A Tesoro Logistics LP pipeline has spilled more than 20,000 barrels of crude oil into a rural North Dakota field, the biggest leak in the state since it became a major U.S. producer.
The pipeline was carrying crude oil from the Bakken shale play, which has lifted North Dakota into the No. 2 spot in terms of oil production among U.S. states. The affected part of the line has been shut down, Tesoro said.
The leak, first discovered by a landowner on September 29 in a low-lying hilltop nine miles northeast of Tioga, North Dakota, did not pose an immediate threat to groundwater sources, Kris Roberts, who leads the environmental response team at the state Department of Health, told Reuters.
At an estimated 20,600 barrels, the spill would rank among the country’s biggest in recent years. U.S. pipelines are pumping more oil than ever to bring shale oil and Canadian crude to refiners, and critics are raising questions about safety.
Authorities said there were no surface bodies of water like lakes, streams or rivers within a five-mile radius of the site. Still, the incident could add to a fractious political debate over the construction of more pipelines, such as the much larger Keystone XL from Canada to Oklahoma.
San Antonio, Texas-based Tesoro Logistics said the leak occurred on a small, 6-inch diameter pipeline that Was carrying Bakken oil to the Stampede rail facility, outside Columbus, North Dakota.
The line is part of the company’s “High Plains” pipeline system in North Dakota and Montana, which gathers oil from the Bakken shale and delivers it to another Enbridge pipeline and Tesoro’s 68,000 bpd Mandan refinery in North Dakota.
It was not clear what caused the spill or how long it lasted, according to Tesoro and the state regulators. Tesoro had initially reported that 1,000 barrels of oil leaked from the pipeline.
“The pipeline was shut immediately and the leak is now contained,” said Tina Barbee, a Tesoro spokeswoman.
The leak was isolated in an immediate 7.3-acres area of the spill and within the top 10 feet of clay soil, according to a report filed with the National Response Center on October 8.
Such reports are publicly available on the National Response Center website within 24 hours of their filing but the services were interrupted last week because of the U.S. government shutdown.
Tesoro had initially estimated that only 1,000 barrels of oil leaked from the pipeline.
Tesoro’s 68,000 barrels-per-day refinery in Mandan, North Dakota is operating normally but third party shippers who were transporting oil on the pipeline have been affected by the shutdown, Barbee said. It is not clear if the refinery is directly linked to the shut pipeline.
Repairs on the line, along with containment and remediation work, could cost the company $4 million, Tesoro said in a statement released Thursday.
Tesoro said the U.S. Environmental Protection Agency and the Pipeline and Hazardous Materials Safety Administration (PHMSA) were at the site monitoring its response.
The regional EPA office could not be reached because of the government shutdown.
This is the biggest oil spill in North Dakota since 1 million barrels of salt water brine, a by-product of oil production, leaked from a well site in 2006, according to the state Department of Health. Another pipeline leak in 1989 also released large volumes of oil to the environment.
North Dakota produced more than 874,000 barrels per day in July.