Caracterização hidrogeológica ambiental da áerea de influência da mina Lapa Vermelha, na região cárstica de Lagoa Santa, MG

Abstract

This study consists of the hydrogeologic environmental characterization of the influential area of the Lapa Vermelha Mine located in the karst region of Lagoa Santa, in the State of Minas Gerais, Brazil. In operation since 1976, the mine, which belongs to the Sociedade de Empreendimentos Industriais Comerciais e Mineração SOEICON S. A., extracts the calcareous rock in an open air mining area, whose current pit is of 735 meters. In 1992, when the water level of the carbonatic aquifer was reached, the downdrawing activities of the water table began. To realize this study, some initial tasks were carried out aiming the gathering of specific information (e.g. topographical, geomorphological, geologicalstructural and hydrogeological field researches; water balance) to characterize the main conditioning factors of the aquifer system considered. Once these tasks were completed, it was possible to propose a conceptual hydrogeological model, in a regional scale,which allowed the creation of a computational hydrogeological model capable of describing the hydrodynamic behavior of the groundwater in the circumscript area of the Lapa Vermelha Mine mining area. For so much, the Visual ModFlow was used as auxiliary tool, being the karst area study approached as an equivalent porous medium. Based on the hydrogeological model proposed, the hydrogeological and hydrological impacts that had already been caused by the mining activity in the MinaLapa Vermelha Mine were analyzed. And also the impacts that may be provoked by the drawdown of the water table, in this mine, to the point of 680 meters were evaluated. The results of the simulation of the computational hydrogeological model, obtained with the use of the software Visual ModFlow, suggest that the current digging activities have not yet impacted significantly the carbonatic aquifer in the region.Parallel to this, we register that when the mining in the Mina Lapa Vermelha deepens to the point of 700 and 680 meters, some karst sources of the region will have their outflow suppressed, as well as will the Lagoa Santa have a reduction of approximately 6 centimeters of its water surface height.