Talk:Dunwall Sewers/@comment-16533050-20150624200120/@comment-16533050-20150626015005

If a city is of a set size and then built sewers beneath it, then a new District was created and a new sewer system created beneath that, then it could be possible.

The sewer may also be designed for a set purpose, such as controlling the flow of a canal, such as Millenary Canal.

In my home city there is a water treatment system that also has its own separate sewer system. It provides drinking water to a large area in my city and was of such importance during the 1940s that it actually had military personnel protecting it during World War II. Nowadays the facility isn't that important with advances in technology and newer sewer systems built, but it was kept separate from the regular sewers when it was built.

There are even rainwater overflow canals which are named to identify it.

They name separate systems all the time to be honest and not all of them are connected. :)