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isee FIGURES IA, 7B, AND 7C and TABLE 4-WELL CONSTRUCTION. <br /> CONCJ.JS I ONS <br /> The results of ground water monitoring, January i2, 1990, <br /> indicate that the ground water has risen approximately one foot <br /> since early December and iF flowing to the southeast. Chemical <br /> results of the water samples takan from the monitor wells show <br /> minor contamination to the ground water with gasoline range <br /> hydrocarbons. <br /> A former Chevron site, located northwest of the site, across <br /> Harding and E1 Dorado, maybe contributing to the ground water <br /> contamination. A review of the file on this site has been <br /> arranged. <br /> Soil contamination is limited to beneath the eastern half of the <br /> island and beneath the southeastern half of the tank <br /> pump excavation. This Contamination is of gasoline range hydrocarbons <br /> to the 30 foot depth beneath the excavation and to the 15 foot <br /> depth beneath the pump island. <br /> RECOMMENDATIONS <br /> I. Place an onsite ground water monitoring well near the <br /> intersection of Harding and El Dorado streets. This well will <br /> help define the ground water gradient and may determine if the <br /> • former Chevron site, across the street, is influencing the ground <br /> water beneath this site. <br /> 2. Overexcavate the tank excavation to the 30 foot depth, <br /> or as deep as possible, see FIGURES 7A and 7C. <br /> 3. Install a vapor recovery well in the excavation to the <br /> 45' depth, see FIGURES 7A and 7C. <br /> 4. Use the clean aerated soil, to backfill the excavation <br /> once the vapor recovery well has been installed. <br /> 5. Place vapor recovery wells within the piping trenches <br /> near the middle and eastern pump islands. <br /> G. Manifold all vapor recovery wells to a common treatment <br /> facility near the dumpster area of the site, see FIGURE 7B. <br /> 7. Perform a cost/benefit for the hest means to treat the <br /> vapors generated by a recovery system. <br /> 8. Perform quarterly ground water monitoring. <br /> 4 <br />