Cleanup crews have so far removed an estimated 1,435 tons of soil that was tainted by an oil spill discovered on the Fort Peck Reservation on April 27.
That's more than 50 large dump trucks full, and there's still more contaminated soil to be scraped up and hauled away.
The soil is being transported to a disposal facility near Glendive, Oaks Disposal Services, said Joyel Dhieux, federal on-scene coordinator for the Environmental Protection Agency. The agency is overseeing the cleanup for the reservation.
The well had been shut down and was last inspected in December. It’s believed that the wellhead froze and cracked in what was a brutally cold winter in the region. The crack leaked an estimated 90,000 barrels of brine with 600 barrels of crude oil from an Anadarko Minerals Inc. well in Valley County. The spill was discovered by a rancher flying his plane over the remote area.
The leaked mixture flowed downhill for about a third of a mile and into a stock pond.
"On May 7, AMI received approval to proceed with excavation of the oil and brine contaminated soils along the drainage from the well pad to the stock pond," according to the Environmental Protection Agency's website. "Based on an initial assessment, three to six inches of soil will be removed along the drainage. The excavation will be deeper, up to twelve inches, in the area adjacent to the well pad. The oil and brine emulsion concentrated into a pool of fluid adjacent to the well pad before discharging into the drainage."
Crews are removing oil from the shoreline of the stock pond using "high volume, low pressure flushing and raking activities," EPA said. "Flushing and oil removal activities are expected to be completed by May 18."
The EPA does not yet have a cost estimate of the damage, said Dhieux, and "Anadarko Minerals is still evaluating options for the cleanup of brine in the stock pond." Anadarko is required to pay for the cleanup costs.
There are no known effects to downstream water users from the spill, according to EPA’s website. Water and soil samples were collected for analysis.
Anadarko Minerals Inc. is an Oklahoma oil and gas exploration company. The spill occurred in a remote area about eight miles west of the small community of Lustre.
The well site was on top of a hill that’s located south of the Lustre Grain Road and just west of Porcupine Creek, a tributary to the Missouri River. The oil-brine mixture flowed downhill blackening the surrounding vegetation before entering a stock pond, which had about 3 inches of oil atop the water. Fencing has been erected around the spill, and cattle were removed.
“This isn’t going to be a short-term project,” said Shane Findley, supervisory mineral resource specialist for the BLM in Miles City, told the Gazette in an earlier story. “I’m guessing it will take more than a month and require long-term monitoring.”
A 2013 online pamphlet touts the Fort Peck Reservation to oil and gas companies. The handout notes: “Elimination of the dual production tax, a tax holiday, and joint venture opportunities make Fort Peck the place to be!”
Oil exploration is nothing new to the reservation, which is home to the Sioux and Assiniboine tribes. The pamphlet noted: “Oil was first discovered on the Fort Peck Indian Reservation in 1951 by Murphy Oil. That well opened the East Poplar Oil Field on the Poplar Dome. The unitized field has produced 50 million barrels of crude, ranking it in the top 10 largest producers in Montana.”
The western part of the reservation, where the spill occurred, was first developed in the 1980s. As of 2013 the pamphlet reported the Lustre Field had produced 7 million barrels of oil from approximately 50 wells.
Clean water is a precious commodity on the reservation. A 2014 study by the U.S. Geological Survey found that oil exploration in the 1950s contributed to groundwater contamination near Poplar spreading across 17.9 square miles.
Test wells showed the aquifer was being contaminated by brine, which is almost 10 times saltier than the ocean. A 1997 USGS study had identified benzene, a common component of crude oil, in the groundwater. Long-term exposure to benzene can cause cancer and other health problems. A 1990 study identified high levels of nitrates in the water.
The brine plume had seeped southwest to Poplar, the Poplar River and the Missouri River, along the way contaminating 100 wells that serve about 3,000 people.
The groundwater contamination prompted the community of Poplar to seek a new source of water for its 2,900 residents, as well as the rest of the reservation. The portion of the Fort Peck-Dry Prairie Regional Water System that serves Poplar was finished in 2012.