Since Barack Obama was sworn in as President of the United States in 2009, the Environmental Protection Agency (EPA) has proposed and promulgated numerous regulations under many of the 11 pollution control statutes Congress has directed it to implement. Most of these statutes were enacted decades ago and have not been amended for more than a decade, yet the agency is still addressing for the first time numerous directives given to it by Congress, while also addressing newly emerging pollution problems and issues. The statutes also mandate that EPA conduct periodic reviews of many of the standards and rules that it issues. The agency has conducted these reviews, as well, and revised some regulations in response to the reviews. Although supporters have maintained that EPA is just doing its job, the agency's regulatory actions over the eight years have drawn attention for several reasons. In some cases, such as regulation of greenhouse gas emissions, they represented a new departure. Based on a 2007 Supreme Court ruling that greenhouse gas emissions are air pollutants under the Clean Air Act's definition of that term, the agency undertook numerous regulatory actions setting emission standards or laying the framework for a future regulatory structure. In other cases, the agency revised emissions, effluent, and waste management regulatory decisions made during earlier Administrations and promulgated more stringent standards to address pollution that persists as long as 40 years after Congress directed the agency to take action. These actions were driven by statutory requirements to reexamine regulations, by legal challenges and court decisions, or because of changing technologies or new and evolving scientific information. EPA's actions, both individually and in sum, generated controversy. For example, the U.S. Chamber of Commerce described EPA's actions as "a series of one-sided, politically-charged regulations that are intended to take the place of legislation that cannot achieve a consensus in the Congress." Affected parties, such as the National Petrochemical & Refiners Association (now known as the American Fuel and Petrochemical Manufacturers), labeled the agency's actions "overreaching government regulation" and "a clear distortion of current environmental law," while the National Mining Association said that "even at a time of great economic stress, EPA is poised to enact a series of back-door mandates that threaten to cost millions of American jobs, and increase the cost of their electricity while they're at it." Both Democrats and Republicans in Congress expressed concerns and criticism, through bipartisan letters commenting on proposed regulations, in statements at congressional hearings, and through introduced legislation that would delay, limit, or prevent certain EPA actions. Committees have conducted vigorous oversight of the agency's actions; oversight and efforts to limit EPA's activities accelerated in the 114 th Congress. Arguing in favor of riders to the FY2016 Interior, Environment, and Related Agencies appropriations bill intended to restrain the Administration's regulatory efforts, the Senate majority leader reportedly referred to Administration regulatory efforts as "an all-out assault on the American economy.... But in all the overreach, none has been more dramatic than at the EPA." In response to announcement of a final rule defining "waters of the United States" under the Clean Water Act, the chairman of the Senate Environment and Public Works Committee characterized the rule as "a measure that hugely expands the ability of this aggressive agency to disregard the conservation efforts of American states and interfere with the daily lives and property of the American people." EPA was not silent as the agency's actions came under attack. In a 2010 letter to the ranking members of the Energy and Commerce Committee and its Subcommittee on Oversight and Investigations, then-EPA Administrator Lisa Jackson stated the following: The pace of EPA's Clean Air Act regulatory work under this administration is actually not faster than the pace under either of the two previous administrations. In fact, EPA has finalized or proposed fewer Clean Air Act rules (87) over the past 21 months than in the first two years of either President George W. Bush's administration (146) or President Clinton's administration (115). In congressional testimony and other fora, Administrator Gina McCarthy, head of the agency from July 2013 to January 2017, sought to rebut critics' challenges to EPA's actions and initiatives. When it comes to the American economy, cutting pollution doesn't dull our competitive edge, it sharpens it. Thanks to our fuel efficiency standards, the auto industry is once again a source of economic strength. The number of cars coming off American assembly lines, made by American workers, is the highest it's been in 12 years. From catalytic converters to smoke-stack scrubbers, America has a legacy of innovating the world's leading environmental technologies—accounting for more than 1.5 million jobs and $44 billion in exports in 2008 alone. That's more than other big sectors like plastics and rubber products. If you want to talk return on investment, in over four decades, we've cut air pollution by 70 percent, while our GDP has tripled. Environmental groups generally believe that the agency moved in the right direction, but in several cases they would have liked the regulatory actions to be stronger or to have occurred sooner. Many also feared that decisions to delay the issuance or implementation of several standards were bad omens. Commenting on EPA's 2010 request to delay the issuance of air emission standards for boilers, for example, Clean Air Watch stated that "there is an unfortunate appearance here that political pressure from Congress is affecting the situation. That EPA is running scared." While industry groups have been the most frequent critics of EPA regulation, industry sometimes complains of a lack of EPA action. In 2014, the CEO of the American Petroleum Institute complained that regulations dealing with renewable fuels were overdue, calling it "unacceptable," and "an example of government at its worst." The American Fuel and Petrochemical Manufacturers, seeking issuance of the same rule, called the agency's track record in failing to issue regulations "an egregious pattern of non-compliance." It is not this report's purpose to render a verdict on whether EPA overreached, ran scared, or followed the directions and used the authorities given to it by Congress during the eight years of the Obama presidency. Statements characterizing EPA's actions, such as those cited above, depend on judgments as to whether the agency correctly determined the level of stringency needed to address an environmental problem, and whether the agency's actions are justified by the legislative mandates that Congress imposed and statutory authorities that Congress provided. Congress and the courts may render these judgments. This report provides a factual basis for discussion of these issues, which must ultimately be evaluated on a case-by-case basis. The report identifies and briefly characterizes major regulatory actions promulgated, proposed, or under development by EPA from January 2009 to late 2016. The report uses data from EPA's Semiannual Regulatory Agendas and the list of economically significant reviews completed by the Office of Management and Budget (OMB) to compile a list of regulatory actions proposed, promulgated, or under development by the agency. The list includes most EPA rules considered "economically significant" by OMB since January 2009, as well as some others that were not so designated but have been widely discussed. Each entry in this report (1) gives the name or, where appropriate, the common name of the regulatory action (e.g., the Clean Power Plan or Mountaintop Mining in Appalachia); (2) explains what the action does; (3) states the current status of the rule or action (e.g., proposed September 20, 2013); (4) explains the significance of the action, providing information on estimated costs and benefits, where available; (5) discusses the timeline for implementation, and whether there is a nondiscretionary congressional deadline or a court order or remand driving its development; and (6) identifies a CRS analyst who would be the contact for further information. To simplify presentation, in some cases, we have summarized several separate, but related, regulations under one heading. This is not a complete list of the regulations that EPA has proposed or promulgated during the Obama Administration. Rather, it is an attempt to identify the most significant and most controversial. A complete list would be substantially longer. Not all of the rules discussed here are Obama Administration initiatives. Many began development under the Bush Administration (or earlier, in some cases), including several that were promulgated under that Administration and subsequently were vacated or remanded to EPA by the courts. Within the Clean Air Act group, for example, most of the major rules, including the agency's boiler rules and two of the major rules affecting electric power plants (the Cross-State Air Pollution Rule and the Utility MACT/MATS rule) fit that description. Similarly, EPA's regulation of power plant cooling water intake structures under the Clean Water Act is governed by a 1995 consent decree and rules issued and proposed in several phases beginning in 2001. Other EPA actions, such as reconsideration of the ozone air quality standard, actually delayed for several years implementation of Bush Administration rules that strengthened existing standards. All of these are described in detail below. Several other generalizations are worth underlining: Many proposed and "pre-proposal" rules linger for years without being promulgated. They may also be substantially altered before they become final and take effect, as a result of the proposal and public comment process, and/or judicial review. For proposed rules, we attempted to provide known deadlines, whether statutory or court-ordered. If there were no known deadlines, we attempted to provide EPA's estimate of the schedule for promulgation. Proposal or promulgation often took longer than estimated in cases that did not have a court-ordered deadline. Although they were the most likely deadlines to be met, even court-ordered dates for proposal or promulgation occasionally changed. It was not uncommon for EPA to request extensions of time, often due to the need to analyze extensive comments or reevaluate technical information. Promulgation of standards is not the end of the road. Virtually all major EPA regulatory actions are subjected to court challenge, frequently delaying implementation for years.