Mine Dewatering and Water Management at Barrick Goldstrike Mine in the Carlin Trend, Nevada Johnny...

Mine Dewatering and Water Management at Barrick Goldstrike Mine in the Carlin Trend, Nevada

Johnny Zhan, Ph.D.

Presented at U.S. EPA Hardrock Mining Conference 2012

Denver, CO, USA, April 3-5, 2012

1. Introduction to Barrick and Goldstrike

2. Goldstrike Dewatering System

3. Goldstrike Monitoring System

4. Impact Evaluation

5. Conclusions

April 3-5, 2012 U.S. EPA Hardrock Mining Conference 2012

Presentation ContentsPresentation Contents

2

Distance:

1 meter = 3.3 feet

Flow rate:

1 liters/second = 16 gallons/minute (gpm)

Weight (Gold):

1 tonne = 32,000 troy ounces

April 3-5, 2012

Unit ConversionUnit Conversion

U.S. EPA Hardrock Mining Conference 2012 3

1. Introduction – Barrick

April 3-5, 2012 U.S. EPA Hardrock Mining Conference 2012 4

SouthAmerica

Lagunas NortePierina

ZaldívarCerro Casale

Pascua-Lama Veladero

NorthAmerica

Donlin Creek

GoldenSunlight

Hemlo

GoldstrikeTurquoise Ridge

MarigoldBald Mountain

CortezRuby Hill

Round Mountain

Pueblo Viejo

ProjectMine

AfricanBarrick

North MaraKabangaTulawaka

BulyanhuluBuzwagi

AustraliaPacific

Porgera

CowalGranny Smith

KalgoorlieKanowna

Plutonic DarlotLawlers

Reko DiqJabal Sayid

Lumwana

Barrick Global Operations – Equinox Addition

PlutonicDarlot

Kalgoorlie

Lawlers

Cowal

KanownaGranny Smith

Porgera

A U S T R A L I A

P A P U AN E W G U I N E A

Mines Projects

Lumwana

Jabal Sayid

ZAMBIA

SAUDI ARABIA

April 3-5, 2012 5U.S. EPA Hardrock Mining

Conference 2012


1. Introduction – Goldstrike Mine1. Introduction – Goldstrike Mine

6


Open PitOpen Pit

400 m400 m

3,700 m3,700 m

2,000 m2,000 m

7


Underground MinesUnderground Mines

Pre-mining water table

1600 m amsl

Current water table

1100 m amsl

with a drawdown of 500 m

8


2. Goldstrike Dewatering System2. Goldstrike Dewatering System

9


Dewatering System - ActiveDewatering System - Active

Pumping well -

Depth: 1000 m

Diameter: 50 cm

Rate: 200 l/s (3,000 gpm)

Power: 2,000 HP

Cost: US$3 Million/Each

10


Dewatering System - ActiveDewatering System - Active

Piezometer

Local WellRegional Well

11


Dewatering System - PassiveDewatering System - Passive

12


Dewatering System - PassiveDewatering System - Passive

HD (1994 – 2002)• Numbers: 1800

• Length: 10 – 450 m

• Total Length: 380 km

13


Water Management System Water Management System

560,000 m2/Each

14


Cumulative Water BalanceCumulative Water Balance

10%

27%

52%

6%

5%

Mine Use Irrigation Infiltration/Injection Discharge to Humboldt River Flood Irrigation and Evap

15


3. Goldstrike Monitoring System – 15,000 km2

3. Goldstrike Monitoring System – 15,000 km2

Manual/Automatic Surface Water Monitoring

Manual/Automatic Groundwater Monitoring

16


Water Level Change To-DateWater Level Change To-Date

Drawdown

Mounding

17

New Tools – Ground DeformationNew Tools – Ground Deformation

A New Assessment Tool - Interferometric Synthetic Aperture Radar (InSAR)

Identified Subsidence/Uplift Associated with Mine Dewatering

100km x 100km coverage at 5m pixel resolution

April 3-5, 2012 18U.S. EPA Hardrock Mining Conference 2012

From Massonnet, 1997


Ground Deformation – InSAR ResultsGround Deformation – InSAR Results

Subsidence

Uplift

Subsidence and Uplift

June 1, 1992 – Nov 26, 2000

From Katzenstein, 2008

19


Monitoring System – InSAR ResultsMonitoring System – InSAR Results

0

2

4

6

8

10

12

14

16

1992 1994 1996 1998 2000 2002 2004 2006

Def

orm

atio

n R

ate

(cm

/yr)

Time (Calendar Year)

Deformation Rate vs. TimeFrom Katzenstein, 2008

20


4. Impact Evaluation – Flow Model4. Impact Evaluation – Flow Model

Pre-Mining Water Level

(1990-1991)

MODFLOW

Model Grids

From Maurer et al., 1996

21


Flow Model – Steady State (Pre-mining)Flow Model – Steady State (Pre-mining)

4500

5000

5500

6000

6500

7000

4500 5000 5500 6000 6500 7000

Sim

ula

ted

Wat

er L

evel

(ft

am

sl)

Measured Water Level (ft amsl)

statistics of observed-simulated water levelsnumber of wells 167mean observed head 5,289

root mean square error (ft) 24.9standard deviation of residual error (ft) 25.0bias (mean error in ft) -0.79

calibration ratio 0.0119R-squared 0.9981

22


Flow Model – Transient (Pit Area) Flow Model – Transient (Pit Area)

3,500

3,700

3,900

4,100

4,300

4,500

4,700

4,900

5,100

5,300

1/1/1988 1/1/1992 1/1/1996 1/1/2000 1/1/2004 1/1/2008

Wa

ter

leve

l (ft

am

sl)

Measured Pit Composite

Betze simulated, layer 1



23


Flow Model – Transient (Mountain Block) Flow Model – Transient (Mountain Block)

6,000

6,100

6,200

6,300

6,400

6,500

6,600

6,700

1/1/1988 1/1/1992 1/1/1996 1/1/2000 1/1/2004 1/1/2008

Wa

ter e

leva

tion

(ft a

.m.s

.l.)

NA-37A NA-37B NA-37C

NA-37 simulated, layer 1 NA-37 simulated, layer 2 NA-37 simulated, layer 4

24


Flow Model – Transient (Infiltration Basin) Flow Model – Transient (Infiltration Basin)

4700

4720

4740

4760

4780

4800

4820

4840

4860

4880

1/1/1988 1/1/1992 1/1/1996 1/1/2000 1/1/2004 1/1/2008

Wa

ter e

leva

tion

in ft

a.m

.s.l.

NA-14

NA-14 simulated, layer 1

25


Flow Model – Transient (Surface Water) Flow Model – Transient (Surface Water)

26


Flow Model – ProjectionFlow Model – Projection

3600

3700

3800

3900

4000

4100

4200

4300

4400

4500

4600

4700

4800

4900

5000

5100

5200

0 50 100 150 200 250 300 350 400

Sta

ge

in f

ee

t (a

ms

l)

Recovery Time in Year

Simulated Pit Stage

Groundwater level

Pit water stage

Post-Mining Pit Lake Recovery

Simulated Maximum Drawdown (10 feet)

27


5. Conclusions5. Conclusions

• Groundwater pumping at Goldstrike has resulted in 520 m of drawdown around the mine site.

• Most of the water pumped at the mine has been returned to the same hydrologic basin.

• Extensive monitoring program, assisted by modern satellite technology and by robust modeling, has identified aquifer responses.

• Improvement of the water-management system, the monitoring network, the modeling and analysis continue at Goldstrike.

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Thank You for Your Attention!Thank You for Your Attention!

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Mine Dewatering and Water Management at Barrick Goldstrike Mine in the Carlin Trend, Nevada Johnny...

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