Bronson Watermain Microtunnelling Project

In 2019, the City of Ottawa undertook a major infrastructure upgrade involving the installation of a new watermain beneath Bronson Avenue and directly under Highway 417, one of the busiest transportation corridors in the city. Due to the depth of the installation, challenging rock conditions, and the need to maintain uninterrupted traffic flow above ground, conventional open-cut excavation methods were not considered practical for the project.

To complete the installation safely and efficiently, Marathon Underground utilized microtunnelling technology, a trenchless construction method that combines remotely controlled tunnel boring equipment with pipe jacking techniques to install underground infrastructure with minimal surface disruption. Microtunnelling is particularly effective in congested urban environments where maintaining existing roadways, utilities, and public access is critical.

The process involved the use of a remotely operated microtunnel boring machine (MTBM) that advanced through the rock beneath the roadway while maintaining precise line and grade control. As excavation progressed, the pipeline was simultaneously installed behind the machine using hydraulic pipe jacking methods. Supporting shoring systems and shotcrete stabilization measures were also implemented to ensure safe excavation and underground access throughout construction.

Compared with traditional open-cut construction, the microtunnelling approach significantly reduced surface disruption, minimized environmental impact, and improved safety conditions for both workers and the surrounding community. The trenchless installation also allowed the project team to maintain a more direct underground alignment beneath existing infrastructure while avoiding major disturbances to traffic operations along Bronson Avenue and Highway 417.

Despite the difficult rock conditions and constrained urban environment, Marathon Underground achieved an average production rate of approximately eight metres per day throughout tunnelling operations. This level of productivity would have been difficult to achieve using conventional excavation methods in similar ground conditions.

The Bronson Watermain Microtunnelling Project was successfully completed on schedule, on budget, and without significant safety or environmental incidents, demonstrating Marathon Underground’s expertise in complex urban trenchless infrastructure construction and microtunnelling operations.