Wastewater upgrades wrap up near Kepa Road, Ruakākā
Published on 01 July 2025
Pipelines and manholes have been replaced in the area surrounding Kepa Road to the Sime Road pump station (pictured).
A project to rectify issues and strengthen the wastewater system near the industrial area close to Kepa Road in Ruakākā is nearing completion.
Wastewater in this area is conveyed from residential, commercial and industrial properties to a pump station on Sime Road before being pumped to the nearby Ruakākā Wastewater Treatment Plant.
In early 2023, Council was alerted to a series of tomos (openings in the ground) from Tiki Place, across the recreation reserve and in the industrial area that backs on to it, prompting urgent investigations.
Despite wastewater pipes in this area being only ~35 to 50 years old and having an 80- to 100-year lifespan, investigations found some corrosion, which was allowing sand and groundwater to enter the system, leaving cavities in the ground.
Project Engineer Kevin Rooney said that, during 2023, Council completed construction works to replace sections of deteriorated concrete piping with PVC pipes.
However, in December 2023, additional tomos had formed further down the wastewater line from Kepa Road towards the Sime Road pump station, leading to an extension of works and more detailed investigations in the area.
“These investigations indicated what’s known as ‘H2S attack’, where hydrogen sulfide builds up inside pipes and manholes and corrodes the concrete. This can happen when there are slower wastewater flows or highly concentrated wastewater, and would have been exacerbated by high groundwater levels in this case,” said Mr Rooney.
“To address the issue, new polyethylene piping, which is less likely to be affected by H2S, was installed from the industrial area that borders the park, across Kepa Road and underneath several businesses to the Sime Road pump station.
“Remediation also involved replacing an unsalvageable manhole and repairing those showing early signs of damage. Manholes were coated with an H2S-resistant product, known as calcium aluminate, to protect them from future attacks.”
The project involved substantial temporary works to ensure the safety of workers and the public, the area was kept as clean as possible, and the system could continue to function.
“Temporary piping was laid above ground to bypass the construction area and allow daily wastewater flows to travel to the pump station during works,” said Rooney.
"Due to the high groundwater table and sandy ground conditions in this area, as well as the infrastructure being particularly deep, it was necessary to dewater each section individually as new piping was installed. This process involved isolating each section and removing the groundwater to create dry working conditions, allowing the pipes to be laid below groundwater level.
“While you can’t see much because it’s all underground, there’s been a tonne of work go into this complex project, and the team at TDG Environmental did a great job. We’d like to thank nearby residents, businesses and landowners for their patience and cooperation during works as well.”
Since remediation was carried out, wastewater flow volumes have decreased by approximately 28% (flow data from May / June 2022 to May / June 2025), indicating that the piping and manholes are well sealed and more resistant to groundwater infiltration. It is expected that the lesser flows could help ease pressure on the wastewater treatment plant, which is nearing capacity and in the early stages of a major upgrade.
With works near completion, the caravan dump station on Sime Road has reopened. The community may see workers in the area during July 2025 as some minor reinstatement works are carried out, and roads will be resealed when the drier construction season starts in September 2025.