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Water: Total Maximum Daily Loads (303d)


Guidance for Water Quality-Based Decisions:
The TMDL Process

This document, "Guidance for the Implementation of Water Quality-based Decisions: The TMDL Process," is intended to define and clarify the requirements under section 303(d) of the Clean Water Act. Its purpose is to help State water quality program managers understand the application of total maximum daily loads within the water quality-based approach to establish pollution control limits for waters not meeting water quality standards.

Water quality management has become increasingly more complicated. Problems such as toxic contaminants, sediments, nutrients, and habitat alteration result from a variety of point and nonpoint sources. The TMDL process is established under the Clean Water Act as the Mechanism to address these problems in a comprehensive manner in situations where technology-based controls are not adequate.

Through this guidance we hope to reduce the uncertainties associated with TMDLs and to establish the TMDL process as an effective water quality management tool for both point and nonpoint source pollution control.

Martha G. Prothro, Director
Office of Water Regulations and Standards
US Environmental Protection Agency
Washington, D.C.

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