AIR DISPERSION MODELING PROTOCOL (REVISION 1)

ANADARKO PETROLEUM CORPORATION  EGOM DRILLING, COMPLETION,

AND MAINTENANCE PROJECT 

Prepared for:

ANADARKO PETROLEUM CORPORATION

1201 Lake Robbins Drive

The Woodlands, TX 77380

Prepared by:

TRINITY CONSULTANTS

301 Main Street.

Suite 900

Baton Rouge, LA 70825

(225) 346-4003

August 2013

Project 131901.0020

 
Anadarko ii Trinity Consultants

TABLE OF CONTENTS

1. INTRODUCTION .................................................................................................................. 6

1.1 PROJECT DESCRIPTION........................................................................................................ 6

1.2 PROJECT LOCATION ............................................................................................................ 7

1.3 DESCRIPTION OF MODELING PROCEDURES ........................................................................ 9

1.4 CONTENTS OF THE MODELING PROTOCOL ....................................................................... 10

2. SOURCE DESCRIPTION .................................................................................................... 11

2.1 DESCRIPTION OF PROPOSED OCS SOURCE ....................................................................... 11

2.2 EMISSION SOURCES........................................................................................................... 12

2.3 POTENTIAL EMISSIONS...................................................................................................... 12

2.4 Q/D ANALYSIS .................................................................................................................. 12

3. CLASS II AIR QUALITY DISPERSION MODELING REQUIREMENTS .............................. 14

3.1 PSD SIGNIFICANCE ANALYSIS.......................................................................................... 15

3.1.1 PRE-CONSTRUCTION MONITORING ANALYSIS .................................................... 18

3.1.2 SPECIAL CONSIDERATIONS FOR PM2.5 ................................................................. 18

3.2 ADDITIONAL IMPACTS ANALYSIS..................................................................................... 20

3.2.1 GROWTH ANALYSIS ............................................................................................. 21

3.2.2 SOILS AND VEGETATION ANALYSIS .................................................................... 21

3.2.3 VISIBILITY ANALYSIS .......................................................................................... 21

4. CLASS I AIR QUALITY DISPERSION MODELING REQUIREMENTS................................ 23

4.1 CLASS I AREA PSD INCREMENT ....................................................................................... 23

4.2 CLASS I AQRV ANALYSES ............................................................................................... 24

4.2.1 DEPOSITION.......................................................................................................... 25

4.2.2 VISIBILITY............................................................................................................ 26

4.2.3 OZONE.................................................................................................................. 30

5. MODELING METHODOLOGY AND INPUTS...................................................................... 32

5.1 MODEL SELECTION ........................................................................................................... 32

5.2 MODEL DOMAINS.............................................................................................................. 33

5.3 REPRESENTATION OF MODELED SOURCES ....................................................................... 34

5.4 RECEPTOR LOCATIONS FOR CLASS I AREAS..................................................................... 35

5.5 RECEPTOR LOCATIONS FOR CLASS II AREAS ................................................................... 35

5.6 EMISSIONS SPECIATION .................................................................................................... 35

5.7 TERRAIN PROCESSING FOR CLASS II ANALYSIS ............................................................... 36

5.8 BUILDING DOWNWASH ..................................................................................................... 36

5.9 BACKGROUND CONCENTRATIONS .................................................................................... 36

5.10 CALMET (METEOROLOGICAL DATA) PROCESSING ........................................................ 36

5.11 CALPUFF PROCESSING.................................................................................................... 37

5.11.1 OZONE................................................................................................................. 37

5.11.2 AMMONIA............................................................................................................ 38

5.11.3 CALPUFF PROCESSING CONTROL ..................................................................... 38

5.12 CALPOST POSTPROCESSING ANALYSIS .......................................................................... 38
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6. MODELING REPORT CONTENTS ..................................................................................... 40
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LIST OF TABLES 

TABLE 1-1. LOCATION OF LEASE BLOCKS RELATIVE TO NEAREST CLASS I AREAS AND SHORELINE. 7

TABLE 3-1. APPLICABLE PSD AIR QUALITY LEVELS.......................................................................... 15

TABLE 4-1. CLASS I AREA PSD INCREMENTS & MODELING SIGNIFICANCE LEVELS ......................... 23

TABLE 4-2. MONTHLY FS(RH), FL(RH) AND FSS(RH) FOR BRETON NWR........................................... 28

TABLE 4-3. MONTHLY FS(RH), FL(RH) AND FSS(RH) FOR ST. MARKS................................................ 29

TABLE 4-4. ANNUAL AVERAGE BACKGROUND VALUES FOR BRETON & ST. MARKS ........................ 29

TABLE 5-1. VERTICAL GRID STRUCTURE ............................................................................................ 34
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LIST OF FIGURES

FIGURE 1-1. ANADARKO’S LEASE BLOCKS IN EASTERN GULF OF MEXICO.......................................... 8

FIGURE 3-1. GENERAL PSD MODELING FLOWCHART......................................................................... 17

FIGURE 5-1. VISTAS RHR MODEL DOMAINS ...................................................................................... 33
Anadarko Petroleum, Inc. 6 

1. INTRODUCTION

1.1 PROJECT DESCRIPTION

Anadarko Petroleum Corporation (Anadarko) is applying for a pre-construction (PSD) and operating 

permit (Title V) for conducting exploratory drilling and other activity on the Outer Continental Shelf 

(OCS) of the Gulf of Mexico. The proposed project will consist of the initial drilling phase, a well 

completion phase and a maintenance operation phase. The proposed activities are planned to be 

conducted at various lease blocks within the Desoto Canyon using a dynamically positioned drillship 

and associated support vessels in the Eastern Gulf of Mexico (EGOM), east of the 87.5 degree 

longitude. A map outlining the “wedge” in the Gulf of Mexico (GOM) identified by the boundary 

presented on the map located in Figure 1-1. Within the wedge there are both active lease blocks 

(currently leased or available for lease) and lease blocks that could potentially be available for lease 

by Bureau of Ocean Energy Management (BOEM) in the future. The area within the boundary line 

identified as “wedge”, is bounded by the following limits.

1. The 87.5 longitude line to the west (Environmental Protection Agency Jurisdiction)

2. The 86.88 longitude line to the east (Military Mission Line)

3. The limit of 100 miles to the shore in the BOEM Central Planning area

4. The limit of 125 miles to the shore in the BOEM Eastern Planning area

An OCS source is considered PSD major if potential emissions of any PSD-regulated pollutant 

exceed the major source thresholds of 250 tons per year (tpy) and the operations are considered a 

major source under the PSD program. The PSD program regulates the emissions of all criteria 

pollutants and several non-criteria pollutants such as total reduced sulfur compounds, sulfuric acid 

mist (H2SO4), and fluorides (not including hydrogen fluoride). 

Based on the preliminary project analysis and emissions calculations, it is expected that the proposed 

OCS source will be subject to requirements of the PSD program and PSD review may be required for 

particulate matter (PM), particulate matter with an aerodynamic diameter less than 10 microns 

(PM10), particulate matter with an aerodynamic diameter less than 2.5 microns (PM2.5), nitrogen 

oxides (NOX), sulfur dioxide (SO2), carbon monoxide (CO), greenhouse gases (GHG), and volatile 

organic compounds (VOC). Accordingly, Anadarko is currently preparing a permit application for 

the PSD construction permit as well as the 5-year renewable Title V operating permit.

As a part of the PSD/Title V application, an air quality modeling analysis will be presented to 

demonstrate that the new facility will not:

 cause or significantly contribute to a violation of the National Ambient Air Quality Standards 

(NAAQS);

 cause ambient concentrations that exceed PSD Increments, or

 cause any other adverse impacts to the surrounding area [i.e. impacts on soil and vegetation, 

visibility degradation, etc.].

Additionally, based on the location of the proposed drilling sites and preliminary analysis of project 

emissions, air quality modeling analyses of the impacts on federally protected Class I areas, a 
Anadarko Petroleum, Inc. 7 

component of a PSD review, will also need to be performed to demonstrate compliance with PSD 

Class I area Increment standards and air quality related values (AQRV) thresholds for regional haze 

and deposition.

1

In accordance with 40 CFR 52.21(p), “the Federal Land Manager and the Federal official charged 

with direct responsibility for management of such lands have an affirmative responsibility to protect 

the air quality related values (including visibility) of such lands and to consider, in consultation with 

the Administrator, whether a proposed source or modification will have an adverse impact on such 

values.” Therefore, the Federal Land Manager (FLM) has the authority to request that proposed PSD 

major sources perform Class I modeling to demonstrate that the AQRVs of Class I areas are not 

adversely affected. 

This modeling protocol which includes the methodology Anadarko is proposing for both Class I and 

Class II modeling analyses have been prepared and is being provided for submittal to the FLM and 

U.S. EPA Region 4. 

1.2 PROJECT LOCATION

Anadarko has identified all lease blocks currently available for drilling operations in EGOM within 

the lease block and has determined which of these lease blocks are closest to all nearby Class I and 

nearest state shoreline areas. Table 1-1 below provides the approximate distance of the worst-case 

(nearest) lease blocks within the area to where each Class I area is located relative to the lease block,

the corresponding FLM for each Class I area, and the nearest lease block to shoreline for Class II 

modeling. A map showing the location of worst-case lease blocks relative to the nearest Class I areas 

and surrounding onshore areas is provided in Figure 1-1.

TABLE 1-1. LOCATION OF LEASE BLOCKS RELATIVE TO NEAREST CLASS I AREAS AND 

SHORELINE

Class I Area (State) & 

Nearest State Shoreline

Lease 

Block Direction Distance (km) Federal Land Manager

Breton NWR (LA) 141 NW 167 U.S. Fish & Wildlife Service (FWS)

St. Marks NWR (FL) 149 NE 286 U.S. Fish & Wildlife Service (FWS)

Bradwell Bay Wilderness (FL) 149 NE 282 U.S. Forest Service (FS)

Nearest State Shoreline 141 NW 161

 

1

Anadarko’s Project lease blocks are located within three federally protected Class I areas in the Southern United 

States. 
Anadarko Petroleum, Inc. 8 

FIGURE 1-1. ANADARKO’S LEASE BLOCKS IN EASTERN GULF OF MEXICO
Anadarko 9 Trinity Consultants

1.3 DESCRIPTION OF MODELING PROCEDURES

On behalf of Anadarko, Trinity Consultants (Trinity) is submitting this air quality modeling protocol 

to present U.S. EPA Region 4 with a description of the proposed modeling procedures and data 

resources in advance of a PSD permit application, which will provide the results of all modeling 

analyses. The methodology described in the protocol will be further utilized in the final modeling 

report to demonstrate compliance with applicable standards. Since the closest receptor for both Class 

I and Class II modeling is more than 50 km from the nearest lease block and worst-case drilling 

location, the air quality impact analyses involve long-range transport and dispersion conditions. 

Hence, CALPUFF air dispersion modeling system will be used for the modeling analysis. 

The CALPUFF air dispersion modeling system is currently the U.S. EPA recommended model for 

assessment of long-range pollutant transport and chemical transformation.2Trinity will conduct the 

modeling analyses in a manner that conforms to the applicable rules and requirements for dispersion 

modeling, including rules and guidance provided in:

 U.S. EPA: Guideline on Air Quality Models, 40 CFR Part 51 - Appendix W (Revised, 

November 9, 2005) (referred to hereafter as Guideline),

 The applicable guidance memorandum from Support Center for Atmospheric Modeling 

(SCRAM) website, the Draft New Source Review Workshop Manual 3,

 The Interagency Workgroup on Air Quality Modeling (IWAQM) Phase 2 Summary Report 4,

 Reassessment of the Interagency Workgroup on Air Quality Modeling (IWAQM) Phase 2 

Summary Report: Revisions to Phase 2 recommendations(Draft 2009 report) 5, 

 The Federal Land Managers’ Air Quality Related Values Workgroup (FLAG) Revised Phase 

I Report (FLAG 2010 report) 6, 

 The U.S. EPA’s Guidance for Estimating Natural Visibility Conditions under the Regional 

Haze Rule7, 

 The U.S. EPA’s Regional Haze Regulations and Guidelines for Best Available Retrofit 

Technology (BART) Determinations8, 

 Previous communications between Trinity and EPA Region 4,

9

and 

 Previous communications between Trinity and the FLM for the three Class I areas. 10

 

2

40 CFR Part 51, Appendix A to Appendix W (Revised, November 9, 2005).

3

EPA’s New Source Review Workshop Manual (DRAFT) (1990).

4

U.S. EPA, IWAQM Phase 2 Summary Report and Recommendations for Modeling Long-Range Transport 

Impacts, Research Triangle Park, North Carolina, EPA-454/R-95-006, December 1998.

5

U.S. EPA, Reassessment of IWAQM Phase 2 Summary Report: Revisions to Phase 2 Recommendations, 

Research Triangle Park, North Carolina, EPA-454/R-09-XXX, May 2009 Draft.

6

U.S. Forest Service – Air Quality Program, National Park Service – Air Resources Division, U.S. Fish and 

Wildlife Service – Air Quality Branch, Phase I Report of the Federal Land Managers’ Air Quality Related Values

Workgroup (FLAG)--Revised, 2010.

7

U.S. EPA, Guidance for Estimating Natural Visibility Conditions under the Regional Haze Rule, September 

2003.

8

U.S EPA, Regional Haze Regulations and Guidelines for Best Available Retrofit Technology (BART) 

Determinations, July 6, 2005.

9

Based on Personal Communication: Phone conversation between Mr. Stan Krivo (EPA Region 4) and Mr. Rahul 

Pendse (Trinity) on September 21, 2012.
Anadarko 10 Trinity Consultants

.

1.4 CONTENTS OF THE MODELING PROTOCOL

The remainder of this modeling protocol is organized as follows: 

 Section 2 provides a description of the OCS source, summary of emission sources and 

potential emissions, and a description of Q/d analysis;

 Section 3 describes the applicable modeling requirements, which includes a discussion of the 

steps involved in a Class II Area modeling analysis; 

 Section 4 describes the applicable modeling requirements, which includes a discussion of the 

steps involved in a Class I Area modeling analysis; 

 Section 5 describes the modeling methodology and inputs, which includes a discussion of the 

selected dispersion models, meteorological data, representation of sources, background 

concentrations, building downwash analysis, receptor locations, and other model inputs; and

 Section 6 describes the content of the modeling report that will be submitted to the FLM and 

U.S. EPA Region 4 for review. 

 

10 Based on Personal Communication: Phone conversation between Ms. Jill Webster (FWS) and Mr. Rahul Pendse 

(Trinity) on October 12, 2012; E-mail from Ms. Jill Webster (FWS) to Mr. Dhesikan Venkatesan (Trinity) sent on October 

10, 2012; and Phone conversation between Ms. Melanie Pitrolo (FS) and Mr. Rahul Pendse (Trinity) on October 18, 2012.
Anadarko 11 Trinity Consultants

2. SOURCE DESCRIPTION 

2.1 DESCRIPTION OF PROPOSED OCS SOURCE

The exploratory drilling activity will consist of the initial drilling phase, a well completion phase 

and/or a maintenance operation phase. Anadarko is requesting the flexibility to drill one or more 

wells in any of the lease blocks provided in Section 1-2 while complying with any operational and 

emission limitations specified in the air permits that will be issued. The proposed operations will be

conducted using the drillship Blackhawk, and associated support vessels. 

The Blackhawk is a dynamically-positioned drillship that is designed for operation in the deep water. 

As a dynamically-positioned drillship, it maintain their position over the desired location by using the 

computer-controlled thruster propellers rather than by using anchors and is not required to be attached 

to the seabed in order to establish or maintain its position like a traditional drillship. As discussed in 

Section 1, 40 CFR 55.2 states that a vessel shall only be considered an OCS source when 

“Permanently or temporarily attached to the seabed and erected thereon and used for the purpose of 

exploring, developing or producing resources therefrom...” Therefore, Blackhawk will qualify as an 

OCS source after the drillship is temporarily or permanently attached to the seabed during the 

proposed operations. 

The major sources of emissions on the drillship as well as the support vessels will primarily consist of 

diesel-fired internal combustion engines and fuel storage tanks. The miscellaneous maintenance 

activities (such as welding, painting) resulting in air emissions will be conducted on the drillship. 

The permit application will provide a detailed description of all the sources of air pollution including 

diesel engines, fuel storage tanks, and miscellaneous activities.

The associated support vessels will include a combination of crew boats and work boats, stimulation 

vessels, tug and/or barge boats that will be used to transport personnel, supplies, and fuel to the 

drillship, as required, during the entire duration of the proposed project. As it is presently not known 

which specific vessels will be available when the drilling commences, the support vessels will be 

used interchangeably depending upon availability. For purposes of the air permit applications and the 

modeling analysis, the worst-case emissions from the each category of the support vessels will be 

utilized. The emissions from the support vessels will be considered for the modeling analysis while 

the support vessels are at the drillship, and while enroute to or from the drillship when within 25 

miles of the drillship. All assumptions made for estimating the worst-case support vessel emissions 

as well as all support vessels and their respective functions will be appropriately documented in the 

final modeling report of the permit application.

In addition to the boats, the support vessel fleet will also include a helicopter that will be used for 

transporting supplies and personnel. The helicopter typically makes two trips per day to the drillship. 

Since the helicopter takes small amount of time to travel 25 miles from the drillship, expected air 
Anadarko 12 Trinity Consultants

emissions are negligible. Hence based on previous communications and discussions with U.S. EPA 

Region 4, the helicopter emissions are not included in the PSD permitting effort. 

11

 

2.2 EMISSION SOURCES

The sources of emissions for Blackhawk primarily consist of:

 internal combustion engines, 

 painting operation, 

 welding operation, 

 dust collectors, 

 mud-degassing operation, 

 water blasting operation,

 miscellaneous equipment, and

 fuel storage tanks. 

For the support vessels, the emission sources include internal combustion engines and fuel storage 

tanks. The methodology used to determine the “worst-case” drillship and support vessel emissions

modeled will be described in details in the application.

2.3 POTENTIAL EMISSIONS

As previously mentioned, the proposed project will consist of the initial drilling phase, a well 

completion phase, and/or a maintenance operation phase. The well completion and maintenance 

operation phase are expected to have lower emissions than the drilling phase. The permit application 

will include the detailed description of the maximum hourly (1-hour), maximum daily (24-hour) and 

annual emissions resulting from the proposed exploratory drilling, completion, and maintenance 

activities over entire duration of the project. The worst case emissions will be utilized for air 

dispersion modeling.

2.4 Q/D ANALYSIS

Anadarko will complete the Q/d calculation based on the potential-to-emit from the proposed project

to assess potential impacts of the proposed drilling operations on the nearest Class I areas. The Q/d 

analysis compares the ratio of the sum of proposed annualized maximum 24-hour emission rates of all 

visibility impairing pollutants (in tons per year) and the distance to the nearest Class I area (in km) to 

a threshold value of 10, as determined by the FLM. 

The “Q” is the combined emissions increase from a source of SO2, NOX, PM10, and H2SO4 in tons per 

year (tpy) based on annualized 24-hour maximum allowable emissions and “d” is the nearest distance 

to a Class I area in km from the source.

12

 Emissions from sources that operate intermittently or 

seasonally will be adjusted to account for year round operation. Based on the preliminary analysis, a 

Class I area AQRV analysis is required for this project because the Q/d ratio for the proposed source 

 

11 Personal Communication: Phone conversation between Mr. Stan Krivo (EPA Region 4) and Mr. Rahul Pendse 

(Trinity) on September 21, 2012.

12 U.S. Forest Service – Air Quality Program, National Park Service – Air Resources Division, U.S. Fish and 

Wildlife Service – Air Quality Branch, Phase I Report of the Federal Land Managers’ Air Quality Related Values

Workgroup (FLAG)--Revised, 2010.

.
Anadarko 13 Trinity Consultants

is expected to be greater than 10. Although Anadarko is still in the process of finalizing potential 

emission rates, Anadarko does not expect the Q/d to be less than 10. A copy of the Q/d analysis will 

be included in the final modeling report.
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3. CLASS II AIR QUALITY DISPERSION MODELING REQUIREMENTS

As the proposed OCS source will be subject to the PSD program requirements, an air quality analysis 

is required to demonstrate that emissions of these pollutants do not cause or contribute to a violation 

of a National Ambient Air Quality Standard (NAAQS) or exceed a Class II area PSD Increment. Per 

Guideline, this is accomplished by conducting an Air Dispersion Modeling analysis. A Class II PSD 

Air Dispersion Modeling Analysis may consist of two distinct phases:

 The first phase, PSD significance analysis, is a screening analysis. The significance 

analysis determines whether 40 CFR 52.21 requires a full impact analysis for compliance. 

The significance analysis considers only the emissions associated with the proposed 

project to determine if the net emissions changes will have a significant impact upon the 

surrounding area. A “significant” impact occurs when the modeled ambient concentration 

resulting from the modeled emission rates equals to or exceeds applicable ambient 

concentration thresholds commonly referred to as the Significant Impact Levels (SILs)

also known as Modeling Significance Levels (MSLs). In addition, the significance 

analysis determines the Significant Impact Area (SIA) and whether the applicant is exempt 

from preconstruction ambient monitoring requirements for the proposed project. 

 The second phase is a “full impact” or “cumulative” analysis. For pollutants with modeled 

concentrations greater than the SIL, PSD regulations require a NAAQS analysis and a 

PSD Increment analysis. A full impact analysis is performed at each off-property receptor 

where the maximum concentration exceeds the applicable SIL as determined in the 

significance analysis. The NAAQS analysis demonstrates that the post-project emissions 

in conjunction with other applicable emissions from existing sources will not cause nor 

contribute to an exceedance of the applicable air quality standard. The PSD Increment 

analysis demonstrates that the proposed project in conjunction with other applicable 

emissions from existing sources will neither cause nor contribute to an exceedance of the 

applicable air quality standard.

Table 3-1 lists the SILs, NAAQS, and PSD Increments for all relevant PSD-regulated pollutants for 

this dispersion modeling analysis. 
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TABLE 3-1. APPLICABLE PSD AIR QUALITY LEVELS

Pollutant

Averaging

Period

PSD 

Modeling

SIL

(g/m3)

Primary and 

Secondary

NAAQS

(g/m3)

Class II 

Area PSD

Increment

(g/m3)

Significant

Monitoring 

Concentration

(g/m3)

CO 1-hour

8-hour

2,000

500

40,000 (35 ppm)1

10,000 (9 ppm)1

--

--

--

575

SO2

9 3-hour

24-hour

Annual

1-hour8

25

5

1

--

1,300 (0.5 ppm)1

--

--

196 (0.075 ppm)4

512

91

20

--

--

13

--

--

NO2 Annual

1-hour7

1

--

100 (0.053 ppm)2

188 (0.100 ppm)

4

25

--

14

--

PM10 24-hour

Annual

5

1

1503

--

30

17

10

--

PM2.5 24-hour

Annual

1.2

0.3

355

12

6

9

4

4

--

1 Not to be exceeded more than once per year.

2 Annual arithmetic average.

3 Not to be exceeded more than once per year on average over 3 years.

4 3-year average of the 98th percentile of the annual distribution of daily maximum 1-hour concentrations.

5 98th percentile of concentrations in a given year, averaged over 3 years.

6 Annual arithmetic mean from single or multiple monitors, averaged over 3 years.

7 PSD Increments, Modeling SILs, and Monitoring De Minimis Concentration level for the 1-hour NO2 standard 

have not been proposed yet. However, interim modeling significance levels of 4 ppb was provided by EPA in 

general guidance implementation memo dated June 28, 2010.

8 PSD Increments, Modeling SILs, and Monitoring De Minimis Concentration level for the 1-hour SO2 standard 

have not been proposed yet. However, interim modeling significance levels of 3 ppb was provided by EPA in 

general guidance implementation memo dated August 23, 2010.

9 The existing annual and 24-hour SO2 standards will be revoked one year after the effective date in areas with a 

designated status for the revised SO2 NAAQS, per 40 CFR 50.4(e).

A summary of the tasks that are performed in a standard PSD Air Dispersion Modeling analysis is 

presented in the flow chart provided as Figure 3-1. Each of the principle steps involved in a PSD Air 

Dispersion Modeling analysis are discussed in detail below. The dispersion modeling analysis will be 

conducted in a manner that conforms to the applicable rules and requirements for dispersion modeling 

issued by the U.S. Environmental Protection Agency (EPA).13 

3.1 PSD SIGNIFICANCE ANALYSIS

The Significance Analysis is conducted to determine whether the emissions associated with the 

proposed OCS source would cause a significant impact upon the area surrounding the OCS source. 

As shown in Figure 3-1, if the highest modeled ambient concentrations for a pollutant for all 

 

13 40 CFR 51, Appendix W, Revision to Guideline on Air Quality Models, November 9, 2005; and EPA’s New 

Source Review Workshop Manual (DRAFT) (1990).
Anadarko 16 Trinity Consultants

averaging periods are less than the applicable SILs shown in Table 3-1, when emission from only the 

project are modeled, then further analyses (i.e., NAAQS and PSD Increment) are not required for that 

pollutant and the project’s impact is considered not significant. If, however, modeled impacts equal 

to or exceed the SIL for any averaging period, a full impact (i.e., NAAQS and PSD Increment)

analysis is required for that pollutant to demonstrate that the project neither causes nor contributes to 

any exceedances. A special consideration shall be given to PM2.5 since direct comparison of the 

primary PM2.5 concentration with PM2.5 SIL is not allowed without prior approval from the regulatory 

agency. Refer to Section 3.1.3 for further discussion regarding this topic. 

Based on the preliminary emission calculations and previous experiences, Anadarko expects that 

concentration of all pollutants will be less than their respective SILs. Hence, in that case, full impact 

analysis will not be required for these pollutants. Hence this protocol does not address requirements 

for the full impact analysis. If the significance levels for applicable pollutants and averaging periods

are exceeded in the final modeling analyses, an addendum to this protocol will be submitted to EPA 

Region 4 for review and approval. 
Anadarko 17 Trinity Consultants

FIGURE 3-1. GENERAL PSD MODELING FLOWCHART
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3.1.1 PRE-CONSTRUCTION MONITORING ANALYSIS

In addition to determining whether the applicant can forego further modeling analyses, the PSD 

Significance Analysis is also used to determine whether the applicant is exempt from ambient 

monitoring requirements. To determine whether pre-construction monitoring should be considered, 

the maximum impacts attributable to the emissions increases from a project are compared with the

Significant Monitoring Concentrations (SMCs) shown in Table 3-1. If either the predicted modeled 

impact from an emissions increase or the existing ambient concentration is less than the SMC, an 

applicant is exempt from pre-construction ambient monitoring. If the predicted modeled impact is 

equal to or greater than the SMC, an applicant may provide existing data representative of ambient air 

quality in the affected area or, if such data are not available, collect background air quality data.14 

If the predicted modeled impacts are lower than the SMC, Anadarko expects that pre-construction 

monitoring for this project will not be required by U.S. EPA Region 4. If the predicted modeled 

impacts equal to or exceed the SMCs, Anadarko will submit an addendum to this protocol and seek 

approval from EPA Region 4.

Additionally, although no SMCs have been established for ozone, 40 CFR 52.21(i)(5)(i) specifies that 

for any net emissions increase of 100 tons per year or more of VOC or NOX subject to PSD, an 

applicant would be required to perform an ozone impact analysis. As the NOX emissions from the 

proposed OCS source are expected to be greater than 100 tons per year, Anadarko will be subject to 

the requirements of 40 CFR 52.21(i)(5)(i). Due to the remote offshore location of the proposed 

operations, very minimal contribution in the formation of ozone is expected from the proposed 

operation. Since an adequate ozone formation model is not available for this type of a single 

source application, Anadarko proposes to address this requirement using qualitative approach 

similar to the one described in the preliminary statement of basis for permit no. OCS-EPA-R4006

prepared by the EPA Region 4.

15

3.1.2 SPECIAL CONSIDERATIONS FOR PM2.5

On May 16, 2008, U.S. EPA issued the final PM2.5 New Source Review (NSR) Implementation Rule, 

which requires sources to conduct an ambient air quality analysis for PM2.5 in accordance with 40 

CFR §52.21(m).16 While the preamble to this rule states that no changes to the PSD regulations on air 

quality impact analyses were made for purposes of implementing the PM2.5 NSR program, conducting 

an ambient air quality analysis using the current regulatory air dispersion models for a pollutant like 

PM2.5, which can be formed from precursors through atmospheric reactions downwind of an industrial 

source poses several technical difficulties. Therefore, when implementing the current U.S. EPArecommended model and relevant PSD modeling guidance, sources need to evaluate ambient impacts 

from direct total (filterable and condensable) PM2.5 emissions and secondary PM2.5 emissions. 

EPA recommended in a memorandum that the highest average of the modeled annual averages of 

PM2.5 concentrations based on 5 years of National Weather Service data or the highest modeled 

 

14 U.S. EPA New Source Review Workshop Manual (Draft, 1990), pages C.18–19.

15 U.S. EPA Region 4, Preliminary Determination & Statement of Basis Outer Continental Shelf Air Permit OCSEPA-R4006, August 19, 2011.

16 Federal Register, Vol. 73, p. 28,321.
Anadarko 19 Trinity Consultants

annual average of PM2.5 concentration based on 1 year of site-specific meteorological data be 

compared to the annual SIL. 17 Similarly, it was recommended that the highest average of the 

maximum 24-hour averages of PM2.5 concentrations based on 5 years of National Weather Service 

data or the highest modeled 24-hour average of PM2.5 concentration based on 1 year of site-specific 

meteorological data be compared to the 24-hour SIL. Anadarko is proposing to use the annual and 

24-hour options based on three year meteorological dataset (2001-2003) developed by the Visibility 

Improvement State and Tribal Association of the Southeast (VISTAS) for the PSD Class II impact 

assessments.

On September 29, 2010, the U.S. EPA issued a final ruling establishing several components for 

making PSD permitting determinations for PM2.5. As such, the promulgated PSD increments, SILs, 

and SMCs for PM2.5 have been incorporated into Table 3-1 of this modeling protocol.

The EPA has historically allowed the use of screening tools to help facilitate the implementation of 

the PSD program and streamline the permitting process in circumstances where proposed 

construction is projected to have an insignificant (or de-minimis) impact on air quality. These 

screening tools have included SERs, SILs, and SMCs. The EPA established a SER for PM2.5 in a 

2008 rule and promulgated SILs and an SMC for PM2.5 in 2010. 

18 However, on January 22, 2013, the 

U.S. Court of Appeals for the District of Columbia Circuit vacated the SMC for PM2.5 and two 

provisions in EPA’s PSD regulations containing SILs for PM2.5.

19 The Court concluded that the PM2.5

SMC provisions (40 CFR 51.166(i)(5)(c) and 40 CFR 52.21(i)(5)(i)(c)) were inconsistent with the 

requirements of Section 165(e)(2) of the CAA. The Court granted the EPA’s request to remand and 

vacate the SIL provisions in Sections 40 CFR 51.166(k)(2) and 40 CFR 52.21(k)(2) of the regulations 

so that the EPA could correct an error in these provisions that came to the EPA’s attention after the 

court challenge was filed. 

The EPA released draft guidance (EPA draft guidance for PM2.5 modeling) for PM2.5 modeling which 

reflects EPA's preliminary recommendations for how a stationary source seeking a PSD permit may 

demonstrate that it will not cause or contribute to a violation of the NAAQS and PSD increments for 

PM2.5, as required under Section 165(a)(3) of the CAA and 40 CFR 51.166(k) and 40 CFR 52.21 (k). 

The draft Guidance for PM2.5 permit modeling incorporates the modeling procedures and 

recommendations from the March 23, 2010, guidance memorandum "Modeling Procedures for 

Demonstrating Compliance with PM2.5 NAAQS," and further clarifies procedures for adequately 

addressing primary and secondarily formed PM2.5 in a NAAQS compliance demonstration under the 

PSD program. Due to lack of other final guidance, Anadarko proposes to model PM2.5 emissions 

consistent with the recommendations prescribed in the draft guidance document.

Per EPA draft guidance for PM2.5 modeling, “The vacated provisions of the regulations inadvertently 

restricted the discretion of permitting authorities to conduct or require more than a screening 

analysis in some circumstances where the EPA had called for permitting authorities to consider 

 

17 Based on U.S. EPA Memorandum from Stephen D. Page to Bill Harnett, et al. titled, “Modeling Procedures for 

Demonstrating Compliance with PM2.5 NAAQS”. March 23, 2010.

18 73 FR 28321 and 75 FR 64864.

19 Sierra Club v. EPA, No. 10-1413 (D.C. Circuit), 2013 WL 216018.
Anadarko 20 Trinity Consultants

whether additional analysis was needed to make the demonstration required by Section 165(a)(3) of 

the CAA. Due to the court decision, the EPA will not rely, and advised permitting authorities with 

State Implementation Plan (SIP) approved PSD programs not to rely, on the SMCs for PM2.5 to 

exempt permit applicants from compiling preconstruction monitoring data for PM2.5 in accordance 

with Sections 40 CFR 51.166(m) and 40 CFR 52.21(m). However, the EPA believes PSD permit 

applicants may continue to meet the preconstruction monitoring requirements in these regulations by 

using data from existing monitors that are determined by the applicable permitting authority to be 

representative of background conditions in the affected area. The court decision does not preclude 

the use of SILs for PM2.5, but requires that EPA correct the error in the SIL regulations for PM2.5 at 

40 CFR 51.166(k)(2) and 40 CFR 52.21(k)(2). In the interim, the EPA believes permitting authorities 

may continue to apply SILs for PM2.5 to support a PSD permitting decision, but permitting authorities 

should take care to ensure that SILs are not used in a manner that is inconsistent with the 

requirements of Section 165(a)(3) of the CAA....”

20

 

Per EPA draft guidance for PM2.5 modeling, “Any permitting authority wishing to use a particular 

SIL value as a screening tool in a significant impact analysis should determine whether a substantial 

portion of the NAAQS has already been consumed. Preconstruction monitoring data (or adequately 

representative onshore monitoring data from an existing onshore monitoring network) should be 

evaluated against the respective PM2.5 NAAQS. If the difference between the NAAQS and the 

measured or representative PM2.5 background in the area is greater than the applicable SIL value, 

then the EPA believes it would be sufficient in most cases for permitting authorities to conclude that a 

source with an impact below that SIL value will not cause a new NAAQS violation...” 

Anadarko is proposing to subtract background PM2.5 concentrations from the NAAQS standards to 

assess whether a substantial portion of NAAQS has already been consumed. If the difference 

between the NAAQS standard and the background concentration is greater than the respective PM2.5

SIL then Anadarko is proposing to compare modeled PM2.5 concentrations against the respective 

PM2.5 SILs. Also, Anadarko proposes to address the impact of the secondary PM2.5 formation 

qualitatively. If the modeled PM2.5 concentration is equal or greater than the respective SILs then 

Anadarko will submit an addendum to this application for conducting the full impact analysis.

3.2 ADDITIONAL IMPACTS ANALYSIS

PSD regulations require that three additional impact analyses be performed as part of a PSD permit 

action. The PSD application to be prepared for the proposed project will contain three additional 

impact analyses: 1) an analysis of the air quality impact projected for the area as a result of any 

commercial, residential, and industrial growth associated with the proposed facility, 2) an analysis of 

the impairment to soils, vegetation, and animals that may occur as a result of the proposed facility, 

and 3) an analysis of impairment to visibility (haze at distant Class I areas and plume impairment at 

sensitive Class II receptors) that may occur as a result of the proposed facility. This section of the 

protocol discusses the methodologies that will be followed in completing and presenting the 

additional impacts analyses. Anadarko believes that the approach outlined will satisfy Anadarko’s 

obligations in this regard for this project. 

 

20 http://www.epa.gov/scram001/guidance/guide/Draft_Guidance_for_PM25_Permit_Modeling.pdf.
Anadarko 21 Trinity Consultants

3.2.1 GROWTH ANALYSIS

The purpose of the growth analysis is to quantify project-associated growth; that is, to predict how

much new growth is likely to occur in order to support the source under review, and then to estimate 

the air quality impacts from this growth either quantitatively or qualitatively. Typically, the amount 

of residential growth depends on the size of the available work force, the number of new employees, 

and the availability of housing in the area. Associated commercial and industrial growth consists of 

new sources providing goods and services to the new employees and to the new industrial source 

itself. Because of the seasonal and temporary nature of the proposed OCS source, Anadarko

anticipates that any industrial, commercial and residential growth will be insignificant. 

3.2.2 SOILS AND VEGETATION ANALYSIS

The EPA, through the CAA, has promulgated primary and secondary ambient air quality standards. 

The primary air quality standards are set at levels necessary to provide an adequate margin of safety 

to protect human health. The secondary standards are set at levels to provide for protection of public 

welfare, where welfare is defined to include the following: soils, water, vegetation, manmade 

materials, animals, wildlife, weather, visibility, climate, and damage to or deterioration of property.21

Table 3-1 shows the secondary NAAQS for each relevant regulated air pollutant for this modeling 

analysis. To satisfy this requirement, Trinity will assess the modeling results against the secondary 

NAAQS, for determination of impacts to soil and vegetation. If ambient air concentrations are found 

to be less than the secondary NAAQS, it will be presumed that emissions from the proposed sources 

will not result in harmful effects to either soil or vegetation.22 Alternatively, due to the location of the 

proposed exploration activities being more than 100 km from the nearest shoreline if ambient air 

concentrations are found to be less than the SILs, it will be presumed that emissions from the 

proposed sources will not result in harmful effects to either soil or vegetation.

3.2.3 VISIBILITY ANALYSIS

As per the U.S. EPA New Source Review Workshop Manual, visibility impairment analysis should be 

performed for impacts that occur within the area affected by proposed project.23 The EPA’s 

Workbook for Plume Visual Impact Screening and Analysis (Workbook) provides guidance for 

conducting a visibility impairments analysis through the use of VISCREEN, a plume visibility impact 

model.24 The methods in this workbook are designed for Class I area impacts; however, the 

procedures are generally applicable to other areas as well. The VISCREEN model is recommended 

for the first level (Level 1) screen. If predicted values from the VISCREEN model are greater than 

the standardized screening values, the emissions are judged to have the potential for visibility 

impairment. 

 

21 Sections 109 and 302 of the Clean Air Act. 

22 U.S. EPA, Office of Air Quality Planning and Standards, New Source Review Workshop Manual, Research 

Triangle Park, NC, October 1990.

23 U.S. EPA, New Source Review Workshop Manual (Draft): Prevention of Significant Deterioration and 

Nonattainment Area Permitting, October 1990.

24 U.S. EPA Office of Air Quality Planning and Standards. Workbook for Plume Visual Impact Screening and 

Analysis. Research Triangle Park, NC. EPA-450/4-88-015. 
Anadarko 22 Trinity Consultants

If the potential for visibility impairment is indicated, the next level analysis, Level 2 analysis, is 

required. Although VISCREEN is primarily designed for assessing plume visual impacts in Class I 

areas, as noted in the Workbook for Plume Visual Impact Screening and Analysis, it can also be 

applied in PSD Class II areas. Default values will be used for background ozone (0.04 ppm), stability 

class (6), and wind speed (1 m/s). Per the workbook, distances from the emission source for the Class 

II area evaluations can be specified “arbitrarily.” The application of VISCREEN is limited to 

distances less than or equal to 50 km. Therefore to conservatively estimate the potential visual impact 

in the impact area that is more than 50 km from the drilling location, the 50 km distance will be used 

in the VISCREEN analysis.
Anadarko 23 Trinity Consultants

4. CLASS I AIR QUALITY DISPERSION MODELING REQUIREMENTS

Two principal air quality impacts are considered for Class I areas: PSD Increments for NOX, PM2.5, 

and PM10, and AQRVs. This section of the protocol describes the procedural requirements for 

assessing the impacts of emissions from Anadarko’s proposed drillship on Breton NWR, St. Marks 

NWR, and Bradwell Bay Wilderness areas.

4.1 CLASS I AREA PSD INCREMENT

In general, all PSD permit applications are required to demonstrate through air quality modeling that 

the emissions increases from the proposed project will not cause or contribute to any violations of 

allowable increments within affected Class I areas, which are protected to a greater degree (i.e., the 

allowable increments are lower) than Class II areas. A significant contribution to Class I Increment 

consumption is defined as a modeled concentration in excess of the significant impact levels (SILs) 

summarized in Table 4-1, which were originally developed as part of the 1996 NSR reform 

rulemaking and have subsequently been adopted as informal modeling significance levels for Class I 

Area analyses that are used to determine if a project is likely to cause or contribute to a Class I area 

Increment violation. 

TABLE 4-1. CLASS I AREA PSD INCREMENTS & MODELING SIGNIFICANCE LEVELS

Pollutant Averaging Period

Class I Increment

(g/m3)

Significance Level

(g/m3)

PM10 24-hour 8.0 0.32

Annual 4.0 0.16

PM2.5 24-hour 2.0 0.07

Annual 1.0 0.06

NO2 [1] Annual 2.5 0.1

[1] On February 9, 2010, U.S. EPA Promulgated a NO2 NAAQS for the 1-hr averaging period. However, a NO2 PSD 

Increment standard for the 1-hr averaging period was not established as part of this action. See 75 Fed. Reg. 6474, Primary 

National Ambient Air Quality Standards for Nitrogen Dioxide (February 9, 2010).

Since the proposed OCS source will have potential emissions of NOX, PM2.5, and PM10 in excess of the 

PSD Significant Emission Rates (SERs), the Class I area PSD Increment analysis will be completed 

for each of these pollutants.

25

 

 

25 VISTAS, Protocol for the Application of the CALPUFF Model for Analyses of Best Available Retrofit 

Technology (BART), Revision3.2, revised August 31, 2006.

http://www.vistas-sesarm.org/documents/BARTModelingProtocol_rev3.2_31Aug06.pdf
Anadarko 24 Trinity Consultants

If the significance levels for NOX, PM2.5, and PM10 are exceeded, a regional inventory will be 

developed and the impacts caused by the OCS source and the regional inventory will be compared 

against the Class I Area Increments.

4.2 CLASS I AQRV ANALYSES

The FLAG Phase I report provides the following definitions relating to AQRV:26

Air Quality Related Value - A resource, as identified by the FLM for one or more 

Federal areas that may be adversely impacted by a change in air quality. The resource 

may include visibility or a specific scenic, cultural, physical, biological, ecological, or 

recreational resource identified by the FLM for a particular area.

Adverse Impact On Visibility - Visibility impairment which interferes with the 

management, protection, preservation, or enjoyment of a visitor's visual experience of a 

Federal Class I or Class II area. This determination must be made on a case-by-case 

basis taking into account the geographic extent, intensity, duration, frequency and time 

of visibility impairments, and how these factors correlate with (1) times of visitor use of 

the Class I area, and (2) the frequency and timing of natural conditions that reduce 

visibility. This term does not include effects on integral vistas. [40 CFR §51.301(a)]

Adverse Impact on an AQRV - An unacceptable effect, as identified by an FLM that 

results from current, or would result from predicted, deterioration of air quality in a 

Federal Class I or Class II area. A determination of unacceptable effect shall be made 

on a case-by-case basis for each area taking into account existing air quality conditions. 

It should be based on a demonstration that the current or predicted deterioration of air 

quality will cause or contribute to a diminishment of the area's national significance, 

impairment of the structure and functioning of the area's ecosystem, or impairment of the 

quality of the visitor experience in the area.

AQRV indicators typically identified by FLM include nitrogen deposition, sulfur deposition, and 

visibility degradation. Based on discussion with FWS, Anadarko is required to perform AQRV 

analyses for all three indicators mentioned above for Breton and St. Marks Class I areas.27 Based on 

guidance received from FS, the AQRV analysis for Bradwell Bay is required to be performed for 

nitrogen deposition, sulfur deposition, and ozone. An AQRV analysis for visibility at Bradwell Bay 

is not required.28 

 

26 U.S. Forest Service – Air Quality Program, National Park Service – Air Resources Division, U.S. Fish and 

Wildlife Service – Air Quality Branch, Phase I Report of the Federal Land Managers’ Air Quality Related Values

Workgroup (FLAG)--Revised, 2010.

27 Based on Personal Communication, Phone conversation between Ms. Jill Webster (FWS) and and Mr. Rahul 

Pendse (Trinity) on October 12, 2012; E-mail from Ms. Jill Webster (FWS) to Mr. Dhesikan Venkatesan (Trinity) sent on 

October 10, 2012; and Phone conversation between Ms. Melanie Pitrolo (FS) and Mr. Rahul Pendse (Trinity) on October 18, 

2012.

28 Based on Personal Communication, Phone conversation Ms. Melanie Pitrolo (FS) and Mr. Rahul Pendse 

(Trinity) on October 18, 2012, visibility has not been established as an AQRV for Bradwell Bay.
Anadarko 25 Trinity Consultants

4.2.1 DEPOSITION

In the deposition analysis, the contribution of Anadarko’s proposed drilling operations to 

the deposition of chemical species in the Class I area will be evaluated against the 

deposition assessment threshold (DAT) values for sulfate and nitrate set by the FLM. The 

DAT represents “the additional amount of N or S deposition within a Class I area, below 

which estimated impacts from a proposed new or modified source are considered 

insignificant.” The threshold is not necessarily an adverse impact threshold and coastal 

ecosystems have evolved under naturally higher sulfur deposition rates. FLM guidance for 

assessment of deposition impacts suggests that an appropriate sulfur and nitrogen DAT is 

0.005 kg/ha/yr and 0.01 kg/ha/yr respectively, for all Class I areas in the Eastern United 

States.29 The procedures specified in the FLAG Phase I report (revised 2010) will be used 

to model nitrogen and sulfur deposition. 30 For sulfur, both wet and dry fluxes of SO2 and 

sulfates (SO4) will be modeled. The sum of wet and dry deposition fluxes for SO2 and SO4

represents the total sulfur deposition as shown in Equation 3.

 

  2 4 2 4 dry

2 4 2 4 wet

 flux[SO ] flux[(NH ) S O ]

Sulfur Deposition (kg/ha/yr) flux [SO ] flux [(NH ) S O ]



  

Equation 3

For nitrogen, the dry flux for NOx, and wet and dry deposition fluxes for nitrates (NO3), 

nitric acid (HNO3), and ammonium ion (NH4) from ammonium nitrate (NH4NO3) and 

ammonium sulfate (NH4)2SO4) will be modeled. Therefore, the sum of dry flux for NOx

and wet and dry deposition fluxes for NO3, HNO3, and ammonium ion (NH4) from 

ammonium nitrate and sulfate represents the total nitrogen deposition, as shown in 

Equation 4.

 

 (flux[NOx] flux[NH NO ] flux[HNO ] flux[(NH ) S O ]) 

Nitrogen Deposition (kg/ha/yr) flux[NH NO ] flux[HNO ] flux[(NH ) S O ]

4 3 3 4 2 4 dry

4 3 3 4 2 4 wet

   

  

Equation 4

In accordance with the FLAG Phase I report (revised 2010), gas phase deposition will be 

modeled for SO2, NOx, and HNO3, and particle phase deposition will be modeled for SO4

and NO3. The contribution of the proposed project to the deposition of nitrogen and sulfur 

species in each Class I area will be estimated and assessed against the appropriate DAT in 

the modeling report. 

 

29 U.S. National Park Service (NPS) - Air Resources Division and U.S. Fish and Wildlife Service - Air Quality 

Branch, Interagency Guidance on Nitrogen and Sulfur Deposition Analyses, accessed on November, 2011 via NPS website -

www.nature.nps.gov/air/Pubs/pdf/flag/nsDATGuidance.pdf.

30 U.S. Forest Service – Air Quality Program, National Park Service – Air Resources Division, U.S. Fish and 

Wildlife Service – Air Quality Branch, Phase I Report of the Federal Land Managers’ Air Quality Related Values

Workgroup (FLAG)--Revised, 2010.
Anadarko 26 Trinity Consultants

4.2.2 VISIBILITY

Visibility can be affected by plume impairment (heterogeneous) or regional haze 

(homogeneous). Plume impairment results when there is a contrast or color difference 

between the plume and a viewed background (the sky or a terrain feature). Plume 

impairment is generally only of concern when the Class I area is near the proposed source 

(i.e., less than 50 km). Since the distance between the proposed OCS source and the 

nearest Class I area evaluated is greater than 50 km, only regional haze will be considered 

in this analysis.

Regional haze occurs at distances where the plume has become evenly dispersed into the 

atmosphere such that there is no definable plume. The primary causes of regional haze are 

sulfates (SO4) and nitrates (NO3) (primarily as ammonium salts), which are formed from 

emissions of SO2 and NOX through chemical reactions in the atmosphere. These reactions 

take time, hence distance. Near the emissions source little NOX or SO2 will have formed 

nitrate or sulfate, whereas far from a source nearly all SO2 will have formed sulfate and 

most NOX will have formed nitrate. Particulate emissions also contribute to regional haze 

but to a lesser extent since sulfates and nitrates are hygroscopic species that increasingly 

reduce visibility with increased relative humidity.

Regional haze is measured using the light extinction coefficient (bext). To determine a 

change in regional haze, the percentage change of the light extinction coefficient (bext) 

will be evaluated as shown in the following Equation 5:

ext background

ext project

ext b

b

b

,

,

 

Equation 5

The Δbext value attributable to a single facility that is generally acceptable to the FLM is 

5% on a 24-hour average basis. There are a number of available methods that can be used 

to estimate the percentage change of light extinction coefficient associated with an 

emissions source. The peak 24-hour average visibility impairment as predicted by the air 

quality model is one conservative measure used to attribute visibility affects to a single 

source. However, as stated in the preamble of the U.S. EPA’s Regional Haze Regulations 

and Guidelines for Best Available Retrofit Technology (BART) Determinations, the 

CALPUFF model uses a simplified chemistry that “...tends to magnify the actual visibility 

effects” of a source. 31 Therefore, the U.S EPA recommends the consideration of the 98th

percentile of modeled visibility values to assess visibility impacts, and states in the 

preamble, “...we believe it is appropriate to use the 98th percentile—a more robust 

approach that does not give undue weight to the extreme tail of the distribution. The use of 

the 98th percentile of modeled visibility values would appear to exclude roughly 7 days per 

year from consideration. In our judgment, this approach will effectively capture the 

sources that contribute to visibility impairment in a Class I area, while minimizing the 

likelihood that the highest modeled visibility impacts might be caused by unusual 

 

31 U.S EPA, Regional Haze Regulations and Guidelines for Best Available Retrofit Technology (BART) 

Determinations, July 6, 2005.
Anadarko 27 Trinity Consultants

meteorology or conservative assumptions in the model.” The use of the 98th percentile 

approach has also been formalized in the FLAG Phase I report (revised 2010).

In the revised FLAG Phase I report (revised 2010), FLAG has proposed a new algorithm 

for calculating the background extinction coefficient based on the revised method in the 

Interagency Monitoring of Protected Visual Environments (IMPROVE) protocol. 

IMPROVE protocols for reconstructing ambient light extinction from measured aerosol 

species are used in evaluating compliance under the Regional Haze Rule (RHR) and also 

are relied on for conducting Class I area AQRV analyses. The algorithm based on the 

IMPROVE protocols is recommended as the regulatory default background extinction 

calculation methodology by the FLAG Phase I report (revised 2010), and so Trinity shall 

use these procedures to calculate the background extinction coefficient, as explained 

below. 

October 2010 FLAG Phase I Revised Report – Calpost “Method 8”

In CALPOST “Method 8”, bext is computed using a monthly average relative humidity 

adjustment particular to each Class I area, applied to background and modeled 

concentrations of large and small sulfates and nitrates, and sea salt. Because a monthly 

average is used, no cap on f(RH) is necessary and the results tend to be smoothed, since 

peak short-term humidity events are not considered. 

Procedures specified in the FLAG Phase I report (revised 2010) will be used to determine 

the background extinction using “Method 8”.The background extinction coefficient 

bext,background is calculated using the IMPROVE equation for calculating light extinction, as 

shown in Equation 6 obtained from Figure 5 of the FLAG Phase I report (revised 2010):

32

bext, background = 2.2 × fS(RH) × [Small Sulfate] + 4.8 × fL(RH) × [Large Sulfate] 

 + 2.4 × fS(RH) × [Small Nitrate] + 5.1 × fL(RH) × [Large Nitrate] 

 + 2.8 × [Small Organic Mass] + 6.1 × [Large Organic Mass] 

 + 10 × [Elemental Carbon] + 1 × [Fine Soil] + 0.6 × [Coarse Mass] 

 + 1.7 × fSS(RH) × [Sea Salt] + Rayleigh Scattering (Site Specific) 

 + 0.1755 × [NO2] Equation 6

where:

[ ] indicates concentrations in μg/m3

fS(RH) = Relative humidity adjustment factor for small sulfate and nitrate 

fL(RH) = Relative humidity adjustment factor for large sulfate and nitrate 

fSS(RH) = Relative humidity adjustment factor for sea salt 

 

32 U.S. Forest Service – Air Quality Program, National Park Service – Air Resources Division, U.S. Fish and 

Wildlife Service – Air Quality Branch, Phase I Report of the Federal Land Managers’ Air Quality Related Values

Workgroup (FLAG)--Revised, 2010.
Anadarko 28 Trinity Consultants

Monthly average fL(RH), fS(RH) and fSS(RH) values for Breton NWR and St. Marks are 

shown in Table 4-2 and Table 4-3, as obtained from Tables 7, 8, and 9 respectively of the 

FLAG Phase I report (revised 2010). 

TABLE 4-2. MONTHLY FS(RH), FL(RH) AND FSS(RH) FOR BRETON NWR

Month Average fs (RH) Average fL(RH) Average fss (RH)

January 4.08 2.91 4.10

February 3.82 2.76 3.89

March 3.79 2.74 3.87

April 3.74 2.72 3.85

May 3.94 2.83 4.02

June 4.12 2.94 4.21

July 4.41 3.10 4.44

August 4.37 3.07 4.38

September 4.18 2.97 4.23

October 3.92 2.82 3.99

November 3.93 2.83 4.01

December 4.06 2.90 4.11
Anadarko 29 Trinity Consultants

TABLE 4-3. MONTHLY FS(RH), FL(RH) AND FSS(RH) FOR ST. MARKS

Month Average fs (RH) Average fL(RH) Average fss (RH)

January 4.24 2.98 4.18

February 3.89 2.78 3.89

March 3.79 2.73 3.82

April 3.72 2.69 3.76

May 3.79 2.74 3.85

June 4.32 3.04 4.30

July 4.56 3.17 4.49

August 4.63 3.21 4.54

September 4.43 3.1 4.39

October 4.19 2.96 4.19

November 4.16 2.94 4.15

December 4.39 3.06 4.30

Additionally, the most recent values for the annual average background concentrations at 

Breton and St. Marks obtained from Table 6 of the FLAG Phase I report (revised 2010) 

are provided in Table 4-4.33 These values will be used to calculate background extinction.

TABLE 4-4. ANNUAL AVERAGE BACKGROUND VALUES FOR BRETON & ST. MARKS

Species

Breton

(g/m3)

St. Marks

(g/m3)

Ammonium Sulfate 0.23 0.23

Ammonium Nitrate 0.10 0.10

Organic Carbon Mass 1.78 1.80

Elemental Carbon 0.02 0.02

Soil 0.48 0.50

Coarse Mass 3.01 3.00

Sea Salt 0.19 0.10

Rayleigh Scattering 11 Mm-1 11 Mm-1

The methodology presented in Figure 5 of the FLAG Phase I report (revised 2010) will be 

used to calculate large and small nitrates, large and small sulfates, and large and small 

organic mass.

 

33 U.S. Forest Service – Air Quality Program, National Park Service – Air Resources Division, U.S. Fish and 

Wildlife Service – Air Quality Branch, Phase I Report of the Federal Land Managers’ Air Quality Related Values

Workgroup (FLAG)--Revised, 2010.
Anadarko 30 Trinity Consultants

The extinction coefficient attributable to emissions increases from the proposed project 

bext,project will also calculated. The extinction resulting from the project is calculated as 

shown in Equation 7 34:

bext, project = 2.2 × fS(RH) × [Small Sulfate] + 4.8 × fL(RH) × [Large Sulfate] 

+ 2.4 × fS(RH) × [Small Nitrate] + 5.1 × fL(RH) × [Large Nitrate] 

+ 2.8 × [Small Organic Mass] + 6.1 × [Large Organic Mass] + 1 × [Fine Soil] 

+ 0.6 × [Coarse Mass] + 0.1755 × [NO2] 

 Equation 7

where:

[ ] indicates concentrations in μg/m3

fS(RH) = Relative humidity adjustment factor for small sulfate and nitrate 

fL(RH) = Relative humidity adjustment factor for large sulfate and nitrate 

The 98th percentile Δbext percentage change results using “Method 8” will be calculated 

and presented in the modeling report.

4.2.3 OZONE

Ozone is a toxic air pollutant that is formed on warm, sunny days when its precursors NO 

and VOC react in the presence of sunlight. Because ozone is a regional pollutant, 

precursor sources both near and far from Class I areas can contribute to ozone formation. 

However, due to the complex photochemical reactions that are involved in the formation of 

ozone, it is difficult to quantify specific relationships between precursor emissions and 

ambient ozone concentrations at a Class I area, and also to quantify the specific 

relationship between ambient ozone at a Class I area and vegetation response. Therefore, 

FLAG has chosen to focus on the effects of ozone on vegetation and the levels of ozone 

generally known to be phytotoxic in Class I areas as indicators of concern regarding ozone 

impacts on AQRVs. Based on previous discussions with FS for similar EGOM projects 

Anadarko will address the impacts of ozone exposure as a result of the proposed drilling 

operations on vegetation at Bradwell Bay.35

Based on review of available dispersion models and discussion with FS, it has been found 

that there are currently no dispersion models available that can relate emissions from a 

single source to changes in ozone concentrations at particular receptor locations. However, 

as previously discussed with FS, since single source attribution modeling is possible for 

both visibility and deposition, Trinity proposes to demonstrate compliance with the 

 

34 Equation 7 has been obtained based on Equation 6 except that there will be no project extinctions due to EC and 

sea salt, since no elemental carbon or sea salt will be emitted from the proposed project, as described in Section 2 of the 

report. 

35 Based on Personal Communication, Phone conversation between Ms. Melanie Pitrolo (FS) to Mr. Rahul Pendse 

(Trinity) on October 18, 2012. 
Anadarko 31 Trinity Consultants

deposition thresholds at Bradwell Bay as a method of addressing impacts of ozone on the 

vegetation at Bradwell Bay.36

Demonstrating compliance with the deposition thresholds shall provide an indication of 

whether the proposed project operations NOX emissions are likely to cause an adverse 

impact on soils, and/or surface waters. If the results of deposition modeling are below the 

DATs, it shall demonstrate that the project’s NOX emissions do not cause any adverse 

impacts on soils and/or surface water, and since all FLM areas are assumed to be NOXlimited for formation of ozone, it can be deduced that there are no ozone impacts on the 

vegetation at Bradwell Bay.37 It should also be noted that if the PSD Class I area modeling 

analysis demonstrates that Class I area SILs are not exceeded for NO2, then that would 

provide additional demonstration that no significant impact on ozone levels at Bradwell 

Bay would occur.

If the results of the deposition modeling exceed DATs, then Trinity shall consult with FS 

to determine the procedures for conducting an analysis for assessing impacts of ozone 

exposure on the vegetation at Bradwell Bay. Consistent with the methodology used in the 

similar OCS applications submitted to EPA in the past, a monitoring station in Sumatra,

Florida will be assumed to be a representative monitoring station for obtaining the ambient 

ozone monitoring data for years 2001 through 2003 respectively. This data will be 

provided in the final modeling report.

 

36 Based on Personal Communication, Phone conversation between Ms. Melanie Pitrolo (FS) and Mr. Rahul 

Pendse (Trinity) on October 18, 2012. Per discussion with Ms. Melanie Pitrolo (FS) and Mr. Rahul Pendse (Trinity), 

visibility has not been established as an AQRV for Bradwell Bay.

37 Per Section 3.4.5 of Phase I Report of the Federal Land Managers’ Air Quality Related Values Workgroup 

(FLAG)--Revised, 2010.
Anadarko 32 Trinity Consultants

5. MODELING METHODOLOGY AND INPUTS

This section of the modeling report describes the modeling procedures and data resources utilized in 

the Class I and Class II Area air quality modeling analyses.

5.1 MODEL SELECTION

Dispersion models predict downwind pollutant concentrations by simulating the evolution of the 

pollutant plume over time and space given data inputs. These data inputs include the quantity of 

emissions and the initial conditions of the stack exhaust to the atmosphere. According to the 

Guideline, the extent to which a specific air quality model is suitable for the evaluation of source 

impacts depends on (1) the meteorological and topographical complexities of the area; (2) the level of 

detail and accuracy needed in the analysis; (3) the technical competence of those undertaking such 

simulation modeling; (4) the resources available; and (5) the accuracy of the database (i.e., emissions 

inventory, meteorological, and air quality data). 

The preferred model for analyzing long-range pollutant transport (i.e., distances greater than 50 km) 

is the CALPUFF modeling system. The EPA-approved version (Version 5.8) of the CALPUFF 

model will be used to determine the possible impacts of the proposed project. The post-processing of 

the CALPUFF data will be performed using the recently EPA-approved version (Version 6.221) of 

the CALPOST. 38

CALPUFF is a multi-layer, multi-species, non-steady-state Lagrangian puff model, which can 

simulate the effects of time- and space-varying meteorological conditions on pollutant transport, 

transformation, and removal. For this refined analysis, meteorological fields generated by CALMET 

will be used as inputs to the CALPUFF model to ensure that the effects of terrain and spatially 

varying surface characteristics on meteorology are considered.

In addition to meteorological data, the CALPUFF model uses several other input files to specify 

source and receptor parameters. The selection and control of CALPUFF options are determined by 

user-specific inputs contained in the control file. This file contains all of the necessary information to 

define a model run (e.g., starting date, run length, grid specifications, technical options, output 

options). The air quality modeling will be performed using CALPUFF default options unless 

otherwise noted, as specified in the federal Guideline, the applicable guidance memorandum from 

Support Center for Atmospheric Modeling (SCRAM) website, FLAG Phase I Report - revised

(October 2010), and IWAQM documents. The EPA approved default options do not include the 

deposition and chemistry components of the CALPUFF model; hence, these options will not be used 

while estimating concentrations for comparison against the EPA established significance thresholds. 

The following sections describe the modeling domain, meteorological data, background 

concentrations, and model implementation to be used for the analysis of the proposed Anadarko

drilling operations.

 

38 http://www.epa.gov/ttn/scram/dispersion_prefrec.htm#calpuff.
Anadarko 33 Trinity Consultants

5.2 MODEL DOMAINS

The Class I and Class II modeling analysis will be performed in the Lambert Conformal Conic (LCC) 

coordinate system based on the design of the VISTAS Regional Haze Rule (RHR) modeling, with 

standard parallels of 33o N and 45o N latitude, and reference latitude and longitude of 40o N and 97o 

W respectively.

39

 VISTAS RHR Model Domain 2 will be utilized as the CALMET meteorological 

domain.40 The different VISTAS RHR Model Domains are shown below in Figure 5-1. 

FIGURE 5-1. VISTAS RHR MODEL DOMAINS

The CALPUFF computational domain will be chosen as a subset of the CALMET meteorological 

domain such that it encompasses both the OCS source and all receptors in the Class I and Class II

areas, with ample area beyond all receptors (50 km) to allow for the possible recirculation of puffs. 

The grid resolution for the domain will be 4 km.

 

39

VISTAS, Protocol for the Application of the CALPUFF Model for Analyses of Best Available Retrofit 

Technology (BART), December 22, 2005, revised August 31, 2006.

40 Phone conversation between Ms. Jill Webster (FLM, Breton NWR) and Mr. Rahul Pendse (Trinity) on 

October 12, 2012; and Email from Ms. Jill Webster (FWS) and Mr. Dhesikan Venkatesan (Trinity) sent on October 10, 

2012.
Anadarko 34 Trinity Consultants

TABLE 5-1. VERTICAL GRID STRUCTURE

Vertical Grid Cell

Cell Face Height

(meters)

1 20

2 40

3 80

4 160

5 320

6 640

7 1,200

8 2,000

9 3,000

10 4,000

Vertical grid structure is defined by the cell face height. The cell face height of each cell indicates its 

vertical extent. The vertical domain will be composed of terrain-following grid cells, the number and 

size of which are chosen so as to constrain the boundary layer in which dispersion and chemical 

transformations take place. Based on information available in the VISTAS RHR Modeling Protocol, 

and the IWAQM guidance document, the vertical grid structure selected for this analysis is presented 

above in Table 5-1.

41

 CALMET and CALPUFF will use the same cell face heights.

5.3 REPRESENTATION OF MODELED SOURCES

Anadarko proposes to model the PM2.5, PM10, CO, and NO2 emissions from the proposed OCS source 

assuming that all emissions would be emitted through a single stack which would be representative of 

the expected impacts. The stack will be modeled with worst-case coordinates, with the drillship 

assumed to be located at the closest point in the lease block within the “wedge” to the nearest Class I

and Class II area. For Breton, the worst-case location shall be the NW corner of the worst-case lease 

block. For St. Marks and Bradwell Bay, the NE corner of the worst-case lease blocks shall be 

considered as the worst-case location. 

For purposes of the Class I and Class II modeling analysis, all emissions from the drillship will be 

modeled as a single point source with the emissions emitted through a single stack. The worst-case 

support vessels emissions will be modeled as one point source. The point source representing the 

support vessels will be placed on the straight line connecting the drillship location and the nearest 

receptor location at 25 nautical miles from the drillship location. 

 

41 VISTAS, Protocol for the Application of the CALPUFF Model for Analyses of Best Available Retrofit 

Technology (BART), December 22, 2005, revised August 31, 2006, and the U.S. EPA, IWAQM Phase 2 Summary Report 

and Recommendations for Modeling Long-Range Transport Impacts, Research Triangle Park, North Carolina, EPA-454/R95-006, December 1998.
Anadarko 35 Trinity Consultants

Additionally, the stack parameters for the stack representing drillship emissions will be based on the 

stacks associated with the main engines on the drillship, which are the largest sources of PM2.5, PM10, 

CO, SO2, and NO2 emissions. Similarly, the stack parameters for the stack representing the support 

vessels emissions will be based on the stack parameters for the highest emitting engines. The stack 

height will represent the height above the sea level (water line) to the main engine stack. A summary 

of the modeling parameters, source parameters and emission rates used in the modeling analysis shall 

be provided with the final modeling report. 

5.4 RECEPTOR LOCATIONS FOR CLASS I AREAS

The National Park Service (NPS) Air Resources Division (ARD) has developed a database of 

modeling receptors for all of the Class I areas in the United States.42 The database provides the 

location (lat/long, dd) coordinates and elevation information for receptors for each Class I area. 

Receptor locations obtained from the database for each Class I area shall be were converted to the 

LCC coordinate system using appropriate conversion factors and will be used in these Class I 

analyses.

5.5 RECEPTOR LOCATIONS FOR CLASS II AREAS

The seaward boundaries and Air Quality Control Regions for Louisiana, Mississippi and Alabama 

extend for three nautical miles offshore and for nine nautical miles offshore Florida. For Anadarko’s

Class II modeling analysis, discrete receptors were located 25 nautical miles from the seaward 

boundaries of Louisiana, Mississippi, Alabama and Florida. The receptors were placed at 1-km 

intervals as per Guidance received from EPA region 4. The actual sets of receptors used in Class II 

analysis were provided by EPA Region 4.

43

 Because all of these receptors are over water, terrain 

elevations were assigned an elevation of 0 m (i.e., sea level) for Class II impact analysis. If the 

NAAQS and PSD Increment analyses is required, an addendum to this protocol will be submitted to 

the EPA Region 4 for approval. 

5.6 EMISSIONS SPECIATION

Modeling of visibility impairment due to PM emissions requires that the components of the exhaust 

stream be speciated because different size and phases of particulate matter affect visibility to varying 

extents. The amount by which a mass of a certain species scatters or absorbs light is termed the 

extinction efficiency or coefficient, and varies considerably from coarse particulate matter to 

elemental carbon. 

Anadarko proposes to estimate speciated PM emissions associated with the proposed project based on 

AP-42 emission factors and conservative engineering estimates. Emission sources used for the 

proposed drilling project will primarily comprise of large diesel fired engines. Although the drillship 

will also have a few small diesel-fired engines, the large diesel-fired engines will contribute the 

majority of the emissions from the proposed drilling operations. Therefore, Anadarko proposes the 

use of particle size-specific emission factors for large diesel fired engines from AP-42, Table 3.4-2, 

 

42 http://www.nature.nps.gov/air/maps/receptors/index.cfm

43 Based on Personal Communication, E-mail from Mr. Stan Krivo (EPA Region 4) and Mr. Rahul Pendse 

(Trinity) on October 1, 2012.
Anadarko 36 Trinity Consultants

Particulate and Particle-sizing Emission Factors for Large Uncontrolled Stationary Diesel Engines

(October 1996) to determine PM speciation for emissions from the drillship.

5.7 TERRAIN PROCESSING FOR CLASS II ANALYSIS

As the proposed OCS source is located in the GOM and corresponding Class II receptors will be 

placed 25 miles away from respective state seaward boundary, the entire modeling domain will be 

located completely over water in the Gulf of Mexico. Therefore, all modeled sources and Class II 

receptors are assumed to be situated at sea level and the elevations for off-property sources and 

receptors will be set to zero for the Class II modeling analysis. 

5.8 BUILDING DOWNWASH

Building downwash accounts for the effects of nearby structures on the flow of emissions from their 

respective release structures. However, building downwash effects were not included in the modeling 

as they will not significantly affect concentrations when the nearest receptors are located more than 

50 km from the worst-case drillship location. Hence, due to the relatively large distance of the 

proposed drillship from the Class I and Class II area, building downwash will not be enabled. 44 

5.9 BACKGROUND CONCENTRATIONS

As described in the Section 3-1.3, a background concentration of PM2.5 will be required for assessing 

validity of use of PM2.5 SIL. Since there are no monitors at the Inner OCS and Outer OCS boundary 

(i.e., 25 nautical miles from the nearest state seaward boundary), a representative onshore background 

concentration will be used per discussions with EPA Region 4.45

5.10 CALMET (METEOROLOGICAL DATA) PROCESSING

CALMET is the meteorological preprocessor that compiles meteorological data from raw 

observations of surface and upper air conditions, precipitation measurements, mesoscale model 

output, and geophysical parameters into a single hourly, gridded data set for input to CALPUFF. 

Based on the previous guidance received from the FLM and EPA Region 4, three years of mesoscale 

meteorological (MM) data in the form of CALPUFF-ready meteorological files developed by the 

VISTAS for the period 2001-2003 (for VISTAS Domain 2) obtained from the Florida Department of 

Environmental Protection (DEP) will be used in this analysis.46 No additional meteorological data 

processing is expected for this analysis. In lieu of recent discussions with EPA Region 4 instead of 

the five year meteorological data, the three year meteorological dataset (2001-2003) developed by the 

VISTAS will be used for the PSD Class II impact assessments.

 

44 Per guidance provided on Pg. 45 of the VISTAS, Protocol for the Application of the CALPUFF Model for 

Analyses of Best Available Retrofit Technology (BART), December 22, 2005, revised August 31, 2006.

45 Based on Personal Communication: Phone conversation among Mr. Stan Krivo (EPA Region 4), Ms. Sara 

Carlson (Anadarko), and Mr. Rahul Pendse (Trinity) on July 9, 2013.

46 Based on Personal Communication; Phone conversation between Ms. Jill Webster (FLM, Breton NWR) and Mr. 

Rahul Pendse (Trinity) on October 12, 2012, and Phone conversation between Mr. Stan Krivo (EPA Region 4) and Mr. 

Rahul Pendse (Trinity) on October 10, 2012; and Email from Ms. Jill Webster (FWS) and Mr. Dhesikan Venkatesan 

(Trinity) sent on October 10, 2012. The meteorological data was obtained from Mr. Tom Rogers, Florida DEP, based on 

instructions from EPA Region 4. 
Anadarko 37 Trinity Consultants

5.11 CALPUFF PROCESSING

Using the data provided by CALMET, CALPUFF simulates the dispersion, deposition, and chemical 

transformation of discrete puffs of mass from emission sources. Each puff contains emissions of 

NOX, SO2, CO, PM2.5, and PM10 and is transported throughout the domain while deposition and 

chemical transformation processes take place. CALPUFF is a Lagrangian puff model, the principle 

advantages of which are that pollutant plumes can evolve dynamically and chemically over time and 

can respond to complex winds caused by terrain effects, stagnation, or recirculation. 

Emissions data and stack parameters will be entered into CALPUFF as previously described under 

Section 5.3 of this protocol. Due to the relatively large distance of the proposed drillship from the 

Class I and Class II area, building downwash will not be enabled. 47 

This analysis will be performed with the deposition and chemical transformation algorithms enabled 

for Class I AQRV analysis and disabled for the PSD Class I and Class II modeling analysis. A full 

resistance model is provided in CALPUFF for the computation of dry deposition rates of gases and 

particulate matter as a function of geophysical parameters, meteorological conditions, and pollutant 

species. An empirical scavenging coefficient approach using default options will be enabled in 

CALPUFF to compute the depletion and wet deposition fluxes due to precipitation scavenging.

The CALPUFF model is capable of simulating linear chemical transformation effects by using 

pseudo-first-order chemical reaction mechanisms for the conversions of SO2 to SO4, and NOX, which 

consists of nitrogen oxide (NO) and nitrogen dioxide (NO2), to NO3 and HNO3. In this study, 

chemical transformations involving five species (SO2, SO4, NOX, HNO3, and NO3) will be modeled 

using the MESOPUFF II chemical transformation scheme, per IWAQM guidance.48 There are two 

user-selected input parameters that affect the MESOPUFF II chemical transformation, ammonia 

concentrations and ozone concentrations. The selection of each parameter is discussed separately.

5.11.1 OZONE

Ambient ozone concentrations can be input to the model as a background level or using 

hourly, spatially varying observations. For this analysis, Anadarko proposes the use of 

data from the monitor at Sumatra, Florida (code - SUM 156). The proposed monitoring 

station is one of the closest monitoring stations from the modeling domain. Also, this 

station has all required meteorological data available. Information on the monitoring 

station can be obtained from the CASTNET website.49 Based on previous guidance 

received from FLM and EPA region 4, the ozone background level for the analysis will be 

set at 80 ppb.

 

47 Per guidance provided on Pg. 45 of the VISTAS, Protocol for the Application of the CALPUFF Model for 

Analyses of Best Available Retrofit Technology (BART), December 22, 2005, revised August 31, 2006.

48 U.S. EPA, IWAQM Phase 2 Summary Report and Recommendations for Modeling Long-Range Transport 

Impacts, Research Triangle Park, North Carolina, EPA-454/R-95-006, December 1998.

49 Information on the site monitor is available at www.epa.gov/castnet/sites/sum156.html. Information on ozone 

data available at EPA’s CASNET website – www.epa.gov/casnet/data.html
Anadarko 38 Trinity Consultants

5.11.2 AMMONIA

IWAQM Phase 2 recommends the use of spatially constant background ammonia 

concentrations to participate in the MESOPUFF-II chemical transformation mechanism.50 

In the absence of an extensive monitoring network for ammonia and due to the limitation 

of CALPUFF to simulate only a single, domain-average background ammonia level for 

each month of analysis, a single value will be used. The IWAQM guidance recommends 

the ammonia value be set between 0.5 parts per billion (ppb) for forested areas and 10 ppb 

for grasslands. Based on previous guidance received from FWS, the ammonia background 

level for the analysis will be set at 3 ppb.51

5.11.3 CALPUFF PROCESSING CONTROL

CALPUFF modeling will be conducted generally using the recommended regulatory 

default options specified in Appendix B of the IWAQM guidance. The integrated puff 

representation will be used and puff splitting will be conservatively disabled.

5.12 CALPOST POSTPROCESSING ANALYSIS

The CALPOST postprocessor will be used to compute the ambient concentrations of CO, PM2.5, 

PM10, SO2, and NO2 at Class I and Class II areas for assessment against the PSD Class I Increment 

modeling significance levels and PSD Class II modeling levels, the total deposition of sulfur and 

nitrogen within each Class I area for assessment against the DAT, and the 98th percentile of modeled 

visibility values 24-hour average change in light extinction using Methods 8.

For PM10 assessment against the PSD Class I and Class II significance levels, POSTUTIL will first be 

used to combine the speciated PM (PMC, PMF, and SOA) to calculate total PM10 concentration. The 

PM10 concentration will then be processed using CALPOST and compared to the appropriate Class I

and Class II SILs. Similar methodology will be utilize for PM2.5 post processing. The secondary 

PM2.5 impacts will be addressed qualitatively.

For estimating the extent of nitrogen and sulfur deposition, POSTUTIL will first be used to combine 

the appropriate wet and dry fluxes of nitrogen- and sulfur-bearing species deposited as particles and 

gases. These combined fluxes will then be processed using CALPOST to obtain the nitrogen and 

sulfur deposition values. 

To determine the extent of change in light extinction from the proposed project, the Ammonia 

Limiting Method (ALM) will first be used to repartition the nitrate mass and recompute HNO3 and 

NO3 concentrations. This methodology estimates the amount of ammonia available for the formation 

of ammonium nitrates after the preferential consumption of ammonia from the formation of 

ammonium sulfates. The ALM will be applied based on guidance provided in the VISTAS BART 

 

50 U.S. EPA, IWAQM Phase 2 Summary Report and Recommendations for Modeling Long-Range Transport 

Impacts, Research Triangle Park, North Carolina, EPA-454/R-95-006, December 1998.

51 Based on Personal Communication; Phone conversation between Ms. Jill Webster (FWS) and Mr. Rahul Pendse 

(Trinity) on October 12, 2012; and E-mail from Ms. Jill Webster (FWS) to Mr. Dhesikan Venkatesan (Trinity) sent on 

October 10, 2012. 
Anadarko 39 Trinity Consultants

Modeling Protocol.

52

 Visibility change will then be computed using “Method 8”, and results will be 

reported for the 98th percentile for “Method 8”, for each of the three years of meteorological data 

modeled.

 

52 VISTAS; Protocol for the Application of the CALPUFF Model for Analyses of Best Available Retrofit

Technologies (BART). December 22, 2005. 

http://www.vistas-sesarm.org/documents/BARTModelingProtocol_rev3.2_31Aug06.pdf , accessed on March 24, 2010. 
Anadarko 40 Trinity Consultants

6. MODELING REPORT CONTENTS

A document that details the modeling methodology and summarizes the modeling results will be 

submitted to the FLM, as well as U.S. EPA Region 4. The air dispersion modeling report will include 

the following information:

 Brief overview of the proposed project;

 An area map indicating location of the source, receptors, model domain,and true north;

 Emissions rate summary for all proposed emission sources, with units consistent with 

modeling;

 Stack parameter summary for all proposed emission sources, with units consistent with 

modeling;

 Any calculations for stack parameters unless previously approved by U.S. EPA Region 4;

 Approved modeling protocol;

 Technical basis for any nonstandard procedures;

 Summary of all model inputs (e.g., model used, met data, rural or urban dispersion 

coefficients, etc.);

 Comparison of all modeling results to the applicable standards; and

 Electronic copies of all modeling files, including model input files, output files, met data with 

appropriate documentation if processing performed.

If required, Anadarko will submit additional information to U.S. EPA Region 4 and FLM upon 

request.