Best Available Retrofit Technology 

(BART) Exemption Modeling Results 

for the: 

ConocoPhillips Alaska Natural Gas Corporation 

(CPANGC) BART-Eligible Sources 

prepared for: 

ConocoPhillips Alaska Inc. 

prepared by: 

April 2008 
Best Available Retrofit Technology (BART) 

Exemption Modeling Results for the ConocoPhillips 

Alaska Natural Gas Corporation (CPANGC) 

BART-Eligible Sources 

April 2008 

prepared for 

ConocoPhillips Alaska Inc. 

Anchorage, Alaska

prepared by 

Hoefler Consulting Group 

3401 Minnesota Dr., Suite 300 

Anchorage, Alaska 99503 

(907) 563-2137 
Page 1 

Best Available Retrofit Technology (BART) Exemption Modeling Results 

for the ConocoPhillips Alaska Natural Gas Corporation (CPANGC) 

BART-Eligible Sources 

Summary

With the enactment of the Regional Haze Rule, the United States Environmental 

Protection Agency (EPA) and state and local agencies have established a mechanism to 

address certain existing sources of air pollutant emissions that are shown to contribute to 

visibility impacts within Class I areas. This Best Available Retrofit Technology (BART) 

requirement applies to any BART-eligible source that ‘‘emits any air pollutant which may 

reasonably be anticipated to cause or contribute to any impairment of visibility” in any 

mandatory Class I area. 

Under 40 Code of Federal Regulation (CFR) Part 51, Appendix Y (BART guideline), a 

BART-eligible source is considered to “contribute” to visibility impairment in a Class I area 

if the modeled change in deciviews is equal to or greater than the “contribution threshold.” 

Any BART-eligible source determined to cause or contribute to visibility impairment in any 

Class I area is subject to BART. Based on current regulatory guidance, a “contribution 

threshold” of 0.5 deciviews (dv) is the threshold at which modeled BART eligible source 

may contribute to visibility impairment. 

A state has the option to exempt potentially BART-eligible sources from the BART 

requirements if a demonstration can be made that the source cannot reasonably cause or 

contribute to visibility impairment in a Class I area. States, including Alaska, have 

established criteria and procedures for identifying BART-eligible sources. The Alaska 

Department of Environmental Conservation (ADEC) has developed regulations regarding 

BART-eligible sources (18 AAC 50.260, effective December 30, 2007). 

ADEC has identified eleven CPANGC Alaska Kenai Liquefied Natural Gas (LNG) Plant 

emission units as being BART-eligible sources1

. In accordance with 18 AAC 50.260, 

CPANGC has requested an exemption from BART regulations. The exemption request 

was based on the likelihood that dispersion modeling would demonstrate that the 

emissions from the Kenai LNG Plant emission units would not cause or contribute to 

visibility impairment in any Class I area. A modeling protocol was submitted to ADEC in 

February 2008 and approved later that month. 

The emissions from the Kenai LNG Plant BART-eligible emission units have been 

modeled. The modeling results at the Denali Class I area are less than the contribution 

 

1

 CPANGC acknowledges but disagrees with the identification of the Kenai LNG Plant as a source subject 

to BART. 
Page 2 

threshold of 0.5 dv. The modeling results are slightly above the contribution threshold at 

the much closer Tuxedni Class I area. 

Background

In 2007, the ADEC developed a list of Alaska BART-eligible sources based on the federal 

BART guidelines, conducted preliminary dispersion modeling of these BART-eligible 

sources, and released the results of a regional BART screening analysis that included all 

BART-eligible sources in the state. 

The modeling was completed by the Western Regional Air Partnership (WRAP) on behalf 

of ADEC. The simulations were done using CALPUFF and a single year, 2002, of 

processed MM5 CALMET data. The simulations were performed to evaluate whether the 

BART-eligible sources were subject to a BART determination based on predicted impacts 

to visibility within two Alaska Class I areas, the Tuxedni National Wildlife Refuge 

designated as a National Wilderness Area (Tuxedni) and the Denali National Park 

including the Denali Wilderness but excluding Denali National Preserve (Denali). As noted 

above, BART-eligible sources are exempt from BART if the visibility impacts are below 

screening criteria set by ADEC, EPA, and the Federal Land Managers (FLMs). Nonexempt BART-eligible sources are potentially subject to costly additional pollution controls 

on the certain BART-eligible emission units. 

WRAP used the CALPUFF modeling system to assess BART-eligible emission units 

based on the 15 kilometer (km) MM5 output data for 2002. The CALPUFF model grid 

spacing was 2 km, significantly different than the MM5 grid spacing of 15 km. In addition, 

because only one year was simulated, BART exemption simulations performed by WRAP 

used the highest modeled visibility degradation, not the 98th percentile as allowed under 

EPA guidance. 

 

Of the BART-eligible sources, twelve Kenai LNG Plant emission units were identified in the 

ADEC BART assessment as being BART-eligible sources based on definition and 

modeled visibility impact. Based on a requested review of BART-eligible sources, ADEC 

removed one of the Kenai LNG Plant emission units from BART eligibility (May 7, 2007 

letter from ADEC to Marta Czarnezki), leaving a total of eleven emission units potentially 

subject to BART. 

Despite the ADEC modeling findings of significant impacts, CPANGC believed that these 

impacts are overly conservative, requested an exemption from BART, and submitted a 

modeling protocol to demonstrate that impacts from Kenai LNG Plant BART-eligible 

sources would not exceed threshold levels at the Class I areas, exempting the Kenai LNG 

Plant emission units from BART. 
Page 3 

Modeling Overview

The Kenai LNG Plant BART exemption modeling included the following elements: 

• Three-years of Geomatrix-updated MM5 and processed CALMET files; 

• The most recent EPA-approved version of CALPUFF (5.8); 

• Daily maximum emission estimates; 

• Exhaust parameters reflecting daily firing; 

• Appropriate background values for ozone and ammonia; and 

• Use of the 98th percentile visibility value to assess impact at both Tuxedni and 

Denali. 

During discussions with ADEC, the owners of many of the Alaska BART-eligible sources 

agreed to fund Geomatrix to develop two additional years of CALMET meteorological 

data, so that the appropriate 98th percentile values could be used in determining impacts 

within Class I areas. Geomatrix provided 3-years of processed CALMET data (2002 

through 2004) in accordance with an ADEC approved protocol. These CALMET data 

were used in the analysis. 

EPA has recently released an updated approved version of CALPUFF and the associated 

suite of processors (version 5.8). This version and the associated pre- and postprocessors were used in the BART exemption visibility assessment. The CALPUFF 

modeling system consists of three main processors, CALMET, CALPUFF, and CALPOST. 

CALMET is the meteorological model that generates hourly three-dimensional 

meteorological fields of variables such as wind and temperature. CALPUFF simulates the 

transport, dispersion, and transformation of pollutants emitted from an emission unit and 

calculates hourly concentration values for visibility impairing compounds at each receptor 

located in the modeling domain. CALPOST calculates time-averaged concentration 

values from the CALPUFF predictions and performs visibility calculations. 

Visibility impacts are determined on a daily basis. Therefore, modeled BART emission 

rates and exhaust parameters reflect the actual maximum daily source operating 

scenarios. The Kenai LNG Plant BART-eligible turbine emissions were modeled based on 

the conservative assumption that the turbines operated up to their compressor limited rate 

with inlet air pre-heating. Because emissions from the BART-eligible turbines cause 

approximately 96 percent of the modeled visibility impacts, the other Kenai LNG Plant 

BART-eligible emission units were modeled using the average daily emissions. These 

average daily emissions are the best reasonably available emission rates. 

Other inputs included appropriate background concentrations of ammonia (0.5 parts per 

billion [ppb]) and hourly ozone data from Denali National Park with missing values filled 

using 40 ppb. 
Page 4 

Once CALPUFF was run and values have been determined at each receptor in the Class I 

areas, the post-processor CALPOST was used to estimate the maximum daily change in 

visibility associated with the Kenai LNG Plant modeled emission units as compared to 

natural background conditions at both Tuxedni and Denali. Changes in visibility are 

provided by the model in delta-deciview units. The 98th percentile maximum impact was 

compared with the exemption threshold of 0.5 delta-deciviews. 

CALPUFF Modeling Inputs and Results

The CALPUFF model emission unit parameters are shown in Table 1. These parameters 

were developed from the inputs shown in Table 2 (turbine inlet temperature and 

compressor limited characteristics) and Table 3 (emission rate calculations). The modeled 

parameters previously used in the ADEC-sponsored WRAP analysis are provided in Table 

4. 

The 12 monthly CALMET files for each year were sequentially read in a single year long 

run by setting NMET = 12. Hourly ozone data for Denali was obtained from the EPA 

CASTNET website for each year. Any missing values were filled with 40 ppb and 

formatted into the updated ozone.dat format. Default settings were used. 

Two separate modeling runs were done, one for each Class I area. Because the settings 

of the modeling domain exceeded the default values in the EPA version of CALPUFF, the 

executables were recompiled to conform to the Geomatrix grid settings (mx = 270, my = 

325). The computational grid for the Denali runs maintained the larger domain (270 by 

325), whereas the runs for Tuxedni used a smaller computational grid (200 by 200). 

CALPUFF was run for each year of the three year period and concentration, deposition, 

and visibility files were saved. The values in these files were subsequently used as input 

to CALPOST to determine visibility impacts. 

The impact of the Kenai LNG Plant modeled emission units was calculated from the daily 

visibility values for each receptor by determining the change in deciviews compared 

against natural visibility conditions. Relative humidity can play an important role in 

atmospheric visibility as sulfates and nitrates accrete water and scatter more light at higher 

humidities. The relative humidity factor values listed in Guidance for Estimating Natural 

Visibility Conditions Under the Regional Haze Rule, EPA-454/B03-005 (September 2003) 

were applied and those values used are shown in Table 5. To determine whether a 

source may reasonably be anticipated to cause or contribute to visibility impairment at a 

Class I area, the impacts predicted by CALPUFF are compared against the pertinent 

natural visibility background and the selected threshold. 
Page 5 

The locations of the modeled Kenai LNG Plant emission units relative to the Class I area 

receptors is shown in Figure 1. Also depicted is the extent of the CALPUFF modeling 

domain and the terrain used in the analysis. As seen in Figure 1, the Tuxedni Class I area 

is much nearer the Kenai plant site, but much more confined than the farther away but 

much larger Denali receptor grid. Receptor heights and locations were obtained from FLM 

files. 

CALPOST was run using Method 6 (MVISBK=6) for calculating extinction. The monthly f 

(RH) adjustment factors listed in Table 5 were applied directly to the background and 

modeled sulfate and nitrate concentrations, as recommended in the BART guidelines. 

The EPA BART guidance recommends that the threshold value for defining whether a 

source “contributes” to visibility impairment is 0.5 dv change from natural conditions. 

Alaska has opted to use the 0.5 dv threshold. 

Results of the modeling are shown in Table 6 in deciviews for each year for each Class I 

area. As shown in the table, none of the 98th percentile deciview values exceed the 

threshold at the many Denali receptors that were modeled. Therefore, the Kenai LNG 

Plant BART-eligible sources are exempt from BART regulations for the Denali Class I 

area. 

The results at the more proximate Tuxedni receptors suggest the potential to affect 

visibility exists because the 98th percentile values exceed the contribution threshold value 

of 0.5 deciviews. CPANGC believes these results to be conservative, given the modeling 

approach and the fact that the highest impacts occur during winter conditions which tend 

to naturally limit visibility. 

 

Modeling Files

The CALPUFF and CALPOST input and list files are provided on CD for each Class I 

area. The re-compiled executables are also provided. Geomatrix has already supplied 

ADEC with the CALMET files used in the analysis. 
Page 6 

Table 1. Kenai LNG Plant - BART-Eligible Modeled Source Parameters 

Model Location (LCC) Emissi

ID 

Emission 

Unit X (km) Y (km) 

Stack 

Height 

(m) 

Base 

Elevation 

(m msl) 

Stack 

Diameter 

(m) 

Exit 

Velocity 

(m/s) 

Exit Temp 

(K) 

Downwash 

SO2 SO4 NO

AK37 

GE Frame 5 

Turbine 

#151 

-20.886 186.612 21.34 36.6 2.15 42.5 657 0 0 0 6.53 

AK38 

GE Frame 5 

Turbine 

#152 

-20.887 186.612 21.34 36.6 2.15 42.5 657 0 0 0 6.5

AK39 

GE Frame 5 

Turbine 

#251 

-20.883 186.612 21.34 36.6 2.15 51.4 714 0 0 0 8.8

AK40 

GE Frame 5 

Turbine 

#252 

-20.884 186.612 21.34 36.6 2.15 51.4 714 0 0 0 8.8

AK41 

GE Frame 5 

Turbine 

#351 

-20.886 186.612 21.34 36.6 2.15 41.9 680 0 0 0 6.4 

AK42 

GE Frame 5 

Turbine 

#353 

-20.887 186.612 21.34 36.6 2.15 41.9 680 0 0 0 6.4 

AK44 Erie City 9M Boiler #501 -20.878 186.612 18.98 36.6 0.97 9.71 460.9 0 0 0 0.32 AK45 Erie City 9M Boiler #502 -20.878 186.612 18.98 36.6 0.97 9.71 460.9 0 0 0 0.3 AK46 Erie City 9M Boiler #511 -20.877 186.612 18.98 36.6 0.97 9.51 460.9 0 0 0 0.3AK47 

Cat D-379 

Emergency 

Generator 

-20.879 186.612 4.27 36.6 0.2 32.9 749.8 0 0.11 0 0.4

AK48 

Ground 

Flare 

(including 

pilot) 

-20.9 186.644 0.91 36.6 13.7 0.001 1273 0 0 0 0.32 
Page 7 

Table 2. Kenai LNG Plant – BART-Eligible Turbine Emission Parameters – 

Compressor Limited – Pre-heat Inlet 

Amb 

Temp 

Intake 

Temp 

Power 1 HC 2 Exh Flow Exh Temp Velocity NOX 

(° F) (° F) (bhp) (MMBtu/hr) (lb/hr) (° K) (m/sec) (g/sec) 

GE Frame 5 Turbines #151 and #152 – Model ID AK 37 and AK38 

-35.5 40 13,166 151.5 631,954 677 42.46861 6.5305 

-26.5 40 13,166 151.5 631,954 677 42.46861 6.5305 

-17.5 40 13,166 151.5 631,954 677 42.46861 6.5305 

-8.5 40 13,166 151.5 631,954 677 42.46861 6.5305 

0.5 40 13,166 151.5 631,954 677 42.46861 6.5305 

9.5 40 13,166 151.5 631,954 677 42.46861 6.5305 

18.5 40 13,166 151.5 631,954 677 42.46861 6.5305 

27.5 40 13,166 151.5 631,954 677 42.46861 6.5305 

36.5 40 13,166 151.5 631,954 677 42.46861 6.5305 

45.5 45.5 13,166 151.7 628,000 684 42.60017 6.5412 

54.5 54.5 13,166 152.2 621,673 694 42.81419 6.5586 

63.5 63.5 13,166 152.6 615,516 705 43.02667 6.5759 

72.5 72.5 13,166 153.0 609,522 715 43.23764 6.5931 

81.5 81.5 13,166 153.3 603,684 725 43.44715 6.6101 

GE Frame 5 Turbines #251 and #252 – Model ID AK 39 and AK40 

-35.5 40 18,545 205.7 714,087 725 51.36614 8.8682 

-26.5 40 18,545 204.8 714,087 725 51.36614 8.8291 

-17.5 40 18,545 204.8 714,087 725 51.36614 8.8291 

-8.5 40 18,545 204.8 714,087 725 51.36614 8.8291 

0.5 40 18,545 204.8 714,087 725 51.36614 8.8291 

9.5 40 18,545 204.8 714,087 725 51.36614 8.8291 

18.5 40 18,545 204.8 714,087 725 51.36614 8.8291 

27.5 40 18,545 204.8 714,087 725 51.36614 8.8291 

36.5 40 18,545 204.8 714,087 725 51.36614 8.8291 

45.5 45.5 18,545 205.1 708,993 732 51.49408 8.8388 

54.5 54.5 18,545 205.4 700,836 744 51.70202 8.8545 

63.5 63.5 18,545 205.8 692,894 755 51.90824 8.8701 

72.5 72.5 18,545 206.1 685,156 767 52.11277 8.8856 

81.5 81.5 18,545 206.5 677,616 778 52.31566 8.9009 

GE Frame 5 Turbines #351 and #352 – Model ID AK 41 and AK42 

-35.5 40 13,436 148.5 629,385 671 41.89056 6.4008 

-26.5 40 13,436 148.5 629,385 671 41.89056 6.4008 

-17.5 40 13,436 148.5 629,385 671 41.89056 6.4008 

-8.5 40 13,436 148.5 629,385 671 41.89056 6.4008 

0.5 40 13,436 148.5 629,385 671 41.89056 6.4008 

9.5 40 13,436 148.5 629,385 671 41.89056 6.4008 

18.5 40 13,436 148.5 629,385 671 41.89056 6.4008 

27.5 40 13,436 148.5 629,385 671 41.89056 6.4008 

36.5 40 13,436 148.5 629,385 671 41.89056 6.4008 

45.5 45.5 13,436 148.8 625,499 677 42.03629 6.4125 

54.5 54.5 13,436 149.2 619,280 688 42.27336 6.4317 

63.5 63.5 13,436 149.6 613,228 699 42.50873 6.4507 

72.5 72.5 13,436 150.1 607,337 709 42.74243 6.4696 

81.5 81.5 13,436 150.5 601,600 720 42.97448 6.4883 
Page 8 

Table 3. Kenai LNG Plant - Actual Emissions from BART-Eligible Emission Units Other than Combu

Emission Unit Pollutant Fuel Emission Factor Maximum Capacity Actual 

Operation 

Model 

ID 

Name ton/yr Reference 

AK44 Erie City 9M Boiler #501 6.2 NOX Nat. gas 140 lb/MMscf AP-42 Table 1.4-1 (7/98) 47 MMBtu/hr 4,836 hr/year AK45 Erie City 9M Boiler #502 7.4 NOX Nat. gas 140 lb/MMscf AP-42 Table 1.4-1 (7/98) 47 MMBtu/hr 6,156 hr/year AK46 Erie City 9M Boiler #511 7.9 NOX Nat. gas 140 lb/MMscf AP-42 Table 1.4-1 (7/98) 46 MMBtu/hr 6,048 hr/year AK47 

Cat D-379 Emergency Generator 

0.07 NOX Diesel 4.41 lb/MMBtu AP-42 Table 3.3-1 (10/96) 350 kW 36 hr/year 

AK48 

Ground Flare (including pilot) 

1.12 NOX Nat. gas 0.068 lb/MMBtu AP-42 Table 13.5-1 (1/95) 148 MMscf/day 881 hr/year 

Notes: 1. Natural gas has a sulfur content of 0.0 ppmv and a heat content of 1,000 Btu/scf. 

 2. Distillate has a sulfur content of 0.1 wt. pct. and a density of 7.0 lb/gal. 
Page 9 

Table 4. Kenai LNG Plant – ADEC-Sponsored WRAP Modeled Source Parameters 

Model Location (LCC) Emissio

ID 

Emission 

Unit X (km) Y (km) 

Stack 

Height 

(m) 

Base 

Elevation 

(m msl) 

Stack 

Diameter 

(m) 

Exit 

Velocity 

(m/s) 

Exit Temp 

(K) 

Downwash SO2 SO4 NOX 

AK37 CPAI Kenai LNG (90) -20.8859 186.6209 21.3360 -999.0000 2.1336 32.6136 755.3722 0 0.0000 0.00 6.273AK38 CPAI Kenai LNG (90) -20.8859 186.6209 21.3360 -999.0000 2.1336 32.6136 755.3722 0 0.0000 0.00 6.273AK39 CPAI Kenai LNG (90) -20.8859 186.6209 21.3360 -999.0000 2.1336 49.9872 777.0389 0 0.0000 0.00 9.430AK40 CPAI Kenai LNG (90) -20.8859 186.6209 21.3360 -999.0000 2.1336 49.0728 777.0389 0 0.0000 0.00 9.221AK41 CPAI Kenai LNG (90) -20.8859 186.6209 21.3360 -999.0000 2.1336 32.6136 755.3722 0 0.0000 0.00 6.305AK42 CPAI Kenai LNG (90) -20.8859 186.6209 21.3360 -999.0000 2.1336 32.6136 755.3722 0 0.0000 0.00 6.305AK44 CPAI Kenai LNG (90) -20.8859 186.6209 18.8976 -999.0000 0.9144 9.7536 460.9278 0 0.0000 0.00 0.580AK45 CPAI Kenai LNG (90) -20.8859 186.6209 18.8976 -999.0000 0.9144 9.7536 460.9278 0 0.0000 0.00 0.580AK46 CPAI Kenai LNG (90) -20.8859 186.6209 18.8976 -999.0000 0.9144 9.4488 460.9278 0 0.0000 0.00 0.094AK47 CPAI Kenai LNG (90) -20.8859 186.6209 4.2672 -999.0000 0.3048 32.9184 749.8167 0 0.0767 0.00 1.832AK48 CPAI Kenai LNG (90) -20.8859 186.6209 62.1792 -999.0000 13.7160 0.0010 1273.1500 0 0.0000 0.00 53.89
Page 10 

Table 5. Kenai LNG Plant – Monthly RHFAC Values for Each Class I Area 

Jan Feb Mar Apr May Jun Jul Aug Sep Oct 

Tuxedni 

3.6 3.4 2.9 2.8 2.8 2.9 3.6 3.9 3.8 3.4 

Denali 

2.5 2.3 2.1 1.9 1.8 2.1 2.5 2.9 2.8 3 
Page 11 

Table 6. Kenai LNG Plant – 98th Percentile Delta Deciview Values 

for Each Class I Area 

2002 2003 2004 Threshold 

Denali 

0.122 0.099 0.128 0.5 

Tuxedni 

0.567 0.883 0.687 0.5 
Page 12 

-200.00 -100.00 0.00 100.00 200.00 300.00

0.00

100.00

200.00

300.00

400.00

500.00

600.00

Denali Receptors

Tuxedni

Receptors

Figure 1. Kenai LNG Plant – Calpuff Modeling Domain and Locations of Emission 

Units (red star) and Class I Area Receptors (Tuxedni and Denali) 
Page 13 

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