Constructed between 1912 and 1970, the City of Saskatoon’s Interceptor Trunk Sewer conveys wastewater from all areas of Saskatoon. The City completed a study of the trunk in 2006 to determine its current structural condition and formulate a rehabilitation program. Among the study’s findings was that the downstream portion of the trunk required rehabilitation in the near future. This section is a 2,100 mm (84 inch) reinforced concrete pipe, 307 m (1,007 ft) in length. All of the city’s wastewater traverses this portion of the Interceptor. The project included cleaning and CIPP lining, complete with a large temporary bypass.
The City has never undertaken a bypass pumping project of this magnitude; this is the first sanitary sewer bypass pumping project of this magnitude in Western Canada. Due to the large diameter of the pipe and the high base flows through it (up to 1,700 L/s [27,000 USgpm]), there was a high level of difficulty and risk associated with executing this project. Following a pre-qualification process and tendering of the project, the construction contract was awarded to Insituform.
Construction commenced with site preparation starting in November 2011. The bypass pumping system was constructed in early 2012, with the pumping system started on February 25, following which the Interceptor was prepped, inspected, and lined, and then reinstated to normal service on March 15.
Project challenges included the following:
- Challenging schedule: In addition to undertaking the project during dry weather months to avoid the need for significant bypass pumping and flow control, due to the extensive bypass required, pipe preparation and lining activities were planned and executed as efficiently as possible. The bypass system operation costs were $40,000 per day, making any unplanned delays very costly.
- Cold climate working conditions: during construction of the project, temperatures dropped as low as -38 C (-37 F). During bypass system operation and lining, temperatures were as low as -19 C (-2 F). This created an extremely challenging construction environment.
- Large diameter lining: the installed liner was 2,100 mm (84 inch) diameter. CIPP lining installations of this size are not frequently undertaken. Beyond the challenges of fabricating, delivering, handling and installing the liner, Installation equipment of this size needed to be brought in from a great distance, complicating scheduling and coordination challenges for the project.
Through remarkable planning, coordination, and execution by the City, Insituform, and Insituform’s subcontractors, the project team was able to overcome these unique challenges, making this a landmark project for all involved.
NASTT-NW would like to encourage all of its members who are conducting interesting trenchless projects to consider applying for the annual Northwest Trenchless Project of the Year and to take the opportunity to provide presentations of their projects at local technical lunches, the annual conference, No-Dig, and other regional events to truly highlight our region’s leadership in trenchless technology. Please watch the website and your email inbox for notices regarding the next annual Project of the Year.