Concrete issues discovered in Silver Line extension project

HERNDON, Va. - There is concern over concrete panels installed in the $2.6 billion Silver Line project that will extend Metrorail service to Dulles International Airport.

The Metropolitan Washington Airports Authority (MWAA), which is in charge of the project, said the agency and the general contractor discovered three issues with the concrete paneling when they were conducting quality control tests:

- Some of the panels were poured with a concrete mix that had too much water, which makes it more susceptible to moisture in the future.
- Some of the panels also did not have enough microscopic air bubbles to allow the water to expand and contract as it freezes and thaws, which could lead to cracking after several years.
- In some panels, the steel inside is too close to the edge, leaving it susceptible to rusting.

"The contractor did non-destructive testing of over 1,700 panels and found that only 60 needed to be replaced," said Charles Stark, senior vice president of the Dulles Corridor Metrorail Project. "These are panels that are already in the stations so they need to be taken out of the stations and new panels put in."

Stark said 31 panels have already been replaced. In addition to those concrete panel replacements, the general contractor on the project, Capital Rail Constructors (on behalf of supplier Universal Concrete Products), will have to coat all 1,750 concrete panels with what is known as Silane every 10 years to seal them away from moisture. They will incur the cost of that, but Stark said it will not set the completion date of the project back.

Stark also told FOX 5 the issues found with the concrete slabs will not affect safety or the viability of the structure, but rather the longevity of the concrete in relation to water damage and rusting.

Five stations along the Silver Line have the affected slabs that need to be replaced. The future Dulles Airport station is not one of them.