An aerial view of Pāpāmoa East. Photo / File
The estimated cost of a major wastewater project in fast-growing Pāpāmoa East has ballooned from $47 million to about $160m in two years.
And ratepayers may have to foot more of the bill than originally planned.
Senior council staff have defended the increase as part of the normal development of a project over time and a shift to a more "worst-case scenario" costing approach, among other factors.
In a meeting on Tuesday, however, they also said work that produced the 2018 estimate was "not robust enough".
The eastern corridor wastewater programme would provide new and upgraded mains pipes and pump stations in Pāpāmoa East and Te Tumu. Construction is planned to start next year.
The upgrades would add capacity to the wastewater network for a predicted doubling of the area's population from 28,000 over 50 years.
The network was already strained, according to council staff.
The "weakest link" was the biggest pump station in Opal Drive. Formerly a wastewater treatment plant, it was converted nearly 30 years ago as a "temporary measure" intended to last a few years.
It was now "extremely overloaded" and at increasing risk of failures and overflows such as the one in 2018 that leaked sewage into neighbouring properties.
Work to plan for the Pāpāmoa East corridor started two decades ago but stopped after the Global Financial Crisis.
The project was picked up again in 2018 and a preliminary budget of $47m was put in the council's 2018-28 long-term plan.
The estimate has now more than tripled to approximately $160m.
The staff report put the escalation down to necessary added costs, more conservative estimating, increased market costs, and new features needed to comply with strategies and policies.
City and infrastructure planning manager Andrew Mead said the council used to budget for the "likely" cost of a project, but now worked off almost the "worst-case scenario" - a change resulting from experience on other projects.
Mead also said the 2018 costing work for the wastewater project was "probably not robust enough".
The council has had a series of budget blowouts in recent years on capital projects. This month it abandoned the partially built Harington St transport hub to avoid a predicted blowout after engineering issues.
Some councillors were concerned the escalation would be seen as a "budget blowout" but strategy and growth general manager Christine Jones said that was not a fair label and it was usual for budgets to develop over time in the lead-up to implementation.
Former deputy mayor Larry Baldock said the project was "essential to the growth of our city".
The project will be funded by a mix of development contributions - money the council collects from developers to help pay for new growth infrastructure - and rates. Development contributions are locked in at the resource consent stage.
Claudia Hellberg, the council's team leader of waters strategy and planning, told the Bay of Plenty Times the $160m would be split between 4 per cent ratepayer-funded loans, 30 per cent ratepayer-funded depreciation and 66 per cent growth funding.
A shortfall in development contributions, however, meant $15 to $20m of growth funding was expected to be converted into ratepayer-funded debt.
"The exact amount will depend on the amount and timing of future development contribution revenue and will therefore not be transferred to the ratepayer until we are certain that we cannot collect it from developers," she said.
The council voted unanimously to proceed with the first stage of the programme - the Opal Drive pump station and rising main - subject to budget approvals.
Delivery of the rest of the programme was agreed in principle.
Houses for homeless to go
Nine houses built for homeless people will be moved off council land in Pāpāmoa, with no plan yet for where they will go.
The houses are among 19 relocatable homes that make up Kāinga Atawha, the transitional housing village opened at 45 Opal Drive in 2017 in response to growing rates of homelessness in Tauranga.
The council leased the land in two parts to Kainga Ora (then Housing New Zealand), which contracted management of the village to the Tauranga Community Housing Trust.
One part had a 15-year lease, but the other was given only five years because the council had it set aside for a new wastewater pump station.
On Tuesday, the council confirmed that, subject to budget confirmation, it would go ahead with building the pump station, meaning nine houses would have to be removed before the lease ran out in July 2022.
The council agreed to "endeavour to minimise" the impact of the new infrastructure on Kāinga Ora and the trust, but made no guarantees.
Staff were looking at options such as using another piece of council land, but had yet to find a solution. Putting the pump station somewhere else had been ruled out.
Trust chairwoman Jo Gravit and general manager Jacqui Ferrell urged the council to do whatever it could to retain the village - a temporary home to 61 families in 2.5 years - in its current form.
Removing half the houses would raise viability issues, and potentially having the village split across two sites would force a rethink of how it operated.
After the meeting, Gravit said she was happy the council had recognised and understood the need for a solution for the village.
Andrew Booker of Kāinga Ora said the need for the transitional homes in Tauranga remained.
"We've always understood that we had temporary use of the land. That is why we have made the homes relocatable."
He said the organisation and the Ministry of Housing Urban Development looked forward to working with the council or other land owners to find a new location for the homes.
The council has also been served with judicial review proceedings.