PT Indo Rak Resources (RAK), a subsidiary of Middle East Coal and a joint owner of the Marwa Wahau deposit along with PT TOP, commissioned SRK to undertake a feasibility study of the property. The thermal coal greenfield project, sitting over a large resource, is poised to be one of the biggest open-cast projects in Kalimantan.
It is located in the District of Marwa Wahau, Kutai Timur, East Kalimantan, Indonesia. Of the two blocks, North and South, the North block is thoroughly explored. The workable S2 seam has a reported JORC resource of around 500Mt; the coal is known to extend into the South Block.
Beginning in 2008, SRK assisted RAK in evaluating the deposit with an independent audit of its exploration data and reported resources. Following that study, SRK joined SMGC, a geological consultant from Jakarta, in advising RAK.
In March 2009, SRK started a scoping study of the North block using the geological models and resources prepared by SMGC. The study used comparative methods of scope definition and cost estimating.
The current 2009 report estimates the total geological resource to be 937Mt within the North block. Only measured and indicated resource categories were applied to estimate potentially mineable coal, forming the basis of mine planning and economic evaluation. An early interpretation of slope stability and a basic understanding of groundwater conditions was completed by others.
The pre-feasibility study defines an open-cut strip mining operation utilising conventional truck and shovel equipment for overburden removal, Continuous Surface Miner for coal mining and waste backfilling to maximise in-pit dumping thereby ensuring minimal environmental disturbance. The method divides the coal block into longitudinal strips of similar width from one end of the block to the other. Once coal is removed from one strip, it is backfilled with the waste rock generated from the next strip.
This method is most apt for areas with flat terrain and low dipping coal seams with long strike length. It facilitates early backfilling, reduces the need for external dumps, improves environmental outcomes and promotes progressive rehabilitation.
The mine is planned for 21Mt per annum with a project life of 19 years. The quantity of open-pit mineable coal from the North block is estimated at 388Mt at a life-of-mine stripping ratio of 1.42:1. No inferred category resources were included in the calculation. SRK evaluated different mining technologies and selected the preferred option. SRK has also planned for the mine and support infrastructure for the target capacity.
Based on this work, SRK recommended that the project proceed to a definitive feasibility study.
