Environment Waikato and Matamata Piako District Council are to approach the Government for Crown funding to clean up the abandoned Tui Mine near Te Aroha.
The two Councils have received a comprehensive report about the mine, which was licensed by the Crown and operated by Norpac Mining Ltd between 1966 and 1973 to extract a range of metals, including copper, lead and zinc. The company abandoned the site and was liquidated in 1975.
For some years there has been concern about the condition of the tailings dam, the effects on water quality and health risks for people in the area.
An abandoned tailings dam at the site is potentially unstable, and acid drainage from the tailings and the abandoned mine workings have contaminated two streams. The tailings dam is on land owned by the District Council with the mine itself on Crown land administered by DoC.
Environment Waikato and Matamata Piako District Council have been told that there were serious water quality issues downstream, with discharges from the old mine workings and tailings impoundment containing contaminants, particularly metals. The Tui Stream downstream was essentially devoid of life and the Tunakohoia Stream downstream of the mine workings supported only limited stream life.
There had been attempts over the past 25 years to address the issues and to lessen the risk but no significant progress had been made since the 1970s.
Various attempts at lessening the risk had been undertaken. Hauraki Catchment Board did engineering and drainage works on the tailings after the site closed but they were not intended to be a permanent solution. More recently the District Council had done some further maintenance works.
There are risks of mass movement of the tailings should the dam fail, which would result in accelerated siltation of the stream and further deterioration in water quality at best. At worst, there would be a sudden infilling of much of the Tui Stream channel by potentially acid producing sediment and consequent adverse effects on the water in the Waihou River. The contaminated water and tailings could also flood adjacent land.
Over the last few years an informal working party of Environment Waikato, the Matamata Piako District Council, Ministry of Economic Development, DoC, Waihi Gold and the NZ Minerals Industry Association had been investigating options.
Three reports had been prepared, and this year a report on remedial options identified only one that is viable – stabilisation of the tailings dump, with on-going monitoring and maintenance and damming and drainage controls on the mine workings has also been recommended.
Investigative work so far has been funded by the Councils and Ministry for the Environment. Estimated costs of the preferred remedial option total $5.3 million.
Environment Waikato Chairman Neil Clarke and Matamata Piako Mayor Hugh Vercoe said the Councils had asked them to meet with Environment Minister Marian Hobbs, as there was a clear Crown interest - the Crown had authorised the mining operation, and owned the minerals that were mined.