Sewage stench lingers in wake of floods

Steve and Geri Nielsen used to enjoy the marine life in the clear waters and mangroves around their jetty on the shore of Ngataringa Bay, where eels, fish, herons, shags and many other species were often seen. But since late January, the water has been black and often stinking of sewage – and the birds and sea life have largely vanished.

A sewerage-system failure in late January, apparently beneath or near the Navy’s North Yard facility on Jim Titchener Pde, has led to sewage flowing from a stormwater culvert opposite the Navy site, into the channel in the mudflats behind the Nielsens’ Lytton St home.

They have endured the frequent stench and potential health risks ever since. Though they were told a test by Auckland Council confirmed sewage pollution in the water – and two official warning signs were put up – the fault is yet to be located or rectified.

Steve, a semi-retired environmental consultant, said the discharge from the culvert is “classic toxic anaerobic water” carrying a strong smell of sewage and hydrogen sulphide, meaning the couple has rarely been able to open their windows or sit outside since January.

“The smell we sometimes experience at our house is nauseating, and has made us feel dizzy at times,” he said.

The Worksafe website warns that exposure to hydrogen sulphide can be fatal and that even in small amounts it can be dangerous to health.

“How will it be affecting our health?” Steve asked.

Council staff told the Nielsens that a sewerage and stormwater system has an intersection beneath the Navy base, and that a sewage pipe was likely blocked with debris, causing it to divert to the stormwater culvert.

They were told the leak was council organisation Watercare’s responsibility, but have been unable to speak to anyone from Watercare in the months since.

The couple know that the authorities have been overwhelmed with drainage issues since January. “That’s why we’ve been patient,” Geri said. “But we just want some communication, to know if we’re on the list.”

After a previous sewage leak in 2015, the fault was repaired immediately and the problem solved within a few days.

The general manager of council department Healthy Waters, Craig Mcilroy, confirmed that the council had identified wastewater contamination at Ngataringa Bay Reserve, near the Naval base, in mid-March.

Healthy Waters was conducting an investigation to identify the cause of the discharge, Mcilroy said. This involved identifying key manholes to try and isolate the source of the contamination.

“A specialist drainage contractor has visited this site, and two upstream properties, to understand if these were linked to the contamination, which they did not appear to be. We have identified a key manhole where our contractor is conducting regular sampling every few days to try and characterise the contamination patterns.”

No blockages had yet been identified, but investigations were continuing, he said.

“We can understand the customer’s frustration that this issue is yet to be resolved. However, this is a complex investigation, and we are working hard to find a resolution as soon as possible.”

Steve Nielsen believes the current issue has been exacerbated by the blockage of the channel from the culvert through the mangroves.

The channel was once regularly dredged by the council of the day, though that practice ceased sometime prior to the Nielsens’ arrival in 2000. It remained functional, despite silting and the encroachment of mangroves, until the floods early this year.

Since then, blockages have meant it does not empty at low tide, remaining backed up into the culvert and the drainage system beyond. “The water never disappears,” Steve said.

Residents affected by flooding on and around Patuone Pl, on the other side of the Navy site, suspect this blockage may have contributed to their problems.

The Nielsens want the sewage leak fixed and the channel dredged. Steve said a good digger operator could do the dredging in a day or two at minimal cost.

Humans have not been the only victims of the pollution, he said. “Of equal importance are the effects of this toxic water on the fish and wildlife, and on the Hauraki Gulf itself.”

• Though Navy staff told the Nielsens informally that a sewage smell is noticeable, a Navy spokesperson told the Flagstaff: “There are no drainage issues or smells at the base, following the floods.”

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