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<br />Comment 22. State desired uses and applicable water quality standards for the proposed lined <br />water storage reservoir. <br />• Anticipated uses for the proposed reservoir water might include but are not limited to <br />domestic or agricultural use or evaporative loss augmentation for other facilities owned <br />by the applicant. Applicable domestic use standards are presented in Attachment M. <br />Colorado Standards and Methodologies for Surface Water do not contain agricultural use <br />standards for the organic constituents listed in the DMG comment. It should be noted <br />that water impounded in the lined structure will not be in hydrologic connection with the <br />ground water system in the area of the project site. <br />Comment 23. What is the presence andlor potential for soil and ground water contamination at <br />the proposed Tanabe site, including water stored in the proposed lined reservoir and wetland <br />area. <br />• The presence of known ground water contamination within or near the site is illustrated <br />in Attachment K and Attachment L as part of the response to Comment 20. Literature <br />associated with RMA remedial activities suggests that soils near the proposed site are not <br />a risk [o human health or the environment from contamination originating from the RMA. <br />Soil or alluvial ground water contamination of the proposed site during or after mining <br />and reclamation activities is not likely. The identified areas of contamination and <br />delineated contaminant plumes have been steadily decreasing since remedial activities at <br />RMA were initiated in the 1970's. Additionally, identified pathways of contaminant <br />migration do not generally cross the proposed Tanabe site. With the decreasing area of <br />contamination, the concentration of constituents is also steadily decreasing. The <br />boundary containment systems constructed at the north and northwest boundaries of the <br />RMA prevent off-site migration of additional contaminants. Concentrations of <br />constituents in alluvial ground water that remain near or upgradient of the proposed site <br />continue to decrease due to degradation, dilution, discharge to surface waters, and <br />volatilization. <br />It should be noted that the Addendum to the Phase I Environmental Site Assessment <br />(Attachment I), developed by ERO Resources for the Tanabe site, May 23, 2000, presents <br />additional response to this comment. This document concludes that the DIMP and other <br />COCs are unlikely to pose significant environmental concerns. <br />To evaluate potential contamination at the proposed Tanabe site during mining and <br />reclamation activities, the maximum area of influence from pit dewatering was estimated. <br />The estimated maximum area of influence (dewatering drawdown) is illustrated in <br />Attachment N and extends approximately 750 feet from the proposed pit boundary (see <br />Attachment P for details). Using the 1999 constituent concentrations presented in <br />Attachment L for Comment 20, the mass of each constituent potentially drawn into pit ,~1`` <br />dewatering flows was estimated. As seen in Attachment N, the DIMP plumes make up ~•~'~~;'`'> <br />approximately 20 percent of the drawdown area. It was assumed that 9 percent of the 9q~ <br />~water~ne ~w contained non-DiMp constituent concentations, The mass of each <br />constituent was then combined with the estimated total flow of water drawn into the pit <br />i <br />Page 8 I <br />