Dredging proposal for Cairns Port / Trinity Inlet

info sheet

Ports North is proposing to undertake a major dredging operation in Trinity Inlet, however there are serious environmental risks and major community concerns with the proposal.

This proposal is reportedly to allow larger cruise liners to enter Trinity Inlet. The claim is that this will provide economic benefits to the city, however this is yet to be backed up by verifiable economic data.  An alternative exists and is already in operation transferring passengers from the largest cruise ships to shore via tenders to Yorkeys Knob. Our concern is that this major dredging operation will jeopardise the health of the marine ecosystems that many of our tourists come to see.

Giant Clam, Great Barrier Reef. Photo (c) Josh Coates

Giant Clam, Great Barrier Reef – Dredge spoil can smother and choke filter feeding animals and cut off light for photosynthesis. Seagrass, corals, larvae, plankton and hence the whole food chain are at risk. Photo (c) Josh Coates

This Information sheet can be downloaded for printing here: info sheet updated july 2014 web

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Why is new capital dredging of Trinity Inlet a bad idea?

Given the proximity of the Inlet to the Great Barrier Reef (GBR) and its value to the tourism industry, we believe that the risks are too high and that this activity should only go ahead if it can be clearly shown that the dredging will have no adverse impact on the natural environment.

Leading scientists including Professor Terry Hughes Director of the ARC Centre of Excellence for Coral Reef Studies, James Cook University have called for a ban on dredging and dumping in the Great Barrier Reef region.

Concerns over Port Expansions and dredging have lead the UNESCO World Heritage Committee to express concerns and consider listing the GBR as ‘World Heritage in Danger’.

Issues of concern include:

  • Direct impacts on marine life such as  fish, corals, dugongs and turtles.
  • The impact of environmental damage from dredging on the tourism industry, recreational fishing and commercial fishing. Events after capital (new) dredging in Gladstone, including a major fish kill and the devestation of the local fishing industry, should send a clear warning about potential impacts in Trinity Inlet.
  • The release of potentially contaminated sediment into the greater Trinity environment and its impact on both human and wildlife health.
  • Impacts on critical habitat including seagrass beds and coral reef.
  • The cumulative impact of this proposal in the context of the broader Great Barrier Reef (GBR) environment and the massive increase in maintenance dredging that would be required.
  • The environmental and amenity damage of increased (possibly toxic) mud washing up on our Northern beaches.

What is proposed?

Ports North proposes to widen the existing outer channel from 90m to 120-130m, and increase depth of the outer and inner harbour channel from 8.3m to 9.4m. This would mean the removal and disposal of around 4.4 million m3 of dredge spoil from the channel and inlet. Annual maintenance dredging amounts would also be significantly increased.

dredge spoil disposal options map

dredge spoil disposal options map

To give you a feel for just how much this is – Governments have spent over $200 million over 5 years (2009-2013) on a Reef Plan including projects to improve agricultural practices and revegetate stream banks in order to reduce sediment and nutrient run-off into the GBR. These worthy projects have resulted in an estimated prevention of 123,020 tonnes of sediment runoff per year for the whole GBR coastline. Compare this to the proposed dumping of  4.4 million m3 (estimated to be between 4,800,000 to 7,000,000 tonnes dry weight depending on the estimation method used) in one year from Cairns Port alone. This would be a slap in the face for our farmers and other land managers working and investing to protect our reef.

Where would the spoil be dumped?

Options for dredge spoil disposal include dumping in the GBR Marine Park or onshore dumping, both of which pose risks to marine life by increasing sediment and nutrient load and introducing contaminants. Onshore dumping poses risks to terrestrial habitats as well as marine environments. It is estimated that around 80% of the soil to be dredged is potentially contaminated with acid sulphate soils. In contact with oxygen from air or water this material turns into sulphuric acid. Acid sulphate soils are a problem that is well known to Cairns people – over 30 years and millions of dollars have been spent in the ongoing remediation of East Trinity from an ill-conceived bund wall mistake, a mistake we can not afford to repeat.

What does suspending more sediment (dredge spoil) do to our environment?

Dredging and spoil dumping increases water turbidity (muddyness) which smothers and cuts off light to corals and seagrass beds. Our seagrass is in its worst state in recorded history and has not recovered from cyclone Yasi as it should have.

The recently released draft strategic assessment for the GBR World Heritage Area has identified most of the reef as being in poor health and sediment and nutrient load as a major threat to reef health.

Dredge spoil dumped in our region impacts on offshore reefs and would further muddy our beaches.

Resuspension of sediment into the greater Trinity environment could lead to wildlife, and perhaps even human, health impacts. We only need to look at the outcomes of dredging in Gladstone harbour which was associated with fish disease outbreaks and devastated recreational and commercial fishing industries. Recently cover ups and misinformation regarding Gladstone’s world famous water quality problems have come to light and Federal Environment Minister Greg Hunt announced that the Federal Government will no longer allow offshore spoil dumping in the area. We need to prevent the same thing happening locally before the impacts, not after.

Read more about the issue here.