There is certainly no shortage of bridges in Australia that fascinate the whole world with their design. The most famous of all is probably the Sydney Harbour Bridge, completed in 1932. Its fame is due in part to the fact that it is situated close to the famous Sydney Opera House that was built forty years later and soon became the symbol of the city itself – in architectural terms – as well as of the whole country. Moreover, it remains the highest steel arch bridge in the world. But it is not the only Australian bridge worthy of attention. There is also the famous Story Bridge of Brisbane, built during the Great Depression, or the bridge that for many years was the longest concrete arch bridge in the world, the Gladesville Bridge, or the fascinating cable-stayed Anzac Bridge (both in Sydney). However, the most scenic of all the Australian bridges in recent years is probably the Sea Cliff Bridge, one of the few offshore parallel to coast bridges in the world (there are only 7 in total). Let’s find out why the construction of this unusual bridge was necessary and how the project was tackled.
The location of the Sea Cliff Bridge
The road that the Sea Cliff Bridge was constructed along is not just any old road. It is in fact the Lawrence Hargrave Drive, a coastal road that dates back to 1870 and winds its way from Helensburg to Thirrou. The Lawrence Hargrave Drive is part of the Grand Pacific Drive, a tourist road that links Sydney with the south coast of South Wales, snaking along for 140 kilometres beside the Ocean. More specifically, the northern section of the Grand Pacific Drive starts from the Royal National Park, just to the south of Sydney, and continues on to Wollongong, Shellharbour, Kiama and Shoalhaven. The bridge in question, the Sea Cliff Bridge, is located 10 kilometres south of Helensburgh, linking the small towns of Coalcliff and Clifton.
The history of the Sea Cliff Bridge
For many years the Lawrence Hargrave Drive enabled people to drive from north to south without the need for any bridge, along a long stretch of asphalt that followed the rocky coastline. However, in the early 2000s there were several landslides that caused frequent closures of the road, creating a host of problems and much inconvenience for nearby towns. The problems began in the summer of 2002, when the Roads and Traffic Authority (RTA) closed the road for 6 weeks in order to deal with the hazards posed by the rocky slopes overhanging the road. That long road closure was only the first of many, however. In view of the coastline conditions, the RTA decided a few months later to introduce a specific road closure measure: the section of the Lawrence Hargrave Drive between Coalcliff and Clifton would be automatically closed whenever there was heavy rain (the precise figure established was 25 millimetres of rain in situations of constant rainfall). Two fixed road blocks were installed in order to ensure compliance with this regulation. During the months between December 2002 and June 2003 the road was closed at least 10 times, often for several days. It became obvious therefore that the situation was no longer sustainable: the road was closed altogether while the government set to work to look for a definitive solution.
The road closure led to serious problems for companies with offices to the south of the stretch of road affected: during that time there was a sharp increase in businesses closing down. It also caused problems for all the families whose children attended schools beyond the closed section of road. In fact, those 900 metres of closed road constituted a minor disaster for the various communities in the area: it was a dark period that only ended some years later with the opening of the Sea Cliff Bridge.
The design and construction of the Sea Cliff Bridge
Rock falls, landslides and mud flows: the instability of the rocky walls above the road between Coalcliff and Clifton required a definitive solution. Various ideas were considered in order to be able to guarantee continuous vehicle transit despite the incessant coastal erosion. Some suggested constructing avalanche shelters to protect the road from rock falls in the event of heavy rain, or even the construction of an underground tunnel. But the idea that prevailed over all the rest was to build an off-shore bridge just off the coast. Specifically, it was to be a cantilever, incrementally launched bridge with a total length of over 640 metres. To be absolutely precise, it consists of two distinct units: the actual Sea Cliff Bridge, which is a cantilever bridge 455 metres long, and the Lawrence Hargrave Drive Bridge, that is 210 metres long and incrementally launched. The bridge is 41 metres high at its highest point, and up to 70 metres from the original carriageway of the old Lawrence Hargrave Drive in places.
The bridge is unique in that it follows the curving line of the coast, so that each individual segment is different and separate in its own way, as well as having its own specific complexity. The bridge has two two lanes for motor vehicles, each between 3.5 and 3.8 metres wide, as well as a pedestrian pathway on one side that is 2.3 metres wide; cyclists can use the side shoulders that are 1.2 metres wide.
Inauguration and use of the bridge
Work on the construction of the bridge was completed in December 2005, at an overall cost of 52 million Australian dollars. The official inauguration took place on 11 December 2005, little more than two years after the closure of the road. The person who cut the ribbon was young Mackenzie Russel, the schoolgirl who won the competition to come up with the name for the new bridge: it was her idea to call it the Sea Cliff Bridge. From that time on, the bridge has become a big tourist attraction, as it is only an hour away by car from Sydney.