# 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

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- sided printing.

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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 (S pray Dry FGD) for sulfur dioxide (SO 2 

### ) control

, Low NO

x 

### burners (LNB) for nitrogen oxides (NO

x 

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

S pray Dry FGD with a) LN B controls on two (non

- BART) Babcock and Wilcox (B&W) boilers, and b) credits SO 2 

### , NO

x 

### and PM emission reduction s from shutting down 3 pulp dr yers . 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 B oilers. In this r eport, 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 B oilers and p ulp d ryers ) affected by the alternative in their pre

- BART condition.

Model r esults for the “BART Alternative” scenario indicate that visibility improves an additional 0.159 ∆ dv on the 22 nd 

### 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

red uction 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 we re hig hest , the shift from

SO 2 

### control to additional NO

x 

### control will also result in a slight ly 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 Alterna tive 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 mitigati on benefits by more than doubling the NO

x 

### 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 miti gate 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.

### 4



## Introduction

The Amalgamated Sugar Company LLC (TASCO) at Nampa, Idaho has requested revision of the initial Best Available Retrofit Technology (BART) determination for NO

x 

### 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 (S pray Dry FGD) for sulfur dioxide (SO 2 

### ) control

, Low NO

x 

### burners (LNB) for nitrogen oxides (NO

x 

### ) 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, a nd b) SO 2 

### , NO

x 

### and PM emission reduction cred its for shutting down 3 pulp dry ers. 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 r eport. The benchmark scenario provides a common pre

- BART basis against which the regional haze impacts of both the BART and BART Alternat ive scenarios can be compared.



## Control Scenarios Modeled

The revised BART and BART Alternative determinations are discu ssed 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 deg radation 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 I D wzI10495) includes R iley B oiler 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 bag house, Spray Dry FGD, and LNB

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

 Pulp Dryers

, full oper ation ( benchmark emissions of sources affected by the BART Alternative)

“ BART Alternative ” Modeling Scenario

This s cenario (Run ID wzI10493) includes the BART NO

x 

### controls on the Riley boiler, along

with Low

- NO

x 

### burners on two other non

- BART Babcock and W ilcox (B&W) boilers . The B&W

NO

x 

### controls along with credits for shutting down three pulp dryers, is proposed by TASCO a s an alternative for SO 2 

### control using Spray

- Dry FGD.

 Riley Boiler with existing baghouse and LNB

 B&W Boilers #1 and #2 with LNB

 Pulp D ryers 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 scenari o. It provides a common benchmark for comparison of the “BART” and “BART Alternative” scenarios on an equ ivalent

basis:

 Riley Boiler with existing baghouse

 B&W Boilers #1 and #2

, full operation

 Pulp Dryers

, full operation



## Methods

The dispersion and visibility modeling de scribed in this report is based o n 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 determ ine the

delta

- deciview (Δ dv ) visibility impacts, the number of days per year above the 0.5 Δ dv threshold, and t he number of days per the three

– year period above the 0.5 Δ dv threshold. The modeling was performed in accordance with the BART Modeling Protocol 1 

### , 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 i n 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 Nat ional 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 Wilder ness 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)



### T he 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 t he 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.

### 6

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

. 3



### Primary particulate matter from these sources is a relatively small contributor to regional haze. Nevertheless, detailed particulate matter speciation was estimated using Na tional 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 (SO 4 

### ) in Table 3 is shown as (and input to CALPUFF) as pounds per hour SO 4



### . However, when totaling the aerosol species under “Total PM 10 

### ” it is converted to a stoichiometric equivalent mass of ammonium sulfate ( (NH 4 

### ) 2 

### SO 4 

### ), 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) CALP UFF (pink) domains with Class I

areas within 300

- km radius (blue) of TASCO Nam pa Factory (red dot).

3 CALMET Statistical Report, CALMET Fields for BART Modeling , Id aho, Oregon and Washington, Geomatrix Consultants, Inc., Lynnwood WA 98036, July 2006

.

4 National Park Service, Particulate Matter Speciation, Coal

- Fired Boiler PM 10 , http:// www.nature.nps.gov/air/Permits/ect/ectCoalFiredBoiler.cfm

### 7

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)

St ack 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% Cont rol) 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

Nor th 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 75 3 74.7 3.35 440.0 

### 11.7

### 8

Table 3 Emission Rates used in CALPUFF Modeling (a)

Unit Control Equipment SO 2 lb/hr SO 4

lb/hr NOX

lb/h r HNO 3

lb/hr NO 3

lb/hr PMC

lb/hr PMF

lb/hr EC

lb/hr SOA

lb/hr Total

PM 10 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” Sce nario (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 Implementat ion (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 (SO 2 ), Nitrogen oxides (NO

x = NO + NO 2 ), nitric acid (HNO 3 ) and speciated particulate matter species (SO 4 ), particulate nitrate
(NO 3 ), coarse particulate matter 2.5

– 10  m in aerodynamic diameter (PMC), fin e 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 (PM 10 ). (b) Total PM 10 is not used directly in the model but represents total of PM speci es for information only. SO 4 is added into total PM 10 as ammonium sulfate (SO 4 lb/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

### 9



## BART Alternat ive 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 98 th 

### 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 98 th 

### percentile

, the top 7 days in any year, or top 21 days in three year s
, EPA intended to minimize the effects of extrem e meteorology and conservative assumptions.

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

 

### 8 th 

### highest Δ dv value for each of the years modeled (2003

- 2005 ), representing the 98th percentile (8/365 = 0.02) cutoff for Δ dv in the each year. In addition the numbers of days in each year above the 0.5 Δ dv threshold are shown.

 

### 22 nd 

### highest value for the entire period from 2003 through 2005, representing the 98th

p ercentile (22/1095 = 0.02) cutoff for Δ dv over three years. In addition the numbers of days in all three years above the 0.5 Δ dv 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” (>0.5 Δ dv) 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 ben chmark 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 0.5 Δ dv threshold at all

sites. Figure 2 clearly shows that the m odel

- predicted visibility impacts at Eagle Cap ( due to the

exi sting Riley boile r) we re 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 0.5 Δ dv threshold for a 98 th 

### 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, out side of the October

– February period. However it does “cause” haze impacts (>1 Δ dv) 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 m onitored aerosol extinction at IMPROVE monitoring sites

. For this purpose, it is

useful to understand ho w light extinction is determined from aerosol species concentrations and

### 10

how extinction relates to the “haze index” or changes in visibi lity relative to the background visibility in terms of delta deciviews ( Δ dv). Light extinction (b ext) 

### is computed from aerosol species concentrations and reported in units of reciprocal megameters ( Mm - 1 

### ) according to the equation:

b ext 

### = 3 f(RH) [(NH 4 

### ) 2 

### SO 4 

### ] + 3 f(RH) [NH 4 

### NO 3 

### ] + 4[OC] + 1[Soil] + 0.6[Coarse Mass] + 10[EC] + b R ay



### ( 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

, b Ray 

### is Raleigh scattering due to a ir molecules, Mm - 1



### [(NH 4 

### ) 2 

### SO 4 

### ] is the ammonium sulfate concentration formed from SO

s 

### , μg/m 3



### [NH 4 

### NO 3 

### ] is the ammonium nitrate concentration formed from NO
x 

### , μg/m 3



### [OC] is the organic carbon concentration, μg/m 3 

### (equivalent to “SOA” in 

### Table 3 ) [Soil] is the fine geologic particulate matter, μg/m 3 

### (equivalent to “PMF” in 

### Table 3 ), [Coarse Mass] is the coarse particulate matter, μg/m 3 

### (equivalent to “PMC” in 

### Table 3 ), and [EC] is th e elemental carbon, μg/m 3



### Light extinction is not measured directly at IMPROVE sites, but is calculated based on aerosol measurements of the species in E quation 1 . In this document, the terms “measured extinction” or

“ monitored extinction” refer to light ext inction 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

b

ext (sourc e) 

### is compared to background extinction , b ext (bkg), 

### to predict the haze in dex in terms of

delta

- deciviews :

 dv = 10 ln [ ( b ext (bkg) 

### + b ext (source) 

### ) / ( b ext (bkg) 

### ) ] (Eqn 2 )

A time series view of 2004 l ight ex tinction 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 200 4 stagnation episode produced the greatest monitored and modeled aerosol extinction over the 3 year period. The similarity in m onitor

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

model captures the seasona l 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 mid

October.

Summary of “BART” results. The visibility improvement for the “ BART” scenario, in compa rison to the Alternative Benchmark scenario ( Table 4 ) shows a reduction in the three

- year 22 nd 

### highest Δ dv of 0.689 Δ dv at Eagle Cap, the most impacted area, and 0.119 Δ dv at Jarbidge Wilderness, the least impacted

area. Similarly, the number of days in three years above the 0.5 Δ dv threshold at Eagle Cap decreases from 195 days to 149 days, a 46 day reduct ion, while Jarbidge is projected to see only a three day reduction. The sum of days in 3 years above 0.5 Δ dv 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 d ays overall.

### 11

Summary of “ BART A lternative ” 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 22 nd 

### highest Δ d v at Eagle Cap from 2.201 to 1.411 Δ dv, a visibility improvement of 0.790 Δ dv. The number of days in the three

- year period above the 0.5 Δ dv 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 Δ dv 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 ver y small visibility degradation appears at Selway

- Bitterroot Wilderness Area.

### 12 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 Benchm ark ” (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) 0.1 92 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 Impr ovement (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 Reducti on 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 f or 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 S pray Dry FGD and LNB controls plus the pre

- BART emissions of the B&W boilers 1&2 and three pu lp dryer s 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 ” sce nario 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 Benchmar k ” (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 ” (wzI1049 2) 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 ” (w zI10493) 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 1 1 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 “B ART 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)

(wzI1 0495) “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 Wilde rness, 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 22 nd 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

- decivi ew impact s due to TASCO's Riley Boiler

(existing control) , over the three model years

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

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

### 16



## Other Considerat ions

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 reducin g the level of SO 2 

### control and replacing it with increased NO

x 

### control. As a result, DEQ reassessed the selection of emission

sources included in BART A lternative modeling and evaluated whether inordinate visibility impacts we re 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 SO 2 

### emissions by Spray Dry

- FGD were proposed by TASCO, in

li ght of both the high cost and the environmental impairment due to the waste stream produced by S pray Dry FGD. During the evaluation, the FLMs suggested that in seeking alternative emission reductions, DEQ sho uld examine the entire facility

- wide emission in ventory 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 precursor s in the facility

- wide emission inventor y 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 NO

x 

### , SO 2 

### and PM 10 

### 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 c omprise 97% of the total facility

- wide NO

x 

### emissions , 99% of the

SO 2 

### emissions and 98% of PM 10 

### 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 R eplacing SO 2 

### Control with A ddition al NO

x 

### Control The proposed BART Alternative replaces the Spray

- Dry Flue Gas Desulfurization SO 2 

### control on the Riley Boiler with additional NO

x 

### controls on the two Babcock & Wilcox boilers and with

additional NO

x 

### , SO 2 

### and PM 10 

### reductions achieved by shutt ing 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 d uring 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 data 5 

### 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 monitore d aerosol impacts, with the exception of isolated wildfire impacts that affect sites throughout the west.

M onitoring 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 measur ed 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 simil ar patterns of observed seasonal visibility degradation and aerosol composition. A review of Figure 7 through Figure 12 indicates that:

 The g reatest non

- carbon impacts a re in the winter, when nitrate pr edominates 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

carb on predominates e xtinction (~120

– 280 Mm - 1 

### ) , likely from wildfires in the region, nitrate is negligible, and sulfate i s 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 ca n 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 impa ct in 3 years reaching just over 20 Mm - 1



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

winter and sum mer when extinction reaches 120 to 300 Mm - 1 

### most years.

The Starkey IMPROVE site represents the two Class I are as 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 w ere obtained

from the WRAP

- TSS 5 

### and summarized into mont hly average extinction values. Figure 13 shows monthly averaged total extinction at Starkey, and average extinction b y 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 experien ce 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 extincti on 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.

L ess Impacted Areas The TASCO Nampa Factory modeled impacts for the “Alternative Benchmark” sc enario 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 22 nd 

### highest

Δ dv days. None of the 22 nd 

### highest days exceed 0.5 Δ dv, t he 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, 20 04 and 2005 are shown for Sawtooth Wilderness in Figure

15

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

, Figu re 19 , and Figure 20 ; for Craters of the Moon Wilderness in Figure 21

, Figure 22 , and Figure 23 ; and for the Selway

- Bitterroot Wilderne ss 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 an d 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 indica te 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 Fac tory . C arbon dominate d at these sites during the summer wildfire season, peaking around 130 Mm - 1 

### at Sawtooth and over 350 Mm - 1 

### at Selway

- Bitterroot. S ulfate was more significant in the spring with most days below 5

- 6 Mm - 1 

### and 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 magnitud e to sulfate at all the other sites, typically around 5

- 10 Mm - 1 

### or less, and never exceed s 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 Clas s 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, pr obably 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 - 1 

### on the average day and 8

- 12 Mm - 1 

### on 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 emiss ions 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 gr eater reductions in haze

on the 98 th 

### percentile days, and more days below the 0.5 Δ dv threshold than the “BART” scenario because it more effectively addresses the primary aerosol contributor (nitrates) during the most impacted season at the most impacted Cl ass 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

SO 2 

### c ontrol in lieu of more NO

x 

### 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 “BAR T” 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 hel ped 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 NO

x 

### ozone precursor emissions,

i ncluding 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 F actory 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 NO

x 

### . The NO

x 

### reducti ons 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 NO

x 

### reductions are most effective, NO

x 

### reductions of around 2 tons per d ay 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 lowe ring 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 su mmertime. Thus, when TASCO’s winter processing campaign is over in the spring, less boiler capacity is required and at times the B&W B oilers 1&

### 20

2 are not used, in which case summer ozone benefits from lowering the NO

x 

### emissions from the

B&W boilers would n ot 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 NO

x 

### 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 NO

x 

### reduction of any ozone control measures DEQ has evaluated to date. While NO

x 

### - only controls are not as effective as combined NO

x 

### 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 r esults 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 SO 2 

### controls on the Riley Boiler with

low

- NO

x 

### 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 A lternative ” 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 SO 2 

### control with increased NO

x 

### control provides greater reductions on more poor visibility days. An analysis of seasonal aero sol 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 backgro und dominates the extinction.

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

22 nd 

### highest impacted day at Eagle Cap was reduced by an additional 0.101 Δ dv for the “BART Alternative” scenario in comparison t o the “ BART” scenario, and there were projected to be 23 less days at Eagle Cap over the 0.5 Δ dv threshold. Taking a broader geographic view, the combined number of days at all seven areas above the 0.5 Δ dv threshold were reduced by an additional 41 days f

or the “BART Alternative” scenario in comparison to the “ BART” scenario.

Finally, the “BART Alternative” scenario provides significantly greater NO

x 

### 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 NO

x Emissions

Figure 5 TASCO Nampa Facility

- Wide SO2 Emissions

Figure 6 TASCO Nampa Facility

- Wide PM 10 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 Star key 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 concentratio ns 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 mea sured 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 Lig ht 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.

Figu re 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 Wil derness 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 me asured 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

- Bitte rroot 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 “A lternative Benchmark ”, selected “ BART”, and “BART Alternative” Scenarios.

Figure 28 History of Treasure Valley Ozone Design Values and NAAQ S.