THE mining company Rio Tinto will spend $US230 million ($242 million) to expand its iron ore capacity at Dampier Port by 5 million tonnes a year. The investment takes annual capacity in the Pilbara to 230 million tonnes a year in the first quarter of 2012, in addition to the $US91 million allocated earlier this year for a separate 5 million tonnes a year upgrade, which is being implemented. The Rio Tinto Iron Ore chief executive, Sam Walsh, said the capital allocation would boost iron ore supplies and increase the value of its business. ''This investment will demonstrate our ability to bring incremental capacity on line at very low capital cost and without disrupting existing operations or schedules,'' he said. ''Rio Tinto's Parker Point facility at Dampier Port is our single largest and busiest port operation.