Decision analysis for limiting leaching of metals from mine waste along a road

A quantitative decision analytical framework is used for a decision characterized by uncertainty, including hydro-geology, environmental effects, investment costs and economically-valued environmental losses. The method is illustrated by assessment of four alternatives for reconstruction of a road section in central Sweden situated on old, metal-rich, mine tailings. The following inputs included predictions of the amount of leached metals; the costs of alternative actions; the possible environmental losses associated with alternative decisions; and uncertainties in the hydro-geological situation. Stochastic simulations are used for predicting the amount of leached metals (zinc). It is found that the removal of the mine tailings was never cost-efficient because of high investment costs combined with a significant probability for the leaching of metals. If environmental losses are valued at the lower end of their range then no protective measures are needed although they are given the highest values then the investment costs introduce ambiguity into the decisions. The greatest uncertainty in the amount of leached metals is due to the heterogeneity of the leachable material.