After months of digging forward about 40 feet a day, a 500-ton Herrenknecht boring machine is scheduled to complete a 2,240-foot-long subway tunnel beneath the Allegheny River by mid-July. Once it reaches its destination, the borer will turn around and dig another five months until a second, parallel tunnel is complete. When both tunnels are functional in 2011, they will link downtown Pittsburgh with the sports stadiums and exhibition halls of the North Shore.

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