One pipe system for wastewater and stormwater
In the early years of wastewater collection system development, both Halifax and Dartmouth used a “one pipe” solution, where wastewater (sewage) and rainwater were collected in a single pipe. This system, known as a combined sewer, still exists in some older areas of the municipality, including the Halifax peninsula. Today, the combined flow of wastewater and stormwater is directed to one of Halifax Water’s wastewater treatment facilities for processing before being discharged into the harbour. However, during heavy rainfall, relief points—called combined sewer overflow (CSO) discharge points—may release screened, untreated flow to prevent system overload. These CSO discharge locations, associated with the Harbour Solutions facilities, are outlined on the map below.
Phase 1 - Harbour Solutions Project
By the late 1990’s there were more than 70 combined flow outfalls that were flowing directly to the harbour with no treatment. As a result, to better manage the wastewater and help reduce the impact on Halifax Harbour, the municipality initiated the Halifax Harbour Solutions project. This included the construction of three wastewater treatment facilities, approximately 16 kilometres of interceptor piping and 19 overflow facilities. When completed in 2007/08, these wastewater treatment facilities were designed to treat four-times the ‘Average Dry Weather Flow’ or ADWF. However, any flow above 4xADWF (usually during significant rainfall events) is screened and overflows to the harbour at one of the 19 designated overflow facilities shown on the map.
Phase 2 - Sewer Separation Initiatives
As the municipality has grown and infrastructure is being replaced or upgraded, combined sewer systems are being separated into two-pipe systems (one for wastewater and one for rain/stormwater). By separating them, it allows wastewater to be directed to Wastewater Treatment facilities where it can be treated before it is released into Halifax Harbour. Limiting the amount of rain/stormwater that is flowing to these facilities, reduces the volume of water being managed by the treatment plant which reduces treatment costs and reduces overflow events. Eventually, the goal is to further reduce the number of times Halifax Water Wastewater Treatment facilities exceed the ADWF.
While the Sewer Separation Initiatives are significant investments to help reduce the amount of water being treated at wastewater treatment facilities, there is still more work to be done.
Some homeowners have downspouts and sump pumps that are connected to the wastewater/sewer system. These connections are not permitted, and must be redirected to the yard, rain garden, and/or rain barrel(s). Removing these connections helps to reduce volumes heading to the treatment plant, ultimately helping to reduce the number of times ADWF is exceeded.
Prior to disconnecting downspouts or sump pumps from the wastewater system, please visit halifaxwater.ca/downspout-disconnection-program or contact Inflow@halifaxwater.ca. Please note that redirecting to the ground surface should only be done if there is enough yard area where water can soak in.