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Western Beaches Tunnel Pumping System Improvements

Helping reduce combined sewer overflows into Lake Ontario

  • 3.7KM


  • 60

    Metres Deep

  • $10M

    Construction Value

  • Toronto, Ontario

    Toronto, Ontario

Configuring to provide better functionality, control, and operation

The Western Beaches Tunnel was constructed in 2000 to reduce the discharge of untreated storm water and combined sewer overflows (CSO) into Lake Ontario. It collects, stores, and treats CSOs from 10 sewer outlets before they reach the lake. The system consists of three large vertical shafts up to 60 m deep and multiple smaller drop shafts inter-connected by a 3.7 km long tunnel, providing a capacity of 85,000 m3.

Numerous problems plagued the pumping system due to the large range of operating conditions required by the existing configuration—it failed after the first storm event. City operations staff have experienced issues with system control, inability of the pumps to empty out stored CSO flows, removal and reinstallation of the pumps, inadequate sediment flushing and removal, flow surges causing damage to the structures, and flooding of surrounding areas. The UV disinfection system was also not in use.

Stantec helped the City simplify the configuration to provide better functionality, control, and operation. This included installation of new shaft dewatering pumps with capacities up to 43 ML/d and addition of dedicated grit/debris pumps located at the bottom of the shaft. We also inspected and helped improve the three shafts and tunnel. A new sediment fluidization system was designed using Computational Fluid Dynamics modeling. Upgrades to other building systems support the system improvements.

Our services included preliminary design, detail design, contract administration, and inspection of the works.

At a Glance

Meet Our Team

Susan Alarcon, Senior Associate, Water

Our team brings valuable water solutions and resources to communities across Ontario, improving the quality of life for everyone living there.
Susan Alarcon Senior Associate, Water Read More

Jian Li, Associate, Senior Environmental Engineer

My focus—service, performance, and the team. Providing practical engineering solutions to environmental challenges in our communities.
Jian Li Associate, Senior Environmental Engineer Read More

Fangbiao Lin, Vice President, Global Practice Leader for Environmental Hydraulics

CFD modeling is my passion, solving flow problems is my satisfaction!
Fangbiao Lin Vice President, Global Practice Leader for Environmental Hydraulics Read More

Steve Fradkin, Tunneling Technology Manager

Although the work and results are generally unseen, the results of my work benefit everyone.
Steve Fradkin Tunneling Technology Manager Read More
  • Susan Alarcon

    Senior Associate, Water

  • Jian Li

    Associate, Senior Environmental Engineer

  • Fangbiao Lin

    Vice President, Global Practice Leader for Environmental Hydraulics

  • Steve Fradkin

    Tunneling Technology Manager

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