Total Maximum Daily Load (TMDL)
& Impacts On Business

TMDL is one of the major steps to restoring our watersheds in the U.S. and it influences the choices you have when creating and implementing a stormwater management plan.  All watersheds with TMDLs are subject to stormwater discharge limits for the pollutant(s) of concern.  As stormwater enters a pipe, it becomes subject to regulations and is then classified as a point source discharge.  All point source discharges are subject to water quality standards.  The enforcement of these standards is based on the Clean Water Act. 

TMDL History

Section 303(d) of the Clean Water Act (CWA) requires “states to submit lists of surface waters that do not meet applicable water quality standards (impaired waters) after implementation of technology-based effluent limitations, and establish TMDLs for these waters on a prioritized schedule.”  

EPA Quick Overview of TMDL

Search State by State TMDLs

TMDLs Influence on
Best Management Practice (BMP) Selection

When implementing a TMDL, actions may include the development or implementation of Best Management Practices to achieve the pollutant load reduction.  Due to the unique nature of watersheds in each state, issuance of stormwater permits may include revisions or conditions that specifically relate to numeric effluent limitations or require using the combination of structural and non-structural BMPs. An example of regulations based on TMDL requirements include several watersheds in Portland ,Oregon area, which require 65% reduction in total phosphorus.

Best Management Practices Available

The TMDL Process
How it Works

• Every water body is classified within a state into a specific use class. 
  A specific set of criteria is determined by the state for each use class, and this is based on historical data, social factors, and economic influences. 

• The water body is tested to see if it meets all criteria for its particular class.  If not, it becomes listed as a non-attainment water.
  (ex: Maine uses letter grades, (AA,A,B,C))

• All waters designated as non-attainment are subject to a TMDL.

• Tests are implemented to determine the pollutant load of the water body on a daily basis while still being able to meet its designated use criteria.

Articles

The Twenty Needs Report: How Research Can Improve the TMDL Program
EPA Stressor Identification Guidance
EPA Protocol for Developing Pathogen TMDLs: First Edition (2M),
EPA Protocol for Developing Sediment TMDLs
EPA Compendium of Tools for Watershed Assessment and TMDL Development,
EPA Water Quality Modeling and Total Maximum Daily Load Guidance