TRENCHLESS | PROJECT REPORT
Top: Construction of Chamber with Hydraulic Flume Installed.
Middle 1: Bow River next to Launch Shaft.
Middle 2: Bow River next to Launch Shaft.
Bottom: Excavating to 1950mm-diameter trunk next to LRT.
machine in the dry. In addition, the Phase One contractor installed temporary, removable half-pipe benching, which channelled sewage flow from the sewer into the IST prior to Phase Two being completed. The temporary benching was removed during Phase Two, allowing the MTBM to enter the chamber on grade and in the dry. For Phase Two the launch shaft was designed and
located to be used for a total of three drives. To minimise the width of the shaft, the twin pipes crossing the Bow River were separated by a width of one pipe diameter horizontally. These pipes were at a lower elevation in the shaft and were installed first. Once these drives were completed, a steel platform was installed in the shaft to accommodate the jacking frame as the invert was approximately 7m higher than the river crossing pipes. Once the final drive was completed the platform was removed, the siphon riser pipes installed, and the shaft backfilled with low strength flowable concrete.
Live connections to sewers The IST project required six live sewer connections and bypass pumping was not an option in four connections as existing flows were too high. The live connections included connecting to the treatment headworks, a 2100mm x 1500mm duct, and pipes of diameter 1800mm, 2286mm and 1500mm. During Phase One of the project, the first live sewer
connection to the duct was completed within a newly acquired utility right of way on private property, at an asphalt shingles plant. The connection was required to combine and equalise flows from the existing West 15 St sanitary trunk with the new flows from IST, and split before being directed to the treatment plant. The contractor built a steel flume to account for max flows of 2.2 m3/s while they constructed a cast-in-place flow-through chamber. The chamber was designed and constructed with operational flexibility and could have stop logs installed for future inspection and maintenance in all four ducts. The second live sewer connection to the treatment plant headworks utilised stop logs to allow the connection to be completed in the dry with only minor pumping of leakage. The third live sewer connection occurred during
Utilized shafts for multiple drives Both launch and reception shafts were located throughout the project such that they could be used for multiple drives wherever possible in an effort to reduce overall construction costs and limit impacts on the public and environment. Shaft 1-1 was constructed around an existing 1800mm-
diameter sanitary main. It was sized to allow reception of the MTBM from both Phase One and Phase Two, and constructed with an isolated channel along its west wall to act as a flow bypass and allowed reception of the
22 | June 2026
Phase One within the intersection of a residential neighbourhood approximately 100m from Bow River. I t took approximately 28 weeks to construct and complete. The connection and chamber had to incorporate the ability for MTBM retrieval for Phase One and future Phase Two, and could not be dewatered as groundwater inflows — directly influenced by the river — were in excess of 3400 l/min/m and too large for pumping. Nuisance dewatering was allowed at this location, but the contractor was required to treat the water onsite prior to disposal into the storm sewer system which directly flowed into the river. A large octagonal shaft was built with 56No secant
piles. The majority of the 880mm-diameter piles were driven to a depth of 14.5m except for those located around the existing 1800mm-diameter Inner City sanitary trunk. Once piling was completed, the MTBM from the last drive of Phase One entered the shaft in buried material,
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