The MIS conveys flow to Jones Island or South Shore for treatment. Clean water is discharged to Lake Michigan. If the plants cannot handle all of the flow in the MIS, it is diverted to the deep tunnels through the collector sewer and dropshaft, where it is stored until the plants have the capacity to treat it. Sanitary sewage travels from property owners' lateral sewers into local combined sewers, owned by the municipality, where it mixes with stormwater. The process is then the same as in the separated sewer area.
Sanitary sewage travels from property owners' lateral sewers into local sanitary sewers.
The MIS conveys flow to the treatment plants. If local sanitary sewers or the MIS cannot handle all of the flow caused by excessive infiltration and inflow of clear water into the sanitary sewer system, it is bypassed to nearby waterways. Flows are also diverted to the deep tunnel, where it is stored until the plants have the capacity to treat it. Sanitary sewage travels from property owners' lateral sewers into local combined sewers, where it mixes with stormwater from runoff. Flow from local combined sewers empties into the MIS, and excess flow is bypassed to nearby waterways at combined sewer outfalls.