Large Trunk Sewer Siltation Headaches; Working Towards a Cure

Abstract

For decades water authorities around Australia have struggled with managing siltation problems in large trunk sewers (>3m diameter), and the difficulties in removing silt from these critical sewers whilst they are in operation at nearly peak capacity with difficult access and limited means for diverting flows. This was a problem experienced by Sydney’s Northern Suburbs Ocean Outfall Sewer (NSOOS) that demanded a solution to avoid dry weather overflows caused by loss of capacity from siltation. A collaborative arrangement was developed between Sydney Water, SASTTI and experienced delivery contractors to tackle the problem. This led to the development of three new innovative technologies to remove silt under different live sewer conditions that are currently being employed successfully to remove siltation. This paper traces the path by which these technologies came to fruition, provides the basic details of the technologies and the conditions under which they operate and explains how they can be employed to address similar problems elsewhere in Australia. The paper demonstrates how the collaborative working arrangement used for this project can be employed to tackle similar difficult problems that appears have no available solutions.