1 Technical Support Document

Michigan Area Designations for the 2010 SO 2 Primary National Ambient Air Quality Standard

Summary

Pursuant to section 107(d) of the Clean Air Act (CAA), the U.S. Environmental Protection Agency (EPA , or the Agency ) must designate areas as either “unclassifiable

, ” “attainment

, ” or
“nonattainment” for the 2010 one

- hour sulfur dioxide (SO 2 ) primary nation al ambien t air quality standard (NAAQS). The CAA defines a nonattainment area as one that does not meet the NAAQS or that contributes to a violation in a nearby area. An attainment area is defined as any
area other than a nonattainm ent area that meets the NAAQS. Unclassifiable areas are defined as those that cannot be classified on the basis of available information as meeting or not meeting the NAAQS.

Michigan submitted updated recommendations on September 18, 2015

, ahead of a Jul y 2, 2016,
deadline for EPA to designate certain areas established by the U.S. District Court for the
Northern District of California. This deadline is the first of three deadlines established by the

court for EPA to complete area designations for the 2010 SO 2 NAAQS

. Table 1 below lists Michigan’s recommendations and identifies the counties or portions of counties in Michigan that
EPA intends to designate by July 2, 2016 based on an assessment and characterization of air quality through ambient air quality data, air dispersion modeling , other evidence and supporting information, or a combination of the above

.

Table 1. Michigan's Recommended and EPA's Intended Designations

Area Michigan’s

Recommended Area
Definition Michigan’s
Recommended Designation EPA’s Intended Area

Definition EPA’s Intended Designation

St. Clair, MI Within St. Clair Co.:

Area defined by the St. Clair River on the east, State Highway M

- 29 to
Church Road to Arnold Road to County Line Road on the south, County Line
Road and the Macomb/ St. Clair County boundary to
Stoddard Road to Wales Ridge Road on the west, and Alpine Road to Fitz
Road to Smith Creek Road to Range Road to Huron
Avenue to the St. Clair
River on the north. Nonattainment Within St. Clair Co.: Area defined by the St.
Clair River for the east ern boundary

, an extension
from the St. Clair River straight west to the
intersection of State Highway M

- 29 and St. Clair River Drive, continuing west on State Highway M

- 29 to Church
Road to Arnold Road to County Line Road for the southern boundary , County
Line Road and the Macomb/ St. Clair County boundary to Stoddard Road to Wales Ridge Road for the western boundary , and Alpine Road to Fitz Road Nonattainment2 to Smith Creek Road to Range Road to Huron
Avenue , extending straight
east from the intersection
of Huron Road and River
Road to the St. Clair River for the northern boundary

. Bay County,

MI Bay County Attainment Same as State’s
Recommendation Unclassifiable

Lansing, MI Eaton and Ingham

Counties Attainment Same as State’s
Recommendation Unclassifiable/
Attainment Marquette County , MI Marquette County Attainment Same as State’s
Recommendation Unclassifiable/
Attainment

Monroe County, MI Monroe County Attainment Same as State’s
Recommendation Unclassifiable

Ottawa County, MI Ottawa County Attainment Same as State’s
Recommendation Unclassifiable/
Attainment

Background

On June 3, 2010, EPA revised the primary (health based) SO 2 NAAQS by establishing a new

one

- hour standard at a level of 75 parts per billion (ppb) which is attained when the three

- year average of the 99th percentile of one

- hour daily maximum concentrations does not exceed 75 ppb. This NAAQS was published in the F ederal Register on June 22, 2010 (75 FR 35520) and is
codified at 40 CFR 50.17

. EPA determined this is the level necessary to protect public health with an adequate margin of safety, especially for children, the elderly

, and those with asthma.
These groups are particularly susceptible to the health effects associated with breathing SO 2

. T he two prior primary standards of 140 ppb evaluated over 24 hours, and 30 ppb evaluated over an entire year, codified at 40 CFR 50.4, remain applicable

. 1 However

, E PA is not currently designating areas on the basis of either of these two primary standards. Similarly, the secondary
standard for SO 2

, set at 500 ppb evaluated over 3 hours has not been revised, and EPA is also not currently designating areas on the basis of the secondary standard.

General Approach and Schedule

Section 107(d) of the Clean Air Act requires that not later than one year after promulgation of a new or revised NAAQS, state g overnors must submit their recommendations for designations
and boundaries to EPA. Section 107(d) also requires EPA to provide notification to states no
less than 120 days prior to promulgating an initial area designation that is a modification of a
state’s recommendation. If a state does not submit designation recom mendations, EPA will promulgate the designations that it deems appropriate. If a state or tribe disagrees with EPA ’s intended designations, they are given an opportunity within the 120 day period to demonstrate why any proposed modification is inappropria te.

1 40 CFR 50.4(e) provides that the two prior primary NAAQS will no longer apply to an area one year after its designation under the 2010 NAAQS, except that for areas desi gnated nonattainment under the prior NAAQS as of August 22, 2010, and areas not meeting the requirements of a SIP Call under the prior NAAQS, the prior NAAQS will apply until that area submits and EPA approves a SIP providing for attainment of the 2010 NAA QS.3

On August 5, 2013, EPA published a final rule establishing air quality designations for 29 areas in the United States for the 2010 SO 2 NAAQS, based on recorded air quality monitoring data
from 2009

- 2011 showing violations of the NAAQS (78 FR 47191). In that rulemaking, EPA committed to address, in separate future actions, the designations for all other areas for which the Agency was n ot yet prepared to issue designations.

Following the initial August 5, 2013 designations, three lawsuits were filed against EPA in different U.S. District Courts, alleging the A gency had failed to perform a nondiscretionary duty under the CAA by not desi gnating all portions of the country by the June 2013 deadline. In an effort intended to resolve the litigation in one of those cases, plaintiffs Sierra Club and the
Natural Resources Defense Council and EPA filed a proposed consent decree with the U.S.
Di strict Court for the Northern District of California

. On March 2, 2015, the court entered the
consent decree and issued an enforceable order for EPA to complete the area designations according to the court

- ordered schedule.

According to the court

- order ed schedule

, EPA must complete the remaining desi gnations by three specific deadlines. By no later than July 2, 2016 (16 months from the court’s order)

, EPA must designate two groups of areas: (1) areas that have newly monitored violations of the 2010
SO 2 N AAQS and (2) areas that contain any stationary s ources that ha d not been announced as of March 2, 2015 for retirement and that according to EPA ’s Air Markets Datab a se emitted in 2012 either (i) more than 16,000 tons of SO 2 or (ii) mor e than 2,600 tons of SO 2 with an annual average emission rate of at least 0.45 pounds of SO 2 per one million British thermal units (lbs
SO 2 /MM BTU)

. Specifically, a stationary source with a coal

- fired unit that as of January 1, 2010 had a capacity of over 5 megawatts and other wise meets the emissions criteria, is excluded from the July 2, 2016 deadline if it had announced through a company public announcement, public utilities commission filing, consent decree, public legal settlement, final state or federal permit filing, or o ther similar means of communication, by March 2, 2015, that it will cease burning
coal at that unit.

The last two deadlines for completing remaining designations are December 31, 2 0 17, and
Decembe r 31, 2020

. EPA has separ ately promulgated requirements for states and other air agencies to provide additional monitoring or modeling information on a timetable consistent wi th these designation deadlines. We expect this information to become available in time to help
inform the se subsequent designations

. These requirements were promulgated on August 2 1

, 2015 (80 FR 51052) , in a rule known as the SO 2 Data Requireme nts Rule (DRR)

.

Updated designations guidance was issued by EPA through a March 20, 2015 memorandum from Stephen D. Page, Director, U.S. EPA, Office of Air Quality Planning and Standards, to Air Division Directors, U.S. EPA Regions I

- X. This memorandum supersedes earlier designation guidance for the 2010 SO 2 N AAQS, i ssued on March 24, 2011, and it i dentifies factors that EPA intends to evaluate in determining whether areas are in violation of the 2010 SO 2 NAAQS. The guidance also contains the factors EPA intends to evaluate in determining the boundaries for all remaining areas in the country, consistent with the court’s order and schedule. These factors include: 1) Air quality characterization via ambient monitoring or dispersion modeling results; 2)
Emissions

- related data; 3) Meteorology; 4) Geography and topography; and 5) Jurisdictional4

boundaries. This guidance was supplemented by two technical assistance documents intended to assist states and other interested parties in their efforts to characterize air quality through air dispersion modeling or ambie nt air quality monitoring for sources that emit SO 2

. Notably, EPA released its most recent versions of documents titled, “SO 2 NAAQS Designations Modeling Technical Assistance Document” (Modeling TAD) and “SO 2 NAAQS Designations Source

Oriented Monitoring Technical Assistance Document” (Monitoring TAD) in December 2013.

Based on ambient air quality data collected between 2012 and 2014, no violations of the 2010
SO 2 NAAQS have been recorded in a ny undesignated part of the state. 2 However, there are eight sources in the state meeting the emissions criteria of the consent decree for which EPA must complete designations by July 2, 2016. In this draft technical support document, EPA discusses its review and technical analysis of Michigan’s updated recommendations for the areas that we must designate

. EPA also discusses any intended modifications from the state’s
recommendation based on all available data before us

.

The following a re d efinition s of important terms used in this document: 1) 2010 SO 2 NAAQS

– The primary NAAQS for SO 2 promulgated in 2010. This NAAQS is 75 ppb, based on the three year average of the 99th percentile of the annual distribution of daily maximum one

- hour ave rage concentrations. See 40 CFR 50.17. 2) Design Value

- a statistic computed according to the data handling procedures of the NAAQS (in 40 CFR part 50 Appendix T) that, by comparison to the level of the NAAQS, indicates whether the area is violating the NAAQS. 3) Designated nonattainment area

– an area which EPA has determined has violated the
2010 SO 2 NAAQS or contribute d to a violation in a nearby area. A nonattainment designation reflect s considerations of state recommendations and all of the information
discussed in this document. EPA ’s decision is based on all available information including the most recent 3 years of air quality monitoring data, available modeling analysis, and any other relevant information. 4) Designated unclassifiable area

– an are a which EPA cannot determine based on all
available information whether or not it meets the 2010 SO 2 NAAQS. 5) Designated unclassifiable/attainment area

– an area which EPA has determined to have
sufficient evidence to find either is attaining or is likely to be attaining the NAAQS

. EPA ’s decision is based on all available information including the most recent 3 years of air quality monitoring data, available modeling analysis, and any other relevant
information. 6) Modeled violation

– a violation based on air dispersion modeling

.

2 For designations based on ambient air quality monitoring data that violates the 2010 SO 2 NAAQS, the consent decree directs the EPA to evaluate data collected between 2013 and 2015. Absent complete, quality assured and certified data for 2015, the analyses of applicable areas for the EPA’s intended designations will be informed by data
collec ted between 2012 and 2014. States with monitors that have recorded a violation of the 2010 SO 2 NAAQS during these years have the option of submitting complete, quality assured and certified data for calendar year 2015 by April 19, 2016 to the EPA for eval uation. If after our review, the ambient air quality data for the area indicates that no violation of the NAAQS occurred between 2013 and 2015, the consent decree does not obligate the EPA to complete the designation. Instead, we may designate the area a nd all other previously undesignated areas in the state on a schedule consistent with the prescribed timing of the court order , i.e., by December 31, 2017, or December 31, 2020.5

7) Recommended attainment area

– an area a state or tribe has recommended that EPA designate as attainment. 8) Recommended nonattainment area

– an area a state or tribe has recommended that EPA designate as nonattainment. 9) Recommended unclassifiable area

– an area a state or tribe has recommended that EPA designate as unclassifiable. 10) Recommended unclassifiable/attainment area

– an area a state or tribe h as recommended
that EPA designate as uncl assifiable/attainment. 11) Violating monitor

– an ambient air monitor meeting all methods, quality assurance and siting criteria and requirements whose valid design value exceeds 75 ppb, based on data analysis conducted in accordance with Appendix T of 40 CFR part 50.6 Technical Analysis for the St. Clair, Michigan Area

Introduc tion

St. Clair County, Michigan contains two stationary source s that according to EPA ’s Air Markets

Database emitted in 2012 either more than 16,000 tons of SO 2 or more than 2,600 tons of SO 2 and had an annual average emission rate of at least 0.45 lbs SO 2 /MM BTU

. A s of March 2, 2015,

th e s e stationary source s had not met the specific requirements for being “announced for

retirement

. ” Specifically, in 2012, the Belle River Power Plant emitted 24,869 tons of SO 2 , and

had an emissions rate of 0.621 lbs SO 2 /MM BTU

, and the St. Clair Power Plant emitted

28

, 208.476 tons of SO 2 , and had an emissions rate of 0.935 lbs SO 2 /MM BTU. P ursuant to the March 2, 2015 court

- ordered schedule

, EPA must designate the area surrounding the se facilit ies by July 2, 2016

.

In its submission, Michigan recommended that the area surrounding the Belle River and St. Clair

Power Plants , specifically a defined portion of St. Clair County 3

, be designated as non attainment based on an assessment and characterization of air quality from the facility and other nearby sources which may have a potential impact in the area where maximum concentrations of SO 2 are expected

. This assessment and characterization was performed using air dispersion modeling software, i.e., AERMOD , analyzing actual emissions

. After careful review of the state’s assessment, supporting documentation, and all availabl e data, EPA agrees with the state’s

recommendati on for the area, and intends to designate the area as nonattainment.

The Belle River and St. Clair Power Plants are located in eastern Michigan in the southeastern portion of St. Clair County. As seen i n Figure 1 below, the fac ilit ies are located next to each other, approximately 6 km southeast of the center of St. Clair along the St. Clair River. Also included in the figure are n earby emitters of SO 2 , the state’s recommended area for the
nonattainment designation

, and EPA ’s intended nonattainment designation for the area.

3 The portion of St. Clair County recommended by Michigan is defined by the St. Clair River on the east, State Highway M

- 29 to Church Road to Arnold Road to County Line Road on the south, County Line Road and the Macomb/ St. Clair County boundary to Stoddard Road to Wales Ridge Road on the west, and Alpine Road to Fitz
Road to Smi th Creek Road to Range Road to Huron Avenue to the St. Clair River on the north.7

Figure 1

. EPA ’s intended designation for St. Clair

, MI

The discussion and analysis that follows below will reference the state’s use of the Modeling
TAD

, EPA ’s assessment of the state’s modeling in accordance with the Modeling TAD, and the
factors for evaluation contained in EPA ’s March 20, 2015 guidance, as appropriate.

Detailed Assessment

Air Quality Data

This factor considers the SO 2 air quality monitoring data in the area surrounding Belle River and
St. Clair Power Plants

. The facilit ies are located in St. Clair County, and the state included monitoring data from the closest monitor ( Air Quality System (AQS) site number 26

- 147

- 0005) to the facility in its recommendation. This monitor is located at 2525 Dove Road, Port Huron in St. Clair County , and is about 21 km away from Belle River and St. Clair Power Plants. D ata collected at this monitor indicates a valid design value for the 2012 to 2014 design period of 69.4 ppb, showing attainment of the 75 ppb standard. This monitor is not located in the recommended nonattainment area, but rather the portion of the county for which Michigan did not make a designation recommendation. Given the distance of this monitor from the power plants, the
monitor does not provide reliable evidence as to whether the area near the plants is attaining the NAAQS.

Model Selection and Modeling Components

EPA ’s Modeling TAD notes that for area designations under the 2010 SO 2 NAAQS, the AERMOD modeling system should be used , unless use of an alternative model can be justified.8

In some instances the recommended model may be a model other than AERMOD, such as the BLP model for buoyant line sources. The AERMOD modeling system contains the following
components:

- AERMOD: the dis persion model

- AERMAP: the terrain processor for AERMOD

- AERMET: the meteorological data processor for AERMOD

- BPIPPRIME: the building input processor

- AERMINUTE: a pre

- processor to AERMET incorporating 1

- minute automated surface observation system ( ASOS ) win d data

- AERSURFACE: the surface characteristics processor for AERMET

- AERSCREEN: a screening version of AERMOD

The state used AERMOD version 15181 , and a discussion of the individual components will be referenced in the corresponding discussion that follows

, as appropriate.

Modeling Parameter: Rural or Urban Dispersion

EPA ’s recommended procedure for characterizing an area by prevalent land use is based on evaluating the dispersion environment with 3 km of the facility. According to EPA ’s mod eling guidelines, rural dispersion coefficients are to be used in the dispersion modeling analysis if
more than 50 percent of the area within a 3 km radius of the facility is classified as rural. Conversely, if more than 50 percent of the area is urban, urban dispersion coefficients should be used in the modeling analysis. When performing the modeling for the area , the state determined that it was most appropriate to run the model in rural mode.

Modeling Parameter: Area of Analys is (Receptor Grid)

EPA believes that a reasonable first step towards characterization of air quality in the area surrounding the Belle River and St. Clair Power Plants (“the St. Clair area”) is to determine the extent of the area of analysis, i.e., receptor grid. Considerations presented in the Modeling TAD
include but are not limited to: the location of the SO 2 emission sources or facilities considered for modeling; the extent of significant concentration gradients of nearby sources; and sufficient receptor coverage and density to adequately capture and resolve the model predicted maximum
SO 2 concentrations. For the St. Clair area, the state has not included other emitters of SO 2 . E.B. Eddy and Cargill Salt, both located in Port Huron, were originally included, but have recently
shut down. The state determined that 10 kilometers ( km ) was the appropriate distance in order to adequately characterize air quality from the facility and other nea rby sources which may have a potential impact in the area where maximum concentrations of SO 2 are expected. A side from exceptionally large sources, sources farther than 10 km from the Belle River and St. Clair Power Plants would not cause significant concentration gradients in the St. Clair area and therefore need
not be modeled. The grid receptor spacing for th e area chosen by the state is as follows:

- 50 m eters (m) out to 500m;

- 100m out to 4 km;

- 250 m out to 10 km9

The receptor network contained 17,259 receptors, and the network covered ten kilometers from the facilities’ fence lines excluding international land, waterways, roadways, secured property,
and landfills.

Consistent with the Modeling TAD, receptors for the purposes of this designation effort were placed only in areas where it would also be feasible to place a monitor and record ambie nt air impacts

. The impacts of the area’s geography and topography will be discussed later within this
document.

Figure 2 : Receptor Grid for the St. Clair, MI Area

Modeling Parameter: Source Characterization

The state characterized the sources within the area of analysis in accordance with t he best practices outlined in the Modeling TAD. Specifically, the state used actual stack heights in conjunction with actual emissions. The state also adequately characterized the source s building layout and location, as well as the stack parameters, e.g., exit temperature, exit velocity, location,
and diameter. Where appropriate, the AERMOD component BPIPPRIME was used to assist in addressing building downwash.

Modeling Parameter: Emissions

EPA ’s Modeling TAD notes that for the purposes of modeling to characterize air quality for use in designations, the recommended approach is to use the most recent 3 years of actual emissions10

data and concurrent meteorologic al data. The Modeling TAD highly encourages the use of the most detailed throughput, operating schedule and emissions information available.

Variable emissions, temperature, and flow data can be modeled using AERMOD’s hourly varying emissions keyword HOUREMIS or variable emission factor keyword EMISFACT. EPA
believes that continuous emissions monitor ing systems (CEMS) data provide valuable his torical
emissions information

, when it is available, and that these data are available for many electric generating units. However, the TAD also provide s the option to use allowable emissions reflecting the applicable, federally enforceable emission limit (referred to as PTE or the
allowable emissions rate )

.

In certain instances, states and other interested parties may find that it is more advantageous or simpler to use PTE rates as part of their modeling runs. Specifically, a facility may have recently adopted a new federally enforceable emissions limit, been subject to a federally enforceable consent decree, or implemented other federally enforceable mechanisms and control technologies to limit SO 2 emissions to a level that indicates compliance with the NAAQS. The se new limits or conditions may be used in the application of AERMOD. In these cases, the Modeling TAD notes that the existing SO 2 emissions inventories used for permitting or SIP planning demonstrations should contain the necessary emissions information for designations

related modeling. In the event that these short

- term emissions are not readily available, they may be calculated using the methodology in Table 8

- 1 of Appendix W to 40 CFR Part 51 titled, “Guideline on Air Quality Models.”

T he Belle River and St. Clair Plants have stacks that are 2 km apart , and have adjacent
fencelines . Therefore, EPA finds it appropriate that Michigan considered the joint impact of these two sources and recommended a combined study area.

As previously no ted, the state ’s modeling included only the Belle River and St. Clair Power Plants, finding no other emitters of SO 2 within 10 km in the area

. This distance and these
facilities w ere selected because the state believes that this area adequately represents the area
where maximum concentrations of SO 2 are expected and adequately includes the sources which might contribute to those concentrations

. E.B. Eddy and Cargill Salt were previously sources of
SO 2 in the area, but have recently shut down the ir coal fired boilers and therefore were not included in the modeling. No other sources within or beyond 10 km were determined by the state to have the potential to cause significant concentration gradient impacts within t he area of analysis. The facilities in the area and their associated annual actual SO 2 emissions between
2012 and 2014 are summarized below.

Table 2 : Actual SO 2 Emissions between 2012

– 2014 from Facilities in the St. Clair, Michigan
Area

Facility Name Actual SO 2 Emissions (tons per year (tpy) )

2012 2013 2014

Belle River Power Plant 24,869 24,787 24,467

St. Clair Power Plant 28,208 30,111 27,453
Total Emissions From All Facilities in the State’s Area of Analysis 53,077 54,898 51,92011

For both Belle River and St. Clair Power Plants , the state used actual emissions from the most
recent 3

- year data set, i.e., 2012

– 2014. Th e s e emissions data w ere obtained from CEMs

.

Modeling Parameter: Meteorology and Surface Characteristics

The most recent 3 years of meteorological data (concurrent with the most recent 3 years of emissions data) should be used in designations efforts. As noted in the Modeling TAD, the selection of data should be based on spatial and climatological (temporal) representativeness. The representativeness of the data are based on: 1) the proximity of the meteorological monitoring site to the area under consideration, 2) the complexity of terrain, 3) the exposure of the meteorological site, and 4) the period of ti me during which data are collected. Sources of meteorological data include National Weather Service (NWS) stations, site

- specific or onsite data, and other sources such as universities, Federal Aviation Administration (FAA), and military stations.

For th e St. Clair area, surface meteorology from Pontiac ( 77 km away ) , and coincident upper air

observations from White Lake Township, MI, 82 km to the west

, were selected as best representative of meteorological conditions within the area

.

The state used AERSURFACE version 14134 using data from the NWS station in Pontiac, Michigan (located at 42.665 ° N , 83.41806 ° W ) to estimate the surface characteristics of the area

. T he state also estimated values for albedo (the fraction of solar energy reflected from the earth back into space), the Bowen ratio (representing the ratio of sensible heat flux to latent heat flux at the ground level), and the surface roughness (representing the influence of ground feature s such as buildings and vegetation on surface wind flow)

. In the figure below, generated by EPA

, the location of the Pontiac, MI station is shown relative to the St. Clair area

.12

Figure 3 : St. Clair Area and the Pontiac, MI NWS Station

Below is t he 3

- year surface wind rose for Pontiac, MI

. In Figure 4

, the frequency and magnitude of wind speed and direction are defined in terms of from where the wind is blowing. The winds predominantly appear to be from westerly directions.13

Figure 4 : Pontiac, MI Cumulative Annual Wind Rose for Years 2012

– 2014

Meteorological data from the above surface and upper air stations were used in generating

AERMOD

- ready files with the AERMET processor. The output meteorological data created by the AERMET processor is suitable for being applied with AERMOD input files for AERMOD modeling runs. The state followed the methodology and settings presented in “Regional Meteorological Data Processing Protocol E PA Region V and States,” Draft, August 2014, in the processing of the raw meteor o logical data into an AERMOD

- ready format, and used AERSURFACE to best represent surface characteristics.

H ourly surface meteorological data records are read by AERMET, and i nclude all the necessary elements for data processing. However, wind data taken at hourly intervals may not always portray wind conditions for the entire hour, which can be variable in nature. Hourly wind data may also be overly prone to indicate calm co nditions, which are not modeled by AERMOD. In order to better represent actual wind conditions at the meteorological tower, wind data of one minute duration was provided from the same instrument tower, but in a different formatted file to be processed by a separate preprocessor, AERMINUTE. Th e s e data were subsequently integrated into the AERMET processing to produce final hourly wind records of AERMOD

ready meteorological data that better estimate actual hourly average conditions and that are less14

prone t o over

- report calm wind conditions. This allows AERMOD to apply more hours of meteorology to modeled inputs, and therefore produce a more complete set of concentration

estimates

. As a guard against excessively high concentrations that could be produced by

AERMOD in very light wind conditions, the state set a minimum threshold of 0.5 meters per second in processing meteorological data for use in AERMOD. This approach is consistent with a March 2013 EPA memo titled, “Use of ASOS meteorological data in AER MOD dispersion Modeling.” In setting this threshold, no wind speeds lower than this value would be used for determining concentrations. This threshold was specifically applied to the one minute wind data

.

Modeling Parameter: Geography and Terrain

The terrain in the area is best described as relatively flat

. Nevertheless, t o account for terrain changes, the AERMAP terrain program within AERMOD was used to specify terrain elevations for all the receptors. The source of the elevation data incorporated into the model is from the

USGS National Elevation Database.

Modeling Parameter: Background Concentrations of SO 2

The Modeling TAD offers two mechanisms for characterizing background concentrations of SO 2 that are ultimately added to the modeled design values: 1) a “first tier” approach, based on monitored design values, or 2) a temporally varying approach, based on the 99 th percentile monitored concentrations by hour of day and season or month. For the S t. Clair area , the state applied a “first tier ” approach using a fixed background concentration. The state determined the

value as the Port Huron Monitor design value among selected hours, excluding times when the wind was blowing from the east, reflective of refinerie s in Canada that would be less likely to impact the power plants, and when the wind was from the south, which would be reflective of the power plants that are being modeled.

. The background concentration for this area was determined by the state to be 39.3 micrograms per cubic meter ( μg/m 3 ), or 15 ppb

, 4 and that value was incorporated into the final AERMOD results.

Summary of Modeling Results

The AERMOD modeling parameters for the St. Clair area are summarized below in T able 3

.

Table 3 : AERMOD Modeling Parameters for the St. Clair, MI Area

St. Clair Area

AERMOD Version 15181 Dispersion Characteristics Rural

Modeled Sources 2

Modeled Stacks 5

4 The conversion factor for SO 2 (at the standard conditions applied in the ambient SO 2 reference method) is 1ppb = approximately 2.62 μg/m 3

.15 Modeled Structures 77

Modeled Fencelines 2 Total receptors 17,259 Emissions Type Actual

Emissions Years 2012

- 2014 Meteorology Years 2012

- 2014 Surface Meteorology Station Pontiac, MI Upper Air Meteorology Station White Lake Township, MI

Methodology for Calculating Background SO 2 Concentration Nearby monitor except hours
when wind was from modeled
facilities or Canadian facilities Calculated Background SO 2 Concentration 39.3 μg/m 3

The results presented below in T able 4 show the magnitude and geographic location of the highest predicted modeled concentration based on actual emissions

.

Table 4 : Maximum Predicted 99th Percentile 1

- Hour SO 2 Concentration in the St. Clair, MI Area Based on Actual Emissions

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

UTM/Latitude UTM/Longitude Modeled (including background) NAAQS
99th Percentile
1

- Hour Average 2012

- 2014 377100 4733900 345.1 196.4

The state’s modeling indicates that the predicted 99 th percentile 1

- hour average concentration within the chosen modeling domain is 345.1 μg/m 3 , or 131.7 ppb. This modeled concentration

included the background concentration of SO 2 , and is based on actual emissions from the

facilities. Figure 5 below was included as part of the state’s recommendation, and indicates that the predicted value occurred about 3 km southwest of the power plants

.16

Figure 5 : Maximum Predicted 99 th Percentile 1

- Hour SO 2 Concentrations in the St. Clair Area

Based on Actual Emissions

Jurisdictional Boundaries

Once the geographic area associated with the Belle River and St. Clair Power Plants was determined, existing jurisdictional boundaries we re considered for the pur pose of informing our

intended nonattainment area, specifically with respect to clearly defined legal boundaries.

Michigan recommended a partial county area for this nonattainment area defined by the St. Clair River on the east, State Highway M

- 29 to Church Road to Arnold Road to Coun ty Line Road on the south, County Line Road and the Macomb/ St. Clair County boundary to Stoddard Road to Wales Ridge Road on the west, and Alpine Road to Fitz Road to Smith Creek Road to Range

Road to Huron Avenue to the St. Clair River on the north. Thi s area includes all receptors that

were model ed to be above the standard as well as all sources contributing to the modeled

violations

.

EPA believes that the boundaries of Michigan’s recommended nonattainment area warrant slight

clarifications

, particularly at the two points where the pertinent roadways do not precisely

int ersect with the St. Clair River. However, aside from these slight modifications to assure that the nonattainment area is a closed polygon, EPA agrees with the boundaries that Michigan recommended, finding that they otherwise represent appropriate boundaries for the area.17

Other Relevant Information

The Sierra Club also submitted modeling showing violations of the standards from the Belle

River and St. Clair Power Plants. Sier ra Club did not make specific recommendations for nonattainment area boundaries, but the area where Sierra Club modeled violations is within the area Michigan recommended as nonattainment, so that this information supports Michigan’s

recommendations.

Conclusion

After careful evaluation of the state’s recommendation and supporting information, as well as all available relevant information, EPA intends to designate the area around St. Clair and Belle
River Power Plant as nonattainment for the 2010 SO 2 N AAQS. Specifically, the boundaries are a partial county area defined by the St. Clair River for the eastern boundary, an extension from the St. Clair River straight west to the intersection of State Highway M

- 29 and St. Clair River Drive, continuing west on State Highway M

- 29 to Church Road to Arnold Road to County Line Road for the southern boundary, County Line Road and the Macomb/ St. Clair County boundary to Stoddard Road to Wales Ridge Road for the western boundary, and Alpine Road to Fitz Road
to Smi th Creek Road to Range Road to Huron Avenue, extending straight east from the intersection of Huron Road and River Road to the St. Clair River for the northern boundary. These boundaries define the same area as Michigan evidently intended, but better define the area by including short connecting lines at the northeast and southeast corners of the area to assure that the boundaries are completely unambiguous.

At this time, our intended designations for the state only apply to this area and t he other areas
addressed in this technical support document. Consistent with the conditions in the March 2,
2015 court

- ordered schedule, EPA will evaluate and designate all remaining undesignated areas
in Michigan by either December 31, 2017, or December 31, 2020.18 Technical Analysis for the Bay County, Michigan Area

Introduction

Bay County , Michigan contains a stationary source that according to EPA ’s Air Markets Database emitted in 2012 either more than 16,000 tons of SO 2 or more than 2,600 tons of SO 2 and had an annual average emission rate of at least 0.45 lbs SO 2 /MM BTU. As of March 2, 2015, this stationary source had not met the specific requirements for being “announced for retirement.” Specifically, the D.E. Karn Generating Complex (“D.E. Karn”) emitted 6 ,850 tons of SO 2 , and had an emissions rate of 0. 546 lbs SO 2 /MM BTU. Pursuant to the March 2, 2015

co urt

- ordered schedule, EPA must designate the area surrounding the facility by July 2, 2016.

In its submission, Michigan recommended that the area surrounding D.E. Karn, specifically the entirety of Bay County, be designated as attainment based on an assessment and characterization of air quality from the facility and other nearby sources which may have a potential impact i n the

area where maximum concentrations of SO 2 are expected. This assessment and characterization was performed using air dispersion modeling sof tware, i.e., AERMOD, analyzing actual and
allowable emissions. In this analysis, the JC Weadock Generating Co mplex (JCW ), a facility
that is co

- located with D.E. Karn, was not included in the modeling because, due to a Federal consent decree, the units at JCW must be retired by April 15, 2016. After careful review of the state’s assessment, supporting documentati on, and all available data, EPA agrees that the modeling, assuming the shutdown of JCW, shows attainment of the NAAQS . H owever, since the assumption of the shutdown does not reflect the current state of the Bay County air quality,
EPA intends t o designate Bay County as unclassifiable . EPA anticipates finalizing the designation of the area as unclassifiable/attainment once the source is confirmed as shutdown.

D.E. Karn is located in eastern Michigan in the southeastern portion of Bay County . As seen in Figure 6 below, the fac ility is located approximately 7 km north east of the center of Bay City, situated on the Saginaw Bay, part of Lake Huron. Also included in the figure are nearby emitters
of SO 2 , the state’s recommended area for the attainment designation, and the coterminous area
that EPA intend s to designate as unclassifiable/ attainment

.19

Figure 6

. EPA’s intended designation for Bay County, MI

The discussion and analysis that follows below will reference the state ’s use of the Modeling TAD, EPA’s assessment of the state’s modeling in accordance with the Modeling TAD, and the
factors for evaluation cont ained in EPA’s March 20, 2015 guidance, as appropriate.

Detailed Assessment

Air Quality Data
No monitors are located in or near Bay County to inform the designation for this area.

Model Selection and Modeling Components

EPA’s Modeling TAD notes that for area designations under the 2010 SO 2 NAAQS, the AERMOD modeling system should be used, unless use of an alternative model can b e justified. In some instances the recommended model may be a model other than AERMOD, such as the BLP model for buoyant line sources. The AERMOD modeling system contains the following
components:

- AERMOD: the dispersion model

- AERMAP: the terrain process or for AERMOD

- AERMET: the meteorological data processor for AERMOD

- BPIPPRIME: the building input processor

- AERMINUTE: a pre

- processor to AERMET incorporating 1

- minute automated surface observation system (ASOS) wind data

- AERSURFACE: the surface character istics processor for AERMET20

- AERSCREEN: a screening version of AERMOD

The state used AERMOD version 14134 , and a discussion of the individual components will be referenced in the corresponding discussion that follows, as appropriate.

Modeling Parameter: Rural or Urban Dispersion

EPA’s recommended procedure for characterizing an area by prevalent land use is based on evaluating the dispersion environment with 3 km of the facility. According to EPA’s modeling guidelines, rural dispersion coefficients are to be used in the dispersion modeling analysis if
more than 50 percent of the area within a 3 km radius of the facility is classified as rural. Conversely, if more than 50 percent of the area is urban, urban dispersion coefficients should be
used in the m odeling analysis. When performing the modeling for the area , the state determined
that it was most a ppropriate to run the model in rural mode

. This determination was reached by using Auer’s land use methodology.

Modeling Parameter: Area of Analysis (Receptor Grid)

EPA believes that a reasonable first step towards characterization of air quality in the area surrounding D.E. Karn is to determine the extent of the area of analysis, i.e., receptor grid. Considerations presented in the Modeling TAD incl ude but are not limited to: the location of the
SO 2 emission sources or facilities considered for modeling; the extent of significant concentration gradients of nearby sources; and sufficient receptor coverage and density to adequately capture and resolve the model predicted maximum SO 2 concentrations. For the Bay County area, the state has not included other emitters of SO 2

. D.E. Karn is co

- located with JCW which is comprised of coal

- fired utility boiler Units 7 and 8 and ancillary equipment ; however,

un der a federally enforceable consent decree, Units 7 and 8 are required to be retired no later than April 15, 2016

. Therefore JCW was not included in this modeling analysis. The state determined that 10 km was the appropriate distance in order to adequately characterize air quality from the facility and other nearby sources which may have a potential impact in the area where maximum concentrations of SO 2 are expected. A side f rom exceptionally large sources, sources farther than 10 km from D.E. Karn would not cause significant concentration gradients in the Bay County area and therefore need not be modeled. The grid receptor spacing for the area of analysis chosen by the state is as follows:

- 100 m spacing from fenceline to 2 km from the facility

- 200 m spacing from 2 km to 10 km from the facility

- 500 m spacing from 10 km to 20 km from the facility

- 1 km spacing from 20 to 50 km from the facility

- An additional nested receptor grid at 100 meter spacing was placed in the area of the maximum impacts which were occurring beyond 2 kilometers from the facility.

The receptor network contained 15,361 receptors, and the network covered an area 50 km from the facility fenceline, excluding t he Saginaw River and Saginaw Bay.

Figure 7 , included in the state’s recommendation, show s the receptor grid for the area

. Consistent with the Modeling TAD, receptors for the purposes of this designation effort were21

placed only in areas where it would also be feasible to place a monitor and record ambient air impacts . The impacts of the area’s geography and topography will be discussed later within this
document.

Figure 7 : Receptor Grid for the Bay County, MI Area

Modeling Parameter: Source Characterization

The state characterized the source(s) within the area in accordance with the best practices outlined in the Modeling TAD. Specifically, the state used actual stack heights in conjunction
with actual emissions and allowable emissions sinc e all stacks were lower than EPA’s good engineering practices (GEP) stack height. This approach is in accordance with EPA policy for
allowable emissions limits. The state also adequately characterized the source’(s) building layout and location, as well as the stack parameters, e.g., exit temperature, exit velocity, location,
and diameter. Where appropriate, the AERMOD component BPIPPRIME was used to assist in
ad dressing building downwash.22

Modeling Parameter: Emissions

EPA’s Modeling TAD notes that for the purposes of modeling to characterize air quality for use in designations, the recommended approach is to use the most recent 3 years of actual emissions data and concurrent meteorological data. The Modeling TAD highly encourages the use of the most detailed throughput, operating schedule and emissions information available.

Variable emissions, temperature, and flow data can be modeled using AERMOD’s hourly varying emissions keyword HOUREMIS or variable emission facto r keyword EMISFACT. EPA believes that continuous emissions monitoring systems (CEMS) data provide valuable

, historical emissions information, when it is available, and that these data are available for many electric generating units. However, the TAD also provide s the option to use allowable emissions reflecting the applicable, federally enforceable emission limit (referred to as PTE or the
allowable emissions rate )

.

In certain instances, states and other interested parties may find that it is more ad vantageous or simpler to use PTE rates as part of their modeling runs. Specifically, a facility may have recently adopted a new federally enforceable emissions limit, been subject to a federally enforceable consent decree, or implemented other federally e nforceable mechanisms and control technologies to limit SO 2 emissions to a level that indicates compliance with the NAAQS. These new limits or conditions may be used in the application of AERMOD. In these cases, the Modeling TAD notes that the existing S O 2 emissions inventories used for permitting or SIP planning demonstrations should contain the necessary emissions information for designations

related modeling. In the event that these short

- term emissions are not readily available, they may
be calculate d using the methodology in Table 8

- 1 of Appendix W to 40 CFR Part 51 titled, “Guideline on Air Quality Models.”

As previously noted, the state included D.E. Karn as the only significant SO2 source with in the

area . JCW, since it is being required in a federal consent decree to shut down by April 15, 2016,
is treated as having a PTE of 0 tpy, and was therefore not included in the modeling. The state
looked for other sources within 10 km of D.E. Karn because the state believes that this area adequately r epresents the area where maximum concentrations of SO 2 are expected and adequately includes the sources which might contribute to those concentrations

. No other

sources within or beyond 10 km were determined by the state to have the potential to cause sig nificant concentration gradients within the area

. For this area , the state has opted to use a hybrid approach, where emissions from certain facilities are expressed as actual emissions, and those from other facilities are expressed as PTE rates. EPA also identified no other sources of
SO 2 in the county or otherwise near to D.E. Karn over 100 tpy of SO 2

.

For D.E. Karn , annual actual SO 2 emissions between 2012 and 2014 are summarized below by
unit

.

Table 5 : Actual SO 2 Emissions between 2012

– 2014 from D.E. Karn23 Unit Name SO2 Emissions ( tpy )

2012 2013 2014
Unit 1 3,477 3,550 2,565

Unit 2 3,303 4,936 3,751

Unit 3 27 36 2

Unit 4 43 34 34

Total Emissions From All Units at D.E. Karn 6,850 8,556 6,352

For D.E. Karn Units 3 and 4 , the state used actual emissions from the most recent 3

- year data set, i.e., 2012

– 2014. This emissions data was obtained from CEMs. These units are peaker units, and only sporadically used, so actual emissions are a better representation than the allo wable
limits.

For D.E. Karn Units 1 and 2 , the state has chosen to model the most recent federally enforceable
PTE limits for SO 2 , which are summarized below. Units 3 and 4 share one stack and Units 1 and
2 have their own stacks . As a result, EPA considers the emissions of Units 1 and 2 to be sufficiently independent of the emissions of Units 3 and 4 to justify accepting the different approaches for these pairs of units, i.e., for Michigan’s modeling of PTE for Units 1 and 2 and modeling actua l emissions for 3 and 4 to be acceptable.

Table 6 : SO 2 Emissions modeled based on PTE for the Bay County Area

Unit Name SO 2 Emissions (lbs/hr, based on PTE) SO 2 Emissions ( tpy /hr, based on PTE)

Karn Unit 1 225.0 985.5

Karn Unit 2 228.6 1,001.3

JC Weadock 0 0

Total Emissions 453.6 1,986.8
Source in italics was not included in the modeling due to a consent decree required shutdown date of April 15, 2016.

The PTE limit s for the D.E. Karn units were the result of an installation permit issued on April 30, 2015 to reflect new SO 2 control technology

.

In summary, Michigan modeled the actual emissions of D.E. Karn Units 3 and 4 shown in Table
5 and the allowable emissions of D.E. Kar n Units 1 and 2 shown in Table 6 , and modeled JC
Weadock as being shut down.

Modeling Parameter: Meteorology and Surface Characteristics

The most recent 3 years of meteorological data (concurrent with the most recent 3 years of emissions data) should be used in designations efforts. As noted in the Modeling TAD, the selection of data should be based on spatial and climatological (temporal) representativeness. The representativeness of the data are based on: 1) the proximity of the meteorological monitoring site to the area under consideration, 2) the complexity of terrain, 3) the exposure of the meteorological site, and 4) the period of time during which data are collected. Sources of24

meteorological data include National Weather Service (NWS) stations, site

- specific or onsite data, and other sources such as univ ersities, Federal Aviation Administration (FAA), and military stations.

For the Bay County area, surface meteorology from the Saginaw MBS Airport station

, 23 km to

the south west , and coincident upper air observations from the White Lake station

, 109 km to the

south were selected as best representative of meteorological conditions within the area

.

The state used AERSURFACE using data from the Saginaw MBS Airport station (located at

43.53306 ° N

, - 84.07972 ° W ) to estimate the surface characteristics of the area. The state

estimated values for 12 spatial sectors out to 1 km at a monthly temporal resolution for average

conditions. The state also estimated values for albedo (the fraction of solar energy reflect ed from the earth back into space), the Bowen ratio (representing the ratio of sensible heat flux to latent heat flux at the ground level ) , and the surface roughness (representing the influence of ground features such as buildings and vegetation on surface wind flow)

. In the figure below, generated by EPA, the location of the Saginaw MBS Airport station is shown relative to D.E. Karn area

.

Figure 8 : D.E. Karn Area and the Saginaw MBS Airport S tation

As part of its recommendation, the state provided the 3

- year surface wind rose for the Saginaw,

MI surface station

. In Figure 9 , the frequency and magnitude of wind speed and direction are defined in terms of from where the wind is blowing. The wind dire ction is predominantly from the southwest, occurring about 12.5 percent of the time.25

Figure 9 : Saginaw, MI Cumulative Annual Wind Rose for Years 2012

– 2014

Meteorological data from the above surface and upper air stations were used in generating

AERMOD

- ready files with the AERMET processor. The output meteorological data created by the AERMET processor is suitable for being applied with AERMOD input files for AERMOD modeling runs. The state followed the methodology and settings presented in the modeling TAD in the processing of the raw meteorological data into an AERMOD

- ready format, and used AERSURFACE to best represent surface characteristics.

Hourly surface meteorological data records are read by AERMET, and include all the necessary

element s for data processing. However, wind data taken at hourly intervals may not always portray wind conditions for the entire hour, which can be variable in nature. Hourly wind data may also be overly prone to indicate calm conditions, which are not modeled by AERMOD. In order to better represent actual wind conditions at the meteorological tower, wind data of one minute duration was provided from the same instrument tower, but in a different formatted file to be processed by a separate preprocessor, AERMINU TE. These data were subsequently integrated into the AERMET processing to produce final hourly wind records of AERMOD

ready meteorological data that better estimate actual hourly average conditions and that are less26

prone to over

- report calm wind conditio ns. This allows AERMOD to apply more hours of meteorology to modeled inputs, and therefore produce a more complete set of concentration

estimates. As a guard against excessively high concentrations that could be produced by AERMOD in very light wind cond itions, the state set a minimum threshold of 0.5 meters per second in processing meteorological data for use in AERMOD. This approach is consistent with a March 2013 EPA memo titled, “Use of ASOS meteorological data in AERMOD dispersion Modeling.” In setting this threshold, no wind speeds lower than this value would be used for determining concentrations. This threshold was specifically applied to the one minute wind data.

Modeling Parameter: Geography and Terrain

The terrain in the area is bes t described as relatively flat

. Nevertheless, t o account for terrain changes, the AERMAP terrain program within AERMOD was used to specify terrain elevations for all the receptors. The source of the elevation data incorporated into the model is from the

USGS National Elevation Database.

Modeling Parameter: Background Concentrations of SO 2

The Modeling TAD offers two mechanisms for characterizing background concentrations of SO 2 that are ultimately added to the modeled design values: 1) a “first tier” approach, based on monitored design values, or 2) a temporally varying approach, based on the 99 th percentile monitored concentrations by hour of day and season or month. For Bay C ounty , the state applied a “first tier” approach using a fixed background concentration. The state used the design

concentration from the Lansing, MI monitor ( AQS site number 26

- 065

- 0012) to determine Bay County background concentrations. The background concentration for this area was determined by the state to be 46.9 μg/m 3 , or 17.9 ppb, 5 and that value was incorporated into the final

AERMOD results.

Summary of Modeling Results

The AERMOD modeling parameters for the Bay County area are summarized below in Table 7

.

Table 7 : AERMOD Modeling Parameters for the Bay County, MI Area Bay County, MI Area

AERMOD Version 14134 Dispersion Characteristics Rural

Modeled Sources 1

Modeled Stacks 3

Modeled Structures 2

Modeled Fencelines 1

5 The conversion factor for SO 2 (at the standard conditions applied in the ambient SO 2 reference method) is 1ppb = approximately 2.62 μg/m 3

.27 Total receptors 15361 Emissions Type Actual and PTE

Emissions Years Actual emissions: 2012

- 2014
Allowable emissions: Limit
effective 2014/ 2015 (see text) Meteorology Years 2012

- 2014

Surface Meteorology Station Saginaw MBS Airport Station,

MI Upper Air Meteorology Station White Lake Station, MI Methodology for Calculating Background SO 2 Concentration Fixed value derived from Lansing m onitor data Calculated Background SO 2 Concentration 46.9 μg/m 3

The results presented below in T able 8 show the magnitude and geographic location of the highest predicted modeled concentration based on actual and PTE emissions.

Table 8 : Maximum Predicted 99th Percentile 1

- Hour SO 2 Concentration in the Bay County Area Based on Actual and PTE Emissions

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

UTM/Latitude UTM/Longitude Modeled (including background) NAAQS
99th Percentile
1

- Hour Average 2 012

- 2014 267425 4832577 122.6 196.4 * *Equivalent to the 2010 SO 2 NAAQS set at 75 ppb

The state’s modeling indicates that the predicted 99 th percentile 1

- hour average concentration within the chosen modeling domain is 122.6 μg/m 3 , or 46.8 ppb. This modeled concentration

included the background concentration of SO 2 , and is based on actual emissions from Units 3

and 4 and allowable emissions Units 1 and 2 of D.E. Karn

. Figure 1 0 below was included as part of the state’s recommendation, and indicates that the predicted value occurred about 5 km to the southwest of the facility

.28

Figure 1 0 : Maximum Predicted 99 th Percentile 1

- Hour SO 2 Concentrations in the Bay County,

MI Area Based on Actual and PTE Emissions

Jurisdictional Boundaries

Once the geographic area associated with D.E. Karn was determined, existing jurisdictional

boundaries we re considered for the purpose of informing our intended unclassifiable area, specifically with respect to clearly defined legal boundaries.

Michigan recommended the entirety of Bay County, MI be designated attainment. The modeling grid extended to 50 km, covering the entirety of the county and portions of the surrounding area

. With the exception of JCW, EPA determined that there are no other significant sources of SO 2 in

or near the county ’s borders emitting at or above 500 tpy but for the single source, i.e., D.E. Karn, included in the state’s modeling analysis. EPA does not have any information on JCW’s current impact on the area, but does not believe that there are any other sources of SO 2 in or around Bay County with the potential to cause or contribute to a violation of the NAAQS within the state’s recommended boundary

.29

EPA believes that our intended unclassifiable area, consisting of Bay County, MI

, is comprised of clearly defined lega l boundaries, and we find these boundaries to be a suitably clear basis for defining our intended unclassifiable area.

Other Relevant Information

No other relevant information was received for this area.

Conclusion

After careful evaluation of the state’s recommendation and supporting information, EPA is unable at this time to determine whether the area is meeting or not meeting the NAAQS, and
therefore intends to designate the area around D.E. Karn as unclassifiable for the 2010 SO 2 NAAQS. EPA agrees that the modeling analysis assuming the shutdown of JCW shows attainment of the standard, but EPA does not have any information on JCW’s current impact on
the area , so therefore cannot determine the collective impact of D.E. Karn and JCW . EPA intends to designate the entirety of Bay County, MI as unclassifiable, but anticipates finalizing the designation of the area as unclassifiable/attainment once the source is confirmed as
shutdown.

At this time, our intended desig nations for the state only apply to this area and the other areas
addressed in this technical support document. Consistent with the conditions in the March 2,
2015 court

- ordered schedule, EPA will evaluate and designate all remaining undesignated areas
in Michigan by either December 3 1, 2017, or December 31, 2020.30 Technical Analysis for the Lansing, MI Area

Introduction

The Lansing area contains two stationary source s that according to EPA ’s Air Markets Database
emitted in 2012 either more than 16,000 tons of SO 2 or more than 2,600 tons of SO 2 and had an annual average emission rate of at least 0.45 lbs SO 2 /MM BTU. As of March 2, 2015, th e s e stationary source s had not met the specific requirements for being “announced for retirement.” Specifical ly, in 2012, the Eckert Generating Station (“Eckert”) emitted 3,677 tons of SO 2 , and
had an emissions rate of 0.58 lbs SO 2 /MM BTU and the Erickson Generating Station (“Erickson”) emitted 2,685 tons of SO 2 , and had an emissions rate of 0.64 lbs SO 2 /MM BTU. Pursuant to the March 2, 2015 court

- ordered schedule, EPA must designate the area surrounding
the se facilit ies by July 2, 2016.

In its submission, Michigan recommended that the area surrounding the se two plants

, specifically the entirety of Ingham and Eaton Counties, be designated as attainment based on an assessment and characterization of air quality from the facility and other nearby sources which may have a potential impact in the area where maximum concentrations of SO 2 are expected.
Th is assessment and characterization was performed using air dispersion modeling software, i.e., AERMOD, analyzing actual emissions. After careful review of the state’s assessment, supporting documentation, and all available data, EPA agrees that the area i s attaining the standard, and intends to designate Ingham and Eaton Counties as unclassifiable/attainment

The Eckert and Erickson Power Stations are located in Lansing in central Michigan, and are 9 km apart . The Eckert Power Station is in Ingham County along the Grand River near central Lansing, about 2 km from downtown Lansing. The Erickson Power Station is located in Easton County on the southwest side of Lansing, about 10 km from the downtown area. Figure 1 1
below shows the locations of the facilit ies, nearby emitters of SO 2 , the state’s recommended area
for the attainment designation, and EPA ’s intended coterminous unclassifiable/ attainment designation for the area.31

Figure 1 1

. EPA ’s intended designation for Lansing, MI

The discussion and analysis that follows below will reference the state’s use of the Modeling TAD, EPA ’s assessment of the state’s modeling in accordance with the Modeling TAD, and the
factors for evaluation contained in EPA ’s March 20, 2015 guidance, as a ppropriate.

Detailed Assessment

Air Quality Data An ambient air quality monitor, (AQS site number 26

- 065

- 00 12 ), located approximate ly 3 km
from the Eckert Power Station and 11 km from the Erickson Power Station . The design value for
this monitor for the 2012

- 2014 design period was 18 ppb. Although Michigan based its designation recommendations on modeling rather than monitoring information, this nearby monitor was relied upon to determine the background concen tration for this area

.

Model Selection and Modeling Components

EPA ’s Modeling TAD notes that for area designations under the 2010 SO 2 NAAQS, the AERMOD modeling system should be used, unless use of an alternative model can be justified. In some instances the recommended model may be a model other than AERMOD, such as the BLP model for buoyant line sources. The AERMOD modeling system c ontains the following
components:

- AERMOD: the dispersion model

- AERMAP: the terrain processor for AERMOD

- AERMET: the meteorological data processor for AERMOD32

- BPIPPRIME: the building input processor

- AERMINUTE: a pre

- processor to AERMET incorporating 1

- minute automated surface observation system (ASOS) wind data

- AERSURFACE: the surface characteristics processor for AERMET

- AERSCREEN: a screening version of AERMOD

The state used AERMOD version 14134 , a nd a discussion of the individual components will be referenced in the corresponding discussion that follows, as appropriate.

Modeling Parameter: Rural or Urban Dispersion

EPA ’s recommended procedure for characterizing an area by prevalent land use is ba sed on evaluating the dispersion environment with 3 km of the facility. According to EPA ’s modeling guidelines, rural dispersion coefficients are to be used in the dispersion modeling analysis if
more than 50 percent of the area within a 3 km radius of the facility is classified as rural. Conversely, if more than 50 percent of the area is urban, urban dispersion coefficients should be used in the modeling analysis. When performing the modeling for the area , the stat e determined that it was most appropriate to run the model in rural mode. A land use analysis showed the area around the Eckert Station to be 53 percent urban. However, a historic modeling analysis
demonstrated that rural coefficient s represent this bord erline urban area more accurately. The Ericson facility is more clearly rural through population and land use analyses.

Modeling Parameter: Area of Analysis (Receptor Grid)

EPA believes that a reasonable first step towards characterization of air quality in the area surrounding the Eckert and Erickson Power Stations is to determine the extent of the area of analysis, i.e., receptor grid. Considerations presented in the Modeling TAD include but are not
limited to: the location of the SO 2 emission sources or facilities considered for modeling; the extent of significant concentration gradients of nearby sources; and sufficient receptor coverage and density to adequately capture and resolve the model predicted maximum SO 2 concentrations.
For the Lansing area, the state has included 3 other emitters of SO 2 within 10 km of either Eckert

or Erickson in any direction. The state determined that this was the appropriate distance in order to adequately characterize air quality from the facilit ies and other nearby sources which may have a potential significant impact in the area where maximum concentrations of SO 2 are expected. Aside from exceptionally large sources, sources farther than 1 0 km from the Eckert
and Erickson Power Stations would not cause significant concentration gradients in the Lansing
area and therefore need not be modeled. In addition to Eckert and Erickson , the other emitters of
SO 2 included in the area are: Michigan State University, Thompson

- McCully Asphalt, and Superior Asphalt

. The grid receptor spacing for the area chosen by the state is as follows:

- 100 m spacing from facility center s to 2 km from the facilit ies

- 250 m spacing from 2 km to 10 km from the facilit ie s

- 5,000 m spacing from 15 km to 35 km from the facilit ies

- An additional nested receptor grid at 50 meter spacing was placed in the area of the maximum impacts. The receptor network contained 18,816 receptors, and the network covered portions of Ingham
and Eaton Counties.33

Figure 12, included in the state’s recommendation, show s the receptor grid for the area

. Although in principle Michigan placed receptors only in areas where it would also be feasible to place a monitor , in practice Michigan conservatively placed receptors at all locations according to the above grid except for receptors within the fencelines of Eckert and Erickson . The impacts of the area’s geography and topography will be discussed later within this document.

Figure 1 2 : Receptor Grid for the Lansing, MI Area

Modeling Parameter: Source Characterization

The state characterized the source s within the area in accordance with the best practices outlined in the Modeling TAD. Specifically, the state used actual stack heights in conjunction with actual
emissions and followed EPA ’s good engineering practices (GEP) policy in conjunction with
allowable emissions limits. The state also adequ ately characterized the source s ’ building layout
and locations, as well as the stack parameters, e.g., exit temperature, exit velocity, location, and
diameter. Where appropriate, the AERMOD component BPIPPRIME was used to assist in addressing building downwash.

Modeling Parameter: Emissions

E PA ’s Modeling TAD notes that for the purposes of modeling to characterize air quality for use in designations, the recommended approach is to use the most recent 3 years of actual emissions34

data and concurrent meteorological data. The Modeling TAD highly encourages the use of the most detailed throughput, operating schedule and emissions information available.

Variable emissions, temperature, and flow data can be modeled using AERMOD’s hourly varying emissions keyword HOUREMIS or variable emission factor keyword EMISFACT. EPA believes that continuous emissions monitoring systems (CEMS) data provide valuable his torical emissions information, when it is available, and that these data are available for many electric generating units. However, the TAD also provides the option to use allowable emissions reflecting the applicable, federally enforceable emission limit (referred to as PTE or the allowable emissions rate).

In certain instances, states and other interested parties may find that it is more advantageous or simpler to use PTE rates as part of their modeling runs. Specifically, a facility may have recently adopted a new federally enforceable emissions limit, been subject to a federally enforceable consent decree, or implemented other federally enforceable mechanisms and control technologies to limit SO 2 emissions to a level that indicates compliance with the NAAQS. These new limits or conditions may be used in the application of AERMOD. In these cases, the Modeling TAD notes that the existing SO 2 emissions inventories used for permitting or SIP planning demonstrations should contain the necessary emissions information for designations

related modeling

. In the event that these short

- term emissions are not readily available, they may be calculated using the methodology in Table 8

- 1 of Appendix W to 40 CFR Part 51 titled, “Guideline on Air Quality Models.”

A s previously noted, the state included Eckert and Erickson and 3 other emitters of SO 2 within
10 km in the area

. The state selected this d istance and facilities because the state believes that
this area adequately represents the area where maximum concentrations of SO 2 are expected and adequately includes the sources which might contribute to those concentrations. No other

sources within or beyond 10 km were determined by the state to have the potential to cause significant concentration gradients within the area

. For this area , the state has opted to use a hybrid approach, using actual emissions from certain facilities and PTE rates from other
facilities.

This information is summarized below , showing the most recently available actual or PTE
emissions (as pertinent) for the facilities in the area

.

Table 9 : Actual and Allowable SO 2 Emissions Between from Facilities in the Lansing, MI Area

Facility Name Allowable
Emissions ( tpy ) SO2 Actual Emissions

( tpy ) Distance

from
Eckert (km) Distance

from
Erickson (km) 2012 2013 2014

Eckert Power Station

---- 3,677 2,256 2,312

---- 9

Erickson Power Stations

---- 2,685 3,903 3,627 9

---- Thompson

- McCully Company 241

---- ---- ---- 12 4

Superior Asphalt, Inc. 81

---- ---- ---- 9 0.5

Michigan State University *

---- ( 809 ) ( 475 ) 473 6 1535

Total Emissions From All Facilities in the Area of Analysis* *

---- 7,157 6,954 6,734 *Michigan modeled the only the 2014 actual emissions fo r Michigan State University, but the 2012 and 2013 emissions are shown to get a general emissions profile of the area.

* * Includes allowable emission s for Thompson

- McCully Company and Superior Asphalt, Inc. in all three years and assumes the same actual value for Michigan State University for all three years.

For both Eckert and Erickson , the state used actual emissions from the most recent 3

- year data set, i.e., 2012

– 2014. These emissions data were obtained from CEMs.

For Michigan State University, the state used a ctual emissions from 2014. Emissions data for this facility were obtained from Michigan’s annual emissions inventory. Although the state used 2014 only data instead of using data for 2012 and 2013 that more closely reflect emissions for those years

, the three year average of 586 tpy is not significantly higher than the 2014 tpy of

473. Modeling for t his area, using the lowered modeled rate for Michigan State University,

estimates concentrations well below the standard, so this emissions discrepancy is no t significant enough to warrant concern about the attainment status of this area.

For the Thompson

- McCully Company and Superior Asphalt facilities, the state has chosen to
model the facilities using the most recent federally enforceable PTE limits for SO 2 . The PTE
limits for these facilities were chosen as the most conservative approach using available data.

Modeling Parameter: Meteorology and Surface Characteristics

The most recent 3 years of meteorological data (concurrent with the most recent 3 years of emissions data) should be used in designations efforts. As noted in the Modeling TAD, the selection of data should be based on spatial and climatological (temporal) representativeness. The representativeness of the data are based on: 1) the proximity of the meteorological monitoring site to the area under consideration, 2) the complexity of terrain, 3) the exposure of the meteorological site, and 4) the period of ti me during which data are collected

. Sources of meteorological data include National Weather Service (NWS) stations, site

- specific or onsite data, and other sources such as universities, Federal Aviation Administration (FAA), and military stations.

For th e Lansing area, surface meteorology from Capitol City Airport, 7 km to the north of Eckert

Power Station , and coincident upper air observations from White Lake, MI, 88 km to the east

, were selected as best representative of meteorological conditions within the area.

The state used AERSURFACE using data from the Capitol City Airport station in Lansing (located at 42.78028 ° N

, - 84.57889 ° W ) to estimate the surface characteristics of the area. The state estimated values for 12 spatial sectors out to 1 km at a monthly temporal resolution for average conditions. The state also estimated values for albedo (the fraction of solar energy reflected from the earth back into space), the Bowen ra tio ( representing the ratio of sensible heat flux to latent heat flux at the ground level ), and the surface roughness ( representing the influence of ground features such as buildings and vegetation on surface wind flow ). In the figure below,36

generated by EPA , the location of the Capitol City Airport station is shown relative to Eckert and

Erickson

.

Figure 1 3 : Eckert and Erickson and the Capitol City Airport Station

In Figure 1 4 , the frequency and magnitude of wind speed and direction are defined in terms of from where the wind is blowing

. The wind is most frequently from the southwest, occurring

about 11 percent of the time.37

Figure 1 4 : Capitol City Airport Cumulative Annual Wind Rose for Years 2012

– 2014

Meteorological data from the above surface and upper air stations were used in generating

AERMOD

- ready files with the AERMET processor. The output meteorological data created by the AERMET processor is suitable for being applied with AERMOD input files fo r AERMOD modeling runs. The state followed the methodology and settings presented in the modeling TAD in the processing of the raw meteorological data into an AERMOD

- ready format, and used AERSURFACE to best represent surface characteristics.

Hourly sur face meteorological data records are read by AERMET, and include all the necessary elements for data processing. However, wind data taken at hourly intervals may not always portray wind conditions for the entire hour, which can be variable in nature. Hourly wind data may also be overly prone to indicate calm conditions, which are not modeled by AERMOD. In order to better represent actual wind conditions at the meteorological tower, wind data of one minute duration was provided from the same instrument tower, but in a different formatted file to be processed by a separate preprocessor, AERMINUTE. These data were subsequently integrated into the AERMET processing to produce final hourly wind records of AERMOD

-38

ready meteorological data that better estima te actual hourly average conditions and that are less
prone to over

- report calm wind conditions. This allows AERMOD to apply more hours of meteorology to modeled inputs, and therefore produce a more complete set of concentration

estimates. As a guard aga inst excessively high concentrations that could be produced by AERMOD in very light wind conditions, the state set a minimum threshold of 0.5 meters per second in processing meteorological data for use in AERMOD. This approach is consistent with

a March 2 013 EPA memo titled, “Use of ASOS meteorological data in AERMOD dispersion Modeling.” In setting this threshold, no wind speeds lower than this value would be used for determining concentrations. This threshold was specifically applie d to the one minute wind data.

Modeling Parameter: Geography and Terrain

The terrain in the area is best described as relatively flat

. Nevertheless, t o account for terrain changes, the AERMAP terrain program within AERMOD was used to specify terrain elevations for all the receptors. The source of the elevation data incorporated into the model is from the

USGS National Elevation Database.

Modeling Par

ameter: Background Concentrations of SO 2

The Modeling TAD offers two mechanisms for characterizing background concentrations of SO 2 that are ultimately added to the modeled design values: 1) a “first tier” approach, based on monitored design values, or 2) a temporally varying approach, based on the 99 th percentile monitored concentrations by hour of day and season or month. For the Lansing area , the state

chose the monitored design value from the Ingham County monitor. The background

concentration for th is area was determined by the state to be 46.9 micrograms per cubic meter ( μg/m 3 ), or 17.9 ppb, 6 and that value was incorporated into the final AERMOD results.

Summary of Modeling Results

The AERMOD modeling parameters for the Lansing area are summarized below in Table 10.

Table 10 : AERMOD Modeling Parameters for the Lansing, MI Area Lansing, MI Area

AERMOD Version 14134 Dispersion Characteristics Rural

Modeled Sources 5

Modeled Stacks 12

Modeled Structures 17

Modeled Fencelines 5 Total receptors 18816

6 The conversion factor for SO 2 (at the standard conditions applied in the ambient SO 2 reference method) is 1ppb = approximately 2.62 μg/m 3

.39 Emissions Type Actual and PTE

Emissions Years 2012

- 2014 Meteorology Years 2012

- 2014

Surface Meteorology Station Capitol City Airport, Lansing,

MI Upper Air Meteorology Station White Lake, MI Methodology for Calculating Background SO 2 Concentration Ingham County monitor Calculated Background SO 2 Concentration 46.9 μg/m 3

The results presented below in table 10 show the magnitude and geographic location of the highest predicted modeled concentration base d on actual and PTE emissions.

Table 11 : Maximum Predicted 99th Percentile 1

- Hour SO 2 Concentration in the Lansing, MI Area Based on Actual and PTE Emissions

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

UTM/Latitude UTM/Longitude Modeled (including background) NAAQS
99th Percentile
1

- Hour Average 2012

- 2014 691025 472577 6 139.6 196.4 * *Equivalent to the 2010 SO 2 NAAQS set at 75 ppb

The state’s modeling indicates that the predicted 99 th percentile 1

- hour average concentration

within the c hosen modeling domain is 139.6 μg/m 3 , or 53.3 ppb. This modeled concentration

included the background concentration of SO 2 , and is based on actual and or PTE emissions from

the facilities. Figure 1 5 below was included as part of the state’s recommendation, and indicates that the predicted value occurred 3 km south of Erickson , and 11 km southwest of Eckert

. The state’s receptor grid is also shown in the figure.40

Figure 1 5 : Maximum Predicted 99 th Percentile 1

- Hour SO 2 Concentrations in the Lansing, MI

Area Based on Actual and PTE Emissions

Jurisdictional Boundaries

Once the geographic area of analysis associated with Eckert and Erickson was determined, existing jurisdictional boundaries are considered for the purpose of informing our intended

unclassifiable/ attainment area, specifically with respect to clearly defined legal boundaries. Michigan recommended the entirety of Ingham and Eaton C ounties, M ichigan be designated

unclassifiable/ attainment . The modeling grid extended to 35 km, covering the majority of the two counties and additional surrounding area. EPA determined that there are no other significant

sources of SO 2 in either of the counties or near their borders emitting at or above 100 tpy but for the sources included in the state’s modeling analysis. As a result, EPA does not believe that there are any sources of SO 2 in or around these counties with the potential to cause or contr ibute to a violation of the NAAQS within the state’s recommended boundaries

.

EPA believes that our intended unclassifiable/ attainment area, consisting of Ingham and Eaton

Counties , are comprised of clearly defined legal boundaries, and we find these boundaries to be a suitably clear basis for defining our intended unclassifiable/ at tainment area.

Other Relevant Information41

No other relevant information was received for this area.

Conclusion

After careful evaluation of the state’s recommendation and supporting information, as well as all available relevant information, EPA intends to designate the area around Eckert and Erickson as
unclassifiable/ attainment for the 2010 SO 2 NAAQS

. Specifically, EPA intends for the designated area to include the entirety of Ingham and Eaton Counties.

At this time, our intended designations for the state only apply to this area and the other areas
addressed in this technical support document

. Con sistent with the conditions in the March 2,
2015 court

- ordered schedule, EPA will evaluate and designate all remaining undesignated areas
in Michigan by either December 31, 2017, or December 31, 2020

.42 Technical Analysis for the Marquette County , MI Area

Introduction

Marquette County contains a stationary source that according to EPA ’s Air Markets Database emitted in 2012 either more than 16,000 tons of SO 2 or more than 2,600 tons of SO 2 and had an annual average emission rate of at least 0.45 lbs SO 2 / MM BTU. As of March 2, 2015, this stationary source had not met the specific requirements for being “announced for retirement.” Specifically, in 2012, the Presque Isle Power Plant (“Presque Isle”) emitted 6,028 tons of SO 2 ,
an d had an emissions rate of 0. 5 13 lbs SO 2 /MM BTU. Pursuant to the March 2, 2015 court

ordered schedule, EPA must designate the area surrounding the facility by July 2, 2016.

In its submission, Michigan recommended that the area surrounding Presque Isle

, specifically the entirety of M a rquette County, be designated as attainment based on an assessment and characterization of air quality from the facility and other nearby sources which may have a potential impact in the area where maximum concentrations of SO 2 are expected. This assessment and characterization was performed using air dispersion modeling software, i.e., AERMOD, analyzing actual and allowable emissions. After careful review of the state’s assessment, supporting documentation, and all available data, EPA agrees that the area is attaining the standard, and intends to designate M arquette County as unclassifiable/attainment.

Presque Isle is located in Marquette County in the Upper Peninsula of Michigan. As seen in Figure 1 6 below, the fac ility is located approximately 4 km north of the center of Marquette along the Dead River adjacent to Lake Superior. Also included in the figure are nearby emitters
of SO 2 , the state’s recommended area for the attainment designation, and EPA ’s intended area for the unclassifiable/ attainment designation.43

Figure 1 6

. EPA ’s intended designation for Marquette County , MI

The discussion and analysis that follows below will reference the state’s use of the Modeling TAD, EPA ’s assessment of the state’s modeling in accordance with the Modeling TAD, and the
factors for evaluation contained in EPA ’s March 20, 2015 guidance, as appropriate.

Detailed Assessment

Air Quality Data
No monitors are located in or near Marquette County to inform the designation for this area.

Model Selection and Modeling Components

EPA ’s Modeling TAD notes that for area designations under the 2010 SO 2 NAAQS, the AERMOD modeling system should be used, unless use of an alternative model can be justified. In some instances the recommended model may be a model other than AERMOD, such as the BLP model for buoyant line sources. The AERMOD modeling system c ontains the following
components:

- AERMOD: the dispersion model

- AERMAP: the terrain processor for AERMOD

- AERMET: the meteorological data processor for AERMOD

- BPIPPRIME: the building input processor

- AERMINUTE: a pre

- processor to AERMET incorporating 1

- minut e automated surface observation system (ASOS) wind data

- AERSURFACE: the surface characteristics processor for AERMET

- AERSCREEN: a screening version of AERMOD44

The state used AERMOD version 14134 , and a discussion of the individual components will be
refer enced in the corresponding discussion that follows, as appropriate.

Modeling Parameter: Rural or Urban Dispersion

EPA ’s recommended procedure for characterizing an area by prevalent land use is based on evaluating the dispersion environment with 3 km of the facility. According to EPA ’s modeling guidelines, rural dispersion coefficients are to be used in the dispersion modeling analysis if
more than 50 percent of the area within a 3 km radius of the facility is classified as rural. Conversely, if more than 50 percent of the area is urban, urban dispersion coefficients should be used in the modeling analysis. When performing the modeling for the area , the state determined
that it was most a ppropriate to run the model in rural mode based on a land use/ l and cover analysis.

Modeling Parameter: Area of Analysis (Receptor Grid)

EPA believes that a reasonable first step towards characterization of air quality in the area surrounding the Presque Isle is to determine the extent of the area of analysis, i.e. , receptor grid. Considerations presented in the Modeling TAD include but are not limited to: the location of the
SO 2 emission sources or facilities considered for modeling; the extent of significant concentration gradients of nearby sources; and sufficient receptor coverage and density to adequately capture and resolve the model predicted maximum SO 2 concentrations. Fo r the Marquette County area, the state has included 2 other emitters of SO 2 within 10 km of Presque
Isle Power Plant in any direction. The state determined that this was the appropriate distance in order to adequately characterize air quality from the fac ility and other nearby sources which may
have a significant impact in the area where maximum concentrations of SO 2 are expected. Aside from exceptionally large sources, sources farther than 10 km from Presque Isle would not cause significant concentration gradients in the Marquette County area and therefore need not be
modeled. In addition to the Presque Isle Power Plant , the other emitters of SO 2 included in the

area are: Marquette Board of Light and Power and Northern Michigan University

. The grid receptor spacing for the area of analysis chosen by the state is as follows:

- 25 m along the fenceline

- 100 m spacing from fenceline to 2.5 km from the facility

- 500 m spacing from 2.5 km to 15 km from the facility

- No receptors were place d on Lake Superior

The re ceptor network contained 3,120 rec eptors, and the network covering an eastern portion of Marquette County including Marquette Township and the City of Marquette.

Figure 17, included in the state’s recommendation, shows the receptor grid for the area. Consistent with the Modeling TAD, receptors for the purposes of this designation effort were placed only in areas where it would also be feasible to place a monitor and record ambient air impacts . In particular, no receptors were placed over Lake Su perior. The impacts of the area’s geography and topography will be discussed later within this document.45

Figure 17 : Recepto r Grid for the Marquette County , MI Area

Modeling Parameter: Source Characterization

The state characterized the sources within the area in accordance with the best practices outlined in the Modeling TAD. Specifically, the state used actual stack heights in con junction with actual
emissions and fo llowed EPA ’s GEP policy in conjunction with allowable emissions limits. The state also adequ ately characterized the source’ s building layout and locations, as well as the stack parameters, e.g., exit temperature, exit velocity, location, and diameter. Where appropria te, the AERMOD component BPIPPRIME was used to assist in addressing building downwash.

Modeling Parameter: Emissions

EPA ’s Modeling TAD notes that for the purposes of modeling to characterize air quality for use in designations, the recommended approach is to use the most recent 3 years of actual emissions data and concurrent meteorological data. The Modeling TAD highly encourages the use of the most detailed throughput, operating schedule and emissions information available.

Variable emissions, temper ature, and flow data can be modeled using AERMOD’s hourly varying emissions keyword HOUREMIS or variable emission factor keyword EMISFACT. EPA
believes that CEMS data provide valuable historical emissions information, when it is available, and that these data are available for many electric generating units. However, the TAD also provides the option to use allowable emissions reflecting the applicable, federally enforceable
emission l imit (referred to as PTE or the allowable emissions rate).

In certain instances, states and other interested parties may find that it is more advantageous or simpler to use PTE rates as part of their modeling runs. Specifically, a facility may have recen tly46

adopted a new federally enforceable emissions limit, been subject to a federally enforceable consent decree, or implemented other federally enforceable mechanisms and control technologies to limit SO 2 emissions to a level that indicates compliance with the NAAQS. These new limits or conditions may be used in the application of AERMOD. In these cases, the Modeling TAD notes that the existing SO 2 emissions inventories used for permitting or SIP planning demonstrations should contain the necessary emissi ons information for designations

related modeling. In the event that these short

- term emissions are not readily available, they may be calculated using the methodology in Table 8

- 1 of Appendix W to 40 CFR Part 51 titled, “Guideline on Air Quality Models.”

As previously noted, the state included Presque Isle and 2 other emitters of SO 2 that are within
10 km of Presque Isle

. The state selected this distance and these facilities because the state believes that this area adequately represents the area where maximum concentrations of SO 2 are expected and adequately includes the sources which might contribute to those concentrations.
No other sources within or beyond 10 km were determined by the state to have the potential to cause significant concentration gradients within the area

. For this area, the state has opted to use a hybrid approach, where emissions from certain facilities are expressed as actual emis sions, and those from other facilities are expressed as PTE rates.

Table 1 2 shows the emissions of Presque Isle Power Plant and all other sources of SO2 in Marquette County emitting over 100 tpy, showing the data EPA considered in determining the appropriateness of the sources included in the modeling analysis. Sources outside M arquette County are even less likely to have significant impacts in the Presque Isle area.

Table 12 : SO 2 Emissions from Facilities in the Marquette County, MI

Facility Name Allowable
Emissions (tpy) Actual SO 2 Emissions (tpy) Distance from Presque Isle
Power Plant (km) 2012 2013 2014 Presque Isle Power Plant

---- 6,028 6,001 6,304

---- Marquette Board of Light and Power*

---- ( 304 ) ( 404 ) 1,160 2

Northern Michigan University 100

---- ---- ---- 5

Empire Iron Mining Partnership ----

---- ---- 319 22

Tilden Mining Company ----

---- ---- 976 25

Total Emissions From All Modeled Facilities in the Area of Analysis** ---- 6,432 6,505 7,564 *Michigan modeled the 2014 actual emissions for Marquette Board of Light and Power

, but the 2012 and 2013 emissions are shown to get a general emissions profile of the area.

* *Includes allowables for Northern Michigan University in all three years. Facilities in italics were not included in the modeling domain or in the Total Emissions from All Facilities in the Area of Analysis.

For Presque Isle the state used actual emissions from the most recent 3

- year data set, i.e., 2012

– 2014. Th e s e emissions data w ere obtained from CEMS.

For the Marquette Board of Power and Light, the state u sed actual emissions from
2014. Emissions data for this facility were obtained from Michigan’s annual emissions47

inventory. Although the state used 2014 only data instead of using data for 2012 and 2013 that more closely reflect emissions for those years, the three year average of 623 tpy is lower than the 2014 tpy of 1,160. Therefore, this use of annual actual emissions from 2014 was a more conservative approach than using year

- specific emissions data

.

The PTE limit for Northern Michigan University was chosen as the most conservative approach using available data.

Modeling Parameter: Meteorology and Surface Characteristics

The most recent 3 years of meteorological data (concurrent with the most recent 3 years of

e missions data) should be used in design ations efforts. As noted in the Modeling TAD, the selection of data should be based on spatial and climatological (temporal) representativeness. The representativeness of the data are based on: 1) the proximity of the meteorological monitoring site to th e area under consideration, 2) the complexity of terrain, 3) the exposure of the meteorological site, and 4) the period of time during which data are collected. Sources of meteorological data include National Weather Service (NWS) stations, site

- specific or onsite data, and other sources such as universities, Federal Aviation Administration (FAA), and military stations.

For the Marquette County area, surface meteorology fro m the NWS station in Munising, MI , 6 0

km to the northwest , and coincident upper air observations from Gaylord, MI

, 272 km to the southeast were selected as best representative of meteorological conditions within the area

.

The state used AERSURFACE data from the NWS station in Munising, MI (located at

46.41667 ° N , 86.65 ° W ) to estimate the surface characteristics of the area

. The state estimated values for 12 spatial sectors out to 1 km at a monthly temporal resolution for average conditions. The state also estimated values for albedo (the fraction of solar energy reflected from the earth back into space), the Bowen ratio ( representing the ratio of sensible heat flux to latent heat flux at the ground level ), and the surface roughness ( represen ting the influence of ground features such as buildings and vegetation on surface wind flow ). In the figure below, generated by EPA

, the location of the NWS station in Munising, MI is shown relative to the Presque Isle Power

Plant area

.48

Figure 18 : Presq ue Isle Power Area and the Munising, MI NWS station

As part of its recommendation, the state provided th e 3

- year surface wind data for Munising, MI

. In Figure 19 , the frequency and magnitude of wind speed and direction are defined in terms of from where the wind is blowing. The winds are predominantly from a southerly direction, occurring about 22 percent of the time.49

Figure 19 : Munising, MI Cumulative Annual Wind Rose for Years 2012

– 2014

Meteorological data from the above surface and upper air stations were used in generating

AERMOD

- ready files with the AERMET processor. The output meteorological data created by the AERMET processor is suitable for being applied with AERMOD input files for AERMOD modeling runs. The state followed the methodology and settings presented in “Regional Meteorological Data Processing Protocol EPA Region V and States

, ” Draft, August 2014, in the processing of the raw meteorological data into an AERMOD

- ready format, and used AERSURFACE to best represent surface characteristics.

Hourly surface meteorological data records are read by AERMET, and include all the necessary elements for data processing. However, w ind data taken at hourly intervals may not always portray wind conditions for the entire hour, which can be variable in nature. Hourly wind data may also be overly prone to indicate calm conditions, which are not modeled by AERMOD. In order to better rep resent actual wind conditions at the meteorological tower, wind data of one minute duration was provided from the same instrument tower, but in a different formatted file to50

be processed by a separate preprocessor, AERMINUTE. These data were subsequently integrated into the AERMET processing to produce final hourly wind records of AERMOD

ready meteorological data that better estimate actual hourly average conditions and that are less
prone to over

- report calm wind conditions. This allows AERMOD to apply m ore hours of meteorology to modeled inputs, and therefore produce a more complete set of concentration

estimates. As a guard against excessively high concentrations that could be produced by AERMOD in very light wind conditions, the state set a minimum th reshold of 0.5 meters per second in processing meteorological data for use in AERMOD. This approach is consistent with a March 2013 EPA memo titled, “Use of ASOS meteorological data in AERMOD dispersion Modeling.” In setting this threshold, no wind speed s lower than this value would be used for determining concentrations. This threshold was specifically applied to the one minute wind data.

Modeling Parameter: Geography and Terrain

The terrain in the area is best described as relatively flat

. Nevertheless, t o account for terrain changes, the AERMAP terrain program within AERMOD was used to specify terrain elevations for all the receptors. The source of the elevation data incorporated into the model is from the

USGS National Elevation Database.

Modeling Parameter: Background Concentrations of SO 2

The Modeling TAD offers two mechanisms for characterizing background concentrations of SO 2 that are ultimately added to the modeled design values: 1) a “first tier” approach, based on monitored desig n values, or 2) a temporally varying approach, based on the 99 th percentile monitored concentrations by hour of day and season or month. For the Marquette County area, the state applied a “first tier” approach using a fixed background concentration. The state
determined the value as the design value from the Forest County, WI monitor

, AQS site number

55

- 041

- 0007, without excluding any times for purposes of eliminating source impacts. While this monitor is somewhat distant from Marquette County, the environs are similar, and so the Forest County monitor likely provides a reasonable estimate of the background concentrations encountered in Marquette County. The background concentration f or this area was determined by the state to be 17.9 micrograms per cubic meter ( μg/m 3 ), or 6.8 ppb, 7 and that value was incorporated into the final AERMOD results.

Summary of Modeling Results

The AERMOD modeling parameters for the Marquette County area are summarized below in

Table 13.

7 The conversion factor for SO 2 (at the standard conditions applied in the ambient SO 2 reference method) is 1ppb = approximately 2.62 μg/m 3

.51

Table 13 : AERMOD Modeling Parameters for the Marquette County , MI Area

Marquette County , MI Area

AERMOD Version 14134 Dispersion Characteristics Rural

Modeled Sources 4

Modeled Stacks 4

Modeled Structures 4

Modeled Fencelines 3 Total receptors 3120

Emissions Type Northern Michigan University:

PTE Presque Isle and others: Actual

Emissions Years 2012

- 2014 or 2014 Meteorology Years 2012

- 2014 Surface Meteorology Station Munising, MI Upper Air Meteorology Station Gaylord, MI

Methodology for Calculating Background SO 2 Concentration Design value from Forest County, WI ( AQS site number
55

- 041

- 0007) Calculated Background SO 2 Concentration 17.8 μg/m 3

The results presented below in T able 14 show the magnitude and geographic location of the highest predicted modeled concentration based on the combination of actual and PTE emissions

described above

.

Table 1 4 : Maximum Predicted 99th Percentile 1

- Hour SO 2 Concentration in the Marquette County

, MI Area Based on Actual and Emissions

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

UTM/Latitude UTM/Longitude Modeled (including background) NAAQS
99th Percentile
1

- Hour Average 2012

- 2014 466725 5151475 104.5 196.4 * *Equivalent to the 2010 SO 2 NAAQS set at 75 ppb

The state’s modeling indicates that the predicted 99 th percentile 1

- hour average concentration within the chosen modeling domain is 104.5 μg/m 3 , or 39.9 ppb. This modeled concentration

included the background concentration of SO 2 , and is based on actual and PTE emissions from

the facilities. Figure 2 0 below was included as part of the state’s recommendation, and indicates that the predicted value occurred about 7.5 km south west of the power plant

.52

Figure 2 0 : Maximum Predicted 99 th Percentile 1

- Hour SO 2 Concentrations in the Marquette County , MI Area Based on Actual and PTE Emissions

Jurisdictional Boundaries

Once the geographic area of analysis associated with Presque Isle wa s determined, existing jurisdictional boundaries we re considered for the purpose of informing our intende d designated area, specifically with respect to cl early defined legal boundaries. The state recommended designating the entirety of Marquette County

. While the modeling analysis did not include the

emissions from either Tilden Mining or Empire Iron Mining, EPA does not believe that emissions from these facilities are causing or contributing to violations of the NAAQS within the area of analysis, and

, co n sequently

, the entirety of Marquette County. The contractor modeled a

15 km grid around Presque Isle as attaining the standard with the maximum impact 7 .5 km away from the facility. Based on the distance between Pres que Isle and Tilden Mining and Empire Iron Mining (approximately 22 km), EPA does not believe that emissions from either of these sources would impact the modeled maximum concentration. Therefore, EPA believes that our intended unclassifiable/attainment area, consisting of the entirety of Ma rquette County, applies clearly defined legal boundaries, and we find these boundaries to be a suitably clear basis for defining our intended unclassifiable/attainment area.

Other Relevant Information53

No other relevant information was received for this area.

Conclusion

After careful evaluation of the state’s recommendation and supporting information, as well as all available relevant information, EPA intends to designate the area around Presque Isle Power
Plant as unclassifiable/ attainment for the 2010 SO 2 NAAQS. Specifically, the area are comprised of the entirety of Marquette County, MI

.

At this time, our intended designations for the state only apply to this area and the other areas presented in this technical support document. Consi stent with the conditions in the March 2,
2015 court

- ordered schedule, EPA will evaluate and designate all remaining undesignated areas
in Michigan by either December 31, 2017, or December 31, 2020.54 Technical Analysis for the Monroe County, MI Area

Introduction

Monroe County , Michigan contains a stationary source that according to EPA ’s Air Markets Database emitted in 2012 either more than 16,000 tons of SO 2 or more than 2,600 tons of SO 2 and had an annual average emission rate of at least 0.45 lbs SO 2 /MM BTU. As of March 2, 2015, this stationary source had not met the specific requirements for being “announced for retirement.” Specifically, in 2012 the Monroe Power Plant (“Monroe”) emitted 49,151 tons of
SO 2 , and had an emissions rate of 0.62 SO 2 /MM BTU. Pursuant to the March 2, 2015 court

ordered schedule, EPA must designate the area surrounding the facility by July 2, 2016.

In its submission, Michigan recommended that the area surrounding Monroe , specifically the entirety of Monroe County, be d esignated as attainment based on an assessment and characterization of air quality from the facility and other nearby sources which may have a potential impact in the area where maximum concentrations of SO 2 are expected. This assessment and characterization was performed using air dispersion modeling software, i.e., AERMOD, analyzing allowable emissions. In this analysis, the J

. R

. Whiting Generating Complex (Whiting) was not included in the modeling becaus e, due to a Federal consent decree, Whiting must be retired by April 15, 2016. After careful review of the state’s assessment, supporting documentati on, and all available data, EPA agrees that the modeling, assuming the
shutdown of Whiting , shows attainme nt of the NAAQS. However, since the assumption of the
shutdown does not reflect the current state of the Monroe County air quality, EPA intends to designate Monroe County as unclassifiable. EPA anticipates finalizing the designation of the
area as unclas sifiable/attainment once the source is confirmed as shutdown.

Monroe is located in south east ern Michigan in the eastern portion of Monroe County. As seen in Figure 2 1 below, the fac ility is located approximately 5 km southeast of the center of the City of Monroe along Lake Erie near the mouth of the River Raisin . Also included in the figure are nearby emitters of SO 2 , the state’s recommended area for the Monroe designation, and EPA ’s
intended coterminous unclassifiable designation for the area.5 5

Figure 2 1

. EPA ’s intended designation for Monroe County, MI

The discussion and analysis that follows below will reference the state’s use of the Modeling TAD, EPA ’s assessment of the state’s modeling in accordance with the Modeling TAD, and the
factors for evaluation contained in EPA ’s March 20, 2015 guidance, as appropriate. The discussion and analysis that follows below will reference the Modeling TAD and the fa ctors for
evaluation contained in EPA ’s March 20, 2015 guidance, as appropriate.

Detailed Assessment

Air Quality Data

A n ambient air quality monitor, (AQS site number 26

- 115

- 0006 ) , located approximate 3 .5 km north of Monroe, began operation at the beginning of 2013. The average of the 99 th percentile of daily maximum concentrations for 2013 and 2014 was 18.1 μg/m 3 . Although Michigan did not analyze whether this site is indicat iv e of maximum concentration s near Monroe, and Michigan based its designation recommendations on modeling rather than monitoring information, this information helps support a finding that this area is attaining the SO 2 NAAQS.

Model Selection and Modeling Components

EPA ’s Modeling TAD notes that for area designations under the 2010 SO 2 NAAQS, the AERMOD modeling system should be used, unless use of an alternative model can be justified. In some instances the recommended model may be a model other than AERMOD, such as the
BLP model for buoyant line sources

. The AERMOD modeling system contains the following
components:56

- AERMOD: the dispersion model

- AERMAP: the terrain processor for AERMOD

- AERMET: the meteorological data processor for AERMOD

- BPIPPRIME: the building input processor

- AER MINUTE: a pre

- processor to AERMET incorporating 1

- minute automated surface observation system (ASOS) wind data

- AERSURFACE: the surface characteristics processor for AERMET

- AERSCREEN: a screening version of AERMOD

The state used AERMOD version 14134 , and a discussion of the individual components will be referenced in the corresponding discussion that follows, as appropriate.

Modeling Parameter: Rural or Urban Dispersion

EPA ’s recommended procedure for characterizing an area by prevalent land use is based on evaluating the dispersion environment with 3 km of the facility. According to EPA ’s modeling guidelines, rural dispersion coefficients are to be used in the dispersion modeling analysis if
more than 50 percent of the area within a 3 km radius of the facility is classified as rural. Conversely, if more than 50 percent of the area is urban, urban dispersion coefficients should be used in the modeling analysis. When performing the modeling for the area , the stat e determined
that it was most a ppropriate to run the model in rural mode based on a la nd use analysis.

Modeling Parameter: Area of Analysis (Receptor Grid)

EPA believes that a reasonable first step towards characterization of air quality in the area

surr ounding the Monroe Power Plant is to determine the extent of the area of analysis, i.e., receptor grid. Considerations presented in the Modeling TAD include but are not limited to: the
location of the SO 2 emission sources or facilities considered for modeling; the extent of significant concentration gradients of nearby sources; and sufficient receptor coverage and density to adequately capture and resolve the model predicted maximum SO 2 concentrations.
Fo r the Monroe County area, the state has included 3 other emitters of SO 2 within 2 2 km of the
Monroe in any direction

. The state determined that generally 10 km was the appropriate distance in order to adequately characterize air quality from the facility and other nearby sources which may have a potential impact in the area where maximum concentrations of SO 2 are expected

, and that aside from exceptionally large sources, sources farther than 10 km from the power plants would not cause significant concentra tion gradients in the area , and therefore would not need to be modeled. However, in this case , the contractor running the model decided to take a more conservative approach tha n what the state had recommended for the other areas and include an extra source outside of the 10 km but within the recommended attainment area of the county boundary . In addition to the Monroe , the other emitters of SO 2 included in the area of analysis

are: IKO Monroe, Guardian Industries, and Gerdau Mac Steel Monroe. Whiting , under a federally enforceable consent decree, is required to be retired no later than April 15, 2016 and

was t herefore not included in this modeling analysis. The grid receptor spacing for the area of analysis chosen by the state i s as follows:

- 25 m along the Monroe fenceline

- 50 m spacing from fenceline to 2 km from Monroe Power Plant57

- 250 m spacing from 2 km to 5 km from Monroe Power Plant

- 500 m spacing from 5 km to 10 km from Monroe Power Plant

- Except that no r eceptors were placed over water bodies such as Lake Erie

The rec eptor network contained 68,145 receptors, and the network covered the eastern portion of Monroe County, MI.

Figure 2 2 , included in the state’s recommendation, show s the receptor grid for the area

. Consistent with the Modeling TAD, receptors for the purposes of this designation effort were placed only in areas where it would also be feasible to place a monitor and record ambient air impacts ; for example, no receptors were placed over Lake Erie

. The impacts of the area’s geography and topography will be discussed later within this document

.

Figure 2 2 : Receptor Grid for the Monroe, MI Area

Modeling Parameter: Source Characterization

The state characterized the source(s) within the area in accordance with the best practices outlined in the Modeling TAD. Specifically, the state used actual stack heights in conjunction
with actual emissions and followed EPA ’s good engineering practices (GEP) policy in conjunction with allowable emissions limits. The state also adequ ately characterized the

source s ’ building layout and location s , as well as the stack parameters, e.g., exit temperature, exit58

velocity, location, and diameter. Where appropriate, the AERMOD component BPIPPRIME
was used to assi st in addressing building downwash.

Modeling Parameter: Emissions

EPA ’s Modeling TAD notes that for the purposes of modeling to characterize air quality for use in designations, the recommended approach is to use the most recent 3 years of actual emissi ons data and concurrent meteorological data. T he Modeling TAD highly encourages the use of the most detailed throughput, operating schedule and emissions information available.

Variable emissions, temperature, and flow data can be modeled using AERMOD’s hourly varying emissions keyword HOUREMIS or variable emission factor keyword EMISFACT. EPA believes that continuous emissions monitoring systems (CEMS) data provide valuable his torical emissions information, when it is available, and that these data are available for many electric generating units. However, the TAD also provides the option to use allowable emissions reflecting the applicable, federally enforceable emission limit (referred to as PTE or the allowable emissions rate).

In certain instances, states and other interested parties may find that it is more advantageous or simpler to use PTE rates as part of their modeling runs. Specifically, a facility may have recently adopted a new federally enforceable emissions limit, been subject to a federally enforceable consent decree, or implemented other federally enforceable mechanisms and control technologies to limit SO 2 emissions to a level that indicates compliance with th e NAAQS. These new limits or conditions may be used in the application of AERMOD. In these cases, the Modeling TAD notes that the existing SO 2 emissions inventories used for permitting or SIP planning demonstrations should contain the necessary emissions information for designations

related modeling

. In the event that these short

- term emissions are not readily available, they may be calculated using the methodology in Table 8

- 1 of Appendix W to 40 CFR Part 51 titled, “Guideline on Air Quality Models.”

As previ ously noted, the state included the Monroe Power Plant and 3 other emitters of SO 2 within 2 2 km in the area

. The state selected this distance and facilities because the state believes
that this area adequately represents the area where maximum concentrations of SO 2 are expected and adequately includes the sources which might contribute to those concentrations. No other sources beyond 2 2 km were determined by the state to have the potential to cause significant concentration gradients within the area

. Whiting, since it is being required in a federal consent decree to shut down by April 15, 2016, is treated as having a PTE of 0 tpy, and was therefore not included in the modeling. For this area , the s tate has opted to use a hybrid approach, where emissions from certain facilities are expressed as actual emissions, and those from other facilities are expressed as PTE rates.

This information is summarized below is the most recently available actual or PTE emissions for
the facilities in the area

.59

Table 15 : Actual and Allowable SO 2 Emissions Between from Facilities in the Monroe County,

MI Area

Facility Name Allowable
Emissions ( tpy ) SO2 Actual Emissions

( tpy ) Distance from

Monroe Power Plant (km) 2012 2013 2014

Monroe Power Plant 14,293 49,151 43,766 6,286

----
Guardian Industries *

---- ( 613 ) (581) 581 22

Gerdau MacSteel Monro e *

---- (22) ( 23 ) 22 1

IKO Monroe 88

---- ----- ---- 7

J.R. Whiting 0

---- ---- ---- 14

Total Emissions From All Modeled Facilities in the Area of Analysis** 14,984 Source in italics was not included in the modeling due to a consent decree required shutdown date of April 15, 2016. *Michigan modeled the 2014 actual emissions for Guardian Industries and Gerdau MacSteel Monroe

, but the 2012 and 2013 emissions are shown to get a general emissions profile of the area.
**Includes allowables for Monroe Power Plant and IKO Monroe in all three years and assumes the same 2014
actual value for Guardian Industries and Gerdau MacSteel Monroe for all three years.

For the Guardian Industries and Gerdau MacSteel Monroe facilities, the state used actual

emissions from 2014 instead of using data for 2012 and 2013 that more closely reflect emissions for those years

. Emission s data for both facilities for 2012 and 2013 was obtained from Michigan’s annual emissions inventory. For the Gerdau MacSteel Monroe facility, the three year average for 2012 to 2014 is the same as emissions in 2014. The three year average for

Guardian I ndustries of 592 tpy is not significantly higher than the 2014 emissions of 581
tpy

. Modeling for t his area, using the lower modeled rate for these facilities, estimated

concentrations well below the standard , so these emissions discrepancies are not sign ificant enough to warrant concern about the attainment status of this area.

For Monroe and IKO Monroe facilities, the state ha s chosen to model the facilities using the most recent federally enforceable PTE limits for SO 2

. The PTE limit for the Monroe Power
Plant was associated with the use of new control technology. The PTE limit for the IKO Monroe facility was chosen as the most conservative approach using available data.

Modeling Parameter: Meteorology and Surface Characteristics

The most recent 3 years of meteorological data (concurrent with the most recent 3 years of emissions data) should be used in designations efforts. As noted in the Modeling TAD, the selection of data should be based on spatial and climatological (temporal) representativene ss. The representativeness of the data are based on: 1) the proximity of the meteorological monitoring site to the area under consideration, 2) the complexity of terrain, 3) the exposure of the meteorological site, and 4) the period of time during which d ata are collected. Sources of meteorological data include National Weather Service (NWS) stations, site

- specific or onsite data, and other sources such as universities, Federal Aviation Administration (FAA), and military stations.60

For the Monroe County a rea , surface meteorology from the station in Toledo

, OH, 50 km to the

south west , and coincide nt upper air observations from the NWS station in White Lake Township, MI

, 90 km to the north, were selected as best representative of meteorological

conditions within the area

.

The state used AERSURFACE version 13016 using data from the station in Toledo, OH (located

at 41.58861 ° N , 83.80139 ° W ) to estimate the surface characteristics of the area

. The state estimated values for 12 spatial sectors out to 1 km at a monthly temporal resolution for average

conditions. The state also estimated values for albedo (the fraction of solar energy reflected from the earth back into space), the Bowen rat io ( representing the ratio of sensible heat flux to latent heat flux at the ground level ), and the surface roughness ( representing the influence of ground features such as buildings and vegetation on surface wind flow ). In the figure below, generated by E PA , the location of the Toledo, OH station is shown relative to the Monroe area

.

Figure 2 3 : Monroe Power Plant Area and the Toledo, OH

As part of its recommendation, the state provided the 3

- year surface wind data for Toledo, OH

. In Figure 2 4 , the frequency and magnitude of wind speed and direction are defined in terms of from where the wind is blowing

. The wind predominantly blows from southwesterly directions.61

Figure 2 4 : Toledo, OH Cumulative Annual Wind Rose for Years 2012

– 2014

Meteorological data from the above surface and upper air stations were used in generating

AERMOD

- ready files with the AERMET processor. The output meteorological data created by the AERMET processor is suitable for being applied with AERMOD input files fo r AERMOD modeling runs. The state followed the methodology and settings presented in “Regional Meteorological Data Processing Protocol EPA Region V and States,” Draft, August 2014, in the processing of the raw meteorological data into an AERMOD

- ready form at, and used AERSURFACE to best represent surface characteristics.

Hourly surface meteorological data records are read by AERMET, and include all the necessary elements for data processing. However, wind data taken at hourly intervals may not always

por tray wind conditions for the entire hour, which can be variable in nature. Hourly wind data may also be overly prone to indicate calm conditions, which are not modeled by AERMOD. In order to better represent actual wind conditions at the meteorological t ower, wind data of one minute duration was provided from the same instrument tower, but in a different formatted file to be processed by a separate preprocessor, AERMINUTE. These data were subsequently62

integrated into the AERMET processing to produce fina l hourly wind records of AERMOD

ready meteorological data that better estimate actual hourly average conditions and that are less
prone to over

- report calm wind conditions. This allows AERMOD to apply more hours of meteorology to modeled inputs, and there fore produce a more complete set of concentration

estimates. As a guard against excessively high concentrations that could be produced by AERMOD in very light wind conditions, the state set a minimum threshold of 0.5 meters per second in processing meteor ological data for use in AERMOD. This approach is consistent with a March 2013 EPA memo titled, “Use of ASOS meteorological data in AERMOD dispersion Modeling.” In setting this threshold, no wind speeds lower than this value would be used for determining concentrations. This threshold was specifically applied to the one minute wind data.

Modeling Parameter: Geography and Terrain

The terrain in the area is best described as flat and simple

. To account for these terrain changes, the AERMAP terrain program within AERMOD was used to specify terrain elevations for all the
receptors. The source of the elevation data incorporated into the model is from the USGS

Nati onal Elevation Database.

Modeling Parameter: Background Concentrations of SO 2

The Modeling TAD offers two mechanisms for characterizing background concentrations of SO 2 that are ultimately added to the modeled design values: 1) a “first tier” approach, based on monitored design values, or 2) a temporally varying approach, based on the 99 th percentile monitored concentrations by hour of day and season or month. For the M onroe County area , the

state chose a conservative variation on the first tier approach. The background concentration was based on a monitor from the nearby Sterling State Park (monitor number 26

- 115

- 0006) without data when the Monroe Power Plant was impac ting the monitor. However, only two years of data were available, so the highest 4 th high was selected from the two years. T he result was higher, and therefore more conservative, than the result from the Michigan City , IN monitor that has been previously relied upon for this area , and more generally the result, despite being based on less than three years of data, may be considered a reasonable estimate of a conservative background concentration

. The background concentration for this area was determined by the

state to be 47.7 micrograms per cubic meter ( μg/m 3 ), or 18.2 ppb, 8 and that value was incorporated into the final AERMOD results.

Summary of Modeling Results

The AERMOD modeling parameters for the Monroe County area are summarized below in

Table 16

.

8 The conversion factor for SO 2 (at the standard conditions applied in the ambient SO 2 reference method) is 1ppb = approximately 2.62 μg/m 3

.63

Table 16 : AERMOD Modeling Parameters for the Monroe County, MI Area Monroe County, MI Area

AERMOD Version 14134 Dispersion Characteristics Rural

Modeled Sources 4

Modeled Stacks 7

Modeled Structures 35

Modeled Fencelines 4 Total receptors 68145

Emissions Type Monroe and IKO Monroe:

PTE

Guardian Industries and Gerdau

MacSteel Monroe: Actual

Emissions Years 2014 Meteorology Years 2012

- 2014 Surface Meteorology Station Toledo, OH Upper Air Meteorology Station White Lake Township, MI Methodology for Calculating Background SO 2 Concentration Sterling State Park Monitor Calculated Background SO 2 Concentration 47.7 μg/m 3

The results presented below in T able 17 show the magnitude and geographic location of the highest predicted modeled concentration based on actual and PTE emissions.

Table 17 : Maximum Predicted 99th Percentile 1

- Hour SO 2 Concentration in the Monroe County, MI Area Based on Actual and PTE Emiss ions

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

UTM/Latitude UTM/Longitude Modeled (including background) NAAQS
99th Percentile
1

- Hour Average 2012

- 2014 303710 4642500 159.8 196.4 * *Equivalent to the 2010 SO 2 NAAQS set at 75 ppb

The state’s modeling indicates that the predicted 99 th percentile 1

- hour average concentration within the chosen modeling domain is 159.8 μg/m 3 , or 6 1 ppb. This modeled concentration

included the background concentration of SO 2 , and is based on PTE emissions for Monroe and IKO Monroe and actual average emissions from Guardian Industries and Gerdau MacSteel

Monroe. Figure 25 below was included as part of the state’s recommendation, and indicates that the predicted value occurred 3 km northwest of the Monroe Power Plant.64

Figure 25 : Maximum Predicted 99 th Percentile 1

- Hour SO 2 Concentrations in the Monroe County Area Based on a Combination of Actual and PTE Emissions

Jurisdictional Boundaries

Once the geographic area of analysis associated with the Monroe Power Plant wa s determined, existing jurisdictional boundaries we re considered for the purpose of informing our intended

unclassifiable/ attainment area, specifically with respect to clearly de fined legal boundaries.

Michigan recommended the entirety of Monroe County, MI be designated attainment. Monroe County is bordered by an existing nonattainment area, in Wayne County, but the monitored violation and most of the sources contributing to violations in the Detroit area are in or near to the City of Detroit, over 15 km from the Monroe County border, and no sources in Wayne County would be considered to cont ribute to any potential air quality problems in Monroe County

. In the Toledo, Ohio area, south of Monroe County, the Bay Shore Power Plant emitted 2,002 tpy in 2014. Bay Shore is 5 km from the southeast border of Monroe County. Monroe County is also in the least frequent wind direction from the source. Therefore, Bay Shore is likely to be characterized under the DRR, but is unlikely to cause or contribute to a violation of the NAAQS within the state’s recommended boundaries. EPA does not have any infor mation on Whiting’s current impact on the area, and therefore cannot determine the collective impact of Monroe, Whiting, IKO Monroe, Guardian Industries, and Gerdau MacSteel Monroe . However

, EPA does not believe that there are any other sources of SO 2 in or around Monroe County with65

the potential to cause or contribute to a violation of the NAAQS within the state’s recommended boundary.

EPA believes that our intended unclassifiable area, consisting of Monroe County

, is comprised of clearly defined legal bo undaries, and we find these boundaries to be a suitably clear basis for defining our intended unclassifiable area.

Other Relevant Information

The Sierra Club also submitted modeling to EPA on September 17, 2015. This modeling

showed a violation of the standard for the Monroe Power Plant. The main difference between modeling from the state and modeling from Sierra Club is the emission levels modeled . Sierra

Club modeled actual emissions from 2012 to 2014. However, the actual emissions do not account for the recent controls and emission limits that were effective for the plant in 2014. EPA

believes that the federally enforceable emissions limits relied by the state are an appropriate basis

fo r the designation of Monroe County, notwithstanding the evidence from the Sierra Club that actual emissions from 2012 to 2014 may have caused violations of the SO 2 NAAQS.

Conclusion

After careful evaluation of the state’s recommendation and supporting i nformation, EPA is unable at this time to determine whether the area is meeting or not meeting the NAAQS, and
therefore intends to designate the area around the Monroe Power Plant as unclassifiable for the
2010 SO 2 NAAQS. EPA agrees that the modeling analysis assuming the shutdown of Whiting shows attainment of the standard, but EPA does not have any information on Whiting’s current impact on the area

, and therefore cannot determine the collective impact of all the sources in the

area . EPA intends to designate the entirety of Monroe County, MI as unclassifiable, but anticipates finalizing the designation of the area as unclassifiable/attainment once the source is
confirmed as shutdown.

At this time, our intended designat ions for the state only apply to this area and the other areas presented in this technical support document

. Consistent with the conditions in the March 2,
2015 court

- ordered schedule, EPA will evaluate and designate all remaining undesignated areas
in Michigan by either December 31, 2017, or December 31, 2020.66 Technical Analysis for the Ottawa County, MI Area

Introduction

Ottawa County contains a stationary source that according to EPA ’s Air Markets Database emitted in 2012 either more than 16,000 tons of SO 2 or more than 2,600 tons of SO 2 and had an annual average emission rate of at least 0.45 lbs SO 2 /MM BTU. As of March 2, 2015, this stationary source had not met the specific requirements for being “announced for retirement.” Specifically, in 2012

, the J.H. Campbell Generating Station (“J.H. Campbell”) emitted 21,501

tons of SO 2 , and had an emissions rate of 0.52 lbs SO 2 /MM BTU. Pursuant to the March 2, 2015

court

- ordered schedule, EPA must designate the area surrounding the facility by July 2, 2016.

In its submission, Michigan recommended that the area surrounding J.H. Campbell, specifically the entirety of Ottawa County, be designated as attainment based on an assessment and characterization of air quality from the facility and other nearby s ources which may have a potential impact in the area where maximum concentrations of SO 2 are expected. This assessment and characterization was performed using air dispersion modeling software, i.e., AERMOD, analyzing actual emissions. After careful revi ew of the state’s assessment, supporting documentation, and all available data, EPA agrees that the area is attaining the standard, and intends to designate Ottawa County as unclassifiable/attainment.

J.H. Campbell is located in Western Michigan in the c entral western end of Ottawa County adjacent to Lake Michigan approximately 16 km north of Holland, Michigan. Figure 26, below,

include s nearby emitters of SO 2 , the state’s recommended area for the attainment designation,

and EPA ’s intended unclassifiable/attainment designation for the area.67

Figure 26

. EPA ’s intended designation for Ottawa County, M I

The discussion and analysis that follows below will reference the state’s use of the Modeling TAD, EPA ’s assessment of the state’s modeli ng in accordance with the Modeling TAD, and the

factors for evaluation contained in EPA ’s March 20, 2015 guidance, as appropriate.

Detailed Assessment

Air Quality Data

This factor considers the SO 2 air quality monitoring data in the area near J.H. Campbell

. Michigan now operates a monitoring site in West Olive, in Ottawa County ( AQS site number 26

- 139

- 0011). However, this site only began operation in January 2015, so this site does not yet provide a useful indication of air quality in the Ottawa County area . Michigan previously operated a site in Jenison, also in Ottawa County ( AQS site number 26

- 139

- 0005). This site operated only in 2012 and 2013, for which the average of the two years’ 99 th per centile of daily maximum concentrations was 15 ppb, but this site did not collect sufficient data to provide a valid design value. Therefore, air quality monitoring in Ottawa County does not provide a reliable indication of whether the area is meeting the SO 2 NAAQS. A monitor in neighboring Kent County is not indicative of whether Ottawa County is meeting the SO 2 NAAQS.

Model Selection and Modeling Components68

EPA ’s Modeling TAD notes that for area designations under the 2010 SO 2 NAAQS, the AERMOD modeling system should be used, unless use of an alternative model can be justified. In some instances the recommended model may be a model other than AERMOD, such as the BLP model for buoyant line sources

. The AERMOD modeling system c ontains the following
components:

- AERMOD: the dispersion model

- AERMAP: the terrain processor for AERMOD

- AERMET: the meteorological data processor for AERMOD

- BPIPPRIME: the building input processor

- AERMINUTE: a pre

- processor to AERMET incorporating 1

- minute automated surface observation system (ASOS) wind data

- AERSURFACE: the surface characteristics processor for AERMET

- AERSCREEN: a screening version of AERMOD

Michigan relied on modeling performed on behalf of the owner of J.H. Campbell by a contractor named Horizon Environmental Corporation. The contractor used AERMOD version 14134. A discussion of the individual components will be referenced in the corresponding discussion that follows, as appro priate.

Modeling Parameter: Rural or Urban Dispersion

EPA ’s recommended procedure for characterizing an area by prevalent land use is based on evaluating the dispersion environment with 3 km of the facility. According to EPA ’s modeling guidelines, rural dispersion coefficients are to be used in the dispersion modeling analysis if

more than 50 percent of the area within a 3 km radius of the facility is classified as rural. Conversely, if more than 50 percent of the area is urban, urban dispersion coeffic ients should be used in the modeling analysis. When performing the modeling for the area , the state determined that it was most appropriate to run the model in rural mode. This approach, based on an Auer analysis of nearby land use, is consistent with th e generally rural nature of the area.

Modeling Parameter: Area of Analysis (Receptor Grid)

EPA believes that a reasonable first step towards characterization of air quality in the area surrounding J.H. Campbell is to determine the extent of the area of analysis, i.e., receptor grid

. Considerations presented in the Modeling TAD include but are not limited to: the location of the

SO 2 emission sources or facilities considered for modeling; the extent of significant concentration gradients of nearby sources; and sufficient receptor coverage and density to adequately capture and resolve the model predic ted maximum SO 2 concentrations

. For the Ottawa County area , the state identified no other significant emitters of SO 2 within 10 km of J.H. Campbell in any direction and more generally no other facilities that warranted being modeled in this analysis

. A si de from exceptionally large sources, sources farther than 10 km from J.H. Campbell would not cause significant concentration gradients in the Ottawa County area and69

therefore need not be modeled. The grid receptor spacing for the area chosen by the contra ctor is approximately as follows:

- Along the fenceline, receptors every 50 meters

- From the facility to 2 km, receptors every 100 meters

- From 2 km to 10 km, receptors every 200 meters

- From 10 km to 20 km, receptors every 500 meters

- From 20 km to 50 km, receptors every 1000 meters

The receptor network contained 12,447 receptors, and the network covered Ottawa County and portions of neighboring Allegan, Muskegon, and Kent Counties.

Figure 27 , included in the state’s recommendation, show s the receptor grid for the area

. Consistent with the Modeling TAD, receptors for the purposes of this designation effort were placed only in areas where it would also be feasible to place a monitor and record ambient air impacts . The contractor placed no receptors over Lake Michigan, and also did not place any receptors within the fenceline of J.H. Campbell. The impacts of the area’s geography and topography will be discussed later within this document.

Figure 27 : Receptor Grid for the J.H. Campbell Modeling Analysis

Modeling Parameter: Source Characterization

The contractor characterized J.H. Campbell in accordance with the best practices outlined in the Modeling TAD. Specifically, the contractor used actual stack heights in conjunction with actual

emissions. The contractor also adequately characterized J.H. Campbell’s building layout and70

location, as well as the stack parameters, e.g., exit temperature, exit velocity, location, and

diameter. Where appropriate, the AERMOD component BPIPPRIME was used to assist in addressing building downwash.

Modeling Parameter: Emissions

EPA ’s Modeling TAD notes that for the purposes of modeling to characterize air quality for use in designations, the recommended approach is to use the most recent 3 years of actual emissions data and concurrent meteorological data. The Modeling TAD highly encourages the use of the most detailed throughput, operating schedule, and emissions informat ion available.

Variable emissions, temperature, and flow data can be modeled using AERMOD’s hourly varying emissions keyword HOUREMIS or variable emission factor keyword EMISFACT. EPA believes that continuous emissions monitoring systems (CEMS) data pro vide valuable historical emissions information, when it is available, and that these data are available for m any electric generating units.

However, the TAD also provides the option to use allowable emissions reflecting the applicable, federally enforceab le emission limit (referred to as PTE or the allowable emissions rate). In certain instances, states and other interested parties may find that it is more advantageous or simpler to use PTE rates as part of their modeling runs

. Specifically, a facility m ay have recently adopted a new federally enforceable emissions limit, been subject to a federally enforceable consent decree, or implemented other federally enforceable mechanisms and control technologies to limit SO 2 emissions to a level that indicates co mpliance with the NAAQS

. These new limits or conditions may be used in the application of AERMOD

. In these cases, the Modeling TAD notes that the existing SO 2 emissions inventories used for permitting or SIP planning demonstrations should contain the nec essary emissions information for designations

related modeling

. In the event that these short

- term emissions are not readily available, they may be calculated using the methodology in Table 8

- 1 of Appendix W to 40 CFR Part 51 titled, “Guideline on Air Qua lity Models.”

J.H. Campbell has recently become subject to emission limits requiring significant emission reductions at the facility. However, the designation process must consider current air quality, and these limits do not take effect until June 30, 2016 for some units and December 31, 2016 for other units. Therefore, modeling for this analysis was primarily based on actual emissions, with the exception that the combustion turbine at the facility was modeled at an emission rate reflecting current wor st case fuel oil quality (15 ppm sulfur content) and at rated capacity.

As previously noted, the state included only J.H. Campbell in this analysis. Other sources in Ottawa County have sufficiently low emissions and are sufficient distance from J.H. Camp bell that the sources are causing no significant concentration gradient near J.H. Campbell, and their impacts may be considered as part of the monitored background concentration.71

Table 18 shows the emissions of J.H. Campbell and the other sources in Ott awa County emitting

over 100 tpy , showing the data EPA considered in concluding that these other sources need not be included in the J.H. Campbell modeling analysis. Sources outside Ottawa County are even less likely to have significant impacts in the Ottawa County area

.

Table 18 : Actual SO 2 Emissions from Facilities in Ottawa County, MI

Facility Name Actual SO 2 Emissions (tpy) Distance

from J.H. Campbell (km)

2012 2013 2014 J.H. Campbell 21,501 23,627 25,760

----

J.B. Sims 287 175 167 18

Holland WWTP 1,823 (Based on 2011 NEI) 15

Total Emissions in the Contractor’s Area of Analysis 21,501 23,627 25,760
Facilities in italics were not included in the modeling domain or in the Total Emissions in the Contractor’s Area of Analysis.

For J.H. Campbell, for the primary, coal

- fired emission units, the state used actual emissions

from the most recent 3

- year data set, i.e., 2012

– 2014

. These emissions data were obtained from

CEMS. For a combustion turbine at this fac ility, fired with diesel oil, the modeled emissions reflected worst case actual fuel quality (15 ppm sulfur) and capacity operation. (In discussion below, this combination of actual emissions data based on CEMS for the coal

- fired boilers with

maximum actu al emissions for the oil

- fired turbine will be referred to as based on actual emissions.)

Modeling Parameter: Meteorology and Surface Characteristics

The most recent 3 years of meteorological data (concurrent with the most recent 3 years of

emissions data) should be used in designations efforts

. As noted in the Modeling TAD, the selection of data should be based on spatial and climatological (temporal) representativeness

. The representativeness of the data are based on: 1) the proximity of the meteor ological monitoring site to the area under consideration, 2) the complexity of terrain, 3) the exposure of the meteorological site, and 4) the period of time during which data are collected

. Sources of meteorological data include National Weather Service (NWS) stations, site

- specific or onsite data, and other sources such as universities, Federal Aviation Administration (FAA), and military stations.

For the Ottawa County area , surface meteorology from the NWS station in Muskegon, Michigan,

29 km to the no rth, and coincident upper air observations from the NWS station in Green Bay, Wisconsin, approximately 230 km to the northwest, were selected as best representative of meteorological conditions within the area.72

The state used AERSURFACE using data from t he NWS station in Muskegon, Michigan ( located at 4 3.1711 1 ° N, 8 6.23667 ° W) to estimate the surface characteristics of the area . These surface characteristics are the albedo (the fraction of solar energy reflected from the earth back into space), the Bowen ratio (representing the ratio of sensible heat flux to latent heat flux at the ground level), and the surface roughness (representing the influence of ground features such as buildings and vege tation on surface wind flow). The state estimated values for 12 wind direction sectors, examining surface roughness out to 1 km and albedo and Bowen ratio for a 10 km square area centered on the NWS station. In the figure below, generated by EPA , the location of the Muskegon, Michigan NWS station is shown relative to J.H. Campbell.

Figure 28 : Ottawa County area and the Muskegon, Michigan NWS

As part of its recommendation, the state provided the 3

- year surface wind rose for Muskegon, Michigan. In Figure 29 , the frequency and magnitude of wind speed and direction are defined in terms of from where the wind is blowing. This figure shows that, if one examines all wind speeds, winds are somewhat more prone to blow from the west northwest, the south southwest, and the southeast, while if one focuses on low wind speeds, these winds are especially prone to

blow from the southeast.73

Figure 29 : Muskegon, Michigan Cumulative Annual Wind Rose for Years 2012

– 2014

Meteorological data from the above surface and uppe r air stations were used in generating

AERMOD

- ready files with the AERMET processor

. The output meteorological data created by the AERMET processor is suitable for being applied with AERMOD input files for AERMOD modeling runs

. The contractor followed th e methodology and settings presented in “Regional Meteorological Data Processing Protocol, EPA Region 5 and States,” Draft, August 2014, in the processing of the raw meteorological data into an AERMOD

- ready format, and used AERSURFACE to best represent sur face characteristics.

Hourly surface meteorological data records are read by AERMET, and include all the necessary elements for data processing

. However, wind data taken at hourly intervals may not always portray wind conditions for the entire hour, which can be variable in nature. Hourly wind data may also be overly prone to indicate calm conditions, which are not modeled by AERMOD

. In order to better represent actual wind conditions at the meteorological tower, wind data of one

minute duration was provided from the same instrument tower, but in a different formatted file to be processed by a separate preprocessor, AERMINUTE. These data were subsequently integrated into the AERMET processing to produce final hourly wind records of AERMOD

ready mete orological data that better estimate actual hourly average conditions and that are less
prone to over

- report calm wind conditions. This allows AERMOD to apply more hours of74

meteorology to modeled inputs, and therefore produce a more complete set of concen tration estimates. As a guard against excessively high concentrations that could be produced by AERMOD in very light wind conditions, the state set a minimum threshold of 0.5 meters per second in processing meteorological data for use in AERMOD. This app roach is consistent with a March 2013 EPA memo titled, “Use of ASOS meteorological data in AERMOD dispersion Modeling.” In setting this threshold, no wind speeds lower than this value would be used for determining concentrations. This threshold was speci fically applied to the one minute wind data.

Modeling Parameter: Geography and Terrain

The terrain in the area is best described as relatively flat. Nevertheless, to account for terrain changes, the AERMAP terrain program within AERMOD was used to spec ify terrain elevations for all the receptors. The source of the elevation data incorporated into the model is from the

USGS National Elevation Database.

Modeling Parameter: Background Concentrations of SO 2

The Modeling TAD offers two mechanisms for cha racterizing background concentrations of SO 2 that are ultimately added to the modeled design values: 1) a “first tier” approach, based on monitored design values, or 2) a temporally varying approach, based on the 99 th percentile monitored concentrations by hour of day and season or month. For the Ottawa County area , the state recommended a “first tier” approach based on data from the Grand Rapids ambient monitor ( AQS site number 26

- 081

- 0020) for the period 2012 to 201 4. The background concentration for

this area was determined by the state to be 27 micrograms per cubic meter ( μg/m 3 ), or 10.3 ppb, 9 and that value was incorporated into the final AERMOD results.

Summary of Modeling Results

The AERMOD modeling parameters for the Ottawa County area are summarized below in Table

19

.

Table 19 : AERMOD Modeling Parameters for the Ottawa County Area

J.H. Campbell, Michigan Area

AERMOD Version 14134 Dispersion Characteristics Rural

Modeled Sources 1

Modeled Stacks 3

Modeled Structures 1

Modeled Fencelines 1 Total receptors 12,447

9 The conversion factor for SO 2 (at the standard conditions applied in the ambient SO 2 reference method) is 1ppb = approximately 2.62 μg/m 3

.75 Emissions Type Boilers 1

- 3: Actual

Turbine: Maximum actual

Emissions Years 2012

- 2014 Meteorology Years 2012

- 2014 Surface Meteorology Station Muskegon, Michigan Upper Air Meteorology Station Green Bay, Wisconsin Methodology for Calculating Background SO 2 Concentration Fixed Concentration from Grand Rapids, Michigan Calculated Background SO 2 Concentration 27 μg/m 3

The results presented below in T able 20 show the magnitude and geographic location of the highest predicted modeled concentration based on actual emissions.

Table 20 : Maximum Predicted 99th Percentile 1

- Hour SO 2 Concentration in the Ottawa County

Area Based on Actual Emissions

Averaging

Peri od Data Period Receptor Location SO 2 Concentration ( μg/m 3 )

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

99th Percentile

1

- Hour Average 2012

- 2014 332800 4121600 139 196.4 * *Equivalent to the 2010 SO 2 NAAQS set at 75 ppb

The state’s modeling indicates that the predicted 99 th percentile 1

- hour average concentration within the chosen modeling domain is 139 μg/m 3 , or 53 ppb. This modeled concentration

included the background concentration of SO 2 , and is based on actual emissions from J .H. Campbell (with turbine emissions based on maximum actual emissions). Figure 3 0 below was included as part of the state’s recommendation, and indicates that the predicted value occurred 3.5 km northeast of the facility.76

Figure 3 0 : Maximum Predicted 99 th Percentile 1

- Hour SO 2 Concentrations in Ottawa County

Area Based on Actual Emissions

Jurisdictional Boundaries

Once the geographic area of analysis associated with J.H. Campbell was determined, existing jurisdictional boundaries were considered for the purpose of informing our intended unclassifiable/attainment area, specifically with respect to clearly defined legal boundaries

. The state recommended designation of the entirety of Ottawa County. Ottawa County has clearly defined, well known boundaries that appropriately define the area to be designated. While the contractor’s modeling analysis did not include the emissions from either Holland WWTP or J.B. Sims, EPA does not believe that emissions from these facilities are causing or contribu ting to violations of the NAAQS within the area of analysis, and subsequently

– the entirety of Ottawa County. T he contractor modeled a 50 km grid around J.B. Campbell as attaining the standard with the maximum impact 3.5 km away from the facility. Based on the distance between J.H. Campbell and either Holland WWTP or J.B. Sims (approximately 15 km), EPA does not believe that emissions from either of these sources would impact the modeled maximum concentration. The B.C. Cobb Generating Station, in Muskeg on County, 14 km north of Ottawa County’s northern boundary, and 38 km north of J.H. Campbell, emitted 9,266 tons of SO 2 in 2014. B.C. Cobb is not only far enough from J.H. Campbell to be unlikely to cause significant concentration gradients near J.H. Cam pbell, it is also of sufficient distance from the intended

unclassifiable/attainment area , considering its size, as to be unlikely to causing or contributing to

a violation within the area. For comparison, as noted above, J.H. Campbell , emitting an average

of 23,629 tons per year in 2012 to 2014, had a peak concentration (below the NAAQS) at a

distance of 3.5 km from the plant. In addition , due to a consent decree, B.C. Cobb must retire or switch to natural gas by April 15, 2106. Ther efore, EPA believes that our intended77

unclassifiable/attainment area, consisting of the entirety of Ottawa County, applies clearly defined legal boundaries, and we find these boundaries to be a suitably clear basis for defining

our intended unclassifiable/ attainment area.

Other Relevant Information

No other relevant information was received for this area.

Conclusion

After careful evaluation of the state’s recommendation and supporting information, as well as all available relevant information, EPA intends to designate the area around J.H Campbell as

unclassifiable/attainment for the 2010 SO 2 NAAQS. Specifically, the unclassifiable/attainment

area would be defined to incl ude the entire Ottawa County.

At this time, our intended designations for t he state only apply to this area and the other areas presented in this technical support document. Consistent with the conditions in the March 2,

2015 court

- ordered schedule, EPA will evaluate and designate all remaining undesignated areas in Michigan by either December 31, 2017, or December 31, 2020.