|
|
|
|
HistoryA Brief history of the Rapid Bay Jetty may be found on the main page. David Cowan of the Society
for Underwater Historical Research has kindly prepared the following
document. THE HISTORY OF RAPID BAY JETTY The open cut mine at Rapid Bay was a major source of limestone for Broken Hill Proprietary Ltd (BHP) during the years 1942 - 1981. The limestone was shipped to BHP's steelworks at Whyalla, Newcastle and Port Kembla where it was used as metallurgical flux in production of steel. The jetty was constructed as part of the works undertaken to establish the mine during the period 1938 to 1942. The works also included the small town located immediately above what is now the camping ground for accommodation of the construction personnel and the future mine's workforce as well as a high voltage power line from Willunga to Rapid Bay. Construction of the jetty started in September 1940 and was finished in March 1942. Work was carried out around the clock due to the availability of electricity to supply floodlighting. The presence of bedrock close to the surface of the seabed slowed progress for the first 183 m as drilling and blasting was required before timber piles could be driven into the seabed. The jetty was first used on 5 September 1942 when 5,286 tons (5382 tonnes) of limestone loaded onto the SS Iron Knob for transport to Whyalla. The completed jetty consisted of an approach jetty of 448 m length connecting to a wharf (known as a 'T-Head') of 198.12 m length. About a third of the approach jetty's 6.9 m width was occupied by a conveyor. This conveyor which was a dominant feature of the jetty until its final removal in 1996 rose to a maximum height of 14 m above the jetty deck before terminating as a retractable boom at the jetty end. The 'T-Head' consisted of a main deck (supporting the end of the conveyor), 6 dolphins and connecting walkways. The dolphins (9.76 m x 9.76 m) served for fenders for docking ships and as mooring points for ships being loaded. The original jetty was built of steel and timber. The approach jetty's support structure consists of a set of 3 timber piles connected at the top & bottom by steel & timber cross-beams and stiffened by steel cross-bracing. This element of structure which is known as a 'Bent' is spaced at 4.88 m centres. The dolphins were supported by 5 Bents each containing 5 timber piles, each at 1.95 m centres. The superstructure to the entire jetty consisted of timber decking fixed to timber bearers supported on steel 'I' beams braced by steel angle bracing. In January 1942, it was discovered that test piles installed in 1938 had failed due to Teredo worm attack. From February 1943 to January 1949, 296 piles supporting the approach jetty were enclosed with concrete collars from seabed to the low water mark. However, this work proved to be ineffective as the portion of the pile above the collar remained exposed to seawater. These concrete collars can be still be observed by divers either around timber piles or lying on the seabed. The dolphins were excluded from this remedial work because of the need for these structures to be flexible as possible to absorb the large loads applied by docking ships. By 1958, the combined effect of teredo worm and docking ships had caused all 6 dolphins to become very unstable, thereby threatening the stability of the entire 'T-Head' and adjoining parts of the approach jetty. Underwater inspection was unable to determine the extent of the Teredo worm damage. During subsequent reconstruction, it was discovered that the first dolphin to be rebuilt only had 3 of its 25 piles either still fixed to the seabed or having a diameter large enough to be structurally sufficient. Reconstruction works carried out during either the late 1950s or early 1960s replaced all timber piles supporting the 'T-Head and part of the adjoining approach jetty with steel piles. The works also included the expansion of the 'T-Head' to a length of 224.48 m (including enlargement of the dolphins to 10.37 m x 10.37 m) and the provision of fender systems to the 'T-Head' including a separate structure consisting of 2 dolphins located immediately below under the main deck. The latter structure is well-known to divers as the pair of dense 'forests' of piles where large schools of fish gather and hang like 'leaves'. Also, a range of corrosion protection measures were used including surface preparation (i.e. shot blasting & acid etching), surface coatings (i.e. paint & galvanising) and sacrificial anodes. In late 1981, the South Australian Government accepted an offer from BHP to acquire the ownership of the jetty at no cost with the date of transfer being 1 January 1982. Also, during 1981, BHP sold the mining operation to Adelaide Brighton Cement Ltd (ABC). In May 1982, the SA Government leased the jetty to ABC. ABC shipped limestone to its Birkenhead cement plant until 1988 when the Rapid Bay operation was scaled down in favour of increased production at the Klein Point mine. The jetty's commercial life concluded in 1991. All subsequent shipments of limestone from the mine have been conveyed by truck. The above was summarised from an unpublished Flinders University archaeology honours thesis entitled 'The Use and Abuse of Jetties - State Government Control in the Construction and Maintenance of Jetties in South Australia' written by Julie Ford in 1999. This summary was prepared by David Cowan of the Society for Underwater Historical Research (http://www.communitywebs.org/~SUHR/home1.html).
|
|
