Background
The Government of Canada created a $2 billion Disaster Mitigation and Adaptation Fund intended to support large infrastructure projects that, among other things, contribute to the resilience of critical infrastructure in the face of increased risks of damage due to climate change. The City proposed the construction of flood protection at the Adelaide and Greenway Wastewater Treatment Plants as major projects that fit this description, and the City’s proposal was accepted.
The City of London owns and operates five wastewater treatment plants. The Greenway Wastewater Treatment Plant, located at 109 Greenside Avenue, is the City’s largest plant and treats approximately 60% of the wastewater produced in London. Wastewater generally flows by gravity to these plants for treatment prior to discharge to the Thames River, and as a result, these plants are situated immediately adjacent to the river in low-lying areas. Many of the essential treatment plant components are located within the floodplain.
With climate change, the City of London and other communities are experiencing more frequent and intense wet weather events and flooding. Flooding is a concern at the City’s wastewater treatment plants for two main reasons:
- Damage of treatment plant components, including equipment and tanks, due to inundation of rising river levels at these sites, and
- Environmental impacts associated with the bypass of untreated or partially treated wastewater for several days following an intense wet weather event.
Flood barriers, such as berms and floodwalls, provide a potential approach to provide flood protection at the Greenway Wastewater Treatment Plant. A flood barrier was recently constructed at the Vauxhall Wastewater Treatment Plant.
Wastewater treatment plants discharge treated water into adjacent watercourse either by gravity or by pumping. During severe flooding, high water levels in the adjacent watercourse prevent gravity discharge. Wastewater treatment plants that rely only on gravity discharge, such as Greenway, cannot fully function during severe flood events.
Pumping stations allow treated water to be discharged to watercourses when water levels are too high for gravity drainage. As a result, wastewater treatments plants can fully function during severe flooding which reduces the environmental impacts of these events. For instance, improving treatment capabilities during severe floods supports the City’s commitment to the Lake Erie Domestic Action Plan by reducing phosphorus discharge to the Thames River.
