The 99th Avenue Sanitary Trunk Sewer has been a critical component of the City of Edmonton‘s wastewater collection system since the 1970s. The 1.1 kilometre long sanitary trunk sewer is located approximately 30 metres below ground and serves a crucial role in conveying combined sanitary flows from the city’s west end through residential and commercial areas in the West Jasper Place neighbourhood. Over the decades, exposure to hydrogen sulfide gas and natural wear led to significant degradation of the sewer.

EPCOR Utilities manages the City of Edmonton’s wastewater and water systems. Recognizing the urgency of addressing the deteriorating condition of the sewer to prevent potential service disruptions, EPCOR retained Shanghai Construction Group, with Associated on their team, to construct Phase 1 of the project.

The primary objective of the project was to rehabilitate the existing trunk sewer to restore its structural integrity and enhance its capacity to handle future wastewater flows. This included the construction of a new 1.6 kilometre bypass sewer using advanced microtunneling technology, to divert flows during the rehabilitation process, and provide additional capacity for future development.

With the sewer’s location in a densely populated urban area, it was essential to minimize disruptions to the community and ensure the safety of residents and workers. Significant technical challenges included complex geological conditions, deep tunnel alignments, and proximity to existing infrastructure and environmentally sensitive areas. EPCOR and project partners devoted considerable time and resources to developing a comprehensive plan that would address the project’s technical, logistical, and community-related challenges. To minimize community impact, the project was delivered in two stages spanning three years and incorporated proactive community engagement.

One of the most significant challenges of the project was selecting an appropriate alignment for the bypass sewer. We conducted extensive geotechnical investigations to understand the soil conditions along the proposed alignments. This involved drilling numerous boreholes and conducting soil tests to assess the composition and stability of the ground at various depths.

This assessment showed a number of challenging conditions for the tunnelling to traverse. This includes rafted bedrock, sand seams, with boulder fields all within the dense clay till.

Employing advanced construction techniques were critical to addressing technical challenges and the success of the project. One key decision was selecting microtunneling as the preferred construction methodology. Microtunneling allowed for the installation of underground pipelines with minimal surface disruption. This was particularly important for this project, given the depth of the tunnel and the proximity to existing infrastructure. Significant secant structures were constructed in order to reach the depth needed for the installations.

A significant portion of the project was located within the North Saskatchewan River Valley, one of Edmonton’s most environmentally sensitive areas. The river valley is not only a vital ecological corridor, but also a cherished natural asset, providing habitat for wildlife, as well as recreational spaces. The project team implemented rigorous environmental protection measures. Construction activities were carefully planned and executed to minimize disruption to the natural environment, particularly within the river valley. Special attention was given to preserving the integrity of the existing landscape, and the overall ecological balance of the area.

North American Society for Trenchless Technology’s 2024 Project of the Year Award Winner

The Sanitary Trunk Bypass not only enhances the resilience of Edmonton’s wastewater system, but also sets a new standard for considerations for long-term resiliency of new infrastructure.

Our team supported our client, Shanghai Construction Group, with the complex design components of the works left which included the hand tunnel connections, manhole structures, and inflow bypass and abandonment plans. With the support of our survey team, a 974 metre microtunnel drive was successfully completed with the boring machine reaching its target within 150 millimetres at the end, which is an amazing achievement.

Associated’s team was led by Jason Lueke and included Chris Lamont, Sam Saunders, Ryan Krausher, Dusanka Stevanovic, Caitlin Lou, and Greg Walker.

Stay tuned for our work as the Design Build Engineering Lead working with Shanghai Construction for the rehabilitation work of the existing tunnel that is currently under construction.

The post Award-winning infrastructure project provides reliable, long-term wastewater collection service for Edmontonians first appeared on Associated Engineering.