An oil and gas production site is shown in Williams County, North Dakota, in September 2024. Regulators are investigating a spill at a different oil well site in Mountrail County, North Dakota. (Photo by Kyle Martin/For the North Dakota Monitor)
A pipeline leak in northwest North Dakota has spilled an estimated 20,000 barrels, or 840,000 gallons, of crude oil and produced water onto agricultural land, the Department of Environmental Quality said Monday.
The spill about 4 miles northwest of Stanley in Mountrail County involved emulsion, a mixture of crude oil and produced water that emerges from a well before they are separated, the department said. Produced water, also known as saltwater or brine, is a waste byproduct of oil production.
The contamination flowed for 250 yards before it was contained by the construction of a clay berm, according to the incident report.
It is unknown how long the leak went undetected by Hess Corp., which owns the pipeline. Bill Suess, manager of the Department of Environmental Quality’s spill investigation program, said the company first became aware of a potential problem Sept. 2 when they “started getting an indication their numbers weren’t right” – 10 days before the spill was discovered and reported.
“They went in and did some tests. The tests came back negative,” said Suess. “And then on the 12th they found the dead vegetation.”
Hess discovered and reported the spill on Friday, according to the incident report.
The cause of the spill has not been identified beyond “equipment failure” and remains under investigation, according to Suess.
The leak occurred from a 6-inch carbon steel pipeline called a “flow line,” used to transport the oil, natural gas and produced water from a well to a treater unit where the products are separated. Regulators are still investigating the extent of the spill underground, including possible groundwater impacts, Suess said.
There is no risk to drinking water, Suess said. The department said no water resources have been impacted at this time.
“We don’t know yet how deep the impacts go,” said Suess.
Cleanup is expected to last until at least mid-November, according to the incident report. That’s an “optimistic” estimate from Hess, Suess said.
“This is a big one,” Suess said.
A Hess representative said the flow line has been isolated and the surface impact was contained to a field between two oil well pads. Hess notified the Department of Environmental Quality and mobilized a third-party environmental contractor, the representative said.
“Safety and the protection of people and the environment are our top priorities,” the Hess representative said in a statement.
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