Gov. Mark Dayton is asking a federal board to require an environmental study of a railroad track that could send "high hazard" freight trains through Minneapolis and west suburbs, including Crystal, Robbinsdale, Golden Valley and Plymouth.

In a letter Thursday to the acting chair of the Surface Transportation Board, Dayton said he shares cities' concerns about increased train traffic, including oil trains, not typically seen there. Dayton added he wants the state to make a case for the railroad companies to study the environmental impact before going ahead.

BNSF Railway and Canadian Pacific are in talks about constructing the track in Crystal. The Surface Transportation Board would need to approve the plans before construction begins.

The proposed track would connect an eastbound Canadian Pacific mainline and BNSF's southbound Monticello branch. BNSF says the change would shift traffic from the Canadian Pacific line, which sees about 25 trains a day.

Some communities already are taking action to at least slow the proposal. Crystal issued a resolution this week calling on the Surface Transportation Board to require an environmental impact statement before moving forward.

Crystal's city planner John Sutter says a new rail track would halt emergency traffic at major roadways that crisscross the city.

"If they build the connector and start diverting these long freight trains, one to two miles long, from the CP down to BNSF, that means that a single train would close all five at-grade crossings," Sutter said.

Crystal city officials suspect BNSF is trying to avoid an environmental impact statement by buying the land prior to submitting plans to the federal board. City officials believe the feds may be less inclined to require the review if the railroad owns the land where the connecting track is supposed to go.

BNSF spokeswoman Amy McBeth said the company is not seeking an exemption. She noted the federal government requires an environmental review, but the Surface Transportation Board recognizes construction of a connector track as "routine and on a smaller scale than construction of a main line."

McBeth said the goal of the project is to use an underutilized railroad track by allowing CP trains to cross over to BNSF lines.

Map of proposed track from the city of Crystal

Editor's note (Feb. 20, 2015): This story has been updated to more accurately characterize the nature of BNSF and Canadian Pacific's talks.