;PA-450/3-76-007
[arch 1976
JO
TALL STACKS
AND THE
ATMOSPHERIC
ENVIRONMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
-------
EPA-450/3-76-007
TALL STACKS
AND THE ATMOSPHERIC
ENVIRONMENT
by
Dr. Jeremy M. Hales
Baltelle, Pacific Northwest Laboratories
P.O. Box 99
Richland, Washington 99352
Contract No. 68-02-1982
Program Element No. 2AC129
EPA Project Officer: Joseph A. Tikvart
Prepared for
ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
March 1976
-------
This report is issued by the Environmental Protection Agency to report technical
data of interest to a limited number of readers. Copies are available free of
charge to Federal employees, current contractors and grantees, and nonprofit
organizations - as supplies permit - from the Air Pollution Technical Information
Center, Environmental Protection Agency , Research Triangle Park, North
Carolina 27711; or, for a fee, from the National Technical Information Service,
5285 Port Royal Road, Springfield, Virginia 22161.
This report was furnished to the Environmental Protection Agency by Battelle,
Pacific Northwest Laboratories, Richland, Washington 99352, in fulfillment
of Contract No. 68-02-1982. The contents of this report are reproduced
herein as received from Battelle, Pacific Northwest Laboratories. The
opinions, findings, and conclusions expressed are those of the author
and not necessarily those of the Environmental Protection Agency. Mention
of company or product names is not to be considered as an endorsement
by the Environmental Protection Agency.
Publication No. EPA-450/3-76-007
11
-------
PREFACE
During the past decade tall stacks have been employed with increasing fre-
quency, particularly on coal and oil-fired power plants. This trend has gen-
erated considerable debate concerning the impact of emissions from tall
stacks on the air environment. Clearly, the present state of knowledge
regarding the effectiveness of tall stacks as a means of achieving acceptable
ambient air quality needs to be assessed.
Dr. Jeremy M. Hales, Battelle, Pacific Northwest Laboratories was asked to
undertake the in-depth review of the effectiveness of tall stacks. Due to
their research in plume chemistry and physics, Dr. Hales and his colleagues
at Battelle are nationally recognized experts in dispersion from stacks.
Another reason Dr. Hales was asked to undertake this review is that neither
he nor Battelle is identified with pro or con positions on tall stacks.
Moreover, to insure the independence of Dr. Hales' efforts, the EPA project
officer and his associates conscientiously refrained from actions which might
influence the review. Thus, this report is presented as an unbiased, tech-
nical assessment of the tall stack and its place in the effort to maintain
and improve the quality of the air environment.
It should be noted that this assessment of tall stacks was undertaken prior
to publication of the "Stack Height Increase Guideline" by the Environmental
Protection Agency. The guideline is based on three recent court rulings
T
Environmental Protection Agency, "Stack Height Increase Guideline," Federal
Register, pp. 7450-7452, February 18, 1976.
111
-------
which interpret Section 110(a)(2)(B) of the Clean Air Act as requiring the
use of constant emission limitations (as opposed to dispersion-dependent
technology such as tall stacks) as the primary means for achieving ambient
air quality standards. Dr. Hales1 assessment of tall stacks also provides
a valuable technical background for users of that quideline.
Joseph A. Tikvart
Project Officer
Environmental Protection Agency
IV
-------
CONTENTS
PREFACE 111
LIST OF FIGURES vii
LIST OF TABLES viii
ACKNOWLEDGEMENTS ix
SECTION I
CONCLUSIONS 1
SECTION II
INTRODUCTION AND OBJECTIVES 5
SECTION III
BASIC ASPECTS OF TALL STACKS 7
THE SIGNIFICANCE OF TALL STACKS 7
CRITERIA FOR "TALL" STACKS 17
SECTION IV
POTENTIAL CONSEQUENCES OF INCREASED STACK HEIGHT —
ATMOSPHERIC INTERACTIONS 19
PRELIMINARY ANALYSIS 19
INTERACTIONS OF PLUMES FROM TALL STACKS WITHIN
THE PLANETARY BOUNDARY LAYER 22
General Aspects 22
Effects of Surface Roughness 30
Atmospheric Complexities and their Implications
with Regard to Stack Height 32
Effects of Plume Rise 33
Applied Diffusion Modeling of Plume Behavior in
Upper Regions of the Planetary Boundary Layer ... 34
SECTION V
THE AIR QUALITY IMPACT OF TALL STACKS
AS ISOLATED SOURCES 37
INTRODUCTION 37
FIELD STUDIES OF TALL STACK PERFORMANCE 37
Field Studies of Tall Stack Performance:
Long Term Monitoring Studies 42
Field Studies of Tall Stack Performance:
Specific Circumstances Leading to High
Surface Concentrations 48
Moderate Wind Speed, Neutral Conditions 49
-------
Surface-Inversion Breakup 50
Additional Mechanisms for Fumigation:
Shoreline and Urban Phenomena 57
Thermal Instability - Looping Plumes 63
Trapping Beneath Elevated Inversions 65
Effects of Complex Terrain 68
Achieving Acceptable Sulfate Levels 72
Conclusions Pertaining to Tall Stacks as
Isolated Sources 76
SECTION VI
THE AIR QUALITY IMPACT OF TALL STACKS AS MULTIPLE
SOURCES 77
INTRODUCTION 77
OVERLAPPING PLUMES 80
MULTIPLE SOURCES AND LONG-RANGE TRANSPORT:
MODELING INVESTIGATIONS 81
CONCLUSIONS PERTAINING TO TALL STACKS AS
MULTIPLE SOURCES 88
SECTION VII
TALL STACKS AND ADDITIONAL ASPECTS OF AIR QUALITY 91
WET-REMOVAL PROCESSES 91
DRY-REMOVAL PROCESSES 99
MEASUREMENTS OF LARGE-SCALE IMPACTS FROM WET AND
DRY DEPOSITION 101
WEATHER MODIFICATION AND VISIBILITY 104
CONCLUSIONS RELATED TO THE INFLUENCE OF TALL STACKS
ON ADDITIONAL ASPECTS OF AIR QUALITY 107
SECTION VIII
REFERENCES 109
APPENDIX A
AIR QUALITY STANDARDS A-l
APPENDIX B
SUMMARY OF STACKS ABOVE 122 METERS IN ELEVATION CURRENTLY
EXISTING WITHIN THE UNITED STATES B-l
APPENDIX C
ANNOTATED BIBLIOGRAPHY OF PERTINENT LITERATURE
ON TALL STACKS C-l
-------
FIGURES
No. Page
1 Past and Predicted Electrical Generating Trends 8
2 Projected U.S. SC^ Emissions 9
3 Stack Height Trends in U.S. Power Industry 10
4 Generating Unit Size Trends in the U.S. 11
5 Characteristics of Neutral Boundary Layers 25
6 Characteristics of Stable Boundary Layers 25
7 Characteristics of Unstable Boundary Layers 26
8 Characteristics of Shallow Unstable Boundary Layers 26
9 Effects of Surface Roughness on Neutral Boundary Layers 31
10 Calculated Ground-Level Concentrations During Inversion Breakup 54
11 Schematic of Plume Interactions with Boundary Layer Induced by
Onshore Flow - Adapted from Figure of Lyons 60
12 Schematic of Lake Breeze Circulation 61
13 Calculations of Plume Depletion by Dry Deposition Using
Horst's Model 75
14 Six-hourly Plume Plots for Continuous Releases from Nine Cities,
Beginning at 0000 GMT 4/19/74 78
15 Schematic Representation of In- and Below-Cloud Scavenging 93
16 Washout Coefficients* for Size-Distributed Aerosols of
Geometric Mean Diameters a and Standard Deviations a for a
Typical Rain Spectrum 9 9 94
vii
-------
TABLES
No.
1 Summary of Pertinent Field Investigations of Tall-Stack -g
Plume Dispersion
2 Summary of Observed and Postulated Conditions for High
Ground Level Concentrations in the Vicinity of Tall
Chimneys 49
3 Power Plants Included in the TVA Full Scale Study of
Inversion Breakup 51
4 Summary of TVA Results for Inversion Breakup Fumigations 53
5 Power Plants Included in the LAPPES Investigation 55
viii
-------
ACKNOWLEDGEMENTS
This report was written with the help and useful comments of several indi-
viduals and organizations in the Federal Government and private industry,
and I would like to express my sincere appreciation to these groups and
individuals for their assistance. Paricularly noteworthy in this regard
are the personnel of the Federal Energy Administration and the EPA Source-
Receptor Analysis Branch, who provided substantial support in data and
information retrieval as well as in numerous additional areas. The NOAA
Office of Aerial Charting and Cartography also contributed significantly
to this project by granting access to their computer files on high obsta-
cles within the United States. This capability was largely responsible
for compilation of the table of stacks appearing in Appendix B.
Draft copies of this report were reviewed by a number of prominent meteor-
ologists, whose highly constructive comments have been reflected to vary-
ing degrees in this final document. These reviewers are as follows:
F. A. Gifford ATMOSPHERIC TURBULENCE AND DIFFUSION LABORATORY,
NOAA
P. L. Finkelstein U.S. ENVIRONMENTAL PROTECTION AGENCY (on assign-
ment from NOAA)
D. R. Matt ATMOSPHERIC TURBULENCE AND DIFFUSION LABORATORY,
NOAA
L. E. Niemeyer U.S. ENVIRONMENTAL PROTECTION AGENCY (on assign-
ment from NOAA)
J. V. Ramsdell BATTELLE, PACIFIC NORTHWEST LABORATORIES
M. E. Smith SMITH-SINGER METEOROLOGISTS, INCORPORATED
IX
-------
I express my appreciation to each of these individuals for their assistance
on this project. Although many of their ideas have been incorporated, it
is emphasized that no implication exists for their full or partial agreement
with the report's content, for which I as author am solely responsible.
-------
SECTION I
CONCLUSIONS
This report has addressed the current state of knowledge regarding the per-
formance of tall-stacks and their effect on the atmospheric environment. In
performing this analysis it has been convenient to consider both the
collective impact of multiple tall-stack usage on large geographic scales
and the performance of individual units under hypothetical conditions where
plumes are emitted into clean background environments and do not interact
with effluents from other sources. While this "isolated-source" situation
is never satisfied totally in practice, it is a useful concept both for
interpreting the influence of individual sources on multiple, interacting
plume systems and for analyzing tall-stack performance at distances relatively
close to the point of emission. Key conclusions from this survey are
itemized as follows:
1. From the survey in this report, it is readily apparent that in the prox-
imity of an isolated source, the tall-stack provides an attractive means
for minimizing the impact of emissions on ground-level air quality. This
is not to say that ambient air quality standards are not violated by efflu-
ents from tall-stacks in specific situations, nor that simply providing a
tall-stack will permit unlimited release of pollutants into the atmosphere.
The available information does indicate strongly, however, that eleva-
ting the point of release without an increase in effluent will usually
be accompanied by considerable benefit in the lowering of ground-level
1
-------
concentrations of primary pollutants. However, it is obvious that much of
a tall stack's benefit will be lost if it is placed in an area of complex
terrain where the plume may intercept the surrounding ground surface.
2. The collective impact of primary pollutants has been analyzed by applying
conservative assumptions in conjunction with a simple elevated area-source
model. These results indicate that, although emissions from collective
sources tend to usurp available clean air over large areas, ground-level
concentrations of primary pollutants in source regions can be reduced by
increasing emission height.
3. In contrast to the situation for SCL and other primary pollutants, ground-
level concentrations of sulfates cannot be controlled adequately simply by
increasing emission height. Diffusion model calculations indicate that,
taken as an isolated source, any tall stack capable of satisfying existing
annual S02 standards will be capable also of promoting acceptable annual
ground-level sulfate concentrations under most atmospheric conditions.
It must be noted here, however, that the long (approximately 1000 km)
distances associated with sulfate transport renders this "isolated-source"
analysis of limited usefulness.
On a collective basis, widespread tall-stack utilization combined with
projected increases in fuel consumption without control of sulfur compound
emissions will aggravate existing ground-level sulfate concentration levels
throughout the United States. Concentrations currently measured in some
-------
United States metropolitan areas often exceed levels that are suspected
to cause adverse health effects.
4. Although any effect of weather and climate modification is uncertain,
it is reasonable to expect that a projected utilization of tall stacks
without absolute source control for sulfur compounds will effect a
measurable decrease in atmospheric visibility throughout much of the
United States and the northern hemisphere.
Such a utilization is also likely to produce a significant deteriora-
tion in precipitation quality. Resulting effects on soils, surface
waters and surface ecosystems will depend to a large extent on the chem-
ical composition of the local mantle. Data obtained to date suggest
that the expected changes in precipitation chemistry will have a pro-
nounced negative impact in a number of regions, especially on a long
term basis.
5. Critical circumstances that determine the design basis for tall stacks
differ according to power plant characteristics and geographical loca-
tion. Conditions that are often the most important in promoting high
ground-level concentrations in the vicinities of tall stacks are as follows:
* Trapping beneath subsidence inversions, especially under low-wind
conditions,
• Fumigation under inversion-breakup conditions,
• Fumigation from on-shore flows,
-------
• Return-flow conditions, either in shoreline or inland environments, and
• Interaction with complex terrain.
6. The large-scale field data currently available are adequate to define the
near-source transport and diffusion characteristics of primary pollutants
from tall stacks under a majority of circumstances, and little additional
field effort is needed in this area other than for routine siting and
verification programs. The limited exceptions where further intensive
near-source field study of transport and diffusion is recommended
include complex terrain, stagnation conditions, and onshore flows.
-------
SECTION II
INTRODUCTION AND OBJECTIVES
The trend toward taller industrial chimneys has progressed to a point where
stacks approaching 400 meters in height are becoming increasingly prevalent
throughout the United States and abroad. Because of their expanding deploy-
ment and also because of the rapid increases in fossil fuel consumption
associated with their use, there has been substantial concern over the
individual and collective impact of tall stacks on the atmospheric environ-
ment. This concern has resulted in considerable debate during the past
decade. Many opposing viewpoints appear to exist, and presently it is
apparent that a strong need exists to consolidate and summarize the cur-
rent state of knowledge in this field.
The primary objective of this report is to fulfill this need by providing a
comprehensive, critical review of published material regarding tall stacks
and atmospheric quality. It is intended that this review will be useful in
resolving some of the controversy that has been associated with tall-
stacks during recent years. In addition, tlrjs report is intended to identify
some of the important unresolved questions regarding tall-stack performance,
and thus help identify future research needs.
The two sections immediately following describe pertinent general aspects
regarding tall-stack trends and performance, and interactions of plumes in
the upper regions of the planetary boundary layer.
-------
These initial sections are followed by a critical review of articles pertinent
to the question of transport and dispersion of pollutants from tall stacks.
For convenience, the critical review is divided into three units. The first
of these deals directly with the ability of tall stacks to promote acceptable
ground-level pollutant concentrations under hypothetical "isolated-source"
conditions, wherein their plumes are emitted into clean background environ-
ments and are assumed not to interact with emissions from other sources
during their course of travel. The second unit addresses this same question
for tall-stack effluents that interact with emissions from other sources.
The final review section deals with aspects of tall-stack effluents that are
not directly associated with standards, such as dry deposition, precipitation
scavenging, visibility, and climate and weather modification. Conclusions
of this report are summarized in Section I, and an annotated bibliography of
tall-stack literature is presented in Appendix C.
-------
SECTION III
BASIC ASPECTS OF TALL STACKS
THE SIGNIFICANCE OF TALL STACKS
The subject of tall-stacks is an increasingly important one at the present time
for several reasons, which are keyed strongly to the rapidly increasing energy
demands in the United States and abroad. Presently these demands are result-
ing in large increases in fossil-fuel consumption, pressing the need for
substantial improvements in atmospheric pollution-control procedures. In
addition, this situation has forced the shift toward less desirable fuels --
from the sulfur pollution standpoint, at least; and as a consequence there
is a distinct tendency for sulfur emissions to experience an increase even
greater than that of energy production itself. Moreover, the costs and
technological problems associated with sulfur emission-control processes
have provided a clear incentive for large sulfur emitters to rely on tall
stacks as a basic means for maintaining ambient air quality standards.
This last aspect - reflecting the intrinsic relationship between tall-stack
utilization and absolute emission control (such as flue-gas desulfurization) -
is a subject of strong and continuing conjecture.
Several of the above points are illustrated graphically in Figures 1-4.
Figure 1 reflects the rapidly increasing utilization of fossil fuels in
this country. Total generation of electricity by fossil fuels has increased to
-------
o
h-
<
LU
LU
O
I
O
0
TOTAL FOSSIL-FUEL
1940
1950
1960
1970
YEAR
1980
1990
2000
FIGURE 1.
Past and Predicted Electrical Generating Trends.
Sources: Dupree and West,2 Nassikas.3 See also
FEA,4 Chapman, et al.,5 Schurr and Netschert,6
Evans, et al.,?nU.S. Bureau of Census,8 Macrakis,9
and Intertech.
8
-------
SMIL'S PROJECTIONS:
A FOSSIL FUTURE
D MIXED FOSSIL/NUCLEAR FUTURE
O PROJECTED FROM FIGURE 1-
NO CONTROLS
EPA~~ PROJECTIONS:
NO CONTROL VS
CONTROL IMPLEMENTATION
1940
2000
FIGURE 2. Projected U.S. S02 Emissions.
-------
400
300
to
o 200
UJ
IE
o
t—
CO
100
SOURCE: FEDERAL POWER COMMISSION
FORM FPC-67 DATA
HEIGHTOFTALLESTSTACKv
AVERAGE STACK HEIGHT
INSTALLED IN GIVEN YEAR
1910
1930
1950
1970
YEAR
FIGURE 3. Stack Height Trends in U.S. Power Industry.
10
-------
2000
SOURCE: FEDERAL POWER COMMISSION
FORM FPC-67 DATA
1500
o
<
D_
<
O
O
Qi
UJ
O
o
SIZE OF LARGEST UN IT
1000
500
\
AVERAGE UN IT SIZE
INSTALLED IN GIVEN YEAR
0
1910
1930 1950
YEAR
1970
FIGURE 4. Generating Unit Size Trends in the U.S.
11
-------
over twice Hie 1960 level by 1975, and is projected to more than double again by the year
2000.* Owing primarily to sulfur pollution considerations, coal utilization
has increased proportionately slowly during recent years, but is expected to
increase rapidly in the future as a consequence of the current national
2
energy situation. Previous estimates suggest that the percentage of coal
used in generation of electricity (both directly and in converted form) will
increase from a current 55 percent to about 70 percent by the year 2000.
Figure 2 shows trends and projections of SOp emissions from United States
power generation facilities. The upper projection is based simply on
extrapolation with the projected fuel utilization rate, assuming SOp source
control will not be implemented. The two lower curves are taken from the
projections of Smil, who estimates future emissions based upon various
assumptions regarding future energy sources and emission controls for
IP - .
SOp. Previous EPA estimates (dashed lines) are shown for comparison.
The large Discrepancies between the projections in Figure 2 reflect the
uncertainty that presently exists with regard to several aspects of future
energy supply. Smil's curves are lower partly because they are based upon
electricity demand estimates that are reduced from those traditionally
applied, and also because of their obvious reflection of anticipated control
technology. Other estimates ' generally range between the extremes shown
in the figure, and it is apparent that while the upper curve obviously
* One should note that at the present time forecasts of generating demand
are clouded by a host of uncertainties, and a number of varying pre-
dictions of future energy trends exist. Several of these are cited
in Figure 1.
12
-------
represents a high asymptote, it is still not totally unreasonable to
speculate that future SCL emissions may be appreciably higher than those
suggested by the lower curves.
Figure 3 indicates the trend in electric-utility stack heights in the
United States, and a complete listing of all stacks over 122 meters is
given in Appendix B. Figure 3 demonstrates that a considerable increase
in the size of the tallest stacks has materialized during the more recent
past. This increase in stack height has accompanied a similar increase
in individual generating unit size, as shown in Figure 4. This figure
indicates that average unit size has more than doubled since 1960, demon-
strating that in addition to increasing their productivity, fossil-fueled
electrical generating facilities have become more concentrated in terms of
individual output. This concentration has become possible in large part
because of the use of tall stacks which promote more widespread distribution
of the effluent material, thus permitting higher emission rates than would
be acceptable otherwise.
From Figure 2 it is apparent that the total input of sulfur pollutants from
fossil-fuel generation in the United States has increased from 9.2 x 109
kg/yr in 1960 to 1.7 x 10 kg/yr presently. Assuming no emission controls
will be incorporated, this level would increase to over 4 x 10 kg/yr by the
year 2000. These United States emission values for electrical utilities can
be compared with estimates of world emissions from natural sources, which
are in the neighborhood of 1.3 x 1011 kg/yr (Robinson and Robbins13).
13
-------
It is apparent that tall stacks can influence the amounts and distribution
of atmospheric pollution in two major ways. The first and most obvious of
these is the tall stack's ability, by injecting its effluents at higher
levels in the atmosphere, to cause significant changes in the transport and
dispersion of pollutants. Often this results in a substantial advantage in
producing lower ground-level concentrations near the source. The second effect of
tall stacks is the indirect-tendency -- because of the advantages created
by the first -- to increase the amounts of pollutant emitted to the atmos-
phere.
The first effect is important in increasing the spacial influence of indi-
vidual sources. Typically, the effective spacial domain of a given pollu-
tion source is dictated both by its magnitude with respect to surrounding
sources and by the lifetime of the pollutant in the atmosphere. In this
context it is important to note the comparison of natural and fossil-fuel
sulfur emission rates given above, and to note also that higher emission
elevations tend to increase atmospheric residence times of pollutants.
From this, it is not unreasonable to expect that these combined effects are
creating a situation of regional or even global consequence from one that
has previously been considered primarily local in scale.
While the second major influence of tall chimney use -- that of providing a
tendency towards increased total emissions — is rather indirect in nature,
it is potentially of major importance. An example of this is the intrin-
sic relationship between tall-stack performance and the operation of "inter-
mittent control systems", which is a procedure for varying emission source
14
-------
strength with atmospheric conditions to produce acceptable ambient air
18
quality levels . This incentive has been reduced by legislation and recent
I Q
court action under the Clean Air Act, which places limitations on circum-
stances where increasing the height of a chimney is considered acceptable
as an air pollution control measure.
Although tall stacks have been most frequently associated with SC^-related
problems and electric-power production, they are an important consideration
in the context of additional industries and pollutants as well. A prime
example is the smelter industry which, in fact, has pioneered in the
application of tall stacks for air quality control (Smith [1966]t,
20
Hill, et al ). Currently the world's tallest stack is associated with
a smelting operation; this unit is owned by the International Nickel
Company in Sudbury, Ontario, and has a height of 381 meters.
Despite the fact that the advanced fuel processing techniques of coal
gasification, liquefaction, and shale-oil conversion are insignificant at
the present time, these industries undoubtedly will become important
in future years; and the advent of these processes with their noted
emissions of nitrogen and sulfur gases will promote a strong tendency
toward the increased use of tall stacks if emission control techniques for
these substances are not developed to a significantly advanced state by
that time.
t References denoted in this manner appear in the annotated bibliography
in Appendix C. Those denoted conventionally are listed in Section VIII.
15
-------
Emissions from both smelters and fossil-fueled power plants include metals
21
and transition elements. Although metals from smelters have been associ-
22
ated with measurable adverse health effects, recent survey studies for
23
power plants indicate that direct adverse health effects from airborne
metals in power plant effluents should be rather unlikely. Carbon monoxide
and hydrocarbons, especially aldehydes and the polycyclics, have been obser-
24
ved in power plant effluents. The associated concentrations, however,
are sufficiently low to preclude expectation of any adverse effects on
human health.
Oxides of nitrogen emitted from power plants are of some concern, although
the quantities of NO and NOg typically emitted are substantially less than
24 25
those of SO^. Cavender et al show that the United States emissions of
nitrogen oxides are increasing somewhat. This Increase 1s partially a
result of greater fossil fuel consumption and higher firing temperatures.
26
It has been speculated recently by Davis et al that ozone may be formed
as a secondary pollutant in power plant plumes to an extent sufficient to
exceed Federal Ambient Air Quality Standards. This speculation, however,
was based primarily on aircraft plume measurements with fast-response
instrumentation, and was not related to surface measurements over periods
of time appropriate to the established standards. At the present time this
speculation is not widely accepted by others in the field.
As a consequence of the above discussion it may be concluded that, while
other pollutants and industries may be of some limited consequence, the
tall-stack problem is related primarily to sulfur oxides and the smelting
16
-------
27
and electric power industries (cf. EPA ). Accordingly, the prime emphasis
of the following text will focus on these specific areas.
CRITERIA FOR "TALL" STACKS
Because of extensive usage of the term, there is a tendency to expect that
some set criterion exists to distinguish between a "tall" stack and one
that is not. Despite this expectancy, however, and although several arbi-
trary standards have been applied in the past, no really obvious or satis-
factory criterion of this type exists.
*
A somewhat useful index in this regard is the "2 1/2 times rule," which
is often applied in stack-height determination. One could, for example,
designate "tall" stacks as ones that exceed the 2 1/2 times rule, and
"short" stacks as ones that do not. An alternative criterion that has
been applied in the past by several authors (c.f. Thomas, et a!., [1963])
is to state an arbitrary height (200 m, say) above which all chimneys are
considered to be "tall". Some basis for this approach exists in a chrono-
logical analysis of stack-height trends, such as in Figure 3. In view of
the fact that such a distinction says nothing about performance of chimneys,
however, it's practical utility is marginal.
The 2 1/2 times rule,often applied in both the United States and Great
Britain, states that chimney heights 2 1/2 times the height of the tallest
surrounding structure should be adequate to minimize downwash effects in
the vicinity of a source. This rule is based primarily upon direct obser-
vations from existing facilities.
17
-------
A third possible criterion of tallness is the relationship between stack
height and some reasonably persistent, key feature of the atmosphere, such
as the depth of the planetary boundary layer. Tall stacks, for example,
could be designated as those whose plumes penetrate the top of the boundary
layer under a majority of circumstances. Unfortunately, the large vari-
ability and rather poor definition of such atmospheric features makes such
distinctions of relatively little value for present purposes.
Consideration of the above possibilities in the context of the objectives
of this report leads to the conclusion that possession of a set criterion
for "tall" stacks is unimportant. Accordingly, we shall focus primarily
on variations of plume behavior with release height, and deemphasize any
arbitrary demarkations between "tall" and "short" chimneys. Some of the
more pertinent aspects of the interactions of high plumes in the plane-
tary boundary will be presented in Section IV of this report.
18
-------
SECTION IV
POTENTIAL CONSEQUENCES OF INCREASED STACK HEIGHT
— ATMOSPHERIC INTERACTIONS
PRELIMINARY ANALYSIS
Upon emission into the atmosphere from an elevated source, an effluent plume
is transported and diluted into its surrounding environment by a variety of
mechanisms. In addition to its lateral acceleration and advection by the
prevailing mean wind, the effluent is transported vertically by virtue of
its exit momentum and its buoyancy to an extent governed both by the efflu-
ent's exit properties and by those of the surrounding atmosphere. Pronounced
velocity gradients and other perturbations which occur during this process
promote turbulence, and this combined with local environmental turbulence
leads to further dilution of the plume by diffusion.
Upon considering these features in the context of the highly variable and
structured nature of the lower troposphere, it is immediately evident that
increasing the height of an effluent's release may modify its subsequent
atmospheric behavior in a number of ways. Specifically, and insofar as
purely the effects of transport and dispersion are concerned, increasing ar,
effluent's release height may be expected to:
• Provide a greater transport distance — and therefore a
greater time for atmospheric dispersion -- both vertically
19
-------
and horizontally between the release point and ground-level
receptors. Ostensibly this should result in a lowering of
ground-level concentrations to values below those resulting
from the use of shorter stacks.
« Release the effluent in a region less affected by aerodynamic
downwash, thus preventing high, local, ground-level concentra-
tions that might otherwise be encountered.
• Emit the effluent in a region where wind shear, turbulence,
and mean wind direction differ from those features below,
thus modifying gross plume structure, concentrations and
direction of travel.
• Release the effluent in a region where velocity and vertical
temperature structure of the local atmosphere differ from
those features below, consequently modifying plume-rise behavior
and associated mixing phenomena.
Related to these purely transport-dispersion effects are numerous additional
potential modifications of pollutant behavior. It seems obvious that
atmospheric residence times of primary pollutants (i.e., those originating at
the source) will be extended with increasing stack height, since many of the
associated atmospheric natural-recovery processes (dry-deposition, for
example), will be altered accordingly. Conversely, some modification of
aerial deposition patterns, precipitation chemistry, and associated features
20
-------
should be expected to occur. Residence-time modification of secondary
pollutants (those generated by reaction of the primary pollutants) is also
expected. The combination of all of the above factors may be expected
to result -- to a greater or lesser extent -- in modifying such atmospheric
features as visibility, weather, and climate.
21
-------
INTERACTIONS OF PLUMES FROM TALL STACKS WITHIN
THE PLANETARY BOUNDARY LAYER
General Aspects
Because the effects of increased emission height are influenced so profoundly
by vertical structure of the atmosphere, it is expedient at this stage to
discuss briefly some of the more pertinent aspects of this structure prior to
embarking on an analysis of literature in the tall-stack field. Such
structural variability results from frictional and thermal interactions of
the lower troposphere with the Earth's surface; it is typically most pronounced
adjacent to the surface and tends to decay with altitude to approach "free"
atmospheric conditions aloft. Such behavior has encouraged the concept of
the existence of a well-defined "boundary layer", within which frictional
effects influence atmospheric structure directly. This region, which is
known as the friction layer or planetary boundary layer, may range from
several meters to kilometers in depth, and is influenced by surface
roughness and thermal exchange as well as by large-scale pressure gradients.
Numerous publications pertaining to aspects of boundary-layer meteorology are
available,28'29'30'31'32'33'34'35 and the reader is referred to these works for
a more detailed description than the qualitative treatment presented here.
Within the planetary boundary layer, momentum of the air aloft 1s trans-
ferred by turbulent mixing to the earth's surface, where it 1s dissipated
by friction. Air turbulence necessary for this purpose can be generated
by mechanical interaction of the atmosphere with the surface, or by
22
-------
thermal instability. Furthermore stable thermal conditions, when they
exist, can act to dampen turbulence generated mechanically and thus
discourage mixing processes that might occur under more neutral conditions.
This range of possibilities suggests that significant differences should
exist between planetary boundary layers in neutral, stable, and unstable
environments, and that in addition substantial differences in character
should occur with variations in the roughness of underlying terrain.
As indicated previously, vertical variations within the planetary boundary
layer typically include the following:
• Variations of wind speed with altitude,
• Variations of wind direction with altitude,
• Variations of turbulence with altitude, and
• Variations of temperature with altitude.
The above variations and the atmospheric relationships leading to their
existence have been studied in detail in the lower portions of the planetary
boundary layer, and at the present time a great deal of practical knowledge
exists pertaining to behavior in this region. Unfortunately, much less is
known regarding behavior in regions beyond a few tens of meters from
the surface; sufficient knowledge does exist, however, to provide at least
a qualitative picture of behavior under more-or-less ideal circumstances,
23
-------
where reasonably uniform air masses and generally persistent synoptic
conditions exist.
Idealized characterizations of boundary layer behavior under a variety of
such conditions are represented in Figures 5-8, which indicate vertical
variations in wind speed, wind direction and diffusivity for cases of
neutral, stable, and unstable boundary layers over uniform terrain. These
figures were prepared from sounding data published by Pasquill and by
oc
Clarke, and represent composite results of numerous measurements.
Abscissas for the diagrams express ratios of actual to "free-atmosphere"
wind velocities and directions (denoted by subscript G); diffusional
A *
behavior is depicted by dimensionless diffusivities Km . Three-hundred
meter stacks are shown at the left of each diagram to provide some physi-
cal appreciation for vertical scale and expected plume behavior. One
should note in this context that no corresponding longitudinal distance
coordinate is furnished, and this must be implied visually from the
vertical scale shown on the graphs.
*Diffusion coefficients are expressed in dimensionless form here using the
Coriolis parameter, f and the friction velocity u* = VT/P, where T is the
surface shear stress and p depicts air density. Use of the dimensionless
diffusivities (K^) rather than their dimensional counterparts (KM) is nec-
essary because of the manner in which Clarke presented his published data.
24
-------
DIMENSION LESS
MOMENTUM DIFFUSIV1TY
0 0.005
1000
800
X
LU
X
UJ
X
0.2 0.4 0.6 0.8 1.0 1.2
WIND ANGLE AND VELOCITY RATIO, alcu AND V/Vr
(3 b
5. Characteristics of Neutral Boundary Layers
DIM EN SI ON LESS
MOMENTUM DIFFUSIVITY
0 0.1 0.2 0.3
1000 I 1 1 r
0 °-2 0.4 0.6 0.8 1.0 1.2 1.4
VELOCITY RATIO V/V..
0
EIGURE 6- Characteristics of Stable Boundary Layers
25
-------
DIMENSIONLESS
MOMENTUM OIFFUSIVITY
*2
1000
f/ll
f/u
0 0.025 0.050
0 0.2 0.4 0.6 0.8 1.0
VELOCITY RATIO. MNn
1.2 1.4
FIGURE 7. Characteristics of Unstable Boundary Layers
DIMENSIONLESS
MOMENTUM DIFFUSIVITY
A *2
1000
0 0.01 0.02 0.03
0.2
0.4 0.6 0.8
VELOCITY RATIO, V/V,
1.2
1.4
FIGURE 8.
Characteristics of Shallow Unstable Boundary Layers;
Note lateral compression of schematic plume (see text),
26
-------
In neutral atmospheres the vertical temperature structure neither promotes
nor discourages turbulence, and so the planetary boundary layer is dominated
by mixing effects that are generated totally by mechanical interaction with
the earth's surface. Such a situation is depicted in Figure 5 which shows
results from two data sets: the well-known "Leipzig profile" and that
generated by Australian researchers as reported by Clarke. Key points to
note from this figure are the depth of the boundary layer relative to
the plume height, the veering of the (Leipzig) wind with altitude, and
the diffusivity profiles. The diffusivity profiles are particularly note-
worthy owing to their direct relationship with plume dilution rates.
In view of this importance, it is rather perplexing to observe the extremely
poor agreement between the curves representing the German and Australian
data in the upper portions of the boundary layer. As discussed by Pasquill ,
this lack of agreement reflects to some extent the general weaknesses in the
procedure of applying velocity data as a means for obtaining diffusion
parameters. It is also likely, however, that much of this disagreement
arises from actual differences in transport behavior between the observed
air masses, and provides some indication of variability exhibited by the
atmosphere and of our current lack of understanding regarding processes
that occur in the upper regions of the planetary boundary layer. This
indication is supported also by noting that measurements of turbulence in
these regions often have indicated a highly time-variant and rather
37 38
unpredictable structure. ' It is also supported to some extent by
additional analyses of high-elevation diffusion measurements such as those
by Shaffer and by Zilitinkevich et. al, who indicate a wide range of
diffusional conditions can exist under apparently similar meteorological
circumstances.
27
-------
Under stable atmospheric conditions the change of temperature with height
is such that any air parcel that is displaced vertically upward becomes more
dense than its surroundings. Under such circumstances, therefore, all ver-
tical displacements of air are discouraged and atmospheric mixing in the
planetary boundary layer is minimized.
Stable conditions can be promoted in the atmosphere by a number of phenomena,
and the vertical placement and extent of stable layers vary accordingly.
Specifically, large-scale subsidence of upper air in high-pressure areas
often leads to high-elevation temperature inversions where stable conditions
are promoted aloft. Advection of warmer air masses over underlying cool
air can also promote stable conditions. Finally, cooling of surface air
by nocturnal radiation promotes the well-known radiation inversion, which is
commonly associated with urban pollution phenomena.
Figure 6 provides a description of the planetary boundary layer under stable
conditions, obtained from further composite balloon sounding data of Clarke.
Important points to note here are the reduced vertical extent of the boundary
layer as compared to that shown previously for neutral conditions and the
low values of K^ near the gound. From these features, it is readily apparent
that stacks sufficiently tall to clear such low-elevation, stable boundary
layers benefit substantially from the fact that, owing to the low turbulence
and favorable buoyancy, diffusion of effluent to the ground is minimized.
Stable layers aloft such as those associated with subsidence inversions,
however, may be expected to have somewhat the opposite effect, and have been
28
-------
noted (c.f. Montgomery [1968]) as conditions under which the value of tall
stacks (up to any currently practical height, at least) is limited.
Under unstable atmospheric conditions the temperature decreases with height
at a rate sufficiently large so that any air parcel displaced upward becomes
less dense than its surroundings. Under such circumstances vertical dis-
placements of air tend to occur spontaneously, with a subsequent high rate
29
of mixing in the boundary layer. As noted by Plate , this case where mix-
ing is dominated by thermally-generated turbulence can be considered as a
situation opposite to that of neutral boundary layers (mixing induced totally
by frictional effects).
Unstable conditions can be promoted by advection, by water condensation
and precipitation phenomena, and by radiational heating of surface layers.
A schematic diagram of the planetary boundary layer, under conditions where
the unstable layer is large in vertical extent, is shown in Figure 7.
Particularly noteworthy aspects of Figure 7 are the deepness of the planetary
boundary layer, the disturbed nature of the vertical velocity profile, and
/\
the high level of turbulence (as reflected by KjJ.
Under conditions where unstable atmospheres occur close tp_ the surface
and are bounded by more stable layers aloft, the associated decay of
turbulence with height limits mixing except in layers close to the ground.
A composite schematic depicting the planetary boundary layer under such
circumstances is shown in Figure 8. If stack height is sufficient to
essentially prevent the effluents' contact with the underlying turbulent
29
-------
region, then mixing of pollutants to ground level will be minimized.
On the other hand, if the vertical extent of the turbulent boundary layer
is sufficient to envelope the plume, then high ground-level concentrations
may occur as a consequence of the concentrated plume being rapidly trans-
ported downward. Typically , contact of the plume with the ground by this
mechanism occurs only at moderately large distances downwind from the
source. In this context one should note that the apparent downwind
distance of the contact of the schematic plume in Figure 8 is unrealistic
since, owing to the problem of presenting it on the graph, the schematic
plume has been "compressed" in the longitudinal direction. This mechanism
for promoting high ground-level concentrations has been cited as potentially
one of the most disadvantageous for tall stacks (Pooler [1964]) and a
number of field studies have been conducted to examine this effect.
Effects of Surface Roughness
Since turbulence in planetary boundary layers in neutral environments is
generated by mechanical interaction with the earth's surface, it follows
that the character of the boundary layer should depend strongly upon surface
roughness. This effect is illustrated in Figure 9, which is a plot of
velocity profiles in neutrally-stratified boundary layers over areas of
different surface roughness. These profiles, calculated from empirical
relationships given by Davenport (c.f. Plate29) , show a dramatic change
in boundary-layer depth with changes in terrain. Again the implications
with regard to effects of stack height are obvious.
30
-------
600
400 -
n:
o
200
0
WOODLAND FOREST
OPEN, FLAT COUNTRY /
OPEN, SMOOTH WATER
0 0.2 0.4 0.6 0.8
VELOCITY RATIO, V/Vr
b
FIGURE 9. Effects of Surface Roughness on Neutral Boundary Layers
1.0
31
-------
Under stable conditions, mixing in the boundary layer is constrained, and
any perturbations induced by mechanical interactions will be dampened
accordingly. Under highly unstable conditions the turbulence is dominated
by thermal effects, and the effect of surface roughness will be attenuated
from that experienced under neutral conditions.
Atmospheric Complexities and their Implications
with Regard to Stack Height
The foregoing description of planetary boundary layers was presented in
a rather idealized manner to portray some of the more pertinent aspects
of plume interactions in the atmosphere and the associated significance
of emission height. It is important at this point, therefore, to indicate
some additional complications experienced in the atmosphere and to point
out how these nonidealities could possibly affect the performance of all
tall stacks.
The first point in this regard is the realization that the atmospheres
considered in Figures 5-8 were taken essentially as steady-state, uniform
air masses, far removed from any fronts or associated discontinuities.
The exceedingly complex flows in frontal situations involving transients
in wind fields, mixing, and stability, can be expected to influence plume
behavior accordingly. In addition, the precipitation systems commonly
associated with fronts pose an additional degree of complexity -- both in
atmospheric dynamics and in the wet removal process. Little quantitative
information is available concerning pollutant mixing and transport in frontal
32
-------
systems, although this subject is receiving increased research emphasis at
41 42
the present time. '
The second area of non-ideality reflects the assumption of a steady-state
process in the previous discussion. In real situations transients always
exist and can appear through a number of phenomena. As indicated previ-
ously, it has been noted that upper boundary-layer turbulence can vary sig-
nificantly with both time and space. The tacit assumption of stationary,
isotropic, uniform turbulence at any given elevation used to derive the KM
values in Figures 5-8 is challenged accordingly.
Effects of Plume Rise
As indicated previously, plume-rise considerations are an important factor
in determining both the transport and the dispersion of effluent material,
especially at locations near the source. For any given source an increase
in plume rise may modify plume behavior for the same variety of reasons cited
previously in the context of increased stack height. Moreover, turbulence
generated by a rising plume is often a predominant factor in determining
mixing processes during its early stages. In noting these features, it is
important also to observe that plume-rise behavior is influenced strongly by
atmospheric conditions in the vicinity of the stack exit. Thus, increasing
a stack's height may result in a combination of effects related to the
plume-rise phenomenon.
33
-------
Plume rise has been the subject of a number of comprehensive reviews during
43 44
the recent past, and these have been summarized and extended by Briggs ' .
The reader is referred to these publications for a detailed quantitative
examination of plume rise phenomena.
Applied Diffusion Modeling of Plume Behavior in
Upper Regions of the Planetary Boundary Layer
During recent years, a substantial amount of mathematical modeling has been
devoted to describing the behavior of effluent released from tall stacks.
Models of transport and diffusion of plumes from both high and low sources
31 32 45 46 47 48 49 50
have been summarized in a number of recent reviews ' ' »™,T/, ">•* »
45
and Pasquill has classified these efforts into individual categories,
which include
• Statistical Theory
• Gradient Transfer Theory
• Similarity Theory, and
• Higher-Order Closure Theory.
Although efforts in the above areas have resulted in some highly sophistica-
ted and/or complex new treatments, it is interesting to note that the over-
whelming preponderance of applied models utilized for practical tall-stack
analysis has occurred through direct or modified extension of simple tradi-
tional forms such as those advanced in the early works of Sutton and Pas-
quill. To account for such effects as directional shear and variations in
diffusivity with height, these extensions have taken the approach of (1)
34
-------
applying modified dispersion parameters obtained from elevated-source data
to existing formulae or (2) modifying the basic formulae themselves. Num-
erous examples of applications of this type appear in the literature review
presented in the following section and in the annotated bibliography which
appears in Appendix C.
35
-------
SECTION V
THE AIR QUALITY IMPACT OF TALL STACKS
AS ISOLATED SOURCES
INTRODUCTION
The purposes of this and the following section are to (1) review the pub-
lished literature concerning tall stacks, and (2) utilize this informa-
tion to indicate the effectiveness of tall stacks in achieving acceptable
levels of ambient air quality. In accordance with the direction indicated
in Section I, the present section addresses the question of tall-stack
performance under the rather hypothetical "isolated-source" conditions
wherein interactions,of the plume with pollutants from other sources are
assumed negligible. Section VI is concerned primarily with interacting
plumes, and focuses more strongly upon aspects of long range transport.
Literature discussed in the present section is presented in summarized
form in the annotated bibliography appearing in Appendix C.
FIELD STUDIES OF TALL STACK PERFORMANCE
52
Following the pioneering investigations performed by Hewson and Gill
near the smelter at Trail, British Columbia, a number of field studies
in the United States, Great Britain, and elsewhere have been conducted
to assess transport and dispersion properties of plumes from tall stacks.
Although pollution from other "background" sources was noted in several
37
-------
of these studies, these analyses were conducted basically to assess stack
emissions as individual sources. While many pertinent measurements have
been conducted privately and are not generally available at the present
time, the open literature does contain a sufficient quantity of material
for a reasonably complete evaluation insofar as pollution by S0? is con-
cerned. Much less information is available concerning other pollutants,
especially those such as sulfate which are formed by reaction of primary
pollutants and are accordingly more difficult to evaluate.
Table 1 provides a summary of some of the more pertinent field investi-
gations that have been documented in the open literature, and at the out-
set it should be noted that even in the simplified context of isolated-
source conditions a concise presentation of this material is complicated
by several factors. The first of these arises from the large number of
physical variables in addition to stack height that influence air quality
and are reported to varying degrees of completeness in the literature.
These variables include firing conditions, fuel composition (especially
with regard to sulfur content), topography, and meteorological circum-
stances. Although some consolidation of these features can be achieved
with the use of dispersion models, they are difficult to treat in a
concise manner that is totally satisfactory for the present analysis.
The necessity to intercompare air quality measurements arising from a
large variety of sampling times and sampler arrays adds an additional
degree of complexity, with sample averaging time being a particularly
38
-------
TABLE 1.
SUMMARY OF PERTINENT FIELD INVESTIGATIONS
OF TALL-STACK PLUME DISPERSION
Investigation
Large Power Plant
Effluent Study
(LAPPES)
Location and
Plant(s)
(Hwe/s.h. (m)l
Western
Pennsylvania
Keystone
(1800/244)
Homer City
(1380/244)
Conemaugh
(1300/305)
Period Description of Measurements
1967-1971 Helicopter SO?. Ground Level Bubblers,
Met. Support, LIDAR, Aerosols,
Turbulence, Helicopter SO?
Reference (in Appendix B)
Schiermeier (1970, 1972)
Pooler and Niemeyer (1970)
Niemeyer and Schiermeier (1969)
Johnson and Uthe (1969, 1971)
Johnson (1969)
Niemann, et al. (1970)
Proudfit (1970)
Full Scale Study
of Inversion
Breakup at Large
Power Plants
Kentucky/
Tennessee
Paradise
(1908/183)
Shawnee
(1500/76)
Johnsonville
(1350/82, 122)
1966
Helicopter SOj, Ground Level Monitors,
Met. Support
TVA (1970)
Montgomery, et al. (1973)
Carpenter, et al. (1971)
Full Scale Study
of Trapping at
Large Power Plants
Kentucky/
Tennessee
Paradise
(1908/183)
Bull Run
(900/244)
1970
Helicopter S02, Ground Level Monitors,
Met. Support
TVA (1970)
Montgomery, et al. (1973)
Carpenter, et al. (1971)
Full Scale Study
of Plume Rise at
Large Power
Plants
Southern U.S.
Paradise
(1908/183)
Gallatin
(1256/152)
Snawnee
(1750/76)
Johnsonville
(691/123)
Colbert
(4824/91)
Widows Creek
(525/152)
1962-1965
Helicopter Soundings and Met. Support;
Plume Photography
Carpenter, et al. (1968)
Gartrell, et al. (1965)
Thomas, et al. (1970)
Full Scale Study
of Plume Dispersion
at Large Power
Plants
Alabama/
Tennessee
Colburt
(800/91)
Gallatin
(1256/152)
1958-1962 Helicopter S02, Met. Support
Gartrell, et al. (1965)
Thomas (1969)
Thomas, et al. (1963)
Gartrell (19f«)
Muskingum River
Measurements
1969-1973 Ground Level SO? Monitoring Network
Muskingum River
(1440/251)
Smith and Frankenberg (1975)
Cardinal
Measurements
1965-1969 Ground Level S02 Monitoring Network
Cardinal
(1200/251)
Frankenberg, et al. (1970)
Denotes megawatts electrical output/stack height in meters.
39
-------
TABLE 1. (Continued)
Investigation
Clifty Creek/
Kyger Creek
Measurements
Location and
Plant(s) «
(Mwe/s.h. (m)l
Ohio
Clifty Creek
(1300/208)
Kyger Creek
(1100/163)
Period
Description of Measurements
1952-1959 Ground Level SO? Monitoring Network
References (1ti Appendix B)
Frankenberg (1968)
Navajo
Measurements
Arizona
Navajo
(2250/236)
1974-1975 Ground Level SOj Monitoring Network,
Aircraft 502 Tracing, Met. Support
Navajo (1975)
CEGB Routine
Surveys
England/
Wales
Kingsnorth
(2000/198)
Fawley
(2000/198)
Pembroke
(2000/213)
Ratcllffe
(2000/198)
Eggborough
(2000/198)
Fiddler's Ferry
(2000/198)
1966-1973 Ground Level S02, Monitoring Network .
Clarke and Spurr, et al. (1975)
High Marnham/
West Burton
Studies
England
High Marnham
(1000/137)
West Burton
(2000/183)
1963-1969
Ground Level S02, Monitoring Network,
LIDAR, Elevated S02 Samplers
Martin and Barber (1967,1973)
Stone and Clarke (1967)
Tilbury Study
England
Tilbury
(360/100)
Northfleet
(720/150)
1962-1966 Ground Level SO?, Monitoring Network,
Extensive Met. Support, LIDAR,
Searchlight
Stone and Clarke (1967)
Lucas, et al. (1967)
Moore (1969, (1974)
Scriven (1967), (1969)
Lake Michigan
Studies
Illinois/
Wisconsin
Oak Creek
(s.h. up to 168 m)
Waukegan
(s.h. up to 137 m)
1970-1974 Ground Level/Airborne SO? and
Paniculate Met. Support,
Turbulence
Lyons, et al. (1972), (1974)
ARL Studies
Utah
Huntington
Canyon
(s.h. * 183 m)
Garfield
Smelter
(s.h. = 122 m)
1973
Airborne and Surface SFg Measurements,
Met. Support
Start, et al. (1974), (1975)
Sioux Study
Missouri
(1050/183)
1968-1970
Ground Level S02, Monitoring Network,
Met, Support
McLaughUn, et al. (1970)
40
-------
important factor. Pollutant concentrations reported in the literature
correspond to averaging times ranging from "instantaneous" to over
24 hours . Because of the complex nature of plume fluctuations, these
values are difficult to intercompare on a meaningful and straightforward
basis. Attempts to overcome this difficulty have generally followed a
semiempirical statistical approach, and often have resulted in expressions
relating "peak-to-mean" ratios to averaging time, i.e.,
peak-to-mean ratio =
maximum concentration observed at reference averaging time t*
concentration observed at any time t > t*
= f(t) . (1)
The substantial amount of material devoted to this subject in the litera-
ture " indicates in general that peak-to-mean relationships tend to
be rather specific to given source and meteorological conditions. These
relationships will be applied, when appropriate, in the following
discussion.
A final complicating factor in the present analysis is the existence of
essentially two basic types of field studies of tall-stack performance.
The first of these types is composed basically of long-term monitoring
studies involving the use of fixed samplers over extended periods of
time. The second type of field study is that which is addressed primarily
41
-------
to the assessment of specific physical circumstances expected to be impor-
tant in promoting high ambient pollutant concentrations. The following
text is subdivided accordingly to provide a discussion of pertinent long-
term monitoring studies, followed by consideration of the more specific
investigations.
Field Studies of Tall Stack Performance:
Long Term Monitoring Studies
Although field studies involving long-term monitoring with fixed sampling
networks lack some of the desirable features of the more specifically
oriented investigations, they offer the distinct advantage of providing
records over lengths of time sufficient to complete climatological
assessments and relate directly to the longer term ambient air quality
standards. Furthermore, their continuous nature obviously allows them to
provide some indication of stack performance under specific, critical
meteorological conditions even though their fixed placement precludes
sampling in the most pertinent locations under all circumstances.
The most significant tall-stack monitoring studies that have been con-
ducted within the United States and documented in the open literature
thus far are those performed near plants in the American Electric
Power (AEP) and Tennessee Valley Authority (TVA) networks. The first
significant study of this type conducted within the AEP network was a
comparatively limited investigation involving SCL sampling in the vicinity
42
-------
of two plants located in a comparatively low background area (Frankenberg (1968)).
These plants (Clifty Creek s.h. = 208 m and Kyger Creek s.h. = 163 m) were
surveyed between 1955 and 1959 by placing three monitors at locations near
each plant. Analysis of the approximately four-year span of data revealed
no hourly concentrations in excess of 1 ppm. There appeared to be a ten-
dency for higher concentrations to occur during mid-morning hours and on a
elevated plateau in the vicinity of the Clifty Creek plant. Concentrations
measured by the monitors, however, tended to be lower than those pre-
dicted, especially in situations involving inversion-breakup conditions.
Following the Clifty Creek and Kyger Creek investigations, a somewhat more
detailed field study was conducted at the Ohio River site of the then pro-
posed Cardinal plant (Frankenberg, et al.,(1970)). Somewhat in contrast to
the previous situations, this site was characterized by rather high back-
ground SOp levels which were produced in part by contributions of two smaller,
existing power plants (Windsor and Tidd), both having stacks less than
100 meters high. Accordingly, a primary objective of the Cardinal study was
to assess S02 pollution levels before and after operation of the new plant
to evaluate its contribution to total ambient concentrations.
The array of S0? monitors consisted of six units located at distances
between about three and ten miles in the prevailing downwind direction from
the plant. Average yearly, daily and hourly concentrations obtained prior
and subsequent to plant operation were somewhat inconclusive with respect to
the contribution of ground level S0? from the 251 meter stacks of the new
43
-------
1200 Mwe facility. Although the S02 levels monitored by the stations were
often higher than those allowed by present ambient air quality standards, it
was apparent that most of the pollutant had originated from sources other
than the Cardinal plant. The authors conclude that although long-term
monitoring is necessary to establish the changes caused by the plant's
presence, the data obtained to date suggest these effects to be minimal,
even under adverse meteorological situations.
The results of a study reported very recently pertain to the measurement
of ambient concentrations downwind from the Muskingum River plant (Smith and
Frankenberg (1975)) during and after the period its stacks were being modi-
fied from 83 meters to 251 meters in height. The S02 emission rate from this
plant is approximately 10 kg/sec. Data obtained from the four S02 monitors
employed for this investigation indicate that a significant decrease in
ground level SC^ concentrations occurred after the new stacks were put
into operation, and all National Ambient Air Quality Standards have been
maintained since that time.
Monitoring studies conducted by the TVA have included extensive measurements
in areas surrounding each of their major generating facilities. In general,
these long-term monitoring results can be described most adequately in terms
of the semiempirical dispersion relationships developed by the TVA for
practical estimation purposes (cf Montgomery, et al.,(1973)). These will be
discussed in greater detail later in the context of specific meteorological
circumstances.
44
-------
The results of a relatively short-term, but extensive, monitoring study in
the vicinity of the new Navajo plant (s.h. = 236 m) near Page, Arizona have
been documented, (Navajo (1975)). As with the TVA work, this monitoring
was conducted concurrently with intensive support investigations to eluci-
date effects of specific meteorological and physical circumstances; accord-
ingly, a more detailed discussion of this study will be deferred until later
in this section.
Further studies along these general lines have been conducted outside of the
United States, especially in Great Britain as a consequence of activities of
the Central Electricity Generating Board (C.E.G.B.) which is a publicly-owned
organization responsible for construction and operation of all major electric
utilities in England and Wales. The earliest such investigation of signifi-
cance to the present discussion is the High Marnham study, which was con-
ducted during the period between 1963 and 1965, (Stone and Clark (1967),
Martin and Barber (1966)). The relatively low (137 m) stacks of the
High Marnham plant make this study of somewhat marginal interest in the
present context, but it is significant in that it typifies the findings of
all succeeding C.E.G.B. studies involving high stacks. Specifically, these
findings are that air quality downwind from tall stacks in England generally
is dictated primarily by low-elevation background sources, and that the
contributions of high-elevation releases are difficult to ascertain under
such circumstances. In the High Marnham survey a compilation of data
obtained from the 16 SCL monitors located in the plant's vicinity indicated
maximum hourly concentrations up to 0.5 ppm arising from the plant alone,
while those from combined sources ranged up to roughly 0.7 ppm. The highest
45
-------
observed 24-hour concentration arising from the High Marnham power plant was
0.11 ppm, indicating that - as an isolated source - the plant should not
have difficulty in maintaining primary Federal Ambient Air Quality Standards.
In comparing these results with those obtained by the AEP and TVA networks,
however, one should note that the 1-2 percent sulfur content of coal burned
by the British plants is significantly lower than that typically burned in
the eastern United States. This corresponds to emission rates that often
are more than four times less than those from comparably sized eastern
United States plants, and the resulting ambient S02 concentrations must be
judged accordingly.
A composite set of investigations for six British power plants has been
reported recently by the C.E.G.B. (cf Clarke and Spurr (1975)) which gives
additional information on operation of tall stacks from some of the largest
facilities now in existence in Great Britain. The plants chosen for this
survey are each of 2000 Mwe output capacity, and are distributed widely
throughout England and Wales providing a range of topographical and mete-
orological conditions. Included are the Kingsworth, Fawley, Pembroke,
Ratcliffe, Eggborough, and Fiddlers Ferry plants; with the exception of
Pembroke (s.h. = 213 m) the stack height on each of these plants is 198 meters,
Full-load emission rates for these plants range from about 2 to 8 kg SOp/sec.
Long-term monitoring was conducted using automatic S02 Instrumentation at
approximately twelve selected sites located around each plant at distances
out to about 20 kilometers. Monthly and seasonal trends were analyzed, and
46
-------
statistical comparisons of daily results were obtained using upwind versus
downwind data.
The common conclusion reached from an analysis of data from all six power
plants was that, although a great deal of variability in surface S02 con-
centrations occurred in the vicinity of the plants, these levels were account-
able almost totally to background sources. The authors state that "in all
six cases studied it is not possible to detect an effect from the power station
on the trends of monthly and seasonal averages of sulfur dioxide pollution
levels". Insofar as daily averages are concerned, they estimate that contri-
butions to the surface concentrations by the plants were less than about
0.01 ppm.
The indication of the long-term monitoring results presented thus far is
that, insofar as SOp concentrations at ground level are concerned, consider-
able benefit is achieved by implementation of stacks with increased height.
This indication may be criticized in part because, owing to the fixed loca-
tions of the pollutant monitors in these studies, they were limited in their
ability to seek out regions of maximum concentration during specific condi-
tions. Further studies using mobile samplers in attempts to resolve this
difficulty are described in the following section.
47
-------
Field Studies of Tall Stack Performance:
Specific Circumstances Leading to High Surface Concentrations
The previous text has indicated that a number of specific physical conditions
have been identified as potentially important in promoting high surface con-
centrations of pollutants emitted from tall stacks. Several field studies
have been conducted to assess the relative importance of these conditions,
and in general it has been found that those most critical for a given plant
depend primarily upon local climatology and topography, with stack height
being an important deciding factor as well. As stack heights have increased,
there has been a marked corresponding change in meteorological conditions
associated with high ground-level concentrations in their vicinity.
Critical conditions most commonly discussed in the literature are summa-
rized in Table 2. While the proceeding discussion has touched upon some of
these conditions in its description of long-term monitoring studies, the
present discussion is addressed more specifically to investigations pertain-
ing directly to these categories.
48
-------
TABLE 2.
SUMMARY OF OBSERVED AND POSTULATED CONDITIONS
FOR HIGH GROUND LEVEL CONCENTRATIONS
IN THE VICINITY OF TALL CHIMNEYS
Studies Of Plume Behavior Under
Physical Conditions Noted Conditions
High Wind, Neutral Conditions Gartrell (1965), Carpenter, et al. (1971),
Pooler and Niemeyer (1970), Thomas, et al. (1963)
Inversion Breakup TVA (1970), Pooler (1965), Schiermeier (1970, 1972),
Frankenberg (1968), Frankenberg, et al. (1968),
Montgomery, et al. (1973), Johnson (1969),
Carpenter, et al. (1971), Navajo (1975)
Shoreline/Urban Phenomena Van der Hoven (1967).Lyons, et al. (1972),
(Fumigations and Recirculation) Lyons and Cole (1973), Clarke (1969)
Thermal Instability - Looping Plumes Schiermeier (1970, 1972), Martin and
Barber (1967, 1973), Stone and Clarke (1967)
Trapping by High Inversions Thomas (1969), Pooler and Niemeyer (1970),
(Especially Under Stagnation Johnson and Uthe (1969, 1971), Montgomery,
Conditions) et al. (1973), Carpenter, et al. (1971)
Complex Terrain Schiermeier (1972), Start, et al. (1974),
Navajo (1975)
Moderate Wind Speed, Neutral Conditions
Moderate wind speed, neutral conditions have been traditionally associated
with high surface concentrations downwind from shorter stacks, and there
has been some early concern (Gartrell (1965), Thomas, et al. (1963))
that such conditions may adversely affect the performance of tall stacks
as well. The basic reason that such conditions are important is that,
although greater wind speeds result in more efficient dilution of the
plume, they also attenuate plume rise; and these two effects work counter
to one another in establishing corresponding ground level concentrations.
The expected result is that concentration should vary with wind velocity
and maximize at some "critical wind speed", which is dictated by plant
operating conditions and by meteorology (cf. Nelson and Shenfeld (1965)).
49
-------
More recent field studies, however, (cf. Carpenter, et al [1973]), have indi-
cated that surface concentrations downwind from tall stacks should be less
dependent on this effect. While there is still some disagreement concerning
this point at the present time , it appears that moderate wind-speed,
neutral conditions are not usually of critical importance insofar as taller
stacks are concerned.
Surface-Inversion Breakup
More recently the conditions of surface-inversion breakup have received con-
siderable attention for their importance in promoting high ground level con-
centrations in the vicinity of tall stacks. The most important class of
these conditions occurs when solar heating of the surface creates low-level
instabilities in the nocturnal inversion layer. The rapid mixing thus
induced causes the plume to be transported to ground level, as indicated
schematically in Figure 8.
As a result of extensive monitoring and special studies in conjunction with
its fossil-fuel fired power plants (note Table 1), the TVA (cf. Montgomery,
et al. (1973)) has identified the inversion-breakup condition as one of
the more disadvantageous insofar as high concentrations in the vicinity
of tall stacks are concerned. These authors note that in the TVA regions
nocturnal inversion-breakup conditions may occur on 200-300 days of the
year. The magnitudes of the resulting ground level concentrations often
are not significant, however, owing to limited vertical propagation of
the mixed layers. In addition, high surface concentrations resulting from
50
-------
inversion breakup are of relatively short (30-40 min) duration, owing to the
transient nature of the phenomena involved.
During the past decade two large federally-sponsored investigations have
been conducted which have provided substantial information with regard to
tall-stack performance under inversion breakup conditions. The first of
these was the TVA "Full Scale Study of Inversion Breakup at Large Power
Plants", which was conducted during 1966. The second was the NAPCA (now EPA)
"Large Power Plant Effluent Study" (LAPPES), completed in 1971 (note Table 1).
Both of these studies involved helicopter measurement of ground-level con-
centrations using relatively fast-response S0? instrumentation.
The TVA study focused upon three steam plants with the stack heights shown
in Table 3. Helicopter measurements during this series included pre-
breakup plume cross sections and longitudinal ground-level flights after
inversion breakup was in progress. This study was limited to sixteen test
days with helicopter operation.
TABLE 3. Power Plants Included in the TVA
Full Scale Study of Inversion Breakup
Plant Stack Height(s)
m
Paradise 183
Johnsonville 122 and 82
Shawnee 76
51
-------
Surface SCL measurements obtained by the helicopter were averaged with
respect to time to arrive at the hourly concentrations shown in Table 4.
Although averages over periods exceeding one hour were not presented, the
TVA group (cf. Montgomery, et al. (1973)) suggests their estimation
utilizing a peak-to-mean approach which involves multiplying the hourly
values by 2/3 and 1/5 to obtain respective estimates of the 3- and 24-hour
averages. Estimates obtained in this fashion are included in Table 4,
along with lower-limit estimates computed on the assumption that the
plumes were totally absent at times other than the original one-hour
periods.
Although limited to only a few sampling days, the data provided in this
study are significant in the sense that they demonstrate that substantial
portions of the plume from a tall stack such as that at the Paradise
plant can be brought to ground level during the inversion breakup process.
Furthermore there is strong evidence that even though observed instantaneous
concentrations may be rather high, the persistence of the breakup process
is of sufficiently short duration so that concentrations averaged over 3-
and 24-hour terms are reduced appreciably.
The TVA has utilized the data in Table 4 to develop a correlation for ground-
level concentration under inversion breakup conditions. This correlation
applies only to situations where the plume is sufficiently low to be cap-
tured by the inversion breakup process, and the TVA researchers suggest that
inversion-breakup conditions should serve to reduce ground-level concentra-
tions in at least two ways. The first of these arises simply from the fact
52
-------
TABLE 4.
SUMMARY OF TVA RESULTS FOR
INVERSION BREAKUP FUMIGATIONS
Date
1966 Plant
9/16 Paradise
(s.h. = 183 m)
9/29
9/22
10/3
10/5 Shawnee
10/6
10/7
10/11
10/28 Johnsonville
SO., Emission
c Rate
kg/sec
5.
5.
4,
5,
8.
7.
6,
7.
5.
.3
.0
.8
.0
.3
.9
,1
,9
.3
Distance
from Plant
km
14
14
5
11
8
8
6
6
16
Average Ground Level, Centerline
SO,, Concentrations (ppm)
Hourly 3-hr Estimates*
0.
0.
o.
6.
0.
1.
0.
1.
0.
52
27
72
.18
,40
,10
88
,18
74
.35
.18
.48
.12
.27
.73
.59
.79
.49
(.17)
(.09)
(.24)
(.06)
(.13)
(.37)
(.24)
(.39)
(.25)
24-hr Estimates*
.10 (
.05 (.
.14 (
.04 (
.08 (
.22 (
.18 (
.24 (
.15 (
.02)
.01)
.03)
.01)
.02)
.05)
.04)
.05)
.03)
(s.h. - 122, 82 m)
10/25 - 82 m stack only -
4.6
*See Text
24
0.57
.38 (.19)
.11 (.02)
Note: National Ambient Air Quality S0£ Standards are 0.50 and 0.14 ppm for 3-hr and 24-hr
averaging times.
that an increase in the (effective) stack height serves to provide greater
dilution of the effluent. The second effect, as indicated previously, occurs
because an increasing emission height tends to reduce the number of circum-
stances under which the plume may be captured within the inversion-breakup
process.
A simple example of predictions based upon the TVA correlation is shown in
Figure 10. This plot gives expected maximum hourly S0£ concentrations under
inversion breakup conditions as a function of stack height, and is based
upon assumed values of emission rate, plume rise and wind speed typical of
those experienced with a large power plant.*
*These calculations may be performed conveniently using the TVA monograms
(Montgomery et al. (1973)).
53
-------
300
200
o
O
100
A TV A HOURLY
O WEIL AND HOULT
MEAN MAXIMUM
KEYSTONE STACK, 244 M
24-HR STANDARD
-HR STANDARD
0 0.2 0.4 0.6 0.8 1.0 1.2
PREDICTED MAXIMUM GROUND-LEVEL CONCENTRATION, PPM
FIGURE 10. Calculated Ground-Level Concentrations During Inversion Breakup
Based upon Q = 4 kg/sec, u = 5 m/sec, and Ah = 200 meters.
54
-------
The Large Power Plant Effluent Study (LAPPES) helicopter measurements were
conducted in a manner rather similar to those performed in the TVA study.
These involved cross-sectioning of the plumes at various (4, 10, and 16 km)
distances downwind from the source, as well as ground-level flights down-
wind along and normal to the plume centerlines. Stack heights and typical
S02 emission rates of the three power plants included in the LAPPES program
are given in Table 5.
TABLE 5.
POWER PLANTS INCLUDED
IN THE LAPPES INVESTIGATION
Plant
Keystone
Homer City
Conemaugh
Stack Height(s)
m
244
244
305
Typical SOo Emission
Rate at FULL LOAD
kg/sec
8.5
5.9
8.5
This series included a total of 170 experiment days in which helicopter
flights were performed. Of these, 95 flight days were conducted in the
Keystone plume, and 46 and 29 flight days were performed in the plumes of
Conemaugh and Homer City, respectively. Although not limited to this aspect,
special emphasis of the LAPPES project was placed in evaluating fumigations
during the inversion-breakup process. During the total study period, which
included flights in all weather conditions that permitted aircraft operation,
measurable concentrations of S02 (>_ 0.01 ppm) were observed at ground level
via the breakup process on a total of (at least) 90 days. Instantaneous
concentrations in excess of 0.3 ppm were experienced with fair regularity,
55
-------
with maximum observed values (under verified breakup conditions) in excess
of 1 ppm.
Inversion-breakup fumigation data for the LAPPES program have been analyzed
by Weil and Hoult (1973), who developed an expression for the height of the
inversion-breakup layer on the basis of an energy balance. This was employed
with an equation for plume loft to determine conditions under which fumiga-
tions would occur, and the result was subsequently correlated with observed
instantaneous ground level concentrations .
It is important to note that the underlying basis for the Weil and Hoult anal-
ysis differs radically from that by the TVA, which visualized a vertically
well-mixed plume beneath an inversion "lid". Weil and Hoult have the con-
cept of a mixing plume which is looping to the ground, spending part of its
time at ground level and the remainder aloft. An example of their predic-
tion is compared to its TVA counterpart in Figure 10 for similar conditions
of Ah, Q, and u. It is interesting to note that the instantaneous concen-
trations predicted by Weil's and Hoult's analysis are less than the one-
hour average values obtained from the TVA correlation.
Although a direct comparison of the instantaneous and one-hour concentrations
shown in Figure 10 with 3- and 24-hour ambient air quality standards is dif-
ficult, the results do imply a great deal with regard to the effect of stack
height on ground level concentration during inversion-breakup. This is
tempered in part by noting that the curve pertains to average maxima, and
observed values were often higher by a factor of two or more. Additionally,
56
-------
it should be emphasized that all of the data used in Weil's and Hoult's
analysis were obtained from situations involving a single (244 m) stack
height, and the use of their relationship to investigate the effects of
varying stack height must be regarded as dubious. On the other hand it
should be emphasized that one additional effect of increased stack height
predicted by this model is not evident from the figure. This is the capa-
bility of the taller stacks to eliminate entrainment into breakup layers
that entrain plumes from lower sources, and thus (according to the model)
provide a larger number of circumstances when the plume does not approach
the ground at all. In view of these features this analysis must be consid-
ered to provide considerable support to the proposition that, insofar as
maintaining acceptable SC^ concentrations downwind from isolated sources
under inversion-breakup conditions is concerned, considerable benefit can
be obtained from increased stack height.
Additional Mechanisms for Fumigation:
Shoreline and Urban Phenomena
Although the inversion-breakup fumigation has received the majority of
attention to date, it is important to note that additional mechanisms for
fumigation exist which may be of considerable importance to the behavior
of plumes from tall stacks. In contrast to the nocturnal inversion-breakup
process, where the depth of the mixed layer is characteristically time vari-
ant and uniform in extent, these additional types of fumigations are typi-
cally caused by changes in planetary boundary layer thickness with position
57
-------
downwind. Such changes can be induced by thermal or surface roughness vari-
ations, which in turn can be generated by artificial (i.e., large cities)
or natural causes.
The most important example of naturally induced fumigations of this type are
associated with onshore flows under stable or neutral conditions. If, for
example, stable air is flowing shoreward over smooth water, the mixed layer
will be normally at most only a few meters deep (note Figure 6). Upon
approaching the shore, however, a deeper boundary layer begins to build,
owing to increases in surface roughness and, depending on conditions, to
surface heating effects. Turbulence measurements of this effect have been
obtained in the Chesapeake Bay experiments of Slade and technical aspects
of the problem have been analyzed by Van der Hoven (1967). Some limited
tracer measurements of plume behavior under these conditions have been
conducted by researchers at the Brookhaven Laboratories .
Several field measurements of this type of fumigation in power plant plumes
have been conducted by Lyons and his coworkers (1972, 1973) . The plants
studied were located on the west shore of Lake Michigan. The investigations
consisted of visual plume observations, airborne and surface S02 and par-
ti cul ate monitoring, and surface and elevated temperature measurements,
with aircraft turbulence observations.
The meteorological situations during these studies involved onshore gradient
flows of air from the east under clear conditions, where solar heating often
raised surface air temperatures to levels as much as 15°C higher than the
58
-------
surface waters of the lake. This created growing inland boundary layers as
shown in Figure 11, which effectively convected the plumes to the surface.
Instantaneous surface concentrations from the (up to 168 m) stacks were
observed to exceed 0.7 parts per million for sources having strengths in
the area of 4 kg S02/sec. Owing to wide short-term fluctuations, however,
no violations of the Federal Ambient Air Quality Standards were observed.
Lyons concludes that although onshore fumigations can result in high surface
concentrations, factors such as wind shear and overall transient phenomena
will tend to reduce this effect. Owing to the relative persistence of the
meteorological phenomena (as compared to nocturnal inversion breakup),
however, onshore fumigations are expected to be potentially capable of
causing standards violations from power plants with tall stacks unless
extreme care is exercised in siting and design. From the schematic
in Figure 11 it is apparent that, in order to avoid the fumigation process
totally, power plant stacks would have to be extended to unreasonable heights
in many situtations.
An additional aspect of shore-lake breeze effects, also described at length
by Lyons and his coworkers, is the appearance of local circulation patterns.
Considering, for example, a warm land parcel adjoining a cooler body of
water with air aloft moving toward the lake, such as shown in Figure 12, it
is evident that because of the lake-breeze effect the lower air will tend
to move landward where it will warm and rise, only to be drawn outward
again with the prevailing flow. Once over the water this air will show a
59
-------
u o
2 O) O
s- >>
CO O _l
C -C
O «*-
•p- C O
4-» O
O O)
> s-
S- JD 3
0) O)
-M -O •!-
C O) U_
I— i O
=5 E
0) -O O
E C S.
3 •— i M-
O. S- TD
0) Ol
Q.
(t3
O
u
E -0
-------
c
o
to
3
U
N
0)
CU
CQ
O)
J^
ID
O
U
•P
(O
o
CM
61
-------
tendency to subside to satisfy the divergence of low-level air, and a cir-
culation pattern is thus induced.
If a plume were entrained in such a circulation pattern, one would expect
severe concentration buildups to occur. Lyons notes, however, that the
lake-breeze flow pattern is rarely two-dimensional, but instead follows a
helical pattern that progresses along the shoreline in one direction or the
other. Because of this behavior, portions of the plume that actually come
back upon the plant itself are usually diluted substantially. If a row of
sources and receptors were to exist along the shoreline, however, this
helical pattern could be capable of promoting substantial ground level con-
centrations through the additive effects of the sources.
The observation of fumigations from boundary-layer transitions over cities
has been hampered by poorer definition of boundaries and by the multitude
of sources usually existing in such areas. Accordingly, the most pertinent
information that has been obtained thus far regarding the behavior of plumes
from tall stacks under such conditions pertains to boundary-layer investiga-
tions.7'68' Such studies have indicated that the combination of roughness
and thermal release can increase the depth of the urban boundary layer
several hundred meters over its rural counterpart, with obvious implications
to the behavior of high plumes in the vicinity. It is expected that the
Regional Air Pollution Study (RAPS), currently being conducted by the EPA in
St. Louis, will generate significant new information in this regard.
62
-------
Thermal Instability - Looping Plumes
The looping plume has been traditionally identified with thermally unstable
atmospheres. Under such conditions convective exchange by large-scale
vertical eddies transports portions of the plume virtually intact to lower
levels of the atmosphere as indicated schematically in Figure 7.
At the present time there is some lack of agreement in the mete-
orological literature regarding the distinction between inversion-breakup
fumigations and looping plumes. Weil and Hoult (1973) for example, have
applied a looping-plume model to describe inversion-breakup fumigations.
This has contrasted rather sharply with the uniform-mixing concepts applied
to such cases by the majority of previous authors. Moore (1974) has recently
treated this situation using a two-parameter model which assumes looping-
plume conditions to occur as a consequence of unstable pockets of air imbedded
in neutral or weakly stable surroundings. The observations of Lyons and
Cole (1972) demonstrate that under appropriate conditions looping and fumi-
gating plumes can coexist in the same locality. As seen from Figure 11, the
plume from the larger power plant involved in their investigation had become
entrained in the boundary layer from aloft, resulting in a fumigation situ-
ation. In contrast the plume from a smaller plant, by virtue of the place-
ment of its release in the boundary layer, produced a classical looping
piume.
It seems obvious that high instabilities and absence of overlying stable
layers are conditions conducive to the existence of looping plumes. It is
63
-------
also apparent that during breakup of a nocturnal inversion a fumigating
situation may evolve into one involving a looping plume if strong solar-
radiation conditions persist for times sufficient to eliminate the inver-
sion "lid", or at least raise it to a position appreciably above the emis-
sion height.
Martin and Barber (1967, 1973) have called attention to the importance of
looping plumes in promoting high ground-level concentrations in conjunction
with the British High Marnham-West Burton measurements. These authors have
observed peak 3-minute average SCL concentrations as high as 0.9 parts per
million at distances from about 0;8 kilometers to 5 kilometers from the
High Marnham plant (s.h. = 137 m, 1.7 kg SOp/sec) under thermally unstable
conditions. Corresponding hourly averages were as high as 0.44 ppm. The
relatively short residence time of the looping plume in any set location,
however, resulted in a considerable lowering of values for longer-term averages.
The maximum observed 24-hour average, for example, was about 0.06 ppm.
Further measurements of ambient S02 concentrations were conducted by Martin
and Barber during periods when both the High Marnham and the new West Burton
plants were in operation. These again showed relatively high concentrations
to occur at close distances under thermally unstable conditions. Concentra-
tions in the vicinity of the West Burton plant, however, were substantially
less than those at High Marnham. This outcome was somewhat surprising
because of the approximately doubled emission rate of the West Burton plant,
and was attributed primarily to the increased stack height (183 m vs. 137 m
for High Marnham) of this facility.
64
-------
It is interesting to note that substantial disagreement appears to exist
regarding the importance of the looping plume situation - disagreement that
may be caused to a major extent by variations in local climatology. In
apparent contrast to Martin and Barber, the TVA group has concluded that the
looping plume situation is of sufficiently small significance so that it may
be essentially disregarded as a critical stack-design factor. Smith and
Frankenberg, on the other hand, suggest that this is probably the most
important mechanism for raising ground level concentrations in the vicinity
of the Muskingum River plant (s.h. = 251 m).
Additional dafa regarding the behavior of looping plumes from high stacks
were obtained during the LAPPES series mentioned previously. Plume looping
(aside from terrain effects) produced the highest surface S02 concentrations
observed during this study, with instantaneous values exceeding one ppm on
numerous occasions. In accordance with the High Marnham - West Burton
observations, longer-term averages (as measured by bubblers) were sub-
stantially lower than the instantaneous values and indicated that current
Ambient Air Quality Standards would not be exceeded under looping-plume
conditions.
Trapping Beneath Elevated Inversions
During recent years the mechanism of trapping beneath elevated inversions
has received considerable attention. It has been found to be quite important
in promoting high surface concentrations in the vicinities of tall stacks.
65
-------
Typically, high-elevation inversions are caused by subsidence of upper air
under anticyclonic conditions. Adiabatic compression of this air during its
descent from aloft results in heating, which promotes inversions whose bases
range from thousands of meters in elevation to near ground level under some
circumstances.
If such an inversion lies substantially above the effective release height
of the plume, a "trapping" condition is promoted wherein the pollutant is
prevented from mixing upward. Such conditions are significant considerations
for stacks of all heights. They are especially pertinent to tall-stack design,
however, since it is impractical to build stacks sufficiently tall to pene-
trate typical inversions of this type. The advantages that are enjoyed by
tall stacks under other conditions, therefore, are largely precluded under
these meteorological circumstances.
From its monitoring and analysis program the TVA (1974) has concluded that
trapping beneath elevated inversions is the most restrictive meteorological
circumstance under which to judge the performance of tall stacks - at least
insofar as their own power plants are concerned. This conclusion resulted
from an analysis of days when surface S02 concentrations in the vicinity
of the Bull Run Plant (s.h. = 244 m) were substantially higher than pre-
dicted by the conventional coning plume model. Review of the meteorological
conditions prevalent during these circumstances revealed that "in almost
every case the region was dominated by a near stationary high pressure system
with pronounced stability throughout the lower 1000-1500 m." This observa-
tion was substantiated by further studies at the Paradise Plant (s.h. = 183 m),
and a corresponding dispersion model has been subsequently formulated.,
66
-------
Results indicate that ma,xtmum concentrations from this type of trapping may
persist for two to four hours; thus this condition is viewed as more apt to
result in air-quality standards violations than that of inversion breakup,
which normally persists for appreciably shorter periods of time.
Plume trapping by elevated inversions was noted also in the LAPPES program
(Pooler and Niemeyer (1971)), where half-hourly ground-level SO^ concentra-
tions as high as 0.3 ppm were observed. Lidar observations of the Keystone
plume by Johnson (1969) and Johnson and Uthe (1969, 1971) supported the
general concept of trapping beneath elevated inversions, although total plume
behavior was noted to be complicated by tilting and shearing under such
circumstances.
Simple diffusion models of the trapping process have been advanced by Healy
and Baker (1968), Heines and Peters (1973), and Scriven (1967), which (in
contrast to the TVA trapping model) consider the plume as a diffusing entity that
is reflected downward from an elevated stable layer. The results of these
models are in general agreement that while an inversion lid close to the
effective release height may increase ground-level concentrations by factors
of as much as two or more (depending on the model), the effect of the
inversion decreases rapidly as its height increases. With inversions over-
lying neutral layers at elevations greater than twice the emission height
the effect of the trapping process is negligible.
67
-------
Effects of Complex Terrain
There is little disagreement at present that terrain of sufficient complex-
ity can have severely detrimental effects on the performances of even the
tallest of chimneys. Conjecture does exist, however, concerning several
aspects of plume interactions with complex terrain- These include plume
impingement on elevated surfaces, channeling effects and downwash
phenomena.
One of the most well documented accounts of downwash of an elevated plume
in complex terrain is the LAPPES investigation of the Conemaugh Plant
(s.h. = 305 m) (Shiermeier (1972)). This power plant is situated approxi-
mately 6 km to the northwest of Laurel Ridge, which possesses peaks as high
as 200 meters above stack top. With southeast winds under neutral condi-
tions the Conemaugh plume was observed to approach the surface within a very
short distance from the plant, yielding instantaneous S0£ concentrations
significantly greater than 2 ppm on some occasions. At greater distances
the ground-level concentrations decreased rapidly, only to increase once
again on the lee side of the second ridge, approximately 12 km northwest of
the stacks. With wind from the opposite direction the plume was observed to
rise well over Laurel Ridge and mix throughout a deep layer on the leeward .
side, with resulting low surface SOp concentration. The lee downwash effect
at Conemaugh appears to occur only under neutral conditions. On days when
sufficient radiation occurred to promote appreciable surface heating, the
plume was observed to loft in its normal manner.
68
-------
The question of plume "impingement" on elevated surfaces was drawn into
72
sharp focus by Van der Hoven as a consequence of the Southwest Energy
Study. This is of special significance to the operation of tall stacks
near mountainous terrain, since much of a tall stack's benefit will be
removed if its plume intercepts elevated surfaces in the surround-
ing area. Simple modeling efforts in this area have ranged between the
extremes of assuming either that plume height rises directly with terrain
features, or else that it does not rise at all. Compromise measures, such
as assuming that the plume rises essentially one-half as rapidly as the
terrain, have also been employed.
Several wind-tunnel and tow-tank measurements of flows in complex terrain
73 74
have been conducted ' which provide some insight pertaining to the
impingement problem. In general, these experiments have indicated that
conformity of plume elevation with topographical features is stability
dependent, and under stably stratified conditions high concentrations in
the vicinity of elevated terrain should be expected. Lin and his coworkers
performed tow-tank investigations of a simulated plume upstream from a
mountain ridge bordered by two mountain peaks. Their results indicated a
strong blockage of the plume by the ridge under stable conditions, which
led to high surface concentrations on the upstream side. High concentra-
tions on the lee side of the ridge were also experienced, owing to the lee-
wave effect.
69
-------
Prompted in part by the Southwest Energy Study, a recent field investiga-
tion of plume diffusion in mountainous terrain has been conducted by the
NOAA Air Resources Laboratory. This study (Start, et al. (1974), (1975))
was centered in two locations in Utah where tall stacks were in operation.
The first of these locations was Huntington Canyon, the site of a new power
plant located in a valley with walls rising approximately 800 m above the
183 m primary stack. The second location was near Garfield on the south shore
of the Great Salt Lake. This site was bordered by steep slopes of the
Oquirrh Mountains directly to the south. The two principal stacks of the
smelter at this location were 122 m high.
Basically, the experiments conducted in this investigation consisted of releas-
ing halogenated tracer compounds from the stacks, and measuring their concen-
trations downwind with airborne and ground-level sampling facilities. In addi-
tion to other important results, these measurements demonstrated vividly that
although rough terrain appears to enhance their dilution, plumes from the
stacks impinge against the surrounding elevated terrain frequently. The bulk of
the experiments involving high surface concentrations occurred under unstable
conditions with a stable capping layer aloft. As indicated by the tow-tank
experiments described earlier, however, even higher surface concentrations
would be expected under pronounced stably stratified conditions.
A second major field program prompted by the Southwest Energy Study is the
S0£ monitoring project completed recently in the vicinity of the Navajo
power plant (s.h. = 236 m) currently under construction near Page, Arizona.
Two of the three 750 MWe units of this plant are presently in operation,
with the third scheduled for service in mid 1976.
70
-------
The Navajo site is located in typical desert terrain, with pronounced eleva-
ted areas located in several directions from the plant. An array of 26 S02
monitors surrounding the plant was utilized in conjunction with an aircraft
S02 - analyzer system to assess plume behavior in the region. Particular
efforts were made to determine the extent of the plume's impact on elevated
terrain.
One area of particular interest in this regard was the Vermin ion Cliffs,
which rise approximately three hundred meters above the stack exits. The
Navajo study demonstrated that plume impingement does indeed occur at this
site, and results in relatively high surface concentrations. These concen-
trations were not judged sufficiently high, however, to warrant implementa-
tion of flue gas desulfurization at the plant, providing the sulfur content
of the coal did not exceed 0.6-0.7 percent and the heat content of the coal
was not less than 12,000 BTU. In agreement with the findings of previous
studies, these measurements indicated that high local concentrations in the
elevated regions occurred primarily under stable atmospheric conditions.
As a summary to this discussion on the effects of complex terrin, it may be
concluded that highly complex topography will interfere strongly with a tall
stack's ability to promote acceptable ground-level concentrations. Although
the processes responsible for these interferences are not well understood
at the present time, the preponderance of recent experimental evidence testi-
fies strongly to the severity of these effects. Accordingly, any decision to
site a tall stack in a topographically complex area always should be preceeded
by a comprehensive meteorological analysis of the specific area in question.
71
-------
Achieving Acceptable Sulfate Levels
The question of whether the tall stack, as an isolated source, is effec-
tive in achieving acceptable levels of sulfates is complicated by the
fact that the majority of airborne sulfate is generated by chemical
reaction in the atmosphere; that is, it is a secondary pollutant. Rate
behavior of this reaction -- of prime importance for modeling calcula-
tions ~ is poorly understood at the present time. Also, the relatively
ubiquitous presence of sulfate in the atmosphere renders the assump-
tion of an "isolated" source of somewhat questionable value in the pre-
sent application.
27
Recent epidemiological studies have indicated that adverse health
3
effects are associated with annual sulfate levels in the 10 yg/m
region. The significance of this level can be appreciated by consider-
ing a hypothetical situation where S02 existing at the 0.03 ppm (80 yg/
m ) annual standard is completely transformed to sulfate. The result-
ing sulfate concentration of 120 ug/m would require a factor of twelve
greater control to achieve an annual average sulfate concentration of
10 pg/m3.
It is fortunate in this respect that the S02 - sulfate conversion occurs
rather slowly in the atmosphere, and (close to the source, at least) the
majority of airborne sulfur exists as SO^. Although a wide range of
72
-------
reaction rates have been published it is apparent that typical values
are in the range of 1-5% per hour. Standard diffusion calculations
indicate that under normal meteorological circumstances the plume will
be advected long distances before appreciable sulfate is formed. At
such distances an isolated plume will be sufficiently dispersed to pre-
clude exceeding any reasonable standard. Obvious exceptions to this are
return-flow and stagnation conditions, and possibly extended trapping
and/or fumigation. When acceptable annual average concentrations are
considered, however, such circumstances are not normally expected to
weigh into the average to a significant extent.
It is important to note that the consideration of plume-borne sulfate
refocuses concern at much greater distances from the source. This is
significant in that most plume-modeling efforts to date have concen-
trated on the regions of maximum surface concentrations of primary
pollutants, and modeling of plumes at extended distances is still at
a relatively early stage. This extended range of the problem increases
the probability for interaction of the plume with plumes from other
sources, and once again suggests that the concept of an "isolated" plume
is of doubtful utility in this context.
Finally, a first-order analysis of the problem indicates that, since the
effects of stack height become less pronounced with increasing downwind
distance, increases in stack height should be of relatively little benefit
73
-------
insofar as sulfate is concerned. A more detailed analysis including the
effects of dry deposition suggests that tall stacks may be even detrimental
in this respect. This can be demonstrated by performing computations based
78
on the simple depositing plume model of Horst using appropriate values
of deposition velocity and dispersion parameters. Choosing for an example
a 5 m/sec wind speed under neutral conditions with a 0.01 m/sec deposition
velocity (roughly appropriate for 802), this model predicts amounts of mat-
erial remaining in depositing plumes relative to nondepositing plumes as a
*
function of distance as shown in Figure 13.
The curves in Figure 13 pertain to a nonreactive, primary pollutant, and
thus do not relate directly to a secondary pollutant such as sulfate. Taking
the primary pollutant as SOp, however, and recognizing that depletion of
this substance by dry deposition must ultimately result in reduction of
reaction-product sulfate, provides some insight regarding the influence of
stack height on sulfate levels.
Figure 13 also indicates rather dramatically the influence that deposition
may have on concentrations at large distances from the source. This points
to the fact that consideration of removal terms, while relatively unimportant
in assessing local plume effects, can be critically important as distances
from the source become large. These effects will be considered within the
discussion of interacting sources that appears in the following section.
*0ther models have been applied for similar analyses with rather varied
results (cf. Smith79).
74
-------
GROUND-LEVEL RELEASE
h = 100M
200M
D = 300M
A h=400M
40 60
DOWN WIND DISTANCE, KM
FIGURE 13. Calculations of Plume Depletion
by Dry Deposition Using Horst's
Model.
75
-------
Conclusions Pertaining to Tall Stacks as Isolated Sources
From the survey in this section it is readily apparent that in the proximity
of an isolated source, the tall stack provides an attractive means for
minimizing the impact of emissions on ground-level air quality. This is not
to say that such standards are not violated by effluents from tall stacks in
specific situations, nor that simply providing a tall stack will permit
unlimited release of pollutants into the atmosphere. The available informa-
tion does indicate strongly, however, that elevating the point of release
without increasing the effluent, will usually be accompanied by considerable
lowering of ground-level concentrations of primary pollutants.
Exceptions to this finding are circumstances involving onshore flows, lake-
breeze circulations, highly complex terrain, and elevated inversions. It
is imperative that detailed meteorological analyses for sites experiencing
any of these conditions be performed prior to deploying tall stacks in these
areas.
It may be expected also that an isolated source able to satisfy existing
SOp standards would also be capable of achieving acceptable levels of
sulfate. This finding, which is based on the assumption that in-plume
oxidation processes for S02 are rather slow, is tempered somewhat by the
tall stacks' discouragement of deposition processes. It is tempered also
because of the expected long transport distance for sulfate, which renders
the concept of an "isolated source" generally inapplicable for this purpose.
76
-------
SECTION VI
THE AIR QUALITY IMPACT OF TALL STACKS
AS MULTIPLE SOURCES
INTRODUCTION
The preceding text has indicated strongly that, when considered as isolated
sources, tall stacks are highly effective in promoting low surface concen-
trations in the immediate regions of emission. One of the secondary effects of
increasing stack height, however, is to extend the downwind range of concern,
and along with it the probability for interaction of plumes from other
sources. Depending upon rates of removal, these effluents may become of
regional or even global significance. In considering such aspects it
becomes progressively naive to retain the concept of an isolated point source.
A simplified visual example of potential plume interactions on a regional
scale is given in Figure 14. This figure shows results computed from a
80
Lagrangian "puff" model of Wendell corresponding to several sources located
in the eastern United States and Canada, whose plumes were advected by wind
fields obtained from historical weather data. Although the modeling
procedures utilized to create Figure 14 are rather approximate, the indica-
tion that plumes on a regional scale interact strongly in a highly complex
fashion cannot be escaped.
77
-------
," ;
/,/ >
\ j
f l'
1200 M719/74
1800 0-47^9/7';
r^.,^\: \ XT r
/ - ^'^ S S
v»->c-i / J >
\ 'i• .'* I 7^ ^-r- '. /
0600 &4720/71
1800 04720/74
000p_&472l /74
FIGURE 14. Six-hourly plume plots for continuous releases from nine cities,
beginning at 0000 GMT 4/19/74. Wind data used for advection were
from 850 mb NMC analyses. Plume widths are ay. The lines across
a plume indicate positions of points leaving the source at 1 hour
intervals. (From "puff" model of Wendell.)
78
-------
0600 &4721/74
0000_&472(2/74
0600_0-<7i2/74
POO
1800 &4722/7-1
0000 04723/74
' ' 4^^%^l
^j^<$^
1?&- > , ->£?'.*&>-*-&f&
zimp*"
fitf^ vl'
fs. X-,'
FIGURE 14. (Continued)
79
-------
The present section deals with the problem of plume interaction and long-
range transport by first considering some simple examples of overlap of two
plumes. This is followed by a discussion of pertinent work in the multi-
source, long-range transport field. Individual effects, such as scavenging,
deposition, and transformations are included intrinsically in much of this
work, and these accordingly will be incorporated in the context of this
discussion when appropriate. An individual discussion of these separate
effects is given in the following section of this report.
OVERLAPPING PLUMES
Although the overlapping of two plumes from separate sources is obviously a
common occurrence, lack of plume definition at the distances involved usually
precludes a vivid observation of the interactions. Two-plume interactions
have been included in modeling calculations for a number of scoping studies.
A comprehensive analysis of State Implementation Plan strategy performed by
the Walden Corporation (1973), for example, utilized a simple Gaussian,
straight-trajectory approach, which included overlap of plumes from multiple
sources under conditions when these sources were in close proximity to
one another.
During the LAPPES investigation, Schiermeier(1970) observed interactions
between the Keystone and Homer City plumes. Such interactions were noted
also in the High Marnham-West Burton plumes by Martin and Barber (1967, 1973).
These authors point out, however, that plume interaction is less persistent
than one would expect on the basis of linear trajectories owing to the
80
-------
normal meandering and curvature from shear effects. They emphasize in
addition that while actual mixing of the two plumes was not highly persistent,
long-term concentration measurements in general distinctly reflected the
overlay Of the two plumes.
MULTIPLE SOURCES AND LONG-RANGE TRANSPORT: MODELING INVESTIGATIONS
For longer distances and larger numbers of sources, individual plumes rapidly
lose their identity. Furthermore, scavenging, deposition, and transformation
processes begin to dominate, and accordingly these features must be incorpo-
rated into related modeling efforts in a realistic fashion.
Despite the above-noted tendency for plumes to lose their individual
identities as they interact downwind with emissions from other sources,
it is often convenient to visualize single or multiple discrete plumes for
modeling purposes. This is the approach taken by Wendell (note Figure 14),
81
and also by Hefter et al. These authors employ a normal dispersion model
along a wind-dictated trajectory and provide for deposition, scavenging,
and/or transformations for each discrete parcel. A striking feature of these
models is their indication that ambient air concentrations become extremely
sensitive to the deposition and scavenging parameters as the transit times
grow large.
A number of detailed analyses devoted specifically to long-range sulfur
82 83
transport have been published during recent years. Scriven and Fisher,
81
-------
for example, present a two-part analysis which initially considers S02 from
an area source which has drifted sufficiently far downwind so that a uniform
concentration is established vertically between the surface and some given
mixing-layer height. Deposition and washout are incorporated into the
model using a deposition-velocity and washout-coefficient approach, and
resulting mean transport distances prior to deposition are estimated.
For the case of SCL removal solely by dry deposition, Scriven and Fisher
estimate mean transport distances of 100-1000 kilometers prior to removal.
Under typical rain conditions washout is estimated to reduce this mean
distance to about 50 kilometers. On this basis the authors conclude that
washout of S02 dominates dry deposition under rain conditions, but on a
long-term basis these two effects are of about equal significance. They
also conclude that much of the airborne SOp is removed by rain before it can
be converted to sulfate.
The S0? washout calculations of Scriven and Fisher can be criticized because
of the fact that they employ washout-coefficient theory to a gas, which
84
has been demonstrated previously to disobey such behavior. In view of
these more recent findings it is probably preferable to assume that the rain
approaches the surface saturated with S02 at its ambient ground-level
concentration. Following this approach one can estimate that actual S02
washout is about three orders of magnitude less than that predicted by
Scriven and Fisher and that certain of their above conclusions should be
reversed accordingly.
82
-------
Although they do not deal extensively with the sulfate formation and removal
problem, Scriven and Fisher note that deposition velocities for sulfate
aerosol are probably an order of magnitude less than for SCL and accordingly
the washout process is expected to dominate removal of this substance both
during rain periods and on the long-term basis.
Scriven's and Fisher's initial analysis.in general, presumes complete vertical
mixing, and aside from noting that pollutant from high sources may not enter
into the mixing layers considered in their model, the effect of stack height
QO
is largely ignored. In their subsequent paper , however, these authors
employ a K-theory approximation to assess the effects of vertical profiles
caused both by elevated release points and by the dry-deposition process.
In general,these results indicate that increasing the height of release
increases the mean transit distance and residence time of S0?. An example
calculated for typical nonrain conditions suggested that extending the
release height from ground level to 200 meters would result in an increase
in the mean transit distance from 500 to 680 kilometers. These authors
also indicated that S02 concentrations in the vicinity of the surface should
be attenuated by virtue of the diffusion-deposition process.
In a similar, but more emission-height oriented analysis, Lucas (1975) has
presented results of calculations of S02 concentrations downwind from area
sources of assumed emission elevation. Button's dispersion equation was
employed for these calculations, and cases involving neutral conditions and
inversion heights ranging from 200 to 1000 meters were considered. The
83
-------
emissions from these sources were assumed to be uniform over the extended
areas of release, and typical meteorological parameters (5 m/sec wind speed,
and Pasquill-type mixing categories) were employed.
Typical results from Lucas1 analysis, presented as plots of ambient S02
concentration versus downwind distance, indicate that the increase of
emission height promotes a marked lowering of ground-level concentrations
in the area-source vicinity. For limited mixing-layer conditions this
effect of source elevation becomes negligible at large downwind distances,
the model's results reducing asymptotically to those of simple, well-mixed
ventilation models such as those suggested by Holzworth.
Lucas' calculations indicate that for metropolitan sources with expected
ranges of emission rates, ground-level SOp concentrations can be maintained
at acceptably low levels simply by raising the effective release height a
reasonable distance. Similar results are indicated for larger geographical
areas such as the continental United States, although it should be empha-
sized that at such large downwind distances stack height has little rele-
vance to the predictions, which are comparable to those of the simple
ventilation models. An example calculation of this type using as assumed
wind speed of 5 m/sec, mixing height of 1000 meters, and S02 emission flux
2
of 0.16 yg/m sec results in an ambient ground-level SOp concentration of
3
approximately 30 yg/m at a point 1000 km downwind, assuming that none of
the emitted S02 is removed or oxidized to sulfate enroute. If all of the
2
SO is assumed to be converted to sulfate by this point, the corresponding
3
sulfate concentration is 45 yg/m .
84
-------
The deficiencies of this simplistic type of calculation should be emphasized.
The neglect of removal processes in the latter examples have been compensated
to some degree by choosing an emission rate value characteristic of the aver-
age United States and by limiting the downwind extent of the calculation (1000
km) to a distance that can be associated with a reasonable estimate of the
transit range of airborne sulfur. Idealizations of the source distribution
and meteorology are further points for criticism; bearing these difficulties
in mind, however, such an application has some value as a scoping exercise.
Comparison of the sulfur oxide concentrations estimated above with present
and suggested standards (cf. Appendix A)in this manner indicates that,
while S02 does not appear as a significant problem in this context, that
of sulfate may indeed be critical. This indication is underscored by the
3
fact that measured sulfate levels in excess of 45 yg/m are not uncommon
or QC
at some points in the United States today. As pointed out by Trijonis
this situation can be expected to worsen significantly in the future as
sulfur emissions from tall stacks, or indeed from any other type of
source, increase.
87
Bolin and Persson have utilized a somewhat more sophisticated approach
to the modeling of long-range sulfur transport which employs a statistical
description of transport and sink mechanisms. This is essentially a
climatological trajectory model which incorporates reasonable parameter!'za-
tions of dry-deposition and washout phenomena. In its simplest form it
ignores chemical conversion by treating all sulfur species as if they existed
as a single compound.
85
-------
In a simplified example Bolin and Persson utilize gridded emission data over
western Europe in conjunction with historical wind data to estimate wet and
dry sulfur deposition as a function of location. Using this approach* they
estimate that significant amounts of sulfur deposited in Sweden have
originated from outside the country. Between five and twenty percent of the
total deposited sulfur in Sweden, for example, was calculated to originate
from the British Isles.
For their simplified calculations Bolin and Persson have assumed an average
emission height of 85 meters. They note that lower heights will tend to
increase the relative importance of dry deposition and decrease the transit
distance of airborne sulfur. Somewhat in contrast to some of the previous
authors, however, they indicate that increasing emission height above this
level will have little effect on subsequent behavior of the emitted material.
The indication by the above modeling programs that sulfur is transported over
comparatively large distances prior to its removal from the atmosphere is
supported, in general, by a number of measurement programs that have
been conducted during the past decade. Many of these programs have consisted
essentially of observing air and/or rainborne sulfur concentrations and
then utilizing trajectory analyses in attempts to establish the pollutants'
origin.
86
-------
Numerous studies of this type have been conducted by Scandinavian researchers.
In addition to noting that high sulfate concentrations in Scandinavia often
are associated with air trajectories that have passed over the industrialized
regions of Great Britain and northern Europe, several of these investigators
89 90
(cf. Prahm et al., Brosset et al. ) have obtained data demonstrating
that the chemical composition of sulfate aerosol can differ markedly depend-
ing upon its origin. Similar results have been obtained within the United
91
States by Charlson and his coworkers, who have utilized sulfate aerosol
concentration and composition measurements in conjunction with trajectory
information to indicate that sulfate in the St. Louis, Missouri, area
originates primarily from distant sources.
In addition to these primarily receptor-oriented measurements, a number of
experiments involving tracking of pollutants from mixed area sources have
provided substantial evidence on behalf of the long-range sulfur transport
concept. Particularly noteworthy in this regard are the simultaneous SCL,
sulfate, lead-212 and radon-222 measurements conducted onboard ship off
92
the French Mediterranian coast by Cuong and his coworkers. These studies
provided strong evidence that, while near-surface SO,, was depleted rapidly
by dry deposition to the sea surface, sulfate aerosol was advected over
considerable distances prior to removal.
Although an assessment of vertical diffusion of S02 was attempted using the
lead and radon measurements, this study suffered the drawback that depletion
87
-------
of SOp aloft could not be measured directly. This handicap was largely over-
come in the aircraft plume tracking experiments performed by Smith and
Jeffrey93 off the English coast. These authors employed carefully gridded
SOp emission inventories in conjunction with their aircraft measurements of
S02 and sulfate, and using a back-trajectory technique with an integral
material balance were able to infer rates of S02 transformation and dry
deposition. In accordance with the previous authors, the work of Smith
and Jeffrey provides substantial evidence that sulfur compounds, especially
those emitted from elevated sources, are transported substantial distances
downwind prior to their removal.
CONCLUSIONS PERTAINING TO TALL STACKS AS MULTIPLE SOURCES
The conclusion regarding multiple arrays of tall stacks and their ability
to promote acceptable ambient SOp concentrations under a majority of conditions
is similar to that determined for isolated sources. It is evident that
elevating the release points will be effective in reducing the collective
concentrations at ground-level points downwind until uniform vertical
mixing in the boundary layer is attained. For typical mixing-layer depths
it is apparent that sufficient ventilation air is usually available to
dilute the emissions to levels below the existing standards beyond that point.
The above conclusion is, of course, qualified by the special constraints of
complex topography, land-sea effects, and elevated inversions. In particular,
widespread stagnation in conjunction with a capping inversion would appear to
88
-------
be particularly disadvantageous in this respect, and in some instances the
current air quality standards may be exceeded under these conditions.
In contrast to the conclusions for SCL and other pollutants for which stand-
ards currently exist, it is apparent that the widespread utilization of tall
stacks in lieu of sulfur emission control may pose a serious problem insofar
as achieving acceptable ambient sulfate concentrations is concerned. It
is safe to conclude that airborne sulfate is typically advected over long
distances prior to removal. This fact, combined with rough ventilation
calculations, leads to the reasonable conclusion that sulfate in the atmos-
phere originating from composite source patterns is likely to constitute
a significant problem, particularly in future years if increasing emission
trends continue.
In making this conclusion, however, it is important to note that even with
emission limitations in force the tall stack is a useful and important fac-
tor in maintaining ground-level air quality. This is true both because of
the stack's role in dispersing pollution not retained by the control pro-
cess, and because of its capability to reduce the consequences of temporary
failures in emission control systems. From these considerations, it is
probable that many situations may require both tall stacks and reduction
in order to achieve optimal control.
89
-------
SECTION VII
TALL STACKS AND ADDITIONAL ASPECTS OF AIR QUALITY
Previous sections of this report have primarily addressed the analysis of tall
stacks and their relation to ground-level pollutant concentrations. This is
a subject of principal importance to the question of existing and anticipated
ambient air quality standards. In contrast, this final section will consider
briefly some aspects of air quality not directly related to these standards.
These additional aspects generally reflect total atmospheric loading more than
they do surface concentrations, and include wet and dry removal processes,
visibility, and weather modification.
Comparatively little has been published which directly addresses the question
of tall stacks and their influence on these additional features, and because
of this the present section will not be devoted to a prolonged discussion of
published literature. Rather, this section will present a brief examination
of the individual mechanisms for the specific interactions and will utilize
this information to assess related consequences of increased emission height.
WET-REMOVAL PROCESSES
The fact that natural precipitation has a cleansing effect on air polluted
from both low and elevated sources has been well established. Early experi-
mental investigations such as those by Chamberlain and May95 determined
approximate relationships between aerosol particle size, rainfall rate, and
91
-------
washout rates for below-cloud processes. Both below-cloud and in-cloud
removal processes (cf. Figure 15) have been the subject of extensive continued
research up to the present time.
Following Chamberlain's and May's original suggestions, below-cloud scavenging
of aerosols may be analyzed most conveniently utilizing the washout coef-
ficient approach. This method of analysis is based essentially on the assump-
tion that falling raindrops capture aerosol particles with some given
collection efficiency. Once captured, these particles are carried to the
ground with no chance of subsequent release from the raindrop. A typical
plot of washout coefficient versus aerosol particle size is shown in
Figure 16.
From a knowledge of the washout coefficient and the area! distribution of
pollutant, one can proceed to calculate removal rates and deposition fluxes
in a straight-forward manner. It is sufficient for the purposes of this
discussion, however, to note simply that the washout coefficient, A (units
of fraction of material/t),is a direct measure of the fractional removal rate
from the plume. Thus, if one considers a small parcel, or "puff", of plume as
it drifts downwind, the fractional change in the mass of this material
owing to washout in a short time period At is given simply by AAt.*
*In more exact terms, we may express this relationship as dQ/dt = - AQ,
where Q is the amount of pollutant in the puff at any given time.
This may be integrated to give the relationship Q = Q0 e"At, where
Q0 is the initial value of Q.
92
-------
en
CD
£Z
OJ
>
c
0.
-------
-a
c
(O
to
S_
O)
ECO
(13 •
•i- CO
-O OJ
a;
E -O
E
O fO
4-> C
a> n3
E Q
O
V £
C7> O
4- U_
O
O 3
V) S_
O -U
s- o
cu a;
ro d.
to
T3
CU C
4-> T-
13 rO
.0 S-
-(-> ro
10 O
•r— •!—
T3 Q-
01
E C •
O) O
O -M
•r- ro
0)
(O
S_
ro
q-
c
o
o
8
c>
CU CU
o -o
3 ui
LU
D:
O3
i — i
U.
i"O
CU
N
rO
\-
'f/V
94
-------
Two important features of this analysis should be emphasized. The first of
these is the prediction that, as a first approximation, below-cloud
scavenging of_ aerosols i_s_ independent of release height. The second
important feature, as noted from Figure 16, is that under moderate rain
conditions the times for aerosol plume depletion by below-cloud scavenging
can be relatively long. A one percent removal of a homogeneous 1-micron
aerosol by a 1 mm/hr rain, for example, (A=0.01 hr~ from a = 1 curve
in Figure 16) would take about one hour to occur. If the plume in
question were drifting with the wind at 5 m/sec this would correspond to
a distance of 18 kilometers. From this analysis, therefore, it is
apparent that if below-cloud scavenging were the only process active in
depleting the plume, the distance scales of interest are typically of
the order of hundreds of kilometers under rain conditions. If the plume
were emitted under nonrain conditions, and subsequently encountered
precipitation, these time and distance scales would be altered accordingly.
Although there is considerable doubt that the scavenging of sulfate from
power-plant plumes occurs through a simple aerosol-capture process such as
that depicted here, it is still of interest to compare these values with
actual field measurements of sulfate washout from power-plant plumes. These
have fallen in the range between zero and about three percent per minute,
-1 96-99
corresponding to a A between zero and 1.8 hr .
The below-cloud scavenging of gases such as S02 does not adhere to the
irreversible behavior implied by washout-coefficient theory. This fact
95
-------
was demonstrated vividly in washout measurements beneath the Keystone plume
where observed S02 concentrations in rain were found to be as much as three
orders of magnitude lower than those predicted on the basis of washout-
qj
coefficient theory . Under some conditions "negative" washout even
occurred; that is, background SOp existing in the rain prior to its contact
with the plume was released back to the gas phase after its encounter.
The experiences at the Keystone plume were verified by later experiments
and a generalized theory of gas scavenging is now available. ' ' As a
consequence of this development it is now accepted that, if vertical
concentration gradients are sufficiently small, the amount of S02 (or any
other gas) existing in precipitation at ground level depends soley on the
ambient, ground-level pollutant concentration and the solubility of the gas
in rain.
Two important features emerge as a consequence of this behavior. The first
of these is that, in contrast to aerosol scavenging which depends upon a
vertically-integrated exposure of the raindrop to the pollutant, gas
scavenging depends strongly upon near-surface concentrations. Thus stack
height, while an unimportant consideration for aerosol scavenging, is
extremely important to the scavenging of gases. Tall stacks, in general,
discourage gas scavenging and thus tend to extend deposition by this process
over greater areas. This behavior forms the basis for the earlier criticism
of Scriven's and Fisher's analysis, which treated S02 washout in terms of
washout-coefficient theory.
96
-------
The second important feature arising from the reversible nature of gas
scavenging is that it often introduces a nonlinear response to increased
emission rates. It has been demonstrated, for example,103 that SCL solubility
varies with concentration in a manner that leads to proportionately less
removal for greater S02 concentrations. On this basis one would expect dis-
proportionately large increases in airborne pollutant concentration with
increasing emission rates. Conversely, a rollback in SCL emissions would
tend to effect a more than linear reduction in ambient air concentration.
In-cloud scavenging of pollutants is understood more poorly than its below-
cloud counterpart, and depends in general upon the type and intensity of the
precipitation process, the nature of the pollutant, and its location within
the precipitating system. Basically, the in-cloud scavenging process can be
considered to occur as a consequence of three consecutive steps, each of
which may be important as a rate-limiting factor in the overall phenomenon.
These are:
1) Transport of pollutant into the precipitating system,
2) Mixing of pollutant within the system, and its attachment to
the precipitation elements, and
3) Transport of the pollutant-laden precipitation elements from
the cloud to ground level.
97
-------
Approximate scavenging relationships based upon this sequence of steps have
been formulated ' and detailed storm dynamics models currently are being
applied for the analysis of in-cloud scavenging processes. ' For present
purposes, however, it is sufficient to note that the three-step in-cloud
scavenging process described here implies that little direct relationship
exists between source height and in-cloud removal. Potentially, step 1
could reflect emission height to some extent, but because of the large
differences between the elevations of typical in-cloud phenomena and tall-
stack release heights, this effect should be minimal. This lack of influence
is underscored by noting that most frequently plumes encounter in-cloud
systems only at large distances downwind, where most of the source-height
dependence of the plume's distribution has been removed.
In contrast to direct effects, source-height related factors of an indirect
nature may have significant influence on the processes and amounts of
in-cloud scavenging. These effects include the shift in pollution loadings
"in-cloud" that will tend to occur as a consequence of the less effective
dry deposition and below-cloud gas scavenging* associated with tall stacks.
In addition to these features, weather modification effects arising from
tall-stack related shifts in atmospheric loadings may be of some consequence
to the nature and extent of the in-cloud scavenging process. This aspect
will be examined in greater detail in a following subsection of this report.
*This assumes that a typical removal pathway for a gas (S0?, say), is its
reaction to form a nonvolatile species with subsequent in-cloud removal.
98
-------
DRY REMOVAL PROCESSES
Although some aspects of the dry-deposition process are poorly understood at
the present time, there is little argument that it is influenced strongly by
the airborne pollutant concentration adjacent to the ground. Accordingly,
the dry-deposition process is most commonly represented in terms of the
equation.
FD = V0 » W
2 3
where FD (m/H t) is the deposition flux to the surface, x0(m/^ ) is the
ground-level concentration, and VD(2,/t) is known as the deposition velocity.
Equation (1) is rather unsatisfactory for a number of reasons, the most
important of which is its implication of irreversible deposition, a
stipulation which may be violated by resuspension of aerosols or by
reemission of deposited gases. A second difficulty of the deposition
"velocity" approach is that it tends to give the impression that all
deposition occurs solely through some deterministic "fallout" process, and
thus accounts for diffusional transport only in a rather artificial manner.
Much of this difficulty can be removed, conceptually at least, by
expressing deposition flux in terms of the alternative form
FD = kD
-------
where \ (m/a ) is an equivalent concentration from the reemitting surface
o
substrate and kD(x,/t) is a mass-transfer coefficient.*
Under conditions where the predominant mechanism for deposition is diffusional
transport, one can apply a momentum-mass transfer similarity assumption
(cf. Pasquill) to obtain the result
VD -
u
( = VD when xs = 0) , (3)
where u (i/t) is the wind velocity at some reference height above the
ground (where x0 is measured -- 1 meter, say) and u* U/t) is the previously
defined friction velocity. Equation (3) predicts values of kQ in the
range of 1 cm/sec, a region where many measured deposition velocities have
been observed.
Regardless of the exact form for expressing deposition flux, it is evident
that increasing emission height will tend strongly to reduce the amount of
material deposited at downwind locations close to the source. This has been
discussed previously in the context of Figure 13, from which it can be noted
that changes in stack height between 50 and 300 meters might be expected to
*0ne should note that kg and VD possess the same units, and are, indeed,
equivalent in cases when xs = °- Use of kp is preferable, however, because
it contains no false implications regarding deposition mechanism and has
been utilized extensively for diffusion-drift applications in the past
(cf. Bird, et al.108).
TOO
-------
result in as much as a 25 percent increase in the amount of material
existing in the plume at points downwind.
Since precipitation scavenging mechanisms (aside from gas scavenging) tend
to reflect emission height only weakly, one expected result of increasing
release height will be a decrease in the relative amount of material removed
by dry processes. Various current estimates of the relative importance of
dry and wet removal processes for tropospheric emissions indicate that
dry deposition is of somewhat greater importance at the present time. The
extensive utilization of tall stacks may change this situation appreciably.
MEASUREMENTS OF LARGE-SCALE IMPACTS FROM WET AND DRY DEPOSITION
Trends in the chemical composition of precipitation have been monitored on
a rather widespread basis for several years using various precipitation
chemistry networks. By far the most extensive of these is the European
network, which has been in existence since the late 1940's . From this
network it has been determined that sulfate deposition in rain is currently
increasing at a rate of 2-3 percent per year, roughly in parallel with
emissions over northern Europe. As noted previously, various Scandinavian
researchers have analyzed these data in conjunction with historical meteoro-
logical records and have concluded that much of the sulfate in Scandinavian
precipitation occurs as a consequence of long-range transport from British
and continental-European sources. Since the acidity associated with sulfate
deposition is considered to have a pronounced adverse effect on Scandinavian
101
-------
soils and surface waters, this conjecture poses a strong argument against the
use of tall stacks rather than absolute emission controls — even in locali-
ties such as the British Isles where the extent of the surrounding land mass
is limited.
Corresponding measurements of precipitation-chemistry trends throughout the
United States have been hampered by the discontinuance of networks and by
their limited coverage. Nisbet'^ has utilized data from networks in
existence during 1955-56 and 1965-66 to demonstrate that a 60-65 percent
increase in the sulfate content of precipitation has occurred during this
ten-year period. This increase, which shows signs of continuing after a
leveling off during the five-year period ending 1970, is reflected by a
decrease in rain pH levels throughout the country. A comparison of the
measured sulfate levels with U.S. emission inventories suggests that
30-40 percent of emitted sulfur returns to the land surface as rain-borne
sulfate.
112
Although there is some argument to the contrary, strong evidence supports
the suggestion that increases in precipitation acidity in the United States
are largely the result of increased fossil-fuel consumption. Specifically,
the fact that observed changes in precipitation chemistry closely parallel
trends in fossil-fuel consumption would seem to indicate this relationship
strongly. Furthermore, the observation that geographic areas of deposition
coincide with those of emission makes any argument to the contrary extremely
difficult.
102
-------
Nisbet has combined an assumed relationship between sources and precipita-
tion chemistry with fuel-utilization projections to estimate sulfate con-
tent and pH of rain in the United States by the year 1980. From his analysis,
Nisbet calculates that if absolute source controls are utilized extensively,
the United States sulfate deposition from rain will not change appreciably
from its estimated 1972 level of 5.7 million tons per year. If tall stacks
are chosen as an alternative to absolute emission control, the precipita-
tion input rate will increase to 8.2 million tons per year, 3.9 million
tons of which will exist essentially in the form of sulfuric acid. This
corresponds to approximately two kilograms of sulfuric acid delivered, on
the average, to each acre of surface per year.
Obviously, the surface impact of increased dry and wet deposition rates
of sulfates and other acid-forming materials depends strongly upon the
buffering capabilities of soils and surface waters. Given strong buffering
conditions, the deposition of these materials may be largely inconsequential
or even beneficial in some cases. On the other hand, severe adverse impact of
sulfate deposition has been demonstrated in a number of cases. Aside from'
the well-known Scandinavian situation, the most dramatic example of this
phenomenon is the locality near the Sudbury, Ontario, smelter area.
Here a number of lakes have become acidified to pH values below 4.0.
This has resulted in loss of fishery, marked changes in both zoo- and phyto-
plankton, and decreases in biomass and productivity by over one order of
magnitude.
103
-------
WEATHER MODIFICATION AND VISIBILITY
Atmospheric pollutant materials can be expected to influence climate and
the weather in at least three basic ways:
1) by changing the earth's albedo either locally or
globally,
2) by changing the absorptive character of the atmosphere
with regard to solar and terrestrial radiation, and
3) by modifying in-cloud evaporation-condensation
phenomena, which in turn affects (1) and (2) above,
in addition to modifying storm dynamics and precipita-
tion phenomena.
Since most of these influences are related strongly to light-transmission charac-
teristics, they are of key interest to the question of visibility as well.
This subsection is addressed to a brief analysis of these aspects on global
and local scales to assess the impact of tall stacks on these additional
features of the atmospheric environment.
Several comprehensive documents have been published on the subject of
inadvertent weather and climate modification, ' ' and the reader is
referred to these publications for a more detailed account of the subject.
Insofar as global climatology is concerned,these analyses have generally
concluded that natural variations in the earth's climate have precluded
any definite measurement of trends in mean temperature attributable to
the impact of man. On the other hand, trends have been identified in more
104
-------
specific areas. Notably, a continuous drop in solar radiation incidence
at ground level arising from increased turbidity has been identified in
the northern hemisphere at latitudes above about 30°N. These observations
are supported by similar trends in atmospheric conductivity measurements,
which are an indirect indication of aerosol loadings.
Although it is largely evident that anthropogenic aerosol is responsible
for the observed decrease in sjolar incidence, the question of its effect
on climatic temperature trends is not Immediately obvious. Machta and
Telegadas emphasize that atmospheric aerosol both absorbs and scatters
incoming solar radiation; whether the presence of additional particles will
result in a warming or cooling trend depends upon several factors, including
vertical placement of the aerosol in the atmosphere, surface albedo, and
the ratio of absorbed to scattered energy.
In view of our current inability to measure or predict reliably the anthro-
pogenic impact on climatic temperature variations, it is extremely diffi-
cult to anticipate any effect of tall stacks in this regard. From the
discussion presented in previous sections, however, it is evident that
tall stacks tend to increase the amount of aerosol in the atmosphere by
several direct and indirect mechanisms:
• increasing the atmospheric residence times of primary
particulates by discouraging deposition processes,
105
-------
• increasing the amounts and residence times of secondary
participates (e.g., sulfates, nitrates) by discouraging
deposition of both, and
• indirectly increasing the amounts of both primary and
secondary particulates by discouraging the use of
absolute emission control techniques.
Any prediction of additional particulate loadings arising from the above
mechanisms is extremely tenuous, owing to the host of uncertainties
involved. From a semi quantitative assessment of information regarding
• fossil-fuel trends,
• source terms for aerosol precursor gases (NO , SCL),
A ^
• source-height-deposition relationships,
• source terms for primary aerosol, and
• background sources,
however, an estimate of a two-fold anthropogenic aerosol increase by the
year 2000 does not seem unreasonable for remote locations through much of
the northern hemisphere if a widespread utilization of tall stacks with-
out source control is implemented. From current trends in atmospheric
turbidity this increase could correspond to a further turbidity increase
of twenty percent or more.
On smaller scales of distance, anthropogenic influences on climate and the
weather become less difficult to verify. Turbidity trends in cities, for
example, in general show distinct increases over long periods and pronounced
106
-------
weekly cycling. The enhancement of precipitation from both frontal and
convective storms by urban effects has been documented in several instances,
although extensive conjecture about measurement, interpretation, and cause-
effect relationships continues.1^' ^ Somewhat in contrast to urban loca-
tions, few results have been obtained regarding the influence of isolated
sources on weather, although Hobbs and Shumway^1 have shown evidence of
increased rainfall downwind from the stack of a kraft mill (large primary
particulate sulfate source) in Washington State. However, since a majority
of the particulate expected to be active in cloud and precipitation forma-
tion is secondary aerosol in the case of smelters and power plants, the
most significant weather-modification effects from such sources may occur
at comparatively large distances downwind, where they are extremely diffi-
cult to identify.
Insofar as cities themselves are concerned, local ground level sources
undoubtedly contribute to turbidity to an extent where the effect of a
remote elevated source typically will have negligible additional impact.
Elevation of sources located within or near to the urban area, on the other
hand, will certainly improve local horizontal visibility and (through
confinement of the plume) will tend to reduce solar attenuation as well.
CONCLUSIONS RELATED TO THE INFLUENCE OF TALL STACKS ON
ADDITIONAL ASPECTS OF AIR QUALITY
As a consequence of this analysis of the impact of tall stacks on aspects
of air quality not directly related to Federal Ambient Air Quality Standards,
107
-------
it is concluded that evidence exists to indicate that a significant down-
ward trend in the quality of the atmospheric environment will occur if
widespread tall stack usage is implemented in lieu of source emission con-
trol. Some positive aspects of tall stacks emerge in this regard. They
are effective, for example, in preventing intolerably high S02 deposition
rates at short distances from sources. This positive effect, however, is
offset by the collective impact of multiple sources at long distances.
It is also limited to some extent by the fact that limitation of removal
processes close in are necessarily accompanied by higher atmospheric
loadings, residence times, and (on a collective basis) concentrations.
Insofar as weather and climate modification are concerned, no really
conclusive statement can be made with regard to the influence of tall stack
usage on gross aspects such as mean temperature and precipitation. In
contrast to other weather-related aspects, trends in visibility can be
estimated in a relatively straightforward manner. Accordingly, decreases
in this parameter in the northern hemisphere probably will be the most
evident weather-related effect of a widespread implementation of tall
stack policy during future years.
108
-------
SECTION VIII
REFERENCES
1. Engdahl, R. B., "A Critical Review of Regulations for the Control of
Sulfur Oxide Emissions," APCA Journal, 23: 364-375 (1973).
2. Dupree, W. G., and J. A. West, "United States Energy through the Year
2000," U. S. Dept. of Interior (1972).
3. Nassikas, J. N., "National Energy Policy: Directions and Development,"
IEEE Trans. Ind. Appl.. 1A-9: 498-505 (1973).
4. F.E.A., "Final Environmental Statement, Coal Conversion Program,"
FES 75-1 (1975).
5. Chapman, D., T. Tyrell, and T. Mount, "Electricity Demand and the
Energy Crisis," Science, 178: 703 (1972).
6. Schurr, S. H., and B. C. Netschert, "Energy in the American Economy
1850-1975," Johns Hopkins, Baltimore, (1960).
7. Evans, R. K., ed., "Fuels - A Special Report," Power. S1-S48 (1968).
8. U.S. Bureau of the Census, "Statistical Abstract of the United States
1973" (94th edition), Washington, D.C. (1973).
9. Macrakis, M. C., "Energy: Demand, Conservation, and Institutional
Problems," MIT Press, Cambridge, Mass. (1974).
10. Intertechnology Corp., "The U.S. Energy Problem," Report to NSF/RANN,
ITC Report C645 (1975).
11. Smil, V., "Energy and Air Pollution: USA 1970-2020," APCA Journal.
25: 233-236 (1975).
12. EPA, "Position Paper on Regulation of Atmospheric Sulfates," EPA
Report EPA-450/2-75-007 (1975).
13. Robinson, E., and R. C. Robbins, "Sources, Abundance, and Fate of Gas-
eous Atmospheric Pollutants," Final report to API by Stanford Research
Institute, PR-6755 (1968).
14. Hill, J. A., "Testimony Before the House Science and Technology Com-
mittee," Subcommittee on the Environment and the Atmosphere, July 14,
1975.
109
-------
15. National Academy of Engineering, "Abatement of Sulfur Oxide Emissions
from Stationary Combustion Sources," COPAC-2 (1974).
16. EPA, "SIP Rulemaking: Use of Stack Height as an Air Pollution Control
Measure," Memorandum from Asst. Administrator for Air and Waste Manage-
ment, Environmental Protection Agency (1975).
17. Dunlap, R. W., "Control of Ambient Sulfur Dioxide Concentrations with
Tall Stacks and Intermittent Control Systems," Air Quality and Station-
ary Source Emission Control, NAS/NAE (1975).
18. Montgomery, T. L., J. W. Frey, and W. B. Norn's, "Intermittent Control
Systems," Env. Sci. Technol.. 9: 528-533 (1975).
19. Environmental Protection Agency, "Stack Height Increases Guideline,"
Federal Register, pp. 7450-7452, February 18, 1976.
20. Hill, G. R., M. D. Thomas, and J. N. Abersold, "High Stacks Overcome
Concentrations of Gases," Mining Congress Journal, 21-34 (1945).
21. Kawkinen, J. W., R. M. Jorden, M. H. Lawasani, and R. E. West, "Trace
Element Behavior in Coal Fired Power Plant," Env. Sci. Tech., 9: 862-
869 (1975).
22. EPA, "Helena Valley, Montana, Area Environmental Pollution Study,"
EPA Report AP-91 (1972).
23. Vaughn, B. E., et al., "Review of Potential Impact on Health and Envi-
ronmental Quality from Metals Entering the Environment as a Result of
Coal Utilization," Battelle Energy Program Report (1975).
24. Cuffe, S. T., and R. W. Gerstle, "Emissions from Coal Fired Power
Plants: A Comprehensive Summary," USPHS Pub 999-AP-35 (1967).
25. Cavender, H. H., D. S. Kircher, and A. J. Hoffman, "Nationwide Air
Pollutant Emission Trends 1940-1970," U.S. EPA Pub AP-15 (1973).
26. Davis, D. D., G. Smith, and G. Klauber, "Trace Gas Analysis of Power
Plant Plumes Via Aircraft Measurement: 03, S02, and NOX Chemistry,"
Science 186: 733-736 (1974).
27. EPA, "Health Consequences of Sulfur Oxides," EPA Report EPA-650/1-74-
004 (1974).
28. Sellars, W. D., "Physical Climatology" U. of Chicago Press, Chicago
(1965).
110
-------
29. Plate, E. 0., "Aerodynamic Characteristics of Atmospheric Boundary Lay-
ers," USAEC Critical Review Series, Oak Ridge (1971).
30. Haugen, D. A., "Workshop in Micrometeorology," American Meteorological
Soc., Boston (1972).
31. Pasquill, F., "Atmospheric Diffusion," 2nd Edition, Halstead, New York
(1974).
32. Pasquill, F., "Some Topics Relating to Modeling of Dispersion in Bound-
ary Layer," EPA Report EPA-650/4-75-015 (1975).
33. Hanna, S. R., "Characteristics of Winds and Turbulence in the Planetary
Boundary Layer," ESSA Tech. Memo ERLTM-ARL-8 (1969).
34. Agee, E. M., D. E. Brown, T. S. Chen, and K. E. Dowell, "A Height
Dependent Model of Eddy Viscosity in the Planetary Boundary Layer,"
JAM., 12: 409-412 (1973).
35. O'Brien, J. J., "A Note on the Vertical Structure of the Eddy Exchange
Coefficient in the Planetary Boundary Layer," J. Atmos. Sci., 27: 1213-
1215 (1970).
36. Clarke, R. H., "Observational Studies in the Atmospheric Boundary
Layer," Quart. J. Roy. Met. Soc., 96: 91-114 (1970).
37. MacCready, P. B., T. B. Smith, and M. A. Wolf, "Vertical Diffusion
from a Low Altitude Line Source," Final Report to U.S. Army Chemical
Corp., Dugway Proving Ground, MRI Contract DA-42-007-CML-504 (1961).
38. MacCready, P. B., L. B. Baboolal, and P. B. S. Lissaman, "Diffusion
and Turbulence Aloft over Complex Terrain," Symp. on Atm. Diff. and
Air Poll., AMS, Santa Barbara 218-232 (1975).
39. Shaffer, W. A., "Atmospheric Diffusion of Radon in a Time-Height Regime,"
PhD Thesis, Drexel University (1973).
40. Zilitinkevich, S. S., D. L. Laikhtman, and A. S. Monin, "Dynamics of
the Atmospheric Boundary Layer," Izv., Atm. and Oceanic Physics,
3: 297-333 (1967).
41. Wendell, L. L., and D. C. Powell, "Regional Transport, Dispersion, and
Removal of Atmospheric Pollutants," Pacific Northwest Laboratory Annual
Report to the USAEC Division of Biomedical and Environmental Research
BNWL-1950 Pt 3., 29-33 (1975).
42. Nudelman, H. I., and J. A. Frizzola, "An Air Pollution Incident Due to
a Stationary Front," APCA Journal. 24: 140-144 (1974).
Ill
-------
43. Briggs, G. A., Plume Rise, U.S. Atomic Energy Commision, Oak Ridge
(1969).
44. Briggs, G. A., "Plume Rise Predictions," AMS Lectures on Air Pollution
and Environmental Impact Analyses, D. A. Haugen, Editor, American
Meteorological Society, Boston (1975).
45. Pasquill, F., "The Dispersion of Material in the Atmospheric Boundary
Layer - The Basis for Generalization," AMS Lectures on Air Pollution
and Environmental Impact Analyses, D. A. Haugen, Editor, American .
Meteorological Society, Boston (1975).
46. Gifford, F. H., "Atmospheric Dispersion Models for Environmental Pol-
lution Applications," AMS Lectures on Air Pollution and Environmental
Impact Analyses, D. A. Haugen, Editor, American Meteorological Society,
Boston (1975).
47. Pasquill, F., "The Estimation of Windborne Material," Meteorological
Magazine, 90: 33-49 (1961).
48. Csanady, G. T., "Turbulent Diffusion in the Environment," Reidel,
Boston (1973).
49. Smith, M., "Recommended Guide for the Prediction of the Dispersion of
Airborne Effluents," Am. Soc. Mech. Engrs., New York (1968).
50. Slade, D. H., "Meteorology and Atomic Energy," USAEC, Oak Ridge (1968).
51. Turner, D. B., Workbook on Atmospheric Dispersion Estimates, USPHS
Publication 999-AP-26, U.S. Public Health Service, Cincinnati (1967).
52. Hewson, E. W., and G. C. Gill, "Meteorological Investigations in
Columbia River Valley Near Trail," B.C., U.S. Bureau of Mines Bull
453 (1944).
53. Montgomery, T. L., and J. H. Coleman, "Empirical Relationships Between
Time-Averaged S02 Concentrations," Envi. Sci. Tech., 9: 953-956 (1975).
54. Naden, R. A., and J. V. Leeds, "The Modification of Plume Models to
Account for Long Averaging Times," Atm. Envi.. 6: 829-845 (1972).
55. Larsen, R. I., "An New Mathematical Model of Air Pollutant Concentra-
tion Averaging Time and Frequency." APCA Journal, 19: 24-30 (1969).
56. Larsen, R. I., "An Air Quality Data Analysis System for Interrelating
Effects, Standards, and Needed Source Reductions," APCA Journal,
23: 933-940 (1973).
112
-------
57. Larsen, R. I., "An Air Quality Data Analysis System for Interrelating
Effects, Standards, and Needed Source Reduction," APCA Journal, 24:
551-558 (1974).
58. Hino, M., "Maximum Ground Level Concentration and Sampling Time," Atm.
Envi.. 2: 149-165 (1968).
59. Gifford, F. A., "Peak to Mean Concentration Ratios According to a
"Top-Hat" Fluctuating Plume Model," NOAA ATDL Report 45 (1971).
60. McGuire, T., and K. E. Noll, "Relationship Between Concentration of
Atmospheric Pollutants and Averaging Time," Atm. Envi., 5: 291-298
(1971).
61. Kornreich, L. D., ed., "Proc. Symposium on Statistical Aspects of Air
Quality Data," EPA Report EPA-650/4-74-038 (1974).
62. Ramsdell, J. V., and W. T. Hinds, "Concentration Fluctuations and
Peak-to-Mean Concentration Ratios in Plumes From a Ground-Level Con-
tinuous Point Source," Atm. Envi., 5: 483-495 (1971).
63. Pollack, R. I., "Studies of Pollutant Concentration Frequency Distribu-
tions," EPA Report EPA-650/4-75-004 (1975).
64. Mills, M. T., and F. A. Record, "Comprehensive Analysis of Time-
Concentration Relationships and the Validation of a Single Source
Dispersion Model," GCA Corp. Final Report to EPA GCA-TR-75-4-G (1975).
65. Slade, D. H., "Atmospheric Dispersion Over Chesapeake Bay," Mon. Weath.
Rev., 90: 217-224 (1962).
66. Lyons, W. A., "Turbulent Diffusion and Pollutant Transport in Shoreline
Environments," AMS Lectures on Air Pollution and Environmental Impact
Analyses, D. A. Haugen, Editor, American Meteorological Society,
Boston (1975).
67. Clarke, J. F., "Nocturnal Urban Boundary Layer over Cincinnati, Ohio,"
Mon. Weath. Rev.. 97: 582-589 (1969).
68. McElroy, J. L., "A Comparative Study of Urban and Rural Dispersion,"
J. Appl. Met.. 8: 19-31 (1969).
69. Vukoyich, F. , "Theoretical Analysis of the Effect of Mean Wind and
Stability on a Heat Island Circulation Characteristic of an Urban
Complex," Mon. Weath. Rev.. 99: 919-926 (1971).
70. Egan, B. A., "Turbulent Diffusion in Complex Terrain," in Lectures on
Air Pollution and Environmental Impact Analyses, Am. Met. Soc., Boston
(1975).
113
-------
71. Stumpke, H., "Investigations on the Turbulent Dispersion of Stack Gases
Over Uneven Terrain," Staub. 26: 97-104 (1966).
72. Van der Hoven, I., "Atmospheric Transport and Diffusion at Coastal
Sites," Nuclear Safety, 8: 490-499 (1967).
73. Lin, J, T., et al., "Laboratory and Numerical Simulation of Plume Dis-
persion in Stably Stratified Flow Over Complex Terrain," EPA Report
EPA 654/4-74-044 (1973).
74. Liu, H., and J. Lin, "Laboratory Simulation of Plume Dispersion from a
Lead Smelter in Glover, Missouri," Flow Research, Inc., Report No. 55
to EPA (1975).
75. AHshuller, A. P., "Atmospheric Sulfur Dioxide and Sulfate," Env. Sci.
Technol., 7: 709-712 (1973).
76. Levy, A., and D. R. Drewes, "A Review and Selection of S0p-S04= Con-
version Rates and Mechanisms," Final Report to EPA, BatteTle Memorial
Institute. In Preparation.
77. Calvert, J. G., "Interactions of Air Pollutants," In Health Effects of
Air Pollutants, U.S. Senate Comm. on Public Works, 5ev. 93-15 (1973).
78. Horst, T. W., "A Surface Depletion Model for Deposition from a Gaussian
Plume. Proc. Atmosphere - Surface Exchange of Particulate and Gaseous
Pollutants," U.S. ERDA Symp. Ser. CONF-740921. In Press.
79. Smith, M. E., "Statement of Maynard E. Smith, Smith-Singer Associates,
Inc., National Governors' Conference on Coal Utilization Scrubbers and
Other Options," (November 19, 1975).
80. Wendell, L. L., D. C. Powell, and R. L. Drake, "A Regional Scale Model
for Computing Deposition and Ground Level Air Concentration of S02 and
$04 from an Elevated Source," Battelle, Pacific Northwest Laboratories
Annual Report for 1975 to ERDA. In Press.
81. Hefter, J. L., A. D. Taylor, and G. J. Ferber, "A Regional-Continental
Scale Transport, Diffusion, and Deposition Model," NOAA Tech. Memo
ERL ARL-50 (1975).
82. Scriven, R. A., and B. E. A. Fisher, "The Long Range Transport of Air-
borne Material and Its Removal by Deposition and Washout - I. General
Considerations," Atm. Envi.. 8: 49-59 (1975).
83. Scriven, R. A., and B. E. A. Fisher, "The Long Range Transport of Air-
borne Material and Its Removal by Deposition and Washout-II. The Effect
of Turbulent Diffusion," Atm. Envi., 8: 59-69 (1975).
84. Hales, J. M., "Fundamentals of the Theory of Gas Scavenging by Rain,"
Atm. Envi.. 6: 635-659 (1972).
114
-------
85. Holzworth, G. C., "Mixing Heights, Wind Speeds, and Potential for Urban
Pollution Throughout the Contiguous United States," EPA Pub. AP-101
(1972).
86. Trijonis, J., "The Relationship of Sulfur Dioxide Emissions to Sulfur
Dioxide and Sulfate Air Quality," In Air Quality and Stationary Source
Emission Control, NAS/NAE Report to U.S. Senate Committee on Public
Works, Ser. No. 94-4 (1975).
87. Bolin, B., and C. Persson, "Regional Dispersion and Deposition of
Atmospheric Pollutants with Particular Application of Sulfur Pollu-
tion over Western Europe," Tell us. 27: 281-308 (1975).
88. Sweden's Case Study Contribution to the United Nations Conference on
the Human Environment. Royal Ministry of National Affairs, Sweden
(1971).
89. Prahm, L.P., H. S. Buch, and U. Torp, "Long Range Transport of Atmos-
pheric Pollutants over the Atlantic," Symp. on Atm. Diff. and Air
Poll., AMS, Santa Barbara, 190-195 (1975).
90. Brosset, C., K. Andreasson, and M. Perm, "The Nature and Possible
Origin of Acid Particles Observed at the Swedish West Coast," Atm.
Envi., 9: 631-642 (1975).
91. Charlson, R. J., A. H. Vanderpool, D. S. Covert, A. P. Waggoner, and
N. C. Ahlquist, "H2S04/(NH4)2S04 Background Aerosol: Optical Detection
in St. Louis Region," Atm. Envi., 8: 1257-1267 (1974).
92. Cuong, N. B., B. Bonsang, G. Lambert, and J. L. Pasquier, "Residence Time
of Sulfur Dioxide in the Marine Atmosphere," Adv. Geophys. In Press.
93. Smith, F. B., and G. H. Jeffrey, "Airborne Transport of Sulphur Dioxide
from the U.K.," Atm. Envir.. 9:643-659 (1975).
94. Chamberlain, A. C., "Aspects of Travel and Deposition of Aerosol and
Vapor Clouds," AERE, HP/R 1261 HMSD (1953).
95. May, F. G., "The Washout of Lycopodium Spores by Rain," Quart. J. Roy.
Met. Soc., 84: 451-458 (1958).
96. Dana, M. T., and J. M. Hales, "Statistical Aspects of the Washout of
Polydisperse Aerosols," Atm. Envi. In Press.
97. Hales, J. M., J. M. Thorp, and M. A. Wolf, "Field Investigation of sul-
fur Dioxide Washout from the Plume of a Large, Coal-Fired Power P'ant
by Natural Precipitation," Final Report to EPA CPA 22-69-150 (197").
98. Dana, M. T., J. M. Hales, and M. A. Wolf, "Rain Scavenging of S02 and
Sulfate from Power Plant Plumes," J. Geophys. Res., 80: 4119-4129 (1975).
115
-------
99. Hutcheson, M. R., and F. P. Hall, "Sulfate Washout from a Coal-Fired
Power Plant Plume," Atm. Envi.. 8: 23-28 (1974).
100. Granat, L., and H. Rohde, "A Study of Fallout by Precipitation Around
an Oil-Fired Power Plant," Final Report, Inst. of Meteorology, Univ.
of Stockholm (1972).
101. Hales, J. M., "A Linear Model for Predicting the Washout of Pollutant
Gases from Industrial Plumes," AlChe Journal, 19: 292-297 (1973).
102. Dana, M. T., J. M. Hales, W. G. N. Slinn, and M. A. Wolf, "National
Precipitation Washout of Sulfur Compounds from Plumes," Final Report
to EPA, EPA-R3-73-047 (1973).
103. Hales, J. M., and S. L. Sutter, "Solubility of S02 in Water at Dilute
Concentrations," Atm. Envi., 6: 635-639 (1972).
104. Englemann, R. J., "Scavenging Prediction Using Ratios of Concentration
in Air and Precipitation," J. Appl. Met., 10: 493-497 (1971).
105. Slinn, W. G. N., "Precipitation Scavenging: Some Problems, Approximate
Solutions, and Suggestions for Further Research," In Precipitation
Scavenging 1974, R. W. Beadle, and R. G. Semonin, eds., ERDA Publica-
tion. In Press.
106. Kreitzberg, C. W., "Precipitation Cleansing Computation in a Numerical
Weather Prediction Model," In Fate of Pollutants, Wiley, New York,
In Press.
107. Hane, C. E., "Precipitation Scavenging in a Squall Line," Pacific North-
west Laboratories Annual Report to USAEC/DBER BNWL-1850 (1974).
108. Bird, R. B., W. E. Stewart, and E. N. Lighfoot, "Transport Phenomena,"
Wiley, New York (1960).
109. Miller, J. M., "The Collection and Chemical Analysis of Precipitation
in North America," Proc. AlChe Water Reuse Conference, Chicago (1975).
110. Nisbet, I., "Sulfates and Acidity in Precipitation," In Air Quality
and Stationary Source Emission Control. NAS/NAE Report to U.S. Senate
Committee on Public Works, Ser. No. 94-4 (1975).
111. Cogbill, C. V., and G. E. Likens, "Acid Precipitation in the North-
eastern United States," Water Resour. Res., 10: 1133-1137 (1974).
112. Frohlinger, J. 0., and R. Kane, "Precipitation: Its Acidic Nature,"
Science. 189: 455-457 (1975).
113. Cramer, J. R., "Fate of Atmospheric Sulfur Dioxide and Related Substan-
ces as Indicated by Chemistry of Precipitation," Final Report to Ministry
of Environment, Air Management Branch (1973).
116
-------
114. SMIC, "Inadvertent Climate Modification," MIT Press, Cambridge (1971).
115. Hess, W. W., ed., "Weather and Climate Modification," Wiley, New York
(1974).
116. Machta, L., and K. Telegadas, "Inadvertent Large Scale Weather Modifi-
cation," In Weather and Climate Modification, W. W. Hess, ed., Wiley,
New York (1974).
117. Landsberg, H., "Inadvertent Climate Modification Through Urbanization,"
In Weather and Climate Modification, W. W. Hess, ed., Wiley, New
York (1974).
118. Sax. R. I., et al., "Weather Modification: Where Are We Now, and Where
Should We Be Going?" J. Appl. Met., 14: 652-672 (1975).
119. Hobbs, P. V., and S. E. Shumway, "Cloud Condensation Nuclei from Indust-
rial Sources and Their Apparent Influence on Precipitation in Washington
State," J. Atm. Sci., 27: 81-89 (1970).
117
-------
APPENDIX A
AMBIENT AIR QUALITY STANDARDS
National primary and secondary ambient air quality standards that exist at
the present time are summarized in Table A-l. The primary standards define
levels of air quality necessary to protect the public health with an adequate
margin of safety. National secondary standards define levels of air quality
necessary to protect the public welfare from any known or anticipated
adverse effects of a pollutant. Recent reviews conducted by the National
Academy of Sciences, the EPA, and independent groups have essentially
supported these standards as they currently exist. As noted in the pre-
vious text, the sulfur dioxide standards are at present the most signifi-
cant in the context of tall-stack performance, and are followed in importance
by the oxides of nitrogen.
A-l
-------
TABLE A-1. SUMMARY OF EXISTING FEDERAL
AMBIENT AIR QUALITY STANDARDS
Pollutant
Type of
Standard
Sampling
Time
Sulfur Dioxide
Nitrogen Dioxide
Total Particulate
Photochemical
Oxidants
Carbon Monoxide
Hydrocarbons
(non-methane)
Primary
Primary*
Secondary*
Primary and
Secondary
Primary
Primary*
Secondary**
Secondary*
Primary and
Secondary
Primary and
Secondary*
Primary and
Secondary*
Primary and
1 year
24 hr
3 hr
1 year
1 yeart
24 hr
1 yeart
24 hr
1 hr
8 hr
1 hr
3 hr
Secondary***
Concentration of
Standard
80 yg/m - 0.03 ppm
365 yg/m3 - 0.14 ppm
1,300 yg/m3 - 0.5 ppm
100 yg/m3 - 0.05 ppm
75 yg/m3
260 yg/m3
60 yg/m3
150 yg/m3
3
160 yg/m - 0.08 ppm
10,000 yg/m3 - 9 ppm
40,000 yg/m3 - 35 ppm
160 yg/m - 0.24 ppm
*Not to be exceeded more than once per year
**As a guide to be used in assessing implementation plans to achieve the
24-hour standard
***As a guide in devising implementation plans for achieving oxidant
standards
tGeometric means
A-2
-------
APPENDIX B
1974 SUMMARY OF U.S. STACKS
TALLER THAN 122 METERS
The summary of stack heights given in the following table was prepared by
accessing the computer files of the NOAA office of Aeronautical Charting
and Cartography, and applying this information in conjunction with 1972,
Federal Power Commission Form FPC-67 data and further information from
the EPA document Steam Electric Power Generating Point Source Category,
EPA 440/1-74 029-a, 1974. The author expresses his sincere appreciation
to staff members of NOAA and the EPA, who have contributed significantly to
the creation of this table.
B-l
-------
1974 SUMMARY OF U.S. STACKS
TALLER THAN 122 METERS
Plant Name
State
Location
Height (type)*
(meters)
Gorgas
E. C. Gaston
Barry
Brown's Ferry Nuclear
Widows Creek
Colbert
Alabama
Gorgas
Wilsonville
Bucks
Decatur
Stevenson
Pride
229 (P)
229 (P)
183 (P)
183 (N)
152 (P)
152 (P)
Navajo
Mohave
Arizona
Hayden
Page
Morend
Douglas
San Manuel
Clark Co., Nev.
305/183
236
236
171
168
153
S
P
S
S
(S)
(P)
Ritchie
Arkansas
Helena
137 (P)
Moss Landing
Contra Costa
Morro Bay
Pittsburg
California
Moss Landing
Benicia
Antioch
Morro Bay
Pittsburg
152 (P)
142 (R)
137 (P)
137 (P)
137 (P)
Comanche
Cherokee
Colorado
Pueblo
Denver
152 (P)
122 (P)
B-2
-------
TABLE l.(contd)
Plant Name
State
Location
Height (type)*
(meters)
Middletown
Bridgeport Harbor
Connecticut
Middletown
Bridgeport
152 (P)
151 (P)
Delaware
Delaware City
152 (P)
Crystal River
Anclote #1
Manatee
Big Bend
Fort Meyers
Crist
Cape Kennedy
Turkey Pt.
Sanford
Florida
Red Level
Tarpon Springs
Port Manatee
Tampa
Fort Meyers
Pensacola
Cocoa
Florida City
Lake Monroe
154 (P)
153 (P)
152 (P)
149 (P)
137 (P)
127 (P)
122 (P)
122 (P)
122 (P)
Bowen
Wansley 1 & 2
Harlee Branch
McDonough
Yates
Hammond
Arkwright
Mitchell
Georgia
Bartow County
Carroll ton
Milledgeville
Cobb County
Newnan
Floyd County
Bibb County
Daugherty County
305 (P)
305 (P)
305 (P)
253 (P)
251/244 (P)
229 (P)
177 (P)
152 (P)
B-3
-------
TABLE l.(contd)
State
.ocation
Height (type)*
(meters)
Baldwin
Joliet
Powerton
Coffeen
E. D. Edwards
Kincaid
Waukegan
Will County
Fisk
Clifty Creek
E. W. Stout
Breed
Petersburg
Tanners Creek
Gallagher
Cayuga
Gibson . .
Michigan City
R. M. Schafer
Warrick
State Line
Baillv
Illinois
Baldwin
Joliet
Pekin
Coffeen
Bartonville
Kincaid
Waukegan
Lockport
Chicago
Indiana
Clifty Creek
Indianapolis
Sullivan
Petersburg
Lawrenceburg
New Albany
Cayuga
Princeton
Michigan City
Wheatfield
Newburgh
Hammond
Dune Acres
185 (P)
168 (P)
161 (P)
152 (P)
152 (P)
152 (P)
137 (P)
137 (P)
137 (P)
208 (P)
172 (P)
168 (P)
168 (P)
168 (P)
168 (P)
152 (P)
152 (P)
152 (P)
152 (P)
152/122 (P)
140 (P)
124 (P)
Neal #1 & 2
Iowa
Salix
122 (P)
La Cygne
Kansas
Linn County
213 (P)
B-4
-------
TABLE 1. (contd)
Plant Name
State
Location
Height (type)*
(meters)
Big Sandy
Ohio River #1
J. M. Stuart
Paradise
Ghent
Elmer Smith
Mill Creek
E. W. Brown
Cane Run
Kentucky
Louisa
Maysville
Aberdeen, Ohio
Drakesboro
Ghent
Owensboro
Louisville
Burgin
Louisville
252 (P)
245 (P)
244 (P)
244 (P)
201 (P)
198 (P)
183 (P)
172 (P)
152 (P)
Louisiana
Chalmette
154 (A)
MorgajTtpwn
Chalk Point
Dickerson
Maryland
Newbura
Luke
Aquasco
Dickerson
213 (P)
183 (P)
122 (P)
122 (P)
Mystic
Salem Harbor
Brayton Point
Canal
Massachusetts
Everett
Salem
Somerset
Sandwich
152 (P)
152 (P)
152 (P)
152 (P)
B-5
-------
TABLE 1 (contd)
State
Plant Name
Location
Height (type)*
ight (ty
(meters)
Monroe
B. C. Cobb
Weadock
St. Clair
Trenton Channel
Karn
River Rouge
Campbel 1
King
j
Sherbourne
Black Dog
High Bridge
Riverside
Bo swell
G, Andrus
Jack Watson
Labadie
Rush Island
Sibley
Sioux
Hawthorne
New Madrid
Thomas
Asburv
Michigan
Monroe
Muskegon
Essexville
E. China Township
Trenton Channel
White Pine
Essexville
River Rouge
West Olive
Minnesota
Oak Park Hts.
Becker
Minneapol is
St. Paul
Minneapolis
Cohasset
Mississippi
Greenville
Gulf port
- Missouri
Labadie
Crystal City
Sibley
West Alton
Kansas City
New Madrid
Randolph County
As bury
244 (P)
198 (P)
198 (P)
183 (P)
172 (P)
154 (S)
152 (P)
130 (P)
123 (P)
239 (P)
198 (P)
183 (P)
174 (P)
145 (P)
122 (P)
152 (P)
122 (P)
216 (P)
216 (P)
213 (P)
183 (P)
183 (P)
183 (P)
123 (P)
122 (P)
B-6
-------
TABLE l.(contd)
Plant Name
State
Location
Height (type)*
(meters)
Col strip #1-4
Montana
McGill
Anaconda
Great Falls
Col strip
230 (S)
178 (S)
157 (S)
154 (P)
J. 0. Newington #1
New Hampshire
Newington
127 (P)
Hudson
New Jersey
Jersey City
Woodbridge
152 (P)
122 (S)
New Mexico
Hurley
Animas
192 (S)
183 (S)
Oswego
Northport
Ravenswood
59th & 74th Sts.
Authur Kill
Waterside
Port Jefferson
New York
Oswego
Northport
New York
New York
New York
New York
Port Jefferson
Upton
213 (P)
183 (P)
152 (P)
152 (P)
152 (P)
142 (P)
130 (P)
129 (N)
B-7
-------
TABLE l,(contd)
Plant Name
State
Location
Height (type)*
(meters)
Roxboro
Belews Creek
L. V. Sutton
Cliffside
North Carolina
Roxboro
North Winston
Wilmington
Cliffside
244 (P)
182 (P)
168 (P)
155 (P)
Leland Olds
North Dakota
Stanton
152 (P)
Gavin
W. H. Sammis
Burger
Cardinal
Muskingum River
Conesville 5 & 6
J. M. Stuart
Miami Fort
Toronto
Avon Lake
East Lake
Kyger Creek
W. C. Beckjord
Conesville 1-4
Ashtabula
Ohio
Cheshire
Stratton
Shadyside
Brilliant
Beverly
Conesville
Aberdeen
North Bend
Toronto
Avon Lake
East Lake
Cheshire
New Richmond
Conesville
Ashtabula
335 (P)
305/259/154 (P)
259 (P)
251 (P)
252 (P)
245 (P)
244 (P)
244 (P)
198 (P)
183 (P)
183 (P)
163 (P)
145 (P)
137 (P)
122 (P)
B-8
-------
TABLE 1. (contd)
Plant Name
State
Location
Height (type)*
(meters)
Homer City
Conemaugh
Bruce Mansfield
Cheswick
Keystone
Hatfield's Ferry
Seward
Martins Creek
Shawville
Montour
Brunner Island
Peach Bottom Nuclear
Portland
Susquehanna Nuclear
Pennsylvania
Homer City
Indiana County
Shippingport
Springdale
Shelocta
Masontown
Seward
Martins Creek
Shawville
Washingtonville
York Haven
Langloth
Peach Bottom
Morgantown
Portland
Tunkhannock
366/244 (P)
305 (P)
289 (P)
244 (P)
244 (P)
244 (P)
184 (P)
183 (P)
183 (P)
183 (P)
183 (P)
152 (S)
151 (P)
122 (S)
122 (P)
122 (P)
Georgetown
South Carolina
Georgetown
123 (P)
Big Stone
South Dakota
Grant
152 (P)
Kingston
Cumberland
Bull Run
Gal latin
T. H. Allen
Johnsonville
Tennessee
Kingston
Cumberland
Clinton
Gallatin
Memphis
Johnsonville
306 (P)
305 (P)
244 (P)
152 (P)
132 (P)
123 (P)
B-9
-------
TABLE U(contd)
Plant Name
State
Location
Height (type^
(meters)
Big Brown
Texas
El Paso
La Porte
Amarillo
Port Arthur
Fairfield
Monticello
251/186 (S)
147 (R)
125 (S)
123 (R)
122 (P)
122 (R)
Huntington Canyon #1 & 2
Utah
Huntington
Murray
Salt Lake City
Garfield
183 (P)
139 (S)
138 (S)
122 (S)
Yorktown
Clinch River
Glen Lyn
Chesterfield
Virginia
Yorktown
Car bo
Glen Lyn
Chesterfield
149 (P)
138 (P)
134 (P)
129 (P)
Centralia
Washington
Tacoma
Centralia
181 (S)
144 (P)
Mitchell
Harrison
Amos
Kammer
Philip Sporn
Mt. Storm
Ft. Martin
West Virginia
Moundsville
Haywood
St. Albans
Ravenswood
Captina
Graham
Mt. Storm
Maidsville
B-10
366 (P)
306 (P)
274 (P)
187 (S)
183 (P)
183 (P)
183 (P)
168 (P)
-------
TABLE 1.(contd)
State
Height (type)*
Plant Name Location (meters)
Wisconsin
Alma Alma 213 (P)
South Oak Creek Oak Creek 168 (P)
Genoa #3 Genoa 152 (P)
Columbia Portage 152 (P)
Port Washington Port Washington 152 (P)
Valley Milwaukee 122 (P)
Wyoming
Bridger Rock Springs 154 (P)
*Symbols: P - power plant
S - smelting or metals processing
N - experimental nuclear reactor
R - refinery
B-ll
-------
APPENDIX C
ANNOTATED BIBLIOGRAPHY OF PERTINENT
LITERATURE ON TALL STACKS
This section presents an annotated bibliography of selected articles and
reports related to the subject of transport and dispersion of plumes from
tall stacks. The material presented here was selected on the basis of its
direct relationship to dispersion from tall stacks, its technical merit,
and its general accessability. It is restricted primarily to publications
in the English language.
It should be noted that primary emphasis is given to the more recent litera-
ture , and that there are two basic reasons for this. The first of these
is that stack-height trends necessarily restrict literature pertaining to
the taller stacks to a relatively late period. Secondly, much of the early
work has been discussed previously in detailed publications by Slade,
Pasquill, and Csanady,4^ to mention but a few. The reader is referred to
these refrences for a more thorough examination of the earlier work.
Finally, it is emphasized that, in order to obtain a more objective
presentation, the abstracts have been written to reflect the original
authors' intents as much as possible. To help accomplish this, the wording
of the abstracts has been chosen to reflect the time period when the article
was published. This material does not necessarily reflect a viewpoint of
anyone other than the original authors.
C-l
-------
The references appear in reverse chronological order, except in cases
where continuity of series of reports demands grouping otherwise.
NAVAJO
Navajo Generating Station Sulfur Dioxide Field Monitoring Program.
Volume I, Final Program Report, Rockwell International, Meteorology
Research Incorporated, Systems Applications Incorporated (1975).
The purpose of this program was to determine the amount of flue gas
desulfurization necessary to satisfy ambient S02 standards in the
vicinity of the Navajo generating station. This facility currently
has two 750 Mwe units in operation; a third unit of similar size is
scheduled for operation in April, 1976. Effluent from each unit passes
through individual, 236 m stacks.
The primary impetus for this program was the previous Southwest Energy
Study, which indicated that without S02 source control, air quality
standards would be violated. A particularly important aspect of this
study - open to considerable debate - was the behavior of pollutant
plumes as they encountered elevated surfaces. In addition to this question
of plume impingement, meteorological situations involving plume looping,
fumigation, and limited mixing received special emphasis. The air
monitoring component of this program consisted of an array of 26 fixed
S02 monitors, used in conjunction with aircraft plume measurements to
determine dispersion behavior downwind from the Navajo plant. The data
obtained in this manner were utilized in conjunction with a dispersion
model to predict the expected frequency of occurence of surface concentra-
tions in excess of the 1300 yg/m3 three-hour standard.
The principal conclusion of the program is that the expected frequency of
occurrence of SOg concentrations above the three-hour standard is less than
twice per year. The implementation of flue gas desulfurization at the
Navajo plant is therefore judged to be unnecessary.
Situations leading to highest observed ground-level concentrations were
those involving impingement of the olume on elevated terrain, and
fumigation conditions. Particular emphasis was placed upon 'impinge-
ment at the Vermillion Cliffs area, where the terrain rose
abruptly of the order of one thousand feet above the stack exit. In
general impingement was observed to occur principally under conditions
involving light, steady winds in stable atmospheres.
C-2
-------
Clarke, A. J.5 and G. Spurr.
Routine Sulfur Dioxide Surveys Around Large Modern Power Stations
Part I - Summary paper. Central Electricity Generating Board (1975).
This series of papers describes sulfur dioxide measurements at six of the
Central Electricity Generating Board's more modern power plants. These
include Kingsworth, Fawley, Pembroke, Ratcliffe, Eggborough, and
Fiddler's Ferry. With the exception of Pembroke (s.h. = 213 m) the
stack height of all of these 2000 MWe plants is 198 m.
Sampler locations for these surveys were such that uniform distributions
around each power station were achieved. In addition to S02 monitors,
more sophisticated plume detectors such as Lidar were employed.
Natural diurnal, seasonal, and long-term variations in ground level S02
concentrations have precluded detection of contributions by any of the
plants insofar as monthly and seasonal averages are concerned. Comparisons
of daily upwind and downwind measurements provides more sensitivity in
this regard, but the effects of the plants' contributions have not been
detected even with this method. On the basis of these results it is
concluded that contributions by the plants to daily mean S02 levels is
less than 7 yg/m^. This almost complete absence of a measurable power
station contribution is surprising since an occasional effect on the daily
mean S02 concentration is expected on the basis of diffusion theory. This
suggests that "some hitherto unaccounted process is assisting in the
dilution of the plumes."
These results are unequivocal in their finding that S02 pollution can be
controlled effectively by tall stacks. It is emphasized, however, that
these measurements do not consider other aspects of power-plant air pollution,
such as S02 reactions, or its ultimate fate.
Parts II-VI of this report follow this summary section, and are authored by
various individuals as follows:
Part II: Fawley and Pembroke - R. T. Jarman and C. M. deTurville
Part III: Kingsworth - A. W. Powell and P. A. Tatchell
Part IV: Ratcliffe-on-Soar - F. R. Barber and A. Martin
Part V: Eggborough - D. L. Dolman and P. M. Owens
Part VI: Fiddler's Ferry - F. Dale
Start, G. E., C. R. Dickson, and L. L. Wendell.
Diffusion in a Canyon Within Rough Mountainous Terrain. JAM, 1_4,
333-341 (1975).
A field test was conducted to assess the effect of complex terrain on the
dispersion of airborne effluents. Specifically, the project had two primary
C-3
-------
goals: 1) to evaluate plume "impaction" on elevated terrain and 2) to
assess diffusion in the complex areas as compared to that over flat terrain.
The site of the study was the Huntington Canyon area where a 183-meter power-
plant stack was utilized to disperse oil-fog and SF6 tracers. The stack was
situated' in the trough of a narrow valley with steep walls, which possessed
a number of sizeable feeder canyons along its length. Measurement techniques
included helicopter and ground-level SFs sampling in addition to plume
photography. Under daytime lapse conditions little deviation between
measured dispersion and expected flat-terrain values was observed. Under
neutral and stable conditions, however, observed mixing rates were several
times higher than flat-terrain values. Frequent occurrences of impaction
of the plumes on elevated terrain were observed.
Lucas, D. H.
The Effect of Emission Height in Very Large Areas of Emission.
Atm. Env. 9. 607-622 (1975).
Calculations have been performed to determine the effects of emission
height on ground level air concentrations in and downwind from uniform
area sources. The calculations employed Button's plume equation for
typical atmospheric conditions, which included neutral and isothermal
cases, as well as stable stratifications at elevations of 200, 400 and
1000 m. The pollutant ($02) was considered to act as an inert substance,
and zero background concentration was assumed.
Graphs of concentration versus distance based on these calculations gave
the following indications:
• large chimneys reduce the maximum ground-level concentrations of
pollutants under all meteorological conditions
• the required chimney height to promote acceptable ground-level
concentrations increases with increasing size of the area
source, and such concentrations can be achieved with chimney
heights currently practical
• raising the height of emission above the bottom of stable layers
essentially eliminates the possibility of pollutant diffusing to
ground level
• while sufficiently tall stacks can reduce concentrations sub-
stantially in the area of emission, they do not increase downwind
concentrations as a result.
Further calculations indicate that a 90% reduction in the sulfur emissions
from high-elevation sources would result in less than ten percent reduction
C-4
-------
in ambient ground-level concentrations inside even moderately large
cities. This is because low elevation sources contribute dispropor-
tionately to ground-level concentrations.
This paper does not deal with the problem of sulfate formation; it is
noted, however, that in view of the U.S. Environmental Protection Agency's
position that flue gas desulfurization is preferable to the use of tall
stacks, the burden of proof that tall stacks are unacceptable is on this
agency. Accordingly, the EPA should utilize their resources to "demonstrate
the relative effects of emission control and stack-height control in real
situations."
Smith, M. E., and T. T. Frankenberg.
Improvement of Ambient Sulfur Dioxide Concentrations by Conversion
from Low to High Stacks. JAPCA 25. 595-601 (1975).
During the last twenty years the stacks of the Muskingum River Power Plant
have increased in height from 83 m to 251 m. Because of this increase and
also because of the rural, unpolluted environment of the plant, an excellent
opportunity to assess the true effects of stack height has been provided.
This study began with a monitoring program in 1969 when the plant was
operating with 133 m stacks. It consisted of a monitoring program that
extended through 1973, when only the 251 m stacks were employed.
Plume concentrations were predicted for this study utilizing ASME standard
procedures which had been modified to account for directional shear and
variation of velocity with elevation. S02 monitoring was conducted with
automatic instrumentation at four sites, located between 4 and 20 km from
the plant.
Comparison of concentrations predicted for situations with the 133 and
251 m stacks indicated that an approximately two-fold decrease in ground-
level concentration should result from the use of the taller chimneys, and
this prediction is borne out by the actual measurements. Further analysis
of the measurements indicate that, in contrast to the case with shorter
stacks, the predominant mechanism for promoting high ground level concentra-
tions is downward mixing under daytime conditions, where unstable conditions
exist in a relatively deep layer.
Although EPA primary and secondary standards were exceeded on occasion
with the shorter stacks, there have been no observations of S02 in excess
of standards since the 251 m stacks were implemented.
C-5
-------
Miller, S.
The Building of Tall (and Not So Tall) Stacks. Envi. Sci. Tech. 9,
523-527 (1975).
The purpose of the tall stack is high-level dispersion of pollutants
to reduce concentrations at ground level. Several aspects make the subject
of tall stacks especially pertinent today:
• in 20 years S0£ emission to the atmosphere will have nearly
doubled;
• the number of tall stacks is increasing at a rapid pace; and
• additional effects not directly related to ground-level concen-
trations, such as acid rain, are currently being associated with
industrial air pollution.
Proponents of tall stacks point out that such units are able to reduce
ground level concentrations of S02, and can document such claims with data
from monitoring networks. These proponents, however, fail to recognize
that material vented must ultimately come back to the surface despite the
height of release.
Early indications are clear that S02 emissions from tall stacks can penetrate
through inversion layers. There are strong indications, however, that
such emissions convert to sulfates and are removed as "acid rain" at some
distance from the source. Increases in rain acidity within the U.S. have
been noted during recent years, and some specialists are now proposing
that such increases are directly associated with changes in anti-pollution
technology.
Dunlap, R. N.
Control of Ambient Sulfur Dioxide Concentrations with Tall Stacks
and/or Intermittent Control Systems. Air Quality and Stationary
Source Emission Control NAS/NAE (1975).
The advantages of particular meteorological conditions for maintaining
high air quality suggest that control systems for power plants need only
be operated intermittently, under adverse conditions. Intermittent Control
Systems (ICS) are often closely associated with tall stacks, owing to the
latter's enhanced dispersion capability. The TVA estimates, for instance,
that ICS requirements for the Kingston plant would be reduced from 55 to 0
days per year if the stacks were extended to 1000 feet.
Proposed EPA regulations do not accept increases in stack height beyond
levels of "good engineering practice" as acceptable air quality control
C-6
-------
measures, unless this is accomplished as a part of an ICS program. An
acceptable ICS program, in addition, must adhere to several stringent
guidelines. The suggestion that tall stacks be used for meeting ambient
ground-level S02 standards is a controversial one. The sizable amount of
evidence indicating that they are often effective for this purpose is
tempered by the fact that, over an extended period of time, they result in
only a negligible reduction in the amount of pollutants emitted. This is
the major reason for limitations on the use of tall stacks by the EPA,
which contends that the use of emission limitations in preference to
dispersion-enhancement techniques is required by the Federal Clean Air
Act. The limits of acceptable flue-gas-desulfurization (FGD) measures in
conjunction with ICS programs is currently being debated in several court
cases, with results which are largely conflicting at the present time.
A few tall-stack ICS programs are now operating, but few data exist to
indicate their performance. Data for TVA's Paradise Steam Plant are most
extensive, and indicate that the ICS (which has included substantial
stack-height increases) is resulting in compliance with Federal Ambient
Air Quality Standards (AAQS). Similar results have been observed with the
ASARCO Tacoma smelter, although more stringent local AAQS have been continued
to be violated. ASARCO's El Paso smelter (8281 and 611' stacks) demonstrated
an improvement in ambient air quality upon initiating an ICS. The success
of this program was limited by problems associated with the complex terrain
in the area, however. In summary, the results to date indicate mixed
results from ICS tall stack application, with terrain effects being a
major complicating factor.
Aside from maintaining primary Federal AAQS's, much controversy has arisen
over other effects. These include the biological impact of sulfate aerosol,
precipitation chemistry, visibility effects, and climate and weather
modification. Unfortunately most of these impacts are not well understood
qualitatively, rendering most related decisions with regard to tall stacks
rather subjective in nature. The EPA has suggested that sulfate levels
above 6-10 ygm/nr are associated with adverse health effects, and has
concluded that use of tall-stack-ICS control systems will aggravate the
sulfate problem. An opposing viewpoint (by the FEA, the TVA, and the AEP
Service Corporation) suggests that if sulfate is indeed a problem, appropriate
AAQSs should be set. If information is insufficient to issue a criteria
document, then tall-stack-ICS technology should not be rejected on this
basis.
This NAS/NAE study suggests that a compromise position can be identified
where ICS-tall-stack technology could be accepted for carefully defined
situations as an interim control technique on the basis of the need to:
1. select suitable interim techniques during large scale implemen-
tation of FGD technology, and
2. reduce the clean fuels deficit while complying with AAQSs (for
SC-2 if not for S04).
C-7
-------
The study concludes with the finding that "tall-stack-ICS technology is a
potentially important technological option for control of ambient sulfur
dioxide." Much disagreement exists with regard to the question of sulfate
aerosol, however.
Wai den Research Corporation
Modeling Analysis of Power Plants for Compliance Extensions in
51 Air Quality Control Regions. Summary Report to EPA
contract 68-02-0049, (1975).
This report summarizes individual reports covering modeling analysis of
power plants in a number of Air Quality Control Regions (AQCR's). Its
purpose is to determine the extent that variances could be granted for
certain plants to relieve the aggregate low-sulfur coal deficit.
Input data for the model (Gaussian with Briggs' plume rise) were taken
from the Federal Power Commission (FPC Form 67), in conjunction with
measured meteorological data for the year 1964. Terrain effects are
compensated by adjustment of the virtual emission height in the Gaussian
model. An additional short-term model for valley terrain was also employed.
Interaction of plumes from individual plants was considered when warranted
by their proximity.
The report concludes that a power plant variance strategy appears to offer
a viable approach to reducing the low-sulfur coal deficit without jeopar-
dizing attainment of primary Federal Ambient Air Quality Standards.
Start, G. E., C. R. Dickson, and N. R. Ricks
Effluent Dilutions over Mountainous Terrain and Within Mountainous
Canyons. Proc. Symposium on Atmospheric Diffusion and Air Pollution.
AMS, Santa Barbara Conf. (1974).
A field study was conducted to evaluate the effects of complex terrain on
plume dilution and to determine the extent of impingement of plumes on
elevated surfaces. The study involved helicopter and ground-level sampling
of plumes emitted from the surface and from stacks in two different locations.
The first of these was a 183 meter stack in the Valley of Huntington Canyon;in
the second was the 122 m stack located near Garfield, Utah, on the south
shore of Great Salt Lake.
These measurements showed that center!ine concentrations of plumes that
flowed over complex terrain were significantly more dilute than those
predicted using Pasquill categories and the Gaussian plume model. These
deviations became increasingly pronounced with increasing stability,
reflecting the relative importance of mechanically-induced mixing under
these conditions.
C-8
-------
Four physical mechanisms are suggested as important in enhancing dilution
in complex terrain. These are: mechanical mixing, overshoot from slope
winds, wake turbulence, and vertical directional shear.
There was no question that the plumes impacted the terrain, but generally
impaction was only a few minutes in duration at any given location.
Lucas, D.
Pollution Control by Tall Chimneys. New Scientist. 790-791
(26 Sept 1974).
An evaluative technique which is based on the concept of an elevated area
source has been employed to determine the consequences of increasing
release height in areas of concentrated SO? emission. The results of this
analysis indicate that increasing release height should reduce downwind
S02 concentrations appreciably; and this result is used as a basis to
argue against United States EPA source control policy, which emphasizes
removal of S02 at its source.
Moore, D. J.
The Prediction of the Mean Hourly Average Maximum Ground Level
Concentration of Sulfur Dioxide. Atm. Env. 8, 543-554 (1974).
Previously-derived equations for the hourly, maximum ground-level concentra-
tion in a power plant plume, developed from measurements at the Northfleet
plant, were applied for analysis of results from Tilbury. These equations
had the form
Cm = [(M/H)2 + (C/U2)2]1/2(Q/H2) (unstable conditions)
and
= [{M/H) + (C/U2)2](Q/H2) (all other conditions),
where
H = 100 + 475 pJ/4/U,
Q, = heat release, U = wind speed, and M and C are stability-dependent
parameters.
C-9
-------
The physical basis for the above equations rests in the fact that downward
diffusion from sources above about 150 m takes place through an environment
that is always stably stratified to some degree. Observations of insta-
bility arise from local inhomogeneities (i.e., thermals) which are always
embedded in a slightly stable environment. The observed diffusivity thus
can be considered to consist of two terms: M, which depends upon mechanical
stirring of the boundary layer, and C, which reflects convective activity.
Application of the above equations using M and C determined from the
Northfleet measurements to the Tilbury data demonstrates excellent agree-
ment.
Start, G. E., N. R. Ricks, and C. R. Dickson.
Effluent Dilutions over Mountainous Terrain NOAA TM ERL ARL-51 (1974).
A tracer sampling program was undertaken at Garfield, Utah to determine
the effect of complex terrain on the behavior of plumes. Specifically,
the objectives were (!) to determine the dilution attributable to rough
terrain, (2) to examine the "impaction" of plumes against elevated surfaces,
and (3) to establish a modest data base to aid in diffusion analysis at
this and similar sites.
The Garfield smelter (s.h. = 122 m) is located near the south shore of
Great Salt Lake immediately north of the steep slopes of the Oquirrh
Mountains. The experiments consisted primarily of releasing SF5 tracer
from the smelter stacks and performing airborne and ground level measure-
ments of this substance at points downwind. These plus visual plume
observations verified the fact that plumes often came in contact with
mountain surfaces. These occurrences were strongly influenced by atmo-
spheric stability, with the most pronounced contact occurring under stably-
stratified conditions.
Measured Pasquill plume-spread parameters indicated that plumes that
flowed over the rough terrain experienced as much as four times the dilution
expected from similar plumes flowing over flat surfaces.
Moore, D. J.
Observed and Calculated Magnitudes and Distances of Maximum Ground
Level Concentration of Gaseous Effluent Material Downwind From a
Tall Stack. Adv. Geophys. 18^201-221 (1974).
A revised approach to a previously-derived method was utilized to predict
the distance of maximum ground-level concentration downwind from an elevated
source. This revision incorporated a provision to account for early
stages of plumes, where mixing is dominated by plume-generated turbulence.
C-10
-------
The starting point for this analysis was the plume model of Moore, which
assumes a normal distribution with mixing dictated by separate thermal and
mechanical components. This model expresses maximum ground-level concentra-
tion in terms of two fitted parameters A and C, which respectively reflect
mechanical and thermal turbulence. The model also can be utilized to
calculate a downwind distance of the maximum concentration, but this is an
inappropriate value, owing to the model's tacit neglect of plume-generated
turbulence during its early stages.
To remedy this situation an expression for the virtual location of the
source (the location of the source of an imaginary plume possessing no
plume-generated turbulence) was derived. Predictions based upon this
expression were compared with observations from the Tilbury and Northfleet
Plants, where acceptable comparisons were obtained except under light
wind, unstable conditions, stable situations, and conditions involving
high winds.
Moore, D. 0.
Comparison of the Trajectories of Buoyant Plumes with Theoretical/
Empirical Models. Atm. Envi. 8, 441-57 (1974).
Many attempts to describe plume rise are based upon a two-dimensional
concept of plume behavior. This concept is only partially applicable in
early plume stages, owing to the "lumpy" nature of the plume under such
conditions, suggesting that a more three-dimensional characterization
might be more appropriate. Parameterized two- and three-dimensional
approaches can be force-fit to data from moderate-sized stacks and power
plants with approximately equal success. The results of this study,
however, indicate that for stack heights greater than 120 m, the three-
dimensional -based form
Ah = 2.4 Q°'25 x* °'75/U
describes the data in a more satisfactory manner.
Martin, A., and F. R. Barber.
"Further Measurements Around Modern Power Stations" Atm. Env. 7,
17-37 (1973).
Beginning in 1966 a program was conducted to assess ambient sulfur dioxide
levels from the West Burton Power Station (s.h. = 183 m). Measurements
were also taken in the vicinity of the High Marnham Station (s.h. = 137 m),
which is located some 15 km to the south. Measurements included those
taken from arrays of ground-level SOp instrumentation, elevated (tower)
measurements, and Lidar.
C-ll
-------
The highest concentrations at ground level were observed during looping-
plume conditions. Fumigation from inversion break-up processes were no
more severe than concentrations observed during steady state conditions
with similar wind speeds and lapse rates. Ambient S0£ levels caused by
the plants are less than one tenth those contributed by background sources.
Despite its approximately doubled firing rate, ambient S02 concentrations
from the West Burton Plant are somewhat less than those from High Marnham.
This is attributed to the higher stack of the West Burton facility.
Weil, J. C., and D. P. Hoult.
A Correlation of Ground-Level Concentrations of Sulfur Dioxide
Downwind of the Keystone Stacks. Atm. Env. 7, 707-721 (1973).
A partial energy balance is employed to obtain an expression relating
meteorological variables and solar radiation to the heights of unstable
mixing layers developing below overlying stable air. This expression is
fit empirically to observed mixing heights in the Keystone plant area, and
combined with plume-rise estimates to predict the incidence of plume
interception by the mixing layers.
A relatively simple plume dispersion expression, relating ground-level
concentration under plume interception conditions to the effective emission
height, source strength, and wind velocity is then fit empirically to
surface measurements to obtain a means for estimating ground-level concen-
trations under these conditions.
Lyons, W. A., and H. S. Cole.
Fumigation and Plume Trapping on the Shores of Lake Michigan
During Stable Onshore Flow. J. Appl. Met., 1_2, 494-510, (1973).
Fumigation and plume trapping can occur under conditions of onshore, gradient
flow owing to the associated perturbations in the boundary layer. When air
flowing onshore from a cooler lake environment progresses inland surface
heating and roughness creates a developing turbulent boundary layer. Plumes
emitted into the overlying stable air may be drawn into the deepening
turbulent boundary layer causing fumigation to occur.
This paper discusses field observations of power plant plume behavior under
such circumstances, and describes models developed to calculate associated
ground-level concentrations.
C-12
-------
Heines, T. S., and L. K. Peters.
The Effect of a Horizontal Impervious Layer Caused by a Temperature
Inversion Aloft on the Dispersion of Pollutants in the Atmosphere.
Atm. Env. 7, 39-48 (1973).
A Laplace-transformation technique was used to obtain solutions to a contin-
uity equation for pollutants having diffusion coefficients obeying a power
law. The solutions pertained to line and point sources, and were constrained
by zero flux boundary conditions at the surface and at some elevated
height z = H*.
For a point source the effect of rising H* was to decrease ground level
concentration.
For inversion heights beyond two-thirds higher than the stack height the
effect of the inversion was negligible.
Allen, R. G.
Facts to Consider when Evaluating Stack Height. Power 117, 30-31,
(1973).
Tall stacks are effective and economical devices for reducing ground-level
pollution. Downwash caused by local terrain features may hinder the per-
formance of a tall stack, but the solution in such circumstances is an
even taller stack. Other nonideal features such as sea-land breeze circula-
tions are more difficult to estimate. Fortunately the associated problems
are often solved automatically using conventional analyses for tall stacks.
Montgomery, T. L., W. B. Norris, F. W. Thomas, and S. B. Carpenter.
Simplified Technique Used to Evaluate Atmospheric Dispersion of
Emissions from Large Power Plants, JAPCA 23, 388-394 (1973).
Nomograms corresponding to predictions from three atmospheric dispersion
models are presented. The model types include those for coning, inversion
breakup, and trapping, and are intended for use in predicting ambient
concentrations resulting from large power plants.
Inversion breakup and trapping dispersion processes have been identified
with the highest observed ground-level concentrations in TVA's experience,
and have generally been associated with the newer plants having tall
stacks (75 m or more). The coning model is most closely associated with
critical conditions for plants with shorter stacks. Inversion breakup
results in high surface concentrations which are of relatively short
C-13
-------
duration (30-45 min). In the TVA region inversion breakup may occur on
200-300 days per year; the resulting magnitudes of surface concentrations,
however, normally do not reach high levels at any single location more
than a few times a year, owing to the variable sector of the plume and
dependence on initial inversion height.
Plume trapping, identified with rapid vertical mixing below an inversion
layer, can result in high concentrations for periods of 2-5 hours. The
trapping condition is found to apply to large power plants on about
30-40 days per year in the TVA region.
Schiermeier, F. A., and L. E. Niemeyer.
Large Power Plant Effluent Study [Lappes] Volume 1 - Instrumentation,
Procedures, and Data Tabulations
Control Administration APTD 70-2
1968), USPHS National Air Pollution
1970
Considerable debate is presently underway regarding the use of tall stacks
for air pollution management. Accordingly, the National Air Pollution
Control Administration is conducting a 5-year comprehensive field study to
determine the behavior of plumes from tall stacks. Centered in Western
Pennsylvania in the vicinity of three new large power sources, the specific
objectives of the study are:
1. To develop and validate transport and diffusion models with
which to calculate ground-level concentrations resulting from
tall stacks,
2. To measure the magnitude, frequency, and spatial distribution of
ground-level concentrations from large power plants with tall
stacks, singly and in combination, and to compare the observed
data with calculated predictions, and
3. To evaluate the effects of sulfur compounds and other effluents
from a large power plant complex on vegetation.
The three power stations of primary significance to this study are Keystone
(1800 MWe, s.h. = 244m), Homer City (1280 MWe, s.h. = 244m), and Conemaugh
(1800 MWe, s.h. = 305m).
The primary measurements of plume concentration in this study are conducted
with a helicopter, instrumented for S02, altitude, temperature, and wet-
bulb depression measurements. Support measurements include portable bubblers
for ground-level S02 measurement, and radiosonde and pilot balloon facilities.
Typical observational days consist of two helicopter flights, about
150 minutes in duration. The first flight is conducted near dawn while
the plume is normally isolated from the surface by low-level stable layers,
C-14
-------
and consists of three cross sections at 4, 10, and 16 km preceded and
followed by 1000 meter temperature soundings just upwind of the stacks.
The second helicopter flight is begun during normal inversion breakup
conditions to assess concentrations attained under circumstances when the
plume may be brought near the ground. This includes treetop-level mapping
of the plume distribution as well as additional temperature soundings.
This volume presents results obtained from this program during March, May,
July, and October of 1968. Maximum ground-level S02 concentration measured
in the Keystone plume by the helicopter in this series was 1.39 ppm.
Maximum half-hour bubbler sampler concentration was 0.3 ppm.
Schiermeier, F. A.
Large Power Plant Effluent Study [Lappes] Volume 2 - Instrumentation,
Procedures, and Data Tabulations (1967 and 1969). USPHS National Air
Pollution Control Administration APTD-0589 (1970).
This report includes the descriptive material given in Volume 1, and
presents Lappes S02, climatology, and meteorology data as well as plant
(Homer City and Keystone) operating data for operations conducted during
1967 and 1969.
During these series helicopter measurements were conducted in both the
Homer City and Keystone plumes. Maximum ground-level concentrations
observed by helicopter were 1.62 ppm for the Keystone plume and 1.39 ppm
for that of Homer City. Maximum half-hourly bubbler sampler concentra-
tions were 0.23 ppm for Keystone and 0.14 ppm for Homer City.
Schiermeier, F. A.
Large Power Plant Effluent Study [Lappes] Volume 3 - Instrumentation,
Procedures, and Data Tabulations (1970) .Environmental Protection
Agency APTD-0735 (1972).
This report includes the descriptive material given in Volumes 1 and 2,
and presents Lappes S02» climatology, and meteorology data as well as
plant (Conemaugh and Homer City) operating data for operations conducted
during 1970.
During this series helicopter measurements were conducted in plumes of the
Homer City and Conemaugh plants. Maximum ground-level concentrations
observed by helicopter were above 2.2 ppm for both plants. Maximum half-
hourly bubbler-sampler concentrations were 0.15 ppm for Homer City and
0.21 ppm for Conemaugh.
C-15
-------
Schiermeier, F. A.
Large Power Plant Effluent Study [Lappes] Volume 4 - Instrumentation,
Procedures and Data Tabulations (1971) and Project,.Summary"!
Environmental Protection Agency APTD-1143 (1972).
This report includes the descriptive material given in Volumes 1 and 2,
and presents Lappes $63, climatology, and meteorology data as well as
plant (Conemaugh and Keystone) operating data for operations conducted
during 1971. Helicopter S02 measurements in this series were conducted
primarily in the Conemaugh plume, where the maximum ground-level concentra-
tion observed was 2.09 ppm. The maximum half-hourly bubbler-sampler
concentration was 0.19 ppm.
The report summarizes the total Lappes project, and describes contractor
support, which includes the following:
• Stanford Research Institute - Lidar plume studies
• Sign-x Laboratories - Plume rise studies
• Meteorology Research, Incorporated - Aerosol and turbulence
studies
• IITRI - Cooling tower plume studies
• Battelle-Northwest - Precipitation scavenging and dry deposition
studies.
• French Meteorological Services - Water tunnel modeling
• Brookhaven National Laboratory - Isotopic S02 conversion studies.
Montgomery, T. L., S. B. Carpenter, W. C. Colbaugh, and F. W. Thomas-
Results of Recent TVA Investigations of Plume Rise. OAPCA 22.
779-784 (1972).
The loft of plumes from power-plant stacks has been investigated in a number
of previous studies. The progressive trend of increasing unit sizes and
stack heights, however, has necessitated further investigation. TVA has
collected plume-rise data from three of its power plants - Bull Run
(950 MWe, s.h. = 244 m), Paradise (2558 Mwe, s.h. = 244 m), and Gallatin
(1255 MWe, s.h. = 152 m) for this purpose.
Evaluation of these data indicated that plume loft was not primarily
dependent on stack height, although correlated variables such as vertical
temperature structure were highly important. Separating into three stability
C-16
-------
classes, three equations were obtained, which pertain to neutral, moderately
stable, and very stable conditions. At any particular distance from the
stack the data for all stabilities can be correlated in terms of a single
expression containing the potential temperature gradient.
Lyons, W. A., and L. E. Olsson.
Mesoscale Air Pollution Transport in the Chicago Lake Breeze.
JAPCA. 22, 876-881, (1972).
A two day program was conducted during the summer of 1967 to elucidate the
behavior of lake-breeze circulation patterns in the Chicago area. Observa-
tions included the use of pibals, tetroons, and surface S02 monitors in
conjunction with aircraft state and aerosol measurements.
On the two observation days light northeasterly gradient winds prevailed
aloft. The inflow layer caused by the lake breeze was observed to grow
in depth to a level of about 800 m. It protruded several tens of kilometers
inland and was capped by an outflow layer, which induced a distinct circula-
tion pattern. Constant density-level tetroons were used to track the
trajectories of the circulation patterns, and indicated helical trajectories
parallel to the lake shore.
Plumes from ground-level and elevated sources entrained in such circulation
patterns can result in high ground-level concentrations if the sources are
positioned so that the cycling process creates additive effects.
Carpenter, S. B., T. L. Montgomery, J. M. Leavitt, W. C. Colbaugh, and
F. W. Thomas.
Principal Plume Dispersion Models: TVA Power Plants- JAPCA 21,
491-495 (1971).
The provision of higher stacks at TVA generating plants has partially
compensated for higher S0£ surface concentrations. This trend toward
higher stacks and larger generating units has been accompanied by a change
in plume dispersion models applied.
Plume dispersion models include those considering coning, fanning, and
inversion breakup, looping, and trapping. TVA experience indicates that
high surface concentrations may result from inversion breakup, but the
durations associated with this condition are short. Looping conditions
have not, in general, resulted in severely high ground-level concentrations
from tall stacks. Trapping conditions, however, have resulted in some
persistent, adverse conditions. These were first noted with the Bull Run
Plant (s.h. = 244 m), and later verified with similar measurements at the
. C-17
-------
Paradise facility. Trapping is associated, in most circumstances, with
deep stable layers caused by high-pressure subsidence. Under these condi-
tions stack height is a minor determinant of plume height, and tall stacks
therefore lose much of the effectiveness that they have under other
meteorological conditions.
Johnson, W. B., and E. E. Uthe.
Lidar Study of the Keystone Stack Plume. Atm. Env., 5_, 703-724 (1971).
A Lidar study of the plume from the Keystone Power Plant was conducted in
May and October, 1968. This study provided a number of measurements of
plume dispersion phenomena and plume rise, and indicated that the following
factors were particularly important in determining plume behavior:
• fanning and tilting due to wind shear with height,
• plume trapping by elevated stable layers, and
• fumigation.
A comparison between predictions of the Briggs/ASME plume rise formula and
17 different Lidar measurements gave a mean absolute difference of 30 m in
effective stack height.
Thomas, F. W. , S. B. Carpenter, and W. C. Colbaugh-
Plume Rise Estimates for Electric Generating Stations. JAPCA 20, 170
(1970).
The "Full-Scale Study of Plume Rise at Large Electric Generating Stations"
involved investigation of plume rise from six TVA generating plants, which
possessed stacks ranging from 76 to 183 meters in height. Extensive plume
photography and support measurements were employed to determine plume
rise, which was subsequently compared with numerous predictive formulae,
including those of Holland, Bosanquet, et al . , Csanady, Davidson, Lucas,
et al., and CONCAWE.
Of these formulae, the CONCAWE and Csanady expressions were optimized to
conform with the observed TVA data. The resulting expressions were as
follows:
Ah = 133(F/J3)'27 Csanady
Q '
Ah = 0.414 H CONCAWE
J '
C-18
-------
where F and Q^ are the "buoyancy flux" and heat emission rate, respectively.
Plume rise can also be expressed by a 2/3-law relationship as
Ah = 114CF1/3/J
where C is a stability parameter given by the equation
C = 1.065 - 6.2675-
A9 M
where AZ is the potential temperature gradient in °C/M. Although the
Csanady and CONCAWE formulae provide good estimates of plume rise, the
2/3-power equation is recommended for use whenever sufficient meteorological
information is available.
Clarke, A. J., D. H. Lucas, and F. F. Ross.
Tall Stacks - How Effective Are They? Proc. 2nd Int. Clean Air Cong.
Wash.,D.C. (1970).
The information in this paper is directed toward facilitating a fair
assessment of the capabilities of the tall stack. The benefits of tall
stacks often are taken for granted in industrial circles, but have not
been largely accepted elsewhere.
Tall chimneys are effective in reducing "total pollution", and lower
concentrations at all distances from the source. "It is unlikely that
tall stacks cause greater increases in the acidity of rainfall at greater
distances than at lesser distances."
The high chimney is a cheap, reliable, and indispensible means of reducing
pollution by gases, and their criticism has been largely misguided.
Periano, A.
The Tall Stack - Technical and Social Aspects. Proc. 2nd Int.
Clean Air Cong.. Wash.,D.C. (1970).
This paper is presented as an example of how not to proceed in designing
and constructing a large power plant with regard to air pollution control,
The case in point is the Reading station in north Tel Aviv, which was
constructed near the shoreline of the Mediterranean Sea to the west of a
growing, populated area.
Evaluations of the stack height necessary to achieve acceptable ambient
S0£ levels were performed by several expert groups who, under various
assumptions, specified stack heights ranging from 38-861 m. Calculations
C-19
-------
performed by the author indicate several deficiencies in the approaches
utilized. The resulting state of affairs suggests that an emission standard,
if present, would have precluded much of the turmoil experienced in siting
the plant.
Niemeyer, L. E., R. A. McCormick, and J. H. Ludwig.
Environmental Aspects of Power Plants. IAEA Symposium on Env. Aspects
of Nuclear Power Stations, New York (Aug 1970), p. 10-14.
Assuming no source control is imposed, the emissions of SOX, NOX, and
optically active particulates are estimated to increase in the U.S.
5, 3.5, and 4 times, respectively. This indicates that anthropogenic S02
sources will soon exceed natural sources globally. Tall stacks have been
applied in increasing numbers to lower ground-level concentrations of
these effluents. Because of differing meteorological circumstances at
higher elevations, however, the standard dispersion formulae, developed
for smaller stacks, cannot be expected to apply.
New experiments for evaluating tall-stack behavior have been funded by the
NAPCA. These are the LAPPES and TVA studies, the second of which is
presently complete. Although these studies are in apparent agreement
regarding several aspects of plume behavior, our knowledge in this area is
highly incomplete. Our lack of knowledge of diffusion and transport is
compounded by a similar lack regarding transformation and removal processes.
Although tall stacks are effective in some respects, the accumulation of
scientific evidence combined with the fact that energy production is
increasing enormously indicates the prudence of preventing emissions,
rather than relying on procedures that are directed only toward the
reduction of ground-level concentrations.
Tennessee Valley Authority
Report on Full-Scale Study on Inversion Breakup at Large Power
Plants.T.V.A., Muscle Shoals, Alabama (1970).
The trend toward increasing stack height in the electric utility industry
has been accompanied by a corresponding shift in meteorological conditions
associated with maximum ground-level pollutant concentrations. For plants
with 200-400 ft stacks maximum ground-level concentrations often are
identified with moderate-to-high wind speeds under near-neutral stability
conditions. With higher stacks, however, the inversion breakup situation
may be more significant. Accordingly, this study has been conducted to
assess surface S02 concentrations in the vicinity of large power plants
under inversion-breakup conditions.
C-20
-------
Three TVA plants were included in this study. These were: Paradise
(1400 MWe, s.h. = 183m), Shawnee (1500 MWe, s.h. = 76m) and Johnsonville
(750 MWe, s.h. = 122m, 82m). Basic measurements were performed with an
instrumented helicopter (SO?, temperature, humidity, and altitude).
Support measurements included pilot balloon measurements and data from
stationary SO? instrumentation. In addition to the three principal
plants, data from stationary S0£ monitors at the Widows Creek and Kingston
plants are reported.
Helicopter measurements were performed before and during inversion breakup.
Before breakup temperature soundings were made to approximately 300m, and
plume cross sectioning - usually at 5 and 10 miles from the sources - was
performed. During breakup low-level flights were made to assess surface
concentrations, and additional cross sections and soundings were performed.
Maximum observed surface concentrations were as follows: Paradise 0.90 ppm;
Shawnee 1.78 ppm; Johnsonville 2.04 ppm. Maxima were observed at relatively
large downwind distances, ranging up to 20 miles from the sources.
Under stable conditions the elevated plumes were found to follow quasi-
Gaussian behavior, and Gaussian plume parameters were obtained for these
conditions by adjustment to fit the measured data. Under inversion-
breakup conditions this same treatment indicated a relatively large spread
along the y axis.
Stationary S02 sampler data analysis indicated that most of the stationary
samplers were sited too near the source to adequately reflect surface
inversion breakup conditions.
Niemann, B. L., M. C. Day, and P. B. MacCready.
Particulate Emissions, Plume Rise, and Diffusion from a Tall Stack.
Final Report to National Air Pollution Control Administration contract
CPA 22-69-20 METEOROLOGY RESEARCH, Inc. (1970).
Airborne turbulence and aerosol measurements, as well as plume photography
were performed at the Keystone Power Plant (1800 MWe, s.h. = 244m).
Typical sampling flights were initiated by performing a sounding to obtain
meteorological conditions and background aerosol concentrations to altitudes
of 5000 ft msl. Five or six horizontal plume traverses were then performed
at distances of two, five, and ten miles downwind, after which a second
sounding was performed and an along-plume traverse was flown back to the
power plant.
Estimates of the surface shear stress (TO) and surface roughness (Z0)
were performed assuming a constant-stress relationship. Measurements of
plume and environmental turbulence exhibited wide scatter, but show a
tendency to conform to previous basic predictions regarding the initial
decay of plume turbulence.
C-21
-------
Aerosols collected on a moving slide impactor were sized using optical and
scanning electron microscopes. High variability, however, cast much doubt
upon the exact size distributions of the airborne flyash.
Pooler, F., and L. E. Niemeyer.
Dispersion from Tall Stacks: An Evaluation Proc. 2nd Int. Clean Air
Cong., Wash., DC (1970).
The Large Power Plant Effluent Study was initiated with the following
objectives:
• to develop and validate transport and diffusion models with which
to calculate ground-level concentrations from large power plants
with tall stacks,
• to measure in the field the magnitude, frequency and spatial
distribution of these concentrations, and
• evaluate the associated effects on vegetation.
Primary emphasis in this study has been given to high-wind, neutral stability
regimes, and low-wind regimes.
In addition to meteorological measurements, S02 concentration measurements
were obtained by cross-sectioning the plume with an instrumented helicopter,
and these data were used to calculate plume dispersion and rise. Observed
plume rise was found to agree with Briggs1 formula within experimental
error. Horizontal spreading of the plume was observed to be closely
related to directional wind shear, and measurements of tilt and horizontal
spread were employed in attempts to quantify this relationship.
There appears to be sufficient turbulence within early stages of the plume
to cause substantial vertical diffusion. This conclusion stems both from
the plume cross-section observations and from actual turbulence measure-
ments. Beyond 10 km downwind, however, this turbulence is suspected to be
attenuated substantially.
Attempts to calculate plume dispersion from a high plume through a growing,
surface mixing layer indicate that maximum ground-level concentrations will
occur at distances greater than 60 km from the plant. The few ground-level
S02 measurements obtained at comparable distances (0.2 - 0.36 ppm) are in
fair agreement with calculated values. If the surface mixing layer
envelopes the plume, it is carried to the ground within a few kilometers
from the stack. Both looping and trapping of the plume are of concern in
this respect.
C-22
-------
Other than for general observations of higher S02 concentrations at high
points and in the lee of hills, no discernable topographic effects were
noted at the Keystone Plant. The Conemaugh Plant, however, is located
adjacent to a high (400-450 m) ridge, and experiences radical downwash when
the plant is in the lee of the ridge.
Tall stacks are concluded to help reduce, or in some cases eliminate,
occurrences of ground-level concentrations that might be found with shorter
stacks. This is particularly true for neutral, high-wind conditions and
during inversion breakup. On the other hand, increasing the stack height
(within reasonable limits) will not reduce significantly the concentrations
associated with the trapped-plume, limited mixing layer situation. In
addition, the effect on precipitation chemistry is expected to be significant
regardless of stack height. Additional areas where tall stacks are expected
to be of little or no value are those of large-scale transport, with multiple
source overlap, and the effects of pollutants in weather modification,
visibility, and associated phenomena.
Mclaughlin, J. F., M. E. Smith, and I. A. Singer.
Survey of Ground-Level S0? Concentrations Near Alton, Illinois. Proc.
2nd Int. Clean Air Cong. Wash., DC (1970).
A network of five SO;? monitors with meteorological support information was
implemented in the vicinity of the new Souix generating plant between 1968
and 1970. The Souix plant (1050 MWe, s.h. = 183 m, S02 emissions = 3.3 kg/
sec), began operations prior to network installation. Thus, the data reflect
the influence of the plant during this 1 1/2 year study.
The five monitors were located at distances ranging between 4 and 12 km from
the plant site. Above-standard S02 concentrations were observed most often
with moderate winds from the southeast, indicating that the major source of
ground-level S02 in the area is not the plant, but a complex of emissions
lying to the southeast of the sampler array. Ground-level concentrations of
S02 originating from the plant, itself, were consistently below those esti-
mated by standard dispersion formulae.
Frankenberg, T. T., I. Singer, and M. E. Smith.
Sulfur Dioxide in the Vicinity of the Cardinal Plant of the American
Electric Power System.. Proc. 2nd Int. Clean Air Cong. Wash., D.C. (1970)
A pollution study in the vicinity of the Cardinal Power Plant (s.h. = 252 m)
was initiated with the primary objective of measuring ground-level S02
concentrations before and after operation of this new facility. Developing
a functional sampling network for this purpose was complicated by the
existence of other S02 sources and the difficult terrain in the region.
C-23
-------
The sampling network contained six S02 monitors, some of which were sited
primarily to evaluate contributions from other sources and others for the
purpose of assessing pollution levels at sites expected to be most severely
affected by the Cardinal Plant. Most of these latter sites were at elevations
substantially higher than plant grade, in highly complex terrain.
From the resulting data it is apparent that no trend in S02 level occurred
at any of the stations, either before or after plant startup. If present,
the additions caused by the Cardinal Plant are largely masked in the
variability of pollution arising from other sources.
Proudfit, B. R.
Plume Rise From Keystone Plant. Sign-X Labs. Report to USPHS National
Air Pollution Control Administration, contract PH-86-68-94 (1970).
A helicopter, instrumented for SOg* temperature, and charged aerosol was
used to measure plume rise from the chimneys of the Keystone (1800 MWe,
s.h. = 244m) generating plant. The measurement procedure involved per-
forming an initial temperature sounding immediately upwind of the plume,
and then flying traverses through the plume itself.
Approximately 60 hours of flight data were obtained, and 20 cases were
selected for analysis. The analysis indicates that a single formula will
not accurately predict plume rise for all conditions of stability and wind
speed. By introducing the concept of the maximum potential temperature
difference that can be penetrated by the plume, however, one can utilize
diagrams to estimate rise relatively quickly and easily.
Fortak, H.
Comparison of Calculated and Measured Maximum Ground Level SO?
Concentrations Downwind from Strong Emission Sources (Power Plants)
Staub 29, 14-20 (1969).
A simple Gaussian plume equation, adjusted for averaging time, was utilized
to model maximum hourly surface concentrations in the vicinity of the High
Marnham, Paradise, Bull Run, and Keystone plants. Modification of the
plume rise equation utilized by this model subject to the observed data
resulted in a direct expression to calculate the minimum stack height
necessary to promote acceptable ground-level concentrations downwind from
large power plants.
NAPCA
Tall Stacks, Various Atmospheric Phenomena, and Related Aspects.
$
National Air Pollution Control Administration Document PB 194 805 (1969)
This document is a compilation of abstracts of articles dealing with tall
stacks. It is true that under any given set of meteorological conditions
C-24
-------
the increase of emission height will result in a decrease of ground-level
concentration. This source-receptor relationship, however, is dictated
by a number of variables, and specific critical conditions exist under
which ground-level concentrations are expected to reach peak values.
Although the usefulness of tall stacks in reducing pollution in the vicinity
of a plant is acknowledged, they do not reduce the amount of pollution
emitted to the atmosphere. Other means must be found to prevent over-
burdening the atmosphere with pollution.
Clarke, A. J.
The Application of Air Pollution Research to Power Station Design.
Phil. Trans. Roy. Soc. London A 265. 269-272 (1969).
The concentration levels of pollutant arising from emissions from power
plants depend upon two controllable variables: the amount released and
the emission height. The Central Electricity Generating Board has taken
the approach of controlling the source term for particulates; for gaseous
emissions, however, control at present is effected by maintaining a
suitably large emission height. Trends in chimney design have been to
consolidate all effluents into a single chimney to take advantage of
enhanced plume rise.
Moore, D. J.
The Distribution pf Surface Concentrations of Sulfur Dioxide
Emitted from Tall Chimneys, Phil. Trans. Roy. Soc. A 265,
245-259 (1969).
Hourly SC>2 concentration measurements at the Tilbury (s.h. = 100 m) and
Northfleet (s.h. = 120 m) plants for the period November 1964 - May 1966
are reported. Mean hourly surface concentrations were observed to fall
in the range between 0 and ^25 pphm, and were found to agree well with
predictions of a simple Gaussian plume model for high wind speed condi-
tions. The model was found to over-predict under low to moderate wind
speed conditions. An empirical correction factor can be applied to en-
hance agreement between experiment and theory in all cases.
Cumulative frequency distributions for hourly ground level concentrations
are presented for segments of the data, which permit estimates of vari-
ability about the mean values.
Cross-wind integrals of surface concentrations indicated that the down-
wind point of maximum concentration is only weakly dependent on wind speed,
except possibly under light wind conditions. Crosswind spread also seems
to be relatively independent of wind speed, the expression ay = O.OSx
fitting most of the data for distances out to about 12 km.
C-25
-------
It is concluded that while the semi empirical relationships provided in this
paper correlate well with the Tilbury-Northfleet measurements, they are
probably invalid for stacks much below 100 m. This is because lower stacks
are likely to vent their effluents into the lower, mechanically-stirred
boundary layer, where different mixing mechanisms prevail.
Klug, W.
Determination of Industrial Stack Heights. Phil. Trans. Roy.
Soc. A-265, 205-208 (1969).
A technique is described for selecting appropriate stack heights for a
proposed plant on the basis of source, topographic, and wind and diffusion
information. To apply this technique, a stack height must be chosen, and
resulting isopleths of ground-level concentrations are generated for
evaluation.
Thomas, F. W.
TVA's Air Quality Management Program. Proc. Am. Soc. Civil Engrs.,
J. Power Div., Paper 6483:131-143, March 1969.
TVA has sought to prevent deleterious effects from SOz emission principally
through the use of high stacks. Stack heights have increased with increasing
plant size, with the largest current stack being 244 m high. The stack at
the Cumberland City plant will be 305 m. With a few exceptions this approach
has permitted ground-level air quality criteria to be met.
Research operations under the TVA Air Management Program have included
studies of diffusion, plume rise, and inversion breakup. Fumigations
resulting from inversion breakup conditions in the vicinity of stacks
greater than 150 m tall are substantially less severe than estimated by
standard formulae.
While more definitive studies are needed, the limited data to date indi-
cates that the critical situation for relatively tall stacks involves
limiting mixing layers generally associated with high-pressure meteoro-
logical systems. Under such conditions the plume might be expected to
rise until it is entrained into a layer of moderate stability. Subse-
quent downward mixing from solar-induced turbulence can then cause fumi-
gations lasting several hours.
Williams, David H., Jr., and John T. Dowd.
Design and Construction Features of the 1600 MW Mitchell Plant.
Combustion, 41_, 19-23, August 1969.
C-26
-------
Determination of the stack configuration for the Mitchell plant arose from
several considerations, including:
• local terrain out to 20 miles from the plant
* local, state and federal air pollution regulations
• the growing body of literature regarding dispersive properties
of tall stacks
• properties of the fuel to be used, and
• data from the existing Kammer Plant.
These considerations were combined with model calculations, and a single,
366 m stack was ultimately specified. The plant is not yet operational,
but is scheduled to begin operations in June, 1970.
Johnson, W. B.
Lidar Observations on the Diffusion and Rise of Stack Plumes.
J. Appl. Meteor, 8., 443-449 (1969).
Several general features of the Keystone (s.h. = 244 m) plume are apparent
from the results ofalidar study performed there during the spring and fall
of 1968. Maximum particulate concentrations are usually found near the top
of the plume, owing to enhanced buoyancy. In addition, the tilting and
fanning of the plume arising from wind shear under stable conditions
is highly evident. Some evidence of terrain-channeling effects is also
present under special conditions.
Fumigation with resulting high concentrations at ground level was observed
in one of the four cases considered. This was apparently caused by rapid
vertical mixing below an inversion at 900-1000 m.
Frankel, R. J.
Problems of Meeting Multiple Air Quality Objectives for Coal-Fired
Utility Boilers. JAPCA, 1_9, 18-23 (1969).
Methods for controlling sulfur oxides from power sources include desulfuri-
zation of fuels, fuel substitution, and the use of tall stacks. It has
been demonstrated that desulfurization cannot reduce the sulfur content
of coal to meet proposed fuel standards in most cases.
The use of ambient air standards for SOp will allow better utilization for
tall stacks. Although they do not eliminate the overall quantity of wastes
discharged, such units reduce ground-level S02 concentrations by promoting
greater dispersion and providing longer airborne periods for chemical decay.
C-27
-------
Johnson, W. B. , Jr. and E. E. Uthe.
Lidar Study of Stack Plumes. (Final Report) Stanford Research Inst..
Menlo Park, CA, Contract PH 22-68-33, Proj. 7289, (1969).
This study established the feasibility of lidar analysis for tall-stack
plume studies. The test site was the Keystone Plant (s.h. = 245 m), where
some 3800 lidar observations were recorded during the study. From these
observations the following conclusions, which relate primarily to tall
stacks, were made:
• directional shear, which is important in promoting plume
tilting and fanning, requires reconsideration in the
definition of plume rise
• fanning is a very common feature of plumes from high stacks,
and must be included in any realistic diffusion theory.
• effects of elevated inversions and other levels of increasing
stability with height were observed frequently in the Keystone
plume
• plume fumigation occurs often, probably more frequently than
previously expected.
Niemeyer, L. E., and F. A. Schiermeier-
Tall Stack Study Underway. Power Engineering, 27_, 42-51 (1969).
Considerable debate is underway regarding the effectiveness of tall stacks.
It is obvious that increasing stack height will result in lower ground level
concentrations, but it must be noted that tall chimneys do nothing to limit
the total amount of pollution released to the atmosphere.
A study by the National Air Pollution Control Administration (NAPCA) is
currently underway in western Pennsylvania to assess the performance of
tall chimneys. This study focuses upon three large power stations:
Keystone, Homer City, and Conemaugh. NAPCA has contracted SRI to perform
lidar observations, and Sign-X to measure plume rise using airborne instru-
mentation. Additional airborne and ground level pollution and meteorologi-
cal measurements are being conducted by NAPCA personnel. Data collected
in this program will be used to develop and test plume rise dispersion
theories applicable to tall stacks.
C-28
-------
Scriven, R. A.
Variability and Upper Bounds for Maximum Ground Level Concentrations.
Phil. Trans. Roy. Soc. Lond. A 265. 209-220 (1969).
Results from the Tilbury-Northfleet tests were analyzed using a similarity
approach combined with solutions to the diffusion equation including vari-
able wind and diffusivity profiles. The results of this more rigorous
treatment provide a basis for the previous finding that simple formulae
tend to show good agreement with measured mean concentrations. Three
cases were considered: boundary-layer flow, flows in the unbounded atmo-
sphere, and effects arising from stable layers aloft. In these examina-
tions it is apparent that different factors acting in opposing directions
act to lower errors in the mean ground-level concentrations.
Thomas, F. W., S. B. Carpenter, and W. C. Colbaugh.
Recent Results of Measurements. Plume Rise Estimates for Electric
Generating Stations. IV. Phil. Trans. Roy. Soc. Lond. A 265,
221-243 (1969).
The objective of this NAPCA-sponsored work was to compile and analyze data
for definition of plume rise from six TVA power plants, whose stacks ranged
in height from 76 to 183 m. Plume photography, plus extensive meteorologi-
cal measurements composed the bulk of the study. Plume rise data obtained
in this manner were compared with the models of Holland, Bosanquet, et al.,
Davidson-Bryant, Csanady, CONCAWE, and Lucas, et al. Of these the Csanady
and CONCAWE formulae generally showed the best conformity with experiment.
These formulae were "optimized" with the data to provide improved forms
for applied estimation.
Carpenter, S. B., 0. M. Leavitt, F. W. Thomas, J. A. Frizzola, and
M. E. Smith.
Full-Scale Study of Plume Rise at Large Coal-Fired Electric Generating
Stations. JAPCA. J_8, 458-465 (1968).
Limited plume rise information has been obtained during the USPHS/TVA
"Full-Scale Study of Dispersion of Stack Gases", conducted over the five-
year period 1957-62. Starting in 1962 a second research project, the "Full
Scale Study of Plume Rise at Large Electric Generating Stations' was begun.
The objective of this study was to collect data on and assess the nature of
plume rise from power plants over a wide range of conditions. Stack heights
on the power plants selected for the study ranged from 76 to 182 m.
C-29
-------
Data included photography, transit readings5 and helicopter measurements.
In all, 133 composite plume rise measurements were made. These results
were plotted as a function of values predicted by various plume rise
equations.
McLaughlin, J. F., Jr.
Progress in Meeting Power Plant Air Pollution Problems.
EEI Bull., 36, 155-159 (1968)
Fly ash from power plants is not a problem if high-efficiency electrostatic
precipitators and tall stacks are employed. Sulfur dioxide is the most
difficult problem area at the present time, because there is no way of
collecting oxides of sulfur.
In any meaningful discussion of control measures, an objective treatment
of the tall stack is essential. British experience with tall stacks leads
them to state definitely that such units are an effective technique for S02
control. Such an acceptance is not evident in the U.S., however; reasons
for this hesitancy are a noted reluctance to accept small, but finite
increases in ambient S02 levels, concern for behavior under "unusual"
meteorological conditions, and lack of knowledge pertaining to S02 reaction
products.
Frankenberg, T. T.
High Stacks for the Diffusion of Sulfur Dioxide and Other Gases
Emitted by Electric Power Plants. Am. Ind. Hyg. Assoc. J., 29, 181-
185 (1968).
Despite strong evidence to the contrary, there is a tendency to ignore
the major role that the tall stack can play in reducing ground level
concentrations of S02 resulting from the combustion of fuel. The purpose
of this paper is to describe the experience gained from measurements
taken in the vicinity of the Clifty Creek (s.h. = 224 m) and Kyger Creek
(s.h. = 127 m) steam plants, which supports the tall stack concept.
In this experiment, S02 monitors and dustfall collectors were placed
primarily in regions in the predominant downwind direction from the sources.
An analysis of the data reveals that no hourly mean concentrations in excess
of 1 ppm were observed, and the dispersion models generally over-predicted
actual conditions. The analysis demonstrates also that these tall stacks
"completely eliminate ground-level concentrations during inversions."
C-30
-------
Moroz, W. J. and E. Koczkur.
Plume Rise and Dispersion Near the Shoreline of a Large Lake when
Flow Patterns are Dominated by the Lake Breeze. Proc. USAEC
Meteorological Meeting, C. A. Mawson, ed. AECL-2787 (1967).
An observational study was conducted near the power plant on the north
shore of Lake Ontario to assess the effects of the lake breeze on diffu-
sion and rise of the plume from the 152 meter stacks.
During this study aircraft temperature soundings were conducted three times
daily inland as well as over the lake. These were supported by bi-hourly
pibal observations and surface measurements. Actual plume measurements
were made using a photographic technique, in conjunction with subsequent
densitometer analyses.
From these results it was suggested that vertical dispersion of the plume
for onshore flows under near neutral conditions could be represented by
the form
If the plume were to avoid the lake circulation patterns under such condi-
tions it would have to rise to a level 500 to 750 m above the surface.
McLaughlin, J. F., Jr.
Atmospheric Pollution Considerations Affecting the Ultimate Capacity
of a Thermal-Electric Power Plant Site. JAPCA, V7_, 470-473 (1967)
At the present time adequate means are available to predict stack heights
required to provide acceptable ground-level pollutant concentrations in
the vicinity of power plants. Tall stacks are presently the only method
for controlling the sulfur oxide problem. These units will, in most cases,
enable construction of power plants at any given site and permit success-
ful operation from the standpoint of air pollution. On the other hand it
may be necessary at some sites to place a limitation on maximum capacity.
Determination of an appropriate stack height depends upon a number of
factors, including topography, meteorology, land use planning, and source
conditions.
Stone, 6. N., and A. J. Clarke.
British Experience with Tall Stacks for Air Pollution Control on
Large, Fossil-Fueled Power Plants. American Power Conference,
Illinois Inst. Tech., April 27, 1967.
With increasing demands for power generation, there has been a strong trend
within the Central Electricity Generating Board complex to increase both
C-31
-------
the sizes of generating units and the heights of chimneys. There has also
been a tendency to incorporate single - rather than multiple - chimneys,
and to limit efflux velocities to those sufficient to minimize downwash in
all but exceptionally high winds.
For more than fifteen years it has been standard practice to monitor S02 and
dustfall around each new power station with six to eif/nt field stations.
The principal conclusion that has emerged from these studies is that a modern
power station with tall stacks does not materially increase the general
pollution levels which already existed before the plant was built.
In 1963 a major pollution survey was begun at the High Marnham Power Plant
(s.h. = 137 m), and it was continued until 1965 when the monitoring instru-
mentation was redeployed to the West Burton Plant area. Twenty-four SOg
recorders were located around the plant at distances out to approximately
10 km. The data obtained indicated that hourly S02 levels from the plant
did not exceed 0.5 ppm, and that pollution from other sources was much more
significant than that from the plant itself.
Following the High Marnham study, a more comprehensive investigation - aimed
at examining causal relationships - was initiated at the Tilbury Plant
(s.h. = 100 m). Here twenty-two S02 monitors were employed at distances
out to approximately 12 km from the plant. Although still continuing at
the present time, useful preliminary results are available. Specifically,
there is substantial support for a maximum plume rise formula of the form
Zn,ax
where a is a constant for a given chimney and site. It is also apparent
that plume rise is dependent on stack height, owing to decreasing turbulence
aloft - thus a plume emitted at a greater height will experience a greater
rise.
The question of whether the power industry significantly affects S02 concen-
trations can be examined by comparing trends in emission rates with those
in concentration. Although SOg emissions by power production have nearly
tripled between 1951 and 1966, ambient ground-level S02 concentrations have
decreased. Thus it may be concluded that "all the power plants over a large
geographical area can collectively operate without any detectable influence
on the trend of ground-level SOo concentrations in the area."
Lucas, D. H.
SO? Concentration Measurements Near Tilbury Power Station. Atm. Env. ,J_
389-410 (1967) also p. 421-424.
This paper discusses reliability of data obtained from the Tilbury experi-
ment, and summarizes some of the more important findings, including derived
expressions for maximum ground level concentration and plume rise.
C-32
-------
Bender, R. J.
Tall Stacks, A Potent Weapon in the Fight Against Air Pollution.
Power, m, 94-96 (1967)
Tall stacks for public utilities and industrial plants are an effective
remedy for gaseous pollution. While they obviously do not prevent
pollution from escaping into the atmosphere, they do reduce contamination
at ground level. There is little doubt that tall stacks provide a signifi-
cant remedy to the problem of ground-level contamination while alternative
methods - such as flue gas desulfurization - are under development.
Martin, A. and F. R. Barber.
Sulphur Dioxide Concentrations Measured at Various Distances from a
Modern Power Station. Atmos. Env.. 1, 655-677 (1967)..
S02 measurements in the vicinity of the West Burton power station, still
under construction, were obtained to assess effects of background contri-
butions. One source of background was the High Marnham station (s.h. =
137 m), approximately 14 km to the south.
Six-month average S02 concentrations ranged from .011 to .072 ppm, and little
difference between sites in the High Marnham and West Burton areas was ob-
served. Most of the pollution was suspected of originating from low-level
urban sources. Ground-level S02 originating solely from High Marnham
showed six-month averages peaking at .005 ppm, at distances within 5 km
from the stacks. In addition to the six-month averages, 3 minute maxima
are presented, along with hourly, daily, and monthly means.
Maximum concentrations coming from High Marnham were higher than those pre-
dicted by dispersion models about 16 percent of the time. Thermal insta-
bility conditions (strong sunshine, light winds) gave rise to relatively
high (0.90 ppm in one case) concentrations near the source. The absence of
larger concentrations at higher sampling stations indicated that the plume
essentially rises with topographical contours.
Scriven, R. A.
Properties of the Maximum Ground Level Concentration from an
Elevated Source. Atm. Envi.. 1, 411-419 (1967).
Often high ground-level concentrations are associated with atmospheric
situations involving stably stratified air above the stack, with well-
mixed conditions below. Such situations are more appropriately treated
with two-layer models, rather than the conventional one-layer versions.
C-33
-------
The simple two-layer model described in this paper indicates, as expected,
that ground level concentrations are highly sensitive to the height of the
stable layer, if this layer is below 1-1/4 source heights from the ground.
They are also sensitive to small changes in mixing in the stable layer.
This model can be applied with statistical data pertaining to inversion
height frequency to provide frequency distributions of the correction
factors required to adjust single-layer models to account for layered
conditions.
Van der Hoven, I.
Atmospheric Transport and Diffusion at Coastal Sites.
Nuclear Safety, 8_, 490-499 (1967)
Atmospheric diffusion over wide expanses of water is expected to be reduced
owing to two factors: the decrease of mechanically-generated turbulence
arising from the relatively smooth surface, and the normally cooler water
surfaces with their resultant low thermal turbulence. Such expectations
have been borne out with measurements taken over the past decade, which
show substantial decreases in plume spread below those that would be
expected under similar conditions over land.
Transitions of surface roughness and heating accompanying on-shore flows
can cause fumigation under some conditions, where a confined plume suddenly
experiences rapid mixing conditions. Diurnal effects involving land-sea
breeze conditions can cause extremely complex flows, which again can result
in high ground-level concentrations.
Smith, M. E.
Reduction of Ambient Air Concentrations of Pollutants by Dispersion
from High Stacks. Proc. Third Nat. Conf. on Air Poll., Wash. D.C.
(1966).
In the past 15 years the tall stack has become symbolic of good industrial
air pollution practice; and, led by the smelting industry, there is a distinct
trend toward the use of taller stacks in the utilities industry at the present
time. Under any meteorological conditions, a tall stack located in open,
uncomplicated terrain will produce dramatic reduction in ground-level pollu-
tants compared to the same emission released at lower levels. It is also
important to note that a tall stack in open terrain converts the least
favorable meteorological conditions into the most favorable, that is if a
stack is sufficiently high to penetrate an inversion layer, then its effluent
is essentially prevented from mixing to the ground, rather than the converse
for shorter stacks. Tall stacks are also effective in eliminating effects
from local circulation patterns that tend to result in high ground-level
pollutant concentrations.
C-34
-------
It is emphasized that tall stacks possess no magic power to eliminate a
pollutant, but simply distribute it differently in the atmosphere. This is
the basis for a criticism of tall stacks which is valid as long as the
pollutant does not change to a less objectionable form while airborne.
Airborne $63 is estimated to decay with a half-life of 12 hr. or less, and
thus tall stacks have the effect of actually reducing pollutant amounts.
The previous predictions of others concerning the importance of inversion
breakup in promoting high ground-level concentrations appears to have doubt-
ful support in the field results obtained to date. Specifically, measure-
ments in the vicinity of the Clifty Creek and Kyger Creek plants as well as
those in the TVA region have not resulted in concentrations nearly as high
as predicted.
Nonhebel, G.
British Charts for Heights of Industrial Chimneys. Int. J. Air.
Water Poll., K), 183-189 (1966).
The Memorandum on Chimney Heights was published by the Ministry of Housing
and Local Government in 1963, subsequent to the issuance of an advisory
report by a working party of the Department of Scientific and Industrial
Research. This memo applys only to smaller industrial power plants, as
larger plants and public power supply stations are covered under the
inspection of the Alkali Inspectorate. The values of chimneys height
estimated using this guide reflect the requirement that it is necessary to
vent effluents at least 2-1/2 times higher than surrounding obstructions.
Pooler, F.
Potential Dispersion of Plumes From Large Power Plants. USPHS
Document PB 168790 (1965).
Estimates of plume dispersion from power plants in the 1000-5000 MWe cate-
gory currently rely on extrapolations from existing data for smaller
plants. Assuming that the stack is constructed so as to minimize down-
wash effects, however, the analysis of worst-case dispersion is expected
to be reduced to a few specific cases. These include: 1) high wind
fumigations, 2) inversion breakup, and 3) limited mixing, light-wind
situations.
Inversion-breakup fumigations are expected to produce the highest ground
level concentrations, but will be confined to a relatively small area at
any given time. Limited mixing layer fumigations are potentially more
troublesome owing to the wore widespread nature of the effect and the
relative lack of influence of stack height in promoting low ground-level
concentrations.
C-35
-------
Ground level S02 concentrations in the vicinities of hypothetical 1000 MWe
and 5000 MWe generating plants were estimated from specific formulae derived
for the three critical circumstances. For high-wind neutral conditions
these estimates were based on Button's equation in conjunction with Holland's
plume rise formula. For inversion breakup the estimates were obtained from
an independent estimate of plume height, assuming complete mixing between
the inversion and ground level. A similar expression was employed for
limited mixing conditions, with the inversion height determining the verti-
cal extent of the plume.
Gartrell, F. E.
Monitoring of S02 in the Vicinity of Coal-Fired Power Plants - TVA
Experience. Proc. Am. Power Conf. (Presented at 27th Annual Meeting
of the American Power Conference, Chicago, IL, Apr. 27-29, 1965).
This paper presents results of the extensive appraisal program conducted
by TVA with regard to air pollution in the vicinity of its fossil-fuel
electricity generation plants. It is observed that plots of frequency
of occurrence versus SO? concentration on semi log paper exhibit reasonably
straight lines. Limited data to date indicate that such plots for 183 m
stacks may be somewhat different than those for lower stacks, with a trend
toward lower S02 frequency at ground level.
Under stagnation conditions, ambient air quality measurements in the vicinity
of the Kingston Steam plant (s.h. = 91 m) have indicated that no significant
buildup of pollution occurs. Under such circumstances, it appears that air
pollution potential forecasts need to consider power plants as a special
case for which the meteorological criteria normally employed may not be
applicable.
Nelson, F., and L. Shenfeld.
Economics, Engineering, and Air Pollution in the Design of Large
Chimneys. JAPCA, 1_5_, 536-539 (1965), (Presented at the 58th Annual
Meeting, Air Pollution Control Association, Toronto, Canada,
June 20-24, 1965, Paper No. 65-144).
The present state of Sfy removal technology has led technical men in the
power industry to the general opinion that S02 pollution from generation
sources is still best handled by dispersion from tall stacks.
Selection of an appropriate chimney height can be performed using standard
formulae in conjunction with source and climatological data. The paper
illustrates the application of such an approach for large power stations.
C-36
-------
stack heights from an extrapolation of plant and environmental data obtained
from existing facilities. Diffusion analysis is also applicable for this
purpose using dispersion parameters compiled by previous authors. Stack
design for neutral meteorological conditions generally provides for accept-
able performance under all other commonly encountered conditions. Higher
heat emissions from larger plants may provide sufficient bouyant lift to
prevent trapping by inversions. In addition, they are often capable of
inducing "thermals" under unstable conditions which elevate the plume
thousands of feet. Stack exit velocity is of questionable effectiveness
in promoting plume rise, and for this reason, velocities above the 50-60 fps
needed to eliminate stack downwash are not recommended.
C-38
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 REPORT NO.
EPA-450/3-76-007
2.
3. RECIPIENT'S ACCESSIOI*NO.
4. TITLE AND SUBTITLE
Tall Stacks and the Atmospheric Environment
5. REPORT DATE
March 1976
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Jeremy M. Hales
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORG "^NIZATION NAME AND ADDRESS
Battelle-Northwest
P. O. Box 999
Richland, Washington 99352
10. PROGRAM ELEMENT NO.
2AC 129
11. CONTRACT/GRANT NO.
68-02-1982
12. SPONSORING AGENCY NAME AND ADDRESS
Office of Air Quality Planning and Standards
Environmental Protection Agency
Research Triangle Park, North Carolina 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The question of the effectiveness of tall stacks has become an increasingly
important subject for several reasons, which are keyed strongly to the rapidly
growing energy demands in the U.S. and abroad. This report addresses this
subject by presenting a review of literature pertinent to tall stacks, and by
assessing the potential effects of their large-scale implementation. A compre-
hensive annotated bibliography is included as an appendix to the report.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Fieid/Group
Stacks
Atmosphere
Environment
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
169
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
-------
ID
re
2
m
O
O
T3
TJ
O
33
H
-<
m
S
•o
|—
O
•<
m
3)
<
33
3 2* 2
to o o
5T » a)
CD
2^
O 3
0 m
3 o
-
H
I-H
O
o :3"
Q. Q)
CD 3
.
O)
M CD
Q. "»
o __
o
\
CO
O
o
Dl
0. CD
— o
O CD
CD CD
— CD
3 ^
2. w
c
-M
^ ! i
(Q -
OJ
3- :
OU co-J
sii'ii
* *5
NO m
i c^
-> -<
<
33
i m m
O m
Z>
>D
O
m
------- |