Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
3 Introduction 1.1 Project Goal and Overview This report represents the culmination of an extensive effort to evaluate measurement and modeling techniques to better understand their uses and limitations in quantifying the contribution of airports to local air quality. The main goal of the report is to provide airport operators with guidance to combine the use of measurement equipment with air quality models to allow comprehensive quantifications of pollutant concentrations in the vicinity of airports. The guidance was developed from a combination of literature reviews and from assessments conducted using data gathered from a test airport. As presented in the appendices, the detailed assessments included evaluations of measured data and modeling capabilities. The guidance presents conclusions and findings from the assessments, recommendations for equipment usage and model applications, discussion of the gaps and limitations of the various techniques, and recommendations for improvements. All of the information gathered as part of this project is intended to add to the growing knowl- edge base of airport air quality assessments. The results provide a basis for further airport air quality research and procedures for airport operators. 1.2 Background There can be many reasons for conducting an airport air quality study, including compli- ance under NEPA to support the Clean Air Act (CAA); local (e.g., city and state) environmental regulations; and community health concerns (CFR 2008 and USEPAa 2007). If a project does not meet an exclusionary condition and an emissions inventory does not suffice, dispersion model- ing and/or atmospheric measurements may be required to demonstrate compliance by showing concentration levels are below the limits set by these regulations. The intention of regulatory acts like NEPA is to prevent or eliminate damage to the environment by various activities involving the use of federal funds. NEPA directs federal agencies like the FAA to incorporate environment in decision-making processes. The current airport air quality handbook promulgated by the FAA is the Air Quality Proce- dures for Civilian Airports and Air Force Bases, which is consistent with FAA Order 1050 and represents an effort by the FAA to provide an easy-to-understand explanation of the regulatory and decision-making process (FAA 1997). This guidance document provides interpretations for each of the regulations applicable to an airport air quality analysis and provides specific instruc- tions for each step of the assessment process [e.g., emissions inventory development, indirect source review, conformity assessments, and National Ambient Air Quality Standards (NAAQS) C h a p t e r 1
4 Guidance for Quantifying the Contribution of airport emissions to Local air Quality assessment]. The decisions made as part of the assessment for NAAQS determine whether or not atmospheric concentrations need to be determined. These regulatory-type guidance documents assume that the tools from the FAA and the USEPA will be used appropriately based on existing supporting documents (e.g., user guides and tech- nical reports). Although the supporting documents for these tools and the regulatory guidance materials appear to be sufficient, the application of the tools to airports still needs clarification. Compared to emissions inventory development, very few studies have been conducted on airport air quality issues. Due to the costs of conducting such assessments, most airport operators prefer not to conduct such work unless they are absolutely necessary (i.e., no alternatives are available). Airport air quality assessments can be complex and resource-intensive, especially for larger airports. In the interest of cost-effectiveness and resource efficiency, computer-based models generally provide the primary capability for assessing airport contributions to local air quality. But given the current shortcomings of available emissions and dispersion models, measurement programs may be necessary to compensate for model shortcomings and limitations. However, a significant component of shortcomings in model predictions is related to uncertainties or limi- tations of emissions inputs to the model. Improving methodologies for emissions factors and having accurate airport activity data will lead to greater confidence in model-based assessments. Although technological advances are allowing more and more continuous measurements, the equipment and overall resources required to conduct such work is still very expensive, and, in many cases, prohibitively expensive. As such, any use of air quality modeling work to reduce or replace measurements will be attractive to airport operators. However, the use of models (with atmospheric dispersion) can also be resource-intensive and poses greater risk of errors. In addition to the inherent errors associated with the modeling techniques employed in mod- els such as the USEPAâs workhorse dispersion model, AERMOD, myriad other sources of error are associated with the input data: aircraft fleet mix, auxiliary power unit (APU) usage times, ground access vehicle (GAV) speeds, weather data, source locations, and so forth. Any one of these datasets can have significant repercussions on the accuracy of both the resulting emissions inventories and modeled atmospheric concentrations. Although significant improvements have been (and are being) made to improve modeling capabilities by both the USEPA and FAA, much more work needs to be accomplished to make the associated tools more accurate as well as more robust and easier to use. Currently, the air quality modeling capabilities in the FAAâs Emissions and Dispersion Mod- eling System (EDMS) have some limitations concerning comprehensive analyses of airport contributions to local air quality. This is partly due to some limitations with emissions model- ing, but in larger part due to limitations such as the inability to model chemical reactions in AERMOD as implemented within EDMS. As such, the combined use of measurements and modeling are recommended in certain situations to better understand airport contributions. 1.3 Scope of Work The project involved two sets of work: 1. A comprehensive literature review of airport air quality measurements and modeling techniques. 2. Airport field data collection efforts to assess measurement and modeling techniques. The literature review involved complete coverage of all applicable USEPA models and measure- ment techniques (including associated equipment). The reviews and ensuing selections were largely based on following requirements and recommendations provided by both the USEPA and FAA.
Introduction 5 The field work started with the selection of a suitable airport (Washington-Dulles Interna- tional Airport [IAD]) to conduct extensive field measurements. The field work mainly involved the collection of ambient measurements and source (e.g., GAV movements) activity data. The activity data, as well as various other source data obtained from the airport, were used to con- duct corresponding modeling of atmospheric concentrations to evaluate the models. Tables 1-1 and 1-2 summarize the overall scope of the measurement and modeling work. Three measurement campaigns were conducted at IAD: ⢠April 17â28, 2009 ⢠January 16â24, 2010 ⢠July 9â23, 2010 In order to better understand airport contributions to local air quality and develop guidance for combining measurements with modeling, both the collected data and the corresponding modeled outputs were assessed for their adequacy in being able to explain airport air quality impacts. The overall objective of conducting the case study was to determine the adequacy of combin- ing the selected modeling and measurement techniques and identify existing gaps in the assess- ment methods relative to airport contributions to local air quality. The evaluation work involved various considerations: ⢠Model output assessments involving modeled-versus-measured comparisons and focused sensitivity assessments to understand model behavior and confidence; Equipment Pollutant or item Data type Real-time gas analyzers CO, NOx, SOx, and O3 Second-by-second concentrations Minivol gas samples CO, NOx, and SOx 1-hour average concentrations Minivol PM samples PM10, PM2.5, OC/EC, nitrate, and elemental metals 24-hour average concentrations RDI PM and elemental metals 3-hour average concentrations for 8 size categories Summa Canisters VOCs 1-hour average concentrations DNPH Cartridges, TO11 Aldehydes 1-hour average concentrations HOBO Weather stations Meteorology Wind speed, wind direction, temperature, and relative humidity Noise monitors Sound level SEL, Leq, Lmax Table 1-1. Measurement equipment and data. Models Pollutants Sources Data Resolution EDMS/AEDT CO, THC, NMHC, VOC, TOG, NOx, SOx, PM10, PM2.5, various HAPs compounds Aircraft, APUs, GSEs, GAVs on local roadways, GAVs on parking lots, Stationary boilers, Mobile Lounges 1-hour and 24-hour average concentrations at receptor locations CMAAQ CO, NO, NO2, PM2.5 components, PM10 components, VOC species, various HAPs Anthropogenic (major point, area, on-road, nonroad, locomotive, marine) and Natural (agricultural, fire, biogenic, dust) and EDMS sources 1-hour average concentrations at 12 km and 4 km grids with 34 vertical layers Table 1-2. Modeling domain.
6 Guidance for Quantifying the Contribution of airport emissions to Local air Quality ⢠Evaluation of modeling options and their impacts on modeled concentrations; ⢠Adequacy of modeled and measured data to explain seasonal, weekly, and diurnal effects; ⢠Adequacy of modeled and measured data to support regulatory needs and health impact assessments; and ⢠Source contribution assessments. These evaluations were used to develop various conclusions and recommendations which highlight significant findings as well as gaps within the resources available under this project. In conducting the measurement and modeling work, the main objective was to assess how the conclusions and recommendations apply to quantifying airport contributions to local air quality. Therefore, while some model evaluations including modeled-versus-measured and sensitivity- type assessments were conducted, this project did not include formal model validation and uncer- tainty assessments such as those specified by the USEPA (USEPAc 2011). Also, while there are some overlaps, the report generally tends to reference information found in existing documents (e.g., model user guides, modeling theories and techniques, equipment usage instructions, and laboratory assessment techniques) rather than repeating them. The purpose of the included guid- ance is mainly to support the better understanding of the application of the necessary models and equipment to quantify airport contributions to local air quality. Although some background information is provided, the guidance material was not devel- oped to serve as a primer for novice users. Various resources from the FAA and USEPA can serve as air quality measurement and modeling primers. The guidance requires a working knowledge of air quality measurement equipment and models as well as familiarity with airport air quality issues. Although an extensive set of IAD-specific data was collected through the field work, the pur- pose was not to conduct an air quality analysis of the specific airport, but to use the data to assess measurement and modeling techniques with findings that can be generalized to all airports and identify gaps for future research. In addition to the source-oriented modeling work, a concerted assessment was conducted using the measured PM data with receptor modeling techniques. This work was conducted as a supplemental analysis to demonstrate the âreverseâ process of starting with the measured concen- trations to predict source contributions to air quality. While receptor modeling is not currently (or for the foreseeable future) considered necessary in meeting regulatory requirements involving air quality assessments, its usefulness has been demonstrated in various studies, and therefore, has been included in this project for completeness in demonstrating different techniques. 1.4 Report Structure This report has been organized such that the guidance and detailed assessments are clearly separated as indicated below. 1. Main body of the reportâfocuses on the findings and guidance from the literature reviews and the assessments conducted. 2. Appendicesâpresent details of the assessment work as well as how the research work was conducted, including various decisions made. Rather than combining the guidance and assessment materials together, they were purposely separated to allow easier use of the report. The main body allows the user to concentrate on the guidance, findings, and recommendations, without being inundated by detail. In contrast, each of the appendices allow the user to focus on a specific topic that provides technical details mostly associated with the assessments conducted as part of the airport case study work.
Introduction 7 Chapter 1 provides introductory materials that explain the overall goal and the scope of workâ what is and is not included in this reportâas well as some background information explain- ing the impetus for this project. Chapter 2 summarizes the existing state of regulations and the capabilities and limitations of existing measurement and modeling techniques. In addition, a survey of recent airport air quality studies is also presented. These two first sections provide background information mainly for novice users. The measurement and modeling reviews and considerations presented in Chapter 2 help to set the stage to better understand the modeling, measurements, and integration guidance materials found in Chapters 3 through 5. As part of the guidance, important findings from the study are presented and discussed. Chapter 6 summarizes the overall conclusions and recommendations from all of the assessments. Appendixes A through H are provided on CRP-CD-ROM-115, which accompanies this report. Appendix A provides overviews of the various measurement equipment and models as well as the reasoning behind the selections used in this project. Appendix B explains the process used to select the test case airport. Appendix C provides details on how the measurement campaigns were con- ducted. Appendix D presents the assessments conducted with the measured data. Appendixes E and F provide the modeling evaluations conducted using EDMS and CMAQ, respectively. Appen- dix G covers the details on the supporting receptor modeling assessments. Appendix H describes the assessments to determine the usability of noise data in conducting airport air quality work.
