Erionite can and has killed people, by causing mesothelioma, a cancer more readily associated with asbestos.
Auckland is one of the few places in the world that has the rare mineral under it, in rocks called the Waitematā Group sediments that are themselves widespread.
Research to pinpoint exactly where it is, gauge the risk of exposure and prompt testing and standards to cope with erionite, has won $7.7m in Endeavour Fund support. It is led by Jenny Salmond, an associate professor at Auckland University.
"We know erionite's a carcinogen, we know it's here," Salmond said.
"The question is, is it escaping from the rocks?
"If it's contained within the rock, it's not a problem. But if it gets into the soil and then gets into the air, or gets directly from the rock into the air, then it's a problem."
The potential threat is twofold: From dust, such as from drilling and tunnelling, and what's done with any waste dirt afterwards, such as the massive amounts coming out of Waterview Tunnel previously, or the City Rail Link project now.
Crown entity unhappy
CRL said the research to date suggested a "very low" chance of any erionite in the 3.45km rail corridor, and none had been found so far, from hundreds of test bore holes.
The Crown entity was upset at the researchers' early warnings that emerged at an erionite briefing with Auckland Council last November.
"City Rail Link Ltd and others did challenge some of the language used in the Erionite Research Group's draft briefing paper," CRL told RNZ in a statement.
"It was felt that the language used could create an impression that the safety and health impacts on construction work were not being managed adequately for workers or the public.
"This perception is incorrect and the group's published paper addressed our comments."
That paper, in a Medical Association journal in July, said the scale of earthworks meant it was urgent to quantify the potential for "significant exposure" of Aucklanders to erionite dust if dust management strategies were not carefully implemented.
CRL "did not threaten, nor consider, legal action regarding the erionite report", City Rail Link said, adding it was collaborating with the researchers.
Extra borehole samples were being analysed for erionite overseas - as this country lacked the necessary labs - and the data shared, it said.
Salmond said the collaboration was solid.
Industry "will help us to steer our research to help them. And our research will steer their activities".
"As with any emerging risks, there's a challenge to how we deal with it," she said.
Erionite exposure has been fatal: It caused about half of all deaths in three villages in Cappadocia, Turkey, till the alarm went up several decades ago. They had inadvertently used erionite to build homes.
An early warning went up about the mineral in New Zealand in 2011, in a geologist's report to the Environment Court.
"It seems prudent to ... consider what hazard the erionite deposits might pose for the people of Auckland, and introduce precautionary measures into resource consents to minimise any possible health hazard," the submission read.
Nothing came of it, though asbestos researchers mentioned it in 2015.
New Zealand has a high rate of mesothelioma but no one knows exactly why.
The Auckland Council said its geologists doubted any erionite was under the central city, and they were collaborating with the researchers.
"We have already taken steps to ensure we are ready to manage any risk which may arise ... particularly in key construction sites," said the council's manager of regulatory compliance Steve Pearce.
CRL was currently the only project of interest, and the only one with resources consents that specifically mentioned erionite, but all earthworks required protocols for the discovery of unexpected contaminants, Pearce said.
The air-quality monitoring at the rail project's Aotea and Mt Eden stations was updated in March to include erionite, and is independently reviewed.
However, it remains unclear if or how waste from the tunnels is being analysed for the mineral; RNZ is seeking to clarify that, and if the waste is currently being treated as cleanfill.
"Only natural soils or rock where soil contaminants are absent can be disposed of to cleanfill disposal facilities," Pearce said.
Implication for harbour tunnel
Concern was not limited to major projects, said another of the researchers, geology associate professor Martin Brook.
"Greenfield residential developments, if erionite is in rocks or soils close to the surface there, that could be a problem," Brook said.
One major tunnelling project ahead could be a harbour crossing.
The Transport Agency said its Additional Waitematā Harbour Connections (AWHC) business case had now been completed.
This is part of a $100m-plus investigation of what to do to ease Auckland congestion.
The business case "builds on previous work exploring the feasibility of a tunnel crossing, and while this remains the most likely option there is still further planning required to investigate the need, timing, function and form of an additional crossing before a final decision is made", the agency told RNZ in a statement yesterday.
Any tunnel was more than a decade away, it said.
Developers of any cross-harbour tunnel would need to watch out for any zeolite rocks or sandstone, Brook said.
"Some of that zeolite should be tested for erionite," he said.
"It's just a question then of dealing with it.
"Normally, it would be disposed of as cleanfill but if it's got erionite in it, then it probably needs classifying as contaminated fill."
Professor Salmond said researchers would be collaborating with industry, medical and social scientists here and overseas, with Italy in particular providing useful expertise.
"We're trying to prevent erionite from being inadvertently disturbed - that's the whole point of this research, to make sure that we're not too late," she said.
Work was also going on to set international erionite exposure limits for workplaces, like there are for asbestos, Salmond said.
The regulator in this country, WorkSafe, said it was awaiting the findings of the research.
"Businesses which may be concerned should have a dust management plan in place," it said.
City Rail Link said it was cutting the general risk from dust by:
• Using a tunnel boring machine with a sealed cutter head, that produces waste that is a sludge (road header machines can be used to tunnel but make a lot more dust).
• Damping down dust, maintaining exclusion zones, and monitoring; using personal protective equipment.
• Transporting waste covered and damped down; analysing spoil before transporting it.
"The scale of CRL gives the project a great opportunity to provide more data about erionite and to share that information with research groups and the wider construction industry," CRL said.
The air-quality management regime would be reviewed and updated if erionite was found, it said.
