2010-03-11_PERMIT FILE - M2008012

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Memorandum 2 10 March 2010 112d Conversion Review Nuvemco LLC Last Chance Mine Depending on the ultimate depth and length of mine workings, formation of a mine pool should be added as a potential disturbance to the prevailing hydrologic balance. Exhibit T: Part 7. Facilities Evaluation "...should significant water accumulate in the retention pond, it will be collected and analyzed." DRMS response: Please describe what is meant by "significant water." Exhibit T• Part 8, Ground water information Applicant states "....on this mesa with many mine workings perched several hundred feet above the Paradox Valley and cut by numerous steep canyons, the potential aquifers are dry." Later, wells are described that "....apparently tap the groundwater aquifer within the Upper Triassic-age Chinle formation, which is considerably below the mining zone of the proposed project and separated from it by the Summerville formation confining unit." DRMS response: It seems possible that the "many mine workings" could serve as a mode of conveyance for the groundwater that would normally occupy the aquifers now dry. Thus, the likely location of any potential adverse ground water impacts may be the Upper Triassic Chinle formation aquifer. Applicant should describe the measures to be taken to monitor and protect the Upper Triassic Chinle formation aquifer. Appendix B, Ore and Waste Sample Analyses Analytical methods must use detection limits that are at or below the state water quality regulatory criteria. For the SPLP results, the data for arsenic, lead, selenium, and uranium are of no use because the detection limits are above the relevant regulatory criteria. The samples must be run again and the analyses must have adequate detection limits. Applicant must provide sufficiently detailed location maps that reference the sample number to a location on the ground that would allow DRMS staff to find where the sample was collected. Applicant must also provide photo-documentation of the locations on the ground where SPLP rock samples were collected, plus photographs of the samples themselves. Since the project has been elevated to the status of a Designated Mining Operation, the analytical suite for SPLP leachate and monitoring wells samples must incorporate all relevant regulated parameters for ground water, which includes the following: All parameters listed on Table 1 through 4 in State of Colorado Water Quality Control Commission Regulation 41 - Basic Standards for Ground Water. The following may be omitted: Total Coliforms, Asbestos, Free Cyanide, Chlorophenol, Color, Corrosivity, Foaming Agents, Odor, and Phenol. The applicant must also include Radium 226 and Radium 228 from the Radioactive Materials Standards. Regulation 41 is available at: http•//www cdphe state co us/regulations/wgccre s/100241wgccbasiestandardsforgroundwater.pdf