The Minnesota Historical Society and two Dakota bands have consented to a wind farm near the Jeffers Petroglyphs after the developer moved its turbines farther away from the ancient and sacred site.

The Big Bend project near Comfrey would be one of the state's largest wind farms, and it would be paired with a big solar array — a unique arrangement for renewable energy developments. The historical society and the the Upper and Lower Sioux Indian communities objected to the original plan, saying nearby wind turbines would diminish the integrity of the petroglyphs.

In June, state utility regulators who must approve the project made it clear they weren't satisfied with Big Bend's plans to locate turbines as close as 5.2 miles from the petroglyphs. The historical society and the Sioux bands wanted at least an 8-mile buffer.

Apex Clean Energy, Big Bend's developer, revised the project so that all but two of the 50-plus turbines would be at least 7 miles from the petroglyphs. The remaining two would be be 6.5 to 7 miles away. Apex, the tribes and the historical society signed a settlement agreement earlier this month.

"It is not perfect from our point of view, and it is not perfect from their point of view, but that is a sign of good negotiation," said Robert Larsen, council president of the Lower Sioux Indian Community.

Kevin Maijala, the historical society's senior director of learning initiatives, said that computer-generated visuals of Apex's latest turbine proposal showed "a reasonable compromise. There is still some impact, but it is minimal."

The turbines will be visible from the petroglyphs, a collection of about 5,000 rock carvings listed on the National Register of Historic Places. The carvings date back 7,000 years and are considered sacred to several tribal nations, including the Dakota, Cheyenne, Arapaho and Ojibwe.

The settlement should obviate the need for a "contested case" over the petroglyphs issue, which would require more steps in the regulatory process, delaying the wind project by several months.

The Minnesota Public Utilities Commission (PUC), which still must approve the settlement, earlier this year ordered the contested case — which includes a proceeding before an administrative law judge.

Commissioner Joe Sullivan said at a June meeting he was "deeply concerned" about opposition to the Big Bend project. "I will not support wind turbines 5 miles from the petroglyph site."

Other commissioners echoed his concern.

"That was an impetus" for the compromise agreement, said Dylan Ikkala, Big Bend's project director. "There was a clear a direction from the PUC."

The petroglyphs issue was prickly enough for the PUC to schedule a rare field trip to the site. Sullivan and Commissioner Matt Schuerger went Monday.

A pounding rain cut short their tour, but not before Chuck Broste, a historical society archaeologist, explained the petroglyphs' importance.

"They are trying to tell us something," he said gesturing toward ancient depictions of tools, weapons, stick-figured people and lots of animals — buffalo, birds, deer, turtles. Some images are of spirits.

The petroglyphs are carved into a 23-mile outcropping of quartzite, a hard rock, maroonish in color. The carvings sit on 160 acres, with the largest collection in a rectangle of 300 feet by 50 feet. The historical society owns the site, which is open to the public.

Broste explained that state archaeologists have increasingly worked with tribal elders over the past two decades to interpret the carvings. "It's a different kind of perspective that leads you to ask different questions," he said.

"In the world of the elders, this is place is like a university, a place of knowledge," he said. "It is a teaching space, and it is a sacred space."

The historical society keeps the sites' gates open at all times, so that Native Americans have unimpeded access for spiritual ceremonies.

"It is a very personal spiritual thing when you come here for a ceremony," Larsen said. Ceremony timing varies, and details are not shared openly, he said. "It's not like you put it up on Facebook."

Larsen said the petroglyphs have always been a sacred space for the Dakota people. "But this particular area isn't just us," he added. "We happen to be located at this point since contact [by white people]."

A key issue posed by the Big Bend wind farm is its intrusion into tribal cultural and spiritual practices. For example, a "vision-quest" — hanbdeceya in Dakota — ceremony is a solitary practice involving three or four days of fasting.

"That is your time to talk and listen to the creator, and man-made structures can get in the way," Larsen said. "They can make it more difficult."

Apex's original plans for the wind farm called for some turbines to be only 2 miles away from the Jeffers Petroglyphs — a nonstarter for the Dakota and the historical society. So, last year Apex proposed to plant its turbines a minimum of 5.2 miles away, and to cut their number from 64 to 56.

But to maintain the wind farm's total production capacity, Apex swapped in bigger turbines. At a height of 655 feet, they will be 85 feet taller than what was in the original plans — and considerably higher than any existing wind turbines in Minnesota.

With Apex's 2020 plan, both the proximity and the height of the turbines became a problem. Under the settlement, the height of the turbines would remain the same, though the number cut back to 52.

Apex says the more powerful turbines will still allow Big Bend to produce up to 300 megawatts of electricity, making it one of the largest wind farms in Minnesota. Big Bend is scheduled to go online by the end of 2023.