As if the Rail-to-Dulles project didn’t have enough hurdles already, the U.S. Department of Transportation’s inspector general is launching an audit of the project, which is projected to cost $4 billion or more. Reports the Washington Post:

In a letter sent last week to the Federal Transit Administration, the inspector general’s office said such a “major project monitoring effort” was needed in this case because of the large amount of federal money expected to be spent on it: roughly $900 million.

Also justifying extra scrutiny, the letter stated, was Virginia’s transferal of control of the project to the Metropolitan Washington Airports Authority. Because the authority leases its airports from the federal government, the letter states, the authority’s role in the rail project gives further reason for the federal government to have a “vested interest in ensuring that the Dulles Corridor Metrorail Project is completed efficiently and effectively.”

The project, a top priority of the Kaine administration, has stalled while a task force recommends whether or not to include a tunnel underneath portions of Tysons Corner. The addition of a tunnel would add to the project’s expense, threatening to render it cost ineffective according to federal guidelines, which would threaten the loss of federal funds. But many Fairfax County officials deem the tunnel crucial for long-term plans to re-engineer Tysons into a more cohesive, pedestrian-friendly community.