The proposal for the Carmacks copper mine lacks certainty, says Chief Eddie Skookum of the Little Salmon-Carmacks First Nation.

He argues it's potentially disastrous to allow the Western Copper Corp. to proceed with its proposal without nailing down exactly a precise method to ensure its heap leach system does not fail.

Should the system fail, resulting in the release of sulphuric acid into the Yukon River watershed, the river's rich salmon bounty could be irreversibly threatened, Skookum suggested in an interview with the Star this morning.

'Our worry is the heap leach system has really not been tested in the Yukon,' the chief said. 'And it is close to the river system.

'If there is ever a leak and that powerful stuff is leaked into the river system, who will be affected? It will be everyone who consumes salmon, and not just the first nations.'

Skookum said he wants to meet with the chiefs of the other first nations along the Yukon River system to share his concerns and gather their opinions.

His first nation, the chief emphasized, is not opposed to mining as long as everything is done right.

He pointed out the proposed heap leach pad will cover a huge area, and if there was ever any failure in the design, the impact would be catastrophic.

The Little Salmon-Carmacks First Nation has already been saddled with the toxic mess left behind at Mount Nansen by BYG Natural Resources, the company that abandoned the mine after a couple of years of profit. Canadian taxpayers are now paying in excess of $1 million a year to maintain water treatment and look after the property.

Skookum said the first nation doesn't need another BYG.

The 230-page screening report and recommendations on the Carmacks Copper proposal were released last month for public comment.

The executive committee of the Yukon Environmental and Socio-economic Assessment Board announced Wednesday it was extending the comment period from yesterday's original deadline for a further 21 days, until Feb. 6.

Several submissions requested the extension, given the complexity of the proposal, as well as the fact the document was released Dec. 17, just as people were starting the Christmas holiday season.

Western Copper is proposing an open-pit mine, operating 200 days a year. It is planning to use sulphuric acid to leach copper from ore deposited on a large pad measuring 90 metres by 300 metres.

The company estimates there will be a full-time workforce averaging 150 employees through the seven to eight years of mine life.

YESAB is recommending approval of the project, provided Western Copper complies with 142 conditions.

Once comments are received, the assessment board will finalize its report and recommendations, which will be sent to the Yukon government, the decision body in this case because the proposal involves the use of Yukon Crown land.

Dale Corman, the company's chief executive officer and co-chair of the board of directors, was in meetings this morning and unavailable to respond to Skookum's concerns.

Western Copper, however, has insisted previously that it has satisfied the YESAB process with its heap leach plans, as it did previously under the federal review process.

The Yukon Conservation Society, however, insists the company can't provide absolute certainty about its plan, because nowhere in the world is there an example of an operational heap leach system using sulphuric acid being successfully neutralized.

The society acknowledged there are all kinds of successful reclamation stories for heap leach systems using cyanide to recover gold.

There's nothing on record anywhere showing the successful reclamation of commercial operations using sulphuric acid systems, the society points out in its five-page submission filed yesterday with the assessment board.

The society argues that because of the uncertainty, the Yukon government must insist on a long-term reclamation and monitoring plan, which goes well beyond the four or five years the company is proposing after closure. The company needs to put up the financial certainty to support that plan, the society insists.

A review of Western Copper's proposal by Dr. David Chambers, a scholar with extensive mining experience in the Yukon and Alaska who was retained by the society, is critical of the company's proposal.

'I can't tell how much work was put into developing this closure cost estimate,' Chamber writes as part of the conservation society's submission.

'It appears they went into some level of detail, since some equipment costs and personnel rates are referenced. However, the cover page implies they are relying on work done largely over 10 years ago, which doesn't inspire a great deal of confidence in the level of effort they put into the estimate �- I hope the Yukon government is going to have its own consultant look at this in detail.'

In addition to concerns with environmental impact, Chief Skookum would like the company to enter into an Impact Benefits Agreement with the first nation.

Western Copper, he points out, maintains it is not obligated to do so, given the proposed mine is on Crown land, not settlement land.

Skookum, however, said it is still within the traditional territory of the first nation, and having an agreement would provide certainty of economic benefits for Little Salmon-Carmacks citizens.

The Carmacks Development Corp., owned by the first nation, maintains the Carmacks business community would need to make significant investments to take advantage of economic opportunities presented by the mine, the corporation writes in its YESAB submission.

Corporation director Mike Kenny writes that having an Impact Benefit Agreement would provide local businesses with the assurance that their investments are secured by an official arrangement with the company.