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Section 4 <br />Pofenfia/forRock fo be Toxic Forming <br />• is naturally enriched in metals and metalloids. This natural enrichment is spatially <br />and genetically associated with the uranium and vanadium mineralization at the <br />mines. <br />4.1.5 Summary of Findings <br />A number of inorganic constituents of development rock were measured from <br />samples collected from the development rock area at the Van 4 Mine. Generally, <br />concentrations observed in these samples were higher than background <br />concentrations measured in surrounding soils, indicating that development rock does <br />reflect the mineralization that justified development of the mine. With the exception <br />of arsenic, maximum concentrations of 11 metals/ metalloids addressed by BLM were <br />RMCs for direct contact with soils. Further evaluation of arsenic, using site-specific <br />exposure considerations and measured bioavailability of arsenic in development rock, <br />indicate that an appropriate site-specific RMC is greater than maximum arsenic <br />concentrations. <br />Additional evaluation of metals other than the 11 constituents for which BLM RMCs <br />are available was performed using conservative RSLs from EPA. This evaluation did <br />not identify any constituents in development rock at concentrations exceeding their <br />respective RSLs. Notably, concentrations of uranium and vanadium, target metals for <br />mining operations, were less than appropriate screening criteria. <br />• Media besides soil are either not present at the site (sediment, surface water) or are <br />not accessible (groundwater). Thus, RMCs based on direct contact with soils are <br />appropriate for evaluating possible toxic-forming materials. In addition, the most <br />restrictive (e.g., lowest) RMC for arsenic is based on a worker that might visit the site <br />to perform such activities as control of invasive species and abatement of fire hazards. <br />If this worker is protected, other visitors to the site - campers, ATV riders, surveyors - <br />will also be protected. Based on the BLM land management plan for this area, future <br />land use for the site is assumed to be mineral development and reclamation, and thus <br />future residents were not evaluated. Based on the above results, the following <br />conclusions are justified: <br />¦ A worker scenario is the most restrictive of applicable exposure scenarios for the <br />Sunday Mines Group, and conclusions concerning toxic-forming potential are <br />appropriately based on this receptor <br />¦ Groundwater at the site is present only at a depth that precludes contact for visitors <br />to the site, including campers, ATV riders, surveyors and workers. Thus, RMCs <br />based on direct contact with soil are appropriate for evaluating toxic-forming <br />potential <br />¦ Metals concentrations in development rock are higher than regional background <br />and screening against health-protective criteria is appropriate for evaluation of <br />toxic-forming potential <br />0 <br />4-7