The Yukon Conservation Society is welcoming a decision by the Yukon Environmental and Socio-economic Assessment Board (YESAB) to send a massive and controversial mining project to the highest level of review.

YESAB announced on Thursday that the Casino Mining Corp.'s proposed copper and gold mine would be subject to a panel review, the first in YESAB's history.

"It is uncharted territory," said Lewis Rifkind of the Yukon Conservation Society, referring to the panel review. "It's going to be a learning curve for everybody."

"At least YESAB is taking the time to do a proper analysis of what could be a huge mining project, bigger than Faro [mine], and we all know how Faro ended up. So let's examine this, and get it right so we don't end up with a mess."

YESAB's decision to call for a panel review was guided by concerns over two aspects of the proposed mine project — an earth-fill dam that would be the largest tailings dam in the world, and the mine's potential impact on the Klaza caribou herd.

Casino mine

The proposed Casino Mine, approximately 400 kilometres northwest of Whitehorse, would be the largest mine in Yukon's history. (Cathie Archbould/Casino Mining Corp.)

Rifkind shares those concerns, and others. He said the mine project plans to use liquefied natural gas (LNG) for power, significantly contributing to the territory's greenhouse gas emissions.

But the biggest worry is the dam, Rifkind said. Other aspects of the mine proposal could be modified or altered to answer concerns, but the dam is "a non-starter," he said.

"That tailings dam is just so big, and the potential for failure is so great," he said, citing the failure of a similar dam at B.C.'s Mount Polley mine site, in 2014.

"It's not appropriate anywhere in the world, let alone in the North."

Western Copper and Gold said in a statement on Thursday that it also welcomed the YESAB panel review, "to demonstrate that the Casino mine can be built without significant adverse effects."

YESAB has notified the federal environment minister about the panel review. It must be completed within 15 months of the minister's response.