A model for prioritizing sites and reclamation methods at abandoned mines

Abandoned mines present numerous safety and environmental problems due to altered topography and poor management of mine waste. Few guidelines are available for selecting reclamation methods to address these problems, and many existing decision models lack transparency, leave out important parameters and reclamation methods, and/or lack model calibration. Consequently, a decision model was developed that includes: (1) a mine hazard index for prioritizing sites for reclamation, (2) a reclamation method screening table for narrowing viable reclamation methods, and (3) a reclamation method ranking matrix for ranking the applicability of reclamation methods at a site. These three processes form the abandoned mine decision model, optimized for topographic reconstruction and waste disposal at abandoned mines. The hazard index quantifies geologic and hydrologic hazards using measurable parameters, sub-parameters, and a range of sub-parameter conditions. Main and sub-parameter weighting factors were determined using the analytic hierarchy process and Delphi method. Reconciling differences between initial parameter weighting factors for the two methods resulted in an improved decision-making technique. The decision model was calibrated with 25 abandoned metal mines in the western USA. Mine hazard index thresholds were determined for mines having low, medium, and high priority. The screening table and ranking matrix were effective at narrowing the number of viable reclamation methods. Further validation of the decision model was evident by the implemented reclamation method being among the four highest scoring alternatives 80 % of the time. This model provides a quantitative and transparent process that overcomes the deficiencies found in many existing mine reclamation decision models.