Total Maximum Daily Load
(TMDL) Initiative

Introduction–Why a TMDL is needed

According to the EPA/NOAA-sponsored Long Island Sound Study , 40% of the bottom area of Long Island Sound is "marginal to unusable" habitat for many marine animal species during the summer months due to oxygen depletion (maps). Nitrogen from sewage systems and runoff catalyzes the excessive growth of algae, which ultimately decompose and rob the water of oxygen needed by marine life. Population increases over the last 50 years near the coastal areas of New York and Connecticut have generated quantities of nitrogen laden sewage beyond the capabilities of current technology-based strategies to treat it before it enters Long Island Sound. A vital water quality goal in the Sound is the attainment of dissolved oxygen levels that will support all marine life. The oxygen depletion problem is not unique to Long Island Sound. See Hypoxia - National Picture.

Most of the human-caused nitrogen load comes from wastewater treatment plants. Under the federal Clean Water Act, a plant operator must assure that pollutants in a plant’s discharge do not exceed the levels achievable by a specified type of wastewater treatment technology. Nitrogen, a major source of pollution in Long Island Sound, is not currently one of those regulated pollutants, and consequently, technology-based pollution limits have fallen short of achieving water quality goals for the Sound.

The federal Clean Water Act at USC Title 33 §1313(d) mandates a process for calculating and assigning to each discharger a maximum load of a pollutant that a waterbody can receive and still attain water quality goals. The process calls for a Total Maximum Daily Load ("TMDL") assessment for the pollutant of concern. The result of this process will require dischargers to remove a particular pollutant to a greater degree than the current standard pollution control technologies require. The greatest challenge facing dischargers around Long Island Sound under a total nitrogen TMDL is to treat a pollutant they have not been required to treat in the past. See EPA Decision Guidance for TMDL’s .

With this new treatment requirement in mind, the US Environmental Protection Agency (USEPA) and state environmental agencies in New York and Connecticut have developed a draft TMDL for nitrogen that enters Long Island Sound. The TMDL will be used to calculate the nitrogen inputs from wastewater treatment plants and convert them into enforceable permit limitations. It will also be used to estimate nitrogen inputs from nonpoint sources, the atmosphere, and natural (terrestrial) sources.

TMDL / PHASED TMDL LINKS

Long Island Sound Related Web Sites

Federal Sites

State Sites (see EPA's TMDL Links for a comprehensive list)

Advocacy Sites

TMDL Assessments

Water Quality Links–Oxygen Depletion

Other Interesting Links