Simultaneous stochastic optimization of production scheduling at Twin Creeks Mining Complex, Nevada

Twin Creeks is a gold mining complex part of Newmont’s Nevada Operations. The mining complex is comprised of two open pits, Mega and Vista, external ore sources and a set of existing stockpiles, all providing ore for an autoclave, an oxide mill and a heap leach. Mega pit provides sulphide ore for the autoclave whereas Vista pit provides oxide ore for the oxide mill and the heap leach. Both pits operate the same mining equipment and therefore their extraction sequence must be optimized simultaneously. Stringent blending requirements are associated with the operation of the autoclave for the sulfide ore. Strategic blending optimization at large scale has brought significant value to the operation by increasing synergies. This paper presents the implementation of a stochastic optimization framework for the long-term production planning at Twin Creeks that simultaneously optimizes mining, stockpiling, blending and processing decision variables. The uncertainty and variability associated with the different sources of material is incorporated in the optimization model by means of stochastic simulations. The stochastic solution generated shows substantial potential benefits by increasing expected recoverable gold, leading to increased expected cash flows, while reducing the risk of not achieving the forecasts by increasing the probabilities of meeting production and blending targets.