Public Works: Preparing Sewage Treatment Plants for Climate Change

Torontoist

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Public Works: Preparing Sewage Treatment Plants for Climate Change

As Toronto anticipates worse storms and more flooding, Boston's Deer Island wastewater facility has planned for the worst.

Public Works looks at public space, urban design, and city-building innovations from around the world, and considers what Toronto might learn from them.

Photo courtesy of the Massachusetts Water Resources Authority.

Boston’s massive sewage treatment plant was built to last, no matter how the Atlantic coast’s climate changes over the next 35 years.

Deer Island Wastewater Treatment Plant, on a spit of land in Boston Harbor, handles the effluent of up to 43 communities at a rate of 4.8 billion litres per day.

Its sewage holding tanks were built 58 centimetres off the ground—a trifling-sounding adjustment, but just enough to keep the plant safe from projected changes in sea levels through 2050.

Completed in 2000, Deer Island was one of the first wastewater facilities in the world to accommodate the predicted effects of climate change, including rising water levels and major storms. The plant also has widened sewage tunnels to increase capacity in case of extreme precipitation—which means there’s a smaller chance that the plant could get overwhelmed, which, in turn, would mean sewage (not only human excrement, but oily, polluted runoff from roads) bypassing treatment and going straight into the ocean.

The threat of climate change to city infrastructure—water treatment included—is as much a problem here on the shores of the Great Lakes as it is on the Atlantic coast.

As a 2012 City of Toronto study explained, “The operation of critical infrastructure such as the electrical grid, water treatment plants, sewers and culverts, public transport and roads are sensitive to particular temperature and weather thresholds.…Variation in the patterns of extreme weather pose a particular challenge to the operation of municipal and provincial infrastructure.”

Some environmentalists are already troubled by whether or not Toronto’s wastewater treatment plants can handle sewage during extreme weather. In July 2014, eco-charity Lake Ontario Waterkeeper called for the City to issue alerts whenever sewage bypasses treatment facilities.

The organization estimated that, during the summer storm of 2013, Toronto let loose at least a billion litres of sewage into Lake Ontario. City staff countered that whatever wastewater Toronto does bypass is a small percentage compared to the amount that it treats.

Whether or not Lake Ontario Waterkeeper’s estimate was accurate, Toronto’s wastewater system is going to be challenged in the coming years by severe weather.

That 2012 municipal study predicted that, by the 2040s, there will be fewer rainstorms per year, but they will be more extreme, and Toronto is projected to see a rainfall increase of more than 80 per cent in July, followed by 50 per cent more in August.

Of course, we’re already experiencing the summer storms and flooding. If the expected increases come to fruition, our wastewater treatment plants could be in trouble. Toronto’s largest treatment plant, at Ashbridges Bay, is getting a $1.7 billion 10-year makeover just to ensure it can handle its current capacity.

The City’s website lists a handful of actions taken in preparation for climate change, including changing the size of storm sewers and culverts, and changing slopes of land to direct runoff away from properties.

Thought is being put toward how climate change will affect the way we interact with water. The key as Toronto moves ahead will be not copying Deer Island’s design but, rather, its spirit of proactivity. Careful planning today can save us millions of dollars in updates, construction, and even environmental cleanup in the future.

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