Recruitment for submarine service is hard. Spending seven weeks or more crammed in a steel tube with about 60 other people isn't the most attractive job out there.
And finding recruits for this work is so much harder when the base is about 3000 kilometres from most of the country's population.
That's the main reason why Australia will establish an east-coast base for some of our eight planned nuclear submarines. The facility will supplement the one we have near Perth that currently supports our six diesel boats.
If Newcastle is chosen, the facility will almost certainly be on the former industrial land at Mayfield or on the south side of Kooragang Island. The Stockton Bridge says so.
The base probably would support at least four Australian submarines plus visiting US and British boats and employ more than 1000 people, including the submarine crews. Supplier companies would set up nearby, too.
In general, the jobs would be highly skilled and well paid.
A Newcastle defence industry is already growing around RAAF Williamtown. With a submarine base, it would surge.
Although Australia's submariners come from all over the country, it's easier to hire and keep people from the area near a base. With a population of just over 2 million, Perth just doesn't offer a big catchment area.
This problem will worsen as we increase the size of our fleet. Also, the nuclear boats will have bigger crews.
A base at Newcastle or Wollongong would have Sydney within its catchment area. Brisbane might offer fewer people, but at least it would be on the more populous side of the country.
Having a base for nuclear submarines in a city means having nuclear reactors there: each boat has one. But the safety record of nuclear propulsion in Western warships is outstanding.
In operating our future submarines, Australia will have to absorb the safety obsessions of the US and British navies, train to their high standards and buy all the necessary equipment. Our allies won't let us have nuclear technology if we don't.
Still, it's easy to foresee political opposition to a new base.
In any possible location, "there will be just as many people who don't want this as those who do want it," says Marcus Hellyer, an analyst with the Australian Strategic Policy Institute.
We're talking big money. Morrison says the base will be part of new submarine infrastructure costing $10 billion. This is partly explained by the exacting standards that must be applied to anything associated with naval nuclear propulsion.
The base will need maintenance facilities and space for at least its own submarines, each 100 metres or more in length. There may be a ship lift for taking the vessels, each weighing at least 7000 tonnes, out of the water.
Training equipment, such as simulators, will be needed, along with an administration centre and warehouses. Facilities for storing ammunition (not nuclear weapons in our case) may also be needed; they can't be too close to residences.
A naval base should not be upstream from a bridge, because air attack - for example, by cruise missile - might collapse the structure and thereby block access to the sea.
Since the government is not likely to pay for a replacement tunnel, this means a Newcastle base would have to be downstream from Stockton Bridge. That limits the possibilities to sites at Mayfield or on Kooragang.
A Newcastle base would have to be downstream from Stockton Bridge.
As the government considers its candidate locations, it will note that Newcastle and Wollongong have the advantage of being close to the surface warships kept at Sydney. These need to exercise with submarines.
Wollongong has the further advantage of closeness to HMAS Albatross at Jervis Bay, the landward home of the navy's helicopters. They're tasked with hunting submarines, so having some home-ported 80 kilometres up the coast would be convenient for practice.
Yet Newcastle is only 260 kilometres from the aviation installation, not at all far by the standards of nuclear submarines, and it has air-defence coverage from the country's biggest fighter base.
Commercial maritime traffic presents problems. At Newcastle there's a lot of it, so the navy might not always be able to come and go as it pleases.
Also, the navy would have to worry about the presence of Chinese merchant ships near a base. It's not far-fetched to imagine an attack launched from an apparently innocent vessel at the outbreak of a war.
Another consideration is whether a fully laden bulk carrier could be thrown sideways and rapidly scuttled in the deep channel of the Newcastle Harbour entrance, blocking it.
Port Kembla's entrance is narrow, too.
Tugs should be able to control a ship attempting to swing off course, but presumably the crews would have to be alert to the danger.
It's hard to see the government wanting to pay financially and politically for a special channel for submarines through the neck of Stockton.
The three cities are the candidates because other population centres can't be. Our submarines generally head north for operations, so Melbourne is an unsuitable choice. Adelaide's location is even worse, and its population is smaller than Perth's.
A base for diesel submarines might have been squeezed into the navy's facilities in Sydney, but that possibility disappeared with last year's decision to switch to nuclear propulsion. Our future submarines will certainly need more room than is available at the current Sydney base, Hellyer says.
Buying more land fronting Sydney Harbour would be madly expensive, and the navy seems never to have considered Botany Bay as a candidate. A lot of it is shallow.
Bradley Perrett is a regular ACM columnist with a focus on Australia's relationship with China, covering defence, strategy, trade, economics and domestic policy. He was based in Beijing as a journalist from 2004 to 2020.
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