Mount Polley Mine management was awaiting a second permit amendment from the B.C. government to increase water released from its tailings facilities when the tailings pond dam breached in the early hours of Aug. 4.
Ministry of Environment records show the mine has had an effluent permit since 1997, and has operated since startup with a water surplus due to precipitation. In 2009 the company applied to amend the permit to allow discharge of up to 1.4 million cubic meters of water a year to discharge dam seepage effluent into Hazeltine Creek.
That permit was approved in 2012 after an independent report was commissioned to examine water quality impacts from sediment and contaminants, and measures needed to control them.
With the mine and its tailings facilities expanding and an exhausted pit being converted to underground mining, Mount Polley applied for another amendment to discharge up to three million cubic meters of treated water to Polley Lake.
“That application was received by the ministry this summer and is being considered,” the Ministry of Environment said in a statement Wednesday.
Energy and Mines Minister Bill Bennett said Mount Polley mine does not have acid-producing rock, which reacts with contaminants such as arsenic and mercury and allows them to mix with water. Bennett was on site this week with mine inspectors and environment ministry staff.
“We will find out if the company was not in compliance,” Bennett said Wednesday. “If they were hiding anything, if they made mistakes in building the dam higher, we will find out and hold them to account.”
Brian Kynoch, president of parent company Imperial Metals, was asked about the latest permit amendment at a public meeting in Likely Tuesday, where residents were shocked at the devastation and worried about the water quality in their lakes and rivers.
“I think we’re about to get the increase,” Kynoch said.
Kynoch said the breach did not occur at the highest point of the tailings dam, where water pressure was greatest, and the pond level was 2.5 metres below the top of the dam at the time.
Ministry records show Mount Polley was warned about high pond levels May 24, with the level returning to authorized levels by June 30. In April the company was issued an advisory about bypass of authorized treatment works due to high water flows in the spring runoff period.
Samples of tailings pond water taken Aug. 4 showed selenium concentration 2.8 times the drinking water guideline. Concentration of nitrates, cadmium, copper, iron and selenium have occasionally exceeded aquatic life guidelines in recent years. The permit required water volume not to exceed 35 per cent of the creek flow to dilute it.