Woods supported Tararua District Council in planning climate-resilient 3 waters infrastructure to meet the demands of rapid growth and increasingly extreme weather.

Key challenges

The towns within Tararua District have experienced faster-than-expected population growth, placing increased pressure on infrastructure that was already operating near or over capacity. Much of the existing 3 waters network is aging and vulnerable, struggling to keep up with demand — especially as more frequent and intense weather events expose system weaknesses. One of the major issues identified was inflow and infiltration, where stormwater and groundwater enter the wastewater network, overloading it during heavy rainfall and reducing its effectiveness. Addressing these problems required not only technical insight but also careful consideration of environmental, cultural, social, and economic factors to ensure that proposed solutions would be resilient, cost-effective, and community-focused.

Our role

Woods partnered with WSP to deliver comprehensive 3 waters master planning for the Tararua District’s four largest towns. Our role included the assessment and modelling of stormwater, wastewater, and water supply systems to identify where current networks are under pressure — and how best to upgrade them for long-term resilience.

Using InfoWorks ICM, Woods developed and calibrated integrated models of the wastewater and stormwater systems. These models revealed where stormwater and groundwater were entering the ageing wastewater network — causing inflow and infiltration issues and overwhelming the system during heavy rain events.

To guide future investment, Woods conducted a Multi-Criteria Analysis (MCA), engaging stakeholders to evaluate upgrade options across environmental, economic, cultural, and social dimensions.

Outcome

Through robust modelling and a collaborative planning process, Woods equipped Tararua District Council with the insights needed to make informed decisions. The project provided a clear view of current system vulnerabilities and a prioritised list of infrastructure upgrades tailored to the district’s unique growth and climate challenges.

Woods’ involvement has helped TDC take a major step toward delivering climate-resilient, sustainable water infrastructure for its communities — ensuring the district is better prepared for the future.