It could take more than 50 years for B.C.'s Cheakamus River to recover from a massive toxic spill last summer, according to government reports.

A CN freight train derailed about 30 kilometres north of Squamish, dumping 41,000 litres of sodium hydroxide into the Cheakamus River Canyon in August 2005.

The derailment last August

Government biologists estimate more than 500,000 fish died after the tank car ruptured, the Vancouver Sun reported Tuesday, citing government documents. The tank car was among a number of freight cars that fell off a bridge and went into the canyon.

Almost all the fish in an 18-kilometre section of the river were killed. Fish downstream of the spill in the Squamish River were affected, and animals that ate the fish could also have been harmed, the reports said.

Rail company helping restore stocks

Just after the spill, the federal Department of Fisheries and Oceans said it and CN had agreed to restore salmon stocks in the river.

The company "agreed to contribute funds for additional enhancement of Cheakamus River chinook and pink salmon stocks," while department staff were collecting larger than usual numbers of salmon eggs to incubate in a fish hatchery, the newspaper quotes the government reports as saying.

The impacts on the river were predicted within days of the spill.

As the last freight car was removed from the valley on Aug. 12, the B.C. Wildlife Federation said "pink and chinook salmon have been returning to this system for the last several weeks. It is assumed that the chemical spill destroyed a large portion of these spawning fish and may have destroyed their eggs. Coho fry in the system were also affected."

The river is home to five kinds of salmon, trout and other fish.

The B.C. government said CN was responsible for paying for the cleanup.

B.C. Environment Minister Barry Penner said at the time that charges would be laid if federal and provincial investigators found evidence of wrongdoing.