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Section 4 <br />Potential for Rock to be Toxic-Forming <br />In general, detected concentrations of metals in development rock and ore are greater than <br />respective background soil concentrations. This observation is consistent with the difference in <br />nature of the materials. Specifically, samples of background soils were collected on the ridge <br />south of the Sunday Mines Group in areas where the rock is not mineralized. Development rock <br />and ore samples were collected from rock removed from the mines, which is naturally enriched <br />in metals and metalloids. This natural enrichment is spatially and genetically associated with <br />the uranium and vanadium mineralization at the mines. <br />4.1.5 Summary of Findings <br />A number of inorganic constituents of development rock were measured from several samples <br />collected from waste piles at the Sunday Mines Group. Generally, concentrations observed in <br />these samples were higher than background concentrations measured in surround soils, <br />indicating that development rock does reflect the mineralization that justified development of <br />the mine. With the exception of arsenic, maximum concentrations of 11 metals/metalloids <br />addressed by BLM were below risk management criteria (RMCs) for direct contact with soils. <br />Further evaluation of arsenic, using site-specific exposure considerations and measured <br />bioavailability of arsenic in development rock, indicated that an appropriate site-specific RMC <br />is greater than maximum arsenic concentrations. <br />Additional evaluation of metals other than the 11 constituents for which BLM RMCs are <br />available was performed using conservative RSLs from EPA. This evaluation did not identify <br />any constituents in development rock at concentrations exceeding their respective RSLs. <br />Notably, concentrations of uranium and vanadium, target metals for mining operations, were <br />less than appropriate screening criteria. <br />Media besides soil are either not present at the site (sediment, surface water) or are not <br />accessible (groundwater). Thus, RMCs based on direct contact with soils are appropriate for <br />evaluating possible toxic-forming materials. In addition, the most restrictive (e.g., lowest) RMC <br />for arsenic is based on a worker that might visit the site to perform such activities as control of <br />invasive species and abatement of fire hazards. If this worker is protected, other visitors to the <br />site - campers, ATV riders, surveyors - will also be protected. Based on the BLM land <br />management plan for this area, future land use for the site is assumed to be non-motorized <br />recreation, and thus future residents were not evaluated. Based on the above results, the <br />following conclusions are justified: <br />• A worker scenario is the most restrictive of applicable exposure scenarios for the Sunday <br />Mines Group, and conclusions concerning toxic-forming potential are appropriately <br />based on this receptor <br />• Groundwater at the site is present only at a depth that precludes contact for visitors to <br />the site, including campers, ATV riders, surveyors and workers. Thus, RMCs based on <br />direct contact with soil are appropriate for evaluating toxic-forming potential <br />• Metals concentrations in development rock are higher than regional background and <br />screening against health-protective criteria is appropriate for evaluation of toxic-forming <br />potential <br />• <br />Cm 4-7 <br />T:184986-Denison MineslTask Order 3 - DMO Sampling and Analysis Plan%Task 3.12 - Soil. Ore. Rack Data Assessment ReporllSunday Rods Repo?nal repornReporrlFinal Sunday Mures Group Sal Ore Rock <br />Date Assessment Repon_g51509.dac