Mineralized uranium was discovered during the construction of Chimney Hollow Reservoir. Northern Water and project participants have been studying how the uranium minerals mobilize into water and what concentration to expect when the reservoir fills. All testing to date has been small scale and laboratory based. The addition of a small amount of fresh water in the reservoir, less than 2 percent of the total reservoir volume, will provide a better opportunity to study real-world conditions. In addition, Northern Water has sampled groundwater in the area to characterize baseline water quality conditions. This information, paired with data collected from the initial inflow of water in the reservoir, will inform further management options.
While the discovery of mineralized uranium has caused Northern Water and the Chimney Hollow participants to modify their plans, its presence can be safely managed. The new reservoir remains an important part of securing additional water supply for northern Colorado and its future. Please visit the Water Quality page for more information and a list of Frequently Asked Questions.