Earth Dam Monitoring in the Soil Take Care Project

The Cartagena-La Unión mountain range was the focus of an intense mining activity between early XIX and late XX centuries. Most of Spanish national production of lead and zinc was extracted from its mines. During the ore concentration process, contaminated wastes containing heavy metal minerals, cyanides and sulfates were produced and deposited in earth dams. The Spanish National Institute of Geology and Mining had catalogued 75 earth dams in the councils of Cartagena and La Unión. These deposits pose a potential risk for the environment and nearby populations. Without suitable and precautionary measures, contaminated particles can be transported far away due to the wind action and runoff water, and may be incorporated to the food chain. This risk is increase due to the fact that it is a seismically active area, and breakage of these dams can lead to the dumping of thousands of tons of contaminated wastes. The SOIL TAKE CARE Project is an international project co financed by the European Regional Development Fund (ERDF) through the Interreg Sudoe Cooperation Programme. It aims to improve the management and rehabilitation of contaminated soils in South-Western Europe that includes Spain, Portugal and south of France. The University of Oviedo takes part of that Project by the instrumentation and monitoring of two of those earth dams. Among the work realized so far highlights the perforation of two boreholes and the installation of several sensors. It aims a double objective: to analyze the erosion and infiltration capacity of rainfall into the dams and to detect possible symptoms of slope instability. Although the investigation is still in course, preliminary results shows fast rainfall infiltration into the superficial soil layers, being discharge curves much more extended. This water retention capacity, coupled with the existence of impermeable layers into the dams, could lead to a complete saturation of superficial soil layers and trigger slope instability processes.