DRAFT AIR QUALITY TECHNICAL 

SUPPORT DOCUMENT FOR THE 

JONAH INFILL DRILLING PROJECT 

ENVIRONMENTAL IMPACT STATEMENT 

Prepared for 

Bureau of Land Management

Wyoming State Office

Cheyenne, Wyoming 

Pinedale Field Office 

Pinedale, Wyoming 

and 

Jonah Infill Drilling Project Operators 

Prepared by 

TRC Environmental Corporation

Laramie, Wyoming 

November 2004 
DRAFT 

AIR QUALITY TECHNICAL SUPPORT DOCUMENT FOR

THE JONAH INFILL DRILLING PROJECT

ENVIRONMENTAL IMPACT STATEMENTS

Prepared for 

Bureau of Land Management

Wyoming State Office

Cheyenne, Wyoming

and 

Pinedale Field Office

Pinedale, Wyoming

and 

Jonah Infill Drilling Project Operators 

By 

TRC Environmental Corporation

Laramie, Wyoming

MAI Project 35982

November 2004
Air Quality Technical Support Document, Jonah Infill Drilling Project i 

EXECUTIVE SUMMARY


To be completed upon receipt of agency comments. 

35982 TRC Environmental Corporation 
ii Air Quality Technical Support Document, Jonah Infill Drilling Project 

35982 TRC Environmental Corporation 
Air Quality Technical Support Document, Jonah Infill Drilling Project iii 

TABLE OF CONTENTS


Page 

LIST OF ACRONYMS AND ABBREVIATIONS...................................................................... vii


1.0 INTRODUCTION.................................................................................................................. 1


1.1 PROJECT DESCRIPTION........................................................................................ 4


1.2 ALTERNATIVES EVALUATED............................................................................. 5


1.3 STUDY TASKS......................................................................................................... 7


2.0 EMISSIONS INVENTORY .................................................................................................. 9


2.1 PROJECT EMISSIONS............................................................................................. 9


2.1.1 Construction Emissions .............................................................................. 9


2.1.2 Production Emissions ................................................................................. 11


2.1.3 Total Field Emissions ................................................................................. 14


2.2 REGIONAL EMISSIONS INVENTORY ................................................................. 14


3.0 NEAR-FIELD MODELING ANALYSES ............................................................................ 25


3.1 MODELING METHODOLOGY .............................................................................. 25


3.2 METEOROLOGY DATA ......................................................................................... 25


3.3 BACKGROUND POLLUTANT CONCENTRATIONS.......................................... 27


3.4 CRITERIA POLLUTANT IMPACT ASSESSMENT .............................................. 28


3.4.1 PM10/PM2.5.................................................................................................. 29


3.4.2 SO2 .............................................................................................................. 32


3.4.3 NO2 ............................................................................................................. 32


3.4.4 CO............................................................................................................... 37


3.4.4 O3 ................................................................................................................ 38


3.5 HAP IMPACT ASSESSMENT................................................................................. 40


4.0 MID-FIELD AND FAR-FIELD ANALYSES....................................................................... 47


4.1 MODELING METHODOLOGY .............................................................................. 48


4.2 PROJECT ALTERNATIVE MODELING SCENARIOS......................................... 49


4.3 METEOROLOGICAL MODEL INPUT AND OPTIONS........................................ 51


4.4 DISPERSION MODEL INPUT AND OPTIONS ..................................................... 55


4.4.1 Chemical Species......................................................................................... 55


4.4.2 Model Receptors ......................................................................................... 56


4.4.3 Source Parameters....................................................................................... 56


4.5 BACKGROUND DATA ........................................................................................... 61


4.5.1 Criteria Pollutants ....................................................................................... 61


4.5.2 Visibility ..................................................................................................... 61


4.5.3 Lake Chemistry ........................................................................................... 65


4.6 IMPACT ASSESSMENT.......................................................................................... 65


4.6.1 Concentration.............................................................................................. 66


4.6.2 Deposition................................................................................................... 70


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iv Air Quality Technical Support Document, Jonah Infill Drilling Project 

TABLE OF CONTENTS (CONTINUED) 

Page 

4.6.3 Sensitive Lakes ........................................................................................... 71


4.6.4 Visibility ..................................................................................................... 71


5.0 REFERENCES ...................................................................................................................... 79 

APPENDIX A: AIR QUALITY ASSESSMENT PROTOCOL 

APPENDIX B: PROJECT EMISSIONS INVENTORIES 

APPENDIX C: CUMULATIVE EMISSIONS INVENTORIES 

APPENDIX D: REGIONAL COMPRESSION EXISTING AND PROPOSED 

APPENDIX E: CALMET INPUT DATA 

APPENDIX F: MAXIMUM PREDICTED MID-FIELD AND FAR-FIELD IMPACTS 

LIST OF MAPS 

Page 

Map 1.1 Jonah Infill Drilling Project Location, Sublette County, Wyoming ..................... 2 

Map 1.2 Air Quality Study Area/Modeling Domain........................................................... 3 

Map 2.1 Regional Inventory Area and Included NEPA Project Areas ............................... 23 

LIST OF TABLES 

Page 

Table 2.1	 Single-well Construction Emissions Summary for Both Straight and 

Directionally Drilled Wells................................................................................... 12 

Table 2.2	 Single-Well Production Emissions Summary....................................................... 13


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Air Quality Technical Support Document, Jonah Infill Drilling Project v 

LIST OF TABLES (CONTINUED) 

Page 

Table 2.3 Estimated Jonah Infill Drilling Project Maximum Annual In-field 

Emissions Summary - Construction and Production ............................................ 15


Table 2.4 Regional Inventory Summary of Emissions Changes from


January 1, 2001, to June 30, 2003......................................................................... 24


Table 3.1 Near-Field Analysis Background Ambient Air Quality Concentrations


(Micrograms per Cubic Meter [μg/m3])................................................................ 27


Table 3.2 Ambient Air Quality Standards and Class II PSD Increments for


Comparison to Near-Field Analysis Results (μg/m3

) ........................................... 28


Table 3.3 Maximum Modeled PM10/PM2.5 Concentrations, Jonah Infill Drilling


Project ................................................................................................................... 31


Table 3.4 Maximum Modeled SO2 Concentrations, Jonah Infill Drilling Project................ 34


Table 3.5 Maximum Modeled Annual NO2 Concentrations, Jonah Infill Drilling


Project ................................................................................................................... 37


Table 3.6 Maximum Modeled CO Concentrations, Jonah Infill Drilling Project................. 38


Table 3.7 Maximum Modeled O3 Concentrations, Jonah Infill Drilling Project .................. 40


Table 3.8 Maximum Modeled 1-Hour HAP Concentrations, Jonah Infill Drilling


Project ................................................................................................................... 43


Table 3.9 Maximum Modeled Long-term (Annual) HAP Concentrations, Jonah Infill


Drilling Project...................................................................................................... 44


Table 3.10 Long-term Modeled MLE and MEI Cancer Risk Analyses, Jonah Infill


Drilling Project...................................................................................................... 46


Table 4.1 Summary of Modeled Project Alternatives, Jonah Infill Drilling Project,


Sublette County, Wyoming, 2004......................................................................... 50


Table 4.2 Summary of Maximum Modeled Field-Wide Emissions (tpy), Jonah Infill


Drilling Project, Sublette County, Wyoming, 2004.............................................. 52


Table 4.3 Far-field Analysis Background of Ambient Air Quality Concentrations


(μg/m3).................................................................................................................. 64


Table 4.4 IMPROVE Background Aerosol Extinction Values............................................. 64


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vi Air Quality Technical Support Document, Jonah Infill Drilling Project 

LIST OF TABLES (CONTINUED) 

Page 

Table 4.5 Background ANC Values for Acid Sensitive Lakes ............................................. 65


Table 4.6 Modeling Scenarios Analyzed for Project Alternative and Regional


Emissions, Jonah Infill Drilling Project, Sublette County, Wyoming, 2004 ........ 67


Table 4.7 NAAQS, WAAQS, PSD Class I and Class II Increments, and PSD Class I


and Class II Significance Levels for Comparison to Far-field Analysis 

Results (μg/m3) ..................................................................................................... 68


Table 4.8 FLAG Report Background Extinction Values ...................................................... 73


Table 4.9 Monthly f(RH) Factors Factors from Regional Haze Rule Guidance................... 74


LIST OF FIGURES 

Page 

Figure 2.1 Approximate Single-Well Development Timeline ............................................... 10


Figure 3.1 Wind Rose, Jonah Field, 1999 .............................................................................. 26


Figure 3.2 Near-field Modeling PM10/PM2.5 Source and Receptor Layout ........................... 30


Figure 3.3 Near-field Modeling SO2 Source and Receptor Layout........................................ 33


Figure 3.4 Near-field Modeling NOx, CO, and HAPs Source and Receptor Layout ............. 35


Figure 3.5 Short-term HAPs Source and Receptor Layout .................................................... 41


Figure 4.1 Mid-field Modeling Receptor Locations............................................................... 57


Figure 4.2 Far-field Modeling Receptor Locations................................................................ 58


Figure 4.3 Far-field Modeling Area Compressor Locations .................................................. 59


Figure 4.4 Far-field Modeling Project-Specific Point and Area Source Locations................ 60


Figure 4.5 Far-field Modeling Idealization of NEPA Project Areas...................................... 62


Figure 4.6 Far-field Modeling Idealization of County Oil and Gas Well Area Sources ........ 63


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Air Quality Technical Support Document, Jonah Infill Drilling Project vii 

LIST OF ACRONYMS AND ABBREVIATIONS 

μeq/l Microequivalents per liter 

μg/m3 Micrograms per cubic meter 

ANC Acid neutralizing capacity 

AQD Air Quality Division 

AQRV Air Quality Related Value 

AQTSD Air Quality Technical Support Document 

ARS Air Resource Specialists 

BACT Best available control technology 

BLM Bureau of Land Management 

BP BP America Production Company 

BTEX Benzene, toluene, ethylbenzene, and xylene 

BTNF-MA Bridger-Teton National Forest Management Area 

C.F.R. Code of Federal Regulations 

CDPHE/APCD Colorado Department of Public Health and Environment/Air Pollution 

Control Division 

CD/WII Continental Divide/Wamsutter II 

CO Carbon monoxide 

COGCC Colorado Oil and Gas Conservation Commission 

DAT Deposition analysis thresholds 

DEM Digitized elevation map 

dv Deciview 

EIS Environmental impact statement 

EnCana EnCana Oil & Gas (USA) Inc. 

EPA Environmental Protection Agency 

FLAG Federal Land Managers' Air Quality Related Values Workgroup 

FLM Federal Land Managers 

f(RH) Relative humidity factor 

GRI Gas Research Institute 

HAP Hazardous air pollutant 

HNO3 Nitric acid 

hp Horsepower 

hp-hr Horsepower-hour 

IDEQ Idaho Division of Environment Quality 

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viii Air Quality Technical Support Document, Jonah Infill Drilling Project 

IDLH Immediately dangerous to life or health 

IOGCC Idaho Oil and Gas Conservation Commission 

IWAQM Interagency Workgroup on Air Quality Modeling 

JIDPA Jonah Infill Drilling Project Area 

kg/ha-yr Kilograms per hectare per year 

LAC Level of Acceptable Change 

LOP Life of Project 

LULC Land use and land cover 

MEI Maximum exposed individual 

MLE Most likely exposure 

MM5 Mesoscale meteorological model 

N Nitrogen 

NAAQS National Ambient Air Quality Standards 

NEPA National Environmental Policy Act 

NH3 Ammonia 

NIOSH National Institute for Occupational Safety and Health 

NO2 Nitrogen dioxide 

NO3 Nitrate 

NOI Notice of Installation 

NOx Nitrogen oxides 

NPS National Park Service 

NSR New Source Review 

NWS National Weather Service 

O3 Ozone 

Operators EnCana Oil and Gas (USA) Inc., BP America Production Company, and 

other oil and gas companies 

PAPA Pinedale Anticline Project Area 

P-BACT Presumptive BACT 

PFO Pinedale Field Office 

PM10 Particulate matter less than or equal to 10 microns in size 

PM2.5 Particulate matter less than or equal to 2.5 microns in size 

ppb Parts per billion 

ppm Parts per million 

Project Jonah Infill Drilling Project 

Protocol Air Quality Impact Assessment Protocol 

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Air Quality Technical Support Document, Jonah Infill Drilling Project ix 

LIST OF ACRONYMS AND ABBREVIATIONS (CONTINUED)


PSD Prevention of Significant Deterioration 

QA/QC Quality Assurance/Quality Control 

REL Reference exposure level 

RfC Reference Concentrations for Chronic Inhalation 

RFD Reasonably foreseeable development 

RFFA Reasonably foreseeable future action 

RMP Resource Management Plan 

ROD Record of Decision 

RT Round trip 

S Sulfur 

SO2 Sulfur dioxide 

SO4 Sulfate 

SWWYTAF Southwest Wyoming Technical Air Forum 

tpy Tons per year 

TRC TRC Environmental Corporation 

TSP Total suspended particulates 

UDEQ-AQD Utah Department of Environmental Quality-Air Quality Division 

UDNR-DOGM Utah Department of Natural Resources-Division of Oil, Gas, and Mining 

URF Unit risk factor 

USDA U.S. Department of Agriculture 

USGS U.S. Geological Survey 

VOC Volatile organic compound 

VMT Vehicle miles traveled 

WAAQS Wyoming Ambient Air Quality Standards 

WAQSR Wyoming Air Quality Standards and Regulations 

WDEQ Wyoming Department of Environmental Quality 

WDR Well development rate 

WOGCC Wyoming Oil and Gas Conservation Commission 

WRAP Western Regional Air Partnership 

WYDOT Wyoming Department of Transportation 

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Air Quality Technical Support Document, Jonah Infill Drilling Project 

1.0 INTRODUCTION


This Air Quality Technical Support Document (AQTSD) was prepared to summarize analyses 

performed to quantify potential air quality impacts from the proposed Jonah Infill Drilling 

Project (Project). The methodologies utilized in the analysis were originally defined in an air 

quality impact assessment protocol (Protocol) prepared by TRC Environmental Corporation 

(TRC) (2003) with input from the lead agency, U.S. Department of Interior Bureau of Land 

Management (BLM), and project stakeholders including the U.S. Environmental Protection 

Agency (EPA), National Park Service (NPS), U.S. Department of Agriculture Forest Service 

(USDA Forest Service), and Wyoming Department of Environmental Quality Air Quality 

Division (WDEQ-AQD). The AQTSD discusses those methodologies as necessary and 

summarizes the findings of the air emissions inventories and subsequent dispersion modeling 

analyses. 

The Project's location in west-central Wyoming required the examination of Project and 

cumulative source impacts in Wyoming, northwestern Colorado, northeastern Utah, and 

southeastern Idaho within a defined study area (modeling domain) (Maps 1.1 and 1.2). The 

analysis area includes the area surrounding the proposed Project area (JIDPA) and all or a portion 

of the Bridger, Fitzpatrick, Popo Agie, Teton, and Washakie Wilderness Areas; the Wind River 

Roadless Area; and Grand Teton and Yellowstone National Parks. 

Impacts analyzed include those on air quality and air quality related values (AQRVs) resulting 

from air emissions from: 1) project sources within the JIDPA, 2) non-project state-permitted and 

reasonably foreseeable future action (RFFA) sources within the modeling domain, and 

3) non-project reasonably foreseeable development (RFD) within the modeling domain. The 

Project source emissions inventory was performed in accordance with the Protocol and following 

WDEQ-AQD oil and gas inventory guidance (WDEQ-AQD 2001). Portions of the inventory 

were submitted to WDEQ-AQD for review prior to inventory finalization. Non-project sources 

were inventoried as part of a cooperative effort between the BLM Wyoming State Office, the 

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4 Air Quality Technical Support Document, Jonah Infill Drilling Project 

Project proponents, and the Atlantic Rim Natural Gas Development Project proponents. These 

data were obtained for use in the Rawlins and Pinedale Resource Management Plan (RMP) 

revisions, the Project environmental impact statement (EIS) air quality analysis, and the Atlantic 

Rim Natural Gas Development Project EIS air quality analysis. Chapter 2.0 specifically presents 

an overview of the emissions inventories. 

The remainder of this AQTSD describes the Project in further detail, provides a description of 

the alternatives proposed and evaluated, and presents a list of tasks performed for the study. 

Descriptions of the near-field air quality impact assessment methodology and impacts are 

provided in Chapter 3.0, and Chapter 4.0 describes the CALPUFF analyses performed for 

assessment of in-field cumulative, mid-field cumulative, and far-field Project direct and 

cumulative impacts. 

1.1 PROJECT DESCRIPTION 

EnCana Oil & Gas (USA) Inc. (EnCana), BP America Production Company (BP), and other oil 

and gas companies (collectively referred to as the Operators) have notified the BLM, Pinedale 

Field Office (PFO), that they propose to continue development of natural gas resources located 

within the JIDPA (see Map 1.1). The JIDPA is generally located in Townships 28 and 29 North, 

Ranges 107 through 109 West, Sublette County, Wyoming. The JIDPA encompasses 

approximately 30,500 acres, of which 28,580 acres are federal surface/federal mineral estate, 

1,280 acres are State of Wyoming surface/mineral estate, and 640 acres are private 

surface/federal mineral estate. 

The Operator Proposed Action for this Project involves the development of up to 3,100 new 

natural gas wells on up to 16,200 acres of new surface disturbance. However, additional 

alternatives involving alternate well pad densities, alternate well numbers, and variable 

mitigations are also analyzed. The maximum number of wells would be 3,100, assuming an 

approximately 5- to 10-acre down-hole well spacing throughout the JIDPA. Depending upon the 

authorized rate of development (75, 150, or 250 wells per year), development operations are 

35982 TRC Environmental Corporation 
Air Quality Technical Support Document, Jonah Infill Drilling Project 5 

expected to last from approximately 5 to 42 years, with a total life-of-field (LOF) of 

approximately 43 to 85 years. The JIDPA is currently accessed by existing developed roads. 

Approximately 63-87 days would be required to develop each well (four days to construct the 

well pad and access road, from one to four days for rig-up, generally from 18 to 36 days for 

drilling [an average of 23 days is used in this air quality analysis], 35 days over a 60-day period 

for completion and testing, from one to four days for rig-down, and four days for pipeline 

construction). The estimated size of each single-well drill pad is 3.8 acres, of which 

approximately 2.9 acres would be reclaimed after the well is completed and the gas gathering 

pipeline is installed. A reserve pit would be constructed at each drill site location to hold drilling 

fluids and cuttings. Non-productive and non-economical wells would be reclaimed as soon as 

practical to appropriate federal, state, or private landowner specifications. 

The gas produced within the JIDPA would be transported by existing pipelines from the field. 

To facilitate a complete cumulative impact assessment and since gas compression needs for the 

Project cannot reasonably be separated from those necessary for the adjacent Pinedale Anticline 

Project Area (PAPA), future compression requirements for the PAPA are also considered in this 

air quality analysis. Projections of future compression requirements supporting both the JIDPA 

and the PAPA were obtained from pipeline companies currently transporting gas from these 

areas. This total regional compression estimate was analyzed as part of both the Proposed Action 

and alternatives. 

1.2 ALTERNATIVES EVALUATED 

Nine project alternatives are currently being analyzed in the National Environmental Policy Act 

(NEPA) EIS for this Project. These alternatives are summarized below: 

•	 the No Action Alternative - no further development includes 533 wells from 

497 well pads; LOF is approximately 43 years; 

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6 Air Quality Technical Support Document, Jonah Infill Drilling Project 

•	 the Proposed Action - up to 3,100 new wells (2,705 straight, 395 directional) on 

up to 16,200 acres of new surface disturbance, a well development rate (WDR) of 

250 wells/year (WDR250), and an LOF of 56 years; 

•	 Alternative A - up to 3,100 new wells (all straight) from approximately 3,100 new 

well pads, WDRs of 75, 150, and 250, and an LOF from 56 to 85 years; 

•	 Alternative B - up to 3,100 new wells (all directional) from the existing 497 well 

pads, WDRs of 75, 150, and 250, and an LOF from 56 to 85 years; 

•	 Alternative C - up to 1,250 new wells (all straight) from a maximum of 1,250 new 

well pads, WDRs of 75, 150, and 250, and an LOF from 48 to 60 years; 

•	 Alternative D - up to 2,200 new wells (all straight) from a maximum of 2,200 new 

well pads, WDRs of 75, 150, and 250, and an LOF from 52 to 73 years; 

•	 Alternative E - up to 3,100 new wells (266 straight, 2,834 directional) on up to 

266 new well pads (16 total pads/section), WDRs of 75, 150, and 250, and an 

LOF from 56 to 85 years; 

•	 Alternative F - up to 3,100 new wells (1,028 straight, 2,072 directional) on up to 

1,028 new pads (32 total pads/section), WDRs of 75, 150, and 250, and an LOF 

from 56 to 85 years; 

•	 Alternative G - up to 3,100 new wells (2,553 straight, 547 directional) on up to 

2,553 new well pads (64 total pads/section), WDRs of 75, 150, and 250, and an 

LOF from 56 to 85 years; and 

•	 Preferred Alternative - up to 3,100 new wells (2,553 straight, 547 directional), 

WDRs of 75, 150, and 250, and an LOF from 56 to 85 years.. 

Modeling analyses were performed to quantify near-field pollutant concentrations within and 

nearby the JIDPA from project-related emissions sources for the range of alternatives to assure 

that the maximum near-field impacts were estimated. Impacts from scenarios considering 1,250 

and 3,100 wells in production, at various well-spacing densities of 5, 10, 20, and 40 acres were 

modeled. Emissions from directional and straight drilling and construction of alternate well pads 

sizes of 3.8, 7.0, and 10.0 acres were evaluated. Near-field impacts are described in detail in 

Chapter 3.0. 

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Air Quality Technical Support Document, Jonah Infill Drilling Project 7 

Direct project and cumulative mid-field and far-field modeling analyses were not performed for 

every NEPA alternative analyzed, since there is considerable similarity of modeled air quality 

components within many proposed alternatives, and due to the additional time and resources 

required for performing all of the potential analyses. Modeling scenarios were developed to 

approximate a range of project development alternatives including: No Action, Proposed Action, 

Alternative A, Alternative B, Alternative C, and Alternative F. These modeling scenarios 

assumed the maximum field emissions which could potentially occur concurrently (i.e., the final 

year of construction representing the maximum annual construction activity rate combined with 

nearly full-field production). Three WDRs were analyzed--250 wells/year (WDR250), 

150 wells/year (WDR150), and 75 wells/year (WDR75). Development rates considered both 

straight and directional drilling operations and are generally consistent with the proposed Project 

alternatives. 

Mid-field and far-field impacts and their applicability to each alternative are described in greater 

detail in Chapter 4.0. 

1.3 STUDY TASKS 

The following eight tasks were performed for air quality and AQRVs impact assessment: 

1.	 Project Air Emissions Inventory. Development of an air pollutant emissions inventory 

for the Project. 

2.	 Regional Air Emissions Inventory. Development of an air pollutant emissions 

inventory for other regional sources not represented by background air quality 

measurements, including state-permitted sources, RFFA, and RFD. 

3.	 Project Near-Field Analysis. Assessment of near-field air quality concentration impacts 

resulting from activities proposed within the JIDPA. 

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8 Air Quality Technical Support Document, Jonah Infill Drilling Project 

4.	 Regional Near-Field Analysis. Assessment of near-field air quality concentration 

impacts resulting from activities proposed within the JIDPA in combination with other 

existing and proposed regional compressor stations. 

5.	 In-Field Cumulative Analysis. Assessment of concentration impacts within the JIDPA 

resulting from the project and other regional sources inventoried under item 2 above. 

6.	 Mid-Field Cumulative Analysis. Assessment of mid-field visibility impacts to regional 

communities resulting from the Project and other regional sources. 

7.	 Far-Field Direct Project Impact Analysis. Assessment of far-field air quality 

concentration and AQRV impacts resulting from proposed Project activities. 

8.	 Far-Field Cumulative Impact Analysis. Assessment of far-field air quality 

concentration and AQRV impacts resulting from activities proposed within the JIDPA 

combined with other regional sources inventoried under item 2 above. 

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Air Quality Technical Support Document, Jonah Infill Drilling Project 9 

2.0 EMISSIONS INVENTORY 

2.1 PROJECT EMISSIONS 

The Proposed Action includes the development of up to 3,100 natural gas wells. Wells may be 

developed on single well pads, on multiple well pads, or on a combination thereof. 

Criteria pollutant and hazardous air pollutant (HAP) emissions were inventoried for construction 

activities, production activities, and ancillary facilities. Criteria pollutants included nitrogen 

oxides (NOx), carbon monoxide (CO), sulfur dioxide (SO2), volatile organic compounds (VOCs), 

particulate matter less than 10 microns in diameter (PM10), and particulate matter less than 

2.5 microns in diameter (PM2.5). HAPs consisted of n-hexane; benzene, toluene, ethylbenzene, 

and xylene (BTEX); and formaldehyde. All emission calculations were completed in accordance 

with WDEQ-AQD oil and gas guidance (WDEQ-AQD 2001) in effect at the time the inventory 

was conducted, stack test data, EPA's AP-42, or other accepted engineering methods (see 

Appendix A, Protocol). Additions to WDEQ-AQD Oil and Gas Production Facility Emission 

Control and Permitting Requirements for the Jonah and Pinedale Anticline Gas Fields were 

approved by the Air Quality Advisory Board on July 28, 2004. The additional guidance became 

effective upon approval and applies to all wells reported to WOGCC after the approval date of 

July 28, 2004. The additional guidance revised emission control requirements and permitting 

process currently utilized under WDEQ-AQD Notice of Intent (NOI)/Presumptive Best Available 

Control Technology (P-BACT) permitting processes. Because the Project air emissions 

inventory and dispersion modeling analysis was complete prior to the adoption of the guidance 

referenced above, the revised guidance is not reflected in this analysis. 

2.1.1 Construction Emissions 

Construction activities are a source of primarily criteria pollutants. Emissions would occur from 

well pad and resource road construction and traffic, rig-move/drilling and associated traffic, 

completion/testing and associated traffic, pipeline installation and associated traffic, and wind 

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10 Air Quality Technical Support Document, Jonah Infill Drilling Project 

erosion during construction activities. A timeline illustrating the duration of construction 

activities for a single well is provided in Figure 2.1. Up to 3,100 natural gas wells may be 

developed; however, a lesser number of developed wells are considered under two alternatives. 

Regardless of total wells developed, three separate WDRs were examined in this emissions 

inventory: 75, 150, and 250 wells developed per year. 

Well pad and resource road emissions would include fugitive PM10 and PM2.5 emissions from 

1) construction activities and 2) traffic to and from the construction site. Other criteria pollutant 

emissions would occur from diesel combustion in haul trucks and heavy construction equipment. 

On resource roads, water would be used for fugitive dust control, effecting a control efficiency of 

50%. On collector roads (e.g., Luman Road) magnesium chloride would be used for dust 

control, effecting a control efficiency of 85%. 

After the pad is prepared, rig-move/drilling would begin. Emissions would include fugitives 

from unpaved road travel to and from the drilling site and emissions from diesel drilling engines 

(three total engines). At directionally drilled wells the amount of traffic would increase by 20%, 

and one additional drilling engine (a total of four engines) would be utilized. Emissions from 

well completion and testing would include fugitive PM10 and PM2.5 emissions from traffic and 

Figure 2.1 Approximate Single-Well Development Timeline. 

Days 

5 10 15 20 25 30 35 40 45 50 55 60 65 70 

Activity 

Well Pad and Access 

Road Construction 

(4 days) 

Rig-move and 

Drilling (22-26 days) 

Completion and 

Testing (35 days) 

Pipeline Construction 

(4 days) 

29 

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Air Quality Technical Support Document, Jonah Infill Drilling Project 11 

emissions from diesel haul truck tailpipes. During the completion phase, gas and condensate are 

both vented to the atmosphere and combusted (flared). Emissions from the venting of natural gas 

include HAPs and VOCs. Flaring emissions from the combustion of natural gas and condensate 

include NOx, CO, VOCs, and HAPs. 

Pollutant emissions would also occur from pipeline installation activities, including general 

construction activities, travel to and from the pipeline construction site, and diesel combustion 

from on-site construction equipment. 

Fugitive dust (PM10 and PM2.5) would occur during well pad, road, and pipeline construction due 

to wind erosion on disturbed areas. 

A summary of single-well construction emissions for both straight and directionally drilled wells 

are shown in Table 2.1. Construction emission calculations are provided in detail, showing all 

emission factors, input parameters, and assumptions, in Appendix B (Project Emissions 

Inventory). 

2.1.2 Production Emissions 

Field production equipment and operations would be a source of criteria pollutants and HAPs 

including BTEX, n-hexane, and formaldehyde. Pollutant emission sources during field 

production would include: 

• combustion engine emissions and dust from road travel to and from well sites; 

• diesel combustion emissions from haul trucks; 

• combustion emissions from well site heaters; 

• fugitive HAP/VOC emissions from well site equipment leaks; 

• condensate storage tank flashing and flashing control; 

• glycol dehydrator still vent flashing; 

• wind erosion from well pad disturbed areas; and 

• natural gas-fired reciprocating internal combustion compressor engines. 

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12 Air Quality Technical Support Document, Jonah Infill Drilling Project 

Table 2.1 Single-well Construction Emissions Summary for Both Straight and Directionally 

Drilled Wells. 

Well Pad and Access Completion and 

Road Construction Rig Move and Drilling Testing Pipeline Construction Totals

 Pollutant (lb/hr) (tons/well) (lb/hr) (tons/well) (lb/hr) (tons/well) (lb/hr) (tons/well) (lb/hr) (tons/well) 

Emissions for one straight well 

NOx 12.23 0.23 9.782 2.24 0.35 0.10 7.81 0.067 30.17 2.6362 

CO 3.76 0.071 3.762 1.47 0.45 0.13 3.03 0.024 11.00 1.6938 

SO2 1.46 0.028 0.312 0.071 0.0096 0.00 0.74 0.74 0.0067 0.8400 

PM10 10.761 0.21 3.112 0.80 6.56 1.95 4.883 0.073 25.30 3.0388 

PM2.5 3.521 0.069 0.932 0.23 1.00 0.30 1.523 0.019 6.97 0.6136 

VOC 0.90 0.017 1.972 0.45 0.17 57.62 0.76 0.76 0.0066 58.8545 

Emissions for one directional well 

NOx 12.234 0.23 12.095 3.34 0.356 0.10 7.816 0.067 32.48 3.7420 

CO 3.764 0.071 7.895 2.19 0.456 0.13 3.036 0.024 15.13 2.4130 

SO2 1.464 0.028 0.385 0.106 0.00965 0.00 0.746 0.74 2.60 0.8751 

PM10 10.764 0.21 3.285 1.00 6.565 1.95 4.883,6 0.073 25.47 3.2358 

PM2.5 3.524 0.069 1.075 0.31 1.005 0.30 1.523,6 0.019 7.11 0.6958 

VOC 0.904 0.017 2.435 0.67 0.175 57.62 0.766 0.76 4.26 59.0756 

1 Sum of well pad construction, road construction, well pad and road construction traffic, and construction heavy equipment tailpipe 

emissions. 2 Sum of straight drilling traffic, straight drilling engines, and straight drilling heavy equipment tailpipe emissions. 3 Sum of pipeline construction, pipeline construction traffic, and pipeline heavy equipment tailpipe emissions. 4 Well pad and access road construction emissions for one directionally drilled well are equal to emissions for one straight drilled well. 5 Sum of directional drilling traffic, directional drilling engines, and directional drilling heavy equipment tailpipe emissions. 6 Completion and testing emissions and pipeline construction emissions are the same for straight and directional wells. 

Fugitive PM10 and PM2.5 emissions would occur from road travel and wind erosion from well 

pad disturbances. Criteria pollutant emissions would occur from diesel combustion in haul 

trucks traveling in the field during production. 

Heaters required at each well site include an indirect heater, a dehydrator reboiler heater, and a 

separator heater. Stack testing was performed for NOx and CO on these heaters by Operators in 

2003 to obtain an accurate estimate of these emissions from these sources. These stack test 

emissions were used throughout this air quality analysis. Heater emissions for all other 

pollutants were calculated using AP-42. 

35982 TRC Environmental Corporation 
Air Quality Technical Support Document, Jonah Infill Drilling Project 13 

HAPs and VOC emissions would occur from fugitive equipment leaks (i.e., valves, flanges, 

connections, pump seals, and opened lines). Condensate storage tank flashing and glycol 

dehydrator still vent flashing emissions also would include VOC/HAP emissions. Emissions 

from these sources were provided by Operators. 

Total production emissions of criteria pollutants and HAPs occurring from a single well are 

presented in Table 2.2. Production emission calculations are provided in detail, in Appendix B, 

showing all emission factors, input parameters, and assumptions. 

Table 2.2 Single-Well Production Emissions Summary. 

Traffic Emissions 1 Production Emissions 2 Total Emissions 

Pollutant (tpy) (tpy) (tpy) 

NOx 0.0084 0.045 0.054 

CO 0.011 0.43 0.45 

SO2 0.00024 0.00 0.0024 

PM10 0.23 0.0087 0.24 

PM2.5 0.035 0.0087 0.043 

VOC 0.0042 18.59 18.59 

Benzene -- 1.22 1.22 

Toluene -- 2.47 2.47 

Ethylbenzene -- 0.13 0.13 

Xylene -- 1.33 1.33 

n-hexane -- 0.50 0.50 

1 Includes emissions from all traffic associated with full-field production. PM10 and PM2.5 emissions calculations 

assume 20 wells can be visited per day. Light trucks/pickups emissions on primary access roads (see 

Table B.2.1) are adjusted to assume 20 wells can be visited per day. 2 Includes emissions from indirect heater, separator heater, dehydrator heater, and dehydrator flashing, and 

fugitive HAP/VOC. Assumes 25% of the dehydrators have BTEX control, and the remaining 75% have a pump 

limit. 

35982 TRC Environmental Corporation 
14 Air Quality Technical Support Document, Jonah Infill Drilling Project 

2.1.3 Total Field Emissions 

Annual emissions in the JIDPA under the Proposed Action and each alternative at WDRs of 75, 

150, and 250 are shown in Table 2.3. Emissions assume construction and production occurring 

simultaneously in the field and include one year of maximum construction emissions plus one 

year of production at maximum emission rates. 

Construction emissions were based on well construction, drilling, drilling traffic, completion 

traffic, and completion flaring. Well construction emissions were based on the number of wells 

constructed per year and the type of well constructed. Drilling, drilling traffic, completion 

traffic, and completion flaring were based on the number of wells developed per year. 

Completion flaring operations were assumed to occur at 20% of the wells under construction. 

For alternatives with both directional and straight wells, a proportional split between straight and 

directional wells was used to determine the number of straight and directional drilling rigs. 

Production emissions were calculated based on the total number of producing wells in the field. 

Total producing wells were equal to the difference in number of wells proposed and the number 

of wells constructed per year. 

2.2 REGIONAL EMISSIONS INVENTORY 

An emissions inventory of industrial sources within the JIDPA cumulative modeling domain was 

prepared for use in the cumulative air quality analysis. The modeling domain included portions 

of Wyoming, Colorado, Utah, and Idaho (see Map 1.2). Industrial sources and oil and gas wells 

permitted within a defined time frame (January 1, 2001 through June 30, 2003) through state air 

quality regulatory agencies and state oil and gas permitting agencies were first researched. The 

subset of these sources which had begun operation as of the inventory end-date was classified as 

35982 TRC Environmental Corporation 
Air Quality Technical Support Document, Jonah Infill Drilling Project 15 

Table 2.3 Estimated Jonah Infill Drilling Project Maximum Annual In-field Emissions 

Summary - Construction and Production. 

Annual Annual Total 

Annual Construction Total Total Production Annual 

Development Emissions1 Proposed Producing Emissions2 Emissions 

Alternative Rate Pollutant (tpy) Wells Wells (tpy) (tpy) 

Proposed Action (Maximum 250 NOx 744.5 3,100 2,850 360.6 1,105.1 

Recovery) (395 directional, 

2,705 straight) CO 803.9 1,412.9 2,216.8 

SO2 25.9 0.7 26.6 

PM10 976.7 676.1 1,652.8 

PM2.5 190.1 123.8 313.9 

VOC 3,154.0 53,069.9 56,223.9 

HAPs 243.6 16,118.2 16,361.8 

Alternative A 250 NOx 716.5 3,100 2,850 360.6 1,077.1 

(100% straight) CO 783.2 1,412.9 2,196.1 

SO2 25.6 0.7 26.3 

PM10 985.7 676.7 1,662.5 

PM2.5 191.7 123.9 315.6 

VOC 3,147.4 53,069.9 56,217.3 

HAPs 243.6 16,118.2 16,361.8 

150 NOx 429.9 3,100 2,950 366.0 795.9 

CO 469.9 1,457.4 1,927.3 

SO2 15.4 0.7 16.1 

PM10 591.4 700.5 1,291.9 

PM2.5 115.0 128.2 243.3 

VOC 1,888.5 54,929.0 56,817.4 

HAPs 146.2 16,683.3 16,829.4 

75 NOx 212.7 3,100 3,025 370.0 582.8 

CO 233.5 1,490.8 1,724.3 

SO2 7.6 0.7 8.3 

PM10 295.6 718.3 1,013.9 

PM2.5 57.4 131.5 188.9 

VOC 943.8 56,323.2 57,267.0 

HAPs 73.1 17,107.0 17,180.1 

35982 TRC Environmental Corporation 
16 Air Quality Technical Support Document, Jonah Infill Drilling Project 

Table 2.3 (Continued) 

Annual Annual Total 

Annual Construction Total Total Production Annual 

Development Emissions1 Proposed Producing Emissions2 Emissions 

Alternative Rate Pollutant (tpy) Wells Wells (tpy) (tpy) 

Alternative B4 250 NOx 935.3 3,100 2,850 360.6 1,295.9 

(all directional, no new 

pads) CO 945.0 1,412.9 2,357.9 

SO2 27.5 0.7 28.2 

PM10 914.6 671.6 1,586.2 

PM2.5 179.0 123.1 302.1 

VOC 3,198.5 53,069.9 56,268.4 

HAPs 243.6 16,118.2 16,361.8 

150 NOx 561.2 3,100 2,950 366.0 927.1 

CO 567.0 1,457.4 2,024.4 

SO2 16.5 0.7 17.2 

PM10 548.7 695.2 1,243.9 

PM2.5 107.4 127.4 234.9 

VOC 1,919.1 54,929.0 56,848.1 

HAPs 146.2 16,683.3 16,829.4 

75 NOx 277.3 3,100 3,025 370.0 647.3 

CO 281.4 1,490.8 1,772.2 

SO2 8.1 0.7 8.9 

PM10 274.2 712.9 987.1 

PM2.5 53.5 130.7 184.2 

VOC 958.9 56,323.2 57,282.2 

HAPs 73.1 17,107.0 17,180.1 

Alternative C 250 NOx 716.5 1,250 1,000 261.2 977.7 

(100% straight) CO 783.2 589.5 1,372.7 

SO2 25.6 0.2 25.9 

PM10 985.7 237.5 1,223.2 

PM2.5 191.7 43.5 235.2 

VOC 3,147.4 18,677.3 21,824.7 

HAPs 243.6 5,664.9 5,908.5 

35982 TRC Environmental Corporation 
Air Quality Technical Support Document, Jonah Infill Drilling Project 17 

Table 2.3 (Continued) 

Annual Annual Total 

Annual Construction Total Total Production Annual 

Development Emissions1 Proposed Producing Emissions2 Emissions 

Alternative Rate Pollutant (tpy) Wells Wells (tpy) (tpy) 

Alternative C (cont.) 150 NOx 429.9 1,250 1,100 266.6 696.5 

CO 469.9 634.0 1,103.9 

SO2 15.4 0.3 15.6 

PM10 591.4 261.2 852.6 

PM2.5 115.0 47.8 162.8 

VOC 1,888.5 20,536.3 22,424.8 

HAPs 146.2 6,229.9 6,376.1 

75 NOx 212.7 1,250 1,175 270.6 483.3 

CO 233.5 667.4 900.9 

SO2 7.6 0.3 7.9 

PM10 295.6 279.0 574.6 

PM2.5 57.4 51.1 108.5 

VOC 943.8 21,930.6 22,874.4 

HAPs 73.1 6,653.7 6,726.8 

Alternative D 250 NOx 716.5 2,200 1,950 312.2 1,028.7 

(100% straight) CO 783.2 1,012.3 1,795.5 

SO2 25.6 0.5 26.1 

PM10 985.7 463.0 1,448.8 

PM2.5 191.7 84.8 276.5 

VOC 3,147.4 36,338.3 39,485.8 

HAPs 243.6 11,032.8 11,276.4 

150 NOx 429.9 2,200 2,050 317.6 747.5 

CO 469.9 1,056.8 1,526.8 

SO2 15.4 0.5 15.9 

PM10 591.4 486.8 1,078.2 

PM2.5 115.0 89.1 204.1 

VOC 1,888.5 38,197.4 40,085.9 

HAPs 146.2 11,597.9 11,744.0 

35982 TRC Environmental Corporation 
18 Air Quality Technical Support Document, Jonah Infill Drilling Project 

Table 2.3 (Continued) 

Annual Annual Total 

Annual Construction Total Total Production Annual 

Development Emissions1 Proposed Producing Emissions2 Emissions 

Alternative Rate Pollutant (tpy) Wells Wells (tpy) (tpy) 

Alternative D (cont.) 75 NOx 212.7 2,200 2,125 321.7 534.4 

CO 233.5 1,090.2 1,323.8 

SO2 7.6 0.5 8.1 

PM10 295.6 504.6 800.2 

PM2.5 57.4 92.4 149.8 

VOC 943.8 39,591.7 40,535.5 

HAPs 73.1 12,021.6 12,094.7 

Alternative E4 250 NOx 917.0 3,100 2,850 360.6 1,277.6 

(2,834 directional, 

266 straight, 266 new pads) CO 931.5 1,412.9 2,344.3 

SO2 27.4 0.7 28.0 

PM10 920.7 672.1 1,592.8 

PM2.5 180.1 123.2 303.3 

VOC 3,194.2 16,190.4 19,384.7 

HAPs 243.6 16,118.2 16,361.8 

150 NOx 549.7 3,100 2,950 366.0 915.7 

CO 558.6 1,457.4 2,016.0 

SO2 16.4 0.7 17.1 

PM10 552.4 695.7 1,248.0 

PM2.5 108.0 127.5 235.6 

VOC 1,916.5 54,929.0 56,845.4 

HAPs 146.2 16,683.3 16,829.4 

75 NOx 275.4 3,100 3,025 370.0 645.4 

CO 279.7 1,490.8 1,770.4 

SO2 8.2 0.7 8.9 

PM10 276.3 713.4 989.6 

PM2.5 54.1 130.8 184.8 

VOC 958.3 56,323.2 57,281.6 

HAPs 73.1 17,107.0 17,180.1 

35982 TRC Environmental Corporation 
Air Quality Technical Support Document, Jonah Infill Drilling Project 19 

Table 2.3 (Continued) 

Annual Annual Total 

Annual Construction Total Total Production Annual 

Development Emissions1 Proposed Producing Emissions2 Emissions 

Alternative Rate Pollutant (tpy) Wells Wells (tpy) (tpy) 

Alternative F4 250 NOx 862.6 3,100 2,850 360.6 1,223.2 

(2,072 directional, 

1,028 straight, CO 891.3 1,412.9 2,304.2 

1,028 new pads) SO2 26.9 0.7 27.6 

PM10 938.1 673.3 1,611.5 

PM2.5 183.2 123.4 306.6 

VOC 3,181.6 53,069.9 56,251.5 

HAPs 243.6 16,118.2 16,361.8 

150 NOx 517.3 3,100 2,950 366.0 883.3 

CO 534.6 1,457.4 1,992.0 

SO2 16.1 0.7 16.8 

PM10 562.8 697.0 1,259.8 

PM2.5 109.9 127.7 237.6 

VOC 1,908.9 54,929.0 56,837.8 

HAPs 146.2 16,683.3 16,829.4 

75 NOx 258.7 3,100 3,025 370.0 628.7 

CO 267.3 1,490.8 1,758.1 

SO2 8.1 0.7 8.8 

PM10 281.4 714.7 996.1 

PM2.5 55.0 131.0 185.9 

VOC 954.4 56,323.2 57,277.7 

HAPs 73.1 17,107.0 17,180.1 

Alternative G4 250 NOx 754.9 3,100 2,850 360.6 1,115.5 

(547 directional, 

2,553 straight, CO 811.7 1,412.9 2,224.6 

2,553 new pads) SO2 26.0 0.7 26.6 

PM10 973.1 673.3 1,646.5 

PM2.5 189.5 123.4 312.8 

VOC 3,156.4 53,069.9 56,226.3 

HAPs 243.6 16,118.2 16,361.8 

35982 TRC Environmental Corporation 
20 Air Quality Technical Support Document, Jonah Infill Drilling Project 

Table 2.3 (Continued) 

Annual Annual Total 

Annual Construction Total Total Production Annual 

Development Emissions1 Proposed Producing Emissions2 Emissions 

Alternative Rate Pollutant (tpy) Wells Wells (tpy) (tpy) 

Alternative G (cont.) 150 NOx 452.5 3,100 2,950 366.0 818.5 

CO 486.7 1,457.4 1,944.1 

SO2 15.6 0.7 16.3 

PM10 583.8 699.6 1,283.4 

PM2.5 113.6 128.1 241.7 

VOC 1,893.8 54,929.0 56,822.7 

HAPs 146.2 16,683.3 16,829.4 

75 NOx 226.3 3,100 3,025 370.0 596.3 

CO 243.4 1,490.8 1,734.1 

SO2 7.8 0.7 8.5 

PM10 291.9 717.3 1,009.2 

PM2.5 56.8 131.4 188.2 

VOC 946.9 56,323.2 57,270.1 

HAPs 73.1 17,107.0 17,180.1 

Preferred Alternative 250 NOx 754.9 3,100 2,850 360.6 1,115.5 

(547 directional, 

2,553 straight, CO 811.7 1,412.9 2,224.6 

2,553 new pads) SO2 26.0 0.7 26.6 

PM10 973.1 673.3 1,646.5 

PM2.5 189.5 123.4 312.8 

VOC 3,156.4 53,069.9 56,226.3 

HAPs 243.6 16,118.2 16,361.8 

150 NOx 452.5 3,100 2,950 366.0 818.5 

CO 486.7 1,457.4 1,944.1 

SO2 15.6 0.7 16.3 

PM10 583.8 699.6 1,283.4 

PM2.5 113.6 128.1 241.7 

VOC 1,893.8 54,929.0 56,822.7 

HAPs 146.2 16,683.3 16,829.4 

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Air Quality Technical Support Document, Jonah Infill Drilling Project 21 

Table 2.3 (Continued) 

Annual Annual Total 

Annual Construction Total Total Production Annual 

Development Emissions1 Proposed Producing Emissions2 Emissions 

Alternative Rate Pollutant (tpy) Wells Wells (tpy) (tpy) 

Preferred Alternative (cont.) 75 NOx 226.3 3,100 3,025 370.0 596.3 

CO 243.4 1,490.8 1,734.1 

SO2 7.8 0.7 8.5 

PM10 291.9 717.3 1,009.2 

PM2.5 56.8 131.4 188.2 

VOC 946.9 56,323.2 57,270.1 

HAPs 73.1 17,107.0 17,180.1 

1 Includes emissions from well pad and access road construction and associated traffic (see Tables B.1.1, B.1.2, 

B.1.3, and B.1.4), rig moving and drilling and associated traffic (see Tables B.1.10, B.1.11, and B.1.12). 2 Includes emissions from indirect heater (see Table B.2.3), separator heater (see Table B.2.4), dehydrator heater 

(see Table B.2.4), dehydrator flashing (see table B.2.6), fugitive HAP/VOC (see Table B.2.7), and traffic 

associated with full-field production (see Tables B.2.1 and B.2.2). Assumes 50% of condensate storage tanks are 

controlled and 50% are uncontrolled, and 25% of the dehydrators have BTEX control, and the remaining 75% 

have a pump limit. 3 At WDR of 250, assumes emissions include 250 drilling operations occurring during the year including 125 rigs 

with Tier 1 emission levels (see Table B.1.8) and 125 rigs with Tier 2 emission levels (see Table B.1.9). 

Emissions also include 50 completion flares (see Table B.1.12) operating during the year. 4 At WDR of 150, assumes emissions include 150 drilling operations occurring during the year including 75 rigs 

with Tier 1 emission levels (see Table B.1.8) and 75 rigs with Tier 2 emission levels (see Table B.1.9). 

Emissions also include 30 completion flares (see Table B.1.12) operating during the year. 5 At WDR of 75, assumes emissions include 75 drilling operations occurring during the year including 37 rigs 

with Tier 1 emission levels (see Table B.1.8) and 37 rigs with Tier 2 emission levels (see Table B.1.9). 

Emissions also include 15 completion flares (see Table B.1.12) operating during the year. 

35982 TRC Environmental Corporation 
22 Air Quality Technical Support Document, Jonah Infill Drilling Project 

state-permitted sources, and those not yet in operation were classified as RFFA. Also included 

in the regional inventory were industrial sources proposed under NEPA in the State of Wyoming. 

The developed portions of these projects were assumed to be either included in monitored 

ambient background or included in the state-permitted source inventory. The undeveloped 

portions of projects proposed under NEPA were classified as RFD. In accordance with 

definitions agreed upon by BLM, EPA, WDEQ-AQD, and USDA Forest Service for use in EIS 

projects, RFD was defined as 1) the NEPA-authorized but not yet developed portions of 

Wyoming NEPA projects, and 2) not yet authorized NEPA projects for which air quality analyses 

were in progress and for which emissions had been quantified. 

Map 2.1 shows the regional inventory area with NEPA project areas, and a summary of the 

regional inventory is shown in Table 2.4. Values presented in Table 2.4 represent the change in 

emissions between the inventory start-date (January 1, 2001) and the inventory end-date 

(June 30, 2003). 

The regional inventory including methodologies used to compile the regional source emissions 

are provided in Appendix C and include a description of the data collected, the period of record 

for the data collected, inclusion and exclusion methodology, stack parameter processing 

methods, and the state-specific methodologies required due to significant differences in the 

content and completeness of data obtained from each state. 

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24 Air Quality Technical Support Document, Jonah Infill Drilling Project 

Table 2.4 Regional Inventory Summary of Emissions Changes from January 1, 2001 to 

June 30, 2003. 

Emission 

State 

Colorado 

Source Category 

State-permitted1 

RFFA 

RFD 

Excluded 

Quantity of 

Sources 

17 

0 

0 

203 

NOx 

(tpy) 

177.1 

--

--

--

SO2 

(tpy) 

2.7 

--

--

--

PM10 

(tpy) 

64.8 

--

--

--

PM2.5 

(tpy)

22.6 

--

--

--

Idaho State-permitted2 

RFFA 

RFD 

Excluded 

17 

0 

0 

37 

568.4

--

--

--

 (112.2) 

--

--

--

61.6 

--

--

--

61.6 

--

--

--

Utah State-permitted3 

RFD 

RFFA 

Excluded 

126

0 

0 

202 

2,619.9

--

--

--

 47.1

--

--

--

 424.5

--

--

--

 424.1 

--

--

--

Wyoming State-permitted4 

RFFA5 

RFD6 

Excluded 

34 

47 

42

693 

733.5 

486.3

 3,166.5

--

1.0 

(1,407.0)

 56.1

--

8.3 

(1,282.8)

 84.0

--

8.3 

(586.6) 

81.9 

--

Total State Permitted7 194 4,098.9 (61.4) 559.2 516.6 

RFFA 47 486.3 (1,407.0) (1,282.8) (586.6) 

RFD 42 3,166.5 56.1 84.0 81.9 

Excluded 1,135 -- -- -- --

Total Change -- 7,751.7 (1,412.3) (639.6) 11.9 

1 See Appendix C, Table C.1 2 See Appendix C, Table C.3. 3 Includes state-permitted oil and gas well emissions. See Appendix C, Tables C.5 and C.9. 4 Includes state-permitted oil and gas well emissions. See Appendix C, Tables C.7 and C.9. 5 See Appendix C, Table C.11. 6 See Appendix C, Table C.12. 7 Includes state-permitted oil and gas well emissions. 

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Air Quality Technical Support Document, Jonah Infill Drilling Project 25 

3.0 NEAR-FIELD MODELING ANALYSES 

3.1 MODELING METHODOLOGY 

A near-field ambient air quality impact analysis was performed to quantify the maximum criteria 

pollutants (PM10, PM2.5, CO, NO2, SO2, and ozone [O3]) and HAPs (BTEX, n-hexane, and 

formaldehyde) impacts that could occur within and near the JIDPA. These impacts would result 

from emissions associated with Project construction and production activities, and are compared 

to applicable ambient air quality standards, and significance thresholds. All modeling analyses 

were generally performed in accordance with the Protocol presented in Appendix A with input 

from the BLM and members of the air quality stake holders' group, including the EPA, USDA 

Forest Service, and WDEQ-AQD. 

The EPA's proposed guideline dispersion model, AERMOD (version 02222), was used to assess 

near-field impacts of criteria pollutants PM10, PM2.5, CO, NO2 and SO2, and to estimate 

short-term and long-term HAP impacts. This version of AERMOD utilizes the PRIME building 

downwash algorithms which are the most recent "state of science" algorithms for modeling 

applications where aerodynamic building downwash is a concern. One year of JIDPA 

meteorology data was used with the AERMOD dispersion model to estimate these pollutant 

impacts. O3 impacts were estimated from a screening methodology developed by Scheffe (1988) 

that utilizes NOx and VOC emissions ratios to calculate O3 concentrations. Various construction 

and production activities were modeled to provide for a complete range of alternatives and 

activities. For each pollutant, the magnitude and duration of emissions from each Project phase 

(i.e., construction or production) emissions activity were examined to determine the maximum 

emissions scenario for modeling. 

3.2 METEOROLOGY DATA 

One year of surface meteorological data, collected in the JIDPA from January 1999 through 

January 2000, was used in the analysis. A wind rose for these data is presented in Figure 3.1. 

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26 Air Quality Technical Support Document, Jonah Infill Drilling Project 

Figure 3.1 Wind Rose, Jonah Field, 1999. 

35982 TRC Environmental Corporation 
Air Quality Technical Support Document, Jonah Infill Drilling Project 27 

The JIDPA meteorology data included hourly surface measurements of wind speed, wind 

direction, standard deviation of wind direction [sigma theta], and temperature. These data were 

processed using the AERMET preprocessor to produce a dataset compatible with the AERMOD 

dispersion model. AERMET was used to combine the JIDPA surface measurements with twice 

daily sounding data from Riverton, Wyoming, cloud cover data collected at Big Piney, 

Wyoming, and solar radiation measurements collected at Pinedale, Wyoming. 

3.3 BACKGROUND POLLUTANT CONCENTRATIONS 

Background concentration data collected for criteria pollutants at regional monitoring sites were 

added to concentrations modeled in the near-field analysis to establish total pollutant 

concentrations for comparison to ambient air quality standards. The most representative 

monitored regional background concentrations available for criteria pollutants are shown in 

Table 3.1. 

Table 3.1 Near-Field Analysis Background Ambient Air Quality Concentrations 

(Micrograms per Cubic Meter [μg/m3]). 

Pollutant Averaging Period Measured Background Concentration 

CO1 

NO2 

2 

O3 

3 

1-hour 

8-hour 

Annual 

1-hour 

8-hour 

3,336 

1,381 

3.4 

169 

147 

PM10 4 24-hour 

Annual 

33 

16 

PM2.5 4 24-hour 

Annual 

13 

5 

SO2 

5 3-hour 

24-hour 

132 

43 

Annual 9 

1 Data collected by Amoco at Ryckman Creek for an 8-month period during 1978-1979, summarized in the Riley Ridge EIS 

(BLM 1983). 2 Data collected at Green River Basin Visibility Study site, Green River, Wyoming, during period January-December 2001 

(Air Resource Specialists [ARS] 2002). 3 Data collected at Green River Basin Visibility Study site, Green River, Wyoming, during period June 10, 1998, through 

December 31, 2001 (ARS 2002). 4 Data collected by WDEQ-AQD at Emerson Building, Cheyenne, Wyoming, Year 2001, second highest 24-hour 

concentrations. These data were determined by WDEQ-AQD to be the most representative co-located PM10 and PM2.5 data 

available. 5 Data collected at LaBarge Study Area, Northwest Pipeline Craven Creek Site 1982-1983. 

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28 Air Quality Technical Support Document, Jonah Infill Drilling Project 

3.4 CRITERIA POLLUTANT IMPACT ASSESSMENT 

The near-field criteria pollutant impact assessment was performed to estimate maximum 

potential impacts of PM10, PM2.5, NO2, SO2, CO, and O3 from project emissions sources 

including well site and compressor station emissions. Maximum predicted concentrations in the 

vicinity of project emissions sources were compared with the Wyoming Ambient Air Quality 

Standards (WAAQS), National Ambient Air Quality Standards (NAAQS), and applicable 

Prevention of Significant Deterioration (PSD) Class II increments shown in Table 3.2. This 

NEPA analysis compared potential air quality impacts from Project alternatives to applicable 

ambient air quality standards and PSD increments. The comparisons to the PSD Class I and II 

increments are intended to evaluate a threshold of concern for potential impacts, and does not 

represent a regulatory PSD increment comparison. Such a regulatory analysis is the 

responsibility of the state air quality agency (under EPA oversight) and would be conducted 

during the permitting process. 

Table 3.2 Ambient Air Quality Standards and Class II PSD Increments for Comparison to 

Near-Field Analysis Results (μg/m3

). 

Pollutant/Averaging Time NAAQS WAAQS PSD Class II Increment 

CO 

1-hour1 40,000 40,000 --

2 

8-hour1 10,000 10,000 -­

NO2 

Annual3 100 100 25 

O3 

1-hour 1 235 235 -­

8-hour4 157 157 -­

PM10 

24-hour1 150 150 30 

Annual3 50 50 17 

PM2.5 

24-hour1 65 655 -­

Annual3 15 155 -­

SO2 

3-hour1 1,300 1,300 512 

24-hour1 365 260 91 

Annual3 80 60 20 

1 No more than one exceedance per year. 2 -- = No PSD Class II Increment has been established for this pollutant. 3 Annual arithmetic mean. 4 Average of annual fourth-highest daily maximum 8-hour average. 5 Standard not yet enforced in Wyoming. 

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Air Quality Technical Support Document, Jonah Infill Drilling Project 29 

The EPA's proposed guideline dispersion model, AERMOD, was used to model the near-field 

concentrations of PM10, PM2.5, CO, NO2, and SO2. AERMOD was run using one year of 

AERMET preprocessed JIDPA meteorology data following all regulatory default switch settings. 

Since PM10/PM2.5 emissions would be greatest during the resource road/well pad construction 

phase of field development, construction emissions sources were modeled to determine 

compliance with the PM10/PM2.5 WAAQS and NAAQS. Similarly, SO2 emissions would be 

greatest from well drilling operations during construction. CO and NOx emissions primarily 

from compressor stations would be greatest during well production. 

O3 impacts were estimated using the screening methodology developed by Scheffe (1988) which 

utilizes NOx and VOC emissions ratios to calculate O3 concentrations. NOx and VOC emissions 

would be greatest during production activities, and these emissions were used to estimate O3 

impacts. 

3.4.1 PM10/PM2.5 

Maximum localized PM10/PM2.5 impacts would result from well pad and road construction 

activities and from wind erosion. Three different approximate well pad sizes are proposed within 

the range of Project alternatives; 3.8 acres, 7.0 acres, and 10.0 acres. Modeling scenarios were 

developed for each of these well pad sizes, with each scenario consisting of a well pad and a 

2.5-mi resource road using the emissions estimates provided in Section 2.1. Model receptors 

were placed at 100-m intervals beginning 200 m from the edge of the well pad and road. Flat 

terrain was assumed for each modeling scenario. Figure 3.2 presents the configurations used to 

model each well pad and resource road scenario. Volume sources were used to represent 

emissions from well pads and roads. Hourly emission rate adjustment factors were applied to 

limit construction emissions to daytime hours. AERMOD was used to model each scenario 

36 times, once at each of 36 10o rotations, to ensure that impacts from all directional layout 

configurations and meteorological conditions were assessed. Wind erosion emissions were 

modeled for all hours where the wind speed exceeded a threshold velocity defined by emissions 

calculations performed using AP-42 Section 13.2.5, Industrial Wind Erosion (EPA 2004). 

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Air Quality Technical Support Document, Jonah Infill Drilling Project 31 

Table 3.3 presents the maximum modeled PM10/PM2.5 concentrations, for each well pad 

scenario. When the maximum modeled concentration was added to representative background 

concentrations, it was demonstrated that PM10 and PM2.5 concentrations for all scenarios comply 

with the WAAQS and NAAQS for PM10 and proposed standards for PM2.5. 

Emissions associated with temporary construction activities do not consume PSD Increment; 

therefore, temporary PM10 emissions from well pad and road construction are excluded from 

increment consumption analyses. 

Table 3.3 Maximum Modeled PM10/PM2.5 Concentrations, Jonah Infill Drilling Project. 

Scenario 

3.8-acre pad 

Pollutant 

PM10 

PM2.5 

Averaging 

Time 

24-Hour 

Annual 

24-Hour 

Annual 

Direct Modeled 

(μg/m3) 

74.1 

3.4 

27.0 

1.3 

Background 

(μg/m3) 

33 

16 

13 

5 

Total Predicted 

(μg/m3) 

107.1 

19.4 

40.0 

6.3 

WAAQS 

(μg/m3) 

150 

50 

65 

15 

NAAQS 

(μg/m3) 

150 

50 

65 

15 

7-acre pad PM10 

PM2.5 

24-Hour 

Annual 

24-Hour 

Annual 

94.0 

4.7 

31.0 

1.6 

33 

16 

13 

5 

127.0 

20.7 

44.0 

6.6 

150 

50 

65 

15 

150 

50 

65 

15 

10-acre pad PM10 

PM2.5 

24-Hour 

Annual 

24-Hour 

Annual 

102.1 

5.6 

32.2 

1.8 

33 

16 

13 

5 

135.1 

21.6 

45.2 

6.8 

150 

50 

65 

15 

150 

50 

65 

15 

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32 Air Quality Technical Support Document, Jonah Infill Drilling Project 

3.4.2 SO2 

Emissions from construction drilling operations would result in maximum SO2 concentrations of 

all other project phases. Both straight well drilling and directional well drilling are proposed as 

part of the Project. Therefore, modeling scenarios were developed that included a drilling rig at 

the center of a pad, with model receptors placed along 100-m intervals, 100 m from the drilling 

engines, for both straight and directional drilling operations. Drilling rigs were modeled as point 

sources, with aerodynamic building downwash from the rig structure. Figure 3.3 illustrates the 

modeling configuration used for drilling rig SO2 emissions. 

AERMOD was used to model drilling rig SO2 emissions for both straight and directional drilling 

operations. The maximum predicted concentrations are provided in Table 3.4. The modeled SO2 

impacts, when added to representative background concentrations, are below the applicable 

standards and, as with PM10 construction emissions, emissions from drilling rigs are temporary 

and do not consume SO2 PSD Increment. 

3.4.3 NO2 

Emissions from production activities (well site and compression) would result in the maximum 

near-field NO2 concentrations. Analyses were performed to quantify the maximum NO2 impacts 

that could occur within and nearby the JIDPA using the emissions from existing in-field 

compressor station and well emissions, anticipated future compression expansions, and proposed 

Project alternatives. Proposed well emissions include those from well site heaters, truck traffic, 

and from a water disposal well engine. Although no increases to compression are proposed as 

part of the Project, anticipated future compression expansions were obtained from the gas 

transmission companies that operate within the region and were considered in the modeling 

analyses. Anticipated future compression expansions were provided for the Bird Canyon, 

Falcon, Gobblers Knob, Jonah, Luman, and Paradise compressor stations. Bird Canyon, Falcon, 

Luman, and Jonah are primarily associated with the Jonah Field, whereas Gobblers Knob and 

Paradise are considered part of the Pinedale Anticline Project. 

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34 Air Quality Technical Support Document, Jonah Infill Drilling Project 

Table 3.4 Maximum Modeled SO2 Concentrations, Jonah Infill Drilling Project. 

Averaging Direct Modeled Background Total Predicted WAAQS NAAQS 

Scenario Pollutant Time (μg/m3) (μg/m3) (μg/m3) (μg/m3) (μg/m3) 

Straight Drilling SO2	 3-Hour 103.8 132 235.8 1,300 1,300 

24-Hour 36.7 43 79.7 260 365 

Annual 5.2 9 14.2 60 80 

Directional Drilling SO2	 3-Hour 128.3 132 260.3 1,300 1,300 

24-Hour 45.3 43 88.3 260 365 

Annual 6.4 9 15.4 60 80 

Two modeling analyses were performed to estimate near-field NO2 concentrations. Scenario 1 

utilized compressor emissions from the proposed compressor station expansions within the Jonah 

Field in combination with well emissions from the Proposed Action and alternative expansions 

of either 3,100 or 1,250 wells (the maximum range of well development for all Project 

alternatives). Scenario 2 utilized the projected compression expansions proposed within the 

Jonah and Pinedale Anticline fields, well site heater emissions from 198 wells developed in the 

JIDPA since January 2002, well site emissions from either 3,100 or 1,250 proposed wells and an 

inventory of existing regional compressor station emissions provided by the WDEQ-AQD. A 

WDEQ-AQD regional compressor station inventory has historically been required for use in 

ambient air quality compliance demonstrations performed under WDEQ-AQD guidance. The 

modeled impacts from the first analysis are reported as the maximum predicted direct impacts 

from the Proposed Action and alternatives, and results of the second analysis are representative 

of near-field cumulative impacts, since they include contributions from additional regional 

emissions. This near-field cumulative analysis is presented to further demonstrate regional 

compliance with ambient air quality standards and PSD increments. 

Figure 3.4 illustrates all components of modeled Scenarios 1 and 2, above. NOx emissions 

provided in Section 2.1.2 for well site heaters and truck tail pipe emissions were modeled 

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36 Air Quality Technical Support Document, Jonah Infill Drilling Project 

using 1-km-spaced area sources placed throughout the JIDPA. Emissions scalars were used to 

adjust the heater emissions for seasonal variations. Point sources were used for modeling all 

compressor station emissions and water disposal well emissions. The compressor station 

emissions and modeling parameters utilized in near-field NOx modeling Scenarios 1 and 2 are 

provided in Appendix D. 

Refined receptor grids were placed around the Bird Canyon, Jonah, and Luman compressor 

stations, which are the largest compressor stations associated with the Jonah Field operations. 

Model receptors were placed at 25-m intervals along the fence lines of these compressor stations 

and at 100-m intervals from the fence lines out to 2 km, and at 1-km intervals between 2 km and 

5 km from the fence lines of the Bird Canyon and Luman compressor stations, and at 1-km 

intervals throughout the JIDPA. AERMAP was used to determine receptor height parameters 

from digitized elevation map (DEM) data. Aerodynamic building downwash parameters were 

considered for each compressor station. 

The AERMOD model was used to predict maximum NOx impacts for modeled Scenario 1 (direct 

project impacts) and modeled Scenario 2 (cumulative impacts). The maximum modeled 

concentrations occurred near the Luman compressor station, near the southwest end of the 

JIDPA. Maximum modeled NO2 concentrations were determined by multiplying maximum 

predicted NOx concentrations by 0.75, in accordance with EPA's Tier 2 NOx to NO2 conversion 

method (EPA 2003a). Maximum predicted NO2 concentrations are given in Table 3.5. 

As shown in Table 3.5, direct modeled NO2 concentrations from both project sources and from 

cumulative sources are below the PSD Class II Increment for NO2. In addition, when these NO2 

impacts are combined with representative background NO2 concentrations, they are below the 

applicable WAAQS and NAAQS. 

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Air Quality Technical Support Document, Jonah Infill Drilling Project 37 

Table 3.5 Maximum Modeled Annual NO2 Concentrations, Jonah Infill Drilling Project. 

Direct PSD Class II 

Modeled Increment Background Total Predicted WAAQS NAAQS 

Scenario Pollutant (μg/m3) (μg/m3) (μg/m3) (μg/m3) (μg/m3) (μg/m3) 

Scenario 1, Project NO2 6.8 25 3.4 10.2 100 100 

Alone, 3,100 Wells 

Scenario 1, Project NO2 6.5 25 3.4 9.9 100 100 

Alone, 1,250 Wells 

Scenario 2, NO2 18.9 25 3.4 22.3 100 100 

Cumulative Sources, 

3,100 Wells 

Scenario 2, NO2 18.6 25 3.4 22.0 100 100 

Cumulative Sources, 

1,250 Wells 

3.4.4 CO 

Maximum CO emissions would occur from the same production activities (well site and 

compression) that result in maximum NO2 impacts. The modeling scenarios used to model NO2 

impacts were also used to determine maximum CO direct Project and cumulative impacts (see 

Figure 3.4). 

AERMOD was used to predict maximum CO impacts for model Scenario 1 (direct Project 

impacts) and model Scenario 2 (cumulative impacts). Maximum predicted CO concentrations 

are shown in Table 3.6. As indicated in Table 3.6, maximum modeled CO concentrations, when 

combined with representative background CO concentrations, are below the applicable WAAQS 

and NAAQS. 

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38 Air Quality Technical Support Document, Jonah Infill Drilling Project 

Table 3.6 Maximum Modeled CO Concentrations, Jonah Infill Drilling Project. 

Scenario Pollutant 

Averaging 

Time 

Direct Modeled 

(μg/m3) 

Background 

(μg/m3) 

Total Predicted 

μg/m3) 

WAAQS 

(μg/m3) 

NAAQS 

(μg/m3) 

Scenario 1, 

Project Alone, 

3,100 Wells 

CO 1-Hour 

8-Hour 

425.3 

113.5 

3,336 

1,381 

3,761.3 

1,494.5 

40,000 

10,000 

40,000 

10,000 

Scenario 1, 

Project Alone 

1,250 Wells 

CO 1-Hour 

8-Hour 

171.5 

45.8 

3,336 

1,381 

3,507.5 

1,426.8 

40,000 

10,000 

40,000 

10,000 

Scenario 2, 

Cumulative 

Sources, 

3,100 Wells 

CO 1-Hour 

8-Hour 

459.1 

266.0 

3,336 

1,381 

3,795.1 

1,647.0 

40,000 

10,000 

40,000 

10,000 

Scenario 2, 

Cumulative 

Sources, 

1,250 Wells 

CO 1-Hour 

8-Hour 

439.0 

262.1 

3,336 

1,381 

3,775.0 

1,643.1 

40,000 

10,000 

40,000 

10,000 

3.4.4 O3 

O3 is formed in the atmosphere as a result of photochemical reactions involving ambient 

concentrations of NO2 and VOCs. Because of the complex photochemical reactions necessary to 

form O3, compliance with ambient air quality standards cannot be determined with conventional 

dispersion models. Instead, a nomograph developed from the Reactive Plume Model (Scheffe 

1988) was used to predict maximum ozone impacts. This screening methodology, utilizes NOx 

and VOC emissions ratios to estimate ozone concentrations. 

NOx and VOC emissions are greatest during production activities and these emissions were used 

to estimate O3 impacts. Emissions from a 1-mi2 "patch" of 128 wells, which is the maximum 

proposed Project well density (128 wells per mi2; 5-acre spacing) and the emissions from the 

Luman compressor station were used. This scenario was selected since the Luman station is the 

largest compressor station and the largest NOx source within or adjacent to the JIDPA. The 

emissions assumed for the Luman station were 171.6 and 124.7 tons per year (tpy) of NOx and 

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Air Quality Technical Support Document, Jonah Infill Drilling Project 39 

VOC, respectively, and these emissions include anticipated future compression expansion. The 

emissions used for the 128 well section were 5.8 tpy (NOx) and 3,703.5 tpy (VOC), and assume 

that all wells have no VOC control. The ratio of total VOC emissions to total NOx emissions is 

3,828.2:177.3 or 21.6. At this ratio, the estimated maximum potential 1-hour O3 concentration is 

0.057 parts per million (ppm) or 111.8 micrograms/cubic meter (μg/m3). Using EPA's 

recommended screening conversion factor of 0.7 to convert 1-hour concentrations to 8-hour 

values (EPA 1977), the predicted 8-hour O3 concentration is 78.3 μg/m3

. Predicted maximum O3 

impacts are summarized in Table 3.7. 

The maximum O3 impacts shown in Table 3.7 represent the amount of O3 that could potentially 

form within and nearby the JIDPA as a result of the ratio of direct project emissions of NOx and 

VOC. Direct modeled concentrations shown in Table 3.7 were added to average hourly 

background O3 conditions monitored as part of the Green River Basin Visibility Study (ARS 

2002) during the period June 10, 1998, through December 31, 2001. This value 75.2 μg/m3

 is 

slightly higher than the background O3 concentration of 62.6 μg/m3

 used in the RPM modeling to 

derive the Scheffe nomograph. The highest, second highest O3 concentrations measured over the 

monitoring period of record, shown in Table 3.1, were not added concentrations estimated with 

the Scheffe method since it is overly conservative to add a maximum concentration to a 

screening level estimated concentration. O3 formation is a complex atmospheric chemistry 

process that varies greatly due to meteorological conditions and the presence of ambient 

atmospheric concentrations of many chemical species. Adding NOx and VOC emissions to the 

ambient air, where some amount of O3 has already formed, is not necessarily an indication that 

the potential for ozone formation has increased. In fact, it could decrease, since the ambient 

background conditions that caused O3 formation have changed, and the new mixture of chemical 

species in the atmosphere may not be conducive to O3 formation. In addition, the concentrations 

shown in Table 3.7 are likely overestimates of the actual O3 impacts that would occur, since the 

Reactive Plume Model nomograph used to derive these estimates was developed using 

meteorological conditions (high temperatures and stagnant conditions) more conducive to 

forming O3 than the conditions found in southwestern Wyoming. 

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40 Air Quality Technical Support Document, Jonah Infill Drilling Project 

Table 3.7 Maximum Modeled O3 Concentrations, Jonah Infill Drilling Project. 

Pollutant Averaging Time 

Direct Modeled 

(μg/m3) 

GRBVS Average 

1-hour Background 

(μg/m3

) 

Total Predicted 

(μg/m3) 

WAAQS 

(μg/m3) 

NAAQS 

(μg/m3) 

O3 1-Hour 111.8 75.2 187.0 235 235 

8-Hour 78.3 75.2 153.5 157 157 

3.5 HAP IMPACT ASSESSMENT 

AERMOD was used to determine HAP impacts in the immediate vicinity of the JIDPA emission 

sources for short-term (acute) exposure assessment and at the nearest residences to the JIDPA for 

calculation of long-term risk. Sources of HAPs include well-site fugitive emissions (BTEX and 

n-hexane), completion flaring and venting (BTEX and n-hexane), and compressor station 

combustion emissions (formaldehyde). Because maximum field-wide annual emissions of HAPs 

occur during the production phase, only HAP emissions from production were analyzed for 

long-term risk assessment. Short-term exposure assessments were performed for production 

HAP emissions using various well densities, and for an individual well construction completion 

(venting and flaring) event. 

Four modeling scenarios were developed for modeling short-term (1-hour) HAPs (BTEX, and 

n-hexane) from well-site fugitive emissions. These scenarios were developed to represent the 

complete range of well densities proposed for the Proposed Action and alternatives. The 

scenarios include one-section areas (1 mi2), with wells at 5-, 10-, 20-, and 40-acre surface 

spacing. These modeling scenarios represent well densities of 128, 64, 32, and 16 wells per 

section, respectively. The purpose of modeling this range of well density was to determine the 

maximum HAP short-term (1-hour) impacts that could occur within and near the JIDPA. 

Volume sources were used for modeling the well-site fugitive HAP emissions. The HAP 

emissions for wells with uncontrolled VOC emissions were used. Flat terrain receptors were 

spaced evenly and at a maximum distance of 100 m from a well, throughout each section. The 

source and receptor layouts utilized for the short-term HAP modeling are presented in Figure 3.5. 

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42 Air Quality Technical Support Document, Jonah Infill Drilling Project 

A single scenario was developed for modeling long-term (annual) fugitive HAP emissions. This 

scenario utilized the same 1-km spaced area sources placed throughout the JIDPA that were used 

for modeling NOx emissions from well site heaters (see Section 3.4.3 and Figure 3.4). Fugitive 

HAP model runs were performed for both 3,100 and 1,250 wells in production. Field-wide 

emissions scenarios were developed using the individual well emissions provided in Section 2.2, 

assuming 50% of condensate storage tanks are equipped with a control device and 25% of 

dehydrators are equipped with a control device. Receptor grids (3 x 3) using 1-km spacing were 

placed at the nearest residential locations along the New Fork River north of the JIDPA (see 

Figure 3.4). Receptor elevations were determined from U.S. Geological Survey (USGS) DEM 

data using AERMAP. 

For modeling formaldehyde emissions from compressor station sources, an analysis similar to 

that performed for NO2 and CO (see Sections 3.4.3 and 3.4.4) was used. Formaldehyde 

emissions from anticipated future compression expansions at the Bird Canyon, Falcon, Gobblers 

Knob, Jonah, Luman, and Paradise compressor stations were modeled in combination with 

emissions from the WDEQ-AQD inventory of existing regional compressor stations. These 

emissions are provided in Appendix D. Modeled Scenarios 1 and 2 were analyzed as described 

in Section 3.4. The modeling parameters and receptor grids developed for the NOx and CO 

impacts analyses and the receptor grids at the nearest residential locations along the New Fork 

River were utilized for modeling formaldehyde impacts. Long-term impacts are reported for the 

residential receptor locations. The source and receptor layout for modeling formaldehyde impacts 

is presented in Figure 3.4. 

Reference Exposure Levels (RELs) are defined as concentrations at or below which no adverse 

health effects are expected. Since no RELs are available for ethylbenzene and n-hexane, the 

available Immediately Dangerous to Life or Health (IDLH) values were used. These REL and 

IDLH values are determined by the National Institute for Occupational Safety and Health 

(NIOSH) and were obtained from EPA's Air Toxics Database (EPA 2002). Modeled short-term 

HAP concentrations are compared to REL and IDLH values in Table 3.8. As shown in Table 3.8 

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Air Quality Technical Support Document, Jonah Infill Drilling Project 

Table 3.8 Maximum Modeled 1-Hour HAP Concentrations, Jonah Infill Drilling Project. 

Direct Modeled Concentration by Modeling Scenario (μg/m3) REL or IDLH1 

HAP 5-Acre Spacing 10-Acre Spacing 20-Acre Spacing 40-Acre Spacing (μg/m3) 

Benzene 996 566 590 309 1,300 

Toluene 1,994 1,132 1,181 619 37,000 

Ethylbenzene 109 62 64 34 35,000 

Xylene 1,085 616 643 337 22,000 

n-Hexane 536 304 317 166 39,000 

Project Alone Cumulative Sources 

Formaldehyde 22.1 31.9 -- -- 94 

EPA (2002). 

the maximum predicted short-term HAP impacts within and near the JIDPA would be below the 

REL or IDLH values under all Project alternatives. 

Additional modeling analyses with AERMOD were performed to quantify the maximum short 

term HAP (BTEX and n-hexane) concentrations that could potential occur from well site 

completion venting and flaring. For wells that require these activities, it is estimated that venting 

operations could last up to 4 hours and flaring could last up to 80 hours. A single volume source 

was used for modeling completion venting and a single point source was used for modeling 

flaring. 100-m spaced receptors beginning at a distance of 100 m from each source were used. 

The results of these modeling analyses indicated that from flaring operations short-term HAP 

concentration would be below the REL or IDLH values. From venting operations short-term 

benzene concentrations could potentially exceed the thresholds within 500 meters of a 

completion venting operation, however, all other HAP concentrations would be below the REL 

or IDLH. 

Long-term (annual) modeled HAP concentrations at the nearest residence are compared to 

Reference Concentrations for Chronic Inhalation (RfCs). A RfC is defined by EPA as the daily 

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44 Air Quality Technical Support Document, Jonah Infill Drilling Project 

inhalation concentration at which no long-term adverse health effects are expected. RfCs exist 

for both non-carcinogenic and carcinogenic effects on human health (EPA 2002). The maximum 

predicted annual HAP concentrations at the nearest residential area are compared to the 

corresponding non-carcinogenic RfC in Table 3.9. 

As shown in Table 3.9 the maximum predicted long-term (annual) HAP impacts at the nearest 

residence locations along the New Fork River would be below the RfCs for all analyzed 

alternatives. In addition, formaldehyde impacts at the nearest residence are shown to be below 

the RfC thresholds when Project source impacts are combined with regional source impacts. 

Long-term exposures to emissions of suspected carcinogens (benzene and formaldehyde) were 

evaluated based on estimates of the increased latent cancer risk over a 70-year lifetime. This 

analysis presents the potential incremental risk from these pollutants, and does not represent a 

total risk analysis. The cancer risks were calculated using the maximum predicted annual 

concentrations and EPA's chronic inhalation unit risk factors (URF) for carcinogenic constituents 

Table 3.9 Maximum Modeled Long-term (Annual) HAP Concentrations, Jonah Infill 

Drilling Project. 

Direct Modeled Concentration at Nearest Residence by 

Modeling Scenario (μg/m3

) Non-carcinogenic RfC1 

HAP 3,100 Wells 1,250 Wells (μg/m3) 

Benzene 0.85 0.35 30 

Toluene 1.73 0.71 400 

Ethylbenzene 0.09 0.04 1,000 

Xylene 0.93 0.38 430 

n-Hexane 0.35 0.14 200 

Project Alone Cumulative Sources 

Formaldehyde 0.003 0.02 9.8 

EPA (2002). 

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Air Quality Technical Support Document, Jonah Infill Drilling Project 45 

(EPA 2002). Estimated cancer risks were evaluated based on the Superfund National Oil and 

Hazardous Substances Pollution Contingency Plan (EPA 1993), where a cancer risk range of 1 x 

10-6 to 1 x 10-4 is generally acceptable. Two estimates of cancer risk are presented: 1) a most 

likely exposure (MLE) scenario; and 2) a maximum exposed individual (MEI) scenario. The 

estimated cancer risks are adjusted to account for duration of exposure and time spent at home. 

The adjustment for the MLE scenario is assumed to be 9 years, which corresponds to the mean 

duration that a family remains at a residence (EPA 1993). This duration corresponds to an 

adjustment factor of 9/70 = 0.13. The duration of exposure for the MEI scenario is assumed to 

be 50 years (i.e., the LOF), corresponding to an adjustment factor of 50/70 = 0.71. A second 

adjustment is made for time spent at home versus time spent elsewhere. For the MLE scenario, 

the at-home time fraction is 0.64 (EPA 1993), and it is assumed that during the rest of the day the 

individual would remain in an area where annual HAP concentrations would be one quarter as 

large as the maximum annual average concentration. Therefore, the final MLE adjustment factor 

is (0.13) x [(0.64 x 1.0) + (0.36 x 0.25)] = 0.0949. The MEI scenario assumes that the individual 

is at home 100% of the time, for a final MEI adjustment factor of (0.71 x 1.0) = 0.71. 

For each constituent, the cancer risk is computed by multiplying the maximum predicted annual 

concentration by the URF and by the overall exposure adjustment factor. The cancer risks for 

both constituents are then summed to provide an estimate of the total inhalation cancer risk. 

The modeled long-term risk from benzene and formaldehyde are shown in Table 3.10 for both 

the 3,100-well and 1,250-well scenarios. For each scenario, the maximum predicted 

formaldehyde concentration representative of cumulative impacts was used. Under the MLE 

scenario, the estimated cancer risk associated with long-term exposure to benzene and 

formaldehyde is below 1 x 10-6 for both 3,100-well and 1,250-well cases. Under the MEI 

analyses, for each modeling scenario, the incremental risk for formaldehyde is less than 1 x 10-6, 

and both the incremental risk for benzene and the combined incremental risk fall on the lower 

end of the cancer risk range of 1 x 10-6 to 1 x 10-4. 

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Air Quality Technical Support Document, Jonah Infill Drilling Project 

Table 3.10 Long-term Modeled MLE and MEI Cancer Risk Analyses, Jonah Infill Drilling 

Project. 

Modeled 

Concentration Exposure 

Modeling Scenario Analysis HAP Constituent (μg/m3) Unit Risk Factor 1/(μg/m3) Adjustment Factor Cancer Risk 

3,100 Wells MLE Benzene 0.85 7.8 x 10-6 0.0949 0.63 x 10-6 

Formaldehyde 0.02 1.3 x 10-5 0.0949 0.02 x 10-6 

Total Combined 0.6 x 10-6 

3,100 Wells MEI Benzene 0.85 7.8 x 10-6 0.71 4.73 x 10-6 

Formaldehyde 0.02 1.3 x 10-5 0.71 0.18 x 10-6 

Total Combined 4.9 x 10-6 

1,250 Wells MLE Benzene 0.35 7.8 x 10-6 0.0949 0.26 x 10-6 

Formaldehyde 0.02 1.3 x 10-5 0.0949 0.02 x 10-6 

Total Combined 0.3 x 10-6 

1,250 Wells MEI Benzene 0.35 7.8 x 10-6 0.71 1.94 x 10-6 

Formaldehyde 0.02 1.3 x 10-5 0.71 0.18 x 10-6 

Total Combined1 2.1 x 10-6 

Total risk is calculated here; however, the additive effects of multiple chemicals are not fully understood and this should be taken into 

account when viewing these results. 

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Air Quality Technical Support Document, Jonah Infill Drilling Project 47 

4.0 MID-FIELD AND FAR-FIELD ANALYSES


The purpose of the mid-field and far-field analyses were to quantify potential air quality impacts 

on Class I and Class II areas from air pollutant emissions of NOx, SO2, PM10, and PM2.5 expected 

to result from the development of the Project. The analyses were performed using the EPA 

CALMET/CALPUFF modeling system to predict air quality impacts from Project and regional 

sources at far-field PSD Class I and sensitive Class II areas and at several mid-field PSD Class II 

areas. The PSD Class I areas and sensitive Class II areas analyzed are shown on Map 1.2 and 

include: 

• the Bridger Wilderness Area (Class I); 

• the Fitzpatrick Wilderness Area (Class I); 

• the Popo Agie Wilderness Area (Class II); 

• the Wind River Roadless Area (Class II) 

• Grand Teton National Park (Class I); 

• the Teton Wilderness Area (Class I); 

• Yellowstone National Park (Class I); and 

• the Washakie Wilderness Area (Class I). 

Modeled pollutant concentrations at these sensitive areas were compared to applicable WAAQS, 

NAAQS, and PSD Class I and Class II increments, and were used to assess potential impacts to 

AQRVs (i.e., visibility [regional haze] and acid deposition). Note that visibility is protected in 

Class I areas; Class II areas are included here to further define impacts in potentially sensitive 

areas. In addition, analyses were performed for seven lakes designated as acid sensitive located 

within the sensitive PSD Class I and Class II wilderness areas to assess potential lake 

acidification from acid deposition impacts (see Map 1.2). These lakes include: 

• Deep Lake in the Bridger Wilderness Area; 

• Black Joe Lake in the Bridger Wilderness Area; 

• Hobbs Lake in the Bridger Wilderness Area; 

• Upper Frozen Lake in the Bridger Wilderness Area; 

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48 Air Quality Technical Support Document, Jonah Infill Drilling Project 

• Lazy Boy Lake in the Bridger Wilderness Area; 

• Ross Lake in the Fitzpatrick Wilderness Area; and 

• Lower Saddlebag Lake in the Popo Agie Wilderness Area. 

The mid-field analysis assessed direct project and regional source impacts at in-field locations 

within the JIDPA and other mid-field locations defined as Class II areas (regional communities) 

(see Map 1.2), which include the Wyoming communities of: 

• Big Piney; 

• Big Sandy; 

• Boulder; 

• Bronx; 

• Cora; 

• Daniel; 

• Farson; 

• La Barge; 

• Merna; and 

• Pinedale. 

Predicted pollutant impacts at in-field locations were compared to applicable ambient air quality 

standards, and mid-field Wyoming community locations impacts to visibility (regional haze) 

were assessed. 

4.1 MODELING METHODOLOGY 

The EPA-approved CALMET/CALPUFF modeling system (CALMET Version 5.53, Level 

030709, and CALPUFF Version 5.711, Level 030625) was used for the mid-field and far-field 

modeling analyses. The CALMET meteorological model was used to develop wind fields for a 

year of meteorological data (1995) and the CALPUFF dispersion model combined these wind 

fields with Project-specific and regional emissions inventories of SO2, NOx, PM10, and PM2.5 to 

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estimate ambient concentrations and AQRV impacts at mid-field and far-field receptor locations. 

The study area is shown in Map 1.2. 

The CALMET and CALPUFF models were utilized in this analysis generally following the 

methods described in the Protocol (Appendix A) and the following guidance sources: 

• Guideline on Air Quality Models, 40 Code of Federal Regulations (C.F.R.), 

Part 51, Appendix W (EPA 2003a); 

• Interagency Work Group on Air Quality Modeling (IWAQM) Phase 2 Summary 

Report and Recommendations for Modeling Long Range Transport Impacts, 

EPA-454/R-98-019, Office of Air Quality Planning and Standards, December 

1998 (IWAQM 1998); and 

• Federal Land Managers - Air Quality Related Values Workgroup (FLAG), 

Phase I Report, December 2000 (FLAG 2000). 

The CALMET wind fields developed for this analysis follow the CALMET methodologies 

established as part of the Southwest Wyoming Technical Air Forum (SWWYTAF) for southwest 

Wyoming, and were further enhanced through the use of additional meteorological datasets and 

revised CALMET model code. 

4.2 PROJECT ALTERNATIVE MODELING SCENARIOS 

Modeling scenarios were developed for a range of proposed project development including the 

Proposed Action, Alternative A, Alternative B, Alternative C, and Alternative F. WDRs of 

250 wells/year, 150 wells/year, and 75 wells/year were analyzed. The Proposed Action, and 

Alternatives A, B, and F are proposals for 3,100 new wells; Alternative C proposes 1,250 new 

wells. As discussed in Section 1.2, modeling analyses were not performed for every NEPA 

alternative analyzed because there is considerable similarity of modeled air quality components 

within many proposed alternatives, and due to the additional time and resources required for 

performing all of the potential analyses. A summary of the modeled Project Alternatives is 

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provided in Table 4.1 that indicates the expected impact ranges for the alternatives that were not 

modeled. 

Maximum field-wide emissions scenarios were determined for each analyzed alternative and 

reflect the last year of field development, at the maximum WDR, combined with nearly full-field 

production. An additional field-wide emissions scenario was developed for the Proposed Action 

assuming only full-field development (i.e., maximum field-wide productions emissions). 

Table 4.1 Summary of Modeled Project Alternatives, Jonah Infill Drilling Project, Sublette 

County, Wyoming, 2004. 

Alternative Number of Wells and Type 

Modeled 

(Y/N) 

Well Development 

Rates Modeled 

(wells/year) Comments 

Proposed Action 395 directional, 2,705 straight1 Yes 0, 250 Alternative A WDR250 used 

to approximate the Proposed 

Action WDR250 scenario 

Alternative A 3,100 straight Yes 250, 150, 75 

Alternative B 3,100 directional Yes 250, 150, 75 

Alternative C 1,250 straight Yes 250, 150, 75 

Alternative D 2,200 straight wells No -- Alternative D impacts are 

expected to fall between 

Alternative A and 

Alternative C 

Alternative E 2,834 directional, 266 straight2 No -- Alternative E impacts are 

expected to fall between 

Alternative B and 

Alternative F 

Alternative F 2,072 directional, 1,028 straight Yes 250, 150, 75 

Alternative G and 

Preferred Alternative 

547 directional, 2,553 straight No - Alternative G impacts are 

expected to fall between 

Alternative A and 

Alternative F 

1 Modeled as all straight (3,100 wells). 2 Modeled as 50% straight and 50% directional (1,550 straight wells and 1,550 directional wells). 

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The maximum emissions scenarios conservatively assume that both production emissions 

(producing wellsites and operational ancillary equipment including compressor stations) and 

construction emissions (drilling rigs and pit flaring operations) occur simultaneously throughout 

the year. Anticipated future compression expansions for the Bird Canyon, Falcon, Jonah, and 

Luman compressor stations were included in the field-wide emissions scenarios. Future 

compression in the field was assumed to operate at 90% of fully permitted capacity, which 

Operators indicated was a reasonable assumption based on field operation expectations. The 

WDR250 case assumed 20 drilling rigs and 3 pit flares operating continuously throughout the 

year, WDR150 assumed 12 drilling rigs and 2 pit flares, and WDR75 assumed 6 drilling rigs and 

1 pit flare. 

Development rates considered both straight and directional drilling operations generally 

consistent with the proposed project alternatives. The Proposed Action, Alternative A, and 

Alternative C scenarios assume all straight drilling. The Alternative B scenario assumes all 

directional drilling, and the Alternative F scenarios assume 50% straight drilling and 50% 

directional drilling. The scenario developed for Alternative A, with WDR250, approximates the 

Proposed Action. 

The maximum field-wide emissions scenarios are summarized in Table 4.2 for the Proposed 

Action and Alternatives A, B, C, and F. The emissions used to develop these field-wide 

scenarios are described in Chapter 2.0. 

4.3 METEOROLOGICAL MODEL INPUT AND OPTIONS 

CALMET was used to develop wind fields for the study area shown in Map 1.2. Model domain 

extent was selected based on available refined mesoscale meteorological model (MM5) data 

from the SWWYTAF study and the locations of the PSD Class I and sensitive Class II 

Wilderness areas that were selected for air quality analyses. 

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The modeling domain was processed to a uniform horizontal grid using 4-km resolution, based 

on a Lambert Conformal Projection defined with a central longitude/latitude at (-108.55°/42.55°) 

and first and second latitude parallels at 30° and 60°. The modeling grid consisted of 116 x 112 

4-km grid cells that cover the Project area and all analyzed Class I and sensitive Class II areas. 

The total area of the modeling domain is 288 x 278 mi (464 x 448 km). Ten vertical layers were 

used, with heights of 20, 40, 100, 140, 320, 580, 1,020, 1,480, 2,220, and 2,980 m. 

The CALMET analysis utilized the MM5 data, (which was processed at a 20-km horizontal 

grid spacing), data from 55 surface meteorological stations and 155 precipitation stations, 

and four upper air meteorological stations to supplement MM5 upper air estimates. USGS 

1:250,000-Scale Land Use and Land Cover (LULC) data, and USGS 1o DEM data were used for 

land use and terrain data in the development of the CALMET wind fields. Listings of the surface 

and upper air meteorological stations, and the precipitation stations that were used in this analysis 

are provided in Appendix E. The CALMET model was run following control switch settings that 

were developed as part of SWWYTAF to develop the one-year (1995) wind field data set. 

The modeling domain extended as far north as possible given the available refined MM5 data. 

The IWAQM guidance for CALMET/CALPUFF recommends that the horizontal domain of the 

model grid extend 50 to 80 km beyond the receptors and sources being modeled, for modeling 

potential recirculation wind flow effects. Because the area of Yellowstone National Park 

included in the modeling is along the boundary of the modeling domain, and the northern 

portions of Grand Teton National Park, and the Teton and Washakie Wilderness Areas are less 

than 50 km from the modeling grid boundary, the recirculation wind patterns may not be 

completely resolved by CALMET in those areas. However, because the direct wind flow 

patterns that could transport potential Project and regional source emissions to these areas are 

fully characterized in the modeling domain, any potential impacts from Project sources in these 

areas would be fully captured. 

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4.4 DISPERSION MODEL INPUT AND OPTIONS 

The CALPUFF model was used to model Project-specific and regional emissions of NOx, SO2, 

PM10, and PM2.5. CALPUFF was run using the IWAQM-recommended default control file 

switch settings for all parameters. Chemical transformations were modeled based on the 

MESOPUFF II chemistry mechanism for conversion of SO2 to sulfate (SO4) and NOx to nitric 

acid (HNO3) and nitrate (NO3). Each of these pollutant species was included in the CALPUFF 

model runs. NOx, HNO3, and SO2 were modeled with gaseous deposition, and SO4, NO3, PM10, 

and PM2.5 were modeled using particle deposition. The PM10 emissions input to CALPUFF 

included only the PM10 emissions greater than the PM2.5 (i.e., modeled PM10 = PM10 emission 

rate – PM2.5 emission rate). Total PM10 impacts were determined in the post-processing of 

modeled impacts, as discussed in Section 4.5. 

4.4.1 Chemical Species 

The CALPUFF chemistry algorithms require hourly estimates of background O3 and ammonia 

(NH3) concentrations for the conversion of SO2 and NO/NO2 to sulfates and nitrates, 

respectively. Background O3 data, for the meteorology 1995 modeling year, were available for 

six stations within the modeling domain: 

• Pinedale, Wyoming, 

• Centennial, Wyoming, 

• Yellowstone National Park, Wyoming, 

• Craters of the Moon National Park, Idaho, 

• Highland, Utah, and 

• Mount Zirkel Visibility Study, Hayden, Colorado. 

Hourly O3 data from these stations was used in the CALPUFF modeling, with a default value of 

44.7 parts per billion (ppb) (7 a.m.-7 p.m. mean) used for missing hours. A background NH3 

concentration of 1.0 ppb was used as suggested in the IWAQM guidance for arid lands. 

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4.4.2 Model Receptors 

Input to CALPUFF were model receptors at which the concentration, deposition, and AQRV 

impacts were calculated. Receptors were placed along the boundaries of all Class I and other 

sensitive areas at 2-km spacing, and within the boundaries of these areas on a 4-km Cartesian 

grid. Discrete receptors were placed on a Cartesian grid at 1-km spacing within the JIDPA. 

Individual receptor points were determined for each of the seven acid-sensitive lakes. Grids of at 

least 3 x 3 1-km spaced receptors were used for modeling each of the mid-field Wyoming 

communities. Receptor elevations for all sensitive Class I and Class II areas were determined 

from 1:250,000 scale USGS DEM data. Elevations for the sensitive lake receptors were derived 

from 7.5-minute USGS topographical maps. All model receptors utilized in the mid-field and 

far-field analyses are shown in Figures 4.1 and 4.2. 

4.4.3 Source Parameters 

CALPUFF source parameters were determined for all Project and regional source emissions of 

NOx, SO2, PM10, and PM2.5. Project sources were input to CALPUFF using point sources to 

idealize compressor stations, drilling rigs, pit flares, and water disposal well engines. 

Additionally, 148 1-km2 area sources at 1-km spacing were placed throughout the JIDPA to 

idealize well site heater, vehicle traffic, and wind erosion emissions. Locations of Jonah Field 

compressor stations with anticipated future expansions are shown in Figure 4.3. Compressor 

station emissions and modeled parameters are provided in Appendix D. Parameters used in 

modeling the drilling rigs, pit flares, water disposal well, and wind erosion are given in 

Appendix B and illustrated in Figure 4.4. Field-wide emissions from well heaters and traffic for 

each analyzed Project alternative are summarized in Section 4.2. Monthly emissions scalars 

were used to adjust the heater emissions for seasonal variations. 

Non-project regional emissions were input to CALPUFF using area sources to idealize 

non-compression RFD sources and county-wide well sites, and point sources to idealize 

state-permitted sources, RFD compression sources, and RFFA. The source parameters used in 

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modeling all state-permitted and RFFA sources are provided in Appendix C. Non-compression 

RFD emissions were modeled using area sources developed for each proposed field development 

as a "best fit" to the respective project area. The area sources developed for each RFD project are 

shown in Figure 4.5. County-wide well emissions were modeled using area sources developed as 

a best fit to the respective county area. The area sources used to model county-wide well site 

emissions are shown in Figure 4.6. Seasonal emission-rate adjustment factors were applied to 

emissions from well site heaters to account for seasonal variations in heater use. Source 

elevations for all RFD and county-wide area sources were determined from 1:250,000 scale 

USGS DEM data. 

4.5 BACKGROUND DATA 

4.5.1 Criteria Pollutants 

Ambient air concentration data collected at monitoring sites in the region provide a measure of 

the background conditions during the most recent available time period. Regional 

monitoring-based background values for criteria pollutants (PM10, PM2.5, NO2, and SO2) were 

collected at monitoring sites in Wyoming and northwestern Colorado, and are summarized in 

Table 4.3. Although O3 is also a criteria pollutant, it is not utilized in the far-field modeling as a 

background concentration and is therefore excluded from this table. These ambient air 

background concentrations were added to modeled pollutant concentrations (expressed in μg/m3

) 

to arrive at total ambient air quality impacts for comparison to NAAQS and WAAQS. 

4.5.2 Visibility 

Background visibility data representative of the study area were collected from IMPROVE 

monitoring sites located at Yellowstone National Park and the Bridger Wilderness Area 

(Table 4.4). Background visibility data were used in combination with modeled pollutant 

impacts to estimate change in visibility conditions (measured as change in light extinction). The 

IMPROVE background visibility data are provided as reconstructed aerosol total extinction data, 

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Table 4.3 Far-field Analysis Background of Ambient Air Quality Concentrations (μg/m3). 

Pollutant Averaging Period Measured Background Concentration 

NO2 

1 Annual 3.4 

PM10 2 24-hour 

Annual 

33 

16 

PM2.5 2 24-hour 

Annual 

13 

5 

SO2 

3 3-hour 

24-hour 

132 

43 

Annual 9 

1 Data collected at Green River Basin Visibility Study site, Green River, Wyoming during period JanuaryDecember 2001 (ARS 2002). 2 Data collected by WDEQ-AQD at Emerson Building, Cheyenne, Wyoming, Year 2001. 3 Data collected at LaBarge Study Area at the Northwest Pipeline Craven Creek Site 1982-1983. 

Table 4.4 IMPROVE Background Aerosol Extinction Values.1 

IMPROVE Site Quarter 

Hygroscopic 

(Mm-1)

2 

Non-hygroscopic 

(Mm-1)

2 Monitoring Period 

Bridger Wilderness Area 1 0.845 1.666 1989-2002 

2 1.730 3.800 1988-2002 

3 1.902 5.637 1988-2002 

4 0.915 2.035 1988-2002 

Yellowstone National Park 1 1.126 2.973 1988-2002 

2 1.502 4.531 1988-2002 

3 1.811 7.330 1988-2002 

4 1.033 2.990 1988-2002 

1 Cooperative Institute for Research in the Atmosphere (2003). 2 Mm-1 = inverse megameters. 

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based on the quarterly mean of the 20% cleanest days measured at the Bridger Wilderness Area 

and Yellowstone National Park IMPROVE sites for the historical monitoring period of record 

through December 2002. 

4.5.3 Lake Chemistry 

The most recent lake chemistry background acid neutralizing capacity (ANC) data were obtained 

for each sensitive lake included in the analysis. The 10th percentile lowest ANC values were 

calculated for each lake following procedures provided by the USDA Forest Service. These 

ANC values and the number of samples used in the calculation of the 10th percentile lowest ANC 

values are provided in Table 4.5. 

4.6 IMPACT ASSESSMENT 

CALPUFF modeling was performed to compute direct Project impacts for each of the analyzed 

alternatives and for estimating cumulative impacts from potential Project and regional sources. 

The analyzed alternatives, as described in Section 4.2, included the Proposed Action, and 

Alternatives A, B, C, and F. Maximum emissions scenarios for each alternative included the last 

Table 4.5 Background ANC Values for Acid Sensitive Lakes. 

10th Percentile 

Latitude Longitude Lowest ANC Value Number of Monitoring 

Wilderness Area Lake (Deg-Min-Sec) (Deg-Min-Sec) (μeq/l) Samples Period 

Bridger Black Joe 42o44'22" 109o10'16" 67.0 61 1984-2003 

Bridger Deep 42o43'10" 109o10'15" 59.9 58 1984-2003 

Bridger Hobbs 43o02'08" 109o40'20" 69.9 65 1984-2003 

Bridger Lazy Boy 43o19'57" 109o43'47" 18.8 1 1997 

Bridger Upper Frozen 42o41'13" 109o09'39" 5.0 6 1997-2003 

Fitzpatrick Ross 43o22'41" 109o39'30" 53.5 44 1988-2003 

Popo Agie Lower Saddlebag 42o37'24" 108o59'38" 55.5 43 1989-2003 

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year of field development, at the maximum annual construction activity rate, combined with 

nearly full-field production. Three well development rates (WDR250, WDR150, and WDR75), 

were analyzed. An additional full-field development emissions scenario was developed for the 

Proposed Action assuming maximum production emissions. Regional emissions inventories of 

existing state-permitted RFD and RFFA sources, as described in Chapter 2.0, were modeled 

alone to estimate cumulative impacts for the No Action Alternative. These regional inventories 

were modeled in combination with Project alternatives to provide cumulative impact estimates 

for each alternative. A total of 27 modeling scenarios were evaluated in this analysis. A list of 

these scenarios is summarized in Table 4.6. 

For each far-field sensitive area, CALPUFF-modeled concentration impacts were post-processed 

with POSTUTIL and CALPOST to derive: 1) concentrations for comparison to ambient air 

quality standards (WAAQS and NAAQS), PSD Class I significance thresholds, and PSD Class I 

and II Increments; 2) deposition rates for comparison to sulfur (S) and nitrogen (N) deposition 

levels of concern and to calculate changes to ANC at sensitive lakes; and 3) light extinction 

changes for comparison to visibility impact thresholds. For the mid-field analyses, CALPOST 

concentrations were post-processed to estimate light extinction changes at regional communities 

for comparison to the visibility impact thresholds. For in-field locations, CALPUFF 

concentrations were post-processed to compute maximum concentration impacts for comparison 

to WAAQS and NAAQS. 

4.6.1 Concentration 

The CALPOST and POSTUTIL post-processors were used to summarize concentration impacts 

of NO2, SO2, PM10, and PM2.5 at PSD Class I and sensitive PSD Class II areas, and at in-field 

locations. Predicted impacts are compared to applicable ambient air quality standards, PSD 

Class I and Class II increments, and significance levels as shown in Table 4.7. 

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Table 4.6 Modeling Scenarios Analyzed for Project Alternative and Regional Emissions, 

Jonah Infill Drilling Project, Sublette County, Wyoming, 2004.1 

Modeling 

Scenario 

Source Impacts 

Evaluated Project Alternative 

Number of New Wells 

in Production 

Number of Wells under 

Construction 

Well Drilling 

Rig Type 

1 Direct Project Proposed Action 3,100 0 --

2 Direct Project Proposed Action and 

Alternative A 

2,850 250/year Straight 

3 Direct Project Alternative A 2,950 150/year Straight 

4 Direct Project Alternative A 3,025 75/year Straight 

5 Direct Project Alternative B 2,850 250/year Directional 

6 Direct Project Alternative B 2,950 150/year Directional 

7 Direct Project Alternative B 3,025 75/year Directional 

8 Direct Project Alternative C 1,000 250/year Straight 

9 Direct Project Alternative C 1,100 150/year Straight 

10 Direct Project Alternative C 1,175 75/year Straight 

11 Direct Project Alternative F 2,850 250/year 50% Straight/ 

50% Directional 

12 Direct Project Alternative F 2,950 150/year 50% Straight/ 

50% Directional 

13 Direct Project Alternative F 3,025 75/year 50% Straight/ 

50% Directional 

14 Cumulative No Action1 0 0 --

15 Cumulative Proposed Action 3,100 0 --

16 Cumulative Proposed Action and 

Alternative A 

2,850 250/year Straight 

17 Cumulative Alternative A 2,950 150/year Straight 

18 Cumulative Alternative A 3,025 75/year Straight 

19 Cumulative Alternative B 2,850 250/year Directional 

20 Cumulative Alternative B 2,950 150/year Directional 

21 Cumulative Alternative B 3,025 75/year Directional 

22 Cumulative Alternative C 1,000 250/year Straight 

23 Cumulative Alternative C 1,100 150/year Straight 

24 Cumulative Alternative C 1,175 75/year Straight 

25 Cumulative Alternative F 2,850 250/year 50% Straight/ 

50% Directional 

26 Cumulative Alternative F 2,950 150/year 50% Straight/ 

50% Directional 

27 Cumulative Alternative F 3,025 75/year 50% Straight/ 

50% Directional 

Includes 198 wells in Jonah Field which began production after 2001 as RFD. 

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Table 4.7	 NAAQS, WAAQS, PSD Class I and Class II Increments, and PSD Class I and 

Class II Significance Levels for Comparison to Far-field Analysis Results 

(μg/m3

). 

PSD Class I PSD Class II PSD Class I PSD Class II 

Pollutant/Averaging Time NAAQS WAAQS Increment Increment Significance Level1 Significance Level 

NO2 

Annual2 100 100 2.5 25 0.1 1.0 

SO2 

3-hour3 1,300 1,300 25 512 1.0 25.0 

24-hour3 365 260 5 91 0.2 5.0 

Annual2 80 60 2 20 0.1 1.0 

PM10 

24-hour3 150 150 8 30 0.3 5.0 

Annual2 50 50 4 17 0.2 1.0 

PM2.5 

24-hour4 65 65 -- -- -- --

Annual 4 15 15 -- -- -- --

1 Proposed Class I significance levels from 61 Federal Register 142, pg. 38292, July 23, 1996. 2 Annual arithmetic mean. 3 No more than one exceedance per year is allowed. 4 Standard not yet enforced in Wyoming; -- = no current or proposed value. 

PM10 concentrations were computed by adding predicted CALPUFF concentrations of PM10 

(fraction of PM greater than PM2.5), PM2.5, SO4, and NO3. PM2.5 concentrations were calculated 

as the sum of modeled PM2.5, SO4, and NO3 concentrations. In post-processing the PM10 impacts 

at all far-field receptor locations, Project alternative traffic emissions of PM10 (production and 

construction) were not included in the total estimated impacts, only the PM2.5 impacts were 

considered. This assumption was based on supporting documentation from the Western 

Regional Air Partnership (WRAP) analyses of mechanically generated fugitive dust emissions 

that suggest that particles larger than PM2.5 tend to deposit out rapidly near the emissions source 

and do not transport over long distances (Countess et al. 2001). This phenomenon is not 

modeled adequately in CALPUFF; therefore, to avoid overestimates of PM10 impacts at far-field 

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locations, these sources were not considered in the total modeled impacts. However, the total 

PM10 impacts from traffic emissions were included in all in-field concentration estimates. 

Far-field Results 

The maximum predicted concentrations of NO2, SO2, PM10, and PM2.5 at each of the analyzed 

PSD Class I and sensitive Class II areas, for each of the 27 modeled direct Project alternatives 

and cumulative source scenarios, are provided in Appendix F. Predicted direct impacts are 

compared to applicable PSD Class I and Class II increments and significance levels, then added 

to representative background pollutant concentrations (see Table 4.3), the total concentration is 

compared to applicable NAAQS and WAAQS. Cumulative impacts from all analyzed 

alternatives are compared directly to applicable PSD Class I and Class II increments, and to the 

NAAQS and WAAQS when background pollutant concentrations are added. Tables F.1.1-F.1.27 

provide the maximum modeled NO2 concentrations at each of the sensitive areas. The maximum 

modeled SO2 concentrations are provided in Tables F.2.1-F.2.27, and the maximum modeled 

PM10 and PM2.5 impacts are provided in Tables F.3.1-F.3.27, and Tables F.4.1-F.4.27, 

respectively. Summaries of results by alternative for NOx, SO2, PM10, and PM2.5 are provided in 

Tables F.10.1-F10.2, F.10.3-F.10.4, F.10.5-F.10.6, and F.10.7-F.10.8, respectively. 

The modeling results indicate that neither direct Project impacts nor cumulative source impacts 

would exceed any ambient air quality standards (WAAQS and NAAQS) or PSD Increment (see 

Tables F.1.1-F.4.27). Direct Project NO2 impacts at the Bridger Class I Wilderness Area are 

above the proposed PSD Class I significance level of 0.1 μg/m3 for NO2. A direct Project 

maximum NO2 concentration of 0.15 μg/m3

 is predicted under Alternative B (see Table F.1.5). 

In addition, direct Project impacts of 24-hour PM10, concentrations are above the proposed 

Class I significance level of 0.3 μg/m3 under each alternative, with a maximum of 1.70 μg/m3 

predicted under Alternative B WDR250 (see Table F.3.5). 

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In-Field Results 

The maximum predicted concentrations of NO2, SO2, PM10, and PM2.5 within and nearby the 

JIDPA, for each of the 27 modeled direct Project and cumulative scenarios are provided in 

Appendix F, Tables F.5.1 - F.5.27. A summary of results by alternative is provided in 

Tables F.10.9 - F.10.10. Predicted direct Project and cumulative impacts are added to 

representative background pollutant concentrations and are compared to applicable NAAQS and 

WAAQS. As shown in Tables F.5.1 - F.5.27, there would be no exceedances of the NAAQS or 

WAAQS within and nearby the JIDPA from field-wide Project sources or cumulative sources. 

This analysis further supports the compliance demonstrations shown in Section 3.4 for maximum 

near-field impacts. 

4.6.2 Deposition 

Maximum predicted S and N deposition impacts were estimated for each analyzed Project 

alternative and cumulative source scenario. The POSTUTIL utility was used to estimate total S 

and N fluxes from CALPUFF predicted wet and dry fluxes of SO2, SO4, NOx, NO3, and HNO3. 

CALPOST was then used to summarize the annual S and N deposition values from the 

POSTUTIL program. Predicted direct Project impacts were compared to the NPS deposition 

analysis thresholds (DATs) for total N and S deposition in the western U.S., which are defined as 

0.005 kilograms per hectare per year (kg/ha-year) for both N and S. Cumulative deposition 

impacts from Project alternative and regional sources were compared to USDA Forest Service 

levels of concern, defined as 5 kg/ha-yr for S and 3 kg/ha-yr for N (Fox et al. 1989) below which 

no adverse impacts from acid deposition are likely. 

The maximum predicted N and S deposition impacts for each of the analyzed alternatives are 

provided in Appendix F, Tables F.6.1 – F.6.4. A summary of results by alternative is provided in 

Tables F.10.11 - F.10.14. Modeling results for Project sources under each Alternative indicate 

that there would be no direct project S deposition impacts above the DAT, and that all 

cumulative N and S deposition impacts would be well below the cumulative analysis levels of 

concern. Modeling results do indicate that there could be direct project N deposition impacts at 

the Bridger and Fitzpatrick Class I Wilderness Areas, and at the Wind River Roadless 

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Area that are above the DAT under each Project alternative (see Table F.6.1). The maximum 

predicted nitrogen deposition impacts occurred under Alternative B and are 0.04, 0.02, and 

0.01 kg/ha-yr, at Bridger and Fitzpatrick Wilderness Areas, and at the Wind River Roadless 

Area, respectively (see Table F.6.1). 

4.6.3 Sensitive Lakes 

The CALPUFF-predicted annual deposition fluxes of S and N at sensitive lake receptors listed in 

Section 4.2.3 were used to estimate the change in ANC. The change in ANC was calculated 

following the January 2000, USDA Forest Service Rocky Mountain Region's Screening 

Methodology for Calculating ANC Change to High Elevation Lakes, User's Guide (USDA Forest 

Service 2000). The predicted changes in ANC are compared with the USDA Forest Service's 

Level of Acceptable Change (LAC) thresholds of 10% for lakes with ANC values greater than 

25 microequivalents per liter (ì eq/l) and 1 ì eq/l for lakes with background ANC values of 

25 ì eq/l or less. Of the seven lakes listed in Table 4.5 and identified by the USDA Forest Service 

as acid sensitive, Upper Frozen and Lazy Boy lakes are considered extremely acid sensitive. 

ANC calculations were performed for each of the analyzed Project alternative and cumulative 

source scenarios, with the results presented in Appendix F, Tables F.7.1 – F.7.27. A summary of 

results by alternative is provided in Tables F.10.15 - F.10.16. The modeling results indicate that 

deposition impacts from direct Project and cumulative emissions would not exceed the LAC 

threshold for ANC at any of the sensitive lakes. 

4.6.4 Visibility 

The CALPUFF model-predicted concentration impacts at far-field PSD Class I and sensitive 

Class II areas and at mid-field regional community locations were post-processed with 

CALPOST to estimate potential impacts to visibility (regional haze) for each analyzed alternative 

and cumulative source scenario for comparison to visibility impact thresholds. CALPOST 

estimated visibility impacts from predicted concentrations of PM10, PM2.5, SO4, and NO3. 

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PM10 emissions from Project traffic emissions were not included in the total estimated impacts 

(see Section 4.6.1), only the impacts to visibility from PM2.5 were considered. 

Visibility impairment calculations were performed using estimated natural background visibility 

conditions obtained from FLAG (2000) (FLAG method) and measured background visibility 

conditions from the Bridger Wilderness Area and Yellowstone National Park IMPROVE sites 

(IMPROVE method). IMPROVE-method data are based on the quarterly mean of the 20% 

cleanest days as shown in Table 4.4. The IMPROVE background visibility data are provided as 

reconstructed aerosol total extinction data, based on the quarterly mean of the 20% cleanest days 

measured at the Bridger Wilderness Area and Yellowstone National Park IMPROVE sites for the 

historical monitoring period of record through December 2002. 

For the FLAG method, estimated natural background visibility values as provided in 

Appendix 2.B of FLAG (2000), and monthly relative humidity factors as provided in the 

Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule (EPA 

2003b) were used. The natural background visibility data used with the FLAG visibility analysis 

for each area analyzed are shown in Table 4.8. 

The IMPROVE method used the measured background conditions at the Bridger Wilderness 

Area and at the Yellowstone National Park site, and the monthly relative humidity factors as 

provided in EPA (2003b). Visibility data from the Bridger Wilderness Area IMPROVE site were 

used for the Bridger, Fitzpatrick, and Popo Agie Wilderness Areas and for the Wind River 

Roadless Area, and visibility data from the Yellowstone National Park IMPROVE site were used 

for the Teton and Washakie Wilderness Areas and for Grand Teton and Yellowstone National 

Parks. 

Background visibility data monitored at the Bridger Class I Wilderness Area IMPROVE site, an 

area more pristine than populated residential areas, were used to estimate potential visibility 

impairment at the regional community locations. 

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Table 4.8 FLAG Report Background Extinction Values.1 

Site Season 

Hygroscopic 

(Mm-1)

2 

Non-hygroscopic

 (Mm-1)

2 

Bridger Wilderness Area3 Winter 0.6 4.5 

Spring 0.6 4.5 

Summer 0.6 4.5 

Fall 0.6 4.5 

Fitzpatrick Wilderness Area Winter 0.6 4.5 

Spring 0.6 4.5 

Summer 0.6 4.5 

Fall 0.6 4.5 

Teton Wilderness Area Winter 0.6 4.5 

Spring 0.6 4.5 

Summer 0.6 4.5 

Fall 0.6 4.5 

Washakie Wilderness Area Winter 0.6 4.5 

Spring 0.6 4.5 

Summer 0.6 4.5 

Fall 0.6 4.5 

Grand Teton National Park Winter 0.6 4.5 

Spring 0.6 4.5 

Summer 0.6 4.5 

Fall 0.6 4.5 

Yellowstone National Park Winter 0.6 4.5 

Spring 0.6 4.5 

Summer 0.6 4.5 

Fall 0.6 4.5 

1 FLAG (2000). 2 Mm-1 = inverse megameters 3 Also used for Popo Agie Wilderness, Wind River Roadless Area, and regional communities. 

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As recommended in EPA (2003b), monthly relative humidity factors determined from the 

Bridger IMPROVE site were used for the Bridger and Fitzpatrick Wilderness Areas; Yellowstone 

IMPROVE data were used for Yellowstone and Grand Teton National Parks and for the Teton 

Wilderness Area; and North Absaroka IMPROVE data were used for the Washakie Wilderness 

Area. Relative humidity data for the Bridger site were also used for the Popo Agie Wilderness 

Area and for the Wind River Roadless Area. Table 4.9 provides the relative humidity factors 

(f[RH]) that were used in the analyses. 

Change in atmospheric light extinction relative to background conditions is used to measure 

regional haze. Analysis thresholds for atmospheric light extinction are set forth in FLAG (2000), 

with the results reported in percent change in light extinction and change in deciview (dv). The 

thresholds are defined as 5% and 10% of the reference background visibility or 0.5 and 1.0 dv for 

Project sources alone and cumulative source impacts, respectively. The BLM considers a 1.0 dv 

Table 4.9 Monthly f(RH) Factors from Regional Haze Rule Guidance. 

IMPROVE Site	 Quarter Months f(RH) Values 

Bridger Wilderness Area1	 1 Jan, Feb, Mar 2.5, 2.3, 2.3 

2 Apr, May, Jun 2.1, 2.1, 1.8 

3 Jul, Aug, Sep 1.5, 1.5, 1.8 

4 Oct, Nov, Dec 2.0, 2.5, 2.4 

North Absaroka Wilderness Area2	 1 Jan, Feb, Mar 2.4, 2.2, 2.2 

2 Apr, May, Jun 2.1, 2.1, 1.9 

3 Jul, Aug, Sep 1.6, 1.5, 1.8 

4 Oct, Nov, Dec 2.0, 2.3, 2.4 

Yellowstone National Park3	 1 Jan, Feb, Mar 2.5, 2.3, 2.2 

2 Apr, May, Jun 2.1, 2.1, 1.9 

3 Jul, Aug, Sep 1.7, 1.6, 1.8 

4 Oct, Nov, Dec 2.1, 2.4, 2.5 

1 Also used for Fitzpatrick and Popo Agie Wilderness Areas, Wind River Roadless Area, and regional communities. 2 Also used for Washakie Wilderness Area. 3 Also used for Teton Wilderness Area and Grand Teton National Park. 

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change as a significant adverse impact; however, there are no applicable local, state, tribal, or 

federal regulatory visibility standards. It is the responsibility of the Federal Land Manager (FLM) 

or Tribal government responsible for that land to determine when adverse impacts are significant 

or not, and these may differ from BLM levels for significant adverse impacts (e.g., the USFS 

considers a 0.5-dv change as a threshold in order to protect visibility in sensitive areas). 

Far-Field Results 

The maximum predicted far-field visibility impacts for each of the analyzed Project alternatives 

are provided in Appendix F, Tables F.8.1 – F.8.27. A summary of results by alternative is 

provided in Tables F.10.17 - F.10.20. Predicted impacts are shown using both the FLAG and 

IMPROVE background visibility data. For each Class I and sensitive Class II area the maximum 

predicted change in dv and the estimated number of days per year that could potentially exceed 

0.5 and 1.0 dv thresholds are provided. Note that visibility is protected in Class I areas; Class II 

areas are included here to further define impacts in potentially sensitive areas. 

Direct visibility impacts from the Project sources were predicted to be above the 0.5-dv threshold 

at the Bridger, Fitzpatrick and Popo Agie Wilderness Areas, and at the Wind River Roadless 

Area (for proposed 3,100 well Alternatives only) using both the FLAG and IMPROVE 

background visibility data, and above the 1.0-dv threshold at the Bridger Wilderness area using 

both sets of background data. The highest frequency of predicted visibility impacts occurred at 

the Bridger Wilderness under Alternative B (WDR250) where there were 30 days per year 

(FLAG) and 33 days per year (IMPROVE) when visibility impacts were predicted to be above 

the 0.5-dv threshold, and 11 days per year (FLAG and IMPROVE) above the 1.0-dv threshold 

(see Table F.8.5). The maximum dv change was estimated as 3.3 dv (FLAG) and 3.7 dv 

(IMPROVE) (see Table F.8.5). 

Cumulative visibility impacts from the Project and regional sources were predicted to be above 

the 1.0-dv threshold at the Bridger and Popo Agie Wilderness Areas, and at the Wind River 

Roadless Area. The highest frequency of predicted cumulative visibility impacts occurred at the 

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Bridger Wilderness under Alternative B (WDR250) where there were 15 days per year (FLAG) 

and 19 days per year (IMPROVE) when visibility impacts were predicted to be above the 1.0-dv 

(see Table F.8.19) threshold. The maximum dv change at the Bridger Wilderness Area was 

estimated as 3.8 dv (FLAG) and 4.2 dv (IMPROVE) (see Table F.8.19). 

Tables are also provided in Appendix F (Tables F.8.28 – F.8.35), for each Class I and sensitive 

Class II area where the maximum predicted change in dv is estimated to potentially exceed 0.5 

and 1.0 dv thresholds, that present all predicted impacts above the thresholds and lists the days 

when the impacts were predict to occur. 

Mid-Field Results 

The maximum predicted mid-field visibility impacts for each of the analyzed Project Alternative 

scenarios are provided in Appendix F, Tables F.9.1 – F.9.27. A summary of results by 

alternative is provided in Tables F.10.21 - F.10.24. Predicted impacts are shown using both the 

FLAG and IMPROVE background visibility data. The maximum predicted visibility impacts 

(change in dv) at regional communities and the estimated number of days per year that could 

potentially exceed the 1.0 dv threshold are provided for each community location using both the 

FLAG and IMPROVE background visibility data. 

Modeling results for direct Project alternative scenarios indicate impacts above the 1.0-dv 

threshold at all regional community locations, with the exception of Merna, where there are no 

predicted impacts above the 1.0-dv threshold under any of the alternatives. The highest 

frequency of predicted visibility impacts occurred at Big Sandy under Alternative B (WDR250) 

where there were 24 days per year (FLAG) and 26 days per year (IMPROVE) when visibility 

impacts were predicted to be above the 1.0-dv threshold (Table F.9.5). The maximum dv 

change, 4.3 dv (FLAG), and 4.9 dv (IMPROVE) was predicted to occur at Pinedale (see 

Table F.9.5). Modeling analyses using the Proposed Action maximum production emissions 

indicate that there would be only 1 day above the 1.0-dv threshold (IMPROVE), occurring at 

Pinedale, with a maximum impact of 1.1 dv (Table F.9.1). 

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Air Quality Technical Support Document, Jonah Infill Drilling Project 77 

Cumulative impacts from Project and regional sources indicate impacts above the 1.0-dv 

threshold at all regional community locations (all WDR250 and most WDR150 scenarios). The 

highest frequency of predicted cumulative visibility impacts is estimated for Big Sandy under 

Alternative B where there were 36 days per year (FLAG) and 34 days per year (IMPROVE) when 

the visibility impacts were predicted to be above the 1.0-dv threshold (see Table F.9.19). The 

maximum dv change, 4.4 dv (FLAG), and 5.0 dv (IMPROVE) was predicted to occur at Pinedale 

(see Table F.9.19). 

Tables are also provided in Appendix F (Tables F.9.28 – F.9.47), for each regional community 

location, that present all predicted impacts above the thresholds and lists the days when the 

impacts were predict to occur. 

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5.0 REFERENCES


Air Resource Specialists. 2002. Green River Basin Visibility Study. Monitored Air Quality 

Data. Air Resource Specialists, Fort Collins, Colorado. 

Bureau of Land Management. 1983. Riley Ridge Natural Gas Project Air Resources Technical 

Report. U.S. Department of Interior, Bureau of Land Management, Kemmerer Field 

Office, Kemmerer, Wyoming, in cooperation with Environmental Research and 

Technology Inc. 

. 1988. Pinedale Resource Management Plan Record of Decision. U.S. Department of 

Interior, Bureau of Land Management, Pinedale Resource Area, Rock Springs District, 

Rock Springs, Wyoming. 

. 1990. Record of Decision and Approved Resource Management Plan for the Great 

Divide Resource Area. U.S. Department of Interior, Bureau of Land Management, Great 

Divide Resource Area, Rawlins District. Rawlins, Wyoming. 

. 1997. Record of Decision and Green River Resource Management Plan. U.S. 

Department of Interior Bureau of Land Management, Green River Resource Area, Rock 

Springs District, Rock Springs, Wyoming. 

. 1999a. Pinedale Anticline Oil and Gas Exploration and Development Project Draft 

Environmental Impact Statement-Technical Report. U.S. Department of Interior, Bureau 

of Land Management, Pinedale Field Office, Pinedale, Wyoming, in cooperation with 

U.S. Forest Service, U.S. Army Corps of Engineers, and State of Wyoming. 

. 1999b. Continental Divide/Wamsutter II and South Baggs Natural Gas Development 

Projects, Environmental Impact Statement, Air Quality Impact Assessment, Technical 

Support Document, Volume II, Far-Field Analysis. U.S. Department of Interior, Bureau 

of Land Management, Rock Springs Field Office, Rock Springs, Wyoming, in 

cooperation with Earth Tech, Inc., Concord, Massachusetts. 

. 2003. Desolation Flats Natural Gas Exploration and Development Project - Technical 

Support Documents for the Ambient Air Quality Impact Analysis. U.S. Department of 

Interior Bureau of Land Management in cooperation with Buys & Associates, Inc. 

Cooperative Institute for Research in Atmosphere. 2003. Interagency Monitoring of Protected 

Visual Environments (IMPROVE) summary data provided by Scott Copeland, 

Cooperative Institute for Research in the Atmosphere, Colorado State University, October 

2003. 

35982 TRC Environmental Corporation 
80 Air Quality Technical Support Document, Jonah Infill Drilling Project 

Countess, R.J., W.R. Barnard, C.S. Claiborn, D.A. Gillette, D.A. Latimer, T.G. Pace, J.G. 

Watson. 2001. Methodology for Estimating Fugitive Windblown and Mechanically 

Resuspended Road Dust Emissions Applicable for Regional Scale Air Quality Modeling. 

Report No. 30203-9. Western Regional Air Partnership, Denver, Colorado. 

Earth Tech. 2001. The Southwest Wyoming Regional CALPUFF Air Quality Modeling Study 

Final Report. Earth Tech, Inc., Concord, Massachusetts. February 2001. 

. 2003. CALMET/CALPUFF Air Quality Modeling System. Earth Tech, Inc., Concord, 

Massachusetts. 

Environmental Protection Agency. 1977. Guideline for Air Quality Maintenance and Planning 

and Analysis, Vol. 10, (Revised). Office of Air Quality Planning and Standards, 

Research Triangle Park, North Carolina. EPA-450/4-77-001. 

. 1985. Compilation of Air Pollutant Emission Factors, AP-42, Volume II: Mobile 

Sources, Fourth Edition. 

. 1990. National Oil and Hazardous Substances Contingency Plan. Final Rule, 40 

C.F.R. Part 300. 

. 1993. Superfund's Standard Default Exposure Factors for the Central Tendency and 

Reasonable Maximum Exposure. Preliminary Review Draft. 

. 1995. Compilation of Air Pollutant Emission Factors (AP-42), Vol. 1, Stationary Point 

and Area Sources, Fifth Edition. Office of Air Quality Planning and Standards, Research 

Triangle Park, North Carolina. 

. 2002. Air Toxics Database. Dose-Response Assessment for Assessing Health Risks 

Associated With Exposure to Hazardous Air Pollutants, Table 2. Office of Air Quality 

Planning and Standards (OAQPS). Technology Transfer Network Air Toxics Website. 

<http://www.epa.gov/ttn/atw/toxsource/summary.html>. Data accessed June 20, 2003. 

. 2003a. Guideline On Air Quality Models. 40 C.F.R. Part 51 Appendix W, July 2003. 

. 2003b. Guidance for Estimating Natural Visibility Conditions Under the Regional 

Haze Rule. Office of Air Quality Planning and Standards, Research Triangle Park, North 

Carolina. 

. 2004. Compilation of Air Pollutant Emission Factors, AP-42, Volume I: Stationary 

Point and Area Sources, Fifth Edition. 

Federal Land Managers' Air Quality Related Values Workgroup. 2000. Federal Land Managers' 

Air Quality Related Values Workgroup (FLAG) Phase I Report. U.S. Forest Service-Air 

Quality Program, National Park Service-Air Resources Division, U.S. Fish and Wildlife 

Service-Air Quality Branch. December 2000. 

35982 TRC Environmental Corporation 
Air Quality Technical Support Document, Jonah Infill Drilling Project 81 

Fox, Douglas, Ann M. Bartuska, James G. Byrne, Ellis Cowling, Rich Fisher, Gene E. Likens, 

Steven E. Lindberg, Rick A. Linthurst, Jay Messer, and Dale S. Nichols. 1989. A 

Screening Procedure to Evaluate Air Pollution Effects on Class I Wilderness Areas. 

General Technical Report RM-168. USDA Forest Service, Rocky Mountain Forest and 

Range Experiment Station, Fort Collins, Colorado. 36 pp. 

Gas Research Institute. 1999. GRI-HAPCalc® Version 3.01. Gas Research Institute. Des 

Plaines, Illinois. 

Interagency Workgroup on Air Quality Modeling. 1998. Interagency Workgroup on Air Quality 

Modeling (IWAQM) Phase 2 Summary Report and Recommendations for Modeling 

Long Range Transport Impacts. EPA-454/R-98-019. Office of Quality Planning and 

Standards. U.S. EPA, Research Triangle Park, North Carolina. December 1998. 

National Park Service. 2001. Guidance on Nitrogen and Sulfur Deposition Analysis Thresholds. 

National Park Service and U.S. Fish and Wildlife Service. National Park Service Air 

Resources Division. <http://www.aqd.nps.gov/ard/flagfree/2001>, Data accessed July 

2003. 

Pfleider, Eugene, P. 1972. Surface Mining. Seeley W. Mudd Series. American Institute of 

Mining, Metallurgical, and Petroleum Engineers, Inc., New York. 

Scheffe, Richard D. 1988. VOC/NOx Point Source Screening Tables. Office of Air Quality 

Planning and Standards, Research Triangle Park, North Carolina. August 1988. 

USDA Forest Service. 2000. Screening Methodology for Calculating ANC Change to High 

Elevation Lakes, User's Guide. U.S. Department of Agriculture (USDA) Forest Service, 

Rocky Mountain Region. January 2000. 

Wyoming Department of Environmental Quality. 2001. Oil and Gas Production Facilities 

Chapter 6, Section 2 Permitting Guidance, Wyoming Department of Environmental 

Quality-Air Quality Division. June 1997 with revisions through August 2001. 

. 2003. Wyoming's Long Term Strategy for Visibility Protection, 2003 Review Report. 

Appendix E, Visibility Monitoring Data Assessment. Wyoming Department of 

Environmental Quality-Air Quality Division (WDEQ-AQD). 

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