New Mt. Polley report concludes metals could affect important fish species

Researchers from the University of Northern British Columbia (UNBC) were some of the first on the scene after an August 4, 2014 tailings pond breach released an estimated 2.6 billion gallons of wastewater and 1.3 billion cubic yards of tailings into the watershed in the Polley Lake/Hazeltine Creek/Quesnel Lake area of British Columbia.

The scientists were already well familiar with the area, having collaborated on other projects in Quesnel Lake. They began sampling right away and continued to gather data for two months.  A report on their findings, co-authored by five researchers and their collaborators, has been published in the online journal Geophysical Research Letters.

Some findings:

– Both the level of the lake and the temperature of the lake bottom have increased. The level increased by 7.7 cm, and the temperature increased by 1 to 2.5 degrees C.

– Observable impacts of a sediment plume may be reduced, but tailings and scour materials continue to be transported throughout Quesnel Lake.

– Ultra-fine sediment is still suspended in the lake (enough to cover a surface area of around 642 square miles).

– Each spring this lake experiences isothermic conditions during which the temperature is the same from top to bottom of the lake. These conditions allow for ready mixing of materials, potentially bringing settled tailings and scour material back into the water column. 

– Waste materials currently present in the lake could affect the metal content of aquatic food webs and are a potential hazard to the “growth, survival, and behavior of important fish species.”

In their report, researchers wrote that they expect spill-related metals in Quesnel Lake to accumulate in salmon and trout over time, and said further study is warranted to measure and evaluate how the contaminants move and enter food webs, as well as “long-term trends in metals of concern in resident and migratory fish species.”

While immediate impacts to fish were not observed in the days following the spill, it is unclear how they could be affected over time. The UNBC report notes that juvenile salmon “likely entered the turbid bottom waters and were exposed to materials associated with the mine spill for substantial periods each day.” In addition, the “progeny of the 2013 nondominant cycle line were rearing within Quesnel Lake during and following the breach event.”

UNBC press release

Full Report: The impact of a catastrophic mine tailings impoundment spill into one of North America’s largest fjord lakes: Quesnel Lake, British Columbia, Canada

Read more: Vancouver Sun article