After the spill, a population monitoring program on Polley Lake indicated there had probably been a reduction in the age class of the population of Rainbow Trout (as upper Hazeltine Creek was the main spawning area for these trout). There was spawning observed in Frypan Creek at the north end of Polley Lake, however it was noted to be a much smaller habitat. The Mount Polley Environmental Team (MPET) recognized it was important to allow the fish to spawn in Hazeltine Creek, but the Habitat Remediation Working Group (HRWG) had concerns whether the spawn in the reconstructed Hazeltine Creek would be successful.
The MPET developed a backup plan. With guidance provided by Minnow Environmental and David Petkovich (Aqua-culturist), over 11,000 Rainbow Trout fry were raised in an on-site fish hatchery in spring 2018. Eggs were harvested and fertilized from some of the local Rainbow Trout that had returned to upper Hazeltine Creek to spawn.
The fertilized eggs were incubated in trays so temperature, flow and dissolved oxygen levels could be regularly monitored. Water intake was sourced from below the thermocline in Polley Lake in order to maintain cooler water temperatures.
Within two months, the eggs hatched into alevins (yolk-sac fry) and within another two weeks the yolk sacs were completely absorbed. Throughout the incubation stage the eggs were counted, and unfertilized eggs removed.
The fry were then transferred from the incubation trays to shallow rearing tanks. When the fish reached their target biomass, they were transferred into deeper rearing tanks, and from there released into the Polley Lake watershed.
The MPET and Minnow Environmental released over 11,100 Rainbow trout fry from the hatchery into Polley Lake on September 25 and 26, 2018. The adipose fins from each fry were clipped as a means of tagging (identification). On the second day, students, parents and a teacher from Columneetza Middle School’s Greenologists / Enviro Club based in Williams Lake assisted with the Rainbow Trout fry release
Mount Polley strongly encourages Polley Lake fishers to report if they catch fish with a clipped adipose fin to firstname.lastname@example.org. This will help the MPET determine how successfully the hatchery trout are surviving. Thank you!
In 2018 a milestone was celebrated by the Mount Polley Environmental Team (MPET) when the efforts of the remediation work rebuilding Hazeltine Creek witnessed the return of Rainbow Trout, Redside Shiners and Long Nose Suckers to the rebuilt part of the creek.
After the August 2014 tailings spill, fish from Polley Lake were prevented from entering Hazeltine Creek by fish fences above the Polley Lake Weir, while the habitat underwent reconstruction. During the winter of 2014-2015, the creek channel was cleaned up, tailings and debris removed, and a new Hazeltine Creek channel was built and rocked-in.
In April 2015, the Habitat
Remediation Working Group (HRWG*), including the T’exelc
First Nation (Williams Lake First Nation) and Xatśūll First Nation (Soda Creek
Indian Band) and their consultants, and Mount Polley Mining Corporation
(MPMC) representatives and their consultants (Envirowest and Golder), began discussing
options for constructing new fish habitat in upper Hazeltine Creek, and
requirements MPMC would need to meet in order for fish to be allowed to return
to the creek.
*HRWG also includes representatives of the federal
Department of Fisheries and Oceans, the provincial Ministry of Environment, and
the provincial Ministry of Forest Lands and Natural Resource Operations, both
water stewardship and fisheries sections.
Mount Polley employees, consultants, contractors, First Nations and community partners began ecological remediation work on Hazeltine Creek in 2015. By May 2015 the water in Hazeltine was running clear, and the bugs (invertebrates that provide food for fish) were starting to grow in the creek, so it was decided that the installation of new fish habitat could begin and this work started in 2016.
HRWG members looked at historical records to
determine what the local conditions were before the spill, and remediation
planning was based on that information. The planning was also constrained by the
configuration of the constructed rocked-in channel. The group agreed to a field
fit approach for the remediation. Conceptual designs were developed by Mount
Polley and their consultants, and the plans were reviewed by the HRWG.
The design approach was to naturalize the rocked-in channel by adding sinuosity (curves and bends), building a sequence of pools, riffles and weirs, and installing boulders, large woody debris and gravel at the bottom of the creek, to provide appropriate spawning and rearing habitat for the fish known to have used upper Hazeltine Creek before the spill, particularly Rainbow Trout, an important species in Polley Lake.
After two years of habitat construction (2016-2017)
approximately 2.5 km of spawning and rearing habitat was completed in the upper
part of Hazeltine creek from the outlet of Polley Lake to the Gavin Lake Road
Bridge. In late 2017, the MPET believed conditions were right to let the fish
back into the creek. There was habitat, flowing water, and food, and the water
quality met aquatic guidelines.
In December 2017, the HRWG began
detailed discussions on the approach to allowing the Rainbow Trout back into
Hazeltine Creek. Discussion included requirements for fish monitoring, water
quality, sediment quality, habitat quality and quantity, Polley Lake access and
egress etc, and the permits and licenses that Mount Polley would have to apply
for and comply with from the Ministry of Forests, Lands, Natural Resource
Operations and Rural Development Water Stewardship Group.
In March 2018, new fish fences were
installed in Hazeltine Creek approximately 2.6 km from the outlet of Polley
Lake to prevent fish from going further downstream than the area where habitat
reconstruction have been completed. On April 26, 2018, the fish fences at the
outlet of Polley Lake to Hazeltine Creek were removed and the Rainbow Trout
once again had access to the first 2.6 km of upper Hazeltine Creek.
Note: the lower part of Hazeltine Creek includes a
steep rock canyon that is a natural barrier preventing Quesnel Lake fish from
entering middle and upper Hazeltine Creek and Polley Lake. However, in the
natural creek system, fish from Polley Lake can be swept down the creek into
Quesnel Lake once all the fish habitat reconstruction is completed and fish
fences are removed.
In addition to ingress into Hazeltine Creek, the fish also needed to be able to return to Polley Lake. This required that a fishway (ladder) be built for the fish to bypass the Polley Lake Weir water control structure. An engineered fishway was installed by Mount Polley maintenance staff at the Polley Lake weir and the flows are monitored to properly maintain water levels for fish passage. The fishway was designed so the flow can be adapted to seasonal changes.
Fish monitoring was intense in 2018. MPET worked
with Minnow Environmental conducting weekly surveys of the fish populations to track
the 2018 spawn and fish activity. The surveys included counting fish at
established monitoring stations and pools, and observing how the fish used the
creek (i.e. seeking shelter under woody debris or behind boulders). Temperature
data and dissolved oxygen levels were also monitored in Hazeltine Creek.
Results of the 2018 Hazeltine Creek fish re-introduction were very impressive. Fish monitors estimated almost 5,000 Rainbow Trout accessed the creek to spawn in spring 2018. The spawn was successful. A spawning survey in July 2018 observed over 18,600 Rainbow Trout in upper Hazeltine Creek, the majority being from the 2018 spawn.
In the Mount Polley
Mine, run-of-mine ore from the open pits and underground is hauled to the
crusher. The crusher has three stages of
crushing involving five crushers, twenty conveyors and four sets of screens. Ore is dumped by the surface mining fleet
into the feed pocket of the primary gyratory crusher, and is then crushed in
three stages to produce a product at finer than 16 mm for the grinding circuit.
Periodically, the crusher also used for the production of aggregates used in
tailings construction and other tasks.
The grinding circuit
consists of two parallel rod mill/ball mill circuits and a pebble mill circuit.
Crusher product is first split between two rod mills where water is added to
form slurries. The rod mill discharge is
pumped to the primary hydrocyclones that classify the particles by size. The larger particles flow to feed the ball
mills while the fine particles report to two flash flotation cells. The ball
mills are in “closed circuit”, meaning that the discharge is pumped to the
classifying units (primary hydrocyclones) and the particles will not pass to
the next grinding stage until they are fine enough to feed through the flash
flotation cells. The underflow from the
flash flotation cells is pumped to the secondary hydrocyclones, the flash
flotation product can report directly to the concentrate circuit or to regrind
for further upgrading.
The coarse particles
classified by the secondary hydrocyclones reports to three pebble mills for
further size reduction. The pebble mills are in “closed circuit” with the
secondary hydrocyclones and product that is sized at 65% finer than 200-mesh is
fed to the flotation circuit. Pebbles obtained from the triple deck screen in
the crusher are used as grinding media in the pebble mills.
The flotation circuit
separates the valuable minerals from the rest of the crushed rocks. With the
addition of reagents, the valuable minerals, mostly in the form of sulphide
minerals chalcopyrite and bornite, are separated by flotation and are collected
and upgraded to produce a concentrate. Initial separation is completed in a
rougher/scavenger circuit, where the remaining minerals are discarded as
tailings (which flow by gravity to the Tailings Storage Facility). Rougher concentrate is reground in a regrind
mill and further upgraded in a cleaner circuit to produce the final concentrate
product. Cleaner tailings are recycled to the scavenger circuit.
The concentrate from
the flotation circuit is dewatered in two stages: the thickener settles
particles and decants water so that the settled particles form a sludge by
sedimentation and have a reduced water content of roughly 25%-30%; pressure
filtration further reduces water content to approximately 8%. The water removed
is utilized as process water. The filtered concentrate is stored in the
load-out building and loaded onto 40-tonne trucks for shipping. Tailings
materials generated by mill operations are piped via gravity to the TSF.
The broken rock in the open pit is segregated into ore and waste based on the assay of rock cuttings sourced from the blasthole production drills.
This assay analysis determines the sulphide copper percentage and gold grams per tonne for material within the vicinity of each blasthole.
The forecasted metal prices and metallurgical recovery is used to calculate copper equivalent percentage.
A forecast of mining and treatment costs establishes the mining cutoff grade and hence the material to be trucked to the plant for processing.
The plant uses three stage crushing, and conventional rod and ball mills with a flotation and dewatering circuit to produce a copper /gold concentrate.
When the mine is up-and-running, it mine moves 80,000-90,000 tonnes of material per day, the mill has a capacity to process 17,800 to 22,000 tonnes per day (tpd) of ore depending on hardness. Mount Polley concentrates are trucked to facilities at the Port of Vancouver and then shipped to overseas smelters.
At Mount Polley, we look for individuals to
join our workforce who display a variety of skills and training levels.
We have a training department that will train
workers from other industries.
Our key goal is to source workers locally. The
furthest away workers are usually recruited from is Quesnel or Williams Lake.
Several of Mount Polley’s staff are from Big Lake, Horsefly, and Likely, and
live near the mine.
Staffing Numbers at Mount Polley
When Mount Polley is in full operation, we have
as many as 370 staff working on rotation at the mine, most often in four crews.
Shifts are typically a 12-hour day shift and
12-hour night shift; four crews; seven days on, seven days off.
Additionally, we have about 50 support staff including administrators, supervisors, warehouse workers, engineers, geologists, assayers, technical personnel, and human resource staff.
Imperial congratulations to Dr. ‘Lyn Anglin on being named a
recipient of the Canadian Institute of Mining, Metallurgy and Petroleum’s (CIM)
Distinguished Lecturer award. The CIM Awards
honour the mining industry’s “finest for
their outstanding contributions in various fields. Their achievements and
dedication are what make Canada’s global mineral industry a force to be
Due to her extensive experience in
geoscience research and engagement with the public, Dr. Anglin was hired
as Imperial’s Chief Scientific Officer in 2014 to assist with the response to
the Mount Polley tailings spill.
During ‘Lyn’s tenure, she provided technical advice to the Company’s
spill response team, and liaised with First Nations, local communities,
government regulators and industry associations regarding the spill response
and progress on remediation.
The area around Likely has a long and fascinating
history of placer mining. Placer mining refers to mining materials (mostly
gold) deposited in ancient stream beds that are still largely unconsolidated (i.e.
relatively loose materials).
Some of the earliest gold discoveries in the area were made in 1859, one in the Horsefly River, and one in the Dancing Bill Gulch. The latter became known as the China Pit and then the Bullion Pit, and is located just downstream of Likely on the west side of the Quesnel River. The Bullion Pit is now a local historic site with a public walking trail.
Placer gold was also discovered near the mouth of
Keithley Creek on the Cariboo River about 12 km upstream from Quesnel Forks in
July 1860. Other significant discoveries were subsequently made just 4 km south
of Likely on Cedar Creek, and in Quesnel River itself.
In 1897, the Golden River Canal Co. decided to build a dam across the Quesnel River at the outlet from Quesnel Lake in order to block the river and be able to work the gravels from the bottom of the river. The tent town that developed on the site was known as ‘Quesnel Dam’. In 1920, the dam was dynamited and the remnants of the dam can be seen just north of the Likely Bridge in Likely. After the removal of the dam, the residents decided to rename the town ‘Likely’ after a local prospector, John Likely.
The Bullion Pit ulimately became a very significant gold producer in the area. BC Minfile report number 093A 025 states that “In 1897, the Consolidated Hydraulic Mining Company commenced full scale operations and between 1898 and 1902, the company processed 5,912,700 cubic metres of mixed materials, recovering 1,402,316 grams of gold at a recoverable grade of 0.132 grams per tonne gold… Estimations indicate that a total of 200 million tonnes of material were removed by hydraulic methods and 5.463 million grams (175,644 ounces) of gold were produced.” Indications are that much of this material was discharged directly into the Quesnel River.
The shortage of water in the early 1900s led the operators of the Bullion Pit to construct a number of water control and diversion works on local streams and lakes to gather water for the hydraulic operations at the pit. Photos from the BC archives, including ones featured in the TV program “Gold Trails and Ghost Towns – The Bullion Pit episode”, document weirs and diversion ditches built on Polley Lake and Hazeltine Creek and other creeks in the area.
This Facebook page gives regular updates on the areas in BC that were part of the mine’s early gold mining history.
Many placer mines continue to operate in the area around Likely, including near Quesnel Forks. Quesnel Forks is a restored ghost town located 12 km outside of Likely with a rich mining history and is also worth a visit. It is situated at the point where Cariboo River meets the Quesnel River, and features a beautiful campground and a number of restored and partially restored old buildings.
Mount Polley takes water quality very seriously. Extensive monitoring is evidencing the effectiveness of the remediation and site water management programs undertaken by Mount Polley.
How is water quality monitored in Polley and Quesnel Lakes to ensure proper environmental monitoring is being carried out?
Mount Polley follows the 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.
Polley Lake water met all BC Water Quality Guidelines for aquatic life parameters in 2019 with the exception of phosphorus, which was elevated even prior to mining. As Polley Lake is immediately adjacent to the mine site, this indicates the mine is doing a very good job of capturing and controlling run-off.
A number of sites are monitored in Quesnel Lake, and in 2019 there were no exceedances of acute BC Water Quality Guidelines.
At one monitoring site in Quesnel Lake, there was one minor copper exceedance of chronic BC Water Quality Guidelines in 2019, but as copper is also naturally occurring in the native soils and sediments around Quesnel Lake, and there are a number of creeks that empty into the lake near this sample site, it is difficult to know if this exceedance was natural or related to the mine.
We often get asked if we continue to discharge into Polley Lake or Quesnel Lake?
The mine discharges mine site water, that meets strict permit limits, through diffusers at depth into Quesnel Lake. This water is the only substance the mine is discharging to Quesnel Lake. The mine does not discharge water into Polley Lake.
Mount Polley discharges only mine site water that meets strict Environmental Management Act (EMA) permit guidelines.
treated by a water treatment plant, when needed to meet permit requirements, before being released into Quesnel Lake. The water going into the treatment plant (influent) is monitored on an ongoing basis, 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.
Continued monitoring data confirm that remediation efforts are effective.
Currently, there are no indications in the monitoring data that the water discharged from Mount Polley is having any negative effects on Quesnel Lake water quality or aquatic life.
If you are interested in looking at water quality data collected on surface water in the area around the Mount Polley mine, in addition to data in the mine’s annual reports, results are available through the BC Government Surface Water Monitoring Sites Interactive Map.
The remediation effort at Mount Polley is ongoing; however, we are very proud of the major milestones that have been completed to-date.
Repair of lower Edney Creek, re-establishment of link to Quesnel Lake and installation of new fish habitat for spawners from Quesnel Lake, completed in spring 2015, with evidence of successful spawning by Interior Coho, Kokanee and Sockeye Salmon.
Completion of construction of a new Hazeltine Creek channel in May 2015, to control erosion and provide base for remediation of the creek itself and the creek valley.
Ongoing planting of native trees and shrubs in the riparian and upland areas along the creek, now totally more than 600,000 trees and shrubs planted.
Installation of over 6 kilometres of new fish spawning and rearing habitat in upper to middle Hazeltine Creek. Evidence of successful 2018 and 2019 Rainbow trout spawning in upper Hazeltine Creek.
Clean-up and repair of 400 metres of Quesnel Lake shoreline, including placement of new fish spawning gravels.
Re-establishment of wetlands in the Polley Flats area adjacent to the repaired TSF.
We hope that you and your family are staying safe and following the preventative measures and actions you can take to stay healthy and prevent the spread of COVID-19.
We are doing our part during COVID-19. Imperial Metals Mount Polley mine has donated two boxes of N95 masks and four boxes of surgical gloves to the Williams Lake Hospital.
Newcrest-Imperial Metals Red Chris mine is providing additional medical support in Iskut, Dease Lake and Telegraph Creek, and is working with the Tahltan Nation to support the provision of basic groceries to the Iskut, Dease Lake and Telegraph Creek communities. In addition, Newcrest will help source health and sanitary supplies pending availability and lead times.