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Attachment 1: Supplemental Technical Support for Missouri’s Area Recommendations for the 2010 1-hour SO2 Standard: December 2017 Designations The purpose of this supplemental document is to provide additional information to the U.S. Environmental Protection Agency (EPA) prior to the promulgation of designations in December 2017. In this document, the Missouri Department of Natural Resources’ Air Pollution Control Program (air program) is responding to EPA’s letter and corresponding technical support document (TSD) titled, “Chapter 22: Intended Round 3 Area Designations for the 2010 1-Hour SO2 Primary National Ambient Air Quality Standard for Missouri”, which the air program received on August 22, 2017. Background In July 2011 and April 2013, the air program submitted to the EPA the first sets of state area designation recommendations (e.g. attainment, nonattainment, unclassifiable) for the 2010 1-hour SO2 standard. These recommendations addressed the entire state with an ultimate recommendation of nonattainment for portions of Jackson and Jefferson Counties and unclassifiable for the remainder of the state. These recommendations went through the state’s public process and the Missouri Air Conservation Commission adopted them on June 30, 2011 and April 25, 2013, respectively. Since then, the EPA has designated 2 nonattainment areas, 2 unclassifiable areas, and 1 unclassifiable/attainment area in two separate actions. In December 2016, the air program submitted to the EPA an additional set of area designation recommendations for all remaining undesignated areas in Missouri except areas that are associated with sources for which a new SO2 monitoring network has been installed and has begun operation. Specifically, this included revised recommendations based on technical evaluations using air quality modeling to address seven parts of the State of Missouri: the areas surrounding the Ameren Meramec Energy Center, Empire District - Asbury plant, Montrose Generating Station, Sibley Generating Station, Sikeston Power Station, City Utilities of Springfield - John Twitty Energy Center, and the Thomas Hill Energy Center Power Division. These areas are located in a portion of St. Louis County; Jasper County (adjacent to Barton County); Henry County; a portion of Jackson County; Scott County; Greene County; and Randolph County, respectively. Currently, EPA is in the process of promulgating designations based on states’ recommendations. EPA’s August 22, 2017, letter served as their 120-day notification to the state of EPA’s proposed designations in December 2017. For Henry County, a portion of St. Louis County, Jasper County, Barton County and Randolph County, EPA’s intended unclassifiable/attainment designation is conceptually consistent with our attainment recommendations as submitted in December 2016. The air program agrees with the remainder of EPA’s proposed area designations in Missouri with one exception. EPA is intending to designate Greene County as unclassifiable, although Missouri’s recommendation was a designation of attainment for this area. The air program disagrees with the intended designation and reaffirms the recommendation of an attainment designation for Greene County.

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The technical analysis included in this document provides detailed information that supports Missouri’s recommendation of attainment for Greene County (i.e. the area surrounding the City Utilities facility). This analysis also addresses the concerns and issues raised by EPA’s August 22, 2017, letter and corresponding TSD. Specifically, the air program updated the analysis for this area to include an evaluation of 2015 emissions data for the City Utilities facility and corrections to interactive source emission rates. The analysis utilizes the most recent version of EPA’s dispersion model and processors to take advantage of improvements made in the most recent update (version 16216) and adheres to the modeling protocol submitted with the December 2016 recommendations. The December 2016 area recommendations and the associated modeling files are available on the air program’s webpage: https://dnr.mo.gov/env/apcp/so2.htm. The vast majority of the original modeling files were unchanged during this updated analysis. All changes made to the previously submitted modeling are outlined in this technical documentation. Excerpts of updated modeling files are included in this attachment. Attainment Area Recommendation: Greene County For the area surrounding the City Utilities, Springfield—John Twitty Energy Center (City Utilities), the air program reaffirms the recommendation of an attainment designation for Greene County. EPA has indicated they agree with Missouri’s proposed area boundaries, but has modified Missouri’s recommendation of attainment to unclassifiable due to data issues at the City Utilities plant. Greene County contains one source affected by the federal SO2 data requirements rule: City Utilities Springfield – John Twitty Energy Center. The state selected to characterize the air quality surrounding this source through air dispersion modeling. The air program modeled City Utilities using the most recent three years (2013-2015) of actual emissions data and concurrent representative meteorological data to approximate a monitored design value for the area. The modeled results supported an attainment designation for all of Greene County, and the air program submitted this recommendation to the EPA in our December 2016 submittal.

During the same time period, City Utilities notified the air program of possible moisture issues with the probe used to record SO2 continuous emissions monitoring system (CEMS) readings for the John Twitty Energy Center Unit 1 (JTEC1). The moisture in the probe caused an underestimation of the SO2 emissions in the CEMS readings and invalidated two (2) years of CEMS data: 2015 and 2016. EPA indicated in their TSD that the state’s modeling analysis could not be relied upon for designation purposes since the state’s modeling included an invalidated year of CEMS data.

Subsequently, the air program evaluated several sources of available data to develop an SO2 emissions profile that could be used as a substitute in the modeling analysis. The air program evaluated the use of heat input values, a constant SO2 emission factor, and dynamic SO2 emission factors based on the sulfur content of each plant delivery of coal (e.g. coal receipts). Ultimately the air program decided that the use of the calculated sulfur emission rate from the sulfur and BTU content from the coal receipt data would be the most accurate, and also most conservative

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approach for substituting 2015 emission data for JT EC1 at the City Utilities facility in the modeling analysis.

The updated dispersion modeling for the area surrounding the City Utilities facility results in modeled SO2 design values below the level of the 2010 SO2 NAAQS at all model receptor locations. The maximum modeled result of any receptor in the updated modeling run was 112.4 µg/m3 (42.9 ppb). This is well below the level of the 2010 SO2 NAAQS (196.5 µg/m3 or 75 ppb), thus demonstrating attainment with the NAAQS throughout the entire receptor grid.

Emissions Data for Model Input

The air program updated the modeling analysis for Greene County to include an evaluation of 2015 emissions data for the City Utilities facility and corrections to interactive source emission rates. All other aspects of the modeling analysis, such as the meteorological data and receptor grid, remain the same as submitted in December 2016. Due to a probe malfunction issue at JTEC1, the 2015 CEMS data for this unit, which was used in the modeling analysis for Greene County in our December 2016 submittal, was invalidated. The air program evaluated several sources of available data to develop an SO2 emissions profile that could be used as a substitute in the modeling analysis. The air program determined that calculating the SO2 emission rate for this unit from the coal receipt data from the facility for 2015 was a reasonable and conservatively appropriate approach. The coal receipt data from the facility includes the sulfur and BTU content of all the coal shipments they received in 2015 based on ASTM Test methods D4239 (sulfur content) and D5865 (BTU content). With this information, an SO2 emission rate in lbs SO2/mmBTU was calculated for each coal shipment received. The emission data substitution method utilized for the updated modeling assumes that the calculated SO2 emission rate based on the coal receipt data is held constant between coal shipments and changes each time a new coal shipment is received. A table providing sulfur content, BTU content, and calculated SO2 emissions rate for each shipment received by the facility in 2015 is provided in Table 2. Combining the emission rate with the heat input data (which was not invalidated) reported to the EPA’s Clean Air Markets Division gives temporally allocated hourly SO2 emissions for this unit for the entire year. Table 3 provides an excerpt of the substituted hourly emissions for the entire 2015 calendar year for John Twitty Unit 1. In addition to the issues with the CEMS data, the air program also reviewed the emissions data for the interactive source inventory and discovered a unit conversion error for the interactive sources in Greene County. For the sources without hourly CEMS data, the highest annual emission rate was chosen from the time period 2013-2015 to represent actual emissions from that source in the model analysis. Since the error occurred in the conversion from tons to grams, the error does not affect the evaluation of annual emissions; however, it does change the grams per second value in the model. Table 1 details the corrected interactive source inventory. 

Table 1 – Greene County Interactive Source Inventory

Source Name Original average unit emission rate in modeling (g/s)

Updated average unit emission rate in modeling (g/s)

Distance to the facility (km)

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John Twitty Energy Center (077-0039)

Hourly CEMS (2013-2015)

Unit 1: corrected by coal sulfur data in

Hourly CEMS

0

Unit2: The Same Hourly CEMS

James River Power Station (077-0005)

Hourly CEMS The Same Hourly CEMS for All Units

12

Timken SMO LLC (077-0004)

Unit09: 0.00077 Unit09: 2.861 5.6 Unit10: 0.000101 Unit10: 0.109

Euticals Inc., Springfield (077-0017)

Unit12A: 0.00077 Unit12A: 0.138 7.2

Noble Hill Landfill Renewable Energy Center (077-0170)

E101: 0.0000164 E101: 0.033 25 E102: 0.0000148 E101: 0.0296

Modeling Results

In our December 2016 submittal, the 99th percentile maximum daily 1-hour SO2 modeled concentrations for 2013-2015 for the area was 82.6 μg/m3 or 31.6 ppb. Based on the updated emissions data, the maximum modeled concentration is 112.4 µg/m3 or 42.9 ppb.

The updated modeling analysis did increase the maximum modeled SO2 design values in the area surrounding the City Utilities facility. This was expected because the adjustments to the interactive source inventory and the SO2 data substitution method for 2015 emissions at John Twitty Unit 1 both increased the emissions data when compared to the analysis performed in the December 2016 recommendations. However, the updated analysis still comfortably demonstrates attainment with the 2010 SO2 NAAQS, with a maximum modeled design value of 112.4 µg/m3 (42.9 ppb), which is approximately 57 percent of the level of the standard.

Figure 1, displays the 2013-2015 modeled design values for all receptors in this updated modeling analysis.

                                                            1 This unit was operated only 218 hours during the highest‐rate year. 

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Figure 1 – Greene County Revised Modeled SO2 Concentrations

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Conclusion Based on the updated modeling analysis, the area surrounding the John Twitty Energy Center is in compliance with the 2010 SO2 NAAQS. This modeling analysis was performed in accordance with the EPA’s SO2 data requirements rule and applicable EPA guidance. The updated analysis addresses all concerns that EPA noted in the August 22, 2017, letter and TSD including an adjustment for the 2015 emissions data at Unit 1 for the facility. In addition, corrections were made to the interactive source emissions rates used in the modeling analysis. Finally, the updated analysis was performed using the latest EPA dispersion model and preprocessor software. Therefore, the air program reaffirms its recommendation of attainment for Greene County.

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Table 2. City Utilities of Springfield-John Twitty Energy Center--Coal Receipt Data 

Date Coal Received

Dry Sulfur Content (%)

Dry BTU Content

(BTU/lb coal)

Calculated SO2 Emission Factor

(lb/MMBtu) 2/7/2015 0.30 12159 0.49

2/12/2015 0.37 12241 0.60 2/17/2015 0.27 12075 0.45 2/21/2015 0.40 12082 0.66 2/23/2015 0.26 12061 0.43 2/25/2015 0.29 12135 0.48 3/2/2015 0.32 12226 0.52 3/5/2015 0.29 12097 0.48 3/6/2015 0.25 12057 0.41 3/9/2015 0.28 12105 0.46

3/17/2015 0.29 11981 0.48 4/9/2015 0.30 12192 0.49

4/14/2015 0.41 12184 0.67 5/14/2015 0.3 12118 0.50 5/22/2015 0.32 12291 0.52 5/30/2015 0.40 12199 0.66 6/6/2015 0.29 12189 0.48

6/13/2015 0.30 12264 0.49 6/21/2015 0.31 12264 0.51 6/30/2015 0.47 12142 0.77 7/20/2015 0.23 12056 0.38 7/28/2015 0.26 11991 0.43 8/5/2015 0.30 12061 0.50

8/12/2015 0.28 12009 0.47 8/19/2015 0.28 12172 0.46 8/21/2015 0.40 12194 0.66 8/26/2015 0.37 12157 0.61 8/27/2015 0.43 12097 0.71 9/3/2015 0.38 12078 0.63 9/9/2015 0.33 12213 0.54

9/11/2015 0.40 12076 0.66 9/17/2015 0.39 12286 0.63 9/19/2015 0.38 11973 0.63 9/25/2015 0.29 12104 0.48 9/27/2015 0.35 12091 0.58

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10/4/2015 0.32 12132 0.53 10/11/2015 0.37 12251 0.60 10/8/2015 0.27 12191 0.44

10/16/2015 0.27 12032 0.45 10/19/2015 0.23 12111 0.38 10/22/2015 0.28 12128 0.46 10/26/2015 0.25 12187 0.41 11/2/2015 0.34 12080 0.56 11/9/2015 0.30 12041 0.50

11/16/2015 0.28 12205 0.46 11/23/2015 0.29 12177 0.48 12/3/2015 0.25 12178 0.41

12/14/2015 0.23 12138 0.38 12/28/2015 0.26 12174 0.43

 

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Table 3. City Utilities of Springfield-John Twitty Energy Center, Unit 1—Excerpt of substituted hourly emissions data for AERMOD

CAMD Date

CAMD Hour

CAMD Hourly Heat Input

(MMBtu)

Calculated SO2 Emission Factor

(lb SO2/MMBTU)

Calculated SO2 Emission

Rate (grams/second)

3/1/2015 0 1667.2 0.48 100.83 3/1/2015 1 1651 0.48 99.85 3/1/2015 2 1656.9 0.48 100.21 3/1/2015 3 1639.2 0.48 99.14 3/1/2015 4 1645.1 0.48 99.49 3/1/2015 5 1701.9 0.48 102.93 3/1/2015 6 1708.8 0.48 103.35 3/1/2015 7 1722.7 0.48 104.19 3/1/2015 8 1678.6 0.48 101.52 3/1/2015 9 1612.6 0.48 97.53 3/1/2015 10 1679 0.48 101.54 3/1/2015 11 1649.4 0.48 99.75 3/1/2015 12 1641 0.48 99.25 3/1/2015 13 1670.7 0.48 101.04 3/1/2015 14 1619.3 0.48 97.93 3/1/2015 15 1525.7 0.48 92.27 3/1/2015 16 1661.7 0.48 100.50 3/1/2015 17 1700.7 0.48 102.86 3/1/2015 18 1657.5 0.48 100.24 3/1/2015 19 1655.7 0.48 100.13 3/1/2015 20 1681.6 0.48 101.70 3/1/2015 21 1650.5 0.48 99.82 3/1/2015 22 1674.6 0.48 101.28 3/1/2015 23 1653.8 0.48 100.02 3/2/2015 0 1661 0.52 108.83 3/2/2015 1 1678.3 0.52 109.96 3/2/2015 2 1665 0.52 109.09 3/2/2015 3 1705.8 0.52 111.76 3/2/2015 4 1673.3 0.52 109.63 3/2/2015 5 1744.1 0.52 114.27 3/2/2015 6 1776.8 0.52 116.41 3/2/2015 7 1789.6 0.52 117.25 3/2/2015 8 1672.9 0.52 109.61 3/2/2015 9 1703 0.52 111.58 3/2/2015 10 1478.2 0.52 96.85

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3/2/2015 11 1651.4 0.52 108.20 3/2/2015 12 1703.6 0.52 111.62 3/2/2015 13 1629.7 0.52 106.78 3/2/2015 14 1625.8 0.52 106.52 3/2/2015 15 1650.6 0.52 108.14 3/2/2015 16 1615 0.52 105.81 3/2/2015 17 1623 0.52 106.34 3/2/2015 18 1656.9 0.52 108.56 3/2/2015 19 1651.4 0.52 108.20 3/2/2015 20 1628.3 0.52 106.68 3/2/2015 21 1637.4 0.52 107.28 3/2/2015 22 1623.6 0.52 106.38 3/2/2015 23 1625.2 0.52 106.48 3/3/2015 0 1621.5 0.52 106.24 3/3/2015 1 1616.9 0.52 105.94 3/3/2015 2 1605.6 0.52 105.20 3/3/2015 3 1597.4 0.52 104.66 3/3/2015 4 1601.6 0.52 104.93 3/3/2015 5 1669.5 0.52 109.38 3/3/2015 6 1698.9 0.52 111.31 3/3/2015 7 1720.6 0.52 112.73 3/3/2015 8 1631.8 0.52 106.91 3/3/2015 9 1669.9 0.52 109.41 3/3/2015 10 1628.7 0.52 106.71 3/3/2015 11 1392.6 0.52 91.24 3/3/2015 12 1650.2 0.52 108.12 3/3/2015 13 1733.4 0.52 113.57 3/3/2015 14 1724.1 0.52 112.96 3/3/2015 15 1657 0.52 108.56 3/3/2015 16 1686.3 0.52 110.48 3/3/2015 17 1723.1 0.52 112.90 3/3/2015 18 1743.4 0.52 114.23 3/3/2015 19 1748.9 0.52 114.59 3/3/2015 20 1703.9 0.52 111.64 3/3/2015 21 1685 0.52 110.40 3/3/2015 22 1706.9 0.52 111.83 3/3/2015 23 1708.2 0.52 111.92 3/4/2015 0 1762.6 0.52 115.48 3/4/2015 1 1792 0.52 117.41 3/4/2015 2 1741.3 0.52 114.09 3/4/2015 3 1710.9 0.52 112.10 3/4/2015 4 1753.4 0.52 114.88 3/4/2015 5 1789.4 0.52 117.24

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3/4/2015 6 1831.8 0.52 120.02 3/4/2015 7 1860.6 0.52 121.90 3/4/2015 8 1738.2 0.52 113.88 3/4/2015 9 1505.8 0.52 98.66 3/4/2015 10 1814.3 0.52 118.87 3/4/2015 11 1803.7 0.52 118.18 3/4/2015 12 1831.4 0.52 119.99 3/4/2015 13 1814.4 0.52 118.88 3/4/2015 14 1820.4 0.52 119.27 3/4/2015 15 1792 0.52 117.41 3/4/2015 16 1806.6 0.52 118.37 3/4/2015 17 1811.3 0.52 118.67 3/4/2015 18 1824.6 0.52 119.55 3/4/2015 19 1820.9 0.52 119.30 3/4/2015 20 1795.8 0.52 117.66 3/4/2015 21 1812.9 0.52 118.78 3/4/2015 22 1821.7 0.52 119.36 3/4/2015 23 1832.9 0.52 120.09 3/5/2015 0 1829.6 0.48 110.65 3/5/2015 1 1829 0.48 110.62 3/5/2015 2 1834.9 0.48 110.97 3/5/2015 3 1839.4 0.48 111.24 3/5/2015 4 1858.2 0.48 112.38 3/5/2015 5 1915.5 0.48 115.85 3/5/2015 6 1957.3 0.48 118.37 3/5/2015 7 1978.8 0.48 119.68 3/5/2015 8 1838.8 0.48 111.21 3/5/2015 9 1816.4 0.48 109.85 3/5/2015 10 1865.4 0.48 112.82 3/5/2015 11 1825.4 0.48 110.40 3/5/2015 12 1832.7 0.48 110.84 3/5/2015 13 1834.5 0.48 110.95 3/5/2015 14 1823.9 0.48 110.31 3/5/2015 15 1831 0.48 110.74 3/5/2015 16 1839.4 0.48 111.24 3/5/2015 17 1798.5 0.48 108.77 3/5/2015 18 1823.7 0.48 110.29 3/5/2015 19 1841.2 0.48 111.35 3/5/2015 20 1845.7 0.48 111.63 3/5/2015 21 1837.3 0.48 111.12 3/5/2015 22 1824.1 0.48 110.32 3/5/2015 23 1863.1 0.48 112.68 3/6/2015 0 1857.4 0.41 95.95

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3/6/2015 1 1839.9 0.41 95.05 3/6/2015 2 1864.6 0.41 96.32 3/6/2015 3 1824.4 0.41 94.25 3/6/2015 4 1836.2 0.41 94.86 3/6/2015 5 1902.9 0.41 98.30 3/6/2015 6 1600.4 0.41 82.67 3/6/2015 7 1212.2 0.41 62.62 3/6/2015 8 1218.9 0.41 62.97 3/6/2015 9 1150.8 0.41 59.45 3/6/2015 10 1130.8 0.41 58.42 3/6/2015 11 1158.4 0.41 59.84 3/6/2015 12 1183.3 0.41 61.13 3/6/2015 13 1163.9 0.41 60.13 3/6/2015 14 1151.3 0.41 59.47 3/6/2015 15 1124.1 0.41 58.07 3/6/2015 16 1153.3 0.41 59.58 3/6/2015 17 1159.5 0.41 59.90 3/6/2015 18 1162.4 0.41 60.05 3/6/2015 19 1166 0.41 60.23 3/6/2015 20 1178.1 0.41 60.86 3/6/2015 21 1173.8 0.41 60.64 3/6/2015 22 1155.2 0.41 59.68 3/6/2015 23 1155 0.41 59.67 3/7/2015 0 1155.4 0.41 59.69