
Executive Summary:
      On June 22, 2010, the EPA revised the primary SO2 NAAQS, establishing a new 1-hour (1-hr) SO2 standard of 75 parts per billion (ppb). Under the EPA's regulations at 40 CFR part 50, the 2010 1-hr SO2 NAAQS is met at a monitoring site when the 3-year average of the annual 99[th] percentile of daily maximum 1-hour average concentrations is less than or equal to 75 ppb (based on the rounding convention in 40 CFR part 50, appendix T).  Upon promulgation of a new or revised NAAQS, the CAA requires the EPA to designate any area that does not meet (or that contributes to ambient air quality in a nearby area that does not meet) the NAAQS as nonattainment. On August 5, 2013, the EPA designated a portion of Jackson County, Missouri, as nonattainment for the 2010 1-hr primary SO2 NAAQS, effective October 4, 2013. The nonattainment designation was based on 2009-2011 monitoring data from the Troost monitor in Kansas City, Missouri, showing violations of the NAAQS. Figure 1 shows a map of the nonattainment area boundary and the Troost design value monitor. The nonattainment designation action established an attainment date of October 4, 2018 (i.e., five years after the effective date of the nonattainment designation). 
      Missouri was required to submit a SIP for the Jackson County SO2 nonattainment area that meets the requirements of CAA sections 110, 172(c) and 191-192 by April 4, 2015 (i.e., within 18 months of the effective date of the nonattainment designation). The State submitted the "Nonattainment Area Plan for the 2010 1-hour Sulfur Dioxide National Ambient Air Quality Standard Jackson County Sulfur Dioxide Nonattainment Area" on October 16, 2015 and subsequently withdrew the plan on June 11, 2018 (except for the 2011 baseline inventory required by CAA section 172(c)(3)). The EPA approved the State's 2011 baseline inventory on February 13, 2019. 
      On May 4, 2018, the State submitted a request for the EPA to determine that the Jackson County SO2 nonattainment area attained the 2010 1-hour primary SO2 NAAQS per the EPA's Clean Data Policy (a clean data determination or CDD). The CDD policy represents the EPA's interpretation that certain planning-related requirements of part D of the CAA, such as the attainment demonstration, are suspended for areas that are attaining the NAAQS. A determination of attainment, or CDD, does not constitute a formal redesignation to attainment. The EPA published a notice of proposed rulemaking (NPRM) to approve the State's request for a CDD in the Federal Register on April 15, 2020 and published a Notice of Final Rulemaking (NFRM) approving the request in the Federal Register on July 9, 2020. 

	
                                          
      Figure 1. Map of the Jackson County SO2 Nonattainment Area Boundary.
                                       

      On February 18, 2021, the State submitted a request for redesignation of the nonattainment area to attainment and a SIP revision containing a 10-year maintenance plan for the area. The primary SO2 control strategy for the area consisted of switching from burning coal to natural gas at the Vicinity Energy-Kansas City (Vicinity, formerly Veolia) steam plant located in downtown Kansas City, Missouri. The location of the Vicinity facility is depicted in Figure 1. On September 7, 2021, the State submitted a supplement to the maintenance plan including a Consent Agreement with Vicinity to make the fuel switch permanent and enforceable, along with an updated modeling demonstration.  
 
      The EPA is publishing a NPRM in the Federal Register proposing to approve the State's redesignation request and maintenance plan. The requirements for redesignation and maintenance are discussed in the NPRM. This technical support document (TSD) for the proposed redesignation discusses the EPA's review of certain elements of the redesignation request, the maintenance plan, supplemental modeling information, and the Consent Agreement. This TSD discusses the EPA's review of the following CAA section 107(d)(3)(E) redesignation criteria:  (i) a determination of attainment; (iii) a determination that the improvement in air quality is due to permanent and enforceable reductions in emissions; and (iv) a fully approved maintenance plan. It also addresses CAA section 175A maintenance plan criteria: 1) attainment inventory; 2) maintenance demonstration; and 3) continued monitoring. The EPA's review of the remaining redesignation and maintenance plan criteria are sufficiently addressed in the NPRM. 
      This TSD provides support for EPA's proposed approval of the request to redesignate the area to attainment and of the 10-year maintenance plan.
What are the Criteria for Redesignation from Nonattainment?
      The CAA provides the requirements for redesignating a nonattainment area to attainment. Specifically, section 107(d)(3)(E) of the CAA allows for redesignation of a nonattainment area provided that:
      (i) the Administrator determines that the area has attained the applicable NAAQS;
      (ii) the Administrator has fully approved the applicable implementation plan for the area under section 110(k);
      (iii) the Administrator determines that the improvement in air quality is due to permanent and enforceable reductions in emissions resulting from implementation of the applicable SIP and applicable federal air pollutant control regulations and other permanent and enforceable reductions;
      (iv) the Administrator has fully approved a maintenance plan for the area as meeting the requirements of section 175A; and
      (v) the State containing such area has met all requirements applicable to the area for purposes of redesignation under section 110 and part D of the CAA.
      This TSD discusses the EPA's review of redesignation criterion (i) (the Administrator determines that the area has attained the applicable NAAQS), criterion (iii) (the Administrator determines that the improvement in air quality is due to permanent and enforceable reductions in emissions) and portions of criterion (iv) (the Administrator has fully approved a maintenance plan for the area as meeting the requirements of section 175A). The EPA's review of criterion (ii) (the Administrator has fully approved the applicable implementation plan for the area under section 110(k)) and criterion (v) (the State containing such area has met all requirements applicable to the area for purposes of redesignation under section 110 and part D of the CAA) are sufficiently addressed in the NPRM.
      On April 16, 1992, the EPA provided guidance on redesignation in the General Preamble for the Implementation of Title I of the CAA Amendments of 1990 and supplemented this guidance on April 28, 1992.[,] The EPA has provided further guidance on processing redesignation requests in several guidance documents. This TSD references two of these documents: (1) The September 4, 1992 memo "Procedures for Processing Requests to Redesignate Areas to Attainment" (Calcagni Memo); and (2) the EPA's April 23, 2014 memorandum "Guidance for 1-hour SO2 Nonattainment Area SIP Submissions" (hereafter 2014 SO2 Guidance). The EPA also references the code of federal regulations (CFR) 40 CFR Part 51, Appendix W, Guideline on Air Quality Models (Appendix W) in this document.

What are the Criteria for a Maintenance Plan?
      The CAA requires the EPA to determine that the area has a fully approved maintenance plan pursuant to section 175A of the CAA (criterion (iv)) to redesignate an area to attainment. CAA section 175A sets forth the elements of a maintenance plan for areas seeking redesignation from nonattainment to attainment. The maintenance plan must demonstrate continued attainment of the applicable NAAQS for at least 10 years after the Administrator approves a redesignation to attainment. Eight years after the redesignation, the State must submit a revised maintenance plan demonstrating that attainment will continue to be maintained for the 10 years following the initial 10-year period. To address the possibility of future NAAQS violations, the maintenance plan must contain contingency measures as the EPA deems necessary to assure prompt correction of any future 2010 1-hr SO2 NAAQS violations. The Calcagni Memo provides further guidance on the content of a maintenance plan, explaining that a maintenance plan should address five requirements:
 An attainment emissions inventory;
 A maintenance demonstration; 
 Continued monitoring; 
 Verification of continued attainment; and 
 A contingency plan. 
      This TSD only discusses the EPA's review of the maintenance plan criteria 1) attainment emissions inventory, 2) maintenance demonstration and 3) continued monitoring. The EPA's review of maintenance plan criteria 4) verification of continued attainment and 5) contingency plan requirements are sufficiently addressed in the preamble to the NPRM.
Redesignation Criterion (i) Determination of Attainment of the NAAQS
      To redesignate a nonattainment area to attainment, the CAA requires the EPA to determine that the area has attained the applicable NAAQS. The two primary methods for evaluating ambient air quality impacted by SO2 emissions are through air quality monitoring and dispersion modeling. Monitoring data are evaluated in accordance with 40 CFR 50.17 and Appendix T of part 50, based on three complete, consecutive calendar years of quality-assured air quality monitoring data. For the monitoring data to support a conclusion that the area is attaining the NAAQS, the 3-year average of the annual 99[th] percentile (fourth highest value) of daily maximum 1-hr average concentrations measured at each monitor within an area must be less than or equal to 75 ppb. The data must be collected and quality-assured in accordance with 40 CFR part 58 and recorded in the EPA Air Quality System (AQS). The EPA's determination of attainment can be based on monitoring data alone, without the need for dispersion modeling analyses, if the air agency provides an analysis demonstrating that the monitor(s) for the affected area is in the area of maximum concentration of SO2.
      The Troost design value monitor is the only State and Local Air Monitoring Station (SLAMS) or SLAMS-like monitor operational in the nonattainment area. The JFK monitor, which is located near the nonattainment area in Kansas, was used for the background SO2 concentration analysis discussed in the Maintenance Demonstration section of this TSD. Figure 2 shows the Troost and JFK monitors in relation to the nonattainment area. 
      Figure 2. Location of SO2 Monitors In or Near the Nonattainment Area.
      
      On May 4, 2018, the State submitted a request asking the EPA to determine that the Jackson County nonattainment area attained the 2010 1-hr primary SO2 NAAQS per the EPA's Clean Data Policy. The CDD policy represents the EPA's interpretation that certain planning-related requirements of part D of the Act, such as the attainment demonstration, reasonably available control measures (RACM), and reasonable further progress (RFP), are suspended for areas that are attaining the NAAQS. A determination of attainment, or CDD, does not constitute a formal redesignation to attainment. If the EPA subsequently determines that an area is no longer attaining the standard, those requirements that were suspended by the CDD would again be required.
      The May 2018 request was based on the most recent three years of complete, quality-assured, and certified ambient air monitoring data from the 2015-2017 monitoring period from the Troost monitor; the design value for 2015-2017 was 57.0 ppb. In a response letter, dated November 13, 2018, the EPA stated that because the request did not include a modeling demonstration showing attainment utilizing the most recent three years of actual emissions or a demonstration that the monitor was located in the area of maximum concentration for the nonattainment area, the State's request did not contain the necessary supporting information as outlined in the 2014 SO2 Guidance. In a letter dated March 1, 2019, the State provided modeling of the most recent three years of actual emissions (2016-2018) for the nonattainment area. Through subsequent email communications, the State supplemented its modeling demonstration by adding emission sources to the analysis and updating the SO2 background concentration. The EPA published a NPRM to approve the State's CDD request in the Federal Register on April 15, 2020, based on 2016-2018 monitoring data and on modeling of 2016-2018 actual emissions from all permitted sources of SO2 emissions located inside the nonattainment area and within 20 km of the NAA boundary.  After public notice and comment, the EPA published a NFRM in the Federal Register on July 9, 2020, determining that the area attained the 2010 1-hr SO2 NAAQS. 
      On February 18, 2021, the State submitted a request for redesignation of the nonattainment area to attainment and a SIP revision containing a 10-year maintenance plan for the area. After receiving the State's request for redesignation, the EPA reviewed the most recent, 2018-2020, 99[th] percentile 1-hr SO2 values and the 3-year averages of those values (i.e., design value) from the Troost monitor to confirm that the area is still attaining the standard. Data from 2015-2020 at the Troost Monitor are summarized in Table 1. 
      
Table 1. 2015-2020 Troost Street Monitor Data (parts per billion (ppb)); 99[th] Percentile (99[th] %) and 3-year design value (dv)
                                     Site
                                2015 99[th]  %
                                2016 99[th]  %
                                2017 99[th]  %
                                2018 99[th]  %
                                2019 99[th]  %
                                 2020 99[th] %
                                 2015-2017 dv
                                 2016-2018 dv
                                 2017-2019 dv
                                2018 - 2020 dv
                                    Troost
                                       
                                     142.0
                                       
                                      9.4
                                       
                                     18.4
                                       
                                      6.1
                                       
                                      6.5
                                       
                                      7.1
                                       
                                     57.0
                                       
                                     11.0
                                       
                                     10.0
                                       
                                      7.0
      
      The most recent 3-year design value (7.0 ppb for the 2018-2020 period) for the Troost monitor continues to meet and is well below the 2010 1-hr SO2 NAAQS. The Vicinity facility transitioned from burning coal to natural gas beginning in 2016 and ceased burning coal completely in 2017. The SO2 emission reductions resulting from the fuel switch have yielded air quality improvements, as shown in the Troost monitoring data beginning in 2016. The maintenance plan contains provisions for the continued operation of the Troost monitor to verify continued attainment/maintenance of the NAAQS.
Redesignation Criterion (iii) Permanent and Enforceable Emissions
      The EPA is proposing to approve the cessation of coal combustion at the Vicinity facility as the permanent and enforceable emission reduction measure necessary for the area to maintain the NAAQS. Vicinity's construction permit #CP122016-009 restricts Boilers 1A, 6, and 8 to combusting exclusively natural gas, and its current operating permit #OP2018-006 requires natural gas in all four boilers (including Boiler 7). In lieu of submitting these permits for inclusion in the Missouri SIP in order to make the fuel switch requirements permanent, Missouri elected to enter into a Consent Agreement with Vicinity and submit it for approval into the SIP as Appendix 1 of the September 2021 maintenance plan supplement.
      Section 1.A of the Vicinity/MoDNR Consent Agreement prohibits the future combustion of coal in Boilers 1A, 6, 7, and 8.  It also allows Vicinity to utilize natural gas, ultra-low sulfur diesel (ULSD) containing no more than 15 parts per million (ppm) sulfur by volume, biofuel containing no more than 15 ppm sulfur by volume, or a blend of biofuel and ULSD containing no more than 15 ppm sulfur by volume, as long as the facility obtains any necessary air permits in the future. While the Consent Agreement may be terminated under state law by mutual agreement by both parties, once it has been approved into the SIP, the requirements are permanent and federally enforceable. The requirements of the Consent Agreement remain applicable until Missouri submits a SIP revision that is approved by EPA. That revision must include a demonstration that it would not interfere with the attainment or maintenance of any NAAQS, pursuant to CAA section 110(l). The EPA is proposing to find that the fuel sulfur content limit of 15 ppm by volume for Vicinity's four boilers is protective of the 1-hour SO2 NAAQS based on the modeling demonstration included in the September 2021 submittal. Details about the modeling demonstration are in the "Maintenance Plan Criterion (2) Maintenance Demonstration" section below. 
      The EPA is proposing to determine that the fuel switch provisions in the Vicinity/MoDNR Consent Agreement are practically enforceable because they require Vicinity to demonstrate compliance with the fuel restrictions by maintaining a record of fuel deliveries and fuel supplier information, including the sulfur content of purchased fuels. Furthermore, Vicinity must maintain a record of the current inventory of fuels and the date(s) of removal of all coal handling equipment located at the facility and make these records available to MoDNR immediately upon request. If Vicinity combusts any fuel not allowed by the Consent Agreement, it must report this noncompliance to MoDNR within 10 days after the end of the month that the prohibited fuel is combusted.
Redesignation Criterion (iv) Approved Maintenance Plan
      Maintenance Plan Criterion (1) Attainment Emissions Inventory and Future Year Projections
      The Calcagni memo describes two ways for a State to demonstrate maintenance of the NAAQS for a period of 10 years following the redesignation of the area: 1) the State can show that future emissions of a pollutant will not exceed the level of the attainment inventory, or 2) the State can model to show that the future mix of sources and emission rates will not cause a violation of the standard. The memo goes on to say that areas required to model to demonstrate attainment of the standard should complete the same level of modeling to demonstrate that the permanent and enforceable emissions are enough to maintain the standard. 
      The State completed multiple modeling demonstrations to show that the standard will be maintained. Because the modeling (particularly the supplemental modeling information submitted on September 7, 2021) demonstrating continued maintenance is based on permanent and enforceable emission reductions, the State contends, and the EPA proposes to agree, that the future mix of sources and emission rates will not cause a violation of the standard. Because the supplemental modeling analysis demonstrates continued maintenance, the State did not submit a projected future-year emissions inventory. This section of the TSD summarizes the baseline and attainment year emissions inventories for the Jackson County SO2 nonattainment area. Missouri selected 2011 as the baseline emissions inventory year and 2017 as the attainment inventory year. 
      2011 Baseline Emissions Inventory
      The State's 2011 baseline inventory required by CAA section 172(c)(3) was included in the 2015 attainment plan submittal. In June 2018, the State withdrew its attainment plan except the 2011 baseline emissions inventory, and the EPA approved the State's 2011 baseline inventory on February 13, 2019.  For the baseline inventory, the State used whole county National Emissions Inventory (NEI) data for point, nonpoint and mobile source emissions. The State estimated that 2011 SO2 emissions for the entirety of Jackson County were 27,668 tons per year (tpy). This includes 27,513 tpy from point sources; 87 tpy from nonpoint sources; and 68 tpy from mobile sources.
      2017 Attainment Year Emissions Inventory
      A State's maintenance plan should include an attainment inventory that identifies the level of emissions in the affected area sufficient for attaining and maintaining the SO2 NAAQS. The State chose 2017 as the attainment year inventory, except 2018 emissions were used for the Vicinity facility. Because Vicinity continued burning coal on a select number of days in 2017, MoDNR's use of 2018 emissions for this facility reflects the completion of the fuel switch from coal to natural gas combustion. The State estimated that the nonattainment area's 2017 SO2 emissions were 156.96 tpy. This includes 6.59 tpy from point sources; 81.62 tpy from nonpoint sources; and 68.75 tpy from mobile sources. The State's estimates for SO2 emissions from nonpoint sources and mobile sources included emissions from these source categories from the entirety of Jackson County. 
      The point source portion of the 2011 baseline inventory included point sources located throughout Jackson County, while the 2017 attainment year emissions inventory only covered point sources inside the nonattainment area. Therefore, total point source emissions in the 2011 baseline inventory cannot be directly compared to total point source emissions in the 2017 attainment year. For this reason, Table 2 summarizes facility-level SO2 emissions for only those sources located inside the nonattainment area for the 2011 baseline and 2017 attainment year. As shown in the table, the greatest reduction in point source SO2 emissions from the 2011 baseline and 2017 attainment year emissions inventories is attributed to Vicinity, as a result of the permanent and enforceable termination of coal combustion at the facility. 
      
      
      
      
      
      
Table 2.  Facility-level SO2 Emissions Comparison from 2011 Baseline and 2017 Attainment Year Emissions Inventories
FACILITY NAME
                                       
                               Tons Per Year SO2

                                     2011
                                     2017
Vicinity
                                     6,742
                                     0.93
Superior Bowen Asphalt
                                     0.432
                                       0
A-1 Painting
                                     0.008
                                       0
United States Postal Service
                                     0.008
                                       0
Mizkan Americas
                                       0
                                       0
General Mills
                                     0.013
                                       0
KCPL Northeast Station
                                     0.325
                                     0.18
Land O'Lakes Purina Feed
                                     0.002
                                       0
Blue River Treatment Plant
                                     0.222
                                     5.48
Gateway Packing Company
                                     0.003
                                     0.003
Profile Cabinet
                                     0.016
                                       0
Brenntag Mid-South Inc
                                       0
                                       0
Allied Lithographing Company
                                     0.002
                                       0
Moly-Cop USA
                                     0.059
                                       0
G and K Services
                                     0.003
                                       0
Mid-America Car Inc
                                     0.761
                                       0
Sprint Communications
                                     0.012
                                       0
Midwest Block and Brick
                                     0.004
                                       0
Solvent Recovery LLC
                                     0.000
                                       0
Total Nonattainment Area Point Source Emissions
                                     6,744
                                     6.59 

      Table 3 provides a comparison of the baseline (2011) and attainment year (2017) emissions for the nonpoint and mobile source categories for the entirety of Jackson County. The EPA proposes to approve the attainment year inventory as reflective of actual emissions in an attainment year. 
Table 3. Jackson County Base Year (2011) and Attainment Year (2017) SO2 Emissions Comparison for Nonpoint and Mobile Sources, tons per year (tpy)
                              Emissions Category
                           2011 SO2 Emissions (tpy)
                           2017 SO2 Emissions (tpy)
Nonpoint Source¹
                                      87
                                     81.62
Mobile Source¹[,] ²
                                      68
                                     68.75
¹ Nonpoint and Mobile Source emissions were estimated using EPA guidelines and State-specific data.
² Mobile source includes onroad and nonroad mobile source categories.

   Maintenance Plan Criterion (2) Maintenance Demonstration
   This TSD discusses the EPA's review of modeling submitted by the State for its redesignation request and the maintenance plan. The modeling review in this TSD focuses on the updated modeling demonstration submitted with the maintenance plan supplement in September 2021 (supplemental modeling). 
   As the EPA's review confirms, the supplemental modeling aligns with the modeling guidelines of Appendix W. The EPA is basing its proposed approval of the maintenance plan upon the supplemental modeling analysis submitted by the State in September 2021. A summary of the model inputs is shown in Table 4. MoDNR used the most recent versions of the models that were available at the beginning of this effort. Only regulatory default options were utilized in this demonstration.
   
   
   
   
   
   
   
   
   
Table 4. Model Inputs Used in Supplemental Modeling
AERMOD
19191
AERMET
19191
AERSURFACE
13016
Building Downwash
Included for Vicinity, Ingredion, and Hawthorn facilities
Meteorology 
2013-2017; Charles Wheeler Downtown Kansas City Airport (surface data); Topeka, KS (upper air data)[1]
Receptor grid
100-meter spacing throughout the entire nonattainment area
Stack Height
The lesser of the source's actual stack height, or Good Engineering Practice (GEP) stack height
Stack Parameter Characteristics (exit velocity and exit temperature)
Hawthorn unit 5A stack parameters include hourly variable temperatures and exit velocities based on 2014-2018 CEMS data. 

The stack parameters for sources without continuous emissions monitoring systems were modeled at constant temperatures and exit velocities obtained from the facilities, consistent with  the CDD 
Background Value (ppb)
8.9 μg/m[3] or 3.4 ppb, JFK Monitor
Explicitly Modeled Sources
All permitted sources with any SO2 emissions within the nonattainment areas; Ingredion and Hawthorn facilities outside of the nonattainment area 


Meteorology

      The state followed the methodology and procedures in Appendix W and the 2014 SO2 Guidance in the selection and processing of raw meteorological data into an AERMOD-ready format.
The selection of meteorological data should be based on spatial and climatological (temporal) representativeness. The representativeness of the data is determined based on: 1) the proximity of the meteorological monitoring site to the area under consideration, 2) the complexity of terrain, 3) the exposure of the meteorological site, and 4) the period of time during which data are collected. Sources of meteorological data include National Weather Service (NWS) stations, site-specific or onsite data, and other sources such as universities, Federal Aviation Administration (FAA), and military stations. 

      Consistent with the meteorological data selection for the CDD, this modeling analysis used National Weather Service (NWS) surface meteorology from the Charles B. Wheeler Downtown Kansas City Airport (WBAN No. 13988, located at +39.13 -94.6, approximately 4 km to the north of the nonattainment area), and coincident upper air observations from Topeka Regional Airport in Kansas (WBAN No. 13996, located at +39.07 -95.63, approximately 115 km west of the nonattainment area), as representative of meteorological conditions within the modeling domain. The most recent certified data available covering the five-year from 2014-2018 were used in this analysis. 
      
      The surface wind rose for 2014-2018 for the Charles B. Wheeler Downtown Kansas City Airport is depicted in Figure 3. The frequency and magnitude of wind speed and direction are defined in terms of where the wind is blowing from. The predominant wind direction during the five-year period is from the south/southwest, occurring approximately 6.75% of the time. The highest percentage wind speed range, occurring 33% of the time, was in the 3.6  -  5.7 m/s range. Charles B. Wheeler Downtown Kansas City Airport had a 99.72% data availability, with 0.42% calms identified. In addition, there were 122 incomplete or missing records from the total 43,828 hours available. From the wind rose, the EPA concludes hourly impacts will occur in all directions with predominant transport of emissions to the north based on higher frequency of SSW winds.


Figure 3. Charles B. Wheeler Downtown Kansas City Airport Cumulative Annual Wind Rose for 2014 - 2018


                                       


      The meteorological data was processed using AERMET (version 19191), the met data preprocessor for the AERMOD modeling system, with the ADJ_U* option. AERMET extracts and processes met data in order to calculate the boundary layer parameters that are necessary for the calculation of pollutant concentrations within the atmosphere.

      The met data included 1-minute Automated Surface Observing System (ASOS) wind data obtained from the National Climatic Data Center in the TD-6405 data format that includes the 2-minute average wind speed and direction for each minute within an hour. The use of 1-minute ASOS data more accurately depicts the average hourly wind flow than single instantaneous readings of wind speed and direction.

      The EPA concludes the processing of meteorological data follows EPA guidance and is representative of meteorological conditions in the Jackson County nonattainment area. 
      
Receptor Grid
      The modeling domain is centered on the nonattainment area boundary. The modeling domain
extends a sufficient distance to define the impacts from any source that may cause or contribute to a violation of the 2010 1-hour SO2 NAAQS within the nonattainment area. The receptor grid extends to the Jackson/Clay county border to the north and includes the portions of the river in Jackson County. Receptors were placed along the perimeter of the nonattainment area at 100-meter intervals, and a grid of receptors inside the nonattainment area are also spaced at 100-meter intervals.

Source Characteristics (Stack Heights and Building Downwash; Stack Exit Temperature and Velocity)
      In its supplemental modeling, the State's source characterization was consistent with Appendix W and the 2014 SO2 Guidance, which recommend that source characterization include source types, use of accurate stack parameters, inclusion of building dimensions for building downwash (if available), and adherence to GEP stack height regulations. Sources with site-specific data availability were modeled at the lesser of their actual stack height or GEP stack height as determined by BPIPPRIM, the 2014 SO2 guidance states:
      
      "Consistent with previous SO2 modeling guidance (U.S. EPA, 1994) and section 6.2.2 of Appendix W, for stacks with heights that are within the limits of Good Engineering Practice (GEP), actual heights should be used in modeling." 
      "If stack heights exceed GEP, then GEP heights should be used with the individual stack's other parameters (temperature, diameter, exit velocity). For stacks modeled with actual heights below GEP, building downwash should be considered as this can impact concentrations near the source (Section 6.2.2b, Appendix W). If building downwash is being considered, the BPIPPRM program (U.S. EPA, 2004d) should be used to input building parameters for AERMOD."
      For sources without CEMS, the State modeled facilities using constant temperature and exit velocities as reported by the facilities. For Hawthorn unit 5A, which is the one explicitly modeled source  equipped with CEMS, the state used the CEMS-reported hourly variable temperatures and exit velocities for all hours for which the facility reported emissions during the five years of the modeling analysis. 
      
      Modeled Sources and Emission Rates	
      The State explicitly modeled all permitted sources of SO2 emissions inside the nonattainment area and two nearby sources outside the nonattainment area. These are the same sources located in the nonattainment area that were included in the clean data determination modeling analysis for the Jackson County SO2 nonattainment area. 
      Appendix W defines "nearby sources" as individual sources located in the vicinity of the source(s) under consideration for emissions limits that are not adequately represented by ambient monitoring data (i.e., the background concentration). The ambient contributions from these nearby sources are accounted for by explicitly modeling their emissions. The two nearby sources included in the modeling are the Hawthorn power plant and the Ingredion facility, which produces modified corn starches, gluten meal, gluten feed, germ and high-solids steepwater. 

      The modeled emission rates for sources located within the nonattainment area and the Ingredion facility were based on assumed continuous operation at their maximum permitted emission levels (or maximum hourly design rates, MHDR) for the five-year period of 2014-2018. The derivation of the modeled emission rates for the Vicinity and Hawthorn facilities is discussed below. 
      The explicitly modeled sources and emission rates are listed in Table 5, and the locations of the sources are displayed in Figure 4. Most of the sources (16 of the 21) explicitly modeled in the demonstration emit less than 5 tons per year of SO2.
      
      
      
      
      
      
      
      
      
      
      
      

Table 5. Sources Included in Supplemental Modeling Analysis
                                 Fig. 3 Map ID
                                     FIPS
                                   Source ID
                                  Source Name
                   Max Allowable SO2 Emission Rate (tons/yr)
                  Source of Max Allowable SO2 Emission Rate**
                                  Model ID***
                                       1
                                     29095
                                     0021
Vicinity Energy - Kansas City (formerly Veolia)
                                                                          12.23
                      Consent Agreement No. APCP-2021-007
                                     VEPx
                                       2
                                     29095
                                     0176
Superior Bowen Asphalt
                                                                           4.85
                                     MHDR
                                     SBACx
                                       3
                                     29095
                                     2031
A-1 Painting
                                                                           0.26
                                     MHDR
                                      A11
                                       4
                                     29095
                                     2207
United States Postal Service*
                                                                           0.00
                                     MHDR
                                     USPS1
                                       5
                                     29095
                                     2161
Mizkan Americas
                                                                           0.06
                                     MHDR
                                     MKAx
                                       6
                                     29095
                                     0019
General Mills
                                                                           0.09
                                     MHDR
                                      GMx
                                       7
                                     29095
                                     0023
Evergy (formerly Kansas City Power & Light) -  Northeast Station
                                                                         353.90
                                     MHDR
                                    KCPLNx
                                       8
                                     29095
                                     0036
Land O'Lakes Purina Feed*
                                                                           0.00
                                     MHDR
                                     LOL5
                                       9
                                     29095
                                     0039
Blue River Treatment Plant
                                                                           8.60
                                     MHDR
                                     BRTPx
                                      10
                                     29095
                                     0065
Gateway Packing Company
                                                                           0.03
                                     MHDR
                                     GPCx
                                      11
                                     29095
                                     2065
Profile Cabinet
                                                                           0.97
                                     MHDR
                                      PC1
                                      12
                                     29095
                                     0068
Breentag Mid-South Inc.
                                                                           0.04
                                     MHDR
                                     BMSI4
                                      13
                                     29095
                                     0016
Allied Lithographing Company
                                                                           0.02
                                     MHDR
                                     ALCx
                                      14
                                     29095
                                     2230
Moly-Cop USA
                                                                           0.27
                                     MHDR
                                      MCx
                                      15
                                     29095
                                     2466
G and K Services
                                                                           0.02
                                     MHDR
                                      GK1
                                      16
                                     29095
                                     2015
Mid-America Car Inc.
                                                                           0.05
                                     MHDR
                                     MACx
                                      17
                                     29095
                                     2226
Sprint Communications
                                                                           2.56
                                     MHDR
                                    SPRNTx
                                      18
                                     29095
                                     2128
Midwest Block and Brick
                                                                           0.03
                                     MHDR
                                     MBB29
                                      19
                                     29047
                                     0002
Ingredion, Inc. - North Kansas City
                                                                         139.68
                                     MHDR
                                     INGx
                                      20
                                     29095
                                     2162
Solvent Recovery LLC
                                                                           1.05
                                     MHDR
                                     SR14
                                      21
                                     29095
                                     0022
Evergy (formerly Kansas City Power & Light) - Hawthorn Generating Station
                                                                           2014
                                                                      14,738.17
24-hr SO2 emission limit from KCMO Permit No. 888,  with adjustments based on 2014-2018 CEMS data
                                    HAWTHx




                                                                           2015
                                                                      14,093.18






                                                                           2016
                                                                      13,464.80






                                                                           2017
                                                                      13,550.43






                                                                           2018
                                                                      13,358.97


      *Out of business
      ** Maximum hourly design rate
      *** The model ID is a unique code used to identify the emission release point(s) for each source in the AERMOD input file. Sources with more than one emission release point have multiple model IDs, which are denoted with an "x" in the table. 
      
      
      
      
      
      
      Figure 4. Modeled Sources In and Near the Nonattainment Area.
      
      
      Vicinity was the primary contributor to the violation of the 2010 SO2 standard that resulted in the initial nonattainment designation for the area. Vicinity operates a district heating and cooling system that provides steam, hot water, and/or chilled water to industrial, commercial, governmental and residential facilities in the downtown Kansas City area. The facility operates four boilers that provide steam for process heating, comfort heating, or hot water.
      
      In the supplemental modeling demonstration, the emission rates for Vicinity are based on the maximum allowable emission rates in the consent agreement. Specifically, the emission rates assume Vicinity burns ULSD with 15 ppm sulfur by volume in each of its boilers at maximum capacity continuously during the five-year modeled period. 
      The emission rates for Vicinity's four boilers were calculated by first dividing maximum design heat input capacities for each boiler by the average heat content per 1,000 gallons of ULSD (140 million British thermal units or MMBtu/1000 gallons), which results in maximum hourly throughput (1000 gallons/hr). The maximum hourly throughput was then multiplied by the AP-42 emission factor for SO2 for distillate oil (0.213 lb SO2/1000 gallons). The emission factor was derived from the formula 142 * S, where S is the percent sulfur of ULSD (0.0015%) (AP-42 Table 1.3-1, boilers > 100 MMBtu/hr, no. 2 oil-fired). Table 6 provides the values for each boiler used in the calculations, along with the modeled emission rates.
Table 6. Modeled SO2 Emission Rates for Vicinity
                                   Boiler ID
                                   Model ID
                          Max Design Rate (MMBtu/Hr)
                       Max Throughput (1000 gallons/hr)
                       Modeled SO2 Emission Rate (lb/hr)
                                      1A
                                     VEP1A
                                     326.0
                                      2.3
                                    0.4960
                                       6
                                     VEP2*
                                     483.7
                                      3.5
                                    0.7359
                                       7
                                     VEP3
                                     517.0
                                      3.7
                                    0.7866
                                       8
                                     VEP2*
                                     507.6
                                      3.6
                                    0.7723
* Emissions from boilers 6 and 8 are released through a common stack.
      
      The State developed modeled SO2 emission rates for Hawthorn's unit 5A based on its permitted SO2 emission limit in accordance with the 2014 SO2 Guidance and Table 8.1 of 40 CFR 51 Appendix W, which states that nearby sources should be modeled based on their allowable emission rates with an adjustment to reflect actual operational levels. Hawthorn's unit 5A, a 6,745 MMBtu/hour coal-fired electric generating unit, is subject to a 24-hour average emission rate limit of 0.54 lb SO2/MMBtu (City of Kansas City Health Department, Air Quality Section, Permit No. 888, amended in 2001). 
      
      The 2014 SO2 Guidance contains a method for adjusting SO2 emission rate limits with longer averaging times to a 1-hour emission limit for consistency with the 1-hour NAAQS. The method is based on determining the ratio between actual 1-hour 99th percentile emission rates and the 99th percentile emission rates for the applicable averaging time (24 hours in this case). CEMS data for the 5-year period from 2014-2018 was used to apply this method to Hawthorn unit 5A as follows:  

 The 99th percentile hourly emission rate for the 5-year period was determined to be 1,553 lb SO2/hour.

 Average 24-hour emission rates were calculated by separating hourly SO2 lb/hour data into 24-hour blocks (calendar days), removing all hours with zero operation, and then calculating the average of the hourly emission rates for each 24-hour block. The 99th percentile of the average 24-hour emission rate for the 5-year period was determined to be 1,038 lb SO2/hour. 

 The 1-hour 99[th] percentile value (1,553 lb SO2/hr) was divided by the 24-hour 99[th] percentile value (1,038 lb SO2/hr), which yields a ratio of 1.496. 

 The 24-hour average permitted emission rate limit of 0.54 lb/MMBtu was multiplied by 1.496, which resulted in an adjusted 1-hour emission rate of 0.808 lb SO2/MMBtu.

      Variable hourly emission rates in units of lb SO2/hour were calculated for the model by multiplying the adjusted 1-hour emission rate of 0.808 lb SO2/MMBtu by the actual hourly heat input values in MMBtu/hr as recorded by the CEMS for unit 5A. For the hours unit 5A was not operating, the average modeled hourly emission rate for the 5-year period (2,296.71 l SO2 lb/hr or 301.98 g SO2/s) was used as a substitute.  

      Using this method to calculate variable hourly emission rates, the average annual SO2 emissions modeled for the Hawthorn facility for all five years is 13,821.11 tons/year. In comparison, the average of the actual annual SO2 emissions modeled for Hawthorn for the three-year period evaluated for the clean data determination modeling analysis (2016-2018) was 1,104.35 tons/year. Figure 5, provided in the state's February 2021 submittal, shows a comparison of actual (CEMS) hourly SO2 emission data and modeled hourly SO2 emissions data. This demonstrates the conservative nature of the modeling analysis as actual hourly emissions are much lower than the modeled hourly emission rates.
      
Figure 5.  Hawthorn SO2 CEMS Data vs. SO2 Modeled Emissions Rates (from MoDNR Maintenance Plan)
                                       
      Background Concentration
      Appendix W defines "other sources" as the portion of the background attributable to natural sources, other unidentified sources in the vicinity of the project, and regional transport contributions from more distant sources (domestic and international). The ambient contributions from these sources are typically accounted for through use of ambient monitoring data, i.e., a background concentration.
      The SO2 background concentration used in the modeling demonstration was based on an analysis of 2016-2018 SO2 monitoring data from the JFK air quality monitor and wind direction data from the downtown Kansas City airport. As shown in Figure 6, the JFK monitor is least impacted by the explicitly modeled SO2 emission sources when the wind direction ranges from zero to 45 degrees and 135 to 360 degrees. The State determined the hourly SO2 concentrations at the JFK monitor for the years 2016-2018 when winds were blowing from within these two sectors (excluding data for hours when winds were from the 70-135 degree sector to avoid double-counting of explicitly modeled sources) and calculated the annual 99th percentile of these values. Table 7 provides the results from this analysis. The background SO2 concentration used in the modeling demonstration is 3.4 ppb or 8.9 ug/m[3], which is the three-year average of 99th percentile values. The EPA concludes that a background value of 3.4 ppb is acceptable for this area.
      
Figure 6. Permitted SO2 Emission Source Locations and Wind Sectors Analyzed at the JFK Monitor to Determine the Background Concentration (from MoDNR Maintenance Plan)
      

      
Table 7. JFK Monitor's 99[th] Percentile Hourly SO2 Concentrations from Wind Sectors Analyzed to Determine Background Concentration
                                     Year
99[th] Percentile Hourly SO2 Concentrations from 0-45 Degrees and 135-360 Degree Wind Sectors (ppb)
                                     2016
                                      4.0
                                     2017
                                      2.9
                                     2018
                                      3.0
                                3-Year Average
                                      3.4

      
Modeling Results
      Table 8 presents the overall maximum modeled SO2 impact as well as maximum modeled contributions from individual sources. As shown in the table, the highest modeled impact (with a State derived 8.9 μg/m3 background) is 189.0 μg/m[3] or 72.1 ppb. The State has demonstrated via the supplemental modeling demonstration that the area is currently attaining and will continue to maintain the standard for a period of at least 10 years following the redesignation of the area. As shown in Figure 7, the highest modeled concentrations are in the center-northwest and eastern portions of the nonattainment area. 
      
Table 8.  Jackson County Maintenance Demonstration Modeling Results
                                    Source
                 5-Year Design Value Concentration (ug/m[3])
                                   Vicinity
                                      1.0
                                   Hawthorn
                                     127.0
                                   Ingredion
                                     179.6
                                  Background
                                      8.9
                           All Sources + Background
                                     189.0




Figure 7. Modeled Results (99[th] Percentile Highest Daily Maximum 1-hr SO2 (μg/m[3])) from the Supplemental Jackson County Maintenance Modeling Submittal.
                                       

Maintenance Plan Criterion (3) Verification of Continued Monitoring
Please see monitoring discussion beginning on page 4 of this TSD and the "Monitoring Network" section of the EPA's NPRM for this action for additional information. The EPA proposes that the State will meet its continued monitoring obligations through its commitment to continue operating  the Troost SLAMS monitor.
Summary of what the EPA is Proposing to Approve:
      As described in the NPRM and this document, the EPA is proposing to approve that the following criteria have been met:
Redesignation Criterion (i) Determination of Attainment of the NAAQS
 The EPA published a NFRM approving the State's CDD request in the Federal Register on July 9, 2020.
Redesignation Criterion (iii) Permanent and Enforceable Emissions
 The EPA is proposing to approve the cessation of coal combustion at Vicinity imposed by the Consent Agreement between Vicinity and the State (Appendix 1 of the September 2021 maintenance plan supplement) as the permanent and enforceable measure necessary for the area to maintain the NAAQS.
Redesignation Criterion (iv) Approved Maintenance Plan
      Maintenance Plan Criterion (1) Attainment Emissions Inventory and Future Year Projections
 The EPA proposes to approve the attainment year inventory as reflective of actual emissions in the 2017 attainment year.
 The EPA proposes to agree with the State that the future mix of sources and emission rates will not cause a violation of the standard based on the supplemental modeling analyses. As such, we are not relying on an attainment year vs. future year inventory comparison.
   	Maintenance Plan Criterion (2) Maintenance Demonstration
 The EPA is proposing to determine that the supplemental modeling demonstrates attainment and maintenance of the NAAQS for a period of at least 10 years following the redesignation of the area.
 The EPA is proposing to find that the stack parameters used in the supplemental modeling comport with the 2014 SO2 Guidance, which states "Since modeling would be done with maximum allowable or potential emissions levels at each stack, the stack's parameters such as exit temperature, diameter, and exit velocity should reflect those emissions levels." 
 The EPA is proposing to find that the State's supplemental modeling of all SO2 sources inside of the nonattainment area was done in accordance with the 2014 SO2 Guidance and Appendix W.
 The EPA is proposing to find that the State appropriately modeled Hawthorn and Ingredion as "nearby sources."
 The EPA proposes that 8.9 μg/m3 (3.4 ppb) is an appropriate background concentration.
   	Maintenance Plan Criterion (3) Verification of Continued Monitoring
The EPA is proposing that the State will meet its continued monitoring requirements through its commitment to continue operating the Troost monitor. 

