Inglewood Sanitary Trunk Phase 1
Client:
City of Calgary
Location:
Calgary, Alberta
Year:
2018-2020
Project Scope
The Inglewood Sanitary Trunk Phase 1 was one of the most significant utility contracts in the City of Calgary's history, that Whissell delivered as Prime Contractor. The project installed 3,470 metres of 2500mm and 2286mm HDPE-lined concrete pipe via pressurized-face microtunnelling across eight shaft locations, with tunnel depths reaching 15.8 metres and the longest single drive spanning 856 metres. The scope also included 400 metres of open-cut box culvert, live-flow tie-ins to existing 1800mm sanitary ducts, relocation of storm, water, and sanitary force mains, and full surface restoration. Whissell partnered with Sarcee Gravel Products Ltd., a Tsuut'ina Nation enterprise, for aggregate supply and fill disposal as part of the project's social procurement commitment.
- 3,470 m of 2500mm/2286mm HDPE-lined concrete pipe via microtunnelling (Herrenknecht AVND boring machines); drives up to 856 m at depths to 15.8 m
- Eight launch/reception shafts (7.0 m to 15.8 m deep; up to 9 m ID), including one trapezoidal secant pile shaft
- 400 m of open-cut box culvert (3.0 m × 1.5 m) with precast and cast-in-place chambers
- Live-flow tie-ins to two existing 1800mm sanitary ducts with custom internal diversion structures
- Relocation of storm, water, and sanitary force mains; alteration of existing utilities
- 30,000 m³ of tunnelling spoil handling and disposal using sealed trucks per environmental regulations
- Full traffic accommodation, site security, rail monitoring, and surface restoration
Challenge & Mitigation
Navigating highly variable ground conditions near the Bow River, ranging from bedrock to coarse granular channel deposits, required secant pile rings and injection grouting for ground improvement around the most sensitive shaft. An 856 m shallow curved drive beneath a major roadway with a rail crossing demanded an intensive deformation monitoring program to prevent frac-outs and surface settlement. Two emergency excavations were completed to repair the microtunnelling head mid-drive, demonstrating Whissell's ability to resolve critical equipment issues without losing the tunnel alignment.
Value Add Solution
The original reception shaft was designed as an unconstructible 18-metre oval structure. Whissell redesigned it as a cast-in-place structure with slide gates, generating significant savings in bypass and downstream costs. An alternate bypass system further reduced pumping duration, producing additional cost avoidance. The project was completed on schedule and under budget.
