To some, light rail tunnel looks more like a berm

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April 18, 2014 // UPDATED 1:38 pm - April 22, 2014
By: Dylan Thomas
This is the Southwest light rail tunnel design many expected, but parts of one tunnel will actually rise above ground
Image provided by Metropolitan Council
Dylan Thomas
Minneapolis says design is “inconsistent” with Met Council’s previously stated plans

UPDATE: On Friday, several hours after this story was first posted, Metropolitan Council Chair Sue Haigh released a statement indicating the planning documents Southwest light rail staff sent to Minneapolis included the wrong design for tunnels.

"Southwest project staff made an error and submitted incorrect municipal consent plans to the City of Minneapolis this week," Haigh wrote. "I regret this error and I have directed staff to rescind and replace the plans on Monday with the version recommended by the Corridor Management Committee and adopted by the Metropolitan Council. We look forward to working with the City of Minneapolis to advance this project in the coming weeks."

It was not immediately known how the mix-up might impact the timeline for a municipal consent vote in Minneapolis. Met Council previously set a deadline of June 29, but that was contingent on Minneapolis recieving the municipal consent package April 10.

KENWOOD — Opponents of the current design for Southwest light rail are crying foul over plans for a tunnel they say contradict previous statements by the Metropolitan Council.

Minneapolis officials are currently looking over detailed plans for the two shallow tunnels that are intended to carry light rail trains through the narrow Kenilworth Corridor. In the plans, the more northerly of the two tunnels looks to some more like a berm, as it rises as much as 12 feet above grade.

The plans were contained in the municipal consent package sent last week to cities along the light rail corridor after the Met Council voted to approve the scope and budget of the 15.8-mile, nearly $1.7-billion line. Met Council officials have said the project will only move forward if all cities grant their official approval, known as municipal consent.

On Friday, Minneapolis officials said the tunnel design was “not the same” as designs previously shown to city engineers. Asked for a response, project spokesperson Laura Baenen said Met Council planners will “continue discussing the north tunnel elevation with Minneapolis staff.”

The tunnels were previously described by Met Council planners as “cut-and-cover,” meaning crews would first excavate a shallow trench and then cap it. One of those trenches will be shallower than many expected, so that the tunnel roof, while still covered, is not at ground level but above it.

“I was surprised, to say the least,” said Courtney Kiernat of LRT Done Right, a citizen group that rallied against the shallow tunnel proposal. Kiernat, who lives in the Kenwood neighborhood near the Kenilworth Corridor, said the plans amounted to the “bait and switch” many warned was coming if Met Council moved forward with the controversial tunnel plan.

“They’re going to dig somewhat, and then they’re going to use that dirt to cover up the structure,” she said.

Minneapolis has long been on record opposing the tunnel plan or any other design for “co-location” of light rail and freight rail trains in the Kenilworth Corridor. The city wanted freight rail traffic first shifted to St. Louis Park so that light rail trains could run at-grade, but did not prevail against stiff opposition from the suburb and Twin Cities & Western, the railroad that operates in the corridor.

Minneapolis City Attorney Susan Segal released this statement Friday afternoon:

“The design for the north ‘shallow tunnel’ submitted for municipal consent by the Metropolitan Council on April 10, 2014 is not the same as was previously discussed. Under this new design, the LRT trains will travel in an enclosure or berm which is as much as 10–12 feet higher than current ground level. This design is inconsistent with previous representations made by the Metropolitan Council. Neither the Corridor Management Committee (CMC), the City of Minneapolis, nor the public were ever shown a berm design.

“Metropolitan Council staff have indicated that the new design is intended to keep the LRT enclosure above the water table. This is also inconsistent with previous representations. 

“The design for the south tunnel appears to be consistent with previous representations.”

The plans show the floor of the tunnels, for much of their length, will sit below the local water table.

Water infiltration and the tunnels’ potential interaction with the nearby Chain of Lakes had been a source of concern. Those issues were studied in a water resources evaluation released in January and updated in March.

The design of the tunnels is intended to isolate them from groundwater and minimize leakage, but some water may have to be pumped out of the tunnels to keep the tracks dry. Still, the study found no “fatal flaws” in the design.

It wasn’t clear from the Met Council statements if the northern tunnel design was, as Segal stated, an effort to keep at least a portion of the tunnels entirely or mostly above the water table.

Baenen wrote in a statement, "Southwest LRT staff will be working closely with the City of Minneapolis to address any concerns they have with the north shallow tunnel and to ensure that the design represents that which was conveyed in the public municipal consent process."

The tunnel designs are included in this document. [NOTE: On April 22, the linked document was updated to "corrected and re-issued" version.]