The Sounds of Accumulation, page-394

In fact the Maruwai Basin (tops of mountains) LOL and surrounding areas, are the only Coking Coal in all of Indonesia other than some poor quality SSCC in Papua.
Adaro bought the 7 CCoWs that contain 80 to 90% of that coking coal.
The most economical way to get coal out of the Basin is via combination Rail and Barge operation.
Rail lines can go East to Melak and Barge down the Mahakam River. BHP determined this to be the lowest cost and most reliable route.
Rail south to around Adaro's thermal port on Barito River (Kelanis). 12,000 tonne barges from there 100% availability.
Rail south to Kapaus River 100% reliable
Rail East to Balikpapan {no barging) but very challenging swamp land and mountains.
All of these have had studies completed and costed.
Would be great for likes of Cokal to jump on any of these routes but the ones south would be best.
JUST FOR INTEREST I put some names in so you can google.