Modeling Guidance and Examples for Commonly Asked Questions (Part 1) Rachel Melton and Matthew Kovar Air Permits Division Texas Commission on Environmental Quality Advanced Air Permitting Seminar 2014
Agenda • Representative Background Monitor: • Selecting/Justifying a Representative Monitor • Calculating the Design Value • 1-hr NO2 NAAQS: • Treatment of Intermittent Emissions • Tier 3 Options for NOx-to-NO2Conversion
Purpose of a Representative Monitor The purpose of a representative monitor is to estimate existing ambient air quality at the project site and in areas which may be affected by emissions from the project.
What Is a Representative Monitor? • A monitor that can capture nearby sources not explicitly modeled in an air dispersion modeling analysis • Nearby sources may include: • mobile sources & non-stationary sources • natural sources & unidentified sources
Selecting a Representative Monitor • Factors to consider: • proximity of the monitor to the project site; • similarity of topography, meteorology, and land-use for the project and monitor site; • stationary source types and amount of emissions around the monitor compared to the project site; • emissions from mobile or other non-stationary source activities; and • meets completeness criteria
Resources for Selecting a Representative Monitor EPA AirData EPA Design Values Texas Air Monitoring Information System (TAMIS) Yearly Summary Reports
Justifying a Representative Monitor • The applicant must justify why the monitoring data selected are representative of the existing air quality in the area of the project site • Qualitative assessment • Quantitative assessment
Qualitative Assessment:Monitor site relative to project site • Proximity, topography, and land-use: • aerial photography • Meteorology: • prevailing winds / influential sources
Quantitative Assessment:Monitor site relative to project site • County wide comparison: • population • emissions: • similar source categories • mobile & other non-stationary source • Nearby emissions (10 km) comparison: • quantify emissions for RNs near the project site and monitor site Houston Deer Park #2 monitor, highlighted RNs within 10kms
ExampleProject site Site located near Port Arthur in Jefferson County adjacent to various industrial sites; 786 TPY of reported PM2.5 emissions near the site.
ExamplePM2.5 monitor for use as a background The background monitor located in Harris County near Galveston Bay in a residential area with only a few industrial sites nearby; 282 TPY of reported PM2.5 emissions near the monitor.
ExamplePM2.5 monitor for use in justifying the SIL The monitor for SIL justification located in Harris County near industrial sites; 2765 TPY of PM2.5 near the monitor.
Determine the Monitored Design Value • EPA Completeness Criteria • The representative background concentration should be in the form of the standard: • Exceedance-based: • Example 1-hr CO: • H2H from most recent year • Statistically-based: • Example 1-hr NO2: • 3-year average of the 98th percentile of the annual distribution of maximum daily 1-hr concentrations
Contact Information • Rachel Melton • Air Dispersion Modeling Team • (512) 239-2358 • firstname.lastname@example.org • Matthew Kovar • Air Dispersion Modeling Team • (512) 239-0180 • email@example.com Matthew Kovar Rachel Melton (512) 239-2358 firstname.lastname@example.org (512) 239-0180 email@example.com Air Permits Division Air Permits Division