or the second time in two weeks, the 500-ton boring machine digging Pittsburgh’s North Shore Connector light-rail project is jammed. Shortly after the first jam, the machine’s outtake became clogged with wood. The machine has been down for 10 days and will not be functioning again for about two weeks, says David Whipkey, spokesman for Port Authority of Allegheny County, owner of the project. The blockage stopped tunneling work on the North Shore Connector. When completed, it will include twin tunnels beneath the Allegheny River that will connect the city’s light-rail system in downtown Pittsburgh to the city’s north side. The boring machine had dug 720 ft of tunnel from its launch pit and is about 10 ft from the river. Drilling began on Jan. 22 and had been progressing at 30 ft per day, exceeding the Port Authority’s daily goal by 5 ft. Herrenknecht AG, based in Schwanau, Germany, manufactured the boring machine. The project contractor is a partnership of Trumbull Corp., Pittsburgh, and Tokyo-based Obayashi Corp.