Ms. Susan Hedman 

Regional Administrator U.S. Environmental Protection Agency 

Region 5 

77 West Jackson Boulevard Chicago, IL 60604-3950 

Dear Ms. Hedman: 

Re: Preliminary Recommendations Concerning 

Round 2 Air Quality Designations for the 

2010 Primary 1-Hour Sulfur Dioxide 

National Ambient Air Quality Standard 

This letter is in response to the United States Environmental Protection Agency's 

(U.S. EPA's) March 20, 2015 updated guidance concerning air quality designations for 

the 2010 primary 1-hour sulfur dioxide (S02) National Ambient Air Quality Standard 

(NAAQS). 

On March 2, 2015, the U.S. District Court for the Northern District of California 

accepted an enforceable order agreement (Consent Decree) between U.S. EPA, the 

Sierra Club, and the Natural Resources Defense Council to resolve litigation concerning 

deadlines for completing 1-hour S02 NAAQS air quality designations for the remainder 

of the country. U.S. EPA must complete remaining designations in three additional 

rounds: Round 2 by July 2, 2016, Round 3 by December 31, 2017, and Round 4 by 

December 31, 2020. U.S. EPA will complete these designations by designating areas 

as either nonattainment, attainment, or unclassifiable. 

The court order directs U.S. EPA to designate two groups of areas under Round 

2 air quality designations for the 2010 primary 1-hour S02 NAAQS: (1) areas that have 

current monitored design values in violation of the NAAQS that were not previously 

designated during Round 1 designations and (2) areas that contain any stationary 

source(s) that, according to U.S. EPA's Air Quality Markets Database either emitted 

more than 16,000 tons of S02 in 2012 or emitted more than 2,600 tons of S02 and had 

an annual average emission rate of at least 0.45 lbs S02/MMBtu (pounds per one 

million British thermal units) in 2012 and that has not been announced (as of March 2, 

2015) for retirement. 

A n Equal Opportunity Employer 0 (i) Recycled Paper A State 
Spencer Rockport 54,390 0.583 Generating Station 

Jefferson Clifty Creek 52,839 1.767 Generating Station 

Gibson Gibson 22,447 0.249 Generating Station 

LaPorte Michigan City 11,584 1.006 Generating Station 

Posey A.B. Brown 7,091 0.521 Generating Station 

U.S. EPA is providing states the opportunity to submit updated recommendations 

and supporting information for consideration for the affected areas. The guidance 

indicates U.S. EPA's intention to propose state designations on or about February 3, 

2016, and finalize them by July 2, 2016. As such, the guidance requests that states 

submit their recommendations for area designations by September 18, 2015. 

Enclosed you will find Indiana's assessment to support final boundary 

determinations for Round 2 designations for the 2010 primary 1-hour S02 NAAQS 

(Enclosure 3). Indiana has also enclosed quality-assured ambient air quality monitoring 

data from 2012-2014 for Indiana's SOz monitoring network (Enclosure 2). Based on this 

data, there are no new areas in the state that monitored concentrations above the 

standard in addition to those identified in Round 1 air quality designations. 

The following enclosures are included with this letter: 

• Enclosure 1 Indiana's Preliminary Designation Recommendations 

Concerning Round 2 Air Quality Designation 

Recommendations for the 2010 Primary 1-Hour SOz 

. Standard 

• Enclosure 2 Indiana's 2012-2014 SOz Monitoring Data Summary 

Compared to the 1-Hour Standard 

• Enclosure 3 Indiana's Assessment of Round 2 Air Quality Designations 

for the 2010 Primary 1-Hour S02 Standard 

Indiana is recommending that U.S. EPA use county boundaries for the purposes 

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

enforcement functions for the area. 
g

, 

y 

that these facilities, based on 2012-2014 quality-assured ambient air quality monitoring 

data and ambient air quality modeling, are not located in an area currently violating the 

NAAQS or are causing or contributing to a monitored violation of the standard. 

An electronic version of this request in PDF format, as well as a disk containing 

input and output files used to conduct appropriate air dispersion modeling analyses to 

support Indiana's assessment have been sent to Randy Robinson and John 

Summerhays of U.S. EPA Region 5. 

Indiana reserves the right to supplement and/or revise the recommendations 

contained herein as additional monitoring and/or modeling information becomes 

available. I would like to thank you for this opportunity to provide feedback to U.S. EPA 

regarding Round 2 air quality designations for the 201 0 primary 1-hour S02 NAAQS. 

We look forward to working with your staff as U.S. EPA moves forward with the 

designations process. If you have any questions regarding Indiana's designation 

recommendations, please feel free to contact me at (317) 232-8611 or by email at 

ccomer@idem.IN.gov or Keith Baugues, Assistant Commissioner, Office of Air Quality, 

at (317) 232-8222 or by e-mail at kbaugues@idem.IN.gov. 

CSC/kb/sd/bc/gf 

Attachments: 

Commissioner 

cc: George Czerniak, U.S. EPA Region 5 (no enclosure) 

Chris Panos, U.S. EPA Region 5 (no enclosure) 

Randy Robinson, U.S. EPA Region 5 (no enclosure) 

John Summerhays, U.S. EPA Region 5 (no enclosure) 

Doug Aburano, U.S. EPA Region 5 (no enclosure) 

Keith Baugues, IDEM-OAQ (no enclosure) 

Scott Deloney, IDEM-OAQ (no enclosure) 

Brian Callahan, IDEM-OAQ (w/ enclosure) Mark Derf, IDEM-OAQ (w/ enclosure) 

Gale Ferris, IDEM-OAQ (w/ enclosure) 

File Copy 

County Recommendation 

Gibson Attainment 

Jefferson Attainment 

LaPorte Attainment 

Posey Attainment 

Spencer Attainment 

Page I of I 

Monitor Design 

County Site ID 2012 2013 2014 Value 

Bartholomew 18-005-0007 16.2* 17.4 17** 

Daviess 18-027-0002 78 150 107 112 

Floyd 18-04 3-0004 38 30 65 44 

Floyd 18-043-1004 32 20.5 43.8 32 

Fountain 18-045-000 1 30 34 22 29 

Gibson 18-051-0002 76 64 77 72 

Wabash, IL 17-185-0001 89 55 53 66 

JaSQer 18-073-0002 33 40 25 33 

Lake 18-089-0022 47 43 .2 53.1 48 

Lake 18-089-2008 28 23.7 20.2 24 

LaPorte 18-091-0005 21 15* 15 17** 

Marion 18-097-0057 91.5 78.1 105.6 92 

Marion 18-097-0073 56 42.3 59.1 53 Marion 18-097-0078 61.1 70 80* 70** 

Morgan 18-109-1001 82 64 90 79 

Pike 18-125-0005 140.2 169.4 156.7 155 

Porter 18-127-0011 36 36 27 33 

Vanderburgh 18-163-0021 16.5 18.6 32.3 22 

Vi go 18-167-0018 72.5 79.1 85 79 ll 

Vi go 18-167-1014 128 103 120 117 

Wayne 18-177-0006 22.4 14.3 7 15 

Whitley 18-183-0003 5.8 13.3 10** 

*Not a complete year of data 

* * Less than three years of data 

Design Value greater than or equal to 76 ppb u r 

Illinois Monitor 

Page I of 4 
Indiana S02 2008-2014 Monitoring Data Summary Compared to the 1-Hour Standard 

:-.rote: U.S. EPA established a new !-hour primary S02 standard on June 2. 2010. The new !-hour standard is 75 parts per billion (ppb). Attainment is determined by evaluating the three-year average of the 99'h percentile 

values of the daily ma'<imum !-hour average at each monitor within an area, which must not exceed 75 ppb. Any three-year design value over the !-hour standard has been highlighted in yellow. Data prior to 2010 were 

compared to the annual and 24-hour sol standards. 

99'b Per centile Values (ppb) Three-Year Design Value (ppb) 

County Site ID I I I 2008 2009 2010 2011 2012 2013 2014 08-10 09-ll 10-12 11-13 12-14 

Bartholomew 18-005-0007 Monitor began operation on 05/02/20 13. 16.2 17.4 Operation began operation on 16 17 05/0212013. 

Daviess 18-027-0002 122 138 115 100 78 !50 107 125 118 98 109 112 

Floyd 18-043-0004 117 87 72 36 38 30 65 92 65 49 35 44 

Floyd 18-043-1004 138 125 123 38 32 20.5 43.8 129 95 64 30 32 

Fountain 18-045-000 I 236 38 26 29 30 34 22 100 31 28 31 29 

Gibson 18-05 1-0002 90 65 74 68 76 64 77 76 69 73 69 72 

Wabash. IL 17-185-0001 90 69 66 47 89 55 53 75 61 67 64 66 

Jasper 18-073-0002 61 88 39 32 33 40 25 63 53 35 35 33 

Lake 18-089-0022 67 59 57.2 58 47 43.2 53.1 61 58 54 49 48 

Lake 18-089-2008 37 37 34.3 40 28 23.7 20.2 36 37 34 31 24 

LaPorte 18-091-0005 29 23 30 19 21 15 15 27 24 23 18 17 

Marion 18-097-0057 79 75 103.4 63 91.5 78.1 105.6 86 80 86 78 92 

Marion 18-097-0073 29 61 47.7 59.5 56 42.3 59.1 46 56 54 53 53 

Marion 18-097-0078 Monitor began operation in 20 59.7 61.1 70 80 20 40 47 64 70 

2010. 

Morgan 18-109-1001 91 98 105 96 82 64 90 98 100 9-4 ! 79 

Pike 18-125-0005 205 194 21 1 119 140.2 169.4 156.7 203 175 157 1-43 155 

Porter 18-127-0011 82 51 62 44 36 36 27 65 52 47 39 33 

Vanderburgh 18-163-0012/21 41 17 18.8 19.4 16.5 18.6 32.3 26 18 18 18 22 

Vi go 18-167-0018 120 115 61.4 95.2 72.5 79.1 85 99 91 76 82 79 

Vi go 18-167-1014 137 142 169 139 128 103 120 149 150 145 123 117 

Wayne 18-177-0006 109 70 95.2 79.1 22.4 14.3 7 9 1

1 8 1 66 39 15 

Whitley 18-183-0003 Monitor began operation in 2013. 5.8 13.3 Monitor began operation in 2013. 6 10 

One Year of Data Two Years of Data Incomplete Data lllinois Monitor Design Yalue greater than or equal to 76 ppb 

Page 2 of4 
Source-Oriented 

10# 18-127-0011 

Source-Oriented 

10# 18-073-0002 

Source-Oriented 

10# 18-045-0001 

Terre HauteLafayette Ave. 

10# 18-167-0018 

Source-Oriented 

I 0# 18-027-0002 

Source-Oriented 

10# 17-185-0001 

Evansville - Buena Vista 

10# 18-163-0021 

Note: Monitor Site Identification Numbers Used by U.S. EPA's 

Nr Quality System Database 

Oate:OS/11/2015 

Mapped by: L. Fergusoo, OAQ 

Sourcu: Offioe of Air Q uality 

Map Projection: UTM Zone 16 N 

Map Datum: NAD83 

I 0# 18-183-0003 

All!n 

Pula!ki 

Wabash ¢8' 

"'"' W!lls Adams 

Howard Gr! nt 

O inton Tipton 

llontgomery Boone Hamilton 

0 

I Indiana-Operated S02 Monitor 0 

0 Source-Operated S02 Monitor 

Page 3 of4 

lndpls -Washington Park 

I 0# 18-097-0078 

lndpls -E. 16th St 

I 0# 18-097-0073 

Source-Oriented 

10# 18-177-0006 

Source-Oriented 

10# 18-109-1001 

Hope 

10# 18-005-0007 

Source-Oriented 

10# 18-043-0004 

New Albany 

I 0# 18-043-1 004 

25 50 mi 

I 

25 50 km 

N 

w 

s 
ID# 18-045-0001 

29 

ID# 18-167-1014 

117 

Terre Haute· 

Lafayette Ave. 

79 

ID# 18-027-0002 

112 

ID# 18-125-0005 

155 

ID# 17-185-00 01 

66 

Evansville · Buena Vista 

22 

Note: 1-Hour Design 

Values for 201 2-2014 

in parts per billion (ppb) 

Dale: OS/1 0120 15 

Mapped by: L. FErgus on. O AO 

Sources: Offia: of Air Quality 

Map Projection: UTM Zone 1tl N 

Map Datum: NAOS3 

Benton 

Werren 

D 

D 

• + 

Allen 

Pulaski 

Wabash ,_o<:-

Miami ;...f!l Wells .odanu 

Hcwerd Grant Jfr.j 

lippEOSnoe 

Clinton lipton 

Del"'vare 

Montgomery Boone Hamilton 

Daviess 

Pike 

Vlgo 

Non attainment Area 0 

I 

ID# 18-177-0006 

15 

lndpls · Harding St. 

92 

ID# 18-043-0004 

44 

25 50 mi 

I 

Attainment/U nclassifiable 0 25 50 km 

S02 Monitor less than or equal to 75 ppb S02 Monitor greater than 75 ppb 

Page 4 of4 
Bacl{ground 

On June 2, 2010, the United States Environmental Protection Agency (U.S. EPA) revised the 

primary National Ambient Air Quality Standard (NAAQS) for sulfur dioxide (S02) [75 FR 

35520]. U.S. EPA revoked both the previous 24-hour and annual primary S02 standards and 

established a new 1-hour so2 standard at a level of 7 5 pmis per billion (ppb ), based on the tlu-ee 

year average of the mmual 99111 percentile of the 1-hour daily maximum concentrations. 

On August 5, 2013, U.S. EPA published a notice announcing designations of twenty-nine (29) 

areas in sixteen (16) states as nonattainment for the 2010 primary 1-hour S02 NAAQS, based on 

certified ambient air quality monitoring data for the years 2009-201 1 that showed these areas 

were violating the standard (78 FR 47191). 1 In the State oflndiana, four areas comprised of nine 

townships in five counties were designated nonattainment. However, at that time U.S. EPA was 

not yet prepared to issue designations for the remaining areas. 

On March 2, 2015, the U.S. District Court for the Northern District of California accepted, as an 

enforceable order, an agreement between U.S. EPA, the Sierra Club, and the Natural Resources 

Defense Council to resolve litigation concerning the deadline for completing air quality 

designations for the remainder of the country? The court's order directs U.S. EPA to complete 

remaining designations in three additional rounds: Round 2 by July 2, 2016, Round 3 by 

December 31, 2017, and Round 4 by December 31 , 2020. U.S. EPA will complete these 

designations by designating areas as either nonattainment, attainment, or unclassifiable. 

The court order directs U.S. EPA to designate two groups of areas under Round 2 ofthe air 

quality designations: (1) areas that have newly monitored violations of the 2010 primary S02 

NAAQS that were not previously designated during Round 1 designations and (2) areas that 

contain any stationary source(s) that, according to U.S. EPA's Air Quality Markets Database, 

either emitted more than 16,000 tons of so2 in 2012 or emitted more than 2,600 tons of so2, had 

an annual average emission rate of at least 0.45 lbs S02/MMBtu (pounds per one million British 

thermal units) in 2012, and that has not been announced (as of March 2, 2015) for retirement. 

1 http://www.gpo.gov/fdsys/pkg/FR-20 13-08-05/pdf/20 13- 18835.pdf 

2 http://www .epa. gov/airqual ity/sul furdioxide/designations/pdfs/20 1503 FinaiCourtOrder.pdf 

Page 1 of34 
County 

Spencer 

Jefferson 

Gibson 

LaPmte 

Posey 

Round 2 Air Quality Designation Criteria 

Facility Name 

2012 S02 Emissions 2012 S02 Emission Rate 

(tons) (lbs/MMBtu) 

Rockport 54,390 0.583 Generating Station 

Clifty Creek 52,839 1.767 Generating Station 

Gibson 22,447 0.249 Generating Station 

Michigan City 11,584 1.006 Generating Station 

A.B. Brown 7,091 0.521 Generating Station 

The March 2, 2015, comt order directs U.S. EPA to complete the second round of area 

designations by July 2, 2016. States may submit updated recommendations and supporting 

information to U.S. EPA for consideration for the affected areas by no later than September 18, 

2015. 

U.S. EPA's final area designations are expected to be based on 2012-2014 ambient air quality 

monitoring data reported from S02 monitors currently in place, as well as refined modeling 

states choose to conduct specifically for area designations. U.S. EPA expects to designate areas 

in the following mmmer: 

• Nonattainment: An area that U.S. EPA has determined violates the 2010 primary!-

hour S02 NAAQS, based on the most recent three years of ambient air quality monitoring 

data or an appropriate modeling analysis, or that U.S. EPA has determined contributes to 

a violation in a nearby area. 

• Attainment: An area that U.S. EPA has determined meets the 2010 primary !-hour S02 

NAAQS and does not contribute to a violation of the NAAQS in a nearby area based on 

either: a) the most recent tiu·ee (3) years of ambient air quality monitoring data from a 

Page 2 of34 
and whether the area contributes to a violation in a nearby area. 

Indiana's Assessment 

Consistent with U.S. EPA's March 20,2015, guidance memorandum titled "Updated Guidance 

for Area Designations for the 2010 Primary Sulfur Dioxide National Ambient Air Quality 

Standard,"4 the Indiana Department of Environmental Management (IDEM) has conducted a 

thorough review of the affected areas in Indiana. IDEM's review focused on the following 

analysis criteria outlined in the guidance: 

• Ambient air quality data or dispersion modeling r·esults: Indiana's evaluation is 

based on 2012-2014 monitoring data and air dispersion modeling results. The air quality 

analysis evaluated the three-year average of the 99111 percentile of the yearly distribution 

of 1-hour daily maximum S02 concentrations. Ambient air quality monitoring data was 

retrieved from U.S. EPA's Air Quality System (AQS) and refined dispersion modeling 

was performed using the American Meteorological Society/Envirorunental Protection 

Agency Regulatory Model (AERMOD) version 15181 to assess air quality in a particular 

location. U.S. EPA Region V reviewed IDEM's modeling protocol and provided 

comments which were addressed. Modeling results were conducted using 4111 high 

maximum daily 1-hour values averaged over the tlu·ee-year modeled period combined 

with representative temporally varying seasonal S02 background concentrations to 

indicate whether the area violated the standard or contributed to a violation in a nearby 

area. Modeling was performed to show that the existing monitor(s) are properly sited to 

assess air quality in the area. 

• Emissions-related data: Indiana examined detailed emissions information from the 

Clifty Creek Generating Station (Jefferson Cotmty), A.B. Brown Generating Station 

(Posey County), Michigan City Generating Station (LaPmte County), and Rockport 

Generating Station (Spencer County) and all other significant sources of S02 emissions 

located in nearby areas. Significant emission levels in nearby areas indicate potential for 

the area to contribute to observed or modeled violations of the standard. Tables 

3 http://www.epa.gov/airquality/sulfurdioxide/pdfs/S02ModelingTAD.pdf 

4 http://www .epa. gov/airqual ity/su I furdioxide/pd fs/20 150320S02designations.pdf 

Page 3 of34 
to ambient S02 concentrations. 

• Geography/topography: The geography and topography analysis considered physical 

features and land use that might have an effect on the air shed and therefore, the 

distribution of pollutants over an area. Indiana does not have any significant topographic 

features that influence the distribution of SOz concentrations within the state. 

• Jurisdictional boundaries: Indiana is recommending that U.S. EPA use county 

boundaries for the purpose of providing a clearly defined legal boundary for carrying out 

the air quality plmming and enforcement functions for the area. 

Indiana has developed the following evaluation for determining m·ea designations and 

appropriate area boundaries for the 2010 !-hour primary S02 standard. Indiana relied on 2012-

2014 site-specific monitoring data in determining whether the Gibson Generating Station is 

located in an area that violates or contributes to a violation of the !-hour S02 NAAQS in a 

nearby area. Indiana relied on AERMOD air dispersion modeling of the Clifty Creek Generating 

Station, A.B. Brown Generating Station, Michigan City Generating Station, and Rockport 

Generating Station for area attainment designation recommendations as there are no site-specific 

monitors associated with these facilities. 

Based on the results of this evaluation, Indiana recommends that Gibson, Jefferson, LaPorte, 

Posey, and Spencer counties be designated as attainment under the 20 I 0 !-hour primary SOz 

standard. This recommendation is based on the fact that Indiana's assessment, performed in 

accordance with U.S. EPA's updated guidance, clearly demonstrates that these facilities, based 

on 2012-2014 quality-assured monitoring data and ambient air quality modeling, are not located 

in an area currently violating the NAAQS or are causing or contributing to a violation in a 

nearby area. 

Methodology for the Ah· Quality Modeling and Meteorology Inputs 

U.S. EPA provided guidance in order to conduct appropriate air dispersion modeling analyses to 

support !-hour S02 designation recommendations. U.S. EPA's S02 NAAQS Designations 

Modeling TAD guidance has several recommendations for modeling methodology for 

determining attainment designations including: 

Page 4 of34 
Indiana followed U.S. EPA's recommendations to conduct !-hour S02 designation modeling in 

order to meet the requirements of the Consent Decree to determine whether there are modeled 

violations of the !-hour SOz NAAQS. Modeling results look at the 41h high maximum daily 1-

hour concentration averaged over the 3-year modeled period combined with representative 

temporally varying seasonal S02 background concentrations to determine the attai11111ent status 

of the area where the Consent Decree emission sources reside. 

Model Selection 

In accordance with Appendix A of Appendix W to 40 Code of Federal Regulations (CFR) Part 

51, Indiana used AERMOD version 15181 for all dispersion modeling of the A.B. Brown 

Generating Station, Clifty Creek Generating Station, Michigan City Generating Station, and 

Rockport Generating Station, as well as nearby areas. Additionally, the regulatory default and 

rural mode options were selected. U.S. EPA's S02 NAAQS Designations Modeling TAD, 

specific to attai11111ent designation modeling, recommended using actual stack heights when 

modeling actual emissions instead of following the GEP requirement. 

AERMAP 

The AERMOD terrain preprocessor mapping program, AERMAP, was used to determine all the 

elevation terrain heights for the receptor, building, and source locations using the Universal 

Transverse Mercator (UTM) coordinate system. The most recent AERMAP version Ill 03 was 

used to assign the elevations from the National Elevation Dataset (NED) using the North 

American Datum (NAD) 1983 as recommended in "40 CFR Pmi 51, Revision to the Guideline 

on Air Quality Models" Appendix W and later revised in the "AERMOD Implementation 

Guide." 

Receptor Grid and Modeling Domain 

The receptor grid and modeling domain was based on U.S. EPA's March 20, 2015, S02 guidance 

and S02 NAAQS Designations Modeling TAD. Indiana conducted modeling with a multinested rectangular receptor grid with appropriate spacing of receptors based on the distance from 

the modeled emission points to detect significant concentration gradients. Indiana has conducted 

Page 5 of34 
• Receptor spacing at the fence line for each facility were placed every 50 meters. 

• Receptor spacing at 100 meters out to a distance of3,000 meters (3 km) beyond each 

facility (extended if modeling results warranted). 

• Receptor spacing at 250 meters out to a distance of 5,000 meters (5 Ian) beyond each 

facility (extended if modeling results warranted). 

• Receptor spacing at 500 meters out to a distance of 10,000 meters (1 0 km) beyond each 

facility (extended if modeling results warranted). 

Based on the S02 NAAQS Designations Modeling TAD Section 4.2, Indiana placed modeling 

receptors only where it was feasible to place a monitor. Indiana matched up each modeling 

domain for the four sources modeled with Google Maps projections to ensure the proximity of 

receptor locations. 

Modeled S02 Emissions 

Indiana modeled the hourly continuous emissions monitoring (CEM) data from each source 

mentioned in the Consent Decree. Along with the hourly emission data, hourly stack gas flow 

rate and temperature of the exhaust stream (when available) were modeled as these parameters 

tend to vary. This variation can influence the dispersion characteristics of the exhaust stream and 

have an impact on modeled 1-hour S02 concentration(s). In some cases federally enforceable 

emission limits anticipated to be in place by the July 2, 2016, date for final so2 area designations 

were modeled. Documentation of all controls and/or emission limits implemented at the sources 

by the compliance date, contrary to the 2012-2014 CEMS data, are provided for each source 's 

attainment designation recommendation. 

Intermittent Sources 

Intermittent sources, such as emergency generators, fire pumps, and startup/shutdown emissions 

will be handled consistent with U.S. EPA's March 1, 2011 , guidance "Additional Clarification 

Regarding Application of Appendix W Modeling Guidance for the 1-hour N02 NAAQS."5 This 

5 http://www.epa.gov/ttn/scram/guidance/clari ficationl Additional Clarifications Appendix W Hourly-N02-

NAAOS FINAL 03-0 l-20 l l.pdf 

Page 6 of34 
per year and on a random and infrequent basis that cannot be anticipated. Exploratory modeling 

was conducted on these intermittent sources and results showed a negligible impact from these 

auxiliary or emergency processes on the maximum modeled !-hour S02 receptors from the 

electric generating units (EGUs). Indiana believes the intent of the Consent Decree is to 

determine the attainment status of the area su!1'ounding the EGUs based on the actual emissions 

coming from the EGUs identified by U.S. EPA; therefore the EGUs were Indiana's main focus 

in its assessment. 

Treatment of Inventory Sources 

Emission sources located in the vicinity of the Consent Decree sources were evaluated to 

determine if they could cause or contribute to a NAAQS violation near the Consent Decree 

source. Based on U.S. EPA's March I, 2011 guidance, Indiana focused on areas within 10 km 

for each of the modeled Consent Decree sources. U.S. EPA's S02 NAAQS Designations 

Modeling TAD Section 4.1, page 7 mentions that the number of sources to be explicitly modeled 

should cause a significant concentration gradient and the number of those sources to be modeled 

would generally be small. Indiana retrieved a list of all S02 emission sources in the county of 

the source addressed by the Consent Decree, as well as S02 emission sources in adjacent 

counties in Indiana and Kentucky, in order to determine which sources should be included in the 

modeling analyses. Seven Indiana sources and six Kentucky sources were identified with S02 

emissions of250 tpy or more located within 30 km of one of the Consent Decree sources. 

Actual emissions taken from the year 2013, the most recently available year, were modeled for 

all sources. 

Meteorological Data 

As stated in 40 CFR Part 51, Appendix W, section 8.3.1.2 and the S02 NAAQS Designations 

Modeling TAD, Indiana used three years (2012-2014) ofNational Weather Service (NWS) 

surface and upper air meteorological data. The Indianapolis, Evansville, and South Bend NWS 

surface data and upper air data taken from Lincoln, Illinois and Wilmington, Ohio, were 

processed with the latest version of the AERMOD meteorological data preprocessor program, 

AERMET (version 15181), and used in the modeling of the Clifty Creek Generating Station, 

A.B. Brown Generating Station, Michigan City Generating Station, Rockport Generating Station, 

and nearby areas. Meteorological data, taken from the Gary-Illinois Institute of Technology 

Page 7 of34 
AERMINUTE/AERSURF ACE 

The NWS meteorological data can contain a number of calm wind speeds greater than ten 

percent of the 8,760 annual observation hours. The !-minute wind speed and wind direction 

Automated Surface Observing System (ASOS) data from the NWS stations were processed with 

U.S. EPA's !-minute data processor program, AERMINUTE version 14237. 

U.S EPA's program, AERSURFACE, was used to determine the surface characteristics: albedo, 

Bowen ratio, and surface roughness for the Indianapolis, Evansville, and South Bend NWS 

meteorological tower locations. Surface characteristics were determined at each NWS location 

for each of the 12 wind direction sectors with a recommended default radius of one km. The 

albedo and Bowen ratio surface characteristics were adjusted during the three winter months of 

January, February, and December in accordance with U.S. EPA Region V's document "Regional 

Meteorological Data Processing Protocol," dated August 2014. Additionally, a dry or wet 

Bowen ratio value was used during months when soil moisture conditions were abnormally dry 

or wet; otherwise the Bowen ratio value for average soil moisture conditions was used. The 

surface roughness value for snow cover was used if more than half of the month had days with at 

least one inch of snow on the ground. Otherwise, the no snow cover surface roughness value 

was used. 

Indiana's Recommendations 

Duke Energy Indiana, Inc.- Gibson Generating Station 

The Gibson Generating Station (Gibson Station) is a coal-fired power plant consisting of five 

units that have a capacity to generate 3,342 megawatts (MW) of electricity combined. The 

Gibson Station is located on the bank of the Wabash River in Montgomery Township, Gibson 

County, Indiana, approximately 1.5 miles southeast of Mount Carmel, Illinois and 7.5 miles 

northwest of Owensville, Indiana. The plant is operated by Duke Energy Indiana, Inc. (DEI) and 

owned by DEI, Wabash Valley Power Association, Inc., and the Indiana Municipal Power 

Agency. Gibson Station is a stationary electric utility generating station with five coal-fired 

boilers; two boilers are rated at 5,875 MMBtu/hr, two boilers are rated at 5,987 MMBtu/hr, and a 

fifth boiler is rated at 5,900 MMBtu/hr. 

Page 8 of34 
station in Wabash County, Illinois. The Coal Road and Mt. Carmel monitors have been in 

operation since 1979 and report data to U.S. EPA's AQS database. Two additional monitors, the 

Tower and Schrodt monitors, operated until December 2010 and also reported data to the AQS. The Pumphouse monitor, which became operational on August 21, 2014, is not reported to U.S. 

EPA's AQS and is, therefore, not comparable to the standard. The Pumphouse, Tower, and 

Schrodt monitors have been included as weight-of-evidence to illustrate that ambient S02 

concentrations in the area have historically been, and currently are, below the standard and that 

the current ambient network is adequate to characterize potential impacts of the Gibson Station. 

Page 9 of34 
I 

0 1 km 

Mapp.d By: L FOtgu• co. Olice clAir Qu.olny 

Date: 07115/2015 

Sou reo: IDEM. Office ofAr ond EPA, AQS 

Map Proj..,tlon :UTM Zono 1e N 

Map Ollllum: NAD83 

* Gibson Generating Station 

Active S02 Monitors 

Inactive S02 Monitors 

(Discontinued 12131110) 

Thii m.1p h to n rvt 1-1 1n lid In GtlphlortpttstntJIIon only. lhh into.rmJtion il net warr1ntaO for accuraOJ ot olhar purpcu -1. 

Page 10 of34 
and Mt. Carmel monitoring sites are properly located to adequately characterize peak ambient 

S02 concentrations and source-oriented impacts from the Gibson Station. 

Page II of34 
I 

0 1 km ~lap ped By: l. Ferguson, Office of Air Quality 

Dale:08/1412015 

Sourcu:Non Orthophotography Data· IDEM, 

OAQ, Indiana GIO, EPAAQS and Duke Energy ~lap Pro)acUon: UTM Zone 16 N 

llap Datum: NAD83 

Gibson Generating Station 

S02 Monitors 

• S02Impact ~ Location of Highest Impact 

This map Is Intended to serve as an aid in graphic rep<esenlalion only. This Information Is no! warranted lor accuracy or oCher purposes. 

Page 12 of 34 
Graph 1: 

Gibson Station S02 Monitoring Network Historical Design Values 

200 

180 

160 

rt:: 140 I- -

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.... 120 t-- -

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0 f- ..___.. -1- ---........ -1- ...__,._.. 4- 4-

2005-2007 2006-2008 2007-2009 2008-2010 2009-2011 2010-2012 2011-2013 2012-2014 

- Coal Road - Gibson Tower - Mt. Carmel - Schrodt - 2010 1-Hour S02 Standard 

The Evansville National Weather Service wind rose plots are shown in Figure 3. The wind roses 

show the frequency of the wind direction every 1 0 degrees for each of the wind speed ranges for 

the three-year modeled period of 2012-2014. The wind direction is the direction the wind is 

blowing from in compass degrees and the wind speeds are in meters per second (tn!s). The wind 

roses demonstrate that the Coal Road monitor is sited appropriately to accurately characterize 

ambient S02 concentrations near the Gibson Station. 

Page 13 of34 
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As shown in Figure 2, elevated levels of S02 were also found on Gibson Station property to the 

southwest of the main stacks. In response, Duke Energy installed the Pumphouse S02 monitor to 

assess ambient S02 concentrations. Table 2 outlines the daily 1-hour maximum S02 values for 

the Pumphouse monitoring site for August 21, 2014-July 31, 2015. Monitoring data from this • 

monitor is not reported to U.S. EPA's AQS and is, therefore, not comparable to the standard, but 

has been included as weight-of-evidence to show S02 concentrations recorded at this monitor 

have been well below the standard. 

Table 2: 

Top Ten Daily 1-Hour S02 Maximum Values for the Pumphouse Monitoring Site 

Daily 1-Hour 

Maximum Value 

Rank (ppb) Date 

1 69 4/28/2015 

2 64 5/13/2015 

3 61 9/27/2014 

4 60 10/22/2014 

5 51 9/14/2014 

6 48 3/2/2015 

7 40 9/23/2014 

8 38 9/7/2014 

9 38 9/26/2014 

10 37 8/25/2014 

Page 14 of 34 
Gibson Station, based on 2012-2014 quality-assured monitoring data, is not located in an area 

violating the NAAQS or causing or contributing to a violation of the NAAQS in a nearby area. 

Indiana-Kentucky Electric Corporation- Clifty Creek Generating Station 

The Clifty Creek Generating Station (Clifty Creek) is a coal-fired power plant on the northern 

bank of the Ohio River in Madison Township, Jefferson County, Indiana. The power plant is 

located at 1335 Clifty Hollow Road in Madison, Indiana. The plant is owned by Ohio Valley 

Electric Corporation (OVEC) and its wholly owned subsidiary, Indiana-Kentucky Electric 

Corporation (IKEC), a consortium of several power companies including American Electric 

Power (AEP). All six of its generating units are rated at 217.26 MW and have a capacity to 

generate 1,303.56 megawatts (MW) of electricity combined. Five (5) of the units are wet-bottom 

pulverized coal-fired boilers identified as Units 1 through 5, with construction completed in 

1955, each with a rated capacity of 1,869 MMBtu/hr. The sixth unit is a wet-bottom pulverized 

coal-fired boiler identified as Unit 6, with construction completed in 1956, with a rated capacity 

of 1,869 MMBtu/hr. Clifty Creek installed a flue gas desulfurization (FGD) system to provide 

S02 controls for its six generating units. The FGD system came online in July 2013. 

Due to conditions set fmih in the Consent Decree and subsequent U.S. EPA guidance, Indiana 

relied on AERMOD air dispersion modeling to determine the attainment designation 

recommendation for the Clifty Creek Generating Station as there is no site-specific S02 air 

quality monitor associated with this facility. Modeling results were conducted using 4111 high 

maximum daily 1-hour values averaged over the three-year modeled period combined with 

representative temporally varying seasonal S02 background concentrations to indicate whether 

the area violates the standard or causes or contributes to a violation of the standard. 

Indiana used meteorological data from the surface and upper air stations outlined in Table 3 to 

conduct modeling for Clifty Creek. 

Table3: 

Surface and Upper Ait· Meteorological Stations 

Facility Surface Met Upper Air Met 

Clifty Creek Generating Station Louisville, KY NWS Wilmington, OH NWS 

Page 15 of34 
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Modeling of Clifty Creek used adjusted (i.e. without upwind major source impacts) temporally 

varying seasonal background concentrations. The New Albany S02 monitor data, listed in Table 

4, is considered representative background for Jefferson County, Indiana. 991h percentile S02 

concentrations by season (winter, spring, summer and fall) for each hour of the day were 

calculated for 2012-2014 to determine the temporally varying seasonal S02 background, which 

were used directly in the model. 

Winter 

Spring 

Summer 

Fall 

Table 4: 

991h Percentiles for Temporally Varying Seasonal 802 

Background Values (ppb) for 2012-2014 

Hr1 Hr2 Hr·3 Hr4 Hr5 Hr6 Hr7 

6.61 7.81 5.50 5.57 4.25 5.09 4.89 

8.10 5.36 7.03 8.25 5.64 4.85 3.51 

6.84 4.05 3.99 5.35 4.14 3.10 4.40 

3.34 3.50 3.69 3.64 2.80 3.36 3.39 

Page 16 of34 

Hr8 

5.95 5.39 

4.62 4.62 
Hr 17 Hr 18 Hr19 Hr20 Hl"21 Hr22 Hr23 Hr24 

Winter 10.38 8.80 8.90 6.90 6.15 8.28 6.28 8.04 

Spring 17.56 15.06 13.38 11.96 9.41 7.69 5.08 9.02 

Summer 7.80 8.64 10.04 10.26 8.10 6.14 7.44 6.50 

Fall 10.81 12.77 7.85 6.35 3.90 3.30 4.70 5.55 

Meteorological data from the nearest station to the Floyd County New Albany monitor, the 

Charlestown State Park meterological station listed in Table 5, was used to develop temporally 

varying seasonal S02 background values for Clifty Creek. 

Table 5: 

Location of the New Albany S02 Monitor and Charlestown State Park 

Meteorological Station for Background Analysis 

S02 Monitor Monitor Meteorological Station Station 

and lD # Location and lD # Location Distance 

New Albany 38.31°N Charlestown State Park 38.39°N 10.7 

18-043-1004 85.83° w 18-019-0008 85.66° w miles 

Indiana evaluated S02 sources within 30 km of Clifty Creek. Clifty Creek is the only significant 

source of S02 emissions in Indiana in that region; however there are two large S02 emission 

sources in the State of Kentucky that were evaluated to determine possible impacts on Clifty 

Creek. 2013 actual emissions for these facilities, listed in Table 6, were modeled to evaluate 

whether these sources could be causing or contributing to a NAAQS violation in the area. 

Table 6: 

Canoll and Trimble Counties-Kentucky: 1-Hom· S02 Modeling Source Inventories 

2013 S02 

Source Source ID Location Emissions (tpy) 

Ghent Generating Station 21-041-00010 Carroll County, KY 3,522 

Trimble County Generating Station 21-223-00002 Trimble County, KY 13,424 

Page 17 of34 
• Four ( 4) No. 2 fuel oil-fired coal transfer station heaters, installed in 1993: 

(I) One (I) with a design heat capacity of 1.25 MMBtu/hr for Station 2; 

(2) One (I) with a design heat capacity of 1.75 MMBtu/hr for Station 5; and, 

(3) Two (2) each with design heat capacities of2.75 MMBtu/hr for Stations B3 and 84. 

• Stationary emergency fire pumps 

Based on information provided by Clifty Creek, the transfer station heaters' actual emissions are 

estimated to be less than one (I) ton per year as ultra-low sulfur diesel is used to fuel these 

heaters. Due to the operation of the stationary emergency fire pumps, emissions are estimated to 

be less than 0.25 tons per year. 

All these units are listed in their Part 70 Title V permit as "insignificant activities" as defined in 

326 lAC 2-7-1 (21). IDEM did not include these sources in the modeling analysis since their 

level of activity was insignificant, intermittent, and random in nature. 

Initial modeling, using hourly CEM data from 2012-2014, showed high modeled !-hour S02 

concentrations. This modeling included emissions before and after Clifty Creek had installed the 

FGD system. A decrease of90% or more of S02 emissions occurred as a result of the 

installation and operation of the FGD system. Pursuant to Section 5 of the S02 NAAQS 

Designations Modeling TAD, "sources that implement emission controls during the relevant 3-

year period and that becomes subject to an emission limit requiring that control may wish to 

demonstrate that limit assures attainment, even though the 3-year average emissions level would 

be estimated to yield NAAQS violations." Fmiher discussion with U.S. EPA Region Vindicated 

that federally enforceable emission limits in place by the final S02 area designation date of July 

2, 2016, would be recognized as an appropriate assessment of an area's attainment designation. 

Therefore, Indiana modeled the S02 emissions from Clifty Creek after the FGD system became 

operational to determine the attainment designation. Modeled concentrations for Clifty Creek 

including the impact of nearby large S02 emission sources and temporally varying seasonal S02 

background concentrations, as outlined in Table 7, are well below the !-hour S02 NAAQS. 

Page 18 of34 
Clifty Creek 71.6 196.2 Yes Generating Station 

Indiana recommends that Jefferson County, Indiana be designated as attainment under the 2010 

!-hour primary S02 standard. This recommendation is based on the fact that Indiana's 

assessment performed in accordance with U.S. EPA's updated guidance clearly demonstrates 

that the facility is not located in an area violating the NAAQS or causing or contributing to a 

violation of the NAAQS in a nearby area. 

Vectren- A.B. Brown Generating Station 

The A. B. Brown Generating Station (A.B. Brown) is a coal-fired power plant on the northern 

bank of the Ohio River in Marrs Township, Posey County, Indiana. The plant is located 

approximately 8 miles east of Mount Vernon, Indiana, and 5 miles southwest of Evansville, 

Indiana, just west of the Posey-Vanderburgh County Line. A.B. Brown is owned by Vectren 

(formerly Southern Indiana Gas and Electric Company). Each of the two coal-fired EGUs has a 

rated capacity of265.2 MW. Unit No. I, constructed in 1974 with a startup date of 1979, 

consists of one dry bottom, pulverized coal-fired boiler with a design fuel heat input capacity of 

2,518 MMBtu/hr. Unit No. 2, also a dry bottom, pulverized coal-fired boiler with a design fuel 

heat input capacity of2,530 MMBtulhr, was constructed in 1979 and had a startup date of 1985. 

Due to conditions set forth in the Consent Decree and subsequent U.S. EPA guidance, Indiana 

relied on AERMOD air dispersion modeling to detennine the attainment designation 

recommendation for the A.B. Brown Station as there is no site-specific air quality monitor 

associated with this facility. Modeling results were conducted using 4111 high maximum daily!-

hour values averaged over the three-year modeled period combined with representative 

temporally varying seasonal S02 background concentrations to indicate whether the area violates 

the standard or causes or contributes to a violation of the standard. 

Indiana used meteorological data from the surface and upper air stations, outlined in Table 8, to 

conduct modeling for A.B. Brown. 

Page 19 of34 
Modeling of A.B. Brown used adjusted (i.e. without upwind major source impacts) temporally 

varying seasonal background concentrations. The Evansville-Buena Vista monitor data, listed in 

Table 9, is considered representative background for Vanderburgh County, Indiana. Because 

A.B. Brown and the modeled inventory sources (see Table 11) are located southwest of the 

Evansville-Buena Vista monitor, impacts from the southwest direction were removed from the 

monitoring data. 99th percentile S02 concentrations by season (winter, spring, summer and fall) 

for each hour of the day were calculated for 2012-2014 to determine the temporally varying 

seasonal S02 background, which were used directly in the model. 

Winter 

Spring 

Summer 

Fall 

Winter 

Spring 

Summer 

Fall 

Winter 

Spring 

Summer 

Fall 

Table 9: 

99th Percentiles for Temporally Varying Seasonal S02 

Background Values (ppb) for 2012-2014 

Hr1 Hr2 Hr3 Hr4 HrS Hr6 Hr7 

6.00 4.22 3.88 4.27 6.02 4.95 5.25 

4.99 3.83 4.30 4.34 3.30 4.47 7.75 

2.71 2.22 1.00 1.00 2.87 3.45 3.34 

3.46 3.30 2.85 3.52 4.00 4.35 4.80 

Hr9 Hr 10 Hrll Hr 12 Hr13 Hr14 Hr15 

8.89 11.94 13.62 10.29 14.74 19.17 19.48 

9.82 9.05 13.37 13.25 15.49 12.02 9.34 

10.12 12.58 9.14 7.55 7.47 4.65 4.08 

7.73 11.66 15.88 11.70 11.26 10.28 10.03 

Hr 17 Hr18 Hr19 Hr20 Hr21 Ht·22 Hr23 

16.64 16.70 9.18 6.89 8.01 6.59 6.74 

13.01 12.93 11.32 8.26 5.59 3.81 5.90 

7.88 8.56 7.12 2.71 2.72 2.22 2.86 

10.11 9.85 8.87 8.51 5.70 2.59 3.06 

Hr8 

7.43 

9.52 

5.99 

5.28 

Hr16 

19.76 

10.70 

6.05 

9.08 

Hr24 

6.22 

6.10 

3.40 

3.31 

Meteorological data from the nearest station to the Evansville-Buena Vista monitor, the 

Evansville, IN NWS station, listed in Table 10, was used to develop temporally varying seasonal 

so2 background values. 

Page 20 of34 
va

sv

e

ue

a V

sta 38.0

N 

Evansville, IN NWS 

38.05

N 

4.3 miles 18-163-0021 87.58° w 87.52° w 

Indiana evaluated S02 sources within 30 !an of A.B. Brown. Posey County, Indiana has two 

additional sources, listed in Table 11, contributing S02 emissions above 250 tpy. 2013 actual 

emissions for these facilities were modeled to evaluate whether these sources could be causing or 

contributing to a NAAQS violation of the standard in the area. 

Table 11: 

Posey County, Indiana: 1-Hour S02 Modeling Source Inventories 

2013 so2 

Source Source ID Location Emissions (tpy) 

SABIC Innovative Plastics 129-00002 Posey County, IN 5,407 

Countrymark Refining and Logistics 129-00003 Posey County, IN 476 

Intermittent Source Justification 

Aside ti·om A.B. Brown's two coal-fired EGUs, there are several smaller emission units that are 

intetmittent with random operational schedules or emit small amounts of S02 emissions. 

• One (I) simple-cycle, natural gas-fired combustion turbine, designated as unit ABB No. 

3, constructed in 1991, with a design fuel heat input capacity of897.4 MMBtu/hr 

(nominal low heating value), utilizing distillate oil (No. 2 fuel oil) as a backup fuel with a 

CEM system for nitrogen oxides (NOx) and S02, with a water injection system for 

control ofNOx emissions, exhausting to Stack No. 3. 

• One(!) simple cycle, natural gas-fired combustion turbine, designated as unit ABB No. 

4, constructed in 2002, with a design fuel heat input capacity of 1,146 MMBtu/hour 

(maximum high heating value) with inlet fogger for power augmentation during high 

ambient temperature operation, with CEM system for NOx and S02, with dry low-NOx 

combustion, exhausting to Stack No. 4. 

Page 21 of34 
Specifically Regulated Insignificant Sources 

Insignificant activities at A.B. Brown, as covered by 326 Indiana Administrative Code 2-7-1 (21 ), 

include: 

• Two (2) diesel generators not exceeding 1,600 horsepower. The distillate oil-fired 

emergency generators were installed in 1974 and are rated at 398 boiler horsepower (bhp) 

each. 

• One (1) additional distillate oil-fired fire pump was installed in 1974 and is rated at 200 

bhp. 

The total emissions from all three units are no more than 0.55 tpy based on a maximum of 500 

hours of operation. IDEM did not include these sources in the analysis since their level of 

activity was insignificant, intermittent, and random in nature. 

Initial modeling, using A.B. Brown's hourly CEM data from 2012-2014, showed that modeled!-

hour S02 concentrations from A.B. Brown and inventory sources would be above the !-hour SOz 

NAAQS. After follow-up discussions with A.B. Brown, the company has agreed to modify their 

current PSD/Title V permit to lower their S02 emission's limit for coal-fired EGU No. 1 from 

1.2 lbs/MMBtu to 0.8571lbs/MMBtu, while maintaining the 0.69 lbs/MMBtu limit for Unit No. 

2. This equates to emission rates of3,021.6lbs/hr for Unit No. 1 and 1,745.7 lbs/hr for Unit 

No.2. Both units can never exceed 2,158.2 lbs/hr when operating together. As such, Unit No. I 

cannot operate at full capacity when Unit No.2 is running at 0.69lbs/MMBtu. The revised 

emission's limit for Unit No. 1 would account for a total S02 emissions reduction of2,609.1 

lbs/hr. A.B. Brown plans on moving forward with the permit modification request and having 

contt·ols installed and operational on Unit No. 1 by no later than March 2016 in order to meet the 

lower S02 emission's limit, well in advance of the July 2, 2016 consent decree deadline. 

Indiana modeled the proposed S02 emission limits recommended by A.B. Brown. Five 

scenarios were modeled. Modeled concentrations for the worst case scenario (i.e. Unit No. 2 

operating at 0.69lbs/MMBtu and Unit No. 1 operating at 0.164lbs/MMBtu) added to the 

temporally varying seasonal S02 background concentrations, as outlined in Table 12, are below 

the !-hour S02 NAAQS. 

Page 22 of34 
A.B. Brown Generating 196.08 196.2 Yes Station 

Indiana recommends that Posey County, Indiana be designated as attainment under the 2010 1-

hour primary S02 standard. This recommendation is based on the fact that Indiana's assessment, 

performed in accordance with U.S. EPA's updated guidance, demonstrates that the facility is not 

located in an area violating the NAAQS or causing or contributing to a violation of the NAAQS 

in a nearby area. Furthermore, limits supported by IDEM's attainment modeling will be 

incorporated into the applicable permit well in advance of the effective date of designations to 

ensure ongoing compliance with the 1-hour S02 NAAQS. 

Northern Indiana Public Service Company- Michigan City Generating 

Station 

The Michigan City Generating Station is a coal and natural gas-fired power plant on the southern 

shore of Lake Michigan in Michigan Township, LaPmie County, Indiana. The power plant is 

located at 101 Wabash Street in Michigan City, Indiana. The facility is owned by the Nmihem 

Indiana Public Service Company (NIPSCO) and operated by NiSource. The facility consists of 

one cyclone coal-fired boiler, identified as Boiler 12, with a design heat input capacity of 4,650 

MMBtu/lu·, an activated carbon injection system for control of mercury emissions permitted in 

2014, and an electrostatic precipitator with a flue gas conditioning system for control of 

pmiiculate matter, exhausting to Stack 4. Construction on Boiler 12 was completed in May 

1974. Natural gas can be fired during startup, shutdown, and malfunctions. Boiler 12 has a 

selective catalytic reduction (SCR) system for NOx control. A circulating dry scrubber FGD 

system and a fabric filter baghouse were petmitted to be installed on Boiler 12 in 2013. 

Due to conditions set forth in the Consent Decree and subsequent U.S. EPA guidance, Indiana 

relied on AERMOD air dispersion modeling to determine the attainment designation 

recommendation for the Michigan City Generating Station. The receptor grid for the Michigan 

City Generating Station was revised in order to account for Lake Michigan and the inability to 

place a monitor in the water. Therefore, no modeling receptors were placed at locations that lie 

over Lake Michigan. There is one monitor that measured ambient S02 air quality monitoring 

data in the area through the year 2014. The monitor, as shown in Figure 5 with ID# 18-091-

Page 23 of34 
Figure 5: 

Michigan City, Indiana Area S02 Monitors 

Mappod By: L. Ferguson, Office of Nr Quality 

Dale: 0911112015 

Sou«e: IDEM. OAO end EPA ·AOS 

Map ProjecUon: UThl Zone 16 N 

Map Da1urn: NADSJ 

* Michigan City Generating Station 

• Source-Operated S02 Monitor (Discontinued 1213112014) 

Page 24 of34 
Location 

o

to

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LaPorte 

18-091-0005 Michigan 21 15* 15 17* County, IN City 

*Incomplete data 

Indiana used meteorological data from the surface and upper air stations outlined in Table 14 to 

conduct modeling for the Michigan City Generating Station. In order to address U.S. EPA 

Region V's comments on Indiana's consent decree modeling protocol, Indiana processed wind 

and meteorological parameters from IDEM's Gary-IITRI monitoring station in northern Lake 

County. The Gary-IITRI meteorological parameters were processed with South Bend data to 

compile a meteorological dataset representative of the Northwest Indiana area. The Gary-IITRI 

monitoring location was used with AERSURF ACE for determining the first priority surface 

characteristics. However, since snow depth and precipitation data are not readily available from 

the Gary-IITRI monitoring site, adjustments to the albedo and Bowen ratio surface 

characteristics still used the precipitation, soil moisture, and snow depth data during the winter 

months from the South Bend NWS location. 

Table 14: 

Surface and Upper Air Meteorological Stations 

Facility Surface Met Upper Air Met 

Michigan City Gary-IITRI monitoring Lincoln, IL NWS Generating Station station/South Bend, IN NWS 

Modeling of the Michigan City Generating Station used adjusted (i.e. without upwind major 

source impacts) temporally varying seasonal background concentrations. The ID# 18-091-0005 

monitor, listed in Table 15, is considered representative background for LaPorte County, Indiana. 

991h percentile S02 concentrations by season (winter, spring, summer and fall) for each hour of 

the day were calculated for 2012-2014 to determine the temporally varying seasonal S02 

background, which were included directly into the model. 

Page 25 of34 
Spring 

Summer 

Fall 

Winter 

Spring 

Summer 

Fall 

Winter 

Spring 

Summer 

Fall 

7.85 8.88 8.87 8.85 8.00 8.00 8.85 

7.00 6.71 6.00 6.00 6.00 7.00 6.00 

5.69 5.69 6.00 6.66 6.26 5.67 6.71 

Hr9 Ht·10 Hrll Hr 12 Hr13 Hr 14 Hr15 

7.00 8.00 9.00 8.00 8.00 9.00 7.00 

7.92 7.99 8.00 9.00 7.94 8.00 7.90 

8.00 8.91 7.92 8.91 7.88 7.00 8.00 

7.76 8.00 8.00 8.00 8.73 8.54 7.76 

Hr17 Hr 18 Hr 19 Ht·20 Hr21 Hr22 Hr23 

7.79 7.00 7.00 8.00 7.56 7.00 6.80 

6.98 7.00 6.96 7.00 7.00 7.86 8.00 

8.86 6.00 7.00 6.00 7.00 6.75 6.00 

5.65 6.28 6.16 6.00 5.60 5.61 5.00 

8.88 

7.00 

6.69 

Hr16 

8.00 

6.00 

8.00 

6.71 

Hr24 

7.00 

8.00 

8.00 

5.00 

Meteorological data from the nearest station to the Michigan City monitor, i.e. the Gary-IITRI 

meteorological station, listed in Table 16, was used to develop temporally varying seasonal S02 

background values for the Michigan City Generating Station. 

Table 16: 

Location of the Michigan City S02 Monitor and Gary-IITRI 

Meteorological Station for Bacl•ground Analysis 

Monitor Meteorological Station Station MonitoriD Location Location Distance and ID # 

18-091-0005 41.72°N Gary-IITRI 41.61°N 21.5 86.91°W 18-089-0022 87.30° w miles 

The South Bend NWS wind rose plots are shown in Figure 6, and the Gary-IITRl meteorological 

data site wind rose plots are shown in Figure 7. As shown in a comparison of the two wind 

roses, the Gary-IITRI wind rose has a higher frequency of northeast and northerly wind 

directions and southerly wind directions indicating the Gary-IITRI meteorological site is 

capturing the Lake Michigan lake/land breeze influence. This provides the justification for using 

Page 26 of34 
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0 91" 

Indiana evaluated S02 sources within 30 km of the Michigan City Generating Station. Porter 

County, Indiana has two sources, listed in Table 17, contributing S02 emissions above 250 tpy. 

2013 actual emissions for these facilities were modeled to evaluate whether these sources could 

be causing or contributing to a NAAQS violation in the area. 

Page 27 of34 
ArcelorMittal Bums Harbor 127-00001 Pmter County 13,864 

Intermittent Source Justification 

Aside from Michigan City Generating Station's coal-fired boiler, there are several smaller 

emission units that are intermittent with random operational schedules or emit small amounts of 

SOz emissions. 

• One (I) natural gas-fired auxiliary boiler, identified as AUXl, rated at 109 MMBtu/hr, 

constructed in 2003, equipped with low NOx burners, exhausting to Stack AUX1, with a 

CEMS for NOx. 

Boiler AUXl operated 2,062 hours in 2013, the highest annual operating hours of any of the last 

three years (i.e. 2012-20 14). Based on these hours of operation, Boiler AUXl emitted 

approximately 134.88 pounds ofS02 in 2013. Since the total annual S02 emissions were very 

low from this auxiliary boiler, IDEM did not include this emission source in the modeling 

analysis. 

Specifically Regulated Insignificant Activities 

Insignificant activities at Michigan City Generating Station, as covered by 326 Indiana 

Administrative Code 2-7-1(21), include: 

• One (1) 480,000 British thermal unit (BTU) boiler located in the Gate House, constructed 

in 1964. 

• One (I) 297,000 BTU boiler located in the Relay House (Substation Bldg. #015), 

constructed in 1953. 

Due to the fact that SOz emissions from these types of sources are typically very low and the 

boilers have a heat input capacity of less than 1 MMBtu/hr, IDEM did not include these emission 

sources in the modeling analysis. 

Page 28 of34 
Table 18: 

Michigan City Generating Station 1-Hour S02 Modeling Results 

Modeled Concentration 1-Hour S02 Facility 

Including Seasonal Hourly NAAQS Models 

Modeled Source Background Attainment 

Michigan City 169.9 196.2 Yes Generating Station 

Indiana recommends that LaPorte County, Indiana be designated as attaimnent under the 2010 !-

hour primary S02 standard. This recommendation is based on the fact that Indiana's assessment 

performed in accordance with U.S. EPA's updated guidance clearly demonstrates that the facility 

is not located in an area violating the NAAQS or causing or contributing to a violation of the 

NAAQS in a nearby area. 

American Electric Power - Rockport Generating Station 

The Rockport Generating Station (Rockport Station) is a coal-fired power plant located along the 

Ohio River in Ohio Township, Spencer County, Indiana. The power plant is located near 

Rockport, Indiana along U.S. Route 23 I, approximately one mile nmih of the William H. 

Natcher Bridge spanning the Ohio River. The facility is owned by Indiana Michigan Power, a 

unit of AEP. Each of the two coal-fired electric generating units has a rated capacity of 12,374 

MMBtu/hr. The boilers consist of two dry-bottom, pulverized coal-fired opposed wall boilers, 

identified as units MBI and MB2, both constructed in 1977 with startup dates of 1984 and 1989. 

Emissions from MBI and MB2 are exhausted through a common stack, Stack CSOI2. The 

facility also has two No.2 fuel oil-fired boilers, Auxiliary Boiler I and Auxiliary Boiler 2, 

constructed in 1977 with a stmiup date of 1983 and each with a design heat input capacity of 603 

MMBtu/hr, both exhausting through Stack ABI2. 

Page 29 of34 
the standard or causes or contributes to a violation in a nearby area. 

Indiana used meteorological data from the surface and upper air stations outlined in Table 19 to 

conduct modeling for the Rockpmi Station. 

Table 19: 

Surface and Upper Air Meteorological Stations 

Facility Surface Met Uppe1· Air Met 

Rockport Generating Station Evansville, IN NWS Lincoln, IL NWS 

Modeling for the Rockport Station used adjusted (i.e. without upwind major source impacts) 

temporally varying seasonal background concentrations. The Evansville-Buena Vista S02 

monitor data, listed in Table 20, is considered representative background for Spencer County, 

Indiana. 991h percentile S02 concentrations by season (winter, spring, summer and fall) for each 

hour of the day were calculated for 2012-2014 to determine the temporally varying seasonal S02 

background, which was included directly into the model. 

Winter 

Spring 

Summer 

Fall 

Winter 

Spring 

Summer 

Fall 

Table 20: 

991h Percentiles for Tempomlly Varying Seasonal Hourly S02 

Background Values (ppb) for 2012-2014 

Hr1 Hr2 Hr3 Hr4 HrS Hr6 Hr7 

6.00 4.25 3.81 4.20 5.75 4.76 5.66 

4.48 3.87 3.57 4.06 2.91 3.31 4.47 

2.37 2.38 1.00 1.00 3.60 3.90 3.83 

2.23 2.28 2.22 3.20 3.54 3.00 3.99 

Hr9 Hr10 Hrll Hr 12 H1·l3 Hr 14 Hr 15 

8.86 10.80 12.58 10.87 14.64 19.51 19.33 

8.36 8.89 13.01 11.98 8.85 11.87 10.46 

5.55 12.12 8.41 8.80 5.72 4.40 4.81 

7.56 11.32 11.34 11.68 10.07 10.39 7.16 

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Hr8 

7.41 

8.25 

4.26 

5.26 

Hr16 

19.31 

12.29 

5.27 

7.79 
The modeling analysis used temporally varying seasonal background values taken from the 

Evansville-Buena Vista S02 monitor located in Evansville, Vanderburgh County, Indiana. !-

hour S02 impacts from the southeast direction were removed from the monitoring data because 

the Rockport Station and the modeled inventory sources are located southeast ofthe monitor. 

Meteorological data from the nearest station to the Evansville-Buena Vista monitor, i.e. the 

Evansville NWS station, listed in Table 21, was used for !-hour S02 background values for the 

Rockport Station. 

Table 21: 

Location of the Evansville-Buena Vista S02 Monitor and Evansville NWS 

Meteorological Station for Bacl,ground Analysis 

so2 Monitor Station Monitor Location Meteorological Station Location Distance and ID # 

Evansville-Buena Vista 38.01°N 

Evansville NWS Station 

38.05° N 

4.3 miles 18-063-0021 87.58° w 87.52° w 

Indiana evaluated S02 sources within 30 km of the Rockport Station. Warrick County, Indiana 

has three additional sources contributing S02 emissions above 250 tpy. Four S02 emission 

sources in the State of Kentucky were also included in the modeling analysis to determine 

possible impacts. 2013 actual emissions for these facilities, listed in Table 22, were modeled to 

evaluate whether these sources could be causing or contributing to a NAAQS violation in the 

area. 

Page 31 of34 
(tpy) 

ALCOA Warrick Power Plant 18-173-00002 Warrick County, IN 5,699 

ALCOA Warrick Operations 18-173-00007 Warrick County, IN 3,853 

SIGECO Culley 18-173-00001 Wanick County, IN 1,948 

Big Rivers Electric Corp 21-091-00003 Hancock County, KY 8,146 

Owensboro Municipal Utilities 21-059-00027 Daviess County, KY 8,064 

Century Aluminum ofKY 21-091-00004 Hancock County, KY 2,262 

Owensboro Grain Co. 21-059-00039 Daviess County, KY 382 

Intermittent Source Justification 

Aside from AEP Rockport Station's two coal-fired Main Boilers, MB1 and MB2, there are 

several smaller emission units that are intermittent with random operating schedules or emit 

small amounts of S02 emissions. 

• Two (2) No. 2 fuel oil-fired boilers, identified as Auxiliary Boiler 1 and Auxiliary Boiler 

2, constructed in 1977 with a stmiup date of 1983, each with a design heat input capacity 

of 603 MMBtu/hr, both exhausting through Stack AB 12. 

• Three (3) No.2 fuel oil-fired emergency diesel generators, identified as DG1, DG2, and 

DG3, each with a design heat input capacity of25.16 MMBtu/hr. 

The highest annual operating hours for Auxiliary Boiler 1 and Auxiliary Boiler 2, during the last 

three years, 2012-2014, were 149 hours and 108 hours, respectively. In 2014, annual S02 

emissions from both auxiliary boilers totaled 0.4 tpy. Emergency diesel generators DG 1, DG2, 

and DG3 are restricted to operating no more than 780 hours per twelve (12) consecutive month 

period when main boilers MB1 and MB2 are in operation. In 2014, annual S02 emissions from 

the emergency diesel generators totaled 0.02 tpy. IDEM did not include these sources in the 

modeling analysis since their level of activity was insignificant, intermittent, and random in 

nature and annual emissions were well below 1 tpy. 

Page 32 of34 
g

p

p

, 

MMBtu/hr, 2.75 MMBtu/hr, 3.5 MMBtu/hr, 4.5 MMBtu/hr, and 2.2 MMBtu/hr, 

respectively. 

• Two (2) No.2 fuel oil-fired space heaters, identified as WHU-1 and WHU-2, each with 

design heat input capacities of 1.1 MMBtu/hr. 

Since the total annual S02 emissions from these insignificant activities were not reported through 

Indiana's Emission Inventory Tracking System (EMITS) and are not expected to be significant, 

IDEM did not include these emission sources in the modeling analysis. 

Modeling, using Rockport Station's hourly CEM data from 2012-2014, showed that modeled!-

hour S02 concentrations from the Rockport Station and inventory sources would be below the !-

hour SOz NAAQS. Modeled concentrations for the Rockpmt Station, when added to the 

temporally varying seasonal S02 background concentrations, as outlined in Table 23, are well 

below the !-hour S02 NAAQS. 

Table 23: 

Rockport Generating Station 1-Hour S02 Modeling Results 

Modeled Concentration 1-HourSOz Facility 

Including Seasonal Hourly NAAQS Models 

Modeled Source Background (~o~g/m ) (~o~g/mJ) Attainment 

Rockport Generating Station 152.1 196.2 Yes 

Indiana recommends that Spencer County, Indiana be designated as attainment under the 20 I 0 !-

hour primary S02 standard. This recommendation is based on the fact that Indiana's assessment 

performed in accordance with U.S. EPA's updated guidance clearly demonstrates that the 

Rockpmt Station is not located in an area violating the NAAQS or causing or contributing to a 

violation of the NAAQS in a nearby area. 

Page 33 of34 
on 2012-2014 quality-assured monitoring data and ambient air quality modeling, are not located 

in an area currently violating the NAAQS or causing or contributing to a violation of the 

NAAQS in a nearby area. 

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