mine closure and sustainable water management by prof carolyn oldham

Mine closure and sustainable water management

Prof. Carolyn OldhamSchool of Environmental Systems Engineering

Mine Lake 116Central German coal district

Island Copper LakeBritish Columbia, Canada

Photo: T. Fischer

Lake StocktonCollie coal district

Lake StocktonCollie coal district

Gravel pitCentral German coal district

Chicken Creek Pit, Collie Coal Basin

Sustainable water management

• Optimisation:– Impact on downstream water resources– Impact on environment– Beneficial end uses – Social impact– Ongoing management costs– Mine operations

• Unlikely to be a “walk-away” solution

Outline

• Mine life stages

• Conceptual model

• Water balances

• Water quality modelling

• Validation

• AMCER Protocol

Phases of mine life

Island Copper LakeBritish Columbia, Canada

Photo: T. Fischer

1. Collate any existing site data

Exploration data, decision:Mine feasible

2. Site-specific conceptual model

5. Design and begin data collection program

4. Assess potential environmental impact and end uses

7. As input data collected, update predictions

WQ“poor”

No solution: reassess?

1. Mine plan, history

General conceptual

model

6. Document all data, calculations (+assumptions), sampling plan

8. As external and internal validation data collected, test prediction;

if necessary, improve

Goal: pit lake with beneficial end uses or acceptable impact for

minimum cost

WQ good/ impact acceptable

4. Scenario testing: - prevention possible?- remediation possible?- backfilling feasible?- downstream mitigation?

3. Quantify/predict likely WQ evolution

WQ modelling

tools

Flow chart of mine water assessment

Development of a hydrological conceptual model

Development of a lake conceptual model

Island Copper LakeBritish Columbia, Canada

Bathymetry

Bathymetry - landscaping

WO5BCollie, Australia

Meteorological data

Island Copper LakeBritish Columbia, Canada

Photo: T. Fischer

Mass balances - groundwater inflow

Chicken CreekCollie, Australia

Mass balances - inputs from surface runoff

1. Collate any existing site data

Exploration data, decision:Mine feasible

2. Site-specific conceptual model

5. Design and begin data collection program

4. Assess potential environmental impact and end uses

7. As input data collected, update predictions

WQ“poor”

No solution: reassess?

1. Mine plan, history

General conceptual

model

6. Document all data, calculations (+assumptions), sampling plan

8. As external and internal validation data collected, test prediction;

if necessary, improve

Goal: pit lake with beneficial end uses or acceptable impact for

minimum cost

WQ good/ impact acceptable

4. Scenario testing: - prevention possible?- remediation possible?- backfilling feasible?- downstream mitigation?

3. Quantify/predict likely WQ evolution

WQ modelling

tools

Flow chart of mine water assessment

Water balances - inputs

Water balance - outputs

Water balance

Huber et al. 2008

Meteorological data

Impact of wind speeds on water balance

Impact of wind sheltering on water levels

100% surface wind speed

10% surface wind speed

Huber et al. 2008

Effect of wind on stratification

Effect of wind sheltering on stratification

DYRESM - 100% surface wind speed

DYRESM - 10% surface wind speed

1. Collate any existing site data

Exploration data, decision:Mine feasible

2. Site-specific conceptual model

5. Design and begin data collection program

4. Assess potential environmental impact and end uses

7. As input data collected, update predictions

WQ“poor”

No solution: reassess?

1. Mine plan, history

General conceptual

model

6. Document all data, calculations (+assumptions), sampling plan

8. As external and internal validation data collected, test prediction;

if necessary, improve

Goal: pit lake with beneficial end uses or acceptable impact for

minimum cost

WQ good/ impact acceptable

4. Scenario testing: - prevention possible?- remediation possible?- backfilling feasible?- downstream mitigation?

3. Quantify/predict likely WQ evolution

WQ modelling

tools

Flow chart of mine water assessment

Mass balances - AMD from walls

Chicken CreekCollie, Australia

Mass balances - AMD from overburden runoff

Chicken CreekCollie, Australia

Surface inflow assumptions

CAEDYM - Fe(III) and Fe(II) – assuming 100% seepage through black shale

CAEDYM - Fe(III) and Fe(II) – assuming 10% seepage through black shale

During Filling Monitoring

• Geochemical characterisation of mine void and surrounds, to determine changes in contaminant release

• Changing pit bathymetry

• On-site meteorological forcing

• Establish current and predicted mass balances

• On-site water column sensor chains

• Water quality sampling

Island Copper LakeBritish Columbia, Canada

Mass balances - inflows

Photo: T. Fischer

On-site water column sensor chains

Photo: T. Fischer

On-site water column sensor chains

WO5BCollie, Australia

river diversion

LDS data, Oct 2003LDS data, Oct 2003--May 2005May 2005

Lake KepwariCollie, Australia

Post-filling Monitoring

• Geochemical characterisation of local mineralogy

• Geochemical characterisation of source waters

• On-site meteorological forcing

• Establish current and predicted mass balances

• On-site water column sensor chains

• Water quality sampling

Water quality sampling

temperature, salinity,

dissolved oxygen pH

turbidity

T salinity DO% sat

LakeKepwariCollie coal istrict

Water quality sampling

LakeKepwariColliecoal district

Water quality sampling

river diversion

LDS data, Oct 2003LDS data, Oct 2003--May 2005May 2005

Water quality sampling

Water Quality Modelling

• Range of models– Lake stratification models– Geochemical models– Ecological models

All require input data

Field

DYRESM

Model validation

Forward prediction - 10 year

Where to start

Oldham et al., ACMER Protocol

Where to start

Oldham et al., ACMER Protocol

1. Collate any existing site data

Exploration data, decision:Mine feasible

2. Site-specific conceptual model

5. Design and begin data collection program

4. Assess potential environmental impact and end uses

7. As input data collected, update predictions

WQ“poor”

No solution: reassess?

1. Mine plan, history

General conceptual

model

6. Document all data, calculations (+assumptions), sampling plan

8. As external and internal validation data collected, test prediction;

if necessary, improve

Goal: pit lake with beneficial end uses or acceptable impact for

minimum cost

WQ good/ impact acceptable

4. Scenario testing: - prevention possible?- remediation possible?- backfilling feasible?- downstream mitigation?

3. Quantify/predict likely WQ evolution

WQ modelling

tools

Flow chart of mine water assessment

The team

Team leaders Carolyn OldhamGreg IveyJason Plumb, CSIRO

Research Assoc.BibhashNathUrsula Salmon

Matt Hipsey, CWRGeoff Wake

PhD students Deborah ReadHuynh Pham

Masters students Anita HuberAlisa Krasnostein

Honours students Emma CravenPeter ChapmanTung Nguyen

ManuellaSusantoAlice TurnbullTom ZdunAaron Brunt

The funding

Australian Research Council

ACMERCentre for Sustainable

Mine LakesState Government of

Western AustraliaWesfarmers Premier CoalGriffin CoalSons of GwaliaCollie Shire CouncilUniversity of Western

Australia

Thank you