Condominium residents along the planned Southwest Corridor light-rail route in Minneapolis want assurances that a transit tunnel won’t hurt their buildings.

The residents of 143 units along the future light-rail route south of Cedar Lake Parkway say the trains will run through a tunnel on rails 12 feet from the foundations of their condos and parking structure.

“We have received no assurance that operation of 200 trains per day … will not materially undermine their integrity and safety,” read a letter this week from a lawyer for the Calhoun-Isles Condominium Association to Minneapolis Mayor Betsy Hodges and the City Council. “No one knows what all of the effects will be, but it is certain that they will be significant and harmful.

“We respectfully request that you supply us with assurance that these concerns will be accounted for,” the letter continued.

The condo association prefers the tunnel to having light-rail trains at ground level alongside freight trains near their buildings. In March it urged Hodges to drop efforts to reroute the freight so the light-rail trains could run at ground level, and instead focus on ways to lessen the negative effects on the buildings.

Nancy Green, a member of the condo association active on Southwest issues, said Wednesday the group isn’t backing away from the tunnel but is seeking assurances that potential noise, vibration and damage to the building will be thoroughly studied.

“We’d like as much support as we can,” Green said.

The letter was sent this week as Minneapolis officials negotiate behind closed doors with Metropolitan Council members seeking the city’s consent of Southwest light-rail plans, which include two tunnels in the Kenilworth corridor. Green said she hoped the city would represent the condo concerns during the talks, which include a retired federal judge acting as mediator. “We’re saying, ‘Look at the very serious concerns and conditions that we have.’ ”

The letter said condo residents worry that “construction of the tunnel, and the operation of the trains, will render their homes uninhabitable.”

Met Council engineers have been testing the ground near the condos where the tunnel would be dug.

Agency spokeswoman Laura Baenen said, “We believe the condos will remain habitable with Southwest LRT. We have been meeting with the condo association to discuss the project office’s studies. We will continue to coordinate with them to conduct further field evaluation and engineering study on the design and construction of the shallow tunnels.”

The condo association also worries that the tests won’t be completed until after July 14, the deadline for the city to vote on approving or rejecting the Southwest plan.