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27 October 2000 <br /> ~� AGE-NC Project No. 98-0497 <br /> Page 2 of 8 <br /> 2.2. UNDERGROUND STORAGE TANK REMOVAL <br /> On 29 September 1998, two 12,000-gallon diesel USTs (Tank No. 1 and Tank No. 2), two fuel <br /> dispensers and all associated product piping were removed from the site. Laboratory analysis of soil <br /> samples collected beneath the former UST areas detected total petroleum hydrocarbons quantified <br /> as diesel (TPH-d) at concentrations up to 5,100 mg/kg (milligrams per kilogram). <br /> 2.3. 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 thick 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 California <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 origin. <br /> 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 in 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 and overlying recent alluvium are the principal <br /> sources of domestic groundwater 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 Duck Creek, approximately 1,000 feet south of the property. <br /> 3.0. PROCEDURES <br /> _ On 14 and 15 August 2000, four soil probe borings were advanced at the site; three were completed <br /> as ground water monitoring wells which were purged and sampled on 23 August 2000. The scope <br /> of work was performed in accordance with the PHS--IHD-approved Monitoring Well Installation <br /> Work Plan dated 05 June 2000, prepared by AGE. <br /> Advanced GeoEnvironmental,Inc. <br />