Background

• The Port of Hay Point is located 40km south of Mackay (see Map)
• The Ports Corporation of Queensland proposed to undertake capital dredging works in 2006 to increase port efficiency and capacity
• An Environmental Impact Statement (EIS) was undertaken for the project and all relevant Commonwealth and State approvals obtained by the proponent
• An Environmental Management Plan (EMP) was developed in conjunction with regulatory agencies, in particular the Great Barrier Reef Marine Park Authority, to address environmental monitoring and management of the project.

Project details

• Works comprised a ship manoeuvring apron (500m) and a departure path from apron to sea (300- 500m wide, 9.5km long) (see Map)
• The departure path was largely within the Great Barrier Reef Marine Park, with the remainder of the area dredged completely within the Great Barrier Reef World Heritage Area
• Dredging was undertaken using the world’s largest trailer hopper suction dredger, the WD Fairway  from 9 May to 17 October 2006. Dredged material was placed offshore at a material relocation site in the Marine Park (see Map).

Existing environment

• Great Barrier Reef World Heritage Area, Marine Park and existing port
  
• Scattered marine plants and corals, particularly around Round Top Island, Flat Top Island and Victor Islet
• Some turtles and cetaceans (whales and dolphins)
  
• Seafloor was silts and silty fine sands underlain by very stiff clays
  
• Native Title claim over area
  
• Low tourism, recreational and commercial fishing
  
• Sediment to be dredged was uncontaminated with low nutrients.

Predicted impacts (from EIS)

• The EIS identified specific risk-based environmental issues (see below)
• Minimal impact predicted on mangrove and saltmarsh communities, local beaches, air quality, cultural heritage and socio-economic environment
• Low risk to turtles, cetaceans and dugong
• Predicted impact on water quality (increased turbidity) that consequently would impact on coral and seagrass environments at Round Top Island and Victor Islet (impact sites)
• Prediction of 20 per cent loss of coral at Round Top Island and unspecified at Victor Islet
• Predicted impacts on benthos (habitat change - sand to clay)
• Predicted minor change to bathymetry and hydrodynamics
• Removal and burial of marine plants
• Hydrodynamic model showed increase in turbidity at both impact sites.

Environmental risks

An initial risk assessment was done of the project and the preliminary risks were Extreme for five issues of which three could be mitigated to High risk and two to Low risk.

Monitoring and management of project

• Implementation of EMP and environmental aspects of the project managed by a Management Reference Group which comprised the proponent, regulators and environmental consultants
• WD Fairway fitted with turtle excluding devices and dredging limited between April and October to minimise risk to turtles
• Seagrass monitoring comprising two pre-dredge surveys, monthly surveys throughout dredging and six post-dredge surveys
• Introduced marine pest monitoring conducted pre and post dredging
• Fringing coral reef communities at Round Top Island and Victor Islet monitored to determine coral reef condition and change over time
• Sophisticated water quality monitoring undertaken to determine extent of plume and associated turbidity
• An innovative technique using satellite images and modelling was developed by Geosciences Australia and GBRMPA and this was particularly useful for tracking the direction and scale of the surface sediment plumes
• Consultation with community and other stakeholders via Technical Advisory Consultative Committee, public displays, distribution of newsletters and project websites
• Traditional Owners kept updated throughout the project on environmental monitoring outcomes and one Elder undertook a site visit on the WD Fairway.

Project outcomes

• Although the risk assessment for the project identified some significant risks, there was overall minimal environmental impact from the project
• No megafauna captured or injured throughout the campaign
• No marine pests introduced into the port, Marine Park or Great Barrier Reef World Heritage Area from the project
• Hydrodynamic model underestimated turbidity at impact sites due to unanticipated effect of wind/waves
• Victor Islet experienced the highest amount of turbidity and sediment deposition.
• Over 95 per cent of corals remained healthy throughout dredging which is a major positive outcome for the project
• Post-dredge surveys (November 2006 and April 2007) showed most corals had lost sediment cover and were showing signs of recovery.

Lessons learnt

• This was the largest dredging project ever to occur in the Marine Park. It has been regarded by the proponent, scientific community and managers as best practice management
• However, there were some surprises such as very high levels of turbidity (over 1000 NTU). Corals were impacted due to sedimentation (smothering) and turbidity (low light) and fortunately there were generally less impacts on corals at adjacent islands than originally predicted (less than five per cent compared to predictions of up to 20 per cent).
• There will be future capital and maintenance dredging at Hay Point to maintain channel depth. The proponent, community and management agencies will work in partnership to ensure appropriate works are supported by the best science and management to ensure sustainable development and protection of the Marine Park.

More information

• Hay Point project web page