Honoré Mercier Bridge

The Honoré Mercier Bridge, which is co-managed by the provincial government and JCCBI, serves as an example for collaboration with the Mohawk Council of Kahnawà:ke and the expertise of Mohawk contractors.

The Honoré Mercier Bridge crosses the St. Lawrence River and the seaway, on the west side of the Island of Montreal.

Named after the Honourable Honoré Mercier, a former Premier of Quebec, and his son, a former Minister of Lands and Forests, this bridge became the fourth structure to connect the Island of Montreal to the South Shore after the Victoria Bridge (1860), the Lachine Bridge (1885), and the Jacques Cartier Bridge (1930).


Initially made up of two lanes that belonged to the Corporation du pont du lac Saint-Louis, the Honoré Mercier Bridge was inaugurated in 1934, and its administration was transferred to the Government of Quebec in 1942.

Its steel structure was built by the Dominion Bridge Company Limited as part of work funded by the government to address the economic downturn. The bridge was designed by 11 French Canadian engineers who were graduates of the École Polytechnique de Montréal.

The bridge was opened to traffic on June 22, 1934, or 10 months before the scheduled completion date. It was originally 1361.25 m long. Its main steel arch span was 121.87 m long, and it had 11 steel spans and 31 reinforced concrete spans.

HM-2 HM-pics-1

Key dates 

1958-1959: For the St. Lawrence Seaway construction project, the St. Lawrence Seaway Management Corporation (SLSMC) started work to raise and extend the south section so that ships could pass underneath.

1963: Construction of the second bridge downstream from the first, currently managed by the provincial government.

1998: The management of the federal section of the Honoré Mercier Bridge and its south approaches is transferred to JCCBI.


Piers (provincial section)

The bridge engineers had to devise an innovative method to erect the bridge piers, given the thick layer of glacier marl over the rock, the river’s depth, and the speed of the current.

Since the St. Lawrence River is so deep at this point, the engineers decided not to use cofferdams and instead chose pneumatic caissons, a method that had not been used in Montreal in 25 years.

The Second Bridge

In 1963, it was felt that the Mercier Bridge’s two lanes were inadequate for the constantly increasing traffic travelling across it, so the Ministère des Travaux publics du Québec had a second bridge built downstream from the first.

In the federal section, the deck of the old bridge was modified so that it would have the same capacity as its “twin.” Minor changes were also made to the piers, as each pier was fully resurfaced with a new layer of reinforced concrete and were reshaped to match the piers of the new bridge.

Together, the new and old bridge doubled the number of lanes between both shores from two to four (two lanes per direction). Traffic to the South Shore then started passing over the old bridge, and traffic to Montreal was routed over the new one.


Exposed over the years to heavy traffic, weather conditions, and an abundant use of road salt, the structure of the Honoré-Mercier Bridge needed major repair work to increase its life span.

JCCBI adopted an active and preventive management approach and decided to fully replace the deck in the federal section of the Honoré Mercier Bridge, in 2008.

After eight years of highly complex work, the deck replacement program on the federal section of the Honoré Mercier Bridge was completed on August 14, 2016. In total, 982 panels were required to complete the new bridge deck and extend the bridge’s service life for at least 75 years. This major rehabilitation project represents one of the largest contracts carried out by Aboriginal Canadians.

The deck is made of precast concrete panels, which have many benefits:

  • This method is faster and more effective
  • This method limits road obstructions
  • The bridge will last longer compared to other methods (lifespan of 75 years)

Precast concrete is a high-quality construction material whose great resilience means both fast installation and a long service life. Also, the high-performance concrete mixtures combined with controlled production provide durability and reliability.


Normal traffic lane configuration


Mornings from 5:30 a.m. to 9:30 a.m.

  • Continuously: one lane open from Châteauguay
  • Alternating (traffic lights): one lane open from Châteauguay or from La Prairie
  • Two lanes open towards the South Shore

Daytime, evenings, nights, and weekends 

  • Two lanes open towards the South Shore
  • Two lanes open towards Montreal (one from Châteauguay and one from La Prairie)

Traffic is managed by the provincial government.