Tui Mine remediation delivers excellent stream improvements

Work to remediate the contaminated Tui Mine on Mt Te Aroha has led to water quality improvements and a return of aquatic life in two local streams, latest monitoring results show.

Past problems meant Tunakohoia Stream was contaminated with heavy metals leaching from the mine and was unsuitable for swimming, fishing, drinking or irrigation. The Tui Stream was dead and unable to support any aquatic life. Both streams flow into the Waihou River, and eventually into the Firth of Thames, so the mine’s toxic legacy has extended well beyond Te Aroha.

Now post-remediation monitoring undertaken for Waikato Regional Council shows an excellent improvement in the ecological health of both the Tunakohoia and Tui streams.

The $21.7 million remediation project, which ended in May last year, involved the regional council, the Ministry for the Environment, Matamata-Piako District Council, the Department of Conservation and local iwi.

“It’s great to see this investment paying real dividends for the environment and the local community,” said regional council chairperson Paula Southgate.

The new monitoring results show there has been increased diversity and abundance of aquatic macroinvertebrates, such as stoneflies, caddisflies and diptera, which live in water for at least part of their lifecycle.

These small animals are highly sensitive to pollutants, so an abundance of them is a very positive sign that the water quality is improving in both streams.

“These sorts of results are very positive as they indicate the project is on track to meet water quality levels which will enable swimming in the next 15 years,” said Ms Southgate.

The council’s special projects manager Ghassan Basheer also said that in the Tui Stream there has been a significant reduction in contaminants downstream of the remediated tailings dam.

“While water quality goals for Tunakohoia Stream haven’t reached the levels expected at this stage in the process, water quality is improving and the total weight of contaminants going into the stream is generally on the decline,” Mr Basheer said.

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