2023 review of maintenance dredging of Queensland ports
This review has been prepared by the Queensland Ports Association as part of reporting requirements under the Maintenance Dredging Strategy for Great Barrier Reef World Heritage Area Ports.
Queensland ports require routine maintenance dredging to remove sediments that have accumulated in channels, berths and swing basins due to siltation and sediment transport processes. Most ports cannot sustainably function without maintenance dredging. Maintenance dredging has occurred in Queensland since ports were first established.
Most maintenance dredging is carried out by the Trailing Suction Hopper Dredge Brisbane which undertakes an annual dredging program of Queensland ports over a period of 6–8 months. The dredge, based in Brisbane and operated by the Port of Brisbane Pty Ltd, was specifically designed and built for Queensland conditions with the vessel applying high standards of environmental management. The environmental management mechanisms are equivalent to the features installed in the latest Trailing Suction Hopper Dredge models used around the world and ensure environmental impact is minimised during the dredging works.
In accordance with the Queensland Maintenance Dredging Strategy for Great Barrier Reef World Heritage Area Ports, a high-level schedule of maintenance dredging activities for 2023 was prepared and provided to the Department of Transport and Main Roads. The schedule specifically considered opportunities to minimise both the extent and footprint of dredging activities.
During 2023, maintenance dredging was undertaken at the following ports:
This maintenance dredge program is now complete.
The sections below summarise the outcomes of the 2023 dredge program at each of the above ports in relation to timing, volume and outcomes of monitoring. The comprehensive assessment of disposal options for all maintenance dredge campaigns is undertaken as part of each ports Long Term Maintenance Dredging Management Plan.
Amrun
Maintenance dredging
A total of 34,600m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 9 May 2023 to 11 May 2023. Dredging was undertaken at the Amrun approach and berth pocket.
All works were compliant with state and federal approvals and no environmental incidents or complaints were reported.
Environmental assessments
Seagrass
Seagrass populations around Amrun are located within Boyd Bay, outside the area of impact and no monitoring is required under the Long Term Maintenance Dredging Management Plan.
Water
Visual observations and satellite imagery collected during dredging identified the plume was localised around the dredge vessel.
No vessel-based monitoring is required under the dredge management or environmental management plans based on the volume dredged.
Sediment
A Sediment Characterisation Study was completed in 2023 as per the 5-yearly requirement under the National Assessment Guidelines for Dredging 2009. The sampling confirmed compliance of maintenance dredge material to the guidelines and continued suitability for ocean disposal at the current approved Amrun Material Placement Area. A new Sediment Characterisation Study will be completed prior to the 2028 maintenance dredging campaign.
Turtles and dugongs
Visual observations were completed and recorded in dredge logs. No interactions or observations were recorded during dredging or placement operations.
Biosecurity
All vessels underwent a marine pest risk assessment prior to mobilising to site in which all vessels were assessed as low risk. No marine pests were identified during dredging activities.
Port of Brisbane
Maintenance dredging
A total of 619,752m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 1 January 2023 to 14 April 2023 and the Clam Dredger Ken Harvey from September–December 2023. Dredging was undertaken in the Brisbane River.
Activities were fully compliant with all state approvals (Environmental Authority, Marine Park Permit and Allocation of Quarry Material). No permit non-compliances, environmental incidents or complaints were reported regarding maintenance dredging operations or activities.
Environmental assessments
Seagrass
The Port of Brisbane Seagrass Monitoring Program – the annual survey was undertaken by BMT from 20 July 2023 to 1 August 2023. The results show a broadscale expansion of seagrass meadows at all sites between the 2022 and 2023 surveys. The 2022–2023 period was drier than the previous reporting period providing suitable conditions for seagrass recolonisation and partial recovery following the 2022 flood event. This pattern of seagrass recolonisation was noted following the 2011 and 2013 flooding events, and full recovery will likely take a number of years. The Port of Brisbane continues to work with various catchment management stakeholders to address the causes of excessive sediment generated in rain events.
Water
Triennial dredging turbidity monitoring was last undertaken in February 2023. Reported results were consistent with previous investigations. The monitoring found that the dredging activity created larger plumes than the dredged material disposal. Plumes remained within both dredging areas and the dredged material placement area and there were no impacts on sensitive receptor sites.
Sediment
The annual Sediment Sampling and Analysis Plan was undertaken during September 2023. A total of 35 sites were samples, comprising 26 sample locations within the proposed dredging area and nine reference locations. Results from 2023 were generally comparable to previous, however, zone 2 was observed to have a lower fines concentration than in previous years. Sediments within the dredging zones were found to be suitable for ocean disposal in accordance with the National Assessment Guidelines for Dredging 2009. Nickel concentrations in zones 2,3,4 and some reference sites were reported to be lower than 2022. This is likely a result of lower fines content, which is positively correlated with Nickel. Of interest, pesticide concentrations were reported below the limit of reporting, but had been elevated in previous investigations, specifically following flood events.
Turtles and dugongs
No interaction with dredging.
Biosecurity
In January 2020 the marine pest species White Colonial Sea Squirt (Didemnum perlucidum) was first detected at the Port of Brisbane. This species of marine pest has been detected in subsequent sampling campaigns.
View Port of Brisbane monitoring reports.
Port of Bundaberg
Maintenance dredging
A total of 54,144m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 21 April 2023 to 30 April 2023. Dredging was undertaken at the berths, swing basins, inner and outer channels.
No permit non-compliances, environmental incidents or complaints were reported.
Environmental assessments
Seagrass
The Port of Bundaberg Long Term Maintenance Dredging Management Plan monitoring for seagrass, benthic and particle size analysis assessment at the offshore Material Relocation Area (the area) is undertaken every 5 years with the last survey carried out in 2020. The study showed the presence of a large deep-water seagrass meadow within and outside the area. No differences were found in seagrass biomass and sediment particle size distribution between inside and outside the area. Infauna communities were more diverse and abundant outside the area, however no relationship with increasing distance from the area was found. Therefore, the study showed no evidence of dredge material placement impacts on seagrass and benthic communities occurring outside the area.
Water
A water quality monitoring program has been designed and implemented prior, during and post maintenance dredging operations to ensure water quality does not deteriorate as a result of maintenance dredging plumes and thus to protect sensitive receptors in the area. Turbidity is collected and in the dredging phase data screened against developed turbidity triggers. The monitoring is paired with a tailored adaptive management framework ensuring appropriate actions are taken when turbidity levels reach the above mentioned triggers. No water quality impact was detected from the activity.
Sediment
Sediment quality assessment following the National Assessment Guidelines for Dredging 2009 was last conducted in 2019, with sediments within the dredge footprint found to be suitable for sea placement.
Turtles and dugongs
These include fitting of turtle exclusion devices and includes visual observations with protocols on when to stop activities, wait, and re-commence activity, plus guidance on reporting. Indirect impacts to these species are mitigated through the management of water quality during maintenance dredging activities. No impacts to marine megafauna were identified from the activity.
Biosecurity
No marine pests identified during the activity.
View Port of Bundaberg monitoring reports.
Port of Cairns
Maintenance dredging
A total of 308,303m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 15 July 2023 to 6 August 2023. Dredging was undertaken at the Port of Cairns channel.
A total of 27,870m3 was dredged by the Willunga Grab Dredge throughout the year at portions of the inner port wharves (1–12), Navy Base and marinas.
The permits (including the dredge material placement area location) resolved with the Great Barrier Reef Marine Park Authority during February 2022 were utilised. All works were compliant and consistent with Environmental Authority, Marine Park, and Sea Dumping Permit conditions. The volume dredged was within the annual permit limit. The annual fee for the Environmental Authority was submitted.
No permit non-compliances, environmental incidents or complaints were reported.
Environmental assessments
Seagrass
Cairns Harbour and Trinity Inlet Long Term Seagrass Long Term Monitoring Program – annual survey completed by James Cook University, TropWater, during September (helicopter) and October(vessel). Light data collection and seed viability surveys continued.
Water
Water quality verification under the long-term maintenance dredging management plan or environmental management plan was not required during the period, with campaign specific sampling conducted to validate the hydrodynamic model and address in 2022.
Sediment
Sediment Analysis Plan – implemented during March 2023 for the channel, inner port, marina, and Navy Base areas.
No detection of contaminants exceeding National Assessment Guidelines for Dredging 2009 limits, and material assessed as suitable for unconfined at sea placement under permit conditions.
Turtles and dugongs
No interactions or observations recorded during dredging or placement operations of either the Trailing Suction Hopper Dredge Brisbane or Willunga-tug and barge activity.
Biosecurity
Surveys of areas to be dredged as set out in the Sediment Analysis Plan, along with periodic checks of the monitoring devices within the inner port area were conducted. No detections of actual or suspect material were reported during the year or via the Sediment Analysis Plan process, however ongoing observations of the black scar oyster were made. Implementation of Biosecurity Queensland’s Seaports eDNA Surveillance (Q-SEAS) program continues to be enacted, for ongoing surveillance, with no detections reported.
Port of Gladstone
Maintenance dredging
A total of 276,872m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 9 August 2023 to 11 September 2023, with 252,414m3 placed at the offshore material relocation area and 24,458m3 placed at the in-channel material placement area adjacent to Tide Island. Dredging was undertaken at the berths, swing basins, inner and outer channels.
No permit non-compliances, environmental incidents or complaints were reported.
Environmental assessments
Seagrass
Light is monitored in real time at a seagrass meadow within the zone of influence before, during and after dredging. During the dredging phase, light values as a 14-day rolling average are screened against a light requirement threshold developed through field and laboratory studies. The light monitoring program is incorporated into an adaptive management plan which follows a multi staged approach allowing to implement management responses to reduced light conditions as a result of dredging operations to occur before potential environmental harm to seagrass meadows and sensitive receptors occur.
This is supported by a comprehensive annual seagrass monitoring program that assesses the health of seagrass meadows through three key metrics: surface area, biomass and species composition.
No impact was detected from the activity with environmental factors such as ambient light levels and tidal state.
Water
Real time turbidity monitoring is undertaken at a compliance and support site whose locations have been determined by maintenance dredging plumes modelling and impact assessment. During dredging, turbidity at the compliance site is screened against developed triggers. Adaptive management steps have been developed ensuring appropriate procedures and actions are undertaken when turbidity reaches such triggers in turn ensuring potential environmental harm from dredging related turbidity plumes is identified, assessed, prevented or minimised.
No water quality impact was detected from the activity with environmental factors such as tidal cycles and winds appearing to be the drivers behind turbidity patterns in line with historical data and maintenance dredging campaigns.
Sediment
In line with the Port of Gladstone Long Term Maintenance Dredging Management Plan long-term monitoring schedule and the National Assessment Guidelines for Dredging 2009, sediment quality in the main channels is assessed every 5 years. The sediment quality was assessed in 2022 following the guidelines and found to be suitable for sea placement.
Turtles and dugongs
Direct impacts are mitigated through controls documented in environmental management plans. These include fitting of turtle exclusion devices (where possible) and including visual observation with protocols on when to stop activities, wait, increase visual observations and commence or re-commence activity and guidance on reporting.
Indirect impacts to these species are mitigated through the management of water quality during maintenance dredging activities.
No impacts to marine megafauna were identified from the activity.
Biosecurity
As per the Port of Gladstone Long Term Maintenance Dredging Management Plan long-term monitoring schedule, a survey to identify any marine pests within the port is undertaken every five years. In 2019-2020, the Gladstone Ports Corporation in conjunction with the Department of Agriculture and Fisheries carried out monitoring within the harbour and at the offshore material placement area. Results from the monitoring and related samples collected showed no marine pests detections.
View Port of Gladstone monitoring reports.
Port of Karumba
Maintenance dredging
A total of 79,425m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 23 June 2023 to 8 July 2023. Dredging was undertaken at the channel including amended alignment for the established navigational area.
Bed levelling was also undertaken from 23 June 2023 to 9 July 2023 by the bed levelling vessel Pacific Titan.
Activities were completed under the permit resolved with the Australian Government and an amended Environmental Authority resolved with the Queensland Government during May 2022. All works compliant and consistent with Environmental Authority and Sea Dumping Permit conditions. The volume dredged was within the annual permit limit. The annual fee for the Environmental Authority was submitted.
No permit non-compliances, environmental incidents or complaints were reported.
Environmental assessments
Seagrass
Long Term Seagrass Long Term Monitoring Program – annual surveys were completed by James Cook University, TropWater.
Continued robust and productive meadows were observed in late 2022 and in some areas at near record density or biomass. Potential influence of the near record extended early 2023 wet season across the southern Gulf of Carpentaria on seagrass status was considered in preparation for the mid-year dredging campaign. Outcomes of the annual survey in October 2023 verified continued robust condition of the meadows.
Water
Water quality verification under the Environmental Authority was required during the period, and campaign specific sampling conducted and outcomes satisfactory.
Sediment
Sediment Analysis Plan – 5-year process implemented in March 2020, along with specific sampling of the channel bend navigation area so as to inform application process.
No events recorded within intervening period likely to have caused a change in contaminant status.
Turtles and dugongs
No interactions or observations recorded during dredging or placement operations of the Trailing Suction Hopper Dredge Brisbane activity.
Biosecurity
Benthic surveys were completed in 2020, with no detections within the areas to be dredged or at the dredge material placement area as set out in the Sediment Analysis Plan. There were no detections or reports of actual or suspect material during 2023 period.
Port of Townsville
Maintenance dredging
A total of 306,562m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 13 September 2023 to 11 October 2023. Dredging was undertaken at the Platypus Channel, outer harbours, inner harbour and authorised berth pockets.
A total of 26,937m3 was dredged by the PMG121 Dredge Barge from 5 October 2023 to 21 December 2023 at the Ross River.
Two on board permit compliance observations were undertaken for the Trailing Suction Hopper Dredge Brisbane and three on board observations were undertaken for the Ross River dredging. No environmental incidents or complaints were reported.
Environmental assessments
Seagrass
Seagrass monitoring within Cleveland Bay was undertaken in September and October 2023. The report will be made available on Port’s website once finalised in early 2024.
View the 2022 Cleveland Bay monitoring report.
Water
26 routine marine water monitoring sites were sampled in March, June, August and November 2023 within or adjacent to the receiving environment (Ross River, Ross Creek, Cleveland Bay, Inner Harbour, Outer Harbour, Platypus and Sea Channels). Samples were analysed for suspended solids, nutrients and metals. Results were similar to previous years. Results have contributed to the Dry Tropics Partnership for Healthy Waters Annual Report Card. The 2023 Report Card is based on monitoring data from the previous year, collected from July 2021 to June 2022.
Turbidity and light data was collected in 2023 at several underwater locations in Cleveland Bay. Two real time water quality buoys in Cleveland Bay also measured turbidity, temperature and electrical conductivity. In 2022–2023 one of the water quality buoys had to be removed from the water for an extended period (December 2022 to August 2023) due to equipment failure and long procurement timelines. However, it was redeployed prior to maintenance dredging and placement activities occurring.
Cleveland Bay experienced prolonged and unseasonably high turbidity between July and October 2023. The region between the Burdekin River and Hinchinbrook experienced abnormally high cloud cover and wind for the time of year, causing an increase in turbidity and a decrease in light. In response to these conditions, the Port of Townsville undertook adaptive management and voluntarily implemented additional operational controls for the dredger and water quality was monitored daily using real time water quality buoys during the campaign. The Port’s maintenance dredging Technical Advisory and Consultative Committee was advised and updated throughout this period.
Sediment
In line with the National Assessment Guidelines for Dredging 2009, sediment quality is assessed every five years. The sediment sampling and analysis plan was undertaken in late 2021 and authorised in early 2022. All material, except that in Ross Creek, Berths 3, 5, 8, and Berths 6/7 (no longer in use), and Ross Creek was authorised for unconfined sea placement.
Should any material from these locations need dredging, the Port has sufficient land placement areas to cater for this material.
219 routine marine sediment monitoring sites were sampled in June and October 2023 in and adjacent the Port’s receiving environment. This grab sampling aids in monitoring sediment between the 5-yearly Sampling and Analysis Plan programs.
Turtles and dugongs
Marine fauna visual observations were undertaken during dredging and placement conditions, as per the Port’s permit conditions, and the dredge Environmental Management Plan requirements.
Biosecurity
Port of Townsville partners with Biosecurity Queensland and other Queensland port authorities on the Queensland Seaports eDNA Surveillance (Q-SEAS) marine pest monitoring program. The White Colonial Sea Squirt continues to be sighted in the Townsville Marine Precinct and has been confirmed by eDNA analysis on Berth 11 piles in 2022.
Port of Weipa
Maintenance dredging
A total of 781,300m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 5 May 2023 to 19 June 2023. Dredging was undertaken at the Port of Weipa South Channel, inner harbour and berths.
All works were compliant with state and federal approvals and no environmental incidents or complaints were reported.
Environmental assessments
Seagrass
Annual seagrass monitoring was conducted in the Port of Weipa during August and September 2023. The report will be made available on North Queensland Bulk Port’s website once finalised.
View the Port of Weipa annual monitoring report.
Water
North Queensland Bulk Ports completed ambient marine water quality monitoring prior to, during and post the maintenance dredging program. Data from the water quality monitoring as well as satellite-derived turbidity data was analysed.
The data showed that during the 2023 maintenance dredging program, the turbidity was generally driven by the natural conditions (tidal currents and wind/wave conditions). The Port of Weipa 2023 maintenance dredging program did not influence the regional turbidity of the area.
View the summary of the turbidity monitoring report.
Sediment
A Sediment Characterisation Study was completed in January 2023 as per the 5-yearly requirement under the National Assessment Guidelines for Dredging 2009. The sampling confirmed compliance of maintenance dredge material to the guidelines and continued suitability for ocean disposal at the approved Albatross Bay Dredged Material Placement Area.
Turtles and dugongs
Visual observations were undertaken and recorded in dredge logs. No interactions or observations recorded during dredging or placement operations.
Biosecurity
No marine pests identified during activity.
Specific management measures were implemented during dredging activity at Weipa to minimise the incursion of marine pest species (Dredge Environmental Management Plan).
- Last updated 14 May 2024