system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How do cities know how big to make the sewers for future growth?

Say a sewer system exists but a new development is going to be built.  How does the city know how big to make the sewers?  And how does it know if another development will occur down the road in 5 years, necessitating an even bigger sewer?  Do they have to go and dig up the entire line to make it bigger all the way tot he sewer plant?
gpt
Cities usually makes plans further down the line. This is also why developers have to apply to the city planning commission before they build anything. If the utilities are not designed to handle the new development they will get denied and will have to wait for the utilities to be expanded. The city and developers are constantly talking to make sure the city grows at the right pace. Quite often the city might ask for development of new housing somewhere and build utilities to the site well ahead of time. Other times the developers might see an opportunity for new development and might have to help build the utilities to be allowed to build there.