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<br />. <br /> <br />. <br /> <br />. <br /> <br />Agenda Item II, September 21-22, 1998. Board Meeting <br />Page 3 <br /> <br />the Nation's waters. The EPA is pi arming on holding a series of full-day public meetings to <br />discuss the issues presented in this ANPRM. The issues identified in this ANPRM include <br />designated uses, water quality criteria, anti degradation policies, mixing zones, and independent <br />application. The EP A also requests comments on how to address the potential resource <br />constraints for states and tribes in implementing new refined water quality standards program. <br />The EP A expects to receive comments from interested parties concerning this ANPRM by <br />January 4, 1999. <br /> <br />The following is a brief summary of the EPA's current policy and guidance identified in this <br />ANPRM: <br /> <br />a. Use, Criteria, and Antidegradation <br /> <br />The EPA's water quality standards for surface waters consist of three elements: "designated <br />uses", "criteria", and "antidegradation." The designated uses describe the intended uses of a <br />water body such as public water supply, agriculture, recreation, and protection of fish and <br />wildlife. Water quality criteria describe the quality of water that will support a given <br />designated use. Under the authority of the CW A, the EP A publishes water quality criteria that <br />reflect the Maximum Concentration Levels (MCLs) of specific chemicals in water that will <br />- protect aquatic life or human health. The states and tribes use these criteria as guidelines to <br />develop enforceable water quality criteria, based on local environmental conditions and human <br />exposure patterns. An antidegradation policy ensures that existing water quality is maintained <br />and protected, yet it provides the framework for making decisions about changes in water <br />quality. Antidegradation policy advocates conserving water quality where possible and lower <br />only when necessary. <br /> <br />Water quality criteria are expressed in either numeric form or narrative form. The EPA <br />reviews and approves the state and tribal water quality standards every three years (triennial <br />reviews) . <br /> <br />b. Mixing Zone <br /> <br />Mixing zone is an area where wastewater is discharged into the receiving water. In a mixing <br />zone, water quality criteria can be exceeded as long as acutely toxic conditions are prevented. <br />The EP A's current policy limits size or location of mixing zones to prevent lethality to <br />nonmotile benthic as well as to swimming and drifting organisms. <br />