Combine Sewer Overflows


Combined Sewer Overflow – or CSO – occurs when wet weather overwhelms the City's sewage treatment process, and results in approximately 27 billion gallons of untreated wastewater being discharged into the estuary. While experts consider CSO pollution to be the leading threat to water quality in the estuary, it is of particular concern to the wide range of waterfront users that work, learn and recreate right where CSOs happen.


The Ecology Center offers a variety of curricula and materials for examining New York City’s water infrastructure and CSO pollution.


Make Your Own CSO Model

Make Your Own CSO Model is a portable, working model of a NYC combined sewer, treatment plant, storm drains, overflows and all.


The Water Underground

The Ecology Center partnered with Center for Urban Pedagogy, City-as-School, and RECYouth to explore the Water Underground–the millions of gallons of water that enters the city, get used in various ways and discharged to local waterways each day. During this semester-long project, students and teachers developed The Water Underground, a video about their investigations. The Water Underground video is a 25-minute student-led exploration of where water comes from, where it goes and what happens along the way.


The Citizen’s Guide to the Sewershed

The Citizen's Guide to the Sewershed is a printable handbook to the City’s largest drainage area, the Newtown Creek Sewershed. The guide includes maps, photos and facts about the area’s natural history, modern infrastructure, residents and representatives and provides information on the issue of combined sewer overflow (CSO) in the Newtown Creek drainage area of New York City. PDF