HMAS Adelaide Decommissioning & Scuttling
McMahon Services decommissions and sends ex-HMAS Adelaide on her final journey
The ex-HMAS Adelaide has settled in her final resting place on the bottom of the sea, 1.8 kilometres off Avoca beach on the New South Wales central coast after a textbook scuttling carried out by McMahon Services. The scuttling event on 13 April was seen by millions around Australia and the globe, however few saw the extensive amount of work undertaken by McMahon Services to prepare the 138-metre vessel for the historic occasion.
Countless hours were spent cleaning and stripping the ex-HMAS Adelaide to ensure it could be scuttled safely and begin its new life as a world class recreational dive site. Led by project Manager Andy Levett and General Manager, Andrew McMahon, the McMahon Services team undertook a rigorous and thorough program to prepare the former Navy vessel.
The program included the removal of:
- 80 tonnes of lead ballast
- 180,000 litres of hydrocarbons in the form of diesel fuel and oily water
- 300 tonnes of steel bulkheads and equipment
- 60 tonnes of rubbish including timber and plastic foam
- 150,000 square metres of fiberglass insulation
- 500,000 lineal meters of electrical communication cable
- 20 tonnes of materials including batteries, mercury switches, fluorescent lights and transformers containing printed circuit boards and asbestos containing materials
Andrew McMahon said a total surface area of 350,000 square metres was cleaned by hand and over 500 tonnes of equipment was removed.
“This was an exciting and extremely challenging project. We effectively stripped the ship from inside out – there wasn’t a single surface we left untouched,” he said.
“We also removed and modified the vessel’s machinery spaces, bulkheads, non-structural partitions and decks to make the vessel safe and more interesting for divers. This included inserting barriers for unsafe areas without limiting vision, and altering sections of the ship to allow light to penetrate.”
On Monday 11 April, the ex-HMAS Adelaide began her final journey just after 6am. With a heavy police presence and a small flotilla of other vessels, three tugboats guided the ship from her berth at Glebe Island Wharf in Sydney Harbour, through the Sydney heads towards Avoca Beach. Spectators lined vantage points, mediacrews scrambled to get the best shots and helicopters circled above as the ex-HMAS Adelaide proudly made her final appearances beneath the Harbour Bridge and Sydney Opera House.
After the three-hour journey, the ex-HMAS Adelaide spent two nights anchored off Avoca Beach before the scuttling, scheduled for 10.30am on Wednesday 13 April. To sink the vessel, Andrew McMahon said the experienced McMahon Services team had attached a series of cutting charges to the frigate’s hull.
“The linear cutting charges consisted of an explosive core and an external copper sheath to cut the steel by forming a jet of liquefied copper,” he said.
“The low speed explosive charge would cause a collision of the external copper sheath, effectively melting the copper strip and forming a plasma jet to cut through the ship’s hull.
“The cutting charges were designed to simultaneously blow eight holes, approximately one square metre in size, in both sides of the ship’s hull. We had also cut 19 holes in the ship’s hull above the water line to assist the sinking process.”
All was in readiness for the occasion. Conditions were perfect and thousands of people were joined by eager media crews to witness the historic event from outside the one kilometre exclusion zone. Just moments before detonation – a splash was spotted near the ex-HMAS Adelaide. A pod of inquisitive dolphins had entered the exclusion zone forcing officialsto lure them away – a process that delayed the scuttling for around an hour.
Despite the interruption, the lucky winner of a “Push the Button” competition was able to simulate the actual ignition by a computer based digital electronic initiating system. To visually enhance the occasion, McMahon Services installed a series of pyrotechnic explosions on the vessel’s deck as the cutting charges detonated below the water line.
The ex-HMAS Adelaide went down just before midday. It took a couple of minutes for the vessel to disappear below the surface. The bow of the vessel went down first as water flooded through holes created by the explosive cutting charges. She eventually came to rest in an upright position on the ocean floor, 32 metres down.
As a result of McMahon Services’ meticulous planning, preparation and execution on the day, the ex-HMAS Adelaide is now destined to become one of the world’s premier recreational dive sites with many divers already enjoying the underwater experience.
