Impaired Waters and Stormwater
Throughout the United States 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 in part 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 NPDES permits.
Resources for Developing Stormwater-Source TMDLs
TMDL-Stormwater Permit Case Studies:
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.
Archived Versions of TMDL Webcasts
TMDL-Stormwater Technical Resources
Revisions to the November 22, 2002 Memorandum “Establishing Total Maximum Daily Load (TMDL) Wasteload Allocations (WLAs) for Stormwater Sources and NPDES Permit Requirements Based on Those WLAs,” November 26, 2014
Understanding Impaired Waters and TMDLs for Municipal Stormwater Programs (PDF), January 2008(5 pp, 617 K, EPA 833-F-07-009)
Evaluating the Effectiveness of Municipal Stormwater Programs (PDF), January 2008(6 pp, 375 K, EPA 833-F-07-010)
Incorporating Environmentally Sensitive Development Into Municipal Stormwater Programs (PDF), January 2008(7 pp, 418 K, EPA 833-F-07-011)
Funding Stormwater Programs (PDF), January 2008(5 pp, 193 K, EPA 833-F-07-012)