Reducing Wastewater Overflows: Optimising Capital Investment in Christchurch

Christchurch has a large and complex wastewater network serving 384,000 people. Past efforts to reduce wet weather overflows were based on traditional trial-and-error modelling, and the system upgrades stemming from those modelling efforts have not been as effective as hoped, despite costing more than $150 million. Even with those upgrades in place, there remains an overflow volume of 38,000 m³ to waterways and a further 40,000 m³ overflows from 165 manholes during a 3-year ARI (average recurrence interval) storm.

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