THE NECESSITY of a Metrorail extension to Dulles International Airport is no longer in great dispute. It's an essential commuter connection. But how best to get there remains up in the air when it should be below ground. Should Tysons Corner -- the region's second booming downtown -- be sliced and overshadowed by an elevated, pedestrian-unfriendly and hardly gorgeous roof of tracking and platforms, or is an underground tunnel the better way to go?
Leading congressional supporters of the Metrorail project -- Virginia Republican Reps. Frank R. Wolf and Thomas M. Davis III warned last week that a tunnel plan could delay or even doom the project because of increased costs. Legitimate concerns, to be sure, but if a fresh cost analysis by an independent panel is solid, not cause to junk the tunnel route.
As reported Saturday by The Post's Alec MacGillis, local officials who were briefed by a Virginia-commissioned study panel of engineers say the experts strongly recommend going underground. They have concluded that a tunnel would not be prohibitively more expensive for the four-mile stretch through Tysons. The officials said the panel estimates the cost for the first phase of the extension project with a tunnel would be about $2.5 billion. The cost of an elevated track, according to an estimate done months ago, would be about $2.1 billion, but that estimate has been rising by the week and contractors now suggest the cost is closer to $2.3 billion. Add to this the cost of shutting down Tysons roads for aboveground construction and the gap could narrow even more.
As for delay, local officials said the group reported that it probably would not be necessary to do a full environmental review of the tunnel plan, which could take as long as two years. That needs to be determined because, as Mr. Wolf has noted, the federal government's strict cost standards grade transit projects on their overall cost -- no matter who is buying in -- and if it is deemed too high, the Dulles rail backers could risk losing the $900 million that the federal government is expected to provide.
It is up to Virginia Gov. Timothy M. Kaine (D) and state Transportation Secretary Pierce R. Homer to decide -- by the end of August, they have said -- how to proceed. Clearly they need to review hard numbers with Mr. Wolf and Mr. Davis. Are Tysons landowners serious about ponying up more money through special district taxes? Is the Metropolitan Washington Airports Authority -- which is in the process of taking control of the Dulles rail project and is slated to pay more than half of its costs with revenue from the Dulles toll road -- ready to pay more through unpopular toll increases?
At stake is the long-term vibrancy of Tysons as a booming urban hub. Far better to do it right -- and for now, the right choice looks to be underground.