1

Draft Technical Support Document

North Carolina

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

Summary

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

Agency (EPA, or the Agency) must designate areas as either “unclassifiable,” “attainment,” or 

“nonattainment” for the 2010 one-hour sulfur dioxide (SO2) primary national ambient air quality 

standard (NAAQS). The CAA defines a nonattainment area as one that does not meet the 

NAAQS or that contributes to a violation in a nearby area. An attainment area is defined as any 

area other than a nonattainment area that meets the NAAQS. Unclassifiable areas are defined as 

those that cannot be classified on the basis of available information as meeting or not meeting the 

NAAQS.

North Carolina submitted updated recommendations on September 18, 2015, ahead of a July 2, 

2016 deadline for the EPA to designate certain areas. This deadline established by the U.S. 

District Court for the Northern District of California is the first of three deadlines established by 

the court for the EPA to complete area designations for the 2010 SO2 NAAQS. Table 1 below 

lists North Carolina’s recommendations and identifies the counties or portions of counties in 

North Carolina 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. North Carolina’s Recommended and the EPA’s Intended Designations

Area

North Carolina’s 

Recommended 

Area Definition

North Carolina’s 

Recommended 

Designation

The EPA’s Intended 

Area Definition

The EPA’s 

Intended 

Designation

Brunswick 

County, 

North 

Carolina

All Townships 

within Brunswick 

County and New 

Hanover County

Attainment

All Townships 

within Brunswick 

County except for 

Northwest Township

Unclassifiable/

Attainment

Background

On June 3, 2010, the EPA revised the primary (health-based) SO2 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 Federal Register on June 22, 2010 (75 FR 35520) and is 

codified at 40 CFR 50.17. The EPA determined this is the level necessary to protect public health 

with an adequate margin of safety, especially for children, the elderly and those with asthma. 

These groups are particularly susceptible to the health effects associated with breathing SO2. The 

two prior primary standards of 140 ppb evaluated over 24 hours, and 30 ppb evaluated over an 
2

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 SO2, 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 governors must submit their recommendations for designations and 

boundaries to the 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 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 120 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 SO2 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 designations.

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. 

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 designations 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 SO2 NAAQS and (2) areas that contain any stationary sources that had not been announced 

as of March 2, 2015 for retirement and that according to the EPA’s Air Markets Database 

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

an annual average emission rate of at least 0.45 pounds of SO2 per one million British thermal 

units (lbs SO2/MMBtu). Specifically, a stationary source with a coal-fired unit that as of January 

1, 2010 had a capacity of over 5 megawatts and otherwise meets the emissions criteria, is 

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

 

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. Brunswick County, North Carolina is not such an area.
3

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

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

will cease burning coal at that unit. 

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

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

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

these designation deadlines. The EPA expects this information to become available in time to 

help inform these subsequent designations. These requirements were promulgated on August 21, 

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

 

Updated designations guidance was issued by 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 designation 

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

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

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

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

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

results; 2) Emissions-related data; 3) Meteorology; 4) Geography and topography; and 5) 

Jurisdictional boundaries. This guidance was supplemented by two technical assistance 

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

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

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

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

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

in December 2013.

Based on ambient air quality data collected between 2012 and 2014, no monitored violations of 

the 2010 SO2 NAAQS have been recorded in any undesignated part of the state.2 However, 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 North Carolina’s updated recommendations for the 

area that the EPA must designate. The EPA also discusses any intended modifications from the 

State’s recommendation based on all available data before us. 

 

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

decree directs the EPA to evaluate data collected between 2013 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 SO2 NAAQS 

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

by April 19, 2016 to 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, 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 court order, i.e., by December 31, 2017, or December 

31, 2020. 
4

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

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

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

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

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

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

indicates whether the area is violating the NAAQS.

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

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

designation reflects 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 

available information whether or not it meets the 2010 SO2 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 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. 

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 has recommended 

that the EPA designate as unclassifiable/attainment.

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

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

analysis conducted in accordance with Appendix T of 40 CFR part 50. 
5

Technical Analysis for the CPI Southport – Brunswick County Area

Introduction

The Brunswick County, North Carolina area contains a stationary source that according to the 

EPA’s Air Markets Database emitted in 2012 either more than 16,000 tons of SO2 or more than 

2,600 tons of SO2 and had an annual average emission rate of at least 0.45 lbs SO2/MMBtu. As 

of March 2, 2015, this stationary source had not met the specific requirements for being 

“announced for retirement.” Specifically, in 2012, the Capital Power Incorporated (CPI) USA

North Carolina LLC – Southport Plant (CPI Southport) emitted 2,923 tons of SO2 and had an 

average emissions rate of 0.74 lbs SO2/MMBtu. Pursuant to the March 2, 2015 court-ordered 

schedule, the EPA must designate the area surrounding the facility by July 2, 2016. CPI operates 

two electric generating units (EGUs) at the CPI Southport Cape Fear facility that are permitted to 

combust a variety of solid fuels, including coal, woody biomass fuels, and tire derived fuel. The 

two EGUs are each comprised of three (3) boilers, operating at 223 MMBtu/hr. Each‐boiler EGU 

exhausts from a single stack.

In its submission, North Carolina recommended that the area surrounding the CPI Southport 

facility, specifically the entirety of Brunswick and New Hanover Counties, 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 SO2 are expected. This assessment and characterization was performed using 

air dispersion modeling software, i.e., AERMOD, analyzing actual emissions from the CPI 

facility.

3 The assessment and characterization was originally conducted by Trinity Consultants 

and prepared for CPI Southport. North Carolina then reviewed and submitted the information to 

the EPA.4 After careful review of the state’s assessment, supporting documentation, and all 

available data, the EPA agrees that most of Brunswick County is attaining the standard, and

intends to designate as unclassifiable/attainment all the townships within the county except for 

the Northwest township which captures the DAK Americas, LLC facility. While North Carolina 

has indicated that DAK Americas, LLC is shutdown as of September 2013, the facility still has 

an active operating permit and has a total facility-wide potential to emit of 10,324 tpy for SO2 on 

a rolling 12-month basis. Before shutdown, the facility was emitting approximately 1,442 tpy of 

actual SO2 emissions. In fact, the operating permit was renewed on November 5, 2013, and does 

not expire until October 31, 2018. The EPA is, not yet issuing an intended designation for New 

Hanover County or the Northwest Township (i.e., the location of DAK Americas, LLC) at this 

time. Instead, the Agency will designate the aforementioned areas and all other undesignated 

 

3 The modeling analysis submitted by state of North Carolina was performed by Trinity Consultants at the request of 

CPI. Throughout this document, the EPA will refer to the state of North Carolina when discussing modeling 

information provided to support their designation recommendation.

 

4 Throughout this document, the state of North Carolina will be referred to as having assessed air quality in the area 

because the state agreed with CPI Southport’s air quality assessment and characterization of the area of 

analysis,(with minor modifications) officially submitting the report to the EPA to support their designation 

recommendation. 
6

areas of North Carolina by either December 31, 2017, or December 31, 2020, consistent with the 

deadlines in the final consent decree.

The CPI Southport facility is located on the coast in southeastern North Carolina in the 

southeastern portion of Brunswick County. As seen in Figure 1 below, the facility is located 

approximately 2 kilometers (km) north-northeast of the center of Southport and 2.5 km due west 

of the Atlantic Ocean. Also included in the figure are nearby emitters of SO2, the state’s 

recommended area for the attainment designation, and the EPA’s intended

unclassifiable/attainment designation for the Brunswick County Area.

Figure 1. The EPA’s intended designation for Brunswick County, North Carolina

The discussion 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 guidance, as appropriate.
7

Detailed Assessment

Model Selection and Modeling Components

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

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

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

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

components:

 AERMOD: the dispersion model

 AERMAP: the terrain processor for AERMOD

 AERMET: the meteorological data processor for AERMOD

 BPIPPRIME: the building input processor 

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

observation system (ASOS) wind data

 AERSURFACE: the surface characteristics processor for AERMET

 AERSCREEN: a screening version of AERMOD

The state used AERMOD version 15181, and a discussion of the individual components will be 

referenced in the corresponding discussion that follows as appropriate. The impact assessment 

provided to the state by the CPI Southport facility was conducted using AERMOD version 

14134.

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 within 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. The state determined that the surrounding land use was 

more than 50 percent rural based on analysis of land use types within a 3 km radius from the 

center of the facility. Based on this analysis, the state established that is was most appropriate to 

run the model with rural dispersion coefficients.

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 CPI Southport facility is to determine the extent of the area of analysis, i.e., 

receptor grid. Considerations presented in the Modeling TAD include but are not limited to: the 

location of the SO2 emission sources or facilities considered for modeling; the extent of 

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

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

the Brunswick County Area, North Carolina identified SO2 emission sources in Brunswick and 
8

New Hanover counties and evaluated 2013 actual emissions from the identified facilities based 

on a 10 km5area of analysis but the modeling domain extends up to 30 km. The state determined 

that this was an appropriate distance to characterize air quality from CPI Southport facility and 

other nearby sources which may have a potential impact in the area of analysis. Given the 

emissions levels and distance from the CPI Southport facility the state determined that most of 

the emissions sources would not interfere with attainment of the SO2 NAAQS.

The state also identified two large SO2 emission emissions sources DAK Americas, LLC in 

Brunswick County and Duke Energy Progress, LLC - L.V. Sutton in New Hanover County but 

did not model these sources because according to the North Carolina both sources have 

shutdown operations thereby indicating a zero level for potential to emit (PTE). More detail on 

these two sources is provided below.

DAK Americas, LLC is located in the northeast portion of Brunswick County (within the 

Northwest Township) and is approximately 42 km from CPI Southport, and less than 2 km from 

the New Hanover County border. According to press releases and information obtained from the 

state, DAK Americas, LLC was shutdown in September 2013, ceasing all combustion operations 

and demolishing its units. However, the operating permit has not been rescinded, and in fact, was 

renewed November 5, 2013, and does not expire until October 31, 2018. Therefore, the 

shutdown is not considered permanent and enforceable for purposes of designations because the 

source still has a potential to emit, although some modification to the facility may be necessary.

The source has a total facility-wide potential to emit of 10,324 tpy for SO2 on a rolling 12-month 

basis. The source reported emissions of 1,442 tons in 2012 and 1,149 tons in 2013, and no SO2

emissions were reported in 2014. 

Duke Energy Progress, LLC - L.V. Sutton Electric Plant in New Hanover County (east of 

Brunswick) is located approximately 38 km from CPI Southport and less than 1 km from the 

Brunswick County border. The source’s three coal fired units were retired in November 20136as 

a result of the operation of a new, gas-fired combined-cycle unit. The source reported 32 tons of 

actual SO2 emissions in 2014.

For the Brunswick County Area, the state decided to include two other sources of SO2 emissions 

(i.e., in addition to the source that meets the threshold in the consent decree for the July 2, 2016, 

designations) in the modeling analysis because of the SO2 emissions from these sources and 

close proximity to the CPI Southport facility (less than 2 km). These two sources include: Archer 

Daniels Midland (ADM) and Duke Energy Progress Brunswick Nuclear Plant. The grid receptor 

spacing for the area of analysis chosen by the state is as follows:

The grid spacing for the impact assessment conducted by the CPI Southport facility and 

submitted to the state was:

 25-meter resolution about the CPI Southport facility and ADM facilities

 

5 North Carolina referenced the EPA’s guidance entitled “Additional Clarification Regarding Application of 

Appendix W Modeling Guidance for the 1‐hour NO2 National Ambient Air Quality Standard.”

6 See https://www.duke-energy.com/power-plants/coal-fired/sutton.asp
9 

 100-meter resolution from the fence line to a distance of 2 km 

 500-meter resolution from a distance of 2 to 10 km

 1,000-meter resolution from a distance of 10 to 30 km 

All maximum impacts were modeled with grids of 100-meter resolution. 

The receptor network contained 4,829 receptors, covered the southeastern portion of Brunswick 

County and the southern portion of New Hanover County. The state indicated that their ambient 

impact assessment, and the separate analysis conducted by the CPI Southport facility, followed 

the TAD guidance. The EPA agrees with the state’s assessment with the exception of the 

potential exclusion of specific sources and the extent of the boundary. 

Figures 2 and 3, included in the state’s recommendation, show an aerial view of the CPI South 

facility and the ADM facility 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 

Figure 2: Brunswick County Area of Analysis Source: CPI USA North Carolina, Southport 

Facility 1-Hour S02 NAAQS Modeling Analysis prepared by Trinity Consultants, June 20, 2015. 
10

Figure 3: Receptor Grid for the Brunswick County Area of Analysis. Source: CPI USA North 

Carolina, Southport Facility 1-Hour S02 NAAQS Modeling Analysis prepared by Trinity 

Consultants, June 20, 2015.

Modeling Parameter: Source Characterization

The state generally characterized the sources within the area of analysis in accordance with the 

best practices outlined in the Modeling TAD. Specifically, the state used actual stack heights in 

conjunction with actual emissions. The state also adequately characterized the included 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.

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 

PTE or allowable) emissions rate.

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

acceptable historical emissions information, when it is available, and that these data are available 
11

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 keyword EMISFACT. When choosing 

one of these methods, the EPA believes that detailed throughput, operating schedules, and 

emissions information from the impacted sources should be used. 

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

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

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

consent decree, or implemented other federally-enforceable mechanisms and control 

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

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

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

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

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

“Guideline on Air Quality Models.” 

As previously noted, the state included the CPI Southport facility and 2 other emitters of SO2

(ADM and Duke Energy Brunswick Nuclear Plant both of which are less than 2 km from 

CPI)within the 10 km area of analysis with the modeling domain extending up to 30 km in all 

directions. This distance and these facilities were selected because the state believes that this area 

of analysis adequately represents the area where maximum concentrations of SO2 are expected 

and adequately includes the sources which might contribute to those concentrations. No other 

sources beyond 30 km were determined by the state to have the potential to cause significant 

concentration gradient impacts within the area of analysis. According to North Carolina, two 

sources DAK Americas in Brunswick County and Duke Energy Progress, LLC - L.V. Sutton 

Electric Plant in New Hanover have ceased operations, are officially shutdown and were not 

included in the modeling analysis. 

DAK Americas, LLC, Cape Fear facility is located in the northeast portion of Brunswick County 

and is approximately 42 km from the CPI Southport facility, and less than 2 km from the New 

Hanover County border (within the Northwest Township). The source reported emissions of 

1,442 tons in 2012 and 1,149 tons in 2013, and no SO2 emissions were reported in 2014. DAK

Americas, LLC was not included in the modeling analysis nor were its 2012-2014 actual 

emissions included in the background concentration since the calculation only accounted for a 

design value for year 2014. According to press releases and information obtained from the state,

DAK Americas, LLC was shutdown in September 2013, ceasing all combustion operations 

including the demolition of its units but has not rescinded its operating permit. However, the 

facility’s title V permit was renewed in in November 5, 2013, and is valid through October 31,

2018. The source has a total facility-wide potential to emit of 10,324 tpy for SO2 on a rolling 12-

month basis.

Even though DAK Americas is located 42 km from the CPI Southport facility which is distant 

enough that it would not potentially impact the area of analysis, it could, however, potentially 

impact the northeast portion of Brunswick County as well as portions of New Hanover County
12

because of an open operating permit. Based on this information, the EPA has reason to believe 

the shutdown may not be permanent and enforceable for purposes of designations because the 

source still has a potential to emit, although modification to the facility may be necessary. This 

potential to emit could result in concentration gradients in portions of Brunswick and New 

Hanover Counties to cause a violation of the NAAQS.

Duke Energy Progress, LLC - L.V. Sutton Electric Plant in New Hanover County (east of 

Brunswick) is located approximately 38 km from the CPI Southport facility and less than 1 km 

from the Brunswick County border. The sources three coal fired units were retired were retired in 

November 20137 as a result of the operation of a new, gas-fired combined-cycle unit. The source 

reported 32 tons of actual SO2 emissions in 2014. The EPA notes additional sources in nearby 

counties bordering Brunswick including International Paper – Riegelwood Mill facility in 

Columbus County, approximately 3.6 km west of the Brunswick County border. This facility 

emitted 1,200 of SO2 according to the 2014 actual emissions. The EPA observes that the 

predominant wind pattern in the area blows from either the southwest or the northeast, and 

therefore the impacts from International Paper are not likely to influence the area of modeled 

maximum concentration from the CPI Southport facility. Additionally, the modeling analysis for 

CPI Southport indicates that the maximum predicted concentrations of SO2 from the 3 facilities 

in the area of analysis are within 600 m of CPI Southport. Based on available information, the 

EPA does not have reason to believe that the emissions from International Paper combined with 

the distance to the county border are likely to cause or contribute to a violation of the NAAQS in 

Brunswick County. 

Wilbara, LLC located in New Hanover County is located approximately 41. 5 km from CPI 

Southport and 3 km the Brunswick County border(shortest distance) and 119 tons of actual 

emissions in 119. Considering the source’s emissions, distance to the area of analysis and 

predominant wind direction in the area from blowing from either the southwest or the northeast,

the EPA has reason to believe that emissions from this source will not cause concentration 

gradients within the area or analysis or portions of Brunswick and New Hanover Counties.

Other than the two sources included in the modeling analysis, the EPA is not aware of any other 

SO2 emitting sources in Brunswick County emitting over 100 tpy according to 2014 actual 

emissions. Furthermore, according to the review of 2014 actual emissions, there are no other 

sources emitting over 50 tpy or more of SO2 (other those previously specified) that border

Brunswick County (i.e., Columbus, Pender, New Hanover and Horry County, South Carolina). 

The EPA has no reason to believe that these sources would cause or contribute to a violation of 

the NAAQS in the area of analysis or Brunswick County.

The facilities in the area of analysis and their associated annual actual SO2 emissions between 

2012 and 2014, or most recently available actual emissions data, are summarized in Table 2

below.

 
13

Table 2: Actual SO2 Emissions Between 2012 – 2014 from Facilities in the Brunswick County 

Area of Analysis

Facility Name

SO2 Emissions (tons per year (tpy))

2012 2013 2014

CPI Southport82922.749 3564.7 4089.8

2014 Emissions(tpy)

9

ADM 1.36

Duke Energy 

Brunswick 

Nuclear Plant 1.9

For the CPI Southport facility in the area of analysis, the state used actual emissions from the 

most recent 3-year data set, i.e., 2012 – 2014. These emissions data were obtained from CEMS.

For ADM in the area of analysis, the state used the highest actual 1-hour emissions rate from the 

2014 emissions inventory data.

For Duke Energy Brunswick Nuclear Plant in the area of analysis, SO2 emissions occur on an 

intermittent basis during testing and operation of the emergency generators and mitigation 

pumps. The facility-wide total hourly emissions, based on the 2012 – 2014 emissions inventory, 

were conservatively assumed to be emitted every hour of each year.

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 of 

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

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

data, and other sources such as universities, Federal Aviation Administration, and military 

stations.

For the Brunswick County Area of analysis, surface meteorology from the NWS station in 

Wilmington, North Carolina, approximately 37 km to the north-northeast, and coincident upper 

air observations from the NWS station in Newport, North Carolina, approximately 140 km to the 

 

8 Actual emissions data for units at CPI Southport were obtained from EPA’s Air Markets Database.

9 The 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/.
14

northeast were selected as best representative of meteorological conditions within the area of 

analysis. These data were recommended by the state for all facilities in Brunswick County. The 

most recent years of data (2010 – 2014) were used. Note that the CPI Southport-provided impact 

analyses were performed for both the 3-year period (2012 – 2014) to match the monitored design 

value as well as the 5-year period (2010 – 2014) to determine the modeled design value.

In the Figure 4 below, generated by the EPA, the location of the Wilmington, North Carolina

NWS station is shown relative to the Brunswick County Area of analysis.
15

Figure 4: The Brunswick County Area of Analysis and the Wilmington, North Carolina NWS 
16

A three-year surface wind rose for Wilmington, North Carolina is depicted in Figure 5. In this 

figure, the frequency and magnitude of wind speed and direction are defined in terms of where 

the wind is blowing from. As shown on the wind rose, the predominant winds blow from the 

southwest and south-southwest primarily at mid-level speeds from 2 to 9 meters/second (m/s). 

Also, winds blow from the North-northeast a significant amount of time. 

Figure 5: Wilmington, North Carolina Cumulative Annual Wind Rose for Years 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 EPA’s 

Modeling TAD in the processing of the raw meteorological data into an AERMOD-ready format.

WRPLOT View - Lakes Environmental Software

WIND ROSE PLOT:

Station #13748 - WILMINGTON/NEW HANOVER COUNTY, NC 

COMMENTS:

Created by Rick Gillam

EPA Region 4

11/17/15

COMPANY NAME:

MODELER:

DATE:

11/18/2015

PROJECT NO.:

NORTH

SOUTH

WEST EAST

2%

4%

6%

8%

10%

WIND SPEED 

(m/s)

 >= 11.1

 8.8 - 11.1

 5.7 - 8.8

 3.6 - 5.7

 2.1 - 3.6

 0.5 - 2.1

Calms: 21.03%

TOTAL COUNT:

26272 hrs.

CALM WINDS:

21.03%

DATA PERIOD:

Start Date: 1/1/2012 - 01:00

End Date: 12/31/2014 - 23:00

AVG. WIND SPEED:

3.14 m/s

DISPLAY:

 Wind Speed

Direction (blowing from)
17

Modeling Parameter: Geography and Terrain

The terrain in the area of analysis is best described as relatively flat and not of significance in the 

modeling analysis. 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 SO2

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

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

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

monitored concentrations by hour of day and season or month. For the Brunswick County Area 

of analysis, the state chose a representative background concentration from the SO2 ambient 

monitor located in New Hanover County for the year 2014. The background concentration for 

this area of analysis was determined by the state to be 7.9 micrograms per cubic meter (μg/m3), 

or 3.0 ppb,

10 which is the 99th percentile value from the monitor in 2014. This background 

concentration value was added into the final AERMOD modeling results. This was the same 

background concentration selected for the impact assessment conducted by the CPI Southport

facility.

Summary of Modeling Results

The AERMOD modeling parameters for the Brunswick County Area of analysis are summarized 

below in Table 3.

 

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

approximately 2.62 μg/m3.
18

Table 3: AERMOD Modeling Parameters for the Brunswick County Area of Analysis

Brunswick County Area of Analysis

AERMOD Version 15181

Dispersion Characteristics Rural

Modeled Sources 3

Modeled Stacks 10

Modeled Structures unavailable

Modeled Fencelines 3

Total receptors 4,829

Emissions Type Actual

Emissions Years 2012 - 2014

Meteorology Years 2012 - 2014

Surface Meteorology Station Wilmington, North Carolina

Upper Air Meteorology Station Newport, North Carolina

Methodology for Calculating 

Background SO2 Concentration 1

st tier 

Calculated Background SO2

Concentration 7.9 μg/m3

The results presented below in Table 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 SO2

Concentration in the Brunswick County Area of Analysis Based on Actual Emissions

Averaging Period Data Period

Receptor Location SO2 Concentration (μg/m3

)

UTM/Latitude UTM/Longitude Modeled (including 

background) NAAQS

99th Percentile 

1-Hour Average 2012-2014 221003.5 3759899.6 191.2 196.5*

*Equivalent to the 2010 SO2 NAAQS set at 75 ppb

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

within the chosen modeling domain is 191.2 μg/m3, or 70.1 ppb. This modeled concentration 

included the background concentration of SO2, and is based on actual emissions from the 

facilities. Figure 6 generated by the EPA, indicates that the predicted value occurred 

approximately 600 meters west of the CPI Southport facility.
19

Figure 6: Maximum Predicted 99th Percentile 1-Hour SO2 Concentrations in the 

Brunswick County Area of Analysis Based on Actual Emissions

Jurisdictional Boundaries:

Once the geographic area of analysis associated with the CPI Southport facility, other nearby 

sources, and background concentration was determined, existing jurisdictional boundaries were

considered for the purpose of informing our intended unclassifiable/attainment area, specifically 

with respect to clearly defined legal boundaries. The state recommended attainment for 

Brunswick and New Hanover County requesting designations at the township level due to the 

relatively short averaging time of the 2010 SO2 NAAQS and recommended an attainment 

designation for all townships within Brunswick and New Hanover Counties.

The EPA notes that DAK Americas, LLC, located approximately 42 km north of CPI Southport 

facility within Brunswick County, reported less than 2,000 in 2012 and 2013. Public media 

reports, the source shutdown operations in September 2013 which is supported by the source 

reporting no emissions in 2014. According to North Carolina, DAK Americas, LLC, was 

shutdown in September 2013, ceasing all combustion operations including the demolition of its 

units. However, the Facility’s title V permit was renewed in November 5, 2013, and is valid 

through October 31, 2018. Potential emissions from DAK Americas, LLC, as allowed by the 
20

active operating permit were not included in the modeling analysis for CPI Southport nor were 

its 2012-2014 actual emissions accounted for in the background concentration from the SO2

ambient monitor located in New Hanover County because it only accounted for emissions for the 

year 2014. Additionally, the source has a total facility-wide potential to emit of 10,324 tpy for 

SO2 on a rolling 12-month basis. Before shutdown, the facility was emitting approximately 1,442 

tpy of actual SO2 emissions.

The EPA notes additional sources in nearby counties bordering Brunswick including 

International Paper – Riegelwood Mill facility in Columbus County, approximately 3.6 km west 

of the Brunswick County border. This facility emitted 1,200 of SO2 according to the 2014 actual 

emissions. The EPA observes that the predominant wind pattern in the area blows from either the 

southwest or the northeast, and therefore the impacts from International Paper are not likely to 

influence the area of modeled maximum concentration from CPI Southport. Based on available 

information, the EPA does not have reason to believe that the emissions from International Paper 

combined with the distance to the county border are likely to cause or contribute to a violation of 

the NAAQS in Brunswick County. 

Wilbara, LLC located in New Hanover County is located approximately 41. 5 km from CPI 

Southport and 3 km the Brunswick County border (shortest distance), and 119 tons of actual 

emissions in 2014 Considering the source’s emissions, distance to the area of analysis and 

predominant wind direction in the area from blowing from either the southwest or the northeast 

the EPA has reason to believe that emissions from this source will not cause concentration 

gradients within the area or analysis or portions of Brunswick and New Hanover Counties.

Other than the two sources (ADM and Duke Energy Progress Nuclear Plant) included in the 

modeling analysis, the EPA is not aware of any other SO2sources in Brunswick County emitting 

over 100 tpy according to 2014 actual emissions. Furthermore, according to the review of 2014 

actual emissions, there are no other sources emitting over 50 tpy or more of SO2 (other those 

previously specified) that border Brunswick County (i.e., Columbus, Pender, New Hanover and 

Horry County, South Carolina). The EPA has no reason to believe that these sources would 

cause or contribute to a violation of the NAAQS in the area of analysis or Brunswick County.

North Carolina recommended that the EPA designate New Hanover County as attainment due to 

the SO2 monitor located there with a 2012-2014 design value of 32 ppb for the 1-hour ozone 

standards as a result of recent shutdowns and retirements, the most notable of which was the 

Duke Energy Progress: L.V. Sutton Plant. This facility emitted approximately 13,000 tons of 

SO2 according to the 2011 national emissions inventory, the compilation of EIS reporting 

completed every three years pursuant to 40 CFR Part 51, Subpart A, but the coal-fired units were 

retired in 2013 when a new gas-fired combined-cycle unit began operation. The most recently 

reported emissions from this facility were 32.13 tons according to 2014 actual emissions. No 

portion of New Hanover County has been designated as nonattainment for the 2010 SO2 NAAQS 

in the past. However, a township level designation limited to portions of Brunswick County is 

appropriate at this time, because the state’s supporting information for the immediate area that 

the EPA must designate by July 2, 2016, consists of air dispersion modeling indicating 

compliance with the NAAQS for the area around CPI Southport but does not extend into New 
21

Hanover County. Although based on currently available information, the EPA does not have 

reason to expect sources in New Hanover County to cause or contribute to a violation of the 

NAAQS in Brunswick County, the state’s rationale for why the EPA should also designate New 

Hanover County as attainment (i.e., an ambient air quality monitor with a 2012 – 2014 design 

value of 32 ppb), in the absence of any other technical justification, may not adequately address 

air quality within the entirety of New Hanover County. Moreover, except in unique 

circumstances, EPA has not yet generally issued designations under the 2010 SO2 NAAQS based 

on the existence of a non-violating monitor alone, where, as here, the state has not yet 

demonstrated that the monitor is located in the expected site of maximum ambient concentrations 

for the area under analysis. As a result, the EPA will designate New Hanover County and all 

other remaining undesignated portions of North Carolina by either December 31, 2017, or 

December 31, 2020. 

Regarding DAK Americas, LLC, in Brunswick County, North Carolina indicated that the facility 

shutdown in September 2013. Despite the shutdown, the facility renewed its permit and has an 

operating permitting that is valid until October 31, 2018. While the source is located 42 km from 

CPI Southport which is considered far enough that it would not impact the area of analysis 

around CPI Southport, it could, if operations were to resume, potentially impact the northeast 

portion of Brunswick County as well as portions of New Hanover County. Because of the active 

operating permit, the EPA does not believe, at this time, that the shutdown is permanent and 

enforceable for purposes of designations. Based on this information, the EPA intends to 

designate as unclassifiable/attainment all the townships within Brunswick County except for the 

Northwest Township which contains the DAK Americas, LLC facility. The EPA will consider 

all additional information during the 120-day process pursuant to section 107(d) of CAA for the 

Brunswick County Area. The EPA believes that our intended unclassifiable/attainment area, 

consisting of a portion of Brunswick County, is comprised of clearly defined legal boundaries, 

and the Agency finds these boundaries to be a suitably clear basis for defining the intended 

unclassifiable/attainment area.

Other Relevant Information

Except as explained below, the EPA did not receive any additional information about the area in 

the immediate vicinity of the CPI Southport facility.

The state of North Carolina has stated that it believes that the basis for designations should be 

monitoring data and that modeling should not be relied upon to designate areas.11 Despite their 

concerns regarding modeling accuracy, and due to the timeline required by the March 2, 2015

U.S. District Court for the Northern District of California consent decree, the state has provided 

modeling information that was considered along with monitoring data and emission data from 

the region to characterize air quality near the CPI Southport facility. North Carolina 

 

11 North Carolina Department of Environmental Quality September 18, 2015, updated recommendations submitted 

to EPA for the 2010 1-hour Sulfur Dioxide Boundary Recommendation for Brunswick County and New Hanover 

County.
22

recommended that the EPA designate New Hanover County, specifically, as attainment because

the SO2 monitor readings for the 1-hour standard for the period of 2012-2014 design value was 

32 ppb. For the reasons explained above, the EPA is not today issuing an intended designation 

for New Hanover County on this basis.

In developing the recommendation for the Brunswick County Area, the state considered the air 

quality impact assessment prepared by CPI Southport facility’s environmental consultant, which 

was submitted to the state. The CPI Southport facility modeling was used as the basis for the 

state’s impact assessment. North Carolina, however, expanded the modeling submitted by the 

CPI Southport facility in three areas: 1) the state used maximum 1-hour actual emission rates for 

the ADM source; 2) North Carolina added a small, unpermitted ADM source that was omitted in 

the CPI Southport facility impact assessment; and 3) the state included the Duke Energy Progress

Brunswick Nuclear Plant because of its proximity. The CPI Southport modeling assessment 

reported the 3-year average of the high 4th High Daily Maximum 1-hour concentration of 195.6 

μg/m3, which is larger than North Carolina’s modeled maximum concentration but which is less 

than the NAAQS.

Conclusion

Based on the collective modeling results, air quality measurements, emission records, and other 

factors, the state concluded that all townships within Brunswick and New Hanover Counties 

should be designated attainment for the 2010 SO2 NAAQS.

After careful evaluation of the state’s recommendation and supporting information, as well as all 

available relevant information, the EPA intends to designate the area around the CPI Southport 

facility as unclassifiable/attainment for the 2010 SO2 NAAQS. Specifically, the boundary is 

comprised of all the townships within Brunswick County except for the Northwest Township 

which includes the DAK Americas, LLC facility for reasons described earlier in this TSD. North 

Carolina recommended inclusion of New Hanover County because the SO2 monitor meeting the 

1-hour standard with a 2012-2014 design value of 32 ppb as a result of recent shutdowns and 

retirements. However, as explained above, the EPA does not intend on designating New Hanover 

County by July 2, 2016, because a singular ambient air quality monitor indicating compliance 

with the NAAQS in the absence of any other technical justification may not adequately 

characterize air quality within the entirety of that county. The EPA will consider the designation 

of New Hanover County and the townships contained therein in a later action. 

At this time, our intended designations for the state only apply to this area (Brunswick County). 

Consistent with the conditions in the March 2, 2015 court-ordered schedule, the EPA will 

evaluate and designate all remaining undesignated areas in North Carolina, including the 

Northwest Township in Brunswick County, and New Hanover County and the townships 

contained therein, by either December 31, 2017, or December 31, 2020.