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• Remedial Status Report-Tosco(Former BP)Station No 11194 <br /> A nl 24,2002 <br /> Groundwater Analytical Data and MtBE Mass Removal <br /> MTBE concentrations from the grab samples were used to estimate the mass of MTBE removed in <br /> groundwater purged from the UST pit at the site An estimated MTBE concentration for each purging <br /> event was derived from averaging MTBE concentrations from groundwater samples collected on <br /> dates prior to and following the corresponding purging event The estimated concentrations were <br /> used to calculate the MTBE mass removed during each event Based on this method, the estimated <br /> total MTBE mass removed in groundwater purged from the UST pit between August 12, 2001 and <br /> January 27, 2001 is 130 pounds The estimated amount of MTBE removed from the site since the <br /> start date of May 3, 2000 is 163 09 pounds The estimated amount of MTBE removed for each event, <br /> the cumulative MTBE removed,and the calculation methods are listed in Table 1 <br /> Conclusions and Recommendations <br /> Based on the analytical results of the groundwater samples collected most recently from OBS-W <br /> and selected monitoring wells at the subject site (Table 1), MTBE concentrations are generally <br /> consistent with the baseline concentrations previously observed at the subject site Therefore, GR <br /> recommends that Tosco discontinue all groundwater purging and sampling activities at the site It <br /> is our understanding that BP Oil Company will continue with the current quarterly monitoring and <br /> sampling of the groundwater monitoring wells at the site <br /> . If you have any questions regarding this report,please call us in our Dublin office at(925)551-7555 <br /> Sincerely, <br /> Gettler-Ryan ne. <br /> Andrew Smith GEO� <br /> Staff Geologist ��C�oO�G J <br /> No. 6882 <br /> Dou las Lee <br /> Project Manager <br /> R G No 6882 ATF OF CAI.����� <br /> Attachments Table 1 -Groundwater Removal and Analytical Data <br /> Figure 1 -Site Plan <br /> Laboratory Analytical Reports and Chain of Custody Documents <br /> cc Mr Harlin Knoll—San Joaquin County Public Health Services <br /> Mr Scott Hooton—BP Oil Company <br /> • 14018704-4 <br /> 2 <br />