What are Combined Sewer Overflows?
Combined Sewer Overflows (CSO’s) are the largest contributor of bacteria and viruses to the Bay. CSO’s combine residential, commercial and industrial wastes which carries pollutants in the form of sewage solids, metals, oil, grease and bacteria. During periods of heavy rain, the water in the CSO’s combine with the storm water running over the land. The CSO then becomes overwhelmed with water which forces it to discharge untreated or partially treated wastewater into Narragansett Bay through the combined sewer overflow. Each year, billions of gallons of untreated sewage from combined sewer outflows are released into the Bay and its tributaries.
