Assessing the Robustness of Antamina’s Site Wide Water Balance/Water Quality Model Over 5 Years of Implementation

Predicting water chemistry resulting from mining activities is arguably one of the most important aspects of environmental management at mines. The water quality within waste storage facilities presents an especially important consideration in mine planning and the ability to accurately simulate the chemical evolution within such facilities is a major goal for environmental planning.

To illustrate the concepts in development of a predictive model, a water quality model for the tailings storage facility (TSF) at the Antamina mine in Peru is presented. The model is based on fundamental mineralogical and thermodynamic controls and monitoring data from the mine’s regular monitoring and field research programs.

The model has developed as a collaborative effort between KCB and Antamina. The geochemical controls and water balance mechanisms simulate the interaction in the TSF and these are continually calibrated against observed data. This iterative process has resulted in the construction of a robust model that can predict, with confidence, water quality originating from the facility for the life of mine and after closure.

Here we outline the main control mechanisms built into the model and compare these to the observations of the tailings storage facility at Antamina. By introducing ‘stresses’, such as erroneous water flows or large inputs of sulfate, we can demonstrate that the model is robust and able to handle a variety of alternative scenarios. We also use established geochemical modelling software, such as PHREEQC and GWB, to cross-check predicted mineral and geochemical controls and compare the equilibria predicted in these models to those that have been constructed in the Antamina water quality model. The results show that that model’s mechanisms and simulation algorithms are robust and versatile and may be utilised successfully at this mine site but also in a variety of mining waste rock dumps, tailings storage facilities and water catchments.

Tuff, J., B. Harrison, S.Y. Choy, R. Strand, B. Usher. 2015. “Assessing the Robustness of Antamina’s Site Wide Water Balance/Water Quality Model Over 5 Years of Implementation,” in 10th International Conference on Acid Rock Drainage and IMWA Annual Conference, April 20-25, 2015, Santiago, Chile.