,

I

COMPANY:

FACILITY:

Gtf11!e Ih1/ (j\i'{b(/c ZIJA,0'n1 ir - vt11'-1'1 Ju-ch~ DEPART:\1ENT OF ENVIRONMENTAL QUALITY I I

DIVISION OF AIR QUALITY

Permit Application Analysis, NSR-AP-C92

April :4,2002

Black Hills Corporation

WYGEN2

FACILITY LOCATION:

TYPE OF FACILITY:

13 151 Highway 51

Gillette, WY

Section 27. T50N. R71W

Campbell County, Wyoming

Coal Fired Stearn Electric Generating Plant

RESPONSIBLE OFFICIAL: Tom Ohlmacher

Senior V.P. Power Supply and Operations -----~._--------------

COMPANY REPRESENTATIVE:

MAILING ADDRESS:

REVIEWED BY:

PURPOSE OF APPLICATION:

Fred Carl

Environmental Coordinator

P.O. Box 1400

Rapid City, SD 57709-1400

Stewart Griner, Air Quality Engineer

Ken Rairigh. Air Quality EngineerlModeler

Black Hills Corporation submitted an application to construct a 500 megawatt (MW) pulverized coal

(PC) fired electric generating facility to be known as WYGEN 2. The proposed facility consists of one

PC boiler burning coal from the nearby Wyodak coal mine with associated coal and lime handling and

flue gas desulfurization (FGD) waste product handling. Parameters used for design values, based on coal

from the Wyodak mine, include a design heat content of7,950 Btullb and a maximum sulfur content of

1.2%. The maximum design heat input to the facility will be 5,145.7 MMBtu/hr.

The applicant identified the following emission sources in the permit application:

TB002538
Black Hills Corporation ( JYGEN 2)

Permit Application Ana!ys:s, NSR-AP-C92

Page 2

So rce No. Source

?2-O01

C.)C-OOI

C:'>C-002

C::>C-003

CDC-004

LDC-OOIA

LDC-OOIB

RDC-OOI

RDC-002A

RDC-002B

500 MW PC Boiler

Coal Storage Silo Dust Collector (top)

Coal Storage Silo Dust Collector (bottom)

Coal Transfer Building Dust Collector

Unit Transfer and Silos Dust Collector

Lime Unloading Silo Dust Collector

Lime Unloading Silo Dust Collector

FGD Waste Recycle Storage Bin Dust Collector

FGD Waste Loadout Silo Dust Collector

FGD Waste Loadout Silo Dust Collector

SUMMARY OF POTENTIAL EMISSIONS:

.Potential emissions for this facility are based on proposed limits with the exception of ammonia and

hazardous air pollutants (HAPs). Ammonia emissions are calculated in an April 16, 2002 memo to file

NSR-AP-C92. HAP emissions are detailed in the following section on HAP emissions and maximum

available control technology (MACD. Potential emissions are estimated in the following table:

Source # Potential Emissions (tpy)

NOx S02 PMlPM,o CO VOC NH3 HAPs

PC-OOI 1578 3381 270 3381 225 97.4 110

CDC-OOI 8

CDC-002 2.5

CDC-003 2.5

CDC-004 11

LDC-OOIA 0.5

LDC-OOIB 0.5

RDC-OOI 1

RDC-002A/B* 2

*

TOTAL 1578 3381 298 3381 225 97.4

Only one ofthese units (RDC-002A or RDC-002B) will be in service at anyone time.

110

TB002539
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 3

CHAPTER 6, SECTION 4 - PSD APPLICABILITY:

The proposed WYGEN 2 facility is subject to Prevention of Significant Deterioration (PSD) review

under Chapter 6, Section 4 ofthe Wyoming Air Quality Standards and Regulations C'NAQSR) because it

is classified as a "major emitting facility." Fossil-fuel fired steam electric plants of more than two

hundred and fifty million Btulhour heat input with the potential to emit one hundred tons per year or

more of any regulated pollutant are considered "major emitting facilities" under Chapter 6, Section

4(a)(i) ofthe WAQSR. Potential emission rates from the WYGEN 2 facility and the PSD significance

levels are shown in the following table:

Pollutant PC Boiler Potential PSD Significant PSD Review

Emission Level Emission Rate • Emission Rate Required?

(LblMMBtu) (fPY) (fPY)

NOx 0.07 1578 40 Yes

S02 0.15 3381 40 Yes -- -----~ -----~ "----

PMJPM10 0.012 298 b 25/15 Yes

CO 0.15 3,381 100 Yes

VOC 0.01 225 40 Yes

H2SO4 4.62 x 10') 104 7 Yes

Lead 2.53 x 10.5 0.57 0.6 No

Fluorides 3.69 x 10~ 8.3 3 Yes

Total Reduced Sulfur Negligible Negligtble 10 No (including H2S)

Mercury' 1.24 x 10.5 0.28 0.1 Yes

BerylliumC 7.54 x 10-6 0.17 0.0004 Yes

• Based on 5,145.711MBtu/hr and 8760 hours per year.

b Includes 28 tpy from material handling based on 6.4 lblhr per the August 2001 supplement.

C Mercury and Beryllium are excluded from federal PSD regulations since 1990 per Section 112(b)(6) of

the Clean Air Act but still included in WAQSR, Chapter 6, Section 4(a)(xxi).

The proposed WYGEN 2 facility is subject to a Prevention of Significant Deterioration (PSD) review

consisting ofthe following:

1) A Best Available Control Technology (BACT) analysis is required for all regulated pollutant

emitted in significant amounts.

2) An ambient air quality impact determination is required for all regulated pollutants emitted in

significant amounts and any other pollutants required by the Administrator.

TB002540
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 4

3) An increment consumption analysis is required for regulated pollutants based on allowable

emission rates as well as increment consuming emissions from other sources in the region. The

total deterioration determined from this analysis must comply with the allowable increments

established for PM 1o, S02' and NO. for the classification ofthe area (i.e. Class I or Class II) in

which the increment consumption is predicted.

4) An analysis is required to assess the impairment to visibility, soils, and vegetation resulting from

the facility and general commercial, residential, industrial, and other growth associated with the

facility.

BEST AVAlLABLE CONTROL TECHNOLOGY (BACT):

A best available control technology (BACf) analysis for NOx , S02' PMJPM1o, CO, VOC, H2S04, and

fluoride is required because each ofthese pollutants is emitted above PSD significant emission rates.

Additionally, a BACT analysis is required for beryllium and mercury under Chapter 6, Section 4(a)(xxi)

of the WAQSR. The BACT analysis for each emission source is presented in the following sections:

I. 500 MW PC Boiler - NO. Control

Black Hills Corporation proposed low NOx burners and SCR with an emission limit ofO.09lblMMBtu

as BACT. The Division reviewed the RACTIBA(.lfLAER Clearinghouse (RBLC) and information from

EPA Regional offices to find permined or proposed PC utility boilers with NO. emissions equal or lower

than 0.09 1~lMMBtu as shown in the following table:

Facility

Kansas City Power & Light Co. -

Hawthorne Station

State Size

(MW)

MO 570

Control

Device

SCR

NOx Emissions

(IblMMBtu)

0.08 (30 day)·

Status

Operational

May 2001

0.121blMMBtu (30 day) limit for first 3 years, then 0.081blMMBtu ifdemonstrated feasible. According

to Missouri DNR., Hawthorne Station is currently meeting the 0.08 IblMMBtu limit.

•

Great Plains Power - Weston Bend

Generating Station MO 820 SCR 0.08 (30 day) Proposed

Emission Control Technologies

Black Hills Corporation considered the following controls for NOx reduction:

Combustion Controls - Low NOx burners (LNB), overfire air (OFA), and advanced gas reburn (AGR) all

serve to reduce peak combustion temperatures thus lowering NOx emissions. Although none ofthese

controls can achieve emission levels comparable to post combustion controls, they do prevent some of

the initial formation ofNOx. Black Hills Corporation selected low NOx burners in combination with

post-eombustion controls because the lower emissions generated result in lower capital cost and reagent

use.

TB002541
Black Hills Corporation (WYGEN 2)

Pennit Application Analysis, NSR-AP-C92

Page 5

Selective Catalytic Reduction (SCR) - SCR is a post combustion control teclmique in whi.:~ the flue gas

is combined with vaporized ammonia in the presence of a catalyst and NO. is reduced to nitrogen and

water. Black Hills Corporation evaluated SCR at emission levels of 0.06, 0.08, and 0.09 :o,'MMBtu.

Selective Non-Catalytic Reduction (SNCR) - SNCR is similar to SCR in that it involves t::e injection of a

reducing agent such as ammonia or urea into the flue gas stream. The reduction chemistr:!, however,

takes place without the aid of a catalyst. SNCR systems rely on appropriate injection tem:;eratures,

proper reagent/gas mixing and prolonged retention time in place of the catalyst. SNCR s; 'stems are very

sensitive to temperature changes and typically have lower emissions reduction (up to. fifr! or sixty

percent) and higher ammonia slip. Black Hills Corporation did not further consider SNC';' because of the

lower emissions reduction and the lack of any operational advantage over SCR.

Hybrid SNCRJCatalyst System - These systems were developed to combine the relatively 'ow capital cost

and high ammonia slip associated with SNCR with the high reduction potential and low ammonia slip

inherent to SCR. The first part ofthe system is a typical SNCR system with increased re:::.:ent flow for

additional NOx reduction. A small catalyst follows to reduce ammonia slip and possibly :chieve

additional NOx reduction. This system requires more ammonia but uses a smaller cataly:.. Black Hills

_____-----'C'-'orporation-did-not-furtheHlensidef"~ybrid_systern-becauseofpussfule l'toolems aclile'.'~'g adequate

distribution of ammonia and because there is no operational or emission reduction advanLge over SCR.

Energy and Environmental Evaluation

Black Hills Corporation evaluated the energy and environmental considerations for SCR. An SCR

system consumes electrical energy for ammonia transport and vaporization and for incremental fan

demand to overcome pressure drop across the catalyst.

Environmental considerations include ammonia slip, a slight increase in SO) emissions, a possible slight

increase in PM10 emissions, and ammonia handling and storage. Ammonia slip emissions of 2 to 5 ppm

and a 1 to 2 percent increase in SO) emissions are expected. Unreacted ammonia and SO) can react to

form ammonia bisulfate and ammonia sulfate salts in the form ofPM1o emissions. Ammonia is a

hazardous material and adequate design precautions are necessary for handling and storage.

Economic Evaluation of Alternatives

Black Hills Corporation evaluated the combination of Low NOx burners and SCR at emission levels of

0.06, 0.08, and 0.09 IblMMBtu. An economizer bypass is required to keep temperatures in the optimum

range in order to meet the 0.06 or 0.08 Ib/MMBtu emission limits at 50% load. Consequently, the

incremental cost is higher from 0.09IbtM:MBtu to 0.08 IblMMBtu than from 0.09 Ib/MMBtu to levels

lower than 0.08 IblMMBtu. The results are shown in the following table:

TB002542
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 6

Annual Emissions

Emissions Reduction

Total Annualized Cost

Total Cost Effectiveness

Incremental Reduction·

Incremental Annualized

Cost

Incremental Cost

Effectiveness

Baseline

0.25 IblMMBtu

5,635 tpy

Baseline

Baseline

Baseline

LNB/SCR LNB/SCR LNB/SCR

r.09lblMMBtu 0.08 IblMMBtu 0.06 Ib/MMBtu

2,028 tpy 1,803 tpy 1.352 tpy

3,606 tpy 3,832 tpy 4,283 tpy

$12,563,000 SI5,582,000 $17,798,000

$3,484/ton $4,067/ton $4,156/ton

Baseline 225 tpy 676 tpy

Baseline $3,019,000 $5,235,000

Baseline $13.395/ton $7,742/ton

• The Division calculated incremental costs based on a 0.09 IblMMBtu baseline for both 0.08 and 0.06

IblMMBtu because an economizer bypass is required to achieve either~rJL06IblMMBtu~ - -

Black Hills Corporation chose 0.09 IblMMBtu as BACT because they considered the incremental cost

effectiveness to be unreasonable for the lower emission levels and because they were unable to find an

issued permit with a limit less than 0.12 IblMMBtu for a PC boiler. (Note that the Hawthorne Station

boiler in Missouri has a limit ofO.12lblMMBtu for 3 years and then a limit ofO.08lblM:MBtu unless the

permittee can demonstrate that 0.08 IblMMBtu is not feasible.) According to Missouri DNR, Hawthorne

Station is meeting the 0.08 IblMMBtu limit. Missouri DNR is also working on a permit for Great Plains

Power with a proposed limit of 0.08 IblMMBtu. Although Great Plains Power requested 3 years to

determine ifthey can comply with the limit as allowed in the Hawthorne Station permit, Missouri DNR

indicated that they do not plan to issue the permit with any exceptions to the 0.08 IblM:MBtu limit.

The Division evaluated the control efficiency required to meet limits of 0.09,0.08, and 0.06 Ib/MMBtu

using a baseline of 0.25 IblMMBtu as shown in the following table:

Emission Level

(lbt1vfMBtu)

0.09

0.08

0.06

Control Efficiency

(%)

64

68

76

These efficiencies seem low based on information that vendors are designing and providing guarantees

for SCR systems with at least 90% control efficiencies. For example, Montour Steam Electric Station in

Allentown, PA retrofitted two 750 MW coal fired boilers with SCR systems designed for 90% control

efficiency and 0.04 IblMMBtu using eastern bituminous coal. It should be noted that these are design

levels to meet acid rain requirements and there are no permit limits requiring this level ofreduction.

TB002543
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 7

The BACf analysis indicates that 0.06 IblMMBtu is technically feasible and the Division considers the

total and incremental cost effectiveness to be reasonable. Note that the incremental cost effectiveness is

much lower when considering emission limits less than 0.08 IblMMBtu because an economizer bypass is

required to achieve emission limits of 0.08 IblMMBtu or less. Although the BACT analysis indicates an

emission level of 0.06 IblMMBtu, Black Hills Corporation has expressed uncertainty about meeting 0.06

Ibl1v1MBtu on a cO:ltinuous basis. The Division and Black Hills Corporation discussed various options

for dealing with t;;;5 uncertainty while setting an appropriate BACT level. One option discussed was

0.06 Ibl1v1MBtu a::::ual average and 0.08 IblMMBtu 30 day average. This option still left Black Hills

Corporation with:. :neasure of uncertainty in regards to meeting the annual limit and they requested that

the 0.06IbIMMB:t:.limit not become effective until issuance ofthe Title V operating permit in order to

allow additional :....e to demonstrate compliance. Even with the additional time for compliance, Black

Hills Corporation expressed concern about meeting a 0.061blMMBtu limit and discussed options if they

could not meet the :imit. Upon further discussion, the Division and Black Hills Corporation agreed that a

30 day limit ofO.C7lblMMBtu would be more stringent than any existing limit for an operating PC

boiler and could C~ met without'additional time to demonstrate compliance. The Division concludes that

Low NOx burners <:'l1d SCR with an emission limit ofO.07lblMMBtu (30 day rolling average) represent

BACf.

II. 500 MW PC :-"'Jiler - S02 Control

~----------- --------- --_.-

Black Hills Corporation proposed a semi-dry lime spray dryer absorber with emission limits of 0.15

IblMMBtu (30 day average) and 0.17 IblMMBtu (2 hour block). The Division reviewed the

RACfIBACfILAER Clearinghouse (RBLC) and information from EPA Regional offices to find

permitted or proposed PC utility boilers with S02 emissions lower than 0.15 Ib/MMBtu as shown in the

following table:

TB002544
Black Hills Corporation (WYGEN 2)

Pennit Application Analysis, NSR-AP-C92

Page 8

Facility State Size- Control S02 Status

Device -- Emissions

(lblMMBtu)

Deseret Generation and UT 500MW Wet Lime 0.0976 Permit Issued

Transmission Company FGD (12 month) 3/16/98

SEI Birchwood, Inc. VA 2200 Semi-Dry 0.1 Permit Issued

MMBtuIhr Lime FGD (30 day) 8/23/93

Kansas City Power & Light Co. MO 570MW Semi-Dry 0.12 Startup May

- Hawthorne Station Lime FGD (30 day) 2001

Great Plains Power - Weston MO 820MW Semi-Dry 0.12 Proposed Bend Generating Station Lime FGD (30 day)

Maple Street Powerhouse - MA 30MW Semi-Dry 0.12 Permit Issued

Unit 2 - Ware Lime FGD 12/2191

-----Semi ~-Dry- PermitIssued ----Platte-River-PWR--="Rawhide-- - --CO 250 ~- Lime FGD 0.13 5/22180

375 Semi - Dry Permit Issued Cogentrix ofRichmond VA MMBtulhr 0.13

each LimeFGD 1/2191

375 Semi - Dry Permit Issued Cogentrix of Dinwiddie VA MMBtuIhr 0.13

each Lime FGD 4/16/92

HCC Chemical Company - 312.5 Permit Issued LA MMBtuIhr FGD 0.14 Convent each 11/6/80

- For comparison, WYGEN 2 is 5145.7 MMBtuIhr and 500 MW.

** Semi-Dry Lime Flue Gas Desulfurization (FGD) includes Lime Spray Dryer/Absorbers and Dry

Lime Scrubbers. A Lime Spray Dryer/Absorber is proposed for WYGEN 2.

Emission Control Technologies

Black Hills Corporation considered the following controls for S02 reduction:

Wet Lime and Limestone Based Flue Gas Desulfurization (FGD) - In wet lime FGD, S02 is reacted with

a lime slurry to produce calcium sulfite or calcium sulfate (gypsum). Wet lime FGD can achieve high

removal efficiencies (>95%) when burning high or low sulfur coals. It can achieve higher removal

efficiencies than semi-dry FGD when burning high sulfur coals but there is no advantage with low sulfur

coals. Wet FGD uses more water than serni-dry FGD and has a visible moisture plume.

Semi-Dry Lime Based FGD - Semi-dry FGD processes include lime spray dryer/absorbers and dry lime

scrubbers. In these processes, S02 is reacted with Ca(OH)2 as either a slurry or a dry powder to produce

TB002545
Black Hills Corporation (WYGEN 2)

Pennit Application Analysis, NSR-AP-C92

Page 9

calcium sulfite or calcium sulfate (gypsum). Significantly less water is used in these processes compared

to wet lime FGD and there is typically no visible moisture plume. Semi-dry FGD can achieve removal

efficiencies comparable to wet FGD with the low sulfur coal proposed for this plant.

Energy and Environmental Evaluation

Black Hills Corporation evaluated the energy and environmental considerations for the processes

described above. The majority of energy consumption for the wet FGD process is attributed to reagent

preparation (grinding limestone) and the high pumping power due to a high liquid to gas ratio. The lime

spray dryer has the lowest energy demand.

Environmental considerations include visible moisture plumes, H2SO. formation, waste disposal, and

water consumption. As discussed above, wet lime FGD produces a visible moisture plume but semi-dry

FGD typically does nol. H2SO. can be formed by the reaction of SO) from the combustion process with

moisture in the flue gas. The H2SO. can also condense resulting in increased PM10 emissions and

opacity. These concerns are less of an issue with semi-dry FGD because this process is more effective at

removing SO) and there is less moisture in the flue gas. Waste disposal is an issue with either the wet or

dry process. The wet process has an advantage In tlUlt fly ash is collected prior to the FGD process

allowing the sale of fly ash rather than disposal at a landfill. However, the semi-dry process has the

advantage of dry byproducts allowing easier handling and transport. The mixture of fly ash and

unreacted lime that results from the semi-dry process can be conditioned with water to produce a

cementatious product with low permeability resulting in lower leachate and fewer handling problems at

the landf!ll. Water consumption rates for the sem-dry process are about 20 to 30 percent less than the

wet process which is important for areas with low water availability.

Economic Evaluation of Alternatives

An economic evaluation was performed for semi-dry FGD at emission levels of 0.15 and 0.131blMMBtu

and for wet FGD at emission levels of 0.13 and 0.10 Ib/MMBtu as shown in the following table:

TB002546
Black Hills COllloration (WYGEN 2)

Permit Application Analysis, NSR-AP·C92

Page 10

Baseline SDFGD· SDFGD· WFGD.... WFGD**

2.13 0.15 0.13 0.13 0.10

IbfMMBtu IblMMBtu IblMMBtu IblMMB:'" lblMMBtu

Annual Emissions 48,147 tpy 3,382 tpy 2,932 tpy 2,932 tpy 2,250 tpy

EmIssions Reduction Baseline 44,765 tpy 45,215 tpy 45,215 tpy 45,897 tpy

Total Annualized Baseline $21,080,000 $21,271,000 $26,567,000 $26,952,000 Cost

Total Cost Baseline $471/ton $4701ton $588/ton $587/ton Effectiveness

Incremental Baseline 450 tpy 450 tpy 1,132 tpy Reduction

Incremental Baseline $191,000 $5,487,000 $5,872,000 Annualized Cost

."--------

---------mcremental Cost

Effecti veness

• Semi-Dry Flue Gas Desulfurization

.. Wet Flue Gas Desulfurization

Baseline $424/ton $12,193 $5,1 87/ton

Due to the considerations discussed above and the fact that semi-dry FGD can achieve removal

efficiencies comparable to wet FGD with low sulfur coal, Black Hills Corporation chose semi-dry FGD

(lime spray dryer/absorber) with an emission level of 0.15 IblMMBtu. The above data suggests that

BACT should be closer to 0.10 IbIMMBtu without consideration of the removal efficiency necessary to

achieve 0.10 Ib/MMBtu. The design heating value ofthe coal for WYGEN 2 is 7,950 Btullb and the

design sulfur content is 1.2%. This equates to uncontrolled emissions ofJUSt over 3 Ib S02IMMBtu as

shown in the following calculation:

lbeaal

7,950 Btu x 12lbS

100lbeaal x 10 6 BtuMMBtu

64lbS02 x

32lbS

3.02 lb S02

MMBtu

An emission limit of 0.1 0 Ib/MMBtu equates to a 97% removal efficiency as follows:

3.02 - 0.10 x 100 = 97%

3.02

The proposed limit ofO.15lblMMBtu results in a 95% removal efficiency. Black Hills Corporation

claims that 95% removal efficiency on a continuous basis is higher than the proven performance for lime

spray dryer/absorbers. The Division compared coal properties and removal efficiencies for several ofthe

facilities listed above as follows:

1) The SEI Birchwood facility in Virginia is permitted at 0.1 IblMMBtu (30 day average) using semidry FGD but the coal has different properties. Although the sulfur content is approximately the same

TB002547
Black Hills Corpcration (WYGEN 2)

Pennit Applicalloil Analysis, NSR-AP-C92

Page II

(limited to 1.2% maximum and 1% annual average), the heating value is higher (average of

approximately 12,500 Btullb according to the Virginia Department of Environmental Quality).

Using a he::::ng value of 12,500 Btullb and a sulfur content of 1.2% in the above equations results In

a 94.8% rcr:-.oval efficiency to achieve O. I IbIMMBtu. The permit for the SEI Birchwood facility

also cont.,:::: a minimum efficiency limit of90% for the semi-dry FGD.

2) Kansas Ci~' ?ower & Light's Hawthorne Station is permitted at 0.12 IblMMBtu using semi-dry

FGD. Acc:~ding to Missouri DNR, this facility uses low sulfur, sub-bituminous, Wyoming coal

(pRB coal) with sulfur contents ranging from 0.5 to I percent. Assuming a heat value of 8,000

Btullb and a sulfur content of I% in the above equations results in a 95% removal efficiency to

achieve 0.12IblMMBtu.

3) Platte River Power's Rawhide Station is permitted at 0.13 IblMMBtu (30 day average) using semidry FGD. According to the Colorado Department of Public Health and Environment, the actual

properties of coal used during the year 2000 averaged 8,850 Ib/MMBtu and 0.2% sulfur. This

equates to a 71 % removal efficiency to achieve 0.13 IblMMBtu. However, the operating permit for

this facility contains a minimum efficiency limit of 80% for the semi-dry FGD.

._. -_.. - ._--.'.------------

Note that the above calculations use the upper end ofthe sulfur range. If average sulfur contents were

used, the resulting removal efficiencies would be lower than the above values. These average sulfur

removal efficiencies would be less than 95% which supports the claim by Black Hills Corporation that a

95% control level has not been proven on a continuous basis. An emission limit of 0.15 IblMMBtu for

design case coal (7,950 BtuIlb, 1.2% sulfur) results in a removal efficiency of 95% which is at least as

stringent as other recent BACT determinations. However, 0.15 IblMMBtu could be achieved at a much

lower efficiency when burning coal with a higher heating value and/or lower sulfur content. Requiring a

minimum removal efficiency of90% as required for the SEI Birchwood facility in Virginia will ensure

that the control device is operated to achieve a good control efficiency regardless of coal properties.

The requested 2 hour limit ofO.17lblMMBtu is to allow for short term spikes in the coal sulfur content

and time to adjust scrubber operating parameters. The Division concludes that a semi-dry lime spray

dryer absorber with an emission limit of 0.15 IblMMBtu (30 day average), 0.171blMMBtu (2 hour

block), and a minimum removal efficiency of90% represents BACT.

Ill. 500 MW PC Boiler - PMJPM,o Control

Black Hills Corporation proposed fabric filters (Ryton Bags) with an emission limit of 0.0 18 IblMMBtu

as BACT. The Division reviewed the RACTIBACTILAER Clearinghouse (RBLC) and information from

EPA Regional offices to fmd permitted or proposed PC boilers with PMlPM,o emissions lower than

0.018 IblMMBtu as shown in the following table:

TB002548
Black Hills Corporation (WYGEN 2)

Pennit Application Analysis, NSR-AP-C92

Page 12

Facility State Size Control PMlPM\o Status

Device Emissions

(IbIMMBtu)

Firestone Tire & Rubber· Permit

Decatur (pC Industrial Boiler) IL 178 MMBtu/hr Fabric Filter 0.01 Issued

7/1/85

Saginaw Steering Gear - Permit

AL 121.4 MMBtulhr Fabric Filter 0.013 Issued Athens (pC Industrial Boiler) 10/15/80

Central Power and Lime, Inc. Permit

- Brooksville (PC Industrial FL 1850 MMBtu/hr Fabric Filter 0.0135 Issued

Boiler) 8/15/95

HCC Chemical Company - Permit

Convent (PC Industrial LA 312.5 MMBtu/hr Fabric Filter 0.014 Issued

Boiler) - -~ _..-------- 1116/80___ -- .-----.------

Mon Valley Energy Limited Permit

Partnership - Poland Mines PA 966 MMBtu/hr Fabric Filter 0.015 Issued

(PC Electric Utility Boiler) 8/8/95

B.F. Goodrich Chemical Permit

Group - Convent (pC LA 338 MMBtu/hr Fabric Filter 0.015 Issued

Industrial Boiler) 11124/80

Emission Control Technologies

Black Hills Corporation considered the following controls for PMlPM,o reduction:

Electrostatic Precipitators - Electrostatic precipitators remove particulate matter from the flue gas stream

by charging the particulate matter with a DC electrode and attracting the charged particles to grounded

collecting plates. A layer of collected particles forms on the plates and is removed periodically by

rapping the electrodes. Precipitator performance and sizing is dependent on the quantity and chemical

composition ofthe particulate matter and flue gas.

Fabric Filters - Fabric Filters use fabric bags in compartments to collect particulate matter. As the

thickness ofthe collected particulate matter (dustcake) increases, the pressure drop across the bags

increases proportionally. The bags are cleaned periodically by dislodging a large portion ofthe dustcake

with a pulse of air pressure. Fabric filters are well suited for use with a lime spray dryer system because

the flue gas passes through a dustcake of unreacted reagent and reaction products on the filter surface

resulting in additional removal of S02 and air toxics. Black Hills Corporation chose Fabric Filters as the

top control option because they are more effective than electrostatic precipitators at controlling PM\o and

air toxics.

TB002549
Black Hills Corporation (WYGEN 2)

Pemut Application Analysis, NSR-A.P-C92

Page J3

Energy and Environmental Evaluation

Black Hills Corporation evaluated fabric filters at emission levels of 0.0 18,0.0 IS, and 0.012 IbIMMBtu.

There are no significant energy or environmental differences between these options other than the

emission levels.

Economic Evaluation of Alternatives

Black Hills Corporation evaluated Ryton filter bags at an emission level of 0.0 18 IblMMBtu and

membrane filter bags (e.g. Gore Tex) at emission levels of 0.0 15 and 0.012 IbIMMBtu. The results are

shown in the following table:

Baseline Ryton Bags Membrane Bags Membrane Bags

10.2 0.018 0.015 0.012

IblMMBtu IblMMBtu IblMMBtu IblMMBtu

Annual Emissions 231,032 tpy 406 tpy 338 tpy 270 tpy ---- - ~- -- --------- EnusslOns Reduction Baseline 230,626 tpy 230,694 tpy 230,762 tpy

Total Annualized Cost Baseline $536,000 $1,331,000 $1,331,000

Total Cost Effectiveness Baseline $2.3/ton $5.8/ton $5.8110n

Incremental Reduction Baseline 68 tpy 136 tpy

Incremental Annualized Baseline $795,000 $795,000 Cost

Incremental Cost Baseline $11,691/ton $5,846/ton Effectiveness

Black Hills Corporation chose 0.018 IblMMBtu as BACT because they considered the incremental cost

effectiveness to be unreasonable for the lower emission levels. Note that the incremental cost is higher

for 0.015 IbfMMBtu because membrane bags are required to achieve either 0.015 or 0.012 IblMMBtu.

The Division considers the total and incremental cost effectiveness to be reasonable for 0.012 IblMMBtu

and the RBLC shows other facilities with pennitted emission levels in this vicinity. Additionally, fabric

filters with an emission limit of 0.012 IblMMBtu represent maximum available control technology

(MAC!) in the following MACT analysis. The Division concludes that fabric filters with an emission

limit ofO.012lblMMBtu represent BACT.

IV. 500 MW PC Boiler - CO and VOC Control

Black Hills Corporation proposed good combustion controls with an emissions limit of 0.09 Ib

NOxIMMBtu as BACT. Measures taken to minimize the formation of NOx during combustion inhibit

complete combustion and increase emissions ofCO and VOe. (post combustion NOx controls such as

SCR do not increase emissions ofCO and voe.) To ensure a valid comparison, the Division reviewed

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Black Hills Corporation (WYGEN 2)

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CO and VOC limits for the facilities previously listed under the NOx control section with emissions

equal or lower than 0.09 Ib NOxIMMBtu. The CO and VOC limits for these facilities are shown in the

following table:

Facility

Kansas City Power &

Light Co. - Hawthorne

Station

Great Plains Power -

Weston Bend

Generating Station

State Size Control CO VC: Status

Device Emissions Emis2:ons

(MW) (IblMMBtu) (lbMy.~3tu)

MO 570 Combustion 0.16 0.0;;}6 Operational

Controls May 2001

MO 820 Combustion 0.16 0.0036 Proposed Controls

--- ------ - ----- ---- ---------

Emission Control Technologies

--_.. -- ._- ---

Black Hills Corporation considered the following controls for CO and VOC reduction:

Oxidation Catalyst - A catalytic oxidation method is available for gas and oil fueled combustion sources.

The process is a straight catalytic oxidation/reduction reaction requiring no reagent. The required

operating temperature for these catalysts is approximately 650 to 750 OF and emission reductions are on

the order of 80 percent for CO and 20 percent for VQC. An oxidation catalyst has never been applied to

a coal fired source and application ofthis technology presents substantial challenges. The oxidation

catalyst will not only oxidize CO and VOC but also a predominate portion of S02 to SO), Combination of

this SO) with ammonia from the SCR system may result in fouling ofthe air heater. Plugging and

erosion ofthe catalyst would also occur due to fly ash and abrasive combustion products. Finally, the

acid gases and trace metals in the flue gas would poison the catalyst. For these reasons, Black Hills

Corporation considered catalytic oxidation technically infeasible.

Good Combustion Controls - The RBLC does not show any BACT determinations using post combustion

controls for CO and VOC from PC boilers. Therefore, Black Hills Corporation selected good

combustion controls to achieve emission rates of 0.15 Ib COlMMBtu and 0.01 Ib VOClMMBtu as BACT

for CO and VOC, respectively. The proposed limits correspond to 3381 tpy CO and 225 tpy VOC.

Energy and Environmental Evaluation

There are no energy or environmental considerations for good combustion controls.

Economic Evaluation of Alternatives

An economic evaluation is not required since good combustion controls is the only feasible option.

The proposed emission limit of 0.15 IblM:MBtu for CO is lower than the determinations listed above.

Although the proposed limit of 0.01 IblM:MBtu for VOC is higher than the determinations listed above,

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the method of control is the same. Requiring an emission limit of 0.0036 IblMMBtu would have no

effect on actual emissions. The Division concurs that good combustion controls with an emission limit

of 0.15 IblMMBtu for CO and an emission limit of 0.0 I IblMMBtu for VOC represents BACT.

V. 500 MW PC Boiler - Sulfuric Acid Mist Control

Black Hills Corpora::on proposed a semi-dry lime spray dryer/absorber as BACT for sulfuric acid

(H2S04 ) mist. A percentage ofthe S02 in the flue gas will be oxidized to SO), This SO) can combine

with moisture in the _~ue gas to form H2S04 , The semi-dry lime spray dryer/absorber proposed for S02

control removes S02 Lhat could be oxidized to SO) and also removes SO) and H2S04 in the flue gas by

reacting condensed ~cid with the alkaline reagent. Black Hills Corporation estimates that the lime spray

dryer/absorber will r~move approximately 95% ofpotential H2S04 emissions for a potential emissions

rate of 104 tpy. As c-'plained in the previous discussion on S02 control, the semi-dry process does not

typically result in a v~sible moisture plume because there is less moi!>ture in the flue gas and the semi-dry

process is more effec:ive at removing SO) as compared to wet flue gas desulfurization. The Division

concurs that a semi-<:.} lime spray dryer/absorber represents BACT for H2S04 ,

----- _.- ----- ______VI~OO_MW_PC--Be:: ~p--Fluoride-Control- --

Fluorides are regulatt:d under the PSD program and the more specific pollutant hydrogen fluoride

(hydrofluoric acid) is regulated as a hazardous air pollutant. They are the same, for all practical

purposes, for this analysis because hydrogen fluoride is the expected form of fluoride emissions. A more

detailed discussion on fluoride emissions is included in the subsequent MACT section. Black Hills

Corporation proposed a semi-dry lime spray dryer/absorber and a fabric filter as BACT (and MACf) for

hydrogen fluoride and the Division concurs.

VII. 500 MW PC Boiler - Beryllium Control

Beryllium is excluded from federal PSD regulations since 1990 per Section 112(b)(6) ofthe Clean Air

Act but still included in Chapter 6, Section 4(a)(xxi) of the WAQSR. Beryllium is regulated as a

hazardous air pollutant. A more detailed discussion on beryllium emissions is included in the subsequent

MACT section. Black Hills Corporation proposed a fabric filter as BACT (and MACf) for beryllium

and the Division concurs.

VITI. 500 MW PC Boiler - Mercury Control

Mercury is excluded from federal PSD regulations since 1990 per Section 112(b)(6) ofthe Clean Air Act

but still included in Chapter 6. Section 4(a)(xxi) of the WAQSR. Mercury is regulated as a hazardous air

pollutant. A more detailed discussion on mercury emissions is included in the subsequent MACT

section. Black Hills Corporation proposed good combustion controls, SCR, a semi-dry lime spray

dryer/absorber, and a fabric filter as BACT (and MACf) for mercury and the Division concurs.

IX. 500 MW PC Boiler - Ammonia Control (Chapter 6, Section 2)

BACT is required for ammonia emissions under WAQSR, Chapter 6. Section 2(c)(v). Black Hills

Corporation stated that ammonia slip emissions of 2 to 5 pprIly are expected and that catalyst

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manufacturers will guarantee ammonia slip emissions of 5 pplTly or less. The Division concurs that

ammonia slip emissions of 5 ppm, or less (dry basis, corrected to 3% OJ represent BACT.

X. Material Handling - PMlPM10 Control

Black Hills Corporation proposed fabric filters with an emission limit of 0.009 gr/dscf as BACf for coal

handling and fabric filters with an emission limit of 0.0 I gr/dscf as BACT for other material handling.

Fabric filters have the highest control efficiency of any ofthe particulate matter control options and

Black Hills Corporation chose them as the top option. The Division concurs that fabric filters with an

emission limit of 0.009 gr/dscfrepresent BACf for coal handling and fabric filters with an emission limit

of 0.01 gr/dscfrepresent BACT for other material handling.

XI. Miscellaneous Sources - PMJPM10 Control

The Division evaluated BACT for fugitive PMlPM10 emissions from unpaved haul roads, coal conveying,

unloading lime trucks, loading FGD Waste, and truck transport. The haul roads at the Wyodak coal mine

are treated with suitable chemical dust suppressants in addition to water to control fugitive dust. _~

______~em......... iS''''''s'"'jons.._1"he_same_method~be_used_fonmpaved roads at WYGE1'r2 and the Division considers

this BACT for unpaved haul roads. The application indicates that coal is transferred from the Wyodak

coal mine through the coal storage silo fill system and plant feed systems, both ofwhich are covered to

the maximum extent practical with bolted metal shrouds. The Division considers covered conveying

systems to represent BACf. The application shows lime unloading will be accomplished with a

pneumatic transfer system controlled with the lime unloading silo baghouses (LDC-OO 1A and LDC00IB). The Division considers this BACT for lime unloading. The FGD Waste Loadout Silos are

controlled with baghouses and these baghouses can also be used to control fugitive dust from loading

FGD Waste. The Division considers loading spouts with an outer sleeve for dust withdrawal or

equivalent connected to the silo baghouses (RDC-002A, RDC-002B) to represent BACf for loading

FGD Waste. The Division considers enclosing the loads to represent BACT for truck transport

emissions.

CHAPTER 6, SECTION 6 - HAZARDOUS AIR POLLUTANT (HAP) EMISSIONS AND

~AVAllABLECONTROLTECHNOLOGY~cn:

This facility is subject to a case·by-case MACf review under the requirements ofWAQSR Chapter 6,

Section 6 and Section 112(g) ofthe 1990 Clean Aii Act Amendments (40 CFR 63, Subpart B) because it

is a major source of hazardous air pollutants and the specific MACT standard for this source category has

not been promulgated yet. The exclusion for electric utility steam generating units in Chapter 6, Section

6(c) is no longer in effect because electric utility steam generating units were added to the source

category list on December 20,2000 [Federal Register Notice, Volume 65, Number 245, Pages 79825-

79831] pursuant to section 112(c)(5) ofthe Clean Air Act.

WAQSR, Chapter 6, Section 6(h)(iii)(A) requires the MACT limit to be no less stringent than achieved

in practice by the best controlled similar source. WAQSR, Chapter 6, Section 6(h)(iii)(B) requires the

MACT limit to achieve the maximum degree ofreduction which can be achieved utilizing the control

technologies identified from "available information."

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"Available infonnation" is defined in Chapter 6, Section 6(£)(iii) and includes:

(A) A relevant proposed regulation, including all supporting information;

(B) Background information documents for a draft or proposed regulation;

(C) Data and information available from the EPA Control Technology Center developed pursuant to

Section 113 of the Act;

(D) Data and information contained in the EPA Aerometric Information Retrieval System including

infonnation in the MACT data base;

(E) Any additional information that can be expeditiously provided by EPA; and

(F) For the purpose of determinations by the Division, any additional information provided by the

applicant or others, and any additional infonnation considered available by the Division.

According to EPA, a regulation will be proposed for coal fired utility boilers but a draft is not available

yet. The Division reviewed EPA's Aerometric Information Retrieval System and was unable to find a

MACT data base. The available information that the Division could locate is RACTIBACTILAER

Clearinghouse (RBLC) data from the EPA Control Technology Center, EPA's Electric Utility Air Toxics

Study, information from the August 2001 U.S. EPA-DOE-EPRl Combined Power Plant Air Pollution

---------jContruI-Symposium. The MegcrSymposnlm, and informatIon from {lie August 2001 AIr ~aste---~

Management Association Specialty Conference on Mercury Emissions: Fate, Effects, and Control. The

information reviewed discussed general control concepts but provided little infonnation on emission

rates for specific HAPs.

Black Hills Corporation estimated HAP emissions from this facility using AP-42 and 1991 Wyodak coal

analysis data. A summary ofHAP emissions is shown in the following table:

HAP Emissions

Pollutant Emission Factor Unconll"Olled Controlled

Emission lUte Emission IUle

(1bIlon) (lblhr)' (lb/hr)'

2.4-DinilTOlolueneA 2.80E~7 9.06E~5

2-ehloroacetophenone' 7.00E~6 2.27E~3

Acetaldehyde' S.70E4I 1.84E~1

Acctophenonc' I.S0E~S 4.8SE~3

Acrolein' 2.9OE4I 9.38E~2

Antimony" 2.S9E~1 2.59E~2

~ic" 1.94E+OO 1.94E~1

Benzenc' 1.30E~3 4.2IE~1

Benzyl Chloride' 7.00E4I 2.27E~1

Beryllium' 3.88E~1 3.88E~2

Biphcnyr 1.70E~ 5.50E4I

Bis(2-ethylhexyl)phthalate' 7.30E~S 2.36E~2

Bromoform' 3.9OE~S 1.26E~2

Cadmium! S.10E~5 1.65E~1 1.65E~2

Carbon Disulfidc' 1.30E4I 4.21E~2

Chlorinc

Chlorobenzene" 2.20E~S 7.l2E~3

Chlorofonn' S.9OE~S 1.91E~2

Chromium' 7.77E+OO 7.77E~1

Cobalt' 1.29E+OO 1.29E~1

Cumene' 5.30E~6 1.72E~3

Cyanide" 2.50E~3 8.09E-Ol

Control

Efficiency

("/.)

90

90

90

90

90

90

Potential

Emissions

(tpy)'

3.97E4I

9.92E~3

8.08E~1

2.13E~2

4.IIE~1

1.13E~1

8.S0E~1

1.84E+OO

9.92E~1

1.70E~1

2.4IE~3

1.03E-Ol

5.53E~2

7.23E~2

1.84E~1

3.l2E~2

8.36E-02

3.40E+OO

5.67E-Ol

7.5IE~3

3.54E+OO

TB002554
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

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HAP Emissions (Continued)

Pollul2nl EmIssion Factor Uncontrolled Controlled Control Potential

Emission lUte Emission lUte ::.•::iency Emissions

(lblton) (lbIh~ (lblhr)' (%) (tpy)'

Dimethyl Sulfale· 480E..()S I.SSE-02 6.80E"()2

Ethyl Chloride· 4.20E-oS 1.36E-02 S.9SE-02

Ethylbenzene" 9.40E-oS 3.04E"()2 1.33E"()1

Ethylene Dibromide· 1.20E-Q6 3.8SE..()4 \.70E-03

Ethylene Dichlonde· 4.00E-oS 1.29E-02 S.67E-02

Fluorine

Formaldehyde" 2.40E..()4 7.77E"()2 3.40E-01

Hexancd 6.70E-oS 3.SSE+Q2 2.17E-02 96 9.S0E-02

Hydrogen Chloridc..... 1.20E+OO 4.gSE+Ol \.SSE+OI 96 6.S0E+01

Hydrogen Fluoride"'J l.SOE-01 \.94E+OO S.50E+OO

Isophorone· S.80E..()4 \.SSE-ol S.22E-01

Lead' 1.30E..()I S.69E-ol

Manganese' 6.47E"()2 I.SIE+OO 3 7.94E+OO

Mercury" 6.2SE-02 2.7SE-01

Methyl Bromide· 1.60E..()4 S.ISE"()2 2.27E-ol

Methyl Chloride' S.30E..()4 I.72E-01 7.SIE"()1

MethyLEJhyl Ke!Ql]e~___. 390Edl4 .._--L26E-oI----- -- j:S~E-oIMethyl Hydrazinc· 1.70E..()4 S.SOE"()2 2.41 E-ol

Methyl Methacrylate" 2.00E"()S 6.47E..()3 2.S3E-02

Methyl Tert Butyl Ether' 3.S0E-oS I. 13E-02 4.96E-02

Methylene Chloride' 2.9OE..()4 9.3SE-02 4.IIE"()1

Naphthalene' 1.30E-oS 9.71E+OO 4.21 E-03 90 I.S4E-02

Nickel" 9.71E-ol 4.2SE+OO

Phenol" 1.60E"()S S.ISE"()3 2.27E-02

Polychlorinaterl Dibenzofu~nS> 2.01E-07 6.S0E-oS 2.SSE..()4

Polychlorinated Dibenzo-p-dioxins' 4.2SE-oS 1.39E-oS 6.07E-oS

Propionaldehyde· 3.80E..()4 1.23E-01 S.39E-01

Selenium' 1.30E"()3 J.7SE-02 4.21E-ol 54 1.S4E+OO

Styrene" 2.S0E"()S S.09E-03 3.S4E-02

Tetrachloroethylene' 4.30E-oS 1.39E-02 6.09E"()2

Toluene' 2.40E..()4 7.77E-02 3.40E..() I

Vinyl Acetate' 7.60E-06 2.46E-03 1.0SE-02

Xylencs (0 and m)" 3.70E-oS 1.20E-02 S.24E-02 .. - - - - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - Total 110

'Emissions based on a coal bum nte of 323.6 tonslhr.

"Emission lUte from AP-42 Table 1.1-12. Assumes emission control from spray drye~ and fabric filte~.

"Emission lUte from AP-42 Table 1.1-13. Assumes emission control from spny dryers and fabric filters.

"Emission Rate from AP-42 Table 1.1-14. Assumes emission control from spray dryers and fabric liltm.

'Emission Rate from AP-42 Table 1.1-1S. Assumes emission control from spray dryers and fabric filtm.

fEmission Rate from AP-42 Table I.I-IS. Assumes emission control from spray dryers and fabric filte~.

•Assumed 96% control efficiency.

'1991 Wyodak coal analysis. Assumed 90% control efficiency. Mercury assumed 3% control efficiency.

'Assumed 100% ofChlorine is converted to Hydrogen Chloride.

'Assumed 100% of Fluorine is corm:ned to Hydrogen Fluoride.

'Assumed 9S% control efficiency. Lead emission was based on an emission factor published by the USEPA in a document entitled, Toxic

Air Pollutalll Emission Faclors-A Compilation/or Selected Air Toxic Compounds and Sources.

Design, Equipment Work practice, or Operational Standards

WAQSR Chapter 6, Section 6(h)(iii)(C) allows a specific design, equipment, work practice, or

operational standard if it is not feasible to prescribe or enforce an emission limitation under the en'reria

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set forth in section 112(h)(2) ofthe Clean Air Act (CAA). Section 112(h)(2) of the CM defines "not

feasible to prescribe or enforce an emission standard" as any situation in which the Administrator

determines that:

I) a hazardous air pollutant or pollutants c~;::ot be emitted through a conveyance designed and

constructed to emit or capture such polh':::':lt, or

2) the application of measurement methodo:c D' to a particular class ofsources is not practicable

due to technological and economic limitLi:.Jns.

The first criteria is obviously not an issue because the HAPs are emitted through the PC boiler stack.

The second criteria, however, is an issue for this :·-:ility. Although this section ofthe CM appears to be

directed toward writing standards for a class ofsources rather than an individual source, the fact remains

that there is a lack of ex.isting data available.to e~': .:tively establish emission limitations for each

applicable HAP. Therefore, Black Hills Corpora::~n proposed multi-pollutant controls (i.e. a low NOx

burner with selective catalytic reduction, two spr:::' dryer absorbers, and two baghouses) rather than

emission limitations for each HAP. Although the~: technologies were originally intended to control

criteria pollutants, recent data shows that they ar" ..:so effective in controlling ~s,-_Several ~x.amj.)les

------------are-given-below:"- ._~_.

Beryllium Control - Black Hills Corporation proposed a fabric filter for control ofberyllium. The fate of

beryllium compounds through a PC boiler and post combustion air quality control devices is similar to

that of coal ash. Some ofthe beryllium will be retained in the bottom ash while most will be collected in

the particulate collection device. Beryllium emissions from different facilities vary with the amount of

beryllium in the coal burned. However, the use of a particulate control device, such as a fabric filter or

electrostatic precipitator, is consistently the BACf for beryllium in the RACfIBACfILAER

Clearinghouse (RBLC). Black Hills Corporation estimates that the fabric filter will remove

approximately 90% of beryllium emissions for a potential emissions rate of 0.2 tpy.

Hydrogen Chloride Control - Black Hills Corporation proposed a semi-dry lime spray dryer/absorber and

a fabric filter for control of hydrogen chloride. Hydrogen chloride will react with lime (the reagent for

the spray dryer/absorber) to form calcium chloride. Calcium chloride is a stable solid and can be

removed with a fabric filter. Black Hills Corporation estimates that the lime spray dryer/absorber and

fabric filter will remove approximately 96% of hydrogen chloride emissions for a potential emissions

rate of 68 tpy.

Hydrogen Fluoride Control - Black Hills Corporation proposed a semi-dry lime spray dryer/absorber and

a fabric filter for control of hydrogen fluoride. Fluoride emissions are formed from hydrogenation of

fuel-bound fluorides. Hydrogen fluoride dissolves in water to form hydrofluoric acid. Hydrogen fluoride

will react with lime (the reagent for the spray dryer/absorber) to form calcium fluoride. Calcium fluoride

is a stable solid and can be removed with a fabric filter. Black Hills Corporation estimates that the lime

spray dryer/absorber and fabric filter will remove approximately 96% of hydrogen fluoride emissions for

a potential emissions rate of 8.5 tpy.

Mercury Control - Black Hills Corporation proposed good combustion controls, SCR, a semi-dry lime

spray dryer/absorber, and a fabric filter for control ofmercury. Mercury emissions result from trace

levels ofthe element in the coal combusted. Mercury can be emitted as different compounds, including

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Black Hills CorporanoD (WYGEN 2)

Permit Apphcauon AnalysIS, NSR·AP·C92

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elemental mercury, organic mercW)', Inorgamc mercury, and mercuric chloride to name a few. Because

ofthe many patentlal forms, the amount of mercury generated from PC boilers and the amount of

reduction acruany achieved by air quality control deVlces is difficult to predict. The fate of mercury

compounds through a PC boiler and post combustlon air quality control deVlces is not well understood

and vanes sigmficantly from boiler to boiler and coal to coal. Some ofthe mercury will be retamed m

the bonom ash while most will pass through and be reduced by various amounts in the air quahty control

dev1ces. The use of multi-pollutant control technologies has been shown effective in conrroillng

mercury. Although selective catalytiC reduction (SCR) does not directly capture mercury, it does

partially oxidize some of the elemental mercury which aids in collection downsrream in the fabnc filter.

Some of the mercury may be adsorbed by the lime (the reagent for the spray dryer/absorber) which also

aids in collection downstream in the fabric filter. Good combustion controls to minimize the amount of

fuel burned also decrease the amount of mercury emitted. Black Hills Corporation estimates that good

combustion controls, SCR, a semi-dry lime spray dryer/absorber, and a fabric filter will remove

approximately 3% of mercury emiSSions for a potential emissions rate of 0.3 tpy. -;= &00 -A- /yeCA. ("

Particulate Metal HAP Control- Black Hills Corporation proposed a spray dryer/absorber and a fabnc

filter for control of particulate metal HAP emissions. These HAPs are trace metals which would are not

-expectedlo-volatili~trdingantimony, arseniC, be1jthum, chromIum, cobalt. manganese, nickel, and

selenium. Black Hills Corporation estimates that the spray dryer/absorber and fabric filter will remove

approximately 9QO/o of particulate metal HAP emissions.

Proper Operation and Maintenance

Section I 12(h)(2) ofthe CAA indicates that requirements to assure proper operation and maintenance

should be included if a design or equipment standard is used. Proper operation and maintenance of the

control equipmeot will be necessary In order to meet the emission limits for criteria pollutants and

continuous monitoring is required for NOx, S02' and opacity.

Fabric Filter Control Efficiency

The multi-pollutant controls (i.e. a low NOx burner with selective catalytic reduction, two spray dryer

absorbers, and two baghouses) proposed by Black Hills Corporation ultimately rely on the baghouse to

collect HAP containing particles. Low NOx burners and selective catalytic reduction (SCR) increase the

carbon content of fly ash. HAPs are adsorbed onto the fly ash carbon and subsequently captured in the

downstream baghouse. Spray dryer absorber (SDA) systems spray water containing an acid gas sorhent

into a reaction vessel where the acid gases and other pollutants are reacted to form solid particles that can

be collected in the downstream baghouse. Because the baghouse ultimately collects the HAP contaimng

particles, the control efficiency ofthe baghouse is cntical. The Division focused the remainder of the

case·by-case MACT Tev1eW on baghouse collection efficiencies.

The RBLC data for PMlPM10 reviewed in the prev10us BACT section indicates that 0.0135IbIMMBtu is

the best controlled similar source. Although the RBLC shows two units with emission limits less than

0.0135 IblMMBru. these are much smaller units and are not considered "similar sources" under WAQSR.,

Chapter 6, Section 6(O(xiv). Note that the best controlled PC Electric Utility Boiler has an emission

limit orO.015 IbIMMBtu.

TB002557
Black Hills Corporation (WYGEN 2)

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As previously discussed, WAQSR, Chapter 6, Section 6(h)(iii)(B) requires the MACT limit to achieve

the maximum degree ofreduction which can be achieved utilizing the control technologies identified

from "available information." Black Hills Corporation evaluated baghouses at emtssion levels of 0.0 18,

0.015, and 0.0121bfMMBtu as discussed in the previous section on BACT. Based on the informatIOn

provided, an emission level of 0.0 12 IbfMMBtu can be achieved using membrane bags.

Subsequent Promulgation of a MACT Standard

WAQSR, Chapter 6, Section 6(i)(iii) dIscusses promulgation of a specific MACT standard after a caseby-case MACT standard is issued. According to EPA. the target date for submittal of the proposed

MACT standard is December 15,2003 with a promulgation date of December 15, 2004. If EPA meets

these target dates, there will be a MACT standard in place when this facility is scheduled to begin

operation in June 2005 and the facility will have to comply. Once the specific MACT standard is

promulgated, the Division may in its discretion use any more stringent provisions of this case-by-case

MACT determination when issuing or revising the Chapter 6, Section 3 operating permit.

Conclusion

In summary, it has been shown that multi-pollutant controls for criteria pollutants are effective in

controlling HAPs. The emission limits and control efficiency requirements for criteria pollutants serve

as surrogates for HAP limits. The Division concludes that a low NOx burner with selective catalytic

reduction, two spray dryer absorbers with a minimum 90% S02 removal efficiency, and two baghouses

with an emission limit of 0.0 12 IbfMMBtu represent MACT.

CHAPTER 5, SECfION 2 - NEW SOURCE PERFORMANCE STANDARDS (NSPS):

New Source Performance Standards Subparts Da and Yare applicable to the proposed source in

accordance with WAQSR, Chapter 5, Section 2. Subpart Da applies to electric utility steam generating

units capable of combusting more than 250 MMBtulhour heat input for which construction or

modification is commenced after September 18, 1978. The proposed PC boiler has a maximum heat

input of 5, 145.7 MMBtuIhr (323.6 tons of coal per hour). Subpart Y applies to coal preparation plants

which process more than 200 tons per day with facilities that are constructed or modified after October

24,1974.

Subpart Da - PC Boiler:

Particulate Maller:

Subpart Da limits particulate emissions from coal fired plants to 0.03 IblMMBtu, and 99% reduction of

potential combustion concentration. Opacity is limited to 20% (6 minute average) except for one six

minute period per hour of not more than 27%. The proposed boiler emission limit ofO.0121blMMBtu

will show compliance with the NSPS particulate matter emission limit. Furthermore, Subpart Da,

Section 60.46a(a) states that compliance with the particulate matter emission limitation constitutes

compliance with percent reduction requirements for particulate matter. Section 60.47a(a) requires the

operation of a continuous monitoring system for measuring the opacity of emissions discharged to the

atmosphere.

TB002558
Black Hills Corporation (WYGEN 2)

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Sulfur Dioxide:

Subpart Da limits S02 emissions from the proposed coal-fired boiler to either: I) 1.20 IblMMBtu and

90% reduction of potential emissions or 2) less than 0.60 IblMMBtu and 70c"" reduction of potential

emissions. Compliance with the Subpart Da emission limitation and percent :-eduction requirements are

both determined on a 30 day rolling average basis.

The proposed boiler emission limits ofO.15Ib/MMBtu (30 day average), 0.1: IblMMBtu (2 hour

average), and 90% reduction of potential emissions will demonstrate complia~.;e with the NSPS emission

limitations. S02 inlet and outlet continuous emission monitoring is required under Subpart Da to

demonstrate compliance with the emission limit and percent reduction require:-nents across the control

device. Subpart Da also requires the operation of a continuous monitoring syr-tem to measure oxygen or

carbon dioxide content ofthe flue gases at each location where sulfur dioxic..; vr nitrogen oxide

emissions are monitored.

Nitrogen Oxides:

------The""NSPSNO.-enm-ston1irmt for sources constrUcted after JUly 9, 199T1sl. ~lbTmegawatt-hourgross-- --

energy output (30 day rolling avg.) and 0.15 IblMMBtu heat input (30 day rc. :ng avg.).

The proposed NO. emission limit ofO.07lblMMBtu (30 day rolling average) is well below the NSPS

limit of 0.15 IbfMMBtu. 0.07lblMMBtu corresponds to O.72lb/megawatt-hour at full load, which is

considerably less than the NSPS limit of 1.6 Ib/megawatt-hour, as shown in the following calculation:

0.07 /b

MMBru x 5,145.7 MMB/u

hr

500MW = 0.72 Ib

MW-hr

NO. continuous emission monitoring, a continuous flow monitoring system, and a wattmeter to

continuously record gross electrical output in megawatt-hours are required under Subpart Da. Subpart

Da also requires the operation of a continuous monitoring system to measure oxygen or carbon dioxide

content of the flue gases at each location where sulfur dioxide or nitrogen oxide emissions are monitored.

Subpart Y - Coal Handling Facilities:

Subpart Y ofthe New Source Performance Standards limits opacity to less than 20% from all coal

processing and conveying equipment (including breakers and crushers), coal storage systems. and coal

transfer and loading systems at WYGEN 2.

ALLOWABLE EMISSIONS:

The allowable emissions for each point source, based on the BACT and MACT reviews and the

'lblMW-hr NOx limit of NSPS Subpart Da, are shown in the following tables:

TB002559
Black Hills Corporation (WYGEN 2)

Pennit Application Analysis, NSR-AP-C92

Page 23

PC Boi1n~ Emissions (PC-OOl)

Pollutant IblMMBtu Iblhr' IbfMW-hr tpf

NO. 0.07 (30-day rolling) 360.2 (30-day rolling) 1.6 (30-day

rolling) 1,578

3,381 771.9 (30-day rolling)

874.8 (2-hr block)

0.15 (30-day rolling)

0.17 (2-hr block)

90% Minimum Removal Efficie:1cy

(30-day rolling) ................................................................................................u _ _ •••••••••••••••••••

PMJPM\o 0.012 61.7 270

CO 0.15 771.9 3,381 ............................................................................................................................................................._ - _-_.- _ ".

VOCs 0.01 51.5 225

IEmissions based on 5,145.7 MMBtuIhr heat input.

2Based on 8,760 operating hours per year.

----- ---~---- ---------- --- - -----

Material Handling PMJPM,o Emissions

Source No. Source gr/dscf dscfm lblhr tpyl

CDC-OOI Coal Storage Silo Top Dust

Collector 0.009 23,604 1.8 8.0

CDC-002 Coal Storage Silo Bottom Dust

Collector 0.009 7,343 0.6 2.5

CDC-003 Coal Transfer Building Dust

Collector 0.009 7,343 0.6 2.5

CDC-004 Unit Transfer and Silos Dust

Collector 0.009 32,521 2.5 11.0

LDC-001A Lime Unloading Silo Dust Collector 0.01 1,259 0.1 0.5

LDC-001B Lime Unloading Silo Dust Collector 0.01 1,259 0.1 0.5

RDC-OOI FGD Waste Recycle Storage Bin

Dust Collector 0.01 2,623 0.2 1.0

RDC-002A/B2 FGD Waste Loadout Silo Dust

Collectors 0.01 5,245 0.4 2.0

I Based on 8,760 operating hours per year.

2Only one ofthese units (RDC-002A or RDC-002B) will be in service at anyone time.

TB002560
Black Hills Corporation (WYGEN 2)

Pennit Application Analysis, NSR-AP-C92

Page 24

ANALYSIS OF AIR QUALITY MODELING:

PSD Applicabilitv:

As stated previously, the proposed WYGEN 2 electrical generating facility is classified as a "major

emitting facility" as defined in Chapter 6, Section 4(a)(i) ofthe Wyoming Air Quality Standards and

Regulations 0NAQSR). Therefore, PSD regulations are applicable for the proposed construction of this

facility. Potential annual emissions in tons per year (TPY) from the proposed construction of the

WYGEN 2 facility are provided in the Prevention of Significant Deterioration (PSD) Applicability

section.

As an applicz.::: for a PSD permit, Black Hills Corporation (BHe) must conduct ambient air quality

analyses for t~:~ proposed WYGEN 2 facility to verify compliance with Wyoming Ambient Air Quality

Standards 0Nn.A.QS) and Prevention of Significant Deterioration (PSD) increments. Specifically, an

analysis ofth~ Jredicted impacts on the ambient air quality from the proposed facility is required for all

pollutants fo:- which standards have been established under PSD regulations, WAQSR, or the Federal

Clean Air Ac:. 2I1d are emitted in significant amounts. Regulated pollutants include (1) pollutants for

which a NatiC'::,1 Ambient Air Quality Standard (NAAQS) exists (crit~lutants) and (2)pth.er

pollutantS, whi:li are regulated bytne Environmental Protection Agency (EPA), for which no NAAQS

exist (non-cri~:~a pollutants).

Based on the comparison ofthe emission rates from the proposed facility to the PSD significant emission

rates provided in the PSD Applicability section, the pollutants emitted in significant quantities are NO.,

CO, S02' PM,o, VOCs, sulfuric acid mist, fluorides, as hydrogen fluoride (HF), mercury, and beryllium,

and a full impact analysis is required under PSD regulations for these nine (9) pollutants. As shown in

the emissions table in the PSD Applicability section of this analysis, the proposed emissions ofTotal

Reduced Sulfur compounds (TRS) and lead are estimated to be below the PSD significant emission rates

as a result of the proposed operation ofthe WYGEN 2 facility, and these two (2) pollutants are not

subject to any further air quality impact analyses under PSD regulations.

There are no PSD increments for VOCs or ozone. Additionally, there are no regulatory models

applicable to modeling VOC emissions from stationary sources in rural areas to assess potential ozone

formation, therefore, an ambient impact analysis was not performed for VOC emissions associated with

the proposed modification. Additionally, Wyoming's regulations do not contain ambient standards for

sulfuric acid mist mercury, or beryllium. However, Wyoming's regulations do require that sulfuric acid

mist, mercury, and beryllium emissions be addressed through analysis ofBest Available Control

Technology (BACT). The Division's review ofBACT for sulfuric acid mist, mercury, and beryllium

emissions from the proposed WYGEN 2 facility has addressed the emissions ofthese pollutants in

sufficient detail, and the application ofBACT will minimize the ambient impacts from the emissions of

these three (3) pollutants. As a result, no modeling analyses are required by the Division for assessing

the impacts ofthese pollutants on the ambient air quality.

Significant Impact Analysis:

The proposed emissions ofNO., CO, S02' and PM\O from the WYGEN 2 facility were modeled for these

four (4) criteria pollutants to determine the significant impact area for each criteria pollutant. HF

emissions were not included in this analysis, as HF is not a regulated pollutant under PSD. The

significant impact area is a circular area defined by the radius of influence (R01) for which the required

TB002561
Black Hills Corporation (WYGEN 2)

Pennit Application Analysis, NSR-AP-C92

Page 25

air quality modeling analyses for the WAAQS and PSD increments are carried out. The ROJ is the

distance from the proposed source or modification to the most distant point where the dispersion

modeling analyses predicts a significant ambient impact will occur. Table 1 shows the maximum

modeled NO.. CO, S02' and PM ,o impacts from the proposed WYGEN 2 facility, and compares the

maximum concentrations to the PSD Class II significant impact levels (SILs) and pre-construction

monitoring levels. The designated Class II SILs as specified by the EPA, and in WAQSR, Chapter 6,

Section 2(c)(ii)(A) are also provided In Table I.

Table 1

Comparison of Maximum Modeled Ambient Impacts to PSD Class II SILs

and

Pre-Construction Monitoring Levels

WYGEN2 PC lITM Location of PSD PSD Pre Constr.

Ambient Boiler Maximum Impact Qass II Further DeMinimis Monitoring

Ave. Impact Load (meters) Significance Analysis Levels Required

Pollutant Period (Jlglml

) (%) Levels RegtJ~ ~~r1]J). (Yesl1'-lo) . ..- _.-.- ----- --East l'lonn (Jlg/mJ

) (YesINo)

NO, Annual 0.1 50 473124 4901600 I No 14 No

CO I-bour 69.2 100 469024 4902900 2,000 No -- -

8-hour 15.5 75 468324 4904400 500 No 575 No

S02 3-hour 44.1 100 469024 4902900 25 Yes -- -

24-hour 7.3 100 469024 4902900 5 Yes 13 No

Annual 0.2 50 473124 4901600 I No -- -

24-bour 4.6 100 468824 4903600 5 No 10 No

PM10

Annual 0.6 100 469324 4904200 1 No -- --

EPA guidance contained in the New Source Review Workshop Manual, October 1990, states that in the

event that the maximum modeled ambient impact of a proposed emissions increase is below the

appropriate ambient air quality significance level for all locations and averaging periods, the EPA does

not require any further NAAQS or PSD Class II increment analyses for that pollutant. As shown in Table

1, the maximum predicted ambient air concentrations of NOx' CO, and PM10 are all less than the

significance levels for Class II areas for all applicable averaging periods. Additionally, the model

predicted impacts are also below the significant monitoring concentrations for all four (4) criteria

pollutants. Therefore, no further NAAQS, or equivalently, no further WAAQS modeling analyses for

NOx, CO, or PMJO are required.

While pre-construction monitoring is not required, the applicant has established an ambient S~

monitoring site located approximately 1.6 kilometers south-southeast ofthe proposed WYGEN 2 facility,

next to the Wyodak Resources Site 4 monitor. The ambient monitoring site began collecting hourly

TB002562
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 26

ambient S02 data on September 27, 2001. The UTM coordinates of the mo::itor location are Zone 13

(470083,4902531).

Based on the applicant's significant Impact analysis using the 1999 on-site :-:-eteorological data from

Pacificorp's Wyodak monitoring site, the only criteria pollutant which has !:-:1pacts above the PSD Class

II SILs is S~, and based on this analysis, it was determined that the 3-hou!" Jnd 24-hour SOJ ROI were

approximately 2.1 Ian and 10.2 lan, respectively. PSD guidance recommends that a distance of 50 km be

added onto the ROls to define the maximum distance out to which the interacting source inventory would

be compiled and used in the WAAQS and PSD increment analyses. Based on the significant impact

analysis, the Division compiled an interactive S~ source inventory for the applicant to be used in the

WAAQS and PSD increment consumption modeling analyses. This inventory primarily consisted of

existing S02 sources located at the Wyodak complex, where the WYGEN 2 facility is being proposed.

The Two Elk Unit One PC Boiler was also included in the inventory, and is located approximately 71

kilometers southeast ofthe proposed WYGEN 2 facility.

Analvsis Overview:

The applicant has submitted ambient air quality analyses to evaluate model predicted impacts on near-

------ffIetdand--rar-fle1~ceptors.Thenear-he1oanalyses consIst of WAAQS, PSD Class II increment

consumption analyses, and ambient air impacts ofHazardous Air Pollutants (HAPs) associated with the

proposed WYGEN 2 facility, which were completed using the Industrial Source Complex model (ISC3).

The far-field analyses consist of PSD Class I increment consumption and analyses of impacts to Air

Quality Related Values (AQRVs), and were completed using the CALPUFF modeling system.

Near-Field Modeling Analysis

Model Justification:

The applicant used the Environmental Protection Agency (EPA) Industrial Source Complex 3rd

generation model (lSC3), version 00101 to assess the air quality impacts from the WYGEN 2 facility on

near-source receptors « 50 kilometers). The short-term version (lSCSD) ofthe model was used to

determine annual and short-term near-field concentration estimates ofND., CO, S02' PM\o, HF, and

HAPs. The dispersion model simulations were nul with recommended regulatory defaults, and in

accordance with the current Guideline on Air Quality Models. Options used in the analyses were rural

dispersion coefficients with no exponential decay, final plume rise, stack tip downwash, default wind

profile exponents, default vertical potential temperature gradients, and calms processing routines.

Buoyancy-induced dispersion is used except where the Schulman-Scire downwash algorithms are

employed by the model.

In addition, the applicant used Trinity Consultant's version of EPA's Building Profile Input Program to

determine downwash parameters to include m the ISCSD model runs. Terram at or near the WYGEN 2

facility is rolling with terram heights exceeding some stack top elevations, and can be characterized as

complex terram. EPA has specified that the model of choice for multiple sources in an mdustrial setting

located in complex terrain, with source-receptor distances less than 50 kilometers is ISC3.

Meteorological Data:

Initially, the applicant used one year ofsurface meteorological data collected by Hampshire Energy in

1981 for a proposed facility near Wyodak, WY. The meteorological tower used to collect the data was

TB002563
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 27

located approximately 16 kilometers SSE of the proposed WYGEN 2 facility. The surface

meteorological data were obtained from October 15, 1980 - October 14, 1981 at a height of 60 meters. It

was later detennined that Pacificorp already had an on-site meteorological data monitoring program

established for the Wyodak complex. Thel"~fore, the Division required the modeling analyses submitted

for the WYGEN 2 facility to be simulated t:sing the Wyodak meteorological data collected by Pacificorp.

These data were collected from March I, IS:)9 - February 28, 2000; the winds were measured using an

anemometer height of 10 meters.

Twice-daily upper air soundings collected ~: Rapid City, South Dakota (Station #24090) were processed

for the same time period and merged with t..;:; Pacificorp Wyodak hourly data. A wind rose which

represents the annual average surface wind :::attems from the Wyodak meteorological data for 1999-2000

is shown in Figure I. The average of the w:-:d flow data statistics for this meteorological data indicates

the predominant winds originate'from the '.. ' ..it-southwest through the southeast directions approximately

46% ofthe time, The annual average calcul::.ted wind speed for this data is approximately 7.5 meters/sec

(16.7 miles per hour). The percentage ofc:':n winds for this data set equates to 0.79% (68 hours). A

comparison between the two meteorologic~" data sets indicated that the modeled impacts were similar for

both sets of data and adequately demonstr:. ...:3 compliance with all applicable ambient air quality

------standards:·---

Backeround Concentrations:

The S02 background values used in the Wyoming Ambient Air Quality Standards (WAAQS) modeling

analysis for S02 were obtained from the ambient monitoring data conducted by Pacific Power and Light

at three sites over the course of one year. The S02 background values listed in Table 2 were obtained

from two ofthose sites located near the Wyodak area, either the North or Tower monitoring sites,

depending upon which site produced the maximum background value for each averaging period.

Table 2

Background Concentrations Used in WYGEN 2 Near-Field Modeling Analyses

Pollutant Averaging Period Background Concentration

S02 3-Hour 99 Ilglm3

S02 24-Hour 36 Ilglm3

SO, Annual 3 ug/m3

Emissions and Stack Parameters:

The emission rates and stack parameters for all proposed sources at the WYGEN 2 facility are provided

in Table 3. There are two (2) sources identified as FGD Waste Loadout Silo Dust Collectors being

proposed for the WYGEN 2 facility. The applicant has indicated that only one ofthe two FGD Waste

Loadout Silo Dust Collectors will be operated at any time. Both of these sources have the same proposed

PM,o emission rates and stack parameters, therefore, only one ofthese sources (RDC002A) was included

in the modeling analyses.

TB002564
N

w E

CALM WINDS .79%

WIND SPEED CLASS BOUNDARIES

(METERS/SECOND)

NOTES:

DIAGRAM OF THE FREQUENCY OF

OCCURRENCE OF EACH WIND DIRECTION.

WIND DIRECTION IS THE DIRECTION

FROM WInCH THE WIND IS BLOWING.

EXAMPLE - WIND IS BLOWING FRO;! THE

NORTH 4.6 PERCENT OF THE TI::E.

FIGURE 1

WINDROSE

STATION NO: 99999

PERIOD: 1999

FILE: WYODAK99.ASC

PACIFICORP WYODAK

SUBMITTED BY B V

$ort .... [

BEE-LINE

TB002565

S

,11.0

8.5 I

]

1.8 3.3 5.4
Table 3

Stack Parameters and Emission Rates or WYGEN 2 Sources

Flow

I~ ;1}

1.978.496

1,483.872

989,2411

1,978,

1,483.812

989,248

Vs Os

Emission Sources and Stack Parameters Represented in BHC W GEN 2 WAAQS and PSD Modeling Analyses

Modeled UTM Zone 13 Modeled Paramclers (SI11011.11

Source UTM (N) Elev. 115 1'5 Vs Os

~Hgk'

500 MW PC Boiler (100% Load) ASTKl00 469.435 4,903.973

500 MW PC Boiler 05% Load) ASTK75 469,435 4,903,973

500 MW PC Boller (50% Load) ASTK50 469,435 4,903,973

500 MW PC Boiler (100% Load) STSTKl00 469,435 4.903.973 344 20.00

500 MW PC Boiler (75% Load) STSTK75 469.435 4,903,973 344 1500

500 MW PC Boller (50% Load) STSTK50 469,435 4,903,973 344 10.00

n

Coal Silo Dust Collector (Top) CDCOOI 469,197 4,903.574 1.344 67.67 293 10.35 1.143 3.1 222.00 68 33.95 3.75 22.500

Coal Silo Dust Collector (Bottom) CDC002 469,209 4,903.576 1,344 2.44 293 10.43 0.635 1.1 8.00 68 34.22 2.08 7.000

Coal Transfer Bldg Dust Collector CDCl103 469.384 4,903.636 1,344 2.44 293 10.43 0.635 1.1 800 68 34.22 2.08 7.000

Unil Transfer & Silo Dust Collector CDC004 469,508 4,903,868 1,341 78.64 293 10.28 1.346 5.1 258.00 68 3372 4.42 31.000

FGD Wasle Storage Bin Dust Collector RDCOOI 469.491 4.903.920 1,341 20.12 293 10.35 0.381 0.9 66.00 68 33.95 125 2.500

Lime Unloading Silo Dust Collector A LDCOOIA 469.467 4,903,869 1.341 42.67 293 11.18 0.254 0.4 140.00 68 36.67 083 1.200

Lime Unloading Silo Dust Collector B LDC001B 469.467 4.903.869 1,341 42.67 293 11.18 0.254 0.4 140.00 68 36.67 0.83 1,200

. ;1' 'VaSle Loadoul Silo Dust Collector AI RDC002A 469.518 4,903.977 1.341 44.20 293 10.56 0.533 1.8 145.00 68 34.65 1.15 5,000

I ( ;i Llle FGD Waste Loadout SUo Dust Collector will be operated at any time.

,rt-term emission rates used In modeling analyses.

Bolb Silo Dust Collectors have the same slACk parameters and proposed PMIO emission rates. I

I

I

I

I

I

,
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP·C92

Page 28

Both the WAAQS and increment modeling analyses included several interactive (nearby) sources of S~,

which are provided in Table 3a. Emission rates for all sources were represented in the modeling analyses

based on an operational schedule of 8,760 hours per year.

Good Engineering Practice lGEP) Stack Height Determination:

The building downwash effect on a plume is governed by the projected buildir::-; width, the building

height, the exhaust stack height, and the relative location ofthe exhaust stack :.;) :ny nearby buildings or

structures. The applicant used Trinity Consultant's version of the EPA Buildin<:: .Jrofile Input Program

(BPIP) to determine downwash parameters to include in the model runs for eaC.l :lew source at the

WYGEN 2 facility. The BPIP software program performs a detailed downwas~ analysis using the most

current EPA approved BPIP to determine Good Engineering Practice (GEP) su.:.: height for each source.

A comparison ofthe BPIP calculated GEP Equation #1 stack heights versus the: ;:roposed stack heights

for all point sources at the WYGEN 2 facility indicates that the proposed stack ::eight of the PC Boiler is

equal to GEP, and the particulate handling sources are all less than the GEP Ec;c:"'tion # I stack height, or

below GEP. Therefore, direction specific building dimensions for all structures •.1at have the potential to

induce building downwash on the particulate handling sources at WYGEN 2 \\ ''; used in the modelit.:!g. _

--------1;s:nirmutrlations;-Adcumparisonofth'e'catculated GEP EquatIOn 1fTSfilCKheighiS ve.-s~s the proposed stack

heights for the new sources at the WYGEN 2 facility is provided in Table 4.

Table 4

WYGEN 2 Proposed (Modeled) Stack Height

vs.

Calculated Maximum GEP Equation 1 Stack Heieht

Source ill Source Description Proposed Stack GEP Eq. 1

Heieht (m) Stack Heif;?;ht (m)

PCSTK100 PC Boiler 190.5 190.5

CDC001 Coal Silo Dust Collector (Top) 67.7 174.5

CDC002 Coal Silo Dust Collector (Bottom) 2.4 174.5

CDC003 Coal Transfer Bldg Dust Collector 2.4 187.5

CDC004 Unit Transfer & Silo Dust Collector 78.6 190.5

RDCOOI FGD Waste Storage Bin Dust Collector 20.1 190.5

LDC001A Lime Unloading Silo Dust Collector A 42.7 190.5

LDCOOIB Lime Unloading Silo Dust Collector B 42.7 190.5

RDC002A FGD Waste Loadout Silo Dust Collector A 44.2 190.5

K JI [II 'HI Fnn Wpdp T.nlllrinl1t ~iln nm:t r, R 44 ? lQO Ii

1 Only one of the two (2) FGD Waste Loadout Silo Dust Collectors will be operated at any time.

TB002567
Table 3a

Stack Parameters and Emission Rates for Interactive Sources of S02

Interactive S02 Emission Sources and Stack Parameters Repres~nted in WAAQS and PSD Modeling Analyses

Modeled Consumes lITM Zone JJ lSI HnILs) Modeled Parameter:! (English llulU)

Source SOJ UTM (E) UTM (Nil Eley. Vs Ds 115 Ts Vs Ds Flow

(ID) (ft) (odm)

TB002S6H

Page 1 of 1
Black HiEs Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 29

Receptor Grid:

The near-field (WAAQS and PSD Class II) modeling simulations were conducted using the receptor

configuration shown in Figure 2, with the exception that the additional (11 x 11 matrix) 100 meter fine

grid was only added into the receptor grid for the NO. and S02 analyses. Receptor locations used In the

far-field modeling analyses are described in the associated text.

The modeling analyses were completed using 1,188 discrete Cartesian receptors in a nested rectangular

grid network that extended 15 kilometers from the location ofthe proposed WYGEN 2 facility. The

receptor grid network consisted ofreceptors laid out using: 100 meter spacing from the property line out

to appro;~imately 3 kilometers (east boundary) to 8 kilometers (west boundary), 500 meter spacing out to

5 kilomc::=rs, and 1,000 meter spacing out to 15 kilometers, along with discrete receptors placed along

the faci;;:y fence line. Specifically, eighty-one (81) discrete Cartesian receptors were placed at 50 meter

intervals ~long the Wyodak complex fence line.

Recepto:- :ocations used in the near-field modeling analyses were interpolated from electronically

formatte .. terrain maps in the vicinity ofthe WYGEN 2 facility. The terrain data have been created from

United ~-~~es Geological Survey (USGS) 7.5 minute Digital Elevation Model (DEM) files, and include

---------7(X--mld1·~.JcarionnrrUTM-cOOl'dirunes, anae1evabons 10 eIther feet or meters. The density of the terrain

data poi- ; is approximately 30 meters in both the east-west and north-south directions, and does not vary

with latitude. A two-dimensional representation ofthe local topography, based on the elevations ofthe

selected receptors is shown in Figure 2a.

WYOMING AMBIENT AIR QUALITY STANDARDS (WAAQS) ANALYSIS

As stated earlier, the applicant used the on-site Wyodak meteorological data in a revised modeling

analysis for the proposed WYGEN 2 facility, and demonstrated that the ambient impacts from the

proposed WYGEN 2 facility were greater than the PSD Class II SILs for So.z for the 3-hour and 24-hour

averaging periods. Therefore, according to EPA guidance, the applicant is required to conduct a full

impact analysis for this criteria pollutant, which includes considering emissions from interactive or

nearby emission sources (proposed and existing), and separate analyses for the WAAQS and PSD

increments.

• Sulfur Dioxide (S02) •

The applicant modeled the proposed S02 sources at the WYGEN 2 facility, along with the emissions of

S02 from nine (9) nearby (interactive) sources to determine compliance with the 3-hour, 24-hour and

annual WAAQS of 1300 Jlg/m3

, 260 Jlg/m3

, and 60 Jlg/m), respectively. The highest second highest

(HSH) modeled 3-hour and 24-hour ambient S~ concentrations were 327.1 Jlg/m3 and 124.2 Jlg/m3,

respectively, and the maximum model predicted annual So.z concentration was 9 Jlg/m3

• Results ofthe

WAAQS analysis for S02 indicate that the modeled concentrations from all S02 sources are below the 3-

hour, 24-hour and annual WAAQS for S02 after adding in S02 background concentrations to the model

predicted impacts. Based on the results ofthis analysis, the Division is satisfied that the WAAQS for

S02 will be protected. Results ofthe WAAQS modeling analysis for S02 are provided in Tables 5-7.

Isopleth plots ofthe 3-hour, 24-hour and annual modeled So.z impacts are shown in Figures 3-5,

respectively.

TB002569
FIGURE 2

BHC WYGEN 2

RECEPTOR GRID USED IN MODELING ANALYSIS FOR S02

455000 460000 465000 470000 475000 480000

4915000 4915000

4910000 _

C1

a

...

a

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4905000 -

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4890000

_ 4910000

CI)

J.4

Q)

+J -----aJa

-

UTM EASTING (meters)

Total Receptors in grid = 1819 receptors

Fence line Receptors = 81 receptors

TB002570
FIGURE 2a

ELEVATION CONTOURS REPRESENTING LOCJ~ TOPOGRAPHY

IN WYGEN 2 MODELING ANAL~~ES

460000 462000 464000 466000 468000 470000 472000 47"::0 476000 478000

4900000

4894000

4896000

4898000

4902000

4904000 t!

:z

:I

EC£

EO

4908000

-Ci

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4906000 +

Q

e....

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-(I)

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Q)

a

-

460000 462000 464000 466000 468000 470000 472000 474000 476000 478000

UTM EASTING (meters)

CONTOUR INTERVAL = 20 Meters

TB002571
FIGURE 3

WAAQS ANALYSIS - HSH 3-HOUR S02 CONC

IMPACTS FROM WYGEN 2 + NEARBY SOURCES

455000 460000 465000 470000 475000 480000

.-. - _. _. - - ----._-- .. ... '

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4915000 4915000

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So~,\ ,r-"", ,;>t)[ 4890000

L...-,---l----J.,--!..-~~-~, --'~ ~,_,_' __ _LJ

-

til

Cl

- 4890000 .~ ~l

•

~.~IQ

- 4910000

(J)

<U

-IJ

<U

a

- 4905000

C!)

Z

H

:z:

E-i

0 4900000 Z

rJ

p

455000 460000 465000 470000 475000 480000

UTM EASTING (meters)

HSH Modeled 3-HR Impact - 1999 Pacificorp Wyodak Met Data

(BACKGROUND NOT INCLUDED)

TB002572
FIGURE 4

WAAQS ANALYSIS - HSH 24-HOUR S02 CONe

IMPACTS FROM WYGEN 2 + NEARBY SOURCES

460000 465000 470000 475000 480000

4915000 4915000

4910000 _

J

i

4895000

.J

i

.,

I

i

,

i 4890000

." /---.\ , ' -./

I

r--J

--_....:.... -'-~-'--~

<0.-

\

I

/

/

I

a

$.

Q . / \ \ 0+-

. - ....•~: " ,./ 0 .,.~~.~:>--,-=,--- - ~905000 -.' '__."-6> ~.- .' / H5H 2~HR 502 Pedicted Impact. i . .. '::." .,_.' . 124.2 ug/m3 at (470,024; 4,902,800): ,. ~~." .~.- '. ~()

,/:\ ~.> ,"

.. _. ....l.-....:..-__•__._... ..

WYGEN 2 FENCE UNE .

._----- ,

4890000 -,

i

,

4900000

4895000 -

4905000

_ 4910000

(I)

OJ

+l

OJ

----S-

-

455000 460000 465000 470000 475000 480000

UTM EASTING (meters)

HSH Modeled 24-HR Impact - 1999 Pacificorp Wyodak Met Data

(BACKGROUND NOT INCLUDED)

TB002573
FIGURE 5

WAAQS ANALYSIS - ANNUAL S02 CONC

IMPACTS FROM WYGEN 2 + NEARBY SOURCES

455000

4915000

4900000

.- 4895000 ..

'"

460000 465000 470000 475000

/

\

-'-

480000

\

4915000

4910000 ...

l

I

(

4

(

,

4905000

4895000

4890000

455000 460000 465000 470000 475000 480000

UTM EASTING (meters)

Annual Modeled Impact - 1999 Pacificorp Wyodak Met Data

(BACKGROUND NOT INCLUDED)

TB0025i4
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 30

The S02 contribution from the sources at the proposed WYGEN 2 facility at the maximum impact

receptor location was 14.7 j.1g!m3 (HSH 3-hour), 2.4 j.1g/m3 (HSH 24-hou:) and 0.1 llg!m3 (annual), which

indicates that less than 5% of the maximum modeled S~ impact from a:: sources can be attributed to the

emissions ofsulfur dioxide from the proposed WYGEN 2 facility.

Table 5

Highest Second Highest 3-Hour SOl Modeling Results for WAAQS Analysis

Receptor Percent

Modeled Location HSH Background To::' 3-Hour of

Year 3-Hour 3-Hour 3-Hour S02 3-hour

(Zone 13) SOl Cone. S02 Cone. S02 CC71C. WAAQS WAAQS

X(m) Y(m) (uwmJ

) (llwm3

) (uJ;. :-:-j) (llg/m3

) for SO~

1999 468724 I 4903400 327.1 99 42C._ 1300 33%

Table 6

-------HighestlIecond Highest-2~HourSOiMolieling-Resultsic"WAAQS·AnalysIs

Receptor Percent

Modeled Location HSH Background Total 24-Hour of

Year 24-Hour 24-Hour 24-Hour S02 24-hour

(Zone 13) S02 Cone. S02 Cone. S02 Cone. WAAQS WAAQS

X(m) Y(m) (llg!m3

) (llg!m3) (Ilg!nr) (llg/m3

) for SO~

1999 470024 I 4902800 124.2 36 160.2 260 62%

Table 7

Annual S02 Modeling Results for WAAQS Analysis

Receptor Percent

Modeled Location Maximum Background Total Annual of

Year Annual Annual Annual S02 Annual

(Zone 13) S02 Cone. S02 Cone. S02 Cone. WAAQS WAAQS

X(m) Y(m) (llg!m3

) (j.1g/m3

) (llg!m3

) (llg!m3

) for SO,

1999 470024 I 4902700 9 3 12 60 20%

• Hydrogen Fluoride (HF).

Total hydrogen fluoride (HF) emissions from the proposed WYGEN 2 facility will be 8.5 TPY. HF

emission factors were detennined based on a 1991 Wyodak Mine coal analysis which indicated 63.0 ppm

by weight fluorine content. It was assumed that all fluorine in the coal is converted to HF when the coal

is combusted. HF emissions will be controlled through the use ofspray dryer absorbers in conjunction

with a baghouse system. The HF acid gases will react with the calcium oxide (CaO) in the SOz scrubbing

process. The resulting particulate, calcium fluoride (CaFJ, is then removed by the fabric filter baghouse.

TB002575
Black Hills Corporation (WYGEN 2)

Pennit Application Analysis, NSR-AP-C92

Page 31

The applicant modeled the proposed HF e:r:ssions to determine the maximum I2-hour, 24-hour, 7-day,

and 30-day concentrations ofHF on the am"::>ient air quality. The HF impacts were based on the

maximum model predicted concentration ;::.Jffi the applicant's ISC3 model simulation for the PC boiler

stack using an emission rate input of 0.2<15 :..,Tams per second.

The ISCSD model does not have an optic:-. for calculating impacts for a 7-day averaging period.

Therefore, the 24-hour impacts were assu:-:.~d to conservatively represent the 7-day impacts. The

maximum predicted HF impacts are sumrr.:.rized in Table 8. Based on the results of this analysis, it is

apparent that the modeled impacts of HF are well below Wyoming's standards, and no violations of the

Wyoming standards for HF were predicted.

Table 8

HF Modeling Results for WAAQS Analysis

Averaging Maximum Predicted HF Standard

Period Concentration (~glm3) (~g/m3)

-- If.015-- 12nours 3.0

24 hours 0.001 1.8

7 days 0.001 0.5

30 days 0.002 0.4

Hazardous Air Pollutants <HAPs) Analysis:

Emissions associated with the PC Boiler contain certain pollutant species which are listed under Title III

of the U.S. Clean Air Act Amendments of 1990, as Hazardous Air Pollutants (HAPs). The HAPs emitted

in the greatest quantities are benzene, chromium, cyanide, hydrogen chloride, hydrogen fluoride,

manganese, nickel, and selenium. Specifically, it was estimated by the applicant that emissions of

hydrogen chloride would be 68 TPY, and t.;e total potential HAPs emitted by the PC Boiler are estimated

to be 110 tons per year (TPY).

The applicant modeled ambient air concentrations from fifty-five (55) different HAPs at or beyond the

facility property line using the ISCSD model. A constant emission rate of 10 lblhr was used in the

modeling simulations, and the modeled concentrations were ratioed up or down using the estimated HAP

emission rate to derive the individual impacts from each HAP. The HAP concentrations were predicted

by the model for I-hour, 8-hour, 24-hour, and annual averaging periods. The HAP concentrations were

compared to pollutant impacts listed in the National Air Toxics Information Clearinghouse's (NATICR)

Data Base Report of Federal, State, and Local Air Toxics Activities (September 1992). The NATICH

data base lists Acceptable Ambient Levels (AALs) for I-hour, 8-hour, 24-hour, and annual averaging

periods for various states in the United States. Wyoming has not established standards for the HAPs

listed in the NATICH Data Base, therefore the modeled HAP concentrations were compared to the least

stringent and most stringent AALs found in the NATICH data base for each emitted HAP and applicable

averaging periods.

TB0025i6
Black Hills '::vrporalion (WYGEN 2)

Permit Appi.:ation Analysis, NSR-AP-C92

Page 32

A total of220 modeled concentrations (55 HAPs x 4 averaging periods) were compared to the available

concentrations listed in the NATICH data base, and nineteen (19) ofthe 220 comparisons were found to

exceed the most stringent AALs, with some ofthe 19 values representing the same HAP for a different

averaging period, and none of the modeled HAP concentrations exceeded the least stringent AALs. A

listing ofthe HAP impacts compared to most stringent and least stringent NATICH AALs are provided In

Table 9. It should be noted that a large majority ofthe modeled HAP concentrations were one to four

orders of magnitude lower than the corresponding AALs referenced in the NATICH data base.

Gfthe fifty-five HAP pollutants emitted by the proposed WYGEN 2 PC Boiler, seven (7) HAPs are

listed as known or suspected carcinogenic compounds as referenced in EPA's Integrated Risk Information

System (~S) Data Base. A unit risk factor was obtained for each ofthese seven (7) compounds to

calculate t::e incremental risk associated with inhalation due to long-term exposure. The unit risk factors

have been cenved to quantify the number of people that could potentially contract cancer per million

people in 2~ average population. The risk factors are extremely conservative based on the assumption

that the saro.,Jled population will be exposed to the maximum model predicted concentration of the

carcinogen of interest for 24 hours per day over a period of 70 years.

--The-increr::~:1tahisk-asscrciJnedwtthmh-alanondue tolong-term exposure was calculated by multiplying

each maxi:--.:m model predicted annual HAP concentration by the unit risk factor for each of the seven

HAPs, and multiplying this estimated value by one million to determine the risk on the basis of 1 in a

million. Results ofthe risk assessment are shown below:

Pollutants

Acetaldehyde

Arsenic

Beryllium

Bromoform

Cadmium

Chloroform

Formaldehyde

Modeled

Concentrations

5.9 x 10's Ilg/m3

6.2 x 10's Jlg/nt

1.2 x 10's Jlg/m3

4.0 x 1O~ Ilg/m3

5.3 x 10~ Ilg/m3

6.1 x 1O~ Jlg/m3

2.5 x 10's Jlg/m3

Unit Risk Factors

2.2 x 1O~ m3/Jlg

4.3 x 10.3 ml/Jlg

2.4 x 1003 m3/Jlg

1.1 x 10~ m3/Jlg

1.8 x 10.3 m)/Jlg

2.3 x lO-sm3/llg

1.3 x lO'sm)/llg

Calculated Risk

Less than IlMillion

Less than IlMillion

Less than IlMillion

Less than IlMillion

Less than IlMillion

Less than I1Million

Less than IlMillion

The risk assessment indicates that the calculated risk of contracting cancer due to long-term exposure

from any of the seven (7) carcinogenic HAPs is less than one in a million. This analysis has addressed

the estimated carcinogenic HAPs from this modification, and the results indicate that the operation of the

proposed WYGEN 2 facility should not pose any extreme risks from long-term exposure.

PREVENTION OF SIGNIFICANT DETERIORAnON (PSD) ANALYSIS

Based on the results ofthe significant impact analysis, the BHC must conduct ambient air quality

analyses to evaluate the impact ofS~ emissions from the proposed WYGEN 2 facility, including all

interacting increment consuming sources of SO:z located within the significant impact area + 50 Ian of the

proposed modification to demonstrate compliance with applicable PSD Class 1 and Class II increments.

Additionally, as required by Wyoming Air Quality Standards and Regulations (WAQSR) Chapter 6,

Section 4(b)(i)(B), the applicant must submit additional impact analyses related to impacts on visibility,

TB002577
Table 9 I

Comparison of Modeled HAP Concentrations fro~ WYGEN 2 to NATICH Values

\

I

='

Hazardous Air Pollutant Impacts Compared to the Most Stringent and Least Stringent NATICH Limits

NATICII NATICH NATICH NATfH NATICH NATICH NATICI·1 NATIOI

Most leasl Most le sl Most leost Most I.cnsl

Stringent Slrlngcl1l Stringenl Slrln&enl Slrlngenl Stringent Sfringcnl Siringcni

Annual Annual Annual I-llour I-Hour I-II0ur 8-lIour 8-Hour g-Hollr 24-lIour 24-lIour 24-IIOllr

Impact Impacl Impacl Impacl Impaci Imp,cl Implel Impact Impacl Impact Impacl ImpOtl

l'ollUlanl (ltg/ml

) (ug/m') (Ilg/m') "IKlm') (Ilg/m') (1lg/1111

) (ltg/m') (ltg/m') (ltglm') (Ilg/m') (ltg/m') (Ilg/m')

2.4-Dinilrololuene 2.90E-oS 1.I0E-02 1.50E-02 41S7E-06 4.20£+01 4.20E~01 1.22E-06 1.50e-02 3.57E+01 460E·07 3.60e+00 1.50E+01

2·Chloroacetophenone 7.25E-07 3.20E-01 3.20E-01 1.22E-04 - 3.06E-05 3.00E-03 6.00E+00 1.15E·05 7.20E-o I 7.50E+00

Acetaldehyde 5.90E-05 4.ooE-01 5.00E-OI 9.9IE-03 2.70E+00 ,JOt] 2.49E·03 I.SOE+OO 4.29E+03 9.36E-04 4.S9E+00 1.80£+04

Acelophenone I.SSE-06 1.00E+02 1.00E+02 2J61 E·04 1.50E+02 1.50E 02 6.55E-05 - 2.46£-05 4.00£+00 4.9IE+03

Acrolein 3.00£·05 4.00E-04 8.30£-0 I 5;04E·03 690E-03 6.70£ 00 1.27£-03 2.30£-03 5.40£+00 4.76£-04 6.00£-01 380E+05

Antimony 828£-06 3.00E-01 4.00£+01 1.39E·03 1.50£+01 1.50E+01 3.49£·04 5.00£-03 1.19E+01 1.3IE-04 1.20£+00 1.00E+01

Arsenic 6.2IE-05 2.30E-07 670E-01 1.04£-02 3.20E-01 3.20Elol 2.62E-03 2.00E-03 2.00E+00 9.86E-04 2.00E-02 3.30E+00

Benzene 1.35E-04 I.OOE·OI 1.00E+02 2.26E·02 6.30E+02 .,DEr 5.68E-03 3.00E-01 1.60E+02 2.14E-03 1.14E+00 320E+02

Benzyl Chloride 7.2SE-05 1.00E-02 1.67E+01 1.22E·02 2.00E+01 2.00E 01 3.06E-03 5.00E-02 1.00E+02 1.15E-03 7.34E+00 1.03E+02

Beryllium 1.24E-05 4.IOE·06 1.00E-02 2.09E-03 6.00E-02 6.00E 02 5.2'F.-O~ 2.00E-05 2.00E-02 1.97E-04 1.00E-03 2.00E-02

Biphenyl iliF.-07 1.00E-02 S.OOE+OO 296E-05 742E-06 1.30E-02 3,IOE+01 2.79E-06 3.40E-01 1.26E+02

Bls(2-elhylhexyl)phlhalote 7.56E-06 2.30E-01 1.20E+02 1.27E·03 1.00E-01

'JOT

319E-04 S.00E-02 SOOE+OI 1.20E-04 3.00E-02 200E+02

OrOlllororm 4.04E-06 1.00E-02 S,OOE+OO 6,78E-04 150E+02 ISOE 02 1.70E-04 520E-02 1.00E+02 641 E-OS 1.20E+01 5 I7E+02

Cadmillm 5.28£·06 5.50E-06 I 67E-01 887E-04 170E+00 I 70£ 00 2.23E-04 1.00E.()4 5.00E-01 838E-05 3.00E-03 8.30E-01

Carbon Disulfile 1.35E-05 1.00E·02 1.00E+02 2.26E·03 910£+01 9.IOE 01 5.6sE-04 3.00E-01 8.60E+01 2.14E-04 1.86£-01 7.14£+02

Chlorine - I.5E+OO 1.00E+01 2.90E·02 6.90E 01 1.50E-02 6.00E+01 - 3.75E-02 750E+01

Chlorobenzcne 2.28E-06 - 3.83E-04 - 6.00E±'

961E-05 - 36IE-05

Chlororornl 611E-06 4.30E-03 1.67E+02 103E-03 600£+01 2.58E-04 5,00E-01 1.20E+03 969E-OS 1.60E+01 490E+02

Chromium 2.49E·04 8.30E-08 680E-OI 4.17E-02 I.IOE+OI 1.1 OE 1 1.05E-02 5.00E-04 2.S0E+00 3.94E·03 1.20E-01 8.30E+00

Coball 4.14E-05 5.00E-02 3.30E-01 6.96E-03 - - I 1.75E-03 5.00E-04 2.00E+00 6.51E-04 120E-01 S.30E-01

Cumelle 5.49E-07 9.00E-OJ S.83E+02 9.22E-05 - I 2.31 E-05 2.46E+OO 5,86E+03 8.71 E-06 588E+02 246E+04

Cyanide 2.S9E-04 5.00E+01 167E+01 435E-02 - 1.09E-02 5.00E-02 HOE-OI 4.11 E·03 830E+01 I 25E+02

Dimelhyl SlIlfnle 4.97E-06 1.00E-02 2.40E+00 8.35E-04 - \ 2.IOE-04 5.00E-03 250E+00 7.88£-OS 3.00E-03 S.20E+OO

Elhyl Chloride 4.35E-06 - 7.30E-04 . I 1.83E-04 - - 6.90E-05 -

Elhylbenzene 9.73E-06 1.18E+02 1.45E+03 1.63E-03 4.50E+03 4.50E+/lJ 4.IOE-04 4.34E+00 4.35E+04 I.S4E·04 1.ISE+02 4.34E+04

Elhylene Dlbromide 1.24E-07 6.70E-OS 2.47E+00 2.09E-05 910E-02 9.IOE-~2 5.24E-06 720E+02 ISSE+03 1.97E-06 240E-02 770E+02

Elhylene Dichloride 4.14E-06 3.80E-OJ 1.48E+02 6.9SE-04 530E+01 530E+ 3 1.75E-04 400E-01 1.00E+03 6.57E·05 960E+00 670E+02

Fluorine - 2.00E-01 S.OO£+OI 3 IOE-02 600E+00 160E-02 2.00E+02 4,80E-0 I 270£+01

Formaldehyde 2.49E-05 7.69E-02 7.69E+00 417E-03 2.00E+01 200E+QI 1,05E-03 ISOE-02 1.80E+01 3.94E-04 3.30E-01 1.20E+01

lIexane 6.94E-06 1.76E+02 1.76E+02 1.1 ~E-03 SJOE+03 5.30E+d~ 293E-04 I 76E+00 3,60E+04 1.IOE-04 I.IOE+OO 290E+04

Note: Facility exceedances ofthe NATICH limits are presented in bold and underlined. I

'£8002578
Table 9 (CODtiDuel

Comparison of Modeled HAP Concentrations from WYGEN 2 to NATICH Values I

1

Hazardous Air Pollutant Impacts Compared to the Most Stri~gent and Least Stringent NATICH Limits

NATICH NATICH NATICH NATIC;:H NATICH NATICH NATICH NATICH

Most Least Most Leasl Most Least Most Lell5t

Stringent Stringent Stringent Slring~nt Stringent Stringent Stringent Stringenl

Annual Annual Annual I-Hour I-Hour I-Hour 8-lIour 8-Hour 8-Hour 24-Hour 24-Hour 24-Hour

Impact Impact Impacl Impacl Impact Impa¢t Impact Impact Impact Impaci Impact Impact

Pollutant (Ilg/m') (Ilg/m') (J.lg/m') (ilg/m') (Ilg/m') (J.lg/m'l) (J.lg/m') (Jlg/m') (J.lg/m') (JIg/m') (J.lg/m') (Jlg/m')

Hydrogen Chloride 4.97E-03 1.00E-01 1.40E+02 8_35[-01 7.50E-02 2.00~j~3 2.10£-01 1.40E-01 1.80E+02 7.88E-02 2.03E+00 2.00E+03

Hydrogen Fluoride 6.21 E-04 340E-01 1.00E+02 j"]4[:'Oi 260E-02 5.63E.~2 2.62[-02 2.50E-02 6.19E+01 986E-03 3.00E-02 1 88E+02

Isophorone 6.0IE-05 2JOE+01 8.33E+01 1.01 E-02 2 80E-0 I 280E- I 2~3E·03 250E-01 4.60E+02 9.53E-04 600E"01 226£+03

Lead 416E·05 700E·02 1S0E"00 698[·03 1.7SE-OJ I 50[·03 3.00E·' 00 6.60[-04 1.40E·01 251lF+01l

Mangnnesc 580E-04

I

2.40E·0 I 1 19E"02 9.7-4[-02 3ll0E-II~ 250l:+PI USE-02 1.00[·02 500E+01 9.20E·03 3 IOr·02 100E~m

Mercury 2.01 E-05 1.00E·02 2.40E-01 :J17E-iD 1.50E+00 1S0E+PO 8.47£-04 HOE·04 200E+00 3.19E-04 6.00£-04 1.70£+04

Methyl Bromide 1.66E-OS 6.00£-03 4.80E+02 278E·03 5.00E+02 5.00E~2 699E·04 190E-01 4.00E+02 263E-04 528E+00 320E+02

Methyl Chloride 549E-05 1.00E-02 2.52E+03 9.22E·03 2.07E+00 HOE I 2.3 I[-03 1.03E+00 2.IOE+·03 8.71£-04 9.50£+00 1.70£+03

Methyl Elhyl Kelune 4.04E-05 321E+01 197E+03 6.78E·03 885E+00 740E+P3 1.70[-03 590E+00 1.40E+04 6.41 E-04 370E+00 5.90E+04

Melhyl Hydrnzine 1 76E-OS 2.20E·02 1 17E+00 2.96E-03 300£+0(J 300E+00 742[-04 ROOE-03 1.90E-01 279£-04 4561'.-02 1.901'.+00

Melhyl Maerylllic 2.01E-06 2.23[+(J 1 I 37[+03 3481:·0-1

760;1' R7JE-O~ 4.10[+00 4.10[+04 329E-05 820EI(J0 103E+O,(

Mcthyl Ter! Ulltyl Ether 3.62E-06 - 6.09E-04 - 1.53[-04 5.7SE-05

Methylene Chloride 3.00E-05 240E-02 84E+03 5.04E-03 1.74E+01 1.21E-03 180E+00 1.00E+03 4.76E-04 9.45E+00 875E+03

Naphthalene 1 35E-06 1.43E+01 1.67E+02 226E-04 7.90E-01 6.30E+ 2 5.68E-OS 5.00E-01 1,00E+03 2.14E-05 1.43E+01 500E+04

Nickel 3.11 [-04 3.30E-OS 3.30E+00 S.22E-02 570E+00 5.70E+bo 1.31 [-02 2.00E·03 S.OOE+OO 493E-03 6.00E-03 1.70E+01

Phenol 1.66E-06 1.90E+01 4.56E+02 2.78E-04 9.50E-01 3.20~+r2 699E·OS 190E·01 1.90E+03 2.63E-05 4.56E+01 320E+02

Polychlorinated Dibel1l0hlfftl1s 2.08E-08 349E-06 - 878E-01 3.30E-07 -

Polychlorinated Dibenzo-p·dloxlns 4.43E-09 7.44E-07 - 1.87E-07 - 7.o3E-08

Propionoldcyde 3.93E-OS - - 6.6IE-03 - - 1.66E-03 4.29E+03 4.29E+(l1 r ., --: 01 -

Selenium 1.3SE·04 200E-01 4.80£+00 2.26E-02 6.00E+00 6.00E~0 5,68[·03 200E-03 4.76EIOiJ 2 :~ CJ 4::: ') I 2(E JI

Styrene 2.59E-06 1.15E+00 7.16E+02 4.35E-04 1.06E+01 3.50E 3 1.09E-04 213E+00 S.07E+03 4.11 E-05 J34E+00 213E+04

Tetrachloroethylene 4.45E-06 1.00E-02 804E+03 7.48E-04 137E+01 1.IOE+~4 1.88E-04 339E+00 3.75E+03 1.06E-05 7.10E+02 5.70E+03

Toluene 2.49E-05 1.02E+0 I 7.50E+03 4.I7E-03 I.OOE+OO 4.70E+ J I.OSE-03 377E+OO 8.90E+03 3.94E-04 4.70E+00 317E+04

Vinyl Acetate 7.78E-07 9.57E+00 I.SOE+OI 132E-04 7.00E·01 7.00E-~1 332E·.05 3.50E·0 I 830E+02 1.25E-05 4.00E-01 580E+02

Xylcnes (0 And 111) 3.83E-06 1.18E+01 1.45E+03 6.43E-04 65 IE+OO S.50E+ 3 I 62£-04 4.34£+00 103E+04 6.08E-OS 2.10E+00 4.34E+04

Note: Facility exceedances of the NATIel! limits are presented in bold and underlined.

'1'8002579
Black Hills Corporation (WYGEN 2)

Permit Application Analysis. NSR-AP-C92

Page 33

soils and vegetation, acid deposition and secondary growth effects associated with the proposed

modification.

PSD Class II Increment Consumption:

• Sulfur Dioxide (SOl) •

The proposed SO~ emissions from the \-IYGEN 2 facility are 3,381 TPY, which is above the PSD

significant emission rate of 40 TPY. 7;erefore, a PSD analysis is required under Wyoming Air Quality

Standards and Regulations, Chapter 6, ection 4 (b)(i)(A)(I), to determine impacts from all S~ sources

within the significant impact area for ',.YGEN 2 which consume increment in Class II areas.

The emission rates and stack paramete,::; for all proposed SO~ sources at the WYGEN 2 facility are

provided in Table 3, and the interactiv;; ~nearby) sources of S02' are provided in Table 3a. The applicant

submitted a modeling analysis to com;::re the predicted impacts to the PSD Class II 3-hour, 24-hour and

annual increment levels of512 Jlg/nt, 91 Jlg/m3 and 20 Jlg/m3

, respectively. Several of the interacting

S02 sources are located at the Wyodal: (:omplex. which is also the proposed location of the WYGEN 2

facility.

The highest second highest 3-hour ane' '"'4-hour ambient S~ concentrations predicted in this analysis

were 247.6 Jlg/m3 and 80.5 Jlg/m3

, respectively; the maximum model predicted annual S~ concentration

was 6 Jlg/m3

• The SO:! contribution from all sources at the WYGEN 2 facility at the maximum impact

receptor locations was 14.3 Jlg/m3 (3-hour) and 3.2 Jlg/m3 (24-hour), and 0.05 Jlg/nt (annual), which

indicates that less than 5% ofthe modeled PSD Class II increment for S~ is consumed by the sources at

the proposed WYGEN 2 facility.

Results of the PSD Class II increment analysis for SOz indicate that the model predicted impacts from all

S02 sources at the proposed WYGEN 2 facility are below the 3-hour, 24-hour and annual PSD Class II

increments for S02' Therefore, the Division is satisfied that the proposed facility will not exceed the

PSD Class II increments for S~. Isopleth plots showing the 3-hour, 24-hour and annual modeled So,

increment consumption are shown in Figures 6-8, respectively. A summary ofthe ISCSTI model

predicted concentrations from the increment consumption analysis are provided in Table 10 below:

Table 10

Comparison of Modeled S02 Impacts to PSD Class II Increments

PSD PSD Contribution Location

Class II Class II from

Averaging Modeled Increment WYGEN2

Impact (l!g/m3

) UThl-E UTM-N

Pollutant Period

(lIo/mJ) (l!g/m3

) (m) (m)

Annual 6 20 0.05 469,424 4,903,100

S02 24-hour 80.5 91 3.2 469,324 4,903,100

3-hour 247.6 512 14.3 469,424 4,903.100

TB002580
FIGURE 6

PSD IC ANALYSIS - HSH 3-HOUR S02 CONC

IMPACTS FROM WYGEN 2 + NEARBY IC SOURCES

460000 465000 470000 475000 480000

4915000 -.

.__ ;_-L..,-_ ..- - ..... _.

,-- '""-,

!

.,

4915000

4910000 J

-(I)

I

(lJ

+J

~~ - 4905000 ...J

t!)

Z

H

:x=

o -~Z2i' 4900000

4895000

4890000

WYGEN 2 FENCE UNE --\ . -,

(.... -~~ "" , ooסס491 \

\ ~~~ ~.> \ ','--' '1 : ,,/~ ...; (

--os~~)':~; -=ur490SOOO

c, I 25,\ ",'\ ., ~.t; ,!~) 1 E

v· ""- / I

!:iSH 3-HR 502 Pedicted Increment - 4900000 (

-SO> . ~47.6 uglm3 at (469,424; 4,903,100) _

'"'

t I \"-

I, ,,';J 0:

11)1 4895000

V

t4890000

455000 460000 465000 470000 475000 480000

UTM EASTING (meters)

HSH Modeled 3-HR Impact - 1999 Pacificorp Wyodak Met Data

TB002581
FIGURE 7

PSD IC ANALYSIS - HSH 24-HOUR S02 CONC

IMPACTS FROM WYGEN 2 + NEARBY IC SOURCES

455000 460000 465000 470000 475000 480000

4915000 4915000

4890000

/ ._----"'_-"

:........ II)

" r \

, I

I

4890000 L

i

i

jO

4895000'l

f

4900000 o.

I

lii\~~ 4905000 '

_ 4910000

en

QJ

+oJ

-

455000 460000 465000 470000 475000 480000

UTM EASTING (meters)

aSH Modeled 24-HR Impact - 1999 Pacificorp Wyodak Met Data

TB002582
FIGURE 8

PSD Ie ANALYSIS - MAX ANNUAL S02 CONC

IMPACTS FROM WYGEN 2 + NEARBY IC SOURCES

455000 460000 465000 470000 475000 480000

... ~,--._ .......,._---, ·I-·---·-~-- -.-~_.."---.- _..

4915000 - .. 4915000

i

LI

_ 4910000 I

fIl

Q)

+l

: 4910000 •

,- WYGEN 2 FENCE UNE - I (''-,

; \

I

/\_" ,-./

----~- - - - "'~- - -' ----\_~----~. --/;;~

"~ ) 0 J----

4905000 -- '\ <..../ .J

l <tc \ ~,~ "'1

1Annual

6 ug/m3

502

at (469,424;

Pedleted

4,903,100)

Inc..me,' Con,umptio, (,~ r

1

t!>

Z

H

tI:

0 4900000 Z

D

4895000

-

4890000

455000 460000 465000 470000 475000

UTM EASTING (meters)

Maximum Annual Impact - 1999 Pacificorp Wyodak Met Data

TB002583
-

Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C~:

Page 34

Far-Field Modeling Analysis

~odeIJustification:

To evaluate potential impacts at receo'')rs farther away than 50 km from the proposed WYGEN 2

facility, the applicant used CALPUF -;:hich is a Long Range Transport (LRT) model. Specifically, the

CALPUFF modeling software packal':: ~onsists of a meteorological data pre-processor (CALMET), an

air dispersion model (CALPUFF), wL:h uses meteorological data processed by the CALMET model,

and a post-processor program (CALPCST) that uses the hourly concentration (or deposition) values

estimated by CALPUFF to provide various outputs, including visibility impacts and acid deposition

estimates. Although the CALPUFF model has not been formally accepted as an Appendix A model

listed in the Guideline on Air Quality Models, it was designed and developed as a generalized nonsteady-state air quality modeling system for regulatory use. A short description of each of the three

models that comprise the CALPUFF modeling software package is provided below.

CALMET Model:

CALMET is a diagnostic model that develops hourly wind and temperature fields on a three-dimensional

gridded modeling domain. Associated two-dimensional fields such as mixing height, surface

characteristics and~isper~ioni>roperrie£-{)f--the-terrain-are-inclndedin the fi1e-produced bythe-cALMET

model. CALMET includes a diagnostic wind field generator containing objective analysis procedures,

parameterized treatments of diurnal slope flows, kinematic terrain effects, terrain blocking effects, a

divergence minimization procedure, and a micro-meteorological model for overland and overwater

boundary layers, Additionally, the CALMET model can utilize gridded prognostic meteorological data

from various mesoscale models such as MM5 to better represent regional wind flows and slope/valley

circulations. The CALMET model allows the user to "weight" various terrain influence parameters by

defining the radius of influence for surface and upper air meteorological observations in the domain to

characterize the 10caJi~eq meteorological conditions. Version 5_2, Level 000602a of the CALMET

model was used for this analysis.

CALPUFF Model:

CALPUFF is a multi-layer, multi-species non-steady state Lagrangian puff transport model which can

simulate the effects of time- and space--:arying meteorological conditions on pollutant transport,

transformation, and removal. CALPUFF can use the three-dimensional wind fields developed by the

CALMET model, or simple single stat:~n winds in a format consistent with the meteorological files used

to drive the ISCST3 steady-state Gauss:an dispersion model (screen mode). The Class I Area modeling

analyses were completed using CALPUFF in a refined mode, which uses three-dimensional wind fields.

CALPUFF uses terrain-following coordinates and has several options available to consider terrain effects

on ground-level concentrations. CALPUFF also has the ability to treat subgrid scale complex terrain.

CALPUFF contains a puffsplitting algorithm based on the dividing streamline calculated internally by

the model. CALPUFF also has the ability to incorporate several optional methods for estimating

dispersion coefficients based on similarity theory, turbulence measurements, Pasquill-Gifford (PG) or

McElroy-Pooler coefficients. CALPUFF contains algorithms for near-source effects such as building

downwash, transitional plume rise, partial plume penetration, subgrid scale terrain interactions. as well as

longer range effects such as vertical wind shear, wet scavenging, dry deposition, chemical transformation

using aqueous-phase or dry-phase chemistry. CALPUFF can accommodate arbitrarily-varying poin!

source and grldded area emissions. Most of the algorithms contain options to treat the physical processes

TB002584
Black E:lls Corporation (WYGEN 2)

Pennit A;:plication Analysis, NSR-AP-C92

Page 35

at different levels of detail depending on the options used in the model application. Version 5.4, Level

000602_01 ofthe CALPUFF model was used for this analysis.

CALPOST Model:

CALPOST is a post-processing program designed to produce ranked tabulations of averages ofselected

pollutant concentrations, with various options for computing time-averaged concentrations and

deposition fluxes predicted by the CALPUFF model. CALPOST can process hourly sulfate and nitrate

concentrations using concurrent hourly relative humidity values to produce extinction coefficients for the

time-averaging periods of interest. CALPOST computes visibility impacts in accordance with the

Interagency Workgroup on Air Quality Models (IWAQM) guidance, and the Federal Land Managers' Air

Quality Related Values Workgroup (FLAG) Phase I Report. Version 5.4, Level 000602_1 ofthe

CALPOST model was used for this analysis.

CALPUFF Screening Analysis

Initially, ~he applicant used the CALPUFF modeling system to run CALPUFF in the screening mode,

commc-y referred to as "CALPUFF Lite". In this mode, CALPUFF can be driven by data from a single

___~eJ~Q[C .'gicaLstationlhatis~ompatible--with-the--lSC-8B--air-tiispersion-model;-which-bypassesthe neea

to run C .LMET, a complex model that generates a 3-dimensional wind field based on the selected

meteorc.Jgy, along with terrain and land use data files. In the single-station mode, CALPUFF assigns

the single value of each variable read from the meteorological data file to all grid points in the domain.

resulting in a spatially uniform gridded field. However, the CALPUFF model does not assume that the

meteorological conditions are steady-state, which allows the important effects of causality to be

simulated even with the single-station meteorological data. This approach is not as onerous as a refined

CALPUFF simulation using fully developed three dimensional wind fields. However, using CALPUFF

in the screening mode h;lS the potential ofproducing higher maximum impa~SC-3--mooelusing -

--~thesame meteorology, because the CALPUFF model can handle phenomena such as calm winds, wind

reversals, and fumigation events, and causality, which the ISC3 model neglects.

The meteorological data used in the CALPUFF screening modeling analysis consisted of five years of

surface observations (1986-1990) for Casper, Wyoming. These data were taken from the National

Climatic Data Center's (NCDC) Solar and Meteorological Surface Observational Network (SAMSON)

CD-ROM set. These five (5) years were then combined with Rapid City, South Dakota upper air

twice-<1aily mixing height data downloaded from EPA's SCRAM web site for the same five-year period.

This data set was processed for wet deposition to provide CALPUFF with sufficient data to execute the

MESOPUFF II chemistry transformation algorithms that are built into the CALPUFF modeling system.

The meteorological data set also included the extended meteorological variables, which are the surface

friction velocity, Monin-Obukhov length, a time-varying surface roughness length, precipitation rate and

precipitation type code. which are required if dry or wet deposition are being modeled.

The IWAQM Phase II guidance recommends that the domain should extend at least 50 Ian beyond the

outer most receptor ring. The grid cells used to define the domain for each Class I or Class II area are

different sizes due to the relative distance from the proposed WYGEN 2 facility to each area of interest.

The size of the grid cells ranged between 193 km and 263 km on a side, after including the 50 km

distance.

TB002585
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 36

Significant Impacts at Oass I Areas:

The applicant used CALPUFF in the screening mode to compare the model predicted impacts on the

mandatory Class I Areas with the proposed PSD Class I Significant Impact Levels (SILs) for NO., S02,

and PM\o' The CALPUFF screening analysis for the Class I Sll..s was based on operation ofthe PC

Boiler at 100 percent of base load. The stack parameters and emission rates for the PC Boiler that were

used in the CALPUFF screening analysis for assessing Class I impacts at the mandatory Federal Class I

Areas: Wind Cave National Park (WCNP) and Badlands National Park (BNP), and at the Tribal Class I

Area: Northern Cheyenne Indian Reservation (NCIR) are presented below:

SOl

Rate

NO.

Rate

PM,o

Rate

Note: Sulfuric acid mist (HIS0,) emissions were represented in the CALPUFF model as SO.

The receptors used in the CALPUFF screening analysis for comparison against thqrroposed Class I SILs-

--~~--c"On-slsre(rorapaffialnrig~Ofreceptors, also known as receptor arcs. The receptor arcs used in the

CALPUFF screening analyses subtending an angle of approximately 90 degrees, extending out from

either edge ofthe Class I area with the receptors spaced circumferentially every one degree within the

receptor are, as per the EPA guidance document entitled, Long-Range-Transport Screening Technique

Using CALPUFF. A single receptor arc was used for each Class I area: WCNP, BNP, and NCIR.

The results ofthe CALPUFF screening analysis indicated that the NO, and PM10 impacts were below the

proposed Class I SILs. However, the SO} impacts at the two (2) mandatory Federal Class I Areas

(W€NP;BNPT,-andlhe-Ttib"aIClas-n-l\Tea{NCIR") were-aoo-ve theproposedClass IsrLs f~~ the 3-hour

and 24-hour averaging periods, but were below the annual Class I SIL for SOz. Therefore, additional

Class I increment analyses for SOl were conducted using CALPUFF in a refined mode.

Visibility Analvsis:

The applicant submitted a visibility impact analysis using the CALPUFF screening methodology, and

followed the methodologies provided in the FLAG Phase I Report, (December 2000). The applicant

originally submitted the visibility analysis using the proposed emission rates. However, based on the

Division's BACT review, and the subsequent establishment of BACT emission rates for NO, and PM IO •

the applicant reran the CALPUFF screening analysis using thc revised emiSSIOn rates. The stack

parameters and emission rates for the PC Boiler that were used in the CALPUFF screemng analysis for

assessing visibility impacts at the Class and Class II areas are presented below:

S02 S04 NO, PM10 Stack Stack Stack Stack

Rate Rate Rate Rate Height Temp Velocity Diameter

Source (g/s) (g/s) (gls) (g/s) (m) (OK) (m/s) (m)

PI Rnilf'r 11077 70d 4'i \0 77R lQO .;; 144 \ ')() 0 771

Note: Sulfunc acid mist (H}SOJ) emissions were represented in the CALPUFF model as SO.

TB002586
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 37

The receptors used in the CALPUFF screening analysis for determining visibility impacts consisted of

the same receptor arcs as used to determine significant impacts at Class I areas. However, an additional

receptor arc was added for the Cloud Peak Wilderness Area (CPWA), which is a Class II area.

The backgrOlmd extinction computation was carried out by the CALPOST model using Visibility

Method Option #6, which computes extinction from speciated PM measurements, and uses the FLAG

relative humidity (RH) hourly adjustment factor applied to the observed and modeled sulfate and nitrate.

The applicant used seasonal values for hygroscopic light extinction efficiency, dry extinction efficiency,

j(R.H), baseline light extinction at BNP and WCNP that were provided as natural background estimates i~

the FLAG Phase I Report, as suggested by the National Park Service (NPS). However, there were no

values for NCIR or CPWA. Therefore, the data to calculate light extinction at WCNP were used to

represent the NCIR and CPWA, as suggested by the National Park Service (NPS).

The light extinction for the hygroscopic species were computed using seasonalj(RH) adjustment factors

for both the model predicted concentrations and for the background concentrations. The RH factors are

unitless, and the values that were used in the visibility impact analysis for Badlands were taken from the

FLAG Phase I Report: 3.1 (Winter), 2.6 (Spring), 2.2 (Summer), and 2.8 (Fall). The corresponding

j(RH) values for Wind Cave were obtained in the same manner. - ------

In the applicant's analysis, the background sulfate concentration was set to 0.2 ug!nr for all 12 months,

and the background soil concentration was set to 4.5 uglnt for all 12 months, the remaining four (4)

background extinction coefficients for nitrates (N0l)' coarse particulate matter (pMC), organic carbon

(OC), and elemental carbon (BC) were set to zero for all 12 months, as recommended in the FLAG Phase

I Report. A background ozone value of 40 ppb and a background ammonia value of 10 ppb were used in

the CALPUFF and CALPOST simulations for the visibility impact analyses. After the CALPOST model

calculates the seasonal background light extinction from all species, light extinction due. to Rilyleigb _

scattering-isTdOeOt01liecalculated seasonal background extinc-tion. The value for Rayleigh scattering

used in this analysis was 10 inverse megameters (Mm-I

).

The regional haze impacts were based on the maximum modeled 24-hour average sulfate (sq0) and

nitrate (NO)'), and PM10 concentrations (~g/m) predicted by the CALPUFF model. The nitrate and

sulfate transformation rates were computed internally by the CALPUFF model using the MESOPUFF II

dry chemistry scheme, which assumes that all nitrate and sulfate flux fully convert to ammonium sulfate

«(NH4)2S04) and ammonium nitrate «(NlL)NO). A 24-hour source extinction (b1Oun:C)' expressed in

IDverse megameters (Mm·I

) is determined by the CALPOST model using the following equation:

where: 1.375

1.29

JtRH)

3

0.6

the ratio of ammonium sulfate to sulfate molecular weights

the ratio of ammonium nitrate to nitrate molecular weights

= the hourly relative humidity factor for a given hour

the light scattering efficiency for nitrates and sulfates (m2/gram)

the light scattering efficiency for coarse particles PM1o·PMu (m2/gram)

The 24-hour average source and seasonal background extinction, expressed in Mm", are used to estimate

the corresponding 24-hour average change in extinction by the following equation:

TB002587
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 38

where:

~bal%=(b~·100

~bex,% is the incremental change in regional h<:.Z~, expressed in percent

Using this method, the maximum CALPUFF predicted 24-hour co::.:entrations of S02' SO., NO., lINO),

NO), and PM\o were used to calculate the change in light extinctic- =rom the proposed WYGEN 2 PC

Boiler. This change in extinction was compared to a five percent (:i%) and 10 percent (10%) change in

light extinction over the seasonal backgroWld extinctions for WCl\.), BNP, and NCIR.. which are Class I

areas, and also for the CPWA, which is a Class II area.

The results ofthe visibility impact analysis at the WCNP, BNP, NCIR., and CPWA using the CALPUFF

screening methodology were greater than the 5% change in light extinction at each Class I area, and were

above a 10% change in light extinction for one (1) day at CPWA. The maximum change in extinction

from the proposed PC Boiler, the number of days greater than 5% change, and number of days greater

than 10% change in light extinction using the CALPUFF screening methodology are shown below:

Results from CALPUFF Screening Visibility Analysis Using BACf Emission Rates

. _ --Max-Change.in ---#-J)ays->-5o/crA--# Days->-t 0% ti .

Class I Areas:

Badlands National Park

North Cheyenne Reservation

Wind Cave National Park

Class II Area:

Cloud Peak Wilderness Area

Light Extinction

7.3%

8.5%

8.0%

15.3%

Light Extinction

1

11

6

19

Light Extinction

o

o

o

The applicant conducted a variation ofthe screening analysis by using a small subset ofthe receptor arcs

that were located at the Class I and Class II areas of interest. As a result, 8 receptors were used in the arc

for WCNP, 16 receptors were used in the arc for BNP, 25 receptors were used in the arc for NCIR, and 4

receptors were used in the arc for CPWA. The results ofthis additional analysis indicated smaller

changes in light extinction at each Class I and Class IT area, and the total number of days with a change in

light extinction greater than 5% decreased, as well as producing zero days having greater than a 10%

change in light extinction.

Results of Additional CALPUFF Screening Analysis Using BACT Emission Rates

With a Subset of the Receptors in the Arcs

Class I Areas:

Badlands National Park

North Cheyenne Reservation

Wind Cave National Park

Class II Area:

Cloud Peak Wilderness Area

Max Change in

Lil!ht ExtinctIOn

4.4%

1.8%

5.2%

8.1%

# Days> 5%

Light Extinction

o

o

1

# Days > 10%ti

LilZht Extinction

o

o

o

o

TB002588
Blac!: -·lills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 3S!

Basec on the results ofthe additional CALPUFF screening analysis using the smaller arcs ofreceptors,

no fi..;r-••ler visibility impact analyses were submitted for the proposed WYGEN 2 facility.

CALPUFF Refined Analysis

The :-. ~licant conducted a Class I increment consumption analysis for S02 using a refmed CALPUFF

anal:'~ .J, based on a three-dimensional CALMET wind field created by the Division. This CALMET

wine _.eld was developed by the Division to enable applicants to use CALPUFF in a refined mode in

order ~J estimate air quality impacts from new sources as part ofthe New Source Review (NSR) process.

Computational & Sampling Grids:

The computational grid used to define the modeling domain for the WYGEN 2 analysis was developed

for the Division's ~orth £ast Y{yoming METeorological (NEWMET) project, and included the

development of a new expanded MM5/CALMET database for the Powder River Basin that includes

several downwind Class I areas. This computational, or meteorological grid, consists of 134 east-west

and 94 north-south 5 krn x 5 krn grid cells, including cell elevation and land use. Total areal coverage of

the NEWMET computational domain was 670 krn x 470 Ian. Recepmrs.ateach..areaofinterest were··· .

spaced every two (2) kilometers.-

Meteorolo~ical Inputs:

The NEWMET database included two hundred forty (240) surface meteorological sites based on several

different monitoring networks. The monitoring networks and number ofsites are provided below:

Surface Data Monitoring Network

National Climatic Data Center (NCDC) National Weather Service Sites(NWSL

Automated-Weather Data Ne1W6rk{A-wDN)' - . --

Remote Automated Weather Stations (RAWS)

North Dakota S02 Monitoring Sites

CASTNET Sites

Powder River Basin (PRE) Surface Coal Mines

# Sites

64

40

118

3

3

12

MM5 Data

The CALMET wind field data were initialized using 36 kilometer resolution data from the National

Center for Atmospheric Research (NCAR) Mesoscale Meteorological model, Srh Generation (M!vlS)

prognostic data from the calender year of 1996.

Upper Air Data:

Upper-air meteorological measurements are very sparse in the domain (typically 300-krn apart or more)

and are only collected twice daily; the resultant three-dimensional meteorological fields generated by

CALMET using upper air observations are typically highly uncertain and not dynamically balanced.

However, much improved and more realistic meteorological fields are obtained when output from a

coarse grid prognostic meteorological model, such as MMS, is used as input to CALMET. For the

NEWMET project, the 1996 36-km resolution MMS meteorological model database generated by the

U.S. EPA Office of Air Quality and Planning Standards (OAQPS) was used. Since the 1996 MMS

database essentially provides an hourly upper-air meteorological sounding every 36-km across the

TB002589
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 40

modeling domain with dynamically balanced meteorological variables, upper air observational data were

not used in the CALMET simulations. Sensitivity tests were done both with, and without the upper air

observations, and it was concluded that the omission of the observed upper air data would not

significantly affect the resulting CALMET wind field.

Vertical Layers

Eight (8) vertical layers were used in developing the CALMET wind field, with vertical cell face heights

located at 0,20,50, 100,250,500, 750, 1000, and 3000 m above ground level (AGL). Additional

vertical layers could be added to enhance the vertical resolution in CALMET.

Composite Wind Field:

The geophysical, prognostic, surface air, upper air, and precipitation data were processed an~ merged

into single monthly files to generate large CALMET.DAT files (-1.4-GB/month), which are used to run

the CALPUFF and CALPOST simulations. The CALMET.DAT file contains gridded fields ofu and v

wind components, mixing heights, PGT stability categories, micro meteorological parameters, RH, and

precipitation data based on the meteorological data input to the CALMET diagnostic wind model. All

meteorological and geophysical data are then used in CALMET to produce a three-dimensional wind

fieJeton.a griqd~~LmQdeUng domain. .-.---- - . -_. ---

Due to the large extent ofthis computational grid, the curvature of the earth must be taken into account

when calculating distances. To account for the earth's curvature in the modeling domain, the grid cells

are identified using a Lambert-<:onfonnal projection. and the locations of all sources and receptors used

in the CALPUFF analyses were converted to this projection system to maintain the correct reference.

Elevations for these discrete receptors were derived from electronic I :250,000 scale DEMs.

The applicant initially found severeD problel!l~. i!l.Jh~ .wiIl9 fiell;! .inpuls.JQr~ months, and could not

run the refinedCAL"fiUFF analyses with the chemistry (CHEM) and dry deposition (DRY) switches

- turned on, without the CALPUFF model simulation aborting. As a result, the applicant only used the

CALPUFF refmed analysis to evaluate the impact on Class I increments. The Division and the consultant

that developed the MM5/CALMET database were able to determine the cause of the problems with the

wind field were related to surface pressure values at some of the Powder River Basin (PRE) monitoring

sites which were extremely small, ranging from

°millibar to 200 millibar, which affected the chemistry

and dry deposition algorithms, and caused the CALPUFF model to stop running. These data values were

reset to represent missing surface pressure values, and there were no longer any problems \vith the

CALPUFF or CALPOST simulations. However, these problems were corrected too late in the DIVlsion's

review of the applicant's modeling analyses, and the applicant determined that it was not feasible to

utilize the revised wind field inputs in the AQRV analyses.

As a result of the problems discovered in the wind field mput data, the inputs to the composite wind field

underwent a thorough quality assurance/quality control review by the Division and the consultant that

developed the wind field, and additional review of the data are now being evaluated by the Di,:,ision. As

a result, it appears that additional refinements in the wind field may be necessary, and additional quality

assurance/quality control reviews will be required.

TB002590

- -
Black Hills Corp<>ration (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 41

Post Processing of CALPUFF Concentrations:

The CALPOST model generates concentration values and wet and dry deposition values for various

averaging periods, as well as producing deciview change and change in light extinction for evaluating

visibility impacts. The applicant used CALPOST to post-process CALPUFF concentrations to obtain

estimated 24-hour averaged S02, sulfate (SO.), NO., nitric acid (HN0J)' nitrate (NO), and PM10

concentrations at each receptor, and to estimate the Top-50 24-hour average sulfate and nitrate

concentrations. CALPOST will only allow the processing of a single species at a time, therefore, four (4)

sets ofCALPOST simulations were run, one simulation for each area of interest. CALPOST was also

used to calculate 3-hour and 24-hour and annual averaged S02 concentrations for determining Class I

increment consumption at the three (3) Class J Areas: Wind Cave National Park (WCNP), Badlands

National Park (BNP), and the Northern Cheyenne Indian Reservation (NCIR).

PSD Class I Increment Consumption:

• Sulfur Dioxide (SOJ •

The proposed S02 emissions from the WYGEN 2 facility are 3,381 TPY, which is above the PSD

significant emission rate of 40IPY. Therefo~ILana~sisJSJequiredlJ!lderWyoming Air Quality

---:::CStandards and Regulations, Chapter 6, Section 4 (b)(i)(A)(D, to determine impacts from all S02 sources

within the significant impact area for WYGEN 2 which consume increment at Class I areas.

Based on the results of the Class I SIL analysis using the CALPUFF screening methodology, the

applicant conducted a Class I increment consumption analysis for S02 using CALPUFF in a refined

mode. The S02 emission rates proposed by the applicant for the PC Boiler at 100 percent of base load

were used in the PSD Class I increment analyses, and the model predicted impacts were compared to the

PSD Class I 3-hour, 24-hour, and annual increment levels of 25 ~glmJ, 5~m3 and 2 j.lg!m!,

respectively. AsurTirilaiYofthe S02 emissions andstick parameters for all sources, including interacting

sources that were represented in the PSD Class I increment consumption analysis are presented in Table

11 below:

TB002591
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 42

Table 11

Stack Parameters and S02 Emission Rates Used in

PSD Class I Increment Consumption Analysis

S02 S02 Stack Stack Stack

Rate Rate Height Stack Te~") Velocity Diameter

Source (g/s) (TPY) (m) rK) (m/s) (m)

PC Boiler 110.22 3,831 190.5 344 20.00 7.71 - KFx Heat 1 0.05 2 18.3 466 I 11.91 0.91

KFx Heat 2 0.05 2 18.3 466 11.91 0.91

KFx Incinerator 1.38 48 30.5 477 19.75 0.91

- Two Elk Unit 1 57.27 1,991 103.6 344 27.40 4.94

- - WYGEN 1 25.58 889 89.9 342 I 27.44 2.82 . .. _~. __ .- - -

.- Neil Simpson 2 25SR- ----889 --89...9-- - -342-+--R:44- c----z:8l-- '0 ---- - - .-

ENCOAL Buckskin 2.41 84 68.6 353 13.72 1.22

Total S02 Emissions: 7,736 TPY

Several of the interacting S02 sources are located at the Wyodak complex, which is also the location of

the proposed WYGEN 2 facility:

- Results of the PSDClassfincrement analysis for SO! indicate that the model predicted impacts from all

S02 sources at the proposed WYGEN 2 facility and the interacting sources are below the 3-hour, 24-hour

and annual PSD Class I increments for SO!, Therefore, the Division is satisfied that the proposed

facility will not exceed the PSD Class I increments for S02' A summary of the CALPUFF predicted S02

increment consumption from the proposed WYGEN 2 facility are provided in Table 12, and the total

increment consumed by all S02 sources represented in this analysis are provided in Table 13.

TB002592
P';.ck Hills Corporation (WYGEN 2)

f'e8lit Application Analysis, NSR-AP-C92

fa;e43

Table 12

Comparison of Modeled SOl Impacts From WYGEN 2

PC Boiler to PSD Class I Increments

Badlands 3-Hour 121 185.833 -25.780 0.9 4%

24-Hour 3 164.662 -49.005 0.3 7%

Annual 3 164.662 -49.005 0.03 3%

Wind Cave 3-Hour 735 117.374 -40.747 1.3 5%

24-Hour 735 117J74 -40.747 0.6 12%

Annual 748 117.371 -36.879 0.05 5%

-- Jrth£he)'enne . ~our- -289 -112MO --t-5~~1a- L8 -70~

24-Hour 301 -129.383 153.22438 OJ 6%

Annual 520 -96.640 168.684 0.01 1%

Table 13

Comparison of Modeled S02 Impacts From All

Increment Consuming SOz Sources to PSD .class! Increments

0.04 4%

197.3783 -12.236

164.662 -49.005

117.371 -36.879

119.300 -38.812

117.371 -36.879

-113.976 149.359

-152.493 147.429

Annual 520 -96.639 180.278

Annual 748 0.13 13%

North Cheyenne 3-Hour 273 2.7 11%

TB002593
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 44

Commercial. Residential. and Industrial Growth Analysis:

There will be an increase in the local labor force during the construction phase associated with this

modification, but this increase will be temporary, and will not result in permanent significant commercial

or residential growth. It is anticipated that most ofthe labor force during the construction phase will

commute from nearby communities. The electrical generating capacity created by the proposed

modification should not have a significant effect upon the industrial growth in the immediate area as the

total electrical generating capacity will be sold to the power grid and used by several other states.

Population increase is a secondary growth indicator of potential increases in air quality levels. Changes

in air quality due to population increases are related to the amount of vehicle traffic, commercial and

industrial facilities, and domestic fuel usage. No new long termjobs will be created as a result ofthe

proposed modification, therefore, it can be concluded that there will be minimal effects to air quality

associate with secondary growth.

Soils and Vegetation Analysis:

The soils in this area have textural and drainage characteristics that limit the amount of water the soils

can retain and make available for plant growth. Vegetation in this region of northeastern Wyoming is

sparse. predomi~~ly sagebrush. The applicant reI'Qrts that_there arc no ]istedthreatened-or ~dangered-­

species known to exist in this region.

The National Ambient Air Quality Standards (NAAQS), or equivalently, the WAAQS have been

established to protect public health and 'welfare from any adverse effects of criteria pollutants. The

WAAQS analyses for N02. S02' HF, and PM\o indicated that the modeled impacts for these pollutants

were below the WAAQS for all applicable averaging periods. Therefore, it is expected that there would

not be any adverse impact to soils and vegetation in the vicinity of the proposed WYGEN 2 facility or at

other sites distant from the plant.

Acid Deposition Analysis:

As stated earlier, the applicant is proposing to increase emission rates of S02 above the significant

emission rate that triggers PSD review for this pollutant. Therefore, an acid depositlOn analysis is

required to examine the impacts from sulfate deposition as part of the analysis for AQRVs.

Emissions of nitrogen oxides. sulfur dioxide, and other sulfur compounds have the potential to convert to

nitrate and sulfate compounds in the atmosphere, and can be deposited as nitric and sulfuric acids into

sensitive lakes and other water bodies. and increase the acidity ofthese water bodies; nitrogen and sulfur

that is deposited in a dry deposition mode may also contribute to acid deposition impacts. All of the

effects of acid deposition are not well known, however, large amounts of acidic deposition can

slgmficantly affect soils, vegetation, lake chemistry and aquatic habitats ofsensitive species.

The applicant submitted the results sources represented in the acid deposition analyses consist of the

proposed PC Boiler at WYGEN 2. The USFS has identified a sensitive lake: Florence Lake, in which

potential acid deposition impacts are to be evaluated. Florence Lake is in the Cloud Peak Wilderness

Area (Class II area). The estimation of the percent change in acid neutralizing capacity (~ANC), or

alkalinity, was evaluated by the applicant for Florence Lake using a screening level assessment to

determine acid deposition impacts. The screening level assessment to calculate changes in ANC was

perfonned using the guidance document, Screening Methodology for Calculating ANC Change to High

TB002594
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 45

Elevation Lakes. authored by the USFS, and released in January, 2000. This technique quantitative>;

estimates the change in alkalinity of a sensitive water body (i.e., mountain lake) associated with pre~icted

ambient modeled concentrations ofsulfates and nitrates.

The total potential loss of ANC, in ~eqJL, was compared to the baseline ANC for Florence Lake. F.::::d

on the baseline ANC value for Florence Lake, the calculated percent change in ANC was comparee; tt:"

the significance criteria established by the USFS, which are 10% for water bodies with baseline Al\':' 3

greater than 25 ~eqlL, and a 1.0 ~eqlL change for water bodies with a baseline ANC less than 25 ~e:' :..

The baseline ANC for Florence lake is 38.3 ueqlL, and the maximum calculated MNC for Florence .~:J.ke

was 0.86%, which is below the 10% significance criteria. Therefore, it can be shown that the chang,:~ in

ANC from potential acid deposition impacts due to the proposed WYGEN 2 facility are below the

applicable USFS significance criteria, and are expected to be minimal.

SummarY:

The modeled ambient impact ofthe proposed facility by itself was below the PSD Class II significart

impact levels for all pollutants but sulfur dioxide (SOl)' The applicant's modeling analyses demons:.. .:.te

compliance with Wyoming Ambient Air Quality Standards for all criteria pollutants and hydrogen

fluoride"and also indicat~themodelpredictedimpactsonP~D·Glass+andtlassiI-areas are l:: ;ow

all applicable PSD increments.

The Division has reviewed and verified the source parameters, default settings, and related modeling

inputs used in the near-field and far-field modeling analyses that were submitted in the WYGEN 2 pennit

application and subsequent revisions. Selected options used in the far-field modeling input files were

chosen based on sensible meteorological and geophysical data assessments to accurately represent the

modeling domain, associated wind field, and puff transport and dispersion in a systematic approach. As

a result, the Division is _~tisfi~d that th~icanthas demonstrated compliance with all applicable

-ambIent air quality standards through the required modeling analyses using EPA approved models and

methodologies.

CONCLUSION:

The Division is satisfied that the proposed WYGEN 2 facility will comply with all applicable Wyoming

Air Quality Standards and Regulations. The Division is proposing to issue a pennit for the facility with

the following pennit conditions:

PERJ"tIT CONDITIONS:

L Authorized representatives of the DiVIsion of AIr Quality shall be given permission to enter and

inspect any property, premise or place on or at which an air pollution source is located or is being

constructed or installed for the purpose of investigating actual or potential sources of air

pollution. and for determining compliance or non-compliance with any rules, regulations.

standards, permits or orders.

2. All commitments and descriptions set forth in the application for this permit, unless superseded

by a specific condition of this permit, are incorporated herein by this reference and are

enforceable as conditIOns of this permit.

TB002595
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 46

3. A major source, as defined by Chapter 6, Section 3 (b)(xvii} 0:the WAQSR, shall file a complete

application to obtain an operating permit within 12 months a::.:r commencing operations.

4. All notifications, reports and correspondence required by th: -; ~ennit shall be submitted to the

Stationary Source Compliance Program Manager, Air Quali ~. Division, 122 West 25th Street.

Cheyenne, WY 82002 and a copy shall be submitted to the [.:trict Engineer, Air Quality

Division, 1043 Coffeen Ave, Suite D, Sheridan, WY 82801.

5. Owner or operator shall furnish the Administrator written notification of: (i) the anticipated date

of initial startup not more than 60 days or less than 30 days prior to such date, and; (ii) the actual

date of initial start-up within 15 days after such date in accordance with Chapter 6, Section 2(i)

ofthe WAQSR.

6.

----~---

The date of commencement of construction shall be reported to the Administrator within 30 days

ofsuch date. The pennit shall become invalid if construction or modification is not commenced

within 24 months ofthe date ofpermit issuance or if construction is discontinued for a period of

24 months or more iILaccordancewith Chapter 6TSection-2(h}.of.the.WA~The

Administrator may extend such time period(s) upon a satisfactory showing that an extension is

justified.

7. Performance tests shall be conducted and a written report of the results submitted within 30 days

of achieving maximum design rate but not later than 90 days following initial start-up in

accordance with Chapter 6, Section 2(j) ofthe WAQSR. The operator shall provide 15 days

prior notice of the test date. Ifmaximum design production rate is not achieved within 90 days

ofstart-up, the Administrator may ~effilire testinA-at rate ~cttievedandagain when maximum

rate IS-achIeved. -- -

8. Emission rates shall not exceed levels in the following tables:

PC Boiler Emissions (PC-OO 1)

Pollutant IbtM:MBtu Iblhr IblMW-hr tpy

3,381 771.9 (30-day rolling)

874.8 (2-hr block)

NO, 0.07 (30-day rolling) 360.2 (30-day rolling) 1.6 (30-day rolling) 1,578 .........................................................................................................................-- _ _--_ -

0.15 (30-day rolling)

0.17 (2-hr block)

90% Minimum Removal

Efficiency (30-day rolling)

0.012 61.7 270

CO 0.15 771.9 3,381 ••••••••••••••••• u •• _ _ •• _ .

VOCs 0.01 51.5 225

TB002596
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 47

Material Handling PMlPM,o Emissions

Source No.

COC-oOl

Source gr/dscf

Coal Storage Silo Top Dust Collector 0.009

Ib/hr

1.8

tpy

8.0

CDC-002

CDC-003

CDC..{)04

LDC-oOIA

LOC-001B

RDC-oOl

Coal Storage Silo Bottom Dust Collector

Coal Transfer Building Dust Collector

Unit Transfer ane Silos Dust Collector

Lime Unloading:;]o Dust Collector

Lime Unloading S:lo Dust Collector

FGD Waste Recyc.e Storage Bin Dust Collector

0.009

0.009

0.009

0.01

0.01

0.01

0.6

0.6

2.5

0.1

0.1

0.2

2.5

2.5

11.0

0.5

0.5

1.0

RDC-oO2AlBI FGD Waste Loacout Silo Dust Collectors 0.01 0.4 2.0

I Only one of these units (RDC-002A c..- RDC-002B) will be in service at anyone time.

------~---- -------------------

9. Initial performance tests, reqt:.•. ed by Condition 7 ofthis permit, shall consist of the following

unless an alternative is approved in writing by the Division:

A) NO. 30 day rolling average - Initial testing and compliance determination shall follow 40

CFR 60.46a, 40 CFR 60.47a, and 40 CFR 60.48a.

B) S02 - EPA Method 6C or equivalent shall beemIJIoyed to detennine initjal compliance

- with the SO~ 2llOUT enussion limit. Tests shall consist of 3 runs of 2 hours each.

C) S02 30 day rolling averagelPercent Reduction Requirements - Initial testing and

compliance determination shall follow 40 CFR 60.46a, 40 CFR 60.47a, and 40 CFR

60.48a.

D) PMlPM10 - Material Handling: EPA Methods 1-5, front half only, shall be employed to

determine initial compliance with the particulate

emission limits established by this permit.

PC Boiler: Testing shall follow 40 CFR 60.48a

E) Opacity - PC Boiler and Coal Handling: EPA Method 9 and the procedures In

WAQSR, Chapter 5, Section 2(i) shall be

employed to determine initial compliance with

opacity limits established by this permit.

FGD Waste and Lime Handling: EPA Method 9 shall be employed to

determine initial compliance with opacity

limits established by this permit.

TB002597
Black Hills Corporation (WYGEN 2)

Permit Application Analysis. NSR-AP-C92

Page 48

F) CO - EPA Method 10 or equivalent shall be employed to determine initial compliance

with the CO emission limit established by this permit.

G) VOCs - EPA Method 18 and Method 25 or equivalent shall be employed to determine

initial compliance with the VOC emission limit established by this permit.

10. The following testing shall be performed and a written report ofthe results submitted within 90

days after initial start-up:

A) PC Boiler Stack shall be tested to determine NIl) emissions following EPA Conditional

Test Method 27 (CfM-027) or equivalent methods. Results ofthe tests shall be reported

in units oflblhr and ppm., on a dry basis corrected to 3 percent O2,

B) PC Boiler exhaust shall be tested prior to control devices and at the PC Boiler Stack to

determine total fluoride emissions and control efficiency following EPA Method 13A,

13B, or equivalent methods. Results of the tests shall be reported in units of lblhr and

-.E0ntrol efficiency~ . .~_ -~---

---

C) PC Boiler exhaust shall be tested prior to control devices and at the PC Boiler Stack to

determine hydrogen chloride emissions and control efficiency following EPA Method 26

or equivalent methods. Results of the tests shall be reported in units of lblhr and control

efficiency.

11. Prior to any performance testing or monitor certification testing required by this permit, a test

protocol shall be submitted to the Div~ion for~pproval, at least 30 d~ys priJ2!" to testing. Results

.onne testS-snalroe"submitted tothis office within 45 days of completing.

12. Opacity shall be limited as follows:

A) Visible emissions from the PC boiler (PC-001) shall be limited to 20% opacity (6-minute

average) except for one 6-minute period per hour of not more than 27 percent opacity in

accordance with NSPS. Subpart Da, 40 CFR 60.42a(b).

B) Opacity shall be limited to less than 20% from all coal processing and conveying

equipment (including breakers and crushers), coal storage systems, and coal transfer and

loading systems in accordance with NSPS, Subpart Y, 40 CFR 60.252(c) as determined

by 40 CFR Part 60, Appendix A, Method 9.

C) Opacity from any other source of emissions at this facility shall be limited to 20%

opacity in accordance with WAQSR, Chapter 3, Section 2(a) as determined by 40 CFR

Part 60. Appendix A, Method 9.

13. Black Hills Corporation (BHC) shall use the following in-stack continuous emission monitoring

(CEM) equipment on the PC Boiler stack to demonstrate continuous compliance with the

emIssion limits set forth in this permit:

TB002598
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 49

A) BHC shall install, calibrate, operate, and maintain a monitoring system, and recorc.. the

output ofthe system, for measuring NO. emissions discharged to the atmosphere :..., units

IblMW-hr, IblMMBtu and lb/hr. The NO. monitoring system shall consist oftt.-;

fonowing:

i) A continuous emission NO. monitor located in the PC boiler stack

ii) A continuous flow monitoring system for measuring the flow of exhaust gases

discharged into the atmosphere.

iii) A watt meter to measure gross electrical output in megawatt-hours on a

continuous basis.

iv) An in-stack oxygen or carbon dioxide monitor for measuring oxygen or

carbon dioxide content ofthe flue gas at the location NO. emissions are

monitored.

B) Black Hills Corporation shall install, calibrate. operate, and maintain a S02 monitoring

system, and record the output ofthe system, for measuring emissions discharged to the

atmosphere in units of IbIMMBtu, lb/hr and measuring the control efficiency of the S02

control device. The S02 monitoring system shall consist ofthe f?l1owing:

i) Continuous emission S02 monitors located at the inlet and outlet to the S02

control device.

ii) A continuous flow monitoring system for measuring the flow of exhaust gases

discharged into the atmosphere.

iii) An in-stack oxygen or carbon dioxide monitor for measuring oxygen or

carbon dioxide content ofthe flue gas at the location of each SO~ monitor.

C) Black Hills Corporation shall install, calibrate, operate, and maintain a monitoring

system, and record the output of the system, for measuring the opacity ofthe emissions

discharged to the atmosphere.

D) Each continuous monitor system listed in this condition shall comply with the following:

i) NSPS Subpart Da, Standards of Performance for Electric Utility Steam

Generating Units (40 CFR 60.47a).

ii) Monitoring requirements of WAQSR, Chapter 5, Section 2m including the

following:

a) 40 CFR 60, Appendix B, Performance Specification I for opacity,

Performance Specification 2 for NO, and SO!' and Performance

TB002599
Black Hills Corp<lration (WYGEN 2)

Permit Application Analysis, NSR-AP-C92

Page 50

Specification 3 for O2or CO2, The monitoring systems must

demonstrate linearity in accordance with Division requirements and be

certified in both concentration (ppm) and units ofthe standard

(lblMMBtu, IblMW-hr and lblhr).

b) Quality Assurance requirements c~ 40 CFR 60, Appendix F.

c) Black Hills Corporation shall de'!~20p and submit for the Division's

approval a Quality Assurance pl~_ for the monitoring systems listed in

this condition.

14. Following the initial performance tests, compliance with t--~ limits set forth in this permit shall

be determined with data from the continuous monitoring bjstems required by Condition 13 of

this permit as follows:

A) Exceedances ofthe limits shall be defined as foIlco's:

i) Any 30-dax__~"01ling average of NO, eL_ "3ions which exceedsJIJ~JblMW-hr

output-based standard or IblMMBtu 1:' ":t calculated in accordance 40 CFR

Part 60. Subpart Da, 60.46a, 6O.47a, 60.48a. Any 30-day rolling average

which exceeds the lblhr NO. limit as calculated following the methodology in

Subpart Da for the IblMMBtu emission limit.

ii) Any calculated 2-hour block average of S02 emissions as measured by the PC

Boiler stack S02 outlet CEM which exceeds the IblMMBtu or lblhr limit

established in this permit. The 2-hour average emission rate shall be

determIned at the endOfeacn "i-hour operating block,and calculated"as the

arithmetic average ofthe previous two operating hours S02 stack emission

rates.

iii) Any 30-day rolling average which exceeds the Ib/MMBtu S02 limit and the

percent reduction requirements calculated in accordance 40 CFR Part 60,

Subpart Da, 60.46a, 60.47a, and 60.48a. Any 30-day rolling average which

exceeds the lblhr S02 limit as calculated following the methodology in

Subpart Da for the IblMMBtu emission limit.

iv) Any 6-minute average opacity, except for one 6-minute period per hour of not

more than 27 percent opacity, in excess of 20 percent in accordance with

NSPS, Subpart Da, 40 CFR 60,42a(b).

B) Black Hills Corporation will comply with all reporting and record keeping requirements

as specified in WAQSR, Chapter 5, Section 2(g) and 40 CFR Part 60, Subpart Da.

Reporting and record keeping requirements for the 30-day rolling lblhr NO. and S02 and

2-hour fixed S02 emission rates shall follow the same requirements as the NSPS

IblMMBtu standards.

TB002600
Black Hills Corporation (WYGEN 2)

Permit Application Analysis, NSR-AP-Cn

Page 51

15. Black Hills Corporation sr.~:: comply with all applicable requirements of 40 CFR 60 Subpart Da

and Subpart Y.

16. Black Hills Corporation sl:~.:l install, operate, and maintain a loading spout designed to minimize

fugitive dust from loading .7:D waste. The loading spout shall have an outer sleeve for dust

withdrawal or equivalent ac. .. shall be connected to the FGD Waste Loadout Silo baghouses

(RDC-002A, RDC-002B) ·c.) :ninimize fugitive dust

17. To minimize transport emissions, lime and FGD waste shall be entirely enclosed in the haul

trucks. Unpaved haul roads will be treated with suitable chemical dust suppressants in addition

to water to control fugitive dust emissions. All treated roads will be maintained on a continuous

basis to the extent that the surface treatment remains viable as a control measure.

18. Black Hills Corporation shall comply with acid rain program regulations in WAQSR, Chapter

11, Section 2.

19. That Black Hills Corporation shall continue to operate in accordance with the requirements of 40 _

----------eFRi>ans--50-and 58 an approved'amolent S02 monitoring program. The monitor shall be

operated through September of2002 and shall resume upon startup ofWYGEN 2. Data

generated shall be submitted in an approved format on a quarterly basis, within 60 days

following the end of the quarter. A quality assurance plan for the monitoring network.. as

required by 40 CFR Part 58, shall be submitted for approval within 30 days of startup of

WYGEN2.

20. Records required by any applicable regulation or permit condition shall be maintained for a

minimum-perioo1:'ffivei-5) years.md shallberea-auyaccessi01e to Division representatives,

TB002601