United States 

Department of

Agriculture

Forest 

Service

Southwestern

Region

Prescott National Forest

Air Quality

Specialist Report

Compiled December, 2011

and Updated March, 2014

for the

Forest Plan Revision

Environmental Impact Statement

Submitted by: __/s/ _________________________

Mary C. Rasmussen

Forest Planning - Team Leader and Ecologist

Prescott National Forest

Reviewed by: Edwin Paul

Forest Fuels Specialist

Prescott National Forest

Ron Sherron

Air Quality Specialist

Arizona Dept. of Environmental Quality
Air Quality Specialist Report – Prescott National Forest

Table of Contents

Table of Contents......................................................................................................................... i

Introduction.................................................................................................................................. 1

Relevant Laws, Regulations, and Policy that Apply.......................................................... 1

Description of Affected Environment (Existing Condition)............................................. 4

NAAQS: ................................................................................................................................... 4

Visibility:................................................................................................................................... 6

Air Quality Threats: ................................................................................................................ 7

Needs for Change Addressed in this Analysis ............................................................................. 9

Summary of Alternatives .......................................................................................................... 9

Alternative A – 1987 Forest Plan Direction:........................................................................ 9

Alternative B – The Proposed Revised Plan:..................................................................... 9

Alternative C - Vegetation and Wildlife Emphasis:.......................................................... 10

Alternative D – Dispersed Recreation Emphasis: ........................................................... 10

Assumptions...............................................................................................................................11

Methodology and Analysis Process.................................................................................... 13

Environmental Consequences .................................................................................................... 14

Cumulative Environmental Consequences ............................................................................... 17

Unavoidable Adverse Impacts, Irreversible and Irretrievable Commitment of 

Resources ............................................................................................................................. 18

References ................................................................................................................................. 19
Air Quality Specialist Report - Prescott National Forest 1

Introduction

The purpose of this report is to evaluate the potential environmental consequences to air quality

that may result with the adoption of a revised land management plan. It examines the 

consequences of taking no action to revise the existing plan and of three alternative actions: the 

proposed revision of the Forest Plan, an alternative that emphasizes vegetation and wildlife

habitat restoration, and an alternative that emphasizes dispersed recreation opportunities. 

This report describes:

 The laws that are relevant to air quality and smoke management on the Prescott National 

Forest

 The environment affected by the alternatives

 The needs for change identified in revising the existing plan

 The portions of the alternative considered in detail that are relevant to air quality and 

smoke management

 The environmental consequences of the alternatives

 The cumulative effects to the environment of the alternatives 

Relevant Laws, Regulations, and Policy that Apply 

In 1955, Congress passed the first Federal Clean Air Act with later amendments in 1967, 1970, 

1977, and 1990. Implementation of this Federal Law is largely the responsibility of the States 

which may develop programs that are more restrictive than the Clean Air Act requires but never 

less. The State of Arizona has a State Implementation Plan that outlines how the State is 

implementing the goals of the Clean Air Act, and Statutes that regulate burning, including use of 

wildland fire on Federal and State lands. Two types of air quality impacts are addressed by these 

laws and regulations: health hazards from pollutants, and visibility impacts in Class I Airsheds.

The Clean Air Act establishes National Ambient Air Quality Standards (NAAQS) for six principal 

pollutants that pose health hazards: carbon monoxide (CO), lead, nitrogen dioxide, particulate 

matter less than 10 microns in size (PM 10), particulate matter less than 2.5 microns in size (PM 

2.5), ozone, and sulfur dioxide. The major pollutant of concern in smoke from wildland fire, both 

planned and unplanned ignitions, is fine particulate matter (Ottmar 2001). Particles larger than 10 

microns in size tend to settle out of the air; smaller particles remain airborne, and can cause 

respiratory problems. Studies indicate that 90 percent of smoke particles emitted during wildland 

fires are PM 10, and about 90 percent of PM 10 is PM 2.5 (Ward and Hardy 1991). Human 

health studies on the effects of particulate matter indicate that it is PM 2.5 that is largely 

responsible for health effects (Dockery and others 1993). Because of its small size, PM 2.5 has an 

especially long residence time in the atmosphere and penetrates deeply into the lungs (Ottmar 

2001). The Clean Air Act defines the NAAQS for PM 2.5 as an annual mean of 15μg/m3, and a 
Air Quality Specialist Report - Prescott National Forest 2

24 hour average of 35μg/m3. At this concentration or above, PM 2.5 is considered to have a 

detrimental effect on public health. It is important to note that it is not the total amount of 

emissions from a fire that have effects on human health, but rather how concentrated pollutants in 

ambient air are for a period of time. Atmospheric conditions during a fire have a considerable 

influence on how particulate matter is distributed through the ambient air, and its potential to 

affect public health. Wind speed, wind direction, mixing layer height, atmospheric temperature 

profile upward in the atmosphere, and atmospheric stability all effect where and how well smoke 

will disperse. 

Regional haze is air pollution that is transported long distances, causing reduced visibility in 

national parks and wilderness areas. The same particulate matter that poses health risks is also 

largely responsible for these impairments to visibility. “The combination of light absorption by 

elemental carbon and light scattering caused by the very small particles that make up wildland 

fire smoke explains why emissions from wildland fire play such an important role in visibility 

impairment” (Core 2001). 

Over 280 million people visit our nation’s national parks and wildernesses areas every year. 

Visitors expect to view the scenery through clean fresh air. To protect visibility in these areas of 

high scenic value, Congress designated all wilderness areas over 5,000 acres and all national 

parks over 6,000 acres as mandatory federal Class I areas in 1977, subject to the visibility 

protection requirements in the Clean Air Act. There are 156 national parks and wilderness areas 

that have been designated by Congress as “mandatory federal Class I areas”. There are two Class 

I areas most likely to be effected by Prescott National Forest activities: Pine Mountain Wilderness

and Sycamore Canyon Wilderness. The national visibility goal of the Clean Air Act is, “the 

prevention of any future, and the remedying of any existing, impairment of visibility in 

mandatory Class I areas in which impairment results from manmade air pollution.” Some 

manmade sources of visibility impairment are industry, transportation, construction, mining, 

agricultural activities, and home heating; prescribed fires fall into this category. Wildfires are 

considered to be natural sources of visibility impairment, and generally outside State control or 

prevention.

Land managers are increasingly using planned and unplanned ignitions to achieve resource 

objectives, and to reduce future risk of high severity wildfires. Federal land managers have 

somewhat conflicting roles when it comes to protecting visibility in Class I areas. On the one 

hand, they are given the responsibility of protecting and meeting visibility standards. On the other 

hand they are tasked to allow fire, as nearly as possible, to function in its natural role in the 

ecosystem (USDA, USDI 1995). This puts the land manager in the awkward position of being the 

polluter, and in the difficult position of explaining why wildland smoke may be acceptable, while 

other types of pollution are not. The response to this dilemma is that wildernesses and national 

parks are managed to preserve and protect natural conditions and processes. So in this context, 

smoke and visibility impairment from wildland fire that closely mimics what would occur 

naturally is generally viewed as acceptable (Peterson 2001).
Air Quality Specialist Report - Prescott National Forest 3

The Regional Haze Rule, 40 CFR 51.308-309 (US EPA 1999), provides direction to the states for 

developing and adopting regional haze implementation plans. Under section 309, the State of 

Arizona has developed a State Implementation (SIP) plan with long-term strategies out to the year 

2064 to make “reasonable progress in improving visibility in Class I areas inside the state and in 

neighboring jurisdictions (US EPA 1999),” and focuses on anthropogenic sources of emissions. 

The Arizona SIP outlines an Enhanced Smoke Management Plan meeting criteria in the Regional 

Haze Rule that comprises a series of key policies and management practices to address visibility 

protection.

Visibility is measured in deciviews (dv). Deciviews are a metric of visibility proportional to the 

logarithm of the atmospheric condition. The deciview haze index corresponds to incremental 

changes in visual perception from pristine to highly impaired conditions. Visibility conditions are 

monitored and tracked through the Interagency Monitoring of Protected Visual Environments 

(IMPROVE) network. This site serves as a data clearinghouse for all of the Class I areas that have 

monitors, including Sycamore Canyon and Pine Mountain wilderness areas. The data can be 

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

The key policy resulting from the Enhanced Smoke Management Plan pertaining to planned 

ignitions in Arizona is Arizona Revised Statute Title 18 Chapter 2 Article 15. This law regulates 

burning by Federal and State land managers, as well as burning by Tribal, private, and municipal 

burners who have a Memorandum of Understanding with the Arizona Department of 

Environmental Quality (ADEQ). This Statute defines the request and approval process for all 

planned ignitions, and provides the mechanisms for tracking emissions from those ignitions. 

Enforcement of this statute is facilitated by the Smoke Management Group, housed at ADEQ. 

This group is comprised of a Forest Service employee, a Dept. of Interior employee, and an 

ADEQ employee. This group collects all planned ignition requests daily, makes 

recommendations to ADEQ on requests to be approved based on forecasted meteorological 

conditions, number of concurrent planned and unplanned ignitions, residual pollutants from 

previous planned ignitions or other sources, and other factors. This group also performs much of 

the work to track and summarize annual emissions from planned and unplanned ignitions to 

prepare required annual reports, and monitors regional haze levels. 

 

Problem or Nuisance Smoke is defined by the Environmental Protection Agency (EPA) as the 

amount of smoke in the ambient air that interferes with a right or privilege common to members 

of the public, including the use or enjoyment of public or private resources. While there are no 

laws or regulations governing nuisance smoke, it effectively limits opportunities of land 

managers to use planned and unplanned ignitions to meet resource objectives. Public outcry 

regarding nuisance smoke often occurs long before smoke exposures reach levels that violate 

NAAQS (Achtemeir and others 2001). “Probably the most common air quality issues facing 

wildland fire managers are those related to public complaints about nuisance smoke. Complaints 

may be about the odor or soiling effects of smoke, poor visibility, and impaired ability to breathe 

or other health-related effects. Sometimes complaints come from the fact that some people don’t 

like or are fearful of smoke intruding into their lives (Hardy and others 2001).”
Air Quality Specialist Report - Prescott National Forest 4

Description of Affected Environment (Existing Condition)

Prescott National Forest lies within three airsheds as defined by ADEQ: the Verde River, the Gila 

River Basin, and the Colorado River/Mexico airsheds as shown in figure 1. The majority of the 

PNF falls within the Verde River airshed. 

Figure 1. Airsheds for the state of Arizona.

NAAQS:

Air quality monitoring data has been collected in Yavapai County for three of the six criteria 

pollutants that pose a threat to human health (ground-level ozone, particles larger than 10 

microns, and particles less than 2.5 microns in size) on a limited basis since 1993. Monitoring 

sites have varied from year to year with no one location having a complete monitoring record (US 

EPA, 2009a). Ground-level ozone measurements have been collected from only one site in 

western Yavapai County. The annual average ozone concentration exceeded the national standard 

7 out of 8 years during the period from 1997 to 2004. For both sizes of particulate matter (larger 
Air Quality Specialist Report - Prescott National Forest 5

than 10 microns and less than 2.5 microns), several locations throughout Yavapai County were 

monitored, and the seasonally adjusted annual averages were far less than the national standard 

for each of the years 1990 to 2010. 

The EPA has developed an Air Quality Index (AQI) for reporting how clean or unhealthy the air 

is and the associated health effects that may be a concern to the general public or sensitive groups 

(such as children, older adults, or those suffering from asthma or lung disease). The index is 

calculated from raw measurements and converted into a separate AQI value for each pollutant 

(ground-level ozone, particulate matter, carbon monoxide, and sulfur dioxide). The highest of 

these AQI values is reported as the AQI value for that day.

Air quality data used to calculate the AQI indicate that most residents of Yavapai County and 

visitors to the Prescott NF enjoy good air quality (see Figure x). Since 2001, 73 percent or more 

of the days monitored1 were assigned to the Good category of the EPA Air Quality Index. Good is 

the best rating, where air pollution poses little risk to human health. Less than three percent of 

days per year were rated in the Unhealthy for Sensitive Groups category, and no days were rated 

Unhealthy, Very Unhealthy or Hazardous (US EPA, 2010). These air quality index ratings include 

emissions from Prescott NF prescribed fire activity that has averaged 7,640 acres per year under 

the direction of the 1987 Plan.

Figure X. Yavapai County Air Quality Indices 2001-2010.

Source:http://www.epa.gov/aircompare/index.htm

 

1

Some counties may not measure every pollutant used to calculate the AQI and the number of 

days each pollutant is measured may vary from one county to another.
Air Quality Specialist Report - Prescott National Forest 6

Visibility:

There are a total of 12 mandatory Class I areas in Arizona (figure 2). Sycamore Canyon 

Wilderness and Pine Mountain Wilderness are the Class I areas designated within or adjacent to 

the Prescott NF. Class I airsheds are represented only by the air directly above each individual 

wilderness. Although this is a political boundary, air quality is affected by pollutants that are 

generated from within the wilderness, such as smoke from fires, and also by pollutants that flow 

into the airshed from other sources. This might include wood smoke from homes or prescribed 

fire, and dust from rock quarries or roads. Long range transport of pollutants from metropolitan 

areas and large industry many miles away is also possible. 

Figure 2. Arizona Class I Areas (Source: ADEQ 2003).

Visibility in Pine Mountain and Sycamore Canyon wilderness areas, through implementation of 

the Regional Haze Rule, and the Arizona SIP, are projected to steadily improve (table 1). By 

2064, visibility on the 20 percent of the average worst days should improve by 6.72 dv for Pine 

Mountain, and 8.24 dv for Sycamore Canyon (USFS 2009a). 
Air Quality Specialist Report - Prescott National Forest 7

Air Quality Threats:

Threats to air quality in the form of particulate emissions come from many sources. The most 

prevelant ones include fossil fuel combustion, electricity generation, residential wood 

combustion, wildland fires, and road dust (US EPA 2009b). 

In central and northern Arizona, the primary sources of particulate emissions are the activities 

associated with wildland fire management. Road dust has not been demonstrated to be a 

measurable contributor on a regional level to visibility in the Sycamore Canyon Wilderness and 

15 other Class I areas located on the Colorado Plateau (ADEQ 2003). Under the direction of the 

1987 forest Plan, the Prescott NF has burned an average of 7,640 acres per year using planned 

ignitions (figure 3).

Figure 3. Summary of prescribed fire activity for vegetation types of the Prescott NF.

Wildfires also contribute to air quality impacts. If ignited by lighting, the Forest Service may use 

wildfires to achieve resource objectives if current and expected fire behavior is desirable (USDA,

USDI 1995). In 2007, the Prescott NF amended the existing forest Plan to allow implementation 

of this policy for areas outside of designated wilderness and away from communities at the 

0

5,000

10,000

15,000

20,000

198719881989199019911992199319941995199619971998199920002001200220032004200520062007200820092010

Acres Treated

Prescott NF: Prescribed Fire Activity 1987-2010

Grass

Chaparral

Pine

Woodland

All Rx Fire

Rx Fire Trend

Table 1. Baseline conditions and projected 2064 natural conditions for Class I Areas associated with the 

Prescott National Forest 

Class I Airsheds

Baseline Data

2064 as Measured by Deciview

Measured by Deciview Years

Pine Mountain Wilderness 13.4 dv 2000-2004 6.68 dv

Sycamore Canyon Wilderness 15.2 dv 2001-2004 6.96 dv

Source: IMPROVE Data (CSU 2006)
Air Quality Specialist Report - Prescott National Forest 8

wildland urban interface. In the three-year period since, two unplanned lightning-caused fires 

(totaling 1,034 acres) have been managed to meet resource objectives (USFS 2009c, USFS 2008). 

Among the many factors fire managers and line officers must carefully weigh when deciding 

whether to suppress a wildfire, or manage it to perform its natural role in the ecosystem, is 

whether the potential benefits of the wildfire outweigh the smoke impacts to the airshed, affected 

communities and rural residents. On these fires, fire managers are able to manage smoke impacts 

to some degree. Burn out operations can often be timed to occur when ventilation conditions are 

favorable. It may be possible to check a fire’s edge on days when reduced emissions are needed. 

Wildland fire activities in an airshed can be coordinated between fire managers, in conjunction 

with ADEQ, to either spread high emission producing events across several incidents over several 

days to reduce the concentration of pollutants, or facilitate these events to occur simultaneously 

on days with favorable ventilation to move the pollutants up and out of the airshed all at once, 

and reduce the duration of smoke impacts. Figure 4 displays the wildfire acres by ignition source

that have occurred on the Prescott NF since 1970. Lightning accounts for 60 percent of the 

ignitions reported and 55 percent of the acres burned. The total area burned per year has averaged 

3, 369 acres (range 15 – 33,652 acres).

Figure 4. Wildfire occurrence on the Prescott National Forest for the period 1970-2010.

Other land management activities, such as tree and shrub thinning, that reduce the likelihood of 

high severity wildfires in the future, have indirect beneficial effects on reducing smoke emissions. 

They alter stand structure so that wildfires burn as surface fires, thereby burning only 

accumulated litter and duff on the forest floor, but not the available fuels in the tree canopies, 

resulting in reduced air quality impacts, even though these results are not immediately realized at 

the time of project implementation. 1970 1972 1974 1976 1978 1980 1982

19841986198819901992199419961998200020022004200620082010

1

10

100

1000

10000

100000

Acres

Prescott NF Wildfire Acres 1970-2010

Human

Lightning
Air Quality Specialist Report - Prescott National Forest 9

Needs for Change Addressed in this Analysis

During an analysis of the management situation (USFS 2009b), the absence of specific goals 

and/or desired conditions related to air quality was identified as a need for change to the existing 

forest plan. With internal and external collaboration, the following desired conditions for air 

quality were drafted as components of the revised forest plan and are evaluated in this report:

 Fire as a natural disturbance process occurs across the landscape. 

 Smoke or dust levels meet national ambient air quality standards (NAAQS). Conflicts 

between smoke aversion and improvement of ecosystems using fire are minimized and 

smoke impacts to communities are minimized. Citizens are aware of timing, ignition 

sources, and benefits of fires and their resulting smoke. 

 Forest Service management activities do not contribute to diminished visibility or 

increased atmospheric deposition of pollutants within the Sycamore Canyon Wilderness 

and Pine Mountain Wilderness. 

Summary of Alternatives

The sections below describe the alternatives in terms of vegetation, fire and fuel management 

activities as they relate to air quality and smoke management.

Alternative A – 1987 Forest Plan Direction:

Alternative A would continue management under the existing plan for the Prescott National 

Forest. The plan provides for timber production, fuelwood harvest, hazardous fuel reduction 

treatments, prescribed fire and management of unplanned ignitions to meet resource objectives.

Under Alternative A, thinning to alter or restore vegetation structure and composition would 

continue to occur on about 550 acres per year in ponderosa pine and on 300 acres per year in 

pinon-juniper vegetation. Fire managers would continue to treat about 7,835 acres per year using 

prescribed fire across all vegetation types (e.g. forests, woodlands, shrublands, and grasslands). 

Planned ignitions would be coordinated with the Arizona Department of Environmental Quality, 

as well as with adjacent agencies, to ensure that exceedences of State or Federal emissions 

standards do not result.

Alternative B – The Proposed Revised Plan:

Alternative B represents approximately 1-2 years of collaborative work with citizens, agencies, 

and Prescott NF employees in an iterative manner to respond to suggested changes in proposed 

plan components. It places an emphasis on restoring vegetation, structure, composition, and 

desired characteristics of fire to five ecosystems that are moderately or highly-departed from 

desired conditions. It also addresses citizen concerns related to smoke emissions and responds to 

the anticipated effects of climate change. Eight potential wilderness areas are recommended. 
Air Quality Specialist Report - Prescott National Forest 10

Alternative B would increase the amount of thinning and prescribed fire occurring across the 

landscape. Planned ignitions would range from 10,600 to 25,300 acres per year on average. 

Thinning treatments to forests and woodlands would range from 750 to 6,500 acres per year on 

average. 

Planned ignitions would be coordinated with the Arizona Department of Environmental Quality, 

as well as with adjacent agencies, to ensure that exceedences of State or Federal emissions 

standards do not result. Additionally, wildland urban interface (WUI) areas would be given high 

priority for fuel reduction treatments, using mechanical methods and/or domestic animals in lieu 

of planned ignitions. 

Alternative C - Vegetation and Wildlife Emphasis:

Alternative C includes many of the same components of Alternative B, however, it responds to 

public comments to increase emphasis on vegetation trends within both grassland and ponderosa 

pine types. This focus improves vegetation conditions within important wildlife habitats and 

places less emphasis on some vegetation communities and recreational components. In addition, 

Alternative C includes more management treatment for native fish and other aquatic species and 

pronghorn habitats; there is much less emphasis on recommendation of potential wilderness 

areas.

Alternative C would emphasize a higher range of prescribed fire and a lower range of thinning 

activity compared to Alternatives A and B. Planned ignitions would range from 15,500 to 22,800 

acres per year on average and would be focused in grassland and ponderosa pine vegtation. 

Thinning treatments would range from 750 to 4,000 acres per year on average. 

Response to smoke emissions in Alternative C is the same as that described in Alternative B.

Alternative D – Dispersed Recreation Emphasis:

Alternative D includes an emphasis on providing increased dispersed recreation opportunities. 

Vegetation treatments would be similar to those in Alternative B or slightly reduced. Emphasis 

on pronghorn and native fish would be identical to Alternative B. Within recreational 

opportunities, there would be reduced emphasis on developed recreation, such as campgrounds, 

and increased emphasis on dispersed recreation such as adding trails, improving trailheads and 

adding designated dispersed sites. This alternative also includes recommendation of the highest 

number of potential wilderness areas. 

Alternative D would emphasize less prescribed fire than Alternatives B and C, and similar or less 

thinning activity. Planned ignitions would range from 10,600 to 18,800 acres per year on average.

Thinning treatments to forests and woodlands would range from 750 to 4,000 acres per year on 

average (the same as Alternative C). 

Response to smoke emissions in Alternative D is the same as that described in Alternative B.
Air Quality Specialist Report - Prescott National Forest 11

Alternative E – The Preferred Alternative:

Alternative E was developed between draft and final versions of the proposed plan and EIS in 

response to issues and concerns heard during the public comment period. Alternative E is similar 

to alternative B in most elements, but with a reduced emphasis on developed recreation and trail 

maintenance and more clarity of direction for watersheds, forest access, and land acquisitions. 

This alternative recommends fewer acres for wilderness designation than alternatives B and D.

Alternative E proposes the same amount of thinning and prescribed fire occurring across the 

landscape as Alternative B. Prescribed fire and wildfires managed for resource objectives would 

range from an about 10,600 to 25,300 acres per year on average. Thinning treatments would 

range from about 750 to 6,500 acres per year on average. 

Response to smoke emissions in Alternative E is the same as that described in Alternative B.

Table 2 displays the range of proposed treatment activities by alternative.

Table 2: Proposed Average Annual Treatment Activity

Alt A

Alt B/E

low

Alt B/E

high

Alt C 

low Alt C high Alt D low

Alt D 

high

Rx Fire 7,835 10,600 25,300 15,500 22,800 10,600 18,800

Rx Thin 1,027 750 6,500 750 4,000 750 4,000

Totals 8,862 11,350 31,800 16,250 26,800 11,350 22,800

Assumptions

Air quality is not expected to be a primary driver in selecting one alternative over another, as 

predicted impacts between alternatives are not dramatically different. The reasons large 

differences do not exist include:

 Smoke is a by-product of restoring fire adapted ecosystems. Fire is a necessary part of the 

equation, and therefore air quality impacts are part of all alternatives. 

 All alternatives are expected to achieve the desired conditions for air quality in the 

proposed Plan.

 During windows of opportunity, whenever fire weather and fire effects are favorable, fire 

managers strive to treat as many acres with wildland fire as possible, yet still remain 

within legal, climatological, social, and logistical limits. In other words, the number of 

acres treated with wildland fire per year, under all alternatives, is likely to be the same, 

due to limitations imposed by these constraints. This is true under the current Plan, and 

expected to continue under all alternatives to the revised Plan. 
Air Quality Specialist Report - Prescott National Forest 12

 Legal limits to smoke emissions from prescribed fires are imposed by Federal and State 

Law. Therefore, there is an upper limit to the number of acres that can be treated with 

wildland fire imposed by regulation. Wildfire emissions, including those from unplanned 

ignitions that are being used to meet resource objectives, are not regulated by Law. 

However, fire managers are guided to include smoke management objectives on all fires. 

Strategy and tactics are greatly influenced by smoke sensitive receptors. 

 Impacts of smoke from planned and unplanned ignitions on the Prescott NF, as well as 

on other federal and state lands, are cumulative. Therefore wildland fire activities on 

other agency lands may further limit the ability to utilize wildland fire on the Forest.

 Climatological limits are set by weather and fuel moisture, which profoundly affect fire 

behavior and fire effects. As weather varies from year to year so does the risk of high 

severity fires and the ability to use planned and unplanned ignitions to achieve resource 

objectives. The number of days of opportunity varies widely from year to year, creating 

huge fluctuations in the number of acres treated with wildland fire. Running averages 

over many years are needed in order to observe trends in the use of wildland fire or to 

observe undesirable fire effects. 

 Meteorological conditions also limit how much smoke the airshed can absorb at any 

point in time without violating NAAQS, or visibility thresholds.

 Public tolerance for smoke, though not law, regulation, or policy, effectively sets the 

social limit to the number of acres treated with wildland fire. Community public 

relations and education coupled with pre-burn notification greatly improve public 

acceptance of fire management programs. The general public will tolerate several days in 

a row, and several weeks a year, but even the most supportive and educated have 

tolerance limits. In order to maintain public support for the use of wildland fire, land 

managers must be responsive to the public’s tolerance thresholds. 

 Public acceptance of smoke varies greatly from year to year. Acceptance of smoke from 

planned and unplanned ignitions is high following seasons with high profile, high 

severity events, and during extremely dry years when the threat of large, high severity 

incidents is elevated. Conversely, acceptance wanes during wetter years when the threat 

of uncharacteristic fires is low. This is unfortunate because, climatology in milder years is 

the most favorable for achieving desired fire effects, especially in areas highly departed 

from reference conditions. 

 Logistical limits are also set by the capacity of firefighting resources available. Capacity 

varies from year to year due to congressional funding, or resources absorbed by other 

wildfire activity in the region, or nationally.

This analysis uses the running averages of acres treated by wildland fire from the objectives for 

each alternative as a fixed number per year in order to make broad comparisons between 
Air Quality Specialist Report - Prescott National Forest 13

alternatives. In reality, the climatological, social, and logistical limits discussed above, create

wide fluctuations in the number of acres treated each year.

Fuel model, fuel loading and fuel moisture are highly variable over time and distance. For 

making broad comparisons between the alternatives of “least”, “more”, and “most” air quality 

impacts, these inputs are greatly simplified. For site-specific projects, fuel loadings are more 

precisely estimated, and emissions are predicted in accordance with Arizona Statutes, and ADEQ 

regulations.

This analysis does not attempt or pretend to predict the actual total emissions that would be 

produced under each alternative. Rather it aims to present a rationale for which alternatives are 

likely to produce more or less emissions. It assumes that, over time, there is some degree of 

correlation between total emission production, and total air quality impacts; while impacts are 

measured as the concentration of emissions, not the total amount of emissions, over the course of 

ten, twenty, forty or eighty years, the alternative that produces the most emissions is likely to have 

the most air quality consequences. Though meteorological conditions vary immensely by time of 

day, and from one weather system to the next, over the course of years these varying conditions 

should have an averaging effect over time, allowing a correlation between total emissions and 

total impacts. 

Methodology and Analysis Process

Comparison of air quality effects was analyzed using outputs from the Vegetation Dynamics 

Development Tool (VDDT).

VDDT is a Windows-based computer tool which provides a modeling framework for examining 

the role of various disturbance agents and management actions in vegetation change. The 

interaction of human activity, fires, insects, pathogens, growth and competition is complex, and 

the combined effects are difficult to predict over long periods. The development tool allows for 

testing of the sensitivity of the ecosystem to a multitude of activities and agents of disturbance, to 

compare alternatives. With the tool a vegetation type is assigned various states, some of which 

are seral states found within the historic range of variability, and others that are uncharacteristic 

states not present in the historic range of variability. Inputs to the model are agents of disturbance, 

such as number of acres mechanically treated to restore stand structure, or acres that are burned 

by fire under low to moderate fire weather conditions; outputs are the transition of the vegetation, 

by percent, from one state to another. For example, a thinning or prescribed fire input would 

move a percentage of dense states to more open states. Each vegetation type is described by its 

own set of states and transitions. For a full discussion of the development, calibrations, and 

assumptions used in the VDDT models for the Prescott NF, as well as all outputs from the model, 

refer to the Vegetation and Fire Ecology Specialist Report (USFS 2011).

VDDT models for ponderosa pine-gambel oak, ponderosa-pine evergreen oak, piñon-juniper 

evergreen shrubland, and juniper grassland were developed by the Forest Service at the Regional 

level to be used specifically to compare alternatives for Forest Land Management Plans in Region 

3. The development process for these models is documented at 
Air Quality Specialist Report - Prescott National Forest 14

http://fsweb.r3.fs.fed.us/eap/nfma//vddt/preside/index.shtml. Each model provides a base 

comparison of the relative progress Plan alternatives are predicted to make toward desired 

conditions; outputs are then supplemented by other extra-model information. VDDT models for 

interior chaparral, semi-desert grassland, and Great Basin grassland were developed by the Forest 

Service at the Forest level and reviewed at the regional level prior to use. 

Each state within a VDDT model is classified as either “open” or “closed” based on the amount 

of expected vegetation canopy cover. Open states are defined as 30% or less canopy cover and 

closed states are defined as greater than 30% canopy cover. The piñon-juniper models recognize 

three open states, the pine-evergreen oak model recognizes two open states and the pine-gambel 

oak model recognizes six open states. The grassland models recognize one or two open states.

The percent of open states achieved among the PNVTs over time for each alternative is the 

indicator used to compare air quality impacts across alternatives. Higher proportions of open state 

conditions influence future fire behavior and indicate reduced particulate emissions over the longterm. 

Environmental Consequences

The land management plan provides a programmatic framework that guides site-specific actions 

but does not authorize, fund, or carryout any project or activity. Because the land management 

plan does not authorize or mandate any site-specific projects or activities (including grounddisturbing actions) there can be no direct effects. However, there may be implications, or longer 

term environmental consequences, related to management of the Prescott NF under this 

programmatic framework. 

Transient impacts to air quality from wildland fire are present in all alternatives. Most of the 

Prescott NF is occupied by fire adapted vegetation types (USFS 2009b), and smoke from fires, 

regardless of ignition source or combustion stage, is inevitable. 

All alternatives are expected to achieve the Prescott NF desired conditions for air quality stated 

on page 9 of this report.

For planned ignitions, the Smoke Management Group, housed at ADEQ, greatly facilitates the 

Forest’s ability to implement the Arizona SIP, and adhere to Federal and State regulations. This 

condition is true for all alternatives.

Smoke from unplanned ignitions also contributes to air quality impacts. Emissions from wildfires 

are considered to be natural events, and are excluded from determinations of exceedances and 

(NAAQS) violations. On most wildfires, however, fire managers can greatly influence the 

emission production by suppressing fires when small, checking or redirecting the growth of the 

fire, or through emission reduction techniques, such as performing burn-out operations when 

ventilation conditions are optimal, or limiting acreage burned when ventilation is poor. Other 

wildfires burn with rates of spread and intensity levels that are largely outside the control of fire 

managers; in these cases a change in weather or fuel conditions is usually necessary before 
Air Quality Specialist Report - Prescott National Forest 15

firefighters can contain or control the incident. These wildfires burn outside the historic range of 

variability, outside of proposed desired conditions for the vegetation type, and produce large 

quantities and concentrations of emissions. This condition is true for all alternatives. 

Some comparison in air quality can be made between alternatives by looking at the condition of 

the vegetation through time and its effects on future fire behavior and particulate emissions.

Vegetation management activities that involve thinning and removal of trees and shrubs to restore 

structure and composition have indirect beneficial effects on air quality because they alter future 

fire behavior. Forest and woodlands with higher proportions of open states, are more likely to 

exhibit surface fire behavior, even under elevated fire weather conditions. Where closed states are 

mechanically thinned, the crown bulk density is lower, and gaps and interspaces in the canopy 

inhibit the spread of active crown fire from group to group (Friederici 2005, Rothermel 1991, 

Scott and Reinhardt 2001). Less biomass is consumed during a surface fire, because primarily 

only litter, debris, and living herbs on forest floor are consumed, but not the crown fuels of the 

trees and shrubs. 

The amount of tree and shrub thinning and prescribed fire proposed under each alternative, as 

modelled in VDDT, influences the attainment of open states, which in turn influences the relative 

amount of emissions from subsequent planned and unplanned ignitions. 

In other words: 

Higher percentage of stands in open states = more surface fire = reduced particulate emissions

Figure 5 shows the percent of open states achieved across PNVTs for each alternative for the 

current, 10-year, 20-year, 40-year, and 80-year time intervals. The proposed treatment activities 

result in observable changes in open state proportions for the grassland and ponderosa pine 

PNVTs, but not for the piñon-juniper communities. Chaparral vegetation was excluded from 

this analysis due to the closed-canopy character of this vegetation type. See the Vegetation and 

Fire Ecology Specialist Report (USFS 2012) for additional discussion on chaparral.

The alternative with the least predicted air quality consequences is Alternative C: 

Vegetation and Wildlife Emphasis. Focused application of thinning and prescribed fire to move 

vegetation towards desired conditions increases the percentage of open states in the grassland and 

ponderosa pine dominated communities. Future fire behavior is expected to produce the lowest 

particulate emissions among the alternatives.

The second best alternative from the air quality perspective is shared equally between 

Alternative B: Proposed Revised Plan and Alternative D: Dispersed Recreation Emphasis.

These alternatives have fewer proposed thinning and prescribed fire treatments than Alternative C 

and as a result less open state conditions are created over time. Compared to Alternative A, these 

alternatives show a measurable increase in open state proportions for the ponderosa pine-gambel 

oak and semi-desert grasslands. Future fire behavior is expected to produce particulate emissions 

that are more than Alternative C and less than Alternative A. 
Air Quality Specialist Report - Prescott National Forest 16

The alternative with the greatest predicted air quality consequences is Alternative A: 1987 

Forest Plan Direction. This alternative proposes the least amount of thinning and prescribed fire 

to move vegetation towards desired conditions. The estimated outcome is higher proportions of 

closed states and a lower liklihood of future surface fire behavior and associated reduced 

particulate emissions. 

Figure 5. Percentage of Open State Conditions Achieved by PNVT by Alternative 

Semi-desert Grass Great Basin Grass 

Open States = B Desired Amount = 80% Open States = B,C Desired Amount = 93%

Percentage of Open States Over Time Percentage of Open States Over Time

Years Alt A Alt B/E,D Alt C Years Alt A Alt B/E,D Alt C

0 20 20 20 0 80 80 80

10 23 30-44 44-49 10 86 86-86 86-86

20 26 41-64 64-70 20 87 88-88 88-89

40 33 57-82 82-86 40 90 90-91 91-93

80 35 61-84 84-86 80 93 94-95 93-95

Juniper/Piñon Grass P-J Shrubland 

Open States = B,C,D Desired Amount = 75% Open States = B,C,D Desired Amount = 95%

Percentage of Open States Over Time Percentage of Open States Over Time

Years Alt A Alt B/E,D Alt C Years Alt A Alt B/E Alt C/D

0 37 37 37 0 24 24 24

10 43 42-43 42-43 10 33 32-33 33-33

20 47 46-47 46-47 20 38 38-38 38-39

40 53 53-54 53-54 40 45 46-46 46-46

80 60 60-60 60-60 80 50 51-52 51-51

Pine-Evergreen Oak Pine-Gambel Oak 

Open States = C,D Desired Amount = 84% Open States = B,C,D,E,J,K Desired Amount = 83%

Percentage of Open States Over Time Percentage of Open States Over Time

Years Alt A Alt B/E,D Alt C Years Alt A Alt B/E,D Alt C

0 3 3 3 0 3 3 3

10 24 22-27 22-29 10 17 18-22 19-25

20 30 28-34 28-35 20 23 24-29 24-32

40 34 29-35 30-36 40 28 30-34 30-37

80 32 29-34 28-34 80 31 32-36 33-37
Air Quality Specialist Report - Prescott National Forest 17

Cumulative Environmental Consequences

Examining cumulative effects from smoke on air quality differs from the evaluation of 

cumulative effects for many other resources; this is due to the transient nature of air quality 

impacts from smoke. It is a relatively simple exercise to estimate the total tons per acres of 

emissions from planned ignitions on the Prescott NF, and other land management agencies, but 

there is no calculation that correlates total annual emissions to total concentrations of emissions. 

Again, impacts are measured as concentrations of emissions, whether it’s in μg/m3 for NAAQS, 

or in deciviews measuring visibility in Class I Areas. Cumulative effects are not the total 

emissions produced in a day or a year, but rather the concentration of all fire emissions in a given 

airshed at a given time. For NAAQS these concentrations have a varying time weighted period 

depending on the pollutant. For PM10 and PM2.5, they are measured as a 24 hour average, and as 

an annual arithmetic mean. 

Cumulative effects from planned and unplanned ignitions that are not being actively suppressed 

on Federal, State, and Tribal lands, are largely mitigated through implementation of the Enhanced 

Smoke Management Program, in the Arizona SIP, by the previously mentioned Smoke 

Management Group. When the Federal land managers actively began prescribed fire programs in 

the 1970s, they became rapidly aware that smoke does not respond to artificial boundaries or 

delineations, and that a pro-active program for the coordination of prescribed fires would be vital 

to obtain and continue support of prescribed fire programs by ADEQ and the public. An 

interagency Smoke Management Group was developed in partnership with the State, and housed 

in the ADEQ offices in Phoenix. The personnel in the group are funded largely by the Federal 

agencies, demonstrating the initiative of the agencies to, in some degree, self-regulate emissions 

production from prescribed fires, across Federal and State boundaries.

This group assists Arizona land managers in not exceeding NAAQS or visibility thresholds 

through the following services:

 Serves as a central collection point for all prescribed fire requests from the numerous 

Federal, State, and Tribal land managers who are all competing to produce smoke that 

will impact the same airsheds during limited windows of opportunity.

 Evaluates potential emissions from individual and multiple, and determines how 

meteorological forecasts will affect smoke concentrations both during the burn, and 

during diurnal settling. The Group considers cross-boundary impacts; and weighs burning 

decisions against possible health, visibility, and nuisance effects.

 Assists in coordinating activities within and between agencies when potential emissions 

would likely exceed desired conditions.

 Makes recommendations on the approval or disapproval of each prescriebd fire request to 

ADEQ officials.

 Tracks the use of Best Management Practices and Emission Reduction Techniques used 

by land managers, to document efforts by land managers to minimize impacts to Air 

Quality. This information is used promote support from both ADEQ and the public. 
Air Quality Specialist Report - Prescott National Forest 18

 Monitors data gathered from the IMPROVE network to assess visibility impacts in Class 

I areas, and track progress towards Arizona SIP goals.

While emissions from wildfires are not regulated, Federal, State, and Tribal land managers 

understand their responsibility to balance the ecological benefits of wildfires with the social 

impacts of the smoke they produce. The Smoke Management Group also assists land managers in 

this area through:

 Limiting prescribed fire approvals during periods when wildfires are already impacting 

an airshed.

 Making recommendations on the timing, or assisting in the coordination between units, of 

tactical operations such as burn outs, that will produce large amounts of emissions, so 

that they are done, when possible, when ventilation conditions are most favorable, or 

spread out over several burning periods to reduce total emissions when ventilation is not 

as good. 

 Assisting land managers in determining the strategy to take on new wildfires. There may 

be enough fires burning that suppression on a new start is recommended to reduce 

cumulative smoke impacts even though all other fire effects would be desirable, and 

move the fire area towards desired conditions as stated in the Land Management Plan. 

 Acting as a sounding board for public complaints. In keeping tabs on the type and 

number of complaints, the Group is able to provide land managers feedback from beyond 

their local publics on the state of public smoke tolerance. This is vital in maintaining 

general public support of allowing wildfires to perform their natural role in the ecosystem 

under the right circumstances in future windows of opportunity. 

Through the services of the Smoke Management Group, cumulative effects from wildland fire 

that are within the control of Federal and State Land Managers, are thus managed to keep air 

quality across Arizona within desired conditions, including not exceeding NAAQS, protecting 

visibility in Class I Areas, and additionally promoting general public support of wildland fire

management programs. 

Unavoidable Adverse Impacts, Irreversible and Irretrievable 

Commitment of Resources 

The land management plan provides a programmatic framework that guides site-specific actions 

but does not authorize, fund, or carryout any project or activity. Before any ground-disturbing 

actions take place, they must be authorized in a subsequent site-specific environmental analysis. 

For planned ignitions this includes both National Environmental Policy Act analysis, and a 

prescribed fire burn plan signed by the authorizing line officer. For unplanned ignitions, the 

analysis, objectives, and courses of action selected for an incident are supported, documented, 
Air Quality Specialist Report - Prescott National Forest 19

and signed in the Wildfire Decision Support System (WFDSS). Because the land management 

plan does not authorize or mandate any site-specific project or activity, none of the alternatives 

cause unavoidable adverse impacts, or cause an irreversible or irretrievable commitment of 

resources. 

References

Achtemeier, G. L., B. Jackson, J. D. Brenner, 2001. Problem and Nuisance Smoke. Smoke 

Management Guide for Prescribed and Wildland Fire 2001 Edition. NWCG. PMS 420-2, NFES 

1279. Boise, ID.

ADEQ, 2003. Regional Haze State Implementation Plan for the State of Arizona. Phoenix, AZ. 

http://www.azdeq.gov/environ/air/haze/download/2sip.pdf

ADEQ, 2004. Revision State Implementation Plan for Regional Haze. Phoenix, AZ 

http://www.azdeq.gov/environ/air/haze/download/2004_RH_SIP_Revision.pdf

ADEQ, 2004. Title 18 Environmental Quality, Chapter 2 DEQ Pollution Control, Article 15 

Forest and Range Management Burns. Phoenix, AZ. 

http://www.azdeq.gov/environ/air/smoke/download/prules.pdf

Core, J. E. 2001. Visibility. Smoke Management Guide for Prescribed and Wildland Fire 2001 

Edition. NWCG. PMS 420-2, NFES 1279. Boise, ID.

Dockery D.W., C.A. Pope 3rd, X. Xu, J.D. Spengler, J.H. Ware, M.E. Fay, B.G. Ferris Jr, F.E. 

Speizer. 1993. An association between air pollution and mortality in six U.S. cities. 

N Engl J Med. Dec 9:329(24):1753-9.

Friederici, P. 2005. Restoration of Ponderosa Pine Forests to Presettlement Conditions. Ecological 

Research Institute: Working Papers in Southwestern Pine Forest Restoration, Number 9. 

Flagstaff, AZ.

Hardy, C. C., S. M. Hermann, John E. Core. The Smoke Management Imperative. Smoke 

Management Guide for Prescribed and Wildland Fire 2001 Edition. NWCG. PMS 420-2, 

NFES 1279. Boise, ID.

Ottmar, R. D. 2001. Smoke Source Characteristics. Smoke Management Guide for Prescribed 

and Wildland Fire 2001 Edition. NWCG. PMS 420-2, NFES 1279. Boise, ID.

Peterson, J. L. 2001. Regulations for Smoke Management. Smoke Management Guide for 

Prescribed and Wildland Fire 2001 Edition. NWCG. PMS 420-2, NFES 1279. Boise, ID.

Rothermel, R. C. 1991. Predicting behavior and size of crown fires in the Northern Rocky 

Mountains. USDA Forest Service Intermountain Reasearch Station Research Paper INT438. Ogden, UT.
Air Quality Specialist Report - Prescott National Forest 20

Scott, J., E. D. Reinhardt. 2001. Assessing crown fire potential by linking models of surface and 

crown fire behavior. USDA Forest Service Rocky Mountain Research Station Research 

Paper RMRS-RP-29. Fort Collins, CO.

United States Department of Agriculture and United States Department of Interior. 1995. “Federal 

Wildland Fire Management: Policy and Program Review: Final Report.” Washington, 

D.C.

USDA Forest Service 2012. Vegetation and Fire Ecology Specialist Report for the Prescott 

National Forest. Prescott, AZ.

USDA Forest Service 2009a. Ecological Sustainability Report for the Prescott National Forest. 

Prescott, AZ.

USDA Forest Service 2009b. Analysis of the Management Situation the Prescott National Forest.

Prescott, AZ.

USDA Forest Service 2009c.Forest Plan Monitoring and Evaluation Report – Prescott National 

Forest. Prescott, AZ.

USDA Forest Service 2008. Forest Plan Monitoring and Evaluation Report – Prescott National 

Forest. Prescott, AZ.

US Environmental Protection Agency. 2010. Air Quality Index Charts for Yavapai County. 

http://www.epa.gov/air/data/reports.html

US Environmental Protection Agency. 2009a. Air Quality Trends by Pollutant. 

http://www.epa.gov/air/airtrends/where.html

US Environmental Protection Agency. 2009b. Air Emission Sources – Particulate Matter. 

http://www.epa.gov/air/emissions/index.htm

US Environmental Protection Agency. 1999. Regional Haze Rule. 40 CFR 51.300-309. 

http://www.epa.gov/ttncaaa1/t1/fr_notices/rhfedreg.pdf

U.S. Laws , Statutes, etc.; Public Law 101-549. Clean Air Act as Amended Nov. 1990. 42 U.S.C. 

§ 7401.

Ward, D. E., C. C. Hardy. 1991. Smoke emissions from wildland fires. Environmental 

International, Vol 17:117-134.