Building CN's St. Clair River Tunnel

Just over a century after the construction of what was then one of the world's most-impressive railway tunnels, a sequel is bing put together that matches the original for engineering spectacle. CN's new tunnel under the St. Clair River, between Sarnia. Ont., Port Huron. Mich., which will replace one that went into service more than a century ago, is being built by a massive tunnel-boring machine, named Excalibor, that is 31.2 feet tall, nearly 272 feel long, weighs 724 metric tons and cost $17 million (C).