Managing our Footprint

DMA: Effluent and Waste

Detour Gold recognizes the importance of managing the waste generated by our operations in ways that protect human health and the environment. We have comprehensive waste and hazardous materials management programs. Safely managing tailings and waste rock are primary concerns for us – as they are for the mining industry as a whole – and we aim to be industry leaders in managing them.

Tailings Management

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Detour Lake Mine’s tailings contain low levels of cyanide, cyanide decomposition products and trace metals produced during mining and gold processing. Our main objectives are to confine the tailings in containment ponds, re-use water from the ponds in our operations, and minimize the risk of discharging contaminants to the natural environment.

Our tailings management area (TMA) will ultimately consist of three separate ponds (or “cells”) built over the mine life. Each cell will be built as the mine evolves, and each will have about six to seven years of planned use. To date, there is one cell constructed where we actively deposit tailings and another area has been cleared in preparation for use. Tailings are pumped into the pond as slurry (half water, half solids). The solids settle over time, and we use a decant system to reclaim the water for re-use in our operations.

To ensure our tailings pond is safely managed, we have included several prevention measures in the facility design. We also regularly monitor the structure and integrity of the dam as well as water quality in and around our facilities. All data is documented in an annual report submitted to the provincial and federal government, and our four Aboriginal partners.

In 2016, we hired a third-party Dam Safety Review (DSR) engineer to complete a comprehensive assessment of the TMA. The assessment focused on aspects such as dam design, construction methodologies, operating practices, surveillance and monitoring, and water balance. The review concluded that our dams are “being maintained and the site is being operated in a safe manner in accordance with the existing protocols. There is a comprehensive dam safety management system encompassing all aspects of operation, surveillance and maintenance.”

The report also identified opportunities for improvement, which were shared with the Engineer of Record and the operations team for implementation in our design, construction and operating practices. Annually, our Engineer of Record also completes a Dam Safety Inspection (DSI). These reports are shared with regulators and Aboriginal communities engaged in monitoring impacts of the mine.

In 2017, we will start the construction of our second cell in the TMA. Experience of the past five years and the recommendations from the DSR have been incorporated into the design of this second cell.

Annual Tailings Volume into Tailings Cell 1 (mt)

Waste Rock Management

We have extensive plans for managing waste rock specifically around mitigating the risks of potential acid rock drainage (ARD). These plans have been reviewed and acknowledged as sound practice by Environment Canada, the Ministry of Northern Development and Mines, the Ministry of Natural Resources and Forestry and our Aboriginal partners.

Geochemical studies have concluded there is no evidence of acid rock drainage at the Detour Lake site. As well, after more than 26 years of monitoring the previous mine operation, there continues to be no acid rock drainage. While this tells us that the current mine has a low risk of causing acidity or metal leaching issues, we are nevertheless partnering with teams at the University of Waterloo and the University of Alberta to further our understanding of waste rock reactivity and factors that affect internal reactions.

In the meantime, we are taking a conservative approach to managing and monitoring waste rock, which includes:

  • Routine sampling of every pit blast.
  • Analyzing the rock for sulfur and carbon content as an indicator of potential acidity and for neutralizing minerals that would counter the acidity.
  • Segregating and storing different rock types in specific piles for potentially acid generating material (PAG) and non-acid generating material (NAG).
  • Monitoring water quality through an extensive network of collection ditches and ponds around waste rock piles and groundwater wells.

Our comprehensive research indicates that ARD onset has not occurred in the waste rock from the previous mine and about 17% of the new waste rock is potentially acid generating. The ongoing research and monitoring programs will help optimize our waste rock management plan both during operations and well past the eventual closure of the mine. Results of our mineral waste segregation and movement are provided to regulators and to aboriginal communities in our annual reports.

Waste Rock Volumes

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2016:

60 Mt of waste rock, including:
14 Mt PAG
46 Mt NAG

Total to date:

200 Mt of waste rock, including:
41 Mt PAG
160 Mt NAG

Domestic and Other Wastes

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Detour Gold applies best practices to identify and manage the secondary waste materials we generate. By establishing special management systems early on, we minimize the risk of contaminating the environment throughout the mine life. Collectively, the results of these programs will allow an efficient closure of the mine.

We are committed to understanding the life cycle of the materials that we use and integrating that knowledge into our management systems. Where possible, we promote re-use and recycling as the preferred waste management approaches over disposal. For example, waste oil from equipment maintenance that would normally be shipped off site for disposal or refining is instead tested to ensure its safety and re-used to heat our buildings. This reduces our GHG emissions and the potential risks associated with offsite transport and disposal. It also reduces our energy costs.

The mine has a permitted landfill on the north-west side of the property. We specifically chose the site because there are no surface water receptors within 500 metres of the area. As a precaution, groundwater monitoring wells have been installed to monitor migration of contaminants. We also developed a rigorous landfill management procedure as part of the environmental management system:

  • Operators control all authorized waste materials deposited to the landfill, which is secured by a gate.
  • All material is classified under one of several categories, which determine the proper disposal procedure. The landfill site only accepts non-hazardous construction waste and domestic waste from our employee camps.
  • We conduct training on these procedures for contractors and operations personnel.
  • We track and report the volume of each material type in annual reports.

We recycle or dispose of material not suitable for the landfill in a safe, environmentally responsible manner. We have set up several locations around the process plant site to safely and securely house these materials until disposal. This includes a safe storage area for hazardous waste for off-site disposal by a certified contractor, and an area for steel, copper, tires, and waste oil that will be recycled by specialized companies. Scrap wood is stored separately in the landfill area for potential chipping or burning.

In 2016, we began a program with our catering services supplier, CreeQuest Aramark, to measure waste from our kitchen operations, which will be the starting point for developing waste reduction initiatives. Aramark is currently transitioning to a "Wipe out Waste" program, and has been doing some preliminary waste tracking. Current estimates are that each camp kitchen staff will produce roughly 30-35kg of organic waste per day.’

Spills and Compliance Management

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We take any discharge to the environment very seriously and have systems to prevent such incidents and to ensure an immediate, safe and effective response in the event of a spill. Our operation is regulated by multiple permits obtained through a rigorous review process involving government regulators and Aboriginal communities. We report any activity resulting in non-compliance with our operating permits or regulations. In the event of non-compliance, we report the situation to the appropriate regulatory body and investigate internally to identify root causes and corrective actions.

Spill prevention includes an inspection and maintenance program, training personnel in proper handling of materials, and building secondary containment structures in key areas.

Our emergency response program is part of the core operating plan for the site. The program includes a rigorous system to respond to small spills within the pit or mill areas. Specialized responders direct activities to control the spill area and clean up the spill and contaminated material. The operations manual outlines emergency procedures and we train the entire emergency response team. Our program also applies to the contractors who operate in the tailings management area, the mill and the pit.

We safely and responsibly manage any contaminated materials from a spill to minimize any long-term effects. After testing, any contaminated soils are either removed off-site to an approved disposal facility or stockpiled and processed through the mill in small quantities to avoid disrupting the gold recovery process.

All spills are recorded in a database for monthly and annual reports. The compiled information includes the cause of each spill, which is then discussed with work crews to avoid similar events in the future. A spill is considered to be significant if it adversely affects the water quality or local wildlife.

0 incidents

There were no significant environmental incidents in 2016.

Case Study

Safety Frist: Our Approach to Tailings Management

Our Tailings Management Area (TMA) is the largest engineered feature constructed at the Detour Gold site. In simple terms, the TMA is an earth and rock dam built to hold tailings and water. The reality is that our TMA touches all aspects of our operation and it is imperative that we design, build and operate it correctly.

The TMA is designed, built and operated in keeping with the guidelines and technical bulletins of the Ontario Ministry of Natural Resources and Forestry and the Canadian Dam Association. Initially, an independent licensed engineer designed the TMA and Aboriginal communities had the opportunity to provide input and ask questions directly to regulators and to Detour Gold. The plans were then submitted to the government for final review and approval.

Since the start of construction, the dam has been subject to daily, weekly, monthly and annual inspections by Detour Gold staff and third-party inspectors. Annually, a dam safety report measuring our compliance with the original design and operation plans is produced by a third-party engineer and circulated to government and Aboriginal partners.

In 2015-2016, we elected to tender for an independent dam safety review (DSR) of the TMA facility. Knowing that we would be building the second cell of our TMA in 2017, this was intended to ensure that the design features, operation and assessment of human and nature risks identified at the start of the mine reflected current conditions.

We also felt that it was important to include our Aboriginal partners in the DSR process in the interests of transparency and building trust. Our partners helped us craft the terms of reference for the study and shortlist a qualified consultant for the work. We also shared with them the engineer’s final report, which validated our operating practices and dam safety management system.

“The dam(s) are being maintained and the site is being operated in a safe manner in accordance with the existing protocols. There is a comprehensive dam safety management system encompassing all aspects of operation, surveillance and maintenance.” (Golder Associates, 2016)

All in all, it was a good result with good learnings that we can apply to the TMA expansion and future projects.

The Business Case

for safe tailings management

  • Ensuing TMAs are designed, built and operated following strict application guidelines is critical to managing the risk associated with these large structures.
  • Without a functioning tailings area, the mine cannot operate. Monitoring the behaviour and structure while constantly looking for risks and opportunities helps to ensure uninterrupted operation.
  • The TMA is in a constant state of construction to accommodate our growing operation. Implementing best practice design and construction methods helps keep our employees and the environment safe, while lowering costs and increasing efficiency.