Cabbage Tree Point Dredging 2016

Cabbage Tree Point Maintenance Dredging and Beach Nourishment 2016

Principal: Gold Coast Waterways Authority

Principal Contractor: Neumann Contractors

Location: Cabbage Tree Point, Queensland

Contract Value: $190,000

Completion Date: November 2016

Cabbage Tree Point Dredging – 2016

Neumann Contractors was contracted by the Gold Coast Waterways Authority to undertake maintenance dredging in the Main Channel North at Cabbage Tree Point.

Over 15,000m3 of material was required to be dredged from the channel to a design depth of -2.7m LAT. The sand was placed on the foreshore at Cabbage Tree Point, adjacent to the channel.

The works are required to maintain safe navigable depth within the Main Channel North, which has been impacted by significant sand deposition and shoaling. This channel forms the primary movement channel for vessels travelling between the northern and southern areas of Moreton Bay, and it is therefore important to maintain navigable depths under all tidal conditions. Due to build-up of sand, water depths within the defined navigation channel at low tide were reduced to under one metre in some areas. Beach nourishment for recreational amenity was the selected dredge material management option to improve the amenity of the foreshore and provide additional protection to land which has been subject to steady erosion.

Scope of Work

  • Mobilisation of a 250mm cutter suction dredge, the Nu Discovery, and 500m of 250mm poly pipeline.
  • Dredging of 15,000m3 of marine sediments for the main channel.
  • Pumping the sediment through pipeline to the deposition site adjacent to the channel.

Challenges

  • Strict environmental guidelines.
  • Maintaining suitable access through the channel and maintaining access to the busy boat ramp.
Nu Discovery - Drawing.jpg

Nu Discovery
, a 250mm Cutter Suction Dredge

The Nu Discovery is a 250mm cutter suction dredge from the Nu Explorer series of dredges. The Nu Explorer series of dredges have been designed and constructed by Neumann Contractors to specifically suit the typical dredging conditions encountered in projects like the Corrie Channel. There are three dredges in the Nu Explorer series that currently complement our fleet (total of 9 Cutter Suction Dredges):

  • Nu Explorer(original dredge in the Nu Explorer Series) has been working in the OTML Mine in PNG for the last two years,
  • Nu Discovery has recently completed work in the Iluka Boat Harbour and Entrance Channel Dredging project,
  • Nu Investigator, is the latest in the fleet and has just completed initial trials and testing at Neumann Contractors, Corridor Sands plant at Woongoolba.

The Nu Discovery is a 227kW (305hp) 250mm three wire cutter suction dredge. The dredge is capable of dredging up to 120m3 per hour (in optimal conditions), dredge to a maximum depth of 6.5 metres, and pump the material up to 1,000m in distance.

The Nu Discovery is manoeuvred by a three wire anchoring system and can be setup to cut the entire width of a channel including any batters in just one cut width. The side anchor ropes remain on the sea bed while the dredge is in operation, which will minimise any inconvenience to other boating traffic through the affected channel areas. The dredge can easily move to one side of the channel to allow for vessel movements.

Cabbage Tree Point - Google Maps Link