Combined Sewer Overflow

Combined Sewer Overflow (CSO) is one of the greatest sources of pollution impacting Newtown Creek. Large upland areas surrounding Newtown Creek, like most of New York City, are serviced by a combined sewer system which sends both sanitary sewage and stormwater to local wastewater treatment plants. Unfortunately, wet weather events can overwhelm the system and send untreated sewage and stormwater directly into a local waterbody via CSO outfalls. As little as 1/10 an inch of rain over the course of an hour can trigger CSO events on Newtown Creek; as shown in the most recent modeling numbers over 1.2 billion gallons of CSO are discharged into the Creek each year.

There are 22 CSO outfalls in Newtown Creek, but over 90% of the total volume is released via just 4 of those outfalls which are all placed at the heads of tributaries (Dutch Kills, Maspeth Creek, East Branch and English Kills) where wind and tidal current conditions are more stagnant and less effective at flushing out pollution. In addition to creating health risks for human users, combined sewer overflow can negatively impact a wide range of local wildlife when nutrient imbalances and algae blooms create low dissolved oxygen levels and ecological ‘dead zones’. Additionally, CSOs often release large amount of floatable plastic debris that pollutes the Creek and poses further risk to wildlife.

Ways to Fix the Problem
There are generally two approaches to use in reducing CSO. The first involves increasing the capacity to collect, store and treat combined sewage, an approach known as Grey Infrastructure. Examples of Grey Infrastructure include upgrading and increasing capacity of treatment plants or creating large storage tanks or tunnels to hold CSO during rain events. There are numerous examples of these in both NYC and other older North American cities.

The other approach involves capturing rain water through natural systems before it enters and overwhelms the combined sewer system, an approach known as Green Infrastructure (GI). GI project often put rain water directly into the soil or even slow the rate of runoff, examples including Green Roofs, Bioswales, rain gardens, downspout planters and rain barrel programs. Learn more about NCA’s work with Green Infrastructure work here.

NYC has begun investing in both approaches to alleviate impacts of CSO. Unfortunately the amount of impervious surface in the City and gigantic volumes of runoff entering the combined sewer system requires much greater investment to prevent CSO from occurring during most rainstorms.

NCA Projects to Lessen CSO Impacts
In an effort to educate more community members about CSO, NCA created our Weather in the Watershed program in 2014 (funded by Hudson River Foundation and Deutsche Bank Americas Foundation). The project centered around creating a real time alert system to notify residents when CSO was occurring and conserve water use to limit the volume of pollutants being flushed into Newtown Creek. Learn more about our CSO alert system and Weather in the Watershed programming here. Since our pilot project launched NYC pursued their own program to encourage residents to conserve water usage during rain events. It was first piloted in the Newtown Creek Watershed and then launched city-wide a few years later as the WAIT… program.

In 2015 NCA partnered with the Open Sewer Atlas Project to launch the Grey to Green program, an effort to encourage GI investment and water conservation within a specific and highly important subsection of the Newtown Creek watershed. We focussed on the area that drains to CSO outfall NCB-015 at the head of English Kills, which includes areas in and around the neighborhood of Bushwick, Brooklyn. The campaign included data analysis, community outreach and hands on workshops. Visit the full project webpage here.

Further Resources:
NYC Department of Environmental Protection (DEP) Resources and Links
NCA Overview of the Long Term Control Plan
2017 DEP Long Term Control Plan
See where CSO discharges from at Open Sewer Atlas
Green Infrastructure in Newtown Creek Watershed
Green Roofs in Industrial Areas
NYS DEC info on CSOs 
S.W.I.M. Coalition