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

• Total Maximum Daily Loads with Stormwater Sources: A Summary of 17 TMDLs, July 2007, EPA 841-R-07-002
• Total Maximum Daily Loads and National Pollutant Discharge Elimination System Storm Water Permits for Impaired Water Bodies: A Summary of State Practices, Sept. 15, 2007

TMDL-Stormwater Permit Case Studies:

• The Minnehaha Creek Watershed District (Minnesota) Nine Lakes TMDL (2005)

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, July 2006
• A Total Maximum Daily Load Analysis for Eagleville Brook, Mansfield, Connecticut, Feb. 8, 2007

Hydrology

• Total Maximum Daily Load to Address Biological Impairment in Potash Brook (VT05-11) Chittenden County, Vermont, Oct. 2006

Archived Versions of TMDL Webcasts

• National Association of Counties (NACo) "Stormwater Runoff for Counties" Webinar, November 12, 2009

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
• Incorporating Green Infrastructure into TMDLs
• An Approach for Using Load Duration Curves in the Development of TMDLs, Aug. 2007
• Options for Expressing Daily Loads in TMDLs, June 22, 2007
• Stressor Identification Guidance Document (pdf) (228 pp, 1.9 MB, EPA 822-B-00-025)
• CADDIS.
• TMDL Model Evaluation and Research Needs, 2005
• 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)

Other EPA Stormwater Resources

• Nonpoint Source Urban Website
• Stormwater Program
• Stormwater Discharges from Construction Activities
• Stormwater Discharges from Industrial Facilities
• Stormwater Discharges from Municipal Separate Storm Sewer Systems (MS4s) Program
• Stormwater Best Management Practices Calculator
• Bioassessment and Biocriteria