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x <br /> 17 June 2003 <br /> AGE-NC Project No. 03-1035 <br /> Page 2 of 6 <br /> The Province is bordered by the Coast Ranges to the west, the Klamath Mountains and Cascade <br /> Range to the north, and the Sierra Nevada to the east. <br /> The Great Valley has been filled with sediments derived from both marine and continental sources. <br /> Thickness of the sedimentary fill ranges from thin veneers along the valley edges to more than <br /> 20,000 feet in the south central portion of the valley. The sedimentary formations range in age from <br /> Jurassic to Recent,with the older deposits being primarily marine in origin and the younger deposits <br /> being primarily continental. Continental-derived sediments were primarily deposited in lacustrine, <br /> fluvial,and alluvial environments with sediment sources being the mountain ranges surrounding the <br /> valley(Olmsted and Davis, 1961);the site itself is located on unconsolidated and semi-consolidated <br /> alluvium, lake, playa and terrace deposits of Quaternary age (California Division of Mines and <br /> Geology, 1977).Rocks composing the basement complex of the Province have not been completely <br /> defined but are believed to be metamorphic and igneous in origin. <br /> The Modesto, Riverbank and Turlock Lake Formations and overlying Recent alluvium are the <br /> principal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground <br /> Water Basin(Basin 5-22). The estimated depth to ground water at the site is approximately 50 to 60 <br /> feet below surface grade(bsg)based on information from Lines of Equal Depth of Water Wells Fall <br /> 1999,published by the San Joaquin County Flood Control District and Water Conservation District- <br /> FCD&WCD. Based on the map titled Lines of Equal Elevation of Groundwater Spring 1999 also <br /> published by the San Joaquin County FCD&WCD, the ground water elevation is estimated at <br /> approximately 35 feet below surface grade and ground water flow generally toward the <br /> east/southeast. However, this may be greatly modified by local recharge and discharge patterns. <br /> 2.2. UNDERGROUND STORAGE TANK REMOVAL <br /> One 500-gallon gasoline underground storage tank(UST)was removed from the site in September <br /> 1989; the UST was reported to have held leaded gasoline,and to have been out-of-service for 20 to <br /> 25 years prior to removal. Following tank removal, a one soil sample was collected approximately <br /> one foot below the pipeline(P-1) and one from approximately 3 feet below the former UST(T-1). <br /> Laboratory analytical results detected toluene at a concentration of 1.3 milligrams per kilogram <br /> (mg/kg) from pipeline sample P-1 and total lead at concentrations of 208 mg/kg and 74.5 mg/kg <br /> from P-1 and the UST sample T-1,respectively;total petroleum hydrocarbons as gasoline(TPH-g), <br /> benzene, ethylbenzene, xylenes and ethylene dibromide (EDB) were not detected in the analyzed <br /> samples. In November 1989,the pipeline sample P-1 was analyzed for organic lead; the result was <br /> non-detect (<2.5 mg/kg). <br /> Advanced GeoEnvironmental,Inc. <br />