DEPARTMENT of ENVIRONMENT 

and NATURAL RESOURCES 

PMB 2020
 

JOE FOSS BUILDING
 

523 EAST CAPITOL
 

PIERRE, SOUTH DAKOTA 57501-3182
 

www.state.sd.us/denr 

June 2, 2011 

James B. Martin 

Regional Administrator 

U.S. Environmental Protection Agency, Region 8 

1595 Wynkoop Street 

Denver, CO 80202-1129 

Dear Mr. Martin: 

On March 24, 20 II, EPA notified the Governor of South Dakota that EPA revised the sulfur 

dioxide National Ambient Air Quality Standard and initial area designations are due by June 3, 

2011. EPA revised the primary sulfur dioxide standard by adding a I-hour average 

concentration. 

On January 18, 2011, Governor Daugaard submitted a letter to you designating the Secretary of 

the Department of Environment and Natural Resources as his designee for submitting 

designations and other matters which involves South Dakota's Air Quality Program. In that 

capacity, I recommend EPA designate all counties in South Dakota as attaining the I-hour sulfur 

dioxide standard (see Attachment A) based on the attached supportive document. Attachment B 

provides the technical analysis for designating all of South Dakota's counties in attainment. 

Attachment C provides a copy of the Air Quality System AMP450 repOli showing the yearly 99th 

percentile concentrations for each site and includes the one year of data collected near the Big 

Stone Power Plant in Roberts County. 

Thank you for the opportunity to propose designations for the revised primary sulfur dioxide 

standard and I look forward to your concurrence. If you have questions, please contact Brian 

Gustafson at 605-773-3151. 

~,Steven M. Pi mer 

Secretary 

Attachments 

RECEIVED 

cc:	 Monica Morales, EPA Region 8 U.S. EPA Region 8 

RA's Office 

JUN 07 2011 
.~.

Attachment A 

South Dakota Area Designations 

I-hour Sulfur Dioxide Standard 

Desi2Dated Area Desi2nation Type Classification Type 

Aurora County Attainment 

Beadle County Attainment 

Bennett County Attainment 

Bon Homme County Attainment 

Brookin2s County Attainment 

Brown County Attainment 

Brule County Attainment 

Buffalo County Attainment 

Butte County Attainment 

Campbell County Attainment 

Charles County Attainment 

Clark County Attainment 

Clay County Attainment 

Codin2ton County Attainment 

Corson County Attainment 

Custer County Attainment 

Davison County Attainment 

Day County Attainment 

Deuel County Attainment 

Dewey County Attainment 

Dou21as County Attainment 

Edmunds County Attainment 

Fall River County Attainment 

Faulk County Attainment 

Grant County Attainment 

Gregory County Attainment 

Haakon County Attainment 

Hamlin County Attainment 

Hand County Attainment 

Hanson County Attainment 

Hardin2 County Attainment 

HU2hes County Attainment 

Hutchinson County Attainment 

Hyde County Attainment 

Jackson County Attainment 

Jerauld County Attainment 

Jones County Attainment 

Kin2sbury County Attainment 

Lake County Attainment 

A-I 
Desi2l1ated Area Designation Type Classification Type 

Lawrence County Attainment 

Lincoln County Attainment 

Lyman County Attainment 

Marshall County Attainment 

McCook County Attainment 

McPherson County Attainment 

Meade County Attainment 

Mellette County Attainment 

Miner County Attainment 

Minnehaha County Attainment 

Moody County Attainment 

Pennington County Attainment 

Perkins County Attainment 

Potter County Attainment 

Roberts County Attainment 

Sanborn County Attainment 

Shannon County Attainment 

Spink County Attainment 

Stanley County Attainment 

Sully County Attainment 

Todd County Attainment 

Tripp County Attainment 

Turner County Attainment 

Union County Attainment 

Walworth County Attainment 

Yankton County Attainment 

Ziebach County Attainment 

A-2 
Attachment B
 

Determining Area Designations
 

1. Air Monitoring 

Sulfur dioxide I-hour concentrations in South Dakota are low statewide. The highest design value 

concentration was recorded at the SD School Site in Sioux Falls at 19% ofthe new I-hour standard. 

The Badlands and Wind Cave sites have the lowest design value concentrations at 8% of the standard. 

The concentrations in South Dakota are low for several reasons. First, the state's population and sulfur 

dioxide emissions from area sources are low. Second, all but five sources with Title V air quality 

permits in the state emit sulfur dioxide emissions less than 100 tons per year. Finally, sulfur dioxide 

emissions from area sources will continue to decline because of the move to ultra low sulfur fuels that 

began in 2010. 

Table B-1 displays the three year calculated design value concentration for each site. The design 

value concentration for the SD School, Wind Cave, and Badlands Sites used data from 2008 to 2010. 

Both Union County sites have only two years of data. Roberts County only has 13 months of data. 

a e hi B -1 - S' lte D eSll(n . V.a I ues c oncentrations In . Sout hDak ota

I 

Site County 99th Percentile 3-Year Avera~e Attainment 

SD School Minnehaha 2008 - 27 parts per billion 14 parts per billion Yes 

2009 - 10 parts per billion 

2010- 5 parts per billion 

Badlands Jackson 2008 - 5 parts per billion 6 parts per billion Yes 

2009 - 5 parts per billion 

2010- 9 parts per billion 

Wind Cave Custer 2008 - 3 parts per billion 6 parts per billion Yes 

2009 - 10 parts per billion 

2010- 5 parts per billion 

UC#l Union 2009 - 10 parts per billion 11 parts per billion I 

2010 - 12 parts per billion 

UC#2 Union 2009 - 6 parts per billion 7 parts per billion I 

2010- 9 parts per billion 

Big Stone II Roberts 2001 - 5 parts per billion 10 parts per billion I 

2002 - 14 parts per billion 

_ Not comparable to the standard because there is less than 3 years of data. 

The sulfur dioxide I-hour concentrations collected in the state during the years of2001 to 2002 and 

2008 to 2010 demonstrate there were no I-hour concentrations exceeding the new primary standard as 

calculated following the form of the standard. The highest three year average was recorded at the SD 

School Site with a three year average concentration level of 14 parts per billion. 

Figure B-1 provides a graph comparison of the design values for each site compared to the I-hour 

sulfur dioxide standard. Although the Big Stone II, Union County #1 and Union County #2 Sites do 

not have three years of data, the two year average of the 99th percentile is provided for comparison 

purposes. 

B-1 
Figure B-1 - Data Compared to the I-hour Sulfur Dioxide Standard 

Ic=J 3-Year A-.erage -Standard I 

80 

70 

r:::: 60 

~A	 

11 

H 6 6 I I I I I I

- 0 

50 iii 

... 

<Il	 40 

11. 

30 

III 

11. 20

7 10 I I I 0 

SO School Badlands Wind Ca-.e UC#1 UC#2 

Sites 

The Badlands and Wind Cave sites represent rural areas consisting mainly of rangeland and forested 

areas in the western half of South Dakota while the Union County sites represent the farming area in 

the eastern half of South Dakota. The SD School Site represents South Dakota's largest populated 

area in the Sioux Falls Metropolitan Statistical Area (MSA). The Big Stone II site represents sulfur 

dioxide concentrations near South Dakota's largest emitting sulfur dioxide source. Based on the 

monitoring data which reflects the potential highest and lowest sulfur dioxide concentrations in the 

state, South Dakota is attaining the I-hour sulfur dioxide National Ambient Air Quality Standard in 

every county in the state. 

2. Air Modeling 

EPA's Memorandum from Stephen D. Page to Regional Air Division Directors, I-X, dated March 24, 

2011, indicates EPA may initially designate an area as attainment if it is clear it meets the new sulfur 

dioxide National Ambient Air Quality Standards (NAAQS). EPA further states it does not believe it 

would be appropriate to designate areas as attainment without appropriate refined dispersion modeling 

and where available, air quality monitoring data indicating no violations of the NAAQS. DENR 

agrees modeling may be used as a tool by states but disagrees it is the only tool to demonstrate 

attainment for the following reasons: 

1.	 DENR recently used AERMOD to model the impacts of an existing coal-fired electric power 

plant using sulfur dioxide emissions being reported to EPA in accordance with the Acid Rain 

Program. A receptor was placed on two ambient air quality monitoring sites to compare hourly 

monitoring data to the hourly modeling data. This comparison assumed no other sulfur dioxide 

emitting sources were impacting the monitors. In realty, if the model was accurate, the 

modeling results would be less than the monitoring results. The comparison indicated 

AERMOD may over-predict the concentrations of sulfur dioxide greater than a factor of two 

(see Appendix D for analysis). 

B-2 
2.	 In accordance with 40 CFR Part 51, Appendix W, uncertainties and accuracy of the models are 

discussed. As noted in section 9.1.2, Studies of Model Accuracy, "(1) Models are more 

reliable for estimating longer time-averaged concentrations than for estimating short-term 

concentrations at specific locations; and (2) the models are reasonably reliable in estimating 

the magnitude of highest concentrations occurring sometime, somewhere within an area. For 

example, errors in highest estimated concentrations of ± 10 to 40 percent are found to be 

typical, i.e., certainly well within the often quoted factor-of-two accuracy that has long been 

recognized for these models. However, estimates of concentrations that occur at a specific time 

and site are poorly correlated with actually observed concentrations and are much less 

reliable." 

3.	 EPA did not provide states or the public an opportunity to comment on EPA's new policy of 

placing more confidence on a model for designations than ambient air quality monitoring. In 

the proposed rule, EPA stated it would use monitoring for designation purposes but in the final 

rule it required modeling for attainment designations. This flip flop was initiated by one city 

and three states suggesting the use of modeling for designations. If you tum this around, 47 

states and the rest of the nation's cities agreed monitoring should be used for designations. 

4.	 This flip flop is also contrary to EPA's previous decisions, court cases, and rule: 

a.	 On page 26382 of the Federal Register, Vol. 43, No. 118, June 19,1972, EPA states in the 

preamble to the 1977 PSD rules, " ...EPA intends that monitoring should generally focus 

on obtaining data necessary for required review against NAAQS. Although the increment 

consumption must of necessity be tracked through the use of modeling, EPA does not 

intend that there be no "real world" checks on the accuracy of modeling." 

b.	 In Alabama Power Co. v. Costle C.A.D.C. 1979, the U.S. Court of Appeals, District of 

Columbia Circuit states, "We discern from the statute a technology-forcing objective. 

Congress intended that monitoring would impose a certain discipline on the use of 

modeling techniques, which would be the principal device relied upon for the projection of 

the impact on air quality of emissions from a regulated source. This projects that the 

employment of modeling techniques be held to earth by a continual process of 

confirmation and reassessment, a process that enhances confidence in modeling, as a 

means for realistic projection of air quality." 

c.	 This is further emphasized by EPA's current rules under the Prevention of Significant 

Deterioration program. In accordance with 40 CFR §52.21 (m)(2), if the Administrator 

believes it is necessary, the owner or operator shall conduct ambient air quality monitoring, 

" ... to determine the effect emissions from the stationary source or modification may have, 

or are having, on air quality in any area." Even after a PSD source has demonstrated it is 

can construct and operate and not cause a violation of the National Ambient Air Quality 

standard or PSD increment using modeling, EPA may require a source to conduct 

monitoring to ensure the modeling provided realistic results and no violations will occur. 

Historically, both Congress and EPA intended for monitoring to be the real determination on if an area 

is attaining the National Ambient Air Quality Standards. If EPA wants to use modeling as the only 

tool to designate areas attaining or not attaining the I-hour sulfur dioxide standard, the actual 

requirement to use modeling should have been proposed in the rule to allow everyone an opportunity 

to comment on this decision. DENR believes monitoring provides the reality check both Congress and 

EPA believe are necessary for states to demonstrate an area is attaining or not attaining the standard 

and should be used for the I-hour sulfur dioxide standard. 

B-3 
3. Sulfur Dioxide Monitoring Network in South Dakota 

The first sampling effort in South Dakota to collect hourly sulfur dioxide data was near the Big Stone 

Power Plant. The monitoring location for sulfur dioxide was based on modeling indicating the area of 

highest concentrations near the facility and in South Dakota. A continuous 12-month period of air 

monitoring was completed in the years of 2001 and 2002 as part of a Prevention of Significant 

Deterioration permit application. Sulfur dioxide levels were low with a 99th percentile I-hour average 

concentration level of 10 parts per billion. 

DENR operates a network of air monitoring sites which began collecting hourly sulfur dioxide data in 

2002. The first site was established at the Hilltop Site in Sioux Falls. The monitor was later moved to 

the SD School Site and continues today. In 2005, two more locations were added at the Badlands and 

Wind Cave National Parks. In 2009, two more locations were added in Union County. 

The current sampling network includes sites in several counties around the state with goals of high 

concentration, population, source impact, background and regional transport. See Figure B-2 for a 

map of the state showing the counties with sulfur dioxide air monitoring data. 

Figure B-2 - South Dakota Counties with Sulfur Dioxide Data 

Legend 

3 Years of Data 0 2 Years of Data _ 1 Year of Data 0 No Sampling 

B-4 
4. South Dakota's Population and Sulfur Dioxide Emissions 

If EPA still wishes to use a policy of using modeling for designation purposes, the final rule on page 

35551 states, " ...we believe that for a short-term I-hour standard it is more technically appropriate, 

efficient, and effective to use modeling as the principle means of assessing compliance for medium to 

larger source, and to rely more on monitoring for groups of small sources and sources not as 

conductive to modeling." 

Sulfur dioxide emissions from Title V major sources throughout South Dakota are low to medium 

with one source that could be considered large. Table B-2 provides a list of the top 10 major sources 

emitting sulfur dioxide in calendar year 2009 and represents 75% of the state's total emissions from 

permitted sources. 

# County 

1 Grant 

2 Pennington 

3 Pennington 

4 Brookings 

5 Sioux Falls 

6 Brookings 

7 Spink 

8 Turner 

9 Minnehaha 

10 Codington 

Table B-2 - Top 10 Sulfur Dioxide Emitters in South Dakota (tons per year) 

Facility 

Otter Tail Power Company - Big Stone I 

Black Hills Corporation - Ben French 

GCC Dacotah 

South Dakota State University 

John Morrell & Company 

Valero Renewable Fuels Company 

Redfield Energy 

Great Plains Ethanol 

Sioux Falls Water Reclamation Facility 

Glacial Lakes Energy 

TonslYear 

11,651 

823 

285 

183 

170 

85 

42 

21 

13 

11 

13,284 

17,826 

Top 10 Total = 

Total for Entire State 

South Dakota has counties with low population and no large sources of sulfur dioxide emissions as 

can be seen in Table B-2. The sulfur dioxide concentrations in these areas would be similar to the 

concentrations South Dakota is experiencing at its Badlands, Wind Cave, and Union County 

monitoring sites depending on what rural area one is located. DENR believes these sites meet EPA's 

requirement that monitoring should be used for designation purposes, not modeling. 

South Dakota has other counties with low population and several sources of sulfur dioxide that would 

not be considered large sources of sulfur dioxide emissions (see Attachment E). These counties 

would have concentrations somewhere in between the concentrations at the rural sites and SD School 

Site. DENR believes these sites meet EPA's requirement that monitoring should be used for 

designation purposes, not modeling. 

The largest city in South Dakota is Sioux Falls with a population ofless than 153,888. The largest of 

the three MSAs in the state includes the city of Sioux Falls and includes the counties of Minnehaha, 

Lincoln, McCook, and Turner. The combined 2010 Census population for the Sioux Falls MSA is 

228,261. Table B-3 provides a list of the top 10 most populated counties in the state and the largest 

city within the county. The largest populated area in South Dakota has sources of sulfur dioxide 

B-5 
emissions that would not be considered large sources of sulfur dioxide. DENR believes even this site 

meets EPA's requirement that monitoring should be used for designation purposes, not modeling. 

a hie B-3 - en H:IgJhest Pl' opu ation C ountles In. SouthD a k ota 

Number County Population Lar~est City Population

1 Minnehaha 169,468 Sioux Falls 153,888

2 Pennington 100,948 Rapid City 67,956

3 Lincoln 44,828 Sioux Falls 153,888

4 Brown 36,531 Aberdeen 26,091

5 Brookings 31,965 Brookings 22,056

6 Codington 27,227 Watertown 21,482

7 Meade 25,434 Sturgis 6,627

8 Lawrence 24,097 Spearfish 10,494

9 Yankton 22,438 Yankton 14,454

10 Davison 19,504 Mitchell 15,254

Grant County has the highest emission total for sulfur dioxide in South Dakota and the emissions are 

generated by the Big Stone I Power Plant. DENR does not believe modeling is necessary even at this 

site since modeling was used to detennine the location of highest concentrations and an ambient air 

monitor was located at the modeling site in Roberts County and recorded concentrations just over 

13% of the I-hour sulfur dioxide standard. In addition, sulfur dioxide emissions will be lowered from 

Big Stone I once the control equipment required by the Regional Haze Program is installed. Therefore, 

even Grant County should be designated attainment based on monitoring results. 

B-6 
Attachment C
 

Air Quality System Report AMP450
 

UNITED STATES ENVIRONMENTAL PROTECTION 

AIR QUALITY SYSTEM 

QUICK LOOK REPORT (AMP450) 

AGENCY 

May 11, 2011 

Sulfur dioxid~ (42401) 

P 

0 

IrE 1D c PQAO CITY 

46-033-0132 3 0973 Not in a city 

46-033-0132 3 0973 Not in a city 

46-033-0132 3 0973 Not in a city 

46-071-0001 3 0973 NOt if'l a city 

46-071-0001 3 0973 Not in a ci ty 

46-071-0001 3 0973 Not in a city 

16-099-0008 3 0973 Sioux falls 

46-099-0008 3 0973 Sioux falls 

46-099-0008 3 0973 Sioux Falls 

46-109-4003 3 0973 Not in a city 

46-109-4003 3 0973 Not in a city 

46-127-0001 3 0973 Not in a city 

COUNTY 

Cugter 

Custer 

Custer 

Jackson 

Jackson 

Jack.son 

~innehaha

Hi nnehaha 

Minnehaha 

Roberts 

Robert.s 

Union 

ADDRESS YEAR 

WIND CAVE 200S 

NATIONAL 

PARK, SOUTH 

DAKOTA 

WIND CAVE 2009 

NATIONAL 

PARK, SOUTH 

DAKOTA 

WIND CAVE 2010 

NA.TIONAL 

PARK, SOUTH 

DAKOTA 

BADLANDS PO .2008 

BOX 6 

HEADQUARTER 

5 

BADLANDS PO 2009 

BOX 6 

HEADQUARTER 

S 

BADLANDS PO 2010 

BOX 6 

HEADQUARTER 

5 

2001 E 8th 2008 

St 

2001 88th 2009 

St 

2001 E 8th 2010 

St 

482ND AVE 2001 

48.2ND AVE 2002 

319B6 475th 2009 

Ave 

South Dakota 

COMP 

METH aBS QTRS 

060 8678 4 

060 6487 3 

060 8640 4 

060 8616 4 

060 8645 4 

060 8307 4 

060 8095 3 

060 8184 4 

060 8678 4 

060 1390 0 

060 6935 3 

560 8589 4 

15T 

MAX 

I-HR 

4.0 

32.0 

16.0 

7.0 

7.0 

17.0 

31.0 

18.0 

6.0 

5.0 

28.0 

10.5 

2ND 

MAX 

I-HR 

4.0 

20.0 

10.0 

6.0 

6.0 

11. 0 

30.0 

14.0 

6.0 

5.0 

20.0 

10.0 

99TH 

perL 

I-HR 

3.0 

10.0 

5.0 

5.0 

5.0 

9.0 

27.0 

10.0 

5.0 

5.0 

14 .0 

9.6 

15T 

MAX 

24-HR 

1.4 

5.7 

2.8 

6 0 

3.2 

3.7 

10.0 

2. B 

1.9 

.7 

5.3 

4.3 

2ND 

MAX 

24-HR 

1.3 

3.0 

2.6 

5.0 

2.9 

3.3 

B.9 

2.3 

1.7 

.7 

4.0 

3.5 

Parts per 

Days 

>24HR ARITH 

STD MEAN 

0 .23 

0 .53" 

0 .12 

0 1. 28 

0 . B4 

0 1. 04 

0 .89 

0 .20 

0 .25 

0 .04 • 

0 .19* 

0 .22 

bililon 

CERr EDT 

N 

N 

N 

(008) 

Note; The" 

not satisfy 

iQdicates that the 

summary criterla. 

mean does 

Page 2 of 5 

C-l 
,. 

UNITED STi\TES ~NV!RONMENrAL PROTECTION AGE:NCY
 

AIR QUALITY SYSTEM
 

QUICK LOOt< R~PORT (A.HP450)
 

May. 11, 2011 

Sulfur dioxide (42401) South Dakotd: PartS per billion (008) 

p 1ST 2NO 99T~ 1ST 2ND Days
 

0 COMP MAX MAX PCrL MAX MAX >24HR ARItH
 

IrE ID c PQAO crry COUNTY ADDRE:SS YEAR METH OBS QTRS l-KR 1-Hl' 1-KR 24-HR 24-HR STD MEAN CERT EDT
 

3 0973 Not in .a C1ty Union 31986 475th 2010 560 8640 4 30.3 26.0 11.5 8.2 4.2 0 .40 

Ave 

46-127-0002 3 0973 Not in a city Onion 31307 473rd 2009 560 8657 4 9.0 9.0 6.0 3.3 1.3 0 .16 

Ave 

46-127-0002 3 0973 Not 1n a city Union 31307 473rd 2010 560 8628 26.2 15.9 8.6 3.8 3.5 0 .32 • Ave 

Note: The .. indicaces. that the mean does 

not sacisfy ~ul1Lq:ary criteria. Page 3 of 5 

C-2 
Attachment D
 

AERMOD Modeling Accuracy
 

This analysis was taken from DENR's section 4.4.1 - Modeling Accuracy of the Statement of Basis 

for Hyperion Energy Center's extension request for it Prevention of Significant Deterioration air 

quality permit #28.0701-PSD. 

4.4.1 Model Accuracy 

The modeling analysis indicates Hyperion will not cause or contribute to a violation of the new I-hour 

sulfur dioxide National Ambient Air Quality Standard; but the analysis does show the modeled 

concentration plus the background monitoring concentration is within 2 percent of the new I-hour 

sulfur dioxide National Ambient Air Quality Standard. Therefore, DENR considered several factors 

involving how realistic the models predict the concentration and what facility or facilities is 

contributing to the modeling concentration. 

The high modeled sulfur dioxide concentrations are located in the southeast corner of the modeling 

domain. The facility contributing to the high modeled concentration for sulfur dioxide (greater than 

90% contribution) is the MidAmerican George Neal facilities in Iowa. During these periods when 

MidAmerican George Neal is the majority contributor, Hyperion's contribution is less than 1%. 

In accordance with 40 CFR Part 51, Appendix W, uncertainties and accuracy of the models are 

discussed. As noted in section 9.1.2, Studies of Model Accuracy, "(1) Models are more reliable for 

estimating longer time-averaged concentrations than for estimating short-term concentrations at 

specific locations; and (2) the models are reasonably reliable in estimating the magnitude of highest 

concentrations occurring sometime, somewhere within an area. For example, errors in highest 

estimated concentrations of ± 10 to 40 percent are found to be typical, i.e., certainly well within the 

often quoted factor-of-two accuracy that has long been recognized for these models. However, 

estimates of concentrations that occur at a specific time and site, are poorly correlated with actually 

observed concentrations and are much less reliable." 

To determine if the AERMOD is correctly quantifying the sulfur dioxide concentration, DENR 

conducted a screening test to determine if AERMOD would meet a minimum operational performance 

for the I-hour sulfur dioxide National Ambient Air Quality Standard. DENR used the fractional bias 

procedure identified in EPA's Protocol for Determining the Best Performing Model (EPA - 454/R-92­

025). DENR modeled MidAmerican George Neal facilities actual emissions from March 31, 2009 

through March 31, 2010, at two receptor points in South Dakota using the two meteorological data 

sets for Union County. The two receptor points used were the location of the two sulfur dioxide 

monitoring stations currently being operated by DENR in Union County. The modeled results were 

then compared to the monitored results using the screening approach specified in EPA's protocol. 

Since the new I-hour sulfur dioxide National Ambient Air Quality standard represents a new form of 

a standard, DENR compared both the highest 25 hourly readings and the highest 25 readings 

representing the form of the standard (e.g., highest 25 daily I-hour values). 

Figure 4-1 shows a graphical representation of the screening test. As identified in the protocol 

"Models that plot close to the center (0,0) are relatively free from bias, while models that plot further 

0-1 
away from the center tend to over or under-predict. Values equal to -0.67 are equivalent to overpredictions by a factor of two while values equal to +0.67 are equivalent to under-predictions by a 

factor of two. As the graph indicates, AERMOD over-predicts the concentrations of sulfur dioxide 

with five of the eight scenarios indicating the model would over-predict the concentrations greater 

than a factor of two. 

Figure 4-1 - Screening Test 

-­ Under-predicts '----­ - impacts 

........... 

-­

.~ -1.5 -I 45 

~M 1 1.5 

............ 

/ 

1000r-pre~ IImpacts I 

Bias of Average 

• UCSF #1 Standard • UCSF #1 Hourly • UCSF #2 Standard • UCSF #2 Hourly 

• UCSC #1 Standard. UCSC #1 Hourly • UCSC #2 Standard. UCSC #2 Hourly 

Based on the analysis, the model is over-predicting the impact MidAmerican George Neal will have 

on the sulfur dioxide concentrations in the modeling domain. If it is over-predicting MidAmerican 

George Neal it is also likely over-predicting all of the sources in the area including Hyperion. Since 

the approved models are inherently conservative, DENR believes actual monitoring data will be lower 

then what is being predicted by the models. 

D-2 
Attachment E
 

South Dakota's Sulfur Dioxide Emissions
 

From National Emission Inventory
 

Table E-I contains sulfur dioxide emissions data from the National Emission Inventory (NEI) for 

2002 and 2009. The 2002 NEI was included because the inventory included a calculation of emission 

from area and fugitive sources of sulfur dioxide. Union County is shown as the fourth highest county 

with sulfur dioxide emissions even though there are no existing Title V sources in the county that 

emits sulfur dioxide emissions in that quantity. DENR investigated this further and found the sulfur 

dioxide emissions in the 2002 NEI inventory are the result of coal burning. There is no coal burning 

facility in Union County. Therefore, the information for Union County is inaccurate. The 2009 

emissions are from Title V sources only. 

Table E-l- Sulfur Dioxide Emissions in 2002 and 2009 

County 

2002 NEI Emissions 

(tons) 

2009 Title V Source Emissions 

(tons) 

Grant 11,918.8 11,652.0 

Minnehaha 3,320.1 182.4 

Pennington 2,738.6 1,118.1 

Union 1,531.7 0.0 

Brookings 1,237.7 267.5 

Codington 904.6 11.5 

Brown 680.6 2.9 

Yankton 603.2 0.2 

Davison 431.2 1.1 

Lincoln 295.3 0.9 

Beadle 290.8 0.3 

Lake 263.1 2.4 

Hutchinson 202.7 0.0 

Lawrence 179.5 2.3 

Spink 160.2 41.7 

Roberts 158.1 0.1 

Bon Homme 143.2 0.1 

Marshall 140.4 0.0 

Meade 135.7 0.0 

Kingsbury 134.7 0.2 

Day 131.9 0.0 

Charles Mix 128.5 0.0 

Moody 111.2 0.0 

McCook 108.6 0.0 

Clay 107.3 1.0 

Turner 99.7 23.4 

Clark 98.1 1.0 

Edmunds 91.7 8.9 

£-1 
County 

2002 NEI Emissions 

(tons) 

90.6 

90.3 

87.9 

87.3 

85.2 

83.1 

80.4 

76.1 

74.7 

72.8 

72.7 

68.7 

68.2 

66.4 

65.8 

63.9 

63.4 

2009 Title V Source Emissions 

(tons) 

0.0 

0.0 

0.0 

0.0 

2.5 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

2.3 

0.5 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.1 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

Fall River 

Tripp 

Hamlin 

Hand 

Deuel 

Custer 

Perkins 

Sanborn 

Hughes 

Lyman 

Potter 

Miner 

Butte 

Walworth 

Gregory 

Brule 

Faulk 

Douglas 59.2 

56.1 

55.2 

54.8 

52.5 

51.0 

50.1 

44.7 

44.0 

41.6 

36.2 

35.5 

33.6 

32.6 

30.8 

29.9 

22.8 

15.7 

13.7 

11.1 

McPherson 

Haakon 

Hanson 

Sully 

Aurora 

Corson 

Jackson 

Campbell 

Todd 

Jones 

Bennett 

Jerauld 

Hyde 

Dewey 

Shannon 

Stanley 

Mellette 

Ziebach 

Harding 

Buffalo 9.1 

28,425 

0.0 

Statewide Total 13,323

£-2