By Cam Fortems , Kamloops This Week
A proposed North Thompson copper mine that includes a wet tailings facility to store acid-generating rock is among projects that must submit a report on alternatives.
Yellowhead Mining Inc. has submitted its application to the harmonized federal-provincial comprehensive environmental assessment. A final public comment period closed last month.
The project garnered almost no opposition. It is located in a sub-alpine area about 10 kilometres southwest of Vavenby, which is about 150 kilometres northeast of Kamloops.
Yellowhead Mining estimates mine life at 28 years for the open-pit copper project. It expects to employ 450 workers. As part of its application, the company is required to outline scenarios for overtopping of the dam or its failure. The panel that studied the Mount Polley tailings dam breach pointed to Greens Creek, Alaska — which uses filtered, or dry-stack tailings — as best practice and the only way to eliminate risk of collapse.
The Cariboo mine’s tailings dam collapsed in August of 2014, sending millions of gallons of contaminated water into Polley and Quesnel lakes.
Yellowhead spokeswoman Charlene Higgins confirmed the mine must submit a report on its proposed wet tailings facility.
“All the proposals, regardless of where they are in the review — it will take more time,” she said.
KGHM Ajax in Kamloops is doing a study on using dry-stack tailings in its proposed mine plan in wake of the panel recommendations. Its original plan for its proposed open-pit copper and gold mine south of Aberdeen included a dry stack, but it then changed to a wet tailings pond when moving the operation farther south.
Harper Creek’s proposed wet tailings is located in the North Thompson watershed. It drains into Harper Creek, Barriere River and, eventually, the North Thompson River.
“The residual effects from both an overtopping of the tailings-management facility and from a catastrophic tailings-management facility dam failure would likely be significant and many effects would endure far in the future,” states the application to the federal and provincial governments.
The project risk class for the tailings dam is rated as very high, the fourth-highest of five levels. Downstream watercourses are rich in fish, including coho, sockeye and chinook salmon, rainbow trout, steelhead, burbot, dolly varden and whitefish.
Unlike Ajax, Harper Creek’s tailings dam contains potentially acid-generating rock.
Higgins declined to speak on pros and cons of tailings storage for Yellowhead’s proposed open-pit copper mine.
But, last month, an Ontario expert on tailings storage told a public forum organized by Kamloops Exploration Group that dry storage is expensive, not ideal in every case and, if mandatory, may tilt some projects into becoming uneconomic to undertake.
Engineer Eric Domingue also said dry stacking of tailings comprised of acid-generating rock may cause leaching and related environmental problems in wet climates.
The provincial environmental-assessment office stated it in letters to mine proponents it will consider extensions so they have time to complete the reports detailing alternative tailings storage options.