Andrew Watson

8/9/2019 Andrew Watson

1/43

Andrew H. WatsonAndrew H. Watson – – General Manager, MWH PeruGeneral Manager, MWH Peru

Selection of the Best AlternativeSelection of the Best Alternative


2/43

• Define Alternative Tailing Disposal (ATD)

• Understand why we consider Alternative Tailing Disposal (ATD).

Presentation OutlinePresentation Outline

• Understand how to decide on an disposal method.

• Discuss the challenges and unanswered questions.

• Conclusions and a call to action


3/43

Tailings DisposalTailings Disposal


4/43

Define Alternative Tailing Disposal (ATD)

Understand why we consider Alternative Tailing Disposal (ATD).


Understand how to decide on an disposal method.

Discuss the challenges and unanswered questions .

Conclusions and a call to action .


5/43

Conventional Tailing Disposal


6/43

Thickened Tailing Disposal


7/43

Paste Tailing Disposal


8/43

Filtered “Dry Stack” Tailing Disposal


9/43

The Benefits of ATDThe Benefits of ATD


10/43





Discuss the challenges and unanswered questions.

Conclusions and a call to action.


11/43

Why we consider ATD: Water SavingsWhy we consider ATD: Water Savings


12/43

Tailing

FacilityStewardship

Why we consider ATD: Risk ReductionWhy we consider ATD: Risk Reduction


13/43

Why we consider ATD: Risk Reduction*Why we consider ATD: Risk Reduction*


14/43

All of the ATD methods save

space over conventionaldisposal, however

Filtered Tailin Dis osal saves

Why we consider ATD: Space Limitation

the most.


15/43

Why we consider ATD:Why we consider ATD:Reduced Embankment VolumeReduced Embankment Volume

The higher yield stress preventsthe need for a tailings dam.


16/43

Many miners, regulators, and

NGOs are asking that filteredtailing disposal be considered

for any major expansion or green

It’s All About Water and Risk ReductionIt’s All About Water and Risk Reduction

e s e. Evaluations require considerable

effort!

A simple screening methodologyhas been used to assess fatal

flaws and initial feasibility.


17/43





Discuss the challenges and unanswered questions .

Conclusions and a call to action .


18/43

Fatal Flaw Analysis

Multiple Accounts Analysis

Qualitative Evaluation Ranking

Screening Options for Tailing DisposalScreening Options for Tailing Disposal

e a e uan a ve an ng Cost Analysis


19/43

Site Characteristics Topography

Seismicity

Climate

Space

Water Balance

Requirements for Tailing DisposalRequirements for Tailing Disposal

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


20/43

Fatal Flaw ScreeningFatal Flaw Screening

Plentiful Limited

Large footprint Small(er) footprint

Dry or wet Dry or wet

High degree of care Medium degree of care

Steep or valley Steep or flat

SeismicitySeismicity

TopographyTopography

ClimateClimate

SpaceSpace

Water BalanceWater Balance

F

I

C

O

N

V


Less More

Difficult Easier

Higher Lower


High & low fines/plasticity High fines/high plasticity

Time needed Quick/easyClosureClosure

Gradation & PlasticityGradation & Plasticity

GeochemistryGeochemistry

Implications of FailureImplications of Failure

PermittingPermitting

Adjacent Land UseAdjacent Land Use

CostCost

T

E

R

E

D

N

T

I

O

N

A

L


21/43

Range of Global Sites to be ConsideredRange of Global Sites to be Considered Eastern Europe Latin America

Western Europe Central America


22/43

Wet site (rainfall exceeds evaporation)

Steep topography

High seismicity

Limited to no space for expansion

Mine life controlled b tailin stora e

Latin America Latin America

Production rate 6 Mtpa

High clay content in tailing

Filter tailing considered as combined

disposal for expansion of capacity

•

•


23/43

Neutral

Disadvantage

Major Disadvantage or

Fatal Flaw

Favorable







ClimateClimate

SpaceSpace

F

C

O

N

TopographyTopographySuitable for dry

stack if fill

across valley

TopographyTopographyTopographyTopographyVery steep valley,efficient for wet

disposal

TopographyTopography – – Steep, rugged, valleySteep, rugged, valley

Less More

Difficult Easier

Higher Lower



Time needed Quick/easy

Plentiful LimitedWater BalanceWater Balance

ClosureClosure






CostCost

L

T

E

R

ED

E

N

T

I

O

N

A

L


24/43

Plentiful Limited







ClimateClimate

SpaceSpace


F

I

C

O

N

V



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

SeismicitySeismicity -- HighHigh

Neutral

Disadvantage


Fatal Flaw

Favorable

Less More

Difficult Easier

Higher Lower









CostCost

T

E

R

E

D

N

T

I

O

N

A

L


25/43

Plentiful Limited







ClimateClimate

SpaceSpace


F

I

C

O

N

V


Wet disposal can

accommodate

wet conditions

with pond

management

Wet disposal can

accommodate

wet conditions

with pond

management

Placement during

wet season may

require special

measures or

specific wet

material

placement areas

Placement during

wet season may

require special

measures or

specific wet

material

placement areas

ClimateClimate

ClimateClimate – – Defined wet and dry season,Defined wet and dry season,

rain fall exceeds evaporationrain fall exceeds evaporation

Neutral

Disadvantage


Fatal Flaw

Favorable

Less More

Difficult Easier

Higher Lower









CostCost

T

E

R

E

D

N

T

I

O

N

A

L


26/43

Plentiful Limited







ClimateClimate

SpaceSpace


F

I

C

O

N

V


Large facility with

low density tailing

Large facility with

low density tailing

Small footprint,

high density,

efficient use of

space

Small footprint,

high density,

efficient use of

space

SpaceSpace

SpaceSpace – – Very tight property boundaryVery tight property boundary

Neutral

Disadvantage


Fatal FlawFavorable

Less More

Difficult Easier

Higher Lower









CostCost

T

E

R

E

D

N

T

I

O

N

A

L


27/43

Plentiful Limited







ClimateClimate

SpaceSpace


F

I

C

O

N

V


Large portion of

excess water is

Large portion of

excess water is

Filtered water

has to be stored

Filtered water

has to be storedWater BalanceWater Balance

Water BalanceWater Balance – – Positive water balance, process water,Positive water balance, process water,seepage water, and contact water must be treated to be releasedseepage water, and contact water must be treated to be released

Neutral

Disadvantage


Fatal Flaw

Favorable

Less More

Difficult Easier

Higher Lower









CostCost

T

E

R

E

D

N

T

I

O

N

A

L

stored in tailing

void space

stored in tailing

void space

at site or treated

and released

at site or treated

and released


28/43


Steep topography

Moderate seismicity Storage space is constrained

Production planned at 13.1 Mtpa

CentralCentral EuropeEurope

Tailing seepage and runoff from tailing

are expected to have CN above

discharge standards

Therefore, water treatment for CNrequired prior to discharge

• •


29/43

Plentiful Limited







ClimateClimate

SpaceSpace


F

I

C

O

N

V


Large portion of

excess water is

Large portion of

excess water is

Filtered water

has to be stored

Filtered water

has to be storedWater BalanceWater Balance

Water BalanceWater Balance – – Positive water balance, process water,Positive water balance, process water,seepage water, and contact water must be treated to be releasedseepage water, and contact water must be treated to be released

Neutral

Disadvantage


Fatal Flaw

Favorable

Less More

Difficult Easier

Higher Lower









CostCost

T

E

R

E

D

N

T

I

O

N

A

L

void space. Largepond areas for

storage of 2 PMFs

void space. Largepond areas for

storage of 2 PMFs

and released.Would required

separate

treatment plant

for CN.

Discharge

standards arevery restrictive

and released.Would required

separate

treatment plant

for CN.

Discharge

standards arevery restrictive


30/43

Plentiful Limited







ClimateClimate

SpaceSpace


F

I

C

O

N

V


Gradation & PlasticityGradation & Plasticity – – Fine grindFine grind

ore contains high clay contentore contains high clay content

Neutral

Disadvantage


Fatal Flaw

Favorable

Less More

Difficult Easier

Higher Lower









CostCost

T

E

R

E

D

N

T

I

O

N

A

L

Low density, slow

beach

development, low

strength beach

Low density, slow

beach

development, low

strength beach

cu o er

due to high claycontent, requires

cyclone pre-

treatment and wet

storage for over-

flow

cu o er

due to high claycontent, requires

cyclone pre-

treatment and wet

storage for over-

flow



31/43

Plentiful Limited







ClimateClimate

SpaceSpace


F

I

C

O

N

V


Implications of FailureImplications of Failure – – High, localHigh, local

residences, directly downstream of facilityresidences, directly downstream of facility

Less More

Difficult Easier

Higher Lower









CostCost

T

E

R

E

D

N

T

I

O

N

A

L

High impact

associated with

tailing release

High impact

associated with

tailing release

Still requires wet

disposal of

cyclone overflow

which requiresD/S construction

Still requires wet

disposal of

cyclone overflow

which requiresD/S construction



32/43

Plentiful Limited







ClimateClimate

SpaceSpace


F

I

C

O

N

V


PermittingPermitting – – Based on recent experience,Based on recent experience,

both could be permittedboth could be permitted

Neutral

Disadvantage


Fatal Flaw

Favorable

Less More

Difficult Easier

Higher Lower









CostCost

T

E

R

E

D

N

T

I

O

N

A

L

Initial permitswere approved for

wet storage

concept

Initial permitswere approved for

wet storage

concept

Could be easier topermit due to

lower volume of

wet storage

Could be easier topermit due to

lower volume of

wet storage



33/43

Plentiful Limited







ClimateClimate

SpaceSpace


F

I

C

O

N

V


Adjacent Land UseAdjacent Land Use – – Grazing of cattleGrazing of cattle

and some home constructionand some home construction

Neutral

Disadvantage


Fatal Flaw

Favorable

Less More

Difficult Easier

Higher Lower









CostCost

T

E

R

E

D

N

T

I

O

N

A

L

Acceptable based

on initial

submission

Acceptable based

on initial

submission

Could be

considered to be

more favorable

Could be

considered to be

more favorableAdjacent Land UseAdjacent Land Use


34/43


Moderate to steep topography

High seismicity Storage space is constrained

Production is ~1.5 Mtpa

CentralCentral AmericaAmerica

Existing facility at capacity

Additional capacity required

Filtered facility the primary alternative


35/43

Plentiful Limited







ClimateClimate

SpaceSpace


F

I

C

O

N

V



Less More

Difficult Easier

Higher Lower









CostCost

T

E

R

E

D

N

T

I

O

NA

L

Not possible to

permit

Not possible to

permitPossible to permitPossible to permitPermittingPermitting


36/43

Wet site

Flat topography

Moderate seismicity

Storage space is very constrained

Hi h land value

Range of Sites to be Considered:Range of Sites to be Considered:

Western EuropeWestern Europe

Existing facility at capacity

Considered filtering for new production

as well as reprocessing of exiting

tailing

Neutral


37/43

Plentiful Limited







ClimateClimate

SpaceSpace


F

I

C

O

N

V


Large facility with

low density tailing

Large facility with

low density tailing

Small footprint,

high density,

efficient use of

space

Small footprint,

high density,

efficient use of

space

SpaceSpace

SpaceSpace – – No expansion space, high valueNo expansion space, high value

propertyproperty

Neutral

Disadvantage


Fatal Flaw

Favorable

Less More

Difficult Easier

Higher Lower









CostCost

T

E

R

E

D

N

T

I

O

NA

L


38/43








39/43

The mining industry needs a broader set of project

evaluations and better benchmarking data.

For each methodology, we need to understand:

As an industry, we need to know more….As an industry, we need to know more….

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!


40/43








41/43

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

ConclusionsConclusions

.

Site and project characteristics have to be amenable to theimplementation 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.


42/43

High cost.

Equipment performance has not kept up with the increase in

production rates.

So why isn’t everyone doing it?So why isn’t everyone doing it?

ere are s many ques ons o e answere .


43/43

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

Call to ActionCall to Action

industry.

Andrew Watson

Documents

Transcript of Andrew Watson