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MMRR Quarry, M-2004-067 <br />Response to Jan. 21 Adequacy Review <br />March 23, 2005 <br />Page 9 <br />obtained at discharge points will be compared with the <br />toxicology standards provided below. <br />Toxicology of Airborne Uranium Dust. Federal standards <br />have been developed that address uranium from the <br />standpoint of both chemical and radiological toxicity. For <br />safety in situations that may involve prolonged exposure to <br />airborne uranium, OSHA (Occupational Health and Safety <br />Administration) has established a concentration of 0.2 <br />milligrams/cubic meter of uranium dust. This limit is found in <br />10 CFR 20, Appendix B, and again for the construction <br />industry at 29 CFR 1926.55. Though it is unlikely that the <br />level of uranium mineralization at the MMRR Quarry will <br />cause this type of concentration of uranium in dust, the <br />operator will monitor for compliance with this standards as <br />set forth in this plan. <br />A survey of Clean Air Act regulations in Colorado reveals no <br />ambient air quality standard that would provide a <br />measurable benchmark for uranium dust safety at the <br />MMRR Quarry. The operator will, however, seek all <br />appropriate permits and conform to any applicable regulation <br />under the Clean Air Act. <br />Toxicology of Uranium Suspended or Dissolved in <br />Runoff. There could be a potential for the mobilization of <br />small amounts of uranium or other minerals from the various <br />exposed rocks and fines in the quarry. If this were to occur, <br />it would be as the result of precipitation leaching the uranium <br />from the rock, or washing sediment particles into the runoff <br />stream leading to the sediment ponds. The leaching of any <br />minerals from this rock in significant quantities is unlikely <br />because of the infrequent occurance and low depths of <br />precipitation. The runoff from mined areas in the mining <br />districts near Blackhawk and Central City having high metals <br />concentrations is the product of different geologic conditions. <br />The mines are located in mineralized zones with sulfate <br />ores. The sulfate exposed in the mine workings and waste <br />rocks on these other sites causes acidic conditions, which <br />contribute to the leaching of metals from the rock. The rock <br />in the MMRR Quarry, on the other hand, is not mineralized in <br />this manner and runoff from the rock at the MMRR Quarry is <br />not anticipated to be acidic or to contain significant <br />concentrations of metals. <br />