Pittsburgh’s $528-million North Shore Connector project is now nearing completion on schedule, despite a month-long jam of a tunnel-boring machine in 2008. The Port Authority of Allegheny County says there are no claims or liquidated damages.
The 1.2-mile extension of the city’s 25-mile light-rail system extends from downtown beneath the Allegheny River to the city’s North Side. The work involved three major components: construction of the twin-bore tunnels, reconfiguration of the existing Gateway Station and a new North Side station.
In April 2008, the 500-ton boring machine clogged with sticky clay and tree roots, and work stalled for a month. The TBM had dug 720 ft and had been progressing at 30 ft per day, exceeding the daily goal by five feet. Winston Simmonds, port authority rail engineer, says North Shore Constructors, a joint venture of Toyko-based Obayashi Corp. and Pittsburgh-based Trumbull Corp., recovered the lost time. All heavy civil work in the $156.6-million contract is on track to be completed this month.
The twin tunnels, each nearly 23 ft in diameter, pierce a geology of alluvium, fluvioglacial, claystone, siltstone and limestone. Service on the new line is expected to begin in March 2012. The joint venture also excavated the Gateway Station shell under a $48.9-million contract. The new center platform is 385 ft long and as deep as 35 ft.
The old Gateway Station was a single-side platform about 320 ft long and 30 ft deep. Simmonds says the station finishes will be done by March 2012.
The light-rail extension is part of a $1-billion redevelopment of Pittsburgh’s North Side. The TBM bored 20 ft beneath the foundations of a major building on a narrow street�a feat that required settlement-monitoring machines.
Fittingly, that building is the new home of Trumbull Corp., the joint-venture partner. John Murray, construction manager for North Shore Constructors, says the proximity helped acquaint Trumbull’s employees to the tunneling industry, adding that the firm has bid on other tunneling projects.