Response to Comments

Division of Air Pollution Control Response to Comments

Ohio EPA’s Request for Designation to Attainment/Unclassifiable for the Sulfur Dioxide National Ambient Air Quality Standard for the Gallia County, OH and Partial Meigs County, OH Area

Agency Contacts for this Project

Anjelica Moreno, Division of Air Pollution Control, 614-644-1961, [email protected]

Ohio EPA held a public comment period beginning March 9, 2020 regarding the draft Ohio’s Request for Designation to Attainment/Unclassifiable for the Sulfur Dioxide National Ambient Air Quality Standard for the Gallia County, OH and Partial Meigs County, OH Area. This document summarizes the comments and questions received during the comment period, which ended on April 13, 2020.

Ohio EPA reviewed and considered all comments received during the public comment period. By law, Ohio EPA has authority to consider specific issues related to protection of the environment and public health.

In an effort to help you review this document, the questions are grouped by topic and organized in a consistent format. The name of the commenter follows the comment.

Overall Concerns

Comment 1: Comments were received from the Ohio Valley Electric Corporation (OVEC) in support of Ohio’s proposed request. The full comment letter can be found at the end of this response to comments document. (J. Michael Brown, Environmental, Health & Safety Director, OVEC)

Response 1: Thank you for your comment. Ohio EPA agrees a designation of attainment/unclassifiable is warranted.

Comment 2: Comments were received from the Gavin Power Plant, LLC in support of Ohio’s proposed request. The full comment letter can be found at the end of this response to comments document. (Nicholas Tipple, Gavin Power Plant Manager)

Response 2: Thank you for your comment. Ohio EPA agrees a designation of attainment/unclassifiable is warranted.

Comment 3: Comments were received from the American Electric Power and its subsidiaries AEP Ohio, Appalachian Power Company, and Indiana Michigan Power Company who own portions of the Ohio Valley Electric Company Kyger Creek facility in support of Ohio’s proposed request. The full comment can be found at the end of this response to comments document. (Scott Weaver, Director Air Quality Services, American Electric Power)

Response 3: Thank you for your comment. Ohio EPA agrees a designation of attainment/unclassifiable is warranted.

Comment 4: Comments were received from Sierra Club. The comments include a substantial background discussion and incorporation by reference of “the expert report, Evaluation of Compliance with the 1-hour NAAQS for SO2, April 17, 2020, conducted by Steven Klafka, P.E., BCEE Wingra Engineering, S.C., Madison, Wisconsin (“Wingra Report,” attached as Exhibit 1), and supporting modeling files.” Sierra Club also attached an incorporated by reference “comments submitted by Sierra Club regarding prior EPA actions taken in the development of the Ohio area designations under the 2010 National Ambient Air Quality Standards (“NAAQS”) for sulfur dioxide (“SO2”). See Evaluation of Compliance with the 1-hour NAAQS for SO2, March 29,2016 (“Sierra Club 2016 Report,” attached as Exhibit 2), EPA-HQ-OAR-2014-0464-0332.” The full comment letter can be found at the end of this response to comments document. (Megan Wachspress, Associate Attorney, Sierra Club)

Response 4: Thank you for your comments. Sierra Club’s comments cover three areas: 1) “Expert Air Quality Modeling Indicates Concentrations of SO2 in Excess of the 2010 1-Hour NAAQS”; 2) “Ohio’s Belated Choice of Monitoring Instead of Modeling is Not Justified”; and 3) “Ohio EPA Did Not Place the Monitors in the Areas of Greatest SO2 Concentration.” The substantive elements of those comments along with Ohio EPA’s responses may be found in items 4a through 4c below.

Comment 4a: “Expert Air Quality Modeling Indicates Concentrations of SO2 in Excess of the 2010 1-Hour NAAQS.” Comments included attached reports with modeling for the three-year periods of 2016-2018 and 2017-2019. Sierra Club contends this modeling warrants a designation of nonattainment.

Response 4a: Sierra Club asserts this modeling uses Ohio’s own modeling files and indicates SO2 levels in excess of the 1-hour SO2 NAAQS. Ohio EPA has never submitted a modeling analysis to U.S. EPA indicating SO2 levels in excess of the 1-hour SO2 NAAQS. Ohio EPA did provide modeling files to Sierra Club in response to a data request, but the modeling and report provided by Sierra Club attached to these comments indicate that several changes were made to Ohio EPA’s modeling, including the use of flagpole receptors and modifications to the hourly emissions file.

On July 12, 2016, U.S. EPA made an initial designation of unclassifiable for this area (81 FR 45039). During the designation process, Ohio EPA submitted two separate modeling analyses to U.S. EPA, and Sierra Club submitted one modeling analysis. Both of Ohio EPA’s modeling analyses indicated attainment. Ultimately, U.S. EPA’s position was that they could not determine, based on available modeling, whether the area was meeting the SO2 NAAQS. As a result, Ohio EPA, in cooperation with the facilities, took the initiative to quickly deploy an air monitoring network of four sites around these facilities in order to collect three years of quality assured data that would provide for a valid design value.

Ohio EPA contends that model performance in this area and for these sources is not sufficient for the purposes of designation. Model versus monitor performance in this area has been evaluated by both Ohio EPA and third-party groups. These evaluations consistently show poor model performance in this area using default modeling methods. The challenges associated with appropriately characterizing this area’s attainment status through modeling indicate the best method of characterization is through monitoring itself. Therefore, Ohio EPA believes the modeling conducted by Sierra Club is not relevant to the designation process that is currently underway. Regardless, Ohio EPA wishes to make a few observations.

The modeling submitted by Sierra Club also demonstrates poor model performance, where modeled design values at the monitor locations overpredict monitored design values between 24 to 65%.

Sierra Club used hourly variable emissions inputs for the Gavin and Kyger Creek power plants, years 2016-2018 and 2017-2019. These data were obtained from U.S. EPA’s Clean Air Markets Data (CAMD). Ohio EPA does not consider CAMD data as ideally acceptable for use as input into a refined dispersion model for multiple reasons. Firstly, data reported to CAMD is done so for the accounting of emission allowance consumption, in accordance with 40 CFR Part 75 monitoring and reporting requirements. Accordingly, the data tends to overstate emissions when there are errors in the monitoring equipment or during periods of missing data, as described in the programs monitoring and reporting requirements. The data substitution methodologies employed via 40 CFR Part 75 requirements for the purposes of allowance accounting can lead to severe overestimations of emissions data, and consequently overstatement of ground level impacts determined from refined dispersion modeling. These data were never intended to serve as a repository for hourly emissions suitable for refined dispersion modeling although they are used by various entities, such as Sierra Club, for preparing a conservative estimate of emissions impacts. In addition to overstating emissions, the database does not contain hourly exit temperature values, which are a critical component necessary to accurately model hourly plume rise and exit velocities. The shortcomings of the CAMD data are made more apparent when applied to stringent 1-hour standards.

In the modeling submitted by Sierra Club for the 2016-2018 and 2017-2019 periods, exit velocities were derived from publicly available sources which Ohio EPA has not validated for application at the Gavin and Kyger Creek power plants. The modeling submitted for this period also used fixed exit temperatures, which fails to capture the variability of operations, a critical component when attempting to accurately model ground-level SO2 concentrations.

When conducting modeling for the purpose of a true characterization and for regulatory implications such as designations, an accurate source characterization would be the result of intensive analysis and consultation with relevant plant operators and technical staff to identify spurious emissions data and to compile a complete and accurate hourly database of emissions, exit temperatures, and exit velocities for each source included in the modeling domain. Ohio EPA has engaged in this type of assessment on multiple occasions, and even with accurate source characterizations has found the model to perform poorly in this area, especially when using default modeling methods. Therefore, Ohio EPA continues to contend the best method of characterization at this time is via monitoring.

Comment 4b: Ohio’s Belated Choice of Monitoring Instead of Modeling is Not Justified”. Sierra Club contends Ohio EPA’s decision to rely on monitoring is “arbitrary and unjustified” and “contrary to both EPA guidance and deadlines.”

Response 4b: Ohio EPA followed all appropriate guidance for developing a monitoring network (as discussed in Response 4c) issued by U.S. EPA specifically for preparing SO2 monitoring networks to address the 2010 SO2 NAAQS. As noted above, U.S. EPA’s 2016 designation process resulted in an unclassifiable designation for this area based on the lack of available evidence to designate it otherwise. While U.S. EPA guidance did require states to notify U.S. EPA by July 1, 2016 of their choice of monitoring or modeling, Ohio EPA could not meet this deadline because U.S. EPA’s designation of unclassifiable did not occur until later in July of 2016. However, in consultation with U.S. EPA, Ohio EPA determined the best path forward for determining whether an attainment/unclassifiable or nonattainment designation is appropriate would be via actual ambient air monitoring given the difficulties in properly characterizing air quality in this area via modeling methods. Ohio EPA quickly worked to ensure that a U.S. EPA approved monitoring network could be deployed that would meet all regulatory requirements and U.S. EPA deadlines for implementation of monitoring under U.S. EPA’s Round 4 monitoring timelines that would provide for three years of valid air monitoring data. As planned and approved by U.S. EPA, the monitoring network began monitoring on January 1, 2017, consistent with the deadline. While not the conventional path to Round 4 monitoring, this was the logical path necessary to gather adequate data that could provide a true characterization of this area’s air quality. Consistent with all other source areas where states performed monitoring between 2017 and 2019 to generate valid design values, Ohio EPA is requesting U.S. EPA to make a final designation for the Gavin-Kyger source area based upon the monitoring data alone. The challenges associated with appropriately characterizing this area’s attainment status through modeling indicate the best method of characterization is through monitoring itself. Due to the vastness and representativeness of the monitors characterizing this area, Ohio EPA believes the results show attainment is occurring throughout the entire area.

Comment 4c: “Ohio EPA Did Not Place the Monitors in the Areas of Greatest SO2 Concentration.” Sierra Club states the data is also incomplete. Therefore, Sierra Club asserts that the data is insufficient to demonstrate SO2 in the area is below the 1- hour SO2 NAAQS.

Response 4c: The monitoring network established in the area near to the Gavin and Kyger Creek power plants were sited in accordance with the Data Requirements Rule for the 2010 1-Hour Sulfur Dioxide (SO2) Primary National Ambient Air Quality Standard (NAAQS), 80 FR 51052 and the February 2016 draft SO2 NAAQS Designations Source-Oriented Monitoring Technical Assistance Document.

Ohio EPA, in accordance with 40 CFR Part 58, Section 58.10 included the Gavin-Kyger monitoring network in the 2017-2018 Annual Network Plan, which was available for a 30-day public comment period. Appendix D of that document provided maps of the locations of all monitors in Ohio EPA’s network, inclusive of the Gavin-Kyger network. Ohio EPA received no adverse comments with respect to the location of any monitor in the network. Appendix G of that document indicates U.S. EPA concurrence with Ohio’s annual network plan.

In reality, when siting monitors, monitors rarely can be located precisely in the locations where the model predicts both peak and frequent impacts to occur. Ohio EPA agrees with the following statement in the Wingra Report: “The AERMOD dispersion modeling results are a prediction. Its accuracy is greater for the overall maximum design value rather than for a specific location.” By understanding that modeling has inherent limitations, Ohio EPA did not rely completely on modeling alone to establish the proper siting location of these monitors. In fact, Ohio EPA is required to consider a host of other requirements outlined in 40 CFR Part 58 regarding specific siting criteria and quite often compliance with those criteria prohibit siting monitors precisely in the locations where the model predicts both peak and frequent impacts to occur.

Rather, using the modeling as a guide, Ohio EPA modeling and air monitoring quality assurance staff, in cooperation with Shell Engineering and technical staff from American Electric Power, conducted two field studies in 2016 to evaluate potential monitor locations. These evaluations considered not only the U.S. EPA SO2 monitoring guidance sited above, but also all U.S. EPA SO2 monitor siting criteria contained in 40 CFR Part 58 and applicable to all SO2 monitoring used for comparison to the NAAQS. This includes consideration of factors such as proximity to roadways and trees. In addition to U.S. EPA specific siting criteria adherence, it is also necessary to consider factors such as the availability of power, landowner permission, and operator safety. Additionally, Ohio EPA considered other factors such as prevailing wind directions, terrain, and the extensive technical expertise of Ohio’s air monitoring program to inform monitor siting. These siting criteria and other practical limitations routinely preclude the ability to place a monitor in the exact location where modeling predicts peak and frequent impacts. Ultimately, after these field studies, Ohio EPA determined an expansive network of four monitors should be dedicated to this area in order to capture multiple locations where peak and frequent impacts could occur. Ohio EPA submitted to U.S. EPA extensive data inclusive of modeling results, site visit results, and siting criteria. On December 12, 2016 Ohio EPA additionally submitted to U.S. EPA a draft Air Monitoring Network Plan for the Gavin-Kyger Creek area. Based on this outreach and extensive discussion, U.S. EPA issued a letter of concurrence to Ohio EPA on December 20, 2016 regarding the siting of these monitors.

Ohio EPA notes again here that the modeling submitted by Sierra Club relies on derived rather than measured exit velocities and uses a fixed exit temperature. As such, Ohio EPA does not believe that the Sierra Club modeling accurately predicts the location of peak and frequent impacts.

All four monitors in the Gavin-Kyger monitoring network meet minimum data completeness criteria for a valid design value. 40 CFR, Appendix T to Part 50, paragraph (3)(b) states “An SO2 1- hour primary standard design value is valid if it encompasses three consecutive calendar years of complete data. A year meets data completeness requirements when all 4 quarters are complete. A quarter is complete when at least 75 percent of the sampling days for each quarter have complete data. A sampling day has complete data if 75 percent of the hourly concentration values, including State-flagged data affected by exceptional events which have been approved for exclusion by the Administrator, are reported.” Thus, completeness of 91 to 95% easily meets the 75 percent data completeness criteria. The design values are valid for regulatory purposes and this monitoring data was certified to U.S. EPA on January 23, 2020.

End of Response to Comments

OHIO VALLEY ELECTRIC CORPORATION 3932 U. S. Route 23 P. O. Box 468 Piketon, Ohio 45661 740-289-7200

WRITER’S DIRECT DIAL NO: 740-289-7299

April 9, 2020

Document Submitted Electronically

Ms. Anjelica Moreno Ohio Environmental Protection Agency, DAPC P.O. Box 1049 Columbus, Ohio, 43215

Dear Ms. Moreno,

Re: Comments in Support of Ohio EPA’s Request for Designation of Gallia County, OH and Partial Meigs County, OH to Attainment/Unclassifiable as Part of U.S. EPA’s Round 4 Designation Process associated with the 2010 SO2 NAAQS

Ohio Valley Electric Corporation (OVEC), appreciates the opportunity to provide the following comments in support of the above-referenced agency action. OVEC owns and operates the Kyger Creek Generating Station located in Gallia County, Ohio. Emissions from the Kyger Creek Station were evaluated as part of Ohio EPA’s evaluation of this area, and OVEC has a substantial interest in the outcome of this designation request.

General Comments:

The United States Environmental Protection Agency (U.S. EPA) promulgated the revised National Ambient Air Quality Standard (NAAQS) for sulfur dioxide (SO2) on June 2, 2010, and replaced the 24-hour and annual standards with a short-term one-hour standard of 75 parts per billion (ppb). This one-hour SO2 standard was published on June 22, 2010, (75 FR 35520) and became effective on August 23, 2010. This SO2 NAAQS standard is based on the three-year average of the annual 99th percentile of one-hour daily maximum concentrations.

Attainment/Nonattainment area designations for the one-hour SO2 standard across the country were subject to litigation and on March 2, 2015, the U.S. District Court for the Northern District of California accepted as an enforceable order an agreement between the U.S. EPA and Sierra Club and the Natural Resources Defense Council to resolve litigation concerning the deadline for completing designations. The court’s order directed U.S. EPA to complete the remaining designations in three steps: Round 2 by July 2, 2016; Round 3 by December 31, 2017, and Round 4 by December 31, 2020. Ms. Anjelica Moreno 2 April 9, 2020

Areas of the United States that contained stationary sources that emitted more than 16,000 tons of SO2 in 2012, or emitted more than 2,600 tons of SO2 and had an emission rate of at least 0.45 lbs. SO2/MMBtu in 2012 (including the Gallia County and the portion of the Meigs County area subject to this Public Notice), were originally part of the round two determination. However, as described in their Final Technical Support Document, U. S. EPA found after considering the available information that a reliable basis did not exist for designating Gallia County and those portions of Meigs County, Ohio as either attainment or nonattainment.

As a result, U.S. EPA made a preliminary designation of unclassifiable, and Ohio EPA (OEPA) designed, evaluated, and directed the installation and operation of an extensive State and Local Air Monitoring (SLAMS) network around the General James M. Gavin and Kyger Creek Generating Stations located in Gallia County, Ohio. The monitoring network was sited using multiple modeling runs to assure that monitors captured data at locations that could reasonably be anticipated to experience the highest ambient concentrations of SO2. The network began gathering ambient air quality data on January 1, 2017, which was the deadline for initiating monitoring under Round 4 designations. The data collected from this monitoring network is robust and has undergone extensive review, including multiple on-site audits by state and federal regulatory agencies, and was collected in accordance with an approved Quality Assurance Action Plan.

The results obtained following calculation of the three-year average of the annual 99th percentile of one-hour daily maximum concentrations from the three-year data set for the years 2017 through 2019, show the SO2 NAAQS standard is being attained and maintained. Given the above, OVEC supports OEPA’s request to U.S. EPA asking that the area in question be designated as attainment/unclassifiable as part of the Round 4 designations. A summary of the initial three years of data collected from this network is included in Ohio EPA’s technical support document, and is reproduced in the table below.

Table 1: 3-Year Design Values for SO2 monitors surrounding the Gavin-Kyger Creek source area.

Year (ppb) 3-Yr Design Value Site ID Site Name 2017 2018 2019 (ppb) 39-053- Cheshire 27 41 54 41 0004 Elementary 39-053- Ridge 34 38 54 42 0005 39-053- Guiding Hand 38 28 54 40 0006 54-053- Lakin WV 35 57 61 51 0001 Ms. Anjelica Moreno 3 April 9, 2020

The 3-year design values are all well below the 75 ppb standard, and strongly support the requested designation.

Pursuant to section 107(d) of the Clean Air Act (CAA), U.S. EPA must initially designate areas as either “unclassifiable”, “attainment”, or “nonattainment” for the 2010 one-hour SO2 standard. Further, U.S. EPA’s Area Designations for the 2010 Primary Sulfur Dioxide National Ambient Air Quality Standard - Round 4, indicates that EPA may designate an area as attainment/unclassifiable if information indicates it meets the SO2 NAAQS and does not likely contribute to a violation in a nearby area based on the most recent three years (i.e., 2017-2019) of ambient air quality monitoring data.

Based upon the data above, all monitors meet the 75 ppb 2010 one-hour SO2 NAAQS and warrant a designation of attainment/unclassifiable. OVEC reaffirms its support of OEPA’s request to U.S. EPA asking the agency to designate the area around Gavin and Kyger Creek (specifically, all of Gallia County and the western half of Meigs County, which includes Bedford, Columbia, Rutland, Salem, Salisbury, and Scipio Townships) as attainment/unclassifiable as a part of U.S. EPA’s Round 4 designations.

Should you have any questions, please feel free to contact me at (740) 289-7299.

Sincerely,

J. Michael Brown Environmental, Safety and Health Director

JMB:klr

Kaloz, Holly

From: Scott Weaver Sent: Monday, April 13, 2020 4:26 PM To: Moreno, Anjelica Subject: Re: Comments in Support of Ohio EPA’s Request for Designation of Gallia County, OH and Partial Meigs County, OH to Attainment/Unclassifiable as Part of U.S. EPA’s Round 4 Designation Process associated with the 2010 SO2 NAAQS

Ms. Moreno:

On behalf of American Electric Power and its subsidiaries AEP Ohio, Appalachian Power Company, and Indiana Michigan Power Company who own portions of the Ohio Valley Electric Company, we are pleased to offer the following comments on Ohio EPA’s proposal to USEPA to redesignate Gallia and Portions of Meigs County from Unclassifiable to Unclassifiable/Attainment with the 2010 1-Hour SO2 Standard.

The request brought forward by Ohio EPA is reasonable and well supported by the ambient monitoring record in the area surrounding the Gavin and Kyger Creek Power Plants over the period 2017 to 2019. This monitoring complies with all USEPA requirements and all Data Requirements Rule requirements to support a designation in Round 4 of the Data Requirements Rule no later than December 31, 2020. We therefore encourage Ohio EPA to encourage USEPA to take prompt action on this request redesignate this area to Unclassifiable/Attainment.

If you have any questions, please feel free to contact me at 614-716-3771 or David Long of my staff at 614-716-1245.

Sincerely,

Scott Weaver

SCOTT WEAVER | DIR AIR QUALITY SERVICES [email protected] | D:614.716.3771 1 RIVERSIDE PLAZA, COLUMBUS, OH 43215

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April 20, 2020

Attn: Anjelica Moreno Ohio Environmental Protection Agency, DAPC P.O. Box 1049 Columbus, Ohio 43215

Submitted electronically via email to [email protected]

RE: State of Ohio 2010 Revised Sulfur Dioxide National Ambient Air Quality Standard Request for Designation to Attainment/Unclassifiable as a Part of EPA’s Round 4 Designation Process: Gallia County, OH and Partial Meigs County, OH Area Dear Anjelica Moreno,

Sierra Club1 hereby submits these comments on the State of Ohio’s 2010 Revised Sulfur Dioxide National Ambient Air Quality Standard Request for Designation to Attainment/Unclassifiable as a Part of EPA’s Round 4 Designation Process: Gallia County, OH and Partial Meigs County, OH Area (hereafter the “Proposed Redesignation”).2 In support of these comments, Sierra Club incorporates by reference the expert report, Evaluation of

Compliance with the 1-hour NAAQS for SO2, April 17, 2020, conducted by Steven Klafka, P.E., BCEE Wingra Engineering, S.C., Madison, Wisconsin (“Wingra Report,” attached as Exhibit 1), and supporting modeling files. We also attach and incorporate by reference comments submitted by Sierra Club regarding prior EPA actions taken in the development of the Ohio area designations under the 2010 National Ambient Air Quality Standards (“NAAQS”) for sulfur

1 Founded in 1892, Sierra Club is the nation’s oldest and largest nonprofit grassroots environmental organization, with nearly 780,000 members nationwide, including over 22,000 in Ohio. Sierra Club’s purposes are to explore, enjoy, and protect the wild places of the Earth; to practice and promote the responsible use of the Earth’s ecosystems and resources; to educate and enlist humanity in the protection and restoration of the quality of the natural and human environment; and to use all lawful means to carry out these objectives. Sierra Club members are greatly concerned about air quality, and the Club has a long history of involvement in air quality related activities on both the local and national levels, including in Ohio.

2 See https://www.epa.ohio.gov/portals/27/SIP/SO2/GavinKyg_Desig_Rnd4_DRAFT.pdf

dioxide (“SO2”). See Evaluation of Compliance with the 1-hour NAAQS for SO2, March 29, 2016 (“Sierra Club 2016 Report,” attached as Exhibit 2), EPA-HQ-OAR-2014-0464-0332.

Modeling analyses—both Ohio EPA’s own and Sierra Club’s—have consistently shown that emissions from the Gavin and Kyger Creek plants cause the concentration of sulfur dioxide in Gallia County to exceed the limits set by the 2010 1-hour SO2 NAAQS. AERMOD dispersion modeling consistent with EPA guidance and using actual emissions data from 2016 through 2019

shows significant exceedances of the 2010 1-hour SO2 NAAQS within Gallia County, precluding any redesignation to attainment. This modeling is consistent with Sierra Club’s and Ohio EPA’s previous modeling from March and April 2016, which indicated (absent an unjustified 38% reduction in background concentrations applied by Ohio EPA and rejected by the U.S. EPA) concentrations in excess of the NAAQS between 2012 and 2014. See Sierra Club 2016 Report.

Ohio EPA’s reliance on monitoring in lieu of modeling is misplaced, as are the selected monitors themselves. Sierra Club’s updated modeling and expert report confirm what is evident from Ohio EPA’s own technical justification for the placement of monitors relied upon in its Proposed Redesignation: these monitors are not located where Ohio EPA’s own modeling

indicates the maximum concentrations of SO2 will occur and, moreover, are missing a significant portion of the hourly data for the three-year period.

Given the inadequacies of Ohio EPA’s monitoring data and strong modeling evidence from 2016, updated with emissions from the past three years, that SO2 concentrations continue to exceed NAAQS near the Gavin and Kyger Creek power plants, Ohio EPA lacks sufficient basis on which to request a redesignation of Gallia County as attainment; indeed, if any redesignation is to happen, it ought to be redesignation to nonattainment.

I. Background

The General J. M. Gavin Power Plant in Gallia County is the fifth largest emitter of SO2 3 pollution in the United States, emitting more than 27,000 tons of SO2 in 2018 alone. Also in Gallia County, and less than 4km south-southwest of Gavin, is the Kyger Creek Power Plant, which emitted 4,970 tons of SO2 in 2018. These emissions impact the almost-30,000 people in Gallia County and the surrounding area. As the U.S. EPA (hereafter, “EPA”) documented in its

promulgation of the 2010 1-hour SO2 NAAQS, even very short-term exposure to elevated SO2 levels can have severe human health consequences. See Primary National Ambient Air Quality Standard for Sulfur Dioxide Final Rule, 75 Fed. Reg. 35,520, 35,525 (June 22, 2010). Notwithstanding the magnitude of these emissions and the risks associated with elevated concentrations, Ohio has previously sought an attainment designation for Gallia County under

the 2010 1-hour SO2 NAAQS. EPA rejected Ohio’s recommendation, instead designating the

3 See eGRID 2018 Database, at https://www.epa.gov/energy/emissions-generation-resource- integrated-database-egrid.

area as “unclassifiable,” a designation that was subject to legal challenge resolved on procedural grounds.

A. The Sulfur Dioxide NAAQS and Human Health

Exposure to SO2 in even very short time periods—such as five minutes—has significant health impacts, including decrements in lung function, aggravation of asthma, and respiratory and cardiovascular morbidity. See 75 Fed. Reg. 35,520, 35,525 (June 22, 2010). EPA has

determined that exposure to SO2 pollution can also aggravate existing heart disease, leading to increased hospitalizations and premature deaths. Id. Accordingly, on June 2, 2010, EPA revised

the primary SO2 NAAQS by establishing a new one-hour standard at a level of 75 parts per billion (“ppb”) which is met when the 3-year average of the annual 99th percentile of the daily maximum one-hour average concentrations is less than or equal to 75 ppb or 196.4 μg/m3.4 See id. at 35,520. EPA estimated that the new standard would prevent 2,300 to 5,900 premature deaths and 54,000 asthma attacks each year. See Final Regulatory Impact Analysis (RIA) for the 5 SO2 National Ambient Air Quality Standards (NAAQS), at 5-35 Table 5.14 (June 2010).

B. Implementation of the NAAQS

EPA’s promulgation of the 2010 1-hour SO2 NAAQS triggered the agency’s statutory obligation to “designate” all areas of the country according to whether they comply with the standard. 42 U.S.C. § 7407(d)(1)(B)(i). Areas that comply are designated “attainment.” Id. § 7407(d)(1)(A)(ii). Areas that do not comply must be designated “nonattainment.” Id. § 7407(d)(1)(A)(i). Areas that “cannot be classified on the basis of available information” as complying or not complying with the standard are designated “unclassifiable.” Id. § 7407(d)(1)(A)(iii). As an initial step, states are charged with submitting initial designation recommendations for areas within their jurisdiction, and then EPA may make any modifications it “deems necessary.” Id. § 7407(d)(1)(A), (B)(ii).

As a result of a consent decree following litigation by Sierra Club, EPA was required to 6 issue final designations for the areas with the largest sources of SO2 by July 2, 2016. Consent

4 As explained in footnote 7 on p. 3 of the Wingra Report, the conversion calculation from parts per billion to micrograms per cubic meter is 75/0.3823 = 196.2 μg/m3. The Wingra Report uses conversion has been used for consistency with prior modeling reports; Tables 2 and 3, which are reproduced from the Wingra Report, use 196.2 μg/m3 as well. EPA has recently converted the 75 ppb standard to 196.4 μg/m3, however, the alternative USEPA concentration does not change the conclusions of the Wingra Report or materially affect these comments.

5 Available at https://www3.epa.gov/ttnecas1/regdata/RIAs/fso2ria100602full.pdf.

6 EPA was required to promulgate designations for undesignated areas, which (a) based on air quality monitoring had violated the 2010 SO2 NAAQS within the preceding three calendar years, or (b) contained any stationary source that had not been announced for retirement and which had 3

Decree ¶ 1, Sierra Club v. McCarthy, No. 3:13-cv-3953-SI (N.D. Cal. Mar. 2, 2015), ECF No. 163, EPA-HQ-OAR-2014-0464-0202.

To facilitate the implementation of the NAAQS, on August 10, 2015, EPA finalized the Data Requirements Rule (“DRR”), which requires states to provide data to characterize air quality around many major sources of SO2. Data Requirements Rule for the 2010 1-Hour Sulfur Dioxide (SO2) Primary National Ambient Air Quality Standard (NAAQS), 80 Fed. Reg. 51,052 (Aug. 21, 2015) (codified at 40 C.F.R. §51, Subpart BB). For areas around any source that emits

2,000 tons per year (“tpy”) or more of SO2, states were required to notify EPA by July 1, 2016, whether they intended to: (1) characterize air quality through ambient monitoring; (2) characterize air quality through air quality modeling; or (3) whether it will be subjecting the pertinent source or sources to enforceable emission limits that will keep the source below this rule’s 2,000 tpy threshold.

Under the DRR, if the state intended to rely on monitoring to demonstrate attainment for a specific source, it was required to include information about the planned new monitors in the annual monitoring plan that the air agency was required to submit to EPA by July 1, 2016; and the air agency was required to ensure that the new monitors are operational by January 1, 2017. See 40 C.F.R. §51.1203. Moreover, if the state’s new monitors were not approved and operational by January 1, 2017, the state was then required to demonstrate attainment with air dispersion modeling. Id.; see also 80 Fed. Reg. at 51,074, 51,087-88.

Pursuant to the 2015 Consent Decree, in July 2016, EPA issued a second round of designations covering 61 areas in 24 states. Air Quality Designations for the 2010 Sulfur

Dioxide (SO2) Primary National Ambient Air Quality Standard—Round 2, 81 Fed. Reg. 45,039 (July 12, 2016) (“Round 2 Designations”). Gallia County, together with a portion of adjacent Meigs County (collectively “Gallia County”), where the General James M. Gavin (“Gavin”) and Kyger Creek coal-fired power plants are located, was one of the 61 areas included in these Round 2 designations. See EPA-HQ-OAR-2014-0464-0405 at 8, 12 (“Final Technical Support Document (‘TSD’) for Ohio”).7

either (i) emitted more than 16,000 tons of SO2 in 2012 or (ii) emitted more than 2,600 tons of SO2 and had an annual average emission rate of 0.45 lbs SO2/Mmbtu or higher in 2012. Consent Decree ¶ 1.

7 Available at https://www.epa.ohio.gov/portals/27/SIP/SO2/R5_OH_final%20designation%20TSD_06302016 .pdf

C. Ohio EPA’s Prior Request for an Attainment Designation for Gallia County and Subsequent Litigation

In the months prior to EPA’s final designation of Gallia County, the Ohio EPA and Sierra Club both provided comments and air dispersion modeling to inform the agency’s determination.

On September 16, 2015, Ohio EPA submitted comments and air quality modeling of SO2 emissions dispersion from Gavin and Kyger Creek, the two largest emission sources located within the modeling region. EPA-HQ-OAR-2014-0464-0070.8 On the basis of its modeling, Ohio EPA recommended that EPA designate the Gallia County area as attainment. Id. at 1. On September 17, 2015, Sierra Club submitted modeling which indicated NAAQS violations and recommended that EPA designate the Gallia County area as nonattainment. EPA-HQ-OAR- 2014-0464-0075.9

In February 2016, EPA rejected Ohio EPA’s recommendation of attainment designation. EPA-HQ-OAR-2014-0464-0134, (“February 2016 TSD for Ohio”).10 EPA disapproved of Ohio EPA’s air quality modeling, finding that Ohio EPA had improperly applied two non-default options, also called “beta options,” without prior approval from EPA, and found Ohio EPA’s modeling unreliable. See February 2016 TSD for Ohio at 28-29.

In response, on April 19, 2016, Ohio EPA submitted supplemental modeling and, once again, recommended that EPA designate the Gallia County area as attainment. EPA-HQ-OAR- 2014-0464-0352 (“April Ohio model”).11 In its supplemental modeling, Ohio EPA (1) excluded the beta options, (2) substituted revised emissions data and revised meteorological data, and (3) replaced its fixed background parameter with a temporally varying background concentration, to which Ohio EPA applied a flat 38% discount. Id. at 3-5. Based on this analysis, Ohio EPA once more recommended designating the area as attainment. See id. at 5. Sierra Club also submitted revised modeling on March 31, 2016 that included a recreation of Ohio’s initial modeling performed without the beta options and once more indicated Gallia County’s NAAQS violations. See EPA-HQ-OAR-2014-0464-0332; Final TSD for Ohio at 19-20.

In its Final Technical Support Document, EPA once again rejected Ohio EPA’s recommendation. See Final TSD for Ohio at 21. Although EPA found that Ohio EPA’s use of a variable background was “appropriate,” the agency rejected the 38% discount that Ohio EPA applied to background values. Id. at 16-17. With Ohio EPA’s unjustified discount, the

8 Available at https://www.epa.ohio.gov/portals/27/SIP/SO2/GavinKyg_Desig_Draft.pdf.

9 Available at https://www.regulations.gov/document?D=EPA-HQ-OAR-2014-0464-0075.

10 Available at https://www.epa.state.oh.us/portals/27/SIP/SO2/05_OH_tsd_9-16-15_LTR.pdf.

11 Available at https://www.epa.ohio.gov/portals/27/SIP/OhioEPA_TSD_120DResp_4-19- 16.pdf.

5 maximum modeled impact was 195.4 μg/m3. Id. at 18. This value is about 0.4 ppb—or 1

μg/m3—below the 2010 1-hour SO2 NAAQS of 196.4 μg/m3. Id. Nevertheless, EPA implausibly determined it could not, with the data provided by Ohio EPA, mathematically undo Ohio EPA’s faulty modeling to determine with certainty that the relevant concentrations exceeded the NAAQS, and designated Gallia County as unclassifiable. 81 Fed. Reg. at 45,053.

Sierra Club petitioned the Circuit Court for the District of Columbia for review of EPA’s designation. See Masias v. Envtl. Prot. Agency, 906 F.3d 1069, 1075-77 (D.C. Cir. 2018). Because EPA determined that Ohio EPA had improperly applied a flat 38% discount to its April 19, 2016 modeling, and because even with that discount, Ohio EPA’s model indicated a maximum impact within 1 μg/m3 of the NAAQS, Sierra Club argued, EPA had sufficient information to classify Gallia County as nonattainment. See 42 U.S.C. § 7407(d)(1)(A)(iii) (defining “unclassifiable” as “any area that cannot be classified on the basis of available information as meeting or not meeting” the NAAQS). However, the Court upheld EPA’s “unclassifiable” designation on procedural grounds. Masias, 906 F.3d at 1075.12

D. Proposed Redesignation and Switch to Monitoring

After EPA issued its Final Technical Support Document designating Gallia County as “unclassifiable,” and more than five months after the July 1, 2016 deadline for states to notify EPA whether they intend to characterize air quality through ambient monitoring or air quality monitoring, Ohio EPA submitted monitor site information to EPA for four locations near the Gavin and Kyger Creek facilities. See Appendix D to Proposed Redesignation (“Appendix D”); cf. 80 Fed. Reg. at 51,074; 40 C.F.R. § 51.1203.13 On December 20, 2016, eight days after Ohio EPA submitted the four proposed locations, U.S. EPA replied by letter with its approval.

Ohio EPA began collecting monitoring data in January 2017, and issued a draft Proposed Redesignation for public comment in February 2020. According to the Proposed Redesignation, th 99 percentile SO2 concentrations at the four locations did not exceed the NAAQS limit of 75 ppb during the years 2017-2019. See Proposed Redesignation, Table 1, reproduced as Table 1 below.

12 In upholding the EPA’s designation, the Court did not reach the merits of Sierra Club’s argument. Instead, the D.C. Circuit held that Sierra Club failed to raise this argument—that Ohio EPA’s own model with the improper 38% background concentration discount reversed was sufficient to show nonattainment—prior to the close of public comments. Masias, 906 F.3d at 1075. Because Ohio EPA submitted this revised model after the close of public comment, Sierra Club’s argument regarding the inadequacy of the April Ohio model would be appropriately considered on a motion for reconsideration of the EPA’s designation. Id.

13 Available at https://epa.ohio.gov/Portals/27/SIP/SO2/D1-GavKygerRnd4_ConcurLtr.pdf.

Table 1: 3-Year Design Values for SO2 monitors surrounding the Gavin-Kyger Creek Area Reproduced from Proposed Designation, Table 1 (at p. 6) Year (ppb) 3-Yr Design Value Side ID Site Name 2017 2018 2019 (ppb) 39-053-0004 Cheshire Elem. 27 41 54 41 39-053-0005 Ridge 34 38 54 42 39-053-0006 Guiding Hand 38 28 54 40 39-053-0001 Lakin WV 35 57 61 51

Based on this monitoring data, Ohio EPA now seeks to reclassify Gallia County as

attainment with respect to the 1-hour SO2 NAAQS.

II. Substantive Comments

The Proposed Redesignation purports to demonstrate attainment through monitoring, rather than modeling. However this belated switch in methodology does not support an attainment designation. As the attached expert report shows, modeling conducted on the basis of actual emissions data from the three-year periods of 2016-18 and 2017-19, and using Ohio’s own

modeling files, indicates SO2 concentrations in Gallia County reach levels well in excess of the 1-hour SO2 NAAQS. Conversely, Ohio EPA’s monitoring purporting to show the contrary is flawed: Ohio EPA has failed to select monitoring sites at the location of maximum ambient

concentrations of SO2, making monitoring data from the sites selected insufficient to demonstrate that SO2 in the entire area surrounding the Gavin and Kyger plants are below the 1- hour SO2 NAAQS.

A. Expert Air Quality Modeling Indicates Concentrations of SO2 in Excess of the 2010 1-Hour NAAQS

Modeling conducted on actual emissions during the years 2017 through 2019 shows SO2 concentrations in Gallia County well in excess of the 2010 1-hour SO2 NAAQS. These modeling results preclude a designation of attainment for Gallia County (and indeed, provide ample evidence for a redesignation as nonattainment). As shown in the attached Wingra Report, modeling analysis conducted using actual hourly emissions from the Clean Air Markets Program Data (“CAMD”) for two 3-year periods, 2016-18 and 2017-19 and the same modeling files from th 3 the Ohio EPA analysis in 2016 indicates 99 percentile SO2 concentrations of 231.0 μg/m for 2017-19 (including emissions from both plants) and 201.7 μg/m3 for 2016-18. See Wingra th Report Table 2, at p. 4. For the most recent three-year period, the 99 percentile SO2 concentration in Gallia County exceeded the NAAQS by more than 17%.

Even including the 38% reduction in background concentrations adopted by Ohio EPA in its 2016 model analysis—a reduction EPA criticized as unfounded in its prior designation of th Gallia County as “unclassifiable”—the 99 percentile SO2 concentrations for 2017-19 was 223.0

μg/m3, or more than 13% higher than the NAAQS. Tables summarizing the results of this modeling are reproduced below:

Table 2 - SO2 Modeling Results using Ohio EPA-Adjusted Background Concentrations Reproduced from Wingra Report, at p. 4

99th Percentile 1-hour Daily Maximum Complies with (µg/m3) Period Facility NAAQS? Total NAAQS Gavin 171.2 196.2 Yes

2016-18 Kyger Creek 52.8 196.2 Yes

Both Plants 190.5 196.2 Yes

Gavin 202.3 196.2 No 2017-19 Kyger Creek 50.2 196.2 Yes

Both Plants 223.0 196.2 No

Table 3 - SO2 Modeling Results using Original Background Concentrations Reproduced from Wingra Report, at p. 4

99th Percentile 1-hour Daily Maximum Complies with (µg/m3) Period Facility NAAQS? Total NAAQS Gavin 182.8 196.2 Yes

2016-18 Kyger Creek 67.9 196.2 Yes

Both Plants 201.7 196.2 No

Gavin 212.0 196.2 No 2017-19 Kyger Creek 65.4 196.2 Yes

Both Plants 231.0 196.2 No

Notably, this updated model addresses the concerns which EPA raised about the March 2016 Sierra Club model showing nonattainment on the basis of 2012-14 actual emissions data. In its prior designation of Gallia County as “unclassifiable,” EPA declined to accept the Sierra Club March 2016 model (and thus the recommendation of a nonattainment designation for Gallia County) on two grounds. First, EPA criticized Sierra Club’s model for substituting emission

rates for data points that were blank or zero in the CAMD data set. See Final Technical Support Document for Final Action on Ohio Area Designations, at p. 19. The updated model does not substitute any missing CAMD values. Wingra Report, at p. 7. Second, EPA found Sierra Club’s use of a fixed background concentration of 10 ppb to be “unnecessarily conservative.” The updated model uses the same temporally varying concentrations used by the Ohio EPA in its 2016 analysis. Id. Using these varying background concentrations, the model indicates 99th

percentile SO2 concentrations in excess of the 1-hour NAAQS both with and without the 38% adjustment (improperly) adopted by the Ohio EPA in its April 2016 model.

Modeling using Ohio EPA’s own files and own background concentrations shows that far

from attaining the standard, Gallia County has SO2 concentrations well in excess of the 1-hour NAAQS. These findings are inconsistent with Ohio EPA’s Proposed Redesignation. In finalizing its area designations, EPA is required to base its decisions on all relevant data before it. See Motor Vehicles Manufacturing Ass’n of U.S., Inc. v. State Farm, 463 U.S. 29, 30-31 (1983). EPA cannot adopt Ohio EPA’s recommended attainment designation when relevant modeling data shows nonattainment. Ohio EPA should therefore withdraw its recommendation and reevaluate its approach to adequately and accurately reflect the true SO2 concentration maxima within Gallia County.

B. Ohio’s Belated Choice of Monitoring Instead of Modeling is Not Justified

In seeking an attainment redesignation, Ohio EPA’s decision to rely on monitoring is arbitrary and unjustified. In issuing the 2010 SO2 NAAQS, EPA recognized dispersion modeling as “the most technically appropriate, efficient, and readily available method for

assessing short-term ambient SO2 concentrations in areas with large point sources.” 75 Fed. Reg. at 35,551. As EPA explained, “[d]ue to the generally localized impacts of SO2, [the Agency has] not historically considered monitoring alone to be an adequate, nor the most

appropriate, tool to identify all maximum concentrations of SO2.” Id.; cf. Catawba County v. EPA, 571 F.3d 20, 30 (D.C. Cir. 2009) (acknowledging the inherent problem of using monitored data for criteria pollutants, namely that “a monitor only measures air quality in its immediate vicinity”). “[I]t is more appropriate and efficient to principally use modeling to assess compliance for medium to larger sources,” 75 Fed. Reg. at 35,570, because it “better address[es] several potentially problematic issues than would the narrower monitoring-focused approach . . ., including the unique source-specific impacts of SO2 emissions and the special challenges SO2 emissions have historically presented in terms of monitoring short-term SO2 levels for comparison with the NAAQS in many situations (75 Fed. Reg. 35,550).” U.S. EPA,

Implementation of the 1-Hour SO2 NAAQS Draft White Paper for Discussion at 3, fn. 1.

EPA has endorsed and relied on the use of modeling throughout the 2010 SO2 NAAQS 14 implementation process. EPA’s use of modeling to assess compliance with the 2010 SO2 NAAQS is consistent with the Agency’s historic use of such modeling for multiple NAAQS implementation purposes, including for attainment designations. As EPA explained:

Historically, we have favored dispersion modeling to support SO2 NAAQS compliance determinations for areas with sources that have the potential to cause an SO2 NAAQS violation, and we have explained that for an area to be designated as “attainment,” dispersion modeling regarding such sources needs to show the absence of violations even if monitoring does not show a violation. This has been our general position throughout the history of implementation of the SO2 NAAQS program. 75 Fed. Reg. at 35,551 (citing 43 Fed. Reg. 40,412, 40,415–16 (Sept. 11, 1978); 43 Fed Reg. 45,993, 46,000–02 (Oct. 5, 1978); 57 Fed. Reg. 13,498, 13,545, 13,547–48 (Apr. 16, 1992); 58 Fed. Reg. 41,430 (Aug. 4, 1993); 59 Fed. Reg. 12,886, 12,887 (Mar. 18, 1994); 60 Fed. Reg. 12,492, 12,494–95 (Mar. 7, 1995); 67 Fed. Reg. 22,167, 22,170–71, 22,183–87 (May 2, 2002)).

Ohio EPA’s choice of monitoring in its redesignation request is therefore contrary to both EPA guidance and deadlines. Pursuant to 40 C.F.R. §51.1203, state air agencies were required to choose, for each “source area subject to requirements for air quality characterization,” between ambient air quality monitoring, air quality modeling techniques, or federally enforceable emission limitations as a means of designating that site with respect to the 2010 1- hour SO2 NAAQS, and notify EPA, by July 1, 2016. See 80 Fed. Reg. 51,052-01.

Ohio EPA did not notify EPA by July 1, 2016 that it sought to use monitoring for designation purposes for Gavin or Kyger Creek. To the contrary, Ohio EPA, in September 2015

14 See, e.g., Memorandum from Stephen D. Page, Director of EPA Office of Air Quality Planning and Standards, at 2, 4-5 (hereinafter, 2015 Page Memo), available at https://www.epa.gov/sites/production/files/201604/documents/20150320so2designations.pdf (recognizing modeling as “an appropriate tool to indicate a violation of the SO2 NAAQS” and anticipating “that in many areas the most reliable information for informing these designations will be based on source modeling”); EPA, Draft SO2 NAAQS Designation Modeling Technical Assistance Document, Aug. 2016, available at https://www.epa.gov/sites/production/files/2016- 06/documents/so2modelingtad.pdf (additional guidance document to assist states and other parties in characterizing air quality through air dispersion modeling for purposes of assessing compliance with the 2010 SO2 NAAQS); EPA, Responses to Significant Comments on the Designation Recommendations for the 2010 SO2 NAAQS – Supplement for Four Areas in Texas Not Addressed in June 30, 2016, Version Nov. 29, 2016 (hereinafter, Nov. 2016 Response to Comments), available at https://www.epa.gov/sites/production/files/2016- 11/documents/rtc_so2_comments_received_ document_4_tx_sources_final_0.pdf (“Modeling has proved to be an accurate and reliable tool for remedying the occasional weakness of SO2 monitoring, and obviously in some cases is the only tool available where there is no SO2 monitor in place to assess air quality.”).

and again in April 2016, submitted modeling data to EPA in support of its request for an “attainment” designation for the Gallia County area. As described above, EPA found that the April 2016 Ohio EPA model included an “inappropriate adjustment” to the background concentrations, whereby Ohio EPA arbitrarily reduced those concentrations by 38% based on data from a monitor 13km from the Gavin plant.15 With this adjustment, the 99th percentile 1- hour average for the 2012-14 period was 195.4 μg/m3, a mere 1 μg/m3 or 0.5% below the NAAQS. As discussed above, EPA found that because background concentrations varied, it could not determine whether, correcting for the improper 38% reduction in background concentrations, the NAAQS had been exceeded. EPA thus designated Gallia County unclassifiable in July 2016.

Five months later, well after the deadline set by 40 C.F.R. §51.1203 and after failing to obtain an attainment designation using modeling, Ohio EPA sent a letter to EPA requesting concurrence in the siting of four monitors near the Gavin and Kyger Creek power plants. Ohio EPA has now elected to use monitors as the basis for its Proposed Redesignation. This untimely change in strategy is contrary to EPA rules and unjustified.

The Proposed Redesignation does not offer any justification for Ohio EPA’s decision to now proceed on the basis of monitoring. The Proposed Redesignation simply asserts that because Ohio EPA “believe[s] that these monitors are well sited to represent maximum concentrations in the area,” no additional modeling is necessary. Proposed Redesignation, at p.

5. Given the intrinsic limitations of monitors to capture localized impacts of SO2 emissions, EPA’s stated preference for modeling for attainment designations with respect to the 2010 1-

hour SO2 NAAQS, and Ohio EPA’s own prior reliance on modeling, Ohio EPA’s reversal and choice to rely solely on monitoring is arbitrary.

The only other justification offered for Ohio’s choice of monitoring data is that one of the four monitors is located in “an area that is already designated attainment/unclassifiable,” Mason County, West Virginia. But closer inspection of the Mason County designation shows that, to the contrary, there is a high likelihood that concentrations in Gallia County exceed the NAAQS and thus that modeling is particularly important to ensure the highest concentrations in the area are captured. The modeled 99th percentile daily 1-hour maximum concentrations for Mason County during the years 2012-14 was 196.02 μg/m3, less than a half a microgram shy of the NAAQS limit.16 This concentration (and other concentrations exceeding 175 μg/m3) was predicted to occur just south of Kyger Creek—on the border with Gallia County. That Mason

15 See EPA-HQ-OAR-2014-0464-0405 at 8, 12 (“Final Technical Support Document (‘TSD’) for Ohio”), available at https://www.epa.gov/sites/production/files/2016- 07/documents/r5_oh_final_designation_tsd_06302016.pdf, at p. 17

16 https://www.epa.gov/sites/production/files/2017-12/documents/43-wv-so2-rd3-final.pdf, at p. 26.

County was designated attainment by the narrowest of margins based on emissions between six and eight years ago with an EPA-approved model indicating maximum concentrations at the border with Gallia County, hardly supports Ohio’s recommendation of an attainment designation solely on the basis of air quality monitoring. Short of near-perfect monitor siting, it is highly unlikely that four monitors could provide assurance that nowhere in Gallia County along its

border with West Virginia do SO2 concentrations rise even a single microgram per square meter th above the highest predicted 99 percentile levels in Mason County.

In short, Ohio EPA must explain why, after seeking—and failing to obtain—an attainment designation on the basis of EPA’s preferred methodology, it has chosen to rely solely on monitors instead, and should engage in supplemental modeling to justify its recommendation.

C. Ohio EPA Did Not Place the Monitors in the Areas of Greatest SO2 Concentration

Even if monitoring alone could be an adequate basis for an attainment designation, the monitoring conducted here is fundamentally flawed because Ohio EPA failed to site the monitors

at the locations Ohio EPA predicted to have the highest concentrations of SO2. The Proposed th Redesignation relies on monitoring data purporting to show the 99 percentile SO2 concentration at the four monitoring sites as falling below the 196.4 μg/m3 or 75 ppb 1-hour NAAQS. See Proposed Redesignation, Table 1, at p. 6 and Appendix A. However, the technical documentation accompanying this data undermines the assertion—the fundamental premise of the Proposed Redesignation—that these monitors captured the peak ambient concentrations of

SO2 within Gallia County. The monitors were not placed in the areas predicted to suffer from the highest SO2 concentrations in Gallia County and, moreover, missed a significant percentage of hourly data. The fact that concentrations at these locations did not exceed the 1-hour NAAQS does not undermine the conclusions of the Wingra Report, which indicate nonattainment, much less support an attainment designation for an area where modeling continues to show exceedances.

Ohio EPA did not place its monitors in those locations near Gavin and Kyger Creek that

its own modeling predicted would have the highest SO2 concentrations. Appendix C to the Proposed Redesignation shows the analysis on which Ohio relied on in placing the four monitors. According to Appendix C, Ohio modeled the 2012-14 normalized actual emissions to rank receptors by both the 4th highest maximum daily value (i.e., the 1-hour 99th percentile) and the frequency with which the maximum daily value occurred at that receptor. Ohio then identified the 250 highest ranked receptors based on these two criteria. This methodology is

consistent with EPA’s Technical Assistance Document on SO2 NAAQS Designations Source- Oriented Monitoring. See U.S. EPA, SO2 NAAQS Designations Source-Oriented Monitoring Technical Assistance Document (February 2016).17 However, Appendix C does not identify

17 Available at https://www3.epa.gov/airquality/so2implementation/SO2MonitoringTAD.pdf.

what the composite rank of the four selected sites selected from the “250 highest ranked receptors” actually were. Notably, Appendix C does not state that any of the sites selected were “at or very near the receptor having both the highest normalized design value [i.e., the highest

relative SO2 concentration reading] and frequency of 1-hour daily maxima,” or, if different, the receptor with the highest composite rank—only that the “[h]ighest ranked receptors” were “near” the general vicinity (Cheshire, Lakin, and Addison) where the monitors were actually placed. Cf. id. at A-0.

On closer examination, Figure 21 of Appendix C, which shows the four monitoring sites superimposed on the composite contour plot of modeling from Ohio’s four meteorological datasets, actually shows all four monitoring sites as located outside the mapped region with the highest concentration of SO2 according to the models on which Ohio relied in placing monitors. Modeling conducted as part of the Wingra Report confirms that the monitors were placed significantly southeast of where maximum impacts from the Gavin and Kyger Creek plants occur. See Figure 1. This same modeling indicated there are 647 receptors with higher 99th percentile 1-hour concentrations than the receptors selected for monitor sites. See Wingra Report, at p. 11.

[Figure 1 on following page]

Figure 1: Monitor locations18 and the recent AERMOD modeling using the un-adjusted background concentrations

18 Monitor 4 is Cheshire Elem. (Site ID 39-053-0004), Monitor 5 is Ridge (Site ID 39-053-0005), Monitor 6 is Guiding Hand (Site ID 39-053-0006), Monitor 1 is Lakin WV (Site ID 39-053- 0001).

In short, the monitors on which Ohio EPA relies in asserting attainment were not placed

in the locations in Gallia County where SO2 concentrations are highest, according to either the models used by Ohio EPA in placing them, or a third-party (Sierra Club) model conducted in adherence with all available EPA guidance. The data from these monitors is also incomplete. The Data Certification materials included as Appendix B to the Proposed Redesignation includes a 2019 Audit which shows the “Percent Complete” for each of the four monitors as ranging from 91-95%; there are thus in total more than 5,250 hourly readings missing from the data for the three-year period. These missing readings—in a context where the fourth highest reading in a given year is relevant to the standard—underscore the weakness of Ohio EPA’s belated reliance on monitoring.

III. Conclusion

Ohio EPA cannot reasonably recommend EPA redesignate Gallia County as attainment. On its second try for such a designation, Ohio EPA relies on monitoring data, rather than

modeling. Modeling using AERMOD shows that SO2 concentrations near the Gavin and Kyger Creek plants exceed the NAAQS by 17%, threatening the health of Gallia County residents. These models are consistent with the models approved by EPA for Mason, West Virginia, which show extraordinarily narrow attainment—by a mere microgram per cubic meter—and with the

2016 Sierra Club and Ohio EPA models, which indicated SO2 concentrations at or above NAAQS even (in the case of the Ohio EPA model) with an unjustified 38% discount on background concentrations. Given this extensive evidence in support of nonattainment, the fact that four monitors placed outside the areas of highest SO2 concentration and missing more than 1300 hourly measurements each did not capture any concentrations in excess of the NAAQS cannot support an attainment designation. Ohio’s choice to rely on monitoring—made more than five months after the deadline to notify EPA of its choice and after EPA considered and rejected Ohio EPA’s use of a 38% background reduction as part of its modeling in support of an attainment designation—is at odds with EPA guidance. Ohio EPA should rescind its Proposed

Redesignation and redouble its efforts to reduce SO2 emissions from the Gavin and Kyger Creek plants to actually bring Gallia County into attainment with the 2010 1-hour SO2 NAAQS.

Sincerely,

/s/ Megan Wachspress Associate Attorney Sierra Club 2101 Webster St., 13th Floor Oakland, CA 94612 (415) 977-5635 [email protected]

Zachary M. Fabish Senior Attorney Sierra Club 50 F Street NW, 8th Floor Washington, D.C. 20001 (202) 675-7917 [email protected]

Kristin Henry Managing Attorney Sierra Club 2101 Webster Street, Suite 1300 Oakland, CA 94612 (415) 977-5716 [email protected]

Tony Mendoza Senior Attorney Sierra Club 2101 Webster St., 13th Floor Oakland, CA 94612 (415) 977-5589 [email protected]

Exhibit 1 Gavin Power Plant and Kyger Creek Station

Cheshire, Ohio

Evaluation of Compliance with the 1-hour NAAQS for SO2

April 17, 2020

Conducted by:

Steven Klafka, P.E., BCEE

Wingra Engineering, S.C.

Madison, Wisconsin Evaluation of Compliance with the 1-hour NAAQS for SO2 April 17, 2020 Page 2

1. Introduction

Wingra Engineering, S.C. was hired by Sierra Club to conduct an air modeling impact analysis to help the U.S. Environmental Protection Agency (USEPA), state, and local air agencies identify facilities that are likely causing exceedances of the 2010 1-hour sulfur dioxide (SO2) national ambient air quality standard (NAAQS). This document describes the results and procedures for an evaluation conducted for the Gavin Power Plant and Kyger Creek Station, both located in Cheshire, Ohio.

The last modeling analyses for these plants was conducted in 2016. These include an analysis conducted for the Sierra Club as described in a March 29, 2016 report and an analysis conducted by the Ohio EPA as described in its April 19, 2016 report.1 USEPA subsequently used the results from these two analyses in its Final Technical Support Document to designate Gallia County as unclassified.2

The enclosed modeling analysis updates the 2016 modeling analyses using actual emissions and stack parameters from two recent 3-year periods: 2016-2018 and 2017-2019. Except for the emissions, stack parameters and meteorology for the more recent 3-year periods, it uses the same modeling files from the Ohio EPA analysis in 2016.3

To determine the influence of background SO2 concentrations, two scenarios were evaluated. The first uses the same background concentrations used by Ohio EPA in 2016. These concentrations had been adjusted downward by the agency to estimate the influence of emissions from the Gavin and Kyger Creek plants. The second scenario uses the original measured background concentrations with no adjustment. In its Final Technical Support Document comments on the Ohio EPA modeling analysis, USEPA concluded it was unnecessary to adjust the background concentrations downward.

The dispersion modeling analysis predicted ambient air concentrations for comparison with the 1- hour SO2 NAAQS. The modeling was performed using the most-recent version of AERMOD, AERMET, and AERMINUTE, with data provided to Sierra Club by regulatory air agencies or obtained through other publicly-available sources as documented below. The analysis was conducted in adherence with all available USEPA guidance for evaluating source impacts on attainment of the 1-hour SO2 NAAQS via air dispersion modeling, including the AERMOD Implementation Guide; USEPA's Applicability of Appendix W Modeling Guidance for the 1-hour SO2 National Ambient Air Quality Standard, August 23, 2010; modeling guidance promulgated by

1 Ohio EPA, Dispersion Modeling Analysis for General James M. Gavin Source Area: 2010 SO2 NAAQS: Response to U.S. EPA 120-Day Letter, April 19, 2016. 2 USEPA, Final Technical Support Document for Final Addition on Ohio Area Designations for the 2010 SO2 Primary National Ambient Air Quality Standard, June 30, 2016. 3 Gavin_Kyger_12_14_Revised_AllDefault_3yrs_SO2.LST Evaluation of Compliance with the 1-hour NAAQS for SO2 April 17, 2020 Page 3

USEPA in Appendix W to 40 CFR Part 51; USEPA’s March 2011 Modeling Guidance for SO2 4 NAAQS Designations; and, USEPA’s December 2013 SO2 NAAQS Designations Technical Assistance Document.5

2. Compliance with the 1-hour SO2 NAAQS

2.1 1-hour SO2 NAAQS

th The 1-hour SO2 NAAQS takes the form of a three-year average of the 99 -percentile of the annual distribution of daily maximum 1-hour concentrations, which cannot exceed 75 parts per billion (ppb).6 Compliance with this standard was assessed using USEPA’s AERMOD air dispersion 3 model, which produces air concentrations in units of µg/m . The 1-hour SO2 NAAQS of 75 ppb equals 196.2 µg/m3, and this is the value used for determining whether modeled impacts exceed the NAAQS.7 The 99th-percentile of the annual distribution of daily maximum 1-hour concentrations corresponds to the fourth-highest value at each receptor for a given year.

2.2 Modeling Results

Modeling results for Gavin Power Plant and Kyger Creek Station are summarized in Tables 1 and 2. Results varied depending on the time period under consideration and the assumed 1-hour average background concentrations for SO2. Results are provided using variable hourly emissions and exit velocities from two time periods: 2016-18 and 2017-2019. Table 1 presents the modeling results using the background concentrations originally used by Ohio EPA for its 2016 modeling analysis. Table 2 presents the modeling results using the original background concentrations.

Table 1, using the Ohio EPA-adjusted background concentrations, shows that violations of the 1- hour NAAQS for SO2 are predicted for the 2017-2019 period.

Table 2, using the original background concentration measurements, shows that violations of the 1- hour NAAQS for SO2 are predicted for both the 2016-2018 and 2017-2019 periods.

4 http://www.epa.gov/scram001/so2_modeling_guidance.htm 5 http://www.epa.gov/oaqps001/sulfurdioxide/pdfs/SO2ModelingTAD.pdf 6 USEPA, Applicability of Appendix W Modeling Guidance for the 1-hour SO2 National Ambient Air Quality Standard, August 23, 2010. 7 The ppb to µg/m3 conversion is found in the source code to AERMOD v. 19191, subroutine Modules. The conversion calculation is 75/0.3823 = 196.2 µg/m3. This conversion has been used for consistency with prior modeling reports. While USEPA has recently converted the 75 ppb standard to 196.4 µg/m3, the alternative USEPA concentration does not change the conclusions of this report. Evaluation of Compliance with the 1-hour NAAQS for SO2 April 17, 2020 Page 4

Table 1 - SO2 Modeling Results using Ohio EPA-Adjusted Background Concentrations

99th Percentile 1-hour Daily Maximum (µg/m3) Complies with Period Facility Total NAAQS NAAQS?

Gavin 171.2 196.2 Yes

2016-18 Kyger Creek 52.8 196.2 Yes

Both Plants 190.5 196.2 Yes

Gavin 202.3 196.2 No

2017-19 Kyger Creek 50.2 196.2 Yes

Both Plants 223.0 196.2 No

Table 2 - SO2 Modeling Results using Original Background Concentrations

99th Percentile 1-hour Daily Maximum (µg/m3) Complies with Period Facility Total NAAQS NAAQS?

Gavin 182.8 196.2 Yes

2016-18 Kyger Creek 67.9 196.2 Yes

Both Plants 201.7 196.2 No

Gavin 212.0 196.2 No

2017-19 Kyger Creek 65.4 196.2 Yes

Both Plants 231.0 196.2 No

Figure 1 shows the geographic extent of NAAQS violations based on actual emissions from both plants for the 2016-18 period using the original background concentrations. These results are presented in Table 2. Violations are predicted to occur approximately 3 km northeast of the Gavin plant and 5 km northeast of the Kyger Creek plant.

Figure 2 shows the geographic extent of NAAQS violations based on actual emissions from both plants for 2017-19 period using the original background concentrations. These results are presented in Table 2. Violations are predicted to occur approximately 2 km northeast of the Gavin plant and 4 km northeast of the Kyger Creek plant.

Evaluation of Compliance with the 1-hour NAAQS for SO2 April 17, 2020 Page 5

Figure 1 - NAAQS Exceedences Based on Actual Emissions from 2016-2018

Evaluation of Compliance with the 1-hour NAAQS for SO2 April 17, 2020 Page 6

Figure 2 - NAAQS Exceedences Based on Actual Emissions from 2017-2019

Evaluation of Compliance with the 1-hour NAAQS for SO2 April 17, 2020 Page 7

The modeling analysis was conducted using actual hourly emissions for two 3-year periods: 2016-18 and 2017-19. The actual emission measurements were taken from USEPA Clean Air Markets Program Data (CAMD).8

In its June 30, 2016 technical support document, USEPA had questioned the insertion emission measurements into blank and questionable hours within the CAMD data used for the 2016 modeling conducted for the Sierra Club. For the enclosed analysis, there was no substitution of hourly emission rates into those provided by the 2016 to 2019 CAMD data.

A typical modeling analysis is conducted using fixed stack exit velocities. To more accurately predict the dispersion of emissions, hourly exit velocities were used for both power plants. Continuous emissions monitor measurements were not publicly available to provide these values for the two 3-year periods evaluated, so exit velocities were derived from the hourly flow rates and heat input in the USEPA CAMD database and the Emissions Modeling Clearinghouse State-Level 9 Hourly Sulfur Dioxide (SO2) Data.

The Clearinghouse provides both hourly flow rate and heat input measurements. These were used to derive a relationship between flow rate and heat input in units of scf per mmbtu. For Gavin, the ratios for Units 1 and 2 were 18,259 and 18,419, respectively. For Kyger Creek, the ratios for CS12 (Units 1 and 2) and CS35 (Units 3,4 and 5) were 20,612 and 21,360, respectively.

To convert from standard to actual flue gas temperatures, an average temperature was derived for each stack. These temperatures were based on the continuous emissions monitor measurements for the 2012-14 period which had been used by Ohio EPA for its 2016 modeling analysis. For Gavin, the temperatures for Units 1 and 2 were 324 and 325 ºK, respectively. For Kyger Creek, the temperatures for CS12 (Units 1 and 2) and CS35 (Units 3,4 and 5) were both 324 °K. If continuous emissions monitor measurements are provided for the two 3-year periods evaluated for this updated analysis, the modeling could be repeated to improve the accuracy of the modeling results.

For the modeling results summarized in Table 1, background concentrations are the same temporally varying (by hour and season) concentrations used by the Ohio EPA for its 2016 analysis. These are presented in Table 3. Ohio EPA obtained these concentrations from the Pomeroy monitor located north of Gavin and Kyger Creek. It then processed these measurements to develop temporally varying (by hour and season) concentrations. These 96 concentrations vary for each hour of the day for each of the four seasons (i.e. winter, spring, summer and fall). Ohio EPA further adjusted these concentrations to remove bias, reducing the temporally varying background concentrations by 38%.

8 http://ampd.epa.gov/ampd/ 9 https://www3.epa.gov/ttn/chief/emch/so2naaqs/index.html Evaluation of Compliance with the 1-hour NAAQS for SO2 April 17, 2020 Page 8

In its 2016 review of the state modeling analysis, USEPA concluded that the 38% reduction of background concentrations used by Ohio EPA was an inappropriate adjustment. It states on Page 17:

EPA does not agree that a bias adjustment to the background concentrations is appropriate. The rationale for the adjustment is based on a comparison of model estimates to monitored concentrations at a monitor location, approximately 13 kilometers from the facilities. At this distance, well removed from the expected location of peak concentrations in the area, the comparison of model estimates and monitored concentrations does not provide a reliable indication of how well the model is performing. In any case, even if the monitor were located closer to the expected location of peak concentrations, EPA does not agree that adjustment of background concentrations (or adjustment of any other model input or output) is appropriate. EPA finds that the temporally varying approach was acceptable and consistent with the Modeling TAD, but EPA finds that the state’s 38% reduction of background concentrations is an inappropriate adjustment.

For the modeling results summarized in Table 2, the analysis used the original temporally varying (by hour and season) concentrations developed by Ohio EPA from the Pomeroy monitor measurements. These original background concentrations are presented in Table 4.

Evaluation of Compliance with the 1-hour NAAQS for SO2 April 17, 2020 Page 9

Table 3 - Adjusted Background Concentrations (ppb)

Hour Winter Spring Summer Fall 1:00 1.80 2.00 0.50 0.50 2:00 1.70 1.70 0.70 0.70 3:00 2.00 1.50 0.70 1.00 4:00 1.70 1.30 0.70 0.70 5:00 1.80 1.30 0.50 0.50 6:00 1.70 1.50 0.70 0.50 7:00 2.00 2.00 0.80 0.50 8:00 1.70 2.40 1.30 1.20 9:00 2.00 2.20 1.70 1.70 10:00 2.50 3.00 2.00 1.80 11:00 2.70 5.40 3.50 2.70 12:00 3.50 3.50 5.20 4.70 13:00 3.90 4.20 6.60 4.40 14:00 4.40 4.90 6.60 6.60 15:00 4.20 2.90 4.90 3.90 16:00 3.70 4.70 7.10 4.20 17:00 4.20 3.50 5.50 4.50 18:00 4.70 3.00 4.90 4.70 19:00 4.70 2.90 2.70 4.00 20:00 3.90 3.00 1.20 2.40 21:00 2.90 2.50 0.70 1.30 22:00 2.40 1.80 0.70 1.70 23:00 2.40 1.80 0.60 1.30 24:00 2.50 1.80 0.50 1.00

Evaluation of Compliance with the 1-hour NAAQS for SO2 April 17, 2020 Page 10

Table 4 – Original Background Concentrations (ppb)

Hour Winter Spring Summer Fall 1:00 3.67 4.00 1.00 1.00 2:00 3.33 3.33 1.33 1.33 3:00 4.00 3.00 1.33 2.00 4:00 3.33 2.67 1.33 1.33 5:00 3.67 2.67 1.00 1.00 6:00 3.33 3.00 1.33 1.00 7:00 4.00 4.00 1.67 1.00 8:00 3.33 4.67 2.67 2.33 9:00 4.00 4.33 3.33 3.33 10:00 5.00 6.00 4.00 3.67 11:00 5.33 10.67 7.00 5.33 12:00 7.00 7.00 10.33 9.33 13:00 7.67 8.33 13.00 8.67 14:00 8.67 9.67 13.00 13.00 15:00 8.33 5.67 9.67 7.67 16:00 7.33 9.33 14.00 8.33 17:00 8.33 7.00 11.00 9.00 18:00 9.33 6.00 9.67 9.33 19:00 9.33 5.67 5.33 8.00 20:00 7.67 6.00 2.33 4.67 21:00 5.67 5.00 1.33 2.67 22:00 4.67 3.67 1.33 3.33 23:00 4.83 3.67 1.17 2.67 24:00 5.00 3.67 1.00 2.00

Evaluation of Compliance with the 1-hour NAAQS for SO2 April 17, 2020 Page 11

2.3 Comparison with Ambient Monitor Measurements

In 2017, Ohio EPA began operating four ambient monitoring stations near the Gavin and Kyger 10 Creek plants. In its report to USEPA, Ohio EPA presented the SO2 measurements and design values for each of the four sites for the 2017-19 period. They concluded that “these data suffice without any supplemental modeling data as a basis for designating this area attainment/unclassifiable.”

The updated modeling analysis presented in this report includes the predicted design values for the 2017-19 period based on actual hourly emissions from the Gavin and Kyger Creek plant. The modeling results presented in Figure 2 were updated to show the locations of the four ambient monitors from the Ohio EPA study. This is presented in Figure 3.

The full length of the area predicted to exceed the NAAQS is 3 kilometers. Despite the large size of this area which is predicted to exceed the NAAQS, these maximum SO2 concentrations do not occur at the same locations as the four ambient monitors. For the three monitors located north of the Gavin plant, maximum predicted concentrations are further north and west of the monitors. This suggests the monitors were not located to measure the peak SO2 impacts from the Gavin and Kyger Creek plants during the 2017-2019 period.

One of the bases for selecting the monitor locations was used of the receptors representing the 1st to 125th maximum design values predicted by a Ohio EPA modeling analysis. Review of the enclosed monitoring results for the 2017-19 period shows there are 647 receptors predicted to exceed the NAAQS.

Table 5 compares the design values measured by the four ambient monitors with those predicted at the same locations. The AERMOD results are provided for the ‘a’ scenario based on the background concentrations adjusted downward by Ohio EPA and ‘b’ scenario which removes this adjustment.

The AERMOD results are higher than the monitored values. Some of the reasons the monitor design values and modeling results do not agree could include the following:

 In its certification report to USEPA, Ohio EPA concluded these four monitors had data completeness from 91 to 95%.11 The missing measurements may include values greater than those obtained.

10 Ohio EPA, State of Ohio 2010 Revised Sulfur Dioxide National Ambient Air Quality Standard Request for Designation to Attainment/Unclassifiable as a Part of U.S. EPA’s Round 4 Designation Process: Gallia County, OH and Partial Meigs County, OH Area, February 2020 11 Ohio EPA, 2019 Early Data Certification for the Gavin-Kyger Sulfur Dioxide Monitoring Network, January 23, 2020. Evaluation of Compliance with the 1-hour NAAQS for SO2 April 17, 2020 Page 12

 The AERMOD dispersion modeling results are a prediction. Its accuracy is greater for the overall maximum design value rather than for a specific location.

Table 5 - Comparison of Ambient Monitor Measurements and AERMOD Results for 2017-2019

Measured AERMOD Results (ppb) Site ID Site Name Site Name UTM (m) UTM (m) Design Value a b (ppb) 54-053-0001 Monitor 1 Lakin WV 405669 4312510 51 67 71 39-053-0004 Monitor 4 Cheshire Elem. 402776 4311852 41 46 51 39-053-0005 Monitor 5 Ridge 400391 4305755 42 60 65 39-053-0006 Monitor 6 Guiding Hand 403800 4311812 40 62 66

2.4 Conservative Modeling Assumptions

A dispersion modeling analysis requires the selection of numerous parameters which affect the predicted concentrations. The enclosed evaluation used the input modeling files provided by Ohio EPA for their 2016 analysis including stack parameters, building downwash, receptor grid and terrain elevations. Changes included the use of hourly SO2 emissions, hourly stack exit velocity, stack temperature, and meteorology for two recent 3-year periods.

Initial modeling results used the background concentrations provided in the Ohio EPA modeling files. These SO2 concentrations had been lowered by Ohio EPA to account for interference from SO2 emission sources in the region. In its review of the Ohio EPA modeling analysis, USEPA concluded that no adjustment to the background measurements were necessary. This meant the Ohio EPA modeling results likely under-estimated the impacts of the Gavin and Kyger Creek plants. To address this overly conservative assumption, the enclosed modeling analysis was conducted using both the background concentrations adjusted downward by Ohio EPA and the original measurements with no adjustment.

Evaluation of Compliance with the 1-hour NAAQS for SO2 April 17, 2020 Page 13

Figure 3 - NAAQS Exceedences Based on Actual Emissions from 2017-2019 with Ambient Monitor Locations

Evaluation of Compliance with the 1-hour NAAQS for SO2 April 17, 2020 Page 14

3. Modeling Methodology

3.1 Air Dispersion Model

The modeling analysis used USEPA’s AERMOD program, v. 19191. AERMOD, as available from the Support Center for Regulatory Atmospheric Modeling (SCRAM) website, was used in conjunction with a third-party modeling software program, AERMOD View, sold by Lakes Environmental Software.

3.2 Control Options

The AERMOD model was run with the following control options:

 1-hour average air concentrations  Regulatory defaults

It is customary for Sierra Club analyses to use 1.5-meter flagpole receptor height to reflect representative inhalation level. However, this was not used for this analysis to be consistent with the modeling analysis conducted by Ohio EPA in 2016.

An evaluation was conducted to determine if the modeled facility was located in a rural or urban setting using USEPA’s methodology outlined in Section 7.2.3 of the Guideline on Air Quality Models.12 For urban sources, the URBANOPT option is used in conjunction with the urban population from an appropriate nearby city and a default surface roughness of 1.0 meter. This evaluation is described further in Section 4.1.

3.3 Output Options

The AERMOD analysis was based on three years of recent meteorological data. The modeling analyses used two runs with three years of sequential meteorological data from the 2016-2018 and 2017-19 periods. Consistent with USEPA’s Modeling Guidance for SO2 NAAQS Designations, AERMOD provided a table of fourth-high 1-hour SO2 impacts concentrations consistent with the 13 form of the 1-hour SO2 NAAQS.

Please refer to Tables 1 and 2 for the modeling results.

12 USEPA, Revision to the Guideline on Air Quality Models: Adoption of a Preferred General Purpose (Flat and Complex Terrain) Dispersion Model and Other Revisions, Appendix W to 40 CFR Part 51, November 9, 2005. 13 USEPA, Area Designations for the 2010 Revised Primary Sulfur Dioxide National Ambient Air Quality Standards, Attachment 3, March 24, 2011, pp. 24-26. Evaluation of Compliance with the 1-hour NAAQS for SO2 April 17, 2020 Page 15

4. Model Inputs

4.1 Geographical Inputs

The “ground floor” of all air dispersion modeling analyses is establishing a coordinate system for identifying the geographical location of emission sources and receptors. These geographical locations are used to determine local characteristics (such as land use and elevation), and also to ascertain source to receptor distances and relationships.

The Universal Transverse Mercator (UTM) NAD83 coordinate system was used for identifying the easting (x) and northing (y) coordinates of the modeled sources and receptors. Stack locations were obtained from prior modeling files provided by the state regulatory agency. The stack locations were then verified using aerial photographs.

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. Land use within a three-kilometer radius circle surrounding the facility was considered. USEPA guidance states that urban dispersion coefficients are used if more than 50% of the area within 3 kilometers has urban land uses. Otherwise, rural dispersion coefficients are appropriate.14

For the prior modeling analyses conducted in 2016, both Ohio EPA and USEPA agreed that rural dispersion coefficients were appropriate for the region surrounding the Gavin and Kyger Creek plants.

4.2 Emission Rates and Source Parameters

The modeling analysis considered SO2 emissions from both the Gavin and Kyger Creek plants. Other off-site sources were not considered. Stack parameters used for the modeling analysis are summarized in Table 6. These were the same parameters used for the Ohio EPA modeling analysis in 2016.

A typical modeling analysis is conducted using fixed stack exit velocities. To more accurately predict the dispersion of emissions, hourly exit velocities were used for both power plants. Continuous emissions monitor measurements were not publicly available to provide these values for the two 3- year periods evaluated, so exit velocities were derived from the hourly flow rates and heat input in the USEPA CAMD database and the Emissions Modeling Clearinghouse State-Level Hourly Sulfur

Dioxide (SO2) Data. Procedures for calculating the hourly exit velocities were described in Section 2.2.

Table 6 – Facility Stack Parameters

Facility Gavin Kyger Creek Stack UNIT1 UNIT2 CS12 CS35 Description Unit 1 Unit 2 Units 1-2 Units 3-5 X Coord. [m] 403277.18 403277.18 402257.17 402248.17 Y Coord. [m] 4310126.46 4310126.46 4308093.45 4308099.45 Base Elevation [m] 172.8 172.8 178.6 178.6 Release Height [m] 252.98 252.98 252.984 252.984 Gas Exit Temperature [°K] 328.15 328.15 326.2 326.2 Inside Diameter [m] 12.802 12.802 7.53 9.23 Gas Exit Velocity [m/s] - - - - Emission Rate [g/s] - - - -

4.3 Building Dimensions

The enclosed evaluation used the modeling files provided by the Ohio EPA for its modeling analysis in 2016. These included building dimensions so a downwash evaluation was conducted.

4.4 Receptors

The enclosed evaluation used the modeling files provided by the Ohio EPA for its modeling analysis in 2016. The discrete receptor grid from these files were used. This included 34,225 receptors extending to a distance of 50 kilometers from the Gavin and Kyger Creek plants. Receptors were excluded from the plant property.

Elevations for the receptors were obtained from National Elevation Dataset (NED) GeoTiff data. GeoTiff is a binary file that includes data descriptors and geo-referencing information necessary for extracting terrain elevations. These elevations were extracted from 1 arc-second (30 meter) resolution NED files. The current version of USEPA software program AERMAP v. 18081 was used for these tasks.

4.5 Meteorological Data

To improve the accuracy of the modeling analysis, recent meteorological data for the 2016-2018 and 2017-19 periods were prepared using the USEPA’s program AERMET which creates the model- Evaluation of Compliance with the 1-hour NAAQS for SO2 April 17, 2020 Page 17

ready surface and profile data files required by AERMOD.

Meteorological data for 2016 and 2017 were obtained from the Ohio EPA modeling web site. Data for 2018 and 2019 were not available from the agency so were prepared for the enclosed evaluation.

Required data inputs to AERMET included surface meteorological measurements, twice-daily soundings of upper air measurements, and the micrometeorological parameters surface roughness, albedo, and Bowen ratio. One-minute ASOS data were available so USEPA methods were used to reduce calm and missing hours.15 The USEPA software program AERMINUTE v. 15272 was used for these tasks.

This section discusses how the meteorological data was prepared for use in the 1-hour SO2 NAAQS modeling analyses. The USEPA software program AERMET v. 18081 was used for these tasks.

4.5.1 Surface Meteorology

Surface meteorology was obtained for Huntington Tri-State Airport, West Virginia located near the Gavin Power Plant. Integrated Surface Hourly (ISH) data for 2018 and 2019 were obtained from the National Climatic Data Center (NCDC). The ISH surface data was processed through AERMET Stage 1, which performs data extraction and quality control checks.

This surface station is the same used by Ohio EPA for its modeling analysis conducted in 2016.

4.5.2 Upper Air Data

Upper-air data are collected by a “weather balloon” that is released twice per day at selected locations. As the balloon is released, it rises through the atmosphere, and radios the data back to the surface. The measuring and transmitting device is known as either a radiosonde, or rawindsonde. Data collected and radioed back include: air pressure, height, temperature, dew point, wind speed, and wind direction. The upper air data were processed through AERMET Stage 1, which performs data extraction and quality control checks.

The concurrent upper air data from twice-daily radiosonde measurements obtained at the most representative location were used. This location was the Pittsburgh, Pennsylvania measurement station. These data are in Forecast Systems Laboratory (FSL) format and were downloaded in ASCII text format from NOAA’s FSL website.16 All reporting levels were downloaded and processed with AERMET.

15 USEPA, Area Designations for the 2010 Revised Primary Sulfur Dioxide National Ambient Air Quality Standards, Attachment 3, March 24, 2011, p. 19. 16 Available at: http://esrl.noaa.gov/raobs/ Evaluation of Compliance with the 1-hour NAAQS for SO2 April 17, 2020 Page 18

This upper-air station is the same used by Ohio EPA for its modeling analysis in 2016.

4.5.3 AERSURFACE

AERSURFACE is a program that extracts surface roughness, albedo, and daytime Bowen ratio for an area surrounding a given location. AERSURFACE uses land use and land cover (LULC) data in the U.S. Geological Survey’s 1992 National Land Cover Dataset to extract the necessary micrometeorological data. LULC data was used for processing meteorological data sets used as input to AERMOD.

The meteorological data for 2016 and 2017 were obtained from Ohio EPA so did not require processing with AERSURFACE. To prepare the meteorological data for 2018 and 2019, the surface roughness, albedo, and daytime Bowen ratio values for the Huntington Tri-State Airport for prior years were obtained from Ohio EPA.17 Monthly precipitation for 2018 and 2019 were obtained from the National Climatic Data Center to determine if months were classified by AERSURFACE as Dry, Average or Wet, and then assigned an appropriate Bowen ratio for each sector.18 The AERSURFACE output file for each year was then manually prepared and used to process the year using AERMET.

4.5.4 Data Review

Missing meteorological data were not filled as the data file met USEPA’s 90% data completeness requirement.19 The AERMOD output file shows there were 1.48% and 2.4% missing data for the 2016-18 and 2017-19 periods, respectively.

5. Background SO2 Concentrations

Background concentrations were determined consistent with USEPA’s Modeling Guidance for SO2 NAAQS Designations.20, 21 The USEPA modeling TAD offers two methods for characterizing background concentrations of SO2 that are added to the modeled design values: 1) a fixed value based on monitored design values, or 2) a temporally varying approach, based on the 99th percentile

17 Email, C. Beekman – Ohio EPA to S. Klafka – Wingra Engineering, S.C., Meteorological Data for Gallia County for 2018, January 14, 2020. 18 Local Climatological Data (LCD), Data Tools, Climate Data Online (CDO), National Climatic Data Center (NCDC), Daily Summary, https://gis.ncdc.noaa.gov/maps/ncei/lcd 19 USEPA, Meteorological Monitoring Guidance for Regulatory Modeling Applications, EPA-454/R-99-05, February 2000, Section 5.3.2, pp. 5-4 to 5-5. 20 USEPA, Area Designations for the 2010 Revised Primary Sulfur Dioxide National Ambient Air Quality Standards, Attachment 3, March 24, 2011, pp. 20-23. 21 USEPA, SO2 NAAQS Designations Modeling Technical Assistance Document, Dec. 2013, section 8.1, pp 27-28. Evaluation of Compliance with the 1-hour NAAQS for SO2 April 17, 2020 Page 19

monitored concentrations by hour of day and season or month. For its 2016 modeling analysis, the Ohio EPA chose to characterize background concentrations with a temporally varying approach.

As discussed in Section 2.2, background concentrations used for the enclosed evaluation are the same temporally varying (by hour and season) concentrations used by the Ohio EPA for its 2016 analysis. Ohio EPA obtained these concentrations from the Pomeroy monitor located north of Gavin and Kyger Creek. It then processed these measurements to develop temporally varying (by hour and season) concentrations. These 96 concentrations vary for each hour of the day for each of the four seasons (i.e. winter, spring, summer and fall). Ohio EPA further adjusted these concentrations to remove bias, reducing the temporally varying background concentrations by 38%.

In its 2016 review of the state modeling analysis, USEPA concluded that the 38% reduction of background concentrations used by Ohio EPA was an inappropriate adjustment. Therefore, a second modeling analysis in the enclosed evaluation using the original temporally varying (by hour and season) concentrations developed by Ohio EPA from the Pomeroy monitor measurements.

6. Reporting

All files from the programs used for this modeling analysis are available to regulatory agencies. These include analyses prepared with AERSURFACE, AERMET, AERMAP, and AERMOD.

Exhibit 2 Gavin Power Plant

Cheshire, Ohio

Evaluation of Compliance with the 1-hour NAAQS for SO2

March 29, 2016

Conducted by:

Steven Klafka, P.E., BCEE

Wingra Engineering, S.C.

Madison, Wisconsin Evaluation of Compliance with the 1-hour NAAQS for SO2 March 29, 2016 Page 2

1. Introduction

Wingra Engineering, S.C. was hired by Sierra Club to conduct an air modeling impact analysis to help the U.S. Environmental Protection Agency (USEPA), state, and local air agencies identify

facilities that are likely causing exceedances of the 2010 1-hour sulfur dioxide (SO2) national ambient air quality standard (NAAQS). This document describes the results and procedures for an evaluation conducted for the Gavin Power Plant located in Cheshire, Ohio.

To ensure the modeling analysis reflected the cumulative concentration of SO2 emissions, this analysis included emissions from the Kyger Creek Station in Cheshire, Ohio, which is located within 50 kilometers of the Gavin Power Plant.

This analysis supplements the evaluation described in my September 16, 2015 report prepared on behalf of Sierra Club. This analysis addresses comments on the 2015 analysis provided by the Ohio Environmental Protection Agency (Ohio EPA) in its Review and Analysis of Sierra Club Submitted

Gavin Power Plant Evaluation of Compliance with the 1-hour NAAQS for SO2. In particular, this evaluation responds to the Ohio EPA comments by: i) using variable stack parameter inputs; ii) relying on actual configuration for the two stacks at the Kyger Creek plant; iii) not incorporating

emissions from the Mountaineer Power Plant; and, iv) using the background SO2 concentration determined by Ohio EPA, among other changes from the 2015 analysis.

The dispersion modeling analysis predicted ambient air concentrations for comparison with the 1-

hour SO2 NAAQS. The modeling was performed using the most-recent version of AERMOD, AERMET, and AERMINUTE, with data provided to Sierra Club by regulatory air agencies or obtained through other publicly-available sources as documented below. The analysis was conducted in adherence with all available USEPA guidance for evaluating source impacts on

attainment of the 1-hour SO2 NAAQS via air dispersion modeling, including the AERMOD Implementation Guide; USEPA's Applicability of Appendix W Modeling Guidance for the 1-hour

SO2 National Ambient Air Quality Standard, August 23, 2010; modeling guidance promulgated by USEPA in Appendix W to 40 CFR Part 51; USEPA’s March 2011 Modeling Guidance for SO2 1 NAAQS Designations; and, USEPA’s December 2013 SO2 NAAQS Designations Technical Assistance Document.2

1 http://www.epa.gov/scram001/so2_modeling_guidance.htm 2 http://www.epa.gov/oaqps001/sulfurdioxide/pdfs/SO2ModelingTAD.pdf Evaluation of Compliance with the 1-hour NAAQS for SO2 March 29, 2016 Page 3

2. Compliance with the 1-hour SO2 NAAQS

2.1 1-hour SO2 NAAQS

th The 1-hour SO2 NAAQS takes the form of a three-year average of the 99 -percentile of the annual distribution of daily maximum 1-hour concentrations, which cannot exceed 75 parts per billion (ppb).3 Compliance with this standard was assessed using USEPA’s AERMOD air dispersion 3 model, which produces air concentrations in units of µg/m . The 1-hour SO2 NAAQS of 75 ppb equals 196.2 µg/m3, and this is the value used for determining whether modeled impacts exceed the NAAQS.4 The 99th-percentile of the annual distribution of daily maximum 1-hour concentrations corresponds to the fourth-highest value at each receptor for a given year.

2.2 Modeling Results

Modeling results for Gavin Power Plant and Kyger Creek Station are summarized in Table 1. Two scenarios were evaluated:

1. Actual hourly emissions and variable stack exit velocities for the 2012-14 period 2. Actual hourly emissions and variable stack exit velocities for the 2013-15 period

Results are provided for each source alone, and for both plants combined. It was determined that based on measured actual emissions for both of the three-year periods examined, the Gavin Power

Plant is estimated to create downwind SO2 concentrations that exceed the 1-hour NAAQS.

“Actual” represents the emissions which occurred during each hour of two 3-year periods: 2012-14 and 2013-15. Actual emission measurements were taken from two databases, USEPA Clean Air Markets Program Data (CAMD)5 and the Emissions Modeling Clearinghouse State-Level Hourly 6 Sulfur Dioxide (SO2) Data.

To more accurately predict the dispersion of emissions, hourly exit velocities were used for both power plants. Continuous emissions monitor measurements were not publicly available for this analysis so exit velocities were derived from the hourly flow rates and heat input in the USEPA Clearinghouse and CAMD databases. For the 2012-14 period, velocities were derived from the hourly flow rates reported in the Clearinghouse. For the 2013-15 period, the Clearinghouse

3 40 C.F.R. § 50.17; see also USEPA, Applicability of Appendix W Modeling Guidance for the 1-hour SO2 National Ambient Air Quality Standard, August 23, 2010. 4 The ppb to µg/m3 conversion is found in the source code to AERMOD v. 15181, subroutine Modules. The conversion calculation is 75/0.3823 = 196.2 µg/m3. 5 http://ampd.epa.gov/ampd/ 6 https://www3.epa.gov/ttn/chief/emch/so2naaqs/index.html Evaluation of Compliance with the 1-hour NAAQS for SO2 March 29, 2016 Page 4

emissions and exit velocities for 2013-14 were supplemented with CAMD emissions for 2015. The velocities for 2015 were derived from the hourly heat input reported in CAMD.

Further, a third scenario was used to evaluate AERMOD files provided by Ohio EPA for their modeling analysis of the Gavin and Kyger plants.7 Ohio EPA had used proposed options for AERMET and AERMOD: ADJ_U* and LOWWIND3. In its comments on the Ohio EPA modeling analysis of Gavin, EPA stated: "EPA does not believe that the air quality modeling results obtained from the use of this beta option can be used at this time as a reliable indicator of attainment status in Gallia County." The Ohio EPA analysis was re-run for the 2012-14 period without the ADJ_U* and LOWWIND3 options using the meteorological data prepared for the Sierra Club modeling analyses. Without these two beta options, the results significantly increased and more closely matched the updated modeling results presented in this report. This analysis demonstrates that if Ohio EPA had not selected these two beta options, its air modeling analysis for Gavin and Kyger Creek very likely would have predicted nonattainment of the NAAQS.

In this evaluation, air quality impacts in Ohio are based on a background concentration of 26.16 µg/m3. This is the 2012-14 design value used by the Ohio EPA in its own modeling evaluation of the same power plants.8

Table 1 - SO2 Modeling Results using Actual Hourly Emissions and Exit Velocities

99th Percentile 1-hour Daily Maximum (µg/m3) Complies with Period Facility Impact Background Total NAAQS NAAQS?

Gavin 207.8 26.2 234.0 196.2 No

2012-14 Kyger Creek 98.7 26.2 124.9 196.2 Yes

Both Plants 240.8 26.2 267.0 196.2 No

Gavin 193.5 26.2 219.7 196.2 No

2013-15 Kyger Creek 95.4 26.2 121.6 196.2 Yes

Both Plants 239.0 26.2 265.2 196.2 No

Ohio EPA Results without ADJ_U* and LOWWIND3 Options

2012-14 Both Plants 217.3 26.2 243.5 196.2 No

7 This AERMOD file for the Ohio EPA modeling analysis was Gavin_Kyger_12_14_v5.DTA. 8 See USEPA’s Technical Support Document, Ohio, Area Designations for the 2010 SO2 Primary National Ambient Air Quality Standard, p. 30. Evaluation of Compliance with the 1-hour NAAQS for SO2 March 29, 2016 Page 5

Figure 1 shows the geographic extent of NAAQS violations based on actual emissions from all sources for the 2012-14 period.

Figure 2 shows the geographic extent of NAAQS violations based on actual emissions from all sources for the 2013-15 period.

2.3 Conservative Modeling Assumptions

A dispersion modeling analysis requires the selection of numerous parameters which affect the predicted concentrations. For the enclosed analysis, several parameters were selected which under- predict facility impacts.

Assumptions used in this modeling analysis which likely under-estimate concentrations include the following:

 No consideration of building or structure downwash. These downwash effects typically increase predicted concentrations near the facility.  Except for the Kyger Creek plant, no consideration of off-site sources. These other sources of SO2 will increase the predicted impacts, and as USEPA notes, there are many significant 9 sources of SO2 emissions within 50 km of the Gavin Plant.

9 USEPA’s Technical Support Document, Ohio, Area Designations for the 2010 SO2 Primary National Ambient Air Quality Standard, pp. 25, 32. Evaluation of Compliance with the 1-hour NAAQS for SO2 March 29, 2016 Page 6

Figure 1 – Regional View of Impacts Due to Actual Emissions from Both Plants for the 2012-14 Period Evaluation of Compliance with the 1-hour NAAQS for SO2 March 29, 2016 Page 7

Figure 2 - Regional View of Impacts Due to Actual Emissions from Both Plants for the 2013-15 Period Evaluation of Compliance with the 1-hour NAAQS for SO2 March 29, 2016 Page 8

3. Modeling Methodology

3.1 Air Dispersion Model

The modeling analysis used USEPA’s AERMOD program, v. 15181. AERMOD, as available from the Support Center for Regulatory Atmospheric Modeling (SCRAM) website, was used in conjunction with a third-party modeling software program, AERMOD View, sold by Lakes Environmental Software.

3.2 Control Options

The AERMOD model was run with the following control options:  1-hour average air concentrations  Regulatory defaults  Flagpole receptors To reflect a representative inhalation level, a flagpole height of 1.5 meters was used for all modeled receptors. This parameter was added to the receptor file when running AERMAP, as described in Section 4.4.

An evaluation was conducted to determine if the modeled facility was located in a rural or urban setting using USEPA’s methodology outlined in Section 7.2.3 of the Guideline on Air Quality Models.10 For urban sources, the URBANOPT option is used in conjunction with the urban population from an appropriate nearby city and a default surface roughness of 1.0 meter. Methods described in Section 4.1 were used to determine whether rural or urban dispersion coefficients were appropriate for the modeling analysis.

3.3 Output Options

The AERMOD analysis was based on three years of recent meteorological data. The modeling analyses used two runs with three years of sequential meteorological data from the 2012-2014 and

2013-15 periods. Consistent with USEPA’s Modeling Guidance for SO2 NAAQS Designations,

AERMOD provided a table of fourth-high 1-hour SO2 impacts concentrations consistent with the 11 form of the 1-hour SO2 NAAQS.

10 USEPA, Revision to the Guideline on Air Quality Models: Adoption of a Preferred General Purpose (Flat and Complex Terrain) Dispersion Model and Other Revisions, Appendix W to 40 CFR Part 51, November 9, 2005. 11 USEPA, Area Designations for the 2010 Revised Primary Sulfur Dioxide National Ambient Air Quality Standards, Attachment 3, March 24, 2011, pp. 24-26. Evaluation of Compliance with the 1-hour NAAQS for SO2 March 29, 2016 Page 9

Please refer to Table 1 for the modeling results.

4. Model Inputs

4.1 Geographical Inputs

The Universal Transverse Mercator (UTM) NAD83 coordinate system 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 aerial photographs.

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 within 3 kilometers. Based on the output from the AERSURFACE, approximately 7.6% of surrounding 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 – Commercial / Industrial / Transportation.

This is less than the 50% value considered appropriate for the use of urban dispersion coefficients. Based on the AERSURFACE analysis, it was concluded that the rural option would be used for the modeling summarized in this report. Please refer to Section 4.5.3 for a discussion of the AERSURFACE analysis.

4.2 Emission Rates and Source Parameters

The modeling analysis considered SO2 emissions from the Kyger Creek power plant. Other off-site sources were not considered. Stack parameters used for the modeling analysis are summarized in Table 2. The exit temperature was held constant but the hourly exit velocity varied based on flow rate and heat input information provided by USEPA Clearinghouse and CAMD databases.

Table 2 – Facility Stack Parameters13

Facility Gavin Kyger Creek Stack G01 G02 K12 K35 Description Unit 1 Unit 2 Units 1-2 Units 3-5 X Coord. [m] 403338 403295 402264.53 402253.99 Y Coord. [m] 4310252 4310124 4308112.02 4308119.27 Base Elevation [m] 172.82 172.82 176.17 176.17 Release Height [m] 252.98 252.98 255.42 255.42 Gas Exit Temperature [°K] 323.15 323.15 327.594 327.594 Gas Exit Velocity [m/s] - - - - Inside Diameter [m] 12.802 12.802 7.53 9.2

The above stack parameters and emissions were obtained from regulatory agency documents and databases identified in Section 2.2. Stack location, height and diameter were verified using aerial photographs, and flue gas flow rate and temperature were verified using combustion calculations.

4.3 Building Dimensions

No building dimensions or prior downwash evaluations were available. Therefore this modeling analysis did not address the effects of downwash and this may under-predict impacts.

4.4 Receptors

For Gavin Power Plant, three receptor grids were employed:

1. A 100-meter Cartesian receptor grid centered on Gavin Power Plant and extending out 5 kilometers. 2. A 500-meter Cartesian receptor grid centered on Gavin Power Plant and extending out 10 kilometers. 3. A 1,000-meter Cartesian receptor grid centered on Gavin Power Plant and extending out 50

13 Stack elevation, height and exit area were obtained from the USEPA Emissions Modeling Clearinghouse State-Level Hourly Sulfur Dioxide (SO2) Data. The exit area matched the diameters provided by Ohio EPA in their review of the 2015 modeling analysis. Stack temperatures were obtained from Ohio EPA. Evaluation of Compliance with the 1-hour NAAQS for SO2 March 29, 2016 Page 11

kilometers. 50 kilometers is the maximum distance accepted by USEPA for the use of the AERMOD dispersion model.14

A flagpole height of 1.5 meters was used for all these receptors. Elevations from stacks and receptors were obtained from National Elevation Dataset (NED) GeoTiff data. GeoTiff is a binary file that includes data descriptors and geo-referencing information necessary for extracting terrain elevations. These elevations were extracted from 1 arc-second (30 meter) resolution NED files. The USEPA software program AERMAP v. 11103 is used for these tasks.

4.5 Meteorological Data

To improve the accuracy of the modeling analysis, recent meteorological data for the 2012-2014 and 2013-15 periods were prepared using the USEPA’s program AERMET which creates the model- ready surface and profile data files required by AERMOD. Required data inputs to AERMET included surface meteorological measurements, twice-daily soundings of upper air measurements, and the micrometeorological parameters surface roughness, albedo, and Bowen ratio. One-minute ASOS data were available so USEPA methods were used to reduce calm and missing hours.15 The USEPA software program AERMINUTE v. 15272 is used for these tasks.

This section discusses how the meteorological data was prepared for use in the 1-hour SO2 NAAQS modeling analyses. The USEPA software program AERMET v. 15181 is used for these tasks.

4.5.1 Surface Meteorology

Surface meteorology was obtained for Huntington Tri-State Airport, West Virginia located near the Gavin Power Plant. Integrated Surface Hourly (ISH) data for the 2012-2014 and 2013-2015 periods were obtained from the National Climatic Data Center (NCDC). The ISH surface data was processed through AERMET Stage 1, which performs data extraction and quality control checks.

4.5.2 Upper Air Data

14 USEPA, Revision to the Guideline on Air Quality Models: Adoption of a Preferred General Purpose (Flat and Complex Terrain) Dispersion Model and Other Revisions, Appendix W to 40 CFR Part 51, Section A.1.(1), November 9, 2005. 15 USEPA, Area Designations for the 2010 Revised Primary Sulfur Dioxide National Ambient Air Quality Standards, Attachment 3, March 24, 2011, p. 19. Evaluation of Compliance with the 1-hour NAAQS for SO2 March 29, 2016 Page 12

Data collected and radioed back include: air pressure, height, temperature, dew point, wind speed, and wind direction. The upper air data were processed through AERMET Stage 1, which performs data extraction and quality control checks.

For Gavin Power Plant, the concurrent upper air data from twice-daily radiosonde measurements obtained at the most representative location were used. This location was the Pittsburgh, Pennsylvania measurement station. These data are in Forecast Systems Laboratory (FSL) format and were downloaded in ASCII text format from NOAA’s FSL website.16 All reporting levels were downloaded and processed with AERMET.

4.5.3 AERSURFACE

AERSURFACE v. 13016 was used to develop surface roughness, albedo, and daytime Bowen ratio values in a region surrounding the meteorological data collection site. AERSURFACE was used to develop surface roughness in a one kilometer radius surrounding the data collection site. 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 continuous snow cover.

4.5.4 Data Review

Missing meteorological data were not filled as the data file met USEPA’s 90% data completeness requirement.17 The AERMOD output file shows there were 0.87% and 1.09% missing data for the 2012-14 and 2013-15 periods, respectively.

To confirm the representativeness of the airport meteorological data, the surface characteristics of the airport data collection site and the modeled source location were compared. Since the Huntington Tri-State Airport, West Virginia is located close to Gavin Power Plant, this meteorological data set was considered appropriate for this modeling analysis.18 This weather station provided high quality

16 Available at: http://esrl.noaa.gov/raobs/ 17 USEPA, Meteorological Monitoring Guidance for Regulatory Modeling Applications, EPA-454/R-99-05, February 2000, Section 5.3.2, pp. 5-4 to 5-5. 18 USEPA, AERMOD Implementation Guide, March 19, 2009, pp. 3-4. Evaluation of Compliance with the 1-hour NAAQS for SO2 March 29, 2016 Page 13

surface measurements for the 2012-14 and 2013-15 periods, and had similar land use, surface characteristics, terrain features and climate. Finally, the use of meteorological data from the selected surface and upper air stations were recommended by the Ohio Environmental Protection Agency for modeling facilities located in Gallia County.19

5. Background SO2 Concentrations

Background concentrations were determined consistent with USEPA’s Modeling Guidance for SO2 20, 21 th NAAQS Designations. To preserve the form of the 1-hour SO2 standard, based on the 99 percentile of the annual distribution of daily maximum 1-hour concentrations averaged across the

number of years modeled, the background fourth-highest daily maximum 1-hour SO2 concentration 22 was added to the modeled fourth-highest daily maximum 1-hour SO2 concentration. The background concentration was based on the 2012-14 design value used by Ohio EPA in its 2015 modeling analysis of the same facilities.

6. Reporting

All files from the programs used for this modeling analysis are available to regulatory agencies. These include analyses prepared with AERSURFACE, AERMET, AERMAP, and AERMOD.

19 Ohio EPA, AERMET Output Files for AERMOD Model Input,http://epa.ohio.gov/dapc/model/modeling/metfiles.aspx 20 USEPA, Area Designations for the 2010 Revised Primary Sulfur Dioxide National Ambient Air Quality Standards, Attachment 3, March 24, 2011, pp. 20-23. 21 USEPA, SO2 NAAQS Designations Modeling Technical Assistance Document, Dec. 2013, section 8.1, pp 27-28. 22 USEPA, Applicability of Appendix W Modeling Guidance for the 1-hour SO2 National Ambient Air Quality Standard, August 23, 2010, p. 3.