Virginia officials are awaiting U.S. Federal Transit Administration approval before releasing details of a public-private proposal to design and build a 23-mile extension of the Washington Metro subway beyond Dulles Airport.

Officials of FTA, which will also fund the estimated $4-billion project, have been reviewing the draft agreement for nearly a year with Dulles Transit Partners, the Bechtel Infrastructure Corp. and Washington Group International (WGI) venture that proposed it. FTA won’t say when it expects to complete the review, but state officials say it should be soon.

The Washington Metropolitan Transit Authority’s board of directors approved the proposal April 15. The agency normally procures design and construction for Metro, but Virginia stepped in on this portion because WMATA does not have authority for a public-private venture, says James Haggins, director of construction. "We will act as the technical manager,’’ he says.

Private involvement on the project dates to 1998 when Raytheon Corp. submitted an unsolicited proposal to the state. WGI took over after it acquired some Raytheon assets. When the project was released for competition, only Bechtel responded, says Karen Rae, director of Virginia’s Dept. of Rail and Public Transportation. "The two melded into one after the competitive process," she says.

Rick Clawson, a state spokesman, says Bechtel-WGI "is offering us parts of the project on a firm fixed-price and will absorb overages within reason." The team also will be paid a development fee. It helped create a tax district that will pay for the local share of the project’s first 11-mile phase, say state officials. The Fairfax County Board of Supervisors approved the new district in February.

FTA would not say what it is focusing on in the draft agreement. State officials expect it is the management plan, which critics say is too complex. Others speculate that FTA is analyzing risk allocation and the team’s reported $11-million development fee, since the project was never competitively procured. "Is it fair? Bechtel-WGI gets a sole source contract and a development fee,’’ says the source. "If there is a cost overrun, to what degree does FTA bear the risk?’’