The bottleneck is the low draft barging from the mine to the transfer port with shallow draft barges.
-At this stage we don't know what the minimum dept of the river is (how shallow draft the barge has to be)
-Is a special shallow draft tug(s) needed? (some Vietnamese low draft sand barges are self propelled)
-What time is the return trip of the shallow draft barge likely to take? (incl load/unload)
-What is the capacity in tons of the shallow draft barge?
We know that a floating body displaces its weight in water.
We know that a Cu/M of coal is 1.1 ton approx
We know that a Cu/M of water is 1 ton
Now this is pure speculation due to no data being available:
If the safe water depth of the reaches of the Barrita is say 2 meters, then the height of load should be safely 1.5 meters
So lets say that the barge is 10m W x 30 M L then it could carry about 450 ton
3 of these chained together would give us say 1500 ton
If the round trip is say 4 days, then this would pan out at about 11,250 t/p/m or about 130K t/p/a.
It would require 8 of these, IMO, to deliver 1 mil/t/p/a.
Perhaps some "Coalies" or engineers could comment?
NB: The key to all this is the minimum depth of the river which at this stage is unknown to shareholders.
