The first run-of-the-river generating station of the James Bay project necessitated 401,000 m3 of concrete, 290,000 m2 of formwork and 19,000 tons of reinforcing steel. Pomerleau completed an average of 7 to 12 concrete pours per day. In total, 86,000 m3 of concrete were placed between June and October 1990, 235,000 m3 in 1991 and 80,000 m3 in 1992.
The geometry of the work was of a complexity that is seldom seen. Five sets of formworks were needed because of the tight schedule. The formworks for constructing the much less complicated semi-spiral cases were prefabricated on the site.
The generating station houses 12 blocks of turbine-alternator sets with a total installed power of 1,368 MW.
The project involved constructing the following:
- A long dike using backfill;
- A 100 m long gravity dam;
- A concrete sectional gravity dam supporting the spillway, which is 45 m long and has 8 floodgates. Its discharge capacity is 16,280 m3 per second;
- The generating station is 33 m long, 60 m wide and 60 m high;
- The transition dam and the southern gravity dam.
All the site's process water was pumped directly from the La Grande River using a 70 m3/hour platform that fed a 120,000 L surge tank located in the concrete plant to keep it from freezing over. This tank also fed the site's water supply system and the fire fighting system.
A 1 x 200 hp dry compressed air generating facility was installed in the service area to distribute compressed air by means of two upstream and downstream collectors.
- 4 rail mounted tower cranes were installed;
- Formworks: Because the formworks had to be handled millions of times, we used the climbing type;
- Concreting: huge rail mounted concreting masts (110 m) were installed along the water intake and the generating station in order to complete the major concrete pours.
- A concrete plant that could make concrete at 7°C and had an output capacity of 1,000 m3/hour was put in place and operated by the contractor on site.
Deploying equipment and manpower on a 20/24-hour and 6/7-day basis, we completed all the originally planned work, into which more than 5,000 change orders had to be integrated, 5 months ahead of schedule.