Total Maximum Daily Loads

Lakes and rivers become polluted when the contaminants entering the water overcome the capacity of the water body to clean itself.

States and local governments can keep water clean by limiting pollutants to levels that are less than their total maximum daily loads (TMDLs) for the different water bodies.

A TMDL is both a budget and a permit. We support the hard work of developing these permitted limits across our member states.

States are required by the Clean Water Act to identify water bodies that are failing to meet their water quality standards. Scientists analyze impaired water bodies to determine the daily amount, or load, of a pollutant they can absorb without significantly impairing the health of the water.

The states use those findings to establish the acceptable load, identify the pollutant’s source, and specify where and when reductions will be made so the load isn’t exceeded. This proposed TMDL permit is subject to approval by the EPA.

The banks of a river

Executing a TMDL can be complex, difficult, and expensive. NEIWPCC is contributing to TMDL work underway on many water bodies in New England and New York State, such as the New York-New Jersey Harbor and Long Island Sound.

We hold annual workgroup meetings to discuss news from the field and current issues. These meetings, which include personnel from state and federal environmental agencies and others, provide a forum in which to develop solutions, anticipate and plan for future challenges and potential conflicts.

NEIWPCC also hosts national informational webinars for state, federal, and tribal TMDL program staff, as well as other non-governmental stakeholders when appropriate.

NEIWPCC worked with the U.S. Geological Survey to develop the New England Regional SPARROW (Spatially Referenced Regressions on Watershed Attributes) model, helpful in developing nutrient TMDLs. NEIWPCC worked with all of its member states on the Northeast Regional Mercury TMDL to reduce atmospheric deposition of mercury and work toward eliminating fish consumption advisories.

In the policy arena, NEIWPCC monitors EPA’s TMDL guidance, and writes comment letters, if necessary, on behalf of our member states.

For more information on TMDLs, contact Emma Gildesgame.