Modernization of the Beauharnois–Les Cèdres hydropower complex

Beauharnois Generating Station

Beauharnois generating station is a run-of-river hydroelectric generating station built in three phases between 1929 and 1961. During this period, with its installed capacity of 1,643 MW, it became the largest generating station in Canada! Today, its 36 generating units with an installed capacity of 1,912 MW make it the fifth largest generating station in Québec and the largest run-of-river facility. Hydro-Québec became the owner of Beauharnois generating station in 1944, during the first phase of the nationalization of electricity in Québec.

Les Cèdres generating station

It is the second oldest (after Shawinigan-2, built in 1911) of the hydropower generating stations operated by Hydro-Québec and the first to result from the alliance between Shawinigan Water & Power and Montreal Light, Heat & Power. At the time of its commissioning, it was the most powerful facility in Québec with 74.8 MW. Today, its installed capacity is of 113 MW.

Coteau-1 dam

This dam, built in 1933 by the Beauharnois Light, Heat and Power Company, is one of four dams on the Coteau whose main functions are to maintain the level of Lac Saint-François and to facilitate the flow of water to the Beauharnois canal and Les Cèdres generating station headrace canal.

• Length: 320 m
• Number of gates: There are 20 openings in which 18 gates are located. Two openings have been sealed with concrete beams

Coteau-2 dam

This dam, built in 1934 by the Beauharnois Light, Heat and Power Company, is one of four dams on the Coteau whose main functions are to maintain the level of Lac Saint-François and to facilitate the flow of water to the Beauharnois canal and Les Cèdres generating station headrace canal.

• Length: 130 m
• Number of gates: The dams’s eight gates were concreted over in the 1990s

Coteau-3 dam

This dam, built in 1940 by the Beauharnois Light, Heat and Power Company, is one of four dams on the Coteau whose main functions are to maintain the level of Lac Saint-François and to facilitate the flow of water to the Beauharnois canal and Les Cèdres generating station intake canal.

• Length: 270 m
• Number of gates: 16

Coteau-4 dam

This dam, built in 1943 by the Beauharnois Light, Heat and Power Company, is one of four dams on the Coteau whose main functions are to maintain the level of Lac Saint-François and to facilitate the flow of water to the Beauharnois canal and Les Cèdres generating station intake canal. This is a retaining structure that complements the other three.

Length: 900 m

Île Juillet-1 dam

This dam was built in 1940 by the Beauharnois Light, Heat and Power Company to increase the flow through Les Cèdres generating station headrace canal and to restore water levels between the Coteau rapids and the generating station.

• Length: 91 m
• Number of gates: 5

Île Juillet-2 dam

This dam was built in 1941 by the Beauharnois Light, Heat and Power Company to increase the flow through Les Cèdres generating station headrace canal and to restore water levels between the Coteau rapids and the generating station.

• Length: 150 m
• Number of gates: 9

Pointe-des-Cascades dam

Like the Saint-Timothée and Pointe-du-Buisson dams, this dam was built in 1964 by Hydro-Québec to create water bodies to meet the concerns of property owners near the dam and restore the river to its original appearance.

The dam is 1,721 m long and includes a spillway with 14 gates, a weir with two sections on either side of the Île des Cascades (518 m and 210 m) and a skimmer near the right bank, which maintains an ecological flow downstream from the structure.

Pointe-du-Buisson dam

The construction of the Pointe-du-Buisson (1960-1962), Pointe-des-Cascades (1964) and Saint-Timothée (1971) dams reflects the desire to create bodies of water for recreational and tourist uses between Saint-Timothée and Pointe-des-Cascades, and more specifically between the Île-Juillet and Lac Saint-Louis dams.

The dam is 1,588 m long and has three sections: a spillway, a weir and a skimmer. The spillway is 215 m long and has 14 gates. The weir, on the left bank, measures 457 m. The skimmer has two gates and ensures that an ecological flow is maintained downstream of the structure.

Saint-Timothée dam

The construction of the Pointe-du-Buisson (1960-1962), Pointe-des-Cascades (1964) and Saint-Timothée (1971) dams reflects the desire to create bodies of water for recreational and tourist uses between Saint-Timothée and Pointe-des-Cascades, and more specifically between the Île-Juillet and Lac Saint-Louis dams.

• Length of spillway: 144 m
• Number of gates: 10
• Embankment with skimmer: 272 m
• Rockfill dike: 345 m

Structure-1

This dike holding back water between the Rivière Saint-Charles and the Saint-Timothée basin underwent maintenance work in spring 2020.

Beauharnois canal dikes

Les Cèdres generating station dike (les Cèdres right bank embankment)

The dam of Les Cèdres generating station was built in 1913 and 1914 at the same time as the generating station of the same name, in order to direct the water to the headrace canal to turn the turbines. The dam is currently undergoing a rehabilitation project.

Lac Saint-Louis

The second widening of the Saint-Laurent east of Lake Ontario, this 148-km2 lake is located upstream from the island of Montréal. Water from the Saint-Laurent exiting the Beauharnois generating station turbines and the spillway of the Pointe-des-Cascades dam flows into this lake, as do two of the four outlets of the rivière des Outaouais (Ottawa River).

Lac Saint-François

At the outlet of this first widening of the Saint-Laurent east of Lake Ontario, with a surface area of 233 km², the water follows the natural course of the river or passes through the Beauharnois canal.

Beauharnois canal and St. Lawrence Seaway

Between Lac Saint-François and Lac Saint-Louis, the Saint-Laurent has a difference in elevation of 25 m and an average flow of 7,400 m3/s. To take advantage of this hydroelectric potential, the Beauharnois Light, Heat and Power Company (BLHPC) asked the federal government to obtain the right to divert the Saint-Laurent and develop Beauharnois generating station. In 1929, the company was granted permission to build this canal, which is 25 km long and 1 km wide, on the condition that its primary purpose be the navigation of the St. Lawrence Seaway. Two locks were built on the left bank of Beauharnois generating station to allow ships to travel the difference in elevation.

Pointe-du-Buisson basin

This basin is located between the Saint-Timothée and Pointe-du-Buisson dams. Following the reduction in flow that occurred in the natural riverbed of the Saint-Laurent from 1930 to 1960, structures were built to maintain water levels that met the community’s needs, including vacationing needs. In addition, because managing the ice on the Saint-Laurent is a challenge every winter, some structures have been designed to stay open during the winter to reduce ice-related issues. Due to their design, these structures cannot be operated in the winter. Water levels are therefore always low during this season.

Pointe-des-Cascades basin

This basin is located between the Pointe-du-Buisson and Pointe-des-Cascades dams. Following the reduction in flow that occurred in the natural riverbed of the Saint-Laurent from 1930 to 1960, structures were built to maintain water levels that met the community’s needs, including vacationing needs. In addition, because managing the ice on the Saint-Laurent is a challenge every winter, some structures have been designed to stay open during the winter to reduce ice-related issues. Due to their design, these structures cannot be operated in the winter. Water levels are therefore always low during this season.

Saint-Timothée basin

This basin is located between the Île-Juillet and Saint-Timothée dams. Following the reduction in flow that occurred in the natural riverbed of the Saint-Laurent from 1930 to 1960, structures were built to maintain water levels that met the community’s needs, including vacationing needs. In addition, because managing the ice on the Saint-Laurent is a challenge every winter, some structures have been designed to stay open during the winter to reduce ice-related issues. Due to their design, these structures cannot be operated in the winter. Water levels are therefore always low during this season.

Beauharnois locks

Saint-Louis (Hungry Bay) canal intake

This water intake was built in 1929 to regulate the flow of water through the Saint-Louis canal.