Imperial Metals Corp., owner of the mine that caused Canada's worst mining disaster in history, has started limited production at an even bigger mine, which could be a threat to Alaska's $2-billion annual salmon and tourism business.

Meanwhile, Imperial has applied for a temporary restart of Mount Polley Mine, where a tailings storage pond failed in August 2014, spewing 4.3 billion gallons of water and 10.3 million cu yd of mine tailings and construction waste into two lakes and a creek that are part of the Fraser River watershed in British Columbia.

The Mount Polley spillage affected Quesnel Lake—a fjord-type lake in which salmon spawn—dumping chromium, cobalt, copper, iron, silver, vanadium and zinc. Hazeltine Creek, between Polley Lake and Quesnel Lake, got those same minerals as well as arsenic, manganese, mercury, nickel, thallium and titanium.

However, the other British Columbia mines—under construction, in startup or still undergoing assessment—pose a greater threat: acids that are common in copper and gold mining and other metals toxic to aquatic life.

The effects from Mount Polley "may take years to be felt by salmon," thanks to the metals bound to sediment settling in the lake bottom, says Aaron Hill, executive director of Watershed Watch Salmon Society. The greater danger, he says, is with the other mines.

"Even though Mount Polley was one of the biggest environmental disasters in Canadian history, the impact would be much worse from a catastrophic failure at a project like Red Chris and KSM [Kerr-Sulphurets-Mitchell] that are acid- draining, with much larger tailings impoundments," he says.

"KSM, which was quietly approved by the federal government over the Christmas holiday, would have two tailings impoundments around the same size as Hoover Dam," he adds.

Red Chris Mine, also owned by Imperial Metals, Vancouver, is a $643-million, open-pit gold and copper mine in northwest B.C. It got a permit in February, effective through May, to begin filling its tailings pond "but not to go into production," the B.C. Ministry of Energy and Mines (MEM) says.

KSM is a copper, gold, silver and molybdenum mine, located 22 miles from the Alaska border and proposed by Seabridge Gold, Toronto. It would be a combination open-pit and underground mine, with a pair of tunnels, running under a glacier, connecting the work. It is projected to process 143,000 tons of ore daily for 52 years.

Harper Creek Mine, an open-pit copper mine planned by Yellowhead Mining Corp. near the North Thompson River, got a "very high" dam-hazard classification from the Canadian Dam Association. The province Environmental Assessment Office told the company to resubmit paperwork on its tailings management plans.