The seventh flight of the week in pursuit of mining. From Vancouver to the airport of many names: Santa Ana, John Wayne, or Orange County, California. Call is what you will. The sun is shining, the sea sparkling, and the grandkids lively and curious.
The work-meetings were on the topic of groundwater in mining. Here are two readily available resources on this topic:
The Edumine course I wrote on Groundwater in Mining.
Neither of these resources deal with the issues of today’s meeting: namely how to control groundwater so that it does not affect the stability of a tailings facility. I have written a paper on this topic for the upcoming conference Tailings and Mine Waste 2012. The summary is that you need to drain the area of the tailings facility so that the groundwater does not seep into the impoundment or seep out of the impoundment.
Although as you deposit the tailings, the water that is part of the deposited tailings does seep into the ground and hence to the groundwater. Let us call that the deposition exfiltration. How much depends on the way the spigotted tailings flow and give up water to the foundation materials; how many side pools develop and act as infiltration sources; and how the consolidating tailings push water into the foundation. I have never seen a full and credible analysis of these many events.
Then to the question: how to limit seepage from the impoundment? Liners are useless; they cost money and will fail in the goodness of time. Put a low permeability cover on at closure is all you can do.
There is a myth that the lower layer of tailings will consolidate and form a “liner.” Again I have never seen a credible analysis to prove this, although the maths is simple.
Geochemists are needed to tell us how the chemicals seeping from the tailings will behave. Will they be attenuated? Will they be diluted?
There are conferences coming up on these topics. Here is a link to one. Actually they will discuss many more topics, including:
• Strategies for Sourcing & Minimizing Water to Achieve Long-Term Sustainability
• How to Assess, Select and Develop Your Optimal Water Management System
• Moving and Storing Water Cost-Effectively
• Project-Related Water: An Assessment of Different Purity Criteria for Different Uses
• Monitoring of Water Quality Water Management
• Lessons From the Oil & Gas Shale Drilling Boom
• Treating Wastewater From Mining Operations for Discharge, Recyling or Reuse
• Dealing With Acid Mine Drainage
• Seawater vs. Desalinated Water: When is it Appropriate
• Desal/Water Reuse v. Fresh Water Use: A Cost/Benefit Analysis
• Integrating Public and Private Water Needs
• Metals Recovery From Produced Water and Tailings: Adding a Revenue Stream.
Whatever the topic, the tailings are where the water is lost, from which seepage is significant, and where you can make or loose money, and impact or protect the environment. What we really need is a conference on tailings and groundwater. How about organizing one?