### DEPARTMENT OF ENVIRONMENTAL QUALITY AIR QUALITY DIVISION

Revised NO

x 

### BART Impact Analysis

AP

- 604 7 A

January 3, 2011

NAME OF FIRM: Basin Electric Power Cooperative

NAME OF FACILITY: Laramie River Station

FACILITY LOCATION: 347 Grayrocks Road

Platte County (Wheatland) , Wyoming
UTM Zone 13, NAD 27:

509

, 9 00 m E ; 4

, 661

, 675 m N

TYPE OF OPERATION: Electric Power Generating Station

RESPONSIBLE OFFICIAL: Mr. Robert Eriksen

MAILING ADDRESS: 1717 East Interstate Avenue Bismarck, North Dakota 58503

TELEPHONE NUMBER: ( 701 ) 355

- 565 4

REVIEW ER S : Cole Anderson , Air Quality Engineer Josh Nall, Air Quality Modeler

1. INTRODUCTION

The Division of Air Quality of the Wyoming Department of Environmental Quality issued NO

x 

### and PM Best Available Retrofit Technology (BART) determinations for Basin Electric Power Cooperative’s (Basin Electric) Laramie River Station in Air Quality Permit MD

- 6047 . The permit w as issued on December 31, 200 9

. On March 8, 2010, Basin Electric filed an appeal and petition for review with the Wyoming Environmental Quality Council (EQC), in accordance with Chapter I, Section 16, of the Department of Environmental Quality’s General Rules of Practice

and Procedure. Basin Electric appeal ed Air Quality Permit MD

- 6047 and petition ed EQC to
review the AQD’s p ermit Condition 16 regarding additional add

- on NO

x 

### controls. Permit

c onditions 1 through 15 were not subject to appeal or protest. EQC established Docket No. 10

- 28 02 for the appeal and petition for review. Basin Electric and the AQD entered into settlement negotiations and through negotiation were able to reach a settlement. On November 16, 2010, the AQD and Basin Electric filed a proposed settlement with the EQC. A copy of the settlement is attached as Appendix A. Subsequently, EQC issued two orders, one approving the settlement agreement and staying appeal pending final dismissal and one denying Basin Electric’s motion for summary judgment, on November 19, 2010

.

This analysis presents a summary of modeling conducted to predict visibility impacts fr om the

BART emissions levels associated with the s ettlement a greement

. Additional NO

x 

### emissions

reductions achieved in the settlement, which are beyond BART

, are discussed in the Long

- T erm S trategy section of this analysis.Laramie River Station

AP

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x BART Impact Analysis Page 2



### 2

. REVISED IMPACT ANALYSIS

Modeling was conducted by the AQD using the EPA CALPUFF modeling system

, with the same CALMET/CALPUFF/CALPOST setup that was used for previous BART modeling of the LRS. In particular, the AQD used the larger CALMET windfield that was described on Page 24 and shown in Figure 3 of the AQD’s BART Application Analysis for MD

- 6047 (May 28, 2009). Although this larger CALMET windfield included Rawah Wilde rness Area and Rocky Mountain National Park in Colorado, previous refined CALPUFF modeling by the AQD showed that predicted visibility impacts at these two Class I areas were less than 0.5 dv for the baseline

scenario for each of the three units at the LRS , and therefore the AQD focused on Wind Cave and

Badlands national parks in South Dakota for the modeling described here. Visibility modeling was conducted for the following emissions scenarios :

• Baseline from the BART Application Analysis for MD

- 6047

• NO

x 

### emissions from BART Permit MD

- 6047 (0.23 lb/MMBtu, 30

- day rolling)

• NO

x 

### emissions from BART Settlement Agreement (0.21 lb/MMbtu, 30

- day rolling)

• NO

x 

### Add

- On Control s (SCR)

INTENTIONALLY LEFT BLANKLaramie River Station

AP

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x BART Impact Analysis Page 3



### Tables 2

- 1 and 2

- 2 list the modeling parameters and emission rates that were used for the modeling for Units 1 through 3 at the LRS.

Table 2

- 1 : Baseline Source Parameters

Parameter Unit 1: LNB, WFGD, ESP Unit 2: LNB, WFGD, ESP Unit 3: LNB, DFGD, ESP

Heat Input (MMBtu/yr) 46,814,433 46,557,738 47,765,529

Base Elevation (m) 1348 1348 1348

Stack Height (m) 184.4 184.4 184.40

Stack Diameter (m) 8.69 8.69 8.69

Stack Temperature (K) 338.7 338.7 352.0

Exit Velocity (m/s) 21.33 21.03 22.25

SO 2 Emissions (lb/MMBtu) 0.16 0.16 0.17

SO 2 Emissions (tpy) 3745 3725 4060

HS 2 O 4 Emissions (tpy) 3.06 2.8 0 0.22

NO

x Emissions (lb/MMBtu) 0.27 0.27 0.27

NO

x Emissions (tpy) 6320 6285 6448

PM Fine Emissions (lb/MMBtu) 0.03 0.03 0.03

PM Fine Emissions (tpy) 702 698 716

Note : Boiler h eat input and lb/MMBtu emissions for NO

x and SO 2 based on continuous emissions monitoring (CEM) annual average s for 2001

- 2003

.

DFGD = dry flue gas desulfurization ESP = electrostatic precipitator

H 2 SO 4 = sulfuric acid

K = Kelvin lb/MMBtu = pounds per million British thermal units

LNB = low

- NO

x burners

m = meters m/s = meters per second

MMBtu/ yr = million British thermal units per year NO

x = nitrogen oxides PM = particulate matter

SO 2 = sulfur dioxide

tpy = tons per year WFGD = wet flue gas desulfurizationLaramie River Station

AP

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x BART Impact Analysis Page 4



### Table 2

- 2 : Source Parameters and Emissions for BART Control Options

Parameter NO

x Emissions from New LNB +

OFA Scenario from MD

- 6047 Application Analysis NO

x Emissions from BART Settlement Agreement

Unit 1 Unit 2 Unit 3 Unit 1 Unit 2 Unit 3

Base Elevation (m) 1348 1348 1348 1348 1348 1348

Stack Height (m) 184.4 184.4 184.4 184.4 184.4 184.4

Stack Diameter (m) 8.69 8.69 8.69 8.69 8.69 8.69

Stack Temperature (K) 338.7 338.7 352.0 338.7 338.7 352.0

Exit Velocity (m/s) 21.33 21.03 22.25 21.33 21.03 22.25

SO 2 Emissions (lb/MMBtu) 0.16 0.16 0.17 0.16 0.16 0.17

SO 2 Emissions (tpy) 3745 3725 4060 3745 3725 4060

H 2 SO 4 Emissions (tpy) 3.18 3.25 0.22 3.18 3.25 0.22

NO

x Emissions (lb/MMBtu) 0.23 0.23 0.23 0.2 1 0. 2 1 0. 2 1

NO

x Emissions (tpy) 5384 5354 5493 4916 4889 5015

PM Fine Emissions (lb/MMBtu) 0.03 0 0.03 0 0.03 0 0.03 0 0.03 0 0.03 0

PM Fine Emissions (tpy) 702 698 716 702 698 716

H 2 SO 4 = sulfuric acid

K = Kelvin lb/MMBtu = pounds per million British thermal units

LNB = low NO

x burners

m = meters m/s = meters per second

NO

x = nitrogen oxides

OFA = overfire air PM = particulate matter SCR = selective catalytic reduction

SO 2 = sulfur dioxide

tpy = tons per y ear



### INTENTIONALLY LEFT BLANKLaramie River Station

AP

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x BART Impact Analysis Page 5



### Table 2

- 2 : Source Parameters and Emissions for BART Control Options (cont.)

Parameter NO

x Control: SCR

Unit 1 Unit 2 Unit 3

Base Elevation (m) 1348 1348 1348

Stack Height (m) 184.4 184.4 184.4

Stack Diameter (m) 8.69 8.69 8.69

Stack Temperature (K) 338.7 338.7 352.0

Exit Velocity (m/s) 21.33 21.03 22.25

SO 2 Emissions (lb/MMBtu) 0.16 0.16 0.17

SO 2 Emissions (tpy) 3745 3725 4060

H 2 SO 4 Emissions (tpy) 3.18 3.25 0.22

NO

x Emissions (lb/MMBtu) 0.07 0.07 0.07

NO

x Emissions (tpy) 1639 1630 1672

PM Fine Emissions (lb/MMBtu) 0.03 0 0.03 0 0.03 0

PM Fine Emissions (tpy) 702 698 716

H 2 SO 4 = sulfuric acid

K = Kelvin lb/MMBtu = pounds per million British thermal units

LNB = low NO

x burners

m = meters m/s = meters per second

NO

x = nitrogen oxides

OFA = overfire air PM = particulate matter SCR = selective catalytic reduction

SO 2 = sulfur dioxide

tpy = tons per year



### INTENTIONALLY LEFT BLANKLaramie River Station

AP

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x BART Impact Analysis Page 6



### Table 2

- 3 presents a summary of the results of the visibility modeling in terms of the 98 th


### percentile delta deciview ( dv ) levels and the number of days with predicted impacts above 0.5 dv for each of the four modeling scenarios. Figures 2

- 1 and 2

- 2 present the results graphi cally.

Table 2

- 3 : CALPUFF Visibility Modeling Results for Laramie River Station

Class I Area Unit 1 Unit 2 Unit 3

98th

Percentile

Value (Δdv) No. of Days > 0.5

Δdv 98th

Percentile

Value (Δdv) No. of Days > 0.5

Δdv 98th

Percentile

Value (Δdv) No. of Days > 0.5

Δdv

Baseline

– LNB, Wet FGD, ESP :

Badlands NP 0.73 14.7 0.73 14.7 0.74 14.3

Wind Cave NP 0.72 14.0 0.72 14.0 0.73 14.0

NO

x from December 2009 BART Permit (MD

- 6047) :

Badlands NP 0.66 10.7 0.65 11.3 0.67 12.3

Wind Cave NP 0.66 11.0 0.66 11.0 0.66 11.7

NO

x from November 2010 Settlement Agreement :

Badlands NP 0.62 9.0 0.61 9.0 0.63 10.7

Wind Cave NP 0.62 9.7 0.63 9.7 0.62 10.7

Add

- On NO

x Control

– SCR :

Badlands NP 0.34 4.3 0.35 4.3 0.36 4.7

Wind Cave NP 0.39 4.0 0.39 4.0 0.40 4.7

Note: Modeling results represent the three

- year average of results using 2001

- 2003 meteorology

.



### INTENTIONALLY LEFT BLANKLaramie River Station

AP

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x BART Impact Analysis Page 7



### Figure 2

- 1: Modeled BART Impacts: Number of Days > 0.5 delta

- dv

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0

LRS U1 LRS U2 LRS U3 LRS U1 LRS U2 LRS U3(# Days) 

### Baseline

Initial BART

BART Settlement

SCR

(Modeling results represent the three

- year average using 2001

- 2003 meteorology) 

### LRS U1 = Laramie River Station Unit 1 (550 MW)
LRS U2 = Laramie River Station Unit 2 (550 MW)
LRS U3 = Laramie River Station Unit 3 (550 MW)



## ----------------- Badlands

------------------- ----------------- Wind Cave

------------------Laramie River Station

AP

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x BART Impact Analysis Page 8



### Figure 2

- 2: Modeled BART Impacts: 98 th 

### Percentile (delta

- dv)

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80

LRS U1 LRS U2 LRS U3 LRS U1 LRS U2 LRS U3(Delta-dv) 

### Baseline

Initial BART

BART Settlement

SCR

(Modeling results represent the three

- year average using 2001

- 2003 meteorology) 

### LRS U1 = Laramie River Station Unit 1 (550 MW)
LRS U2 = Laramie River Station Unit 2 (550 MW)
LRS U3 = Laramie River Station Unit 3 (550 MW)

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

## Badlands

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

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

## Wind Cave

----------------------Laramie River Station

AP

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x BART Impact Analysis Page 9



### 3

. BART IMPACTS

After considering Basin Electric’s proposed new NO

x 

### BART levels in relation to all five statutory BART factors, the AQD noted the following impacts to the standing B ART determination of the installation and operation of new low NO

x 

### burners and overfire air for each of the three unit s a t the Laramie River

Station :

1. The NO

x 

### control level of 0. 21 lb/MMBtu on a 30

- day rolling average is lower than EPA’s established presumptive limit fo r dry

- bottom, wall

- fired boilers burning sub

- bituminous coal.

2. The 3

- year averaged cumulative visibility improvement as compared to the baseline across Wind

Cave NP and Badlands NP achieved with new LNB with OFA at the 30

- day limit of 0. 21 lb/MMBtu (based on the 98 th 

### percentile modeled results) was 0. 21

- 0.22 Δdv from each of the

three units. The e xpected visibility improvement over the course of a full annual period would be even greater due to the annual BART limit that is based on 0.1 7 lb/MMBtu.

3. Annual NO

x 

### emission reductions from baseline achieved in the settlement from the installation of

new LNB with OFA on Units 1, 2, and 3 are 1, 508

- 1, 540 tons per unit for a total annual reduction

of 4,580 tons.

4. The 3

- year averaged cumulative visibility improvement for SCR

, above the improvement achieved by new LNB with OFA

, summed across Wind Cave NP an d Badlands NP (based on the

98 th 

### percentile modeled results) was 0. 49

- 0.5 1 Δdv fo r each of the three units.

Unit

- by

- unit NO

x 

### BART levels from settlement :

Laramie River Unit 1 : 0.2 1 lb/MMBtu (30

- day rolling average)

, 1, 220 lb/hr (30

- day rolling average)

, and 4

, 780 tpy (12

- month rolling) as BART for NO

x 

### .

Laramie River Unit 2 : 0.2 1 lb/MMBtu (30

- day rolling average)

, 1, 220 lb/hr (30

- day rolling average)

, and 4,780 tpy (12

- month rolling) as BART for NO

x 

### .

Laramie River Unit 3 : 0.2 1 lb/MMBtu (30

- day rolling average)

, 1, 254 lb/hr (30

- day rolling average)

, and 4,914 tpy (12

- month rolling) as BART for NO

x 

### .

The performance/efficiency

- based , 30

- day rolling average emission rate of 0.2 1 lb/MMBtu is set to allow for continuous compliance with proper operation of the control equipment, while taking into account the normal operational variability that is typical for a boiler. The 30

- day limits that are expressed in terms of mass emissions (lb/hr) are based on 0. 19 lb/MMBtu. Because reduce d steam loads on a boiler can result in periods of in creased emissions in terms of lb/MMBtu but lower emissions in terms of lb/hr, the AQD

has chosen to set the dual 30

- day limits, one set at 0.2 1 lb/MMBtu and one expressed in lb/hr based on

0.1 9 lb/MMBtu. For the 12

- month rolling emission limits, the AQD considered the ability of the source

to maintain a lower mass emission rate over a longer time period and set the long

- term limit (expressed in tpy) based on 0.1 7 lb/MMBtu.Laramie River Station

AP

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x BART Impact Analysis Page 10



### 4. LONG

- TERM STRATEGY FOR REGIONAL HAZE

Additional NO

x 

### emission reductions were required under the Long

- Term Strategy of the Wyoming § 309(g) Regional Haze SIP and were based on the AQD’s extensive BART analysis. Based on the costs and visibility improvement presented by Basin El ectric in the BART applications for Laramie River

Station Units 1

- 3, and taking into consideration the logistical challenge of managing multiple pollution control installations within the regulatory timeframe allotted for BART, the AQD requir ed installatio n of

two SCR ( or equivalent performing ) emission control systems under the Long

- Term Strategy (LTS) of the Wyoming Regional Haze State Implementation Plan. Each proposed add

- on NO

x 

### control would

achieve an emission rate, on an individual unit basis, at or below 0.07 lb/MMBtu on a 30

- day rolling

average. Additional add

- on controls were required to be installed and operational on one of the Laramie River Station units by December 31, 2018 and on a second Laramie River Station unit by December 31,

2023. The requirement to install additional add

- on NO

x 

### control was contained in permit condition 16 of Air Quality Permit MD

- 6047.

Upon entering into the settlement agreement, the AQD agreed to remove condition 16 from Air Quality

Permit MD

- 6047, thereby removing the requirement for Basin Electric to install additional add

- on NO

x 

### controls by December 31, 2018 and December 31, 2023. The AQD agreed to remove condition 16 because Basin Electric agreed to additional NO

x 

### emissions reductions, which are contained in Sections
7C, 7D, 7E , and 7F of the settlement. Lower BART levels, as evaluated in this analysis, are stipulated in Section 7C. Section 7D contains an agreement whereby Basin Electric will further reduce NO

x 

### emissions below the levels proposed in Section 7C. By December 31, 2017, NO

x 

### emissions from the three boilers will be reduced from 14,474 tons to 12,773 tons for a net reduction of 1,701 additional tons. In doing so, the AQD agrees to not require further NO

x 

### r eductions from Units 1

- 3 for the purposes of meeting BART

or the Long

- Term Strategy requirements and/or Reasonable Progress goals in the Wyoming Regional Haze SIP through December 31, 2018. Additional requirements may be imposed, for the purposes of regional haze, after 2018. In accordance with Section 7F, Basin Electric will submit a permit application by December 31, 2015, requesting to incorporate the 12,773 tons NO

x 

### limit for the three boilers into a permit. If Basin Electric determines that additional NO

x 

### control technology is required in order to comply with the 12,773 tons limit, then a demonstration that such control technology will be operated at the designed performance levels is required in the application under Section 7E.

By entering into a settlement with Basin Electric, the AQD h as secured additional reductions beyond

those achieved in Air Quality Permit MD

- 6047 during the first planning period (20 0 8

- 2018). Under the

initial NO

x 

### BART /LTS scenario, the AQD would have reduced NO

x 

### emissions during the period of 2013

- 2019 by 20,64 6 tons. NO

x 

### emissions for the same period will now be reduced by 30,88 7 tons, an additional reduction of 10,24 1 tons, in accordance with the settlement agreement. Figure 4

- 1 depicts the

reductions on an annual basis. And while the AQD has committed to no t requiring additional NO

x 

### reductions for purposes of regional haze during the 20 08

- 2018 planning period, additional reduction may be necessary from the Laramie River Station in subsequent planning periods.Laramie River Station

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x BART Impact Analysis Page 11



### Figure 4

- 1: Annual NO

x 

### Emission Reductions from Units 1

- 3 ( tons )

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000

2013 2014 2015 2016 2017 2018 2019NOxReduction from Baseline (tons) Initial

Settlement

Total Reduction

from Baseline
(2013

- 2019)

Initial: 20,646 tons
Settlement: 30,887 tons

# Appendix A

Copy of Settlement Agreement Between Wyoming Department of Environmental Quality, Air Quality Division,

and Basin Electric Power Cooperative