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a <br /> CAMBRIA <br />` E <br /> 4 <br /> F <br /> l <br /> SCM FINDINGS <br /> The SCM prepared for this site has identified the following key findings: <br /> • The chemical of concern(COC)at the site is methyl tertiary butyl ether(MTBE). Total <br /> petroleum hydrocarbons asgasoline (TPH ), and benzene, toluene, eth lbenzene, and <br /> xylenes(BTEX)do not appear to be i COCl at the site. <br /> • <br /> ,to+ <br /> The vertical and lateral extent of TPHg and BTEX in soil has been defined at the site <br /> The lateral extent of MTBE in soil is defined in the downgradient•direction, and the <br /> vertical extent is defined to the typical groundwater table at the site. � �� i. <br /> • The lateral extent of MTBE in groundwater has been defined to the extent feasible. �'� <br /> SII <br /> The vertical extent of MTBE in groundwater has been defined by non-detect results in <br /> E <br /> r' <br /> depthdiscrete grab groundwater samples collected downgradient of the:USTs and <br /> dispenser islands at the site. <br /> • The MTBE plume from the 7-Eleven site appears to have migrated beneath the <br /> southern portion of the Shell-site. Based on the groundwater flow direction, which <br /> typically flows northward,the groundwater plumes are likely co-mingled. <br /> • A sensitive receptor survey performed for the site did not identify any groundwater <br /> wells or'surface water bodies that are likely to be impacted by the site conditions. <br /> • Shell initiated periodic groundwater extraction (GWE) as an interim remedial measure <br /> at the'site during August 2005. It appears-that periodic GWE has been effective in <br /> E <br /> reducing MTBE concentrations in wells MW-1 and MW-6. <br /> RECOMMENDATIONS <br /> Shell recommends continuing periodic GWE at this site and continued evaluation of the <br /> effectiveness of this interim remedial measure. Monthly groundwater samples are being collected <br /> from MW-1 and MW-6 to better evaluate concentration trends -in the two wells undergoing <br /> periodic GWE.', <br /> 14 1661 2 <br />