SITE INFORMATION AND CORRESPONDENCE

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STATE OF CALIFORNIA GEORGE DEUKMEJIAN,Governor CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— CENTRAL VALLEY REGION 3443 ROUTIER ROAD SACRAMENTO,CA 95827-3098 29 August 1989 Ms. Diane Hinson, Registered Environmental Health Specialist Environmental Health Division San Joaquin County Department of Public Health Services P.O. Box 2009 Stockton CA 95201 HOLT BROTHERS TRACTOR COMPANY, 1521 WEST CHARTER WAY, STOCKTON, PROPOSED ADDITIONAL INVESTIGATION We have reviewed the "Site Investigation Report" (dated 31 January 1989) , and the "Soil Gas Survey" (dated 13 July 1989) , both prepared by Dames & Moore, and the "Overview of Comprehensive Site Characterization and Remediation" (dated 12 July 1989) , prepared by Bio National Corporation, for the Holt Brothers site. The first two documents present the findings from two phases of site investigation and include recommendations for additional investigation to better define the extent of soil and ground water contamination. The 12 July 1989 document presents a conceptual plan for in-situ bio-remediation of site contamination. The additional ground water investigation proposed will provide useful information to direct the next phase of investigation and aid in the evaluation of remediation system alternatives. However, the scope of the investigation is limited to one well in the known plume area, and one to two wells approximately 350 feet downgradient. Therefore, it is doubtful that the investigation will provide enough information on the nature and extent of contamination to design a comprehensive remediation system. This is particularly true for a bio-remediation system such as the one proposed. At this time we believe it is premature to consider any proposal for remediation of site contamination. The actual site remediation proposal must be based on adequate technical information. To design and implement an effective bio-remediation system it is essential that the site hydrogeology be thoroughly and accurately understood. The nature and extent of the contamination and the potential for the contaminants to be biodegraded should also be fully evaluated to determine whether the contamination is amenable to bio-remediation. In addition, we note that the four existing on-site wells have only been sampled one time. Additional rounds of sampling will provide a more valid statistical basis for evaluating the nature and extent of ground water contamination and remediation options. Mr. Todd of Bio National Corporation has expressed concern that the rainy season may begin before the proposed scope of work is approved. We share Mr. Todd's concern for the implications of the coming rainy season and, therefore, encourage you to approve the well