Thermopolis as seen from Round Top with the Wind River Canyon and Owl Creek Mountains in the background. (Jonathan Green/Wikimedia Commons/GNU Free Documentation License)

Thermopolis residents have won a 79-day extension to comment on a plan to release thousands of tons of oilfield pollutants monthly into the Boysen Reservoir upstream of the source of their drinking water.

The Wyoming Department of Environmental Quality, in response to a request from Thermopolis Mayor Mike Chimenti and others, agreed to extend the deadline from tomorrow, April 17, until close of business July 5. In addition to authorizing the 79-day extension, the state agency agreed to host two public meetings to “present an overview of the proposed permit revision and be available to answer questions related to the discharges and permitting process.”

Chimenti, who had asked for a 120-day extension and for a public meeting within 30 days of his April 2 letter to DEQ, said in a telephone interview with WyoFile on Tuesday that he was satisfied with the new timetable. But, he said that before he even begins to question the new discharge proposal, he wants to know what pollutants are currently being released upstream of his town.

“My question is I want to know if there’s wastewater from other locations being discharged into Boysen Reservoir,” he said. “I’m concerned about the existing situation.”

DEQ will host the first meeting at 5:30 p.m. May 20 in the Central Wyoming College ITEC building room 116 in Riverton. The second is scheduled at 5:30 p.m. May 21 in the Thermopolis High School auditorium in Thermopolis.

Chimenti said that when he read the DEQ plan to authorize Aethon Energy’s proposal for the discharge of up to 8.27 million gallons a day of “produced water” from a 4,250-well expansion of the Moneta Divide oil and gas field, he was surprised to learn there already were pollutants flowing.

“I am all for oil exploring and drilling oil wells because that is what our state relies on,” Chimenti said. As mayor of Thermopolis, however, “my first concern is the protection of Thermopolis residents.” He wants to know the “immediate and long-range effect of contaminants on our water supply,” he said.

The town is home to 2,930 residents, according to U.S. Census data through 2017. A town drinking-water plant takes in water from the Bighorn River some 15 miles downstream of Boysen Reservoir, into which the discharges and pollutants are proposed to flow.

Town residents have tuned into the issue, he said, which was first reported by WyoFile. “They saw the article in the paper and they’re concerned about that,” Chimenti said.

Oil and gas operators led by Aethon Energy would be permitted to discharge up to 2,161 tons a month of total dissolved solids in the flow, including more than 1,000 tons each of sodium and sulfate. Those flows would mix with purer water in the reservoir, according to the draft permit.

The diluted stream would then be released into the Wind River below Boysen Dam just above Wind River Canyon, a 12-mile reach with Wyoming’s highest water quality designation — Class 1. At the end of the canyon the river’s name changes to the Bighorn, and that flows through Thermopolis.

Also a source for agricultural irrigation

The Bighorn also supplies water to at least nine major canals and ditches. They irrigate 70,575 acres of crop and range land, according to WyoFile calculations based on state water documents. Farmers grow beans and barley, plus grass for cattle, among other crops, the mayor said.

While drinking water is the primary issue for Thermopolis residents, they also worry about agriculture and wildlife, Chimenti said.

“We have to protect our agriculture,” he said. “Without the farmers, we don’t eat.”

DEQ acknowledged the public outcry.

“Because of the complexity of the proposed permit, the [Water Quality Division] has received numerous requests from individuals, conservation organizations and local government officials for an extension of the comment period,” DEQ said in a statement announcing the comment extension. “Also requested is a desire for informational public meetings to better understand the proposed revisions and potential consequences to human health and the environment from the expanded discharges.”

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A DEQ official has said the pollutants “would be lost in the normal background fluctuation,” of the existing river condition.

“We are trying to maintain the quality of the Wind River below Boysen Dam,” Bill DiRienzo, DEQ’s discharge program manager told WyoFile last month. Most people will say “oh my God, that looks like a lot,” he said of the weights proposed for discharge. “It’s not really.”

Compared to the existing background level of pollutants, the proposed discharges, “are small fractions,” he has said.

Angus M. Thuermer Jr. is the natural resources reporter for WyoFile. He is a veteran Wyoming reporter and editor with more than 35 years experience in Wyoming. Contact him at or (307)...

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