Porirua’s new central city sewage storage tank is set to cost more than double its original budget, although work is set to finish ahead of schedule.
By Justin Wong of Local Democracy Reporting
With enough room for three Olympic swimming pools of wastewater, the tank between State Highway 59 and the rail lines had a $48 million budget when construction began in 2022.
Subsequent issues – relocating native skinks, inflation, moving fibre ducts and upgrading wastewater infrastructure – pushed it to $97m.
The tank would hold sewage during heavy rain before it could be pumped to the local wastewater treatment plant at nearby Tītahi Bay.
However, the latest budget, reported to the Porirua City Council’s Te Puna Kōrero committee on Thursday, put the figure at $99m "with the majority of the construction risks closed out".
Construction was expected to wrap up in April, three months ahead of schedule.
Thursday’s meeting, which also discussed updates to the city’s major projects, only briefly touched on the wastewater tank because Wellington Water chief executive Pat Dogherty was due to appear at a council workshop on March 19, before a request for councillors to increase the budget.
"It’s to do with the way with how Wellington Water allocates costs," the council’s infrastructure general manager Mike Mendonça told councillors at the meeting. "Rather than try and and explain that to you here, we have invited the chief executive to come along and do that in person."
A Wellington Water spokesperson referred a request for comment by Local Democracy Reporting to the briefing in two weeks' time: "It would be inappropriate to comment ahead of that discussion or preempt any Council decisions.
"What we can say is that the project is currently ahead of schedule and, once completed, will significantly reduce the risk of wastewater overflows into the environment."
In the latest update, as of late December the tank’s pump station had been commissioned using fresh water and the interconnecting pipework was expected to have been finished in late February.
The presence of northern grass skinks meant the project’s earthworks were put on hold for months because they could not be moved during winter. Over September and October 2023, the workers caught 59 skinks using lizard-friendly traps or by hand and moved them to a nearby new fenced-off home.
Each trapped skink was weighed, measured and individually photographed.
Wellington Water said at that time the tank’s surroundings would be planted with skink-friendly plants like coprosmas, hebes, flaxes and vines.
– Local Democracy Reporting is local body journalism co-funded by RNZ and NZ On Air.
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