2021 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 2021 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 2021, maintenance dredging was undertaken at the following ports:
This maintenance dredge program is now complete.
The sections below summarise the outcomes of the 2021 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.
It should be noted that in 2020, the marine pest species White Colonial Sea Squirt (Didemnum perlucidum) was detected at a number of ports throughout Queensland. Detections of this species were also recorded in 2021. The fecundity of this species limits potential eradication options however Queensland Ports Association will continue to work with Biosecurity Queensland for any further management measures that may be required.
The outcomes of this review will be considered and incorporated into the maintenance dredging schedule for 2022.
Port of Brisbane
Maintenance dredging
A total of 98,000m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 28 December 2020 to 23 March 2021 and 8 July 2021 to 30 September 2021. 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) and no environmental incidents or complaints were reported.
Environmental assessments
Seagrass
The Port of Brisbane Seagrass Monitoring Program annual survey was undertaken by BMT in July and August 2021. Six seagrass species were recorded (Cymodacea serrulate was detected for the first time). Year to year variability in composition and extent of seagrass meadows has continued. Seagrass depth range has remained stable at Fisherman Islands since 2018. Overall, there has been a long-term trend of increasing seagrass meadow extent at Fisherman Islands which continues to represent a critical ecosystem component in western Moreton Bay.
Water
Triennial dredging turbidity monitoring was last undertaken in February 2020. 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 was no impacts on sensitive receptor sites.
Sediment
The annual Sediment Sampling and Analysis Plan was undertaken in June 2021. 43 samples across 4 zones plus reference and placement sites. All sediment determined to be suitable for unconfined ocean disposal. Nickel and pesticide concentrations continuing to decline.
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 88,522m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 25 March 2021 to 3 April 2021. 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
Direct impacts are mitigated through controls documented in environmental management plans. 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 428,858m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 10 June 2021 to 4 July 2021. Dredging was undertaken at the Port of Cairns channel.
At portions of the inner port wharves (1–12), Navy Base and marinas the Willunga Grab Dredge dredged 31,407m3 throughout the year.
All works were compliant and consistent with approval conditions. The volume dredged was within annual permit limit. The annual return and 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 November (helicopter) and December (vessel) 2020. Light data collection and seed viability surveys continued.
Water
Water quality verification under the management plans not required during the period, and no campaign specific sampling conducted.
Sediment
Sediment Analysis Plan was implemented during May 2021 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, with detections of actual or suspect material during 2021 period, however ongoing observations of the black scar oyster were made, and two detections of Asian Green Mussel from two separate sources were reported in September and remain subject of ongoing surveillance to determine if any further presence has occurred. Implementation of Biosecurity Queensland’s Seaports eDNA Surveillance (Q-SEAS) program continues to be enacted.
Port of Gladstone
Maintenance dredging
A total of 239,228m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 2 October 2021 to 4 November 2021. Dredging was undertaken at the berths, swing basins, inner and outer channels.
No permit non-compliances or complaints were reported. One record-keeping anomaly was communicated to the federal environment department where the railing Suction Hopper Dredge plotted an erroneous dump run which did not reflect the actual material disposed lawfully within the East Banks site.
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 3 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 (high or low tide around midday) found to be the main drivers in light changes.
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 2017 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 5 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 100,165m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 19 May 2021 to 5 June 2021. Dredging was undertaken at the Port of Karumba channel.
Bed levelling was also undertaken from 25 May 2021 to 7 June 2021 by the bed levelling vessel Pacific Conquest.
All works were compliant and consistent with approval conditions. The volume dredged was within annual permit limit. The annual return and 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 survey completed by James Cook University, TropWater, during October. Continued recovery was noted since the flood event decline in 2019.
Water
Water quality verification under the management plans not required during the period, and no campaign specific sampling conducted.
Sediment
Sediment Analysis Plan – 5-yearly process implemented in March 2020. 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 2021 period.
Port of Townsville
Maintenance dredging
A total of 259,138m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 5 April 2021 to 22 April 2021. Dredging was undertaken at the Platypus and Sea channels, inner and outer harbours.
At Ross Creek, 9,398m3 was dredged by a Grab Dredge from 13 May 2021 to 4 June 2021. A mini cutter-section dredge dredged 700m3 at berths 9 and 10 on 10 October 2021 and 30 October 2021 to 3 November 2021.
No complaints were reported and there was 1 incident associated with Trailing Suction Hopper Dredge placement of unauthorised material at sea (in the dredge material placement area). Both state and federal environment departments were notified. Material not currently authorised for placement at sea (berths 7 and 8) was dredged and placed in the Port’s dredge material placement area in early April 2021. No environmental harm was caused by the incident.
Environmental assessments
Seagrass
Seagrass monitoring within Cleveland Bay was undertaken in September and October 2021.
View the 2020 Cleveland Bay monitoring report.
Water
Marine water quality monitoring was undertaken 4 times during 2021 at 31 locations 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.
Turbidity and light data was collected in 2021 at several underwater locations in Cleveland Bay. Two real time water quality buoys in Cleveland Bay also measured turbidity, temperature and electrical conductivity throughout the year, including during maintenance dredging and placement activities. Turbidity levels were within the ambient levels throughout maintenance dredging and placement activities.
Sediment
In line with the National Assessment Guidelines for Dredging 2009, sediment quality is assessed every 5 years. The sediment quality was assessed in 2017 and 2018 and all material, except that in Berths 2, 3, 7 and 8, has been found to be suitable for placement at sea. In 2020 sediment quality in Ross Creek was assessed against the guidelines and was determined not suitable for placement at sea. New Sampling and Analysis Plan sampling was undertaken in November 2021. The Sampling and Analysis Plan Implementation Report is pending, due for submission to regulators in February 2022.
Turtles and dugongs
Visual observations were undertaken during dredging. Dredge logs reports were provided, no interactions with marine megafauna occurred.
Biosecurity
Port of Townsville partnering 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 was detected again in the Townsville Marine Precinct as part of this program. All users of the precinct were informed and measures and monitoring put in place to minimise potential spread of this marine pest.
Port of Weipa
Maintenance dredging
A total of 322,833m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 26 April 2021 to 18 May 2021. 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 between the 20 and 24 August 2021. Monitoring in 2021 found seagrasses in the Port of Weipa were in overall good condition. Meadow biomass, area and species composition were similar to monitoring undertaken in 2020.
Total area of seagrass meadows in the region closest to the port (Intensive Monitoring Area) continued to be above the long-term average.
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 2021 maintenance dredging program, the turbidity was generally driven by the natural conditions (tidal currents and wind/wave conditions), with higher turbidity occurring during periods with larger waves. The Port of Weipa 2021 maintenance dredging program did not influence the regional turbidity of the area.
Sediment
A Sediment Characterisation Study was completed in March 2018 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
No interactions or observations were recorded during dredging or placement operations. Mitigation measures such as turtle deflectors and spotter records were assessed as compliant during the Internal Environmental Audit completed during the works.
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