Mining giant BHP Billiton has filed an application with the federal government to expand tailings storage capacity at its Olympic Dam operation in South Australia.

The company plans to increase the size of the facility from 30m to 40m above ground level.

Planned to be completed by September 2023, the planned expansion will increase the radioactive fluids holding capacity of the dam to 64.8 million cubic metres 48.4 million cubic metres.

Australian Conservation Foundation spokesman Dave Sweeney was quoted by Sydney Morning Herald as saying that the increased volume of tailings storage would probably cause more leakage.

"We see tailings management as one of the big, unspoken problems with uranium mining. It is an unresolved environmental management problem."

BHP said in the application that raising the tailings storage will not increase seepage rates and no additional environmental impact is expected.

The company also claimed that the proposed plan offers environmental benefits such as eliminating the need for an additional tailings cell, which would increase surface area of toxic material.

In November last year, BHP started trialling heap leaching process at the Olympic Dam operation.

The trial will continue for three years to decide on further expansion plans.