Personnel in the Australian coastal mine hunter HMAS Yarra have used their diving expertise to recover an anchor and shackles weighing one tonne from the seabed near Ashmore Island.
The anchor, belonging to Armidale class patrol boat HMAS Bundaberg, was cut lose when it firmly wedged beneath a large boulder and the sea floor during a recent patrol for Operation RESOLUTE – the Australian Defence Force’s contribution to the whole-of-government effort to protect Australia’s borders and offshore maritime interests.
Yarra, also assigned to Operation RESOLUTE, conducted a reconnaissance dive at the site on the 22 June 2014.
Commanding Officer of Yarra, Lieutenant Commander Brendan O’Hara, said the initial reconnaissance dive took approximately one hour.
“Before leaving the area, Bundaberg marked the location of the anchor using an orange pimple buoy,” he said.
“During the recon dive, the divers identified the required direction to pull the anchor using a magnetic compass, and then we developed a plan on how to recover the anchor.”
The recovery serial took place the following day, commencing at 9:30am with the launch of the dive boat and ending with the anchor recovery at 11:30am.
Once in the water, the divers made their way to the anchor to connect the recovery line. The ship was then moved into position using Auxiliary Power Units to pull the anchor out from beneath the boulder on a bearing provided by the divers.
Next, a tow line was passed to the ship and connected to the stern. The ship’s main engine was started and, in conjunction with the Auxiliary Power Units, the anchor was successfully retrieved.
The recovery of the anchor to the waterline was next tackled using Yarra’s sweep winch. Once on the waterline, a lifting strop was connected to the starboard-side crane on the sweep deck and the anchor was lifted onto the deck.
Lieutenant Commander O’Hara said having to use the ship in a tow-configuration to pull the anchor out from under the boulder was unique.
“We don’t train specifically for this, but we utilised the same techniques that we might use to recover a mine from the seabed,” he said.
“The recovery was a good opportunity to put our skills in planning and execution to the test.”
Bundaberg’s anchor has now been returned to Patrol Boat Group via HMAS Coonawarra in Darwin.