Hutt City Nondestructive Technologies Assess Pipeline

An article published on New Zealand Infrastructure Online discusses Hutt City’s proactive management of critical infrastructure through the use of advanced non-destructive technologies.

Hutt City used PureEM™ to assess the condition of the Main Outfall Pipeline – a rubber ring jointed, non-cylinder prestressed pipe – and locate broken prestressing wires.

This pipeline is 18 kilometers long and takes treated wastewater from Seaview to Pencarrow for discharge into the Cook Strait. It serves the combined Lower Hutt and Upper Hutt population of 140,000.

Built in 1962, the pipeline is made up of more than 4000 sections of pipe and has an internal diameter of 1300-mm (51-inches). The cost replacement estimate for this pipeline is $60 million and would be very difficult to complete because there is no longer sufficient space in the narrow road that winds around the Eastern Bays of Wellington Harbour.

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Inspection Tool

In favour of capital replacement, Hutt City opted to find and employ advanced technologies to assess the pipeline and address the most distressed areas. MWH Global was contracted by Hutt City Council to investigate the repair or renovation of the pipeline and seek resource consents for pipeline inspection.

Assessing the condition of the pipeline was a challenging task but one MWH identified as being best performed using a combination of non-destructive testing technology, internal visual inspection and engineering science and judgement. MWH contracted Aqua-Environmental (a Pure Technologies company) for the condition assessment.

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New Zealand Infrastructure (NZI) provides stakeholders in the infrastructure industry with timely information, critical insights and detailed developments from within the country and around the globe that influence the planning, design and implementation of New Zealand infrastructure.

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