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Comments Submitted by Denver Water <br />August 20, 2010 <br />Revised EPP <br />Cotter's revised EPP was issued on July 31, 2010, which is a date after the draft <br />permit was issued. The revised EPP was issued during the public comment period and thus <br />represents new information relevant to the establishment of effluent limits. Pollutant <br />sources identified in the revised EPP include the East Waste Rock Pile, the West Waste Rock <br />Pile, the Mine Pool, the Alluvial Fill area, and Seeps within the Alluvial Fill Area. Table 1 <br />summarizes information from the EPP regarding the flows and uranium concentrations from <br />the sources influencing Ralston Creek. The information is incomplete for some sources and <br />this is a concern that raises a question regarding the adequacy of reclamation. If pollutant <br />loadings are unknown for some sources, it will not be possible to determine the adequacy of <br />reclamation and it will be difficult to determine whether Cotter is in compliance with <br />applicable water quality standards. <br />Table 1. Pollutant Loadings Influencing Ralston Creeklo <br />Source Uranium Unit Loading Flow Daily Loading <br /> Concentration @ 1 gpm3 ( gpm) (Ibs/day) <br /> m /L Ibs/da / m <br />East Waste ?s 75 75 75 <br />Rock Pile' <br />West Waste ?5 75 75 75 <br />Rock Pile' <br />Mine Poo12 606 0.72 Ibs/day/gpm3,8 75 75 <br />Alluvial Fill 0.01687 0.0002 1009 0.0202 <br />Treatment Ibs/day/gpm Ibs/day Max. <br />System3 <br />Seeps in 24 0.024 7s,9 75,9 <br />Alluvial Fi114 Ibs/da / m <br />'Page 9-4 of the revised EPP reports a detectable influence of waste rock piles on <br />alluvial groundwater from "solubilized uranium from reactive surfaces on waste rock <br />and fill". See also page 11-7 of the revised EPP which suggests that Ralston Creek <br />data for uranium is inconclusive for determining the contribution from the waste rock <br />piles. Also, see Section 15. <br />2Page 9-4 of the revised EPP suggests that the mine pool could contribute 0.8 to 8% of <br />the alluvial flow. See Footnote 3. <br />3Page 8-14, the average pumping rate documented for the alluvial fill is 104 gpm, 1 <br />gpm is approximately 1%. <br />4Data in the Table for Monitoring Well MW9 suggests the recent trend uranium <br />concentration as alluvial fill thins out at the creek is approximately 2 mg/L. If seeps <br />Page 3 of 8