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Daniel Arnold, Esq. April 6, 2011 <br />Denver Water Page 5 of 12 <br />COMMENTS BY WHETSTONE (ATTACHMENT 2) <br />The comments by Whetstone begin with an acknowledgement that additional new data <br />and historical records have been collected since the EPP was issued. The additional data <br />gathering efforts to better understand the site are appreciated. <br />A comment is made that the data do not support that the sump pumping brings in clean <br />water from the creek and does not dilute groundwater concentrations. However, no <br />additional data are presented to support this comment. Calculations contained in our EPP <br />Review demonstrate that sump pumping in excess of approximately 30 gpm (i.e., the <br />estimated groundwater flow through the alluvial aquifer based on site - specific data) <br />would induce flow from the creek. If there was no inflow from the creek, then the sump <br />pumping would likely desaturate the alluvium because pumping rates have been much <br />greater than 30 gpm; denaturation of the alluvium has not occurred. <br />A discussion of the angled corehole that was discovered in July 2010 is presented with <br />new information on its projection and depth. The discussion identifies the corehole as J- <br />10 and attempts to de- couple the corehole water from the mine pool. Although the <br />corehole water has slightly different chemistry, the uranium concentration is still elevated <br />and similar to the mine pool water. The corehole is said to be hydraulically connected to <br />the mine pool because there was an immediate water level drop in the mine pool level <br />when the corehole started to flow. The corehole does not have to terminate in mine <br />workings or voids to convey mine pool water via fractures in the bedrock. This corehole <br />is discussed later in this Addendum. <br />The potential for leachate from the waste rock piles to impact groundwater is discussed <br />and it is stated that there is "no evidence that the waste rock piles are affecting alluvial <br />groundwater." The simple fact that MW -0, located at the base of the south rock pile, <br />consistently has uranium concentrations in the 0.2 to 0.6 mg /L range, is sufficient <br />evidence this area is a source. The claim of no impact from waste rock appears to be <br />overstated, considering that there are no monitoring wells beneath or within the waste <br />rock to substantiate that claim. Additional data collection and analysis are therefore <br />needed at the waste rock piles. It is also stated that historic mine spoils (fill) are beneath <br />the waste rock and that the fill is the source. The fill is still a mine waste and probably <br />similar in composition as the waste rock. Thus, there is little difference between the two <br />and if the fill is ultimately shown to be contributor of uranium loading to Ralston Creek it <br />will have to be controlled. There have been no plans presented to further investigate this <br />area and to evaluate corrective measures. <br />A discussion of the sump pumping and water levels is presented. New graphs of water <br />levels in MW -6, MW -7, and MW -9 are used to show that when the sumps were shut <br />down in 2002, water levels rose and contacted rock surfaces that had been unsaturated for <br />