Inflow and Infiltration (I & I) Program

In June 2011, the City of Dubuque began an Inflow and Infiltration (I&I) Program to reduce sanitary sewer overflows and sewer back-ups by eliminating storm water inflow and groundwater infiltration into the City’s sanitary sewer collector system.

What is I&I?

Inflow is a direct connection of “clear” water (rain/storm water) into the wastewater (sanitary sewer) collection system. Infiltration is an indirect connection of “clear” water to the wastewater (sanitary sewer) system. Inflow is by far the larger problem of the two and occurs in direct proportion to rainfall. Inflow is most often the result of improperly installed sump pumps (used by many homeowners to keep groundwater out of basements), roof downspouts, and foundation drains illegally connected to the City’s sanitary sewer system. Sump pumps are also sometimes illegally connected to the sanitary sewer system via a hose leading from the sump to a laundry tub or floor drain. Infiltration occurs when groundwater seeps into sewer pipes through cracks, leaky joints or deteriorated manholes. 
Inflow and Infiltration program
The City’s sanitary sewer master plan, finalized in 2009, identified five sewersheds, or areas of the community which are the sources of high sanitary sewer flows during rainfall events. These high flows have caused sanitary sewer back-ups into basements, overflows into creeks and wetlands, and increased operational costs at the Water & Resource Recovery Center. These five areas include approximately 7,000 properties.

What is the City doing to reduce and eliminate I&I?

To reduce and eliminate I&I, the City has implemented a program that addresses private property and public infrastructure. Private property inspections and smoke testing are used to identify improper private property connections. Meanwhile, smoke testing, manhole inspections, and a sanitary sewer grading are used to identify I&I in the public infrastructure.

For a list of FAQs related to the project, click here. 

How Do I Schedule an Inspection?    

You will receive a letter when your neighborhood is scheduled for inspections. The letter will instruct you to call the City at 563-589-4270 or email
More About the Program    
Dubuque’s I&I program is part of an agreement with United States Environmental Protection Agency and the Iowa Department of Natural Resources. Other actions being taken by the City to address I&I include: sanitary sewer capacity upgrades, inspection of manholes and sewer lines to identify inflow and infiltration sources, rehabilitation and reconstruction of manholes and sewer lines prone to infiltration. For more information on Dubuque’s I&I program, contact the City of Dubuque Engineering Department at 563-589-4270.