BHP Billiton plans to run a trial of drawing water from a hypersaline aquifer below its proposed open pit expansion of the Olympic Dam mine in outback South Australia.

A 25-kilometre pipe has been installed north of Roxby Downs to remove water from below the mine site and inject it into a nearby aquifer, instead of letting it run onto the ground.

If the mine expansion is approved, the saline water would be extracted and used for tasks including suppression of dust.

Anita Poddar, for BHP Billiton, says without access to the aquifer, the company would have to look for other water sources, such as more desalination or water from the Great Artesian Basin.

"It's good that we don't have to use that water and obviously it's a better environmental alternative," she said.

The proposed trial has government backing and has been discussed with the Arid Lands Natural Resources Management Board and the Pastoral Board.