Lots of cities around the world, including Toronto, have (at least partially) what is called a combined sewer system. If the sewer system was built prior to the 1940s and it hasn't been replaced, there's a good chance that it could be a combined system. About a quarter of Toronto and about 60% of New York City still run on combined systems.

What this means is that both stormwater and sewage run in the same pipes. Most of the time this is fine, but if there's a heavy precipitation event and the system backs up, then you have poop getting diverted into rivers, lakes, and other bodies of water. In Toronto, this happens in places like the Don River and the inner harbor, and in Paris it happens in places like the Seine.

I was recently reading something suggesting that sewage generally gets dumped into the Seine about 12x per year as result of major rain events. This is why it's such a difficult and expensive task to make these bodies of water swimmable, which is something that Paris wants to do before it hosts the Olympics next year.

Thankfully, Toronto also wants to do the same. And in 2018, it started construction on the largest stormwater management program in the city's history. The overall budget is about $3 billion. Once complete, it should more or less eliminate combined sewer overflows, meaning our waters will become a lot cleaner and more swimmable.

This certainly isn't the sexiest capital project to announce and talk about. It largely happens behind the scenes. But it is going to lead to a significant quality of life upgrade for the cities willing to take it on -- one that will pay dividends well into the future.

Photo by Andre Gaulin on Unsplash