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Section 13 <br />Geochemical Data and Analysis <br />ore samples. The MWMP analysis provides data that can be used for a screening- <br />level evaluation to assess if the rock piles have the potential to generate leachate <br />containing metals concentrations such that the rock could be considered a toxic- <br />forming material; and <br />¦ The volume of percolation through the rock piles. Percolation was estimated using <br />two methods: 1) a water-balance approach that considers precipitation, <br />evaporation, and available water holding capacity; and 2) computer modeling <br />using a software program called UNSAT-H, which provides a more rigorous <br />evaluation through simulation of the processes of precipitation, infiltration, <br />evaporation and percolation. Estimation of the volume of percolation through the <br />rock piles addresses uncertainties associated with the rock to soil ratio used in the <br />MWMP tests as compared to actual field conditions; and <br />A comparison of MWMP leachate data to the Colorado groundwater standards <br />indicates that a number of constituents were detected at concentrations that are <br />greater than the Colorado groundwater standards. Below is a list of constituents <br />detected in MWMP leachate that were detected at concentrations greater than the <br />screening criteria for each of the development rock samples: <br />¦ DM-V4WR-1: arsenic, molybdenum, selenium, sulfate, uranium, vanadium. <br />¦ DM-V4WR-2: antimony, arsenic, molybdenum, selenium, sulfate, uranium, <br />• vanadium. <br />¦ DM-V4WR-3: arsenic, molybdenum, selenium, sulfate, uranium, vanadium. <br />It should be noted that groundwater in the vicinity of the Van 4 Mine is not classified <br />with respect to designated uses (CDPHE Regulation 42); and therefore, the human <br />health, drinking water and agricultural criteria are not formal standards for <br />groundwater at the Van 4 Mine. In addition, current groundwater uses in the vicinity <br />of the mine do not include Human Health, Drinking Water and Agricultural uses. <br />Additional information regarding current and future uses of groundwater in the area <br />is included in Hydrogeologic Evaluation of the Van 4 Mine, Montrose County, Colorado <br />(CDM 2009b), which is included in this document as Attachment H and also in <br />Section 8.1 - Existing and Potential Future Groundwater Uses. <br />The MWMP test is a screening tool, and other factors must be considered to fully <br />evaluate the potential for development rock to produce leachate. These additional <br />evaluations are presented in the following paragraphs. Although groundwater <br />standards are used to assist in the screening process, there are no regulatory <br />standards that apply to MWMP test results. <br />To further evaluate if the development rock should be considered as a toxic-forming <br />material, this section evaluates the potential for the rock piles to generate leachate in <br />• significant volumes. This is a factor of the climate of the area and the physical <br />characteristics of the piles. Two methods were used in this analysis: <br />13-4 <br />7:184986-Denison Mines\Task Order 4 - EPP Sunday Mines Group-Van41Van4TlNAL ReportTINAL - Environmental Protection Plan Van4.doc