The East River, a tidal strait separating Manhattan and the Bronx from Brooklyn and Queens, is a significant urban waterway in New York City. Despite its name, it is a saltwater estuary connecting Upper New York Bay to Long Island Sound. Public concern often surrounds its pollution levels, raising questions about its safety for various uses.
Understanding Current Water Quality
The East River’s water quality has improved over the years, though challenges remain. A key indicator is the level of bacteria, particularly enterococci, which signals the presence of sewage. Bacteria levels generally meet federal guidelines for swimming on most days, though readings vary significantly near outflows like Newtown Creek or the Gowanus Canal. The New York City Department of Environmental Protection (DEP) categorizes the East River as Use Classification I, suitable for secondary contact activities like boating and fishing.
Dissolved oxygen (DO) levels are vital for aquatic life. Historically, DO levels in the East River declined significantly, reaching as low as 13% saturation by 1926, a point where most fish species cannot survive. However, improvements have occurred, with average June-September near-bottom dissolved oxygen increasing from 3 mg/L in 1970 to 6.6 mg/L in 2008. While some areas do not consistently meet the 50 percent saturation requirement, DO levels have generally increased.
Nutrient levels, including nitrogen and phosphorus, also impact water quality. Excess nitrogen can lead to excessive algae growth, depleting oxygen and creating “dead zones.” The East River has high nutrient concentrations, particularly dissolved inorganic nitrogen, often exceeding 20 µM. Despite this, chlorophyll-a concentrations, an indicator of algal biomass, remain relatively low, likely due to suspended silt blocking light penetration.
Key Sources of Pollution
Combined Sewer Overflows (CSOs) are a primary contributor to the East River’s pollution. New York City’s sewer system is approximately 60% combined, carrying both stormwater runoff and sewage in a single pipe. During heavy rainfall, when capacity is exceeded, this mixture of untreated sewage and stormwater discharges directly into waterways like the East River. These CSO events occur about 70 times annually, releasing billions of gallons of combined sewage.
Stormwater runoff from urban areas also contributes significantly, carrying pollutants like chemicals, pesticides, and bacteria directly into the river. Historically, industrial legacy pollutants have impacted the East River. During the 19th and early 20th centuries, factories discharged industrial waste, including petroleum residues and heavy metals, directly into the water. Newtown Creek, a tributary, is a notable example of a waterway heavily contaminated by oil refineries and petrochemical plants, leaving toxic sludge.
Impacts on Ecosystems and People
Pollution in the East River impacts its ecosystem. Depleted dissolved oxygen levels, often from nutrient overload, can suffocate aquatic life, decreasing fish and other species. Historical accounts describe a drastic reduction in animal life and darkening water as pollution increased, leading to the decline of underwater vegetation like seagrass. Excess nitrogen from sewage discharge also contributes to hypoxic “dead zones” in the East River and Long Island Sound, impacting organisms.
Contact with polluted East River water carries potential human health risks. Bacteria like enterococci, found in sewage, can cause infections. While water quality has improved, contact, especially after heavy rainfall, can pose risks of skin or gastrointestinal issues. Though biodiversity has increased with the return of some marine life, consuming seafood caught from the river may have implications due to bioaccumulation of historical industrial pollutants like PCBs.
Ongoing Efforts for Improvement
Various initiatives are underway to improve the East River’s water quality. The New York City Department of Environmental Protection (DEP) has invested over $17 billion in upgrading wastewater treatment plants and water quality projects since 2002. These upgrades aim to reduce nitrogen levels discharged into the East River and Long Island Sound, with efforts to cut nitrogen from four plants by over 52 percent. City wastewater treatment plants now meet monthly Clean Water Act standards for pollutant removal.
Managing Combined Sewer Overflows (CSOs) is another focus. The DEP implements Long Term Control Plans (LTCPs) for waterways, including the East River, to identify and implement CSO controls. These plans involve optimizing CSO regulators and exploring solutions like green infrastructure, which manages stormwater runoff and reduces combined sewage discharge. Community-led conservation efforts and advocacy groups also push for stricter water quality standards and faster implementation of reduction strategies.
Navigating Recreational Use and Safety
Understanding water quality fluctuations is important for recreational activities in the East River. It is generally safer for contact activities after dry weather, as heavy rainfall significantly increases bacteria levels due to Combined Sewer Overflows (CSOs). Official advisories and water quality dashboards, often from organizations like Riverkeeper, offer current data on enterococci levels, helping individuals make informed decisions.
While generally safe for secondary contact activities like boating and fishing, direct swimming in the East River is often discouraged due to strong, unpredictable currents. The swift current, moving as fast as four knots, poses a significant danger to swimmers. If fishing, “catch and release” practices are recommended, and it is advised to avoid consuming certain fish species due to potential bioaccumulation of pollutants.