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4 years later, crews completing cleanup of ND's largest oil pipeline spill

Crews use a mobile thermal desorption unit to "bake" oil out of soil that was contaminated by the oil pipeline spill discovered Sept. 29, 2013, near Tioga, N.D. Andeavor, formerly known as Tesoro Logistics, had spent $73 million on cleanup as of February 2017. Amy Dalrymple / Bismarck Tribune 1 / 2
Landowners Steve and Patty Jensen are shown Tuesday, Sept. 26, 2017, in their former wheat field near Tioga, N.D., where an oil pipeline spilled 20,600 barrels four years earlier. Amy Dalrymple / Bismarck Tribune2 / 2

TIOGA, N.D. — Four years after discovering North Dakota's largest oil pipeline spill, Steve and Patty Jensen are looking forward to removing the last contaminated soil from their former wheat field.

Crews are nearly done excavating soil from what remains a massive operation to clean up 20,600 barrels — 865,200 gallons — of Bakken crude that Steve Jensen discovered while harvesting wheat on Sept. 29, 2013.

Patty Jensen, surveying the progress last week, took a photo from the industrial site and hopes to stand in the same spot in two years and photograph a wheat field.

"It's like we're starting to see light at the end of the tunnel," she said.

Andeavor, the pipeline owner formerly known as Tesoro Logistics, plans to continue treating a stockpile of contaminated soil through the winter, said Dallas Burnum, project manager.

Contractors "bake" the oil out of the soil using an environmental remediation technology known as thermal desorption. Two mobile thermal desorption units are on site and crews from Nelson Environmental Remediation of Alberta, Canada, heat the soil around the clock.

Soil samples are tested by a third party and clean soil is returned to the pit, which was excavated in some areas more than 50 feet deep to capture oil that spread.

Burnum said his goal is to return the land to the Jensens next spring, but weather and other factors could affect the progress. Ultimately, it will be up to the North Dakota Department of Health to determine when cleanup is complete.

"It was a very massive amount of work that was put into this," said Dave Glatt, enforcement chief for the Environmental Health Section. "I do think the progress is good. We haven't seen this type of remediation to this extent before."

About 6,000 barrels, or 30 percent of the spilled oil, was recovered. The rest of the light, sweet crude oil seeped into the ground, which in that area contains a lot of permeable sand and gravel that allowed the oil to spread.

"When this occurred, they had no idea that it was going to go this deep," said Bill Suess, spill investigation program manager for the health department. "That's been the biggest challenge of it."

The total area being cleaned up is about 14 acres, but the company has leased 75 acres from the Jensens to store equipment and stockpile clean and treated soils, said Andeavor spokeswoman Destin Singleton.

Contractors have excavated 650,000 cubic yards of soil, according to Singleton, noting that not all of the excavated soil required treatment.

Health department staff are on site regularly to inspect and oversee the cleanup, including Suess who said he aims to be on site every other week.

North Dakota State University soil scientists have test plots on site where they have been experimenting during the past two growing seasons to help return the soil to productive farmland.

"We've learned a lot about soil function after a disturbance and strategies to better improve that soil productivity," said Tom DeSutter, associate professor.

Andeavor has provided $300,000 for the first phase of research, and NDSU is working with the company on a plan for a second phase.

The test plots, which use different soil mixtures, have shown promising results with mixing the thermally treated soil with topsoil, DeSutter said.

"We're in a region where there's not lots of topsoil just laying around available," he said. "Sometimes, we have to think outside the box and make soil, if you will."

The oil spill did not affect drinking water sources, Suess said. Monitoring wells installed on site allow health officials to watch for potential groundwater contamination.

After the cleanup is considered complete, the health department will continue oversight of the monitoring wells for three to five more years, Suess said. That timeframe could be extended if necessary, but the monitoring would stop if conditions have improved.

"That doesn't seem like enough for me," Patty Jensen said.

If contamination is discovered years in the future, Andeavor would be considered responsible for the site forever, Suess said.

The Jensens have a friendly relationship with workers who have been cleaning their farmland for the past four years, with Patty Jensen often bringing homemade pies and the crews ready with hot coffee for the landowners.

But it's been challenging at times, they say.

"There's been times it's mentally draining," Steve Jensen said.

The Jensens say they're afraid to think about what could have happened if the spill had been caused by a company without the resources to follow through. Andeavor has spent at least $73 million so far on cleanup, according to what the company reported in February.

The state health department fined Andeavor $454,000 for the incident.

"For us, it's not so much about the fine as it is how committed they are to follow through with the cleanup," Glatt said.

The Jensens have invited members of the North Dakota Industrial Commission to visit and see the cleanup site firsthand. Gov. Doug Burgum, chairman of the commission that regulates oil and gas development, toured the site in July. The Jensens said they hope Agriculture Commissioner Doug Goehring will visit to see what a challenge it will be to return the land to a productive field.

"Anyone sitting on the Industrial Commission should see it," Patty Jensen said. "They need to see what can happen."

The North Dakota Public Service Commission, which approves oil transmission pipelines, recently met with Andeavor representatives to discuss the spill, but commissioners have not visited the site.

Following the spill, an investigation confirmed that the likely cause was a hole in the pipeline caused by electrical discharge, consistent with a lightning strike. The size of the spill highlighted the importance of technology to prevent spills and detect leaks sooner.

"Through this whole process, hopefully oil companies have learned that leak detection is really invaluable," Patty Jensen said. "I'm sure it pays for itself."