Untreated sewage can end up in our waterways in multiple ways. Combined sewer overflows (CSOs) are one major source, where pipes that carry wastewater from our houses and businesses also carry stormwater to treatment plants. In heavy rainstorms, more water than the treatment plant can handle accumulates, activating overflow points that redirect untreated water into our waterways- our rivers, lakes and ocean.
The OLW Network is tracking this measure in three ways: how many CSO locations exist across the country, how many municipalities have them, and what the volume of the untreated sewage entering our waterways is.
We know that any of these measures on their own have limitations: measuring the # of CSO locations only disguises the knowledge that some CSO locations overflow more than others, in addition to some technological solutions that reduce CSO overflow events such as real time controls. Measuring volume (at this time) also presents some problems: the reliability of volume data is not consistent across the country, with some discharge locations reporting based on models not actual measurements, and others having noticeable gaps in the reporting.
Tracking all three of these metrics however gives us a more complete picture, while allowing us to focus on a suite of solutions, from reducing the total number of CSO locations across the country as well as pursuing other solutions to reduce the amount of untreated sewage that comes from these sources.
5-Year target: to report on this measure, and see a reduction in any of the three metrics. The ultimate goal is for no untreated sewage to enter our waterways and for CSOs to be replaced across the whole country.
Last updated April 2018