A "technical problem" buried within a U.S. Defense Department spending bill has endangered $150 million in federal funding for vital road projects in Fairfax County.

Members of the county's Board of Supervisors sent a letter to Virginia's congressional delegation, calling on the state's representatives to securethe $150 million before it's too late.

"To have this funding pulled out from under us, potentially, would be devastating," said Supervisor Jeff McKay, D-Lee, who signed the letter with Board Chairwoman Sharon Bulova and Supervisor Gerald Hyland, D-Mount Vernon.

The Army plans to relocate up to 19,000 employees to Fairfax's Fort Belvoir in September 2011 as part of its military job shift.

The resulting crush of commuters threatens to bog down Route 1 and other area roads unless local and federal officials are able to complete a slew of planned transportation projects.

The House of Representatives last year approved a Defense Department appropriations bill that allocated $150 million to pay for access improvements around Fort Belvoir -- improvements that would alleviate expected traffic congestion on nearby Route 1. County officials had for months believed those funds were secured.

But the Fort Belvoir transportation funds, McKay explained, were tied to other unrelated projects that were subsequently pulled from the appropriations bill and voted down by the Senate.

Without the Route 1 improvements, local drivers will face "disastrous" traffic backups once the Army moves into the new Belvoir Community Hospital on the grounds of the base, McKay said.

U.S. Rep. Jim Moran, D-Va., recently submitted a bill that separated the Fort Belvoir funds from less popular projects, but the revised bill requires congressional approval.

McKay said that approval won't come until after the November elections, if ever.

"The best case scenario is we're going to lose five or six months on this project," McKay said. "But the appropriations bill could be defeated again."

The county has started preliminary engineering and land acquisition measures, and construction was expected to begin next year. But now county officials will have to wait for Congress to act.

"This is a huge setback," McKay said.