Combined sewer system is designed to have a combined sewer overflow (CSO) to discharge into local waterways during rainstorms, in order to prevent overwhelming wastewater treatment plant. CSO carries untreated sewage and stormwater runoff to urban rivers, elevates nutrients ( phosphate, ammonia), turbidity and bacteria (fecal coliform, E.Coli, enterococcus) levels, degrades water quality, making river not swimmable or fishable. CSO is the major pollution source in New York City (NYC) and other urban areas. Any topic relates to CSO impact on water quality are welcome to this session.