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6131 Pacific Avenue • • January 13, 2010 <br /> Shell-Branded Service Station page 2 <br /> information. Additionally, CRA states that this area will not be targeted for groundwater <br /> remediation. The EHD does not approve any additional investigation by CPT at this time, but <br /> will reconsider the proposal if provided a technical justification. <br /> CRA proposes to install two groundwater monitoring wells, one to approximately 58 feet bsg <br /> adjacent to VEW-2 and one to approximately 43 feet bsg adjacent to VEW-4. The EHD <br /> approves the installation of one deep screened monitoring well in the area of the former tank <br /> pit on condition it is screened in a distinctly different water bearing zone deeper than VEW-4. <br /> The boring for the well should be continuously cored starting at 70 feet bsg to find an <br /> appropriate sand interval in which to set the screen. <br /> The screened interval of monitoring wells MW-1, MW-2 and MW-3 have been submerged <br /> since 1996. Prior to that time, the contaminant concentrations in MW-1 had reduced to non- <br /> detect levels, and in MW-2 had reduced to <100 micrograms per liter (Ng/1) TPHg and 1.0 <br /> Ng/I benzene. Additionally, well VEW-5 was installed in February 2006 between the former <br /> tank pit area and MW-2, intercepts shallow groundwater, and is reported non-detect. The <br /> EHD does not approve the installation of additional shallow groundwater monitoring wells in <br /> this area. Contaminant concentrations in MW-3 remained high until the year 2000. In <br /> correspondence dated May 1, 2006, because several of the shallow wells onsite were <br /> submerged, the EHD directed investigation of the contaminant concentrations in the shallow <br /> groundwater. Cambria/Shell responded with a proposal to install one groundwater monitoring <br /> well on the south side of the property midway between wells MW-3 and MW-4. The well, <br /> MW-14, was installed in September 2006 and has reported a maximum contaminant <br /> concentration of 310 pg/I TPHg. <br /> In summary, the EHD approves installation of one deep groundwater monitoring well in the <br /> area of the former tank pit, screened at a depth below the screen interval of VEW-4. Please <br /> proceed with submittal of a San Joaquin County Well Permit Application, $89.00 permit fee <br /> and with scheduling the approved work. The EHD strongly recommends CRA use the drilling <br /> of this boring to collect any soil samples needed to conduct a bench scale test for the <br /> proposed ISCO remediation, as resumption of remediation of the source area contamination <br /> is the highest priority at this site. <br /> If you have any questions please contact Lori Duncan at (209) 468-0337 or by email at <br /> Iduncan@sjcehd.com. <br /> Sincerely, <br /> (&,,t - <br /> Lori Duncan, REHS Nuel C. Henderson, Jr. PG <br /> Senior Registered Environmental Health Specialist Engineering Geologist <br /> c: James Barton, CVRWQCB, 10020 Sun Center Drive#200, Rancho Cordova, CA 95670 <br /> Ann Rosecrance, CRA, 19449 Riverside Drive #230, Sonoma, CA 94576 <br />