This section provides information on the risks posed by unsafe drinking water, the authority EPA gives to states under SDWA, differences among community water systems, EPA and the states’ processes for entering water systems’ data into SDWIS/Fed, EPA’s Enforcement Response Policy and Enforcement Targeting Tool, and EPA’s strategic targets for compliance with SDWA. While the nation’s public drinking water supplies are much less prone to outbreaks of waterborne diseases such as cholera and typhoid than they were in the 19th and early 20th centuries, waterborne-disease outbreaks caused by microorganisms do still occur. For example, according to a 2006 study, an estimated 4.3 million to 11.7 million annual cases of acute gastrointestinal illnesses in the United States are attributable to drinking water from community drinking water systems supplied by surface-water and ground-water sources. Other contaminants found in drinking water may also pose a threat to human health from long-term exposure at certain levels. For example: Long-term exposure to disinfectants—such as chlorine—that are added to water to control microorganisms and the byproducts of disinfectants may cause anemia, stomach discomfort, and eye or nose irritations. In small children and infants, inappropriate exposure to disinfectants could lead to nervous system problems. In addition, long-term ingestion of water with disinfection byproducts may increase the risk of cancer and may affect the nervous system, liver, and kidneys. Arsenic, which occurs naturally and in industrial waste, may cause skin damage and circulatory system problems and increase the risk of cancer if it is not treated. Lead and copper introduced into drinking water from the corrosion of household plumbing systems or the erosion of natural deposits may cause liver or kidney damage. Long-term exposure to lead may delay physical or mental development in infants and children. Nitrate, which comes from fertilizer runoff, septic tanks, and erosion of natural deposits, is especially harmful to infants below the age of 6 months, and exposure may cause shortness of breathe, a serious illness known as blue-baby syndrome, and, if left untreated, death. Under SDWA, EPA may authorize states meeting specified requirements to implement the PWSS program—referred to as primacy authority. For example, states must have regulations for contaminants that are no less stringent than those promulgated by EPA, adequate record keeping and reporting requirements, and adequate enforcement authority to compel water systems to comply with drinking water requirements. EPA has approved primacy authority for 49 states, 5 territories, and the Navajo Nation. EPA’s regions administer the programs in Wyoming and the District of Columbia, and for most tribes. EPA provides annual grants through the PWSS program to the states using a formula that takes into account population, geographical area, and the number of water systems covered. (EPA may also consider other relevant factors in its allocation formula.) In recent years, total EPA allocations to these grants have averaged about $100 million per year. States must provide matching funds; under the act, the PWSS grant can provide no more than 75 percent of the costs expended by a state to carry out its PWSS program. EPA’s drinking water program guidance instructs EPA regions to work with the states to develop grant workplans that include the states’ commitments to report key activities. For example, the State of Washington’s workplan includes a commitment to assure complete and accurate identification and reporting of public water system compliance. As of July 2009, more than 51,000 community water systems supplied water to the same populations year-round. Community water systems vary widely in the number of people they serve, from 25 to over a million. As figure 1 shows, small systems are the most common. However, the 8 percent of community water systems that serve more than 10,000 people supply approximately 82 percent of all community water system users. Figure 1 shows the number of community water systems in 2009 categorized by the number of people they serve. Community water systems obtain their water from groundwater reserves or from surface water sources. They may obtain, treat, and distribute their water entirely on their own, or they may purchase treated water from another system. Treatment generally consists of filtration, sedimentation, and other processes to remove impurities and harmful agents, and disinfection processes such as chlorination to eliminate biological contaminants. Community water systems must meet a variety of health-based requirements under SDWA. These include providing drinking water that meets numerical limits for some contaminants, using treatment techniques for other contaminants, and using laboratory testing to monitor and report on the quality of the drinking water that they provide. Under SDWA, EPA may establish an enforceable standard—called a maximum contaminant level, or MCL—that limits the amount of a contaminant that may be present in drinking water. If EPA determines it is not economically or technically feasible to ascertain the level of a contaminant, the agency may instead establish a treatment technique to prevent known or anticipated health effects. In total, EPA has set MCL or treatment technique standards—known as the National Primary Drinking Water Regulations—for 89 regulated contaminants. We refer to violations of these standards as health-based violations. EPA has also established monitoring, reporting, and other requirements for each of the 89 regulated contaminants. In this report we refer to these requirements collectively as monitoring requirements and refer to violations of these requirements as monitoring violations. These requirements may vary depending on several factors. For example, the frequency of monitoring may depend on whether the system obtains its water from ground water or surface water sources or upon the size of the water system. Additionally, if the water system detects certain contaminants above a specified amount, it may need to increase the frequency of its monitoring. Community water systems must also notify the public within specified times about the occurrence of health-based or monitoring violations and provide their customers with an annual Consumer Confidence Report containing data on the presence and concentrations of the 89 regulated contaminants. Most of the states enter data they collect and generate on community water systems into a version of SDWIS designed for use by the states known as SDWIS/State. As EPA promulgates new or revised regulations for particular contaminants, it develops new SDWIS versions to capture data associated with those regulations. EPA encourages the states to place their water systems’ data into SDWIS/State but the states may choose not to if they have an alternative database that meets their needs while also complying with EPA recordkeeping requirements. The data include inventory information about each system, such as its name, owner, address, and the size of the population it serves. The data also include the results of the water monitoring conducted according to contaminant- specific schedules by each system, the state’s determination of whether the system has committed violations, and a record of enforcement actions taken. According to EPA, every 3 months, the states must transfer certain information from either SDWIS/State or their alternative data system to SDWIS/Fed. Specifically, the states transfer to SDWIS/Fed data on the health and monitoring violations identified and enforcement actions taken, and whether the state has determined that the system has returned to compliance. SDWIS/Fed is the data system EPA uses to gauge community water systems’ compliance with SDWA. In 2006, EPA and the Association of State Drinking Water Administrators set a goal that 90 percent of health- based drinking water violations be completely and accurately reported to SDWIS/Fed. EPA, however, does not have a goal for the completeness and accuracy of data on monitoring violations. Under its 2009 Drinking Water Enforcement Response Policy, EPA is to identify water systems with the most serious compliance problems and direct enforcement resources to these systems. An important component of EPA’s enforcement policy is its Enforcement Targeting Tool for identifying water systems with the most serious compliance problems. The Enforcement Targeting Tool assigns a score to each water system based on an accounting of unresolved violations over a 5-year period. Because some violations may have more serious health consequences than others, the tool assigns each violation a “weight” or number of points based on the potential threat to public health: acute health violations are worth 10 points, other health violations and some major monitoring violations are worth 5 points, and all other monitoring violations are worth 1 point. Additional points are added for each year a violation remains unresolved. Points for each violation at a water system are summed to generate the system’s score. Water systems whose scores meet or exceed a certain threshold—EPA has set the threshold at 11 points—are considered to have serious compliance problems and are placed on a priority list of water systems that the states and EPA are to target for enforcement. Using this approach, EPA and the states target resources to address those water systems that EPA determines have the most significant problems complying with SDWA’s requirements. EPA’s Enforcement Response Policy also provides guidance on the amount of time in which states and EPA regions should address violations at priority water systems. Once systems have been targeted as a priority, states and the regions have 6 months to work with them in whatever manner they deem appropriate to resolve violations and return the system to compliance. Enforcement and compliance assistance may include a range of actions such as providing violation notification letters to systems, offering them technical assistance, conducting site visits to resolve violations, entering into compliance agreements such as consent orders, and additional formal actions such as issuing administrative orders, assessing fines or penalties, and filing or referring judicial cases. In situations where the system is unlikely to return to compliance within the 6-month time frame, EPA’s policy calls for states or the regions to take a formal enforcement action within 6 months that will put the system “on the path” to compliance by laying out future actions and time frames the system needs to follow. According to EPA, states and the regions are required to enter information on enforcement actions, including violation resolution, into SDWIS/State or the equivalent system as they occur and send those data to SDWIS/Fed every 3 months.