September 2, 2015

Via Hand Delivery

Sean Alteri, Director

Division for Air Quality

200 Fair Oaks Lane, First Floor

Frankfort, Kentucky 40601

RE: John Sherman Cooper Power Station (AI 3808)

Burnside, Pulaski County, Kentucky

2010 1-Hour SO2 NAAQS Designation Analysis

Dear Mr. Alteri:

East Kentucky Power Cooperative, Inc. (EKPC) submits the enclosed Air Dispersion 

Modeling Report – Cooper Station -- SO2 NAAQS Designation Analysis (the Report), prepared 

by Trinity Consultants, for the Division’s review and use. This analysis was prepared in support 

of the Division’s response to the U.S. Environmental Protection Agency’s (EPA) March 20, 

2015 letter to Commissioner Bruce Scott of the Kentucky Department of Environmental 

Protection (KDEP). The Report is the result of the dispersion modeling conducted pursuant to 

the Air Dispersion Modeling Protocol for Cooper Station SO2 Designation Analysis submitted by 

EKPC to the Division on August 3, 2015, as revised in response to subsequent discussion of 

comments from the Division and EPA, including the discussion on the August 27, 2015 

conference call among EPA, the Division and EKPC. 

A. Summary of Report Conclusions

The analysis demonstrates that the maximum modeled impacts (expressed in the form of 

the 1-hour SO2 National Ambient Air Quality Standard (NAAQS)) including emissions from 

Cooper Station, emissions from the selected regional sources, and the background concentration 

are below the 1-hour SO2 NAAQS. Specifically, the maximum combined impact is 173.1 μg/m3

as compared to the 1-hour SO2 NAAQS of 196 μg/m3 (75 ppb). Therefore, this modeling 

demonstrates that the area surrounding the Cooper Station should be designated attainment for 

the 1-hour SO2 NAAQS.

B. Federally Enforceable Limits

As explained in the Report, EKPC modeled actual emissions from Cooper Unit 2 and 

allowable emissions from Cooper Unit 1. Cooper Unit 2 is subject to a federally enforceable

SO2 emission limit of 95 percent removal efficiency 30-day rolling average or 0.100 lb/MMBtu 

SO2 30-day rolling average, which has been in place since July 1, 2012. See Condition B.2.c. of 

Title V Permit No. V-12-019R1, which was added to the permit pursuant to the Consent Decree 

4775 Lexington Road 40391 Tel. (859) 744-4812

P.O. Box 707, Winchester Fax: (859) 744-6008

Kentucky 40392-0707 http://www.ekpc.coop
September 3, 2015

Page | 2

between EPA and EKPC entered September 24, 2007 in Civil Action No. 04-34-KSF. The Unit 

2 modeled actual emissions reflect operation of the unit in compliance with this limit. 

For Cooper Unit 1, EKPC modeled an allowable emission rate of 178 pounds/hour (0.165 

lb/MMBtu) derived from the existing Title V permit limit of 3.3 lb/MMBtu SO2 24-hour average 

assuming 95 percent reduction and operating at 1080 MMBtu/hr for 8,760 hours per year. The 

95 percent reduction was applied to the existing permit limit because EKPC expects to meet a 

federally enforceable SO2 emission limit of 95 percent removal efficiency 30-day rolling average 

or 0.100 lb/MMBtu SO2 30-day rolling average on both Cooper units once the tie-in of Unit 1 

into the Unit 2 Dry Flue Gas Desulfurization (DFGD) System is complete later this year. EKPC 

chose to model Unit 1 at 0.165 lb/MMBtu instead of 0.100 lb/MMBtu to account for the dual 

nature of the limit (either 95 percent removal or 0.100 lb/MMBtu) and the associated averaging 

period. 

Although EKPC’s implementation of the Cooper 1 Reroute Project (with resulting 

emission reductions) was initiated to comply with the Consent Decree requirement for a 

Pollution Control Upgrade Analysis, upon further review, EKPC has determined that the better 

course is to submit an application for revision of the Title V permit to impose the same limitation 

on Cooper Unit 1 as already spelled out in the permit for Unit 2. EKPC will work with the 

Division to assure that the permit revision is finalized before the July 2, 2016 deadline for EPA 

to make its designations of attainment status for the NAAQS. Once these limits are in place, 

EKPC’s position is that the Report reflects modeling of federally enforceable limits and that no 

other limits are necessary.

EKPC appreciates DAQ’s review of this submittal and use of this supplemental 

information in support of the classification of Pulaski County as attainment for the 1-hour SO2

NAAQS. As the Division and EPA are aware, EKPC has significantly reduced SO2 emissions 

from Cooper Station since 2012. Pursuant to the 2007 EPA Consent Decree, EKPC 

implemented additional SO2 controls on Cooper Unit 2. EKPC is now in the process of adding 

SO2 controls to Cooper Unit 1 through the reroute project mentioned above which will be 

completed by the beginning of 2016. Cooper 1 and 2 will also meet the requirements of the 

Mercury and Air Toxics Standards (MATS) by April 16, 2016 in accordance with the one-year 

extension of the initial deadline. EKPC’s significant investment in Cooper Station demonstrates 

its importance to the EKPC generation and transmission system and the cooperatives it serves. 

If you have any questions regarding this letter or the enclosed report, please let me know. 

In addition to the two hard copies of the Report enclosed herewith, an electronic copy of the 

Report, including modeling files, is being transmitted today via email by Trinity Consultants to 

Messrs. Ben Cordes and Kevin Davis.

Sincerely,

Jerry Purvis

Director Environmental Affairs

2
September 3, 2015

Page | 3

Enclosure

cc w/o enc.: Jackie Quarles – DAQ

Rick Shewekah – DAQ

Ben Cordes – DAQ

Kevin Davis – DAQ

John West – OGC

Lance Huffman – OGC

George Schewe – Trinity

John Colebrook – Trinity

Louis Petrey - EKPC

3
Environmental solutions delivered uncommonly well 

AIR DISPERSION MODELING REPORT 

COOPER STATION 

SO2 NAAQS DESIGNATION ANALYSIS

Prepared for:

Jerry	Purvis	

Director,	Environmental	Affairs	

East	Kentucky	Power	Cooperative	

4775	Lexington	Road,	P.O.	Box	707	

Winchester,	KY	40392‐0707	

Prepared By:

TRINITY	CONSULTANTS	

1717	Dixie	Highway	

Suite	900	

Covington,	Kentucky	41011	

September	1,	2015	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report i 

TABLE OF CONTENTS 

1. EXECUTIVE SUMMARY 1-1

2. INTRODUCTION 2-1

2.1. Facility Information..............................................................................................................................................2‐1

2.2. Basis for Analysis...................................................................................................................................................2‐3

3. 1‐HOUR SO2 DESIGNATION MODELING METHODOLOGY 3-1

3.1. Model Selection......................................................................................................................................................3‐1

3.2. Rural/Urban Option Selection in AERMOD...................................................................................................3‐2

3.3. Meteorological Data..............................................................................................................................................3‐4

3.3.1. Surface Data................................................................................................................................................................................3‐7

3.3.2. Upper Air Data ...........................................................................................................................................................................3‐7

3.3.3. Land Use Analysis......................................................................................................................................................................3‐8

3.4. Coordinate System ................................................................................................................................................3‐9

3.5. Receptor Locations ...............................................................................................................................................3‐9

3.6. Terrain Elevations..............................................................................................................................................3‐11

3.7. Cooper Station Emission Sources ..................................................................................................................3‐12

3.7.1. Cooper Unit 1 Modeled Emission Rate .......................................................................................................................... 3‐13

3.7.2. Cooper Unit 2 Modeled Emission Rate .......................................................................................................................... 3‐14

3.7.3. Combined Cooper Units 1 and 2 Modeled Emission Rate ..................................................................................... 3‐16

3.7.4. Stack Parameter Selection................................................................................................................................................. 3‐16

3.7.5. Hourly Emissions File Creation........................................................................................................................................ 3‐17

3.8. Other Source Inventory ....................................................................................................................................3‐17

3.9. Building Influences ............................................................................................................................................3‐21

3.10. Background Concentrations.........................................................................................................................3‐22

3.11. Modeling Files ...................................................................................................................................................3‐25

4. 1‐HOUR SO2 DESIGNATION MODELING RESULTS 4-1

APPENDIX A: USE OF U* IN COOPER DISPERSION MODELING A-1

Criteria 3.2.2.e.i	‐	Scientific Peer Review ............................................................................................................... A‐2

Criteria 3.2.2.e.ii‐	Applicable on a Theoretical Basis ......................................................................................... A‐3

Criteria 3.2.2.e.iii – Availability of Databases....................................................................................................... A‐7

Criteria 3.2.2.e.iv – Demonstration of No Biases Towards Underestimates............................................... A‐7

Criteria 3.2.2.e.v – A Protocol Has Been Established.......................................................................................... A‐8

APPENDIX B: NAAQS REGIONAL SOURCE INVENTORY

APPENDIX C: MODELING FILES ON CD

		
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report ii 

LIST OF FIGURES 

Figure	2‐1.		Aerial	Photograph	of	Cooper	Station	 2‐2

Figure	2‐2.		Area	Map	of	Cooper	Station	 2‐3

Figure	3‐1.		Distribution	of	Land	Use	within	3km	of	Cooper	Station	 3‐3

Figure	3‐2.		Meteorological	Stations	and	SO2	Monitors	in	the	Area	near	Cooper	Station	 3‐6

Figure	3‐3.		Modeling	TAD	Receptor	Grid	Showing	Example	Excluded	Locations	over	Water	 3‐10

Figure	3‐4.		Innermost	Portion	of	the	Proposed	Modeling	Receptor	Grid	for	Cooper	 3‐11

Figure	3‐5.		Relief	Map	of	Area	within	20	km	of	Cooper	Station	 3‐12

Figure	3‐6.	Map	Showing	Regional	Source	Locations	and	SO2	Emissions	Magnitude	near	Cooper	Station	 3‐20

Figure	3‐7.		Results	of	Regional	Source	Screening	Evaluation	based	on	Q/d	Analysis	 3‐21

Figure	3‐8.		Wind	Rose	for	London‐Corbin	Airport	from	July	2012	–	June	2015	 3‐24

Figure	4‐1.		Spatial	Display	of	3‐year	Average	99th	Percentile	Annual	Distribution	of	Daily	Maximum	1‐hr	SO2

Concentrations	Including	Background	 4‐2

Figure	A‐1.			Comparison	of	the	AERMOD	Model	with	and	without	the	u*	Adjustment	 A‐2

Figure	A‐2.		Distribution	of	Hourly	Observations	by	Wind	Speed	Category	Bin	 A‐5

Figure	A‐3.		Distribution	of	Wind	Speeds	for	Cooper	Station	Impacts	above	100	μg/m3	with	the	Default	AERMET	

Dataset	 A‐6

Figure	A‐4.		Distribution	of	Wind	Speeds	for	Cooper	Station	Impacts	above	100	μg/m3	with	the	U*_ADJ	AERMET	

Dataset	 A‐6

Figure	A‐5.		Residual	Plots	Showing	Improved	Performance	with	u*	and	No	Bias	toward	Underestimation	 A‐7
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report iii 

LIST OF TABLES 

Table	3‐1.		Modeling	TAD	Urban	/	Rural	Categories	 3‐3

Table	3‐2.		Cooper	Station	Urban/Rural	Determination	 3‐4

Table	3‐3.		Proximity	Analysis	of	Meteorological	Stations	to	Cooper	Station	 3‐7

Table	3‐4.		Moisture	Calculation	for	Jackson	Airport	(inches	of	precipitation)	 3‐9

Table	3‐5.		Example	of	Missing/OOC	SO2	Emissions	Data	Filling	Technique	 3‐15

Table	3‐6.		Example	of	Unit	2	SO2	Emissions	during	Downtime	 3‐16

Table	3‐7.		Cooper	Station	Source	Parameters	 3‐17

Table	3‐8.		Summary	of	SO2	Emissions	from	KyEIS	Facilities	near	Cooper	Station	and	Candidate	SO2	Monitoring	

Stations	 3‐23

Table	3‐9.		Selected	SO2	Background	Concentration	 3‐24

Table	4‐1.		Highest	4th	High	Modeled	1‐hour	SO2	Results	for	Comparison	to	the	NAAQS	 4‐1	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 1-1 

1. EXECUTIVE SUMMARY 

Eastern	Kentucky	Power	Cooperative,	Inc.	(EKPC)	in	association	with	our	air	quality	contractor,	Trinity	

Consultants	(Trinity),	submits	this	dispersion	modeling	report	for	the	air	quality	modeling	analysis	that	was	

performed	with	respect	to	EKPC’s	John	Sherman	Cooper	Power	Station	(Cooper)	and	the	surrounding	area.		

Cooper	consists	of	two	coal‐fired	electricity	generating	units	referred	to	as	Unit	1	and	Unit	2.		This	work	was	

undertaken	in	support	of	the	Kentucky	Division	for	Air	Quality	(KDAQ	or	Division)	response	to	the	March	20,	

2015	letter	from	the	U.S.	Environmental	Protection	Agency	(U.S.	EPA)	to	Commissioner	Scott	of	the	Kentucky	

Department	for	Environmental	Protection	(KDEP)	regarding	designations	of	areas	currently	unclassified	with	

respect	to	the	2010	1‐hour	SO2	National	Ambient	Air	Quality	Standard	(NAAQS).	

In	that	letter,	U.S.	EPA	identified	the	Cooper	Station	as	one	of	the	Kentucky	sources	meeting	the	criteria	for	

evaluation	of	unclassified	areas	in	the	first	round	of	designations	as	part	of	a	required	response	by	U.S.	EPA	to	

the	recent	Sierra	Club	vs.	Regina	McCarthy	Consent	Decree1.		Cooper	was	also	identified	on	the	U.S.	EPA	website	

listing	all	areas	where	designations	would	be	required	under	the	Consent	Decree	by	July	2,	20162,	which	is	

accelerated	as	compared	to	the	final	Data	Requirements	Rule	(DRR)	schedule.3		The	criteria	to	determine	if	a	

source	was	subject	to	the	Consent	Decree	are:		1)	a	nearby	monitor	showing	a	violation,	or	2)	that	an	area	

contains	a	stationary	source	that	according	to	the	EPA’s	Air	Markets	Database	either	emitted	more	than	16,000	

tons	of	SO2	in	2012	or	emitted	more	than	2,600	tons	of	SO2	and	had	an	emission	rate	of	at	least	

0.45	lb	SO2/MMBtu	in	2012.		According	to	EPA’s	Air	Markets	Database,	the	Cooper	Station	emitted	7,428	tons	

SO2	in	2012	and	had	an	average	SO2	emission	rate	of	1.07	lb	SO2/MMBtu	in	2012.		U.S.	EPA	stated	that	it	would	

base	the	designation	of	the	Pulaski	County	and	surrounding	area	on	these	emission	criteria	alone	as	no	SO2

monitors	are	in	the	area	unless	KDAQ	submits	updated	recommendations	and	supporting	information	that	could	

be	considered	in	the	final	designations.		To	that	end,	EKPC	is	facilitating	a	modeling	analysis	to	aid	in	the	

designation	determination	for	the	Pulaski	County	area.	

Dispersion	modeling	conducted	in	support	of	the	SO2	NAAQS	attainment	demonstration	was	conducted	

following	the	modeling	Technical	Assistance	Document	(TAD)	guidance.4		As	favored	by	the	guidance	and	

described	in	the	modeling	protocol	submitted	on	August	3,	2015,	three	years	of	Continuous	Emissions	

Monitoring	System	(CEMS)	data	were	utilized	for	emissions	from	Unit	2.		As	recommended	by	U.S.	EPA	in	their	

comments	provided	on	the	modeling	protocol5,	SO2	emissions	from	Unit	1	were	modeled	at	an	allowable	hourly	

emission	rate	assuming	8,760	hours	of	operation,	determined	from	the	suite	of	permit	limits	that	will	be	

applicable	to	this	unit	after	the	proposed	dry	flue	gas	desulfurization	(DFGD)	SO2	control	system	tie‐in	project	is	

completed	in	2015.		Because	this	air	pollution	control	project	will	be	completed	well	before	the	July	2016	

attainment	designation	deadline,	the	Unit	1	modeled	emission	rate	reflects	the	allowable	emission	rate	that	will	

be	in	place	at	the	time	of	the	SO2	NAAQS	designations	under	the	Consent	Decree.		Modeling	the	post‐control	

allowable	emission	rate	on	a	continuous	basis	for	an	affected	unit	scheduled	to	be	controlled	prior	to	the	

attainment	designation	deadline	is	an	acceptable	approach	under	both	the	modeling	TAD6	and	the	final	DRR.7		

These	emissions	were	paired	with	static	(not	varying	by	hour)	engineering	estimates	of	exit	velocity	and	

																																																															

1		Order Granting Joint Motion to Approve and Enter Consent Decree and Denying Other Motions as Moot,	Sierra	Club	et.	al.	v.	Regina	

McCarthy,	Administrator	of	the	United	States	Environmental	Protection	Agency,	United	States	District	Court,	Northern	District	of	

California,	Docket	Nos.	120,	149,	March	2,	2015.			

2		http://www.epa.gov/airquality/sulfurdioxide/designations/pdfs/sourceareas.pdf	 3		Data Requirements Rule for the 1‐Hour Sulfur Dioxide (SO2) Primary National Ambient Air Quality Standards (NAAQS): Final Rule,

Federal	Register	Vol.	90	No.	162,	pages	51052‐51088,	August	21,	2015.	 4		SO2 NAAQS Designations Modeling Technical Assistance Document,	Draft,	U.S.	EPA,	Research	Triangle	Park,	NC,	December	2013.	 5		Email	from	Rick	Gillam	(U.S.	EPA,	Region	4)	to	Ben	Cordes	(KDAQ),	August	25,	2015	 6		Ibid.	

7		Ibid.	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 1-2 

temperature	for	the	two	relevant	stack	configurations	following	the	Unit	1	DFGD	tie‐in:		1)	Case	1	when	only	

Unit	1	is	operational,	and	2)	Case	2	when	both	Units	1	and	2	are	operational.		The	actual	stack	height	was	used	

because	the	combined	Unit	1	and	2	stack	does	not	exceed	Good	Engineering	Practice	(GEP)	stack	height.			

Nearby	sources	were	considered	within	the	TAD‐suggested	20	km	range	of	Cooper,	but	also	out	to	50	km	to	

allow	comprehensive	consideration	of	large	nearby	sources.		Of	these,	the	Kingsford	Manufacturing	Company	

facility	(located	~	3	km	south	of	Cooper)	was	determined	to	be	the	only	regional	source	which	has	the	potential	

to	significantly	contribute	to	the	location	of	Cooper	Station’s	maximum	modeled	impacts.		All	other	sources	were	

distant	enough	to	fall	outside	of	the	TAD	general	consideration	guidance	and	were	likely	captured	as	part	of	the	

regional,	rural	background	concentration	selected	for	the	modeling	(26.9	μg/m3)	from	the	SO2	monitor	located	

at	Mammoth	Cave	National	Park.		This	monitor	was	determined	to	be	representative	of	background	conditions	

in	Pulaski	County	and	not	influenced	by	either	Cooper	or	Kingsford.	

Given	this	strategy	and	characterization	of	sources	affecting	air	quality	in	the	Pulaski	County	area,	the	analysis	

demonstrated	that	the	maximum	modeled	impacts	(expressed	in	the	form	of	the	1‐hr	SO2	NAAQS)	including	

emissions	from	Cooper	Station,	emissions	from	the	selected	regional	sources,	and	the	background	concentration	

are	below	the	1‐hour	SO2	NAAQS.		Specifically,	the	maximum	combined	impact	is	173.1	μg/m3	as	compared	to	

the	1‐hour	SO2	NAAQS	of	196	μg/m3	(75	ppb).		Therefore,	this	modeling	demonstrates	that	the	area	surrounding	

the	Cooper	Station	should	be	considered	for	designation	as	attainment.	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 2-1 

2. INTRODUCTION 

This	section	of	the	modeling	report	provides	an	overview	of	the	Cooper	Station	along	with	background	

information	for	the	basis	for	the	SO2 designation	modeling.	

2.1. FACILITY INFORMATION 

EKPC	owns	and	operates	a	364	MW	coal	fired	power	plant,	the	John	S.	Cooper	Station	(Cooper),	located	in	

Pulaski	County,	approximately	three	quarters	of	a	mile	northeast	of	the	town	of	Burnside,	Kentucky.		Cooper	

consists	of	two	generating	units	(Title	V	ID	EU01	and	EU02).		The	first	power	generating	unit	(EU01,	herein	

referred	to	as	Unit	1)	is	a	pulverized	coal	fired	boiler	with	a	maximum	continuous	rating	of	1,080	MMBtu/hr.		

The	second	unit	(EU02,	herein	referred	to	as	Unit	2)	is	a	pulverized	coal	fired	boiler	with	a	maximum	continuous	

rating	of	2,089	MMBtu/hr.	

Unit	1	is	currently	equipped	with	multiple	control	devices	to	reduce	emissions	of	pollutants	regulated	under	

various	Federal	and	Commonwealth	programs.		The	current	controls	include	an	electrostatic	precipitator	(ESP)	

for	PM	control	and	low	NOX burners	for	NOX	control.		Unit	1	is	undergoing	a	duct	reroute	project	to	tie	its	

exhaust	into	the	existing	Unit	2	ductwork,	to	allow	for	further	control	utilizing	both	an	DFGD	for	SO2	control	and	

a	pulse	jet	fabric	filter	for	additional	PM	control.		Unit	2	is	equipped	with	low	NOX	burners,	selective	catalytic	

reduction	(SCR),	FuelSolv	treatment,	DFGD,	and	pulse	jet	fabric	filter.		These	units	and	other	emissions	

generating	activities	(emergency	generators,	etc.,	not	considered	under	the	Consent	Decree)	at	Cooper	Station	

are	subject	to	Title	V	operating	permit	V‐12‐019	R1,	issued	by	KDAQ	on	August	14,	2013.		Unit	1	and	Unit	2	are	

the	only	significant	sources	of	SO2 emissions	at	Cooper	station,	and	as	such,	these	are	the	only	sources	

represented	in	the	modeling	analysis.		

An	aerial	photograph	and	area	map	of	the	facility	and	surrounding	area	are	provided	in	Figures	2‐1	and	2‐2,	

respectively.		Figure	2‐1	shows	the	fence	line	and	buildings	at	Cooper.		Figure	2‐2	shows	the	facility	relative	to	

predominant	geographical	features	such	as	roads,	rivers,	and	towns.		These	figures	and	the	locations	of	all	

emission	sources,	structures,	and	receptors	in	the	modeling	analysis	are	represented	in	the	Universal	

Transverse	Mercator	(UTM)	coordinate	system.		The	datum	is	based	on	North	American	Datum	1983	(NAD	83).		

UTM	coordinates	for	this	analysis	are	located	in	UTM	Zone	16.		The	central	location	of	Cooper	Station	is	

approximately	714,250	meters	East	and	4,097,343	meters	North	in	Zone	16	of	the	UTM	system.	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 2-2 

Figure 2‐1.		Aerial Photograph of Cooper Station
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 2-3 

Figure 2‐2.		Area Map of Cooper Station

2.2. BASIS FOR ANALYSIS 

Following	the	May	2014	publication	of	the	proposed	Data	Requirements	Rule,	the	U.S.	EPA	was	sued	for	“failing	

to	undertake	a	certain	nondiscretionary	duty	under	the	Clean	Air	Act	(“CAA”),	42	U.S.C.	§§	7401‐7671q,	and	that	

such	alleged	failure	is	actionable	under	section	304(a)(2)	of	the	CAA,	42	U.S.C.	§	7604(a)(2).”		The	lawsuit	

resulted	in	the	Consent	Decree	that	was	entered	on	March	2,	2015	in	the	U.S.	District	Court	for	the	Northern	

District	of	California	(same	as	that	mentioned	above	and	referenced	in	Footnote	1).		As	a	result	of	the	Consent	

Decree,	an	additional	designation	phase	was	added	to	the	two	designation	phases	that	were	already	included	in	

the	U.S.	EPA’s	August	2015	final	Data	Requirements	Rule.		The	additional	phase	affects	areas	with	stationary	

sources	that	meet	specific	emissions	criteria	laid	out	in	the	Consent	Decree.		The	U.S.	EPA	released	a	

memorandum	on	March	20,	2015	(referred	to	herein	as	the	2015	SO2	Area	Designation	Guidance)	to	the	

Regional	Directors	clarifying	the	path	forward	for	states	with	sources	affected	by	the	decree.	8		EKPC	is	very	

																																																															

8		Updated Guidance for Area Designations for the 2010 Primary Sulfur Dioxide National Ambient Air Quality Standard,	memorandum	

from	Stephen	Page	to	Regional	Air	division	Directors,	Regions	1‐10,	March	20,	2015.	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 2-4 

aware	of	these	requirements	and	has	conferred	with	KDAQ	to	determine	a	path	forward	to	meet	the	deadlines	

for	modeling,	strategic	assessment,	and	eventual	designation	of	the	area	around	Cooper	Station.	

Under	the	DRR,	KDAQ	has	the	option	of	installing	a	new	monitor	in	the	area	around	Cooper	Station	or	

performing	dispersion	modeling.		A	schedule	for	completion	of	the	designations	under	DRR	is	established	as	

December	31,	2017	for	modeling	and	December	31,	2020	for	monitoring.		The	deadline	required	by	the	Consent	

Decree,	however,	is	that	the	U.S.	EPA	will	complete	a	round	of	SO2	designations	by	July	2,	2016.		To	meet	this	

deadline,	KDAQ	is	required	to	perform	dispersion	modeling	unless	an	existing	ambient	air	monitor	can	be	

shown	to	be	representative	of	the	area	(insufficient	time	is	available	to	begin	a	new	ambient	source‐oriented	

monitoring	system).		Because	the	exclusive	use	of	monitoring	data	for	the	designation	process	is	unlikely	due	to	

the	lack	of	a	monitoring	station	in	sufficient	proximity	to	the	Cooper	Station,	modeling	must	be	performed.		

Results	of	the	modeling	analysis	will	be	used	to	allow	appropriate	designation	of	the	unclassified	area	around	

Cooper	as	in	attainment	of	the	1‐hour	SO2	NAAQS.	

EKPC	has	performed	this	modeling	analysis	and	is	providing	the	results	to	KDAQ	to	assist	in	the	designation	

process.		This	modeling	follows	the	methodology	and	modeling	guidance	from	the	U.S.	EPA	in	the	form	of	the	SO2

NAAQS	designation	modeling	guidance	TAD	and	assists	in	KDAQ’s	determination	of	the	ambient	levels	of	SO2	at	

the	1‐hour	averaging	period	in	the	area	around	Cooper	Station.		This	report	only	covers	the	dispersion	modeling	

requirement	and	does	not	cover	any	other	items	KDAQ	may	wish	to	include	within	the	Pulaski	County	1‐hr	SO2

NAAQS	attainment	recommendation	due	to	be	submitted	to	U.S.	EPA	by	September	18,	2105.	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-1 

3. 1-HOUR SO2 DESIGNATION MODELING METHODOLOGY 

As	prescribed	by	the	U.S.	EPA	in	the	modeling	TAD,	dispersion	modeling	can	be	used	in	place	of	ambient	

monitoring	to	evaluate	the	attainment	status	of	an	area	in	the	vicinity	of	a	specific	source,	in	this	case	the	EKPC	

Cooper	Station.		U.S.	EPA’s	rationale	for	this	is	the	distinction	that	SO2	sources	are	limited	in	terms	of	the	

distance	to	where	ambient	concentration	impacts	occur.		In	preparation	for	providing	modeling	guidance	for	

designation	analysis,	U.S.	EPA	reviewed	SO2	ambient	monitoring	and	modeling	of	concentrations	around	and	

near	SO2	sources	and	found	that	most	of	the	highest	impacts	fall	within	a	few	10’s	of	kilometers	from	large	

sources	and	a	few	kilometers	for	smaller	sources.		Also	of	note	was	that	the	gradient	of	these	concentrations	falls	

off	significantly	after	the	maximum	is	reached.		Thus,	the	modeling	focuses	on	the	use	of	near‐field	

computational	methods	such	that	U.S.	EPA’s	primary	preferred	industrial	source	model,	the	AERMOD	Model9,	is	

the	primary	model	recommended	for	use.		In	addition	to	AERMOD	and	to	allow	the	best	representation	of	

simulated	ambient	air	concentrations,	the	modeling	TAD	recommends:	

Using	actual	emissions	as	an	input	for	assessing	violations	to	provide	results	that	reflect	current	actual	air	

quality	(i.e.,	modeling	that	simulates	a	monitor)(allowable	emissions	may	also	be	used	which	will	result	in	a	

more	conservative	estimate	of	actual	ambient	air	impacts	of	the	source);	

Using	three	years	of	modeling	results	to	calculate	a	simulated	design	value	consistent	with	the	3‐year	

monitoring	period	required	to	develop	a	monitor	design	value	for	comparison	to	the	NAAQS;	

Placing	receptors	for	the	modeling	only	in	locations	where	a	monitor	could	be	placed;	and	

Using	actual	stack	heights	rather	than	following	the	Good	Engineering	Practice	stack	height	policy	when	

using	actual	emissions.	

Following	this	modeling	philosophy	and	guidance,	the	remainder	of	this	section	provides	an	overview	of	the	

modeling	applied	to	the	Cooper	Station	consistent	with	the	modeling	protocol	submitted	to	KDAQ	on	August	3,	

2015,	unless	stated	otherwise.	

3.1. MODEL SELECTION 

Modeling	was	performed	for	the	1‐hour	SO2	analysis	following	the	modeling	TAD	guidance.		The	AERMOD	Model	

Version	1518110,	the	most	current	version	released	by	U.S.	EPA	on	July	24,	2015	on	the	Support	Center	for	

Regulatory	Air	Modeling	(SCRAM)	website11,	was	used	to	perform	the	dispersion	modeling.		The	proposed	

update	to	U.S.	EPA’s	modeling	guidance	in	the	form	of	the	Guideline on Air Quality Models12,	was	released	on	July	

15,	2015	via	the	U.S.	EPA	technical	website13.		This	proposed	guidance	and	revised	AERMOD	model	have	options

that	could	affect	the	outcome	of	dispersion	modeling	studies	and	specifically	the	designation	modeling	herein.		

Some	of	these	options	address	the	U.S.	EPA	and	modeling	community	concerns	that	AERMOD	does	not	perform	

well	during	low	wind	conditions	because	turbulence	under	stable	conditions	is	underestimated.			

	 	

																																																															

9		Addendum User’s Guide for the AMS/EPA Regulatory Model – AERMOD,	EPA‐454/B‐03‐001,	U.	S.	Environmental	Protection	Agency,	

Research	Triangle	Park,	NC,	September	2004,	Revised	May	2014.	

10		Stated	by	U.S.	EPA	to	be	part	of	the	docket	at	Docket	ID	No.	EPA‐HQ‐OAR‐2015‐0310	and	available	as	of	date	of	submittal	of	this	

report.	

11		http://www.epa.gov/ttn/scram/dispersion_prefrec.htm#aermod	 12		Guideline on Air Quality Models.		Appendix	W	to	40	CFR	Parts	51	and	52.		Federal	Register,	November	9,	2005.		pp.	68217‐68261.	 13		http://www.epa.gov/ttn/scram/	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-2 

When	AERMOD	is	run	with	a	meteorological	dataset	derived	from	one‐minute	meteorological	data	as	is	

currently	recommended	by	U.S.	EPA,	low	wind	speeds	are	much	more	prevalent	than	in	prior	versions	of	the	

modeling	system	that	did	not	rely	on	one‐minute	meteorological	data.		These	low	wind	speeds	have	been	linked	

to	potential	overestimates	in	ambient	concentrations	by	AERMOD.14		These	overestimates	occur,	in	part,	due	to	

an	underestimate	of	friction	velocity	(u*)	by	the	AERMET	meteorological	processor.		EPA	recognized	this	

underestimation	as	a	potential	issue	with	AERMET	(and	subsequently,	AERMOD)	and	released	AERMET	Version	

12345	which	included	a	beta	option,	ADJ_U*,	which	allowed	the	friction	velocity	(u*)	to	be	adjusted	using	the	

methods	of	Qian	and	Venkatram15	to	better	account	for	turbulence	in	the	atmosphere	during	low	wind	speed	

stable	conditions.		This	beta	option	was	first	released	in	AERMET	version	12345,	was	updated	to	incorporate	a	

modified	Bulk	Richardson	Number	in	version	13350,	was	further	modified	to	adjust	u*	for	low	solar	elevation	

angles	with	version	14134,	and	was	most	recently	in	Version	15181,	used	to	modify	the	calculation	of	the	

turbulence	measure,	Monin‐Obukhov	length.16		Given	the	refined	nature	of	this	beta	option	and	the	peer	

reviewed	studies	which	have	acknowledged	its	accuracy,	EKPC	has	incorporated	this	option	into	the	modeling	

analysis	to	allow	more	representative	and	more	accurate	modeling	results.		Further	justification	for	inclusion	of	

the	beta	option	ADJ_U*	for	AERMET	is	presented	in	Appendix	A.	

The	pollutant	identification	was	set	to	“SO2”	in	AERMOD,	which	allowed	for	additional	internal	model	options	to	

be	available,	thus	enabling	the	output	options	to	be	configured	properly.		Because	of	the	probabilistic	form	of	the	

1‐hour	NAAQS,	selecting	these	correct	input	options	allowed	AERMOD	to	properly	calculate	an	SO2	design	value	

based	on	the	3‐year	average	of	the	99th	percentile	of	the	annual	distribution	of	the	daily	maximum	1‐hour	

concentrations	for	comparison	with	the	1‐hour	SO2	NAAQS	of	196	g/m3	(75	ppb).	

3.2. RURAL/URBAN OPTION SELECTION IN AERMOD 

As	stated	in	Section	6.3,	Urban/Rural	Determination,	of	the	modeling	TAD,	for	any	dispersion	modeling	exercise	

for	SO2,	the	“urban”	or	“rural”	determination	of	the	location	surrounding	the	subject	source	is	important	in	

determining	the	applicable	boundary	layer	characteristics	that	affect	a	model’s	calculation	of	ambient	

concentrations	as	well	as	the	possible	invocation	of	AERMOD’s	4‐hour	half‐life	applicable	to	SO2	in	urban	areas.		

Thus,	a	determination	was	made	of	whether	the	area	around	the	Cooper	Station	was	urban	or	rural.			

The	first	method	discussed	in	the	modeling	TAD	(also	referring	therein	to	Section	7.2.3c	of	the	Guideline	on	Air	

Quality	Models,	Appendix	W)	was	used	to	determine	the	urban	or	rural	status	of	the	area	around	Cooper.		This	is	

the	“land	use”	technique	because	it	examines	the	various	land	use	within	3	km	of	Cooper	and	quantifies	the	

percentage	of	area	in	various	land	use	categories.		Following	this	guidance,	2011	land	use	data	(most	recent	

available)	were	obtained	from	the	U.S.	Geological	Survey17	through	ArcGIS	and	a	3	km	radius	circle	inscribed	

electronically	around	the	Cooper	stack	coordinates.		All	data	were	georeferenced	and	tabulated	using	the	

categories	shown	in	Table	3‐1	for	urban	and	rural	designation.	

	 	

																																																															

14		Wenjun Qian and Akula Venkatram, “Performance of Steady State Dispersion Models Under Low Wind‐Speed Conditions,”

Boundary‐Layer Meteorology, no. 138 (2011): 475‐491. 15		Ibid.	 16		http://www.epa.gov/ttn/scram/7thconf/aermod/aermet_mcb3.txt;	

http://www.epa.gov/ttn/scram/7thconf/aermod/aermet_mcb4.txt;	

http://www.epa.gov/ttn/scram/7thconf/aermod/AERMET_mcb5.pdf;	

http://www.epa.gov/ttn/scram/7thconf/aermod/AERMET_mcb6.pdf 17		http://www.mrlc.gov/viewerjs/	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-3 

Figure	3‐1	shows	the	layout	of	the	land	use	where	greens,	yellows	and	browns	are	farmland,	forests,	and	

grasses,	pinks	are	non‐urban	developed	lands,	and	red	and	dark	red	are	urban	areas.		Table	3‐2	shows	the	

results	of	this	land	categorization	process.		As	can	be	seen	the	area	is	predominantly	rural	by	an	overwhelming	

margin	at	93	percent,	and	therefore,	was	treated	as	rural	in	the	AERMOD	Model.			

Table 3‐1.		Modeling TAD Urban / Rural Categories

Figure 3‐1.		Distribution of Land Use within 3km of Cooper Station

Modeling TAD 

Rural or Urban

11 Open Water A5 Water Surfaces rural

12 Perennial Ice/Snow A5 Water Surfaces rural

21 Developed, Open Space A1 Metropolitan Natural rural

22 Developed, Low Intensity R1 Common Residential rural

23 Developed, Medium Intensity I1, I2, C1, R2, R3 Industrial/Commercial/Compact 

Residential urban

24 Developed, High Intensity I1, I2, C1, R2, R3 Industrial/Commercial/Compact 

Residential urban

31 Barren Land A3 Undeveloped (Grasses/Shrub) rural

41 Deciduous Forest A4 Undeveloped (Wooded) rural

42 Evergreen Forest A4 Undeveloped (Wooded) rural

43 Mixed Forest A4 Undeveloped (Wooded) rural

52 Shrub/Scrub A3 Undeveloped (Grasses/Shrub) rural

71 Grassland/Herbaceous A3 Undeveloped (Grasses/Shrub) rural

81 Pasture/Hay A2 Agricultural rural

82 Cultivated Crops A2 Agricultural rural

90 Woody Wetlands A4 Undeveloped (Wooded) rural

95 Emergent Herbaceous Wetlands A3 Undeveloped (Grasses/Shrub) rural

2011 NLCD Land Cover Classification Auer Land-Use Classification
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-4 

Table 3‐2.		Cooper Station Urban/Rural Determination

3.3. METEOROLOGICAL DATA 

Meteorological	data	was	required	as	input	to	the	AERMOD	model	to	allow	the	characterization	of	the	transport	

and	dispersion	of	the	Cooper	Station	emissions	in	the	atmosphere.		As	per	the	modeling	TAD,	three	years	of	

recent	data	coincidental	with	the	latest	three	years	of	Cooper	CEMS	data	reflecting	SO2	controls	on	Unit	2	

(beginning	July	1,	2012)	was	obtained	from	the	most	representative	and	nearby	National	Weather	Service	

(NWS)	sites.		Data	obtained	from	the	NWS	included	surface	(generally,	10	m	tower‐based)	and	upper	air	

(radiosonde)	meteorological	data	for	the	most	recent	three	full	year	data	set	(July	1,	2012	through	June	30,	

2015)	and	was	processed	from	archived	data	from	the	most	representative	NWS	meteorological	station	in	the	

vicinity	of	the	Cooper	Station.		Representativeness	was	determined	on	the	basis	of	proximity,	similarity	in	terms	

of	land	use	(and	its	effect	on	surface	roughness,	albedo,	and	Bowen	ratio),	and	meteorological	judgement.		

AERMOD‐ready	meteorological	data	was	prepared	using	the	latest	version	of	the	AERMET	meteorological	

processing	utility	(Version	15181).		Standard	U.S.	EPA	meteorological	data	processing	guidance	was	used	as	

outlined	in	a	recent	U.S.	EPA	memorandum18	as	well	as	other	AERMET	and	associated	processor	documentation.		

Additionally,	the	beta	option	ADJ_U*	was	selected	during	processing,	as	mentioned	in	Section	3.1.	

A	preliminary	evaluation	of	the	NWS	meteorological	data	sites	within	approximately	150	km	indicated	that	

several	airports	were	located	in	the	region	including	Somerset‐Pulaski	Airport	(KSME,	6.6	km	to	Cooper	

Station),	Wayne	County	Airport	(KEKQ,	28.3	km	to	Cooper	Station),	and	London‐Corbin	McGee	Field	(KLOZ,	46.9	

km	to	Cooper	Station).		Figure	3‐2	shows	the	locations	of	the	airports	having	meteorological	data	sets	that	were	

considered	for	this	modeling.		Of	these	candidate	sites,	the	most	representative	site,	the	London‐Corbin	Airport,	

was	the	only	site	having	the	sufficient	hour‐by‐hour	and	one‐minute	meteorological	data	sets	that	can	be	used	in	

the	dispersion	modeling.		Table	3‐3	presents	the	results	of	a	NWS	identification	exercise	based	on	proximity	to	

																																																															

18		Fox,	Tyler,	U.S.	Environmental	Protection	Agency.	2013.		“Use	of	ASOS	Meteorological	Data	in	AERMOD	Dispersion	Modeling.”	

Available	Online:	http://www.epa.gov/ttn/scram/guidance/clarification/20130308_Met_Data_Clarification.pdf

Category ID Category Description Percent

11 Open Water 12.9%

21 Developed, Open Space 9.2%

22 Developed, Low Intensity 14.4%

23 Developed, Medium Intensity 5.3%

24 Developed, High Intensity 1.7%

31 Barren Land 3.9%

41 Deciduous Forest 31.1%

42 Evergreen Forest 0.9%

43 Mixed Forest 2.7%

52 Shrub/Scrub 0.2%

71 Grassland/Herbaceous 5.4%

81 Pasture/Hay 11.9%

82 Cultivated Crops 0.4%

95 Emergent Herbaceous Wetlands 0.3%

Total 100.0%

Urban 7.0%

Rural 93.0%

Pecent Land Categorization ArcGIS Analysis Results for Cooper Station
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-5 

Cooper	Station	where	meteorological	stations	without	adequate	data	are	designated	with	red	highlighting	and	

candidate	stations	for	the	modeling	analysis	are	designated	without	highlighting.		As	can	be	seen,	other	

candidate	sites	have	the	appropriate	one	minute	data	sets,	but	are	located	farther	away	and	in	a	different	

geographical	setting	than	the	Cooper	Station.		Oak	Ridge	Airport	(KOQT)	is	in	a	much	more	rugged	terrain	and	

Blue	Grass	Airport	in	Lexington	is	located	in	much	more	open	and	rolling	terrain.	

Thus,	based	on	the	site	proximity,	similarity	of	land	use	and	geographical	setting,	and	general	climatic	features,	

the	most	representative	July	1,	2012	through	June	30,	2015	surface	meteorology	data	for	the	modeling	of	the	

Cooper	Station	was	determined	to	be	that	of	the	London‐Corbin	Airport	(KLOZ,	WBAN	No.	03849).		With	regard	

to	the	required	upper	air	data,	which	is	more	regional	in	nature	and	reflects	the	overall	higher	altitude	

meteorological	conditions,	the	closest	and	most	representative	site	is	from	the	Nashville	International	Airport	

(KBNA,	WBAN	No.	13897).	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-6 

Figure 3‐2.		Meteorological Stations and SO2 Monitors in the Area near Cooper Station
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-7 

Table 3‐3.		Proximity Analysis of Meteorological Stations to Cooper Station

3.3.1. Surface Data 

Unprocessed	hourly	surface	meteorological	field	data	was	obtained	from	the	U.S.	National	Climatic	Data	Center	

(NCDC)	for	the	London‐Corbin	Airport	Regional	Airport	(KLOZ)	for	July	1,	2012	through	June	30,	2015	in	the	

standard	ISHD	(integrated	surface	hourly	data)	format19.		This	data	was	supplemented	with	TD‐6405	(“1‐

minute”)	wind	data	for	each	station20	and	processed	using	the	latest	version	of	the	AERMINUTE	pre‐processing	

tool	(version	14337).		A	threshold	wind	speed	of	0.5	m/s	was	used	in	AERMET	as	per	U.S.	EPA	guidance.		The	

“Ice‐Free	Winds	Group”	AERMINUTE	option	was	selected	due	to	the	fact	that	a	sonic	anemometer	was	installed	

at	KLOZ	on	November	11,	200521.	

3.3.2. Upper Air Data 

In	addition	to	surface	meteorological	data,	AERMET	requires	the	use	of	data	from	an	upper	air	sounding	to	

estimate	mixing	heights.		Upper	air	data	from	the	nearest	U.S.	National	Weather	Service	(NWS)	radiosonde	

equipped	station	was	utilized	in	the	modeling	analysis.	In	this	case,	upper	air	data	from	the	Nashville	

International	Airport	(KBNA,	WBAN	No.	13897)	was	obtained	from	the	National	Oceanic	and	Atmospheric	

Administration	(NOAA)	in	FSL	(Forecast	Systems	Laboratory)	format22	for	July	1,	2012	through	June	30,	2015.	

	 	

																																																															

19		ftp://ftp.ncdc.noaa.gov/pub/data/noaa/	

20		ftp://ftp.ncdc.noaa.gov/pub/data/asos‐onemin	

21		http://www.nws.noaa.gov/ops2/Surface/documents/IFW_stat.pdf	 22		http://www.esrl.noaa.gov/raobs/	

Station Name

WBAN

Station

ID

Station

Call Sign Lat. Long.

UTM East

(m)

UTM North

(m)

ASOS One

Minute Data

Available?

Distance

to Cooper

(km)

Somerset‐Pulaski	Co‐J.T.	Wils 63815 KSME 37.054 ‐84.615 712,075 4,103,523 No 6.6

Wayne	County	Airport 63882 KEKQ 36.855 ‐84.856 691,139 4,080,933 No 28.3

Ldon‐Crbn	Apt‐Mgee	Fld	Apt 03849 KLOZ 37.087 ‐84.077 759,811 4,108,522 Yes 46.9

Stuart	Powell	Fld 99999 KDVK 37.578 ‐84.77 696,918 4,161,333 No 66.3

Middlesboro‐Bell	County	Airpo 63875 K1A6 36.611 ‐83.738 791,758 4,056,677 No 87.5

Oak	Ridge 53868 KOQT 36.024 ‐84.238 748,887 3,990,140 Yes 112.7

Blue	Grass	Airport 93820 KLEX 38.041 ‐84.606 710,085 4,213,070 Yes 115.8

Crossville	7	Nw 63855 ‐‐ 36.014 ‐85.135 668,068 3,987,110 No 119.5

Glasgow	Municipal	Airport 00361 KGLW 37.033 ‐85.95 593,386 4,099,049 No 120.9

Versailles	3	Nnw 63838 ‐‐ 38.095 ‐84.747 697,564 4,218,753 No 122.6

Crossville	Memorial	‐Whitson 03847 KCSV 35.951 ‐85.081 673,072 3,980,216 Yes 124.2

Lee	County	Airport 00274 K0VG 36.654 ‐83.218 838,097 4,063,158 No 128.5

Mount	Sterling	Montgomery	Cou 00146 KIOB 38.067 ‐83.983 764,673 4,217,548 No 130.4

Julian	Carroll	Airport 03889 KJKL 37.591 ‐83.314 825,468 4,166,829 Yes 131.1

Upper	Cumberland	Rgnl 99999 KSRB 36.056 ‐85.531 632,308 3,991,158 No 134.1

Capital	City	Airport 53841 KFFT 38.185 ‐84.903 683,657 4,228,420 Yes 134.6

Mc	Ghee	Tyson	Airport 13891 KTYS 35.818 ‐83.986 772,307 3,967,956 Yes 141.8

Bowling	Green	21	Nne 63849 NBWG 37.25 ‐86.233 568,021 4,122,882 No 148.4

Godman	Aaf	Airport 13807 KFTK 37.9 ‐85.967 590,819 4,195,223 No 157.5

Louisville		Intl‐Standiford	F 93821 KSDF 38.181 ‐85.739 610,442 4,226,649 Yes 165.8

Bowman	Field	Airport 13810 KLOU 38.228 ‐85.664 616,936 4,231,956 Yes 166.1

Central Coordinates of Cooper: 714,250 4,097,343
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-8 

3.3.3. Land Use Analysis 

Parameters	derived	from	analysis	of	land	use	data	(surface	roughness,	Bowen	ratio,	and	albedo)	are	also	

required	by	AERMET.		In	accordance	with	U.S.	EPA	guidance,	these	values	were	determined	using	the	latest	

version	of	the	AERSURFACE	tool	(version	13016).23			AERSURFACE	reads	gridded	land	use,	land	cover	data	as	

provided	by	the	United	States	Geological	Survey	(USGS)24	and	associates	such	data	with	representative	values	of	

the	three	parameters	listed	above.		Typically,	the	land	use	analysis	would	be	based	on	moisture	conditions	at	the	

location	of	the	meteorological	data,	that	is,	the	London‐Corbin	Airport	which	would	be	the	best	representation	of	

the	data	in	terms	of	wet,	dry,	or	average	conditions	in	comparison	to	the	30‐yr	averages	for	the	most	recent	

complete	calendar	years	(in	this	case,	1985	through	2014).		The	London‐Corbin	Airport,	however,	is	missing	

several	years	in	this	time	period	and	thus,	another	more	complete,	nearby	set	of	precipitation	data	was	used,	

namely	that	of	the	Jackson	Julian	Carroll	Airport	located	in	Breathitt	County,	Kentucky	about	80	km	to	the	

northeast	in	similar	terrain	to	that	of	London‐Corbin	Airport.		To	make	the	moisture	conditions	determination,	

climatological	records	of	the	annual	precipitation	in	each	modeled	year	(July	1,	2012	through	June	30,	2015)	

were	compared	to	the	1985‐2014	climatological	record25.			

Table	3‐4	shows	the	30	year	precipitation	by	month	for	Jackson	along	with	the	seasonal	totals,	averages,	and	

30th	percentile	high	and	low	values.		These	were	compared	to	the	actual	rainfall	in	each	season	for	each	year	of	

July	1,	2012	through	June	30,	2015	which	determined	the	average,	wet,	or	dry	option	in	AERSURFACE.		Other	

specific	AERSURFACE	settings	were	used	that	represent	the	location	of	the	London‐Corbin	Airport	

meteorological	station.		These	settings	include	location	coordinates,	monthly	versus	seasonal	differentiation,	

aridity,	and,	of	course,	the	surface	moisture	determination	which	was	just	discussed.		This	determination	is	used	

in	AERSURFACE	to	adjust	the	Bowen	ratio	estimated	by	AERSURFACE,	which	in	turn	affects	the	calculation	of	

the	daytime	mixing	heights	used	in	AERMOD.		

	 	

																																																															

23		U.S.	Environmental	Protection	Agency.		2013.	“AERSURFACE	User’s	Guide.”		EPA‐454/B‐08‐001,	Revised	01/16/2013.		Available	

Online:	http://www.epa.gov/scram001/7thconf/aermod/aersurface_userguide.pdf 24		http://www.mrlc.gov/viewerjs/	

25		National	Climactic	Data	Center.	2014	Local	Climatological	Data	(LCD).		
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-9 

Table 3‐4.		Moisture Calculation for Jackson Airport (inches of precipitation)

3.4. COORDINATE SYSTEM 

In	all	modeling	input	and	output	files,	the	locations	of	emission	sources,	structures,	and	receptors	are	

represented	in	the	appropriate	Zone	of	the	Universal	Transverse	Mercator	(UTM)	coordinate	system	using	the	

North	American	Datum	1983	(NAD83).		The	Cooper	Station	and	the	surrounding	area	lies	within	Zone	16.			

3.5. RECEPTOR LOCATIONS 

The	dispersion	modeling	followed	the	guidance	of	the	modeling	TAD	in	terms	of	only	putting	receptors	in	areas	

where	it	is	feasible	to	place	an	actual	monitor.		Consistent	with	the	example	in	Figure	3‐3	from	the	modeling	

TAD,	no	receptors	were	placed	in	lakes,	rivers	or	similar	areas.		As	the	modeling	TAD	states:	

		

“In areas where it is not feasible to place a monitor (water bodies, etc.), receptors can be ignored or not

placed in those locations.		In any case, receptor placement should be of sufficient density to provide

resolution needed to detect significant gradients in the concentrations, with receptors placed closer

together near the source to detect local gradients and placed farther apart away from the source. In

addition, the user should place receptors at key locations such as around facility fence lines (which define

the ambient air boundary for a particular source) or monitor locations (for comparison to monitored

concentrations for model evaluation purposes).”

YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANNUAL Winter Spring Summer Fall 

1985 3.50 2.02 3.27 0.78 5.50 4.19 9.74 5.24 1.40 4.97 6.89 1.74 49.24 7.26 9.55 19.17 13.26

1986 1.84 5.44 1.56 0.95 2.42 2.15 2.73 2.49 3.27 2.38 9.32 3.06 37.61 10.34 4.93 7.37 14.97

1987 2.70 3.46 1.90 3.70 2.25 3.22 6.37 2.64 2.92 0.51 3.15 5.98 38.80 12.14 7.85 12.23 6.58

1988 2.59 2.00 3.09 2.97 4.50 1.37 4.56 4.15 7.82 1.85 6.12 4.03 45.05 8.62 10.56 10.08 15.79

1989 3.48 7.61 6.74 3.23 6.43 6.96 2.21 5.22 7.37 7.36 4.28 2.40 63.29 13.49 16.4 14.39 19.01

1990 2.56 6.27 3.16 2.95 5.08 4.02 4.18 4.21 1.86 4.73 2.91 12.97 54.90 21.8 11.19 12.41 9.5

1991 3.16 4.46 6.08 2.67 4.99 7.01 4.46 2.96 2.62 2.13 5.22 9.35 55.11 16.97 13.74 14.43 9.97

1992 1.87 3.12 5.80 1.66 4.61 4.08 6.67 3.20 3.66 1.60 3.23 4.92 44.42 9.91 12.07 13.95 8.49

1993 2.05 3.54 5.28 3.26 3.74 4.82 4.70 7.70 6.58 4.63 5.08 4.28 55.66 9.87 12.28 17.22 16.29

1994 7.28 7.42 11.78 5.52 3.37 4.85 3.74 6.11 2.45 2.53 2.73 2.98 60.76 17.68 20.67 14.7 7.71

1995 7.16 3.71 3.51 4.90 9.91 4.22 1.77 2.07 4.01 5.03 4.18 2.36 52.83 13.23 18.32 8.06 13.22

1996 5.63 3.11 5.46 5.95 5.86 4.35 4.96 3.01 6.47 4.00 7.28 2.72 58.80 11.46 17.27 12.32 17.75

1997 3.53 2.97 9.76 1.51 5.01 9.15 2.40 4.38 2.03 2.29 4.04 2.21 49.28 8.71 16.28 15.93 8.36

1998 3.76 4.45 2.86 10.00 6.28 8.29 2.46 2.47 2.09 2.59 2.98 5.16 53.39 13.37 19.14 13.22 7.66

1999 6.55 3.04 3.17 3.44 2.47 2.66 2.75 6.58 1.13 3.08 2.65 2.56 40.08 12.15 9.08 11.99 6.86

2000 2.63 3.53 1.94 4.97 4.33 6.80 5.69 4.38 4.92 1.07 1.47 4.35 46.08 10.51 11.24 16.87 7.46

2001 2.50 3.72 2.17 1.69 4.39 4.19 6.43 2.41 1.09 1.41 1.82 2.55 34.37 8.77 8.25 13.03 4.32

2002 4.09 1.24 7.96 4.11 5.23 4.98 5.50 1.72 3.48 6.39 3.61 4.28 52.59 9.61 17.3 12.2 13.48

2003 2.10 7.89 1.47 5.14 5.98 7.54 3.95 5.12 4.33 2.20 5.49 3.78 54.99 13.77 12.59 16.61 12.02

2004 4.23 3.77 3.87 4.01 10.78 6.18 7.02 2.39 7.55 4.96 4.37 3.27 62.40 11.27 18.66 15.59 16.88

2005 5.12 3.03 3.52 7.47 2.50 2.78 4.08 3.92 0.51 1.57 2.66 3.18 40.34 11.33 13.49 10.78 4.74

2006 5.57 1.85 2.89 4.57 3.61 3.24 3.87 3.69 6.39 5.49 2.43 2.03 45.63 9.45 11.07 10.8 14.31

2007 2.83 1.20 2.71 3.22 1.82 2.15 4.05 2.64 2.49 3.80 3.37 5.18 35.46 9.21 7.75 8.84 9.66

2008 2.46 3.41 4.14 4.00 3.24 3.94 6.13 1.16 0.67 1.46 3.03 6.86 40.50 12.73 11.38 11.23 5.16

2009 5.80 1.73 3.52 3.64 9.22 7.03 6.40 3.55 4.88 3.54 0.80 5.96 56.07 13.49 16.38 16.98 9.22

2010 4.27 3.11 2.43 2.61 7.92 5.60 3.34 3.51 2.05 1.68 5.77 2.97 45.26 10.35 12.96 12.45 9.5

2011 2.72 3.97 4.74 10.20 6.69 5.49 6.02 3.07 3.20 4.25 5.48 4.18 60.01 10.87 21.63 14.58 12.93

2012 4.86 3.90 4.07 2.67 4.20 1.91 7.39 4.75 6.77 4.24 0.84 6.39 51.99 15.15 10.94 14.05 11.85

2013 5.73 1.91 4.63 3.70 4.23 6.36 6.62 10.04 1.27 2.13 3.01 7.09 56.72 14.73 12.56 23.02 6.41

2014 3.15 4.47 5.51 5.43 2.30 3.12 5.77 8.55 2.35 7.77 2.97 2.49 53.88 10.11 13.24 17.44 13.09

2015 2.12 4.06 6.26 10.29 1.74 7.42 6.18 18.29 7.42 0

Precipitation location from http://www.ncdc.noaa.gov/cdo-web/datatools/findstation Upper 30th 13.27 16.31 14.97 13.23

KJLK precipitation data - obtained 2014 cumulative report from http://www1.ncdc.noaa.gov/pub/orders Lower 30th 10.05 11.15 12.22 8.17

2010 A A A A

A = average precip 2011 A W A A

W = wet precip 2012 W D A A

D = dry precip 2013 W A W D

2014 A A W A

2015 D W W

Note: 30year Local climatological Data for Jackson, KY was used due to missing data for London-Corbin airport
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-10 

Figure 3‐3.		Modeling TAD Receptor Grid Showing Example Excluded Locations over Water

The	proposed	receptor	grid	for	the	modeling	of	the	Cooper	Station	combined	a	multi‐nested,	circular	Cartesian	

grid	at	various	spacing	intervals	centered	on	the	main	Cooper	Station	stack	along	with	receptor	points	on	the	

facility’s	fence	line.		For	the	air	dispersion	modeling	analyses,	ground‐level	concentrations	were	calculated	from	

the	fence	line	out	to	the	location	and	magnitude	of	the	significant	concentration	gradient	as	specified	by	the	

modeling	TAD.		To	accommodate	the	possible	farthest	extent	of	this	modeling	domain	and	receptor	grid,	the	

receptors	are	a	series	of	nested	grids	as	follows:	

Fence Line Grid:		“Fence	line”	grid	consisting	of	evenly‐spaced	receptors	50	meters	apart	placed	along	the	

main	fence	line	of	the	Cooper	Station,	

Fine Cartesian Grid:		A	“fine”	grid	containing	100‐meter	spaced	receptors	extending	to	3	km	from	the	

center	of	the	property	and	beyond	the	fence	line,	

Medium‐Fine Cartesian Grid:		A	“medium‐fine”	grid	containing	250‐meter	spaced	receptors	extending	

from	3	km	to	5	km	from	the	center	of	the	facility,	exclusive	of	receptors	on	the	fine	grid,		

Medium‐Coarse Cartesian Grid:		A	“medium‐coarse”	grid	containing	500‐meter	spaced	receptors	

extending	from	5	km	to	10	km	from	the	center	of	the	facility,	exclusive	of	receptors	on	the	fine	and	medium‐

fine	grids,	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-11 

Coarse Cartesian Grid:		A	“coarse	grid”	containing	1,000‐meter	spaced	receptors	extending	from	10	km	to	

20	km	from	the	center	of	the	facility,	exclusive	of	receptors	on	the	fine,	medium‐fine,	and	medium‐coarse	

grids.	

Figure	3‐4	shows	the	innermost	grids	of	the	proposed	receptors	used	in	the	modeling.		As	can	be	seen,	receptors	

in	the	Cumberland	River	have	been	eliminated.		Also	shown	is	the	current	fence	line	of	the	facility	(innermost	

line	of	yellow	receptors)	and	the	property	line	as	a	red	annotation	to	show	the	extent	of	EKPC	property	holdings	

in	the	area.	

Figure 3‐4.		Innermost Portion of the Proposed Modeling Receptor Grid for Cooper

3.6. TERRAIN ELEVATIONS 

The	terrain	elevation	for	each	receptor,	building,	and	emission	source	was	determined	using	USGS	1	arc‐second	

National	Elevation	Data	(NED).		The	NED,	obtained	from	the	USGS26,	has	terrain	elevations	at	30‐meter	intervals.		

Using	the	AERMOD	terrain	processor,	AERMAP	(version	11103),	the	terrain	height	for	each	receptor,	and	

outlying	buildings	included	in	the	model	was	determined	by	assigning	the	interpolated	height	from	the	digital	

terrain	elevations	surrounding	each	source.		These	were	used	directly	in	the	AERMOD	model.	

In	addition,	AERMAP	was	used	to	compute	the	hill	height	scales	associated	with	each	elevated	receptor	located	

above	the	Cooper	Station	source	base	elevation.		This	computation	enables	the	model	to	determine	the	effect	

that	terrain	will	have	on	plumes	from	the	sources.		AERMAP	searches	all	nearby	elevation	points	for	the	terrain	

height	and	location	that	has	the	greatest	influence	on	each	receptor	to	determine	the	hill	height	scale	for	that	

receptor.		AERMOD	then	uses	the	hill	height	scale	in	order	to	select	the	point	where	a	plume	may	divide	between	

																																																															

26		http://www.mrlc.gov/viewerjs/	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-12 

going	around	a	terrain	feature	and	lofting	over	the	feature.			Review	of	the	area	indicates	that	a	few	hills	exist	

near	the	Cooper	Station	and	thus,	the	inclusion	of	terrain	elevations	in	the	modeling	is	paramount.		Figure	3‐5	

shows	a	relief	map	of	the	area.	

Figure 3‐5.		Relief Map of Area within 20 km of Cooper Station

3.7. COOPER STATION EMISSION SOURCES 

The	Cooper	Station	has	only	one	major	source	of	continuous	SO2	emissions,	which	is	the	main	stack	associated	

with	coal‐fired	Units	1	and	2.		Other	intermittent	sources	of	SO2	emissions	include	an	Emergency	Diesel	

Generator	(Unit	08),	a	Communication	Tower	Emergency	Generator	(Unit	12),	Fire	Pump	Engine	(Unit	13),	and	

the	Burnside	Service	Center	Emergency	Generator	(Unit	14).		All	are	permitted	to	operate	no	more	than	100	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-13 

hours	per	year	in	non‐emergency	situations	and	thus,	do	not	contribute	to	the	annual	distribution	of	daily	

maximum	1‐hour	SO2	concentrations.27			

In	addition,	actual	hourly	and	annual	SO2	emissions	from	these	diesel	fuel	and	propane‐fired	emergency	engines	

are	negligible	given	the	relatively	small	horsepower	rating	of	the	engines	and	the	very	low	sulfur	content	of	the	

fuels	used.		Consistent	with	U.S.	EPA’s	guidance28	for	treatment	of	intermittently	operated	source	like	emergency

engines	in	1‐hr	SO2	and	NO2	NAAQS	demonstrations,	EKPC	excluded	these	engines	from	the	modeled	source	

inventory	and	only	considered	SO2	emissions	from	Units	1	and	2	in	the	modeling	analysis.	

The	preferred	modeling	approach	for	establishing	modeled	emission	rates	recommended	in	the	modeling	TAD	is	

the	use	of	CEMS	data,	where	available,	as	a	CEMS‐derived,	hour‐by‐hour	modeled	emission	rate	dataset	provides	

the	most	accurate	representation	of	the	actual	emissions	history	of	the	source	for	the	relevant	time	period	

considered	in	the	modeling.		Currently	and	in	the	future,	the	combined	flows	of	each	unit	at	Cooper	Station	exit	

through	a	common	stack.		The	following	discussion	recognizes	this	fact	and	is	geared	towards	defining	the	

individual	and	combined	stack	emissions	and	flows.	

Further	details	regarding	the	derivation	of	the	modeled	hour‐by‐hour	SO2	emission	rates	representing	the	sum	

of	the	actual	emissions	from	Unit	2	and	the	allowable	emissions	from	Unit	1	and	the	combined	Unit	1	and	2	stack	

parameters	for	each	relevant	Cooper	Station	operating	mode	(i.e.,	both	units	running	and	only	Unit	1	running)	

are	presented	in	the	following	subsections	with	explicit	references	to	the	associated	model	input	parameter	

derivation	spreadsheet	included	in	Appendix	C	to	this	modeling	report.	

3.7.1. Cooper Unit 1 Modeled Emission Rate 

Because	Unit	1	is	undergoing	modification	to	tie‐in	the	exhaust	gases	into	the	existing	dry	flue	gas	

desulfurization	(DFGD)	currently	serving	Unit	2,	use	of	Unit	1	CEMS	data	from	the	relevant	time	period	is	not	

representative	of	future	emissions	or	impacts.		This	SO2	emissions	control	project	for	Unit	1	is	expected	to	be	

completed	by	January	1,	2016	which	is	well	before	the	consent	decree‐driven	July	2016	SO2	NAAQS	attainment	

designation	deadline.	

Under	these	circumstances,	an	allowable	SO2	emission	rate	for	Unit	1	is	applied	for	every	hour	of	the	modeled	

meteorological	period.		The	Unit	1	allowable	SO2	emission	rate	in	its	current	configuration	is	3.3	lb/MMBtu	on	a	

24‐hour	average	basis	(refer	to	Condition	B.2.c	for	Unit	1	on	page	3	of	80).		In	addition,	after	Unit	1	is	tied	into	

the	DFGD,	it	will	become	subject	to	an	additional	limit	of	95%	control	or	0.100	lb/MMBtu	on	a	30‐day	rolling	

average.		Based	on	this	suite	of	SO2	emission	limits	which	will	be	federally	enforceable,	EKPC	performed	

dispersion	modeling	of	an	emission	rate	equivalent	to	0.165	lb	SO2/MMBtu	(i.e.,	178	lb/hr	based	on	the	

maximum	heat	input	capacity	of	Unit	1	of	1,080	MMBtu/hr).		This	emission	rate	is	derived	by	taking	95%	of	the	

current	Title	V	permit	limit	of	3.3	lb	SO2/MMBtu.		As	a	further	measure	of	added	conservatism,	this	rate	was	

modeled	assuming	8,760	hours	of	operation,	rather	than	only	modeling	this	rate	at	times	when	Unit	1	was	

actually	running	during	the	modeled	three‐year	period.		EKPC	believes	that	the	emission	limits	discussed	above	

(i.e.,	3.3	lb	SO2/MMBtu	and	95%	reduction	or	0.100	lb	SO2/MMBtu)	are	sufficient	to	support	the	modeled	

emission	rate,	and	no	additional	limits	are	necessary.		This	modeling	approach	is	different	than	proposed	in	the	

																																																															

27		Additional Clarification Regarding Application of Appendix W Modeling Guidance for the 1‐Hour NO2 National Ambient Air Quality

Standard,	Memorandum	from	Tyler	fox,	Leader	Air	Quality	Modeling	Group	to	U.S.	EPA	Regional	Air	Division	Directors,	March	1,	

2011.	

28	Ibid.	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-14 

modeling	protocol,	but	reflects	consideration	of	EPA	Region	4’s	comments	on	the	modeling	protocol29	and	

discussions	with	KDAQ.	

3.7.2. Cooper Unit 2 Modeled Emission Rate 

As	referenced	in	Section	2.6	of	the	modeling	protocol	submitted	on	August	3,	2015,	EKPC	has	relied	on	CEMS	

data	from	Unit	2	directly	with	no	alterations	or	refinements	because	this	boiler	has	been	tied	into	the	DFGD	

system	during	the	entire	modeling	period.		This	data	is	also	expected	to	represent	future	operation	of	this	unit	

after	the	Unit	1	duct	rerouting	project	is	completed	and	in	any	year	after	the	July	2016	SO2	NAAQS	designation	

deadline.		Using	coal	heat	input	capacity	as	a	measure	of	the	size	of	each	electric	generating	unit	at	the	Cooper	

Station,	Unit	2	is	nearly	two	times	larger	than	Unit	1	(i.e.,	2,089	MMBtu/hr	for	Unit	2	versus	1,080	MMBtu/hr	for	

Unit	1).		Design	evaluations	and	engineering	judgement	suggest	the	Unit	2	SO2	emissions	profile	will	not	change	

as	a	result	of	adding	a	relatively	small	amount	of	additional	exhaust	flow	and	SO2	emissions	loading	contributed	

by	the	smaller	Unit	1	after	the	tie‐in.		In	light	of	these	facts,	EKPC	possesses	a	complete	three‐year	record	of	valid	

SO2	emissions	data	reflective	of	current	and	future	operation	of	Unit	2	while	operating	under	a	federally	

enforceable	SO2	emission	limit	that	mandates	efficient	operation	of	the	DFGD	(refer	to	the	95%	SO2	removal	

efficiency	or	0.100	lb	SO2/MMBtu	emission	limit	applicable	on	a	30‐day	rolling	average	basis	in	Condition	B.2.c	

of	Title	V	Permit	V‐12‐019	R1	on	page	11	of	80).		With	basically	two‐thirds	of	the	future	SO2	emissions	from	

Cooper	Station	characterized	by	CEMS	data	collected	in	the	representative	three‐year	timeframe	selected	for	the	

modeling,	EKPC	does	not	believe	it	would	be	appropriate	or	justified	to	consider	other	modeled	emission	rate	

derivation	techniques	for	Unit	2	(e.g.,	modeling	an	allowable	emission	rate).	

The	CEMS	data	handling	and	acquisition	system	(DHAS)	for	Unit	2	produces	hourly	average	SO2	emission	rates	

(refer	to	column	C	of	the	1. Unit 1 & 2 Emissions	tab	in	model	input	parameter	spreadsheet	in	Appendix	C)	based	

on	the	measured	SO2	concentration	and	flow	rate	in	the	Unit	2	exhaust	after	it	exits	the	DGFD	but	before	it	

merges	with	the	currently	uncontrolled	(for	SO2	)	Unit	1	exhaust	stream	at	the	base	of	the	combined	Unit	1	and	2	

stack.		A	comprehensive	review	of	the	hourly	SO2	emissions	dataset	for	Unit	2	generated	by	the	DAHS	indicates	

two	issues	requiring	data	substitution	techniques.			

First,	missing	and	out‐of‐control	data	flagged	by	the	DAHS	was	indicated	(refer	to	TRUE	values	in	column	D	of	

the	1. Unit 1 & 2 Emissions	tab	in	the	model	input	parameter	spreadsheet	in	Appendix	C).		Missing	values	and	

out‐of‐control	(OOC)	data	periods	are	required	to	be	filled	with	estimated	SO2	emission	rates	because	actual	

emissions	were	occurring	during	these	events.		The	emissions	were	just	not	being	measured	and	recorded	

properly	for	these	hours.		Of	the	26,280	data	points	in	the	3‐year	hourly	SO2	emission	rate	data	set	for	Unit	2,	

only	48	hours	spread	over	19	events	were	flagged	by	the	DAHS	as	missing	or	OOC	when	Unit	2	was	in	operation	

(99.92%	data	completeness	in	3‐year	period).		No	single	missing	or	OOC	data	period	exceeds	more	than	6	hours	

in	duration.			

Given	the	very	limited	number	and	duration	of	missing/OOC	data	periods,	EKPC	chose	a	linear	interpolation	

filling	technique	using	the	two	good	data	points	surrounding	the	missing/OOC	data	period	rather	than	a	more	

complex	technique	involving	emission	factors	or	use	of	peak	values	from	a	representative	range	of	boiler	

operating	conditions.		This	interpolation	technique	was	performed	using	the	FORECAST	function	in	Microsoft®

Excel.		The	first	required	field	to	execute	this	function	is	a	missing/OOC	data	period	count	(refer	to	column	F	of	

the	1. Unit 1 & 2 Emissions	in	the	model	input	parameter	spreadsheet	in	Appendix	C)	that	starts	at	1	for	the	first	

missing/OOC	hour	from	an	event	and	continues	counting	until	a	valid	data	point	is	encountered.		The	sequential	

integer	list	of	missing/OOC	hours	for	each	event	defines	the	number	of	data	points	for	which	an	interpolation	

																																																															

29		Email	from	Mr.	Rick	Gillam,	EPA	Region	4	Environmental	Engineer/Air	Modeler	to	Mr.	Ben	Cordes,	KDAQ	Air	Dispersion	

Modeling	Section	Supervisor,	RE: EKPC Cooper Station	‐	1‐Hour SO2 Air Dispersion Modeling Protocol,	August	17,	2015	and	email	

from	Mr.	Gillam	to	Mr.	Cordes	on	August	25,	2015;	conference	call	between	EKPC,	KDAQ	and	EPA	Region	4	on	August	27,	2015.	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-15 

calculation	is	required.		For	example,	if	three	sequential	data	points	were	missing,	the	counter	sets	the	first	

missing	hour	to	1,	the	second	missing	hour	to	2,	and	the	third	missing	hour	to	3.		The	next	field	required	for	this	

function	is	the	last	good	hour	before	the	missing/OOC	data	period	starts	and	the	first	good	hour	after	the	

missing/OOC	data	period	ceases.		These	SO2	emission	rates	define	the	starting	point	and	end	point	for	the	linear	

interpolation	(refer	to	columns	G	and	H	of	the	1. Unit 1 & 2 Emissions	in	the	model	input	parameter	spreadsheet	

in	Appendix	C).		The	final	field	required	for	the	function	is	the	range	of	missing/OOC	hours	where	a	0	is	assigned	

to	the	position	of	the	last	good	hour,	and	a	value	one	greater	than	the	duration	of	the	missing/OOC	event	is	

assigned	for	the	first	good	value	after	the	missing/OOC	period.		Table	3‐5	provides	an	example	of	how	the	

FORECAST	function	is	applied	to	perform	linear	interpolation	where	blue	text	indicates	data	directly	from	the	

CEMS	DAHS,	black	text	indicates	a	calculated	value,	green	highlights	indicate	a	good	data	hour,	and	orange	

highlights	indicate	a	missing/OOC	hour	requiring	filling.	

Table 3‐5.		Example of Missing/OOC SO2 Emissions Data Filling Technique

	 	

The	missing/OOC	data	flag	built	into	the	DAHS	indicates	a	6‐hour	block	of	missing	data	occurred	from	11/14/12	

11	AM	until	11/14/12	at	5	PM.		The	last	good	reading	before	the	missing/OOC	data	period	starts	(1.10	lb/hr)	

and	the	first	good	reading	after	the	missing/OOC	ends	(13.60	lb/hr)	defines	the	bounds	for	the	SO2	emission	rate	

interpolation	(i.e.,	range	of	“Y”	values).		The	starting	“X”	value	for	the	interpolation	is	always	set	to	hour	0	and	

the	ending	“X”	value	is	set	to	one	hour	higher	than	the	duration	of	the	event	(7	in	this	case).		With	these	inputs,	

the	results	of	the	FORECAST	function	creates	a	smooth	line	of	6	data	points	connecting	the	last	good	hour	before	

the	event	to	the	first	good	hour	after	the	event.		An	identical	approach	was	applied	to	all	19	events	in	the	Unit	2	

SO2	emissions	data	set.	

The	second	issue	requiring	additional	data	processing	occurred	when	the	operating	parameter	data	tag	for	Unit	

2	operating	time	(refer	to	column	E	in	the	1. Unit 1 & 2 Emissions	tab	of	the	model	input	parameter	spreadsheet	

in	Appendix	C)	is	set	to	zero	for	several	hours	while	the	Unit	2	CEMS	is	indicating	emissions	greater	than	zero	

(refer	to	column	C	in	the	1.	Unit	1	&	2	Emissions	tab	of	the	model	input	parameter	spreadsheet	in	Appendix	C).		

During	the	vast	majority	of	these	hours,	Unit	1	is	running.		The	Unit	2	operating	hour	tag	is	a	definitive	indication	

of	operating	status,	so	EKPC	zeroed	out	the	anomalous	Unit	2	SO2	emissions	data	during	Unit	2	downtime.		This	

data	substitution	for	Unit	2	downtime	was	accomplished	by	simply	adding	logic	to	the	filled	Unit	2	SO2	emission	

rate	calculation	(refer	to	column	K	of	the	1. Unit 1 & 2 Emissions	in	the	model	input	parameter	spreadsheet	in	

Appendix	C)	that	uses	the	CEMS‐monitored	SO2	emission	rate	only	if	the	operating	time	flag	is	greater	than	0	

minutes.		The	first	instance	in	the	3‐year	data	period	where	this	type	of	data	substitution	was	completed	for	an	

invalid	hour	is	shown	in	Table	3‐6.	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-16 

Table 3‐6.		Example of Unit 2 SO2 Emissions during Downtime

The	modeled	emission	rate	discussion	in	Section	2.6	of	the	modeling	protocol	indicated	startup	and	shutdown	

emissions	would	be	handled	in	a	manner	consistent	with	U.S.	EPA’s	intermittent	source	guidance	regarding	

whether	or	not	such	events	could	be	excluded	from	the	modeling	analysis.		In	accordance	with	relevant	

guidance,	the	CEMS	data	was	not	further	processed	to	remove	SO2	emissions	during	startup	or	shutdown	of	Unit	

2.	

3.7.3. Combined Cooper Units 1 and 2 Modeled Emission Rate 

The	combined	stack	for	Cooper	Units	1	and	2	is	represented	as	a	single	point	source	in	the	SO2	modeling	

analysis.		As	such,	the	modeled	emission	rate	must	represent	the	combined	SO2	emissions	from	both	Units	1	and	

2.		The	filled	Unit	2	actual	emissions	dataset	obtained	from	the	CEMS	defines	the	SO2	emissions	contribution	

from	Unit	2	on	an	hour‐by‐hour	basis	(refer	to	Column	D	of	the	3. Model Input Parameters	tab	of	the	model	input	

parameter	spreadsheet	in	Appendix	C).		The	fixed	allowable	emission	rate	for	Unit	1	applied	on	a	continuous	

basis	(refer	to	Column	C	of	the	3. Model Input Parameters	tab	of	the	model	input	parameter	spreadsheet	in	

Appendix	C)	is	added	to	the	Unit	2	actual	emission	rate	that	varies	on	an	hour‐by‐hour	basis	to	define	the	

modeled	emission	rate	for	the	combined	Unit	1	and	2	stack	(refer	to	Columns	E	and	F	of	the	3. Model Input

Parameters	tab	of	the	model	input	parameter	spreadsheet	in	Appendix	C).	

3.7.4. Stack Parameter Selection 

In	Table	2‐3	of	the	modeling	protocol,	EKPC	indicated	a	single	set	of	stack	parameters	would	be	used	for	all	

hours	of	the	modeling	analysis	based	on	the	design	stack	gas	conditions	when	both	Units	1	and	2	are	running	

determined	from	the	design	study	supporting	the	Unit	1	DFGD	tie‐in	project.		Upon	further	consideration,	EKPC	

determined	that	such	an	approach	could	overestimate	the	stack	exit	velocity	at	times	when	only	Unit	1	was	

operating.		To	address	this	issue,	the	final	selection	process	involved	picking	from	two	sets	of	design	flow	rates:		

1)	both	Units	1	and	2	running	with	both	units	exhaust	routed	through	the	DFGD	(i.e.,	the	original	design	case	

presented	in	Table	2‐3	of	the	modeling	protocol),	and	2)	only	Unit	1	running	with	its	exhaust	routed	through	the	

DFGD.		The	flow	rates	and	corresponding	exit	velocities	assigned	in	these	two	cases	are	documented	in	the	

modeling	input	parameter	spreadsheet	in	Appendix	C	(refer	to	Columns	H	and	I	of	the	2. Stack Parameters	tab	in	

the	model	input	parameter	spreadsheet	in	Appendix	C)	and	are	presented	in	Table	3‐7.			

Finally,	the	stack	temperature	for	all	Cooper	Station	operating	cases	is	set	to	160	deg.	F	which	represents	the	

design	basis	for	the	DFGD	and	provides	the	best	estimate	of	the	exhaust	conditions	from	the	combined	Unit	1	

and	2	stack	after	the	Unit	1	DFGD	tie‐in	project	is	completed.		Review	of	actual	in‐duct	exhaust	temperatures	for	

Unit	2	downstream	of	the	DFGD	indicates	this	design	value	may	underestimate	actual	stack	temperatures	that	

will	occur	after	the	Unit	1	tie‐in,	and	thus,	this	input	parameter	is	expected	to	result	in	conservatively	high	

modeled	impacts	(i.e.,	lower	stack	temperatures	produce	lower	thermal	buoyancy,	less	plume	rise,	and	higher	

modeled	impacts	when	all	other	parameters	are	held	constant).	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-17 

Table 3‐7.		Cooper Station Source Parameters

3.7.5. Hourly Emissions File Creation 

The	final	step	in	the	process	of	assigning	model	input	parameters	for	the	Cooper	Station	1‐hr	SO2	NAAQS	

attainment	demonstration	modeling	analysis	is	developing	the	hourly	emission	rate	and	stack	parameter	file	fed	

to	AERMOD.		The	previously	discussed	hour‐by‐hour	varying	modeled	emission	rate	for	Units	1	and	2	on	a	

combined	basis	is	assigned	to	the	hourly	emissions	file.		The	Cooper	Station	operating	status‐based	exit	velocity	

is	then	assigned	depending	on	whether	both	units	are	operating	or	only	Unit	1	is	operating	(refer	to	column	G	of	

the	3. Model Input Parameters	tab	in	the	model	input	parameter	spreadsheet	carried	forward	from	column	I	of	

the	2. Stack Parameters	tab	in	the	model	input	parameter	spreadsheet	in	Appendix	C).		The	constant	exit	

temperature	discussed	previously	is	assigned	to	every	hour	in	the	modeling	period.		Finally,	the	modeled	

emission	rate,	stack	temperature,	and	exit	velocity	are	merged	into	an	hour‐by‐hour	text	string	which	matches	

the	syntax	of	the	AERMOD	hourly	emissions	file	invoked	with	the	SO	HOUREMIS	keyword	(refer	column	J	of	the	

3. Model Input Parameters	tab	in	the	model	input	parameter	spreadsheet	in	Appendix	C).	

3.8. OTHER SOURCE INVENTORY 

Other	sources	of	SO2	emissions	in	the	area	surrounding	the	Cooper	Station	were	evaluated	for	inclusion	in	the	

modeling.		This	evaluation	is	documented	in	the	regional	inventory	processing	spreadsheet	provided	on	the	CD	

in	Appendix	C.	

Consistent	with	the	modeling	TAD,	the	determination	of	which	sources	to	model	followed	a	multi‐step	process.		

With	the	goal	of	the	modeling	being	to	determine	those	sources	that	could	cause	or	contribute	to	a	NAAQS	

violation,	the	factors	considered	in	developing	the	modeling	inventory	included	the	magnitude	of	the	SO2

emissions,	the	source	parameters,	the	proximity	to	Cooper,	and	the	level	and	extent	of	the	impact	of	the	nearby	

source.		As	recommended	(and	referred	to	by	the	modeling	TAD)	by	the	additional	clarifications	memorandum	

of	201130	which	is	applicable	to	both	SO2	and	NO2,	several	options	for	screening	out	regional	inventory	sources	

were	considered	(the	AERSCREEN	model	approach	in	the	2011	memorandum	was	not	used)	and	include:		

1. Analyzed	contour	plots	of	each	fully	modeled	source	(AERMOD)	which	clearly	depict	the	impact	area	of	

the	source,	preferably	overlaid	on	a	map	that	identifies	key	geographic	features	that	may	influence	the	

dispersion	patterns.		The	concentration	contour	plot	also	served	to	visually	depict	the	concentration	

gradients	associated	with	the	source’s	impact	and	the	overlay	of	adjacent	concentration	gradients	from	

nearby	sources.	

																																																															

30		Additional Clarification Regarding Application of Appendix W Modeling Guidance for the 1‐hour NO2 National Ambient Air Quality

Standard,	memorandum	form	Tyler	Fox	to	Regional	Air	Division	Directors,	March	1,	2011.	

Model ID Description

UTM

Easting3

(m)

UTM

Northing3

(m)

Elevation

(m)

Emission

Rate

(lb/hr)

Stack

Height

(ft)

Temp.

(F)

Flow

Rate1

(acfm)

Exit

Velocity1

(ft/s)

Diameter

(ft) Note

COOPER Units	1	&	2	Operating 714,250 4,097,343 243.84 CEMS 260 160.0 1,100,000 72.05 18.0 2

COOPER Only	Unit	1	Operating 714,250 4,097,343 243.84 178.20 260 160.0 260,000 17.03 18.0 2

1

		Stack	flow	rates	and	exit	velocities	for	Units	1	&	2	in	operation	and	Unit	1	operating	alone	are	based	on	design	study	performed	by	engineering	

firm	contracted	to	perform	Unit	1	tie‐in	to	DFGD.

2

		As	indicated,	only	one	Modeling	ID	exists	in	the	AERMOD	input	file,	however	stack	exit	velocity	is	varied	within	an	hourly	emission	input	file	

with	respect	to	the	specific	Units	operating	for	a	given	hour.

3

	UTM	coordinates	are	represented	in	NAD83	datum	Zone	16.
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-18 

2. Identified	meteorological	conditions	that	control	the	source’s	impacts.		Use	the	MAXDAILY	or	

MXDYBYYR	AERMOD	output	options	to	help	identify	the	appropriate	time	periods	to	be	used	to	

calculate	controlling	design	values.		Meteorological	data	sets	were	cross‐checked	with	model‐generated	

dates	of	highest	concentrations	to	assist	in	identifying	these	controlling	meteorological	conditions.	

3. Using	a	wind	rose	of	the	meteorological	data	in	the	modeling	can	help	to	analyze	flow	patterns	and	

determine	the	potential	for	the	cross‐coincidence	of	impacts	from	various	sources.

EKPC	implemented	elements	of	all	three	regional	screening	methods.		Because	this	implementation	was	more	

robust	than	applying	the	AERSCREEN	Model,	that	method	was	not	deemed	necessary	and	was,	thus,	not	used.	

An	additional	technique	for	differentiating	contributing	sources	is	the	use	the	“20D	method”31.		The	20D	method	

says	that	if	the	ratio	of	the	emissions	to	the	distance	between	sources	is	less	than	20	(Q/d	<	20),	a	source	does	

not	need	to	be	included	in	the	modeling.		The	specification	of	the	variables	in	the	20D	analysis	include:	

 Q	=		Annual	actual/potential	emissions	in	tons/year	

 d	=		Distance	from	the	target	source	in	kilometers	to	the	Cooper	Station	

Because	both	allowable	(or	potential)	and	actual	emissions	are	referenced	in	the	modeling	TAD	for	use	in	

modeling	regional	sources,	a	Q/d	ratio	based	on	both	site‐wide	actual	and	site‐wide	potential	emissions	has	

been	developed	(refer	to	the	Q‐D	Analysis	tab	in	the	regional	inventory	processing	spreadsheet	provided	on	the	

CD	in	Appendix	C).			

Figure	3‐6	shows	all	SO2	source	locations	within	50	km	of	the	Cooper	Station	that	reported	actual	SO2	emissions	

in	2013.		An	actual	annual	SO2	emissions	magnitude	indicator	categorized	by	size	and	color	of	the	source	marker	

on	the	map	is	used	to	differentiate	larger	sources	from	smaller	sources	(see	legend	on	figure).		Of	the	16	facilities	

emitting	SO2	within	20	km	of	the	Cooper	Station,	only	one	source	[Kingsford	Manufacturing	Company	(KMC)]	

has	actual	annual	emissions	greater	than	2.5	tpy.		With	the	exception	of	KMC,	the	cumulative	annual	SO2

emissions	from	all	sources	within	20	km	of	Cooper	are	only	8.5	tpy	on	actual	emissions	basis	and	40	tpy	on	a	

potential	emissions	basis	(refer	to	columns	G	and	I	in	the	NAAQS 20D List	tab	of	the	regional	inventory	

processing	spreadsheet	in	Appendix	C).		In	comparison	to	the	modeled	SO2	emission	rates	from	Cooper	Unit	1	

and	2,	these	small	sources	generate	negligible	quantities	of	SO2	emissions.		Furthermore,	the	vast	majority	of	

these	sources	are	located	to	the	north	of	Cooper	Station	which	is	in	a	low	frequency	wind	sector	for	wind	

directions	causing	transport	from	the	regional	source	locations	to	the	area	of	highest	impacts	for	Cooper	(refer	

to	frequencies	for	“blowing	from”	wind	sectors	in	Figure	3‐8	for	north,	northeast,	and	northwest	quadrants	of	

the	London‐Corbin	airport	meteorological	station’s	wind	rose).		Finally,	the	cumulative	Q/d	ratio	for	all	sources	

within	20	km	of	the	Cooper	Station	other	than	KMC	is	1.5	tpy/km	on	an	actual	emissions	basis	and	6.2	tpy/km	

on	a	potential	emissions	basis,	which	are	both	well	below	the	20	tpy/km	threshold	that	applies	on	an	individual	

source	basis.		Based	on	this	Q/d	profile	for	sources	within	20	km	of	Cooper	Station,	even	if	all	sources	were	

considered	to	form	a	“cluster”,	their	cumulative	Q/d	ratio	would	still	support	screening	the	sources	out	of	the	

regional	inventory.			

When	the	additional	38	facilities	located	between	20	and	50	km	from	the	Cooper	Station	are	added	to	the	

regional	inventory	evaluation,	all	but	one	source	[EKPC	Laurel	Ridge	Landfill	Gas	to	Energy	(LGTE)	Facility]	has	

actual	annual	SO2	emissions	below	3.5	tpy.		The	EKPC	Laurel	Ridge	LGTE	Facility	(with	actual	SO2	emissions	of	

36.1	tpy	and	potential	SO2	emissions	of	41.3	tpy)	is	located	approximately	45	km	east	of	the	Cooper	Station.		The	

London‐Corbin	airport	meteorological	station	wind	rose	in	Figure	3‐8	indicates	a	very	low	frequency	of	winds	

																																																															

31		A Screening Method for PSD,	letter	from	Eldewins	Haynes,	North	Carolina	Air	Permit	Unit	to	Lewis	Nagler,	EPA,	Region	4,	

Meteorologist,	July	22,	1985.	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-19 

blowing	from	the	East	to	the	West	that	would	favor	transport	of	SO2	emissions	from	the	Laurel	Ridge	LGTE	

Facility	to	the	area	surrounding	the	Cooper	Station.		In	addition,	the	single	stack	located	at	the	Laurel	Ridge	

LGTE	Facility	is	only	33	feet	tall	which	does	not	favor	the	type	of	long	range	transport	needed	to	significantly	

overlap	with	the	Cooper	Station	impacts,	especially	considering	the	moderately	complex	terrain	associated	with	

the	area	between	the	landfill	and	Cooper	Station.		As	a	final	screening	technique,	EKPC	evaluated	the	combined	

Q/d	for	all	sources	between	20	km	and	50	km	from	the	Cooper	Station	and	again	determined	these	ratios	(1.1	

tpy/km	on	an	actual	emissions	basis	and	5.7	on	a	potential	emissions	basis)	do	not	support	the	addition	of	any	

regional	inventory	sources	beyond	20	km	of	the	Cooper	Station.	

To	ensure	any	SO2	impacts	from	the	small	sources	screened	out	of	the	inventory	are	accounted	for	within	the	

NAAQS	analysis,	EKPC	is	proposing	to	use	a	conservative	background	concentration	based	on	the	design	value	in	

the	form	of	the	1‐hr	SO2	NAAQS	from	the	selected	Mammoth	Cave	SO2	monitoring	station	(refer	to	Section	3.10).		

Selecting	the	design	value	from	a	background	monitor	versus	temporal	pairing	of	monitored	background	

concentrations	with	modeled	concentrations	generally	offers	the	ability	to	implement	more	extensive	screening	

of	small	regional	sources	due	to	the	higher	magnitude	of	the	background	concentration	included	in	the	NAAQS	

demonstration.		Therefore,	EKPC	believes	the	regional	inventory	screening	process	and	background	

concentration	selection	applied	for	the	Cooper	SO2	NAAQS	analysis	achieve	an	appropriate	balance	between	

more	extensive	regional	source	screening	and	selection	of	a	conservatively	high	background	concentration.	

As	shown	in	Figure	3‐7	and	Tables	B‐1.1	and	B‐1.2	of	Appendix	B,	the	KMC	facility	in	Burnside,	Kentucky	is	the	

only	nearby	SO2	emissions	source	that	is	of	sufficient	magnitude	and	proximity	to	warrant	consideration	in	the	

refined	modeling.		The	modeled	source	parameters	for	KMC	are	provided	in	Table	B‐1.1	of	Appendix	B.		
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-20 

Figure 3‐6. Map Showing Regional Source Locations and SO2 Emissions Magnitude near Cooper Station
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-21 

Figure 3‐7.		Results of Regional Source Screening Evaluation based on Q/d Analysis

3.9. BUILDING INFLUENCES 

The	U.S.	EPA’s	Building	Profile	Input	Program	(BPIP)	with	Plume	Rise	Model	Enhancements	(PRIME)	(version	

04274),	was	used	to	account	for	building	downwash	influences	on	the	Unit	1	&	2	main	stack.		The	purpose	of	a	

building	downwash	analysis	is	to	determine	if	the	plume	discharged	from	a	stack	will	be	influenced	by	the	

turbulent	wake	of	any	onsite	buildings	or	other	structures,	resulting	in	downwash	of	the	plume.		The	downwash	

of	the	plume	can	result	in	elevated	ground‐level	concentrations	in	the	near	wake	of	a	building	and	is	required	for	

consideration	in	the	modeling.		For	“other”	sources	that	are	modeled	in	the	area,	downwash	was	not	considered,	

as	considering	this	phenomenon	would	reduce	the	impacts	from	these	sources	at	the	location	of	the	Cooper	

Station’s	maximum	impacts.	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-22 

3.10. BACKGROUND CONCENTRATIONS 

As	described	in	Section	8	of	the	modeling	TAD,	the	inclusion	of	background	ambient	monitored	concentrations	

as	part	of	the	NAAQS	demonstration	is	important	in	determining	and	deciphering	the	cumulative	ambient	air	

impacts.		As	recommended	by	the	modeling	TAD,	a	first	tier	approach	(i.e.,	the	most	conservative	option	from	

among	the	available	background	concentration	selection	techniques)	based	on	monitored	design	values	for	the	

latest	three	year	period	was	implemented	for	the	Cooper	Station	NAAQS	analysis.	

As	with	many	locations	in	Kentucky,	a	nearby	SO2	monitor	within	the	immediate	vicinity	of	the	Cooper	Station	

does	not	exist	and,	therefore,	regional	sites	were	evaluated	for	use	to	characterize	the	background	

concentration.		This	selected	monitoring	site	should	not	be	influenced	by	the	subject	facility,	which	is	not	

expected	to	be	the	case	for	SO2	emissions	from	Cooper	Station	and	any	of	the	candidate	monitoring	locations.		

Nearby	sources	with	a	significant	concentration	gradient	were	explicitly	modeled,	and	the	closest	monitors	were	

assessed	to	determine	similarity	of	natural	and	insignificant	local	source	contributions	to	those	around	the	

Cooper	Station.	

Due	to	the	lack	of	a	proximal	SO2	monitoring	site,	a	regional	site	was	determined	to	be	the	best	choice	for	

characterizing	background	concentrations.		As	shown	in	Figure	3‐2,	three	SO2	monitors	are	located	within	150	

km	of	the	Cooper	Station,	namely:		

1. Nicholasville	(21‐113‐0001)		

2. Lexington	(21‐067‐0012)	

3. Mammoth	Cave	National	Park	(21‐061‐0501)	

Consideration	of	each	monitor	as	an	appropriate	background	monitor	includes	the	following	site‐specific	

selection	criteria	(adapted	from	the	guidance	provided	in	Section	8.2	of	Appendix	W):			

1. The	distance	from	Cooper	Station	to	the	monitor,		

2. The	land	use	in	the	surrounding	area	as	compared	between	Cooper	Station	and	the	monitor,		

3. The	likelihood	of	influence	from	nearby	local	population‐related	sources	(vehicles,	residential	heating,	etc.)	

and	industrial	sources,	and	

4. Ability	of	the	monitor	to	capture	the	impacts	of	sources	that	are	small	and/or	distant	from	the	Cooper	

Station	not	explicitly	modeled	due	to	being	screened	out	of	the	regional	inventory.	

The	Nicholasville	monitor	(21‐113‐0001)	site	is	located	approximately	99	km	north	of	Cooper	Station	and	18	km	

southwest	of	the	city	center	of	Lexington.		The	Nicholasville	site	has	a	monitoring	objective	of	population	

exposure	and	an	urban	measurement	scale	with	a	scale	definition	of	4	km	to	50	km.		The	surrounding	land	use	

and	location	are	light	density	residential/commercial	surrounded	by	rural	agricultural	areas.		To	assess	the	

influence	of	nearby	industrial	sources	on	monitored	concentrations,	EKPC	evaluated	the	sum	of	annual	actual	

and	potential	emissions	from	all	facilities	located	within	the	same	two	screening	distances	applied	in	the	

regional	inventory	selection	process	(i.e.,	20	km	and	50	km).		As	shown	in	Table	3‐8,	the	combined	SO2

emissions	from	industrial	sources	within	both	20	km	and	50	km	from	the	Nicholasville	monitor	is	not	at	all	

comparable	to	the	combined	SO2	emissions	in	the	Cooper	Station	airshed.		The	higher	SO2	emissions	totals	in	the	

area	surrounding	the	Nicholasville	monitor	would	likely	explain	the	significantly	higher	1‐hr	SO2	NAAQS	design	

value	from	this	monitor	(40.0	μg/m3)	in	the	most	recent	three‐year	period	(2012	through	2014)	as	compared	to	

the	same	three‐year	average	design	values	from	the	other	candidate	monitoring	stations	(34.8	μg/m3	for	the	

Lexington	monitor	and	26.9	μg/m3	for	the	Mammoth	Cave	monitor).		Considering	these	relevant	features	of	the	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-23 

Nicholasville	monitor,	EKPC	does	not	consider	the	SO2	ambient	concentrations	measured	at	this	monitoring	site	

to	be	representative	of	the	expected	background	concentrations	in	the	area	surrounding	the	Cooper	Station.	

Table 3‐8.		Summary of SO2 Emissions from KyEIS Facilities near

Cooper Station and Candidate SO2 Monitoring Stations

The	Lexington	monitor	(21‐067‐0012)	site	is	the	next	closest	SO2	monitoring	station	located	at	approximately	

119	km	north	of	Cooper	Station	within	the	city	of	Lexington,	KY.		The	surrounding	land	use	and	location	are	

medium	density	residential/commercial	because	the	site	is	located	just	north	of	the	urban	center	of	Lexington.		

Due	to	the	urban	setting	of	this	monitor,	the	site	captures	numerous	urban	SO2	sources	including	a	high	density	

of	stationary	industrial	sources,	mobile	sources,	and	residential	and	commercial	sources.		The	influence	from	

these	urban	sources	is	not	representative	of	the	area	surrounding	Cooper	Station.		The	industrial	SO2	emissions	

profile	affecting	the	Lexington	monitor	characterized	by	the	KyEIS	summary	data	presented	in	Table	3‐8	is	also	

not	comparable	to	the	industrial	SO2	emissions	profile	of	the	Cooper	Station’s	airshed.	

The	Mammoth	Cave	National	Park	monitor	(21‐061‐0501)	monitor	is	located	approximately	139	km	to	the	west	

of	Cooper	Station.		It	has	a	monitoring	objective	of	general/background	without	a	specified	measurement	scale.		

Due	to	its	background	status,	this	monitor	is	thought	to	be	representative	of	rural	areas	with	similar	influences	

to	the	air	quality	around	Cooper	Station.		The	Mammoth	Cave	monitoring	site	has	the	lowest	SO2	design	value	of	

the	candidate	monitoring	stations	most	likely	due	to	the	significantly	lower	SO2	emissions	totals	from	industrial	

sources	surrounding	the	monitoring	station.		As	shown	in	Table	3‐8,	the	SO2	emissions	totals	in	the	area	

surrounding	the	Mammoth	Cave	monitor	are	most	comparable	to	the	Cooper	Station’s	airshed	from	among	the	

candidate	monitoring	stations.		Also,	given	the	wind	patterns	in	the	area	(as	shown	by	the	London‐Corbin	

Airport	wind	rose	in	Figure	3‐8),	this	monitor	is	expected	to	reflect	the	minor	contributions	from	sources	in	the	

area	surrounding	the	Bowling	Green‐Glasgow	combined	statistical	area	(CSA)	which	has	a	similar	population	

(218,870)	to	the	combined	populations	of	the	two	nearby	micropolitan	statistical	areas	surrounding	the	Cooper	

Station,	namely	Somerset,	Kentucky	and	London,	Kentucky	(191,141).		In	addition,	the	Lexington‐Fayette	

metropolitan	statistical	area	(MSA)	in	which	the	Nicholasville	and	Lexington	monitors	are	located	has	a	much	

higher	population	(494,189)	than	any	of	the	urban	centers	located	near	the	Mammoth	Cave	monitoring	site	or	

Cooper	Station.		As	population	is	the	most	direct	indication	of	regulated	air	pollutant	emissions	from	non‐

industrial	sources	(i.e.,	mobile	sources,	residential/commercial	sources,	etc.),	these	observed	population	trends	

can	be	used	with	the	industrial	source	SO2	emissions	data	summary	in	Table	3‐8	to	obtain	an	overall	

characterization	of	the	SO2	emissions	profile	affecting	the	Cooper	Station	and	each	of	the	candidate	monitoring	

sites.	

Location

Sum of Annual Actual SO2

Emissions for Facilities

within 20 km1

(tpy)

Sum of Annual Potential

SO2 Emissions for

Facilities within 20 km1

(tpy)

Sum of Annual Actual SO2

Emissions for Facilities

within 50 km1

(tpy)

Sum of Annual Potential

SO2 Emissions for

Facilities within 50 km1

(tpy)

Cooper	Station2 53.58 238.50 205.45 1,123.85

Nicholasville	Monitor 2,098.07 8,211.61 3,387.71 40,809.09

Lexington	Monitor 138.50 7,644.32 3,378.49 40,887.00

Mammoth	Cave	Monitor 0.56 44.29 9.15 572.03

1

		Sum	of	annual	actual	or	potential	emissions	from	2013	KyEIS	export	within	specified	distances	from	Cooper	Station	or	candidate	

monitoring	locations.

2

		Combined	SO2	emissions	from	facilities	in	area	surrounding	Cooper	Station	excludes	emissions	from	Cooper	Station,	as	these	emissions	

are	the	subject	of	the	1‐hr	SO2	NAAQS	demonstration	modeling.
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-24 

Figure 3‐8.		Wind Rose for London‐Corbin Airport from July 2012 – June 2015

Based	on	an	application	of	the	aforementioned	background	monitor	selection	criteria	to	the	candidate	sites	

within	150	km	of	the	Cooper	Station,	the	Mammoth	Cave	National	Park	site	was	chosen	to	represent	the	

background	concentration	for	the	Cooper	Station	modeling	analysis.		Since	the	Mammoth	Cave	monitor	is	

already	located	such	that	it	will	capture	a	true	background	concentration	for	the	Cooper	Station,	no	further	

processing	of	the	monitor	data	was	necessary	to	generate	temporally	varying	background	concentrations	or	to	

exclude	influences	from	modeled	sources.		As	shown	in	Table	3‐9,	the	fourth	highest	daily	maximum	1‐hr	SO2

concentrations	per	year	average	over	the	most	recent	three‐year	period	(2012‐2014)	from	the	Mammoth	Cave	

monitor	was	used	to	calculate	the	background	concentration	applied	using	the	BACKGROUND	keyword	in	

AERMOD	input	file.	

Table 3‐9.		Selected SO2 Background Concentration

Site ID City County State

Downwind

Direction to

Monitor

Distance

to Cooper

(km)

SO2

Background

Concentration1

(μg/m3)

21‐061‐0501 ‐‐ Edmonson KY W 139.1 26.9

1

		Three‐year	average	for	2012‐2014	of	the	99th	percentile	(4th	highest)	1‐hour	daily	

maximum	concentrations.
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 3-25 

3.11. MODELING FILES 

All	modeling	files	are	provided	to	KDAQ	in	electronic	format	on	a	compact	disk	included	in	Appendix	C.		Model	

and	processor	input,	output,	and	data	files	are	included.		Spreadsheets	tabulating	Cooper	Station	and	regional	

source	model	input	parameters	referenced	in	previous	sections	of	this	modeling	report	are	also	provided	on	the	

modeling	file	CD	in	Appendix	C.	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 4-1 

4. 1-HOUR SO2 DESIGNATION MODELING RESULTS 

Dispersion	modeling	of	the	Cooper	Station	was	conducted	using	the	AERMOD	Model	(Version	15181).		Included	

in	this	modeling	were	the	Cooper	Station	CEMS	emissions	data	for	Unit	2,	Cooper	Station	allowable	emissions	

data	for	Unit	1,	Kingsford	Manufacturing	Company	potential	emission	rates,	and	an	appropriate	background	

concentration.		Table	4‐1	presents	the	overall	results	of	the	Cooper	Station	1‐hr	SO2	NAAQS	designation	

modeling	including	contributions	from	all	modeled	sources	and	the	background	concentration	expressed	in	the	

form	of	the	1‐hour	SO2	NAAQS	(a	3‐year	average	of	the	99th	percentile	of	the	annual	distribution	of	daily	

maximum	1‐hr	concentrations).		As	can	be	seen	from	Table	4‐1,	the	combined	maximum	concentration	is	less	

than	the	NAAQS	and	thus,	the	area	surrounding	the	Cooper	Station	is	expected	to	be	achieving	the	1‐hr	SO2

NAAQS	and	should	be	designated	as	attainment	in	the	upcoming	round	of	Consent	Decree‐driven	attainment	

designations.	

Table 4‐1.		Highest 4th High Modeled 1‐hour SO2 Results for Comparison to the NAAQS

Figure	4‐1	shows	the	distribution	of	1‐hour	SO2	concentrations	across	a	portion	of	the	modeling	domain	closest

to	Cooper	Station	and	the	area	of	maximum	impacts	as	a	further	graphical	presentation	of	the	concentration	

estimates	and	their	distribution.		The	maximum	impacts	as	described	with	coordinates	in	Table	4‐1	and	as	

shown	with	the	orange	isopleth	in	Figure	4‐1	occur	to	the	northeast	of	the	Cooper	Station	on	and	near	a	hill	in	

the	prevailing	wind	direction.		Concentrations	of	SO2	in	other	areas	are	much	less	as	can	be	seen	by	the	

distribution	around	the	Cooper	Station.	

	 	

Averaging

Period Year for Met. Data

NAAQS

(μg/m3)

Maximum

Impact

(μg/m3)

Background

Concentration2

(μg/m3)

Combined

Maximum

Impact

(μg/m3)

UTM

East3

(m)

UTM

North3

(m) Date

Exceeds

NAAQS?

1‐hr1 Max.	3‐yr	Avg. 196							 															146.2 																		26.9 													 714,550 173.1 		4,098,043 ‐‐ No

1

	Evaluated	the	three‐year	average	4th	highest	daily	maximum	1‐hour	output	for	comparison	against	the	NAAQS.

3

	UTM	coordinates	are	represented	in	NAD83	datum	Zone	16.

2

	Based	on	SO2	ambient	monitoring	data	from	the	Edmonson	County	monitor	in	Bowling	Green,	Kentucky	(Site	ID	21‐061‐0501)	located	within	

Mammoth	Cave	National	Park.	Background	concentration	for	1‐hr	modeling	is	the	three‐year	average	from	2012	to	2014	of	the	99th	percentile	daily	

maximum	1‐hr	concentrations.
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report 4-2 

Figure 4‐1.		Spatial Display of 3‐year Average 99th Percentile Annual Distribution

of Daily Maximum 1‐hr SO2 Concentrations Including Background
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report A-1 

APPENDIX A: USE OF U* IN COOPER DISPERSION MODELING 

When	AERMOD	is	run	with	a	meteorological	dataset	derived	from	one‐minute	meteorological	data	as	is	

currently	recommended	by	U.S.	EPA,	low	wind	speeds	are	much	more	prevalent	than	in	prior	versions	of	the	

modeling	system	that	did	not	rely	on	one‐minute	meteorological	data.		These	low	wind	speeds	have	been	linked	

to	potential	overestimates	in	ambient	concentrations	by	AERMOD.32		These	overestimates	occur,	in	part,	due	to	

an	underestimate	of	friction	velocity	(u*)	by	the	AERMET	meteorological	processor.		EPA	recognized	this	

underestimation	as	a	potential	issue	with	AERMET	and	released	AERMET	Version	12345	which	included	a	beta	

option,	ADJ_U*.		The	ADJ_U*	beta	option	allows	the	friction	velocity	(u*)	to	be	adjusted	using	the	methods	of	Qian	

and	Venkatram33	to	better	account	for	turbulence	in	the	atmosphere	during	low	wind	speed	stable	conditions.		

This	beta	option	was	updated	to	incorporate	a	modified	Bulk	Richardson	Number	in	version	13350,	was	further	

modified	to	adjust	u*	for	low	solar	elevation	angles	with	version	14134,	and	was	most	recently	used	to	modify	

the	calculation	of	the	turbulence	measure,	Monin‐Obukhov	length	in	Version	15181.34		Given	the	refined	nature	

of	this	beta	option	and	the	peer	reviewed	studies	which	have	acknowledged	its	accuracy,	EKPC	has	incorporated	

this	option	into	the	modeling	analysis	to	allow	more	representative	and	more	accurate	modeling	results.	

Because	the	u*	option	is	not	a	default	option	in	AERMOD,	the	combined	use	of	AERMOD	plus	the	u*	adjustment	

in	the	meteorology	file	(generated	by	AERMET)	would	no	longer	have	“preferred”	status	in	the	sense	that	it	is	a	

model	to	be	used	for	regulatory	purposes	without	additional	regulatory	authority	approval.		To	substantiate	that	

the	adjusted	friction	velocity	option	in	AERMOD	is	a	valid	model	to	use	in	this	situation,	Section	3.2	of	Appendix	

W	describes	steps	to	be	considered	to	allow	the	use	of	the	u*	adjusted	AERMOD	as	an	acceptable	alternative	

model.		The	section	also	describes	criteria	for	determining	the	acceptability	of	an	alternative	model.			Section	

3.2.2.b	states	that	satisfying	any	one	of	the	three	alternative	conditions	may	make	use	of	an	alternative	model	

acceptable.		Condition	1	states	that	the	alternative	model	will	demonstrate	equivalency.		But	in	this	case	the	

AERMOD	Model	is	the	preferred	model	of	choice	with	just	an	option	change	(making	it	alternative).		Because	the	

model	cannot	have	a	demonstration	of	equivalency	to	itself	and	the	option	change	will	result	in	different	results,	

this	condition	is	not	applicable.		This	leaves	the	satisfaction	of	Conditions	2	and	3	as	criteria	to	accept	the	u*	

option	in	AERMOD.		Condition	2	requires	the	formal	submittal	of	a	protocol	to	allow	demonstration	of	superior	

performance	which	is	acceptable	to	the	control	agency	and	to	EKPC.		This	type	of	study	would	require	

appropriate	ambient	air	quality	monitoring	and	side‐by‐side	modeling	and	comparisons	which	were	beyond	the	

scope	of	this	project.	

Thus,	Condition	3	was	reviewed	and	followed	along	with	the	individual	criteria	to	meet	its	requirements.		

Section	3.2.2.e	states	that	a	preferred	model	may	be	used	provided	that	five	criteria	are	met.		These	are:	

i. The	model	has	received	a	scientific	peer	review;	

ii. The	model	can	be	demonstrated	to	be	applicable	to	the	problem	on	a	theoretical	basis;	

iii. The	data	bases	which	are	necessary	to	perform	the	analysis	are	available	and	adequate;	

iv. Appropriate	performance	evaluations	of	the	model	have	shown	that	the	model	is	not	biased	towards	

underestimates;	and	

v. A	protocol	on	methods	and	procedures	to	be	followed	has	been	established.	

																																																															

32		Wenjun Qian and Akula Venkatram, “Performance of Steady State Dispersion Models Under Low Wind‐Speed Conditions,”

Boundary‐Layer Meteorology, no. 138 (2011): 475‐491. 33		Ibid.	

34		http://www.epa.gov/ttn/scram/7thconf/aermod/aermet_mcb3.txt;	

http://www.epa.gov/ttn/scram/7thconf/aermod/aermet_mcb4.txt;	

http://www.epa.gov/ttn/scram/7thconf/aermod/AERMET_mcb5.pdf;	

http://www.epa.gov/ttn/scram/7thconf/aermod/AERMET_mcb6.pdf
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report A-2 

Review	of	these	criteria	as	well	as	the	responses	to	each	within	the	context	of	modeling	the	Cooper	Station	have	

shown	the	use	of	the	u*	option,	as	generated	by	AERMET	in	the	meteorological	file	and	used	in	AERMOD,	to	be	

valid	and	representative	for	the	modeling	domain	in	the	vicinity	of	the	Cooper	Station.		The	response	to	each	

criteria	is	given	in	the	following	Appendix	A	subsections.	

CRITERIA 3.2.2.e.i - SCIENTIFIC PEER REVIEW 

The	use	of	an	adjusted	friction	velocity	in	AERMOD	has	received	scientific	peer	review	and	been	evaluated	both	

by	U.S.	EPA	modelers	as	well	as	others	in	the	scientific	and	modeling	community.		Two	examples	are:	

The	paper	entitled	“Performance	of	Steady‐State	Dispersion	Models	Under	Low	Wind‐Speed	Conditions”	by	

Wenjun	Qian	and	Akula	Venkatram,	Boundary	Layer	Meteorology,	Volume	138,	pp	475‐491,	2011.		This	

paper	examined	the	AERMOD	Model	to	estimate	dispersion	under	low	wind	speed	events.		Two	tracer	

studies,	the	Prairie	Grass	Experiment	and	the	Idaho	Falls	experiment,	were	compared	to	the	use	of	AERMOD	

with	and	without	u*	adjustments.		The	analysis	reports	that	the	tendency	of	AERMOD	to	overestimate	

ambient	air	impacts	during	low	wind	speed	events	was	reduced	by	incorporating	an	empirical	modification.		

This	modification	is	incorporated	into	the	AERMET	program	through	the	U*_ADJ	keyword.		This	option	

generates	the	enhanced	friction	velocity	sets	on	a	low	wind	speed,	stable	atmosphere,	hour‐by‐hour	basis.		

Also	in	his	email	memorandum	dated	June	26,	2013,	George	Bridgers	of	the	U.S.	EPA’s	Office	of	Air	Quality	

Planning	and	Standards,	notes	that	“The	AERMET	BETA	option	is	based	on	a	peer	reviewed	study	(Qian	and	

Venkatram,	2011)	which	also	includes	independent	evaluations	of	the	new	u‐star	estimates...”.	

In	his	April	23,	2013	presentation	at	the	Regional/State/Local	Modeling	Meeting	in	Dallas,	Texas,	Roger	

Brode	showed	“improved	AERMOD	performance”	when	including	the	u*	adjustment.		The	figures	below	

from	Mr.	Brode’s	presentation	demonstrate	the	enhanced	performance	of	AERMOD	for	two	field	data	bases,	

namely	the	Oak	Ridge	Study	and	the	Idaho	Falls	Study.		The	closer	the	points	are	to	the	center	line	of	each	

graph,	the	better	the	model	performance.	

Figure A‐2.			Comparison of the AERMOD Model with and without the u* Adjustment
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report A-3 

CRITERIA 3.2.2.e.ii- APPLICABLE ON A THEORETICAL BASIS 

Over	the	past	several	years	many	scientific	studies	have	noted	that	Gaussian	dispersion	models	tend	to	over	

predict	concentrations	at	low	wind	speeds.		In	the	early	days	of	dispersion	modeling	when	the	threshold	

velocities	of	the	National	Weather	Service	anemometers	were	a	few	miles	per	hour,	the	common	use	of	1.0	m/s	

as	the	lowest	wind	speed	that	would	be	considered	in	the	model	was	prevalent.		The	modeling	community	

recognized	that	winds	lower	than	that	would	result	in	ambient	concentration	estimates	that	were	not	

coincidental	with	ambient	monitored	values	at	these	same	low	wind	speed	conditions.		Because	concentration	is	

inversely	proportional	to	wind	speed	as	wind	speeds	dip	below	1	m/s,	concentrations	are	greater.		In	addition,	

other	studies	and	field	research	showed	that	winds	tend	to	meander	during	low	wind	speeds,	meaning	that	the	

wind	was	not	in	only	one	direction	during	the	time	step	of	the	Gaussian	models,	namely	one	hour,	but	tended	to	

change	over	the	time	step.		The	relationship	between	this	phenomenon	and	the	friction	velocity	calculations	in	

AERMET	determined	that	adjusting	the	u*	could	have	the	same	effect	as	adjusting	plume	meander	and	was	

better	estimated	empirically	(as	demonstrated	in	the	peer	review	paper	by	Qian	and	Venkatram).	

In	reviewing	the	frequency	distribution	of	winds	from	the	London‐Corbin	(MaGee	Field)	Airport	for	the	period	

of	record	of	this	modeling	analysis,	the	number	of	hours	in	the	range	of	0.28	m/s	(the	lower	limit	where	

AERMOD	will	make	a	calculation)	and	less	than	2.1	m/s	wind	speed	is	11,224	hours	over	the	three	year	period	

of	record	or	42.7%.		This	distribution	is	shown	in	Table	A‐1	and	Figure	A‐2.		Thus,	the	consideration	of	better	

science	in	terms	of	the	u*	adjustment	is	applicable	and	reasonable	given	this	relatively	high	frequency	of	low	

wind	occurrences.	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report A-4 

Table A‐1.		Distribution of Hourly Observations by Wind Speed and Wind Direction

	 	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report A-5 

Figure A‐3.		Distribution of Hourly Observations by Wind Speed Category Bin

As	a	further	measure	of	assessing	the	importance	of	low	wind	speeds	in	the	meteorological	dataset	for	the	

Cooper	Station	SO2	NAAQS	demonstration,	EKPC	evaluated	the	wind	speeds	associated	with	maximum	

concentrations	when	the	default	AERMET	processing	was	employed	and	when	the	U*_ADJ	option	was	

implemented.		For	any	hourly	impact	from	the	Cooper	Station	above	100	μg/m3	(approximately	50%	of	the	1‐hr	

SO2	NAAQS)	identified	in	the	results	from	the	default	and	U*_ADJ	modeling	runs,	EKPC	determined	a	wind	speed	

associated	with	the	event.		The	resulting	wind	speed	dataset	was	then	plotted	in	a	histogram	format	to	

determine	the	cumulative	frequency	of	impacts	within	selected	bins	of	wind	speed.		These	plots,	shown	in	

Figures	A‐3	and	A‐4	for	the	default	and	U*_ADJ	cases,	respectively,	show	a	significant	bias	towards	low	wind	

conditions	in	the	default	mode	relative	to	the	overall	distribution	of	wind	speeds	within	the	meteorological	

dataset.		The	percentage	of	wind	speeds	below	2.1	m/s	contributing	to	Cooper	Station	impacts	above	100	μg/m3	

in	the	default	case	is	78.3%	versus	only	42.7%	in	the	overall	wind	speed	distribution.		When	such	a	large	

percentage	of	high	impacts	are	controlled	by	a	single	type	of	meteorological	condition	(i.e.,	low	wind	speeds	in	

stable	conditions),	a	potential	overestimate	inherent	to	the	model	is	most	likely	the	cause	rather	than	an	

underlying	meteorological	phenomenon	influencing	plume	dispersion.		When	the	U*_ADJ	option	is	used,	the	

percentage	of	winds	below	2.1	m/s	contributing	to	Cooper	Station	impacts	above	100	μg/m3	drops	significantly	

to	only	49.3%.		This	value	is	in	line	with	the	overall	percentage	of	wind	speeds	below	2.1	m/s	in	the	selected	

meteorological	dataset	(42.7%),	and	thus,	indicates	the	U*_ADJ	option	yields	a	profile	of	controlling	

meteorological	conditions	for	maximum	impacts	that	is	not	unrealistically	biased	towards	low	winds.	

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

Cumulative Percentage of Valid Hours

Number of Valid Hours

Wind Speed Category Bins (m/s)

Freq.

Cum.	%
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report A-6 

Figure A‐4.		Distribution of Wind Speeds for Cooper Station Impacts above 100 μg/m3

with the Default AERMET Dataset

Figure A‐5.		Distribution of Wind Speeds for Cooper Station Impacts above 100 μg/m3

with the U*_ADJ AERMET Dataset

	 	

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

Cumulative Percentage of Hours w/ 1‐hr

SO2 Impacts >100 μg/m3

Number of Hours of 1‐hr SO2

Impacts >100 μg/m3

Wind Speed Category Bins (m/s)

Freq.

Cum.%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0

200

400

600

800

1,000

1,200

1,400

1,600

<3 0.3‐1.0 1.0‐2.1 2.1‐3.6 3‐6‐5.7 5.7‐8.8 8.8‐11

Cumulative Percentage of Hours w/ 1‐hr

SO2 Impacts >100 μg/m3

Number of Hours of 1‐hr SO2

Impacts >100 μg/m3

Wind Speed Category Bins (m/s)

Freq.

Cum.%
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report A-7 

CRITERIA 3.2.2.e.iii – AVAILABILITY OF DATABASES 

The	test	data	bases	and	reporting	for	low	wind	speed	observations	and	evaluation	are	available	to	assess	model	

performance.		The	data	bases	applicable	to	this	discussion	and	use	of	the	u*	option	in	AERMET	and	AERMOD	

are:	

Idaho	Falls	Study‐	Sagendorf	JF,	Dickson	CR	(1974)	Diffusion	under	low	wind	speed,	inversion	conditions.	

NOAA	Technical	Memorandum	ERL	ARL‐52,	89	pp.	

Prairie	Grass	Study	‐	Barad	ML	(ed)	(1958)	Project	Prairie	Grass.		A	field	program	in	diffusion.	Geophysical	

research	paper	no.	59,	vols	I	(300	pp)	and	II	(221	pp).	AFCRF‐TR‐58‐235.	Air	Force	Cambridge	Research	

Center,	Bedford,	Massachusetts;	under	Model	Evaluation	Databases	on	U.S	EPA’s	website	‐	

http://www.epa.gov/ttn/scram/dispersion_prefrec.htm

Oak	Ridge	Study	‐	NOAA	Technical	Memorandum	ERL	ARL‐61,	1976.	Diffusion	under	Low	Wind	Speed	

Conditions	near	Oak	Ridge,	Tennessee.	Wilson,	R.	B.,	G.	Start,	C.	Dickson,	N.	Ricks.	Air	Resources	Laboratory,	

Idaho	Falls,	Idaho.	

In	addition,	the	AERMET	source	code	and	all	input	data	required	for	implementing	the	U*_ADJ	are	publicly	

available	on	U.S.	EPA’s	SCRAM	website.	

CRITERIA 3.2.2.e.iv – DEMONSTRATION OF NO BIASES TOWARDS UNDERESTIMATES 

As	demonstrated	in	a	number	of	studies	over	the	past	3‐5	years,	including	the	2010	study	by	AECOM35,	the	use	

of	the	u*	adjustment	in	dispersion	modeling	has	not	shown	any	bias	towards	underestimating	the	ambient	

concentrations	due	to	sources	and	emissions.		A	repeat	use	of	the	same	Oak	Ridge	data	set	in	2013	by	the	U.S.	

EPA	in	their	model	performance	evaluation	demonstrates	both	the	improved	performance	of	AERMOD	with	u*	

option	and	no	bias	towards	underestimation	as	shown	in	Figure	A‐5.	

Figure A‐6.		Residual Plots Showing Improved Performance with u* and No Bias toward Underestimation

																																																															

35		AERMOD	Low	Wind	Speed	Evaluation	Study	Results,	AECOM	prepared	for	the	American	Petroleum	Institute,	Washington,	DC,	

March	22,	2010.	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Report A-8 

CRITERIA 3.2.2.e.v – A PROTOCOL HAS BEEN ESTABLISHED 

A	modeling	protocol	was	provided	to	KDAQ	by	EKPC	on	August	3,	201536	which	provided	a	detailed	overview	of	

the	model	selection	process,	potential	options	to	be	considered,	source	and	building	considerations,	receptor	

grids,	meteorological	data,	other	source	inventories,	and	anticipated	tabular	and	graphical	outputs.		Section	2.1	

of	the	protocol	describes	the	potential	frequent	occurrence	of	low	winds	due	to	the	EPA‐recommended	use	of	

the	one‐minute	meteorological	data	available	from	the	National	Oceanic	and	Atmospheric	Administration	

website.		The	consideration	of	the	use	of	the	LOWWIND	options	was	briefly	mentioned	in	the	modeling	protocol.		

The	additional	and	separate	consideration	of	the	u*	option	was	certainly	of	interest	although	not	called	out	

specifically	in	the	protocol.		Comments	received	via	email	from	Rick	Gillam	(U.S.	EPA,	Region	4)	on	August	17,	

2015	included	one	reference	to	the	selection	of	the	use	of	the	low	wind	options,	that	being:	

Section 2.1, Page 11:		The protocol discusses the possibility of using the LOWWIND “beta‐options”

contained in the latest version of AERMOD (Version 15181).		Use of these options could be allowed, but it is

important to understand that these are non‐regulatory “beta‐options,” and thus are “alternative model

options” requiring approval from EPA Region 4 pursuant to Section 3.2.2 of 40 CFR Part 51, Appendix W.			

EKPC	selected	the	U*_ADJ	option	instead	of	the	LOWWIND	option	mentioned	in	the	protocol	because	it	is	a	

better	representation	of	impacts	due	to	the	Cooper	Station	in	low	wind,	stable	atmospheric	conditions	that	are	

common	in	the	area.		The	u*	option	has	also	been	subject	to	extensive	peer	review	and	thus	the	likelihood	of	the	

approval	of	its	use	for	this	modeling	exercise	is	greater.		

No	specific	protocol	for	implementing	the	U*_ADJ	option	in	AERMET	is	needed	since	invoking	this	option	only	

includes	the	selection	of	a	single	keyword.	

																																																															

36	August	3,	2015	Letter	from	Jerry	Purvis	(Director,	Environmental	Affairs,	EKPC)	to	Sean	Alteri	(Director,	Division	for	Air	Quality,	

Commonwealth	of	Kentucky),	Air Dispersion Modeling Protocol Cooper Station SO2 Designation Analysis	(dated	July	31,	2015).	
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Approach B-1 

APPENDIX B: NAAQS REGIONAL SOURCE INVENTORY 
Model ID Description

UTM 

Easting1 

(m)

UTM 

Northing1

(m)

Elevation2

(m)

PTE 

Emission 

Rate 

(tpy)

Emission 

Rate 

(g/s)

Stack 

Height

(ft)

Stack 

Height

(m)

Temp.

(F)

Temp.

(K)

Exit Velocity

(ft/s)

Exit Ve

(m/s

KINGFRD1 ACC Stack 714,965 4,094,231 263.73 5.78 0.166389 74.00 22.56 1,800.00 1,255.4 46.3 14.1

KINGFRD2 Briquet Dryer A Stack 714,948 4,094,126 268.32 41.00 1.179360 75.00 22.86 232.00 384.3 67.1 20.4

KINGFRD3 Briquet Dryer B Stack 714,964 4,094,141 267.36 29.74 0.855540 75.00 22.86 235.00 385.9 53.7 16.3

KINGFRD4 Briquet Dryer C Stack 714,973 4,094,148 266.52 31.19 0.897120 75.00 22.86 259.00 399.3 51.2 15.5

KINGFRD5 Waste Heat Boiler Stack 714,992 4,094,424 264.03 27.90 0.802694 20.00 6.10 400.00 477.6 42.44 12.9

B-1. AERMOD Model Inputs: SO2 NAAQS Inventory Sources

2 Source coordinates obtained from to-scale site plan in Figure 2-2 of the May 2013 Title V renewal application.5 No stack parameters are included for the Waste Heater Boiler (KyEIS Eqpt. ID COMB001) in the 2014 KyEIS. Stack parameters were obtained from Section II of the DEP7007 N 

Title V renewal application.

3 Imported sources into AERMOD and ran AERMAP with 1-arc second (approximately 30 meter resolution) NED data to get source elevations.1 Unless otherwise noted, source parameters are obtained from the 2014 KyEIS report for the Kingsford Manufacturing Company facility in Burnside, KY.4 Stack parameters for ACC Stack and Briquet Dryer A, B, & C Stacks obtained from the 2014 KyEIS Faciltiy General Report differed from those parameters obtained through Sec

submitted with the May 2013 Title V renewal application. Due to the discrepancy, the Title V renewal application stack parameters were taken as the most up to date parameters fo

Table B-1.1. Kentucky Regional Inventory Sources Modeled as Point Sources for SO2 NAAQS Analysis1

East Kentucky Power CooperativeCooper StationBurnside, Kentucky 
B-1. AERMOD Model Inputs: SO2 NAAQS Inventory Sources

AI ID Facility Name

UTM East 

(m)

UTM North

(m)

Distance to 

Cooper, (d)

(km)

Plant-wide 

Actual 

Emissions (Q)

(tpy)

Actual Q/d

(tpy/km)

Plant-wid

Potentia

Emissions 

(tpy)

3837 Somerset Wood Products Inc 714,167 4,096,069 1.3 0.9 0.7 

108315 Bluegrass Wireless LLC - Bend of the Lake (COW2) 715,141 4,099,610 2.4 0.0 0.0 39770 Hinkle Contracting Co LLC - Tatesville Asphalt Plant 716,645 4,093,017 4.9 0.0 0.0 6340 Glen Oak Lumber & Milling Inc 715,368 4,103,286 6.0 0.0 0.0 99096 Forever Pets Cremation Services LLC 711,127 4,102,727 6.2 0.4 0.1 3813

Armstrong Hardwood Flooring Co 715,287 4,103,592 6.3 0.2 0.0 

3804

American Standard Brands 713,166 4,103,958 6.7 0.0 0.0 

76491 River Metals Recycling LLC Somerset 713,205 4,104,431 7.2 2.3 0.3 116249 KY Utilities Co - Alcalde Substation 718,966 4,102,792 7.2 0.0 0.0 108314 Bluegrass Wireless LLC - Slate Branch (COW14) 706,577 4,098,872 7.8 0.0 0.0 108316 Bluegrass Wireless LLC - Somerset Bypass East 716,184 4,105,219 8.1 0.0 0.0 3842 Continental Refining Company LLC 712,519 4,105,527 8.4 0.1 0.0 3809 General Electric Lighting LLC - Somerset Glass Plant 711,611 4,109,205 12.2 2.0 0.2 71569 Hinkle Contracting Co LLC - Somerset Asphalt Plant 715,110 4,109,540 12.2 0.3 0.0 3806 Eagle Hardwoods Inc 710,601 4,112,048 15.2 2.2 0.1 4171 Monticello Flooring & Lumber 692,401 4,081,670 26.9 0.6 0.0 81844 Cowboy Charcoal USA 692,897 4,079,461 27.9 0.7 0.0 4170 Mago Construction Co LLC - Monticello Plant 693,230 4,077,896 28.6 1.8 0.1 37652 Hinkle Contracting Co LLC - Casey Asphalt Plant 697,890 4,124,384 31.6 0.3 0.0 38966 East Anderson Hardwoods LLC 708,180 4,132,991 36.2 0.3 0.0 3893 Superior Battery Manufacturing Co 678,696 4,104,394 36.2 0.0 0.0 108206 Bluegrass Wireless LLC - Cold Hill 751,979 4,105,255 38.5 0.0 0.0 40420 Federal Bureau Of Prisons 733,125 4,063,318 38.9 0.0 0.0 8882 Wayne Dry Kilns Inc 682,971 4,072,423 40.0 0.2 0.0 4162

American Woodmark Corp 682,571 4,072,073 40.5 0.0 0.0 

108068 Cumberland Cellular GP - Casey South 680,966 4,121,535 41.1 0.0 0.0 

Table B-1.2. List of Regional Inventory Sources Eliminated from the 1-hr SO2 NAAQS 

Inventory Due to "20D"' Rule1

East Kentucky Power CooperativeCooper StationBurnside, Kentucky 
AI ID Facility Name

UTM East 

(m)

UTM North

(m)

Distance to 

Cooper, (d)

(km)

Plant-wide 

Actual 

Emissions (Q)

(tpy)

Actual Q/d

(tpy/km)

Plant-wid

Potentia

Emissions 

(tpy)

108705 Cumberland Cellular GP - Dunnville 677,268 4,116,184 41.5 0.0 0.0 

38846 BPM Lumber LLC 752,839 4,114,950 42.4 0.8 0.0 750 Tarter Gate Co Inc 676,855 4,118,729 43.1 0.0 0.0 38878 Doric Products Co 757,990 4,097,719 43.7 0.0 0.0 37648 Columbia Gulf - Clementsville Transmission Station 674,505 4,117,083 44.4 0.2 0.0 40452 East KY Power Coop - Laurel Ridge Landfill 758,536 4,102,707 44.6 36.1 0.8 2581 Laurel Ridge Landfill 758,665 4,102,526 44.7 0.0 0.0 40268 Elmo Greer & Sons Inc - Portable Hanson Quarry Plant 734,592 4,137,300 44.8 1.1 0.0 108069 Cumberland Cellular GP - Pricetown 681,435 4,128,360 45.2 0.0 0.0 51036 Metal Products Inc 759,420 4,095,721 45.2 0.0 0.0 84396 Hinkle Contracting Co LLC - London Portable Asphalt Plant 758,248 4,108,900 45.5 0.5 0.0 108060 Cumberland Cellular GP - Liberty 683,637 4,131,307 45.7 0.0 0.0 50732 Accent Marble Inc 755,137 4,118,555 46.1 0.0 0.0 108181 Bluegrass Wireless LLC - Corbin Station 760,399 4,094,402 46.2 0.0 0.0 2571 Bimbo Bakeries USA Inc 757,897 4,113,888 46.7 0.0 0.0 2556 Aisin Automotive Casting Inc 761,029 4,102,747 47.1 0.0 0.0 108125 Bluegrass Wireless LLC - Lily (COW13) Portable 761,464 4,104,803 47.8 0.0 0.0 40709 Elmo Greer & Sons LLC - Morentown Rd - Portable 758,384 4,115,723 47.8 0.3 0.0 38869 London Rotary Forms Inc 760,096 4,112,289 48.2 0.0 0.0 2573 Elmo Greer & Sons LLC - Farriston Asphalt Plant 908 761,662 4,106,413 48.3 0.1 0.0 38861 Jasper Iron & Metal Co 761,805 4,105,770 48.3 3.4 0.1 2568 Cumberland Forest Product - Fariston Facility 761,693 4,106,693 48.4 0.0 0.0 2591 Robinson Stave Co 754,550 4,124,091 48.4 0.2 0.0 2559 Chaney Lumber Co 762,199 4,104,313 48.5 0.5 0.0 108182 Bluegrass Wireless LLC - Siler 762,520 4,092,277 48.5 0.0 0.0 45671 CTA Acoustics Inc - Corbin Facility 763,071 4,088,900 49.5 0.1 0.0 108072 Cumberland Cellular GP - Cartwright 673,173 4,069,541 49.6 0.0 0.0 

1 Source list excludes facilities with plant-wide actual emissions of 0 tpy SO2.

East Kentucky Power CooperativeCooper StationBurnside, Kentucky 
East Kentucky Power Cooperative – Cooper Station 

1-Hour SO2 NAAQS Designation Modeling Approach C-1 

APPENDIX C: MODELING FILES ON CD