Port Kembla is firming up as the mostly likely option as the home for Australia's first nuclear submarine base, but it is still far from a done deal.
As well as the port south of Wollongong, the Department of Defence is also considering Brisbane and Newcastle.
All three locations have common features which make them lead candidates for a naval base.
Highly skilled workforce
Dr Paul Di Pietro, the defence strategy lead at the University of Wollongong, said all the candidates had access to a suitable workforce.
Up to 5,000 workers will be needed at the base, according to some estimates.
"All three [sites] have access to a very strong industrial base, they have access to large populations to draw on and a wonderful university," he said.
"Having Garden Island nearby, having HMAS Albatross, having HMAS Creswell means there is already that capability that exists very close to Wollongong."
The Port of Newcastle is also positioned close to a defence facility, the Air Force base Williamtown.
Chair of the Hunter Defence Taskforce Tim Owen said its proximity to the air base offered better protection for the submarines.
He said Newcastle's established defence manufacturing industry may provide a cost saving, if the location was chosen.
Nuclear expertise
Port Kembla is also situated close to Australia's only nuclear reactor, run by Australia's Nuclear Science and Technology Organisation (ANSTO) in Lucas Heights.
Dr Di Pietro said having access to the ANSTO workforce was likely to be a consideration for the government.
"Having a reactor nearby would not be necessary because the subs are fully contained and the nuclear reactor is sealed onto them, but having the expertise at ANSTO would be helpful" he said.
"Expertise in radiation training is going to be absolutely crucial and we have access to that at the university."
Access to deep water
Despite the similar population profiles of the three sites, there are significant differences when considering their geographical suitability.
Port Kembla's Outer Harbour has the easiest access to the safety of deep water.
"In Wollongong's case, we have that deep port as well as access to the Continental Shelf," Dr Di Pietro said.
"It does offer that ability to dive very, very quickly."
Sarah Pavillard, who runs a defence consultancy firm, said this feature could be looked upon favourably.
"We're talking about a stealthy capability, so one of the requirements is for a submarine to move off a wharf and be in a dive as quickly as possible," Ms Pavillard said.
What about Brisbane?
The Port of Brisbane is the only site which has a history of maintaining submarines and was home to 11 US Navy boats during World War II.
Brisbane also has a naval presence at its port, with HMAS Moreton providing administrative and logistical support for visiting naval vessels.
However, University of Queensland civil engineer Dr Alistair Grinham said one of the biggest issues would be the risk of flood and the build-up of sediment that could compromise the subs.
"As the floods come down from the whole catchment, the energy goes from being really confined to being in a big open area and it causes seabed level changes," Dr Grinham said.
"Millions of cubic metres of mud deposited needs to be dredged and that takes months."
Newcastle port ownership
A submarine base at the Port of Newcastle would face an additional challenge in that it is 50 per cent owned by a Chinese company.
When the NSW government privatised it in 2014 for $1.75 billion, China Merchants Port Holdings Company bought a 50 per cent stake.
Mr Owen said he did not believe this would be an impediment, but he said it could be a reason why Port Kembla was emerging as the favoured option.
