The old Tui mine at Te Aroha in Waikato is getting a clean-up as part of a memorandum of understanding between the Government and the Green Party.
The Government is to contribute $15.2 million, with $1 million coming from two councils.
Environment Minister Nick Smith says the mine poses real safety and environmental risks for the community.
Reports show that a modest earthquake or severe storm could put lives at risk and cause damage of up to $168 million if the tailings dam fails.
Stabilisation of a dam at the former copper, lead, and zinc mine will involve pumping in concrete and lime to strengthen 160,000 tonnes of soil, and lock in the heavy metal contaminants.
Meanwhile the Government has announced a new national standard for better managing contaminated sites.