The operation of an airport involves many activities that can affect the environment. In addition to potential impacts to local air and water quality, aircraft noise levels may affect property values or the quality of life of residents in nearby communities. Certain activities or projects to address airport environmental impacts may qualify for federal funding. For example, in its FY2008 budget, the Federal Aviation Administration (FAA) requested $354 million to meet the agency's "Environmental Stewardship" goals. Among other uses, those funds may be spent on projects to abate airport noise impacts (e.g., soundproofing of residential homes, purchases of noise barriers and monitors, and relocation of persons or businesses); to minimize water quality impacts (e.g., funding of projects that would control the discharge of deicing chemicals); and to reduce airport-controllable air emissions (e.g., purchases of alternative fuel vehicles). Funds also are authorized for research into new aircraft technology that would reduce noise and air emissions. Funding authorization for FAA programs set forth in Vision 100—Century of Aviation Reauthorization Act ( P.L. 108 - 176 , hereinafter referred to as "Vision 100") expired at the end of FY2007. On February 14, 2007, the FAA's reauthorization proposal, entitled the Next Generation Air Transportation System Financing Reform Act of 2007 ( H.R. 1356 and S. 1076 , hereinafter referred to as "the FAA proposal"), was introduced by request. Subsequently, reauthorization proposals have been passed by the House ( H.R. 2881 , the FAA Reauthorization Act of 2007) and reported by the Senate ( S. 1300 ; S.Rept. 110 - 144 , the Aviation Investment and Modernization Act of 2007). Each bill includes environment-related provisions that would fund projects intended to minimize environmental impacts or help airports comply with regulatory obligations; fund research, such as new technology that would produce quieter, more fuel-efficient aircraft; and amend existing environmental regulatory requirements. To illustrate why airports may need these funds and how they could potentially utilize them, this report provides an overview of the main environmental impacts associated with airport operations: noise, water quality, and air quality. Also discussed are the environmental review requirements of the National Environmental Policy Act of 1969 (NEPA, 42 U.S.C. §§ 4321-4347) and an overview of environmental provisions in proposed legislation to reauthorize FAA programs. This report does not discuss the national or international environmental impacts of aviation in general. Therefore, a discussion of the aviation industry's potential contribution to global warming is not discussed. However, information about this issue is included in the "For Additional Information" section below. In the next 15 years, air travel is projected to grow significantly. As a result, airport development and expansion projects will likely become increasingly important. A potential challenge to the completion of these projects is community concern regarding airport environmental impacts. Airport operations involve a range of activities that affect the environment, including the operation of aircraft; the operation of airport and passenger vehicles, and airport ground service equipment (GSE); cleaning and maintenance of aircraft, GSE, and motor vehicles; deicing and anti-icing of aircraft and airfields; fueling and fuel storage of aircraft and vehicles; airport facility operations and maintenance; and construction. The environmental impacts of these activities may intensify if an airport is undergoing expansion. In some cases, before a state or local agency will allow an airport to move forward with an expansion project, the airport authority must agree to implement certain environmental mitigation projects. Community concern regarding environmental impacts has caused projects to be delayed or cancelled. All airports, regardless of size or location, are regulated to some degree under local, state, tribal, or federal environmental requirements. Many of the environmental regulatory requirements applicable to noise, water, and air quality have been in effect for years—airport managers are accustomed to their compliance requirements. However, the anticipated growth in air travel has heightened the significance and complexity of some environmental regulatory issues. Also, several new requirements are expected to result in potentially significant changes to airport operations (in terms of procedural changes and potential investment in infrastructure). The most significant issues include continuing community concern about noise, changes to Environmental Protection Agency (EPA) regulations applicable to aircraft and airfield deicing operations, changes to EPA regulations applicable to oil spill prevention planning, and state and local agency directives to monitor and control air pollution, particularly toxic air pollutants. Each of these issues is discussed below within the context of requirements applicable to noise, water quality, and air quality issues. Primarily, the issues discussed in this report involve activities that are unique to airport operations (e.g., deicing and aircraft noise). Environmental compliance requirements commonly applicable to all industrial operations (e.g., waste management, pesticide use, chemical use reporting) are not discussed in this report. Aviation noise may have a negative impact on the quality of life and property values of members of a surrounding community. (Direct health impacts of noise are more difficult to determine.) Although the percentage of people affected by aircraft noise has been significantly reduced during the past 35 years by advancements in aircraft technology and noise abatement efforts, aircraft noise is often the principal focus for community groups and larger non-governmental organizations that oppose runway expansion. Despite improvements, noise continues to be a significant problem because the amount of air traffic is growing, the number of airliners and corporate jets is increasing, and airline traffic and noise is concentrated at a small number of airports that are also likely to be among the largest airports. An airport may use various approaches to address airport noise issues. Selected approaches, and challenges to implementing them, are summarized in Table 1 . Each approach is potentially eligible for federal funding. Ultimately, decisions regarding mitigation measures and operational changes are made by the airport authority in accordance with requirements of the state or local government; land use restrictions can be suggested by the airport authority, but are implemented entirely at the discretion of local government. The federal role is primarily to fund those efforts, establish aircraft noise limits, and fund research. Interested stakeholders have debated for a long time how funding dollars should be allocated. Airports are likely to prefer funding short-term operational and mitigation strategies to address immediate needs. Others argue that an increased proportion of federal funding should be directed toward research. For example, according to the NAS, the National Aeronautical and Space Administration (NASA) has set technically feasible noise reduction goals, but the level of funding for its research programs is too low to achieve the current goals on schedule or to remove noise as an impediment to the growth of aviation. For more information on airport noise requirements, see the "Mitigating Aircraft Noise Through Policy and Technology" section of CRS Report RL33698, Reauthorization of the Federal Aviation Administration: Background and Issues for Congress , by [author name scrubbed] et al., and CRS Report RS20531, Noise Abatement and Control: The Federal Role , by [author name scrubbed]. Airport operations include many activities likely to result in the discharge of pollutants to adjacent water bodies. Those activities include aircraft and airfield deicing and anti-icing, fuel storage and refueling, aircraft and vehicle cleaning and maintenance, and construction. These activities are regulated under provisions of the Clean Water Act (CWA). The CWA prohibits any "point source" (a discrete conveyance such as a drainage ditch, pipe, or other outfall) from discharging pollutants into waters of the United States. The primary mechanism for controlling pollutant discharges is through the administration of the National Pollutant Discharge Elimination System (NPDES) permit program, which is implemented, in most cases, by individual states. The NPDES permit program regulates discharges of stormwater and wastewater. Due to the nature of their outdoor operations and because airports are included in one of the industrial categories regulated under the NPDES stormwater permitting program (under the Standard Industrial Classification code "Transportation by Air"), all airports are required to have a stormwater permit. Airports that discharge other wastewater, such as from equipment maintenance and cleaning operations, require an additional NPDES wastewater permit. Discharges associated with stormwater often pose the greatest challenge to airport managers, because airports may be spread out over a wide surface area, with a majority of operations exposed to the elements. For example, the Dallas Forth Worth International Airport encompasses 18,000 square acres and has 62 stormwater outfalls. Controlling or monitoring every outfall is difficult. The primary method for controlling stormwater discharges is the implementation of best management practices (BMPs) that prevent or minimize the discharge of pollutants into a water body (e.g., construction of a stormwater retention pond to prevent stormwater drainage directly into receiving waters). BMPs appropriate for one airport are not necessarily appropriate for another. Factors that may affect permit requirements (i.e., appropriate BMPs), include the local climate (dry versus rainy/wet, cold versus warm); the type or size of adjacent water bodies—pollutants are diluted depending on the size of the water body receiving the discharge (e.g., a creek or stream versus a river or ocean); the water quality of adjacent water bodies—local permitting authorities consider existing pollutant levels when controlling airport discharges; and airport size. To comply with the Clean Water Act, most airport operators are particularly concerned about managing deicing chemicals and preventing oil spills. With regard to water quality compliance issues, the management of deicing and anti-icing chemicals poses the greatest challenge to many airport operators. The deicing and anti-icing of aircraft and airfield surfaces is required by the FAA to ensure the safety of passengers. However, when performed without discharge controls in place, airport deicing operations can result in environmental impacts. Discharges from deicing operations have the potential to cause fish kills, algae blooms, and contamination to surface or ground waters.