Burrill Lake Bridge Upgrade, New South Wales, Australia
Burril Lake bridge is located on the A1 Princes Highway, 4km south of Ulladulla in New South Wales (NSW), Australia.
The A1 Princes Highway crosses Burril lake on a causeway and a long low-level bridge, and is the key transport corridor on NSW's south coast.
The bridge is more than 50 years-old and handles 8,000 vehicles a day. Though it is structurally in good condition, a significant maintenance was thought to be essential in the next five years to enhance its longevity.
However, after considering all the possible options, the Roads and Maritime Services in association with the NSW government has decided to replace the existing bridge with a new structure.
BGC Contracting received a $32m contract to replace the existing Burrill Lake Bridge. The scope of the contract includes road works, management of environmental issues, piling and substructure of bridge, demolition of causeway and bridge, utility relocation and landscaping.
Major works related to the project began in April 2016 and completion is expected by early 2018.
Burril Lake bridge project background
The Burrill Lake bridge is a 54.86m-long composite pre-stressed structure built in 1958.
It has an 8.5m-wide carriageway, a 1.53m-wide footway on the westside and a 150m-long causeway to the north. Reinforced concrete safety barriers are located on each side of the bridge.
The bridge is supported by 15m-long concrete piles, which are driven into the floor of the lake.
Twenty four of the total 35 piles are in bad shape due to the weakening of the concrete caused by the curing process. This type of concrete deterioration is called delayed ettringite formation (DEF).
This requires the bridge to undergo significant maintenance to increase its life, even though the DEF does not currently pose any immediate threat to the structural integrity of the bridge.
The bridge is also prone to flooding, being one of the most low-lying bridges on the Princes Highway.
Roads and Maritime has conducted a series of investigations to decide whether to maintain the existing bridge or to replace it with a new bridge. Since the maintenance option would not mitigate the risk from floods, the department has decided to build a new bridge.
Features of the new bridge over Burril Lake
Roads and Maritime Services has developed a concept design for the new bridge after conducting a range of technical, economic and social investigations and compiling community feedback.
The proposed project aims to provide a direct streamlined connection between the Roe Highway and the Port of Fremantle, Australia.
The design includes a 290m-long bridge spanning the lake on a new alignment towards the east of the existing bridge. The existing bridge and the causeway will be completely removed.
Roundabouts will be constructed on either side of the crossing to connect the Princes Highway to local roads.
A pedestrian and a cycle path will be laid on the new bridge, which connects to the new paths on both sides and links to the Ulladulla cycle path.
Below both ends of the bridge will be pedestrian paths and five locations for the pedestrians to safely cross the highway.
The bridge and highway would be higher than the predicted 1-in-100-year flood level, in order to reduce the impact of flooding.
Fishing platforms and picnic areas will also be created on the foreshore.
Benefits of the Burrill Lake bridge project
The new higher bridge will improve the overall reliability of the Princes Highway on the south coast by reducing future maintenance issues.
The bridge will also be safer as it will be constructed above the predicted flood level. Provision of new intersections improves road safety, and pedestrian and cyclist access.