Wastewater from an central city apartment building has been spilling into Wellington Harbour for at least 10 years and it is likely not the only case of crossed pipes.
Wellington Water contractors found the problem at the Cubana Apartments building on Cuba St after tracing the source of contaminated water readings.
Those readings remained high even after a burst wastewater pipe under Willis St was repaired following a separate incident just before Christmas, in which thousands of litres of sewage gushed into the harbour.
Wellington Water spokesman Alex van Paassen said the problem at the Cubana apartments was caused by pipes being incorrectly laid some time in the past 40 years.
Wastewater and stormwater pipes are required to run separately, but at some point those pipes had been cross-connected, he said.
The apartment complex was constructed in 2009 and contains 15 apartments but the mistake could have been made well before then.
“It’s a bit of a mystery as to why we haven’t found the cross-connection before now. It’s all a bit random.”
There were several potential reasons the mistake had not been picked up until now.
Sewage from the property flowed intermittently along the wastewater pipe, and it could potentially be decontaminated to an extent by the time it reached the harbour.
Water samples taken for testing were also relatively small compared to the size of the harbour.
“It’s an inexact science, at best.
“But on the flipside, they are doing that testing and those tests are coming back clear.”
Although the majority of Wellington Harbour has now been deemed safe for swimming, there are still no-swim signs near Whairepo Lagoon and the diving platform near Te Papa.
Van Paassen said the Cuba St cross-connection, which was probably one of the main causes of regular shutdowns of the diving platform, was definitely not the only one in Wellington.
“We don’t know how many – that is part of the problem.”
The pipes were set up so blockages overflowed into the stormwater and into the sea, van Paassen said.
This was the “lesser of two evils” – the other option was wastewater backing up into homes and businesses.
Although there would have been a relatively steady stream of wastewater, including sewage, going into the harbour over 10 years or more, there would have been times the water was safe.
A Wellington City Council spokesman said staff would need to delve deep into its archives to figure out when and how the mistake occurred.
“An initial search shows there are multiple consents relating to the construction of the apartment building, but that it’s entirely possible the cross-connection could have been mistakenly installed many years earlier and not been uncovered when the apartment building was constructed.
“If this is the case, then the extra toilets, showers, dishwashers and washing machines at the address in recent years would have exacerbated the problem.”
Work to fix the problem is expected to take a couple of days.
Wellington Water was paying for the repairs on Cuba St but could look to recover costs if another party was found to be at fault.
Source - stuff
