Large sections of the Silver Spring Transit Center have to be rebuilt because they don’t meet safety standards, prolonging the construction-related traffic snarls that have inconvenienced residents for nearly four years. An engineer discovered that the concrete on the second level of the three-story center — the planned location of 32 bus bays — did not meet the standards of either Metro or the American Concrete Institute, said Montgomery County Department of General Services Director David Dise. He said he has no idea when the project will be completed.

Some of the concrete slabs are not thick enough, and some surfaces are not durable enough, explained Metro spokesman Dan Stessel. Metro will not use the $101 million facility until the error is fixed.