What is I and I?

Inflow and Infiltration

Inflow is a direct connection of clear water into the wastewater collection system.

infiltration is an indirect connection of clear water to the wastewater system.

Inflow

Inflow is usually traced to sump pumps (used by many homeowners to keep groundwater out of basements), roof downspouts, and foundation drains that are connected to the city’s sanitary sewer system. Sumps pumps are often connected to the sanitary sewer system via a hose leading from the sump to a laundry tub or a floor drain.

Infiltration

Infiltration results from groundwater seeping into cracked sewer lines, manholes or deteriorating lateral connections, and requires sealing of the wastewater collection system.

Why is I and I a problem?

Clear water reduces capacity in the regional wastewater collection and treatment system and, during heavy rainfall, can cause sewer backups and overflows.

Why are cities being asked to reduce inflow and infiltration? Because the Met Council estimates it would cost the region a minimum of $900 million to build the infrastructure just to convey the excess flows to wastewater treatment plants. Costs to expand treatment plants are also prohibitive due to the lack of available building space.

For more information on the regional impacts of inflow and infiltration, visit the Met Council’s Web site on Inflow and Infiltration.

So, why should you care?

Your sewer may overflow…

First, I and I may affect your home—clear water reduces capacity in the regional wastewater collection and treatment system and, during heavy rainfall, may cause sewer backups and overflows.

…and backup into your budget

Second, if not addressed, I and I will affect the city’s budget. The Met Council has identified Minnetonka as a major contributor to the I and I problem—and under a currently proposed surcharge system, Minnetonka would be charged an additional $400,000 annually to treat the city’s waste.

The good news

The good news is the city has five years to correct the problem. During that time, the city can use the money it would have paid in surcharges to implement an education, inspection and repair program designed to reduce the I and I problem. This includes home inspections to identify improper connections to the sanitary sewer system and funding a matching grant program to assist homeowners with necessary repairs.