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' 11 November 1999 AGE-NC Project No 97-0230 ' Page 2 of 7 ' 2 2 UNDERGROUND STORAGE TANK REMOVAL The three USTs were removed from the site on 24 February 1999 Soil samples were collected from ' beneath the tank pit and product piping and were submitted to a California Department of Health Services (DHS)-certified laboratory for analysis of total petroleum hydrocarbons quantified as gasoline, diesel and motor oil (TPH-g, TPH-d and TPH-mo, respectively), volatile aromatic ' compounds (benzene,toluene, ethylbenzene and xylene BTEX) and total lead TPH-d and TPH-mo were detected in product piping samples at concentrations ranging as high as 92 milligrams per ' kilogram (mg/kg) BTEX compounds were detected in samples collected beneath the USTs and product piping at concentrations ranging as high as 7 3 mg/kg Total lead was detected in samples collected from product piping samples at concentrations ranging as high as 40 mg/kg Analytical ' results of soil samples collected during tank removal activities are summarized in Table 1 23 REGIONAL GEOLOGIC SETTING The property is situated within the Great Valley Geomorphic Province of California, a large, elongate, northwest trending, asymmetric structural trough The Great Valley Province has been filled with thick sequences of sediment ranging in age from Jurassic to Recent, creating a nearly fiat- lying 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 metamorphic 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 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 source of domestic ground water in the 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 Calaveras River located approximately 2,500 feet north of the site • Advanced GeoEnvironmental.Inc