The tunnels when completed will be 2,400-feet long. Construction is not visible to drivers because it is behind a crew fence along Route 123 near International Drive.
During construction, crews are using sensor technology to monitor the tunnel and nearby roads for any movements. Soil in the tunnel area is a combination of gravel, clay and sand.
Businesses and residents of the Tysons area have been told to expect major traffic pattern changes all along the one-mile rail construction zone of Route 7 from the Dulles Toll Road east to Route 123 in the coming weeks. For example the service roads along the edges of the east and westbound lanes of Route 7 will be closed so that the edges of Route 7 itself can be pushed out to the edges of the service roads and beyond to make room for construction of the rail line and stations in the median of the road bed.
Near the two stations to be built along Route 7-Tysons Central 7 (near SAIC and Marshalls) and Tysons West (between Spring Hill and Tyco Roads), the eastbound lanes will balloon out into the parking areas of some businesses. Also, along the eastbound lanes, crews will be building retention walls to support the new roadbed as crews must build up many existing service roads to the levels of Route 7.
Preliminary construction work is beginning near all five station sites: four in Tysons and one at Wiehle Avenue in Reston. Work is most visible near the Wiehle Avenue Station in the middle of the Dulles International Airport Access Highway between Wiehle Avenue and Reston Parkway and at the Tysons East Station at Route 123 and Scotts Crossing Road near Capital One.
Along the Dulles Connector Road, near I-66, piers and caissons are sprouting up to support a flyover for the rail line from the Orange line to the Connector Road. Pile driving to support new bridges at Idylwood and Magarity Roads and Pimmit Run continues.
Rail construction trucks are using I-66 inside the Capital Beltway during restricted day and night hours. Up to 74 trucks per day will be allowed to the Lee Highway/Washington Boulevard exit to turn around and go westbound on I-66.