out of sight: the science and economics of visibility impairment

8/9/2019 Out of Sight: The Science and Economics of Visibility Impairment

1/86

Abt Associates Inc. # 4800 Montgomery Lane #

Bethesda, MD 20814-5341 # www.abtassoc.com

Out of Sight:The Science andEconomics ofVisibility Impairment


2/86

Out of Sight:The Science and Economics of

Visibility Impairment

August 2000

Prepared for

Clean Air Task Force

Boston, MA

Project Manager:

Dr. L. Bruce Hill

Prepared by

Abt Associates Inc.

4800 Montgomery Lane

Bethesda, MD 20814-5341

www.abtassoc.com


3/86

Abt Associates Environmental Research Area provides multi-disciplinary scientific research andenvironmental policy analysis to the EPA, the U.S. Agency for International Development, the Inter-American

Development Bank, the World Bank, and directly to foreign, state and local governments. Abt Associates has

extensive experience in estimating the potential public health improvements and economic costs and benefits

from improving ambient air quality. The Environmental Research Area conducted extensive health analysis

for the U.S. EPA in support of the 1997 revisions to both the ozone and the particulate matter National

Ambient Air Quality Standards. They also prepared the health and economic analyses for EPAs 1997 Report

to Congress The Benefits and Costs of the Clean Air Act: 1970 to 1990, and conducted similar policy, health

and economic analyses for EPA of regulations on the electric generating industry, automobile exhaust, and

potential policies for climate change mitigation strategies. Abt Associates Environmental Research Area

conducts public health analysis projects worldwide, including air pollution health assessment projects with the

environmental and health ministries in Argentina, Brazil, Canada, Chile, Korea, Russia, Thailand, the Ukraine

and the World Health Organization.

Mr. Kenneth Davidson specializes in the analysis of air quality policy. He has a master's degree in resource

economics and policy from Duke University's Nicholas School of the Environment, and as a student workedwith the Innovative Strategies and Economics Group at the U.S. EPA's Office of Air Quality Planning and

Standards.

Dr. Leland Deck specializes in economic and risk analysis of environmental policies. His research projectsinclude estimating the risks and economic value of health and welfare benefits from reducing air pollution, the

costs of alternative pollution prevention technologies, and designing effective and enforceable economic

incentive programs as a part of an overall strategy for controlling pollution from stationary and mobile sources.

In addition to his own research projects, Dr. Deck manages Abt Associates Environmental Economics

Practice, and is a Vice President of Abt Associates.

Dr. Don McCubbin has eleven years of experience in the analysis of environmental issues, with a special

emphasis on the adverse effects of criteria air pollutants.

Dr. Ellen Post has fourteen years of experience in the scientific, economic, and policy analysis ofenvironmental issues, with particular emphasis on (1) criteria air pollution risk assessment and economic

benefit analysis, and (2) methods of assessing uncertainty surrounding individual estimates. She is one of the

primary analysts conducting a particulate matter air pollution risk assessment for EPAs Office of Air Quality

Planning and Standards, and has been a key economist in ongoing work analyzing the economic benefits

associated with risk reductions from a number of air quality regulations, including the implementation of

proposed particulate matter and ozone standards in the United States.


4/86

Table of Contents

EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ES-1

1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2. VISIBILITY IMPAIRMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.1 Causes of Visibility Impairment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2 Observing and Measuring Visibility Impairment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.2.1 People Can Tell When Views Are Impaired . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.2.2 How Visibility Impairment is Measured . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3. TRENDS IN VISIBILITY IMPAIRMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.1 Recent Visibility Trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3.1.1 Visibility at Parks Where the Vista Is Integral to the Experience . . . . . . . . . . . 14

3.1.2 Visibility at Smaller Parks and Wilderness Areas . . . . . . . . . . . . . . . . . . . . . . 22

3.1.3 Visibility in Urban Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

4. LEGISLATIVE AND REGULATORY HISTORY OF VISIBILITY IMPAIRMENT . . . . . . . 26

5. ECONOMICS: VISIBILITY IMPAIRMENT AND PARK VISITATION . . . . . . . . . . . . . . . 31

5.1 An Undisturbed Environment, Including Clean, Clear Air and Good Visibility, is Very

Important to Park Visitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

5.2 Visitors are Willing to Alter Their Length of Stay Based on Visual Air Quality Conditions at

National Parks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

5.3 What is at Stake to the Economy if Visitation Rates Decline? . . . . . . . . . . . . . . . . . . . 34

5.4 Local Economic Benefits from Visibility Improvements . . . . . . . . . . . . . . . . . . . . . . . . 36

6. ECONOMICS: THE NON-MARKET VALUE OF VISIBILITY . . . . . . . . . . . . . . . . . . . . . . 416.1 The Economic Valuation of Visibility Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . 42

6.2 The Value of Visibility Improvements at National Parks: Evidence from Studies . . . . . 43

6.3 The Value of Visibility Improvements in Residential Areas: Evidence from Studies . . . 46

6.4 Applying the Information from Studies to Assess the Visibility Benefits of Reducing Air

Pollution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

7. POWER PLANT EMISSION REDUCTIONS AND ASSOCIATED VISIBILITY BENEFITS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

8. CONCLUSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

9. REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

APPENDIX A DETAILED TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1

APPENDIX B METHOD TO ESTIMATE VISIBILITY BENEFITS . . . . . . . . . . . . . . . . . . . . . . . . B-1

B.1 Basic Utility Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-2

B.2 Measure of Visibility: Environmental Goods Versus Bads . . . . . . . . . . . . . . . . . . B-3

B.3 Estimating the Parameters for Visibility at Class I Areas: the (s and *s . . . . . . . . . . B-5B.3.1 Estimating Region-Specific Recreational Visibility Parameters for the Region

Covered in the Chestnut and Rowe Study (Regions 1, 2, and 3) . . . . . . . . . . B-8


5/86

B.3.2 Inferring Region-Specific Recreational Visibility Parameters for Regions Not

Covered in the Chestnut and Rowe Study (Regions 4, 5, and 6) . . . . . . . . . . B-8

B.3.3 Estimating Park- and Wilderness Area-Specific Parameters . . . . . . . . . . . . . B-10

B.3.4 Derivation of Region-specific WTP for National Parks and Wilderness Areas

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-10

B.3.5 Derivation of park- and wilderness area-specific WTPs, given region-specific WTPs

for national parks and wilderness areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-11

B.3.6 Derivation of park- and wilderness area-specific parameters, given park- and

wilderness area-specific WTPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-12

B.4 Estimating the Parameter for Visibility in Residential Areas: 2 . . . . . . . . . . . . . . . . B-13

B.5 Putting it All Together: the Household Utility and WTP Functions . . . . . . . . . . . . . B-13


6/86

List of Exhibits

Exhibit 1-1 Denver on a Clear Day and on a Hazy Day . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Exhibit 2-1a Visible Plume from Local Stacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Exhibit 2-1b Layered Haze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Exhibit 2-1c Regional Haze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Exhibit 2-2 National Emissions of Nitrogen Oxides and Sulfur Dioxide by Source in 1998 . . . . . . . . . . . 4

Exhibit 2-3a Contribution to Visibility Impairment in the Eastern U.S. . . . . . . . . . . . . . . . . . . . . . . . . . 5

Exhibit 2-3b Contribution to Visibility Impairment in the Mid-West . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Exhibit 2-3c Contribution to Visibility Impairment in the West . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Exhibit 2-4 Scattering and Absorption of Image-Forming Light from the Observers Sight Path . . . . . . . 7

Exhibit 2-5 Aerosol Size and Light Scattering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Exhibit 2-6 Types of Particulate Matter and Impact on Image-Forming Light . . . . . . . . . . . . . . . . . . . . 8

Exhibit 2-7 Relationship Between Perceived Visual Air Quality and the Amount of Particulate Matter in the

Air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Exhibit 2-8 Inverse Relationship Between Visual Range and the Deciview Index . . . . . . . . . . . . . . . . . . 11

Exhibit 3-1 Airport Visual Data: Trend in 75th

Percentile Light Extinction Coefficient for July-September(measured in km-1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Exhibit 3-2 Visibility Trends at Acadia National Park, Maine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Exhibit 3-3 Visibility Trends at Grand Canyon National Park, Arizona . . . . . . . . . . . . . . . . . . . . . . . . 17

Exhibit 3-4 Visibility Trends at Great Smoky Mountains National Park, Tennessee . . . . . . . . . . . . . . . 18

Exhibit 3-5 Visibility Trends at Shenandoah National Park, Virginia . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Exhibit 3-6 Visibility Trends at Yosemite National Park, California . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Exhibit 3-7a Extreme Visibility Days at Acadia National Park . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Exhibit 3-7b Extreme Visibility Days at Grand Canyon National Park . . . . . . . . . . . . . . . . . . . . . . . . . 21

Exhibit 3-7c Extreme Visibility Days at Great Smoky Mountains National Park . . . . . . . . . . . . . . . . . 21

Exhibit 3-7d Extreme Visibility Days at Shenandoah National Park . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Exhibit 3-7e Extreme Visibility Days at Yosemite National Park . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Exhibit 3-8 Visibility Trends at San Gorgonio Wilderness Area, California . . . . . . . . . . . . . . . . . . . . . 23Exhibit 3-9 Visibility Trends at Chassahowitzka Wilderness Area, Florida . . . . . . . . . . . . . . . . . . . . . 23

Exhibit 3-10 Visibility Trends in Washington, D.C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Exhibit 4-1 Map of Mandatory Class I Areas with Visibility Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Exhibit 5-1 Visitor Rated Importance of Park Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Exhibit 5-2 Total Recreation Visits to U.S. National Parks, 1951-1998 . . . . . . . . . . . . . . . . . . . . . . . . 35

Exhibit 5-3 Sales Increase Near Park Due to an Increase in Park Visitation . . . . . . . . . . . . . . . . . . . . . 39

Exhibit 5-4 Tax Revenue Increase Near Park Due to an Increase in Park Visitation . . . . . . . . . . . . . . . 39

Exhibit 5-5 Local Job Increase Near Park Due to an Increase in Park Visitation . . . . . . . . . . . . . . . . . . 40

Exhibit 6-1 Economic Valuation Studies for Recreational and Residential Visibility . . . . . . . . . . . . . . . 44

Exhibit 6-2 Visibility Benefits from Different Policy Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Exhibit 7-1 Residential (Urban) Visibility Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Exhibit 7-2 Recreational Visibility Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Exhibit 7-3 State-Level Recreational Visibility Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Exhibit 7-4 WinHaze Split-Images at Great Smoky Mountains National Park for Status Quo, No-EGU, and

Partial-EGU Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Exhibit A-1 Percentage Contribution of Constituents to Visibility Impairment on Good, Mid-Range, and Poor

Visibility Days . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1

Exhibit A-2 Annual Slope Estimates with Probabilities for Rejection for the Average of the Worst, Median,

and Best Visibility Days . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-3

Exhibit A-3 Visibility Benefits from Different Policy Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-4

Exhibit B-1 Available Information on WTP for Visibility Improvements in National Parks . . . . . . . . B-6


7/86

Exhibit B-2 Summary of Region-Specific Recreational Visibility Parameters to be Estimated in Household

Utility Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-7


8/86

Abt Associates Inc. August 20001

Exhibit 1-1 Denver on a Clear Day and on a Hazy Day

1. INTRODUCTION

Visibility impairment is a basic form of air pollution, one that people can see and recognize without

special instruments. It is also one of the scientifically best-understood air quality-related impacts of fossil fuel

combustion. Despite this common knowledge, the full costs of impaired visibility are not well understood by

policymakers and the public. Some people are not aware that visibility is impaired at all, incorrectly believing

that the milky-white haze that blankets parts of the country is somehow a natural phenomenon associated with

humidity, especially on hot summer days. In fact, visibility impairment is a major problem in the United States,

with both aesthetic and economic consequences.

A variety of sources contribute to the air pollutant

emissions that lead to visibility impairment, including power

plants, motor vehicles, wildfires and industrial processes like

smelting. The largest source in many areas is power plant

emissions. This report is meant to give the educated reader a

basic understanding of the nature and science of visibility

impairment and to provide an overview of the economic costsof visibility due to sources such as power plants. The report

is not, however, meant to go into great depth in every area,

although there is a large reference section that one can refer to

in order to get more detail on particular topic discussed here.

The report begins with a general overview of the basics behind the nature and science of visibility.

Included in this section is a discussion on what causes visibility impairment, how visibility is impaired, how

humans perceive visibility impairment, and how it is measured. The second section presents both historical

trends on national visibility and examples of visibility degradation at specific places. The legislative history

in specific regard to visibility regulation is then presented, along with a discussion on other air pollution

policies that have had an impact on visual air quality. The economics of visibility follows, and is presented

in two separate sections. The first discusses the economics of visibility in terms of its impact on the directconsumption of visibility as a resource, or, in other words, how visibility impacts visitation and tourism

behavior. The next section presents the economics of visibility in terms of non-direct consumption, or how

people value improvements in visibility in areas where they may or may not be experiencing it directly. Finally,

an applied example of the valuation of visibility improvements is provided, specifically calculating the visibility

benefits associated with reductions in power plant emissions.


9/86


2. VISIBILITY IMPAIRMENT

Visibility impairment comes in a variety of forms: intrusive plumes from local smokestacks, a dirty

low-lying inversion layer, a milky or brown regional haze blanketing the view in all directions. Each of these

forms of visibility impairment is a function of the nature and source of emissions and the prevailing

meteorological conditions (Malm, 1999, p. 20). With stable atmospheric conditions and large, local emission

sources, plumes and layered hazes are likely to occur (Exhibits 2-1a and 2-1b). Regional haze occurs under

meteorological conditions favorable for regional transport (Exhibit 2-1c).

Plumes, layered haze, and regional haze differ from the clouds and fog that we might see on a rainy

day, and instead are manmade impediments to visibility that federal, state, and local governments are actively

trying to reduce. For regulatory purposes, the Environmental Protection Agency distinguishes between

visibility impairment that is caused by one or a small group of sources, such as a the plume from a smoke

stack, and visibility impairment that is caused by emissions over a wide geographic region. The distinction is

made because emissions over a wide region are more diffuse and less easy to attribute to specific sources and,

thus, more difficult to identify and control.

When the view is obscured by pollution, it especially affects peoples enjoyment and sense of

wilderness experience. Many visitors to our nations parks and wilderness areas are unable to see the

spectacular vistas they had expected, because a veil of white or brown haze hangs in the air blurring the view.

Because this reduction can significantly reduce peoples enjoyment of the views, and it may reduce the

likelihood that they come back to visit, this can have a significant local economic impact. As we discuss in

subsequent chapters, there is also evidence that people value visibility at parks even when they are at home,

whether they visited the area or not.

Exhibit 2-1a Visible Plume from Local StacksSource: Malm (1999, Figure 1-5) and NPS-CIRA (2000b).


10/86


Exhibit 2-1b Layered HazeSource: Malm (1999, Figure 1-5) and NPS-CIRA (2000b).

Exhibit 2-1c Regional HazeSource: Malm (1999, Figure 1-5) and NPS-CIRA (2000b).

2.1 Causes of Visibility Impairment

Most visibility impairment is caused by human-induced particulate air pollution, the same pollutionlinked to premature death (Pope et al., 1995) and acid rain (NAPAP, 1990). Because of its very small particle

size, this pollution is often carried by the wind hundreds of miles from where it originated. The large coal-fired

electric utilities in the Ohio valley, some with stacks approaching 1000 feet tall, contribute the largest share

to visibility problems over a wide area of the Eastern and Midwestern U.S. Other contributors include motor

vehicles, industrial fuel burning, manufacturing operations, and natural sources such as windblown dust,

volatile organic compounds from plants, and soot from wildfires.


11/86


0%

10%

20%

30%

40%

50%

60%

70%

Electric Utilities Industry Transport Other

Nitrogen Oxides Sulfur Dioxide

Exhibit 2-2 National Emissions of Nitrogen Oxides and Sulfur Dioxide by Source in 1998

These emission sources contribute primary particles, which are particulates emitted directly into the

air, and secondary particles, which form from gases often carried many miles from their source. Both

primary emissions and secondary formation of particles contribute to visibility impairment. Primary particles

come from a variety of sources including diesel and wood combustion, and dust from industrial activities and

natural sources. Secondary particles form in the atmosphere from gases emitted from power plants, cars, and

a number of other sources, and are the most important in forming haze. Sulfate is, in most areas, the most

important secondary particulate, and forms from sulfur dioxide and ammonia emissions. Other secondary

particulates include nitrates, forming from nitrogen oxide and ammonia emissions, and organic carbon particles

from condensed hydrocarbon emissions.

Some particles, like sulfates and nitrates become more effective during humid conditions as they absorb

atmospheric moisture and grow (Day et al., 2000, p. 716; Sisler, 1996, p. 4-7; U.S. EPA, 1996, p. 8-44).

Sulfates and nitrates can more than triple in size as relative humidity increases, thus making visibility worse

during periods of high humidity, such as the humid summer months in the East (National Research Council,

1993, p. 103). However, humidity alone does not cause visibility impairment.

The impact of particles can be measured many miles away. California and Mexico both make

substantial contributions to sulfate particles in the Grand Canyon (Eatough et al., 2000, Figure 9; Malm, 1999,p. 51). The U.S., east of the Mississippi, and Canada are both affected by emissions from power plants.

Electric utilities are perhaps the single largest contributor to poor visibility. Nationwide in 1998, electric

utilities contributed 67 percent of sulfur dioxide emissions and 25 percent of nitrogen oxide emissions (Exhibit

2-2 based on U.S. EPA, 2000, Tables A-2 and A-4). Coal-powered electric utilities dominate these emissions,

contributing 94 percent of sulfur dioxide and 88 percent of nitrogen oxide emissions from electric utilities.

Sulfur dioxide gas is especially important because it contributes to the formation of sulfates, which

often dominate other causes of visibility impairment, particularly in the Eastern U.S. Exhibits 2-3a, 2-3b, and

2-3c present the average contribution to visibility impairment of different particulate matter constituents at a

variety of mainly rural monitoring sites through out the U.S., and Exhibit A-1 presents the park-level data

underlying these regional averages. The exhibits present the contribution on a good, medium and bad visibility

days. The sites presented in the exhibits are typically located in national parks, with the exception of

Washington D.C.


12/86


0%

10%

20%

30%

40%

50%

60%

70%

80%

ContributiontoVisib

ilit

Impairment(%)

Good Day Median Day Poor Day

Eastern U.S.

Sulfate

Nitrate

Organic Carbon

Light Absorbing

Carbon

Coarse Matter and

Fine Soil

0%

10%

20%

30%

40%

50%

60%

70%

80%

ContributiontoVisibility

Im

pairment(%)


Mid-Western U.S.

Sulfate

Nitrate

Organic Carbon

Light Absorbing

Carbon

Coarse Matter and

Fine Soil

In the eastern and mid-western U.S., sulfates account for the majority of visibility impairment. In the

West, sulfates and organic carbon play about equal roles. Throughout the U.S., nitrates typically account for

less than 10 percent of visibility impairment in most locations, with a notable exception of San Gorgonio,

located in southern California, where nitrates can contribute over 30 percent of visibility impairment (Exhibit

A-1). Perhaps most significantly, in almost all locations, sulfates are responsible for a greater percentage of

visibility impairment on bad visibility days than on good visibility days. In Great Smoky Mountains National

Park, sulfates account for 46 percent of impairment on a good day, 63 percent on a median day, and 76 percent

on a bad visibility day. In Acadia, sulfates account for 37 percent, 48 percent, and 69 percent, respectively

(Exhibit A-1). In most of the East, sulfur dioxide emissions, largely from electric utilities, account for two

thirds to three quarters of the visibility impairment on haziest days.

Exhibit 2-3a Contribution to Visibility Impairment in the Eastern U.S.Source: NPS-CIRA (2000a).

Exhibit 2-3b Contribution to Visibility Impairment in the Mid-WestSource: NPS-CIRA (2000a).


13/86


0%

10%

20%

30%

40%

50%

60%

70%

80%

ContributiontoVisibility

Impairment

(%)


Western U.S.

Sulfate

Nitrate

Organic Carbon

Light Absorbing

Carbon

Coarse Matter and

Fine Soil

Exhibit 2-3c Contribution to Visibility Impairment in the WestSource: NPS-CIRA (2000a).

2.2 Observing and Measuring Visibility Impairment

To better understand visibility impairment it is useful to consider the nature of light and how the human

eye functions. The human eye recognizes a spectrum of colors from blues with a wavelength of about 0.4

microns to reds with a wavelength of 0.7 microns (Malm, 1999, p. 3). We perceive a rose to be red because

it absorbs all of the wavelengths in the visible spectrum except for those around 0.7 microns, and we perceive

a blue butterfly because it absorbs most of the visible spectrum except for those wavelengths around 0.4

microns. The range of color we see are simply light with different wavelengths reflected back to us and

captured by our eyes. The same process of differential absorption and reflection of light occurs with visibility

impairment.

When we observe a low-lying brownish layered haze caused by nitrogen dioxide emissions, it appears

brown because nitrogen-dioxide absorbs blue light and reflects back to us the remainder of the spectrum

(Malm, 1999, p.4). When we see a dark plume coming from a smokestack, it appears black because the carbon

soot and other emissions absorb all of the visible spectrum. Conversely, a white plume of water vapor coming

from a power plants cooling tower appears white because it absorbs none of the incoming light and simply

scatters and reflects back the full spectrum to the eye.

When we are on a mountain top enjoying a view of the landscape or just walking down the street and

looking at a distant object, a number of processes interfere with the light that is reflected from objects that we

are trying to see (Exhibit 2-4). Our ability to see a distant mountain depends on transmission radiance and

air light (U.S. EPA, 1996, p. 8-23). Transmission radiance refers to the light reflected from the mountainand the subsequent interaction of this light in the atmosphere. As this light is absorbed and scattered by gases

and particles in the atmosphere, our ability to see the mountain is reduced. Scattering by particles is usually

the most important source of interference. Another source is air light, which has a variety of effects and refers

to the light from sources other than the object of interest that are scattered towards us and affect what we are

trying to see. Air light scattered from behind the mountain provides backlighting and makes the mountain

standout, while air light scattered from particles and gases between the mountain and our eye obscures our

vision (National Research Council, 1993, p. 82).


14/86


Exhibit 2-4 Scattering and Absorption of Image-Forming Light from the Observers Sight PathSource: Malm (1999, Figure 1-5) and NPS-CIRA (2000b).

Transmission radiance usually dominates visibility impairment, and the scattering of photons is the

most important process in transmission radiance. Although gaseous pollutants, such as nitrogen dioxide,

contribute to visibility impairment, they usually play a small role, and instead scattering due to particulates

dominate the visibility impairment. However, not all particles are equally important in scattering light (Exhibit

2-5). Particles about the same size as the visible spectrum are the most efficient at scattering light (Malm,

1999, p.8).


15/86


Exhibit 2-5 Aerosol Size and Light ScatteringSource: Malm (1999, Figure 1-5) and NPS-CIRA (2000b).

These fine particles, ultra-efficient at scattering light, include: sulfates, nitrates, organics, and soil

(Malm, 1999, p. 26). Elemental carbon is another fine particle that contributes to visibility impairment by

efficiently absorbing light because of its black color (Exhibit 2-6). In contrast to white sulfur, which absorbs

little light and instead scatters it effectively, elemental carbon absorbs light, much like a blacktop absorbs heat

on a hot summer day. However, the contribution of absorption by elemental carbon is generally less than 10

percent of the loss in transmission radiance. Sulfates often dominate, particularly in the East, and can

contribute 80 percent or more of the loss in transmission radiance (Exhibit 2-3a).

Exhibit 2-6 Types of Particulate Matter and Impact on Image-Forming LightSource: Malm (1999, Figure 1-5) and NPS-CIRA (2000b).


16/86


1

2

3

4

5

6

7

8

9

1 2 3 4 5 6 7 8 9 10

Particulate Concentration (ug/m3)

Poor

-------------------------------------------------

Good

Per

ceivedVisualAirQuality(PVAQ)

Exhibit 2-7 Relationship Between Perceived Visual Air Qualityand the Amount of Particulate Matter in the Air

2.2.1 People Can Tell When Views Are Impaired

It is well known how visibility is impaired by air pollution, and how the human eye perceives these

changes. However, do humans regard visibility impairment in a consistent and equal fashion? That is, when

visibility is impaired, do humans perceive that visibility has changed equally? This is an important question

to answer because, if impaired visibility is not perceived equally between people from region to region, it would

be nearly impossible to measure and regulate.

In the first perception and judgement studies, conducted by the NPS (NPS, 1988), people were asked

to judge the visual air quality in several slides depicting vistas under different visibility conditions using a scale

of one to ten, one being worst and ten being best. The one to ten judgement is called perceived visual air

quality (PVAQ), and it reflects peoples perceptions and judgements concerning the visual air quality depicted

in the slide. Studying the differences among the slides and their average PVAQ has helped researchers

determine what factors are most important to human observers in their judgements of visual air quality.

These studies first addressed the question of whether individuals judged poor visibility in the slides

similarly to actual views under the same air quality conditions. It was found that the PVAQ judgements were

comparable and that the use of slides in studies concerning perceived visual air quality was a valid method forcomparing perceptions of visual air quality. They also found that, regardless of the demographic

characteristics of the individual (age, sex, education), PVAQ judgements made by different people were

consistent with each other. This suggested that for a given slide, people generally judged air quality in a similar

fashion.

The analysis of the PVAQ

judgments revealed that increases in

air pollution are more noticeable and

objectionable to the human observer

when the air is relatively clean.

Exhibit 2-7, based on NPS (1988,

Figure 3-1), demonstrates therelationship between the PVAQ

judgement and ambient particulate

levels. The curved line indicates that

a one-unit increase in particulates will

result in a much larger decrease in an

individuals PVAQ at the lower

particulate levels than at the higher

particulate levels.

These studies were also able

to test whether the visual air qualityperceived by individuals is more

sensitive to changes in air pollution at

some vistas than at others. The

results indicate that people find

increases in air pollution more

objectionable in vistas with features

that are more highly colored and

textured.


17/86

1 The Federal Register (July 1, 1999, vol. 64, no. 126, p. 35,725) discusses the choice of the deciview index for EPA'sregional haze program.


These first few perception and judgement studies set the foundation for subsequent research on the

effects of visual air quality on the visitor experience. These studies suggested that visitors do have preferences

concerning visibility conditions and that a variety of circumstances, such as what is actually being viewed and

how good the air quality was prior to the pollution, influence changes in perceived visual air quality.

2.2.2 How Visibility Impairment is Measured

It is important to determine that people can actually perceive changes in visibility condition, which is

why the perceived visual air quality (PVAQ) index was developed. However, this index is not an actual

measure of visibility conditions as they exist from place to place. To conduct meaningful analyses of how

visibility changes due to the presence of pollution in the atmosphere, there must be some standardized approach

to measuring visual air quality. Visibility conditions are, therefore, commonly expressed in terms of three

mathematically related metrics: standard visual range (SVR), light extinction (ext), and deciviews (dv).

Standard visual range is the metric best known by the general public. It is the maximum distance at which one

can identify a black object against the horizon, and is typically described in kilometers (or miles). Higher visual

range estimates mean better visibility. While the theoretical maximum is 391 kilometers on a perfectly clear

day, this is never achieved due to the natural scattering of light by gases in the atmosphere, so-called Rayleighscattering (U.S. EPA, 1996, p. 8-12). While standard visual range is a simple measure that can be easily used

to characterize visual conditions, it is somewhat imprecise and cannot be used to effectively determine the

relative importance of the contributors to reduced visibility. It is also useless in cloudy conditions near

monitors.

Light extinction is a somewhat better alternative than visual range because it allows one to express

more objectively the relative contribution of a PM constituent to overall visibility impairment. Light extinction

is the sum of the light scattering and light absorption by particles and gases in the atmosphere, and is measured

in inverse megameters (Mm-1), relating how much light is extinguished per megameter. Higher extinction

values mean worse visibility. This is the inverse of visual range, where higher visual range estimates suggest

better visibility (U.S. EPA, 1996, p. 8-56). For example, in the Great Smoky Mountains, a relatively clear day

has an extinction of 47 Mm-1 and a visual range of 82 kilometers, and a hazy day has an extinction of about211 Mm-1 and a visual range of 19 kilometers. Both extinction and visual range are similar in that they are not

proportional to human perception (Malm, 1999, p. 35). In other words, a one unit change in either light

extinction or visual range is perceived differently, depending on the starting point. For example, a five mile

change in visual range can be either very apparent or not perceptible, depending on whether the starting point

is a clear day or a hazy one.

A third measure of visibility is the deciview index, which EPA selected as the standard metric for

tracking progress in EPA's regional haze program, largely because it provides a linear scale for perceived visual

changes over a wide range of conditions.1 On a particle-free, pristine day, the deciview index has a value of

zero (SVR=391 km). On a relatively clear day in the Great Smoky Mountains the deciview index might be

about 16 (SVR=79 km) and on a relatively hazy day the deciview index might be about 31 (SVR=201 km).For each 10 percent increase in light-extinction, the deciview index goes up by one. So, higher deciview values

mean worse visibility (Exhibit 2-8). This logarithmic scaling is analogous to the decibel scale used for the

perception of sound (U.S. EPA, 1996, p. 8-57). Under many scenic conditions, a change of one deciview is

considered to be just perceptible by the average person. However, it is important to understand that the same

amount of pollution can have dramatically different effects on visibility depending on existing conditions. Most


18/86


0

50

100

150

200

250

300

350

400

0 5 10 15 20 25 30 35 40 45

Deciview Index

VisualRange(km)

Grand Canyon Good Day

Shenandoah Bad Da

Shenandoah Good Day

Shenandoah Median Day

importantly, visibility in cleaner environments is more sensitive to increases in particle concentrations than

visibility in more polluted areas.

Exhibit 2-8 Inverse Relationship Between Visual Range and the Deciview IndexSource: NPS-CIRA (2000a).

Visibility impairment is roughly proportional to the product of ambient particle levels and viewing

distance (National Research Council, 1993, Figure 4-3). As particle levels increase, we must move closer to

an object to see it as well as before. This phenomenon is particularly a problem in pristine areas, where long-

range transport of pollution may increase naturally low particulate levels and significantly reduce viewing

distance. For example, in pristine areas of the Southwest, where visibility is exceptionally good, small

increases in sulfate concentrations can lead to readily apparent reductions in visibility (National Research

Council, 1993, p. 106).

This principle is illustrated in Exhibits 2-9, which characterize a range of visibility conditions at

Shenandoah National Park. Generated by the WinHaze computer program (Air Resource Specialists Inc.,

1998), the two top scenes in Exhibit 2-9 are of a clear day at Shenandoah in 1998 with a visual range of 94

miles, and a day slightly worse than the median, with a visual range of 40 miles. The two bottom scenes areof relatively hazy days with a visual range of 13 and 11 miles. In both the top and bottom sequences, the

difference in visual range is the result of an additional five g/m 3of sulfates in the atmosphere. This illustrates

that the perceived change in visibility due to an additional five g/m 3 of sulfates to an already degraded

atmosphere is less noticeable than adding it to a pristine atmosphere. Thus, to achieve a given level of

perceived visibility improvement, a larger reduction in fine particle concentrations is needed in more polluted

areas. Conversely, a small amount of pollution in a clean area can dramatically decrease visibility.


19/86


(a) Clear Day visual range 94 kilometers

0

20

40

60

80

100

13 18 23 28 33 38 43Deciview Index

VisualRange(km)

Clear Day

Clear Day + 5 ug/m3

sulfate

Haz Day

Hazy Day + 5 ug/m3

sulfate

(b) Clear Day + 5 g/m3 sulfate visual range 40 kilometers

(c) Hazy Day visual range 18 kilometers (d) Hazy Day + 5 g/m3

sulfate visual range 14 kilometers

Exhibit 2-9 Shenandoah National Park: WinHaze Photos Showing Effect of a Five g/m3 Incrementof Sulfate on a Clear Day and a Hazy Day


20/86


Exhibit 3-1 Airport Visual Data: Trend in 75th

Percentile Light Extinction Coefficient for July-

September (measured in km-1)

3. TRENDS IN VISIBILITY IMPAIRMENT

Historical airport visibility data shows that visibility declined significantly in the 1940s up through the

1960s in the Western U.S. In the East, this decline continued up until about 1980. Based on EPA (1998,

Figure 6-4), Exhibit 3-1 depicts 75 th percentile light extinction at airports across the U.S. from 1970 to 1990.

Since then, while there have been some areas of improvement, significant problems remain.

A variety of ways to record atmospheric

visibility have been used to provide an idea of

how visibility impairment has changed over time.

Human eye observations of visual range have

been recorded at airport weather stations for most

of the 20th century and have only recently been

phased out in favor of more quantitative

measures. One of the best sources of recent data

is the Interagency Monitoring of Protected Visual

Environments (IMPROVE) program, which wasestablished in 1987 to provide a variety of

visibility measurements including detailed

measurements of particulate constituents (U.S.

EPA, 1996, Table 8-3).

The airport data are the most extensive,

as they cover hundreds of stations across the

United States, and go back to the early 1900s.

While these data are somewhat limited because of

variations in observers and inconsistent reporting

procedures, they are nevertheless useful in

developing historical trends. After analyzingthese data, Malm (1999, pp. 39-41) reported that

in the East visibility has generally worsened

between the late 1940s and early 1980s, especially

during the summer in the Southeast. This decline

in visibility is closely matched with an increase in

sulfur emissions (Malm, 1999, Figure 6.16b). In

the Rocky Mountains southwest, the trends are

mixed from 1948-1976. While in California

visibility declined from the late 1940s to 1966,

and has since generally improved. However,

Malm noted that while the overall average isimproving in California, the number of very good

or superior visibility days at a couple of pristine

monitoring sites has gradually declined.


21/86

2 Air Resources Specialists, Inc. (2000c) did not report the deciview levels for the pictures of Half Dome, Yosemite. Using

a guide of roughly 4 deciviews for a good day and 16 deciviews for a poor day, we chose Half Dome pictures that comparedreasonably well with WinHaze photos of comparable deciview levels.


3.1 Recent Visibility Trends

In this section, we consider more closely how visibility has changed in specific areas throughout the

country; in areas where the vista is an integral characteristic of the place itself, at smaller parks and wilderness

areas, and in urban settings with scenic, postcard skylines. We have comprehensive visibility data since

1987, when the IMPROVE network of monitors was established at national parks throughout the nation.

3.1.1 Visibility at Parks Where the Vista Is Integral to the Experience

Pristine national parks and wilderness areas are clearly some of the areas where visibility is extremely

important. To provide a sample of visibility at national parks where the vista is integral to the experience, we

chose five well-known parks from throughout the country. They are Acadia National Park in Maine, Grand

Canyon National Park in Arizona, Great Smoky Mountain National Park in Tennessee and North Carolina,

Shenandoah National Park in Virginia, and Yosemite National Park in California.

The National Park Service (NPS-CIRA, 2000a) sorted each park's daily visibility measurements from

low to high for each year, and placed them into three groups for analysis: good visibility days are the lowest20 percent of daily measurements, mid-range days are the middle 40-60 percent, and poor visibility days are

those days above the 80th percentile of the ordered data. We then plotted the annual average visibility

measurement for each of these categories. To put the visibility category ranges observed at each park into

perspective, we present actual photographs that represent the deciview levels for each national park for the

good and poor visibility categories.2 Exhibits 3-2 through 3-6 present the trends graph and companion photos

for each park. These trends were also examined by Sisler and Malm (2000), who conducted a statistical

analysis of the slopes of the park-specific visibility trend lines. Exhibit A-2 contains the slope of the visibility

trend line for each park, and many additional parks, over the last decade and identifies whether or not the trend

identified by the slope is statistically significant.

The good, midrange, and poor categories that we considered represent averages for the visibility

levels within each group, and do not capture the full range of visibility levels at these parks. In Exhibit 3-7 wepresent photographs to capture the range of conditions for each park, from pristine to extremely poor visibility

days.

Over the last decade there were no major changes to visibility levels at the parks examined in this

analysis. Both improvements and declines in visibility were generally very slight between 1988 and 1998,

though there was a significant amount of variation in visibility in the range of years. The points plotted on the

graphs do not lead to smooth trend lines in one direction or another for any of the parks. It appears that some

of the air quality controls already in effect may be preventing significant additional deterioration to visibility

at these national parks.

At Acadia National Park, visibility improved slightly from 1988 to 1998 in each of the three visibilitycategories, however, only the visibility trends in the good visibility and median visibility categories were

statistically significant (Exhibit A-2). Like Acadia, visibility improved slightly at Grand Canyon National Park

in each of the three categories over the last decade. However, only the trend over good days was even

marginally significant. Between 1988 and 1998, visibility at Great Smoky Mountains National Park worsened


22/86


on the poorest days, and improved slightly on mid-range days and good days. None of the trends, though, were

statistically significant. Shenandoah National Park experienced declines in visual air quality on the poorest

visibility days and improvements in visibility on the mid-range and good days. Only improvements on the mid-

range days were found to be marginally significant. Finally, at Yosemite National Park, visibility improved

on the good and mid-range days, and worsened on the poor visibility days. None of the Yosemite trends,

however, were found to be significant.


23/86

16Abt Associates Inc. August 2000

Acadia National ParkMeasurements of haze (in deciviews) and its effect on visibility

9

11

13

15

17

19

21

23

25

27

88 89 90 91 92 93 94 95 96 97 98

Year

Deciviews

Good Visibi lity Days Mid-Range Poor Visibili ty Days

Good Visibility Day (10 deciviews) Poor Visibility Day (23 deciviews)

Exhibit 3-2 Visibility Trends at Acadia National Park, Maine( Photos: Air Resource Specialists Inc., 2000a, Img0004.pcd and Img0009.pcd; IMPROVE data: NPS-CIRA, 2000a)


24/86


Grand Canyon National ParkMeasurements of haze (in deciviews) and its effect on visibility

4

6

8

10

12

14

89 90 91 92 93 94 95 96 97 98

Year

Deciviews

Good Visibility Days Mid-Range Poor Visibil ity Days


Exhibit 3-3 Visibility Trends at Grand Canyon National Park, Arizona( Photos: Air Resource Specialists Inc., 1997, Img0015.pcd and Img0023.pcd; IMPROVE data: NPS-CIRA, 2000a)


25/86


Great Smoky Mountains National ParkMeasurements of haze (in deciviews) and its effect on visibility

13

15

17

19

21

23

25

27

29

31

88 89 90 91 92 93 94 95 96 97 98

Year

Deciviews

Good Visibility Days Mid-Range Poor Visibil ity Days


Exhibit 3-4 Visibility Trends at Great Smoky Mountains National Park, Tennessee( Photos: Air Resource Specialists Inc., 2000b, Img0008.pcd and Img0013.pcd; IMPROVE data: NPS-CIRA, 2000a)


26/86


Shenandoah National ParkMeasurements of haze (in deciviews) and its effect on visibility

14

16

18

20

22

24

26

28

30

32

88 89 90 91 92 93 94 95 96 97 98

Year

Deciviews

Good Visibility Days Mid-Range Poor Visibility Days


Exhibit 3-5 Visibility Trends at Shenandoah National Park, Virginia( Photos: Air Resource Specialists Inc., 1999, Img0082.pcd and Img0085.pcd; IMPROVE data: NPS-CIRA, 2000a)


27/86


Yosemite National ParkMeasurements of haze (in deciviews) and its effect on visibility

3

5

7

9

11

13

15

17

19

21

88 89 90 91 92 93 94 95 96 97 98

Year

Deciviews

Good Visibili ty Days Mid-Range Poor Visibi lity Days

Poor Visibility DayGood Visibility Day

Exhibit 3-6 Visibility Trends at Yosemite National Park, California( Photos: Air Resource Specialists Inc., 2000c, Img0002.pcd and Img0004.pcd; IMPROVE data: NPS-CIRA, 2000a)


28/86


Excellent Visibility Day (3 deciviews) Bad Visibility Day (33 deciviews)



Exhibit 3-7a Extreme Visibility Days at Acadia National Park(Air Resource Specialists Inc., 2000a, Img0001.pcd and Img0012.pcd)

Exhibit 3-7b Extreme Visibility Days at Grand Canyon National Park(Air Resource Specialists Inc., 1997, Img0010.pcd and Img0024.pcd)

Exhibit 3-7c Extreme Visibility Days at Great Smoky Mountains National Park(Air Resource Specialists Inc., 2000b, Img0016.pcd and Img0026.pcd)


29/86



Excellent Visibility Day Bad Visibility Day

Exhibit 3-7d Extreme Visibility Days at Shenandoah National Park(Air Resource Specialists Inc., 1999, Img0001.pcd and Img0011.pcd)

Exhibit 3-7e Extreme Visibility Days at Yosemite National Park(Air Resource Specialists Inc., 2000c, Img0001.pcd and Img0005.pcd)

3.1.2 Visibility at Smaller Parks and Wilderness Areas

We may only think of major national parks when we think of the impacts of visibility impairment, but

poor visual air quality impacts smaller parks and wilderness areas, as well. Though the data may be sparse

for these parks, more data are added annually as the IMPROVE system includes new areas into the monitoring

system (NPS-CIRA, 2000a). We considered visibility trends at two lesser known areas, San Gorgonio

Wilderness Area in California and Chassahowitzka in Florida to demonstrate that visibility trends observed

at larger, well known parks can also be observed at smaller parks and wilderness areas.

At the San Gorgonio Wilderness Area, visibility on poor days improved between 1988 and 1998

(Exhibit 3-8), due primarily to a reduction in ambient ammonium nitrate (NPS-CIRA, 2000a). This trend was

found to be statistically significant (Exhibit A-2). Mid-range days and good days also experienced

improvements in visibility, though they were slight and not statistically significant. At the Chassahowitzka

wilderness area, where visibility data has only been collected since 1993, we again see the visibility day


30/86


San Gorgonio Wilderness AreaMeasurements of haze (in deciviews) and its effect on visibility

468

101214

161820222426

88 89 90 91 92 93 94 95 96 97 98

Year

Deciviews


Chassahowitzka Wilderness AreaMeasurements of haze (in deciviews) and its effect on visibility

17

1921

23

25

27

29

93 94 95 96 97 98

Year

Deciviews


categories remained relatively constant over the six year time period (Exhibit 3-9). The significance of the

trends for each of the visibility day categories, however, were not calculated, so no inference on the statistical

significance of the trends can be made. There appears, however, to be a slight increase in 1998 deciview levels

compared to those in 1993. The absence of large swings in visual air quality echo the trends seen at the larger

parks that visibility has not changed dramatically over the last decade and that improvements can still be

made.

Exhibit 3-8 Visibility Trends at San Gorgonio Wilderness Area, California(IMPROVE data: NPS-CIRA, 2000a)

Exhibit 3-9 Visibility Trends at Chassahowitzka Wilderness Area, Florida(IMPROVE data: NPS-CIRA, 2000a)


31/86

3 Savig (2000) did not report the deciview levels for a series of five pictures of Washington, D.C., ranging from excellent to

very poor visibility. To estimate good and poor visibility levels, we present the second and fourth pictures of the series.


3.1.3 Visibility in Urban Settings

Urban settings are also impacted by trends in visibility. The IMPROVE network has acknowledged

this fact by placing a monitor in Washington, D.C., a tourist destination where the vistas of the historical sights

and monuments play an integral role to the attraction of the city. Though data and photos are only examined

here for Washington, D.C., the importance of visibility in other urban areas with a postcard skyline, like New

York City, San Francisco, or Boston, should not be overlooked. Exhibit 3-10 shows that visibility levels for

all visibility day categories have improved slightly between 1988 and 1998, though the trends were not found

to be significant (NPS-CIRA, 2000a).3


32/86


Washington, DCMeasurements of haze (in deciviews) and its effect on visibility

17

19

21

23

25

2729

31

33

89 90 91 92 93 94 95 96 97 98

Year

Deciviews

Good Visibi lity Days Mid-Range Poor Visibility Days

Good Visibility Day Poor Visibility Day

Exhibit 3-10 Visibility Trends in Washington, D.C.( IMPROVE data: NPS-CIRA, 2000a; Savig, 2000, naca_2.jpg and naca_4.jpg)


33/86


4. LEGISLATIVE AND REGULATORY HISTORY OF VISIBILITY IMPAIRMENT

Over the past 25 years there have been a number of legislative and regulatory initiatives designed to

improve visibility, such as the Clean Air Act Amendments of 1977 and the 1999 Regional Haze Rule. In

addition, there are a number of other legislative and regulatory initiatives that should reduce visibility

impairment in addition to the primary goal of reducing ambient pollutant levels. For example, the Title IV acid

rain provision of the Clean Air Act is reducing SO2 emissions, which will reduce the visibility impairment

related to sulfate aerosols. Similarly, tighter tailpipe emission standards for gasoline and diesel-powered

vehicles, along with programs for cleaner-burning fuels, will further reduce visibility impairment in some areas.

The Clean Air Act Amendments of 1977 included the first significant federal legislation that

specifically addresses visibility impairment. The 1977 Amendments established a national goal of prevention

of any future, and the remedying of any existing, impairment of visibility in Class I Areas which impairment

comes from manmade pollution. It included two programs aimed at visibility impairment in Class I Areas

(pristine wilderness locations of great scenic importance). The first is the prevention of significant

deterioration (PSD) program outlined in Sections 160-169, which is aimed at reducing ambient levels of criteria

pollutants. The PSD program requires that new or modified major emitting facilities must not adversely affectnearby Class I Areas. The second is the Section 169 regional haze program, where Congress set a national

goal of preventing and remedying visibility impairment in pristine areas of the U.S.

The pristine areas identified in the legislation come from a group of so-called mandatory Class I

Areas, which are selected national monuments, wilderness, wildlife refuge and memorial areas and parks

larger than 5,000 acres, national parks over 6,000 acres, and all international parks in existence on the day

President Carter signed the 1977 Amendments into law. The legislation required EPA to identify from the 158

mandatory Class I Areas those in which visibility is an important value. In November 1979, EPA complied

and identified 156 areas including one international park in the Virgin Islands (Scott and Stonefield, 1990,

Table 1). Three federal agencies have primary responsibility for most of these areas: Forest Service (98

wilderness areas), National Park Service (36 national), and Fish & Wildlife Service (21 wilderness areas).

Exhibit 4-1 maps the 156 parks and wilderness areas chosen by EPA. Adding new Class I Areas would requirean Act of Congress.

In addition to identifying areas where visibility is an important value, the 1977 Amendments require

EPA to promulgate regulations to assure reasonable progress in meeting the goal of preventing and remedying

visibility impairment. Impairment causes were categorized as either reasonably attributable to an individual

source or small group of sources, or as regional haze, which emanate(s) from a variety of ...regionally

distributed sources. As a first major step in 1980, EPA established regulations to address visibility

impairment in Class I Areas that could be reasonably attributed to major stationary air pollution sources (U.S.

EPA, 1996, p. 8-2). At that time, EPA deferred regulatory action on regional haze until they had better

scientific tools, and instead focused on more local problems.

Responsibility for identifying and regulating specific sources that impair visibility involves three

different parties: the federal agency managing a Class I Area , the state where the source is located, and the

EPA. If a Federal Land Manager establishes that visibility at the Class I Area is impaired, the EPA must make

a reasonably attributable decision linking the impairment with a specific source. The State then conducts

a case-by-case review to determine what is the best available retrofit technology (BART) to control the sources

emissions. The BART determination for a specific source depends on a number of factors, including the

control technologies that are available, the cost installing and operating the available technologies, all

environmental impacts of compliance, pollution control equipment already existing at the source, the remaining

useful life of the source, and the degree of improvement in visibility that may result from the use of BART.


34/86


Aside from the possibility that large point sources chose not to locate near Class I Areas, the 1980

regulations developed by EPA had limited impact on existing point sources. Identifying specific sources that

impair visibility has proven to be difficult, in large part because visibility is a regional problem with

contributions from many sources over a wide area (Latimer, 1990, p. 51). EPA has initiated separate studies

of the Navajo Generating Station (NGS) and the Mojave Power project. To date only the NGS, a large power

plant in Page, Arizona, has added BART to its facility. Extensive atmospheric studies demonstrated that the

NGS, located on the Colorado River at the north-eastern edge of the Grand Canyon National Park, was a major

cause of haze within the Canyon during certain wintertime conditions. At other times of the year the NGS is

only one of many sources that contribute to the major haze problem within the Canyon. In 1991 the NGS

BART review resulted in a negotiated settlement to reduce sulfur emissions from NGS by 90 percent, with

additional reductions in NOx fine particle emissions. Those emissions controls are now operating at the NGS,

helping to improve visibility not only at the Grand Canyon but throughout the golden circle of National Parks

and Monuments on the Colorado Plateau

Negotiated agreements to improve Class I visibility have also been reached involving two other major

western power plants: the Mojave and Centralia Power Plants. A 1996 negotiated settlement avoided a formal

and potentially lengthy BART proceeding, while successfully leading to a reduction in emission producing haze

at Mt. Rainier National Park in the State of Washington. The Centralia Power Plant is located 50 milessouthwest of Mt. Rainier, and is the largest remaining point source of sulfur emissions in the western United

States. Emitting over 69,000 tons of sulfur annually, Centralia is estimated to cause a third of the visibility-

impairing sulfur concentrations at Mr. Rainier NP, and a quarter of the haze-induced bad visibility days. The

agreement reached by the State of Washington, local regulatory agencies, the National Park Service, the EPA,

and PacifiCorp (one of the plants owners) will reduce sulfur emissions by 90 percent by 2002 (National Park

Service, 1997).

Another negotiated agreement reached in 1999 involves the Mojave Power Plant, located 75 miles west

of the Grand Canyon in Laughlin, Nevada. Like NGS, Mojave has also been linked to haze in the Grand

Canyon. The settlement will reduce Mojaves sulfur emissions by over 85 percent. Construction planning is

beginning, and Mojave will meet the new emission limits by the end of 2005.

Progress on controlling regional haze began with the 1990 Clean Air Act Amendments, which added

Section 169B authorizing EPA to conduct research on regional haze (National Research Council, 1993, p. 61).

The research involves an expansion of visibility-related monitoring, assessment of sources of visibility-

impairing pollution, adaption of air quality models to measure visibility, studies on the chemistry and physics

of visibility, and an assessment of visibility levels in Class I Areas every five years. The 1990 Amendments

also allowed EPA to establish visibility transport regions for any Class I Area whose visibility is impaired

by the interstate transport of air pollution, and required establishing a transport region for the Grand Canyon

National Park. EPA later expanded this to include 15 other Class I parks and wilderness areas on the Colorado

Plateau (U.S. EPA, 1996, p. 8-2). The Grand Canyon Transport Commission must assess current and

projected emission sources and suggest corrective action, and in turn EPA must develop regulations that result

in reasonable progress toward reducing visibility impairment. The regulations to protect the Colorado Plateaumust also be coordinated with other federal regional haze and PM programs.

In response to the problem of regional haze, the National Academy of Science established a committee

to address regional haze in national parks and wilderness areas. The committee considered the state of

knowledge on a variety of issues including determining individual source contributions to visibility impairment,

factors that affect haze, improvements in air quality models, and emission controls. In 1993, the committee

published an influential report of their findings (National Research Council, 1993). The report stated that the

current state of science is adequate and control technologies are available to improve and protect visibility.


35/86


However, a regional approach is necessary to control visibility impairment, and an approach that focuses on

individual emission sources is doomed to failure (p. 7).

In part propelled by this report, on July 31, 1997, EPA published proposed amendments to its 1980

regulations that would require control of regional haze. TheRegional Haze Rule calls for state and federal

agencies to work together to improve visibility, and establishes goals for each Class I Area that are designed

to improve visibility on the worst days and prevent degradation of visibility on the best days. Each state must

address its contribution to visibility problems in national parks and wilderness areas both within and outside

its borders, and to develop long-term strategies aimed at returning visibility to natural conditions. The first

State plans for regional haze are due by 2008.

The Grand Canyon Visibility Transport Commission (GCVTC) is the only visibility transport

commission established to date. The GCVTC consists of the governors of eight western states, leaders of five

Native American Tribes, and five federal agencies. They conducted an extensive scientific and policy analysis

project designed to identify an effective combination of policy recommendations to protect and improve

visibility at 16 National Parks and Wilderness Areas that make up the Golden Circle of parks on the

Colorado Plateau. The GCVTC emphasized the importance of active participation by a broad range of stake

holders, and participants ranged from individual firms to environmental organizations. In 1996 the GCVTCcompleted their recommendations, designed to improve visibility on the Colorado Plateau by limiting emissions,

protecting clean air corridors, increasing the monitoring, and integrating visibility considerations into forest

fire management policies.

Although the GCVTC is the only visibility transport commission, other multi-state organizations are

involved with regional visibility as part of integrated regional air quality planning activities covering all

portions of the continental United States. These organizations are sponsoring a wide range of activities to

understand the unique causes, effects, and policy alternatives for improving all aspects of air pollution

including visibility within their region. Currently, regional organizations include:

! The Western Region Air Partnership, or WRAP [http://www.wrapair.org] is a successor

organization to the GCVTC, with a goal of implementing the GCVTC recommendations. Itincludes 12 states: Arizona, California, Colorado, Idaho, Montana, New Mexico, North

Dakota, Oregon, South Dakota, Utah, Washington and Wyoming.

! The Western States Air Resources Council, WESTAR [http://www.westar.org] is an

organization of air agencies from 15 western states: Alaska, Arizona California, Colorado,

Hawaii, Idaho, Montana, Nevada, New Mexico, North Dakota, Oregon, South Dakota, Utah,

Washington, Wyoming.

! The Central States Air Resource Agencies, CesSARA [http://www.censara.org] includes air

agencies from nine states: Nebraska, Kansas, Oklahoma, Texas, Minnesota, Iowa, Missouri,

Arkansas and Louisiana.

! The Lake Michigan Air Directors Consortium, LADCO [http://www.ladco.org] includes the

four states: Illinois, Indiana, Michigan, and Wisconsin.

! The Mid-Atlantic Regional Air Management Association, MARAMA

[http://www.marama.org] includes nine states: Delaware, the District of Columbia, Maryland,

New Jersey, North Carolina, Pennsylvania, Virginia, West Virginia and the District of

Columbia.


36/86


! The Northeast States for Coordinated Air Use Management, NESCAUM

[http://www.nescaum.org] includes eight states: Maine, New Hampshire, Vermont,

Massachusetts, Connecticut, Rhode Island, New York and New Jersey.

! The Southeastern States Air Resources Managers, SESARM [http://www.metro4.org]

includes 8 states: Florida, Georgia, Alabama, Mississippi, Tennessee, Kentucky, North

Carolina and South Carolina..

! The Ozone Transport Commission, OTC [http://www.sso.org/otc] includes 14 states:

Connecticut, Delaware, the District of Columbia, Maine, Maryland, Massachusetts, New

Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Virginia .

! The Southern Appalachian Mountains Initiative, SAMI [http://www.saminet.org] focuses on

the mountainous regions of 8 states: Alabama, Georgia, Kentucky, North Carolina, South

Carolina, Tennessee, Virginia, and West Virginia

The EPA maintains a website [http://www.epa.gov/oar/vis/] with links to each of the regional visibility

planning organizations, as well as other federal agencies and programs involved with regional visibility issues.


37/86


Exhibit 4-1 Map of Mandatory Class I Areas with Visibility Value(Source: http://www.epa.gov/oar/vis/)


38/86


5. ECONOMICS: VISIBILITY IMPAIRMENT AND PARK VISITATION

Most people would probably say they want good visibility both in the communities where they live,

and in the national parks and scenic areas they visit for relaxation and recreation and the evidence suggests

that it is not just talk. It is one thing to say you want something; it is another to actually be willing to pay for

it. In fact, that is how economists measure the economic value of something by how much people are willing

to pay for it. If it is a good that can be bought in a store, the market price reflects its value. Visibility,

however, is a commodity that can not be bought or sold; in economic terms, visibility is considered a non-

market good. This makes it difficult to measure what it is worth to people.

Another fundamental challenge to valuing visibility is that a change in visibility must be perceptible

to people if they are going to place some value on that change. However, it is not so obvious how small

changes in visibility conditions should be treated when trying to gauge how people feel about visibility

impairment. Some changes, especially when measured in seasonal or annual averages, may not exceed

perception thresholds. For instance, a change in visibility may be less than one deciview, though one deciview

is approximately described as a just noticeable difference in visual air quality. When visibility changes are this

low, it is often suggested that they have no value. This conclusion, however, is wrong for two reasons. First,whether or not a change is interpreted as perceptible may depend on the averaging time used to measure the

change. Visibility changes may be largest during certain times of the year on certain days. When these changes

are averaged over a season or the entire year, however, the overall change may appear to be quite small and

incorrectly treated as having no value. Second, while a single change may not be perceptible, the cumulative

effect of all visibility changes over an extended time period may be perceptible. Yet, specific policy decisions

that affect visibility are most always evaluated individually and incrementally. A policy scenario may only

create a small, perhaps even imperceptible, change in visibility. The change should still be valued, however,

because this change contributes to overall visibility improvements and may make a very large difference over

time.

Despite these obstacles that visibility is a non-market good and visibility often changes in increments

the public may or may not notice economists are devising ways of measuring the value of changes invisibility. One approach that has been used by economists measures what improved visibility is worth to

people based upon what they say their willingness to pay for better visibility is, both at home and in natural

settings. This approach does not depend on a persons actual behavior, but on what they say their behavior

would be with better visibility. Chapter 6 discusses this approach in detail.

Another approach is to measure the economic impacts of peoples behavior based upon improvements

or declines in a particular resource. There are a number of behavioral changes people may make when

confronted with poor visual air quality. For instance, people may base their decision to purchase a house, at

least in part, on the quality of the surrounding views and visibility, which can impact the housing market. If

the decision to relocate to an entirely new area is also influenced by visual air quality, the economic impacts

could reach beyond just the housing market and impact the entire local economy. These types of economicimpacts have the potential to be quite substantial if visibility is extremely poor. However, to isolate that

portion of the impact due to poor visibility from all of the additional factors that go into purchasing a house

or relocating to another area is extremely difficult to do.

Another type of behavioral change that is much easier to measure, and easier to attribute to visibility,

is the affect poor air quality has on a persons decision to recreate. If, because of poor visibility, a person

decides to shorten their visit to a particular park, or go to another recreation site altogether, the economic

impacts will be felt in the way of lost revenue at the recreation site (park fees, lodging, concessions) and lost

revenue in the communities close to the site (gas, food, lodging, concessions, additional tourist attractions).


39/86


While visibility degradation is likely to affect most types of outdoor recreation to one degree or another, the

impacts of impaired visibility are perhaps most pronounced at national parks.

5.1 An Undisturbed Environment, Including Clean, Clear Air and Good Visibility, is VeryImportant to Park Visitors

It has consistently been shown that American vacationers believe that one of the leading attributes of

a desirable travel destination is beautiful scenery and clean, clear air. In fact, the National Park Service (NPS)

has conducted a number of studies that have examined the importance of clean air as a park feature. The

results of these studies were summarized by the NPS (1988).

A 1983 NPS study confirmed that visitors are able to perceive different degrees of visibility

impairment. Visitors were asked if they had noticed haze at the parks, and if so, whether they thought it was

slightly, moderately, very, or extremely hazy. After comparing their responses to actual visibility measures

taken on the same day, they found that when the range of view was lower, visitors were more aware of haze

and were more likely to say it was very to extremely hazy. This same study also found that visitors to the

Grand Canyon and Mesa Verde National Parks who said the view was hazy enjoyed the park less than thosevisitors who said they were not aware of haze or were aware of only slight to moderate haze. This meant that

not only did park visitors notice haze, but when they considered the view to be relatively hazy, it detracted from

their enjoyment of the park.

Another series of NPS studies conducted during the summers of 1983, 1984, and 1985, found that

people visit parks first to experience a natural setting and second to enjoy specific unique features associated

with various parks. Surveys were given to visitors at Grand Canyon, Mesa Verde, Mount Rainier, Great

Smoky Mountains, and Everglades National Parks. The surveys listed a number of park features and asked

visitors how important each one was to their recreational experience. Some of the listed features were the same

at all the parks and some were specific to each park. For example, clean, clear air and interpretive

signs/information were listed for all the parks while viewing canyon rims was listed for the Grand Canyon,

ruins on mesa tops was listed for Mesa Verde, and views of chimney tops (natural landscape features inthe area) was listed for Great Smoky Mountains.

The survey results revealed that it is very important to visitors that parks be natural and free of

pollution; in other words, as undisturbed by humans as possible. In fact, the survey consistently showed the

importance of clean air to the recreational experience, with clean, clear air one of the top four features at

every park. At the Grand Canyon, over 80 percent of the respondents rated clean, clear air as very important

or extremely important to their recreational experience.

Additional analysis of these surveys was conducted to determine if, when asked what the most

important features were at these parks, visitors identified features that belonged to a common recreational

theme. For example, features such as clean, clear air and park cleanliness were grouped into anaturalness category. Based on work by the National Park Service (1988), Exhibit 5-1 shows the groups

of park features and their relative importance at three sample parks: Grand Canyon, Mesa Verde, and Great

Smoky Mountain. The most significant finding was that the group of naturalness features (which included

clean, clear air) was rated the most important at each park. The second most important set of park features

was associated with each parks unique qualities. For example, while naturalness was the most important

group of features at both Grand Canyon and Mesa Verde, viewing scenic vistas at Grand Canyon and

information/park history at Mesa Verde ranked as the second most important group of features at those

parks, respectively.


40/86


Viewing

Information

Naturalness

Activity Related

Visual Obscurement

Not at AllImportant

SlightlyImportant

ModeratelyImportant

VeryImportant

ExtremelyImportant

Grand

Canyon

Naturalness

Viewing

Information

Activity Related

Visual Obscurement

Mesa

Verde

Naturalness

Backcountry

Information

Flora-Fauna

Viewing

Management

Backcountry Reservations

Great Smoky

Mountains

Exhibit 5-1 Visitor Rated Importance of Park Features

5.2 Visitors are Willing to Alter Their Length of Stay Based on Visual Air Quality Conditions atNational Parks

The above findings suggest that if visibility as a park resource was allowed to deteriorate, visitor

enjoyment of the parks would decline. But how would a change in visual air quality affect visitation patterns?

When confronted with poor visibility at their destination, it is likely that travelers will do one of two things:

shorten their stay at a national park or go elsewhere. In either case, we assume that people will allocate the

time available to them in such a way as to maximize their enjoyment. There have been a number of studies

conducted to evaluate whether visitors would be willing to spend more time traveling to alternative viewing sites


41/86


in order to obtain better visual air quality during their park visit. Results from these studies provide evidence

that changes in visual air quality affects visitor use patterns.

Summarized in NPS (1988), a 1983 NPS study conducted at Grand Canyon National Park asked

visitors to rank possible alternative combinations of travel time to vistas and visibility conditions through the

use of photographs. These rankings revealed that the average change in the amount of time a visitor was

willing to spend traveling to a vista for a 10 Mm-1 change in visibility was between 15 minutes and 4 hours.

Studies conducted outside the scope of the NPS also support the finding that as perceived visual air

quality gets worse, visitation patterns to national parks is altered. One study found that if visibility at a vista

in either the Grand Canyon or Mesa Verde national parks changed from average to poor, 61 percent of

the survey participants said they would spend less time at the vista, while 80 percent said they would spend less

time total at the park (MacFarland et al., 1983). The average stated reduction in park visitation was about 13

hours, which is quite significant when compared to the average park visit of 14 hours.

In a 1985 study conducted at Grand Canyon National Park (Bell et al., 1985), visitors were asked to

participate in a simulation where they could choose between four hypothetical activities: viewing three vista

points (depicted on photographs) and touring an archaeological site. The driving time, scenic beauty, andvisibility

out of sight: the science and economics of visibility impairment

Documents