Discover, Develop, Operate

Remediation Q&A

What does it mean to conduct remediation?

According to the BC Environmental Management Act, “remediation” means action to eliminate, limit, correct, counteract, mitigate or remove any contaminant or the adverse effects on the environment or human health of any contaminant.

At Mount Polley, using the results of the detailed site investigations, and the human health and ecological risk assessments, the goal of the mine’s environmental remediation work is to repair and rehabilitate the areas impacted by the tailings spill such that they are on a path to self-sustaining ecological processes that result in productive and connected habitats for aquatic and terrestrial species. As the impacts of the spill were determined to be primarily physical and not chemical, this has meant that the focus of the work has been on repairing and rebuilding habitats.

What has the Company done to clean up the tailings spill?

To date, the Company has spent on the order of $70 million on clean-up, environmental impact and risk assessment studies, and remediation and monitoring of areas impacted by the spill. The clean-up work included:

  • gathering woody debris from Quesnel Lake and Hazeltine Creek valley
  • removing tailings from along Hazeltine and lower Edney creeks
  • rebuilding Hazeltine Creek and the mouth of Edney Creek
  • repairing the impacted Quesnel Lake shoreline
  • annual seed gathering and spreading
  • planting over 600,000 native shrubs and trees in riparian and uplands areas
  • installing new fish spawning and rearing habitat in Hazeltine Creek and at the mouth of Edney Creek, and
  • the mine built a rainbow trout hatchery on-site in 2018 to raise more rainbow trout for Polley Lake

Are taxpayers paying for the clean-up?

No. Imperial Metals, with support of its shareholders and lenders, has paid for the clean-up and remediation work. No government funding (taxpayers’ money) has been spent on the clean-up or repair work done at the site.

Is Mount Polley still operating? Did the Company go bankrupt?

Mount Polley mine operations were suspended in May 2019 due to low copper prices. The mine will remain on care and maintenance status until the economics of mining improve. The mine is staffed by a small care and maintenance team who are overseeing the site. All the environmental monitoring work is continuing during this time, and the mine continued its remediation work during the summer of 2019.

Is the clean-up work done?

There is still work being done to complete the rebuilding of fish habitat in Hazeltine Creek. The rebuilding and revegetating of the lower part of the creek will be the last part of the remediation work to be done. Have a look at our Community Updates which provide information on the progress of the work done to date.

Who has done the clean-up work?

The mine staff, our First Nation business partners, local contractors, and consultants have all been involved in the clean-up and response to the spill.

What is the water quality at Polley Lake now?

Polley Lake water quality is monitored by Mount Polley following our BC-ENV approved Comprehensive Environmental Monitoring Plan. The results for all our monitoring sites are published in the publicly available Annual Environmental and Reclamation Reports (2018 Report). Polley Lake water met all BC Water Quality Guidelines for aquatic life parameters in 2018 with the exception of phosphorus, which has been elevated since prior to mining.

Is mine site waste water being discharged into Quesnel Lake and Polley Lake?

Mount Polley discharges mine site water into Quesnel Lake, through diffusers at depth, which meets the strict Environmental Management Act (EMA) permit guidelines. This water is the only substance the mine is discharging into Quesnel Lake.

The mine does not discharge water into Polley Lake.

Mine site water is collected, and when needed to meet the EMA permit requirements, is treated by a by a Veolia ACTIFLO™ water treatment plant before release into Quesnel Lake (ref: for how treatment systems work). The water directed into the water treatment plant (influent) is monitored on an ongoing basis (measurements of turbidity every 15 seconds) and the treated water leaving the plant (effluent) is sampled regularly for analysis. Not all water at Mount Polley requires treatment to meet EMA permit water quality guidelines before discharge, and in the past, water that was simply stored in Springer Pit was found suitable for passive discharge. The lake water quality is also routinely monitored and sampled regularly as part of the mine’s Comprehensive Environmental Monitoring Plan.

Is Mount Polley’s discharge having negative effects on Quesnel Lake?

There are no indications in the monitoring data that the Mount Polley discharge is having any negative effects on Quesnel Lake water quality. If you are interested in looking at some of the water quality data that has been collected on surface water in the area around the Mount Polley Mine, the results are available through the BC Government Surface Water Monitoring Sites Interactive Map.

Is the water in Quesnel Lake contaminated? Is it safe to drink?

At this time, there are no indications of contamination of Quesnel Lake water from the Mount Polley spill. The mine, and the Ministry of Environment and Environment Canada, continue to monitor Quesnel Lake. With the exception of natural causes, the lake does not exceed environmental guidelines for any of the constituents of concern that are found in the Mount Polley tailings.

As early as August 12, 2014, BC’s Interior Health Authority (IHA) rescinded all water use restrictions from Quesnel Lake (including for “drinking water, personal use, fishing, swimming and recreational purposes”), except for the immediate impact zone where Hazeltine Creek entered Quesnel Lake. The IHA notice also stated that “Interior Health has no reason to believe that this water was ever exposed to unsafe levels of contaminants from the mine breach. As a result, flushing and testing of individual water supply systems is not considered necessary.”

All water use restrictions were fully rescinded July 13, 2015. (Note: IHA always advises that surface water be treated for pathogens prior to use/consumption.)

Where can I find data about the water quality in Quesnel Lake?

The BC government website hosts an interactive map of surface water monitoring sites in the Province which gives access to results of water sampling and analyses, including Quesnel Lake and other surface water sites around the area of the mine.

How much is the mine discharging into Quesnel Lake?

The Environmental Management Act permit annual average authorized discharge rate is 29,000 cubic meters per day. The actual discharge rate depends upon the rainfall experienced at site which varies from year to year. In 2019, the annual average discharge rate has been 14,883 cubic meters per day, significantly less than the mine’s permit allows.

Is there any risk of metal contamination to humans or wildlife in the area of the spill?

Consultants from a number of experienced firms were involved in carrying out extensive research and analysis in support of a Human Health Risk Assessment, and an Ecological Risk Assessment, for the areas impacted by the Mount Polley spill. The results of these studies indicate that human health and wildlife are at low risk of any metal contamination related to the spill.

Also, for Quesnel Lake, BC’s Interior Health Authority (IHA) notice released on August 12, 2014, noted that “Interior Health has no reason to believe that this water was ever exposed to unsafe levels of contaminants from the mine breach”.

What has the company done to repair Hazeltine Creek?

The mine has removed as much of the spilled tailings material as was practical (i.e would not cause additional environmental damage by its removal), and returned most of this material to the Tailings Storage Facility. A small amount of the removed material has been stockpiled for potential use in remediation. Previous studies of Mount Polley’s tailings have shown them to be very unreactive in the environment, and thus are suitable as a construction material and for use in reclamation work.

In addition, the mine has undertaken installation of new fish habitat, specifically spawning and rearing habitat for Rainbow trout, in Hazeltine Creek. This work has been undertaken by a local contractor from Horsefly who has had extensive experience with installing new fish habitat. To date, the upper 6 kilometres of Hazeltine Creek new fish habitat construction has been completed. Fish from Polley Lake, most importantly the rainbow trout, were allowed back into the rebuilt Hazeltine Creek in May 2018, where they very successfully spawned and thousands of trout fry returned to Polley Lake. [ref: Community Updates 2019 Issue 2; 2019 Issue 3]

Is it safe to eat fish from Quesnel lake? Or from Polley Lake?


On August 12, 2014 BC’s Interior Health Authority (IHA) issued an Advisory Entitled “Mount Polley Tailings Pond Breach – Fish Consumption Deemed Safe –“, which stated:

Following consultation and discussion with a number of agencies regarding the impacts of the Mount Polley Mine’s tailings pond breach on the human health risks associated with eating fish, Interior Health’s Medical Health Officer (MHO) has deemed all fish outside of the revised August 12, 2014 “Do Not Use” water advisory as safe for human consumption. Individuals should refrain from consuming fish from the remaining impact zone, which includes Polley Lake, Hazeltine Creek, and a small portion of Quesnel Lake that has a visible sediment plume.

“I recognize the important role fishing plays to local residents, First Nations community members, and visitors impacted by the Polley Mine spill and I wholeheartedly appreciate the concerns that are being expressed regarding safety,” said Dr. Trevor Corneil, Medical Health Officer, IH. “I have consulted with numerous experts in this field, and I am reassured that the current fish living in these waterways, and those that may travel through it via the Fraser River or spawn in it are safe to consume.”

The decision on fish consumption was made after review of water and sediment sample results, which show fish were not exposed to unsafe levels of contaminants from the mine breach. Fish testing currently underway continues to demonstrate no immediate harm to any local fish.

Prior to reaching this decision, Interior Health’s MHO consulted extensively with officials from the Ministry of Environment (MoE) Water Quality Division, Ministry of Forests, Lands and Natural Resource Operations (FLNRO) Fish and Wildlife, Department of Fisheries and Oceans Canada (DFO), Cariboo Regional District (CRD), and Northern Health Authority (NHA) and engaged in discussions with the First Nations Health Authority (FNHA).

Fish from Polley Lake were deemed safe for consumption as of July 13, 2015.

Have fish returned to Hazeltine Creek or Edney Creek?

Yes! Thousands of rainbow trout from Polley Lake returned to Upper Hazeltine Creek in 2018 and 2019, using the rebuilt fish habitat for spawning and rearing. [ref: Community Updates 2019 Issue 2; 2019 Issue 3]

In lower Hazeltine Creek, the remediation work is not yet complete so fish are still excluded from this part of the creek. Salmon spawning was not significant in Hazeltine Creek prior to the spill as there is a natural barrier to their migration upstream at about 800 metres from the shore, and in the years prior to the spill, most of Lower Hazeltine was inaccessible to salmon because of a beaver dam.

The mouth of Edney Creek was damaged in the spill, and because it was a direct link to Quesnel Lake (Hazeltine Creek was the smaller creek and flowed into Edney before reaching Quesnel Lake), it was prioritized for repair in winter 2014 so that it would be available for any spawners returning to this watershed in 2015. Fish have been observed using Edney Creek since the summer of 2015.

Approximately 30 sockeye salmon were observed on September 17, 2019 migrating through and spawning in the reconstructed part of the creek.

What are tailings?

Tailings are essentially crushed rock, and are the leftover material after the minerals containing the elements of interest (at Mount Polley, these are copper, gold and silver) have been removed. The minerals containing the valuable elements are liberated by crushing and grinding the mined rock down to sand and silt sized particles. At Mount Polley, a process known as flotation is then used to separate the important copper-bearing minerals (chalcopyrite and bornite) from the rest of the crushed ground rock. The remaining crushed rock is considered gangue (waste) and is what makes up the tailings. No cyanide is used at Mount Polley.

What is in the Mount Polley tailings?

At Mount Polley, the valuable elements are copper, gold and silver and they are found most commonly in the sulphide minerals, chalcopyrite and bornite. The leftover minerals found in the gangue are piped as a slurry with water to the tailings storage facility. [ref: Community Updates 2017 Issue 3; 2016 Apr Issue 2]

The rocks that are mined at Mount Polley are around 200 million years old and represent ancient volcanic rocks and magma that intruded into these rocks. The intrusive rocks host the copper, gold and silver mineralization. The rocks which host most of the ore are made up primarily of the minerals orthoclase (potassium feldspar), albite (sodium plagioclase), magnetite (iron oxide), Ca-plagioclase (calcium plagioclase), diopside (pyroxene), garnet, biotite (mica), epidote and calcite (calcium carbonate). These minerals are all common rock-forming minerals, and represent 90% of what ends up in the Mount Polley tailings pond. Of the other 10 percent, most are also common minerals, with a minor amount of sulphide minerals, including a little bit of chalcopyrite (0.17%) that didn’t get captured in the mill and a small amount of pyrite (0.04%). Another copper mineral, chrysocolla, a copper silicate, is also found in the tailings in very small amounts (0.03%).

What is unusual about Mount Polley is that, when compared to many other copper deposits (and the reason why these tailings are considered by geochemists to be chemically quite benign) there is very little pyrite (iron sulphide) and a fair amount of calcite (calcium carbonate) in the tailings. Due to this, Mount Polley’s tailings do not generate “acid rock drainage”. This is the process that happens when sulphide minerals, especially pyrite, are exposed to the atmosphere and react to form sulphuric acid, which then can leach metals out of tailings and lead to metal mobility and potential contamination.

Mount Polley’s tailings do not have this “acid rock drainage” problem, as there is very little pyrite, and calcite acts as a neutralizing agent if any of the minor amount of sulphide in the tailings breaks down. The vast majority of the rest of the minerals in Mount Polley’s tailings are very stable (ie. do not react easily with air or water), and are very similar to natural sand.

Have the tailings been removed from Hazeltine Creek?

The mine has removed as much of the spilled tailings material as was environmentally sound (i.e would not cause excessive additional environmental damage by its removal), and returned most of this material to the Tailings Storage Facility. A small amount of the removed material has been stockpiled for potential use in remediation. Previous studies of Mount Polley’s tailings have shown them to be very unreactive in the environment, and thus are suitable for some reclamation work, and as construction material, on the site.

Have the tailings been removed from the bottom of Quesnel Lake?

No. The tailings that were deposited at the bottom of Quesnel Lake are still there. Extensive monitoring and sampling (water, sediment, benthics and fish) have determined that the tailings at the bottom of the lake are chemically and physically quite stable, and they are at over 100 metres of water depth.

Analysis of options for remediation had determined that the course of action with the lowest environmental impact is to leave them undisturbed, and to let natural sediments slowly cover them and the lake continue to recover naturally. Specifically, it was determined that dredging these materials from the bottom would create much more environmental damage than leaving them undisturbed.

Why was the decision made to leave the tailings at the bottom of Quesnel Lake?

Research and monitoring of the physical and chemical stability of the tailings on the bottom of Quesnel Lake indicate that they are not causing pollution and studies of the benthic (bottom-dwelling) organisms have shown that they are slowly recolonizing the lake bottom as native sediment slowly deposits on top of the organic-poor tailings, bringing organic matter to the lake floor.

After completing a Net Environmental Benefit (NEB) assessment, experts recommended that the best approach for remediation of the tailings in Quesnel Lake was to leave them alone and cause no further disturbance. The experts determined that any attempt to remove the tailings could significantly disrupt the present ecosystem and set back the progress that had already occurred. Remediation at Mount Polley is all about creating the conditions for successful natural recovery, and not doing more damage.

Why has the mine not switched to dry stacking of the tailings?

Tailings deposition in the tailings storage facility is closely regulated by the Environmental Management Act permit authorizing the monthly average rate of discharge of tailings slurry of 55,500 cubic meters per day. The mine is currently in care and maintenance so there is no tailings deposition by processing operations, just the tailings dredged from the Springer Pit. Dry stacking of tailings was considered as a tailings storage option. The advantages are minimal however, because a dam to store recycled water would still be required.

What is dry stacking?

To achieve dry stacking, tailings are dewatered to a paste then filtered to a wet (saturated) and/or dry (unsaturated) cake that can no longer be transported by pipeline due to its low moisture content. The filtered tailings are normally transported by conveyor or truck, and deposited, spread and compacted to form an unsaturated tailings deposit. This type of tailings storage produces a stable deposit usually requiring no retention bunding (constructed retaining wall) and referred to as a dry stack.