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