SITE INFORMATION AND CORRESPONDENCE

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Ms. Nancy Bishop - 2 - 21 September 2001 In order to identify if undesireable byproducts are threatening water quality, the compliance point shall be downgradient monitoring well MW-5. WFS must be prepared to implement a contingency plan if the general mineral constituents in the compliance well exceed the average of each of these constituents obtained from the four baseline sample points. Although a corrective action plan cannot be developed for an unknown event, WFS should provide a contingency outline of several remedial strategies that could be modified or developed into corrective action plans if the compliance well shows water quality degradation due to the pilot test. The contingency plan could entail extracting the remaining HRC and undesireable byproducts, or exerting hydraulic containment, or oxygenating the area of HRC influence, or other strategies. Conditional Approval Of Work Plan The Work Plan is approved subject to the following conditions: • The general mineral analyses shall include pH (field and laboratory) and soluble metals, including arsenic, chromium, copper, mercury, nickel and zinc. • Prior to implementing the pilot test, WFS shall provide an outline of possible contingency plans that can be developed into specific corrective action plans if water quality in MW-5 exceeds the threshold described below. • If compliance well MW-5 contains concentrations of any of the general mineral analytes in concentrations exceeding the 90% upper confidence limit of the statistical average of the corresponding baseline constituent concentrations, then WFS must notify Board staff within one week of receiving the analytical results and submit a corrective action plan within 60 days of receiving the analytical results. Board staff will revise the Monitoring and Reporting Program to incorporate the pilot test monitoring schedule. As discussed in our 18 September approval letter, WFS will provide the initial HRC report and baseline sampling results in the Annual Monitoring Report which is due 30 January 2002. Subsequent annual reports shall include evaluations of the effectiveness of the pilot. Insitu remediation of groundwater using a carbon amendment such as HRC is a promising technology for this site that is too constrained to implement many of the traditional remedial treatments. We look forward to wor ing with you to develop insitu remediation into a more familiar technology. If you have any Cniestions ou may contact me at (916) 255-3080. AMY T A Private Sites Cleanup Unit cc: Ms. Carol Oz, San Joaquin County Environmental Health Department, Stockton Mr. Fred Strauss, Western Farm Service, Vernalis Mr. Frank R. Fossati, Shell Oil Company, Lake Forest Ms. Carolyn Kneiblher, GeoSyntec Consultants, Walnut Creek