SOUTH EAST QUEENSLAND
Palm Beach Artificial Reef – June 2020
volume to Palm Beach would be in the range from 200,000 cubic metres to 450,000 cubic metres, with the area benefited extending from Nineteenth Avenue south to the Palm Beach Surf Life Saving Club. Other predicted benefits included improved surfing amenity over and inshore of the artificial reef and reduced storm erosion inshore. Project Delivery Delivery of the project took place in two phases, starting with sand nourishment in 2017. More than 470,000 cubic metres of sand was delivered along Palm Beach via a split hopper dredge, the Balder R, owned and operated by dredging specialists Rohde Nielsen. The sand was sourced from deposits outside the surf zone in deeper water and placed into shallower nearshore depths within the surf zone via bottom dumping and rainbowing. The sand nourishment was not delivered in a usual ‘Point A-Point B’ continuous progression and
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instead was delivered to different sections of Palm Beach at various times throughout a wider City nourishment campaign. This allowed for flexible sand delivery to minimise the impact to community use of the beach and the provided temporary enhancement of surf amenity. The construction of the PBAR took place between May and September 2019; the second and final phase of the project. The complex marine construction works was undertaken by a joint venture between Hall Contracting and Heron Construction. The PBAR was built approximately 270 metres offshore from Nineteenth Avenue between the beach and the existing, much larger, Palm Beach natural reef. The artificial reef footprint is 160 metres long, 80 metres wide and is 1.5 metres below the average water level at its highest point. The artificial reef was constructed using 60,000 tonnes of a combination of basalt and
ENGINEERING FOR PUBLIC WORKS | SEPT 2020
greenstone rock boulders sourced from quarries across south-east Queensland. The rocks were classed into four sizes at the quarry, with smaller rocks making up the core of the structure ranging between 300-1000 kilograms and armour rocks ranging between one to eight tonnes each. The rocks were loaded onto split hopper barges at the Port of Brisbane before being shipped to the construction site at Palm Beach. Once on site, the barges were positioned and the rocks placed on the seafloor through the split-hopper hull of the barge. A specialist marine backhoe dredger, the Machiavelli, then moved the rocks into position using GPS technology. The backhoe dredger was fitted with a sophisticated machine-controlled computer system that allowed the operator to visualise the seafloor level, the artificial reef design levels and the position of the backhoe dredger in real time. The rocks could then be accurately