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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 designate areas as either 

“nonattainment,” “attainment,” or “unclassifiable” 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 (“Commonwealth or “Pennsylvania” or “PA”) that EPA is 

initially designating nonattainment based on monitored violations. EPA is not yet prepared to 

designate other areas in Pennsylvania, and will address them in a future final designations action.

Pennsylvania submitted designation recommendations on June 23, 2011. On February 6, 2013, 

EPA sent out a letter with intended designations for Pennsylvania. Pennsylvania responded in a 

letter dated April 8, 2013. Table 1 below identifies the portions of counties in the 

Commonwealth that EPA is initially designating “nonattainment” based on monitored violations.

In Pennsylvania’s April 8, 2013 letter, they indicated that only partial counties should be 

included in the proposed Allegheny, Beaver, and Warren Nonattainment Areas and that no 

portion of Armstrong County should be included in the Indiana County Nonattainment Area. In 

addition to comments from the Commonwealth, EPA received comments from NRG Energy 

supporting EPA’s proposed nonattainment area for Allegheny County in so far as a portion of 

Washington County should not be included in the nonattainment area. EPA also received 

comments from the Allegheny County Health Department and U. S. Steel which indicated that 

while a portion of Allegheny County should be nonattainment, a portion of Washington County 

PA should be part of the Allegheny County nonattainment area. Specific technical comments 

from the Commonwealth and the additional commenters will be addressed in this TSD in the 

discussion for the appropriate nonattainment areas. 

Table 1. Nonattainment Area Designations for Pennsylvania

Area 

Pennsylvania’s 

Recommended 

Designations of 

Areas/Counties

EPA’s Designations of 

Areas/Counties

Allegheny, PA 

 Allegheny County (partial) 

City of Clairton, City of 

Duquesne, City of Mckeesport, 

Borough of Braddock, 

Nonattainment** Nonattainment
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Borough of Dravosburg, 

Borough of East Mckeesport, 

Borough of East Pittsburgh, 

Borough of Elizabeth, Borough 

of Glassport, Borough of 

Jefferson Hills, Borough of 

Liberty, Borough of Lincoln, 

Borough of North Braddock, 

Borough of Pleasant Hills, 

Borough of Port Vue, Borough 

of Versailles, Borough of Wall, 

Borough of West Elizabeth, 

Borough of West Mifflin, 

Elizabeth Township, Forward 

Township, North Versailles 

Township

Beaver, PA 

 Beaver County (partial)

Industry Borough, Midland 

Borough, Shippingport 

Borough, Brighton Township, 

Potter Township and Vanport 

Township

Nonattainment Nonattainment 

Indiana, PA

 Indiana County

 Armstrong County (partial)

Elderton Borough 

Plumcreek Township

South Bend Township

 

Nonattainment

Unclassifiable

Nonattainment

Nonattainment

Warren, PA

 Warren County (partial)

City of Warren, Conewago 

Township, Glade Township, 

Pleasant Township

Nonattainment Nonattainment

** PA’s response did not include the following portions of Allegheny County: City of Duquesne, 

Borough of Braddock, Borough of East Mckeesport, Borough of East Pittsburgh, Borough of 

North Braddock, Borough of Wall, North Versailles Township

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 met at an ambient air quality 

monitoring site when the 3-year average of the annual 99th percentile of the daily maximum 1-

hour average concentrations does not exceed 75 ppb, as determined in accordance with Appendix 

T of 40 CFR part 50. 40 CFR 50.17(a)-(b). EPA has determined that this is the level necessary 
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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 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 tribal government 

does not submit designation recommendations, EPA will promulgate the designations that it 

deems appropriate. States and tribal governments were given an opportunity to demonstrate why 

any proposed modification is inappropriate where their recommendations disagreed with EPA’s 

intended designations. 

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 evaluated

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); and 5) jurisdictional 

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

metropolitan planning organization), among any other information deemed relevant to 

establishing appropriate area 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, tribal governments and/or 

EPA may support a different boundary than a default county boundary.

In this technical support document (TSD), EPA discusses its review and technical analysis of the 

recommendations submitted by the Commonwealth and other commenters in response to EPA’s 

proposed nonattainment area designations for Pennsylvania for the 1-hour SO2 standard which 

were also made available for public comment (78 FR 11124) on February 15, 2013. 

Definitions of important terms used in this document:
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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. 

2) Recommended nonattainment area – an area a state or tribal government has recommended 

to EPA to 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. 

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

designation recommendation. On April 8, 2013, the Commonwealth submitted a response to 

EPA’s 120-day letter and recommended that only portions of Allegheny County, Beaver and 

Warren Counties be designated as nonattainment. Pennsylvania also indicated that no portion of 

Armstrong County should be designated nonattainment. EPA received additional comments on 

the proposed Allegheny County nonattainment area from three commenters. 

Based on EPA’s technical analysis, EPA is initially designating four areas as nonattainment 

(Table 1) based on monitored violations of the NAAQS: 1) the Allegheny, PA Nonattainment

Area. which consists of the following portions of the county: City of Clairton, City of Duquesne, 

City of McKeesport, Borough of Braddock, Borough of Dravosburg, Borough of East 

McKeesport, Borough of East Pittsburgh, Borough of Elizabeth, Borough of Glassport, Borough 

of Jefferson Hills, Borough of Liberty, Borough of Lincoln, Borough of North Braddock, 

Borough of Pleasant Hills, Borough of Port Vue, Borough of Versailles, Borough of Wall, 

Borough of West Elizabeth, Borough of West Mifflin, Elizabeth Township, Forward Township, 

and North Versailles Township; 2) the Beaver PA Nonattainment Area, which consists of:

Industry Borough, Midland Borough, Shippingport Borough, Brighton Township, Potter 

Township and Vanport Township; 3) the Indiana PA Nonattainment Area, which consists of 

Indiana County in its entirety and the following portions of Armstrong County: Elderton 
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Borough, Plumcreek Township and South Bend Township; and 4) the Warren PA 

Nonattainment Area, which consists of the City of Warren, Conewago Township, Glade 

Township, and Pleasant Township.

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 three year period 2009-2011. 

Additional information provided regarding monitored data and analysis of data from 

2010-2012 from the Commonwealth in their response to EPA’s 120 day letters as well as 

information provided by other commenters was also considered. 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 determined in accordance with Appendix T of 40 CFR part 

50. 40 CFR 50.17(a)-(b). 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 75% of its hours

are complete. Data substitution tests are described in Appendix T of 40 CFR part 50. 

Areas where monitoring data 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). EPA reviewed data for the point source and non point 

source categories from version 3 of the 2008 National Emissions Inventory (NEI) which 

is the most current version of the national inventory now available (see

http://www.epa.gov/ttn/chief/net/2008inventory.html), additional emissions information 

from the Commonwealth and other commenters was considered as well as information

from the EPA 2012 Clean Air Markets Division (CAMD) and Pennsylvania’s EFACTS 

system. Generally, the point source inventory represents the bulk of the SO2 emissions in

Pennsylvania.

EPA examined recent revisions to the 2008 NEI (version 3) and 2012 CAMD emissions 

data and emissions changes appeared to be minimal.

3. Meteorology (weather/transport patterns). EPA originally evaluated meteorological data 

to help determine how weather conditions, including wind speed and direction, affect 

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 
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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.

The Commonwealth also included discussions on impacts of temperature inversions and 

air-parcel trajectories from the National Oceanic and Atmospheric Administration’s 

(NOAA) Air Resource Lab’s HYbrid Single-Particle Lagrangian Integrated Trajectory or 

HYSPLIT model. EPA will discuss some of these analyses in the individual 

nonattainment areas sections of this document.

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

the physical land features and their possible impacts SO2 concentrations. 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. EPA also 

considered any additional information provided by the Commonwealth and other 

commenter’s in relation to specific areas. 

5. Jurisdictional boundaries As discussed in the Pennsylvania TSD that was included in the 

docket as part of EPA’s proposal for nonattainment areas (78 FR 11124) on February 15, 

2013, EPA reviewed several possible boundaries but generally used county boundaries for 

the proposed Pennsylvania nonattainment areas. In response to EPA’s proposal, 

Pennsylvania generally recommended that the boundaries for all but one nonattainment 

area (Indiana) consist of partial counties and that boundaries could be determined based 

on more local jurisdictions such as cities, boroughs, and townships. 

Technical Analysis for the Allegheny PA Nonattainment Area

In EPA’s 120 day letter, EPA proposed that the initial Allegheny PA Nonattainment Area consist 

of Allegheny County in its entirety. In response to EPA’s 120 day letter, the Commonwealth and 

the Allegheny County Health Department (ACHD) recommended that only a portion of 

Allegheny County be included in the final nonattainment area. ACHD also requested that a 

portion of Washington County also be included in the nonattainment area. A commenter on 

behalf of US Steel also indicated that a portion of Washington County should be included while 

a commenter on behalf of NRG Energy agreed with EPA’s original proposal that did not include 

areas outside Allegheny County. Each commenter provided some information to support their 

response. 
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Based on EPA’s technical analysis described below, EPA concurs with the Commonwealth and 

ACHD to the extent that only a portion of Allegheny County needs to be included as part of this 

initial nonattainment designation. However, EPA is adding some additional municipalities in 

Allegheny County to the nonattainment area to those municipalities suggested by the 

Commonwealth and ACHD. See the information in Table 1for detailed information on

municipalities included in the nonattainment area. In regard to Washington County, EPA agrees 

with the Commonwealth and generally NRG Energy and is not adding a portion of Washington 

County to the initial nonattainment area as suggested by ACHD and U. S. Steel. The EPA will 

address these and other initially excluded areas and their sources in a future final designations 

action. 

Air Quality Data 

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

County based on certified data for the 2009-2011 time period. As supporting information, the 

Commonwealth and ACDH reported that the preliminary 2010-12 design value at the Liberty 

monitor, located in the southeast portion of Allegheny County was 141 ppb. Monitors in other 

portions of Allegheny County and nearby Washington County do not show violations of the 

standard and have significantly lower concentrations than Liberty. Monitors not showing 

violations of the 1-hour SO2 NAAQS in other portions of the county support reducing the initial 

nonattainment area to include only portions of southeastern Allegheny County.

One-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 39 28 48 40

*Monitor in bold has the highest 2009-2011 design value in the respective county.

The Commonwealth also included an analysis of exceedances from 2010-12. They noted that 

exceedances at the Liberty monitor primarily occurred during the overnight hours and further 
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explained that this tendency for exceedances to occur during the overnight hours was due to 

nocturnal inversions interacting with local emission sources. EPA reviewed exceedances from 

2007 to 2011 and found a similar pattern with elevated SO2 concentrations occurring at the 

Liberty monitor primarily during the overnight hours. Similar patterns are also observed in 

Liberty’s PM-2.5 concentrations.

Emissions and Emissions-Related Data

Emissions 

Table 3 shows total emissions of SO2 in tons per year (tpy) for sources in and around the

Allegheny Area and sources emitting or contributing greater than 100 tpy of SO2 according to 

the 2008 NEI. 

Table 3. SO2 Emissions in Allegheny Area

County

Facility 

Located in 

State’s 

Original

Recommended 

Nonattainment 

Area?

Facility Name

2008 NEI 

Total 

Facility

SO2

Emissions 

(tpy)

2011 

eFACTS 

Total 

Facility SO2

Emissions 

(tpy) **

CAMD 2012 

SO2 Emissions 

(tpy) except as 

noted

Allegheny Yes Us Steel 

Corporation -

Irvin Plant

475 419

Allegheny Yes Shenango Inc 333 372

Allegheny Yes Orion Power 

Midwest 

Cheswick 

Station

30,300 9,290 1,911

Allegheny Yes Uss Corporation 

- Edgar 

Thomson Works

1,536 1,279

Allegheny Yes Uss - Clairton 

Works

1,517 1,468

Allegheny Yes Bellefield Boiler 

Plant

795 0.4

Allegheny Yes Bay Valley 

Foods, LLC

487 313

Washington No Orion 

Power/Elrama 

Power Station

2,572 428 250

Washington No Allegheny 

Energy/Mitchell 

Power Station

934 864 1,570

Westmoreland No Arcelormittal 

Monesson 

396
9

LLC/Monesson 

Coke Plant

Washington No Langeloth 

Metallurgical

186 31

** 2011 SO2 emssions from PA DEP eFACTS 

(http://www.ahs.dep.pa.gov/eFACTSWeb/criteria_facilityemissions.aspx)

 

The Commonwealth provided an analysis of exceedances in 2012 at the Liberty monitor and 

daily emissions from the Elrama facility. It should be noted that according to the comment letter 

from NRG Energy and other comments from the Commonwealth that the Elrama facility has not 

been operating since June 2012. However, CAMD indicates that Elrama Unit 4 operated for 342 

hours in the third quarter of 2012 but no units at Elrama operated since that time through first 

quarter of 2013. NRG also indicated that more exeedances were recorded at the Liberty monitor

between 2010-2012 versus 2007-2009 even though emissions from the Elrama facility were 

much higher during 2007-2009. The Commonwealth also provided analyses showing that on 23 

days of exceedances at the Liberty monitor in 2012 the Elrama facility was only operating on 

three of those days and emitted less than 10 tons of SO2 on any of the three days. While ACHD 

reviewed 2010 emissions data, they simply identified sources that would need further analysis 

based on EPA’s Q/d methodology. U. S. Steel also generally contends that the area where the 

Elrama facility is located should be included in the nonattainment area but this view is not 

informed by more recent information such as the analysis provided by the Commonwealth 

indicating that more recent emissions from Elrama appeared to have little impact on exceedances 

of the standard especially in 2012. Therefore there does not appear to be sufficient information 

to include the Elrama facility in Washington County in the initial nonattainment area at this time, 

and we will further address this source in a future final designations action. 

In addition to Elrama, EPA extracted the Mitchell power plant’s SO2 emissions data from its 

CAMD website for 2011 and 2012. Mitchell’s emissions (from CAMD) increased from 862 tpy 

in 2011 to 1,570 tpy in 2012. This was primarily due to an increase in hours of operation for 

Mitchell’s large coal unit. This unit was operated for 4,756 hrs in 2011 and 6,047 hrs in 2012. 

Averaged annual emissions at Mitchell were relatively unchanged between 2011 (0.21 

lbs/MMbtu) and 2012 (0.25 lbs/MMbtu). Mitchell’s coal unit is controlled and appears to be 

well operated, achieving about 90% removal efficiency on average. EPA does not feel there is 

sufficient information to include the Mitchell power plant in the initial nonattainment area at this 

time, and will further address this source in a future final designations action. Also other sources 

in Washington county and Westmoreland County in the table above appear to have relatively 

small emissions and are not likely to be contributing to violations in Allegheny County. These 

areas and sources will be addressed in a future designations action. 

The Cheswick power plant appears to be the largest SO2 emission source in Allegheny County. 

Cheswick’s emissions, however, have been significantly scaled back since installation and 

operation of its SO2 control equipment. Information from EPA’s CAMD website indicates a 

large decrease in between the 2011 and 2012 annual SO2 emissions which is primarily due to 

increased control efficiency. In 2011, Cheswick’s coal-fired unit ran for 6,160 hrs at an annually 

averaged emission rate of 0.71 lbs/MMbtu. In 2012, Cheswick’s coal unit ran slightly less at 
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5,715 hrs with an annually averaged emission rate of 0.15 lbs/MMbtu. In light of Cheswick’s 

lower emission rates, distance (~24 km) from the Liberty monitor, and minimal change in the 

monitored values at Liberty, EPA is not prepared at this time to include this source in the initial

nonattainment area, and will further address it in a future final designations action.

EPA summarized SO2 emissions from PA DEP’s eFACTS in table 3. After the Cheswick power 

plant, the next three largest SO2 emission sources are U.S. Steel facilities. These include the 

Clariton Coke Works, the Edgar Thompson Works and the Irvin Plant, which are considered part 

of U.S. Steel’s Mon Valley Works. County emissions suggest these three U.S. steel facilities 

should be included in the nonattainment area.

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 1.

Figure 1.
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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).

The Commonwealth conducted an analysis of the Liberty monitor’s wind measurements from 

2010 through 2012. They specifically examined winds during hours in which the Liberty 

monitor exceeded the 1-hr SO2 NAAQS and then compared them to the entire data set. Winds 

were mainly from the southwest during exceedance hours. A similar wind direction tendency 

was noted for the entire data set though it was not as pronounced as the exceedance only wind 

fields.

EPA conducted a similar analysis using winds from the Allegheny County Airport, located about 

4.5 km to the northwest of the Liberty monitor. Pennsylvania noted that the Allegheny Airport 

sits at a higher elevation than the Liberty monitor and therefore may not measure some of the 

local wind patterns that are thought to contribute to the Liberty monitor’s exceedances of the 1-

hr SO2 NAAQS.

EPA downloaded the 1-minute ASOS files for 2009 through 2011 and processed them into onehour wind files using its AERMET preprocessor. Adjustments were made to the ASOS wind 

data to account for local time. The one-hour AERMET wind files were then processed using 
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Lakes Environmental’s WRPLOT program to produce a wind rose for those hours (with valid 

wind data) that exceeded the 1-hr SO2 NAAQS. EPA constructed a wind rose, shown in figure 2 

is similar to the one that Pennsylvania constructed. This suggests local flow patterns and 

possibly the nonattainment problem in general may be slightly more widespread than indicated 

in the Commonwealth’s analysis. 

Figure 2.

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 3 below.

NORTH

SOUTH

WEST EAST

9%

18%

27%

36%

45%

WIND SPEED 

(Knots)

 >= 25

 11 - 25

 9 - 11

 7 - 9

 5 - 7

 3 - 5

 1 - 2

Calms: 0.00%
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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 3.

Jurisdictional boundaries 

EPA provided information about all boundaries considered prior to proposing nonattainment 

areas and this information can be found in the Pennsylvania TSD as part of the docket on 

proposed designations (78 FR 11124) and is not restated here. EPA originally proposed 

including all of Allegheny County in the initial nonattainment area. However additional 

information provided by the Commonwealth and ACHD in response to EPA’s proposal 

demonstrates that the monitors and sources of concern within Allegheny County are only a 

portion of the county. However EPA noted that the area of the county suggested for inclusion by 

the Commonwealth and ACHD as part of the Allegheny PA Nonattainment Area did not include 

potions of the county where the Edgar Thompson Works was located. EPA feels this source is 
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impacting SO2 values in the county and has also included this portion of the county in the initial 

nonattainment area. Therefore, EPA is designating the portions of Allegheny County as 

identified in Table 1 as nonattainment. 

Conclusion for the Allegheny Nonattainment Area

After considering the factors described above, EPA finds that the portions of Allegheny County 

that are nonattainment for the 2010 SO2 NAAQS include the following: City of Clairton, City of 

Duquesne, City of Mckeesport, Borough of Braddock, Borough of Dravosburg, Borough of East 

Mckeesport, Borough of East Pittsburgh, Borough of Elizabeth, Borough of Glassport, Borough 

of Jefferson Hills, Borough of Liberty, Borough of Lincoln, Borough of North Braddock, 

Borough of Pleasant Hills, Borough of Port Vue, Borough of Versailles, Borough of Wall, 

Borough of West Elizabeth, Borough of West Mifflin, Elizabeth Township, Forward Township, 

and North Versailles Township. These areas are identified in Table 1 with the area name

Allegheny PA Nonattainment Area. Refer to Figure 4 for a depiction of the nonattainment area. 

The air quality monitor which is the Liberty monitor in this area of Allegheny County shows 

violations of the 2010 SO2 NAAQS, based on certified 2009-2011 air quality data and additional 

data from 2012 provided by the Commonwealth and ACHD. Additionally, in response to EPA’s 

120-day letter, the Commonwealth and ACHD provided supporting information as referenced in 

the five factor analysis that assisted EPA in concluding that only a portion of Allegheny County 

should be initially included in the Allegheny County, PA Nonattainment Area, leaving remaining 

portions to be addressed in a future final designations action. Available emissions, 

meteorological data, and geographical data suggest that the sources in the cities, boroughs and 

townships as identified in Table 1 contribute to SO2 NAAQS violations in Allegheny County. 

 

Current information about sources located in Washington County as described above is not 

sufficient for us to conclude at this time to that they are likely to contribute to nonattainment at 

the Liberty monitor in Allegheny County. We will further address these sources in a future final 

designations action.

Based on the consideration of all the relevant and available information, as described above, 

EPA believes that the boundaries described herein encompass the nonattainment area based on 

the violating monitor in Allegheny County in Pennsylvania. Areas and sources that we are not 

yet prepared to conclude are contributing to the monitored violation or to other possible 

violations are not included in this initial nonattainment area. In a subsequent round of 

designations we will further address such areas and sources and make final designations 

decisions for areas that are not currently included in the nonattainment area designation 

addressed in this TSD.

Figure 4.
15

Technical Analysis for the Beaver Nonattainment Area

In EPA’s 120 day letter, EPA proposed that the initial Beaver PA Nonattainment Area consist of 

Beaver County in its entirety. In response to EPA’s 120 day letter, the Commonwealth 

recommended that only a portion of Beaver County (Industry Borough, Shippingport Borough, 

Midland Borough, Brighton Township, Potter Township and Vanport Township) be included in 

the nonattainment area and provided an analysis to support their response. 
16

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

recommendation and is initially designating a portion of the county as nonattainment for the 

2010 SO2 NAAQS based on the violating monitors in Beaver County. The Beaver PA 

Nonattainment Area consists of Industry Borough, Shippingport Borough, Midland Borough, 

Brighton Township, Potter Township and Vanport Township.

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 based on certified data for the 2009-2011

period. In addition, more recent air monitoring data included in the Commonwealth’s response 

to EPA’s proposal was also considered. 

The 2011 1-hour SO2 design value for the monitors 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 have been falling over the last several 

years. As supporting information, the Commonwealth indicated that the preliminary 2012 design 

value for this monitor is 57 ppb while the 2012 design value at the Brighton monitor was 149 

ppb. These values were confirmed by EPA. Monitors within the 50 kilometer zone of the 

violating monitors in the neighboring counties in PA (Lawrence, Allegheny and Washington) are 

not recording violations.

The Commonwealth also looked at exceedances at the Brighton Township and Hookstown 

monitors in Beaver County. Both monitors showed distinctly different patterns as to when 1-hr 

SO2 exceedances occurred. The Brighton Township monitor tended to have exceedances during 

the overnight hours while exceedances at the Hookstown monitor tended to occur during the 

daytime hours. EPA examined 1-hr SO2 concentrations from 2009-11 for both monitors and 

generally confirmed the Commonwealth’s findings. EPA would add that while exceedances at 

the Brighton Township monitor generally occurred during the overnight hours, there were still a 

number of exceedances observed during the daytime. EPA also calculated the correlation 

coefficients for both the Brighton Township and Hookstown monitors. One-hour SO2

concentrations from the Brighton Township and Hookstown monitors are not well correlated, 

which supports designating only a portion of Beaver County as nonattainment.
17

Emissions and Emissions-Related Data

Emissions 

In response to EPA’s letter, the Commonwealth indicated that four major sources with SO2

emissions over 100 tpy for the 2008-2011 period are located within 5 miles of the Brighton 

Township monitor, which is still showing violations of the NAAQS. The Commonwealth 

identified the sources as: Jewel Acquisition -Midland, First Energy Generation Bruce Mansfied, 

Alleghency Energy Beaver Valley and Horsehead Corporation-Monaca Smelter. All of these 

sources are included in the portion of Beaver County that is designated nonattainment.

Table 5 shows total emissions of SO2 in tons per year (tpy) for sources in and around the Beaver 

Area which are 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 

Original State

Recommended 

Nonattainment 

Area?

Facility Name 

CAMD 2012 

Total SO2 Point 

Emissions (tpy)

Total Facility 

SO2 Emissions 

2008 NEI 

v3(tpy)

Beaver, PA Yes First 

Energy/Bruce 

Mansfield Plant

11,019 19,082

Beaver, PA Yes Horsehead 

Corp./Monaca 

Smelter

3,320

Beaver, PA Yes AES Beaver 

Valley 

3,113 3,205

Jefferson, 

OH

Yes W.H. Sammis 

Plant

102,197 4,064

Jefferson, 

OH

Yes Cardinal Power 

Plant

33,317 8,144

Jefferson, 

OH

Yes Severstal 

Wheeling, Inc.

700

Westmoreland, PANo Arcelormittal 

Monesson 

LLC/Monesson 

Coke Plant

396

Brooke, 

WV

Yes Mountain State 

Carbon, LLC

731

Hancock, 

WV

Yes Arcelormittal 

Weirton Inc.

597

Lawrence, 

PA

No Orion Power 

Midwest/New 

Castle Power 

Plant

12,923 4,995

Lawrence, 

PA

No ESSROC/ 

Bessemer

910
18

Lawrence, 

PA

No CEMEX/

Wampum 

Cement Plant

674

Allegheny, 

PA

Yes Shenango Inc 333

Allegheny, 

PA

Yes Bellefield 

Boiler Plant

795

Allegheny, 

PA

Yes Bay Valley 

Foods, LLC

487

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 2008-12 Emissions Summary of SO2 Emissions in tpy

Facility County Distance*

CAMD2008CAMD2009CAMD2010CAMD2011CAMD2012

AES Beaver 

Valley

Beaver 3.2 Not 

Available

3,500 3,416 3,086 3,205

First 

Energy/Bruce 

Mansfield 

Beaver 7.6 11,117 17,704 21,757 21,196 19,082

W.H. Sammis 

Plant

Jefferson 11.3 102,619 73,614 12,761 4,202 4,064

Orion Power/New 

Castle Power 

Plant

Lawrence 28.1 12,923 7,629 9,572 7,510 4,995

Cardinal Power 

Plant

Jefferson 36.6 32,497 34,751 32,522 25,200 8,144

*Distance from Beaver County SO2 monitor in kilometers.

Emissions Controls

EPA has evaluated additional information from the 2008 NEI and CAMD and notes that 

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 
19

installed wet scrubbers on their units. SO2 emissions from 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 plant may be responsible for the declining SO2 concentrations 

observed at the Hookstown monitor near the PA-WV border. The Commonwealth also indicated 

that the decline in SO2 at the Hookstown monitor was likely due to SO2 controls at major power 

plants to the west of Beaver County. At this time EPA is not including any portions of counties 

outside of Beaver county in the nonattainment area since it is unlikely they are impacting the 

remaining violating monitor in Beaver County. In some instances sources may be included in 

other initial nonattainment areas. Areas and sources that we are not yet prepared to conclude are 

contributing to the monitored violation or to other possible violations are not included in this 

initial nonattainment area. In a subsequent round of designations we will further address such 

areas and sources and make final designations decisions for areas that are not currently included 

in the nonattainment area designation addressed in this TSD.

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 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 5). 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 at this 

time 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. We will further address these sources in a future final 

designations action.

The Commonwealth presented wind roses from the Brighton Township monitor for periods when 

the monitor exceeded the 1-hr SO2 NAAQS and the entire period. Wind directions were 

generally limited to a southerly direction during hours when 1-hr SO2 concentrations exceeded 

the NAAQS. Pennsylvania suggested that the predominant wind directions during periods of 

exceedances were due to inversions and local sources.
20

EPA examined stack heights from the 2005 NEI for the four local sources included in 

Pennsylvania’s proposed nonattainment area. Three of the four sources (Bruce Mansfield, AES 

Beaver Valley, Horsehead Corporation) have stacks exceeding 200 ft making emissions from 

these sources difficult to trap under nocturnal inversions. Additional information on this topic is 

found in the section below. Despite this shortcoming, EPA generally agrees that local sources are 

impacting the Brighton Township monitor.

 Figure 5.

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

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. The Commonwealth also provides 

similar analyses in their response. 
21

As noted in the section on Meteorology, EPA examined stack heights from the 2005 NEI. This 

information in addition to elevation information was used to determine the approximate release 

height for the four (4) sources nearest the Brighton Township monitor. Stack heights at Bruce 

Mansfield are listed at 950 ft making the release height well above the surrounding terrain and 

ensuring that emissions from this source are not overly influenced by nocturnal inversions. 

Stack heights at the Jewel Acquisition/Midland facility are generally less than 80 ft making 

impact from this source more local. Stack heights at AES Beaver Valley and Horsehead 

Corporation are in the 200-400 ft range. Release heights for both of these sources are 

approximately the same elevation as the Brighton Township monitor making direct impacts from 

these sources more likely. This may explain the wind patterns during periods of exceedances 

that the Commonwealth included in its analysis.

Jurisdictional boundaries 

EPA provided information about all boundaries considered prior to proposing nonattainment 

areas and this information can be found in the Pennsylvania TSD as part of the docket on 

proposed designations (78 FR 11124) and is not restated here. EPA originally proposed 

including all of Beaver County in the nonattainment area. However additional information 

provided by the Commonwealth in response to EPA’s proposal demonstrates that the monitors 

and sources of concern in this area of the Commonwealth that are most likely impacting the 

violating monitor are all located in Industry Borough, Shippingport Borough, Midland Borough, 

Brighton Township, Potter Township and Vanport Township. Therefore, EPA is designating 

these portions of Beaver County as the initial Beaver PA Nonattainment Area. 

Conclusion for the Beaver PA Nonattainment Area

After considering the factors described above, EPA finds that the boundary for the portion of 

Beaver County, PA with a current violating monitor consists of the portion of Beaver County 

that include Industry Borough, Shippingport Borough, Midland Borough, Brighton Township, 

Potter Township and Vanport Township. 

The air quality monitor in this area of Beaver County shows violations of the 2010 SO2 NAAQS, 

based on certified 2009-2011 air quality data and additional data from 2012 provided by the 

Commonwealth. Available emissions, meteorological data, and geographical data suggest that 

the sources in the boroughs and townships located within about a 5 km radius of the Brighton 

Township monitor likely impact and contribute to monitored SO2 NAAQS violations in Beaver

County. Some sources outside Beaver County are also being included in other nonattainment 

areas in West Virginia. Since the Hookstown monitor is now not showing a violation and 

sources likely impacting Hookstowsn have recently had emissions decreases due to the 

installation and use of SO2 controls, we are not prepared to conclude that additional areas in the 

county are likely having a significant impact on the Brighton monitor. Therefore such other 

areas in the county are not included in the initial Beaver PA Nonattainment Area, and will be 

further addressed in a future final designations action. 
22

Additionally, in response to EPA’s 120-day letter, the Commonwealth provided supporting 

information as referenced in the five factor analysis that assisted EPA in concluding that only a 

portion of Beaver County should be included in the initial Beaver PA Nonattainment Area. 

Based on the consideration of all the relevant and available information, as described above, 

EPA believes that the boundaries described herein encompass the initial nonattainment area 

based on the violating monitor in Beaver County in Pennsylvania. Areas and sources that we are 

not yet prepared to conclude are contributing to the monitored violation or other potential 

violations are not included in this initial nonattainment area. In a subsequent round of 

designations we will further address such areas and sources and make final designations 

decisions for areas that are not currently included in the nonattainment area designation 

addressed in this TSD.

Figure 6. 
23

Technical Analysis for the Indiana Nonattainment Area

In EPA’s 120 day letter, EPA proposed that the initial Indiana PA Nonattainment Area consist of 

Indiana County in its entirety and a portion of Armstrong County (Elderton Borough, Plumcreek

Township and South Bend Township). In response to EPA’s 120 day letter, the Commonwealth 

agreed that Indiana County in its entirety should be nonattainment but recommended that no 

portion of Armstrong County be included in the nonattainment area. 

Based on EPA's technical analysis described below, EPA agrees in part with the 

Commonwealth’s response and is initially designating all of Indiana County as nonattainment. 

EPA, however, disagrees with the Commonwealth’s recommendation regarding Armstrong 

County and is also designating the originally proposed portion of Armstrong County along with 

all of Indiana County as nonattainment for the 2010 SO2 NAAQS. 

Air Quality Data

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

calculated for the 2009-11 time period for all air quality monitors within 50 kilometers of the

Indiana County monitor.

The 2009-11 1-hour SO2 design value for the Strongstown monitor located in Indiana County is

shown in Table 7. The Commonwealth also provided data indicating that the 2012 design value 

was 81 ppb and EPA verified this design value is correct. 

Table 7. 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

The Commonwealth presented information regarding the timing and occurrence of 1-hr SO2

NAAQS exceedances and noted that exceedances at Strongstown generally occurred during the 

daytime hours. EPA examined Strongstown’s SO2 concentrations from the 2009-11 time period 

and confirmed that exceedances of the 1-hr SO2 NAAQS generally occur during the daylight 

hours though overnight peak concentrations at Strongstown can still be quite high.

The Commonwealth also examined and compared design value trends at the Strongstown 

monitor in Indiana County, PA and the York monitor in York County, PA. The York monitor 

has shown significant decreases in 1-hr SO2 concentrations after the installation of SO2 controls 
24

at the nearby Brunner Island power plant. In contrast, the Commonwealth pointed out that 

concentration trends at Strongstown have shown little decline even with controls being installed 

at the nearby Keystone power plant in Armstrong County and suggested that this lack of change

at the Strongstown monitor indicates sources other than Keystone are impacting the monitor.

EPA reviewed the number of exceedances at Strongstown over the 2007-2011 time period and 

found a slight decrease in the number of 1-hr SO2 exceedances (see Table 7). This result may 

indicate that while controls at Keystone may not be affecting overall SO2 concentrations as much 

as observed near the Brunner Island power plant they likely contributed to fewer exceedances 

(post 2009) measured at the Strongstown monitor. This result suggests Keystone is still 

impacting the monitor. Note that no statistical analysis was performed on the Commonwealth’s 

analysis of design value trends or EPA’s analysis of exceedance trends.

 

Table 7. Indiana County Monitor Exceedance Trend: 1-Hour SO2 Exceedances over the 

2007-11 Time Period

2007 2008 2009 2010 2011

Strongstown Exceedances 11 8 4 7 2

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 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 Name

Total Facility SO2

Emissions (tpy) 2008 

NEI

CAMD 2012 Total

SO2 Point 

Emissions (tpy)

Facility 

Located in 

State

Recommended 

Nonattainment 

Area?

Indiana, 

PA

Yes Homer City 

Generating

Station

102,486 99,774

Indiana, 

PA

Yes Seward 

Generating 

Station

15,549 4,333

Indiana, 

PA

Yes Genon

Conemaugh 

6,286 6,312
25

Plant

Armstrong, 

PA

No Keystone 

Power 

Station

189,983 29,420

Cambria, 

PA

No Colver Power 

Project

2,576 2,547

Cambria, 

PA

No Cambria 

Cogen

2,782 1,755

Cambria, 

PA

No Ebensburg 

Cogen

1,815 2,033

Blair, PA No Norfolk 

Southern 

Railway Co/ 

Juniata 

Locomotive 

Shops

392

SO2 emissions for 2011 are available on PA DEP’s eFACTS website 

(http://www.ahs.dep.pa.gov/eFACTSWeb/criteria_facilityemissions.aspx). Surveying the 2011 

regional emission information confirms that Keystone was the second largest point source in the 

Commonwealth behind Homer City.

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 2008-12 Emissions Summary of SO2 Emissions in tpy

Facility County Distance*

CAMD2008CAMD2009CAMD

-2010

CAMD

-2011

CAMD2012

Colver Power 

Project Cambria 10.3

Not 

Available 30,759 2,901 2,881 2,547

Ebensburg 

Cogen Cambria 18.9

Not 

Available 2,044 2,404 1,937 2.003

Seward Power 

Plant Indiana 19.8 7,771 7,756 8,458 7,003 4,333

Cambria 

Cogen Cambria 20.4

Not 

Available 6,947 2,070 1,942 1,755

Conemaugh Indiana 23.2 6,282 7,222 7,056 7,189 6,312

Homer City 

Generating 

Station Indiana 24.1 102,484 101,334

112,95

1 83,596 99,774

Keystone

Armstro

ng 37.1 189,994 113,137 39,114 46,441 29,420

*Distance from Indiana County, PA SO2 monitor in kilometers.
26

Emissions Controls

 

EPA’s 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).

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

The Commonwealth noted the controls recently installed on Keystone Units 1 and 2. These 

controls decreased Keystone’s SO2 emissions by approximately 85% in 2012. Annual SO2

emissions data for Keystone and Conemaugh, which are similarly sized facilities, was pulled 

from EPA’s CAMD website. Table 10 shows annual emissions and emission rates (in 

lbs/MMbtu) for both plants in 2012. This table shows that while both plants are similar in size 
27

their annual emissions and average annual emission rates are significantly different. Keystone’s 

annual emissions are four and a half times larger than Conemaugh even though Keystone’s units 

were run less than Conemaugh’s in 2012. Keystone’s units average annual emission rate was 

four to almost six times higher than Conemaugh. This illustrates that while emission controls are 

important, control efficiency may be equally important.

Table 11. Keystone and Conemaugh’s 2012 CAMD SO2 Emissions with calculated average 

annual emission rate in lbs/MMbtu.

Facility 

Name County

Unit 

ID Year

SO2 

(tons)

Heat Input 

(MMBtu)

Operating 

Time

Gross 

Load 

(MW-h)

Avg 

lbs/Mmbtu

Conemaugh Indiana 1 2012 2,963 51,080,093 7,808 5,594,629 0.12

Conemaugh Indiana 2 2012 3,349 53,881,056 8,121 5,781,428 0.12

Keystone Armstrong 1 2012 17,383 51,332,293 7,653 5,503,604 0.68

Keystone Armstrong 2 2012 12,037 44,348,039 6,281 4,718,662 0.54

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 7). 

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

information, EPA is not at this time 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. We will further address these sources in a future final

designations action.

 
28

Figure 7.

The Commonwealth constructed back trajectories using the NOAA Air Resource Laboratory’s 

HYSPLIT trajectory model. Back trajectories were run for exceedances before and after SO2

controls were installed on the Keystone power plant in Armstrong County, PA. The 

Commonwealth used these trajectories to illustrate that while there were significant SO2

emission reductions at Keystone, concentrations were only 5 ppb lower after controls were 

installed and concluded that “[T]his illustrates that Keystone cannot be considered the sole 

contributor in either of the violations, even though the trajectories on these two days originate 

from the region surrounding Keystone.”

EPA examined the Commonwealth’s s trajectory analysis and constructed its own back

trajectories for 2010-12 using NOAA’s HYSPLIT trajectory model (figure 8). Daily emissions 

from EPA’s CAMD were also examined to determine the level of power plant operations at the 

time exceedances occurred. The analyses indicate that emissions from the Keystone power plant 

in Armstrong County are contributing to exceedances and noncompliance with the 1-hr SO2

NAAQS at the Strongstown monitor. EPA acknowledges and agrees with the contention that 

Keystone is not the sole contributor to exceedances at Strongstown but it appears the Keystone 

power plant is contributing to nonattainment in Indiana County and should be included within 

the initial nonattainment area based on monitored nonattainment at the monitor in Indiana 

County. 
29

Figure 8.

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

Figure 8 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.

 
30

Figure9.

The Commonwealth included analysis of terrain and approximate release heights (base elevation 

plus stake heights) for the Keystone and Homer City power plants. The analysis noted that there 

is intermediate terrain (terrain above the release height) between Keystone and the Strongstown 

monitor. These, according to the Commonwealth, would likely lead to larger impacts on terrain 

features west of the Strongstown monitor and not at the Strongstown monitor itself.

There are stack height differences between the Commonwealth’s information and EPA’s 

information on stack heights. Base elevations for both power plants and the Strongstown 

monitor appear to be correct. Stack heights for Keystone units 1 and 2 found in EPA’s Large 

Power Plant Effluent Study (LAPPES) and the 2005 NEI are listed at 244 m or 800 ft. This 

gives Keystone an approximate release height of 1,800 ft (stack height plus base elevation), 

which is similar to the elevation of the Strongstown monitor (~1,900 ft). The Commonwealth’s

approximate release height for Keystone was 1,573 ft, significantly lower than EPA’s estimate. 

If EPA’s estimated release heights for Keystone are correct then there would be much less if any 

intermediate terrain between Keystone and the Strongstown monitor. Regardless, the 

Commonwealth’s contention that intermediate terrain would significantly lessen the impact of 

Keystone’s emissions is unlikely. While maximum plant impacts from Keystone would most 

undoubtedly fall close to the facility, Keystone’s emissions would have ample time to disperse 

vertically, especially during daytime hours when vertical mixing is enhanced. Based on the 

Commonwealth’s and EPA’s analysis, exceedances are more likely to occur at the Strongstown 

monitor during these times. Vertical distribution via plume rise and daytime plume mixing 

would indicate that emissions from the Keystone power plant in Armstrong County, PA are

significantly impacting the Strongstown monitor.
31

Jurisdictional boundaries 

EPA provided information about all boundaries considered prior to proposing nonattainment 

areas and this information can be found in the Pennsylvania TSD as part of the docket on 

proposed designations (78 FR 11124) and is not restated here. EPA originally proposed 

including all of Indiana County and a portion of Armstrong County (list portions) in the 

nonattainment area. Although the Commonwealth does not agree that a portion of Armstrong 

County should be included, EPA is including the originally proposed portions of Armstrong 

County in the initial Indiana County Nonattainment Area. Therefore, EPA is designating all of 

Indiana County and Elderton Borough and Plumcreek and South Bend Townships in Armstrong 

County PA as the Indiana PA Nonattainment Area. 

Conclusion for the Indiana Nonattainment Area

After considering the factors described above, EPA is initially designating all of Indiana County 

and a portion of Armstrong County (Elderton Borough, Plumcreek Township and South Bend 

Township) based on the violating monitor in Indiana County, as the Indiana PA Nonattainment 

Area for the 2010 SO2 NAAQS. Sources examined in Cambria and Blair counties have 

relatively small emissions and are generally upwind of the violating monitor, so at this time, 

these sources and areas are not included in the initial nonattainment area. However, these 

sources will be addressed in a future final designations action.

The air quality monitor in Indiana County shows a violation of the 2010 SO2 NAAQS, based on 

2009-2011 air quality data and data provide by the Commonwealth. The nearby Keystone power 

plant in neighboring Armstrong County likely contributes to nonattainment in Indiana County as 

well. Previous studies as discussed in the TSD that accompanied the proposed nonattainment 

area boundary (78 FR 11124) 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 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 Indiana County. 
32

Figure 10.
33

Technical Analysis for the Warren Nonattainment Area

In EPA’s 120 day letter, EPA proposed that the initial Warren PA Nonattainment Area consist of 

Warren County in its entirety. In response to EPA’s 120 day letter, the Commonwealth 

recommended that only a portion of Warren County (the City of Warren and Conewago, Glade 

and Pleasant Townships) be included in the nonattainment area and provided an analysis to 

support their response. 

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

recommendation and is initially designating a portion of the county as nonattainment for the 

2010 SO2 NAAQS based on the violating monitors in Warren County. The Warren PA 

Nonattainment Area consists of Conewago, Glade and Pleasant Townships and the City of 

Warren.

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 based on certified data for the 2009-2011

period. 

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

12.

Table 12. 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

The Commonwealth indicated that the design value for 2010-2012 was 102 ppb and this was 

confirmed by EPA.

The Commonwealth examined hourly SO2 concentrations at the Warren County, PA monitor and 

noted exceedances of the 1-hr SO2 NAAQS generally occurred during the overnight hours. This 

was attributed to limited mixing during nocturnal inversions. EPA examined the Warren 

County, PA monitor’s hourly SO2 concentrations from 2009-11 and confirmed that peak 

concentrations and exceedances primarily occur during the overnight hours. This would support 

that meteorological conditions, namely nocturnal inversions, are contributing to exceedances in 

the area of the Warren County, PA monitor.
34

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 

Table 13 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 emitting greater than 100 tpy 

of SO2 according to the 2008 NEI. 

Table 13. SO2 Emissions in the Warren Nonattainment Area

County

Facility 

Located in 

State’s 

Original

Recommended 

Nonattainment 

Area?

Facility 

Name

Total 

Facility SO2

Emissions 

(tpy) CAMD 2012 (tpy)

Warren, PA Yes United 

Refining 

Warren Plant

1,612

McKean, 

PA

No American 

Refining 

Group/ 

Bradford

1,479

Chautauqua, 

NY

No Samuel A. 

Carlson 

Generating 

Station

3,736 215

 

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 14. CAMD 2008-12 Emissions Summary of SO2 Emissions in tpy

Facility County Distance*

CAMD2008CAMD2009CAMD2010CAMD2011CAMD2012

Samuel A. Chautauqua 28.41 3,736 1,885 1,272 664
35

Carlson 

Generating 

Station 215

*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. 

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.

The Commonwealth included a wind analysis that shows wind directions are primarily from the 

east during hours in which the Warren County, PA monitor exceeds the 1-hr SO2 NAAQS. No 

data was submitted to support this analysis. Pennsylvania’s analysis, however, appears to make 

sense given the primary SO2 source near the monitor resides to the east.

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

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 original 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 at this time 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. We will further address 

these sources in a future final designations action. Additional information provided in the 
36

Commonwealth’s recent response further supports the recommendation that only a portion of 

Warren County which includes the United Refining source should be included in the initial 

nonattainment Area.

Jurisdictional boundaries 

EPA provided information about all boundaries considered prior to proposing nonattainment 

areas and this information can be found in the Pennsylvania TSD as part of the docket on 

proposed designations (78 FR 11124) and is not restated here. EPA originally proposed 

including all of Warren County in the nonattainment area. However additional information 

provided by the Commonwealth in response to EPA’s proposal demonstrates that the monitor 

and sources of concern in this area of the Commonwealth that are most likely impacting the 

violating monitor are all located within the City of Warren, Conewago Township, Glade 

Township and Pleasant Township. Therefore, EPA is initially designating these portions of 

Warren County as the Warren, PA nonattainment area. 

Conclusion for the Warren Nonattainment Area

After considering the factors described above, EPA is designation the following portions of 

Warren County as the Warren PA Nonattainment Area: Conewago Township, Glade Township, 

Pleasant Township and the City of Warren. The air quality monitor in Warren County shows a 

violation of the 2010 SO2 NAAQS, based on certified 2009-2011 air quality data and additional 

data provided by the Commonwealth. This monitor indicates that there are 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. Additional information provided 

by the Commonwealth also supports this analysis. EPA believes that the boundaries described 

herein encompass the appropriate initial area that does not meet the 2010 SO2 NAAQS. Areas 

and sources that we are not yet prepared to conclude are contributing to the monitored violation 

are not included in this initial nonattainment area. In a subsequent round of designations we will 

further address such areas and sources and make final designations decisions for areas that are 

not currently included in the nonattainment area designation addressed in this TSD.

Figure 11.
37

EPA’s Area Designations Conclusion for Pennsylvania

EPA has reviewed the information above and is designating based on monitored violations the 

counties and/or portions of counties listed in Table 1 as nonattainment for the 2010 SO2

NAAQS. EPA considered 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 nonattainment in a 

nearby area) the 2010 SO2 NAAQS. Areas and sources that we are not yet prepared to conclude 

are contributing to the monitored violation are not included in this initial nonattainment area. In 

a subsequent round of designations we will further address such areas and sources and make 
38

final designations decisions for areas that are not currently included in the nonattainment area 

designation addressed in this TSD.