1 Draft Technical Support Document

Georgia 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 nation al 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.

Georgia submitted updated recommendations on September 1 7 , 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 Georgia’s recommendations and identifies the counties or portions of counties in Georgia 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 e vidence and supporting information, or a combination of the above

.

Table 1. Georgia's Recommended and the EPA's Intended Designations

Area Georgia’s

Recommended
Area Definition Georgia’s

Recommended Designation The EPA’s

Intended Area
Definition The EPA’s Intended

Designation

Juliette, Georgia Monroe County

Bibb County Jones County Jasper County Butts County Lamar County Upson County
and
Crawford County Attainment Same as the
State’s
recommendation with the exception of Bibb County Unclassifiable/
At tainment

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 752

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 he 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 state’s
recommendation. If a state does not submit designation recommendatio ns, 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 120 day period to demonstrate why any proposed modification is inappropriat e.

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 wa s not yet prepared to issue designations.

Following the initial August 5, 2013 designations, three lawsuits were filed against the EPA in
different U.S. District Courts, alleging the a gency had failed to perform a nondiscretionary duty under the CAA by n ot 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 t he U.S.
District Court for the Northern District of California

. On March 2, 2015, the court entered the consent decree and issued an enforceable order for 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 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 violations of the
2010 SO 2 NAAQS and (2) areas that contain any stationary s ources that ha d not been announced

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 state implementation plan ( 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 Juliette Area was not designated nonattainmen t under the prior SO 2 NAAQS nor is it not meeting the requirements of a SIP Call under the prior NAAQS.3

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 January 1, 2010 had a capacity of over 5 megawatts and otherwise meets the emissions criteria, is excluded from the July 2, 2016 deadline if it had announced through a company public announcement, public utilities commission filing, consent decree, public legal settlement, final state or federal permit filing, or other similar means of communication, by March 2, 2015, that it will cease burning coal at that unit.

The last two deadlines for completing re maining 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 d eadlines. We expect this information to become available in time to help inform these 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 I

- X. This memorandum supersedes earlier desi gnation 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 intends to eva luate 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 th rough 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, “SO 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, violations 2 of the 2010 SO 2 NAAQS were only recorded in Chatham County , GA and no other monitored violations have been recorded in any other undesignated part of the state

. 3 Furthermore there are no air quality

2 Georgia early certified their 2015 1

- hour SO 2 a ir quality data for the Chatham County monitor (at Lanthorp & August Air Quality System ID: 13

- 051

- 100 2 on January 20, 2016. The EPA’s review of the 2013

- 2015 1

- hour SO 2 data i ndicates no violation of the 2010 SO 2 NAAQS. Therefore, the consent decree does not obligate the EPA to complete the designation for Chatham County. Instead, the EPA will designate t he area and all other previously undesignated areas in the s tate on a schedule consistent with the prescribed timing of the consent order, i.e., December 31, 2017, or December 31, 2020.

3 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 2013 and 2015. Absent complete, quality assured and4

monitors in Monroe County. In a ddition, there is one source 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 Georgia’s updated recommendations for the areas that we must designate

. The EPA also
discu sses any intended 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 reflect 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

a vailable 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 de cision 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 ar ea

– 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.

certified data for 2015, the analyses of applicable areas for the EPA’s intended designations will be in formed 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 that no violation of the NAAQS occurred between 2013 and 2015, the consent decree does not obligate the EPA to complete the designation. Instead, we may d esignate the area and all other previously undesignated areas in the state on a schedule consistent with the prescribed timing of the court order , i.e., by December 31, 2017, or December 31,
2020.5

11) Violating monitor

– an ambien t 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 50.6 Technical Analysis for the Juliette Area

Introduc tion

Plant Scherer is 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 Robert W. Scherer Power Plant (Plant Scherer ) emitted 42,349.16 tons of SO 2 , and
had an emissions rate of 0.372 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

. Plant Scherer is an electric power generation plant with four sub

- critical pulverized coal

- fired boilers

.

In its submission, Georgia recommended that the area surrounding Plant Scherer

, specifically the entirety of Monroe, Bibb, Jones, Jasper, Butts, Lamar, Upson and Crawford Counties

, be designated as unclassifiable/ 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 and characterization was performed using air dispersion m odeling software, i.e., AERMOD

, analyzing actual emissions

. After careful review of the s tate’s assessment, supporting documentation, and all available data, the EPA agrees , in part, that the area is attaining the standard, and intends to designate the maj ority of the state’s recommended area as
unclassifiable/attainment , i.e., Monroe, Jones, Jasper, Butts, Lamar, Upson, and Crawford
Counties . At this time, the EPA does not intend to designat e Bibb County; instead, the Agency will designate this county and all other remainin g undesignated areas of Georgia not addressed in
this TSD by either December 31, 2017, or December 31, 2020, consistent with the deadlines of
the final consent decree

.

Plant Scherer is located in central Georgia in the town of Juliette

, which is in the northeastern part of Monroe County. T he facility is located approximately 3 miles south of the center of Juliette, Georgia just north of Macon, Georgia and approximately 70 miles south of Atlanta, Georgia. Figure 1 below includes n earby emitters of SO 2 , the s tate’s recommended area for the
unclassifiable/attainment designation

, and the EPA’s intended designation for the Juliette A rea

.7

Figure 1. The EPA’s I ntended D esignation s for Plant Scherer and the Juliette Area

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

Detailed Assessment

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 dis persion model

 AERMAP: the terrain processor for AERMOD

 AERMET: the meteorological data processor for AERMOD8

 BPIPPRIME: the building input processor

 AERMINUTE: a pre

- processor to AERMET incorporating 1

- minute automated surface observation system ( ASOS ) win d data

 AERSURFACE: the surface characteristics processor for AERMET

 AERSCREEN: a screening version of AERMOD

The s tate used AERMOD version 14134 ( released May 14, 2014 ) , 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 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. As shown in F igure 2 below

, the 3

- km area surrounding Plant Scherer is predominantly rural. Therefore, the state determined that is was most appropriat e to run the model with rural dispersion coefficients.9

Figure 2 : Land Use Analysis Within 3 Kilometers of Plant Scherer

. Source: “ Modeling Report

Plant Scherer 1

- hour SO 2 NAAQS Modeling” prepared by AECOM for Georgia Power Company, July 2015.10

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 Scherer 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
Juliette A rea , the s tate evaluated offsite SO 2 sources within 70 km of the facility in any direction and determined that it was not necessary to includ e any offsite sources in order to adequately characterize air quality on the vicinity of Plant Scherer. This determination was based on the actual 2013 emissions at each facility and the distance of each facility from Plant Scherer

. Table 2 of the Septembe r 14, 2015, designations recommendations from the s tate of Georgia details the
results of this evaluation. In addition, Georgia Power Company Plant Branch, located 49 km to the east of Plant Scherer, was not included in the modeling because it ceased operations in 2015 and any impacts from this distant source are accounted for in the background concentration included with the modeling results

. The s tate determined that a receptor grid extending 5 0 km in all directions from Plant Scherer was appropriate in order to adequately characterize air quality from the facility. . The s tate 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 i n the area of analysis where maximum concentrations of SO 2 are expected.

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

 100 meter spacing from the center of the plant out to 2 km

 250 meter spacing from 2 kilometers out to 3 km

 500 meter spacing from 3 kilometers out to 10 km

 1,000 meter spacing from 10 kilometers out to 5 0 km

 Maximum concentrations were resolved to 100 meter spacing

The receptor network contained 1 5,550 receptors, and the network covered the following counties in Georgia: most of Monroe County, western Jones County, extreme southeastern Butts County, southwestern Jasper County and extreme northern Bibb County

.

Figures 3 and 4

, included in the state’s recommendation, show the s tate’s chosen area of analysis surrounding Plant Scherer , as well as the 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.11

Figure 3 : Juliette Area of Analysis . Source: “Modeling Report Plant Scherer 1

- hour SO 2 NAAQS Modeling” prepared by AECOM for Georgia Power Company, July 2015.

Red circles are placed in 10 km increments out to 50 km.12

Figure 4 : Receptor Grid for Juliette Area of Analysis . Source: “Modeling Report Plant Scherer

1

- hour SO 2 NAAQS Modeling” prepared by AECOM for Georgia Power Company, July 2015.

Modeling Parameter: Source Characterization

The s tate characterized the source(s) within the area of analysis in accordance with t he best practices outlined in the Modeling TAD. Specifically, the state used actual stack heights in conjunction with actual emissions

. The s tate also adequately characterized the source’s 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.

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.13

The EPA believes that continuous emissions monitor ing systems (CEMS) data provide acceptable historical emissions i nformation 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 o f 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, s tates 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 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, they may be calculated using the methodology in Table 8

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

As previously noted, the s tate included Plant Scherer and no other emitters of SO 2 within 5 0 km in the area of analysis

. The s tate evaluated offsite SO 2 sources within 70 km of Plant Scherer in any direction and determined that it was not necessary to include any offsite sources in order to adequately characterize air quality on the vic inity of Plant Scherer. This determination was based on the actual 2013 emissions at each facility and the distance of each facility from Plant Scherer

. T his distance was selected because the state believes that this area of analysis adequately represents the area where maximum concentrations of SO 2 are expected

. Ge orgia Power Plant
Branch in Putnam County located approximately 49 km northeast of Plant Scherer and 45 km from the Monroe County border reported emissions of 32,544 tons of SO 2 in 2014. According to
information available to the EPA 4 , all units at Plant Branch were permanently shutdown by April
2015 resulting in zero potential to emit

. Plant Branch wa s not explicitly included in the modeling analysis for Plant Scherer, but rather was considered in the background concentrations accounting for impacts from nearby sources including Plant Branch’s historic actual emissions

. Considering the distance from Plant Scherer and Monroe County border, and consideration of
cumulative impacts ca ptured 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 Juliette Area of analysis

.

Additionally, Graphic Packaging Macon Mill located in Bibb County emitted reported 254 tons
in 2013 and 620 tons in 2014 and is a major prevention of significant deterioration (PSD) source that Georgia did not explicitly include in the modeling analysis fo r Plant Scherer . This source

4 In September 2013, Georgia Power retired Plant Branch U nit 2 and as well as Units 1, 3, and 4 in April 2015. Georgia Power certified under penalty of law that the retirements are permanent in the Retired Unit Exemption (RUE) forms submitted to the EPA under the Acid Rain, CAIR, and CSAPR programs.14

was, however, considered in the calculated background concentration . This source is approximately 35 km from Plant Scherer, which is distant enough that its impacts would be significantly reduced in terms of overlapping with those of Plant Scherer shown in Figure 3

. Cherokee Brick and Title Company also located in Bibb County

, emitted 146.8 tons of SO 2 in
2014. The source is located app roximately 29.5 km from Plant Scherer and 17.6 km to Monroe County border . The source is also located 10.5 km from Jones County which is the nearest
county the EPA intends to designate as unclassifiable/attainment. Given that this source is far enough from Plant Scherer and Monroe County that impacts are reduced in terms of overlapping
with those of Plant Scherer EPA has no reason to believe, this source would cause or contribute
to a violation of the SO 2 NAAQS within the Juliette Area of analysis. Both sources are currently operating as major PSD sources in Bibb County and as such could potentially model impact s within the ir respective fenceline s

.

Plant Scherer is the only SO 2 source in Monroe County, Georgia emitting 100 tpy or more of
SO 2

. B ased on an analysis of actual emissions for sources within 5 0 km of Plant Scherer, n o other sources were determined by the s tate to have the potential to cause significant concentration gradient impacts within t he area of analysis. No other SO 2 emitting so urces within the area of analysis were found to emit over 6 tpy of SO 2 emissions including in Monroe County
based on 2014 actual emissions

. A ctual annual SO 2 emissions for Plant Scherer between 2012
and 2014 are summarized below.

Table 2 : Actual SO 2 Emissions Between 2012

– 2014 for Plant Scherer 5

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

2012 2013 2014

Plant Scherer 42,349.16 24,074.58 5,175.49

For Plant Scherer , the s tate used actual emissions from the most recent 3

- year data set, i.e., 2012

– 2014. Th e s e emissions data w ere obtained from CEMs

.

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 d esignations 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 proxi mity of the meteorological monitoring site to the area under consideration, 2) the complexity of terrain, 3) the exposure of the meteorological site, and 4) the period of time during which data are collected. Sources of meteorological data include National Weather Service (NWS) stations, site

- specifi c or onsite data, and other sources such as universities, Federal Aviation Administration, and military

stations.

5 Actual emissions data were obtained from CEMS and reflect the same emissions reported to the EPA ’s A ir
Markets Database.15

For the Juliette A rea of analysis, surface meteorology from the NWS station in Macon

, Georgia ( 4 4 km to the south ) , and coincident upper air observations from the NWS station in Peachtree City

, Georgia ( 80 km to the northwest ), were selected as best representative of meteorological conditions within the area of analysis.

The s tate used AERSURFACE version 14134 using data from the NWS station in Macon, Georgia, (located at latitude 32.6878 , long itude 83. 6544 ) to estimate the surface characteristics

of the ar ea of analysis. The s tate estimated values for 12 spatial sectors out to 1 km at a seasonal temporal resolution for average conditions. T he s tate 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 (som etimes referred to as “Zo” ). In the figure below, included in the s tate’s recommendation

, the

location of the Macon

, Georgia NWS station is shown relative to the Juliette A rea of analysis.16

Figure 5 : Juliette Area of Analysis and the Macon, Georgia NWS Station (Middle Georgia Regional Airport) and the Peachtree City NWS Station

. Source: “Modeling Report Plant Scherer

1

- hour SO 2 NAAQS Modeling” prepared by AECOM for Georgia Power Company , July 2015

.17

As part of its recommendation, the state provided the 3

- year surface wind rose for Macon, Georgia for the period 2012

- 2014

. In Figure 6 , the frequency and magnitude of wind speed and

direction are defined in terms o f from where the wind is blowing

. This wind rose shows that the predominant wind direction in Macon is from the west.

Figure 6 : Macon Georgia Cumulative Annual 3

- Year Wind Rose For 2012

- 2014

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 state followed the methodology and settings presented in the AERMOD implementation guide (09078) i n the processing of the raw meteor o logical data into an

AERMOD

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

Modeling Parameter: Geography and Terrain

The terrain in the area of an alysis is best described as gently rolling . 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 the United States Geological Survey National Elevation Database. Modeling Parameter: Background Concentrations of SO 218

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 Plant Scherer analysis, the
state chose to use the 2011

- 2013 1

- hour SO 2 design value for the Decatur, Georgia monitor. The
state determined t his monitor to be representative of background concentrations in the area. The background concentration for this area of analysis was determined by the state to be 30.3 micrograms per c ubic meter ( μg/m 3 ), or 11.6 ppb

, 6 and that value was incorporated into the final
AERMOD results provided by the state

.

The EPA has performed an additional analysis of available b ackground monitoring data in the area and has identified an ambient air monitor in Bibb County which has a 201 2

- 201 4 design
value of 1 5 ppb ( 39.3 μ g/m 3 ). The EPA has determined that the Bibb County monitor provides a more appropriate background concentrat ion for the analysis , due to its proximity to the area of analysis . Adding the Bibb County monitor background value to the 99 th percentile modeled
value of 98.24 μg/m 3 r esult s in a total SO 2 concentration of 1 37.54 μ g/m 3 ( v ersus the SO 2 t otal

conc en tration provided by the state of 128.54 μ g/m 3 using the Decatur background value)

Summary of Modeling Results

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

T able 3

.

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

.19 Table 3 : AERMOD Modeling Parameters for the Juliette Area of Analysis

Plant Scherer Analysis

AERMOD Version 14134 Dispersion Characteristics Rural

Modeled Sources 1

Modeled Stacks 4

Modeled Structures 6

Modeled Fencelines 0 Total receptors 1 5,550 Emissions Type Actual

Emissions Years 2012

- 2014 Meteorology Years 2012

- 2014 Surface Meteorology Station Macon, Georgia Upper Air Meteorology Station Peachtree City, Georgia Methodology for Calculating Background SO 2 Concentration 1 st tier

– monitored design
value Calculated Background SO 2 Concentration 1 5 ppb ( 39.3 μg/m 3 )

The results presented below in T able 4 show the magnitude and geographic location of the highest predicted modeled concentration based on actual emissions

.

Table 4 : Maximum Predicted 99th Percentile 1

- Hour SO 2 Concentration in the Juliette Area of Analysis Based on Actual Emissions

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

UTM East (meters) UTM North

(meters) Modeled (including

background) NAAQS
99th Percentile
1

- Hour Average 2012

- 2014 234 0 00 3659550 137.54 196.5* *Equivalent to the 2010 SO 2 NAAQS set at 75 ppb

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

- hour average concentration within the chosen modeling domain is 98.21 μg/m 3 , or 37.5 ppb. When the representative background value from the Bibb County monitor is added to the modeled value, the total

concentration is 137.54 μg/m 3 , or 52.5 ppb

. This modeled concentration is based on actual

emissions from Plant Scherer . Figure 7 below was included as part of the state’s recommendation, and indicates that the predicted value occurred approximately 3. 6 kilometers

west of Plant Scherer . The state’s receptor grid is shown in F igure 4

.20

Figure 7 : Maximum Predicted 99 th Percentile 1

- Hour SO 2 Concentrations in the Juliette Area of Analysis Based on Actual Emissions. Source: Georgia’s “ Additional Plant Scherer Dispersion

Modeling for the SO 2 NAAQS, February 2, 2016”

Jurisdictional Boundaries:

Once the geographic area of analysis associated with Plant Scherer and background

concentration is determined, existing jurisdictional boundaries are considered for the purpose of informing our intended unclassifiable/attainment area, specifically with respect to clearly defined legal boundaries. Georgia’s designation recommendations included Monroe Cou nty and seven

additional counties ( Bibb, Jones

, Jasper

, Butts, Lamar, Upson , and Crawford) based on a modeling analysis with a 50 km radius modeling domain centered around Plant Scherer. Georgia

evaluated offsite SO 2 sources within 70 km of Plant Scherer facility in any direction and determined that it was not necessary to include any offsite sources in order to adequately characterize air quality on the vicinity of Plant Scherer. This determination was based on the

a ctual 2013 emissions at each facility and the distance of each facility from Plant Scherer

. Plant Scherer is the only SO 2 source in Monroe County, Georgia emitting 100 tpy or more of
SO 2 . Of the seven additional counties Georgia recommended, six ha ve no stationary sources that21

emitted SO 2 over 6 tpy (based on 2014 actual emissions )

. 7 Therefore, these sources have no potential to cause significant concentration gradient impacts within the area of analysis. EPA has
reason to be lieve there are no additio nal sources in areas adjacent to our intended area that are likely to cause or contribute to a violation of the NAAQS in the area of analysis.

Bibb County , includes two SO 2 emitting sources that emitted over 100 tpy of SO 2 in 2014. Graphic Packaging Macon Mill

, considered a major PSD stationary source

, is located approximately 35 km from Plant Scherer and 21 km from Monroe County border , which is distant enough that its impacts would be significantly reduced in terms of overlapping with those
of Plant Scherer shown in Figure 3

. The source showed 254 tpy in 2013, and reported 620 tpy in
2014 and was not include d in the state’s modeling analysis due to it distance from Plant Scherer
relative to its emissions . This source ’s 2012

- 2014 emissions were however considered in the
calculated background concentrations

. The EPA has reason to believe that this source would not cause significant concentration gradient imp acts within the area of analysis.

Additionally, Cherokee Brick and Title Company also located in Bibb County, emitted 146.8
tons of SO 2 in 2014. The source is located approximately 29.5 km from Plant Scherer and 17.6 km to Monroe County border. The source is also located 10.5 km from Jones County which is the nearest county the EPA intends to designat e as unclassifiable/attainment. Given the distance
from Plant Scherer and Monroe and Jones Counties these two sources are distant enough that impacts are reduced in terms of overlapping with those of Plant Scherer . Therefore, the EPA has
no reason to belie ve, these two sources would cause or contribute to a violation of the SO 2 NAAQS within the Juliette Area of analysis. However, even though GA EPD’s 50 km model
do main extends into Bibb C ounty, both sources are currently o perating major PSD source s with
the potential to cause concentration gradient impacts within Bibb County near the vicinity of the
source’s fence line when considering PSD permitting . Therefore the EPA has reason to believe that designations for Bibb County, at this time, should be de ferred . C onsistent with the conditions in the March 2, 2015 court

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

.

The EPA notes that Georgia Power’s Plant Branch in Putnam County , located approximately 45,
22 , and 12 km from Monroe, Jasper and Jones c ounty border s respectively reported 201 4
emissions of 32

, 544.7 tons

. However

, operations at Plant Brach had ceased by April 2015

. Specifically, U nit 2 was retired in September 2013 and Units 1, 3, and 4 were retired in Ap ril
2015 and therefore the facility’s potential to emit SO 2 emissions is effectively zero

. Furthermore,
the 2012

- 2014 background concentration 39.3 μg/m 3 or 15 ppb accounts for cumulative impact s from nearby source s including Plant Branch’s historic actual emissions. As a result, 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 NAAQS in the Monroe area of analysis or other neighboring
counties.

The EPA believes that our intended unclass ifiable/attainment area, consisting of Monroe County,

GA

, and surrounding counties of Jones, Jasper, Butts, Lamar, Upson and Crawford, is comprised

7 Unless otherwise noted, 2014 annual emissions data were obtained via the Emissions Inventory System (EIS) gateway, 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/

.22

of clearly defined legal boundaries, and we find this boundar y to be a suitably clear basis for defining our intended unclassifiable/ attainment designation. T he consent decree directs the EPA to designat e the area around Plant Scherer, which may be confined only t o the county where the facility is located, i.e., Monroe County , provided the plant’s impacts were of such limited scope

. However, we has reason to believe that the stat e has adequately addressed air quality in the

counties that we intend to designate as unclassifiable/attainment . Specifically, Georgia’s modeling analysis extending 50 km from Plant Scherer indicates compliance with the NAAQS in the additional counties included in our intended designation , and the EPA has determined that

th ere are no additional sources in areas adjacent to our intended area that are likely to cause or contribute to a violation of the NAAQS in the area of analysis . Therefore, the EPA intends to designate the majority of the state’s recommended area as u nclassifiable/attainment, but

reiterates that we are deferring the designation for Bibb County at this time

.

Other Relevant Information

The EPA received air dispersion modeling results from the Sierra Club, in which the submitter

asserts that SO 2 emissions from Plant Scherer, when considered alone or in tandem with other local sources, are causing a violation of the NAAQS. A discussion of the modeling performed by

the Sierra Club follows below, with references to the EPA’s Modeling TAD as appropri ate. The Sierra Club modeling was performed using the mo st recent version of AERMOD, AERMET, and AERMINUTE, with data provided to the Sierra Club by regulatory air agencies

and through other publicly

- available sources as documented below. Sierra Club state d that the analysis was conducted in adherence to all available EPA guidance for evaluating source impacts

on attainment of the 1

- hour SO 2 NAAQS via aerial dispersion modeling. Georgia evaluated Sierra Club’s modeling and provided a n explanation in their modeling report why the conservative assumptions Sierra Club used in the modeling were not appropriate. The following text from Georgia ’s revised recommendation summarizes the inappropriate assumptions made in the Sierra Club modeling:

“

... The modeling presented here appropriately matched emissions with the appropriate stack. However, the modeling submitted by the Sierra Club did not. The Si erra Club modeling modeled all emissions (scrubbed and not scrubbed) out of the scrubber stack. Clearly, this is not appropriate and will lead to unrealistically high modeled design

values since uncontrolled SO 2 emissions are modeled out of the shorter and cooler (less plume rise) stacks. As a result, the Sierra Club modeling shows modeled violations of the

SO 2 NAAQS while the Georgia Power modeling shows that the modeled design value is 36% below the NAAQS.”

– Excerpt from Pages 3

- 4 of Georgia August 24, 2 015 Modeling Summary Document

The EPA agrees with Georgia’s assessment of the Sierra Club’s modeling. Emissions that have

been scrubbed will be emit ted from one of the shorter 847 feet tall stacks. Non

- scrubbed

emissions will e mit from one of the taller 1

, 000 feet tall bypass stacks. The Sierra Club assumed that all emissions (scrubbed and non

- scrubbed) are emitted from the shorter scrubber stacks (847 feet). This would not properly represent stack conditions when the scrubber is either not installed

or tur ned off and the emissions are being vented to the taller bypass stack. As indicated in the23

excerpt above, if any portion of the actual emissions for Plant Scherer are not modeled from the appropriate stack, the difference in stack height and exit temperatu re could cause the model to predict reduced atmospheric dispersion therefore resulting in over

- predictions of surface level

ambient concentrations. Therefore, having reviewed Georgia’s modeling, Sierra Club’s modeling

, and G eorgia ’s assessment , the EPA preliminarily agrees with Georgia ’s assessment

.

Conclusion

The EPA considered modeling submitted by both the state of Georgia and Sierra Club and determined that Georgia’s assumptions and input parameters regarding the behavior of emissions through the scrubbers was more representative of actual operations at Plant Scherer and resulting

SO 2 emissions

.

Based on the a ir quality characterization conducted within the Juliette Area of analysis in
accordance with the EPA’s Modeling TAD

, the s tate concluded that Monroe, Bibb, Jones, Jasper, Butts, Lamar, Upson and Crawford Counties be designated as unclassifiable/ attainment

. This recommendation is based on Georgia’s assessment that there were no large SO 2 emitting sources beyond the 5 0 km analysis a rea that could impact the area

. As previously discussed, all units at Georgia Power’s Plant Branch in Putnam County have ceased operation, and therefore the EPA does not expect emissions from this facility to cause or contribute to a future violation
of the NAAQS in our intended unclassifiable/attainment area.

After careful evaluation of the s tate’s recommendation and supporting information, as well as all available relevant information, the EPA intends to designate the area around Plant Scherer as uncl assifiable/attainment for the 2010 SO 2 NAAQS. Specifically, the boundaries are comprised
of Monroe, Jones, Jasper, Butts, Lamar, Upson and Crawford Counties

.

At this time, our intended designations for the state only apply to this area and the other area s presented in this technical support document. The EPA does not intend on designating Bibb County at this time. Instead, c onsistent with the conditions in the March 2, 2015 court

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