Work has started cleaning up the old Waiuta mine site - described as New Zealand's most toxic contaminated site - in a joint $3 million operation.
Arsenic levels at the Prohibition and Alexander mines at Waiuta, south of Reefton, are among the highest recorded anywhere in the world at 400,000 parts per million on land - 500 times safe levels.
Decontamination work started at the ghost town last week. The road to the Prohibition Mine is now officially closed, downhill at Dingbat Flat. The access road to Big River remains open.
Department of Conservation acting conservation services director Roy Grose said the remediation work would start in April, with material from the nearby Alexander Mine site to be moved to the encapsulation pit at Waiuta.
The $3.1m cost is being shared between DOC and the Ministry for the Environment. The clean-up was announced in 2013.