There has been recent speculation about whether or not Mount Polley is dumping waste into Quesnel Lake. In short, the answer is no. Current treatment of water at Mount Polley, including the dilution zone at depth in Quesnel Lake, ensures water released into Quesnel Lake is in line with BC and Canadian water quality standards. Mount Polley discharges only treated mine site water that meets strict Environmental Management Act (EMA) permit guidelines.
All mine site water is collected and is treated by a Veolia ACTIFLO™ water treatment plant before it is released into Quesnel Lake. (see veoliawatertech.com for more information on their treatment systems and how they work.) The water going into the WTP (influent) is monitored on an ongoing basis (measurements of turbidity every 15 seconds) and the treated water leaving the plant (effluent) is sampled regularly for analysis. The lake water quality is also routinely monitored and sampled regularly as part of the mine’s Comprehensive Environmental Monitoring Plan.
The following are facts that explore, in more detail, the discharge from Mount Polley into Quesnel Lake. We hope this information provides factual clarity about Mount Polley’s approved activities.
Is Mount Polley’s discharge having negative effects on Quesnel Lake?
There are no indications in the monitoring data that the Mount Polley discharge is having any negative effects on Quesnel Lake water quality. If you are interested in looking at some of the water quality data that has been collected on surface water in the area around the Mount Polley Mine, the results are available through the BC Government Surface Water Monitoring Sites Interactive Map
Is the water in Quesnel Lake contaminated? Is it safe to drink?
At this time, there are no indications of contamination of Quesnel Lake water from the Mount Polley spill. The mine, and the Ministry of Environment and Environment Canada, continue to monitor Quesnel Lake. With the exception of natural causes, the lake does not exceed environmental guidelines for any of the constituents of concern that are found in the Mount Polley tailings.
As early as August 12, 2014, BC’s Interior Health Authority (IHA) rescinded all water use restrictions from Quesnel Lake (including for “drinking water, personal use, fishing, swimming and recreational purposes”), except for the immediate impact zone where Hazeltine Creek entered Quesnel Lake. The IHA notice also stated that “Interior Health has no reason to believe that this water was ever exposed to unsafe levels of contaminants from the mine breach. As a result, flushing and testing of individual water supply systems is not considered necessary.”
All water use restrictions were fully rescinded July 13, 2015. (Note: IHA always advises that surface water be treated for pathogens prior to use/consumption.)
How much is the mine discharging into Quesnel Lake?
The Environmental Management Act permit annual average authorized discharge rate is 29,000 cubic meters per day. The actual discharge rate depends upon the rainfall experienced at site which varies from year to year. In 2019, the annual average discharge rate has been 14,883 cubic meters per day, significantly less than the mine’s permit allows.