4
PRODUCTION SCHEDULING CASE
STUDY BASE CASE
The workflow was applied to evaluating value creation
opportunities for an operation consisting of a copper mine
and mill. Details of the example, including assuming all
blocks have sulfide geometallurgy, have been modified for
confidentiality and simplification of presentation. With the
cost and price assumptions and multipliers used (Table 1),
the breakeven cutoff for mill vs waste is 0.4% Cu. The base
plan has been solved using base case mill capacity of 20Mt/
year and mine capacity of 40Mt/year constrained to a sink
rate of six 15 m benches/year vertical advance in any given
layback.
Recoverable resources were provided by conditional
simulation calibrated to expected ore control selectivity. For
this study, the results of nine conditional simulations were
accumulated from all simulations of every block within
each panel of each layback. This grade-tonnage reporting
method ensures that the planning process reflects the same
mining selectivity as the conditional simulations. Tonnages
are tracked using 20 increments to provide both tonnage
and grade resolution (Figure 2). The geologic model reflects
strong copper mineralization surrounded by barren wall
rock.
A nested pit approach was used to define 10 laybacks
(Figure 3). Panels were defined as the sum of two consecu-
tive benches within a layback. More discussion of layback
definition is presented later in the paper.
A series of dashboard graphs shows the results of the
production schedule optimization with base case mining
Table 1. Case study cost and price inputs
Parameter Value Units
Discount Rate, pv 10% /yr
Price, pr 6500 $/t Cu
Marketing, cK 1100 $/t Cu
Royalty, rD 0%
Mining, CM 2.50 $/ton mined
Increase w/depth 0.03 $/bench/ton mined
Ex-mine mill, cX 0.50 $/ton hauled
Ex-mine waste, cX 0.10 $/ton hauled
Mill-direct, cDD 17.00 $/ton milled
Mill-stkpile, cDS 17.00 $/ton milled
Stockpiling, cS 0.15 $/ton stockpiled
Reclaiming, cR 0.60 $/ton reclaimed
Recovery-direct, yD 85%
Recovery-stkpile, yS 80%
and milling capacity constraints (40Mt/yr and 20Mt/yr).
The base mining schedule shows full utilization of mining
capacity through year 15 with lower grade tonnages stock-
piled in the first twelve years (Figure 4a). Alternate display
formats emphasize vertical advance (Figure 4b), or tons per
layback (Figure 4c) and how many laybacks are active in a
given year (Figure 4d). Starting in year 16, the mining rate
is scaled back below the maximum possible rate because the
remaining material in laybacks 9 and 10 has a low profit
margin which provides little incentive for mining faster and
elevating the cutoff grade to accelerate metal production at
the expense of higher current mining and stockpiling costs
and eventual lower recovery for stockpiled ore.
The results of the mining schedule can also be mapped
back to the block model for 3D viewing or cross-section
viewing (Figure 5).
The process schedule shows 24.5 years of full mill capac-
ity utilization, with only limited stockpile reclaim through
year 17 (Figure 6a direct feed from pit color coded by grade
Figure 2. Case study grade-tonnage distribution
Figure 3. Case study long section (NE-SW): Cu grades
(simulation #6) (top) and layback definitions (bottom)
PRODUCTION SCHEDULING CASE
STUDY BASE CASE
The workflow was applied to evaluating value creation
opportunities for an operation consisting of a copper mine
and mill. Details of the example, including assuming all
blocks have sulfide geometallurgy, have been modified for
confidentiality and simplification of presentation. With the
cost and price assumptions and multipliers used (Table 1),
the breakeven cutoff for mill vs waste is 0.4% Cu. The base
plan has been solved using base case mill capacity of 20Mt/
year and mine capacity of 40Mt/year constrained to a sink
rate of six 15 m benches/year vertical advance in any given
layback.
Recoverable resources were provided by conditional
simulation calibrated to expected ore control selectivity. For
this study, the results of nine conditional simulations were
accumulated from all simulations of every block within
each panel of each layback. This grade-tonnage reporting
method ensures that the planning process reflects the same
mining selectivity as the conditional simulations. Tonnages
are tracked using 20 increments to provide both tonnage
and grade resolution (Figure 2). The geologic model reflects
strong copper mineralization surrounded by barren wall
rock.
A nested pit approach was used to define 10 laybacks
(Figure 3). Panels were defined as the sum of two consecu-
tive benches within a layback. More discussion of layback
definition is presented later in the paper.
A series of dashboard graphs shows the results of the
production schedule optimization with base case mining
Table 1. Case study cost and price inputs
Parameter Value Units
Discount Rate, pv 10% /yr
Price, pr 6500 $/t Cu
Marketing, cK 1100 $/t Cu
Royalty, rD 0%
Mining, CM 2.50 $/ton mined
Increase w/depth 0.03 $/bench/ton mined
Ex-mine mill, cX 0.50 $/ton hauled
Ex-mine waste, cX 0.10 $/ton hauled
Mill-direct, cDD 17.00 $/ton milled
Mill-stkpile, cDS 17.00 $/ton milled
Stockpiling, cS 0.15 $/ton stockpiled
Reclaiming, cR 0.60 $/ton reclaimed
Recovery-direct, yD 85%
Recovery-stkpile, yS 80%
and milling capacity constraints (40Mt/yr and 20Mt/yr).
The base mining schedule shows full utilization of mining
capacity through year 15 with lower grade tonnages stock-
piled in the first twelve years (Figure 4a). Alternate display
formats emphasize vertical advance (Figure 4b), or tons per
layback (Figure 4c) and how many laybacks are active in a
given year (Figure 4d). Starting in year 16, the mining rate
is scaled back below the maximum possible rate because the
remaining material in laybacks 9 and 10 has a low profit
margin which provides little incentive for mining faster and
elevating the cutoff grade to accelerate metal production at
the expense of higher current mining and stockpiling costs
and eventual lower recovery for stockpiled ore.
The results of the mining schedule can also be mapped
back to the block model for 3D viewing or cross-section
viewing (Figure 5).
The process schedule shows 24.5 years of full mill capac-
ity utilization, with only limited stockpile reclaim through
year 17 (Figure 6a direct feed from pit color coded by grade
Figure 2. Case study grade-tonnage distribution
Figure 3. Case study long section (NE-SW): Cu grades
(simulation #6) (top) and layback definitions (bottom)