Rare wartime underground fuel storage facility in Marsiling to undergo extensive study

SINGAPORE – Nestled in a 12.5ha forested patch in northern Singapore is a graffiti-ridden concrete tunnel system filled with mud, handprints and pipes.

It is pitch-dark and extremely challenging to navigate safely without a torch – that is, if one even finds the entrance, concealed within a jungle that is home to wild dogs, thorny palms and gnarly vines.

About 20 years after a group called the Singapore Paranormal Investigators reportedly stumbled upon it, the Marsiling Tunnels – an informal name for the tunnels in the area – will be part of a wide-ranging investigation that will inform further plans for the site.

The tunnels are home to the “only known surviving pre-World War II or wartime underground fuel storage tank in Singapore and the region”, said the Singapore Land Authority (SLA), National Heritage Board (NHB) and Urban Redevelopment Authority (URA) in a statement to The Straits Times.

SLA had called a tender to study the site – comprising state land bounded by Admiralty Road West, Admiralty Road and Marsiling Crescent – which closed on Oct 27.

“The appointed consultant’s investigations include heritage and archaeological surveys, geophysical surveys, environmental site assessment, structural integrity inspections, unexploded ordnance surveys and other testing works,” said the agencies.

Besides the fuel storage facility, the Marsiling Tunnels include a nearby bunker that is also heavily graffitied. The historical purpose of the bunker – which includes tunnels so cramped that only squatting room is available – is not known.

The study area is zoned a reserve site in URA’s masterplan, meaning that its use has yet to be determined.

SLA, NHB and URA said there are “no firm plans” for the site at this point, adding: “Where necessary, agencies will also undertake environmental consultations and studies as part of future planning for the site.”

John Kwok, a historian at consultancy Total Heritage, said the Singapore Paranormal Investigators in 2006 stumbled upon the Marsiling Tunnels, but could not ascertain what the structures were.

In 2007, group founder Kenny Fong approached Kwok – who was then a PhD student – about the structures, and the pair went on to determine their roots.

Tunnels in Marsiling were first mentioned in newspaper reports from December 1952, after four schoolboys reportedly found a “camouflaged ventilation shaft of a secret tunnel”, sparking “a big treasure hunt”.

One contractor even spent $4,000 on excavations in the hope of finding treasure, but left empty-handed.

Kwok and Fong first considered if the Singapore, Japanese or British governments could have built the tunnels, but ruled out Singapore and Japan after finding no relevant records.

It was Lieutenant-General Arthur Percival’s War Dispatch, published in February 1948, that revealed the British origins of the tunnels where the oil tanks are.

Percival was famously the General Officer Commanding of the British Commonwealth forces during the Battle of Malaya, and the one who signed the surrender of Singapore in February 1942.

Writing on strategic fuel depots in Singapore, Percival said in his dispatch: “The main Air Force petrol reserve was held in specially constructed underground tanks at Woodlands on Singapore Island a little south of the Causeway.”

Kwok said the facility was reportedly completed by February 1942, adding that British intelligence reports from November 1944 indicate that Japanese troops had modified the facility for their use.

These reports described five large underground tanks with a total capacity of about 4,180 tonnes, more than the volume of 1½ Olympic-size swimming pools.

Today, the walls of the five storage tanks can be seen, with each tank labelled numerically and linked by a series of pipes that run through a main tunnel that is at least 50m.

Although there are lights installed in the tunnel, the electrical wires that presumably powered them are no longer in place, and whether the lights are still operational is not known.

Cracks in the tunnel walls expose reinforcement bars – a sign of the wear that the tunnel has suffered over time.

SLA’s tender documents state that the appointed consultants are to investigate and document inaccessible, buried or partially collapsed tunnel sections “to the extent reasonably practicable”. They add that a “full-scale archaeological excavation” may be required, depending on the findings of a heritage survey that is part of the study.

The documents say that while tunnel restoration and repair works are not part of the study, “post-restoration 3D modelling” is required to “define the desired end-state deliverable should restoration works be undertaken subsequently”.

Kwok said: “This is a well-preserved and large wartime structure, making it a rare find in the Pacific region. Its remote location preserved the structure from decades of development that took place elsewhere in Singapore.”

It is not known if any of the tanks still contain fuel, and Kwok – who noted that wartime fuel contained high levels of lead and benzene – cautioned that a soil investigation may be required before any development is done in the area, if fuel has leaked into the ground.

While other wartime tunnel complexes exist in Singapore, such as at Fort Canning and Fort Siloso, Kwok noted that these had a different role compared with the tunnel at the Marsiling facility.

The tunnel complex in Fort Siloso enabled soldiers to move safely from place to place within the coastal defence system, he said, while the tunnel in Marsiling was likely a service tunnel where depot staff would check on the volume of oil stored in the tanks, or operate valves to move oil out of the facility.

The SLA-commissioned study is slated to be completed by the first half of 2028.

SLA, URA and NHB said parts of the site, including the tunnels, will be barricaded or cordoned off during the investigation works as a safety precaution. “Members of the public are advised not to enter the barricaded areas for their own safety,” they added.