The 17-year power agreement, which extends from the existing contract, will take effect on 1 November 2011. The plants to supply the power are at the Rocky Reach and Rock Island dams.
The international aluminium producer said that the deal would also enable it to increase production at the smelter by 42,000 tonnes per year, or 42%, to 142,000 tonnes per year.
Alcoa’s announcement of the planned production boost followed approval of the power supply contract by Public Utility District (PUD) Number One of Chelan County, Washington state. The contract terms have yet to be finalised, Alcoa added.