Роберт Бурасса: Крупнейшая ГЭС Квебека

Hydroelectric power station in Québec, Canada

The Robert Bourassa generating station, formerly known as La Grande 2 (LG 2), is a hydroelectric power station on the La Grande River that is part of Hydro Québec's James Bay Project in Canada. The station can generate 5,616 MW and its 16 units were gradually commissioned between 1979 and 1981. Annual generation is in the vicinity of 26500 GWh. Together with the adjacent 2,106 MW La Grande 2 A generating station (LG 2 A), commissioned in 1991–1992, it uses the reservoir and dam system of the Robert Bourassa Reservoir to generate electricity. The two plants taken together account for more than 20% of Hydro Québec's total installed capacity of 36,810 MW in 2009. Initially known as La Grande 2, it was renamed after Robert Bourassa who, as Premier of Quebec (1970–1976 and 1985–1994) gave the James Bay Project a vital political impetus.

The Robert Bourassa generating station is the main facility of the James Bay hydroelectric project, a large hydroelectric complex built on the La Grande River, a large river in Quebec's sparsely populated northern Quebec. It was also the first to be built, between 1974 and 1981. It was inaugurated by Premier René Lévesque of Quebec, on October 27, 1979. Conception work on the generating station, dam and reservoir began in October 1970 when Montreal based engineering firm Rousseau Sauvé Warren (RSW) was given by Hydro Québec to make the case for the development of the La Grande River. Another engineering firm, Asselin, Benoît, Boucher, Ducharme & Lapointe (ABBDL) was tasked with a feasibility study on the more southerly NBR (Nottaway, Broadback, Rupert) concept. At RSW the development of the La Grande River was championed by François Rousseau, one of firm's associates and a former Hydro Québec senior engineer. A final decision to build the hydroelectric complex on the La Grande hydrographic system was made in 1972, after engineers determined the NBR project would be less cost effective because of the silty nature of the soils in the NBR area. The La Grande option had the added advantages of a lesser impact on First Nations hunting and fishing, on the boreal forest and would require less flooding.

The main dam is located from the mouth of the river, in the transition zone between the plateau and the coastal plain, and has a maximum height of Twenty nine dykes of various sizes close the reservoir. They are organized in three group: dykes D1 D4 are located north of the spillway, nicknamed the Staircase of the Giants, D5 D14 are located on the left shore of the river while a third group, nicknamed the Duncan dykes (D17 D27), are located south. The dam and dykes hold a reservoir covering an area of with a useful capacity of 19.365 billion m³. The generating station itself is located underground, downstream from the main dam. It hosts 16 Francis turbines, set up in two groups of eight each.

The first step towards the construction of the La Grande 2 generating station took place in June 1971, in Matagami, a small mining town located south of La Grande River. Engineering firm Desjardins, Sauriol and Associates were tasked with the construction of a basic road to the future site and the Cree settlement at Fort George. The deadline was tight: 450 mile (724 km) in 450 days. The first challenge involved deploying teams of land surveyors and lumberjacks by seaplanes and helicopters to clear a path for a permanent road. Parallel to the path, a few kilometres away, an ice road was built to move heavy machinery north. The first milestone was reached on February 11, 1972, with the opening of the ice bridge crossing the Rupert River. The temporary road reached the La Grande River in December 1972, allowing the minimum necessary level of access needed to begin work – namely to construct housing for the thousands of people who would work on the dam for the next decade. A permanent road surfaced with gravel was completed on October 20, 1974, at a cost of $348 million, and was paved over the next two years.

The first stage of construction was the temporary diversion of the La Grande River; the tunnels had to be big enough to protect the construction site from floods, but not so large as to unnecessarily increase cost. Two diversion tunnels were drilled into the left bank of the river and were opened on April 27, 1975. For the next three and a half years the flow of the river would be diverted through the tunnels. Each tunnel was wide and high; the north tunnel was long and the south, The tunnels were designed to carry the 65 year flood flow of the La Grande River, calculated at
Since the original construction schedule called for completion on February 15, 1980, the south diversion tunnel was scheduled to be closed in November 1978, during low river flows in the winter. However, the deadline was revised forward by 60 days, and the tunnel had to be reinforced to withstand harsh autumn conditions. After the dam was completed, the tunnels are still used as flood control outlet works and have a design flow of .

The Robert Bourassa dam is located from the mouth of the La Grande River, in the transition zone between the Laurentian Plateau (the elevated Canadian Shield) and the coastal plain. It has a maximum height of and is long at the crest. The core of the earthfill dam is made of glacial moraine which is impervious, and available in large quantities within a radius of the dam site, due to extensive glaciation of the area during the last ice age. The core is slightly inclined upstream, to increase resistance against the immense pressure of water in the reservoir. The layers above consist of fill zones of varying coarseness, and is surfaced with riprap to reduce erosion. The original plan envisioned the construction of a concrete face rock fill dam, but this was rejected in favor of a more conventional embankment design, partly because of the lower cost, and also because the concrete face would have to be inspected from time to time requiring drainage of the reservoir. Because of the huge size of the reservoir, this would be essentially impossible. In order to hold the reservoir at its operating height of , 29 dikes surround the reservoir basin at various locations. Dikes D 1 to D 4 are located immediately to the north; D 5 to D 14 (the "Forebay dikes") to the south; and D 17 to D 27 (the "Duncan dikes") about 30 mile (48 km) further south. They range in size from D 26B, long, to D 20, long. +Dams and dikes of the Robert Bourassa developmentTypeCrestlengthMax. heightMin. topwidthExcavationvolumeFillvolumemftmftmftm3ft3m3ft3North dikes (D1 D4)Main damForebay dikes (D5 D14)Duncan dikes (D14 D27)Total

Covering an area of – greater in size than Luxembourg – the vast Robert Bourassa Reservoir is fed by an upstream catchment of , plus water diversions from the James Bay Project, the Caniapiscau Reservoir and the EOL (Eastmain Opinaca La Grande) diversion project. About is active or usable storage for power generation, out of a total volume of Because of its great size, it is inhabited by a diverse array of aquatic flora and fauna. On November 27, 1978, the diversion tunnels were closed and water began to back up behind the dam. The enormous reservoir took over a year to completely fill. The water initially rose very fast: during the first week, with on the first day alone. The reservoir reached its minimum operational level of on September 2, 1979, and reached its normal maximum level of in December 1979.

The construction of the Duncan dikes partially blocked the flow of the Dessaulniers River, which is located to the southeast of the Robert Bourassa Reservoir. The river flowed into Dessaulniers Lake at an elevation of , below the level of the Robert Bourassa Reservoir. To prevent the flooding of an additional and preserve the lake in its natural state, a pump station was installed which removes water from the Dessaulniers to the Robert Bourassa Reservoir. The pump station was designed to remove an annual average of , from a drainage area of
The pump station was commissioned in June 1977. It has four pumps with a capacity of each, with a maximum lift of Each pump is powered by a 1,120 KW (1,500 hp) motor. The pumping station also served to divert water away from the Dessaulniers river bed, during the construction of dike D 20.

The spillway, nicknamed Staircase of the Giants, is near the north end of the main dam and is part of dike D 4. It consists of a concrete control structure and a man made waterfall discharging into a stilling basin below the dam. The spillway has eight wide gates, separated by thick columns. The gates are opened and closed by cable winches, in order to control spills. The eight gates are all opened at the same time once every 15 years. Having passed through the gates, the kinetic energy of the water is dissipated in a basin at the foot of the control structure. It then flows down a long rock channel with a vertical drop of on its way back into the La Grande river. The channel has 10 steps ranging from in height and in length. The flow rate increases from at the top of the spillway to at the bottom.