Emissions from oil and gas exploration, development, and production activities in the outer continental shelf (OCS) of the Gulf of Mexico Region (GOMR) can contribute to a range of impacts in the region, including increased levels of criteria air pollutants (e.g., ozone and particulate matter [PM2.5 and PM10]), acid deposition, and decreased visibility. This is of direct importance to public health and welfare as there are areas around the Gulf that are in nonattainment with the National Ambient Air Quality Standards (NAAQS; e.g., the Houston area for ozone) and the presence of both Class I and Class II areas. Class I areas are given special air quality and visibility protection by the Clean Air Act (CAA). These areas include national parks larger than 6,000 acres and national wilderness areas larger than 5,000 acres that were in existence when the CAA was amended in 1977. All other areas have somewhat less stringent protection from air quality deterioration and are designated as Class II.
The Bureau of Ocean Energy Management (BOEM) is required to comply with the NAAQS, set by the Environmental Protection Agency (EPA) for pollutants considered harmful to public health and the environment, to the extent that oil and gas exploration, development, and production sources in the OCS significantly affect the air quality of any state10. BOEM meets these requirements by conducting dispersion and photochemical modeling, and using the results to estimate the individual and cumulative impacts of offshore oil and gas exploration, development, and production activities. If these offshore oil and gas activities significantly affect air quality of any state or Class I/II national park and wilderness areas, the OCS facility is subject to regulations and emissions controls to ensure compliance with the NAAQS.
BOEM’s air quality analyses for the GOMR have not been updated in decades. The last cumulative impacts modeling assessment, Gulf of Mexico Air Quality Study, was completed in 1995 (Systems Applications International et al., 1995). Likewise, BOEM’s current emission exemption thresholds (EETs), which screen for whether a proposed source can be expected to cause or contribute to a violation of the NAAQS, were developed in the 1980s and the NAAQS has undergone several revisions since that time. To update BOEM’s impact assessments and to ensure compliance with the Outer Continental Shelf Lands Act and National Environmental Policy Act, BOEM asked a team of contractors in 2014 to conduct the Air Quality Modeling in the Gulf of Mexico Region Study (the “Study”). The analysis includes developing input datasets—such as emissions estimates for all sources, meteorology, and pre-existing pollutant concentrations—and conducting dispersion and photochemical modeling of how OCS oil and gas activities may affect nearby states (see Table 1.1).
Because the Study will likely lead to regulatory changes, BOEM determined that the Study may be “highly influential” and asked the National Academies of Sciences, Engineering, and Medicine (the National Academies) to provide an independent technical review of the Study. The National Academies Board on Atmospheric Sciences and Climate (BASC) appointed an ad hoc
10 Text modified in January 2020. Removed mention of the Clean Air Act to keep the focus on the NAAQS and the Study objectives.
committee to conduct this review. The committee’s statement of task states that the committee should provide an overall critique of the study and address the following questions:
- Does the study meet its stated goals?
- Does the study accurately reflect the scientific literature? Are there any critical content areas missing from the study?
- Are the data inputs to modeling analyses reasonable, well documented and adequately supported by existing literature?
- Are the approaches to quantitative modeling reasonable and adequately supported by existing literature?
- Are the findings documented in a consistent, transparent, and credible way?
- Is the study consistent with guidelines in Appendix W of 40 CFR part 51 (EPA)?
The Study was previously reviewed by three experts in a “Science Review Group” and was also reviewed by several EPA and Gulf state personnel. Following those reviews, the Study was
Table 1.1 Mapping of Study Objectives to Study Sections
|Specific Objectives of the “Air Quality Modeling in the GOM Study”||Where Addressed in the Study|
|A.||To evaluate current Weather Research and Forecasting (WRF) model datasets for the Gulf of Mexico (GOM) and, if necessary, develop a new GOM 5-year meteorological WRF dataset that is sufficient to serve as input for air quality models.||Chapter 2 and Appendix B-1|
|B.||To perform a 40 CFR Part 51 Appendix W Section 3.2.2 “Equivalency Demonstration” for modeling purposes (i.e., AERMOD-Coupled Ocean Atmosphere Response Experiment) for the GOM.||Chapter 5 and Appendix E-1|
|C.||To examine through use of dispersion and photochemical air quality modeling if the current existing exemption levels are protective of the annual and short-term NAAQS onshore.||Chapter 5 and Appendices E-2 to E-7|
|D.||To develop new exemption level thresholds, if necessary, using modeling and statistical methods if the existing exemption level thresholds are not protective of all NAAQS.||Chapter 5 and Appendix E-8|
|E.||To assess air quality cumulative impacts to any state from offshore OCS activities, including assessing Multi-Sale 2017-2022 Scenario impacts, using photochemical air quality modeling.||Chapters 3 and 4, Appendices C-1, C-2 and D-1|
|F.||To conduct visibility impact analysis for the GOM Class I areas: Breton Wilderness, Saint Marks Wilderness, Chassahowitzka Wilderness, and Bradwell Bay.||Chapter 4|
NOTE: BOEM provided the committee with the Study objectives, which are not clearly identified in the Study.
revised and published in September 2019.11 The issues raised in this review will be considered for a separate, future update to the Study. A previous version of the Study was contained in an Environmental Impact Statement, which was open to public comment.12
To address its charge, committee members read the full Study and held one in-person meeting on July 16-18, 2019, in Washington, DC. This meeting included an open session to speak with a BOEM representative and the Study authors to ask clarifying questions. The committee also heard from experts from the oil and gas industry to provide more context on OCS emissions, and from the EPA Office of Air Quality Planning and Standards to provide an overview of air quality modeling requirements. Furthermore, the committee held one webinar on August 13. In closed sessions, the committee members discussed the Study and prepared their report.
This report’s Chapter 2 provides the committee’s review of the Study and includes both an overall assessment as well as feedback specific to the individual chapters. Subsequent sections also assess how well the Study meets its objectives and provide recommendations for improvements to the Study. The committee is mindful that some of the recommendations would require a significant amount of work, and therefore, may be better suited for future BOEM air quality modeling studies. Minor comments and editorial suggestions were not a significant focus for the committee.
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