Outardes-4 is a hydroelectric power station and dam on the Outardes River 70 km northwest of Baie-Comeau, Quebec, Canada. The power station was commissioned in 1969 and is supplied by the Outardes-4 Reservoir which is created by seven additional dams.

Construction

Outardes-4 was built in conjunction with the Manicouagan-Outardes project and is the northernmost power station on the Outardes River. Construction on the diversion tunnel for the Outardes River began in September 1964 and was finished in April 1965. A cofferdam was constructed upstream to direct the river into the diversion tunnel; none was built downstream because the river's grade was sufficient. Once the river was diverted, work commenced on Dam No. 1's foundation. Workers and engineers cleared alluvial material from the riverbed but ran into uplift faults and pot-holes. Around six pot-holes with 10 ft to 15 ft diameters and up to 60 ft deep had to be excavated, partly by hand. Eventually, those under the dam's foundation were filled in with concrete.

Dams

The Outardes-4 Reservoir is impounded by eight different dams. The main dam is Dam No. 1 and is a rock-fill, earthen embankment dam along with Dam No. 2. The six other dams are saddle and auxiliary dams; one is rock and earth-fill, four are earth-fill dikes and one serves as a controlled concrete spillway. Dam No. 1 is 2087 ft long and 437 ft high and made of 9600000 yd3 of material while the second largest dam, No. 2 is 2383 ft long and 335 ft high. Dam No. 2 is located 2 km north of No. 1 on a side-valley is made of 6100000 yd3 of material. Water from the reservoir helps regulate river flow and power generation at the downstream Outardes-3 and Outardes-2 power stations.

Power station

The Outardes-4 power station is located on the west bank of the Outardes River, adjacent to Dam No. 1. Four 850 ft long, 20 ft wide penstocks deliver water from the reservoir to each of the power station's turbines. The power station was commissioned in 1969 and currently has a 785 MW capacity. The power station's turbines were rehabilitated in 2009 which had increased generation capacity by 56 MW.