How Are Communities Affected by Inflow and Infiltration?

Many small towns throughout Kentucky have aging wastewater collection systems that are failing or in desperate need of repair. Most still use brick sewers built more than 100 years ago, while many more rely on dated combined systems to collect both wastewater and stormwater flows. The term infiltration is used by wastewater professionals to describe the excess water that sometimes seeps, trickles or flows into old or damaged collection systems from the surrounding soil. The term inflow is used to describe any unwanted water that enters the collection system from aboveground sources, such as storm events, thawing of snow or more commonly, private residences that have drains from gutters or basements that connect directly into sanitary sewers.

When collection systems are old and in disrepair, it is often very difficult to determine exactly how much of the extra wastewater in the system is the result of inflow versus infiltration. Inflow and Infiltration problems also place additional burden on the community collection and wastewater treatment facilities.  Collection systems can be damaged when they are forced to transport larger volumes of flow than they are equipped to handle. In many cases, pipes can collapse causing the pavement to buckle or possibly, in extreme cases, cave in. Damage to pipes from inflow and infiltration can also allow wastewater to contaminate vital groundwater and drinking water sources.

Inflow and infiltration also increase operation and treatment costs for the facilities that receive the additional wastewater flow. Sanitary and combined sewer overflows can occur when wastewater flow exceeds the designed capacity of the community’s treatment plant. If the treatment plant cannot store the extra flow for later treatment, the excess water could have the ability to bypass the plant and be dumped untreated into receiving waters. Storm sewer overflows and combined sewer overflows can be very costly to communities, as well, by exceeding their National Pollutant Discharge Elimination System (NPDES) permit requirements.

The only way community officials can identify whether inflow and infiltration, or any other problems, exist in the community’s wastewater collection system is by performing an evaluation of the system, followed by a methodical inventory of the collection system, known as a sanitary system evaluation survey (SSES). Small communities can effectively conduct their own SSESs and correct their own problems without hiring outside consultants. But if after the investigation, there is evidence of serious system problems, community leaders should look into hiring an experienced professional who specializes in sewage system evaluations. Regardless of the issues at hand, community leaders should always gather information about their sewage system from people in their community.

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