Total Maximum Daily Load
What is Total Maximum Daily Load (TMDL)?
A TMDL or total maximum daily load is a
calculation of the maximum amount of pollutant that a water
body can receive and
still meet water quality standards. The standards are related
to a water body’s use, which is designated by the state,
territory or tribal nation within which the water body lies.
Examples of a water body’s use are drinking water supply,
recreational contact, and aquatic life support. A TMDL is the
sum of the allowable loads of a single pollutant from all contributing
point and non-point sources. The Clean Water Act, section 303(d),
outlines the states’ responsibilities for identifying
impaired waters as well as developing TMDLs to assure the
water meets its designated use.
Over 40% of the waters in the United States assessed by the EPA do not meet the water quality standards. Understanding and implementing the TMDL program presents significant challenges for the state environmental agencies charged with the responsibility for the Clean Water Act program implementation. Within the New England Land Grant Universities, Volunteer Water Quality Monitoring programs are providing data to identify water bodies to add to the 303(d) list of impaired waters and to monitor the effectiveness of TMDL implementation. Also, New England Non-point Education for Municipal Officials (NEMO) programs educate municipal officials on issues related to improving water quality and watershed management.
Important Components of TMDL Process:
Describe current water quality impairments and identify possible causes
TMDLs set goals to achieve water quality standards and support public uses
Follow up monitoring to assess effectiveness of TMDL implementation
Provide watershed approach to water quality management
Public participation is an integral part of decision making process
TMDLs must be adopted and formally approved by the Environmental
Protection Agency
Online Resources:
Connecticut:Connecticut
Department of Environmental Protection TMDL 
Maine:
Maine
Department of Environmental Protection TMDL Massachusetts:
Massachusetts
Department of Environmental Protection TMDL New Hampshire
New
Hampshire Department of Environmental Services TMDL Rhode Island:
State
of Rhode Island Department of Environmental Management Office
of Water Resources TMDL Vermont:
Vermont
Department of Environmental Conservation Water Quality Division