Planning best practice tailings disposal, management and rehabilitation strategies

Presented by

Mike Gowan

2Tailings – Brisbane 28/02/06

The Simple Early Mining Life

3Tailings – Brisbane 28/02/06

Before TSFs – Sand Dumps

4Tailings – Brisbane 28/02/06

The Simple Life – Cocopan Haulage

5Tailings – Brisbane 28/02/06

Before Tailings Pumping Systems

6Tailings – Brisbane 28/02/06

Early TSF Construction

7Tailings – Brisbane 28/02/06

TAILINGS STORAGE FACILITIES

Named a TSF Includes:

Storage walls and footprintSlurry pipelinesReturn water damReturn water system

But they do not always “store” the tailings

8Tailings – Brisbane 28/02/06

Kalgoorlie before Kaltails

Wind and Water Erosion

9Tailings – Brisbane 28/02/06

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

10Tailings – Brisbane 28/02/06

20 Years On using Tailings!

Upstream raised gold TSF

11Tailings – Brisbane 28/02/06

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!!!

12Tailings – Brisbane 28/02/06

TSF Failures

At least 2 TSF failures reported annually

Many more not reportedFailure includes:

Wall failureWall breachOvertoppingRelease of contaminated liquor Contaminated seepage

13Tailings – Brisbane 28/02/06

Unreported Wall Failure

Out of Sight

14Tailings – Brisbane 28/02/06

Unreported TSF Failure

No Injuries

15Tailings – Brisbane 28/02/06

Unreported Contaminated Flow

“Contained”

16Tailings – Brisbane 28/02/06

In-River Tailings Disposal

In river

17Tailings – Brisbane 28/02/06

Result of Failures?

Poor public perceptionOmaiBaie MareMarcopperLos Frailes

Leads to a lack of trust

18Tailings – Brisbane 28/02/06

Failures

No TSF failures are unexpectedAll failures can be predicted with

hindsightFailures due to one or more of:

Poor designPoor construction managementPoor operationChanging management during

operationLack of rigorous and regular

inspection

19Tailings – Brisbane 28/02/06

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

20Tailings – Brisbane 28/02/06

Appropriate Tailings Disposal

Design must:Meet project requirementsSatisfy legislative standardsFollow current engineering

knowledgeLook to better environmental

expectations

21Tailings – Brisbane 28/02/06

Transportation

Low solids content slurryHigh solids slurryPasteCakeDry

22Tailings – Brisbane 28/02/06

Ash - 12% Solids

23Tailings – Brisbane 28/02/06

Diamonds - 45% Solids

24Tailings – Brisbane 28/02/06

Gold - 70% Solids

25Tailings – Brisbane 28/02/06

Tailings Placement

PumpingLow solids contentHigh solids content

ConveyingTrucking or railing

26Tailings – Brisbane 28/02/06

Conventional

2 Stage Pumping for Codisposal

27Tailings – Brisbane 28/02/06

Paste

1 MW Diaphragm Positive Displacement Pump - Flyash

28Tailings – Brisbane 28/02/06

Conveying

Flyash

DryFlyash

DewateredTailings

29Tailings – Brisbane 28/02/06

Trucking

Flyash

30Tailings – Brisbane 28/02/06

Why Change?

The drier the tailings the lower:Water losses Chemical lossesRisks of environmental contamination Rehabilitation costs

Increased risk of:DustErosion

31Tailings – Brisbane 28/02/06

Dust & Erosion

Dust

Erosion

32Tailings – Brisbane 28/02/06

Understand the Tailings

SeepageWater qualityDustRadiation InstabilityGeomorphological processes

33Tailings – Brisbane 28/02/06

Seepage in a Dry Environment

HDPE Liner to reduce Seepage

34Tailings – Brisbane 28/02/06

Radiation

Subaqueous to reduce Radiation

35Tailings – Brisbane 28/02/06

Accidents do Happen!!

The Human Element

36Tailings – Brisbane 28/02/06

Mine Expansion

Two mining realities:The full tonnage is achieved well

ahead of scheduleMore ore is found

SO:Plan for full tonnage earlierConsider expansion

• Do not limit expansion through design

• Consider the next TSF site

37Tailings – Brisbane 28/02/06

Conclusion

Endeavour to place tailings back in mine

Legislated in California

Plan for tailings retreatmentProvide comprehensive

Operational Management Documentation

38Tailings – Brisbane 28/02/06

Coal Tailings In Final Void

39Tailings – Brisbane 28/02/06

Paste Backfilling Underground

Paste Backfill

40Tailings – Brisbane 28/02/06

In-Pit Codisposal - Gold

Tailings Waste

41Tailings – Brisbane 28/02/06

The EndMy 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!!??