Categories
Remediation

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.

General

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 https://lamotte.com/technical-tips/post/turbidity

(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:https://doi.org/ 10.1029/2019WR025790.

Categories
Mining facts

Likely Area Mining History

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.

Quesnel Forks information sign at the entrance to the historic townsite

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.

Drone image of the Bullion Pit near Likely, BC

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.

Polley Lake Outlet Structure: water works for placer mining — early 1900s. Courtesy of BC Archives.

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.

To learn more about Likely’s mining history, visit the Cedar City Museum and Info Center located in the Cedar Point Provincial Park in Likely, BC.

This Facebook page gives regular updates on the areas in BC that were part of the mine’s early gold mining history.

Historic building in Quesnel Forks

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.

Historic building in Quesnel Forks. Courtesy of Mount Polley
Historic building in Quesnel Forks overlooking Quesnel River. Part of the history of the Mount Polley site and surrounding area.
View of Quesnel River at confluence with Cariboo River from Quesnel Forks historic townsite
View of Quensel River from Quesnel Forks historic townsite.
Cedar City Museum and information centre in Cedar Point Provincial Park in Likely, BC on Quesnel Lake.
Historic mining equipment on display in Cedar Point Provincial Park in Likely, BC