Chuck Samuelson/Dulles Metrorail Corridor Project photo. One of the Silver Line test trains operates near the end of the new line at Wiehle-Reston East station.
Preliminary construction of Phase 2 of the Dulles Corridor Metrorail Project has begun in the Washington, D.C., area.
The $1.77 billion construction contract for the major portion of the phase has been awarded to Capital Rail Constructors, a joint venture of Clark Construction Group and Kiewit Infrastructure South Co. Completion is expected in 2018.
At press time, geotechnical work, utility location identification, and surveys were being conducted. Work is mainly concentrated at the Dulles Airport, but will soon spread to the Dulles International Airport Access Highway corridor and the Dulles Greenway corridor, as well.
Heavy construction is expected to begin in 2014. Phase 2 is 11.4 mi. (18.3 km) long and includes six stations: Reston Town Center, Herndon, Innovation Center, Dulles International Airport, Route 606 and Route 772. It will run from Wiehle Avenue to Ashburn in eastern Loudoun County.
This portion of work is the second phase of a 23-mi. (37 km) extension of the existing Metrorail system being constructed by the Metropolitan Washington Airports Authority (MWAA). The extension will become part of the existing DC Metro system will be operated by the Washington Metropolitan Area Transit Authority. The extension will run from East Falls Church to Washington Dulles International Airport west to Ashburn. A total of 11 new stations will be included.
The extension will serve Virginia’s largest employment center, Tysons Corner, and the state’s second largest employment concentration, the Reston/Herndon area and will provide a one-seat ride from Dulles Airport to downtown D.C.
Phase 1 runs from East Falls Church through Tysons Corner to Wiehle Avenue on the eastern edge of Reston. Stations include Mclean, Tysons Corner, Greensboro, Spring Hill and Wiehle-Reston East. The Tysons Corner stops are Tysons East, Tysons Central 123, Tysons Central 7 and Tysons West.
The Airports Authority and Dulles Transit partners, the Phase 1 design build contractor, signed a $1.6 billion fixed-price construction contract in March 2008 to build the project. Construction began in March 2009.
Construction of the first phase is nearing completion, but an opening date has not been set. When the line is completed, it will be turned over to the Washington Metropolitan Area Transit Authority, and the agency will set an opening date.
According to project officials, station structures are complete. Finishing touches are now under way around and inside the stations and at the exteriors of the pavilions and pedestrian bridges. Paving is being restored, previously closed lanes are now open, landscaping is being done, and bus lanes are being built along Tysons Boulevard.
The total cost of Phase 1 is $2.9 billion.
According to Marcia McAllister, communications manager of the Dulles Corridor Metrorail Project, its purpose is “to provide high-quality, high capacity transit service in the Dulles Corridor. New Metrorail service in the corridor will result in travel time savings between the corridor and downtown D.C., expand the reach of the existing regional rail system, offer a viable alternative to automobile travel, and support future transit-oriented development along the corridor.”
Phase 1 involves a total of 6 mi. (9.6 km) of aerial track — 3 mi. (4.8 km) inbound and 3 mi. outbound. The 6 mi. includes five at-grade new bridges and segmental bridge construction. Tunnels were built using the New Austrian Tunneling Method (NATM), in which tunnels are excavated and initial lining construction completed in short, sequential portions. This also is known as the sequential excavation method (SEM) or sprayed concrete lining (SCL) method.
“This cost-effective method of tunneling is ideal for the existing ground conditions, while allowing for adaptations to any changes in ground conditions,” McAllister said. “This method successfully limited surface settlements and deformations to sensitive utilities and structures, and also allowed roads to remain open to traffic throughout excavation.”
Tunnel depth varies between 7 and 30 ft. (2.1 and 9.1 m) and approximately 100,000 cu. yds. (76,455 cu m) of earth was excavated in all. Equipment included an Atlas Copco Boomer E2C 18 drill jumbo with an automated pipe arch canopy system, tunnel excavators, a Shotcrete batch plant and Shotcrete robots for application.
Phase 1 wasn’t without challenges.
“One was building the core of Phase 1 through Tysons Corner, a densely developed area about the same size as downtown Boston — where more than 25,000 people commute in to work each day, primarily in cars, and thousands of others shop at the nation’s fifth largest shopping mall — with a minimum disruption of traffic flow and business operations,” McAllister said. “Another was building tunnels in Tysons Corner under one of the busiest intersections in the state and close to existing structures, utilities, water lines and sensitive high-tech cabling.
Another challenging task noted by McAllister was the construction of the aerial guideway and bridges (6 mi., three in each direction) through Tysons Corner and high above I-495, the ring road around the nation’s capital, using three horizontal cranes.
Finally, connecting the Silver Line extension to the existing Metrorail system via a merging of tracks between stations was no easy task.