Final lap for Kahika wastewater upgrade

28/05/2024
Before a line is drawn under the $22m Kahika wastewater upgrade that will see overflows reduced and complex clean ups and repairs a thing of the past, we need to install the final touches of the pipeline. 
 
Project manager Alastair Stewart says these final touches on the replacement pipeline will be the installation of five air valve cabinets and odour filtration domes. 
 
“Air valves are commonly found on large pressure pipelines to enable them to operate efficiently by releasing air that builds up during the operation. 
 
“The odour filtration domes will be installed next to the air valve cabinets to filter out any unpleasant smells from the built-up air that’s released from the cabinets.” 
 
Stewart says three small construction zones have been set up by Watercare’s construction partner CB Civil along Kaipātiki Road and Easton Park Parade to complete this work.   
 
“This time round works won’t be as disruptive as last year’s installation works and will take about three weeks to complete. 
 
“Once the air valve cabinets and odour filtration domes have been installed, the replacement pipeline will be ready to undergo commissioning and be brought into service later this year.” 
 
Stewart says ground crews will also be completing rerouting works of five local network sewers happening in nearby streets and within private property. 
 
“As part of the project, our contractors are diverting local networks away from the current wastewater pipeline to the Kahika pump station which will pump wastewater directly into the new pipeline.
 
“The remaining works will take approximately another three to four months to complete.”
 
Stewart says the pipeline will replace the current 50-year-old pipeline that has experienced four significant failures, resulting in complex repairs and significant clean-up costs.

“Most of these wastewater leaks have occurred because of internal abrasion to the concrete lining and the outer wall of the existing 450mm concrete-lined steel pipe.
 
“Fortunately, the leaks have occurred near the southern side of Kaipātiki Creek which is relatively accessible and straightforward to clean up. 
 
“However, if a failure occurred at the northern side of Kaipātiki Creek or the bridge that carries the pipeline over the creek, the cost of the clean-up and repairs – and ultimately to the environment – would be huge.
 
“This is why this new pipeline is essential.  It will be able to carry twice the amount of wastewater compared to the existing pipeline enabling population growth and reducing the number of overflows into Kaipātiki Creek.
 
“The replacement pipeline has been built using both 700mm polyethylene and 600mm fibreglass pipes which are more resilient to internal abrasion.”
 
Stewart says once the replacement pipeline is in service the team will begin decommissioning the old pipeline by filling it with grout and removing above-ground assets such as manholes to ensure no water can enter it.  
 
“Since most of the changes to the local sewer network are on private property these local network works will not cause traffic disruptions along Kaipātiki Road and Easton Park Parade. 
 
“However, the installation of air valves and green domes and some final road reinstatement at the intersection of Glady's Ave and Easton Park Parade will be our final works on the major roads in the area.” 
 
Stewart thanks locals for their patience as ground crews worked to install this critical infrastructure and allow flood recovery repairs and upgrades to take place.
 
“We know that the significant infrastructure work completed in this area in the past year has caused a lot of disruption to the community.  
 
“Not only have we been working to construct a new pipeline to prevent overflows, we have coordinated our works with Healthy Waters, Auckland Transport and Fletcher Building to construct two new retaining walls and twin culverts from a housing development. This dig-once approach keeps costs down and minimises disruption for the community.”