Under normal conditions, wastewater from combined sewers is conveyed to a treatment plant where it is processed before being discharged. Key actions include separating the sanitary and storm sewer systems, with a focus on the Clark Drive catchment area, and implementing specific projects, such as storage facilities and mechanisms to redirect overflows at the Clark Drive outfall. These projects combined are expected to decrease the discharge of wastewater from the outfall by at least a further 20 per cent in the next 5 years. About 85 per cent of the region is serviced by two separate sewer systems. Sanitary sewers carry wastewater to treatment plants.
Storm sewers carry runoff from rainfall to the nearest stream, river, lake or ocean.
In the older areas, combined sewers carry both wastewater and storm water in the same pipe. Nearly half the volume of combined sewer overflows that occur happen at the Clark Drive outfall, with the remainder coming from about 40 other outfalls around the region. The region has explicitly committed to eliminating these overflows as part of the new Liquid Waste Management Plan. Since the 1960s, efforts have been underway to eliminate the discharge of untreated wastewater to the region s waterways. Prior to 1960 all wastewater in the region was discharged without receiving treatment.