SITE INFORMATION AND CORRESPONDENCE FILE 1

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L Chevron NOM - Chevron Chevron U.S.A.Products Company 6001 Bollinger Canyon Road July 22, 1996 Building L San Ramon,CA 94583 P0.Box 5004 San Ramon,CA 94583-0804 Ms.Mary Meays Marketing—Northwest Region San Joaquin County Environmental Health Phone 510 842 9500 P:O.Box 388 Stockton,CA 95201-0388 Re: Chevron Station#9-0557, 139 South Center Street, Stockton, CA Attached groundwater monitoring report(Blaine Tech,6/14/96) Dear Ms.Meays: Please find attached a report dated June 14, 1996,which was prepared by Chevron's consultant,Blaine Tech Services Inc. (Blaine Tech),to describe the results of groundwater monitoring that was performed at the subject site on May 17, 1996. In May Blaine Tech gauged.and sampled all seven site-related wells. All samples were analyzed for the presence of TPHGas,BTEX constituents,and MTBE. The measured direction of groundwater flow beneath the subject site was again, southeasterly. The groundwater elevations were the highest ever measured at the subject site. Detectable concentrations of dissolved petroleum hydrocarbons were measured at wells MW-2,MW-S, and MW-7. The measured levels-at MW-2 and MW-5 appeared to be consistent with those previously detected.However,a comparison of monitoring-well completion intervals and depth to water indicates that screened intervals at all wells,except-MW-7,are submerged. This may have affected those contaminant concentrations measured at wells MW-1,MW-2,and MW-6 since May, 1-995.as their respective concentrations are lower:than-they were prior to the screens becoming submerged. In your letter dated June 17, 1996 you requested replies to comments made in your January 25, 1996 letter.Please note that these replies have been provided in a separate correspondence. You also commented on the need for a workplan addendum to describe further groundwater investigation as well-` as, a remedial feasibility study to evaluate alternatives for reducing soil and groundwater contamination levels. Further investigation and remediation may be necessary at the subject site. However, rather than proceed at this time with additional.work, Chevron would like to evaluate the actual risk(s)-that may be associated with the contamination and then propose.further action that would be most appropriate based on the findings. If your agency is agreeable-to this approach,,Chevron would like to schedule a meeting in August to discuss the site-specific factors to be considered in evaluating risk and in developing a practical approach. If.you have any questions or comments, I can be reached at(510)842-8695. Sincerely,