Sewage
From SimCity Wiki
Sewage is the waste product produced by the sims.
If sewage is not properly disposed of, it turns into ground pollution.
Sewage output pipe can be constructed to transport the waste to a remote part of the city.
Sewage Maps
Sewage - shows sewage levels and where sewage is flowing to.
Ground pollution - shows the location and severity of ground pollution and the building producing it.