I THINK MINING

Denver and the USSD Workshop on Dam Break Analysis Applied to Tailings Dams.  In the past two days, we have heard many fine presentations on the evaluation of what happens when a tailings dam breaks, fails, or otherwise allows water and tailings to flow out.

Tailings dam break analyses have been mandatory in South Africa and Australia for decades.  Now they are required in Nevada.   A dam break analysis for the Marlin mine in Guatemala is one of the reasons they are converting to filter press, dry stack tailings disposal.

There are many unknowns surrounding dam break analysis applied to tailings impoundments.  Not the least are the tailings failure modes leading to outflow, the percentage of tailings and water that may flow out if the embankment fails, how the material will flow, and how far it will flow. 

Case histories are few and those that exist are not well documented.  Computer codes abound, but few fully replicate the features of tailings flow. 

This is an area of study in the discipline of tailings disposal that truly demands a lot more attention.  The conference participants have agreed to press forward with forming  a group to study the problems further.  The organizers have agreed to post the proceedings, at least the PowerPoint presentations on InfoMine sometime in the future.   

In the meantime, contact me if you need further links to the folk who talked and the topics they discussed.  I will help if I can.

I will work on a more detailed summary and report, but for now let me note only that the conference presentations and discussions exploded a few myths to which I had hitherto subscribed, including these:

1. Tailings dams are no longer failing:  truth is that five failed last year in the US alone, but none are documented for reference.
2. Regulations are adequate: all the regulators who spoke admit to the need for a better job to be done.
3. Consultants have the answers:  all the consultants who spoke admit to vast gaps in knowledge and no agreement on standard practice.
4. There is no need for such analyses: it is obvious that a tailings dam break analysis should be the central part of a full evaluation of the design of a tailings impoundment.  At the least a dam break analysis could prove that impoundment should not be built.  At the most, a dam break analysis could lead to improvements in design and operation. 

The scary thoughts that haunted me during the conference are these:

1. Should we provide secondary containment facilities around tailings impoundments?
2. Should we ban disposal of fluid tailings and demand dry, stacks only?
3. Is the Alberta ERCB truly ahead of the crowd in demanding that oil sand tailings have a strength of 10 kPa two years after deposition?

Stand by.  I will write more on these ideas, and later you can access on InfoMine the presentations to decide for yourself.  In the meantime, we must praise the organizers for arranging this conference.