Completion of the New Westminster Interceptor (NWI) Columbia Section Rehabilitation project represents a defining moment for trenchless technology in the Lower Mainland. This project, delivered for Metro Vancouver, proves that large-diameter live sliplining is a viable methodology for future rehabilitation projects. The NWI Columbia Section was in poor condition with all segments rated as 4 or 5 per Pipeline Condition Assessment Program, significantly worse than the inspection 5 years earlier, indicating accelerated deterioration. There were many challenges to consider: flow diversion was not feasible, bypass pumping was impractical due to the size of pumps and piping, sections of the NWI operated under full surcharge conditions, accurate flow monitoring data was not available, limited work area and utility congestion precluded open cut replacement, high potential existed for contaminated soils, and pipe velocities pushed the boundaries for sliplining methodology. The team had to consider limited local large-diameter live sliplining experience, traffic management issues, and schedule constraints related to City permitting and the Pattullo Bridge Replacement.

Our work on this project considered congested work areas, varying and extreme flow conditions, historical market conditions, sustainability goals, social impacts, and efficient use of public funds to minimize the high cost of living in our communities. It is also a significant milestone, as the longest and largest-diameter instance of sliplining completed in the lower mainland region. As much of the large-diameter infrastructure in the Lower Mainland is reaching the end of its useful life and needs replacement or rehabilitation in the near future, this project can be used as a case study to give confidence in rehabilitation solutions and serve as a reference point for future projects striving to provide the best overall triple bottom line outcome.

Jacobs worked with Metro Vancouver to develop a rehabilitation program that met engineering and operational requirements, was feasible to construct, and was mindful of public impacts. Unknown conditions and unprecedented weather conditions conspired to delay the project. Three technical factors were pivotal in keeping the project on a pathway to success.

Optimized Methodology: Several rehabilitation methodologies were evaluated. Jacobs recommended live sliplining as the optimum rehabilitation methodology, which could overcome the need for bypass pumping, high peak velocities and surcharge conditions in the sewer.

Risk Mitigation: Jacobs recognized that the combined risk of potential sewer collapse and live sliplining in a high-velocity sewer required a variety of risk mitigation measures, such as emergency sewer closure systems, construction traffic loading management, and overlapping design and procurement timelines to implement a timely solution.

Technical Flexibility: This project required multiple levels of flexibility from design, operations and maintenance, constructability, and contract administration standpoints. In the face of each new hurdle, the project stakeholders quickly brainstormed options, weighed their merits, and together decided on the path forward to mitigate impacts.

Jacobs assessed solutions that provided an overall triple bottom line solution, developed, and executed the solution. The result was a rehabilitated sewer that eliminated the immediate risk of catastrophic failure, is now operationally safe, and provided a new sewer to continue reliably servicing the community for a 75+ year design life. This project validated that this methodology is feasible locally, provides an example live sliplining benefits, and expanded the envelope of design scenarios.