Orakei Sewer Slip Lining
Constructed in 1910, the Orakei sewer is a critical piece of Auckland’s wastewater infrastructure, carrying sewage from Auckland’s central western suburbs to the wastewater tunnel at Hobson Bay. A 250m section carries the pipeline under the Stanley Street motorway onramp, through the Auckland Domain and under the Auckland Tennis Centre. Overtime the structural integrity of the egg-shaped 2.4m x 1.5m structure had become severely compromised, requiring urgent repair.
Pipeworks developed two proposals for the relining of the pipeline: a CIPP (Cured in Place Pipe) Liner option and a Glass Reinforced Pipe (GRP) alternative. Although the CIPP option offered significant cost advantages, the GRP option was selected because of the reduced risk profile. Pipeworks constructed a temporary pump station and rising main to enable bypass pumping of the pipeline, before relining the sewer using 25mm thick sections of GRP.
The rehabilitation works extended the life of the pipeline by 50 years.
The project involved one of the largest and most challenging by-pass pumping operations in the country - more than 800 litres per second of raw sewage using submersible pumps.
Construction of a 7m deep Insertion Pit.
The GRP sections were installed during the wet winter season.
Construction of an 8.5m deep pump pit to accommodate the by-pass pumps.