The Minnesota Department of Commerce released a 5,000-page study of a 340-mile long proposed oil pipeline across the state Thursday, a major regulatory step in Enbridge Energy's 3-year long quest to open a new oil corridor across northern Minnesota.

The final environmental impact statement of the so-called "Line 3" project does not issue a final decision on whether the pipeline can be built.

Rather it analyzes the environmental and social costs and benefits of approving the project, contrasts several proposed routes if a pipeline is approved, and explores methods of reducing adverse impacts of the project.

Its findings will inform recommendations made by two administrative law judges who will hold hearings on the proposal, and also the final decision on the pipeline due from the state Public Utilities Commission in April 2018.

The report finds that Enbridge's preferred route for a new pipeline affects fewer drinking water sources and cultural resources than its current pipeline, or an alternative route that would avoid northern Minnesota's lake country.

But it would affect more biological areas of importance, as well as key areas for recreation and tourism.

Those are just a few of the trade-offs state regulators will have to balance. And some Minnesotans are likely to feel aggrieved no matter what the ultimate decision is.

Tribal members who submitted comments during the environmental review process, the study notes, "reported that all of the proposed routes, including either keeping the current Line 3 in place or abandoning it, would add to the negative mental, spiritual, and physical health impacts already disproportionately suffered by American Indian populations."

Enbridge built the existing Line 3 in the 1960s, a part of its Mainline system, which consists of 4,100 miles of pipeline that currently ships an estimated 2.4 million barrels of crude oil a day from the oil sands region of Alberta, Canada, across northern Minnesota.

After nearly 50 years of operation, it has corroded and cracked, the report states, necessitating more than 950 excavations in the last 16 years. Since 1990, it's experienced 15 failures that released more than 50 barrels of oil during each incident, including seven in Minnesota.

As a result Enbridge has reduced the pipeline's capacity to 390,000 barrels of oil per day. The new pipeline the company has proposed would boost the amount of oil it transports to 760,000 barrels per day.

The company has also proposed a new route for the line. It would follow the existing pipeline corridor to Clearbrook, Minn., but then it would leave the existing path to cut south toward Park Rapids, before swerving east again to Enbridge's pipeline terminal in Superior, Wis. Tribes, environmental groups and some lawmakers identified several concerns with the draft environmental impact statement, released in May.

They asked for more analysis of tribal and climate change concerns, as well as Enbridge's plan to abandon the existing Line 3 in place if a new line is approved.

The draft report acknowledges that creates potential environmental risks of leaving existing contamination surrounding the pipe in the ground.

But it also identified safety and environmental risks in trying to remove the pipeline, which is only 10 to 15 feet away from other pipelines within the corridor.

This is the first time an environmental impact statement has been conducted for an oil pipeline in Minnesota. It was only ordered by the state Public Utilities Commission after a successful lawsuit filed by citizens' group Friends of the Headwaters.

President Richard Smith said his group had major problems with the draft study of the proposed pipeline in some of the most fragile water resources in the state.

"There has not been time to address those problems in a serious way, so we are pessimistic that this process is going to be informed by the kind of hard look at environmental impacts the law requires," he said.

Business and labor groups have supported Enbridge's plans, which are projected to create around 2,000 local construction jobs if the pipeline moves forward.

Nancy Norr, chair of Jobs for Minnesotans, called the release of the environmental report an important milestone.

"This report does suggest that Enbridge's preferred route for the Line 3 replacement minimizes environmental risks while maintaining a vital link to our safe energy transportation system," she said.