Tweed River Entrance and Beach replenishment project. April 1995 - June 1995
Updated: Jul 20, 2020
Pearl River, the then, largest dredge of its kind in the world
The Ngamotu built-in 1959, originally steam-powered and converted to diesel in the early 1980s
Material Amount: 1.7 million cubic meters
The Company worked for: Dredeco
Our return to Kirra Beach in 1995 seen Bonelli Plant Hire undertaking a much larger project with the Pearl River, the world’s then-largest trailing suction hopper dredger. It had a cubic capacity at the time of 17,000m3 but would generally pump ashore between 9,000 and 12,000m3 in approximately 1hr through the 1m diameter shoreline pipe. That’s a lot of material and water to manage in the hour with a relatively quick turnaround of approximately 3hrs to get ready for the next pump. It was a great job to be a part of. Bonelli Plant Hire successfully provided the machinery and operators to deliver the land reclamation component of the beach replenishment work from Kirra point to Rainbow Bay and North Kirra.
The Ngamotu was a smaller trailing suction hopper dredger which was used for the shallower bar areas. It had a capacity of a mere 490m3 by comparison to the Pearl River’s 17,000m3. It was used to establish a channel through the Tweed Bar. Of significance, whilst on this job, the famous Kirra Beach surf took its toll on the Ngamotu. She suffered a serious incident when operating in a heavy swell, she rolled onto her drag head and was badly damaged. Temporary repairs were made at anchorage before she went to Brisbane for slipping and permanent repairs.
This is Bonelli Plant Hire pushing in a 1500m long by 1m diameter submerged pipeline we built along the southern end of Kirra beach. From memory, we had around 12 machines, dozers, loaders and excavators. Nothing too large, 20-30T excavators, D6-D7 dozers and loaders up to around 30t. The decision was made to try using the existing flanged pipe system that was available from the previous contract just completed at Brisbane port. The pipes were 12m lengths and 20mm thick so approximately 1000 ton of steel once together. Normally this pipeline would be welded together for strength and resistance to leakage. We pushed the pipeline in the water in one piece twice, only to have the bolts shear in several areas due to the breaking surf Kirra is famous for. Once retrieved the engineers came up with a gusset design over the top of the bolted flanges. Once these were welded on we managed a successful launch and the pipeline was sunk in a 20m wide pre-surveyed easement to allow enough depth for the Pearl River to couple up and discharge it's 11000 cubes ashore for us to spread around and place at predetermined heights. This was an amazing project to be a part of working alongside my father Mario who always had a wealth of knowledge to share from decades doing this type of work. Have a look at the photos below.
Below, an aerial view of the pump out on Kirra beach. Quite visible is the contrast between the newly reclaimed sandy beach and the pump out area that still needs sand replenishment.
Below: Looking back from the other direction, the amount of material reclaimed can be clearly seen.
Below: looking along Rainbow Beach
Below: Stripping out the pipeline along Coolangatta Beach at the end of the job.
Below: Pipe line assembly, note the gusset design over the flanges.