The rising of groundwater level in the “metalliferous ring” of Iglesiente Mining District (SW Sardinia – Italy) (Am04036)

The important mine district of Iglesiente, in the SW of Sardinia Island (Italy) count a number of shafts where lead, zinc and silver ores are mined. The ores occur in a carbonate rock complex of the Lower Cambrian highly folded and faulted with the remobilization of the mineral deposits and the development of various karst cycles. In this highly permeable complex flow large quantities of groundwater that posed serious problems for a modern mining activity since XIX century. Several dewatering plants were realized in time at various levels below the sea level. Being almost exhausted the mineral while working dewatering plant al -100 m below sea level, discharging 1.35 m3/s of high chlorined water, the hydrogeologic problem was studied at the whole with the economic support of EC. A new dewatering plant at – 200 m bsl was planned and start in 1985. Unfortunately, the prices of the lead and zinc fell down in the early 2000 and were taken the decision to close all the mine activity. When the dewatering plant was turned off, in all the mining district the groundwater began to rise. A number of electronic gauges putted into several shaft have measured the draw up, together with the main hydrochemical parameters. This paper summarized all the data and observation about the complex phenomena happened during the rise up, with the hope to provide a useful precedent for the number mining activity with the same problems all wide the world.