Water Quality Monitoring in Chimney Hollow Reservoir
This dashboard displays uranium levels in Chimney Hollow Reservoir and in nearby sampling locations from early April 2026, when water was first introduced into the reservoir. Water sampling for uranium occurs weekly with final results typically available within two months of the sampling date. Final data will be posted to the dashboard when received, and it may not be received in chronological order due to processes at the testing laboratory.
The water currently in Chimney Hollow Reservoir represents less than 2 percent of its total capacity, and no additional water will be added during initial monitoring. The initial monitoring period provides Northern Water time to appropriately sample the new waterbody and determine a strategy to manage the naturally occurring uranium moving forward.
No water will be released from Chimney Hollow Reservoir until a management plan is identified.
The EPA standard for uranium after it has been treated by the local water provider is 30 µg/L (or parts per billion). The reported values provided below are the sampling results of the raw (untreated) water presently held in the reservoir. For context, and as a comparison to nearby waterbodies, reported values for Flatiron Reservoir (outlet), Carter Lake and Horsetooth Reservoir are also provided.
View additional data collected throughout Northern Water’s boundaries, as well as more information about Chimney Hollow water quality.