Photo (left): Construction of the plant’s superstructure took place in 1913. More than 300 carpenters and joiners were hired to build this portion of the plant.
Photo (right): When commissioned in 1914, the Les Cedres hydroelectric generating station had nine Francis units in place as well as three exciter units. Nine other Francis units were added over the next 10 years.
The 130-MW Les Cedres generating station in Canada is a landmark in the history of Quebec hydropower. Hydro-Quebec recently celebrated the station’s 100th year of operation, as well as its induction into the Hydro Hall of Fame.
The 130-MW Les Cedres hydroelectric development is located on the Saint-Laurent (St. Lawrence) River in the Canadian province of Quebec, about 1.2 miles (2 km) east of the municipality of Les Cedres. Construction began in 1912, and the hydro facility was commissioned in 1914 by Cedars Rapids Manufacturing and Power Co. The development, which has been owned by Canadian provincial utility Hydro-Quebec since 1944, is still active, making it the second-oldest Hydro-Quebec facility in operation, after the 200-MW Shawinigan-2 plant. Les Cedres includes a powerhouse incorporated into the main gravity dam, as well as two spillways, a transformer substation and nine control structures.
The Les Cedres hydro facility is located in a narrowing of the St. Lawrence River between Lake Saint-Francois (upstream) and Lake Saint-Louis (downstream). This stretch of the river is characterized by a series of three rapids — Coteau, Les Cedres and Cascades — with drops totaling close to 82 feet (25 m) over a distance of 15 miles (24 km). To compensate for the low head of 31 feet (9.5 m) at Les Cedres Rapids, the hydro development comprises 4.7 miles (7.6 km) of retaining and control structures. The generating station extends only partway across the river, a dike having been built parallel to the shore to funnel part of the flow of the river to the turbines, while leaving a channel open for navigation.
In July 2014, the Les Cedres facility was inducted into the Hydro Review Hydro Hall of Fame during the HydroVision International event in Nashville, Tenn, U.S. The Hall of Fame recognizes hydropower plants across the globe that have been in continuous operation for 100 years or more. (For more information or to nominate a hydro facility for this award, visit www.hydroworld.com/index/hall-of-fame.html.)
From the early 18th century, the hydraulic potential of this stretch of the St. Lawrence River was harnessed by watermills. In 1904, a local family joined with partners to create Cedar Rapids Manufacturing and Power in order to develop a hydropower project at this site of the Les Cedres plant. By 1911, the company had obtained the necessary government authorizations, as well as a long-term lease for the site. However, finding sufficient investors proved difficult and the company was sold to a local businessman, D. Lorne McGibbon, later that year, who continued to operate it under the same name.
In 1912, McGibbon managed to involve Quebec’s two largest electrical utilities — Montreal Light, Heat and Power Co. and Shawinigan Water and Power Co. — by guaranteeing them distribution rights for part of the plant’s output (30 MW). That same year, Cedars Rapids Manufacturing and Power signed a 99-year agreement with aluminum producer Alcoa to export 45 MW of electricity to that company’s aluminum smelter in Massena, N.Y. Under the agreement, Alcoa also undertook to build the transmission line between the hydropower plant and its own facilities. As a result of this arrangement, Les Cedres became the first hydroelectric development in Quebec built with a view to exporting part of its output.
In the summer of 1912, the first phase of construction began, based on a 1910 design by engineer Henry Holgate. This phase included installation of cofferdams, dewatering of the site, construction of jobsite buildings, laying out of railroad tracks to transport the materials, and excavation.
In 1913, work began on the dam’s foundation and the generating station’s superstructure, including the outer facade. Whereas most powerhouses of the period were brick, Cedars Rapids Manufacturing and Power opted for an innovative construction system patented in 1912 by the American firm Unit Construction. This system employed prefabricated reinforced concrete panels, a technique mainly used in Europe that allowed work on the generating units to proceed unimpeded.
|Still in operation 100 years after its inauguration, the Les Cedres plant is the second-oldest Hydro-Quebec facility in use today.|
The structure was completed in the spring of 1914, and the workers went on to install the interior machinery and equipment. Nearly 300 carpenters and joiners were employed at the Les Cedres job site, along with other specialists such as engineers, masons and electricians.
Construction of the facility was completed in November 1914, and the generating station was commissioned shortly thereafter. It contained nine main generating units and three auxiliary exciter units. The main units were among the first vertical-axis Francis units installed in Quebec and among the largest generating units in Canada. The turbine runners were 17.7 feet (5.41 m) in diameter and weighed 72 tonnes.
The use of turbines this massive and powerful was only possible thanks to another major technological breakthrough — the Kingsbury bearing. This type of thrust bearing, which uses an oil film as a lubricant between the moving part and the shoe, was able to support the weight of the turbines while minimizing the mechanical wear that occurs with conventional bearings.
At its inauguration, the Les Cedres generating station’s capacity was 74.8 MW, making it the most powerful facility in Quebec. In the summer of 1915, a 10th generating unit was brought on stream, adding 10 MW of capacity. Eight more units were added between 1918 and 1924, for a total of 18 units and 162 MW, which corresponds to the plant’s planned capacity. This required expanding the substation building to accommodate three additional bays in order to handle the extra capacity.
The Les Cedres generating station was designed as a function of the site’s low head and high flow rate. Resting on bedrock outcrops, the 131-foot-high (40 m), 1,201-foot-long (366 m) structure includes the dam, powerhouse and water intake facilities.
Built in the modern industrial style, it comprises a metallic structure onto which prefabricated concrete panels were attached. The hydro plant’s aesthetic stems from the rhythmic succession of full concrete and glass bays separated by pilasters. The overall layout of the facade, with its regular arrangement of openings and the pleasing proportions of its different components, evokes classical architecture, making it a particularly unique sight along the waterway. The generator hall has a clerestory roof, which was rebuilt in 2000. Its large, articulated windows run along the entire length of the building, providing light and ventilation.
A notable feature of the powerhouse is the impressive size of the machine hall, which occupies the entire length and height of the structure. Stairs on the upstream side lead to an overhanging area where the water intake gates are operated. On the downstream side, the auxiliary and control equipment are distributed on two levels, the second a mezzanine.
The transformer substation is completely separate from the powerhouse, which is rare for a facility of this size. The substation building is rectangular and resembles the powerhouse but is distinguished by its smaller size, the slightly different use of the prefabricated concrete construction system, and the arrangement of its glass bays. The control room was upgraded in the 1970s and again in recent years. However, three transformers and some control panels from the original facility were kept for educational purposes.
Changes and rehabilitation
In 1944, during the first phase of the nationalization of electricity in Quebec, the provincial government acquired Montreal Light, Heat and Power, which had been the sole owner of Les Cedres generating station since 1921. Ownership of the Les Cedres hydroelectric development and all of the company’s other facilities was transferred to Hydro-Quebec.
During the 1970s, a large-scale rehabilitation program was launched to modernize Hydro-Quebec’s generating fleet. Changes made to the Les Cedres facility under this program included automating operations, modernizing control structures and replacing substation equipment, which is now located outdoors.
A number of manufacturers and suppliers assisted with the work undertaken during this program. One example is L&S Electric of Schofield, Wisc., which provided five governors to replace the previously installed I.P. Morris governors, as well as wicket gates and feedback devices.
Throughout these and subsequent modifications, the generating station has largely retained its architectural and technological integrity.
In addition to its architecturally unique design, the Les Cedres facility constitutes an early example of technological innovation that continues in the same tradition today. For example, when it was commissioned in 1914, its thrust bearings were the largest ever designed by Kingsbury and the first to have eight shoes.
An overhaul program had been implemented to extend the useful life of six of the station’s generating units for another 40 years. Two units were refurbished between 2010 and 2014 using traditional runner casting methods.
For the overhaul of the next unit, the runner blades will be made from pressed skin plates rather than by casting — a first for Hydro-Quebec and a world first for such a large runner. If it proves successful, this technique could be used in future refurbishments because it would reduce manufacturing lead times. In addition, electric servomotors will be installed to operate the wicket gates, thus eliminating the need for large quantities of oil. This is another first for Hydro-Quebec and the results will be closely monitored.
Les Cedres generating station was a symbol of innovation when it was built, and it continues to innovate 100 years later.
To mark the facility’s centennial, Hydro-Quebec employees and retirees and the general public were invited to an open house at Les Cedres on June 14, 2014. The event, which included a commemorative ceremony along with an exhibition and guided tours of the facility, was a huge success, with more than 1,200 people in attendance.
Recognizing Canada’s historic plants
Les Cedres is the eighth Canadian plant to be inducted into the Hydro Hall of Fame since its inception. Other historic facilities in the country, and the year they were inducted, are:
DeCew Falls No. 1, 1998
Petty Harbour, 2003
William Birch Rankine, 2005
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