The Defence Force is downplaying the risks to people using groundwater that may have been contaminated by runoff of firefighting foam from Whenuapai airbase.
The military is in the early stages of investigating firefighting foam contamination around the west Auckland base.
This is part of nationwide investigations into water and soil contamination by a suite of longlasting, potentially harmful chemicals called PFAS.
"Preliminary advice from NZDF's consultants and Auckland Council specialists is that while there some people may be using groundwater at properties close to Whenuapai Air Base, the water is sourced from bores at a depth of between 200-300 metres and below a thick layer of fine sediment that is expected to exclude PFAS," the Defence Force said in a statement to RNZ.
In August 2017, Defence told the government there was a "significant land contamination issue" at Whenuapai and Devonport.
A Cabinet paper in April said that at Devonport "further testing has been carried out, and results are expected in May".
That appears to have been delayed, according to Defence's latest statement to RNZ: "We started some initial testing and are currently in discussions with Auckland Council and the AoG group to ensure the scope of the testing programme at Devonport and Whenuapai is carried out in the context of the wider Waitemata Harbour and so provides best support to Auckland Council's own work."
Auckland is one of 16 or so unitary and regional councils ordered by the government to identify possible sources of PFAS contamination, such as factories.
Only in February 2018 did officials say that "new information" suggested some people might be using bore water around Whenuapai for drinking, even though a 2011 research report had identified more than 500 bores in the wider area.
A source has told RNZ that wastewater from Whenuapai was routinely processed at the nearby Hobsonville base, before that recently became a large housing development.
The developer and Defence have both said that Hobsonville does not have any contamination.
However, tests for PFAS in the water have not taken place there.
"Investigations have found that the Hobsonville Base has not been used as a firefighter training site and so is not of concern," a Cabinet paper in April said.
"Occasional use of foam may have taken place at Hobsonville. From the information available, the New Zealand Defence Force is confident that any usage was insufficient to leave significant residues in the soil."
At Devonport naval base, Defence has known since it did tests in 2016 that the groundwater is contaminated, in places at very high levels. It did not tell the Auckland Council this till February 2018.
There is low-level contamination in the mangroves and Ngataringa Bay.