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0 Section 4 <br />Assessment of Potential Toxic-Forming Rock <br />The section presents an assessment of the potential for development rock at the Van 4 <br />mine to be acid- forming as defined by the HRMMR. Specifically, HRMMR §1.1(1) <br />provides the following definition of acid and toxic producing materials: <br />"Acid and toxic producing materials" means natural or reworked earth materials <br />having acid or toxic chemical and physical characteristics that, under mining or post- <br />mining conditions of drainage, exposure, or other processes, produce materials which <br />contain detrimental amounts of chemical constituents such as acids, bases, or metallic <br />compounds. <br />This section presents an evaluation of the potential for development rock and ore to <br />be toxic-forming as defined by HRMMR §1.1(1). Specifically, this evaluation considers <br />mining conditions related to drainage and exposure, and examines: <br />¦ The potential for development rock and ore to contain metals with concentrations <br />that could be of concern to human health and the environment via direct contact; <br />and <br />¦ The potential for development rock and ore to form leachate that contains <br />concentrations that could be of concern regarding impacts to human health or the <br />• environment. <br />4.1 Potential for Direct Contact Risks <br />As described previously, the Van 4 Mine is located on federal lands managed by BLM. <br />This screening-level evaluation is based on comparison of the total metals <br />concentrations detected in development rock and ore with appropriate screening <br />criteria developed by U.S. Bureau of Land Management (BLM) for metals in soils in <br />the guidance document titled, Risk Based Criteria for Metals at BLM Mining Sites (BLM <br />2004). This BLM document provides risk management criteria (RMC) for human <br />exposure to soils for various land uses on BLM property including residents, campers, <br />all terrain vehicle (ATV) drivers, workers, and surveyors. In addition, BLM has <br />developed RMCs for wildlife and livestock for ecological risk management on BLM <br />property. The BLM RMC values support land management of former mine sites and <br />are used as a benchmark concentration to which environmental concentrations may <br />be compared, assisting land managers in protecting humans and wildlife on BLM <br />lands. In particular, BLM RMC values were developed such that "people will not <br />experience adverse health effects from metal contamination on BLM lands during <br />their lifetimes if exposure is limited to soil... with concentrations at or less than the <br />RMC" (BLM 2004, p. 3). <br />BLM RMCs have not been identified for several site-specific metals of interest at the <br />Van 4 Mine including uranium. In order to assess the potential toxicity of the <br />following metals in development rock and ore, EPA Regional Screening Levels (RSL; <br />0 am <br />4-1 <br />TA64986-Denison Mines\Te