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Mr. David Berry <br />May 14, 2010 <br />Page 3 <br />also regulated in drinking water. In addition, the EPP states that the water level in the <br />mine has reached "equilibrium" at approximately 23.7 feet below the Steve Level, <br />approximately 26 feet above Ralston Creek. This is a significant amount of hydraulic <br />head and, coupled with the noted faults, fractured bedrock, and unsealed boreholes <br />identified in the EPP, suggests a much stronger influence and correlation between the <br />mine water and Ralston Creek. It is contradictory to allege in one part of the report that <br />bedrock at the mine site "has very low permeability," suggesting that water does not flow <br />out of the mine into the Ralston Creek, then state in another portion of the report that <br />water inflow to the mine "occurred from several sources including infiltration of <br />groundwater through porous bedrock." <br />Waste Rock Piles: The EPP states that there are, "no impacts to water quality in Ralston <br />Creek detectable from the waste rock piles." However, there is little if any evidence to <br />support this assertion. According to the EPP, the rock piles are of similar composition to <br />the fill material that was placed in the valley floor and which has been identified as a <br />source of uranium contamination in Ralston Creek. Stating that the rock piles are capped <br />and stable is insufficient evidence to prove that their presence immediately adjacent to <br />the creek has no impact upon water quality. <br />Alluvial Fill: The waste rock material that was placed in the valley floor during <br />construction of the Schwartzwalder Mine is of significant concern to Denver Water. In <br />addition to placement of this fill, Ralston Creek was apparently diverted to a new location <br />to allow more room for mining-support buildings. The EPP is clear that this fill material <br />is a source of uranium loading to Ralston Creek. However, the report is unclear about <br />how significant the relocation of Ralston Creek and historical creek hydrology might be. <br />In addition, the EPP states that the contaminated water in the flooded mine may be a <br />"minor source" of contamination to the alluvium. What is clear is that both the fill and <br />alluvial groundwater have uranium concentrations which exceed the Colorado drinking <br />water standard for uranium, and are having a direct impact on water quality in Ralston <br />Creek. <br />Denver Water is very concerned that Cotter's EPP places a high reliance on Denver <br />Water's operations for dilution of contaminated water in Ralston Creek. The document shows a <br />significant lack of understanding about how Denver's water collection system works, how it is <br />used it -to deliver water to customers, and about maintenance activities. In several places <br />throughout the document, the EPP states that water from Ralston Creek receives "significant <br />additional mixing" when water from Ralston Creek is mixed with water from Denver's Moffat <br />Collection System. Unfortunately, this is not always true. A large construction project on the <br />South Boulder Canal made other water sources into Ralston Reservoir unavailable for 210 days <br />in 2007, 151 days in 2008, and 63 days in 2009. This project will continue into the future with <br />more planned canal outages. In addition, water from Long Lakes, diverted directly from Ralston <br />Creek, can and has been delivered downstream of Ralston Reservoir. This water, which <br />apparently can contain high concentrations of uranium and other metals, bypasses Ralston <br />Reservoir and flows directly into Arvada Reservoir. Deliveries to Arvada and other raw water