The Minnesota Pollution Control Agency has approved draft permits for the construction of Enbridge’s controversial Line 3 oil pipeline project, triggering a public comment period.

The MPCA permits are among the key approvals that Calgary, Alberta-based Enbridge must get before starting to build a $2.6 billion, 340-mile pipeline that would ferry Canadian oil across northern Minnesota to its terminal in Superior, Wis.

Perhaps the most critical MPCA permit is a “401” certification, which deals with water-quality issues that arise with pipeline construction. “The MPCA proposes to certify the project and has preliminarily determined that the project as certified will satisfy the antidegradation standards” in Minnesota law, the agency said.

However, the deadline for final approval of the 401 permit isn’t until Aug. 15., meaning that if the MPCA needs until then for its decision, Enbridge couldn’t start building until well into the 2020 construction season.

Enbridge, in a statement Thursday, said the PCA draft permits are ”a significant milestone and a positive step forward.”

The MPCA will initiate a 30-day public comment period on Monday. The MPCA plans to conduct three public meetings on the draft water-quality permits: on March 17 at the Sanford Center in Bemidji; on March 18 at Timberlake Lodge Hotel in Grand Rapids; and on April 1 at the Shooting Star Casino in Mahnomen.

Given the intense interest in the Line 3 project, “we are trying to be very available and do as much public engagement as possible,” Katrina Kessler, assistant MPCA commissioner, said at a news conference Thursday.

The Minnesota Public Utilities Commission (PUC), by a vote of 3-1, earlier this month reapproved the $2.6 billion pipeline, which would replace Enbridge’s aging Line 3. The PUC originally approved the pipeline in June 2018, but court challenges forced the commission to redo its vote.

The PUC is the primary regulator of oil pipelines in Minnesota, including determining risk of oil-spill hazards — in water and on land — of pipelines once they are in operation.

But before Enbridge can begin construction, it must receive more technical permits from MPCA, the Minnesota Department of Natural Resources and the U.S. Army Corps of Engineers. The federal permit from the Corps is also a water quality permit connected to pipeline construction.

The MPCA’s 401 review goes in tandem with the Army Corps’ “404” review. The state’s 401 certification must be done by Aug. 15, PCA officials said. If it’s not, the Army Corps can waive the requirement for the state’s water-quality review and go ahead and issue its 404 certification.

The water-quality permits are necessary as the new pipeline would cross many waterways, and construction would affect wetlands.

Enbridge has declined to say when it intends to start construction — assuming it gets the remaining permits — but it’s likely that the company would get moving as soon as it can this spring.

The MPCA determined there’s “a reasonable assurance that the [construction] will be conducted in a manner that will not violate applicable water quality standards,” provided Enbridge complies with several environmental protection conditions, the draft permit said.

The new pipeline would replace Enbridge’s 1960s-vintage Line 3, which is corroding and operating at only 51% capacity. The new Line 3 would be a significant safety improvement, Enbridge and its supporters said; it would also restore the full oil flow, boosting the company’s earnings.

Environmental groups and some Ojibwe bands that have strongly opposed the pipeline said it will exacerbate climate change and open a new region of Minnesota’s lakes, rivers and wild-rice waters to degradation from oil spills.