Ground water quality evaluation near mining area and development of heavy metal pollution index

Opencast as well as underground coal mining are likely to disturb the underground water table in terms of quantity as well as quality. Added to this is the problem of leachates from the large number of industrial waste and overburden dumps that are in abundance in mining areas, reaching the ground water and adversely affecting its quality. Enhancement of heavy metals contamination of the ground water is one eventuality. In the present work, concentrations of 7 heavy metals have been evaluated at 20 important ground water sampling stations at Dhanbad township situated very near to Jharia coalfields. The concentration of heavy metals in general was found to be below the permissible levels although concentration of iron and manganese was found above the permissible limits at a few stations. These data have been used for the calculation of heavy metal pollution index (HPI). The HPI of ground water in total was found to be 6.8860 which is far below the critical index limit of 100 pointing to the fact that the ground water is not polluted with respect to heavy metals in spite of the prolific growth of mining and allied industrial activities near the town.