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Section 13 <br />Geochemical Data and Analysis <br />concentrations may be a result of trace barite (BaSO4) within the samples rather than <br />40 sulfide minerals. <br />The effluent pH values from the MWMP analyses provide additional data to evaluate <br />the potential for the rock to be acid forming. These data range from 8.03 standard <br />units (su) to 8.26 su. These development rock and ore sample data indicate pH values <br />well above the pH criteria of 5.8 su set forth in HRMMR §1.1(2) and support that the <br />Van 4 Mine development rock is unlikely to generate acid rock drainage and is not <br />considered acid-forming material. <br />13.2.2 Assessment of Potential Toxic-Forming Rock <br />This section presents evaluation of the potential for development rock and ore to be <br />toxic-forming as defined by HRMMR §1.1(1). <br />This evaluation considers mining conditions related to drainage and exposure, and <br />examines: <br />¦ The potential for development rock and ore to contain detrimental amounts of <br />chemical constituents, which could lead to direct contact risks to humans as a <br />result of incidental ingestion or inhalation; and <br />¦ The potential for development rock and ore to form leachate that contains <br />detrimental amounts of chemical constituents. <br />• Potential for Direct Contact Risks <br />A number of inorganic constituents of development rock were measured from <br />samples collected from waste piles at the Van 4 Mine. Generally, concentrations <br />observed in these samples were higher than background concentrations measured in <br />surrounding soils, indicating that development rock does reflect the mineralization <br />that justified development of the mine. These concentrations were compared to <br />screening criteria developed by BLM for metals in soils in Risk Based Criteria for Metals <br />at BLM Mining Sites (BLM 2004). With the exception of arsenic, maximum <br />concentrations of 11 metals/ metalloids addressed by BLM were below risk <br />management criteria (RMCs) for direct contact with soils. Further evaluation of <br />arsenic, using site-specific exposure considerations and measured bioavailability of <br />arsenic in development rock, indicate that an appropriate site-specific RMC is greater <br />than maximum arsenic concentrations. <br />Additional evaluation of metals other than the 11 constituents for which BLM RMCs <br />are available was performed using conservative regional screening levels (RSLs) from <br />EPA. This evaluation did not identify any constituents in development rock at <br />concentrations exceeding their respective RSLs. Notably, concentrations of uranium <br />and vanadium, target metals for mining operations, were less than appropriate <br />screening criteria. <br />• Media besides soil are either not present within the affected areas of the Van 4 Mine <br />(sediment, surface water) or are not accessible (groundwater). Thus, RMCs based on <br />13-2 <br />7:\84988-Denison Mines\Task Order 4- EPP Sunday Mines Grouo-VarutWan4\FlNAL Report\FINAL -Environmental Protection Plan Van4.doc