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W.T. Nickerson July 14, 1997 Page 5 "5.6.3 Vaporization The document states that 1,2-DCP "will continue to vaporize from groundwater until it can no longer be detected." Given the physical conditions at this site, how long will it take for 1,2-DCP to vaporize from groundwater until it can no longer be detected?" This statement is predicated on the assumption that all provenance of 1,2-DCP to ground water has ceased. At this time we have insufficient data to predict how long complete volatilization might take in the absence of any new 1,2-DCP being introduced from soil. Studies can be conducted which will provide information on average ambient subsurface conditions affecting volatilization. These data will also be useful in the consideration of natural attenuation by other processes, such as chemical adsorption, diffusion, dilution, and biodegradation. "6.0 Evaluation of Groundwater Alternatives The report is not a true feasibility study for groundwater cleanup. The Basin Plan states that the discharger is to submit a"feasibility study of cleanup alternatives which compare effectiveness, cost, and time to achieve cleanup levels." The report contains only a qualitative discussion of the effectiveness of various cleanup alternatives. In this section of the report, cost is used as a rationale for discarding various alternatives. However, the Basin Plan states that "economic feasibility does not refer to the subjective measurement of the ability of the discharger to pay the costs of cleanup, but rather to the objective balancing of the incremental benefit of attaining more stringent levels of constituents of concern as compared with the incremental cost of achieving those levels." The report does not consider economics in this manner. The report also states that "there is no practical method" for removing 1,2-DCP from the groundwater. However,the report does not contain enough quantitative detail to determine whether this is a true statement. The Basin Plan requires that technologic feasibility be determined by"assessing the availability of technologies which have been shown to be effective in reducing the concentrations of the constituents of concern to the established cleanup levels. Bench-scale and/or pilot-scale studies may be necessary to make this feasibility assessment in the context of constituent, hydrologic, and other site-specific factors." The Board's policy is noted. Production of this report has resulted in the Board's comprehensive review of previous investigations at this site, and has prompted these review comments, which provide a regulatory objective and scope in addressing environmental concerns with respect to groundwater at the site. "6.1. 6.2. 6.3 Pum iinng/Hydraulic Containment Aquifer tests have not been conducted at this site. Therefore, the discussion of these three alternatives is subjective. Before these alternatives can be discarded,the discharger needs to provide more data regarding the pumping characteristics of the aquifer."