2009-06-08_REVISION - M1997032 (21)

Home Browse Search

Secfion 4 Rofenfia/forRockfo be Toxic Forming iron sulfide (probably pyrite) wh ch would be stable in stomach fluid. The highest concentration of arsenic found in any soil particle examined was found in associated with crystalline iron sulfide. Other forms of arsenic were encounter less frequently. Thus, an estimate of 64 percent for development rock from the Van 4 mine can be anticipated to adequately (and conservatively) represent potential uptake of arsenic after accidental soil ingestion. When the RMC estimated for ars nic (37 mg/kg) is adjusted assuming a bioavailability factor of 64%, the resulting site-specific RMC is 58 mg/ kg. The site- specific criterion for arsenic of 58 mg/kg is higher than any total arsenic reported from development rock samples. Therefore, based on the measured concentrations of arsenic and the calculated criteria protective of workers, development rock at the Van- mine is not expected to be a toxicrforming material. 4.1.3 Evaluation of Inorgalnic Constituents not Addressed by BLM BLM RMCs have not been ident:i?ied for several metals detected at the Van 4 Mine including uranium. In order to a. Bess the potential toxicity of these metals in development rock, EPA RSLs for a commercial/ industrial exposure scenario were utilized as screening level conce. trations for the following metals to assess if development rock and ore are a otential toxic producing material: aluminum, barium., beryllium, boron, chromium, cobalt, iron, molybdenum, thallium, tin, titanium, uranium and vanadiui . Although the commercial/indu expected post-mining land use conservative; that is, the scenar: metals on the site than what is For example, commercial/indu compared to 40 days per year h additional metals evaluated usi indicating that constituents not direct contact. 4.1.4 Background Soil Cc All inorganic constituents detect naturally in soil and rock. Thus, development rock that is unrelat were collected at the Van 4 mine shown in Table 4-3. In general, detected concentrat respective background soil con difference in nature of the mate collected from an area north of Development rock samples we exposure scenario is not the same as the the property, RSLs provided for this scenario are provides additional human health exposure to ticipated given the anticipated post-mining land use. -ial workers are exposed 250 days per year the BLM worker. No maximum concentrations of RSLs (Table 4-1) exceed screening criteria, )nsidered by BLM pose no toxic-forming threat for d in development rock at the Van 4 Mine occur ame level of these constituents will be found in d to mining activity. Two background soil samples Concentrations of metals in these samples are as of metals in development rock are greater than ntrations. This observation is consistent with the als. Specifically, samples of background soils were ie Van 4 mine where the rock is not mineralized. collected from rock removed from the mine, which • • 4-6