Case Study: Extending the Life of Critical Process Pipework at the City of Winnipeg North End Sewage Treatment Plant

The City of Winnipeg faced challenges with the condition of their Return Activated Sludge (RAS) piping within the North End Sewage Treatment Plant. Non-destructive and destructive condition assessment techniques were used to determine that the critical process piping was life expired, and required replacement or rehabilitation to maintain process level of service until the plant is upgraded. Replacement of a RAS piping system is akin to major heart surgery on a sewage treatment plant. To manage the process risk, in situ structural renewal using an engineered Carbon Fibre Reinforced Polymer (CFRP) external wrap system to encapsulate the original carbon steel piping was chosen. Selection of the rehabilitation method reduced the schedule by two years compared to the replacement option and minimized operational risk, as process outages were reduced to a few short-term events. Offline testing of mock-ups and emphasis on environmental and quality control further managed the risks associated with CFRP installation. The project faced unique challenges due to the complex configuration of the RAS piping, which was located inside a congested plant gallery with surrounding equipment, piping, and electrical services in continuous operation. To effectively convey information during planning, design, tender, and construction, a digital 3D model was developed using laser scanning to capture the detailed configuration of the piping and surrounding physical constraints. The 3D model was embedded with data to define the rehabilitation scope, locations of existing pipe leaks requiring immediate repair, rework of pipe supports to accommodate the CFRP installation, and other aspects relevant to the work. This model was a highly effective tool used for collaborative review by all project team members throughout design and construction, leading to successful completion of the RAS piping rehabilitation.