Miners excavating the tunnels that will carry Dulles Corridor Metrorail tracks from the Tysons Central 123 Station under the highest natural point in Fairfax County, Va., soon will complete the mining portion of the construction endeavors.

Dulles Transit Partners, the design-build contractor for the Rail Project, is mining the tunnels. In late October, crews 'holed through' the west end of the outbound tunnel near the busy intersection of Routes 7 and 123 just more than a year after beginning excavations.

Mining of the inbound tunnel is scheduled for completion in mid-December. Then crews will remove the temporary road inside the tunnels, rearrange temporary utilities, back fill and install a smoothing layer of special sprayable concrete used to reinforce the tunnel. Then comes waterproofing, more reinforcement and concrete installation, and construction of the safety walkway. Tunnel construction is expected to be finished at the end of 2011.

Connecting Dulles Rail tracks to Metro's Orange Line

Construction is more than 22 percent complete along Phase 1 of the 11.5-mile Dulles Corridor Metrorail Project from Falls Church to Reston.

One of the most complicated areas of construction is where the Dulles Connector Road (Route 267) breaks away from I-66 near West Falls Church. This is where the rail extension will merge with Metro's existing Orange Line.

Last Memorial Day weekend, Metro shut down rail service between the East and West Falls Church stations so that pier construction and testing could take place close to existing tracks in this area. Now piers have been completed and bridges to carry the aerial tracks across I-66 are visible.

A third truss coming to cross beltway

A third huge truss that will be used to build more bridges for the rail line in Tysons Corner is being assembled in a cloverleaf of Route 123 and I-495.

This truss will function a bit differently from the other two that have been building bridges above the Dulles Connector Road across Route 123 and along Route 123 near Scotts Crossing Road. The latest addition to the big yellow fleet of horizontal cranes will be used to build the bridges that will carry tracks across the Capital Beltway in the coming year.

Meanwhile, the skyline at Tysons continues to be filled with these trusses, working day and night to build bridges for rail.