Technical Support Document
Louisiana

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) must designate areas as either “u nclassifiable,” “attainment ,” or “nonattainment” for the 2010 one-hour sulfur dioxide (SO 2 ) 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 ne arby area. An attainment area is defined as any area other than a nonattainment area that meets the NAAQS. Unclassi fiable areas are defined as those that cannot
be classified on the basis of available info rmation as meeting or not meeting the NAAQS.

Louisiana submitted updated recommendations on November 17, 2015, ahead of a July 2, 2016, deadline for the EPA to designate certain areas es tablished by the U.S. District Court for the
Northern District of California. This deadline is the first of three deadlines established by the court for the EPA to complete area designations for the 2010 SO 2 NAAQS. Table 1 below lists
Louisiana’s recommendations and identifies the coun ties or portions of coun ties in Louisiana that the EPA intends to designate by July 2, 2016 base d on an assessment and characterization of air quality through ambient air quality data, air di spersion modeling, other evidence and supporting information, or a combination of the above.

Table 1: Louisiana’s Recommended and EPA’s Intended Designations

Area Louisiana’s
Recommended
Area Definition Louisiana’s
Recommended

Designation EPA’s Intended Area
Definition EPA’s Intended Designation

DeSoto Parish,
Louisiana Within the
Southeast Quadrant of
DeSoto Parish Attainment Portions of Desoto Parish, Louisiana:

The area bounded by the following UTM Coordinates* (NAD 83 Datum, UTM Zone 15):

X Y 441287, 3541019 441287, 3562019 450500, 3562019 450500, 3541019

* Nonattainment area excludes portions of Red River Parish, Louisiana
that fall within this UTM-based boundary Nonattainment2 Calcasieu Parish,
Louisiana Within
Calcasieu Parish
Borders Attainment Same as State’s
Recommendation Unclassifiable

Background

On June 3, 2010, the EPA revised the primary (health based) SO 2 NAAQS by establishing a new
one-hour standard at a level of 75 parts per billion (ppb) which is attained when the three-year average of the 99th percentile of one-hour da ily maximum concentrations does not exceed 75 ppb. This NAAQS was published in the Federal Re gister 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 th e health effects associated with breathing SO 2 . The two prior primary standards of 140 ppb evaluate d 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 ei ther of these two primary sta ndards. Similarly, the secondary
standard for SO 2, set at 500 ppb evaluated over 3 hours has no t been revised, and the EPA is also not currently designating areas on the basis of th e secondary standard.

General Approach and Schedule

Section 107(d) of the Clean Air Ac t requires that, no later than one year after promulgation of a new or revised NAAQS, state governors must s ubmit their recommendations for designations and boundaries to EPA. Section 107(d) also require s the EPA to provide notification to states no less than 120 days prior to promulgating an initial area desi gnation 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 opportun ity within the 120-day period to demonstrate why any proposed modificati on is inappropriate.

On August 5, 2013, the EPA published a final rule establishing air quali ty 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 th e 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, th ree lawsuits were file d against the EPA in different U.S. District Courts, alleging the ag ency 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

1 40 CFR 50.4(e) provides that the two prior primary NAAQ S will no longer apply to an area one year after its designation under the 2010 NAAQS, except that for areas designated nonattainment under the prior NAAQS as of August 22, 2010, and areas not meeting the requirements of a SIP Call under the prior NAAQS, the prior NAAQS will apply until that area submits and EPA approves a SIP providing for attainment of the 2010 NAAQS.3 effort intended to resolve the litigation in one of those cases, plaintiffs Sierra Club and the
Natural Resources Defense Council and the EPA f iled 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 consent decree schedule.

According to the consent decree, the EPA mu st complete the remaining designations on a schedule that contains three spec ific deadlines. By no later than July 2, 2016 (16 months from the court’s order), the EPA must desi gnate two groups of areas: (1) areas that have newly monitored
violations of the 2010 SO 2 NAAQS and (2) areas that contain a ny stationary sources that had not been announced as of March 2, 2015 for retiremen t; and that according to the EPA’s Air Markets Database emitted in 2012 either (i) more than 16,000 tons of SO 2 or (ii) more 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 me gawatts and otherwise meets the emissions criteria, is excluded from the July 2, 2016 dead line if it had announced through a company public announcement, public utilities commission filing, c onsent decree, public le gal 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, 2017, and December 31, 2020. The EPA has separately promul gated requirements for states and other air agencies to provide additional monitoring or mode ling information on a timetable consistent with these designation deadlines. We expect 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 SO 2 Data Requirements Rule (DRR).

The EPA through a March 20, 2015 memorandum from Stephen D. Page, Director, U.S. EPA, Office of Air Quality Planning and Standards issued updated designati ons guidance, to Air Division Directors, U.S. EPA Regions I-X. This memorandum s upersedes earlier designation guidance for the 2010 SO 2 NAAQS, issued on March 24, 2011, a nd it identifies factors that the EPA intends to evaluate in determining wh ether areas are in vi olation of the 2010 SO 2 NAAQS. The guidance also contains the factors the EPA in tends to evaluate in determining the boundaries for all remaining areas in the country, consiste nt with the court’s or der and schedule. These factors include: 1) Air quality characterizati on via ambient monitoring or dispersion modeling results; 2) Emissions-related data; 3) Meteor ology; 4) Geography and topography; and 5) Jurisdictional boundaries. This guidance was su pplemented by two technical assistance
documents intended to assist states and other interested parties in their efforts to characterize air quality through air dispersion modeling or ambient air quality monitoring for sources that emit
SO 2 . Notably, the EPA released its most r ecent versions of documents titled, “SO 2 NAAQS Designations Modeling Technical Assist ance Document” (Modeling TAD) and “SO 2 NAAQS Designations Source-Oriented Monitoring Tech nical Assistance Document” (Monitoring TAD)
in December 2013.4 Based on ambient air quality data collected between 2012 and 2014, no violations of the 2010
SO 2 NAAQS have been recorded in a ny undesignated part of the state. 2 However, there are 3 sources in the state meeting the emissions criteri a of the consent decree for which the EPA must complete designations by July 2, 2016. In th is draft technical support document, the EPA
discusses its review and technical analysis of Louisiana’s recomm endations for the areas that we must designate. The EPA also discusses a ny intended modifications from the state’s
recommendation based on all av ailable data before us.

The following are definitions of import ant 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 th e 99th percentile of th e annual distribution of daily maximum one-hour averag e 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 SO 2 NAAQS or contributed to a violation in a n earby area. A nonattainment designation would reflect cons iderations of state recomm endations and all of the
information discussed in this document. The EPA’s decision would be based on all available information including the most rece nt 3 years of air quality monitoring data, available modeling analysis, and any other relevant information. 4) Designated unclassifiable area – an area wh ich the EPA cannot determine based on all
available information whethe r or not it meets the 2010 SO 2 NAAQS. 5) Designated unclassifiable/atta inment area – an area which the EPA has determined to
have sufficient evidence to find either is attaining or is like ly to be attaining the NAAQS.
The EPA’s decision would be based on all av ailable 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 st ate or tribe has reco mmended that the EPA designate as attainment. 8) Recommended nonattainment area – an area a st ate or tribe has r ecommended that the EPA designate as nonattainment. 9) Recommended unclassifiable area – an area a state or tribe has recommended that the EPA designate as unclassifiable.

2 For designations based on ambient air quality monitoring data that violates the 2010 SO 2 NAAQS, the consent
decree directs the EPA to evaluate data collected betw een 2013 and 2015. Absent complete, quality assured and certified data for 2015, the analyses of applicable areas fo r the EPA’s intended designations will be informed by data
collected between 2012 and 2014. States with monitors that have recorded a violation of the 2010 SO 2 NAAQS during these years have the option of submitting complete, quality assured and certified da ta 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 designate the area and all other previously unde signated areas in the state on a schedule consistent with the prescribed timing of th e consent decree, i.e., by December 31, 2017, or December 31, 2020.5 10) Recommended unclassifiable/attainment area – an area a state or tr ibe has recommended that the EPA designate as unclassifiable/attainment. 11) Violating monitor – an ambien t air monitor meeting all me thods, quality assurance and siting criteria and requ irements whose valid design valu e exceeds 75 ppb, based on data analysis conducted in accordance wi th Appendix T of 40 CFR part 50.6 Technical Analysis for the DeSoto Parish, Louisiana Area

Introduction

The Dolet Hills Power Station contains a sta tionary 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 emissi on rate of at least 0.45 pounds of SO 2 per one million British thermal units (lbs SO 2 /mmBTU). As of March 2, 2015, this stationary source has not met the specific requirements for being “announced fo r retirement.” Specifically, in 2012, the Dolet Hills Power Station (Dolet Hills) emitted 20,887 tons of SO 2 , and had an emissions rate of 0.80
lbs SO 2 /mmBTU. Pursuant to the March 2, 2015 cons ent decree, the EPA must designate the area surrounding the facility by July 2, 2016.

In its November 17, 2015 recommendation, Louisian a through its state environmental agency, the Louisiana Department of Environmental Quality (LDEQ), recommended that the area surrounding Dolet Hills, specifically the southeast quadran t of DeSoto Parish, be designated as
unclassifiable based on information included in a monitoring siting report. The report assessed and characterized air quality for the facility a nd other nearby sources. Our review and analysis indicated that this initial modeling intended to jus tify the siting of monitors did not follow either the monitoring TAD or modeling TAD in certa in respects and only provided normalized estimates of impacts rather than absolute results.

The EPA also received air modeling performed by Sierra Club (initially in September 2015 and updated in December 2015), asserting that the area around Dolet Hills experiences impacts in exceedance of the NAAQS. The state reviewed th is modeling, and subsequently performed its own revised modeling using the input parameters provided by Si erra Club. These assessments and characterization were performed using ai r dispersion modeling software, i.e., AERMOD, analyzing actual emissions. However, the state factored and used the cu rrently non-default beta option low wind speed modification (LOWWIND 3). This revised modeling using LOWWIND3 predicted peak concentrations slightly below the NAAQS. As a result, the state changed its
unclassifiable recommendation to attainment.

The EPA notes that the use of beta options , such as ADJ_U* and LOWWIND3, in AERMOD for any regulatory applications requi res adherence with Appendix W, Section 3.2.2. This is further explained in the EPA’s December 10, 2015 Memo randum titled, “Clarification on the Approval Process for Regulatory Application of the AERMOD Modeling System Beta Options.” Among other conditions, the use of beta options requires cons ultation with the appropriate EPA Regional Offices. Upon concurrence by the EPA’s Modeli ng Clearinghouse, EPA Regional Offices may approve the use of these beta options for regulatory applicatio ns as an alternative model. However, LDEQ performed air dispersion modeli ng intended to characterize air quality as a
result of SO 2 emissions from Dolet Hills without prio r consultation with and approval from an EPA Regional Office, and therefore has not met the applicable regulatory requirements contained in Appendix W, Section 3.2.2. As a result, the EPA does not believe that the air quality modeling results obtained from the use of these beta options can be used as a reliable indicator of
attainment status in the area around Dolet Hills until appropriate alternative model approval is7 granted or these beta options are promulgate d as regulatory options in AERMOD through EPA rulemaking.

After careful review of the st ate’s assessment, supporting docume ntation, and all available data, the EPA does not agree with the state’s recomme ndation for the area, and intends to designate the area as non-attainment. Sp ecifically, the boundaries for ou r intended nonattainment area consist of the portions of DeSoto Parish bound by the following Universal Transverse Mercator (UTM) Coordinates (NAD 83 Datum, UTM Zone 15):

X Y

441287 3541019

441287 3562019

450500 3562019

450500 3541019

However, this intended nonattainment area exclud es portions of Red River Parish, Louisiana that fall within this UTM-based boundary. The modeli ng analyses indicates that there were no violating receptors in Red River Parish. Also, Figures 3 and 4 show that the impact area based on actual emissions did not extend past DeSoto Parish borders and, therefore, the defined

nonattainment area should be contained within.

Dolet Hills is located in northwestern Louisiana in the eastern portion of DeSoto Parish. As seen in Figure 1 below, the facility is located appr oximately 12.5 km directly east of the center of
Mansfield. Also included in the fi gure are major nearby emitters of SO 2 , and the DeSoto Parish boundary. EPA’s intended nonattainment designation ar ea is the area within DeSoto Parish that lies within a rectangular ar ea defined by UTM coordinates (See Figure 1 below). The nonattainment area excludes porti ons of Red River Parish, Louisi ana that fall within this UTMbased boundary.8 Figure 1: SO 2 Nonattainment Area Designation for Dolet Hills

The discussion and analysis that follows below will reference the state’s use of the Modeling TAD in its revised modeling analysis, Sierra Club’s use of the Modeling TAD, the EPA’s assessment of the competing modeling in accord ance with the Modeling TAD, and the factors
for evaluation contained in the EPA’s Ma rch 20, 2015 guidance, as appropriate.

Detailed Assessment

Air Quality Data

There are no SO 2 air quality monitors in DeSoto Parish. There are no SO 2 air quality monitors in surrounding parishes that are repr esentative of the maximum or higher elevated levels of SO 2 around Dolet Hills.9 Model Selection and Modeling Components

The EPA’s Modeling TAD notes that fo r area designations under the 2010 SO 2 NAAQS, the AERMOD modeling system should be used, unless us e of an alternative m odel 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 AERM OD 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 in corporating 1-minute automated surface observation system (ASOS) wind data

- AERSURFACE: the surface characte ristics processor for AERMET

- AERSCREEN: a screening version of AERMOD

The Sierra Club initial modeli ng (Sept. 2015) was conducted with the previous regulatory version of AERMOD (v14134). The state reviewed Sierra Club’s modeling and found that the inputs for the actual emissions were acceptable. The state reran the Sie rra Club modeling on the most recent version of AERMOD version 15181, using LOWWIND3 as the only altered model option. A discussion of the individual component s will be referenced in the corresponding discussion that follows as appropriate. Sie rra Club submitted updated modeling in December
2015 and used the most recent version of AE RMOD that was released in July 2015 (v15181).

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, urban dispersion coefficien ts are to be used in the dispersion modeling analysis if more than 50% of the area within a 3 km radius of the facility is classified as urban. Otherwise, the source is considered a rural source.

When performing the modeling for the area of anal ysis, the state agreed with Sierra Club’s analysis to use rural mode. Sierra Club us ed a Geographic Information System (GIS) to determine whether rural or urban dispersion co efficients applied. La nd use within a threekilometer radius circle surrounding the facili ty was considered. USEPA’s AERSURFACE v. 13016 was used to develop the meteorological data for the modeling analysis. This model was also used to evaluate surrounding land use w ithin 3 kilometers. Based on the output from the AERSURFACE, approximately 0.02% of surroundi ng land use around the modeled facility was of urban land use types including Type 21 – Low Intensity Residential, Type 22 – High Intensity Residential and Type 23 – Commer cial / Industrial / Transportati on. This is less than the 50% value considered appropriate for the use of urban dispersion coe fficients. Based on the AERSURFACE analysis, it was concluded that th e rural option would be used for the modeling summarized in this report.10 Modeling Parameter: Area of Analysis (Receptor Grid)

The EPA believes that a reasonable first step toward characterizati on of air quality in the area surrounding Dolet Hills is to determine the extent of the area of analysis, i.e., receptor grid. Considerations presented in the Modeling TAD incl ude but are not limited to: the location of the
SO 2 emission sources or facilities considered for modeling; the ex tent of significant concentration gradients of nearby sources; and sufficient receptor coverage and density to adequately capture and resolve the model predicted maximum SO 2 concentrations.

For the DeSoto Parish area, the state recogni zed in its monitoring siting report 519 permitted facilities in the parish, with 10 Title V facilit ies, and only one that represented a major SO 2 emitter within 20 kilometers (km) in any direction of Dolet Hills. The state determined that this was the appropriate distance as described in the 2013 Monitoring TAD. In addition to Dolet Hills, one other major emitter of SO 2 is located within the area of analysis, International Paper Company (IP), is 14 km to the north of Dolet H ills. Neither Sierra Club nor the state’s modeling
included emissions from IP. The st ate asserted that emissions from this facility are represented by the background monitor data; however, the EPA does not agree that th e background monitor data used adequately represents any potential concentration gradients that may occur in the area
of concern from IP’s emissions. Based on th e modeling provided by Sierra Club and LDEQ, industry modeling for siting a monitor, one of th e higher areas with near modeled exceedances was to the south of the facility. When winds are out of the north and resulting in some of the highest values modeled around Dolet Hills, the IP source would be upwind and could contribute to concentration gradients around Dolet Hills and to the south of Dolet Hills. Coupling this with the proximity to Dolet Hills (approx. 14km), and size of IP emissions warrant consideration for explicit modeling, as suggested by Appendix W, because it is likely that the source causes concentration gradients that extend to area impacted by Dolet Hills with some of the higher
modeled values that are near the standard.

The grid receptor spacing by Sierra Club was re tained by the state in their modeling analysis along with all associated elevations and processing informati on that could potentially impact the area of analysis where maximum SO 2 concentrations are expected. The receptor network contained 21201 receptors (no graphical represen tation of the receptor grid was provided):

- A 100-meter Cartesian receptor grid centered on Dolet Hills and extending out 5 km.

- A 500-meter Cartesian receptor grid center ed on Dolet Hills and extending out 10
kilometers.

- A 1,000-meter Cartesian receptor grid centered on Dolet Hills and extending out 50 kilometers. 50 kilometers is the maximum distance accepted by USEPA for the use of the AERMOD dispersion model.

- A flagpole height of 1.5 meters wa s used for all these receptors.

This is a larger grid than we might normally recommend but this grid is acceptable for this analysis. Sierra Club modeling used a slightly elevated flagpole receptor height, but if this was
corrected to EPA’s recommended he ight we would expect only a slight change in the modeled11 numbers and the area of exceedances and magnit ude of the values would be basically the equivalent and not change our proposed action. Figure 2 shows the area surroundi ng Dolet Hills originally provi ded in the state’s monitoring siting report provided to the EPA showing the location of all minor and major sources of SO 2 in DeSoto Parish. The state originally recommended that the area designated unclassifiable should be limited to the southeast quadrant of the parish bounded by United States Highway 84 on the north, United States Highway 171 on the west, a nd the parish boundary on the east and south. As discussed elsewhere, the state re vised their recommendation that a ll of DeSoto Parish should be designated attainment/unc lassifiable. EPA’s intended nonattai nment designation area is the area
within DeSoto Parish that lies within a rect angular area defined by UTM coordinates (See Figure 1 above). The nonattainment area excludes portions of Red River Parish, Louisiana that fall within this UTM-based boundary.

Figure 2: Dolet Hills Area of Analysis by the State

Sierra Club’s elevations for stacks and receptors were obtained from National Elevation Dataset (NED) GeoTiff data. GeoTiff is a binary file th at includes data descript ors and geo-referencing information necessary for extracti ng terrain elevations. The elevations were extracted from 1 arcsecond (30 meter) resolution NED files. The USEPA software program AERMAP v. 11103 was
used for these tasks.

Modeling Parameter: Source Characterization

Sierra Club modeled constant exit flowrate and temperat ure based on 100% load. No consideration was given of facility operation at less than 100% load. Stack parameters such as exit flow rate and temperature are typically lowe r at less than full load , having the effect of reducing pollutant dispersion and increasing pred icted air quality impacts. In addition, no12 consideration was given to building or structure downwash. Do wnwash effects typically increase predicted concentrations near the facility. Th e state identified Internat ional Paper located 14 km
north of the Dolet Hills facil ity with annual emissions exceed ing 1,300 tpy as the only other large nearby emission source. However, no sources other than Dolet Hills were included in the modeling performed by the Sierra Club or the state.

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 r ecent 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 th ese data are available for many electric generating units. In the abse nce of CEMS data, th e EPA’s Modeling TAD highly encourages the use of AERMOD’s hourly varying emissions keyword HOUREMIS, or through the use of AERMOD’s variable emission s factors keyword EMI SFACT. When choosing one of these methods, the EPA believes that detailed throughput, ope rating schedules, and emissions information from the impacted source(s) should be used.

In certain instances, states and ot her 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 li mit, been subject to a federally enforceable consent decree, or implemented other fede rally enforceable mechanisms and control technologies to limit SO 2 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 SO 2 emissions inventories used for permitting or SIP planning demonstrations should contain the nece ssary emissions information for designationsrelated modeling. In the ev ent 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 only Dole t Hills in its modeling but identified one other large emitter of SO 2 within 20 km in the area of analys is. The associated annual actual SO 2 emissions between 2012 and 2014 are summarized below.

Table 2: Actual SO 2 Emissions (2012 – 2014) from Facilities in the DeSoto Parish Area

Company ID Facility Name SO 2 Emissions (tons per year)

2012 2013 2014 CLECO Power LLC Dolet Hills 20,887 14,612 14,177 International Paper Co. Mansfield Mill 1,569 1,296 1,557 Total Emissions All Facilities 22,456 15,908 15,73413 Initial state modeling for the pur pose of monitor siting used normalized hourly emissions and actual stack temperature and exit velocity from the CEMS for 2012-2014. Sierra Club modeling utilized hourly emissions data measured by th e CEMS from CAMD (2012-2014) and constant stack temperature and exit veloci ty. The state’s revised modeling utilized the Sierra Club model inputs for emissions and stack parameters, but the EPA reiterates that the emissions from IP were not included in the modeling analysis.

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 climatologica l (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 tim e during which data are collected. Sources of meteorological data include National Weather Se rvice (NWS) stations, s ite-specific or onsite data, and other sources such as universitie s, Federal Aviation Ad ministration (FAA), and military stations.

For the Dolet Hills area of analysis, surface meteorology was obtained for Shreveport Regional Airport located near Dolet Hill s. Integrated Surface Hourly (ISH) data for the 2012-2014 period
were obtained from the National Climatic Data Center (NCDC).

The state and Sierra Club used AERSURFA CE version 13016 to develop surface roughness, albedo, and daytime Bowen ratio values in a region surrounding the meteorological data
collection site. AERSURFACE was used to deve lop surface roughness in a one kilometer radius surrounding the data collection si te. Bowen ratio and albedo was developed for a 10 kilometer by 10 kilometer area centered on the meteorological data collection site. These micrometeorological data were processed for seasonal periods using 30 -degree sectors. Seasonal moisture conditions were considered average with winter months having no continuous snow cover.

Upper-air data are collected by a “weather balloon ” that is released twi ce per day at selected
locations. As the balloon is releas ed, it rises through the atmosphere , and radios the data back to the surface. The measuring and transmitting de vice is known as eith er a radiosonde, or
rawindsonde. Data collected and radioed back in clude: air pressure, height, temperature, dew point, wind speed, and wind dire ction. The upper air data were processed through AERMET Stage 1, which performs data extrac tion and quality control checks.

For Dolet Hills, the concurre nt 2012-2014 upper air data fr om twice-daily radiosonde measurements obtained at the most representati ve location were used. This location was the Shreveport, Louisiana measurement station. Th ese data are in Forecast Systems Laboratory (FSL) format and were downloaded in ASC II text format from NOAA’s FSL website. All reporting levels were downloaded and processed with AERMET (v14134).14 Modeling Parameter: Geography and Terrain

The UTM NAD83 coordinate system (Zone 15) was used for identifying the easting (x) and northing (y) coordinates of the modeled sources and receptors. Stack locations were obtained from facility permits and prior modeling files provided by the state regulatory agency. The stack locations were then verified using aeria l photographs and confirmed with GIS.

The facility was evaluated to determine if it should be modeled using the rural or urban dispersion coefficient option in AERMOD. A Geographic Information System (GIS) was used to determine whether rural or urban dispersion coefficients apply to a site. Based on the AERSURFACE analysis, it was concluded that th e rural option would be used for the modeling summarized in this report. Please refer to Sec tion 4.5.3 of the Sierra Club modeling report for a discussion of the AERSURFACE analysis.

Modeling Parameter: Background Concentrations of SO 2

The Modeling TAD offers two mechanisms for ch aracterizing background concentrations of SO 2 that are ultimately added to the modeled desi gn values: 1) a “first tier” approach, based on monitored design values, or 2) a tempor ally varying approach, based on the 99 th percentile monitored concentrations by hour of day and s eason or month. For the Dolet Hills area of analysis, consistent with the background concentration identifi ed by the Sierra Club in their analysis, the state chose the 99 th percentile of the annual distribution of daily maximum 1-hour concentrations averaged across 2011-2013 for the Bossier Parish monitor – the lowest measured background concentration in th e state. The background SO 2 concentration was added to the modeled fourth-highest daily maximum 1-hour SO 2 concentration. The background concentration for this area of analysis was de termined by the state to be 31.4 micrograms per cubic meter ( μ g/m 3 ), or 12.0 ppb, 3 and that value was incorporated into the final AERMOD
results.

Summary of Modeling Results

The AERMOD modeling parameters for the DeSoto Parish area of analysis are summarized

below in table 3:

Table 3: AERMOD Modeling Parameters for the DeSoto Parish Area of Analysis

DeSoto Parish Area of Analysis

AERMOD Version 15181 Dispersion Characteristics Rural

Modeled Sources 1

Modeled Stacks 1

3 The conversion factor for SO 2 (at the standard conditions applied in the ambient SO 2 reference method) is 1ppb
SO 2 = approximately 2.62 μ g/m 3 SO 2 at 25C and 1 atm.15 Modeled Structures No

Modeled Fence lines - Total receptors 21201 Emissions Type Actual - CEM

Emissions Years 2012-2014 Meteorology Years 2012-2014

Surface Meteorology Station Shreveport Regional Airport (Shreveport, LA)

Upper Air Meteorology Station Shreveport, LA measurement
station

Methodology for Calculating Background SO 2 Concentration 99 th percentile of the annual distribution of daily maximum 1-hour concentrations averaged

across 2011-2013 for Bossier
Parish Calculated Background SO 2 Concentration 12 ppb (31.4 μg/m 3 )

The results presented below in table 4 show the magnitude and geographic location of the highest predicted modeled concentr ation based on actual emissions.

Table 4: Max 99th Percentile 1-Hr SO 2 Conc.in DeSoto Parish Area Based on Actual Emissions

Averaging

Period Data
Period Receptor Location SO 2 Concentration ( μ g/m 3 )

UTM
Latitude UTM Longitude Modeled (including background) NAAQS

LDEQ
revised modeling 99th Percentile 1-Hour Avg. 2012-2014 Not provided Not provided 194.5 196.5*

Sierra
Club modeling 99th Percentile 1-Hour Avg. 2012-2014 Not provided Not provided 218.7 196.5*

The state’s modeling 4 (with the LOWWIND3 non-default opti on) indicates that the predicted

99 th percentile 1-hour average co ncentration within the chosen modeling domain is 194.5 μ g/m 3

, or 74.31 ppb. This modeled concentration included the background concentration of SO 2 . This predicted value is graphically represented along with all the ot her receptors below in Figure 3. Sierra Club December modeling predicted 99 th percentile 1-hour averag e concentration within the chosen modeling domain is 218.7 μ g/m 3 , or 83.55 ppb. This modeled concentration included

4 State modeling based on Sierra Club files and not the state’s normalized emission modeling.16 the same background concentration of SO 2 . This predicted concentrations are graphically represented along with all othe r receptors with values abov e the NAAQS below in Figure 4.

Figure 3: Maximum Predicted 99 th Percentile 1-Hour SO 2 Concentrations in the Dolet Hills Area of Analysis Based on Actual Emissions (LDEQ’s modeling using Sierra Club’s inputs)17 Figure 4: Maximum Predicted 99 th Percentile 1-Hour SO 2 Concentrations in the Dolet Hills Area of Analysis Based on Actual Emissions (Sierra Club)

As discussed previously, the st ate reran Sierra Club’s initial modeling factoring in a low wind non-default modification (beta option) to the mode l. The Sierra Club modeling provided a peak value of 218.7 μg/m 3 , above the standard of 196.5 μg/m 3 . The state reran that modeling using the proposed LOWWIND3 option, resulting in a peak value of 194.5 μg/m 3 , just below the standard (see Figure 4 above). As previously discussed, the EPA notes that th e use of beta options, such as ADJ_U* and LOWWIND3, in AERMOD for any re gulatory applications requires adherence with Appendix W, Section 3.2.2. This is fu rther explained in the EPA’s December 10, 2015 Memorandum titled, “Clarification on the Approval Process for Regulatory Application of the AERMOD Modeling System Beta Options.” Among other conditions, the use of beta options requires consultation with the appropriate EPA Regional Offices. Upon concurrence by the18 EPA’s Modeling Clearinghouse, EP A Regional Offices may approve the use of these beta options for regulatory applicati ons as an alternative model. However, LDEQ performed air dispersion modeling intended to character ize air quality as a result of SO 2 emissions from Dolet Hills without prior consultation with and approva l from an EPA Regional Office, and therefore has not met the applicable regu latory requirements contained in Appendix W, Section 3.2.2. As a result, the EPA does not believe that the air quality modeling results obtained from the use of these beta options can be used as a reliable indica tor of attainment status in the area around Dolet Hills until appropriate alternative model approv al is granted or these beta options are promulgated as regulatory options in AERMOD through EPA rulemaking.

The Sierra Club modeling, and the state’s re vised modeling using LO WWIND3, only included constant stack velocity and temperature and di d not include building downwash or the nearby International Paper causing some uncertainty in the modeling results. The lack of downwash and variable temperature/velocity, wi th the non-inclusion of IP, however , generally bias the results of Sierra Club’s modeling low. As a result, we believe that Sierra Club’s modeling provides

sufficient information to determine that the area is not meeting the standard, and therefore we intend to designate it as nonattainment.

Jurisdictional Boundaries:

After the geographic area of anal ysis associated with the immedi ate area surrounding Dolet Hills, nearby sources which may potentially be contributing to elev ated levels of SO 2 , and background concentration was determined, existing jurisdic tional boundaries were considered for the purpose of informing our intended nonattainment area, speci fically with respect to clearly defined legal

boundaries. The EPA believes that while there are no clear jurisdictional boundaries that encompass our intended nonattainment area, UT M coordinates result in clearly defined

boundaries.

The state originally recommended an area in the S outheastern quadrant as unclassifiabl e and then

revised that recommendation to at tainment for all of DeSoto Parish. Based on our analysis and consideration of modeling results provided by Sie rra Club and the state, as well as other nearby sources such as IP, the EPA intends to designate portions of DeSoto Pari sh as nonattainment. As

discussed above when winds are from the north IP is a background source that could contribute significantly to some of the higher modeled values that are on the south side of Dolet Hills and very near the standard. Modeling results for monitor siting indicated the west side and south side were the two primary areas with high frequenc y of maximum values using normalized emissions.

The EPA believes that the IP faci lity has reported emissions that are large enough such that if they were explicitly modeled in accordance with the Modeling TAD would likely be shown to

contribute to the ambient concentrations that have already been modeled to show violations, or near violation, of the NAAQS. Inclusion of IP em issions may likely increase modeled values just

below the standard to exceedance levels. Ther efore, our intended ar ea includes portions of

DeSoto Parish that include the area of modeled exceedances and near exc eedances as well as the IP facility because of its likel y contribution to the modeled ambi ent concentrations resulting in additional potential NAAQS violations if IP were included in the modeling.19 The EPA believes that our intended nonattainment area, consisting of the area around Dolet Hills and including Internatio nal Paper, is comprised of clearly defined boundaries, and we find these boundaries to be a suitably clear basis fo r defining our intended nonattainment area.

Conclusion

After careful evaluation of the state’s recommendation and supporti ng information, as well as all available relevant information, the EPA intends to designate the area around Dolet Hills in DeSoto Parish, Louisiana as nonattainment for the 2010 SO 2 NAAQS. Specifically, the intended nonattainment area is comprised of the portion of DeSoto Parish bounded by the following UTM Coordinates in meters (NAD83 Datum, Zone 15):

X Y

441287 3541019

441287 3562019

450500 3562019

450500 3541019

The nonattainment area excludes the portion of Red River Parish, Loui siana that falls within the area bounded by the listed UTM coordinates. Figure 1 above graphically i llustrates our intended
nonattainment area.

In its original submission, the state recomme nded that the area surrounding Dolet Hills, specifically the southeast quadrant of DeSoto Pari sh, be designated as unclassifiable based on a monitoring siting report. The stat e reran modeling using the input parameters provided by Sierra Club and additionally factored in a low wind sp eed modification. Based on this modeling, the state changed their recommended designation from unclassifiable to attainment. After careful
review of the state’s assessmen t, supporting documentation, and a ll available data, the EPA does not agree with the state’s recommendation fo r the area and cannot rely upon the modeling provided by the state, and intends to designate the area as nonattainment.

At this time, our intended designations for the st ate only apply to this area and the other area presented in this technical support document. Co nsistent with the conditions in the March 2, 2015 consent decree, the EPA will evaluate and designate all remaining undesignated areas in Louisiana by either December 31, 2017, or December 31, 2020.20 Technical Analysis for the Calcasieu Parish Area

Introduction

The Calcasieu Parish area contains two stationary sources that, according to the EPA’s Clean 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 emissi on rate of at least 0.45 pounds of SO 2 per one million British thermal units (lbs SO 2 /mmBTU). As of March 2, 2015, thes e stationary sources have not met the specific requirements for being “announ ced for retirement.” Specifically, in 2012, the Nelson Electric Generating Plant emitted 12,513 tons of SO 2 with an emissions rate of 0.7 lbs
SO 2 /mmBTU; and the Nelson Industrial Steam Company emitted 6,706 tons of SO 2 with an
emissions rate of 0.7 lbs SO 2 /mmBTU. Pursuant to the Marc h 2, 2015 consent decree, the EPA must designate the area surrounding these facilities by July 2, 2016.

In its submission, Louisiana recommended th at the area surrounding the Nelson Electric Generating Plant and the Nelson Industrial St eam Company, specifically the entirety of Calcasieu Parish, be designated as attainment. This was based on review of available monitor data, an assessment and characte rization of air quality from th e facilities, and other nearby sources that may have a potential impact in the area of analysis where maximum concentrations
of SO 2 are expected. This air quality assessment and characterization was performed using air dispersion modeling software, i. e., AERMOD, analyzing actual emissions by a group of local industries and then provided to the state. After careful revi ew of the industry and state’s assessment, supporting documentation, and all ava ilable data, the EPA doe s not agree with the state’s recommendation for the area, and intends to designate the area as unclassifiable. Specifically, the area we intend to designate unclassifiable consists of Calcasieu Parish.

Both the Nelson Electric Generating Plant and th e Nelson Industrial Steam Company are located in southwestern Louisiana in the central portion of Calcasieu Parish. As seen in Figure 1 below, the facilities (0.06 km apart) ar e located approximately 8 km north west of the center of Lake Charles. Also included in the figure are nearby emitters of SO 2 identified by LDEQ and the EPA’s recommended unclassifiable parish area designation, which is th e same recommended area as the state’s intended attainment designation.21 Figure 1: The EPA’s Intended Unclassifiable Area for Calcasieu Parish with Large Emitters of
SO 2

A group of local industries in Lake Charles area provided 1-Hour SO 2 modeling to the state to use in submission of state recommendations, from this point we will refer to the modeling as ‘industry modeling’. -The discussion and analysis that follows below will reference the use of the Modeling TAD, the EPA’s assessment of th e industry modeling in accordance with the Modeling TAD, and the factors for evaluation co ntained in the EPA’s March 20, 2015 guidance, as appropriate.

Detailed Assessment

Air Quality Data

There is a SO 2 air quality monitor in Calcasieu Parish but it is approximately 2.5 km from the Nelson facilities and was not located to yiel d the maximum concentrations from the Nelson
facilities. The Westlake monitor (AQS ID 220-19-0008) monitoring data for 2012 to 2014 (three year average of the 99th percentile 1-hour daily maximum values) is 35 ppb which is approximately 91.7 μ g/m 3 . The monitored concentration is approximately 47% of the NAAQS (75 ppb). This monitor is approximately 2.5 km to the South and East of the Nelson facilities and is not representative of the maximum from Nelson facilities and other cumulative sources.22 Therefore there is no monitoring data that is re presentative of the maximum or higher elevated
levels of SO 2 around the Nelson facilities.

Model Selection and Modeling Components

The EPA’s Modeling TAD notes that fo r area designations under the 2010 SO 2 NAAQS, the AERMOD modeling system should be used, unless us e of an alternative m odel 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 AERM OD 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 in corporating 1-minute automated surface observation system (ASOS) wind data

- AERSURFACE: the surface characte ristics processor for AERMET

- AERSCREEN: a screening version of AERMOD

The industry modeling used AERMOD versi on 14134, and a discussion of the individual components will be referenced in the corresponding discussion that follows as appropriate. EPA released a newer version of AERMOD (versi on 15181) in July 2015 while LDEQ’s modeling work was already well underway. The EPA does not believe that substantial changes in the modeling results would have been seen if the industry modeling used the more recent version.

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, rura l dispersion coefficients are to be used in the dispersion modeling analysis if more than 50% of the area within a 3 km radius of the facility is classified as rural. Conversely, if more than 50% of the area is urban, urban dispersi on coefficients should be used in the modeling analysis

. When performing the modeling for th e area of analysis, the industry determined that it was most appropriate to run the model in rural mode based on Auer’s land use methodology.

Modeling Parameter: Area of Analysis (Receptor Grid)

The EPA believes that a reasonable first step toward characterizati on of air quality in the area surrounding both the Nelson Electric Generating Plant and the Nels on Industrial Steam Company
is to determine the extent of th e area of analysis, i.e., receptor gr id. 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 concentra tion gradients of nearby sources; and sufficient receptor coverage and de nsity to adequately capture and resolve the model predicted maximum SO 2 concentrations.23 For the Calcasieu Parish area, the industry modeling report identifies all emitters of SO 2 greater than 100 tons per year (tpy) SO 2 based on 2013 emissions data from LDEQ’s Emission Reporting and Inventory Center (ERIC). 2013 emissi ons were selected to reflect the emission
reductions due to installation of a scrubber at Rain CII in 2012. Temporary, non-routine, and emergency sources were removed from the list of emission sources, as provided in the Modeling
TAD. In addition to the Nelson Electric Ge nerating Plant and the Nelson Industrial Steam Company, the other emitters of SO 2 included in the area of an alysis were: Phillips 66 Co., Louisiana Pigment Co. LP, Citgo Petroleum Co rp., Rain CII Carbon LLC, and Reynolds Metals Company. Given the large area bei ng analyzed the grid receptor sp acing for the area of analysis chosen by the industrial group was as follows:

- An initial 15x25 square km receptor grid was placed at the center of the industrial area with 100 m spacing.

- A second receptor grid with 250 m spaci ng extended 5 km beyond the first grid.

- A third grid with 500 m spacing extended an additional 5 km from the second grid.

- Receptors lying within industrial boundaries or outside of the parish boundary were
removed.

The receptor network included 44,946 total receptors. The report did not specifically explain the total network coverage area. From the informati on provided it was not clear if the modeling grid receptors were sufficient to adequately capture a ll the anticipated high-elevated concentrations in the area of analysis.

Figure 2 shows the area surrounding the Nels on Electric Generating Plant and the Nelson Industrial Steam Company and is similar to Figure 1 but also includes all reported point sources
of SO 2 with varying circle sizes based on total emissions, but does not include a map of the receptor grid for the area of analysis.24 Figure 2: Large Emitters of SO 2 in the Vicinity of the Nelson Generating Plant and Nelson Industrial Steam Company

The EPA recognizes that there are 2 emitters of SO 2 with reported 2011 NEI emissions above 100 tpy in neighboring Orange County, Texas. Echo Carbon Black Plant (4,247 tpy of SO 2 ) is located approximately 2 km from the western Ca lcasieu Parish border, and Orange Mill (2,472 tpy of SO 2 ) is located approximately 3 km from the western Calcasieu Parish border. These

sources are close to the western boundary but are over 30 km west of the modeling grid provided by industry that focuses on the Lake Charles area. These two Texas sources would not be expected to cause a concentration gradient in the industry modeling grid for the Lake Charles area due to distance and the winds do not transport we st to east often such that transport of these

two sources towards the Lake Charles area occurs . Since there is no modeling of these two Texas sources and any potential impacts on the western area of Calcasieu Parish, the EPA is unable to determine at this time whether these nearby s ources and areas may contribute to ambient air quality impacts within Calcas ieu Parish. We note that the Echo Carbon Black Plant was identified by Texas as DRR source and Texas will have to assess what impacts occur from the DRR source in the area, including consideration of other sources that have potential impacts on local concentration gradients such as the Orange Mill, in the future designation rounds. Texas

will have to consider if the SO 2 DRR source (and other nearby s ources) have a potential impacts

in the western area of Calcasieu Parish.25 Modeling Parameter: Source Characterization

The industry modeling included sources within th e area of analysis that exceeded 100 tpy SO 2 emissions based on 2013 emissions data. The indus try modeling utilized act ual stack heights in conjunction with actual annual 2013 emissions. Stack exit temperature and exit velocity were modeled using a single value for the entire modeling period from emission inventories and permitting data. The industry modeling characterized the sources’ plume downwash from available building layout and locations using the BPIP AERMOD component.

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 r ecent 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 th ese data are available for many electric generating units. In the abse nce of CEMS data, th e EPA’s Modeling TAD highly encourages the use of AERMOD’s hourly varying emissions keyword HOUREMIS, or through the use of AERMOD’s variable emission s factors keyword EMI SFACT. When choosing one of these methods, the EPA believes that detailed throughput, ope rating schedules, and emissions information from the impacted source(s) should be used.

In certain instances, states and ot her 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 li mit, been subject to a federally enforceable consent decree, or implemented other fede rally enforceable mechanisms and control technologies to limit SO 2 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 SO 2 emissions inventories used for permitting or SIP planning demonstrations should contain the nece ssary emissions information for designationsrelated modeling. In the ev ent 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 industry modeling incl uded Nelson Electric Generating Plant and the Nelson Industrial Steam Company, toge ther with 7 other emitters of SO 2 within the area of analysis. The facilities in the area of analysis and thei r associated annual actual SO 2 emissions
between 2012 and 2014 are summarized below in Table 1.26 Table 1: Actual SO 2 Emissions Between 2012 – 2014 from Faci lities in the Calcasieu Parish Area of Analysis

Company ID Facility Name SO 2 Emissions (tons per year)

2012 2013 2014 Entergy Gulf States LA LLC Nelson Industrial Steam Co. 6,706 6,836 6,107 Entergy Gulf States LA LLC Nelson Electric Generating Plant 12,513 11,461 10,544 Phillips 66 Co. Lake Charles Refinery 465 586 510

Citgo Petroleum Group Lake Charles Manufacturing Complex 1,997 1,898 1,731

Louisiana Pigment Co. LP Titanium Dioxide Plant 504 606 525 Rain CII Carbon LLC Lake Charles Calcining Plant 9,162 5,471 4,432 Reynolds Metal Co. Lake Charles Carbon Co. 4730 4,922 4,926
Total Emissions All Facilities 36,077 31,780 28,775

The industry modeling report listed actual annual emissions sour ce data for 2013 only, instead of using the most recent 3 years of actual emissions data. The actual emissions data listed in the
table above were obtained from the State’s Emissions Reporting and Inventory Center (ERIC), which is based on annualized inventory data. In other words, hourly CEMs data available for Nelson Electric Generating Plant and the Nelson I ndustrial Steam Company were not utilized in the modeling, which is an inconsistency with th e TAD. Additionally, the industry’s modeling did not include any varying emission ra tes for any of the facilities and the same rate was modeled for all years; this approach is al so inconsistent with the TAD.

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 climatologica l (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 tim e during which data are collected. Sources of meteorological data include National Weather Se rvice (NWS) stations, s ite-specific or onsite data, and other sources such as universitie s, Federal Aviation Ad ministration (FAA), and military stations.

For the Nelson Electric Generating Plant and th e Nelson Industrial Steam Company areas of analysis, surface meteorology from the Baton Rouge surface and Lake Charles upper air National

Weather Service Station meteorol ogical data for the years 2009 through 2013 was used for this analysis using AERMET. LDEQ’s modeling guidance indicates the NWS site in Lake Charles should be used for the surface meteorology. The meteorological data should be representative

of the area. The use of Baton R ouge surface data instead of Lake Charles data in the industry modeling does not follow the guida nce in the TAD regarding the proximity of the site to area under consideration nor does it follow LDEQ’s own guidance for modeling in Southwestern27 Louisiana. Baton Rouge is further from the co ast and would have different surface meteorology, including wind speed and direction than the Lake Charles surface station. The differences in surface meteorology would impact the frequency of wind directions and speeds that impact maximum concentrations and would also impact how often certain sources align to yield

maximum concentrations downwind of sources. W ithout modeling with corre ct surface data it is impossible to assess how the maximum and exceedance concentrations (see discussion below about taking into account erro rs and inappropriate background results in the existing modeling

that result in modeled exceedance s) would change and if the m odeling would still have modeled exceedances, but we know it would give us different results.

The industry modeling report indica ted that it used AERSURFACE to determine the site specific

surface characteristics. The industr y modeling report estimated values for albedo (the fraction of solar energy reflected from the earth back in to space), the Bowen ratio (the method generally used to calculate heat lost or heat gained in a substance), and the surface roughness (sometimes referred to as “Zo”).

Modeling Parameter: Geography and Terrain

The terrain elevation for each modeled recepto r was determined utilizing USGS National Elevation Dataset (NED) data in conjunction wi th the most recent version of AERMAP. No flagpole receptors were used. AERMAP was used to develo p the elevations for buildings, sources, and receptors.

Modeling Parameter: Background Concentrations of SO 2

The Modeling TAD offers two mechanisms for ch aracterizing background concentrations of SO 2 that are ultimately added to the modeled desi gn values: 1) a “first tier” approach, based on monitored design values, or 2) a tempor ally varying approach, based on the 99 th percentile monitored concentrations by hour of day and season or month. For the Nelson Electric Generating Plant and the Nelson In dustrial Steam Company areas of analysis, the industry group chose a “first tier” approach, based on monito red design values from the Westlake monitor, excluding monitored values from a 90-degree sect or centered on the center line from the modeled

sources to the monitor. After excluding a large amount of the monitoring values, the industry group estimated background concentration for this area of analysis was determined to be 37.61 micrograms per cubic meter ( μ g/m 3 ), or 14.37 ppb, 5 and that value was incorporated into the final AERMOD results. See below our analysis of this type of exclusion of some data with impacts of local sources from some wind direct ions from the monitoring data in developing a modified background monitor value. We note that the industry group interpolated the 99 th percentile value rather than selecting the four th highest value for each year. Following the industry group’s methodology but correcting for th is error would change the background value from 14.37 ppb to 14.90 ppb (39 μ g/m 3 )

.

5 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

.28 Typically, any exclusion of m onitoring data and generation of an alternate background concentration is accompanied by a protocol justif ication, as each situation where an alternate background concentration may be appropriate is uni que. Given the close proximity of the sources (primarily Entergy and Sasol) to the Westlake m onitor, we have concerns that more data was excluded than should have been by using the 90 de gree arc. The underlying principle is to allow some data to be dropped when winds transpor t a local source to a monitor, to only have monitoring data that is not signi ficantly impacted by local sources. This new data set can then be used to generate a ‘background’ concentration. The 90 degree arc is potentially reasonable for

intermediate distant sources due to plume spread, etc.; but if a sour ce is fairly close (as in this case) the use of 90 degree arcs drops more monitoring data from the monitoring dataset to estimate background. If more appropriate (smaller) arcs were used then more data would be included in the estimate of background data a nd it would be expectedto yield a higher representative background concentr ation value than used by the indus try. The result of correcting this issue would be higher background value (m ore data would most likely result in a higher value and could not result in a lower value) which when added to modeling would result in higher values than the current an alysis presents. Thus the modeli ng results are biased low due to

this issue. low.

Summary of Modeling Results

The AERMOD modeling parameters for the Nels on Electric Generating Plant and the Nelson Industrial Steam Company areas of analys is are summarized below in Table 2.

Table 2: AERMOD Modeling Parameters for the Calcasieu Area of Analysis

Calcasieu Parish Area of Analysis

AERMOD Version 14134 Dispersion Characteristics Rural

Modeled Sources 8

Modeled Stacks 228

Modeled Structures Yes – when data available

Modeled Fence Lines - Total receptors 44,946 Emissions Type Actual (Annual Avg.) Emissions Years 2013 only Meteorology Years 2009 through 2013 Surface Meteorology Station Baton Rouge Upper Air Meteorology St ation Lake Charles

Methodology for Calculating Background SO 2 Concentration Wind Sector screening and
then1 st tier approach using monitoring values not
excluded29 Calculated Background SO 2 Concentration 14.37/14.9 ppb

The results presented below in table 2 show th e magnitude of the highest predicted modeled

concentration based on actual emissions.

Table 3: Maximum Predicted 99th Percentile 1-Hour SO 2 Concentration in the Calcasieu Parish Area of Analysis Based on Actual Emissions *Equivalent to the 2010 SO 2 NAAQS set at 75 ppb

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

UTM/Latitude UTM/Longitude Modeled (including background) NAAQS

99th Percentile 1-Hour Average 2009-2013 468169.80 3337572.70 206.61 196.5*

We note an error in the conve rsion of the AERMOD modeled 99 th percentile impact from μ g/m 3 to ppb. The industry gro up’s report converts 168.6 μ g/m 3 to 59.77 ppb. However, based on standard conditions of 25C, 1 atm, and a molecular weight of 64 for SO 2 , 168.6 μ g/m 3 equals 64.41 ppb. The industry group’s modeling indi cates that the predicted 99 th percentile 1-hour average concentration within th e chosen modeling domain is 206.61 μ g/m 3 , or 78.78 ppb. This

modeled concentration included the industry group’s calculated background concentration of

SO 2 , and is based on actual annual emissions from the facilities. Based on our correction to the industry group’s calculated backgrou nd concentration, the predicted 99 th percentile 1-hour average is 207.6 μ g/m 3 or 79.31ppb.

The EPA investigated where the maxi mum modeled concentrations of SO 2 are likely to occur because the supporting information provided by the industry group did not include any concentration contour plots or other modeling graphics. Figure 3 is a plot of the maximum impacts from each facility using source groupin g and also the maximum total impact from all sources (not including the b ackground monitor value). The two Entergy Nelson facilities impacted by the July 2, 2016 deadline are in the ar ea north of I-10 (two larg est circles north of I10). Source tagging modeling results for just th e Nelson Electric Generating Plant and Nelson Industrial Steam Company have pred icted maximum impacts of 53 and 83 μ g/m 3 respectively, not including other sources or background concentrations of SO 2 in these values. The maximum impacts in the modeling that were near the stan dard are in the area south of I-10. The maximum

and near maximum modeled values were to the s outh of Citgo and near two other large emitters

of SO 2 , specifically Alcoa and Rain. Based on the EPA’s preliminary source grouping analysis and the cumulative analysis, it appears that the ma ximum impact from all fa cilities is to the south of the Nelson facilities, 10+ km away from Ne lson facilities and closer to Citgo, Alcoa, and Rain. The maximum predicted impact from all f acilities without background concentrations of30 SO 2 near Rain and Citgo was 168.6 μ g/m 3 before the arithmetic corr ections described above, and the maximum predicted impact value from Alcoa was 162 μ g/m 3 , without accounting for other sources or background concentrations of SO 2 . While the ambient air quali ty data collected at the Westlake monitor (AQS ID 220-19-0008) may not adequately characterize the emissions from the two Nelson facilities, the most recent desi gn value based on data co llected between 2012 and 2014 at the Westlake monitor was 35 ppb. This mon itor is located approximately 2.5 km south of the Nelson facilities, and 10 km north of the area where the greatest impacts of SO 2 are expected based on our grouping analysis. While this moni tor is not a good monitor for the maximum impacts of Nelson and other sources, it is cl ose enough that the two Nelson facilities could impact often enough to impact the Westlake monito r’s design value and is informative that the two Nelson facilities may not be causing exceedances. Therefore, the EPA does not believe that the Nelson facilities are the primary contributors to the predicted maximum concentrations of

SO 2 near Rain, Citgo, and Alcoa.

As discussed above the modeling utilized Baton Rouge surface winds (speed & direction) instead

of the Lake Charles surface winds that should have been used. The differences in surface meteorology would impact the frequency of wind directions and speeds that impact maximum concentrations and would also impact how of ten certain sources al ign to yield maximum

concentrations downwind of sources. Without mode ling with correct surface data it is impossible

to assess how the maximum and exceedance concen trations would change and if the modeling would still have modeled exceedances, but we know it would give us different results even if the rest of the modeling was acceptabl e and followed the modeling TAD. In order for the modeling to be a reliable indicator of attainment status, it would need to be reassessed with appropriate

surface station data for the Lake Charles area. In addition there are several other issues that

would need to be addressed: further refineme nts in variable emissions , refinements to stack parameters, refinements in downwash, and a more appropriate background value to assess the

areas around the Nelson facilities and other large emitters of SO 2 . While the corrected modeling values indicate possible exceedances around the area around Rain, Citgo, and Alcoa, the modeling is just too uncertai n and undefendable to make a conclusion that would support designation of nonattainment, even if this modeling indicates nonattainment for part of Calcasieu

Parish. Both Rain and Alcoa are on the SO 2 DRR list submitted by LDEQ to EPA on January 15,

2016 and will have to be addressed in future wo rk with the appropriate surface meteorology and

other source emissions and characterizations. Th e culpability of the Nelson facilities will also have to be addressed in future air quality an alysis. These refinements in inputs and using appropriate surface meteorology would likely result in changes in modeling values and locations of the maximum values, and better support an acc urate determination of the area’s attainment

status.31 Figure 3: Predicted Maximum SO 2 Impacts for Facilities Near the Nelson Industrial Steam Company and the Nelson Industrial Steam Company

Jurisdictional Boundaries:

Once the geographic area of analysis associated with the Nelson Electric Generating Plant, the Nelson Industrial Steam Compa ny, other nearby sources, and background concentration is determined, existing jurisdictiona l boundaries are considered for the purpose of informing our intended unclassifiable area, sp ecifically with respect to cl early defined legal boundaries.

As noted above the EPA recognizes that there are 2 emitters of SO 2 with reported 2011 NEI emissions above 100 tpy in neighboring Orange County, Texas. Echo Carbon Black Plant (4,247 tpy of SO 2 ) is located approximately 2 km from the Calcasieu Parish border, and Orange Mill (2,472 tpy of SO 2 ) is located approximately 3 km from the Calcasieu Parish border. On the basis of no modeling or monitoring data available, the EPA is unable to determine at this time whether these nearby Texas’s sources contribute to ambient air quality impacts within the western edges

of Calcasieu Parish. We note that the Echo Ca rbon Black Plant was identified by Texas as a

DRR source and Texas will have to assess what im pacts occur from the DRR source in the area, including consideration of other sources that have potenti al impacts on local concentration gradients such as the Orange Mill, in the futu re designation rounds. Texas will have to consider if the DRR source (and other nearby sources) have a potential impacts in the western area of

Calcasieu Parish.32 The EPA believes that our intended unclassifiabl e area, consisting of Calcasieu Parish, is comprised of clearly defined legal boundaries, an d we find these boundaries to be a suitably clear basis for defining our inte nded unclassifiable area.

Other Relevant Information

The EPA did not receive any additional informati on about the area in the immediate vicinity of

the two Nelson facilities.

Conclusion

After careful evaluation of the state’s recommendation and supporti ng information, as well as all available relevant information, the EPA intends to designate the area around the Nelson Electric Generating Plant and the Nelson Industrial St eam Company as unclassifiable for the 2010 SO 2 NAAQS. Specifically, the bounda ries are comprised of all area w ithin Calcasieu Parish Borders.

When evaluating the modeling submitted by the i ndustry, it was determined that the industry modeling approach is not consistent with the SO 2 Modeling TAD. The surface meteorological station used in the modeling does not appear to be representative a nd there is an NWS site that is more appropriate in Calcasieu Parish. Furtherm ore, there was an erro r in unit conversion of
modeled results in μ g/m 3 to ppb, selection of appropriate 99 th percentile value from background monitoring data and the background calculation dr opped out more monitored data than should have been done and resulted in a lower backgr ound concentration than is appropriate. Other concerns: the modeling only take s into account 2013 act ual annual emissions based on LDEQ inventory data; the hourly CEM data for Ne lson Electric Generating Plant and the Nelson Industrial Steam Company for the 2012-2014 period was not utilized in the modeling; and constant, rather than hourly-variab le, stack temperature and exit veloci ty were utilized. It is also unclear what building information was availabl e for downwash. Lastly, the background monitor value used may not reflect actual conditions in the area that e xperiences the predicted maximum impacts of SO 2

.

As discussed above, we also do not have info rmation on any potential impacts on the western part of Calcasieu Parish from 2 large Orange County, Texas sources near the western border, which also provide some uncertainty in designating Calcasieu Parish.

For these reasons and based on available inform ation, EPA does not have sufficient information to decide whether the area is attaining the st andard. Therefore, the EP A’s intended designation
for the area within Calcasieu Parish is unclassifiable.

At this time, our intended designations for the st ate only apply to this area and the other area presented in this technical support document. Co nsistent with the conditions in the March 2, 2015 consent decree, the EPA will evaluate and designate all remaining undesignated areas in Louisiana by either December 31, 2017, or December 31, 2020.