Combined sewer system

What is a combined sewer system

The sewer system in Edmonton includes three types of sewers.

  1. The sanitary system moves wastewater from our homes and businesses through underground pipes to the Gold Bar Wastewater Treatment Plant.
  2. The stormwater sewer system moves the water on our streets from snowmelt and rain storms into the stormwater facilities and underground pipes that takes water to the North Saskatchewan River and other creeks in the city.
  3. A combined sewer system is a single pipe that moves both stormwater and snowmelt from city streets and wastewater from our homes to the wastewater treatment plant. The combined sewer system was developed prior to 1960 and at the time was considered to be more economical that building two separate sewer systems. The construction of combined sewers was discontinued due to environmental concerns and as a result of the population growth in Edmonton.

How a combined sewer system works

During small and medium rain storms or when snow melts in the winter and spring all water in the combined sewer system is treated at the wastewater treatment plant. When storm events are more intense and the system is over capacity the water in the pipes will flow directly into the North Saskatchewan River. These are known as Combined Sewer Overflow (CSO) events. When the combined sewer system overflows to the North Saskatchewan River the frequency and volume of the event is reported to both the provincial and federal government.

EPCOR is committed to reducing the impact of Combined Sewer Overflow events in Edmonton. Our Stormwater Integrated Resource Plan is focused on identifying opportunities to slow stormwater from entering the sewer system during intense rain events by storing it in green infrastructure.

Combined sewer and odours

The combined sewer system can contribute to odour problems in Edmonton neighbourhoods. These pipes were designed to move large volumes of untreated wastewater during rain storms. When there are no storms, only wastewater is flowing in the pipes and sewer odour may escape from catch basins and manholes connected to the combined system. EPCOR has a corrosion and odour reduction strategy in place to reduce the impacts of sewer corrosion and odours, and to improve the quality of life for Edmontonians.

Questions or concerns with the combined sewer overflow system?

If you have a concern about sewer odours in your neighbourhood you can contact our 24 hour emergency line at 780-412-4500 to report the problem.

Does combined sewer overflow (CSO) affect Edmonton's drinking water?
Will upgrades to the combined sewer system change the color of the river?
Is there a health risk in doing river sports?
Why can't storm and sanitary sewers be separated?
Why is it taking so long to develop and implement a solution?

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