It’s a long-standing question in the world of tunneling: Which TBM has been operating the longest? What makes it so durable?

In May 2011, I visited the site of the Centennial Parkway Sanitary Sewer Tunnel in Hamilton, Ontario, Canada to find some answers.  The rock portion of the tunnel, located in the shale of the Niagara Escarpment, is being bored by a Robbins Main Beam TBM in operation since 1968.  The 2.7 m (8.8 ft) diameter machine was first used for a Hydroelectric Tunnel in Tasmania, and is now owned by McNally Construction, who has used it on multiple sewer tunnels in Toronto and Ottawa since 1972.

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