The East River is a narrowly defined tidal strait about 25 km long, connecting the Harlem River, the Long Island Sound and the New York Harbor. The mean depth of the river is roughly 10 meters, with depths of more than 20 meters immediately north and south of Hell’s Gate. The Harlem River is also a narrow strait of roughly 12 km long, which connects directly to both the Hudson River and the East River at Hell’s Gate. The average depth of the Harlem River is 6.8 meters and the topography of the sea floor is relatively uniform. The tides of the East River are typically semidiurnal, or occur approximately every 12 hours. These tides create such water surface elevation that the strongest currents in the region occur in the river.
The history of water quality issues in the East and Harlem Rivers parallels the history of urbanization and wastewater. When European settlers first colonized the land surrounding the New York Harbor, the population increased so much that the watershed, a convenient place for sewage and refuse disposal, soon became severely degraded. The abundant fishing and oyster harvesting that the Canarsie Indians and the Dutch had previously reveled in quickly dissipated, and by the early twentieth century typhoid outbreaks from bacteria contamination coupled with dredging and industrial pollution effectively shut down the entire oyster industry. Similarly, the waters were so polluted that very few fish could survive.
Watersheds all over the country were equally as degraded as the New York Harbor. To rectify this, congress passed an amendment to the Federal Water Pollution Control Act called the Clean Water Act (CWA). The CWA established permitting requirements for discharging pollution into waterways. The goal of the CWA is to make all waters in the US swimmable and fishable. While waters in the US, including those of New York Harbor, have greatly improved from the 1970s, some have criticized the CWA for unsuccessfully dealing with the problem of urban stormwater runoff and other causes of water quality impairment such as combined sewer overflows (CSOs).
Water quality indicators that are often looked at by the Environmental Protection Agency (EPA) or other state environmental departments such as the NYS Department of Environmental Conservation (DEC) include fecal coliforms, which can indicate the presence of pathogens that can make people sick if ingested; dissolved oxygen, which is necessary for fish survival and is often impeded by nutrient loading; nutrients, such as nitrogen or phosphorus, which can cause algal blooms and low oxygen levels; and water clarity, which can be impeded by solids in the water such as sediment or algae and can also lower oxygen levels.
Water quality in the East and Harlem Rivers has improved dramatically since the 1970s. Most importantly, dissolved oxygen levels have risen, which means aquatic life is in better shape than it used to be. However, the East and Harlem Rivers still do not meet all of the water quality standards, mostly because of stormwater runoff and CSOs.
One of the most prolific pollutants in the East and Harlem Rivers is mercury, a heavy metal that is a serious human health risk, especially to pregnant women and young children. Mercury is transferred to our waterways via stormwater runoff, CSOs, and can even be deposited from the atmosphere. Fish ingest mercury and the metal becomes stored in the fatty tissue of the fish, thus creating a hazard for those who may fish in New York City waters.
To deal with the mercury issue, New York City, in collaboration with the EPA, developed what is known as a Total Maximum Daily Load (TMDL), which is essentially a pollution budget meant to lower loading levels of mercury in the water. To date, mercury is still problematic in the East and Harlem Rivers, as well as all of New York Harbor. Some have criticized the TMDL program for not being able to effectively deal with the issue of nonpoint source pollution. Nonpoint source pollution is pollution that does not come from a fixed point, i.e. the end of a pipe, but rather it comes from water runoff during wet weather events that picks up pollutants from roadways and roofs and deposits them into the waterway.
- The DEP is investing in grey or engineered infrastructure to reduce nitrogen in the wastewater effluent, or the filtered water that is put back into the water cycle after passing through the water treatment facility.
- The DEP is also investing in green infrastructure, such as enhanced tree pits and bioswales, and is working with many different organizations in New York to implement this technology which will assist in the capturing and filtration of stormwater.
- Partnerships such as the Oyster Restoration Feasibility Study, are multi-organizational programs that are investing in education, outreach and technology concerning the future of the ecosystem in the New York Harbor.