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CDOW Rebuttal Statement - Regulation 37 December 2010 Reg. 37 Rule-Making Hearing Generally, a complete evaluation of an ambient-based approach would be facilitated by an evaluation of the water-quality data, including calculation of ambient-based numeric standards. In its PHS, CAM did not provide water-quality data in an electronic format amenable to this task, and the WQCD has requested that these data be provided in a suitable electronic format (WQCD RPHS, page 5). However, it is notable that CAM Site UNC-06 (3 sampling dates) appears to be the only site with water-quality data available within the WQCD's proposed Segment 13e. This may limit the data available for the calculation of ambient quality-based standards, but the location of the site in close proximity to proposed mining activities is particularly relevant in terms of documenting existing conditions. While the CDOW supports the WQCD's ambient quality-based approach, if data limitations preclude such an approach at this time, the CDOW recommends that any new Segment 13e retain the water-quality standards presently assigned to existing Segment 13a. Based on the testimony supplied by all parties to-date, there appears to be general agreement that any proposed Segment 13e should retain the Warm 2 Aquatic Life Use Classification currently applied to Segment 13a. Additionally, the WQCD has presented evidence to support that a new Segment 13e also should retain the Recreation P Use Classification currently applied to Segment 13a (WQCD RPHS page 6), and the WQCD has provided information suggesting that irrigation uses exist in the area (WQCD RPHS, pages 6-7; Table 3, page 8; Figures 3 & 4, page 10). This information suggests that a new Segment 13e should have the same classified uses as existing Segment 13a, and this is reflected in the WQCD's alternative proposal (See Table 1 above). If a limited water- quality dataset precludes an ambient quality-based approach to inorganics and metals standards, the CDOW believes it would be appropriate that any standards applied to proposed Segment 13e would be similar to, rather than substantially different from, those presently applied to Segment 13a. Conclusions The CDOW remains concerned about several aspects of CAM's original proposal and would be opposed to adoption of the proposal without submittal of additional evidence to -support that the substantially relaxed standards proposed by CAM for Segment 43e are--- adequate to protect the proposed segment's aquatic life. However, the CDOW can support the WQCD's alternative approach. The WQCD's alternative proposal is suitably scaled to cover only the more rigorously-surveyed streams from CAM's proposal, it appropriately retains near-perennial streams in Segment 13a, and it approaches standards for dissolved oxygen and pH in a manner consistent with other similarly classified segments in Colorado. The CDOW also expects that an ambient quality-based approach to inorganics and metals would adequately protect existing conditions and the macroinvertebrate community expected to occur in the WQCD's proposed Segment 13e. Should water-quality data prove to be insufficient to support such an approach at this time, the CDOW recommends that the water-quality standards for inorganics and metals be set to those presently assigned to existing Segment 13a. December 1, 2010