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Healthy Rivers board supports INSTAR sediment and metals study for Lincoln Creek; county commissioners informed
Summary
The Healthy Rivers and Streams board unanimously recommended funding a revised INSTAR (CU) proposal to analyze a newly observed aluminum-rich flocculent and mobile metals in the Lincoln Creek/Grizzly Reservoir system; Pitkin County commissioners heard the presentation and Healthy Rivers’ recommendation.
Professor Diane McKnight and CU collaborators presented a revised proposal and data from a sediment core taken from Grizzly Reservoir that show rising concentrations of iron, aluminum and copper in recent layers. The Healthy Rivers and Streams board held a special meeting May 27 and unanimously voted to recommend the revised Institute of Arctic and Alpine Research (INSTAR) proposal for funding; the item was then presented to the Pitkin County Board of County Commissioners on June 10.
McKnight said researchers observed a white, aluminum‑rich precipitate and red iron oxide flocculent downstream of a mineralized tributary and the Ruby Mine that drains into Lincoln Creek and then Grizzly Reservoir. Samples taken in 2024 showed dissolved copper concentrations in the mineralized tributary at levels several orders of magnitude above aquatic-toxicity thresholds during late summer; the team is concerned that mobile metal‑rich flocculent material deposited in the reservoir could be remobilized and affect downstream water quality.
INSTAR researchers collected a reservoir sediment core while the reservoir was drained; laboratory analyses show that flocculent layers have become more common in upper (recent) core sections. The revised proposal requests funding for radiometric dating (carbon‑14 and lead‑210) to convert core depths into a dated record, and for leach tests to assess metal solubility and bioavailability from the sediments. The team proposed monitoring surface and interstitial seep water in the mineralized tributary and comparing new samples to the small set collected in 2024.
Commissioners and Healthy Rivers board members praised the collaborative Lincoln Creek work group and asked the researchers to present results to the Colorado River Roundtable. The Healthy Rivers program indicated funds are already appropriated for the grant cycle and the board’s recommendation was to proceed with the revised INSTAR request.
