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/ - f <br /> JIMCO Truck Plaza Page 2 <br /> 1022 East Frontage Road January 31, 2008 <br /> Ripon, California <br /> Based on favorable results from SVE and SVE/AS pilot tests conducted in September 2005, the <br /> ,EHD concurs with the recommendation by CRA to install an SVE/AS system to remediate <br /> MTBE and other petroleum hydrocarbon contamination detected in soil and groundwater samples <br /> collected near the former UST area. EHD recommends that a tracer be included to monitor the <br /> capture of air if air is injected in low permeable zones. Please submit a work plan to EHD by <br /> 'May 1,2008,for the installation of an SVE/AS system. <br /> In Site Assessment Report, CRA states that "The extent of dissolved—phase MTBE is adequately <br /> defined both'jlaterally and vertically in the vicinity of the former gasoline USTs." The EHD <br /> agrees that MTBE contamination is vertically defined; however, the EHD is not convinced <br /> MTBE is adequately defined laterally to the west of the former gasoline UST. Groundwater <br /> sample concentrations collected from MW-10 continue to be significantly higher than <br /> groundwater sample concentrations collected.from MW-9, the monitoring well located nearest the <br /> former USTs Additional investigation may be necessary to define the MTBE plume west of <br /> MW-10. <br /> The EHD approves the removal of EDB, 1,2-DCA, DIPE, and ETBE from the analytical list since <br /> these compounds were reported "non-detect" during the four quarterly sampling events for 2007. <br /> The EHD does not approve the removal of TEPH-mo from the analytical list for MW-1, MW-2, <br /> and MW-9, and directs that groundwater collected from MW-6 also be analyzed for TEPH-mo. <br /> This decision is based on laboratory results indicating that TEPH—mo is present in soil and/or <br /> groundwater samples collected from at least six of the ten soil borings advanced in March of <br /> 2007. TBA continues to be detected in groundwater samples collected quarterly from MW-1, <br /> MW-2, MW-8, and MW-9; therefore, continue to analyze for TBA in groundwater samples <br /> collected from these four monitoring wells; and TAME continues to be detected in groundwater <br /> samples collected quarterly from MW-8, so continue to analyze for TAME in groundwater <br /> samples collected from this monitoring well. <br /> If you have any questions please contact Vicki McCartney at (209) 468-9852 or by email at <br /> --mceartney_.,..sjcchd.corn. <br /> Sincerely, <br /> Victoria L. McCartney, Senior REHS Nuel C. Henderson,Jr., PG <br /> Local Oversight Program Engineering Geologist <br /> Local Oversight Program <br /> c: Mr. Ron Scheele, PG, Conestoga-Rovers & Associates, 5900 Hollis Street, Suite A, <br /> Emeryville, California 94608 <br /> Mr. JamesiL.L. Barton, PG, California Regional Water Quality Control Board Central Valley <br /> Region, 11020 Sun Center Drive, Suite 200,Rancho Cordova, CA 95670 <br /> f <br />