Newly released documents show banned toxic firefighting foam chemicals have contaminated a bay in Devonport in Auckland.
The briefing, obtained under the Official Information Act, was from Defence Force chief Tim Keating to Defence Minister Ron Mark on 9 November.
It showed that as far back as November, the Defence Force was calling the foam contamination at Devonport and the Whenuapai airbase a "significant land contamination issue" that "has implications across the Defence Estate".
Scroll to the end or click here to read the full document
"Soils, sediments and site runoff at the Sea Safety Training Squadron on the shoreline of Ngataringa Bay are contaminated with PFAS compounds," the briefing said.
The release also revealed that a well - which until recently provided drinking water at Woodbourne airbase near Blenheim - is also contaminated above safe levels.
"An alternative well supply that is no longer used contains PFAS compounds at concentrations above current [health safety] guidelines," it said.
"In recent years, water from that well has formed a significant part of the potable supply."
Now the Defence Force is trying to figure out how long that well has been contaminated.
The OIA confirms the previous Defence Minister in the National-led government was briefed by Defence on the foam threat on 3 August, while Mr Mark's November briefing came a month before the Defence Force first went public about the contamination.
It suggested then it was limited to Ōhakea and Woodbourne. This OIA shows it knew the threat was across almost all its bases.
When RNZ asked Defence about the Devonport Naval Base last week, it said the base's drinking water supply had tested clear, but said nothing about Ngataringa Bay where it is located.
However the November briefing said testing would be conducted in the harbour beside both bases.
It has not previously publicly admitted either the well contamination or the contamination at Devonport and Whenuapai. It told RNZ last week some onsite testing was going on at Devonport, and Whenuapai was at a preliminary investigatory stage.
"This step will inevitably result in media attention and public awareness of PFAS as an environmental and potential health issue not only for the ... Defence Force but also for other users of firefighting foam nationwide," Lieutenant General Keating cautioned the Minister.
It also reveals Defence decided in 2014 it must test the water, triggered by alerts about PFAS from overseas and professional networks. It does not say when it was alerted.
The briefing did not reveal the extent of the contamination - for instance whether it affected the sand nearby - and Defence has not responded to RNZ's questions about that.
Toxic foam chemicals
PFAS is a class of long-lasting manmade chemicals that accumulates in the body with continued exposure.
They are contained in firefighting foams PFOS and PFOA, and in a study of 70,000 people in the US in 2008 were linked to two types of cancer and other health and environmental risks.
International alarms have rung about these since at least 2002.
Defence stopped using this type of foam in 2002 but the chemicals persist for thousands of years. The contamination levels in groundwater at its firefighting training areas, especially in Ōhakea, remain very, very high.
The safety guidelines are in the parts per billion, but were only introduced in April this year by copying Australia's new guidelines.
Health authorities here keep stressing the mounting global research showing bad health impacts from PFAS are inconclusive.
In 2003, an Australian Defence study recommended site testing of soil and water where firefighting foam was used and the Australian government issued an alert about environmental and health concerns from the foam, and ordered the PFOS and PFOA types be restricted to essential use only.
The Australian Defence Force told RNZ it had no record of alerting the New Zealand Defence Force to that 2003 study.