Two-phase clean up
Two-phase clean up
The first phase is to prepare the site and remediate the underground parts of the mine. The $4.5 million cost of this is funded by the Ministry for the Environment’s Contaminated Sites Remediation Fund.
Preparing the site and remediation of the underground parts of the mine:
- installation of a concrete bulkhead at the lowest discharge point from the mine
- injections of limestone slurry into the mine workings to reduce the potential for acid rock drainage
- re-contouring and stabilisation of waste rock stockpiles dumped in the Tunakohoia Stream when the mine was operating; this will significantly reduce the contaminant loads that are currently being discharged into the environment.
Proposed action plan (subject to consent)
- Upgrade of Tui Rd, Mount Te Aroha access road and access tracks at the site.
- Lime injections into the mine workings will continue with regular repeats for about the next two years, and then periodically as required. This process was tested and confirmed to be sucessful as part of the remediation trials in October 2009.
- Works within the underground workings, involving the installation of safety features within the Champion level 4 and 5 adit entrances, coffer dams, limestone bunds and outlet control works, and installing the Champion level 5 bulkhead. This is expected to take about eight months.
Some of these upgrade works were completed during the remediation trials late in 2009, while the extension of the surfacing of the Tui Rd was completed late February 2010.
- Work to remediate the waste rock piles at level 4 and 5 adits (entrances to the mine) will take about two months.
- General maintenance and monitoring of the site will be ongoing from 2011.
The Ministry for the Environment is seeking the estimated $13 million funding for the second phase which involves remediating the tailings dam area and making the former ore processing area safe for public access. The second phase includes:
- stabilising the tailings dam using a combination of in-situ stabilisation and blending of tailings, waste rock and lime/cement to provide a geotechnically stable landform with significantly less acid rock drainage potential
- making safe the former ore processing area and tailings dam for general public access and further improving the site through plantings and recreational/educational opportunities.