Environmental impacts of subsidence around the Barapukuria Coal Mining area in Bangladesh

Abstract

Underground coal mining-induced land subsidence has large impacts on different components of natural environment such as changing the morphology of land settlements and soil characteristics, interrupting the hydrologic environment, damaging different structures, disordering the chain of social environment and so on. In view of these consequences, primarily this research recognized and estimated subsidence in field which compared with empirically predicted maximum depth and type of subsidence in the area. Secondly, the current situations of various environmental components were studied under intensive field investigations. From the field, it has observed that more than one square kilometer land settlements subsided with a depth at the center of subsidence is about 1 m. In fact, the depth of subsidence decreased gradually toward the virgin area, hence formed a trough shape structure which is more or less matched with the empirically predicted trough subsidence around the mine. The present noticeable impact of subsidence on different structures such as mud wall, brick wall of house, road, yard, land and others are deformed very slight to slight, and very few cases are severe. In the case of water environment, this study recognized that the whole trough area appeared as a big nonnatural lake/water reservoir where the water quality analysis revealed that major cations and anions excluding pH values are slightly below the standard limit suggested the degradation of water quality; then, water level data analysis reflected that the water level lowered considerably with respect to its previous state. These scenarios also directly or indirectly supported by the soil permeability analysis even as the permeable properties of soil reduced than the virgin area which might be interrupted the natural water recharge condition as a result depleted the groundwater level. Moreover, from the community consultations around the mines, it is realized that the impact of subsidence on social environment is noticeable and tormenting for future. In conclusion, the research provides recommendations for planning and management of subsidence and safe environment which ultimately be helpful for sound production of coal from the mine for present and future.