Giant Mine Long-Term Remediation Project – Yellowknife, Canada

  • Crown-Indigenous Relations and Northern Affairs Canada
Project Value

$4.38 billion CAD (estimated total value as of 2023)


Energy And Environment, Water And Wastewater


Program/Construction Management (PM/CM), Sustainability

Giant Mine is an abandoned, 2,300-acre, gold mine near Yellowknife, Canada, about 250 miles south of the Arctic Circle. The mine operated from 1948 to 2004 under a series of owners, extracting more than 7 million ounces of gold. These riches left behind significant contamination – as much as 237,000 tons of arsenic trioxide dust, as well as large amounts of contaminated tailings and soil. The cleanup of the Giant Mine site became the joint responsibility of the Canadian Federal Government and Government of Northwest Territories.

First Remediation Project

The first major project undertaken in the overall cleanup began in 2013. Parsons was hired as the general contractor for the Giant Mine Roaster Complex Deconstruction, a project to decontaminate and deconstruct the 10 major structures at the Roaster Complex. At the time, these were Canada’s most contaminated buildings, containing large amounts of arsenic trioxide (a byproduct of the mine’s ore roasting process) and asbestos. To keep the arsenic trioxide and asbestos from escaping and potentially creating hazardous conditions in the community, the buildings were decontaminated within a containment system and remaining building components were sprayed with a glue sealant, making the area safe until further remediation efforts could be completed.

As part of the Site Stabilization Plan, we successfully removed more than 10,000 tons of highly toxic arsenic trioxide while ensuring the safety of workers, the community, and the environment.

A Continued Partnership

Since 2015, we have served as the main construction manager and care and maintenance operator of the Giant Mine Remediation Project. During the first term, we managed many projects including:

  • Construction of an on-site, non-hazardous waste landfill and operation of the landfill
  • Stabilization of the underground by backfilling the mine stopes
  • Construction of a freeze pad, including rock blasting
  • Hazardous waste removal from buildings, decontamination, and deconstruction of buildings

We also performed constructability reviews on all design works, created the project implementation plan, and performed site care and maintenance.

The second term of our contract began in February 2023, following the announcement of our contract amendment with the Government of Canada. We will continue to provide construction management for the implementation of the remediation project, providing long-term containment and management of contaminated tailings and soils, construction of a new water treatment plant, demolition and landfilling, care and maintenance of the surface and underground infrastructure and facilities, site safety, environmental compliance, delivering on indigenous and local socioeconomic commitments, and full mine project and construction management services.

Elegant Engineering

Giant Mine’s remote location requires constant and meticulous coordination planning. Edmonton, the closest major city, is a two-day drive, making this project a logistical challenge.

With such a vast amount of waste and contamination, the only solution is to keep waste from contacting the environment and community.  For example, we are using an innovative process that freezes the arsenic trioxide waste in place in chambers deep underground by installing passive thermosyphons. By leveraging the frigid winter environment to treat the waste, the design engineers drive ambient cold temperatures into the ground, freezing the rock around the arsenic waste to prevent it from contaminating groundwater.

Successful Community Engagement

Since the remediation is taking place on Indigenous lands, it was important for us to design our contracting system to incorporate Indigenous and local contractors and deliver substantial opportunities and benefits to the Indigenous groups affected by the Giant Mine.

One of our initial priorities on the project involved establishing a socioeconomic framework to maximize opportunities for these groups, which include the Yellowknives Dene First Nation, North Slave Metis Alliance, and the Tlicho. Our goal was to create a lasting structure to make sure that as many Indigenous businesses as possible can participate on the project.

We are working directly with the Economic Development Corporations including Deton Cho Management (Yellowknives Dene First Nation), Metcor (North Slave Metis Alliance), and Tlicho Investment Corporation (Tlicho) to support partnerships which help provide resources and equipment, enabling businesses to compete more effectively for procurement opportunities, and regularly reviewing local Indigenous ability to undertake the project’s Construction Work Packages (CWPs).

To date, we have worked with several Indigenous businesses, including Deton Cho Nuna, Deton Cho Nahanni, Metcor, DJRM, Forward Mining, Ekedia Bear Monitoring Services, and Nahanni Construction.

For the duration of this project, our goal is to ensure that we meet the project’s objective of maximizing socio-economic benefits to northern Indigenous people and northern businesses.

Learn more about Parsons’ decade-long remediation efforts and our continued activities at Giant Mine:

Learn more about the Giant Mine Remediation Project:


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