At least on the US side the EPA's CSO laws have "just recently" ratcheted past the point that even "grandfathered" cities are having to make major accommodation

At least on the US side the EPA's CSO laws have "just recently" ratcheted past the point that even "grandfathered" cities are having to make major accommodations for CSO overflow. If you live in a US city with sewers older than 1900 or so and are paying huge sewage taxes, it's likely because your city just built or is in the process of building massive CSO basins, uncombining sewers, and/or other costly capital expense mitigations. It's kind of interesting if you dig into your local projects what they are doing and why and how. (In a semi-related one of those projects my city's water company recently excavated a mid-1800s water main valve that was still in apparently active use up until just recently and it was pretty neat the photos and description of it in the local newspaper. Built to last.) (Disclaimer: I vaguely worked on software projects that were CSO mitigation adjacent. Which at least explains some the interest in the projects.)