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Section 2 <br />Potential for Adverse Impacts <br />2.2.1 Designated Chemicals <br />• As defined in the HRMMR §1.1(13): <br />"Designated Chemicals" are toxic or acidic chemicals used within the permit <br />area in extractive metallurgical processing, the use of zvhich, at certain <br />concentrations, represents a potential threat to human health, property, or the <br />environment. <br />By definition, designated chemicals are chemicals used in extractive metallurgical <br />processing and this type of processing is not conducted at the Van 4 Mine. Therefore, <br />no designated chemicals are present on site. <br />2.2.2 Acid and Toxic Producing Materials <br />As defined in the HRMMR § 1.1 (1): <br />"Acid and Toxic Producing Materials" means natural or rezvorked earth <br />materials having acid or toxic chemical and physical characteristics that, <br />under mining or post-mining conditions of drainage, exposure, or other <br />processes, produce materials zvhich contain detrimental amounts of chemical <br />constituents such as acids, bases, or metallic compounds." <br />Detailed evaluation of acid base accounting (ABA) data, field observations, and <br />meteoric water mobility procedure (MWMP) data indicate that the development rock <br />are extremely unlikely to generate acid rock drainage and are not considered acid- <br />forming material. <br />The potential for stockpiled development rock to be classified as toxic-forming was <br />evaluated by considering two pathways for potential toxic effects: <br />¦ Direct contact risks; and <br />¦ Development of toxic leachate. <br />Preliminary screening of direct contact risks based on comparison of total metals <br />concentrations to toxicity screening levels provided by U.S. Bureau of Land <br />Management (BLM) and EPA indicate that most metals, including uranium and <br />vanadium, do not exceed the screening criteria, and therefore do not present direct <br />contact risks. Additional evaluation of potential direct contact risks related to arsenic <br />was conducted to evaluate the bioavailability of arsenic in development rock. This <br />assessment included specific in-vitro assays, electron microbe analyses, and detailed <br />evaluation of potential direct contact risks. This work concludes that available data for <br />development rock present at the Van 4 Mine does not suggest significant toxic- <br />forming potential. <br />The potential for the development rock to generate toxic leachate was evaluated using <br />MWMP testing and evaluation of the volume of percolation that would be expected <br />2-2 <br />TA64986-Denison Mines\Task Order 4 - EPP Sunday Mines Group-Van41Van4TlNAL Report%FINAL - Environmental Protection Plan Van4.doc