To understand how to decrease the risk of flooding, it helps to understand how our city handles waste water.
Like most municipalities, the City of Saskatoon has two sewer systems:
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The Storm Sewer System
This system carries rainfall and other surface runoff from parking lots, roads and private properties directly to the South Saskatchewan River. This water is not treated before entering the river.
This pipe is large in order to handle great volumes of water that can be produced by major storms. |
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The Sanitary Sewer System
This system carries wastewater from homes, buildings and industries to the Wastewater Treatment Plant. After being treated, the water is returned to the South Saskatchewan River.
This pipe is smaller. |
When water meant for the larger Storm Sewer flows into the smaller Sanitary Sewer, the Sanitary Sewer can backup (surcharge) and overflow! When this happens, residences are at risk of experiencing sewer backup. Residences located at lower elevations, especially those with inadequate backflow protection, are most at risk.
Another unfortunate side effect is that when storm water goes through the Sanitary Sewer, the Wastewater Treatment Plant is forced to treat it, which drives up overall handling and processing costs. If the Sanitary Sewage System is severely overloaded, untreated sewage may overflow into the river.
Where is all this water coming from, and how is it getting into the Sanitary Sewer System?
In some homes, eavestrough downspouts are connected to plumbing that empties into the Sanitary Sewer System. Other homes (generally, those built between 1965 and 2004) have a foundation drainage system, also known as weeping tile, which diverts water from the backfill zone into the floor drain in the basement. These systems can contribute to the overload of the Sanitary Sewer System.
During a long or heavy rainstorm, hundreds of litres of water from one property can run into the Sanitary Sewer System. Multiply that by thousands of homes, and the runoff can cause serious problems.
What is the City doing to reduce the risk?
In addition to encouraging homeowners to remove their property drainage from the sanitary sewer system, the City is taking a number of steps to reduce the risk of Sanitary Sewer backup, including:
- increasing the storage capacity of the Sanitary Sewer System;
- sealing off sanitary manholes at intersections which flood frequently; and
- creating an Emergency Diversion Plan for critical sanitary sewers.
As of February 1, 1997, the City has a mandate which requires all new residences to have backflow prevention devices. The City also encourages owners of residences constructed before that date to have a backflow prevention device installed.
What should I do?
Evaluate your home’s current plumbing and drainage system. If your eavestroughs empty into interior plumbing, have them disconnected and add downspouts to disperse the water at least two metres (six feet) away from your home’s foundation.
Many homes built between 1965 and 2004 have a foundation drainage system, also known as weeping tile, which diverts water from the backfill zone into the floor drain in the basement. In this situation, the weeping tile system can be disconnected from the basement drain and reconnected to a sump pump system.
Less water in the Sanitary Sewer System will lower the chance of sewer backup in your home or neighbourhood, and in all areas of the city. However, no municipal sewer system can guarantee every house complete protection. Protective plumbing should be used in all residences.