Inflow & Infiltration

Inflow and Infiltration (I/I) is the excess flow of clear water into the City's sanitary sewer system. Reference City Code Section 28-50 for more I/I information. 

  • underground utilityInflow is when clear water from illegal connections of sump pumps, downspouts, and foundation drains is channeled directly into sanitary sewer pipes.
  • Infiltration is when groundwater seeps into sewer pipes via cracks or leaky joints.

Because the sanitary sewer system was not designed to handle this excess clear water, it becomes overloaded during times of high groundwater or heavy rainfall. This can cause basement flooding or bypassing of raw wastewater to local streams and lakes.

What's The Problem?

The excess clear water from I/I problems uses sanitary sewer capacity needed for wastewater. The result is sewer backups and increased costs (about $300-$400 million annually) for needlessly putting clear water through the wastewater treatment process.

The Metropolitan Council Environmental Services (MCES), which provides regional wastewater collection and treatment for the metropolitan area, requires communities with excess I/I to invest in local reduction remedies such as disconnecting sump pumps and foundation drains from sanitary sewers and repairing leaky sanitary sewer pipes. Such actions will cost roughly $150 million, instead of the nearly $1 billion it would cost to build additional sewer infrastructure to provide capacity during big rain storms. To urge compliance, MCES incorporated surcharges for communities with excess I/I.

Golden Valley was identified as a contributor of excess I/I and is working to resolve the problem.

  1. Inspections Program
  2. Steps For Inflow & Infiltration Inspection
  3. Sump Pumps
  4. Steps for Sump Pump Inspection