2018 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 was prepared on 29 March 2018 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 2018, maintenance dredging was undertaken at the following ports:
This maintenance dredge program is now complete.
The sections below summarise the outcomes of the 2018 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.
The outcomes of this review will be considered and incorporated into the maintenance dredging schedule for 2019.
Amrun
Maintenance dredging
A total of 42,038m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 1 May 2018 to 4 May 2018. Dredging was undertaken at the Amrun export facility.
Activities were undertaken in accordance with approval requirements including locations, dredge volumes and reporting requirements. No permit non-compliances, environmental incidents or complaints were reported.
View the annual Amrun compliance report.
Environmental assessments
Seagrass
A small area of seagrass has been recorded adjacent to the Boyd Bay beach (north of Boyd Point) with no seagrass found within the Boyd Point to Pera Head area with physical conditions, sediment and prevailing bathymetry unlikely to support seagrass in close proximity to the Port. Based on this and the information presented on water quality, impacts to seagrass are expected to be nil to low.
Water
Dredging and disposal operations occurred over four days and therefore water quality impacts would be temporary (short term) and of a shorter duration than those experienced naturally in the wet season. Boat-based turbidity monitoring was completed daily using a hand-held water quality probe that recorded turbidity at five inshore water quality monitoring locations with 5 readings collected approximately 1m from the seabed. Based on the data collected plume water quality impacts associated with dredging are assessed as nil to low.
View the water quality report.
Sediment
As above.
Turtles and dugongs
No interaction or observations were recorded during dredging or placement operations.
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 no detections of actual or suspect material. There is an established marine pest surveillance program which forms part of the monitoring arrangements defined in the Port Maintenance Dredge Management Plan.
Port of Bundaberg
Maintenance dredging
A total of 51,272m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 26 March 2018 to 30 March 2018. 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 Long Term Maintenance Dredging Management Plan monitoring schedule for seagrass, benthic and particle size analysis assessment at the disposal site is scheduled for monitoring every five years with the last survey undertaken in 2015.
Water
A water quality monitoring program has been designed and implemented to maintain water quality and protect sensitive receptors in the area. This includes real time turbidity monitoring. No water quality impact was detected from the activity.
Sediment
Sediment Quality assessment against the National Assessment Guidelines for Dredging 2009 was last conducted in 2014 and found to be suitable for placement at sea.
Turtles and dugongs
Indirect impacts to these species are mitigated through the management of water quality during maintenance dredging activities. Direct impacts are mitigated through controls documented in environmental management plans. These include fitting of turtle exclusion devices where possible, visual observation, dredge management, retrieval and reporting protocols. No impacts to marine megafauna from the activity.
Biosecurity
No marine pests identified during the activity.
Port of Cairns
Maintenance dredging
A total of 513,858m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 11 August 2018 to 6 September 2018 and 29 October 2018 to 3 November 2018. Dredging was undertaken at the Port of Cairns channel.
At portions of the inner port wharves (1–8), the Marlin Marina (northern), the Willunga Grab Dredge dredged 3,889m3 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 during September. No permit non-compliances, environmental incidents or complaints were reported.
Environmental assessments
Seagrass
The Cairns Harbour and Trinity Inlet Long Term Seagrass Long Term Monitoring Program annual survey was completed by James Cook University, TropWater, during October (helicopter) and December (vessel) 2018.
Quarterly light data collection and seed viability surveys continued.
Water
Water quality verification was not required during the period. The program for the Trinity Inlet inner port areas continued periodically, with outcomes consistent with long-term trends. Dry season data collection at one of the sites for the Cairns Shipping Development Project was inclusive of the late October maintenance dredging period.
Sediment
The Sediment Analysis Plan was implemented between April and August for the channel, inner port, marina, and Navy Base areas.
No detection of contaminants exceeding the National Assessment Guidelines for Dredging 2009 limits, some required phase three for certain areas (2 marinas) above screening guidelines levels. The material was ultimately 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 no detections of actual or suspect material during 2018 period.
Ports North is also partnering with Biosecurity Queensland and other Queensland port authorities in an early warning pilot study.
Port of Gladstone
Maintenance dredging
A total of 211,102m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 14 November 2018 to 17 December 2018. Dredging was undertaken at the berths, swing basins, inner and outer channels.
At the Boyne River mouth, a Grab Dredge dredged 30,580m3 throughout 24 February 2018 to 15 September 2018. No permit non-compliances, environmental incidents or complaints were reported.
Environmental assessments
Seagrass
The monitoring program for the Grab Dredge campaign was designed around the Queensland Government common conditions appropriate to the size of the campaign and based on the known Benthic Photosynthetic Active Radiation or light thresholds of seagrasses in the Port of Gladstone area. This included visually observations, spot checks and using an adaptive management flowchart to guide decision making. No impacts to seagrass were identified from dredging activity.
For the Trailing Suction Hopper Dredge campaign, a light monitor is deployed at the seagrass meadow within the potential zone of influence of maintenance dredging plumes. Light thresholds have been established for seagrass at the Port of Gladstone and are applied to maintain growing season light requirements in conjunction with an adaptive management flowchart that prompts evaluation and management actions to protect seagrass. This is supported by ongoing ambient seagrass monitoring programs that map and monitor the health of meadows. No impact was detected from the 2018 campaign.
Water
The monitoring program for the Grab Dredge campaign was designed around the Queensland Government common conditions appropriate to the size of the campaign. This included daily visual plume (impact detection) monitoring with adaptive management rules and actions. This was supported by spot check impact detection turbidity monitoring upstream, downstream and at sensitive receptors with an adaptive management flow chart to feed back into the visual plume monitoring adaptive management. No impact to water quality was detected.
For the Trailing Suction Hopper Dredge campaign, real time turbidity monitoring is undertaken inside and outside the potential “zone of influence” as determined by hydrodynamic modelling of maintenance dredging plumes. It is used in conjunction with an adaptive management flowchart that prompts evaluation and management actions. Impact detection water quality sites are sampled before, during and after dredging. This includes sampling for metals and Tributyltin at near and far field monitoring sites. This is supported by ambient real time water quality monitoring by Gladstone Ports Corporation at sites within the Port of Gladstone and support for the Port Curtis Integrated Monitoring Program and Gladstone Healthy Harbour Partnership. No impact was detected from the 2018 campaign.
Sediment
For the Grab Dredge, sediment quality was assessed using the National Environment Protection (Assessment of Site Contamination) Measure and National Assessment Guidelines for Dredging 2009 and was found to be suitable for placement on land. The Acid Sulphate Soil Management Plan included protocols for testing, treating and validating any potential acid sulphate soils in line with Queensland Government guidelines. No potential acid sulphate soils were detected in the sediments brought to land, therefore no treatment or validation testing was required.
For the Trailing Suction Hopper Dredge, in line with the monitoring schedule in the Long Term Maintenance Dredging Management Plan, sediment quality in the main channels is assessed every 5 years. The sediment quality was assessed in 2017 using the National Assessment Guidelines for Dredging 2009 and was found to be suitable for placement at sea.
Indirect impacts to these species are mitigated through the management of water quality and seagrass meadows during maintenance dredging activities. Direct impacts are mitigated through controls documented in environmental management plans. These include fitting of turtle exclusion devices where possible, visual observation, dredge management, retrieval and reporting protocols.
No interactions or incidents recorded.
Biosecurity
The Port of Gladstone Long Term Maintenance Dredging Management Plan has a 5-yearly marine pest survey schedule, due next in 2019/2020. None of the species recorded in the 2015 Biosecurity Survey of the Port of Gladstone are included in the Australian Emergency Marine Pest Plan Trigger List. Additionally, none of the species are listed as “high risk” species in either the Introduced Marine Pest or Declared Pest lists on National System for the Prevention and Management of Marine Pest Incursions.
The Gladstone Ports Corporation is also partnering with Biosecurity Queensland and other Queensland port authorities in an early warning pilot study.
No marine pests were identified during activities.
Port of Karumba
Maintenance dredging
A total of 508,841m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 5 May 2018 to 19 July 2018. Dredging was undertaken at the channel.
All works were compliant and consistent with approval conditions. The volume dredged was within the annual forecast. The annual return for the Environmental Authority was submitted during July. No permit non-compliances, environmental incidents or complaints were reported.
Environmental assessments
Seagrass
The Port of Karumba Long Term Seagrass Long Term Monitoring Program annual survey was completed by James Cook University, TropWater, during November 2018, with sustained very good seagrass meadows present, and continued high biomass and seed bank stability.
Water
Water quality verification not triggered or required during the period. No significant wet season events in the months preceding the 2018 campaign.
Sediment
The Sediment Analysis Plan was implemented in 2015, with no noted evets likely to have changed the contamination status of the outer channel area. All past work has confirmed suitability for unconfined at sea placement under permit conditions.
Turtles and dugongs
No interactions or observations recorded.
Biosecurity
Surveys of areas to be dredged as set out in the Sediment Analysis Plan in 2015 verified, with no reports of detections from the state or federal governments of any actual or suspect material during the 2018 period.
Port of Townsville
Maintenance dredging
A total of 376,135m3 was dredged by the Trailing Suction Hopper Dredge Brisbane during July, August and November. Dredging was undertaken at the Platypus Channel, berths, inner and outer harbours. A Grab Dredge also dredged 2,260m3 at Berth 3 in January and February.
No permit non-compliances, environmental incidents or complaints were reported.
Environmental assessments
Seagrass
Seagrass monitoring within Cleveland Bay was undertaken in October 2018 with verbal confirmation that many dugong feed trails were again seen throughout the monitoring meadows. The report will be made available on Port of Townsville Limited website once finalised and provided to the federal environment department as required by the deed of agreement.
Water
Marine water quality monitoring was undertaken 4 times during the year for locations within, adjacent to or within the surrounding receiving environment (Ross River, Ross Creek, Cleveland Bay). Samples were analysed for suspended solids, nutrients and metals. Results were similar to previous years sampling. Results showed nutrient input via Ross River, and nutrient and metals input via Ross Creek.
Turbidity and light data was also collected in 2018 at several underwater locations within Cleveland Bay. The preliminary report shows that Turbidity results appear to be influenced by climatic events, with seasonal variation evident. These results in turn influence the seabed light readings. Strong correlations between turbidity and light indicate strong relationships between these parameters. Correlations between turbidity and total suspended solids were also explored, however no strong relationships between these parameters were identified.
In 2018 a number of real time water quality buoys were deployed in Cleveland Bay to measure turbidity, pH, temperature and electrical conductivity. The real time continuous data that is being generated is helping to understand the ambient water quality conditions in Cleveland Bay. A water quality dashboard is being finalised to display the data on Port of Townsville Limited's website.
Monitoring was undertaken during maintenance dredging and placement activities in July/August. The buoys were positioned one kilometre from the edge of the dredge material placement area; and in two bays on Magnetic Island. There were no changes to turbidity levels recorded in this time, all recorded to be within the normal background levels throughout both maintenance dredging and placement activities. Results have contributed to the Dry Tropics Partnerships for Health Waters – Waterway Health Report Card, which is due for release in early April 2019.
Sediment
A Sediment Sampling and Analysis Plan was undertaken in 2017 as per the 5-yearly requirement under the National Assessment Guidelines for Dredging 2009. All material, except that in berths 2, 3, 7 and 8, has been approved for unconfined sea placement as per the guidelines.
A targeted analysis of berths 2, 3, 7 and 8 was undertaken in 2018, the final report is pending.
Turtles and dugongs
No interactions recorded.
Biosecurity
Formal marine biosecurity monitoring within the inner harbour undertaken. Ad-hoc visual observations on vessels removed from the harbour (for cleaning/repairs).
Port of Townsville Limited is also partnering with Biosecurity Queensland and other Queensland port authorities in an early warning pilot study.
Port of Weipa
Maintenance dredging
A total of 591,875m3 was dredged by the Trailing Suction Hopper Dredge Brisbane from 5 April 2018 to 30 April 2018.
A dredging incident occurred within the Port of Weipa on 22 April 2018 which involved one dredge run of the dredging work being undertaken outside of the approved dredge area (500m3); but within the existing navigation channel. An investigation completed by North Queensland Bulk Ports concluded that it was very unlikely environmental harm was caused and recommended several corrective actions.
In response to this, in November 2018, the federal environment department issued a caution notification for contravention of the permit. The department confirmed it was satisfied that 'the incident was unlikely to have caused substantive environment impacts' and informed that no further action would be taken.
No environmental complaints were reported.
Environmental assessments
Seagrass
The most recent seagrass survey was completed in November 2018, reports are currently being finalised. The 2017 surveys found seagrasses within the Weipa area to be in a strong condition.
Preliminary results from the 2018 surveys indicate seagrasses remained in a strong condition with distribution likely to be similar to previous years. In particular it was noted that Enhalus acoroides meadows showed good coverage, prolific flowering and minimal leaf burning with dugong feeding trails throughout.
Water
Whilst not required as part of current approval obligations, North Queensland Bulk Ports commenced voluntary ambient marine water quality monitoring in January 2018. This program is ongoing and includes in-situ real-time loggers alongside six-weekly vessel-based laboratory sampling. Reports for the 2017–2018 period are currently being finalised. Preliminary results from the high frequency seafloor-mounted loggers continue to demonstrate an important coastal process both along the east coast ports and Weipa – that wave pressure (swell and tide) continues to be the main drivers of suspended sediment concentrations in the water column, well above local water quality guidelines.
Sediment
The Sediment Characterisation Study completed in March 2018 confirmed compliance of maintenance dredge material to the National Assessment Guidelines for Dredging 2009 and continued suitability for ocean disposal at the current approved material relocation area.
Turtles and dugongs
No interactions or observations recorded during dredging or placement operations of the Trailing Suction Hopper Dredge Brisbane. Mitigation measures such as turtle deflectors and spotter records were assessed as compliant during the internal environmental audit completed during the works.
Biosecurity
North Queensland Bulk Ports undertake an ambient early-detection monitoring program of settlement plates within the Weipa marine port area. In mid-2017 a single detection of an Asian Green Mussel was identified in the Weipa area (Amrun). The monitoring program was ramped up to response mode and was maintained at this level throughout the full 2018 dredge campaign. No further detections have since been found, monitoring continues.
The Department of Transport and Main Roads Risk Assessment completed prior to commencement of this years’ campaign also included details regarding vessel inspections and low level of risk prior to commencement.
North Queensland Bulk Ports is also partnering with Biosecurity Queensland and other Queensland port authorities in an early warning pilot study.
- Last updated 14 May 2024