APPENDIX (

EVIDENCE OF PUBLIC PARTICIPATION; PUBLIC 

COMMENTS AND NEVADA’S RESPONSES
(This page left intentionally blank.)
NOTICE OF PUBLIC COMMENT PERIOD BEGINNING APRIL 19, 2013 

AND A PUBLIC HEARING ON MAY 20, 2013, IF REQUESTED 

Conducted by the 

Nevada Division of Environmental Protection, Bureau of Air Quality Planning 

Pursuant to the public hearing requirements in Title 40 of the Code of Federal Regulations Part 51 

section 102, the Nevada Division of Environmental Protection (NDEP) is issuing the following notice to 

solicit comments on a proposal to certify that the existing Nevada State Implementation Plan (SIP) is 

adequate for implementation of the 2010 sulfur dioxide (SO2) national ambient air quality standards 

(NAAQS) in those areas under the NDEP’s jurisdiction. 

On June 22, 2010, the United States Environmental Protection Agency (US EPA) established a new 1-

hour SO2 standard at a level of 75 parts per billion (75 FR 35520). Clean Air Act section 110(a)(1) 

requires each state to submit a plan showing it has the authority and programs needed to implement, 

maintain, and enforce any new or revised standard, regardless of designation status; section 110(a)(2) 

lists the elements that must be addressed in the plan. Because many of the section 110(a)(2) elements 

relate to the general information and authorities that constitute the infrastructure of a state’s air 

quality management program, the 110(a) plans are generally referred to as “infrastructure SIPs.” The 

NDEP’s portion of Nevada’s 2010 SO2 NAAQS infrastructure SIP is a compilation of existing authorities 

and programs to demonstrate that the NDEP has a plan in place to address the 2010 SO2 NAAQS. 

Nevada’s SO2 infrastructure SIP will be submitted to US EPA in May 2013.

The NDEP is responsible for developing and implementing state plans in the 15 rural counties of 

Nevada. Clark County and Washoe County have their own air quality agencies, which are responsible 

for their respective counties. The NDEP’s portion of the Nevada SO2 infrastructure SIP and related 

materials are available on the NDEP website at http://ndep.nv.gov/admin/public.htm, click on “Air 

Quality Planning.” Access to the draft documents may also be obtained by contacting Tony Roberts at 

NDEP, 901 S. Stewart Street, Suite 4001, Carson City, NV 89701; (775) 687-9543; or e-mail to 

aroberts@ndep.nv.gov. 

Persons wishing to comment on the draft plan or to request a public hearing should submit their 

written comments or request either in person or by mail or fax to Tony Roberts at the above address 

or by fax at (775) 687-6396. A request for a hearing must be received by May 13, 2013. Written 

comments will be received by the NDEP until 5:00 PM PDT, May 20, 2013 and will be retained 

and considered.

Upon receipt of a valid written request, the NDEP will hold a public hearing in Carson City on: 

May 20, 2013 

11:00 a.m. to 1:00 p.m. 

Great Basin Conference Room, 4th Floor 

901 South Stewart Street 

Carson City, Nevada 

An agenda will be posted on the NDEP web site at least 3 working days before the hearing. Oral 

comments will be received at the Hearing. If no request for a public hearing is received by May 13, 

2013, the hearing will be cancelled. Persons may check on the status of the hearing on the NDEP web 

site at http://ndep.nv.gov/admin/public.htm, click on “Air Quality Planning,” or you may call the 

NDEP Bureau of Air Quality Planning at (775) 687-9349. 

This notice has been published in the Las Vegas Review-Journal and the Reno Gazette Journal newspapers. It has been posted 

at the NDEP offices in Carson City and Las Vegas, at the State Library in Carson City and at County libraries throughout Nevada. 

Members of the public who are disabled and require special accommodations or assistance at the hearing are requested to notify 

Tony Roberts or Cathy Douglas (775-687-9349) no later than 3 working days before the hearing. 04/17/2013 






NOTICE OF CANCELLATION OF PUBLIC HEARING ON May 20, 2013 

Nevada Division of Environmental Protection 

Bureau of Air Quality Planning 

Pursuant to the public hearing provisions in Title 40 of the Code of Federal Regulations Part 51 

section 102, the Nevada Division of Environmental Protection (NDEP) is cancelling the following 

public hearing because no request for a hearing was received: 

May 20, 2013 

11:00 a.m. to 1:00 p.m. 

Great Basin Conference Room, 4th Floor 

901 South Stewart Street 

Carson City, Nevada 

The NDEP’s draft Sulfur Dioxide Infrastructure State Implementation Plan (SIP) and related 

materials are available on the NDEP website at http://ndep.nv.gov/admin/public.htm, click on 

“Air Quality Planning.” Persons may also check on the status of Nevada’s Sulfur Dioxide

Infrastructure SIP revision by telephone at (775) 687-9543. 
Public Comments and Nevada’s Responses

(Only one comment was received)
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North Valmy Generating Station 

Valmy, Nevada 

Sierra Club Evaluation of Compliance with 1-hour SO2 NAAQS 

May 16, 2013 

Conducted by: 

Steven Klafka, P.E., BCEE 

Wingra Engineering, S.C. 

Madison, Wisconsin
Sierra Club Evaluation of Compliance with 1-hour SO2 NAAQS 

May 16, 2013 

Page 2

1. Introduction 

The Sierra Club prepared an air modeling impact analysis to help USEPA, state and local air 

agencies identify facilities that are likely causing violations of the 1-hour sulfur dioxide (SO2) 

national ambient air quality standard (NAAQS). This document describes the results and procedures 

for an evaluation conducted for the North Valmy Generating Station located in Valmy, Nevada. 

The dispersion modeling analysis predicted ambient air concentrations for comparison with the one 

hour SO2 NAAQS. The modeling was performed using the most recent version of AERMOD, 

AERMET, and AERMINUTE, with data provided to the Sierra Club by regulatory air agencies and 

through other publicly-available sources as documented below. The analysis was conducted in 

adherence to all available USEPA guidance for evaluating source impacts on attainment of the 1-

hour SO2 NAAQS via aerial dispersion modeling, including the AERMOD Implementation Guide; 

USEPA's Applicability of Appendix W Modeling Guidance for the 1-hour SO2 National Ambient 

Air Quality Standard, August 23, 2010; modeling guidance promulgated by USEPA in Appendix W 

to 40 CFR Part 51; and, USEPA’s March 2011 Modeling Guidance for SO2 NAAQS Designations, 

available at http://www.epa.gov/ttn/scram/SO2%20Designations%20Guidance%202011.pdf. 

2. Compliance with the 1-hour SO2 NAAQS 

2.1 1-hour SO2 NAAQS 

The 1-hour SO2 NAAQS takes the form of a three-year average of the 99th-percentile of the annual 

distribution of daily maximum 1-hour concentrations, which cannot exceed 75 ppb.1 Compliance 

with this standard was verified using USEPA’s AERMOD air dispersion model, which produces air 

concentrations in units of μg/m3. The 1-hour SO2 NAAQS of 75 ppb equals 196.2 μg/m3, and this is 

the value used for determining whether modeled impacts exceed the NAAQS.2 The 99th-percentile 

of the annual distribution of daily maximum 1-hour concentrations corresponds to the fourth-highest 

value at each receptor for a given year. 

2.2 Modeling Results 

Modeling results for North Valmy Generating Station are summarized in Table 1. It was determined 

that based on either currently permitted emissions or measured actual emissions, the North Valmy 

Generating Station is estimated to create downwind SO2 concentrations which exceed the 1-hour 

NAAQS. 

 

1 USEPA, Applicability of Appendix W Modeling Guidance for the 1-hour SO2 National Ambient Air Quality Standard, 

August 23, 2010.

2 The ppb to μg/m3

 conversion is found in the source code to AERMOD v. 12325, subroutine Modules. The conversion 

calculation is 75/0.3823 = 196.2 μg/m3

. 
Sierra Club Evaluation of Compliance with 1-hour SO2 NAAQS 

May 16, 2013 

Page 3 

The currently permitted emissions and measured actual emissions used for the modeling analysis are 

summarized in Table 2. Based on the modeling results, emission reductions from current rates 

considered necessary to achieve compliance with the 1-hour NAAQS were calculated and presented 

in Table 3. 

Predicted exceedences of the 1-hour NAAQS for SO2 extend throughout the region to a maximum 

distance of 40 kilometers. 

Figure 1 shows the extent of NAAQS violations throughout the entire 50 kilometer modeling 

domain. 

Figure 2 provides a close-up local view of NAAQS violations. 

Air quality impacts in Nevada are based on a background concentration of 14.4 μg/m3

. This is the 

2008-10 design value for Washoe County, Nevada - the lowest measured background concentration 

in the state. This is the most recently available design value. 

2.3 Conservative Modeling Assumptions 

A dispersion modeling analysis requires the selection of numerous parameters which affect the 

predicted concentrations. For the enclosed analysis, several parameters were selected which underpredict facility impacts. 

Assumptions used in this modeling analysis which likely under-estimate concentrations include the 

following: 

 Allowable emissions are based on a limitation with an averaging period which is greater than 

the 1-hour average used for the SO2 air quality standard. Emissions and impacts during any 

1-hour period may be higher than assumed for the modeling analysis. 

 No consideration of facility operation at less than 100% load. Stack parameters such as exit 

flow rate and temperature are typically lower at less than full load, reducing pollutant 

dispersion and increasing predicted air quality impacts. 

 No consideration of building or structure downwash. These downwash effects typically 

increase predicted concentrations near the facility. 

 No consideration of off-site sources. These other sources of SO2 will increase the predicted 

impacts. 
Sierra Club Evaluation of Compliance with 1-hour SO2 NAAQS 

May 16, 2013 

Page 4 

Table 1 - SO2 Modeling Results for North Valmy Generating Station Modeling Analysis 

Emission Rates Averaging 

Period 

99th Percentile 1-hour Daily Maximum (μg/m3

) 

Complies with NAAQS? 

Impact Background Total NAAQS 

Allowable 1-hour 480.6 14.4 495.0 196.2 No 

Maximum 1-hour 303.9 14.4 318.3 196.2 No 

Table 2 - Modeled SO2 Emissions from North Valmy Generating Station 3,4

Stack 

ID 

Unit 

ID 

Allowable Emissions 

3-hour Average 

 (lbs/hr) 

Maximum Emissions

1-hour Average 

(lbs/hr) 

S01 Unit 1 3,072.0 1,083 

S02 Unit 2 1,728.6 1,672 

Stack Total All Units 4,800.6 2,755 

Table 3 - Required Emission Reductions for Compliance with 1-hour SO2 NAAQS 

Acceptable Impact 

(NAAQS - Background) 

99th Percentile 

1-hour Daily Max 

(μg/m3) 

Required 

Total Facility 

Reduction Based on 

Allowable Emissions 

(%) 

Required 

Total Facility 

Emission Rate 

(lbs/hr) 

Required 

Total Facility 

Emission Rate 

(lbs/mmbtu) 

181.8 62.2% 1,814.6 0.33 

 

 

3

 Nevada Department of Conservation and Natural Resources, Bureau of Air Pollution Control, Class I Air Quality 

Operating Permit No. AP4911-0457.01, June 23, 2009. 4

 Maximum emissions are measured hourly rates reported for 2011 in USEPA, Clean Air Markets - Data and Maps. 
Sierra Club Evaluation of Compliance with 1-hour SO2 NAAQS 

May 16, 2013 

Page 5 

Figure 1 - Regional View - North Valmy Generating Station - Based on Allowable Emissions

 
Sierra Club Evaluation of Compliance with 1-hour SO2 NAAQS 

May 16, 2013 

Page 6 

Figure 2 – Local View - North Valmy Generating Station - Based on Allowable Emissions 

 
Sierra Club Evaluation of Compliance with 1-hour SO2 NAAQS 

May 16, 2013 

Page 7 

3. Modeling Methodology 

3.1 Air Dispersion Model 

The modeling analysis used USEPA’s AERMOD program, version 12345. AERMOD, as available 

from the Support Center for Regulatory Atmospheric Modeling (SCRAM) website, was used in 

conjunction with a third-party modeling software program, AERMOD View, sold by Lakes 

Environmental Software. 

3.2 Control Options 

 

The AERMOD model was run with the following control options: 

 1-hour average air concentrations 

 Regulatory defaults 

 Flagpole receptors 

To reflect a representative inhalation level, a flagpole height of 1.5 meters was used for all modeled 

receptors. This parameter was added to the receptor file when running AERMAP, as described in 

Section 4.4. 

An evaluation was conducted to determine if the modeled facility was located in a rural or urban 

setting using USEPA’s methodology outlined in Section 7.2.3 of the Guideline on Air Quality 

Models.5

 For urban sources, the URBANOPT option is used in conjunction with the urban 

population from an appropriate nearby city and a default surface roughness of 1.0 meter. Methods 

described in Section 4.1 to determine whether rural or urban dispersion coefficients were used. 

 

3.3 Output Options 

The AERMOD analysis was based on five years of recent meteorological data. The modeling 

analyses used one run with five years of sequential meteorological data from 2007-2011. Consistent 

with USEPA’s Modeling Guidance for SO2 NAAQS Designations, AERMOD provided a table of 

fourth-high 1-hour SO2 impacts concentrations consistent with the form of the 1-hour SO2 NAAQS.6

 

Please refer to Table 1 for the modeling results. 

 

 

5

 USEPA, Revision to the Guideline on Air Quality Models: Adoption of a Preferred General Purpose (Flat and Complex 

Terrain) Dispersion Model and Other Revisions, Appendix W to 40 CFR Part 51, November 9, 2005.

6 USEPA, Area Designations for the 2010 Revised Primary Sulfur Dioxide National Ambient Air Quality Standards, 

Attachment 3, March 24, 2011, pp. 24-26. 
Sierra Club Evaluation of Compliance with 1-hour SO2 NAAQS 

May 16, 2013 

Page 8 

4. Model Inputs 

4.1 Geographical Inputs 

The “ground floor” of all air dispersion modeling analyses is establishing a coordinate system for 

identifying the geographical location of emission sources and receptors. These geographical 

locations are used to determine local characteristics (such as land use and elevation), and also to 

ascertain source to receptor distances and relationships. 

The Universal Transverse Mercator (UTM) NAD83 coordinate system was used for identifying the 

easting (x) and northing (y) coordinates of the modeled sources and receptors. Stack locations were 

obtained from facility permits and prior modeling files provided by the state regulatory agency. The 

stack locations were then verified using aerial photographs. 

The facility was evaluated to determine if it should be modeled using the rural or urban dispersion 

coefficient option in AERMOD. A GIS was used to determine whether rural or urban dispersion 

coefficients apply to a site. Land use within a three-kilometer radius circle surrounding the facility 

was considered. USEPA guidance states that urban dispersion coefficients are used if more than 50% 

of the area within 3 kilometers has urban land uses. Otherwise, rural dispersion coefficients are 

appropriate.7

 

USEPA’s AERSURACE model Version 08009 was used to develop the meteorological data for the 

modeling analysis. This model was also used to evaluate surrounding land use within 3 kilometers. 

Based on the output from the AERSURFACE, approximately 1.9% of surrounding land use around 

the airport was of urban land use types including: 21 – Low Intensity Residential, 22 – High 

Intensity Residential, and 23 - Commercial/Industrial/Transportation. 

This is less than the 50% value considered appropriate for the use of urban dispersion coefficients. 

Based on the AERSURFACE analysis, it was concluded that the rural option would be used for the 

modeling summarized in this report. Please refer to Section 4.5.3 for a discussion of the 

AERSURFACE analysis.

 

 

7

 USEPA, Revision to the Guideline on Air Quality Models: Adoption of a Preferred General Purpose (Flat and Complex 

Terrain) Dispersion Model and Other Revisions, Appendix W to 40 CFR Part 51, November 9, 2005, Section 7.2.3. 
Sierra Club Evaluation of Compliance with 1-hour SO2 NAAQS 

May 16, 2013 

Page 9 

4.2 Emission Rates and Source Parameters 

The modeling analyses only considered SO2 emissions from the facility. Off-site sources were not 

considered. Concentrations were predicted for two scenarios shown in Table 2: 

1) approved or allowable emissions based on permits issued by the regulatory agency, and 

2) measured actual hourly SO2 emissions obtained from USEPA’s Clean Air Markets 

Database. To assure realistic emission rates were used, emissions from all units at the facility 

were combined and the hour with the maximum total facility emissions was used to 

determine the actual emissions. 

Stack parameters and emissions used for the modeling analysis are summarized in Table 4. 

Table 4 – Facility Stack Parameters and Emissions 8

Stack S01 S02 

Description Unit 1 Unit 2 

X Coord. [m] 487131.86 487214.26 

Y Coord. [m] 4525611.27 4525674.1 

Base Elevation [m] 1357.97 1358 

Release Height [m] 153.89 137.22 

Gas Exit Temperature [°K] 413.817 368.15 

Gas Exit Velocity [m/s] 20.133 20.734 

Inside Diameter [m] 5.621 5.182 

Allowable Emission Rate [g/s] 387.1 217.8 

Maximum Emission Rate [g/s] 136.5 210.7 

The above stack parameters and emissions were obtained from regulatory agency documents and 

databases identified in Section 2.3. The analysis was conducted based on 100% operating load using 

maximum exhaust flow rates and emission rates. Operation at less than full capacity loads was not 

considered. This assumption tends to under-predict impacts since stack parameters such as exit flow 

rate and temperature are typically lower at less than full load, reducing pollutant dispersion and 

increasing predicted air quality impacts. Stack location, height and diameter were verified using 

aerial photographs, and flue gas flow rate and temperature were verified using combustion 

calculations. 

 

 

8 Nevada Department of Conservation and Natural Resources, Bureau of Air Pollution Control, Class I Air Quality 

Operating Permit No. AP4911-0457.01, August 17, 2005. 
Sierra Club Evaluation of Compliance with 1-hour SO2 NAAQS 

May 16, 2013 

Page 10 

4.3 Building Dimensions and GEP 

No building dimensions or prior downwash evaluations were available. Therefore this modeling 

analysis did not address the effects of downwash which may increase predicted concentrations. 

4.4 Receptors 

For North Valmy Generating Station, three receptor grids were employed: 

1. A 100-meter Cartesian receptor grid centered on North Valmy Generating Station and 

extending out 5 kilometers. 

2. A 500-meter Cartesian receptor grid centered on North Valmy Generating Station and 

extending out 10 kilometers. 

3. A 1,000-meter Cartesian receptor grid centered on North Valmy Generating Station and 

extending out 50 kilometers. 50 kilometers is the maximum distance accepted by USEPA for 

the use of the AERMOD dispersion model.9

A flagpole height of 1.5 meters was used for all these receptors. 

Elevations from stacks and receptors were obtained from National Elevation Dataset (NED) GeoTiff 

data. GeoTiff is a binary file that includes data descriptors and geo-referencing information 

necessary for extracting terrain elevations. These elevations were extracted from 1 arc-second (30 

meter) resolution NED files. The USEPA software program AERMAP v. 11103 is used for these 

tasks. 

4.5 Meteorological Data 

To improve the accuracy of the modeling analysis, recent meteorological data for the 2007 to 2011 

period were prepared using the USEPA’s program AERMET which creates the model-ready surface 

and profile data files required by AERMOD. Required data inputs to AERMET included surface 

meteorological measurements, twice-daily soundings of upper air measurements, and the 

micrometeorological parameters surface roughness, albedo, and Bowen ratio. One-minute ASOS 

data were available so USEPA methods were used to reduce calm and missing hours.10 The USEPA 

software program AERMINUTE v. 11325 is used for these tasks. 

 

9

 USEPA, Revision to the Guideline on Air Quality Models: Adoption of a Preferred General Purpose (Flat and Complex 

Terrain) Dispersion Model and Other Revisions, Appendix W to 40 CFR Part 51, Section A.1.(1), November 9, 

2005. 10 USEPA, Area Designations for the 2010 Revised Primary Sulfur Dioxide National Ambient Air Quality Standards, 

Attachment 3, March 24, 2011, p. 19. 
Sierra Club Evaluation of Compliance with 1-hour SO2 NAAQS 

May 16, 2013 

Page 11 

This section discusses how the meteorological data was prepared for use in the 1-hour SO2 NAAQS 

modeling analyses. The USEPA software program AERMET v. 11059 is used for these tasks. 

4.5.1 Surface Meteorology 

Surface meteorology was obtained for Winnemucca Municipal Airport located near the North Valmy 

Generating Station. Integrated Surface Hourly (ISH) data for the 2007 to 2011 period were obtained 

from the National Climatic Data Center (NCDC). The ISH surface data was processed through 

AERMET Stage 1, which performs data extraction and quality control checks. 

4.5.2 Upper Air Data 

Upper-air data are collected by a “weather balloon” that is released twice per day at selected 

locations. As the balloon is released, it rises through the atmosphere, and radios the data back to the 

surface. The measuring and transmitting device is known as either a radiosonde, or rawindsonde. 

Data collected and radioed back include: air pressure, height, temperature, dew point, wind speed, 

and wind direction. The upper air data were processed through AERMET Stage 1, which performs 

data extraction and quality control checks. 

For North Valmy Generating Station, the concurrent 2007 through 2011 upper air data from twicedaily radiosonde measurements obtained at the most representative location were used. This 

location was the Elko, Nevada measurement station. These data are in Forecast Systems Laboratory 

(FSL) format and were downloaded in ASCII text format from NOAA’s FSL website.11 All 

reporting levels were downloaded and processed with AERMET. 

4.5.3 AERSURFACE 

AERSURFACE is a non-guideline program that extracts surface roughness, albedo, and daytime 

Bowen ratio for an area surrounding a given location. AERSURFACE uses land use and land cover 

(LULC) data in the U.S. Geological Survey’s 1992 National Land Cover Dataset to extract the 

necessary micrometeorological data. LULC data was used for processing meteorological data sets 

used as input to AERMOD. 

AERSURFACE v. 08009 was used to develop surface roughness, albedo, and daytime Bowen ratio 

values in a region surrounding the meteorological data collection site. AERSURFACE was used to 

develop surface roughness in a one kilometer radius surrounding the data collection site. Bowen 

ratio and albedo was developed for a 10 kilometer by 10 kilometer area centered on the 

meteorological data collection site. These micrometeorological data were processed for seasonal 

 

11 Available at: http://esrl.noaa.gov/raobs/ 
Sierra Club Evaluation of Compliance with 1-hour SO2 NAAQS 

May 16, 2013 

Page 12 

periods using 30-degree sectors. Seasonal moisture conditions were considered average with no 

months with continuous snow cover. 

4.5.4 Data Review 

Missing meteorological data were not filled as the data file met USEPA’s 90% data completeness 

requirement.12 The AERMOD output file shows there were 4.2% missing data. 

The representativeness of airport meteorological data is a potential concern in modeling industrial 

source sites.13 The surface characteristics of the airport data collection site and the modeled source 

location were compared. Since the Winnemucca Municipal Airport is located close to North Valmy 

Generating Station, this meteorological data set was considered appropriate for this modeling 

analysis. 

5. Background SO2 Concentrations 

Background concentrations were determined consistent with USEPA’s Modeling Guidance for SO2

NAAQS Designations.14 To preserve the form of the 1-hour SO2 standard, based on the 99th

percentile of the annual distribution of daily maximum 1-hour concentrations averaged across the 

number of years modeled, the background fourth-highest daily maximum 1-hour SO2 concentration 

was added to the modeled fourth-highest daily maximum 1-hour SO2 concentration.15 

Background concentrations were based on the 2008-10 design value measured by the ambient 

monitors located in Nevada.16 

6. Reporting 

All files from the programs used for this modeling analysis are available to regulatory agencies. 

These include analyses prepared with AERSURFACE, AERMET, AERMAP, and AERMOD. 

 

12 USEPA, Meteorological Monitoring Guidance for Regulatory Modeling Applications, EPA-454/R-99-05, February 

2000, Section 5.3.2, pp. 5-4 to 5-5. 

13 USEPA, AERMOD Implementation Guide, March 19, 2009, pp. 3-4. 

14 USEPA, Area Designations for the 2010 Revised Primary Sulfur Dioxide National Ambient Air Quality Standards, 

Attachment 3, March 24, 2011, pp. 20-23. 

15 USEPA, Applicability of Appendix W Modeling Guidance for the 1-hour SO2 National Ambient Air Quality Standard, 

August 23, 2010, p. 3. 

16 http://www.epa.gov/airtrends/values.html 
Case: 10-1252 Document: 1276211 Filed: 11/08/2010 Page: 1

ORAL ARGUMENT NOT YET SCHEDULED

UNITED STATES COURT OF APPEALS FOR

THE DISTRICT OF COLUMBIA CIRCUIT

) 

NATIONAL ENVIRONMENTAL ) 

DEVELOPMENT ASSOCIATION’S ) 

CLEAN AIR PROJECT, ) 

) 

Petitioner, ) 

)

v. ) Docket No. 10-1252

) (and consolidated cases) 

UNITED STATES ENVIRONMENTAL ) 

PROTECTION AGENCY, ) 

) 

Respondent. ) 

 ) 

RESPONDENT’S OPPOSITION TO MOTION OF THE STATE OF

NORTH DAKOTA FOR A STAY OF EPA’S 1-HOUR SULFUR 

DIOXIDE AMBIENT STANDARD RULE

Respondent United States Environmental Protection Agency (“EPA”) 

submits this Opposition to the Motion of the State of North Dakota for a Stay of 

EPA’s 1-Hour Sulfur Dioxide Ambient Standard Rule (“Stay Motion”). In its Stay 

Motion, North Dakota seeks a stay of the rule in its entirety or, in the alternative, a 

stay of the statutory directive that States submit any recommendations for 

attainment/nonattainment designations no later than June 3, 2011. The motion 

should be denied because North Dakota has not satisfied the stringent requirements
Case: 10-1252 Document: 1276211 Filed: 11/08/2010 Page: 2

2

for obtaining a stay of agency action. The motion fails to address any of the 

elements for obtaining a stay with regard to any of the promulgated elements of the 

rule, i.e., the revised sulfur dioxide (“SO2”) standard itself and the promulgated

revisions to the SO2 monitoring network. Rather, the motion is addressed solely to

an advisory discussion in the final rule preamble regarding EPA’s anticipated 

approach to implementing the revised NAAQS. Thus, the motion provides no 

basis to stay the rule as a whole.

The motion must also be denied with regard to the alternative relief requested. 

First, North Dakota has not demonstrated a substantial likelihood of success on the

merits. It challenges only advisory statements in the final rule preamble concerning

EPA’s contemplated approach for making initial attainment designations by the

June 2012 statutory deadline, an approach the Agency will be addressing in future

actions. As the preamble makes clear, EPA has taken no final action nor

promulgated any regulatory requirements regarding designations, and, in particular,

has taken no final action on its approach to making attainment determinations. To

the contrary, the preamble specifically preserves EPA’s ability to make those

decisions solely on the basis of monitoring data. 75 Fed. Reg. 

35,520, 35,552 n.22 (June 22, 2010). Because these preamble statements are not 

final agency action, the Court lacks jurisdiction to review them, and North Dakota 

has no substantial likelihood of prevailing on the merits.
Case: 10-1252 Document: 1276211 Filed: 11/08/2010 Page: 3

3

Moreover, even if the challenged preamble statements could be read as final 

agency action, the Agency has historically relied on modeling to make designations 

for sulfur dioxide. To the extent the proposal preamble reflected a possible change 

to that practice, it clearly left open the possibility that the Agency would choose

not to adopt the proposed change. Interested parties should have known that EPA 

might retain its past practice, and had ample opportunity to comment on that 

possibility. Thus, North Dakota cannot demonstrate a likelihood of success on its 

claim that it lacked an opportunity to comment on the approach to initial 

designations discussed in the preamble.

Second, North Dakota cannot demonstrate that it will suffer irreparable harm 

from the statutory directive that it submit designation recommendationsto EPA by 

June 2011. North Dakota claims harm from an alleged bar to the use of monitoring 

data as the sole basis for its designation recommendations. But, nothing in the SO2

Rule prevents North Dakota from basing its recommendationssolely on monitoring

data, and thus the Rule does not cause the harm North Dakota claims. Id.

Furthermore, designation recommendations have no independent legal effect. An 

area is not designated until EPA promulgates the designation, which EPA is

required to do by June 20121/ (a requirement that would not be affected by a stay of

1/ The date can be extended to June 2013 if EPA lacks sufficient information to act 

in 2012. 42 U.S.C. § 7407(d)(1)(B)(i). 
Case: 10-1252 Document: 1276211 Filed: 11/08/2010 Page: 4

4

the 2011 recommendation submission date). Moreover, EPA is not bound by the 

State’s recommendations and must promulgate a designation for an area even if the 

State submits no recommendation at all.

Finally, a stay of the SO2 Rule will cause harm to other parties and is 

contrary to the public interest. The rule under review revises the primary ambient 

air quality standard for sulfur dioxide based on findings by EPA that the prior

standards were not requisite to protect human health with an adequate margin of 

safety. A stay of the rule’s regulatory provisions promulgating the new standard 

would delay implementation of the measures needed to achieve attainment with the 

new standard, including requirements associated with the permitting of new and 

modified major stationary sources which became effective on the effective date of 

the standard. A stay of the Rule would thus prolong the time during which existing 

air quality causes adverse impacts to public health. A stay of the 2011 deadline for 

States to submit recommendationsto EPA would not alter EPA’s obligation to 

promulgate designations by 2012, but would increase the burden on EPA to

develop the designations.

BACKGROUND

The consolidated petitions in this case seek review of an EPA regulation 

revising the primary National Ambient Air Quality Standards (“NAAQS”) and 

associated regulatory requirements for oxides of sulfur as measured by SO2
Case: 10-1252 Document: 1276211 Filed: 11/08/2010 Page: 5

5

pursuant to section 109 of the Clean Air Act, 42 U.S.C. § 7409. 75 Fed. Reg.

35,520 (June 22, 2010) (“SO2 Rule”). Those regulatory requirementstook effect 

on August 23, 2010, and are currently being implemented. The NAAQS

provisions of the Clean Air Act establish a comprehensive scheme to protect public 

health and welfare from ubiquitous air pollutants. 42 U.S.C. § 7409. Primary 

standards must be set at levels that, in the judgment of the Administrator, are 

requisite to protect public health with an adequate margin of safety. Id. 

§ 7409(b)(1). The Act requires periodic review of the NAAQS. Id. § 7409(d). 

See generally American Lung Ass’n v. EPA, 134 F.3d 388, 388-89 (D.C. Cir. 

1998).

EPA first promulgated a primary NAAQS for sulfur dioxide in 1971. 36

Fed. Reg. 8187 (April 30, 1971). In May 1996, after a lengthy review, EPA

announced a final decision not to revise the NAAQS. 61 Fed. Reg. 25,566 (May 

22, 1996). Petitions for review of that decision were filed in this Court, and the 

Court held that EPA had failed to adequately explain the basis for its conclusion 

that short-term SO2 exposures to asthmatics do not constitute a public health

problem. American Lung Ass’n v. EPA, 134 F.3d 388. In the rule under review

here EPA has addressed that issue by replacing the prior 24-hour and annual 

primary standards with a new 1-hour primary standard. The new standard is now

in effect, and is being implemented in EPA’s prevention of significant deterioration
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permitting program for new and modified major stationary sources. See 57 Fed.

Reg. at 35,580/1.

Within one year after promulgation of a new or revised NAAQS (or sooner 

if required by EPA) States are directed to submit to EPA a list of all areas that the 

State recommends be designated by EPA as attainment, nonattainment, or 

unclassifiable for the new or revised NAAQS. 42 U.S.C. § 7407(d)(1)(A). In the 

case of the revised SO2 standards, such designations are due by June 3, 2011, one

year after EPA promulgated the revised NAAQS by signing and publicly

disseminating the notice of final rulemaking. Within two years of promulgation (or 

three years if EPA lacks sufficient information), the Act requires EPA to 

promulgate designations. Id. § 7407(d)(1)(B)(i). EPA may modify any submitted 

list of designations provided by a State if it gives the State 120 days notice, and 

must promulgate designations as EPA deems appropriate for any area for which no 

designation recommendation is provided by a State. Id. § 7407(d)(1)(B)(ii). 

Thus, EPA’s statutory obligation to promulgate designations is independent of 

whether a State submits recommendations.

The SO2 Rule, like its predecessors, includes regulatory provisions that 

establish the NAAQS itself, as well as regulations governing the installation and 

use of monitors utilized to measure ambient concentrations of SO2. See, e.g., 40

C.F.R. §§ 50.4(e); 50.14(c)(2)(vi); 50.17; part 50 Appendices A-1 and T; part 53,
Case: 10-1252 Document: 1276211 Filed: 11/08/2010 Page: 7

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and part 58. Historically, to determine if an area is in attainment with the SO2

NAAQS, EPA has used a combination of results from regulation-required monitors 

and air quality modeling, even though in the NAAQS regulations themselves EPA 

has not promulgated requirements that States or sources conduct modeling.

Instead, at 40 C.F.R. part 51, Appendix W, EPA has promulgated guidelines on air 

quality models, to be used for regulatory purposes such as State Implementation 

Plan (“SIP”) development and new source review and

prevention-of-significant-deterioration permitting actions. See, e.g., 40 C.F.R. part

51, Appendix W, § 1.0. In the current rule EPA has revised the regulatory 

requirements for the minimum number and placement of monitors and adopted a 

new reference method for detecting ambient SO2, but did not promulgate or revise 

any requirements regarding modeling.

In the preamble to the proposed SO2 Rule, EPA discussed the revisions to 

the monitoring network proposed to account for the revision of the standard, i.e., 

the change from the 24-hour and annual standards to a single one-hour standard.

74 Fed. Reg. 64,810, 64,846-55 (Dec. 8, 2009). In the proposal EPA did not 

discuss its historic and current uses of modeling in implementing the then-effective 

annual and 24-hour SO2 standards. In public comments on the proposal, numerous 

parties suggested that the proposed monitoring network was both inadequate in 

scope and overly burdensome to administer, and some commenters suggested that
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modeling should be used to relieve the administrative burden that a more extensive 

monitoring regime would otherwise impose. 75 Fed. Reg. at 35,551/1.

In the preamble to the final rule, EPA explained in response to comments

that the Agency anticipated in subsequent actions to continue its historic practice of 

relying on both modeling and monitoring for determining whether an area is in 

attainment with the SO2 NAAQS and adopted rules for a smaller monitoring 

network than initially proposed. 75 Fed. Reg. at 35,550-51. However, the

preamble makes clear that, except for the promulgated requirements relating to the 

scope of the monitoring network and detection method, the Agency is still 

developing its policy for such future actions as designations and SIP 

approvals/disapprovals and intends to issue further guidance in the future through a 

notice-and-comment process. Id. The preamble also states EPA’s expectation that 

any decisions about whether to base an attainment designation or determination on 

monitoring alone, without reliance on modeling, would be made on a case-by-case 

basis. Id. at 35,552 n.22.

Following promulgation of the rule, numerous parties filed petitions for 

review with this Court, and each of those parties also submitted to EPA 

administrative petitions for reconsideration of the rule under section 307(d)(7)(B) 

of the Act, 42 U.S.C. § 7607(d)(7)(B). The petitions for reconsideration objected 

to EPA’s final rulemaking preamble discussion explaining EPA’s anticipated
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approaches in future designations and SIP actions. In addition, each requested that 

EPA administratively stay the final rule pending such reconsideration. EPA is 

currently evaluating the petitions for reconsideration and has not yet formally 

responded to them, but, as the Agency stated in its pending motion filed with the 

Court seeking a short-term abeyance of the instant litigation, EPA intends to 

provide initial responses to the petitions for reconsideration, including the requests 

for a stay of the rule, by January 8, 2011.

STANDARD OF REVIEW

A stay is a disfavored remedy. “On a motion for stay, it is the movant’s 

obligation to justify the court’s exercise of such an extraordinary remedy.” Cuomo

v. United States Nuclear Regulatory Comm’n, 772 F.2d 972, 978 (D.C. Cir. 1985). 

The factors for determining whether a stay is warranted are: (1) whether the

movant has demonstrated a substantial likelihood that it will prevail on the merits; 

(2) the prospect of irreparable injury to the moving party if relief is withheld; (3) 

the possibility of harm to other parties if relief is granted; and (4) the public 

interest. Nken v. Holder, 129 S. Ct. 1749, 1761 (2009). These four prongs of the

stay standard are to be applied stringently. Aberdeen & Rockfish R.R. Co. v.

Students Challenging Regulatory Agency Procedures, 409 U.S. 1207, 1218 (1972). 

“A stay is not a matter of right, even if irreparable injury might otherwise result.” 

Nken, 129 S. Ct. at 1760 (citation omitted).
Case: 10-1252 Document: 1276211 Filed: 11/08/2010 Page: 10

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To demonstrate a substantial likelihood of success on the merits, a petitioner 

must show that it is likely to persuade this Court that EPA’s action is “arbitrary, 

capricious, an abuse of discretion, or otherwise not in accordance with law.” 42

U.S.C. § 7607(d)(9)(A). This narrow, deferential standard prohibits a court from 

substituting its judgment for that of the agency and presumes the validity of agency 

actions. Motor Vehicle Mfrs. Ass’n v. State Farm Mut. Auto. Ins. Co., 463 U.S.

29, 43-44 (1983). Judicial deference also typically extends to an agency’s 

interpretation of a statute it administers, United States v. Mead Corp., 533 U.S.

218, 227-31 (2001); Chevron, U.S.A., Inc. v. Natural Res. Def. Council, Inc., 467

U.S. 837, 842-45 (1984), and of its own regulations. Auer v. Robbins, 519 U.S.

452, 457 (1997).

To establish irreparable harm, a petitioner must demonstrate an injury that is 

“both certain and great; it must be actual and not theoretical.” Wisconsin Gas Co.

v. FERC, 758 F.2d 669, 674 (D.C. Cir. 1985). A movant for injunctive relief must 

show that “[t]he injury complained of [is] of such imminence that there is a clear 

and present need for equitable relief to prevent irreparable harm.” Id. (citation 

omitted). The movant must “substantiate the claim that irreparable injury is 'likely' 

to occur,” and “show that the alleged harm will directly result from the action which

the movant seeks to enjoin.” Id; see also Nken, 129 S. Ct. at 1761 (more than a 

“mere possibility” of success on the merits is required, and the standard for 
Case: 10-1252 Document: 1276211 Filed: 11/08/2010 Page: 11

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irreparable harm is more than showing the “possibility” of harm); Winter v.

NRDC, 129 S. Ct. 365, 375-76 (2008) (holding that in a preliminary injunction 

case, plaintiffs must demonstrate that irreparable injury is “likely,” not just 

“possible”).

ARGUMENT 

I. THE MOTION IS PREMATURE

Fed. R. App. Proc. 18(a) requires that a petitioner must ordinarily move first 

before the agency for a stay of its order before seeking a stay in the Court of 

Appeals, or else show that moving before the agency would be impracticable. In 

this case, although North Dakota (and other Petitioners) have sought a stay of the 

SO2 Rule from EPA, EPA has not yet acted on that request, and North Dakota has

not demonstrated that it is impracticable to wait for EPA to act on those requests

before seeking a stay from this Court. As described in EPA’s Motion to Hold Case 

in Abeyance, EPA intends to act on the pending administrative petitions for 

reconsideration by January 8, 2011. At that time EPA will also act on the included 

requests for a stay, as the Agency previously informed Petitioners. Implicit in Rule

18's requirementsis that a petitioner must receive a response to its request for a 

stay from the agency before seeking a judicial stay. North Dakota has neither 

waited for that response, nor demonstrated why doing so would be impracticable 

for submitting a recommendation that is not due until June 2011. Because North
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12

Dakota’s request for a stay is still pending before the Agency and the Agency has 

committed to responding in a timely fashion, North Dakota’s motion for stay in 

this Court is premature and should be denied.

II. NORTH DAKOTA HAS PRESENTED NO BASIS FOR STAYING 

THE ENTIRE SO2 RULE

In its motion, North Dakota asks the Court to stay the SO2 Rule in its

entirety (including the standard itself and the associated monitoring provisions) or, 

in the alternative, to stay the June 3, 2011 statutory deadline by which States may 

submit recommended designations to EPA. North Dakota, however, identifies no 

grounds for staying the entire rule. With regard to the merits, North Dakota 

advances no objection to the promulgated standard or the promulgated

requirements related to monitoring. Nor does it present any claim that it will suffer 

irreparable harm from either the revised standard or the revised requirements

related to monitoring. In fact, North Dakota does not address any aspect of the 

Rule except the non-binding preamble discussion concerning how EPA expects to 

use modeling in future area designations and SIP actions. Thus, North Dakota has 

not met the stringent standard for obtaining a stay of the Rule as a whole, and that 

request must be denied.
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III. NORTH DAKOTA CANNOT DEMONSTRATE A SUBSTANTIAL 

LIKELIHOOD OF SUCCESS ON THE MERITS

The sole claim on the merits presented in the Stay Motion is that the 

preamble of the final rule allegedly requires the use of air quality modeling for 

determining whether an area is in attainment with the revised SO2 NAAQS, that

this approach differs from the approach discussed in the preamble to the proposal,

and that the public did not have an opportunity to comment on the approach 

discussed in the final rule. This claim lacks merit for two reasons.

First, North Dakota is not challenging any provision of the promulgated 

regulations, but rather a discussion in the preamble, i.e., 75 Fed. Reg. at 35,550-54. 

Although some preamble discussions may constitute final agency action, it is clear 

that this particular discussion does not. Rather, the challenged discussion

regarding the potential use of modeling is, at most, non-binding guidance that the

Court lacks jurisdiction to review. The preamble specifically states: 

In many respects, both the overview discussion below and the

subsequent more detailed discussions explain our expected and 

intended future action in implementing the 1-hour NAAQS – in 

other words, they constitute guidance, rather than final agency action

– and it is possible that our approaches may continue to evolve as we,

States, and other stakeholders proceed with actual implementation. In 

other respects, such as in the final regulatory provisions regarding the 

promulgated monitoring network, we are explaining EPA’s final 

conclusions regarding what is required by this rule. We expect to issue

further guidance regarding implementation . . . . EPA intends to solicit

public comment prior to finalizing this guidance.

Id. at 35,550/3 (emphasis added).
Case: 10-1252 Document: 1276211 Filed: 11/08/2010 Page: 14

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Moreover, nowhere in the preamble (much less in any promulgated

regulation) does EPA state that modeling must be used for designating areas as 

attainment, nonattainment or unclassifiable. Thus, the alleged requirement North 

Dakota seeks to challenge does not exist. Rather, the preamble states: “We expect 

that EPA’s final area designation decisions in 2012 would be based principally on 

data reported from SO2 monitors currently in place today, and any refined 

modeling the State chooses to conduct specifically for initial designations.” Id. at

35,552/1 (emphasis added). The preamble then goes on to say “EPA anticipates 

making the determination of when monitoring alone is ‘appropriate’ for a specific 

area on a case-by-case basis, informed by the area’s factual record, as part of the 

designation process.” Id. at 35,552 n.22.

In short, EPA has simply not taken the final agency action alleged by North 

Dakota and there is no such action for the Court to review or to stay. To the 

contrary, the preamble states that EPA believes that its historic approach to SO2

designations continues to appear to be appropriate, while at the same time giving

States the flexibility to recommend the appropriate mix of data to rely on, 

including the possibility of relying entirely on monitoring if supportable.

Second, even if the preamble could be construed as final agency action, 

North Dakota’s claim that the public lacked notice of the possibility that EPA 

might continue to use modeling when making designations is without merit. As
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EPA has frequently explained, because of the nature of SO2 pollution, EPA has 

historically relied on air quality modeling (in addition to any required monitoring)

to determine whether an area is violating the SO2 NAAQS. 75 Fed. Reg. at

35,551/2-3, 35,559/2-3; see SO2 Guideline Document (available at

www.epa.gov/ttn/oarpg/t1/memoranda/so2_guide_092109.pdf) at 2-5 (“For SO2 

attainment demonstrations, monitoring data alone will generally not be adequate.”) 

and at 2-1 (“Attainment determinationsfor SO2 will generally not rely on ambient 

monitoring data alone, but instead will be supported by an acceptable modeling 

analysis which quantifies that the SIP strategy is sound and that enforceable 

emission limits are responsible for attainment.”) As a State responsible for 

recommending whether an area should be designated attainment or nonattainment, 

North Dakota certainly should have been aware of the Agency’s historical 

approach.

Thus, to the extent the approach to designations described in the proposal 

preamble was limited to monitoring, in de-emphasizing the role modeling has long 

played in SO2 implementation it represented a departure from the Agency’s prior

practice. In such circumstances, affected parties are surely aware that not adopting

the proposed change is a possibility. American Iron & Steel Inst. v. EPA, 886 F.2d

390, 400 (D.C. Cir. 1989) (“One logical outgrowth of a proposal is surely, as EPA

says, to refrain from taking the proposed step.”) In fact, the Agency did receive
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comments urging the Agency to retain its historic approach. 75 Fed. Reg. at

35,551/1. Accordingly, there is no basis for North Dakota’s claim that it lacked 

notice that the Agency might choose not to adopt a more monitoring-focused 

approach as discussed in the proposal preamble, but instead to expect to retain its 

historic approach in which modeling is generally, though not always, utilized.

IV. NORTH DAKOTA CANNOT DEMONSTRATE AN IMMINENT 

THREAT OF IRREPARABLE HARM

There is no merit to North Dakota’s claim that it will suffer irreparable harm 

if the SO2 Rule or the statutory deadline to submit designation recommendationsis 

not stayed. North Dakota first claims that it will be harmed because the SO2 Rule 

“casts a cloud” over its ability to use its monitoring data and “deprive[s] the state

of its right to manage its air resources.” Stay Motion at 17. As demonstrated 

above, there is no factual basis for this claim because neither the SO2 Rule itself 

nor the preamble discussion prohibits North Dakota from basing its recommended 

designations on its monitoring data alone. 75 Fed. Reg. at 35,552 n.22. Nor does 

anything in the Rule or preamble prohibit EPA from basing its designations for 

North Dakota on monitoring data alone if EPA determines that the monitoring data 

is sufficient to determine North Dakota’s attainment status.2/

2/ If EPA were to determine that the monitoring data was not sufficient to determine 

an area’s attainment status, and thus that the area would have to be categorized as 

unclassifiable until sufficient monitoring data or modeling results were available,

(continued...)
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Moreover, the State’s recommended designations, which are due June 3,

2011, have no legal effect on sources. Not until EPA promulgates the actual 

designations, which the statute requires it do by June 3, 2012 (or 2013 if extended), 

will there be a designation in place that has legal effect. Thus, North Dakota can 

suffer no actual harm from submitting its recommended designations.

North Dakota’s second claim of harm, that the use of modeling will result in 

more areas being designated as nonattainment because modeling is more 

“conservative,” Stay Motion at 17-18, is purely speculative. North Dakota presents 

no evidence at all to support its assertion that modeling will necessarily result in 

areas of the State being designated as nonattainment inappropriately, and thus there 

is no basis on which the Court could find that North Dakota could suffer injury.

3/

Furthermore, as the preamble states, the modeling guidance that EPA intends to

2/

(...continued)

that designation would be result of the insufficiencies in the data, not of anything 

that EPA has done in the Rule.

3/ While it might seem at first blush as if actual monitoring should be inherently more

accurate than modeling, this is not necessarily the case. In fact, “[i]n the past, EPA

used a combination of modeling and monitoring for SO2 during permitting, 

designations and re-designationsin recognition of the fact that a single monitoring 

site is generally not adequate to fully characterize ambient concentrations,

including the maximum ground level concentrations, which exist around stationary

SO2 sources.” 75 Fed. Reg. at 35,559. This is especially important because “[t]he

1-hour NAAQS is intended to provide protection against short-term (5 minute to

24 hour) peak exposures”. Id. See American Lung Ass’n v. EPA, 134 F. 3d at

392-93 (remanding EPA’s determination that such exposures do not constitute a 

threat to public health) and 75 Fed. Reg. at 35,536 (5-10 minute SO2 exposures can 

result in adverse health effects to asthmatics).
Case: 10-1252 Document: 1276211 Filed: 11/08/2010 Page: 18

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provide States for use in determining attainment of the revised SO2 standard is still 

under development. 75 Fed. Reg. at 35,552-54. Thus, any statements about how

the use of modeling affects the designation process for the revised SO2 standard are 

necessarily speculative.

Finally, the actual designations will be made by EPA, an action that EPA 

expects to take by June 3, 2012. States have an opportunity under the Act to 

provide input on the designations before they are made, and EPA’s designations 

are subject to judicial review. Any claim that modeling is inappropriately used by 

EPA for a particular designation can and should be raised in that process.

V. A STAY WOULD HARM THIRD PARTIES AND IS CONTRARY TO 

THE PUBLIC INTEREST

A stay of the SO2 Rule, whether in whole or in part, would cause harm to 

third parties and is contrary to the public interest because it would delay

achievement of the public health benefits of the revised standard, which is now in 

effect and being used for the Act’s New Source Review and Prevention of 

Significant Deterioration permitting programs. After an exhaustive review of the 

existing data, EPA determined that the prior SO2 standard was not adequately

protective of human health and required revision, a conclusion amply supported by

the record. EPA’s statutorily mandated science review committee, the Clean Air 

Scientific Advisory Committee, recommended unanimously that the current 

standard be revised because the current standards are not adequate to protect the
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19

public health, and that EPA should adopt a one-hour standard in their place. 75

Fed. Reg. at 35,530, 35,538. Short-term exposure to SO2 results in adverse 

respiratory effects such as bronchoconstriction (narrowing of the airways) and 

increased asthma symptoms. Id. at 35,525-26. Studies also show an association 

between short-term SO2 exposure and increased emergency department visits and 

hospital admissions for respiratory illness, particularly among children, the elderly, 

and asthmatics. Id. at 35,547.

Importantly, the data demonstrate that these adverse health effects can occur 

at concentration levels that are allowed by the prior SO2 NAAQS. Id. at

35,535-36. Thus, implementation of the revised standard is necessary to reduce the

adverse health effects associated with these exposures. North Dakota’s motion 

does not address this issue at all, and thus fails to address two of the elements 

needed for a stay of agency action.

A stay of the SO2 Rule, either in whole or in part, is likely to delay 

attainment of the revised standard. A delay of the SO2 Rule as a whole will delay 

States’ implementation of the control measures needed to achieve compliance with

the revised standard and the requirement for new or modified major stationary 

sources to implement necessary controls pursuant to the Clean Air Act’s New 

Source Review and Prevention of Significant Deterioration permit requirements.
Case: 10-1252 Document: 1276211 Filed: 11/08/2010 Page: 20

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A stay of the date for States to recommend designations for areas as 

attainment, nonattainment, or unclassifiable will not delay EPA’s independent 

obligation to promulgate designations. However, it could complicate the process 

of establishing area designations and impose additional burdens on EPA if States 

do not submit designation recommendations because EPA would not have the

States’ recommended designations as a starting point. Thus, a stay of the SO2 Rule 

will harm third parties and be adverse to the public interest by delaying the public

health benefits of the revised standard.

CONCLUSION

For the reasons stated above, North Dakota’s motion for a stay of the SO2

Rule should be denied.

Respectfully submitted, 

IGNACIA S. MORENO

Assistant Attorney General

/S/ Norman L. Rave, Jr. 

NORMAN L. RAVE, JR. 

Environmental Defense Section

Environment & Natural Resources Division

United States Department of Justice

P.O. Box 23986

Washington, D.C. 20026-3986 

(202) 616-7568

Counsel for Respondent
Case: 10-1252 Document: 1276211 Filed: 11/08/2010 Page: 21

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Of Counsel:

STEVEN SILVERMAN 

MICHAEL THRIFT 

Office of General Counsel

U. S. Environmental Protection Agency

1200 Pennsylvania Ave., NW 

Washington, DC 20460

November 8, 2010
Case: 10-1252 Document: 1276211 Filed: 11/08/2010 Page: 22

CERTIFICATE OF SERVICE

I hereby certify that on this 8th day of November, 2010, I caused a copy of 

the foregoing document to be served by the Court’s CM/ECF system on:

Andrea Bear Field

Lucinda Minton Langworthy

Hunton & Williams LLP

1900 K Street, N.W. 

Washington, DC 20006

Leslie Sue Ritts

Ritts Law Group, PLLC

620 Fort Williams Parkway

Carriage House

Alexandria, Virginia 22304

Donald Trahan

State of Louisiana Dept. of Environmental Quality

P.O. Box 82282

Legal Affairs Division

Baton Rouge, Louisiana 70884-2282

David S. Baron 

Seth Lee Johnson

Earthjustice Legal Defense Fund

1625 Massachusetts Ave., NW 

Suite 702

Washington, DC 20036-2212

Roxanne Giedd

Office of the Attorney General, 

State of South Dakota

1302 East Highway 14

Suite 1 

Pierre, South Dakota 57501-8501

Nhu Q. Nguyen

Office of the Attorney General, 

State of Nevada

100 North Carson Street

Carson, Nevada 89701-4717
Case: 10-1252 Document: 1276211 Filed: 11/08/2010 Page: 23

Sandra Patricia Franco 

Robert N. Steinwurtzel 

Bingham McCutchen LLP

2020 K Street, NW 

Washington, DC 20006-1806

Margaret I. Olson

Assistant Attorney General 

Office of the Attorney General 

State of North Dakota

Solicitor General

500 North 9th Street

Bismark, North Dakota 58501-4509

Paul M. Seby 

Marian C. Larsen 

Moye White, LLP

1400 16th Street

6th Floor

Denver, Colorado 80202-1486

Nancy Elizabeth Olinger 

Assistant Attorney General 

Environmental Protection and

Administrative Law Division 

P.O. Box 12548 (MC-018) 

Austin, Texas 78711-2548

Benjamin Joseph Alke

Goetz, Gallik & Baldwin, PC

35 North Grand

P.O. Box 6580

Bozeman, Montana 59771-6580

/S/ Norman L. Rave, Jr.

Norman L. Rave, Jr. 

2



I l-45-i995 2,37at.1 FROi.1

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i , t I r ' -! | t / r\.-,,. l;lJ \/ v/'v/Lf lJ

JOHN K. VAt{ DE KFr}{p, Attorney General.

of the State of California

ANDREA SHERIDA}I ORDTN

Chief Assistant Attorney General

THEODORA BERGER

Assistant Attorney General

CRAIG C. THOI.'PSON

EDWARD G. WETL

CLI FFORD RECH?SCHAFF€N

Deputy Attorneys General

21ol webster Street

Oakland, CA 94612

Telephone: (415) 464-0572

FILED

SUPERTOR CCURT

SAfITA 8r'l"FrlilA

DEC 03 1990

xE}c{Erh A Pil ir ;, ouuf:/ ctsil'FrcoErf

PLE OF THE S?ATE

I. JOHN K. VAIIT DE

neral of the State

Plaintiffs,

v.

A MARIA CHILI, rNc.

Defendant1. I am currently

Environruental protection

(hereafter the "Region',

COUNTY OP SHITA BARBARA

oF CALIFORNfA ex. ) No. SM 64010

KAHP, Attorney

of California, ) (Case transferred to

) South County, Z/26/eol

DECI.ERATTON OF JOEN C.

vruo!|:l

DATE: Dec. 14, 1990

TIME: 9:oo a.m,

Dept: To Be Assigned

ey: { yol.; (ls*

u u$*ane riootns. oc|fu crn'Frcort

Attorneyg for the peopte of the state of carifornia

SUPERIOR COTIRT OF THE STATE OF CALTFORNIA

T, John C. Vinont, declare:

enployed by the United States

Agency (hereatter ilEpArr), Region IX

or rrRegional Officer') as the Regional

Heteorologist. I have been ernployed in this posltion since June

1987.

a. As the Regional l{eteorologist f serve as the

Regionrs expert on air guality nrodeling, neteorological

information and anbient air irnpact analyses. My position is
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within the Air and Toxics Division of the Regional Office. f

provide support to that dlvlslon; to the other divisions witnin

the Region, such as the Haeardous waste oivision; and to state

and locar agencies vithin Region rX. one of the prinary duties

of ny position is to ensure that appropriate air quality rnodeling

techniqres are used by this and other ageneies when conducting

anrbient air quality irrpact analyses.

b. There are a variety of ,'air guality models.il

These include conceptual nrodels, qualitative descriptions of the

behavior of pollutants in tne atrnosphere; physical rnodels, scaled

nodels of pollution sources and their surroundings studied in a

conLrolled environment, Euch as a wind tunnelt statisticar

modeLs, which encompags statisticalJ.y based descriptions of

source-receptor relationships; and mathematical nodels, which are

mathehatical representations of the physical processes which lead

to transport and dispersion of pollutants in the atmosphere. The

focus of tbe remaining dlscussion is on mathematical. rrodelsi

hereafter any reference to an air guarity rrodel is inpricitly

meant to refer to a mathematical air guality nodeI.

c. f perform, review and oversee air quality nodeling

for a variety of different sources and source types. These

include stationary aources with enissions emanating fron a stack,

including st,ack sources with aerodynanlc downwash induced by

nearby buildings; stationary sources htlth emLssions emanating

f,rom a broad area, coruoonly called area sgurces; mobile sources,

emissions from autonobiles, trucks, busses, al.rcraft, etc.; and

urban and regional scale roodeling, which enconpasses modeling aI).
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of the above processes together on the scare of an entlre urban

area or over a number of urban areas together.

d. The pollutants modeled include both inert

pollutants, those which renain cheurically stable for long periods

of tine in the atnosphere, and chemicarry reactive pollutants,

those which undergo relatively rapid chemlcal transformation and

t'hose which are not directry enitted, but rather forrn through a

series of chemical reactions withln the atnosphere.

2. Previous to rny ernployrnent at EpA, I worked from Marcir

1982 to June 1987 as an Environrnental Engineering Specialist in

the Air Quality Bureau of the State of New Mexico. My primary

responsibillties there htere very siurilar to rny current position

at EPA. f performed, anbient inrpact analyses of various air

porlution sources and conducted engineering analyses of the

sources to deternine ernission characteristics. The prinary focus

of the analyses was on inert pollutants from stationary sources.

a- prom August 1978 to March 1982 r worked for the

Atnospheric science Departnent at Colorado State University (csu)

as a Research Assistant. r vorked on a varlety of baeic

scientific researc.h projects dealing with croud physics. My

prirrary area of research dealt with the uptake of acidic

pollutants in snow,

b- Fron Novernber Lg77 to August LgTg r worked as a

Physlcar science Aide for the pacj.fic Marine Environrnentar

Laboratory of the National oceanographic and Atrnospheric

Adninistration. My duties there involved writing a
1

2

3

4

5

6

7

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climatological suEaar)r of h.rget Sound and analyzing the affects

of r.rlnds on o11 spill transport in hrget Sound.

3. I received a Bachelor of Science Degree ln Atnospheric

sciences fron the university of waEhington 1n 1978 and a Haster

of Science Degree in Atnospheric Science froro Colorado State

University.

4. As the Regional Meteorologiet, I routlnely evaluate the

adequacy of air cruality nodering on a technical basis and with

respect to its acceptability in the reguLatory fraroework.

Acceptable air quality rnodeling and analysis procedures are

outlined in The Guideline on Alr ouatitv Hodels (Revised) (EPA

450/2-78-027R, July 1986, supplement A, July tggz) (hereafter the

'rcuidelinen). The Guideline was first published in April 19?B to

satisfy the requirenents of g32O of the 1977 aruendrnents to the

Cl-ean Air Act. The Guideline specifies appropriate modele to use

and provides guidance on their appropriate apptication. The

Guideline provides a common basis for estinating the air quarity

concentrations used in assessing control strategies and

developing emission linits. The nodeling technigr:es ernbodied in

the Guideline are subjected to public, scientific revierr in

aeeordanee with 5320 of the CAA.

a, EPA has four prinary, on-going activities to

provide direct input for consistency in inplementation and for

revisions to the Guideline. The first is a series of annual EPA

workshops conducted for the purpose of ensuring consistency and

providing clarification in the applicatlon of nodels. The second

activity, directed toward the inprovenent of nodeling procedures,
1 l-45-1995 2,39At'1 FROi'1 P 5

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2

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is the cooPerative agreenent that EPA has vlth the scj.entlfic

co-'r'runity represented by the Anerican Heteorological Society.

This agreement provides scientific assessDent of procedures and

proposed techniques and EPonsors workshops on key technical

iseues. The third activity is the solicitation and reviev of new

models fron the technical and user connunity. In the lilarch 27,

19Bo Feder4l..Register, a procedure was outlined for the subnittal

to EpA of privately developed models. After extensive evaluation

and scientifj.c review, these models, as well as those made

available by EPA, are considered for recognltlon ln the

Guideline. The fourth activity is the extensive, on-going

research efforts by EPA and others in air quality and

meteoroloqrical nodel lng.

b. From the aforementioned process a number of models

vere selected as being refined ruodels, suitable for regulatory

application. Each refined urodeL unde:rrent intensive evaluation.

The evaluation exercises include statistical measures of model

perfomance in conrparison with Deasured air quality data and,

where possible, peer scientific reviews.

c. After a model has been selected as a refined nodel

for a partieular €ype of apPlication, EPA considers the model

appropriate for general use for that type of application without

undergoinlt case-by-case evaluatlon, provided that the application

fol.Ior"rs the EPA reeonnendations specified in the Cuideline.

5. The fndustrial Source Conplex models (hereafter ISC) '

have been deened refined rnodels by EPA for application to

industrial complexes. The fSC nodels consist of a short tetm
1

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6

7

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EodeL (rscsr) and a long tern nodel (rscLT). r,ong teln rnoders,

such as rsclT, are only appropriate for sarcul.ating anblent

concentrations for averaging periods of months to a year. short

term urodels, such as rscsT, can be used for averaging tines fron

one hour up to a year. (Hereafter my connents referring to rsc

apply to both fScST and fSCLT, unless othelrrise speclfied- ) I'he

rse model is appropriate for sinulating the emisslons of a

variety of industriaL air enissions. These would, inctude

ernissions from rree standing stac)<s and vents; stacks and vents

which are infruenced by the aerodynarnic effects of nearby

structures; enissions fron area sourcee, such as storage piles or

evaporative emissions frorn open tanlcr; line sources, such as

roaduays; and volume souree,s, such as rarge openings in buildings

from which enissions emanate. The noder is approprlate for

siruulating the anbient inpacts of relativery inert pollutants,

such as ethyrene oxide, vhich do not undergo rapid chemical

transfonratlon in the atnosphere. ?he rnoder will ealcurate the

anbient concentrations at a number of user-specified rrreceptor',

locations.

a- For simulating a stack-type 6ource, rsc requires

tbe input of the location, emission rate, physical stack height,

stack gas exit verocity, stack inside diameter, and stack gas

temperature. rf the source l"s affected by the aerodynanic

effects of buildings then inputs would alao lnclude information

about the building dinensions.

b. The ISC nodel also requires meteorological data as

input- These data include the wind speed, wind direclion,

P.6
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2

3

4

5

5

7

8

9

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tenperatrrre, stablllty class and nixing height. The

meteorological data nust be representative of the geographic area

being modeled to be accepted for a refined regulatory

application.

c. The fSC nodel has gone through a nunber of

perfotrorance evaluation studieE, as outlined above. The following

are several references of evaluation studies invoLving fSC:

(1) Bowers, J, F., and A, J. Anderson, 1991. A n

Evaluation Study for the Industrial Source Conplex (fSC)

Disperslon ltodel, EPA PubLication No. EPA-AiO/{-81.-002. U. S.

Environmental Protection Agency, Research Triangle Park, .Nc.

(2, Bowers, J. F.; A. J. Anderson, and W. R .

Hargraves, 1982. Tests of the fndustrial Source Conplex (ISC)

Dispersion Model at the Armco Hiddle-town, Ohio Steel UiIL, EpA

Publication No, EPA-450/4-82-006. U. S. Envj.ronmental Protection

Agency, Research Triangle Park, NC.

(3) Seire, J. S., and L. L. Schulman, 1981.

Evaluation of the BLP and rsc Models with sF5 Tracer Data and soz

Measurements at Aluninum Reduction Plants. Air Pollution Control

Association Specia,Ity Conferenee on Dispersion Modeling for

Complex Sources, St. LouiE, MO.

(4) Schulman, L. L. and S. R. Hanna, 1986.

Evaluation of Downwash Modifications to the Industrial Source

CompLex Model. Journal of the Air Pollution Control Association,

36:258-264 .

d. fn uy experlence of conductlng and reviening air

quality modeling analyses, I have found that of the EPA approved
I

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3

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6

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models, the ISC nodel is the most widely used nodel for

determining the aubient concentrations of emissions from

industrlal sources. This is prinarily due to its abillty to

simulate alnost any t)T)e of lndustrial conflgnrratl.on and its

status aa a refined model under EPA giuidelines. EPA considers it

appropriate for use without undergoing case by case perforruance

evaluation.

6. When EPA has a refined nodeL appropriate for a specific

type of applicati,on, sueh as the ISC nodel, the nodeling results,

based on the appropriate input data, are generally preferred by

EPA over ambient rnonitoring data for detenuinl-ng emission

lirnitations for both new and existing sources. Nornrally, EPA

does not accept aonitoring data as the sole basis for deternining

an emission liroitation. When a refined nodel is available, EPA

generally considers the nodel results alone (including background

concentrations) sufficient for deteraining anbient concentrations

of enissions from industrial sources and setting appropriate

emission Lirnitations.

a. Monitoring data suffers frora a nunber of

limitations. One of the prinary linitations is that any given

nonitor can only neasure what is happening at the location where

the rnonitsor is physically located and at the tine it is

operating. In order to adequately detect the naxinun inpact of

any particular source, many nonitors would have to be run gver a

nurnber of years. A monitoring progran designed to adeguately

detect a naximum concentratlon and to adequately characterize the

concentration field would be very expensive. A nurnber of years

P.a

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of data qrould be necessar-y to collect enough sanples to cover aII

possible rneteorological situations in conbination vlth the

different operating conditions of the facility. A monLtoring

progran slth only one or tso monitors or of a ve!')t short duration

would be inadequate to e,nsure that naximun anbient inpacts would

be detected.

b, The usual intent of conducting an arabient inpact

analysis of an air pollution source is to deteraine if the

emissions are likely to affect hunan health or affect the

environrnent. The arnbient coneentrations are compared against

health or environmental affects data. Rather than helping to

resolve a problem, a prolonged ambient monitoring study allons

continued air guatity degradation, which in turn affects the

health or environrnental guality which vas to be protected. For a

new source being proposed, it is inpossible to measure its

impacts, since it is not yet builtc. The rnethod of analysis preferred by EPA for

determining the ambient concentrations resultlng from emissions

into the atmosphere of industrial sources, including toxic air

emissions, is ruodeling. As discussed above, before EPA

determines a model', such as ISC, to be a refined model,

appropriate for general use. the rnodel undergoes rigorous

evaluation and is determined to yield accurate estimates of the

ambient air concentratlonE resulting fron emission sources under

a variety of eonditione. With a model, the Bource can be

simulated under the full range of its potential operating and

eruission conditions, rather than being linited to the specific

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operating conditions occurring durlng the period of a linitea

nonitorlng study. Tlre uodel can also yleLd anbient concentration

data at any nunber of receptor loeationsr'rather than only at the

linited nunber of locations where a tronltor is physically

located. Also, iD air quality uodel provldes the only practical

nethod of estirnating the anbient lnpacts of a new source. A

model provides flexibility in an analysis and ean be :ltn

relatively quickly, at relativety little expense.

d. Modeling also allops source contributions to a

particular anbient concentration to be ascertained- If two

sources each eroit tbe sane pollutant, it is impossible to tell

from an anbl,ent meaEureDent of the specific pollutant, the

relative contributions to the measured arnbient concentration,

unless there is sone unigue surrogiate being ernitted fron one of

the facilities. Also, there is the uncertainty of whether a

heretofore unknown source of the pollutant of concern has

contributed to the measurernent. Hodeling, allows the impact of

each source to be calculated separately and in combination.

e. The use of rnonitoring data also Pre-suPposes that

there are acceptable and reliable nronitoring techniques available

for the pollutant^of interest. fn the past, this has generally

been the case. EPA has established acceptable and reliable

methods of rneasuring a nurnber of pollutants whtcn were regulated

under the Clean Air Act. Recently, howcver, the issue of toxic

air contarninants has arisen. Ambient heasurement techniques,

which can adeguately and accurately detect a speciflc toxic air

contarninant, are not necessarily available. The transport and
11-05-1995 2 42AM FROM P. 11 

1 dispersion of buoyant or neutral plumes of gaseous pollutants, 

2 which are relatively inert in the atmosphere, is the same, 

3 regardless of the specific chemical constituents of the gas. 

4 Therefore, modeling provides a useful technique for detecting 

5 levels of pollutants in the air if reliable ambient measurement 

6 techniques are not available. 

7 f. EPA does recognize the usefulness of ambient 

8 measurements for information on background concentrations, 

9 provided reliable monitoring techniques are available. EPA does 

10 not recommend, however, that ambient measurements be used as the 

11 sole basis of setting emission limitations or determining the 

12 ambient concentrations resulting from emissions from an 

13 industrial source. These should be based on an appropriate 

14 modeling analysis. 

15 I declare under penalty of perjury that the foregoing is 

16 true and correct. 

17 DATED: #o V~mbfr- ..JO /f90 ./ 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 
Case: 10-1252 Document: 1288492 Filed: 01/18/2011 Page: 1

ORAL ARGUMENT NOT YET SCHEDULED 

UNITED STATES COURT OF APPEALS 

FOR THE DISTRICT OF COLUMBIA CIRCUIT 

NATIONAL ENVIRONMENTAL 

DEVELOPMENT ASSOCIATION'S 

CLEAN AIR PROJECT, 

Petitioner, 

v. 

UNITED STATES ENVIRONMENTAL 

PROTECTION AGENCY, 

Respondent. 

) 

Docket No. 10-1252 

(and consolidated cases) 

DECLARATION OF ROGER W. BRODE 

1. My name is Roger W. Brode. I hold B.S. and M.S. degrees in Atmospheric Sciences and I 

am currently assigned as a physical scientist in the Air Quality Modeling Group within the 

Air Quality Assessment Division of the Office of Air and Radiation's Office of Air Quality 

Planning and Standards at the U.S. Environmental Protection Agency ("EPA"), where my 

1 
Case: 10-1252 Document: 1288492 Filed: 01/18/2011 Page: 2

responsibilities include the development, evaluation and application of air quality dispersion 

models and the development of guidance associated with application of such models in 

support of EPA regulations governing the Prevention of Significant Deterioration 

("PSD")_permitting program. I have been involved in the development, evaluation, testing, 

and documentation of the American Meteorological Society EPA Regulatory Model 

("AERMOD") throughout its history. I currently serve as co-chair of the AMS/EP A 

Regulatory Model Improvement Committee (AERMIC) consisting of atmospheric scientists 

and dispersion model experts overseeing the further technical development of the model, and 

as co-chair of the AERMOD Implementation Workgroup consisting of EPA Regional Office 

and State dispersion modelers whose charge has been to indentify and assess potential issues 

with implementation of the AERMOD model as EPA's preferred model under Appendix W 

of Part 51 of the Code ofF ederal Regulations. 

2. The revised primary national ambient air quality standard for oxides of sulfur ("S02 

NAAQS") requires that the three year average ofthe annual 99111 percentile of the daily 

maximum 1-hour average concentrations ofS02 be less than or equal to 75 parts per billion. 

In addition, owners and operators of a new major stationary source or a major source 

undergoing a major modification located in areas not designated "nonattainment" for the S02 

NAAQS must obtain a PSD permit, and to do so must demonstrate (among other things) that 

the emissions increases from the new or modified source will not cause or contribute to a 

violation ofthe revised S02 NAAQS. Existing air quality models, including AERMOD, are 

readily capable of accurately predicting whether the revised primary S02 NAAQS is attained 

and whether individual sources cause or contribute to a violation of the S02 NAAQS. 

Specifically, dispersion models that are used to demonstrate compliance with the S02 (and 

2 
Case: 10-1252 Document: 1288492 Filed: 01/18/2011 Page: 3

other) NAAQS, including under PSD permitting programs, use sequential hourly 

meteorological data as the basis for estimating ambient concentration levels. These data are 

combined with other inputs (chiefly source emission information, background emissions, and 

receptor information) to predict transport and dispersion of emitted pollutant plumes. Since 

the key varying inputs to these models are input on an hourly basis, all applications of these 

models under the guidance in Appendix W (40 CFR Part 51) are predicated upon the models' 

ability to predict hourly ambient concentrations. These models thus generate one-hour air 

quality distributions from which the three year average of the annual 99th percentile of daily 

maximum 1-hour average concentration of S02 can be readily calculated or otherwise 

reasonably approximated. 

3. As part ofthe basis for EPA adopting the AERMOD model as the preferred model for nearfield applications in the Guideline on Air Quality Models, Appendix W to 40 CFR Part 51, 

the performance ofthe AERMOD model was extensively evaluated based on a total of 17 

field study data bases (AERMOD: Latest Features and Evaluation Results. EPA-454/R-03-

003. U.S. Environmental Protection Agency, Research Triangle Park (2003), portions of 

which are attached to this affidavit) ("EPA 2003"). The scope of the model evaluations 

conducted for AERMOD far exceeds the scope of evaluations conducted on any other model 

that has been adopted in Appendix W to Part 51. These evaluations demonstrate the overall 

good performance of the AERMOD model based on technically sound model evaluation 

procedures, and also illustrate the significant advancement in the science of dispersion 

modeling represented by the AERMOD model as compared to other models that have been 

used in the past. In particular, adoption of the AERMOD model has significantly reduced the 

3 
Case: 10-1252 Document: 1288492 Filed: 01/18/2011 Page: 4

potential for overestimation of ambient impacts from elevated sources in complex terrain 

compared to other-models. 

4. Some of the field studies used to evaluate AERMOD model performance involved ambient 

sampling of S02 for a period of one year or more at several (typically about 1 0) monitors 

sited around operating power plants. Other field studies involved sampling of controlled 

releases of non-reactive tracers, typically SF6, generally over a shorter duration than the 

operational studies, but with more robust sampling to facilitate more detailed diagnosis of 

model performance. Although the long-term field studies associated with operating power 

plants included assessments of 3-hour, 24-hour and even annual average impacts from the 

model, evaluation results for 1-hour averages were routinely included for all of the field 

studies. As shown in Tables 2 and 3 of EPA 2003, modeling and monitored results for 1-

hour averages are in excellent correlation in these studies, with the ratio of predicted to 

observed performance approaching 1: 1 in most instances. Thus, in my opinion, the 

performance of the AERMOD model for estimating 1-hour ambient concentrations is welldocumented and the form of the new 1-hour S02 standard raises no questions or concerns 

regarding the appropriateness of AERMOD. 

5. The S02 NAAQS Coalition states that the revised S02 NAAQS is a "probabilistic" standard 

and asserts that this makes modeling more problematic, especially as compared to the 

previous "deterministic" standard. (Coalition p. 5.) The terms "probabilistic" and 

"deterministic" do not have an ordinarily understood meaning in this context, but it appears 

that the assertion is that predictive models like AERMOD are not suitable for a standard 

which includes a percentile-based form (where the relevant comparison is to a percentile of 

air quality from an air quality distribution), as opposed to an expected exceedance form 

4 
Case: 10-1252 Document: 1288492 Filed: 01/18/2011 Page: 5

(whereby a standard may exceeded on a given number of days and compliance is assessed 

based on air quality on the designated day once the allowed exceedance days are removed 

from the distribution). I know of no reason that AERMOD and other similar types of models 

is suitable for one type of form and not the other. As just stated in paragraph 2, the models 

readily generate air quality distributions from which either percentiles (for the revised S02 

NAAQS, the 991h percentile) or exceeding days can be determined. In fact, the percentile 

form of the 1-hour S02 NAAQS is a more "stable" metric than a standard based on the 1

51-

highest or 2"d -highest concentrations, since the potential impact of "outliers" in the 

distribution is mitigated, especially when the multi-year average aspect of the S02 NAAQS 

is accounted for. 

6. Both the S02 NAAQS Coalition and their affiant Mr. Paine raise a number of points 

regarding the issue of whether allowable or actual source emissions should be modeled, 

stating that use of allowable emissions overstates sources' impacts. See, e.g. Paine Decl. at 1[ 

~ 11-14. This issue is independent of the predictive accuracy of AERMOD or other models. 

7. EPA's rules and guidance provide significant flexibility in the choice of which models to use 

in determining if sources cause of contribute to NAAQS violations for purposes ofPSD 

permitting. EPA's rules specify that "where an air quality model specified in Appendix W of 

this part ... is inappropriate, the model may be modified or another model substituted" with 

written approval from EPA. 40 C.F.R. §51. 166 (1)(2). The rules therefore allow flexibility, 

subject to appropriate requirements, for alternative modeling techniques to be applied on a 

case-by-case basis subject to approval by appropriate reviewing authority. 

8. The declaration of Michael E. Long voices concerns regarding the use of the AERMOD 

dispersion model to support implementation of the 1-hour S02 standard, and asserts that 

5 
Case: 10-1252 Document: 1288492 Filed: 01/18/2011 Page: 6

"AERMOD significantly over predicts the actual one-hour ambient concentrations in our 

area when the available information is used in the model as directed by EPA." Long Decl. at 

~ 8. This assertion is based on a comparison bf model-predicted ambient concentrations to 

ambient 802 concentrations reported for 2008 at local EPA monitoring stations in the 

vicinity of the ArcelorMittal facilities being modeled. Mr. Long reports that the "AERMOD 

model predicted one-hour concentrations that were higher than the monitored values 90% of 

the time and the predicted values were as much as 373,131 times higher than the actual 

monitored values." Id. Lacking any additional details regarding the model-to-monitor 

comparisons cited by Mr. Long, the response here is necessarily limited to a general 

discussion of issues involved in such comparisons. A number of factors can affect the 

comparison of a modeled concentration with a monitored concentration, including the 

accuracy of the emission rate and other source characteristics input to the model, the 

representativeness of the meteorological data input to the model, and the influence of local 

geographical features and land use characteristics on the transport and dispersion of the 

plume. Another key factor that affects comparisons of modeled vs. monitored 

concentrations, paired in time and space, is the potential error or uncertainty in the wind 

direction input to the model for that hour since the wind direction will determine the 

transport direction of the plume. Slight errors in the transport wind direction may account for 

significant differences in modeled vs. monitored concentrations for a specific hour, 

especially for elevated plumes under stable atmospheric conditions where the lateral spread 

of the plume can be very limited for relatively long transport distances, and errors of a few 

degrees in wind direction can be the difference in the plume directly impacting the monitor 

for a particular hour or the plume missing the monitor completely. In such cases, a factor of 

6 
Case: 10-1252 Document: 1288492 Filed: 01/18/2011 Page: 7

3 73,131 difference between modeled and monitored concentrations could easily be 

attributable to error or uncertainty in the wind direction. Note that wind directions reported 

from routine meteorological monitoring stations located at airports, the most common source 

of meteorological data used in air quality modeling applications, are reported to the nearest 

10 degrees. In addition, the comparison may reflect issues related to use of allowable versus 

actual emissions, which is irrelevant for purposes of determining whether the AERMOD 

model itself is biased. 

9. The declaration of Robert J. Paine addresses practical issues in applying the AERMOD 

model that allegedly arise due to the form of the 1-hour S02 standard, as well as concerns 

regarding the conservatism of the assumptions on source emissions based on Appendix W 

guidance in relation to the 1-hour S02 standard. Responses to these issues are summarized 

below, numbered according to Mr. Paine's declaration, with some responses applying to 

multiple comments: 

(a) 

Paine Decl. ~ 9. : The AERMOD model "does not yet provide results that allow permit 

applicants to follow EPA's guidance for determining whether they comply with the 1-hour S02 

NAAQS because of the unique statistical form of that NAAQS." 

Paine Decl. 11 10.: "The form ofthe 1-hour S02 NAAQS requires the applicable guideline 

dispersion model to compute the highest 1-hour concentration for each day at each modeled 

receptor point, and to keep track of this daily 1-hour maximum concentration statistic for each of 

the 365 days for each year modeled independently at each location modeled. 

7 
Case: 10-1252 Document: 1288492 Filed: 01/18/2011 Page: 8

Paine Decl. ~ 11. : "In the case for which a cumulative modeling analysis is required, this same 

procedure must be applied to the combined contributions of the individual source being 

permitted, nearby sources and regional background." 

Response: As stated in paragraph 2 above, all of these metrics are readily obtainable from model 

outputs. Although the existing version of AERMOD does not contain an algorithm from which 

these metrics emerge automatically as model outputs, this does not change the result that all of 

these metrics are obtainable. In fact, we are aware that Mr. Paine, along with other private sector 

parties, developed post-processing tools to compute the 1-hour S02 design value based on the 

form of the revised S02 NAAQS utilizing model output options available at the time. 

(b) 

Paine Decl. 'II 11. : "Furthermore, EPA in most cases requires a conservatively high regional 

background concentration to be added for all hours modeled, rather than the actual values 

measured during each hour of the modeling simulation." 

Response: EPA issued guidance on a range of issues related to the new 1-hour S02 standard on 

August 23,2010, including a recommendation that the overall highest 1-hour monitored S02 

concentration from a representative monitor could be used to account for the monitored 

background component in a cumulative impact assessment "without further justification." We 

recognize that use of the overall highest 1-hour monitored value may entail a degree of 

conservatism that could prevent a source from demonstrating compliance with NAAQS; 

however, that conservatism forms the basis for allowing the approach to be used without further 

justification. The August 23 memorandum further stated that "Additional refinements to this 

'first tier' approach based on some level of temporal pairing of modeled and monitored values 

8 
Case: 10-1252 Document: 1288492 Filed: 01/18/2011 Page: 9

may be considered on a case-by-case basis, subject to approval by the reviewing authority, with 

adequate justification and documentation." However, we also note that Appendix W explicitly 

makes "no attempt" to "comprehensively define" the criteria involved in determining which 

nearby sources to include in an analysis "owing to both the uniqueness of each modeling 

situation and the large number of variables involved in identifying nearby sources." See 

Appendix W section 8.2.3.b. 

(c) 

Paine Decl. 1! 12.: "Following EPA's regulatory requirements for PSD modeling, the modeled 

predictions of hourly concentrations of a probabilistic standard such as the 99th percentile daily 

maximum hourly S02 concentrations produced by a single source for which a permit is sought 

can be much higher than concentrations that actually occur in the ambient air." 

Response: As noted in paragraph 6 above, the issue of allowable versus actual emissions is 

independent to the question of the accuracy of AERMOD or other models. Also, as stated in 

paragraph 5 aboYe, there is no reason that AERMOD (or other similar models) is not equally 

accurate in predicting percentile air quality distributions or expected exceedances on a given day. 

The underlying data which are input to the model generate air quality distributions which are 

equally suitable for either type of form. 

(d) 

Paine Decl. ~ 12. : "Modeling of peak S02 emissions as if they occur continuously is a 

distortion of reality and will overestimate the ambient air concentrations. This is especially true 

for 1-hour averages, since the variation of emissions for such a short averaging period is 

9 
Case: 10-1252 Document: 1288492 Filed: 01/18/2011 Page: 10

potentially much higher than that for the other S02 NAAQS averaging periods. This makes the 

assumption of constant peak emissions a critical issue for this new standard." 

Response: The purpose of dispersion modeling in the context of the PSD permitting program is 

to demonstrate that the proposed new or modified emissions will not cause or contribute to 

violations of the standard if the permit is granted. This is inherently a predictive exercise since it 

entails an assessment of proposed future emissions. EPA's guidance for conducting such 

analyses is dictated by and consistent with that purpose. Mr. Paine's statement that 1-hour 

averages are more variable than longer averaging periods again does not relate to potential model 

bias and in any case makes a sweeping generalization for situations that differ case-by-case. The 

statement that peak S02 emissions should not be modeled is a restatement of the dispute as to 

use of allowable or actual emissions, and does not relate to the issue of model bias. 

(e) 

Paine Decl. , 13. : "The model overprediction tendency is even more likely to be a problem in a 

cumulative impact analysis because numerous sources (i.e., the source being permitted and 

potentially thousands of other nearby sources) are all modeled at peak emissions at all times and 

added to a regional background level of S02 ... leading to unrealistic predictions that the 1-hour 

S02 NAAQS will be exceeded." 

Response: As noted, the issue of allowable versus actual emissions is independent ofthe issue of 

models' predictive accuracy. However, EPA's August 23,2010 clarification memo regarding 

the applicability of Appendix W guidance for the 1-hour S02 NAAQS cautioned "against the 

literal and uncritical application of very prescriptive procedures for identifying which 

background sources should be included in the modeled emission inventory for NAAQS 

10 
Case: 10-1252 Document: 1288492 Filed: 01/18/2011 Page: 11

compliance demonstrations, including those described in Chapter C, Section IV. C.l of the draft 

New Source Review Workshop Manual (EPA, 1990), noting [again] that Appendix W 

emphasizes the importance of professional judgment in this process." One motivation for that 

caution was a concern that application of such procedures could lead to an overly conservative 

result by including too many background sources in the cumulative impact assessment. As noted 

elsewhere, Section 8.2.3.b of Appendix W suggests that "the number of such sources is expected 

to be small except in unusual situations." 

(f) 

Paine Decl. ~ 13. : "Moreover, since the nearby sources will be modeled individually (but their 

emissions are already accounted for in the regional monitoring), there will inevitably be doublecounting of the background impacts between the components of the "nearby sources" and the 

"regional background", especially for the common situation of the state requiring a single peak 

regional background value to be used for all modeled hours." 

Response: As noted in several responses above, there are many application-specific factors that 

need to be considered in determining how to conduct an adequate assessment of cumulative 

impacts, accounting for contributions from nearby backgroun-d sources explicitly in the model as 

well as a monitored contribution, while avoiding or minimizing the potential for double-counting 

of modeled and monitored impacts. 

(g) 

Paine Decl. ~ 14. : "The distribution of total peak daily emissions over the three-year period of 

2000-2002 [from major S02 sources in central North Dakota] was found to overpredict the 

second-highest monitored 24-hour concentrations by roughly a factor of2 because the emissions 

11 
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on average are lower than peak values assumed in the modeling. For the probabilistic 1-hour 

standard . . . and for closer receptors, the overprediction ratio would likely be even higher than 

for a 24-hour average, causing extensive areas of fictitious modeled NAAQS violations." 

Response: The first statement in this comment merely confirms what was indicated in an earlier 

response, namely that modeled impacts based on maximum allowable emissions should not be 

expected to accurately predict ambient monitored concentrations in most cases, since monitored 

concentrations can only reflect impacts from actual emissions. Overprediction by a factor of 2 

does not suggest a significant degree of conservatism given that modeled emissions reflected 

peak emissions. No rationale is offered to support the assertion that the overprediction ratio 

would likely be even higher for the 1-hour standard, and we see no reason to expect that 

necessarily to be the case. 

(h) 

Paine Decl., 14. : "Based on my experience with modeling the 1-hour NAAQS for nitrogen 

dioxide - a NAAQS that is .similar in form to the 1-hour S02 NAAQS - this overprediction ratio 

could approach a factor of 10 in areas with numerous sources modeled together." 

Response: Although the form of the 1-hour N02 standard is very similar to the form of the 1-

hour S02 standard, the role ofNOx chemistry in modeling ambient N02 impacts associated with 

NOx emissions makes it difficult to draw comparisons between the two standards in terms of the 

potential for the model to overestimate ambient impacts as compared to monitored 

concentrations. The comment does not indicate what assumptions were made in the N02 

modeling analyses regarding the conversion ofNO emissions to ambient N02. An overly 

conservative assumption in relation to that conversion could introduce a significant bias in the 

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modeled concentrations relative to monitored concentrations ofN02 that would have no 

relevance to modeling 1-hour 802 impacts. 

(i) 

Paine Decl. ~ 15. : "If a cumulative modeling assessment shows violations of the NAAQS, then 

the PSD permit applicant can still obtain a permit for its source by showing that the proposed 

source does not contribute significantly to the modeled violation. EPA, however, has not yet 

defined a procedure for determining whether a proposed source that conducts a cumulative 

modeling analysis and finds modeled violations due to other sources is by itself causing or 

contributing to these predicted (and possibly false) 1-hour 802 NAAQS violations. This "safety 

valve" thus does not yet exist for applicants trying to demonstrate that their proposed 802-

emitting sources will not cause or contribute to any modeled violations of the.l-hour 802 

NAAQS." 

Response: Recognizing the importance of the significant contribution test within the PSD 

permitting program, EPA recommended an interim Significant Impact Level (SIL) in its August 

23 guidance memorandum regarding the 1-hour 802 NAAQS. This interim SIL provides the 

"safety valve" that may allow a permit applicant to obtain a permit in cases where the cumulative 

impact assessment shows modeled violations of the 1-hour 802 NAAQ8, if it can be 

demonstrated that the proposed emission increases do not contribute significantly to those 

modeled violations, paired in time and space. Although the form of the 1-hour 802 standard 

may complicate the "bookkeeping" needed to make such a demonstration, the principle of the 

significant contribution test based on the SIL has not changed under the 1-hour 802 NAAQS. 

13 
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Pursuant to 28 U.S.C. § 1746, and under penalty of perjury, I declare the foregoing is 

true and correct to the best of my knowledge. 

Date Roger W. Brode 

14 
Camille Sears 502 W. Lomita Ave., Ojai, CA 93023

Tel: (805) 646-2588 e-mail: camille.marie@sbcglobal.net 

ambient air locations, should n

                                                                 

June 28, 2012 

EPA Docket Center 

1301 Constitution Ave., NW., Room 3334 

Washington DC 20004 

Re: Docket#: EPA-HQ-OAR-2010-1059 

 Comments on USEPA’s Guidance for One-Hour SO2 NAAQS SIP Submissions 

Thank you for the opportunity to comment on USEPA’s guidance for one-hour SO2 NAAQS SIP 

submissions. In the 9/22/2011 public draft of their guidance, USEPA summarizes their planned 

program elements as follows: 

In addition to this guidance document, EPA is also planning a rulemaking to 

address some of the 1-hour SO2 NAAQS implementation program elements. 

These elements include: (1) establishing that compliance with the 1-hour SO2

NAAQS is appropriately based on the results of both air quality modeling and 

monitoring; (2) establishing the modeling requirements necessary to determine 

compliance with the 1-hour SO2 NAAQS; (3) establishing the minimum scope of 

analysis required to demonstrate attainment and maintenance of the 1-hour SO2

NAAQS to comply with the SIP requirements in CAA section 110(a)(1); (4) 

establishing a reasonable time period for sources to comply with any new 

emissions limitations states need to establish in the 110(a)(1) SIPs to demonstrate 

attainment and maintenance of the 1-hour SO2 NAAQS; (5) to set an attainment 

date for areas designated as unclassifiable; and (6) establishing the criteria for 

redesignating areas from “unclassifiable” to “attainment.”1

This document goes on to say: 

EPA will also propose a rulemaking that would codify the hybrid modeling and 

monitoring implementation approach in order to ensure compliance with the 1-

hour SO2 NAAQS in a timely manner.2

In summary, I believe that air dispersion modeling should be the preferred method for 

determining one-hour SO2 impacts from existing sources. Monitoring should be used only in 

specific cases to supplement modeled impacts, and the monitored data, which cannot cover all 

ot be given more weight than the modeled concentrations. In 

1

 USEPA, Guidance for One-Hour SO2 NAAQS SIP Submissions, Public Review Draft, September 22, 2011, pp. iiiiv. (http://www.epa.gov/airquality/sulfurdioxide/pdfs/DraftSO2Guidance_9-22-11.pdf) 2

 Id., p. iv. 
Docket#: EPA-HQ-OAR-2010-1059 

June 28, 2012 

Page - 2 

essence, USEPA’s proposed hybrid modeling and monitoring implementation approach should 

be heavily weighted towards modeling. 

Air dispersion modeling has been used for decades to assess ambient air impacts from proposed 

and existing sources, and for SO2 NAAQS SIP purposes, monitoring alone (or a program based 

predominantly on monitoring) is not a viable alternative. I recently submitted a subset of these 

comments to USEPA’s 10th Conference on Air Quality Modeling docket. 

I specialize in atmospheric dispersion modeling, which uses regulatory-approved computer 

programs to estimate chemical concentrations in the air and deposition fluxes to the ground. In 

the past 30 years I have prepared over 1,000 air dispersion modeling analyses. I hold B.S. 

(1978) and M.S. (1980) degrees in Atmospheric Science from the University of California at 

Davis. A copy of my curriculum vitae is attached. 

My comments on this docket concentrate on the issue of modeling vs. monitoring for verifying 

compliance with the one-hour SO2 NAAQS (attainment determinations). My comments are in 

response to USEPA’s “key questions” presented in their Implementation of the 2010 Primary 1-

Hour SO2 NAAQS: Draft White Paper for Discussion. I address key questions a. and b. on 

monitoring and key questions a., b., c., and d. on modeling. 

Monitoring key questions: 

a. Are the conceptual monitoring networks described above sufficient to determine whether 

ambient SO2 levels meet the NAAQS and are protective of public health without the need for 

additional modeling? If not, then what enhancements should be made to them? In what situations 

should meteorological data collection also be required? 

b. What is an appropriate number of monitors to site around a source to assess air quality? 

I am providing a combined response to the above questions. 

I do not believe that it is feasible for monitoring alone to verify compliance with the one-hour 

SO2 NAAQS. A suitable monitoring program would require many monitors and data would 

need to be collected for at least several years. The number of required monitors would be 

prohibitively expensive and the duration of the monitoring program, while compounding the 

expense, also delays the implementation needed to protect public health from any unhealthy SO2

exposures. 
Docket#: EPA-HQ-OAR-2010-1059 

June 28, 2012 

Page - 3 

                                                                 

The question of modeling or monitoring was discussed in a California Proposition 65 

enforcement declaration by John Vimont, when he was USEPA’s Region IX Regional 

Meteorologist: 

Monitoring data suffers from a number of limitations. One of the primary 

limitations is that any given monitor can only measure what is happening at the 

location where the monitor is physically located and at the time it is operating. In 

order to adequately detect the maximum impact of any particular source, many 

monitors would have to be run over a number of years. A monitoring program 

designed to adequately detect a maximum concentration and to adequately 

characterize the concentration field would be very expensive. A number of years 

of data would be necessary to collect enough samples to cover all possible 

meteorological situations in combination with the different operating conditions 

of the facility. A monitoring program with only one or two monitors or of a very 

short duration would be inadequate to ensure that maximum ambient impacts 

would be detected.3

Mr. Vimont also declared: 

EPA does recognize the usefulness of ambient measurements for information on 

background concentrations, provided reliable monitoring techniques are available. 

EPA does not recommend, however, that ambient measurements be used as the 

sole basis of setting emission limitations or determining the ambient 

concentrations resulting from emissions from an industrial source. These should 

be based on an appropriate modeling analysis.4

I agree with Mr. Vimont on the disadvantages of relying on air monitoring to verify compliance 

with ambient air quality standards. This sentiment is also expressed by the State of California, in 

their Air Toxics Hot Spots Health Risk Assessment (HRA) guidelines: 

Pollutant concentrations are required in HRA calculations to estimate the potential 

cancer risk or hazard indices associated with the emissions of any given facility. 

Although monitoring of a pollutant provides excellent characterization of its 

concentrations, it is time consuming, costly, and typically limited to a few 

receptor locations and snapshots in time. Air dispersion modeling has the 

advantage of being relatively inexpensive and is less time consuming, provided 

that all the model inputs are available. In addition, air dispersion modeling 

provides greater flexibility for placement of receptors, assessment of individual 

3

 Vimont, John, People of the State of California v. Santa Maria Chili, Declaration, November 30, 1990. (see 

attached file: Vimont-John-Declaration.pdf) 4

 Id. 
Docket#: EPA-HQ-OAR-2010-1059 

June 28, 2012 

Page - 4 

                                                                 

and cumulative source contributions, and characterization of concentration over 

greater spatial extents.5

In addition, it is not always possible to place monitors where maximum project or cumulative 

impacts may be occurring. I have first-hand experience with the problem of siting monitors to 

ensure that maximum project impacts are being measured. While I was an employee with the 

Santa Barbara County Air Pollution Control District, I sited over 30 pre- and post-construction 

air quality PSD monitoring systems. These monitors were required by permit conditions for 

various oil and gas processing facilities, and several monitors were to be sited for each project. 

Using air dispersion modeling, we determined where the peak project impacts were likely to 

occur and then attempted to place the air quality monitoring systems at those locations. In 

virtually every case, it was not possible to place the air quality monitor in the desired location. 

Impediments to siting the monitors where we wanted to place them included: power or 

communication constraints, lack of security, denial of landowner permission, lack of access, and 

terrain and vegetation restrictions. In other words, it’s one thing to have an adequate number of 

monitors; it’s quite another thing to place them where they are needed. 

Part of the problem is that there are relatively few existing monitors that can be used for SO2

NAAQS attainment determinations. There are not nearly enough SO2 monitors in place to 

determine attainment status of the existing major SO2 emission sources. Moreover, very few, if 

any, of these monitors are “well-placed” for measuring the maximum ambient air impacts from 

these existing SO2 sources. This situation dictates that in virtually every instance, a monitoring 

program needs to be started from scratch, or air dispersion modeling must be used as the method 

for determining SO2 ambient air concentrations and resulting attainment status. 

The lack of existing major source-specific SO2 monitoring is partly due to a failure of State air 

agencies requiring pre-and post-construction air quality monitoring. In the past few years I have 

reviewed and commented on major SO2 emission source PSD permit applications in Texas, 

Louisiana, Oklahoma, Nevada, Kentucky, North Carolina, South Carolina, Missouri, Kansas, 

South Dakota, Illinois, and Arkansas. With the exception of Nevada, the State air agencies have 

not required pre- or post-construction air quality monitoring, even though the PSD significant 

monitoring concentrations were exceeded. This is the norm for these major sources, and it is one 

of the key reasons that there is a paucity of ambient air quality monitoring data that could be 

used to help determine attainment status surrounding these facilities. It is self-serving if a 

facility that could (should) have been collecting ambient air quality data now argues that SO2

NAAQS attainment determinations must be based on monitoring, not modeling. 

5

 California Office of Environmental Health Hazard Assessment, Air Toxics Hot Spots Program Risk Assessment 

Guidelines: The Air Toxics Hot Spots Program Guidance Manual for Preparation of Health Risk Assessments, 

August 2003, p. 4-1. (http://www.oehha.org/air/hot_spots/pdf/HRAguidefinal.pdf) 
Docket#: EPA-HQ-OAR-2010-1059 

June 28, 2012 

Page - 5 

This same issue applies to pre-construction monitoring for meteorological data. On many 

occasions I have commented that States should require major source facilities, as part of their 

PSD permit analysis, to collect site-specific meteorological data rather than rely on National 

Weather Service (NWS) airport data. On every occasion, my comments were disregarded, even 

though the PSD significant monitoring concentrations were exceeded for the proposed project. 

The State’s response and comment denial followed a common theme, summarized as follows: 

site-specific meteorological data monitoring is unnecessary for modeling purposes and that NWS 

airport data are appropriate for permit application analyses. Although it’s water under the 

bridge, site-specific data could have been collected during these application processes without 

causing time delays to permit issuance. 

USEPA asked the question “In what situations should meteorological data collection also be 

required?” I believe the time has passed when these data could or should have been collected. 

Of course it would be ideal to have additional site-specific meteorological data for modeling 

major SO2 emissions sources. But such a monitoring system will take at least two years to 

implement, and then the modeling will still have to be performed. The data collection itself will 

take a minimum of one year. It will take at least another year for developing the data collection 

protocol, review and approval of the protocol, siting of the system, installation, and afterwards 

post-processing of the data for modeling. Starting a site-specific meteorological data collection 

effort from scratch contributes to an unreasonable delay of the measures that may be needed to 

protect ambient air from any excessive SO2 exposures. 

While I feel that site-specific meteorological data are preferable to NWS airport data, USEPA’s 

AERMINUTE program allows significant improvements to the NWS data in that calms and 

variable wind hours that were previously unusable by AERMOD can now be recaptured. In lieu 

of requiring new site-specific data collection efforts, modeling of SO2 emissions for NAAQS SIP 

submissions should be performed using NWS data prepared with AERMET, in conjunction with 

AERMINUTE. The use of one-minute ASOS data should be a requirement, not a 

recommendation. If available high-quality site-specific meteorological data already exist, then I 

believe they should be used in preference to NWS airport data. 

Based on my experience, site-specific meteorological data tends to result in higher modeled 

impacts than NWS airport data, even when the NWS data is processed with AERMINUTE and 

one-minute ASOS data. For example, I modeled the Homer City, PA power station with three 

different meteorological data sets: One year of site-specific data from the Manor monitoring 

station; 2006 through 2010 NWS data from Johnstown PA, including one-minute ASOS data 

processed with AERMINUTE (KJST); and 2006 through 2010 NWS data from Pittsburgh PA, 

including one-minute ASOS data processed with AERMINUTE (KAGC). All three data sets 
Docket#: EPA-HQ-OAR-2010-1059 

June 28, 2012 

Page - 6 

conditions are included in the 

                                                                 

used Pittsburgh upper air soundings. The peak receptor grid ambient air impacts from 

AERMOD modeling using Manor site-specific data were about twice as high as the KJST or 

KAGC results. And even at specific receptor locations, such as Homer City High School, the 

Manor site-specific data resulted in significantly higher impacts than the NWS/AERMINUTE 

data sets. 

In other words, using available NWS airport data, processed with AERMINUTE, will not likely 

over-predict modeled impacts, as suggested by some stakeholders. Moreover, these data have 

the advantage of being readily available on NCDC data DVDs for years 2007 through 2011, thus 

meeting The Guideline on Air Quality Modeling requirements of at least five years of 

consecutive data from the most recent, readily available five-year period. 6

Modeling key questions: 

a. Should some criteria (e.g., the PWEI concept) be used to identify priority sources to be 

modeled in an area where there is no nearby monitor? 

I do not believe that a population weighted emissions index (PWEI) should be used to identify 

priority sources. The NAAQS, by definition, apply to ambient air, or "... that portion of the 

atmosphere, external to buildings, to which the general public has access."7 Ambient air is the 

defining criteria, and it is not based on the number of people who are exposed, but whether 

anyone could have access to given locations. This includes waterways and unpopulated areas of 

all sorts, so long as someone in the public has access. 

b. How should the modeling be performed – i.e., what changes to the March 24, 2011 guidance 

should be made, such as the use of size cut-offs and use of actual emissions? 

Some stakeholders have suggested that one-hour SO2 modeling analyses used for nonattainment 

SIP modeling should use actual emissions, and not the potential to emit. I understand that using 

allowable emissions may result in higher impacts than the facility’s actual emissions. I have 

modeled many coal-fired EGUs where I analyzed both allowable and actual emissions obtained 

from USEPA’s Clean Air Markets Database (CAMD). The facility permitted emissions are 

often, though not always, greater than the reported actual emissions. This is because the 

permitted allowable emissions are often based on 30-day averaging periods and peak hourly 

emission limits were not set by the State agency in question. Also, startup, shutdown, and upset 

CAMD that may represent quite high actual emission rates. 

6 USEPA, Revision to the Guideline on Air Quality Models: Adoption of a Preferred General Purpose (Flat and 

Complex Terrain) Dispersion Model and Other Revisions, Appendix W to 40 CFR Part 51, November 9, 2005. 

(http://www.epa.gov/ttn/scram/guidance/guide/appw_05.pdf) 7

 40 CFR Part 50.1 (e) (http://ecfr.gpoaccess.gov/cgi/t/text/textidx?c=ecfr&rgn=div5&view=text&node=40:2.0.1.1.1&idno=40#40:2.0.1.1.1.0.1.1) 
Docket#: EPA-HQ-OAR-2010-1059 

June 28, 2012 

Page - 7 

If actual emissions are used for nonattainment SIP modeling, a condition must be added to the 

facility’s permit requiring that emissions must not be greater than the level used in the modeling 

analysis. In other words, a facility that wants to use actual emissions in their modeling analysis 

must agree to an enforceable permit condition limiting their emissions, by unit, to that quantity 

modeled. Also, actual emissions cannot be modeled using full load stack parameters. Stack gas 

exit velocity and temperature will be reduced under less than full load conditions, affecting 

plume rise and resulting modeled impacts. Any AERMOD modeling using actual emission 

levels must use corresponding actual stack gas exit velocity and temperature. I suggest that 

USEPA should develop a method for calculating stack gas exit velocity and temperature as a 

function of load, for use in cases where these data are not directly measured and reported. 

I believe that any emission limits based on actual operating conditions must be rather straightforward and enforceable. For example, the actual emission rates could be based on the 

maximum hourly emissions, by stack, for the latest calendar year (or perhaps the maximum for 

the past three years). Maximum actual emissions could also be for shorter time periods (by 

season, for example), but emission limits by portion of the year may be more difficult to enforce, 

or the facility may not wish to be restricted by this condition. And while it is possible to model 

hour-by-hour actual emissions (using HOUREMIS in AERMOD) coupled with 

contemporaneous meteorological data, this analysis does not ensure that the one-hour SO2

NAAQS will be protected in the future. This is because combinations of meteorology and 

facility emissions that result in peak impacts are virtually unenforceable. 

I believe that USEPA should be very careful in considering emission rate cut-off levels. Without 

modeling, it is very difficult to determine the combined effects that emission rate, stack height, 

source-to-receptor distance and elevation differences, building downwash, background air 

quality, and plume rise will have on ambient air concentrations and NAAQS compliance. 

Obviously not every source will require modeling, but any cut-off criteria should consider all 

parameters that affect air concentration, not simply emission rate. 

c. Are there situations where modeling is preferable to monitoring? If so, then what are these 

situations? Should EPA require modeling in certain situations, or is monitoring alone always a 

sufficient option for areas of concern? 

As discussed above, modeling is preferable to monitoring for determining ambient air 

concentrations and for verifying compliance with the one-hour SO2 NAAQS. I cannot envision a 

feasible air monitoring network that would verify compliance for a major SO2 emission source – 

too many monitors would be needed and the delay in attainment demonstration and resulting 

controls would be unacceptably long. 
Docket#: EPA-HQ-OAR-2010-1059 

June 28, 2012 

Page - 8 

                                                                 

I think it is beneficial to consider how California’s Air Toxics Hot Spots program, also known as 

AB 2588, determined ambient air concentrations of air toxics. This program required thousands 

of facilities in California to quantify emissions of scores of hazardous air pollutants, when 

virtually no inventory of these pollutants previously existed. AB 2588 also required at least 

1,000 facilities state-wide to prepare health risk assessments, which are based on ambient air 

concentrations of the air toxics in question. In all instances, these facilities used air modeling as 

the basis for determining ambient air concentrations. This is based not only on State of 

California guidance (see the Air Toxics Hot Spots program citation in the air monitoring 

comments above), but on the practicality of actually quantifying air concentrations in a 

reasonable fashion. 

I believe that the AB 2588 program required as much or more modeling work than will be 

needed for the one-hour SO2 NAAQS SIP determinations. For example, in Santa Barbara 

County, where I was the Air Toxics Program Coordinator, we prepared air dispersion modeling 

analyses for up to 50 facilities per year. Many of these facilities were very complicated and 

involved numerous toxic air pollutants. Plus, we calculated excess cancer risk and noncarcinogenic health effects from inhalation and all other pathways of exposure. In other words, I 

think State air agencies should be able to handle the effort required in modeling the major SO2

emission sources within their jurisdiction. 

Some stakeholders have expressed concern that AERMOD will over-predict air impacts, 

compared to monitoring results. While this may be true in some circumstances, e.g., at one 

location at a given time, the true value in modeling is the ability to calculate air concentrations at 

many more places and under many physical conditions that cannot be handled by air monitoring. 

On the other hand, there are likely many situations where AERMOD underpredicts air 

concentrations compared to monitoring data. 

USEPA should rely on the detailed AERMOD evaluations that were performed during the model 

development phase. I agree with Roger Brode’s 10th Modeling Conference presentation, where 

he concluded: “AERMOD model performance has been extensively evaluated and shown to 

provide generally unbiased estimates of 1-hr SO2 concentrations across a wide range of 

scenarios.”8

8

 Roger Brode, USEPA/OAQPS, AERMOD Evaluations Under the 1-hour NO2 and SO2 NAAQS, 10th Conference 

on Air Quality Modeling. (http://www.epa.gov/ttn/scram/10thmodconf/presentations/2-8-

Brode_10thMC_AERMOD_Evals_1hr-NO2-SO2_NAAQS_Final_3-25.pdf) 
Docket#: EPA-HQ-OAR-2010-1059 

June 28, 2012 

Page - 9 

                                                                 

I believe that the concerns about AERMOD over-predicting air concentrations are, on the whole, 

without merit. At the 2012 RSL Modelers’ Workshop, George Bridgers and Roger Brode 

presented a summary of AERMOD’s performance evaluation results. They document that 

AERMOD provided better model predictions than ISCST3, ISC-Prime, and CTDMPLUS. In 

addition, they point out that the average ratio of predicted to observed one-hour and three-hour 

robust highest concentration values across all field studies for AERMOD was 0.995.9 This is 

clearly an unbiased estimate of AERMOD’s predictive performance. 

It is also evident that most of the large SO2 emission sources have tall stacks, which were 

rigorously evaluated during AERMOD’s development process. From USEPA’s Compendium of 

Reports from the Peer review Process for AERMOD: 

Concerning the model evaluation, we reiterate that AERMOD has been evaluated 

against 10 substantial data bases, including: 1) four data sets for tall stack buoyant 

plumes in flat terrain (Kincaid SO2, Kincaid SF6, Baldwin, and Clifty Creek), 2) 

four data sets for tall stacks in complex terrain or near elevated terrain (Lovett, 

Martins Creek, Tracy, and Westvaco), 3) a buoyant elevated release in an urban 

environment (Indianapolis), and 4) a nonbuoyant surface release (Prairie Grass). 

We agree that more evaluation would be desirable (as always) especially for 

downwash conditions, urban sources, and surface releases. However, there is a 

key question to the AERMOD development process: Has there been enough 

evaluation already to justify replacing ISC3 by AERMOD? AERMIC believes 

that there has been.10

Thus, any argument that AERMOD is not applicable to tall stack emission sources should be 

dismissed based on the studies used for developing AERMOD. In particular, AERMOD has 

been extensively evaluated for power plant emissions: 

It is worth noting in this regard that all of the AERMOD evaluation data bases 

(except for Prairie Grass) involved tall, non-downwashed, highly buoyant power 

plant stacks (the shortest stack in the group was 84 meters in Indianapolis).11

AERMOD’s evaluation process ultimately comprised 17 separate data sets. I believe that any 

concerns from stakeholders that AERMOD over-predicts power plant impacts, or over-predicts 

impacts from other source types represented in the evaluation databases, should be dismissed. 

9

 George Bridgers and Roger Brode, USEPA/OAQPS, Challenges in Modeling Compliance for New NAAQS: 1-

hour NO2 & SO2 and PM2.5, 2012 RSL Modelers’ Workshop. 

(http://www.cleanairinfo.com/regionalstatelocalmodelingworkshop/archive/2012/presentations/Tues/3-

1_2012RSL_ModelingChallenges_Bridges.pdf) 10 USEPA OAQPS, Compendium of Reports from the Peer review Process for AERMOD, February 2002, pdf page 

38/69. (http://www.epa.gov/scram001/7thconf/aermod/dockrpt.pdf) 11 Id., pdf page 49/69. 
Docket#: EPA-HQ-OAR-2010-1059 

June 28, 2012 

Page - 10 

                                                                 

I would also add that AERMOD’s evaluation analyses included a number of site-specific 

meteorological data sets that incorporate low wind speed conditions. For example, the Tracy 

evaluation included meteorological data with wind speeds as low as 0.39 meter/second (m/s); the 

Westvaco evaluation included wind speeds as low as 0.31 m/s; the Kincaid SO2 evaluation 

included wind speeds as low as 0.37 m/s; and the Lovett evaluation included wind speeds as low 

as 0.30 m/s.12 Concerns raised by stakeholders regarding AERMOD’s ability to model low wind 

speed conditions seem to neglect the data used in actual AERMOD evaluations. 

Some stakeholders are concerned that AERMOD is inaccurate in areas with extreme topography, 

such as complex river valleys and steep hillsides. This concern has already been addressed by 

USEPA in their response to the New Jersey Department of Environmental Protection (NJDEP) 

section 126 petition for SO2 emissions from the Portland Generating Station. In their review of 

NJDEP’s petition, USEPA found that AERMOD is the most appropriate model for determining 

air impacts in the complex terrain and complex wind fields surrounding the Portland facility.13 

USEPA also recognizes that “the performance of the AERMOD model for estimating impacts 

associated with tall stacks in complex terrain settings has been extensively evaluated and 

documented in peer-review journals... and has consistently been shown to perform better than 

competing models.”14

Air monitoring of SO2 is not a feasible alternative to modeling for steep hillsides and other 

complex terrain conditions. Proper air quality monitor siting is extremely difficult in these 

settings, and any siting would depend on prior air dispersion modeling in the first place. 

While I have used CALPUFF to model emissions in complex river valleys, I was able to do so 

only because there were multiple site-specific meteorological monitors to provide the needed 

data to develop the CALMET wind fields. For facilities where adequate meteorological data 

exist to run CALPUFF, I believe this is a possible alternative to running AERMOD. Otherwise, 

AERMOD should be used due to the problems associated with siting and operating an adequate 

monitoring network in these complex terrain environments. 

12 The AERMOD evaluations and modeled meteorological data are at: 

http://www.epa.gov/ttn/scram/dispersion_prefrec.htm 13 USEPA, Air Quality Modeling Technical Support Document: NJ 126 Petition of September 17, 2010, April 2011, 

p. 12 of 63. (http://www.epa.gov/ttn/scram/reports/EPA-HQ-OAR-2011-0081-0026.pdf) 14 Id., p.11 of 63. 
Docket#: EPA-HQ-OAR-2010-1059 

June 28, 2012 

Page - 11 

                                                                 

d. Are there situations where monitoring is preferable to modeling? If so, then what are these 

situations? Should EPA require monitoring in certain situations, or is modeling alone always a 

sufficient option for areas of concern? 

As discussed above, I believe that modeling alone is sufficient for verifying compliance with the 

one-hour SO2 NAAQS. If monitoring is used, as in USEPA’s proposed hybrid modeling and 

monitoring approach, it should be only as a supplement to modeling and the modeling and 

monitoring results should be given equal weight.

I think it is important to remember that all NO2, PM2.5, and SO2 NAAQS and PSD increment 

permit application analyses are performed with air dispersion modeling, such as running 

AERMOD in a manner consistent with the Guideline on Air Quality Models. In order to ensure 

consistency in how air impacts are determined, both existing sources and newly permitted 

sources should be assessed using the same methods. From the Guideline on Air Quality Models: 

The Guideline is used by EPA, States, and industry to prepare and review new 

source permits and State Implementation Plan revisions. The Guideline is 

intended to ensure consistent air quality analyses for activities regulated at 40 

CFR 51.112, 51.117, 51.150, 51.160, 51.166, and 52.21.15

Allowing existing sources to use monitoring (assuming adequate monitoring even exists or could 

exist), results in a lower standard of compliance verification than that being used for new permit 

applicants. 

Concluding Remarks 

Using AERMOD for one-hour SO2 NAAQS SIP submissions is reasonable and reliable. 

AERMOD has undergone rigorous model evaluations, was subjected to numerous peer-reviewed 

studies, and has already been used in hundreds, if not thousands, of air quality impact analyses of 

major emission sources. USEPA must not exchange their existing guideline model for an 

ambient air monitoring program which will never be able to verify compliance with the one-hour 

SO2 NAAQS. 

Based on my experience with both modeling and monitoring, I believe that air modeling, using 

AERMOD, is the best available method for verifying compliance with the one-hour SO2

NAAQS. I suggest that USEPA’s proposed hybrid modeling and monitoring implementation 

15 USEPA, Revision to the Guideline on Air Quality Models: Adoption of a Preferred General Purpose (Flat and 

Complex Terrain) Dispersion Model and Other Revisions, Appendix W to 40 CFR Part 51, November 9, 2005, 

Section II. (http://www.epa.gov/ttn/scram/guidance/guide/appw_05.pdf) 
Docket#: EPA-HQ-OAR-2010-1059

June 28, 2012

Page - 12

approach for one-hour S02 NAAQS SIP submissions should be heavily weighted towards

modeling.

Thank you for the opportunity to submit these comments on USEPA s guidance for one-hour

S02 NAAQS SIP submissions.

Sincerely,

Camille Sears










11-05-1995 2 37AM FROM P 1

,

DEC 03 1990

FILED

SUPERIOR COURT

sArnA E'.t,l""V'.RA

1 JOHN K. VAN DE KAMP, Attorney General

of the state of California

2 ANDREA SHERIDAN ORDIN

Chief Assistant Attorney General

3 THEODORA BERGER

Assistant Attorney General

4 CRAIG C. THOMPSON

EDWARD G. WEIL

5 CLIFFORD RECHTSCHAFFEN

Deputy Attorneys General

6 2101 Webster street

Oakland, CA 94612

7 Telephone: (415) 464-0572

8 Attorneys for the people of the State of California

9 SUPERIOR COURT OF THE STATE OF CALIFORNIA

10 COUNTY OF SANTA BARBARA

v.

Defendant.

Plaintiffs,

ANTA MARIA CHILI, INC. Dec. 14, 1990

9:00 a.m.

To Be Assigned

DATE:

TIME:

Dept:

No. SM 64010

(Case transferred to

South County, 2/26/90)

DECLARATION OF JOHN C.

VIMONT

EOPLE OF THE STATE OF CALIFORNIA ex.

el. JOHN K. VAN DE KAMP, Attorney

eneral of the State of California,

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12

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IS

11

17

13

15

14

19 I, John C. Vimont, declare:

20 1. I am currently employed by the United states

21 Environmental Protection Agency (hereafter "EPA"), Region IX

22 (hereafter the "Region" or "Regional Office!') as the Regional

23 Meteorologist. I have been employed in this position since June

24 1987.

2S a. As the Regional Meteorologist I serve as the

26 Region's expert on air quality ~odelin9, meteorological

27 information and ambient air impact analyses. My position is
11-05-1995 2 38AM FROM P 2

1 within the Air and Toxics Division of the Regional Office. I

2 provide support to that division; to the other divisions within

3 the Region, such as the Hazardous Waste Division; and to state

4 and local agencies vithin Region IX. One of the primary duties

5 of my position is to ensure that appropriate air quality modeling

6 techniques are used by this and other agencies when conducting

7 ambient air quality impact analyses.

8 b. There are a variety of "air quality models."

9 These include conceptual models, qualitative dQ~criptions of the

10 behavior of pollutants in the atmosphere; physical models, scaled

11 models of pollution sources and their surroundings studied in a

12 controlled environment, such as a wind tunnel; statistical

13 models, which encompass statistically based descriptions of

14 source-receptor relationships; and mathematical models, vhich are

15 mathematical representations of the physical processes which lead

16 to transport and dispersion of pollutants in the atmosphere. The

17 focus of the remaining discussion is on mathematical models;

18 hereafter any reference to an air quality model is implicitly

19 meant to refer to a mathematical air quality model.

20 c. I perform, review and oversee air quality modeling

21 for a variety of different sources and source types. These

22 include stationary sources vith emissions emanating from a stack,

23 inclUding stack sources with aerodynamic downwash induced by

24 nearby buildings; stationary sources with emissions emanating

25 from a broad area, commonly called area sources; mobile sources,

26 emissions from automobiles, trucks, busses, aircraft, etc.; and

27 urban and regional scale modeling, which encompasses modeling all
11-05-19952:38AM FPOt·1 P 3

1 of the above processes together on the scale of an entire urban

2 area or over a number of urban areas together.

3 d. The pollutants modeled include both inert

4 pollutants, those which remain chemically stable for long periods

5 of time in the atmosphere, and chemically reactive pollutants,

6 those which undergo relatively rapid chemical transformation and

7 those which are not directly emitted, but rather form through a

8 series of chemical reactions within the atmosphere.

9 2. Previous to my employment at EPA, I worked from March

10 1982 to June 1987 as an Environmental Engineering Specialist in

11 the Air Quality Bureau of the State of New Mexico. My primary

12 responsibilities there were very similar to my current position

13 at EPA. I performed ambient impact analyses of various air

14 pollution sources and conducted engineering analyses of the

15 sources to determine emission characteristics. The primary focus

16 of the analyses was on inert pollutants from stationary sources.

17 a. From August 1978 to March 1982 I worked for the

18 Atmospheric Science Department at COlorado state University (CSU)

19 as a Research Assistant. I worked on a variety of basic

20 scientific research projects dealing with cloud physics. My

21 primary area of research dealt with the uptake of acidic

22 pollutants in snow.

23 b. From November 1977 to August 1978 I worked as a

24 Phys'ical Science Aide for the Pacific Marine Environmental

25 Laboratory of the National oceanographic and Atmospheric

26 Administration. My duties there involved writing a

27
11-05-1995 2:39AM FROM P.d

1 climatological summary of Puget Sound and analyzing the affects

2 of winds on oil spill transport in Puget sound.

J J. I received a Bachelor of Science Degree in Atmospheric

4 Sciences from the university of Washington in 1978 and a Master

5 of Science Degree in Atmospheric Science from Colorado State

6 University.

7 4. As the Regional MQteorologist, I routinely evaluate the

8 adequacy of air quality modeling on a technical basis and with

9 respect to its acceptability in the regulatory framework.

10 Acceptable air quality modeling and analysis procedures are

11 outlined in Ahe Guideline on Air Quality Models (Revised) (EPA

12 450/2-78-027R, 3uly 1986, Supplement A, JUly 1987) (hereafter the

13 "Guideline"). The Guideline was first pUblished in April 1978 to

14 satisfy the requirements of §320 of the 1977 amendments to the

15 Clean Air Act. The Guideline specifies appropriate models to use

16 and provides gUidance on their appropriate application. The

17 Guideline provides a common basis for estimating the air quality

18 concentrations used in assessing control strategies and

19 developing emission limits. The modeling techniques embodied in

20 the Guideline are subjected to public, scientific review in

21 accordance with §320 of the CAA.

22 a. EPA has four primary, on-going activities to

23 provide direct input for consistency in implementation and for

24 revisions to the Guideline. The first is a series of annual EPA

25 workshops conducted for the purpose of ensuring consistency and

26 providing clarification in the application of models. The second

27 activity, directed toward the improvement of modeling procedures,
11-05-1995 239AM FROM P5

1. is the cooperative agreement that EPA has with the scientific

2 community represented by the American Meteorological Society.

3 This agreement provides scientific assessment of procedures and

4 proposed techniques and sponsors workshops on key technical

5 issues. The third activity is the solicitation and review of new

6 models from the technical and user community. In the March 27,

7 1980 Federal Register, a procedure was outlined for the submittal

8 to EPA of privately developed models. After extensive evaluation

9 and scientific review, these models, as well as those made

10 available by EPA, are considered for recognition in the

11 Guideline. The fourth activity is the extensive, on-going

12 research efforts by EPA and others in air quality and

13 meteorological modeling.

14 b. From the aforementioned process a number of models

15 were selected as being refined models, suitable for regulatory

16 application. Each refined model underwent intensive evaluation.

17 The evaluation exercises include statistical measures of model

18 performance in comparison with measured air quality data and,

19 Where possible, peer scientific reviews.

20 c. After a model has been selected as a refined model

21 for a particular type of application, EPA considers the model

22 appropriate for general use for that type of application without

23 undergoing case-by-case evaluation, provided that the application

24 follows the EPA recommendations specified in the Guideline.

25 5. The Industrial Source Complex models (hereafter ISC),

26 have been deemed refined models by EPA for application to

27 industrial complexes. The ISC models consist of a short term
11-05-1995 2.d0AM P.6

1 model (ISCST) and a long term model (ISCLT). Long term models,

2 such as ISCLT, are only appropriate for calculating ambient

3 concentrations for averaging periods of months to a year. Short

4 term models, such as ISCST, can be used for averaging times frOm

5 one hour up to a year. (Hereafter my comments referring to ISC

6 apply to both ISCST and ISCLT, unless otherwise specified.) The

7 ISC model is appropriate for simUlating the emissions of a

8 variety of industrial air emissions. These would include

9 emissions from free standing stacks and vents; stacks and vents

10 which are influenced by the aerodynamic effects of nearby

11 structures; emissions from area sources, such as storage piles or

12 evaporative emissions from open tanks; line sources, such as

13 roadways; and volume sources, such as large openings in buildings

14 from which emissions emanate. The model is appropriate for

15 simulating the ambient impacts of relatively inert pollutants,

16 such as ethylene oxide, Which do not undergo rapid chemical

17 transformation in the atmosphere. The model will calculate the

18 ambient concentrations at a number of user-specified "receptor"

19 locations.

20 a. For simulating a stack-type source, ISC requires

21 the input of the location, emission rate, physical stack height,

22 stack gas exit velocity, stack inside diameter, and stack gas

23 temperature. If the source is affected by the aerodynamic

24 effects of buildings then inputs would also include information

25 about the building dimensions.

26 b. The ISC model also requires meteorological data as

27 input. These data include the wind speed, wind direction,
11-05-1995 240AM FROM P. 7

1 temperature, stability class and mixing height. The

2 meteorological data must be representative of the geographic area

3 being modeled to be accepted for a refined regulatory

4 application.

5 c. The ISC model has gone through a number of

6 performance evaluation studies, as outlined above. The fOllowing

7 are several references of evaluation studies involving ISC:

8 (1) Bowers, J. F., and A. J. Anderson, 1981. An

9 Evaluation study for the Industrial Source Complex elSe)

10 Dispersion Model, EPA Publication No. EPA-450/4-81-002. U. S.

11 Environmental Protection Agency, Research Triangle Park, ·NC.

12 (2) Bowers, J. F.~ A. J. Anderson, and W. R.

13 Hargraves, 1982. Tests of the Industrial Source Complex (lSC)

14 Dispersion Model at the Armco Middle-town, Ohio Steel Mill, EPA

15 Publication No. EPA-450/4-82-006. U. S. Environmental Protection

16 Agency, Research Triangle Park, NC.

17 (3) Scire, J. 5., and L. L. Schulman, 1981.

18 Evaluation or the BLP and ISC Models with SF6 Tracer Data and S02

19 Measurements at Aluminum Reduction Plants. Air Pollution Control

20 Association Specialty Conference on Dispersion Modeling for

21 Complex Sources, St. Louis, MO.

22 (4) Schulman, L. L. and S. R. Hanna, 1986.

23 Evaluation of Downwash Modifications to the Industrial Source

24 Complex Model. Journal of the Air Pollution Control Association,

25 36:258-264.

26 d. In my experience of conducting and reviewing air

27 quality modeling analyses, I have found that of the EPA approved
11-05-19952d0AM FROt1 P.8

1 models, the ISC model is the most widely used model for

2 determining the ambient concentrations of emissions from

3 industrial sources. This is primarily due to its ability to

4 simulate almost any type of industrial configuration and its

5 status as a refined model under EPA guidelines. EPA considers it

6 appropriate for use without undergoing case by case performance

7 evaluation.

S 6. When EPA has a refined model appropriate for a specific

9 type of application, such as the ISC model, the modeling results,

10 based on the appropriate input data, are generally preferred by

11 EPA over ambient monitoring data for determining emission

12 limitations for both new and existing sources. Normally, EPA

13 does not accept monitoring data as the sole basis for determining

14 an emission limitation. When a refined model is available, EPA

15 generally considers the model results alone (including background

16 concentrations) sufficient for determining ambient concentrations

17 of emissions from industrial sources and setting appropriate

18 emission limitations.

19 a. Monitoring data suffers from a number of

20 limitations. One of the primary limitations is that any given

21 monitor can only measure what is happening at the location where

22 the monitor is physically located and at the time it is

23 operating. In order to adequately detect the maximum impact of

24 any partiCUlar source, many monitors would have to be run over a

25 number of years. A monitoring program designed to adequately

26 detect a maximum concentration and to adequately characterize the

27 concentration field would be very expensive. A number of years

R.
11-05-1995 2:d1AM FROt.' P.9

1 of data would be naces~ary to collect enough samples to cover all

2 possible meteorological situations in combination with the

3 different operating conditions of the facility. A monitoring

4 program with only one or two monitors or of a very short duration

5 would be inadequate to ensure that maximum ambient impacts would

6 be detected.

7 b. The usual intent of conducting an ambient impact

8 analysis of an air pollution source is to determine if the

9 emissions are likely to affect human health or affect the

10 environment. The ambient concentrations are compared against

11 health or environmental affects data. Rather than helping to

12 resolve a problem, a prolonged ambient monitoring study allows

13 continued air quality degradation, which in turn affects the

14 health or environmental quality which was to be protected. For a

15 new source being proposed, it is impossible to measure its

16 impacts, since it is not yet built.

17 c. The method of analysis preferred by EPA for

18 determining the ambient concentrations resulting from emissions

19 into the atmosphere of industrial sources, including toxic air

20 emissions, is modeling. As discussed above, before EPA

21 determines a model, such as ISC, to be a refined model,

22 appropriate for general use, the model undergoes rigorous

23 evaluation and is determined to yield accurate estimates of the

24 ambient air concentrations resulting from emission sources under

25 a variety of conditions. With a model, the source can be

26 simulated under the full range of its potential operating and

21 emission conditions, rather than being limited to the specific

9.
11-05-1995 2:d1AM FROt,1 P.10

1 operating conditions occurring during the period of a limited

2 monitoring study. The model can also yield ambient concentration

3 data at any number of receptor locations; rather than only at the

4 limited number Of locations where a monitor is physically

5 located. Also, an air quality model provides the only practical

6 method of estimating the ambient impacts of a new source. A

7 model provides flexibility in an analysis and can be run

8 relatively quickly, at relatively little expense.

9 d. Modeling also allo~s source contributions to a

10 particular ambient concentration to be ascertained. If two

11 sources each emit the same pollutant, it is impossible to tell

12 from an ambient measurement of the specific pollutant, the

13 relative contributions to the measured ambient concentration,

14 unless there is some unique surrogate being emitted from one of

15 the facilities. Also, there is the uncertainty of whether a

16 heretofore unknown source of the pollutant of concern has

17 contributed to the measurement. Modeling, allows the impact of

18 each source to be calculated separately and in combination.

19 e. The use of monitoring data also pre-supposes that

20 there are acceptable and reliable monitoring techniques available

21 for the pollutant-of interest. In the past, this has generally

22 been the case. EPA has established acceptable and reliable

23 methods of measuring a number of pollutants which were regulated

24 under the Clean Air Act. Recently, ho~ever, the issue of toxic

25 air contaminants has arisen. Ambient ~easurement techniques,

26 Which can adequately and accurately detect a specific toxic air

27 contaminant, are not necessarily available. The transport and
11-05-1995 2 42AM FROM P.11

1 dispersion of buoyant or neutral plumes of gaseous pollutants,

2 which are relatively inert in the atmosphere, is the same,

3 regardless of the specific chemical constituents of the gas.

4 Therefore, modeling provides a useful technique for detecting

5 levels of pollutants in the air if reliable ambient measurement

6 techniques are not available.

7 f. EPA does recognize the usefulness of ambient

8 measurements for information on background concentrations,

9 provided reliable monitoring techniques are available. EPA does

10 not recommend, however, that ambient measurements be used as the

11 sole basis of setting emission limitations or determining the

12 ambient concentrations reSUlting from emissions from an

13 industrial source. These should be based on an appropriate

14 modeling analysis.

15 I declare under penalty of perjury that the foregoing is

16 true and correct.

17 DATED:;tJ6 V~m.bf"" 30 /f90 ./

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