Remediating the surface of Giant Mine
Following remediation, the Giant Mine landscape will change.
How will the site be used in the future?
Following remediation of Giant Mine, the landscape will be quite different. The mine buildings will be gone, and some areas will contain new industrial structures, like the freeze and water treatment plants. There will be a rock cover on the tailings ponds. As well, Baker Creek will run along a slightly different route after remediation.
The central area of the site, including areas around the frozen blocks, water treatment plant, and the non-hazardous landfill, will not be available for public use. However, a large part of the site -may be available for a variety of activities. The Project team conducted a Surface Design Engagement process to help determine how the community wants to use the area in the future. Ultimately, however, it will be the City of Yellowknife and the Government of the Northwest Territories that make decisions about future use.
How is the team updating the surface remediation plan?
The Project team is updating the surface remediation plan to address the measures that came out of the Environmental Assessment. This plan looks at the Giant Mine surface, including:
As a part of updating the surface remediation plan, the Project team considered possible uses for the site after remediation. This included what the Giant Mine site will look like, and how later generations could use this area.
In 2015 and 2016, through a Surface Design Engagement process, the team engaged the public to answer these questions. The process was developed with extensive input from the Giant Mine Working Group and the Yellowknives Dene First Nation Giant Mine Advisory Committee. It comprised a series of multi-day workshops, meetings, and information-sharing events over two years.
Participants were able to provide direct input into planning for the surface remediation by developing remediation options and evaluating the options based on the participants' objectives for the site. The process required a significant time commitment from participants who attended several multi-day workshops and meetings. The Project team is giving the outcomes of these meetings careful consideration as they finalize the updated remediation plan.
Knowing how the public imagines the site once remediation is complete helps the team make more detailed plans for specific site elements. While the final plan may not reflect everybody's vision for the surface, the process allowed the Project team to understand the many perspectives they need to consider as they move forward on the planning process.
What will happen to the buildings?
There are currently approximately 85 buildings on the site. This includes those at the Giant Mine town site. Industry best practices requires the disposal all buildings and infrastructure that no longer serve a purpose.
Many of the buildings on site contain hazardous materials. These materials pose risks to workers and the environment during demolition. Therefore, the buildings require decontamination. This is to protect human health and safety, and the environment.
Roaster materials, which are heavily contaminated with arsenic, will be placed underground and frozen as part of the freeze area. Hazardous materials such as leachable lead paint and PCB-containing items will be shipped off-site to licensed facilities for disposal. Non-hazardous material such as wood, steel, and mechanical equipment will be disposed in an on-site, engineered landfill.
Some infrastructure work has already taken place because to reduce health and safety risks. More information can be found here.
What will happen to the tailings?
Tailings are milled and finely crushed rock leftover from separating gold from ore-bearing rock, in the case of Giant Mine. There are four tailings ponds on site that contain approximately 16 million tonnes of tailings. These cover about 95 hectares, or the size of 300 football fields. There is also a section of historic tailings on the shores of Great Slave Lake.
Some of these tailings were mixed with water and cement to form a paste, which was used to stabilize portions of the underground. The rest of the tailings will be relocated and/or covered during remediation.
The Surface Design Engagement process included several options for tailings that were evaluated by participants based on their objectives. Options included:
- relocating tailings or capping in place
- vegetated or rock cover over the tailings
The Surface Design Engagement report summarizes stakeholder input, for consideration by the Project team. The final plan for tailings will include relocating one of the tailings ponds (South Pond) to the Central and North tailings ponds. These two ponds, along with the Northwest tailings pond, will be capped with a geo-synthetic and rock cover.
What will happen with the pits?
There are eight open pits on the mine site; five are large. The Surface Design Engagement process evaluated the following options for pits:
- leaving the pits open with a fence to prevent access
- filling the pits with materials such as:
- clean rock
- contaminated soils
- some combination of the above
The Surface Design Engagement report summarized stakeholder feedback, for consideration. The final plan will involve filling the pits with a combination of coarse waste rock and gravel material.
One of the pits sits on top of two chambers that contain arsenic trioxide waste. This pit will also be filled to allow the Project to carry out the frozen block method.
There are also some quarries and borrow pits. These will be re-sloped to improve drainage and stability. This will reduce physical hazards and return the site to more natural conditions.
What will happen with contaminated soils and waste rock?
The Project team is currently finalizing plans on how to address contaminated soils, including arsenic-impacted soil and waste rock around the mine site. The most heavily impacted soils are found around the former roaster and mill area. This material will be disposed of in the freeze areas.
The Surface Design Engagement process considered various options for cleaning up the soils. The Project team will consider potential future land uses when making decisions in the final surface plan for soils and waste rock in order to minimize impacts to the environment and human health.
What will Baker Creek look like after the remediation is done?
Various sections of Baker Creek have been modified, relocated, or reconstructed many times over the course of Giant Mine's history. The latest relocation, in summer 2006, was done to prevent infiltration of creek water into the mine. As part of the Environmental Assessment measures, the Project team was asked to look at whether Baker Creek should be diverted off-site.
The Project team consulted on this decision with community members and stakeholders through the Surface Design Engagement process. That process is now complete, as is a draft Baker Creek Alignment Report. This report evaluates various Baker Creek alignments and concludes that Baker Creek will remain in an on-site alignment as part of the final remediation plan.
Baker Creek will be remediated by removing contaminated sediments and minimizing the risk of flooding to the underground by constructing an appropriately-sized channel and filling the open pits. Baker Pond will also be dredged and capped. Due to historical impacts from the roaster emissions, waterbodies upstream of Baker have been impacted. Water quality will therefore continue to be impacted on-site, and eating fish from Baker Creek itself will likely be discouraged for many years, even after remediation is complete.
Who decides how the site will be used after remediation?
The City of Yellowknife and the Government of the Northwest Territories (GNWT) will decide how to use the site after remediation. However, the Project team sought to understand what the public envisions and for the City and GNWT to consider while the team develops the remediation plan.
The final report on the Surface Design Engagement was completed in September 2016. It summarizes feedback from the workshops. The report documents the result of the workshops and input received throughout the engagement process. It has been distributed to stakeholders. If you are interested in receiving a copy of the report, email firstname.lastname@example.org or call (867) 669-2426.
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