Watercare upgraded the wastewater treatment facility serving Snells Beach, Algies Bay and the surrounding Mahurangi area. Before the pump station was commissioned, high saline levels were found in the incoming sewage, spiking on the monthly spring tides. High salinity degrades pumps and processing machinery and interrupts the biological treatment process, shortening equipment life and causing ongoing processing problems. To keep the plant running correctly, the point of saline ingress had to be found and stopped.

Watercare knew sewer ran through the inter-tidal zone at Snells Beach and Algies Bay, but the intermittent nature of the ingress needed further investigation to understand the issue and the fix. Snells Beach has permanent residents and is popular with summer visitors, and the daily tides limited both the working window each day and the methods available to repair the pipe and manholes.

ProjectMax had already worked on this asset, repairing short sections of pipe and replacing three chambers. The initial design called for trenchless lining to seal the existing sewer, and plastic chambers to replace the manholes and prevent infiltration.

The pipe was successfully lined using a PVC spiral-wound renewal method. The plastic chambers proved unsuitable given the rock the manholes were originally set in, and full manhole replacement could not be completed within a single tide cycle. ProjectMax worked with the contractor and Watercare to identify manholes that could instead be converted to dry chambers or abandoned.

All the pipe sections identified for lining were completed within the contract period, September 2025 to February 2026, along with minor repairs picked up during additional inspections. Every manhole was repaired, abandoned or converted to a dry chamber, with one plastic manhole installed. Post-renewal testing showed a significant drop in saline readings, bringing salinity back into the acceptable range. One cap later dislodged in a dry chamber, apparently as a result of pump station surcharging, and has been flagged for monitoring by the operations team.