| Historical notes: | With the outbreak of World War II, and Japan's entry into the conflict in 1941, Australia was feeling increasingly vulnerable to invasion by its enemies. Japan's superiority in the air and by sea made the invasion of Australia eminently possible and, with a growing national fear of such an event occurring, various defence measures were quickly planned by the government. Despite defence resources being severely limited, with shortages in skilled manpower and tools, Australia's response was to develop these defence systems and position them along its coast and tablelands.
(McDonald, 1996; SHI Form, 2004)
With particular inland roads being the primary source of communication and movement of populations, stock and supplies, it became increasingly important to control access to these strategic routes in light of the threat of Japanese invasion. To do this, and slow the advance of the enemy if invasion did occur, it was decided that construction of a number of inland defence barriers and anti-tank obstacles was of critical importance to Australia's defence. Up to 50 systems were constructed in eastern NSW during this time, with eight in Dumaresq Shire Council (including the Yooroonah Tank Barrier).
(McDonald, 1996; SHI Form, 2004)
In early January 1942, the Australian Military Forces Eastern Command called for the construction of these inland roadblocks to be carried out simultaneously and to commence immediately. Despite obvious urgency, the shortage of skilled labour and materials saw delays in work on the Dumaresq Shire sites, with work on the Yooroonah Barrier (T/5 and T/5A) commencing in late January.
(McDonald, 1996)
Under the direction and instruction of the Eastern Command and the supervision of the Main Roads Department, workers from Dumaresq Council, local miners and timber workers began construction of the barrier system with the excavation of the tunnel under the old Armidale-Ebor Road. This system was to comprise an approach trench, main tunnel shaft with two iron and concrete-lined explosive chambers (in a 'T' shape, each holding 816kg (1800 pounds of gelignite)), road-fracture lines (lines under the road surface that were to be packed with small charges of explosives) and funk holes (small built shelters to protect personnel from the explosion should the tunnel be detonated).
(McDonald, 1996; SHI Form, 2004)
Two local miners (working for 15 hours a day, six days a week) excavated the tunnel using only hand tools and small charges of gelignite. Machinery to ease the process was available but the hardness of the terrain made drilling difficult and the "fact that the excavation job was successfully completed owes much to the skill and experience of the miners" (McDonald, 1996, p12). Early plans show that the tunnel measured 17m (55 feet 6 inches) and was built to a depth of 4m (10 feet). Under orders from the military authorities, the excavated material was to be cleared and hidden from aerial view while the tunnel entrance was to be sealed (after being charged with 23cm (9 inches) thick concrete and protected by a permanent military guard. Despite these intentions, it is believed that the tunnel was never actually charged.
(McDonald, 1996; Australian Heritage Commission, 2006)
In April 1942, before the excavation of the tunnel was complete, work on the flanking anti-tank barrier (T/5A) had commenced. This supporting system was to consist of concrete tetrahedra and five sections of wooden posts in parallel rows.
(McDonald, 1996)
Although the construction and lining of the tunnel was complete, the explosives had been ordered and the flanking ground-cover barrier was underway, a halt was called on any further progress on the site in May 1942, pending an enquiry into the strategic effectiveness of the barrier system. The system was only going to be successful if there was no alternative route that allowed the invading force to avoid the complex completely. During an inspection of the site by the military authorities, an older superseded section of road was discovered that would allow the enemy to skirt the barrier entirely. Despite the poor site choice, valuable resources of time, money and supplies had already been spent on the barrier system and, by July 1942, it was resolved to continue with its construction.
(McDonald, 1996)
To protect this newly-discovered access point via the superseded road, the wooden barrier system was extended across, what is now, Waterfall Way ('Southern Block'). This section then ran from this point up to the crest of the ridge overlooking the old mined Armidale-Ebor Road (the 'Central' and '75 Blocks'). While the mined roadway is largely protected on its eastern side by the steep ridge, to the west the landscape drops away into a gully with a marshy creek at the bottom and, to protect this section of the site, the 'Tunnel Block' was constructed and extended from the roadside to a rocky outcrop, midway to the creek. From here, the last section of wooden posts were installed and reached to the edge of the creek. However, being timber, it was not feasible to install any posts in the waterlogged marshland and the solution, to protect this potential access point, was the installation of concrete tetrahedra.
(Appleton, 1996)
Although early plans indicate 20 tetrahedra were anticipated for the site, these designs underwent changes (perhaps as a result of shortages in resources or the realisation of the poor choice in site) and only two rows of four tetrahedra were installed in the marshland, at the foot of the gully. Poured on-site, the 1.5m-high tetrahedra were laced together with an anchor cable and set into the ground to a depth of 30cm (12 inches). Each tetrahedra was poured in 11 layers (approximately 14cm thick), topped with a hand-shaped cone and rendered with cement. Following the installation of the tetrahedra in October 1942, the construction of the Yooroonah Tank Barrier was officially complete.
(McDonald, 1996; Appleton, 1996)
While constructing the barriers and managing the site following its completion, the local workers and servicemen constructed a number of crude buildings and outposts across the landscape to enable them to occupy the site within view of the barriers but without attracting the attention of invading forces. A 'quarters' building and small hut were constructed south-west of the site, downstream from the barrier complex, and the remnants indicate they were timber-framed and may have been canvas-walled. However, the 'quarters' were possibly more substantial with evidence of a fireplace and chimney. The local workmen also constructed various stone lookouts at strategic points throughout the landscape and along the ridgeline, overlooking the road.
(Appleton, 1996; Australian Heritage Commission, 2006; SHI Form, 2004)
Although the planning and construction of man-made barriers, alongside the natural obstacles of the landscape, was an important defence effort to guard inland strategic roads against the national threat of invasion during the war, the Yooroonah Tank Barrier was never used.
COMPARISONS WITH OTHER NSW TANK TRAP BARRIER SYSTEMS
The survival of the Yooroonah Tank Barrier site, in its intact form, is rare in terms of other World War II tank barrier systems in NSW. Approximately 50 barrier complexes were built in eastern NSW during the war but most were dismantled or removed soon after the conflict ended. Being a complex of timber and concrete barriers and a mined explosives tunnel is also rare as most of the other surviving barriers are made up of concrete tetrahedra only.
Other tank barrier systems in NSW include the following:
- Port Kembla Heritage Park, relocated from Lake Illawarra (deep trench, timber post barriers submerged in Mullet Creek and concrete tetrahedra relocated to outside Breakwater Battery Museum)
- Smith's Lake, Great Lakes (concrete tetrahedra on the banks of the lake)
- Paddy's Flat on Clarence River, near Tenterfield (concrete post obstacles)
- Mount Lindesay Road, Tenterfield (timber post obstacles)
- Stockton Beach, Newcastle (concrete tetrahedra and rectangular slabs on the beach, can sometimes be covered by sand or partially exposed. Other tetrahedra have been removed and relocated around car park)
- Dee Why Lagoon (concrete tetrahedra)
Compared to these alternative complexes, the Yooroonah Tank Barrier is rare in NSW as a representative of an inland defence system, rather than a coastal barrier. The site is also rare as one of the most intact complexes of defence barriers, in terms of number of elements, their relative intactness and the demonstrated relationship between them. Having been isolated by the construction of the bypass road, following its construction, the Yooroonah barrier complex has also been largely protected from disturbance or deterioration by non-natural forces, ensuring its survival in its current form. |