Mount Polley Mine Corporation continues to work on remediating the site impacted by the Aug. 4, 2014 tailings impoundment breach, including reinforcing the original impoundment with concrete aggregate.
When the tailings impoundment gave way, an estimated seventeen million cubic metres of water and eight million cubic metres of tailings emptied into nearby Polley Lake, Hazeltine Creek and Quesnel Lake.
Once the tailings and water reached Polley Lake and Hazeltine Creek, about five million cubic metres of water went up into the lake, followed by tailings that blocked off the end of the lake.
The soupy tailings created a plug and caused the lake’s level to increase by 1.7 metres.
Pumps were installed in the lake to reduce the water level down to July 2014 levels, which took about three months to achieve.
In its wake, the breach significantly widened the eight kilometre long Hazeltine Creek channel, creating a new landscape where formerly a little creek meandered through the woods.
In order to work in Hazeltine Creek, a water outlet structure was installed to control Polley Lake’s level.
The company has created a new Hazeltine Creek channel and is now at the point of armouring it.
Until the work is completed, fish fences have been installed so the fish cannot enter Hazeltine Creek.
The next step is to install spawning gravel.
The new Hazeltine Creek channel has been designed to handle 1.7 cubic metres of water a second, said Steve Robertson, Imperial Metals vice-president of corporate affairs.
The water treatment plant will discharge at a rate of .3 cubic metres per second, leaving room for some water from Polley Lake.”
Last Friday crews resumed work on nearby Edney Creek in advance of the salmon returning.
Planning also has to take into account other creeks flowing into Hazeltine Creek and rain and snow fall.
The new channel is also being built to handle spring freshet, and with the water control structure, water from Polley Lake can be held back, until all the remediation work is completed.
Part of the restoration has seen the company retrieve trees from the lake, chip them, and bring the chips back to help rehabilitate the banks along Hazeltine Creek.
In other areas, uprooted trees have been placed along the banks as well to help restore vegetation.
Work is also being done at the bottom of Edney Creek before the salmon return in late August.
Minister Bill Bennett said the government has yet to hear from two investigations into the breach being conducted by the Conservation Officer Service and the Chief Inspector of Mines, but noted he anticipates they will impact any future permits for Mount Polley Mine.