Strong solution to protect Howick waterways

Howick wastewater repair to protect stream

Our flood recovery team installed a strong solution to safeguard Howick beaches and waterways in just one week. They opted to go with a more robust repair after two slips – one in mid-November, the other in mid-January – caused major damage to an exposed section of the wastewater pipe below, causing it to overflow into the local waterways behind Selwyn Road.

Land movement from last year’s Auckland Flood event covered parts of the pipe, leading to failure in several areas due to added pressure.

Land movement including two slips damaged a wastewater pipe and caused it to overlow
Photo: The damaged pipe is exposed as the repair work begins

Project manager Aidan Wills says the team was swift to address both overflow events.

“As soon as they happened, we immediately implemented a temporary bypass, raised a black flag for 48 hours to ensure the safety of beachgoers, and flushed out the waterways to reduce ammonia levels at the beach outlet.

“However, after the second overflow, it became evident that a long-term solution was required.”

Wills says to protect the waterways and pipeline from slips while implementing a permanent solution for the community, the flood recovery team got to work and installed a more robust interim solution within seven days. “The interim solution was to reinstate the wastewater pipe and install a culvert the stream would run through, protecting it from overflows.

Concrete is used to hold the bottom of the slip and act a retaining structure

“Both pipes were backfilled with concrete to hold the bottom of the slip to act as a retaining structure.

“We then overlayed both pipelines with riprap – coarse crushed rock - to protect the critical assets from future slips.”

Wills says the team aims to begin work on a more permanent solution by the end of this year.

“Although this may seem far away, much planning is required for a permanent solution that will likely see the pipeline moved away from the waterway into more stable ground.

“In the meantime, the robust interim solution will be strong enough to withstand environmental slips, protect the assets and reduce the likelihood of overflows from the pipeline."

Howick Local Board chair Damian Light says the solution that has been installed hugely benefits the community.

“The interim solution is a bespoke fix that adapts to the changing climate, helps to improve local waterways, and builds more resilience in our networks. We know from our community that protecting our beaches and waterways is a priority and we’re grateful for the work that Watercare has done to achieve this they work on the more permanent solution.”