Inflow and Infiltration

Inflow and infiltration refer to excess water that flows into sanitary sewer pipes from groundwater and stormwater. Infiltration is groundwater that seeps into sanitary sewer pipes through holes, cracks, joint failures, and faulty connections. Inflow is stormwater that quickly flows into sanitary sewers via roof drain downspouts, foundation drains, storm drain cross-connections, and through holes in manhole covers.

Inflow and Infiltration cause the dilution in sanitary sewers, which decreases the efficiency of treatment, and may cause sewage volumes to exceed design capacity.

While these terms might seem technical, they touch upon issues that can have very real consequences for public health.

Overloading Treatment Plants

When excess water enters the sanitary sewer system, it can overtax wastewater treatment facilities. These facilities are designed to handle a certain volume of wastewater. When that volume is exceeded, it can lead to untreated or partially treated sewage being discharged into local waterways. This can result in the contamination of natural water sources, which may be used for drinking, recreation, or as habitats for aquatic life.

Sewage Backups

High levels of inflow and infiltration can cause the sewer systems to overflow, leading to sewage backups into homes and businesses. Not only is this unpleasant, but it also poses serious health risks. Sewage contains pathogens, including bacteria, viruses, and parasites, which can cause a range of illnesses if they come into contact with humans.

Surface Water Contamination

Sewer overflows caused by inflow and infiltration can lead to the release of untreated sewage into the environment. This contamination of surface waters can result in outbreaks of waterborne diseases. People who come in contact with contaminated water – whether through swimming, fishing, or other activities – are at risk.

Groundwater Contamination

Infiltration especially, since it involves groundwater entering the sewer systems, can sometimes work the other way around as well. When sewage systems leak, it can result in sewage permeating into the groundwater, which may eventually be sourced for drinking water. Contaminated groundwater is a critical public health concern, especially in areas reliant on wells or aquifers for drinking water.

Increased Treatment Costs

Treating the excess flow from Inflow and infiltration can lead to increased costs for wastewater treatment plants. These costs are often passed on to the community in the form of higher utility bills. Beyond the economic implication, overburdened treatment plants might also resort to quick, less-effective treatment methods that might not entirely remove all contaminants, compromising water quality .

Image of Plainville 3 Year Sewer Comparison

Promotion of Harmful Algal Blooms

The untreated or partially treated wastewater that gets discharged into water bodies can be rich in nutrients, especially phosphorus and nitrogen  . Aging septic systems are a major contributor to harmful algal blooms because they can leak human waste into local water bodies. These nutrients can stimulate the growth of algae, leading to harmful algal blooms. These blooms can produce toxins that harm aquatic life, make the water unsafe for recreational activities, and can lead to health problems in humans if they consume contaminated water or seafood.

Ecosystem Disruption

The release of untreated wastewater into natural water bodies doesn't just impact humans. Aquatic life is directly exposed to all the chemicals and pathogens present in the sewage. Over time, this can result in a decline in biodiversity and disrupt the natural balance of aquatic ecosystems.

Addressing the issues of inflow and infiltration is more than just a technical endeavor; it's a critical step toward safeguarding public health. Ensuring that our sewer systems are robust and resilient against these challenges not only saves money in the long run but also ensures the well-being of communities and the preservation of the environment.

What has been done to date:

As required by the Massachusetts Department of Environmental Protection, the Town’s consultant has been investigating inflow and infiltration for “The Hill” area of Plainville. The work includes house inspections to determine quantity and location of sump pumps, smoke testing to determine if catch basins or roof leaders are connected, dye testing to check for sources that visually give the appearance that the source could be connected  . The Town’s consultant has also been performing approximately 200 closed circuit television (CCTV) inspections of sewer lines and lateral pipelines. The video camera can determine the location and severity of defects, the likelihood of failure, and rehabilitation needs.

Image of the area know as the "Hill" in Plainville

The area known as “The Hill” is a part of the Moran Street sewer area which encompasses all the sewered area along and west of Washington Street. This is the oldest area of development in town and is the greatest contributor of sanitary sewer inflow and infiltration. The sewer mains date back to the 1970’s and clay. Clay is no longer used due to the porous condition of the pipe; clay becomes brittle over time and susceptible to damage from tree roots. Over time the clay becomes separated Understand that all sewered streets and subdivisions off South Street, West Bacon Street, Walnut Street, and Warren St flow to the Moran Street Sewer Station in N. Attleborough. Excessive flows can overwhelm the station and risk a sanitary sewer overflow (SSO) into the surrounding wetlands and pond.

Image of Clay Pipe

What is the goal of the project:

The priority of the project is to protect public health, safety, and property. The Town’s consultant will develop a design project to reduce infiltration into the sewer system.