The Good Sewer: Why Ottawa’s $232-million sewage storage tunnel is both an engineering marvel and an act of contrition

By Andrew Duffy, Ottawa Citizen, July 12, 2020

For the past three years, some nine storeys beneath downtown Ottawa, work crews have been tunnelling a solution to one of this city’s oldest problems: sewage.

The combined sewage storage tunnel, the CSST, is designed to hold for treatment sewage-contaminated storm water that would otherwise be discharged into the Ottawa River.

Ottawa has polluted its namesake river grossly, relentlessly, for the better part of two centuries. Billions of litres of raw sewage have been dumped into the water since Bytown was founded in 1826.

The city’s sewage management has been controversial for almost as long. The complex array of pipes and pumps built to ferry Ottawa’s sewage to the river has led to fatal typhoid epidemics, exploding manhole covers, and fetid scandal. Until 1963, when the city’s first sewage treatment plant opened, every litre of waste flushed into Ottawa’s sewer system ended up in the river.

(...)The tunnel, scheduled to go into operation later this year, will dramatically reduce the amount of sewage piped into the Ottawa River in a typical year. Sewage will continue to spill into the waterway during the spring melt, but for the rest of the year, the CSST is expected to protect it during all but the most exceptional storms.

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