DULUTH - Along the St. Louis River not far from the site of the 1826 Fond du Lac Treaty signing, a group of Native Americans spent months sifting masses of dirt by hand in search of remains of their ancestors.

The Minnesota Department of Transportation in 2017 disturbed sacred Native American burial grounds when it began its Mission Creek project along Highway 23 in westernmost Duluth without first consulting the Fond du Lac Band of Lake Superior Chippewa. It wasn't the first time the burial grounds were desecrated. In 1869, railroad construction unearthed bodies at Mission Creek, and the initial construction of Highway 23 disturbed the grounds in 1937.

This time, the workers hired to rectify the wrong - many who are Fond du Lac members or descendants - say they've suffered another injustice: poor air quality inside of their MnDOT-built winter workspace that led to fatigue, drowsiness, nausea and difficulty focusing. They also say the state agency failed to address their concerns, an allegation that MnDOT disputes.

Such conditions are tough for most workers, crew and Fond du Lac member Matthew Northrup said, but it's worse when the job is the painstakingly detailed recovery of artifacts and human bones.

"Everything we touch, everything we do here, is done out of respect," he said. "What MnDOT has done to us, is totally disrespectful."

'Dramatic effects'

When MnDOT learned it had disturbed the cemetery, it halted work and hired an archaeology firm overseen by the Minnesota Indian Affairs Council and the Office of the State Archaeologist. The firm hired and trained many Fond du Lac members to help determine the expanse of the burial grounds, and find and catalogue remains and artifacts. They worked through the winter inside a prefabricated building. That's when people began noticing unusual health issues.

Archaeology technician Andrew Wise recalls nodding off while screening dirt for bones, shaking himself awake. Diagnosed with multiple sclerosis at a young age, he feared the unexplained fatigue indicated a turn for the worse.

"It was stressful," he said. "This is work that requires no less than your full attention. You are trying to recover your ancestors' remains. ... I was not given a chance to do my best work."

The simple task of organizing photos of the site into folders grew from a 15-minute job to an hour for Kate Ratkovich, whose charge was to create charcoal drawings of the found artifacts, which were too sacred to photograph.

Northrup had suicidal thoughts while working, he said, and eventually brought a cot to the site to rest when he consistently fell asleep while sifting.

Lisa Lawrence-Northrup had unexplained high blood pressure during the time she worked in the building, according to several readings.

"Sometimes I would come home from work and sleep for three hours," she said.

Minneapolis geophysicist Dave Maki mapped out the burial site. He said he's employed several of the crew members on field projects for years, and didn't know them to complain about illness even under the most grueling conditions.

"In retrospect, it was pretty dramatic," he said, of the times he witnessed workers falling asleep. "And (air quality) information (from MnDOT) was withheld. Most of the people affected ... were from the descendant community. They were hired to recover the remains of their ancestors and treated really poorly through the whole process."

Air quality concerns

As part of a routine inspection, air quality was tested by a MnDOT industrial hygienist on a late January morning during a 30-minute period with about half the crew present. According to the report, levels of carbon monoxide, carbon dioxide and dust were below the state's Occupational Safety and Health Administration's limits. Carbon dioxide, however, exceeded best practice levels three times over.

While regulations allow up to an averaged-over-eight hours exposure of 5,000 parts per million, best practice says not to exceed outdoor levels by 700 ppm. Outdoor levels were 415 ppm at the time of testing, while the indoor carbon dioxide reading was 3,122 ppm.

The industrial hygienist recommended in his report that the building's ventilation system be evaluated, and efforts made to decrease carbon dioxide levels in the building.

The contractor and principal investigator, Sigrid Arnott, of the Minneapolis-based archaeological firm Sigrid Arnott Consulting, wrote in a letter to MnDOT obtained by the News Tribune that those recommendations were disregarded.

"Since MnDOT ignored the industrial hygienist's recommendation to do a full assessment that would have measured the (carbon dioxide) levels over longer periods under different conditions, we all have lost the opportunity to know what levels the burial recovery team was exposed to," Arnott wrote, noting several of her workers had health concerns or medications potentially exacerbated by high levels of carbon dioxide.

Arnott alleges the building's manual operation ventilation system - a single exhaust fan - didn't mesh with the heating system and that workers received inadequate training in its use. She repeatedly asked for guidance - requests that went unheeded, she said.

When the fan was switched on often, it brought in cold air. The cold air kicked on the indoor open-flame propane heaters and ate up oxygen, Ratkovich said, in a "poorly designed system. ... It's part of a pattern of disregard to the crew and the work."

Arnott, who said MnDOT officials were rarely at the site during the winter months, wrote that repeated attempts to obtain the air quality report were ignored until months after the testing, when she filed a public records request.

MnDOT sees the situation differently.

Arnott was verbally given the air quality results by the industrial hygienist following the test, said Duane Hill, a district engineer for MnDOT and a spokesman for the project.

The hygienist explained then how to mitigate the air quality issue by using the ventilation system, Hill said, a claim that Arnott disputes. She said she showed the industrial hygienist how the fan operated, not the other way around.

MnDOT's stance is the building - considered a heated garage - was safe to work in, Hill said, and no further testing was required based on initial results.

"I know there are a ton of negative feelings about this," Hill said, starting with the reason the workers are there. "I know they feel MnDOT didn't support them very well. Our perspective is their employer didn't support them very well," by not sharing the results that January morning.

If a carbon dioxide number was mentioned that January morning, Arnott said, it was "casually, and I didn't have a framework to interpret it. I was told there would be a follow-up conversation and perhaps additional testing."

Neither happened, she said.

"My contract stated that MnDOT was responsible for providing a safe place for us to work," she said, noting other OSHA safety issues related to the propane tanks. "I did not have the expertise to manage air quality."

Arnott wasn't provided the report until she requested it in April via the state open records law because "there was confusion among the different staff involved about who should provide the information," Hill said.

Arnott provided an email that shows MnDOT officials were debating in February whether the report was public information. It is.

MnDOT removed the building doors in April. The contract Arnott's firm had with MnDOT was terminated this spring, and Hamline University has taken over the recovery project. Hill says the contract was ended without cause.

Carbon dioxide

Carbon dioxide poisoning is uncommon, said Katie Schofield, an associate professor with the University of Minnesota Duluth who teaches in the graduate environmental health and safety program.

In mass amounts - far higher than levels reported inside the MnDOT building - it can be life-threatening, she said, because it displaces oxygen. Levels above best practice, while not necessarily dangerous, she said, can cause fatigue and difficulty concentrating. People with underlying health conditions might be more at risk. And while the carbon monoxide level was low during the testing period, chronic exposure to lower levels can be more dangerous than carbon dioxide exposure at higher levels, she said, because of how poisonous it is. Testing for these gases is typically done throughout the day to give a time-weighted average.

Workers inside the building may have been affected by something else entirely, said Dr. George Trachte, interim department chairman of biomedical sciences at the Duluth campus of the University of Minnesota Medical School.

"I'm not disputing that something made the workers sick, but the levels of carbon dioxide are unlikely to have caused major changes physiologically," he said.

'Communication was an issue'

Hamline will hire more people to complete the remaining work at a faster rate, beginning this month, Hill said. The recovery workers could reapply for their jobs, and many were rehired, he said, noting progress to this point "has been outstanding."

"We went from a state of emergency where human remains were scattered on the surface of the soil, to a point where things have stabilized," he said, but work needs to speed up to be respectful to the Fond du Lac Band and to the neighborhood the project lies in.

About 20 percent of the burial grounds are now processed, and MnDOT hopes to finish by winter. The building will be used again, and the ventilation system adjusted, Hill said.

"Communication was an issue and we should have done better," Hill said. "But it was a safe building from our perspective and we were quite surprised to hear people thought they had health issues."

He said MnDOT didn't have a chance to build relationships with the crew, because "the work was so culturally sensitive, we weren't supposed to be there. This was their project."

Arnott said MnDOT and other contractors were asked to knock on the door before entering so sensitive materials could be covered first, but they were welcome to come and go.

Going forward, Hill said, MnDOT will embed an employee with recovery workers to improve communication.

The chairman of the Fond du Lac Band, Kevin Dupuis, didn't return messages seeking comment.

Arnott said she hopes for an outside investigation so the issue isn't repeated, and an apology to the burial recovery team.

The biggest problem, Northrup said, is "a bunch of non-natives trying to dictate culturally how natives are supposed to feel."

What the crew sees as disregard for its concerns is an added toll on top of an already difficult job, he said.

"You uncover a bone from a child. Or you uncover a grave that just barely got touched by the bulldozer. And we cover it back up. It is so emotional," Northrup said.