Today in this is why we can’t have nice things: Cracks in concrete structures meant to support the Silver Line tracks at Dulles International Airport have forced crews to halt work on that part of the project.

Speaking to the Metropolitan Washington Airport Authority’s Board of Directors, the executive director of the project, Charles Stark, said that the cracks are concerning because they have grown since they were first noticed, The Washington Post reported. They have placed eight of the 662 girders, so far.

Officials now must determine both what caused the cracks in the structures and if they can be repaired or if they must be replaced. “This is typically an area of the beam that sees little stress during operation when it’s carrying a train,” he said. “But any crack is something of concern.”

Although Stark called the problem “a hiccup,” the project is already 13 months behind schedule, according to the Post.