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Draft Technical Support Document

PENNSYLVANIA

Area Designations For the 

2010 SO2 Primary National Ambient Air Quality Standard

Summary

Pursuant to section 107(d) of the Clean Air Act (CAA), EPA must initially designate areas as 

either “unclassifiable,” “attainment,” or “nonattainment” for the 2010 1-hour sulfur dioxide 

(SO2) primary national ambient air quality standard (NAAQS). The CAA defines a 

nonattainment area as one that does not meet the NAAQS or that contributes to poor air quality 

in a nearby area that does not meet the NAAQS. Table 1 below identifies the counties or 

portions of counties in the Commonwealth of Pennsylvania (“Pennsylvania” or “PA”) that EPA 

intends to initially designate nonattainment based on monitored violations.

 Table 1. Nonattainment Area Designations for Pennsylvania

Area 

Pennsylvania’s

Recommended 

Designation of 

Areas/Counties

EPA’s Intended Designation 

of Designated 

ofAreas/Counties

Allegheny, PA

 Allegheny County Nonattainment Nonattainment

Beaver, PA

 Beaver County Nonattainment Nonattainment 

Indiana, PA

 Indiana County

Armstrong County (partial)

 Plumcreek Township

 South Bend Township

 Elderton Borough

Nonattainment

Unclassifiable

Nonattainment

Nonattainment

Warren, PA

 Warren County Nonattainment Nonattainment

Background

On June 2, 2010, EPA revised the primary SO2 NAAQS (75 FR 35520), by establishing a new 1-

hour standard at a level of 75 parts per billion (ppb) which is attained when the 3-year average of 

the 99th percentile of daily maximum 1-hour average concentrations at each monitor in an area 

does not exceed 75 ppb. EPA has determined that this is the level necessary to provide 

protection of public health with an adequate margin of safety, especially for children, the elderly 

and those with asthma. These groups are particularly susceptible to the health effects associated 
2

with breathing SO2. The Agency is revoking the two prior primary standards of 140 ppb 

evaluated over 24-hours, and 30 ppb evaluated over an entire year because these standards will 

not add additional public health protection given a 1-hour standard at 75 ppb. Accordingly, EPA 

is not designating areas in this process on the basis of either of these two prior primary standards. 

Similarly, the secondary standard for SO2 has not been revised, so EPA is not designating areas 

in this process on the basis of the secondary standard.

EPA’s SO2 Designation Approach

Section 107(d) of the CAA requires that no later than one year after promulgation of a new or 

revised NAAQS, state Governors must submit their recommendations for designations and 

boundaries to EPA. This deadline was in June 2011. Section 107(d) also requires EPA to 

provide a notification to states of no less than 120 days prior to promulgating an initial area 

designation that is a modification of a state’s recommendation. If a state or tribe did not submit 

designation recommendations, EPA will promulgate the designations that it deems appropriate. 

If a state or tribe disagrees with EPA’s intended area designations, they have an opportunity to 

demonstrate why any proposed modification is inappropriate.

Designations guidance was issued by EPA through a March 24, 2011 memorandum from 

Stephen D. Page, Director, U.S. EPA, Office of Air Quality Planning and Standards, to Air 

Division Directors, U.S. EPA Regions I-X. This memorandum identifies factors EPA intends to 

evaluate in determining boundaries for areas designated nonattainment. These 5 factors include: 

1) Air quality data; 2) Emissions and emissions-related data (location of sources and potential 

contribution to ambient SO2 concentrations); 3) Meteorology (weather/transport patterns); 4) 

Geography/topography (mountain ranges or other air basin boundaries); 5) Jurisdictional boundaries 

(e.g., counties, air districts, pre-existing nonattainment areas, reservations, metropolitan planning 

organization), among any other criteria deemed to be relevant to establishing appropriate areas 

designations and boundaries for the 1-hour SO2 NAAQS.

The March 24, 2011, memo recommended that area boundaries be defaulted to the county boundary 

unless additional provided information justifies a larger or smaller boundary than that of the county. 

EPA believes it is appropriate to evaluate each potential area on a case-by-case basis, and to 

recognize that area-specific analyses conducted by states, tribes and/or EPA may support a different

boundary than that of a default county boundary.

In this TSD, EPA discusses its review and technical analysis of the recommendations submitted by 

Pennsylvania for designations of the 1-hour SO2 standard and any modifications from these 

recommendations regarding areas for which there are monitored violations of the NAAQS. 

Definitions of important terms used in this document:

1) Designated “nonattainment” area – an area which EPA has determined, based on a state 

recommendation and/or on the technical analysis included in this document, has violated the 

2010 SO2 NAAQS, based on the most recent three years of air quality monitoring data, or 

contributes to a violation in a nearby area. 
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2) Recommended nonattainment area – an area a State or Tribe has recommended to EPA be 

designated as nonattainment.

3) Violating monitor – an ambient air monitor meeting all methods, quality assurance and citing 

criteria and requirements whose valid design value exceeds 75 ppb, as described in Appendix T 

of 40 CFR part 50.

4) 2010 SO2 NAAQS - 75 ppb, national ambient air quality standard for SO2 promulgated in 

2010. Based on the 3-year average of the 99th percentile of the annual distribution of daily 

maximum 1-hour average concentrations

5) Design Value – a statistic that describes the air quality status of a given area relative to the 

level of the NAAQS.

Nonattainment Designations

Introduction

In Pennsylvania’s designation recommendation letter to EPA, dated June 23, 2011, Michael L. 

Krancer, Secretary of the Pennsylvania Department of Environmental Protection (PADEP), 

recommended that Allegheny, Beaver, Indiana, and Warren Counties be designated as 

nonattainment for the 2010 SO2 NAAQS based on monitored air quality data from 2008-2010. 

Pennsylvania provided its 5-factor analysis for each of these four counties as part of its 

designation recommendation.

Based on EPA’s technical analysis, EPA intends to initially designate four areas as 

nonattainment (Table 1) based on monitored violations of the 2010 SO2 NAAQS. The 

Allegheny Nonattainment Area consists of Allegheny County; the Beaver Nonattainment Area 

consists of Beaver County; the Indiana Nonattainment Area consists of Indiana County and a 

portion of Armstrong County (Plumcreek and South Bend Townships and Elderton Borough); 

and the Warren Nonattainment Area consists of Warren County. 

The 5 factors were used to analyze the nonattainment areas for 1-hour SO2 designations:

1. Air quality data. This factor considers the SO2 air quality monitoring data from EPA’s 

Air Trends website (see http://www.epa.gov/airtrends/values.html), including the design 

values (ppb) calculated for each monitor in the area for the most recent 3-year period. A 

monitor’s design value indicates whether that monitor violates a specified air quality 

standard. The 2010 SO2 NAAQS is met at a monitoring site when the identified design 

value is valid and less than or equal to 75 ppb as described in Appendix T of 40 CFR part 

50. An ambient air monitor whose valid design value exceeds 75 ppb, as described in 

Appendix T of 40 CFR part 50 is deemed a violating monitor. A design value is only 

valid if minimum data completeness criteria are met. An SO2 design value that meets the 

NAAQS is generally considered valid if it encompasses 3 years of complete data. A year 

is complete when all 4 quarters are complete. A quarter is complete when 75% of the 

days are complete. A day is complete when it has 75% of its hours. Data substitution 

tests are described in Appendix T of 40 CFR part 50. Areas where monitoring data 
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indicate a violation of the 1-hour, 75 ppb primary SO2 standard will be designated as 

nonattainment. 

2. Emissions and emissions-related data (location of sources and potential contribution to 

ambient SO2 concentrations). We reviewed data from the 2008 National Emissions 

Inventory (NEI), version 2 (NEI08V2), which was the most current version of the 

national inventory available in 2011 when these data were compiled for the designations 

process, (see http://www.epa.gov/ttn/chief/net/2008inventory.html.) or other relevant 

sources of data, such as state inventories or inventories from other federal sources. EPA 

recognizes that there might be no new information on any changes in emissions that may 

have occurred after 2008, but would consider more recent years if available. For 

example, certain large sources of emissions in or near an area may have installed 

emission controls or otherwise significantly reduced emissions since 2008. Also any 

additional information we receive on federally-enforceable emissions control that are not 

reflected in recent inventories but which will require compliance before final 

designations are issued were considered. Two source categories from the 2008 NEI were 

examined: the point source inventory and the nonpoint source inventory. Generally, the 

point source inventory represents the bulk of the SO2 emissions in the EPA Region III

states.

Additionally, a source screening analysis, involving an emissions by distance (Q/d) 

methodology, was used to assess the need to examine point sources for further review 

which are located within 50 kilometers of a violating monitor. North Carolina’s 

Prevention of Significant Deterioration (PSD) Guidance document

(http://www.ncair.org/permits/mets/psd_guidance.pdf) describes a screening 

methodology used to identify point sources to be specifically included in a modeled 

impact analysis. According to this method, a source is considered to be significant and, 

therefore, included in the modeling analysis if its annual emissions are greater than or 

equal to twenty (20) times the distance between the source and the point of interest 

(Q/d≥20 or Q/20d≥1), or as used in this case, the violating monitor. While not used for 

the same purpose, this methodology was used to identify point sources near a violating 

monitor for further review. 

Point source emissions data are needed to perform the Q/d analysis. Three sources of 

emissions data were considered for this screening analysis: emissions recorded in the 

2008 NEI, the 2010 Clean Air Markets Division (CAMD) reported emissions, and the 

sources’ permitted emission limits. CAMD emissions were limited to sources with 

continuous emissions monitors (CEMs). Point source emission information from the 

2008 NEI and 2010 CAMD represent actual yearly emission totals, and these values are 

probably less than a point source’s allowable or permitted emission limit. Permitted 

emission limits are generally unavailable since most states lack a central repository or 

permit database at this time. Emissions used in the Q/d screening analysis were chosen 

following the steps outlined below in Figure 1.
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Figure 1. Emission Decision Tree

3. Meteorology (weather/transport patterns). We evaluated meteorological data to help 

determine how weather conditions, including wind speed and direction, affect the plume 

of sources contributing to ambient SO2 concentrations. The National Weather Service 

maintains surface and upper air monitoring sites across the United States. Automated 

Surface Observing System (ASOS) (http://www.weather.gov/asos) sites collect hourly 

averaged wind measurements including wind direction and wind speed. Upper air 

measurements (rawinsonde) are collected at a limited number of sites where vertical wind 

profiles are taken using weather balloons. Measurements taken at ASOS and rawinsonde 

sites are often used in dispersion modeling analyses using EPA’s AERMOD modeling 

system. 

One-minute meteorological wind fields for an area’s nearby airport(s) were downloaded 

and run through AERMOD’s preprocessor AERMINUTE to produce hourly averaged 

wind fields. This data was then run through Lakes Environmental’s WRPLOT software 

to produce wind roses for the airports, showing predominant wind patterns in the area.

4. Geography/topography (mountain ranges or other air basin boundaries). We examined 

the physical features of the land that might affect the distribution of SO2 over an area. 

Mountains or other physical features may affect the distribution of emissions, and may 

help define boundaries. Maps depicting elevations and point sources were constructed 

and evaluated to determine the effects of the topography on point source emissions.

5. Jurisdictional boundaries (e.g., counties, air districts, pre-existing nonattainment areas, 

reservations, metropolitan planning organizations). Once the geographic area associated 

with the area violating the SO2 standard and the nearby area contributing to violations 

were determined, we considered existing jurisdictional boundaries for the purposes of 

providing a clearly defined legal boundary for carrying out the air quality planning and 

enforcement functions for the nonattainment area. If an existing jurisdictional boundary 

is used to help define the nonattainment area, it encompasses all of the area that has been 

identified as meeting the nonattainment definition. These existing boundaries may 

Point-Source Screening Analysis

If Source Emissions (Q) ≥ 20 x Distance from 

Nonattainment Monitor, Source Received Further 

Review

If Source Emissions (Q) ≤ 20 x Distance from 

Nonattainment Monitor, Source Not Considered 

Further 

Point-Source Emission Selection Process

First Preference: Permitted Next: If no recent controls, max 

of NEI or CAMD

or Next: If recent controls 

installed, CAMD

Available Point-Source Emissions

2008 NEI v2

(Actual)

2011 CAMD

(Actual)

Permitted

(Allowable)
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include an existing nonattainment or maintenance area boundary, a county or township 

boundary, a metropolitan area boundary, an air management district, or an urban planning 

boundary established for coordinating business development or transportation activities. 

Where existing jurisdictional boundaries are not adequate to describe the nonattainment 

area, other clearly defined and permanent landmarks or geographic coordinates are used.

Pennsylvania recommended the county boundary for all its nonattainment area 

boundaries, which was the default boundary as per EPA’s March 24, 2011 designations 

guidance. In addition to considering the county boundary, we also examined use of 

Metropolitan Statistical Areas (MSAs) as the jurisdictional boundary. The U.S. Office of 

Management and Budget (OMB) defines metropolitan and micropolitan statistical areas 

according to published standards that are applied to Census Bureau data. The general 

concept of a metropolitan or micropolitan statistical area is that of a core area containing 

a substantial population nucleus, together with adjacent communities having a high 

degree of economic and social integration with that core

(http://www.census.gov/population/www/metroareas/aboutmetro.html). Finally, 

previously established Air Quality Control Regions (AQCRs) were considered as well.

The five factor descriptions above are a combination of descriptions from the March 24, 2011 

memo and other relevant information pertaining to this TSD. 

Technical Analysis for the Allegheny Nonattainment Area

This technical analysis for the intended Allegheny Nonattainment Area identifies the whole 

county with a monitor that violates the 2010 SO2 NAAQS, and evaluates nearby counties for 

contributions to SO2 concentrations in the area. EPA has evaluated this county and nearby

counties based on the weight of evidence of the factors recommended in the March 24, 2011 

guidance issued by EPA.

Based on EPA's technical analysis described below, EPA agrees with Pennsylvania’s

recommendation and initially intends to designate, based on the violating monitor, Allegheny 

County in Pennsylvania as nonattainment for the 2010 SO2 NAAQS as part of the Allegheny

Nonattainment Area.

Air Quality Data 

This factor considers the SO2 design values (in ppb) for air quality monitors in Allegheny 

County in the Allegheny Area based on certified data for the 2009-2011 period. Figure 2 depicts 

the area analyzed and the location of the violating air quality monitor (Liberty monitor). 
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 Figure 2.

The 2010 1-hour SO2 design values for the five monitors located in Allegheny County are shown 

in Table 2.

Table 2. Allegheny County Monitor Trends: 1-Hour SO2 99th % and Design Values 

in Parts Per Billion (ppb)*

Monitor

Name

Monitor 

Air 

Quality 

System ID

99th % Design 

Value

Design 

Value 

2007 2008 2009 2010 2011 2008-10 2009-11

Avalon 42-003-

0002

70 75 61 53 40 63 51

Carnegie 42-003-

0010

75 62 61 35 23 53 40

Liberty 42-003-

0064

192 111 131 141 165 128 146

South 

Fayette

42-003-

0067

74 52 53 63 28 48 40

*Monitor in bold has the highest 2009-2011 design value in the respective county.
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Allegheny County shows a violation of the 2010 1-hour SO2 NAAQS (Liberty monitor). 

Therefore, this county and nearby counties will be reviewed to determine what area should be 

designated as nonattainment. The absence of a violating monitor alone is not a sufficient reason 

to eliminate nearby counties as candidates for nonattainment status. Each area has been 

evaluated based on the five factors and other relevant information. 

Emissions and Emissions-Related Data

Evidence of SO2 emissions sources in the vicinity of a violating monitor is an important factor 

for determining whether a nearby area is contributing to a monitored violation. For this factor, 

EPA evaluated county level emissions data for SO2 and any change in SO2 emitting activities

since the date represented by those emissions data.

Emissions

EPA recognizes that there might be no new information on any changes in emissions that may 

have occurred after 2008, but would consider more recent years if available. Pennsylvania did 

not provide updated emissions information, therefore EPA relied on the 2008 NEI emissions data

(NEI08V2). 

Table 3 shows total emissions of SO2 in tons per year (tpy) for violating and potentially 

contributing counties in and around the Allegheny Area and sources emitting or contributing

greater than 100 tpy of SO2 according to the NEI08V2. 

Table 3. SO2 Emissions in Allegheny Area (source: NEI08V2)

County

Facility 

Located in 

State

Recommended 

Nonattainment 

Area?

Facility Total 

Facility 

SO2

Emissions 

(tpy)

Total 

County 

SO2 Point 

Emissions 

Name EIS Coordinates (tpy)

Allegheny Yes Us Steel 

Corporation -

Irvin Plant

7409411 40.33554,

-79.90168

475 35,844

Allegheny Yes Shenango Inc 7407611 40.492,

-80.07968

333 35,844

Allegheny Yes Orion Power 

Midwest 

Cheswick 

Station

8404811 40.53639,

-79.79222

30,300 35,844

Allegheny Yes Uss 

Corporation -

Edgar Thomson 

Works

7409311 40.39553,

-79.86299

1,536 35,844

Allegheny Yes Uss - Clairton 

Works

8204511 40.3055,

-79.877021

1,517 35,844
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Allegheny Yes Bellefield 

Boiler Plant

8404711 40.442127,

-79.94913

795 35,844

Allegheny Yes Bay Valley 

Foods, LLC

8521211 40.45343,

-79.98584

487 35,844

Washington No Orion 

Power/Elrama 

Power Station

3895011 40.25,

-79.9167

2,572 3,746

Washington No Allegheny 

Energy/Mitchell

Power Station

3894811 40.2228,

-79.9694

934 3,746

Westmoreland No Arcelormittal 

Monesson 

LLC/Monesson 

Coke Plant

8330811 40.161547,

-79.883469

396 569

Washington No Langeloth 

Metallurgical

4778911 40.36346,

-80.401

186 3,746

Q/d Screening Analysis

Using point source emissions data, the emissions by distance (Q/d) screening methodology was 

used to identify sources within 50 kilometers (km) of the Liberty monitor that should receive a 

further review. A total of 11 point sources emitting more than 100 tpy (from the 2008 NEI v2) 

are located within 50 km of the Liberty monitor. Of the 11 point sources, seven are in Allegheny 

County, three are in neighboring Washington County and one is in Westmoreland County. No 

permit information was available for our analysis and only one source, Cheswick Power Station, 

had control equipment installed recently (so the CAMD emissions were used for this source). 

Following the Q/d methodology, we determined that nine of the eleven sources should receive 

further review. These sources are Orion Power Cheswick Station, Bay Valley Foods, Bellefield 

Boiler Plant, USS corporation-Edgar Thomson Works, US Steel Corporation, USS Clairton 

Works, Orion Power Elrama Power Station, Allegheny Energy Mitchell Power Station, and 

Arcelormittal Monessen Coke Plant (Figures 3-4).

 
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Figure 3.

Figure 4. 
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Emissions Controls

Under this factor, the existing level of control of emission sources is taken into consideration. 

The emissions data used by EPA in this technical analysis represents emission levels while 

accounting for any control strategies implemented on stationary sources in the Allegheny Area

up to and including 2008. Although EPA has not received any additional information on 

emissions reductions resulting from controls put into place after 2008, EPA has collected 

additional information. Cheswick Power Station, had control equipment installed recently.

Elrama Power Station in Washington County has had wet scrubbers installed since the mid 

1970’s and was scheduled to shut down in June 2012. Mitchell Power Station in Washington 

County had wet scrubbers installed in 2006 and 2007. 

Meteorology (weather/transport patterns)

Evidence of source-receptor relationships between specific emissions sources and high SO2

values at violating monitors is another important factor in determining the appropriate 

contributing areas and the appropriate extent of the nonattainment area boundary. For this factor, 

EPA considered data from sites that collected hourly averaged wind measurements including 

wind direction and speed for 5 years. There are two meteorological monitoring sites currently 

operating in Allegheny County. An ASOS and rawinsonde site is located at the Pittsburgh 

International Airport in the western part of the county. Another ASOS site is located at the 

Allegheny County Airport in the southern portion of the county. The Allegheny County Airport 

site is closer to the Liberty monitor. Recent wind data from both airports was downloaded and 

run through AERMOD’s preprocessor AERMINUTE to produce hourly averaged wind fields. 

These data were in turn run through Lakes Environmental’s WRPLOT software to produce wind 

roses for both of the surface ASOS sites in Allegheny County and shown below in Figure 5.
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Figure 5.

Wind rose plots for Pittsburgh International and Allegheny County airports show differing wind 

distribution patterns. As shown in the map in Figure 5, the prevailing wind directions at the 

Allegheny County Airport are predominantly out of the south and west. At the Pittsburgh 

International Airport, the prevailing winds are predominantly out of the west/southwest. These 

different wind patterns suggest source emission distributions may be dependent on their locations 

within the county. Differing wind patterns between the two ASOS sites are probably due to the 

county’s complex topography (see explanation under Geography/topography).

Pennsylvania provided its own analysis of meteorological data. They used wind measurements 

collected at the Allegheny County Airport from January 2008 to December 2010 and developed 

a wind rose diagram showing that the wind is primarily out of the west and south at the 

Allegheny County Airport, with secondary peaks out of the north. During the periods when 

there are high SO2 concentrations at the Liberty monitor, the wind is primarily out of the south. 

In addition, wind speeds are generally stronger, indicating that the winds are unimpeded (from 

any terrain) from that direction. Pennsylvania notes that the Allegheny County Airport 

meteorological tower is measuring winds at 55 meters above the Liberty monitor. Therefore, the 

stronger winds at the Allegheny County Airport could potentially signify the long range transport 

of pollutants affecting the Liberty monitor.
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Geography/topography (mountain ranges or other air basin boundaries)

Allegheny County is made up of the high elevations of the Appalachian Mountains with 

dendridic valleys carved out by the Ohio, Allegheny and Monongahela rivers systems. Higher 

terrain lies to the southeast (Laurel Ridge). Elevation differences between the river valleys and 

the ridge tops can exceed 150 meters. See Figure 6 below.

Most of the large (>100 tpy) point sources in Allegheny County reside within the river valleys. 

This is important since these valleys can create complex wind patterns which will impact sources 

with low stacks that cannot overcome neighboring elevated terrain causing the emissions to be 

trapped within the valleys. The ASOS meteorological sites in Allegheny County are both 

located in the higher elevations of the county. This presents a problem in that the meteorological 

measurements may not be representative of the valley flows that can occur under certain 

atmospheric conditions. These atmospheric conditions may define the times of peak 

concentrations for some emissions sources (low stacks for example). Therefore, the large 

sources residing within the river valleys are likely to cause localized air quality problems.

 

Figure 6.

Jurisdictional boundaries 

There is an existing maintenance boundary (i.e., previous nonattainment area) for the 1971 

primary SO2 NAAQS in Allegheny County, in Hazelwood, PA that encompasses the area within 
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a 2-mile radius of the Hazelwood monitor. This boundary is not an appropriate boundary

because it is too small and does not encompass any of the sources impacting the current violating 

monitor (Liberty monitor).

There are other possible boundaries that can be considered: the Pittsburgh, PA MSA and the 

Southwest Pennsylvania Air Quality Control Region (AQCR). The Pittsburgh, PA MSA 

contains seven counties: Allegheny, Armstrong, Beaver, Butler, Fayette, Washington, and 

Westmoreland. The Southwest Pennsylvania AQCR consists of Allegheny, Beaver, Butler, 

Armstrong, Indiana, Westmoreland, Fayette, Greene, and Washington Counties.

Drawing the nonattainment boundary based on the Pittsburgh, PA MSA would add significant 

areas to the proposed 1-hour SO2 nonattainment area (Figures 7-8). Portions of the Pittsburgh, 

PA MSA would extend beyond 50 km from the Liberty monitor. Using the Pittsburgh, PA MSA 

as the nonattainment boundary would include sources and areas that EPA is not prepared to 

conclude are likely to have an impact at the Liberty monitor.

Figure 7.

The Southwest Pennsylvania (SW PA) AQCR, codified in the Code of Federal Regulations 

(CFR) § 81.23, is another possible nonattainment boundary. The SW PA AQCR is similar in 

size to the Pittsburgh, PA MSA but also includes Indiana and Greene counties (Figure 8). The 

SW PA AQCR does include all counties that lie within 50 km of the Liberty monitor, but similar 
15

to the Pittsburgh, PA MSA, it includes a significant area outside this buffer that EPA is not 

prepared to conclude is likely to contain sources contributing to the violating monitor at Liberty. 

Figure 8.

Conclusion for the Allegheny Nonattainment Area

After considering the factors described above, EPA intends to find that it is appropriate to 

include Allegheny County as part of the Allegheny Nonattainment Area for the 2010 SO2

NAAQS. 

The Liberty monitor in Allegheny County, based on certified 2009-2011 air quality data, shows 

high concentration of SO2 emissions in the vicinity. Although meteorological data suggests that 

emissions from large sources south and west could potentially contribute to SO2 NAAQS 

violations in Allegheny County, based on available information, EPA is not prepared to conclude 

that emissions from these sources are contributing to the violating monitor in Allegheny County. 

Elrama Power Station in Washington County has had wet scrubbers installed since the mid 

1970’s and was scheduled to shut down in June 2012. Mitchell Power Station in Washington 

County had wet scrubbers installed in 2006 and 2007. The emissions from Monesson Coke Plant 

in Westmoreland County are relatively low, and it is likely that any impacts from these emissions 

are localized. Furthermore, the emissions from sources nearest the Liberty monitor in Allegheny 

County are likely causing the violation at the Liberty monitor. Based on the consideration of all 

the relevant and available information, as described above, EPA believes that the boundary
16

described herein encompasses the appropriate initial nonattainment area based on the violating 

monitor for the 2010 SO2 NAAQS.

Figure 9.

Technical Analysis for the Beaver Nonattainment Area

This technical analysis for the Beaver Nonattainment Area identifies the whole county with a 

monitor that violates the 2010 SO2 NAAQS, and evaluates nearby counties for contributions to 

SO2 concentrations in the area. Beaver County has two violating monitors. EPA has evaluated 

this county and all nearby counties based on the weight of evidence of the factors recommended 

in the March 24, 2011 guidance issued by EPA. 

Based on EPA's technical analysis described below, EPA agrees with Pennsylvania’s 

recommendation and intends to initially designate, based on monitored violations, Beaver 

County in Pennsylvania as nonattainment for the 2010 SO2 NAAQS as part of the Beaver

Nonattainment Area. 

Air Quality Data

This factor considers the SO2 air quality monitoring data, including design values (in ppb) 

calculated for all air quality monitors in Beaver County in the Beaver Area based on certified 
17

data for the 2009-2011 period. Figure 10 depicts the area analyzed and the location of the 

violating air quality monitors. 

 Figure 10.

The 2010 1-hour SO2 design value for the monitor located in Beaver County is shown in Table 4.

Table 4. Beaver County Monitor Trends: 1-Hour SO2 99th % and Design Value in Parts 

Per Billion (ppb)

Monitor Name Monitor 

Air Quality 

System ID

99th % Design 

Value

Design 

Value

2007 2008 2009 2010 2011 2008-10 2009-11

Hookstown 42-007-

0002

153 122 109 72 58 101 80

Brighton 

Township

42-007-

0005

170 165 176 161 136 167 158

One-hour SO2 design values at the Hookstown monitor appear to be generally falling over the 

last four years though the data are insufficient to clearly establish a definitive trend. Values at 

the Brighton Township monitor appear to be relatively unchanged. The Hookstown monitor’s 

99th % concentrations have fallen by about a factor of two over the last four years while the 

Brighton Township monitor has remained relatively stable. Monitors within the 50 kilometer 
18

zone of the violating monitors in the neighboring counties in PA (Lawrence, Allegheny and 

Washington) are not recording violations. 

Emissions and Emissions-Related Data

Evidence of SO2 emissions sources in the vicinity of a violating monitor is an important factor 

for determining whether a nearby area is contributing to a monitored violation. For this factor, 

EPA evaluated county-level emissions data for SO2 and any change in SO2 emitting activities 

since the date represented by those emissions data.

Emissions 

EPA recognizes that there might be no new information on any changes in emissions that may 

have occurred after 2008, but would consider more recent years if available. Pennsylvania did 

not provide updated emissions information, therefore EPA relied on the 2008 NEI emissions data

(NEI08V2). 

Table 5 shows total emissions of SO2 in tons per year (tpy) for violating and potentially 

contributing counties in and around the Beaver Area and sources emitting greater than 100 tpy of 

SO2 according to the 2008 NEI. 

Table 5. SO2 Emissions in the Beaver Nonattainment Area

County

Facility 

Located in 

State

Recommended 

Nonattainment 

Area?

Facility Total 

Facility SO2

Emissions 

(tpy)

Total 

County SO2

Point 

Emissions 

Name EIS Coordinates (tpy)

Beaver, PA Yes First 

Energy/Bruce 

Mansfield Plant

3853711 40.6344,

-80.42

11,019 17,584

Beaver, PA Yes Horsehead 

Corp./Monaca 

Smelter

7991511 40.67058,

-80.3365

3,320 17,584

Beaver, PA Yes AES Beaver 

Valley 

8141311 40.6558,

-80.3556

3,113 17,584

Jefferson, 

OH

Yes W.H. Sammis 

Plant

8190811 40.5308,

-80.6311

102,195 136,297

Jefferson, 

OH

Yes Cardinal Power 

Plant

8115711 40.2522,

-80.6486

33,317 136,297

Jefferson, 

OH

Yes Severstal 

Wheeling, Inc.

8190711 40.31974,

-80.6042

700 136,297

Westmoreland, PANo Arcelormittal 

Monesson 

LLC/Monesson 

Coke Plant

8330811 40.161547,

-79.883469

396 569

Brooke, 

WV

Yes Mountain State 

Carbon, LLC

4864311 40.34361,

-80.60667

731 767
19

Hancock, 

WV

Yes Arcelormittal 

Weirton Inc.

6153111 40.42194,

-80.60278

597 613

Lawrence, 

PA

No Orion Power 

Midwest/New 

Castle Power 

Plant

3776611 40.9378,

-80.3681

12,923 14,532

Lawrence, 

PA

No ESSROC/ 

Bessemer

6595011 40.9745,

-80.49011

910 14,532

Lawrence, 

PA

No CEMEX/

Wampum Cement 

Plant

6621611 40.87825,

-80.3247

674 14,532

Allegheny, 

PA

Yes Shenango Inc 7407611 40.492,

-80.07968

333 35,844

Allegheny, 

PA

Yes Bellefield Boiler 

Plant

8404711 40.442127,

-79.94913

795 35,844

Allegheny, 

PA

Yes Bay Valley 

Foods, LLC

8521211 40.45343,

-79.98584

487 35,844

Q/d Screening Analysis

Using point source emissions data, the emissions by distance (Q/d) screening methodology was 

used to identify sources within 50 kilometers (km) of a violating monitor in Beaver County. A 

total of 15 point sources emitting more than 100 tpy (from the 2008 NEI v2) are located within 

50 km of the Beaver County monitors. Of these 15 point sources, there are three sources each 

located in Beaver County, PA, Allegheny County, PA, Lawrence County, PA, and Jefferson 

County, OH. There is one source each located in Brooke County, West Virginia, one source in

Hancock County, West Virginia and one source in Washington County, PA. Following the Q/d 

methodology, we determined that eleven of the fifteen sources should be considered for 

additional review. These sources are ESSROC/Bessemer, Orion Power New Castle Power Plant, 

CEMEX/Wampum Cement Plant, Horsehead-Monaca Smelter, AES Beaver Valley, First Energy 

Bruce Mansfield Plant, W.H. Sammis Plant, Arcelormittal Weirton Inc., Mountain State Carbon, 

Severstal Wheeling, Inc., and Cardinal Power Plant (Figures 11-12).

 

 
20

Figure 11.

 Figure 12.
21

CAMD Emissions Analysis

Emissions from sources included in EPA’s CAMD database 

(http://camddataandmaps.epa.gov/gdm/index.cfm?fuseaction=emissions.wizard) were reviewed 

to determine if more recent emissions are available for sources near the Beaver County monitors.

Not all emissions sources within 50 km of the Beaver County monitors are included in the 

CAMD database; only five of the 15 sources within 50 km of the Beaver County monitors

reported their SO2 emissions to the CAMD database. These sources and their reported annual 

emissions are listed in Table 6 along with their distance from the nearest monitor in Beaver

County.

Table 6. CAMD 2008-11 Emissions Summary of SO2 Emissions in tpy

Facility County Distance*

CAMD2008CAMD2009CAMD2010CAMD2011

AES Beaver Valley Beaver 3.2 Not 

Available

3,500 1,491 3,086

First Energy/Bruce 

Mansfield 

Beaver 7.6 11,117 17,704 8,971 21,196

W.H. Sammis Plant Jefferson 11.3 102,619 73,614 12,761 4,202

Orion Power/New Castle 

Power Plant

Lawrence 28.1 12,923 7,629 5,442 7,510

Cardinal Power Plant Jefferson 36.6 32,497 34,751 32,522 25,116

*Distance from Beaver County SO2 monitor in kilometers.

Emissions Controls

Under this factor, the existing level of control of emission sources is taken into consideration. 

The emissions data used by EPA in this technical analysis represents emissions levels while 

accounting for any control strategies implemented on stationary sources in the Beaver Area up to 

and including 2008. Although EPA has not received any additional information on emissions 

reductions resulting from controls put into place after 2008, EPA has evaluated additional 

information from the 2008 NEI and CAMD.

SO2 emissions at four of the five CAMD sources have operating SO2 controls on at least some of 

their units. The Bruce Mansfield and AES Beaver Valley plants had wet scrubbers installed 

prior to 2008. The Cardinal and W. H. Sammis power plants in Jefferson County, OH recently 

installed wet scrubbers on their units. SO2 emissions at the W. H. Sammis plant have fallen 

significantly since the installation and Cardinal’s emissions have decreased as well. Declining 

emissions at the W. H. Sammis and Cardinal plants may be responsible for the declining SO2

concentrations observed at the Hookstown monitor near the PA-WV border.

Meteorology (weather/transport patterns)

Evidence of source-receptor relationships between specific emissions sources and high SO2

values at violating monitors is another important factor in determining the appropriate 
22

contributing areas and the appropriate extent of the nonattainment area boundary. For this factor, 

EPA considered data from sites that collected hourly averaged wind measurements including 

wind direction and speed for 5 years. There are two ASOS sites located within 50 km of the 

Beaver County monitors. The closest surface site is at the Pittsburgh International Airport 

located approximately 22-23 kilometers from either of the Beaver County monitors. The next 

closest ASOS site is the Wheeling/Ohio County Airport located approximately 44 and 61 

kilometers from the Beaver County monitoring sites. The closest rawinsonde site is located at 

the Pittsburgh International Airport located in western Allegheny County approximately 22-23 

km from the monitoring sites.

One-minute meteorological wind fields for the Wood County Airport site was downloaded and 

run through AERMOD’s preprocessor AERMINUTE to produce hourly averaged wind fields. 

This data was then run through Lakes Environmental’s WRPLOT software to produce wind 

roses for both sites (Figure 13). Predominant winds at the Pittsburgh International Airport were 

generally from the west over the 2006-10 time period, while winds at the Wheeling Ohio County 

Airport were generally from the southwest. Given this information, EPA is not prepared to 

conclude that large sources in Lawrence County (ie. ESSROC/Bessemer, Orion Power New 

Castle Power Plant, and CEMEX/Wampum Cement Plant) are likely to contribute to the 

violating monitors in Beaver County.

 Figure 13.
23

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

Figure 14 below depicts elevations and locations of point sources near Beaver County. The Ohio 

and Beaver rivers divide Beaver County into roughly three portions. The Ohio River traverses 

across the county in a roughly east-west direction while the Beaver River flows south into the 

Ohio River near the Borough of Beaver. The river valleys within Beaver County create sharp 

contrasts with the surrounding mountains in western Pennsylvania. Elevations in the valleys are 

in the 220-230 meter range. Higher terrain in the county rises to over 350 meters above mean 

sea level. Terrain can change quite abruptly between the rivers and the mountains. In 

neighboring Allegheny County complex valley flows have been noted. These types of flow 

regimes probably exist in the river valleys of Beaver County also. This is important because the 

vast majority of large point sources reside in the river valleys.

Figure 14.

Jurisdictional boundaries 

There is no existing nonattainment/maintenance boundary for the 1971 primary SO2 NAAQS for 

the Beaver Area, however, there are other possible boundaries that can be considered: the 

Pittsburgh, PA MSA and the Southwest Pennsylvania Intrastate AQCR. The Pittsburgh, PA 

MSA is comprised of seven counties: Allegheny, Armstrong, Beaver, Butler, Fayette, 

Washington, and Westmoreland. The Southwest Pennsylvania Intrastate AQCR consists of nine 

counties: Allegheny, Armstrong, Beaver, Butler, Fayette, Greene, Indiana, Washington, and 

Westmoreland counties.
24

The Pittsburgh, PA MSA extends beyond the 50 kilometer buffer from the Beaver County 

monitors to the east and includes sources outside of the 50 kilometer buffer (Figure 15). 

Drawing the nonattainment boundary based on the Pittsburgh, PA MSA would add additional

areas to Pennsylvania’s designation recommendation for the 1-hour SO2 nonattainment area and 

would include sources that EPA is not prepared to conclude are likely to impact the Beaver 

County monitors.

Figure 15.

The South Pennsylvania Intrastate AQCR, codified in the Code of Federal Regulations (CFR) § 

81.23, is another possible nonattainment boundary. The area is slightly larger than the 

Pittsburgh, PA MSA and includes nine counties (Figure 16). The South Pennsylvania Intrastate 

AQCR does not include all of the counties that lie within 50 km of the Beaver County monitors 

and includes areas with sources which EPA is not prepared to conclude are contributing to the 

violating monitor. For these reasons it would not be practical to use this air quality control 

region as the initial nonattainment boundary based on the violating monitor.
25

Figure 16.

Conclusion for the Beaver Nonattainment Area

After considering the factors described above, EPA intends to find that it is appropriate to 

include Beaver County in the Beaver Nonattainment Area for the 2010 SO2 NAAQS. The air 

quality monitors in Beaver County show a violation of the 2010 SO2 NAAQS, based on certified 

2009-2011 air quality data. Meteorological data suggests that emissions from large sources west 

and southwest of the monitor likely impact the monitor and contribute to SO2 NAAQS violations 

in Beaver County. Based on the consideration of all the relevant and available information, as 

described above, EPA believes that the initial boundaries described herein encompass the area 

that should be initially designated as nonattainment due to causing or contributing to the 

monitored violation of the 2010 SO2 NAAQS in the county. It should be noted that while EPA is 

not prepared to conclude that some sources located outside the county have some amount of 

impact in Beaver County, those sources are already included in proposed nonattainment areas 

(see WV recommendations) and are likely having a larger impact in their own county. 

Therefore, EPA is not prepared to conclude that neighboring areas contribute to the SO2

concentrations in Beaver County. 
26

Figure 17. 

Technical Analysis for the Indiana Nonattainment Area

This technical analysis for the Indiana Nonattainment Area identifies the whole county with a 

monitor that violates the 2010 SO2 NAAQS, and evaluates nearby counties for contributions to 

SO2 concentrations in the area. For this area, Indiana County has a violating monitor. EPA has 

evaluated this county and all other surrounding counties based on the factors recommended in 

the March 24, 2011 guidance issued by EPA. 

Based on EPA's technical analysis described below, EPA intends to expand upon Pennsylvania’s 

recommendation and intends to designate, based on the violating monitor, Indiana County in 

Pennsylvania along with Plumcreek and South Bend Townships, and Elderton Borough in 

Armstrong County, as nonattainment for the 2010 SO2 NAAQS as part of the Indiana 

Nonattainment Area. 

Air Quality Data

This factor considers the SO2 air quality monitoring data, including design values (in ppb) 

calculated for all air quality monitors within 50 kilometers of the Indiana County monitor based 

on data for the 2009-2011 period. Figure 18 depicts the area analyzed and the location of the 

violating air quality monitor. 
27

 Figure 18.

The 2010 1-hour SO2 design value for the monitor located in Indiana County is shown in Table

7.

Table7. Indiana County Monitor Trend: 1-Hour SO2 99th % and Design Value in Parts 

Per Billion (ppb)

Monitor

Name

Monitor 

Air Quality 

System ID

99th % Design 

Value

Design 

Value

2007 2008 2009 2010 2011 2008-10 2009-11

Strongstown 42-063-

0004 88 92 82 95 68 90 82

Emissions and Emissions-Related Data

Evidence of SO2 emissions sources in the vicinity of a violating monitor is an important factor 

for determining whether a nearby area is contributing to a monitored violation. For this factor, 

EPA evaluated county-level emissions data for SO2 and any change in SO2 emitting activities 

since the date represented by those emissions data.

Emissions 

EPA recognizes that there might be no new information on any changes in emissions that may 

have occurred after 2008, but would consider more recent years if available. Pennsylvania did 
28

not provide updated emissions information, therefore EPA relied on the 2008 NEI emissions data

(NEI08V2). 

Table 8 shows total emissions of SO2 in tons per year (tpy) for violating and potentially 

contributing counties in and around the Indiana County Area in Region III and sources emitting 

greater than 100 tpy of SO2 according to the 2008 NEI. 

Table 8. SO2 Emissions in the Indiana Nonattainment Area

County

Facility 

Located in 

State

Recommended 

Nonattainment 

Area?

Facility Total 

Facility 

SO2

Emissions 

(tpy)

Total 

County 

SO2 Point 

Emissions 

Name EIS Coordina (tpy) tes

Indiana, 

PA

Yes Homer City 

Generating 

Station

3005211 40.511,

-79.1968

102,486 124,326

Indiana, 

PA

Yes Seward 

Generating 

Station

3005111 40.4081,

-79.0339

15,549 124,326

Indiana, 

PA

Yes Genon

Conemaugh 

Plant

2905911 40.3842,

-79.0611

6,286 124,326

Armstrong, 

PA

No Keystone 

Power 

Station

3866111 40.6604,

-79.3411

189,983 211,810

Cambria, 

PA

No Colver 

Power 

Project

6594411 40.550378,

-78.804741

2,576 7,183

Cambria, 

PA

No Cambria 

Cogen

6594511 40.4767,

-78.7067

2,782 7,183

Cambria, 

PA

No Ebensburg 

Cogen

6594311 40.455,

-78.7472

1,815 7,183

Blair, PA No Norfolk 

Southern

Railway Co/

Juniata 

Locomotive 

Shops

4730711 40.53289,

-78.38533

392 3,955

Q/d Screening Analysis

Using point source emissions data, the emissions by distance (Q/d) screening methodology was 

used to identify sources for further review within 50 kilometers (km) of a violating monitor in 

Indiana County. A total of eight point sources emitting more than 100 tpy (from the 2008 NEI 

v2) are located within 50 km of the monitor in Indiana County. Of these eight point sources, 

there are three sources each located in Cambria and Indiana counties and one source each in 

Armstrong and Blair Counties. Following the Q/d methodology, we determined that seven of the 

eight sources should be further reviewed. These sources are Keystone, Homer City Generating 
29

Station, Seward Power Plant, Conemaugh, Colver Power Project, Cambria Cogen, and 

Ebensburg Cogen (Figures 19-20).

Figure 19.

Figure 20.
30

CAMD Emissions Analysis

Emissions from sources included in EPA’s CAMD database 

(http://camddataandmaps.epa.gov/gdm/index.cfm?fuseaction=emissions.wizard) were reviewed 

to see if more recent emissions are available for sources near the Indiana County, PA monitor. 

Nearly all of the emission sources within 50 km of the Indiana County monitor are included in 

the CAMD data base since the monitor is essentially surrounded by electric-generating units.

Table 9. CAMD 2008-11 Emissions Summary of SO2 Emissions in tpy

Facility County Distance*

CAMD2008CAMD2009CAMD2010CAMD2011

Colver Power Project Cambria 10.3

Not 

Available 30,759 2,901 2,881

Ebensburg Cogen Cambria 18.9

Not 

Available 2,044 2,404 1,937

Seward Power Plant Indiana 19.8 7,771 7,756 8,458 7,003

Cambria Cogen Cambria 20.4

Not 

Available 6,947 2,070 1,942

Conemaugh Indiana 23.2 6,282 7,222 7,056 7,189

Homer City Generating 

Station Indiana 24.1 102,484 101,334 112,951 83,596

Keystone Armstrong 37.1 189,994 113,137 39,114 46,441

*Distance from Indiana County, PA SO2 monitor in kilometers.

Emissions Controls

Under this factor, the existing level of control of emission sources is taken into consideration. 

The emissions data used by EPA in this technical analysis represents emissions levels while 

accounting for any control strategies implemented on stationary sources in the Indiana Area up to 

and including 2008. Although EPA has not received any additional information on emissions 

reductions resulting from controls put into place after 2008, EPA has collected additional 

information from the 2008 NEI and CAMD. 

Our review of the coal-fired EGU sources within 50 km of the Indiana County monitor indicates 

that all of the facilities have some sort of SO2 emission controls currently operating or planned to 

be operating (as of 2010). Only two sources were projected to have controls installed after 2008 

(Keystone and Homer City). According to EPA’s National Electric Energy Data System 

(NEEDS) database (http://www.epa.gov/airmarkt/progsregs/epaipm/BaseCasev410.html#needs), the only uncontrolled units within 50 km of the Indiana County 

monitor are two units at Homer City (see Table 10 below).
31

Table 10. Summary of Controls Within 50 km of Strongstown Monitor (from NEEDS 

database) 

Plant Name

Unit 

ID County

Capacity 

(MW)

On 

Line 

Year

Modeled 

Fuels Wet/DryScrubber

Scrubber

Online

Keystone 1 Armstrong 850 1967 Bituminous Wet Scrubber 2009

Keystone 2 Armstrong 850 1968 Bituminous Wet Scrubber 2009

Cambria Cogen B1 Cambria 44 1991 Waste Coal Reagent Injection

Cambria Cogen B2 Cambria 44 1991 Waste Coal Reagent Injection

Colver Power 

Project ABB01 Cambria 110 1995 Waste Coal Reagent Injection

Ebensburg Power 031 Cambria 49.5 1990 Waste Coal Reagent Injection

Conemaugh 2 Indiana 850 1971 Bituminous Wet Scrubber 1995

Conemaugh 1 Indiana 850 1970 Bituminous Wet Scrubber 1994

Homer City 

Station 1 Indiana 620 1969 Bituminous

Homer City 

Station 2 Indiana 614 1970 Bituminous

Homer City 

Station 3 Indiana 650 1977 Bituminous Wet Scrubber 2001

Seward 1 Indiana 260.5 2004 Waste Coal Dry Scrubber 2004

Seward 2 Indiana 260.5 2003 Waste Coal Dry Scrubber 2004

Meteorology (weather/transport patterns)

Evidence of source-receptor relationships between specific emissions sources and high SO2

values at violating monitors is another important factor in determining the appropriate 

contributing areas and the appropriate extent of the nonattainment area boundary. For this factor, 

EPA considered data from sites that collected hourly averaged wind measurements including 

wind direction and speed for 5 years. There is only one ASOS site located within 50 km of the 

Indiana County monitor. The closest surface site is the John Murtha Johnstown-Cambria County 

Airport located approximately 30 kilometers south-southeast of the Indiana County monitor. 

The closest rawinsonde site is located at the Pittsburgh International Airport located 

approximately 105 km west of the Indiana County monitor.

One-minute meteorological wind fields for the Johnstown-Cambria County Airport site were

downloaded and run through AERMOD’s preprocessor AERMINUTE to produce hourly 

averaged wind fields. This data was then run through Lakes Environmental’s WRPLOT 

software to produce wind roses for the Johnstown-Cambria County Airport (Figure 21). 

Predominant winds generally ranged from the west over the 2006-10 time period. Given this 

information, EPA is not prepared to conclude that large sources in Cambria County (ie. Colver 

Power Plant, Cambria Cogen, and Ebensburg Cogen) are likely contributing to the violating 

monitor in Indiana County.
32

 Figure 21.

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

Figure 22 below depicts elevations and locations of point sources near Indiana County. Indiana 

County is located east of Pittsburgh in the Allegheny Mountains. The Conemaugh River forms 

the southern boundary of the county. Terrain elevations generally rise as you move east 

culminating along the Chestnut Ridge that marks the eastern boundary of Indiana County. 

Elevations rise above 600 meters along this ridge with the highest elevations in Pennsylvania 

located in neighboring Cambria and Somerset Counties.

 
33

Figure 22.

Jurisdictional boundaries 

There is no existing nonattainment/maintenance boundary for the previous 1971 primary SO2

NAAQS for the Indiana Area and Indiana County is not part of any MSA (as of 2009) but is 

designated as a separate Micropolitan Statistical Area. There is another possible boundary, 

however, that can be considered: the Southwest Pennsylvania Intrastate AQCR, codified in the 

Code of Federal Regulations (CFR) § 81.23. The Southwest Pennsylvania Intrastate AQCR 

consists of Allegheny, Armstrong, Beaver, Butler, Fayette, Greene, Indiana, Washington and 

Westmoreland Counties (Figure 23). The Southwest Pennsylvania Intrastate AQCR does not 

include all of the counties that lie within 50 km of the Indiana County monitor and includes areas 

with sources which EPA is not prepared to conclude are likely to contribute to the violating 

monitor in Indiana County. For these reasons it would not be practical to use this AQCR as the 

initial nonattainment boundary. 

 
34

Figure 23.

Other Information

There have been a number of studies of the Chestnut Ridge area due to the number of large coalfired power plants in the region. One of the earliest studies was done by the US Department of 

Health, Education and Welfare in 1970 (Large Power Plant Effluent Study (LAPPES), National 

Air Pollution Control Administration). A general description of the region’s coal fired power 

plants from this report is included here:

“[T]hree new mine-mouth stations, Keystone, Homer City and Conemaugh are located 

approximately equidistant along a NW-SE line 39 kilometers long about 80 kilometers 

ENE of Pittsburgh. These three stations, combined with the nearby Seward and 

Shawville stations, form a complex whose total annual production of 47,380,305 

megawatt hours exceeds the total electrical output of all but 11 nations of the world.”

Modeling analyses concerning power plants in the Chestnut Ridge region were conducted in the 

1990s and in 2003 at the behest of PADEP to examine compliance with the SO2 NAAQS.

1

 The 

resulting reports examined impacts on the Chestnut Ridge from some of the larger power plants 

that lay to the west. A quick check of plant elevations and stack heights revealed that stack tops 

at Homer City and Keystone are roughly in line with the elevations at the Strongstown SO2

 

1

“AERMOD Modeling Analyses for SO2 NAAQS Compliance for Power Plants in the Laurel Ridge and Chestnut 

Ridge Region of Pennsylvania (TRC Project No. 33275),” March 2003; Prepared by RC Environmental Corp.
35

monitor as well as the rest of the Chestnut Ridge. This suggests that violations could be 

occurring in most of the elevated terrain in eastern Indiana County due to emissions from these 

power plants.

Conclusion for the Indiana Nonattainment Area

After considering the factors described above, EPA intends to find that it is appropriate to 

initially include, based on the violating monitor, Indiana County and a portion of Armstrong 

County (Table 1) in the Indiana Nonattainment Area for the 2010 SO2 NAAQS. The air quality 

monitor in Indiana County shows a violation of the 2010 SO2 NAAQS, based on 2009-2011 air 

quality data. The nearby Keystone Plant in neighboring Armstrong County likely contributes to 

nonattainment in Indiana County as well. Previous studies have shown that stack tops (of Homer 

City and Keystone) are at elevations in line with that of the Strongstown monitor in Indiana 

County. Meteorological data suggests that emissions from large sources west of the monitor 

likely impact the monitor and contribute to SO2 NAAQS violations in Indiana County. Based on 

the consideration of all the relevant and available information, as described above, EPA believes 

that the initial boundaries described herein encompass the area that should be initially designated 

as nonattainment due to causing or contributing to the monitored violation of the 2010 SO2

NAAQS in the county. 

Figure 24.
36

Technical Analysis for the Warren Nonattainment Area

This technical analysis for the Warren Nonattainment Area identifies the whole county with a 

monitor that violates the 2010 SO2 NAAQS, and evaluates nearby counties for contributions to 

SO2 concentrations in the area. For this area, Warren County has a violating monitor. EPA has 

evaluated this county and all other surrounding counties based on the factors recommended in 

the March 24, 2011 guidance issued by EPA. 

Based on EPA's technical analysis described below, EPA agrees with Pennsylvania’s 

recommendation and intends to designate Warren County in Pennsylvania as nonattainment for 

the 2010 SO2 NAAQS as part of the Warren Nonattainment Area. 

Air Quality Data

This factor considers the SO2 air quality monitoring data, including the design value (in ppb) 

calculated for the air quality monitor in Warren County in the Warren Area based on certified 

data for the 2009-2011 period. Figure 24 depicts the area analyzed and the location of the 

violating air quality monitor. 

 

Figure 25.
37

The 2010 1-hour SO2 design value for the monitor located in Warren County is shown in Table

11.

Table 11. Warren County Monitor Trend: 1-Hour SO2 99th % and Design Value in Parts 

Per Billion (ppb)

Monitor Name Monitor 

Air Quality 

System ID

99th % Design 

Value

Design 

Value

2007 2008 2009 2010 2011 2008-10 2009-11

Warren 42-123-

0004 153 146 113 109 94 123 105

One-hour SO2 design values at the Warren County monitor have fallen slightly over the last four 

years. This decline may be attributed to the recent economic recession, which started in 2008. 

Any statistical trend that could be gleaned from the monitor data, however, should be viewed 

with caution due to the minimal amount of data currently available.

Emissions and Emissions-Related Data

Evidence of SO2 emissions sources in the vicinity of a violating monitor is an important factor 

for determining whether a nearby area is contributing to a monitored violation. For this factor, 

EPA evaluated county-level emissions data for SO2 and any change in SO2 emitting activities 

since the date represented by those emissions data.

Emissions 

EPA recognizes that there might be no new information on any changes in emissions that may 

have occurred after 2008, but would consider more recent years if available. Pennsylvania did 

not provide updated emissions information, therefore EPA relied on the 2008 NEI emissions data

(NEI08V2). 

Table 12 shows total emissions of SO2 in tons per year (tpy) for violating and potentially 

contributing counties in and around the Warren Area in Region III and sources emitting greater 

than 100 tpy of SO2 according to the 2008 NEI. 

Table 12. SO2 Emissions in the Warren Nonattainment Area

County

Facility 

Located in 

State

Recommended 

Nonattainment 

Area?

Facility Total 

Facility SO2

Emissions 

(tpy)

Total 

County SO2

Point 

Emissions 

(tpy)

Name EIS Coordinates

Warren, PA Yes United 

Refining 

Warren 

Plant

4966711 41.82992,

-79.12444

1,612 1,616
38

McKean, 

PA

No American 

Refining 

Group/ 

Bradford

6532511 41.96686,

-78.63013

1,479 3,372

Chautauqua, 

NY

No Samuel A. 

Carlson 

Generating 

Station

7806011 42.093543,

-79.247679

3,736 14,412

Q/d Screening Analysis

Using point source emissions data, the emissions by distance (Q/d) screening methodology was 

used to identify sources for additional review within 50 km of a violating monitor in Warren 

County. A total of three point sources emitting more than 100 tpy (from the 2008 NEI v2) are 

located within 50 km of the monitor in Warren County. Sources are located in Warren and 

McKean counties in Pennsylvania and Chautauqua County, NY. Following the Q/d 

methodology, we determined that all three sources should be further reviewed. These sources are 

United Refining Warren Plant, American Refining Group-Bradford, and Samuel A. Carlson 

Generating Station (Figures 26- 27).

 

Figure 26.

 
39

Figure 27. 

CAMD Emissions Analysis

Emissions from sources included in EPA’s CAMD database 

(http://camddataandmaps.epa.gov/gdm/index.cfm?fuseaction=emissions.wizard) were reviewed 

to see if more recent emissions are available for sources near the Warren County, PA monitor. 

Only the Samuel A. Carlson Generating Station in Chautauqua County, NY reported its SO2

emissions to CAMD.

Table 13. CAMD 2008-11 Emissions Summary of SO2 Emissions in tpy

Facility County Distance*

CAMD2008CAMD2009CAMD2010CAMD2011

Samuel A. Carlson 

Generating Station Chautauqua 28.41 3,736 1,885 1,272 664

*Distance from Warren County SO2 monitor in kilometers.

Emissions Controls

Under this factor, EPA considers the existing level of control of emission sources. No SO2

emission controls were noted on any of the sources within 50 kilometers of the Warren County 

monitor.
40

Meteorology (weather/transport patterns)

Evidence of source-receptor relationships between specific emissions sources and high SO2

values at violating monitors is another important factor in determining the appropriate 

contributing areas and the appropriate extent of the nonattainment area boundary. For this factor, 

EPA considered data from sites that collected hourly averaged wind measurements including 

wind direction and speed for 5 years. There is only one ASOS site located within 50 km of the 

Warren County monitor. The closest surface site is the Bradford Regional Airport located 

approximately 44 kilometers east-southeast of the Warren County monitor. The closest 

rawinsonde site is located at the Buffalo Niagara International Airport located approximately 130 

km north of the Warren County monitor.

One-minute meteorological wind fields for the Bradford Regional Airport site were downloaded 

and run through AERMOD’s preprocessor AERMINUTE to produce hourly averaged wind 

fields. This data was then run through Lakes Environmental’s WRPLOT software to produce a 

wind rose for the site (Figure 28). Winds at the Bradford Regional Airport showed a bimodal 

distribution with the predominant winds coming from the west to northwest with a second 

distribution coming from the southeast direction during the 2006-10 time period. Given this 

information, EPA is not prepared to conclude that the large source in McKean County (i.e.,

American Refining Group) is likely to be adversely impacting the monitor in Warren County. 

Pennsylvania’s recommendation provided meteorological information from the Warren 

monitoring location, which is situated within a valley approximately 4 kilometers west of United 

Refining. Their analysis shows that high SO2 concentrations at the monitoring site are likely 

driven by the source that is within close proximity to the air monitor. 

Figure 28.
41

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

Figure 29 below depicts elevations and locations of point sources in the Warren County area. 

Warren County is located in northwest Pennsylvania in the state’s Allegheny Plateau Region. 

The area is made up of dendritic river valleys cut by the Allegheny River and its tributaries 

interspersed with higher terrain. Elevations vary from over 600 meters above mean sea level 

along the plateau to just under 325 meters along the Allegheny River as it drains south into 

Forest County. Higher terrain lies to the west in McKean County with elevations generally 

decreasing as one moves west towards Lake Erie.

Pennsylvania’s recommendation noted the influence of local topography on the Warren County 

monitor. Their analysis examined the monitored wind fields and the timing of exceedances and 

concluded that local topographically-induced meteorological conditions, mainly overnight 

inversions and complex drainage flows, coupled with a nearby local source contributed to the 

monitor’s noncompliance with the 1-hour SO2 NAAQS. Given this information, EPA is not 

prepared to conclude that emissions from the Samuel A. Carlson Generating Station in 

Chautauqua County, NY nor American Refining-Bradford in McKean County, PA are likely to 

contribute to the violating monitor in Warren County, PA.

 

Figure 29.
42

Jurisdictional boundaries 

There are two existing maintenance boundaries (i.e., previous nonattainment areas) in Warren 

County for the 1971 primary SO2 NAAQS. One consists of Warren Borough, Pleasant 

Township, and Glad Township, while the other consists of only Conewango Township. These 

boundaries are not appropriate boundaries because they are too small and would not include 

large sources that are likely to contribute to nonattainment in Warren County.

Although Warren County is not part of any MSA (as of 2009) and is designated as a separate 

MSA, there is another possible boundary that can be considered: Northwest PennsylvaniaYoungstown Interstate AQCR, codified in the Code of Federal Regulations (CFR) § 81.74. The 

Northwest Pennsylvania-Youngstown Interstate AQCR consists of fourteen counties in 

Pennsylvania and Ohio: Cameron, Clairion, Clearfield, Crawford, Elk, Erie, Forest, Jefferson, 

Lawrence, McKean, Mercer, Potter, Venango, and Warren Counties in PA, along with 

Ashtabula, Mahoning and Trumbull Counties in Ohio (Figure 30). The Northwest PennsylvaniaYoungstown Interstate AQCR does not include all of the counties that lie within 50 km of the 

Warren County monitor and includes areas with sources which EPA is not prepared to conclude 

are contributing to the violating monitor. For these reasons, it would not be practical to use this 

AQCR as the initial nonattainment boundary.

 Figure 30.
43

Conclusion for the Warren Nonattainment Area

After considering the factors described above, EPA intends to find that it is appropriate to 

include, based on the violating monitor, Warren County in the Warren Nonattainment Area for 

the 2010 SO2 NAAQS. The air quality monitor in Warren County shows a violation of the 2010 

SO2 NAAQS, based on certified 2009-2011 air quality data. EPA is not prepared to find that any 

nearby areas contribute to the monitored violations in Warren County. The monitor in Warren 

County, based on certified 2009-2011 air quality data, shows high concentrations of SO2

emissions in the vicinity, and both meteorological and topographical data suggest that emissions 

from the large source within close proximity of the monitor likely impact the monitor and 

contribute to SO2 NAAQS violations in Warren County. Additionally, EPA is not prepared to 

conclude that, based on meteorological and topographical data, the large sources in neighboring 

counties are likely to impact the monitor in Warren County. The monitored violation in Warren 

County is likely driven by the source within close proximity of the monitor (i.e. United RefiningWarren Plant). Based on the consideration of all the relevant and available information, as 

described above, EPA believes that the boundaries described herein encompass the appropriate 

initial area that does not meet the 2010 SO2 NAAQS. 

Figure 31.
44

EPA’s Area Designations Conclusion for Pennsylvania

EPA has reviewed the information above and intends to find that it is appropriate to designate

based on monitored violations the counties and/or portions of counties listed in Table 1 as 

nonattainment for the 2010 SO2 NAAQS. EPA intends to designate Allegheny, Beaver, Indiana, 

Warren Counties, and a portion of Armstrong County (Plumcreek and South Bend Townships 

and Elderton Borough) as nonattainment after considering the factors and information described

in this technical support document. The intended nonattainment area boundaries that EPA 

describes above are based on the five factors which include: air quality data, emissions-related 

data, meteorology, geography/topography, and jurisdictional boundaries. Based on the 

consideration of all the relevant and available information, as described above, EPA believes that 

the boundaries described herein encompass the area that does not meet (or that contributes to 

ambient air quality in a nearby area that should be initially designated as nonattainment due to 

causing or contributing to the monitored violation of the 2010 SO2 NAAQS in the county.