What's happening at Giant Mine? Fall 2025

Tracey Forbister (1966 to 2025)

The Giant Mine Remediation Project team was saddened to learn of the passing of our long-time colleague and friend, Tracey Forbister, in July of this year. Through his work with SLR Consulting, Tracey was an integral part of implementing the Air Quality Monitoring system, which is instrumental in helping ensure remediation activities are not adversely affecting residents or the environment.

The Project team is so grateful for all the work Tracey did to keep the community safe. His contributions continue to support the health and safety of the Yellowknife community, and his legacy lives on in the systems that protect people every day. He will be greatly missed.

Aecon Group builds new structures for 2025 YKDFN Xat'o Gathering

This year, Aecon Group Inc., one of the Giant Mine Remediation Project contractors, was proud to provide support to the Yellowknives Dene First Nation ahead of their Xat'o Gathering in the fall. Some of the work included:

• refurbishing the gazebo
• leveling the yard with fresh gravel
• raising and stabilizing the dock
• rebuilding the tent structure for Elders

This support reflects the Project and its contractors' commitment to working alongside Indigenous partners in ways that extend beyond remediation activities. Helping prepare for the Xat'o Gathering is one way partners like Aecon build trust, contribute to community well-being, and honour the important events that bring people together.

Closing of the Summer Season

Though work continues year-round on the mine site, as the cold and snow settle in, some of the activity at site pauses until the warmer months.

Summer 2025 was another big year for the Project. The team made lots of progress on some very large projects, such as furthering the construction of the Water Treatment Plant and Core Demolition work. Care and maintenance and monitoring of the site will continue throughout the winter season.

Project’s use of the Frozen Block Method

The Project has recently been asked why the freeze program was chosen to contain the arsenic trioxide at site, and how this method works.

Safety was the most important factor in choosing the frozen block method to address the arsenic trioxide waste. In looking at the different options for dealing with the arsenic, the Project team determined that removing the waste would be unsafe for the workers and for the nearby communities. In addition, it is not possible to get all the waste out of the chambers and stopes, meaning the Project team would still have to keep managing that area on an ongoing basis. The waste that the Project could potentially remove would also need to be stored, creating another contaminated area.

Freezing the arsenic trioxide in place is the best strategy for managing the arsenic for the long-term to protect people and the environment. Of the many options the Project team considered, it offers the fewest risks.

Freezing the arsenic has the lowest risk of:

• harming worker and community health and safety
• releasing arsenic into the environment
• releasing arsenic over the long term

Currently, the safest way to manage the waste is to freeze it where it is, undisturbed, and prevent it from contaminating the underground water.  This involves cooling the surrounding rock to create a frozen block, or a shell, that isolates the dust from the environment. With the frozen shell around the dust, water will not be able to seep in or out of the frozen zones, which in turn will prevent the release of arsenic.

This is not a decision the Project made lightly or on its own. As part of making this decision, from 2001 to 2003, the Project team conducted extensive scientific and technical research, as well as community consultation. From that research and consultation, the Project team looked at 56 options for managing the arsenic and narrowed the list down to the most promising options. These 12 options were  then studied in detail. Of all these options, the frozen block method was chosen based on:

• scientific evidence
• community input
• support from the Independent Peer Review Panel

Based on all this information, the Project team confirmed that freezing was the best way to manage the arsenic, so submitted this to Mackenzie Valley Land and Water Board as part of the regulatory process. The Board's approval signaled agreement that this is currently the best technology we have to address the arsenic. The Giant Mine Oversight Board also conducted a State of Knowledge study in 2017. Their study also confirmed that the freeze is still the best plan. You can view this independent report (PDF) on their website.

Even though this is the best way we have to deal with the arsenic now, the Project team recognizes that technological advances could mean that, in the future, a better option becomes available. As such, the Project team funds research that could lead to a permanent solution to the arsenic trioxide store underground.  The Giant Mine Oversight Board manages the research. If the research conducted identifies better technological options for a permanent solution, the Project will work with them to determine the best course of action.

Learn more about the Frozen Block Method.