The Metropolitan Council is in talks with a Cedar-Isles-Dean-neighborhood condominium association whose members were pushing for a study of their building before the start of Southwest light rail construction.
In a Feb. 5 letter, Met Council Chair Alene Tchourumoff said the Southwest Light Rail Transit project office was drafting a testing plan to better understand how susceptible the Calhoun-Isles Condos are to vibrations. Testing of the building — a century-old grain elevator converted in the 1980s into a residential tower— is planned for March or April, and an analysis of the findings is expected by late April, Tchourumoff wrote.
State Sen. Scott Dibble and Rep. Frank Hornstein, who both represent the area surrounding the condo building, brought the concerns raised by the Calhoun-Isles Condo Association to a legislative commission in January. Dibble said the Met Council had up to that point given CICA a “stiff arm” in response to its repeated requests for a vibration study.
At that Jan. 24 meeting of the Legislative Commission on Metropolitan Government, CICA presented the findings of an engineering consultant hired to examine their building after residents reported roughly $30,000 in damage from a nearby residential construction project. Lee Petersen, principal engineer of the Itasca Consulting Group, told the commission it was “pretty obvious” the building was “extremely susceptible to vibrations,” and that both light rail construction and future transit operations could exceed acceptable vibration levels.
Petersen presented evidence that the unusual building responded in unexpected ways to vibrations and that Met Council engineers had erred in treating it as a typical reinforced-concrete structure in their reports. He estimated the cost of a study at $100,000. Both Hornstein and Dibble said a pause in the project to rebid the civil construction contract and examine the environmental impact of a crash wall opened a window to complete the study.
“I think there was a pretty strong bipartisan consensus that this was a reasonable request, particularly with the ongoing delays with Southwest,” Hornstein said after the commission meeting.
Also at the commission meeting was Jim Alexander, the Southwest light rail project director, who said he had not had time to read the Itasca report in-depth at that point. But after roughly two years of meeting regularly with the condo association, Alexander said he remained unconvinced of a clear connection between the nearby construction and damage to Calhoun-Isles.
“We just don’t see the correlation,” Alexander said. “It is very unclear for us.”
Alexander noted previous damage to the building was linked to pile driving, while Met Council plans to use the potentially less disruptive hydraulic press-in technique for tunnel construction. The equipment will be tested twice before digging begins, and measurements will be taken during construction to make sure vibrations remain within an acceptable range, he said.
Alexander said Met Council also plans to use “highly resilient fasteners” for rails through the tunnel, which should reduce vibrations once trains begin operating. A series of delays has pushed opening day to 2023.
Calhoun-Isles resident Paul Petzschke said he suspected Met Council was avoiding the study because it could force a different, more expensive tunneling approach — or even a rerouting.
“You could go down a lot of different scenarios,” Petzschke said. “Maybe it kills the project.”