Final element placed for Virginia’s new Midtown Tunnel tube

 

On the left, concrete blocks help weigh down the final tunnel element that’s suspended in the catamaran barge, while on the right, construction continues on one of the tunnel approaches.

Our Skanska-led joint venture on Tuesday reached a major milestone: immersing the final 16,000-ton hollow concrete element for the new Midtown Tunnel tube, the centerpiece of our $2.1 billion Elizabeth River Tunnels public-private partnership. Eleven such behemoths – each about 340 feet long – now form a new tunnel stretching between Norfolk and Portsmouth, Va., that is scheduled to open to traffic next year.

Tuesday’s immersion started at 6 a.m., and the final element was at the bottom of Elizabeth River at the Norfolk shore by noon. It capped years of hard and precise work by our SKW Constructors (Skanska-Kiewit-Weeks) design-build joint venture in planning, designing and executing the extremely technically demanding tunnel.

“It’s great to see it actually come together,” said Wade Watson, Skanska vice president and SKW’s project director.

Looking back over the tunnel work, Watson said he’s most proud of the strong team effort that made it all possible. “This is not something that one person can do,” he said.

Construction on the project is now about 65 percent complete. The end of the element immersion process eliminates a lot of the project’s risk, as the work done with floating equipment in the river will be winding down, Watson said.

Our team cast the tunnel elements in two groups at a graving dock near Baltimore, Md., and then floated them 220 miles down the Chesapeake Bay to the project site. There, they weighed down each element with tons of concrete and filled huge ballast tanks with river water, making it heavy enough so a special catamaran barge could lower it – with the help of GPS positioning – into a trench they carved below the river’s surface. Our team immersed the first element in October 2014, and typically they repeated that process every five weeks. It was risky work, but thanks to extensive planning all 11 immersions went smoothly. (Click here to see a graphic showing the immersion process.)

As crews have been immersing the final tunnel elements, other crews have been flowing through previously placed sections, sequentially doing such activities as installing final seals; removing the stout concrete and steel bulkheads that turned each element into a floating vessel; pouring additional concrete on the floors; and installing fireproof boards. Eventually, this outfitting work will include jet fans, sprinkler pipes, lighting and a blacktop driving surface.

Our team expects to remove the final bulkhead – in the just-placed element – in about two months, Watson said. At that point, our crews will be able to theoretically walk from Norfolk to Portsmouth via the new tube.

Elsewhere with the project, crews are completing the vehicle approaches on both sides of the tunnel; completing remaining rehabilitation work on the two tubes of the project’s other tunnel, the nearby Downtown Tunnel; and building an extension to the Martin Luther King Freeway.

Skanska’s Elizabeth River Tunnels work extends beyond design and construction. Our Elizabeth River Crossings consortium is responsible for ongoing operations and maintenance of the new and existing tunnels, as well as connecting roadways – stretching 51 lane miles in total. That includes operating the electronic tolling system, making roadway repairs and providing gas to stranded motorists.

Click here to see a local TV news report on the project, including an interview with Watson.

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