Just nine days after Minneapolis officials approved the Southwest Corridor light-rail line, a group of residents filed suit in federal court seeking to block the controversial $1.65 billion project — at least until more environmental studies are done along a key spur of the transit route.

The lawsuit, filed Monday in U.S. District Court in Minneapolis by the Lakes and Parks Alliance of Minneapolis, names the Federal Transit Administration, the Metropolitan Council and its chairwoman, Susan Haigh, as defendants.

The Alliance charges that the Met Council, the regional agency overseeing the project, and other governmental bodies violated national and state environmental laws when approving the light-rail route through the "environmentally sensitive" Kenilworth corridor that bisects Cedar Lake and Lake of the Isles.

The Southwest line, the largest public transportation project in Minnesota history, will span a 16-mile stretch from downtown Minneapolis to Eden Prairie and is slated to begin service in 2019.

Plans for the Southwest line have already been approved by cities along its route — including Eden Prairie, St. Louis Park, Minnetonka and Hopkins.

But the path along the Kenilworth corridor in Minneapolis has drawn the ire of some area residents.

George Puzak of the Lakes and Parks Alliance of Minneapolis, joined by supporters, held a news conference Monday at the Hennepin County Government Center to announce a lawsuit to block the Southwest light-rail line.

The new route, a compromise brokered in July, calls for hiding light-rail trains in a tunnel south of the channel between the two lakes. Trains would then surface to cross a bridge over the channel and continue at ground level north through the corridor.

But the Alliance claims that new environmental studies are needed because significant changes have been made to the original light-rail plan, and none of the alternatives initially proposed for the area included any tunnels.

"Both state and federal law — not to mention common sense — dictate that public officials have the facts before acting on a project with so much potential for damage — and even disaster," said George Puzak, an Alliance board member, Isles-area resident and former commissioner on the Minneapolis Park and Recreation Board. He spoke at a news conference attended by the media and about 40 supporters at the Hennepin County Government Center Monday afternoon.

Met Council spokeswoman Meredith Vadis declined to comment on pending litigation. Haigh did not respond to phone calls seeking comment.

Vadis noted that the federal government will publish a Supplemental Draft Environmental Impact Statement early next year that will address new environmental concerns related to the Kenilworth corridor and possible ways to ease any problems that may crop up. Public hearings and a public comment period will follow.

The Alliance was formed as a nonprofit organization on July 28, and Puzak said it is funded by private donations from residents in Minneapolis, the suburbs and outstate Minnesota. "We are absolutely for light rail," he said, when asked if the group wants to stop mass transit in the Lake of the Isles area entirely.

The group is asking a federal judge to declare that, by failing to complete a new Environmental Impact Statement, the Met Council has broken state and federal laws, and that approvals rendered by Minneapolis and other municipalities along the line be declared null and void.

But Vadis told the Star Tribune last week that legal action is not uncommon on these types of projects. She also said in August that work on the project will not be halted by a lawsuit, unless ordered by a court.

Frank Douma, a research scholar at the University of Minnesota's Center for Transportation Studies, said large mass-transit projects attract litigation because "there are a lot of interests involved, and you're not going to be able to please all of the people all of the time."

Both the Hiawatha Blue Line and the Central Corridor Green Line attracted various lawsuits, none of which stopped or significantly delayed either project.

"Some people think [litigation] indicates a failing of our system," Douma said. "It's where people end up when they feel they've been wronged. People, literally, get their day in court. But if it's a good case, it could resolve an important issue."