Metro Considers Tysons Options

Tunneling Might Be More Affordable

The engineer overseeing construction of a subway line in Barcelona is visiting Fairfax County this week to offer advice on whether a planned Metrorail extension through Tysons Corner should be changed dramatically from an aboveground line to a tunnel.

The tunnel idea has been kicked around for several years as Metro, state and local officials mapped the path of a Metrorail extension from Falls Church to Dulles International Airport and beyond. But the idea was rejected as too costly. Under the current plan, less than a half-mile of the four-mile route through Tysons would be underground, with the rest at street level or elevated above the tangle of highways in the area.

Then last fall, Metro officials reconsidered tunneling as they learned more about a technique becoming popular with European transit systems. It's an engineering marvel that can bore through twice as much earth as traditional machines, drilling a hole almost 40 feet wide, instead of the 20 feet achieved during construction of subway tunnels such as Metro's. By excavating the two tunnels needed for the rail line at once, the new system could be more efficient, transit officials said.

It's not known whether the system would save enough time and money to lessen the cost of the project's first phase, estimated to cost $1.8 billion. There are also questions about whether a tunnel would affect a few neighborhoods in McLean.

"It's never too late to analyze a good idea if it's a good idea," said Roger Picard, project executive director for Dulles Transit Partners, a consortium of companies that would design and build the 23-mile rail line. Construction on the first phase, between Falls Church and Wiehle Avenue in Reston, is scheduled to begin in December.

Picard, who managed the $8.2 billion high-speed rail line between London and the English Channel tunnel, said he was skeptical that tunneling would be cheaper even with the more efficient machine because deep excavation is expensive. That's mostly because engineers cannot know all the conditions underground, such as the amount of rock, until they dig. Unforeseen difficulties can increase labor costs and cause delays. Also, tunnels require expensive ventilation that aboveground tracks do not.

Yet sending trains underground would have many advantages, among them less disruption to life in Tysons Corner during years of aboveground construction, less need to purchase land for tracks and stations and no utility lines to move. And an underground train line would avoid the visual impact of elevated lines, which some fear would be an eyesore in Tysons.

"There are some real advantages," said Fairfax County Board of Supervisors Chairman Gerald E. Connolly (D). "Construction can be 24/7. It's weather impervious. Aesthetically it has some advantages."

Metro first approached project officials about tunneling last summer as Virginia was looking for ways to cut the cost of the rail line. Virginia Transportation Secretary Pierce R. Homer asked state project officials to review the potential costs of the new approach.

In recent interviews, officials said they expect to have some estimates by February. The engineer with Dragados, the Spanish firm that has completed about half of a 22-mile subway addition in Barcelona, arrived in Northern Virginia last week and is continuing meetings with the project team this week.

The 4.3-mile tunnel would start at Magarity Road on the road that connects Interstate 66 with the Dulles Toll Road, just west of the West Falls Church station. It would plunge west under Routes 123 and 7, and end near Wolf Trap. That's roughly the same path of the planned line, except that the four-mile tunnel could also dip below some residential streets in the Hunting Ridge and Magarity Mews neighborhoods near McLean.

"They should bring the neighborhoods into the dialogue from the get-go," said Adrienne Whyte, a McLean area civic activist who monitors development in that area. "If this is in the consideration stage, why isn't it being discussed with the affected neighborhoods?"