CHEYENNE, Wyo. (AP) — A 25,000-gallon oil spill in the Powder River Basin occurred after a backhoe nicked a 6-inch underground pipeline and, over time, corrosion turned the minor damage into an oil-spewing hole, the U.S. Bureau of Land Management said Tuesday.
It remained unclear how long ago the backhoe damaged the crude oil pipeline owned by Casper-based Belle Fourche Pipeline, and what sort of construction work the backhoe was doing at the time, BLM officials said.
The company's environmental coordinator, Bob Dundas, declined comment when asked if he could provide that information.
"I'm just not going to discuss that," Dundas said.
He also declined to discuss ongoing work to clean up the three-mile stretch of arid gully contaminated by the May 19 spill 45 miles southeast of Buffalo.
Between May 21 and 23, company officials deliberately ignited and burned off the oil in what was deemed a better and more practical option than using vacuum trucks to clean up the mess in the rugged sagebrush country a few miles east of the Powder River.
However, high levels of petroleum compounds called diesel-range organics remained in the soil of Culp Draw weeks later, according to BLM documents obtained by The Associated Press.
"We have determined that additional work will need to be done to ensure that remediation and reclamation of the spill location will be successful," BLM natural resource specialist Dustin Hill told Dundas in a letter dated July 18.
Cleanup following the spill went well and the spill was mostly resolved, Dundas told the AP on July 18.
Additional work in the draw in recent weeks has included tilling the soil and spreading fertilizer to encourage bioremediation of the diesel-range organics, according to BLM spokeswoman Cindy Wertz.
"BLM will continue to work with the company on the remediation," Wertz said by email.
The oil spilled on BLM and state land and it didn't affect private property. The spill stopped a couple miles short of reaching the Powder River, which flows north into Montana.
The BLM released a handful of documents related to the spill and several photos of the burn operation in response to an AP request for information about the cause.
Jill Morrison with the Powder River Basin Resource Council landowner group said the new information about backhoe damage raises more questions.
"There could have been a leak going on beneath the surface for quite a long time. We don't know," she said.