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1 <br />' 24 August 2000 <br /> . AGE-NC Project No 00-0725 <br />' Page 2 of 6 <br />' 1 2 ENVIRONMENTAL SETTING <br /> 1 2 1 Regional Geology <br />' The site is located within the northern San Joaquin Valley which comprises part of the Great Valley <br /> geomorphic province of California The San Joaquin Valley is formed by the Great Valley <br />' geosyncline, which is a large, elongate northwest-trending asymmetrical structural trough (basin) <br /> It is bordered by the Coast Ranges to the west, the Klamath Mountains and Cascade Range to the <br /> north, and the Sierra Nevada to the east This trough has been filled with sediments derived from <br />' both marine and continental sources Thickness of the sedimentary fill ranges from thin veneers <br /> along the valley edges to greater than 20,000 feet in the south central portion of the valley The <br /> sedimentary formations range in age with the older deposits being primarily marine in origin and the <br />' younger deposits being primarily continental Continental-derived sediments were primarily <br /> deposited in lacustnne, fluvial, and alluvial environments with sources being the mountain ranges <br /> surrounding the valley (OImsted and Davis, 1961) The site is located on unconsolidated and semi- <br /> consolidated alluvium, lake, playa and terrace deposits of Quaternary age (California Division of <br /> Mimes and Geology 1977) <br /> 1 2 2 Regional Hydrogeology <br />' The estimated depth to ground water at the property is approximately 10 feet below surface grade <br /> (bsg), based on the map titled Lines of Equal Depth to Groundwater Spring 1996 published by the <br />' San Joaquin County Flood Control District and Water Conservation District (FCD&WCD) It is <br /> inferred from the map titled Lines of Equal Elevation of Groundwater Spring 1996, also published <br /> by the FCD&WCD, that ground water flows toward the northwest in the general area of the site, but <br /> this may be modified by changing recharge and discharge patterns Ground water is considered to <br /> be of beneficial use and is used for domestic, industrial and commercial purposes <br /> I Information obtained from the soil borings from the site indicates that the depth to groundwater at <br /> the site is between 10 and 12 feet bsg <br />' 1 3 PREVIOUS ENVIRONMENTAL INVESTIGATIONS <br /> A UST gasoline system reportedly operated on the site for approximately thirty years from 1940 <br /> until 1970 <br />