Mining under a limestone aquifer in southern Sardinia: a multiobjective approach

Summary

Alternative schemes to develop mining activities and related regional water resources in south western Sardinia are designed and compared from the viewpoint of the following six objectives: (1) to support mining activities under water hazard; (2) to ensure adequate wastewater disposal; (3) to satisfy projected water requirements over a 50 year horizon; (4) to support industrial and agricultural activities; (5) to preserve or improve environmental factors; (6) to be resilient.

Present mining activities do not occur at a satisfactory level because of water inrushes. At the same time, there is an inefficient distribution of existing resources — especially groundwater — as well as water quality problems. In the present study, the system in general, and then the triplet objectives — specifications — criteria, are defined; specifications include mining characteristics, regional surface and ground water hydrology, water requirements for various users in terms of: seasonal volumes and quality, levels of supply, reliability, unit cost and loss functions. Eleven criteria are defined including both qualitative ordinal measures such as quality indices, and quantitative ones, such as capital and operations costs.

Alternative decisions or pure actions may be: to do nothing, to utilize pumped mine water from existing system after treatment, to change the dewatering method so that soft and saline waters are extracted separately, to recharge used waters near the shore to create a pressure wall and thus avoid salt water intrusion, to reuse treated urban wastewater for agriculture and to decrease unit consumption. These pure actions are combined to form ten alternative schemes, which are rated in terms of the 11 criteria defined before.