Planning best practice tailings disposal, management and rehabilitation strategies Presented by Mike Gowan

Tailings – Brisbane 28/02/06 2 The Simple Early Mining Life

Tailings – Brisbane 28/02/06 3 Before TSFs – Sand Dumps

Tailings – Brisbane 28/02/06 4 The Simple Life – Cocopan Haulage

Tailings – Brisbane 28/02/06 5 Before Tailings Pumping Systems

Tailings – Brisbane 28/02/06 6 Early TSF Construction

Tailings – Brisbane 28/02/06 7 TAILINGS STORAGE FACILITIES Named a TSF Includes: Storage walls and footprint Slurry pipelines Return water dam Return water system But they do not always store the tailings

Tailings – Brisbane 28/02/06 8 Kalgoorlie before Kaltails Wind and Water Erosion

Tailings – Brisbane 28/02/06 9 TSFs Largest dams ever built – seen from space Unlike water dams, have to last for ever Normally built progressively over a long period – up to 50 years Often built with non-engineering materials Should be considered as a living entity

Tailings – Brisbane 28/02/ Years On using Tailings! Upstream raised gold TSF

Tailings – Brisbane 28/02/06 11 Mining Realities Mining a continuous operation TSF at the back end of the operation Generally out of sight and out of mind A cash consumer, not a cash contributor A source of constipation when they go wrong Do it right the first time!!!

Tailings – Brisbane 28/02/06 12 TSF Failures At least 2 TSF failures reported annually Many more not reported Failure includes: Wall failure Wall breach Overtopping Release of contaminated liquor Contaminated seepage

Tailings – Brisbane 28/02/06 13 Unreported Wall Failure Out of Sight

Tailings – Brisbane 28/02/06 14 Unreported TSF Failure No Injuries

Tailings – Brisbane 28/02/06 15 Unreported Contaminated Flow Contained

Tailings – Brisbane 28/02/06 16 In-River Tailings Disposal In river

Tailings – Brisbane 28/02/06 17 Result of Failures? Poor public perception Omai Baie Mare Marcopper Los Frailes Leads to a lack of trust

Tailings – Brisbane 28/02/06 18 Failures No TSF failures are unexpected All failures can be predicted with hindsight Failures due to one or more of: Poor design Poor construction management Poor operation Changing management during operation Lack of rigorous and regular inspection

Tailings – Brisbane 28/02/06 19 OUR DUTY AS DESIGNERS Carry out a rigorous design Provide the owner with clear operating guidelines Stand-up for our role Record, assess and advise

Tailings – Brisbane 28/02/06 20 Appropriate Tailings Disposal Design must: Meet project requirements Satisfy legislative standards Follow current engineering knowledge Look to better environmental expectations

Tailings – Brisbane 28/02/06 21 Transportation Low solids content slurry High solids slurry Paste Cake Dry

Tailings – Brisbane 28/02/06 22 Ash - 12% Solids

Tailings – Brisbane 28/02/06 23 Diamonds - 45% Solids

Tailings – Brisbane 28/02/06 24 Gold - 70% Solids

Tailings – Brisbane 28/02/06 25 Tailings Placement Pumping Low solids content High solids content Conveying Trucking or railing

Tailings – Brisbane 28/02/06 26 Conventional 2 Stage Pumping for Codisposal

Tailings – Brisbane 28/02/06 27 Paste 1 MW Diaphragm Positive Displacement Pump - Flyash

Tailings – Brisbane 28/02/06 28 Conveying Flyash Dry Flyash Dewatered Tailings

Tailings – Brisbane 28/02/06 29 Trucking Flyash

Tailings – Brisbane 28/02/06 30 Why Change? The drier the tailings the lower: Water losses Chemical losses Risks of environmental contamination Rehabilitation costs Increased risk of: Dust Erosion

Tailings – Brisbane 28/02/06 31 Dust & Erosion Dust Erosion

Tailings – Brisbane 28/02/06 32 Understand the Tailings Seepage Water quality Dust Radiation Instability Geomorphological processes

Tailings – Brisbane 28/02/06 33 Seepage in a Dry Environment HDPE Liner to reduce Seepage

Tailings – Brisbane 28/02/06 34 Radiation Subaqueous to reduce Radiation

Tailings – Brisbane 28/02/06 35 Accidents do Happen!! The Human Element

Tailings – Brisbane 28/02/06 36 Mine Expansion Two mining realities: The full tonnage is achieved well ahead of schedule More ore is found SO: Plan for full tonnage earlier Consider expansion Do not limit expansion through design Consider the next TSF site

Tailings – Brisbane 28/02/06 37 Conclusion Endeavour to place tailings back in mine Legislated in California Plan for tailings retreatment Provide comprehensive Operational Management Documentation

Tailings – Brisbane 28/02/06 38 Coal Tailings In Final Void

Tailings – Brisbane 28/02/06 39 Paste Backfilling Underground Paste Backfill

Tailings – Brisbane 28/02/06 40 In-Pit Codisposal - Gold Tailings Waste

Tailings – Brisbane 28/02/06 41 The End My thanks to: Fraser Alexander for old photos Mining clients for use of project photos Various authors quoted without reference My colleagues who keep me on my toes!!??