Uranium Found in Chimney Hollow Dam Source

Northern Water has discovered naturally occurring uranium in the granitic rock that was quarried to supply material for the dam at Chimney Hollow Reservoir. Mineralized uranium naturally occurs in some of Colorado’s geological formations.  

This issue will require close monitoring and management when filling the reservoir, as these rocks will be in direct contact with the water and leaching of uranium will occur. The leaching process is expected to decrease over time, although it is currently uncertain how long it will take. Staff and project participants are working diligently to collect data and investigate operational strategies to mitigate this temporary challenge. No water will be delivered from Chimney Hollow Reservoir until assessments are complete, and a mitigation plan is developed to ensure a safe raw water supply. Dam safety and other tests will continue throughout this process over the next two to three years. 

This is an evolving situation, and Northern Water is committed to keeping the public informed as we gather additional information and progress with the development of mitigation strategies. To help answer any questions you may have, please visit the Chimney Hollow Water Quality webpage where we have included more information and a list of Frequently Asked Questions.