Grouted Screw Moorings Offshore Cairns

Scope of Work

Purpose:

Provide environmentally friendly Public Moorings at selected sites around the Cairns area.

Description of Works by PMG:

• Undertake the fabrication of our 4m long Environmental Mooring pins in our Townsville workshop.
• Preparation of all materials, equipment and crew for transportation to the installation sites selected by QPWS.
• Undertake installation of 13 x Grouted Screw Moorings at the preselected sites as follows:
  • SudburyCayx2
  • FitzroyIslandx7
  • GreenIslandx2
  • Vlasoff Cay x 2
• These environmentally friendly moorings were installed into the seabed by commercial divers operating our specially designed Hydraulic Underwater Mooring Machine (HUMM).
• The diver is supported by a topside crew that pumps grout, via an umbilical, down through the mooring pin as it is screwed into the seabed.
• The rotation of the pin mixes the grout with the substrate material to form a column of concrete 4m deep with a 0.6m diameter.
• Once the concrete has cured a selection of the installed mooring pins were load tested using a 6 tonne vertical load, to confirm they have achieved the required holding power.
• Specialised mooring tackle was then connected to the mooring’s pad eye, at seabed level. This tackle uses a floating line that is suspended vertically using a subsurface buoy to provide catenary action for the vessels using the moorings. This has the effect of minimising shock loading during adverse weather conditions.
• The moorings were installed for use as Public Moorings at selected high use sites in the local Cairns area of the Great Barrier Reef Marine Park.