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Creeks tainted by drilling unable to sustain aquatic life, regulators say

Wyoming DEQ acknowledges years of built-up pollution from Moneta Divide field but has no plan to remove black sludge 6 feet deep.

A DEQ worker collects samples from Alkali Creek below where produced water from the Moneta Divide Field is discharged. (Wyoming DEQ)

by Angus M. Thuermer Jr., WyoFile

Two creeks tainted by decades of dumping from Moneta Divide oilfield drillers are officially “impaired” and unable to sustain aquatic life, state regulators say in a new report.

Parts of Alkali and Badwater creeks in Fremont County are polluted to the point they don’t meet standards for drinking, consumption of resident fish or sustaining aquatic life, a report by the Wyoming Department of Environmental Quality states. The agency listed 40.8 miles of the creeks as impaired in a biannual report required by the U.S. Environmental Protection Agency.

Parts of the creeks are polluted by oilfield discharges, including hydrogen sulfide, ammonia and chloride. The industrial activity is responsible for low levels of oxygen in the water, turbidity and a black sludge that critics say is up to 6 feet deep.

Arsenic also is present, but state monitoring couldn’t determine its origin.

The report catalogs pollution downstream of discharge points where produced water — effluent from natural gas and oil production — flows from the 327,645-acre energy field operated mainly by Aethon Energy Operating in Fremont and Natrona counties.

“They’re not putting the health and safety of these streams’ water quality, fish and downstream water users above the interests and profits of Aethon.” JILL MORRISON

The “impaired” listings are a good thing that set the table for action, said Jill Morrison, who works on the pollution issue for the conservation group Powder River Basin Resource Council. But the listing comes only after years of badgering an agency that now should look to clean up the creeks.

“What we are saying is ‘thank you’ for stepping up to address these issues,” Morrison said. “We wish it was done sooner. You’ve got enforcement power; what steps are you taking to make Aethon clean this up?”

Environmental stewards

The DEQ issued a revised permit to the private Dallas company in 2020 allowing it to discharge oilfield waste into Alkali Creek, which flows into Badwater Creek and the Boysen Reservoir, a source of drinking water for the town of Thermopolis. The permit calls for monitoring and testing, among other things.

About a year ago, however, the DEQ sent the company a letter of violation for “reoccurring exceedances” of water quality standards for sulfide, barium, radium and temperature. That’s a violation of the Wyoming Environmental Quality Act, state rules and regulations, and the permit itself.

The April 28 letter states that the DEQ hopes to resolve the violation through “conference and conciliation.” DEQ wants Aethon “to show good faith efforts toward resolving the problem and to prevent the need for more formal enforcement action by this office.”

The alleged kid-glove treatment rankles Powder River’s Morrison. “They trade, back and forth, nice conversations and nothing happens,” she said.

An Aethon pump jack in the Moneta Divide oil and gas field east of Shoshoni. (Angus M. Thuermer Jr./WyoFile)

DEQ asked Aethon for a response within 30 days. WyoFile requested on March 6 that the agency provide a copy of Aethon’s response but had not received it by publication time. Aethon typically does not respond to media questions regarding regulatory enforcement and did not answer a recent request for comment.

The 2020 permit also requires Aethon to dramatically reduce the amount of chloride — salty water — it pumps onto the landscape. DEQ said the company is preparing to meet a late-summer deadline for that standard.

“Aethon continues to diligently work toward resuming treatment of effluent using the Neptune reverse osmosis treatment plant,” DEQ said in an email, “in accordance with the established chloride compliance schedule.”

Aethon’s website says the company has a “commitment to protect the environment and our people [and] operate responsibly.” The company is a “steward of the environment,” the website states.

Black sludge

The DEQ’s “impaired” listing addresses surface water in the two creeks through what’s known as a draft Integrated 305 (b) report. It is open for comments through March 25. 

But there’s another issue that rankles critics, including the Wyoming Outdoor Council and the Powder River group — black sludge.

DEQ surveys of the creeks revealed “bottom deposits” containing mineral deposits, iron sulfides and dissolved solids, all contributing to low oxygen levels that kill aquatic life. After a phone conference with DEQ in February, Powder River’s Morrison said she learned that the bottom deposit of black sludge extends for about three miles and is from 6 inches to 6 feet deep.

A retired University of Wyoming professor who worked with the Powder River group analyzing Aethon’s permit called the sediments “totally loaded.” Harold Bergman said “that contaminated sediment will be leaching out contaminants into Boysen Reservoir for decades to come.”

He and Joe Meyer, a retired chemist who also worked with the conservation group, wrote that DEQ’s Aethon permit did not require enough testing for deleterious substances, did not consider what impact the mix of substances together has on aquatic life, and allowed as much as five times the proper amount of dissolved solids to flow out of the oilfield.

“You would not have that black gunk sediment if it weren’t for the Aethon discharge,” Meyer said.

A report of monitoring between 2019-’22 shows that aluminum exceeded discharge standards up to 17% of the time. Other than that, there’s still a question of what else is in the sludge.

This image of Alkali Creek shows flows downstream of the Frenchie Draw oil and gas field discharge point in October 2021, according to the image title. The Powder River Basin Resource Council obtained this and other public records through a request to Wyoming DEQ. (DEQ)

“We don’t know about individual organic chemicals,” Meyer said. Reports only mention “the gross measures of organic compounds,” he said.

“That doesn’t tell us about individual chemicals,” Meyer said. How much, if any, BTEX chemicals — Benzene, Toluene, Ethylbenzene and Xylenes that are harmful to humans — are in the sludge “we have no way of knowing.”

He stopped short of accusing DEQ of avoiding the question. For now, “they just wanted to get an overview analysis,” he said.

DEQ said it has a plan for the sludge. “DEQ’s Water Quality Division is monitoring any sediment flow in lower Badwater Creek to determine if there are any sediments that may mobilize towards Boysen Lake,” an agency official said in an email.

For Morrison, “the big question is what DEQ is going to require Aethon to do to clean up this mess,” she wrote in an email. Meyer and Bergman say simply dredging up the sludge is likely too dangerous because such an operation would dislodge substances and send them downstream. A more complex plan would be needed, they said.

Morrison criticized what she sees as the DEQ’s priorities. “They’re not putting the health and safety of these streams’ water quality, fish and downstream water users above the interests and profits of Aethon.”


This article was originally published by WyoFile and is republished here with permission. WyoFile is an independent nonprofit news organization focused on Wyoming people, places and policy.


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