Microtunnel Crossing of Alberta’s Busiest Highway

To allow for future development, the city of Calgary (The City) retained associated engineering (AE) to investigate increasing capacity of a sanitary trunk installed in the 1970s. The design solution was to twin an existing 600 mm diameter trunk crossing Deerfoot Trail with a 750 mm diameter pipe. With an annual average daily traffic (AADT) count of 169,000 vehicles per day, the portion of Deerfoot Trail to be crossed required a trenchless method and micro tunnel boring machine (MTBM) was recommended. The trenchless method selection was considered for existing site constraints including: an 8-lane freeway, a pedestrian bridge, a golf course, a regional pathway, and existing utilities. The selected option was 210 m of 1200 mm diameter casing (750 mm diameter carrier) which passed beneath Deerfoot Trail and the golf course. From design through tender and construction, there were deviations from the original design to achieve the project outcome. This paper focuses on these changes, the construction process, and the final successful outcome.