BART Alternative Visibility Modeling

for the Riley Boiler at

TASCO – Nampa Factory

State of Idaho

Department of Environmental Quality

1410 North Hilton

Boise, ID 83706

October 19, 2011
2

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Executive Summary

The Amalgamated Sugar Company LLC (TASCO) has requested a revision to the BART 

determination for the coal-fired Riley Boiler at their Nampa Factory, and has proposed a BART 

Alternative. The revised BART includes Spray Dry Flue Gas Desulfurization (Spray Dry FGD) 

for sulfur dioxide (SO2) control, Low NOx burners (LNB) for nitrogen oxides (NOx) control, and 

a baghouse for particulate matter (PM) control. The proposed BART Alternative replaces the 

Spray Dry FGD with a) LNB controls on two (non-BART) Babcock and Wilcox (B&W) boilers, 

and b) credits SO2, NOx and PM emission reductions from shutting down 3 pulp dryers. This 

report describes new modeling to assess the resulting visibility changes at Class I areas within 

300 km of the facility.

The modeling was completed in accordance with the three-state BART Modeling 

Protocol which underwent an extensive review and approval process and formed the basis for 

much of the BART modeling conducted in the Pacific Northwest. In order to compare the BART 

Alternative impacts with the selected BART control scheme on the same basis, both scenarios 

were modeled with emissions from all the sources included in the BART Alternative; i.e. the 

pulp dryers and the non-BART B&W Boilers. In this report, the term “BART” (in quotation 

marks) denotes the selected BART technology for the Riley boiler (LNB) along with emissions 

from the other emission sources (B&W Boilers and pulp dryers) affected by the alternative in 

their pre-BART condition.

Model results for the “BART Alternative” scenario indicate that visibility improves an 

additional 0.159 ∆dv on the 22nd highest day at Strawberry Mountain Wilderness and 0.101∆dv 

at Eagle Cap in comparison to the “BART” scenario. The number of days above 0.5 ∆dv is 

reduced by 11 more days at Strawberry Mountain and 23 more days at Eagle Cap, with a total 

reduction of 41 more days at all the Class I areas combined over the three-year modeling period. 

Although the “BART Alternative” scenario reduces the largest visibility impacts during 

the winter when both modeled and monitored regional haze impacts were highest, the shift from 

SO2 control to additional NOx control will also result in a slightly greater visibility impairment in 

the best visibility months of March – June when sulfate dominates the relatively clear air at the 

Starkey IMPROVE site, representing Eagle Cap and Strawberry Mountain wilderness areas. 

However, this impairment from the BART Alternative in the non-winter months is small in 

comparison to the visibility benefits projected in the winter months, and it is clear that the 

proposed BART Alternative produces greater reductions on more high-impact days than the 

“BART” scenario, and is therefore a preferred approach for reducing regional haze. 

In addition to the greater visibility improvements, the BART Alternative provides greater 

ozone mitigation benefits by more than doubling the NOx reductions over those of the “BART” 

scenario (from 2.7 to 6.5 tons per day). DEQ photochemical modeling indicates that this will 

rank amongst the top ozone mitigation measures being evaluated in our efforts to mitigate ozone 

and avoid an ozone non-attainment designation. This is important to the State of Idaho because 

of the health and economic disadvantages that non-attainment status may bring and the potential 

restrictions that the region could incur in the areas of industrial growth, transportation 

improvements, and agricultural and prescribed burning.
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Introduction

The Amalgamated Sugar Company LLC (TASCO) at Nampa, Idaho has requested revision of 

the initial Best Available Retrofit Technology (BART) determination for NOx and approval of a 

BART Alternative to control visibility-impairing pollutant emissions from the Riley Boiler at 

their Nampa Factory. The BART determinations (as revised) include Spray Dry Flue Gas 

Desulfurization (Spray Dry FGD) for sulfur dioxide (SO2) control, Low NOx burners (LNB) for 

nitrogen oxides (NOx) control, and a baghouse for particulate matter (PM) control. The proposed 

BART Alternative replaces the Spray Dry FGD with a) LNB controls on two (non-BART) 

Babcock and Wilcox (B&W) boilers, and b) SO2, NOx and PM emission reduction credits for 

shutting down 3 pulp dryers. Modeling results documenting the visibility impacts of the revised 

BART and the proposed BART Alternative along with an Alternative Benchmark scenario are 

described in this report. The benchmark scenario provides a common pre-BART basis against 

which the regional haze impacts of both the BART and BART Alternative scenarios can be 

compared.

Control Scenarios Modeled

The revised BART and BART Alternative determinations are discussed in the Statement of Basis 

prepared in conjunction with this permitting action. This report addresses the relative differences 

in regional haze impacts for the modeled control scenarios and the measured patterns of aerosol 

extinction and visibility degradation at the Class I areas where the impacts occur. The modeling 

summarized in this memo involves the following scenarios, with computer runs identified by run 

identification numbers:

“BART” Modeling Scenario

This scenario, (Run ID wzI10495) includes Riley Boiler BART emissions along with benchmark 

emissions of sources affected by the BART Alternative. Note, BART (without quotation marks) 

refers to the BART determination control technology involving only the Riley Boiler, while 

“BART” (with quotations) refers to this modeling scenario, which includes the other affected 

emission sources:

 Riley Boiler with existing baghouse, Spray Dry FGD, and LNB

 B&W Boilers #1 and #2 (benchmark emissions of sources affected by the BART 

Alternative)

 Pulp Dryers, full operation (benchmark emissions of sources affected by the BART 

Alternative)

“BART Alternative” Modeling Scenario

This scenario (Run ID wzI10493) includes the BART NOx controls on the Riley boiler, along 

with Low-NOx burners on two other non-BART Babcock and Wilcox (B&W) boilers. The B&W 

NOx controls along with credits for shutting down three pulp dryers, is proposed by TASCO as

an alternative for SO2 control using Spray-Dry FGD. 

 Riley Boiler with existing baghouse and LNB

 B&W Boilers #1 and #2 with LNB

 Pulp Dryers shut down (North, Center, South)
5

“Alternative Benchmark” Modeling Scenario

This scenario (Run ID wzI10492) includes benchmark or pre-BART emissions from the Riley 

Boiler and the other sources affected by the BART Alternative scenario. It provides a common 

benchmark for comparison of the “BART” and “BART Alternative” scenarios on an equivalent

basis: 

 Riley Boiler with existing baghouse

 B&W Boilers #1 and #2, full operation 

 Pulp Dryers, full operation

Methods

The dispersion and visibility modeling described in this report is based on stack parameters and 

emission rates provided by TASCO. The location and stack parameters for all sources involved 

in the modeling of all scenarios are presented in Table 1 and the emission rates for the same 

sources are presented in Table 2. 

DEQ used the CALPUFF (v 6.112) air dispersion modeling system to determine the 

delta-deciview (Δdv) visibility impacts, the number of days per year above the 0.5 Δdv 

threshold, and the number of days per the three–year period above the 0.5 Δdv threshold. The 

modeling was performed in accordance with the BART Modeling Protocol1, which was jointly 

developed by the states of Idaho, Washington, and Oregon, and which has undergone public, 

Federal Land Manager (FLM) and EPA review and approval. This is the identical protocol used 

for DEQ’s Subject-to-BART modeling completed in support of the initial BART Tier II operating 

permit.2 The meteorological and CALPUFF computational domains for the Nampa Factory are 

shown in Figure 1 along with the source location (red dot) and the Class I areas (red with black 

outlines) within 300 km of the source. Class I areas included in this analysis and identifying 

abbreviations used in Figure 1 are shown in Table 1. The Class I areas are primarily wilderness 

areas managed by the United States Forest Service, with the exception of Craters of the Moon 

Wilderness Area, managed by the National Park Service. None of the Class I areas within 300 

miles of Nampa are managed by the United States Fish and Wildlife Service.

Table 1 Class I Areas Included in Modeling Analysis

Eagle Cap Wilderness, OR (eaca2) Sawtooth Wilderness Area, ID (sawt2)

Strawberry Mountain Wilderness, OR (stmo2) Selway-Bitterroot Wilderness Area, ID/MT (selw4)

Hells Canyon Wilderness Area, ID/OR (heca2) Craters of the Moon Wilderness Area, ID (crmowild)

Jarbidge Wilderness Area, ID/NV (jarb2)

The meteorological inputs to CALPUFF for the analysis were the same data set used previously 

for the Subject-to-BART analysis and the BART Determination modeling. The meteorological 

inputs were prepared by Geomatrix, Inc. (now Environ International) under the direction of 

representatives from the states of Washington, Idaho, and Oregon, using Fifth Generation 

 

1 Modeling Protocol for Washington, Oregon and Idaho: Protocol for the Application of the CALPUFF 

Modeling System Pursuant to the Best Available Retrofit Technology (BART) Regulation.

http://www.deq.idaho.gov/air/prog_issues/pollutants/haze_BART_modeling_protocol.pdf

2 Tier II Operating Permit No. T2-2009.0105, issued September 7, 2010.
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Mesoscale Meteorological Model (MM5) data generated by the University of Washington. The 

result was a CALMET output file for the three-year period from 2003 through 2005 that covers 

the entire Pacific Northwest at a 4-km resolution.

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Primary particulate matter from these sources is a relatively small contributor to regional haze. 

Nevertheless, detailed particulate matter speciation was estimated using National Park Service 

particulate speciation spreadsheets for dry bottom pulverized coal-fired boilers with and without 

Spray Dry FGD.4

The resulting speciated emissions of direct particulate matter emissions can be seen in Table 3.

Note, the sulfate (SO4) in Table 3 is shown as (and input to CALPUFF) as pounds per hour SO4. 

However, when totaling the aerosol species under “Total PM10” it is converted to a 

stoichiometric equivalent mass of ammonium sulfate ((NH4)2SO4), since this is the form it 

assumes in the ambient air, and the mass that is measured in a source test.

Figure 1 Meteorological (black) CALPUFF (pink) domains with Class I

areas within 300-km radius (blue) of TASCO Nampa Factory (red dot).

 

3 CALMET Statistical Report, CALMET Fields for BART Modeling, Idaho, Oregon and Washington, 

Geomatrix Consultants, Inc., Lynnwood WA 98036, July 2006.

4 National Park Service, Particulate Matter Speciation, Coal-Fired Boiler PM10, 

http://www.nature.nps.gov/air/Permits/ect/ectCoalFiredBoiler.cfm
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Table 2 Source Locations and Stack Parameters

Unit BART Control Equipment Easting 

(m)

Northing 

(m)

Elevation 

(m)

Stack 

Height 

(m)

Stack 

Diameter 

(m)

Stack Exit 

Temperature 

(K)

Stack Exit 

Velocity 

(m/s)

Stack Parameters for “Alternative Benchmark” Scenario (Run ID wzI10492)

Riley Boiler Existing Baghouse 534.406 4828.031 753 74.7 3.35 445.9 12.0

B&W 1&2 (n/a) 534.406 4828.031 753 74.7 3.35 445.9 12.0

South Pulp Dryer (n/a) 534.413 4828.087 753 23.5 3.017 348.5 4.9

Center Pulp Dryer (n/a) 534.413 4828.099 753 21 3.017 353.4 7.0

North Pulp Dryer (n/a) 534.415 4828.106 753 27.7 2.13 346.4 6.3

Stack Parameters for “BART” Scenario (with affected sources) (Run ID wzI10495)

Riley Boiler FGD + LNB (60.7% Control) 534.406 4828.031 753 74.7 3.35 403.8 11.2

B&W 1&2 LNB (Each 55% Control) 534.406 4828.031 753 74.7 3.35 445.9 12.0

South Pulp Dryer (n/a) 534.413 4828.087 753 23.5 3.017 348.5 4.9

Center Pulp Dryer (n/a) 534.413 4828.099 753 21 3.017 353.4 7.0

North Pulp Dryer (n/a) 534.415 4828.106 753 27.7 2.13 346.4 6.3

Stack Parameters for “BART Alternative” Scenario (Run ID wzI10493)

Riley Boiler LNB (60.7% Control) 534.406 4828.031 753 74.7 3.35 440.0 11.7

B&W 1&2 LNB (Each 55% Control) 534.406 4828.031 753 74.7 3.35 440.0 11.7
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Table 3 Emission Rates used in CALPUFF Modeling (a)

Unit Control Equipment SO2

lb/hr

SO4

lb/hr

NOX 

lb/hr

HNO3

lb/hr

NO3

lb/hr

PMC 

lb/hr

PMF 

lb/hr

EC 

lb/hr

SOA 

lb/hr

Total 

PM10

lb/hr(b)

Emissions from all Sources in Alternative Benchmark Scenario (Run ID wzI10492)

Riley Boiler Existing Baghouse 522.3 6.7 373.8 0 0 0.5 0.5 0 2.3 12.5

B&W 1&2 (c) (n/a) 435.0 30.7 227 0 0 2.1 2.1 0 10.5 56.9

South Pulp Dryer (n/a) 7.5 0.01 80.2 0 0.01 0 31.3 0 5.3 36.6

Center Pulp Dryer (n/a) 7.5 0.01 80.2 0 0.01 0 31.3 0 5.3 36.6

North Pulp Dryer (n/a) 2.9 0.01 30.8 0 0.01 0 14.2 0 5.3 19.5

“Alternative Benchmark” Scenario Totals: 975.1 37.43 792 0 0.03 2.6 79.4 0 28.7 162.2

Emissions from all sources in “BART” Scenario (with affected sources) (Run ID wzI10495)

Riley Boiler Selected BART (FGD + LNB) 104 2.8 147 0 0 0.5 0.5 0 1 5.9

B&W 1&2 (c) Existing Control, B&W Boilers 1&2 435 30.7 227 0 0 2.1 2.1 0 10.5 56.9

South Pulp Dryer (n/a) 7.5 0.01 80.2 0 0.01 0 31.3 0 5.3 36.6

Center Pulp 

Dryer (n/a) 7.5 0.01 80.2 0 0.01 0 31.3 0 5.3 36.6

North Pulp Dryer (n/a) 2.9 0.01 30.8 0 0.01 0 14.2 0 5.3 19.5

“BART” Scenario Totals: 556.8 33.5 565.2 0 0.03 2.6 79.4 0 27.4 155.5

“BART Alternative” Emissions after Implementation (Pulp Dryers shut down) (Run ID wzI10493)

Riley Boiler LNB (60.7% Control) 522.3 6.7 147 0 0 0.5 0.5 0 2.3 12.5

B&W 1&2 (c) LNB (Each 55% Control) 435 30.7 103 0 0 2.1 2.1 0 10.5 56.9

“BART Alternative” Scenario Totals: 957.3 37.4 250 0 0 2.6 2.6 0 12.8 69.4

(a) Pollutant emissions for sulfur dioxide (SO2), Nitrogen oxides (NOx = NO + NO2), nitric acid (HNO3) and speciated particulate matter species (SO4), particulate nitrate 

(NO3), coarse particulate matter 2.5 – 10m in aerodynamic diameter (PMC), fine particulate matter < 2.5m in diameter (PMF), elemental carbon (EC), secondary organic 

aerosol (SOA), and total particulate matter 10m and less in aerodynamic diameter (PM10).

(b) Total PM10 is not used directly in the model but represents total of PM species for information only. SO4is added into total PM10 as ammonium sulfate (SO4lb/hr x 

(132/96)).

(c) B&W Boilers 1&2 refer to two (non-BART) Babcock &Wilcox Boilers, Units 1 and 2 that operate at the Nampa Factory in addition to the Riley Boiler
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BART Alternative Modeling Results

“BART” and “BART Alternative” Model Detailed Results

Detailed model results showing regional haze impacts at all seven Class I areas within 300 km of 

the source are summarized for the “BART” scenario in Table 4, and for the “BART Alternative” 

scenario in Table 5. It is important to emphasize that both the “BART” and the “BART 

Alternative” results shown in Table 4 and Table 5 include all emission sources involved in the 

BART determinations and in the BART Alternative, so that comparison can be made on an 

equivalent basis, with the full precursor mix accounted for from all affected sources. Overall 

(three-year) results for all scenarios are summarized in Table 6 to facilitate comparisons.

In its 2005 BART guidelines, EPA determined that a source whose 98th percentile daily average 

haze impact (haze index) is greater than 0.5 deciview above natural background is considered to 

contribute to regional haze. Impacts above 1.0 deciview are considered to cause regional haze 

impacts. By selecting the 98th percentile, the top 7 days in any year, or top 21 days in three years,

EPA intended to minimize the effects of extreme meteorology and conservative assumptions. 

Table 4 and Table 5 highlight the two averaging periods generally used in BART modeling 

analyses:

 8

th highest Δdv value for each of the years modeled (2003-2005), representing the 

98th percentile (8/365 = 0.02) cutoff for Δdv in the each year. In addition the 

numbers of days in each year above the 0.5 Δdv threshold are shown.

 22nd highest value for the entire period from 2003 through 2005, representing the 98th 

percentile (22/1095 = 0.02) cutoff for Δdv over three years. In addition the numbers 

of days in all three years above the 0.5 Δdv threshold are shown. 

The pre-BART, 3-year modeled impacts shown in Table 4 and Table 5 indicate that the 

“Alternative Benchmark” scenario does not “contribute” (>0.5Δdv) to regional haze at Craters of 

the Moon, Jarbidge, Sawtooth and Selway-Bitterroot wilderness areas, the Class I areas east of 

Nampa. On the other hand, this benchmark scenario does “cause” regional haze impacts 

(>1.0∆dv) at the 3 Class I areas east of the facility, i.e. Eagle Cap, Strawberry Mountain and 

Hells Canyon wilderness areas. In addition, Table 4 and Table 5 show that the meteorology in 

2004 resulted in the highest modeled impacts and most days above the 0.5Δdv threshold at all 

sites. Figure 2 clearly shows that the model-predicted visibility impacts at Eagle Cap (due to the 

existing Riley boiler) were highest in the winter season, and that January 2004 had the highest 

predicted impacts during the three-year model period. In addition, from day 60 through day 280, 

only 3 days in 3 years appear to exceed the 0.5Δdv threshold for a 98th percentile day 

“contributing” to a haze at a Class I area. Since this frequency (3 days in 660) represents only 

0.45% of the non-winter days, it suggests that the Riley boiler does not “contribute” to the haze 

impacts, at the level defined by EPA, outside of the October – February period. However it does 

“cause” haze impacts (>1 Δdv) at the western-most 3 Class I areas during the winter time when 

non-carbon impacts are the greatest.

Comparison to Measured Extinction at IMPROVE monitoring sites

To gain confidence in model results, it is useful to examine how model results behave in

comparison to monitored aerosol extinction at IMPROVE monitoring sites. For this purpose, it is 

useful to understand how light extinction is determined from aerosol species concentrations and 
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how extinction relates to the “haze index” or changes in visibility relative to the background 

visibility in terms of delta deciviews (Δdv). Light extinction (bext) is computed from aerosol 

species concentrations and reported in units of reciprocal megameters (Mm-1) according to the 

equation: 

bext = 3 f(RH) [(NH4)2SO4] + 3 f(RH) [NH4NO3] + 4[OC] + 1[Soil] + 0.6[Coarse Mass] + 10[EC] + bRay

(Eqn 1)

Equation 1 applies to either measured or modeled aerosol concentrations, where:

f(RH) are monthly averaged relative humidity coefficients, specifically tabulated for each 

Class I area each month,

bRay is Raleigh scattering due to air molecules, Mm -1

[(NH4)2SO4] is the ammonium sulfate concentration formed from SOs, μg/m3

[NH4NO3] is the ammonium nitrate concentration formed from NOx, μg/m3

[OC] is the organic carbon concentration, μg/m3(equivalent to “SOA” in Table 3)

[Soil] is the fine geologic particulate matter, μg/m3(equivalent to “PMF” in Table 3),

[Coarse Mass] is the coarse particulate matter, μg/m3(equivalent to “PMC” in Table 3), and

[EC] is the elemental carbon, μg/m3

Light extinction is not measured directly at IMPROVE sites, but is calculated based on aerosol 

measurements of the species in Equation 1. In this document, the terms “measured extinction” or 

“monitored extinction” refer to light extinction calculated by Equation 1 based on direct aerosol 

filter measurements and reported by the IMPROVE monitoring program. When source emissions

are modeled to estimate light extinction impacts resulting from those emissions, the resulting 

bext (source) is compared to background extinction, bext (bkg), to predict the haze index in terms of 

delta-deciviews: 

dv = 10 ln [ ( bext (bkg) + bext (source) ) / ( bext (bkg) ) ] (Eqn 2)

A time series view of 2004 light extinction based on measured aerosol concentrations and 

modeled pre-BART Riley Boiler concentrations at Hells Canyon (Figure 3) again suggests that 

the winter months experience the highest visibility impacts and that the January 2004 stagnation 

episode produced the greatest monitored and modeled aerosol extinction over the 3 year period. 

The similarity in monitor-based and modeled annual patterns shown in Figure 3 suggests that the 

model captures the seasonal variation in haze conditions well and that both the observed and 

modeled visibility impacts are highest in the winter time and much lower from March to midOctober.

Summary of “BART” results. 

The visibility improvement for the “BART” scenario, in comparison to the Alternative 

Benchmark scenario (Table 4) shows a reduction in the three-year 22nd highest Δdv of 0.689 Δdv 

at Eagle Cap, the most impacted area, and 0.119 Δdv at Jarbidge Wilderness, the least impacted 

area. Similarly, the number of days in three years above the 0.5 Δdv threshold at Eagle Cap 

decreases from 195 days to 149 days, a 46 day reduction, while Jarbidge is projected to see only 

a three day reduction. The sum of days in 3 years above 0.5 Δdv at all seven Class I areas 

decreases from 455 days for the Alternative Benchmark scenario to 316 days for the “BART” 

scenario, a reduction of 139 days overall.
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Summary of “BART Alternative” Results

The visibility improvement for the “BART Alternative” scenario in comparison to the 

“Alternative Benchmark” scenario (Table 5) shows a reduction in the three-year 22nd highest Δdv 

at Eagle Cap from 2.201 to 1.411Δdv, a visibility improvement of 0.790 Δdv. The number of 

days in the three-year period above the 0.5 Δdv threshold at Eagle Cap decreases from 195 days 

to 126 days, a 69 day reduction, while Jarbidge is projected to see a three day reduction, identical 

to the “BART” scenario. The sum of days above 0.5 Δdv at all the Class I areas combined drops 

from 455 for the “Alternative Benchmark” scenario to 275 days for the “BART Alternative” 

scenario, a reduction of 180 days. A very small visibility degradation appears at 

Selway-Bitterroot Wilderness Area.
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Table 4 Summary of Visibility Impacts for TASCO-Nampa "BART" Scenario

Class I 

Area Operating Scenario

Change in Visibility Compared Against 20% Best Days (Natural Background)

dv larger than 0.5 from one year period dv > 0.5 over 3 yr

2003 2004 2005 2003-2005

8

th high 

dv(a)

Days > 

0.5dv(b)

8

th high 

dv(a)

Days > 

0.5dv(b)

8

th high 

dv(a)

Days > 

0.5dv(b)

22nd 

Highest(c)

Total Days (d)

>0.5dv

Eagle Cap 

Wilderness, 

OR

“Alternative Benchmark” (wzI10492) 1.611 48 2.212 72 2.178 75 2.201 195

“BART” (e) (wzI10495) 1.103 30 1.551 55 1.509 64 1.512 149

Visibility Improvement (f) 0.508 18 0.661 17 0.669 11 0.689 46

Craters of 

the Moon 

NM

Wilderness, 

ID

“Alternative Benchmark” (wzI10492) 0.336 1 0.407 6 0.318 3 0.393 10

“BART” (e) (wzI10495) 0.239 0 0.273 3 0.233 1 0.267 4

Visibility Improvement (f) 0.097 1 0.134 3 0.085 2 0.126 6

Hells 

Canyon 

Wilderness

ID/OR

“Alternative Benchmark” (wzI10492) 1.269 27 1.693 51 1.515 51 1.582 129

“BART” (e) (wzI10495) 0.884 20 1.163 32 1.049 35 1.092 87

Visibility Improvement (f) 0.385 7 0.530 19 0.466 16 0.490 42

Jarbidge

Wilderness, 

NV

“Alternative Benchmark” (wzI10492) 0.275 1 0.379 3 0.420 4 0.375 8

“BART” (e) (wzI10495) 0.192 1 0.256 2 0.278 2 0.256 5

Visibility Improvement (f) 0.083 0 0.123 1 0.142 2 0.119 3

Sawtooth 

Wilderness, 

ID

“Alternative Benchmark” (wzI10492) 0.470 7 0.519 8 0.435 3 0.470 18

“BART” (e) (wzI10495) 0.340 2 0.349 4 0.293 0 0.319 6

Visibility Improvement (f) 0.130 5 0.170 4 0.142 3 0.151 12

Selway- Bitterroot 

Wilderness, 

ID

“Alternative Benchmark” (wzI10492) 0.317 0 0.587 8 0.492 7 0.439 15

“BART” (e) (wzI10495) 0.212 0 0.387 1 0.327 2 0.281 3

Visibility Improvement (f) 0.105 0 0.200 7 0.165 5 0.158 12

Strawberry 

Mountain 

Wilderness, 

OR

“Alternative Benchmark” (wzI10492) 1.419 18 0.882 22 2.308 40 1.462 80

“BART” (e) (wzI10495) 0.987 13 0.644 15 1.677 34 1.076 62

Visibility Improvement (f) 0.432 5 0.238 7 0.631 6 0.386 18

All Areas Reduction in Total Days > dv, all Class I Areas Combined 2003: 36 2004: 58 2005: 45 3-Yr: 139

(a) The 8th highest delta-deciview impact for the calendar year.

(b) Total number of days in 1 year that exceeded 0.5 delta deciviews.

(c) The 22nd highest delta-deciview impact for the three-year period.

(d) Total number of days in the three-year period that exceed 0.5 delta deciviews.

(e) “BART” (with quotations) refers to the Riley Boiler with Spray Dry FGD and LNB controls plus the pre-BART emissions of the B&W boilers 1&2 and three pulp dryers so that the 

results may be compared to the “BART Alternative” and the “Alternative Benchmark” scenarios on an equivalent basis.

(f) Visibility improvement is calculated as the difference between the “Alternative Benchmark” scenario and the “BART” scenario modeled values.
13

Table 5 Summary of Visibility Impacts for TASCO-Nampa “BART Alternative” Scenario

Class I Area Operating Scenario

Change in Visibility Compared Against 20% Best Days (Natural Background)

dv larger than 0.5 from one year period dv > 0.5 over 3 yr

2003 2004 2005 2003-2005

8

th high 

dv(a)

Days > 

0.5dv(b)

8

th high 

dv(a)

Days > 

0.5dv(b)

8

th high 

dv(a)

Days > 

0.5dv(b)

22nd 

Highest(c)

Total Days(d)

>0.5dv

Eagle Cap 

Wilderness, 

OR

“Alternative Benchmark” (wzI10492) 1.611 48 2.212 72 2.178 75 2.201 195

“BART Alternative” (wzI10493) 0.921 22 1.434 49 1.469 55 1.411 126

Visibility Improvement (e) 0.690 26 0.778 23 0.709 20 0.790 69

Craters of 

the Moon 

NM

Wilderness, 

ID

“Alternative Benchmark” (wzI10492) 0.336 1 0.407 6 0.318 3 0.393 10

“BART Alternative” (wzI10493) 0.230 0 0.260 2 0.200 1 0.245 3

Visibility Improvement (e) 0.106 1 0.147 4 0.118 2 0.148 7

Hells 

Canyon 

Wilderness

ID/OR

“Alternative Benchmark” (wzI10492) 1.269 27 1.693 51 1.515 51 1.582 129

“BART Alternative” (wzI10493) 0.758 17 1.173 31 1.044 32 1.059 80

Visibility Improvement (e) 0.511 10 0.520 20 0.471 19 0.523 49

Jarbidge

Wilderness, 

NV

“Alternative Benchmark” (wzI10492) 0.275 1 0.379 3 0.420 4 0.375 8

“BART Alternative” (wzI10493) 0.193 1 0.252 2 0.251 2 0.234 5

Visibility Improvement (e) 0.082 0 0.127 1 0.169 2 0.141 3

Sawtooth 

Wilderness, 

ID

“Alternative Benchmark” (wzI10492) 0.470 7 0.519 8 0.435 3 0.470 18

“BART Alternative” (wzI10493) 0.268 1 0.340 4 0.278 1 0.307 6

Visibility Improvement (e) 0.202 6 0.179 4 0.157 2 0.163 12

Selway- Bitterroot 

Wilderness, 

ID

“Alternative Benchmark” (wzI10492) 0.317 0 0.587 8 0.492 7 0.439 15

“BART Alternative” (wzI10493) 0.206 0 0.383 2 0.329 2 0.298 4

Visibility Improvement (e) 0.111 0 0.204 6 0.163 5 0.141 11

Strawberry 

Mountain 

Wilderness, 

OR

“Alternative Benchmark” (wzI10492) 1.419 18 0.882 22 2.308 40 1.462 80

“BART Alternative” (wzI10493) 0.737 10 0.540 11 1.487 30 0.917 51

Visibility Improvement (e) 0.682 8 0.342 11 0.821 10 0.545 29

All Areas Reduction in Total Days > 0.5 dv, all Class I Areas Combined 2003: 51 2004: 69 2005: 60 3-Yr: 180

(a) The 8th highest delta-deciview impact for the calendar year.

(b) Total number of days in 1 year that exceeded 0.5 delta deciviews.

(c) The 22nd highest delta-deciview impact for the three-year period.

(d) Total number of days in the three-year period that exceed 0.5 delta deciviews.

(e) Visibility improvement is calculated as the difference between the “Alternative Benchmark” scenario and the “BART Alternative” scenario modeled values.
14

Table 6 Summary of scenarios and net visibility improvement from “BART Alternative” in comparison to “BART” scenario

Class I Area

“Alternative 

Benchmark”(a)

(wzI10492)

“BART”(b)

(wzI10495)

“BART Alternative”(c)

(wzI10493)

Net Visibility Improvement

(“BART” – “BART Alternative”)

22nd 

Highest (d)

Total Days 

>0.5dv (e)

22nd 

Highest (d)

Total Days (e)

>0.5dv

22nd 

Highest 

(d)

Total Days 

>0.5dv (e)

dv Reduction, 

22nd Highest 

Day

Decrease in 

No. of Days 

>0.5 Δdv

Eagle Cap Wilderness, OR 2.201 195 1.512 149 1.411 126 0.101 23

Craters of the Moon Wilderness, ID 0.393 10 0.267 4 0.245 3 0.022 1

Hells Canyon Wilderness, ID/OR 1.582 129 1.092 87 1.059 80 0.033 7

Jarbidge Wilderness, NV 0.375 8 0.256 5 0.234 5 0.022 0

Sawtooth Wilderness, ID 0.47 18 0.319 6 0.307 6 0.012 0

Selway-Bitterroot Wilderness, ID 0.439 15 0.281 3 0.298 4 -0.017 -1

Strawberry Mountain Wilderness, OR 1.462 80 1.076 62 0.917 51 0.159 11

Total Number of Days with Improved Visibility: 455 316 275 41

(a) Includes pre-BART emissions of all sources involved in BART and the BART Alternative: Riley Boiler, B&W Boilers 1&2 and pulp dryers.

(b) Includes all sources involved in BART and the BART Alternative under “BART” operations: Riley Boiler (LNB + SD-FGD), B&W Boilers 1&2, three pulp dryers operating.

(c) Includes all sources involved in BART and the BART Alternative under BART Alternative operations: Riley Boiler (LNB), B&W Boilers 1&2 (LNB), three pulp dryers shut 

down.

(d) The 22nd highest dv value for the three-year period (2003 – 2005).

(e) Total number of days in the three-year period that exceed 0.5dv.
15

Figure 2 Modeled seasonal variation in delta-deciview impacts due to TASCO's Riley Boiler

(existing control), over the three model years

Figure 3 Comparison of modeled extinction due to the Riley Boiler (existing control) (left axis)

and measured total aerosol extinction at the Hells Canyon IMPROVE site (right axis). 
16

Other Considerations

In preliminary discussion of the proposed changes with FLMs, questions were raised about 

finding sufficient alternative controls at the facility to include in a BART alternative and about 

the effect on visibility impacts that would result from reducing the level of SO2 control and 

replacing it with increased NOx control. As a result, DEQ reassessed the selection of emission 

sources included in BART Alternative modeling and evaluated whether inordinate visibility 

impacts were projected to shift impacts to other Class I areas or to other seasons. This section 

describes those evaluations. 

Availability of other Emission Sources for Inclusion in the BART Alternative

Alternatives to the control of SO2 emissions by Spray Dry-FGD were proposed by TASCO, in 

light of both the high cost and the environmental impairment due to the waste stream produced 

by Spray Dry FGD. During the evaluation, the FLMs suggested that in seeking alternative 

emission reductions, DEQ should examine the entire facility-wide emission inventory to 

determine if other emission sources, in addition to the two B&W Boilers and the Pulp Dryers 

could be considered for inclusion as part of a BART Alternative. DEQ examined the primary 

regional haze precursors in the facility-wide emission inventory for the TASCO Nampa Factory 

in the most recent statewide point source emissions inventory (2010). The pulp dryers had been 

shut down by 2010 and did not appear in this inventory, but were included as reductions in the 

BART Alternative. The facility-wide emissions of NOx, SO2 and PM10 are shown in Figure 4, 

Figure 5, and Figure 6 (respectively). These charts indicate that the Riley Boiler and the B&W 

boiler Units 1 & 2 together comprise 97% of the total facility-wide NOx emissions, 99% of the

SO2 emissions and 98% of PM10 emissions. This review confirmed that the emission sources 

contributing the greatest share of visibility-impairing emissions from the Nampa Factory are 

included in the proposed BART Alternative and that no other significant visibility-impairing 

pollutant emission sources are available at the facility for inclusion in the BART Alternative 

control plan.

Effects on Visibility from Replacing SO2 Control with Additional NOx Control

The proposed BART Alternative replaces the Spray-Dry Flue Gas Desulfurization SO2 control 

on the Riley Boiler with additional NOx controls on the two Babcock & Wilcox boilers and with 

additional NOx, SO2 and PM10 reductions achieved by shutting down the 3 pulp dryers. Visibility 

reductions resulting from this proposed change would potentially be limited if the highest 

regional haze impacts were primarily caused by sulfate, or if sulfate was a predominant 

contributor in any particular season during which the facility contributes to significant visibility 

degradation. To assess the importance of nitrate, sulfate and primary particulate matter to the 

regional haze levels, DEQ investigated the monitored impacts at all the Class I areas and seasons

most impacted by the TASCO Nampa Factory. IMPROVE aerosol monitoring data5 for the 

modeling period are presented in this section to provide a multi-year evaluation of pre-BART 

visibility conditions and their seasonal variation. 

 

5 Western Regional Air Partnership (WRAP), WRAP-TSS Web site, September 2011. 

http://vista.cira.colostate.edu/TSS/Results/Monitoring.aspx
17

Most Impacted Areas

The modeled visibility impacts from sources at the TASCO Nampa plant were highest at the 

Class I areas at the west end of the Snake River Valley: Eagle Cap, Strawberry Mountain and 

Hells Canyon wilderness areas. These areas also experience the highest monitored aerosol 

impacts, with the exception of isolated wildfire impacts that affect sites throughout the west. 

Monitoring data for the years of the modeling study, 2003, 2004 and 2005 are shown in Figure 7, 

Figure 8, and Figure 9 (respectively), for the Starkey IMPROVE site. The Starkey site is located 

between Eagle Cap and Strawberry Mountain and is intended to represent both of these 

Wilderness areas. Figure 10, Figure 11, and Figure 12 show the measured aerosol extinction for 

the same three years at Hells Canyon IMPROVE site. The three Class I areas represented by 

these two IMPROVE sites reflect very similar patterns of observed seasonal visibility 

degradation and aerosol composition. A review of Figure 7 through Figure 12 indicates that: 

 The greatest non-carbon impacts are in the winter, when nitrate predominates extinction 

(80 to 150 Mm -1) and sulfate is relatively low. This aerosol formation regime generally 

occurs from November through February.

 The greatest carbon impacts occur in the summer, sometimes extending into fall, when 

carbon predominates extinction (~120 – 280 Mm-1), likely from wildfires in the region, 

nitrate is negligible, and sulfate is relatively low (< 10Mm-1). It is important to note that 

ammonium nitrate is volatile at summertime temperatures and does not exist as an 

aerosol that can impact visibility during these warmer seasons. 

 The season with the best visibility (lowest extinction) is spring, when sulfate 

predominates. During this period, most sulfate impacts appear to be between about 5 and 

10 Mm-1, with the highest sulfate impact in 3 years reaching just over 20 Mm-1.

Nevertheless, the observed aerosol impacts in the spring are relatively low compared to 

winter and summer when extinction reaches 120 to 300 Mm-1 most years.

The Starkey IMPROVE site represents the two Class I areas with greatest modeled impacts from 

the TASCO Nampa boilers so seasonal regional haze impacts measured at Starkey were 

examined in more detail. Daily extinction values for measured aerosol species were obtained 

from the WRAP-TSS5and summarized into monthly average extinction values. Figure 13 shows 

monthly averaged total extinction at Starkey, and average extinction by species for all days in the 

three-year modeling period, 2003 – 2005. Error bars representing the 95% Confidence Intervals 

(CI) are also shown to indicate variability. The total extinction line demonstrates that average 

extinction is the highest in the summer and fall months, as a result of high organic carbon. The 

colder months of November through February experience the second highest total extinction and 

the predominant species is ammonium nitrate. The season with the best visibility (lowest average 

extinction) is spring (March through June) when average aerosol extinction is half to a third of 

that in the higher seasons. Sulfate predominates for most of the spring months averaging around 

5 – 7 Mm-1 with very little variability. Carbon increases to levels comparable to sulfate in May 

and June. 

Figure 14 shows the monthly average extinction pattern for the 20% of days observed each 

month with the worst visibility conditions. For the worst 20% of days, the greatest contributors 

to regional haze impacts are carbon in the summer and fall and nitrate in the winter. Again, 
18

sulfate predominates in the spring when visibility conditions are best, yet still contributes only 

about 8 – 12 Mm-1 when averaged over the 20% of days with the highest extinction. 

Less Impacted Areas

The TASCO Nampa Factory modeled impacts for the “Alternative Benchmark” scenario 

revealed that the other Class I areas further away and to the east of Nampa experienced modeled 

visibility impacts ranging from only 17 to 21% of the impacts at Eagle Cap, for the 22nd highest 

Δdv days. None of the 22nd highest days exceed 0.5Δdv, the EPA suggested threshold for 

“contributing” to a haze problem. The measured haze impacts at Craters, Jarbidge, Sawtooth and 

Selway-Bitterroot were also much lower than those at Starkey and Hells Canyon. The measured 

aerosol extinction charts for 2003, 2004 and 2005 are shown for Sawtooth Wilderness in Figure 

15, Figure 16, and Figure 17 (respectively); for Jarbidge Wilderness in Figure 18, Figure 19, and 

Figure 20; for Craters of the Moon Wilderness in Figure 21, Figure 22, and Figure 23; and for 

the Selway-Bitterroot Wilderness Area in Figure 24, Figure 25, and Figure 26. It should be 

noted, that the scale for each extinction figure changes, and while the highest (nitrate-impacted) 

days at Starkey and Hells Canyon reach 100 to 180 Mm-1, the highest nitrate-impacted days at 

the more distant sites east of Nampa have total extinction levels reaching only 40 to 55 Mm-1. 

The observed aerosol extinction charts for the eastern group of Class I areas indicate that:

 At Jarbidge, Sawtooth and Selway-Bitterroot wilderness areas, measured nitrate aerosol 

extinction was very low, even in winter, suggesting very little impact from the TASCO 

Nampa Factory. Carbon dominated at these sites during the summer wildfire season, 

peaking around 130 Mm-1at Sawtooth and over 350 Mm-1at Selway-Bitterroot. Sulfate 

was more significant in the spring with most days below 5 - 6 Mm-1and only a few days 

in the range 10 – 20 Mm-1. 

 At Craters of the Moon Wilderness Area (Figure 21 through Figure 23) the highest 

observed aerosol extinction resulted from nitrate in winter, up to 55 Mm-1, and carbon in

the summer up to 100 Mm-1. Sulfate at Craters of the Moon was similar in magnitude to 

sulfate at all the other sites, typically around 5 - 10 Mm-1or less, and never exceeds 20 

Mm-1, similar to the other Class I areas. This appears to be indicative of a very consistent 

regional background, with very little variation amongst all 7 Class I area.

Overview of Seasonal Visibility Analysis

The above analysis of seasonal visibility impacts suggests that the greatest impacts occur at 

Starkey and Hells Canyon as a result of wintertime nitrate impacts and summer/fall organic 

carbon impacts, probably from wildfires. A review of sulfate impacts at all the Class I areas 

(above) suggests that the level of springtime sulfate impacts (Figure 13 and Figure 14) at the 

Starkey IMPROVE site (~ 6 Mm-1on the average day and 8 - 12 Mm-1on the highest 20% of 

days) approximates a regional background level, similar to the levels apparent at the Class I areas 

east of Nampa (Jarbidge, Sawtooth, Craters of the Moon and Selway-Bitterroot) where TASCO 

Nampa emissions were found to not “contribute” significantly to the modeled extinction.

To confirm the seasonality of the modeled impacts at Eagle Cap, the 22 highest days from the 

“Alternative Benchmark”, “BART” and “BART Alternative” scenarios were plotted in 
19

Figure 27. All of the highest 22 days were observed in the winter time, and the “BART 

Alternative” results showed a slight improvement over the “BART” results. 

It may be concluded that the “BART Alternative” scenario results in greater reductions in haze 

on the 98th percentile days, and more days below the 0.5Δdv threshold than the “BART” scenario 

because it more effectively addresses the primary aerosol contributor (nitrates) during the most 

impacted season at the most impacted Class I areas. This overall improvement comes at the price 

of slightly less improvement during the best visibility period in the spring, when sulfate is a 

much smaller, but still predominant contributor to visibility degradation. Thus, the reduction in 

SO2 control in lieu of more NOx control results in slightly less visibility improvement on the 

clearest days in the spring (< 5Mm-1). Nevertheless, greater overall improvement in visibility 

conditions occurs with the “BART Alternative” in comparison to the “BART” scenario.

Additional Environmental Benefits in Reducing Ozone

The Treasure Valley, including the Boise River and Snake River Valleys and stretching from 

Mountain Home, Idaho to Malheur County, Oregon, has been struggling with elevated 

summertime ozone conditions for a number of years. As shown in Figure 28, the Treasure Valley 

area remains perilously close to exceeding the ozone National Ambient Air Quality Standard 

(NAAQS). In 2008, the area escaped non-attainment by less than a part per billion. In 2010 the 

area was again very close to the proposed (but now deferred) range of the revised ozone NAAQS 

(60 – 70 ppb). DEQ believes that a recession-induced reduction in traffic, perhaps along with 

beneficial weather patterns has helped to avoid a non-attainment designation in recent years but 

that as traffic increases and weather varies, the attainment status of this area is precarious. As a 

result, Idaho has taken unprecedented steps to lower VOC and NOx ozone precursor emissions, 

including Stage II vapor control requirements and the nation’s only vehicle testing program (to 

our knowledge) that was not mandated by EPA in an ozone non-attainment plan. This testing 

program, started in June 2010 in Canyon County, where the TASCO Nampa Factory is located 

and was recently evaluated to determine the emission reductions it is providing. Based on 

MOVES modeling results, DEQ determined that the program provides approximately a 6.3% 

reduction in VOCs and a 2.7% reduction in NOx. The NOx reductions correspond to a 162 ton 

per year reduction or an annualized reduction of 0.4 tons per day. 

In its ongoing effort to be proactive in addressing the ozone problem, DEQ assessed the ozone 

mitigation benefits of a number of potential control measures in the CMAQ photochemical 

model, ranging from VMT reductions to reductions in emissions from lawn and garden 

equipment and solvent degreasing controls, etc. DEQ found that while VOC plus NOx reductions 

are most effective, NOx reductions of around 2 tons per day from the TASCO Factory is 

expected to result in a reduction of the peak 8-hour ozone concentration of approximately 0.1 

part per billion (ppb) on high ozone days. This is a better reduction than many of the other 

options, including further seasonal lowering of the Reid Vapor Pressure in gasoline, a 54% VOC 

reduction from a solvent-degreasing regulatory program, a 10% reduction in lawn and garden 

emissions, and a 10% reduction in vehicle refueling emissions. 

Ozone mitigation is only beneficial in the summertime. Thus, when TASCO’s winter processing 

campaign is over in the spring, less boiler capacity is required and at times the B&W Boilers 1& 
20

2 are not used, in which case summer ozone benefits from lowering the NOx emissions from the 

B&W boilers would not contribute to ozone mitigation. However, TASCO has confirmed that in 

addition to the Riley Boiler, the B&W boilers usually operate about 30 days during the summer 

ozone season (range is 20 to 60 days). As a result, on a significant number of summer days, DEQ 

anticipates that the BART Alternative will provide ozone reduction benefits in the Treasure 

Valley. 

The “BART Alternative” scenario, achieves 6.5 tons per day of NOx reductions in comparison to 

the “Alternative Benchmark”, more than double the 2.7 tons per day reduction from the “BART” 

scenario. This quantity represents the greatest NOx reduction of any ozone control measures 

DEQ has evaluated to date. While NOx-only controls are not as effective as combined NOx plus 

VOC controls, this large reduction, in conjunction with VOC-only controls should be sufficient 

to significantly reduce the number of unhealthy days and may help to avoid a non-attainment 

designation in the next few years.

Conclusions

This air quality modeling analysis addresses the visibility impacts of the “BART” and “BART 

Alternative” control scenarios for the BART-subject Riley Boiler at TASCO’s Nampa Factory.

The “BART” scenario results in an overall 36% reduction in acid gas emissions, while the 

“BART Alternative” scenario results in a 31% reduction, however total acid gas plus particulate 

matter emissions for the two scenarios are virtually identical. TASCO’s alternative proposal 

involves replacing Spray Dry Flue Gas Desulfurization SO2 controls on the Riley Boiler with 

low-NOx burner controls on two non-BART boilers, along with shutting down three pulp dryers. 

While the total emissions of all species are similar, the “BART Alternative” achieves greater 

improvements in visibility because the most severe non-carbon visibility impairment at the Class 

I areas nearest the Nampa Factory is dominated by ammonium nitrate in the winter and replacing 

some of the SO2 control with increased NOx control provides greater reductions on more poor 

visibility days. An analysis of seasonal aerosol extinction observations indicates that while the 

greatest improvements will occur in the winter when impacts are greatest, there will be a small 

visibility impairment in the spring when the visibility conditions are best and a low-level sulfate 

background dominates the extinction. 

Nevertheless, overall modeled improvements show that the modeled visibility degradation on the 

22nd highest impacted day at Eagle Cap was reduced by an additional 0.101 Δdv for the “BART 

Alternative” scenario in comparison to the “BART” scenario, and there were projected to be 23 

less days at Eagle Cap over the 0.5 Δdv threshold. Taking a broader geographic view, the 

combined number of days at all seven areas above the 0.5 Δdv threshold were reduced by an 

additional 41 days for the “BART Alternative” scenario in comparison to the “BART” scenario.

Finally, the “BART Alternative” scenario provides significantly greater NOx reductions than the 

“BART” scenario (2.4 times greater), and therefore is preferred by DEQ over the “BART”

scenario for additional environmental benefits it is expected to bring to the ozone mitigation 

efforts in the Treasure Valley, in addition to the improved visibility expected for Class I Areas in 

the region.
21

Figure 4 TASCO Nampa Facility-Wide NOx Emissions

Figure 5 TASCO Nampa Facility-Wide SO2 Emissions

Figure 6 TASCO Nampa Facility-Wide PM10 Emissions
22

Figure 7 Light extinction (Mm-1) based on measured aerosol concentrations at Starkey IMPROVE site, representing 

Eagle Cap and Strawberry Mountain, 2003.

Figure 8 Light extinction (Mm-1) based on measured aerosol concentrations at Starkey IMPROVE site, 2004.

Figure 9 Light extinction (Mm-1) based on measured aerosol concentrations at Starkey IMPROVE site, 2005.
23

Figure 10 Light extinction (Mm-1) based on measured aerosol concentrations at Hells Canyon IMPROVE site, 2003.

Figure 11 Light extinction (Mm-1) based on measured aerosol concentrations at Hells Canyon IMPROVE site, 2004.

Figure 12 Light extinction (Mm-1) based on measured aerosol concentrations at Hells Canyon IMPROVE site, 2005.
24

Figure 13 Light extinction (Mm-1) based on measured aerosol concentrations at Starkey IMPROVE Site, 

All Days, 2003 - 2005.

Figure 14 Light extinction (Mm-1) based on measured aerosol concentrations at Starkey IMPROVE Site, 

for 20% Worst Visibility Days, 2003-2005
25

Figure 15 Light extinction (Mm-1) based on measured aerosol concentrations at Sawtooth Wilderness IMPROVE site, 

2003.

Figure 16 Light extinction (Mm-1) based on measured aerosol concentrations at Sawtooth Wilderness IMPROVE site, 

2004.

Figure 17 Light extinction (Mm-1) based on measured aerosol concentrations at Sawtooth Wilderness IMPROVE site, 

2005.
26

Figure 18 Light extinction (Mm-1) based on measured aerosol concentrations at Jarbidge Wilderness IMPROVE site, 

2003.

Figure 19 Light extinction (Mm-1) based on measured aerosol concentrations at Jarbidge Wilderness IMPROVE site, 

2004.

Figure 20 Light extinction (Mm-1) based on measured aerosol concentrations at Jarbidge Wilderness IMPROVE site, 

2005.
27

Figure 21 Light extinction (Mm-1) based on measured aerosol concentrations at Craters of the Moon Wilderness 

IMPROVE site, 2003.

Figure 22 Light extinction (Mm-1) based on measured aerosol concentrations at Craters of the Moon Wilderness 

IMPROVE site, 2004.

Figure 23 Light extinction (Mm-1) based on measured aerosol concentrations at Craters of the Moon Wilderness 

IMPROVE site, 2005.
28

Figure 24 Light extinction (Mm-1) based on measured aerosol concentrations at Selway-Bitterroot Wilderness 

IMPROVE site, 2003.

Figure 25 Light extinction (Mm-1) based on measured aerosol concentrations at Selway-Bitterroot Wilderness 

IMPROVE site, 2004.

Figure 26 Light extinction (Mm-1) based on measured aerosol concentrations at Selway-Bitterroot Wilderness 

IMPROVE site, 2005.
29

Figure 27 Seasonal variation in the modeled three-year highest 22 impacted days at Eagle Cap Wilderness

for the pre-BART “Alternative Benchmark”, selected “BART”, and “BART Alternative” Scenarios.

Figure 28 History of Treasure Valley Ozone Design Values and NAAQS.