Weipa Mission River Bridge Refurbishment

Scope of Work

Pacific Marine Group has carried out numerous diving inspection, maintenance & repair (IMR) works for Rio Tinto Alcan (formerly Comalco) in Weipa during the above period.

The works required some innovate thinking and application, particularly in the area of predator protection for the divers, and installation of the pile splints, as described below. 

The project involved all areas of PMG’s organisation and showcased our innovative skills Approximately 800 of the Mission River Bridge piles were fitted with reinforcing splints, for strengthening of the piles and protection of exposed steel pile tips. The splint half shells were up to 13 metres in length, with each half shell weighing up to 1.5 T. PMG was involved in the initial design and ongoing development of the splints, the splint installation pontoons and the grouting techniques. 

Since 1997 PMG has completed 11 off 3-4 month diving and marine construction campaigns, as well as smaller campaigns in the intervening years. Up to 20 marine, dive and support crew were involved in the major projects in any 1 year. Up to 4 divers were in the water at any one time, with approximately 900 dives and 1800 hours in-water time completed during the major projects.

The main diving works were carried out on the Mission River Bridge, but smaller scale diving & remote operated vehicle (ROV) IMR works have also been carried out at both Lorim Point Wharves, Humbug Wharf, Evans Landing Wharf, Weipa Sea Leads and in various dams and settlement ponds in the Weipa area.

Diving works completed during the project have included:

• Extensive underwater welding / cutting
• Extensive splinting of piles - Installation of steel splint shells and filling with epoxy grout
• Cathodic Protection system installation and maintenance
• Denso pile protection products installation
• Extensive inspection / underwater NDT / photography / video inspection

The Mission River is home to many salt water crocodiles and other dangerous marine predators. Safe access to the piles has always been an issue, and PMG has continually looked at ways to improve safety. Part of this process has seen the design and refinement of a “predator protection pontoon” or PPP. A 40m x 25m floating pontoon forms the diver support area around each pier and is serviced by the main diving platform barge, either PMG1 or PMG124. 500mm x 500mm rope mesh nets are suspended below the pontoon down to the seabed to provide protection. These nets can be raised / lowered as required to facilitate moving to the next pier. The barge and pontoon are kept in place using a network of anchors. The pontoon is winched to subsequent piers by opening one side of the PPP.

Pacific Marine Group worked under Rio Tinto’s rigorous safety standards and requirements. We have an excellent safety record on these very challenging marine and underwater projects.