Systems Overview: Water, Wastewater, Stormwater

The City of Markham's sanitary sewer system collects and moves domestic/industrial wastewater to the Duffin Creek Wastewater Pollution Control Plant located in Pickering, Ontario.

There are pipes throughout your home that only collect wastewater. These pipes are a homeowner's responsibility. They include the drains leading from kitchen sinks, toilets, and showers. Keep these pipes free of debris - like hair or grease - to keep them functioning properly.

The section of sewer pipe that runs beneath your home to the property line is also a homeowner's responsibility. If that section of pipe gets clogged with large objects being flushed down a toilet, baby-wipes, grease buildup, or by tree roots on your front lawn, it is the homeowners' responsibility to have it cleared out.

Baby-wipes go into the garbage and should not be flushed, even if they say "flushable" on the package. Hair and grease into the green bin and not into the wastewater system. Sewer backups are commonly caused by items that should never be flushed down the toilet or poured down the drain.

The City of Markham's sanitary sewer system collects and moves domestic/industrial wastewater to the Duffin Creek Wastewater Pollution Control Plant located in Pickering, Ontario. The Region treats wastewater and releases the cleaned water into Lake Ontario. The quality of the water being released after treatment must meet high standards as set by the Ministry of the Environment, Conservation and Parks.

Once Markham's wastewater reaches the Duffin Creek Wastewater Pollution Control Plant, it goes through an extensive cleaning process. This process includes four general steps.

Step 1: Screening

As wastewater (sewage) enters the Plant, screening removes large, inorganic objects. These objects could include things such as rags, diapers, personal hygiene products, and any other inorganic objects which are removed and sent to landfill.

Step 2: Primary Treatment (Physical)

Organic materials (ie. human waste and food) in the wastewater are removed using settling tanks. These settlement tanks work by using gravity and time to allow the solids to settle to the bottom of the tank where it is collected. A skimmer is then used to remove fats, oils, and grease that float to the top and a chemical is added to remove phosphourous. The remaining liquid portion of the wastewater moves on to secondary treatment.

Step 3: Secondary Treatment (Biological)

Secondary treatment removes small pieces of organic materials from the wastewater using aeration lanes which pump air into the tanks giving helpful bacteria the oxygen they need to break down the organic material and absorb nutrients. Settling tanks are used again to allow the material and bacteria to settle to the bottom where they are collected and removed. The clean water (effluent) from this stage then flows into its final stage, disinfection.

Step 4: Disinfection

Chlorine (sodium hypochlorite) is added to kill and deactivate any remaining harmful bacteria (i.e.. E.coli.). Afterwards, another chemical, sodium bisulphite, is used to remove the chlorine before the clear treated water is released into Lake Ontario.

Flooding of the sanity sewer system can occur on residential/industrial property, or on public and city regulated property. Sanitary sewer backups can be a result of blockages or pipe breaks.

Blockages occur because of excess grease, food or any other materials such as wet wipes, flushed or poured down the drain. This material accumulates in pipes and restricts the flow, causing a backup. Breaks in underground pipes may happen due to faulty installation, pipe age, digging, or invading tree roots.

The City of Markham will repair any blockages or breaks on the Markham-owned portion of the pipes as quickly as possible. However, pipes in a residential/industrial building, as well as the underground pipes from the building to the property line, are the responsibility of the property owner.

Stormwater management facilities, or stormwater ponds, have been used to control stormwater from urban areas in Markham since the late 1980s, intended to ensure that new development does not increase or change the conditions for downstream landowners.  When first introduced, most stormwater ponds were dry, and designed to store water in order to prevent flooding and erosion downstream.  They have evolved over time to also include a permanent pools of water, used to trap sediment and prevent contaminants from our roads and subdivisions from entering our watercourses. 

While ponds can appear as attractive, natural features and are often surrounded by trails and parks, the public is encouraged to exercise caution around facilities, as conditions in stormwater management ponds can change rapidly due to fluctuating water levels and hazards associated with deep pools, fast moving water at inlets and outlets, and thin ice. 

As of May 2020, the city owns and maintains 123 stormwater ponds.  Several new facilities are added in the City of Markham each year.

In February 2013, Council approved a long-term 30-year Flood Control Program which sets funding requirements to achieve level of service improvements for drainage systems in the City of Markham.    

The Flood Control Program is a long term, City-wide initiative to improve storm drainage capacity and limit surface and basement flooding risks in urban areas. Improvements will provide a more consistent level of service across Markham and help protect both public and private property. The program will also make critical infrastructure more resilient to climate change and extreme weather.

The City has prioritized the assessment and upgrade of older drainage systems, constructed prior to 1978, when modern day standards for stormwater drainage were implemented.  Areas constructed prior to 1978 are more susceptible to flooding as they were not designed to convey the amount of water expected during infrequent, very large storm events.   

The Citywide Flood Control Program includes projects that range from major capital improvements to the storm system, to education programs and subsidies for residents to improve their private plumbing systems. 

Staff updated the cost estimates in 2018 for all phases of the Flood Control Program, with an estimated cost of $367-$382M.  To date, the City has received two funding grants for the program: 

• $6.5M from the Clean Water and Wastewater Fund (CWWF) – Ministry of Infrastructure of Ontario
• $48.6M from the Disaster Mitigation and Adaptation Fund (DMAF) – Infrastructure Canada

Nineteen watercourses, including tributaries of the East Don River and the Rouge River, flow through the City of Markham.

Erosion occurs when the forces exerted by the flowing water exceed the resistive forces of the bank and associated vegetation, leading to a change in the shape of a watercourse, and transport of material downstream.

While the process of erosion is natural, it can be exacerbated by the presence of upstream development, extreme weather and human alteration of the watercourse system.  Markham’s Erosion Restoration Program is in place to protect the City’s infrastructure and private property from damage due to erosion.

Debris and falling trees may cause blockages in the City’s watercourses.  In most situations, these blockages occur naturally, and cause no harm to the natural system, and do not result in increases in risk to safety, property or infrastructure.  In some situations, the City may remove the blockage, and restore any bank erosion that has occurred.  

The City conducts erosion inspections annually, and re-prioritizes erosion site restoration through the Erosion Master Plan, completed in 5-7 year intervals. 

Urban development in Markham has extended throughout the last century. The impacts of urbanization on natural watershed processes, if not carefully managed, can alter flow regime, sediment transport, and water quality in the rivers and creeks crossing the City.

Nineteen watercourses, including tributaries of the East Don River and the Rouge River, cross the City of Markham. All of Markham watercourses are situated within a stream corridor that consists of natural or modified vegetation providing riparian habitat as well as shade, which is an important factor in moderating stream temperatures and providing aquatic habitat. There are both cold water and warm water aquatic biota within Markham watercourses. Information about terrestrial and aquatic habitat conditions in Markham stream corridors is available on the Toronto and Region Conservation Authority’s website.

Markham protects the water quality and natural habitat in and around watercourses through implementing an integrated planning and design approach to stormwater management.  Water quality controls (e.g., stormwater management ponds or Low Impact Development practices) are required for all new developments as per the respective Watershed Plans, Subwatershed Studies, Master Environmental Servicing Plan and MECP (Ontario Ministry of the Environment, Conservation and Parks) documents.

The City completes testing and water quality treatment of its stormwater systems on an as needed basis.  Some of the key locations include Swan Lake and Toogood Pond.  For more information on the activities undertaken at Swan Lake, see the Swan Lake page.