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Attachment 1

Annual Reductions in Sulfur Dioxide (SO2) from the Healthy Air Act

0

50,000

100,000

150,000

200,000

250,000

300,000

2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

SO2 Emissions (tons per year)

Note: Graph includes units reporting SO2 emissions to EPA's Clean Air Markets Division

SO2 Annual Emissions from 

Electric Generating Units in Maryland

Healthy Air Act 

SO2 Reductions

January, 2010
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Attachment 2 

One-Hour SO2 trends, after the Healthy Air Act

(Note: the 1-hour SO2 standard is 75 ppb)

SO2 Emissions and Air Monitoring Concentrations in the Wagner Area, 2007-2014

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 3 

years. The 1-hour SO2 standard is 75 parts per billion (ppb), calculated the same way.

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40

80

120

160

200

2004 2006 2008 2010 2012 2014 2016

SO2 (ppb)

Annual Maximum 1-hour SO2

Essex Piney Run HU-Beltsville

Google earth

Phase 1 SO2

controls under 

the Healthy Air 

Act in 2010

SO2 Monitors 

in Maryland

SO2 Monitors

in Maryland

Note: Monitor names are in 

yellow.
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Attachment 3

Summer 2013 Air Monitoring Study Results

A 2013 two-month monitoring study of SO2 concentrations was conducted around Raven Power’s Brandon 

Shores, Herbert A. Wagner, and C.P. Crane Generating Plants. Peak daily 1-hour maximum monitored SO2

values were typically well below the 75 ppb 1-hour SO2 NAAQS.

Monitoring Sites Used in the 2013 Study

Note: Monitoring sites are in yellow on the map; the generating stations are in green.

Monitored Values

Table 1. Top Five Monitored 1-Hour SO2 Values during the 2013 Study

Peak Daily 1-Hour Maximum Monitored Value (ppb)

Note: the 1-hour SO2 standard is 75 ppb.

Rank Cianbro MDYC Shining Star MD Marina Essex

1 101.7 53.2 34.6 13.1 31.3

2 42.2 37.8 28.7 10.5 24.5

3 34.4 37.3 26.8 10.3 24.0

4 31.5 29.6 23.6 10.1 20.7

5 23.9 20.7 21.4 9.5 17.4

Essex

Site

Cianbro

Site

Crane

Generating Plant

Shining Star

MD 

Marina

Site

Ft. Smallwood

Generating Plant

MDYC 

Site
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Table 2. All 1-Hour Daily Maximum SO2 Data during the 2013 Study

1‐hour SO2 Daily Maximum Concentration (ppb)

Note: 1-hour SO2 standard is 75 ppb. The blank cells were dates before a monitor started running, due to delays in obtaining a lease agreement to place the monitor.

In vicinity of Brandon 

& Wagner Plants

In vicinity of C.P. Crane Plant In vicinity of Brandon & 

Wagner Plants

In vicinity of C.P. Crane Plant

Date Cianbro MDYC Shining Star MD Marina Essex Date Cianbro MDYC Shining Star MD Marina Essex

7/25/2013 0.7 0.4 8/25/2013 22.3 2.0 0.7 8.7 10.5

7/26/2013 22.0 4.7 8/26/2013 1.1 1.4 5.3 4.6 1.9

7/27/2013 0.5 9.2 8/27/2013 8.6 29.6 2.4 1.2 2.1

7/28/2013 21.9 10.5 8/28/2013 0.5 1.6 1.1 0.0 1.0

7/29/2013 1.7 1.5 8/29/2013 2.0 2.4 0.6 0.0 1.9

7/30/2013 1.2 1.4 8/30/2013 0.6 1.8 1.1 0.5 8.7

7/31/2013 1.6 13.4 8/31/2013 0.9 2.4 7.7 4.5 7.6

8/1/2013 0.5 0.0 4.0 9/1/2013 13.4 1.6 6.3 3.2 9.3

8/2/2013 2.2 7.2 0.0 2.9 9/2/2013 2.9 7.1 6.7 10.1 4.4

8/3/2013 1.0 1.5 0.0 1.3 9/3/2013 2.8 37.3 1.5 0.3 2.4

8/4/2013 2.0 3.8 0.0 1.7 9/4/2013 15.9 13.0 5.8 3.8 3.0

8/5/2013 17.0 0.3 0.6 2.7 9/5/2013 4.3 20.7 2.3 1.3 2.4

8/6/2013 0.7 0.0 0.2 1.5 9/6/2013 23.9 11.1 19.5 0.3 8.4

8/7/2013 0.6 2.1 0.4 1.3 9/7/2013 101.7 2.4 21.7 10.5 5.2

8/8/2013 1.0 3.1 7.4 11.8 9/8/2013 2.3 7.4 3.8 1.9 2.3

8/9/2013 0.7 4.0 0.7 3.7 9/9/2013 42.2 4.9 32.7 13.1 5.9

8/10/2013 34.4 11.9 0.4 2.5 9/10/2013 1.3 2.6 6.0 1.9 5.5

8/11/2013 20.4 4.0 26.8 13.0 9/11/2013 21.3 17.6 10.1 5.5 31.3

8/12/2013 6.2 6.3 0.0 1.6 9/12/2013 1.8 5.0 4.0 3.0 5.5

8/13/2013 1.4 14.3 2.6 3.4 2.1 9/13/2013 1.9 53.2 1.4 0.0 1.6

8/14/2013 2.9 6.4 1.4 3.0 2.7 9/14/2013 1.5 8.8 1.4 0.0 0.8

8/15/2013 8.5 3.3 1.3 2.2 0.9 9/15/2013 7.6 1.8 5.2 3.1 2.0

8/16/2013 2.4 3.1 1.2 3.2 1.4 9/16/2013 1.3 4.1 3.9 4.7 1.6

8/17/2013 2.0 1.9 1.8 2.5 2.9 9/17/2013 1.7 5.3 1.5 2.2 2.0

8/18/2013 0.6 1.3 0.7 1.9 0.5 9/18/2013 19.9 1.4 17.6 0.0 1.0

8/19/2013 0.6 2.1 1.6 2.5 2.0 9/19/2013 5.7 1.8 5.2 3.8 2.6

8/20/2013 31.5 19.9 24.9 9.5 6.2 9/20/2013 1.6 2.5 10.9 10.3 20.7

8/21/2013 0.8 3.2 2.0 2.8 8.7 9/21/2013 0.7 2.7 1.5 0.0 3.4

8/22/2013 1.8 6.4 5.5 6.2 2.2 9/22/2013 1.6 13.7 1.6 0.0 1.2

8/23/2013 1.1 14.4 0.6 2.4 1.7 9/23/2013 1.1 2.4 1.6 0.0 1.4

8/24/2013 1.2 1.4 0.9 0.0 0.7

The hourly SO2 levels were typically well below the 1-hour SO2 NAAQS. Peak daily 1-hour maximum monitored SO2 values ranged from 

9.5 to 53.2 ppb except on one day during the 2-month study when the Cianbro monitor reached a level of 101.7 ppb. Overall, the study 

suggests that the Wagner area can attain the 1-hour SO2 NAAQS.
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Attachment 4 

Preliminary MDE Modeling Analyses

Preliminary AERMOD (Version 15181) dispersion modeling shows that the Wagner area is attaining the 2010 

1-hour SO2 standard. The modeling uses 2012 - 2014 actual emissions data, including the reductions presently 

being seen from the use of low-sulfur coal for compliance with the Mercury and Air Toxics Standards (MATS)

at Wagner’s unit 2 (see graph below). MDE modeling includes all of the emission units of Raven Power/Talen 

Energy (Wagner, Brandon Shores, and Crane Plants), and other nearby sources (Wheelabrator and Energy 

Answers). The background concentration calculation was based on season and hour-of-day approach included 

in EPA guidance. MDE is working with EPA to finalize this modeling. Attachment 5 provides a summary of 

how the modeling is being conducted.

Predicted Hourly SO2 Levels*

(Note: The 1-hour SO2 standard is 75 ppb, or 196.20 μg/m3)

* Additional reductions are expected in 2016 as new controls required by MATS at Wagner 3 become operational.

**Brandon Shores, Crane, Wheelabrator and Energy Answers

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40,000.00

50,000.00

60,000.00

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500

1000

1500

2000

2500

3000

3500

SO2 (lbs)

Gross Load (MW-h)

Emissions Reductions at Wagner 2, May-Sept. 2015, 

After MATS Compliance

Gross Load (MW-h)

SO2 (lbs)

4

th Highest 

Concentration (μg/m3), 

Without Background

Percentage 

Contribution (% 

contribution to total)

Total with 

Background 

(μg/m3)

Wagner Unit 1 0.009 Negligible

193.47

Wagner Unit 2 26.47 15

Wagner Unit 3 95.26 53

Wagner Unit 4 21.53 11

All other nearby sources** 37.61 21

Switch 

to lowsulfur 

coal
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Attachment 5

MDE Modeling 

MDE is working with EPA Region III, the facility and other interested parties to finalize sophisticated SO2

modeling by early 2016. MDE’s modeling considers methodologies used by the Sierra Club and Raven Power

in their independent modeling of SO2 levels in the Wagner area:

Preliminary MDE modeling used the following inputs:

 AERMOD Version 15181

 Actual 1-hour SO2 emissions data for 2012-2014

 Background 1-hour SO2 concentrations from the MDE Howard University (HU) -Beltsville air 

monitoring station

 Building heights based on Google Earth

 Meteorological data, including Baltimore Washington International Airport (BWI) surface data, and 

Sterling, Virginia upper air data

 The seasonal and hour-of-day approach consistent with the methodology found in section 8, 

“Background Concentrations,” of the “Draft SO2 NAAQS Designations Modeling Technical 

Assistance Document” (EPA, December 2013)

Ongoing modeling includes consideration of the following potential refinements:

 The use the non-regulatory “LOWWIND3” option (BETA option) in AERMOD to address issues with 

model over-prediction under low wind speed conditions. 

 Merged plumes/one stack for Brandon Shores when both units were running simultaneously, following 

EPA guidance

 The use of enhanced tools to evaluate plume rise. Work performed by AECOM, has assessed the effects 

of plume rise adjustments in the AERMOD modeling system by applying the concepts of moisture in 

plume modeling versus dry plume modeling. AERMOD treats the final plume rise based on the 

assumption of a “dry” plume, where the chimney plume is far from being saturated and carries no liquid 

water load. However, the “dry” plume rise in AERMOD might be affecting the final plume rise height in 

the model. AECOM has developed a moist plume rise model (IBJpluris) to estimate plume rise by 

modifying and adjusting the standard Briggs (1975) plume rise formula used in AERMOD. AECOM has 

implemented IBJpluris Ver. 2.7 in the AERMOIST pre-processor. The AERMOIST pre-processor uses a 

set of temperature and RH ranges to automatically build a stack-specific wet plume rise model based on 

the IBJpluris prediction. 

 The use of LIDAR to more accurately estimate the building dimensions to be used as the inputs in the 

Building Profile Interface Program (BPIP) model of the AERMOD modeling system. Correct building 

dimensions are very important to estimate the effects of building downwash on the pollutant concentration 

at the facility. This LIDAR technique can be used to accurately measure the building length, width, and 

height, and stack height, for modeling purposes. The modeling may also use this technique in estimating 

the elevation of ground level for input in AERMAP, the terrain pre processor in the AERMOD model. 

The LIDAR technique is also helpful in plume mapping that depicts the plume rise and spread in the real 

time analyses. 

 MDE is also looking at other potential surface meteorological data sites as input into AERMOD, in 

addition to surface data currently being used from the Baltimore-Washington International (BWI) airport.
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Attachment 6

SO2 Attainment Designation Timeline

 2015: Maryland submits its designation recommendation letter for the Wagner area to EPA Region III.

 2015 – Early 2016: MDE Secretary Ben Grumbles submits to EPA further emissions and modeling 

analyses and information to support the attainment designation or an updated designation 

recommendation.

 2015 - 2018: Monthly calls between MDE and EPA to coordinate on the status of activities related to 

the designation of the Wagner area.

 January 15, 2016: MDE identifies federally enforceable emissions limits or permit conditions that may 

be needed to support the attainment designation, and MDE forwards this information to EPA. EPA’s 

120-day letters, in which EPA notifies states concerning any intended modifications to their designation 

recommendations, are expected on or about January 22, 2016.

 January 2018: Maryland’s target date for providing documentation that the Wagner area is attaining the 

1-hour SO2 NAAQS including any federally enforceable emission limits or permit conditions that may 

be required to insure attainment. Note: If Maryland were to submit a nonattainment area state 

implementation plan (SIP) to EPA to comply with the 1-hour SO2 NAAQS for the Wagner area, then 

January 2018 would be the date by which sources would be required to come to agreement, with states, 

to implement controls in time for a 1-hour SO2 nonattainment area to attain the SO2 NAAQS. This is 

ahead of that schedule.