Why does the channel need to be widened?
Flinders Ports needs to widen the Outer Harbor channel to maintain competitiveness with other capital city ports. Unlike Adelaide, most Australian container ports can accommodate wider Post Panamax vessels which are increasingly being used for freight imports and exports and by cruise ship liners, as they are more economical. Outer Harbor can currently accommodate vessels up to a maximum of 42.2 metres wide with operational restrictions in place. The Outer Harbor Channel Widening Project will enable the Port to accommodate container ships and cruise ships with a maximum width of 49 metres, without operational restrictions. Without this upgrade, the Outer Harbor port faces significant limitations, which will greatly affect the economic viability of South Australia’s trade and tourism industries.
What is dredging?
Dredging is a form of excavation carried out underwater where material, such as shelly sand, silt, clay and limestone, is removed from the area. The removal of material is undertaken by a specialist floating vessel, known as a dredge.
Where will the dredging occur?
Dredging will occur in the swing basin (turning area for ships within the port) and along the channel at Outer Harbor. The channel will be widened from 130 metres to 170 metres and the swing basin (where vessels turn around) from 505 metres diameter to 560 metres diameter to allow larger vessels to easily and safely access the port.
What is the dredge area and the dredge material placement area?
The dredge area is the location where the dredging will occur within the Outer Harbor channel and swing basin. The Dredge Material Placement Area (DMPA) is an approved location in Gulf St Vincent, approximately 30km southwest of Outer Harbor, where material collected from the dredging will be deposited. The same DMPA was used to place material from the previous channel deepening dredging campaign undertaken in 2005.
How will the dredging happen?
A dredge vessel called a Trailing Suction Hopper Dredge (TSHD) will lower a suction pipe and using the draghead (teeth and/or water jets attached to the pipe) it will scrape over the seabed and loosen the material. The sediment-water mixture is brought up through the suction pipe and pumped into the vessel’s hopper. This material is then transported to the Dredge Material Placement Area (DMPA) for deposition.
Another vessel called a Backhoe Dredge (a hydraulic excavator installed on a pontoon) will also be used to dredge the harder material or material not accessible by the Trailing Suction Hopper Dredge. The Backhoe Dredge, once in position, places its spuds on the seabed to hold it in place. The bucket mounted at the end of the stick excavates material from the seabed and lifts it to the surface to load it into a barge for transportation to the Dredge Material Placement Area.
How will the dredging be monitored?
Various measures are in place to monitor dredging and manage environmental impacts. This includes:
- Real-time water quality monitoring, including triggers to inform operators of turbidity levels. This will help the team monitor dredging and implement measures to reduce turbidity, as necessary
- Tracking vessel movements and activities via a GPS monitor, also known as an Automatic Identification System (AIS) unit, to ensure that vessels are placing material in the approved location
- Conducting before and after seagrass coverage and density surveys to measure impact to seagrass (and compare to predicted impacts)
- Trained Marine Mammal Observers working with the dredge team to monitor dolphins and whales in the area and alert operators when mammals are within 150 metres of the dredge vessel, so that measures can be implemented to avoid mammals
Flinders Ports and the dredge contractor will follow an Environment Protection Authority (EPA) approved Dredge Management Plan and Environmental Monitoring Program to comply with the requirements of the dredge licence issued by the EPA. This involves regular reporting on environmental management and monitoring activities. The public can also access environmental monitoring data and reports on our Monitoring and reporting page.
When will dredging occur?
Dredging began early June 2019 and the project is scheduled for completion in September 2019. Dredging has been scheduled for the cooler months to reduce potential environmental impacts, particularly to seagrass, when growth is dormant. If there are delays to the anticipated timeline, Flinders Ports will ensure works are completed within 6 months of commencement. Dredging will not take place in the summer months of December, January and February.
The project timeline illustrates expected timing for various activities associated with the project.
How significant is this project to South Australia?
Channel widening is vital to ensuring South Australia remains competitive and globally accessible in the logistics and tourism industries. Widening the channel will enable more efficient access for the container vessels and cruise ships that already visit Adelaide. More importantly, larger vessels, which are increasingly being used, will also be able to visit instead of bypassing South Australia. This project will support South Australia’s imports and exports industry growth through the Outer Harbor port, which currently exceed $14 billion a year. It also supports the South Australian Tourism Commission’s Cruise Ship Strategy 2020 to increase ship number to 100, adding a further $200 million to the state economy.
What would happen if the dredging didn’t happen?
If the project is not undertaken, there is a risk that containerised trade and cruise shipping may bypass Adelaide and utilise alternative ports that can operate more efficiently and without restrictions. This would create a negative impact on the South Australian economy due to the increased cost of transporting imports and exports and reduced income from cruise liners, as well as the flow on effect from tourism spend.
Will vessels and fisheries still be able to use the channel while the dredge works is being undertaken?
The channel will remain operational throughout the project. Dredging will be undertaken around shipping operations. Boat users should take note of important safety information including:
- Pass at 4 knots or less
- Pass on the side showing two diamonds during the day
- Pass on the side showing two green lights at night
- Do not approach within 100m of the dredge
- Pass to the stern of the vessels, including the survey vessel ‘Bay Lass’
- The vessels are restricted in their ability to manoeuvre
Contact the dredge team using your boat radio on VHF Channel 12, if you’re unsure.
Does dredging involve deepening the channel?
The dredging will not involve deepening the channel. Channel depth will remain at 14.2m. Flinders Ports commissioned a study to assess the appropriate channel width to safely navigate the channel and swing basin (turning area for ships within the port) for increased vessel sizes. This study recommended the channel width increase from 130 metres to 170 metres wide and the swing basin increase from 505 metres diameter to 560 metres diameter.
The channel was dredged in 2005. Why is this happening again?
Prior investment by Flinders Ports deepened the existing channel in 2005 from a depth of 12.2 metres at low tide to the current depth of 14.2 metres. This deepening project was driven by the increasing global use of larger vessels, known as Panamax class vessels.
The current Outer Harbor shipping channel suits the Panamax class of vessel which measure 294 metres in length and 32 metres at its widest point.
Increasingly, Flinders Ports is being asked to receive vessels which are wider, known as New Panamax and Post Panamax, as they are more economical for shipping companies to operate. These vessels are up to 49m wide. Widening of the channel will enable accommodation of these size vessels without restriction.
Where will the dredge material be placed?
How was the dredge material placement area identified?
An area in Gulf St Vincent was identified through detailed assessment as being the most appropriate location for a range of factors, including:
- It is located away from shipping activity and in deep water to avoid any navigational hazards.
- The site does not support any significant marine flora or fauna.
- The site is of sufficient depth and suitable tidal conditions that material is retained at that location (i.e. unlikely to become mobile and travel from site).
- The site is not a known pathway or breeding area for migratory marine species i.e. whales.
How much dredge material needs to be moved?
The Outer Harbor Channel Widening Project involves removing approximately 1.55 million cubic metres of material from the channel and swing basin. In comparison, the 2005 Channel Deepening Project involved dredging approximately 2.7 million cubic metres of material to create a deeper channel and swing basin.