Briefing Note on Hamilton et al 2020 paper

The following provides some comments from Mount Polley Mining Corporation (MPMC) on the Hamilton paper (Hamilton, et al. 2020)[1] regarding Quesnel Lake in relation to the TSF Breach at Mount Polley. The note is divided into general comments, specific comments, and then provides an update on Quesnel Lake water quality, and some key observations from recent sediment and aquatic life monitoring, which support the MPMC comments on the paper. This is not a comprehensive review of the paper.


The Hamilton paper provides a summary of a considerable amount of monitoring data collected in Quesnel Lake, including  from automated moorings. (Note: MPMC contributed to this research through the purchase of a number of new instruments for the moorings in the fall of 2014.)

The paper focusses on seasonal observations of a slight increase in turbidity deep in the West Basin, and on physical lake dynamics. It also introduces some hypotheses regarding new mechanisms of lake water movement. MPMC is pleased to have contributed to this enhanced understanding of water movements in large lakes.

However, we are concerned that important monitoring data, available on our web site or directly from MPMC or our consultants, was not referred to or incorporated into interpretations made in the Hamilton paper. The use of information that is readily available from MPMC’s web site or directly from MPMC or its consultants would have helped address some of the authors’ concerns, particularly about future impacts to aquatic life and contamination.

Unfortunately, the paper does not include data from the mine’s monitoring nor any other data on these topics. The paper contains a number of interesting scientific observations, but these do not necessarily indicate an environmentally consequential measurement.  

Specific Comments on the Hamilton et al (2020) paper:

  1. Mount Polley’s monitoring data indicates that contaminant levels in Quesnel Lake are not elevated. The paper identifies a small turbidity signal at depth, but turbidity does not necessarily indicate contamination.  (See below for a description of “what is turbidity”.)
  2. Hamilton et al’s data from 2015 to 2017 indicate a significant decline in the seasonal turbidity signal they measured since the spill in 2014. This observation agrees with MPMC’s monitoring data.
  3. The turbidity values measured by both MPMC and Hamilton et al are below BC water quality guidelines, which are based on a 30-day average. (The BC Guidelines allow for increases to 10 NTU for short durations.)
  4. There are no data presented in the paper from 2018, 2019 or 2020. This is a significant shortcoming of the paper being able to speak to the current situation, or to future impacts. MPMC has monitoring data for 2018 to 2020 for a number of sites in the lake that the researchers could have used to assess trends after 2017 for both water quality and aquatic ecosystem health.
  5. The levels of turbidity measured by Hamilton et al deep in the West Basin are quite low. (Between winter 2015 and winter 2017 they range from highs of approximately 2.3 FTU, to less than 0.5 FTU.)  Turbidity is a measure of “cloudiness” due to particulates in water, however, the levels of turbidity being measured in this paper are not easily seen with the naked eye (in other words, instruments are required to measure these levels).
  6. The paper provides background (pre-spill) data that indicate that the turbidity signal they observed at depth is at or below the level of natural turbidity events in the West Basin in the past (for example, a plume from the Horsefly River in May 2008 increased the turbidity in surface water of the West Basin to greater than 2.0 FTU as seen in Figure 3 in the paper). Natural turbidity events, such as are associated with heavy rains, spring freshet (snowmelt) or high-water floods, can generate similar or higher levels of turbidity. This summer, high creek and river levels generated muddy, debris-laden, flows into Quesnel Lake. 
  7. The paper postulates suspension of material from an unconsolidated layer of particulates at or near the bottom of the lake. While the unconsolidated layer identified in core samples is interesting, there is no data in the paper on what the particulates are that make up this layer. MPMC has reached out to the authors with an offer to either do this work on their samples or contribute funding to fill this information gap.  Note that the paper does not say that tailings are resuspending off the bottom of the lake. Note also that MPMC sediment monitoring has observed natural material, with organic carbon, settling into sediment traps placed on the bottom of Quesnel Lake and presumably covering tailings.
  8. There is no data in the paper that indicates that the particulates associated with their turbidity signal are contaminated with any metals or chemicals of concern. MPMC’s monitoring shows that water quality in Quesnel Lake is below the BC Water Quality Guidelines, except during spring freshet when area creeks naturally discharge elevated turbidity and copper.
  9. MPMC supports the Hamilton et al observation of no visible colour change in the lake since 2014. This confirms MPMC’s observations.  
  10. Mount Polley’s water discharge is permitted by the BC Government and is within strict permit guidelines that are protective of sensitive aquatic life. The paper noted a small increase in specific conductance associated with the MPMC treated water discharge in 2016, but also noted that there was no turbidity signal associated with this discharge. These data agree with Mount Polley’s monitoring data. MPMC’s monitoring continues to show that water quality in Quesnel Lake is below the BC Water Quality Guidelines except during spring freshet when area creeks naturally discharge elevated turbidity and copper and when MPMC are typically not discharging because of restrictive permit requirements.
  11. The paper expresses concern about the potential resuspension of spill material from Quesnel Lake and its impacts on juvenile sockeye salmon, while not including data DFO collected on juvenile salmon in the West Basin in 2014, the year of the spill, nor acknowledging that the 2014 juveniles were the cohort that “returned in droves” to the Quesnel Lake watershed in 2018. This juvenile salmon cohort would presumably have been the most impacted as they were feeding in Quesnel Lake the year of the spill, yet there has been no indication that the tailings spill had a deleterious effect on their feeding or their returns four years later.
  12. Mount Polley is very pleased to see that the paper noted that the MPMC remediation of Hazeltine Creek reduced sediment loads as no turbidity signal >0.2 FTU above background was detected near its mouth from 2015 through 2017”.

Quesnel Lake Water Quality

  • There is no evidence of pollution being caused in Quesnel Lake related to the Mount Polley spill. This is affirmed by MPMC monitoring and by BC ENV comments to the MPMC’s Public Liaison Committee.
  • Results of the Comprehensive Environmental Monitoring Program (CEMP) – Sediment and Aquatic Life (Minnow, March 2020) monitoring using DGT instruments in Quesnel Lake indicate:
    • copper concentrations in 2019 “were well below [freshwater aquatic life] effects thresholds”
    • there is “strong evidence of … post-depositional stability of the sediments impacted by the breach”, i.e. there is no indication that metals are leaching out of tailings into the water in Quesnel Lake, and
    • “… analytes in 2019 were all below BCWQG’s”, i.e. all metals analyzed using the DGT’s were below the BC Water Quality Guideline thresholds for protection of freshwater aquatic life.

Discussion of Turbidity from

(website accessed 2020-09-01)

The definition of Turbidity is the cloudiness or haziness of a fluid caused by suspended solids that are usually invisible to the naked eye. The measurement of Turbidity is an important test when trying to determine the quality of water. It is an aggregate optical property of the water and does not identify individual substances; it just says something is there. Water almost always contains suspended solids that consist of many different particles of varying sizes. Some of the particles are large enough and heavy enough to eventually settle to the bottom of a container if a sample is left standing (these are the settleable solids). The smaller particles will only settle slowly, if at all (these are the colloidal solids). It’s these particles that cause the water to look turbid.

[1] Hamilton, A. K., B. E. Laval, E. L. Petticrew, S. J. Albers, M. Allchin, S. A. Baldwin, E. C. Carmack, et al. 2020. “Seasonal Turbidity Linked to Physical Dynamics in a Deep Lake Following the Catastrophic 2014 Mount Polley Mine Tailings Spill.” Water Resources Research 56. doi: 10.1029/2019WR025790.


Rainbow trout return to Hazeltine Creek

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.

Fish fences blocking passage from Polley Lake (top left) into upper Hazeltine Creek [2015]
Fish fences blocking passage from Polley Lake (top left) into upper Hazeltine Creek [2015]

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.

Abundant Rainbow Trout observed upstream of fish fences, looking to transit into Hazeltine Creek from Polley Lake to spawn. [May 2017]
Abundant Rainbow Trout observed upstream of fish fences, looking to transit into Hazeltine Creek from Polley Lake to spawn. [May 2017]

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.

Mount Polley fishway ladder
Mount Polley fishway ladder

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.

Spawning rainbow trout in Hazeltine Creek. [late May 2018]
Spawning rainbow trout in Hazeltine Creek. [late May 2018]