Energy, Mines and Resources

Mount Nansen

Mount Nansen: Care & Maintenance

Care and maintenance is the term used to describe the ongoing activities such as site inspections or monitoring and management of water conveyance systems. Care and maintenance operations at the abandoned Mount Nansen mine site are ongoing.

What are the issues at the Mount Nansen abandoned mine site?

The primary issues are the quality of the water leaving the site and the stability of the tailings dam and open pit.

When the site was abandoned, the tailings pond contained high levels of cyanide metals. It was also in danger of spilling over the dam into Dome Creek which links to Victoria Creek and the Nisling River system.

In 2003, when the Government of Yukon became responsible for care and maintenance at the site, the dam holding back the tailings and contaminated water leaked and was determined to be unstable.

The original buildings and mill built in the 1940s and 1960s, along with onsite physical hazards such as pits, trenches and underground workings (called adits) posed safety issues.

What has been done at the abandoned mine site?

Year-round presence at site
In 1999, Government of Canada contracted a care and maintenance operator to manage the site and maintain environmental integrity. Since 2003, the Government of Yukon has contracted a care and maintenance operator to work on the site to ensure year round onsite security, surveillance and monitoring.

Tailings dam
In 2003, the water level behind the dam was reduced, relieving some of the concern with the dam’s integrity. Structural improvements were also made to reinforce the dam itself.

Through the care and maintenance activities, the dam stability is monitored by qualified geotechnical engineers through annual dam inspections, in conjunction with regular inspections by the care and maintenance operator.

Water quality
The Government of Yukon also implemented a water treatment program which reduced the levels of cyanide and improved the quality of the water on the site.

Currently, water treatment for cyanide is no longer required. Government of Yukon continues to monitor the water in the tailings pond and seepage pond.

Onsite safety
The Government of Yukon has removed accessible hazardous chemicals that were stored onsite by the mining company. These chemicals have been disposed of at proper facilities. Adits have been blocked to improve safety at the site. The care and maintenance operator also ensures onsite infrastructure is maintained and safe.

The Government of Yukon’s focus is to maintain the environmental integrity of the site. Dam stability, water quality and site security are closely monitored.