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r STATE OF CALIFORNIA • • GEORGE DEUKMEJIAN.Governor CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— CENTRAL VALLEY REGION 3443 SACRAMENTO, ROAD �i y'\d�A SACRAMENTO,CA 95827-3098u D \1'VwV MPR 2 01 20 March 1989 CN`IPERMTI�tsEav CES SH Kristin B. Gunter Chevron Corporation 576 Standard Ave. Richmond CA. 94802 MITIGATION PLAN AND GROUND WATER MONITORING PLAN FOR ALDEN PARK, SAN JOAQUIN COUNTY We have reviewed the subject documents you submitted in November 1988. Overall we find each plan to be satisfactory and look forward to their implementation. We do feel the objectives of the Mitigation Plan need to be expanded and some small adjustments to the Ground Water Monitoring Plan are necessary. As we understand, the initial phase of remediation will consist of one liquid pumping/bio-venting well . After analyzing the performance of this well , Chevron will design a full scale remediation system. Our main concern with this mitigation plan is that the stated objective is described only as the removal of the nuisance of flowing oil to the residents. While we agree that the oil that flows to the surface is the most obvious problem at the site, the impact the oil has had on the beneficial uses of the ground water has not been fully established. Soil samples in the area have high concentrations of polynuclear aromatic hydrocarbons (PNAs) and water samples from MW-3 have shown low levels of Naphthalene, Phenanthrene, and 2,4-Dimethylphenol . If ground water monitoring confirms contaminant levels threaten the beneficial uses of the ground water, the full scale mitigation system will need to be designed and/or operated to protect or restore these beneficial uses. This may increase the cleanup time and costs considerably. Additionally, the ground water monitoring plan claims that two of the proposed wells to be monitored on a long-term, semiannual basis, MW-2 and -15, are downgradient wells. Actually, MW-2 is an upgradient well and MW-15 is in the center of the oil plume. The plan should be modified to add MW-9 as a down- gradient well in the long-term monitoring. The proposal should be further revised to include ground water gradient measurements on a quarterly basis. As you have suggested, we will review the initial monitoring results when they become available and negotiate changes in the continuing analyses if need be. Our review and suggested modifications will be based, in part, on the need to assess the effectiveness of cleanup measures. We do believe that a round of samples should be collected as soon as possible and prior to beginning the initial remediation efforts.