Analysis
No one has published a risk assessment of what Westport’s container port would mean for the nuclear submarines operating across the water from it. Two reports published by The West Australian on the 7th of October, 2026 show why that gap grows more serious every month.
The reports set out what Australia is building at Henderson, on the mainland shore of Cockburn Sound, and why the submarines it is buying from the United States cannot arrive until a new floating dry dock there is ready. Neither mentions Westport. Read alongside the campaign’s earlier reporting, they describe an AUKUS submarine program being built around a route that Westport’s shipping channel would cross, with no assessment of what happens where the two meet.
The Ask
This campaign asks the United States to conduct a security risk assessment of the proposed Westport container port and its potential interactions with AUKUS operations in Cockburn Sound. That assessment should cover submarine movements, naval operations, commercial freight traffic in Western Australia, and security in the sound. Every development below adds a question it would need to answer.
Henderson Is Now a Precondition for AUKUS
In late July, the federal government selected Leidos Gibbs & Cox Australia to design the floating dry dock. Deputy Prime Minister and Defense Minister Richard Marles and Defense Industry Minister Pat Conroy called the contingency dock “a pre-condition for Australia to receive its first Virginia-class submarine.”
The ministers said the dock would handle critical repairs and maintenance on the Royal Australian Navy’s nuclear submarines from the early 2030s, and heavier depot-level work, including major refits, from the late 2030s. Leidos says the first phase of a functional design is due by mid-2027.
The reason it comes first is safety. A nuclear submarine that is damaged, or needs work that cannot be done at sea or alongside, has to be lifted out of the water, under standards the United States set decades ago. The planned dock is sized for future Virginia-class and SSN-AUKUS boats expected to exceed 10,000 tonnes, about 11,000 US tons.
That makes the route to Henderson part of the safety case for the whole program. Whether that route stays clear is a question for a risk assessment.
An AUKUS Facility, Open to the US Navy
Henderson is not only for Australian boats. Explaining the A$12 billion committed to the precinct in September 2025, Marles said that for submarine maintenance “it is an AUKUS facility,” and that he fully expected it to be available to the United States.
From 2027, up to four US submarines and one British submarine are due to make regular, lengthy visits to HMAS Stirling on Garden Island under Submarine Rotational Force-West. HMAS Stirling will be the operating base and handle in-water maintenance. Anything that needs a boat out of the water goes to Henderson.
American submarines will be making that trip. The United States has a direct interest in knowing what they would be crossing.
Where the Two Projects Meet
HMAS Stirling is on the western shore of Cockburn Sound. Henderson is on the mainland to the north. Westport would build an automated container terminal at Kwinana, further south on the same mainland shore, about six kilometers, or 3.7 miles, across the water from the base.
A submarine moving between Stirling and Henderson crosses the sound. The shipping channel serving the new Kwinana port runs down that same water, so the two routes intersect. The geography is set out in full on The Threat, and The Scenario walks through what a single incident there could look like.
A damaged boat heading for the contingency dock is the vessel that most needs a clear path, and it would be crossing a channel where traffic is projected to more than double, almost entirely on foreign-flagged ships. Those figures are sourced from The Evidence. No one has studied that crossing in public. A risk assessment would.
Two Plans, One Body of Water
Both projects are being planned in the same few kilometers of seabed. Bechtel Infrastructure Australia is drawing up a master plan for the Henderson site, and AECOM Australia is running more than 20 environmental and marine studies across Cockburn Sound. In 2024, the federal parliamentary committee on public works noted the precinct would require dredging in sensitive ecosystems around Cockburn Sound and Garden Island.
Westport has its own program. Its federal referral estimates capital dredging of up to 35 million cubic meters and a second main channel about 21 kilometers, or 13 miles, long, as our report on the sound’s single entrance set out.
Neither report describes any study of how the two programs interact. That is the gap a risk assessment would close.
The Timelines Overlap
The A$12 billion was described as a down payment, and The West Australian reports the full Henderson build-out could reach about A$25 billion over the next decade. In August, the federal and state governments fixed the boundary of the nuclear submarine maintenance zone. “AUKUS is full steam ahead,” Prime Minister Anthony Albanese said.
The dry dock is meant to be operating in the early 2030s, when Australia takes its first Virginia-class boat. Westport’s business case puts the government investment at A$7.2 billion, and its channel construction could run for up to 15 years. The submarine crossing gets busier in the same years the port would be built and filled. An assessment done now can still shape both plans. One done later can only describe them.
The Record Keeps Pointing the Same Way
The Henderson reporting is the latest in a run of evidence that points to the same missing assessment.
In August 2025, two retired Australian officers, Air Vice-Marshal John Blackburn AO (Retd) and Commodore Vince Di Pietro AM CSC RAN (Retd), recommended that the Minister for Defense seek formal assurance on the rigor of any risk assessment conducted since AUKUS was announced. No public answer has been recorded.
In September 2026, a former Army intelligence officer warned that the submarine base has one way in or out, and Westport’s own federal filing called it the sole channel. US officials have separately alleged that Chinese cargo ships gather intelligence off military coastlines. Former officials and experts who have weighed in are collected on What They Say.
Now Australia’s own ministers have tied the first AUKUS submarine to a dock on the far side of Westport’s channel. Each piece raises the stakes. None of them has been answered with an assessment.
Why Washington Has a Stake
Under AUKUS, the United States is to provide Australia with three Virginia-class submarines, and Congress authorized those transfers through the NDAA, the National Defense Authorization Act. The West Australian notes that one open question over the plan is whether the US can afford to sell the boats without leaving its own Navy short.
American taxpayers are funding a submarine presence in Western Australia, and American boats are expected to use Henderson. The location of the Kwinana port was a state decision made before AUKUS existed, as The Evidence documents. The United States is entitled to understand the risk its submarines would be sharing that water with.
What a Risk Assessment Would Answer
- Submarine movements: Has anyone modeled container traffic crossing the route between HMAS Stirling and the Henderson dry dock, including a damaged boat bound for contingency repair?
- Naval operations: How would a blockage at the single entrance, or at the crossing, affect US and Australian boats operating from Stirling and Henderson?
- Commercial freight traffic: What happens to Western Australia’s container supply chain if naval activity closes or restricts the channel serving the Kwinana port?
- Security in Cockburn Sound: How would foreign-flagged ships be screened before entering water beside the base and the dock, and have Henderson’s marine studies and Westport’s ever been compared?
Take Action
Australia has made Henderson a condition of receiving American submarines, and the route to Henderson crosses Westport’s shipping channel. No one has assessed that risk in public. Call your representative and your senators and ask them to support a risk assessment of what the port means for the base, the dock and Western Australia’s freight supply chain. Visit Take Action for everything you need to make that call.
Editor’s note: This site is sponsored by the Maritime Union of Australia, WA Branch. The reporters cited have no connection to the campaign.
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