Management of Mining- Impacted Groundwater, Bingham Canyon Mine, Utah, USA

Kelly PaynePrincipal Advisor, Closure & RemediationKennecott Utah Copper LLC

This Morning’s Discussion

• Nature of Problem

• Regulatory Framework

• Containment and Remediation

• Water Treatment

– Acidic Water

– Neutral Water

• Cleanup Timeframe

Acknowledgements

Technology & Innovation

5 October 2009 Remediation of ARD-Contaminated Groundwater 4

Site Location

Nature of Problem

Source Controls

Regulatory Framework

Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)

• 1986 — EPA begins Preliminary Site Investigation

• 1994 — Site proposed for NPL listing

• 1995 — MOU between EPA, State of Utah, and KUC

• 1998 — RI/FS completed

• 2000 — ROD issued

• 2002 — RDRA completed

• 2008 — Consent Decree entered

• 2008 — NPL proposal withdrawn

Natural Resource Damage

• 1986 — State of Utah files Natural Resources Damage (NRD) claim

• 1992 — Initial settlement rejected, Jordan Valley Water Conservancy District (JVCWD) intervenes

• 1995 — NRD settlement approved, KUC provides $37M to “restore, replace, or acquire equivalent”

• 2004 — State approves a joint Kennecott/JVWCD project

Remedies

• EPA through CERCLA authority for Zone A:

– Maintain source controls

– Contain the plume through pumping

– Remediate the aquifer through pumping and monitored natural attenuation

– Treat extracted groundwater and dispose of treatment residuals

• UDEQ through Natural Resources Damage claim settlement:

– KUCC to construct and operate a RO treatment plant

– KUCC to fund construction of a second RO plant to be owned and operated by local water district

– Each plant to produce 3,500 ac-ft per year for 40 years

Containment and Remediation

Acidic Groundwater Well

Sulfate Groundwater Well

Acidic Groundwater Wells

ECG1146 BSG1201 BSG2784

Installed 1995 2003 2008

Material Stainless Steel Stainless Steel Stainless Steel

Diameter 18-inch 18-inch 18-inch

Total Depth 760 ft bgs 752 ft bgs 870 ft bgs

Screen Intervals 500-700 ft bgs 500-740 ft bgs 490-600 ft bgs700-850 ft bgs

Static Water Level 380 ft bgs 450 ft bgs 410ft bgs

Pumping System 250 HP SS Submersible

200 HP SS Submersible

200 HP SS Submersible

Average Pumping Rate

850 gpm 600 gpm 600 gpm

Sulfate Groundwater Wells

BFG1200 B2G1193 LTG1147

Installed 2001 1998 1995

Material Stainless Steel Stainless Steel Carbon/Stainless

Diameter 18-inch 18-inch 16-inch

Total Depth 820 ft bgs 1070 ft bgs 605 ft bgs

Screen Intervals 420-800 ft bgs 450-1060 ft bgs 400-590 ft bgs

Static Water Level 420 ft bgs 450 ft bgs 420 ft bgs

Pumping System 350 HP SS Sumbersible

350 HP Booster

350 HP SS Sumbersible

350 HP Booster

200 HP SS Sumbersible

250 HP Booster

Average Pumping Rate

1400 gpm 1400 gpm 600 gpm

0

600

1200

1800

2400

3000

BSG27 84 1 7 06

BSG1201 551 1282 1292 1300 869 927

ECG1146 7 1 223 337 464 6 496 1022 954 1115 1527 1495 1419 947

T otal 7 1 223 337 464 6 496 1022 1505 2397 2819 27 96 2289 2,580

96 97 98 99 00 01 02 03 04 05 06 07 08

Acidic Water Extraction

Acr

e-F

ee

t p

er

Ye

ar

1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Sulfa

te (m

g/l)

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

50000

ECG1124A ECG1124B ECG1124C ECG1146 DTW ECG1124B

Screened Intervals and D

epth to Water (feet below

ground surface)

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

A

B

C

E

Water Treatment

Zone A Pump and Treat Strategy

BARRIERWELLS

(~3,300 gpm)

ACID WELLS

(~2,300 gpm)

REVERSE OSMOSISTREATMENT PLANT

HIGH-DENSITY SLUDGELIME TREATMENT

PLANT

TAILINGS LINE

CONCENTRATE

DRINKING WATER(2,400 GPM)

RECYCLE / DISCHARGE

JORDAN VALLEY WATERCONSERVANCY

SOLIDS

AQUEOUS

TAILINGS IMPOUNDMENT

RECYCLE / DISCHARGE

SOLIDS

AQUEOUS

REPOSITORY

DISCHARGEPost mine

closure

Reverse Osmosis Treatment Plant

Configuration Two 2-stage skids

Feed Rate 3000 gpm to membranes

200 gpm to remineralization

3200 gpm total

Membranes Hydranautics ESPA2

(sprial wound polyamide)

Pressure Vessels Protec and CodeLine

Recovery Rate 71 to 74%

Production 2200 gpm permeate

2400 gpm product

Zone A Treatment Plant Water Delivery

0

1,000

2,000

3,000

4,000

Annual 3,843 3,299 3,536

Rolling Avg 3,843 3,571 3,559

YE 5/31/07 YE 5/31/08 YE 5/31/09

Acr

e-F

ee

t p

er

Ye

ar

Picture of RO Scaling

Picture of dumps/reservoir

Picture NP5

Aerial of Tailings System

Picture of NSB

Management Criteria

• The neutralization potential (NP) value of samples collected from the tailings North Splitter Box should be either greater than or equal to the NP of Copperton Mill Tailings for the month or at least 5 t CaCO3 eq/kt, using a six-month rolling average.

• Aqueous alkalinity should be greater than or equal to 10 mg CaCO3 eq/L at least 90% of the time. Aqueous alkalinity will be evaluated as a rolling six-month average.

• The aqueous pH at the North Splitter Box should be greater than or equal to 6.7 during at least 90% of the time over a calendar year.

Tailings Neutralization Potential (t CaCO3/kt)

Monthly 6-Month Average

Date GMT NSB GMT NSB

Jan-08 15 14 25 23

Feb-08 151 147 46 41

Mar-08 31 22 47 40

Apr-08 11 15 44 38

May-08 21 24 46 40

Jun-08 23 21 42 41

Jul-08 149 153 64 64

Aug-08 20 14 43 42

Sep-08 26 30 42 43

Oct-08 104 107 57 58

Nov-08 21 24 57 58

Dec-08 11 15 55 57

Tailings Aqueous Alkalinity (mg CaCO3/l)

Monthly 6-Month Average

Date GMT NSB GMT NSB

Jan-08 23 47 34 57

Feb-08 17 11 30 45

Mar-08 175 103 54 50

Apr-08 51 34 55 43

May-08 59 98 60 59

Jun-08 29 27 59 53

Jul-08 11 <5 57 55

Aug-08 57 82 64 69

Sep-08 26 84 39 65

Oct-08 27 36 35 65

Nov-08 22 15 29 49

Dec-08 20 76 27 59

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan

Tons

Per

Hou

r or G

allo

ns P

er M

inut

e

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

pH

6

7

8

9

10

11

Concentrator Throughput (TPH)Acidic Water Pumping (GPM)Tailings pH at North Splitter Box

Picture of Scaling

Cleanup Timeframe

Column Leaching Study

Geochemical Models

• Extrapolation based on interpretation of earlier column data

• Extrapolation using data from individual wells that have undergone complete recovery

• Expanded 1D geochemical model

• Empirical rinse curve model

• Extended 1D advection-dispersion model with mass extraction

Acidity comprised mostly of mineral acidity in the form of elevated Al and Fe concentrations

Concentration of acidity estimated for water extracted from the two extraction wells, ECG1146 and BSG1201

Calculated lime demand

2000 2005 2010 2015 2020 2025 20300

1

2

3

4

5

6

Lim

e de

man

d (t/

ML)

Year

Rinse curve model Extrapolated well data model Advection-dispersion-extraction model Geochemical model (clean) Geochemical model (transition) Upper 95% confidence limit of all models