A region in NSW is still paying the price for an exotic animal disease outbreak that decimated a poultry farming community 24 years ago.
Almost 2 million birds were slaughtered within a 3-kilometre radius of Mangrove Mountain on the Central Coast to help prevent Newcastle disease from spreading.
The carcasses were then dumped in more than 100 shipping containers and placed in two massive burial pits, while a third site was lined, and filled with potentially virus-contaminated shed litter and manure.
A new rehabilitation project is underway on one of those pits due to subsidence and leachate concerns.
It came as no surprise to long-time local, Margaret Pontifex OAM, who said the outbreak was an experience she would never forget.
She recalled the trauma of watching her family's pet chooks, peacocks and geese euthanised in front of her.
"It didn't matter if your farm was contaminated with Newcastle disease or if it wasn't," she said.
"If it had feathers on it, it had to be killed."
Burial pits resurfaced
The pits are inconspicuous around Mangrove Mountain today — apart from white stacks which stick up out of strangely-contoured ground, releasing methane gas.
The NSW Department of Primary Industries (DPI) was required to keep watch on their long-term environmental impact, which included regular groundwater monitoring.
But more intensive remediation work has started on the pit containing the shed litter, with department documents confirming thousands of litres of leachate had been collected from the property over the years.
According to the documents, "monitoring of the [site] has indicated the presence of elevated nutrients in groundwater".
But the DPI was unable to confirm the source because the pit was understood to be initially excavated into a former effluent storage dam on an old piggery.
The entire waste pit will be re-capped and re-surfaced, without disturbing the contents, in the next three months.
A DPI spokesperson said "all conditions of consent and appropriate biosecurity measures are being taken" while the work was carried out.
The department described it as a "very low" biosecurity risk.
Environmental concerns remain
Ms Pontifex said she had always been critical of the burial pits and their potential long-term impact on the region's drinking water catchment.
"We can't rehabilitate those sites because there's too much chemical, too much methane gas, too much porous sandstone soil," she said.
"I think they'll have to monitor those sites forever."
The department said groundwater monitoring "will continue for the foreseeable future", with samples taken every six months.
The upgrade work on the pit is expected to extend its life for about 25 years.
