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Air Quality Impacts Analysis. Presented to: American Public Power Association APPA New Generation Meeting: Anticipating new permitting issues, IGCC Technology Options, Atmospheric Modeling, and Anticipating the Public’s Reaction Presented by: William B. Jones Project Manager

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Air Quality Impacts Analysis

Presented to:

American Public Power Association

APPA New Generation Meeting: Anticipating new permitting issues,

IGCC Technology Options, Atmospheric Modeling,

and Anticipating the Public’s Reaction

Presented by:

William B. JonesProject Manager

Zephyr Environmental Corporation

June 28, 2006

outline of presentation

Outline of Presentation

What is modeling and why do it?

Types of models

Typical modelinganalyses

Recent modeling activity

what is modeling

What is Modeling?

Running computer programs to predict air pollutant levels

Dates back to 1930’s, looked at smoke from chimneys

Different applications

Complex terrain

Long-range transport


why do modeling

Why do Modeling?

Relative to monitoring, it is



More extensive

Useful regulatory tool

Developing control strategies

Permitting of new/modified industrial facilities

types of models

Types of Models



AERSCREEN (any day now)





features of screening models

Features of Screening Models

Quick and dirty

Required inputs are limited

Meteorological data

Source data

Terrain data

Cursory structure downwash analysis

Conservative (high) results

features of refined models

Features of Refined Models

Required inputs can be substantial

Preprocessed meteorological data

Preprocessed terrain data

Detailed structure downwash analysis



Will become EPA’s official preferred model for most near-field industrial applications on December 9, 2006

Improvements over ISC3

Dispersion within Planetary Boundary Layer

Characterization of meteorological conditions

Terrain depiction

aermod is a steady state model

AERMOD is a steady-state model

Straight line trajectory for plume

Spatially constant meteorological conditions

No “memory” of previous hour’s emissions

when should you use aermod

When should you use AERMOD?

Most industrial applications

When your situation involves

Pollutant concentrations within tens of km of source

Flat or complex terrain (but maybe not “complicated” terrain)

Most NAAQS/PSD Increment analyses

issues with aermod

Issues with AERMOD

The input/output files may look the same as ISC…

But it is much more labor-intensive than ISC



Computer runtimescan measure in days



Non-Steady-State model (Puff model)



ISC vs. CALPUFF animation here



Non-Steady-State model (Puff model)

Source input requirements are more detailed than AERMOD

Terrain input requirements are more detailed than AERMOD

Meteorological data input requirements are quite substantial

MM5 can be run for anywhere in the world

when should you use calpuff

When should you use CALPUFF?

Most long-range transport applications (i.e., greater than 50 km)

Class I impact/visibility assessments

Nearfield analyses involving significant terrain variations

typical modeling analyses

Typical Modeling Analyses

Class II



PSD Increment

Class I

class ii analyses significance modeling

Class II Analyses:Significance Modeling

Consider only project in question (emissions increases and decreases)

Compare against U.S. EPA significance levels

If below, analysis is finished

If above, proceed with more comprehensive NAAQS/PSD Increment analysis

class ii analyses naaqs modeling

Class II Analyses:NAAQS Modeling

Comprehensive assessment of overall air quality

Include all sources at your facility

Include offsite sources

Include representative ambient background pollutant concentrations

class ii analyses psd increment modeling

Class II Analyses:PSD Increment Modeling

Include PSD Increment consuming and expanding sources at your facility

Include PSD Increment consuming and expanding offsite sources

No ambient background pollutant concentrations are included

class i analysis

Class I Analysis

Class I PSD Increments

Air Quality Related Values (AQRV’s)


Acid deposition (sulfate and nitrate)

history of class i analyses

History of Class I Analyses

1993: Interagency Workgroup on Air Quality Modeling (IWAQM) formed, recommended CALPUFF

2000: Federal Land Manager’s Air Quality Related Values Workgroup (FLAG) was written to develop a more consistent approach for the FLMs to evaluate air pollution effects on their resources

history of class i analyses1

History of Class I Analyses

History has shown it’s easier to define what is not a problem vs. what is a problem

Each case is different—for each facility, and each FLM

current typical approach to assessment of visibility impairment

Current (typical) approach to assessment of visibility impairment

Run CALPUFF with 3 years of met data

Calculate 24-hr bext (visibility index)

Compare bext against natural conditions

If < 5%, FLM doesn’t object

If between 5% and 10%, FLM may object

If > 10%, FLM likely to object

but flag guidance may be changing

But FLAG guidancemay be changing!

John Vimont (NPS) spoke at Guideline on Air Quality Models Conference in Denver this past April

Outlined proposed changes to visibility analysis methodology

Different way of accounting for relative humidity

Different way of comparing bext (98th percentile, or 8th high per year)

examples of analyses required of recent coal fired facilities

Examples of analyses required ofrecent coal-fired facilities

Plum Point Energy Station: Osceola, Arkansas

Comanche Generating Station: Pueblo, Colorado

Duke Energy: Cliffside, NC

Sandy Creek: McClennan County, TX

City Public Service: San Antonio, TX

plum point energy station osceola ar class i visibility analysis

Plum Point Energy Station, Osceola, ARClass I Visibility Analysis

Ran CALPUFF, initially found light extinctions > 5%

Developed water content adjustment to modify natural light extinction calculation

  • Re-ran CALPUFF, did not find light extinctions > 5%


Quick Class I Area Tour

comanche generating station pueblo co class i analyses performed

Comanche Generating Station, Pueblo, COClass I Analyses Performed


Found change in light extinction to be less than 5% at all Class I areas, so acceptable

Acid Deposition

Sulfur deposition less than 0.005 kg/ha/yr (Deposition Analysis Threshold, or DAT) (western US value), so acceptable

Class I PSD Increment

PM10 impacts less than Class I significance level of 0.3 ug/m3

comanche generating station pueblo co additional analysis acid neutralizing change

Comanche Generating Station, Pueblo, COAdditional Analysis: Acid Neutralizing Change

U.S. Forest Service has established threshold of concern for acid deposition in Class I areas

Considered three high altitude lakes in Class II areas

Change in ANC resulting from PM10 and H2SO4 emissions evaluated

Percent change found to be below threshold of 10%

duke energy cliffside nc permit application submitted december 16 20051

Duke Energy, Cliffside, NCPermit Application submitted December 16, 2005


NPS required speciation of PM10 emissions by light scattering properties (soils, elemental carbon, and organic aerosols)

Acid Deposition

Used DAT of 0.01 kg/ha/yr (eastern US value)

Class I PSD Increment

PM10 and NOx impacts less than Class I Significance Levels

sandy creek mcclennan county tx updated application submitted march 10 2005

Sandy Creek, McClennan County, TXUpdated application submitted March 10, 2005

Closest Class I area is Wichita Mountains Wilderness (Oklahoma), ~ 370 km away

Did not have to examine any impacts on Class I areas

city public service san antonio tx permit issued january 2006

City Public Service, San Antonio, TXPermit issued January 2006

Closest Class I area is Big Bend National Park (Texas), ~ 440 km away

TCEQ did not require any Class I analysis

CPS assessed visibility and acid deposition at Big Bend and six other Class I areas (out to 870 km)


Light extinction found to be < 5% at all Class I areas

Sulfur and Nitrogen deposition found to be < DAT at all Class I areas



Model selected based on

Type of analysis being conducted

Characteristics of region being modeled

Class II (NAAQS and PSD Increment) analyses will typically use AERMOD

More complicated than ISC was

Class I analyses will typically use CALPUFF

Reach of FLM is increasing

Requirements of analysis are very fluid

useful modeling links

Useful Modeling Links

EPA’s SCRAM Website:


FLAG: (John Seitz (OAQPS) 10/23/97 memo on using PM10 as surrogate for PM2.5 in PSD analyses)