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sufficiently diluted well before reaching the water table. The Division therefore should <br />no longer consider SM-18 Mine to be a Designed Mining Operation unless new evidence <br />justifies reconsideration ofthis conclusion. <br />)n a letter dated March 9, 2006 to Cotter Corporation from the Minerals Progam <br />Supervisor, H. Bruce Humphries, the Division stated that: <br />Cotter Corporation has satisfactorily demonstrated that the [SM-18 Mine] operation does <br />not expose or disturb acid or toxic materials in quantities that adversely affect human <br />health, property or the environment. Staff accepts that contaminates [sic] from the waste <br />rock or underground workings will not have a deleterious effect on the groundwater <br />quality in the immediate area. Therefore, the Division is rescinding its original <br />designation of DMO per Rule 7.2.4(1)(a). <br />The Appellant questions whether a computer model is permissible to demonstrate the <br />lack of impacts from Cotter's operations. Indeed, there is precedent for the Division to allow use <br />of computer modeling which demonstrates, among other things, that dilution of contaminants <br />with fresh water or ground water will result in compliance with ground water numeric protection <br />levels. If dilution is selected as a means of meeting groundwater numeric protection levels, the <br />operator is allowed to construct or use a computer model showing that dilution rates can be <br />expected if rain or snow melts drives pollutants from the rock piles into local ground water. <br />The Division further carefully evaluated the proximity of ore and waste rock piles to <br />surface and ground water resources. This is based on site-specific examinations that consider the <br />proximity to streams, and ground water, as well as the size of ore in waste rock facilities, <br />duration of exposure to weathering, and reclamation and closure techniques. <br />In response to questions raised by the Division, and on behalf of Cotter, GeoScience <br />Services ("GeoScience") presented an October 19, 2005 report to the Division entitled <br />"Evaluation of Potential Contaminant Migration for Uranium Mining Operation at the SM-18 <br />Mine." After a thorough evaluation, GeoScience Services concluded: <br />6.0 Conclusions and Recommendations <br />5 <br />