In October 2008 in Vail, Colorado, I attended the conference Tailings & Mine Waste ’08. The proceedings are a fine volume in book format, but it is expensive. Thanks to the organizers of the conference and the presenters, we can make available here on TechnoMine many of the PowerPoint presentations.

Here is the list and a link to each. All of these are also in our Library. Enjoy.

Dewatering on Horizontal Screens

Simple Mine Waste Management Planning for Successful Operations in the Canadian Low Arctic

Reclamation and Closure Cost Planning and Estimation and the Mining Life Cycle

James Creek Tailings Relocation

Design & Construction of an Evaporation Pond at a Historic Uranium Mining Facility

Pipeline Design for Paste and Thickened Tailings Systems

Developments in the Safety and Security of Mining Industry Dams

Working for Responsible Management of Tailings Facilities

Case Study: Site-Wide Water Balance of the Pierina Gold Mine, Peru

The Past, Present and Future for Selenium Treatment

High Pressure Washing Technology

Capping the Tailings Impoundment at the Jamestown Mine

Evaluation of Geomembrane Puncture Potential and Hydraulic Performance in Mining Applications

Geochemical Characterization of Proposed Waste Dumps over Time and Space

Challenges in Heap Leach Pad Design: Consideration of Thermal Conditions

Gold Quary North Waste Rock Facility Slide Investigation and Stabilization

Applying Numerical Hydrochemical Models as Decision Support Tools for Mine Closure Planning

Experimental Characterization of the Influence of Curing under Stress on the Hydromechanical and Geochemical Properties of Cemented Paste Backfill

Life Cycle Assessment and Tailings Management Trade-Off Studies - Concepts

Stabilized Upstream Tailings Dam and Converted into a Filtered Tailings Facility

Mining Impacts: A Case Study

Innovative Mine Waste Disposal in Two Distinctly Different Setting

Heap Leach Lixiviant Flow: Myth versus Reality

Guidelines for Stabilizing Historic Mine Workings

Liner System Design for Tailings Impoundments and Heap Leach Pads

Stochastic Prediction of Mine Site Water Balance: Gilt Edge Mine Superfund Site, Lawrence County, South Dakota

Uranium Tailings Facility Design and Permitting in the Modern Regulatory Environment

An Overview of the Grouse Creek Mine Tailings Impoundment Closure

I wish I could have written about and commented on each of these fine presentations. I cannot. So here follows three short pieces I did write during the conference.

Conference Conclusions

The conference on Tailings & Mine Waste ‘08 is done. Two days of technical papers lead one to identify these changes in the theory and practice of mine waste in the thirty years the conference has been held:

  1. Liners for impoundments are now accepted as good practice; no longer do we hear how liners are unnecessary components forced on the mining industry.
  2. Covers are now routinely four feet and thicker; gone are the days when the proud brag was a one-foot thick cover.
  3. Side slopes of three to one and even five to one are considered reasonable; no longer do we hear that the angle of repose is stable enough.
  4. Water is a component of interest and value; no longer a side issues and a nuisance.
  5. Regulations including CERCLA and RCRA are mentioned in passing and implemented routinely; no longer are there tirades against unwise regulators.
  6. Stocastic methods are used and the young recognize that extreme events do occur.

These I consider to be good changes. Although they have resulted in significant increases in the cost of tailings and mine waste management.

Best Paper and Best Presentation

My nomination for the best paper and best presentation at the conference Tailings & Mine Waste ‘08 is Gold Quarry North Waste Rock Facility Slide Investigation and Stabiliization by R. J Sheets and E.E. Bates both of Newmont Mining Corporation at the Curlin Surface Mine Operations, Carlin, Nevada. Here is the paper’s abstract:

On February 5th, 2005, approximately 9.1 Megatonnes of the Gold Quarry North Waste Rock Facility (NWRF) collapsed. The slide covered over 460 meter of Nevada State Route 766 and came within 10 meters of a nearby creek. The slope had been at or near its final design configuration since the early 1990’s (3H:1V). Following an extensive geotechnical investigation, it was determined that the NWRF slide resultedfrom strain-softening, fine grained plastic clayey silt that composed the lower 2/3 of the height that failed along the contact with the native ground surface. Instability developed as the clayey silt passed from the peak to residual strength. Stabilization measures to achieve a 5H:1V design slope have included unweighting of approximately 11 Megatonnes and constructing a 1.4 Megatonne buttress. Movement recognized during remediation required design modifications based on current assumptions that the strength properties of the slide surface are two standard deviations less than the average residual strength determined from laboratory tests.

The paper describes a case history that holds a lesson for all geotechnical engineers working for mines: “waste rock” may in fact be clay, and the old Skempton observationof strain softening and loss of strength applies even today.

The authors tell the story well; they present the data and analyses convincingly; and they do not hesitate to share history and insight. They and Newmont are to be thanked for putting this case history into the literature. We would all do well to read and learn from it.

The conference proceedings are an obscure thing. To get the paper you can either buy the proceedings or contact Russell Sheets at Newmont. Hopefully he and his fellow geotechnical engineers will publish on this more widely and in the most respected geotechnical journals.

Most Innovative Thinking

The most forward thinking speculation at Tailings & Mine Waste ‘08 was by Dirk Van Zyl. He joked about his fast-written paper that suggests that somebody seeking a PhD in tailings and mine waste management could do no better than apply the concepts and methods of Life Cycle Assessment(LCA) to tailings impoundments.

For those readers unfamiliar with this grand concept, take a look at what I have written about LCA and its success in proving that Australian mines are more efficient users of water than Australian farmers.

Here is a non-succinct definition of LCA:

LCA addresses the environmental aspects and potential environmental impacts (e.g., use of resources and environmental consequences of releases) throughout a product’s life cycle from raw material acquisition through production, use, end-of-life treatment, recycling and final disposal (i.e., cradle-to-grave.)

A good example would be to study the life cycle benefits of all those expensive clothes that Sarah Palin is wearing. Just think of all the benefits and the limited impacts of the production of those expensive clothes, the uplifting of joy in the eyes of the beholders, the greatful wives of plumbers who become the lucky recipients of the cast-off-gowns, and the income to the makers and breakers of the dresses et al. And so little environmental impact, for they probably are not even washed during the limited vice-presidential campaign life cycle.

As a devoted PhDer, you could dress simply and apply the concepts developed by international agencies to the most difficult issue in mining: what do you do with the tailings impoundment at closure. Some of the best suggestions I heard at the conference include:

1. Turn it into a cemetery for rich people - let them pay in perpetuity.

2. Make a new golf course - lots of sand for bunkers.

3. Build a wind farm atop the structure - just provide jackable foundations to deal with long-term settlement.

No matter what we say people will always mine, need impoundments, dress well, play golf, require energy, and die. How marvelous if we could use the grand, unifying, holistic concepts of LCA to prove this a worthy set of integrated activities atop a slimes dam.