TIOGA, N.D. – Two years after North Dakota's largest oil pipeline spill, landowner Patty Jensen measures progress by how large the dirty pile of soil is compared to the clean pile.

Cleanup operations continue around the clock at the site of the Tesoro Logistics pipeline leak that saturated Patty and Steve Jensen's wheat field with 20,600 barrels of oil.

The company, which has spent $42 million on cleanup as of June 30, is about one-third to half done with the process to treat the contaminated soil, said Bill Suess, spill investigations program manager with the North Dakota Department of Health.

While the pile of contaminated soil dwarfs the piles that have been cleaned, Patty Jensen saw progress Friday during one of her frequent visits to the site.

"It's kind of starting to come together," she said.

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Jensen keeps close tabs on the cleanup site, where the motto is "As long as Miss Patty's happy, everyone's happy." She brings the workers homemade pie and they keep the office Keurig coffee maker stocked for her.

"The relationship between Tesoro and their consultants and subcontractors and the landowners is one of the best I've ever dealt with," Suess said. "That goes a long way to make this a smooth-running project."

The company declined to comment on a potential end date for the cleanup, which has become part of the Jensens' lives since Steve discovered the spill while harvesting on Sept. 29, 2013. Both the Jensens and health officials say Tesoro Logistics has been dedicated to restoring the land.

"Up to this point, they have made an effort to get it fixed," Patty Jensen said. "But it's a pretty big mistake."

Cleanup site grows

The oil spill contaminated about 15 acres of cropland, but the cleanup site has grown to about 35 acres to accommodate areas where excavated soil is being stockpiled, Suess estimates.

"It's so huge," Jensen said.

Crews excavate soil nearly 50 feet deep and use technology called a Thermal Desorption Unit to "bake" the hydrocarbons out of the soil.

The Jensens say they have a lot of confidence in the contractor, Nelson Environmental Remediation of Alberta, Canada, which operates the TDU system and carefully separates topsoil from other layers.

"They've done this all over the world," Jensen said. "They know what they're doing."

Co-owner Warren Nelson said the process will restore the land so it's productive for farming.

"It'll go back to as good if not better condition," Nelson said.

The TDU operates 24/7 can clean up to 1,000 tons of contaminated soil per day. Soil samples are then tested by a third party, and so far all samples have come back clean, Nelson said.

The company has two more TDUs on location, but the natural gas supply to the site is only adequate to run one unit, Suess said.

The region has plenty of natural gas - the state flared 20 percent of natural gas produced in July - but the challenge is getting enough gas to the site by pipeline.

"That would drastically cut back the amount of time needed," Suess said.

Tesoro Logistics is routinely evaluating the operation, including the use of additional natural gas, spokeswoman Tina Barbee said.

In addition to the environmental contractors, Tesoro Logistics is paying North Dakota State University soil scientists $300,000 to help restore the land. They'll begin working with test plots during the next growing season.

"There's a fair bit of work to put it back to productivity," said associate professor Tom DeSutter. "One of the things that we always stress is making sure that when the soil is replaced that the compaction is monitored very closely. The actual soil compaction where the roots will reside can have a lot to do with how productive those soils will be."

Lessons the NDSU scientists learn can be applied to restore land contaminated by oil in other areas of the state, DeSutter said.

Fine still pending

The North Dakota Department of Health will fine Tesoro Logistics because of the spill, but the amount has not yet been determined, said Dave Glatt, chief of the Environmental Health Section.

The penalty will take into consideration how quickly the company responded and how thorough the response is, Glatt said.

"Tesoro has been very responsive in getting to the cleanup, even though it's costing them a lot of money," Glatt said. "They've been committed to getting it cleaned up and bringing in more help as needed."

Jensen said she thinks Tesoro Logistics should be required to reimburse the health department for its costs to investigate and oversee the cleanup.

"It's huge when you think of the time they've had to dedicate to that," Jensen said. "Is that the taxpayers' responsibility? The people shouldn't have to pay for that."

The Pipeline and Hazardous Materials Safety Administration regulates the pipeline, but it's unclear if the federal agency plans to seek civil penalties. The agency did not respond to Forum News Service inquiries last week.

The North Dakota Public Service Commission meets with PHMSA representatives Tuesday, the anniversary of the spill, and commissioner Brian Kalk said the Tesoro Logistics spill is one topic he plans to bring up.

Tesoro Logistics said it works closely with PHMSA in regard to the cleanup, as well as strengthening the controls on its pipeline system.

"We have put systems and controls in place to identify and prevent this type of spill in the future," Barbee said.

An independent, third-party report confirmed that the likely cause of the hole in the pipeline was from electrical discharge, consistent with a lightning strike.

The size of the spill - 865,200 gallons - put a spotlight on the need for stronger controls on pipelines to prevent spills and detect leaks sooner.

Since the spill, the Jensens have approved one natural gas pipeline for their land - already criss-crossed with pipelines - but they've said no to other proposed pipelines.

"We have to let the natural gas lines go in, but I have not let a saltwater go in because I don't trust that the regulation is there," Jensen said.

Jensen said she tries to focus on the positives that can come from the spill, even using some excavated boulders and petrified wood in their landscaping. More important to Jensen are the lessons that can be learned to prevent spills.

A representative of another pipeline company once told her: "Every time I see this in the paper, it makes me work harder that it's not us."

Tesoro Logistics pipeline spill near Tioga

Discovered Sept. 29, 2013

Estimated spill: 20,600 barrels of oil

Estimate of recovered oil: 6,000 barrels of oil, or 30 percent

Area contaminated: 15 acres

Overall site of cleanup: 35 acres of farmland

Amount of soil excavated as of mid-September: 449,543 tons

Average amount of soil cleaned each day: Up to 1,000 tons

Cleanup costs as of June 30: $42 million

Sources: Tesoro Logistics, North Dakota Department of Health and Nelson Environmental