A pipeline rupture spewed more than 176,000 gallons of crude oil into a North Dakota creek and went detected until a landowner discovered the pollution.
The monitoring equipment didn’t detect the leak, according to Wendy Owen, a spokeswoman for True Cos., which operates the Belle Fourche Pipeline.
A landowner discovered the spill near Belfield on Dec. 5, according to Bill Suess, an environmental scientist with the North Dakota Health Department.
The crude migrated about 6 miles from the spill site along Ash Coulee Creek, polluting private and public U.S. Forest Service land. The creek feeds into the Little Missouri River.
Seuss said it appears no oil got that far and that no drinking water sources were threatened.
About 37,000 gallons of oil had been recovered as of Monday.
The pipeline was shut down immediately after the leak was discovered. The pipeline is buried on a hill near Ash Coulee creek and the “hillside sloughed,” which may have ruptured the line, Owen said.
“That is our No.1 theory but nothing is definitive” Owen said. “We have several working theories and the investigation is ongoing.”
True Cos. has a history of oil field-related spills in North Dakota and Montana, including a January 2015 pipeline break into the Yellowstone River. The 32,000-gallon spill temporarily shut down water supplies in the downstream community of Glendive, Montana, after oil was detected in the city’s water treatment system.
The 6-inch steel Belle Fourche Pipeline is mostly underground but was built above ground where it crosses Ash Coulee Creek, Suess said.
Owen said the pipeline was built in the 1980s and is used to gather oil from nearby oil wells to a collection point.
The company has hired Alberta, Canada-based SWAT Consulting Inc. that specializes in cold-weather oil spill cleanups, Suess said.
About 60 workers were on site Dec. 12 and crews have been averaging about 100 yards daily in their cleanup efforts, he said. Some of the oil remains trapped beneath the now frozen creek.
True Cos. operates at least three pipeline companies with a combined 1,648 miles of line in Montana, North Dakota and Wyoming, according to information the companies submitted to federal regulators. Since 2006, the companies have reported 36 spills totaling 320,000 gallons of petroleum products, most of which was never recovered.
Federal pipeline safety regulators initiated 19 enforcement activities against the three True pipeline companies since 2004. Those resulted in $537,500 in proposed penalties, of which the company paid $397,200, according to Department of Transportation records.
The potential for a pipeline leak that might taint drinking water is at the core of the disputed four-state, $3.8 billion Dakota Access Pipeline, where thousands of people have been protesting its construction in southern North Dakota. That pipeline would cross the Missouri River.