The Enbridge Line 3 pipeline project continues to be one of new Gov. Tim Walz's most complex political challenges.

Walz's Commerce Department announced in February that it would continue an appeal of the Minnesota Public Utilities Commission approval of the pipeline, an appeal that started under the administration of former Gov. Mark Dayton.

This was a big blow to the construction trades, which would see lots of additional work on the $2.6 billion crude oil pipeline through northern Minnesota.

Perhaps it was no coincidence that a week later Walz proposed a 20-cent-per-gallon gas tax for roads and bridges that also would be plenty of work for the trades, as would his recent pitch for a $1.3 billion public works package.

I asked a DFL operative about Walz's troubles with his old allies in the construction unions: "It was pretty bad with the trades, especially 49ers and [laborers]. I think he was trying to make up for it with the gas tax. But they also went big there to free up [general fund] money for education and [human services] spending. The bonding bill is great too for [the trades] obviously," said the operative.

Kris Fredson of the Laborers District Council of Minnesota and North Dakota sent me a response: "The governor's transportation funding proposal has nothing to do with 'making up' with the [building trades]. His proposal is about fixing our crumbling roads and deficient bridges to ease congestion and improve safety."

The massive overhaul to the aging pipeline would boost its capacity from 370,000 barrels per day to 760,000 barrels per day, sending crude oil from Alberta to Superior, Wis.

The Line 3 project is drawing intense debate, pitting environmentalists and tribes concerned about the dangers of an oil pipeline against trade unions who say the project will bring a much-needed economic boost to a struggling region of Minnesota.

These groups are significant constituencies for Walz, so the politics are fraught and the stakes are high.

Lt. Gov. Peggy Flanagan's recent comments only deepened the mystery around Walz's Enbridge position.

"This issue is incredibly personal to me. I'm a member of the White Earth Nation. And my tribe is part of one of the lawsuits. At no time can I stop seeing this issue through the lens of being an Ojibwe woman," she said.

She continued: "I certainly make myself clear when I have conversations both with the governor and our agencies. But the point is, we need to make sure people feel seen and heard and valued as part of this process. And that is where I am certainly willing to throw down. The governor has done what he can do in this moment by extending this appeal."

Enbridge recently announced the project won't start shipping oil until the second half of 2020, which assumes it gets permitted, which assumes the Commerce Department appeal fails.

J. Patrick Coolican 651-925-5042 Twitter: @jpcoolican