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Appendix A Statement of Task The purpose of this task order is to engage the National Academy of Sciences’ expertise to help the EPA conceive and implement Section 303(d) of the Clean Water Act (CWA) across the Mississippi River basin and the Gulf of Mexico in order to meet nutrient and sediment reduction objectives. A report will be prepared that addresses the following three questions: 1. Given the state of scientific knowledge, and associated uncertainties, about phosphorous, nitrogen, and sediment reduction applicable to reducing the hypoxic zone in the Gulf and meet the designated uses for Mississippi basin States, how might existing loading estimates and targets be used to initiate pollutant control programs? In addressing this question, the implications of inevitable future improvements in precision and accuracy of monitoring and modeling will be considered. 2. What are the alternative methods to allocate load reductions to the relevant upstream tributaries, states, land uses, and other source classifications? What are the implications of these different allocation approaches on the geographic and sectoral distribution of pollutant load reduction responsibilities? 3. How should the effectiveness of pollutant loading reduction strategies on the gulf hypoxic zone and the states designated uses be documented? In addition, how much time would be required to determine if future reductions in nutrient and sediment loadings are resulting in a reduction in Gulf of Mexico hypoxia? A public workshop will inform the committee in the preparation of its consensus report. 1. Papers and presentations from the workshop will be compiled along with any distilled summary statements and placed in the public access file; 2. Materials presented and discussions at the workshop will help inform the committee in the preparation of its report that addresses the three questions above, and that uses illustrative case examples, to suggest useful alternative strategies for allocating reductions in upstream nutrient loadings that hold promise for achieving both local water quality improvements and improvements in Mississippi River and northern Gulf of Mexico water quality, and; 3. The committee will identify key future issues and challenges regarding scientific and administrative aspects of the Clean Water Act’s TMDL program in the Mississippi River Basin, including nutrient management and load limit allocations. 71

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