History of the Detroit/Windsor Tunnel

Construction of the Tunnel

Construction of the Detroit/Windsor tunnel began in 1928, almost simultaneously on both sides of the border. Three combined methods of tunnel construction were used, known as "Cut and Cover", "Shield", and "Trench and Tube." Completion was considered an accomplishment beyond compare at the time, and the tunnel is still regarded as one of the greatest engineering wonders of the world.

The cut and cover method was used on either side of the river, at the future entrances to the tunnel. Workers who were referred to as "muckers" or "sand hogs" cut the earth away, using nothing but hand tools to cut a path for a giant shield wall. This shield was necessary to give the muckers protection from possible cave-ins and flooding.

The shield method used a huge hollow steel cylinder. One shield was used on the Canadian side of the river, and another on the U.S., side. In each case, the shield lay on its side with one end snug to the earth face that had to be dug. Muckers worked inside a closed compartment, the earth face before them, a bulkhead behind them, and standing on steel platforms. Compressed air kept groundwater out. Tools and building materials were kept in a second and a third compartment behind the first, each sealed by a bulkhead. The muckers cut away at the clay and tossed it onto a conveyor belt that took it out the back end of the cylinder.

As the clay face was cut away, it became necessary to move the shield snug to it once again. 32 hydraulic jacks moved the entire assembly forward, three quarters of a metre (2.5 feet) at a time. A pilot at the back of the shield steered the way through the earth, changing direction by adjusting the jacks. If the tunnel had to be dug downward, the pilot would use only the top jacks. Like some kind of giant earthworm, the shield inched forward 141.2 metres (466 feet) on the US side and 298.8 metres (986 feet) on the Canadian side. As it moved ahead, workers installed a steel tunnel lining behind it. Steel bands were held in place by a mechanical arm and bolted together, creating a tube.

Meanwhile in the river itself, a steam-powered shovel scooped out a trench across the river bottom. This was the trench and tube method. The mud from the excavation was taken away by workboats called "scows." On the Canadian shore, workers built nine steel cylinders (see gallery for more photos). They used steel plates, welded together to create watertight tubes. The tubes were strengthened on the outside with eight-sided support rings and inside rings. Temporary wooden bulkheads were placed at each end, supported by steel trusses inside and covered outside by one-inch steel sheeting and seven-ply waterproofing. Workers entered manholes to complete the roadbed and concrete work. Outside, a concrete keel was poured.

Tugboats positioned each cylinder directly over the trench, where the tube was pumped full of water and sunk. Beginning on the American side of the river, nine sections in all, were placed in the trench. A diver secured them together with large steel pins. Then all the sections were covered in special underwater-setting concrete.

The remaining, most dramatic task was to join the various parts of the tunnel together. First, the landward ends of the underwater tube were covered with at least 4.6 metres (15 feet) of clay. This would allow the workers using digging shields to dig their way right up to the tube's ends. Additional water pressure at the river bottom meant that the landward end of the shield had to be covered with a wooden bulkhead and air pressure inside the shield increased. Navigation of the shield became difficult, as there was no direct line of sight from the shield to the excavated tunnel behind it. Going the wrong direction would be disastrous. Nevertheless, when contact was finally made at both the U.S. and Canadian ends of the underwater tube, the workers were within inches of their targets.

Both shields were left to become part of the tunnel wall. Bulkheads in the tube were torn out and a lining of concrete was poured at the joints. The sidewalk and granite block pavement was laid, the walls were tiled and lighting and ventilation were installed.

A ventilation tower was built at each end of the tunnel.

Each tower was given 12 fans, six to draw in fresh air and six to blow out used air and automobile emissions. The air in the tunnel would be completely changed every 90 seconds.