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Australia
Australia is known for its iconic beaches, with water access playing a major part in the country’s way of life. In many cities and suburbs, seawalls are a valuable asset for protecting low-lying waterfront infrastructure – creating a barrier between open water and its picturesque bordering environments; and reducing erosion and protecting urban assets.
Seawalls are crucial infrastructure for an island continent like Australia, especially for areas alongside rivers and lakes where erosion can have a negative impact on urban environments. Typically made from steel, rock, or concrete, seawalls are constructed to suit the landscape and water conditions.
Vertical seawalls block waves from ocean-facing coastlines while sloped seawalls, or revetments, are designed to dissipate the energy from smaller waves to lower the risk of erosion. Left unprotected, natural foreshores can be at risk of flooding and weakened ground conditions, which can put waterfront structures in danger of collapse.
Remediating before the cracks appear
While seawalls are engineered to withstand marine environments and extreme weather, old or poorly constructed seawalls can be hazardous to people, structures and the surrounding environment. A deteriorating seawall can cause bordering infrastructure to subside, resulting in cracks that can lead to water ingress behind the structure.
This was seen in Sydney, where a historic sandstone seawall, protecting a waterfront apartment on Sydney Harbour, had started to deteriorate following years of tidal currents and water movement. Without proper remediation, the wall would have continued to degrade until it could no longer support the apartment’s patio or the apartment block itself.
Entire strips of tourist-attracting waterfront development could be affected by old or deteriorating seawall infrastructure, and without suitable protection from waves and tides, or a long-term plan to mitigate the effects of water movement, structures may become unsafe, uninhabitable, and unviable for tourist operators and other businesses who rely on the location’s access and safety.
Due to constant contact with water that may be flowing or contain corrosives such as salt, seawalls should be regularly monitored and maintained for signs of deterioration. If sections of the wall are damaged, its footings have eroded, or the soil behind the wall is weakened, the wall may need to be reconstructed or reinforced.
Long term solutions needed
Tailored solutions that provide long-term stabilisation are key to revitalising ageing or deteriorating seawalls. This was a lesson that the City of Bunbury learnt when it discovered damage to the seawall protecting the Marlston waterfront entertainment precinct.
Prolonged exposure to waves and tidal movements had allowed water to penetrate through the wall and under the foundations. A section of the wall had subsided and a large crack had formed in the face of the wall. To address the problem, emergency grouting was carried out in the worst affected area, but proved to be very expensive.
Innovative and cost-effective maintenance
Mainmark provides a range of specialist ground engineering and asset preservation solutions for residential, commercial, industrial, civil infrastructure and mining sectors. Mainmark worked with the City of Bunbury’s engineers to develop an innovative and cost-effective solution for the entire wall repair.
Mainmark’s Teretek® engineered resin proved to be an ideal solution to strengthen the wall by densifying the soil and filling voids where sand had been washed out due to the tidal movement. As urban development continues to increase, seawalls will remain crucial elements for protecting water frontages.
When constructing seawalls, councils should consider an asset remediation plan to help address issues that may arise over time, should sections of the wall start to deteriorate due to ground or water conditions.
