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MMRR Quarry, M-2004-067 <br />Response to Jan. 21 Adequacy Review <br />March 23, 2005 <br />Page 10 <br />It is therefore believed that runoff from the site will contain <br />only insignificant dissolved concentrations of uranium or <br />other metals. Runoff from the quarry operations will also be <br />routed through sediment ponds, therefore most sediments <br />will settle out before water exits the site and reaches the <br />North Fork of Clear Creek. Should the unlikely event of <br />uranium runoff occur, the adjacent reach of the North Clear <br />Creek is subject to water quality standards. The applicable <br />radioactivity standard of 40 pCi/L or natural background <br />where higher is established in Regulation 38 of the State of <br />Colorado implementation of Clean Water Act Water Quality <br />Standards. This level is found in the regulation to be <br />acceptable because it presents statistically small risks to <br />human health. The operator will monitor all waters <br />concentrated on the site at a point of discharge for <br />compliance with this safety standard. Based on an <br />anticipated conversion ratio of 1:1 for units of activity (pCi) to <br />units of mass (ug), monitoring may be based on a safety <br />standard of 40 ug/L. The operator will also be subject to <br />Ciean Water Act regulation through the permitting program <br />under the Department of Public Health and Environment and <br />may determine an appropriate TMDL (total maximum daily <br />load) for uranium through Clean Water Act regulation. <br />Containment and Control. In the event that air or water <br />monitoring detects a uranium level exceeding the toxicology <br />standards (e.g., maximum safe ambient concentration of <br />uranium) defined above, a variety of mitigation measures <br />may be employed based on the severity of the situation. <br />For intermittent, minor variations from the standard, a <br />suitable remedy may allow for continued operations, <br />provided the mitigation measure or measures is successful <br />in addressing the cause of the safety failure. Alternative <br />blasting techniques, premoistening of rock, and other <br />enhanced dust supression techniques may be employed to <br />address ambient air quality. Enlargement or reconfiguration <br />of sediment features, treatment of surfaces and drainage <br />areas with acid neutralizers, and phytoremediation are <br />examples of techniques that may be employed to address <br />marginally unacceptable levels of uranium in runoff. <br />r,~ <br />~~ 4 <br />~` <br />i <br />