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Resonse to DRMS COmmenlS <br />Enuironmenfa/Pr016dion P/an, <br />Denison Van 4Mine <br />provided to Denison prior to installation of the PVC liner panel. The ore <br />storage pad specifications are attached and provide additional QA/QC <br />requirements. <br />Comment 6 ,411achmenlfl. Comment 1. <br />Denison: In the context of questioning whether uranium should be regarded as a <br />toxic forming material due to its presence at low concentrations, the Applicant <br />states "Denison selected the BLM risk management criteria (RMC)(BLM 2004) <br />to be appropriate criteria for the site based on future land use for the mines. " <br />DRMS response: The BLMpublication "Risk Management Criteria for Metals at <br />BLMMining Sites, Technical Note 390 rev., October 2004, " contains no <br />reference information for uranium. If this is the same document to which the <br />Applicant refers, please elaborate on how the information in this document was <br />extrapolated to risk management of uranium at the Denison sites. <br />Response BLM did not develop RMCs for several metals detected at the Van 4 Mine <br />including uranium. In order to assess the potential toxicity of these metals <br />in development rock and ore, EPA Regional Screening Levels (RSLs) for <br />commercial/ industrial exposure scenario were utilized for the following <br />metals: aluminum, tin, titanium, uranium, and vanadium. This <br />assessment approach is described in Appendix A of the EPP, Section 4.1.3 <br />of the report Evaluation of the Environmental Geochemistnj of the Van 4 Mine. <br />As described in this report, maximum concentrations of these metals did <br />not exceed their respective RSLs, indicating that concentrations of these <br />metals in development rock and ore are not a human health risk via <br />direct contact. <br />Comment 7 4ddendum to the ffydl-olozic Epaltialion. <br />Please provide a figure depicting the 3-dimensional nodal discretization of the <br />UNSAT-H model. <br />Response Agreed. This figure is included in the revised attached calculation brief <br />for the UNSAT-H simulations. <br />References <br />Colorado Lining 2010, www.coloradolining.com <br />Final Van 4 RTC v2 Letter.doc