SITE INFORMATION AND CORRESPONDENCE FILE 1

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.. .r Attached with Terra Vac's report is a summary report (4/12/95) which describes the results of a pilot test conducted at the subject site on March 16, 1995. The pilot test was conducted to evaluate the feasibility of dual vapor extraction to remediate soil and groundwater. Based on their findings, Terra Vac recommends that air sparging/soil vapor extraction be implemented instead of soil vapor extraction. This plan was detailed in their Remediation Work Plan dated, October 20, 1994. The final approval of Terra Vac's Remediation Work Plan has not been issued by your agency. Reasons for this were described in your letter dated December 5, 1994. I would like to take this opportunity to address these reasons. The first reason referred to a perceived lack of soil and groundwater contamination definition. As mentioned above, additional onsite definition of contamination will be obtained by Terra Vac concurrent with the installation of their remediation system. However, the most effective remedial approach will also require a full understanding of the extent of offsite contamination. To assist with this, Chevron will obtain and review all pertinent data relating to the unauthorized releases that have occurred at properties to the east and west of the subject site. Until the full extent of contamination has been defined for those releases,Chevron cannot begin remediation at the subject site. The review of available offsite data may demonstrate a need for Chevron to perform additional investigation. In that event, a workplan will be submitted to your agency. The second reason dealt with Chevron's requirement to conduct a feasibility study in order to evaluate remedial alternatives. The feasibility of several alternatives was considered by Tetra Vac in formulating their competitive bid. As such, an addendum to their Remediation Work Plan will be submitted which will fully document their evaluation of alternatives. The third reason given for not approving Terra Vac's Work Plan was that a Problem Assessment Report (PAR) had not been submitted. In performing their site evaluation to formulate a remediation plan bid,Terra Vac did conduct an assessment of the problem. In their Remediation Work Plan, Terra Vac described the extent of the problem in terms of volume and mass and has tailored their remedial approach accordingly. Formal documentation of their problem assessment will also be included in the Work Plan addendum to be submitted, If you have any further comments or questions please call me at(510) 842-8695. Sincerely, � �' 13 Brett L. Hunter Environmental Engineer Site Assessment and Remediation Attachments cc Gordon Boggs, Central Valley RWQCB, Sacramento, CA Ron Berberian, 2021 W. March Lane, Suite 2A, Stockton, CA 95207 Patrick Craig, 721 N. Union St., Stockton, CA 95205 Bette Owen, Chevron USA, Products Company, San Ramon, CA (w/o attachments) Tim Warner,Tena Vac, 14798 Wicks Blvd., San Leandro, CA 94577-6718 (w/o att.)