(Metropolitan Washington Airports Authority)

12:55 p.m. Update: Virginia officials are raising concerns about the airports authority’s decision to endorse an underground station at Dulles International Airport.

Transportation Secretary Sean T. Connaughton addressed the issue in a letter Wednesday to the Metropolitan Washington Airports Authority.

“The tunnel alignment, by all accounts, is a more expensive alignment than the aerial option through the airport, and will place a heavy financial burden on local funding partners and Dulles Toll Road users,” Connaughton said.

Virginia officials said they are concerned about the impact of the costs of the rail project and how it would affect users of the Dulles Toll Road. The authority has pledged toll revenue toward the rail expansion. In 2009 the agency enacted a three-year schedule of toll increases, which began in January 2010. The latest increase took place in January 2011, and the next is scheduled for January 2012. The state transferred responsibility to operate and maintain the Dulles Toll Road to the airports authority in 2009.

Commonwealth officials said their goal is to keep the cost of Phase 2 of the Dulles rail extension as close to the original estimate of $2.5 billion as possible.

The 23-mile extension of Metrorail from East Falls Church to Ashburn is being built in two phases. The first phase, scheduled to open in 2013, is costing $2.75 billion. Estimates for the second phase, however, have been as much as $3.9 billion, depending on the location of the station at Dulles. It is scheduled to be completed in 2016.

Airports officials said the option chosen Wednesday will save up to $330 million compared to the original design estimate due to engineering changes.

The airports authority board voted 9 to 4 in support of the underground option.

The dissenting votes were cast by former Virginia congressman Thomas M. Davis III, Michael L. O’Reilly, Frank M. Conner III and William W. Cobey Jr.

Davis, who was the meeting’s most outspoken critic of an underground station, said he was concerned about its impact on Fairfax and Loudoun counties. Fairfax is funding its portion of the rail project with two special tax districts.

“The financial burden on our end falls to our partners,” he said.

Davis also worried that the additional cost could lead to a hike in tolls on the Dulles Toll Road.

“For a lot of working people, these tolls are the only viable” commute , he said.

(Metropolitan Washington Airports Authority)

Original post: A committee of the Metropolitan Washington Airports Authority voted to build an underground rail stop at Dulles International Airport, citing its easier accessibility to the airport terminal despite the station’s higher cost estimates compared to an aboveground option.

The aboveground option “is yet a trek at another airport that right now has too many treks,” said Mame Reiley, the committee chair.

The committee’s recommendation now goes to the full board, which is scheduled to consider a rail stop option later Wednesday morning.

The underground option is closer to the Dulles terminal, about 550 feet, compared with the aboveground option which is 1,150 feet away.

However, the underground station would cost about $300 million more to build, which is about 5 percent of the total rail project’s cost.

That cost difference has concerned Loudoun and Fairfax counties, which are helping pay for the Dulles Metrorail extension.

Fairfax officials, for example, have endorsed the less-expensive, aboveground option.

But committee members said they will work diligently to find other cost reductions with in the entire rail project.