Giant Mine Remediation Project

Giant Mine was a gold mine operating outside of Yellowknife from 1948 until 2004. When operations ceased, the Government of Canada became the site custodian.

To release the gold found in minerals called arsenopyrite ore, Giant Mine and other legacy mining operations around Yellowknife had to roast the ore at extremely high temperatures. Unfortunately, this roasting process also released arsenic rich gas, a highly toxic by product. In the early days, much of that arsenic was released directly into the environment. As a result, some areas in the Yellowknife area contain increased levels of arsenic. After the mine closed, the 237,000 tonnes of arsenic trioxide waste remained on site.

The Giant Mine Remediation Project addresses the long-term containment and management of the arsenic trioxide waste, the demolition and removal of all buildings on the surface, and the remediation of surface areas including the tailings ponds. It also includes water management and treatment options. This project will take approximately 10 years and is expected to be completed by 2029.

The main objectives of the Giant Mine Remediation project are to:

  • minimize public and worker health and safety risks
  • minimize the release of contaminants from the site to the surrounding environment
  • remediate the site in a manner that instills public confidence
  • implement an approach that is cost-effective and robust over the long term

Who is managing the project?

The Giant Mine Remediation Project is co-managed by the Governments of Canada and the Northwest Territories. For more information on the Giant Mine Cooperation Agreement and how the two governments work together as co-proponents, refer to the Giant Mine Cooperation Agreement.

The Giant Mine Remediation Project submitted its application for a Type A Water Licence to the Mackenzie Valley Land and Water Board on April 1, 2019 and a water licence was issued on August 2020  for a twenty (20) year term. The Mackenzie Valley Land and Water Board Public Registry is where the Project’s documents related to the Water Licence and Land Use Permit will be permanently posted for public access.

Parsons, the Main Construction Manager for the Giant Mine Remediation Project is responsible for the majority of hiring and contracting associated with the Giant Mine Remediation Project. For more information, or if you seek employment, please visit their website at

Remediation Activities began in the summer of 2021! For regular updates on the Giant Mine Remediation Project, visit the project page.

Arsenic Trioxide Waste Storage

237,000 tonnes of arsenic trioxide dust are stored in underground chambers at the Giant Mine site.

There are five stopes and 11 chambers at Giant Mine that contain arsenic trioxide dust. Between 2001-2003 extensive scientific and technical research, and community consultation took place to determine the safest way to manage arsenic trioxide underground. The Project team considered 56 options for managing the arsenic.

Freezing the arsenic trioxide in place was determined to be the best strategy for managing the arsenic for the long-term to protect people and the environment. However, this is not a permanent solution for managing arsenic trioxide. The Giant Mine Oversight Board is tasked with supporting research into technical approaches that could serve as a permanent solution.

Perpetual Care Plan 

Giant Mine’s remediation is expected to take approximately ten years, but the project itself has a defined life of 100 years, with some components that will require operation and maintenance into perpetuity. It is important to ensure that, once active remediation is complete, there is a plan in place for how the site will be managed and how future generations will be informed about the site. This plan also needs to include considerations for how records are managed and how future risk scenarios are assessed that could impact perpetual care of Giant Mine. 

An Advisory Task Force made up of team members and key stakeholders was established to guide the development of the Perpetual Care Plan (PCP). The Task Force has worked collaboratively to develop a detailed preliminary framework that outlines all the main elements of the PCP.

The Project Team, with input from the Task Force will contract the services of an external consultant who can bring the necessary capacity and expertise to help develop the first draft of the PCP in 2022-23. 

How is our health being monitored or studied?

The Yellowknife Health Effects Monitoring Program

The Yellowknife Health Effects Monitoring Program (YKHEMP) was established in 2017 to ensure the remediation activities as part of the Giant Mine Remediation Project (GMRP) will not have a negative impact on people’s health in the communities. YKHEMP was designed to meet the requirements of Measure 9 of the Mackenzie Valley Review Board’s Report of Environmental Assessment from 2014. The study is led by Dr. Laurie Chan and his team at the University of Ottawa.

During the initial phase of the study, Dr. Chan and his team measured arsenic concentrations in urine and toenails collected from participants. In 2014-2018, a total of 2037 residents between the ages of 3 to 79 from Yellowknife, Ndılǫ, and Dettah, including members of the Yellowknives Dene First Nation and North Slave Metis Alliance, participated in the first phase of the program. The University of Ottawa provided summary results from the 2017-2018 baseline data in May 2019; these results gave the research team an understanding of the participants’ exposure to arsenic and other metals of concern as well as their health at the time of testing. A brochure depicting the results can be found here and the YKHEMP Progress Report for 2020 can be found here.

Further testing will reoccur every five years, to align with the GMRP phases and to understand if the GMRP is negatively affecting the health of the community. Trends will also be investigated by the study team to look at long-term relationships between arsenic in urine and toenails, and health effects. Arsenic level monitoring will continue as the study team will be retesting children in spring of 2023, then again in 2027-28. Adults will also be retested in 2027-28.

Hoèla Weteèts’eèdeè: Understanding Community Wellbeing Around Giant Mine

Hoèla Weteèts’eèdeè: Understanding Community Wellbeing Around Giant Mine is a research study on chronic stress related to historic and current activities at the Giant Mine site. This study has been independently developed as a research collaboration between Wilfrid Laurier University and Yellowknives Dene First Nation.  The study will examine lifespan, intergenerational and community impacts of Giant Mine on the stress of people and communities living near the site.

The study will identify communities who have been dealing with more stress than others, highlight strengths and abilities to overcome hard times, and consider ways that we can improve health as the Giant Mine Remediation Project continues. It will also help other local service providers and relevant organizations to improve healing programs and other support opportunities for people and communities in need.