Thousands of tonnes of toxic soil are about to be carefully transported from the far north of the Australian continent to the south.
The Defence Department urgently needs to dispose of 5300 tonnes of chemical-laden soil from the nation's biggest RAAF base at Tindal, near Katherine, in the Top End.
Defence says the highly contaminated soil will be loaded onto a train and sent 3400 kilometres south to a treatment plant in Altona, Victoria for complicated disposal at a high temperatures.
Experts say the 5300 tonnes - the equivalent of 125 B-doubles - is the worst of the estimated 34,000 tonnes of contaminated soil on the air base.
The soil is laden with PFAS, which has been called the forever chemical because of its longevity.
The PFAS was used around the world in firefighting foams because of its ability to help stick and smother flames.
It was used in training by the military at Katherine and other bases like Oakey in Queensland and Williamtown in NSW where contamination issues are also plaguing local communities.
In Katherine, the PFAS foam was used from 1988 to 2004 but it took until 2016 for the alarm to be sounded.
PFAS has been declared safe if avoided by Australian authorities but world health studies say the chemical has been linked to some cancers and diseases.
The chemical has leached from the contaminated soil around the air bases' training area and into the groundwater, moving through the aquifer and under the town of Katherine to empty in the Katherine River.
People have been warned about eating fish from the river for years now.
Defence has paid for a new water treatment plant to clean PFAS from the town's drinking water.
Only in the past week Defence officials said despite all their efforts the contamination is still spreading.
They have a series of pumps working around the clock at the base trying to clean PFAS from the groundwater but experts say PFAS is still leaching from the contaminated soil.
A Defence spokeswoman said about 5300 tonnes of highly contaminated soils will be excavated and sent off-site for destruction.
Defence expects the work to begin next month so it can start transporting the soil in August.
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A product using activated carbon will be mixed with the remaining 28,800 tonnes of less contaminated soils "to immobilise the contamination and prevent leaching of PFAS into groundwater and surface water".
The spokeswoman said the soils would be re-used on site.
The worst of the soil will be excavated and placed in steel containers.
They will be inspected and certified for transportation.
Those containers will be taken by road to the Katherine rail station by a firm accredited by the Northern Territory EPA.
The steel containers will be loaded onto a train and sent to Enviropacific's SOLVE treatment facility in Altona.
Defence said it would be up to the Victorian EPA to consult with environmental authorities "from other jurisdictions through which the soils are transported".
At the Altona facility the PFAS is to be removed from the soil by heating - a process known as thermal desorption.
The PFAS is then destroyed at higher temperatures using a thermal oxidiser which converts the PFAS to carbon dioxide, fluoride and water.
The Defence spokeswoman said this process was different from incineration which typically uses high temperatures without first separating the PFAS from the soil.
Residents from Katherine, Oakey and Williamtown won a $212 million settlement from Defence in a 2020 class action which saw residents paid for lost property values.
That one-off payment is believed to have averaged under $100,000 for more than 1000 residents in Katherine.
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