Get Long Term CSO Control Plan - Env State Ma

Nature-based solutions such as constructed wetlands fit very well with the aim of combined sewer overflow (CSO) treatment. Indeed, constructed wetlands treat CSOs in situ, avoiding the use of first flush tanks, which request to pump the entrapped CSO event again into the sewer at the end of the rainfall.

The combined flow of wastewater and stormwater can overwhelm the system. Permitted outfalls are located throughout the system to act as relief points during wet weather. These outfalls discharge untreated or partially treated stormwater and wastewater into nearby waterbodies. These discharges are called CSOs.

When this occurs, untreated or partially treated combined wastewater discharges from an outfall directly to nearby streams, rivers, and other water bodies. This is called a combined sewer overflow (CSO).

The CSOs can contaminate water and degrade water quality; can carry bacteria and viruses; and cause diseases [2] . During wet weather, discharge points along the Harlem River may discharge rainwater mixed with untreated sewage that contains bacteria and can cause illness.

During certain rainfall events, these combined sewer systems discharge untreated sewage into CT's waterbodies at points known as combined sewer overflows or CSOs. Second, stormwater runoff from impervious or agriculturally impacted areas can carry bacteria and other pollutants into waterbodies.

The Sewer System The City is served by two types of wastewater collection systems: separated and combined. Currently, BWSC's Engineering Department replaces combined sewers with sanitary sewers and storm drains each year to reduce the amount of combined sewer pipe in the system.

Sometimes the amount of runoff exceeds the capacity of the system. When that happens, untreated stormwater and wastewater flows into nearby waterbodies. These events, called combined sewer overflows, are subject to the National Pollutant Discharge Elimination System (NPDES) permitting program.

Expanding grey infrastructure and making better use of existing grey infrastructure enables us to store and treat more stormwater runoff. This reduces the occurrence of CSOs, helping keep untreated sewage and other pollutants out of our waterways.