The inappropriate management of mine wastes such as tailings and waste rock has large implications for environmental impact and costs. Geochemical models can be very useful tools for assessing management options for waste disposal and the associated environmental implications. Models can be used to assist in the understanding the physical and geochemical processes occurring within mine wastes under various scenarios. They can be used to examine the current state of acid generation; predict future contaminant loads and concentration profiles; assess future treatment requirements; compare management and decommissioning options, and support costing studies. Our geochemical models have been used to provide long-term predictions of potential contaminant levels for assessment of bonding requirements for decommissioning, and for permit applications.

We have developed several mathematical computer models that can be applied to predict the long-term geochemical behaviour of tailings (acid-generating or alkaline), waste rock, and entire mining regions (open pits, underground mines, backfill, etc.). As appropriate, we use both deterministic and probabilistic geochemical modelling to characterize the source of the contamination and to examine options for reducing contamination at the source. Probabilistic modelling is a useful tool for investigating uncertainties in waste characterization, acid generation, and contaminant transport.

Each mine site and operation is unique, and the selection and use of the appropriate geochemical model is an important decision that will shape both the scope of the work and determine the nature of the predictions. With more than 15 years of direct hands-on experience, SENES can determine which programs are most suitable to a client's project needs. We have been involved in the development and application of predictive models for acid mine drainage investigations since the mid 1980's, with the development of the Reactive Acid Tailings Assessment Program (RATAP) for the Canadian Centre for Mineral and Energy Technology (CANMET) of Natural Resources Canada (NRCan), as part of the National Uranium Tailings Program (NUTP).

We are familiar with the various conventional equilibrium, thermodynamic, "off-the-shelf" models such as MINTEQ and PHREEQUE. However, specialized models are necessary to assess kinetics (e.g. sulphide oxidation, mineral dissolution), and to simulate the long-term geochemical behaviour of mine wastes. Therefore, SENES has developed several proprietary mathematical (computer) models that have been applied to predict the long-term geochemical behaviour of acid-generating or alkaline tailings, waste rock, and entire mining regions consisting of open pits, underground mines, backfill, etc.