The fastest-growing district in New Zealand has a poo problem

Saturday, 27 June 2026

Selwyn’s Pines wastewater treatment plant, right, is struggling to cope with the rapid expansion of towns like Rolleston, left.

The fastest-growing district in the country is hitting a bottleneck as developers learn the pipes and plants that deal with its sewage are at capacity.

The Press understands several subdivisions in Selwyn have been stymied by stretched infrastructure.

The council has acknowledged constraints are “affecting development timelines” but said much of the recent construction boom was the result of central government intervention.

“Development is happening faster and in areas not originally scheduled for early infrastructure delivery. We’re working with government, developers, and our community to ensure growth remains sustainable and fair.”

The pressure comes as Selwyn is projected to add more than 23,000 residents over the next decade, taking its population from about 82,000 to more than 105,000, according to the council’s long term plan.

Construction analyst Mike Blackburn said he’d heard of several developers ‒ some of them his own clients ‒ striking problems with Selwyn Water, a council-controlled organisation (CCO), particularly over sewerage capacity.

One developer he had spoken to had had their subdivision plans upended as a result.

“[He was] in a pre-resource consent application meeting with Selwyn Council…and he was basically told, ‘No, we would not approve this resource consent because we have no capacity’.”

Rolleston is driving much of Selwyn’s growth.

Another had to compromise to obtain consent for their development (some sections would have storage tanks or macerator systems to regulate sewage discharge) and yet another had been waiting months for approval from Selwyn Water to get the underground services in their new subdivision connected to the wider system.

“Without question, there are capacity constraints,” Blackburn said. “Of the 15 or more builders that I spoke to [this week], they’ve all pretty much confirmed the same thing. They’ve all been told by Selwyn Water that there are capacity restrictions, most specifically in the east of the district, in Prebbleton and towards Templeton.”

The Pines wastewater treatment plant near Rolleston is nearing capacity, a district councillor says.

Selwyn Water was only established as a CCO last year, but has inherited many of the pressures the council faced managing resources in a fast-growing region. This week, it released its Water Services Strategy which noted that development was already exceeding some predictions and “significant capital investment decisions” would be required to manage capacity constraints.

It warned that while existing budgets could accommodate growth for a population of 90,000 to 120,000, longer-term projections of 180,000 to 200,000 would require “substantial additional investment” at the Pines wastewater treatment plant.

Selwyn Water could not comment by deadline, but Selwyn District Council executive director building, planning and regulatory services Robert Love said both treatment plants and networks in the district were under pressure.

“The scale and speed of growth in Selwyn is among the highest in the country, which creates ongoing pressure on all infrastructure networks. While significant investment is being made and major infrastructure upgrades are under way or planned, including working with Selwyn Water, our treatment plants and networks are currently nearing capacity.

“Large areas of land have recently been developed through central government interventions…These changes have allowed growth in more places, often outside council plans and without additional funding to support the extra investment required.”

Birches Village, south of Prebbleton, was one such development. Spanning 530 residential allotments and a commercial precinct, it was rejected by the council but greenlit under the Government’s fast-track legislation in 2024. Selwyn’s then deputy mayor Malcolm Lyall lamented the override at the time. Engineers would “have to scramble” to make sure council infrastructure would cope with the influx of unplanned houses, he said.

Councillor Sophie McInnes says the fast-track process made it difficult to assess the cumulative impact of multiple developments.

“As usual, the council will be left holding the baby.”

Growth, Love said, should be funded by growth. Infrastructure upgrades were a matter of delicate financial balances to ensure ratepayers weren’t unfairly burdened and development didn’t grind to a halt.

“Infrastructure delivery is a critical enabler of housing supply. If upgrades are delayed or constraints persist, there is a potential for impacts on the timing of development in affected areas. This reinforces the importance of coordinated planning, investment certainty, and close alignment between land use planning and infrastructure delivery.”

Selwyn district councillor Sophie McInnes echoed this, and said the Government’s fast-track approvals process could add further pressure.

“If they don’t take [into account] the capacity of the plant and the speed at which we could potentially increase the amount of land for disposal…then we definitely will have a problem.”

Fast-track applications were considered individually, she said, making it difficult to assess their cumulative impact on infrastructure.

Selwyn district councillor John Verry says the sewage treatment plant was not designed to cope with the level of growth the region was now seeing.

“When these different applications come in… the council has to tell them how much capacity there is right now. They don't necessarily get to tell them, ‘But by the way, we also have these other nine applications that also want to put a claim on that remaining capacity’.”

Tawera Malvern ward councillor John Verry said there was little point approving more development such as the proposed Bangor subdivision in Darfield if the network couldn’t cope.

“How can we service the subdivision that’s planned? My view is…with difficulty.

“It’s going to have to be staged.”

He said one possible solution would be for Selwyn Water to develop a dedicated industrial wastewater treatment facility at the iZone industrial park, freeing up capacity at the Pines plant for residential wastewater.

Benno Blaschke, a research fellow at the New Zealand Initiative, said Selwyn, and all of greater Christchurch, had been “quite aggressive” in freeing up land for urban expansion after the earthquakes. This was good, he said, because it kept land prices low. But infrastructure needed to keep pace.

“If you have infrastructure already ready and rolled out, then you can just allow urban expansion to go nuts because the capacity is there,” Blaschke said.

Even compromise solutions like the one Blackburn cited on sewage regulation could work, he said.

“Those kinds of interim solutions are just fine, in my view. If the development can make itself work, I don’t think that supplying everything to the absolute gold standard is necessary.

“What’s not fine is having no solution whatsoever, just saying no.”

Lack of pipes holding up housing

Last week, Blaschke published a report titled Finance Freedom. “New Zealand cannot build enough houses because councils cannot afford the pipes and roads that new suburbs need,” he said in a statement accompanying its release.

The report explored a novel funding approach for councils to combat ever more expensive infrastructure costs. It relied on private investment underwriting the pipes and roads required for a new development so councils didn’t have to carry all the debt.

Recent legislation (the Infrastructure Funding and Financing Act 2020) allowed for something like this, Blaschke said, but not enough. “The model is quite, in its current [form], quite expensive.”