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Rimrock Exploration & Development, Inc. <br />J-Bird Uranium Mine/ DMO/ EPP Geochemical Data and Analysis <br />and creation of lesser (yet potentially more toxic) daughter products. As a radionuclide; <br />uranium toxicity is attributable to two characteristics of the element a) its concentration, <br />and b) the energy associated with it. Low concentrations of natural elements are typically <br />non-toxic and at times, can be essential (as in the case of copper, zinc, and others). <br />Higher concentrations create toxic effects since they exceed a receptor's capacity to <br />detoxify the element. Radionuclides are a unique class of elements in that their `energy' <br />can also be considered a toxic component. Organisms can deal with a certain amount of <br />ubiquitous energy (i.e. UV radiation); however, there comes a point beyond which <br />organisms are able to handle overt amounts of energy. Thus, uranium and its toxicity <br />need to be reviewed in two contexts; a) concentration, and b) energy. These same two <br />characteristics also dictate uranium's mobility in the environment. There is an <br />underlying concern that surface deposition sources of uranium (such as waste rock or ore <br />piles) can act as sources of uranium to underlying groundwater resources, or off-site <br />surface water resources if the uranium were able to solubilize and mobilize from the <br />source. The following analyzes the available sample analysis (Attachment A and B) to <br />put into context' the potential toxicity and mobility of uranium as related to the Mine's <br />surface deposition materials. <br />Hazardous materials/elements are defined as such because they meet one or more of the <br />following characteristics; ignitability, corrosivity, reactivity or toxicity. Natural elements <br />such as uranium have only the potential to be `toxic' under the hazardous definition; and <br />only achieve a toxic state when there is sufficient concentration or energy to cause an <br />adverse effect to human health or the environment. The toxicity of a substance can be <br />evaluated through the use of available literature-derived information. Radionuclides have <br />been well studied and are fairly well understood in terms of their toxicity (to human <br />health and the environment) as well as fate and transport in the environment. The <br />following regulatory-derived sources are used as references in assessing toxicity and <br />mobility potential of constituents detected in surface deposition materials. The <br />Environmental Protection Agency (EPA) regulates soil containing low level hazardous <br />waste if certain potentially hazardous elements occur above levels considered toxic. The <br />EPA bases their `hazardous' definition of solids upon the results of toxicity characteristic <br />leaching procedure (TCLP) analysis results. TCLP is an analysis method similar to <br />SPLP; yet more rigorous in its ability to extract certain elements. The EPA has published <br />TCLP threshold limits that help define whether a soil contains `hazardous elements'. <br />These thresholds are provided within Attachment C for comparative purposes to the <br />SPLP results. Given the differing methods between TCLP and SPLP; there is a <br />significant amount of uncertainty involved with the interpretation of results. The CDPHE <br />23