Northern Water has discovered uranium-bearing minerals in the early phases of water testing at Chimney Hollow Reservoir, a project west of Carter Lake in Larimer County. The project, which will store a maximum of 90,000 acre-feet for the Windy Gap Project that supplies water to Boulder, Broomfield, Larimer and Weld county, is set to begin filling operations in August — a process expected to be completed in 2027, though these plans could change “based on what further testing shows and what mitigation measures make the most sense,” Northern Water public information officer Jeff Stahla said in an email response to questions.
Uranium is found in some of Colorado’s geology. At Chimney Hollow, it is “naturally occurring in the granitic rock formations that were quarried to supply material for the dam,” according to a June 5 press release from Northern Water.
“As the reservoir fills, these rocks will be in direct contact with water, leading to the leaching of uranium into the water,” which the conservancy district will closely monitor during filling operations but expects to decrease over time.
The maximum amount of uranium permissible in drinking water by the EPA is 30 micrograms per liter. Northern Water is conducting tests and modeling what the extent of the uranium leaching could look like as they begin filling it.
Tests will continue over the next several years while Northern Water pursues mitigation strategies, which could include treatment or reduction through significant dilution, according to Stahla. No water will be released from the reservoir until further assessments are completed.
In other news…
- The U.S. Forest Service approved the St. Vrain Forest Health project, a plan to conduct forest management across 43,000 acres of national forest west of Lyons. The plan, which has been in development for four years, includes thinning and prescribed burns throughout the area to fortify the St. Vrain Watershed against wildfire.
- Safeway and Albertsons workers in 14 cities across Colorado, including Boulder, Broomfield and Metro Denver, voted to authorize a strike against unfair labor practices. No start date has been officially announced, but some media outlets have reported that work stoppages could begin as soon as this Sunday. UFCW Local 7 workers’ union contracts expired in January after months of negotiations, leading to a two week King Soopers workers strike in February.