29th September 2016

Long term monitoring and targeted assessments to improve management of mine wastes – The Batu Hijau Project

CSIRO

Brad Angel (CSIRO), Stuart Simpson (CSIRO) and Jorina Waworuntu (PT Amman Mineral Internasional formerly PT NNT)

1 µm Nano CeO21 µm Micron CeO2

Batu Hijau

Batu Hijau project

1986 COW signed

Exploration & Baseline

Feasibility Study &

EIAConstruction

Mine Operation

Mine Closure

Post Mine Closure

1990 Deposit discovered

1995/6 1997 - 1999 2000 - … 2030s

The copper mine

• Operates at ~450 m above sea level, and ~10 km from the South Coast

• The ores mined contain 0.53% copper and 0.4 g/ton gold

• Processes approximately 130,000 tons of ore per day to produce copper

• Fully operational by year 2000

Timeline

Environmental Impact Assessment– Tailing management considerations

2300 Ha land

required for onland

tailings placement

On-land impoundments (TSF) and DSTP options assessed:

• On-land impact to 2,300 haof forest and agricultural land, relocation of communities (>2000 people)

• TSF high long-term risk of failure due to extreme rainfall events (average annual rainfall >2,500 mm) and earthquakes

• Potential ARD issues for tailings

• Managing TSF post-closure

The choice of DSTP

• A deep submarine canyon appropriate for DSTP was available nearby to the mine

• The DSTP eliminates acid rock drainage concerns with tailings

• The deep sea ecosystem was predicted to recover more rapidly after mine closure than the area used for on-land storage (TSF)

Southwest Sumbawa

Senunucanyon

Discharge at the head of Senunu Canyon at 125 m depth, which leads into the Lombok Basin at 3000-4000 m depth

• Ensure that the tailings flow down the canyon and away from the coast and that the tailings are confined below the surface mixed layer

• Ensure there will be no impact to the biologically active near-surface zone including coral reefs, mangroves, beaches or other coastal attributes

• Avoid impacts on commercial and subsistence fisheries

DSTP environmental management objectives

Environmental Impact Assessment– Initial DSTP permit approval

Baseline (1994-1996):

•Bathymetry

•Oceanography (seasonal)

•Sea water quality

•Sediment quality

•Benthos, plankton, coral reef

Impact Prediction:

• Footprint and dispersion model

• Tailing characterisation

Tailings characterisation and toxicity(for permitting)

• Leachate testing on tailings: Copper and zinc concentrations below regulated levels for hazardous waste management and dumping. Other metals below LODs

• Tailings solid: Below levels required for hazardous waste management and dumping

• Tailings liquid toxicity testing: No acute or chronic toxicity of effluent

• Tailings: Daily physico-chemical measurements and liquid and solid composition, weekly dissolved copper & sulfide, monthly for other metals

• Marine water and sediment sampling: Monthly CTD profiles, quarterly dissolved metals and sediment metals / characterisation

• Plankton community, coral reef ecosystem, intertidal ecosystem: Half yearly ecological indices

• Demersal fish and filter feeders: Annual assessment including tissue metal concentrations)

Environmental monitoring

Monitoring of compliance– Tailings

Monitoring of compliance– Tailings

Monitoring of compliance– Tailings

Light Transmission Near Bottom, LIPI Deep Sea Study

November 2013

Monitoring of compliance– Tailings plume turbidity

Turbidity ProfilesRoutine NNT monitoring

Zone A – Senunu Canyon mixing zone (>120 m)

Zone B – Senunu Canyon, <120 m

Monitoring of compliance– Tailings footprint

• Based on tailings thickness, percent tailings in sediment and sediment copper concentration

• Main tailings footprint larger than that predicted in EIA

• Eastward extension not predicted

• Generally >1000 m and >30 km from coast

• Not predicted by turbidity and light transmission

• Shearing currents with depth not measured during baseline studies?

• Additional sediment sampling sites added to monitoring program

Sea water standard is applicable in Zone B and Zone C, and is not applicable in Zone A

Monitoring of compliance– Seawater quality

• Deep sea studies – tracking tailings footprint and refining models, water column suspended solids

• Copper spikes in the water – Investigative studies

• Due Diligence studies in 2004, 2009 & 2015 – to independently verify compliance to the permit

• Tailings re-colonisation – How long for organisms to recover once DSTP ends?

Support studies and validation

Leading to refinement of monitoring

programs and tailing management

Managing variability– Copper spikes in seawater

Issue: Stockpile ore more oxidized than recently extracted ore resulting

in lower copper extraction and tailings with higher copper concentrations

that are more soluble

→ Modifying ore processing to maximise copper recovery and minimise the

discharge of bioavailable copper

• Optimisation of controlled potential sulfidisation – NaSH

• Improved blending of feed materials

• Monitoring indicates fewer incidents of guideline exceedance

Due Diligence Study Results

• Mean ± S.D. concentrations from sites within zones

0

3

6

9

12

15

Zone C Zone B Zone A

Dem

ers

al fi

sh

Zn

(µ

g/g

)

NNT Pre-ops

NNT Operations

CSIRO 2004

CSIRO 2009

CSIRO 2015

0

0.3

0.6

0.9

1.2

1.5

Zone C Zone B Zone A

Dem

ers

al fi

sh

Cu

(µ

g/g

)

NNT Pre-ops

NNT Operations

CSIRO 2004

CSIRO 2009

CSIRO 2015

Zone A – Senunu Canyon mixing zone (>120 m)

Zone B - Senunu Canyon, <120 m

Zone C – Reference sites outside Senunu Canyon

0.01

0.1

1

10

100

Zone C Zone B Zone A

Dis

so

lve

d C

u (

µg

/L)

NNT Pre-ops

NNT Operations

CSIRO 2004

CSIRO 2009

CSIRO 2015

WQG = 1.3 µg/L

0.01

0.1

1

10

100

Zone C Zone B Zone A

Dis

so

lved

Zn

(µ

g/L

)

NNT Pre-ops NNT Operations

CSIRO 2004 CSIRO 2009

CSIRO 2015

WQG = 15 µg/L

Technical Challenges: Closure– Tailings re-colonisation studies

18

The principal questions:

• Will benthos recolonize the final

tailings sediment?

Microcosm and mesocosm

benthos recolonization experiment

(2005-2008, 2009-2012)

• Meiofauna more sensitive than

macrofauna

• Meiofauna recover more rapidly than

macrofauna (significant

reconlonisation within 200 days)

• Tailings footprint larger than predicted, but generally below 1000 m depth and >30 km from coast

• Plumes not measurable using turbidity or light transmission i.e. below detection

• Are they missed in quarterly ‘snap-shot’ studies?

• Tailings dissolved metals low relative to permit

• Spikes in dissolved copper in seawater related to oxidised stockpile ore

• CPS and ore blending employed to remedy

• No elevation of metals in biota near DSTP discharge compared to reference sites

• Tailings recolonisation occurs relatively quickly

Environmental management objectives

– Are they being achieved?

LAND AND WATER FLAGSHIP