Key Dates: Dulles Rail Timeline

Fairfax County officials approved the operating agreement to extend Metro from West Falls Church to Dulles International Airport yesterday. The agreement includes an aboveground segment through Tysons Corner, probably signaling the end of a proposal to build a tunnel.

1994: Virginia and Metro officials initiate a "major investment study" to evaluate rail options for the Dulles corridor. One of 12 options studied is an underground route through Tysons.

1997: The project team, including state, local and Metro officials, publishes a report rejecting an underground route through Tysons because of cost.

2000: Project officials hold three public meetings on the mostly aboveground recommended route. More than 400 people attend; three submit comments in favor of a Tysons tunnel.

2002: The Fairfax County Board of Supervisors and Metro and state officials endorse a mostly aboveground route through Tysons.

January 2006: The state requests that the project's contractors estimate the cost of tunneling through Tysons using a wide-bore digging technology not previously considered.

April-May 2006: The contractors report that the technology would be prohibitively expensive. The Fairfax board seeks an independent evaluation. The state appoints an engineering panel to study a tunnel. The panel endorses the tunnel.

September 2006: Gov. Timothy M. Kaine (D) rejects a tunnel.

January: Tunnel advocates produce engineering plans that they say prove a tunnel is feasible.

March 8: A state study says a rail tunnel under Tysons Corner would take nearly three years longer to build than an elevated track, would cost at least $160 million more and would jeopardize $900 million in federal money for the Metrorail extension.

March 30: Virginia transportation officials announce an agreement with a private contractor to begin construction of the rail extension, with an elevated segment through Tysons Corner.

June 6: The regional airports authority signs a contract launching the extension, also calling for an aboveground segment through Tysons Corner.

Yesterday: Fairfax supervisors reject the tunnel in approving the county's $400 million share for first phase.

Fall 2007: Utility relocation will begin along Route 7 in Tysons Corner.

Winter (early 2008): Federal officials will formally approve a full-funding agreement for the project's first phase. A full-funding agreement is the federal government's commitment to support a transit project over the course of several years.

Late 2008: Expected start of construction.

SOURCES: Dulles Corridor Metrorail Project, Fairfax County, Virginia Department of Transportation