## Monroe Power Plant

Monroe, Michigan

Evaluation of Compliance wi th the 1-hour NAAQS for SO 2



## September 16, 2015

Conducted by:

Steven Klafka, P.E., BCEE

Wingra Engineering, S.C.

Madison, WisconsinEvaluation of Compliance with the 1-hour NAAQS for SO 2 September 16, 2015 Page 2

1. Introduction

Wingra Engineering, S.C. was hi red by Sierra Club to conduct an air modeling impact analysis to help the U.S. Environmental Prot ection Agency (USEPA), state an d local air agencies identify
facilities that are likely causing exceedances of the 1-hour su lfur dioxide (SO 2 ) national ambient air quality standard (NAAQS). This doc ument describes the results and procedures for an evaluation
conducted for the Monroe Power Pl ant located in Monroe, Michiga n.

To ensure the modeling analysis reflected the cumulative concen tration of SO 2 emissions, it included
emissions from the followi ng additional sources of SO 2 emissions located within 50 kilometers of
the Monroe Power Plant:

 River Rouge Power Plant - River Rouge, Michigan

 Trenton Channel Power Plant - Trenton, Michigan

 City of Wyandotte Municipal Pow er Plant - Wyandotte, Michigan

 J.R. Whiting Plant - Erie, Michigan

 Bay Shore Plant - Oregon, Ohio

 U.S. Steel Great Lakes W orks - Ecorse, Michigan

The dispersion modeling analysis predicted ambient air concentr ations for comparison with the 1-
hour SO 2 NAAQS. The modeling was performe d using the most recent versi on of AERMOD, AERMET, and AERMINUTE, with data provided to Sierra Club by reg ulatory air agencies or obtained through other publicly-a vailable sources as documented below. The analysis was
conducted in adherence to all ava ilable USEPA guidance for eval uating source impacts on
attainment of the 1-hour SO 2 NAAQS via aerial dispersion m odeling, including the AERMOD Implementation Guide; USEPA's A pplicability of Appendix W Model ing Guidance for the 1-hour
SO 2 National Ambient Air Qual ity Standard, August 23, 2010; modeli ng guidance promulgated by USEPA in Appendix W to 40 CFR Part 51; USEPA’s March 2011 Model ing Guidance for SO 2 NAAQS Designations; 1 and, USEPA’s December 2013 SO 2 NAAQS Designations Technical
Assistance Document. 2

It was determined that based on eit her current allowable emissi ons or measured actual emissions, the
Monroe Power Plant is estim ated to create downwind SO 2 concentrations which exceed the 1-hour NAAQS.

1 http://www.epa.gov/scram001/ so2_modeling_guidance.htm

2 http://www.epa.gov/oaqps001/sulfurdioxide/pdfs/SO2ModelingTAD. pdfEvaluation of Compliance with the 1-hour NAAQS for SO 2 September 16, 2015 Page 3

2. Compliance with the 1-hour SO 2 NAAQS

2.1 1-hour SO 2 NAAQS

The 1-hour SO 2 NAAQS takes the form of a t hree-year average of the 99 th percentile of the annual distribution of daily maximum 1- hour concentrations, which cann ot exceed 75 parts per billion (ppb). 3 Compliance with this standar d was verified using USEPA’s AERM OD air dispersion model, which produces air concentr ations in units of μg/m 3 . The 1-hour SO 2 NAAQS of 75 ppb equals 196.2 μg/m 3 , and this is the value used for determining whether modeled im pacts exceed the NAAQS. 4 The 99 th percentile of the annual dist ribution of daily maximum 1-hour concentrations corresponds to the fourth-highest value at each receptor for a given year.

2.2 Modeling Results

Modeling results for Monroe Powe r Plant, five other power plant s, and one industrial facility are
summarized in Table 1. Results are provided for the Monroe Powe r Plant alone, and for all facilities
combined. It was determined tha t based on either current allowa ble emissions or measured actual emissions, the Monroe Power Plant is estimated to create downwi nd SO 2 concentrations which exceed the 1-hour NAAQS.

More specifically, the modeling results presented in Table 1, s how exceedances of the NAAQS by the plant’s allowable and actua l emissions. “Allowable” is the peak emission rate from each unit as approved by the current air quali ty operation permit for the fa cility. The allowable emission results are for the six power plants and do n ot include those from the industrial facil ity, US Steel.

For the six power plants, “actua l” are the measured emissions f or each hour between January 1, 2012 and December 31, 2014 as taken from USEPA Air Markets Program Data

. 5 For US Steel, actual emissions are the annual average of emissions reported for cale ndar year 2014.

In addition, the emissions from the other six facilities signif icantly contribute to the ambient SO 2 concentration in the area impacted by Monroe Power Plant.

Air quality impacts in Michi gan are based on a background conce ntration of 2.6 μg/m 3 . This is the 2011-13 design value for Wayne Count y, Michigan - the lowest me asured background concentration in the state. This is the most recently available design value . See Section 5 for f urther discussion of

3 USEPA, Applicability of Appendix W Modeling Guidance for the 1- hour SO 2 National Ambient Air Quality Standard, August 23, 2010.

4 The ppb to μg/m 3 conversion is found in the source code to AERMOD v. 14134, sub routine Modules. The conversion calculation is 75/0.3823 = 196.2 μg/m 3

. 5 http://ampd.epa.gov/ampd/Evaluation of Compliance with the 1-hour NAAQS for SO 2 September 16, 2015 Page 4

the background concentrations used for this analysis.

Table 1 - SO 2 Modeling Results for Monroe Power Plant Modeling Analysis

Emission Rates Facility 99 th Percentile 1-hour Daily Maximum (μg/m 3 ) Complies with NAAQS? Impact Background Total NAAQS

Allowable Monroe 220.8 2.6 223.4 196.2 No

Actual 281.3 2.6 283.9 196.2 No

Allowable All Facilities without Whiting 272.3 2.6 274.9 196.2 No

Actual 289.2 2.6 291.8 196.2 No

Allowable All Facilities 551.6 2.6 554.2 196.2 No

Actual 289.9 2.6 292.5 196.2 No

The emissions used for the mode ling analysis are summarized in Table 2.

Based on the modeling results, Table 3 provides the emission re ductions from current allowable rates necessary to achieve com pliance with the 1-hour NAAQS. T his assumes a one-hour averaging period for the emission rate and that the emission rate is bind ing at all times. However, given the conservative aspects of this modeling protocol, it is extremely likely that this limit is too high to protect the NAAQS. For example , startup or shutdown periods wer e not evaluated. During these periods, decreased gas velocities and temperatures may lead to greater ambient impacts at ground level. Further, the hypothetic al emission limitation in Table 3 would allow Monroe Power Plant to consume the entire NAAQS, leav ing little to no room for any oth er source of SO 2 in the area. No margin of safety has been incl uded in the hypothetical emission limitation.

Predicted exceedances of the 1-hour NAAQS for SO 2 based on allowable emissions extend throughout the region to a maxim um distance of 50 kilometers.

Figure 1 shows the extent of NAA QS violations based on allowabl e emissions from all six power plants.

Figure 2 shows the extent of NAA QS violations based on actual h ourly emissions from all facilities.Evaluation of Compliance with the 1-hour NAAQS for SO 2 September 16, 2015 Page 5

Table 2 - Modeled SO 2 Emissions 6

Stack

ID Unit
ID Allowable Emissions (lbs/hr) Actual Emissions (lbs/hr)

M01 Unit 1 2,462.6 2012-14 CEM M02 Unit 2 2,462.6 2012-14 CEM M03 Unit 3 2,462.6 2012-14 CEM M04 Unit 4 2,462.6 2012-14 CEM Monroe Facility Subtotal 9,850.2 2012-14 CEM Bay Shore - B01 Unit B006 1,897.6 2012-14 CEM R02 Unit 2 3,807.6 2012-14 CEM R03 Unit 3 4,458.9 2012-14 CEM River Rouge Facility Subtotal 8,266.5 2012-14 CEM

T01 Unit 16 907.2 2012-14 CEM

Unit 17 907.2 2012-14 CEM

Unit 18 907.2 2012-14 CEM

Unit 19 907.2 2012-14 CEM Stack Subtotal 3,628.8 2012-14 CEM T02 Unit 9 8,984.8 2012-14 CEM Trenton Channel Facility Subtotal 12,613.6 2012-14 CEM

W07 Boiler 07 390.0 2012-14 CEM

W08 Boiler 08 183.0 2012-14 CEM Wyandotte Facility Subtotal 573.0 2012-14 CEM J01 Boiler 1 1,900.0 2012-14 CEM J02 Boiler 2 2,100.0 2012-14 CEM J03 Boiler 3 2,400.0 2012-14 CEM JR Whiting Facility Subtotal 6,400.0 2012-14 CEM

SV0003 Coke Battery - 18.8 SV0007 Hot Strip Mill - 195.3

SV0013 A Furnace BFG Flare - 38.7 SV0017 D Furnace Baghouse - 14.1

SV0018 D Furnace Stove - 123.0

SV0025 No. 2-1 Boiler - 126.6 US Steel Facility Subtotal 516.5

6 Monroe allowable emissions were taken from MDEQ, Renewal Opera ting Permit MI-ROP-82816-2009a, July 25, 2011. Bay Shore Plant allowable emissions were taken from OEPA, Final Air Pollution Control Title V Permit, P0105130, June 24, 2014. River Rouge allowable emissions were t aken from MDEQ, Renewal Operating Permit MIROP-B2810-2012, April 1, 2012. Trenton Channel Power Plant allo wable emissions were taken from MDEQ, Renewal Operating Permit 199600204, September 22, 2003. Wyandotte Munic ipal Power Plant allowable emissions were taken from MDEQ, Renewal Operating Permit MI-ROP-B2132-2010, April 15 , 2010. J.R. Whiting Plant allowable emissions were taken from MDEQ, Renewal Operating Permit MI-ROP-B2846-201 3, July 1, 2013.Evaluation of Compliance with the 1-hour NAAQS for SO 2 September 16, 2015 Page 6

Table 3 - Required Emission Reductions from Monroe Power Plant for Compliance with the 1-

hour NAAQS for SO 2 Acceptable Impact (NAAQS - Background) 99th Percentile 1-hour Daily Max (μg/m 3 ) Required Total Facility Reduction Based on Allowable Emissions (%) Required Total Facility Emission Rate (lbs/hr) Required Total Facility 1-hour Average Emission Rate

(lbs/mmbtu)

193.6 65% 3,457.2 0.11

2.3 Conservative Modeling Assumptions

A dispersion modeling analysis requires the selection of numero us parameters which affect the predicted concentrations. For the enclosed analysis, several pa rameters were selected which underpredict facility impacts.

Assumptions used in this modeli ng analysis which likely under-e stimate concentrations include the following:

 Allowable emissions are base d on a limitation with an averaging period which is greater than the 1-hour average used for the SO 2 air quality standard. Emissions and impacts during any 1-hour period may be higher than assumed for the modeling analy sis.

 No consideration of facility operation at less than 100% load. Stack parameters such as exit flow rate and temperature are typically lower at less than full load, reducing pollutant dispersion and increasing predic ted air quality impacts.

 No consideration of building or s tructure downwash. These downw ash effects typically increase predicted concentr ations near the facility.

 Except for the five other power plants and the US Steel facilit y, no consideration of off-site

sources. Any other off-site sources of SO 2 will increase the predicted impacts.Evaluation of Compliance with the 1-hour NAAQS for SO 2 September 16, 2015 Page 7

Figure 1 - Regional View of Impacts Based on Allowable Emissions from All Six Power PlantsEvaluation of Compliance with the 1-hour NAAQS for SO 2 September 16, 2015 Page 8

Figure 2 - Regional View of Impacts Based on Actual Emissions from All FacilitiesEvaluation of Compliance with the 1-hour NAAQS for SO 2 September 16, 2015 Page 9

3. Modeling Methodology

3.1 Air Dispersion Model

The modeling analysis used U SEPA’s AERMOD program, v. 14134. A ERMOD, as available from the Support Center for Regulator y Atmospheric Modeling (SCRAM) website, was used in conjunction with a third-par ty modeling software program, AERMOD View , sold by Lakes
Environmental Software.

3.2 Control Options

The AERMOD model was run with t he following control options:

 1-hour average air concentrations

 Regulatory defaults

 Flagpole receptors

To reflect a representative i nhalation level, a flagpole height of 1.5 meters was used for all modeled receptors. This parameter was added to the receptor file when running AERMAP, as described in
Section 4.4.

An evaluation was conducted to det ermine if the modeled facilit y was located in a rural or urban setting using USEPA’s methodology outlined in Section 7.2.3 of the Guideline on Air Quality
Models. 7 For urban sources, the URBANOPT option is used in conjunction with the urban population from an appropriate ne arby city and a default surfac e roughness of 1.0 meter. Methods
described in Section 4.1 were used t o determine whether rural o r urban dispersion coefficients were appropriate for the modeling analysis.

3.3 Output Options

The AERMOD analysis was based on three years of recent meteorol ogical data. The modeling analyses used one run with three ye ars of sequential meteorolog ical data from 2012-2014. Consistent with USEPA’s Modeling Guidance for SO 2 NAAQS Designations, AER MOD provided a table of fourth-high 1-hour SO 2 impacts concentrations consiste nt with the form of the 1-hour SO 2 NAAQS. 8

Please refer to Table 1 for the modeling results.

7 USEPA, Revision to the Guidelin e on Air Quality Models: Adopti on of a Preferred General Purpose (Flat and Complex Terrain) Dispersion Model and Other Revisions, Appendix W to 40 CFR Part 51, November 9, 2005.

8 USEPA, Area Designations for the 2010 Revised Primary Sulfur Di oxide National Ambient Air Quality Standards, Attachment 3, March 24, 2011, pp. 24-26.Evaluation of Compliance with the 1-hour NAAQS for SO 2 September 16, 2015 Page 10

4. Model Inputs

4.1 Geographical Inputs

The “ground floor” of all air dis persion modeling analyses is e stablishing a coordinate system for identifying the geographical loc ation of emission sources and r eceptors. These geographical
locations are used to determine local characteristics (such as land use and elevation), and also to ascertain source to receptor di stances and relationships.

The Universal Transverse Merca tor (UTM) NAD83 coordinate system was used for identifying the easting (x) and northing (y) coordi nates of the modeled sources and receptors. Stack locations were obtained from facility permits and prior modeling files provide d by the state regulatory agency. The
stack locations were then veri fied using aerial photographs.

The facility was evaluated to de termine if it should be modeled using the rural o r urban dispersion coefficient option in AERMOD. A Geographic Information System (GIS) was used to determine whether rural or urban dispersi on coefficients apply to a site. Land use within a three-kilometer radius circle surrounding the f acility was considered. USEPA gu idance states that urban dispersion
coefficients are used if more t han 50% of the area within 3 kil ometers has urban land uses. Otherwise, rural dispersion c oefficients are appropriate. 9

USEPA’s AERSURFACE v. 13016 was use d to develop the meteorologi cal data for the modeling analysis. This model was also us ed to evaluate surrounding land use within 3 kilometers. Based on the output from the AERSURFAC E, approximately 9.9% of surroundi ng land use around the modeled facility was of urban l and use types including Type 21 – Low Intensity Residential, Type 22 – High Intensity Residential and Type 23 – Commercial / Indu strial / Transportation.

This is less than the 50% value c onsidered appropriate for the use of urban dispersion coefficients. Based on the AERSURFACE analysis, i t was concluded that the rur al option would be used for the modeling summarized in this re port. Please refer to Section 4. 5.3 for a discussion of the AERSURFACE analysis.

9 USEPA, Revision to the Guidelin e on Air Quality Models: Adopti on of a Preferred General Purpose (Flat and Complex Terrain) Dispersion Model and Other Revisions, Appendix W to 40 CFR Part 51, November 9, 2005, Section 7.2.3.Evaluation of Compliance with the 1-hour NAAQS for SO 2 September 16, 2015 Page 11

4.2 Emission Rates and Source Parameters

The modeling analysis considered SO 2 emissions from Monroe, five other power plants, and one industrial facility. Other off-s ite sources were not considered . Concentrations were predicted for the
scenarios shown in Tables 1 and 2:

1) allowable emissions based on t he current permit issued by th e regulatory agency, and

2) for the six power plants actua l hourly emissions measured ea ch hour between January 1, 2012 and December 31, 2014 as taken from USEPA Air Markets Program Data

. 10 For the industrial facility, US Steel, a ctual emissions are the annual average of emissions reported for calendar year 2014.

Stack parameters and emissions use d for the modeling analysis a re summarized in Table 4.

The stack parameters and emissi ons were obtained from regulator y agency documents and databases
identified in Section 2.2. The analysis was conducted based on 100% operating load using maximum exhaust flow rates and temperat ures. Operation at less than ful l capacity loads was not considered. This assumption tends to under-pre dict impacts since stack para meters such as exit flow rate and temperature are typically lower at less than fu ll load, reducin g pollutant dispersion and increasing predicted air quality impacts. S tack location, height and diame ter were verified using aerial photographs, and flue gas flow rat e and temperature were verifi ed using combustion calculations.

10 http://ampd.epa.gov/ampd/Evaluation of Compliance with the 1-hour NAAQS for SO2September 16, 2015Page 12Table 4 – Facility Stack Parameters and Emissions11Facility Stack DescriptionX Coordinate[m]Y Coordinate[m]BaseElevation[m]ReleaseHeight[m]ExitTemperature[K]ExitVelocity[m/s]InsideDiameter[m]AllowableEmissions[g/s]ActualEmissions[g/s]MonroeM01 Unit 1 305534 4640274 175.71 176.48 325.928 39.624 6.309 310.3 -M02 Unit 2 305538 4640278 175.92 176.48 325.928 39.624 6.309 310.3 -M03 Unit 3 305379 4640207 177.27 176.48 325.928 39.624 6.309 310.3 -M04 Unit 4 305385 4640211 177.25 176.48 325.928 39.624 6.309 310.3 -TrentonT01 Units 16 to 19 319707 4665685 177.39 170.38 427.59 42.672 4.42 457.2 -T09 Unit 9A 319740 4665610 177.28 171.15 410.93 42.672 4.877 1132 -River RougeR02 Unit 2 325806 4682363 175.03 117.35 420.93 48.768 3.665 479.7 -R03 Unit 3 325771 4682374 175.06 129.54 433.15 48.768 3.911 561.8 -J.R. WhitingJ01 Boiler 1 296512 4629557 176.98 90.53 414.261 16.982 3.231 239.4 -J02 Boiler 2 296512 4629576 176.91 90.53 417.039 17.903 3.231 264.6 -J03 Boiler 3 296512 4629596 176.92 90.53 426.483 11.665 3.523 302.4 -Bay Shore B01 Unit B006 297140 4618518 177.07 91.44 423.706 24.659 3.658 239.1 -WyandotteW07 Unit 7 322901 4675118 175.15 52.73 413.706 8.47 2.794 49.14-W08 Unit 8 322853 4675144 176.51 65.53 435.928 10.71 1.981 23.05 -US SteelSV001 Coke Battery 325930.8 4683222 177.32 14.63 294.261 21.1050.509 - 1.751SV003 Hot Strip Mill 326024.8 4683094 177.06 34.75 366.483 10.349 3.048 - 2.369SV007 A Furnace 325549.8 4681690 175.29 31.09 477.594 1.617 4.267 - 24.61SV0013 D Baghouse 326107.8 4683835 176.6 33.22 544.261 21.184 1.396 - 4.876SV0017 D Stove 326179.8 4683430 177.04 20.73 294.261 15.25 3.292 - 1.777SV0018 No. 2-1 Boiler 326207.8 4683389 176.96 70.1 560.928 13.531 2.819 - 3.301SV0020 No. 1-1 Boiler 326326.8 4683772 176.45 20.73 560.928 17.106 1.676 - 8.53SV0025 No. 2-1 Boiler 326278.8 4683326 176.77 26.82 560.928 7.484 2.972 - 15.9511Monroe, River Rouge, Trenton Channel, Wyandotte and Whiting stack parameters obtained from USEIA, 2012 Form EIA-860 Data - Schedule 6, Stack & Flue Data,http://www.eia.gov/electricity/data/eia860/. Bay Shore stack parameters obtained from OEPA, Facility Profile Report, September8, 2015. US Steel stack parameters andactual emissions obtained from MDEQ, Michigan Air Emissions Reporting System (MAERS) for 2014.Evaluation of Compliance with the 1-hour NAAQS for SO 2 September 16, 2015 Page 13

4.3 Building Dimensions

No building dimensions or prior dow nwash evaluations were avail able. Therefore this modeling analysis
did not address the effects of downwash and this may under-pred ict impacts.

4.4 Receptors

For Monroe Power Plant, three receptor grids were employed:

1. A 100-meter Cartesian receptor gr id centered on Monroe Power Pl ant and extending out 5
kilometers.

2. A 500-meter Cartesian receptor gr id centered on Monroe Power Pl ant and extending out 10
kilometers.
3. A 1,000-meter Cartesian receptor grid centered on Monroe Power Plant and extending out 50 kilometers. 50 kilometers is the maximum distance accepted by U SEPA for the use of the AERMOD dispersion model. 12

A flagpole height of 1.5 meters w as used for all these receptor s.
Elevations from stacks and recep tors were obtained from Nationa l Elevation Dataset (NED) GeoTiff data. GeoTiff is a binary file tha t includes data descriptors a nd geo-referencing information necessary for extracting terrain elevations. The se elevations were extracted from 1 arc-second (30 meter) resolution
NED files. The USEPA softwar e program AERMAP v. 11103 is used f or these tasks.

4.5 Meteorological Data

To improve the accuracy of the modeling analysis, recent meteor ological data for the 2012-2014 period were prepared using the USEPA’s pr ogram AERMET which creates th e model-ready surface and profile data files required by AERMOD. Required data inputs to AERMET included surface meteorological measurements, twice-daily soundi ngs of upper air measurements, and the micrometeorological parameters surface roughness, albedo, and Bowen ratio. One-min ute ASOS data were available so
USEPA methods were used t o reduce calm and missing hours. 13 The USEPA software program
AERMINUTE v. 14237 is used for these tasks.

For this modeling project, pre-pr ocessed meteorological data we re provided by the Michigan Department of Environmental Quality (DEQ). 14, 15 Data for the 2012 to 2013 period wer e downloaded from the DEQ

12 USEPA, Revision to the Guideline on Air Quality Models: Adopti on of a Preferred General Purpose (Flat and Complex Terrain) Dispersion Model and Other Revisions, Appendix W to 40 CFR Part 51, Section A.1.(1), November 9, 2005.

13 USEPA, Area Designations for the 2010 Revised Primary Sulfur D ioxide National Ambient Air Quality Standards, Attachment 3, March 24, 2011, p. 19.

14 Michigan Department of Environmental Quality, Map of Available Meteorological Stations, http://www.michigan.gov/documents/deq/deq-aqd-mm-met_support_25 6121_7.pdfEvaluation of Compliance with the 1-hour NAAQS for SO 2 September 16, 2015 Page 14

web site and data for the 2014 pe riod were provided directly by DEQ. The agency prepared its meteorological data using the proc edures described in this repo rt.

This section discusses how the meteorological data was prepared for use in the 1-hour SO 2 NAAQS modeling analyses. The USEPA software program AERMET v. 14134 is used for these tasks.

4.5.1 Surface Meteorology

Surface meteorology was obtained for Custer Airport located nea r the Monroe Power Plant. Integrated Surface Hourly (ISH) data for the 2012-2014 period were obtaine d from the National Climatic Data Center (NCDC). The ISH surf ace data was processed through AER MET Stage 1, which performs data extraction and qualit y control checks.

4.5.2 Upper Air Data

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

For Monroe Power Plant, the concurrent 2012-2014 upper air datafrom twice-daily radiosonde
measurements obtained at the most representative location were used. This location was the White Lake, Michigan measurement station. These data are in Forecast System s Laboratory (FSL) format and were
downloaded in ASCII text forma t from NOAA’s FSL website. 16 All reporting levels were downloaded and processed with AERMET.

4.5.3 AERSURFACE

AERSURFACE is a program that ex tracts surface roughness, albedo , and daytime Bowen ratio for an area surrounding a given locati on. AERSURFACE uses land use an d land cover (LULC) data in the U.S. Geological Survey’s 1992 Nationa l Land Cover Dataset to extract the necessary micrometeorological data. LULC data was used for proc essing meteorological data se ts used as input to AERMOD.

AERSURFACE v. 13016 was used to deve lop surface roughness, albe do, and daytime Bowen ratio values in a region surrounding the meteorological data collecti on site. AERSURFACE was used to

15 Email from J. Haywood – MDEQ to S. Klafka – Wingra Engineering , S.C., Request for AERMOD Modeling Meteorology for Michigan Power Plants, May 18, 2015.

16 Available at: http://esrl.noaa.gov/raobs/Evaluation of Compliance with the 1-hour NAAQS for SO 2 September 16, 2015 Page 15

develop surface roughness in a one kilometer radius surrounding the data collection site. Bowen ratio and albedo was developed for a 10 kilometer by 10 kilometer are a centered on the meteorological data
collection site.

4.5.4 Data Review

Missing meteorological data were not filled as the data file me t USEPA’s 90% data completeness requirement. 17 The AERMOD output file shows th ere were 2.1% missing data.

To confirm the representativene ss of the airport meteorological data, the surface characteristics of the airport data collection site a nd the modeled source location we re compared. Since the Custer Airport is
located close to Monroe Power Pla nt, this meteorological data s et was considered appropriate for this modeling analysis. 18 This weather station provided high quality surface measurement s for the most recent 3-year time, and had similar land use, surface character istics, terrain features and climate. Finally, DEQ provided pre-processed meteoro logical data for this project and had concluded that the weather stations were representati ve of the project location.

5. Background SO 2 Concentrations

Background concentrations were determined consistent with USEPA ’s Modeling Guidance for SO 2 NAAQS Designations. 19, 20 To preserve the form of the 1-hour SO 2 standard, based on the 99 th percentile
of the annual distri bution of daily maximum 1-hour concentratio ns averaged across the number of years modeled, the background fourth-hig hest daily maximum 1-hour SO 2 concentration was added to the modeled fourth-highest d aily maximum 1-hour SO 2 concentration. 21 Background concentrations were based on the 2011-13 design value meas ured by the ambient monit ors located in Michigan. 22

6. Reporting

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

17 USEPA, Meteorological Monitoring Guidance for Regulatory Modeli ng Applications, EPA-454/R-99-05, February 2000, Section 5.3.2, pp. 5-4 to 5-5.

18 USEPA, AERMOD Implementation Guide, March 19, 2009, pp. 3-4.

19 USEPA, Area Designations for the 2010 Revised Primary Sulfur D ioxide National Ambient Air Quality Standards, Attachment 3, March 24, 2011, pp. 20-23.

20 USEPA, SO 2 NAAQS Designations Modeling Te chnical Assistance Document, Dec . 2013, section 8.1, pp 27-28.

21 USEPA, Applicability of Appendix W Modeling Guidance for the 1- hour SO 2 National Ambient Air Quality Standard, August 23, 2010, p. 3.

22 http://www.epa.gov/airtrends/values.html