Wednesday is a pivotal day for the Carmacks copper mine project.

The open-pit proposal is in the hands of the executive committee of the Yukon Environmental and Socio-economic Assessment Board (YESAB).

The executive committee has until the end of tomorrow to make a decision on whether it requires additional information to complete its assessment.

Western Copper Corp. filed its application with the YESAB a year ago. The board has since received volumes of submissions from Western Copper detailing its project.

Submissions from others have questioned the science involved, and are calling for more time and a much closer examination of the proposal.

The committee has also retained its own consulting expert to provide an independent evaluation of the company's proposal to build and eventually detoxify a heap leach pad which uses sulphuric acid to extract the copper.

"The comments (received) suggest that issues surrounding the detoxification and the closure of the heap are a real concern," Stephen Mills, an executive member of the assessment board, said in a recent press release.

"It has become apparent that more work needs to be done in these areas and we plan to examine them further."

The consultant, hired on Feb. 11, was to have his initial report to the board by Friday.

Most of the terms of reference for the independent consultant involve research into the use of sulphuric acid on a heap leach.

"Are there examples of sulphuric acid heaps being successfully detoxified/closed elsewhere in the world?" is one of several questions the consultant has been asked to answer. "In the circumpolar north?"

Western Copper maintains it has a reclamation method that would allow it to walk away from the operation within five years after the ore body is exhausted, with no strings attached. Information on file currently estimates the mine life at seven to eight years.

In the submission by the Yukon Conservation Society - which has also hired its own expert - the society argues the company can't possibly have an ironclad reclamation proposal.

It maintains that nowhere in the world is there an example of a fully operational sulphuric acid heap leach pad which has been successfully detoxified.

The society points out there are experimental tests of acid heap leaches and so forth, but nothing near the scale proposed for the Carmacks copper mine.

There is ample evidence of the successful reclamation of cyanide heap leach pads, including the Brewery Creek gold mine, which operated near Dawson City in the 1990s, the society acknowledges.

It also argues there is a vast difference in the make-up of cyanide and sulphuric acid; cyanide breaks down fairly quickly when exposed to the elements, but not sulphuric acid.

Similar concerns were expressed by the Little-Salmon Carmacks First Nation, and there was outright opposition from the Selkirk First Nation, which argued the proposal should be rejected straight away because of unproven technology.

Under the review process, once the board is satisfied it has enough information to make a full assessment, it will forward its recommendation to the decision body, which is the territorial government in this case because the application involves the use of Yukon land.

The Yukon government can accept the recommendations, reject them or alter them.

Since the devolution of federal authority over land and resources to the Yukon in 2003, Yukoners have become financially responsible for any mines that are approved.

Previously, Canadian taxpayers were responsible for mines permitted under the federal Department of Indian and Northern Affairs.

Canadians are currently spending millions upon millions of dollars in the Yukon to baby-sit several mines approved by Ottawa, including the Faro mine.

Closure and reclamation of the three open-pits in Faro are expected to cost Canadians anywhere from $400 million to $1 billion, and still there is ongoing monitoring that will be required forever.

The Yukon government has so far permitted the Sherwood Copper Corp.'s Minto mine. It's expected the copper-gold open-pit operation will be in production for 10 years or longer.