"Our first priority is the health and safety of our employees and neighbors, and we are relieved no loss of life or injury have been reported," the company said in a statement following the spill. "We are deeply concerned and are working to mitigate immediate effects and understand the cause."

The estimated 14.5 million cubic meters of tailings and water released from the dam is enough to fill roughly 5,800 Olympic-sized swimming pools.

This breach prompted authorities to immediately issue water use and drinking water bans at Quesnel Lake; Polley Lake; Hazeltine Creek; Cariboo Creek; and the Quesnel and Cariboo river systems, which flow out of Quesnel Lake to the Fraser River.

The sockeye salmon season opened on the lower Fraser River on August 1, and was expected to continue upstream this week.

An estimated 30 million sockeye salmon made their way up the Fraser River during a record run in 2010. Fisheries and Oceans Canada had previously forecast a 2014 run ranging from a low of 7.3 million to a high of 72.5 million, as sockeye salmon that spawned during 2010 return to the Fraser River and its tributaries this year. This estimate has since been downgraded based on the lower than expected number of fish so far and warm water temperatures in the Fraser River.

The B.C. Ministry of Environment of B.C. says the extent of the environmental damage is not yet clear and water in the area is being tested and preliminary results are expected in the coming days.

In the meantime, B.C. Ministry of Energy and Mines has dispatched inspectors to investigate the cause of the dam failure.

“This is a serious incident that should not have happened,” Minister of Energy and Mines Bill Bennett said in an Aug. 5 statement. “We are devoting every appropriate resource working with local officials to clean up the site, mitigate any impacts to communities and the environment, and investigate the cause of the breach. We will determine the cause of the event and we are determined to prevent an incident like this from happening again.”

Imperial said the failed dam is an independently engineered structure that was being operated within design limits and specifications. The company also said monitoring instruments and observations by onsite personnel provided no evidence of an impending breach.

The company has placed Mount Polley mine on care and maintenance for an indefinite amount of time.

“While the damaged area is relatively small compared to the overall size of the dam, it is not known at this time how long it will take to restore operations,” the company said.

The immediate concern, however, is to plug the dam.

“It’s a very important job for the company and government to get their heads together to block any additional drainage,” Bennett said during an Aug. 6 news conference in Williams Lake. “The gap in the wall is large. It was built by machines and men and it can be repaired by machines and men.”

Imperial Metals shares plummeted 44 percent on the news of the dam failure, from C$16.80 per share at market close Monday to C$9.50 shortly after the opening on Tuesday. Imperial Metals’ share price on the Toronto Stock Exchange settled at about $10.00 on Aug. 6.

Moody's Investors Services announced Tuesday that is considering downgrading Imperial Metals’ ratings in light of the dam failure and the effects that will have on the company’s ability to repay its debts.

The ratings review will focus on the costs to remedy the facility breach and restore operations at Mount Polley, including any associated environmental obligations and loss of cash flow net of any insurance proceeds. The review will also focus on Imperial's liquidity, which Moody's is concerned may be inadequate as Imperial is currently heavily reliant on cash flow from Mount Polley to service its debt.

Imperial other operating asset is a 50 percent stake in the Huckleberry copper mine south of Smithers, B.C.

The company is also in the process of developing a mine at its Red Chris copper-gold property near Dease Lake in northwestern B.C.

In mid-July Imperial said on-site construction at Red Chris is well advanced. Interior steel, mechanical installation, and the tailings and reclaim water systems were reported to be 93 percent complete at the time. The company anticipated having electricity to the mine development project in September with commissioning of the milling operation to follow.

The tailings facility at Red Chris and other similar projects, both planned and existing, will likely get closer scrutiny.

Bennett said there are about 20 other operating mines in B.C. with some kind of tailings storage.

“This gives us about the best reason a person could have to really take a step back. Every Canadian has to be concerned about this,” said the mines minister, according to the Vancouver Sun. “This will cause everyone in government across the country to re-examine policies.”

Dam debate spills into Alaska

Conservation groups said the dam failure in B.C. is a prime example of why a mine such as Pebble should not be developed in the Bristol Bay region of Southwest Alaska.

“Our research shows that these tailings dam failures are far more common than the industry wants to admit,” said Bonnie Gestring of Earthworks northwest office. “In the U.S. more than a quarter of the currently operating copper porphyry mines have experienced partial or total tailings pond failures. That’s why the EPA’s plan to restrict mine waste in the Bristol Bay watershed is so critical to the future of our nation’s most valuable wild salmon fishery. ”

Earthworks, an environmental conservation group focused on the mining and energy sectors, said Mt. Polley, an open-pit porphyry copper mine with a modern tailings storage facility located upstream from salmon habitat, is analogous to what is being proposed for Pebble.

“We don’t want this to happen in Bristol Bay,” said Kim Williams, director of Nunamta Aulukestai, an association of Alaska Native Tribes and corporations. “With all the similarities between Pebble and the Mount Polley copper mine, we’re urging the EPA to take immediate action to finalize mine waste restrictions in Bristol Bay.”

Others are drawing comparisons between Mt. Polley and the Seabridge Gold’s KSM copper-gold project, located just east of the Alaska border in northwestern British Columbia.

“This is exactly the type of disaster we are trying to avoid on the Unuk and Nass Rivers by seeking a higher standard of environmental review for the KSM project,” said Brian Lynch of the Petersburg Vessel Owners Association. “We urge that Canada issue no new mine permits in the trans-boundary river region until there is a full investigation of this accident and guarantees that similar accidents won’t occur at larger mines proposed in the Unuk, Stikine and Taku watersheds.”

Lynch has been an outspoken advocate for Salmon Beyond Borders, a group concerned about the effects mining in northwestern British Columbia will have on the salmon bearing streams in Southeast Alaska.

British Columbia issued Seabridge an environmental assessment certificate for KSM late in July.

"This decision confirms that KSM is a well-designed, environmentally responsible project which is technically feasible and offers significant economic benefits to both British Columbia and Canada,” said Seabridge Gold Chairman and CEO Rudi Fronk.

Following a current comment period that ends Aug. 20, the Canada Minister of Environment will decide whether to approve the KSM Project.

Tulsequah Chief, Red Chris, Schaft Creek and Galore Creek are other northwestern B.C. mine development or advanced exploration projects on Salmon Beyond Border’s watch list.