Proposed Phulbari Open Pit Mine
Asia Energy confirmed the resource of 572 million tonnes of high-quality bituminous coal in Phulbari basin. The study also established that open pit mining is the only economically and technically viable option to extract this coal resource.
The proposed Phulbari mining area is approximately 8 kms long in north-south direction and 3 kms wide in east-west direction. Total coal seam thickness varies between 15-70 meters in some 150-270 meters beneath the surface. The coal deposit is overlain by approximately 160 meters of Tertiary sands, silts, gravels and clays, and Permian sediments.
It was established through comparative analysis, and alternative methods study that underground mining at Phulbari is unsafe and uneconomic. Maximum 20 percent or less resource can be extracted in this method which will make the Project nonviable and also a loss of valuable resource of the country. The experience of underground mining in similar geological situation is also very disappointing.
The existing geological and hydrogeological conditions of Phulbari region and other technical limitations offer open pit mining as the acceptable solution. It is the most economic and safe way of extraction of Phulbari coal resource. The method allows extraction of 90 percent or more of the coal including some valuable co-products like kaolin, glass sand, and rock and aggregates economically.
Mining will commence with an initial box cut in the north of the coal basin and progressively move south. The initial open cut mine, including the pit area, associated facilities and infrastructure will cover an area of about 2,000 hectares. The Mine will require a total of 5,192 hectares for the mine and associated infrastructure over the entire life of the mine. Initially the overburden materials will be placed in the ex-pit dump east of the mine. About 25 percent of the overburden materials will be placed in the ex-pit dump area. The mine will advance southerly with an approximate annual rate of 200 meters, and progressive backfilling of the pit after coal extraction will commence within about six years of construction. It is estimated that about 70 percent of the overburden materials will thus be placed in the in-pit dump. In the process of moving mine face from north to south, coal will be extracted removing overburden materials and mined out land will be backfilled progressively. The backfilled mine pit area and overburden dump area will be progressively reclaimed and rehabilitated as part of Mine Closure Plan and put back to productive uses including agriculture.
At full production, the mine will produce annually 15.2 million tonnes of coal over its 35+years mine life. At the end of the mine life a final void (696 hectares will be left approximately after three decades) which would be turned into a freshwater lake to be used for water supply, irrigation, recreation and aquaculture.
Land Rehabilitation
The open pit mining is a temporary change of land use, and the land is continuously rehabilitated back to productive uses. Phulbari Coal Mine, over its 35 plus years life, will progressively use a total of 5,192 ha of land. Rehabilitation of mined land will start immediately after coal extraction, and systematically put back to productive uses, mostly for agriculture and forest, except for a 696 hectares freshwater lake.
Prior to any mining activities, the top 2m of soil (topsoil) will be stripped off separately and preserved under special care. After coal extraction, the mine pit will be progressively backfilled and rehabilitated with the stripped off topsoil being re-laid onto the surface of the reclaimed land. This will help reconstitute soil profiles and support self-sustaining vegetation. Subject-matter specialists will be engaged to oversee the land rehabilitation process and back the land to productive uses.
The general sequence of rehabilitation will be as follows:
removal of various layers of material i.e. topsoil, clay, sand, and hard rock from the area to be disturbed;
placement of the various layers of material to the ex-pit or in-pit overburden dumps;
shaping surface to design levels and contoured to minimise erosion and runoff;
placement of a clay sealing layer over required areas;
placement of a top-soil layer;
revegetation with agreed combination of cereal crops, fruit or timber trees, and native vegetation; and
ongoing maintenance, monitoring and management of the rehabilitated area.
Restoration of mined land is widely practiced around the world and there are many examples of green fields, forests, industrial units, recreational facilities and even airports on top of what used to be open pit mines. With appropriate measures, the reclaimed land, under favorable climatic condition like Bangladesh can be made available for productive agricultural uses within 3-5 years of coal extraction.
The Project final landform after rehabilitation will be a balanced mix of agriculture (43%), forest (33%), water bodies (12%) and settlement (11%).