The results of a third-party review into the design of a northwestern B.C. gold and copper mine says it has the potential to cause significantly more environmental damage than the recent collapse of the Mount Polley tailings pond.

'Any failure of the Red Chris impoundment will likely have a much more significant environmental impact than the Mount Polley failure.' - Report by Engineering firm Klohn Crippen Berger

Engineering firm Klohn Crippen Berger made 22 recommendations for the owner of the mine, Imperial Metals, to improve the tailings dam of the Red Chris mine, 500 kilometres north of Terrace.

The review found the design of the dam is feasible, but that there are issues that must be addressed.

The three-phased review looks at the tailings pond design, water quality predictions and geohazards at the mine site.

It identifies a "major design issue" for the soil on which the dams would be built, noting the porous soil could cause damaging water leaks if the planned installation of a fine-grained tailings blanket isn't enough to limit seepage.

It also suggests that designers carefully monitor the water balance for their tailings reservoir and complete a risk assessment around the effects of another nearby landslide.

Mount Polley tailings pond failure

The August 4 breach at the Mount Polley tailings pond released 17 million cubic metres of water and more than seven million cubic metres of slurry into nearby waterways. (Ministry of the Environment)

Some of the report's other suggestions include more detailed documentation, emergency response measures, environmental testing and design changes.

"Any technical lessons to be learned from Mount Polley cannot be applied to this facility because the forensic investigation into the cause of that failure has not yet been completed," the report said.

"At the same time, any failure of the Red Chris impoundment will likely have a much more significant environmental impact than the Mount Polley failure."

Tahltan elders' concerns prompted review

The Tahltan Central Council instigated the review and Imperial Metals funded it after the company's Mount Polley mine in B.C.'s central Interior failed in August, sending millions of cubic metres of wastewater and silt into a network of salmon-bearing lakes and rivers.

The spill prompted Tahltan members to blockade the Red Chris site with concerns about the mine's human and environmental impact in their territory.

Klabona Keepers blockade - Red Chris mine access road

A group of protesters calling themselves the Klabona Keepers began blockading the road to Imperial Metals' Red Chris mine site south of Iskut, B.C. on Aug. 8. (Klabona Keepers/Facebook)

Tahltan elders involved in the protest were calling themselves the Klabona Keepers and met with Imperial Metals and Tahltan leadership prior to the agreement even though the chief and council didn't endorse the blockade.

After more than two weeks, the protest ended with an agreement between Imperial Metals and the Tahltan Central Council for the engineering firm to review the project.

At the time of the agreement, Imperial Metals said it would address issues identified in the review "to the reasonable satisfaction" of the nation's leadership.

Meanwhile, the B.C. government has ordered inspections of all tailings dams in B.C., including the one at the Red Chris mine, by this December.