19020 33rd Avenue W, Suite 310, Lynnwood, WA 98036-4748 

Tel: +1 425.412.1800 Fax: +1 425.412.1840 

www.environcorp.com

July 20, 2012 

Project No. 29-23586A 

Mr. Gerardo Rios 

U.S. Environmental Protection Agency, Region 9 

75 Hawthorne Street 

San Francisco, California 94105 

Subject: Class II Area Visibility Analysis 

Sierra Pacific Industries Biomass-Fired Cogeneration Project 

Anderson, California 

Dear Mr. Rios:

This letter provides information regarding a Class II area visibility analysis developed in 

response to an e-mail sent by Cleveland Holladay of U.S. EPA Region 9 on July 6, 2012, 

requesting that SPI assess the potential for the biomass-fired cogeneration project proposed 

for installation at SPI”s Anderson facility to cause visual impairment in potentially sensitive 

Federal and State Class II areas, as required by 40 CFR Part 52.21(o). 

Potentially sensitive areas were identified using Google Earth, as well as U.S. Forest Service 

(http://www.fs.fed.us) and California Department of Parks and Recreation 

(http://www.parks.ca.gov) websites. This effort revealed two Federal areas, and two State 

areas within 50 kilometers (km) of the Anderson facility: 

 Sacramento River National Wildlife Refuge (NWR) 

 Whiskeytown National Recreation Area (NRA) 

 Shasta State Historic Park (SHP) 

 William B. Ide Adobe SHP 

The Sacramento River NWR is composed of 27 units along the Sacramento River between 

Red Bluff and Princeton, California, totaling 10,146 acres. The closest unit is approximately 

38.8 km south-southeast of the facility, and most of the 6 northernmost units lie within 50 km 

of the facility. Whiskeytown NRA encompasses 42,497 acres, and is located between 18.3 

and 37.1 km to the northwest of the facility. 

The Shasta SHP is located approximately 20 km northwest of the facility, covers 

approximately 19 acres in the town of Shasta, and consists of four restored or reconstructed 

buildings, some ruins, and a cemetery along State Route 299. William B. Ide Adobe SHP is 

located approximately 32 km south-southeast of the facility, covers approximately 4 acres, 

and consists of three historic structures, a visitor’s center, and a picnic area. 

The two Federal areas were included in the Class II area visibility analysis, but the two State 

areas were not. The historic parks are much smaller, and the exhibits are not subject to 

potential visual impacts from a stack plume in the same way that larger, wild areas are (e.g., 

Sacramento River NWR and Whiskeytown NRA). 
Mr. Gerardo Rios 

SPI-Anderson Biomass-Fired Cogeneration Project 

July 20, 2012 

Page 2 

The visibility impact analyses of the Sacramento River NWR and Whiskeytown NRA were 

conducted using the plume visibility impact screening model VISCREEN. The model was 

exercised in accordance with guidance provided in “Workbook for Plume Visual Impact 

Screening and Analysis (Revised)” (EPA–454/R–92–023; hereafter referred to as “the 

Workbook”). 

Level 1 screening analyses, which use worst-case meteorological conditions to provide a 

conservative estimate of plume visual impacts, were developed for both Class II areas of 

concern. Inputs required for Level 1 are: 1) maximum expected short-term emission rates, 2) 

the maximum and minimum distances to each area of concern, and 3) a background visual 

range for each area of concern. Particulate matter (PM) and oxides of nitrogen (NOX)

emission rates of 9.36 pounds per hour (lb/hr) and 70.2 lb/hr, respectively, were used, and 

primary NO2, elemental carbon, and primary sulfate emission rates were assumed to be zero 

as suggested by the Workbook. The maximum and minimum distances mentioned above 

were used for the areas of concern (the maximum distance for the Sacramento River NWR 

was limited to 50 km, though the maximum distance to the most distant unit of the NWR is 

over 120 km from the facility). Background visual ranges of 110 km for the Sacramento 

NWR and 60 km for the Whiskeytown NRA were obtained from Figure 9 on page 26 of the 

Workbook. 

The results of the Level 1 screening analyses indicated that some of the screening criteria 

were exceeded, necessitating a Level 2 screening analysis. The default screening criteria 

suggested in the Workbook were used: a plume perceptibility (ΔE) of 2.0, and a green color 

contrast value (Cp) of 0.05. 

Level 2 screening analyses are similar to Level 1 analyses except situation-specific 

information can be used for particle size distributions, as well as meteorology and plume 

transport and dispersion patterns. Particle size distribution data specific to the cogeneration 

unit or the areas of concern were not available, so the Level 1 default were used. The five 

years of meteorological data from Redding Airport (KRDD) developed for use with 

AERMOD to predict ambient concentrations in Class II areas for the March 2010 permit 

application were used to develop joint frequency distributions organized by Pasquill-Gifford 

stability class, wind speed in meters per second (m/s), wind direction, and time of day. Per 

the guidance provided by the Workbook, the frequency distributions were stratified using 

four time-of-day “bins”: 0001 to 0600, 0601 to 1200, 1201 to 1800, and 1801 to 2400. Wind 

speed bins are defined by the maximum represented wind speed (e.g., the “3 m/s” wind speed 

bin contains wind speeds from 2.01 to 3 m/s). Wind direction bins were based on the sixteen 

cardinal directions (e.g., the north-northwest, or NNW, bin contains winds from angles 

between 326.25° and 348.75°). 

The Workbook suggests that, if available, visual range data from locations near the source 

area and area of concern can be used for the Level 2 analysis in place of the default values 

used in the Level 1 analyses. Table 10 of the “Federal Land Managers’ Air Quality Related 

Values Work Group (FLAG) Phase 1 Report – Revised (2010)” includes calculated monthly 

average natural range visual ranges for all Class I areas. For the Whiskeytown NRA, the 

median visual range for the Yolla-Bolly-Middle Eel Wilderness Area (258 km) was used, 

and, for the Sacramento River NWR, the median visual range for Lassen Volcanic National 
Mr. Gerardo Rios 

SPI-Anderson Biomass-Fired Cogeneration Project 

July 20, 2012 

Page 3 

Park (267 km) was used. In both cases (and particularly in the case of the Sacramento River 

NWR), the Class I area is located at higher elevations, and has greater visual range than the 

Class II area of concern. The use of Class I area visual ranges adds considerable 

conservatism to the analyses. 

Worst-case dispersion conditions were calculated and ranked for each area of concern 

according to guidance in the Workbook. Dispersion conditions were represented by the 

product of σy (the horizontal Pasquill-Gifford diffusion coefficient, calculated per Appendix 

E of the Workbook), σz (the vertical Pasquill-Gifford diffusion coefficient, calculated per 

Appendix E of the Workbook), and u (the wind speed). Dispersion conditions were 

calculated for the following combinations of stability class and wind speed, as suggested by 

the Workbook: 

 Stability Class F & Wind Speeds of 1, 2, and 3 meters per second (m/s) 

 Stability Class E & Wind Speeds of 1, 2, 3, 4, and 5 m/s 

 Stability Class D & Wind Speeds of 1, 2, 3, 4, 5, 6, 7, and 8 m/s 

For each dispersion condition defined for a given stability class and wind speed, a frequency 

of occurrence was obtained from the joint frequency distribution for the worst-case wind 

direction (i.e., the wind-direction sector most likely to transport a plume from the facility to 

the area of concern – winds from the southeast for Whiskeytown NRA, and from the northnorthwest for Sacramento River NWR), for each of the four time-of-day bins. The dispersion 

condition values (i.e., the product σyσzu) were then ranked, with the smallest value being the 

worst-case condition. Cumulative frequencies were calculated starting with the worst-case 

condition for each time-of-day bin, and the worst-case condition with a cumulative frequency 

of one percent or greater was evaluated using VISCREEN. Table 1 attached to this letter 

provides the dispersion conditions and frequencies for Whiskeytown NRA, and Table 2 

provides analogous information for Sacramento River NWR. Tables 3 and 4 provide 

cumulative frequencies for Whiskeytown NRA and Sacramento River NWR, respectively; in 

each case, the minimum cumulative frequency that exceeded one percent for each time-ofday bin is indicated by a bold border. 

Based on the results shown in Table 2, the Level 2 Whiskeytown NRA analysis used stability 

class D, and a wind speed of 5 m/s; the Level 2 Sacramento River NWR analysis used 

stability class F and a wind speed of 3 m/s as indicated by the results in Table 4. The results 

of these analyses are presented in Table 5 for Whiskeytown NRA and in Table 6 for 

Sacramento River NWR. The default Level 1 screening criteria (i.e., ΔE < 2.0 Cp < 0.05) 

were used to assess potential impacts. 

VISCREEN, which was developed to assess impacts in Class I areas, provides the maximum 

predicted visual impacts for two backgrounds (sky and terrain) and two scattering angles 

(i.e., the angle between the sun’s position and the line of sight) for an observer located inside 

the area of concern, and the same two background and two scattering angles for an observer 

located outside the area of concern. Visual impacts outside the area of concern involve 

plumes that do not interact with, but could potentially be observed from inside the area of 

concern. Tables 5 and 6 present results for observers located inside as well as outside the 
Mr. Gerardo Rios 

SPI-Anderson Biomass-Fired Cogeneration Project 

July 20, 2012 

Page 4 

areas of concern, but, because these analyses are concerned with impacts inside the areas of 

concern, only the results for an observer located inside the areas of concern are considered 

when assessing the potential for the project to contribute to visibility impairment. 

As shown by the VISCREEN Level 2 results for an observer inside the two areas of concern 

in Tables 5 and 6, the proposed project is predicted to not have the potential to contribute to 

visibility impairment at sensitive Class II areas within 50 km. 

We believe that the information provided in this letter addresses the information requested by 

Region 9, and should be considered to amend the submitted PSD permit application. Please 

let me know if Region 9 requires any additional information to finalize the draft permit. If 

you or your staff has any additional questions or need additional information, please do not 

hesitate to contact me at 425.412.1804. 

Sincerely yours, 

ENVIRON INTERNATIONAL, INC. 

Eric Albright 

Senior Manager 

Enclosures 

cc: Omer Shalev, USEPA Region 9 

Cleveland Holladay, USEPA Region 9 

Ross Bell, Shasta County Air Pollution Control District 

Shane Young, Sierra Pacific Industries 

Dave Brown, Sierra Pacific Industries 
Mr. Gerardo Rios 

SPI-Anderson Biomass-Fired Cogeneration Project 

July 20, 2012 

Page 5 

Table 1 

Dispersion Condition Frequencies for Whiskeytown NRA 

Stability 

Class 

Wind

Speed

(m/s) 

σyσzu 

(m3/s) 

Transport

Time 

(hr) 

Frequency 

0001-0600 0601-1200 1201-1800 1801-2400

F 1 27,270 10.2 0.000 0.000 0.000 0.000 

F 2 54,541 3.4 0.002 0.000 0.001 0.002 

E 1 73,370 10.2 0.000 0.000 0.000 0.000 

F 3 81,811 2.6 0.003 0.000 0.000 0.003 

E 2 146,740 2.0 0.000 0.000 0.000 0.000 

D 1 177,519 10.2 0.000 0.000 0.000 0.000 

E 3 220,110 2.6 0.001 0.000 0.000 0.001 

E 4 293,480 1.5 0.002 0.000 0.000 0.002 

D 2 355,039 1.7 0.000 0.000 0.000 0.000 

E 5 366,850 1.5 0.001 0.000 0.000 0.001 

D 3 532,558 1.3 0.000 0.000 0.000 0.000 

D 4 710,078 1.5 0.000 0.000 0.000 0.000 

D 5 887,597 1.1 0.000 0.000 0.000 0.001 

D 6 1,065,117 0.9 0.000 0.000 0.000 0.001 

D 7 1,242,636 0.8 0.000 0.000 0.000 0.000 

D 8 1,420,155 0.7 0.000 0.000 0.000 0.000 

 
Mr. Gerardo Rios 

SPI-Anderson Biomass-Fired Cogeneration Project 

July 20, 2012 

Page 6 

Table 2 

Dispersion Condition Frequencies for Sacramento River NWR 

Stability 

Class 

Wind

Speed

(m/s) 

σyσzu 

(m3

/s) 

Transport

Time 

(hr) 

Frequency 

0001-0600 0601-1200 1201-1800 1801-2400

F 1 66,449 21.6 0.000 0.000 0.000 0.000 

F 2 132,897 7.2 0.006 0.002 0.001 0.002 

E 1 189,490 21.6 0.000 0.000 0.000 0.000 

F 3 199,346 5.4 0.010 0.002 0.001 0.003 

E 2 378,981 4.3 0.000 0.000 0.000 0.000 

D 1 517,083 21.6 0.000 0.000 0.000 0.000 

E 3 568,471 5.4 0.001 0.001 0.000 0.001 

E 4 757,961 3.1 0.007 0.001 0.001 0.004 

E 5 947,451 2.4 0.002 0.001 0.000 0.002 

D 2 1,034,166 3.1 0.000 0.000 0.000 0.000 

D 3 1,551,249 4.3 0.000 0.002 0.001 0.000 

D 4 2,068,332 3.1 0.000 0.002 0.001 0.000 

D 5 2,585,415 2.4 0.001 0.002 0.002 0.002 

D 6 3,102,498 2.0 0.001 0.002 0.003 0.003 

D 7 3,619,581 1.7 0.000 0.001 0.002 0.001 

D 8 4,136,664 1.4 0.000 0.000 0.001 0.000 
Mr. Gerardo Rios 

SPI-Anderson Biomass-Fired Cogeneration Project 

July 20, 2012 

Page 7 

Table 3 

Cumulative Dispersion Condition Frequencies for Whiskeytown NRA 

Stability 

Class 

Wind

Speed

(m/s) 

σyσzu 

(m3/s) 

Transport

Time 

(hr) 

Cumulative Frequency 

0001-0600 0601-1200 1201-1800 1801-2400

F 1 27,270 10.2 0.000 0.000 0.000 0.000 

F 2 54,541 3.4 0.002 0.000 0.001 0.002 

E 1 73,370 10.2 0.002 0.000 0.001 0.002 

F 3 81,811 2.6 0.006 0.000 0.001 0.005 

E 2 146,740 2.0 0.006 0.001 0.001 0.005 

D 1 177,519 10.2 0.006 0.001 0.001 0.005 

E 3 220,110 2.6 0.006 0.001 0.001 0.006 

E 4 293,480 1.5 0.009 0.001 0.001 0.008 

D 2 355,039 1.7 0.009 0.001 0.001 0.008 

E 5 366,850 1.5 0.009 0.001 0.001 0.009 

D 3 532,558 1.3 0.009 0.001 0.001 0.009 

D 4 710,078 1.5 0.010 0.001 0.001 0.009 

D 5 887,597 1.1 0.010 0.001 0.002 0.011 

D 6 1,065,117 0.9 0.010 0.001 0.002 0.012 

D 7 1,242,636 0.8 0.010 0.001 0.002 0.012 

D 8 1,420,155 0.7 0.010 0.001 0.002 0.012 

 
Mr. Gerardo Rios 

SPI-Anderson Biomass-Fired Cogeneration Project 

July 20, 2012 

Page 8 

Table 4 

Cumulative Dispersion Condition Frequencies for Sacramento River NWR 

Stability 

Class 

Wind

Speed

(m/s) 

σyσzu 

(m3

/s) 

Transport

Time 

(hr) 

Cumulative Frequency 

0001-0600 0601-1200 1201-1800 1801-2400

F 1 66,449 21.61 0.000 0.000 0.000 0.000 

F 2 132,897 7.2 0.006 0.002 0.001 0.002 

E 1 189,490 21.61 0.006 0.002 0.001 0.002 

F 3 199,346 5.4 0.016 0.004 0.001 0.005 

E 2 378,981 4.3 0.016 0.005 0.001 0.005 

D 1 517,083 21.61 0.016 0.005 0.001 0.005 

E 3 568,471 5.4 0.018 0.006 0.002 0.006 

E 4 757,961 3.1 0.024 0.007 0.002 0.009 

E 5 947,451 2.4 0.026 0.007 0.002 0.012 

D 2 1,034,166 3.1 0.026 0.008 0.002 0.012 

D 3 1,551,249 4.3 0.026 0.009 0.003 0.012 

D 4 2,068,332 3.1 0.026 0.011 0.004 0.012 

D 5 2,585,415 2.4 0.027 0.013 0.006 0.014 

D 6 3,102,498 2.0 0.028 0.014 0.009 0.016 

D 7 3,619,581 1.7 0.029 0.015 0.011 0.018 

D 8 4,136,664 1.4 0.029 0.015 0.011 0.018 

1 Transport times greater than 12 hours are not included in the cumulative frequency totals. 

 
Mr. Gerardo Rios 

SPI-Anderson Biomass-Fired Cogeneration Project 

July 20, 2012 

Page 9 

Table 5 

Whiskeytown NRA Level 2 VISCREEN Results 

Observer 

Location Background

Theta1

(degrees) 

Distance2

(km) 

Perceptibility3

(ΔE) 

Contrast3

(Cp) 

Inside Sky 10 37.1 0.408 0.005 

Inside Sky 140 37.1 0.24 -0.003 

Inside Terrain 10 37.1 0.911 0.007 

Inside Terrain 140 37.1 0.187 0.001 

Outside Sky 10 1.0 3.278* 0.041 

Outside Sky 140 1.0 1.993 -0.027 

Outside Terrain 10 1.0 6.999* 0.058* 

Outside Terrain 140 1.0 1.493 0.009 

1 The angle between direct solar radiation and the observer’s line of sight. If the observer were 

looking directly towards the sun, the angle would be zero degrees; if the observer were looking 

away from the sun, the angle would be 180 degrees. 

2 Plume parcel downwind distance from source. 

3 An asterisk (*) indicates absolute values that exceed the default screening criteria. The default 

screening criteria are: a plume perceptibility (ΔE) of 2.0, and a green color contrast value (Cp) of 

0.05. Negative contrast values indicate a plume that appears darker than the background. 
Mr. Gerardo Rios 

SPI-Anderson Biomass-Fired Cogeneration Project 

July 20, 2012 

Page 10 

Table 6 

Sacramento River NWR Level 2 VISCREEN Results 

Observer 

Location Background

Theta1

(degrees) 

Distance2

(km) 

Perceptibility2

(ΔE) 

Contrast2

(Cp) 

Inside Sky 10 50.0 0.724 0.01 

Inside Sky 140 50.0 0.47 -0.006 

Inside Terrain 10 38.9 1.209 0.008 

Inside Terrain 140 38.9 0.104 0.001 

Outside Sky 10 1.0 6.832* 0.121* 

Outside Sky 140 1.0 1.465 -0.043 

Outside Terrain 10 1.0 9.892* 0.104* 

Outside Terrain 140 1.0 1.385 0.024 

1 The angle between direct solar radiation and the observer’s line of sight. If the observer were 

looking directly towards the sun, the angle would be zero degrees; if the observer were looking 

away from the sun, the angle would be 180 degrees. 

2 Plume parcel downwind distance from source. 

3 An asterisk (*) indicates absolute values that exceed the default screening criteria. The default 

screening criteria are: a plume perceptibility (ΔE) of 2.0, and a green color contrast value (Cp) of 

0.05. Negative contrast values indicate a plume that appears darker than the background.