Tunnel Back On Table for Dulles Rail

The plans for the rail extension call for it to run underground for about 2,100 feet of the four-mile stretch through Tysons, with the rest of the line running on an elevated track with an average height of 36 feet and with all four stations above ground.

But late last year, Metro officials and Homer asked the contractors to take a closer look at tunneling through all of Tysons using a machine that can dig a hole large enough for two pairs of tracks on top of each other. The machine, which has built tunnels in Europe and Southeast Asia but not in the United States, is expensive. But its ability to churn nonstop is more efficient than conventional "drill and blast" tunneling.

Dragados, the Spanish company, told the contractors that it could build the tunnel and stations affordably enough to keep the first half of the rail extension through Tysons to Reston near the $2 billion limit that the project team believes it needs to win federal funding. The rest of the cost is coming from Dulles Toll Road revenues and a tax on landowners along the line.

Under the contractors' analysis, the tunnel would cost far more. They tacked on $115 million in contingency, saying the tunnel designs were in such an early stage that there were bound to be unforeseen changes. The contractors also added $87 million in overhead and profit for themselves, which they said represents the same share of the total cost that they seek in the existing plan.

The tunnel's "hard" costs alone were $467 million more than the aboveground option's, the contractors said. The tunnel wouldn't save that much in land acquisition because seven aboveground ventilation buildings would be needed. And the Dragados proposal understated the cost of the tunnel's concrete lining, the contractors said.

On top of that, the contractors said, the tunnel wouldn't be as attractive as believed -- the station platform's ceilings would be lower than in most Metro stations. Trucks removing rocks and dirt would affect traffic.

The tunnel's proponents dispute almost all of these points, saying that it seems clear from the contractors' study that they opposed the tunnel from the outset.

"They just took [the tunnel study] as something they were told to do and they had to do and then went about it that way," said James R. Haggins, Metro's director of construction, who puts the difference in cost at less than $200 million.

The contingency fees aren't needed because Dragados knows what it's getting into, said Walter Mergelsberg, who heads the local office of the Dr. Sauer Group, an engineering firm working with Dragados. The profits for the contractors aren't justified, tunnel backers say, because the tunnel will be built separately from the rest of the line. The tunnel studies could be done in months, not years, tunnel proponents say. And the benefit of the digging machine's ability to work around the clock would be incalculable, they say.

In the long term, supporters say, the tunnel would be more durable than an elevated track and easier to use in winter and would allow for more development.

"It's more attractive, it's safer and more pedestrian friendly," said Donna P. Schafer, a senior vice president with WestGroup, a major Tysons landowner. "We owe it to the public to look at it and be absolutely certain that the only way to be on budget is to do it above grade."

Some tunnel proponents are so irked at the contractors' tunnel estimates that they are raising the possibility of breaking the project into parts, with the contractors no longer controlling the Tysons section.

Picard, the consortium's director, said the contractors have an obligation not to promise to complete the project for less than it might cost. "Everyone's throwing stones at us," he said. "I'd love for a tunnel to be the solution, but they just don't have the money."