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• MEMORANDUM . CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 361-5600 Sacramento, CA 95827-3098 // ATSS Phone: 8-495-5600 TO: Antonia K. J. Vorster �, . ' FROM: Camilla Williams Senior WRC Engineer !!!!!! Engineering Geologist DATE: 16 December 1991 SIGNATURE: SUBJECT: REVIEW OF DRAFT WORK PLAN FOR WELL EVALUATION AND ABANDONMENT, DEFENSE DISTRIBUTION REGION WEST (DDRW), TRACY, SAN JOAQUIN COUNTY I have reviewed the Draft Work Plan for Well Evaluation and Abandonment prepared by Woodward-Clyde Consultants and submitted on 17 October 1991 for DDRW, Tracy (Tracy) . The Work Plan proposes sampling four of the supply wells at the site (Wells 1, 2, 4 and 7) and abandonment of two of the supply wells (Wells 1 and 2) and one off-site monitor well (LM-60) . Wells 1 and 2 had been previously abandoned, however the abandonment does not meet the minimum State Standards (which can be found in the Department of Water Resources (DWR) Bulletin 74-81 and the supplement 74-90. ) LM-60 has been proposed for abandonment because it was damaged by agricultural equipment. Overall , the Plan is well prepared and organized. As with previous reports, Woodward- Clyde has done an excellent job of summarizing the data in tables and figures. However, I am concerned that the some of the proposals are overdesigned and are not necessary to complete the task of abandonment and well evaluation. Specifically, I do not concur with the method proposed for abandonment of LM-60 and the analyses of the soils and ground water samples. In addition, the Work Plan did not provide enough information on the intervals to be perforated, job execution and slurry design. The proposals are insufficient to assure that the abandonment will prevent the vertical migration of contaminants. Due to the lack of this information in the planning stages, it appears that too much planning is being left for field decisions. The Work Plan should be resubmitted to address all of our concerns. My comments are listed below. Page 1-1 . Figure 1-1 presents the locations of the supply wells at the Tracy site. Figure 1-3 presents the locations on- and off-site of all of the monitoring wells. These maps need to be combined. In addition, a base map of well locations needs to be produced which depicts the locations of not just the monitoring and supply wells, but the injection and extraction wells for the ground water Interim Remedial Measure (IRM) . Page 2-1 . The Work Plan contains excellent summary tables and figures. We should encourage Woodward-Clyde to continue summarizing the data in these formats as our reviews are expedited. Page 2-2. Figure 2-1 presents the lithology logs for the two supply wells of concern. One of the supply wells (Well 1) extends through the Upper Tulare Formation and Corcoran Clay and into the Lower Tulare Formation. The major concern with the existing abandonment of Well 1 is that it is inadequate because the well may still serve as a potential conduit for contamination from the Upper Tulare to the Lower Tulare Formation. Therefore, it is important that the thicknesses of these regional features are noted on the Figure or in the text.