Proposal to expand dredging operation in Trinity Inlet – issue summary September 2012

Update 2013 – Trinity inlet fact sheet 1

Cairns Port Authority proposes to:
• Widen the existing outer channel (11.2km long) from 90m wide to 140m wide;
• Increase the depth of the outer channel and inner harbour channel from 8.3m to 9.4m;
• Expand the Dredge Material Placement Area (currently an area of 296ha) by 1 nautical mile seawards;
• Create a new swing basin in the inner harbour and most likely expand the 2 existing swing basins;
• Upgrade the existing cruise shipping wharves 1-5 to accommodate larger and heavier cruise ships; and
• Install some other infrastructure (e.g. a fuel line and potable water supply) to the terminal.

Resulting dredge spoil
• 5,073,600 m3 of dredge spoil from the channel
• 89,700 m3 of dredge spoil for the swing basin relocation
• Estimated annual maintenance dredging quantity for the proposed channel is 580,000 m3 (an increase of 260,000 m3/year from current annual average)

• The proposed works would allow mega cruise ships to dock in Cairns
• The proponent claims that the works would result in an additional 61 annual cruise ship visits by 2025 and states that this would deliver regional economic benefits of $436m. No economic feasibility study has been done, so it is unclear how the proponent arrived at this figure.


Channel Depths
The declared depth for the proposed channel deepening is -9.4m LAT, compared to the current channel declared depth of -8.3m LAT. The channel will be dredged to depths greater than the declared depth in some areas (up to a maximum 1.7m) to allow for siltation between maintenance dredging campaigns.

Swing Basins
In addition to the channel design process, preliminary design was also undertaken for two alternative swing basins. The two options considered were expansion of the existing Crystal swing basin adjacent to Wharves 1–3 for specific use by cruise ships and a new swing basin adjacent to Tropical Reef Shipyard, designated as the Smith’s Creek swing basin. The Smith’s Creek swing basin would be required should HMAS Cairns wish to expand in the future.

Fuel Supply
Currently, cruise liners visiting Cairns do not refuel while in port. However, smaller vessels with potential interests in home porting in Cairns would benefit from the possibility of refuelling. Heavy Fuel Oil (HFO) is not currently available and supplied in Cairns. The existing commercial fuel farm within the Port area is the preferred location for new fuel storage infrastructure. A pipeline would be required from the fuel storage area to the cruise wharf.

Fire Fighting Services and Potable Water Supply
It is proposed to upgrade the existing fire Booster Assembly and provide a loop main system around the Terminal building to provide a separated water network for the fire system.
It may also be necessary to reconstruct the existing potable water supply pipeline where it is affected by the wharf structural upgrade. A number of further studies will be necessary to optimise design requirements prior to upgrading land based infrastructure to accommodate larger cruise ships.


For further details visit the EPBC referrals page.