The Cheakamus River derailment occurred on August 5, 2005, when nine cars from a Canadian National Railway freight train derailed into the Cheakamus River in British Columbia. The cars contained approximately 40,000 litres of caustic soda (sodium hydroxide), which entered the river, killing more than 500,000 fish from 10 different species, including chinook salmon, coho salmon, pink salmon, and rainbow trout, both freshwater and ocean-dwelling. The derailment cost CN at least $7 million.