Maximising the value for New Plymouth District Council was the driving force behind the innovative adaptation of its existing water treatment plant, with some great cost and performance outcomes.

With New Plymouth’s population growing, and existing facilities stretched to their limit, New Plymouth District Council needed to upgrade its water treatment plant to cope with the additional demand.

The water treatment plant upgrade resulted in expanding the existing plant capacity from 45,000 m3/d to 70,000 m3/d, as well as an upgraded performance that met the requirements of the new Drinking Water Standards New Zealand.

As the principal designer for the design / build contractor Fulton Hogan, we worked together to maximise the value that could be extracted by innovatively adapting the existing plant. Features of the upgrade include pre-lime and CO2 prior to coagulation for improved coagulation control and reduced water corrosivity (which is important for waters in the Taranaki region); tube settlers installed in the existing clarifiers to enable a 50% increase in capacity; and existing filters fully refurbished, including new floors suitable for a simultaneous air water scour system that provides substantially improved filter washing and a filter-to-waste system.

An additional challenge was that the Council wanted the treatment plant to be fully operational while the upgrades took place. By specifically designing the upgrades and working closely with the contractor and the Council’s operations team, this was achieved.


m³/d upgraded plant capacity


Million $ upgrade


During upgrades

Our People

Clive Rundle

Group Director - Utilities

View on LinkedIn
Email Clive Rundle
Philip la Roche

Technical Director - Water Engineering

View on LinkedIn
Email Philip la Roche