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1 <br /> February 14, 1992 <br /> . ARCO Service Station No 2130, Stockton, California <br /> 1 <br /> of the monitoring wells were referenced to within 0 01 foot of the Bench Mark The <br /> horizontal distances were measured to the nearest 0 1 foot The elevations were taken to <br /> either the notch or the arrow on the well casing Elevations of the ground-water surface <br /> with respect to mean sea level for the January 1992 monitoring event are presented in Table <br /> 6 The local ground-water flow direction was toward the east on January 7, 1992 as shown <br /> on the Potentiometric Map (Plate 3) The evaluated ground-water gradient was 0 0018 <br /> Vapor-Extraction Test <br /> A vapor-extraction test (VET) was conducted on December 30, 1991, to evaluate whether <br /> vapor extraction is feasible at the site Based on data obtained during the VET and the <br /> distances between the wells, RESNA estimates that wellhead flowrates of 30 cubic feet per <br /> minute will result in an effective radius of influences of approximately 25 feet RESNA <br /> . concludes that vapor extraction is a feasible method of remediating soil at this site The <br /> radius of influences and flow rates estimated above can be further refined and the number <br /> and location of additional vapor-extraction wells will be selected during an additional <br /> subsurface environmental investigation A copy of the vapor-extraction test report is <br /> included in Appendix D of this document <br /> SCOPE OF WORK <br /> During the tank removal, we will <br /> o Observe removal of four underground storage tanks and associated product <br /> lines <br /> o Observe excavation of soil in and around the gasoline-tank cavity and product <br /> lines <br /> o Collect and analyze appropriate samples of native soil within 2 feet below the <br /> base of the former tanks to evaluate if hydrocarbons remain in the soil <br /> 30003-4W 7 <br />