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With the increasing scrutiny from the U.S. Environmental Protection Agency (EPA) to combat water pollution, more communities have been forced to take a closer look at their wastewater collection systems. Current regulatory agency rules and regulations now require that communities have an inflow and infiltration (I/I) reduction program that demonstrates significant progress in the elimination of I/I.
What is I/I?
Inflow is a direct connection of clear water into the wastewater collection system. Infiltration is an indirect connection of clear water to the wastewater collection system. Both require a different methodology forremediation. Inflow from areas such as sump pumps, roof leaders and area drains requires removing the connections to the wastewater collection system, while removing infiltration from areas such as cracked sewer lines, leaking manholes or poor lateral connections requires repairing the wastewater collection system.
Past I/I programs focused strictly on the public side (main sewer lines, manholes and storm sewer cross connections) of the wastewater collection systems; however, this makes up only 30 to 40 percent of the total wastewater collection system. A successful I/I remediation program must include rehabilitation activities on private property (residential, commercial and industrial), which makes up the other 60 to 70 percent of the collection system.
Communities must develop a plan of action that consists of the following six activities:
Results of an Ineffective I/I Remediation Plan
I/I can cause EPA compliance problems. Any overflows or bypasses that pollute U.S. waters violate EPA rules.
Wastewater treatment facilities may not be able to meet effluent parameters due to the excessive flows brought about by I/I. Extra water causes additional wear and tear on the entire system. The majority of I/I comes in a sharp short cycle, which hydraulically overloads the system — particularly sewer lines and pumps.
The cost of wastewater treatment goes up because more chemicals and energy are needed to treat more water. Taxes go up to cover the cost to increase treatment capacity.
Polluted waters caused by I/I increase health and safety risks to humans and damage the environment.
I/I can cause sewage backups in basements, which leads to complaint calls to City Hall and costly cleanup for homeowners.
Addressing I/I problems will help meet compliance requirements, reduce treatment costs, extend the life of the collection system, reduce tax burdens, create opportunities for growth and development, minimize or eliminate health risks and protect the environment.
Kirby Van Note, PE