Roughly a third of the more than 3,000 barrels of oil that spilled into a North Dakota creek following a pipeline leak last week has been recovered, a local official said on Tuesday.
An estimated 4,200 barrels of oil leaked from the Belle Fourche Pipeline on a hill just above the Ash Coulee Creek, and an estimated 3,100 barrels made it into the water, said Bill Seuss, a program manager for the North Dakota Department of Health.
The leak was first reported to regulators on Dec. 5, according to the Pipeline and Hazardous Materials Safety Administration (PHMSA).
The pipeline leak occurred about 150 miles from where the Standing Rock Sioux Tribe and other environmental groups have been protesting Energy Transfer's Dakota Access pipeline in recent months. The incident may serve as something of a rallying cry for groups opposing the pipeline, which have said a spill could enter important watersheds and contaminate water.
Frigid temperatures have made cleanup conditions difficult, but has also slowed the movement of oil down the creek because the water has frozen, he added. PHMSA on Tuesday said an investigation into the incident was ongoing.
The cause of the leak is not yet known, Wendy Owen, spokeswoman for Casper, Wyoming-based True Companies, the pipeline's owner, said by phone on Tuesday.
The 24,000 barrel per day, six-inch pipeline runs intermittently, and at maximum has capacity to flow at 1,000 barrels per hour, Owen said.
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Monitoring equipment on the line did not detect the leak, possibly because of intermittent flow, she added.
Two cows were reported dead near the site of the spill, but whether the leak caused their death was unclear, Seuss noted.
Belle Fourche Pipeline Company has reported 12 pipeline leaks since 2010.
In 2011, the company reported two major leaks, one that spilled more than 1,900 barrels of refined products Campbell County, Wyoming, and another that leaked 1,000 barrels of crude in McKenzie County, North Dakota, according to PHMSA data.