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
8/9/2019 Andrew Watson
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
8/9/2019 Andrew Watson
3/43
Tailings DisposalTailings Disposal
8/9/2019 Andrew Watson
4/43
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 .
8/9/2019 Andrew Watson
5/43
Conventional Tailing Disposal
8/9/2019 Andrew Watson
6/43
Thickened Tailing Disposal
8/9/2019 Andrew Watson
7/43
Paste Tailing Disposal
8/9/2019 Andrew Watson
8/43
Filtered “Dry Stack” Tailing Disposal
8/9/2019 Andrew Watson
9/43
The Benefits of ATDThe Benefits of ATD
8/9/2019 Andrew Watson
10/43
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.
8/9/2019 Andrew Watson
11/43
Why we consider ATD: Water SavingsWhy we consider ATD: Water Savings
8/9/2019 Andrew Watson
12/43
Tailing
FacilityStewardship
Why we consider ATD: Risk ReductionWhy we consider ATD: Risk Reduction
8/9/2019 Andrew Watson
13/43
Why we consider ATD: Risk Reduction*Why we consider ATD: Risk Reduction*
8/9/2019 Andrew Watson
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.
8/9/2019 Andrew Watson
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.
8/9/2019 Andrew Watson
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.
8/9/2019 Andrew Watson
17/43
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 .
8/9/2019 Andrew Watson
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
8/9/2019 Andrew Watson
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
8/9/2019 Andrew Watson
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
TopographyTopography
Less More
Difficult Easier
Higher Lower
Large footprint Small(er) footprint
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
8/9/2019 Andrew Watson
21/43
Range of Global Sites to be ConsideredRange of Global Sites to be Considered Eastern Europe Latin America
Western Europe Central America
8/9/2019 Andrew Watson
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
•
•
8/9/2019 Andrew Watson
23/43
Neutral
Disadvantage
Major Disadvantage or
Fatal Flaw
Favorable
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
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
Large footprint Small(er) footprint
High & low fines/plasticity High fines/high plasticity
Time needed Quick/easy
Plentiful LimitedWater BalanceWater Balance
ClosureClosure
Gradation & PlasticityGradation & Plasticity
GeochemistryGeochemistry
Implications of FailureImplications of Failure
PermittingPermitting
Adjacent Land UseAdjacent Land Use
CostCost
L
T
E
R
ED
E
N
T
I
O
N
A
L
8/9/2019 Andrew Watson
24/43
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
TopographyTopography
SeismicitySeismicity
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
Major Disadvantage or
Fatal Flaw
Favorable
Less More
Difficult Easier
Higher Lower
Large footprint Small(er) footprint
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
8/9/2019 Andrew Watson
25/43
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
TopographyTopography
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
Major Disadvantage or
Fatal Flaw
Favorable
Less More
Difficult Easier
Higher Lower
Large footprint Small(er) footprint
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
8/9/2019 Andrew Watson
26/43
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
TopographyTopography
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
Major Disadvantage or
Fatal FlawFavorable
Less More
Difficult Easier
Higher Lower
Large footprint Small(er) footprint
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
8/9/2019 Andrew Watson
27/43
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
TopographyTopography
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
Major Disadvantage or
Fatal Flaw
Favorable
Less More
Difficult Easier
Higher Lower
Large footprint Small(er) footprint
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
stored in tailing
void space
stored in tailing
void space
at site or treated
and released
at site or treated
and released
8/9/2019 Andrew Watson
28/43
Wet site (rainfall exceeds evaporation)
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
• •
8/9/2019 Andrew Watson
29/43
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
TopographyTopography
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
Major Disadvantage or
Fatal Flaw
Favorable
Less More
Difficult Easier
Higher Lower
Large footprint Small(er) footprint
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
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
8/9/2019 Andrew Watson
30/43
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
TopographyTopography
Gradation & PlasticityGradation & Plasticity – – Fine grindFine grind
ore contains high clay contentore contains high clay content
Neutral
Disadvantage
Major Disadvantage or
Fatal Flaw
Favorable
Less More
Difficult Easier
Higher Lower
Large footprint Small(er) footprint
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
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
Gradation & PlasticityGradation & Plasticity
8/9/2019 Andrew Watson
31/43
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
TopographyTopography
Implications of FailureImplications of Failure – – High, localHigh, local
residences, directly downstream of facilityresidences, directly downstream of facility
Less More
Difficult Easier
Higher Lower
Large footprint Small(er) footprint
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
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
Implications of FailureImplications of Failure
8/9/2019 Andrew Watson
32/43
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
TopographyTopography
PermittingPermitting – – Based on recent experience,Based on recent experience,
both could be permittedboth could be permitted
Neutral
Disadvantage
Major Disadvantage or
Fatal Flaw
Favorable
Less More
Difficult Easier
Higher Lower
Large footprint Small(er) footprint
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
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
PermittingPermitting
8/9/2019 Andrew Watson
33/43
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
TopographyTopography
Adjacent Land UseAdjacent Land Use – – Grazing of cattleGrazing of cattle
and some home constructionand some home construction
Neutral
Disadvantage
Major Disadvantage or
Fatal Flaw
Favorable
Less More
Difficult Easier
Higher Lower
Large footprint Small(er) footprint
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
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
8/9/2019 Andrew Watson
34/43
Wet site (rainfall exceeds evaporation)
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
8/9/2019 Andrew Watson
35/43
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
TopographyTopography
PermittingPermitting
Less More
Difficult Easier
Higher Lower
Large footprint Small(er) footprint
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
NA
L
Not possible to
permit
Not possible to
permitPossible to permitPossible to permitPermittingPermitting
8/9/2019 Andrew Watson
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
8/9/2019 Andrew Watson
37/43
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
TopographyTopography
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
Major Disadvantage or
Fatal Flaw
Favorable
Less More
Difficult Easier
Higher Lower
Large footprint Small(er) footprint
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
NA
L
8/9/2019 Andrew Watson
38/43
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.
8/9/2019 Andrew Watson
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!
8/9/2019 Andrew Watson
40/43
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.
8/9/2019 Andrew Watson
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.
8/9/2019 Andrew Watson
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 .
8/9/2019 Andrew Watson
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.