An oil leak in North Dakota is seeping from a hillside and is thousands of gallons larger than initially reported last month, state officials say.
About 504 barrels of oil or more than 20,000 gallons of the highly polluting substance have been recovered since the line leak occurred July 19, the North Dakota Department of Health said in a press release Friday.
The company, Texas-based Denbury Onshore LLC, first said the equivalent of two barrels of oil had been spilled at a facility in the western town of Belfied. But state investigations found the spillage is considerably larger.
Karl Rockeman, director of the Division of Water Quality, said to the Grand Forks Herald Friday that oil was seeping out of a hillside in multiple locations. The actual size of the spill is still undetermined and current figures may also be inaccurate. “It may be larger than that yet as well,” Rockeman said referring to the most recent estimates.
Misreported leak volumes often happen once companies and officials investigate accidents and discover oil seeped deeper in the ground or waterways. Indeed, revised figures are at times much larger than first reported.
In 2014, for instance, an oil spill in North Dakota was first reported to have caused a loss of 750 barrels of oil, but that figure climbed to about 20,600 barrels once the soil was further investigated.
It is unclear whether latest oil spill has reached the groundwater. The investigation and remediation is ongoing, the state said. The Grand Forks Herald said that spills have been reported at the same Denbury site in 2006, 2010, and 2014. The cause of the most recent spill is listed as a failure of an underground flow line.
Oil transportation largely relies on trains and pipelines. Out of those two, pipelines spill less often but larger quantities than trains, yet train accidents can be deadlier since trains are more likely to explode.
Other Denbury Onshore LLC sites have spilled in North Dakota in recent months. Just in May, pastureland in the northwest had to be excavated after more than 120,000 gallons of oil and drilling wastewater overflowed from a company’s tank.
An earlier version of this story wrongly stated that oil pipelines spill more than trains.