 2.3. PREVIOUS SUBSURFACE INVESTIGATION On 20 and 21 October 1997, five soil borings (P-1 through P-5) were advanced at the site to assess the lateral and vertical extent of impacted soil and ground water. A total of 9 soil samples and five grab around water samples were collected during the investigation and submitted for Iaboratory analysis. TPH-g and TPH-d were detected in soil samples collected fi-om probe boring P-1 at concentrations ranging as high as 220 mg/kg. BTEX compounds were detected in soil samples collected from P-1 at concentrations ranging as high as 2.1 mg/kg: fuel oxygenated compounds were not detected by laboratory analysis of the selected soil samples. TPH-g and TPH-d were detected in a grab ground water sample collected from 13-1 at concentrations of 10.000 micrograms per liter (ugil) and 660 µg/1, respectively; MTBE was detected in a ground water sample collected from P-4 at a concentration of 0.61 ,ug/1. No other fuel oxygenated compounds were detected by laboratory analysis of ground Nvater samples. Results of the October 1997 investigation were reported in the PrelinliMil''V 1171,esligutio17 rn7d Evaluation Report (PIER) dated 16 December 1997 prepared by AGE. Analytical results of soil and grab ground Nyater samples collected during the October 1997 investigation are summarized in Tables 2 and 3. 2.4. REGIONAL GEOLOGIC SETTING The property is situated within the Great Valley Geomorphic Province of California.. a large. elongate, northwest trending, asymmetric structural trougin. The Great Valley Province has been filled with thick sequences of sediment ranging in age from.Jurassic to Recent, creating a nearly flat- Iying alluvial plain, extending from the Tehachapi Mountains in the south to the Klamath Mountains in the north. The western and eastern boundaries of this province are comprised of the California Coast Range and the Sierra Nevada, respectively. Rocks composing the basement complex of the province have not been completely defined but are believed to be metannorphic and igneous in origin. 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 w-ithin basins. and 4rhvurrnd GcoEn�ironmcnlal,Inc.