| Australian Broadcasting Corporation | Extract
DARWIN - It is an unlikely setting for the final chapter of an international diplomatic scandal, but Darwin's waste dump holds an extraordinary secret beneath the surface.
"A few years ago, we had a couple of shipping containers turn up here that were required to be buried," Nik Kleine, the City of Darwin's executive manager of waste and capital works, said.
The containers had arrived from the Royal Australian Air Force base at Tindal, near Katherine.
"We were alerted that [there] were aircraft in those containers," Mr Kleine said.
Until now, the specific details of the aircraft remained a mystery outside the Defence community.
But the Defence Department has confirmed to the ABC the aircraft buried in the hazardous waste section of the tip in 2016 were two Russian-made military attack helicopters.
The Mi-24 Hind gunships had been part of a saga known as the Sandline Affair, which made international headlines in the late 1990s.
"It just adds some notoriety to the site, I suppose," Mr Kleine said.
Australia controversially took possession of the choppers in March 1997, after a giant cargo plane transporting the military equipment to Papua New Guinea was diverted to the Northern Territory.
The attack helicopters were part of a $US34 million (K115 million) deal the PNG government had signed with a UK-based private military company called Sandline International.
The choppers, along with several dozen mercenaries, were intended to be deployed in Bougainville in a bid to quash secessionists on the island.
But the plan never eventuated: the mercenaries were booted out of PNG, the country's prime minister Sir Julius Chan was forced to resign, and the cargo plane never made it to its destination.
Instead, it ended up at the Tindal RAAF base, where details about the cargo were initially kept from the public.
The ownership dispute between the PNG government and Sandline International lasted for more than a decade and left the Australian government with little choice but to indefinitely keep hold of the choppers.
It was not until 2016 — almost two decades after the Sandline Affair — that the choppers were finally removed from Tindal.
"The two Mi-24 helicopters were stored at RAAF Base Tindal between March 1997 and July 2016 pending the status of the equipment and subsequent decisions relating to the most effective method of disposal," Defence said in a statement.
"A technical assessment was conducted to ensure that any hazardous materials were removed or contained.
"The helicopters were subsequently disposed of via containment burial at the Shoal Bay Landfill site in Darwin in July 2016."
While Darwin's waste dump now marks the final chapter of the helicopters' story, the issues that brought them to Australia are yet to be fully resolved.
But that could change next month, when Bougainville's 300,000 people begin casting their votes in an independence referendum.