Alcoa plans to sell 34,000 acres, surface and groundwater rights, some plant and equipment assets and its power contracts with Luminant, a Texas energy provider.
The buyer, the Lower Colorada River Authority, supplies electricity and manages both water supply and the environment in the lower Colorado River basin.
Aloca's aluminium smelter, which employs around 70 people, and its aluminium powder operations, will be retained by the company.
The deal will be finalised in early 2013.