Regulatory Requirements For Modeling

Air Quality Model Estimates

• Developing Air Pollution Control Plans• Assessment of Environmental Impacts• Projecting Future Air Quality Trends

Regulatory Requirements for Modeling

FIP/SIP/TIP NSR

Control Strategy PSD

EA/EIS

Air Quality Modeling

• Set of Mathematical Equations• Logically connect Emission Rate (Q) to

Ambient Air Quality Concentration ()• Monitoring Site – Representative location

chosen for sampling• Receptor Site – Model prediction of pollutant

concentration

Need for Air Quality Model

• Limitations in Spatial and Temporal Coverage• Insufficient Monitoring Data to set Emission

Limits • Analyze the impacts of new sources that do

not yet exist• Diversity dictate against modeling “Cookbook”

Suitability of Models

Meteorological &

Topography

Level of Detail&

Accuracy

Technical Competence

Resource Availability Accurate Data

7Source : EPA DREP

Levels of Models

• Screening Model- Simple estimation provides conservative estimates

• Refined Model- More refined least theoretical results

• Screening Technique followed by Refined Model

• Identify “appropriate reviewing authority”

Prevention of Significant Deterioration PSD- 40 CFR § 52.21

• New Major Stationary Source and Major Modification to Existing Source– Ensure compliance with NAAQS and PSD air increments

• Preconstruction Permit Application– Best Available Control Technology (“BACT”)– Ambient Air Quality Impact Analysis: Modeling– Impacts on Soils, Vegetation, and Visibility– Class 1 Area Impacts– Public Comments/Participation

Air Quality Monitoring Requirements 40 CFR § 52.21(i)(5)

PSD De Minimis Monitoring Concentration Pollutant Avg.Period Threshold

Concentration (ug/m3)

CO 8-hour 575NO2 Annual 14

PM10 24-hour 13SO2 24-hour 13O3 NA

Lead 3-month 0.1Fluorides 24-hour 0.25

Total Reduced Sulfur

1-hour 10

H2S 1-hour 0.2Reduced Sulfur 1-hour 10

Air Quality Impact Analysis (AQIA)40 CFR § 52.21(m)

• AQIA shall be based on Guidelines on Air Quality Models – 40 CFR § 51 Appendix W

PSD Increments (ug/m3)Pollutant Class I Class II Class III

Particulate Matter

PM10, annualPM10, 24-hour

48

1730

3460

Sulfur Dioxide

SO2, AnnualSO2, 24-hourSO2, 3-hour

25

25

2091

512

40182700

Nitrogen Dioxide

NO2, Annual

2.5

25

50

Additional Impact & PSD Class 1 Analysis

• Growth– industrial, residential, commercial

• Soil and Vegetation Impacts– harmful effects to resident species

• Visibility Impairment– local visibility impairment

PSD Class I Areas• Notice to Federal Land Managers (FLM)• Air Quality Related Values (“AQRV”)-FLAG• Contribution to regional haze, acid deposition

New Source Review (NSR)Tribal Minor NSR 40 CFR § 49.151

• Reviewing Authority Trigger AQIA– local air quality condition – minor source or modification would cause or

contribute to a NAAQS or PSD increment violation– conduct the AQIA using the dispersion models and

procedures of part 51, Appendix W – AQIA cause or contribute to a NAAQS or PSD• Reduce or mitigate impact

• Non-Attainment NSR (“NANSR”)

Federal/State/Tribal Implementation Plan

• Designation• NAAQS Implementation Schedules• Emission Inventories• Attainment Demonstrations• Strategies and Technology to Reduce

Emissions• NSR and PSD• Regional Haze

Modeling Guidance Resourceshttp://www.epa.gov/ttn/scram/guidance_permit.htm

• 40 CFR Part 51 Appendix W• Air Quality Analysis Checklist• Guideline for Determination of Good

Engineering Practice Stack Height• Regional/State/Local Modelers Workshop