March 2013

Local 5 & Local 201 Ironworkers Complete Aerial Guideway

A Bechtel-led team, along with Local 5 (Washington, D.C.) and Local 201 (Washington, D.C.) ironworkers, has completed construction of a three-mile aerial guideway, part of the 11.7 mile alignment in Phase 1 of the Dulles Corridor Metrorail Project. A guideway is a structure that supports trains or other vehicles that ride over it. This project features both at-grade and aerial guideways. The guideway will carry WMATA Metrorail trains over major highways and through Tysons Corner, Va., a busy suburban Washington business center.

Aerial Track Guideway Construction Facts Summary

Aerial Support Columns/Piers: 214 each
Total Aerial Segments: 2,769 each
Total Aerial Spans: 258 each
Average Segments per Span: 12 each
Average Span Length: 120 feet
Total Aerial Acoustical Barriers: 45,831 linear feet
Total Length of Post-Tensioned Tendons: 39 miles
Total Length of High Strength
Steel Strands in Tendons: 528 miles
Total Length of Aerial Guideway: Six miles
(3 miles inbound and outbound)
Total Trusses Used on Project: Three
Weight of Truss: 365 tons
Length of Truss: 360 feet

Dulles Transit Partners, the design-build contractor for the Dulles Corridor Metrorail Project and a team of ironworkers, equipment operators, electricians and laborers, built the aerial guideway. Approximately 70 ironworkers from Locals 5 and 201 worked more than a quarter of a million manhours on the project.

"The aerial guideway has been one of the most challenging aspects of the project as we had to carry out this work safely above busy highways and in a congested area," said Larry Melton, Bechtel's executive director on the project. "Innovative construction techniques, the work of a dedicated and experienced crew, and patience from the public were critical to the successful completion of the guideway."

The aerial guideway makes up three miles of the 11.7-mile alignment in Phase 1. It was constructed by connecting more than 2,700 reinforced precast concrete segments, each weighing between 25 to 40 tons. The segments were engineered for their specific location on the guideway to ensure a custom fit and were manufactured at a temporary plant built at Dulles Airport for this specific purpose, and then transported, one-by-one, via flatbed truck to their location along the alignment. From there, the segments were lifted into place using one of three giant, 365-ton, 360-foot-long trusses (horizontal cranes). Anywhere from 12 to 15 segments were joined together to form spans between two supporting piers. The segments in each span are then held together by threading six post-tensioning cables through the segments and anchoring them into blocks of steel at each end of the span. The cables are approximately six inches thick and comprised of 19 strands of twisted steel wires. When all of the cables are in place and anchored, they are pulled tight (post-tensioned). The force of the tension, about 4.5 million pounds in an average span, ties them together. The segments were installed by the bright blue and yellow trusses. The giant 365-ton, 360-foot-long trusses were used because of their ‘top-down' construction method.

The completion of the segmental bridge was delivered three weeks earlier than estimated.

For safety reasons, most of the work was done during daylight hours. However, work over active roadways was also performed at night, with road closures and detours coordinated with the Virginia Department of Transportation (VDOT) or the Metropolitan Washington Airports Authority (MWAA), depending on which entity has jurisdiction over the road to be closed.

The use of overhead trusses was deemed the most efficient method for bridge construction in this area. The method is ideal in dense urban environments like Tysons Corner because they use a ‘top-down' construction method and minimized impact to the traveling public.

Traffic was stopped momentarily when the truss moved over a roadway in between piers, and when the truss lifted segments from a truck on to its portion of the alignment. In some cases, to ensure everyone's safety, support work required overnight closures of some main roadways. Contractors adhered to a formal and extensive safety program while executing this work.

Nick Fiore, manager of labor relations for Bechtel, praised the ironworkers for their work, "The quality, productivity, and safety record of the ironworkers on this project was excellent. Their job knowledge and the skill sets they brought to the job made this all possible."

Completion of the guideway marks a milestone in the project. Work will now focus on the completion of the stations and their associated pedestrian bridges and pavilions, as well as on the process of connecting the Dulles extension to the existing WMATA system.

Phase 1 of the Dulles Corridor extension project began in 2009 and was worked under a Heavy and Highway project labor agreement. The project is managed by the Washington Airports Authority and is currently on schedule for completion in late 2013.