1 

# Technical Support Document for the EPA’s Proposed Action on the State of Oregon’s 2010 Interstate Transport SIP for the 2006 24-hour Fine Particulate (PM 2.5 

# ) National Ambient Air Quality Standard

U.S. EPA Region 10
March 20142 

### Table of Contents

I. Interstate Transport and Oregon
A. Overview B. State of Oregon’s Assessment of Transport
C. The EPA’s Evaluation of the State of Oregon’s Assessment of Transport

II. Summary of the EPA’s Transport Assessment A. Transport to Nonattainment Receptors in Western States B. Transport to Maintenance Receptors in Western States C. Transport to Nonattainment and Ma intenance Receptors in Eastern States
D. Conclusion

III. Transport Assessment Methodology
A. Discussion of Nonattainment and Maintenance Receptor Selection Methodology B. Factors Considered in Transport Anal ysis for Nonattainment and Maintenance Receptors

IV. Transport Assessment for Nonattainment Receptors
A. Introduction B. Transport to Bordering States
1. Idaho
2. California C. Transport to Other Western States
1. Utah D. Transport to Eastern States

V. Transport Assessment for Maintenance Receptors
A. Introduction B. Transport to Bordering States
1. California
2. Nevada 3. Washington C. Transport to Other Western States
1. Montana
2. Utah D. Transport to Eastern States3 

### Appendices

Appendix A – Nonattainment and Maintenance Receptors List

Appendix B – Nonattainment Receptors

1. EPA Region 9 States – California

2. EPA Region 8 States –Utah

3. EPA Region 10 States – Idaho

Appendix C – Maintenance Receptors

1. EPA Region 9 States –California and Nevada

2. EPA Region 8 States – Montana and Utah

3. EPA Region 10 States - Washington

Appendix D – PM2.5 Data – IMPROVE Data for the Years 2008-2012

1. Overview and Map of IMPR OVE Monitoring Network Sites

2. Idaho - IMPROVE Data for the Years 2008-2012

3. Montana - IMPROVE Data for the Years 2008-2012

4. Nevada - IMPROVE Data for the Years 2008-2012

5. Utah - IMPROVE Data for the Years 2008-2012

6. Wyoming - IMPROVE Data for the Years 2008-2012

7. California/Oregon Border - IM PROVE Data for the Years 2008-2012

8. Oregon/Washington Border - IM PROVE Data for the Years 2008-20121 I. Interstate Transport and Oregon

I.A. Overview

Section 110(a)(1) of the CAA requires each state to submit to the EPA, within three years (or such shorter period as the Admini strator may prescribe) after th e promulgation of a primary or secondary NAAQS or any revision thereof, a 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 PM 2.5 NAAQS, these infrastructure SIPs were due on September 21, 2009. CAA section 110(a)(2) in cludes a list of spec ific elements that “[e]ach such plan submission” must meet. The in terstate transport prov isions in CAA section 110(a)(2)(D)(i) (also called “good ne ighbor” provisions) require each state to submit a SIP that prohibits emissions that will have certain adve rse air quality effects in other states.

On June 28, 2010, Oregon submitted a SIP revision to meet various CAA section 110(a)(2) infrastructure requirements for multiple NAAQS. Oregon’s SIP submittal cover letter indicated the SIP revision included the “Oregon SIP Infrastr ucture for Addressing the Interstate Transport
of Ozone and Fine Particulate Ma tter” to address the interstate transport requirements of CAA section 110(a)(2)(D)(i) for the 8-hour ozone and PM 2.5 NAAQS (2010 Interstate Transport SIP). 1 Oregon’s June 28, 2010, submittal included public process documentation for the 2010 Interstate Transport SIP and documentation of a duly not iced public hearing on the 2010 Interstate Transport SIP held on December 22, 2009. Oregon subs equently notified the EPA that a clerical
error was made and that the 2010 In terstate Transport SIP had not been attached to the June 28,
2010 cover letter. The State transmitted the 2010 Interstate Transport SIP to the EPA on December 23, 2010.

Based on our evaluation of Oregon’s submittal and additional technical information, as discussed further below, we are proposing to approve the po rtion of the 2010 Interstate Transport SIP with respect to the requirements of CAA section 110(a)(2)(D)(i )(I) for the 2006 24-hour PM 2.5 NAAQS. We are also proposing to conclude that the applicable implementation plan for Oregon is adequate to address the re quirements of CAA section 110(a)(2 )(D)(i)(I) for the 2006 24-hour PM2.5 NAAQS.

I.B. State of Oregon’s Assessment of Transport

To address whether emissions from sources in Oregon significantly cont ribute to nonattainment
or interfere with maintenance of the 2006 24-hour PM 2.5 NAAQS in another state, Oregon stated in the 2010 Interstate Transport SIP that meteor ological and other charac teristics of any areas designated nonattainment for the 2006 24-hour PM 2.5 NAAQS in the border states of Washington, Idaho, Nevada, and California s upport a finding that emissions from Oregon sources do not significantly contribute to nonattainm ent in, or interfere with maintenance of, the
PM 2.5 NAAQS in other states. Oregon expl ained that the closest 2006 24-hour PM 2.5 designated

1 Oregon’s submission addresses the intersta te transport requirements of the 1997 PM 2.5 NAAQS, the 1997 ozone NAAQS, the 2006 24-hour PM 2.5 NAAQS, and the 2008 ozone NAAQS. In this action, the EPA is only taking action with respect to CAA section 110(a)(2)(D)(i)(I) for the 2006 24-hour PM 2.5 NAAQS.2 nonattainment areas in neighboring states are th e Tacoma area (Pierce County) in Washington; the Chico area (portions of Butte County) in Ca lifornia, and the Cache Valley area in Southeast Idaho (portions of Cache County, Utah and Fran klin County, Idaho). Oregon argued in the 2010 Interstate Transport SIP that th e area of highest Oregon emission densities (Portland Metro area) is separated from these 2006 24-hour PM 2.5 nonattainment areas by significant distances and major mountain ranges up to approximately 7000 f eet. Oregon identified one exception – the Portland, Oregon-Vancouver, Washington metro ar ea, which shares a co mmon air shed between Oregon and Washington. Oregon, however, noted that both Portland, Oregon and Vancouver, Washington are in attainme nt with the 2006 24-hour PM 2.5 NAAQS.

Oregon described typical seasonal wind patterns during the winter when PM 2.5 levels are the highest. It noted that wind speeds are typically variable with the majority of wind speeds occurring at less than 8 miles per hour, and a signif icant portion of low winds at less than 5 miles per hour. Oregon explained that these low wind speeds and air stagnation conditions do not lend themselves to long distance air pollution tran sport, and noted that the Portland area can experience high wind speeds in the winter trav elling through the Columbia River Gorge east of
Portland that are not conducive to the buildup of air pollution. Oregon conc luded that general meteorology supports the conclusion that high winter time 24-hour PM 2.5 levels in Pacific Northwest communities are typically domi nated by local emission sources.

Oregon’s 2010 Interstate Transport SIP also pointed to its CAA section 110 infrastructure SIP to show that Oregon Department of Environmental Quality (ODEQ) has the ability to participate as needed in future studies on regiona l air pollution issues, or collaborate with other states if air quality concerns are identified th at require a case-specific evaluati on of interstate transport, and also ensures the legal mechanism for ODEQ to take action as needed to reduce emissions to help attain compliance with Federal NAAQS. Oregon’s 2010 Interstate Transport SIP stated that that high PM 2.5 levels that threat en the 2006 24-hour PM 2.5 NAAQS are investigated as needed to identify contributing sources, including any potential role of interstate transport.

Finally, Oregon explained that it had consulted with air agencies in Washington, Idaho, Nevada, and California and other agencies to evaluate case-specif ic air quality problems that may involve regional transport of air pollution. These sta ff-level communications indicated no impacts on
PM 2.5 concentrations in other states caused by transport from Oregon, providing additional support for Oregon’s view that emissions from Or egon sources do not significantly contribute to
nonattainment or interfere with maintenance of the 2006 24-hour PM 2.5 NAAQS in other states.

Based on the information provided in the 2010 Inte rstate Transport SIP, Oregon concluded that emissions from air pollution sources in Oregon do not significantly cont ribute to nonattainment in, or interfere with maintenance of, the 2006 24-hour PM 2.5 NAAQS in other states.

I.C. The EPA’s Evaluation of the State of Oregon’s Assessment of Transport

Oregon’s submittal, described above, relies on me teorological and other characteristics of the Pacific Northwest to support a finding that em issions from Oregon sources do not significantly contribute to nonattainment in, or interf ere with maintenance of, the 2006 24-hour PM 2.5 NAAQS. We have supplemented our analysis of Oregon’s submittal with additional technical3 information as discussed below, consistent with the methodologies and analyses developed in the Transport Rule (also called the “Cross-State Air Pollution Rule”) 2 in response to the judicial
remand of the 2005 “Clean Air Interstate Rule.” 3

On August 21, 2012, the U.S. Court of Appeals for th e 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 ., No. 12-1182, 572 U.S. ____ slip op. (2014).The State of Oregon was not covered by either CAIR or th e Transport Rule, and the EPA made no determinations in either rule regard ing whether emissions from sources in Oregon significantly contribute to nonatta inment or interfere with maintenance of the 2006 24-hour
PM 2.5 NAAQS in another state.

Based on our review of Oregon’s submittal and our own supplemental assessment of relevant technical information, including the characteris tics of the formation of elevated 24-hour PM 2.5 levels at nonattainment and maintenance receptors in neighboring states, ambient PM 2.5 levels at monitoring sites representative of regional background in nearby st ates, and meteorological and topographical information, we agree with Oregon’s conclusion in the 2010 Interstate Transport SIP that the existing Oregon SIP satisfies the re quirements of CAA section 110(a)(2)(D)(i)(I) for
the 2006 24-hour PM 2.5 NAAQS. Accordingly, we propose to approve the portion of the 2010 Interstate Transport SIP for purposes of CA A section 110(a)(2)(D)(i)(I) for the 2006 24-hour
PM 2.5 NAAQS.

II. Summary of the EPA’s Transport Assessment

II.A. Transport to Nonattainment Receptors in Western States

The EPA independently reviewed relevant technical information to evaluate the potential for Oregon emissions to contribu te significantly to nonatta inment of the 2006 24-hour PM 2.5 NAAQS at specified monitoring sites in the western United States. We first identified as “nonattainment receptors” all m onitoring sites in the western states that had recorded PM 2.5 design values above the level of the 2006 24-hour PM 2.5 NAAQS (35 micrograms per cubic meter (μg/m 3 )) during the years 2010-2012. 4 See section III below (discussing the EPA’s methodology for selection of nonattainment receptors, and a list of western receptors). Because geographic distance is a relevant factor in the assessment of potential pollution transport, the
EPA focused its review on information related to potential transport of PM 2.5 pollution from Oregon to states bordering Oregon that have non attainment receptors, specifically, Idaho and

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

3 70 FR 25172 (May 12, 2005).

4 Because the Clean Air Interstate Rule (CAIR) did not cove r states in the western Unite d States, these data are not significantly impacted by the remanded CAIR and thus could be considered in this analysis. In contrast, recent air quality data in the eastern, midwestern and southern states are significantly impacted by reductions associated with CAIR and because the Transport Rule was developed to replace CAIR, EPA could not consider reductions
associated with the CAIR in the base cas e transport analysis for those states. See 76 FR at 48223-24.4 California. With respect to these states, the EPA believes that the following factors support a finding that emissions from Ore gon do not significantly contribut e to nonattainment of the 2006
24-hour PM 2.5 NAAQS: (1) technical informati on indicating that elevated PM 2.5 levels at nonattainment receptors are predominantly caused by local emission sources and (2) air quality data indicating that region al background levels of PM 2.5 are generally low during the time periods of elevated PM 2.5 at these nonattainment receptors . In addition, with respect to California, technical information indicating that the dominant air flows across California are from the west to the east additionally suppor t a finding that emissions from Oregon do not significantly contribute to nona ttainment of the 2006 24-hour PM 2.5 NAAQS in California. 5

The EPA also evaluated potential PM 2.5 transport to nonattainment receptors in the more distant
western state of Utah. We believe that the following factors support a finding that emissions from Oregon do not significantly contribu te to nonattainment of the 2006 24-hour PM 2.5 NAAQS in Utah: (1) the significant dist ance from Oregon to the nonattainment receptors in these states, (2) technical information i ndicating that elevated PM 2.5 levels at nonattainment receptors in these states are predominantly caused by local emission sources, and (3) air qualit y data indicating that regional background levels of PM 2.5 are generally low during the time periods of elevated PM 2.5 at these nonattainment receptors.

II.B. Transport to Maintenance Receptors in Western States

The EPA independently reviewed relevant technical information to evaluate the potential for Oregon emissions to interfere with maintenance of the 2006 24-hour PM 2.5 standards at specified monitoring sites in the western United States. We first identified as “maintenance receptors” all monitoring sites in the western states that had recorded PM 2.5 design values above the level of the
2006 24-hour PM 2.5 NAAQS (35 μg/m 3 ) during the 2008-2010 and/or 2009-2010 periods but below this standard during the 2010-2012 period. 6 See section III below (discussing the EPA’s methodology for selection of maintenance recep tors). The EPA evaluated the potential for transported Oregon emissions to interfer e with maintenance of the 2006 24-hour PM 2.5 NAAQS at maintenance receptors in California, M ontana, Nevada, Utah, and Washington. The EPA believes that the following factor supports a fi nding that emissions from Oregon do not interfere
with maintenance of the 2006 24-hour PM 2.5 NAAQS in the states of California, Nevada, and Washington which border Oregon: (1) technica l information indicating that elevated PM 2.5 levels at maintenance receptors are predominantly cause d by local emission sources and (2) air quality data indicating that region al background levels of PM 2.5 are generally low during the time periods of elevated PM 2.5 at these maintenance receptors. In a ddition, with respec t to California, technical information indicating that the dominant air flows across California are from the west to the east additionally supports a finding that emissions from Oregon do not interfere with
maintenance of the 2006 24-hour PM 2.5 NAAQS in California. 7

5 As this analysis is focused on interstate transport, the EPA did not evaluate the impact of Oregon emissions on nonattainment receptors within Oregon.

6 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.

7 As this analysis is focused on interstate transport, the EPA did not evaluate the impact of Oregon emissions on maintenance receptors within Oregon.5 The EPA also evaluated potential PM 2.5 transport to maintenance receptors in the more distant
western states of Montana and Utah. The EPA believes that the following factors support a finding that emissions from Oregon do not inte rfere with maintenance of the 2006 24-hour PM 2.5 NAAQS in these states: (1) the significant distance from Oregon to the maintenance receptors in these states, (2) technical inform ation indicating that elevated PM 2.5 levels at maintenance receptors in these states are predominantly caus ed by local emission sources, and (3) air quality data indicating that region al background levels of PM 2.5 are generally low during the time periods of elevated PM 2.5 at these maintenance receptors.

II.C. Transport to Nonattainment and Maintenance Receptors in Eastern States

The EPA has also considered potential PM 2.5 transport from Oregon em ission sources to the nearest potential nonattainment or maintenance recep tors located in the eastern, midwestern and
southern states within the domain of the modeli ng analysis for the Cross State Air Pollution Rule (CSAPR or Transport Rule) (76 FR 48208). The nearest potential nonattainment and/or maintenance receptor identified in the 2012 CSAP R modeling analysis is in Madison County, Illinois. The CSAPR modeling di d not analyze the contribution of Oregon sources to Madison County, Illinois. Thus, the EPA analyzed th e magnitude of Oregon’s sulfur dioxide (SO 2 ) and nitrogen oxides (NOx) emissions relative to st ates whose contribution was modeled for the
CSAPR. The EPA also considered the distance of Oregon from Madison County, Illinois relative
to states modeled for the CSAPR. The EPA beli eves that the following factors support a finding that emissions from Oregon sources do not signifi cantly contribute to nona ttainment or interfere
with maintenance of the 2006 24-hour PM 2.5 NAAQS at this location: (1) the relatively small magnitude of the emission inventory of PM 2.5 precursors (SO 2 and NOx) in Oregon combined with (2) the relativel y long distance between the nearest portion of Oregon to the Madison County, Illinois receptor. 8 The EPA believes that these f actors also support a finding that emissions from Oregon sources do not contribute si gnificantly to nonattainmen t or interfere with
maintenance of the 2006 24-hour PM 2.5 NAAQS at any of the other CSAPR receptors, all of which are farther from Oregon than Madison County, Illinois.

II.D. Conclusion

The EPA’s independent review of available technical information and air quality data supports a conclusion that emissions from Oregon do not significantly contribute to nonattainment or
interfere with maintena nce of the 2006 24-hour PM 2.5 NAAQS in any other state. Based on this evaluation, we propose to approve the portion of the 2010 Interstate Transport SIP submitted for purposes of meeting the requirements of CAA section 110(a)(2)(D)(i)(I) for the 2006 24-hour
PM 2.5 NAAQS, and we propose to conclude that the Oregon SIP satisfies the requirements of CAA section 110(a)(2)(D)(i)(I) for the 2006 24-hour PM 2.5 NAAQS.

8 According to emission inventory data used in the CSAPR modeling analysis, the amount of SO 2 emissions from Oregon is approximately 33% of the SO 2 emissions from Minnesota and that NOx emissions in Oregon are about 52% of NOx emissions in Minnesota. Thus the conclusion that Minnesota does not significantly contribute to nonattainment in Madison, IL, which is also closer to Minnesota than Oregon, demonstrates that emissions from Oregon are even less likely to significantly contribute to nonattainment in Madison. See “Emissions Inventory Final Rule TSD,” Technical Support Docume nt (TSD) for the final Transport Rule, Docket ID No. EPA-HQ-OAR-2009- 0491, June 28, 2011, at Tables 7-1 and 7-2.6 III. Transport Assessment Methodology

III.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 submissi ons to meet the requirements of CAA section 110(a)(2)(D)(i) for the 2006 24-hour PM 2.5 standards. See Memorandum from William T. Harnett, Director, Air Quality Policy Division, to Regional Air Di vision Directors, Regions I-X, “Guidance on SIP Elements Required Under S ections 110(a)(1) and (2 ) for the 2006 24-Hour Fine Particle (PM 2.5 ) National Ambient Air Quality St andards (NAAQS),” September 25, 2009 (”2006 24-hour PM 2.5 NAAQS Infrastructure Guidance” or “Guidance” ). 9 The Guidance recommends that each state explain in its section 110(a)(2)(D )(i)(I) SIP whether or not its emissions contribute significan tly to nonattainment or interfer e with maintenance of the NAAQS in any other state, and to address any such impacts. See Guidance at 3, 4. The Guidance states
as follows:

The state's conclusion must be supported by an adequate technical analysis. Information to support the state's determination with respect to significant contribution to nonattainment might include, but is not limited to, information concerning emissions in the state, meteorological conditions in the state and the potentially impacted states,
monitored ambient concentrati ons in the state and the poten tially impacted states, the
distance to the nearest area that is not a ttaining 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

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 nonattainm ent or interfere with
maintenance in downwind areas. If this fact ual 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 signific antly to nonattainment or interfere with maintenance in other states, th en the state must adopt substantive provisions to
eliminate those emissions. The state could achie ve any required reductions through traditional command and control programs, or at its own elec tion, through participati on 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 ma intenance problems, which we refer to as “receptors.” 12 The EPA notes that no single piece of info rmation is by itself dispositive of the issue. Instead, the total weight of all the evidence taken together is used to evaluate significant

9 Available at: http://www.epa.gov/ttn/caaa/t1/mem oranda/20090925_harnett _pm25_sip_110a12.pdf

10 Guidance at 3.

11 See NO
x 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 th e methodology for identif ying these “receptors.”7 contributions to nonattainment in, or interf erence with maintenan ce of, the 2006 24-hour PM 2.5 NAAQS in another state.

A receptor may be a downwind location that is currently violating the 2006 24-hour PM 2.5 NAAQS, has violated in the past , is projected to violate in the future, or may have trouble maintaining the NAAQS in the future. Nonatta inment and maintenance receptors can be identified using future year mode ling, recent ambient data, or both.

If appropriate future year modeling is not available, 13 nonattainment and maintenance receptors can be identified using recent am bient 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 (cov ering a five-year period) to calculate “design
values” 14 for those periods. Because the EPA uses the most recent three-year design value period for purposes of promulgating air quality de signations and redesigna tions, 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 qua lity problem that may return in the future. The year to year variability of emissions and/or meteorology may cause an area to have trouble maintaining the NAAQS in the future. Therefore, we have identified “maintenance” receptors by examining previous years of data. This methodology is conceptually similar (although not identical) to the methodology that the EPA used in the CSAPR to identify “nonattainment” and “maintenance” receptors.

We applied the following methodology:

Similar to the CSAPR analysis, we examined am bient data which spanned a five-year period. This allows examination of year to year variabil ity. The three most recen t consecutive three-year design value periods are 2008-2010, 2009-2011, and 20010-2012. 15
1) Nonattainment receptors are those sites that are violating the NAAQS in the most recent three-year period. 16
2) Maintenance receptors are those receptors that show attainment in the most recent threeyear design value period ( 2010-2012) but violated the NAAQS in at least one of the previous two periods (2 008-2010 and/or 2009-2011).

Ambient data included the three most recent offi cial 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:

13 Available modeling data should be evaluated for the inte nded purpose. If modeling data is used to establish nonattainment and/or maintenance receptors, it should be fo r 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 accordi ng to the applicable appendix of [40 CFR part 50] for the highest site in an attainment or nona ttainment area.” 40 CFR 58.1 (definitions).

15 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.

16 When evaluating recent design values, it is not necessary to average the desi gn values together to create a fiveyear weighted average. Weighted average data is only necessary when projecting modeling data to the future, since modeled projections are generally based on only a single year (or less) of modeled meteorology.8 http://www.epa.gov/airtrends/values.html. Also informing this list was the EPA’s AirData website: http://www.epa.gov/airquality/a irdata/. A list of receptors selected for this interstate transport analysis is shown below in Figure III.A.1. Receptors with 24-hour PM 2.5 design values
above the 24-hour PM 2.5 standard of 35μg/m 3 for the years 2010 through 2012 are listed as nonattainment receptors. Receptors with 24-hour PM 2.5 design values at or below the 24-hour
PM 2.5 standard of 35μg/m 3 for 2010-2012, but above the standard fo r at least one of the previous three-year periods (2008-2010 or 2009-2011) are listed as maintenance receptors.

To evaluate the potential for si gnificant contribution to nonattain ment in other states, the EPA first evaluated potential transpor t to the nearest states with id entified nonattainment receptors. The states bordering Oregon with nonattainment receptors are Idaho an d California. The EPA then evaluated potential transpor t to other western states with nonattainment receptors located farther away, i.e. Utah. To evaluate the potential for interference with maintenance in other states, the EPA evaluated potential transport to maintenance recep tors in California, Montana, Nevada, Utah, and Washington. 17

17 As this analysis focuses on interstate transport, EPA did not evaluate the impact of Oregon emissions on nonattainment and maintenance receptors within Oregon.9 Table III.A.1: List of Western Counties with Daily PM 2.5 Nonattainment or Maintenance Receptors

State County 2006 NAAQS 24-hr PM2.5 NAAQS

designated
nonattainment area Site 24-hr standard

2008-
2010 2009-
2011 2010-
2012 Receptor Type

California Butte Chico 060070008 51 NA 35 A 34 A Maintenance California Fresno San Joaquin Valley 060190011 54 NA 58 NA 59 NA Nonattainment California Fresno San Joaquin Valley 060195001 47 NA 54 NA 54 NA Nonattainment California Fresno San Joaquin Valley 060195025 43 NA 48 NA 53 NA Nonattainment
California Imperial Imperial County 060250005 32 NV 38 NA 32 A Maintenance California Inyo 060271003 36 NA 36 NA 33 A Maintenance California Kern San Joaquin Valley 060290010 64 NA 65 NV 62 NV Nonattainment California Kern San Joaquin Valley 060290014 62 NA 62 NA 58 NA Nonattainment California Kern San Joaquin Valley 060290016 65 NA 55 NA 47 NA Nonattainment California Kings San Joaquin Valley 060310004 49 NA 46 NA 43 NA Nonattainment California Kings San Joaquin Valley 060311004 49 NV 57 NV 54 NA Nonattainment

California Los Angeles Los Angeles-South Coast
Air Basin 060370002 38 NA 36 NA 31 NV Maintenance

California Madera San Joaquin Valley 060392010 51 NV 55 NV 51 NA Nonattainment California Merced San Joaquin Valley 060470003 41 NV 43 NA 41 NA Nonattainment California Merced San Joaquin Valley 060472510 45 NA 39 NA 40 NA Nonattainment

California Riverside Los Angeles-South Coast
Air Basin 060658001 38 NA 35 A 34 A Maintenance

California Riverside Los Angeles-South Coast
Air Basin 060658005 41 NA 39 NA 37 NA Nonattainment

California Sacramento Sacramento 060670006 40 NA 35 A 31 A Maintenance

California Sacramento Sacramento 060674001 36 NA 35 A 31 A Maintenance

California San
Bernardino Los Angeles-South Coast
Air Basin 060710025 37 NA 34 A 32 A Maintenance

California San
Bernardino Los Angeles-South Coast
Air Basin 060712002 37 NA 31 A 32 A Maintenance

California San Joaquin San Joaquin Valley 060771002 44 NA 38 NA 36 NA Nonattainment

California San Joaquin San Joaquin Valley 060772010 44 NV 41 NV 38 NA Nonattainment California Stanislaus San Joaquin Valley 060990005 49 NA 50 NA 44 NA Nonattainment California Stanislaus San Joaquin Valley 060990006 55 NA 51 NA 49 NA Nonattainment California Sutter Yuba City-Marysville 061010003 36 NA 27 A 26 A Maintenance California Tulare San Joaquin Valley 061072002 51 NA 47 NA 47 NA Nonattainment Idaho Franklin Logan 160410001 46 NA 50 NA 47 NA Nonattainment

Idaho Lemhi 160590004 35 NV 38 NA 38 NA Nonattainment

Idaho Shoshone 160790017 36 NA 38 NA 38 NA Nonattainment

Montana Lewis and
Clark Helena 300490026 35 NV 37 NA 33 A Maintenance

Montana Silver Bow Butte-Silver Bow 300930005 38 NA 39 NA 34 A Maintenance

Nevada Washoe 320310016 38 NA 26 A 18 A Maintenance Oregon Klamath Klamath Falls 410350004 44 NA 39 NA 35 A Maintenance Oregon Lake 410370001 38 NA 36 NA 34 A Maintenance Oregon Lane Oakridge 410392013 38 NA 39 NA 38 NA Nonattainment Utah Box Elder Salt Lake City 490030003 42 NA 40 NA 37 NA Nonattainment10 State County 2006 NAAQS 24-hr PM2.5 NAAQS

designated
nonattainment area Site 24-hr standard

2008-
2010 2009-
2011 2010-
2012 Receptor Type

Utah Cache Logan 490050004 43 NA 42 NA 37 NA Nonattainment Utah Davis Salt Lake City 490110004 38 NA 40 NA 34 A Maintenance Utah Salt Lake Salt Lake City 490350003 45 NA 50 NA A Maintenance Utah Salt Lake Salt Lake City 490353006 44 NA 45 NA 38 NA Nonattainment Utah Salt Lake Salt Lake City 490353007 46 NV NV A Maintenance Utah Salt Lake Salt Lake City 490353008 42 NV NV A Maintenance Utah Salt Lake Salt Lake City 490353010 41 NA 41 NA 35 A Maintenance

Utah Utah Provo 490490002 36 NA 35 A 29 A Maintenance

Utah Utah Provo 490494001 41 NA 41 NA 32 NV Maintenance

Utah Utah Provo 490495008 33 A 38 NA 41 NV Nonattainment

Utah Utah Provo 490495010 39 NA 42 NA 35 A Maintenance Utah Weber Salt Lake City 490570002 37 NA 41 NA 37 NA Nonattainment Utah Weber Salt Lake City 490570007 39 NV NV A Maintenance Utah Weber Salt Lake City 490571003 36 NA 37 NA 33 A Maintenance Washington Pierce Sea ttle-Tacoma, WA 530530029 38 NA 35 A 28 A Maintenance Washington Yakima 530770009 37 NA 35 A 31 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/

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

Consistent with the recommendations in the Guidance, the EPA reviewed emission inventory data, ambient monitoring data, and meteorological conditions within the State of Oregon. In addition, the EPA reviewed PM 2.5 monitoring data in areas repres entative of western regional background levels of PM 2.5 in the states of Idaho, Utah and Ne vada as well as selected remote monitoring sites on the Californi a-Oregon border, and Washington- Oregon border. Finally, the
EPA reviewed technical information related to each of the nonattainment and maintenance receptors in the potentially impacted states, including meteorological conditions and ambient
PM 2.5 monitoring data.

Emission inventories used in the CSAPR modeling analysis pr ovide the following amounts of
NOx and SO 2 emissions for Oregon in 2012: 189,886 tons of NOx and 36,494 tons of SO 2

. 18 The
monitored ambient PM 2.5 concentrations for nonattainment a nd maintenance receptors in the State of Oregon are shown above in Figure III. A.1, “List of Western Counties with Daily PM 2.5 Nonattainment or Maintenance Receptors.”

The EPA then reviewed PM 2.5 monitoring data from relatively remote ambient air monitoring sites that the EPA believes is repr esentative of regional background PM 2.5 levels in the western

18 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 7-2.11 United States. The EPA reviewed five years of data coll ected at the IMPROVE 19 monitoring network at specific National Parks in Idaho a nd the Idaho/Oregon border (Craters of the Moon, Sawtooth National Forest, Hells Canyon, and Starkey), Utah (Bryce Canyon, Canyonlands, Capitol Reef, and Zion National Parks), Nevada (Jarbidge Wilderness Area and Great Basin National Park), at the Californi a-Oregon border (Crater Lake Nati onal Park, Lava Beds National Monument, and Lassen Volcanic National Park), and at the Oregon-Washington border (Mount Hood and the Columbia River Gorge). Ambient PM 2.5 monitoring data, as well as chemical species data (ammonium nitrate, ammonium sulf ate, elemental carbon, organic carbon, sea salt, and soil) is available for each of these m onitoring sites. We provide monitored PM 2.5 data from each of these monitoring sites during the 2008- 2012 period for each day when measurements occurred, as well as a map of th e site locations in Appendix D of this TSD. This provides information about regional background levels of PM 2.5 in the states surrounding Oregon. The chemical composition of the PM 2.5 in these areas is also ava ilable on the IMPROVE website.

Most of the elevated levels of PM 2.5 in the western states are meas ured during the winter months. For example, in 2011 and 2012, each exceedance of the 2006 PM 2.5 NAAQS in Salt Lake City occurred in either December or January of t hose years. Monitor values are accessible on EPA’s
AirData website.

The PM2.5 data for each of the IMPROVE moni toring sites reviewed indicate low background PM2.5 levels throughout the year, but especially dur ing the winter months for each of the years from 2008 through 2012. For example, the PM2.5 va lues for January and December of 2010 at Bryce Canyon National Park, Utah are below 3μg/m 3

.

In the winter, when the measured PM 2.5 values in Salt Lake City are as high as 76 μg/m 3 , the
PM 2.5 values in remote areas ar e very low (below 3 μg/m 3 ), indicating that over 90% of the PM in the urban area is locally gene rated. Because the ambient PM 2.5 at these locations appears to be from local sources, it is reasonable to concl ude that emissions from Oregon do not have a significant impact on nonattainment of the 2006 24-hour PM 2.5 NAAQS in Salt Lake City. In contrast, an analysis of the CSAPR 2012 nonattainment and maintenance receptors shows that a large fraction of the daily PM 2.5 concentrations in Eastern areas are from upwind states. For the 41 CSAPR daily PM 2.5 nonattainment and maintenance recept ors, the modeled upwind sulfate plus nitrate contribution to total PM 2.5 ranged from a low of 20% to a high of 53% with a median
value of 37%. 20 Since CSAPR only tracked the contributions of sulfate and nitrate, these values represent the minimum percenta ge of upwind contribution to the receptors. Accounting for transport of additional primary PM 2.5 species would only increase the upwind percentage and therefore decrease the percentage of PM 2.5 due to local sources.

19 The Interagency Monitoring of Protected Visual Environments (IMPROVE) program is a cooperative measurement effort governed by a st eering committee composed of representa tives from Federal and regional-state organizations. The IMPROVE monitoring program was established in 1985 to aid the creation of Federal and State implementation plans for the protection of visibility in Class I areas. The objectives of IMPROVE include establishing current aerosol conditions in mandatory class I areas; and identifying chemical species and emission sources responsible for existing man-made visibility impairment. http://vista.cira.colostate.edu/improve/O verview/IMPROVEProgram_files/frame.htm

. 20 See Memorandum to File, Brian Timin, EPA, Office of Air Quality Planning and Standards, “CSAPR Daily PM2.5 Upwind Contribution,” July 2012.12 Figure III.B.1. IMPROVE PM 2.5 Data for Bryce Canyon National Park for the Year 2010

In addition to reviewing background monitoring data which indicates that the elevated PM 2.5 levels are not likely due to regi onal transport, the EPA reviewed technical information, such as meteorological conditions and monitored ambient data, related to each of the areas with nonattainment and maintenance recept ors in the potentially impacted states to determine whether
local emissions cause or contribute to the elevated PM 2.5 levels at these locations. We discuss
our evaluation for each of the areas with receptors in the following sections.

IV. Transport Assessment for Nonattainment Receptors

IV.A. Introduction

Based on our methodology for selecting nonattainment receptors in Section III.A, above (Discussion of Nonattainment and Maintenan ce Receptor Selection Methodology), the EPA has identified nonattainment receptors in the followi ng western states: Utah, California, Oregon, and
Idaho. The EPA has evaluated technical inform ation regarding transport for each of the areas with nonattainment receptors identified above, following the methodology discussed in Section III. B. Transport to the states that border Or egon and have nonattainment receptors (Idaho and California) is addressed first. Transport to the more distant western state with nonattainment receptors (Utah) is then addressed. Finally, tran sport to eastern states is addressed. As this analysis focuses on interstate transport, the EPA did not evaluate the impact of Oregon emissions on nonattainment receptors within Oregon.

IV.B. Transport to Bordering States

IV.B.1. Idaho

Given the local characteristics of the elevated PM 2.5 levels at the receptors in Idaho and air quality data indicating that regional background levels of PM 2.5 are generally low during the13 time periods of elevated PM 2.5 at these nonattainment receptors, we believe it is reasonable to conclude that emissions from Oregon sources do not significantly contribute to nonattainment
of the 2006 24-hour PM 2.5 NAAQS at these receptor locations.

Franklin County/Cache County

Portions of Franklin County, Idaho a nd Cache County, Utah are designated as part of the Cache Valley 2006 24-hour PM 2.5 , two-state, nonattainment area. Limited chemical speciation data in the Ca che Valley indicates the PM 2.5 problem is dominated by ammonium nitrate aerosol. Transport of PM 2.5 and precursors from the rural regions at the domain

p eriphery is very small and most of th e observed Wasatch Front and Cache Valley PM 2.5 is formed in-situ (and trapped) via fresh local ly derived emission sources and secondary chemistry.

Local heating emissions from woodstoves, emissi ons from agricultural activities, and mobile emissions may contribute to vi olations of the 2006 24-hour PM 2.5 NAAQS during stable weather events associated with extremely strong inversions as they are trapped in the Cache Valley due to temperature inversi ons, low wind, and local topography.

Shoshone County (Pinehurst)

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

p rimary PM 2.5 that violates the 2006 24-hour PM 2.5 standard during stable weather events associated with strong inversions. These emissi ons and the related effects are limited to the city of Pinehurst airshed, as they are trappe d there due to temperature inversions, low wind and local topography.

Lemhi County (Salmon)

Information from the State of Idaho indicates th at local emissions, incl uding from woodstoves, contribute to primary PM 2.5 that results in elevated daily PM 2.5 values during stable weather events associated with strong inversions. However it is important to note that the design values
calculated in the table do not take into consideration all flagged exceptional events due to recent
wildfires.

IV.B.2. California

Transport to nonattainment recepto rs in California is discussed in detail in Appendix B and is
summarized below.

Southern California – Riverside County

PM 2.5 in Southern California is a combustion gene rated pollutant due to the volume of traffic flow and numbers of sources (both point and area) located in the region. The areas with the highest concentrations are downw ind of an area with ammonia sources associated with dairies and poultry farming. Based on these characteristics, we believe it is reasonable to conclude that14 emissions from Oregon sources do not significan tly contribute to nonattainment of the 2006 24-
hour PM 2.5 NAAQS at these receptor locations.

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

In Central California, the m onitored exceedances of the PM 2.5 standard likely reflect localized sources occurring during wintertime temperature inversions with low winds that persist for several days in an area that trap emissions together with complex topography. The speciation data from high concentration days indicate high le vels of secondary nitrate. On some days elevated levels of organic carbon indicate that residential wood burning also contributes to
elevated levels of PM 2.5

.

Given the local characteristics of the elevated PM 2.5 levels at these locations, which occur during wintertime temperature inversions with low winds th at persist for several days in an area that traps emissions, together with complex topography, we believe it is reasonab le to conclude that emissions from Oregon sources do not significan tly contribute to nonattainment of the 2006 24-
hour PM 2.5 NAAQS at these receptor locations.

IV.C. Transport to Other Western States

IV.C.1. Utah

Elevated levels of PM 2.5 in the Utah nonattainment areas occu r primarily in the winter months. 21

The levels of elevated PM 2.5 in the Provo 2006 24-hour PM 2.5 nonattainment area and the Salt Lake City 2006 24-hour PM 2.5 nonattainment area are primarily due to local emissions, as noted
in the discussion of Provo and Salt Lake City nonattainment areas below.

During the winter months, levels of PM 2.5 at background monitoring sites located west and southwest of the Utah nonattainment receptors 22 are very low, generally below 3μg/m 3

, indicating that the vast majority of the PM in the urban area is locally generated. As discussed above, this supports our fi nding that the elevated PM 2.5 levels are not likely to be caused by transport from other air basins. Th e local characteristics of the PM 2.5 levels during time periods when the standard is exceeded, as well as the low levels of background PM 2.5 during these time periods, support our finding that emissions from Oregon do not cont ribute significantly to
nonattainment of the 2006 24-hour PM 2.5 standard at these nonattainment receptors.

Utah County (Provo)

A large portion of Utah County is designated as the Provo 2006 24-hour PM 2.5 nonattainment area. The Provo NAA is situated in the Utah Valley. Like the other low-lying valleys just west of

21 For example, in 2011 and 2012, each exceedance of the 2006 PM 2.5 NAAQS in Salt Lake City occurred in either December or January of those years. Monitor va lues are accessible on EPA’s AirData website, http://www.epa.gov/airquality/airdata/

. 22 IMPROVE monitoring network at three National Parks in Utah (Bryce Canyon, Capito l Reef and Zion National Parks) and Nevada (Jarbidge Wilderness Area and Great Basin National Park).15 the Wasatch Front, the topography of the Utah Va lley makes it prone to te mperature inversions. During inversions, the Provo NAA features stagnant air masses and calm to light winds. As the airshed is essentially capped, PM 2.5 is formed in-situ (and trapped) via fresh locally derived emission sources and secondary chemistry. 23 Transport of air masses be tween the Salt Lake City and Provo NAAs can occur during inversions, as there is a 4.75-mile gap in the mountains separating these airsheds which is below the ap proximate average inversion height for these

areas. 24

Speciation data from wintertime PM 2.5 exceedance days from 2004-2006 showed the average composition of PM 2.5 in Provo is 71% ammonium nitrat e, with 21% carbon and organic compounds, 8% ammonium sulfate, and 2% crusta l. Several factors, including significant amounts of emissions from mobile, point and area s ources, contribute to primary and secondarily
formed PM 2.5 that violate the 2006 24-hour PM 2.5 NAAQS during stable weather events associated with strong inversions.

Box Elder, Salt Lake and Weber C ounties (Greater Salt Lake Area)

All of Salt Lake county and portions of Box Elde r and Weber counties are designated as part of the Salt Lake City (SLC) 2006 24-hour PM 2.5 nonattainment area (NAA). The SLC NAA is situated in a valley bordered on th e west by the Stansbury Mountains, 25 Promontory Mountains and Great Salt Lake, and on the east by the Wasa tch Front. During inversions, the NAA becomes a closed airshed (save for pot ential transport between the Sa lt Lake City and Provo NAAs) featuring stagnant air masses and light winds whic h typically oscillate back and forth within the
airshed. As the airshed is essent ially capped during inversions, PM 2.5 is formed in-situ (and trapped) via fresh locally derived em ission sources and secondary chemistry. 26

Speciation data from wintertime PM 2.5 exceedance days from 2004-2006 showed the average composition of PM 2.5 in Salt Lake City is 58% ammoni um nitrate, 31% carbon and organic compounds, 8% ammonium sulfate, and 2% crusta l. Several factors, including significant amounts of emissions from mobile, point and area s ources, contribute to primary and secondarily
formed PM 2.5 that violate the standard during stable weather events associated with strong
inversions.

Cache County

See discussion at IV.B.1 Idaho, above.

IV.D. Transport to Eastern States

23 Id.

24 Id. at 41.

25 The Quqirrh Mountains lie between the Wasatch Front an d 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.

26 2006 24-Hour PM 2.5 NAAQS Designations (74 FR 58688, November 13, 2009), Technical Support Document, December 2008, Index 583-669 at 40.16 The EPA has also considered potential PM 2.5 transport from Oregon em ission sources to the nearest potential nonattainment or maintenance recep tors located in the eastern, midwestern, and
southern states within the domain of the modeli ng analysis for the Cross State Air Pollution Rule (CSAPR) (76 FR 48208). The nonattainment and/ or maintenance receptor nearest to Oregon identified in the 2012 CSAPR modeling analysis is Madison County, Illinois. The CSAPR modeling did not analyze the contribution of Ore gon sources to Madison C ounty, Illinois. Thus, the EPA analyzed the magnitude of Oregon’s SO 2 and NOx emissions relative to states found to have emissions that significantly contribute to nonattainment at that receptor. The EPA also considered the distance of Oregon from Madison County, Illinois relative to states found to significantly contribute there. The EPA believes that the following factors support a finding that emissions from Oregon sources do not significan tly contribute to nonattainment of the 2006 24-
hour PM 2.5 NAAQS at this receptor: (1) the relatively small magnitude of the emission inventory
of PM 2.5 precursors (SO 2 and NOx) in Oregon, combined with (2) the relatively long distance between the state of Oregon and th e receptor. The EPA believes th at these factors also support a finding that emissions from Oregon sources do no t significantly contribute to nonattainment of
the 2006 24-hour PM 2.5 NAAQS at any of the other CSAPR receptors farther east.

In the CSAPR modeling, the EPA did not quantify the PM 2.5 contributions from Oregon to Illinois or any of the other East ern nonattainment and maintenance receptors. However, we can make a qualitative conclusion about the likely contribution from Oregon to Illinois and points farther east by comparing the Oregon emissions to a state that was modeled in CSAPR. Minnesota was modeled for CSAPR, and was found below the threshold of significant
contribution to downwind nonattainment and inte rference with maintena nce for all receptors
modeled for CSAPR. The EPA has ev aluated the relative amounts of PM 2.5 precursor (SO 2 and NOx) emissions in Oregon compared to the amounts of PM 2.5 precursor emission in Minnesota,
as modeled in the “2012 CSAPR Base Case.” The emission inventories used in the CSAPR modeling analysis indicate that SO 2 emissions in Oregon are about 33% of SO 2 emissions in Minnesota and NOx emissions in Oregon are ab out 52% of NOx emissions in Minnesota. Specifically, the CSAPR 2012 Base Case inventories 27 provide the following statewide emissions inventory data for th ese two states: 36,494 tons of SO 2 and 189,886 tons of NOx from Oregon emission sources, compared to 109,940 tons of SO 2 and 364,052 tons of NOx from Minnesota emission sources. Even though the relationship between upwind emissions and downwind secondary PM 2.5 formation is not linear, we would expect the Oregon PM 2.5 contribution to Illinois to be much less than that of Minnesota and well below the 1% threshold. In addition, Oregon is a much greater distan ce away from Madison County, Illinois than Minnesota. The distance from Oregon 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 Oregon sources do not cont ribute significantly to
nonattainment of the 2006 24-hour PM 2.5 NAAQS at nonattainment receptors in any eastern

state.

V. Transport Assessment for Maintenance Receptors

V.A. Introduction

27 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 7-2.17 Based on our methodology for selecting maintenance receptors in Section III.A, above (Discussion of Nonattainment and Maintenan ce Receptor Selection Me thodology), the EPA has identified maintenance receptors in the followi ng western states: California, Oregon, Montana, Nevada, Washington and Utah. We evaluated potent ial transport to the maintenance receptors in states bordering Oregon (Califor nia, Nevada and Oregon), in addition to the more distant maintenance receptors in the states of Montana an d Utah. Finally, transport to eastern states is addressed. As this analysis focuses on interstate transport, EPA did not evaluate the impact of Oregon emissions on maintenance receptors within Oregon.

V.B. Transport to Bordering States

V.B.1. California

Transport to maintenance receptors in Califor nia is discussed in detail in Appendix C and
summarized below.

Eastern California – Inyo County

Elevated levels of PM 2.5 in Inyo County are measured at a sing le monitor, the Keeler monitor, which is located adjacent to the Owens Lake Bed. The Owens Lake Bed is surrounded by steep terrain. EPA believes that because of the proximity of the monitor to a large local source of particulate matter, and the nearby terrain, it is reasonable to conclude that emissions from Oregon sources do not interfere with maintenance of the 2006 24-hour PM 2.5 standard at this receptor.

Southern California – Riverside, Lo s Angeles and San Bernadino Counties

PM2 .5 in Southern California is primarily a combus tion generated pollutant due to the volume of
traffic flow and numbers of sour ces (both point and area) located in the region. The areas with the highest concentrations are dow nwind of an area with major a mmonia sources associated with dairies and poultry farming. Based on these char acteristics and the great distance of southern California receptors from Oregon, we believe it is reasonable to conclude that emissions from Oregon sources do not interfere with maintenance of the 2006 24-hour PM 2.5 NAAQS at these receptor locations.

Northern California – Butte, Sa cramento and Sutter Counties

In Northern California, m onitored exceedances of the PM 2.5 standard likely reflect localized sources occurring during wintertime temperature inversions with low winds that persist for several days in an area that trap emissions together with complex topography. The speciation data from high concentration days indicates that as much as 75% of the concentrations are due to organic carbon, which also indica tes that residential wood burni ng emissions are the dominant

source. 28

28 See section 1.3 of Appendix C.18 Given the complex topography in this area and the local charact eristics of the elevated PM 2.5 levels at these locations, which occur during wi ntertime temperature inversions with low winds that persist for several days in an area that traps emissions, we believe it is reasonable to conclude that emissions from Oregon sources do not interfere with maintenance of the 2006 24-
hour PM 2.5 NAAQS at these receptor locations.

California/Mexico Border – Imperial County

The high monitored levels of PM 2.5 are limited to the Calexico – Ethel Street monitoring site,
which is located near the Mexican Border. The elevated PM 2.5 levels occur primarily in the winter months during stagnation conditions, when l ong distance transport is unlikely. On days of
elevated PM 2.5 at the Calexico Ethel Street monitor, the levels of PM 2.5 measured at the other monitors in Imperial County, the Brawley and El Centro sites, are lo wer on all days. The PM 2.5 appears to be from a local source ne ar the California/Mexico Border.

Given the local characteristics of the elevated PM 2.5 levels at this receptor , regional and local air flow patterns, and air qual ity data indicating that re gional background levels of PM 2.5 are generally low during the tim e periods of elevated PM 2.5 at this receptor, we believe it is
reasonable to conclude that emi ssions from Oregon sources do not interfere with maintenance of
the 2006 24-hour PM 2.5 standards at th is receptor.

V.B.2. Nevada

Transport to the single maintenance receptor in Ne vada is discussed in detail in Appendix C and
is summarized below.

The Washoe County receptor is locate d in Reno, Nevada. Elevated daily PM 2.5 levels at the Reno receptor generally occur during wintertime st agnation episodes, with lower levels of PM 2.5 during the other times of the year. Low temperat ures and strong inversions are the dominant contributing factors to the elevated daily PM 2.5 levels. The levels of PM 2.5 measured in March through November in 2008 through 2011 are generally ve ry low. The exception to this is in June and July of 2008 when wildfires had a large impact on PM 2.5 concentrations in this area, and the Washoe County Health Distri ct flagged the affected data as exceptional events. The wintertime
PM 2.5 exceedances occur during periods of strong inversions and are la rgely due to local
emissions. Given the local char acteristics of the elevated PM 2.5 levels at the receptor in Nevada and air quality data indicating th at regional backgr ound levels of PM 2.5 are generally low during the time periods of elevated PM 2.5 at this receptor, we believe it is reasonable to conclude that emissions from Oregon sources do not interf ere with maintenance of the 2006 24-hour PM 2.5 NAAQS at this receptor location.

V.B.3. Washington

Given the local characteristic s of the elevated daily PM 2.5 levels at the receptors in Washington, as well as the low levels of background PM 2.5 during these time periods, we believe it is
reasonable to conclude that emi ssions from Oregon sources do not interfere with maintenance of
the 2006 24-hour PM 2.5 NAAQS at these receptor locations.19 Pierce County (Tacoma)

A portion of Pierce County is designated nonattainment for the 2006 24-hour PM 2.5 NAAQS. Washington State technical analys is of the area indicates that wood smoke associated with home heating is the largest source of PM 2.5 in the nonattainment area. Technical data show the PM 2.5 problem is highly localized. Surface measurements at multiple sites suggest that the only design
values which violate the 2006 PM 2.5 NAAQS are in the core of th e nonattainment area, within about 3 km of the South L St. monitor. Beyond about 3 to 5 km, the design values drop and are well below the NAAQS. On-site sonic anemom eter and vertical temperature profile measurements revealed that exceedances only oc curred: in winter; at night, when there was a surface inversion; below an ambient temperatur e of about 50 degrees Fahrenheit; when wind speeds were less than 1.5 mph. The EPA recently made a clean data determination, finding that recent air quality monitoring data show the area to be attaining the 2006 24-hour PM 2.5 NAAQS (September 4, 2012, 77 FR 53772).

Yakima County (Yakima)

The Yakima County receptor has no t been designated a 2006 24-hour PM 2.5 nonattainment area,
however the area has been includ ed in the list of nonattainment receptors because of recent design values above the 2006 24-hour PM 2.5 NAAQS. Elevated levels at the Yakima receptor generally occur during wintertime air stagnation events.

The EPA has conducted Positive Matrix Factor re ceptor modeling that has identified local wood smoke as a significant co ntributor to 24-hour PM 2.5 NAAQS monitored levels. In addition to wood smoke, Yakima also has significant ae rosol nitrate that contributes to PM 2.5 exceedances.

Specifically, this receptor modeling identified 10 factors contributing to elevated wintertime
PM 2.5 including wood smoke (24%), n itrate rich (24%), gasoline vehicles (16%), organic pyrolysis rich (9%), sulfate rich (7%) and sma ller contributions from other identified factors (iron rich, sea salt, soil, zinc rich, and urban unidentified).

V.C. Transport to Other Western States

V. C .1. Montana

Given the local characteristics of the elevated PM 2.5 levels at the receptors in Montana, air quality data indicating that regional background levels of PM 2.5 are generally low during the time periods of elevated PM 2.5 at this receptor, and the distan ce of these areas from Oregon, we
believe it is reasonable to concl ude that emissions from Oregon sources do not interfere with
maintenance of the 2006 24-hour PM 2.5 standards at these re ceptor locations.

Lewis and Clark County (Helena)20 Elevated levels of PM 2.5 in the Helena area occur primarily in the winter months. 29 The Helena Valley is topographically prone to cold pool inversion conditions during the winter months. 30 Speciation data indicates that emissions from wood smoke are the primary contributor to
exceedances of the PM 2.5 standard in Helena. 31 In the months when violations of the NAAQS occurred at the Helena receptor, the nearby Ga te of the Mountains Wilderness Area monitor did not exceed 2 μg/m 3

. 32 All of these factors ta ken together indicate th at high levels of PM 2.5 in Helena are driven by local emissions, which become trapped and build during wintertime
inversions.

Silver Bow County (Butte)

Elevated levels of PM 2.5 in the Butte area occur primarily in the winter months. 33 The Butte area is topographically prone to wintertime temperatur e inversions, as it is situated in a mountain valley. Speciation data indicates that emissions from wood smoke are the primary contributor to
exceedances of the PM 2.5 standard in Butte. 34 These factors indicate that high levels of PM 2.5 in Butte are driven by local emissions, which become trapped and build during wintertime
inversions.

V.C.2. Utah

Elevated levels of PM 2.5 in the Utah nonattainment areas occu r primarily in the winter months. 35

The levels of elevated PM 2.5 in the Provo 2006 PM 2.5 nonattainment area and the Salt Lake City
2006 PM 2.5 nonattainment area are primarily due to loca l emissions, as noted in the discussion of Provo and Salt Lake City nonattainment areas below.

During the winter months, levels of PM 2.5 at background monitoring sites located east and
northeast of Nevada and west and southw est of the Utah maintenance receptors 36 are very low, generally below 3μg/m 3 , indicating that the vast majority of the PM in the urban area is locally generated. As discussed above, this supports our finding that PM 2.5 levels are not likely to be

29 The maintenance receptor in He lena, MT violated the 2006 PM 2.5 NAAQS only in 2010. Each of the exceedances
of the 2006 PM 2.5 standard at this receptor during 2010 occurred during the winter months, with all but one exceedance occurring in December or January. M onitor values are accessible on EPA’s AirData website, http://www.epa.gov/airquality/airdata/

. 30 Johnson, J. “Case Study of a Persistent Cold Pool in the Helena Valley.” NOAA. November 21, 2000.

31 Ward, T., Lange, T., “The impact of wood smoke on ambient PM 2.5 in northern Rocky Mountain valley communities.” Environmental Pollution 158 (2010) 723–729.

32 The Gate of the Mountains IMRPOVE monitor is locat ed roughly 17 miles from Helena, MT. The IMPROVE monitor data can be found in Appendix D to this TSD, in the docket for this action.

33 In 2009 and 2010, the only recent years in wh ich the Butte maintenance r eceptor violated the 2006 PM 2.5 NAAQS, each exceedance of the NAAQS occurred in either December or January. M onitor values are accessible on EPA’s AirData website, http://www.epa.gov/airquality/airdata/

. 34 Ward, T., Lange, T., “The impact of wood smoke on ambient PM 2.5 in northern Rocky Mountain valley communities.” Environmental Pollution 158 (2010) 723–729.

35 In 2011 and 2012, each exceedance of the 2006 PM 2.5 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/

. 36 IMPROVE monitoring network at three National Parks in Utah (Bryce Canyon, Capitol Reef, and Zion National Parks) and Nevada (Jarbidge Wilderness Area and Great Basin National Park).21 caused by regional elevated PM 2.5 levels. Given the local charact eristics of the elevated PM 2.5 levels at these locations, as well as the low levels of background PM 2.5 during these time periods,
we believe it is reasonable to conclude that em issions from Oregon source s do not interfere with
maintenance of the 2006 24-hour PM 2.5 NAAQS at these rece ptor locations.

Utah County (Provo)

A large portion of Utah County is designated as the Provo 2006 24-hour PM 2.5 nonattainment area. The Provo NAA is situated in the Utah Valley. Like the other low-lying valleys just west of the Wasatch Front, the topography of the Utah Va lley makes it prone to te mperature inversions. During inversions, the Provo NAA features stagnant air masses and calm to light winds. As the airshed is essentially capped, PM 2.5 is formed in-situ (and trapped) via fresh locally derived emission sources and secondary chemistry. 37 Transport of air masses be tween the Salt Lake City and Provo NAAs can occur during inversions, as there is a 4.75-mile gap in the mountains separating these airsheds which is below the ap proximate average inversion height for these

areas. 38

Speciation data from wintertime PM 2.5 exceedance days from 2004-2006 showed the average composition of PM 2.5 in Provo is 71% ammonium nitrat e, with 21% carbon and organic compounds, 8% ammonium sulfate, and 2% crusta l. Several factors, including significant amounts of emissions from mobile, point and area s ources, contribute to primary and secondarily
formed PM 2.5 that violate the standard during stable weather events associated with strong
inversions.

Davis, Salt Lake and Weber Count ies (Greater Salt Lake Area)

All of Davis and Salt Lake counties and portions of Weber County are designated as part of the Salt Lake City (SLC) 2006 24-hour PM 2.5 NAA. The SLC NAA is situated in a valley bordered on the West by the Stansbury Mountains, 39 Promontory Mountains and the Great Salt Lake, and on the East by the Wasatch Front. During invers ions, the NAA becomes a closed airshed (save for potential transport between the Salt Lake City and Provo NAAs) f eaturing stagnant air masses and light winds which typica lly oscillate back and forth within the airshed. As the airshed is essentially capped during inversions, PM 2.5 is formed in-situ (and trapped) via fresh locally
derived emission sources and secondary chemistry. 40

Speciation data from wintertime PM 2.5 exceedance days from 2004-2006 showed the average composition of PM 2.5 in Salt Lake City is 58% ammonium nitrate, 31% carbon and organic compounds, 8% ammonium sulfate, and 2% crusta l. Several factors, including significant mobile, point and area sources contribute to primary and secondarily formed PM 2.5 that violate the standard during stable weather events associated with strong inversions.

37 Id.

38 Id. at 41.

39 The Quqirrh Mountains lie between the Wasatch Fron t and the Stansbury Mountains. However, the EPA determined that some area located west of the Quqirr h Mountains should still be considered part of the SLC
nonattainment area.

40 2006 24-Hour PM 2.5 NAAQS Designations (74 FR 58688, November 13, 2009), Technical Support Document, December 2008, Index 583-669 at 40.22 V. D. Transport to Eastern States

The EPA has also considered potential PM 2.5 transport from Oregon em ission sources to the nearest potential nonattainment or maintenance recep tors located in the eastern, midwestern and
southern states within the domain of the modeli ng analysis for the Cross State Air Pollution Rule (CSAPR) (76 FR 48208). The maintenance rece ptor nearest to Ore gon identified in the 2012 CSAPR modeling analysis is Madison County, I llinois. The CSAPR modeling did not analyze the contribution of Oregon sources to Madison County, Illinois. Thus, the EPA analyzed the magnitude of Oregon’s SO 2 and NOx emissions relative to st ates found to have emissions that significantly contribute to nonattainment at that r eceptor. The EPA also considered the distance of Oregon from Madison County, Illinois relative to states found to signifi cantly contribute there. The EPA believes that the following factors s upport a finding that emissions from Oregon
sources do not interfere with maintenance of the 2006 24-hour PM 2.5 NAAQS at this receptor: (1) the relatively small magnitude of the emission inventory of PM2.5 precursors (SO 2 and NOx) in Oregon, combined with (2) the re latively long distance of Oregon from the receptor. The EPA believes that these factors also support a findi ng that emissions from Oregon sources do not interfere with maintenance of these NAAQS at a ny of the other CSAPR receptors farther east.

In the CSAPR modeling, the EPA did not quantify the PM 2.5 contributions from Oregon to Illinois or any of the other East ern nonattainment and maintenance receptors. However, we can make a qualitative conclusion about the likely contribution from Oregon to Illinois and points farther east by comparing the Oregon emissions to a state that was modeled in CSAPR. Minnesota was modeled for CSAPR, and was found below the threshold of significant
contribution to downwind nonattainment and inte rference with maintena nce for all receptors
modeled for CSAPR. The EPA has ev aluated the relative amounts of PM 2.5 precursor (SO 2 and NOx) emissions in Oregon compared to the amounts of PM 2.5 precursor emission in Minnesota,
as modeled in the “2012 CSAPR Base Case.” The emission inventories used in the CSAPR modeling analysis indicate that SO 2 emissions in Oregon are about 33% of SO 2 emissions in Minnesota and NOx emissions in Oregon are ab out 52% of NOx emissions in Minnesota. Specifically, the CSAPR 2012 Base Case inventories 41 provide the following statewide emissions inventory data for th ese two states: 36,494 tons of SO 2 and 189,886 tons of NOx from Oregon emission sources, compared to 109,940 tons of SO 2 and 364,052 tons of NOx from Minnesota emission sources. Even though the relationship between upwind emissions and downwind secondary PM 2.5 formation is not linear, we would expect the Oregon PM 2.5 contribution to Illinois to be much less than that of Minnesota and well below the 1% threshold. In addition, Oregon is a much greater distan ce away from Madison County, Illinois than Minnesota. The distance from Oregon 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 Oregon sources do not interfere with maintenance
of the 2006 24-hour PM 2.5 NAAQS at nonattainment receptors in any eastern state.

41 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.