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.
The Wastewater System Effluent Regulations (WSER) are federal regulations designed to reduce pollution from wastewater by setting national minimum standards for the quality of treated effluent released into the environment.
Recently, the WSER was updated to include Temporary Bypass Authorizations (TBAs). These authorizations allow wastewater system operators to temporarily bypass treatment processes in order to carry out essential maintenance or repairs. During a bypass, effluent may not meet the usual quality standards, but the discharge is still regulated and authorized under strict conditions.
TBAs may involve discharges from the final treatment facility or from overflow points throughout the system. Each TBA falls into one of three categories based on the level of environmental risk:
- Category 1 – Low risk
- Category 2 – Medium risk
- Category 3 – High risk
Risk levels are determined by factors such as the volume and quality of the bypassed effluent, the duration of the bypass, weather-related impacts, and whether the discharge affects sensitive receiving environments. The different categories have different regulatory requirements. Monitoring programs are required for Category 3 applications.
From April 22 to 30, 2025, Halifax Water completed a Category 3 TBA for The Halifax Wastewater Treatment Facility (WWTF). This bypass was in place to conduct several essential maintenance projects to ensure the continued operation of the system. This work was grouped together and aimed to reduce the likelihood of future bypass events. The bypass had an estimated 337,704 m³ of authorized effluent discharged to the Halifax Harbour through several relief points in the system.
As part of the Category 3 follow-up requirements, Halifax Water conducted a comprehensive monitoring program, including sampling for:
- E. coli
- Total Suspended Solids (TSS)
- Carbonaceous Biochemical Oxygen Demand (cBOD₅)
- Un-ionized Ammonia (at 15°C)
- pH (at 15°C)
Sampling locations were selected across Halifax Harbour, including shoreline areas, sites near discharge points, and sites further out in the harbour. Samples were collected at a depth of 1 meter, starting three weeks before the bypass, continuing weekly during the bypass, and for two weeks afterward.
To make this data accessible, Halifax Water developed the Halifax WWTF Maintenance Harbour Sampling App. This interactive tool displays sampling locations on a map and provides the results collected during the Category 3 TBA monitoring program.
Please Note:
Harbour sampling was conducted; however, interpreting the data presents significant challenges due to the dynamic nature of the harbour environment. Without a clear understanding of the mixing processes, flushing patterns, seasonal variations, and the specific harbour activities occurring at the time of sampling, it is difficult to draw meaningful trends or conclusions. The harbour is subject to constant change, and while natural tidal activity will eventually flush the system, this does not provide insight into the overall water quality at any given time. This is an industrial harbour with numerous commercial activities occurring in and on it daily, and to our knowledge, there is no single entity responsible for monitoring its overall water quality.
Sampling locations situated away from discharge points showed variable results, which is expected given the influence of tides, vessel movements, and other environmental conditions that shape water quality in a complex receiving environment. By contrast, sampling locations directly at discharge points did show temporary increases during periods of active work; however, these values declined promptly once work was completed. Importantly, all results remained below the limits set out in the Wastewater System Effluent Regulations (WSER), indicating that while short term fluctuations were observed, measured concentrations did not approach regulatory thresholds.