Mathematical modeling for optimized mine waste rock disposal: Establishing more effective acid rock drainage management

Acid rock drainage (ARD), produced from sulfide-bearing mine waste (e.g., waste rock, tailings) at active and abandoned mine sites, continues to be a global concern due to the significant impacts on water, soil, biodiversity, and the creation of public health risks. Many examples demonstrate that it is technically challenging to control and manage ARD, with common methods including costly additive treatments. Instead, an improved approach to ARD management is to minimize opportunities for generation from the outset. In this paper, a new mixed-integer programming (MIP) model is proposed to optimize the placement of waste rock into waste dumps with the objective of minimizing ARD formation. The MIP model considers the net neutralizing potential (NNP) value of waste rocks and decides about the best place for each parcel of mining waste within the waste dump, regarding the target NNP value. Moreover, the waste rocks' haulage costs obtained from the proposed model were assessed against a recently practiced model (base case). The distribution of NNP value was also simulated in the dump to evaluate neutralizing of the acidity produced by sulfide oxidation in the dump's different parts. Finally, the capability of the model was evaluated in a real case. The results indicate that the safe threshold conditions (e.g. NNP value >= target NNP) are satisfied in dump cells, leading to the optimal disposal of waste rocks and ARD prevention. In addition to the neutralizing advantage, applying the proposed model results in preventing the re-handling of waste materials and reduces the haulage costs by 6.8% compared to the base case. (C) 2020 Elsevier Ltd. All rights reserved.