The Formation, Use And Conservation Of Arthur Head, Freemantle

Arthur Head, once the dominating headland and hub of early Fremantle is today an attenuated, patched up remnant of coastal limestone crowned by an aged but intriguing limestone building of dodecahedral shape and pierced by a tunnel blocked off at either end.

Arthur Head is a tombolo (tied island) of eolianite some 120,000 years old that formed on top of a coral reef and was isolated by a paleochannel of the Swan River so it is a unique landform of geological significance. It is the site of the so called Round House, the first public building of the Colony of Western Australia, a jail built of squared caprock in 1831. It is also the site of the Whalers Tunnel some 66m long and 3.6m wide and high built by convicts in “soft rock” in 1837. The tunnel was the first underground structure in the State and links with the important whaling industry that was the backbone of the economy in the 1830s. Both are important Australian heritage structures, however the remnant landform, the tunnel and the Round House are now in need of comprehensive conservation. The headland was treated as a quarry; then as the heritage values changed the early remedial work on the eroding cliff faces was inappropriate. About one half of the rock faces on the headland are now covers in limestone or concrete walls of variable styles, colours, textures and stability. The remnant limestone faces show coastal caprock over deeply eroded zone of roots with enhanced corrosion caused by fertilisers from lawn watering.

The west end of the Whalers Tunnel is sagging with some rockfalls so it needs urgent restructuring to secure roof stability. A new west portal is required to sustain the overlying deteriorating rock face. The Round House was restored in a Bicentennial project with the wrong type of limestone that lacks the texture, colour and hardness of the original caprock, so that restoration has not been achieved, merely patching. The dark weathering, easily carved and vandalized, bedded limestone that has been used is not authentic and detracts from the integrity of the original structure. All repairs must be made with limestone compatible with the original caprock.

The WA Government has provided funds for comprehensive remedial works and final proposals are now in place. This report records the geology of the site, its history, the problems posed by human intervention and past vicissitudes. A further report will record the solutions during the year 2000.