Kaiwharawhara stream which runs down past Ngaio into Wellington Harbour. Many Wellington streams have been declared polluted.

Contaminated water flowing into Owhiro Bay is more than 30 times above the safe swimming level, and has been at dangerously high levels for the last 20 years according to Wellington Water.

The problem is so overwhelming that officials aren't even sure where to start.

Almost every urban stream in the Wellington region is graded 'E', marking 'unacceptable levels of risk'. It's the lowest possible grade.

Ross Giblin Almost every urban stream in the Wellington region is graded 'E', marking 'unacceptable levels of risk'. It's the lowest possible grade.

Owhiro Bay residents asked for "protection, leadership and guardianship" from the Greater Wellington Regional Council at a meeting on Thursday.

READ MORE:

* Sewage in Wellington marine reserve 43-times worse than acceptable levels

* Wellington waterways with E coli are 'a public risk', says Forest & Bird

* Contamination and closure of Tahunanui Beach hits businessman in back pocket

"It's enormously distressing in our community," resident Eugene Doyle said.

"There is a tsunami of faecal material coming in down our stream, entering our bay. It's causing a lot of mental anguish... and it poses a risk to human health."

In January, Wellington Water identified three homes whose sewage pipes were accidentally connected to stormwater drains.

ROBERT KITCHIN/STUFF Owhiro Bay resident Eugene Doyle wants authorities to step up efforts to fix a wastewater leak into Taputeranga Marine Reserve.

After resolving the cross-contamination, signage warning beachgoers of the water risk was removed, only to be put up again five days later when contamination levels spiked again.

On February 4, e-coli levels were at 3900 colony-forming units per 100ml of water. Safe levels for swimming are 200 or below.

He called on the council and Wellington Water to launch an intensive investigation to find out where sewage was getting into the system and where outdated pipes were failing.

"Wellington's public assets are in a poor state of repair, the level of investigation into the scale of the problem has been inadequate."

"We want the various agencies involved to wake up from the deep, deep sleep they've been in for years."

MANDY TE/STUFF Roads are set to re-open on Thursday after a tunnel collapse in Wellington CBD caused wastewater to spill into the harbour.

Wellington Water has now put permanent warning signs at the mouth of the stream, but stormwater adviser Ben Fountain said the same warnings could apply to most of the city's waterways.

Stormwater which runs into the Ohwiro stream comes from a number of different sources across a network of pipes, making it difficult to identify contamination sources.

Water quality was only measured at the end of the stream, not further up the network, meaning it was difficult to identify where sewage was getting into the system.

Wellington Water does not know how many houses could have incorrectly connected pipes.

Supplied Warning signs went back up at Owhiro Bay on Wellington's South Coast in February.

Council chair Daran Ponter said he was "dumbfounded" that sewage pipes kept getting accidentally connected to stormwater.

"Either we've got some really thick plumbers, or the network operator is not checking the system."

Councillor Thomas Nash said it was unfair to lay the blame on tradies.

"I'm wary of singling out individual plumbers, because this is a systemic problem."

MONIQUE FORD / STUFF Work is continuing to lay a new pipe under Willis St following a leak which resulted in hundreds of litres of wastewater spilling into Wellington Harbour.

The responsibility for the pipes is spread across a number of agencies. Wellington City Council owns the pipes, while Wellington Water operates the network, and Greater Wellington Regional Council has an oversight role.

Councillor David Lee questioned whether pipe upgrades had been put off for too long due to politics.

KEVIN STENT/STUFF Wellington Water contractors take sludge from the Moa Point Treatment Plant to the Southern Landfill after a wastewater pipe broke under Mt Albert.

"Is the root problem that fixing pipes is not sexy? It's not exactly a voting platform is it?" he said.

A Wastewater pipe mistakenly connected to a stormwater pipe on Cuba Street and Dixon street which sent millions of litres of sewage into the Wellington harbour in December.

In another high-profile failure of Wellington's pipes, a broken pipeline 200 metres underneath Mt Albert has forced Wellington Water to truck sewage 24 hours a day from Moa Point to Southern Landfill.