New Zealand Minerals Sector Environmental Impacts and Mine

Drainage Framework

James Pope

Contents

1. Introduction - where are our minerals?

2. What are the main impacts of mining and how variable are they?

3. Are mine impacts predictable?

4. Mine drainage decision support framework

5. Summary

1 Where are our mineral resources?

Gold mines•Coromandel•West Coast SI•Otago

Coal mines•Waikato•West Coast SI•Southland

Gold potential•Northland•Taupo VZ•Nelson•South Westland

Coal potential•Taranaki•Otago

Platinum potential•Nelson•Southland

2 Impacts and their variability

Onsite (or close) Landscape change Disturbance to flora and

fauna Rock geochemistry Groundwater Noise Dust Vibration

Offsite Mine drainage

Rock Geochemistry and Mine Drainages Mine impact on drainages occurs through exposure of waste rock to

atmospheric weathering conditions– Text book case is Acid Mine Drainage – but mine drainages are variable

Mitigation is through active treatment is common at operating mines– Historic mines abandoned rather than closed

Critical geochemical questions when planning or operating a mine:

1. What mine drainage chemistry will occur?2. What will change with time?

Related issues

– How does mine drainage chemistry differ from local background?– What is the impact of mine discharge?– Is it acceptable?– How can it be treated if necessary?– How can it be minimised, managed and prevented?

Historic coal mines Landscape – Rock Geochemistry – Mine Drainage

Historic gold ore processing

Dave Craw Laura Haffert

Landscape – Rock Geochemistry – Mine Drainage

Current coal mine Landscape – Rock Geochemistry – Mine Drainage

Current gold mine Landscape – Rock Geochemistry – Mine Drainage

How variable are the impacts?

0.0001

0.001

0.01

0.1

1

10

2 3 4 5 6 7 8

pH

Al +

Fe

(mm

ol)

BCM

PCM

MCM

GLM

Morley CM

Gore Lignite Measures

Enrichment above Background

-1

0

1

2

3

4

5

6

H+

Ca

Mg K Na Li Rb B Fe Mn

Ag Al As Ba Bi Cd

Co Cr

Cs

Cu La Mo Ni

Pb Sb Se Sr Tl Sn U V Zn Hg

Log (

enrichm

ent)

Leach

AMD

ARD

0

2

4

6

8

10

12

14

NMD 1 NMD 2 NMD 3 NMD 4 NMD 5 NMD 6 NMD 7 AMD 1

Sample

Fe (p

pm)

< 0.1 um Fe

Fe(II)

Drainages from historic and current mines

4 Are the impacts predictable?Quantify variability and identify underpinning science

Accurate prediction of impact

Proactive management plan

Appropriate mitigation, rehabilitation, offset and/or bonding

Informed resource use decision

Predicting NZ coal mine drainage geochemistry

Rock geochemistry from drill coreMedium-coarse sandstone

0

1

2

3

4

56

7

8

9

10

-150 -100 -50 0 50 100 150 200 250 300

NAPP (kgH2SO4/t)

NAG

pH

Buller

Garvey CreekNAF

PAF

uncertain

uncertain

Brunner Coal MeasuresBrunner Coal Measures

Acid base accounting analysesAcid base accounting analyses

Fine-medium sandstone

0

1

23

4

5

6

78

9

10

-150 -100 -50 0 50 100 150 200 250 300

NAPP (kgH2SO4/t)

NAG

pH

Buller

Garvey CreekNAF

PAF

uncertain

uncertain

Mudstone and siltstone

0

1

2

3

4

5

6

7

8

9

10

-150 -100 -50 0 50 100 150 200 250 300

NAPP (kgH2SO4/t)

NAG

pH

Buller

Garvey CreekNAF

PAF

uncertain

uncertain

Predicting NZ coal mine drainage geochemistry

Kinetic testing

Predicting NZ coal mine drainage geochemistry

Kinetic testing

Predicting NZ epithermal gold mine drainage

Kinetic tests indicate lag periods before acid formation

Trace elements include Cu, Pb, Ni, Zn, Mn, Hg

Predicting NZ meso-thermal gold mine drainage As enriched neutral mine drainages

0.001

0.01

0.1

1

10

100

1000

10000

0 1 2 3 4 5 6 7 8 9 10

As,

mg/l

pH

Dave Craw & Laura Haffert

Predicting impact on aquatic ecosystems

Food web response to mine drainage related

Jon Harding

0

25

50

75

100

Time (hrs)

Sur

viva

l (%

)

pH 3.3

pH 3.5

pH 4.0

0 24 48 72 96

Using our predictions – what is optimal treatment or management

Builds on predictions of mine drainage chemistry

International recognition of our developments and innovations

Passive mine drainage treatment and As, Sb, Mn removal all cutting edge

0.000.050.100.150.200.250.30

0 1 2 3 4 5 6 7 8 9

Months of operation

Ars

enic

(m

g/L)

StocktonBlackball-1Blackball-2

Dave Trumm, Paul Weber and Rachel Rait

5 Mine Drainage Framework

Framework document

Many peer reviewed and conference publications

Framework …integrates current multidisciplinary science

– Geochemistry– Aquatic biology– Treatment/management

…predicts mine drainage chemistry and ecological impact

…provides a decision support system for the mining industry and regulators

…provides general environmental management information on issues that are site specific

…is a multi-level document that includes generic and qualitative guidelines to raw data and scientific papers

The Framework does not…

… provide a prescriptive geochemical or biological testing and analysis regime - guidelines only

… provide a prescriptive recipe for resource management or rehabilitation – guidelines only

… determine ‘acceptable’ vs ‘unaccepable’ ecological impact levels

… determine ‘acceptable’ vs ‘unaccepable’ resource development

6 Summary NZ has substantial and widely distributed mineral resources

NZ has legacy mine drainage issues

Minerals sector impacts are diverse

Rock geochemistry and mine drainage chemistry is highly variable but predictable

Broad prediction of impacts on aquatic ecosystems can be made

Management options are available

Framework for mine drainage issues

Acceptable impact or not ….

Acknowledgements Organisers

MBIE

Oceana Gold, Francis Group, Solid Energy

– Newmont, Buller Coal

DoC, WCRC, Environment Southland

– Waikato Regional Council, Straterra