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Silver Line Guideway Complete, A Major Milestone for Rail to Dulles

Final segment of Phase I lowered into place along Dulles Access Road on Tuesday

Phase I of Metro's Silver Line project celebrated a major milestone Tuesday: completion of the construction of the aerial guideway.

The aerial guideway was finished about noon Tuesday when a final section was ever so slowly lowered into place in the median of the Dulles Access Road.

Applause erupted from a crowd of officials from the Metro Washington Airports Authority, Dulles Metrorail and Bechtel, who were gathered with members of the press to witness the fitting of the last segment.

"The eagle has landed," said Sam Carnaggio, who has directed the project for the Metropolitan Washington Airports Authority, as the last segment fit perfectly after the 45-minute lowering operation.

"With the completion of the aerial guideway you can walk from the Orange Line (in East Falls Church) to Wiehle  Avenue" in Reston said Larry Melton, Project Executive Director for Dulles Transit Partners, which is building the Silver Line for MWAA.

The aerial guideway has dominated the McLean and Tysons Corner skyline since it started its three-mile journey from the median of the Dulles Connector Road at Old Chain Bridge Road to yesterday's point just beyond Route 7, where the Silver Line moves from the air back to the ground to run in the median of the Dulles Access Road.

Phase One of the Silver Line, which runs roughly 11.7 miles, costs $2.9 billion. Phase Two, which runs another 11.4 miles from Reston to Dulles Airport, will cost $2.7 billion.

Construction of the Phase I guideway started in the summer of 2010, when McLean residents began to see a 365-ton machine called a truss lifting re-enforced precast concrete segments into place to form the track bed for the first phase of the Silver Line. Each segment weighs between 25 and 40 tons.

This ribbon of concrete crossed Dolley Madison Boulevard then slowly approached Tysons Corner. Soon, a second truss was erected to heave the segments into the alignment as it swept over the Capital Beltway.

The guideway, now complete, contains 2,700 segments carefully fitted throughout Tysons Corner.

What's next: Laying the actual track. Construction is still underway at the first five stations, four of which are located in McLean and Tysons Corner. Part of that will include completing the pedestrian walkways that will take passengers to and from the stations. And then, electrifying the system for power, communications and train control.

The first phase of the new Silver Line is scheduled to open 15 months from now, when passengers from Reston and Tysons Corner will be whisked to downtown Washington with no change in trains for the first time. The Silver line will use existing Orange Line tracks from East Falls Church into Washington.

"With transit, until you turn the power on at the end, you don't know if you can operate the system effectively and safely," Carnaggio said.

Tom July 18, 2012 at 11:43 AM
I have a question. What holds the segments together? There are "teeth" on the sections, but I can't believe that's what holds up all that weight. Yet while they were building it I saw no bolts or anything else tightening them up.
Bobbi Bowman July 19, 2012 at 02:45 AM
Thank you for your question. Here's the answer: The truss’ lifting mechanisms hoisted the segments into place in the alignment, where they were sealed with epoxy, joined and aligned. The spans have six post tensioned tendons (each approximately six inches thick and made up of up to 19 strands of high strength twisted steel) that were threaded through the interior of each segment. The cables were then anchored into steel blocks at the end of each span and pulled tight (post tensioned) with approximately 4.5 million pounds of force (for an average 130 foot span), locking the individual segments into a single structural unit.
Don Rutledge July 19, 2012 at 05:58 PM
I live near the new Wiehle station and have watched the construction of phase I for several years as I traveled the toll road and the 66 construe. This is truly a marvel of modern engineering and project management: on time and on budget!
G'Ma July 19, 2012 at 06:10 PM
Really? We can now WALK from the East Falls Church station to the Wiehle station? Is this true?
Uncle Smartypants July 19, 2012 at 06:27 PM
Technically, no, YOU can't walk it. What he was trying to convey is that there is now a continuous rail bed in place from the Orange line to Wiehle. If one had the access and permissions, it would be possible to walk the entire distance.

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