To ensure the safe movement of vessels in and around port areas, dredging activities are undertaken at ports around the world.
Tasmania's multi-port system is no exception and TasPorts regularly undertakes dredging activities, in line with its Long-Term Dredge Management Strategy.
Through this strategy, TasPorts is committed to enabling our customers and industry partners, whilst upholding maritime and environmental standards.
By ensuring the water is deep enough for ships to prevent grounding on the seafloor.
A well dredged port enables smoother and faster loading and unloading of cargo from ships.
Efficient and safe port operations support business and industries using the port. If not completed, operations can be restricted, negatively impacting our customers and local economies.
Maintenance dredging enables our ports to adapt to sediment changes and build up that naturally occur over time from flooding, storms, ocean swell and tidal movements.
TasPorts' dredging program currently includes planned maintenance dredging, as well as supporting seabed levelling activities. In addition to this, TasPorts is also exploring capital dredging opportunities.
Seabed levelling is the act of sweeping material on the seabed from a high point to a low point.
Maintenance dredging is the process of removing material from the port waters to original design depths and transporting it to another location. It can be collected and dumped at sea, re-used, recycled or disposed of on land.
Capital dredging involves the removal of material to create new channels, expand existing ones, or deepen existing facilities to allow larger ships to access them.
The Port of Devonport is fed by the Mersey catchment system, which annually accumulates approximately 41,000m3 of silts, as well as additional coastal process sand transport, therefore requires regular maintenance dredging.
Historically, dredging has been managed through a combination of seabed levelling and maintenance dredging campaigns. Seabed levelling was completed in 2019 and 2022 and more recently in early 2024.
The last major maintenance dredge campaign occurred in 2015, where 320,000m3 was dredged from the port and disposed in a federally approved Dredge Spoil Disposal Ground in the Bass Strait.
TasPorts is preparing to undertake a major maintenance dredging campaign during the 2024-2025 financial year.
The dredging campaign will run for approximately 18 weeks and will see the relocation of up to 470,000m3 of accumulated silt, sand and cobbles to a designated disposal ground.
To support the dredging activities, TasPorts is currently applying for a new 10-year Sea Dumping Permit with the Australian Department of Climate Change, Energy, the Environment and Water (DCCEEW).
Consistent with our commitment to sustainable practices, TasPorts has deployed five water quality monitoring buoys in and surrounding the port area at Devonport.
These buoys will provide 24/7 water quality monitoring across five locations near the Mersey River and further offshore, to support the upcoming planned maintenance dredging campaign in early 2025.
The early deployment of the water monitoring buoys will support baseline monitoring, enabling TasPorts to effectively monitor and respond to any changes in water quality during the dredge campaign.
The water monitoring buoys will remain in place until 30 June 2025, following the completion of the maintenance dredge campaign.
As part of its commitment to being open and transparent with our dredging progress, a rolling average of live water quality monitoring data will soon be available here.
In September 2024, TasPorts submitted an application with the Federal Department of Climate Change, Energy, the Environment and Water (DCCEEW) for its 10-year Sea Dumping Permit.
The approval will facilitate the disposal of dredged material at a preferred disposal site, to support maintenance dredging campaigns for the Port of Devonport for the next 10-years.
The application is related to the removal of up to 2 million m3 of dredged material over a period of 10-years. These volumes are proposed to be removed through an initial maintenance campaign in 2025, followed by an ongoing programmed maintenance dredging schedule seeing approximately 300,000m3 of material dredged and disposed every three years.
The application also includes allowance for up to three (3) flood emergency dredging operations, should they be required.
TasPorts has identified its preferred spoil disposal ground, which is located approximately 15km NNW from the Port of Devonport’s entrance.
The selection of the preferred disposal site location was supported by environmental surveys, water quality modelling and other assessments, as well as consultation with TasPorts’ Technical Advisory Consultative Committee (TACC) and other stakeholders, who were identified and engaged with under a project specific Stakeholder and Community Engagement Plan (SCEP).