Appendix B – Nonattainment Receptors 

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Technical Support Document for EPA’s Proposed Action on the 

Oregon 2010 Interstate Transport State Implementation Plan for the 2006 24-hour Fine 

Particulate (PM2.5) National Ambient Air Quality Standard 

Appendix B – Nonattainment Receptors 

1. EPA Region 9 States – California 

1. Southern California –Riverside County 

2. Central California – Fresno, Kern, Kings, Madera, Merced, San Joaquin, Stanislaus, and 

Tulare Counties 

2. EPA Region 8 States –Utah 

1. Utah – Utah County (Provo-Orem) 

2. Utah – Box Elder, Salt Lake, and Weber Counties (Greater Salt Lake Area) 

3. EPA Region 10 States – Idaho 

1. Idaho/Utah – Franklin County/Cache County 

2. Idaho – Shoshone County (Pinehurst) 

3. Idaho – Lemhi County (Salmon) 

 
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1.1. Southern California – Riverside County 

County Site Name Description 

Riverside Mira LomaVan Buren Current monitored values slightly above 35μg/m3. There is a strong 

downward trend. 

The high 24-hour PM2.5 concentrations in the South Coast Air Basin 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, NH4, and VOC) 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 (shown in Figures 1.2.A and 1.2.B, below). 24-hour PM2.5 design value trends show strong 

downward trend at all sites in the South Coast Basin (shown in Figure 1.2.C, below).1

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

sources (both point and area) located 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.2

The South Coast Air Quality DRAFT 2012 Air Quality Management Plan3 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, and that each of these sites will attain the standard in 2014 or sooner (see 

Figure 1.2.D: Maximum 24-Hour Average PM2.5 Design Concentrations: 2008 Baseline, 2014 and 

2014 Controlled). 

The spatial distribution of PM2.5 in the South Coast Basin supports the fact that it is largely of local 

origin. The air quality trends and projections indicate that the emission strategy is effective in reducing 

24-hour PM2.5 levels. Therefore, we believe it is reasonable to conclude that emissions from Oregon do 

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

receptor. 

                                                            

1

 Joe Cassmassi, Scientific, Technical & Modeling Peer Review (STMPR) Advisory Group Meeting, September 22, 2011. 

2

 Final 2007 Air Quality Management Plan (AQMP), Appendix V – Modeling and Attainment Demonstrations June, V-2-10. 3 http://www.aqmd.gov/aqmp/2012aqmp/draft/Chapters/Ch5.pdf
Appendix B – Nonattainment Receptors 

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Figure 1.2.A: Speciated data for Central Los Angeles4

                                                            

4

 STMPR Item # 5 - 2008 PM2.5 Air Quality Characterization, January 19, 2012. Bong-Mann Kim. 
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Figure 1.2.B: Speciated PM2.5 data for the Rubidoux site in Riverside County 5

                                                            

5

 STMPR Item # 5 - 2008 PM2.5 Air Quality Characterization, January 19, 2012. Bong-Mann Kim. 
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Figure 1.2.C: 24-hour PM2.5 Design Value Trends 

 
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Figure 1.2.D: Maximum 24-Hour Average PM2.5 Design Concentrations: 

2008 Baseline, 2014 and 2014 Controlled6

                                                            

6 http://www.aqmd.gov/aqmp/2012aqmp/draft/Chapters/Ch5.pdf
Appendix B – Nonattainment Receptors 

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1.2. Central California – Fresno, Kern, Kings, Madera, Merced, San Joaquin, Stanislaus, and 

Tulare Counties 

County Site Name 

Fresno Fresno-1st Street 

Kern Bakersfield-Planz Road 

Kings Corcoran 

Merced Merced-M Street 

San Joaquin Stockton-Hazelton 

Stanislaus Turlock 

Tulare Visalia 

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

November and December (see Figure 1.3.A, below). PM2.5 builds up in episodes of several days or 

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

humidity, and low mixing depths.7 The peak day composition of PM2.5 at Bakersfield is primarily 

ammonia nitrate (67%) and organic carbon (16%). 

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. 

Because PM2.5 builds up in episodes of several days or weeks, during periods with stagnation, and low 

mixing depths, it is reasonable to conclude that long range transport does not contribute to elevated 24-

hour levels of PM2.5 in the San Joaquin Valley. EPA believes it is reasonable to conclude that emissions 

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

these receptors. 

                                                            

7

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

April 27, 2012. 
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Figure 1.3.A: Monthly Average PM2.5 Concentration in Bakersfield California 
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Figure 1.3.B: 2008-2010 Peak Day Composition in Bakersfield 

 
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2. EPA Region 8 States –Utah8

2.1. Utah – Utah County (Provo-Orem) 

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

(NAA). 

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

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

the Provo NAA features stagnant air masses and calm to light winds. As the airshed is essentially 

capped, PM2.5 is formed in-situ (and trapped) via fresh locally derived emission sources and secondary 

chemistry. Transport of air masses between the Salt Lake City and Provo NAAs can occur during 

inversions, as there is a 4.75-mile gap in the mountains separating these airsheds which is below the 

approximate average inversion height for these areas. 

Speciation data from exceedance days from 2004-2006 showed the average composition of PM2.5 in 

Provo is 71% ammonium nitrate, with 21% carbon and organic compounds, 8% ammonium sulfate, and 

2% crustal. 

Several factors, including significant mobile, point and area sources contribute to primary and 

secondarily formed PM2.5 that violate the 24-hour standard during stable weather events associated with 

strong inversions. 

2.2. Utah – Box Elder, Salt Lake, and Weber Counties (Greater Salt Lake Area) 

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

designated as part of the Salt Lake City 2006 24-hour PM2.5 nonattainment area. 

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

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

becomes a closed airshed (save for potential transport between the Salt Lake City and Provo NAAs) 

featuring stagnant air masses and light winds which typically oscillate back and forth within the airshed. 

As the airshed is essentially capped during inversions, PM2.5 is formed in-situ (and trapped) via fresh 

locally derived emission sources and secondary chemistry. 

Speciation data from 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 mobile, point and area sources contribute to primary and 

secondarily formed PM2.5 that violate the 24-hour standard during stable weather events associated with 

strong inversions. 

                                                            

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 For discussion of the Idaho/Utah – Franklin County/Cache County area, see section 3.1 of this Appendix. 
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Based on the above-described factors, we believe it is reasonable to conclude that emissions from 

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

Utah receptors. 

3. EPA Region 10 States – Idaho 

3.1. Idaho/Utah – Franklin County/Cache County 

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

2006 24-hour PM2.5, two-state, nonattainment area.

Limited chemical speciation data in the Cache Valley indicates the 24-hour PM2.5 problem is 

dominated by ammonium nitrate aerosol similar to nonattainment areas along the Wasatch front in and 

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

considered broadly representative of conditions in the Cache Valley. 

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 very small. In addition, most of the observed Wasatch Front and Cache 

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

chemistry. 

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

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 local topography. The rest of the county is very sparsely 

populated with no significant sources that can contribute to a violation of the 2006 24-hour PM2.5 

standard at the Franklin monitor.

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, 2 soil factors, fireworks, iron rich, 

and urban unidentified). 

3.2. Idaho – Shoshone County (Pinehurst) 

State information indicates that emissions from woodstoves contribute to primary PM2.5 that violates 

the 24-hour standard during stable weather events associated with strong inversions. These emissions 

and the related effects are limited to the city of Pinehurst airshed, as they are trapped there due to 

temperature inversions, low wind and local topography. 

The rest of the county is very sparsely populated with no significant sources that can contribute to a 

violation of the 2006 24-hour PM2.5 NAAQS at the Pinehurst monitor. 

3.3 Idaho – Lemhi County (Salmon) 
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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. 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. 

Based on this information, the EPA believes it is reasonable to conclude that emissions from Oregon do 

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

receptors.