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Dulles Metrorail Extension

An 11.7-mile extension of Washington, D.C.'s Metrorail transit system

A Bechtel joint venture is designing and building Phase 1 of a 23-mile extension of the Metrorail Line for the Metropolitan Washington Airports Authority. The extension—one of the largest construction projects in the United States—will bring rail service to fast-growing areas of Northern Virginia and provide a one-seat ride from Dulles International Airport to downtown Washington, D.C.

In the summer of 2010, work began on one of the key elements of the 11.7-mile first phase—a 6-mile section of elevated track that will carry Metrorail trains above the Capital Beltway and over Tysons Corner at heights up to 65 feet. Construction will require an enormous overhead crane that has been custom-built to lift elevated segments into place between huge piers along the line. The yellow crane, weighing 366 tons, will stretch across 12 lanes of traffic and move by remote control from one segment to the next.

In addition to the elevated track, the project features a 2,400-foot underground tunnel that will connect two Metro stations in Tysons Corner. Tunnel construction began in October 2009, marking the project's first major milestone.

Work also is beginning on new stations for the line. There will be of 11 them—five in the first phase of construction, and six in the second. All the stations will have pedestrian bridges, escalators, and elevators.

The project will extend service from the existing Orange Line at the East Falls Church station in Fairfax County, Virginia, to Route 772 in Loudoun County. The corridor encompasses Tysons Corner and the Reston Herndon area, the state's top employment regions. The new line also will offer direct access to the existing Metro system, enabling passengers to ride into downtown Washington without changing trains.

t's an overhead crane called a truss, custom-built to hoist each of the rail line's elevated segments into place between the giant piers along the line's path and to propel itself by remote control from one stretch to the next. The truss weighs 366 tons and stretches about 360 feet, but it takes up less space than the multiple ground-based cranes and trucks used to build standard girder or beam bridges with 100-foot-long decks.