TMDLs (Total Maximum Daily Loading) define how much of a pollutant a water body can tolerate on a daily basis & still meet the relevant water quality standards. All of the sources of the pollutant in the watershed combined, including non-point sources, are limited to discharging no more than that total limit. EPA is suing states to force them to produce TMDLs. A growing number of California's water bodies are either subject to consent decrees to develop TMDLs, or are the subject of notices of intent to file lawsuits that may have that outcome. This report addresses California's many problems in establishing TMDLs for its impaired water bodies.
Narrative water quality criteria are an integral component of States water quality standards but they pose special problems when incorporated into the TMDL process. The TMDL process is typically a quantitative activity, defining numeric allowable loads necessary to meet a numeric water quality objective. Narrative criteria confound development of quantitative TMDLs, due to the absence of these numeric criteria. The objective of this research was to improve the methods for addressing narrative water quality criteria in the TMDL process. The problems associated with narrative criteria in the TMDL process are known in general terms but, prior to this research, there has not been a thorough review of the use of narrative criteria in TMDLs nor broad guidance on how to address narrative criteria in the TMDL process. The approach taken for this research was to define the range of problems associated with all types of narrative criteria by means of a comprehensive review of 120 narrative TMDLs, and provide guiding principles to help address these problems.
Over the last 30 years, water quality management in the United States has been driven by the control of point sources of pollution and the use of effluent-based water quality standards. Under this paradigm, the quality of the nation's lakes, rivers, reservoirs, groundwater, and coastal waters has generally improved as wastewater treatment plants and industrial dischargers (point sources) have responded to regulations promulgated under authority of the 1972 Clean Water Act. These regulations have required dischargers to comply with effluent-based standards for criteria pollutants, as specified in National Pollutant Discharge Elimination System (NPDES) permits issued by the states and approved by the U.S. Environmental Protection Agency (EPA). Although successful, the NPDES program has not achieved the nation's water quality goals of "fishable and swimmable" waters largely because discharges from other unregulated nonpoint sources of pollution have not been as successfully controlled. Today, pollutants such as nutrients and sediment, which are often associated with nonpoint sources and were not considered criteria pollutants in the Clean Water Act, are jeopardizing water quality, as are habitat destruction, changes in flow regimes, and introduction of exotic species. This array of challenges has shifted the focus of water quality management from effluent-based to ambient- based water quality standards. Given the most recent lists of impaired waters submitted to EPA, there are about 21,000 polluted river segments, lakes, and estuaries making up over 300,000 river and shore miles and 5 million lake acres. The number of TMDLs required for these impaired waters is greater than 40,000. Under the 1992 EPA guidance or the terms of lawsuit settlements, most states are required to meet an 8- to 13-year deadline for completion of TMDLs. Budget requirements for the program are staggering as well, with most states claiming that they do not have the personnel and financial resources necessary to assess the condition of their waters, to list waters on 303d, and to develop TMDLs. A March 2000 report of the General Accounting Office (GAO) highlighted the pervasive lack of data at the state level available to set water quality standards, to determine what waters are impaired, and to develop TMDLs. This report represents the consensus opinion of the eight-member NRC committee assembled to complete this task. The committee met three times during a three-month period and heard the testimony of over 40 interested organizations and stakeholder groups. The NRC committee feels that the data and science have progressed sufficiently over the past 35 years to support the nation's return to ambient-based water quality management. Given reasonable expectations for data availability and the inevitable limits on our conceptual understanding of complex systems, statements about the science behind water quality management must be made with acknowledgment of uncertainties. This report explains that there are creative ways to accommodate this uncertainty while moving forward in addressing the nation's water quality challenges.
Complete, practical coverage of pollution control regulations and water quality modeling Water Quality Modeling for Wasteload Allocations and TMDLs provides practical guidance for engineers charged with determining the volume and character of wastewater that a body of water can receive without suffering environmental damage. Following the discussion on water pollution control regulations and their relationships to water quality modeling and wasteload allocation for determining the total maximum daily load (TMDL), the first half of the book focuses on quantifying the model coefficients to characterize physical, chemical, and biological processes of a variety of water quality problems. The remainder of the book guides engineers in the application of EPA-developed models for regulatory use. Presenting numerous case studies and a substantial amount of data, this comprehensive guide: * Covers practical applications of wasteload allocation * Provides guidance to develop technical information for obtaining National Pollution Discharge Elimination System (NPDES) permits * Demonstrates the application of STREAM, QUAL2E, WASP, and HAR03 Water Quality Modeling for Wasteload Allocations and TMDLs is an essential resource for state and federal water quality agencies, consulting engineering firms, publicly owned treatment works, environmental biologists and chemists, and public health officials involved with pollution control.
