The Challenges of Relining a Brick Culvert in an Urban Environment

Pipeline rehabilitation in urban environments presents major challenges to asset owners. This paper focuses on how Auckland Council overcame these challenges to rehabilitate a 140m length of 1350mm diameter stormwater brick culvert which also carries wastewater overflow in rainfall events from the sewer system serving a portion of the Freemans Bay catchment. The culvert was built in the early 1920s and it was subsequently covered in stages as fill was brought in and placed on top of the culvert over the years. Recent condition assessments indicated that sections of this culvert had experienced severe deterioration, posing high risk for a structural failure. The critical section of the culvert runs under the Freemans Bay School grounds.

The site constraints included 10m deep non-engineered fill, contaminated soil, high water table, tidal inundation, and working in school grounds. Since replacement would have been a very costly solution and resulting in significant community disruption and environmental impacts, a decision was made to rehabilitate in place using a trenchless construction method. A cured-in-place-pipe (CIPP) structural lining was identified as a most appropriate method for rehabilitation. A 10m deep shaft had to be constructed to enable the lining installation. The physical works were successfully completed with minimal inconvenience and disruption to the school, residents, traffic, and community activities.

The paper explores the decision processes in selecting the most adequate rehabilitation method. It describes the investigation, design and construction challenges, the strategies used to manage the risks and the approach ultimately utilised for this unique project.