Mining giant Rio Tinto is planning to invest a further $US790 million to expand its iron ore operations in Western Australia's Pilbara region.

The aim is to expand the capacity of iron operations in the Pilbara to 330Mt/y. The expansion is centred on increasing capacity at its Cape Lambert port from the current 80Mt to 180Mt by 2016.

The miner will construct a new 1.8km jetty and a four-berth wharf to run parallel to the existing jetty.

The latest investment includes $US375M on marine works related to the construction of the new wharf and a further $US415M for the procurement of long lead items such as pile and marine structure, on shore earth works and machines.

Rio Tinto had already announced $US200M worth of dredging works for the Cape Lambert expansion last month.

Rio Tinto’s chief executive for iron ore and Australia Sam Walsh said a key aim was minimising disruptions on existing operations and production schedules.

The miner said early construction works were dependent on government and other approvals with a final investment decision expected by the end of the year.

The ramp up to 330Mt/y would be in a number of steps:

225Mt/y by Q1 2011 through Dampier port systems efficiencies.

230Mt/y by Q2 2012 through Dampier port incremental gains.

280Mt/y by H1 2014 through the first stage of the second Cape Lambert jetty.

330Mt/y by H1 2016 through the second stage of the second Cape Lambert jetty.