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The tunnel boring for Port Authority’s North Shore Connector Project commenced several weeks ago as crews from both Obayashi Corporation and the West Mifflin-based Trumbull Corporation started up the 500-ton tunnel boring machine (TBM).
Television, radio, and newspaper media were given an opportunity to get a firsthand look at the machine located nearly 60-feet below ground near PNC Park. The machine will make its way under the Allegheny River, and finally, to the receiving pit, which is being constructed underneath Stanwix Street in Downtown Pittsburgh.
The laser-guided boring machine will travel 2,200 feet one-way between the North Shore and Stanwix Street. Crews will then turn the machine around to bore another 2,200 feet back to the North Shore. Manufactured by Herrenknecht A.G. of Germany, the TBM will move approximately 30-feet-per-day when in full production and is expected to reach Downtown by spring.
The tunnels will descend from the North Shore launch-pit on a five to seven percent grade. The crown of the tunnel will sit 20 feet below the river bed and approximately 45 feet below the top of the water. At no time will the boring machine touch the Allegheny River.
As the machine tunnels its way towards Downtown, pre-cast rings of concrete will be installed that will become the inner walls of the tunnel.
A substance made of water and clay, known as slurry, is being pumped towards the machine’s cutting head to facilitate boring. Material removed from the earth along with the slurry is being pumped to a slurry-separation plant near the launch pit where earthen material is separated and the slurry is reused. Revenue-service is scheduled to begin in 2011. The 1.2-mile extension of the agency’s light-rail system will connect Port Authority customers with the North Shore area of Pittsburgh.
The project is expected to transport commuters to local attractions such as PNC Park, Heinz Field, Majestic Star Casino, Carnegie Science Center, corporate headquarters of Del Monte Foods and Equitable Resources, Community College of Allegheny County, The Andy Warhol Museum, and numerous restaurants, clubs, and hotels located along the North Shore.
Residents from the South Hills will be able to board a light-rail vehicle and will have the benefits of a convenient ride to Downtown Pittsburgh and to the many North Shore destinations and attractions.
Very soon, Port Authority will include a special link on its web site devoted to the North Shore Project called “The Bore to the Shore.” There, readers can learn more about the project through a variety of new interactive features.
Underwater Tunnel Boring Projects Around the World
While a project involving tunneling under a body of water is unique to Pittsburgh and the surrounding region, it has been successfully accomplished in other places around the world.
- The Channel Tunnel: Finished in 1994, the mega-tunnel under the English Channel was built to link England and France. The 31-mile long facility consists of three 23-mile underwater tunnels carrying rail service between the two countries.
- Yangtze River Project: Beginning in 2009, inhabitants of Nanjing, China will be able to cross the Yangtze River through dual tunnels under the water. The project will include two tunnel bores each containing three traffic lanes. Tunnels will be 3,710 meters in length.
- Westerschelde Tunnel: Completed in March 2003, the facility located in Zeeland in Southern Holland transports between 10,000 and 14,000 vehicles per day. It is more than four miles long as it passes under the estuarial part of the Westerschelde River, located just east of Antwerp.
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