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Case Law Updates on the Environment (CLUE)

Case Law Update Details

Case Title

Vaughn v. FAA

Case No.

2018 WL 6430368


U.S. Court of Appeals - D.C. Circuit






Southern California Metroplex Flight Plans

Project Type


Project Description

In 2016, FAA approved new air traffic control procedures and flight paths at several airports in southern California, known as the Southern California (SoCal) Metroplex project. FAA issued an EA and FONSI to comply with NEPA.

Case Summary

Multiple parties filed petitions for review of FAA’s approval of the SoCal Metroplex project. The petitioners alleged that FAA violated NEPA by failing to adequately analyze noise impacts, greenhouse gas emissions, and cumulative impacts, and failing to consider a reasonable range of alternatives. The petitioners also alleged that FAA violated the Clean Air Act by incorrectly concluding that the project would be in conformity with state implementation plans. The petitioners also claimed that the new flight paths and procedures did not comply with the Vision 100 Act. The court denied the petitioners for review and upheld the project.

Key Holdings


Noise Modeling Software.  The petitioners argued that FAA used an outdated software program to analyze noise levels, in violation of an FAA guidance memorandum. FAA’s guidance memorandum required a new software program to be used for environmental analyses that started after March 1, 2012. FAA stated that although the dataset for its environmental analysis covered the period from December 2012 to November 2013, it began noise screening prior to March 2012. The court held that FAA reasonably interpreted its guidance memorandum to mean that the preliminary noise screening constituted “environmental analysis.” Therefore, deferring to FAA’s interpretation of the guidance memorandum, the court held that FAA was not required to use the new software because its environmental analysis started before March 2012.

Noise Metric.  The petitioners claimed that FAA used the incorrect metric to analyze noise impacts. The petitioners argued that FAA should have used the Cumulative Noise Equivalency Level (CNEL), which weights evening noise more heavily, rather than the Day-Night Sound Level (DNL). According to an FAA order on environmental analysis, DNL is the primary metric for determining noise impacts, but CNEL may be used when a state requires that metric. Because the project did not involve any state environmental review, the court agreed with FAA that it was not required to use CNEL to analyze noise impacts.

Climate Change - GHG Emissions.  The EA determined that the project would not have a significant impact on climate change because it would increase greenhouse gas (GHG) emissions by 35 metric tons (0.41%) in 2016 and 42 metric tons (0.44%) in 2021. The petitioners argued that the Council on Environmental Quality (CEQ) guidance on evaluating GHG and climate change impacts under NEPA did not permit FAA to state that there would be negligible effects based on a small increase in GHG emissions. The court disagreed. The court noted that the CEQ guidance did not recommend a quantitative analysis for emissions below 25,000 metric tons unless quantification could be easily accomplished. “In this case, the 42 MT increase in emissions in 2021 is far less than the 25,000 MT threshold at which disclosure was suggested by the CEQ. As it is not clear the FAA had a duty even to quantify the increase in emissions, we agree with the FAA’s reasonable conclusion that the project would not have a significant effect on the climate.” (Note: The CEQ guidance was later withdrawn in 2017, although the court did not address the impact of this development.)

Cumulative Impacts.  The petitioners claimed that FAA violated NEPA by failing to analyze cumulative noise impacts. The court agreed that FAA was not required to conduct a cumulative impact analysis where it had determined that the project would have no significant noise effect. “[W]e see no reason to think it is arbitrary and capricious for an agency not to conduct a cumulative impact analysis for a particular environmental resource after the agency reasonably has concluded its proposed action will not have a significant effect on that resource.”

Range of Alternatives.  The petitioners argued that the EA was deficient because it only considered the proposed action and the no-action alternative. The court held that the alternatives analysis in the EA was adequate: “As the FAA points out, it evaluated various groups of procedures in different combinations, in order to determine what ‘action alternative’ to present in the Final Environmental Assessment. In our view, given the nature and complexity of the project, the FAA has satisfied its duty to consider appropriate alternatives.”

Clean Air Act

Conformity.  FAA determined that the SoCal Metroplex project qualified as an action that was presumed to conform to an applicable state implementation plan (SIP). Specifically, an FAA regulation provided that modifications to flight routes at or above the mixing height (generally 3,000 feet above ground level) are presumed to conform with a SIP, and modifications below that altitude are presumed to conform with a SIP if they are designed to enhance operational efficiency. The petitioners challenged FAA’s reliance on this conformity presumption for the SoCal Metroplex project. The EA explained that the changes to flight paths would primarily occur at or above 3,000 feet. The court held that any flight path modifications below 3,000 feet were designed to enhance operational efficiency because the purpose of the SoCal Metroplex project was to address congestion and improve safety, even if the changes would slightly increase fuel burn.

Vision 100 Act

The petitioners argued that FAA did not comply with the Vision 100 Act because it did not attempt to reduce noise below pre-existing levels. The court held that the Vision 100 Act required FAA to consider reducing noise and emissions pollution “to the greatest extent practicable” along with six other goals. Here, the court concluded, FAA had sufficiently considered reducing noise levels because it modified the project to address community concerns about noise.

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