1

4.0 Analyses of Individual Nonattainment Areas 

4.8 Region 8 Nonattainment Areas 

4.8.1 Montana

Attachment 1 

Montana 

Area Designations For the 

24-Hour Fine Particle National Ambient Air Quality Standard 

The table below identifies the counties in Montana that EPA has designated as not attaining the 

2006 24-hour fine particle (PM2.5) standard.1

 A county (or part thereof) is designated as 

nonattainment if it has an air quality monitor that is violating the standard or if the county is 

determined to be contributing to the violation of the standard. 

Area State-Recommended 

Nonattainment Counties 

EPA’s Intended 

nonattainment County 

Lincoln County (partial) No state recommendation Lincoln County (partial 

includes Libby only) 

For the Libby area, located in Lincoln County, EPA established nonattainment area boundaries 

for the 1997 PM2.5 NAAQS that was a partial county. This boundary is described in 40 CFR 

81.327 under “Montana – PM2.5” and reads as follows: 

“Libby MT: Lincoln County (part) .... The area bounded by lines from Universal Transverse 

Mercator Zone 11(North American Datum 1983) coordinates beginning at 600,000mE, 

5,370,000mN east to 620,000mE, 5,370,000mN south to 620,000mE, 5,340,000mN west to 

600,000mE, 5,340,000mN north to 600,000mE, 5,370,000mN”. For the reasons described below 

EPA is again designating the same area nonattainment for the 2006 standard as described above 

for the 1997 annual standard for Libby, Montana. 

EPA has designated the remaining counties in the state as “attainment/unclassifiable” for the 

2006 24-hour standard. 

 

1 EPA designated nonattainment areas for the 1997 fine particle standards in 2005. In 2006, the 

24-hour PM2.5 standard was revised from 65 micrograms per cubic meter (average of 98th

percentile values for 3 consecutive years) to 35 micrograms per cubic meter; the level of the 

annual standard for PM2.5 remained unchanged at 15 micrograms per cubic meter (average of 

annual averages for 3 consecutive years). 
 2

EPA Technical Analysis for Libby, Lincoln County

Introduction 

Pursuant to section 107(d) of the Clean Air Act, EPA must designate as nonattainment those 

areas that violate the NAAQS and those areas that contribute to violations. This technical 

analysis for Lincoln County identifies the area with monitors that violate the 24-hour PM2.5 

standard and evaluates nearby counties for contributions to fine particle concentrations in the 

area. EPA has evaluated these counties based on the weight of evidence of the following nine 

factors recommended in EPA guidance and any other relevant information: 

- pollutant emissions 

- air quality data 

- population density and degree of urbanization 

- traffic and commuting patterns 

- growth 

- meteorology 

- geography and topography 

- jurisdictional boundaries 

- level of control of emissions sources 

We also used analytical tools and data such as pollution roses, fine particle composition 

monitoring data, back trajectory analyses and the contributing emission score (CES) to evaluate 

these areas. (See additional discussion of the CES under factor 1 below.) 

Figure 1 below is a map of the counties in the nonattainment area and other relevant information 

such as the locations and design values of air quality monitors, and the metropolitan area 

boundary. 

 
 3

5-29

Figure 5.29 Libby, MT 24-hr PM2.5 Nonattainment Area

Juneau, AK

Figure 1

For this area, EPA previously established PM2.5 nonattainment boundaries for the 1997 PM2.5

National Ambient Air Quality Standard (NAAQS) that included the partial county of Lincoln 

located in Montana. 

In December 2007, Montana recommended that Missoula and Ravalli counties be designated as 

“nonattainment” and all remaining counties be designated as “attainment” for the 2006 24-hour 

PM2.5 standard based on air quality data from 2004-2006. These data are from Federal reference 

method (FRM) monitors located in the state. (Letter to Robbie Roberts, Regional Administrator, 

December 18, 2007)

In August 2008, EPA notified Montana of its intended designations. In this letter, EPA also 

requested that if the State wished to provide comments on EPA’s intended designations, it should 

do so by October 20, 2008. EPA stated that it would consider any additional information 

provided by the State in making final decisions on the designations. 

Based on EPA's technical analysis described below, EPA has designated the same partial area in 

Lincoln County, Montana as previously designated nonattainment for the 1997 PM2.5 standard as 

nonattainment for the 24-hour PM2.5 air-quality standard based upon currently available 

information. The county is listed in the table below. 
 4

Libby/Lincoln County State-Recommended 

Nonattainment Counties 

EPA-Recommended 

Nonattainment Counties 

Montana None Lincoln (partial) 

The Libby area of Lincoln County is a unique topographically isolated area surrounded by the 

Kootenai National Forest within an extremely remote and rural area of Montana. The factors 

that are most relevant for designating this area as nonattainment are Factors 2, 6, and 7 which are 

monitoring, meteorology and topography, respectively. The source of emissions in Libby is 

predominately from the use of residential wood- burning stoves during the wintertime when 

frequent and persistent temperature inversions trap the PM2.5 emissions causing violations of the 

standard. The location of the town of Libby, with a total land area of 1.3 square miles, is within 

Lincoln County with a total land area of 3,675 square miles. Libby is in a narrow valley 

surrounded by mountains 4,000 feet higher than the town. As described here and in Factor 6 and 

7 below, this area is a unique topographical and meteorological situation. 

In the Libby nonattainment designation for the annual PM2.5 standard the Counties of Bonner, 

Sanders, Flathead and Boundary were given consideration and were not included because the 

nine factor analysis concluded there is no contribution to Libby and they do not have violating 

monitors. Thus, after a review of recent information for the 24-hour standard regarding these 

surrounding rural counties, we again concluded there were no factors that indicated they should 

be given any further consideration as candidates for a nonattainment status. 

The following is a technical analysis for EPA Region 8 portion of the Montana area. 

Factor 1: Emissions data 

For this factor, EPA evaluated County level emission data of the following PM2.5 components 

and precursor pollutants: “PM2.5 emissions total,” “PM2.5 emissions carbon,” “PM2.5 emissions 

other,” “SO2,” “NOx,” “VOCs,” and “NH3.” “PM2.5 emissions total” represents direct emissions 

of PM2.5 and includes: “PM2.5 emissions carbon,” “PM2.5 emissions other”, primary sulfate 

(SO4), and primary nitrate. (Although primary sulfate and primary nitrate, which are emitted 

directly from stacks rather than forming in atmospheric reactions with SO2 and NOx, are part of 

“PM2.5 emissions total,” they are not shown in Table 1 as separate items). “PM2.5 emissions 

carbon” represents the sum of organic carbon (OC) and elemental carbon (EC) emissions, and 

“PM2.5 emissions other” represents other inorganic particles (crustal). Emissions of SO2 and 

NOx, which are precursors of the secondary PM2.5 components sulfate and nitrate, are also 

considered. VOCs (volatile organic compounds) and NH3 (ammonia) are also potential PM2.5

precursors and are included for consideration. Emissions data were derived from the 2005 

National Emissions Inventory (NEI), version 1. See 

http://www.epa.gov/ttn/naaqs/pm/pm25_2006_techinfo.html. 

 

EPA also considered the Contributing Emissions Score (CES) for each county. The CES is a 

metric that takes into consideration emissions data, meteorological data, and air quality 

monitoring information to provide a relative ranking of counties in and near an area. Note that 
 5

this metric is not the exclusive manner for considering data for these factors. A summary of the 

CES is included in attachment 2, and a more detailed description can be found at 

http://www.epa.gov/ttn/naaqs/pm/pm25_2006_techinfo.html#C. ] 

Table 1 below shows emissions of PM2.5 and precursor pollutants components (given in tons per 

year) and the CES for violating and potentially contributing counties in the Lincoln County area. 

Counties that are part of the Lincoln County nonattainment area for the 1997 PM2.5 NAAQS are 

shown in boldface. Counties are listed in descending order by CES. 

Table 1. PM2.5 Related Emissions and Contributing Emission Scores 

County State 

Recommended 

Nonattain 

Ment? 

CES PM2.5 

emissions 

total 

(tpy)

PM2.5 

emissions 

carbon

(tpy) 

PM2.5 

emissions 

other 

(tpy)

SO2

(tpy) 

NOx

(tpy) 

VOCs 

(tpy) 

NH3

(tpy) 

Lincoln, 

MT 

No 100 2738 1708 1029 535 3395 7681 506 

Sanders, 

MT 

No 68 3620 2278 1341 391 968 9852 874 

Bonner, ID No 28 1234 608 626 357 4478 6831 328 

Flathead, 

MT 

No 16 2789 1527 1262 1291 5880 9083 877 

Boundary, 

ID 

No 7 996 507 488 113 1117 3179 376 

CES score as provided by EPA Office of Air Quality Planning and Standards (hereafter, OAQPS). 

Note: Emission data are from EPA’s 2005 National Emission Inventory (NEI) and are provided by EPA-OAQPS. 

Based on emissions levels and CES values and in light of the unique aspects of this area as 

explained above, a portion of Lincoln County only is a candidate for a 24-hour PM2.5

nonattainment designation. 

 

Factor 2: Air quality data 

This factor considers the 24-hour PM2.5 design values (in μg/m3

) for air-quality monitors in 

Lincoln, Sanders and Flathead counties based on data for 2005-2007 period. We gave further 

consideration to monitoring for Sanders County and Flathead County in comparison to Lincoln 

County. However, as no violations are occurring in these areas and in light of the unique 

isolating aspects of this area indicating no contribution from these counties as explained above 

no further consideration is given to these two Counties or any others as part of this nonattainment 

area. A monitor’s design value indicates whether that monitor attains a specified air-quality 

standard. The 24-hour PM2.5 standard is met when the 3-year average of a monitor’s 98th

percentile values are 35μg/m3 or less. A design value is only valid if minimum data 

completeness criteria are met. 

The 24-hour PM2.5 design values in the Lincoln County area are shown in Table 2. 
 6

Table 2. Air Quality Data 

County State 

Recommended 

 Nonattainment? 

24-hour PM2.5 Design 

Values, 2004-2006

(μg/m3

) 

24-hour PM2.5 Design

Values, 2005-2007

(μg/m3

) 

Lincoln, MT No 43 41 

Sanders, MT No 20 20 

Flathead, MT No 24 23 

Under this factor, we also consider fine particle composition monitoring data. Air quality 

monitoring data on the composition of fine particle mass are available from the EPA Chemical 

Speciation Network and the IMPROVE monitoring network. Analysis of these data indicates 

that the days with the highest fine particle concentrations occur predominantly in the winter. On 

high days, carbonaceous PM2.5 makes up 92% of the total PM2.5 mass. 

Eligible monitors for providing design value data generally include State and Local Air 

Monitoring Stations (SLAMS) at population-oriented locations with an FRM monitor. All data 

from Special Purpose Monitors (SPM) using an FRM is eligible for comparison to the relevant 

NAAQS, subject to the requirements given in the October 17, 2006 Revision to Ambient Air 

Monitoring Regulations (71 FR 61236). All monitors used to provide data must meet the 

monitor siting and eligibility requirements given in 71 FR 61236 to 61328 in order to be 

acceptable for comparison to the 24-hr PM2.5 NAAQS for designation purposes. Based on the air 

quality data in this factor a portion of Lincoln County only is a candidate for a nonattainment 

designation. However, the absence of a violating monitor alone is not a sufficient reason to 

eliminate counties as candidates for nonattainment status. 

Factor 3: Population density and degree of urbanization (including commercial 

development) 

Table 3 shows the 2005 population for Lincoln County as well as the population density. 

Population data give an indication of whether it is likely that population-based emissions might 

contribute to violations of the 24-hour PM2.5 standards. 

Table 3. Population 

County State 

Recommended 

Nonattainment? 

2005 

Population 

2005 

Population 

Density 

(pop/sq mi) 

Lincoln No 19,182 5 

As shown in Table 3 above, Lincoln County is a sparsely populated rural area. Based on the 

2000 U.S. Census the population for Libby itself 2,626 persons located in a 1.3 square mile area 

with a population density of 1,751 persons per square mile. Based on the population density of 
 7

this factor a portion of Lincoln County only is a candidate for the 24-hour nonattainment 

designation. 

Factor 4: Traffic and commuting patterns

This factor considers the number of commuters in Lincoln County who drive within the County 

and the percent of total commuters as well as the total Vehicle Miles Traveled (VMT) in millions 

of miles. 

Table 4. Traffic and Commuting Patterns 

County State 

Recommended 

Non-attainment? 

2005 

VMT 

(millions 

annually) 

Number 

Commuting to 

any violating 

counties 

Percent 

Commuting to 

any violating 

counties 

Number 

Commuting 

into and within 

statistical area 

Percent 

Commuting 

into and within 

statistical area 

Lincoln No 216 6,180 94 NA NA 

The listing of Counties in Table 4 reflects the number of people commuting within Lincoln 

County only. NA is abbreviation for “not applicable”. 

The 2005 VMT data used for table 4 and table 5 of the 9-factor analysis have been derived using 

methodology such as that described in "Documentation for the 2005 Mobile National Emissions 

Inventory, Version 2," December 2008, prepared for the Emission Inventory Group, U.S. EPA. 

This document may be found at: 

ftp://ftp.epa.gov/EmisInventory/2005_nei/mobile_sector/documentation/2005_mobile_nei_versi

on_2_report.pdf

As shown in Table 4 above 94% of the commuters are within Lincoln County. Based on the 

traffic and commuting in this factor a portion of Lincoln County only is a candidate for the 24-

hour nonattainment designation. 

Factor 5: Growth rates and patterns 

This factor considers population growth for 2000-2005 and growth in vehicle miles travelled 

(VMT) for 2000-2005 for Lincoln County as well as patterns of population and VMT growth. A 

County with rapid population or VMT growth is generally an integral part of an urban area. 

However, Lincoln County is a remote, topographically isolated rural area and has minimal 

changes in growth rates and patterns. 

Table 5 below shows population, population growth, VMT for Lincoln County. 

Table 5. Population and VMT Growth and Percent Change 

Location Population 

(2005) 

Population % 

change (2000 

to 2005) 

2005 VMT 

(millions mi) 

VMT 

Growth 

(1000s 

VMT 

% change 

(2000 to 2005) 
 8

mi from 2000 

to 2005) 

Lincoln 19,182 2 216 4 NA 

Based on the growth rate in this factor a portion of Lincoln County only is a candidate for 

the 24-hour nonattainment designation. 

Factor 6: Meteorology (weather/transport patterns) 

For this factor, EPA considered data from National Weather Service instruments in the area. 

Wind direction and wind speed data for 2004-2006 were analyzed, with an emphasis on “high 

PM2.5 days” for each of two seasons (an October-April “cold” season and a May-September 

“warm” season). These high days are defined as days where any FRM air-quality monitors had 

24-hour PM2.5 concentrations above 95% on a frequency distribution curve of PM2.5 24-hour 

values. 

For each air quality monitoring site, EPA developed a “pollution rose” to understand the 

prevailing wind direction and wind speed on the days with highest fine particle concentrations. 

Figure 2 below identifies 24-hour PM2.5 values by color; days exceeding 35 ug/m3 are denoted 

with a red or black icon. A dot indicates the day occurred in the warm season; a triangle 

indicates the day occurred in the cool season. The center of the figure indicates the location of 

the air quality monitoring site, and the location of the icon in relation to the center indicates the 

direction from which the wind was blowing on that day. An icon that is close to the center 

indicates a low average wind speed on that day. Higher wind speeds are indicated when the icon 

is further away from the center. 
 9

S

W E

2 4 6 8 10 12+

Wind Speed (mph)

Site 300530018

Libby, MT [Lincoln County, MT]

Pollution Rose, 2005-2007

Year

2004

2005

2006

98th %-ile

51.1

40.5

32.2

# days > 35

6

6

.

Design

Value 41-NA

1 exceedance(s) not plotted 

(due to missing or variable wind data) Libby, MT

Meteorological data from 59.8 miles away

KALISPELL_GLACIER_PK_INT'L_AR (ID=24146)

2005

2006

2007

Concentration:

 > 40 μg/m3

 35 - 40 μg/m3

 30 - 35 μg/m3

 < 30 μg/m3

Season:

cool (Oct-Apr)

warm (May-Sep)

Figure 2

The wind rose information as reflected in Figure 2 was created in a national analysis to provide a 

consistent approach and data set for use in all areas. These wind roses were only one factor EPA 

considered in making designations, and were more significant in analyses where they were 

located close to the violating monitor. The wind rose for Libby is based on information from the 

Kalispell Airport which is 67 miles away. The meteorology factor is also considered in each 

county’s Contributing Emissions Score (CES) because the method for deriving this metric 

included an analysis of trajectories of air masses for high PM2.5 days. 

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 nearby thus transport of high background 

concentrations into Libby is 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 the 24-hour PM2.5 standard while winter concentrations are well 

above the standard. The much higher concentrations in winter are typically caused by stagnant 

weather conditions, strong temperature inversions, light winds and high emissions of direct PM2.5

from woodstoves used for residential heating. Based on the meteorology in this factor a portion 

of Lincoln County only is a candidate for a 24-hour nonattainment designation. 
 10

Factor 7: Geography/topography (mountain ranges or other air basin boundaries) 

The geography / topography factor analysis evaluates the physical features of the land that might 

have an effect on the air shed and, therefore, on the distribution of PM2.5 over the Lincoln 

County area. 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 vicinity. Figures 3 

and 4 below show that Lincoln County has numerous geographical and topographical boundaries 

that limit the air shed containing the Libby area to a very narrow valley surrounded by high 

mountain ranges. The town of Libby has a total land area of 1.3 square miles. The elevation of 

the Libby area is 2,601 feet (MSL) and the surrounding ridgetops are 4,000 feet higher. The 

town sits in a narrow valley that runs in a north-south direction (located at 48o23′17′′ north, 

115o33′13′′ west.) The Kootenai River runs adjacent to the town in an east-west direction. The 

Kootenai Basin is dominated by three major mountain ranges. The Rocky Mountain Range and 

the Flathead Range are the eastern boundary and 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 7,000 feet. The 

entire watershed is heavily forested and the majority of Lincoln County is National Forest land 

with no other large metropolitan areas. The nearest large cities are Kalispell which is 90 miles 

due east and Missoula which is 192 miles south. 

The geographical and topographical barriers in Libby significantly limit air pollution from being 

transported into the Libby air shed from elsewhere. Therefore, this factor combined with factor 

6 Meteorology demonstrate how the PM2.5 in the area remains confined to the Libby area. The 

combination of a low lying valley, surrounded by high elevation mountains and the single river 

valley restrict, trap, and concentrate air pollution in the Libby area thus providing the conditions 

for violations of the PM2.5 standard to occur. Based on topography in this factor a portion of 

Lincoln County only is a candidate for a 24-hour nonattainment designation. 
 11

Figure 3: Libby, MT area from Google EarthTM
 12

Figure 4: Libby, MT area with topography from National Atlas.Gov

Factor 8: Jurisdictional boundaries (e.g., existing PM 2.5 areas) 

In evaluating the jurisdictional boundary factor, EPA gave special consideration to areas that 

were already designated nonattainment in 2005 for violating the 1997 fine particle standards. 

Analysis of chemical composition data in these areas indicates that the same components that 

make up most of the PM2.5 mass in the area on an annual average basis (such as sulfate and 

direct PM2.5 carbon in many eastern areas) also are key contributors to the PM2.5 mass on days 

exceeding the 24-hour PM2.5 standard. These data indicate that in many cities, the same source 

categories that contribute to violations of the annual standard also contribute to exceedances of 

the 24-hour standard. 

Most areas that were originally designated nonattainment for the PM2.5 standards still have not 

attained the standards. Thus, EPA has generally concluded that counties that were designated as 

having emissions sources contributing to fine particle concentrations which continue to exceed 

the 1997 standards (all areas violated the annual standard, two also violated the previous 24-hour 

standard) also contribute to fine particle concentrations on the highest days. For this reason, 
 13

EPA believes that for most existing nonattainment areas, the nonattainment area for the 2006 24-

hour standard should be the same. Consideration also should be given to existing boundaries and 

organizations as they may facilitate air quality planning and the implementation of control 

measures to attain the standard. Areas already designated as nonattainment represent important 

boundaries for state air quality planning. 

The analysis of jurisdictional boundaries considered the planning and organizational structure of 

Lincoln County to determine if the implementation of controls in a potential nonattainment area 

can be carried out in a cohesive manner. Air quality planning for the area of Libby is under the 

Lincoln County Health Department who adopts rules and regulations that are reviewed and 

approved by the Montana Department of Environmental Quality. There are no other 

jurisdictions to consider. The State of Montana’s program for air quality protection can be 

carried out in a cohesive manner for addressing the nonattainment issues in Lincoln County. 

In addition, the area is nonattainment for the PM10 standard and the PM2.5 annual standard. The 

State of Montana has recently submitted an attainment plan for the annual standard. The 

jurisdictional boundary proposed for the 24-hour PM2.5 standard is the same boundary described 

for the annual PM2.5 standard. Based on the jurisdiction in this factor a portion of Lincoln 

County only is a candidate for a 24-hour nonattainment designation. 

Factor 9: Level of control of emission sources 

This factor considers emission controls currently implemented in the Lincoln County area. The 

emission estimates in Table 1 (under Factor 1 above) include any control strategies implemented 

by the States before 2005 that may influence emissions of any component of PM2.5 emissions 

(i.e., total carbon, SO2, NOx, and crustal PM2.5). The Montana Department of Environmental 

Quality has recently submitted a plan for attaining the annual PM2.5 standard that includes 

specific rules adopted by Lincoln County for regulating woodstoves and other wood burning 

ordinances. For the 2005-2007 time period, Libby is showing attainment of the annual standard. 

In addition, the Libby area has completed a changeout of more than 1,000 existing non-EPA 

certified woodstoves for low-emitting EPA certified stoves. When fully implemented, this 

program should reduce direct PM2.5 emissions in the cold weather months and help lower fine 

particle concentrations. However, at the current time Libby is still violating the 24 hour 

standard. Based on the level of control in this factor a portion of Lincoln County only is a 

candidate for the 24-hour nonattainment designation. 

Conclusion 

 

Libby in Lincoln County has monitors that, based on both 2004-2006 and 2005-2007 FRM data 

in the EPA Air Quality System (AQS), violate the 2006 24-hour PM2.5 NAAQS. Therefore, this 

area is being designated nonattainment. EPA’s analysis of the nine factors and other analytical 

tools supports the conclusion that the boundaries established for implementing the 1997 PM2.5

NAAQS are also appropriate for implementing the 2006 24-hour PM2.5 NAAQS. 
 14

Both Factors 6 Meteorology and Factor 7 Topography provide further support for the effect of 

mountainous terrain combined with frequent and persistent temperature inversions result in 

violations of the standard. Furthermore, air quality monitoring data on the composition of fine 

particle mass indicates that the days with the highest fine particle concentrations occur 

predominantly in the winter. On high days, carbonaceous PM2.5 makes up 92% of the total 

PM2.5 mass, indicating that residential wood burning emissions located in Libby are a key 

source. Based on all of this data EPA concludes that only the town of Libby located in Lincoln 

County is being designated nonattainment of 24-hour standard. 

The State of Montana did not recommend that the Libby area in Lincoln County be designated as 

nonattainment for the 2006 24-hour PM2.5 standard based on the most recent three years of air 

quality data that was available in December 2007. The Governor’s letter of December 18, 2007 

requested that EPA delay the designation until December of 2009 based on insufficient 

information. However, in previous designations insufficient information was considered to be 

missing or incomplete monitoring data. For the Libby area, EPA has concluded there is 

sufficient information based on data from the Federal reference method (FRM) monitors within 

the State to determine that the area is violating the standard. Thus, EPA is unable to grant the 

Governors request for a one year delay. Since the State did not provide a 9-factor analysis for 

the Libby area, EPA does not have any specific technical information to evaluate from the State. 

The State did not provide a response to EPA’s August 18, 2008 to Governor Brian Schweitzer 

transmitting our nine factor analysis and intended designations. 

Additional information regarding responses to specific State comments can be found in EPA's 

Response to Comments document at 

http://www.epa.gov/pmdesignations/2006standards/tech.htm. ] 
 15

.