1

Technical Support Document for

EPA’s Proposed Action on the

State of New Mexico’s

2009 Infrastructure State Implementation Plan 

(Transport Portion) for the

2006 24-hour Fine Particulate (PM2.5)

National Ambient Air Quality Standard

U.S. EPA Region 6

February 2012
2

For information on this technical support document, please contact:

Erik Snyder

Office of Air Quality Assessment and Analysis

U.S. Environmental Protection Agency – Region 6

1445 Ross Ave. Suite 1200

Dallas, Texas 75202

(214) 665-7305

snyder.erik@epa.gov
3

Table of Contents

I. Interstate Transport and New Mexico

A. Clean Air Act Section 110(a)(2)(D)(i)(I) Requirements for the 2006 Fine 

Particulate Standards

B. Summary of Transport Assessment

1. Transport to Nonattainment Receptors in Western States

2. Transport to Maintenance Receptors in Western States

3. Transport to Nonattainment and Maintenance Receptors in Eastern States

C. Conclusion

II. State of New Mexico’s Assessment of Transport

A. Summary of State of New Mexico’s Assessment of Transport

B. EPA’s Evaluation of the State of New Mexico’s Assessment of Transport

III. Transport Assessment Methodology

A. Discussion of Nonattainment and Maintenance Receptor Selection Methodology

B. Factors Considered in the Transport Analysis for Nonattainment and Maintenance

Receptors

IV. Transport Assessment for Nonattainment Receptors

A. Introduction

B. Transport to Nearby States

1. Utah

C. Transport to Other Western States – Nevada, California, Oregon, Washington, 

Idaho, and Montana

1. Nevada

2. California

3. Oregon

4. Washington

5. Idaho

6. Montana

D. Transport to Eastern States

V. Transport Assessment for Maintenance Receptors

A. Introduction

B. Transport to Nearby States

1. Arizona

2. Utah

3. California

C. Transport to Eastern States 
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Appendices

Appendix A – Nonattainment and Maintenance Receptors List

1. List of Nonattainment and Maintenance Receptors

Appendix B – Nonattainment Receptors

1. EPA Region 8 States – Montana and Utah 

2. EPA Region 9 States – California and Nevada

3. EPA Region 10 States – Idaho, Oregon, and Washington

Appendix C – Maintenance Receptors

1. EPA Region 8 States – Utah

2. EPA Region 9 States – California and Arizona

Appendix D – PM2.5 Data – IMPROVE Data for Utah, Nevada, and California/Oregon Border 

Sites for the Years 2006-2010

1. Map of IMPROVE Monitoring Sites

2. Utah – IMPROVE Data for the Years 2006-2010

3. Nevada – IMPROVE Data for the Years 2006-2010

4. California/Oregon Border – IMPROVE Data for the Years 2006-2010

Appendix E – Additional Technical Data for Greater Salt Lake Area, Utah and Butte, Montana

1. Salt Lake City, Utah PM2.5 Data from 2006-2010

2. Butte, Montana PM2.5 Data from 2007-2010

3. Butte, Montana PM2.5 Speciation Data
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I. Interstate Transport and New Mexico

I.A. Clean Air Act Section 110(a)(2)(D)(i)(I) Requirements for the 2006 Fine Particulate

Standards

Section 110(a)(2)(D)(i)(I) of the Clean Air Act (CAA) requires each state to prohibit emissions 

that contribute significantly to nonattainment, or interfere with maintenance , in any other state 

with respect to any primary or secondary national ambient air quality standard (NAAQS). 

The New Mexico Department of Environmental Quality (NMED) submitted a letter, and 

supporting documentation on October 14, 2009 certifying that NMED has evaluated the New 

Mexico SIP, and found that the existing SIP does satisfy all the requirements of CAA section 

110(a)(2)(D)(i)(I) for the 2006 PM2.5 NAAQS and no further revisions are necessary. The

supporting documentation included a relevant technical analysis supporting New Mexico's

conclusion as recommended by EPA's guidance memorandum that provides recommendations to

states for making SIP submissions to meet the requirements of CAA section 11 O(a)(2)(D)(i) for

the 2006 PM2.s NAAQS ("2006 PM2.s NAAQS Infrastructure Guidance" or "Guidance").

1

Based on our evaluation of NMED’s submittal and other technical information, as discussed 

further below, we are proposing to approve the PM2.5 Transport Analysis and to conclude that 

additional control measures in New Mexico are not necessary under CAA section 

110(a)(2)(D)(i)(I) for the 2006 24-hour PM2.5 NAAQS because emissions from New Mexico

sources do not contribute significantly to nonattainment or interfere with maintenance of these 

standards in any other state.

 

1

See Memorandum from William T. Harnett entitled "Guidance on SIP Elements Required Under Sections

110(a)(l) and (2) for the 2006 24-Hour Fine Particle (PM25) National Ambient Air Quality Standards (NAAQS),"

September 25, 2009, available at

http://www .epa.gov/ttn/caaa!t I /memoranda/20090925 harnett_pm25 sip 110a l2.pdf.; and See Memorandum from 

William T. Harnett entitled “Guidance for State Implementation Plan (SIP) Submission to Meet Current Outstanding 

Obligations Under Section 110(a)(2)(D)(i) for the 8-hour ozone and PM2.5 National Ambient Air Quality 

Standards,” August 15, 2006, available at 

http://www.epa.gov/ttn/caaa/t1/memoranda/section110a2di_sip_guidance.pdf.
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I.B. Summary of Transport Assessment

I.B.1. Transport to Nonattainment Receptors in Western States

EPA reviewed the state of New Mexico’s PM2.5 Transport Analysis and additional technical 

information to evaluate the potential for New Mexico emissions to contribute significantly to 

nonattainment of the 2006 PM2.5 NAAQS at specified monitoring sites in the western United 

States. EPA first identified as “nonattainment receptors” all monitoring sites in the western states 

that had recorded PM2.5 design values above 35 micrograms per cubic meter (μg/m3), the level 

of the 2006 24-hour PM2.5 NAAQS, during the years 2008-2010.2See section III below

(discussing EPA’s methodology for selection of nonattainment receptors, and providing a list 

and map of western receptors). 

As pollution is transported from the source area to a downwind receptor, dispersion of the 

pollutant both vertically and horizontally occurs that results in ambient concentrations decreasing 

the further the distance away from the emission source on a general mathematical order of a 

1/(distance)x where initially the power x is approximately 2 and at longer distances the power x 

value is between 1 and 2. Therefore, geographic distance from a geographical area source of 

emissions to a downwind receptor area is an important relevant factor because the further away a 

receptor is from New Mexico’s emissions, the lower the potential ambient concentrations will be 

from New Mexico’s emissions if transport did occur. Therefore in the assessment of potential 

pollution transport, EPA first focused its review on information related to potential transport of 

PM2.5 pollution from New Mexico to the states bordering New Mexico: Arizona, Utah, 

Colorado, Oklahoma, and Texas. Of these bordering states, EPA identified only Utah as having 

a nonattainment receptor. As discussed further below, EPA believes that the following factors 

support a finding that emissions from New Mexico does not significantly contribute to 

nonattainment of the 2006 PM2.5 NAAQS in Utah: (1) technical information indicating that 

elevated PM2.5 levels at nonattainment receptors are predominantly caused by local emission 

sources, (2) air quality data indicating that regional background levels of PM2.5 are generally 

low during the time periods of elevated PM2.5 at these receptors, (3) the distance to the receptor 

in the northwest quadrant of Utah, and (4) the presence of significant terrain, which creates a 

physical impediment to pollution transport. 

EPA also evaluated potential PM2.5 transport to potential nonattainment receptors in the more 

distant western states of California, Nevada, Oregon, Washington, Idaho, Wyoming, and 

Montana. EPA believes that the following factors support a finding that emissions from New 

Mexico do not significantly contribute to nonattainment of the 2006 PM2.5 NAAQS in any of 

these states (excluding California): (1) the significant distance from the State of New Mexico to 

the nonattainment receptors in these states, (2) technical information indicating that elevated 

PM2.5 levels at nonattainment receptors in these states are predominantly caused by local 

emission sources, (3) air quality data indicating that regional background levels of PM2.5 are 

generally low during the time periods of elevated PM2.5 at these receptors, and (4) the presence 

of significant terrain, which creates a physical impediment to pollution transport. With respect to 

 

2 Because CAIR did not cover states in the western United States, these data are not significantly impacted by the 

remanded CAIR . In contrast, recent air quality data in the eastern, midwestern and southern states are significantly 

impacted by reductions associated with CAIR.
3

California, technical information indicating that elevated PM2.5 levels at the nonattainment 

receptors are predominantly caused by local emission sources and that the dominant air flows 

across California are from the west to the east support a finding that emissions from the state of 

New Mexico do not significantly contribute to nonattainment of the 2006 PM2.5 standards in 

California.

We discuss these evaluations in more detail below.

I.B.2. Transport to Maintenance Receptors in Western States

EPA reviewed the state of New Mexico’s PM2.5 Transport Analysis and additional technical 

information to evaluate the potential for New Mexico emissions to interfere with maintenance of 

the 2006 24-hour PM2.5 standards at specified monitoring sites in the western U.S. EPA first 

identified as “maintenance receptors” all monitoring sites in the western states that had recorded 

PM2.5 design values above the level of the 2006 24-hour PM2.5 NAAQS (35 μg/m3) during the 

2006-2008 and/or 2007-2009 periods but below this standard during the 2008-2010 period.

3

See

section III below (discussing EPA’s methodology for selection of maintenance receptors). All of 

these maintenance receptors in the western states are located in Arizona, Utah and California.

EPA thus evaluated the potential for transported New Mexico emissions to interfere with 

maintenance of the NAAQS at Arizona, Utah and California receptor locations.

4

EPA believes 

that the following factors support a finding that emissions from sources in the State of New 

Mexico do not interfere with maintenance of the 2006 PM2.5 NAAQS in Arizona and Utah: (1) 

the significant distance from the State of New Mexico and the sources of New Mexico’s PM2.5 

pollution to the maintenance receptors in these states, (2) technical information indicating that 

elevated PM2.5 levels at maintenance receptors in these states are predominantly caused by local 

emission sources, (3) air quality data indicating that regional background levels of PM2.5 are 

generally low during the time periods of elevated PM2.5 at these receptors, and (4) the presence 

of significant terrain, which creates a physical impediment to pollution transport. With respect to 

California, technical information indicating that elevated PM2.5 levels at the maintenance 

receptors are predominantly caused by local emission sources and that the dominant air flows 

across California are from the west to the east support a finding that emissions from sources in 

the state of New Mexico do not interfere with maintenance of the 2006 PM2.5 standards in 

California.

We discuss these evaluations in more detail below.

I.B.3. Transport to Nonattainment and Maintenance Receptors in Eastern States

EPA has also considered potential PM2.5 transport from New Mexico emission sources to the 

nearest potential nonattainment or maintenance receptors located in the eastern states within the 

domain of the modeling analysis for the Cross State Air Pollution Rule (CSAPR) (76 FR 48208).

The nearest nonattainment and/or maintenance receptor identified in the 2012 CSAPR modeling 

 

3 As noted above, EPA can consider data from these years for states in the western United States as such data is not 

impacted by the remanded CAIR.

4 As this analysis is focused on interstate transport, EPA did not evaluate the impact of New Mexico emissions on 

maintenance receptors within New Mexico.
4

analysis is in Madison County, Illinois. The CSAPR modeling did not analyze the contribution 

of New Mexico sources to Madison County, Illinois. Thus, EPA analyzed the magnitude of New 

Mexico’s sulfur dioxide (SO2) and nitrogen oxides (NOx) emissions relative to states found to 

have emissions that significantly contribute to nonattainment at that receptor. EPA also 

considered the distance of New Mexico from Madison County, Illinois relative to states found to 

significantly contribute there. EPA believes that the following factors in comparison to other 

areas support a finding that emissions from New Mexico sources do not significantly contribute 

to nonattainment or interfere with maintenance of the 2006 24-hour PM2.5 NAAQS at this 

location: (1) the relatively small magnitude of the emission inventory of PM2.5 precursors (SO2

and NOx) in New Mexico combined with (2) the relatively long distance between the nearest 

portion of the state of New Mexico to the Madison County, Illinois receptor. EPA believes that 

these factors also support a finding that emissions from New Mexico sources do not contribute 

significantly to nonattainment or interfere with maintenance of the 2006 24-hour PM2.5 NAAQS 

at any of the other CSAPR receptors, all of which are farther from New Mexico than Madison 

County, Illinois and are less likely for New Mexico’s emissions to impact. 

I.C. Conclusion

EPA’s review of available technical information and air quality data supports the conclusion in 

New Mexico’s PM2.5 Transport Analysis that emissions of direct PM2.5 and PM2.5 precursors 

from the state of New Mexico do not significantly contribute to nonattainment in, or interfere 

with maintenance by, any other state with respect to the 2006 24-hour PM2.5 standards.

Based on our evaluation of New Mexico’s PM2.5 Transport Analysis and additional technical 

information, as discussed further below, EPA proposes to conclude that emissions of direct 

PM2.5 and PM2.5 precursors from the state of New Mexico do not significantly contribute to 

nonattainment or interfere with maintenance of the 2006 24-hour PM2.5 standards in any other 

state and that CAA section 110(a)(2)(D)(i)(I) therefore does not require New Mexico to adopt 

additional controls to prohibit such impacts.

II. State of New Mexico’s Assessment of Transport

II.A. Summary of State of New Mexico’s Assessment of Transport

New Mexico’s PM2.5 Transport Analysis contains the State’s assessment of the potential for

emissions of PM2.5 and PM2.5 precursors from New Mexico sources to significantly contribute 

to nonattainment or interfere with maintenance of the 24-hour PM2.5 standards in any other 

state.5 The state considered distance, topography and meteorology, stating that, “The closest 

PM2.5 nonattainment area to New Mexico is approximately 600 miles away in northwestern 

Utah.” The state also considered the level of emissions in the state of New Mexico, and PM2.5

monitoring data.

Based on these analyses, NMED concluded that “Due to the lack of PM2.5 nonattainment areas 

in or within close proximity to New Mexico, NMED has concluded that no revisions to the 

state’s 2007 SIP revision for 110(a)(2)(D)(i) are necessary at this time.”6

 

5

See NM letter to EPA June 12, 2009.

6

Id.
5

II.B. EPA’s Evaluation of the State of New Mexico’s Assessment of Transport

. EPA reviewed NMED’s analysis and as explained in Section III below, EPA has supplemented

its evaluation of the PM2.5 Transport Analysis with additional technical information consistent 

with the methodologies and analyses developed in the Transport Rule (also called the “CrossState Air Pollution Rule”)7

and the 2005 “Clean Air Interstate Rule.”

8

 Our proposed action takes 

into account both the State’s assessment in the PM2.5 Transport Analysis and our own 

supplemental assessment of relevant technical information, including the characteristics of the 

formation of elevated PM2.5 at nonattainment and maintenance receptors in neighboring states, 

and ambient PM2.5 levels at monitoring sites representative of regional background in nearby 

states. This information is discussed further below. EPA’s supplemental analysis supports New 

Mexico’s conclusion that no further controls are necessary to prevent contribution to 

nonattainment or interference with maintenance of the 2006PM2.5 NAAQS in areas outside New 

Mexico.

III. Transport Assessment Methodology

III.A. Discussion of Nonattainment and Maintenance Receptor Selection Methodology

On September 25, 2009, EPA issued a guidance memorandum that provides recommendations to 

states for making submissions to meet the requirements of CAA section 110(a)(2)(D)(i) for the 

2006 24-hour PM2.5 standards. See Memorandum from William T. Harnett, Director, Air 

Quality Policy Division, to Regional Air Division Directors, Regions I-X, “Guidance on SIP 

Elements Required Under Sections 110(a)(1) and (2) for the 2006 24-Hour Fine Particle (PM2.5) 

National Ambient Air Quality Standards (NAAQS),” September 25, 2009 (“2006 PM2.5

NAAQS Infrastructure Guidance” or “Guidance” ).9The Guidance recommends that each state 

explain in its section 110(a)(2)(D)(i)(I) SIP whether or not its emissions contribute significantly 

to nonattainment or interfere with maintenance of the NAAQS in any other state, and to address 

any such impacts. See Guidance at 3, 4. The Guidance states as follows: 

The state's conclusion must be supported by an adequate technical analysis. Information 

to support the state's determination with respect to significant contribution to 

nonattainment might include, but is not limited to, information concerning emissions in 

the state, meteorological conditions in the state and the potentially impacted states, 

monitored ambient concentrations in the state and the potentially impacted states, the 

distance to the nearest area that is not attaining the NAAQS in another state, and air 

quality modeling. The EPA believes that it would be appropriate for states to make this 

assessment by considering the impact of current or future emissions on nearby

nonattainment areas, and evaluating the air quality impact and potential mitigation 

strategies.10

 

7

75 FR 45210 (August 2, 2010) (proposed Transport Rule) and 76 FR 48208 (August 8, 2011) (final Transport 

Rule).

8

70 FR 25172 (May 12, 2005).

9 Available at: http://www.epa.gov/ttn/caaa/t1/memoranda/20090925_harnett_pm25_sip_110a12.pdf

10 Guidance at 3.
6

To determine whether the CAA section 110(a)(2)(D)(i)(I) requirement is satisfied, EPA must 

determine whether a state’s emissions contribute significantly to nonattainment or interfere with 

maintenance in downwind areas. If this factual finding is in the negative, then section 

110(a)(2)(D)(i)(I) does not require any changes to a state’s SIP. If, however, the evaluation 

reveals that emissions from sources within the state do contribute significantly to nonattainment 

or interfere with maintenance in other states, then the state must adopt substantive provisions to 

eliminate those emissions. The state could achieve any required reductions through traditional 

command and control programs, or at its own election, through participation in a cap and trade 

program. Consistent with EPA's approach in the 1998 NOx SIP call, the 2005 CAIR, and the 

2011 Transport Rule,11 EPA is evaluating these impacts with respect to specific monitors 

identified as having nonattainment and/or maintenance problems, which we refer to as 

“receptors.”12 EPA notes that no single piece of information is by itself dispositive of the issue. 

Instead, the total weight of all the evidence taken together is used to evaluate significant 

contributions to nonattainment or interference with maintenance of the 2006 24-hour PM2.5

NAAQS in another state.

A receptor may be a downwind location that is currently violating the PM2.5 NAAQS, has 

violated in the past, is projected to violate in the future, or may have trouble maintaining the 

NAAQS in the future. Nonattainment and maintenance receptors can be identified using future 

year modeling, recent ambient data, or both. 

If appropriate future year modeling is not available,

13 nonattainment and maintenance receptors 

can be identified using recent ambient air quality monitoring data. For this action, we evaluated 

the three most recent consecutive 3-year periods for which complete, quality-assured and 

certified air quality data were available (covering a 5-year period) to calculate “design values”14

for those periods. Because EPA uses the most recent 3-year design value period for purposes of 

promulgating air quality designations and redesignations, it is logical to use the most recent 3-

year period to identify “nonattainment” receptors. However, previous violations of the NAAQS 

are indicative of an air quality problem that may return in the future. The year to year variability

of emissions and/or meteorology may cause an area to have trouble maintaining the NAAQS in 

the future. Therefore, we have identified “maintenance” receptors by examining previous years 

of data. This methodology is conceptually similar (although not identical) to the methodology

that EPA used in the CSAPR to identify “nonattainment” and “maintenance” receptors. 

We applied the following methodology:

 

11 See NOx SIP Call, 63 FR 57371 (October 27, 1998); CAIR, 70 FR 25172 (May 12, 2005); and Transport Rule or 

Cross-State Air Pollution Rule, 76 FR 48208 (August 8, 2011).

12 Air quality designations are not relevant to the methodology for identifying these “receptors.”

13 Available modeling data should be evaluated for the intended purpose. If modeling data is used to establish 

nonattainment and/or maintenance receptors, it should be for an appropriate future year (within the time frame of 

downwind attainment dates) and model performance should be shown to be acceptable for the upwind and 

downwind areas being considered. 

14 “Design value” means the “calculated concentration according to the applicable appendix of [40 CFR part 50] for 

the highest site in an attainment or nonattainment area.” 40 CFR 58.1 (definitions).
7

Similar to the CSAPR analysis, we examined ambient data which spanned a 5-year period. This 

allows examination of year to year variability. The three most recent consecutive three-year 

design value periods are 2006-2008, 2007-2009, and 2008-2010.

15

1) Nonattainment receptors are those sites that are violating the NAAQS in the most recent 

3-year period.

16

2) Maintenance receptors are those receptors that show attainment in the most recent 3-year

design value period (2008-2010) but violated the NAAQS in at least one of the previous 

two periods (2006-2008 and/or 2007-2009). 

Ambient data included the three most recent official design value periods available at the time of 

the analysis. The official design values are posted by EPA’s Office of Air Quality Planning and 

Standards (OAQPS) on the Air Trends website and are available at: 

http://www.epa.gov/airtrends/values.html. A list of receptors selected for this interstate transport 

analysis is shown below in Figure III.A.1., and the corresponding map of receptors is shown 

below in Figure III.A.2. Receptors with PM2.5 design values above the PM2.5 standard of 

35μg/m3for the years 2008 through 2010 are listed as nonattainment receptors. Receptors with 

PM2.5 design values at or below the PM2.5 standard of 35μg/m3for 2008-2010 but above the 

standard for at least one of the previous 3-year periods (2006-2008 or 2007-2009) are listed as 

maintenance receptors. Based on this methodology, New Mexico, Colorado, and Wyoming do 

not contain any nonattainment or maintenance receptors.

To evaluate the potential for significant contribution to nonattainment in other states, EPA first

evaluated potential transport to the nearest states with identified nonattainment receptors. The 

states bordering New Mexico with nonattainment receptors are Utah. EPA then evaluated

potential transport to other western states with nonattainment receptors located farther away, i.e.,

California, Nevada, Oregon, Washington, Idaho, and Montana. To evaluate the potential for 

interference with maintenance in other states, EPA evaluated potential transport to maintenance 

receptors in Utah, Arizona and California, which are the only western states (outside of New 

Mexico) with identified maintenance receptors. 

 

15 As noted above, EPA can consider data from these years for states in the western United States as such data is not 

impacted by the remanded CAIR.

16 When evaluating recent design values, it is not necessary to average the design values together to create a fiveyear weighted average. Weighted average data is only necessary when projecting modeling data to the future, since 

modeled projections are generally based on only a single year (or less) of modeled meteorology.
8

Table III.A.1. List of Western Counties with Daily PM2.5

Nonattainment or Maintenance Receptors

State County AIRS ID Design Value

2006-08

Design Value 

2007-09

Design Value 

2008-10

Receptor

Type

New Mexico Pinal 040213013 48 NA 40 NA 31 A Maintenance

New Mexico Santa Cruz 040230004 40 NA 31 A 32 A Maintenance

California Alameda 060010007 36 NA 34 A 30 A Maintenance

California Butte 060070002 69 NA 59 NA 51 NA Nonattainment

California Fresno 060190008 58 NA 60 NA 54 NA Nonattainment

California Imperial 060250005 36 NA 34 inc-a 32 inc-a Maintenance

California Inyo 060271003 34 inc-a 38 NA 36 NA Nonattainment

California Kern 060290016 70 NA 70 NA 65 NA Nonattainment

California Kings 060310004 52 NA 53 NA 49 NA Nonattainment

California Los Angeles 060370002 41 NA 42 NA 38 NA Nonattainment*

California Merced 060472510 50 NA 51 NA 45 NA Nonattainment

California Orange 060590007 38 NA 37 NA 30 A Maintenance

California Riverside 060658005 53 NA 49 NA 41 NA Nonattainment*

California Sacramento 060670006 54 NA 49 NA 40 NA Nonattainment*

California San Bernardino 060712002 52 NA 48 NA 37 NA Nonattainment*

California San Diego 060731011 9 inc-a 9 inc-a 43 NA Nonattainment

California San Joaquin 060771002 51 NA 50 NA 44 NA Nonattainment

California Santa Clara 060850005 36 NA 34 A 30 A Maintenance

California Solano 060950004 36 NA 36 NA 31 A Maintenance

California Stanislaus 060990006 67 inc-na 60 inc-na 55 NA Nonattainment

California Sutter 061010003 47 NA 42 NA 36 NA Nonattainment

California Tulare 061072002 57 NA 59 NA 51 NA Nonattainment

Idaho Franklin 160410001 27 inc-a 31 inc-a 46 NA Nonattainment

Idaho Shoshone 160790017 34 A 34 A 36 NA Nonattainment

Montana Silver Bow 300930005 32 A 32 A 38 NA Nonattainment

Nevada Washoe 320310016 35 A 39 NA 38 NA Nonattainment

Oregon Klamath 410350004 46 NA 47 NA 45 NA Nonattainment

Oregon Lake 410370001 41 inc-na 41 NA 38 NA Nonattainment

Oregon Lane 410392013 40 NA 41 NA 38 NA Nonattainment

Utah Box Elder 490030003 35 A 37 NA 42 NA Nonattainment

Utah Cache 490050004 36 NA 40 NA 43 NA Nonattainment

Utah Davis 490110004 35 A 38 NA 38 NA Nonattainment

Utah Salt Lake 490350003 45 NA 48 NA 45 NA Nonattainment*

Utah Utah 490494001 44 NA 50 NA 41 NA Nonattainment*

Utah Weber 490570002 36 NA 41 NA 38 NA Nonattainment*

Washington Pierce 530530029 44 NA 46 NA 38 NA Nonattainment

Washington Yakima 530770009 36 inc-na 37 NA 37 NA Nonattainment

NA = Not attaining; A = attaining; inc-na = incomplete/not attaining; inc-a = incomplete/attaining

* = This county contains both nonattainment and maintenance receptors. See Appendix A of this TSD for more 

details.
9

Figure III.A.2: Map of Daily PM2.5 Nonattainment and Maintenance Receptors

III.B. Factors Considered in Transport Analysis for Nonattainment and Maintenance 

Receptors. 

Consistent with the recommendations in the Guidance, EPA reviewed emission inventory data,

ambient monitoring data, and meteorological conditions within the state of New Mexico. In 

addition, EPA reviewed PM2.5 monitoring data in areas representative of western regional 

background levels of PM2.5 in the nearby states of Utah and Arizona as well as selected remote 

monitoring sites on the California-Oregon border and in Oregon, Washington, Idaho, and 

Montana. Finally, EPA reviewed technical information related to each of the nonattainment and 

maintenance receptors in the potentially impacted states, including meteorological conditions 

and ambient PM2.5 monitoring data.

Specifically, EPA reviewed the emission inventory data. Based on 2005 and 2012 data in the 

USEPA Transport Rule Modeling, the PM2.5 Transport Analysis provides statewide emissions 

data as follows: 2005 - 343,139 tons of NOx and 50,755 tons of SO2; 2012 – 281,341 tons of 

NOx and 25,254 tons of SO2.

17 The monitored ambient PM2.5 concentrations for nonattainment

 

17 See Tables 7-1and 7-2 of the “Technical Support Document (TSD) for the final Transport Rule Docket ID No. 

EPA-HQ-OAR-2009-0491 Emissions Inventory Final Rule TSD,” June 28, 2011.
10

and maintenance receptors in the state of New Mexico are shown above in Figure III.A.1, “List 

of Daily PM2.5 Nonattainment and Maintenance Receptors.” All design values for the time 

period 2008-2010 within the state of New Mexico are below the PM2.5 24-hour standard of 

35μg/m3. Pinal County has design values above 35μg/m3 for the earlier time periods of 2006-08 

and 2007-09, and Santa Cruz County has design values above 35μg/m3 for 2006-08.

EPA then reviewed PM2.5 monitoring data from relatively remote ambient air monitoring sites 

that EPA believes is representative of regional background PM2.5 levels in the western United 

States. EPA reviewed five years of data collected at the IMPROVE18 monitoring network at each 

of eight National Parks in Utah (Bryce Canyon, Zion, Capitol Reef, and Arches National Parks) 

and Nevada (Jarbidge Wilderness Area and Great Basin National Park), and at the CaliforniaOregon border (Lava Beds National Monument and Crater Lake National Park). Ambient PM2.5

monitoring data, as well as chemical species data (ammonium nitrate, ammonium sulfate,

elemental carbon, organic carbon, sea salt, and soil) is available for each of these monitoring 

sites. We provide monitored PM2.5 data from each of these monitoring sites during the 2006-

2010 period, for each day when measurements occurred, as well as a map of the site locations in 

Appendix D of this TSD. This provides information about regional background levels of PM2.5

in the states surrounding New Mexico, as well as the chemical composition of the PM2.5 in these 

areas.

Most of the elevated levels of PM2.5 in the western states are measured during the winter 

months. For example, of the 17 days with measured values above the standard in 2010 in Salt 

Lake City, eleven days were in January (with levels up to 76μg/m3), and four days were in 

December (with levels up to 53μg/m3). The remaining two days above the standard were March 

30 and April 27. 

The PM2.5 data for each of the eight IMPROVE monitoring sites indicate low background 

PM2.5 levels throughout the year, but especially during the winter months for each of the years 

from 2006 through 2010. For example, the PM2.5 values for January and December of 2010 at 

Bryce Canyon National Park, Utah are below 3μg/m3.

In the winter, when the measured PM2.5 values in Salt Lake City are as high as 76 μg/m3, the 

PM2.5 values in remote areas are very low (below 3 μg/m3), indicating that over 90% of the PM 

in the urban area is locally generated. Because the PM2.5 at these locations is local in nature, it is 

reasonable to conclude that emissions from New Mexico do not have a significant impact on 

nonattainment in Salt Lake City. In contrast, an analysis of the CSAPR 2012 nonattainment and 

maintenance receptors shows that a large fraction of the daily PM2.5 concentrations in Eastern 

areas are from upwind states. For the 41 CSAPR daily PM2.5 nonattainment and maintenance 

receptors, the modeled upwind sulfate plus nitrate contribution to total PM2.5 ranged from a low 

 

18 The Interagency Monitoring of Protected Visual Environments (IMPROVE) program is a cooperative 

measurement effort governed by a steering committee composed of representatives from Federal and regional-state 

organizations. The IMPROVE monitoring program was established in 1985 to aid the creation of Federal and State 

implementation plans for the protection of visibility in Class I areas. The objectives of IMPROVE include 

establishing current aerosol conditions in mandatory class I areas; and identifying chemical species and emission 

sources responsible for existing man-made visibility impairment. 

http://vista.cira.colostate.edu/improve/Overview/IMPROVEProgram_files/frame.htm
11

of 20% to a high of 53% with a median value of 37%.19 Since CSAPR only tracked the 

contributions of sulfate and nitrate, these values represent the minimum percentage of upwind 

contribution to the receptors. Accounting for transport of additional primary PM2.5 species 

would only increase the upwind percentage and therefore decrease the percentage of PM2.5 due 

to local sources.

Figure III.B.1. IMPROVE PM2.5 Data for Bryce Canyon National Park for the Year 2010

In addition to reviewing background monitoring data which indicates that the elevated PM2.5

levels are not likely due to regional transport, EPA reviewed technical information, such as 

meteorological conditions and monitored ambient data, related to each of the areas with 

nonattainment and maintenance receptors in the potentially impacted states to determine whether 

local emissions cause or contribute to the elevated PM2.5 levels at these locations. We discuss 

our evaluation for each of the areas with receptors in the following sections.

IV. Transport Assessment for Nonattainment Receptors

IV.A. Introduction

Based on our methodology for selecting nonattainment receptors in Section III.A, above 

(Discussion of Nonattainment and Maintenance Receptor Selection Methodology), EPA has 

identified nonattainment receptors in seven western states: Utah, Nevada, California, Oregon, 

Washington, Idaho, and Montana. EPA has evaluated technical information regarding transport 

for each of the areas with nonattainment receptors identified above, following the methodology

discussed in Section III. B. Transport to the states which border New Mexico and have 

nonattainment receptors (Utah) is addressed first. Transport to the more distant western states

 

19 See Memorandum to File, Brian Timin, EPA, Office of Air Quality Planning and Standards, “CSAPR Daily 

PM2.5 Upwind Contribution,” July 2012.
12

with nonattainment receptors (Nevada, California, Oregon, Washington, Idaho, and Montana)

are then addressed. Finally, transport to eastern states is addressed.

IV.B. Transport to Nearby States

IV.B.1. Utah20

Elevated levels of PM2.5 in the Utah nonattainment areas occur primarily in the winter months.21

The levels of elevated PM2.5 in the Salt Lake City 2006 PM2.5 nonattainment area and the 

Provo 2006 PM2.5 nonattainment area are primarily due to local emissions, as noted in the 

discussion of Salt Lake City and Provo nonattainment areas below. 

Of the 17 days with measured values above the standard in 2010 in Salt Lake City, eleven days 

were in January (with levels up to 76μg/m3), and four days were in December (with levels up to 

53μg/m3). The remaining two days above the standard were March 30 and April 27. 

During the winter months, levels of PM2.5 at background monitoring sites located north of New 

Mexico and south of the Utah nonattainment receptors22 are very low, generally below 3μg/m3,

indicating that over 90% of the PM in the urban area is locally generated. As discussed above, 

this supports our finding that PM2.5 levels are not likely to be caused by regional elevated 

PM2.5 levels. The local nature of the PM2.5 levels during the time period when the standard is 

exceeded and the low levels of background PM2.5 during these time periods support our finding 

that emissions from the state of New Mexico do not contribute significantly to nonattainment of 

the PM2.5 standard at these nonattainment receptors. 

Box Elder, Davis, Salt Lake, Tooele, and Weber Counties (Greater Salt Lake Area)

All of Davis and Salt Lake counties, and portions of Box Elder, Tooele and Weber counties are 

designated as part of the Salt Lake City (SLC) 2006 PM2.5 nonattainment area (NAA). The SLC 

NAA is situated in a valley bordered on the west by the Stansbury Mountains,23 Promontory

Mountains and Great Salt Lake, and on the east by the Wasatch Front. During inversions, the 

NAA becomes a closed airshed (save for potential transport between the Salt Lake City and 

Provo NAAs) featuring stagnant air masses and light winds which typically oscillate back and 

forth within the airshed. As the airshed is essentially capped during inversions, PM2.5 is formed 

in-situ (and trapped) via fresh locally derived emission sources and secondary chemistry.

24

Speciation data from wintertime PM2.5 exceedance days from 2004-2006 showed the average

composition of PM2.5 in Salt Lake City is 58% ammonium nitrate, 31% carbon and organic 

 

20 For discussion of the Idaho/Utah – Franklin County/Cache County area, see section IV.3.C Idaho of this TSD.

21 See Appendix E at E.1.

22 IMPROVE monitoring network at each of six National Parks in Utah (Bryce Canyon, Zion, Capitol Reef, and 

Arches National Parks) and Nevada (Jarbidge Wilderness Area and Great Basin National Park),

23 The Quqirrh Mountains lie between the Wasatch Front and the Stansbury Mountains. However, EPA determined 

that some areas located west of the Quqirrh Mountains should still be considered part of the SLC nonattainment 

area. 

24 2006 24-Hour PM2.5 NAAQS Designations (74 FR 58688, November 13, 2009), Technical Support Document, 

December 2008, Index 583-669 at 40.
13

compounds, 8% ammonium sulfate, and 2% crustal. Several factors, including significant 

mobile, point, and area sources contribute to primary and secondarily formed PM2.5 that violate 

the standard during stable weather events associated with strong inversions.

Utah County (Provo-Orem)

A large portion of Utah County is designated as the Provo 2006 PM2.5 nonattainment area. The 

Provo NAA is situated in the Utah Valley. Like the other low-lying valleys just west of the 

Wasatch Front, the topography of the Utah Valley makes it prone to temperature inversions. 

During inversions, the Provo NAA features stagnant air masses and calm to light winds. As the 

airshed is essentially capped, PM2.5 is formed in-situ (and trapped) via fresh locally derived 

emission sources and secondary chemistry.

25 Transport of air masses between the Salt Lake City

and Provo NAAs can occur during inversions, as there is a 4.75-mile gap in the mountains

separating these airsheds that is below the approximate average inversion height for these 

areas.26

Speciation data from wintertime PM2.5 exceedance days from 2004-2006 showed the average

composition of PM2.5 in Provo is 71% ammonium nitrate, with 21% carbon and organic 

compounds, 8% ammonium sulfate, and 2% crustal. Several factors, including significant 

amounts of emissions from mobile, point, and area sources, contribute to ambient levels of

primary and secondarily formed PM2.5 that violate the standard during stable weather events 

associated with strong inversions.

IV. C. Transport to Other Western States – Nevada, California, Oregon, Washington, 

Idaho and Montana

IV.C.1. Nevada

PM2.5 formation at the nonattainment receptor in Nevada is discussed in detail in Appendix B 

and is summarized below.

Elevated PM2.5 levels in the Reno area occur during wintertime stagnation episodes. The highest 

values are generally measured in January and December. 27 Wildfires in June and July of 2008 

had a large impact on PM2.5 concentrations in this area; however, the Washoe County Health 

District has flagged the affected data as exceptional events.28 

The IMPROVE PM2.5 monitoring data for the Nevada sites, shown in Appendix D, show very

low levels of PM2.5 (below 3μg/m3) for the months of January and December for each of the 

years from 2006 through 2010. We also note that Nevada areas are even further away than the 

 

25 Id.

26 Id. at 41.

27 Washoe County, Nevada Air Quality Trends (2002-2011). 

http://www.co.washoe.nv.us/repository/files/4/Washoe-County-Air-QualityTrends-2002-2011.pdf

28 Washoe County, Nevada Air Quality Trends (2002-2011). 

http://www.co.washoe.nv.us/repository/files/4/Washoe-County-Air-QualityTrends-2002-2011.pdf
14

Utah areas and more dispersion of New Mexico’s emissions would be expected compared to the 

Utah analysis.

The local nature of the PM2.5 levels during time period when the standard is exceeded and the 

low levels of background PM2.5 during these time periods support our finding that emissions 

from the state of New Mexico do not contribute significantly to nonattainment of the PM2.5

standard at these nonattainment receptors.

IV.C.2. California

Transport to nonattainment receptors in California is discussed in detail in Appendix B and is

summarized below. We note that California areas are even further away than the Utah areas, 

there are more terrain blocking features (mountains and mountain ranges) and more dispersion of 

New Mexico’s emissions (less potential impacts) would be expected compared to the Utah 

analysis. We also note that general transport winds are west to east in California which would 

not typically provide transport of New Mexico’s emissions.

Northern California – Butte, Sacramento, and Sutter Counties

In Northern California, monitored exceedances of the PM2.5 standard appear to result from 

complex topography and localized emissions occurring during wintertime temperature inversions 

with low winds that persist for several days in an area that traps emissions. The speciation data 

from high concentration days indicates that as much as 75% of the concentrations are due to 

organic carbon, which also indicates that residential wood burning emissions are the dominant 

source.29

Given the factors that indicate the elevated PM2.5 levels at these locations are caused by local 

emissions, which occur during wintertime temperature inversions with low winds that persist for 

several days in an area that traps emissions, together with complex topography and the distance 

of the area from New Mexico, we believe it is reasonable to conclude that emissions from New 

Mexico sources do not significantly contribute to nonattainment of the 2006 24-hour PM2.5

NAAQS at these receptor locations.

Central California – Fresno, Kern, Kings, Merced, San Joaquin, Stanislaus, and Tulare Counties

In Central California, the monitored exceedances of the PM2.5 standard appear to result from 

complex topography and localized emissions occurring during wintertime temperature inversions 

with low winds that persist for several days in an area that traps emissions together with complex 

topography. The speciation data from high concentration days indicate high levels of secondary

nitrate. On some days elevated levels of organic carbon indicate that residential wood burning 

also contributes to elevated levels of PM2.5. 

Given the factors that indicate the elevated PM2.5 levels at these locations are caused by local 

emissions, which occur during wintertime temperature inversions with low winds that persist for 

 

29 ARB Almanac website (2006) http://www.arb.ca.gov/ei/maps/statemap/cntymap.htm)
15

several days in an area that traps emissions, together with complex topography and the distance 

of the area from New Mexico, we believe it is reasonable to conclude that emissions from New 

Mexico sources do not significantly contribute to nonattainment of the 2006 24-hour PM2.5

standard at these receptor locations.

Southern California – Los Angeles, Riverside, and San Bernardino Counties

PM2.5 in Southern California is essentially a combustion-generated pollutant and is associated 

with the volume of traffic, and numbers of sources (both point and area) located in the region. It 

is important to note that the areas with the highest concentrations of PM2.5 are directly 

downwind of an area with major ammonia sources associated with dairies and poultry farming.

Eastern California – Inyo County

Elevated levels of PM2.5 in Inyo County are measured at a single monitor, the Keeler monitor, 

which is located adjacent to the Owens Lake Bed. The Owens Lake Bed is surrounded by steep 

terrain. EPA believes that given the proximity of the monitor to a large local source of particulate 

matter and the nearby terrain, it is reasonable to conclude that emissions from New Mexico

sources do not significantly contribute to nonattainment of the 2006 24-hour PM2.5 standard at 

this monitor. 

California/Mexico Border – San Diego County

The La Posta receptor is classified as a nonattainment receptor, based on a single measured 

PM2.5 value of 114 μg/m3 measured on June 1, 2010. All other measured values of PM2.5 at the 

La Posta monitoring site are very low. On June 1, 2010, the La Posta monitor recorded the 

highest measured value in the entire state of California, and 99% of the PM2.5 values for the rest 

of the State were below 20 μg/m3. The monitoring site is located over 700 miles from New 

Mexico. The monitored PM2.5 levels at the two operating monitors in Imperial County, which is 

located just east of San Diego County and the La Posta monitor and far west of New Mexico, on 

June 1, 2010 were 7.12μg/m3and 10.2μg/m3. 

The level of PM2.5 measured at the La Posta monitor on June 1, 2010 appears to be from local

sources, which supports our finding that emissions from New Mexico sources do not

significantly contribute to the elevated PM2.5 levels at this location.

IV.C.3. Oregon

PM2.5 monitoring data from the Crater Lake National Park and Lava Beds IMPROVE 

monitoring site30 are representative of regional background PM2.5 in southern Oregon, and is 

consistently low (below 3μg/m3) in the wintertime. The available data for each of the three areas 

with nonattainment receptors, discussed below, indicate that the cause of elevated PM2.5 levels 

is local. We note that Oregon areas are even further away than the Utah areas and more 

dispersion of New Mexico’s emissions would be expected compared to the Utah analysis. 

 

30 See Appendix D of this TSD.
16

Given the factors that indicate the elevated PM2.5 levels at these locations are caused by local 

emissions, which occur during wintertime temperature inversions with low winds that persist for 

several days in an area that traps emissions, together with complex topography, the low 

background levels of PM2.5 in the area, and the distance of the area from New Mexico, we 

believe it is reasonable to conclude that emissions from New Mexico sources do not significantly 

contribute to nonattainment of the 2006 24-hour PM2.5 standard at these receptor locations.

Klamath County (Klamath Falls)

 

A portion of Klamath County is designated nonattainment for the 2006 PM2.5 NAAQS. Klamath 

Falls is a relatively small urban community located in and supporting a vast rural area in southcentral Oregon. 

The state of Oregon’s analysis includes a 2005 emission inventory that shows that wood stove 

emissions are the most significant source of emissions. Additional air quality monitoring data 

provide supporting evidence that residential wood combustion emissions are the primary cause of 

exceedance days. Data show that exceedances occur during winter months, at a time when 

woodstoves are contributing to smoke in the area. Exceedances occurred from December through 

January, corresponding directly with the winter wood heating season, indicating the exceedances

(except for flagged wildfire events) are a seasonal occurrence. 

Speciation data analysis indicates most of the PM2.5 comes from elemental and organic carbon, 

typical indicators of combustion activities such as wood burning. Meteorological data from 

Klamath Falls show that low wind speeds dominate during violating days, and the Klamath Falls 

area experiences frequent winter-time nocturnal inversions, when PM pollution can build up over 

time. Diurnal concentrations of PM2.5 are observed by hourly light scatter data that correspond 

closely with night-time use of woodstoves. Night-time inversions coupled with low wind speeds 

strongly suggest that pollution in the Klamath Falls area is a localized effect heavily influenced by 

the use of woodstoves. 

EPA Region 10’s Positive Matrix Factor receptor modeling identified the 6 factors contributing 

to elevated wintertime PM2.5 including wood smoke (65%), organic pyrolysis rich (23%), and 

smaller contributions by other identified factors (nitrate rich, soil, sulfate rich, and urban 

unidentified). 

Given the factors that indicate the elevated PM2.5 levels at these locations are caused by local 

emissions, which occur during wintertime temperature inversions with low winds that persist for 

several days in an area that traps emissions, together with complex topography and the distance 

of the area from New Mexico, we believe it is reasonable to conclude that emissions from New 

Mexico sources do not significantly contribute to nonattainment of the 2006 24-hour PM2.5

standard at these receptor locations.

Lane County (Oakridge)

A portion of Lane County is designated nonattainment for the 2006 PM2.5 NAAQS. 
17

EPA’s technical analysis points to residential home heating, using wood burning appliances, as

the main contributors to fine particle pollution in this area. EPA Region 10’s Positive Matrix 

Factor receptor modeling identified seven factors which contribute to elevated wintertime PM2.5

including wood smoke (76%), organic pyrolysis rich (15%), as well as smaller contributions by

other identified factors (gasoline vehicles, iron rich, sulfate rich, sea salt, and soil).

PM2.5 monitoring data from the Crater Lake National Park and Lava Beds IMPROVE 

monitoring sites31 are representative of regional background PM2.5 in southern Oregon, and are

consistently low (below 3μg/m3) in the wintertime. 

Given the factors that indicate the elevated PM2.5 levels at these locations are caused by local 

emissions, monitoring data indicating that regional levels of PM2.5 are low, and the distance of 

the area from New Mexico, we believe it is reasonable to conclude that emissions from New 

Mexico sources do not significantly contribute to nonattainment of the 2006 24-hour PM2.5

standard at these receptor locations.

Lake County (Lakeview)

EPA Region 10’s Positive Matrix Factor receptor modeling identified seven factors contributing to 

PM2.5 including wood smoke (67%), organic pyrolysis rich (13%), nitrate rich (7%), soil (5%),

and smaller contributions by other identified factors (sulfate rich and urban unidentified).

PM2.5 monitoring data from the Crater Lake National Park and Lava Beds IMPROVE 

monitoring sites32 are representative of regional background PM2.5 in southern Oregon, and are

consistently low (below 3μg/m3) in the wintertime. 

Given the factors that indicate the elevated PM2.5 levels at these locations are caused by local 

emissions, the monitoring data, which indicate that regional levels of PM2.5 are low, and the 

distance of the area from New Mexico, we believe it is reasonable to conclude that emissions 

from New Mexico sources do not significantly contribute to nonattainment of the 2006 24-hour 

PM2.5 standard at these receptor locations.

IV.C.4. Washington

Given the factors that indicate the elevated PM2.5 levels at these locations are caused by local 

emissions and the distance of the area from New Mexico, we believe it is reasonable to conclude 

that emissions from New Mexico do not significantly contribute to nonattainment of the 24-hour 

PM2.5 standard at either of the two nonattainment receptor locations in the state of Washington.

We note that Washington areas are even further away than the Utah areas and more dispersion of 

New Mexico’s emissions would be expected compared to the Utah analysis. 

Pierce County (Tacoma)

The state of Washington’s analysis indicates that wood smoke associated with home heating 

 

31 Id.

32 Id.
18

is the largest source of PM2.5 in the Tacoma-Pierce County nonattainment area. Surface 

measurements at multiple sites suggest that the only design values which violate the 2006 

PM2.5 NAAQS are in the core of the nonattainment area, within about 3 kilometers (km) of 

the South L St. monitor. Beyond about 3-5km, the design values drop and are well below the 

NAAQS. 

Yakima County (Yakima)

EPA Region 10’s Positive Matrix Factor receptor modeling identified 10 factors 

contributing to elevated wintertime PM2.5 including wood smoke (24%), nitrate rich 

(24%), gasoline vehicles (16%), organic pyrolysis rich (9%), sulfate rich (7%), and smaller 

contributions from other identified factors (iron rich, sea salt, soil, zinc rich, and urban 

unidentified). 

IV.C.5. Idaho

EPA believes that the factors that indicate the elevated PM2.5 levels at these locations are 

caused by local emissions combined with the distance of the area from New Mexico support 

our finding that emissions from New Mexico do not contribute to nonattainment of the 24-

hour PM2.5 standard at the nonattainment receptors in the state of Idaho. We note that Idaho 

areas are even further away than the Utah areas and more dispersion of New Mexico’s 

emissions would be expected compared to the Utah analysis. 

Franklin County/Cache County

Portions of Franklin County, Idaho and Cache County, Utah are designated as part of the 

Cache Valley 2006 PM2.5, two-state, nonattainment area. Limited chemical speciation data 

in the Cache Valley indicates the PM2.5 problem is dominated by ammonium nitrate aerosol. 

Transport of PM2.5 and precursors from the rural regions at the domain periphery is very

small and most of the observed Wasatch Front and Cache Valley PM2.5 is formed in-situ 

(and trapped) via fresh locally derived emission sources and secondary chemistry.

Local heating emissions from woodstoves, emissions from agricultural activities, and mobile 

emissions may contribute to violations of the PM2.5 NAAQS during stable weather events 

associated with extremely strong inversions as they are trapped in the Cache Valley due to 

temperature inversions, low wind, and local topography.

Shoshone County (Pinehurst)

Information from the state of Idaho indicates that emissions from woodstoves contribute to 

primary PM2.5 that violates the standard during stable weather events associated with strong 

inversions. These emissions and the related effects are limited to the city of Pinehurst airshed, 

as they are trapped there due to temperature inversions, low wind, and local topography.
19

IV.C.6. Montana

EPA believes that the factors that indicate the elevated PM2.5 levels at these locations are 

caused by local emissions combined with the distance of the area from New Mexico

support our finding that emissions from New Mexico do not contribute to nonattainment of 

the 24-hour PM2.5 standard at the nonattainment receptor in the state of Montana. We note 

that Montana areas are even further away than the Utah areas and more dispersion of New 

Mexico’s emissions would be expected compared to the Utah analysis. 

Silver Bow County (Butte)

Elevated levels of PM2.5 in the Butte area occur primarily in the winter months.33 The

Butte area is topographically prone to wintertime temperature inversions, as it is situated in 

a montane valley. Speciation data indicates that emissions from wood smoke are the 

primary contributor to exceedances of the PM2.5 standard in Butte.34 These factors 

indicate that high levels of PM2.5 in Butte are driven by local emissions, which become 

trapped and build during wintertime inversions. 

IV.D. Transport to Eastern States

EPA has also considered potential PM2.5 transport from New Mexico emission sources to the 

nearest potential nonattainment or maintenance receptors located in the eastern, midwestern and 

southern states within the domain of the modeling analysis for the Cross State Air Pollution Rule 

(CSAPR) (76 FR 48208). The nonattainment and/or maintenance receptor nearest to New 

Mexico identified in the 2012 CSAPR modeling analysis is Madison County, Illinois. The 

CSAPR modeling did not analyze the contribution of New Mexico sources to Madison County, 

Illinois. In this action, EPA analyzed the magnitude of New Mexico’s SO2 and NOx emissions 

relative to states found to have emissions that significantly contribute to nonattainment at that 

receptor. EPA also considered the distance of New Mexico from Madison County, Illinois 

relative to states found to significantly contribute there. EPA believes that the following factors 

support a finding that emissions from New Mexico sources do not contribute significantly to 

nonattainment of the 2006 24-hour PM2.5 NAAQS at this receptor: (1) the relatively small 

magnitude of the emission inventory of PM2.5 precursors (SO2 and NOx) in New Mexico, 

combined with (2) the relatively long distance between New Mexico and this receptor. EPA 

believes that these factors also support a finding that New Mexico does not contribute 

significantly to nonattainment of the 2006 24-hour PM2.5 NAAQS at any of the other CSAPR 

receptors farther east.

In the CSAPR modeling, EPA did not quantify the PM2.5 contributions from New Mexico to 

Illinois or any of the other Eastern nonattainment and maintenance receptors. However, we can 

make a qualitative conclusion about the likely contribution from New Mexico to Illinois and 

points farther east by comparing the New Mexico emissions to a state that was modeled in 

CSAPR. Texas is the nearest state to New Mexico that was found to significantly contribute to 

 

33 See Appendix E of this TSD at E.2.

34 Id at E.3.
20

downwind nonattainment in CSAPR. And in fact, Texas was found to contribute significantly to 

the nonattainment receptor in Madison County, Illinois. The 24-hour PM2.5 contribution from 

Texas to Madison County was above the 1% threshold (0.35 μg/m3) used in CSAPR to identify

contributions that were considered not significant (the Texas contribution was 0.37 μg/m

3

). EPA 

has evaluated the relative amounts of PM2.5 precursor (SO2 and NOx) emissions in New 

Mexico compared to the amounts of PM2.5 precursor emissions in Texas, as modeled in the 

2012 CSAPR “base case.” The emission inventories used in the CSAPR modeling analyses

indicate that SO2 emissions in New Mexico are less than 5% of SO2 emissions in Texas, and 

NOx emissions in New Mexico are less than 20% of NOx emissions in Texas. Specifically, the 

CSAPR “2012 Base Case” inventories provide the following statewide emissions inventory data 

for these two states: 281,341 tons of NOx and 25,254 tons of SO2 from New Mexico emission 

sources, compared to 1,501,170 tons of NOx and 712,582 tons of SO2 from Texas emission 

sources.35 Even though the relationship between upwind emissions and downwind secondary

PM2.5 formation is not linear, we would expect the New Mexico PM2.5 contribution to Illinois 

to be much less than that of Texas and well below the 1% threshold. In addition, the distance 

from the closest part of New Mexico to Madison County, Illinois (approximately 800 miles) is 

almost twice the distance to Madison County from the closest part of Texas (415 miles). The 

distance from New Mexico to the other eastern receptors is even greater, therefore, the expected 

impact is even smaller. Given all of these factors, EPA believes it is reasonable to conclude that 

emissions of PM2.5 and PM2.5 precursors from New Mexico sources do not significantly 

contribute to nonattainment of the 2006 24-hour PM2.5 NAAQS in any eastern state.

V. Transport Assessment for Maintenance Receptors 

V.A. Introduction 

Based on our methodology for selecting maintenance receptors in Section III.A, above 

(Discussion of Nonattainment and Maintenance Receptor Selection Methodology), EPA has 

identified maintenance receptors in only three other western states: Arizona, Utah and California. 

Thus, to evaluate the potential for New Mexico emissions to interfere with maintenance in other 

states, we have evaluated technical information related to the maintenance receptors only in 

Arizona, Utah and California. As this analysis focuses on interstate transport, EPA did not 

evaluate the impact of New Mexico emissions on maintenance receptors within New Mexico.

V.B. Transport to Nearby States

V.B.1. Arizona

Pinal County (Cowtown)

This receptor is in the West Central Pinal nonattainment area.

This monitoring site is a middle scale site and is only comparable to the 24-hour NAAQS due to 

its close proximity to nearby sources. Emission inventory data, combined with speciation and 

 

35 See “Emissions Inventory Final Rule TSD,” Technical Support Document (TSD) for the final Transport Rule, 

Docket ID No. EPA-HQ-OAR-2009-0491, June 28, 2011, at Tables 7-1 and 7-2.
21

source apportionment data, point to agricultural activities and cattle feedlots, as well as other 

nearby sources of PM2.5, as primary sources contributing to PM2.5 levels at the Cowtown 

monitor on days with exceedances of the 24-hour PM2.5 NAAQS.

The Cowtown monitor has a consistent PM2.5/PM10 ratio that is lower than other nearby sites, 

suggesting that the causes of Cowtown PM2.5 concentrations are different than for other 

locations. The correlation of the PM2.5/PM10 ratio with PM2.5 concentrations at the Cowtown 

monitor suggests that PM2.5 and PM10 concentrations at the Cowtown monitoring site are 

generated by the same sources. Also, the Cowtown monitor is the only site in the area with a 

pronounced diurnal pattern, with high PM in the morning and evening hours, further suggesting 

the influence of local sources.

Santa Cruz County (Nogales)

This receptor is in the Nogales nonattainment area.

High PM2.5 values in Nogales generally occur under stagnant, light wind conditions during 

winter, and are associated with southerly flow (i.e., from the direction of Mexico). Nighttime 

drainage flow is typically from south to north along the Nogales Wash, and the narrow valley

topography can trap air pollutants, especially during the evening hours when the diurnal flow is 

from the south, out of Nogales, Sonora, Mexico. Measurements of PM2.5 composition show that 

the main emission sources are wood burning, food cooking, open burning, dust emissions, and 

tailpipe emissions from on-road and off-road vehicles.

V.B.2. Utah

Elevated levels of PM2.5 in the Utah nonattainment areas occur primarily in the winter months.36

The levels of elevated PM2.5 in the Salt Lake City 2006 PM2.5 nonattainment area and the 

Provo 2006 PM2.5 nonattainment area are primarily due to local emissions, as noted in the 

discussion of Salt Lake City and Provo nonattainment areas below. 

Of the 17 days with measured values above the standard in 2010 in Salt Lake City, eleven days 

were in January (with levels up to 76μg/m3), and four days were in December (with levels up to 

53μg/m3). The remaining two days above the standard were March 30 and April 27. 

During the winter months, levels of PM2.5 at background monitoring sites located north of New 

Mexico and south of the Utah maintenance receptors37 are very low, generally below 3μg/m3, 

indicating that over 90% of the PM in the urban area is locally generated. As discussed above, 

this supports our finding that PM2.5 levels are not likely to be caused by regional elevated 

PM2.5 levels. The factors that indicate the elevated PM2.5 levels at these locations are caused 

by local emissions, as well as the low levels of background PM2.5 during these time periods, 

 

36 See Appendix E at E.1.

37 IMPROVE monitoring network at each of six National Parks in Utah (Bryce Canyon, Zion, Capitol Reef, and 

Arches National Parks) and Nevada (Jarbidge Wilderness Area and Great Basin National Park).
22

support our finding that emissions from the state of New Mexico do not interfere with 

maintenance of the 2006 24-hour PM2.5 standard at these maintenance receptors. 

Box Elder, Davis, Salt Lake, Tooele, and Weber Counties (Greater Salt Lake Area)

All of Davis and Salt Lake counties, and portions of Box Elder, Tooele, and Weber counties are 

designated as part of the Salt Lake City 2006 PM2.5 nonattainment area. The SLC NAA is 

situated in a valley bordered on the east by the Stansbury Mountains,38 the Promontory

Mountains, and the Great Salt Lake, and on the west by the Wasatch Front. During inversions, 

the NAA becomes a closed airshed (save for potential transport between the Salt Lake City and 

Provo NAAs) featuring stagnant air masses and light winds which typically oscillate back and 

forth within the airshed. As the airshed is essentially capped during inversions, PM2.5 is formed 

in-situ (and trapped) via fresh locally derived emission sources and secondary chemistry.

39

Speciation data from wintertime PM2.5 exceedance days from 2004-2006 showed the average

composition of PM2.5 in Salt Lake City is 58% ammonium nitrate, 31% carbon and organic 

compounds, 8% ammonium sulfate, and 2% crustal. Several factors, including significant 

emissions from mobile, point and area sources, contribute to primary and secondarily formed 

PM2.5 that violate the standard during stable weather events associated with strong inversions.

Utah County (Provo-Orem)

A large portion of Utah County is designated as the Provo 2006 PM2.5 nonattainment area. The 

Provo NAA is situated in the Utah Valley. Like the other low-lying valleys just west of the 

Wasatch Front, the topography of the Utah Valley makes it prone to temperature inversions. 

During inversions, the Provo NAA features stagnant air masses and calm to light winds. As the 

airshed is essentially capped, PM2.5 is formed in-situ (and trapped) via fresh locally derived 

emission sources and secondary chemistry.

40 Transport of air masses between the Salt Lake City

and Provo NAAs can occur during inversions, as there is a 4.75-mile gap in the mountains 

separating these airsheds which is below the approximate average inversion height for these 

areas.41

Speciation data from wintertime PM2.5 exceedance days from 2004-2006 showed the average

composition of PM2.5 in Provo is 71% ammonium nitrate, with 21% carbon and organic 

compounds, 8% ammonium sulfate, and 2% crustal. Several factors, including significant 

mobile, point, and area sources contribute to ambient levels of primary and secondarily formed 

PM2.5 that violate the standard during stable weather events associated with strong inversions.

 

38 The Quqirrh Mountains lie between the Wasatch Front and the Stansbury Mountains. However, EPA determined 

that some area located west of the Quqirrh Mountains should still be considered part of the SLC nonattainment area. 

39 2006 24-Hour PM2.5 NAAQS Designations (74 FR 58688, November 13, 2009), Technical Support Document, 

December 2008, Index 583-669 at 40.

40 Id.

41 Id. at 41.
23

V.B.3. California

Transport to maintenance receptors in California is discussed in detail in Appendix C and 

summarized below. We note that California areas are even further away than the Utah and 

Arizona areas, there are more terrain blocking features (mountains and mountain ranges) and 

more dispersion of New Mexico’s emissions (less potential impacts) would be expected 

compared to the Arizona and Utah analyses. We also note that general transport winds are west 

to east in California which would not typically provide transport of New Mexico’s emissions.

Northern California/San Francisco Bay Area – Alameda, Solano, and Santa Clara County

Receptors

The receptors in these counties are in the San Francisco Bay airshed. The monitored values of 

PM2.5 that exceed the standard likely reflect localized sources because they occur during 

wintertime temperature inversions with low winds that persist for several days, allowing directly 

emitted and secondary PM2.5 to build up over a few days. The Bay Area Air Quality

Management District analyses show that during the winter peak season, wood burning can 

account for 33 to over 80 percent of the PM2.5 concentrations. Ammonium nitrate and 

elemental carbon from diesel sources can also contribute to these high values. 

EPA believes that the factors that indicate the elevated PM2.5 levels at these locations are caused 

by local emissions and the distance of the area from New Mexico support our finding that

emissions from New Mexico do not interfere with maintenance of the 24-hour PM2.5 standard at 

this receptor.

Southern California – Orange County (Maintenance Only) and Los Angeles, Riverside, San 

Bernardino Counties

Given the factors that indicate the elevated PM2.5 levels at these locations are caused by local 

emissions, regional and local flow patterns, and the location of California nonattainment areas 

generally upwind of New Mexico emission sources, we believe it is reasonable to conclude that 

emissions from New Mexico do not interfere with maintenance of the 2006 24-hour PM2.5

standard at this receptor.

California/Mexico Border – Imperial County 

The high monitored levels of PM2.5 are limited to the Calexico – Ethel Street monitoring site, 

which is located near the Mexican Border. The elevated PM2.5 levels occur primarily in the 

winter months during stagnation conditions, when long distance transport is unlikely. On days of 

elevated PM2.5 at the Calexico Ethel Street monitor, the levels of PM2.5 measured at the other 

monitors in Imperial County, the Brawley and El Centro sites, are lower on all days. The PM2.5

appears to be from a local source near the California/Mexico Border. These factors support our 

finding that emissions from New Mexico sources do not interfere with maintenance of the 24-

hour PM2.5 standard at this receptor.
24

Given the factors that indicate the elevated PM2.5 levels at these locations are caused by local 

emissions, regional and local flow patterns, and the location of California nonattainment areas 

generally upwind of New Mexico emission sources, we believe it is reasonable to conclude that 

emissions from New Mexico do not interfere with maintenance of the 2006 24-hour PM2.5

standard at this receptor.

Northern California – Sacramento County

In Northern California, monitored exceedances of the PM2.5 standard likely reflect localized 

sources occurring during wintertime temperature inversions with low winds that persist for 

several days in an area that trap emissions together with complex topography. The speciation 

data from high concentration days indicates that the PM2.5 has a high carbon mass, which also 

indicates that residential wood burning emissions are the dominant source.

42

Given the factors that indicate the elevated PM2.5 levels at these locations are caused by local 

emissions, which occur during wintertime temperature inversions with low winds that persist for 

several days in an area that trap emissions, together with complex topography and the distance of 

the area from New Mexico, we believe it is reasonable to conclude that emissions from New 

Mexico do not interfere with maintenance of the 2006 24-hour PM2.5 standard at these

receptors.

V.C. Transport to Eastern States

EPA has also considered potential PM2.5 transport from New Mexico emission sources to the 

nearest potential nonattainment or maintenance receptors located in the eastern, midwestern and 

southern states within the domain of the modeling analysis for the Cross State Air Pollution Rule 

(CSAPR) (76 FR 48208). The nonattainment and/or maintenance receptor nearest to New 

Mexico identified in the 2012 CSAPR modeling analysis is Madison County, Illinois. The 

CSAPR modeling did not analyze the contribution of New Mexico sources to Madison County, 

Illinois. Thus, EPA analyzed the magnitude of New Mexico’s SO2 and NOx emissions relative to 

states found to have emissions that significantly contribute to nonattainment at that receptor.

EPA also considered the distance of New Mexico from Madison County, Illinois relative to 

states found to significantly contribute there. EPA believes that the following factors support a 

finding that emissions from New Mexico sources do not interfere with maintenance of the 2006 

24-hour PM2.5 NAAQS at this receptor: (1) the relatively small magnitude of the emission 

inventory of PM2.5 precursors (SO2 and NOx) in New Mexico, combined with (2) the relatively 

long distance between New Mexico and this receptor. EPA believes that these factors also 

support a finding that New Mexico emissions do not interfere with maintenance of the 2006 24-

hour PM2.5 NAAQS at any of the other CSAPR receptors farther east.

In the CSAPR modeling, EPA did not quantify the PM2.5 contributions from New Mexico to 

Illinois or any of the other Eastern nonattainment and maintenance receptors. However, we can 

make a qualitative conclusion about the likely contribution from New Mexico to Illinois and 

points farther east by comparing the New Mexico emissions to a state that was modeled in 

 

42 ARB Almanac website (2006) http://www.arb.ca.gov/ei/maps/statemap/cntymap.htm)
25

CSAPR. Texas is the nearest state to New Mexico that was found to significantly contribute to 

downwind nonattainment in CSAPR. And in fact, Texas was found to contribute significantly to 

the nonattainment receptor in Madison County, Illinois. The 24-hour PM2.5 contribution from 

Texas to Madison County was above the 1% threshold (0.35 μg/m

3

) used in CSAPR to identify

contributions that were considered not significant (the Texas contribution was 0.37 μg/m

3

). EPA 

has evaluated the relative amounts of PM2.5 precursor (SO2 and NOx) emissions in New 

Mexico compared to the amounts of PM2.5 precursor emissions in Texas, as modeled in the 

2012 CSAPR “base case.” The emission inventories used in the CSAPR modeling analyses 

indicate that SO2 emissions in New Mexico are less than 5% of SO2 emissions in Texas, and 

NOx emissions in New Mexico are less than 20% of NOx emissions in Texas. Specifically, the 

CSAPR “2012 Base Case” inventories provide the following statewide emissions inventory data 

for these two states: 281,341 tons of NOx and 25,254 tons of SO2 from New Mexico emission 

sources, compared to 1,501,170 tons of NOx and 712,582 tons of SO2 from Texas emission 

sources.43 Even though the relationship between upwind emissions and downwind secondary 

PM2.5 formation is not linear, we would expect the New Mexico PM2.5 contribution to Illinois 

to be much less than that of Texas and well below the 1% threshold. In addition, the distance for 

New Mexico to Illinois is approximately twice the distance as from Texas to Illinois. The 

distance from the closest part of New Mexico to Madison County, Illinois (approximately 800

miles) is more than twice the distance to Madison County from the closest part of Texas (415

miles). The distance from New Mexico to the other eastern receptors is even greater, and 

therefore, the expected impact evensmaller. Given all of these factors, EPA believes it is 

reasonable to conclude that emissions of PM2.5 and PM2.5 precursors from New Mexico

sources do not interfere with maintenance of the 2006 24-hour PM2.5 NAAQS in any eastern 

state.

 

43 See “Emissions Inventory Final Rule TSD,” Technical Support Document (TSD) for the final Transport Rule, 

Docket ID No. EPA-HQ-OAR-2009-0491, June 28, 2011, at Tables 7-1 and 7-2.