Laserfiche WebLink
drinking water standards is also inconsistent with existing or reasonable potential future uses of <br />groundwater in the mine pool. Neither the approved mine reclamation plan, nor any other <br />documents related to the Schwartzwalder Mine, has identified human consumption as a <br />reasonable potential future use of water in the mine pool. No post-mining uses for mine pool <br />water were identified, because flow rates were low and groundwater was expected to be elevated <br />in naturally occurring constituents. As the Cotter Rebuttal points out on page 2, the <br />representative background uranium concentration in bedrock monitoring well MW 11 is 1.75 <br />mg/L, but this value may underestimate the background pre-mining water quality in the ore <br />zone.3 Moreover, the Rebuttal indicates that, even assuming an end point of 0.03 mg/L, using a <br />correct R2 value and a more representative dataset would result in the mine pool reaching <br />background concentration in nine years. See Cotter Rebuttal, Exh. 1, at 3-5. The R2 value, or <br />"coefficient of determination," is a number from 0 to 1 that indicates how closely a trendline <br />corresponds to the actual data. The higher the R2 value, the better the "goodness of fit" of a <br />trendline and the more reliable the prediction. <br />Moreover, the Cotter Rebuttal sets forth how scientific studies and principles support that <br />the trend of declining uranium concentrations will continue, unless disrupted by mine <br />dewatering. As the Rebuttal states on pages 6 to 8, "[t]he concept that uranium is more mobile in <br />oxidizing conditions and less mobile under reducing conditions is well established and <br />irrefutable." Cotter Rebuttal, Exh. 1, at 6. If the mine pool is pumped down to the 500 foot <br />level, all of the wall rocks in the exposed workings would be exposed to oxygen. If the water <br />3 The "ambient groundwater quality" for mining operations permitted prior to January 31, <br />1994 is "the quality of the groundwater at the mine site as of January 31, 1994." 2 CCR 407-1, <br />Rule 1.1(5). Given that the 1981 discharge permit (CO-00001244) listed 2.42 mg/L uranium in <br />raw mine water, the "ambient groundwater quality" in the Schwartzwalder Mine as of <br />January 31, 1994 contained at least 2.42 mg/L. Whetstone Report, Exh. 4, at 4. <br />18