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Windsor Riverfront Retention Treatment Basin and Tunnel Sewer

A world’s first solution to help clean the Detroit River

  • 85%

    Footprint Reduction

  • 680

    ML/d Treatment

  • $40M


  • Windsor, Ontario

    Windsor, Ontario

The world’s largest high-rate retention treatment basin

Fish and wildlife population loss, drinking water restrictions, a designated area of concern—all that paints a picture of environmental degradation in the Detroit River. Much of this impact was caused by an all too common problem: combined sewer overflows. Faced with aging infrastructure, limited space, and not enough funds, the City of Windsor needed a unique solution. With a footprint 85% less than a conventional facility, the Windsor Riverfront High-Rate Retention Treatment Basin (RTB) enhances the City’s riverfront amenities and significantly reduces the pollution entering the river.

A conventional solution would have put three retention treatment basins (each the size of a full hockey rink) in three different locations. There just wasn’t the space or community support for that, so we looked at other options. With the University of Windsor providing scientific input to support our engineering design, we found that we could design a high-rate solution that was 85% smaller. But the significantly smaller size brought its own difficulties.

A smaller RTB meant a high-velocity flow. In a conventional system, solids settle to the bottom, and then the clear water is pumped out. In a high velocity system, the waters are too turbulent for simple settlement. So, how’d we make it perform at the same level as the full-sized option? A polymer-based additive was the answer.

The Environment Canada Wastewater Technology Centre and University of Windsor had been researching a new technique (since 1999), and we brought it to practical application. Dosing the water was a delicate business. Add too much, and the chemicals could flow into the river. Add too little, and untreated sewage would be discharged back into the river. We created an automated dosing system that monitors the concentration of solids and flow rate.

With just the right amount of polymer, the solids are separated so the clean water can be discharged into the river. After that, the remaining solids (and stored CSO) can be sent to the treatment plant, once it’s ready to receive them. The system automatically adjusts to storm type—quick and intense or long and mild. This automated calibration and precise dosing is unique to Windsor’s RTB.

The project comprises a 1,650 mm to 2,250 mm diameter consolidation/conveyance tunnel along the riverfront. The tunnel collects, stores, and conveys combined sewer overflows over a length of 2,400 m at depths up to 9 m to a chemically enhanced 680 ML/d high-rate RTB facility with polymer flocculation. The RTB is an underground concrete structure with a prestressed/precast concrete slab roof comprising 12 (36.9 m x 4.75 m x 3.55 m) storage/treatment cells with a total storage capacity of 8,000 cubic meters.

At a Glance

  • City of Windsor
Consulting Engineers of Ontario, Award of Excellence, 2013

The Combined Sewer Challenge

Many older communities use combined sewer systems to collect surface runoff and sewage. This video shows how combined sewer systems work and how they can sometimes be a problem.

Meet Our Team

Clarence Jubenville, Associate, Senior Municipal Engineer

Don’t sweat the small issues. Keep your eye on the larger picture when tackling any project, or life in general. In the end, the small issues along the way are forgotten.
Clarence Jubenville Associate, Senior Municipal Engineer Read More

Jian Li, Principal, Business Centre Practice Leader, Water

My focus—service, performance, and the team. Providing practical engineering solutions to environmental challenges in our communities.
Jian Li Principal, Business Centre Practice Leader, Water Read More

Oliver Ng, Senior Associate, Senior Structural Engineer

Success of an organization is through team effort and contribution. Contribution from each individual is as valuable as that from a leader.
Oliver Ng Senior Associate, Senior Structural Engineer Read More

Clarence Jubenville

Associate, Senior Municipal Engineer

Jian Li

Principal, Business Centre Practice Leader, Water

Oliver Ng

Senior Associate, Senior Structural Engineer

We’re better together

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  • Design your career

    Work with passionate people who are experts in their field. Our teams love what they do and are driven by how their work makes an impact on the communities they serve.

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