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Wastewater collection system operation Our wastewater collection (sewer) system is made up of: combined sewers interceptor sewers separate sewers land drainage systems lift stations and diversion structures combined and separate sewer areas Combined sewers A system of single pipes that collect both wastewater from homes, businesses and industries as well as surface runoff from rainstorms and snow melt. There are 79 combined sewer outfalls or outlets to the river system. The older, central region of Winnipeg is served by 1,280 km of combined sewer pipes. Prior to 1937, the collected sewage and storm runoff flowed directly into the local river system without being treated. In 1937, an interceptor sewer system was built to carry sewage in the combined sewer system to the North End Treatment Plant. There are 130 kilometers of interceptor sewers in the city that carry sewage to the three treatment plants. Weirs, or small dams, were installed in all combined sewers near the outlet of the pipe to divert sewage to the interceptor sewer system during dry weather conditions. In wet weather conditions, flows are higher because runoff enters the system. A higher flow means the wastewater level in the pipe may become higher than the height of the weir. When this happens, combined sewers overflow to the river system. Combined sewer overflows occur an average of 18 times during the open water recreational season (May 1 – September 30). Top of page

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Separate sewers

• A system of two pipes where one pipe carries wastewater and the other carries land drainage and surface runoff from rainstorms and snow melt.

• The role of the separate sewer system is to collect wastewater from homes, businesses and industries and carry it to a water pollution control centre for treatment.

• Since the 1960s, new property developments in the city have been serviced by a two-pipe system.

• The sewage or sanitary sewer system has about 1,182 km of dedicated pipes that are completely separate from the land drainage system.

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Land drainage sewers

• A system of single pipes that carries rainfall and snow melt runoff from urban areas to the river system.

• There are 1,372 km of land drainage sewers in Winnipeg.

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Lift stations and diversion structures

• Because of Winnipeg's relatively flat terrain, it is necessary to pump wastewater using lift stations to the interceptor sewers or to the water pollution control centres.

• The main purpose of a lift station is to raise sewage to a higher level so that it can be moved into a sewer system where it can flow by gravity.

• There are 76 wastewater pumping stations and 10 gravity-based wastewater diversion facilities located throughout the city.

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Combined and separate sewer areas

• The combined sewer system services an area of approximately 8,700 hectares or about 30% of the city.

• The separate wastewater and land drainage sewers services an area of approximately 22,300 hectares or about 70% of the city.