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Response to DRMS Comments <br />Environmental Protection Plan, <br />Denison Sunday Mines Group <br />via Colorado House Bill (HB) 1161 as signed into law by the governor on <br />May 20, 2008. <br />Many elements that could be considered toxic-forming (e.g., arsenic, <br />cadmium, lead) occur ubiquitously in rocks. Therefore the mere presence <br />of an elemental metal, which is a potential chemical hazard, radiation <br />hazard, or that has associated water quality standards is not a reasonable <br />basis to define toxic-forming. Otherwise, any rock at any mine in <br />Colorado could be defined as toxic forming. Therefore, it is necessary to <br />consider potentially toxic concentrations of the respective elements in <br />mine rock and not only the mere presence of these elements to determine <br />whether mine rock is potentially "toxic-forming". Uranium occurs in low <br />concentrations in all soils and rocks. Average global concentrations of <br />uranium in rocks are shown below based on data provided by Roe et al. <br />(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 />As presented in the EPP, Denison 's proposed approach to evaluating <br />uranium in rock at the Sunday Mines Group as "toxic-forming" is <br />consistent with standard human health and environmental risk <br />assessment protocol developed by regulatory agencies such as EPA, the <br />Colorado Department of Public Health and Environment (CDPHE), and <br />BLM. Risk assessment is the characterization of the potential adverse <br />health effects of human exposures to environmental hazards using a <br />structured method incorporating information on toxicity (i.e., potential <br />adverse health effects of chemicals) and exposure (i.e., contact of an <br />organism with a chemical). Denison selected the BLM risk management <br />criteria (RMC)(BLM 2004) to be appropriate criteria for the site based on <br />future land use for the mines. <br />Final RTC Sunday Mines EPP.doc