One of the big maintenance headaches for our aging Wilmette sewer systems is Infiltration/Inflow (I/I):
Infiltration
- Groundwater seeps into cracks and joints in the sewer lines.
- Water enters via holes caused by tree root penetration.
- Water enters via manhole covers that have holes or gaps due to a poor fit.
- Water is forced from the storm to sanitary lines when both are in the same trench, without proper separation.
- Infiltration increases during storms, especially when the separate storm sewers aren’t clearing runoff.
Inflow
- Inflow is when a storm drain is improperly or illegally connected directly into a sewer line.
- Inflow sources include: sump pumps, downspouts, and drains for roofs, foundations, window wells, basement stairs, and driveways.
Sources of Infiltration/inflow
Source: Village of Wilmette, Separate Sewer Project Compiled Deliverable, by MWH Americas, Inc. (September 2010), p 34.