The July 1996 flood destroyed these Chicoutimi River spillways. Pomerleau was contracted to recreate them, incorporating the revised calculations for probable maximum flood.
Working in winter on sites 2 km apart and with an extremely tight schedule, Pomerleau placed 15,000 m3 of concrete in 3 months (170 pours), used 150,000 tons of granulate for the cofferdams, and excavated an area of 50,000 m2.
The spillways cross the river within about 50 m of their original locations. An 8 m wide service bridge tops each. Pomerleau also constructed water intakes for possible future power stations.
Garneau Falls Spillway:
- 80 m long by 6.25 m high;
- 5 channels with heated mechanical floodgates and releasable stop logs;
- 90 m long by 14 m high rockfilled dam on the left bank.
Arnaud Bridge Spillway:
- 40 m long by 10 m high;
- 2 channels with heated mechanical floodgates and 2 with releasable stop logs;
- 60 m long by 14 m high rockfilled dam blocks off the headrace.