API PUBL 4756:2006

Executive SummaryThe first part of this manual will discuss water quality standards and the listing process, in order to provide a basic understanding of how a water becomes labeled as 'impaired.' Water quality standards, which serve as the basis for comparison to actual water quality, include the designated uses for all waters, and the narrative and numeric water quality criteria necessary to support those uses. This manual addresses many water quality standards issues that facilities may encounter, including existing uses, use attainability analyses (UAAs) to revise designated uses, fish consumption advisories, whole effluent toxicity (WET) criteria, and sediment criteria. In addition, the first part will describe the listing process, through which impairment determinations are made, including state listing methodologies, assessment of waters, identification of impaired waters, and submission of reports to the U.S. Environmental Protection Agency (EPA) for approval. The manual will provide guidance on a number of listing issues, including listings due to violations of narrative criteria and fish consumption advisories, delisting, listing waters that are impaired but do not need a TMDL because they are expected to meet standards through other means, and challenging an erroneous listing determination.The second part of this manual will discuss permitting discharges to impaired waters during the interim period before TMDLs are developed. The manual will describe the development of water quality-based effluent limitations on impaired waters, and will also discuss a number of issues for affected facilities to consider during the permitting process, including timing (when the permit should be issued), watershed permitting, verifying the impairment determination before the permit is issued, other controls available to bring the water into attainment, reasonable potential calculations, voluntary reduction measures, non-numeric effluent limitations, and calculating numeric effluent limitations. The manual will also briefly discuss antidegradation and backsliding issues, as well as stormwater permits. Finally, the manual will discuss some options for obtaining relief from permit limits, including variances, site-specific criteria, and UAAs.