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Mr. Maurice Benson • • <br /> February 23, 2010 <br /> Page 5 <br /> Conclusions <br /> The Annual Report, while detailed and well laid out, depicts a less than accurate picture <br /> of the DDJC-Tracy TCE plume concentrations and lateral extents. The report states <br /> that no TCE was detected in the Upper Hydrologic Zone in 3Q09 but fails to mention <br /> that this was due to monitoring well LMl93AU-NS being destroyed during demolition <br /> activities for the Warehouse after the 2Q09 sampling event reported a concentration of <br /> 104 Ng/L. Less than accurate groundwater plume interpretation was also presented in <br /> sections discussing plume summaries by stating the groundwater plumes were stable or <br /> shrinking. A review of data shows that TCE concentrations beneath Warehouse 10 <br /> have increased during this time period and further migration of the East Banta Road <br /> TCE plume has been verified with recent Hydropunch® data prompting the installation <br /> of guard wells. <br /> The report presents a small section which discusses pesticides in groundwater but <br /> omits information on the discovery of elevated levels of pesticides and herbicides <br /> detected in soil near Areal/Building 237 in March 2009. Specifically, extremely high <br /> concentrations of DDT and dieldrin were reported that exceed U.S. EPA Region IX <br /> Industrial soil PRGs by factors of 160 and 48, respectively. The report should include <br /> some discussion of the elevated pesticide and herbicide concentrations that do not <br /> meet the current industrial land use cleanup standards. <br /> If you have any questions or comments on this letter, please feel free to contact me at <br /> (916) 255-6514 or e-mail at pmacnichadtsc.ca.aov <br /> Sincerely, <br /> Peter MacNicholl, P.E. <br /> Remedial Project Manager <br /> cc: See next page. <br />