The initial cost of building the bridge was approximately $20,000,000, including expropriation expenses. If the approaches are included, the cost was $23,000,000.
1st Awarded Contract – South Shore Piers (May 22, 1925)
The first contract, in the amount of $936,000, was awarded on May 22, 1925 to Quinlan, Robertson and Janin Limited for the piers on the south part of the bridge.
2nd Awarded Contract – Piers and North Approaches (Summer 1925)
In the late summer of 1925, Dufresne Construction Co. Limited obtained a $125,000 contract for the piers and approaches on the north part of the bridge.
Superstructure Erection Contract (October 25, 1925)
The contract to erect the steel superstructure, worth $6,954,000, was awarded to the lowest bidder, Dominion Bridge Company Limited, on October 25, 1925.
Pier 24 Construction – a Major Challenge
The caissons used to construct the piers were built by Canadian Vickers. They were then towed by tugs from the firm’s workshops to the exact location of each pier. Construction of pier 24, one of the two main piers supporting the structure’s cantilever section, presented the most problems and was in itself a considerable challenge for the engineers. The pier was anchored in the river bed and the friable soil made it necessary to dig 11 feet (3.35 m) deep to make it solid. To fill the pier, 3,775 cubic yards (2,886 m) of concrete were required, while above water, 23,000 cubic yards (17,584 m) of concrete and 100 tons of steel were needed. The caisson used to build it was 128 feet (39 m) wide, 52 feet (15.8 m) deep and weighed 1,030 tons. It cost $500,000, an astronomical amount at the time!
Construction of the Superstructure (September 1926 to September 1929)
Construction of the superstructure took place between September 1926 and June 1928 on the South Shore, from October 1928 to February 1929 on the Montreal shore, and from May 1927 to September 1929 in the centre. Construction of the main span in the central, cantilevered section presented a number of difficulties. This type of structure has three distinct sections, namely two anchor arms between the shores and the piers, and two cantilever arms located on either side of the suspended span in the centre. The cantilevered sections have to be built out from the piers towards one another, piece by piece, panel by panel. Each side has to remain in constant balance as it is extended out into space. The sections must be erected and aligned with exact precision so that both halves of the suspended span meet and can be joined together.
Last Girder (July 10, 1929)
The last girder joining the two sections of the bridge was put in place on July 10, 1929. The whole operation was carried out quickly and the workers completed the operation in less than five hours without any problems. On this occasion, the superintendents of both work sites came face to face and shook hands. They had just accomplished their mission brilliantly!
The work was completed so quickly that the contractors were able to deliver the bridge almost a year and a half ahead of schedule, in December 1929 instead of May 1931. It took four years to build, a relatively short period at the time for an undertaking of that size. The construction also took place without ever interfering with traffic in the St. Lawrence.
Jacking of the Bridge (1957 and 1958)
In 1957 and 1958, the deck between piers 9 and 10 had to be jacked up from its original 40 to 120 feet (12.2 m to 36.5 m) above the water for ships to pass through the St. Lawrence Seaway, which was under construction at the time. This work took 16 months and cost $6,698,750. The contract was awarded to the Dominion Bridge Company Limited, under the supervision of consulting engineer Dr. P.L. Pratley. Thirty jacks with a capacity of 362.87 to 544.3 tons were used to raise this section of the bridge. The work was carried out without disrupting traffic on the bridge thanks to the installation of two temporary “Bailey” bridges.
Construction of the Second Access Ramp (1961)
In 1961, a second access ramp to St. Helen’s Island was built downstream of the bridge in section five to allow motorists from Longueuil to access St. Helen’s Island without having to cut across oncoming traffic from Montreal, thereby eliminating a potential source of accidents, particularly during rush hour.