Adani had originally planned to construct a 388km standard-gauge line between the mine and the port, but has now opted for a 1067mm-gauge link, approximately 200km long, at an estimated cost of $A 1bn ($US 717.9m). The new line would connect with Aurizon’s existing 1067mm-guage Goonyella and Newlands open-access rail networks.

“By connecting to the existing network, we can leverage the existing infrastructure to fast-track project delivery and reduce capital expenditure,” Adani Mining chief executive, Mr Lucas Dow, said in a statement on September 13. “We’re 100% committed to getting the Carmichael Project off the ground.”

The company said its Plan B solution would follow the same route, enabling it to use existing approvals and land use agreements.

Adani says the narrow-gauge link would have the same 40 million tonne per annum (mtpa) capacity as Stage 1 of the previously proposed standard-gauge route, which would easily cater for Adani's plans to extract 27.5mtpa from the Carmichael mine.

Trains would consist of three locomotives and 120 wagons as opposed to the three locomotives and 220 wagons envisaged for the standard-gauge route.

The Carmichael mine project has faced fierce opposition from environmental groups and while pre-construction works continue, the project has struggled to gain the necessary finance needed to proceed.