Rail Route In Tysons An Uphill Challenge
Wednesday, July 27, 2005
Most people barely notice the hill that Tysons Corner is built on, even though, at about 515 feet above sea level, it looms as Fairfax County's highest natural summit. For them, the slope demands no more than a nudge at the accelerator.
But for the engineers designing a Metrorail line to the area's malls and offices, the hill at Tysons Corner presents a significant obstacle: Railroad tracks generally must be laid flat or at very slight inclines. Otherwise, the steel wheels lose traction.
"It's just a hill to most people, but for us, the hill in Tysons Corner is one of our biggest engineering challenges," said Dulles project director Sam Carnaggio.
In fact, the fate of the entire rail project turns at least in part on the $100 million conundrum posed by the slope at Tysons Corner.
The effort to extend Metrorail through Tysons, a kind of holy grail for Northern Virginia commuters, has reached a critical juncture.
By late August, project managers must cut the estimated $2.4 billion cost by more than 20 percent -- or else scuttle the idea, they said. And as engineers review cost-cutting design alterations, no single greater problem exists than that presented by the hill.
Engineers could excavate a mile-long relatively level tunnel through the hill. But that could be done only at a budget-busting cost of $132 million, cost estimators say, and project managers have identified the elimination of any underground passage as the largest single cost savings they could make.
Running tracks on or close to the ground would disrupt traffic too much.
So the alternative to the tunnel is to cross the hill on elevated tracks, but that would create its own problems. The aerial tracks and their supports could look like a concrete scar running through Fairfax County's "downtown," many fear. Making matters worse, engineering constraints could force the tracks to be built as high as 80 feet aboveground.
Tysons Corner is the area's second-largest job center and home to two regional malls, and the county's comprehensive land development plan has long envisioned a rail line there -- preferably underground.
"A tunnel rather than an elevated alignment is the preferred mode," according to the comprehensive plan. Aerial tracks would, among other things, "intrude visually."
The dire cost-cutting challenge for the rail project arose last month, when engineering companies reviewing the plan, which would extend the Metro system from West Falls Church through Tysons Corner, estimated that its price had risen 60 percent, to $2.4 billion -- way beyond what planners and public officials consider feasible.