Coal Mining and Environment: A Case Study of Dorli Opencast Coal Mines (NIAS/NSE/EEP/U/RR/06/ 2020)
Source:National Institute of Advanced Studies, Bengaluru (2020)
Keywords:Air pollution; Mine Closure; Opencast coal mine; Pit Lakes; Water pollution
Coal continues to fuel more than 72 percent of the country’s electricity generation and is also a vital input for other core industries like steel and cement. However, the coal sector must incorporate social and ecological sensitivities into the mining process from the planning stage up to final mine closure. In this report, the authors present the results of a study on the water and air environment spread over an area of 163 km2 in and around four opencast coal mines in the Dorli - Bellampalli coalfield located in the State of Telangana. This study is based inter alia on the ambient air concentrations and water quality data extracted from the half-yearly compliance reports submitted by SCCL’s four opencast coal mines between June 2012 and September 2019. In this study, the variations in airborne concentrations and water quality before and after stoppage of coal production from these opencast coal mines have also been compared in order to develop policy recommendations as well as areas for future research. In general, the particulate matter (PM10 and PM2.5) concentrations in the buffer zone around the opencast coal mines in the study area are slightly higher than the corresponding CPCB standards (60 and 40 µg/m3, respectively) when these mines are in operation. Therefore, opencast coal mines must implement more effective dust controls during all phases of the mining and mineral transportation processes and also maintain a suitable thick green belt to separate the core and buffer zones. The pH, electrical conductivity, and total dissolved solids values in the water samples exceed the pre-mining values but are within the prescribed BIS/CPCB limits. The dissolved oxygen values indicate optimal levels of aeration in the surface water. Pit lake systems evolved from open-cast coal mine voids have the potential to be a more cost-effective, environment-friendly and beneficial option for coal mine closure as opposed to the current mandate of backfilling the final void by re-handling the previously excavated and vegetated overburden dumps. According to the designated best use classes specified by the Central Pollution Control Board, the water quality around the opencast coal mines studied indicates the probable use of water for drinking (Class C) after adequate tertiary treatment, Class D for propagation of wildlife and fisheries, and Class E for irrigation. Therefore, it is possible to transform these final voids into water reservoirs for the benefit of the local communities by implementing a scientific approach to the design and management of pit lakes.