1 Draft Technical Support Document

Kentucky Area Designations for the 2010 SO 2 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 or the Agency ) must designate areas as either “unclassifiable

, ” “attainment

, ” or “nonattainment” for the 2010 one

- hour sulfur dioxide (SO 2 ) primary nationa l ambien t 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 nonattainm ent 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.

The Commonwealth of Kentucky (hereafter referred to as “the Commonwealth”) submit ted updated recommendations on September 1 6 , 2015

, ahead of a July 2, 2016, deadline for the EPA to designate certain areas

. This deadline is the first of three deadlines established by the U.S.
District Court for the Northern District of California for the EPA to complete area designations
for the 2010 SO 2 NAAQS . Table 1 below lists Kentucky’s recommendations and identifies the counties or portions of counties in Kentucky that the 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. Kentucky ’ s Recommended and the EPA’s Intended Designations

Area Kentucky’s

Recommended
Area Definition Kentucky’s

Recommended Designation The EPA’s Intended

Area Definition The EPA’s Intended

Designation

Ohio County , KY Ohio County in

its entirety Attainment Same as Commonwealth’s
Recommendation Unclassifiable

Pulaski County

, KY Pulaski County

in its entirety Attainment Same as Commonwealth’s
Recommendation Unclassifiable

Background

On June 3, 2010, the EPA revised the primary (health based) SO 2 NAAQS by establishing a new

one

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

- year average of the 99th percentile of one

- hour daily maximum concentrations does not exceed 75 ppb. This NAAQS was published in the Fe deral Register on June 22, 2010 (75 FR 35520) and is
codified at 40 CFR 50.17

. T he 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 grou ps are particularly susceptible to the health effects associated with breathing SO 2 . T he2

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

, the EPA is not currently designating areas on the basis of either of these two primary standards. Similarly, the secondary
standard for SO 2

, set at 500 ppb evaluated over 3 hours has not been revised, and the EPA is also

not currently designating areas on the basis of the secondary standard.

General Approach and Schedule

Section 107(d) of the CAA requires that not later than one year after promulgation of a new or revised NAAQS, state g overnors must submit their recommendations for designations and boundaries to EPA. Section 107(d) also requires the EPA to provide notification to states no less
than 120 days prior to promulgating an initial area designation that is a modification of a st ate’s
recommendation. If a state does not submit designation recommendations, the EPA will promulgate the designations that it deems appropriate. If a state or tribe disagrees with the EPA’s intended designations, they are given an opportunity within the 1 20 day period to demonstrate why any proposed modification is inappropriate.

On August 5, 2013, the EPA published a final rule establishing air quality designations for 29
areas in the United States for the 2010 SO 2 NAAQS, based on recorded air quality monitoring
data from 2009

- 2011 showing violations of the NAAQS (78 FR 47191). In that rulemaking, the EPA committed to address, in separate future actions, the designations for all other areas for which the Agency was not yet prepared to issue designatio ns.

Following the initial August 5, 2013 designations, three lawsuits were filed against the EPA in different U.S. District Courts, alleging the Agency had failed to perform a nondiscretionary duty 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 the EPA filed a proposed consent decree with the U.S.
Distric t Court for the Northern District of California

. On March 2, 2015, the court entered the
consent decree and issued an enforceable order for the EPA to complete the area designations according to the court

- ordered schedule.

According to the court

- ordered schedule

, the EPA must complete the remaining desi gnations by
that contains three specific deadlines. By no later than July 2, 2016 (16 months from the court’s order) , the EPA must designate two groups of areas: (1) areas that have newly monitored
violatio ns of the 2010 SO 2 NAAQS and (2) areas that contain any stationary s ources that ha d not been announced as of March 2, 2015 for retirement and that according to the EPA ’s Air Markets
Datab a se emitted in 2012 either : (i) more than 16,000 tons of SO 2 or (ii) mor e than 2,600 tons of
SO 2 with an annual average emission rate of at least 0.45 pounds of SO 2 per one million British thermal units (lbs SO 2 /mmBTU)

. Specifically, a stationary source with a coal

- fired unit that as of

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 the EPA approves a SIP providing for attainment of the 2010 NAAQS. The two Kentucky areas are not designated nonattainment under the prior NAAQS n or are they area s not meeting the requirements of a SIP Call under the prior NAAQS.3

January 1, 2010 had a capacity of ove r 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 fede ral 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, 2 0 17, and
Decembe r 31, 2020

. The EPA has separ ately promulgated requirements for states and other air agencies to provide additional monitoring or modeling information on a timetable consistent wi th these designation deadlines. We expect this information to become available in time to help
inform thes e subsequent designations . These requirements were promulgated on August 2 1 , 2015 (80 FR 51052) , in a rule known as the SO 2 Data Requirements Rule (DRR)

.

Updated designations guidance was issued by the 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 1

- 10 . This memorandum supersedes ear lier designation guidance for the 2010 SO 2 N AAQS, issued on March 24, 2011, and it i dentifies factors that the EPA intends to evaluate in determining whether areas are in violation of the 2010 SO 2 NAAQS. The guidance also contains the factors the EPA inten ds 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
SO 2 . Notably, the EPA released its most recent versions of documents titled, “S O 2 NAAQS Designations Modeling Technical Assistance Document” (Modeling TAD) and “SO 2 NAAQS Designations Source

- Oriented Monitoring Technical Assistance Document” (Monitoring TAD)
in December 2013.

Based on ambient air quality data collected between 2012 and 2014, no monitored violations of
the 2010 SO 2 NAAQS have been recorded in a ny undesignated part of the state. 2 However, there

are two sources in the state meeting the emissions criteria of the consent decree for which the EPA must complete designations by July 2, 2016. In this draft technical support document, the EPA discusses its review and technical analysis of Kentucky’s updated recommendations for the

2 For designations based on ambient air quality monitoring data that violates the 2010 SO 2 NAAQS, the consent
decree directs the EPA to evaluate data collected between 201 3 and 2015. Absent complete, quality assured and certified data for 2015, the analyses of applicable areas for the 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 SO 2 NAAQS during these years have the option of submitting complete, quality assured and certified data for calendar year 2015 by April 19, 2016 to the EPA for evaluation. If after our review, the ambient air quality data for the area indicates
th at no violation of the NAAQS occurred between 2013 and 2015, the consent decree does not obligate the EPA to complete the designation. Instead, the 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, 2020.4

areas that we must designate

. The EPA also discusses any intende d modifications from the state’s recommendation based on all available data before us

.

The following are d efinition s of important terms used in this document: 1) 2010 SO 2 NAAQS

– The primary NAAQS for SO 2 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 han dling 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 the EPA has determined has violated the
2010 SO 2 NA AQS or contribute d to a violation in a nearby area. A nonattainment designation r eflect s considerations of state recommendations and all of the information discussed in this document. The EPA’s decision is based on all available information including the most recent 3 years of air quality monitoring data, available modeling analysis, and any other relevant information. 4) Designated unclassifiable area

– an area which the EPA cannot determine based on all

av ailable information whether or not it meets the 2010 SO 2 NAAQS. 5) Designated unclassifiable/attainment area

– an area which the EPA has determined to have sufficient evidence to find either is attaining or is likely to be attaining the NAAQS

. The EPA’s dec ision is based on all available information including the most recent 3 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 the EPA designate as attainment. 8) Recommended nonattainment area

– an area a state or tribe has recommended that the EPA designate as nonattainment. 9) Recommended unclassifiable area

– an area a state or tribe has recommended that the EPA designate as unclassifiable. 10) Recommended unclassifiable/attainment area

– an area a state or tribe h as recommended that the EPA designate as unclassifiable/attainment. 11) Violating monitor

– an ambi ent 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 50.5 Technical Analysis for the Plant D.B. Wilson

– Ohio County A rea

Introduc tion

T he Ohio County A rea contains a stationary source that according to the EPA’s Air Markets
Database emitted in 2012 either more than 16,000 tons of SO 2 or more than 2,600 tons of SO 2 and had an annual average emission rate of at least 0.45 lbs SO 2 /mmBTU

. A s of March 2, 2015, this stationary source had not met the specific requirements for being “ announced for
retirement

. ” Specifically, in 2012, the D.B. Wilson Power Plant (Plant Wilson) emitted 7,387
tons of SO 2 , and had an emissions rate of 0.45 lbs SO 2 /mmBTU

. P ursuant to the March 2, 2015

court

- ordered schedule , the EPA must designate the area surrounding the facility by July 2, 2016

.

In its submission, the Commonwealth of Kentucky (hereafter referred to as “the Commonwealth”) recommended that the area surrounding Plant Wilson , specifically the entirety
of Ohio County

, be designated as attainment based on an assessment and characterization of air quality from the facility and other nearby sources which may have a potential impact in the area of analysis where maximum concentrations of SO 2 are expected. This assessment a nd
characterization w ere performed using air dispersion modeling software, i.e., AERMOD

, analyzin g allowable emissions

. The assessment and characterization w ere originally conducted by Trinity Consultants and prepared for the Big Rivers Electric Corporation (BREC) . The
Commonwealth then reviewed and submitted the information to the EPA. 3

After careful review of the Commonwealth ’s assessment, supporting documentation, and all available data, the EPA intends to designate O hio Co unty in its entirety as unclassifiable 4

because the EPA does not have necessary information at this time to determine the attainment status of the Ohio County Area. Specifically, the future allowable emission limit for Plant
Wilson used to model attainm ent for the Ohio County Area h as not been established as federally

enforceable 5 by the Commonwealth

. In order for the EPA to consider the future allowable
emission limit of 0.85 lbs SO 2 /mmBTU for Plant Wilson for the designations to be finalized no later than July 2, 2016, the Commonwealth will have to ensure that these limits are federally

enforceable (and the EPA has confirmed such) by the time this round of designations is complete. R egarding the Plant Wilson future emission limit, if a limit with an averaging time

3 Throughout this document the Commonwealth will be referred to as having assessed air quality in the area because
the Commonwealth agreed with the BREC’s air quality assessment and characterization of the area of analysis, officially submitting the report to the EPA to support their designation recommendation.

4 Pursuant to the EPA’s April 23, 2014 memorandum entitled “ Guidance for the 1

- Hour SO 2 N onattainment Area
SIP Submissions. ”

5 Consistent with past interpretations of legal requirements, control measures, emission limits and other curtailments need to be installed, operational and federally

- enforceable to be considered when informing final de signation
decisions. The m echanisms for establishing federally enforceable emission limits, control measures, or curtailments for the purpose of informing SO 2 designations include: a source

- specific state implementation plan ( SIP )

- approved by the EPA, a mi nor new source review permit, a title v permit or a consent decree established through Federal civil litigation.6

longer than 1

- hour is desired, supporting technical information will also need to include explanation, of whether the longer term average limit, that the EPA determines is c omparatively stringent to a 1

- hour limit at the critical emission value, ensures attainment of the SO 2 NAAQS.

Also, the EPA needs additional information regarding the operating status of Units 1 and 2 at the
T ennessee V alley A uthority’s (TVA’s)

- Paradise Fossil Plant in Muhlenberg County to
determine if Units 1 and 2 at the source are shut down

. 6 If the TVA

- Paradise Fossil Plant is not shutdown, additional explanation would be necessary as to why these emissions were not included in the modeling for this area. If the Commonwealth cannot provide support ing documentation to confirm the permanent retirement of Units 1 and 2 at the TVA

- Paradise Fossil
Plant , including a ctual historical emissions for these units in the modeling is an option for complete characterization in relation to the proposed Ohio County designation from Kentucky.

Plant Wilson is located in western Kentucky in the western portion of Ohio County. As seen in Figure 1 below, the facility is located approximat ely 8 kilometer ( km ) northwest of the center of
Centertown , KY

. Also included in the figure are n earby emitters of SO 2 , the Commonwealth ’s
recommended area for the attainment designation

, and the EPA’s intended
unclassifiable/attainment designation for the area.

6 Emissions for the TVA: Paradise Fossil Plant are important to the characterization of Ohio County because the source, while in Muhlen berg County, is immediately across the border from Ohio County. The Commonwealth included consideration of emissions from Unit 3 at the TVA: Paradise Fossil Plant in support of their recommendation of attainment for Ohio County.7 Figure 1. The EPA’s intended designation for Ohio County, Kentucky

The discussion and analysis that follows below will reference the Commonwealth’s use of the Modeling TAD, the EPA’s assessment of the Commonwealth’s modeling in accordance with the Modeling TAD, and the factors for evaluation contained in the EPA’s March 20, 2015 guidance, as appropriate

.

Detailed Assessment

Air Quality Data

This factor considers the SO 2 air quality monitoring data in the area surrounding Plant Wilson

. The facility is located in Ohio County, and the Commonwealth included monitoring data from
the closest monitors: Baskett Fire House ( 21

- 101

- 0014 )

, Evansville

- Buena Vista in Indiana ( 18

- 163

- 0021 ) , Mammoth Cave National Park (21

‐ 061

‐ 0501) , and Owensboro Primary (21

- 059

- 0005) , to the facility in its recommendation. The closest monitor is Owensboro Primary , located

at 716 Pleasant Valley Rd

, Owensboro , KY 42303 ( 37.78077

, - 87.0753 ) in Dav iess County, and
is 35 km away from Plant Wilson . Data collected at this monitor is considered indicative of

po pulation exposure but is not representative of the expected background concentrations in the8

area surrounding the Plant Wilson . The Baskett Fire House monitor, located at B askett F ire
D epartment , 7492 Dr

. Hodge Rd

, Henderson , KY 42420 ( 37.8712

, - 87.46375 ) is located within
25 km to several sources to the northwest of Plant Wilson, and the predominant wind direction
indicates that this monitor is reasonably expected to capture the regional effects of these sources

. Table 2 below summarizes the local monitors and design values from recent years in within 100
km of Plant Wilson

.

Table 2 : Historical Ambient Air Quality Data for Nearby Monitors

Monit or AQS ID County 2010

– 2012 Design Value (μg/m 3 ) 2011

– 2013

Design Value (μg/m 3 ) 2012

– 2014

Design Value (μg/m 3 )
Baskett Fire
House 21

- 101

- 0014 Henderson 65.5 7 1.5 71.5

Evansville

Buena Vista 18

- 163

- 0021 Vanderburgh 47.1 47.1 57.6

Mammoth
Cave 21

- 061

- 0501 Edmonson 31.4 26.2 26.2
Owensboro Primary 21

- 059

- 005 Daviess 125.7 107.42 112.6

Model Selection and Modeling Components

The EPA’s Modeling TAD notes that for area designations under the 2010 SO 2 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

The Commonwealth used AERMOD version 15181 , and , as appropriate, a discussion of the individual components will be referenced in the correspo nding discussion.

Modeling Parameter: Rural or Urban Dispersion

The EPA’s recommended procedure for characterizing an area by prevalent land use is based on evaluating the dispersion environment with in 3 km of the facility. According to the EPA’s modeling guidelines, rural dispersion coefficients are to be used in the dispersion modeling9

analysis if more than 50 percent of the area within a 3 km radius of the facility is classified as rural. Conversely, if more than 50 percent of the area is urban, urban dispersion coefficients should be used in the modeling analysis

. When performing the modeling for the area of analysis,
the Commonwealth determined that it was most appropriate to run the model in rural mode. The
Commonwealth used the Auer’s land use methodology to determine the classification. L and use
within a 3 km radius of Plant Wilson was examined and quantified . Based on the visual inspection of the land use types, the Commonwealth determined that the area is predominantly rural by a margin of 99.2 percent and therefore determined that is was most appropriate to run the model with rural dispersion coefficients. See Figure 2 below for a depiction of land

- use around Plant Wilson.

Figure 2 . Distribution of Land Use within 3

- km of Wilson Station

- Source: “Air Dispersion Modeling Report Wilson Station SO 2 Designations Analysis Revision 1” prepared by Trinity

Consultants for the Big Rivers Electric Corporation, August 25, 2015.

Modeling Parameter: Area of Analysis (Receptor Grid)

The EPA believes that a reasonable first step towards characterization of air quality in the area surrounding Plant Wilson 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
SO 2 emission sources or facilities considered for modeling; the extent of significant concentration gradients of nearby sources; and sufficient receptor covera ge and density to adequately capture and resolve the model predicted maximum SO 2 concentrations. For the Ohio10

County A rea , major sources of SO 2 emissions within a 20 km range were considered and larger

sources with in a 20

- 50 km range that were believed to potentially contribute significant concentrations to the area of analysis

. The Commonwealth determined that this was the appropriate distance in order to adequately characterize air quality from the facility and other nearby sources which may have a potent ial impact in the area of analysis where maximum
concentrations of SO 2 are expected

. Sources within these ranges include: Century Aluminum of
Kent ucky, LLC (Hancock County) , Reid/Henderson Station II Generating Station and BREC
Landfill 7 (Webster County )

, Owensboro Municipal Utilities

- Elmer Smith Station (Daviess County)

, ( TVA

- Paradise Station

, and Green River Generating Station

- Kentucky Utilities Company (Muhlenberg County)

.

TVA

- Paradise Fossil Plant is approximately 22 km southeast of Plant Wilson

, and had SO 2 emissions of 19654.55 tpy in 2014 8

. Units 1 and 2 at the facility are scheduled to shut down by
June 2017, according to a n annual report developed by the Energy Information Administration (EIA) 9 which legally requires direct reporting via survey for all energy generating units at or greater than 1 megawatt capacity

. The TVA website also projects a 2017 date for the retirement
of Units 1 and 2. 10 The modeling report prepared for the Commonwealth present s inconsistent information, stating that a public announcement indicating TVA

- Paradise Fossil Plant Units 1
and 2 are slated for retirement by April 2016

. The Commonwealth decided not to evaluate actual
emissions from TVA

- Paradise Fossil Plant Units 1 and 2 because of th e ir scheduled retirement

. In order for the shutdown to be considered for the designations which must be finalized by July 2, 2016, the EPA will need confirmation from the Commonwealth that this shutdown is in effect prior to final designations. 11

Because Unit 3 at TVA

- Paradise Fossil Plant is not scheduled for shut down, its hourly 2012

- 2014 continuous emissions monitoring systems (CEMS) data from the EPA Air Markets Program Data were considered in the modeling analysis for Plant Wilson . However, the unit’s temperature and gas exit velocity were not available from this database and were therefore set equal to data available in Kentucky’s emissions data archive.

7 Comprised of Reid/Hender son Generating Station. The Big Rivers Electric Corporation landfill is located at Reid/Henderson Station II just south of the generating plant and is not a separate source.

8 All 2014 emissions data was accessed via the Emissions Inventory System (EIS) g ateway, in which states report
emissions pursuant to 40 CFR Part 51, Subpart A. The EIS gateway can be accessed via: http://www3.epa.gov/ttnchie1/eis/gateway/

.

9 U.S. Energy Information Administra tion, “Electric Power Monthly with Data for November 2015,” January 2016. See http://www.eia.gov/electricity/monthly/pdf/epm.pdf.

10 See, e.g., https://www.tva.com/Energy/Our

- Power

- System/Fossil

- Fuel

- Generation/Paradise

- Fossil

- Plant

11 The EPA is required to characterize the current air quality around Plant Wilson by July 2, 2016

, according to the
terms of the court ordered consent decree. Therefo re, unless the Commonwealth can provide documentation that
Units 1 and 2 are permanently retire d by that time to the EPA in advance of the promulgation of final designations,
the EPA cannot consider the shutdown emissions and instead actual emissions for t hese units from 2012

- 2014 should be accounted for in any modeling to characterize the air quality around the Plant Wilson area of analysis.11

All units at Green River Generating Station have been retired as of October 2015. 12

. The remaining sources listed above are at least 35 km or more from Plant Wilson which is distant enough that their impacts would be significantly reduced in terms of impacts overlapping with
those of Plant Wilson

. The modeling analysis performed and submitted by the Commonwealth included only future allowable emissions from Plant Wilson and actual emissions from Unit 3 of
TVA

- Paradise Fossil Plant

.

The grid receptor spacing for the area of analysis chosen by the Commonwealth is as follows:

 50

- meter intervals along the fence line

 100

- meter spaced receptors extending to 3 k m from the center of the property and beyond
the fence line

 250

- meter spaced receptors extending from 3 km to 5 km

 500

- meter spaced receptors extending from 5 km to 10 km

 1,000

- meter spaced receptors extending from 10 km to 20 km

 2,000

- meter spaced receptors extending from 20 km to 50 km

The receptor network contained 6,922 receptors, and the network covered a large area spanning
50 km in each direction surrounding Plant Wilson, stretching from the southern edge of Indiana to the northern edge of Tennessee.

Figures 3 thr ough 5 , included in the Commonwealth ’s recommendation, show the
Commonwealth ’s chosen area of analysis surrounding Plant Wilson , as we ll as receptor grid for the area of analysis. Consistent with the Modeling TAD, receptors for the purposes of this designation effort were placed only in areas where it would also be feasible to place a monitor and record ambient air impacts . The impacts of the area’s geography and topography will be
discussed later within this document.

12 The Commonwealth’s modeling report indicated that remaining Units 3 and 4 at Green River Generating station were expected to shutdown by April 2016 (based on http://www.coalage.com/news/latest/4152

‐ green

‐ river

‐ coal

‐ plant

‐ will

‐ remain

‐ in

‐ operation

‐ until

‐ april

‐ 2016.html#.VckdfflVhBc ). However, more recent reports ( https://lge

ku.com/our

- company/community/neighbor

- neighbor/green

- river

- generating

- station ) indicate remaining Units 3 and 4 retirement date was Septembe r 30, 2015 and the EIA January 2016 Electric Power Monthly report ( http://www.eia.gov/electricity/monthly/pdf/epm.pdf ) tracked Units 3 and 4 as permanently retired effective October
2015. Furthermore, no emissions were reported to the EPA Air Markets Database beginning in October 2015 for any federal programs for which Units 3 and 4 would have been subject.12

Figure 3 : Ohio County Area of Analysis Source: “Air Dispersion Modeling Report Wilson
Station SO 2 Designations Analysis Revision 1” prepared by Trinity Consultants for the Big

Rivers Electric Corporation, August 25, 2015.13

Figure 4 : Innermost Portion of Modeling Receptor Grid for the Ohio County Area of Analysis

- Source: “Air Dispersion Modeling Report Wilson Station SO 2 Designations Analysis Revision 1” prepared by Trinity Consultants for the Big Rivers Electric Corporation, August 25, 2015.14

Figure 5 : Overall Modeling Receptor Grid for Wilson Air Dispersion Modeling Report Wilson
Station SO 2 Designations Analysis Revision 1” prepared by Trinity Consultants for the Big

Rivers Electric Corporation, August 25, 2015.

Modeling Parameter: Source Characterization

The Commonwealth characterized the source s within the area of analysis in accordance with t he best practices outlined in the Modeling TAD. Specifically, the Commonwealth followed the EPA’s good engineering practices (GEP) policy in conjunction with actual emissions for TV A

Paradise Fossil Plant Unit 3, and future allowable emissions limits for Plant Wilson . The
Commonwealth also adequately characterized the source’s building layout and location, as well15

as the stack parameters, e.g., exit temperature , exit velocity, locat ion, and diameter. Where appropriate, the AERMOD component BPIPPRIME was used to assist in addressing building
downwash.

Modeling Parameter: Emissions

The 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 3 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 potential to emit ( PTE ) or allowable) emissions rate.

The EPA believes that 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, the 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 keyw ord EMISFACT. When choosing one of these methods, the 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 impleme nted other federally enforceable mechanisms and control technologies to limit SO 2 emissions to a level that indicates compliance with the NAAQS. The se new limits or conditions may be used in the application of AERMOD. In these cases, the Modeling TAD notes that the existing SO 2 emissions inventories used for permitting or SIP planning demonstrations should contain the necessary emissions information for designations

related modeling. In the event that these short

- term emissions are not readily available, th ey 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, the Commonwealth included Plant Wilson and one other emitter of SO 2

, that is expected to continue operating, i.e., Unit 3 at TVA

- Paradise Fossil Plant

, within 20

- 50 k m in the area of analysis. The Commonwealth considered major sources of SO 2 emissions within a
20 km range and larger sources within a 20

- 50 km range that were believed to potentially contribute significant concentrations to the area of analysis

. The Commonwealth selected this
distance and facilities because it believes that this area of analysis adequately represents the area
where maximum concentrations of SO 2 are expected and adequately includes the sources which might contribute to those concentrations

. Plant Wilson is the only major SO 2 emitting source in Ohio County over 100 tpy. Sources the Commonwealth identified within the 20

- 50 km range
other than TVA

- Paradise Fossil Plant included Century Aluminum of Kentucky

, Reid/Henderson Station II Generating Station and BREC Landfill

, Elmer Smith Station and Green River Station

.

TVA

- Paradise Fossil Plant in Muhlenberg County is located approximately 22 km southeast of
Plant Wilson , and had SO 2 emissions of 1

, 9654.55 tpy in 2014. Units 1 and 2 at the facility are16

scheduled to shut down by June 2017, according to report by the EIA and information from the TVA website. However, this information is not consiste nt with the data for Units 1 and 2 provided in the modeling report which indicates the units are expected to retire by April 2016. Because of the anticipated retirement, the Commonwealth did not evaluate actual emissions from
TVA

- Paradise Fossil Plant Unit s 1 and 2 nor are the source’s 2012

- 2014 emissions accounted for
the in the background concentration selected for the area. Therefore, unless the Commonwealth can provide documentation to the EPA in advance of the promulgation of final designations
schedul ed for July 2, 2016

, that Units 1 and 2 will permanently retire

, the EPA may not be able
to consider these shutdown and believes that actual emissions for these units from 2012

- 2014 should be accounted for in any modeling to characterize the air quality around P lant Wilson for the Ohio County Area

. The EPA is required to characterize the current air quality around Plant Wilson by July 2, 2016

, according to the terms of the court ordered consent decree. Therefore
because of the uncertainty of the timing of the permanent shutdown of Units 1 and 2 and the fact
that 2012

- 2014 actual historic emissions were not considered in the modeling analysis for Plant Wilson, the EPA does not have sufficient information to accurately evaluate the source’s impact
on the Ohi o County Area , and thus intends to designate this area

.

The EPA notes that t he Green River Generating Station also in Muhlenberg County is located

a pproximately 10 km from Plant Wilson and less than 0.5 km from the Ohio County border. The source reported 21976.19 tons of SO 2 in 2014 but according to reports from EIA, the last remaining Units 3 and 4 were permanently retired in October 2015 13 resulting in zero potential to
emit. Green River Station was not explicitly included in the modeling analysis for Plant Wilson
due to permanent shutdown and zero potential to emit SO 2 emissions. However, the source was considered in the background concentrations accounting for impacts from nearby sources
includi ng historic actual emissions . Considering the source’s zero potential to emit and the cumulative impacts captured in the background concentrations, the EPA does not have reason to
believe that emissions from this now non

- operational facility are causing or contributing to a
violation of the SO 2 NAAQS in the Ohio County Area.

Other SO 2 emitters the Commonwealth assessed within the 20

- 50 km range that reported SO 2 emissions over 100 tpy included: Century Aluminum of Kentucky, LLC (Hancock County),
Elmer Smith Station (Da viess County), Reid/Henderson Station II Generating Station and BREC Landfill (Webster County)

. These sources were not explicitly included in the modeling analysis because they a re all located 35 km or greater from Plant Wilson (as well as Ohio County Area )
which the Commonwealth d etermined to be far enough that impacts from the facility relative to
Plant Wilson

. Therefore, the Commonwealth assessed that these sources would not potentially contribute significant concentrations to the area of analysis.

The EPA notes that the BREC ’s sources

, Green Station ( Webster County) and Coleman Station ( Hancock County) and Owensboro Grain Company ( Daviess ) also reported 2014 emissions over 100 tpy year

. B ut similar to those sources considered by the Commonwealth

, these are also

13 No emissions were reported to the EPA Air Markets Database beginning in October 2015 for any federal programs for which Green River Generating Station Units 3 and 4 would have been subject. Also, EIA’s US Energy Information Administration “Electric Power Monthly” annual report for January 2016, tracked Units 3 and 4 as permanently ret ired as of October 2015.17

located over 35 km away from Plant Wilson and Ohio County line

. Based on the distance from
Plant Wilson and Ohio County border (>35 km)

, the EPA has reason to believe that these sources
would not cause significant concentration gradients within the area of analysis or Ohio County.
The EPA notes that other sources in counties within the 20

- 50 km range c umulatively emitted
less than 100 tpy of SO 2 emissio ns according to 2014 actual emissions

.

For this area of analysis, the Commonwealth opted to use a hybrid approach, where emissions from certain facilities are expressed as actual emissions, and those from other facilities are expressed as PTE rates. For the following facil ity in the area of analysis, the Commonwealth
included annual actual SO 2 emissions between 2012 and 2014. This information is summarized
below.

Table 3 : Actual SO 2 Emissions Between 2012

– 2014 from Facilities in the Ohio County, Kentucky Area of Analysis

Facility Name SO 2 Emissions (tons per year (tpy) )

2012 2013 2014
TVA : Paradise Fossil Plant
Unit 3 4

, 4 00 2

, 7 00 5 ,000

For Unit 3 at TVA

- Paradise Station the Commonwealth used actual emissions from the most
recent 3

- year data set, i.e., 2012

– 2014. Th ese emissions data w ere obtained from EPA ’s Air Markets Program Data. Temperature and gas exit velocity were not available and were set equal
to that in the Kentucky Department of Air Quality’s archive data (CEMS)

.

For the following facility in the area of analysis, the Commonwealth has chosen to model the facility using a future federally enforceable PTE limit for SO 2 . The facilit y in the
Commonwealth ’s area of analysis and its associated PTE rate are summarized below.

Table 4 : SO 2 Emissions based on PTE from Facilities in the Ohio County Area of Analysis

Facility Name SO 2 Emissions ( tpy , based on PTE)
D.B Wilson
Power Station TPY value not provided by the Commonwealth

, future

limit is 0.853 lb s SO 2 / mmBTU

The PTE limit of 0.853 lb s SO 2 / mmBTU for Plant Wilson was proposed by BREC and modeled
to show attainment for the 1

- hour SO 2 NAAQS

.

Modeling Parameter: Meteorology and Surface Characteristics

The most recent 3 years of meteorological data (concurrent with the most recent 3 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 of18

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 O hio County A rea of analysis, surface meteorology from the U.S. National Climatic Data Center (NCDC) for the Evansville Regional Airport

, 76.5 km to the northwest , and coincident upper air observations from the nearest U.S. NWS radiosonde equipped station, the Nashville International Airport

, 151.7 km to the southeast were selected as best representative of meteorological conditions within the area of analysis.

The Commonwealth used AERSURFACE version 13016 using data from the Evansville Regional Airport i n Evansville, Indiana (located at 38.044

, ‐ 87.521 ) to estimate the surface
characteristics of the ar ea of analysis. The Commonwealth estimated values for 12 spatial sectors

out to 1 km at a seasonal temporal resolution for dry conditions. T he Commonwealth also
estimated values for albedo (the fraction of solar energy reflected from the earth back into space), the Bowen ratio (the method generally used to calculate heat lost or heat gained in a substance), and the surface roughness (sometimes referred to as “Zo” ). In the figure belo w, which was included in the Commonwealth ’s recommendation, the location of the Evansville Regional Airport is shown relative to the Plant Wilson area of analysis.19

Figure 6 : Plant Wilson Area of Analysis and the Evansville Regional Airport Source: “Air Dispersion Modeling Report Wilson Station SO 2 Designations Analysis Revision1” prepared by Trinity Consultants for the Big Rivers Electric Corporation, August 25, 201520

T he 3

- year surface wind rose for Evansville Regional Airport is depicted in Figure 7. In Figure 7

, the frequency and magnitude of wind speed and direction are defined in terms of from where the wind is blowing

. The wind rose indicates that the winds blow predominately from the south

southeast, at low to mid

- level wind speeds of 2.1

- 5.7 m eters/second. Additionally, winds blow from the northeast and northwest a significant amount of time.

Figure 7 : Evansville Regional Airport Cumulative Annual Wind Rose for Years 2012

– 201421

Meteorological data from the above surface and upper air stations 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 modeling runs. The Commonwealth followed the methodology and settings presented in standard U.S. EPA meteorological processing guidance as outlined in a recent memorandum 14 as well as other AERMET and associated preprocessor documentation in the pro cessing of the raw

meteor o logical data into an AERMOD

- ready format, and used AERSURFACE to best represent
surface characteristics.

H ourly 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. Th e s e data were subs equently integrated into the AERMET processing to produce final hourly wind records of AERMOD

ready 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 Commonwealth se t 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

The terrain in the area of an alysis is best described as gently rolling with small hills

. To account
for t hese terrain changes, the AERMAP terrain program within AERMOD was used to specify terrain elevations for all the receptors. The source of the elevation data incorporated into the
model is from the United States Geological Survey National Elevation Databas e.

Modeling Parameter: Background Concentrations of SO 2

The Modeling TAD offers two mechanisms for characterizing background concentrations of SO 2 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 99 th percentile monitored concentrations by hour of day and season or month. For the Ohio County area of analysis, the Commonwealth chose the method which uses the 3

- year averages of the 99 th percentiles by hour of day (across all seasons) . T his was chosen based on the review of the 99 th

14 Fox, Tyler, U.S. Environmental Protection Agency. 2013. “Use of ASOS Meteorological Data in AERMOD Dispersion Modeling.” Available Online: http://www.epa.gov/ttn/scram/guidance/clarification/20130308_Met_Data_Clarification.pdf22

percentile hourly values across 2012

- 2014, which shows a diurnal variation of lowest SO 2 concentrations at night and highest in the day

. The Baskett Fire House Monitor (Site No. 21

- 101

- 0014) was determined to be the representative background monitor for the area. The Basket monitor is classified as a general “population exposure” monitor located about 8

- 9 km southeast

o f Evansvill e , Indiana and about 55 km northwest of Plant Wilson . This monitor was determined to adequately reflect impacts from the SO 2 emissions sources to the northwest of Plant Wilson

. The ambient SO 2 concentrations used as background in the modeling vary from 15

– 50 μg/m 3 (see Figure 8 below).

Figure 8 : 99 th Percentile SO 2 Averages by Hour of Day for Baskett Fire House Monitor (21

- 101

- 0014). Source: “Air Dispersion Modeling Report Wilson Station SO 2 Designations Analysis Revision 1” prepared by Trinity Consultants for the Big Rivers Electric Corporation, August 25,
2015.23

Summary of Modeling Results

The AERMOD modeling parameters for the Ohio County A rea of analysis provided by the
Commonwealth are summarized below in T able 5

.

Table 5 : AERMOD Modeling Parameters for the Ohio County Area of Analysis

Ohio County Area of Analysis

AERMOD Version 15181 Dispersion Characteristics Rural

Modeled Sources 2

Modeled Stacks 2

Modeled Structures 8

Modeled Fencelines 1 Total receptors 6

, 922 Emissions Type PTE

Emissions Years TBD 15 / Effec tive year of new
limits for PTE Meteorology Years 2012

- 2014 Surface Meteorology Station Evansville, Indiana Upper Air Meteorology Station Nashville, Tennessee Methodology for Calculating Background SO 2 Concentration Temporal Varying

Calculated Background SO 2 Concentration Temporally varying between
15

– 50 μg/m 3 (see figure 8

above)

The results presented below in T able 6 show the magnitude and geographic location of the highest predicted modeled concentration based on PTE emissions from Plant Wilson and actual
emissions from TVA: Paradise Fossil Plant

.

Table 6 : Maximum Predicted 99th Percentile 1

- Hour SO 2 Concentration in the Ohio County

Area of Analysis Based on PTE and actual emissions.

Averaging
Period Data Period Receptor Location SO 2 Concentration ( μg/m 3 )

UTM/Latitude UTM/Longitude Modeled (including background) NAAQS
99th Percentile
1

- Hour Average [ 2012

- 2014 ] 490583 4144568 186.5 196.5*

15 Provided the new modeled allowable limit of 0.85 lb SO 2 /mmBTU i s federally

- enforceable by the time that the EPA finalizes the designation for this area and, as applicable, includes a longer term average limit that is comparatively stringent to a 1

- hour limit at the critical emission value.24

*Equivalent to the 2010 SO 2 NAAQS set at 75 ppb

The Commonwealth ’s modeling indicates that the predicted 99 th percentile 1

- hour average concentration within the chosen modeling domain is 186.5 μg/m 3 , or 71.2 ppb. This modeled
concentration included the background concentration of SO 2 of and is based on actual emissions
from TVA

- Paradise Fossil Plant Unit 3, a future allowable limit of 0.85 lb s SO 2 /mmBTU for Plant Wilson, and an assumed zero PTE due to scheduled shutdown of TVA

- Paradise Units 1
and 2

. Figure 9 below was included as part of the Commonwealth ’s recommendation, and indicates that the predicted value occurred approximately 2.3 km west of the Plant Wilson

. The
Commonwealth ’s receptor grid is also shown in the figure.25

Figure 9 : Maximum Predicted 99 th Percentile 1

- Hour SO 2 Concentrations in the Ohio County Area of Analysis Based on PTE Emissions Source: “Air Dispersion Modeling Report Wilson Station SO 2 Designations Analysis Revision 1” prepared by Trinity Consultants

for the Big Rivers Electric Corporation, August 25, 2015

Regarding Plant Wilson’s modeled future allowable limit the Commonwealth did not provide specific information concerning the federal enforceability nor indicate the averaging time and
how it was derived. Consistent with past interpretations of legal requirements, control measures,
emission limits and other curtailm ents need to be installed, operational and federally enforceable to be considered when informing final designation decisions. The mechanisms for establishing federally enforceable emission limits, control measures, or curtailments for the purpose of
inform ing SO 2 designations include: a source

- specific SIP approved by the EPA, a minor new source review permit, a title v permit or a consent decree established through a f ederal civil26

litigation. There was no documentation provided by the Commonwealth on wheth er the averaging time for the future allowable limit is a 1

- hour limit or if a l onger

- term averaging period (e.g., 30

- day rolling average) was established that is comparatively stringent to a 1

- hour
limit at the critical emission value (pursuant to the EPA ’s SO 2 Nonattainment Guidance). 16 Furthermore, the Commonwealth ’ s decision to exclude actual emissions from 2012

- 2014 from
TVA

- Paradise Station Units 1 and 2 was based upon a fu ture retirement of these units which questions whether the model configuration accounts for impacts to the area should these retirements not occur prior to the final designations scheduled for July 2, 2016

.

The EPA notes inconsistent information on the timing of the retirement of TVA

- Paradise Fossil
Plant Units 1 and 2 (i.e., wheth er this will occur by April 2016 or June 2017 )

. The EPA is required to characterize the current air quality around Plant Wilson by July 2, 2016

, according to
the terms of the court ordered consent decree. Therefore based on the uncertainty on the permanent shutdown of Units 1 and 2 and the fact that 2012

- 2014 actual historic emissions were not considered in the modeling analysis for Plant Wilson, the EPA does not have sufficient information to consider the source’s impact on the Ohio County Area. U nless the Commonwealth can provide documentation that Units 1 and 2 will permanently retire in advance of the July 2, 2016, designations to the EPA for consideration prior to the promulgation of final designations, the EPA cannot consider these shutdowns and instead believes that it is more appropriate for the Commonwealth to account for actual emissions for these units from 2012

- 2014 in any modeling to characterize the air quality around Plant Wilson for the Ohio County
Are a.

Because Plant Wilson’s future allowable limit is not yet federally

- enforceable and there is no
indication of a 1

- hour averaging time or a comparatively stringent longer term averaging period, coupled with the uncertainty surrounding the shutdown of TVA Paradise Station Units 1 and 2,
th e EPA intends to designate the Ohio County Area as unclassifiable due to the absence of
relevant information.

However, if the Commonwealth can : (1) establish Plant Wilson’s new allowable limit of 0.85 lb
SO 2 /mmBTU a s federally

- enforceable (through an appropriate mechanism), by April 19, 2016 ; (2) document the 1

- hour averaging time or as applicable, includes a longer term average limit that the EPA determines is comparatively stringent to a 1

- hour limit at the critical e mission value (pursuant to the SO 2 Nonattainment Guidance) ; (3) confirm and document that TVA

- Paradise
Fossil Plant Units 1 and 2 will be permanently retired for the purposes of validating the modeling submitted for the area of analysis and informing final designations scheduled July 2, 2016 ; (4)

n otif y the EPA of these conditions in advance of our promulgation of final designations, the EPA

16 See the EPA’s “Guidance for 1

- hour SO 2 Nonattainment Area SIP Submissions,” dated April 23, 2014 available

at: http://www3.epa.gov/airquality/sulfurdioxide/pdfs/20140423guidance.pdf

. Previous E PA guidance, has suggested that averaging times for SIP emission limits should not exceed the averaging time of the applicable NAAQS the limit is intended to support attainment(i.e. the averaging time for an emission limit for complying with
the 1

- hour pri mary SO 2 NAAQAS should not exceed 1

- hour). ( See S0 2 Guideline Document, U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, N.C. 27711, EPA

- 452/R

94

- 008, February 1994. (See http://www. epa. govlttnl oarpg/t 1 pgm. htm I). The EPA has established a procedure for establishing longer term averaging times (up to 30

- days) that is comparatively stringent to a 1

- hour limit at the
critical emission value.27

may be able to consider a designation of unclassifiable/attainment for the entirety of O hio County

.

Jurisdictional Boundaries:

Once the geographic area of analysis associated with the Plant Wilson , other nearby sources, and background concentration is determined, existing jurisdictional boundaries are considered for the purpose of informing our intended unclassifiabl e/ attainment area, specifically with respect to clearly defined legal boundaries.

For the Ohio County A rea , the Commonwealth considered major sources of SO 2 emissions
within a 20 km range and larger sources within a 20

- 50 km range that were believed to potentially contribute significant concentrations to the area of analysis

. The Commonwealth determined that this was the appropriate distance in order to adequately characterize air quality from the facility and other nearby sources which may have a potential impact in the area of analysis where maximum concentrations of SO 2 from Plant Wilson ar e expected.

The surrounding counties captured in Plant Wilson’s area of analysis includes Ohio, Webster
Henderson

, Daviess

, and Muhlenberg

, none of which have been designated nonattainment for the
1

- hour SO 2 NAAQS. Furthermore, none of these counties, wi th the exception of Daviess County

, have been designated nonattainment for any other NAAQS. Additionally, the large sources
evaluated within the 20

- 50 km range additionally included portions of Grayson, Breckinridge, Hancock, Henderson, Webster, Hopkins an d Butler counties

.

TVA

- Paradise Fossil Plant in Muhlenberg County is located approximately 22 km southeast of
Plant Wilson , and had SO 2 emissions of 1

, 9654.55 tpy in 2014. A ctual emissions data from Unit
3 at TVA

- Paradise Fossil Plant were included in the modeling analysis for the area around Plant
Wilson. The Commonwealth did not model 2012

- 2014 actual emissions for Units 1 and 2 but
rather assumed a zero PTE based upon a future retirement of these units

. The EPA notes
inconsistent in formation on the timing of the retirement of TVA

- Paradise Station Units 1 and 2, whether this will occur by April 2016 or June 2017. Therefore, unl ess the Commonwealth can provide documentation to the EPA that Units 1 and 2 have permanently retired in adv ance of the promulgation of final designations, the EPA cannot consider these shutdowns and instead
believes that the Commonwealth should account for actual emissions for these units from 2012

- 2014 in the modeling analysis characterizing the air quality ar ound Plant Wilson for the Ohio County Area.

T he Green River Generating Station also in Muhlenberg County is located approximately 10 km
from Plant Wilson and less than 0.5 km from the Ohio County border. The source reported
2

, 1976.19 tons of SO 2 in 2014 but according to reports from EIA, the last remaining Units 3 and 4 were permanently retired in October 2015 17 resulting in zero PTE . Green River Station was not

17 N o emissions were reported to the EPA Air Markets Da tabase beginning in October 2015 for any federal programs for which Green River Generating Station Units 3 and 4 would have been subject . Also,28

explicitly included in the modeling analysis for Plant Wilson due to permanent shutdow n and zero potential to emit SO 2 . However, the source was considered in the background concentrations accounting for impacts from nearby sources including historic actual emissions

. Considering the source’s zero PTE and the cumulative impacts captured in the background concentrations, the EPA does not have reason to believe that emissions from this now non

operational facility are causing or contributing to a violation of the SO 2 NAAQS in the Ohio County Area.

Other SO 2 emitters the Commonwealth assessed within the 20

- 50 km range that reported SO 2 emissions over 100 tpy included: Century Aluminum of Kentucky, LLC (Hancock County)(EPA notes this source is just beyond 50 km), Elmer Smith Station (Daviess County), Reid/Hend erson Station II Generating Station and BREC Landfill (Webster County). These sources were not explicitly included in the modeling analysis because they’re all located approximately 35 km or greater from Plant Wilson and/or the Ohio County Area which the Commonwealth d etermined to
be far enough that impacts from the facility relative to Plant Wilson. Based on the Commonwealth’s assessment considering distance from Ohio County Area, the EPA has reason
to believe these sources would not cause or contribute t o a violation of the SO 2 NAAQS within the Ohio County Area.

The EPA notes that two BREC’s sources Green Station (Webster County) and Coleman Station (Hancock County) and Owensboro Grain Company (Daviess) also reported 2014 emissions over 100 tpy year but similar to those sources considered by the Commonwealth are also located over 35 km away from Plant Wilson and Ohio County Area . Based on the distance from Plant Wilson and Ohio County border (>3 5 km), the EPA has reason to believe that these sources would not cause significant concentration gradients within the area of analysis or Ohio County. The EPA
notes that other sources in counties within the 20

- 50 km range cumulatively emitted less than
10 0 tpy of SO 2 emissions according to 2014 actual emissions.

A ny area in Kentucky not designated by July 2, 2016

, will be designated by either December 31, 2017, or December 31, 2020, consistent with the deadlines prescribed in the final consent decree. The Commonwealth’s review of other SO 2 emitting sources in terms of distance from Plant Wilson, potential impacts of other SO 2 emitting sources within Ohio County, and scheduled shut
downs that can be credited for the July 2, 2016

, round of designations support the Commonwealth’s recommendation to designate the entirety of Ohio County.

The EPA’s observation of t he Commonwealth ’s review of nearby sources in and outside of Ohio County revealed that larger sources are far enough away that their impacts would be significantly reduced in terms of its impacts overlapping with those of Plant Wilson

. Green River Generating Station in Muhlenberg County has permanently retired its remaining Units 3 and 4 as of October
2015 , however, there is uncertainty surroun ding the shutdown of TVA

- Paradise Fossil Plant Units 1 and 2. Furthermore, because Plant Wilson’s future allowable limit is not yet federally
enforceable and there is no indication of a 1

- hour averaging time or a comparatively stringent longer term averagi ng period, the EPA intends to designate the Ohio County Area as

EIA’s US Energy Information Administration “Electric Power Monthly” annual report for January 2016,
tracked Units 3 and 4 as permanently retired as of October 2015.29

un classifiable. The intended unclass ifiable designation consisting of Ohio County in its entirety
constitutes a clearly defined legal boundar y

.

Other Relevant Information

The Commonwealth’s recommended designation of attainment for Ohio County is based on air dispersion modeling analysis of a future allowable limit of 0.85 lb SO 2 / mmBTU for Plant
Wilson which is less tha n the current permitted limit of 1.2 lb SO 2 /mmBTU. This lower limit

was proposed by BREC and modeled to show attainment for the 1

- hour SO 2 NAAQS.

Consistent with past interpretations of legal requirements, control measures, emission limits and other curtailments need to be installed, operational and federally enforceable to be considered when informing final designation decisions. The mechanisms for establishing federally enforceable emission limits, control measures, or curtailments for the purpose of informing SO 2 designations include: a source

- specific SIP approved by the EPA, a minor new source review permit, a title v permit or a consent decree established through a f ederal civil litigation. Therefore, t he Commonwealth of Kentucky must ensure this new allowable limit is federally enforceable by April 19, 2016 for the purpose of informing final designations and as applicable, include a longer term average limit that is comparatively stringent to a 1

- hour limit at the critical
emission value p ursuant to the EPA’s April 23, 2014 1

- hour SO 2 nonattainment guida nce. 18 Furthermore, the Commonwealth's decision to exclude actual emissions from 2012

- 2014 from
Units 1 and 2 and TVA

- Paradise Fossil Plant was based upon a future retirement of these units. However, the EPA is required to characterize the current air quality around the Plant Wilson source by July 2, 2016. The EPA notes conflicting information on the timing of the retirement of
TVA

- Paradise Fossil Plant Units 1 and 2, specifically, whether this will occur by April 2016 or
June 2017. T h e Commonwealth and Plant Wilson must ensure that the units will be officially retired by April 19, 2016 for the purposes of validating the modeling submitted for the area of analysis and informing final designations.

The EPA received no additional information regarding Plant Wilson or its surrounding area.

Conclusion

.

The Commonwealth of Kentucky recommended a designation of attainment for the entire ty of Ohio County based on Plant Wilson’s air dispersion modeling ( using AERMOD Model Version 15181) analysis which considered a future allowable emission limit of 0.85 lb SO 2 /mmBTU at the facility, actual emissions from the TVA

- Paradise Station Unit 3 (located just southeast of Plant Wilson in Muhlenberg Count) and background concentrations based on rural and natural background sources as well as regional impacts from distance large SO 2 sources , and assumed
that TVA

- Paradise Units 1 and 2 would be retired

. Additional SO 2

- emitting sources were identified within the analysis area , which extended 50 km out from Plant Wilson. B ut Plant
Wilson determined th at certain sources (i.e., TVA

- Paradise Units 1 and 2 and Green River

18 EPA’s “Guidance for 1

- hour SO 2 Nonattainment Area SIP Submissions,” dated April 23, 2014 available at: http://www3.epa.gov/airquality/sulfurdioxide/pdfs/20140423guidance.pdf30

Station) would be shut down before final designations, and that based on the distance ( at least 35 km) from Plant Wilson and from t he boundary of Ohio County (at least 20 km) , the impacts from remaining sources would be significant ly reduced in terms of potential overlap with those from
Plant Wilson. The areas in other counties surrounding these sources will be designated by one of the other deadlines prescribed by the final consent decree, i.e., December 31, 2017, or December 31, 2020. Based on these factors, Plant Wilson’s modeled 1

- hour design value for its 2 0 km area of analysis, covering the entirety of Ohio County, is 186.5 μg/ m 3

, or 71 ppb . This modeled
concentration is below the level of the 2010 SO 2 NAAQS. Plant Wilson’s modeling parameters, assumptions and inputs were in compliance with the A gency’s Modeling TADs a fter careful
evaluation of the Commonwealth ’s recommendation and supporting information, as well as all
available releva nt information

.

It is unclear in the documentation provided by the Commonwealth whether Plant Wilson’s new
allowable emission limit will be a 1

- hour limit or whether there is some longer

- term ave raging period (e.g., 30

- day rolling average) for the limit. As noted above, t he EPA has developed SO 2 nonattainment implementation guidance which indicates that modeling to determine attainment
with the 1

- hour SO 2 NAAQS should use a higher 1

- hour “critical value” to account for hourly emissions variability in a 30

- day rolling average allowable limit. The details for the EPA’s recommended procedure for calculating the adjustment factor between the 1

- hour critical val ue and an equivalent longer

- term average emissions limit are provided in Appendices B and C of
the EPA’s SO 2 Implementation Guidance. The EPA has informed Kentucky that an appropriate
1

- hour critical value should be used in the modeling if the future allow able limit includes an averaging period longer than 1

- hour.

The EPA notes conflicting information on the timing of the retirement of TVA

- Paradise Fossil Plant Units 1 and 2, specifically, whether this will occur by April 2016 or June 2017. Therefore,
it is unclear these units will be officially retire d prior to the final promulgation of the July 2, 2016 designation of the area surrounding Plant Wilson. Consequently, the EPA intends to designate the area around Plant Wilson Power Station comprised of O hio County as
unclassifiable for the 2010 SO 2 NAAQS

.

However, i f Plant Wilson’s new allowable limit of 0.85 lb s SO 2 /mmBTU is federally

enforceable and, as applicable, includes a longer term average limit that the EPA determines is comparatively stringent to a 1

- hour limit at the critical emission value ; and the Commonwealth
confirms that TVA

- Paradise Fossil Plant Units 1 and 2 will be permanently retired prior to the July 2, 2016

, deadline for designations

, and no tifies the EPA of these condition s in advance of our promulgation of final designations, the EPA anticipates may be able to designate Ohio County unclassifiable/attainment.

Based on all available information, including the reasons discussed above, the EPA is unable at
this time to determine whether the area is meeting or not meeting the NAAQS. At this time, our intended designations for the Commonwealth only applies to this area (Ohio County) and the
other area (Pulaski County) presented in this technical support document. Consisten t with the conditions in the March 2, 2015 court

- ordered consent decree schedule, the EPA will evaluate and designate all remaining undesignated areas in Kentucky by either December 31, 2017, or December 31, 2020.31

Technical Analysis for the Plant Cooper

– Pulaski County Area

Introduction

The Pulaski County A rea contains a stationary source that according to the EPA’s Air Markets Database emitted in 2012 either more than 16,000 tons of SO 2 or more than 2,600 tons of SO 2 and had an annual average emission rate of at least 0.45 lbs SO 2 /mmBTU

. As of March 2, 2015, this stationary source had not met the specific requirements for being “announced for retirement.” Specifically, in 2012, the Cooper Power Station emitted 7,428 t ons of SO 2 , and had
an emissions rate of 1.07 lb s SO 2 /mmBTU. Pursuant to the March 2, 2015 court

- ordered
schedule , the EPA must designate the area surrounding the facility by July 2, 2016.

In its submission, Kentucky recommended that the area surrounding the Cooper Power Station (Cooper Station) , specifically the entirety of Pulaski County

, be designated as attainment based on an assessment and characterization of air quality from the facility and other nearby sources which may have a potential impact in t he area of analysis where maximum concentrations of SO 2 are expected

. This assessment and characterization was performed using air dispersion modeling software, i.e., AERMOD, analyzing actual emissions in part and allowable emissions in part

. The assessment was originally carried out by Trinity Consultants and prepared for the East Kentucky Power Cooperative. The Commonwealth then reviewed and submitted the information to the
EPA. 19

After careful review of the Commonwealth ’s assessment, suppor ting documentation, and all available data, the EPA intends to designate the area as u nclassifiable

. However, if the
Commonwealth provides notification of the following to the EPA prior to the promulgation of the July 2, 2016 designation, the EPA may consider designating the entirety of Pulaski County as unclassifiable/attainment

, provided that are no outstanding technical issues : 1) assurance that the Cooper Station ’s new PTE limit of 0. 165 lb SO 2 /mmBTU for Unit 1 is federally

- enforceable, and, as applicable, includes a longer term average limit that the EPA determines is comparatively stringent to a 1

- hour limit at the critical emission value ; 2) the modeling for Units 1 and 2 at the facility are matched (e.g., PTE emissions or actual emis sions over a common time period); and
3 ) the updated modeling shows that the new PTE limit on Unit 1 or modeled actual emissions will ensure attainment of the NAAQS

.

Cooper Station is located in the southern portion of Pulaski County. As seen in Figure 10 below, the facility is located approximately 1 0 km north of the center of Somerset. The power station is located near the Cumberland River, and there is medium to high land use development in the surrounding area. Also included in the figure are n earby emitters of SO 2 , the Commonwealth ’s
recommended area for the attainment designation

, and the area the EPA intend s to designat e as unclassifiable

.

19 Throughout this document the Commonwealth will be referred to as having assessed air quality in the area
because the Commonwealth agreed with the East Kentucky Power Cooperative’s air quality assessment and characterization of the area of analysis, officially submitting the report to the EPA to support their designation
recommendation.32 Figure 1 0 . The EPA’s intended designation for Pulaski County, Kentucky

The discussion and analysis that f ollows below will reference the Commonwealth’s use of the Modeling TAD, the EPA’s assessment of the Commonwealth’s modeling in accordance with the Modeling TAD, and the factors for evaluation contained in the EPA’s March 20, 2015 guidance, as appropriate

Detailed Assessment

Air Quality Data

This factor considers the SO 2 air quality monitoring data in the area surrounding Cooper Station. The facility is located in Pulaski County, and the Commonwealth included monitoring data from the closest monitors: Nicholasville (21

‐ 113

‐ 0001), Lexington (21

‐ 067

‐ 0012), and Mammoth Cave National Park (21

‐ 061

‐ 0501), to the facility in its recommendation. The closest monitor is Nicholasville, located at KYTC Maintenanc e Garage, 260 Wilson Drive, Nicholasville, KY 40356 (37.89147,

- 84.58825) in Jessamine County, and is 99 km away from Cooper Power
Station. Data collected at this monitor is considered indicative of po pulation exposure but is not representative of the expected background concentrations in the area surrounding the Cooper33

Station. The Mammoth Cave monitor, located at Alfred Cook Road, Park City, KY 42160 (37.131944,

- 86.14778) is thought to be representat ive of rural areas with similar influences to the air quality around Cooper Station. Table 7 below summarizes the local monitors and design
values within 150 km of Cooper Station

.

Table 7 : Historical Ambient Air Quality Data for Nearby Monitors

Monitor A QS ID County 2010

– 2012 Design Value (μg/m 3 ) 2011

– 2013

Design Value (μg/m 3 ) 2012

– 2014

Design Value (μg/m 3 )
Nicholasville 21

- 113

- 0001 Jessamine 68.1 41.9 39.3 Lexington 21

- 067

- 0012 Fayette 68.1 44.5 34.0
Mammoth
Cave 21

- 061

- 0501 Edmonson 31.4 26.2 26.2

Model Selection and Modeling Components

The EPA’s Modeling TAD notes that for area designations under the 2010 SO 2 NAAQS, the AERMOD modeling system should be used, unless use of an alternative model can be justified.
In some instances the recommended mo del 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 scree ning version of AERMOD

The Commonwealth used AERMOD version 15181 , and a discussion of the individual components will be referenced in the corresponding discussion that follows

, as appropriate.

Modeling Parameter: Rural or Urban Dispersion

The EPA’s recommended procedure for characterizing an area by prevalent land use is based on evaluating the dispersion environment with in 3 km of the facility. According to the EPA’s modeling guidelines, rural dispersion coefficients are to be used in the dispersion modeling analysis if more than 50 percent of the area within a 3 km radius of the facility is classified as rural. Conversely, if more than 50 percent of the area is urban, urban dispersion coefficients should be used in the modeling analysis

. When performing the modeling for the area of analysis,
the Commonwealth determined that it was most appropriate to run the model in rural mode. This determination was based on an analysis of land use within 3 km of the Cooper Power Station. Figure 11 below depicts land use within 3 km of the facility where greens, yellows and browns34

are farmland, forests, and grasses, pinks are non

- urban developed lands, and red and dark red are urban areas. As can be seen in Figure 11 , the area is predominantly rural by an overwhelming margin. T herefore the Commonwealth determined that is was most appropriate to run the model with rural dispersion coefficients

Figure 11 . Distribution of Land Use Within 3 km of Cooper Station

- Source: “Air Dispersion Modeling Report Cooper Station SO 2 Designations Analysis Revision 1” prepared by Trinity
Consultants for the East Kentucky Power Cooperative, September 1, 2015

Modeling Parameter: Area of Analysis (Receptor Grid)

The EPA believes that a reasonable first step towards characterization of air quality in the area surrounding the Cooper Station is to determine the extent of the area of analysis, i.e., receptor grid. Considerations presented in the Modeling TAD include b ut are not limited to: the location
of the SO 2 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 m odel predicted maximum SO 2 concentrations. For the Pulaski County A rea , the Commonwealth has included 1 other emitter of SO 2 within 20 km of Cooper Station in any direction. For the Pulaski County Area , the Commonwealth evaluated
offsite SO 2 sources within 50 km of the facility in any direction and determined that it was only necessary to include one offsite source within 20 km of the facility in order to adequately characterize air quality on the vicinity of Cooper Station . This determination was based on the
actual and potential 2013 emissions at each facility and the distance of each facility from Cooper
Power Station

. Table B

- 1. 2 of the September 1 , 2015, modeling report provided to the35

Commonwealth via East Kentucky Power Cooperative on September 2, 201 5

, details this screening assessment. The Commonwealth confirmed that a receptor grid extending 20 km in all directions from Cooper Station was the appropriate distance in order to adequately characterize air quality from the facility and other nearby sour ces which may have a potential impact in the area of analysis where maximum concentrations of SO 2 are expected. In addition to Cooper Station, the only other emitter of SO 2 included in the area of analysis is Kingsford Manufacturing Company (KMC) , located approximately 3 km south of the facility . The grid receptor spacing for the area of analysis chosen by the Commonwealth is as follows:

 “Fence Line” receptors at 50 meter (m) spacing along the main fence line for the facility

 100 m spacing out to 3 km

 250 m spacing from 3 km out to 5 km

 500 m spacing from 5 km to 10 km

 1000 m spacing from 10 km to 20 km

The receptor network contained 4,948 receptors, and the network covered the southern two

thirds of Pulaski County in Kentucky

, extreme north western McCreary County in Kentucky, and extreme northeastern Wayne County in Kentucky

.

Figures 12 and 13, included in the Commonwealth ’s recommendation, show the
Commonwealth ’s chosen area of analysis surrounding the Cooper Station, as well as receptor grid for the area of analysis.

Consistent with the Modeling TAD, receptors for the purposes of this designation effort were placed only in areas where it would also be feasible to place a monitor and record ambient air impacts . The impacts of the area’s geography and topography will be discussed later within this
document.36

Figure 12 : Pulaski County Area of Analysis

- Source: “Air Dispersion Modeling Report Cooper
Station SO 2 Designations Analysis Revision 1” prepared by Trinity Consultants for the East

Kentucky Power Cooperative, September 1, 201537

Figure 1 3 : Innermost Portion of Modeling Receptor Grid for the Pulaski County Area of Analysis

- Source: “Air Dispersion Modeling Report Cooper Station SO 2 Designations Analysis Revision 1” prepared by Trinity Consultants for the East Kentucky Power Cooperative, September 1, 2015

Modeling Parameter: Source Characterization

The Commonwealth characterized the source s within the area of analysis in accordance with the best practices outlined in the Modeling TAD. Specifically, the Commonwealth used actual stack heights in conjunction with future allowable emissions limits for Cooper Station Unit 1 and
actual emission ra tes for Cooper Station Unit 2. Units 1 and 2 share a common stack. The actual stack height does not exceed the GEP stack height. The Commonwealth also adequately characterized the sources building layout and location, as well as the stack parameters, e.g., exit temperature, exit velocity, location, and diameter. Where appropriate, the AERMOD component BPIPPRIME was used to assist in addressing building downwash.38

Modeling Parameter: Emissions

The 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 3 years of actual emissions data and concurrent meteorological data. However, the TAD does provide for the flexibility of using allowable emissions in t he form of the most recently permitted (referred to as PTE or allowable) emissions rate.

The EPA believes that CEMS data provide acceptable historical emissions information, when it is available, and that these data are available for many electric generat ing units. In the absence of CEMS data, the 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, the EPA believes that detailed throughput, operating schedules, and emissions information from the impacted source (s) should
be used.

In certain instances, state s 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 SO 2 emissions to a level that indicates compliance with the NAAQS. The se new limits or conditions may be used in the application of AERMOD. In these cases, the Modeling TAD notes that the existing SO 2 emissions inventories use d for permitting or SIP planning demonstrations should contain the necessary emissions information for designations

related modeling. In the event that these short

- term emissions are not readily available, they may be calculated using the methodology in Ta ble 8

- 1 of Appendix W to 40 CFR Part 51 titled, “Guideline on Air Quality Models.”

As previously noted, the Commonwealth included Cooper Station and one other emitter of SO 2 within the 20 km area of analysis , i.e., KMC . This distance and these facilities were selected
because the Commonwealth believes that this area of analysis adequately represents the area
where maximum concentrations of SO 2 are e xpected and adequately includes the sources which might contribute to those concentrations

. Of the 16 facilities emitting SO 2 within 20 km of the Cooper Station, only KMC has actual annual SO 2 emissions greater than 2.5 tpy (37.97 tpy in
2014 20 )

. No other sources beyond 50 km were determined by the Commonwealth to have the potential to cause significant concentration gradient impacts within the area of analysis.

For Cooper Station

, the Commonwealth chose a hybrid approach for its analysis. Unit 1 operated
with a 24

- hour emission limit during the years consider ed, but a project at the facility will tie Unit 1 in with an existing dry flue gas desulfurization (DFGD) system for Unit 2 prior to the July 2, 2016 deadline for characterizing and designating this area . The Commonwealth anticipates
that both Units 1 and 2 will meet the federally enforceable emission limit currently in place for

20 Unless otherwise noted, all 2014 data was accessed via the Emissions Inventory (EIS) gateway, which states report emissions to in accordance with 40 CFR Part 51, Subpart A. The EIS gateway can be accessed via: http://www3.epa.gov/ttnch ie1/eis/gateway/39

Unit 2 after the project is complete. Therefore, Unit 1 is modeled at its future allowable emission

rate 21 to reflect the future installation of SO 2 emissions controls on that unit. Unit 2 is modeled
with three years of actual emissions from July 1, 2012

, through June 30, 2 015 obtained from
CEMS , reflecting the time for which its DFGD system was operational and its federally
enforceable emission limit in effect . Actual emissions f rom July 31, 2012 through June 30, 2014 for all units (Units 1 and 2) at Cooper Station are summarized in Table 8

.

Table 8 : Actual SO 2 Emissions Between mid

- 2012

– mid

- 201 5 from Cooper Station

Facility Name Unit # SO 2 Emissions ( tpy ) a

2012 b 2013 2014 2015 c

Cooper Station 1 1406.25 2812.09 2681.48 566.27

2 1862.96 1791.62 1642.37 682.58

a Data from EPA’s Air Markets Database.

b Beginning July 1, 2012.

c Ending June 30, 2015

.

For KMC in the area of analysis, the Commonwealth has chosen to model the facility using the most recent federally enforceable PTE limits for SO 2 . The facilities included in the
Commonwealth ’s area of analysis and their associated PTE rate is shown below.

Table 9 : SO 2 Emissions based on PTE from Facilities in the Pulaski County Area of Analysis

Facility Name SO 2 Emissions

( tpy , based on PTE) Kingsford Manufacturing Company 136

All Facilities 136

The PTE limit for Kingsford Manufacturing reflects existing emissions limits.

Modeling Parameter: Meteorology and Surface Characteristics

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

21 Cooper Station Unit 1 is undergoing modification to tie

- in its exhaust gases into the existing DFGD system currently serving Unit 2. This modification is expected to be completed by January 1, 2016. For Cooper Station Unit 1, the Common wealth modeled an allowable emission rate of 178 pounds per hour (.165 pounds per million BTU (lbs/mmBtu)). This was derived from the existing Title V permit limit of 3.3 pounds SO 2 per million BTU (24

- hour average) by assuming a 95 percent reduction in em issions of SO 2 and operating at 1080 mmBtu/hr year round (8,760 hours). A 95 percent reduction was applied to the existing permit limit because the Commonwealth expects the facility to meet a federally enforceable SO 2 emission limit of 95% removal efficien cy (30

- day rolling average) or .1
lbs SO 2 per mmBtu (30

- day rolling average) on both Cooper Units once the tie in of Unit 1 into the Unit 2 DFGD is complete. The Title V permit is expected to be revised by July 2, 2016 to reflect these limits.40

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 NWS stations, site

- specific or onsite data, and other sources such as universities, FAA, and military stations.

For the Pulaski County A rea of anal ysis, surface meteorology from the NWS station in London

, Kentucky, 64 km to the east, and coinciden t upper air observations from t he NWS station in Nashville, Tennessee, 260 km to the southeast were selected as best representative of meteorological conditions within the area of analysis.

The Commonwealth used AERSURFACE version 15181 using data from the NWS station in
London , Kentucky (located at Latitude 37. 087 North

, L ong itude 84. 077 West ) to estimate the surface characteristics of the area of analysis. The Commonwealth estimated values for 12 spatial

sectors out to 1 km at a seasonal temporal resolution for average conditions. The Commonwealth also estimated values for albedo (the fraction of solar energy reflected from the earth back into space), the Bowen ratio (the m ethod generally used to calculate heat lost or heat gained in a substance), and the surface roughness (sometimes referred to as “Zo”). In the figure below, the
location of the London , Kentucky NWS station is shown relative to the Pulaski County A rea of

ana lysis.41

Figure 14 : Cooper Power Station Area and the Nearby Meteorological Stations

- Source: “Air Dispersion Modeling Report Cooper Station SO 2 Designations Analysis Revision 1” prepared by Trinity Consultants for the East Kentucky Power Cooperative, September 1, 201542

As part of its recommendation, the Commonwealth provided t he 3

- year surface wind rose for the
London

- Corbin Airport NWS. In Figure 15

, the frequency and magnitude of wind speed and direction are defined in terms of from where the wind is blowing. As shown in Figure 15 , the predominant winds blow from the south at low to mid

- level wind speeds of 0.5 to 5.7
meters/second.

Figure 15 : London

- Corbin Airport Cumulative Annual Wind Rose from July 2012

– June 2015

Meteorological data from the above surface and upper air stations 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 modeling runs. The Commonwealth followed the methodology and settings presented in standard43

U.S. EPA meteorological processing guidance as outlined in a recent memorandum 22 as well as other AERMET and associated preprocessor documentation in the pro cessing of the raw meteorological data into an AERMOD

- ready format, and used AERSURFACE to best represent
surface characteristics. The Commonwealth selected the beta option ADJ_U* for AERMET. The 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 the EPA’s December 10, 2015 Memorandum titled, “Clarification on the Approval Process for Regulatory Application of the AERM OD Modeling System Beta Options.” Among other conditions, the use of beta options requires consultation with the appropriate EPA Regional Offices. Upon concurrence by the EPA’s Modeling Clearinghouse, the EPA Regional Offices may approve the use of these b eta options for regulatory applications as an alternative model. However, the Commonwealth provided air dispersion modeling intended to characterize air quality as a result of SO 2 emissions from Cooper Station without prior approval from the EPA Region 4

, and therefore has not met the applicable regulatory requirements contained in Appendix W, Section 3.2.2. As a result, the air quality modeling results obtained from the use of these beta options can not be used as a reliable indicator of attainment status i n the Pulaski County Area until appropriate alternative model approval is granted or these beta options are promulgated as regulatory options in AERMOD through the EPA rulemaking. The modeling documentation submitted by the Commonwealth provides informatio n to justify use of the beta ADJ_U* option for this application. The EPA Region 4 will work with the EPA’s Model

C learinghouse to evaluate the use of beta ADJ_U* prior to the final designation of the area

.

Hourly surface meteorological data records are re ad 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 t o 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. Th e s e data were subsequently integrated into the AERMET processing to produce final hourly wind records of AERMOD

ready 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 Commonwealth 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.

22 Fox, Tyler , U.S. Environmental Protection Agency. 2013. “Use of ASOS Meteorological Data in AERMOD Dispersion Modeling.” Available Online: http://www.epa.gov/ttn/scram/guidance/clarification/20130308_Met_Data_Clarification.pdf44

Modeling Parameter: Geography and Terrain

The terrain in the area of anal ysis is best described as complex to hilly . To account for these terrain changes, the AERMAP terrain program within AERMOD was used to specify terrain elevations for all the receptors. The source of the elevation data incorporated into the model is
from th e United States Geological Survey National Elevation Database. Figure 16 provided in
the Commonwealth ’s recommendation shows a relief map of the terrain within 20 km of the Cooper facility.

Figure 16 . Relief map of the terrain within 20 km of the Cooper facility

- Air Dispersion Modeling Report Cooper Station SO 2 Designations Analysis Revision 1” prepared by Trinity
Consultants for the East Kentucky Power Cooperative, September 1, 201545

Modeling Parameter: Background Concentrations of SO 2

The Modeling TAD offers two mechanisms for characterizing background concentrations of SO 2 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 9 9 th percentile monitored concentrations by hour of day and season or month. For the Pulaski County A rea of analysis, the Commonwealth chose to use a first tier approach using the 2012

- 2014 design value
from the Mammoth Cave National Park ambient SO 2 monitoring site located approximately 139 km west of Cooper Station. Two other nearby monitors , summarized in Table 7

, considered for this purpose were Nicholasville (99 km from Cooper Station) and Lexington (119 km from Cooper Station). These monitors we re deemed inappropriate to represent background concentrations near Cooper Station due to their local settings and a relative emissions inventory that compared SO 2 emissions from sources within 20 and 50 km of each monitor and compared with those within the same distances from Cooper Station. The Mammoth Cave site has the most comparable nearby emissions to Cooper Station. In addition, due to predominant wind patter ns in the area, the Mammoth Cave site is expected to represent emissions from small sources in the Bowling Green

- Glasgow combined statistical area (CSA). That CSA has a similar population to the Cooper Station. The Mammoth Cave site has a monitoring object ive of general/background without a specified measurement scale. Due to its background status, this monitor is thought to be representative of rural areas with similar influences to the air quality around Cooper Station.
The b ackg round concentration for th is area of analysis was determined by the Commonwealth to be 26.9 μg/m 3 , or 10.3 ppb, 23 and that value was incorporated into the final AERMOD results.

Summary of Modeling Results

The AERMOD modeling parameters for the Pulaski County A rea of an alysis are summarized
below in T able 10

.

23 The conversion factor for SO 2 (at the standard conditions applied in the ambient SO 2 reference method) is 1 ppb = approximately 2.62 μg/m 3

.46

Table 10 : AERMOD Modeling Parameters for the Pulaski County Area of Analysis

Cooper Station Area of Analysis

AERMOD Version 15181 Dispersion Characteristics Rural

Modeled Sources 2

Modeled Stacks 6
Modeled Structures 1 1

Modeled Fencelines 1 Total receptors 4,948 Emissions Type Actual & PTE
Emissions Years 7

- 1

- 2012 thru 6

- 30

- 2015 Meteorology Years Same as Emissions Years Surface Meteorology Station London, Kentucky Upper Air Meteorology Station Nashville, Tennessee Methodology for Calculating Background SO 2 Concentration 1 st tier

– Monitored Design
Value Calculated Background SO 2 Concentration 10.3 ppb or 26.9 μg/m 3

The results presented below in T able 11 show the magnitude and geographic location of the highest predicted modeled concentration based on modeled emissions

.

Table 11 : Maximum Predicted 99th Percentile 1

- Hour SO 2 Concentration in the Pulaski County

Area of Analysis Based on Actual and E xpected F uture PTE Emissions

Averaging
Pe riod Data Period Receptor Location SO 2 Concentration ( μg/m 3 )

UTM East UTM North Modeled (including background) NAAQS
99th Percentile
1

- Hour Average 7

- 1

- 2012

-

6

- 30

- 2015 714,550 4,098,043 173.1 196.5* *Equivalent to the 2010 SO 2 NAAQS set at 75 ppb

The Commonwealth ’s modeling indicates that the predicted 99 th percentile 1

- hour average concentration within the chosen modeling domain is 173.1 μg/m 3 , or 66.1 p pb. This modeled
concentration included the background concentration of SO 2 , and is based on actual and expected
future PTE emissions from the facilities. This predicted value occurred just northeast of Cooper
Station , and is graphically represented along with all the other receptors below in Figure 17

.47

Figure 17 : Maximum Predicted 99 th Percentile 1

- Hour SO 2 Concentrations in the Pulaski County Area of Analysis Based on Actual and PTE Emissions

– Source Air Dispersion Modeling Report Cooper Station SO 2 Designations Analysis Revision 1” prepared by Trinity Consultants for the

East Kentucky Power Cooperative, September 1, 201548

Jurisdictional Boundaries:

Once the geographic area of analysis associated with the Cooper Station , other nearby sources,

a nd background concentration is determined, existing jurisdictional boundaries are considered for the purpose of informing our intended unclassifiable area, specifically with respect to clearly defined legal boundaries.

Within the 20 km area of analysis around Cooper Station

, 16 SO 2 emitting sources were
identified

, all within Pulaski County. Only one source , i.e., KMC

, has actual annual emissions greater than 2.5 tpy , based on 2013 actual emissions via the Kentucky Emissions Inventory System (KYEIS)

. With the exception of KMC, the cumulative annual SO 2 emissions from all sources within 20 km of Cooper Station are 8.5 tpy on an actual emissions basis and 40 tpy on a potential emissions basis (KYEIS 2013)

. In comparison to the modeled SO 2 emission rates from Cooper Station Unit s 1 and 2, the EPA does not believe that these smaller sources emit SO 2 in quantities that would significantly alter the modeled concentration of SO 2 within the area of analysis. Furthermore, the vast majority of these sources are l ocated to the north of Cooper Station which is in a low frequency wind sector for wind directions causing transport from the regional source locations to the area of highest impacts for Cooper Station

. . See Figure 15 above

.

An additional review of 38 sources l ocated between 20 and 50 km from Cooper Station, which
includes p ortions of McCleary, Wayne, Russel, Casey, Lincoln, Rockcastle, Laurel, and Whitley Counties resulted in only one source with actual SO 2 emissions above 5 tpy. Specifically,
the EKPC Laurel Rid ge La ndfill

- Gas

- to

- Energy facility (EKPC) has actual annual SO 2 emissions of 36.1 tpy based on the 2013 KYEIS and allowable emissions of 41.3 tpy. EKPC is located approximately 45 km east of the Cooper Station , and approximately 19 km from the Pulaski County border

. The London

‐ Corbin airport meteorologic al station wind rose in Figure 15 above indicates a very low frequency of winds from this direction. Based on the low emissions from this facility in conjunction with the distance fr om the Pulaski County border, the EPA does not believe that EKPC’s emissions are causing or contributing to a violation of the NAAQS in Pulaski County.

The i ntended unclassifiable area, consisting of the entirety of Pulaski County constitutes a clearly defined legal boundar y , and the EPA find s this boundary to be a suitably clear basis for defining
our intended unclassifiable area.

Other Relevant Information

The EPA has conducted a review of the modeling performed by Trinity Consultants for th e East Kentucky Power Cooperative and provided by the Commonwealth to support their designation recommendation. The EPA’s review has identified a number of unresolved concerns regarding the procedures and data used in the modeling which have led to the rec ommendation of
unclassifiable for the Pulaski County A rea. The following is a brief summary of significant issues identified in the EPA’s review of the modeling:

 The EPA’s modeling TAD gives the option of modeling 3

- years of actual emissions or allowable emissions

. Cooper Power Station operates two coal

- fired boilers with49

emissions ducted to a common stack . A scrubber wa s installed in 2012 and put into operation for Unit 2, which has a maximum heat input of 2

, 089 mm Btu/hr. Emissions from Unit 1, which has a maximum heat input of 1

, 080 mm Btu/hr, are currently in the process of being ducted to the same scrubber. Cooper modeled Unit 2 with July 2012

- July 2015 actual emissions combined with new expected future allowable emissions for Unit 1, using c alculated design stack flow rates and temperatures for the two units operating together since they are emitted from a single, common stack. The EPA has determined that using a combination of actual and allowable emissions is not appropriate
since the emiss ions from the two units are combined and emitted from a common stack.
The EPA has recommended to the Commonwealth and Cooper Station that the modeling be revised to either use the new expected future allowable (PTE) limits from both units, if
made federall y enforceable in time to inform the final designation, or to use actual
emissions from a common 3

- year time period for both units.

 The EPA’s review of the modeling documentation indicates that Cooper used the 30

- day
roll ing average allowable emission limit for U nit 1 directly as the 1

- hour emission rate input into the AERMOD model. The EPA has developed SO 2 nonattainment implementation guidance 24 which indicates that modeling to dete rmine attainment with
the 1

- hour SO 2 NAAQS should use a higher 1

- hour “ critical value ” to account for hourly emissions variability in 30

- day rolling average allowable limit. The details for the EPA’s recommended procedure for calculating the adjustment factor between the 1

- hour critical value and the equivalent 30

- day rolling average emissions limit are provided in Appendices B and C of the EPA’s SO 2 Implementation Guidance. The EPA has informed Kentucky that an appropriate 1

- hour critical value must be used if Cooper Station decides to revise their modeling to use allowable (PTE) emissions for both units as discussed
above.

The EPA receive d no additional information regarding Cooper Station or its surrounding area

.

Conclusion

The Commonwealth of Kentucky recommended a designation of attainment for the entire ty of
Pulaski County based on Cooper Station’s air dispersion modeling ( using AERMOD Model Version 15181) analysis which considered a future allowable emission limit of 0. 165 lb
SO 2 /mmBTU at Unit 1 and actual emissions Unit 2, assuming background concentrations based

o n rural and natural background sources as well as regional impacts from distance large SO 2

sources. Additional SO 2

- emitting sources were identified within the analysis area , which extended 50 km out from Cooper Station. B ut Cooper Station determined th at c ertain sources
that based on the relatively low emissions for sources within 20 km of Cooper Station ( less than 2.5 tpy ) and for sources outside of Pulaski County , between 20 and 50 km from Cooper Station ( less than 5 tpy) , the impacts from remaining sourc es would be significantly reduced in terms of potential overlap with those from Cooper Station. The areas in other counties surrounding these sources will be designated by one of the other deadlines prescribed by the final consent decree,

24 EPA’s “Guidance for 1

- hour SO2 Nonattainment Area SIP Submissions,” dated April 23, 2014 available at: http://www3.epa.gov/airquality/sulfurdioxide/pdfs/20140423guidance.pdf50

i.e., December 31 , 2017, or December 31, 2020. Based on these factors, Cooper Station’s
modeled 1

- hour design value for its 50 km area of analysis, covering the entirety of Pulaski County, is 173.1 μg/m 3

, or 66 ppb . This modeled concentration is below the level of the 2010
SO 2 NAAQS.

However, i t is unclear in the documentation provided by Kentucky and the East Kentucky Power Cooperative whether Coo p er Station’s new allowable emission limit at Unit 1 will be in place and federally

- enforceable prior to final designation of the area around Cooper Station

. Furthermore, a s indicated above, the EPA would also need to evaluate the emission limit for its applicability for demonstrating compliance with the 1

- hour standard due to its identification as a
30

- day rolling average.

The EPA has determined that if the new PTE limit at Cooper Station’s Unit 1 is federally

enforceable prior to the promulgation of final air quality designations and is consistent with guidance on longer

- term average limits

, Cooper Statio n’s modeling parameters, assumptions and inputs may still not in compliance with the A gency’s Modeling TADs . A fter careful evaluation
of the Commonwealth ’s recommendation and supporting information, as well as all available
releva nt information , the EPA believes that the modeling for this Area should be updated. Specifically, the Commonwealth should provide modeling that uses PTE limits for both Units 1 and 2, or actual emissions from both units over a common three

- year period.

The EPA intends to designate the area around Cooper Station as unclassifiable for the 2010 SO 2 NAAQS. Specifically, the boundar y is comprised of the entirety of Pulaski County, Kentucky

. However, if the Commonwealth provides notification of the following to the EPA prior to the promulgation of the July 2, 2016 designation, the EPA may consider designating the entirety of Pulaski County as unclassifiable/attainment, provided that are no outstanding technical issues : 1) assurance that the Cooper Station ’s new PTE limit of 0. 165 lb SO 2 /mmBTU for Unit 1 is federally

- enforceable, and, as applicable, includes a longer term average limit that the EPA determines is comparatively stringent to a 1

- hour limit at the critical emission value ; 2) the modeling for Units 1 and 2 at t he facility are matched (e.g., PTE emissions or actual emissions over a common time period); and 3) the updated modeling shows that the new PTE limit on Unit
1 or modeled actual emissions will ensure attainment of the NAAQS

.

Based on all available informa tion, including the reasons discussed above, the EPA is unable at this time to determine whether the area is meeting or not meeting the NAAQS. At this time, our intended designations for the Commonwealth only apply to this area (Pulaski County) and the other area presented in this technical support document (Ohio County) . Consistent with the conditions in the March 2, 2015

, court

- ordered schedule, the EPA will evaluate and designate all remaining undesignated areas in Kentucky by either December 31, 2017 , or December 31, 2020.