The objective of the present work was to evaluate the degree of contamination of groundwater in areas under influence of inadequate disposal of residues from coal-processing activities. Charqueadas and São Jerônimo Counties were selected for the study. The contamination of groundwater from the phreatic aquifer was evaluated in a sequence of steps: initially, the target area was selected; then, the piezometers were installed and groundwater was sampled. The location of piezometers was based on the results obtained from the mapping of pollution sources, geophysical and hydrogeological studies. The results showed that the groundwater (phreatic aquifer) from the region studied is influenced, in variables degrees of intensity, by the type and characteristics of residues, the lithological profile of the site and the distance from the pollution sources. Physical and chemical characterization revealed that coal waste influenced more significantly groundwater contamination, evidenced by acidic pH values, as well as high values of conductivity, total dissolved solids (TDS), sulfates, ferrous iron and metals (Ni, Fe, Co, Cr and Mn). The statistical analysis applied to the variables studied gave a General Groundwater Index for each well. By the application of this index, it was possible to highlight the kind of residues and variables that are affecting the groundwater quality.