Pressure sewers – comparative performance assessment of rehabilitation technologies, in Germany

Abstract

Pressure sewers are difficult to inspect and trenchless rehabilitation alternatives to their opencut replacement tend to only be used in situations where excavation is not possible – under rivers, canals, roads, rail or other infrastructure. German network owners have been keen to better understand the capabilities and limits of application of rehabilitation options and commissioned a performance comparison of close fit pipe and cured in place pipe liners at the 1:1 scale. Six representative products were installed into pressure sewers test rigs with simulated damage scenarios typical of those encountered by network owners within their assets. There was also a particular focus on the performance of end seals, connecting the liners to the host pipe, and liner performance through bends. Installed liners were subjected to dynamic pressure regimes and a range of performance tests. Outcomes ranged from very good to fail, across the products, and highlighted key points for addressing quality assurance of installations, including attention to correct dimensioning and quality of end sealing. The rehabilitation study formed the latest part of a 20-year research programme on pressure sewers that also included risk-orientated maintenance strategy, cleaning methods and inspection techniques. On completion of the rehabilitation technology comparisons, the test rig was re-purposed to support a pilot study comparison of pressure sewer inspection sensors and technologies. This was undertaken on behalf of the Dutch research association Sichting Rioned, as part of an EU Horizon funded ‘Consortium of Urban Drainage Laboratories’ project. The findings on their performance are currently being used to inform the conduct of field trials of inspection technologies by Dutch municipalities. This paper summarises the activities and key findings of the rehabilitation research project and highlights the information available from the wider research programme on cleaning, inspection and a risk based approach.