Energy, Mines and Resources

Clinton Creek

Clinton Creek: Care & Maintenance

Generally, care and maintenance is a term used to describe the ongoing activities such as site inspections or environmental monitoring. Care and maintenance activities at the abandoned Clinton Creek mine site are currently limited to quarterly inspections and maintenance work as required.

What are the issues at the Clinton Creek abandoned mine site?

The environmental liabilities and human health concerns at the abandoned Clinton Creek mine site are related to the geophysical changes to the valley that occurred due to mining activities, and airborne asbestos.

During mining operations, 60 million tonnes of waste rock was piled onto the south slope above the Clinton Creek valley. In 1974, the waste rock pile slid down the slope and blocked Clinton Creek. Water pooled in the valley behind the waste rock forming a lake, which became known as Hudgeon Lake. When the valley flooded, vegetation died and decomposed consuming the lake's oxygen except within the lake's top metre.Waters depleted of oxygen are known as being "anoxic." Fish are unable to survive in the lower depths of the lake due to its anoxic state. The water flowing from the creek continued to erode and wash waste rock downstream.

Additionally, during mining operations, the mill emptied 10 million tonnes of tailings onto the west slope above the Wolverine Creek valley. Again in 1974, the tailings slid down the slope and partially blocked Wolverine Creek creating two small ponds. The water flowing from the creek continued to erode and wash tailings downstream. In 1985, the north point of the tailings deposit slumped, again restricting Wolverine Creek.

Both the waste rock piles and the tailings piles remain unstable and are in continual movement towards Clinton Creek and Wolverine Creek respectively. This increases the amount of suspended solids in these streams and increases the probability of flooding. 

There is a concern that heavy rains or a quick springtime snowmelt could accelerate erosion of the Hudgeon Lake outlet and lead to sudden and significant downstream flooding. This erosion could drain the lake in a short period of time, the effects of which would be felt all the way to the Fortymile River. Anyone downstream of Hudgeon Lake would be at risk of getting caught in the flood.

In late 1970s and early 1980s, the mine owner attempted to stabilize the property by constructing a rock channel and weirs to redirect the flow of Wolverine Creek over the tailings slump.

The owner also constructed rock weirs, reinforced the Clinton Creek channel and installed culverts and a gravel shield to protect the Hudgeon Lake outlet from erosion.

In 1982, Clinton Creek broke through the reinforced channel. The reinforcement was reconstructed but a significant flood event in 1997 destroyed the channel and weir structures. The federal government installed gabion baskets (rock-filled mesh cages) in 2002 as a way to stabilize the Clinton Creek steam channel below Hudgeon Lake and allow water flows to resume downstream from the lake outlet. However, Clinton Creek continually alters its course which increases the risks of erosion and flooding.

What has been done at the abandoned mine site?

The Government of Yukon conducts regular inspections of the site in order to monitor site conditions.

Monitoring of the waste rock and tailings piles for movement and erosion is ongoing. Water quality and aquatic effects studies are ongoing to determine the effects of the waste rock and tailings on aquatic life and habitat. Engineered structures are monitored by qualified geotechnical engineers through annual inspections.

Additional gabion structures were constructed and installed in 2003 and 2004 to reduce erosion and stabilize Clinton Creek. The gabion baskets are monitored and maintained on a regular basis.

Following a high flow event in 2010, repairs to the gabion structures were required. In 2011, the repairs were conducted, however one of the gabion structures could not be repaired at the time due to health and safety concerns. In 2015, the Government of Yukon repaired the remaining gabion structure. The gabion structures are monitored and maintained on a regular basis.

Unsafe structures and equipment were demolished and removed from the mine site between 2004 and 2007. Safety measures such as protective berms around the pit perimeter, and barrier ditches, were constructed to reduce safety risks at the site. A permanent gate was installed at the entrance to the abandoned Clinton Creek site  prevent access to the public due to ongoing safety concerns.

Whenever maintenance, monitoring or construction is conducted at the Clinton Creek site appropriate occupational health and safety measures are taken to minimize workers exposure to asbestos.

Why is there no longer any public access to the Clinton Creek mine site?

In the summer 2012, a comprehensive engineering review of the abandoned site was conducted. The engineer’s recommendations were to restrict access as the abandoned mine site is currently unstable and poses a threat to human health and safety.

As a result and in the interest of public safety, Government of Yukon decided to prohibit access at the abandoned Clinton Creek mine site as there is risk of serious injury or death at the site.

A locked gate is installed at the mine site entrance, as well as warning signs notifying that access is prohibited.

In the meantime, Government of Yukon is working with Government of Canada and Tr'ondëk Hwëch'in to evaluate options for the area to ensure the protection of public safety and the environment.

The Government of Yukon’s focus is to maintain the environmental integrity of the site. The site is closely monitored to ensure there are no adverse effects to human health and safety and the environment until a remediation (closure) plan can be developed and implemented.

What are the updates on the closure planning process?

For an update on the remediation (closure) planning process, please see Clinton Creek's remediation page.