The Bolivian Ministry of Sustainable Development and Environment requested technical assistance to assess the environmental
damage and risk from the spillage of toxic materials into the Pilayo and Pilcomayo river system. This was caused by the breach of the retaining dam of a mining waste lagoon at Porco and led to pollution of the waters by various toxic heavy metals. Much of the pollution was deposited along the upper lengths of the river system which drains into the Rio Plata and hence into the south Atlantic.
The Bolivian Ministry requested a fisheries expert to look at related aspects of the problem. ODA required a fisheries expert to join a four person team. The objectives of the study were to assess the extent of the environmental damage already done, the current risk and the likely future risks from seasonal changes in river flow rates. In particular, the effects on the fish population and possible consequent dangers to the human population were assessed.