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Golden Grain Company <br /> June 2, 1989 <br /> 202/799-5045.01 <br /> borings will be continuously cored. Monitoring wells <br /> will be installed in each of the borings, and soil and <br /> groundwater samples will be collected and analyzed. <br /> 3) Aquifer tests will be performed to provide the final <br /> data needed to design a remediation system. <br /> 2.0 SITE SUBSURFACE CHARACTERISTICS <br /> Drill logs from all eight wells installed by SCS Engineers, <br /> Inc. , the original project consultant, show a moist to saturated <br /> clay layer at a depth of approximately 22 to 25 feet. This clay <br /> unit could act as a competent aquitard separating the upper and <br /> lower sandy, water-bearing units. However, if the aquitard is <br /> leaky, allowing groundwater to flow up or down through the clay <br /> between the two sand units, the entire system (sand/clay/sand) <br /> may be considered hydraulically connected. <br /> On May 10, 1989, GTI conducted a small-scale pump test (as <br /> described in our letter to Diane Hinson of the San Joaquin Local <br /> Health District dated April 27, 1989) to find out if groundwater <br /> communicates through the clay. Hand pumping from monitoring well <br /> (MW)-7 (Figure 1; screened between 30 and 50 feet) for an hour at <br /> an average rate of 1.3 gallons per minute produced a drop in <br /> water levels in the four surrounding wells (screened from 10 to <br /> 25 or 30 feet) of as much as an inch. This drop suggests that <br /> Crater does flow between the two saturated sand units through the <br /> clay, and that the clay unit acts as a leaky aquitard, reducing <br /> the rate of communication between the sand units, but not <br /> preventing it. As such, these units should be considered <br /> hydraulically connected. <br /> 2 _ <br /> GROUNDWATER <br /> TECHNOLOGY,L+C- <br />