Selenium levels in the livers and gonads of fish from Polley and Quesnel lakes have tested above the guidelines for human consumption but the fish are still safe to eat, according to B.C. government officials.
Tests for the substance and whether it is showing up in greater concentrations in fish are part of monitoring the province is doing in the wake of an Aug. 4 tailings-dam breach at the Mount Polley mine. Long-term monitoring of sediments is part of that process.
"A person would need to consume about one cup of lake trout and rainbow trout livers and gonads in one day in order to exceed the high consumption threshold," B.C. Environment Minister Mary Polak said Friday in a conference call.
"By comparison, consumption of one cup of lake trout or rainbow trout flesh – not including the livers and the gonads – per day, does not exceed the guideline."
The flesh of the fish remains safe to eat, she said, adding that similarly elevated selenium levels showed up in tests conducted in 2013.
Selenium is a mineral found in soil and can also show up in water and food. High concentrations of the mineral can pose a risk to human health.
Friday was the deadline for the mine owner, Imperial Metals, to file a detailed action plan outlining its cleanup strategies.
That plan will be made public after it is reviewed by the Ministry of Environment, the government said Friday. The breach, which is currently under investigation, sent a torrent of mineral-laden silt and water into nearby lakes and streams and raised questions about the safety of other tailings dams in the province.
The company's plan is expected to outline what steps it will take to prevent more tailings from seeping into area waterways.
A drinking-water ban put in place after the breach has been largely rescinded, but a 'do not use' advisory remains in place for the impact zone directly affected by the breach, including Polley Lake, Hazeltine Creek and and the area within 100 metres of the spot where Hazeltine Creek runs into Quesnel Lake.
Water samples taken from Quesnel Lake near the mouth of Hazeltine Creek have met provincial and federal drinking-water guidelines.
The province this week said there would be an independent investigation into the Mount Polley incident, as well as inspections at other tailings ponds around the province.
During hearings for the proposed Site C hydroelectric facility held earlier this year, a government employee told the proceeding there is an average of one dam failure a year in the province but that most of those failures occur at small, 'low consequence' projects – those considered to pose less risk to people, structures or the environment if they fail.
"I think surprisingly to most folks, on average, we get about one dam failure a year in B.C., but most of these are very, very low consequence and they probably don't even make the papers, so most people are not aware of them," Glen Davidson, of B.C.'s Ministry of Forests, Lands and Natural Resources Operations, said at proceedings held in Fort St. John on January 13.
A transcript of the proceedings was obtained through a Freedom of Information request.