After six years of review, Enbridge is now poised to begin construction on its controversial $2.6 billion oil pipeline across northern Minnesota.

The Minnesota Pollution Control Agency on Monday approved a construction stormwater permit — the last OK needed for workers to break ground on the Line 3 replacement pipeline that will run from the northwest corner of the state to a terminal in Superior, Wis.

The agency issued waterway permits earlier this month for the project, which is a replacement for Enbridge's existing 50-year-old Line 3 pipeline. The Army Corps of Engineers also recently issued a waterway permit, and the Minnesota Public Utilities Commission gave its final approvals.

"Line 3 is poised to provide significant economic benefits for counties, small businesses, Native American communities, and union members — bringing 4,200 family-sustaining, mostly local construction jobs, millions of dollars in local spending and additional tax revenues at a time when northern Minnesota needs it most," Enbridge said in a statement Monday.

Unions and pipeline advocates cheered the news and said construction will benefit the state's economy especially as the pandemic continues to keep folks out of work.

"Even before the pandemic we were struggling with unemployment in northern Minnesota — now more than ever do we need the jobs," said Joel Smith, the state president of Laborers' International Union of North America. "Thousands of our friends and neighbors across Minnesota look forward to using their construction skills to protect our environment and communities by replacing an existing deteriorating pipeline."

Smith said he expects crews to start working in the coming days; Enbridge did not give a start date.

Some staging work has already begun along the route. Once construction begins in full it is expected to wrap up before the end of 2021.

Environmental groups and Native American bands have said the pipeline — which follows a largely new 340-mile route across Minnesota — will open a new region of pristine waters to the prospect of oil spills, as well as exacerbate climate change by allowing more oil production.

"It's unfortunate that Minnesota is issuing permits for an unnecessary tar sands pipeline during a global pandemic that is particularly hitting hard Native and non-Native communities and fragile health care systems along the route even though the appeals process is still underway," said Honor the Earth Executive Director Winona LaDuke. "This is just reckless and irresponsible government that will have consequences for all sides."

The groups also said the PUC approved a faulty and overly rosy long-term oil-demand forecast submitted by Enbridge. The state Department of Commerce cited Enbridge's oil forecast in its own court appeal of the PUC's approval of Line 3.

Due to its age and condition, the existing Line 3 pipeline is restricted to 380,000 barrels per day, half of its maximum capacity. The new Line 3 will restore that capacity and carry an average of 760,000 barrels per day between Hardisty, Alberta, and the company's Superior oil terminal.

Calgary, Alberta-based Enbridge has said the new pipeline is a critical safety enhancement, an argument that prevailed with state regulators.

Pipeline opponents have raised concerns about having so many workers in small northern Minnesota towns when COVID-19 cases are so high, though Enbridge said it has instituted strict and "industry-leading" coronavirus testing and screening protocols for workers, as well as mask requirements and physical distancing on the work sites and sanitation of equipment.

"Safety is our top priority," the company said.

The Red Lake Band of Chippewa and the White Earth Band of Ojibwe last week asked the PUC to stay its approval of pipeline construction, pending the outcome of a case before the Minnesota Court of Appeals. Environmental groups and some bands have also filed an appeal of the PUC's overall approval of the pipeline.