Controversial gold mine’s possible effects on water quality debated at hearings
Monday, 15 June 2026
More testing and information will be needed to understand the risks to water quality of a proposed Central Otago gold mine.
This point was made repeatedly at hearings into Santana Minerals’ application to build a large gold mine in the hills near Cromwell, above the Clutha River.
The contentious proposal is being considered by a fast-track panel, and moved into a second week of expert hearings on Monday in Wellington.
The hearings see experts from Australian company Santana Minerals and other interested parties discuss crucial issues in front of the panel, in what is sometimes known as “hot-tubbing”.
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Risks to water quality from the mine include seepage of chemicals into aquifers used by nearby residents and businesses; into two streams within the mine site and the rivers they flow in to; toxicity of the lake water left in two unfilled mine pits; and in the tailings dam, where 22 million tonnes of chemical waste will be stored forever.
One of Santana’s groundwater experts, Jens Rekker, said while more research could be done, enough was understood about the area’s hydrogeology to know what the mine’s effects were going to be.
Rekker agreed with fast-track panel chairperson Matthew Muir, KC, who suggested it was a case of, “You can always do more, but we think we’ve done enough.”
However, a series of other experts, including some of Santana’s own experts, accepted more information was needed.
This included drilling more monitoring sites to understand the movement of groundwater under the mine site.
Santana expert Ryan Burgess acknowledged that a statement by all the experts who had discussed these issues, noted one monitoring site found “considerably different hydrogeological conditions than anticipated”.
Environmental Defence Society expert Leanne Morgan said insufficient work had been done by Santana, and it was still unclear where groundwater and contaminants would move, and more monitoring wells were required, which would be expensive.
“For a project of this scale, I think there’s a requirement to do this work.”
She suggested further investigations may show that things are quite different to what had been imagined, and it may take two years to obtain the information required.
Otago Regional Council expert Alexandra Badenhop criticised the lack of baseline water quality data for much of the mine area and nearby Ardgour aquifer, and said there had been “ample time” for Santana to collect this data.
The panel also heard arguments about how seepage from the pit lakes and tailings storage facility would be captured, and prevented from entering waterways or aquifers, with one suggestion being that up to 20% of water could escape.
But Santana’s experts said a series of drains and barriers, along with water treatment, would mean loss of contaminants was kept to acceptable levels.
However, Santana expert Paul Weber accepted the site “will require management for a long time into the future after closure”.
At present, mining at the site, which is a mix of open pits and underground tunnelling, is projected to last for 14 years, but there are indications it could be extended beyond this.
Weber has previously suggested active water treatment may be required for 85 years after the mine’s closure, and in a recent joint expert witness statement, he suggested active treatment may be needed for 50 years, but more conservative modelling would mean this was longer.
The Environmental Defence Society’s lawyer, Rob Enright, suggested there was “a level of optimism” in Santana’s modelling about seepage.
Dora Avanidou, a technical expert appointed by the fast-track panel to assist it, agreed more information was needed.
“There are some unknowns that create some uncertainty.
“There’s more work needed to reduce the uncertainty from the modelling and investigations done so far.”
This would include drilling, testing and monitoring, which would take several months at least.
“It’s not a one day exercise, for sure.”
Avanidou warned all engineering systems could fail, and therefore monitoring was crucial to know if a system was working or not.
The fast-track panel has until October 29 to make a decision on whether the mine will go ahead or not.
Avanidou said it was possible for conditions to be imposed by the panel, which would cover the gaps in information.
“It sounds like a drafting nightmare,” Muir replied, highlighting the many contingencies and possibilities.
Santana’s application is seen by many as a test case for the expansion of mining in Central Otago, with many other companies lining up to dig for gold in the region.
It has proved extremely controversial, being championed by Resources Minister Shane Jones and those supporting more jobs for the district, but being seen as an environmental disaster by many, including those involved in the existing tourism and viticulture industries.