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1 Introduction THE RETURN TO AMBIENT-BASED WATER QUALITY MANAGEMENT The Federal Water Pollution Control Act Amendments of 1972 (PL 92-500), as supplemented by the Clean Water Act (CWA) of 1977 and the Water Quality Act of 1987, are the foundation for protecting the na- tionâs water resources. Precursors to the Water Quality Act go back to the Rivers and Harbors Appropriations Act of 1899, often referred to as the Refuse Act, and the Water Pollution Control Acts of 1948 and 1965 (Rodgers, 1994). An important impetus for earlier water quality legisla- tion was protection of public health. Over time, this purpose was sup- plemented by aesthetic and recreational purposes (fishable and swimma- ble) and then by the goal of restoring and maintaining the âchemical, physical, and biological integrity of the Nationâs watersâ (Section 101a of PL 92-500). In practice, each of these general purposes must be restated in opera- tional and measurable terms as ambient water quality standards, which are established by the states and are subject to federal approval. Section 303d of the CWA makes it a responsibility of the states to assess whether ambient standards are being achieved for individual waterbodies. If am- bient standards are not being met, a water quality management program to achieve those standards is anticipated. The data and analytical requirements for determining both the causes of a failure to meet ambient standards and the solutions to such problems have challenged water quality analysts for over half a century. Prior to the 1972 Water Pollution Control Act Amendments, states were expected to identify pollutant sources that were resulting in violations of ambient water quality standards. Once the sources of the problem were carefully identified, controls on polluting activities would be put in place. How- ever, in even modestly complex watersheds, multiple sources of pollut- 12
Conceptual Foundations for Water Quality Management 13 ants made it difficult to unambiguously determine which sources were responsible for the standard violation. One source might insist that the cause of the problem was the discharge from others, or at least that its own contribution to the problem was not as significant as the contribu- tions of others. Neither the available monitoring data nor the analytical methods available at the time allowed the states to defensibly mandate differential load reduction requirements (Houck, 1999). The 1972 amendments recognized this analytical dilemma and shifted the focus of water quality management away from ambient stan- dards. Instead, all dischargers of certain pollutants were expected to limit their discharges by meeting nationally established effluent stan- dards. Effluent standards are specified in National Pollution Discharge Elimination System (NPDES) permits, issued by the states to certain pollutant sources and approved by the U.S. Environmental Protection Agency (EPA). Effluent standards were set at a national level based on available technologies for wastewater treatment appropriate to different industry groups (although in certain waterbodies effluent standards more stringent than the technology-based requirement have been required to meet local water quality goals). The shift to effluent standards elimi- nated the need to link required reductions at particular sources with the ambient condition of a waterbody. Instead, each regulated source was simply required to meet the effluent standard in its wastewater. In the intervening period since passage of PL 92-500, pollutants discharged by industry and municipal treatment plants have declined, and the ambient quality of many of the nationâs lakes, rivers, reservoirs, groundwater, and coastal waters has improved. There were consequences that followed the embracing of effluent- based standards instead of ambient-based standards. First, efforts to measure and communicate water quality accomplishments were often described in terms of compliance with wastewater permit conditions rather than the condition of the waters. Second, effluent standards could only apply to so-called point sources rather than to all sources of a pol- lutant or other forms of pollution (Box 1-1). Pollutants from nonpoint sources (derived from diffuse and hard-to-monitor origins such as land- disturbing agricultural, silvicultural, and construction activities) largely escaped oversight. Third, attention to chemical pollutants measured in discharge water came to dominate water quality policy, and the physical and biological determinants of the ambient condition of a waterbody were less frequently considered. A pollutant is defined as a substance added by humans or human activities. In many cases, the condition of a
14 Assessing the TMDL Approach to Water Quality Management BOX 1-1 Pollution vs. Pollutant Clean Water Act Section 502(6). The term âpollutantâ means dredged spoil, solid waste, incinerator residue, biological materials, radioactive materials, heat, wrecked or discarded equipment, rock, salt, cellar dirt, and industrial, municipal, and agricultural waste discharged into water. This term does not mean (A) âsewage from vesselsâ within the meaning of section 312 of this Act; or (B) water, gas, or the materials which are injected into a well to facilitate production of oil or gas, or water derived in association with oil or gas production and disposed of in a well, if the well used either to facilitate production or for disposal purposes is ap- proved by authority of the State in which the well is located, and if such State determines that such injection or disposal will not result in the deg- radation of ground or surface water resources. Clean Water Act Section 502(19). The term âpollutionâ means the manmade or man-induced alteration of chemical, physical, biological, and radiological integrity of water. In the Clean Water Act, pollution includes pollutants (as described above) as well as other stressors such as habitat destruction, hydrologic modification, etc. waterbody depends on more than the loads of particular pollutants from sources required to meet effluent standards. For example, changes in the hydrologic regime associated with development activities can destabilize streambanks, increase loads of sediment and nutrients, or eliminate key species or otherwise change the aquatic ecosystem. As shown in Box 1- 1, biological, hydrologic, and physical changes to a waterbody that do not fit the definition of pollutant were encompassed in the 1987 actâs definition of pollution. Present-day implementation of Section 303d of the Clean Water Act returns to the pre-1972 focus on ambient water quality standards, even though there are still requirements for meeting effluent standards. Sec- tion 303d requires states to identify waters not meeting ambient water quality standards, define the pollutants and the sources responsible for
Conceptual Foundations for Water Quality Management 15 the degradation of each listed water, establish Total Maximum Daily Loads (TMDLs) necessary to secure those standards, and allocate re- sponsibility to sources for reducing their pollutant releases. Therefore, for each impaired waterbody, the state must identify the amount by which both point and nonpoint source pollutants would need to be re- duced in order for the waterbody to meet ambient water quality stan- dards. Other alterations that do not fit the pollutant definition such as changes of habitat, flow alterations, channelization, and modification or loss of riparian habitat may need to be considered as a reason for not meeting standards. If TMDL language is strictly interpreted, however, these causes may fall outside the TMDL program. Although Section 303d has been in place since the early 1970s, ac- tivity to comply with it was limited until the last decade. States were slow to submit inventories of impaired waters, and measures of water quality program success were often simply documentation of point source permit issuance and compliance. Few TMDLs were prepared, and they often did not incorporate both point and nonpoint source dis- charge controls (Houck, 1999). Action to meet Section 303d require- ments accelerated in the 1990s primarily because of a series of citizen lawsuits against EPA. By 1992, EPA revised the TMDL regulations to require submission of statesâ lists of impaired water bodies every two years. EPA estimates that from 3,800 to 4,000 TMDLs will need to be completed per year to meet the 8- to 13-year deadlines currently imposed on the process. From 1,000 to 1,800 would have to be completed per year to meet consent decree deadlines, while another 1,800 to 2,200 per year need to be resolved through settlement agreements. States have identified about 21,000 impaired river segments, lakes, and estuaries en- compassing more than 300,000 river and shore miles and 5 million lake acres (Brady, 2001). Excess sediments, nutrients, and pathogens are leading reasons for listing according to state reports submitted to EPA. Federal, state, and local governments, regulated and potentially regulated communities, and concerned citizens throughout the nation claim that they face unrealistic deadlines and must use analytical and decision- making procedures that are largely untested. Proposed revisions to the TMDL regulations were submitted in 1999, with a final rule issued July 13, 2000. However, faced with expressions of concern about the practi- cality of the program, a congressional rider prohibited EPA from imple- menting the new rule until October 2001. As a result, the TMDL pro- gram continues under 1992 regulations and, in some cases, consent de-
16 Assessing the TMDL Approach to Water Quality Management crees. The 303d focus on ambient water quality standards has returned the nation to a water quality program that was not considered implementable 35 years ago when there was a paucity of data and analytical tools for determining causes of impairment and assigning responsibility to various sources. Determining the pollutant load from a regulated point source is a relatively straightforward task, although isolating its effect in a com- plex waterbody remains a technical challenge. Such technical uncertain- ties in relating stresses on the waterbody to impairment are compounded when nonpoint sources of pollutants and other forms of pollution are considered. Having returned the focus to ambient water quality condi- tions, are we better positioned today than we were years ago? Do we have more and better data and analytical methods? Do we have a better understanding of watershed events and processes responsible for water quality violations? These are the science questions facing the nation as we implement Section 303d of the Clean Water Act. NATIONAL RESEARCH COUNCIL STUDY Despite recent progress, the demands of the TMDL program weigh heavily on the limited resources of EPA and the states. The TMDL proc- ess requires high-quality data and sophisticated tools to analyze those data. States have reported having insufficient funds, inadequate moni- toring programs, and limited staff to collect and analyze such data (GAO, 2000). According to the General Accounting Office (GAO), only six states have enough data to fully assess the condition of their waterbodies, while only 18 have enough data to place their waterbodies on the list of impaired waters (303d list). Forty states had sufficient high-quality data to determine TMDLs for waterbodies impaired primarily by point sources such as municipal sewage treatment plants, and 29 had sufficient high-quality data to implement these TMDLs. When states were asked about waterbodies impaired primarily by nonpoint sources, however, only three claimed to have sufficient data. The GAO report outlined several critical issues for consideration by the states and EPA. Beyond questions of additional funding for data collection and staff, the states need assistance using watershed models; many reported being unclear where to go for such assistance. There ap- pears to be no formalized process to capitalize on lessons learned, to transfer technology, and to share knowledge. Aside from the reported
Conceptual Foundations for Water Quality Management 17 lack of data to comply with the TMDL regulations, when data are avail- able, they are often not the type needed for source identification and TMDL analyses. . Subsequent to the GAO report, Congress requested that the National Research Council (NRC) analyze on a broad scale the scientific basis of the TMDL program. The NRC was asked to evaluate: â¢ the information required to identify sources of pollutant loadings and their respective contributions to water quality impairment, â¢ the information required to allocate reductions in pollutant load- ings among sources, â¢ whether such information is available for use by the states and whether such information, if available, is reliable, and â¢ if such information is not available or is not reliable, what meth- odologies should be used to obtain such information. While the GAO report was about data, the NRC was charged to fo- cus on reliable information for making decisions. In presentations made to the NRC committee, the terms âdataâ and âinformationâ often were used as synonyms, but data are not the same as information. Unanalyzed data do not constitute information. Data must be interpreted for their meaning through the filter of analytical techniques, and the result of such data analysis is information that can support decision-making. Knowing what data are needed and turning those data into information constitutes, in large part, the science behind a water quality management program. The techniques for transforming data into information include statistical inference methods, simulation modeling of complex systems, and, at times, simply the application of the best professional judgment of the analyst. In all these processes there will always be some uncertainty (and thus some âunreliabilityâ) about whether the resulting information accurately characterizes the water quality problem and the effectiveness of the solutions. Because uncertainty cannot be eliminated, determining whether the information generated from data analysis is reliable is a value judgment. Individuals and groups will have different opinions about whether and how to proceed with water quality management given a certain level of uncertainty. To organize its deliberations, the committee considered the role of science at each step of the TMDL process, from the initial defining of all waters to the implementation of actions to control pollution; the report is structured around this organization. Report recommendations are tar-
18 Assessing the TMDL Approach to Water Quality Management geted (1) at those issues where science can and should make a significant contribution and (2) at barriers (regulatory and otherwise) to the use of science in the TMDL program. Because of this broad scope, the content of the report extends beyond the confines of the charge in the bulleted items above. Chapters 2, 3, and 4 discuss the information (as defined above) required to set water quality standards, to list waters as impaired, and to develop TMDLs (including the identification of pollution sources); Chapter 5 comments on the role of science in allocating pollut- ant loading among sources. Because GAO (2000) already documents a widespread lack of data and information at the state level and because availability of information varies significantly from state to state, the committee did not devote substantial time to determining availability. As mentioned above, whether the information is reliable depends on the de- gree of uncertainty decision-makers are willing to accept when making regulatory or spending choicesâa decidedly nonscientific matter. Chapters 3 and 4 describe in detail the monitoring, modeling, and statis- tical analysis methods needed to collect data and convert it to informa- tion, and to assess and reduce uncertainty. Chapter 5 describes an ap- proach for making decisions in the face of uncertainty. This report represents the culmination of three meetings over three months, including a two-day public session in which 30 presentations from a wide variety of stakeholders were made (see Appendix B). Given the information gathered during the study period and the collective expe- rience of its members, the committee feels that the data and science have progressed sufficiently over the past 35 years to support the nationâs re- turn to ambient-based water quality management. In addition, the need for this approach is made apparent by the inability of a large percentage of the nationâs water to meet water quality standards using point source controls alone. Given reasonable expectations for data availability and inevitable limits on our conceptual understanding of complex systems, statements about the science behind water quality management must be made with acknowledgment of uncertainties. Finally, the committee has concluded that there are creative ways to accommodate this uncertainty while moving forward in addressing the nationâs water quality chal- lenges. These broad conclusions are elaborated upon throughout this report.
Conceptual Foundations for Water Quality Management 19 CURRENT TMDL PROCESS AND REPORT ORGANIZATION Section 303d requires that states identify waters that are not attaining ambient water quality standards (i.e., are impaired). (Although new rules are pending, at the request of Congress, this report focuses on the 1992 regulations that govern the current program.) States must then establish a priority ranking for such waters, taking into account the severity of the impairment and the uses to be made of such waters. For impaired wa- ters, the states must establish TMDLs for pollutants necessary to secure applicable water quality standards. The CWA further requires that once water quality standards are attained they must be maintained. Figure 1-1 depicts the basic steps in the TMDL process. These steps are described briefly below and are considered in greater detail through- out the report. At the beginning of the process are all waterbodies for the state and the development of water quality standards for each waterbody. Water quality standards are established outside the TMDL process and include designated uses for a waterbody and measurable water quality All Waters Determine Designated Use/ Standard Listing Planning Implementation FIGURE 1-1 Conceptualized steps of the TMDL process. criteria designed to assure that each designated use is being achieved.
20 Assessing the TMDL Approach to Water Quality Management Because water quality standards are the foundation on which the entire TMDL program rests, more detailed discussion of standard setting is provided in Chapters 2 and 3. The next step in the process is the listing of impaired waterbodies if evaluation of available data suggests that certain waterbodies are not meeting standards. According to Section 303d, all impaired waterbodies must be listed by the states or responsible agencies and submitted to EPA every two years. In addition, the states should provide priority ranking for the waterbodies on the 303d list. Following its submission, EPA must either approve or disapprove the list. Listing of a waterbody initi- ates a costly planning process and may lead to added costs to implement pollutant controls by point and nonpoint sources. The NRC committee heard testimony that many waterbodies have been listed based on limited or completely absent data and poorly conceived analytical techniques for data evaluation. Chapter 3 reviews the listing process and makes rec- ommendations that will improve the reliability of the listing decision. Once an impaired waterbody is listed, a planning step ensues. Sec- tion 303d specifies that those waters impaired by pollutants should un- dergo calculation of a TMDL. The term TMDL has essentially two meanings (EPA, 1991): â¢ The TMDL process is used for implementing state water quality standardsâthat is, it is a planning process that will lead to the goal of meeting the water quality standards. â¢ The TMDL is a numerical quantity determining the present and near future maximum load of pollutants from point and nonpoint sources as well as from background sources, to receiving waterbodies that will not violate the state water quality standards with an adequate margin of safety. The permissible load is then allocated by the state agency among point and nonpoint sources. The calculation described above requires data collection and various forms of modeling in order to identify sources of pollution and back- ground conditions, calculate the maximum load that will meet water quality standards with a margin of safety, and make allocations of re- sponsibility for load reduction to point and nonpoint sources. Chapter 4 reviews modeling capability, data needs for model implementation, and the appropriate role of modeling in the TMDL planning process. The last step in the process is implementation of the TMDL and the delisting of the waterbody. Implementation is the process of putting the
Conceptual Foundations for Water Quality Management 21 actions envisioned in the TMDL plan in place. Such actions could in- clude limitations on point sources beyond technology-based effluent standards. Also, using best management practices for nonpoint sources, as well as addressing pollution problems, might be part of implementa- tion, although these actions are not required by Section 303d.2 The re- sults of implementation actions need to be assessed before a waterbody can be removed from the list. Monitoring in this phase is necessary to measure the success (or failure) of the plan. Chapter 5 discusses postim- plementation monitoring and a strategy for assuring that the best avail- able science is used in the TMDL implementation phase. When the monitoring proves that the implementation is successful (i.e., the water quality standards are met), the waterbody can be delisted. REFERENCES Brady, D. 2001. Chief of the Watershed Branch in the Assessment and Water- shed Protection Division in the EPA Office of Wetlands, Oceans and Wa- tersheds. Presentation to the NRC Committee. January 25, 2001. Environmental Protection Agency (EPA). 1991. Guidance for Water Quality- based Decisions: The TMDL Process. Washington, DC: EPA Assessment and Watershed Protection Division. General Accounting Office (GAO). 2000. Water Quality - Key EPA and State Decisions Limited by Inconsistent and Incomplete Data. GAO/RCED- 00-54. Washington, DC: GAO. Houck, O. A. 1999. The Clean Water Act TMDL Program: Law, Policy, and Implementation. Washington, DC: Environmental Law Institute. Rodgers, W. H., Jr. 1994. Environmental Law, Second edition. St. Paul, MN: West Publishing Co. 2 Whether nonpoint source controls are required as part of the TMDL program is the source of much of the debate, especially with regard to the 2000 regulations that are now on hold. Under the current (1992) regulations, 303d is a planning exercise only. Implementation must be by some other provisions of the CWA or other programs. Also, states differ in their ability to enforce use of certain best management practices.