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1 Introduction
Pages 12-21

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From page 12...
... of 1977 and the Water Quality Act of 1987, are the foundation for protecting the nation's 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~.
From page 13...
... Neither the available monitoring data nor the analytical methods available at the time allowed the states to defensibly mandate differential load reduction requirements (Houck, 19994. The 1972 amendments recognized this analytical dilemma and shifted the focus of water quality management away from ambient standards.
From page 14...
... As shown in Box 1I, biological, hydrologic, and physical changes to a waterbody that do not fit the definition of pollutant were encompassed in the 1987 act's 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.
From page 15...
... Therefore, for each impaired waterbody, the state must identify the amount by which both point and nonpoint source pollutants would need to be reduced in order for the waterbody to meet ambient water quality standards. Other alterations that do not fit the pollutant definition such as changes of habitat, flow alterations, channelization, and modification or Toss of riparian habitat may need to be considered as a reason for not meeting standards.
From page 16...
... 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.
From page 17...
... 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 "unreliability")
From page 18...
... In addition, the need for this approach is made apparent by the inability of a large percentage of the nation's 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.
From page 19...
... For impaired waters, 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.
From page 20...
... The calculation described above requires data collection and various forms of modeling in order to identify sources of pollution and background conditions, calculate the maximum load that will meet water quality standards with a margin of safety, and make allocations of responsibility 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.
From page 21...
... 1999. The Clean Water Act TMDL Program: Law, Policy, and Implementation.


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