The design of the tailings dam for the proposed Casino mine is being questioned by an international engineering firm retained by the Little Salmon-Carmacks First Nation.

A report prepared by the BGC Engineering Inc. raises several issues about the dam, and recommends the First Nation request answers to 82 specific questions.

“BGC has found significant issues with the project proposal....” reads the executive summary of a 22-page report filed last Thursday with the Yukon Environmental and Socio-economic Assessment Board. “These are considered to be issues that could affect the technical and financial feasibility of the project and should be evaluated carefully in the permitting process.”

The report notes the dam would be 286 metres high – 938 feet, or more than 15 times the height of the law courts on Second Avenue.

It would be the third-highest dam in the world, and there’s nothing currently to compare the design to, so there’s nothing to test the design against, says the report.

“Most dam projects of this size and status engage a review board of experienced tailings dam engineers at the feasibility stage to examine the design for critical components that may affect the technical and financial feasibility of the dam,” says the report.

“The Casino Project should consider involving a review board for the feasibility design to provide guidance on design issues that are beyond the state of the practice and on addressing these design issues in the project proposal.”

The report says the analysis was based on information provided to the assessment board by Western Copper and Gold, the company advancing the Casino Project.

The proposal calls for the largest mine in the Yukon’s history.

The open pit operation northwest of Carmacks would dwarf the former Faro mine, processing some 120,000 tonnes per day compared to 12,000 to 13,000 at Faro. The mine life is estimated at 22 years.

The report recommends the dam design be reviewed by a panel of engineers experienced in dam construction.

Paul West-Sells, president of Western Copper and Gold, said this morning the report from BGC Engineering has been sent to the company’s engineering consultants.

“I certainly wasn’t surprised there would be a detailed report and BGC is a respected company and I expect we will be answering all those questions,” West-Sells said.

“We take the concerns around the Casino tailings dam very seriously and we understand this is going to be something highly scrutinized by YESAB, the regulatory agencies and the public.

“This is the sort of thing where the more input we have, the better,” he said.

Western Copper and Gold is looking to be through the permitting process and ready for construction in 2016, according to the company’s corporate overview.

The company has stated it needs to raise $2.5 billion to build the mine, and it has already spent $20 million doing the work necessary to go through the screening by the assessment board and eventually a review by the Yukon Water Board and Yukon government.

The company filed its project with the assessment board process last January, but requested the review be put on hold so that it could conduct further consultations with the Little Salmon-Carmacks First Nation and other affected First Nations. Little Salmon-Carmacks had filed a petition in the Yukon Supreme Court asking for the project review to be halted, claiming the First Nation was not properly consulted.

The assessment board has just re-activated the review process, as still in the stage of determining whether it has all the information necessary to conduct an assessment of the project.

Robert Moar, an engineer and director of lands, resources and infrastructure for Little Salmon-Carmacks, wrote a brief covering letter to the assessment board upon submitting the BGC report last Thursday.

It notes the First Nation is counting on the assessment board to do a critical review of the project to ensure that it succeeds, and does not become a burden to the First Nation or the Yukon taxpayer.

Moar’s letter points out the federal government is no longer responsible for cleaning up mines in the Yukon that have failed and left a mess behind.

It is now the responsibility of Yukoners to cover the cost of any mines that are permitted by the territorial government but run into problems, the covering letter points out.

The letter states that given last August’s environmental disaster created with the failure of the tailings dam at the Mount Polley Mine in B.C. and the potential liability for Yukon taxpayers, it is essential the assessment board be thorough.

The BGC report questions everything from the integrity of the proposed design, the material the company plans to use for construction of the dam to the earthquake standard it has applied to the project.

It questions the ability of the dam to withstand the passage of time over the next 1,000 years and more, particularly given the watery content and the weight of the massive amount of tailings that will be held back by the dam.