Lawrence Hargrave Drive is one of the most scenic roads in Australia but was notorious for rock falls, embankment slips, mud and rock slides due to high rainfall, marine erosion, weak rock and the weathering of rock features. These rock falls have caused many road closures throughout the road's history.
The road winds its way around the rugged coastal scenery from Stanwell Park to Thirroul, passing through the villages of Coalcliff, Clifton, Scarborough, Wombarra, Coledale, and Austinmer. The road was built in the 1860's and in 1947 the road became Lawrence Hargrave Drive, named after the famous Australian aviation Pioneer Lawrence Hargrave.
Erosion and Rock Slides
The lower area of the rock formation is a section of the Illawarra coal measures. These measures are made up of layers of coal, clay stone and when it is exposed to the extremes of the ocean, it weathers very rapidly. When erosion of the coal occurs, clay, stone and sandstone forms unstable overhangs, causing large collapses of boulders, falling from tens to hundreds of meters. This erosion created a significant risk for motorists. Back to top
In August 2003, a large embankment slip called for a complete road closure. But community protest at the closure swiftly gathered momentum. “The indefinite closure of Lawrence Hargrave Drive is inflicting needless suffering on Northern Suburbs residents and business owners, and it has to stop. It was bad enough when the road was closed every time 35mm of rain fell, but this latest move is crippling the Northern Suburbs”. Cunningham MP Michael Organ said at the time.
In total, the road remained closed for two years and four months to allow for a construction solution and timeline that would enable the reopening of Lawrence Hargrave Drive Back to top
The LDH Link Alliance and the road reopening options
The Roads & Traffic Authority (RTA) signed an alliance agreement with private sector companies on December 8, 2003 to re-connect Lawrence Hargrave Drive between Coalcliff and Clifton. In the six month project development phase the LDH Link Alliance examined 26 options, ranging from pure geotechnical solutions, to tunnels, avalanche type shelters, and bridges. The preferred solution was determined based on a multi criteria analysis, which considered issues such as Aboriginal archaeological heritage, budget restrictions, heritage impacts, environmental approvals, and long-term durability. The LHD Link Alliance engaged the support of the Coast Road Action Coalition (CRAC), the community and other stakeholders, to successfully complete an REF and confirm the preferred design and construction cost within a six month period and then commence with the detailed design and construction by June 2004. The full scope of works included an overall length of road upgrade of 994m, including: - Sea Cliff bridge with a total length of 665m - A mudslide chute and catchment basin - Significant rock face reshaping and stabilisation works - A new stretch of roadway at each end of the bridge - A 120m long cantilevered structural widening of the road at the northern end - A three metre wide pedestrian walkway throughout the full length of the project.
Impact of the continuing Road Closure on the local Community
Whilst the closure was aimed at protecting the safety of motorists, local media reports suggested that the closure of Lawrence Hargrave Drive was having an impact on the community. To quantify the level of impact, the RTA commissioned the Illawarra Regional Information Service (IRIS) to conduct consultative research into the ongoing impact of the closure on the surrounding community (IRIS, 2004).
The 2004 IRIS surveys document the impacts that the road closure was having on the local communities and businesses. Permanent closure of the road would continue to exacerbate these impacts on households. Some of the main findings of the survey included; • The round trip to and from work had increased between 28km and 44km per day depending on location of residence; • The total time taken to travel to and from work had increased by between 34 minutes and 44 minutes per day depending on location of residence; • The average weekly cost associated with travel to work from affected households had increased by $24; • Disruption and extra time and costs to access schools and shops had occurred; and as well as the social impacts outlined above, the closure of Lawrence Hargrave Drive was also having an economic impact on businesses in the Thirroul to Helensburgh area.
Online oral history "Living on the Edge" and "Building Bridges" captures the history, lives, aspirations and frustrations of some of the local people who relied so heavily on Lawrence Hargrave Drive for access, and also provides recorded interviews with those involved in the planning, design, construction and naming of Sea Cliff Bridge.
The construction of Sea Cliff Bridge was extremely complex in nature, with a number of technical hurdles that were overcome. Principal among these was the complexity of the balanced curved bridge design, which determined that each constructed five metre segment had different angles, falls, slope and post-tensioning characteristics. This necessitated millimetric accuracy, first, in surveying of the preceding segment, then, in the placement calculations, so that when tons of plastic concrete was poured into the carefully located traveler formwork, it was in the right position to be tensioned and become part of the advancing cantilever structure.
Geotechnical investigations highlighted the additional complexity of the varied nature of the five Geotechnical Domains across the project site. Each afforded a different risk level, due to both changes in the topography and the nature of the underlying geological strata. As an example, the area covering the southern ampitheatre contained the highest point on the surrounding escarpment and the highest risk of rock fall projection away from the vertical, calculated at up to 45 metres out from the cliff line. As the existing shoreline was only 40 metres from the cliff line, this placed the feet of the bridge firmly in the Pacific Ocean; adding to the technical complexity, firstly of access, requiring a ten metre wide road which, in turn, required construction of a revetment and reclamation of the intertidal boulder zone.
Proximity to the chlorine-laden ocean spray, coupled with the design constraint of a 100-year life span for the bridge, led to the inclusion of an impressed current cathodic corrosion prevention system, and indicated the necessity for micromanagement of concrete quality control to ensure the greatest possible density and resistance to chloride attack.
View the impressive construction statistics and photo archive, or time lapse photography.
While the final Bridge design did not find support with all in the community, the majority supported the road reopening solution - the construction of Sea Cliff Bridge. Since the opening, it has become a major tourist icon, and destination favourite of many of the residents of the Illawarra. The contributions of the RTA, Lawrence Hargrave Drive Link Alliance, and the Community Consultative Committee have been widely recognized, awarded and applauded in the community since the Bridge opening on December 11, 2005.
Footnote: Despite all the good things that the beloved Sea Cliff Bridge has brought to the area, some residents have recently documented (2008) a negative aspect of the opening of the Bridge. It's huge tourism drawcard success has apparently driven some residents to "Overdrive".
Lawrence Hargrave Drive Link Alliance
The Bridge was designed and constructed by the Lawrence Hargrave Drive Link Alliance (Roads and Traffic Authority of NSW , Laing O’Rourke , Maunsell and Coffey Geotechnics). Contract value $52 million.