Port Taranaki knew about groundwater contamination for more than a year before the public was told, documents show.
The contaminated water at test bores is not used for drinking.
The documents show the port learned in July 2017 about high levels of firefighting foam chemicals in one of several monitoring wells – 40 times drinking water guidelines – when it ran an environmental study before leasing the Omata Tank Farm.
This was six months before the public was first alerted to the contamination problem, when New Zealand Defence Force admitted at the end of last year it had contaminated water around several bases.
The council told the public last month about contaminated sites.
The regional council referred RNZ’s questions to the port company which it both owns and regulates.
Tests at wells on port land came up below guideline levels, he said.
Shell has admitted storing banned PFOS foam at both Omata and the nearby Paritūtū tank farm up until last month.
A controversial official report in the US has pushed for much lower safety thresholds.
* The documents released to RNZ are available by contacting the reporter.