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The company behind one of Australia's biggest sources of oil and gas is planning the removal of about half of its platforms, but environmental groups are concerned it will create a toxic dump in a vulnerable wetland.
The Gippsland Basin Joint Venture in the Bass Strait has produced more than half of Australia's crude oil and liquids, and has supplied about 40 per cent of eastern Australia's natural gas since the 1960s.
More than 50 years later, ExxonMobil Australia's subsidiary Esso is planning to decommission its non-operational rigs.
Its facilities are between 12 and 87 kilometres from the coast and are at water depths that range from 38 metres to 402 metres.
So how will they be removed and how will it impact the Gippsland community and environment?
Which structures are being removed and how will it be done?
About half of Esso's Bass Strait facilities are no longer producing oil and gas including 10 platforms, 16 pipelines, and half of the wells drilled.
Esso plans to remove up to 10 steel piled jacket platforms and two monotowers in its decommissioning.
It is proposing to remove all steel platforms down to a depth of 55m below sea level, or at the seabed, "depending on the water depth at each location".
"[This] strikes the right balance between safety of navigation and preserving thriving marine ecosystems which have developed around the jackets," an Esso spokesperson said.
"The steel piled jackets are 98 per cent iron and do not contain any mercury, lead, cadmium, asbestos, or naturally occurring radioactive material.
"The majority of our structures are completely covered in marine life, which is in turn providing a habitat and a source of food for over 55 species of fish and larger marine fauna such as seals and sharks."
Deakin University hazardous materials management senior lecturer Dr Trevor Thornton said decommissioning would involve identifying, extracting, and labelling the hazardous material that would then be sent to a treatment facility.
"You've got to do it in a way that there's going to be no spillage," he said.
"Being on land or even in the ocean it's very important to do so. The techniques are well-established but it's just making sure that they're followed."
When will removal commence?
Esso has committed to begin removal before September 30, 2027, and is making regulatory submissions to fast-track the process.
A contractor was nominated in January this year to remove up to 12 offshore platforms from Bass Strait in late 2027 and transport them to the nearby port at Barry Beach Marine Terminal (BBMT), which sits off the Corner Inlet and is a Ramsar site.
"We have already safely completed over $1 billion of decommissioning work across our offshore operations, including the plug and abandonment of over 100 wells," an Esso spokesperson said.
What are the environmental effects of decommissioning?
Environmental groups have been calling for the removal of the structures from the Gippsland Basin for years due to concerns about hazardous material polluting water.
The facilities in the basin were built and installed in the 1960s and Friends of the Earth offshore fossil gas campaigner Jeff Waters said they were filled with asbestos and radioactive material.
Mr Waters said Esso's plan was to build a "massive, toxic dump" in the middle of a United Nations-listed wetland.
"Bringing all of this hazardous waste including hydrocarbons and mercury and lead … up on to the beach only a few centimetres above the waterline and storing them there for years while they're broken down," he said.
"[It] threatens the nature of the wetland and threatens to spread toxins through the area.
"It will certainly change the character of the area, of the Ramsar wetland, which might bring Australia under international scrutiny."
Friends of the Earth is calling on Esso to instead transport the decommissioned oil and gas platforms to an alternative site in Geelong.
Dr Thornton said Esso should reconsider whether the chosen site is appropriate.
"The process for [decommissioning] is ... relatively safe, unless something goes wrong," he said.
"And if something goes wrong then you probably won't want them in that Ramsar area because the damage it's going to cause is going to be quite significant.
"In my view you would be looking at somewhere that, if something goes wrong, it's going to have minimal effect on the environment, if at all."
Esso says materials are safe
The Esso spokesperson said returning the offshore facilities to BBMT, where they were built in the 1960s, was safe and would benefit future industries.
"No part of any of the structures will come into contact with the water at Corner Inlet," the spokesperson said.
"The platform structures being transported back to BBMT for dismantling are over 95 per cent steel, all of which is planned to be recycled.
"All dismantling activities will be completed responsibly in full compliance with environmental regulations and in a timely manner."
They said the company continued to make the required regulatory submissions so that removal activities could begin as soon as practicable.
"Steel proposed to remain to support the ecosystem contains no hazardous or toxic material," the spokesperson said.
How can the decommissioned rigs be repurposed?
The structures being decommissioned include 60,000 tonnes of steel which could be used in the manufacturing of offshore wind equipment for the Bass Strait.
Esso suggests BBMT could support the maintenance of turbines in Gippsland's offshore wind zone.
"The existing site can safely accommodate both ongoing offshore support and onshore recycling, and importantly, dredging is not required," the Esso spokesperson said.
What will it mean for the Gippsland community?
The decommissioning is expected to create about 100 jobs to prepare and execute onshore recycling activities.
Committee for Gippsland CEO Tony Cantwell said the decommissioning would increase employment locally in South Gippsland and the lower ends of the Wellington Shire while attracting investment in port development.
"By employing people locally you potentially put kids in local schools, you might bring a partner or a family member with a job into the region," he said.
"I think it's probably a good opportunity to look at developing and investing in Gippsland ports rather than just seeing the opportunity go to other areas.
"As the region undergoes an energy transition there'll be employment opportunities in clean energy projects."
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