GREAT FALLS — A study of environmental effects from a proposed Alberta-Montana power line has been released, opening a 45-day period for public comment.

The Montana Alberta Tie Line, proposed by a subsidiary of Toronto-based Tonbridge Power, would extend 203 miles from Lethbridge, Alberta, to Great Falls.

Developers have said the line and related wind-energy projects could lead to $1 billion in investment. Critics include farmers who would have to work around some of the power apparatus.

‘‘We went out and met with people, and in many areas we are able to adjust the lines this way or that way to reduce impacts to farming,’’ said Tom Ring of the Montana Department of Environmental Quality, which joined the U.S. Department of Energy in preparing the environmental-impact study.

Three possible routes for the line are largely unchanged in that document, Ring said.

It describes a system in which the power line would be supported by a combination of single poles and H-shaped frames. The frames are considered easier for farmers to work around, than are the poles.

The study found the overall annual cost to farmers if they must move equipment around poles would range from $57,000 to $82,000.

Landowners would be offered some compensatory payments and tax breaks and with that factored in, the study found, the annual net effect of the project is positive under all three alternatives.

Examining wind farms, the analysis determined that 480 to 960 birds, including 13 to 18 raptors, could be killed over the span of a year if 400 to 533 wind turbines were erected.

The turbines could also threaten several species of bats, according to the report.

Moving forward with the project requires approval of the Montana environmental agency and the U.S. Department of Energy. In the report, the agencies say they do not have a preferred route.

Montana Alberta Tie Ltd., the Tonbridge Power subsidiary, prefers a route with the stateside portion extending from a new substation south of Cut Bank to a location north of Great Falls.

Click here for more information about the Montana Alberta Tie Line