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Remedial Investigation Report -8- 8 March 1991 <br /> DDRW, Sharpe <br /> FINDING <br /> 18. Significantly elevated levels of arsenic, selenium, and Bromacil in the ground <br /> water are almost completely confined to the shallowest aquifer zone. <br /> RESPONSE <br /> 18. I concur with this finding. <br /> FINDING <br /> 19. Spatial and frequency distribution patterns of arsenic occurrence in soil and <br /> ground water do not dictate an on-site source. <br /> RESPONSE <br /> 19. Finding is noted. However, the Report does not present the graphics that would <br /> readily lend themselves to this conclusion. The specific concentrations of <br /> arsenic in the ground water from each well were not plotted on a map. In <br /> addition, the concentrations within the upper five feet of the soils borings were <br /> not plotted on a map. Therefore, it is more difficult to make conclusions <br /> regarding distribution and potential sources areas without the aid of these <br /> graphics. <br /> FINDING <br /> 20. Selenium contamination in soil and ground water at SHAD is minimal . <br /> RESPONSE <br /> 20. In general , I concur with this finding. There are only a few monitor wells which <br /> had selenium concentrations greater than the Primary DWS. <br /> FINDING <br /> 21. Bromacil contamination in soil and ground water at SHAD is minimal . <br /> RESPONSE <br /> 21. In general , I concur with this finding. However, there are several areas of <br /> elevated Bromacil concentrations in the ground water. A DWS has not been <br /> established for Bromacil . The Environmental Protection Agency (EPA) Suggested No <br /> Adverse Response Level (SNARL) for Bromacil is 90 µg/l . The maximum <br /> concentration of Bromacil in well 407A at 773 µg/l is significantly greater than <br /> the EPA SNARL. The areas of highly elevated concentrations of Bromacil may <br /> require remediation. <br /> FINDING <br /> 22. Soil concentrations of arsenic off-site are indistinguishable from those on-site. <br /> RESPONSE <br /> 22. Finding is noted. This finding is based on the comparison of sample populations <br /> using 20 off-site soil samples and 39 on-site soil samples. Over 400 on-site soil <br /> samples were collected for analysis. The Report does not state what criteria were <br />