Problem:
The rising main along Tawhiti Road, Hāwera had reached an advanced
state of age-related deterioration, with corrosion, lining failure, and joint
weaknesses identified through condition assessment. The 750m long
DN150 concrete-lined steel pipeline, installed in the 1930s, presented
increasing leak and failure risks, particularly where it crossed beneath
a live railway and twin 11kV power cables. Given the presence of
critical infrastructure, shallow cover in places, and a busy transport
corridor, open-trench replacement carried significant safety, cost, and
operational challenges. A trenchless rehabilitation method was
required.
Solution:
The ASOE Fabric-Reinforced Flexible Plastic Pipe (FRFPP) is folded into a U-shape, winched through the main,
and expanded with air to form a close-fit, leak-resistant inner hose. It acts independently of the host pipe yet gains
ring stiffness from the casing—ideal where the pipe is mostly sound but excavation is impossible. This installation
was the first ASOE liner deployed in New Zealand, demonstrating its suitability for local pressure.