Extreme rainfall could add $700M per year to maintain Ontario’s storm, wastewater assets

Examples of adaptations to extreme rainfall for linear storm and wastewater infrastructure detailed in a new report from the Financial Accountability Office of Ontario. Graphic: FAO

Without further adaptation to climate change, a new report warns that more extreme rainfall in Ontario could add $6.2 billion to the costs of maintaining storm and wastewater infrastructure by 2030.

The Financial Accountability Office of Ontario (FAO) projection is a 27% increase above a “stable climate scenario,” where the province spends an average of $3 billion per year over the century to bring these assets into a state of good repair and maintain that state.

This includes stormwater assets such as pipes, ditches and culverts, as well as wastewater assets like sewer pipes and sanitary force mains belonging to the province’s 444 municipalities, and valued at $124 billion.

The December FAO report, Costing Climate Change Impacts to Public Infrastructure: Linear Storm and Wastewater, states that as extreme rainfall increases, un-adapted assets will increasingly face capacity constraints, raising the flood risk to surrounding areas.

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On an annual basis, extreme rainfall caused by climate change could cost municipalities in Ontario an additional $700 million a year to maintain storm and wastewater assets.

Peter Weltman, the province’s financial accountability officer and author of the report, said Canadians will really see the impacts of climate change around 2050 if significant action isn’t taken.

Under consistently extreme rainfall, pipes and ditches will require more frequent and costly inspections and preventive maintenance, as more debris, sediment and vegetation are expected to enter stormwater systems. Channel protection will also be subject to accelerated erosion.

For wastewater, increased intensity of short duration rainfall events will increase the inflow of surface water into sewer pipes, while increased intensity of longer duration events will cause groundwater to infiltrate sewer pipes. For sanitary force mains, more extreme rainfall will result in higher inflow and infiltration, increasing the volume of wastewater being conveyed to treatment facilities, as well as the pressure required to do so.

Ontario Green Party leader Mike Schreiner said in a statement following the FAO report that the province is refusing to act on climate change.

“The Ford government’s abject failure to take meaningful action to address or adapt to the climate crisis is already costing billions and will impose a huge financial burden on people today and for future generations,” said Schreiner.

The FAO report states that adapting assets to climate change can mean increasing their capacity or incorporating source control measures such as green infrastructure. However, climate action also comes at a cost, representing a financial increase between 29% and 53%, albeit lower than the cost of inaction, the report states.

“Regardless of which asset management strategy is pursued, the future path of global climate change will be a key determinant in the extent of additional climate-related infrastructure costs,” states the FAO report.

In terms of further emissions impacting assets, a medium emissions scenario, where global emissions peak by mid-century, could mean an additional $1.1 billion per year to maintain assets. In a high emissions scenario, where global emissions continue rising throughout the century, these maintenance costs could increase by $1.8 billion per year.

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