USEPA Office of Water - TMDL Program Results Analysis Fact Sheet 3 - May 5, 2009 Fact Sheet: Total Maximum Daily Loads TOTAL MAXIMUM DAILY LOAD (TMDL) and the CLEAN WATER ACT The goal of the Clean Water Act (CWA) is to restore and maintain the chemical, physical, and biological integrity of our nation's waters. Under CWA section 303(d), states, territories, and authorized tribes are required to develop lists of waterbody segments impaired by a pollutant and needing a TMDL. A TMDL is a technical calculation of the maximum load of a pollutant a waterbody can receive and still meet water quality standards. A TMDL addresses the sum of all point source loads ("waste load allocation") and loads associated with nonpoint sources ("load allocation"). Tens of thousands of TMDLs have been developed nationwide since 1995. TMDL = WLA + LA + MOS WLA Waste Load Allocation Amount of pollutant from existing point sources (e.g., sewage treatment plant; industrial facility; stormwater) LA Load Allocation Amount of pollutant from existing nonpoint sources and natural background (e.g., farm runoff; atmospheric mercury) Adopt Water Quality Standards Monitor & Assess Water F List Impaired & Threatened Waters Develop TMDLs including load and wasteload allocations Implement the TMDL In general, the CWA requires states to establish water quality standards for waters within their borders by designating specific uses for their waters (designated uses) and establishing criteria by which to protect those uses, control pollutant Over 37,000 TM DLs Completed sources, and monitor and assess water quality. MOS Margin of Safety Part of TMDL allocated to uncertainty in analysis States are responsible for submitting biennial lists [section 303(d) lists of impaired waters] and water quality assessment reports [section 305(b) reports] to the Environmental Protection Agency (EPA). States develop TMDLs for listed waters in accordance with priority ranking. EPA provides an 8 to 13 year time frame to complete the development of a TMDL once a waterbody is listed. These loading limits, when fully implemented, should ensure that the state's waters achieve the relevant water quality standards. 40,000 5/5/09 # of TMDLs per fiscal year • Cumulative # of TMDLs ------- USEPA Office of Water - TMDL Program Results Analysis Fact Sheet 3 - May 5, 2009 Nonpoint Source, Point Source, and Mixed TMDLs 44% ED Nonpoint Source I Point Source • Combination of Point and Nonpoint Sources TMDLs established for nonpoint sources far outnumber those completed for point sources. This trend mirrors nonpoint source causes of impairment dominating states' impaired waters lists. These nonpoint source TMDLs are especially challenging to implement, as the Clean Water Act is limited to voluntary controls (e.g., best management practices) on nonpoint sources. A partial list of TMDLs by pollutant from the Assessment, TMDL Tracking and Implementation System (ATTAINS) appears below. For the full list, visit http://iaspub.epa.gov/waters10/attains nation cy.control?p report type=T. National Cumulative TMDLs by Pollutant This chart includes TMDLs since October 1, 1995. Description of this table NOTE: Click on the underlined "Pollutant Group" value to see a detailed list of pollutants. Click on the underlined "Number of TMDLs" value to see a listing of those TMDLs for the pollutant Group. Number of Causes of Pollutant Group Mercury Metals (other than Mercury) Organic Enrichment/Oxygen Depletion Temperature Prolific TMDL development has occurred for some types of TMDLs, such as mercury and pathogen TMDLs, because of: • numerous listings of specific causes of impairment on state impaired waters lists, • templates created by EPA regions or states which greatly increase TMDL development efficiency, and • EPA guidance issued regarding TMDL development for specific, common pollutants. Mercury Pathogens • Ranks second nationally in causes of waterbody impairment • EPA approved the Northeast Regional Mercury TMDL - a multi-state effort - in fiscal year 2008. This TMDL covers over 5,000 mercury-impaired waterbodies in New Hampshire as well as waterbodies in the remaining New England states and New York (http://www.epa.gov/owow/tmdl/examples/mercury.html , http://www.epa.gov/region1/eco/tmdl/approved.html) • Similarly, in MN, over 1,000 TMDLs were approved within a statewide mercury TMDL effort. • To assist other states, EPA has developed information on approaches to mercury: -^ Listing Waters Impaired by Atmospheric Mercury Under Clean Water Act Section 303(d) (http://www.epa.gov/owow/tmdl/mercury5m/) -^ TMDLs Where Mercury Loadings are Predominantly from Air Deposition TMDL checklist document (http://www.epa.gov/owow/tmdl/pdf/document me rcury tmdl elements.pdf) • Rank first nationally in causes of waterbody impairment • Several EPA regions use an approval checklist, which compresses information from potentially lengthy decision rationales to simpler, briefer documents. Also, state-specific, general decision rationales applicable to all bacteria TMDLs in the state are utilized. • EPA has developed information on approaches to addressing pathogens in TMDLs: -^ Options for Expressing Daily Loads in TMDLs (http://www.epa.gov/owow/tmdl/draft daily loads tech.pdf) -^ Total Maximum Daily Loads with Stormwater Sources: A Summary of 17 TMDLs (http://www.epa.gov/owow/tmdl/17 TMDLs Stor mwater Sources.pdf) -^ An Approach for Using Load Duration Curves in the Development of TMDLs (http://www.epa.gov/owow/tmdl/duration curve g uide aug2007.pdf) -^ Protocol for Developing Pathogen TMDLs (http://www.epa.gov/owow/tmdl/pathogen all.pdf) For more information: TMDL Home Page http://www.epa.gov/owow/tmdl/. Contact: Sarah Furtak (202) 566-1167. furtak.sarah@epa.gov ------- |