Aspen Journalism: Lincoln Creek sediment release had high levels of aluminum, iron
Minimal effects on aquatic life
Heather Sackett/Aspen Journalism
Pitkin County officials say that a July release from Grizzly Reservoir that turned Lincoln Creek and the Roaring Fork River orange had minimal biological effects on fish and other aquatic life.
Water quality testing results from the day of the sediment release, July 16, show high levels of iron and aluminum, but they do not show levels of copper high enough to be toxic to fish.
Members of the Lincoln Creek workgroup — which is comprised of officials from Pitkin County, Colorado Parks and Wildlife, Colorado Department of Public Health and Environment, Independence Pass Foundation, and others — met remotely on Wednesday to debrief the July 16 incident. The water quality samples were collected by staff from the Roaring Fork Conservancy and the results are available on River Watch, a statewide, volunteer, water quality monitoring program operated by Parks and Wildlife.
The released sediment was in particulate form and less able to be readily taken up by aquatic life, according to a press release from Pitkin County. There were no fish kills reported to Parks and Wildlife, and the event is not expected to have a significant long-term impact on aquatic ecosystems.
“Most of this indicates that although visually the impact of the event was, you know, scary to look at, it does seem that at least from a copper and biological perspective that there was less of a copper biological risk to fish,” said Megan McConville, Parks and Wildlife River Watch program manager. “The copper has a more toxic effect on aquatic life than the aluminum or the iron.”
Twin Lakes Reservoir & Canal Co., which operates Grizzly Reservoir, drained the reservoir this summer, so it could make repairs to the dam and outlet works. On July 16, a pulse of sediment-laden water from the bottom of the reservoir was released down Lincoln Creek, turning it and the Roaring Fork River orange and alarming Aspen residents and visitors.
A July 1 news release from Pitkin County had warned of the potential for temporary discoloration of the river as the reservoir was drawn down, but the severity of the event shocked many people. The U.S. Army Corps of Engineers is investigating whether the sediment release needed a permit under the Clean Water Act.
Officials say the release is unlikely to pose any ongoing risk to people recreating in local waterways.
Local officials, residents, and environmental groups have long been concerned about water quality on Lincoln Creek and the July 16 release came at a time of increased scrutiny. Officials have determined that a “mineralized tributary,” which feeds into Lincoln Creek above the reservoir near the ghost town of Ruby, is the source of the high concentrations of metals downstream. The contamination seems to have been increasing in recent years and may be exacerbated by climate change as temperatures rise.
High levels of aluminum, iron at testing sites
Water quality samples were taken by Roaring Fork Conservancy staff at six locations on Lincoln Creek and the Roaring Fork on three dates: June 4, June 25, and July 16. The locations were the Grizzly Reservoir inlet, below Grizzly Dam, the Lincoln Gulch Campground on the creek just above the confluence with the the Roaring Fork, the Grottos day-use area, and Difficult Campground. Control samples were also taken from the Roaring Fork just above the Lincoln Creek confluence. An additional location, below the sediment traps on Lincoln Creek about 50 yards below Grizzly Dam, was tested only on July 16.
That data show sharply increasing concentrations of aluminum and iron on July 16, particularly just below the dam. On June 25, there were 258 micrograms (parts per billion) of aluminum in the water below Grizzly Dam, which is still exceeds the chronic water quality standard for aquatic life (on all but one date and location, the amount of aluminum exceeded either the CPW acute or chronic water quality standards for aquatic life). During the release on July 16, that jumped to 1.7 million micrograms. Testing at the second location below the dam, below the sediment traps placed by Twin Lakes, that number was down to 726,600.
“There was a pretty significant drop from what was coming directly out of the dam,” said Chad Rudow, water quality program manager with the Roaring Fork Conservancy. “It kind of shows the sediment traps were doing their job and helping to sequester some of that stuff.”
By the time the release had made it downstream to the confluence of the Roaring Fork, the total iron levels had decreased by 97%, and total aluminum decreased by 98%.
Because there were additional elements in the water, the aluminum was not as toxic to fish as it could have been, McConville said.
“The more carbon you have in the water, the less toxic it makes the aluminum,” she said. “Because we’ve got bottom lake sediments coming down, they were probably pretty high in carbon. … My guess is that a big slug of carbon came down along with the iron and aluminum, and for aluminum in particular, it probably provided some protection for those aquatic organisms.”
The iron levels also exceeded state chronic water quality standards for aquatic life in eight of the 19 sites and days tested, but iron is a 30-day standard and the release was a roughly 36-hour event.
“If that event had gone on for 30 days or a longer duration, then that standard would have been applicable,” McConville said. “But because it was such a short-term event, that sort of clogging, smothering effect that we would expect from that precipitated iron just really didn’t have a chance to occur.”
The reason copper levels below the reservoir were so low is probably because the entirety of Lincoln Creek above the reservoir — the source of copper contamination — is being diverted to the Arkansas River basin through the Twin Lakes Tunnel.
Lincoln Creek and Grizzly Reservoir are part of a highly engineered system that takes about 40% of the water from the headwaters of the Roaring Fork to cities and farms on the east side of the Continental Divide. Water is sent from the reservoir through Twin Lakes Tunnel into Lake Creek, which is then collected in Twin Lakes Reservoir.
Four municipalities own 95% of the shares of water from the Twin Lakes system: Colorado Springs Utilities owns 55%; the Board of Water Works of Pueblo has 23%; Pueblo West Metropolitan District owns 12%; and the city of Aurora has 5%.
Officials said at Wednesday’s meeting that this is just the initial attempt at understanding the water quality testing data around one reservoir release event and there is still a lot of data that needs to be analyzed from other testing agencies.
In addition to the Roaring Fork Conservancy, four other entities are conducting water quality sampling this summer: Pitkin County Environmental Health; the U.S. Forest Service; Parks and Wildlife; and the Institute of Arctic and Alpine Research at the University of Colorado Boulder. The workgroup has hired consultant LRE Water to review the data and an EPA report, make a site visit and comment on the sampling plans of the five different entities.
“The initial plan was to have all of the data come to us at one time, the beginning of next year, but there became this ask for the data around this event; there was a concern around toxicity,” said Kurt Dahl, Pitkin County environmental health director. “There’s still a lot of data that we have out there. … The context of the entire year is going to have to wait until our intended timeframe of early next year to talk about how this looks in comparison to the various other times we’re out there sampling.”
Heather Sackett is the managing editor at Aspen Journalism and the editor and reporter on the Water Desk.
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