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Response to DRMS Comments <br />Environmental Protection Plan, <br />Denison Van 4 Mine <br />Uranium occurs in low concentrations in all soils and rocks. Average <br />global concentrations of uranium in rocks are shown below based on data <br />provided by Roe et al. (1979): <br /> <br />Class <br />Sub-class Average Uranium <br />Concentration <br />(mg/kg) <br />Igneous Ultramafic 0.03 <br />Igneous Mafic 0.53 <br />Igneous Granitic 3.9 <br />Sedimentary Limestone 2.2 <br />Sedimentary Sandstone 1.7 <br />Sedimentary Shale 3.7 <br />Soil 1 <br />Similarly, many other elements that could be considered toxic-forming <br />(e.g., arsenic, cadmium, lead) occur ubiquitously in rocks. Therefore the <br />mere presence of an elemental metal, which is a potential chemical <br />hazard, radiation hazard, or that has associated water quality standards is <br />not a reasonable basis to define toxic-forming. Otherwise, any rock at any <br />mine in Colorado could be defined as toxic forming. Therefore, it is <br />necessary to consider potentially toxic concentrations of the respective <br />elements in mine rock and not only the mere presence of these elements <br />to determine whether mine rock is potentially "toxic-forming". As <br />presented in the EPP, Denison `s proposed approach to evaluating <br />uranium in rock at the Van 4 Mine as "toxic-forming" is consistent with <br />standard human health and environmental risk assessment protocol <br />developed by regulatory agencies such as EPA, the Colorado Department <br />of Public Health and Environment (CDPHE), and BLM. Risk assessment <br />is the characterization of the potential adverse health effects of human <br />exposures to environmental hazards using a structured method <br />incorporating information on toxicity (i.e., potential adverse health effects <br />of chemicals) and exposure (i.e., contact of an organism with a chemical). <br />Denison selected the BLM risk management criteria (RMC)(BLM 2004) to <br />be appropriate criteria for the site based on future land use for the mines. <br />Although Denison does not agree with the determination of uranium as a <br />toxic forming material for the above mentioned reasons, Denison will <br />comply with all applicable rules and regulations, including DMO status. <br />Comment 2 Environmental Protection Facilities (EPFs). In Section 60 Denison states, <br />"...future EPFs are not planned to be constructed, because neither designated <br />DRMS RTC Van4 Mine EPP.doc