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Mr. J. David Holm Water Quality Control Division Page 7 resources and we would expect that the permit would include a requirement to provide the WQCD with the monitoring results concurrent wish their monthly submittal to DMG. These permit terms would remain in place throughout the term of the CDPS permit. The result is that the permit teens would eliminate the West Pit as a source of any potential contamination of the Rito Seco and the associated alluvial aquifer, and would include a comprehensive monitoring plan to assure that the BMP is effectively protecting the surface water resources. Thus, the proposal is fully consistent with your regulations and would assure a comprehensive solution to the water quality issues in a manner that would be consistent with the requirements of both DMG and WQCD. Comments Regardine Construction of a °~Slurrv Wall" A number of commenters continue to demand the construction of some form of "slurry wall" between the West Pit and the Rito Seco to protect water quality, alleging that the terms of the DMG permit require such a structure. This contention is erroneous. The original DMG permit referenced the potential for construction of a slurry wall in the event that the hydrologic conditions encountered during mining resulted in an increased potential for geotechnical stability concerns in the pit wall which could not be fully addressed by a buttress structure. See discussion of buttress and slurry wall concepts by MLRD specialist Mr. Renner at the permit hearing, Mazch 22, 1989 (Attachment B). See transc~t at pn. 11-14. Thus, the slurry wall was never considered originally as a potential solution to water quality concerns. Ironically, the response to this proposal from project opponents at that time, was that such a solution was not adequate and the pit should be back filled up to the level of the stream. See transcript at ua. 32-33. Technical Revision No.18 to the DMG permit approved backfilling the pit to the crest of the pit wall in question and eliminated the slurry wall requirement from the DMG Permit once backfilling was complete. TR-18, cage D_3• Nevertheless, in response to comments from CCCD on TR-26, BMG conducted conceptual engineering on a potential slurry wall and provided the resulting designs to DMG for review (Draft Hydraulic Barrier Design Report, BMRI to DMG, November 5, 1999). DMG explicitly rejected the slurry wall