The proposed high-speed rail line between Duluth and the Twin Cities inched one step closer to possible construction Monday.

The Federal Railroad Administration has released the environmental assessment for the proposed Northern Lights Express. It's now open for public comment for a month. The rail line would cost an estimated $700 million to build for trains capable of 110 mph.

Completing the environmental study is a big milestone for the project, said Bob Manzoline, executive director of the St. Louis and Lake Counties Regional Rail Authority.

"It allows us to then proceed, if everything's approved, proceed with designing the project," Manzoline said.

Next steps include the preliminary engineering, a two-year process that has already been allocated $8 million in state and federal money.

Annual operating costs of the rail line is expected to be $30 million, which Manzoline hopes will be covered largely by fares.

"We're hoping that the ridership will show a positive cost benefit, meaning it will pay for itself," Manzoline said.

The project is a partnership between several cities and counties along the route. But last year Anoka County pulled out of the alliance over concerns that taxpayers might be stuck subsidizing the rail line after construction is finished.