155
5.2.3 Sensitivity analysis
The sensitivity of the results to gold price, underground processing capacity and underground capital development (shaft) is evaluated with the MILP model. This sensitivity analysis was conducted to examine the selected technical or economic parameters that influence
the choice of mining option(s) for the deposit. The sensitivity plot is shown in Figure 10.
In Figure 10, the MILP model is very sensitive to the market price of copper followed by the
quantity of ore processed from the UG mining operation and the completion rate of capital
development.
For this case study, about 9% decrease in the copper price (from $3.18 to $2.89 per lb)
will change the optimal mining option from combined OPUG mining to an independent OP
mining option for a reduced NPV of $227.73. Similarly, when the underground processing
capacity decreases by about 73% (0.81 Mt), the combined OPUG mining will change to an
independent OP mining option. This copper deposit is however less sensitive to the completion rate of underground capital development (shaft) as it did not cause a change in mining
option within the changes tested.
Figure  9. Operational development schedule for the underground mining operation in the OPUG
mining option.
Figure 10. Sensitivity assessment of selected technical and economic parameters used in the MILP
model.
-75%
3500
3000
g
~ 2500
!
~ 2000
]
11500
0
1000
500
- - - UG processing (t)
- - BascCase (OPUG)
Perlotl()·e-..rs)
320
- - - UG capital development (m)
300
· · · · · · · · · Copper Price ($)
- - BaseCase (OP)
...
-50%
_ ..::::--r
-25%
280
260 /
~~0
220
200
0%
% Change in Parameter
-
25%
50%