Xstrata tailings dam failure imminent?

Jack Caldwell | February 3, 2012 | 1:04 am Energy Australia Europe Uranium

This must be every miners nightmare: contradicting opinions on the safety of your tailings facility. At this link is a report that is not all that specific about the technical issues, but pretty clear about the debate. One the negative side we read:

Environment Centre NT director Dr Stuart Blanch said the independent monitor project director Philip Mulvey told a December stakeholder meeting there was an “extreme risk” of bank failure of the tailings dam [at the McArthur River mine, Australia]. The October released monitor’s audit report for 2010 stated the tailings capacity needed to be increased by the start of the 2010-11 wet season. It also said there was an extreme risk of acid caused by leaching, draining into Surprise Creek. Dr Blanch said the Territory Government should require Xstrata to set up a fail-safe containment system for the existing tailings dam before it approves a much larger mine.

Conversely on the positive side, we read:

But Xstrata Zinc Australia chief operating officer Brian Hearne said the company had its own independent reports contradicting the findings. He said the company commissioned report to analyse acid risks in conjunction with the independent monitor stated that there was no risk of a spill. Further he said that annual safety audits verified the wall’s integrity, built to store 1 in 200 year, 2-month duration rains.

How about a discussion of this debate. Some questions to debate:

What to do when there are conflicting expert opinions?
Is 200 years, 2 months a safe criterion or is this inadequate when precipitation seeks to be increasing?
Is wall integrity the only issue of safety–what about overtopping that is a bigger cause of tailings failure than most other single causes?
What is, or should be, a fail-safe containment system for a big tailings dam. It this technically practical?