EPA report says Lincoln Creek contamination is naturally occurring

Increasing metals concentration may be caused by climate change

Heather Sackett
Aspen Journalism
Grizzly Reservoir was a bright shade of turquoise in September 2022. The man-made alpine lake has high concentrations of metals that are toxic to fish, according to a report from the Environmental Protection Agency.
Heather Sackett/Aspen Journalism

The results of water quality testing on Lincoln Creek show that the waterway is toxic to fish and that metals concentrations have been increasing in recent years. But because the main source of the contamination is a nearby tributary — and not a mine — it is unclear who should take responsibility for cleaning it up.

A report released this week by the Environmental Protection Agency shows that Lincoln Creek in the four miles between the Ruby Mine and Grizzly Reservoir exceeds state water quality standards for aquatic life for aluminum, cadmium, copper, iron, lead, manganese and zinc. Aluminum and copper concentrations were higher than standards set by the Colorado Department of Public Health and Environment in multiple locations: in Lincoln Creek downstream of Ruby Mine, in Grizzly Reservoir and in Lincoln Creek downstream of the reservoir.

“The high concentrations of these metals are toxic to aquatic life and make Lincoln Creek uninhabitable for fish,” the report says. 

The report is based on water quality sampling data from 2022.

Karin Teague, executive director of the Independence Pass Foundation, said she is glad the report is finally out so that the community can talk about what to do about the contamination. The foundation’s mission is to restore and protect the ecological integrity of the pass corridor. 

“We have a dead creek on our hands,” Teague said. “It’s a hard thing to see, and it’s a disaster for the living things that used to call the creek home. It’s bad for the wildlife and has human health implications.”

Lincoln Creek was yellow as it flowed into Grizzly Reservoir in September 2022. A report from the Environmental Protection Agency says metals contamination in the creek and reservoir is a result of natural causes, not a nearby mine.
Heather Sackett/Aspen Journalism

But those human health implications remain unclear. 

In addition to exceeding standards for aquatic life, the report says cadmium, copper, iron and nickel were present in concentrations exceeding the state standards for domestic water supply. 

Lincoln Creek feeds into the Twin Lakes Reservoir and Canal Company’s transmountain diversion system, in which Grizzly Reservoir is used as a collection pond before sending water through the Twin Lakes Tunnel to the Front Range, where it is used primarily in Front Range cities, including for drinking water. Colorado Springs Utilities owns the majority of the water in the Twin Lakes system. 

The report says there is a slight potential that the metals are contaminating drinking water, but the substantial mixing, the distance that the water travels and the filtration limit these impacts. Lincoln Creek is a tributary of the Roaring Fork River, but Aspen’s domestic water supply is not affected; the city’s drinking water comes primarily from Castle Creek.  

Colorado Parks and Wildlife stocks Grizzly Reservoir with fish each year, making it a popular and scenic spot for summer alpine fishing and camping. There have been fish die-offs in the reservoir in recent years, including 2021. But CPW aquatic biologist Kendall Bakich said that since Grizzly Reservoir is diluted with water from several surrounding cleaner drainages, fish can still survive there and CPW plans to continue stocking. 

CPW stocks the reservoir with “catchable trout,” meaning anglers can take them out and eat them. Since the trout have been raised in hatcheries with clean water and food, and have probably lived in the reservoir for only a short time (most trout that aren’t caught by anglers during the summer don’t survive the harsh winter in Grizzly), Bakich said they are not likely to pose a risk to human health. But CPW tested the tissue anyway of some of the few fish that made it through the winter since they would have the most exposure to the toxic metals.

“We haven’t gotten the results back on those tissue samples,” Bakich said. “At this point, what we know about copper and how it resides in a fish’s body, it resides in the organs and people don’t eat the organs. If you are harvesting fish in the summer, they have just been put in there.” 

Natural source of contamination

The report points to natural sources as the culprit for creek contamination, referring to a “mineralized tributary.” The mineralized tributary in question is a drainage in a steep slope above Ruby Mine, which flows into Lincoln Creek just below the discharge from the Ruby Mine portal. Prospectors dug for gold, silver, lead and copper at now-defunct Ruby Mine in the early 1900s.

The report says that the mine discharge and the mineralized tributary have very different water chemistry and that the contamination has been traced back to the tributary, not the mine. The report estimates that the mineralized tributary contributes 98.5% of the copper contamination to Lincoln Creek.

“While historical mining does appear to play a role in some of the impacts to Lincoln Creek, all of the data and observations point to natural sources as the major component of metals loading into Lincoln Creek,” the report reads. “Therefore, cleanup or removal activities associated with Ruby Mine would have minimal benefits to improve the overall quality of Lincoln Creek.”

The EPA is authorized to address elevated metals concentrations only from human-caused sources, not contamination from natural sources.

Climate change a cause?

Water quality issues on Lincoln Creek have been a concern for years, with the creek above the reservoir often running a yellowish color, and Grizzly Reservoir often a bright turquoise. In September 2022, Lincoln Creek below the reservoir turned a milky-green color, and white and yellow sediment settled on the streambed, prompting water quality testing in the fall of 2022 and the EPA report. These conditions in 2022 could be seen downstream at the confluence with the Roaring Fork River, sparking concern for local residents and organizations. 

Although water quality issues on Lincoln Creek are not new, according to the report, the metals concentrations — especially copper — have increased over the past 20 years. And climate change may be to blame. 

“While the exact cause for observed trends is not known, it is suspected that climate change may be altering hydrologic cycles and thawing once-frozen rock deep in the mountain,” the report reads. “These processes could expose more metals-bearing rock to oxygen, thereby increasing potential to generate acidic drainage and dissolution of metals.” 

Lincoln Creek, a tributary of the Roaring Fork River, downstream of Grizzly Reservoir was turquoise in places in September 2022. These unusual colors and sediment in the creek near its confluence with the Fork prompted water quality testing and a report from the EPA.
Heather Sackett/Aspen Journalism

Now that the findings have been released, the next step is figuring out what to do about the contamination and which agencies should be involved. Pitkin County Environmental Health Manager Kurt Dahl said a meeting has been scheduled for Thursday with representatives from Pitkin County, CDPHE, the U.S. Forest Service, CPW, the Roaring Fork Conservancy, EPA, and the Colorado Division of Reclamation, Mining and Safety.

“Being a natural source, (EPA) is not going to deal with it,” Dahl said. “Is there another agency that will deal with it? The question of what are the next steps is one of the more important pieces to answer.” 

Teague hopes to learn more about the potential health risks of the contamination and that the community can figure out a solution to clean it up. 

“This is a community that cares a lot about its backyard, the health of its wild places,” she said. “If we can talk about building $50 million trails, maybe we can talk about millions of dollars to bring a creek back to life.”

Aspen Journalism is a nonprofit, investigative news organization covering water, environment, social justice and more. Visit 

Pitkin County supports Aspen Journalism with a grant from the Healthy Community Fund. Aspen Journalism is solely responsible for its editorial content.

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