Port Avatui Redevelopment Dredging Works

Project: Port Avatui Redevelopment Dredging Works
Location: Rarotonga, Cook Islands
Client: Cook Islands Port Authority (Subcontractors to McConnell Dowell)

The backhoe dredge Kimahia and 450m3 hopper barges H7 and H8 were towed from Auckland, New Zealand to Rarotonga in the Cook Islands by the tugs Pacific Way and Christine Mary, a trip of some 1600 nautical miles and 17 days. The Pacific Way remained in Rarotonga to support the dredging operations while the Christine Mary returned to New Zealand. The newly purchased Hitachi ZX 670-3 excavator was shipped up to Rarotonga direct from Auckland. The 65 tonne machine was stripped down to component sizes that the ships cranes could safely lift and was reassembled upon arrival in Rarotonga.

An assessment was undertaken to determine what parts would be required to maintain the Liebherr 984, Hitachi ZX670 and the tug Pacific Way, as a result a 20’ shipping container was packed with oil, lubricants, filters etc to service all the equipment for the 3 month contract duration along with hydraulic pumps and motors, hydraulic cylinders, a splitter box, excavator bucket teeth, hydraulic hoses and fittings of various sizes as well as hydraulic hose crimping machine as there were no facilities in Rarotonga that could provide the backup and service Heron required.

The Kimahia, dredged approximately 80,000m3 of silts, sands and gravels from that Avatui Harbour to create berths and a turning basin to a depth of -8.5m CD. The loaded barges were manoeuvred to the Avatui wharf with the tug Pacific Way, the land based 65 tonne Hitachi excavator transferred the dredged material from the barges into for transportation to the stockpile areas.

An area of very hard coral was encountered adjacent to the new wharf structure that could not be dredged using a traditional heavy duty rock bucket, while drilling and blasting was permitted it was decided that the risk of damaging the newly completed wharf was too great, Heron modified an existing single tyne ripper in our Papakura workshop to suit the backhoe dredge Kimahia. The 4.5 tonne ripper was packaged and loaded into a Boeing 777 and flown to Rarotonga. The ripper successfully fractured the coral rock allowing it to be dredged with the heavy duty rock bucket.

Upon completion of the dredging, the Christine Mary was dispatched from Auckland, the Kimahia was demobilised and together the Pacific Way with the Kimahia and the Christine Mary with Hopper Barges H7 and H8 were towed back to New Zealand.