Although aviation-related activities produce a small amount of the total air pollution in the United States, according to EPA, the types of pollutants emitted by these activities are among the most prevalent and harmful in the atmosphere and are expected to increase based on the forecasted growth in the aviation sector. The major sources of emissions at airports are aircraft, the ground equipment (such as vehicles that transport baggage) that services the aircraft, and vehicles transporting passengers to and from the airport. The emissions produced by these sources include carbon monoxide; toxic substances (such as benzene and formaldehyde); particulate matter; sulfur dioxide; and nitrogen oxides and volatile organic compounds, which contribute to the formation of ozone, a major pollutant in many metropolitan areas and a major concern to many airport operators and to state and local air quality authorities. In addition, the potential health effects of particulate matter are becoming an increasing concern of these groups. In response to concerns about emissions from airport sources, the Vision 100—Century of Aviation Reauthorization Act (Vision 100), signed into law in December 2003, established a voluntary program to reduce airport ground emissions at commercial service airports in air quality nonattainment and maintenance areas. Geographic areas that have levels of a criteria pollutant above those allowed by the standard are called nonattainment areas. Areas that did not meet the standard for a criteria pollutant in the past but have reached attainment and meet certain procedural requirements are known as maintenance areas. The program, according to FAA, is intended to help airports meet their obligations under the CAA, and to assist regional efforts to meet National Ambient Air Quality Standards set by EPA for limiting the amount of the six criteria pollutants considered harmful to public health and the environment. States that have areas exceeding these standards are required to develop and implement a plan, known as a State Implementation Plan (SIP), for bringing the areas into compliance with the standards. Under the CAA conformity provision, no federal agency may approve or provide financial assistance for any activity that does not conform to an applicable SIP. To implement the Vision 100 provisions relating to airport emission reductions, FAA created and began implementing the VALE program in 2004. According to FAA, in the 9-month period between the passage of the act in 2003 and the implementation of the VALE program, the agency—in cooperation with EPA and the Department of Energy—developed program guidelines and application procedures; technical requirements, such as standards for low-emission vehicles; and a system for assigning credits to airports for emission reductions. The FAA relied on experience with the FAA Inherently Low Emission Airport Vehicle (ILEAV) Pilot Program to design the VALE program. Authorized under the Wendell H. Ford Aviation Investment and Reform Act for the 21st Century (AIR-21), the ILEAV pilot program operated from 2001 to 2005. Six airports implemented ILEAV projects with individual grants of up to $2 million each to demonstrate the benefits and economic feasibility of low-emission vehicles and supporting infrastructure. According to FAA, the pilot program projects also provided useful information about the environmental and economic trade-offs of alternative fuels, their safe handling, and the commercial availability of low-emission technology. Airports eligible for the VALE program can apply for federal AIP entitlement funds or discretionary funds under the “set-aside” for noise and air quality projects. With FAA approval, eligible airports may also use their PFCs to finance VALE projects. According to FAA officials, VALE grants using discretionary set-aside funds have no impact on the amount of entitlement funds an airport receives through AIP, since AIP entitlements are based on a legislated apportionment formula tied to the number of passengers an airport enplanes. FAA officials stated that most participating airports seek set-aside funding for VALE projects because VALE projects only compete in this portion of the AIP budget against noise reduction projects. According to FAA officials, the agency considers the approval and funding of VALE projects on a case-by-case basis based on the project’s relative importance to other eligible airport activities. FAA officials stated that prior to the establishment of VALE, the only emission- reduction projects eligible for AIP grants and PFC use were those intended to reduce emissions as a condition of approval of an environmental action associated with an AIP-funded airport development project. These officials also noted that the VALE program expands AIP and PFC eligibility into new areas, such as airport mobile sources, including vehicles. VALE projects may be stand-alone projects (i.e., they do not have to be linked to a project that could increase emissions to be eligible for program funding); however, for a project to be approved, it must meet specific criteria. For example, an airport must demonstrate that the project will result in emission reductions. Although according to FAA officials, these reductions are “surplus” in the sense that they are not required in the SIP for meeting CAA standards. To demonstrate that a project will lower emissions, an airport must prepare estimates comparing the amount of emissions currently produced with the amount of emissions that will be produced after the project is implemented. To prepare these emission estimates, airports use FAA’s Emissions and Dispersion Modeling System (EDMS), which calculates emissions from project-related airport sources, such as aircraft, ground service equipment, and shuttle buses. The airport must also demonstrate, among other things, that the VALE project will result in permanent emission reductions. According to FAA officials, using the EDMS air quality model ensures the reliability of emission- reduction estimates and reduces planning costs. VALE’s authorizing legislation and implementing guidance greatly expanded AIP and PFC eligibility for low-emission technology, including the purchase of low-emitting hybrid vehicles and electric-powered equipment used to service aircraft, such as baggage tugs. FAA officials stated that VALE employs an innovative approach by converting EPA average national fleet standards into low-emission standards for each VALE vehicle purchase. All vehicles and engines that are eligible for AIP or PFC funding under the VALE program must either be EPA certified (new vehicles) or EPA verified (retrofit technology). VALE low-emission standards for all new vehicles are based on EPA average national fleet standards and are referenced, in some cases, to comparable California Air Resources Board standards. The VALE program sets emission standards at cleaner levels than presently required by EPA. According to FAA officials, a goal of the VALE program is to encourage airports to make investments in capital equipment to provide substantial emission-reduction benefits over many years. The VALE program is also intended to support U.S. energy independence by emphasizing domestically produced alternative fuels that are substantially nonpetroleum based. Also, the program is designed to provide airports with financial and regulatory incentives to increase their investments in proven low-emission technologies. FAA officials stated that FAA, EPA, and the Department of Energy coordinate on an ongoing basis VALE program standards, including nonattainment status for airport eligibility and eligible alternative fuels. The legislation authorizing the VALE program also provides a means for airports to receive credits for the emission reductions achieved through VALE projects and use these credits to comply with federal CAA air quality standards. Before the VALE program was instituted, airports could not receive credit for voluntary emission reductions. Therefore, any voluntary reductions lowered an airport’s emission baseline, which is used to calculate the impact of future emissions, and thus airports would need to find further emission reduction options to obtain approval for future projects. In 2003, we reported that because of this situation, some airport officials told us that they waited to initiate emission-reduction efforts until these efforts were needed to gain approval for an expansion project. The EPA issued national guidance in September 2004 on how airports can receive airport emission-reduction credits (AERC) for VALE projects and apply those credits to future airport projects to meet certain CAA requirements. AERCs can be used to mitigate future airport project emissions, as long as they will be earned in the year for which they will be applied. To be approved for the VALE program, an airport must obtain a commitment from the state’s air quality authority that it will approve the use of AERCs for projects to conform to federal air quality requirements, should the airport choose to use them for this purpose. While the number of airports that have undertaken VALE projects since 2004 is relatively small compared with the number of eligible commercial airports—9 of 160—the number of participants is increasing, as are the range of projects being conducted and the amount of money spent on them. Participation in the VALE program has been limited to date, although the number of airports applying for the program is increasing, and FAA expects more airports to seek VALE funding as they become more familiar with the program. About 160 of the 524 commercial service airports are eligible to participate in the VALE program; however, as of September 2008, 9 airports had received VALE program funding. (Fig. 1 shows the locations of airports participating in VALE.) According to FAA officials, all airports that have applied to participate in VALE have been approved. Participation in the VALE program has risen in recent years. For example, in 2005, the first year of the program, FAA approved VALE projects for 2 airports. In fiscal year 2008, FAA approved 11 projects at 6 airports, 4 of which were new participants in the program. Overall, FAA reports that a total of 20 projects at 9 participating airports are under way. In fiscal year 2009, FAA expects additional VALE participants. For example, the Seattle- Tacoma International Airport has proposed a multiyear project to purchase electric ground support equipment, with a $3.1 million first phase beginning in fiscal year 2009. FAA officials stated that FAA regional officials are considering the airport’s application to fund this project through VALE.