The Metrorail line and station construction, 26 miles from Washington, began in August 2009 along the north side of Route 123 (Chain Bridge Road) from the Dulles Connector Road to Route 7 in Tyson’s Corner.
A new bridge will carry Silver Line trains 30ft above the Capital Beltway to the airport. The Beltway will also act as a flyover; at its highest point, the structure will reach 65ft above Tyson’s walkways.
Also under construction is an overhead crane/truss which will hoist 25USt blocks of concrete at a time from a truck, to be suspended from the crane. The concrete blocks, which will be held together by tendons, are being made at nearby Dulles Airport, using specialist moulds, thus creating the specific size and shapes needed for each area of the bridge.
The truss, custom built cranes are required to build the first 11.5 miles of the rail line, expected to be running by 2013.
Construction also is taking place on Route 123; workers are building piers to support a separate project set to widen the Beltway for carpool lanes. The bridge has remained open to 12 lanes of traffic throughout the construction work. Therefore, the flyover has been built and installed in stages, by laying concrete slabs between the piers to support the subway tracks.
