Minister asked to clean up Puhipuhi's toxic mercury mine

Rusting tanks at the old mercury mine site at Puhipuhi.

Members of the Puhipuhi Mining Action Group headed to Waitangi yesterday to ask Conservation Minister Eugenie Sage to support the remediation of an old mercury mine at the settlement.

Ngāti Hau kaumatua Te Raa Nehua led the delegation.

The group has been asking since 2015 for the toxic mine opening and surrounds on Puhipuhi Mountain, 30km north of Whangārei, to be fixed and sealed.

Scientific analysis of samples shows mercury is still being released from the site.

The Northland Regional Council (NRC) and local hapū Ngāti Hau spent 12 months testing water and sediment samples from a number of sites around and below the old mercury mine.

A report from NRC states: "All the sites showed test results above the trigger limits for mercury in sediments. The results ranged from two to 28 times for seven of the sites, with the old mine dam outlet over 500 times greater than the trigger limit."

A study by geologists from the School of Earth Sciences at Melbourne University showed similar results, Puhipuhi Mining Action Group (PMAG) said.

Mercury leachate from the site potentially goes into Northland's biggest water catchment and from there into Kaipara Harbour and the Tasman Sea.

A Niwa study for the integrated Kaipara Harbour Management Group said the greatest amount of sediment into the harbour comes from the Hikurangi Swamp area.

That catchment is fed by the Waiotu, Waiariki and Whakapara Rivers which flow from Puhipuhi then, via the Wairua, Mangakahia and Northern Wairoa Rivers, into the harbour.

PMAG said the immediate priority was to stop the mercury at its source by remediating the old mine: "Work that should have been done decades ago."

The Environment Ministry holds an annual $2.63 million Contaminated Sites Remediation Fund [CSRF], available to regional councils and unitary authorities for the remediation of sites that pose a risk to human health and the environment.

Regional councils and unitary authorities submit information on contaminated sites they consider priorities and the 10 sites determined as posing the greatest risks are placed on the CSRF Priority List. Not all contaminated sites are eligible for funding.

Eugenie Sage is also the Associate Minister for Environment.

Mercury was mined on Puhipuhi off and on until 1945.