The Western Sanitary Sewer Interceptor (WSI) is a hand-mined tunnel that is over 50 years old and conveys more than 35% of the City of Hamilton’s sewage from the outlying suburbs through the western core of the city to the Woodward Avenue Wastewater Treatment Plant. As one of three interceptors in the City, the WSI is 12 km long, with average flows of over 1 m3/s. As such, it is considered a critical infrastructure asset for the City.

Given its criticality, the City decided to rehabilitate a portion of the sewer in need of repair. At
270 m in length and approximately 28 m deep, the section has a diameter of 1525 mm. Due to the depth, consistent high flow, and limited access, the work was undertaken in several phases, and required a team with diverse skills and experience in trenchless technology, sewer rehabilitation, and confined space entry procedures.

The team consisted of the City of Hamilton Engineering Services Group, R.V. Anderson Associates Limited, and Pipeflo Contracting Corp. The success of the project relied on the team’s ability to work closely together as an integrated and cohesive unit to address a number
of challenges—challenges that expanded the project’s complexity far beyond a typical sewer rehabilitation project.