Trans Alta Dawn Farrell 20140429

The power plant will be TransAlta's seventh in Australia. (Larry MacDougal/Canadian Press)

TransAlta will build a natural gas-powered power plant in Western Australia in a deal worth $580 million, the Calgary-based company says.

TransAlta said Monday it will build and operate a 150-megawatt plant in South Hedland, in Western Australia, which will sell electricity to the local utility, Horizon Power, and to a large iron ore mine in the area.

The deal includes a plan to sell power to both its main customers for the next 25 years, but could be expanded to include new customers, TransAlta said.

The plant will be up and running by 2017, and includes a plan to purchase some existing assets from Horizon.  The plant is expected to create 250 jobs during construction and 20 once it's up and running.

It's part of the company's goal of expanding its footprint in Australia, having set up shop in the country in 1996.

"By focusing on serving large industrial customers, we've now been able to invest close to a billion dollars in Australia in assets with stable long-term contracts," said CEO Dawn Farrell in a release.

Currently, TransAlta already owns six power plants in the country, with a combined output of 425 megawatts.