Hill to Hill transmission line: D&C, BOOM and connection arrangements for BHP’s Prominent Hill project

Piper Alderman advised ElectraNet, South Australia’s electricity transmission network owner, on a new high voltage transmission line to supply the Prominent Hill copper and gold mine in the state’s upper north. At the time Prominent Hill was owned by OZ Minerals, which was acquired by BHP in 2023, and the mine now forms part of BHP’s Copper South Australia business. Our mandate covered two distinct workstreams: ElectraNet’s commercial arrangements with OZ Minerals as its customer, and the contract for the delivery of the works.

Prominent Hill had relied on shared access to BHP’s transmission line from Davenport to Olympic Dam, and BHP gave notice that this access would end in August 2020. OZ Minerals needed a new grid connection, independent of BHP, in place before then.

BOOM and transmission connection arrangements with OZ Minerals. We advised ElectraNet on its build, own, operate and maintain (BOOM) arrangements with OZ Minerals, under which ElectraNet would build, own, operate and maintain the new line, and led the development and negotiation of the transmission connection agreement connecting Prominent Hill to the South Australian grid.

Design and construct contract with CIMIC’s UGL. We advised ElectraNet on its approximately $180 million design and construct contract with UGL. Under the contract, UGL designed, constructed and commissioned the switching station infrastructure and approximately 300km of high voltage transmission line. This comprised 275kV line from near Port Augusta to an expanded Mount Gunson South substation, and 132kV line onwards to connect with the existing line to Prominent Hill.

The new line began operating in 2020, replacing the BHP supply arrangement. ElectraNet’s then Chief Executive, Steve Masters, described it as the largest project ElectraNet had undertaken to date. The line also created new capacity in the region, with Mount Gunson South providing a connection point for the Carrapateena mine.

What our Client said

The ElectraNet team said:

“Piper Alderman’s support to the ElectraNet team, combined with legal leadership in developing and negotiating the transmission connection agreement between ElectraNet and OZ Minerals, proved invaluable in achieving a successful outcome for all parties. The Piper Alderman team integrated themselves seamlessly and were prepared to go the extra mile when needed. It was a pleasure to work with Martin and his team over the last six months. Their professionalism, commercial-mindedness, tactful approach, attention to detail, flexibility and availability make them a trusted advisor to ElectraNet. We look forward to working with Martin and the Piper Alderman team on future transmission connection opportunities.”

Piper Alderman Partner, Martin Lovell, said:

“This transmission infrastructure not only provides an end-to-end network solution for OZ Minerals’ Prominent Hill, but also presents opportunities for future load and generation projects in the upper north region of South Australia. It’s great to see the ElectraNet team working with industry to deliver such significant contestable works in a competitive market.”