Muddy water caused by a landslide on the north bank of La Grande River marred Chisasibi’s annual gathering on Fort George Island at the beginning of August.
People were forced to bring their own water to the festival because the river water contained levels of silt 100 times greater than allowed in drinking water under Canadian regulations.
According to Chisasibi’s water treatment operator, Matthew Chiskamish, people traditionally use the river water at Fort George. But this year the NTU reading (a method of measuring the water’s turbidity) reached a level of 50, far higher than the allowable level of 0.5. (The community’s drinking water was unaffected because of the town’s water treatment plant.)
The landslide occurred sometime before July 30, Chiskamish said. People noticed the water colour becoming cloudy – something that normally happens only in the spring or fall. Hydro-Quebec was notified, and the utility investigated by helicopter, discovering the landslide at a place known locally as Shawksathtin, about 30 to 40 km upriver from the LG-1 dam.
The slide measures 200 feet across at the top and almost double that at the bottom, which is “a really big slide,” Chiskamish said. The muddy water in the river did not clear up for five days.
Chisasibi band councillor Eric House says community elders knew something
was about to happen with the river because permafrost was thawing to an unusual degree, while water levels in the river were also much higher than normal at mid-summer.
House notes that Hydro Quebec is conducting tests on two turbines at LG-1 to find the maximum power generating capacity at the facility. “Water levels are only a metre below maximum,” he observed.
But House also says deforestation had a role in the slide, pointing to the logging Cree Construction recently completed in the area between LG-1 and LG-2. He believes that would have affected soil stability in the bank of the river.
A landslide in 1979 upriver from the current slide caused much greater damage, House recalls. An island in the river was almost completely swept away, while a smaller tributary was swamped by the resulting tidal wave. “It wiped everything out,” House said.