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IT Chevron <br /> a Chevron <br /> Chevron U.SA Products Company <br /> 6001 Bollinger Canyon Rd, Bldg L <br /> P 0 Box 5004 <br /> October 26, 1994 San Ramon, CA 94583.OB04 <br /> Site Assessment& Remediation Group <br /> Phone{510)842-9500 <br /> Ms Mary Meays <br /> San Joaquin County Environmental Health <br /> P O Box 2009 <br /> Stockton, CA 95201 <br /> Re Fortner Chevron Station#9-1918,45 East Harding Way, Stockton, CA _ <br /> Attached Vapor Extraction System Performance Evaluation (CRTC, 10121194) <br /> Dear Ms Meays <br /> The attached report, dated October 21, 1994, was prepared by staff hydrogeologists at Chevron <br /> Research and Technology Center(CRTC) The report summarizes the findings of a performance <br /> evaluation of the soil vapor extraction system that was employed at the subject site from <br /> November, 1990 until November, 1992 The main conclusions reached from the evaluation were <br /> that the system was correctly designed, it was operated effectively until asymptotic levels of <br /> hydrocarbon recovery were achieved, and the hydrocarbons remaining in the vadose zone pose <br /> little to no impact to groundwater <br /> A review of all site environmental data has indicated that significant source removal has been <br /> accomplished Source removal to date has consisted of removing all UST's, overexcavating <br /> impacted soil from the tankpit, and conducting extensive in-situ remediation by soil vapor <br /> extraction In addition, recent groundwater monitoring results have shown that dissolved <br /> hydrocarbon concentrations are decreasing, the plume has been contained, and that there is no <br /> significant migration occurring <br /> Considering the above information, Chevron feels that further corrective action at this site is not <br /> warranted However, to ensure the reasonable protection of beneficial uses of groundwater <br /> Chevron would propose the following groundwater monitoring program to contain and manage <br /> any remaining health and/or environmental nsks The proposed program would entail gauging <br /> depth to water at wells MW-2R and MW-9 through MW-14 on a quarterly basis Groundwater <br /> sampling would continue at wells MW-2R, MW-9, MW 11, and MW-13 on a quarterly frequency <br /> and wells MW-10, MW-12, and MW-14 on a semi-annual frequency Any significant changes in <br /> groundwater behavior observed for more than two successive measurements would cause Chevron <br /> to reevaluate the site conditions Chevron requests your concurrence with this proposal and would <br /> appreciate a statement from your agency agreeing to the developability of the subject site <br /> If you have any questions or comments, I can be reached at(510) 842-8695 <br /> • Sincerely, <br /> Qhd <br /> X41 f':Pf�f°td <br /> t4E yt *E3't <br />