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Scientists strive to understand the record of mine-related contamination in sediments under Lake Powell


The first data from a 2018 research project is now published.

(Jerry McBride | The Durango Herald via AP) In this file photo from Thursday, August 6, 2015, people kayak in the Animas River near Durango, Colo. In water colored yellow by a garbage spill mining. A team overseen by the US Environmental Protection Agency has been accused of causing the spill as it attempted to clean up the area near the abandoned Gold King mine. Tribal officials in the Navajo Nation declared a state of emergency on Monday, August 10, as the massive plume of contaminated sewage flowed down the San Juan River to Lake Powell in Utah, which provides a much of the water to the southwest.

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

A containment pond near Silverton, Colo., Was accidentally drilled at the Gold King mine and 3 million gallons of metal-laden sludge was released into the Animas, flowing downstream into the San Juan River.

The river cleared again within days, but much of the heavy metals and other pollutants released from the spill made their way downstream until they hit Lake Powell, along with all of the other sediments that had been transported downstream by the Colorado River and its tributaries since the completion of the Glen Canyon Dam in 1963.

“Lake Powell is the integrator of the entire upper Colorado River basin,” said Scott Hynek, a hydrologist for the United States Geological Survey (USGS) at the Utah Water Science Center. “Once they closed that dam, whatever went through there that was sediment stayed. “

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

The federal government, which oversaw the cleanup of the Gold King mine when the accident occurred, then paid hundreds of millions of dollars in settlements to affected areas of Utah, New Mexico and the Navajo Nation. . He also earmarked funding for the USGS to study sediment samples in Lake Powell, a project led by Hynek in late 2018.

A rotating crew of 20 to 30 people spent more than a month on the reservoir in what Hynek describes as a “kind of floating city” consisting of two to three barges, a barge pusher, a platform. form of a well, a working laboratory and an office. 24 hours a day. The USGS team partnered with the Utah Department of Environmental Quality, the United States Bureau of Reclamation, and the United States National Park Service to extract 30 cores from the beds of the San Juan and Colorado rivers.

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

The objective was to understand not only the potential impacts of the Gold King mine disaster, but also to analyze the record of sediment trapped in the upper part of Lake Powell and 50 feet thick in places.

Initial data collected on the project has just been released and Hynek made a public presentation on the preliminary results earlier this month. He hopes the project will be useful to scientists working across the river basin on a variety of projects. The sediment recording, he explained, “is like the ultimate ground truth about what happened in the upper Colorado River basin on a massive scale over 70 years.”

Core samples taken from the San Juan arm of the reservoir show spikes of lead and zinc that may have been deposited by the Gold King mine spill in 2015, but there are much larger – and more concerning – spikes in the metals. which were likely deposited in the 1970s, when larger mine waste disasters occurred in the watershed.

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

(USGS) Scott Hynek, hydrologist at the Utah Water Science Center, presents preliminary results from the Lake Powell coring project on November 1, 2021.

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

But some of the metal peaks found in the silt from the reservoir aren’t necessarily related to historic mining. The San Juan River, for example, has seen an increase in lead concentrations after monsoon rains fell on burn scars from wildfires.

(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, is 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 Bureau of Reclamation commissioner, Floyd Dominy, who was the main architect of Lake Powell and many other Western dam projects.

Hynek pointed out that the project’s data is only being analyzed now and that much more detailed reports are expected to be released over the next 18 months with more raw data, which he hopes will be used by university professors for a number of research projects. .

“We have a chance to provide a better view of history now than first-hand recordings [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 matching donation to our RFA grant helps her continue to write stories like this; please consider making a tax deductible donation of any amount today by clicking here.


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Mary Cashion

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