The specter of civil unrest — like the protests that erupted over building the Dakota Access pipeline in 2016 — hung over the fourth day of regulatory hearings on a $2.6 billion proposal by Enbridge to build a new pipeline across northern Minnesota.

Utility regulators spent the day talking about what the least-objectionable route for a replacement for Enbridge's 1960s-vintage Line 3 would be — or whether it should be built at all.

The Minnesota Public Utilities Commission (PUC) is expected to decide Thursday or Friday at the latest whether to grant Enbridge a permit for the project and which route to endorse.

It is one of the mostly highly charged issues before the PUC in many years.

PUC Chairwoman Nancy Lange noted the possibility of unrest if Enbridge's proposal is approved. "One of the things that concern me is permitting something that could cause civic disruption," she said.

Lange acknowledged the weaknesses in the route alternatives. But she also asked Enbridge about construction delays if the PUC chose an alternative route of some sort — one with less opposition.

Christy Brusven, an attorney for Enbridge, said the delay would be more than two years. She also noted that alternative routes also would likely meet opposition. "There are a number of groups that are a 'hard no' on the project, whatever it is," she said.

PUC Commissioner John Tuma, while discussing county law-enforcement costs from any protests, brought up the Dakota Access pipeline in North Dakota. The Standing Rock Sioux Tribe opposed the new pipeline, and thousands of people from across the country joined the tribe in tense protests.

"There is a concern about local governments being overwhelmed by a situation if protests arise over a new Line 3," Tuma said. "I don't want them to be caught flat-footed like in North Dakota. … What happened in North Dakota is not going to happen here as long as I can do anything about it."

Winona LaDuke, who leads the pipeline-opposition group Honor the Earth and has called for protests, told the commission she had "deep concerns" that Tuma was even discussing whether law enforcement had the resources it needs. She told the commission "the only way you do not become North Dakota is to not sell out to a Canadian corporation."

Calgary, Alberta-based Enbridge said the new pipeline is a necessary safety measure. Its current Line 3 can only operate at 51 percent of capacity due to safety concerns, the company said. The new Line 3 would restore the full flow of oil to 760,000 barrels per day.

Environmental groups, some local property owners' associations and several Indian tribes oppose the project, saying a new Line 3 would exacerbate climate change and open a new region of Minnesota lakes, rivers and wild rice waters to degradation from possible oil spills.

The five commissioners haven't yet shown their hand, though two of them indicated Wednesday that continued use of the existing Line 3 — which has corrosion problems — is a worse alternative than Enbridge's planned pipeline and its proposed route.

Not building a new Line 3 "leaves a pipe that we know has integrity issues," said PUC Commissioner Katie Sieben. "When we talk about structural safety, it is always best for policymakers to err on the side of safety."

Under Enbridge's proposal, the new pipeline would follow Line 3's current route to Clearbrook, Minn., then jut south toward Park Rapids before heading east to Enbridge's terminal in Superior, Wis. The stretch from Park Rapids to Superior currently hosts no pipelines.

During the three-year Line 3 regulatory process, several alternative routes to Enbridge's preferred new pipeline have been drawn up. One would run north of Enbridge's existing pipeline corridor, one would run south and two would run on or near the company's current pipeline corridor.

"We think [Enbridge's preferred route] is the worst route because the natural resources on that corridor are unique and many are irreplaceable, and they are difficult to get access to in case of remediation," said Scott Strand, an attorney representing Friends of the Headwaters, which opposes the pipeline.

But the alternatives also have problems. The two that follow Enbridge's current Line 3 route pass through the Leech Lake Band of Ojibwe's reservation, and the band is steadfastly against any new pipeline on its land.

Of the other two main alternatives, one crosses the Chippewa National Forest and the other is significantly longer than Enbridge's proposed pipeline, making it inherently more susceptible to leaks.

Several tribes, as well as the Sierra Club and Honor the Earth, would rather see continued operation of the current Line 3 than the construction of a new pipeline. At most, the current line would only operate for 11 more years, given high maintenance costs and 2029 easement expiration dates on the Leech Lake reservation.

The Leech Lake band wants the current Line 3 shut down and removed from its reservation as soon as possible, opting for Enbridge's new pipeline proposal.

Enbridge has said it would continue to operate the current line if its proposal is rejected, though repairs might cost the company up to $2 billion over the next 15 years. "The existing Line 3 can operate safely, [but] the replacement is a safer alternative," said Eric Swanson, an attorney for Enbridge.

Access to the PUC hearings, which are public, has been an issue this week, as it was last week.

For the final hearings, the PUC staff instituted strict rules on attendance, requiring tickets for the public attendees. Space is limited in the main hearing room. And seats in roughly half of the room are allocated for members of groups officially intervening in the case.

Two pipeline opponents with credentials to be seated as intervenors were denied access and threatened with criminal prosecution, according to a PUC filing by the Sierra Club and the Northern Water Alliance. The PUC has been "arbitrarily" and "inconsistently" enforcing the rules, the filing said.