New tunnel option for light rail

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March 12, 2014 // UPDATED 12:43 pm - March 26, 2014
By: Dylan Thomas
A frozen Kenilworth Channel in December. Light rail planners are discussing options for sending trains over or under the water.
File photo
Dylan Thomas
Urged on by the Park Board, planners develop “hybrid” tunnel concept

As the stalemate in the Southwest Light Rail Transit debate drags on toward decision day, project planners have surfaced a twist on the tunnels proposed for the Kenilworth Corridor.

A hybrid tunnel design takes a something from each of two previous tunnel proposals — one shallow and one deep — and seeks a middle ground in both design and cost. Even so, it may not appeal to the Minneapolis City Council, which earlier this month passed a resolution rejecting the shallow-tunnel plan pitched by Metropolitan Council planners.

After the meeting, Mayor Betsy Hodges released a statement expressing surprise that a new tunnel option had surfaced so late in the planning process, adding that “Met Council originally told us this was impossible.”

“We appreciate the Met Council’s responsiveness to the request from the Park Board,” Hodges continued. “However, anything that may harm our lakes needs thorough analysis, which, according to the law, the Met Council must provide.”

Minneapolis leaders would prefer to see a stretch of Twin Cities & Western freight rail track moved from the Kenilworth Corridor to St. Louis Park, so that a future light rail line can run at-grade. Both the railroad and St. Louis Park have rejected that option, and neither appears close to conceding.

At the March 12 meeting of the project’s Corridor Management Committee, local elected officials and agency representatives heard testimony from more than one dozen TC&W customers. Representing grain elevators, farmer cooperatives and other businesses that rely on freight rail to ship and receive goods, they warned of the economic consequences of the reroute, which they said would be less efficient and more costly to operate.

Scott Blumhoeffer, vice president of Heartland Corn Products, said all of the ethanol produced at the company’s Winthrop facility is shipped via rail and warned of the potential ripple effects of a reroute on its 900 member-farmers and their communities.

“What we do has a large impact on our region,” Blumhoeffer said.

In St. Louis Park, safety and the taking of private property are two concerns often raised by residents who object to the reroute. That has frustrated reroute supporters, who say the tracks through the suburb will be designed to national safety standards.

Met Council planners developed their deep-shallow hybrid tunnel proposal in response to a Feb. 5 Minneapolis Park and Recreation Board resolution. The resolution asked planners to consider a tunnel beneath the Kenilworth Channel, a waterway that cuts across the Kenilworth Corridor and ties Cedar Lake to Lake of the Isles.

A deep-bore tunnel would also have buried light rail tracks beneath the channel, but the option was essentially taken off the table last year. It would have added at least $330 million to project costs, a figure that hasn’t since been updated.

In March, planners’ latest estimates put the cost of shallow tunnels at $240 million–$260 million, roughly the same as the most likely freight reroute option.

The design calls for two tunnels dug just below the surface of the Kenilworth Corridor, stretching about 5,800 feet in total. Trains would surface for about 1,100 feet in the middle to cross the Kenilworth Channel on a bridge.

By comparison, the hybrid tunnel would run 25 feet–30 feet below the surface and then dive to twice that depth to pass beneath the channel. But it would be constructed in a cut-and-cover process, like the shallow tunnel, and wouldn’t require an expensive tunnel-boring machine.

Planners developed hybrid tunnel plans of two different lengths, one running the same distance as the shallow tunnels and another surfacing just north of the channel. The latter option would allow for a 21st Street Station in the Kenwood neighborhood, a stop eliminated in other plans.

Depending on length, the hybrid tunnel would cost $40 million–$80 million more than a shallow tunnel. Either hybrid plan would add a year to the project, meaning light rail trains wouldn’t run until at least 2019.

Total costs for the 14.5-mile extension of the Green Line to Eden Prairie are pegged at $1.55 billion.

The Corridor Management Committee is expected to vote April 2 on a preferred alternative. The Met Council vote to approve the project’s scope and budget would follow on April 9.

The Met Council plans to seek municipal consent from each of the five cities on the planned transit line, but that process isn’t legally binding. The project could move ahead even over the objections of either Minneapolis or St. Louis Park.