The objective of the Clean Water Act is to restore and maintain the chemical, physical, and biological integrity of the nation’s waters. The Congress established a series of national goals and policies to achieve this objective, including what is referred to as “fishable/swimmable” water quality. That is, whenever attainable, the quality of the water should be such that it provides for the protection of fish, shellfish, wildlife, and recreation in and on the water. To help meet national water quality goals, the act established the NPDES program, which limits the discharge of pollutants through two basic approaches—one based on technology and the other on water quality. Under the technology-based approach, facilities must stay within the discharge limits attainable under current technologies for treating water pollution. EPA has issued national minimum technology requirements for municipal facilities and 50 categories of industrial dischargers. The states’ and EPA’s permitting authorities use these requirements to establish discharge limits for specific pollutants. In contrast, under the water-quality-based approach, facilities must meet discharge limits derived from states’ water quality standards, which generally consist of (1) “designated uses” for the water bodies (e.g., propagation of fish and wildlife, drinking water, and recreation) and (2) narrative or numeric criteria to protect the designated uses. Narrative criteria are generally statements that describe the desired water quality goal, such as “no toxics in toxic amounts.” Numeric criteria for specific pollutants are generally expressed as concentration levels and target certain toxic pollutants that EPA has designated as “priority pollutants.” In addition to adopting water quality standards, the states may also establish policies concerning certain technical factors that affect the implementation of the standards in the discharge permits. For example, many states have adopted policies for (1) establishing mixing zones (limited areas where discharges mix with receiving waters and where the numeric criteria can be exceeded), (2) determining the amount of available dilution (the ratio of the low flow of the receiving waters to the flow of the discharge), and (3) considering background concentration (the levels of pollutants already present in the receiving waters). When the states’ and EPA’s permitting authorities are deciding how extensively the pollutants should be controlled in a facility’s permit, they first look to the technology-based standards. If the discharge limits derived by applying these standards are not low enough to protect the designated uses of the applicable water body, the permitting authorities turn to the state’s water quality standards to develop more stringent limits. To achieve the tighter limits, a facility may have to install more advanced treatment technology or take measures to reduce the amounts of pollutants needing treatment. For additional information on the role of EPA’s headquarters and regional offices and the state agencies in establishing standards and implementing them in permits, see appendix I. As agreed with your office, this report focuses on the water-quality-based approach to controlling pollution and the way the states’ and EPA’s permitting authorities are implementing water quality standards in the NPDES permits issued to “major” facilities. As of July 1995, approximately 59,000 municipal and industrial facilities nationwide had received permits under the NPDES program, and about 6,800 of these permits were for major facilities, including about 4,000 municipal facilities and 2,800 industrial dischargers. Our review of the data on municipal permits for five commonly discharged toxic pollutants disclosed that decisions about whether and how to control pollutants differed both from state to state and within states. In some instances, differences in the limits themselves, or in the standards and policies used to derive the limits, have led to concerns between neighboring states. Using EPA’s Permits Compliance System database, we extracted data on the 1,407 permits issued to municipal wastewater treatment facilities nationwide between February 5, 1993, and March 21, 1995, to determine what types of controls, if any, the states’ and EPA’s permitting authorities had imposed in these facilities’ discharge permits for five toxic metal pollutants—cadmium, copper, lead, mercury, and zinc. We found that when the permitting authorities decided that some type of control was warranted, some consistently established numeric discharge limits in their permits, and others imposed monitoring requirements in all or almost all cases. For example, North Carolina issued 93 permits during our review period and, whenever it determined that a pollutant warranted controls, it always established numeric discharge limits rather than impose monitoring requirements. Other states, such as New York and West Virginia, also consistently established numeric limits for controlling the five pollutants we examined. In contrast, New Jersey issued 44 permits during our review period and, except for 1 permit that contained a limit for copper, the state always imposed monitoring requirements instead of discharge limits when the state determined that controls were warranted. Oregon, among other states, made similar decisions, as did EPA’s Region VI when it wrote permits for Louisiana, a state not authorized to issue NPDES permits. We also found that some states, such as Vermont and Arkansas, had not imposed discharge limits or monitoring requirements in the following instances in which EPA’s regional officials said that such controls may be warranted. In Vermont, none of the discharge permits for major municipal facilities contained discharge limits or monitoring requirements for the five metals. However, at our request, the cognizant EPA regional staff (in Region I) reviewed 4 of the 15 municipal permits issued by Vermont and determined that for 2 of the facilities, limits or monitoring requirements would probably be appropriate. Vermont officials agreed to review the permits and consider additional requirements. Arkansas, with one exception, had not imposed either limits or monitoring requirements in its municipal permits for the toxic metals we examined. State officials are allowing these facilities to continue operating under “old” permits rather than reissuing them. The officials told us that if the permits were to be formally reopened, the state would be obligated to apply EPA-imposed water quality standards for the metals. Arkansas officials believe that these standards are too stringent and that the facilities would engage the state in a costly appeal process if limits were imposed. Officials from the cognizant EPA regional office (Region VI) said that the Arkansas permits should contain discharge limits but that EPA does not have the authority to impose such limits in a state authorized to issue permits when the state simply declines to reissue them. EPA’s only recourse would be to take back responsibility for the program—an unrealistic option. For facilities, both monitoring requirements and discharge limits can be costly to implement. According to officials in EPA’s Permits Division, the costs of monitoring depend on the frequency of required sampling and on the types of pollutants that must be tested. The costs of installing advanced treatment equipment to meet discharge limits are usually much higher. These officials also said that because of these differences in cost, the facilities that are subject to monitoring requirements generally enjoy an economic advantage over the facilities that must meet discharge limits, all other things being equal. Furthermore, the facilities that are subject to neither type of control enjoy an economic advantage over the facilities that must comply with limits or monitoring requirements. Overall, our analysis disclosed that for each of the five pollutants, about 30 percent of the permits contained limits or monitoring requirements, while about 70 percent contained neither type of control. According to EPA’s permitting regulations and guidance, there can be legitimate reasons for imposing no controls over some pollutants: Generally, either the facilities are not discharging the pollutants or their discharges are deemed too low to interfere with the designated uses of the applicable water bodies. See appendix II for a summary of the control decisions across the nation for the five toxic pollutants included in our analysis and for additional discussion of the reasons for not imposing limits or monitoring requirements on some pollutant discharges. Appendix III presents a state-by-state breakdown of the 1,407 permits included in our analysis. EPA and the states agree that differences in the numeric limits for specific pollutants can and do exist—not only from state to state, but from water body to water body. To illustrate these differences, we extracted data on numeric limits as part of our analysis of EPA’s data on municipal permits. Specifically, from the 1,407 permits for municipal facilities issued nationwide between February 5, 1993, and March 21, 1995, we identified those facilities discharging into freshwater (1) whose permits contained discharge limits for one or more of the five toxic metals and (2) whose plant capacity, or design flow, was included in EPA’s database. For each of the five pollutants, we found significant differences in the amounts that facilities were allowed to discharge across the nation—even for facilities of similar capacity. In the case of zinc, both the highest and the lowest limits were established in the same state. Figure 1 shows the results of our analysis. As figure 1 indicates, differences in the numeric limits for the same pollutant can be significant—in the case of mercury, about 775 times greater at one facility than at another facility of similar capacity. We discuss the causes of the differences in discharge limits later in this report. Variations in the discharge limits, or in the standards and procedures used to derive these limits, have been a source of concern, particularly when neighboring jurisdictions share water bodies and the differences are readily apparent to the permitting authorities and discharging facilities, as the following examples illustrate: In 1995, an industrial facility in Pennsylvania challenged a discharge limit for arsenic because Pennsylvania’s numeric criterion was 2,500 times more stringent than that used by the neighboring state of New York, into which the discharge flowed. Among other things, the discharger argued that having to comply with the more stringent criterion created an economic disadvantage for the company. Eventually, Pennsylvania agreed to reissue the permit with a monitoring requirement for arsenic instead of a discharge limit. The state has also revised its water quality standards using the less stringent criterion. Oklahoma challenged the 1985 permit that EPA issued to an Arkansas municipal wastewater treatment facility that discharges into a tributary of the Illinois River.