andrew watson - 3

8/12/2019 Andrew Watson - 3

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Andrew H. Watson General Manager, MWH Peru

Selection of the Best AlternativeSeptember 14, 2011


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DefineAlternative Tailing Disposal (ATD)

Understand whywe consider Alternative Tailing Disposal (ATD).

Understand howto decide on an disposal method.

Discuss the challengesand unanswered questions.

Conclusions and a call to action

Presentation Outline
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Tailings Disposal


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Understand whywe consider Alternative Tailing Disposal (ATD).

Understand how to decide on an disposal method.


Conclusions and a call to action .



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Conventional Tailing Disposal


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Thickened Tailing Disposal


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Paste Tailing Disposal


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Filtered Dry Stack Tailing Disposal


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The Benefits of ATD


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Define Alternative Tailing Disposal (ATD)

Understandwhy we consider Alternative Tailing Disposal (ATD).

Understand how to decide on an disposal method.


Conclusions and a call to action.



11/43

0

10

20

30

40

50

60

70

80

90

100

Conventional

Tailings

Thickened Tailings Paste Filtered Tailings

WaterRecovery(%)

Water Recovery by Tailings Type

Why we consider ATD: Water Savings


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Tailing

Facility

Stewardship

Why we consider ATD: Risk Reduction


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Why we consider ATD: Risk Reduction*


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All of the ATD methods save

space over conventional

disposal, however

Filtered Tailing Disposal savesthe most.

Why we consider ATD: Space Limitation


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0

200

400

600

800

1000

1200

1400

Convential

Tailings

Thickened

Tailings

Paste Filtered

Tailings

YieldStress(Pa)

Yield Stress by Tailings Type

The higher yield stress prevents

the need for a tailings dam.

Why we consider ATD:

Reduced Embankment Volume


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Many miners, regulators, and

NGOs are asking that filtered

tailing disposal be considered

for any major expansion or greenfield site.

Evaluations require considerable

effort!

A simple screening methodologyhas been used to assess fatal

flaws and initial feasibility.

Its All About Water and Risk Reduction


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Define Alternative Tailing Disposal (ATD)

Understand why we consider Alternative Tailing Disposal (ATD).

Understandhowto decide on an disposal method.

Discuss the challenges and unanswered questions.

Conclusions and a call to action .



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Fatal Flaw Analysis

Multiple Accounts Analysis

Qualitative Evaluation Ranking Detailed Quantitative Ranking

Cost Analysis

Screening Options for Tailing Disposal


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Site Characteristics Topography

Seismicity

Climate

Space

Water Balance

Tailing Characteristics Gradation and Plasticity

Geochemistry

Regulatory Setting/Landuse/Social Implications of Failure

Permitting

Landuse

Closure

Key Criteria for

Assessment

of Fatal Flaws and

Qualitative Evaluation

Requirements for Tailing Disposal


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Fatal Flaw Screening

Less More

Difficult Easier

Higher Lower

Large footprint Small(er) footprint

High & low fines/plasticity High fines/high plasticity

Time needed Quick/easy

Plentiful Limited


Dry or wet Dry or wet

High degree of care Medium degree of care

Steep or valley Steep or flat

Seismicity

Topography

Climate

Space

Water Balance

Closure

Gradation & Plasticity

Geochemistry

Implications of Failure

Permitting

Adjacent Land Use

Cost

F

I

L

T

E

R

E

D

C

O

N

V

E

N

T

I

O

N

A

L

Topography


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Range of Global Sites to be Considered

Eastern Europe

Western Europe

Latin America

Central America


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Wet site (rainfall exceeds evaporation)

Steep topography

High seismicity

Limited to no space for expansion

Mine life controlled by tailing storage

Production rate 6 Mtpa

High clay content in tailing

Filter tailing considered as combined

disposal for expansion of capacity

Currently thickening to 55% .

Evaluated:

paste

filtered

Latin merica


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Neutral

Disadvantage

Major Disadvantage or

Fatal Flaw

Favorable

Less More

Difficult Easier

Higher Lower




Plentiful Limited





Seismicity

Topography

Climate

Space

Water Balance

Closure


Geochemistry


Permitting

Adjacent Land Use

Cost

F

I

L

T

E

R

E

D

C

O

N

V

E

N

T

I

O

N

A

L

Topography

Suitable for dry

stack if fill

across valley

Topographyopographyery steep valley,

efficient for wet

disposal

Topography Steep, rugged, valley


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Less More

Difficult Easier

Higher Lower




Plentiful Limited





Seismicity

Topography

Climate

Space

Water Balance

Closure


Geochemistry


Permitting

Adjacent Land Use

Cost

F

I

L

T

E

R

E

D

C

O

N

V

E

N

T

I

O

N

A

L

Topography

Seismicity

Rockfill dam can

be designed and

constructed to

meet seismic

design criteria

Filtering operation

can be designed

to produce

seismically stable

material after

placement and

compaction

Seismicity - High

Neutral

Disadvantage


Fatal Flaw

Favorable


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Less More

Difficult Easier

Higher Lower




Plentiful Limited





Seismicity

Topography

Climate

Space

Water Balance

Closure


Geochemistry


Permitting

Adjacent Land Use

Cost

F

I

L

T

E

R

E

D

C

O

N

V

E

N

T

I

O

N

A

L

Topography

Wet disposal can

accommodate

wet conditions

with pond

management

Placement during

wet season may

require special

measures or

specific wet

material

placement areas

Climate

Climate Defined wet and dry season,

rain fall exceeds evaporation

Neutral

Disadvantage


Fatal Flaw

Favorable


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Less More

Difficult Easier

Higher Lower




Plentiful Limited





Seismicity

Topography

Climate

Space

Water Balance

Closure


Geochemistry


Permitting

Adjacent Land Use

Cost

F

I

L

T

E

R

E

D

C

O

N

V

E

N

T

I

O

N

A

L

Topography

Large facility with

low density tailing

Small footprint,

high density,

efficient use of

space

Space

Space Very tight property boundary

Neutral

Disadvantage


Fatal Flaw

Favorable


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Less More

Difficult Easier

Higher Lower




Plentiful Limited





Seismicity

Topography

Climate

Space

Water Balance

Closure


Geochemistry


Permitting

Adjacent Land Use

Cost

F

I

L

T

E

R

E

D

C

O

N

V

E

N

T

I

O

N

A

L

Topography

Large portion of

excess water is

stored in tailing

void space

Filtered water

has to be stored

at site or treated

and released

Water Balance

Water Balance

Positive water balance, process water,

seepage water, and contact water must be treated to be released

Neutral

Disadvantage


Fatal Flaw

Favorable


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Wet site (rainfall exceeds evaporation) Steep topography

Moderate seismicity

Storage space is constrained

Production planned at 13.1 Mtpa

Tailing seepage and runoff from tailing

are expected to have CN above

discharge standards

Therefore, water treatment for CNrequired prior to discharge

Currently thickening to 55%.

Evaluated:

paste

filtered

CentralEurope


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Less More

Difficult Easier

Higher Lower




Plentiful Limited





Seismicity

Topography

Climate

Space

Water Balance

Closure


Geochemistry


Permitting

Adjacent Land Use

Cost

F

I

L

T

E

R

E

D

C

O

N

V

E

N

T

I

O

N

A

L

Topography

Large portion of

excess water is

stored in tailing

void space. Large

pond areas for

storage of 2 PMFs

Filtered water

has to be stored

at site or treated

and released.

Would required

separate

treatment plant

for CN.

Discharge

standards are

very restrictive

Water Balance

Water Balance

Positive water balance, process water,

seepage water, and contact water must be treated to be released

Neutral

Disadvantage


Fatal Flaw

Favorable


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Less More

Difficult Easier

Higher Lower




Plentiful Limited





Seismicity

Topography

Climate

Space

Water Balance

Closure


Geochemistry


Permitting

Adjacent Land Use

Cost

F

I

L

T

E

R

E

D

C

O

N

V

E

N

T

I

O

N

A

L

Topography

Low density, slow

beach

development, low

strength beach

Difficult to filter

due to high clay

content, requires

cyclone pre-

treatment and wet

storage for over-

flow


Gradation & Plasticity Fine grind

ore contains high clay content

Neutral

Disadvantage


Fatal Flaw

Favorable


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Less More

Difficult Easier

Higher Lower




Plentiful Limited





Seismicity

Topography

Climate

Space

Water Balance

Closure


Geochemistry


Permitting

Adjacent Land Use

Cost

F

I

L

T

E

R

E

D

C

O

N

V

E

N

T

I

O

N

A

L

Topography

High impact

associated with

tailing release

Still requires wet

disposal of

cyclone overflow

which requires

D/S construction


Implications of Failure High, local

residences, directly downstream of facility


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Less More

Difficult Easier

Higher Lower




Plentiful Limited





Seismicity

Topography

Climate

Space

Water Balance

Closure


Geochemistry


Permitting

Adjacent Land Use

Cost

F

I

L

T

E

R

E

D

C

O

N

V

E

N

T

I

O

N

A

L

Topography

Initial permitswere approved for

wet storage

concept

Could be easier topermit due to

lower volume of

wet storage

Permitting

Permitting Based on recent experience,

both could be permitted

Neutral

Disadvantage


Fatal Flaw

Favorable


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Less More

Difficult Easier

Higher Lower




Plentiful Limited





Seismicity

Topography

Climate

Space

Water Balance

Closure


Geochemistry


Permitting

Adjacent Land Use

Cost

F

I

L

T

E

R

E

D

C

O

N

V

E

N

T

I

O

N

A

L

Topography

Acceptable based

on initial

submission

Could be

considered to be

more favorable

Adjacent Land Use

Adjacent Land Use Grazing of cattle

and some home construction

Neutral

Disadvantage


Fatal Flaw

Favorable


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Wet site (rainfall exceeds evaporation) Moderate to steep topography

High seismicity

Storage space is constrained

Production is ~1.5 Mtpa

Existing facility at capacity

Additional capacity required

Filtered facility the primary alternative

CentralAmerica


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Less More

Difficult Easier

Higher Lower




Plentiful Limited





Seismicity

Topography

Climate

Space

Water Balance

Closure


Geochemistry


Permitting

Adjacent Land Use

Cost

F

I

L

T

E

R

E

D

C

O

N

V

E

N

T

I

O

N

A

L

Topography

Not possible to

permitPossible to permit

ermitting

Permitting


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Wet site

Flat topography

Moderate seismicity

Storage space is very constrained

High land value

Existing facility at capacity Considered filtering for new production

as well as reprocessing of exiting

tailing

Range of Sites to be Considered:

Western Europe


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Less More

Difficult Easier

Higher Lower




Plentiful Limited





Seismicity

Topography

Climate

Space

Water Balance

Closure


Geochemistry


Permitting

Adjacent Land Use

Cost

F

I

L

T

E

R

E

D

C

O

N

V

E

N

T

I

O

N

A

L

Topography

Large facility with

low density tailing

Small footprint,

high density,

efficient use of

space

Space

Space No expansion space, high value

property

Neutral

Disadvantage


Fatal Flaw

Favorable


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Discuss the challengesandunanswered questions.




39/43

The mining industry needs a broader set of project

evaluations and better benchmarking data.

For each methodology, we need to understand:

What slopes can we achieve?

What seepage will result?

How will the paste, thickened or filtered tailing material behave during an

earthquake?

MWH, in cooperation with Paterson & Cooke, have an initiative toanswer these questions. We need your help

As an industry we need to know more.


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Water management is key to controlling risks for tailing facilities.

A tailing stewardship program is required for all tailing facilities (large

and small).

Alternative tailing disposal methods (thickened, paste and filtered) is

one way to reduce the water content of tailing and reduce the risks of

failure during and after operations.

Site and project characteristics have to be amenable to the

implementation of ATD methods.

Wet storage with appropriate dam design may still be the most cost

effective storage method. A high level screening process can be used to identify fatal flaws and

advantages and dis-advantages to determine if further evaluation is

required.

Conclusions


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High cost.

Equipment performance has not kept up with the increase in

production rates.

There are still many questions to be answered.

So why isnt everyone doing it?


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We do not have depth or breadth of project experience that helps

refine/improve the ATD evaluation process.

We call on mining companies to share their learnings

and data to contribute to benchmarking for the

industry.

Call to Action

andrew watson - 3

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