ALCOA is planning to increase the capacity at its alumina refinery in Pinjarra.
The mining company has applied for works approval to increase throughput to five million tonnes of alumina per year.
The proposal is for construction to start in the second quarter of 2020 and operations to start in the December quarter of 2021.
The application has been made to the Environmental Protection Authority and it is out for public comment.
A spokesman for Alcoa said the company was in the early engineering and assessment phase of evaluating the potential to increase production at the Pinjarra refinery.
No investment decision had yet been made.
Visit Work Approval Applications.