Memorandum 

To: Docket 

From: Jeff Hunt, Air Planning Team, EPA Region 10 

Re: Technical Support Document - Washington State Implementation Plan and Interstate 

Transport Requirements for the 2006 24-hour Fine Particulate Matter National Ambient 

Air Quality Standards 

Date: May 13, 2015 

Recommendation 

Based on the weight of the evidence evaluated in this Technical Support Document 

(TSD), it is recommended the EPA propose approval of the Washington State 

Implementation Plan (SIP) as adequately addressing the interstate transport requirements 

of CAA section 110(a)(2)(D)(i)(I) for the 2006 24-hour PM2.5 National Ambient Air 

Quality Standards (NAAQS). This section of the CAA requires that the Washington SIP 

contain adequate provisions prohibiting emissions which will contribute significantly to 

nonattainment in, or interfere with maintenance by, any other state with respect to the 

2006 24-hour PM2.5 NAAQS. The Washington SIP meets these CAA requirements as 

detailed below. 

This TSD is organized as follows: 

Table of Contents

I. Interstate Transport and Washington 

 A. Summary of Proposed Action 

B. Summary of Washington Submittal 

C. Summary of EPA Evaluation and Conclusion 

II. Transport Assessment Methodology 

A. Discussion of Nonattainment and Maintenance Receptor Selection Methodology 

B. Factors Considered in Transport Analysis for Nonattainment and Maintenance 

Receptors 

III. Transport Assessment for Nonattainment Receptors 

A. Introduction 

 B. Transport to Western States 

 1. California 
2 

 2. Idaho 

 3. Montana 

 4. Oregon 

 5. Utah 

C. Transport to Eastern States 

IV. Transport Assessment for Maintenance Receptors 

A. Introduction 

 B. Transport to Western States 

1. California 

 2. Montana 

3. Utah 

C. Transport to Eastern States 

V. Appendix – PM2.5 IMPROVE Data 

 1. Overview of IMPROVE Monitoring Network Sites 

 2. Idaho and Idaho/Oregon Border - IMPROVE Data for the Years 2009-2013 

 3. Montana - IMPROVE Data for the Years 2009-2013 

4. Nevada - IMPROVE Data for the Years 2009-2013 

5. Utah - IMPROVE Data for the Years 2009-2013 

 6. Wyoming - IMPROVE Data for the Years 2009-2013 

7. California/Oregon Border - IMPROVE Data for the Years 2009-2013 

 8. Oregon/Washington Border - IMPROVE Data for the Years 2009-2013 

I. Interstate Transport and Washington 

I.A. Summary of Proposed Action 

Background:

Section 110(a)(1) of the Clean Air Act (CAA) requires each state to submit to the Environmental 

Protection Agency (EPA), within three years (or such shorter period as the Administrator may 

prescribe) after the promulgation of a primary or secondary National Ambient Air Quality 

Standard (NAAQS) or any revision thereof, a State Implementation Plan (SIP) that provides for 

the “implementation, maintenance, and enforcement” of such NAAQS. The EPA refers to these 

specific submittals as “infrastructure” SIPs because they are intended to address basic structural 

SIP requirements for new or revised NAAQS. For the 2006 24-hour PM2.5 NAAQS, these 

infrastructure SIPs were due on September 21, 2009. 
3 

CAA section 110(a)(2) includes a list of specific elements that “[e]ach such plan submission” 

must meet. The interstate transport provisions in CAA section 110(a)(2)(D)(i) (also called “good 

neighbor” provisions) require each state to submit a SIP that contains adequate provisions 

prohibiting air emissions that will have certain adverse air quality effects in other states. CAA 

section 110(a)(2)(D)(i) identifies four distinct elements related to the impacts of air pollutants 

transported across state lines. In this action, the EPA is addressing the first two elements of this 

section, specified at CAA section 110(a)(2)(D)(i)(I) – the requirement that a state SIP: 

“contain adequate provisions— 

(i) prohibiting, consistent with the provisions of this subchapter, any source or other type 

of emissions activity within the State from emitting any air pollutant in amounts which 

will— 

(I) contribute significantly to nonattainment in, or interfere with maintenance by, 

any other State with respect to any such national primary or secondary 

ambient air quality standard” 

Proposed Action: 

In this action, we are proposing to approve the Washington SIP as adequately addressing the 

requirements of CAA section 110(a)(2)(D)(i)(I) for the 2006 24-hour PM2.5 NAAQS. We 

believe that it is reasonable to conclude that, based on the weight of the evidence, emissions from 

sources in Washington do not significantly contribute to nonattainment or interfere with 

maintenance of the 2006 24-hour PM2.5 NAAQS in any other state. 

I.B. Summary of Washington Submittal 

On May 11, 2015, the State of Washington submitted a SIP revision to address the requirements 

of CAA section 110(a)(2)(D)(i)(I) for the 2006 24-hour PM2.5 NAAQS (Washington 2006 PM2.5

Interstate Transport submittal).1 In the submittal, Washington cited the EPA-approved rules 

codified in 40 CFR 52 Subpart WW and concluded that these rules contain adequate provisions 

prohibiting sources or types of emission activity within the State from emitting any air pollutant 

in any amounts that will contribute significantly to nonattainment in any other state with respect 

to the 2006 24-hour PM2.5 NAAQS. Specifically, the EPA-approved regulations at Washington 

Administrative Code (WAC) 173-400-113, and local clean air agency corollaries, require any 

owner or operator of a proposed new source, whether major or minor, to demonstrate to the 

satisfaction of the Washington Department of Ecology (Ecology) or a local clean air agency that 

the proposed source’s projected emissions will not cause or significantly contribute to a violation 

 

1

 The Washington 2006 PM2.5 Interstate Transport submittal addresses only the CAA section 110(a)(2)(D)(i)(I) 

requirements for the 2006 PM2.5 NAAQS. The EPA addressed CAA section 110(a)(2)(D)(i)(II) for the 2006 PM2.5

in a separate action (May 12, 2015, 80 FR 27102). In addition, we previously approved the Washington SIP for 

110(a)(2)(D)(i) with respect to the 1997 PM2.5 NAAQS on January 13, 2009 (74 FR 1591). Finally, Washington 

intends to address the requirements of CAA section 110(a)(2)(D)(i)(I) with respect to the 2012 PM2.5 NAAQS in a 

future action. 
4 

of any NAAQS. This demonstration is not constrained to impacts solely in Washington. For 

example, all estimates of ambient concentrations must be based on the requirements of 40 CFR 

part 51, Appendix W which look to the point of maximum concentration, not a jurisdictional 

boundary. 

The submittal also pointed to emission inventories for Washington State and emissions 

inventories used in the Cross State Air Pollution Rule (CSAPR) modeling analysis.2 The 2005 

base case used in the CSAPR analysis included values for nitrogen oxides (NOx) and sulfer 

dioxide (SO2) emissions of 357,674 tons and 57,580 tons, correspondingly. The NOx and SO2

values for Washington in 2012 are 268,870 tons and 38,581 tons, indicating that Washington’s 

emissions were reduced by 24.8% and 33%, respectively. Washington’s submittal attributes 

these reductions to Federal engine and fuel regulations, Washington’s inspection and 

maintenance (I/M) program, initiatives to decrease diesel exhaust (e.g. exhaust retrofits, Clean 

Diesel Grants, Northwest Ports Clean Air Strategy), Washington’s Air Operating Permit 

Program, and Best Available Retrofit Technology (BART) reductions from the regional haze 

program. 

The Washington 2006 PM2.5 Interstate Transport submittal also analyzed areas thought to be 

experiencing problems attaining and maintaining the 2006 24-hour PM2.5 NAAQS in the 

immediately surrounding states of Idaho and Oregon. Washington concluded that if there were 

no significant impacts to the immediately bordering states of Idaho and Oregon, it was unlikely 

that Washington would significantly impact more distant western states given the geography and 

generally low background levels of monitored PM2.5. The EPA supported Washington’s analysis 

for Idaho and Oregon with an independent analysis of other western states experiencing 

problems attaining and maintaining the 2006 24-hour PM2.5 NAAQS (California, Montana, and 

Utah) as well as eastern states. 

Washington supported their conclusion with information from the Western Regional Air 

Partnership (WRAP) Technical Support System, including Interagency Monitoring of Protected 

Visual Environments (IMPROVE) data.3

 This IMPROVE data measures impacts at monitors in 

National Parks and wilderness areas (class I areas) which provide information on background 

levels helping evaluate whether transported emissions from Washington sources interfere with 

2006 24-hour PM2.5 NAAQS maintenance efforts in other states. Specifically, the submittal 

asserted that winter-time high pressure systems with weak transport and near calm surface winds 

are characteristic of 2006 24-hour PM2.5 NAAQS exceedances in the west – as evidenced in the 

Technical Support Documents (TSDs) of surrounding nonattainment areas reviewed as part of 

 

2

 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 

3 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.
5 

the Washington submittal.4

 The submittal stated that for these winter-time inversion events that 

lead to exceedances, transported PM2.5 and precursors from outside the local cold pool is small to 

nonexistent and is not generally a contributing factor to PM2.5 concentrations in these western 

exceedances areas. Washington asserted that low winter transport of PM2.5 and its precursors is 

supported by the IMPROVE monitoring data. Specifically, most of the IMPROVE monitors in 

the areas surrounding Washington show distinct seasonal variation with most of monitoring sites 

evaluated in the submittal showing generally low background levels.5

 

The Washington submittal concluded that, based on the weight of the evidence, specifically: 

 The low concentrations of daily PM2.5 measured at IMPROVE monitors surrounding Washington 

during times that exceedances occur. 

 The significant role meteorology and topography play in the conditions that lead to 24-hour PM2.5 

NAAQS violations in surrounding states. 

I.C. Summary of EPA Evaluation and Conclusion 

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

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

maintenance in other states. If this factual finding is in the negative, then CAA section 

110(a)(2)(D)(i)(I) does not require any substantive changes to a state’s SIP to impose additional 

emissions controls to alleviate interstate transport. Consistent with the EPA’s approach in the 

eastern United States (1998 NOx SIP call, the 2005 CAIR, and the 2011 Transport Rule), we are 

evaluating potential interstate transport from Washington to other states with respect to specific 

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

“receptors.”6 

It is important to note that on August 21, 2012, the U.S. Court of Appeals for the DC Circuit 

issued a decision to vacate the Transport Rule. See EME Homer City Generation, L.P. v. E.P.A., 

696 F.3d (DC Cir. 2012) cert. granted, 2013 U.S. Lexis 4801 (2013). The DC Circuit also 

ordered the EPA to continue implementing CAIR in the interim. However, on April 29, 2014, 

the U.S. Supreme Court reversed and remanded the D.C. Circuit’s ruling and upheld the EPA’s 

approach in the Transport Rule. EPA v. EME Homer City Generation, L.P., 134 S.Ct. 1584 

(2014). The Supreme Court generally upheld the EPA’s approach in the Transport Rule for the 

issues in front of the Supreme Court for review, and on October 23, 2014, the DC Circuit lifted 

the stay on the Transport Rule.7

 

 

4

 Docket # EPA–HQ–OAR–2007–0562 for the 2006 PM2.5 nonattainment area designations (November 13, 2009, 74 

FR 58688) and Docket # EPA–HQ–OAR–2012–0918 for the 2012 PM2.5 nonattainment area designations (January 

15, 2015, 80 FR 2206). 

5

 Washington 2006 PM2.5 Interstate Transport Submittal, Appendix A, IMPROVE PM2.5 data for the period 2009-

2013. 

6 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). 

7

 USCA Case #11-1302, Document # 1518738, Filed 10/23/2014. 
6 

While our evaluation is consistent with the Transport Rule approach, the State of Washington 

was not covered by either CAIR or the Transport Rule, and the EPA made no determinations in 

either rule regarding whether emissions from sources in Washington significantly contribute to 

nonattainment or interfere with maintenance of the 2006 24-hour PM2.5 NAAQS in another state, 

nor did it attempt to quantify Washington’s obligation.8

 

Evaluation:

In this action, we have evaluated the information available and have determined that no single 

piece of information is by itself dispositive of the issue. As region-wide modeling such as exists 

for the Transport Rule of the 2006 24-hour PM2.5 NAAQS for the western portion of the United 

States, including Washington, is not available for this particular NAAQS, we believe that it is 

appropriate to evaluate the total weight of all the evidence which, taken together can be used to 

evaluate whether Washington emissions significantly contribute to nonattainment or interfere 

with maintenance of the 2006 24-hour PM2.5 NAAQS in any other state. See, Guidance on the 

Use of Models and Other Analyses for Demonstrating Attainment of Air Quality Goals for 

Ozone, PM2.5, and Regional Haze, EPA -454/B-07-002, April 2007. 

We believe that the Washington 2006 PM2.5 Interstate Transport submittal and other 

supplemental evidence explained herein provides important information on the meteorology 

(including temperature inversions, mixing zones, and the like, for example), topography, 

geography, background levels, and technical analysis of violating areas in surrounding states and 

that this information generally supports a conclusion that emissions from sources in Washington 

do not significantly contribute to nonattainment or interfere with maintenance of the 2006 24-

hour PM2.5 NAAQS in any other state. In order to reach a proposed conclusion, we believe it is 

necessary to supplement the information provided in the Washington 2006 PM2.5 Interstate 

Transport submittal with a review of the monitors in other states that are appropriate 

nonattainment and maintenance receptors. 

We also have reviewed monitoring data collected at National Parks and wilderness areas (class I 

areas) in the west which we believe may be considered representative of background (data 

provided in section V. Appendix to this TSD). In addition, we have reviewed technical 

documentation produced by the EPA and states during the designations and attainment planning 

processes for the 2006 24-hour PM2.5 NAAQS under part D, title I of the CAA. This technical 

documentation addresses atmospheric science, meteorology, topography and sources of PM2.5 in 

Washington and surrounding states in the west. While this information was developed for SIPs 

under part D, title I of the CAA, we believe the information helps inform our evaluation of 

interstate transport requirements at CAA section 110(a)(2)(D)(i)(I) for the 2006 24-hour PM2.5 

NAAQS. 

Conclusion: 

Based on the following weight of the evidence, we propose to conclude that the Washington SIP 

meets the requirements of CAA section 110(a)(2)(D)(i)(I) for the 2006 24-hour PM2.5 NAAQS: 

 

8

 Ibid. 
7 

 The evidence in the Washington 2006 PM2.5 Interstate Transport submittal that shows the 

significant role meteorology and topography play in the conditions that lead to violations of the 

24-hour PM2.5 NAAQS in Washington and surrounding western states. 

 The evidence from monitoring data collected at National Parks and wilderness areas (class I 

areas) in the west that indicates there are low background levels of PM2.5 in class I areas located 

between Washington and identified receptors, and in the west in general, at the times when 

violations in the west typically occur (winter months). 

 The evidence from technical support documents produced by the states and the EPA through the 

designations and attainment planning process for the 2006 24-hour PM2.5 NAAQS that indicates 

violations of the 24-hour PM2.5 standard in the western states are generally driven by wintertime 

inversion meteorology in areas impacted by major mountain ranges including the Cascade Range, 

the Wasatch Front, the Sierra Nevada Range, and other significant topography. 

II. Transport Assessment Methodology 

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

On September 25, 2009, the 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 24-hour PM2.5 NAAQS Infrastructure Guidance” or “Guidance” ).9

 The Guidance 

recommends that each state explain in its SIP submission for section 110(a)(2)(D)(i)(I) SIP 

whether or not emissions from sources in the state contribute significantly to nonattainment or 

interfere with maintenance of the NAAQS in any other state, and to address any such impacts if 

they exist. 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

 

9

 Available at: http://www.epa.gov/ttn/caaa/t1/memoranda/20090925_harnett_pm25_sip_110a12.pdf 10 Guidance at 3. 
8 

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

mitigate 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 the EPA’s approach in the 1998 NOx SIP call, the 2005 CAIR, and the 

2011 Transport Rule,11 the 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 The 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 in, 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 2006 24-hour 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 three-year periods for which complete, quality-assured and 

certified air quality data were available (covering a five-year period) to calculate “design 

values”14 for those period. We evaluated the design values for monitors located in the following 

western states, which were not included in the modeling domain for the Transport Rule: 

Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, 

Washington and Wyoming.15

Because the EPA uses the most recent three-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 

 

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). 15 We did not evaluate design values for Alaska or Hawaii. 
9 

that the EPA used in the Transport Rule to identify “nonattainment” and “maintenance” 

receptors. 

In this action we have applied the following methodology: 

Similar to the Transport Rule analysis, we examined ambient data which spanned a five-year 

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

three-year design value periods at the time of our analysis are 2009-2011, 2010-2012, and 2011-

2013.16 

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

three-year period (2011-2013).17

2) Maintenance receptors are those receptors that show attainment in the most recent threeyear design value period (2011-2013) but violated the NAAQS in at least one of the 

previous two periods (2009-2011 and/or 2010-2012). 

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 the Office of Air Quality Planning and 

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

http://www.epa.gov/airtrends/values.html. Also informing this list was the EPA’s AirData 

website: http://www.epa.gov/airquality/airdata/. 

The western receptors identified using this methodology and analyzed in this action are shown in 

Table 1 below. Receptors with 24-hour PM2.5 design values above the 24-hour PM2.5 standard of 

35μg/m3 for the most recent three-year period (2011-2013) are listed as nonattainment receptors. 

Receptors with 24-hour PM2.5 design values at or below the 24-hour PM2.5 standard of 35μg/m3

for the most recent three-year period (2011-2013), but above the standard for at least one of the 

previous three-year periods (2009-2011 or 2010-2012), are listed as maintenance receptors. 

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

first evaluated potential transport to the western states with identified nonattainment receptors: 

California, Montana, Oregon, and Utah.18 To evaluate the potential for interference with 

maintenance in other states, the EPA evaluated potential transport to the western states with 

identified maintenance receptors: California, Montana, and Utah.19

 

 

16 As noted above, the EPA can consider data from these years for states in the western United States as such data is 

not impacted by the remanded CAIR. 

17 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. 

18 As this analysis focuses on interstate transport, EPA did not evaluate the impact of Washington emissions on 

receptors within Washington. 

19 Using the methodology described, no receptors were identified in Arizona, Colorado, Nevada, New Mexico, 

Washington, and Wyoming. 
10 

Table 1: List of Western Counties with Daily PM2.5

Nonattainment or Maintenance Receptors 

State County 

2006 NAAQS 24-hr 

PM2.5 NAAQS 

designated 

nonattainment area 

Site 

24-hr standard (μg/m3) 

2009-

2011 

2010-

2012 

2011-

2013 

Receptor 

Type 

California Fresno San Joaquin Valley 060190011 58 NA 59 NA 62 NA Nonattainment 

California Fresno San Joaquin Valley 060195001 54 NA 54 NA 58 NA Nonattainment 

California Fresno San Joaquin Valley 060195025 48 NA 53 NA 63 NA Nonattainment 

California Imperial 060250005 38 NA 32 A 42 NA Nonattainment 

California Inyo 060271003 36 NA 33 A 38 NA Nonattainment 

California Kern San Joaquin Valley 060290014 62 NA 58 NA 65 NA Nonattainment 

California Kern San Joaquin Valley 060290016 55 NA 47 NA 60 NA Nonattainment 

California Kings San Joaquin Valley 060310004 46 NA 43 NA 49 NA Nonattainment 

California Kings San Joaquin Valley 060311004 57 NV 54 NA 60 NA Nonattainment 

California Los Angeles Los Angeles-South 

Coast Air Basin 060370002 36 NA 31 NV 28 A Maintenance 

California Madera San Joaquin Valley 060392010 55 NV 51 NA 52 NA Nonattainment 

California Merced San Joaquin Valley 060470003 43 NA 41 NA 42 NA Nonattainment 

California Merced San Joaquin Valley 060472510 39 NA 40 NA 49 NA Nonattainment 

California Riverside Los Angeles-South 

Coast Air Basin 060658005 39 NA 37 NA 38 NA Nonattainment 

California Sacramento Sacramento 060670006 35 A 31 A 36 NA Nonattainment 

California San Joaquin San Joaquin Valley 060771002 38 NA 36 NA 45 NA Nonattainment 

California San Joaquin San Joaquin Valley 060772010 41 NV 38 NA 37 NA Nonattainment 

California Stanislaus San Joaquin Valley 060990005 50 NA 44 NA 51 NA Nonattainment 

California Stanislaus San Joaquin Valley 060990006 51 NA 49 NA 53 NA Nonattainment 

California Tulare San Joaquin Valley 061072002 47 NA 47 NA 56 NA Nonattainment 

Idaho Ada 160010010 19 A 27 A 53 NA Nonattainment 

Idaho Franklin Logan 160410001 50 NA 47 NA 42 NA Nonattainment 

Idaho Lemhi 160590004 38 NA 38 NA 38 NA Nonattainment 

Idaho Shoshone 160790017 38 NA 38 NA 40 NA Nonattainment 

Montana Lewis and 

Clark 300490026 37 NA 33 A 29 A Maintenance 

Montana Silver Bow 300930005 39 NA 34 A 39 NA Nonattainment 

Oregon Crook 410130100 31 A 31 A 39 NA Nonattainment 

Oregon Klamath Klamath Falls 410350004 39 NA 35 A 40 NA Nonattainment 

Oregon Lake 410370001 36 NA 34 A 56 NA Nonattainment 

Oregon Lane Oakridge 410392013 39 NA 38 NA 40 NA Nonattainment 

Utah Box Elder Salt Lake City 490030003 40 NA 37 NA 37 NA Nonattainment 

Utah Cache Logan 490050004 42 NA 37 NA 46 NA Nonattainment 

Utah Davis Salt Lake City 490110004 40 NA 34 A 35 A Maintenance 

Utah Salt Lake Salt Lake City 490350003 50 NA Nonattainment 

Utah Salt Lake Salt Lake City 490353006 45 NA 38 NA 41 NA Nonattainment 

Utah Salt Lake Salt Lake City 490353010 41 NA 35 A 39 NA Nonattainment 

Utah Utah Provo 490490002 35 A 29 A 45 NA Nonattainment 

Utah Utah Provo 490494001 41 NA 32 NV 44 NA Nonattainment 

Utah Utah Provo 490495008 38 NA 41 NV 42 NV Nonattainment 

Utah Utah Provo 490495010 42 NA 35 A 46 NA Nonattainment 
11 

State County 

2006 NAAQS 24-hr 

PM2.5 NAAQS 

designated 

nonattainment area 

Site 

24-hr standard (μg/m3) 

2009-

2011 

2010-

2012 

2011-

2013 

Receptor 

Type 

Utah Weber Salt Lake City 490570002 41 NA 37 NA 40 NA Nonattainment 

Utah Weber Salt Lake City 490571003 37 NA 33 A 35 A Maintenance 

NA = Not attaining; A = attaining; NV = incomplete data; Blank = monitor not operating 

Data sources: AirTrends http://www.epa.gov/airtrends/values.html and AirData 

http://www.epa.gov/airquality/airdata/ 

Note: receptors with design values (DV) that would otherwise attain the 24-hour PM2.5 standard from 2011 to 2013 

but for flagged wildfire exceptional events are excluded from this list (i.e. Ravalli, Montana DV = 27 μg/m3

; 

Missoula, Montana DV = 24 μg/m3

; and Jackson, Oregon DV = 34 μg/m3). 

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

Receptors 

Consistent with the recommendations in the Guidance, the EPA reviewed multiple factors to 

evaluate the weight of the evidence. The EPA evaluated emission inventory data, ambient 

monitoring data, and meteorological conditions within the State of Washington. Emission 

inventories used in the Transport Rule modeling analysis provide the following amounts of NOx

and SO2 emissions for Washington in 2012: 268,870 tons of NOx and 38,581tons of SO2.

20 This 

is a significant reduction from the 2005 base year emissions inventories of 357,674 tons of NOx

and 57,580 tons of SO2, with continuing emission reductions projected in 2014. 

In addition, the EPA reviewed PM2.5 monitoring data at National Parks and wilderness areas in 

the west that the EPA believes may be considered representative of western regional background 

levels of PM2.5. As explained in Guidance on the Use of Models and Other Analyses for 

Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, and Regional Haze, EPA -

454/B-07-002, at 98, April 2007, a weight of evidence analysis appropriately considers such 

additional models and supplemental analyses. Specifically, we reviewed five years of data 

collected at the IMPROVE21 monitoring network at specific National Parks and wilderness areas 

(class I areas) in Washington and on the Idaho/Oregon border (Craters of the Moon National 

Monument, Sawtooth Wilderness, Hells Canyon Wilderness, and Starkey), in Utah (Bryce 

Canyon National Park, Canyonlands, Capitol Reef National Park, and Zion), in Nevada (Jarbidge 

Wilderness and Great Basin National Park), at the California-Oregon border (Crater Lake 

National Park, Lava Beds National Monument, and Lassen Volcanic National Park), and at the 

Oregon-Washington border (Mount Hood Wilderness and the Columbia River Gorge).22 

 

20See “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 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/TSS/Results/HazePlanning.aspx 22 See section V. Appendix to this TSD. 
12 

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 in 

section V. Appendix to this TSD. The data provided is for the 2009-2013 period for each day 

when measurements occurred at these class I monitors. This provides information about regional 

background levels of PM2.5 in the states surrounding Washington, and as discussed below, 

provides information about levels of PM2.5 at areas located between Washington and specifically 

identified nonattainment and maintenance receptors. We note that the chemical composition of 

the PM2.5 in these areas is also available on the IMPROVE website.23

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

For example, in 2011 and 2012, each exceedance of the 2006 24-hour PM2.5 NAAQS in Salt 

Lake City occurred in either December or January of those years.24 Monitor values are 

accessible on the EPA’s AirData website. IMPROVE monitoring sites evaluated indicate low 

background PM2.5 levels during the winter months for each of the years from 2009 through 2013. 

For example, the PM2.5 values for January and December of 2010 at Bryce Canyon National 

Park, Utah are below 3μg/m3

. See Figure 1 below. While there are variations in the data, 

including peaks during non-winter months, we believe the data provided in section V. Appendix

to this TSD generally indicates that PM2.5 levels in class I areas, as monitored by the IMPROVE 

network, are generally low at the times when areas in the west are typically experiencing 

elevated 24-hour PM2.5 levels (winter months). 

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

 

23 http://vista.cira.colostate.edu/TSS/Results/HazePlanning.aspx 24 Monitoring data is accessible on the EPA’s AirData website at http://www.epa.gov/airtrends/values.html 2013 

Design Value Report for PM2.5. 
13 

In addition, the EPA reviewed technical information, such as meteorological conditions, 

topography, distance, and monitored ambient data related to each of the areas with nonattainment 

and maintenance receptors in the potentially impacted western states to evaluate the factors that 

cause or contribute to the elevated PM2.5 levels at these locations. We discuss our evaluation of 

the factors with respect to each identified nonattainment and maintenance receptor in the 

following sections. Please note that some states contain both identified nonattainment receptors 

and maintenance receptors, specifically: California, Montana, and Utah. Therefore an evaluation 

for receptors in these states appears in both sections III and IV below. 

III. Transport Assessment for Nonattainment Receptors 

III.A. Introduction 

Based on the methodology for selecting nonattainment receptors described in section II.A above, 

we evaluated nonattainment receptors in the following western states: California, Montana, 

Oregon, and Utah.25 We have also addressed the nearest eastern receptor evaluated in the 

Transport Rule modeling domain.26

III.B. Transport to Western States 

III.B.1. California

Eastern California/ Inyo County Nonattainment Receptor (Site 060271003) 

County Site Name Description 

Inyo Keeler This site is affected primarily is by crustal sources. 

Massive erosion from Owens dry lake; in Owens Valley. 

The EPA identified a single nonattainment receptor in Inyo County, specifically the Keeler 

monitor, which is located adjacent to the Owens Lake Bed. (See Figures 2 through 4 below). 

The Owens Lake Bed is surrounded by steep terrain. 

 

 

25 As this analysis focuses on interstate transport, we did not evaluate the impact of Washington emissions on 

receptors within Washington. 

26 Madison County, Illinois. See “Technical Support Document (TSD) for the final Transport Rule, Docket ID No. 

EPA-HQ-OAR-2009-0491, June 28, 2011. 
14 

Figure 2: Keeler Dunes 27

The Owens Valley Planning Area (OVPA) is located in Inyo County in eastern-central 

California. It is situated at the south end of the deep, long, narrow Owens Valley with the Sierra 

Nevada to the west (maximum elevation 14,495 feet), the Inyo Mountains to the east (maximum 

elevation 14,246 feet), and the Coso Range to the south (maximum elevation 8,160 feet). The 

predominantly dry, alkaline Owens Lake bed is approximately eight miles south of the 

community of Lone Pine on U.S. Highway 395, 60 miles north of the city of Ridgecrest, and 35 

miles west of Death Valley. The bed of Owens Lake is defined as the area below 3,600 feet 

above mean sea level (all elevations will be given in feet above mean sea level). The lake bed 

extends about seventeen miles north and south and ten miles east and west and covers an area of 

approximately 110 square miles (70,000 acres). 

Owens Lake is the largest single source of PM10 in the United States.28 Water was first diverted 

from the Owens River to the City of Los Angeles in 1913, and by 1926 Owens Lake was dry. 

Today, the Owens lakebed produces enormous amounts of windblown dust in exceedance of 

federal air pollution standards for particulate matter. Monitoring and research conducted for 

more than 20 years, as well as three previous State Implementation Plans (SIPs), has determined 

that wind-blown dust from the dry bed of Owens Lake is the dominant cause of NAAQS 

 

27 http://www.gbuapcd.org/owenslake.htm 28 Ibid. 
15 

violations for PM10 in the area.29 Based on the above-described information about the proximity 

of this receptor to the large, eroding dry bed of Owens Lake, the distance from Washington to 

this receptor (≈ 700 miles), and the significant intervening terrain, as described above, we 

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

contribute to nonattainment of the 2006 24-hour PM2.5 NAAQS at this receptor. 

Figure 3: Owens Lake Dust ID Network Map 

 

29 Final 2008 Owens Valley PM10 Planning Area Demonstration of Attainment State Implementation Plan, January 

28, 2008. http://www.gbuapcd.org/ovpm10sip.htm
16 

Figure 4: Owens Lake Contour Map 
17 

Southern California/Riverside County Nonattainment Receptor (Riverside) (Site 060658005) 

The high 24-hour PM2.5 concentrations in the South Coast Air Basin and at the Riverside 

nonattainment receptor are mainly due to the secondary formation of smaller particulates 

resulting from mobile, stationary and area source emissions of precursor gases (i.e., NOx, SOx, 

ammonia (NH4), and VOCs) that are converted to PM in the atmosphere. Speciated PM2.5 data at 

the Central Los Angeles Site (CELA) and the Rubidoux site (RIVR) indicate that organic carbon, 

ammonium nitrate, and ammonium sulfate constitute the major components at each site. See 

Figures 5 and 6 below. 24-hour PM2.5 design value trends show strong downward trends at all 

sites in the South Coast Basin. 30 See Figure 7 below. 

Figure 5: Speciated data for the Central Los Angeles Site31

 

 

30 Joe Cassmassi, Scientific, Technical & Modeling Peer Review (STMPR) Advisory Group Meeting, September 22, 

2011. 

31 STMPR Item # 5 - 2008 PM2.5 Air Quality Characterization, January 19, 2012. Bong-Mann Kim. 
18 

Figure 6: Speciated data for Roubidoux site at Riverside32

 

 

32 Ibid. 
19 

Figure 7: 24-hour PM2.5 Design Value Trends 

PM2.5 is essentially a combustion generated pollutant due to the volume of traffic flow and 

numbers of sources (both point and area) in the region. It is important to note that the areas with 

the highest concentrations are directly downwind of an area with major ammonia sources 

associated with dairies and poultry farming.33

The South Coast Air Quality 2012 Air Quality Management Plan34 air quality projections show 

that the emission control strategy outlined in the plan will result in air quality improvement at 

each of the nonattainment receptors in the plan, and that each of these sites will attain the 

standard in 2014 or sooner. See Figure 8 below. 

 

 

33 Final 2012 Air Quality Management Plan (AQMP), Appendix V – Modeling and Attainment Demonstrations 

February, 2013. 

34 http://www.aqmd.gov/home/library/clean-air-plans
20 

Figure 8: Maximum 24-Hour Average PM2.5 Design Concentrations: 2008 Baseline, 2014, 

and 2014 Controlled35

Based on the air quality trends and projections that indicate that the above-referenced emission 

strategy will be effective in reducing 24-hour PM2.5 levels at this receptor, the distance from 

Washington to this receptor (≈ 900 miles), and the significant intervening terrain including the 

Sierra Nevada (see Figure 9 below), we believe it is reasonable to conclude that emissions from 

Washington do not significantly contribute to nonattainment of the 2006 24-hour PM2.5 NAAQS 

at the Riverside receptor. 

Central California/ Fresno, Kern, Kings, Madera, Merced, San Joaquin, Stanislaus and Tulare 

Counties Nonattainment Receptors (Sites: see table 2 below) 

Table 2: Central California – San Joaquin Valley Nonattainment Receptor Sites 

County Nonattainment Receptor Sites 

Fresno 060190011, 060195001, 060195025 

Kern 060290014, 060290016 

Kings 060310004, 060311004 

Madera 060392010 

Merced 060470003, 060472510 

San Joaquin 060771002, 060772010 

Stanislaus 060990005, 060990006 

Tulare 061072002 

 

35 Source: South Coast Air Quality Management District. http://www.aqmd.gov/home/library/clean-air-plans
21 

PM2.5 levels in the San Joaquin Valley are generally highest in the months of January, February, 

November and December. PM2.5 builds up in episodes of several days or weeks. See Figure 10

below. These episodes generally occur during periods with stagnation, cool temperatures, high 

humidity, and low mixing depths.36 The peak day composition of PM2.5 at Bakersfield is 

primarily ammonia nitrate (67%) and organic carbon (16%). See Figure 11 below. 

Figure 9: Map of California37

 

36 Nature of PM2.5 in the San Joaquin Valley, Karen Magliano, California Air Resources Board, Technical 

Symposium. April 27, 2012. 

37 Source: University of Texas. http://www.lib.utexas.edu
22 

Figure 10: Monthly Average PM2.5 Concentration in Bakersfield California38

Figure 11: 2008 – 2010 Peak Day Composition in Bakersfield39

 

38 Source: South Coast Air Quality Management District. http://www.aqmd.gov/home/library/clean-air-plans 39 Ibid. 
23 

The primary sources of PM2.5 in the region are diesel engines (nitrate), gasoline engines (nitrate), 

and agricultural activities (ammonium) which contribute regionally. Wood smoke (organic 

carbon) and diesel engines (elemental carbon) contribute to the elevated 24-hour levels of PM2.5 

in urban areas. 

Based on the evidence discussed above, that PM2.5 builds up in episodes of several days or 

weeks, during periods with stagnation and low mixing depths, the distance from Washington to 

these receptors (≈ 500 miles), and the significant intervening terrain, including the Sierra Nevada 

Range (see Figure 9 above), we believe it is reasonable to conclude that emissions from 

Washington do not significantly contribute to nonattainment of the 2006 24-hour PM2.5 NAAQS 

at these receptors. 

California/Mexico Border – Imperial County Nonattainment Receptor (Site 060250005) 

Levels of PM2.5 in Imperial County that exceed the 2006 24-hour PM2.5 NAAQS are recorded at 

the Calexico – Ethel Street monitoring site, which is located near the Mexican Border (see 

Figure 13 below). The elevated levels of PM2.5 occur primarily in the wintertime, and seven of 

the nine values above the level of 35 μg/m3

 in the years 2008-2010 occur in December or 

January (See Table 3 below). 

Table 3: Calexico-Ethel Street: Dates of PM2.5 Values Above 35 μg/m3 (2006 - 2010) 

Year Dates 

2008 January 4, and December 22, 25 

2009 September 4, and December 12, 21, 24 

2010 June 28, and December 4 

The levels of PM2.5 measured at the Brawley and El Centro monitoring sites are always lower – 

usually much lower – than those measured at the Calexico Ethel Street monitor on days when the 

PM2.5 levels at the Calexico Ethel Street monitor exceed 35 μg/m3. See Figures 13 and 14 below. 

Because these nearby monitors do not show similar increases in monitored values, it appears that 

the elevated PM2.5 is being significantly influenced by a source near the California/Mexico 

Border. 

Based on the above-described information, distance from Washington to this California receptor 

(≈ 1000 miles), and significant intervening topography, including the Sierra Nevada Range (see 

Figure 9 above), we believe it is reasonable to conclude that emissions from Washington do not 

significantly contribute to nonattainment of the 24-hour PM2.5 standard at this receptor. 
24 

Figure 13: PM2.5 Monitoring Sites in Imperial County California
25 

Figure 14: PM2.5 levels (μg/m3) at Imperial PM2.5 Monitoring Sites, 2006 - 2010, for days of 

elevated 24-hour PM2.5

Northern California – Plumas County Nonattainment Receptor (Site 0600631006) 

County Site Description 

Plumas Quincy This receptor violated the 2006 24-hour PM2.5 NAAQS in the most 

recent design value period (2011-2013) but was in attainment of the 

24-hour PM2.5 NAAQS in the three previous design value periods. 

The EPA identified a single nonattainment receptor in Northern California – the Plumas County 

receptor located in Quincy. While this receptor is located in an area that is designated attainment 

for the 2006 24-hour PM2.5 NAAQS, portions of Plumas County are being considered in the 

designations process for the 2012 annual PM2.5 NAAQS.40 We note that we are not evaluating 

 

40 EPA Technical Support Document for California for the 2012 Primary Annual PM2.5 NAAQS. 

http://www.epa.gov/pmdesignations/2012standards/eparesp/09_CA_120TSD_20140818.pdf

0

10

20

30

40

50

60

70

Calexico ‐Ethel

El Centro

Brawley
26 

interstate transport requirements for the 2012 annual PM2.5 NAAQS in this action, however, we 

believe that the information developed as part of the designations process for the 2012 annual 

PM2.5 NAAQS is informative for our evaluation of this receptor for purposes of interstate 

transport requirements for the 2006 24-hour PM2.5 NAAQS.41

A letter from the Northern Sierra Air Quality Management District, dated June 18, 2014, cites 

wood burning for residential heating in wood stoves and fireplaces, open burn piles for yard 

waste disposal, and prescribed burning in nearby federal lands performed by the U.S. Forest 

Service and a railroad switching yard as the sources affecting PM2.5 concentrations in Portola, 

located in Plumas County, 32 miles from Quincy.42 Elevated PM2.5 in the winter months in 

Portola is generally considered related to emissions from residential wood burning. The letter 

cited the diurnal pattern of PM2.5 concentrations that peak around the two times people use their 

wood stoves most: from 5:00 pm to 12:00 am, and from 5:00 am to 8:00 am. With respect to the 

Quincy receptor, the Northern Sierra Air Quality Management District indicated that similar 

diurnal patterns are found in Quincy, but not to the same degree. The letter stated that “emissions 

in Quincy are also mainly from wood burning appliances (as supported by diurnal PM2.5 

concentration patterns), although Sierra Pacific Industries maintains a biomass-fired 

cogeneration facility in Quincy that emitted an 2010-2012 average of 44 tons per year of total 

particulate matter.”43

The population of Plumas County is 19,940.44 The county lies in the northern Sierra Nevada 

Mountains near the southern border of the Cascade Range. The topography of Plumas County is 

highly variable, including mountain peaks (≈ 7,000 ft.) and valleys with extreme slopes and 

differences in altitude.45 This topography affects and directs airflow, causing shallow vertical 

mixing, and creating areas of high pollutant concentrations by hindering dispersion.46 Quincy is 

located in a small and isolated mountain valley at approximately 5000 feet elevation.47 Prevailing 

winds in Quincy are from the west, and much of the time there is no measureable wind in 

Quincy, as indicated by wind roses developed by Northern Sierra Air Quality Management 

District.48

Based on the nature of the PM2.5 problem in general at this receptor as described above, the 

distance from Washington to this receptor (≈ 500 miles), low background levels of PM2.5 at the 

time when these exceedances generally occur,49 and significant intervening terrain as described 

 

41 EPA Technical Support Document for California for the 2012 Primary Annual PM2.5 NAAQS. 

http://www.epa.gov/pmdesignations/2012standards/eparesp/09_CA_120TSD_20140818.pdf

42 2012 Northern Sierra Air Quality Management District letter dated June 18, 2014. 

http://www.epa.gov/pmdesignations/2012standards/rec/r9carec2.pdf

43 Ibid at page 4. 

44 2010 Census. 

45 EPA Technical Support Document for California for the 2012 Primary Annual PM2.5 NAAQS. 

http://www.epa.gov/pmdesignations/2012standards/eparesp/09_CA_120TSD_20140818.pdf

462012 Northern Sierra Air Quality Management District letter dated June 18, 2014. 

http://www.epa.gov/pmdesignations/2012standards/rec/r9carec2.pdf

47 Ibid. at page 2. 

48 Ibid. at Attachment 6, page 13. 

49 IMPROVE monitoring data at Jarbidge Wilderness Area, NV, and Lassen Volcanic National Park, CA. See 

section V. Appendix to this TSD. 
27 

above, we believe it is reasonable to conclude that emissions from Washington do not contribute 

significantly to nonattainment of the 24-hour PM2.5 standard at this receptor. 

Figure 15: Topographical Map of Plumas County50

III.B.2 Idaho 

Franklin County/Cache County Nonattainment Receptor (Logan) (Site 490050004) 

See discussion of Cache County/Franklin County in section III.B.5. Utah below. 

 

50 EPA Technical Support Document for California for the 2012 Primary Annual PM2.5 NAAQS. 

http://www.epa.gov/pmdesignations/2012standards/eparesp/09_CA_120TSD_20140818.pdf
28 

Shoshone County Nonattainment Receptor (Pinehurst) (Site 160790017) 

The EPA identified a single nonattainment receptor in Shoshone County, Idaho, namely the 

receptor located in Pinehurst. Idaho Department of Environmental Quality identified Pinehurst 

as an area of concern for PM2.5.

51 A portion of Shoshone County (West Silver Valley) was 

included as part of the designations process for the 2012 annual PM2.5 NAAQS (80 FR 2206, 

January 15, 2015).52 We note that we are not evaluating interstate transport requirements for the 

2012 annual PM2.5 NAAQS in this action, however, we believe that the information developed as 

part of the designations process for the 2012 annual PM2.5 NAAQS is informative for our 

evaluation of this receptor for purposes of interstate transport requirements for the 2006 24-hour 

PM2.5 NAAQS.53

Shoshone County is a rural county in the northern panhandle of Idaho. The area is sparsely 

populated and is home to rugged mountainous terrain. Residential wood combustion in the cold, 

winter months is most responsible for elevated particulate matter in the area, while prescribed 

burning in the late autumn and in the spring also contributes substantially. Smoke from wildfires 

can affect the area in the summer. Smoke from crop residue burning is a minor contributor to 

PM2.5 at this receptor. 54

The Pinehurst monitor measures high values in the winter due to a combination of residential 

wood combustion, low wind speeds, and low mixing heights. In the springtime prescribed 

burning contributes to elevated PM2.5. The monitor generally records lower values in the summer 

except for occasional impacts from wildfires. In the autumn season the monitor is again 

influenced by prescribed burning.55

Pinehurst is located in a partially obstructed topographic bowl within the Silver Valley.56 The 

Silver Valley is also the location of the Bunker Hill Superfund site which is a large mining site 

that has been undergoing remediation since the 1980s. The mining site currently has only minor 

emissions associated with movement of product from the underground mining sites. The analysis 

developed for the 2012 annual PM2.5 NAAQS designations process supports a conclusion that the 

majority of the emissions impacting PM2.5 levels, in general, are generated from residential wood 

combustion in close proximity to the Pinehurst monitor. Secondarily, emissions from prescribed 

burning generated in and around the Silver Valley are also expected to contribute to elevated 

PM2.5 levels.57

Topography plays a significant role in channeling winds along valleys in particular 

meteorological situations. See Figure 17 below. 

 

51 https://www.deq.idaho.gov/media/662796-nonattainment_map.pdf 52 EPA Technical Support Document for Idaho for the 2012 Primary Annual PM2.5 NAAQS. EPA docket # EPAHQ-OAR-2012-0918. http://www.epa.gov/pmdesignations/2012standards/eparesp/10_ID_120NAATSD.pdf 53 Ibid at page 5. 

54 Ibid. at page 5. 

55 Ibid. at page 8. 

56 Ibid. at page 29. 

57 Ibid. at page 29. 
29 

Figure 17: Pinehurst Monitor within West Silver Valley Topography

In West Silver Valley the predominant wind directions are southwesterly and westerly, but 

during pollution episodes the wind can also be southerly or northeasterly. During calm, 

wintertime weather conditions, cold surface temperatures, low wind speeds, and constrained 

vertical mixing develop in concert with each other. The deep, narrow mountain valley 

significantly magnifies this effect relative to other nearby areas. The combination of these 

meteorological effects and the mountainous terrain confine the geographical area that could 

contribute emissions to the pollution episode in West Silver Valley. It is hypothesized that the 

particular terrain features around Pinehurst limit mixing in Pinehurst even more so than the rest 

of the West Silver Valley.58

Light westerly winds are often associated with high PM2.5 at the receptor because the monitor is 

located on the east side of town. The light westerly winds collect wintertime residential wood 

combustion PM2.5 and carry it to the monitor to the east where it is constrained within the east 

side of the topographic bowl. At night cold air drainage winds follow the stream valleys from the 

higher terrain around West Silver Valley and into river valley. These winds could bring smoke 

 

58 Ibid. at page 34. 
30 

from smoldering prescribed burns from higher elevation into West Silver Valley. Stronger downvalley northeast winds clear the valley of pollution, while at other times weak northeast winds 

advect pollution to the monitor.59 During cold stagnant periods when PM2.5 is the highest, the 

mountainous terrain strongly limit the ability of the already weak transport winds to bring 

pollution from outside areas into the valley.60

Given the characteristics of the elevated PM2.5 levels at this receptor, air quality data indicating 

that regional background levels of PM2.5 are generally low during the time periods of elevated 

PM2.5 at this receptor61 and the intervening topography between Washington and this receptor, 

we believe it is reasonable to conclude that emissions from Washington sources do not contribute 

significantly to nonattainment of the 2006 24-hour PM2.5 NAAQS at this receptor. 

Lemhi County Nonattainment Receptor (Salmon) (Site 160590004) 

The EPA identified a single nonattainment receptor in Lemhi County, Idaho. Lemhi County 

population is 7,936. The largest city and county seat is Salmon. 

The highest point is Bell Mountain at 11,612 feet above mean sea level (MSL), and the lowest 

point is the Salmon River at approximately 3,000 feet above MSL. The river cuts through the 

center of Lemhi County before turning west. The county’s eastern border with Beaverhead 

County, Montana, is the continental divide. See Figure 18 below. 

The Salmon area is currently listed by the Idaho Department of Environmental Quality as an area 

of concern for PM2.5.62 Information from the State of Idaho indicates that local emissions, 

including from woodstoves, contribute to primary PM2.5 that results in elevated daily PM2.5 

values during stable weather events associated with strong inversions. 

The highest values at this receptor were also associated with significant wildfires in 2012. 

Despite the impacts of wildfire in 2012, Idaho Department of Environmental Quality recognizes 

that residential wood burning in combination with winter inversions meteorology are impacting 

the Salmon receptor. The topography of the area is significant. The Salmon receptor is located 

in a mountain valley surrounding by significant terrain. The Bitteroot Range, part of the Rocky 

Mountains, is situated between Washington and this receptor. 

 

59 Ibid. at page 34. 

60 Ibid. at page 36. 

61 Craters of the Moon, ID, Sawtooth National Forest, ID, Sula Peak Wilderness Area, MT, Gate of the Mountains 

Wilderness Area, MT. See section V. Appendix to this TSD and 

http://vista.cira.colostate.edu/TSS/Results/HazePlanning.aspx 62 https://www.deq.idaho.gov/media/662796-nonattainment_map.pdf
31 

Figure 18: Map of Idaho 
32 

Given the characteristics of the elevated PM2.5 levels at this receptor, air quality data indicating 

that regional background levels of PM2.5 are generally low during the time periods of elevated 

PM2.5 at this receptor,63 and the intervening topography between Washington and this receptor, 

as described above, we believe it is reasonable to conclude that emissions from Washington 

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

this receptor. 

Ada County Nonattainment Receptor (Boise) (Site 160010010) 

Ada County is identified as an area of concern for PM2.5 by the Idaho Department of 

Environmental Quality.64 Ada County is in southwest Idaho and Boise is the county’s most 

populace city. This receptor is in the western Treasure Valley, a basin with surrounding 

mountainous topography. The Boise Front, approximately 6,000 feet above MSL is located to 

the north. The Owyhee Mountains are situated to the southwest. Temperature inversions in Ada 

County occur in the winter months. These stagnation events are cited by Idaho Department of 

Environmental Quality as impacting the area with respect to particulate matter pollution.65

Sources of PM2.5 and precursors are shown in the Table 4 below. 

Table 4: Annual Emissions by Source Category—2015 (tons per year)66

Source 

Type

NOx SO2 VOC PM10 PM2.5 TC 

Point 355.6 65.7 268.1 169.1 142.6 68.5

Area 900.0 23.6 14,551.2 21,107.4 3,651.3 7,806.1 

On-road 5,856.6 33.4 2,939.7 283.0 193.0 246.0 

Non-road 1,979.8 28.2 1,480.7 196.9 185.8 172.7 

Biogenic 202.3 0.0 12,802.5 0.0 0.0 0.0 

Total 9,294.3 150.9 32,042.2 21,756.4 4,172.7 8,293.3 

The design value for the period 2011-2013 at this receptor exceeded the 2006 24-hour PM2.5

NAAQS, however the previous three design value periods attained the 2006 24-hour PM2.5

NAAQS.67 IMPROVE data from the Hells Canyon and Starkey class I areas are generally low 

during the times of elevated 24-hour PM2.5 levels at the Ada County receptor.68 

Given the characteristics of the elevated PM2.5 levels at this receptor, air quality data indicating 

that regional background levels of PM2.5 are generally low during the time periods of elevated 

 

63 Craters of the Moon, ID, Sawtooth National Forest, ID, Sula Peak Wilderness Area, MT, Gate of the Mountains 

Wilderness Area, MT. See section V. Appendix to this TSD and 

http://vista.cira.colostate.edu/TSS/Results/HazePlanning.aspx 64 https://www.deq.idaho.gov/media/662796-nonattainment_map.pdf 65 See Northern Ada County Carbon Monoxide maintenance Plan and Redesignation Request 66 Source: Idaho Department of Environmental Quality. 

67 EPA Airdata. 

68 See section V. Appendix to this TSD. 
33 

PM2.5 at this receptor,69 and the intervening topography between Washington and this receptor, 

we believe it is reasonable to conclude that emissions from Washington sources do not contribute 

significantly to nonattainment of the 2006 24-hour PM2.5 NAAQS at this receptor. 

III.B.3. Montana 

Silver Bow County Nonattainment Receptor (Butte) (Site 300930005) 

Elevated levels of PM2.5 in the Butte area also occur primarily in the winter months.70 The Butte 

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

valley. The mountains of the Lewis Range and the Bitteroot Range, part of the Rocky 

Mountains, are situated to the west of Butte. See Figure 16 below. The tallest peaks in the 

Bitteroot Range reach 7,000 to 11,000 feet. Speciation data indicates that emissions from wood 

smoke are the primary contributor to exceedances of the PM2.5 standard in Butte.71 These factors 

indicate that high levels of PM2.5 in Butte build as emissions become trapped in the mountain 

valley during wintertime inversions.72

Given the characteristics of the elevated PM2.5 levels at this receptor, air quality data indicating 

that regional background levels of PM2.5 are generally low during the time periods of elevated 

PM2.5 at this receptor,73 and the intervening topography between Washington and this receptor, 

as described above, we believe it is reasonable to conclude that emissions from Washington 

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

this receptor. 

 

69 Craters of the Moon, ID, Sawtooth National Forest, ID, Sula Peak Wilderness Area, MT, Gate of the Mountains 

Wilderness Area, MT. See section V. Appendix to this TSD and 

http://vista.cira.colostate.edu/TSS/Results/HazePlanning.aspx 70 In 2009 and 2010, the only recent years in which the Butte maintenance receptor violated the 2006 PM2.5 NAAQS, 

each exceedance of the NAAQS occurred in either December or January. Monitor values are accessible on EPA’s 

AirData website, http://www.epa.gov/airquality/airdata/. 71 Ward, T., Lange, T., “The impact of wood smoke on ambient PM2.5 in northern Rocky Mountain valley 

communities.” Environmental Pollution 158 (2010) 723–729. 

72 Ibid. 

73 Craters of the Moon, ID, Sawtooth National Forest, ID, Sula Peak Wilderness Area, MT, Gate of the Mountains 

Wilderness Area, MT. See section V. Appendix to this TSD and 

http://vista.cira.colostate.edu/TSS/Results/HazePlanning.aspx
34 

Figure 16: Map of Montana74

III.B.4. Oregon 

Crook County Nonattainment Receptor (Site 410130100) 

Crook County is located in central Oregon and the city of Prineville is the county seat - 

population 9,253.75 The Cascade Range borders on the west of the region, with high desert to the 

east and the Ochoco Mountains to the northeast. Prineville is marked with a blue triangle near 

the center of the state as depicted in Figure 17 below. 

 

 

74 Source: University of Texas. http://www.lib.utexas.edu 75 2010 Census. 
35 

Figure 17: Map of Oregon – Prineville, Klamath Falls, Lakeview76

Within Central Oregon, Crook County has a high rate of residential wood burning.77 PM2.5

speciation data is not available for the Prineville receptor, but daily mean PM2.5 concentration 

time series between 2009 and 2013 show that the highest values have typically occurred in the 

winter months of December and January, indicating an association with residential wood burning 

and wintertime inversion meteorology. See Figure 18 below. 

 

 

76 Source: www.lib.utexas.edu 77 See Oregon 2005 Residential Wood Combustion Emission Inventory, Oregon Department of Environmental 

Quality. 
36 

Figure 18: Prineville, Oregon Daily Mean PM2.5 Concentrations 

In addition, PM2.5 levels at IMPROVE monitors in between Washington and this receptor are 

generally low during the winter months (< 5 μg/m3

) when exceedances at the Prineville receptor 

have typically occurred.78 The topography of the Cascade Mountains also separates Western 

Washington (the most significant area of emissions) and this receptor. 

Based on the nature of the PM2.5 problems at this receptor as described above, the distance of this 

receptor from Washington (approximately 100 miles), low background levels at IMPROVE 

monitors in the class I areas between this receptor and Washington when wintertime inversionrelated exceedances of the NAAQS generally occur, 79 and the significant terrain between 

Washington population centers and this receptor as described above, we believe it is reasonable 

to conclude that emissions from Washington do not contribute significantly to nonattainment of 

the 2006 24-hour PM2.5 NAAQS at this receptor.

 

78 IMPROVE monitoring network at Mount Hood Wilderness, OR and Columbia River Gorge, OR. See section V. 

Appendix to this TSD and http://vista.cira.colostate.edu/TSS/Results/HazePlanning.aspx 79 Ibid.
37 

Klamath County Nonattainment Receptor (Klamath Falls) (Site 410350004) 

A portion of Klamath County is designated nonattainment for the 2006 PM2.5 NAAQS.80 

Klamath Falls is a relatively small urban community located in and supporting a vast rural area 

in south-central Oregon, near the California border. See Figure 17 above. The community lies in 

a valley at the northern end of the Klamath basin, a broad valley surrounded by mountains. 

Klamath Falls is at an elevation of approximately 4500 ft. above mean sea level (MSL). 

Surrounding mountains rise to 5000-6000 ft. MSL. A 2005 emission inventory conducted by 

Oregon shows that wood stove emissions are the most significant source of emissions.81 

Additional air quality monitoring data provide supporting evidence that residential wood 

combustion emissions are a primary contributor to exceedance days.82 Data shows 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 and indicate the exceedances are a seasonal occurrence, except flagged 

wildfire events.83

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

typical indicators of combustion activities such as wood burning.84 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 builds when trapped by winter, nighttime inversions. EPA R10 factor analysis modeling identified the following 5 categories of 

aerosol contributing to PM2.5: Nitrate Rich, Organic Pyrolysis Rich, Soil, Sulfate Rich, Wood 

Smoke. EPA R10’s analysis of average factor contributions on winter season days with elevated 

PM2.5 shows Wood Smoke dominating at 72%. 

Based on the above-described information, distance from Washington to this receptor (≈ 240 

miles), low background levels at IMPROVE monitors in class I areas near this receptor at the 

time of elevated PM2.5,

85 and significant intervening terrain (as discussed above), we believe it is 

reasonable to conclude that Washington emissions do not significantly contribute to 

nonattainment of the 2006 24-hour PM2.5 NAAQS at this receptor.

 

 

80 Technical Support Document, Oregon Area Designations for the 24-Hour Fine Particle National Ambient Air 

Quality Standards http://www.epa.gov/pmdesignations/2006standards/final/TSD/tsd_4.0_4.10_4.10.3_r10_OR.pdf 81 Ibid. 

82 Ibid. 

83 Ibid. 

84 Ibid. 

85 IMPROVE monitoring network at Three Sisters Wilderness, OR and Crater Lake National Park, OR. See V. 

Appendix to this TSD and http://vista.cira.colostate.edu/TSS/Results/HazePlanning.aspx
38 

Lake County Nonattainment Receptor (Lakeview) (Site 410370001) 

As seen in Figure 17 above, Lakeview, Oregon is located to the east of Klamath Falls, and is the 

county seat of Lake County, population 2,294.86 Lakeview is located in the Goose Lake Valley 

at the foot of the Warner Mountains to the east. Lakeview is on the edge of the high desert 

country of southeastern Oregon. At an elevation of 4,800 feet (1,500 m), Lakeview is one of the 

highest cities in Oregon.87 The significant topography between Western Washington (the most 

significant emission sources) and this receptor includes over 250 miles of the Cascade Range. 

EPA R10 factor analysis modeling identified the following 7 categories of aerosol contributing 

to PM2.5: Nitrate Rich, Organic Pyrolysis Rich, Potassium Rich, Soil, Sulfate Rich, Urban 

Unidentified, and Wood Smoke. EPA R10’s analysis of average factor contributions on winter 

season days with elevated PM2.5 shows Wood Smoke dominating at 67%. 

Based on the nature of the PM2.5 problem in Lakeview described above, low background levels at 

IMPROVE monitors in class I areas near this receptor during the winter months when 

exceedances typically occur,88 distance from Washington to this receptor (approximately 250 

miles), and significant intervening terrain as described above, we believe it is reasonable to 

conclude that Washington emissions do not significantly contribute to nonattainment of the 2006 

24-hour PM2.5 NAAQS at this receptor.

Lane County Nonattainment Receptor (Oakridge) (Site 410392013) 

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

NAA).89 Elevated levels at the Oakridge nonattainment receptor generally occur during winter 

stagnation events and the technical analysis developed during the designations process by the 

State of Oregon and the EPA points to residential home heating using wood burning appliances, 

as being the main contributor to fine particle pollution in the area.90 The EPA Region 10 factor 

analysis modeling identified the following seven categories of aerosol contributing to PM2.5: 

Gasoline Vehicles, Organic Pyrolysis Rich, Sea Salt, Soil, Sulfate Rich, Urban Unidentified, and 

Wood Smoke. EPA Region 10’s analysis of average factor contributions on winter season days 

with elevated PM2.5 shows Wood Smoke dominating at 72%. 

Oakridge, Oregon is a small, isolated mountain community 35-40 miles east of Eugene, Oregon, 

surrounded by national forest. It is located in Lane County, which stretches from the Pacific 

Ocean to the mountains of the Cascade Range. Vast areas of Lane County are forested mountains 

of the Coast Range and Cascade Range.91 Oakridge lies in an alluvial plain in the foothills at the 

 

86 2010 Census. 

87 Oregon topographic map, United States Geological Survey, United States Department of Interior, Reston, 

Virginia; displayed via ACME mapper, www.acme.com, 19 July 2014. 88 Crater Lake, OR, Lava Beds National Monument, CA, and Starkey, ID. See V. Appendix to this TSD and 

http://vista.cira.colostate.edu/TSS/Results/HazePlanning.aspx 89 2006 24-Hour PM2.5 NAAQS Designations (November 13, 2009; 74 FR 58688). 90 Technical Support Document, Oregon Area Designations for the 24-Hour Fine Particle National Ambient Air 

Quality Standards http://www.epa.gov/pmdesignations/2006standards/final/TSD/tsd_4.0_4.10_4.10.3_r10_OR.pdf 91 Ibid. 
39 

southern end of the Willamette River valley and is 28 miles west of Willamette Pass, the summit 

of the Cascade Mountain Range (approximately 5000 feet in elevation). Elevation in the area 

ranges from 1100 feet at the lower (west) end to 1600 feet with areas of densest population 

situated between 1100 feet and 1200 feet.92 Mountains rise on the north and south sides to 1700 

feet and 1600 feet, respectively.93 There is significant topography between Washington and 

Oakridge, Oregon including the Cascade Range as depicted in Figure 17 above. This terrain 

reaches up to 5000 feet at the summit of Willamette Pass. 

Based on the above information, the distance of this receptor from Washington (≈ 150 miles), 

low background levels at IMPROVE monitors in the class I areas between this receptor and 

Washington94 when wintertime inversion-related exceedances of the NAAQS generally occur, 

and the significant terrain between Washington and this receptor as described above, we believe 

it is reasonable to conclude that emissions from Washington do not contribute significantly to 

nonattainment of the 2006 24-hour PM2.5 NAAQS at this receptor.

 

 

92 Ibid. 

93 Ibid. 

94 IMPROVE monitoring network at Mount Hood Wilderness, OR, Columbia River Gorge, OR, and Three Sisters 

Wilderness, OR. See section V. Appendix to this TSD and 

http://vista.cira.colostate.edu/TSS/Results/HazePlanning.aspx
40 

III.B.5. Utah 

Utah County Nonattainment Receptors (Provo) (Sites 490490002, 490494001, 490495008, 

490495008) 

A large portion of Utah County is designated as the Provo 2006 24-hour PM2.5 nonattainment 

area (Provo NAA).95 The Provo nonattainment receptors identified are 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. See Figure 19 below. The Wasatch 

Mountain Range rises from the valley floor to approximately 7,000 to over 9,000 ft. MSL and 

defines the eastern boundaries of both the Salt Lake Valley to the north and the Utah Valley to 

the south. These valleys are bound on their respective western sides by the Oquirrh Mountains 

which also have heights of 7,000 ft. MSL to well over 9,000 ft. MSL. North of Salt Lake County, 

the Wasatch Mountain Range continues to act as a barrier to the east, while the Great Salt Lake 

serves as the western boundary. 96

Elevated levels of PM2.5 at these receptors occur primarily in the winter months.97 The levels of 

elevated PM2.5 at these receptors are driven by inversion meteorology which traps pollutants and 

leads to exceedances, as noted in the discussion of these receptors below.98 During the winter 

months, levels of PM2.5 at background monitoring sites located north and west of this receptor99

are very low, generally below 3μg/m3

, and the vast majority of the PM2.5 in the urban area is 

generated within the area and trapped during winter inversion meteorology. 

 

 

95 2006 24-Hour PM2.5 NAAQS Designations (74 FR 58688, November 13, 2009), Technical Support Document, 

December 2008. http://www.epa.gov/pmdesignations/2006standards/final/TSD/tsd_4.0_4.8_4.8.2_r08_UT.pdf. 96 Ibid. at page 48. 

97 For example, in 2011 and 2012, each exceedance of the 2006 PM2.5 NAAQS in Salt Lake City occurred in either 

December or January of those years. Monitor values are accessible on EPA’s AirData website, 

http://www.epa.gov/airquality/airdata/. 98 2006 24-Hour PM2.5 NAAQS Designations (74 FR 58688, November 13, 2009), Technical Support Document, 

December 2008. http://www.epa.gov/pmdesignations/2006standards/final/TSD/tsd_4.0_4.8_4.8.2_r08_UT.pdf. At 

page 48. 

99 IMPROVE monitoring network at Craters of the Moon, ID, Sawtooth National Forest, ID and Jarbidge 

Wilderness Area, NV. See section V. Appendix to this TSD and 

http://vista.cira.colostate.edu/TSS/Results/HazePlanning.aspx
41 

Figure 19: Monitoring Network with Counties and Topography100

 

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 emission sources and 

 

100 Source: Utah Department of Environmental Quality. 2006 24-Hour PM2.5 NAAQS Designations (74 FR 58688, 

November 13, 2009), Technical Support Document, December 2008. 

http://www.epa.gov/pmdesignations/2006standards/final/TSD/tsd_4.0_4.8_4.8.2_r08_UT.pdf. at page 19. 
42 

secondary chemistry. Transport of air masses between Salt Lake City and Provo receptors 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.101 

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 primary and secondarily 

formed PM2.5 that violate the 2006 24-hour PM2.5 NAAQS during stable weather events 

associated with strong inversions.102

Based on the meteorology, topography and characteristics of the PM2.5 levels during time periods 

when the 24-hour PM2.5 standard is exceeded as described above, as well as the low levels of 

background PM2.5 during these time periods at IMPROVE monitors in the class I areas between 

Washington and these receptors or near these receptors103 it is reasonable to conclude that 

emissions from Washington do not significantly contribute to nonattainment of the 2006 24-hour 

PM2.5 NAAQS at these receptors.

Box Elder, Salt Lake and Weber Counties Nonattainment Receptors (Greater Salt Lake City) 

(Sites 490030003, 490350003, 490353006, 490353010, 490570002) 

All of Salt Lake county and portions of Box Elder and Weber counties are designated as part of 

the Salt Lake City (SLC) 2006 24-hour PM2.5 nonattainment area (NAA).104 The EPA identified 

nonattainment receptors in each of the three counties. The SLC NAA and these nonattainment 

receptors are situated in a valley bordered on the west by the Stansbury Mountains,105

Promontory Mountains and Great Salt Lake, and on the east by the Wasatch Front. Like the 

other low-lying valleys just west of the Wasatch Front, the topography of the Salt Lake valley 

makes it prone to temperature inversions. See Figure 19 above. 

A western topographic airshed barrier for eastern Box Elder County involves the Promontory 

Mountains and North Promontory Mountains.106 The Promontory Mountains are located 

approximately 24 miles west of both Brigham City and Ogden and show approximate altitudes of 

5,600 ft. (MSL) in the south (extending into the Great Salt Lake), areas of over 6,000 ft. (MSL) 

in the middle, and 5,000 ft. to the North where they meet the southern end of the North 

 

101 Ibid. at page 41. 102 Ibid. at page 34. 

103 IMPROVE monitoring network at Jarbidge Wilderness Area, NV, Crater Lake, OR, and Lava Beds National 

Monument, CA. See section V. Appendix to this TSD and 

http://vista.cira.colostate.edu/TSS/Results/HazePlanning.aspx 104 2006 24-Hour PM2.5 NAAQS Designations (74 FR 58688, November 13, 2009), Technical Support Document, 

December 2008. http://www.epa.gov/pmdesignations/2006standards/final/TSD/tsd_4.0_4.8_4.8.2_r08_UT.pdf. At 

page 25. 

105 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. 106 2006 24-Hour PM2.5 NAAQS Designations (74 FR 58688, November 13, 2009), Technical Support Document, 

December 2008. http://www.epa.gov/pmdesignations/2006standards/final/TSD/tsd_4.0_4.8_4.8.2_r08_UT.pdf. At 

page 48. 
43 

Promontory Mountains. The southern end of the North Promontory Mountains are approximately 

5,000 ft. (MSL) and are also approximately 5,000 ft. (MSL) to the north (northwest of Howell, 

UT.)107

The Stansbury Mountains are located approximately 17 miles west of Tooele City 

(approximately 43 miles southwest of Salt Lake City) and show approximate altitudes of 8,300 

ft. (MSL) in the south, areas 7,000 ft. (MSL) to over 9,500 ft. (MSL) in the middle, and 5,000 ft. 

(MSL) to the North where they meet the Great Salt Lake. Also, an impediment to airflow in this 

area includes the South Mountain ridge located at the southern end of the Tooele Valley. This 

ridge essentially connects the Stansbury Mountains to the Oquirrh Mountains and has a 

maximum height of approximately 6,500 ft. (MSL). Therefore, it is likely that Salt Lake County 

is contributing to Utah County’s high concentration PM2.5 violations and that Utah County is 

contributing to Salt Lake County’s high concentration PM2.5 violations.108

During inversions, the SLC 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 emission sources and secondary 

chemistry.109 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 amounts of emissions from mobile, point and area sources, contribute to primary and 

secondarily formed PM2.5 that violate the 2006 24-hour PM2.5 standard during stable weather 

events associated with strong inversions.110

Based on the meteorology, topography and characteristics of the PM2.5 levels during time periods 

when the 24-hour PM2.5 standard is exceeded, as described above, as well as the low levels of 

background PM2.5 during these time periods at IMPROVE monitors at class I areas near this 

receptor111 it is reasonable to conclude that emissions from Washington do not significantly 

contribute to nonattainment of the 2006 24-hour PM2.5 NAAQS at these receptors. 

Cache County/ Franklin County Nonattainment Receptor (Logan) (Site 490050004) 

Portions of Cache County, Utah and Franklin County, Idaho make up the Cache Valley, a 

mountain valley straddling the Utah-Idaho border. Portions of these two counties are also 

designated as part of the Logan UT-ID 2006 24-hour PM2.5, cross-state nonattainment area 

(Cache Valley NAA).112 See Figure 20 below. 

 

107 Ibid. at page 48. 108 Ibid. at page 49. 109 Ibid. at page 34. 110 Ibid. at page 53. 

111 IMPROVE monitoring network at Jarbidge Wilderness Area, NV, Crater Lake, OR, and Lava Beds National 

Monument, CA. See section V. Appendix to this TSD and 

http://vista.cira.colostate.edu/TSS/Results/HazePlanning.aspx 112 2006 24-Hour PM2.5 NAAQS Designations (74 FR 58688, November 13, 2009), Technical Support Document, 

December 2008. http://www.epa.gov/pmdesignations/2006standards/final/TSD/tsd_4.0_4.8_4.8.2_r08_UT.pdf. At 

page 2. 
44 

Figure 20: Location map showing the Cache Valley and the boundaries for Franklin 

County, Idaho, and Cache County, Utah.113

Limited chemical speciation data indicates the 24-hour PM2.5 problem is dominated by 

ammonium nitrate aerosol similar to nonattainment areas along the Wasatch Front in and near 

 

113 Source Utah Department of Environmental Quality. 
45 

Salt Lake City.114 The chemical speciation monitor in Bountiful is closest to the Cache Valley 

and is considered broadly representative of conditions in the Cache Valley.115 The ridge 

dominated synoptic meteorology during PM2.5 cold pool episodes features weak transport winds 

and near calm surface winds. As a result, transport of PM2.5 and precursors from the rural regions 

at the domain periphery is limited. In addition, most of the observed Wasatch Front and Cache 

Valley PM2.5 is formed in-situ (and trapped) via fresh emission sources and secondary 

chemistry.116

Residential heating emissions from woodstoves, emissions from agricultural activities, and 

mobile source emissions contribute to primary and secondarily formed PM2.5 that violate the 24-

hour standard during stable weather events associated with extremely strong inversions. These 

emissions and the related effects are limited to the Cache Valley, as they are trapped there due to 

temperature inversions, low wind, and significant topography.117

The most prominent topographical features impacting the Cache Valley as a whole include: (1) 

the eastern boundary of the valley which is composed of the Wasatch-Cache National Forest, the 

Bear River Mountain Range, and Monte Cristo Mountain Range, and (2) the western boundary 

which is composed of the northern section of the Wasatch Mountain Range and the Wellsville 

Mountain Range. The mountains to the east rise to approximately 8,300 feet MSL and to the 

west the mountains rise to approximately 9,900 feet MSL. However, the valley floor only ranges 

in altitude from approximately 4,500 feet MSL to 5,200 feet MSL from south to north 

respectively.118

The Wellsville Mountains, Bear River Mountains, and northern Wasatch mountains converge in 

southern Cache County, Utah to form a topographical barrier between the Cache Valley and 

other adjacent Utah counties such as Box Elder and Weber. As with the southern area of the 

Cache Valley, the mountain ranges of the northern area of the Cache Valley, bordering the 

eastern and western portions of Franklin County, effectively meteorologically isolate Franklin 

County from Bannock, Bear Lake, Caribou, and Oneida Counties in Idaho.119

EPA Region 10 Positive Matrix Factor (PMF) receptor modeling identified 11 factors 

contributing to elevated wintertime 24-hour PM2.5 levels at the Bountiful monitoring site 

including nitrate rich (56%), ammonium chloride (15%), wood smoke (10%), organic pyrolysis 

rich (6%), sulfate rich (5%) and smaller contributions by other identified factors (gasoline 

vehicles, two soil factors, fireworks, iron rich, and urban unidentified).

Based on the meteorology, topography and characteristics of the PM2.5 levels during time periods 

when the 24-hour PM2.5 standard is exceeded, as described above, as well as the low levels of 

background PM2.5 during these time periods at IMPROVE monitors at class I areas near this 

 

114 2006 24-Hour PM2.5 NAAQS Designations (74 FR 58688, November 13, 2009), Technical Support Document, 

December 2008. http://www.epa.gov/pmdesignations/2006standards/final/TSD/tsd_4.0_4.8_4.8.2_r08_UT.pdf. At 

page 9. 

115 Ibid. at page 14-15. 116 Ibid. at page 14-15. 117 Ibid. at page 17-18. 118 Ibid. at page 17-18. 119 Ibid. at page 7. 
46 

receptor120 it is reasonable to conclude that emissions from Washington do not significantly 

contribute to nonattainment of the 2006 24-hour PM2.5 NAAQS at this receptor. 

III.C. Transport to Eastern States 

The EPA has also considered potential PM2.5 transport from Washington emission sources to the 

nearest potential receptor located in the eastern, midwestern, and southern states within the 

domain of the modeling analysis for the Transport Rule (76 FR 48208). The receptor nearest to 

Washington evaluated in the Transport Rule modeling analysis is Madison County, Illinois. We 

note, the Transport Rule modeling did not analyze the contribution of Washington sources to 

Madison County, Illinois. Thus, we have analyzed the magnitude of Washington’s SO2 and NOx 

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

at that receptor. The EPA also considered the distance from Washington to Madison County, 

Illinois relative to states found to significantly contribute there. 

We believe that the following factors support a finding that emissions from Washington sources 

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

Madison County, Illinois receptor: (1) the relatively small magnitude of the emission inventory 

of PM2.5 precursors (SO2 and NOx) in Washington as detailed below, combined with (2) the 

relatively long distance between the State of Washington and this receptor (≈ 1400 miles). The 

EPA believes that these factors also support a finding that emissions from Washington sources 

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

other Transport Rule receptors farther east. 

In the Transport Rule analysis, the EPA did not quantify the PM2.5 contributions from 

Washington to Illinois or any of the other Eastern nonattainment and maintenance receptors 

modeled as part of the Transport Rule. However, we can make a qualitative conclusion about the 

likely contribution from Washington to Illinois and points farther east by comparing the 

Washington emissions to a state that was modeled in the Transport Rule. Minnesota was 

modeled for the Transport Rule, and was found below the threshold of significant contribution to 

downwind nonattainment and interference with maintenance of the 24-hour PM2.5 NAAQS for 

all receptors modeled for the Transport Rule. We have evaluated the relative amounts of PM2.5 

precursor (SO2 and NOx) emissions in Washington compared to the amounts of PM2.5 precursor 

emission in Minnesota, as modeled in the “2012 Transport Rule Base Case.” 

The emission inventories used in the Transport Rule modeling analysis indicate that SO2

emissions in Washington are about 35% of SO2 emissions in Minnesota and NOx emissions in 

Washington are about 74% of NOx emissions in Minnesota. Specifically, the Transport Rule 

2012 Base Case inventories121 provide the following statewide emissions inventory data for these 

two states: 38,581 tons of SO2 and 268,870 tons of NOx from Washington emission sources, 

compared to 109,940 tons of SO2 and 364,052 tons of NOx from Minnesota emission sources. 

Even though the relationship between upwind emissions and downwind secondary PM2.5 

 

120 IMPROVE monitoring network at Jarbidge Wilderness Area, NV, Crater Lake, OR, and Lava Beds National 

Monument, CA. See section V. Appendix to this TSD and 

http://vista.cira.colostate.edu/TSS/Results/HazePlanning.aspx 121 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. 
47 

formation is not linear, we would expect the Washington PM2.5 contribution to Illinois to be less 

than that of Minnesota and well below the 1% threshold applied in the initial screening stage of 

the Transport Rule. In addition, Washington is a much greater distance away from Madison 

County, Illinois than Minnesota (≈ 1400 miles vs approximately 300 miles). The distance from 

Washington to the other eastern receptors is even greater, and therefore, the expected impact 

somewhat smaller. 

Given all of these factors, the EPA believes it is reasonable to conclude that emissions from 

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

NAAQS at identified receptors in any eastern state. 

IV. Transport Assessment for Maintenance Receptors 

IV.A. Introduction 

Based on our methodology for selecting maintenance receptors described in section II.A above, 

we have evaluated maintenance receptors in the following western states: California, Montana, 

and Utah. We also evaluated the nearest eastern receptor evaluated in the Transport Rule 

modeling domain.122 

IV.B. Transport to Western States

IV.B.1. California 

Southern California –Los Angeles County Maintenance Receptor (Site 060370002) 

The high 24-hour PM2.5 concentrations in the South Coast Air Basin and at this maintenance 

receptor are mainly due to the secondary formation of smaller particulates resulting from mobile, 

stationary and area source emissions of precursor gases (i.e., NOx, SOx, ammonia (NH4), and 

VOCs) that are converted to PM in the atmosphere. Speciated PM2.5 data at the Central Los 

Angeles Site (CELA) and the Rubidoux site (RIVR) indicate that organic carbon, ammonium 

nitrate, and ammonium sulfate constitute the major components at each site. See Figures 20 and 

21 below. 24-hour PM2.5 design value trends show strong downward trends at all sites in the 

South Coast Basin. 123 See Figure 22 below. 

 

122 Madison County, Illinois. See “Technical Support Document (TSD) for the final Transport Rule, Docket ID No. 

EPA-HQ-OAR-2009-0491, June 28, 2011. 

123 Joe Cassmassi, Scientific, Technical & Modeling Peer Review (STMPR) Advisory Group Meeting, September 

22, 2011. 
48 

Figure 21: Speciated data for the Central Los Angeles Site124

 

 

124 STMPR Item # 5 - 2008 PM2.5 Air Quality Characterization, January 19, 2012. Bong-Mann Kim. 
49 

Figure 22: Speciated data for Roubidoux site at Riverside125

 

 

125 Ibid. 
50 

Figure 23: 24-hour PM2.5 Design Value Trends 

PM2.5 is essentially a combustion generated pollutant due to the volume of traffic flow and 

numbers of sources (both point and area) in the region. It is important to note that the areas with 

the highest concentrations are directly downwind of an area with major ammonia sources 

associated with dairies and poultry farming.126

The South Coast Air Quality 2012 Air Quality Management Plan127 air quality projections show 

that the emission control strategy outlined in the plan will result in air quality improvement at 

each of the nonattainment receptors in the plan, and that each of these sites will attain the 

standard in 2014 or sooner. See Figure 24: Maximum 24-Hour Average PM2.5 Design 

Concentrations: 2008 Baseline, 2014 and 2014 Controlled. 

 

 

126 Final 2012 Air Quality Management Plan (AQMP), Appendix V – Modeling and Attainment Demonstrations 

February, 2013. 

127 http://www.aqmd.gov/home/library/clean-air-plans 
51 

Figure 24: Maximum 24-Hour Average PM2.5 Design Concentrations: 2008 Baseline, 2014, 

and 2014 Controlled128

Based on the air quality trends and projections that indicate that the above-referenced emission 

strategy will be effective in reducing 24-hour PM2.5 levels at these receptors, the distance from 

Washington to these receptors ( > 800 miles), and the significant intervening terrain including 

the Sierra Nevada and Cascade Ranges (See Figure 9 above) we believe it is reasonable to 

conclude that emissions from Washington do not interfere with maintenance of the 2006 24-hour 

PM2.5 NAAQS at these receptors. 

IV.B.2. Montana

Lewis and Clark County Maintenance Receptor (Helena) (Site 300490026) 

Elevated levels of PM2.5 in the Helena area occur primarily in the winter months.129 The Helena 

Valley is topographically prone to cold pool inversion conditions during the winter months.130

The mountains of the Lewis Range and the Bitteroot Range are situated to the west of Helena, 

between Washington and this receptor. See Figure 25 below. Speciation data indicates that 

emissions from wood smoke are the primary contributor to exceedances of the PM2.5 standard in 

Helena.131 In the months when violations of the NAAQS occurred at the Helena receptor, the 

 

128 Source: South Coast Air Quality Management District. http://www.aqmd.gov/home/library/clean-air-plans 129 The maintenance receptor in Helena, MT violated the 2006 PM2.5 NAAQS only in 2010. Each of the exceedances 

of the 2006 PM2.5 standard at this receptor during 2010 occurred during the winter months, with all but one 

exceedance occurring in December or January. Monitor values are accessible on EPA’s AirData website, 

http://www.epa.gov/airquality/airdata/. 130 Johnson, J. “Case Study of a Persistent Cold Pool in the Helena Valley.” NOAA. November 21, 2000. 

131 Ward, T., Lange, T., “The impact of wood smoke on ambient PM2.5 in northern Rocky Mountain valley 

communities.” Environmental Pollution 158 (2010) 723–729. 
52 

nearby Gate of the Mountains Wilderness Area monitor did not exceed 2 μg/m3

.

132 All of these 

factors taken together indicate that high levels of PM2.5 in Helena build as emissions become 

trapped during wintertime inversions. 

Figure 25: Map of Montana133

Given the characteristics of the elevated PM2.5 levels at this receptor, air quality data indicating 

that regional background levels of PM2.5 are generally low at IMPROVE monitors in class I 

areas near this receptor134 during the time periods of elevated PM2.5, and the intervening 

topography between Washington and this receptor (the Bitteroot Range, part of the Rocky 

Mountains) we believe it is reasonable to conclude that emissions from Washington sources do 

not interfere with maintenance of the 2006 24-hour PM2.5 standards at this receptor location. 

IV.B.3. Utah 

Davis and Weber Counties Maintenance Receptors (Greater Salt Lake City) (Sites 490110004 

and 490571003) 

We note that the EPA identified both nonattainment and maintenance receptors in Greater Salt 

Lake City. Therefore, we have included our evaluation in both sections. 

 

132 The Gate of the Mountains IMRPOVE monitor is located roughly 17 miles from Helena, MT. The IMPROVE 

monitor data can be found in section V. Appendix to this TSD and 

http://vista.cira.colostate.edu/TSS/Results/HazePlanning.aspx 133 Source: University of Texas. http://www.lib.utexas.edu 134 Craters of the Moon, ID, Sawtooth National Forest, ID, Sula Peak Wilderness Area, MT, Gate of the Mountains 

Wilderness Area, MT. See section V. Appendix to this TSD and 

http://vista.cira.colostate.edu/TSS/Results/HazePlanning.aspx
53 

Portions of Davis and Weber counties are designated as part of the Salt Lake City (SLC) 2006 

24-hour PM2.5 nonattainment area (NAA).135 The EPA identified maintenance receptors in these 

two counties. The SLC NAA and these maintenance receptors are situated in a valley bordered 

on the west by the Stansbury Mountains,136 Promontory Mountains and Great Salt Lake, and on 

the east by the Wasatch Front. Like the other low-lying valleys just west of the Wasatch Front, 

the topography of the Salt Lake valley makes it prone to temperature inversions. See Figure 26 

below. 

A western topographic airshed barrier for eastern Davis County involves the Promontory 

Mountains and North Promontory Mountains.137 The Promontory Mountains are located 

approximately 24 miles west of both Brigham City and Ogden and show approximate altitudes of 

5,600 ft. (MSL) in the south (extending into the Great Salt Lake), areas of over 6,000 ft. (MSL) 

in the middle, and 5,000 ft. to the North where they meet the southern end of the North 

Promontory Mountains. The southern end of the North Promontory Mountains are approximately 

5,000 ft. (MSL) and are also approximately 5,000 ft. (MSL) to the north (northwest of Howell, 

UT.)138

The Stansbury Mountains are located approximately 17 miles west of Tooele City 

(approximately 43 miles southwest of Salt Lake City) and show approximate altitudes of 8,300 

ft. (MSL) in the south, areas 7,000 ft. (MSL) to over 9,500 ft. (MSL) in the middle, and 5,000 ft. 

(MSL) to the North where they meet the Great Salt Lake. Also, an impediment to airflow in this 

area includes the South Mountain ridge located at the southern end of the Tooele Valley. This 

ridge essentially connects the Stansbury Mountains to the Oquirrh Mountains and has a 

maximum height of approximately 6,500 ft. (MSL). Therefore, it is likely that Salt Lake County 

is contributing to Utah County’s high concentration PM2.5 violations and that Utah County is 

contributing to Salt Lake County’s high concentration PM2.5 violations.139

During inversions, the SLC 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 emission sources and secondary 

chemistry.140 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 amounts of emissions from mobile, point and area sources, contribute to primary and 

 

135 2006 24-Hour PM2.5 NAAQS Designations (74 FR 58688, November 13, 2009), Technical Support Document, 

December 2008. http://www.epa.gov/pmdesignations/2006standards/final/TSD/tsd_4.0_4.8_4.8.2_r08_UT.pdf. 136 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. 137 2006 24-Hour PM2.5 NAAQS Designations (74 FR 58688, November 13, 2009), Technical Support Document, 

December 2008. http://www.epa.gov/pmdesignations/2006standards/final/TSD/tsd_4.0_4.8_4.8.2_r08_UT.pdf. 

at page 48. 

138 Ibid. at page 48. 139 Ibid. at page 49. 140 Ibid. at page 34. 
54 

secondarily formed PM2.5 that violate the 2006 24-hour PM2.5 standard during stable weather 

events associated with strong inversions.141

Figure 26: Monitoring Network with Counties and Topography142

 

 

141 Ibid. at page 53. 142 Source: Utah Department of Environmental Quality. 2006 24-Hour PM2.5 NAAQS Designations (74 FR 58688, 

November 13, 2009), Technical Support Document, December 2008. 

http://www.epa.gov/pmdesignations/2006standards/final/TSD/tsd_4.0_4.8_4.8.2_r08_UT.pdf. At page 19. 
55 

Based on the meteorology, topography and characteristics of the PM2.5 levels during time periods 

when the 24-hour PM2.5 standard is exceeded, as described above, as well as the low levels of 

background PM2.5 during these time periods at IMPROVE monitors at class I areas near this 

receptor143 we believe it is reasonable to conclude that emissions from Washington do not 

interfere with maintenance of the 2006 24-hour PM2.5 NAAQS at these receptors. 

IV.C. Transport to Eastern States 

The EPA has also considered potential PM2.5 transport from Washington emission sources to the 

nearest potential receptor located in the eastern, midwestern, and southern states within the 

domain of the modeling analysis for the Transport Rule (76 FR 48208). The receptor nearest to 

Washington evaluated in the Transport Rule modeling analysis is Madison County, Illinois. We 

note, the Transport Rule modeling did not analyze the contribution of Washington sources to 

Madison County, Illinois. Thus, we have analyzed the magnitude of Washington’s SO2 and NOx 

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

at that receptor. The EPA also considered the distance from Washington to Madison County, 

Illinois relative to states found to significantly contribute there. 

We believe that the following factors support a finding that emissions from Washington sources 

do not interfere with maintenance of the 2006 24-hour PM2.5 NAAQS at the Madison County, 

Illinois receptor: (1) the relatively small magnitude of the emission inventory of PM2.5 precursors 

(SO2 and NOx) in Washington as detailed in the paragraph below, combined with (2) the 

relatively long distance between the state of Washington and this receptor ( ≈ 1500 miles). The 

EPA believes that these factors also support a finding that emissions from Washington sources 

do not interfere with maintenance of the 2006 24-hour PM2.5 NAAQS at any of the other 

Transport Rule receptors farther east. 

In the Transport Rule analysis, the EPA did not quantify the PM2.5 contributions from 

Washington to Illinois or any of the other Eastern receptors modeled as part of the Transport 

Rule. However, we can make a qualitative conclusion about the likely contribution from 

Washington to Illinois and points farther east by comparing the Washington emissions to a state 

that was modeled in the Transport Rule. Minnesota was modeled for the Transport Rule, and 

was found below the threshold of significant contribution to downwind nonattainment and 

interference with maintenance of the 24-hour PM2.5 NAAQS for all receptors modeled for the 

Transport Rule. We have evaluated the relative amounts of PM2.5 precursor (SO2 and NOx) 

emissions in Washington compared to the amounts of PM2.5 precursor emission in Minnesota, as 

modeled in the “2012 Transport Rule Base Case.” 

The emission inventories used in the Transport Rule modeling analysis indicate that SO2

emissions in Washington are about 35% of SO2 emissions in Minnesota and NOx emissions in 

Washington are about 74% of NOx emissions in Minnesota. Specifically, the Transport Rule 

 

143 IMPROVE monitoring network at Craters of the Moon, ID, Sawtooth National Forest, ID and Jarbidge 

Wilderness Area, NV. See section V. Appendix to this TSD and 

http://vista.cira.colostate.edu/TSS/Results/HazePlanning.aspx
56 

2012 Base Case inventories144 provide the following statewide emissions inventory data for these 

two states: 38,581 tons of SO2 and 268,870 tons of NOx from Washington emission sources, 

compared to 109,940 tons of SO2 and 364,052 tons of NOx from Minnesota emission sources. 

Even though the relationship between upwind emissions and downwind secondary PM2.5 

formation is not linear, we would expect the Washington PM2.5 contribution to Illinois to be less 

than that of Minnesota and below the 1% threshold applied in the initial screening stage of the 

Transport Rule. In addition, Washington is a much greater distance away from Madison County, 

Illinois than Minnesota ( ≈ 1500 miles vs approximately 300 miles). The distance from 

Washington to the other eastern receptors is even greater, and therefore, the expected impact 

somewhat smaller. 

Given all of these factors, the EPA believes it is reasonable to conclude that emissions from 

Washington sources do not interfere with maintenance of the 2006 24-hour PM2.5 NAAQS at 

identified receptors in any eastern state. 

V. Appendix – PM2.5 IMPROVE Data 

1. Overview and Map of IMPROVE Monitoring Sites

IMPROVE Monitoring Program Overview 

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 (156 national parks and wilderness areas) as stipulated in 

the 1977 amendments to the Clean Air Act.145 

The objectives of IMPROVE include: 

(1) establishing current visibility and aerosol conditions in mandatory class I areas; and 

(2) identifying chemical species and emission sources responsible for existing man-made 

visibility impairment. 

The particulate monitoring portion of the IMPROVE program measures the concentration of the 

fine (PM2.5) particles for mass, optical absorption, major and trace elements, organic and 

elemental carbon, and nitrate and of PM10 particles for mass. Prior to 2000, IMPROVE sites 

collect two samples per week, on Wednesday and Saturday. With the implementation of the 

Regional Haze Rule the IMPROVE program changed to a 1-in-3 day schedule. 

IMPROVE Monitoring Data 

 

144 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. 

145 http://vista.cira.colostate.edu/improve/Overview/IMPROVEProgram_files/frame.htm 
57 

The data for this report was obtained from the website http://views.cira.colostate.edu/web/. The 

graphs in this report show the PM2.5 (fine) mass monitor values from 2009 to 2013 at selected 

IMPROVE monitoring locations. 

Additional data, such as the chemical composition data in the graph shown below, is also 

available as the http://views.cira.colostate.edu/web/ site, using the composition tool. 

State National Parks, Monuments and Wilderness Areas 

(identifier on IMPROVE Network Map) 

Idaho (and Idaho/Oregon 

Border) 

Craters of the Moon National Monument (69), Sawtooth 

Wilderness (70), Hells Canyon Wilderness (77), Starkey (76) 

Montana Sula Peak (71), Cabinet Mountains Wilderness Area (75), Gate 

of the Mountains Wilderness Area (74) 

 

Nevada Jarbidge Wilderness Area (68), Great Basin National Park 

(116) 

Utah Bryce Canyon National Park (51), Canyonlands (50), Capitol 

Reef National Park (52), Zion (49) 

Wyoming Bridger Wilderness (65), North Absaroka Wilderness Area 

(67), Yellowstone National Park 2 (66) 

California-Oregon Border Crater Lake (86), Lava Beds National Monument (87), Lassen 

Volcanic National Park (90) 

Oregon/Washington Border Mount Hood (85) , Columbia River Gorge (112) 

Source: http://vista.cira.colostate.edu/improve/Overview/IMPROVENetworkExp.htm
58 

 
59 

2. Idaho and Idaho/Oregon Border – IMPROVE Data for the Years 2009-

2013 

Craters of the Moon National Monument, ID 

Sawtooth Wilderness, ID 
60 

Hells Canyon Wilderness, ID 

Starkey, OR 

 
61 

3. Montana - IMPROVE Data for the Years 2009-2013 

Sula Peak, MT 

Cabinets Mountains Wilderness, MT 

 
62 

Gates of the Mountains Wilderness, MT 

4. Nevada- IMPROVE Data for the Years 2009-2013 

Jarbidge Wilderness, NV 

 
63 

Great Basin National Park, NV 

5. Utah – IMPROVE Data for the Years 2009-2013 

Bryce Canyon National Park, UT 

 
64 

Canyonlands National Park, UT 

Capitol Reef National Park, UT 

 
65 

Zion Canyon, UT 

6. Wyoming - IMPROVE Data for the Years 2009-2013 

Bridger Wilderness, WY 

 
66 

North Absaroka Wilderness, WY 

Yellowstone National Park 2, WY 

 
67 

7. California/Oregon Border – IMPROVE Data for the Years 2009-2013 

Crater Lake National Park, OR 

Lava Beds National Monument, CA

 
68 

Lassen Volcanic National Park, CA 

8. Oregon/Washington Border – IMPROVE Data for the Years 2009-2013

Mount Hood Wilderness, OR 

 
69 

Columbia River Gorge, OR