Designated uses are the purposes that a state’s waters are intended to serve. Some waters, for example, serve as a drinking water source, while others are designated to serve as a source of recreation (swimming or boating) and/or to support aquatic life. The state must also develop water quality criteria, which specify pollutant limits that determine whether a water body’s designated use is achieved. These water quality criteria can be expressed, for example, as the maximum allowable concentration of a given pollutant such as iron, or as an important physical or biological characteristic that must be met, such as an allowable temperature range. To develop water quality criteria, states rely heavily on EPA-developed “criteria documents.” These documents contain the technical data that allow states to develop the necessary pollutant limits. EPA is responsible for developing and revising criteria documents in a manner that reflects the latest scientific knowledge. States may adopt these criteria as recommended by EPA, adapt them to meet state needs, or develop criteria using other scientifically defensible methods. States are also required to periodically review both their waters’ designated uses and associated criteria, and make changes as appropriate. Before those changes can take effect, the state must submit them to EPA and obtain approval for them. EPA is required to review and approve or disapprove standards changes proposed by a state within 60 to 90 days. Figure 1 illustrates how states use water quality standards to make key decisions on which waters should be targeted for cleanup. States generally determine if a water body’s designated use is achieved by comparing monitoring data with applicable state water quality criteria. If the water body fails to meet the applicable standards, the state is required to list that water as “impaired”; calculate a pollution budget under EPA’s Total Maximum Daily Load program that specifies how compliance with the standard can be achieved; and then eventually implement a cleanup plan. Thus, as noted in 2001 by the National Academy of Sciences’ National Research Council, water quality standards are the foundation on which the entire TMDL program rests: if the standards are flawed, all subsequent steps in the TMDL process will be affected. We asked the states to report the total number of designated use changes they adopted from 1997 through 2001. While some states made no use changes, others made over 1,000 changes. At the same time, nearly all states told us that designated use changes are needed. Twenty-eight states reported that between 1 to 20 percent of their water bodies need use changes; 11 states reported that between 21 and 50 percent of their water bodies need use changes; and 5 states reported that over 50 percent of their water bodies need use changes. These percentages suggest that future use changes may dwarf the few thousand made between 1997 and 2001. For example, Missouri’s response noted that while the state did not make any use changes from 1997 through 2001, approximately 25 percent of the state’s water bodies need changes to their recreational designated uses and more changes might be needed for other use categories as well. Similarly, Oregon’s response noted that while the state made no use changes from 1997 through 2001, the state needs designated use changes in over 90 percent of its basins. Many states explained their current need to make designated use changes by noting, among other things, that many of the original use decisions they made during the 1970s were not based on accurate data. For example, Utah’s response noted that because of concerns that grant funds would be withheld if designated uses were not assigned quickly, state water quality and wildlife officials set designated uses over a 4- to 5-day period using “best professional judgment.” As states have collected more data in ensuing years, the new data have provided compelling evidence that their uses are either under- or over-protective. In addition to changing designated uses for individual waters to reflect the new data, some states are seeking to develop more subcategories of designated uses to make them more precise and reflective of their waters’ actual uses. For example, a state may wish to create designated use subcategories that distinguish between cold and warm water fisheries, as opposed to a single, more general fishery use. Developing these subcategories of uses has the potential to result in more protective uses in some cases, and less protective uses in others. According to responses to our survey, a key reason state officials have not made more of the needed designated use changes is the uncertainty many of them face over the circumstances in which use changes are acceptable to EPA and the evidence needed to support these changes. EPA regulations specify that in order to remove a designated use, states must provide a reason as to why a use change is needed and demonstrate to EPA that the current designated use is unattainable. To do this, states are required to conduct a use attainability analysis (UAA). A UAA is a structured, scientific assessment of the factors affecting the attainment of the use, which may include physical, chemical, biological, and economic factors. The results of a state’s analysis must be included in its submittal for a use change to EPA. States that want to increase the stringency of a designated use are not required to conduct a UAA. UAAs vary considerably in their scope and complexity and in the time and cost required to complete them. They can range from 15-minute evaluations that are recorded on a single worksheet to more complex analyses that might require years to complete. A Virginia water quality official explained, for example, that some of the state’s UAAs are simple exercises using available data, while others require more detailed analysis involving site visits, monitoring, and laboratory work. In their responses to our survey, states reported that the UAAs they conducted in the past 5 years have cost them anywhere from $100 to $300,000. In 1994, EPA published guidance regarding use changes that specifies the reasons states may remove a designated use. Nonetheless, our survey shows that many states are still uncertain about when to conduct UAAs, or about the type or amount of data they need to provide to EPA to justify their proposed use changes. Forty-three percent of states reported that they need additional clarifying UAA guidance. Among them, Oregon’s response explained that water quality officials need guidance on whether a UAA is required to add subcategories of use for particular fish species. Virginia’s response indicated that the state needs guidance on what reasons can justify recreational use changes, noting further that state water quality officials would like to see examples of UAAs conducted in other states. Louisiana’s response similarly called for specific guidance on what type of and how much data are required for UAAs in order for EPA to approve a designated use change with less protective criteria. EPA headquarters and regional officials acknowledge that states are uncertain about how to change their designated uses and believe better guidance would serve to alleviate some of the confusion. Of particular note, officials from 9 of EPA’s 10 regional offices told us that states need better guidance on when designated use changes are appropriate and the data needed to justify a use change. Chicago regional officials, for example, explained that the states in their region need clarification on when recreational use changes are appropriate and the data needed to support recreational use changes. In this connection, an official from the San Francisco regional office suggested that headquarters develop a national clearinghouse of approved use changes to provide examples for states and regions of what is considered sufficient justification for a use change. A 2002 EPA draft strategy also recognized that this type of clearinghouse would be useful to the states. The strategy calls on EPA’s Office of Science and Technology to conduct a feasibility study to identify ways to provide a cost-effective clearinghouse. According to EPA, the agency plans to conduct the feasibility study in 2004. EPA headquarters officials have also formed a national working group to address the need for guidance. According to the officials, the group plans to develop outreach and support materials addressing nine areas of concern for recreational uses that states have identified as problematic. In addition, the group plans to develop a Web page that includes examples of approved recreational use changes by the end of 2004. The national work groups’ efforts may also help address another concern cited by many states—a lack of consistency among EPA’s regional offices on how they evaluate proposals by their states to change designated uses. Some states’ water quality officials noted in particular that the data needed to justify a use change varies among EPA regions. For example, Rhode Island’s response asserted that the state’s EPA regional office (Boston) requires a much greater burden of proof than EPA guidance suggests or than other regional offices require. The response said that EPA guidance on UAAs should be more uniformly applied by all EPA regional offices. Several EPA regional officials acknowledged the inconsistency and cited an absence of national guidance as the primary cause. EPA headquarters officials concurred that regional offices often require different types and amounts of data to justify a use change and noted that inconsistency among EPA regional offices’ approaches has been a long- standing concern. The officials explained that EPA is trying to reduce inconsistencies while maintaining the flexibility needed to meet region- specific conditions by holding regular work group meetings and conference calls between the regional offices and headquarters. While EPA has developed and published criteria documents for a wide range of pollutants, approximately 50 percent of water quality impairments nationwide concern pollutants for which there are no national numeric water quality criteria. Because water quality criteria are the measures by which states determine if designated uses are being attained, they play a role as important as designated uses in states’ decisions regarding the identification and cleanup of impaired waters. If nationally recommended criteria do not exist for key pollutants, or if states have difficulty using or modifying existing criteria, states may not be able to accurately identify water bodies that are not attaining designated uses. Sedimentation is a key pollutant for which numeric water quality criteria need to be developed. In addition, nutrient criteria are currently being developed, and pathogen criteria need to be revised. Together, according to our analysis of EPA data, sediments, nutrients, and pathogens are responsible for about 40 percent of impairments nationwide.