Section 6.8.1, EPA 9-Factor Analyses for the Designation 

of PM2.5 Montana Nonattainment Areas

(pages 6-347 through 6-352) 
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* Table of Contents (wit-h Acr0ny.m~) (PDF) (3 pp, 56KBj 

* Chapter 1: 1ntrodu.ction (with cover paqe) (PDF) (3 pp, 64KB) 

* Chapter 2: EPAPM2.5 Ivonattainment Desiqnations (PDF) (24 pp., 148KB) 

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* Chapter 6: Nine Factor Analyses of Individual Nonattainment Areas [PDF) (434 

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* Technical support document for April 5, 2005 supplemental notice (PDFJ (75 pp, 4.1MB) 
Technical Support for State and Tribal Air Quality 

Fine Particle (PM2.5) Designations 

December 2004 

U.S. Environmental Protection Agency 

Office of Air Quality Planning and Standards 

Integrated Policy and Strategies Group 

Research Triangle Park, NC 277 1 1 

For information on this document, please contact Mr. Larry Wallace at (91 9) 541-0906 
1.0 INTRODUCTION 

This document contains factual and technical data in support of the U.S. Environmental 

Protection Agency's (EPA) designations of the fine particle nonattainment areas. Fine . 

particles are those less than 2.5 micrometers in aerodynamic diameter and are also 

referred to as "PM2.5." Additional supporting information is contained in the EPA June 

28 and June 29,2004 response letters to the states and tribes. The June letters address 

where EPA agreed with the submitted recommendations and the cases where EPA made 

modifications to the states' and tribes' recommendations as authorized under the Clean 

Air Act (CAA). 

This chapter presents an overview of the PM2.5 designations process. Chapter 2 contains 

two tables of EPA's nonattainment designations for PM2.5. Section 2.1 contains a table 

with nonattainment counties arranged alphabetically by state and then area name. 

Section 2.2 contains nonattainment counties arranged alphabetically by Region, state, and 

area name. Chapter 3 discusses the results and methodology for the urban excess 

calculation. Chapter 4 discusses weighted emissions scores methodology and results. 

Chapter 5 contains information on the nine-factor analysis methodology. Chapter 6 

contains the results of the nine-factor analyses for individual nonattainment areas sorted 

by EPA Region and state. Chapter 7 contains maps, wind roses, and other documentation 

to support EPA's designations. 

1.1 Background 

The CAA establishes a process for air quality management through the national ambient 

air quality standards (NAAQS). Area designations are required after promulgation of a 

new or revised NAAQS. After evaluating numerous health studies and conducting an 

extensive peer review process, on July 18, 1997, EPA promulgated a PM2.5 standard of 

15 micrograms per cubic meter, based on the 3-year average of annual mean PM2.5 

concentrations. The 24-hour standard for PM2.5 is 65 micrograms per cubic meter, 

determined by the 3-year average of the annual 98th percentile concentrations. The CAA 

and the Transportation Equity Act for the 2 1 st Century (TEA-21) required EPA to 

designate all PM2.5 nonattainment areas by July 2000. However, a number of events 

delayed the implementation of the PM2.5 standard. TEA-21 revised the deadline to 

publish nonattainment designations in order to provide additional time to collect three 

years of air quality monitoring data. Additionally, the 1977 NAAQS rule was challenged 

by the American Trucking Association, the U.S. Chamber of Commerce and other state 

and business groups. See American Trucking Assoc. v. EPA, 175 F.3d 1027, 1047-48, 

on rehearing 195 F.3d 4 (D.C. Cir. 1999). In February 2001, the Supreme Court upheld 

EPA's authority under the CAA to set NAAQS that protect the American public from 

harmful effects of air pollution. The Supreme Court remanded the case to the D.C. Court 

of Appeals for disposition of issues the Court did not address in its initial decision. See 

Whitman v. American Trucking Assoc., 12 1 S.Ct. 903, 91 1-914'916-919 (2001) 

(Whitman). In March 2002, the D.C. Circuit rejected all remaining legal challenges to 

the PM2.5 standard. See American Trucking Assoc. v. EPA, 283 F.3d 355 (D.C. Cir. 

2002) ATA 111). 
1.2 Correspondence with States and Tribes 

Section 107(d) of the CAA defines a nonattainment area as "any area that does not meet 

(or that contributes to ambient air quality in a nearby area that does not meet) the national 

primary or secondary ambient air quality standard for the pollutant." In February and 

April 2003, EPA provided guidelines to states and tribes for recommending 

nonattainment area boundaries for the PM2.5 standard. The guidance instructed states 

and tribes to begin their analysis of attainment and nonattainment area boundaries based 

on the boundaries of metropolitan areas. The guidance also instructed states to include in 

the nonattainment areas any nearby counties contributing to fine particle pollution in 

those metropolitan areas. EPA also recommended that states and tribes use common 

boundaries for areas to be designated as nonattainment for both PM2.5 and the 8-hour 

ozone standards in order to facilitate future planning and implementation activities. EPA 

listed nine factors for states and tribes to consider as they developed their boundary 

recommendations. Chapter 5 contains a detailed discussion of these factors and the 

analysis methodology. States and tribes made their initial recommendation of 

nonattainment area designations to EPA in February 2004. 

As stated above, in accordance with the CAA, EPA carefully reviewed the state and tribal 

recommended designations and accompanying documentation to determine where 

modifications needed to be made as deemed necessary in light of the CAA definition of 

nonattainment. On June 28 and 29, 2004 EPA responded to the states' and the tribes' 

recommendations by notifying them regarding where EPA agreed or disagreed with their 

recommendations. Following the June letters, some states and tribes submitted follow-up 

data to support their original recommendations. EPA has carefully reviewed all of the 

requests and the data submitted throughout the designations process. This document 

contains the technical information and rationale supporting EPA decisions to designate 

and classify areas for the PM2.5 NAAQS. 
TABLE OF CONTENTS 

Chapter Page 

Abbreviations and Acronyms iii 

1.0 Introduction ..................................................................................................... 1-1 

1 . 1 Background .............................................................................................. 1-1 

1.2 Correspondence with States and Tribes ................................................... 1-2 

2.0 EPA PM2.5 Nonattainment Designations ........................................................ 2-1 

2.1 PM2.5 Nonattainment Designations by State and Area Name .................... 2-1 

2.2 PM2.5 Nonattainment Designations by EPA Region .......................... 2- 12 

3.0 Urban Excess Methodology ............................................................................. 3-1 

3.1 Concept .................................................................................................... 3-1 

3.2 Derivation of Urban Excess ...................................................................... 3-3 

3.3 Resolution of Uncertainties ...................................................................... 3-4 

3.4 Site Selection ............................................................................................ 3-8 

4.0 Constructing the Weighted Emissions Score Metric ......................................... 4-1 

4.1 Basis and Assumptions ........................................................................ 4-1 

4.2 Calculating the Weighted Emission Scores ........................................... 4-2 

4.3 Comparing Weighted Emissions Scores Among Counties .................... 4-3 

5.0 An Explanation of EPA's Nine-Factor Analysis ............................................... 5-1 

Factor 1 : Emissions in Areas Potentially Included Versus 

Excluded from the Nonattainment Area .......................................... 5-1 

Factor 2: Air Quality in Potentially Included Versus Excluded 

Areas .................................................................................................. 5-2 

Factor 3: Population Density and Degree of Urbanization Including 

Commercial Development in Included Versus Excluded Areas ............ 5-2 

Factor 4: Traffic and Commuting Patterns ............................................ 5-2 

Factor 5: Expected Growth .................................................................... 5-2 

Factor 6: Meteorology .......................................................................... 5-2 

Factor 7: GeographyITopography ......................................................... 5-3 

Factor 8: Jurisdictional Boundaries ...................................................... 5-3 

Factor 9: Level of Control of Emission Sources ................................... 5-3 
TABLE OF CONTENTS CONTINUED 

Chapter Page 

6.0 Nine Factor Analyses of Individual Nonattainment Areas .. ................ ......... ..... 6- 1 

7.0 Supporting Maps and Figures ............. ............................... .......................... 7- 1 
Abbreviations and Acronyms 

CAA- Clean Air Act 

CBSA- Core Based Statistical Area 

CM- Crustal matter 

CNSA- Consolidated Metropolitan Statistical Area 

CSA- Combined Statistical Area 

EC- Elemental carbon 

EPA- United States Environmental Protection Agency 

FIPS- Federal Information Processing Standards 

FTIR - Fourier Transform Infrared 

IMPROVE- Interagency Monitoring of Protected Visual Environments 

MDL- Minimum detection limit 

MOBILE6- Mobile Source Emission Factor Model version 6 

NA- Nonattainment 

NAAQS- National Ambient Air Quality Standards 

NA-P- Part of the county was designated nonattainment 

NEI- National Emissions Inventory 

NOx- Nitrogen Oxides 

OC- Organic carbon 

OMC- Organic mass by carbon 

OP- Pyrolized organics 

PIXE- Particle Included X-Ray Emission 

PM - Particulate Matter 

PM2.5 - Particulate Matter with aerodynamic diameter less than 2.5 microns 

SASS- Source Assessment Sampling System 

SIP- State lmplementation Plan 

STN- Speciation Trends Network 

TEA-2 1 - Transportation Equity Act for the 2 IS' Century (TEA-2 1) 

TCM- Total carbon mass 

TOR -Thermal Optical Reflectance 

TOT- Thermal Optical Transmittance 

U- Unclassifiable 

UE- Urban Excess 

VMT- Vehicle Miles Traveled 

VOC- Volatile Organic Compound 

WES- Weighted Emission Score 
6.8 Region 8 Nonattainment Areas 

6.8.1 EPA 9-Factor Analyses for Montana for the Designation of PM2.5 

Nonattainment Areas 

Based on air quality data for 2001-2003, the PM2.5 monitor at the Libby Courthouse 

Annex is violating the annual PM2.5 standard. EPA utilized the 9 factors identified in 

the April 1, 2003 "Designations for the Fine Particle National Ambient Air Quality 

Standards" guidance to evaluate whether the surrounding rural counties around Lincoln, 

MT should be included as part of the nonattainment area. However, due to the 

topographical features and local meteorology within Lincoln County and more 

specifically around the Libby, Montana vicinity, several of the 9 factors were not 

significant for this particular nonattainment area when looking at adjacent counties to 

Lincoln County, MT. Lincoln County is considered a rural county, according to EPA's 

April 1,2003 "Designations for the Fine Particle National Ambient Air Quality 

Standards" which defines a rural area as counties or areas not included in or adjacent to 

urban areas (metropolitan statistical areas (MSA). The adjacent areas to Lincoln County 

are the Canadian border to the North, Boundary and Bonner County, Idaho to the West, 

Sanders County, MT to the South, and Flathead County, MT to the East. Lincoln County 

contains a violating monitor located in the town of Libby. The Lincoln County PM2.5 

nonattainment issue is unique in that the area of impact is localized within and around the 

vicinity of the town of Libby due to topographical features and meteorology in the area 

impacted by emissions. 

Montana's recommendation identifying the PM2.5 nonattainment area included part of 

Lincoln County (the town of Libby and vicinity). EPA initially responded to Montana's 

recommendation stating that EPA agreed with Montana's recommended nonattainment 

designation for Lincoln County but that EPA intended to modify Montana's 

recommended boundary for the nonattainment area to cover all of Lincoln County. 

However, based upon supplemental information provided by Montana, EPA is 

identifying the boundary of this PM2.5 nonattainment area to include a part of Lincoln 

County as described further below. 

The following is a brief summary of the 9 factor criteria for the Lincoln County, MT area 

and surrounding counties. These analyses were based on existing available data. The 

counties recommended as nonattainment are in bold. 

Factor 1: Emissions in areas potentially included versus excluded from the 

nonattainment area 

For this factor, EPA looked at S02, NOx, carbon and crustal PM2.5 emissions. A 

weighted emissions score was applied to Lincoln County and the adjacent counties 

reflecting the speciation profile of Lincoln County versus the adjacent counties. Counties 

adjacent to the Lincoln County were assigned an emission score as a way to compare the 

emissions from those counties against Lincoln County emissions. The following table 

has the SO2, NOx, carbon, and crustal PM2.5 emissions and composite emission scores. 
This information is from the 2001 NEI. (The recommended nonattainment area is in 

bold.) 

Since Lincoln County is considered to be a rural county as defined in EPA's April 1, 

2003 PM2.5 Designations Guidance and not a metropolitan statistical area, this factor did 

not play a significant role in the decision making process. Also, due to the topographical 

features and meteorology in Lincoln County (see factors 6 and 7 below) and more 

specifically surrounding Libby, MT where the PM2.5 problem is, EPA feels the 

surrounding counties emissions are not impacting the PM2.5 monitor located at the Libby 

Courthouse Annex. 

Factor 2: Air quality in potentially included versus excluded areas 

I PM2.5 2001-2003 

County design value 

Flathead 9.1 

I 

I1 I J * Lincoln County PM2.5 monitor is located at the Libby Courthouse Annex, Libby, MT. 

Bonner 

I 

All adjacent counties to Lincoln, MT are attaining the PM2.5 standard. This factor 

played a significant role in the decision making process. 

8.0 

Boundary 8.2 
Factor 3: Population density and degree of urbanization including commercial 

development in included versus excluded areas 

The following table has the population and population density for Lincoln County and the 

adjacent counties. 

County 2002 Population 1 2002 Population Density (pop. 

Lincoln 

1 Flathead I I 

18,66S4 

77,240 

I I 

* Town of Libby, MT population: 2,626; 

** Town of Libby, MT population density: 2,020 personslsquare mile 

per square mile) 

5** 

15 

Bonner 

Boundary 

Sanders 

The town of Libby, where the PM2.5 problem is located has a much higher population 

density than the remainder of Lincoln County or any of the surrounding counties. Also, 

due to the commuting patterns, topographical features and meteorology in Lincoln 

County (see factors 4, 6 and 7 below), EPA feels the adjacent county populations do not 

impact the PM2.5 monitor located at the Libby Courthouse Annex. This factor played a 

significant role in the decision making process. 

Factor 4: Traffic and commuting patterns 

38,205 

10,085 

10,367 

Commuting Information: 

22 

8 

4 

Lincoln County, the design value county, has a total of 6,721 commuters. 

- Commuters who remain in Lincoln County: 6,177 

Flathead County, an adjacent county, has a total of 34,035 commuters. 

- Commuters from Flathead County to Lincoln County: 85 

- Commuters that remain in Flathead County: 32,956 

Bonner County, an adjacent county, has a total of 15,570 commuters. 

- Commuters from Bonner County to Lincoln County: 0 

- Commuters that remain in Bonner County: 12,968 

Boundary County, an adjacent county, has a total of 3,830 commuters. 

- Commuters from Boundary County to Lincoln County: 10 

- Commuters that remain in Boundary County: 3,3 10 

Sanders County, an adjacent county, has a total of 3,903 commuters. 

- Commuters from Sanders County to Lincoln County: 12 
- Commuters that remain in Sanders County: 3,337 

The following table has the vehicle miles traveled (thousand miles) for Lincoln County 

and the adjacent counties. 

Based on the analysis for this factor there are no adjacent counties impacting the PM2.5 

monitor located at the Libby Courthouse Annex. This factor played a significant role in 

the decision making process. 

Factor 5: Expected growth 

The following table has the population and population growth figures for Lincoln County 

and the adjacent counties. (Nonattainment counties are in bold.) 

Based on the analysis for this factor, there is no significant growth, on either an absolute 

or a percentage basis, to indicate a contribution to the air quality in Lincoln County. This 

factor did not play a significant role in the decision making process. 

Factor 6: Meteorology 

Libby Montana is located in the northwestern part of the state in a narrow north-south 

oriented valley. The ridgetops surrounding Libby are approximately 4,000 feet higher 
than the town. There are no other towns or large emissions sources immediately upwind, 

so transport of high background concentrations into Libby is considered unlikely. The 

highest PM2.5 concentrations in Libby generally occur during the months of November 

through February. During the summer months concentrations typically average less than 

half the level of the annual PM2.5 NAAQS, while winter concentrations may double the 

NAAQS. The much higher concentrations in winter are related to stagnant weather 

conditions dominated by light winds and strong temperature inversions. These 

meteorological conditions may trap emissions within the valley for many days. No recent 

meteorological data is available for Libby, however, data from Kalispell, MT show calm 

wind conditions occur 35 percent of the time in the winter months and only 15 percent of 

the time in the spring and summer. Vertical temperature soundings at Great Falls in 

Western MT also show a very high frequency of surface temperature inversions in the 

winter. 

Due to the meteorology conditions in the town and surrounding vicinity of Libby and due 

to the topographical features within Lincoln County and more specifically around Libby 

(see factor 7 below), that create stagnant weather conditions, EPA feels the adjacent 

counties do not impact the PM2.5 monitor located at the Libby Courthouse Annex and 

that the nonattainment problem is a localized PM2.5 problem. 

This factor played a significant role in the decision making process. 

Factor 7: Geographyttopography 

Lincoln County, MT 

Lincoln County has a land area of 3,675 square miles. The area of concern showing high 

PM2.5 concentrations is located within and around the Libby, Montana vicinity. Lincoln 

County has numerous geographical or topographical boundaries limiting its airshed to a 

very narrow valley including the surrounding vicinity of Libby. The town of Libby has a 

total area of 1.3 miles. As of the 2000 census, there are 2,626 people, 1,132 households, 

and 669 families residing in the city. The elevation for the town of Libby is 2,601 feet. 

The ridgetops surrounding Libby are approximately 4,000 feet higher than the town. The 

town sits in a narrow valley that runs in a north-south direction (4S023'17" North, 
115O33'13" West). The Kootenai River runs adjacent to the town in an east-west 

direction. The Kootenai Basin is largely mountainous and dominated by three major 

ranges. The Rocky Mountain Range and the Flathead Range constitute the eastern 

boundary; the Purcell Range roughly bisects it from north to south. The Selkirk and 

Cabinet Ranges mark the western boundary. Elevations reach a maximum of about 

12,000 feet with most summit elevations between 6,000 and 7,500 feet. Except for a few 

areas, the entire watershed is heavily forested (practically all of Lincoln County and a 

large portion of the surrounding counties consists of National Forest land). The Kootenai 

River has its origins in British Columbia's Kootenay National Park in Canada. From 

there it flows 485 miles into northwest Montana and through the towns of Libby and 

Troy. From there it flows into northern Idaho, then back into Canada and Kootenay 

Lake. Ultimately it joins with the Columbia River. Sixteen miles north of Libby, the 

river is held back by Libby Dam, creating a 90-mile long reservoir that reaches into 

Canada. The river drops less than 1,000 feet (305 meters) in elevation fi-om Canal Flats 

to Kootenay Lake, a distance of over 300 miles (480 krn). However, even along the 

river's slow meandering course, valley-bottom widths are generally less than two miles 

and are characterized by tree-covered rolling hills with few grassland openings. 

Due to the topographical features and meteorological data (see factor 6 above) within and 

surrounding the vicinity of Libby resulting in stagnant weather conditions trapping 

emissions in the valley, EPA feels the adjacent counties do not impact the PM2.5 monitor 

located at the Libby Courthouse Annex. Emissions from adjacent counties would have to 

traverse one or more major mountain ranges, in some cases against the prevailing wind 

direction, in order to impact the town of Libby. 

This factor played a significant role in the decision making process. 

Factor 8: Jurisdictional boundaries 

No areas in Montana or ldaho were designated nonattainment for the 8-hour ozone 

standard on April 15,2004. 

The town of Libby and vicinity within Lincoln County are designated nonattainment for 

PM 10. 

Due to the fact that the town and surrounding vicinity of Libby, Montana was designated 

nonattainment for PMlO and did not include the surrounding counties around Lincoln, 

MT, EPA believes this factor plays a significant role in the decision making process. 

Factor 9: Level of control of emission sources 

The following are sources located in Lincoln County, MT but are not considered major 

PSD sources. 

- Plum Creek Northwest Lumber, Inc. (Ksandka Sawmill), Fortine, MT 

- Eureka Pellet Mills, Eureka, MT