Connecticut Department of Energy & Environmental Protection

Nitrogen Control Program for Long Island Sound

Each summer, the bottom waters in the western half of Long Island Sound experience hypoxia, or very low levels of dissolved oxygen. Extensive monitoring and modeling of Long Island Sound have identified the excessive discharge of nitrogen from human activities as the primary pollutant causing hypoxia. Nitrogen fuels the growth of algae in the Sound, which eventually decays, consuming oxygen in the process. There is enough nitrogen added by human activity to cause a hypoxia problem each summer. 

In 2001, Connecticut DEEP and New York DEC, in concert with US EPA, completed plans for nitrogen control that identifies the maximum amount, or the Total Maximum Daily Load (TMDL), of nitrogen that can be discharged to Long Island Sound without significantly impairing the health of the Sound. One of DEEP’s management strategies to reduce nitrogen loading was to develop an innovative nitrogen-trading program among 79 sewage treatment plants located throughout the state. Through the Nitrogen Credit Exchange, established in 2002, Connecticut has reduced the nitrogen load from that source by nearly 65% by 2014.

On January 2, 2002, pursuant to Public Act 01-180, the Department issued the General Permit for Nitrogen Discharges for Publicly Owned Treatment Works (also known as the Nitrogen General Permit). The Nitrogen General Permit was reissued with revised discharge limits consistent with the Long Island Sound TMDL in January 2006, January 2011, January 2016; and renewed again effective from January 1, 2019 through December 31, 2023.

The current Nitrogen General Permit continues with the same permit limits as listed in the General Permit for the year 2014. These facilities, in aggregate, must continue to achieve a reduction in the annual loading of total nitrogen to Long Island Sound by approximately 64% from the original baseline TMDL in order to continue to meet the target 2014 waste load allocation.

General Permit for Nitrogen Discharges
General Information on the Nitrogen Trading Program
Total Maximum Daily Load (TMDL) for Nitrogen
For more information on:
Nitrogen Credit Exchange Program, please contact Iliana Raffa at (860) 424-3758.
Baseline nitrogen loads, waste load allocation and permitting, please contact CT DEEP at (860) 424-3704.

Content last updated  June 22, 2023