NRW Holdings has officially been awarded the rail earthworks contract for the Roy Hill project.
It received a Letter of Intent to subcontract the works in late August, and was authorised to start work, although work was capped at $20 million at the time.
It now has the full construction contract for the rail formation for the main line between Roy Hill and Port Hedland.
The scope of the works, which are valued at around $620 million, include construction of approximately 330 kilometres of main line heavy haul rail formation together with sidings and level crossing and associated works.
Overall the works will involve the moving of approximately 10.5 million cubic metres of material.
Work has begun already and scheduled for completion in January 2015.
At its peak it will employ a workforce of 1500 people.