As early as 1923 the British Empire began to consider Japan as a potential future threat. To counter this possible threat, the ‘Singapore Strategy’ was developed and put into place, establishing a major naval base in Singapore to protect Britain’s interests in Asia. As part of this strategy, Darwin played a role as a refuelling station for naval ships in the Pacific region.
In 1924, the construction of 11 above-ground oil storage tanks began on Darwin’s Stokes Hill Wharf and by the outbreak of World War II they were ready to be put to use.
The Japanese bombing raid on Darwin on February 19, 1942 caused the deaths of at least 252 people and wounded between 300 and 400, as well devastating Darwin Harbour, sinking 11 ships and destroying military facilities. It also destroyed seven of the 11 oil storage tanks on Stokes Hill Wharf. It became clear that the only safe place oil storage was underground, and engineers soon began looking into British government designs for oil storage.
In 1943, the Civil Construction Corps began work on a series of tunnels dug into the escarpment along Kitchener Drive as part of a project called ‘The Safe Oil Storage.’
Sadly, the tunnels proved to be a failure in both their conception and their construction. When the tunnels were first designed, it was believed that future bombardments by the Japanese would serve to cause the most damage and delays. Instead, it was soft and unstable ground, and water pouring in during the Wet season, along with cave-ins, that slowed the construction of the tunnels to a snail’s pace and caused cost blow-outs. In the end, only five of the planned 11 tunnels were completed. The largest, Tunnel 5, has a 172-metre main storage tank, with two entrances, one of 42 metres and the other 8 metres.
Caption: The 'Neptuna' exploding at Darwin wharf.
PHOTO CREDIT: PETER SPILLETT COLLECTION, NORTHERN TERRITORY LIBRARY
Meanwhile, the Top End remained the target of Japanese air raids, with an estimated more than 70 attacks on the region, from Darwin to Katherine, until November 1943. But by the time the first five tunnels were completed the war was almost over and the threat of bombing had all but disappeared.
The disused tunnels faded into obscurity over the following decades. Tunnels 5 and 6 were used in the 1950s to store jet fuel during a confrontation with Indonesia, in the 1970s the Darwin fire brigade used the tunnels for practice drills, and in 2016 a music festival was held in Tunnel 5. But ultimately, this remarkable feat of engineering was never used for its original, wartime purpose.
But just because the tunnels were unused, doesn’t mean they were forgotten. Over time conspiracy theories began to develop. The fact that the tunnels were never used for their intended purpose, and that they were numbered up to 11 but only five existed, suggested that things weren’t as they seemed. Some people believed the tunnels were used by spies during the war, or that a secret hospital was located deep within one of them. All fun theories, none of which are true.
In February 1992, as part of the 50th-anniversary commemorations of the bombing of Darwin, two of the tunnels were opened to the public and are now a tourist attraction, providing a fascinating insight into one of Australia’s forgotten feats of both civil and military engineering.
Lead Image: Darwin oil tanks aflame in background with pier in foreground.
PHOTO CREDIT: MARYLYN NICHOLS COLLECTION, NORTHERN TERRITORY LIBRARY
Explore more about Darwin’s military history here.