Watershed Management

Protecting downstream water quality is a priority for Pretivm, and is a key interest of Indigenous groups and stakeholders. As a result, water management and stewardship is essential in the planning and execution of all our activities at the Brucejack Mine, so that we can preserve natural water quality and flow volumes in the surrounding environment. Unlike many gold mines, we do not use cyanide in the gold extraction process, so we avoid many of the hazards associated with cyanide management.

Pretivm integrated a watershed management approach in the design of the Brucejack Mine. The mine site receives a high volume of rain and snow throughout the year, with an average snow depth of nearly four metres. All water within the mine site that comes into contact with excavated bedrock material must be treated, so we have designed the mine site to minimize this volume. Channels around the site divert meltwater and surface runoff away from the mine site, reducing the volume of contact water. We collect and contain the runoff water that does contact excavated bedrock, and treat it before discharging to the Waste Rock and Tailings Storage Facility with eventual outflow back to the receiving environment.

Our Water Management Plan is supported by six additional EMPs1 that contribute to different aspects of water management. Various departments within our operation are responsible for specific elements—including groundwater, surface water, and water treatment—and management responsibilities are consolidated in our environmental management system.

The water quality of the Waste Rock and Tailings Storage Facility is the key indicator for success of Pretivm’s watershed management approach. Outflow from the Waste Rock and Tailings Storage Facility forms the majority of flow in Brucejack Creek. Brucejack Creek is not fish bearing due to a natural fish barrier 20 kilometres downstream of the mine site, which prevents fish from traveling further upstream. We discharge treated effluent from the mine site to the Waste Rock and Tailings Storage Facility, and the facility also receives deposits of tailings and waste rock, as explained in Materials and Waste Management. We are committed to managing water quality of outflow from the Waste Rock and Tailings Storage Facility to avoid negative impacts on water quality further downstream.

Data Highlights


17 surface water
monitoring stations
36 groundwater
monitoring wells
2 snow
monitoring stations
3 weather
monitoring stations
1,731 samples
of water and other environmental samples analyzed in 2019
5 air quality
monitoring stations
1EMPs supporting water management include the Aquatic Effects Monitoring Plan, Metal Leaching and Acid Rock Drainage Management Plan, Spill Response Plan, Tailings and Subaqueous Waste Rock Deposition Management Plan, Nitrogen Management Plan, Chromium Management Plan, and the overall Water Management Plan.

Water Withdrawal, Reuse/Recycling & Discharge

 

The Brucejack Mine is located in a humid environment with little development, and the downstream receiving environment is not considered to be water stressed.2 Nonetheless, Pretivm has designed the Brucejack Mine to minimize effects on surrounding water bodies and limit the use of freshwater. The lifecycle of water at the Brucejack Mine includes water collection and withdrawal, re-use/recycling, treatment, and discharge. Water that comes into contact with our site is collected and recycled or re-used where possible, and excess water that is not reused is treated before returning to the natural environment.

Potable water for the mine site is supplied by groundwater well. To provide water for the mill and underground mine processes, we capture groundwater seeping into the underground mine, collect surface runoff from rainfall and snowmelt that has contacted the mine site surface, recycle process water within the mill, and withdraw surface water from the Waste Rock and Tailings Storage Facility to supplement these sources.

In 2019, we recirculated more than half (66%) of all water used in the mill and mining process. We ultimately discharge treated water to the Waste Rock and Tailings Storage Facility, the outflow from which is the effluent discharge to the downstream receiving environment. Federal and provincial legislation regulates effluent discharge at the Mine. We ensure that the effluent meets applicable water quality standards and report this information to provincial and federal regulators.

2As defined by the World Resources Institute, water stress is represented by the ratio of total water withdrawals to total renewable supply in a given area.
Water Withdrawal by Source (Cubic Metres)3
Target
1,200,000

1,000,000

800,000

600,000

400,000

200,000

0

764,000

153,460

580,310

30,230

 

910,582

423,426

461,461

25,695

 

1,080,704

540,427

511,746

28,531

 
201720182019
Groundwater (potable water from well)
Groundwater (captured from underground mine)
Surface water
Water Discharged (Cubic Metres)3
Target
1,500,000
1,250,000
1,000,000
750,000
500,000
250,000
0

797,516

451,516

346,000

 

767,771

256,771

511,000

 

972,797

212,538

760,259

 
201720182019
Volume Discharged with Tailings
Treated Volume Discharged
3Mine operations commenced in mid-2017. Therefore, water withdrawal and discharge volumes are not directly comparable between 2017, 2018, and 2019.

Data Highlights


1,571,936 m3
water used in the mill and mining process
1,031,509 m3
water recirculated in the mill and mining process
66%
of water is recirculated in the mill and mining process

Protecting & Monitoring Water Quality

Pretivm’s commitment to exceptional water management is supported through a program of inspections, audits, environmental monitoring, and continual improvement as described in Environmental Management. For example, weekly water quality monitoring of the Waste Rock and Tailings Storage Facility outflow verifies whether our management measures are effective. We compare the monitoring results to predictions made by water quality models, and input the results back into the model to refine future predictions.

Our goal to meet or exceed regulatory requirements is evident throughout our operation and is particularly relevant to our efforts to protect water. In addition to regulatory compliance, we have established internal triggers for water quality that may prompt management action. These internal triggers are lower than the regulatory limits.

Pretivm’s water quality monitoring program encompasses facilities and natural water bodies in and around the mine site. At the site, we monitor the quality of mill process water, as well as effluent from the on-site sewage treatment plant and industrial water treatment plant. Water quality of the outflow from the Waste Rock and Tailings Storage Facility is also a key indicator, and we monitor water quality within the facility itself, at its outlet, and the downstream receiving environment. We monitor a long list of water quality parameters including general water chemistry and metal concentrations. Some of the key parameters we track are total suspended solids, pH, conductivity, temperature, and metals such as chromium, copper, silver, and iron.

Annual Averages at Waste Rock & Tailings Storage Facility Outflow4

Parameter 2017 2018 2019 Permitted Discharge Criteria5
pH 7.79 7.87 7.91 6.5–8.5
TSS 3.14 2.50 5.18 25 mg/L
T-Cr 0.00017 0.00014 0.00015 0.02 mg/L
T-Cu 0.00034 0.00050 0.00052 0.01 mg/L
T-Ag 0.0000072 0.00002 0.00001 0.0001 mg/L
T-Fe 0.046 0.030 0.032 1.7 mg/L
T-As 0.0035 0.0050 0.0067 0.010 mg/L
4Water quality measured at discharge compliance point BJ 3.10.
5As of December 31, 2019.

Highlight Story

Caring for Our Watershed

Our ability to manage impacts on the environment is predicated on the expertise of our staff, and water management is no exception. Xavier Pinto is one of the most experienced members of Pretivm’s environmental department. He acts as a Qualified Professional (QP) on hydrometrics and meteorology, manages our water management and monitoring system, maintains key instrumentation, prepares reports for government regulators, and provides critical leadership and coaching to our junior and intermediate staff.

As an expert on hydrometrics and meteorology, Xavier is responsible for the water monitoring system at the Brucejack mine site. With past experience in the mining and oil and gas industries, and as an environmental consultant, Xavier finds work at the operating Brucejack Mine to be inherently rewarding. He notes that Pretivm is committed to excellence when it comes to water management, and appreciates that his recommendations are well received by the company.

“This is a company that sees compliance as the minimum standard, and then asks ‘what else can we do’?” Xavier Pinto, Senior Hydrologist