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Mr. David Berry <br />May 14, 2010 <br />Page 4 <br />customers means that contaminated water in Ralston Creek can eventually make its way into <br />Clear Creek and the South Platte River, where it becomes the supply of many other water users. <br />Finally, caretakers at Ralston rely on the reservoir as a water supply for themselves and their <br />families. Denver Water's raw water collection and delivery system was built for the sole purpose <br />of supplying the needs of a municipal water system; it is not a mine reclamation or remediation <br />tool. <br />Recommendations <br />Overall, Denver Water believes that the proposed mitigation plan submitted by Cotter is <br />woefully inadequate. It is our belief that wetlands treatment only temporarily immobilizes and <br />accumulates a limited amount of certain contaminants. Whether sufficient uranium can be <br />removed fast enough through the use of wetlands is questionable. Further, even if plant uptake <br />occurs, there is concern that when wetlands decay or die, the contaminants are again released <br />into the environment. The contamination from the mine property reaches Ralston Creek on a <br />year-round basis, while plant growth is seasonal. For this reason, it seems a wetlands approach <br />would be less effective or even ineffective during winter months. The temporal variations in the <br />concentration of the contaminants require active treatment and not simply the passive treatment, <br />such as wetlands, proposed by Cotter. Additionally, it is not known whether the use of wetlands <br />to improve uranium removal could lead to increased dissolution of other metals. Finally, the <br />Permeable Reactive Barrier is not a permanent solution, as the system has a limited and unknown <br />lifespan. Denver Water believes that neither strategy will stabilize a severely disturbed geo- <br />chemical equilibrium. It seems that an active treatment system that physically removes <br />contaminant mass is necessary, particularly when the water affected is a major drinking water <br />supply. <br />In addition, the proposed schedule for implementation of a solution that will protect <br />public health and the environment is not aggressive enough to address the serious threat posed by <br />contamination in Ralston Creek from the Schwartzwalder Mine. Denver Water suggests that the <br />Division impose specific milestones for compliance, and that an interim solution be proposed <br />within a reasonable timeframe established by the Division (e.g. thirty days). Following the <br />interim solution, a permanent solution should be in place within a reasonable timeframe (e.g. <br />three months). <br />Cotter's EPP does not hide the fact that Ralston Creek water upstream of the <br />Schwartzwalder Mine is relatively pristine. The documentation and studies performed are very <br />clear that the mine itself is the source of the creek's contamination. Denver Water believes that a <br />comprehensive mitigation plan should address all sources of contamination including removal of <br />the waste rock piles, complete removal and remediation of the alluvial fill, and treatment of the <br />mine-pool water. Mitigation measures need to be in place to ensure that these decommissioning <br />activities do not cause additional contamination to Ralston Creek. Efforts to find and seal the <br />thirty-three remaining boreholes should resume. Denver Water also believes that the proposal to <br />remove the existing wastewater treatment plant is not prudent at this time, and that it should be