Watch NZH Local Focus: 'It smelt like sewage' - slimy substance on Waikato River bank

Broadlands Forest resident Graham Sperry knows this stretch of riverbank like the back of his hand, but on Saturday when he was walking his dogs he noticed something odd that made him concerned.

"It smelt like sewage - it smelt like treated sewage, the effluent that runs out of a septic tank or something like that."

Mr Sperry told his wife Anne - their immediate concern was for the health of people nearby.

"A lot of people use the river, we take our dogs down there for a swim , some people swim in there as well so they're getting contaminated with that stuff," Anne Sperry says.

The Sperrys rung Waikato Regional Council - which asked them to take samples of the sludge.

But when Local Focus visited on Monday morning - they still hadn't been picked up.

Mr Sperry says he's done all he can as a citizen.

"They've accepted my report but that's all that's happened , they said to me they may or may not come back to me."

And he doesn't think that is good enough when there may be a potential health risk.

"If it's nothing I can say nothing and that's fine, but if it's something and it is a health risk I will be irresponsible not to alert the authorities , which is what I have done."

He says the samples he has gathered should be tested to confirm if what he saw is sewage or not.

"If it's negative then nothing is lost and nobody is at risk. If it's the other way however then we do need to know."

Waikato Regional Council (WRC) confirmed it had received Mr Sperrys call, but it had no reports from likely sources of a sewage spill in the area.

WRC says there have not been multiple reports of a bad smell in the area - which is what it would expect if a sewage spill had occurred.

They say they won't be collecting Mr Sperry's samples.

Mr Sperry says he's not looking to make a "sensation, I'm just looking to ensure the safety of the public".

There has been sewage spills in the region before.

Just last month sewage escaped into Lake Taupo on two occasions - about 30km upstream from Mr Sperry's home.

But Taupo District Council - which manages the plants where the overflows occured - say it's not likely those spills would have made it down stream, and there is no risk of contamination to the water now.

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