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May 4, 1493 Working To Restore Nature <br />� <br /> Unocal Station No 6981, Stockton, California <br /> shown on Plate 3, Vapor-Extraction Area of Influence In August 1992, a ground-water <br /> i pumping test was performed onsite to assess the aquifer parameters The results of this test <br /> are provided in detail in this report <br /> On August 17 and 18, 1992, RESNA conducted a series of constant-rate pumping tests to <br /> evaluate hydrologic and well conditions and provide baseline information for the possible <br /> design and operation of a ground-water remedial system The testing consisted of a period <br /> of static ground-water monitoring, five short-term constant-rate tests and a longer-term <br /> constant-rate pumping test The long-duration, constant-rate pumping test utilized well <br /> PTW-1 for production and wells MW-6, MW-7, and MW-11 as observation wells <br /> 4.0 SITE CONDITIONS <br /> 4 1 Regional Geology and Hydrology <br /> The site is in the Central Valley geomorphic province of California, which is a <br /> northwestward-trending, asymmetric structural trough that has been filled with 6 to 10 miles <br /> of sediment ranging in age from Jurassic to Holocene (Page, 1986) The topographic <br /> surface is nearly flat with a slight westward slope Based on an extrapolation of a geological <br /> map prepared by Marchand and Atwater (1979), sediments beneath the site consist of <br /> alluvial deposits of the Modesto Formation,which were deposited by the Mokelumne River <br /> The nearest surface stream is the Calaveras River which trends east and west approximately <br /> 1,800 feet southeast of the site <br /> i <br /> 3W32-i3 4 <br />