During significant rain events excessive amounts of rain water enters the sanitary sewer system. The capacity of the sanitary sewer is exceeded and the excess flow, which is a mixture of sewage and rain water, is discharged into Newport Harbor. The overflow is referred to as a Combined Sewer Overflow or CSO. All CSO events are reported to the Rhode Island Department of Environmental Management (RIDEM).
The problem is that there are connections from catch basins, roof drains, yard drains, sump pumps, etc. that collect rainwater or ground water that are connected to the sanitary sewer system rather than a storm drain system or discharged into the ground. During intense rain events, the capacity of the sanitary sewer and the storage at the CSO Facilities is exceeded resulting in an overflow.
The City has two (2) outfalls where CSO's can occur; one from each of the City's CSO Facilities which are shown on the attached map. The Wellington Ave CSO Facility's outfall is north east of the Ida Lewis Rock and the Washington Street CSO Facility outfall is east of the north end of Goat Island. The attached map shows the locations of the outfalls.
The Wellington Avenue and Washington Street Facilities both provide treatment to any CSO that occurs. Treatment includes screening to collect solids and floatables from flow that enters the facilities. The facilities also provide storage which prevents some overflows from occurring. Any flow that is discharged into Newport Harbor is disinfected with chlorine.
There are many factors that affect whether an overflow occurs including the amount and the intensity of a rain event; snow melt, etc. Every storm is different and overflows at the two facilities do not necessarily occur at the same time or for the same duration. The Summary of CSO Events since 2001 is attached.
Since the 1970's the City has constructed several projects to separate the storm water connections to the sanitary sewer. The City has been working since 2004 under a Consent Agreement with the Rhode Island Department of Environmental Management to eliminate CSO's from the Wellington Ave. Facility. The improvements necessary will be identified upon completion of Phase 2 of the project due in February 2009.
A red flag is raised at the CSO facility by staff when an overflow starts and remains up until 24 hours after the overflow stops. A red flag is also raised at the Harbormaster's Building when there is an overflow event.
Additional information on combined sewer overflows and the regulations can be found on EPA's website https://www.epa.gov/npdes/combined-sewer-overflows-csos
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