Main Street Tunnel technique, whereby the tunnel was excavated, the concrete poured, and the structure buried, on top of which the canal channel was built. This avoided costly boring beneath an active waterway; the structure cost C$11 million. This price was split 50–50 between Transport Canada and the St. Lawrence Seaway Authority. The tunnel opened with a parade featuring the Welland Police pipe band and various officials on the morning of May 20, 1972. Main Street Tunnel The Main Street Tunnel, located in Welland, Ontario, Canada, is an underwater tunnel, carrying Niagara Road 27 and the unsigned designation of Highway 7146 under the
Channel Tunnel techniques from the oil industry were employed. Tunnelling was a major engineering challenge, with the only precedent being the undersea Seikan Tunnel in Japan, which opened in 1988. A serious risk with underwater tunnels is major water inflow due to the pressure from the sea above, under weak ground conditions. The tunnel also had the challenge of time: being privately funded, early financial return was paramount. The objective was to construct two rail tunnels, apart, in length; a service tunnel between the two main ones; pairs of cross-passages linking the rail tunnels to the service one at spacing; piston relief