State Of Ohio 2010 Revised Sulfur Dioxide 

National Ambient Air Quality Standard

Recommended Source Area Designation:

W. H. Zimmer Generating Station

Prepared by:

Ohio Environmental Protection Agency

Division of Air Pollution Control

August, 2015
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TABLE OF CONTENTS

CHAPTER ONE: ............................................................................................................. 1

General Discussion ......................................................................................................... 1

History...................................................................................................................... 1

Requirements........................................................................................................... 1

Ohio EPA’s Approach ..................................................................................................... 2

Factor 1: Dispersion Modeling.............................................................................. 3

Factor 2: Emissions Data ..................................................................................... 3

Factor 3: Meteorology .......................................................................................... 4

Factor 4: Topography and Land Use/Land Cover................................................ 5

Factor 5: Jurisdictional Boundaries ...................................................................... 5

CHAPTER TWO: ............................................................................................................ 6

Analysis........................................................................................................................... 6

Discussion:............................................................................................................... 6

Factor 1: Dispersion Modeling.............................................................................. 6

Factor 2: Emissions.............................................................................................. 7

Factor 3: Meteorology .......................................................................................... 9

Factor 4: Topography and Land Use/Land Cover.............................................. 12

Factor 5: Jurisdictional Boundaries .................................................................... 12

APPENDICES

Appendix A: Dispersion Modeling Analysis for William H. Zimmer/Clermont County

Appendix B: William H. Zimmer Source Area Background SO2 Analysis

Appendix C: Modeling Protocol

As referenced in Appendix C:

Appendix D: Region 5 IDEM Q & A Response

Appendix E: Region 5 States Q & A Response

Appendix F: October 14, 2014 Walter C. Beckjord Shutdown Notification

Appendix G: May 28, 2015 Walter C. Beckjord Shutdown Notification

Appendix H: June 11, 2015 Miami Fort Shutdown Notification
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State Of Ohio 2010 Revised Sulfur Dioxide National Ambient Air Quality 

Standard

Recommended Designation:

W. H. Zimmer Generating Station

CHAPTER ONE: 

General Discussion

History

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. U.S. EPA replaced the 24-hour and annual standards 

with a new short-term one-hour standard of 75 parts per billion (ppb). The new 

one-hour SO2 standard was published on June 22, 2010 (75 FR 35520) and 

became effective on August 23, 2010. The standard is based on the three-year 

average of the annual 99th percentile of one-hour daily maximum 

concentrations.

On August 15, 2013, U.S. EPA published (78 FR 47191) the initial SO2

nonattainment area designations for the one-hour SO2 standard across the 

country (effective October 4, 2013). 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 directs U.S. EPA to complete designations in 

three steps: the first by July 2, 2016; the second by December 31, 2017 and the 

third by December 31, 2020. As part of the first round of designations, U.S. EPA 

has identified areas with newly monitored violations of the standard, or areas 

that contain 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. The U.S. EPA has identified two facilities in 

Ohio as meeting one or more of the emissions thresholds: the General James 

M. Gavin Plant and the W.H. Zimmer Generating Station. Ohio EPA must 

submit designation recommendations to U.S. EPA by September 18, 2015.

Requirements

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. Since the original 2011 state submittals of 

designation recommendations and pursuant to the March 2, 2015 court order, 
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new information may be relevant for future designations. CAA Section 107(d) 

does not require states to submit updated recommendations. However, U.S. 

EPA will consider such information. For the round of designations to be 

completed by July 2, 2016, U.S. EPA requests that states submit updated 

recommendations and supporting information for consideration by September 

18, 2015. If U.S. EPA intends to modify any state’s designation 

recommendation, original or updated, the state will be notified no later than 120 

days prior to promulgating the final designations. For the designations due to be 

promulgated on or before July 2, 2016, this notification will occur no later than 

March 2, 2016. Although not required by statute, U.S. EPA will provide a 30-day 

public comment period immediately following issuance of the 120-day letters.

Section 107(d)(1) of the CAA defines an area as “nonattainment” if it is violating 

the NAAQS or if it is contributing to a violation in a nearby area. The first step in 

making designation decisions is to identify areas for which monitoring or 

appropriate modeling information indicate a violation of the NAAQS. U.S. EPA 

may designate an area as attainment if it is clear that that it meets the SO2

NAAQS and does not contribute to a violation in a nearby area.

As stated in the U.S. EPA’s Data Requirements Rule for the 1-Hour Sulfur 

Dioxide (SO2) Primary National Ambient Air Quality Standard (NAAQS); 

Proposed Rule (79 FR 27445), herein referred to as the proposed Data 

Requirements Rule, the purpose of the designations modeling is to assess 

actual, current air quality and that recommendations could include modeling the 

source area as attaining the standard. U.S. EPA intends to designate areas that 

are modeled with actual emissions as “unclassifiable” whereas areas that are 

modeled with allowable emissions may be designated as “attainment.” Areas 

designated as unclassifiable may be subject to additional and continued analysis 

to assess attainment over time. 

Ohio EPA’s Approach

This submittal is Ohio’s recommendation for the designation of the area 

surrounding the William H. Zimmer Generating Station located in Clermont 

County, Ohio. This facility was identified by U.S. EPA as meeting the criteria 

established in the March 2, 2015 court order. In accordance with U.S. EPA’s 

final rule, SO2 Designation Guidance, and a March 20, 2015 memorandum 

Updated Guidance for Area Designations for the 2010 Primary Sulfur Dioxide 

National Ambient Air Quality Standard, the starting point for the area 

designations would be the county boundary associated with a violation or around

the SO2 source(s) in question, unless additional information is provided to U.S. 

EPA demonstrating a different boundary is appropriate. U.S. EPA’s SO2

Designation Guidance states that U.S. EPA generally believes that in the 
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absence of other relevant information it is appropriate to use county boundaries 

to define nonattainment areas, but they recognize that the five-factor analysis 

and other information may support designating only a portion of a county as 

nonattainment. U.S. EPA states that modeling could be used to address several 

of these factors simultaneously. Ohio used the five-factor analysis approach and 

conducted additional modeling analysis as a part of this submittal. While using 

this approach, the SO2 Designation Guidance states this analysis should show 

that: 1) violations are not occurring in nearby portions that are excluded from the 

designation area; and 2) the excluded portions do not contain emission sources 

that contribute to the monitored or modeled violations, if observed.

The following summarizes the major factors included in Ohio’s analysis for the 

designation recommendation for the area surrounding the William H. Zimmer 

Generating Station. Specifically, Ohio has used the five factor analysis 

approach, including refined dispersion modeling, as recommended in the SO2 

Designation Guidance, to support the boundary recommendation. Ohio EPA 

understands, based on the both the December 2013 Draft SO2 NAAQS 

Designations Modeling Technical Assistance Document and the March 20, 2015 

memorandum, that dispersion modeling accounts simultaneously for multiple 

elements of the five-factor analysis. As such, Ohio believes that the modeling 

analysis presented in Appendix A and summarized in this document should 

carry significant weight in the designation process. Where appropriate, Ohio is 

providing additional supporting information with respect to the five-factor 

designation approach.

Factor 1: Dispersion Modeling

Ohio conducted a refined dispersion modeling analysis following the guidance 

issued by U.S. EPA in the December 2013 Draft SO2 NAAQS Designations 

Modeling Technical Assistance Document, the March 20 memorandum, and the 

proposed Data Requirements Rule. The modeling analysis was based on 2012 

to 2014 actual emissions from the William H. Zimmer Generating Station and 

representative meteorological data from the same period. The methodology and 

results of this analysis are provided in Appendix A. 

Factor 2: Emissions Data

Emissions of SO2 for 2014 are derived from Ohio EPA’s Fee Emission Reports 

(FERs) which are the basis for Ohio’s 2014 NEI submittal. Tables identified in 

this analysis show stationary sources with reported SO2 emissions in tons per 

year (TPY) at the facility level within each county relevant to the area around the 

William H. Zimmer facility. U.S. EPA’s Designations Modeling Technical 

Assistance Documents suggests sources greater than the thresholds 

established under the proposed Data Requirements Rule located within 50 
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kilometers of the William H. Zimmer facility should be considered in the analysis 

of emissions data. Further, U.S. EPA Region 5 indicated to the Region 5 states

that sources retired prior to the promulgation of a designation for a particular 

area do not need to be modeled. (Appendix E) This is consistent with the 

language of the proposed Data Requirements Rule. Therefore, Ohio will 

consider the reduction in SO2 emissions due to retirements as part of its 

recommended designation. In addition to the emissions from sources meeting 

the above criteria, the impact of the William H. Zimmer facility are directly 

modeled as a part of Ohio’s designation recommendation analysis. Emissions 

data for the William H. Zimmer facility were provided to Ohio EPA by the 

owner/operator of the facility, Dynegy Zimmer, LLC. 

Factor 3: Meteorology

The meteorology review looks at wind data gathered at stations in and near Ohio 

by the National Weather Service (NWS). Information presented under this 

factor is indicative of annual average winds. These data may also suggest that 

emissions originating from some directions may be more prone to contribute 

than emissions in other directions. 

Ohio is located in what is meteorologically termed the Mid-Latitudes. For 

pollutant dispersion, the most important meteorological parameter is wind speed 

and wind direction. In this region, surface weather systems predominantly 

travel from west to east, guided by either the sub-tropical or polar jet streams. 

The resulting surface transport winds associated with these systems will 

generally have a western component with additional southern components in the 

summer and northern components in the winter, although, on any given day, 

winds can blow from any direction. Discussions regarding this factor will show 

representative wind roses for the source area and SO2 sources surrounding the 

William H. Zimmer facility.

 

The major geographic feature affecting winds in the area surrounding the 

William H. Zimmer facility is the hilly terrain and the Ohio River valley. This area 

has significant forested areas which modify the surface roughness lengths and 

can impact wind speed and wind direction. The Covington airport wind roses 

best illustrate the range of wind directions and wind speeds associated with this 

area.

A significant portion of this factor is accounted for by the dispersion modeling 

analysis conducted for this area. The AERSURFACE preprocessor component 

of the AERMOD model accounts for land use and its impact on surface 

roughness lengths, albedo, and Bowen ratio. The meteorological inputs to 

AERMOD itself are taken from measurements at the Covington airport. 
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Factor 4: Topography and Land Use/Land Cover

The topography and land use/land cover analysis looks at physical features and 

land use or land cover that might have an effect on the airshed and, therefore, 

the distribution of pollutants over an area. The William H. Zimmer facility is 

located in the Ohio River valley, and therefore some portions of the area may 

experience inversions. However, the geographical and topographical features of 

the area are not likely to limit or impact the transport of SO2 in a significant 

manner. Furthermore, the topography of the region is accounted for in the 

dispersion modeling analysis via the AERMAP preprocessor, and the impact of 

land use is accounted for via the AERSURFACE preprocessor. As such, Ohio 

EPA does not consider topography and land use to be a significant factor for this 

analysis beyond what is analyzed directly via the refined dispersion modeling 

analysis. 

Factor 5: Jurisdictional Boundaries

The analysis of jurisdictional boundaries looks at the planning and organizational 

structure of an area to determine if the implementation of controls in a potential 

nonattainment area can be carried out in a cohesive manner. Core Based 

Statistical Areas (CBSAs), comprised of Metropolitan Statistical Areas (MSAs) 

and Combined Statistical Areas (CSAs), boundaries were considered for these 

recommendations. 
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CHAPTER TWO: 

Analysis

Discussion:

Based on the five factor analysis below, Ohio EPA is recommending the portion 

of Clermont County, excluding Pierce Township, be designated as attainment for 

the 2010 one-hour SO2 standard. This recommendation encompasses the 

following townships in Clermont County: Batavia, Franklin, Goshen, Jackson, 

Miami, Monroe, Ohio, Stonelick, Tate, Union, Washington, Wayne, and 

Williamsburg. The following discussion and information is relevant to those 

townships in Clermont County listed above, excluding Pierce Township.

As detailed under Factor 1, Ohio EPA modeled actual SO2 emissions from the 

William H. Zimmer Generating Station, years 2012-2014. No exceedances of 

the standard were modeled inclusive of a conservative 11 ppb background 

concentration. Derivation of the background concentration is detailed in 

Appendix B of this submittal.

Factor 1: Dispersion Modeling

Ohio EPA modeled actual emissions from the William H. Zimmer Generating 

Station for years 2012-2014, inclusive of an 11 ppb background. The full details 

of the modeling analysis are presented in Appendix A of this submittal. 

Appendix C includes the modeling protocol. For this analysis, the maximum 

modeled 3-year design value, years 2012-2014, was 118.2265 g/m3(147.0025 

g/m3, with background). An area meets the standard of 75 ppb if a 

concentration of 196.2 g/m3or lower is modeled. Thus, no exceedance of the 

standard was modeled. The results of this analysis are shown in Figure 1. Note 

that for clarity, only design values of 100 g/m3or greater are displayed.
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Figure 1: Maximum SO2 impacts, William H. Zimmer facility, 2012-2014. 

Concentrations are shown in g/m3.

The maximum 3-year design value was modeled approximately 350 meters from 

the facility fenceline and approximately 1,200 meters from the largest SO2

source. The spatial distribution of modeled concentrations greater than or equal 

to 100 g/m3 were located in a 4 to 5 km radius of the primary emissions source 

at the William H. Zimmer facility, as detailed in Appendix A. It should be noted 

that Ohio’s modeling analysis was conducted over a 50 x 50 kilometer modeling 

domain with additional receptors placed to encompass the entirety of Clermont 

County.

 

Factor 2: Emissions

In 2014, there were 83,038 TPY of actual SO2 emissions from Ohio and 

Kentucky sources within 50 kilometers of the border of Clermont County from 

facilities that might potentially need to be modeled under the requirements of the 

proposed Data Requirements Rule. 46,101 TPY of actual 2014 SO2 emissions 

are within Clermont County itself. These sources are shown in Table 1.
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State County Facility ID Facility Name

2014 SO2 

Emissions (TPY)

Distance from W. H. 

Zimmer (km)

OH Clermont 1413090154 W. H. Zimmer Power Station 13,498 --

OH Clermont 1413100008

Duke Energy Ohio, W.C. Beckjord 

Station 32,603 14.7

Clermont Total 46,101

OH Hamilton 1431350093 Miami Fort Power Station 28,479 57.1

OH Hamilton 1431394148 DTE St. Bernard, LLC 1,666 41.6

Hamilton Total 30,145

KY Boone

Duke Energy Kentucky, East Bend 

Station 2,103 54.53

Boone Total 2,103

KY Mason Spurlock Station 4,689 40.9

Mason Total 4,689

Grand Total 83,038

Table 1: 2014 annual SO2 emissions, William H. Zimmer and nearby sources.
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A significant aspect of Ohio’s recommended designation is the cessation of 

operations at the Walter C. Beckjord Station as of June 1, 2015. (Appendix F, 

Appendix G) This represents an emission reduction of approximately 34% from 

the area surrounding the William H. Zimmer facility, and an approximately 71% 

reduction in Clermont County. Additionally, Unit 6 at the Miami Fort Power 

Station ceased operation as of June 1, 2015. (Appendix H) This unit emitted 

18,865 tons of SO2 in 2014. These shutdowns account for a reduction of 

51,468 tons from 2014, or 62% from the area surrounding the William H. Zimmer

facility. The distance between the remaining facilities and the area impacted by 

emissions from the William H. Zimmer facility, as well as the meteorology of the 

area (Factor 3), would indicate that emissions from these remaining facilities are 

unlikely to impact ambient SO2 concentrations in Clermont County beyond what 

is accounted for in the background concentration.

 

Factor 3: Meteorology

Please refer to the Factor 3 general discussion at the beginning of this document

for general meteorological information applicable to Clermont County and the 

William H. Zimmer facility. Per U.S. EPA guidance, dispersion modeling 

accounts for the majority of topographical and land use features that influence 

the meteorology of Clermont County. Of particular importance in Ohio’s 

designation recommendation for this area is the annual trends and distribution of 

wind directions in this area, which are best represented by data from the 

National Weather Service station located at the Cincinnati Northern Kentucky 

Airport (Covington). Wind roses from this station, years 2012 to 2014, are 

shown in Figure 2, below.
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Figure 2: Covington wind roses, 2012-

2014
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The predominant wind directions were used, in part, to inform which facilities in 

Table 1, in addition to William H. Zimmer, may potentially impact ambient SO2

concentrations in Clermont County not accounted for by background and 

therefore necessitate inclusion in the dispersion modeling analysis. As shown in 

Figure 2, the predominant winds in the source area originate from the south and 

south-west and to a lesser degree from the west. Figure 3 shows the location of 

all facilities in Table 1, as well as a composite wind rose, years 2012-2014, from 

the Covington meteorological station.

Figure 3: SO2 sources within 50 km of Clermont County, Ohio.

 

Considering the predominant wind directions, Ohio does not conclude that 

emissions from Spurlock Station, located to the south-east of the source area,

impact ambient SO2 concentrations in Clermont County. The largest SO2 source

based on 2014 data, Walter C. Beckjord, is no longer operational as of June 1, 

2015. Wind direction data suggests that emissions from Miami Fort Station and 

East Bend, located to the west of Clermont County, could potentially impact 

ambient SO2 concentrations; these sources are more than 40 kilometers distant 

from the nearest part of Clermont County and as such, Ohio does not conclude 

that emissions from these sources impact ambient SO2 concentrations beyond

the background level accounted for in the refined dispersion modeling analysis. 

Lastly, wind direction data suggests that emissions from DTE St. Bernard may 

impact ambient SO2 concentrations in Clermont County under some 

meteorological conditions. Please refer to Factor 2, which shows that this facility 

has relatively low annual emissions. Further, the largest emission unit at DTE 

St. Bernard has a stack height of 65 meters. It is therefore likely that the 
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maximum impacts of this facility would occur within approximately 650 meters of 

the facility. Screen modeling analyses indicate that the maximum impact

decreases by approximately 95% over the 17 kilometers distance to the border 

of Clermont County. Ohio does not conclude that impacts from DTE St. Bernard 

impact ambient SO2 concentrations in Clermont County beyond what is 

accounted for in background. Ohio concludes that, following the closure of the 

Walter C. Beckjord facility, the primary source of SO2 in Clermont County is the 

William H. Zimmer facility, and that the impact of those facilities in Table 1 not 

explicitly modeled are represented adequately and conservatively by the 

background concentration included in the Factor 1 analysis.

 

Factor 4: Topography and Land Use/Land Cover

Please refer to the general discussion of Factor 4 at the beginning of this 

document. Ohio, consistent with U.S. EPA guidance, understands that the 

topography and land use characteristics influencing meteorology and the 

dispersion of SO2 emissions from the William H. Zimmer facility are adequately

accounted for via the dispersion modeling analysis. Please refer to the Factor 1 

section of this Chapter.

Factor 5: Jurisdictional Boundaries

The Cincinnati, OH-KY-IN MSA includes Clermont, Brown, Butler, Hamilton, and 

Warren Counties in Ohio, as well as Boone, Bracken, Campbell, Gallatin, 

Kenton, Mason, Pendleton Counties in Kentucky and Dearborn, Ohio, and Union 

Counties in Indiana. The Ohio EPA Central Office and the Southwest Ohio Air 

Quality Agency are responsible for air quality planning within all areas of 

Clermont County. Clermont County, with the exception of Pierce Township, is 

not currently nonattainment for the 2010 one-hour SO2 standard. The dispersion

modeling analysis conducted by Ohio was inclusive of the entirety of Clermont 

County. Ohio, in a separate submission, is requesting that Pierce Township be 

redesignated maintenance for the 2010 one-hour SO2 standard. In this 

submission, Ohio is recommending, based on a five-factor analysis, that the 

remainder of Clermont County: Batavia, Franklin, Goshen, Jackson, Miami, 

Monroe, Ohio, Stonelick, Tate, Union, Washington, Wayne, and Williamsburg

Townships, be designated unclassifiable/attainment for the 2010 one-hour SO2

standard. Townships in Ohio have well-established boundaries, and Ohio 

believes they are a suitable administrative basis for this recommendation. 
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