Tunnelling under Tysons Corner (photo courtesy of Metropolitan Washington Airports Authority)

U.S. Transportation Secretary Ray LaHood has proposed a compromise to end the bitter feud between the partners building a new subway line out to Dulles Airport in Northern Virginia, a more than $5 billion infrastructure project that's one of the costliest currently under construction in the country. But, as of right now, it's unclear if the partners will agree to it.

For months, disputes over the rising cost of the Dulles Rail project have raged between the two partners. On one side has been the Metropolitan Washington Airports Authority, which is in control of operating the Dulles Rail project. It wants to build an underground train station at the airport that could cost more than $330 million dollars more than an above-ground alternative.

On the other side are local elected officials, who are responsible for allocating the money to pay for the project. This bipartisan group of local supervisors, state legislators and members of Congress have expressed outrage at the Airports Authority's choice of a more expensive rail station option, and have demanded they reverse course. The Airports Authority says an above-ground station would be twice as far from the terminal as the underground alternative, thus making the new subway station inconvenient for travelers, and have refused the elected officials' demands.

LaHood has been mediating discussions to get this massive infrastructure project back on track, and this weekend the head of the Federal Transit Administration sent the project stakeholders a proposal (pdf). The compromise would strip several elements of the Dulles Rail project from Airports Authority control and eliminate the underground station from the project. Among other things, these alterations would shave around $1 billion off of the cost the project, according to a letter laying out the details of the compromise that LaHood's office sent to the partners this weekend.

The Board of Supervisors for one of the local jurisdictions in on the project, Virginia's Loudoun County, is meeting this morning and is expected to approve the compromise. The Board of Directors for the Airports Authority has also met this morning, but according to an Authority spokesman, the issue of the LaHood compromise did not come up. As of right now, no Airports Board members have returned our calls.

UPDATE: Airports Authority Board member Mame Reiley, the chair of its Dulles Rail committee, says the Authority is considering the compromise proposal and that "all options are on the table." Also, the Loudoun County Board of Supervisors chose to defer a vote on the LaHood compromise to a later day.