What is the Dredge Management Plan (DMP)?
Flinders Ports is required to implement an EPA approved DMP which outlines how it will fulfil the conditions of its dredge licence, including management of the dredge methodology and mitigation of potential environmental risks associated with the project.
Developed in line with relevant Commonwealth and State legislation, the DMP covers:
- environmental, economic and governance context
- the scope of work and dredge methodology
- environmental risk assessment and associated management framework
- reporting, quality assurance and control
A fact sheet and the full DMP can be found on the Resources page.
How will Flinders Ports be held accountable for implementing the Dredge Management Plan (DMP)?
Flinders Ports will regularly report to the EPA on activities relating to the environment as a condition of approvals. This includes ongoing monitoring before, during and after dredging, and an adaptive management approach to ensure Flinders Ports is able respond in real-time to any risks.
The EPA will also conduct regular audits throughout the project, which will include:
- General observations on the status of environmental controls for the project
- Ensuring environmental management measures are in place and actively managed
- Assessing monitoring results during the audit period
- Compliance with legislative obligations, including conditions of approval and requirements of the DMP
- Ensuring onsite environmental management controls are effective in managing environmental risk and are being maintained
- Verifying non-conformances are being identified and recorded and that appropriate corrective actions are being undertaken in the event of non-conformance
Monitoring data is also available for public access via our website.
What is the Environmental Monitoring Program (EMP)?
The EMP is a licence requirement for the ongoing monitoring and survey of environmental factors, such as water quality, before, during and after dredging. It works in conjunction with the Dredge Management Plan (DMP) to manage activities throughout the project.
How is turbidity being managed?
There is a strong focus on managing turbidity to minimise environmental impacts. The dredge works will follow an adaptive management approach with turbidity monitored in real-time to allow Flinders Ports and dredge contractor to respond as conditions in the water change. Set limits, as outlined in the dredge licence, will be followed to help monitor and manage turbidity. If limits are exceeded, the dredge contractor will either adjust or crease dredging.
Other measures in place to manage turbidity include:
- Applying a dredging methodology which involves no “double-handling” of dredge material (e.g. no side casting)
- Use of a “green valve” on the Trailing Suction Hopper Dredge
- Dredging at all times within the design dredge footprint and vessels fitted with a tracker (Automatic Identification System (AIS) unit) that maps and monitors movement and the opening and closing of the hopper doors
How often is water quality being monitored?
Water quality is monitored every 10 minutes, allowing the contractors to quickly adapt their approach if conditions change. Monitoring measures include reviewing and responding to:
- Turbidity levels and adjusting or pausing dredging if limits are exceeded
- Photosynthetically Active Radiation (PAR) to understand light on the seafloor available to seagrass
- Dissolved oxygen, pH, salinity and temperature
How will the water quality be tested?
Water quality will be monitored every 10 minutes during dredging at three sites – one site located north of the channel, one site to the south of the channel, and a background site located away from the dredging activity. Turbidity measurements adjacent the dredge area can then be compared to water quality at the background site. This will allow the project team to identify if elevated turbidity is the result of localised conditions i.e. wind, poor weather, or due to dredge activities.
Monitoring will measure turbidity (suspended sediments in water), Photosynthetically Active Radiation (to measure the light on the seafloor available to seagrass) and dissolved oxygen, pH, salinity and temperature.
Turbidity will be measured in Nephelometric Turbidity Units (NTU) which calculates suspended sediment in water. Should nominated limits be exceeded, as per the Dredging Licence conditions, the contractor will follow a set criteria for two levels – Alarm and Hold, and implement associated actions. For more information, see our environmental fact sheet.
If water quality reaches Alarm or Hold level, due to dredging activities, the following actions will occur:
- Alarm (2.8 NTU based on 15 day rolling median or 5.8 NTU based on 6 day rolling median) – Alter dredge methodology to reduce turbidity by changing location or direction of dredging and considering tidal currents, or altering the overflow regime to reduce fines spilt to water.
- Hold (5.8 based on 15 day rolling median or 15.8 NTU based on 6 day rolling median) – Crease dredging until turbidity falls back below specified limits, notify the Environment Protection Authority (EPA) and provide the EPA with a report on activity details and corrective action.
Where can I access monitoring data?
What is the reactive monitoring program?
The reactive monitoring program involves the continuous monitoring of dredging activities and its effect on turbidity levels, ensuring water quality remains within a set limit. If there is a rise in levels due to dredging activities, then the dredge contractor will implement a number of management strategies, see the environmental fact sheet to reduce the levels of turbidity to the approved limit
When did the Environment Protection Authority (EPA) issue the dredging licence?
What are the conditions of the licence?
A copy of the licence detailing all conditions is available on the Flinders Ports website.
The conditions of the licence, which are fully supported by Flinders Ports, have been set to protect the marine environment and effectively minimise and manage the potential immediate and long-term impact of the dredging works.
General conditions include:
- A comprehensive environmental audit
- Thorough and ongoing consultation with key stakeholders, such as the EPA
- Real-time water quality monitoring and reporting, including triggers to manage turbidity levels within defined limits at all times
- Works to be managed and monitored by a comprehensive, EPA approved Dredge Management Plan, Environmental Monitoring Program and Water Quality Monitoring Plan.
- Implementing an improved dredge method compared to the 2005 Outer Harbor Channel Deepening project, which is anticipated to significantly reduce sediment plumes
- Tracking vessel movements and unloading
- Conducting before and after surveys of seagrass coverage and density
- Providing a Significant Environmental Benefit Payment for seagrass loss recorded post-dredging
- Monitoring by trained Marine Mammal Observers to minimise risks to marine mammals
Additional conditions have been set for minimising the risk of Pacific Oyster Mortality Syndrome (POMS) spreading beyond the Port River and managing biosecurity risks.
What measures are in place to track operations and ensure the licence conditions are being followed?
Flinders Ports will implement set measures, as outlined in the Dredging Licence, Dredge Management Plan and Environmental Monitoring Program, to track its operations and ensure it is complying with licence conditions.
We will regularly report to, and be audited by, the Environment Protection Authority (EPA) throughout the dredge works.
Some of the tracking measures in place include:
Water quality monitoring
Water quality will be monitored every 10 minutes during dredging to measure:
- Turbidity (suspended sediments in water): If turbidity limits are exceeded, dredging will be adjusted or stop
- Photosynthetically Active Radiation: To measure the light on the seafloor available to seagrass
- Dissolved oxygen, pH, salinity and temperature
Marine Mammal Observer will work to spot mammals and alert the dredge team if a mammal is seen within 150 metres of the dredge. Works will be paused or delayed if a mammal is within 50 metres of the Backhoe Dredge.
- Seagrass survey before and after dredging works to track impacts and recovery
- Minimising turbidity during dredging
- Dredging in winter and when water temperature is below 18 degrees, as seagrass is less actively growing and less sensitive to reduced light due to turbidity
Marine pests and biosecurity
- Inspections and thorough cleaning of dredge equipment prior to arrival in Australia
- Pacific Oyster Mortality Syndrome (POMS) Management Plan
- Survey and management plan (if required) of Caulerpa taxifolia (a weed species that impacts seagrass) for the dredge area
Vessel location tracking
To accurately manage and monitor location of the dredge and dredge material placement activities.