Modeling Guidance and Examples for Commonly Asked Questions (Part II) Reece Parker and Justin Cherry, P.E. Air Permits Division Texas Commission on Environmental Quality Advanced Air Permitting Seminar 2014

What Is Ozone? Good Stratospheric Ozone O2O2 sunlight O + O O + O 2 O3O3 Bad Ground-level Ozone sunlight VOC + NO x O 3 (and other products)

Ground-level Ozone Is: The main component of smog. Not emitted directly in the air but forms when emissions of precursors, including NO x and VOCs “cook” in the sun: – Emissions from industrial facilities, electric utilities, motor vehicle exhaust, gasoline vapors, and chemical solvents are the major man-made sources of NO x and VOCs. Mainly a summertime pollutant because sunlight and hot weather accelerate its formation. Ozone levels can be high in both urban and rural areas, often due to transport of emissions of ozone precursors.

2008 Ground-level Ozone Standards Primary and secondary 8-hr ozone standards: 75 ppb* *based on the 3-yr average of the annual fourth highest daily maximum 8-hr ozone concentration

Type of Application Non- Attainment Review? PSD Increment: SO 2 PM 10 Property Line: SO 2 H 2 S Health Effects: Benzene PSD Review? SO 2 PM 10 Property Line: SO 2 H 2 S Health Effects: Benzene

Non-attainment vs. Attainment

Non-attainment Review Provide full documentation and details to reduce review time and mitigate potential issues Protocol document should resemble AQA without modeling results Final product? Not exactly... Ozone Impact Analysis not required. Emissions offsets to improve air quality

PSD Review If project is major by itself or a major modification, a protocol is required: – For all criteria pollutants with an increase – Must be sent to EPA Region 6 for review – May include protocol for state-only requirements Items to include in protocol are listed in protocol checklist Consider all the items in the protocol check list before you start on your protocol document An ozone impacts analysis is required when a project emits:  100 tpy or more of VOCs and/or  100 tpy or more of NO x

Ozone Impacts Analysis Obtain representative monitoring data Determine whether the project area is VOC-limited or NO x -limited* Quantitative demonstration Qualitative demonstration *Based on TCEQ’s own SIP photochemical modeling, most of the urban and rural areas of Texas are NO x -limited.

Quantitative Demonstration Photochemical modeling:  Comprehensive Air Quality Model with extensions (CAMx) Screening approach using AERMOD:  Demonstration based on comments by EPA for NO x - limited areas

Quantitative Demonstration (Cont.) Screening approach using AERMOD:  Conservative analysis based on NO x modeling: – Determine if the project is NO x -limited or VOC-limited – If VOC-limited, determine GLC max at a distance of km – Assume 90% conversion of NO x to NO 2 – Assume 3 ozone molecules per NO x molecule – Add result to the representative monitored concentration – Compare to the standard

Example of Quantitative Demonstration Determine a representative monitor concentration Project Location

Example (Cont.) Determine a representative monitor concentration Monitor Location 3-yr avg of 4 th highest daily maximum 8-hr conc. 69 ppb

Example (Cont.) Determine GLC max km from project sources

Example (Cont.) Model Output Converting model result to ppb: 2.96 µg/m 3 x (100 ppb)/(188 µg/m 3 ) =1.57 ppb

Example (Cont.) Assume 90% conversion of NO X to NO 2 : 1.57 ppb x 0.9 = ppb Assume 3 molecules ozone per molecule NO X : 3 x ppb = 4.24 ppb Add result to monitored concentration: 69 ppb ppb = ppb Compare to standard: ppb < 75 ppb

Qualitative Demonstration Assessment of current air quality: – Ozone trends – NO X trends – VOC trends Analysis of the project’s potential ozone impact – Selection of Existing Photochemical Modeling Analyses: – Modeling simulation (Did photochemical modeling follow EPA guidance?) – Source characterization – Meteorological parameters and regional transport

Example Qualitative Demonstration Ozone Trends BPA Area BPA Area Ozone Design Values for all Monitoring Sites ( ) Site ID: Site ID: Site ID: hr Ozone NAAQS 2008 NAAQS Threshold hr Ozone NAAQS 1997 NAAQS Threshold Site ID: Site ID: Site ID: Site ID: Site ID: Site ID: hr Ozone Design Value (ppm)

Example (Cont.) NO x Trends (BPA Area) Summary of NO x Emissions Data in BPA Area (tons per day) NO x Emissions (tons per day) Nonroad Onroad Area Point Area Onroad Nonroad 2005 NEI 2008 NEI2011 NEI

Example (Cont.) NO x Trends (BPA Area) Maximum BPA Area Annual Average NO X Concentration ( ) Annual NO x Concentration (ppb)

Example (Cont.) VOC Trends (BPA Area) Summary of VOC Point and Area Emissions Data in BPA Area (tons per day)

Example (Cont.) VOC Trends (BPA Area) Annual Average Level of Ethylene Measured in the BPA Area ( ) Annual Average Measurements (ppb) Ethylene Emissions Range of Measured Annual Averages Median of Measured Annual Averages Year

Example (Cont.) VOC Trends (BPA Area) Annual Average Level of Propylene Measured in the BPA Area ( ) Annual Average Measurements (ppb) Propylene Emissions Range of Measured Annual Averages Median of Measured Annual Averages Year

Example (Cont.) Source Characterization Photochemical Modeling Project: – 24 Natural Gas-fired Refrigeration Compressor Turbines – 4 Acid Gas Vents – 1 Marine Flare – 2 Wet Gas Flares – 2 Dry Gas Flares – 2 Natural Gas-fired Generator Turbines – 2 Emergency Generators Proposed Project: – 6 Natural Gas-fired Refrigeration Compressor Turbines – 1 LNG Storage LP Flare – 1 Wet/Dry Gas Ground Flare – 1 Auxiliary Boiler – 4 Thermal Oxidizers – 7 Diesel Generators – 1 Natural Gas-fired Essential Generator – 1 Blowdown Vent

Example (Cont.) Source Characterization Photochemical Modeling PTE NO x Emissions 2, tpy PSD Increment: SO 2 PM 10 Property Line: SO 2 H 2 S Health Effects: Benzene Proposed Project PTE NO x Emissions tpy PSD Increment: SO 2 PM 10 Property Line: SO 2 H 2 S Health Effects: Benzene Photochemical modeling approx. 4X more NO x than proposed project.

Example (Cont.) Meteorological Parameters and Regional Transport BPA Area Surface Pressure (HPA)Relative Humidity (%)

Example (Cont.) Meteorological Parameters and Regional Transport BPA Area Surface Roughness (m)Temperature ( o C)

Example (Cont.) Meteorological Parameters and Regional Transport BPA Area Wind Vectors (knts)Wind Velocity (knts)

Example (Cont.) Model Results Photochemical modeling results in the BPA Area based on 4X as much NO x is between ppb.

Questions?

Contact Information Justin Cherry, P.E. – Air Dispersion Modeling Team – (512) – Reece Parker – Air Dispersion Modeling Team – (512) – Air Permits Division (512) Justin Cherry Air Permits Division Reece Parker (512)