I had a summer job in college inspecting manholes and sewer systems for a city. Even in a medium-size midwest town 100+ years of people building stuff underground and keeping shoddy records results in a lot of surprises.
makes a person wonder about NYC. There’s gotta be nearly as much city under the ground as above ground. Probably half of it lost and forgotten. I wonder how many times they run a pipe THROUGH a pipe and wonder what the heck that pipe was they just ran their pipe through...lol
For a while I worked for a company that made systems for remote sewer inspection and repair. “No dig” technology, they call it.
One major function of the systems was to document the exact location and dimensions of each line inspected, and to integrate that into a municipal utility database.