Te Mārua Water Treatment Plant

The Te Mārua Water Treatment Plant upgrade is a key step in future-proofing Wellington’s drinking water supply. By increasing plant output capacity from 80 to 140 million litres a day (ML/d), it’s the plant’s largest upgrade since 1980 – boosting resilience, supporting regional growth, and helping to deliver safe, reliable water to nearly half the region’s population.

Upgrading the Te Mārua Water Treatment Plant became a priority as growing demand and increasing climate variability placed pressure on Wellington’s water supply. With the plant providing nearly half the region’s drinking water, expanding its capacity was essential to avoid the risk of summer shortages.

But the project isn’t just about boosting output. It addresses the complexities of an aging brownfield site, managing seismic risks near the Wellington Fault and future-proofing the infrastructure to support a growing population.

Delivering a project of this scale and complexity called for a carefully coordinated, multidisciplinary effort. From the outset, we adopted a proactive, collaborative approach – bringing together our team, Wellington Water and the contractor as one unified delivery team.

Project management led the way, keeping priorities aligned, communication clear and escalation pathways efficient. Our design team took on the integration of new infrastructure, including a Dissolved Air Flotation (DAF) system, while working through the challenges of seismic risks and the realities of a constrained brownfield site.

Construction monitoring and contract administration worked closely with the contractor to manage risk and keep plant operations running throughout the build. Meanwhile, our digital engineering team used 3D CAD and BIM360 to support real-time coordination, clash detection and long-term asset integration. A strong one team culture underpinned every aspect of delivery. Regular stand-ups, planning sessions, and collaborative problem-solving helped surface issues early and keep the momentum going.

A key milestone came with “Operation One Summer Sooner,” which fast-tracked commissioning to deliver an extra 20 ML/d ahead of the 2024/25 summer peak. This helped to significantly reduce the likelihood of water restrictions over the summer compared to the previous year, giving the client greater resilience and adaptability to face demand challenges.

The Te Mārua upgrade is already making a difference, strengthening water resilience for nearly half of Wellington’s population. With capacity lifted from 80 to 140 ML/d the region is better prepared for the pressures of peak demand. It leaves Wellington in a stronger position to meet the challenges of growth, climate change and aging infrastructure head-on.