Chisasibi residents have 3 hours and 10 minutes to evacuate if the Robert Bourassa (LG-2) Reservoir busts open, according to newly released Hydro-Quebec documents.
The community of 3,500 has about an hour more than we previously reported.
In Aug. 1997, The Nation reported that Chisasibi would be flooded after only 2 hours and 14 minutes.
This information came from a 1989 Hydro-Quebec map that was released to The Nation after an access-to-information request.
The map also seems to suggest that the only road out of town would be cut off after 1 hour and 55 minutes.
But a 1989 disaster study for LG-2 recently released to The Nation shows Chisasibi has a little more time than the map seems to suggest.
The study doesn’t give details on a breach at the main LG-2 dam, but rather at some of the huge dikes holding back the 2,835-square-kilometre Robert Bourassa Reservoir.
One simulation illustrates a breach at the lengthy CD-05 dike, which is adjacent to the LG-2 dam on the dam’s southwest side.
If CD-05 busts, an initial front of water would arrive at Chisasibi after 2 hours and 14 minutes, but would not be initially high enough to immediately flood the community, which is home to the regional Cree hospital.
Chisasibi, which is 50 feet above sea level, would remain dry for another 56 minutes.
The study doesn’t specify when the road out of town would be cut off by the torrent of water.
Water levels at Chisasibi would reach their maximum about 8 hours after the catastrophe. After 8 hours, Chisasibi would be left under 9 metres (29.5 feet) of water.
The study suggests it would take several days before the water recedes from the area of the community, but exactly how long isn’t made clear.
The study is entitled La Grande 2 Reservoir, Rupture of the Dikes CD-05, CD-07, CD-09, CH-20 and CH-21.