A third round of water testing around Ohakea Airforce Base has found ponds and streams too contaminated for swimming, stock water or irrigating crops.

However neighbouring landowner Andy Russell is not too alarmed, because little or none of the water is used for those purposes. He's guessing a lot of the samples were taken from drains surrounding the base tarmac.

"There's no business interruption as far as farming goes."

The tests have been paid for by the New Zealand Defence Force (NZDF), because the contamination is from one of the ingredients of the foams used to fight fires in flammable liquids. The base uses such foams, both for real fires and in training.

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But its spokespeople say it has been conducting training elsewhere since early 2016, and since 2002 the foams it has used contain only tiny amounts of the contaminant - PFAS (per- and poly-fluoroalkyl substances).

They are also found in consumer products such as nonstick frypans and Goretex rain gear, and are very long lasting in the environment.

Horizons Regional Council is still concerned about contamination around Ohakea. The substances have moved 3 to 3.5km from the base, in water, and the council would like to know the full extent.

It issued an abatement notice to the NZDF, and has had a response. The two will be meeting soon, Horizons chief executive Michael McCartney said.

In the third round of testing 39 samples were taken from ponds and streams around Ohakea. Of those, 28 had PFAS. Two exceeded swimming guidelines.

One of these is a pond near the Rangitikei River, which has been fenced off by the Environment Ministry.

Twenty-one of the samples had PFAS levels too high for stock water - but only six of those are actually used for stock water. They were also too high for water used to irrigate fodder crops - but no irrigation is done from them.

Milk from the area is being tested, and PFAS levels there are considered safe, Russell said. Stock raised there are suitable for export.

Manawatū District Council has been proactive. Government has given it $50,000 to fund a study toward putting in a new water scheme for affected people.

"A new water supply would go a long way to solving the problem. Heaven forbid if something doesn't happen. I don't know what people would do," Russell said.

Residents with concrete water tanks are already having them replaced with plastic, which doesn't retain PFAS, and some have had their blood tested for the substances.