One month after the tailings pond breached at the Mount Polley mine in central BC – the mine’s operator now says the amount of contaminated water and waste that spilled into the ecosystem was nearly twice as much as originally estimated.

After the dam burst on Aug. 4, the initial estimates were that 10 million cubic metres of wastewater plus more than four million cubic metres of sediment spilled into Polley Lake, eventually washing down Hazeltine Creek into nearby Quesnel Lake.

Imperial Metals now says nearly 25 million cubic metres of contaminated water and mine waste spilled into surrounding waterways, about 78 per cent more than the first estimates. That total includes:

■10 million cubic metres of water.
■13.8 million cubic metres of tailings slurry.
■0.6 million cubic metres of construction waste from the dam.