CHAPTER 3 "OZONE IN THE WEST: DO WE HAVE THE RIGHT TOOLS IN OUR TOOLBOX?"

• Jurisdiction: United States

Air Quality Issues Affecting Oil, Gas, and Mining Development and Operations (Feb 2018)
CHAPTER 3
"OZONE IN THE WEST: DO WE HAVE THE RIGHT TOOLS IN OUR TOOLBOX?"
Courtney Taylor
Air Quality Scientist and Project Manager
AECOM Environment
Fort Collins, CO

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COURTNEY TAYLOR, M.S., is an Air Quality Scientist and Project Manager with AECOM Environment, in Fort Collins, CO. Ms. Taylor has been professionally engaged in western air quality issues for over 15 years. Ms. Taylor leverages an Atmospheric Scientist's perspective to advise clients and provide technical and engineering solutions. Ms. Taylor's background is particularly relevant to challenges posed by air pollutants formed in the atmosphere via chemical reaction, such as ozone and secondary particulate matter. Ms. Taylor's comprehensive background includes atmospheric modeling, emissions inventory development and review, ambient air monitoring, and project management/coordination. Her diverse project experience spans the United States and includes expert air quality technical support for legal challenges, comments on proposed federal rules and technical analyses, National Environmental Policy Act analyses, Resource Management Plans, Prevention of Significant Deterioration (PSD) permits, and minor source permits. Analyses have benefited many industrial sectors including upstream oil and gas, coal and gold mining, and energy generation. She is an expert modeler for steady-state dispersion models (AERMOD), Lagrangian models (CALPUFF), and emissions inventory developer for photochemical grid modeling (CAMx, CMAQ, and SMOKE). Ms. Taylor integrates her formal training in atmospheric chemistry with a pragmatic understanding of model limitations and uncertainty in order to assess air quality impacts, proposed regulations, and regulatory challenges.

INTRODUCTION

Increasingly sophisticated epidemiological studies are driving more stringent health-based air quality standards. Such is the case when the United States Environmental Protection Agency (USEPA) finalized a new National Ambient Air Quality Standard (NAAQS) for ozone on October 1, 2015, reducing the ozone concentrations allowed in ambient air from 75 parts per billion (ppb) (the standard set in 2008) to 70 ppb over an eight hour period. A reduction of the ozone NAAQS has repercussions throughout the country, but the effects are likely to be felt most in the West, where the conditions that form ozone, relative abundance of precursor emissions, and contributions from international sources are all quite different than other areas of the country.

The hurdles facing western regulators and the regulated community in regards to meeting and demonstrating compliance with the ozone NAAQS are extensive. Issues that challenge regulators in other parts of the country - such as high background levels relative to the standard (i.e., no real "low hanging fruit" remain), overly simplified upwind air quality concentrations in predictive models, ability to demonstrate elevated concentrations are due to an exceptional event, etc. - are just as relevant in the West, if not more substantial.

In addition to national challenges, new concerns are emerging in the West as a result of the lower ozone NAAQS. Western concerns vary widely and include items such as increasing ozone transported from international sources, dated and inaccurate international emissions in models, difficulty modeling mountainous terrain and associated meteorological phenomena, and ozone formation events that occur in the West during winter in snow covered areas.

Unfortunately, the tools available to help regulators determine the optimal control strategy to attain a lower ozone NAAQS are often inadequate to characterize, let alone resolve, western issues. As discussed below, one size does not fit all, particularly when it comes to assessing ozone concentrations and determining optimal solutions for western communities.

OVERVIEW OF ATTAINMENT DESIGNATION PROCESS AND ROLE OF MODELS

When measurements of air quality in an area have concentrations that are below the NAAQS, an area is designated by USEPA as being in "attainment" with the standard. Some areas do not have available measurements, in which case the USEPA designates the area as "unclassifiable." For areas with measurements of air quality that exceed the NAAQS, the area is designated by USEPA as "nonattainment" for that standard.

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For both attainment and nonattainment areas alike, tools are necessary to assess ozone impacts and inform decision makers. For attainment areas, new or modified sources may be required to conduct a modeling analysis to demonstrate that the source would not cause or contribute to an area exceeding the ozone NAAQS as part of Prevention of Significant Deterioration (PSD) permitting process (40 Code of Federal Regulations Part 51). For nonattainment areas where ozone concentrations exceed the standard and are classified as "moderate" or above, states (or tribes) are required to conduct a modeling analysis as part of the State Implementation Plan/Tribal Implementation Plan (SIP/TIP). The primary objective of the modeling analysis for SIPs/TIPs is to demonstrate that planned emissions controls would be sufficient to attain the standard by the attainment deadline.

While tools are necessary to assess ozone impacts and demonstrate control efficacy, available tools have notable limitations, unquantified uncertainty, and are often used inappropriately. Given the challenges we face nationally, and in the West in particular, it is critical that the available tools be improved, the process streamlined, and new tools be developed (and accepted for use) in order to have more reliable results and increased confidence in emission control strategies.

DISCUSSION OF TOOLS

There are a limited number of tools available to help regulators and the regulated community assess and...