SITE INFORMATION AND CORRESPONDENCE_FILE 1

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Chevron Chevron Chevron Products Company Feb 28 1997 6001 Bollinger Canyon Road February Building L San Ramon,CA 94583 P.O. Box 6004 San Ramon,CA 94583-0904 Ms. Mary Meays Marketing—Sales West San Joaquin County Environmental Health Phone 510 842-9500 P.O. Box 388 Stockton, CA 95201-0388 Re: Chevron Station#9-6171,6633 Pacific Avenue, Stockton,CA Attached groundwater monitoring report(Gettler-Ryan, 9/18/96) Dear Ms. Meays: Please find attached a report dated September 18, 1996,which was prepared by Chevron's consultant, Gettler-Ryan, Inc. (Gettler-Ryan),to describe the results of groundwater monitoring that was performed at the subject site on August 12, 1996. During their August site visit Gettler-Ryan gauged and sampled all six site-related wells. All groundwater samples were analyzed for the presence of TPHGas,BTEX constituents,MTBE,and various dissolved ions. In addition, split samples were analyzed for volatile organic compounds(EPA method 8260)to assess the distribution of chlorinated compounds beneath the subject site. The measured direction of groundwater flow was generally toward the southeast. There were detections of TPHGas were reported at five of the six wells. The reported detections were based on the presence of discrete peaks within the C8- C9 range. It is suspected that these discrete peaks are associated with chlorinated compounds that are known to exist in groundwater beneath the subject site. There were detections of BTEX constituents reported at wells MW-2,MW-4,MW-5,and MW-6 by the EPA 8020 method. There were quantifiable BTEX detections reported by the 8260 method at wells MW-5, and MW-6. The inconsistency of BTEX detections between the two methods is related to a difference of reporting limits in the case of well MW-2 and due to a false positive as reported for xylenes in well MW-4. It was only at well MW-5 where the reported BTEX concentrations were above State MCL's(1.3 ppb benzene). All reported concentrations were consistent with previous site measurements. Detectable concentrations of MTBE were only measured at wells MW-5 and MW-6. These results were reported from the 8020 method analyses and not from the 8260 analyses. Chevron is pursuing the results of MTBE from the 8260 analyses. Confirmation of these concentrations will be provided at a later time. The various dissolved ions were measured to quantify the potential for intrinsic biodegradation. An evaluation of this potential has been made and the further analyses of these ions will discontinue. If you have any questions or comments, I can be reached at(510)842-8695. Sincerely, / /S,V� Brett L. Hunter Environmental Engineer Site Assessment and Remediation