Engineers are pumping water from a lake that was dammed in by debris spilt from a breached tailings pond in British Columbia's Cariboo Region.
Imperial Metals Corp., the company that owns the breached pond, is moving water from Polley Lake into Quesnel (kwih-nel) Lake in order to relieve pressure on a wall of debris that formed after the spill.
The provincial environment ministry says water levels in Polley Lake have risen by about two metres.
It says the newly-formed dam is preventing water from flowing out of the lake and authorities are worried material will wash out if pressure on it is not relieved.
Environment Minister Mary Polak says government authorized the company to start pumping after the latest results from Polley Lake suggested water quality is similar to that of samples taken in the 1980s.
A water-use ban on the lake is still in effect, and authorities will be testing water being pumped into Quesnel Lake daily.
Ten million cubic metres of water and 4.5 million cubic metres of silt was spilled after the Mount Polley tailings pond was breached, raising fears about drinking water, fish stocks and the region's ecosystem.