Key lawmakers say the agency planning the Southwest Corridor light-rail line has agreed "to go back to the drawing board" to resolve a dispute that threatens development of the metro area's most costly transit project.

The lawmakers urged the Metropolitan Council, which oversees the light-rail system, to look for other ways to reroute freight train ­traffic into St. Louis Park or other communities to make room for the light-rail line in a ­narrow corridor of Minneapolis. Angry St. Louis Park residents have staged protests and other actions aimed at fighting ­current reroute options.

The Southwest Corridor light rail is expected to run nearly 16 miles from downtown Minneapolis to Eden Prairie and open in 2018. The Met Council recently postponed decisions on the project after revealing that resolving the freight-rail dispute could increase the cost from $1.25 billion to between $1.58 billion and $1.82 billion.

The Met Council on Tuesday acknowledged ongoing discussions with a freight ­railroad but declined to describe them.

"The purpose is to review everything we've done and to see if there's any stone we … didn't uncover," said Mark Wegner, president of Twin Cities and Western Railroad, whose tracks are involved.

In a recent letter to Met Council Chair Susan Haigh, Rep. Frank Hornstein and Sen. Scott Dibble urged Haigh to conduct "a thorough re-examination of less intrusive freight options in St. Louis Park or other communities."

'Back to the drawing board'

"We certainly hope that your agreement to go back to the drawing board with the freight rail carriers bears fruit," wrote Hornstein and Dibble, DFLers from Minneapolis who chair legislative transportation c­ommittees.

They support Minneapolis residents who want the freight traffic rerouted from the Kenilworth corridor in the city or the LRT hidden in a tunnel in the corridor, an area popular with bikers, canoeists and ­hikers.

But a tunnel could cost as much as $330 million, according to the Met Council, raising doubts about whether there is political support for building it.

And two options considered this summer for rerouting freight to St. Louis Park would include laying rails on berms as high as two stories at a cost of about $200 million.

'Bunch of bad choices'

"Everyone's still kind of stunned that we have a whole bunch of bad choices," Dibble said Tuesday. "We're hoping we can turn back the clock a little bit."

The Met Council offered the tunnel and berm options this spring after rejecting a proposed St. Louis Park reroute that the Twin Cities and Western Railroad called unsafe.

Wegner, in a news release in January criticizing the proposed reroute, referenced "an earlier design of the reroute plan, which had more moderate grade increases and gentler curves."

Hennepin County Commissioner Gail Dorfman now wants the Met Council to re-evaluate that earlier design "to address the safety, noise and vibration concerns."

Dorfman said that the earlier design didn't advance in part because of the cost of acquiring homes to make way for the freight rail line.

"But it's a whole lot cheaper than building a tunnel," she said.

However, Wegner said Tuesday that the earlier design features curves that could pose some of the same safety problems associated with the ­proposal that was rejected.

"I haven't had an engineer looking at it yet," he said. "I have a feeling we're going to be asked to, and at that point we'll have our engineer look at it. But I suspect we're going to have the same problem."

Another idea for rerouting freight involves having Twin Cities and Western freight trains transfer to other railroad tracks west of the Twin Cities and avoid the Kenilworth corridor or St. Louis Park when heading east, Hornstein said.

But Wegner said similar ideas were found unworkable. "These things were looked at two, three years ago," he said.

Pat Doyle • 612-673-4504