Modeling Guidance and Examples for Commonly Asked Questions

(Part 1)

Rachel Melton and Matthew KovarAir Permits Division

Texas Commission on Environmental QualityAdvanced 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-NO2 Conversion

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

Population

Harris County4336853

Population

Jefferson County252358

• County wide comparison:– population– emissions:

» similar source categories» mobile & other non-stationary source

Houston Deer Park #2 monitor, highlighted RNs within 10kms

• Nearby emissions (10 km) comparison:– quantify emissions for RNs

near the project site and monitor site

Example Project site

Site located near Port Arthur in Jefferson County adjacent to various industrial sites; 786 TPY of reported PM2.5 emissions near the site.

Example PM2.5 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.

Example PM2.5 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

– rachel.melton@tceq.texas.gov

• Matthew Kovar– Air Dispersion Modeling Team

– (512) 239-0180

– matthew.kovar@tceq.texas.gov

Air Permits Division

(512) 239-2358rachel.melton@tceq.texas.gov

Rachel Melton

Air Permits Division

(512) 239-0180matthew.kovar@tceq.texas.gov

Matthew Kovar