TRENCHLESS | PROJECT REPORT
COMPLETION IN CALGARY
The 11-year project to develop the Inglewood Sanitary Trunk project in Calgary, Alberta, is now complete and microtunnelling played a key role. Report by Melanie Gray, City of Calgary, and Patrick Ilasewich and Marvin McDonald of Aecom. Their paper to No-Dig Show 2026 is published here as an edited version, with permission of the North American Society for Trenchless Technology (NASTT).
ABSTRACT The Inglewood Sanitary Trunk project started in 2014 with one goal: build a sanitary trunk system that could support Calgary’s growing population through 2076. With work now complete, the result is a future-ready system that connects north portions of the city’s wastewater system to its largest Wastewater Treatment Plant, including twin siphons under the Bow River to link three existing trunks. Phase One, completed in November 2020, involved
Top: Inglewood, Calgary, Alberta.
Bottom: IST and Green Line Light Rail Alignments
3.5km of microtunnelling and 250m of opencut work, including the connection to the Bonnybrook Wastewater Treatment Plant. This work provided short-term relief on other sanitary trunks and improved service reliability for several inner-city communities. Phase Two, completed in July 2025, involved
microtunnelling beneath the Bow River to create two, 400m-long tunnels to connect three existing sanitary
trunks on the north and south sides of the river. This phase also involved the construction of a 90m-long tunnel to connect Phase One and Phase Two as well as 20m of opencut work on the north side of the river along a major thoroughfare. Both phases of work, equally complex in their own respects, required a total of six tie-ins to existing sanitary lines, crossing critical railway crossings at four locations, moving power, water, sanitary and storm lines along with obtaining four private land agreements to successfully complete the project. The authors have been on the Inglewood Sanitary Trunk
(IST) since its inception. Completing the project is more than just wrapping up — it’s the end of an 11-year journey, where the project team solved some tough engineering problems and can share lessons learned along the way.
OVERVIEW The Inglewood Sanitary Trunk project is located in the Calgary, Alberta, community of Inglewood which is the city’s oldest neighbourhood and is located at the confluence of the Bow and Elbow rivers, which was a traditional gathering place for First Nations. Inglewood is a vibrant community on the edge of Calgary’s downtown core and is the city’s Arts and Industrial Heritage District. It is a mix of parks, restaurants, shops, and historic buildings as well as home to heavy industry, including Canadian Pacific Kansas City’s (CPKC) Alyth Railyard. The IST project was constructed to provide additional
sewage conveyance capacity to meet population growth to the year 2076. The concept for the IST was to ‘offload’ or divert flows from the northwestern side of the city to free up capacity in the existing 15th St trunks for increased flows from the northeast. This new trunk sewer provides an additional capacity of 8.2 m3/s, which is equivalent to serving an additional 1.1 million people. It connects the northwest portion of Calgary to the Bonnybrook Wastewater Treatment Plant (BBWWTP), the city’s largest. Project design began in 2014 and was a complex
undertaking as there were limited alignment options for a trunk of this size with a requirement to be gravity fed. The topography along the route varied greatly; in some areas the trunk was at 17m depth but near the wastewater treatment plant a box culvert was required due to insufficient cover. There were many alignment constraints, including crossing of the environmentally sensitive Bow River as well as four heavy rail crossings.
20 | June 2026
Images from authors’ original paper, courtesy of NASTT
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