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Tennyson Street Brick Barrel Pipe Condition Assessment and Renewal

As one of New Zealand¡¯s earliest cities, Christchurch has many sewers that were built before the invention of precast concrete pipes and instead use unreinforced brick and concrete. These brick culverts are particularly vulnerable to seismic activity and pervasive deterioration.

The Christchurch City Council invited us to provide a brick barrel analysis model to help prioritise pipe renewals and possible repairs for the Tennyson Street network that could also be used on other brick barrel assets in the city. We compared various assessment methods from Australia, the United Kingdom (UK), and the United States to determine the best approach. We then prepared a UK-based model using multi-factor analysis where each asset had likelihood-of-failure and consequence-of-failure determined. Failures were forecast using factors like age, condition, ground water levels and soil seismic resistance indexes, location, and impact to customers. Our Christchurch team ensured local conditions were included in the parameters of the model build, while our UK team ensured international consistency by reviewing both the modelling and reporting.

Our work to support this assessment and renewal effort helps Christchurch work towards safer and more resilient underground infrastructure for future generations.