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0 Section 5 <br />Conclusions <br />The purpose of this investigation is to characterize the environmental geochemistry of <br />development rock at the Van 4 Mine. This investigation was completed to comply <br />with the Colorado Mined Lands Reclamation Act and associated rules by assessing <br />the potential for designated chemicals and acid- or toxic-forming materials to be <br />present at the mine site. Based on the information provided previously in this report, <br />the data collected during this investigation indicate the following: <br />• Designated chemicals: Designated chemicals are not present at the Van 4 Mine. By <br />definition, designated chemicals are chemicals used in extractive metallurgical <br />processing. Extractive metallurgical processing is not completed at the Van 4 <br />Mine. The ore produced at the mine will be shipped to the Denison mill near <br />Blanding, Utah, for extractive metallurgical processing. <br />• Acid-forming materials: ABA, field observations, and MWMP laboratory data <br />indicate that Van 4 Mine development rock is unlikely to generate acid rock <br />drainage and is not considered acid-forming material as defined in HRMMR <br />§1.1(2). <br />¦ Toxic-forming materials: The potential for stockpiled development rock to be <br />classified as toxic-forming was evaluated by considering two pathways for <br />potential toxic effects: direct contact risks and potential development of toxic <br />leachate. <br />Direct contact: Preliminary screening of direct contact risks based on comparison of <br />total metals concentrations to toxicity screening levels provided by BLM and EPA <br />indicate that most metals, including uranium and vanadium, do not exceed the <br />screening criteria and therefore do not present direct contact risks. However, the <br />preliminary screening indicated that further investigations should be conducted on <br />arsenic to determine if potential direct contact risks are likely. Further evaluation of <br />potential direct contact risks related to arsenic were conducted including electron <br />microprobe analysis of the mineralogical forms of arsenic present at the site, <br />calculation of site-specific screening levels, and testing of the bioavailability of arsenic <br />in stockpiled development rock. This assessment indicates that available data for <br />development rock present at the Van 4 Mine does not suggest significant toxic- <br />forming potential. No restrictions to the currently assumed land use appear necessary <br />for protection of human health for future workers or visitors to the site. <br /> <br />5-1 <br />TA64966.Denison Mines\Ta