The City of Saskatoon needed to extend their existing sanitary and storm trunk sewer system to support the new and growing community of Holmwood to a projected population of 82,000. The design-build team of Michels Canada and Stantec was brought in to lead the project.
The sanitary trunk is just over 1,500 m in length and uses a 1,200 mm diameter HOBAS pipe installed at a depth of between 10 m to 15 m. Due to the depth and location of the sewer alignment alongside a busy road and adjacent to an existing residential subdivision, the pipe was installed by tunneling using a two pass system. The storm trunk parallels the sanitary trunk for the full length and is a 2,400 mm diameter HOBAS pipe installed at similar depths, also using a two pass system. The design for the parallel tunnels was completed with a nominal spacing of 5.3 m between centerlines to facilitate one larger launch and retrieval shaft from which both tunnels were constructed.
With the community in mind, our solution avoided any traffic disruptions and any impact on normal water and sewer services to the surrounding residents.