Wastewater Island: $26 million flood protection aims to protect water treatment plant

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London is building a fortress island of sorts to ensure residents can still flush their toilets as climate change makes Thames River flooding a more common and dangerous threat.

Out of sight of most Londoners on the main branch of the River Thames west of the Forks, construction crews are surrounding the city’s largest wastewater treatment plant in Greenway Park with huge sheets of steel to protect it from floods.

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The 750 sheets, averaging nearly 10 meters long and 9.5 millimeters thick, are being placed on existing earthen embankments surrounding the plant in a $26 million project to effectively turn the massive complex into a island when the river overflows.

All of the plants are in low-lying — and typically flood-prone — areas along the river, said Kirby Oudekerk, manager of the city’s wastewater treatment operations division. “(With) the expected increase in the frequency of high-intensity events, that (flood) risk is getting worse and worse over the years.”

Without the new protection, a flood of the Thames could flood the plant, perhaps shutting it down for a few days in a few annoying inches of water, damaging treatment equipment or possibly leaving the plant out of commission for weeks or months.

The Greenway plant, one of five in the city, processes 60 percent of the city’s wastewater and processes solid waste from all five plants. Oudekerk estimates that the plant treats an average of 120 million liters of wastewater per day, and that’s the good thing.

“That is the amount that would enter (the Thames), either untreated or only partially, until we can get this whole plant back online, which wouldn’t happen overnight,” he said.

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“The potential impact of this far exceeds anything we have seen before in any other aspect of our business.”

The plants typically discharge treated water by gravity, so they are close to the river despite the risk of flooding. But that means high flows in the Thames could prevent treated water from escaping, flooding the plant from the inside, Oudekerk adds.

To address this, the project will install a pumping station to maintain discharge even during a flood. Construction is likely to last until 2027.

District 7 County. Corrine Rahman chairs the council’s infrastructure and corporate services committee, which deals with roads, sewer, water and other city assets. For her, the project is about protecting one of London’s most prized assets and reducing the risk of major problems, such as Calgary’s massive summer water main break that led to weeks of limits on water use.

“We have to make sure that we have the capacity to treat wastewater effectively and for that reason we have to look at mitigation measures,” he said. “What we are seeing is. . . Once-in-250-year storms occur quite frequently, so we want to be prepared for extreme situations. climate and by floods.”

City staff are working to minimize impacts to local trails and parks as construction continues, he added.

Similar flood protection work is planned for the new year at the Adelaide Street North wastewater plant. Between the two plants, the cost will be almost $50 million, with Ottawa covering about 40 per cent.

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