The regional authority that is building the Silver Line for Metro has requested additional tests on a newly constructed rail tunnel through Tysons Corner.
Metropolitan Washington Airports Authority spokesman David Mould said Thursday that surveyors had been asked to determine whether additional settling had occurred in the ground under and around the tunnel.
The tunnel runs from Route 123 to Route 7 and, if the ground has sunk, modifications to the tunnel could be needed to ensure it can safely accommodate trains.
After significant excavation like that undertaken to build the tunnel, settling is common, but when it happens well into or after construction, that can complicate a project.
The test will be conducted Saturday, and the results should be available about a week later, Mould said.
He said they did not know yet whether any needed modifications would add to the cost of the $5.6 billion rail project or delay the first phase of the rail line, which is expected to be completed in December and will run from East Falls Church to Wiehle Avenue.
It isn’t the first time the project has run into snags. The first phase of the rail line is expected to be over budget. There have been troubles with it costing more to move utility lines and put in place Metro safety requirements.
Officials have been monitoring the tunnel for signs of settling since last spring. At the time, surveyors detected some settling, but the movement was less than an inch. Dulles Transit Partners, the project contractor, agreed to continue monitoring. But by August, surveys had detected no more movement.
Exactly what prompted the request for additional testing is not clear.
Metro spokesman Dan Stessel said the transit agency is “not involved with the testing” of the rail cars on the new Silver Line “at this point.”