Each section weighs 32,000 t (31,000 long tons; 35,000 short tons), is 110 metres (360 ft) long, 37 metres (121 ft) wide and rises to a height of 8 metres (26 ft). In total, the bridge–tunnel is 1.8 kilometres (1.1 mi) long. It is estimated that 44 million vehicles drive through it per year, or 120,000 per day. The tunnel was built with sections prefabricated in dry dock and then sunk in the river, 24 metres (79 ft) below the surface of the water. It is one of the largest prestressed concrete structures in the world.
In 1960, the construction of the Trans-Canada Highway (TCH) through Quebec from the Ontario border to Rivière-du-Loup was announced. In Montreal, to avoid having to build a huge bridge that would have disfigured the city and destroyed a neighbourhood, the engineers opted for the construction of a tunnel located under the Saint Lawrence River, and dug a trench under the river bed and buried the tunnel sections 4.6 metres (15 ft) to 6.1 metres (20 ft) under the river bed. The construction was completed in March 1967, just before the opening of Expo 67. Construction cost $75 million.