Where Does the Rain Actually Go?

Rain on a city street is a plumbing problem arriving all at once. This episode digs into the hidden engineering of municipal drainage: the difference between storm sewers and sanitary sewers, why combined systems were a deliberate Victorian design choice rather than a mistake, and how engineers decide how much rain a pipe has to swallow. Then it climbs into the megaprojects — Tokyo's G-Cans cathedral of concrete silos and pillars, London's Tideway Tunnel — and asks the harder question underneath all of it: what happens when the storm is bigger than the design, and whether the discipline is shifting from getting water out of the city fast to keeping it in the city on purpose. Key sources: • Tideway press release, 2025-02. — https://www.tideway.london/news/press-releases/2025/february/london-s-super-sewer-now-fully-connected-promising-a-greener-healthier-river-thames/ • Tideway Annual Report 2025/26. — https://www.tideway.london/media/7697/tideway-annual-report-2025-26.pdf • US EPA, CSO basics. — https://www.epa.gov/npdes/combined-sewer-overflow-basics Episode 5888 — myweirdprompts.com/n/5888 (permanent short link: myweirdprompts.com/732941)