C150094 Long Hollow Dam Phase I Summary

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Long Hollow Dam and Reservoir Phase I Summary Report • According to findings of a San Juan River flow model, which was run by the USBR and simulated the LHR project depletions, the SJRIP primary and secondary flow recommendations will not be impacted from the LHR project. 6.6 Indian Trust Assets The evaluation of the effect of the project on Indian Trust Assets is ongoing, in cooperation with USACE pursuant to appropriate consultations with Native American tribes and nations. 6.7 Findings of Regulatory and Institutional Investigations Based on the work completed, there does not appear to be any fatal flaw for LHR pertaining to institutional, cultural, and resource issues. , ___.__._____.____-----.------__, The process for the issuance of a Section 404 Permit for LHR will include an EA and an ESA Section 7 Consultation with the USF&WS, as well as acceptable mitigation plans for impacts to waters of the U.S. and impacts to two prehistoric archaeological sites. If USACE judges the project to potentially have significant environmental impacts, an Environmental Impact Statement (EIS) may be needed. 7.0 WATER QUALITY Potential impacts to water quality in the La Plata River basin from the LHR project were evaluated by WWE through review of Appendix B-Water Quality to the Final Supplement to the Final Environmental Impact Statement Animas La Plata Project (U.S. Department of the Interior and USBR, April 1996). Appendix B showed that water quality standards for mercury, -,--,__, selenium, silver -sic and man:anese currentl are exceeded at various locations in the La P(Jata River, and that the number of exceedences generally increase in a downstream direction. Appendix B reported that metals from historic mining in the upper La Plata River watershed and irrigation return flows in the lower watershed are the causes of the exceedences. Importantly, the data collected for Appendix B are for total metals, while the stream standards are for dissolved metals. This means that the Appendix B analysis is conservative, and that the La Plata River 991-077.115 Wright Water Engineers, Inc. Page 16 July 2004