SITE INFORMATION AND CORRESPONDENCE

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Tracie Billington, P. E. August 14, 1992 Page Three b. The presence of other contaminants in the ground water is not well defined. Both metals and pesticides have been discussed as potential contaminants of concern. Neither suite of contaminants has been evaluated sufficiently to determine if they pose an environmental risk. C. The leading edge of the VOC plume continues to migrate uncontrolled. If control is not achieved in an expedited fashion, the difficulty and cost of any remedial action may increase exponentially. This is due to the necessity of acquiring multiple lease agreements for additional monitoring and/or extraction wells. Based on these facts, the Department supports the establishment of OU # 1 for VOCs only at this time. Other potential contaminants should be evaluated as part of the continuing site wide RI/FS or developed as a separate operable unit. 2) The Department is concerned that there may be some confusion between aquifer cleanup goals and treatment (effluent) standards for the chosen treatment technology. Clear definitions separating the two terms were not evident in the FS. Aquifer cleanup goals are levels to which the aquifer will be remediated (i.e. maximum or proposed contaminant levels or other regulatory requirements) . Residual contamination will be allowed to remain in the ground water. Treatment standards govern what levels constituents in the effluent must meet prior to being discharged. Levels may be different for various types of disposal. The Department wishes DDRW Tracy to be clear when distinguishing between each set of standards. 3) Heavy metals comprise the predominant set of chemicals not clearly addressed in the OU # 1. The Department recommends that the FS clarify that metals will carried by other RI/FS activities at DDRW Tracy. Potential goals for the metals investigation are: a. Evaluation of the validity of highly turbid samples.