SITE INFORMATION AND CORRESPONDENCE_FILE 1

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aleuron TAL HEALTH � Chevron •�: : �' _i} QCT —C) Pia 1: 21 Chevron U.S.A.Products Company 6001 Bollinger Canyon Road September 30, 1994 Building L San Ramon,CA 94583 P.O.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 2009 Stockton, CA 95201 Re: Chevron Station#9-6171, 6633 Pacific Avenue Stockton CA Dear Ms. Meays: I have reviewed your letter dated August 29, 1994, in which Chevron was told to submit a workplan to define the extent of residual hydrocarbons in soil beneath the subject property. After carefully considering the contents of the letter and after reviewing the most recent (6116194) groundwater monitoring data, I have come to the decision that further investigation is not warranted or necessary. As I pointed out in my letter dated July 5, 1994, the most probable explanation for groundwater contamination at MW-2 was due to the overspill containment boxes on the UST's and not due to any release(s) at the southern pump island. I also pointed out that the spill containment boxes were repaired during December, 1993 and that groundwater contamination would probably be mitigated as a result of these repairs. A review of the latest groundwater monitoring data shows that since the repair of the spill containment boxes, concentrations of dissolved petroleum hydrocarbons have decreased at all site-related wells. These data support the above argument that the source was not at the pump islands but instead, was at the UST complex. As such, the source of groundwater contamination has been defined and mitigated. Therefore, an investigation at the pump islands, or anywhere else, should not be necessary. Chevron feels that the current array of wells adequately defines the extent of contamination. The most recent data from these wells indicates that the plume is not migrating. Quarterly groundwater monitoring will continue to evaluate the long term effects of the mitigation. Should groundwater conditions change considerably, we would adjust our position as necessary, based on the new data. I am aware that San Joaquin County Public Health Services is planning to discuss individual cases with Chevron at an unscheduled meeting in the near future. If the information presented above does not satisfy your agency's concern about the need for additional investigation, I would like to suggest that this matter be resolved through discussion at that meeting. If you have any questions or comments, I can be reached at(510) 842-8695. Sincerely, � ��