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• <br /> ' 26 July 1999 <br /> AGE-NC Project No 97-0301 <br /> Page 2 of 9 <br /> 2 2 UNDERGROUND STORAGE TANK REMOVAL <br /> On 04 September 1998, one 10,000-gallon diesel UST and two 10,000-gallon gasoline USTs and <br /> ' associated fuel dispensers and product piping were removed from the site Laboratory analysis of <br /> soil samples collected beneath the former UST areas detected total petroleum hydrocarbons <br /> quantified as gasoline, diesel and kerosene (TPH-g, TPH-d and TPH-K, respectively) at <br /> ' concentrations up to 9,000 mg/kg(milligrams per kilogram) Volatile aromatic compounds benzene, <br /> toluene,ethylbenzene and xylenes(BTEX)were detected at concentrations up to 520 mg/kg,methyl <br /> tertiary butyl ether (MTBE) was detected in two stockpiled soil samples at concentrations up to <br /> ' 0 012 mg/kg Analytical results of soil samples collected during tank removal activities are <br /> summarized in Table 1 <br /> 23 REGIONAL GEOLOGIC SETTING <br /> ' The property is situated within the Great Valley Geomorphic Province of California, a large, <br /> elongate, northwest trending, asymmetric structural trough The Great Valley Province has been <br /> filled with duck sequences of sediment ranging in age from Jurassic to Recent,creating a nearly flat- <br /> lying alluvial plain,extending from the Tehachapi Mountains in the south to the Klamath Mountains <br /> in the north The western and eastern boundaries of this province are comprised of the Califorrna <br /> ' Coast Range and the Sierra Nevada, respectively Rocks composing the basement complex of the <br /> province have not been completely defined but are believed to be metamorphic and igneous in <br /> origin The northern and southern portions of the Great Valley Province have been designated the <br /> Sacramento and San Joaquin Valleys, respectively <br /> Based on the General Soil Map from the San Joaquin County Soil Survey, published by the United <br /> States Department of Agriculture Soil Conservation Service in 1992, the site area is within the <br /> Jackson-Hallenbeck-Stockton (JHS) association The JHS soils are located within basins, and <br /> generally consist of moderate to poorly drained fine textured soils The soils are generally derived <br /> from both marine and non-marine sediment, and are generally formed in alluvium derived from <br /> mixed rock sources <br /> The Modesto, Riverbank, Turlock Lake Formations andv <br /> o erlymg recent alluvium are the principal <br /> source of domestic ground water in the 13,500 square-mile San Joaquin Valley Ground Water Basin <br /> (Basin 5-22) This basin is drained primarily by the San Joaquin River The nearest surface water <br /> feature in the vicinity of the property is the French Camp Slough located approximately 1,000 feet <br /> ' west of the site <br /> • <br /> Advanced CeoEn{ironmentai,Inc <br /> 1 <br />