EPCOR 99 Avenue Bypass Project

2024 No-Dig North Project of the Year New Installation 

Transforming Edmonton’s Infrastructure: The 99 Avenue Sanitary Trunk Bypass Project


The 99 Avenue Sanitary Trunk Bypass project is a hallmark of modern infrastructure development, addressing the urgent need for the rehabilitation of a critical 1.1-km sanitary trunk sewer in Edmonton, Alberta. 

Over the span of three years, this two-stage project demonstrates EPCOR’s commitment to innovation, environmental stewardship, and community engagement. The project involved the construction of a 1.6-km bypass sewer using advanced microtunnelling technology, allowing for the safe rehabilitation of the aging trunk sewer. 

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The project team overcame significant technical challenges, including complex geological conditions, deep tunnel alignments, and proximity to existing infrastructure, all while minimizing community disruption and maintaining strict environmental standards. The project enhances the resilience of Edmonton’s wastewater system and sets a new standard for urban infrastructure projects across North America. 

Project Background and Objectives

The 99 Avenue Sanitary Trunk Sewer has been a critical component of Edmonton’s wastewater collection system since its construction in the 1970s. This trunk sewer, located approximately 30 m below ground, plays a crucial role in conveying combined sanitary flows from the city’s west end through residential and commercial areas of the West Jasper Place neighborhood. Over the decades, exposure to hydrogen sulfide gas and natural wear led to significant degradation of the sewer.

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EPCOR recognized the urgency of addressing the deteriorating condition of the 99 Avenue Trunk Sewer to prevent potential failures that could disrupt service and cause environmental hazards. 

The primary objective was to restore the existing trunk sewer to restore its structural integrity and enhance its capacity to handle future wastewater flows. This required constructing a new bypass sewer to divert flows during the rehabilitation and add capacity for future needs.

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The project’s urban location required minimizing disruptions to the community and ensuring safety for both residents and workers.

A significant portion of the project is located within the North Saskatchewan River Valley, an environmentally sensitive and protected area. To preserve this vital ecological corridor, EPCOR implemented rigorous environmental protection measures, preserving the natural landscape, including native vegetation and wildlife habitats.

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Detailed Project Planning and Design

The planning and design phase was critical to the project’s success. EPCOR and its partners devoted considerable time and resources to developing a comprehensive plan that would address technical, logistical and community-related challenges.

One of the most significant challenges of the project was the selection of an appropriate alignment for the bypass sewer. After extensive geotechnical investigations, the chosen alignment offered the best balance between technical feasibility and minimal community disruption. The selected route parallels the existing sewer to 148 Street, then turns east along 101 Avenue beneath the MacKinnon Ravine and continues to Ravine Drive, allowing for a more stable geological environment for tunnelling.

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The team opted for microtunnelling due to its precision and minimal surface disruption. Reinforced concrete jacking pipelined with high-density polyethylene (HDPE) were used to provide additional protection against corrosion.

A comprehensive risk management plan was developed to address potential challenges such as unexpected geological conditions and groundwater management. Contingency strategies and emergency response plans ensured swift resolution to any incidents during construction. 

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Overcoming Challenges, Implementing Solutions

The 99 Avenue Sanitary Trunk Bypass project faced several significant technical challenges that required innovative solutions and adaptive problem-solving. The project’s success can be attributed to the team’s ability to anticipate and overcome these challenges while maintaining a strong focus on safety, efficiency, and quality.

The complex geological conditions encountered during the project posed one of the most significant challenges. The soil along the tunnel alignment was highly variable, consisting of glacial clay till interspersed with cobbles, boulders, sand seams, and clay shale bedrock. These conditions created a challenging environment for tunnelling, with the potential for unexpected obstructions, and ground instability. High water table posted additional challenges during shaft and tunnel construction.

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Microtunnelling allows precise excavation with minimal surface disruption, making it ideal for navigating the difficult ground conditions. The remote-controlled microtunnel boring machine (MTBM) used in the project was equipped with a slurry system to manage excavated material and maintain tunnel stability. 

The longest tunnel drive, at 965 m, crossed beneath the sensitive MacKinnon Ravine, and marked the longest single microtunnelling drive in western Canada at the time of execution.

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The depth of the tunnel, approximately 30 m below ground, required the construction of deep working shafts to launch and retrieve the MTBM. These shafts had to be carefully designed to ensure stability and safety throughout the tunnelling process.

The project team employed a combination of secant pile walls to construct the launch and retrieval shafts and liner plate shafts to complete the TBM retrieval. In addition to the main working shafts, the project required the construction of several access manholes along the tunnel alignment. These manholes were strategically placed to facilitate maintenance and future connections to the sewer system. The design of the manholes included HDPE-lined concrete barrels to protect against corrosion and ensure long-term durability.

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Close proximity between the new bypass sewer and the existing trunk sewer posed a risk of damage during construction. EPCOR implemented protective measures, including a secondary lining within the bypass tunnel and monitoring systems to detect any movement or stress. Hand tunneling techniques ensured safe connection between the new bypass sewer and existing sewer.

Environmental considerations included groundwater management, use of bentonite drilling fluids and minimizing surface disruption in the ravine, Restoration efforts helped preserve the natural landscape.

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Project Execution and Timeline

The project was divided into two main phases: the construction of the bypass sewer and the rehabilitation of the existing trunk sewer. 

Phase 1, which involved the construction of the 1.6 km bypass sewer, began in August 2020. This phase required the successful completion of three microtunnelling drives, each with its own unique challenges. The longest drive, at 965 m, was completed in November 2021, despite the difficult ground conditions and the presence of large boulders. The second drive, spanning 390 m, and the final 250-m drive were completed in 2022 followed by all pipe inspection and commissioning work completed by mid-2023. 

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Phase 2, which focuses on the rehabilitation of the existing trunk sewer, began in early 2023. This phase involves sliplining the old 1200 mm x 1,800-mm concrete arch sewer with fibreglass-reinforced polymer (FRP) pipe, a process that restores the structural integrity of the sewer while minimizing excavation. The rehabilitation work is expected to be completed by the end of 2024.

Effective collaboration between EPCOR, Shanghai Construction Group (Canada) Corp., Associated Engineering, and various subcontractors was essential. Regular meetings and a clear communication structure ensured coordination, issue resolution, and project progress. Collaboration with the City of Edmonton also helped minimize conflicts with other infrastructure projects.

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The project team implemented a comprehensive safety management plan that included regular safety audits, training programs, and strict adherence to safety protocols.

In addition to safety, the project team placed a strong emphasis on quality assurance. Quality control measures were implemented at every stage of the project, from the selection of materials to the execution of construction tasks. 

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The project’s location in a residential neighborhood and its proximity to the MacKinnon Ravine required careful management of community and environmental impacts. The project team developed a robust community engagement plan that included regular communication with local residents, businesses, and stakeholders. This plan ensured that the community was kept informed of the project’s progress and that any concerns were promptly addressed.

Environmental management was also a key focus throughout the project. The team implemented measures to protect the natural environment, including the use of biodegradable materials, careful management of groundwater, and restoration of any areas disturbed by construction. 

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Impact and Benefits

The completion of the bypass sewer and the rehabilitation of the existing trunk sewer have significantly enhanced the resilience and reliability of Edmonton’s wastewater system. The upgraded infrastructure is now better equipped to handle peak flows during intense rainfall events, reducing the risk of overflows and surface flooding. Using advanced construction techniques, such as HDPE-lined concrete pipes, ensures long-term durability, reducing maintenance needs and minimizing the risk of system failures.

The project also sets a precedent for future infrastructure projects in Edmonton, demonstrating the value of proactive planning, innovation, and community engagement. As the city continues to expand, the lessons learned from the 99 Avenue Sanitary Trunk Bypass project will inform the planning and execution of new infrastructure initiatives.

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One of the most notable aspects of the project was the successful engagement with the community. EPCOR’s commitment to transparency and open communication contributed to positive relationships with residents and stakeholders, ensuring that the project could progress.

The project team’s efforts to minimize disruptions, such as implementing traffic management plans and coordinating with local businesses, helped to limit concerns and generated positive feedback. The team also addressed environmental concerns by protecting the MacKinnon Ravine and other sensitive areas, as EPCOR maintained a responsible and community-focused approach.

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Lessons Learned and Best Practices

The 99 Avenue Sanitary Trunk Bypass project provided valuable insights and lessons that will inform future infrastructure projects in Edmonton and in the other communities where EPCOR operates across North America. 

Advanced planning, thorough geotechnical investigations, risk assessments, and contingency planning were critical to the project’s success. Real-time monitoring systems, such as slope inclinometres and borehole extensometres, allowed for informed decision-making and timely issue resolution.  

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The project demonstrates the importance of flexibility and adaptability in execution. Despite the challenges posed by the complex geological conditions, the project team adjusted its approach as needed to overcome obstacles. The decision to modify the tunnel alignment and reduce the number of intermediate manholes, for example, helped streamline the construction process and minimize risks.

The team’s ability to adapt to unforeseen challenges, such as the impacts of the COVID-19 pandemic, was also critical to the project’s success. The project team implemented new health and safety protocols to protect workers and ensure that construction could continue safely. These adaptations allowed the project to proceed without significant delays, despite the unprecedented challenges.

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Conclusion

The 99 Avenue Sanitary Trunk Bypass project is an example of how innovation, collaboration, and commitment to excellence can transform urban infrastructure. 

The project’s successful completion, despite the numerous challenges encountered, reflects the dedication and collective skill of the project team. The enhanced resilience and capacity of Edmonton’s wastewater system will support the city’s continued growth and ensure the reliable delivery of essential services. Moreover, the project’s environmental and community-focused approaches have set a new standard for infrastructure development in urban areas.

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This story was compiled by the Trenchless Technology Canada staff from information provided to NASTT for the award submission.

Contributing are Vijayakumar Chinnathambi, P.Eng., PMP., IntPE., APEC Engineer, Project Manager, EPCOR; Yang Bai, Project Manager, Shanghai Construction Group (Canada) Corp.; Christopher Lamont, C.E.T., P.Eng., Associated Engineering; and Chris Jones, P.Eng., Team Lead, Stantec.

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