What is a combined sewer overflow (CSO)?
The City of Ottawa has three types of sewers: wastewater, stormwater, and combined.
Collect wastewater from homes, businesses and industries, and transport the wastewater through a network of sewers, pumping stations and forcemains to main or trunk sewers, and direct it to the Robert O. Pickard Environmental Centre for treatment.
Carry rainfall and other surface water run-off directly to the nearest creek, stream or river, generally without treatment.
Collect and transport both sanitary wastewater and stormwater runoff in a single pipe. This type of collection system was typically installed from 1880 to 1960 and is still in operation in older areas of most Canadian cities.
The practice of discharging overflows during the normal operation of combined sewer systems is accepted by the Ministry of the Environment. In Ottawa, these events are monitored and reported to the Ministry of Environment and downstream users such as water purification plants and special interest groups.
The Above Information was Written and Provided by the City of Ottawa