Winnipeg, MB - The City of Winnipeg is releasing the number of combined sewer overflows (CSO) occurring each year, as well as the volume released in each overflow event.
Reports are now available online for calendar years 2013, 2014, and 2015. Moving forward, additional reports will be made available online annually. Data within the discharge reports are compiled and displayed on a yearly basis, but are also broken down by month in which the reports identify the volume of each overflow event that occurred.
Combined sewer systems are sewers that are designed to collect both land drainage (rainwater and snowmelt) and wastewater (sewage from homes and businesses) in the same pipe. Most of the time, combined sewer systems transport all of the land drainage and wastewater to a sewage treatment plant, where it is treated and then discharged to the river. However, during significant rain events, the wastewater diversion system cannot always handle all of the land drainage that enters the system and it flows directly to the rivers to protect basements from flooding.
The volume of each overflow event disclosed in the discharge reports reflects the total combined volume of the overflow which includes both rainwater and wastewater (sewage). The ratio of rainfall to wastewater for each overflow event will vary depending on rainfall volumes and intensity. For example, after an intense rain event in 2015, 96 percent of the overflow event was rainfall runoff and only 4 percent of the overflow event was wastewater.
The release of combined sewer overflow discharge reports complements the existing public reporting by the City of Winnipeg when incidents occur that interrupt the routine operation of the sewer system resulting in a release of raw sewage into the river system.
The City has made advancements in the monitoring of CSOs, and in 2008 began planning a CSO monitoring program. As part of the program, new instrumented monitoring began in 2009 with further refinements to equipment occurring in 2013. The City’s total investment in improved monitoring tools since 2009 has been $12 million.
In 2013, with more accurate monitoring tools in place, the City was for the first time, able to start collecting reliable validated estimations of CSO events and volume. Improved monitoring has also provided City staff with the ability to form a better day-to-day perspective of CSOs, which assists in targeted planning of improvements to municipal sewer systems.
The City is currently undertaking sewer separation work to reduce the impact of CSOs in three combined sewer districts (Jefferson, Cockburn and Ferry Road) under the CSO and Basement Flood Management Strategy. Sewer separation takes land drainage runoff flows out of the combined system and reduces the risk of CSOs. To date, the City has invested over $300 million on CSOs and Basement Flood Relief (BFR), with another $110 million budgeted for future investment.
Additionally, the City continues to undertake a number of operational, asset management and capital projects to manage and reduce the volume and number of overflows. These projects include pump replacement, sewer cleaning and sewer realigning and rehabilitation.