Wellington backyards could be dug up to fix water woes

Cross-connections were blamed for a recent spike in pollution at Wellington's Owhiro Bay. Photo / WCC

Residential backyards could be dug up to fix Wellington's icky cross-connection water problem.

A cross-connection is where a wastewater pipe is connected into a stormwater pipe. They usually occur when private pipes are plugged into public ones.

These cross-connections were blamed for a recent spike in pollution at Owhiro Bay, which closed the beach to swimmers.

Wastewater from private properties entered the stormwater system, which then flowed into Owhiro Stream and into the Bay.

Five cross connections have been identified in the area and fixed but Wellington Water is continuing to investigate the catchment.

Containers of different coloured dyes will be tipped down different parts of the network over the next few weeks to identify any further problems.

Wellington Water chief executive Colin Crampton said some cross connections were simple to fix, but if they had been in place for a long time, they required more substantial work.

"It usually involves digging of some sort and if it's close to the home, then it would be people's backyards. The mistake has been made on that person's property so that's where it should be fixed", he said.

Wellington Water chief executive Colin Crampton (left) and network strategy and planning group manager Mark Kinvig front to the media. Photo / Georgina Campbell

Property owners would foot the bill if the problem was centred in homes but councils would pick up the tab for cases closer to the main network.

Crampton said it was not black and white where the responsibility fell for cross-connections existing in the first place.

He said whether it was a workmanship issue or an inspection issue, they wanted to create a system where there was "no chance" of cross-connections happening.

"Because we've got to stop having new builds creating new pollution sources in our rivers and streams, it's just unacceptable", Crampton said.

Greater Wellington Regional Council urban water management programme leader Alastair Smaill said his back garden was dug up during suburb wide investigations by Watercare when he lived in Auckland.

"In some places there might only be one or two cross connections and in other places you've got a major suburb wide problem."

Smaill said the issue of who pays was a complicated conversation because, in theory, individual property owners were responsible for their infrastructure.

"But on the other hand, if you actually want action and timely action and you want to do it at a suburb scale, then perhaps some public funding towards that private infrastructure might actually grease the wheel and get that moving."

Wellington Water has pitched the idea of roving crews to councils. These teams would proactively work to detect cross-connections and leaks on private properties as well as private land.

So far Porirua City Council is the only council to agree to a crew putting aside $250,000 in its draft Annual Plan.

GWRC chair Daran Ponter has urged other councils to follow suit.

"Urban stream water quality is a major issue throughout the region and the country and this initiative will see dedicated resource and the supporting bylaws that will help crews find and fix problems quickly."

Half of Wellington's rivers and streams are now graded as having unacceptable levels of e-coli.

GWRC monitors 45 sites across the region and the latest figures showed 47 per cent were graded E or D for e-coli, the lowest possible ratings.

Large urban streams like Kaiwharawhara, Porirua and Karori were all graded E, which is considered representative of all urban streams in Wellington.