1

Draft Technical Support Document

Maryland

Area Designations for the 2010 SO2 Primary National Ambient Air Quality Standard

Summary

Pursuant to section 107(d) of the Clean Air Act (CAA), the U.S. Environmental Protection 

Agency (EPA) must 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 a violation in a nearby area. An attainment area is defined as any area other than a 

nonattainment area that meets the NAAQS. Unclassifiable areas are defined as those that cannot 

be classified on the basis of available information as meeting or not meeting the NAAQS.

Maryland submitted a designation recommendation on April 19, 2011 and updated its

designation recommendation with a letter dated November 20, 2015. EPA is now subject to a 

court-ordered July 2, 2016 deadline to designate certain areas established by the U.S. District 

Court for the Northern District of California. One area in Anne Arundel County, Maryland must 

be designated by EPA by this deadline, due to its having a SO2 source with emissions over 

certain thresholds identified in the court order. This deadline is the first of three deadlines 

established by the court for EPA to complete area designations for the 2010 SO2 NAAQS.

Table 1 below lists Maryland’s 2015 recommendation for the area around Wagner, Maryland’s 

2011 recommendation for Baltimore City, and identifies the portions of counties in Maryland

that EPA intends to designate by July 2, 2016 based on an assessment and characterization of air 

quality through ambient air quality data, air dispersion modeling, other evidence and supporting 

information, or a combination of the above.

Table 1: Maryland’s Recommended and EPA’s Intended Designations

Area Maryland’s

Recommended 

Area Definition

Maryland’s 

Recommended 

Designation

EPA’s Intended 

Area Definition

EPA’s Intended 

Designation 

Anne Arundel

County and 

Baltimore 

County

Area boundary 

not provided

Attainment Portions of 

Anne Arundel and

Baltimore Counties

that are within 35.5 

kilometers of 

Herbert Wagner’s 

Unit 3 stack, which 

is located at 

39.17765N latitude, 

76.52752W 

longitude

Nonattainment
2

Baltimore City Baltimore City Unclassifiable Same as State’s 

Recommendation

Unclassifiable/Attainment

Background

On June 3, 2010, EPA revised the primary (health-based) SO2 NAAQS 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 1-hour daily maximum concentrations does not exceed 75 ppb. This 

NAAQS was published in the Federal Register on June 22, 2010 (75 FR 35520) and is codified 

at 40 CFR 50.17. EPA determined this is the level necessary to protect 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 two 

prior primary standards of 140 ppb evaluated over 24 hours, and 30 ppb evaluated over an entire 

year, codified at 40 CFR 50.4, remain applicable.

1 However, EPA is not currently designating 

areas on the basis of either of these two primary standards. Similarly, the secondary standard for 

SO2, set at 500 ppb evaluated over three hours has not been revised, and EPA is also not currently 

designating areas on the basis of the secondary standard.

General Approach and Schedule

Section 107(d) of the Clean Air Act requires that not later than one year after promulgation of a 

new or revised NAAQS, state governors must submit their recommendations for designations 

and boundaries to EPA. Section 107(d) also requires EPA to provide notification to states no 

less than 120 days prior to promulgating an area designation that is a modification of a state’s 

recommendation. If a state does not submit designation recommendations, EPA will promulgate 

the designations that it deems appropriate. If a state or tribe disagrees with EPA’s intended 

designations, they are given an opportunity within the 120-day period to demonstrate why any 

proposed modification is inappropriate.

On August 5, 2013, EPA published a final rule establishing air quality designations for 29 areas 

in the United States for the 2010 SO2 NAAQS, based on recorded air quality monitoring data 

from 2009 - 2011 showing violations of the NAAQS (78 FR 47191). In that rulemaking, EPA 

committed to address, in separate future actions, the designations for all other areas for which the 

Agency was not yet prepared to issue designations.

Following the initial August 5, 2013 designations, three lawsuits were filed against EPA in 

different U.S. District Courts, alleging the Agency had failed to perform a nondiscretionary duty 

 

1 40 CFR 50.4(e) provides that the two prior primary NAAQS will no longer apply to an area one year after its 

designation under the 2010 NAAQS, except that for areas designated nonattainment under the prior NAAQS as of 

August 22, 2010, and areas not meeting the requirements of a SIP Call under the prior NAAQS, the prior NAAQS 

will apply until that area submits and EPA approves a SIP providing for attainment of the 2010 NAAQS. 
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under the CAA by not designating all portions of the country by the June 2013 deadline. In an 

effort intended to resolve the litigation in one of those cases, plaintiffs Sierra Club and the 

Natural Resources Defense Council and EPA filed a proposed consent decree with the U.S. 

District Court for the Northern District of California. On March 2, 2015, the court entered the 

consent decree and issued an enforceable order for EPA to complete the area designations 

according to the consent decree schedule.

According to the consent decree and court order, EPA must complete the remaining designations 

on a schedule that contains three specific deadlines. By no later than July 2, 2016 (16 months 

from the court’s order), EPA must designate two groups of areas: (1) areas that have newly 

monitored violations of the 2010 SO2 NAAQS, and (2) areas that contain any stationary sources 

that had not been announced as of March 2, 2015 for retirement and that according to EPA’s Air 

Markets Database emitted in 2012 either (i) more than 16,000 tons of SO2 or (ii) more than 2,600 

tons of SO2 with an annual average emission rate of at least 0.45 pounds of SO2 per one million 

British thermal units (lbs SO2/mmBTU). Specifically, a stationary source with a coal-fired unit 

that as of January 1, 2010 had a capacity of over 5 megawatts and otherwise meets the emissions 

criteria, is excluded from the July 2, 2016 deadline if it had announced through a company public 

announcement, public utilities commission filing, consent decree, public legal settlement, final 

state or federal permit filing, or other similar means of communication, by March 2, 2015, that it 

will cease burning coal at that unit. 

The last two deadlines for completing remaining designations are December 31, 2017, and 

December 31, 2020. EPA has separately promulgated requirements for states and other air 

agencies to provide additional monitoring or modeling information on a timetable consistent with 

these designation deadlines. We expect this information to become available in time to help 

inform these subsequent designations. These requirements were promulgated on 

August 21, 2015 (80 FR 51052), in a rule known as the SO2 Data Requirements Rule (DRR). 

 

Updated designations guidance was issued by EPA through a March 20, 2015 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 supersedes earlier designation 

guidance for the 2010 SO2 NAAQS, issued on March 24, 2011, and it identifies factors that EPA 

intends to evaluate in determining whether areas are in violation of the 2010 SO2 NAAQS. The 

guidance also contains the factors EPA intends to evaluate in determining the boundaries for all 

remaining areas in the country, consistent with the court’s order and schedule. These factors 

include: 1) Air quality characterization via ambient monitoring or dispersion modeling results; 

2) Emissions-related data; 3) Meteorology; 4) Geography and topography; and

5) Jurisdictional boundaries. This guidance was supplemented by two technical assistance 

documents intended to assist states and other interested parties in their efforts to characterize air 

quality through air dispersion modeling or ambient air quality monitoring for sources that emit 

SO2. Notably, EPA released its most recent versions of documents titled, “SO2 NAAQS 

Designations Modeling Technical Assistance Document” (Modeling TAD) and “SO2 NAAQS 

Designations Source-Oriented Monitoring Technical Assistance Document” (Monitoring TAD) 

in December 2013.
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Based on ambient air quality data collected between 2012 and 2014, no violations of the 2010 

SO2 NAAQS have been recorded in any undesignated part of Maryland.2 However, there is one 

source in the state meeting the emissions criteria of the consent decree and court order for which 

EPA must complete designations by July 2, 2016. In this draft technical support document, EPA 

discusses its review and technical analysis of the area that we must designate pursuant to the 

consent decree and court order. EPA also discusses any intended modifications from the State’s 

recommendation based on all available data before us. 

The following are definitions of important terms used in this document: 

1) 2010 SO2 NAAQS – The primary NAAQS for SO2 promulgated in 2010. This NAAQS 

is 75 ppb, based on the three-year average of the 99th percentile of the annual distribution 

of daily maximum one-hour average concentrations. See 40 CFR 50.17. 

2) Design Value - a statistic computed according to the data handling procedures of the 

NAAQS (in 40 CFR part 50 Appendix T) that, by comparison to the level of the NAAQS, 

indicates whether the area is violating the NAAQS.

3) Designated nonattainment area – an area which EPA has determined has violated the 

2010 SO2 NAAQS or contributed to a violation in a nearby area. A nonattainment 

designation would reflect considerations of state recommendations and all of the 

information discussed in this document. EPA’s decision would be based on all available 

information including the most recent three years of air quality monitoring data, available 

modeling analysis, and any other relevant information. 

4) Designated unclassifiable area – an area which EPA cannot determine based on all 

available information whether it meets the 2010 SO2 NAAQS. 

5) Designated unclassifiable/attainment area – an area which EPA has determined to have 

sufficient evidence to find either is attaining or is likely to be attaining the NAAQS.

EPA’s decision would be based on all available information including the most recent 

three years of air quality monitoring data, available modeling analysis, and any other 

relevant information. 

6) Modeled violation – a violation based on air dispersion modeling.

7) Recommended attainment area – an area a state or tribe has recommended that EPA 

designate as attainment. 

8) Recommended nonattainment area – an area a state or tribe has recommended that EPA 

designate as nonattainment. 

9) Recommended unclassifiable area – an area a state or tribe has recommended that EPA 

designate as unclassifiable.

 

2 For designations based on ambient air quality monitoring data that violates the 2010 SO2 NAAQS, the consent 

decree directs EPA to evaluate data collected between 2013 and 2015. Absent complete, quality-assured and 

certified data for 2015, the analyses of applicable areas for EPA’s intended designations will be informed by data 

collected between 2012 and 2014. States with monitors that have recorded a violation of the 2010 SO2 NAAQS 

during these years have the option of submitting complete, quality-assured and certified data for calendar year 2015 

by April 19, 2016 to EPA for evaluation. If after our review, the ambient air quality data for the area indicates that 

no violation of the NAAQS occurred between 2013 and 2015, the consent decree does not obligate EPA to complete 

the designation. Instead, EPA may designate the area and all other previously undesignated areas in the state on a 

schedule consistent with the prescribed timing of the consent decree, i.e., by December 31, 2017, or December 31, 

2020. 
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10)Recommended unclassifiable/attainment area – an area a state or tribe has recommended 

that EPA designate as unclassifiable/attainment.

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

siting criteria and requirements whose valid design value exceeds 75 ppb, based on data 

analysis conducted in accordance with Appendix T of 40 CFR part 50. 
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Technical Analysis for the Anne Arundel County and Baltimore County, Maryland Area 

and Baltimore City, Maryland Area

Introduction

The Anne Arundel County and Baltimore County area contains one stationary source that 

according to EPA’s Air Markets Database emitted in 2012 either (a) more than 16,000 tons of 

SO2 or (b) more than 2,600 tons of SO2 and had an annual average emission rate of at least 0.45 

lbs SO2/mmBTU. As of March 2, 2015, this stationary source, Herbert A. Wagner Generating 

Station (Wagner, or the Facility), had not met the specific requirements for being “announced for 

retirement.”3 Specifically, in 2012, Wagner emitted 7,514 tons of SO2, and had an emissions rate 

of 1.105 lbs SO2/mmBTU. Pursuant to the March 2, 2015 consent decree and court order, EPA 

must designate the area surrounding the facility by July 2, 2016.

In its April 19, 2011 submission to EPA for the initial designations for the 2010 SO2 NAAQS, 

Maryland recommended that the area which includes Wagner, specifically the entirety of Anne 

Arundel County, be designated as unclassifiable. Likewise, Maryland’s 2011 submission 

recommended that Baltimore City be designated as unclassifiable. The 2011 submission, 

however, did not include any supporting analyses. Subsequently, in its November 20, 2015 

updated designation recommendation submission to EPA, Maryland recommended that the area 

surrounding Wagner be designated as attainment. Maryland, however, did not recommend any 

particular boundary for the area in its November 20, 2015 submission. Maryland stated that no 

monitors in Maryland violated the 1-hour SO2 NAAQS, and EPA has confirmed this. On 

January 15, 2016, Maryland submitted a supplement to its 2015 recommendation which included 

a modeling analysis for the area around Wagner. Additionally, this supplement included 

comments on air dispersion modeling dated January 4, 2016, performed by Sierra Club and 

submitted to EPA, asserting that violations of the NAAQS are present in the area around 

Wagner. Maryland did not update its recommendation for Baltimore City in its 2015 updated 

recommendation. After careful review of the State’s 2015 recommendation and all submitted 

available data including air quality characterization, emissions data, meteorology, geography,

topography, and modeling analyses for the area around Wagner, EPA disagrees with the State’s 

recommendations, and intends to designate the area surrounding Wagner (portions of Anne 

Arundel County and Baltimore County) as nonattainment, and Baltimore City as 

unclassifiable/attainment.

Wagner is located in eastern Maryland in the northern portion of Anne Arundel County. As seen 

in Figure 1, the facility4is located approximately two (2) kilometers south of the City of 

 

3 However, Wagner Unit 2 is on PJM Interconnection LLC’s (PJM) current list for projected deactivation by June 1, 

2020. See PJM’s projected deactivation list, dated November 25, 2015, available at 

http://www.pjm.com/~/media/planning/gen-retire/pending-deactivationrequests.ashxhttp://www.pjm.com/~/media/planning/gen-retire/pending-deactivation-requests.ashx. PJM is a 

regional transmission organization (RTO) that coordinates the movement of wholesale electricity in all or parts of 13 

states, including Maryland, and the District of Columbia.

4 EPA notes that the Wagner facility is considered one stationary source for purposes of Title V of the CAA and for 

CAA New Source Review (NSR) purposes with the Brandon Shores Generating Station (Brandon Shores) also 
7

Baltimore along the Chesapeake Bay. Also included in the figure is EPA’s intended 

nonattainment designation for the area. Specifically, the boundaries for our intended 

nonattainment area are comprised of the portions of Anne Arundel and Baltimore Counties that 

are within 35.5 kilometers of Herbert Wagner’s Unit 3 stack, which is located at 39.17765N 

latitude, 76.52752W longitude.

Figure 1: EPA’s Intended Designation for Anne Arundel County and Baltimore County Area

The discussion and analysis that follows below will reference the factors for evaluation 

contained in EPA’s March 20, 2015 guidance, as appropriate.

Detailed Assessment for Anne Arundel County and Baltimore County Area

Air Quality Data

This factor considers the SO2 air quality monitoring data in the area surrounding Wagner. The 

Facility is located in Anne Arundel County; however, there are no ambient air quality monitors 

located in this county. There is an ambient air quality monitor geographically near Anne 

 

owned and operated by the same entity which owns and operates Wagner. Collectively, the facilities are known as 

“Fort Smallwood” and are subject to one Title V CAA permit issued by Maryland.
8

Arundel in Baltimore County. Maryland’s updated 2015 designation recommendation included 

design values and the maximum 1-hour SO2 concentrations from 2007-2014 for the Essex 

monitor (Air Quality Systems (AQS) ID 24-005-3001), located in Baltimore County (see Table 

2). The State notes that the design value has decreased since the implementation of Maryland’s 

Healthy Air Act. This monitor, however, is not located near Wagner and is instead located in 

neighboring Baltimore County, approximately 15 kilometers northeast of Wagner. As a result of 

this distance, EPA does not believe that the Essex monitor adequately characterizes air quality as 

a result of emissions from Wagner.

Table 2: Maryland’s SO2 Emissions and Air Monitoring Concentrations in the Vicinity of 

Wagner (in Maryland’s November 20, 2015 submission)

SO2 Emissions (Tons/Year) SO2 Concentrations at Essex 

(ppb)

Year Total Brandon Shores Wagner Crane

Design 

Value* Max 1-hour

2007 92,931 42,041 20,259 30,631 99 173

2008 79,282 39,924 15,006 24,352 86 66

2009 60,391 32,821 15,093 12,477 80 56

2010 15,877 1,260 9,028 5,589 43 33

2011 17,518 2,829 9,007 5,682 34 53

2012 12,494 2,848 7,473 2,173 22 26

2013 16,020 2,870 10,178 2,972 22 31

2014 14,643 3,145 9,610 1,887 22 44

*The design value for the 1-hour SO2 standard is the 99th percentile of the 1-hour daily maximum

concentrations, averaged over three years. The 1-hour SO2 standard is 75 parts per billion (ppb), calculated 

the same way.

Nonetheless, EPA has reviewed the most recent three years of monitoring data, i.e., 2012 – 2014, 

for the Essex monitor since there are no monitors in Anne Arundel County and the Essex 

monitor is the closest monitor to Wagner. Table 3 below shows the data from the Essex monitor 

which were confirmed through EPA’s 2014 design value report for SO2.

5

 

Table 3: Available Air Quality Data Near Wagner 

County Air Quality 

Systems (AQS) 

Monitor ID

Monitor Name Distance to Wagner 

(km)

2012 – 2014 SO2

Design Value in ppb

Baltimore 24-005-3001 Essex 15 22

EPA’s more detailed examination of daily peak 1-hour SO2 concentrations and the 99th percentile

daily 1-hour maximum SO2 concentrations is also presented to gauge how high concentrations 

are in the vicinity of Wagner. The 99th percentile daily peak 1-hour concentrations are shown in 

Table 4 for the 2012-14 time period along with the 99th percentile for the Essex monitor. The 

Essex monitor’s daily peak 1-hour SO2 concentrations exceeded 50 percent of the NAAQS on 

one (1) day during the 2012-14 time period. 

 

5 The design value report for SO2, as well as each of the other NAAQS, can be found at this link: 

http://www3.epa.gov/airtrends/values.html.
9

Table 4: Additional Monitoring Data for the Essex Monitor (24-005-3001)

Day’s Peak 1-

Hour > 37.5 ppb

Total Valid 

Days 2012-14

%Valid Days 

2012-14

99th

percentile

2012

99th percentile

2013

99th percentile

2014

1 1,084 98.9% 19 39 26

In addition, EPA’s evaluation of the monitoring data indicates that 1-hour SO2 concentrations at 

the Beltsville monitor (AQS ID 24-033-0030) in neighboring Prince George’s County are less 

than half of those observed at Essex. This monitor is approximately 33 km west southwest of 

Wagner. Beltsville, unfortunately, does not meet the completeness criteria required to generate a 

valid design value though nearly 96 percent of the days were “complete.” There were no days 

during the 2012-14 time period that exceeded 50 percent of the NAAQS at Beltsville.

Based on available ambient air quality data collected between 2012 and 2014, Anne Arundel’s 

neighboring county, Baltimore County, does not show a violation of the 2010 SO2 NAAQS at its 

monitor. Over the last two years there was only one (1) day in which 1-hour SO2 concentrations 

exceeded 50 percent of the NAAQS.6 However, the absence of a violating monitor when 

considering the distance from the Facility is not a sufficient technical justification to rule out that 

an exceedance of the 2010 SO2 NAAQS may occur in the immediate vicinity of the Facility.

Additionally, Maryland’s November 20, 2015 recommendation references a 2013 two-month 

monitoring study of SO2 concentrations conducted around Raven Power’s Wagner, Brandon 

Shores, and C.P. Crane facilities, and Maryland states that peak daily 1-hour maximum 

monitored SO2 values were generally below 75 ppb, even though one site had a daily peak (101.7 

ppb) that exceeded the 1-hour SO2 NAAQS. The limited duration of this study does not allow 

EPA to make a determination of how frequently the NAAQS is exceeded, but given the 

occurrence of a maximum 1-hour SO2 concentration of 101.7 ppb at the monitor closest to the 

Facility during the summer months, which is far in excess of the 75 ppb standard, an 

extrapolation would indicate that at least one exceedance of the NAAQS occurs quarterly. It 

must be noted, however, that EPA was not provided with any detailed information to permit EPA 

to evaluate the study, critically analyze the study’s data, nor draw any conclusions from the study

at this time. For instance, EPA has no information on how this study was conducted, who 

maintained the monitors in the study, what quality control checks were done on the monitors, nor 

any other critical information such as under what conditions this monitoring study was 

conducted. Given this information, there is a lack of supporting evidence to support an 

attainment designation for the area surrounding Wagner. 

Emissions and Emissions-Related Data

Evidence of SO2 emissions from the Facility meeting the emissions criteria of the March 2, 2015 

consent decree and the court order is an important factor for determining whether the immediate 

area is experiencing elevated levels of SO2 concentrations. Other considerations for this factor 

include county level SO2 emissions data, and data for sources located within 50 km. 

 

6 See Maryland’s November 20, 2015 designation recommendation, attachment 3, Table 2.
10

Maryland’s updated 2015 designation recommendation included annual emissions data for 

sources in Anne Arundel County (i.e. Wagner and Brandon Shores), as well as annual emissions 

data from sources in neighboring Baltimore County (i.e. Crane). Maryland notes that 

implementation of Maryland’s Healthy Air Act in 2010 resulted in a decrease of SO2 emissions 

from Wagner, Brandon Shores, and Crane. Maryland’s recommendation included the data 

provided in Table 2 above. 

EPA confirms that emissions had decreased significantly from 2007 to 2010; however, they have 

not decreased since then, and have in fact increased slightly in 2014 from the 2010 level. 

Additionally, Wagner had been identified in 2015 as meeting the emission criteria outlined in the 

court order, and Wagner’s emissions have not decreased further since 2010 with its SO2

emissions remaining between 9,000 and 10,000 tons per year, As a result, EPA believes that this 

emissions data alone does not support the attainment designation recommended by Maryland. 

Wagner’s emissions also have not decreased as significantly as Brandon Shore’s and Crane’s, 

which may reflect an absence or under-use of SO2 controls.

To evaluate what emission controls are installed for Wagner and neighboring sources, EPA 

reviewed its Air Markets Programs (AMP) database. According to the AMP database, Brandon 

Shores has wet lime flue gas desulfurization (FGD) on Unit 1 and wet limestone SO2 control for 

Unit 2. No SO2 controls are listed in the EPA database for Wagner or C.P. Crane. Table 5 

summarizes unit level controls and fuel types for the eight (8) primary combustion units at 

Wagner, Brandon Shores and C.P. Crane from the AMP database. With the lack of SO2

emissions controls at Wagner and the present level of emissions at the plant, EPA lacks sufficient 

supporting evidence to support an attainment designation for the area around Wagner as 

Maryland has recommended.

Table 5: Air Markets Program Information for Brandon Shores, Wagner and C.P. Crane

Facility Name Unit Fuel Type 

(Primary)

Fuel Type 

(Secondary)

SO2

Control(s)

Particulate 

Matter (PM)

Control(s)

Mercury (Hg)

Control(s)

Brandon 

Shores

1 Coal - Wet Lime 

FGD

Cyclone 

Baghouse

-

Brandon 

Shores

2 Coal - Wet 

Limestone

Cyclone 

Baghouse

-

Herbert A 

Wagner

1 Other Oil Pipeline 

Natural Gas

- Electrostatic 

Precipitator

-

Herbert A 

Wagner

2 Coal - - Electrostatic 

Precipitator

Halogenated 

PAC Sorbent 

Injection

Herbert A 

Wagner

3 Coal - - Electrostatic 

Precipitator

-

Herbert A 

Wagner

4 Other Oil Pipeline 

Natural Gas

- Electrostatic 

Precipitator

-

C P Crane 1 Coal - - Baghouse -

C P Crane 2 Coal - - Baghouse -
11

Further, EPA reviewed the emissions data provided by Maryland and confirmed the data by 

evaluating data obtained from the 2011 and 2013 National Emissions Inventory (NEI). 7 The 

annual SO2 emissions data for point sources emitting at or above 100 tons per year (tpy) in Anne 

Arundel and neighboring Baltimore County and Baltimore City are summarized in Table 6

below. Figure 2 shows the locations of the emissions sources listed in Table 6. One source

labeled in Figure 2, Sparrows Point, LLC, however, is not included in Table 6 because it has 

been permanently shut down and demolished.8

Table 6: 2011 and 2013 NEI SO2 Emissions from Wagner and Other Local Sources

County Owner and 

Operator

Facility 

Complex 

Name

Facility 

Name

Facility 

Subject to 

the 

Emissions 

Criteria of 

the March 

2, 2015 

consent 

decree?

Distance 

to 

Facility 

that 

Meets 

the 

Consent 

Decree 

Criteria 

in km

2011 

Facility 

Total SO2

Emissions 

(tpy)

2013 

Facility 

Total SO2

Emissions

(tpy)

Anne 

Arundel

Raven Power 

Holdings, 

LLC

Fort 

Smallwood9

Wagner Yes 0 11,94310 13,0499

Anne 

Arundel

Raven Power 

Holdings, 

LLC

Fort 

Smallwood

Brandon 

Shores

No 0 11,9439 13,0499

Baltimore Raven Power 

Holdings, 

LLC

N/A C.P. Crane 

LLC

No 22 5,684 2,973

Baltimore 

City

Wheelabrator 

Technologies

N/A Wheelabrator 

Baltimore, 

L.P.

No 12.9 261 321

EPA has also reviewed emissions data from EPA’s AMP database. For 2014, Wagner’s SO2

emissions were 9,610 tpy and Brandon Shores were 3,145 tpy. Figure 3 shows annual SO2

emissions for each unit from EPA’s AMP. Of the eight (8) units reviewed, Wagner’s unit 3 

 

7 Detailed information for the 2011 NEI can be found at this link:

http://www3.epa.gov/ttnchie1/net/2011inventory.html. For more information on the 2013 NEI, contact the Region 

III office.

8 The facility’s Title V permit has expired.

9 As discussed above, Brandon Shores and Wagner are treated as a single stationary source for Title V and NSR 

purposes due to common ownership by Raven Power Holdings, LLC, contiguous location, and same singular major 

industrial grouping. 

10 In both the 2011 and 2013 NEI, emissions from Wagner and Brandon Shores are combined and reported together

as Wagner and Brandon Shores are treated as a single stationary source. Emissions from each facility, however, are 

reported individually in EPA’s Air Markets Database as 9,610 tpy for Wagner in 2014 and 3,145 tpy for Brandon 

Shores in 2014.
12

emitted the largest amount of SO2 during the 2012-14 time period. It should be noted that unit 3 

does not have any SO2 emission control devices installed.

Figure 2: 2013 NEI Annual SO2 Emissions in tons per year
13

Figure 3: 2012-14 Annual Unit SO2 Emissions in tpy from Wagner, Brandon Shores and Crane

The lack of SO2 emissions controls at Wagner, lack of declining emissions trend from Wagner, 

and the present level of emissions at the plant indicates that there could be impacts from this 

plant on SO2 concentrations in the area. EPA lacks sufficient supporting evidence to support an 

attainment designation for the area around Wagner as Maryland has recommended. Based on 

EPA’s review of available emissions data, as well as air dispersion modeling information for the 

area surrounding Wagner discussed later in this draft technical support document, EPA believes 

a designation of nonattainment is appropriate for the area impacted by Wagner.

Emissions Controls

Maryland’s updated 2015 designation recommendation mentions that in mid-April 2015, the 

owners of the Wagner facility, Raven Power, began to use a low sulfur coal at Wagner’s unit 2 as 

a method of compliance with the federal Mercury and Air Toxics Standard (MATS). However, 

EPA has insufficient information on the percent sulfur coal and whether any restrictions on fuel 

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

Herbert A

Wagner

Unit 1

Herbert A

Wagner

Unit 2

Herbert A

Wagner

Unit 3

Herbert A

Wagner

Unit 4

Brandon

Shores Unit

1

Brandon

Shores Unit

2

C P Crane

Unit 1

C P Crane

Unit 2

Raven Power - CAMD SO2Emissions 2012-14

2012 (tons) 2013 (tons) 2014 (tons)
14

sulfur coal are in a permanent, federally enforceable document such as a permit or SIP approved 

requirement. Maryland also mentions that in early 2016, Raven Power will be adding a dry 

sorbent injection (DSI) system to Wagner’s unit 3 to comply with MATS to help reduce SO2

emissions. Again, EPA has no further information at this time regarding the specifications of the 

DSI system, its control efficiency, and operational requirements and no information on whether 

DSI controls are federally enforceable via permits or SIP requirements. In addition, review of 

Wagner’s unit-by-unit emissions reveals that emissions of SO2 from Wagner’s unit 3 are far 

greater than that of unit 2 and hence EPA believes controls and effectiveness of controls at unit 3 

at reducing SO2 are more important to any analysis of impacts from the plant. At this time, there 

are no federally enforceable controls in place at the plant to reduce SO2, and Wagner’s 

obligations to comply with the federal MATs requirements is not sufficient to allow EPA to fully 

evaluate future likely impacts from Wagner on the NAAQS, and are not relevant for evaluating 

whether actual emissions from 2012-2014 caused violations of the NAAQS during that period. 

Maryland has not presented any analysis or information to support that MATS compliance plans 

will reduce SO2 emissions from Wagner to such an extent that the SO2 NAAQS are met. Present 

information from Maryland regarding potential control options at the plant and fuel switching 

options without federally enforceable controls and limits is insufficient to support Maryland’s 

recommendation of attainment for the area. Furthermore, based on EPA’s review of emissions 

control information in conjunction with available air dispersion modeling discussed later in this

draft technical support document, EPA believes a designation of nonattainment is appropriate for 

the area around Wagner. 

Meteorology (Weather & Transport Patterns)

Maryland’s updated 2015 designation recommendation did not address meteorology. Maryland 

did not provide a discussion of the meteorology, nor any analysis or impacts of this factor on the 

area around Wagner. 

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

concentrations in the surrounding area is an important factor in determining the appropriate 

extent of EPA’s intended nonattainment area. The closest hourly reporting meteorological 

monitoring station to Wagner is the Baltimore-Washington International Airport (BWI). BWI is 

located approximately twelve (12) kilometers west of Wagner. A wind rose for the 2012-14 time 

period (Figure 4) shows predominantly westerly winds in the area.
15

Figure 4: BWI 2012-14 Wind Rose
16

Figure 5: Location of BWI Monitoring Location

Geography and Topography (Mountain Ranges or Other Air Basin Boundaries)

Maryland’s updated 2015 designation recommendation did not explicitly address this factor. 

Maryland did provide two topographical maps showing monitoring locations, but did not provide 

a discussion of the geography or topography, nor any analysis or impacts of this factor on the 

area around Wagner. 

EPA has reviewed both the geography and topography of the area surrounding Wagner. Wagner 

and Anne Arundel County lie within the Atlantic Coastal Plain just west of the Chesapeake Bay

(Figure 5). Elevations at the Facility are slightly above sea level. Stack heights at the Facility 

exceed 80 meters. This means that nearly all of the terrain in Anne Arundel County lies below 

the stack tops preventing potential plumes from directly impacting any nearby terrain features. 

The nearest terrain features lie over seventeen (17) kilometers northwest of Wagner.

As noted in EPA’s Modeling TAD, , in areas of flat terrain, such as the area surrounding 

Wagner, the distance to maximum concentration is generally expected to fall within a distance of 

ten (10) stack heights or approximately 1 kilometer from Wagner. Given the lack of terrain, and 
17

using general modeling principals from EPA’s Modeling TAD we expect maximum 

concentrations to occur within a kilometer or so from Wagner. The expected localized impact 

from Wagner is supported in information from the Summer 2013 Monitoring Study submitted by 

Maryland. Monitoring data from this study showed the Cianbro Site, located approximately 

three (3) kilometers west of Wagner, exceeded the 1-hr SO2 NAAQS on one occasion. Although 

this information supports expected maximum concentrations to occur within a kilometer or so 

from Wagner, based on general westerly/northwesterly wind patterns and the lack of terrain, it is 

reasonable to conclude that transport may play some role in dispersing SO2 downwind, and 

thereby causing additional violations of the SO2 NAAQS farther than a kilometer from the 

facility. Based on EPA’s review of this information, EPA believes there is insufficient evidence 

to support an attainment designation for the area surrounding Wagner. Furthermore, based 

EPA’s review of available air dispersion modeling discussed later in this technical support 

document, EPA believes a designation of nonattainment is appropriate for the area impacted by 

Wagner.

Figure 6: Elevation/Topography of Anne Arundel and Surrounding Counties
18

Air Dispersion Modeling 

Detailed Assessment of Maryland’s Modeling

In its November 20, 2015 recommendation, Maryland included a narrative describing 

preliminary modeling analyses that were being conducted by the State. The State notes that the 

modeling uses 2012-2014 actual emissions data, including the reductions in 2015 being seen 

from the use of low-sulfur coal for compliance with MATS at Wagner’s unit 2. EPA, however, 

is not aware of any federally enforceable restrictions on the Wagner plant regarding fuel sulfur 

limits or any SO2 controls. The State furthermore notes that the preliminary modeling includes 

emission units of Wagner, Brandon Shores, Crane, Wheelabrator and Energy Answers, and that 

background concentrations were based on a season and hour-of-day approach delineated in EPA 

guidance. On January 15, 2016, Maryland submitted a set of modeling files and a final modeling 

report as a supplement to its 2015 recommendation. Additionally, Maryland also included 

comments on the modeling analysis submitted by Sierra Club on January 4. 2016, which can be 

found in the docket.

Model Selection and Modeling Components

EPA’s draft Modeling TAD notes that for area designations under the 2010 SO2 NAAQS, the 

AERMOD modeling system should be used, unless use of an alternative model can be justified.

In some instances the recommended model may be a model other than AERMOD, such as the 

BLP model for buoyant line sources. The AERMOD modeling system contains the following 

components:

- AERMOD: the dispersion model

- AERMAP: the terrain processor for AERMOD

- AERMET: the meteorological data processor for AERMOD

- BPIPPRIME: the building input processor 

- AERMINUTE: a pre-processor to AERMET incorporating 1-minute automated surface 

observation system (ASOS) wind data 

- AERSURFACE: the surface characteristics processor for AERMET

- AERSCREEN: a screening version of AERMOD

In June of 2015 the Maryland Department of the Environment (MDE) provided a modeling 

analysis to Raven Power, the owner of Wagner, Brandon Shore (collectively known as Fort 

Smallwood) and Crane generating stations. Raven Power then contacted AECOM to review and 

update MDE’s modeling analysis.

Modeling components used by AECOM are summarized in Table 7. The modeling appears to 

have been completed in January 2016. AECOM included building downwash for the Wagner, 

Brandon Shores and Crane generating stations. No building downwash was determined for 

Wheelabrator Baltimore and Energy Answers, though this information was included in Energy 

Answers’ PSD/NSR application modeling.
19

Table 7: Model Versions Summary

AERMOD Component AECOM Version Current Version

AERMOD 15181 15181

AERSURFACE 13016 13016

AERMAP - 11103

AERMET 15181 15181

AERMINUTE 14337 15272

BPIPPRIME 04274 04274

Modeling Parameter: Rural or Urban Dispersion

EPA’s recommended procedure for characterizing an area by prevalent land use is based on 

evaluating the dispersion environment with 3 km of the facility. According to EPA’s modeling 

guidelines, rural dispersion coefficients are to be used in the dispersion modeling analysis if 

more than 50% of the area within a 3 km radius of the facility is classified as rural. Conversely, 

if more than 50% of the area is urban, urban dispersion coefficients should be used in the 

modeling analysis. AECOM’s modeling analysis utilized rural dispersion coefficients in its 

AERMOD runs. This conclusion was based on a visual inspection of 2011 Land Use Land 

Cover (LULC) information within three (3) kilometers of Fort Smallwood. When performing 

the modeling for the area of analysis, AECOM determined that it was most appropriate to run the 

model in rural mode. No analysis was done to determine if effective stack height exceeded any 

urban mixed layer that could be occurring over the City of Baltimore (see section 5.1 of EPA’s 

AERMOD Implementation Guide). The estimated urban boundary layer is 298.8 meters (see

equation (1) in previous noted section of EPA guidance).

Modeling Parameter: Area of Analysis (Receptor Grid)

EPA believes that a reasonable first step towards characterization of air quality in the area 

surrounding the Herbert A. Wagner Generating Station is to determine the extent of the area of 

analysis, i.e., receptor grid. Considerations presented in the draft Modeling TAD include but are 

not limited to: the location of the SO2 emission sources or facilities considered for modeling; the 

extent of significant concentration gradients of nearby sources; and sufficient receptor coverage 

and density to adequately capture and resolve the model predicted maximum SO2 concentrations. 

For the Wagner area, AECOM has included a total of ten (10) SO2 sources within twenty (20)

kilometers (km) of the Herbert A. Wagner Generating Station. This generally follows guidance 

outlined in EPA’s March 1, 2011 Clarification Memo entitled Additional Clarification 

Regarding Application of Appendix W Modeling Guidance for the 1-hour NO2, National Ambient 

Air Quality11. Standard AECOM included sources controlled by Raven Power (Wagner, 

Brandon Shores and Crane) along with the Baltimore Incinerator (Wheelabrator Baltimore) and 

the proposed Energy Answers municipal waste incinerator. 

Imbedded Cartesian receptor grids were developed by AECOM surrounding the Fort Smallwood 

complex (Brandon Shores and Wagner) and Crane. The receptor grids were developed as 

follows:

 

11 Top paragraph page 16
20

- 25 meter spacing along both facility’s property boundary

- 100 meter spacing out to two (2) km

- 250 meter spacing between two (2) and five (5) km

- 500 meter spacing between five (5) and ten (10) km

The model receptor network contained a total of 6,181 receptors. Model receptors were placed 

in Anne Arundel and Baltimore counties and Baltimore City. AECOM followed EPA’s 

Modeling TAD and attempted to remove receptors that were located over open water and other 

sites where it would not be feasible to site an actual monitor and record ambient impacts. Figure

7 shows AECOM’s chosen area of analysis surrounding the Herbert A. Wagner Generating 

Station, as well as receptor grid for the area of analysis.

Figure 7: AECOM’s Model Receptor Grid for the Wagner Area of Analysis

Modeling Parameter: Source Characterization

AECOM characterized ten (10) sources within the area of analysis in accordance with the best 

practices outlined in the Modeling TAD. All sources were modeled as point sources with no 

horizontal or obstructed stacks. These included all the major SO2 sources operated by Raven 

Power along with two (2) other sources. All coal-fired units were included in the modeling 

analysis along with two (2) large oil-fired units at Wagner that make up the Fort Smallwood 
21

complex. Smaller ancillary emission sources and start-up/shut-down emissions were not 

included in AECOM’s modeling analysis.

Additional stack information is summarized in Table 8. This includes information on emission 

rates, hourly varying stack parameters and how well sources using actual hourly emission rates 

compare to those rates pulled from EPA’s Clear Air Markets website12. In general, Raven 

Power’s modeled hourly emissions matched those extracted from the Clean Air Market’s 

website.

Table 8: Summary of Stack Information for Facilities in the Wagner Area of Analysis

AECOM Source Model Emission 

Rate

Hourly Emission 

Matches CAMD

Variable 

Stack Temp

Variable Stack 

Velocity

Crane 1 Actual, Hourly Nearly Identical No No

Crane 2 Actual, Hourly Nearly Identical No No

Brandon Shores 1 Actual, Hourly Nearly Identical Yes Yes

Brandon Shores 2 Actual, Hourly Nearly Identical Yes Yes

Wagner 1 Actual, Hourly Nearly Identical No No

Wagner 2 Adjusted 

Actual, Hourly

Adjusted to

1.0 lb/MMBtu

Yes Yes

Wagner 3 Actual, Hourly Nearly Identical Yes Yes

Wagner 4 Actual, Hourly Nearly Identical No No

Wheelabrator

Baltimore

Allowable NA No No

Energy Answers Allowable NA No No

Stack parameters pulled from EPA’s 2011 National Emissions Inventory (NEI) are listed for 

comparison to AECOM’s. Additionally, stack parameters for Energy Answers were pulled from 

its PSD/NSR application. The physical stack parameters (stack heights and stack diameters) 

from both data sets generally match. There is a slight discrepancy in Wheelabrator Baltimore’s 

stack diameter. An equivalent stack diameter was taken based on the 2011 NEI since 

Wheelabrator’s stack appears to have three flues contained in one stack (each 2.13 m in 

diameter). AECOM’s stack parameters for Energy Answers are identical to those contained in 

its PSD/NSR application modeling analysis accept for the stack diameter, which was 

significantly larger in the application. There were also slight differences, i.e., a few meters, in 

the stack base elevations for Wheelabrator Baltimore and Energy Answers.

AECOM used a merged stack technique when Brandon Shore Units 1 & 2 operated 

simultaneously. This is in accordance with EPA Clearing House Memorandum 91-II-01 and is 

an appropriate modeling technique since both units share a common stack (dual-flue stack). 

Merging the stacks will slightly enhance the stack velocity and final plume rise. Again, this only 

occurs when both Brandon Shore units are operating.

 

12 http://ampd.epa.gov/ampd/
22

Table 9: AECOM Stack Parameters

Facility Unit

Stack 

Height

(m)

Stack 

Temperature

(K)

Stack 

Velocity

(m/s)

Stack 

Diameter

(m)

Fort Smallwood Brandon Unit 1 121.92 324.817 15.073 9.5

Fort Smallwood Brandon Unit 2 121.92 324.817 14.895 9.5

Fort Smallwood Wagner Unit 1 87.478 330 30.48 3.099

Fort Smallwood Wagner Unit 2 87.48 422.039 30.48 3.1

Fort Smallwood Wagner Unit 3 105.46 416.48 33.817 4.215

Fort Smallwood Wagner Unit 4 104.242 610.928 35.3568 5.334

C.P. Crane Crane Stack 1 107.594 435.93 30.48 3.328

C.P. Crane Crane Stack 2 107.59 438.71 30.48 3.33

Wheelabrator 

Baltimore

96.01 485.93 22.55 2.13

Energy Answers 89.92 439.26 25.94 1.2984

Table 10: EPA 2011 (Version 1) NEI Stack Parameters

Facility Unit

Stack 

Height

(m)

Stack 

Temperature

(K)

Stack 

Velocity

(m/s)

Stack 

Diameter

(m)

Fort Smallwood Brandon Unit 1 121.9 325.4 17.0 9.60

Fort Smallwood Brandon Unit 2 121.9 325.4 17.0 9.60

Fort Smallwood Wagner Unit 1 87.5 438.7 30.5 3.11

Fort Smallwood Wagner Unit 2 87.5 438.7 30.3 3.11

Fort Smallwood Wagner Unit 3 105.5 430.4 32.4 4.11

Fort Smallwood Wagner Unit 4 104.2 610.9 35.4 5.33

C.P. Crane Crane Stack 1 107.6 438.7 30.3 3.32

C.P. Crane Crane Stack 2 107.6 433.2 30.3 3.32

Wheelabrator 

Baltimore

96.0 485.9 22.6 3.70

Table 11: Energy Answers Application (100% Load Run)

Facility Unit

Stack 

Height

(m)

Stack 

Temperature

(K)

Stack 

Velocity

(m/s)

Stack 

Diameter

(m)

Energy Answers 89.92 439.26 25.94 4.26

Modeling Parameter: Emissions 

EPA’s Modeling TAD notes that for the purposes of modeling to characterize air quality for use 

in designations, the recommended approach is to use the most recent three years of actual 

emissions data and concurrent meteorological data. However, the Modeling TAD does provide 

for the flexibility of using allowable emissions in the form of the most recently permitted, 

(referred to as PTE or allowable) emissions rate.
23

EPA believes that continuous emissions monitoring systems (CEMS) data provide acceptable 

historical emissions information when it is available, and that these data are available for many 

electric generating units. In the absence of CEMS data, EPA’s draft Modeling TAD highly 

encourages the use of AERMOD’s hourly varying emissions keyword HOUREMIS, or through 

the use of AERMOD’s variable emissions factors keyword EMISFACT. When choosing one of 

these methods, EPA believes that detailed throughput, operating schedules, and emissions 

information from the impacted source(s) should be used. 

In certain instances, states and other interested parties may find that it is more advantageous or 

simpler to use PTE rates as part of their modeling runs. Specifically, a facility may have recently 

adopted a new federally enforceable emissions limit, been subject to a federally enforceable 

consent decree, or implemented other federally enforceable mechanisms and control 

technologies to limit SO2 emissions to a level that indicates compliance with the NAAQS. These 

new limits or conditions may be used in the application of AERMOD. In these cases, the 

Modeling TAD notes that the existing SO2 emissions inventories used for permitting or SIP 

planning demonstrations should contain the necessary emissions information for designationsrelated modeling. In the event that these short-term emissions are not readily available, they may 

be calculated using the methodology in Table 8-1 of Appendix W to 40 CFR Part 51 titled, 

“Guideline on Air Quality Models.” 

As previously noted, AECOM included ten (10) sources in its SO2 modeling analysis. AECOM 

selected and refined these sources based on earlier modeling conducted by MDE. These sources 

should adequately represent the area where maximum concentrations of SO2 are expected to 

occur and adequately includes the sources which might contribute to those concentrations. There 

are no other larges sources of SO2 that have the potential to cause significant concentration 

gradients within the area of analysis. For this area of analysis, AECOM used a hybrid approach, 

where emissions from most of the sources are expressed as actual emissions, two (2) sources 

used non-federally enforceable emission rates and one (1) source adjusted its historic actual 

emission rates to account for a fuel switch that has recently reduced the unit’s actual SO2

emissions. Tables 12-14 summarize the total emissions included in the modeling analysis. 

Source totals represent a mix of actual, non-federally enforceable and adjusted emission rates.

Table 12: Actual Emissions

Company ID Facility Name Unit

SO2 Emissions (tons per year)

2012 2013 2014

Raven Power Brandon Shores 1 1,546.9 1,389.0 1,669.9

Raven Power Brandon Shores 2 1,301.3 1,481.3 1,475.2

Raven Power Wagner 1 0.2 0.2 72.6

Raven Power Wagner 2 2,512.8 1,551.3 1,939.0

Raven Power Wagner 3 4,960.2 8,553.5 7,276.1

Raven Power Wagner 4 41.2 72.7 322.5

Raven Power Crane 1 1,212.0 831.3 573.4

Raven Power Crane 2 961.2 2,140.3 1,313.8

Total Emissions All Facilities 12,535.8 16,019.6 14,642.5
24

Table 13: Adjusted Emissions Rate Sources

Company ID

Adjusted emissions 

rates (tons per year) 2011 NEI v1 (tons per year)

Wheelabrator Baltimore 439.2 261.3

Energy Answers 479.6

Table 14: Adjusted Wagner Unit 2 Emissions

Unit Emission Rate

SO2 Emissions (tons per year)

2012 2013 2014

Wagner Unit 2 Actual 2,512.8 1,551.3 1,939.0

Wagner Unit 2 Adjusted (1.0 lbs/MMBtu) 2,219.5 1,139.2 1,421.7

Modeling Parameter: Meteorology and Surface Characteristics

The most recent three (3) years of meteorological data (concurrent with the most recent three 

years of emissions data) should be used in designations efforts. As noted in the Modeling TAD, 

the selection of data should be based on spatial and climatological (temporal) representativeness. 

The representativeness of the data are based on: 1) the proximity of the meteorological 

monitoring site to the area under consideration, 2) the complexity of terrain, 3) the exposure of 

the meteorological site, and 4) the period of time during which data are collected. Sources of 

meteorological data include National Weather Service (NWS) stations, site-specific or onsite 

data, and other sources such as universities, Federal Aviation Administration (FAA), and 

military stations.

For the Wagner area of analysis, AECOM used surface meteorology from Baltimore-Washington 

International Airport (BWI). Meteorological data was concurrent with the hourly emission date 

used in the modeling analysis (2012-14). AECOM’s AERMOD file specified BWI’s station 

elevation as 4.4 meters; the station’s actual elevation is 45 meters. AECOM did not provide any 

documentation to determine if the meteorological data is representative of the Wagner area. 

BWI is the closest ASOS first order station and is located a little over 10 kilometers west of Fort 

Smallwood (see Figure 9). Upper Air data used in AERMET was taken from Sterling, VA, 

which is part of Dulles Airport (IAD) and is located approximately 82 kilometers west-southwest 

of Fort Smallwood. AECOM processed the data using AERMET’s Adjust U* non-default 

option. This process adjusts the surface friction velocity for periods of low wind speeds.

EPA notes that the use of beta options, such as ADJ_U* and LOWWIND3, in AERMOD for any 

regulatory applications requires adherence with Appendix W, Section 3.2.2. This is further 

explained in EPA’s December 10, 2015 Memorandum titled, “Clarification on the Approval 

Process for Regulatory Application of the AERMOD Modeling System Beta Options.” Among 

other conditions, the use of beta options requires consultation with the appropriate EPA Regional 

Offices. Upon concurrence by EPA’s Modeling Clearinghouse, EPA Regional Offices may 

approve the use of these beta options for regulatory applications as an alternative model. 

However, Maryland’s air dispersion modeling, performed by AECOM, intended to characterize 
25

air quality as a result of SO2 emissions from Wagner without prior consultation with and 

approval from EPA’s Region 3’s Office, and therefore has not met the applicable regulatory 

requirements contained in Appendix W, Section 3.2.2. As a result, EPA does not believe that the 

air quality modeling results obtained from the use of these beta options can be used as a reliable 

indicator of attainment status in the area around Wagner until appropriate alternative model 

approval is granted or these beta options are promulgated as regulatory options in AERMOD 

through EPA rulemaking. 

AECOM used AERSURFACE using the location of BWI to estimate the surface characteristics 

of the Wagner area of analysis. Estimated values for surface roughness used twelve (12) spatial 

sectors out to 1 km at a monthly temporal resolution for dry, wet, average conditions based on 

BWI’s 30-year precipitation averages. AECOM also estimated values for albedo (the fraction of 

solar energy reflected from the earth back into space) and the Bowen ratio (the method generally 

used to calculate heat lost or heat gained in a substance. No months contained continuous snow 

cover though there may have been continuous snow cover at BWI in January and February of 

2014.

Figure 9: Met Data Sites used in the Wagner Area of Analysis
26

The three-year (2012-14) surface wind rose for Baltimore-Washington Airport (BWI) based on 

the processed surface file is depicted in Figure 10. In this figure, the frequency and magnitude of 

wind speed and direction are defined in terms of where the wind is blowing from. The resultant 

vector shows the dominant direction or mean direction of the wind vectors. Winds were 

predominantly out of the west to northwest.

Figure 10: Surface Met File Cumulative Wind Rose for Years 2012-14

Meteorological data from the surface (BWI) and upper air stations (IAD) were used in generating 

AERMOD-ready files with the AERMET processor. The output meteorological data created by 

the AERMET processor is suitable for being applied with AERMOD input files for AERMOD 
27

modeling runs. AECOM appears to have generally followed the methodology and settings 

presented in the processing of the raw meteorological data into an AERMOD-ready format, and 

used AERSURFACE to best represent surface characteristics. There were differences in the 

AERMOD ready surface and profile files included in AECOM’s documentation; the files 

included in the AERMOD directory do not match those included in the AERMET_V15181 

directory. Notably, the reference measurement heights in the AERMET_V15181 do not match 

anemometer heights at BWI.

Hourly surface meteorological data records are read by AERMET, and include all the necessary 

elements for data processing. However, wind data taken at hourly intervals may not always 

portray wind conditions for the entire hour, which can be variable in nature. Hourly wind data 

may also be overly prone to indicate calm conditions, which are not modeled by AERMOD. In 

order to better represent actual wind conditions at the meteorological tower, wind data of one 

minute duration was provided from the same instrument tower, but in a different formatted file to 

be processed by a separate preprocessor, AERMINUTE. These data were subsequently 

integrated into the AERMET processing to produce final hourly wind records of AERMODready meteorological data that better estimate actual hourly average conditions and that are less 

prone to over-report calm wind conditions. This allows AERMOD to apply more hours of 

meteorology to modeled inputs, and therefore produce a more complete set of concentration 

estimates. As a guard against excessively high concentrations that could be produced by 

AERMOD in very light wind conditions, the state set a minimum threshold of 0.5 meters per 

second in processing meteorological data for use in AERMOD. In setting this threshold, no wind 

speeds lower than this value would be used for determining concentrations. This threshold was 

specifically applied to the one minute wind data. 

Modeling Parameter: Geography and Terrain

Fort Smallwood, Crane, Wheelabrator Baltimore and the proposed Energy Answers facilities are 

all located along the western shoreline of the Chesapeake Bay. This area is generally 

characterized as part of the Atlantic Coastal Plain physiographic region. Terrain is generally flat 

in the vicinity of the modeled sources but rises steeply approximately 17 kilometers to the 

northwest of the Fort Smallwood Complex as the Atlantic Coastal Plain gives way to the 

Piedmont (see Figure 11).
28

Figure 11: Elevations in the AECOM modeling domain

Elevation information for stack-base elevations and model receptors was obtained from National 

Elevation Dataset (NED) GeoTiff data. GeoTiff is a binary file that includes data descriptors and 

geo-referencing information necessary for extracting terrain elevations. These elevations were 

extracted from 1 arc-second (30 meter) resolution NED files using EPA’s AERMAP processor.

Modeling Parameter: Background Concentrations of SO2

The Modeling TAD offers two mechanisms for characterizing background concentrations of SO2

that are ultimately added to the modeled design values: 1) a “first tier” approach, based on 

monitored design values, or 2) a temporally varying approach, based on the 99th percentile 

monitored concentrations by hour of day and season or month. For the Wagner area of analysis, 

AECOM chose to use an hour of day seasonal varying background concentrations. The 

background concentration for this area of analysis was determined by AECOM based on hourly 

monitored concentrations from the Beltsville, MD monitoring site. AECOM substituted a 

constant background concentration of 3.9 μg/m3 whenever wind directions ranged from 70 to 

130 degrees (easterly). This was done to account for a lack of SO2 sources directly to the east of 
29

the Wagner area of analysis; 3.9 μg/m3 was chosen to represent a true pristine background 

concentration.

Summary of Modeling Results

The AERMOD modeling parameters for the Wagner area of analysis are summarized below in 

Table 15. Note that AECOM used several non-default options in their AERMOD analysis. This 

included using Adjust U* in its AERMET processing and using the non-default Low Wind 3 

option in AERMOD. These options were used in tandem and are not currently considered part 

of the regulatory default options in AERMOD. Moreover, Maryland did not seek and has not 

obtained EPA Regional approval for their use in this case. As a result, EPA does not believe that 

the air quality modeling results obtained from the use of these beta options can be used as a 

reliable indicator of attainment status in the area around Wagner until appropriate alternative 

model approval is granted or these beta options are promulgated as regulatory options in 

AERMOD through EPA rulemaking. 

Table 15: AERMOD Modeling Parameters for the Wagner Area of Analysis

Wagner Area of Analysis

AERMOD Version 15181

Dispersion Characteristics Rural

Modeled Sources 4

Modeled Stacks 10

Modeled Structures Multiple, Raven Power Sources Only

Modeled Fencelines 2

Total receptors 6,181

Emissions Type Actual, PTE, Adjusted Actual

Emissions Years Hourly 2012-2014, Current PTE, Retro Adjusted Hourly 

Meteorology Years 2012-2014

Surface Meteorology Station Baltimore-Washington International Airport, MD

Upper Air Meteorology Station Dulles Airport, Sterling, VA

Methodology for Calculating 

Background SO2 Concentration

Hour to Hour, Seasonally Varying, Easterly Winds changed 

to “background”

Non-Default AERMOD Options Adjust U*, Low Wind 3

Calculated Background SO2

Concentration 10.3 μg/m3

The results presented below in Table 16 show the magnitude and geographic location of the 

highest predicted modeled concentration based on emissions compiled by AECOM.
30

Table 16: Maximum Predicted 99th Percentile 1-Hour SO2 Concentration in the Wagner Area of 

Analysis Based on AECOM’s Emission Profile

Averaging Period Data Period

Receptor Location SO2 Concentration (μg/m3

)

UTM/Latitude UTM/Longitude

Modeled (including 

background) NAAQS

99th Percentile 

1-Hour Average 2012-2014 369375 4336940 186.0 196.2*

*Equivalent to the 2010 SO2 NAAQS set at 75 ppb

AECOM’s modeling indicates that the predicted 99th percentile 1-hour average concentration 

within the chosen modeling domain is 186.0 μg/m3, or ~71 ppb. This modeled concentration 

included the background concentration of SO2, and is based on AECOM’s source emission 

profile. This predicted value occurred approximately 1.1 kilometers east-southeast of the Fort 

Smallwood Complex and is graphically represented along with all the other receptors below in 

Figures 12-13. 

Figure 12: Maximum Predicted 99th Percentile 1-Hour SO2 Concentrations in the Wagner Area 

of Analysis Based on AECOM Emission Profile (Close-Up)
31

Figure 13: Maximum Predicted 99th Percentile 1-Hour SO2 Concentrations in the

Wagner Area of Analysis Based on AECOM Emission Profile (Regional)

Detailed Assessment of May 2015 Sierra Club Modeling for Wagner/Brandon Shores/Crane

On January 4, 2016, Sierra Club submitted to EPA an air dispersion modeling analysis of SO2

from Wagner, Brandon Shores, and Crane. The discussion and analysis that follows below will 

reference Sierra Club’s use of the Modeling TAD, EPA’s assessment of Sierra Club’s modeling 

in accordance with the Modeling TAD, and the factors for evaluation contained in EPA’s March 

20, 2015 guidance, as appropriate

Model Selection and Modeling Components

EPA’s draft Modeling TAD notes that for area designations under the 2010 SO2 NAAQS, the 

AERMOD modeling system should be used, unless use of an alternative model can be justified.

In some instances the recommended model may be a model other than AERMOD, such as the 

BLP model for buoyant line sources. The AERMOD modeling system contains the following 

components:

- AERMOD: the dispersion model

- AERMAP: the terrain processor for AERMOD
32

- AERMET: the meteorological data processor for AERMOD

- BPIPPRIME: the building input processor 

- AERMINUTE: a pre-processor to AERMET incorporating 1-minute automated surface 

observation system (ASOS) wind data 

- AERSURFACE: the surface characteristics processor for AERMET

- AERSCREEN: a screening version of AERMOD

Modeling components used by Sierra Club are summarized in Table 17. This modeling analysis 

was completed in May of 2015 so some of the AERMOD components were run using older 

versions that were the latest available at the time. However, EPA does not believe that the use of 

the most recent versions of AERMOD and its components would alter the modeled results in a 

manner that would change our intended designation. Sierra Club used AERMOD version 14134, 

and a discussion of the individual components will be referenced in the corresponding discussion 

that follows as appropriate. While the version of AERMOD used in Sierra Club’s modeling is 

not the latest version of the model available, EPA does not believe that updating the model 

version and rerunning with the same model inputs and options would result in significantly 

different modeled impacts or change our intended designation for the area of analysis. EPA 

conducts tests cases for newly released versions of AERMOD to document the differences in 

several “standard” test case scenarios to compare results with previous releases of the model.13 

Review of version 15181 test case results and comparison with version 14134 shows that the 

updated model version impacts modeled results for only a small subset of the test scenarios 

(capped and horizontal stacks and multiple urban areas), which are not applicable to Wagner. 

Therefore, we do not anticipate that rerunning the model with the later model version would 

significantly impact the modeled concentrations.

No buildings were included in this modeling analysis thus building downwash, which would tend 

to increase impacts, was not evaluated. AERMOD was run in regulatory default mode.

Table 17: Model Versions Summary

AERMOD Component Sierra Club Version Current Version

AERMOD 14134 15181

AERSURFACE 13016 13016

AERMAP 11103 11103

AERMET 14134 15181

AERMINUTE 14237 15272

Modeling Parameter: Rural or Urban Dispersion

EPA’s recommended procedure for characterizing an area by prevalent land use is based on 

evaluating the dispersion environment within 3 km of the facility. According to EPA’s modeling 

guidelines, rural dispersion coefficients are to be used in the dispersion modeling analysis if 

more than 50% of the area within a 3 km radius of the facility is classified as rural. Conversely, 

if more than 50% of the area is urban, urban dispersion coefficients should be used in the 

 

13 AERMOD test case information available at the following website: 

http://www3.epa.gov/ttn/scram/dispersion_prefrec.htm.
33

modeling analysis. The Sierra Club modeling analysis used rural dispersion coefficients in 

AERMOD. This was determined by examining the percentage of land use categories within 

three (3) kilometers of the modeled sources. Land use land cover (LULC) information from 

1992 was processed using AERSURFACE. Rural categorization was supported based on there 

being less than 50% of the LULC categories with urban uses surrounding the modeled sources.

Modeling Parameter: Area of Analysis (Receptor Grid)

EPA believes that a reasonable first step towards characterization of air quality in the Wagner 

area is to determine the extent of the area of analysis, i.e., receptor grid. Considerations 

presented in the Modeling TAD include but are not limited to: the location of the SO2 emission 

sources or facilities considered for modeling; the extent of significant concentration gradients of 

nearby sources; and sufficient receptor coverage and density to adequately capture and resolve 

the model predicted maximum SO2 concentrations.

Sierra Club used an extensive model receptor grid that included a total of 97,081 individual 

receptor grids. A 100-m spaced Cartesian grid was centered around the Fort Smallwood 

(Wagner and Brandon Shores generating units) and the Crane facilities. These facilities are 

roughly 20 kilometers distant from each other. The model receptor grid spacing was increased to 

500 m and extended an additional 10 kilometers from the 100-m grid. Model receptors extended 

over the open waters of the Chesapeake Bay and adjacent rivers and also extended over the 

property boundaries of Fort Smallwood and Crane (these areas would not qualify as ambient air). 

Sierra Club also used flagpole receptors extending 1.5 m above the surface. EPA generally 

recommends receptors be located at ground level though this difference in receptor heights 

should have little impact on final model concentrations.

Figure 14 shows the Sierra Club’s model receptor grid and the locations of the model sources. 

The approximate property/ambient air boundary of the Fort Smallwood complex, which includes 

the Wagner and Brandon Shores generating units, is also shown. Crane is located approximately

20 kilometers northeast of Fort Smallwood.
34

Figure 14: Sierra Club Model Receptor Grid

Modeling Parameter: Source Characterization

Sierra Club only modeled the coal units for Wagner, Brandon Shores and Crane. A total of six 

(6) sources were modeled. In addition to the two (2) coal units, Wagner also has two (2) oil fired 

units, which were not included in the modeling analysis. Table 18 lists the largest SO2 sources 

from these facilities in EPA’s Clean Air Markets Program14 database.

Table 18: Source Listing for Wagner, Brandon Shores (collectively known as Fort Smallwood)

and Crane

Facility Unit Fuel SO2 Control Modeled

H.A. Wagner Unit #1 Oil - No

H.A. Wagner Unit #2 Coal - Yes

H.A. Wagner Unit #3 Coal - Yes

H.A. Wagner Unit #4 Oil - No

 

14 http://ampd.epa.gov/ampd/
35

Brandon Shores Unit #1 Coal FGD Yes

Brandon Shores Unit #2 Coal FGD Yes

C. P. Crane Unit #1 Coal - Yes

C. P. Crane Unit #2 Coal - Yes

Modeling Parameter: Emissions 

EPA’s Modeling TAD notes that for the purposes of modeling to characterize air quality for use 

in designations, the recommended approach is to use the most recent three years of actual 

emissions data and concurrent meteorological data. However, the TAD does provide for the 

flexibility of using allowable emissions in the form of the most recently permitted, (referred to as 

PTE or allowable) emissions rate.

EPA believes that continuous emissions monitoring systems (CEMS) data provide acceptable 

historical emissions information when it is available, and that these data are available for many 

electric generating units. In the absence of CEMS data, EPA’s Modeling TAD highly 

encourages the use of AERMOD’s hourly varying emissions keyword HOUREMIS, or through 

the use of AERMOD’s variable emissions factors keyword EMISFACT. When choosing one of 

these methods, EPA believes that detailed throughput, operating schedules, and emissions 

information from the impacted source(s) should be used. 

In certain instances, states and other interested parties may find that it is more advantageous or 

simpler to use PTE rates as part of their modeling runs. Specifically, a facility may have recently 

adopted a new federally enforceable emissions limit, been subject to a federally enforceable 

consent decree, or implemented other federally enforceable mechanisms and control 

technologies to limit SO2 emissions to a level that indicates compliance with the NAAQS. These 

new limits or conditions may be used in the application of AERMOD. In these cases, the 

Modeling TAD notes that the existing SO2 emissions inventories used for permitting or SIP 

planning demonstrations should contain the necessary emissions information for designationsrelated modeling. In the event that these short-term emissions are not readily available, they may 

be calculated using the methodology in Table 8-1 of Appendix W to 40 CFR Part 51 titled, 

“Guideline on Air Quality Models.” 

 

The Sierra Club modeling analysis included three (3) emissions scenarios, 1)

permitted/maximum allowable emissions, 2) 99th percentile actual hourly emissions, and 3) 

actual hourly emissions. Only the simulation that used actual emissions from the coal-fired units 

at Fort Smallwood (Wagner and Brandon Shores) and Crane are included in our review since 

these runs were done in accordance with EPA’s Modeling TAD.

As noted previously, the modeling analysis did not include SO2 emissions from two (2) oil-fired 

units that are part of Wagner. The coal-fired units included in the modeling analysis are the 

largest SO2 emissions sources in the Baltimore, Maryland area. Other sources in the area are 

generally below 250 tpy with most well under 100 tpy. The facilities in the area of analysis and 

their associated annual actual SO2 emissions between 2012 and 2014 are summarized in Table 

19.
36

Table 19: 2012-14 Actual SO2 Emissions Sources in the Sierra Club’s Modeling Analysis

Facility Name Unit Designation

SO2 Emissions (tpy)

2012 2013 2014

H.A. Wagner Unit #2 2,512.8 1,551.3 1,939.0

H.A. Wagner Unit #3 4,960.2 8,553.5 7,276.1

Brandon Shores Unit #1 1,546.9 1,389.0 1,669.9

Brandon Shores Unit #2 1,301.3 1,481.3 1,475.2

C. P. Crane Unit #1 1,212.0 831.3 573.4

C. P. Crane Unit #2 961.2 2,140.3 1,313.8

Total Emissions 15,194.4 15,946.7 14,247.2

For each of the six (6) coal units included in the modeling analysis, Sierra Club used actual 

hourly emissions from 2012-14. Sierra Club’s hourly emission file was compared to hourly 

emissions from the Clean Air Markets website and found to be nearly identical. Physical stack 

parameters including stack heights and stack diameters were checked with information contained 

in the 2011 (Version 1) NEI. Modeled stack heights and diameters nearly matched those 

contained in the 2011 NEI. Stack temperatures and velocities for the modeled sources were 

taken from recent stack tests according Sierra Club’s documentation. These values were kept 

constant throughout Sierra Club’s modeling analysis. In reality, both stack temperatures and 

velocities will vary according to a unit’s load. This information, however, is not readily 

available from EPA’s Clean Air Market’s website. The stack temperature and velocity 

information in the modeling analysis appears to be reasonable and is similar to values contained 

in the 2011 NEI. Sierra Club’s modeled stack parameters and those taken from the 2011 NEI are 

summarized in Tables 20 and 21.

Table 20: Sierra Club Modeling Stack Parameters

Facility Unit

Stack 

Height

(m)

Stack 

Temperature

(K)

Stack 

Velocity

(m/s)

Stack 

Diameter

(m)

Fort Smallwood Brandon Unit 1 121.9 326.5 13.0 9.51

Fort Smallwood Brandon Unit 2 121.9 326.5 12.0 9.51

Fort Smallwood Wagner Unit 2 87.5 409.8 22.7 3.11

Fort Smallwood Wagner Unit 3 105.5 418.7 28.7 4.21

C.P. Crane Crane Stack 1 107.6 427.6 29.9 3.32

C.P. Crane Crane Stack 2 107.6 427.6 29.1 3.32
37

Table 21: EPA 2011 (Version 1) NEI Stack Parameters

Facility Unit

Stack 

Height

(m)

Stack 

Temperature

(K)

Stack 

Velocity

(m/s)

Stack 

Diameter

(m)

Fort Smallwood Brandon Unit 1 121.9 325.4 17.0 9.60

Fort Smallwood Brandon Unit 2 121.9 325.4 17.0 9.60

Fort Smallwood Wagner Unit 2 87.5 438.7 30.3 3.11

Fort Smallwood Wagner Unit 3 105.5 430.4 32.4 4.11

C.P. Crane Crane Stack 1 107.6 438.7 30.3 3.32

C.P. Crane Crane Stack 2 107.6 433.2 30.3 3.32

Modeling Parameter: Meteorology and Surface Characteristics

The most recent three years of meteorological data (concurrent with the most recent three years 

of emissions data) should be used in designations efforts. As noted in the Modeling TAD, the 

selection of data should be based on spatial and climatological (temporal) representativeness. 

The representativeness of the data are based on: 1) the proximity of the meteorological 

monitoring site to the area under consideration, 2) the complexity of terrain, 3) the exposure of 

the meteorological site, and 4) the period of time during which data are collected. Sources of 

meteorological data include National Weather Service (NWS) stations, site-specific or onsite 

data, and other sources such as universities, Federal Aviation Administration (FAA), and 

military stations.

Sierra Club used hourly meteorological data from the Baltimore-Washington International 

Airport (BWI). Meteorological data was concurrent with the hourly emission date used in the 

modeling analysis (2012-14). Hourly wind measurements were supplemented with 1-minute 

data using EPA’s AERMINUTE processor. Sierra Club did not provide any documentation to 

determine if the meteorological data is representative of the area surrounding Wagner. BWI is 

the closest ASOS first order station and is located a little over 10 kilometers west of Fort 

Smallwood (see Figure 15).

In addition to meteorological variables, AERMET needs surface characteristics to process the 

meteorological information into the format needed to run in AERMOD. Sierra Club used 

AERSURFACE to generate surface characteristics based on the location of the BWI anemometer 

site. The modeled anemometer height (10 meters) was confirmed with available information. 

Surface characteristics were based on twelve 30o sectors in AERSURFACE and developed on a 

seasonal basis. Continuous snow cover during the winter season and average moisture 

conditions were assumed for the entire simulation period. A quick check of snow cover 

information and monthly precipitation values at BWI showed snow cover was only continuous 

over the 2014-15 winter season and seasonal soil moisture conditions varied from average to wet 

to dry in accordance with Section 2.2 of the AERSURFACE user’s guide.
38

Figure 15: Locations of BWI anemometer and Fort Smallwood

The three-year surface wind rose for the Baltimore-Washington Airport is depicted in Figure 16. 

Winds, based on the AERMET processed data, are predominantly from the west. The resultant 

vector shows the dominant direction or mean direction of the wind vectors.
39

Figure 16: Baltimore-Washington Airport Wind Rose for Years 2012 – 2014

Meteorological data from the Baltimore-Washington Airport, MD and Sterling, VA were used in 

generating AERMOD-ready files with the AERMET processor. Output processing files 

provided by Sierra Club indicate the meteorological data is more than 90% complete using 1-

minute data to supplement the hourly surface wind measurements. Minimum wind speed 

thresholds were set to 0.5 m/s as recommended. This approach is consistent with a March 2013 

EPA memo titled, “Use of ASOS meteorological data in AERMOD dispersion Modeling.”
40

Modeling Parameter: Geography and Terrain

Fort Smallwood and Crane are both located along the western shoreline of the Chesapeake Bay. 

This area is generally characterized as part of the Atlantic Coastal Plain physiographic region. 

Terrain is generally flat in the vicinity of the modeled sources but rises steeply approximately 17 

kilometers to the northwest as the Atlantic Coastal Plain gives way to the Piedmont (see Figure 

17).

Figure 17: Elevations in the Sierra Club modeling domain

Elevation information for stack-base elevations and model receptors was obtained from National 

Elevation Dataset (NED) GeoTiff data. GeoTiff is a binary file that includes data descriptors and 

geo-referencing information necessary for extracting terrain elevations. These elevations were 

extracted from 1 arc-second (30 meter) resolution NED files using EPA’s AERMAP processor.

Modeling Parameter: Background Concentrations of SO2

The Modeling TAD offers two mechanisms for characterizing SO2 background concentrations 

that are ultimately added to the modeled design values: 1) a “first tier” approach, based on 

monitored design values, or 2) a temporally varying approach, based on the 99th percentile 
41

monitored concentrations by hour of day and season or month. Sierra Club chose the first option 

and used the Prince George County’s Beltsville monitor’s 2011-13 design value, which had the 

lowest design value of the three (3) monitors in Maryland. Beltsville is located northeast of 

Washington DC and is over 30 km southwest of Fort Smallwood. The background concentration 

for the modeling analysis was 26.2 micrograms per cubic meter (μg/m3), or 10 ppb.15 This 

background value was added to the final AERMOD results. 

Summary of Modeling Results

Sierra Club’s AERMOD modeling summary for the area surrounding Wagner is summarized 

below in Table 22.

Table 22: AERMOD Modeling Parameters for the Wagner Area Modeling Analysis

Sierra Club’s Wagner Area of Analysis

AERMOD Version 14134

Dispersion Characteristics Rural

Modeled Sources 2

Modeled Stacks 6

Modeled Structures None

Modeled Fencelines None

Total receptors 97,081

Emissions Type Actual Hourly Varying

Emissions Years 2012-2014

Meteorology Years 2012-2014

Surface Meteorology Station Baltimore-Washington Airport, MD

Upper Air Meteorology Station Sterling, VA 

Methodology for Calculating Background SO2

Concentration 2011-13 Design Value

Calculated Background SO2 Concentration 26.2 μg/m3

The results presented below in Table 23 and Figure 18 show the magnitude and geographic 

location of the highest predicted modeled concentration based on actual (hourly) emissions.

Table 23: Maximum Predicted 99th Percentile 1-Hour SO2 Concentration in the Wagner Area of 

Analysis Based on Actual (Hourly) Emissions

Averaging Period Data Period

Receptor Location SO2 Concentration (μg/m3

)

UTM/Latitude UTM/Longitude

Modeled (including 

background) NAAQS

99th Percentile 

1-Hour Average 2012-2014 368,753.75 4,337,092.5 293.9 196.2 16

 

15 The conversion factor for SO2 (at the standard conditions applied in the ambient SO2 reference method) is 1ppb = 

approximately 2.62μg/m3.

16 Equivalent to the 2010 SO2 NAAQS set at 75 ppb.
42

Sierra Club’s modeling indicates that the predicted 99th percentile 1-hour average concentration 

within the chosen modeling domain is 293.9 μg/m3, or approximately 112.3 ppb. This modeled 

concentration included a background concentration of SO2, and is based on actual (hourly) 

emissions from six (6) modeled stacks at Fort Smallwood (Wagner and Brandon Shores) and 

Crane. The peak model concentration occurred approximately 500 meters east-southeast of Fort 

Smallwood.

Figure 18: Maximum Predicted 99th Percentile 1-Hour SO2 Concentrations in the Wagner Area 

of Analysis Based on Actual (Hourly) Emissions

Figure 19 shows the locations of all of the model receptors that exceeded the 1-hour SO2

NAAQS and elevation information. Violating model receptors are most concentrated within 

three (3) km of the Fort Smallwood facility. There are three other areas in the northwestern 

portion of the model receptor grid that had model receptors that exceeded the NAAQS. These 

areas are located over 30 km from Fort Smallwood and generally have elevations in the 140 to 

190 meter range. Violating model receptors are located in Anne Arundel and Baltimore 

counties. Sierra Club did not use the MAXDCONT option in their AERMOD analysis so there 

was no information regarding individual stack contributions to the individual model receptor 

violations.
43

Figure 19: Violating Model Receptors and Model Domain Elevations

Modeling Analyses: Summary and Conclusion

Modeling Analysis Summary

EPA received two (2) modeling analyses that included emissions from the Wagner Generating 

Station in Anne Arundel County, Maryland. This facility is part of Raven Power’s Fort 

Smallwood complex, which in addition to Wagner includes the Brandon Shores generating 

facility. The modeling analyses also included emissions from another Raven Power facility, the 

Crane Generating Station located approximately twenty (20) kilometers northeast of Fort 

Smallwood in Baltimore County, Maryland.

The first modeling analysis was submitted to EPA by Sierra Club in correspondence dated 

January 4, 2016. This included a modeling summary that was submitted to the Maryland 

Department of the Environment in June of 2015; the modeling report included in this submittal 

was dated May 4, 2015.

Sierra Club modeled SO2 emissions from coal-fired units at Brandon Shores, Wagner and Crane 

using EPA’s AERMOD dispersion model. Three (3) emissions scenarios were modeled 
44

including each unit’s maximum allowable (permitted) emission rate, the 99th percentile hourly 

emission rate reported to EPA’s Clean Air Market website between 2012 and 2014, and the 

actual hourly emission rates reported to EPA’s Clean Air Market website again for 2012-14. 

Only the model simulations using the actual hourly emission rates were considered for 

attainment designation purposes.

Sierra Club’s modeling analysis utilized an extensive model receptor grid centered on Fort 

Smallwood and Crane that extended nearly 50 km. This represents the approximate limit of 

steady-state Gaussian dispersion models such as AERMOD, as noted in section 6.2.3 (a) of 

EPA’s Guideline on Air Quality Models (Guideline). While compliant with the Guideline, this 

receptor grid extends well beyond the recommended area of focus discussed in EPA’s March 1, 

2011 clarification memo.

17

 In accordance with EPA’s Modeling TAD, model receptor 

concentrations should be parsed to exclude any that occurred over open water or in areas 

otherwise not suitable for siting a physical monitor. Sierra Club’s modeling included receptor 

points over open water, which were not considered in our analysis. While Sierra Club’s 

modeling analysis included flagpole receptors instead of ground receptors, the minimal height of 

these flagpole receptors (1.5 meters) was not expected to significantly impact final model 

concentrations. Background concentrations based on the Beltsville, Maryland monitor’s 2011-13 

design value were added to final modeled concentrations.

Based on the actual hourly emissions, Sierra Club’s maximum modeled 1-hour SO2

concentration (in the form of the NAAQS) was 293. 9 μg/m3, well above the health-based 

standard of 196.2 μg/m3. While there may be some minor differences in final modeled 

concentrations based on Sierra Club’s use of older versions of the AERMOD modeling 

components, some minor aberrations in meteorological processing steps and minor differences in 

stack parameters, these factors should not significantly change the final model concentrations.

EPA received a second modeling analysis from Maryland as a supplement to its 2015

designation recommendation on January 15, 2016. AECOM performed the modeling analysis. 

AECOM was asked by Raven Power to review a previous modeling analysis completed by the 

Maryland Department of the Environment. AECOM’s modeling analysis also utilized EPA’s 

AERMOD modeling system to estimate 1-hour SO2 concentrations in the vicinities of Fort 

Smallwood (Brandon Shores and Wagner) along with Crane. This modeling analysis included 

additional sources that were not part of Sierra Club’s modeling analysis; two (2) oil-fired units at 

Wagner along with Wheelabrator Baltimore and the proposed Energy Answers facilities.

AECOM used a hybrid approach compiling the emission inventory used in their modeling 

analysis. Hourly emissions over 2012-14 were used for the majority of Raven Power’s sources 

included in AECOM’s modeling analysis. Non-federally enforceable emission rates were used 

for Wheelabrator Baltimore and the proposed Energy Answers facilities. Actual emissions for 

Wagner’s coal-fired Unit 2 were retroactively reduced to 1.0 lbs/MMBtu to reflect a recent fuel 

switch (April 2015). Mixing emission rates is not in accordance with EPA’s Modeling TAD.

 

17 See Additional Clarification Regarding Application of Appendix W Modeling Guidance for the 1-hour NO2

National Ambient Air Quality Standard and note that while the memo references the 1-hour NO2 NAAQS it is 

equally applicable to the 1-hour SO2 standard.
45

AECOM’s modeling analysis utilizes an imbedded Cartesian modeling receptor grid on the order 

of 35 by 35 kilometers centered on the Fort Smallwood and Crane facilities. The number of 

receptors was much smaller than Sierra Club’s and focused on areas approximately 10 

kilometers from Raven Power’s sources.

AERMOD processing largely followed standard EPA guidance with two (2) exceptions; 

AECOM used non-default options when it processed its meteorological data via AERMET’s 

adjust U* option and utilized the Low Wind 3 processing option in AERMOD itself. EPA does 

not believe that the air quality modeling results obtained from the use of these beta options can 

be used as a reliable indicator of attainment status in the area around Wagner until appropriate 

alternative model approval is granted or these beta options are promulgated as regulatory options 

in AERMOD through EPA rulemaking. The modeling report submitted by AECOM includes a 

published paper that summarizes an evaluation of low-wind modeling approaches for tall-stack 

sources. While seasonally varying hour-by-hour background concentrations were added to the 

final model concentration, AECOM substituted a much lower background concentration 

(Beltsville, MD) when winds were from an easterly direction.

Final modeled concentrations from AECOM’s modeling analysis were below the 1-hour SO2

NAAQS. The peak model concentration was 186.0 μg/m3 (standard is 196.2 μg/m3).

Modeling Analysis Conclusion to Support Designation

EPA has reviewed the modeling analyses submitted by Sierra Club and AECOM. Both analyses 

used AEMOD to determine model concentrations near the Wagner generating station in northern 

Anne Arundel County, MD. Sierra Club’s modeling analysis indicates 1-hour SO2

concentrations near Wagner exceed the NAAQS. Model violations also occur in portions of 

Baltimore County. Model receptor violations in Baltimore County are over 10 km from Wagner 

and are generally beyond the area EPA recommends 1-hour modeling analyses as the area of 

focus (see EPA March 1, 2011 Clarification Memo). Peak modeled concentrations from 

AECOM’s modeling analysis are significantly lower than Sierra Club’s and are also under the 1-

hour SO2 NAAQS. Peak model concentrations for Sierra Club and AECOM both occur in the 

same general area, approximately 1 kilometer east southeast of Wagner (Fort Smallwood) and 

are shown in Figure 20.
46

Figure 20: Peak Model Concentrations from AECOM and Sierra Club Modeling Analyses

Based on analysis of both modeling studies, EPA believes that Sierra Club’s modeling analysis 

most closely follows the guidance outlined in EPA’s modeling TAD and is more representative 

of actual air quality conditions for the modeled period. While AECOM’s analysis may suggest 

lower concentrations due to more recent emission reductions at Wagner’s coal-fired Unit 2, 

substituting PTE or non-federally enforceable lower hourly emission rates retroactively to 

modify actual emissions does not follow EPA’s modeling TAD, which suggests either using 

actual emissions from impacting sources or using PTE emission rates (either/or). AECOM’s use 

of beta options within the AERMOD system may have also contributed to lower model 

concentrations. As noted earlier, upon concurrence by EPA’s Modeling Clearinghouse, EPA 

Regional Offices may approve the use of these beta options for regulatory applications as an 

alternative model. However, Maryland’s air dispersion modeling, performed by AECOM,

intended to characterize air quality as a result of SO2 emissions from Wagner without prior 

consultation with and approval from EPA’s Region 3’s Office, and therefore has not met the 

applicable regulatory requirements contained in Appendix W, Section 3.2.2. As a result, EPA 

does not believe that the air quality modeling results obtained from the use of these beta options 
47

can be used as a reliable indicator of attainment status in the area around Wagner until 

appropriate alternative model approval is granted or these beta options are promulgated as 

regulatory options in AERMOD through EPA rulemaking. 

Given this information, EPA believes the Sierra Club air dispersion modeling provides 

persuasive evidence that SO2 NAAQS violations are occurring within Baltimore County and 

Anne Arundel County, with the maximum concentration in the immediate vicinity of Wagner. In 

addition, EPA does not believe that AECOM’s modeling provides persuasive evidence that the 

area is meeting the NAAQS based on actual emissions for the period analyzed. 

Jurisdictional Boundaries

Maryland’s original 2011 designation recommendation recommended that the entirety of Anne 

Arundel County be designated as unclassifiable. The State did not provide additional 

explanation nor analysis and chose to recommend the default county boundary at that time. 

Maryland’s updated 2015 designation recommendation did not address this factor, and Maryland 

did not provide a recommended boundary for its recommended attainment designation for the 

Wagner area. Existing jurisdictional boundaries are considered for the purpose of informing our 

intended designation, specifically with respect to a clearly defined legal boundary once the 

geographic area associated with the immediate area surrounding Wagner, other nearby sources, 

and background concentration is determined. 

There are a limited number of sub-county jurisdictional boundaries to use if one would want to 

define attainment boundaries below the county scales. The State of Maryland has 156 municipal 

corporations otherwise known as municipalities. Figure 21 shows the municipal units in the 

Wagner area of analysis. These units, unfortunately, do not create a contiguous entity inside the 

county boundaries, and therefore, do not provide a method for delineating sub-county 

nonattainment boundaries in the Wagner area. There are a total of two (2) municipalities in 

Anne Arundel County and no municipalities that reside totally inside Baltimore County; one 

municipality in a neighboring county does extend into Baltimore County. 
48

Figure 21: Maryland Municipalities in the Wagner Area

There are several other possibilities for defining boundaries below the county level in Maryland: 

US zip codes, US Census tracts, and council districts. Zip codes were created by the US Postal 

Service in the 1960s. Zip Codes, unfortunately, are not true linear features but groups of 

addresses assigned to a single code. Boundaries between individual zip codes are somewhat 

arbitrary and can be as small as a single mailing address. The US Census defines Census Tracts 

to help organize Census information. While these boundaries are sub-county, they can be quite 

small. There are a total of 411 Census tracts in Anne Arundel and Baltimore counties (see 

Figure 22). The number of Census tracts and their relative limited use may make these units 

difficult to use to delineate a nonattainment area that would have sub-county borders. 
49

Figure 22: 2010 Census Tracts within Anne Arundel and Baltimore Counties in Maryland

A county council is a legislative body of the county that performs all local governmental 

functions within its jurisdiction. Both Baltimore and Anne Arundel Counties are divided into

seven (7) council districts (Figure 23). The use of council districts for defining the 

nonattainment area around Wagner would be difficult in that the violations are spread across 

numerous districts, forming a non-contiguous area. Furthermore, because of where the modeled 

violations are located across Baltimore County in relation to Baltimore County’s council district 

boundaries, large areas spanning northward towards Pennsylvania would be included that are 

likely not being impacted by Wagner’s SO2 emissions.
50

Figure 23: Council Districts within Anne Arundel and Baltimore Counties in Maryland

Given that existing jurisdictional boundaries do not appear suitable for defining the 

nonattainment area surrounding Wagner, EPA believes that another alternative to using 

jurisdictional boundaries is to draw a circle around the source and all modeled violating 

receptors. Such a circle would be drawn with Wagner’s Unit 3 stack as the center (located at 

39.17765N latitude, 76.52752W longitude) with a radius extending out 35.5 kilometers in order 

to capture all the violating receptors both within Anne Arundel and Baltimore Counties. Those 

portions of Anne Arundel and Baltimore Counties residing within this circle would encompass 

the nonattainment area. Furthermore, in the absence of information from Maryland concerning 

jurisdictional boundaries, EPA believes that our intended nonattainment area, consisting of 

portions of Anne Arundel County and Baltimore County, is comprised of a clearly defined legal 

boundary, and we find this boundary to be a suitably clear basis for defining our intended 

nonattainment area. There are no previously designated nonattainment areas in the nearby 

vicinity of Wagner whose boundaries could have been considered in this case. The area around 

Wagner would be nonattainment based on available modeling information regarding elevated 

SO2 levels within Anne Arundel and Baltimore Counties, emissions data, emission control 

information, as well as wind patterns and terrain. See the “Air Dispersion Modeling” section for 
51

the assessment of air dispersion modeling provided by Sierra Club. In contrast, this information 

also shows that the jurisdictional area of Baltimore City does not have elevated SO2 levels.

Other Relevant Information

On January 13, 2016, Sierra Club submitted a follow-up to their January 4, 2016 modeling 

submission. In that submission, Sierra Club notes that Maryland’s 2015 designation 

recommendation includes ambient air monitoring data from a two-month study that shows the 

occurrence of a maximum 1-hour SO2 concentration of 101.7 ppb at a monitor closest to 

Wagner, which far exceeds the SO2 NAAQS. Additionally, Sierra Club’s submission included a 

presentation Maryland gave to stakeholders in February 2014, in which Maryland summarizes 

the results of its own and Sierra Club’s prior modeling and explains the unit-specific emission 

rates necessary to ensure compliance with the 1-hour SO2 NAAQS. Sierra Club also included a 

draft SO2 regulation Maryland had previously released to stakeholders that included proposed 

emission rates for sources. Sierra Club explains that the monitoring data provided by the State is 

not supportive of an attainment designation, and also urges EPA to carefully review any newly 

proposed emission limits from Maryland that may differ from those previously identified by 

Maryland in the draft SO2 regulation. Under the “Air Quality Data” section in this draft 

technical support document, EPA acknowledges that the monitoring data from the two-month 

study Maryland submitted is not supportive of an attainment designation. EPA is unable to 

comment on any previously proposed SO2 emission limits released in a draft regulation by 

Maryland as that would have been a work-in-progress and based on modeling that would have 

been done prior to EPA’s Modeling TAD being released. 

On January 20, 2016, Sierra Club submitted further information with regards to Maryland’s 

January 15, 2016 recommendation supplement. Their submission notes that Maryland’s 

January 15, 2016 modeling analysis neither utilized actual historical emission data, nor 

maximum SO2 emissions, and inappropriately utilized options not formally approved under 

Appendix W, and assert that this analysis fails to support an attainment or unclassifiable 

designation. EPA’s analysis of Maryland’s modeling analysis is discussed in detail under the 

section entitled “Air Dispersion Modeling” in this draft technical support document.

Detailed Assessment for Baltimore City Area

Air Dispersion Modeling

Available air dispersion modeling shows persuasive evidence that violations of the SO2 NAAQS 

are not occurring within Baltimore City. See the “Air Dispersion Modeling” section for EPA’s 

detailed review of the analyses. 

Air Quality Data

This factor considers the SO2 air quality monitoring data; however, there are no ambient air 

quality monitors located in Baltimore City, and Maryland’s 2011 designation recommendation 

did not address this factor. The closest ambient air quality monitor to Baltimore City is located 
52

east of Baltimore City in neighboring Baltimore County. The monitor’s 2012-2014 design value 

is 22 ppb (see Tables 2 and 3), well below the SO2 standard. 

Emissions and Emissions-Related Data

Maryland’s 2011 designation recommendation did not address this factor. EPA’s review of 

emissions information shows that there are no large SO2-emitting sources located within 

Baltimore City that could be contributing to elevated levels of SO2 concentrations. The largest 

source in Baltimore City is Wheelabrator Baltimore L.P. with 2013 NEI SO2 emissions of 321 

tpy and 2011 NEI SO2 emissions of 261 tpy (see Table 6); this facility is located approximately 3 

km from the city border.

Traditionally, a source’s modeled impact would be compared to the Significant Impact Level 

(SIL) to gauge if it is significantly impacting a modeled violation. This information, 

unfortunately, is not readily available from either Sierra Club’s or AECOM’s modeling analyses. 

Sierra Club did not include sources inside Baltimore City in its analysis, nor did it provide a 

culpability analysis of its modeled violations using the MAXDCONT function in AERMOD. 

While AECOM did include sources inside Baltimore City (Wheelabrator Baltimore and the 

proposed Energy Answers facility) they did not run MAXDCONT since there were no modeled 

violations in its analysis (MAXDCONT only works for receptors over the NAAQS).

In light of these deficiencies, EPA attempted to gauge Wheelabrator Baltimore’s impact on 

Sierra Club’s violating receptors using AECOM’s modeling for its peak receptor and SCREEN3 

modeling to determine if modeled concentrations would exceed the interim 1-hr SO2 SIL (7.8 

μg/m3).

Table 4-3 in AECOM’s modeling report lists the contributions from each source towards its peak 

modeled concentration. For all other sources, excluding Brandon Shores, Wagner and Crane, the 

total other sources category model concentration (Wheelabrator Baltimore and Energy Answers) 

was 1.4 μg/m3, approximately 0.7% of the NAAQS. This indicates impacts from Wheelabrator 

Baltimore are below the 1-hr SO2 SIL for receptors immediately downwind of Wagner. Based 

on this information, Wheelabrator Baltimore is not significantly contributing to (Sierra Club’s) 

modeled violations surrounding Wagner.

Sierra Club modeling also had violating receptors in several other areas of Baltimore County. 

EPA ran SCREEN3 to gauge if emissions from Wheelabrator Baltimore could significantly 

contribute to these modeled violations. Figure 24 shows the locations of the violating receptors, 

significant emission sources in the Baltimore area and the approximate centerlines between 

Wagner Unit 3 and three (3) groups of violating receptors in Baltimore County and the Sierra 

Club peak receptor. Centerlines are lines drawn from an emission point to the receptor. A 

straight-line dispersion model calculates the maximum concentration along this centerline. 

Model concentrations will “fall off” laterally along the normal line drawn to the centerline 

following some type of Gaussian distribution. Based on the figure, Wheelabrator Baltimore 

generally falls off of the centerline from Wagner Unit 3 (except for the centerline drawn for the 

Sierra Club peak receptor).
53

Figure 24: Centerlines for various sources and modeled violating receptors

EPA ran SCREEN3 using emissions from Wheelabrator Baltimore for different receptors 

representing downwind receptors from Wagner (including Sierra Club’s peak receptor) along 

with roughly three (3) groups of violating receptors based on the Sierra Club modeling. Model 

results are available as an appendix.

An emission rate of 1.0 grams/second (g/s) was used in SCREEN3. Concentrations can then be 

scaled according to Wheelabrator Baltimore’s 2012-14 actual emissions; Energy Answers was 

omitted from the analysis since it had no actual emissions between 2012-14. Table 25

summarizes SCREEN3 results.

Table 24: Wheelabrator Baltimore 2012-14 Actual Emissions

Year tpy g/s

2012 194 5.56548

2013 321 9.23409

2014 (Preliminary) 310 8.91766
54

Table 25: Wheelabrator Baltimore Emissions and SCREEN3 Model Results

Receptor Terrain 

Type

1-hr Model

(μg/m3/1.0 

g/s)

24-hr Model

(μg/m3/1.0 

g/s)18

Adjusted 

2012

(μg/m3)

Adjusted 

2013

(μg/m3)

Adjusted 

2014

(μg/m3)

Fort Smallwood 

Peak

Simple 0.481 - 2.68 4.44 4.29

Sierra Club Peak Simple 0.4793 - 2.67 4.43 4.27

West Violating 

Receptors

Complex - 0.3646 8.12 13.47 13.01

North Violating 

Receptors

Complex - 0.2123 4.73 7.84 7.57

NW Violating 

Receptors

Complex - 0.1518 3.38 5.61 5.41

SCREEN3 results indicate the only receptors where Wheelabrator Baltimore’s contributions 

could potentially exceed the 1-hr SO2 SIL is the group of receptors in western Baltimore County 

(due west of Wheelabrator Baltimore). SCREEN3 values for the West Receptors are 

approximately 7% of the NAAQS, which is over the interim 1-hr SO2 4% SIL. It should be 

noted that the SCREEN3 result is the maximum concentration for the centerline extending 

between this group of receptors and Wheelabrator Baltimore and not the centerline drawn 

between Wagner Unit 3 and the West Receptors. In fact, only the edge of Wheelabrator 

Baltimore’s plume based on the Wagner Unit 3-West Receptor centerline would impact these 

receptors, thus yielding a lower concentration than SCREEN3 would predict. Given that the 

violating receptors’ peak 99th percentile concentrations are occurring during stable overnight 

hours, the lateral spread along the centerline for Wheelabrator Baltimore is probably not large 

enough to extend over these receptors; Wheelabrator Baltimore’s plume would have to laterally 

spread nearly 5 km from the Wagner Unit 3-West Receptor centerline to impact these receptors. 

Further evidence of SCREEN3 overestimation is seen in the Sierra Club peak receptor

concentrations. Based on AECOM’s analysis, Wheelabrator Baltimore’s modeled impact is less 

than 1% of the NAAQS at its peak model receptor. Since both the Sierra Club and AECOM 

peak receptors are nearly in the same place, AECOM’s results indicate SCREEN3 is 

overestimating Wheelabrator Baltimore’s model impacts by nearly a factor of three (3); 1.4 

μg/m3versus 4.43 μg/m3. Using this adjustment, Wheelabrator Baltimore’s model contribution

to the West Receptors is most likely under the interim 1-hr SO2 SIL.

Due to its low emissions, and based on all available information, EPA finds it unlikely that any 

sources within Baltimore City have the potential to cause or contribute to a violation of the 

NAAQS within the city. Furthermore, available modeling analyses further provide evidence that

large SO2 sources located outside of Baltimore City are likewise not impacting SO2 levels within 

Baltimore City. 

 

18 24-hr concentration based on Valley model. Concentrations divided by 0.25 to get 1-hr concentrations in 

accordance with section 3.8 of SCREEN3 User’s Guide.
55

Meteorology (Weather & Transport Patterns)

Maryland’s 2011 designation recommendation did not address meteorology. EPA’s review of 

meteorology shows that the closest hourly reporting meteorological monitoring station to 

Baltimore City is the Baltimore-Washington International Airport, located southwest of 

Baltimore City. A wind rose for the 2012-14 time period (see Figure 4) shows predominantly 

westerly winds in the area. Available modeling analyses provide evidence that westerly winds

do not contribute to elevated levels of SO2 within Baltimore City from large SO2 sources located 

outside of Baltimore City. Likewise, based on SCREEN3 results and our analysis and 

comparison to AECOM’s and Sierra Club’s analyses discussed under the “Emissions and 

Emissions-Related” section, EPA believes there is persuasive evidence indicating that emissions 

from within Baltimore City are not impacting SO2 levels in areas outside of Baltimore City that 

are not meeting the NAAQS.

Geography and Topography (Mountain Ranges or Other Air Basin Boundaries)

Maryland’s 2011 designation recommendation did not address this factor. EPA has reviewed 

both the geography and topography of Baltimore City. Baltimore City lies west of the 

Chesapeake Bay with the southern half lying within the coastal plain and the north/northwest 

corner within the Piedmont plateau (see Figure 6). Given that there is limited terrain in this area, 

topography would likely not contribute to elevated concentrations of SO2 in Baltimore City. 

Available modeling analyses provide evidence that the terrain located in the north/northwest of 

the city does not impact SO2 concentrations within Baltimore City.

Jurisdictional Boundaries

Maryland’s 2011 designation recommendation recommended that the entirety of Baltimore City 

be designated as unclassifiable. The State did not provide additional explanation nor analysis 

and chose to recommend the default city boundary at that time. Existing jurisdictional 

boundaries are considered for the purpose of informing our intended designation, specifically 

with respect to a clearly defined legal boundary. EPA’s review of available air dispersion 

modeling shows persuasive evidence that elevated SO2 levels are not occurring within Baltimore 

City. Therefore, EPA believes that our intended unclassifiable/attainment designation for 

Baltimore City is comprised of an appropriate and clearly defined legal boundary. 

Conclusion for the Anne Arundel County and Baltimore County and Baltimore City Areas

After careful evaluation of the State’s 2011 and 2015 updated recommendations and additional 

information including SO2 emissions, air quality monitoring, air dispersion modeling results,

meteorology, geography and topography, EPA intends to designate the area around the Herbert 

A. Wagner Generating Station as nonattainment for the 2010 SO2 NAAQS. Specifically, EPA 

intends to include portions of Anne Arundel County and Baltimore County in the nonattainment 

area that are within 35.5 kilometers of Herbert A. Wagner’s Unit 3 stack, which is located at 

39.17765N latitude, 76.52752W longitude. Sierra Club’s January 4, 2016 air dispersion 

modeling, which included actual SO2 emissions data from Wagner, provides persuasive evidence 
56

that SO2 NAAQS violations are occurring within Baltimore County and Anne Arundel County, 

with the maximum concentration in the immediate vicinity of Wagner. The modeling also shows 

that violations may be occurring in several locations northwest and west of the Facility in 

neighboring Baltimore County over 30 kilometers away from the Facility. In contrast, 

Maryland’s submitted January 2016 modeling analysis is problematic, not in accordance with 

EPA’s Modeling TAD or Appendix W, and does not support an attainment designation given 

that the Sierra Club modeling demonstrates violations. Given these air dispersion modeling 

results, emissions data, lack of federally enforceable SO2 emission controls at Wagner and 

Crane, as well as general wind patterns and topography, EPA finds it reasonable that the area 

surrounding Wagner be designated as nonattainment, and as such intends to designate portions of

Anne Arundel County and Baltimore County as nonattainment for the 2010 SO2 NAAQS. 

Specifically, those portions of Anne Arundel and Baltimore Counties that are within 35.5 

kilometers of Wagner’s Unit 3 stack, which is located at 39.17765N latitude, 76.52752W 

longitude, would be designated as nonattainment.

Additionally, Sierra Club’s air dispersion modeling shows persuasive evidence that violations are 

not occurring in Baltimore City. Given these modeling results and that there are no large SO2

emissions sources located within Baltimore City that could be impacting areas outside of 

Baltimore City, as well as no violating monitors in the area and limited terrain, EPA believes 

there is persuasive evidence to support a conclusion that Baltimore City is meeting the NAAQS 

and that a designation of unclassifiable/attainment is appropriate. Therefore, EPA intends to 

designate Baltimore City as unclassifiable/attainment for the 2010 SO2 NAAQS.

At this time, our intended designation for the state only applies to the area presented in this 

technical support document. Consistent with the conditions in the March 2, 2015 consent decree

and the court order, EPA will evaluate and designate all remaining undesignated areas in 

Maryland by either December 31, 2017 or December 31, 2020.
57

APPENDIX: SCREEN3 MODEL RESULTS

 02/08/16

 12:00:14

 *** SCREEN3 MODEL RUN ***

 *** VERSION DATED 13043 ***

WheelabratorMD_Screen3 

COMPLEX TERRAIN INPUTS:

 SOURCE TYPE = POINT

 EMISSION RATE (G/S) = 1.000000 

 STACK HT (M) = 96.0100

 STACK DIAMETER (M) = 2.1300

 STACK VELOCITY (M/S) = 22.5500

 STACK GAS TEMP (K) = 485.9300

 AMBIENT AIR TEMP (K) = 287.8000

 RECEPTOR HEIGHT (M) = 0.0000

 URBAN/RURAL OPTION = RURAL

THE REGULATORY (DEFAULT) MIXING HEIGHT OPTION WAS SELECTED.

THE REGULATORY (DEFAULT) ANEMOMETER HEIGHT OF 10.0 METERS WAS ENTERED.

BUOY. FLUX = 102.264 M**4/S**3; MOM. FLUX = 341.593 M**4/S**2.

FINAL STABLE PLUME HEIGHT (M) = 180.5
58

DISTANCE TO FINAL RISE (M) = 150.0

 *VALLEY 24-HR CALCS* **SIMPLE TERRAIN 24-HR CALCS**

 TERR MAX 24-HR PLUME HT PLUME HT

 HT DIST CONC CONC ABOVE STK CONC ABOVE STK U10M USTK

 (M) (M) (UG/M**3) (UG/M**3) BASE (M) (UG/M**3) HGT (M) SC (M/S)

----- ------- ---------- ---------- ------ ---------- ------ -- ---- ----

 154. 9460. 0.9060 0.3646 180.5 0.9060 75.7 6 1.0 3.5

 148. 14040. 0.7316 0.2123 180.5 0.7316 75.7 6 1.0 3.5

 195. 20290. 0.1518 0.1518 180.5 0.000 0.0 0 0.0 0.0

 02/08/16

 12:00:14

 *** SCREEN3 MODEL RUN ***

 *** VERSION DATED 13043 ***

WheelabratorMD_Screen3 

SIMPLE TERRAIN INPUTS:

 SOURCE TYPE = POINT

 EMISSION RATE (G/S) = 1.000000 

 STACK HEIGHT (M) = 96.0100

 STK INSIDE DIAM (M) = 2.1300

 STK EXIT VELOCITY (M/S)= 22.5500

 STK GAS EXIT TEMP (K) = 485.9300

 AMBIENT AIR TEMP (K) = 287.8000

 RECEPTOR HEIGHT (M) = 0.0000

 URBAN/RURAL OPTION = RURAL

 BUILDING HEIGHT (M) = 0.0000

 MIN HORIZ BLDG DIM (M) = 0.0000
59

 MAX HORIZ BLDG DIM (M) = 0.0000

THE REGULATORY (DEFAULT) MIXING HEIGHT OPTION WAS SELECTED.

THE REGULATORY (DEFAULT) ANEMOMETER HEIGHT OF 10.0 METERS WAS ENTERED.

BUOY. FLUX = 102.264 M**4/S**3; MOM. FLUX = 341.593 M**4/S**2.

*** FULL METEOROLOGY ***

*********************************

*** SCREEN DISCRETE DISTANCES ***

*********************************

*** TERRAIN HEIGHT OF 0. M ABOVE STACK BASE USED FOR FOLLOWING DISTANCES ***

 DIST CONC U10M USTK MIX HT PLUME SIGMA SIGMA

 (M) (UG/M**3) STAB (M/S) (M/S) (M) HT (M) Y (M) Z (M) DWASH

------- ---------- ---- ----- ----- ------ ------ ------ ------ -----

 13980. 0.4810 3 1.0 1.3 592.9 591.94 1113.08 697.00 NO

 14040. 0.4793 3 1.0 1.3 592.9 591.94 1117.24 699.63 NO

 DWASH= MEANS NO CALC MADE (CONC = 0.0)

 DWASH=NO MEANS NO BUILDING DOWNWASH USED

 DWASH=HS MEANS HUBER-SNYDER DOWNWASH USED

 DWASH=SS MEANS SCHULMAN-SCIRE DOWNWASH USED

 DWASH=NA MEANS DOWNWASH NOT APPLICABLE, X<3*LB

 ***************************************
60

 *** SUMMARY OF SCREEN MODEL RESULTS ***

 ***************************************

 CALCULATION MAX CONC DIST TO TERRAIN

 PROCEDURE (UG/M**3) MAX (M) HT (M)

-------------- ----------- --------- -------

SIMPLE TERRAIN 0.4810 13980. 0.

COMPLEX TERRAIN 0.9060 9460. 154. (24-HR CONC)

***************************************************

** REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS **

***************************************************