Giant Mine Remediation Project

In this section

Who is managing the project?
Arsenic Trioxide Waste Storage
Perpetual Care Plan
How is our health being monitored or studied?
Video: Overview of the Giant Mine Site
GMRP : Additional Information

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 giantminerp.ca

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

As part of the Environmental Agreement, the GMRP is required to develop a Perpetual Care Plan (PCP) that must address improvements in records management, communication with future generations, long-term access to funds for the Project and analysis of different possible scenarios that might affect the perpetual care of the Project.

The Project held facilitated workshops with signatories of the Environmental Agreement, GMRP team members, and other interested members of the public to review and conduct an initial validation exercise previous work completed. Following these workshops, a Perpetual Care Plan Advisory Task Force was formed with members of the signatories of the Environmental Agreement.

In November 2020, the GMRP submitted the preliminary framework to the Giant Mine Oversight Board.

In Winter 2022, the Project held a series of workshops with the Task Force to scope the Statement of Work for the Perpetual Care Plan work package. The Task Force worked through various Perpetual Care Plan components (e.g., governance, communicating with future generations) to identify the specific goals, tasks, deliverables, and subsequent experience required.

The Final Statement of Work was prepared at the end of March 2023 with a subsequent Request for Information late spring 2023 In 2022-23.

A Request for Proposal was released in January 2024, with contract award and consultant onboarding anticipated for early spring 2024, to begin development of version 1 of the PCP.

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 retested children in the fall of 2023, and will again in 2027-28. Adults will also be retested in 2027-28.