March 9,2009 

Carol Rushin, Acting Regional Administrator 

United States Environmental Protection Agency - Region 8 

80C-EISC 

1595 Wynkoop Street 

Denver, CO 80202- 1 129 

Re: Area Designation Recommendation for 2008 Revised Ozone NAAQS 

Dear Ms. Rushin: 

Thank you for your letter inviting the Southern Ute Indian Tribe to participate in the 

process of designating areas for the 2008 revised ozone national ambient air quality standards. 

Under section 107(d)(l) of the Clean Air Act, areas may be designated as "nonattainrnent" (if the 

area does not meet the standards or contributes to ambient air quality in a nearby area that does 

not meet the standards), "attainment" (if the area meets the standards), or "unclassifiable" (if the 

area cannot be classified on the basis of available information as meeting or not meeting the 

standards). 

EPA's guidance on the area designations for the 2008 revised ozone standard lists nine 

factors that states and tribes should consider in making recommendations for area designations 

and on which EPA will base its designations. With regard to the factors to be considered in 

determining nonattainment area boundaries, the guidance provides that "a state's or tribe's 

demonstration supporting their boundary recommendation for an area should show that: 1) 

violations are not occurring in nearby portions that are excluded from the recommended area, 

and 2) the excluded nearby portions do not contain emission sources that contribute 

meaninnfully to the observed violations." (emphasis added). In carrying out its responsibility 

for designating areas in Indian country, in addition to the factors listed in EPA's guidance 

document, EPA must consider the federal policy of encouraging tribal self-determination and 

economic development, and environmental justice must be considered too. EPA 1984 Indian 

Policy (providing that "in keeping with the Federal trust responsibility, [EPA] will assure that 

tribal concerns and interests are considered whenever EPA's actions andlor decisions may affect 

reservation environments.") 

Based on our evaluation, set forth in the attached Technical Support Document, of air 

quality data, emissions data, and other factors which, according to EPA guidance, should be 

considered in making recommendations for area designations, the Tribe recommends that the 

P.O. Box 737 + IGN.~CIO, CO 81137 + PHONE: 970-563-0100 
area within the exterior boundaries of the Southern Ute Indian Reservation be designated as 

"attainment/unclassifiable" for the 2008 revised ozone NAAQS. Additionally, based on our 

determination that the contribution, if any, from Reservation-based sources to the violation of the 

standard in northwest New Mexico is not meaningful, the Tribe recommends that the 

Reservation not be included in the "nonattainment" area that is likely to be designated for San 

Juan County, and perhaps Rio Arriba County, in New Mexico as a result of the ozone violating 

monitor located in New Mexico near Navajo Lake. In other words, no violations of the revised 

ozone standards are occurring on the Reservation and the sources of air pollution located on the 

Reservation do not contribute meaningfully to the monitored violation at New Mexico's Navajo 

Lake monitor. 

Please contact Vickie Kujawa (Environmental Programs Division Head) (970) 563-01 35 

or James Temte (Air Quality Program Manager) at (970) 563-4705 or Sam W. Maynes (Tribal 

attorney) at (970) 247-1755 if you have any questions about the Tribe's recommendation and 

Technical Support Document. 

L 

Encl. Technical Support Document 

cc: Southern Ute Indian TribeIState of Colorado Environmental Commission 

Martha E. Rudolph, Director of Colorado Environmental Programs 

Paul Tourangeau, Colorado Air Pollution Control Division Director 

Douglas A. Lempke, Colorado Air Quality Control Commission Administrator 

Mary Uhl, New Mexico Air Quality Bureau Chief 

Ernest House, Sr., Chairman, Ute Mountain Ute Tribe 

Scott Clow, Environmental Programs Director, Ute Mountain Ute Tribe 

Joe Shirley Jr., President, Navajo Nation 

Stephen B. Etisitty, Navajo Nation Environmental Protection Agency 

Levi Pesata, President, Jicarilla Apache Nation 

Cordell TeCube, Director, Environmental Protection Office, Jicarilla Apache Nation 

La Plata County Colorado Board of County Commissioners 

Archuleta County Colorado Board of County Commissioners 

Montezuma County Colorado Board of County Commissioners 

State Senator Jim Isgar 

State Representative Ellen Roberts 

U.S. Senator Mark Udall 

U.S. Senator Michael Bennett 

Interior Secretary Ken Salazar 
SOUTHERN UTE INDIAN TRIBE 

Technical Support Document 

For 2008 Revised Ozone NAAQS Area Designation Recommendation 

March 10, 2009 

Southern Ute Environmental Programs Division 

Air Quality Program 

116 Mouache Dr. 

P.O. Box 737 

Ignacio, Colorado 81137 
i

TABLE OF CONTENTS 

Page No. 

List of Tables ..................................................................................................................... iii 

List of Figures .................................................................................................................... iii 

I. Introduction ..............................................................................................................1 

 

II. Nine-Factor Analysis ...............................................................................................3 

 Factor 1. (Air Quality Data) ..................................................................................3 

A. Monitoring Data Show Attainment for the Reservation ..............................3 

 Factor 2. (Meteorology) ........................................................................................6 

 A. Photochemical Source Apportionment Modeling Shows that 

 the Contribution of Reservation Sources to Ozone Formation in 

 Northwest New Mexico is Not Meaningful .................................................6 

B. Wind Roses Show Prevailing Winds Over the San Juan Basin 

 Blow From the West and Southwest ..........................................................17 

 Factor 3. (Emissions Data) ..................................................................................24 

A. Ozone Precursor Emissions from Reservation Sources are only a 

 Small Portion of Ozone Precursor Emissions in the Four 

 Corners Region ..........................................................................................24 

B. Emissions Data Show That Large Engine Sources on the Reservation 

 Already Have Low NOx Emissions ...........................................................28 

 

 Factor 4. (Level of Control of Emission Sources) ..............................................29 

 A. Existing Regulatory Framework on the Reservation .................................29 

 B. Existing Sources on the Reservation are Well-Controlled .........................29 

C. Tribal Efforts to Assume Regulatory Responsibility Will 

 Result in Better Control of Sources and Decreased Emissions .................30 
ii

 

TABLE OF CONTENTS 

Page No. 

 Factor 5. (Growth Rates and Patterns) ................................................................34 

 A. Existing Development ................................................................................34 

 B. 80-Acre Infill Development .......................................................................34 

C. A Nonattainment Designation Based on Possible Future 

 Development is Inappropriate Since NOx Emissions from Reservation 

 Sources (and, Hence, Ozone Levels on the Reservation) are Expected 

 to Decrease Over the Next 20 Years Notwithstanding 

 Infill Development. ....................................................................................35

 Factor 6. (Jurisdictional boundaries) .....................................................................38 

 A. Control of Emission Sources in a Regional Nonattainment Area 

 Would be Spread Among Multiple Jurisdictions and (1) is 

 Unnecessary, (2) Could Slow the Tribe’s and Environmental 

 Commission’s Implementation of Air Pollution Control Measures, 

 and (3) Would Not Efficiently and Effectively Serve the Purpose of 

Improving Air Quality ...............................................................................38 

 B. The Reservation is Already a Separate Air Quality Control Region .........39 

 

 Factor 7. (Geography/Topography) ......................................................................41 

 Factor 8. (Population Density and Degree of Urbanization) ................................42 

 Factor 9. (Traffic and Commuting Patterns) .........................................................44 

III. Other Factors ..........................................................................................................44 

 A. EPA Must Consider Tribal Self-Determination in Making its Area 

Designation for the Reservation .................................................................45 

 B. Environmental Justice Favors an Attainment/Unclassifiable 

 Designation for the Reservation .................................................................45 

 C. In the Alternative, Ongoing Studies May Warrant an Unclassifiable 

Designation for the Reservation .................................................................46 

IV. Conclusion .............................................................................................................46 
iii

LIST OF TABLES 

Page No. 

Table 1: Southern Ute Indian Reservation Ozone Monitoring Data Summary ...............3 

Table 2: Average Predicted Hourly O3 (ppb) for all Hours Above 

 Indicated Threshold at the Navajo Lake Monitor ............................................ 15 

Table 3: Total 8-hour Ozone Predictions and Corresponding SUIT 

 Impacts for High Impact Days ......................................................................... 16 

Table 4: Summary of Regional NOx and VOC Emissions in the Four Corners 

 Area 4C-4km Domain Emissions Summary (t/yr)......................................25-26 

Table 5: Distribution of Reciprocating Internal Combustion Engines on the 

 Reservation in 2005 that Process CBM Gas .................................................... 28 

Table 6: Summary of Conclusions Regarding Additional Controls on Oil and Gas 

 Natural Gas Fired Engines ............................................................................... 30 

Table 7: Reservation Demography – Estimated Population on Reservation ................. 42 

Table 8: Reservation Demography - Estimated Population Growth on Reservation ..... 42 

Table 9: Estimated Total Square Miles on the Reservation ........................................... 43 

Table 10. Estimated Population Density on the Reservation ........................................... 43 

Table 11: Emissions from Vehicle Travel on Paved Roads within the 

 Reservation Boundaries (tons) ......................................................................... 44 

Table 12: Emissions from Vehicle Travel on Unpaved Roads within the SUIT 

 Reservation Boundaries (tons) ......................................................................... 44 

LIST OF FIGURES 

Figure 1: Ute 3 2006-2008 Ozone Monitoring Data .........................................................4 

Figure 2: Ozone Monitor Locations in the Four Corners Region .....................................5 

Figure 3: Hourly Time Series for Navajo Lake Monitor for April 2005 ...........................8 

Figure 4: Hourly Time Series for Navajo Lake Monitor for May 2005 ............................9 

Figure 5: Hourly Time Series for Navajo Lake Monitor for June 2005 ............................10 

Figure 6: Hourly Time Series for Navajo Lake Monitor for July 2005 ............................11 

Figure 7: Hourly Time Series for Navajo Lake Monitor for August 2005 .......................12 

Figure 8: Hourly Time Series for Navajo Lake Monitor for September 2005 ..................13 

Figure 9: Hourly Time Series for Navajo Lake Monitor for October 2005 .................... .14 

Figure 10: 2008 Annual Wind Roses in the Four Corners Area ....................................... 19 

Figure 11: 2008 Annual Daytime Wind Roses .................................................................. 19 

Figure 12: 2008 Annual Nighttime Wind Roses ............................................................... 20 

Figure 13: 2008 Spring Wind Roses ................................................................................. 20 

Figure 14: 2008 Summer Wind Roses............................................................................... 21 

Figure 15: 2008 Summer Daytime Wind Roses ................................................................ 21 

Figure 16: 2008 Summer Nighttime Wind Roses ............................................................. 22 

Figure 17: 2008 Autumn Wind Roses ............................................................................... 22 

Figure 18: 2008 Winter Wind Roses ................................................................................. 23 

Figure 19: Relative Contribution to Total NOx Inventory ................................................ 27 

Figure 20: Relative Contribution to Total VOC Inventory ............................................... 27 

Figure 21: Estimated Production Volume by Year ........................................................... 36 
iv

Figure 22: Actual NOx Emissions from Engines .............................................................. 37 

Figure 23: Geography of the Southern Ute Indian Reservation........................................ 41

 
1

I. Introduction. 

Pursuant to section 107(d) of the Clean Air Act, EPA must designate areas as 

“attainment,” “nonattainment,” or “unclassifiable” whenever a new or revised NAAQS is 

promulgated. In making area designations, EPA guidance provides that the following nine 

factors, as well as any other relevant information, will be considered: 

• Air quality data 

• Emissions data 

• Population density and degree of urbanization 

• Traffic and commuting patterns 

• Growth rates and patterns 

• Meteorology 

• Geography/topography 

• Jurisdictional boundaries 

• Level of control of emission sources 

This technical support document analyzes the nine factors identified above, as well as other 

relevant information, and is provided in support of the Tribe’s recommendation that the 

Reservation be designated “attainment/unclassifiable” and not be included in any 

nonattainment area that may be designated for northwest New Mexico.1

In support of the Tribe’s recommendation, this technical support document includes data 

and analysis performed by Air Quality Resource Management and ENVIRON International 

Corporation, under contract with the Tribe. ENVIRON’s work has included conducting a stateof-the-art three-dimensional multi-scale photochemical/aerosol grid modeling study using 

ENVIRON’s Comprehensive Air Quality Model with Extensions (CAMx, v4.51). An approach 

using ENVIRON’s CAMx model is more robust than performing qualitative analyses using the 

NOAA HYSPLIT back trajectory model. The HYSPLIT model provides an estimated flow only 

at one layer of the atmosphere, and in addition there is uncertainty regarding the accuracy of the 

flow in complex terrain (as in the case of the Navajo Lake monitor). By contrast, the use of a 

photochemical grid model in conjunction with fine scale MM5 meteorological modeling 

provides a complete and accurate picture of transport in the region within the mixed layer and 

provides a quantitative estimate of potential impacts that include the non linear chemistry of 

ozone formation. This work is similar to the modeling analysis of air quality and air quality 

related values impacts within the Four Corners region that is currently being conducted by 

ENVIRON for the Four Corners Air Quality Group (formerly known as the Four Corners Air 

Quality Task Force) under contract with the New Mexico Environmental Department. 

Importantly, and as further explained below, ENVIRON’s CAMx model results show that 

there is no meaningful contribution from sources located on the Southern Ute Indian Reservation 

to elevated ozone concentrations measured at New Mexico’s Navajo Lake monitor. The 

modeling and the analyses of the nine factors support the Tribe’s recommendation that the 

 

1 The nine factors analyzed by the Tribe are the factors listed in EPA’s guidance but the Tribe’s analysis of the 

factors is not presented in the same order as the factors are listed in EPA’s guidance. 
2

Reservation should be designated attainment/unclassifiable. In summary, burdening Reservation 

development with nonattainment requirements in circumstances where (1) Reservation monitors 

show attainment, (2) source apportionment shows the contribution by Reservation sources to a 

measured exceedance at New Mexico’s Navajo Lake monitor is not meaningful, (3) prevailing 

winds blow from the west and southwest onto the Reservation, and (4) the Southern Ute Indian 

Tribe/State of Colorado Environmental Commission and the Tribe already are aggressively 

acting to control emissions, would not likely result in ozone reductions in northwest New 

Mexico and would impose a disproportionate and unfair burden on the Tribe to attempt to help 

northwest New Mexico achieve attainment with the 2008 revised ozone NAAQS. 
3

II. Nine-Factor Analysis. 

Factor 1 (Air Quality Data) 

A. Monitoring Data Show Attainment for the Reservation. 

 The most recent years of quality-assured, certified air quality data collected from the two 

ozone monitors located on the Reservation, including three consecutive years for the Ute 3 

monitor, each sited and operated in accordance with applicable federal requirements, show 

compliance with the 2008 revised ozone NAAQS. The data shown in Table 1 and Figure 1 

demonstrate attaining ozone levels well below the revised NAAQS. 

Table 1. Southern Ute Indian Reservation Ozone Monitoring Data Summary. 

4th Maximum 8-Hour Ozone Values and 3-Year Averages 

Site Name AQS # 

Year 3-Year 

Average 

2005-07 

(ppm) 

3-Year 

Average 

2006-08*

(ppm) 

2005 

(ppm) 

2006 

(ppm) 

2007 

(ppm) 

2008 

(ppm) 

Ute 1-

Ignacio 

08-067-

7001 

(Void) (Void) (Void) 0.067 n/a n/a 

Ute 3- 

Hwy. 

550/Bondad 

08-067-

7003 

0.066 0.063 0.071 0.067 0.066 0.067 

*Note: Data are through October 2008 
4

Figure 1. Ute 3 2006 – 2008 Ozone Monitoring Data. 

 

Daily Maximum of the 4th Highest 8-hour Ozone Average 

at Ute 3 Site (2006-2008)

0.060

0.065

0.070

0.075

0.080

Ute 3 Bondad

Concentration (ppb)

2006-2008

Design Value

Ozone NAAQS = 0.075 ppb
5

The location of the two ozone monitors on the Reservation, as well as the ozone monitors 

in surrounding areas, are shown on Figure 2. 

Figure 2. Ozone Monitor Locations in the Four Corners Region. 

 The Tribe is aware that the monitoring data from New Mexico’s Navajo Lake monitor 

indicates that San Juan County, New Mexico, is not attaining the revised ozone NAAQS of 

0.075 ppm. As shown in Figure 2, New Mexico’s Navajo Lake monitor is located 

approximately 13 miles south of the southern boundary of the Reservation. Emissions from 

Reservation-based sources, however, do not meaningfully contribute to ozone concentrations in 

northwest New Mexico and for that reason and the additional reasons discussed below, the 

Reservation should not be included in any nonattainment area that may be designated for 

northwest New Mexico.2

 

2 The presumptive boundary for a nonattainment area based on the Navajo Lake monitor encompasses San Juan County, New 

Mexico, but does not include the Southern Ute Indian Reservation, because they are in separate Core Based Statistical Areas. 

The EPA’s ozone area designations guidance provides that the Core Based Statistical Area (CBSA) or Combined Statistical Area 

(CSA) should serve as the starting point or presumptive boundary for any nonattainment designation. Where a violating monitor 

is not located in a CBSA or CSA, EPA recommends that the boundary of the county containing the monitor serve as the 

presumptive boundary for the nonattainment area. In this case, the Navajo Lake monitor is located at Navajo Lake State Park, 

which is located in San Juan County, New Mexico. Farmington, New Mexico, is in a CBSA that encompasses San Juan County 

and is designated as a metropolitan statistical area. Durango, Colorado, is in a CBSA that encompasses La Plata County and the

Reservation and is designated as a micropolitan statistical area. Neither statistical area is included in a combined statistical area, 

or CSA. The presumptive nonattainment boundary for the Navajo Lake monitor, therefore, does not include the Reservation. 
6

Factor 2 (Meteorology) 

A. Photochemical Source Apportionment Modeling Shows that the Contribution of 

Reservation Sources to Ozone Formation in Northwest New Mexico is Not 

Meaningful. 

In evaluating if sources within an area should be included in a nearby nonattainment area, 

it is important to identify meaningful source culpability or source attribution from that area to 

elevated ozone concentrations in the nearby nonattainment area. The most quantitative method 

for making that determination is to utilize source apportionment modeling within a 

photochemical grid model that has undergone an accuracy evaluation using actual ozone 

monitoring data. That kind of work is ongoing as part of the modeling analysis being done by 

ENVIRON for the Four Corners Air Quality Group using the CAMx model. 

An approach using ENVIRON’s CAMx model provides a more realistic quantitative 

representation of source contributions than using the NOAA HYSPLIT back trajectory model. 

The use of a photochemical grid model in conjunction with fine scale (4 kilometer) MM5 

meteorological modeling provides a complete, accurate picture of emission transport in the 

region within the mixed layer and provides a quantitative estimate of potential ozone 

contributions that includes non-linear chemistry of ozone formation. As part of the Four Corners 

analysis, the accuracy of the CAMx model was evaluated and found to be within EPA criteria. 

Thus, such a modeling analysis provides a complete picture of Reservation source contributions 

related to elevated ozone concentrations at New Mexico’s Navajo Lake monitor. 

In contrast, the HYSPLIT model only provides an estimated flow at one or several layers 

in the atmosphere and possibly identifies what may be upwind regions from the Navajo Lake 

monitor. Unlike the CAMx model, the HYSPLIT model provides no indication of pollutant 

concentrations. In addition, in complex terrain such as the terrain where the Navajo Lake 

monitor is located, there is uncertainty regarding the accuracy of the wind fields in HYSPLIT. In 

the EPA’s HYSPLIT analysis of the Navajo Lake monitor, there was no indication of the 

meteorological information that was used in the analysis. One critical issue is the size of the 

grids used to estimate meteorological conditions. In a recent analysis regarding the accuracy of 

meteorological modeled wind fields (as used by HYSPLIT) in Wyoming, it was found that wind 

fields modeled with either a 36 kilometer grid or a 12 kilometer grid could not resolve the 

observed terrain influences in meteorological data caused by the Wind River Mountains. It was 

further found that a 4 kilometer grid was necessary in order to obtain an acceptable comparison 

between meteorological data and modeled wind fields3

. 

Thus the CAMx model results provide a more accurate estimate of the contribution from 

Reservation sources to the elevated ozone measurements at the Navajo Lake monitor than 

qualitative HYSPLIT modeling. 

 

3 D.N. Blewitt, 2008, “Evaluation of the Accuracy of MM5/CALMET Generated Wind Fields in Southwestern 

Wyoming” Presented at EPA Modeling Conference October 2008.
7

In this case, the Tribe has had an extensive air quality impact assessment performed by 

Air Quality Resource Management and ENVIRON using ENVIRON’s CAMx model for the Four 

Corners region.4

 ENVIRON’s CAMx model accuracy was evaluated for 2005 emissions and 

meteorology and future year source apportionment modeling was conducted for estimated 2018 

emissions.5

 Because the 2018 modeling used 2005 emissions for Reservation emissions, the 

modeled contributions from Reservation sources represent actual 2005 contributions. Figures 3 

through 8 provide monthly estimates of hourly time series for 2005 predicted ozone 

concentrations at the Navajo Lake monitor for the months of April through October and present 

the contribution from various source groups to total ozone formation at the Navajo Lake 

monitor.6

 The source groups include boundary conditions (BC) which reflect the amount of 

ozone formed as a result of emissions outside the Four Corners region, other sources in the Four 

Corners region (i.e., New Mexico oil and gas, electric generating utilities (EGU), mobile sources, 

area sources, etc.) and Reservation sources. 

Importantly, as shown in Figures 3 through 8, ENVIRON’s modeling for ozone 

evidences that: 

 

• On many of the days with predicted elevated ozone concentrations at the Navajo Lake 

monitor, a contribution from Reservation sources does not exist;

• On days when there are contributions from Reservation sources, the contribution is not 

meaningful;

• A large amount of ozone in northwest New Mexico is the result of ozone transported 

from outside the Four Corners region; and 

• New Mexico sources are responsible for the vast majority of ozone in the region above 

that which is transported from outside the region.

 

4 This analysis was complementary to the Four Corners air quality analysis performed for the Four Corners Air 

Quality Task Force and used the same modeling procedures, emission data, meteorological data and air quality data. 

5 The Four Corners modeling analysis extrapolated the 2005 inventory to estimate 2018 emissions. This 

extrapolation was done using BLM’s Northern San Juan Environmental Impact Statement and Farmington Resource 

Management Plan analyses based on information contained in the Record of Decision and economic growth factors. 

6 Because these figures represent 1-hour average concentrations and not 8-hour concentrations, these figures cannot 

be used to test compliance with the 8-hour ozone standard. 
8

Figure 3. Hourly Time Series for Navajo Lake Monitor for April 2005. 

0

1020304050607080

4/ 1 4/ 2 4/ 3 4/ 4 4/ 5 4/ 6 4/ 7 4/ 8 4/ 9 4/10 4/11 4/12 4/13 4/14 4/15 4/16 4/17 4/18 4/19 4/20 4/21 4/22 4/23 4/24 4/25 4/26 4/27 4

Ozone Concentration (ppb)

Initial Conditions Boundary Conditions Reservation Sources Other Sources 

Note: 1) This information is not comparable to the 75 ppb 8-hour standard  2) Initial conditions are the concentrations that were used to start the CAMx model 
9

Figure 4. Hourly Time Series for Navajo Lake Monitor for May 2005. 

0

102030405060708090

5/ 1 5/ 2 5/ 3 5/ 4 5/ 5 5/ 6 5/ 7 5/ 8 5/ 9 5/10 5/11 5/12 5/13 5/14 5/15 5/16 5/17 5/18 5/19 5/20 5/21 5/22 5/23 5/24 5/25 5/26 5/27 5/28 

Ozone Concentrations (ppb)

Initial Conditions Boundary Conditions Reservation Sources Other Sources 

 Note: 1) This information is not comparable to the 75 ppb 8-hour standard  2) Initial conditions are the concentrations that were used to start the CAMx model 
10

Figure 5. Hourly Time Series for Navajo Lake Monitor for June 2005. 

0

102030405060708090

6/ 1 6/ 2 6/ 3 6/ 4 6/ 5 6/ 6 6/ 7 6/ 8 6/ 9 6/10 6/11 6/12 6/13 6/14 6/15 6/16 6/17 6/18 6/19 6/20 6/21 6/22 6/23 6/24 6/25 6/26 6/27 

Ozone Concentration (ppb)

Initial Conditions Boundary Conditions Reservation Sources Other Sources in the 4 Corn

Note: 1) This information is not comparable to the 75 ppb 8-hour standard  2) Initial conditions are the concentrations that were used to start the CAMx model 
11

Figure 6. Hourly Time Series for Navajo Lake Monitor for July 2005. 

0

102030405060708090

7/ 1 7/ 2 7/ 3 7/ 4 7/ 5 7/ 6 7/ 7 7/ 8 7/ 9 7/107/11 7/127/13 7/147/15 7/167/177/18 7/197/20 7/217/22 7/237/247/25 7/267/27 7/287/29 7/307/

Ozone Concentration (ppb)

Initial Concentration Boundary Conditions Reservation Sources Other Sources in the 4 Corners Re

Note: 1) This information is not comparable to the 75 ppb 8-hour standard  2) Initial conditions are the concentrations that were used to start the CAMx model 
12

Figure 7. Hourly Time Series for Navajo Lake Monitor for August 2005. 

0

102030405060708090

8/ 1 8/ 2 8/ 3 8/ 4 8/ 5 8/ 6 8/ 7 8/ 8 8/ 9 8/10 8/11 8/12 8/13 8/14 8/15 8/16 8/17 8/18 8/19 8/20 8/21 8/22 8/23 8/24 8/25 8/26 8/27 8/28 8/29 8/3

Ozone Concentrations (ppb)

Initial Conditions Boundary Conditions Reservation Sources Other Sources in the 4 Co

Note: 1) This information is not comparable to the 75 ppb 8-hour standard  2) Initial conditions are the concentrations that were used to start the CAMx model 
13

Figure 8. Hourly Time Series for Navajo Lake Monitor for September 2005. 

0

102030405060708090

9/ 1 9/ 2 9/ 3 9/ 4 9/ 5 9/ 6 9/ 7 9/ 8 9/ 9 9/10 9/11 9/12 9/13 9/14 9/15 9/16 9/17 9/18 9/19 9/20 9/21 9/22 9/23 9/24 9/25 9/26 9/27 

Ozone Concentratins (ppb)

Initial Conditions Boundary Conditions Reservation Standards Other Reservati

Note: 1) This information is not comparable to the 75 ppb 8-hour standard  2) Initial conditions are the concentrations that were used to start the CAMx model 
14

Figure 9. Hourly Time Series for Navajo Lake Monitor for October 2005. 

0

102030405060708090

10/ 110/ 210/ 310/ 410/ 510/ 610/ 710/ 810/ 910/1010/1110/1210/1310/1410/1510/1610/1710/1810/1910/2010/2110/2210/2310/2410/2510/2610/2710/28

Ozone Concentration (ppb)

Initial Conditions Boundary Conditions Reservation Sources Other Sources in t

Note: 1) This information is not comparable to the 75 ppb 8-hour standard  2) Initial conditions are the concentrations that were used to start the CAMx model
15

Table 2 quantifies the predicted hourly contributions from sources on the 

Reservation to predicted peak ozone at New Mexico’s Navajo Lake monitor. This table 

presents the number of hours when total predicted concentrations were above 60, 65, 70, 

and 75 ppb, as well as the contribution from sources on the Reservation. As indicated in 

this table, the contribution, on average, from Reservation sources during periods of 

elevated concentrations at New Mexico’s Navajo Lake monitor is so small as to be not 

meaningful. 

 

Table 2. Average Predicted Hourly O3 (ppb) for all Hours Above Indicated Threshold at the 

Navajo Lake Monitor for 2005. 

O3

Concentrations 

Greater than No. Hrs 

Average 

Total 

Impacts 

Sources on 

the 

Reservation

 Other Sources 

in the Four 

Corners Region 

Boundary 

Conditions

60 472 68.4 0.9 28.8 38.7 

65 295 71.9 1.0 32.5 38.3 

70 167 75.4 1.2 36.0 38.2 

75 86 78.2 1.2 39.7 37.3 

Note: Boundary Conditions indicate the amount of ozone formed as a result of sources outside the Four 

Corners region. 
16

Further analyses were conducted to evaluate whether, and if so, by how much, Reservation 

sources were contributing to a predicted exceedance of the 75 ppb 8-hour ozone standard at New 

Mexico’s Navajo Lake monitor. This was done by identifying all predicted hourly concentrations 

that had a total hourly ozone concentration in excess of 70 ppb and when the corresponding 

Reservation contributions were in excess of 1 ppb. Table 3 summarizes these modeling results and 

indicates that Reservation sources are not responsible for any exceedances of the 8-hour ozone 

standard and have a contribution to the overall model predicted concentrations that is not meaningful. 

Table 3. Total 8-Hour Ozone Predictions and Corresponding SUIT Contributions for 

High Impact Days for 2005. 

Rank Date 

Total 

(ppb) 

Reservation 

Sources (ppb) 

Percent 

Contribution of 

Reservation 

Sources to Total 

Other 

Sources in 

the 4 

Corners 

Region 

(ppb) 

Percent Contribution 

of Other 

Four Corners Sources 

to Total 

1 13-Jul 77.3 1.4 1.8 75.9 98.2 

2 1-Aug 75.7 2.6 3.4 73.2 96.6 

3 31-Jul 74.7 1 1.3 73.8 98.7 

4 22-Jul 74.4 1.1 1.5 73.3 98.5 

5 16-Jul 73.4 1.2 1.7 72.2 98.3 

6 20-May 72.8 0.8 1.1 72 98.9 

7 24-Jun 72.3 0.7 1 71.5 99.0 

8 20-Jun 71.9 0.5 0.7 71.4 99.3 

9 1-Jul 71.7 0.7 1 70.9 99.0 

10 12-Jul 71.4 0.9 1.2 70.5 98.8 

11 4-Jul 71.1 0.6 0.9 70.5 99.1 

12 19-Jun 70.9 0.6 0.8 70.3 99.2 

13 7-Jul 70.4 0.2 0.3 70.2 99.7 

14 30-Jul 69.9 0.9 1.2 69 98.8 

15 8-Sep 69.3 0.1 0.2 69.2 99.8 

16 30-Jun 68.9 0.8 1.1 68.2 98.9 

17 25-May 67.6 1.1 1.6 66.5 98.4 

18 6-Sep 66.9 2.1 3.1 64.8 96.9 

19 22-May 66.8 0.9 1.4 65.8 98.6 

20 20-Jul 65.9 3.2 4.8 62.8 95.2 

21 22-Apr 65.7 1 1.6 64.7 98.4 

22 7-Sep 64 0.7 1.1 63.3 98.9 

23 11-Jul 63.3 1.7 2.7 61.6 97.3 

24 23-Aug 62.1 0.9 1.5 61.2 98.5 

25 5-Sep 61.1 1.6 2.5 59.5 97.5 

Average 69.6 1.1 1.6 68.5 98.4 

Note: Regulatory compliance is based on 4th highest concentration 
17

B. Wind Roses Show That Prevailing Winds Over the San Juan Basin Blow 

 from the West and Southwest. 

The Southern Ute Indian Reservation, located in southwestern Colorado, includes 

a substantial portion of the northern San Juan Basin. The Reservation remains generally 

semi-arid throughout the year consistent with its location in the arid/semi-arid continental 

Great Basin. Abundant sunshine and large diurnal temperature ranges occur in the 

region, largely as a result of the significant distance from major oceans. Temperature and 

precipitation data from Ignacio, Colorado, are considered to be representative of climatic 

conditions within the Reservation. However, because elevation, slope and aspect affect 

precipitation and temperatures, the complex terrain of La Plata County, Colorado, creates 

considerable climatic variability. The Reservation can be classified into six climatic 

zones: 

• Zone 1 - semi-desert grasslands at elevations below 6,000 feet; average 

annual precipitation less than 12 inches; 

• Zone 2 - sagebrush savanna at elevations from 6,000 to 6,300 feet; average 

annual precipitation 12 to 13 inches; 

• Zone 3 - piñon-juniper woodland at elevations from 6,000 to 7,200 feet; 

average annual precipitation 13 to 17 inches; 

• Zone 4 - piñon-juniper/mountain browse at elevations from 6,100 to 8,400 

feet; average annual precipitation 14 to 20 inches; 

• Zone 5 - ponderosa pine at elevations from 6,500 to 8,800 feet; 

average precipitation 16 to 23 inches; and 

• Zone 6 - fir-spruce/aspen at elevations from 6,600 to 9,000 feet; 

average precipitation 18 to 27 inches. 

Annual precipitation measurements at Ignacio during the period from 1961 

through 1990 averaged 14.4 inches. From 1993 through 1996, precipitation was well 

distributed throughout the year, with the months from April to June receiving the lowest 

average amounts (0.5 to 0.9 inches) and August the highest levels (1.7 inches). 

Maximum precipitation occurring in the region in late summer and early fall is the result 

of moisture transport from the Gulf of Mexico under the western extension of the 

Bermuda High.7

 Much of this precipitation derives from afternoon convective 

thunderstorms that occur during the late summer “monsoon” season. Snow is another 

dominant form of precipitation on the Reservation, though more snowfall is generally 

seen in the higher elevations just north of the Reservation. During the winter season, the 

Reservation records an average of roughly 3 to 4 inches of precipitation. 

December and January are the coldest months, with average lows of about 10 

degrees Fahrenheit (°F) and highs of about 40°F. The warmest months are July and 

August with average minimum and maximum temperatures of 50°F and 85°F, 

respectively. Based on 30-year climate data (National Oceanic and Atmospheric 

 

7 Tesche, T. W. and Dennis E. McNally, Air Quality Modeling Analysis for the San Juan County Early 

Action Compact: Episode Selection and Conceptual Model. June 17, 2003. 
18

Administration 1992), the norm minimum temperature (about 6°F) occurs in January and 

the normal maximum temperature (88°F) occurs in July. 

Figures 10 through 18 are wind rose figures created using data gathered by the 

meteorological monitoring stations in the Four Corners region that depict the frequency, 

direction, and force of the winds that travel across the Reservation. The distribution of 

wind values are shown on each wind rose map. Note that the directions associated with 

any bar in these figures are the direction from which the wind blows.8 It should be noted 

that all of these data were collected at a ten meter elevation. 

Seasonal and daytime/nighttime wind roses display the predominant light winds 

crossing the Reservation blowing from the northeast with the stronger less frequent winds 

gusting from the west (Figures 10 through 18). During the summer daytime period when 

ozone concentration values are expected at their highest, the wind roses show more 

frequent west and southwest winds at the San Juan Substation, Bloomfield, and Navajo 

Lake sites in northern New Mexico (Figure 15). The Ute 1 and Ute 3 sites also illustrate 

similar characteristics of high frequency winds blowing from the west and southwest 

during the same time period. Overall, the wind rose models show that the winds over the 

San Juan Basin are westerly to southwesterly throughout much of the year. 

 

8 Preprocessed meteorological data used to produce wind roses for each of the monitoring sites were 

obtained from the State of New Mexico Environment Department website, Air Resource Specialists, Inc., 

and EPA’s Air Quality Subsystem (AQS) database. New Mexico meteorological monitoring wind rose 

figures were for the Bloomfield, Substation, and Navajo Lake sites. Data from the Ute 1, Ute 3, Mesa 

Verde National Park, and Shamrock sites were used to produce the Colorado wind roses. 
19

Figure 10. 2008 Annual Wind Roses in the Four Corners Area. 

Figure 11. 2008 Annual Daytime Wind Roses (6am – 6pm). 
20

Figure 12. 2008 Annual Nighttime Wind Roses (6pm – 6am). 

Figure 13. 2008 Spring Wind Roses (March – May). 
21

Figure 14. 2008 Summer Wind Roses (June – August). 

Figure 15. 2008 Summer Daytime Wind Roses (June – August from 6am – 6pm). 
22

Figure 16. 2008 Summer Nighttime Wind Roses (June – August from 6pm – 6am). 

Figure 17. 2008 Autumn Wind Roses (September – November). 
23

Figure 18. 2008 Winter Wind Roses (December – February). 
24

Factor 3 (Emissions Data) 

An evaluation of emissions data for the Reservation demonstrates the following: (1) 

based on a comparison of emission inventories for different areas within the Four Corners 

region, the contribution by sources located on the Reservation to elevated ozone concentrations 

in New Mexico is minimal, and (2) NOx emissions from large engine sources located on the 

Reservation already are within the recently promulgated NSPS regulatory requirements. 

A. Ozone Precursor Emissions from Reservation Sources are only a Small Portion of 

Ozone Precursor Emissions in the Four Corners Region. 

Table 4 demonstrates that the Reservation sources are only a small portion of the NOx 

emissions for the Four Corners region (2 percent or 4,694 tons per year of a total of 221,865 tons 

per year) and an insignificant amount of the VOC emissions (0.4 percent or 1,926 tons per year 

out of 431,649 tons per year). Compared to the other areas in the Four Corners region, 

contribution from the Reservation is much smaller than emissions from other areas in the region. 

For example, NOx emissions from the Reservation amount to 4,694 tons per year, while 

northwestern New Mexico’s sources alone, not including the Navajo Nation, emit 150,493 tons 

per year (approximately 32 times as much as the Reservation), and the Navajo Nation emits 

45,323 tons per year (almost ten times as much as the Reservation). Comparisons of relative 

VOC emissions are similarly illustrative, with sources in northwestern New Mexico emitting 144 

times as many tons per year of VOCs as the Reservation. Further, with respect to hydrocarbons, 

the emissions from Reservation sources are primarily methane and ethane, which are not 

regulated VOC compounds by EPA because of low reactivity, and therefore have very little 

culpability in regional ozone formation. In other words, the Reservation is not a source of VOCs 

– one of the two primary precursors to ozone. 

 The data shown in Table 4 is a summary of the 2005 Four Corners regional emissions 

inventory that was developed as part of the Four Corners Task Force’s modeling project for the 

base case modeling and represent the most accurate emission data in the region. It is important 

to note that all stakeholders involved in the modeling analysis approved this inventory. 
25

Table 4. Summary of Regional NOx and VOC Emissions in the Four Corners Area4C - 4km Domain Emissions Summary (t/yr)2005 NOx Jurisdiction Area Biogenics 

Fugitive 

Dust Off-road On-road

Road 

Dust 

Windblown 

Dust Area Oil & Gas Point Oil & Gas

Electric 

Generating 

Utility 

Non-Elec

Generati

Utility 

Arizona 97 211 0 2,407 4,661 0 0 13 0 0 0 Colorado 302 659 0 1,910 3,757 0 0 921 2,548 0 535 Navajo Nation 0 0 0 0 0 0 0 0 2,570 41,743 1,010 New Mexico 16,036 833 0 11,219 30,182 0 0 37,848 19,834 30,925 3,615 Pueblo of Laguna 0 0 0 0 0 0 0 0 0 0 1,551 Pueblo of Santa Ana 0 0 0 0 0 0 0 0 0 0 209 Southern Ute * * 0 * * 0 0 0 4,694 0 0 Utah 42 130 0 181 741 0 0 51 352 0 78 Ute Mountain Ute 0 0 0 0 0 0 0 0 0 0 0 Grand Total 16,477 1,834 0 15,717 39,340 0 0 38,832 29,998 72,668 6,997 Source: ENVIRON for Four Corners Modeling Group * Area, Biogenics, Off-road and On-road emissions for Southern Ute are included in the numbers shown for Colorado. 
26

4C - 4km Domain Emissions Summary (t/yr) (continued)2005 VOC Jurisdiction Area Biogenics 

Fugitive

Dust Off-road On-road

Road 

Dust 

Windblown 

Dust Area Oil & Gas Point Oil & Gas

Electric 

Generating 

Utility 

Non-Elec

Generati

Utility 

Arizona 2,204 29,202 0 728 3,314 0 0 37 0 0 0 Colorado 3,632 84,822 0 4,884 2,616 0 0 891 1,257 0 348 Navajo Nation 0 0 0 0 0 0 0 0 293 292 121 New Mexico 26,675 108,515 0 5,690 17,079 0 0 109,480 7,857 7 1,849 Pueblo of Laguna 0 0 0 0 0 0 0 0 0 0 11 Pueblo of Santa Ana 0 0 0 0 0 0 0 0 0 0 49 Southern Ute * * 0 * * 0 0 0 1,926** 0 0 Utah 479 15,931 0 388 490 0 0 455 77 0 52 Ute Mountain Ute 0 0 0 0 0 0 0 0 0 0 0 Grand Total 32,989 238,471 0 11,690 23,499 0 0 110,862 11,410 299 2,429 Source: ENVIRON for Four Corners Modeling Group * Area, Biogenics, Off-road and On-road emissions for Southern Ute are included in the numbers shown for Colorado. ** VOC emissions from oil and gas operations are based on the production of coal bed methane which does not contain VOC compoun
27 

As indicated in Figure 19, the contribution to NOx emissions in the Four Corners region 

by sources on the Reservation is only about 2 percent. 

Figure 19. Relative Contribution to Total NOx Inventory

0

10

20

30

40

50

60

70

Arizona

Colorado

Navajo Nation

New Mexico

Pueblo of Laguna

Pueblo of Santa Ana

Southern Ute

Utah

Ute Mountain Reservation

%

As indicated in Figure 20, the contribution to VOC emissions in the Four Corners region 

by Reservation sources is less than 1 percent. 

Figure 20. Relative contribution to Total VOC Inventory

0

10

20

30

40

50

60

70

Arizona

Colorado

Navajo Nation

New Mexico

Puebla of Laguna

Puebla of Santa Anna

Southern Ute

Utah

Ute Mountain Reserva...

%
28 

B. Emissions Data Show Large Engine Sources on the Reservation Already Have 

 Low NOx Emissions. 

Table 5 presents a summary of the level of the distribution of emissions from data 

compiled for engines as part of a 2005 emission inventory for the Reservation. 

Table 5. Distribution of Reciprocating Internal Combustion Engines on the 

Reservation in 2005 that Process CBM Gas. 

Engine Size (hp) 

Number 

of 

Engines 

Number 

of 

Engines 

(percent)

Percentage 

of Capacity 

Average 

NOx 

Emission 

Factor 

(g/hphour) 

Total 

NOx 

Emissions 

(t/yr) 

Emissions 

(percent) 

>500 170 53.0 92 1.5 2,982 71 

<500 >100 76 23.7 6.1 7.7 724 17 

<100 >25 73 22.7 1.8 12.2 510 12 

<25 2 0.6 0.0 27 11 0.3 

Total 321 100 4,227 

As indicated by this analysis, the vast number of engines on the Reservation have 

capacities in excess of 500 horsepower and are controlled with non-selective catalytic reduction 

(NSCR) or are low emitting lean burn engines.9

 Table 5 shows that 71 percent of the emissions 

and 92 percent of the capacity are from engines larger than 500 horsepower. For this size 

engine, the average NOx emission factor is 1.5 g/hp-hour. Currently, therefore, the 

overwhelming majority of the large natural gas fired compressor engines on the Reservation 

already meet or exceed the recently promulgated EPA New Source Performance Standard 

(NSPS) for reciprocating internal combustion engines (RICE). 73 Fed. Reg. 3568 (January 18, 

2008). 

For the small to medium size engines (i.e., engines below 500 hp, which account for 

approximately 29 percent of the emissions shown in Table 5), the Tribe intends to improve the 

controls on those engines and reduce their emissions through implementation of a minor source 

permitting program, which is in the final draft stage and which the Tribe expects will be 

implemented in late 2009 or early 2010. The minor source program will impose restrictions 

upon both new and existing sources. In addition, the Tribe intends to condition its consent to 

new well development on the inclusion of additional controls.

 

9

 It is important to note that the inventory identified only one engine in this size class that was not controlled. 
29 

Factor 4 (Level of Control of Emission Sources) – The Southern Ute Indian Tribe/State of 

Colorado Environmental Commission (Environmental Commission) and the Tribe are 

Taking Responsibility for the Control of Emission Sources on the Reservation. 

A. Existing Regulatory Framework on the Reservation. EPA currently 

implements emission controls for major sources on the Reservation. New sources with a 

potential to emit (PTE) in excess of 250 tons per year are required to obtain a PSD permit prior 

to construction. In addition, sources with PTE in excess of 100 tons per year are required to 

obtain a Title V operating permit. There currently is no federal minor source program for Indian 

country, so sources that do not require a PSD pre-construction permit or a Title V operating 

permit (i.e., minor sources) are unpermitted for the time being.10 

B. Existing Sources on the Reservation Already are Well-Controlled.

The Four Corners Task Force recently published a report regarding mitigation options11, 

which provided a detailed analysis of emission reduction options for oil and gas engine 

mitigation.12 The majority of the controls identified by the Task Force are already in use on the 

Reservation. The others were determined to be ineffective or infeasible. The Four Corners 

report examined: 

• Electrification of natural gas fired compressor engines; 

• Lean burn technology; 

• Non selective catalytic reduction (NSCR); 

• Selective catalytic reduction (SCR); 

• Oxidation catalyst 

Table 6 demonstrates how the mitigation measures have been applied on compressor 

engines on the Reservation, and indicates whether those measures are feasible and effective. 

 

10 On August 21, 2006, EPA issued a notice of proposed rulemaking entitled “Review of New Sources and 

Modifications in Indian Country.” 71 Fed. Reg. 48,696 (2006). In that notice, EPA proposed to promulgate a 

Federal Implementation Plan (“FIP”) covering certain minor emission sources in “Indian country” nationwide. To 

date, however, EPA has not finalized the proposed FIP. 

11 Mitigation is defined as additional emission controls beyond NSPS. 

12 Four Corners Air Quality Task Force Report of Mitigation Options, 2007 
30 

Table 6. Summary of Conclusions Regarding Additional Controls on Natural Gas Fired 

Engines for Oil and Gas 

Mitigation Option Comments 

Electrification of natural gas 

fired compressor engines 

Based on information and belief, a major 

operator on the Reservation (i.e., BP America 

Inc.) plans for all of its new engines 

associated with ongoing infill development 

on the Reservation to be electrically operated 

and, over the next two years, plans to replace 

approximately 100 existing engines with 

electrically operated engines. The effect of 

this conversion to electrically operated 

engines will be to further reduce emissions 

from Reservation sources. 

Lean burn technology Already widely in use 

Non selective catalytic 

reduction (NSCR); 

Already widely in use 

Selective catalytic reduction 

(SCR) 

Not Feasible—Not commercially available 

for remote oil and gas operations 

Oxidation catalyst Already widely in use 

As indicated in Table 6, there is very little opportunity to retrofit existing engines with additional 

reliable and cost effective controls that will further reduce emissions from natural gas fired 

engines on the Reservation below NSPS levels. At the present time, proven technology does not 

exist to reduce emissions below the federally mandated limits. Thus, existing sources within the 

Reservation already are well-controlled. 

 Notwithstanding the conclusion in Table 6 regarding electrification, it is important to 

note that, based on information and belief, a major operator on the Reservation (i.e., BP America 

Inc.) plans for all of its new engines associated with ongoing infill development on the 

Reservation to be electrically operated and, over the next two years, plans to replace 

approximately 100 existing engines with electrically operated engines. The effect of this 

conversion to electrically operated engines will be to further reduce emissions from Reservation 

sources. 

C. Tribal Efforts to Assume Regulatory Responsibility Will Result in Better 

Control of Sources and Decreased Emissions. 

The Tribe is aggressively engaged, in cooperation with the State of Colorado, in 

developing a Reservation air program to regulate all air pollution sources located on the 

Reservation and to maintain the attainment/unclassifiable status of the Reservation area. In 

1999, the Tribe and State entered into an intergovernmental agreement concerning air quality 

control on the Reservation. The purpose of the agreement is to establish a single air quality 

program applicable to all lands within the exterior boundaries of the Reservation. A joint 
31 

Tribal/State Environmental Commission was established with responsibility for selecting the 

Clean Air Act programs and other air programs that will be adopted for the Reservation. Under 

the agreement, the day-to-day administration of the programs is the responsibility of the Tribe. 

In 2004, Congress provided specific statutory authority for the Tribe to regulate all air 

resources within the exterior boundaries of the Reservation. Southern Ute and Colorado 

Intergovernmental Agreement Implementation Act of 2004, Act of October 18, 2004, Pub. L. No. 

108-336, 118 Stat. 1354-56 (Public Law 108-336). Public Law 108-336 accomplished several 

important objectives. First, Public Law 108-336 authorizes the Environmental Protection 

Agency to treat the Tribe as a state under section 301(d) of the Clean Air Act, and allows the 

Tribe to accept delegation of EPA’s authority under the Clean Air Act in the same manner as 

states for purposes of administering air quality programs. Sec. 4(a)(1). Second, Public Law 108-

336 provides that the scope of the Tribe’s delegated authority extends to all air resources within 

the exterior boundaries of the Reservation, including those located on fee land. Sec. 4(a)(2). No 

distinction is made among the various categories of on-Reservation land. Once the delegation is 

made, therefore, the Tribe is authorized to regulate sources of air pollution located anywhere 

within the exterior boundaries of the Reservation. Third, Public Law 108-336 provides 

jurisdiction for enforcement of the Tribe’s delegated powers in the United States District Court 

for the District of Colorado and provides for judicial review in the United States Court of 

Appeals for the Tenth Circuit. Secs. 5(a) and 6, Public Law 108-336. 

 

On January 20, 2009, the Tribe submitted its Application for Treatment as a State 

Pursuant to Section 301(d) of the Clean Air Act and Section 4(a) of the Southern Ute and 

Colorado Intergovernmental Agreement Implementation Act of 2004 for the Purpose of Approval 

of the Southern Ute Indian Tribe’s Part 70 Operating Permit Program (TAS Application) and 

Application for Approval of the Southern Ute Indian Tribe’s 40 CFR Part 70 Operating Permit 

Program (Part 70 Program Application). Upon approval of the TAS Application and Part 70 

Program Application by EPA, the Tribe will become the first Indian tribe in the nation to receive 

a delegation of authority to administer a Part 70 operating permit program. These efforts 

exemplify the Tribe’s commitment to emissions control and clean air. Because the program will 

be administered locally, and because the Tribe will have several staff members devoted solely to 

regulation and inspection of sources located on the Reservation, the Tribe expects that emissions 

from sources located on the Reservation will be more effectively controlled than they are 

currently.13 

Further, the Tribe plans to seek a delegation of authority from EPA, in accordance with 

the process established by its agreement with the State of Colorado, to incorporate as part of the 

Reservation air program certain standards of performance established by EPA pursuant to section 

111 of the Clean Air Act (regulating criteria pollutant emissions from specific categories of new 

sources) (NSPS) and certain National Emission Standards for Hazardous Air Pollutants 

established by EPA pursuant to section 112 of the Clean Air Act (NESHAP) (regulating 

hazardous air pollutant emissions from specific categories of new and existing sources). The 

incorporation will enable the Tribe and the Environmental Commission to exercise 

administrative authority with respect to the incorporated regulations. With that authority will 

 

13 There are five staff members employed as part of the Tribe’s Air Quality Program, which is a ratio of 

approximately 1 staff member to every 8 major sources on the Reservation. 
32 

come the authority to set and implement controls on major sources that are more stringent than 

those that are imposed by the federal government. 

Recognizing the importance of regulating minor sources, the Tribe currently is finalizing 

a minor source permitting program to recommend to the Environmental Commission. The Tribe 

intends to recommend the program in spring 2009 with the expectation that the Environmental 

Commission will adopt the program for implementation in late 2009 or early 2010. The adoption 

of a minor source permitting program is the second priority of the Environmental Commission 

and Tribe under their Long-Term Plan for Reservation Air Program, after the development of the 

Part 70 operating permit program. 

 The minor source permitting program will mirror certain aspects of the proposed federal 

minor source NSR program (71 Fed. Reg. 48,696 (2006)), yet will be tailored towards the 

specific regulatory needs of the Reservation, and will, in some respects, be more stringent than 

the proposed federal program. The purpose of the program is to establish a permitting program 

for existing, new, and modified minor sources of air pollution and for minor modifications at 

major stationary sources located within the exterior boundaries of the Reservation. The draft 

program includes proposed minor source thresholds so that only minor sources with a potential 

to emit (PTE) equal to or higher than those thresholds (and less than the thresholds necessary for 

regulation as a major source) will be subject to the program.14 By regulating existing minor 

sources on the Reservation, the Tribe’s proposed program goes a step further than the proposed 

federal minor source NSR program. Sources subject to the program (including existing, new, 

and modified sources) will be required to apply control technology and be subject to emission 

limits as determined by the Tribe on a case-by-case basis or based on an application of 

presumptive best available control technology that may be established by the Tribe for various 

categories of similar sources with similar control technologies and capabilities. Additionally, the 

Tribe’s draft program will allow otherwise major stationary sources on the Reservation to 

voluntarily accept emission limitations on their PTE to become “synthetic minor sources.” Such 

synthetic minor sources will include sources that emit hazardous air pollutants. 

 The draft program also sets forth the criteria and procedures that the Tribe will use to 

administer the program. In accordance with the IGA and Public Law No. 108-336, the Tribe and 

Environmental Commission will enforce civil compliance with the program. Actions taken by 

the Tribe in the administration of the program will be subject to administrative review by the 

Environmental Commission in accordance with the procedures contained in the program 

regulations. A copy of the minor source program will be provided to EPA-Region 8 for review 

and comment as part of the Environmental Commission’s public review and comment process 

once the Tribe’s recommended program becomes an Environmental Commission proposed 

program. A copy of the Tribe’s draft program is available now, however, and will be provided to 

EPA upon request. 

The development of the minor source permitting program and, specifically, the plan to 

make not only new and modified sources but also existing minor sources subject to emission 

limits and control technology requirements set by the Tribe under the program, demonstrates the 

 

14 The thresholds included in the Tribe’s draft minor source program are the same as the thresholds contained in the 

proposed federal program. 
33 

Tribe’s intention to aggressively control NOx emissions from the estimated 300 to 400 minor 

sources located on the Reservation. This program, coupled with (1) the Tribe’s and 

Environmental Commission’s efforts to reduce NOx emissions from the Reservation’s 40+ major 

sources (in part through aggressive administration of the Part 70 operating permit program once 

it is delegated by EPA to the Tribe (e.g., more frequent inspections) and through the possible 

adoption of more stringent substantive requirements (e.g., NSPS, NESHAPS, and MACT)), and 

(2) the tribal-imposed conditions on new infill well development on the Reservation, should 

ensure maintenance of the attainment/unclassifiable status of the Reservation for the 2008 

revised ozone standards. 

In sum, the programs planned for implementation on the Reservation, particularly the 

minor source program, will be sufficient for the Tribe and Environmental Commission to 

maintain and prevent deterioration of the Reservation’s existing good air quality.
34 

Factor 5 (Growth Rates and Patterns) 

A. Existing Development. 

Emissions associated with mineral extraction activities are the principal source of air 

pollution on the Reservation, where rural population densities and agricultural land uses 

predominate. Development of its coalbed methane and natural gas resources has been and 

continues to be the economic lifeblood of the Tribe. Overall, the wells on the Reservation are on 

the declining end of the production curve. As noted above, the ozone monitors on the 

Reservation show attainment, and a source apportionment study shows that Reservation sources 

do not contribute meaningfully to ozone exceedances that have been measured at New Mexico’s 

Navajo Lake monitor. 

B. 80-Acre Infill Development. 

With the Tribe’s support, well density based on 80 acres rather than 160 acres on lands 

within the exterior boundaries of the Reservation already has been approved by the Colorado Oil 

and Gas Conservation Commission and development of infill wells on non-Indian fee lands has 

begun. Development of infill wells on Tribal land is needed to ensure that the gas reserves that 

are held in trust by the United States for the benefit of the Tribe are efficiently extracted in a 

manner that protects against drainage and is protective of correlative rights. 

For the infill development on the Reservation, all new natural gas-fired compressor 

engines (i.e., the largest NOx emission sources associated with the development) will be required 

to meet the new NSPS emission limits as a matter of federal law. In addition, in order to ensure 

that Reservation mineral resources are extracted in an environmentally compatible manner, the 

Tribal Council has required, as a condition of consenting to 80-acre infill development, the 

presumptive utilization of the best available air emissions control technology for new compressor 

installation, as well as the presumptive upgrade of existing compressors to contemporary best 

available emissions control technology to the maximum extent feasible in a manner consistent 

with optimizing air quality on the Reservation. 

Full infill development of Tribal lands within the Reservation would consist of as many 

as 770 new coalbed methane 80-acre infill wells to be drilled from existing and new well sites on 

the Reservation over a 20-year period. 15 That development, however, will not increase overall 

emissions from Reservation sources. In fact, as demonstrated below, there will be a dramatic 

decline in NOx emissions from Reservation sources over the life of the development. 

 

15 In comparison, according to a 20-year Reasonably Foreseeable Development Scenario supporting a Resource 

Management Plan prepared by the Bureau of Land Management in 2001 for the BLM’s Farmington, New Mexico 

Field Office, there are approximately 12,461 new oil and gas wells that are expected to be completed from 2002-

2022 in the New Mexico portion of the San Juan Basin (i.e., San Juan County and western Rio Arriba County). That 

equates to approximately 623 new wells per year. 
35 

C. A Nonattainment Designation Based on Possible Future Development is 

 Inappropriate Since NOxEmissions from Reservation Sources (and, 

 Hence, Ozone Levels on the Reservation) are Expected to Decrease Over 

 the Next 20 Years Notwithstanding Infill Development. 

Air Quality Resource Management and ENVIRON International Corporation have 

performed an extensive air quality impact analysis assessing the impact of this anticipated 

growth. The analysis conservatively assumes that the requirements of the NSPS will be applied 

only to new compressor installation and assumes no upgrades to existing compressors. Figure 21 

presents annual production estimates through 2027 with and without infill development on the 

Reservation and Figure 22 presents a summary of projected NOx emissions through 2027. As 

indicated by these figures, because of production decline, emissions of NOx (an ozone precursor) 

are projected to dramatically decrease. Furthermore, due to the additional upgrades to existing 

compressors required by the Tribe, this emissions decrease is anticipated to be accelerated. 

While NOx emissions from the Reservation will decrease even with infill development and even 

without the supplemental upgrades to existing compressors, the same probably cannot be said of 

ozone precursor emissions from northwest New Mexico, given that nearly 15 times the amount 

of new wells may be drilled in that area as compared to the Reservation, given that New Mexico 

state law bars the State from implementing regulations that are more stringent than federal NSPS 

regulations, and given the possible construction of an additional coal-fired power plant in the 

northwest New Mexico area. 
36 

Figure 21. E s timated P roduc tion

Volume by Year

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

450,000

2005

2007

2009

2011

2013

2015

2017

2019

2021

2023

2025

2027

Year

Production volumn (MMscf/yr)

E xis ting CBM E xis ting C onventional E xis ting T otal

Fee Infill T ribal Infill T otal
37 

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

5,500

6,000

6,500

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

2017

2018

2019

2020

2021

2022

2023

2024

2025

2026

2027

E xis ting CBM C onventional Gas P lant T ransms sion

E xis ting T otal T ribal Infill Fee Infill T otal (exis ting + infill)

P res s ure C hange

Note: Future year emissions were projected using operating data from 2005. 
38 

Factor 6 (Jurisdictional Boundaries) 

A. Control of Emission Sources in a Regional Nonattainment Area Would be 

Spread Among Multiple Jurisdictions and (1) is Unnecessary, (2) Could Slow 

the Tribe’s and Environmental Commission’s Implementation of Air 

Pollution Control Measures, and (3) Would Not Efficiently and Effectively 

Serve the Purpose of Improving Air Quality. 

In 1984, Congress confirmed the exterior boundaries of the Southern Ute Indian 

Reservation, which contains approximately 710,000 acres of land in southwest Colorado. 

Because of the vagaries of federal Indian policy over the last 125 years, land within the 

Reservation is owned in a checkerboard fashion by a number of different parties, meaning that 

some of the land within the exterior boundaries of the Reservation is owned by Indians and nonIndians in fee, while other land is owned by the United States in trust. The United States holds 

approximately 300,000 surface acres in trust for the Tribe. Additionally, the Tribe is the 

beneficial owner of minerals, including oil, gas and coal, on more than half of the Reservation 

lands. As discussed, the Tribe and Environmental Commission have been recognized by 

Congress as being primarily responsible for air quality on the Reservation, and the 

Environmental Commission’s air pollution control programs will apply to all sources on the 

Reservation, regardless of whether they are located on fee or trust land, and regardless of 

whether the sources are owned by Indian or non-Indian entities. 

Jurisdictional complications are amplified when considering all of the entities that can 

claim jurisdiction in the Four Corners region, given that the region includes four states, three 

EPA regions, and a half-dozen Indian reservations. Control of emission sources in the Four 

Corners region is spread among multiple jurisdictions. On the Reservation, as noted above, 

regulatory authority currently is exercised by EPA but the Environmental Commission has the 

authority to establish CAA and other air pollution control programs for the Reservation. Once 

adopted by the Environmental Commission, the Tribe may (1) apply for a delegation of authority 

from EPA to administer the CAA programs, and (2) administer the non-CAA programs. For 

land outside the exterior boundaries of the Reservation and within Colorado, the State of 

Colorado is the primary regulatory agency. Within northwest New Mexico, regulatory authority 

is split among two EPA regional offices (Region 6 for lands within New Mexico that are not 

within the Navajo Reservation and Region 9 for lands within the Navajo Reservation); the State 

of New Mexico; and the Navajo Nation. A regional nonattainment area would require close 

coordination among all of the entities with regulatory authority. 

The inclusion of the Reservation in a nonattainment area that spans all of those 

jurisdictions, however, is unnecessary given the substantial efforts that the Tribe and 

Environmental Commission already are making to control emissions. As evidenced by the 

progress that the Tribe and the Environmental Commission have made with regard to air quality 

permitting and regulation on the Reservation, as well as the proactive stance they have already 

taken to address emissions, the Tribe and the Environmental Commission will be the most 

effective entities to facilitate air quality planning and implementation of control measures on the 

Reservation to maintain the Reservation’s attainment/unclassifiable status with the 2008 revised 

ozone standard. If the Reservation were to be included in a nonattainment area, the efforts 
39 

required to prepare and implement a plan for bringing the area into attainment could hamper and 

delay the Tribe’s and Environmental Commission’s current efforts to control emissions, their 

progress in that regard, and their ability to efficiently regulate through development of the 

Reservation air program. In sum, further complicating an already difficult jurisdictional situation 

by thrusting the Reservation into an interstate, intergovernmental, nonattainment area would not 

effectively and efficiently serve the purpose of improving air quality. 

B. The Reservation is Already a Separate Air Quality Control Region. 

The nine-factor analysis that will be used in making area designations for the 2008 

revised ozone standard also was used by EPA in making area designations for the 2006 24-hour 

fine particle standard. In the context of the area designations for the 2006 24-hour fine particle 

standard, EPA stated that in evaluating the jurisdictional boundary factor, consideration should 

be given to existing boundaries and organizations that may facilitate air quality planning and the 

implementation of control measures to attain the standard. As explained below, the Reservation 

already has effectively been designated as a separate AQCR via Congressional action and should 

continue to be considered a separate AQCR for purposes of maintenance of an 

attainment/unclassifiable designation for the 2008 revised ozone standard. 

First, by not being part of a region designated by one of the first two means for 

designation under CAA section 107 (i.e., designated as an AQCR by Congress before December 

31, 1970, pursuant to the Air Quality Act of 1967; or by EPA as part of an interstate or major 

intrastate area “necessary or appropriate” for the attainment and maintenance of the NAAQS), 

the Reservation became its own AQCR. 

Second, the Reservation is recognized by Congress in the Southern Ute and Colorado 

Intergovernmental Agreement Implementation Act of 2004 as the geographic area within which 

the Environmental Commission and the Tribe are primarily responsible for assuring air quality 

(by submitting an implementation plan which will specify the manner in which national primary 

and secondary ambient air quality standards will be achieved and maintained within each air 

quality control region in the Reservation area). The purpose of the Southern Ute and Colorado 

Intergovernmental Agreement Implementation Act of 2004 was to: 

provide for the implementation and enforcement of air quality control 

programs under the Clean Air Act (42 U.S.C. 7401 et seq.) and other air 

quality programs developed in accordance with the Intergovernmental 

Agreement that provide for – 

(1) the regulation of air quality within the exterior boundaries of the 

Southern Ute Indian Reservation; and 

(2) the establishment of a Southern Ute Indian Tribe/State of Colorado 

Environmental Commission. 

Pub. L. No. 108-336, § 2(b), 118 Stat. 1354 (2004). This unique arrangement was created to 

specifically address and resolve a complicated jurisdictional issue between the Tribe and State of 
40 

Colorado and, given adequate opportunity, will prove to be an effective means to regulate air 

quality on the Reservation. 

Third, EPA has determined that the CAA operates as a delegation of federal jurisdiction 

to tribes to administer programs with respect to all air resources within the tribe’s reservation. 

See 63 Fed. Reg. 7254 (1998). In other words, in the CAA amendments of 1990, Congress 

authorized tribes to act as primary air quality regulators and recognized their reservations as the 

areas over which they are primarily responsible. CAA § 301; 42 U.S.C. § 7601(d). 
41 

Factor 7 (Geography/Topography) 

The Reservation is located in the northern portion of the San Juan Basin and the eastern 

area of the Colorado Plateau in southwestern Colorado. The Colorado Plateau is a vast 

physiographic province extending throughout western Colorado, northwestern New Mexico, 

most of northern Arizona, and southern and eastern Utah. This physiographic province is 

characterized by generally flat-lying sedimentary deposits divided by faults and monoclines that 

form cliffs and individual plateaus. Steep-sided mesas and buttes capped by erosion-resistant 

rock layers are common. 

The topography of the Reservation varies from moderately steep to steep mountains, 

canyons, and mesas in the north-central and south-central portions, to rolling hills and gently 

sloping river valleys in the eastern and western regions. Elevations range from about 6,000 to 

9,000 feet. 

Figure 23. Geography of the Southern Ute Indian Reservation. 
42 

Factor 8 (Population Density and Degree of Urbanization) 

Data from the U.S. Census Bureau demonstrates that the Southern Ute Indian Reservation 

is sparsely populated, and the degree of urbanization is minimal. Only two small towns, Ignacio 

and Arboles, are located within the Reservation boundaries, and the remainder of the 

Reservation’s population is scattered throughout the portion of the Reservation that is comprised 

of unincorporated areas of Archuleta and La Plata counties. Based on information provided on 

the website for the Colorado State Demography Office, the total population on the Reservation 

for 2007, including both Indians and non-Indians, is estimated to be approximately 16,128. 

As shown in Table 7, the population estimate for the Reservation was calculated using 

the population estimates for the unincorporated portions of Archuleta and La Plata counties 

multiplied by the estimated percentage of those counties that are within the exterior boundaries 

of the Reservation. 

Table 7. Reservation Demography – Estimated Population on Reservation. 

County / Town 

% of 

County/Town 

covered by 

Reservation 

2005 

Population 

2005 Total on 

Reservation 

2006 

Population 

2006 Total on 

Reservation 

2007 

Population 

2007 Total on 

Reservation 

Archuleta 

Unincorporated 

Area 29% 10,055 2,916 10,509 3,048 10,865 3,151 

La Plata 

Unincorporated 

Area 39.6% 29,788 11,796 30,261 11,983 30,912 12,241 

Ignacio 100% 755 755 741 741 736 736 

La Plata Total 12,551 12,724 12,977 

 

Source: http//www.dola.colorado.gov/dlg/demog/pop_munil_estimates.html 

Table 8 shows that, based on the 2006 and 2007 population data, the average growth rate 

on the Reservation is 2.7% (i.e., (3.4 +2.0) ÷ 2 = 2.7%). 

Table 8. Reservation Demography – Estimated Population Growth on Reservation. 

County 

2005 Total 

on 

Reservation 

2006 Total 

on 

Reservation 

2007 Total 

on 

Reservation 

Percent 

Change 

2006 -2007 

Archuleta 

Unincorporated 2,916 3,048 3,151 3.4%

La Plata 

Unincorporated 

and Ignacio 12,551 12,724 12,977 2.0%
43 

The total square miles of both Archuleta and La Plata counties and the estimated portion 

of those counties that lie within the exterior boundaries of the Reservation are shown on Table 9. 

Table 9. Estimated Total Square Miles on the Reservation. 

County 

Total Square 

Miles 

% County 

Covered by 

Reservation 

Total Square 

Miles on 

Reservation 

Archuleta 1,355 29.0% 393.0

La Plata 1,700 39.6% 673.2

Based on the population estimates shown in Table 7, the estimated population density 

within the exterior boundaries of the Reservation is 27 people per square mile, which is well 

below the United States average population density of 80 people per square mile: 

Table 10. Estimated Population Density on the Reservation. 

County 

Total Square 

Miles on 

Reservation 

2005 

Persons Per 

Square Mile 

2006 

Persons Per 

Square Mile 

2007 

Persons Per 

Square Mile 

Archuleta 391.5 7 8 8

La Plata 670.0 19 19 19

TOTAL on 

Reservation 26 27 27

Even combined with the three counties in southwest Colorado, the Reservation population has 

not only a much smaller density than the United States average density, it also is much smaller 

than the population of northwest New Mexico, which is 75 percent higher than the population of 

southwest Colorado. 
44 

Factor 9 (Traffic and Commuting Patterns) 

Traffic volume on the Reservation is relatively low. Approximately 150 miles of state 

and major highway segments cross the Reservation. Table 9 shows daily and annual vehicle 

miles travelled, as well as total emissions from vehicle travel on paved roads within the 

Reservation for 2005. 

Table 11. Emissions from Vehicle Travel on Paved Roads within the Reservation Boundaries 

(tons)** 

Paved Roads Length 

(mi) 

Daily VMT* Annual 

VMT* 

VOC 

(tons) 

CO 

(tons) 

NOx 

(tons) 

PM10

(tons) 

Hwy 550 15.61 100,794 3.6789E+07 56.78 1,011.56 95.43 2.50

Hwy 140 15.658 31,860 1.1628E+07 17.95 319.74 30.16 0.79

Hwy 151 33.96 43,120 1.5738E+07 24.29 432.75 40.82 1.07

US Hwy 160 7.668 65,323 2.3843E+07 46.16 704.20 71.84 1.85

Hwy 172 24.449 102,151 3.72835+07 57.54 1,025.18 96.71 2.53

Other Hwys 52 66,026 2.4099E+07 46.66 711.78 72.61 1.87

Totals 149.40 409,274.00 1.4935E+07 289.21 3,862.95 450.08 11.58

** Southern Ute Indian Tribe Air Emissions Inventory Base Year 2005. 

* Vehicle miles traveled (VMT) data is based on inventory data from the Colorado Department 

of Transportation website. 

According to the Southern Ute Indian Tribe Air Emissions Inventory Base Year 2002, 

there are approximately 3,700 miles of unpaved roads on the Reservation. Table 10 

demonstrates the emissions from vehicle travel on unpaved roads within the Reservation for 

Base Year 2002. 

Table 12. Emissions from Vehicle Travel on Unpaved Roads within the SUIT Reservation 

Boundaries (tons)*

VOC (tons) CO (tons) NOx (tons) PM10 (tons)

Unpaved Road Emissions 12.51 184.0 18.52 8,589

 * Southern Ute Indian Tribe Air Emissions Inventory Base Year 2002. 
45 

III. Other Factors. 

A. EPA Must Consider Tribal Self-Determination in Making its Area 

Designation for the Reservation. 

In the 1984 EPA Indian Policy, EPA committed that, “in keeping with the federal trust 

responsibility,” it would “assure that tribal concerns and interests are considered whenever EPA’s 

actions and/or decisions may affect reservation environments.” The Tribe’s interest in pursuing 

expanded control over emissions on the Reservation and in proposing its 80-acre infill 

development project is linked to the strong federal interests in promoting strong tribal economic 

development, self-sufficiency, and self-governance. In that regard, the Tribe is concerned that 

imposition of a nonattainment designation on the Reservation by EPA, and the corresponding 

nonattainment requirements, would constitute an infringement on the Tribe’s interests in 

territorial autonomy and could damage the long-term economic and social interests of the Tribe. 

The northern San Juan Basin is continuing to be developed and, as noted above, the Colorado Oil 

and Gas Commission already has approved 80-acre infill drilling on lands within the Reservation 

boundaries. Prudent and environmentally protective development of the mineral resources held in 

trust by the United States for the benefit of the Tribe is an important economic development 

objective of the Tribe. In fact, such development is for the express purpose of improving the 

economic and social well-being of the Tribe and its members. A portion of the revenues from 

development of the trust mineral estate are distributed to tribal members and a portion is used by 

the Tribe to fund many important governmental functions and services such as the Tribe’s police 

department, court system, school, education programs, health care services, water treatment 

plants, and recreation programs. Accordingly, the Tribe expects that in keeping with its 

commitment given in the 1984 EPA Indian Policy, EPA will “give special consideration to Tribal 

interests” when considering a designation for Reservation. 

B. Environmental Justice Favors an Attainment/Unclassifiable Designation for 

 the Reservation. 

In 1994, the President issued Executive Order 12,898 on environmental justice in 

minority and low-income populations. Executive Order 12,898: Federal Actions to Address 

Environmental Justice in Minority Populations and Low-Income Populations, 59 Fed. Reg. 7629 

(1994). The purpose of the Order is to identify and address, as appropriate, disproportionately 

high and adverse human health and environmental effects of programs, policies, or activities on 

minority or low-income populations. The mandates of Executive Order 12,898 specifically 

apply to Native American programs. Id. at § 6-606, 59 Fed. Reg. 7629, 7632 (1994). On the 

Reservation, minority populations include Native Americans and Hispanics. Low-income groups 

on the Reservation may include low-income Indians, Hispanics, and Caucasians. The Council on 

Environmental Quality has issued a guidance document on compliance with the President’s order 

on environmental justice that is designed to engender greater tribal involvement. Council on 

Environmental Quality, Environmental Justice: Guidance Under the National Environmental 

Policy Act 1, 9 (Dec. 10, 1997), <ceq.eh.doe.gov/nepa/regs/ej/justice.pdf>. This guidance 

document provides that the environmental justice concerns that federal agencies must address in 

their decision-making arise not only from impacts on the natural and physical environment, but 

also from related social and economic impacts on the affected populations. 
46 

The Tribe is concerned that a nonattainment designation of the Reservation by EPA for 

the 2008 revised ozone NAAQS would have a disproportionate negative impact on the Tribe and 

its members and would be unfair to the Tribe from a social and economic perspective. As noted 

above, comparative emission inventories reveal that emissions from northwestern New Mexico 

far exceed emissions from Reservation sources. Northwest New Mexico and Navajo Nation 

emissions include emissions from two existing coal-fired power plants and EPA recently 

approved a PSD permit for a third. Burdening Reservation development with nonattainment 

requirements in circumstances where (1) Reservation monitors show attainment, (2) source 

apportionment shows the contribution by Reservation sources to a measured exceedance at New 

Mexico’s Navajo Lake monitor is not meaningful, and (3) the Environmental Commission and 

the Tribe already are aggressively acting to control emissions, would impose a disproportionate 

burden on the Tribe to help New Mexico achieve attainment with the 2008 revised ozone 

NAAQS and would be unjust to the Tribe. 

 

In summary, it is the Tribe’s expectation that EPA will take the Tribe’s environmental 

justice concerns into account in making its 2008 revised ozone NAAQS area designation for the 

Reservation. 

C. In the Alternative, Ongoing Studies May Warrant an Unclassifiable 

 Designation for the Reservation.

In the alternative, an unclassifiable designation for the Reservation should be considered 

until officials have a more complete understanding of the root causes of the monitored 

exceedances at New Mexico’s Navajo Lake monitor. The Four Corners Air Quality Group still 

is in the process of evaluating emission reductions that could be achieved, as well as the overall 

air quality benefits that could be achieved as a result of implementation of additional controls on 

sources in the Four Corners region. Those studies include ongoing photochemical analyses that 

will provide more information on the role of VOCs and NOx from different source regions in 

ozone formation. Before including the Reservation in any nonattainment area that may be 

designated as a result of the violation measured at New Mexico’s Navajo Lake monitor, 

therefore, the results of the ongoing studies should be obtained and considered. For that reason, 

a designation of unclassifiable for the Reservation may be warranted. 

IV. Conclusion. 

 In conclusion, the Tribe’s recommendation is that the Reservation area be designated as 

“attainment/unclassifiable” for the 2008 revised ozone NAAQS and not included in any 

nonattainment area that may be designated for northwest New Mexico. The reasons supporting 

this recommendation include: 

• Monitoring data show that the Reservation is attaining the 2008 ozone NAAQS. 

• A source apportionment study shows the contribution from Reservation sources to 

the violation in northwest New Mexico is not meaningful. 

• Prevailing winds blow from the west and southwest onto the Reservation. 
47 

• Emissions from sources located on the Reservation are minimal when compared 

to emissions from sources located in northwest New Mexico. 

• Emissions from large engine sources on the Reservation already are within federal 

limits and additional emission reductions probably are not technologically 

possible at this time. 

• Reservation emissions already are well-controlled and limits and controls that will 

be required on the Reservation as a result of (1) the new NSPS emissions 

regulation, (2) self-imposed conditions to the Tribe’s support for 80-acre infill 

development, and (3) limits and controls that the Tribe currently is planning to 

include as part of the minor source program that it will recommend to the 

Environmental Commission, will be sufficient to maintain compliance with the 

2008 revised ozone NAAQS. Both the conditions for the Tribe’s support for 

infill development and the minor source program that the Tribe plans to 

recommend to the Environmental Commission, will require use of presumptive 

best available control technology (BACT) for not only new or modified minor 

sources but also existing minor sources. The required use of BACT for all minor 

sources on the Reservation is a more stringent control requirement than would be 

required, and will be implemented sooner (within 3 years under the draft minor 

source program) than probably could be required if the Reservation were 

included in a nonattainment area (assuming the nonattainment area would be 

categorized as a “marginal” nonattainment area). In addition, some of the 

controls and limits that will be required on the Reservation probably are 

equivalent to or exceed the controls that would be required if the Reservation 

were included in a “marginal” nonattainment area. 

• Continued development of the Reservation air program by the Environmental 

Commission and the Tribe advance self-determination and environmental justice 

goals. In making its designation for the Reservation area, EPA must consider not 

only its statutory duty, but the federal interest in promoting tribal selfdetermination, as well as the Tribe’s environmental justice concerns. 

Based on the Tribe’s analysis above of the 9-factors that EPA instructs must be 

considered in making recommendations for area designations for the 2008 revised ozone 

NAAQS, and based on the other considerations described above, the Tribe recommends that the 

Reservation be designated “attainment/unclassifiable” and not be included in any 

nonattainment area that may be designated for northwest New Mexico.