The main element in pesticides before World War Two - arsenic - continues to haunt health authorities tasked with cleaning up the poison generations afterwards.
At Jennings, on the Queensland border north of Tenterfield, a century-old processing plant has at last been capped and planted, nullifying the threat of public poisonings for the first time in its history.
The $3.4 million project included the collection of 1650 tonnes of contaminated soil, sealed in a containment cell, Crown Lands reported this week.
The site has been capped with a geosynthetic clay liner, clean soil, compost and overlaid with hessian across an area larger than a football field.
Back in the day, arsenic was the main element in a variety of control measures from bed bugs to cattle dip.
The former Jennings Arsenic Processing Plant was historically used for the production of Prickly Pear poison, developing arsenic trioxide powder from 1923 to 1931.
The site had rehabilitation works in the 1950s and 2000s. Works in the 1950s involved the burial of arsenic impacted soil and drums used in the packaging process. In 2009, works involved rehabilitation to the surface of the site with the addition of topsoil and the creation of surface water control structures.
Arsenic trioxide is used for a range of purpose, from wood preservative to cancer cure, but back then it was key to eradicating a heavy infestation of prickly pear, at the time dominating vast swathes of dry country just to the west.
The early excitement of new industry and opportunity to value-add a commodity in a rural corner of the state gave way to health concerns, after residents reported in 1935 that "poison" washed down the road following heavy rain.
The Tenterfield Star reported at the time that the local council then sent a water sample to the Department of Health, which advised that runoff shouldn't enter natural waterways.
More inspecting and reporting was carried on throughout the 1940s, leading to high hopes for a federal grant to solve the issue. By 1946, 11 years after the alarm was first raised, the local paper reported council to be frustrated by the lack of higher-government resolve.
"That bollocking led to Country Party leader Michael Bruxner raising the matter in parliament receiving assurances from then-premier William McKell that the health minister would 'adjust' the matter," the Star later reported.
"The outcome was the burial of all arsenic-impregnated material onsite, possibly aggravating the problem."
A fence was erected around the site in 1999 to prevent local children using it as a recreational area.
NSW Minister for Lands and Property Steve Kamper said:
"Like many places where historic industrial sites operated, the community at Jennings was left to bear the brunt of contamination from actions that occurred a long time ago.
"The arsenic trioxide produced here may have addressed one problem but left another that has now been finally dealt with."
