Jump to main content or area navigation.

Contact Us

Water: Total Maximum Daily Loads (303d)

Total Maximum Daily Loads (TMDLs) and Stormwater

You will need Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more.


Throughout the U.S. there are thousands of waters listed for impairments from stormwater sources. The most common pollutants coming from stormwater sources include sediment, pathogens, nutrients, and metals. These impaired waters need a Total Maximum Daily Load (TMDL), which identifies the total pollutant loading that a waterbody can receive and still meet water quality standards, and specifies a pollutant allocation to specific point and nonpoint sources. The TMDL is implemented via the National Pollutant Discharge Elimination System (NPDES) stormwater permitting system. States and EPA Regions have used a variety of methods to develop stormwater-source TMDLs during the past decade. With the expansion of NDPES Stormwater regulations to smaller municipalities and smaller construction activities, there has been increasing demand for more detailed quantification of stormwater allocations in TMDLs that are more useful for implementation in NDPES permits.

Top of page

Resources for Developing Stormwater-Source TMDLs and Implementing in NPDES Permits

TMDLs to Stormwater Permits Draft Handbook (PDF) (200 pp, 5.7MB), November 2008. Currently there are thousands of Clean Water Act section 303(d) waters listed as impaired for stormwater-source pollutants such as pathogens, nutrients, sediments and metals.   This Draft Handbook provides a technical reference for TMDL practitioners and permit writers on current methods being used to develop more detailed stormwater-source TMDL allocations, TMDL implementation plans including best management practices, and methods for translating TMDL allocations into NPDES stormwater permit requirements.

TMDL-Stormwater Examples:

Total Maximum Daily Loads with Stormwater Sources: A Summary of 17 TMDLs (PDF) (59 pp, 600K), July 2007, EPA 841-R-07-002. This document summarizes 17 TMDLs that have been developed for stormwater-source pollutants in 16 states, representing a range of pollutants, models used, and different allocation and implementation methods.

Total Maximum Daily Loads and National Pollutant Discharge Elimination System Storm Water Permits for Impaired Water Bodies: A Summary of State Practices (PDF) (111 pp, 1.2MB), Sept. 15, 2007. This EPA report summarizes information on TMDL-stormwater practices in 10 states, provides specific TMDL and permit language, and identifies some specific technical and programmatic challenges.

TMDL-Stormwater Permit Case Studies:

These two case studies describe activities linking stormwater-source TMDLs currently being developed with applicable stormwater permits:

Innovative TMDLs using Surrogates for Stormwater Pollutants

Three states in EPA Region 1 have developed TMDLs using impervious cover and flow as surrogates for stormwater-source pollutants in streams listed for biological impairment.

Impervious Cover:

Barberry Creek, Maine, Total Maximum Daily Load (PDF) (41 pp, 2.7MB), July 2006 Exit EPA Disclaimer

A Total Maximum Daily Load Analysis for Eagleville Brook, Mansfield, Connecticut (PDF) (43 pp, 617K), Feb. 8, 2007 Exit EPA Disclaimer


Total Maximum Daily Load to Address Biological Impairment in Potash Brook (VT05-11) Chittenden County, Vermont (PDF) [BROKEN] (29 pp, 1.1MB) , Oct. 2006 Exit EPA Disclaimer

TMDL-Stormwater Technical Resources:

Incorporating Green Infrastructure into TMDLs (PDF) (11 pp, 358K)
This fact sheet provides examples of how some states describe Green Infrastructure/Low Impact Development activities in their TMDL implementation sections to address stormwater-source impaired waters.

Establishing Total Maximum Daily Load (TMDL) Wasteload Allocations (WLAs) for Storm Water Sources and NPDES Permit Requirements Based on Those WLAs (PDF) (6 pp, 235K) - Robert H. Wayland, III and James A. Hanlon -- Nov. 22, 2002, US EPA, Office of Water This memo clarifies existing EPA regulatory requirements for, and provides guidance on, establishing wasteload allocations (WLAs) for storm water discharges in total maximum daily loads (TMDLs) approved or established by EPA.

An Approach for Using Load Duration Curves in the Development of TMDLs (PDF) (74 pp, 3.3MB), Aug. 2007, EPA-841-B-07-006. This document shows how duration curves can be used for developing TMDLs and includes one case study.

Options for Expressing Daily Loads in TMDLs (PDF) (62 pp, 970K), June 22, 2007. This draft document provides technical options for developing daily load expressions in TMDLs calculated using time frames greater than daily allocations (e.g., annual, monthly, seasonal).

Stressor Identification Guidance Document:EPA 822-B-00-025. USEPA, Washington, DC. This document provides a formal process to identify stressors causing biological impairments in aquatic ecosystems and a structure for organizing the scientific evidence supporting the conclusions.

CADDIS.An online application that helps scientists and engineers in the Regions, States and Tribes find, access, organize, use and share information to conduct causal evaluations related to stressor identification in aquatic systems.

TMDL Model Evaluation and Research Needs (2005) (PDF) (403 pp, 10.82MB), This document provides a comprehensive review of available models for developing TMDLs.

These short fact sheets for state permitting authorities, municipalities and others describe developing and implementing stormwater management programs and linkage to TMDLs:

Top of page

Other Stormwater Resources

EPA Sites

Nonpoint Source Urban Web Site. Provides technical information on control of urban nonpoint source pollution.

Stormwater Program. Contains technical and regulatory information on the NPDES Stormwater program and provides stormwater outreach materials.

Stormwater Discharges from Construction Activities. Provides general information and guidance for construction activities.

Stormwater Discharges from Industrial Facilities. Provides general information and guidance for industrial facilities.

Stormwater Discharges from Municipal Separate Storm Sewer Systems (MS4s) Program. Includes permit requirements and guidance for MS4s.

Urban Stormwater BMP Performance Tool. Provides easy access to more than 220 studies assessing the performance of over 275 best management practices (BMPs) .

Managing Wet Weather with Green Infrastructure. Summarizes common Green Infrastructure approaches and key resources for research, funding and partnerships.

Bioassessment and Biocriteria. Hosts introductory, technical and guidance documents on the use of biological assessments and data.

Top of page

Contact Information

If you have questions about stormwater-source TMDLs, you may send an e-mail to swtmdl-ow@epa.gov and someone on the EPA Headquarters TMDL-Stormwater Team will get back to you.

EPA Headquarters TMDL-Stormwater Team

EPA Regional Office TMDL Contacts

EPA Regional Office NPDES Stormwater Contacts

Top of page

Jump to main content.