Scientists working to understand record of mine-related contamination in sediment below Lake Powell

Initial data from a 2018 research project is now being released.

(Jerry McBride | The Durango Herald via AP) In this Thursday, Aug. 6, 2015 file photo, people kayak in the Animas River near Durango, Colo., in water colored yellow from a mine waste spill. A crew supervised by the U.S. Environmental Protection Agency has been blamed for causing the spill while attempting to clean up the area near the abandoned Gold King Mine. Tribal officials with the Navajo Nation declared an emergency on Monday, Aug. 10, as the massive plume of contaminated wastewater flowed down the San Juan River toward Lake Powell in Utah, which supplies much of the water to the Southwest.

The Durango Herald’s 2015 photograph was instantly recognized as a scene of environmental disaster: three kayakers paddling down the Animas River in southwest Colorado, the water below them as orange and radiant as a Creamsicle.

A containment pond near Silverton, Colo., had been accidentally breached at the Gold King Mine and 3 million gallons of metal-laden sludge were released into the Animas, flowing downstream into the San Juan River.

The river ran clear again within a couple of days, but much of the heavy metals and other pollutants released in the spill worked their way downriver until they hit Lake Powell, along with all the other sediment that had been carried downstream by the Colorado River and its tributaries since the Glen Canyon Dam was completed in 1963.

“Lake Powell is the integrator for the whole upper Colorado River Basin,” said Scott Hynek, a United States Geological Survey (USGS) hydrologist with the Utah Water Science Center. “Once they closed that dam, anything that came through there that was sediment stayed.”

[Related: As Lake Powell shrinks, the Colorado River is coming back to life]

The federal government, which had been supervising cleanup at the Gold King Mine when the accident occurred, later paid out hundreds of millions of dollars in settlements to impacted areas in Utah, New Mexico and the Navajo Nation. It also appropriated funding for the USGS to study sediment samples in Lake Powell, a project which Hynek led in late 2018.

A rotating team of 20 to 30 people spent over a month on the reservoir in what Hynek describes as a “kind of floating city” that consisted of two to three houseboats, a barge pusher, a drilling rig, and a laboratory and office that operated 24 hours a day. The USGS team partnered with the Utah Department of Environmental Quality, U.S. Bureau of Reclamation, and U.S. National Park Service to extract 30 cores in the beds of the San Juan and Colorado rivers.

(USGS) Drill rig used to collect sediment samples on Lake Powell in 2018.

The goal was to understand not just the potential impacts of the Gold King Mine disaster but also to analyze the record of sediment that is trapped in the upper reaches of Lake Powell and is 50 feet thick in places.

The initial data gathered on the project is just now being released, and Hynek gave a public presentation on the preliminary results earlier this month. His hope is that the project will be useful to scientists working across the river basin on a variety of projects. The sediment record, he explained, “is like the ultimate ground truth on what has happened in the upper Colorado River Basin on a very large scale over 70 years.”

Cores taken in the San Juan arm of the reservoir show spikes of lead and zinc that may have been deposited from the Gold King Mine spill in 2015, but there are much bigger — and more concerning — spikes of the metals that were likely deposited in the 1970s when larger mine waste-related disasters occurred in the watershed.

“Bigger things happened in the 70s in the San Juan than the Gold King,” Hynek said.

(USGS) Scott Hynek, a hydrologist with the Utah Water Science Center, presents preliminary findings from the Lake Powell Coring project on Nov. 1, 2021.

The San Juan and its tributaries have a long history of hard rock mining, and copper and lead concentrations are higher in San Juan River sediment cores compared to those collected on the Colorado River arm. The Colorado side had a more active history of uranium mining and milling, including near Moab, and the cores showed higher concentrations of uranium in the Colorado River arm.

But some of the metal spikes found in the reservoir silt are not necessarily related to historic mining. The San Juan River, for example, has seen upticks in lead concentrations after monsoon rains have fallen on burn scars from forest fires.

(Francisco Kjolseth | The Salt Lake Tribune) The so-called Dominy Formation, clearly illustrated by high walls of sediment in Waterhole Canyon, one of the tributaries of the Colorado River in Cataract Canyon, are studied by a team of scientists during a recent trip as part of the Returning Rivers Project. The informal term is named after the controversial former commissioner of the Bureau of Reclamation, Floyd Dominy, who was the prime mover behind Lake Powell and many other Western dam projects.

Hynek emphasized that the data from the project is only just now being analyzed and far more detailed reports are slated to be released over the next 18 months along with more raw data, which he hopes will be used by university professors for a number of research projects.

“We have a chance of actually providing a better view of history now than firsthand records [from the time],” Hynek said.

Zak Podmore is a Report for America corps member and writes about conflict and change in San Juan County for The Salt Lake Tribune. Your donation to match our RFA grant helps keep him writing stories like this one; please consider making a tax-deductible gift of any amount today by clicking here.