SPA-450/4-77-001
CTOBER 1977
IOAQPS NO. 1.2-029 R)
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GUIDELINES FOR AIR QUALITY
MAINTENANCE PLANNING
AND ANALYSIS
VOLUME 10 (REVISED):
PROCEDURES FOR EVALUATING
AIR QUALITY IMPACT OF NEW
STATIONARY SOURCES
ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
of Air QuaJit> Planning and Standards
Research Triangle Park, North Carolina 2771 1
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EPA-450/4-77-001
(OAQPS NO. 1.2-029 R)
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I GUIDELINES FOR AIR QUALITY
_ MAINTENANCE PLANNING AND ANALYSIS
VOLUME 10 (REVISED):
PROCEDURES FOR EVALUATING
. AIR QUALITY IMPACT OF NEW
STATIONARY SOURCES
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by
Laurence J. Budney
Monitoring and Data Analysis Division
Source Receptor Analysis Branch
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
October 1977
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OAQPS GUIDELINE SERIES
This repo/t 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 non-profit organizationsin limited
quantitiesfrom the Library Services Office (MD-35), Research Triangle
Park, North Carolina 27711; or, for a fee, from the National Technical
Information Service, 5285 Port Royal Road, Springfield, Virginia 22161. |
The author, Laurence J. Budney, is on assignment to the Environmental
Protection Agency from the National Oceanic and Atmospheric Adminis- |
tration, U.S. Department of Commerce.
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Publication No. EPA-450/4-77-001 -
OAQPS Guideline No. 1.2-029 R
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FOREWORD
Through the publication of Guidelines for Air Quality Maintenance
Planning and Analysis, the U.S. Environmental Protection Agency provides
State and local agencies with information and guidance for the preparation
of Air Quality Maintenance Plans required under 40 CFR 51. The volumes
in this series are:
Volume
Volume
Volume
Volume
Volume
Volume
Volume
Volume
Volume
Volume
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
Designation of Air Quality Maintenance
Plan Preparation
Control Strategies
Areas
Land Use and Transportation Consideration
Case Studies in Plan Development
Overview of Air Quality Maintenance Area Analysis
Projecting County Emissions
Computer-Assisted Area Source Emissions Gridding
Procedure
Evaluating Indirect Sources
Procedures for Evaluating Air Quality
New Stationary Sources (original versi
Impact of
on titled
"Reviewing New Stationary Sources")
Volume 11: Air Quality Monitoring and Data Analysis
Volume 12: Applying Atmospheric Simulation Models to Air
Quality Maintenance Areas
Volume 13: Allocating Projected Emissions to Sub-County Areas
Appendixes A and B
Supplement: Accounting for New Source Performance
Standards
Volume 14: Designated Air Quality Maintenance Areas
Additional volumes may be issued.
iii
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PREFACE
This document is a revision of an earlier guideline1 for applying
screening techniques to estimate the air quality impact of new (proposed)
stationary sources. The revision is in a more readily useable format
and incorporates changes and additions to the technical approach. Also,
a simple screening procedure has been added. The techniques are appli-
cable to chemically stable, gaseous or fine particulate pollutants. An
important advantage of the techniques is that a sophisticated computer
is not required. A pocket or desk calculator will generally suffice.
If the analysis indicates that a more refined analysis is required,
the user is directed to the Guideline on Air Quality Models2.
ACKNOWLEDGMENTS
Credit is due Mr. Russell F. Lee, Project Officer for EPA on the
preparation of the original version of this document, who continued to
provide valuable technical assistance for this revision. Considerable
support and insight were also provided by Messrs. James L. Dicke, Joseph
A. Tikvart and William H. Keith.
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TABLE OF CONTENTS
Page
Fo rev/o rd iii
Preface iv
List of Tables vi
List of Figures vii
1. Introduction 1-1
2. Source Data 2-1
2.1 Emissions 2-1
2.2 Merged Parameters for Multiple Stacks 2-2
2.3 Topographic Considerations 2-3
3. Meteorological Data 3-1
13.1 Wind Speed and Direction 3-1
3.2 Stability 3-2
3.3 Mixing Height 3-4
B 3.4 Temperature 3-5
4. Estimating Source Impact on Air Quality 4-1
4.1 Simple Screening Procedure 4-1
4.2 Estimating Maximum Short-Term Concentrations 4-6
4.3 Short-Term Concentrations at Specified Locations 4-22
4.4 Annual Average Concentrations 4-27
4.4.1 Annual Average Concentration at a Specified
Location 4-28
4.4.2 Maximum Annual Average Concentration 4-31
4.5 Special Topics 4-32
4.5.1 Concentrations at Receptors on Elevated Terrain 4-32
4.5.2 Contributions from Other Sources 4-34
4.5.3 Long Range Transport 4-38
5. References 5-1
Appendix A: UNAMAP Dispersion Models
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LIST OF TABLES
Table Page
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3-1 Wind Profile Exponent as a Function of Atmospheric
Stability 3-2
3-2 Key to Stability Categories 3-3
4-1 Calculation Procedures to Use with Various Stack Heights 4-10 |
4-2 Downwind Distance to the Maximum Ground-Level Fumigation M
Concentration as a Function of Stack Height and Plume
Height. 4-17
4-3 Maximum Duration of Stability Classes for Selected I
Latitudes and Dates 4-25
4-4 Stability-Wind Speed Combinations that are Considered in
Estimating Annual Average Concentrations 4-30 |
4-5 Wind Speed Intervals Used by the National Climatic Center M
for Joint Frequency Distributions of Wind Speed, Wind I
Direction and Stability 4-30
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LIST OF FIGURES
Figure Page
4-1 Maximum xu/Q as a Function of Plume Height, H
(for use only with the Simple Screening Procedure). 4-4
4-2 Downwind Distance to Maximum Concentration and
Maximum xu/Q as a Function of Stability Class and
Plume Height (m); Rural Terrain. 4-41
4-3 Downwind Distance to Maximum Concentration and
Maximum xu/Q as a Function of Stability Class and
Plume Height (m); Urban Terrain. 4-42
4-4 Horizontal Dispersion Parameter (a ) as a Function
of Downwind Distance and Stability^Class; Rural
Terrain. 4-43
4-5 Vertical Dispersion Parameter (a ) as a Function
of Downwind Distance and Stability Class; Rural
Terrain. 4-44
4-6 Stability Class A; Rural Terrain xu/Q Versus Distance
for Various Plume Heights (H), Assuming Very Restric-
tive Mixing Heights (L). 4-45
4-7 Stability Class B: Rural Terrain xu/Q Versus Distance
for Various Plume Heights (H), Assuming Very Restric-
tive Mixing Heights (L). 4-46
4-8 Stability Class C; Rural Terrain xu/Q Versus Distance
for Various Plume Heights (H), Assuming Very Restric-
tive Mixing Heights (L). 4-47
4-9 Stability Class D; Rural Terrain xu/Q Versus Distance
for Various Plume Heights (H), Assuming Very Restric-
tive Mixing Heights (L). 4-48
4-10 Stability Class E; Rural Terrain xu/Q Versus Distance
for Various Plume Heights (H), Assuming Very Restric-
tive Mixing Heights (L). 4-49
4-11 Stability Class F; Rural Terrain xu/Q Versus Distance
for Various Plume Heights (H), Assuming Very Restric-
tive Mixing Heights (L). 4-50
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4-12 Stability Classes A and B; Urban Terrain xu/Q Versus
Distance for Various Plume Heights (H), Assuming Very I
Restrictive Mixing Heights (L). 4-51
4-13 Stability Class C; Urban Terrain xu/Q Versus Distance g
for Various Plume Heights (H), Assuming Very Restric-
tive Mixing Heights (L). 4-52
4-14 Stability Class D; Urban Terrain xu/Q Versus Distance "
for Various Plume Heights (H), Assuming Very Restric-
tive Mixing Heights (L). 4-53
4-15 Stability Class E; Urban Terrain xu/Q Versus Distance
for Various Plume Heights (H), Assuming Very Restric- M
tive Mixing Heights (L). 4-54 J
4-16 Isopleths of Mean Annual Afternoon Mixing Heights. 4-55
4-17 Isopleths of Mean Annual Morning Mixing Heights. 4-56
4-18 24-Hour x/Q Versus Downwind Distance, Obtained from
the Valley Model. 4-57 |
4-19 Maximum xu/Q as a Function of Downwind Distance and «
Plume Height (H), Assuming a Mixing Height of 500
meters; D Stability 4-58 m
4-20 Maximum xu/Q as a Function of Downwind Distance and I
Plume Height (H); E Stability. 4-59
vin
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1. INTRODUCTION
m Pursuant to Clean Air Act requirements for new sources, addressed
in Title 40 of the Code of Federal Regulations (40 CFR 51.18: Review of
New Sources and Modifications), States are required to enact legally
enforceable review procedures to prevent the construction of pollutant
sources that would result in noncompliance with an approved State
I control strategy, or would cause or contribute to ambient concentrations
in excess of National Ambient Air Quality Standards. A review procedure
for a "major" new stationary source must include an air quality analysis
to estimate the impact of the source on ambient air quality. This
document presents a three-phase approach* that is applicable to the air
I quality analysis:
Phase 1. Apply a simple screening procedure (Section 4.1) to
determine if either (1) the source clearly poses no
air quality problem or (2) the potential for an air
quality problem exists.
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Phase 2. If the simplified screening results indicate a potential
threat to air quality, further analysis is warranted, and
I the detailed screening (basic modeling) procedures described
in Sections 4.2 through 4.5 should be applied.
I Phase 3. If the detailed screening results or other factors
indicate that a more refined analysis is necessary, refer
to the Guideline on Air Quality Models2.
The simple screening procedure (Phase 1) is applied to determine if
the source poses a potential threat to air quality. The purpose of
| applying a simple screening procedure is to conserve resources by elimi-
nating from further consideration those sources that clearly will not
*The techniques described herein can also be used, where appropriate,
to review sources to prevent significant air quality deterioration,
addressed in 40 CFR 52.21 (Significant Deterioration of Air Quality).
1-1
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when:
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cause or contribute to ambient concentrations in excess of short-term
air quality standards or allowable concentration increments. A rela-
tively large degree of "conservatism" is incorporated in that screening
procedure to provide reasonable assurance that maximum concentrations
will not be underestimated.
If the source is not eliminated by the simple screening procedure, if
a detailed screening analysis is then conducted (Phase 2). The Phase 2
analysis will yield a somewhat conservative first approximation (albeit
less conservative than the simple screening estimate) of the source's
maximum impact on air quality. If the Phase 2 analysis indicates that
the new source does not pose an air quality problem, further modeling m
may not be necessary. However, there are situations in which analysis m
beyond the scope of this document (Phase 3) may be required; for example,
1. The accuracy of the estimated concentrations must be maximized
(e.g., if the results of the Phase 2 analysis indicate a
potential air quality problem).
2. The source configuration is complex. m
3. Emission rates are highly variable.
4. Pollutant dispersion is significantly affected by nearby
terrain features or large bodies of water.
In most of those situations., more refined analytical techniques, such
2 "
as computer-based dispersion models , can be of considerable help in
estimating air quality impact.
In all cases, particularly when proceeding beyond the scope of this
guideline, the services of knowledgeable, well-trained air pollution
engineers, meteorologists and air quality analysts should be engaged.
An air quality simulation model applied improperly can lead to serious
misjudgments regarding the source impact.
1-2
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2. SOURCE DATA
In order to estimate the impact of a stationary point source on air
quality, certain characteristics of the source must be known. As a
minimum, the following information should Generally be available:
Pollutant emission rate;
t Stack height;
Stack gas temperature and volume flow rate (for plume rise
calculations);
Location of the point of emission with respect to surrounding
topography, and the character of that topography;
« A detailed description of all structures in the vicinity of
(or attached to) the stack in question. (See the discussion
of aerodynamic downwash in Procedure 4(f) on page 4--18.)
Similar information from other significant sources in the
vicinity of the subject source (or air quality data or
dispersion modeling results that demonstrate the air quality
impact of those sources).
2.1 Emissions
The analysis of air quality impact requires that the emissions from
each source be completely characterized. If the pollutants are not
emitted at a constant rate (most are not), information should be obtained
on how emissions vary with season, day or the week, and hour of the day.
In most cases, emission rates vary with the source production rate or
rate of fuel consumption. For example, for a coal-fired power plant,
emissions are related to the kilowatt-hours of electricity produced,
which is proportional to the tonnage of coal used to produce the electri-
city. If pollutant emission data are not directly available, emissions
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can be estimated from fuel consumption or production rates by multi-
45
plying the rates by appropriate emission factors. ' Emission factors
can be determined using three different methods. They are listed below
in decreasing order of confidence: I
1. Stack-test results or other emission measurements from an
identical or similar source.
2. Material balance calculations based on engineering knowledge
of the process.
3. Emission factors derived for similar sources or obtained from
a compilation by the U.S. Environmental Protection Agency.5 m
In cases where emissions are reduced by control equipment, the
effectiveness of the controls must be accounted for in the emissions jj
analysis. The source operator can estimate control effectiveness in
reducing emissions and how this effectiveness varies with changes in
plant operating conditions. EPA Report No. APTD-1570 is a compilation
of the types of control and control efficiencies for a variety of types
of sources that are reported in the National Emissions Data System I
(NEDS). More detailed guides to the available types and degrees of
control may be found in standard references.
7-16 §
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2.2 Merged Parameters for Multiple Stacks
Sources that emit the same pollutant from several similar stacks
that are within about 100 meters of each other may be analyzed by treat-
4 I
ing all of the emissions as coming from a single representative stack .
For each stack compute the parameter K:
hVT
2-2
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where K = an arbitrary parameter accounting for the relative influence
of stack height, plume rise, and emission rate on concentrations
h = stack height (m)
12 3
V = (u/4) d v = stack gas volume flow rate (m /sec)
d = stack exit diameter (m)
vs
T = stack gas exit temperature (K)
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v = stack gas exit velocity (m/sec)
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Q = pollutant emission rate (g/sec)
I The stack that has the lowest value of K is used as a "representative"
stack. Then the sum of the emissions from all stacks is assumed to be
emitted from the representative stack; i.e., the equivalent source is
fl characterized by h-, , V-j , T , and Q, where subscript 1 indicates the
representative stack and Q = Q-, + Qo + + Qn-
| The parameters from dissimilar stacks should be merged with caution.
For example, if the stacks are located more than about 100 meters apart,
* or if stack heights or volume flow rates differ by more than about 20
f percent, the resulting estimates of concentrations due to the merged
stack procedure may be unacceptably high.
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M 2.3 Topographic Considerations
* It is important to study the topography in the vicinity of the
source being analyzed. Topographic features, through their effects on
plume behavior, will sometimes be a significant factor in determining
I ambient ground-level pollutant concentrations. Important features to
note are the locations of large bodies of water, elevated terrain,
valley configurations, and general terrain roughness in the vicinity of
the source.
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Section 4.5.1 provides guidance on estimating ambient concentra- |
tions at receptors located on elevated terrain features. Any other ^
topographic considerations are beyond the scope of this guideline. *
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3. METEOROLOGICAL DATA
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Each computational procedure given in Section 4 for estimating the
I impact of a stationary source on air quality requires data on one or
more of the following meteorological parameters:
Wind speed and direction
t Stability class
t Mixing height
I Temperature
A discussion of each of those parameters and their relation to the
procedures of Section 4 follows.
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3.1 Wind Speed and Direction
| Wind speed and direction data are required to estimate short-term
_ peak and long-term average concentrations. The wind speed determines
(1) the amount by which a plume is diluted as it leaves the stack and
I (2) the plume rise downwind of the stack. These factors, in turn,
affect the magnitude of and distance to the maximum ground-level con-
P centration.
_ Most wind data are collected near ground level. The wind speed at
plume height can be estimated from the following power law equation:
u = i
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where:
u = the wind speed (m/sec) at height h,
u, = the wind speed at the anemometer height z,, and
p = the stability-related exponent from Table 3-1.
Table 3-1. WIND PROFILE EXPONENT AS A FUNCTION OF ATMOSPHERIC STABILITY |
Stability Class Exponent
A 0.10
B 0.15 I
C 0.20 m
D 0.25 *
E, F 0.30 ft
The wind direction is an approximation to the direction of trans- |
port of the plume. The variability of the direction of transport over a _
period of time is a major factor in estimating ground-level concentra- "
tions averaged over that time period.
Wind speed and direction data from National Weather Service, Air
Weather Service, and Naval Weather Service stations are available from |
the National Climatic Center, Asheville, North Carolina. Wind data are
often also recorded at existing plant sites and at air quality moni-
toring sites. It is important that the equipment used to record such
data be properly designed, sited, and maintained to record data that are
reasonably representative of the direction and speed of the plume. I
3.2 Stability |
Stability categories, as depicted in Tables 3-1 and 3-2, are measures
of atmospheric turbulence. The stability category at any given time will
3-2
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Table 3-2. KEY TO STABILITY CATEGORIES
1
Surface Wind
Speed at a
Height of 10m
(m/sec)
< 2
2-3
3-5
5-6
> 6
Day
Incoming Solar Radiation*
(Insolation)
Strong
A
A-B
B
C
C
Moderate
A-B
B
B-C
C-D
D
Slight
B
C
C
D
D
Night
Thinly Overcast
or
> 4/8 Low
Cloud Cover
E
D
D
D
< 3/8
Cloud
Cover
F
E
D
D
The neutral class (D) should be assumed for all overcast conditions during day
or night.
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*Appropriate insolation categories may be determined through the use of sky cover
and solar elevation information as follows:
Sky Cover
4/8 or Less or
Any Amount of
High Thin Clouds
5/8 to 7/8 Middle
Clouds (7000 feet to
16,000 foot base)
5/8 to 7/8 Low
Clouds (less than
7000 foot base)
Solar Elevation
Angle > 60°
Strong
Moderate
Slight
Solar Elevation
Angle < 60°
But >35°
Moderate
Slight
Slight
Solar Elevation
Angle < 35°
But > 15°
Slight
Slight
Slight
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depend upon static stability (the change in temperature with height), |
thermal turbulence (caused by heating of the air at ground level), and
mechanical turbulence (a function of wind speed and surface roughness).
It is generally estimated by a method given by Turner , which requires B
information on solar elevation angle, cloud cover, ceiling height, and
wind speed (see Table 3-2). 9
The solar elevation angle is a function of the time of year and the
time of day, and is presented in charts in the Smithsonian Meteorologi-
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cal Tables . The hourly weather observations of the National Weather A
Service include cloud cover, ceiling height, and wind speed. These data
are available from the National Climatic Center. |
For computation of seasonal and annual concentrations, a joint fre-
quency distribution of stability class, wind direction, and wind speed
(stability wind rose) is needed. Such frequency distributions can be ft
obtained from the National Climatic Center.
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3.3 Mixing Height _
The mixing height is the distance above the ground to which rela- *
tively free vertical mixing occurs in the atmosphere. When the mixing
height is low (but still above plume height) ambient ground-level con-
centrations will be relatively high because the pollutants are prevented |
from dispersing upward. For estimating long-term average concentration,
it is generally adequate to use an annual-average mixing height rather
than daily values.
Mixing height data are generally derived from surface temperatures
and from the twice-daily upper air soundings which are made at selected I
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mixing heights is one developed by Holzworth . Tabulations and sum-
maries of mixing height data can be obtained from the National Climatic
Center,
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National Weather Service Stations. The procedure used to determine
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3.4 Temperature
I Ambient air temperature must be known in order to calculate the
amount of rise of a buoyant plume. Plume rise is proportional to a
fractional power of the temperature difference between the stack gases
and the ambient air (see Section 4.2). Ambient temperature data are
collected hourly at National Weather Service Stations, and are available
from the National Climatic Center.
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4. ESTIMATING SOURCE IMPACT ON AIR QUALITY
| A three-phase approach, as discussed in the Introduction, is
B recommended for estimating the air quality impact of a proposed major
* source:
Phase 1. Simple screening analysis
Phase 2. Detailed screening (basic modeling) analysis
| Phase 3. Refined modeling analysis*
_ This section presents the simple screening procedure (Section 4.1) and
the detailed screening procedures (Sections 4.2 through 4.5). All of
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the procedures, with the partial exception of Section 4.5.1, are based
upon the bi-variate Gaussian dispersion model assumptions described in
the Workbook of Atmospheric Dispersion Estimates . A consistent set of
_ units (meters, grams, seconds) is used throughout:
Distance (m)
I Pollutant Emission Rate (g/sec)
o
Pollutant Concentration (g/m )
g Wind Speed (m/sec)
4.1 Simple Screening Procedure
The simple screening procedure is the "first phase" that is recom-
mended when assessing the air quality impact of a new point source. The
I purpose of this screening procedure is to eliminate from further considera-
_ tion those sources that clearly will not cause or contribute to ambient
condentrations in excess of short-term air quality standards.
*The Phase 3 analysis is beyond the scope of this guideline, and the
user is referred to the Guideline on Air Quality Models
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The scope of the procedure is confined to point sources, plume
heights of 10 to 300 meters ana concentration averaging times of 1 to 24
hours. The procedure is particularly useful for sources where the
short-term air quality standards are the "controlling" ones; i.e., in
cases where meeting the short-term standards provides good assurance of
meeting the annual standard for that pollutant. Elevated point sources
(i.e., sources for which the emission points are well above ground
level) are often in that category, particularly when they are remote
from other sources.
When applying the screening procedure to elevated point sources,
the following assumptions apply: £
1. No aerodynamic downwash of the effluent plume occurs. (Refer
to Procedure 4(f) on page 4-10 to determine if downwash is
a potential problem.)
2. The plume does not intercept terrain. (Refer to Section 4.5.1
to determine if terrain may be intercepted.)
If the potential for either of those problems is found to exist, the
calculation procedure described in the indicated section should be
applied (in addition to the screening procedure described in this sec-
tion) to estimate the resulting maximum ground-level concentration.
Except for sources close to ground level, the calculation procedures for
aerodynamic downwash and terrain interception will tend to yield higher
concentration estimates than the simple screening procedure.
The screening procedure utilizes the Gaussian dispersion equation
to estimate the maximum 1-hour ground-level concentration likely to
result from the source in question (Computations 1-6 below). To obtain
concentrations for other averaging times up to 24 hours, multiply the
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one-hour value by an appropriate factor (Computation 7). Then account
for background concentrations (Computation 8) to obtain a total concen-
tration estimate. That estimate is then used, in conjunction with any
downwash or terrain estimates, to determine if further analysis of the
source impact is warranted (Computation 9):
1. Compute the normalized plume rise (uAh), utilizing the pro-
cedure described in Step 1 on page 4-7.
2. Divide the uAh value obtained in (1) by each of five wind
speeds (u = 0.5, 1.0, 2.0, 3.0 and 5.0 m/sec) to estimate the actual
I plume rise (Ah) for each wind speed:
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An = meters
3. Compute the plume height (H) that will occur during each wind
speed by adding the respective plume rises to the stack height (h ):
H = h + Ah meters
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4. For each plume height computed in (3), estimate a x^/Q value
from Figure 4-1.
5. Divide each xu/Q value by the respective wind speed to deter-
mine the corresponding x/Q values:
6. Multiply the maximum x/Q value obtained in (5) by the emission
rate Q (g/sec), and incorporate a factor of 2 margin of safety, to
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obtain the maximum 1-hour ground-level concentration x-i (g/i» ) due to
emissions from the stack in question:
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10''
10-4
E
a
10
-5
io-
10
20
50 100 200
PLUME HEIGHT, m
500
1000
Figure 4-1. Maximum xu/Q as a function of plume height, H (for use only
with the simple screening procedure).20
4-4
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X-, = 2Q[X/Q]
« The margin of safety is incorporated in the screening procedure to
account for the potential inaccuracy of concentration estimates obtained
through calculations of this type.
If more than one stack is being considered, and the procedure for
fl merging parameters for multiple stacks is not applicable (Section 2.2),
0 (1) through (6) must be applied for each stack separately. The maximum
values (x-i) found for each stack are then added together to estimate the
I total maximum 1-hour concentration.
7. To obtain a concentration estimate (x_) for an averaging time
|P
greater than one hour, multiply the one-hour value by an appropriate
i factor R. (See the discussion in Step 5 on page 4-2Q, which addresses
multiplication factors for averaging times longer than one hour.)
I 8. Next, contributions from other sources (B) should be taken into
H account, yielding the final screening procedure concentration estimate
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xp = Xl (R)
x = Y + B
Amax Ap
Guidance on estimating concentrations due to other sources is provided
in Section 4.5.2.
9. Based on the estimate of xmax and (if applicable) estimates of
concentrations due to downwash or terrain problems, determine if further
4-5
-------
analysis of the source is warranted: If any of the estimated concentra-
tions exceeds the air quality level of concern (e.g., an air quality
standard';, proceed to Seccion 4.2 for further analysis. If the con-
^ , , + 4-U k
contrafons -v^e hpmw t^p !pyp| of concern, the source can be safely
assumed to pose no threat to that air quality level, and no further
analysis is necessary.*
4.2 Estimating Maximum Short-Term Concentrations
The basic modeling procedures described in the remainder of this I
guideline comprise the recommended "second phase" (or detailed screening)
that may be used in assessing new source air quality impact. The proce-
dures are intended for application in those -uses where the simple
screening procedure (first phase) indicates a potential air quality
problem.
Two parallel approaches are offered. Primary emphasis is given to
an approach that can be applied without the aid of a computer (a pocket
or desk calculator will suffice). The alternative approach, which is
only applicable in certain cases, io to use a series of computer programs
that has been made available by EPA. The series of programs, referred
to as UNAMAP ("User's Network for Applied Modeling of Air Pollution"), is
available through a commercial teleprocessing network and it can be
accessed by remote terminal. Alternatively, a magnetic computer tape of
the UNAMAP programs may be pruchased from the National Technical Informa-
tion Service. (See Appendix A for more information about UNAMAP).
I
*A relatively large degree of "conservatism" is incorporated in the simple
screening procedure and in the procedures for downwash and terrain
situations to provide reasonable assurance that maximum concentrations
will not be underpstimated.
4-6
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This section (4.2) presents the basic procedures for estimating
maximum short-term concentrations for specific meteorological situa-
21 22 23
tions. In Steps 1-3, plume rise ' ' and critical wind speed are
computed. In Step 4, maximum 1-hour concentrations are estimated. In
Step 5, the 1-hour concentrations are used to estimate concentrations
for averaging times up to 24 hours. Contributions from other sources
are accounted for in Step 6.
If aerodynamic downwash is a problem at the facility (see Procedure
4(f) on page 4-18) or if the UNAMAP computer programs are to be used,
begin with Step 4. For area sources, refer to Section 4.5.2 (C) for
guidance. Otherwise, proceed with Step 1:
Step 1. Estimate the normalized plume rise (uAh) that is appli-
cable to the source during neutral and unstable atmospheric conditions.
First, compute a buoyancy term F:
F = * vs d£
= 3.12 V
Ts-Ta
where g
vs
d
= acceleration of gravity (9.8 m/sec )
= stack gas exit velocity (m/sec)*
= inside stack diameter (m)
= stack gas temperature (K)*
*If stack gas temperature or exit velocity data are unavailable, they
may be approximated from guidelines that present typical values for
those parameters for existing plants2**.
4-7
-------
T = ambient air temperature («) (If no ambient temperature data
are available, assume that T = 293 K.) m
3 I
V = actual stack gas flow rate (m /sec)
Normalized plume rise is then given by: B
I
uAh = 21.4F3/4 when F < 55 m4/sec3
uAh = 38.7F3/5 when F >_ 55 m4/sec3
Step 2. Estimate the critical wind speed (u ) applicable to the m
I
source during neutral and unstable atmospheric conditions. The critical
wind speed is a function of two opposing effects that occur with in-
creasing wind speed; namely, increased dilution of the effluent as it
leaves the stack (which tends to decrease the maximum impact on ground-
level concentrations) and suppression of plume rise (tending to increase
the impact). The wind speed at which the interaction of those opposing
effects results in the highest ground-level concentration is the crit-
ical wind speed.
The critical wind speed can be estimated through the following
approximation:
u =
I
Step 3. For sources where the height of emission is greater than
or equal to 50 meters, proceed to Step 4. If the emission height is
less than 50 meters, stable atmospheric conditions may be critical. |
The stable case plume rise (Ah) should be estimated as the smaller of
the following two values: (The second value is the limiting case for
calm and near calm conditions.)
4-8
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1/3
Ah = 2.4
a
AG
Ah = 5F
1/4
£ Ai
T. AZ
-3/8
The value ||- is the change in potential temperature with height. If
typical values of ^- are not known for the site, a value of 0.02 K/m for
AZ
E stability, and 0.035 K/m for F stability may be used for sources with
stacks less than about 100m high. For stacks more than 100m high, use
0.01 K/m and 0.02 K/m respectively.
Step 4. Estimate maximum 1-hour concentrations that will occur
during various dispersion situations. (Note: UNAMAP users begin with
this step.) First, using Table 4-1 as a guide, determine the dispersion
situations and corresponding calculation procedures applicable to the
source being considered. Then apply the applicable calculation pro-
cedures, which are described on the following pages, in order to esti-
mate maximum 1-hour concentrations. Then proceed to Step 5 on page 4-
20.
4-9
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Table 4-1.
Height of Emission
(stack height)
h >50 meters
s ~
10 < h <50 meters
s
h <10 meters
s
hs
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Procedure 4(a): Looping Plume
During very unstable conditions the plume from a stack will be
mixed to ground level relatively close to the source, resulting in high
short-term concentrations. Such a plume is called a looping plume
because of its appearance.
Calculation Procedure:
1. Estimate plume height H, using the values of uAh and u computed
I in Steps 1 and 2 on pages 4-7 and 4-8:
H = 2 hs if uc <_ 3.0 m/sec
I
H = h + "-^f1 if u > 3.0 m/sec
S o. U C
2. Determine the maximum xu/Q from Figure 4-2 (for the rural case)
using the A stability curve, or from Figure 4-3 (urban case) using the
A-B stability curve.
3. Compute the maximum 1-hour concentration
= -
Cxu/Q]
If the computed value of u is greater than 3, set it equal to 3.
An alternate procedure using the UNAMAP series of computer programs
may be applied:
| 1. Using the P1MAX program, enter the emission rate, stack height,
_ stack gas temperature and either the actual stack gas volume flow rate
or the stack diameter and stack gas exit velocity.
2. Assume stability class A.
3. Select the highest 1-hour concentration printed.
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Procedure 4(b): Limited Mixing
Limited mixing (also called plume trapping) occurs when a stable |
layer aloft limits the vertical mixing of the plume. The result can be H
relatively high ground-level concentrations that may persist for hours.
The highest concentrations occur when the mixing height is at or slightly I
above the plume height.
Calculation Procedure: |
1. Estimate plume height H, using the uAh value computed in Step 1
on page 4-7:
H = hs , ^
I
*
The value 2.5 represents the assumed critical wind speed (m/sec).
2. Using the curve for stability C on Figure 4-2 (rural) or Figure
4-3 (urban), determine the maximum 1-hour -
-------
1
1
1
1
1
1
1
1
1
Procedure
Some
4(c) : Coning Plume
buoyant plumes will have their greatest impact on ground-level
concentrations during neutral or near-neutral conditions (coning plume).
Calculation procedure:
1.
2.
Assume that plume height is equal to twice the stack height:
H = 2 h
s
Using the curve for stability C on Figure 4-2 (rural) or Figure
4-3 (urban), determine the maximum 1-hour xu/l| for that plume height.
3.
Compute the maximum 1-hour concentration x-i » using the value of
u computed in Step 2 on page 4-8:
If uc is
expect at
x-, = Q[xu/Q]/uc
substantially greater than wind speeds that one could reasonably
plume height, a more reasonable critical wind speed (u ') may
be specified, and the equation H = h + [uAh]/u ' used for Step 1 and x-i
1
1
1
1
1
= Q[xu/Q]/uc' used for Step 3.
Caution: Wind speeds aloft are generally higher than at the surface,
so that a
common at
wind speed that is rare at the surface may be relatively
plume height.
Alternate procedure using the UNAMAP computer programs:
1.
stack gas
the stack
Using the PTMAX program, enter the emission rate, stack height,
temperature, and either the actual stack gas volume flow or
diameter and stack gas exit velocity.
4-13
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2. Assume stability class C. _
3. Select the highest 1-hour concentration printed.
H = hg + Ah
x-, = [xu/Q] Q/u
and select the highest concentration computed.
4-14
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Procedure 4(d): Fanning Plume
Low-level sources (i.e., sources with stack heights less than about
50 ni) sometimes produce the highest concentrations during stable atmos-
pheric conditions. Under such conditions, the plume's vertical spread I
is severely restricted and horizontal spreading is also reduced. This
results in what is called a fanning plume.
Calculation procedures:
A. For low-level sources with some plume rise, calculate the con-
centration as follows:
1. Compute the plume height (H) that will occur during F
stability (for rural cases) or E stability (for urban cases) and for
wind speeds of 2, 3 and 5 m/sec. Use the stable-case plume rise (Ah)
values obtained in Step 3 on page 4-8:
2. For each wind speed and stability considered in (1), find
the maximum 1-hour xu/Q from Figure 4-2 (rural) or 4-3 (urban). Compute
the maximum 1-hour concentration for each case, using
*
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B. For low-level sources with no plume rise (H = h ), find the |
maximum 1-hour /u/Q from Figure 4-2 (rural caseassume F stability) or .
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4-3 (urban caseassume E stability). Compute the maximum 1-hour con-
centration, assuming that u = 1 m/sec:
X-, = Cxu/Q] Q/u
Alternate procedure using the UNAMAP computer programs:
1. Using PTMAX, follow the procedure given for the "Looping
Plume Model," except apply the procedure for stabilities E and F.
2. If the minimum distance at which the concentration is of
concern (e.g., the distance to the closest point at which the general
public has access) is greater than the distances indicated in the PTMAX
program output, apply the PTDIS model (see Appendix A) and specify the
minimum distance of concern.
3. Select the highest of the 1-hour concentrations computed.
Procedure 4(e): Fumigation
(Note: UNAMAP is not applicable to the fumigation situation.)
Fumigation occurs when a plume that was originally emitted into a
stable layer is mixed rapidly to ground-level when unstable air below
the plume reaches plume level. Fumigation can cause very high ground-
level concentrations. Typical situations in which fumigation occurs
are:
1. "Burning off" of the nocturnal radiation inversion by
solar warming of the ground surface;
2. Advection of pollutants from a stable rural environment
to a turbulent urban environment;
3. "Shoreline fumigation" caused by advection of pollutants V
from a stable marine environment to an unstable inland
environment.
4-15
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The following procedure is for estimating concentrations only due
to the first type of fumigation listed above. (The second and third
25
types can also result in high concentrations . However, procedures
for estimating concentrations during those situations are beyond the
scope of this document.)
1. Compute the plume height (H) that will occur during f stability
and a wind speed of 2.5 m/sec:
H = hs + Ah
I
To obtain a value for Ah, use the procedure described in Step 3 on
page 4-8.
2. Using Table 4-2 (derived from Turner's fumigation procedure ),
estimate the downwind distance at which the maximum fumigation concentra-
tion is expected to occur. (If this distance is less than about 2
kilometers, fumigation concentrations are not likely to significantly 8
exceed -the limited mixing concentrations estimated in Procedure 4(b).)
3. At the distance estimated in (2), determine the values of a
and a for F stability from Figures 4-4 and 4-5.
4. Compute the maximum concentration (;
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I O
C_3 O)
Z l/l
00 r\J
=c
II
z:
o a
iI LU
H- LU
g £
z: a
LU z:
o >i
o a
z: <:
o
>-. u_
S t^
H-( ^f
S I
rs o
s
00
ii CD
X >i
LU LU
" 1
O Q-
C/1
H*
a
a
rc
o
a.
a o
a;
o
o
CO
LO
r^
CM
o
LO
i-nr r-
OOOOOOrOOOCOOOCMCMCMi i
i i i oo^i^LOoOi r~- co i i
COCOCOOOfMCMCMCMCMi i
CXJCMCMOJCMCMCMi i i
CMCMi OOIC^LOCMCT) I I I I
CMCMCMCMi i i i
CO CO CM O CO LO I
o en CT^ oo vo "si- i i i i i
«3
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Procedure 4(f): Downwash |
(Note: UNAMAP is not applicable to the downwash situation.) In
some cases, the aerodynamic turbulence induced by a building will cause
a pollutant emitted from an elevated source to be mixed rapidly toward
the ground (downwash), resulting in higher ground-level concentrations
immediately to the lee of the building than would otherwise occur. |
Thus, when assessing the impact of a source on air quality, the pos-
sibility of downwash problems should be investigated. If downwash is
found to be a potential problem, its effect on air quality should be
estimated.
The best approach to determine if downwash will be a problem at a I
proposed facility is to conduct observations of effluent behavior at a
similar facility. If such a study is not feasible, wind tunnel study is
recommended, particularly if the facility has a complex configuration.
If neither of the above approaches is feasible, and if the facility has
a simple configuration (e.g., a stack adjacent or attached to a single
oc
rectangular building), a simple rule-of-thumb may be applied to
determine the stack height (h ) necessary to avoid downwash problems:
h > h, + 1.5 a,
S D
where h, is building height and "a" is the lesser of either building
height or maximum building width. In other words, if the stack height
is equal to or greater than h, + 1.5 a, downwash is unlikely to be a
problem.
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4-18
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If there is more than one stack at a given facility, the above rule
may be successively applied to each stack. If more than one building is
involved, the rule may be successively applied to each building. For
relatively complex source configurations the rule may not be applicable,
particularly when the building shapes are much different than the simple
I rectangular building for which the above equation was derived.
If it is determined that the potential for downwash exists, the
next step is to estimate the maximum ground-level pollutant concentra-
tions that will occur as a result of the downwash. The impact of
downwash on ground-level concentrations will be a function of many
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factors, including building configuration, emission characteristics,
stack height, wind speed and wind direction. Generally, however, down-
wash will have its greatest impact when the effluent:
(1) has relatively little initial buoyancy or vertical momentum,
and
_ (2) is released from a point on the building itself or from a stack
that is close to the building (within about 3 to 5 building
heights) and substantially below the height (computed above)
that is necessary to avoid downwash.
In such a case, which may be considered a "worst case" condition for
downwash, the maximum 1-hour impact on ground-level concentrations (XT)
will occur within a few building heights of the downwind edge of the
127
building, and can be estimated by the following simple approximation
i
xl " 1.5
where Q is the maximum emission rate likely to occur for the averaging
time of concern, A is the cross-sectional area of the building normal to
4-19
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the wind, and u is wind speed. For u, one should choose the lowest wind |
speed likely to result in entrainment of most or all of the pollutant
into the downwash "cavity" in the lee of the building. If no data are
available from which that minimum wind speed can be estimated, assume a I
speed of 3 m/sec for the worst case.
It is important to recognize that the above equation for x-i is |
only applicable to the worst case described above. (Even for the worst _
case, the equation will tend to overpredict ground-level concentrations,
particularly for relatively tall sources.) For situations significantly B
different than the worst case, and for complex source configurations, a
28 29 8
more detailed analysis is required ' . |
Step 5. Obtain concentration estimates for the averaging times of
concern. The maximum 1-hour concentration is the highest of the concen- I
trations estimated in Step 4. For averaging times greater than one
hour, the maximum concentration will generally be less than that 1-hour |
value. The following discussion describes how that 1-hour value may be _
used to make an estimate of maximum concentrations for longer averaging
times. (This does not apply to the fumigation case described in Procedure
4(e)).
The rat^'o between a longer-term maximum concentration and a 1-hour |
maximum will depend upon the duration of the longer averaging time,
source characteristics, and local climatology and topography. Because *
of the many ways in which such factors interact, it is not practical to ft
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4-20
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_ categorize all situations that will typically result in ?ny specified
ratio between the longer-term and 1-hour maxima. Therefore, ratios are
presented here for a "general case" (where it is assumed that emissions
are constant and there are no terrain or downwash problems), and the
user is given some flexibility to subjectively adjust those ratios to
_ represent more closely any particular point source:
Averaging Time Multiplying Factor
3 hours 0.9 (+ 0.1)
I 8 hours 0.7 (+ 0.2)
24 hours 0.4 (+ 0.2)
To obtain the estimated maximum concentration for a 3, 8 or 24-hour
averaging time, multiply the 1-hour maximum by the given factor. The
numbers in parentheses are recommended limits to which one may diverge
_ from the multiplying factors representing the general case. For example,
if aerodynamic downwash or terrain is a problem at the facility, or if
the emission height is very low, it may be desirable to increase the
factors (within the limits specified in parentheses). On the other
g hand, if the stack is relatively tall and there are no terrain or down-
_ wash problems, it may be appropriate to decrease the factors.
The multiplying factors listed above are based upon general experi-
ence with elevated point sources. The factors are only intended as a
rough guide for estimating maximum concentrations for averaging times
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greater than one hour. A degree of conservatism is incorporated in the
factors to provide reasonable assurance that maximum concentrations for I
3, 8 and 24 hours will not be underestimated.
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Step 6. Add the expected contribution from other sources to the _
concentration estimated in Step 5. Concentrations due to other sources
can be estimated from measured data, or by computing the effect of I
existing sources on air quality in the area being studied. Procedures
for estimating such concentrations are given in Section 4.5.2. |
At this point in the analysis, a first approximation of maximum
short-term ambient concentrations (source impact plus contributions from
other sources) has been obtained. If concentrations at specified
locations, long-term concentrations, or other special topics must be
addressed, refer to applicable portions of Sections 4.3 to 4.5.
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4.3 Short-Term Concentrations at Specified Locations
In Section 4.2, maximum concentrations are generally estimated
without specific attention to the location(s) of the receptor(s). In
some cases, however, it is particularly important to estimate the impact
of a new source on air quality in specified (e.g., critical) areas. For
example, there may be nearby locations at which high pollutant concen-
trations already occur due to other sources, and where a relatively I
small addition to ambient concentrations might cause ambient standards
to be exceeded.
Each of the sources affecting a given location can be expected to
produce its greatest impact during certain meteorological conditions.
4-22
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The composite maximum concentration at that location due to the inter-
action of all the sources may occur under different meteorological
_
conditions than those which produce the highest impact from any one
source. Thus, the analysis of this problem can be difficult, and may
require substantial use of high-speed computers.
| Despite the potential complexity of the problem, some preliminary
calculations can be made that will at least indicate whether or not a
more detailed study is needed. For example, if the preliminary analysis
indicates that the estimated concentrations are near or above the air
quality standards of concern, a more detailed analysis will probably be
required.
m Calculation procedure (If the UNAMAP programs can be used, proceed
to the paragraph following Step 10 below. Otherwise, proceed with Step
I
Step 1 . Compute the normalized plume rise (uAh), utilizing the
procedure described in Step 1 on page 4-7.
Step 2. Divide the uAh value obtained above by each of several
wind speeds (u = 1, 3, 5, 10, and 20 m/sec) to estimate the actual plume
rise (Ah) associated with each wind speed:
.u (uAh)
Ah -
Step 3. Compute the plume height (H) that will occur during each
wind speed by adding the respective plume rises to the stack height
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H = h + Ah
Stability Class Wind Speed (m/sec)
H = hs + Ah
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Step 4. For each stability class-wind speed combination listed
below*, at the downwind distance of the "specified location," determine |
the xu/Q value from Figures 4-6 through 4-9 (rural) or Figures 4-12
through 4-14 (urban). Note in those figures (see the captions) that
very restrictive mixing heights are assumed, resulting in trapping of
the entire plume within a shallow layer.
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A 1,3 "
B 1, 3, 5
C 1, 3, 5, 10,
D 1, 3, 5, 10, 20 I
Step 5. (If the physical stack height is greater than 50 meters,
Steps 5 and 6 may be skipped.) Compute plume heights (H) for stability I
classes E and F, for wind speeds of 1, 3 and 5 m/sec:
I
where Ah is the plume rise as computed in Step 3 on page 4-8.
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*0nly consider those stability-wind speed combinations that can exist
for the length of time it takes the plume to travel to the location of V
interest, plus at least one hour. Refer to Table 4-3 for the maximum
durations of each stability class.
4-24
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Table 4-3. MAXIMUM DURATION OF STABILITY CLASSES FOR SELECTED
LATITUDES AND DATES
Latitude
30°N
40°N
50°N
Date
Dec 22
Feb 9, Nov 3
Mar 8, Oct 6
Apr 3, Sept 10
May 1 , Aug 12
Jun 22
Dec 22
Feb 9, Nov 3
Mar 8, Oct 6
Apr 3, Sept 10
May 1 , Aug 12
Jun 22
Dec 22
Feb 9, Nov 3
Mar 8, Oct 6
Apr 3, Sept 10
May 8, Aug 6
Jun 22
Maximum Duration of
Stability Class (Hours)*
A
0
0
0
2
4
4
0
0
0
0
2
4
0
0
0
0
2
4
B
2
4
6
7
8
8
0
1
5
6
7
8
0
0
1
5
7
8
C
7
8
9
10
11
12
6
7
9
10
11
12
2
6
8
10
11
12
E,F
16
15
14
14
13
12
17
16
14
13
12
11
18
17
15
13
11
10
*Based on duration of solar angle above or below following limits:
Class A - above 60°, Class B - above 35°, Class C - above 15°,
Class E and F - below 0°. (Two hours have been added to the duration
of solar angle below the horizon to account for the stable conditions
that begin to occur about an hour before sunset and persist for an
hour after sunrise.) For stability Classes A, B and C, the hours
are centered on solar noon. Stability D can persist, in all the
above cases, for periods in excess of 24 hours.
4-25
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Step 6. For each stability class-wind speed combination considered
in Step 5, at the downwind distance of the specified location, determine |
a yu/Q value from Figures 4-10 and 4-11 (or Figure 4-15 for the urban _
case). Also, refer to the Step 4 footnote.
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Step 7. For each xu/Q value obtained in Step 4 (and Step 6 if
applicable), compute x/Q- |
x/Q = Exu/Ql/u |
Step 8. Select the largest x/Q and multiply by the source emission
3
rate (g/sec) to obtain a 1-hour concentration value (g/m ):
Xl = QCx/Q]max I
Step 9 . (This step is not applicable if the downwind distance to
the specified location is either (1) less than 2 kilometers or (2) less
than the distance to the maximum fumigation concentration, obtained
from Table 4-2.) Compute the maximum 1-hour concentration, x.f» that
will occur due to fumigation (discussed in Procedure 4(e) on page 4-15)
using the following equation :
. I
f /2T u (0 + H/8)(H + 2oz) _
Assume a wind speed of 2.5 m/sec and stability class F. From Figures
4-4 and 4-5 obtain a and a values for the downwind distance in ques-
tion. Plume rise (used to determine H) is computed as in Step 3 on page
4-8.
4-26
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Step 10. The highest 1-hour concentration at the specified loca-
I tion (not accounting for contributions from other sources) is the larger
_ of the concentration values estimated in Steps 8 and 9. To estimate
concentrations for averaging times greater than one hour, take the 1-
hour value estimated in Step 8 only, and then refer to the averaging
time procedure described earlier (Step 5 on page 4-20). To account for
| contributions from other sources, see Section 4.5.2.
I If the UNAMAP series of computer programs is available, Steps 1
through 8 above can be accomplished as follows:
I 1. Using the PTMAX program, obtain plume heights (H) for each
wind speed-stability combination considered in Step 4 (and Step 5 if
applicable).
I 2. Using the PTDIS program, estimate the maximum concentra-
tion at the specified distance for each wind speed-stability combination
I considered in (1). For the mixing height input to PTDIS, use plume
height (H) for stabilities A-D (and for the E stability urban case) and
use 5000 meters for stabilities E and F (rural).
I 3. For the highest 1-hour concentration at the specified
location, use the largest value obtained in (2).
4.4 Annual Average Concentrations
J This section presents procedures for estimating annual average
ambient concentrations caused by a single point source. The procedure
for estimating the annual concentration at a specified location is
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UAh = 21.4 F when F < 55 nT/sec*
uAh = 38.7 F3/5 when F >_ 55 m4/sec3
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presented first, followed by a suggestion of how that procedure can be
expanded to estimate the overall maximum annual concentration (regard-
less of location).
The procedures assume that the emissions are continuous and at a I
constant rate. The data required are emission rate, stack height, stack
gas volume flow rate (or diameter and exit velocity), stack gas tern-
perature, average afternoon mixing height, and a representative stability
wind rose.* Refer to Sections 2 and 3 for a discussion of such data.
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4.4.1 Annual Average Concentration at a Specified Location
Calculation procedure:
Step T_. (Applicable to stability categories A through D) Using I
the procedure described in Step 1 on page 4-7, obtain a normalized plume
rise value (uAh): |
I
Step 2. (Applicable to stability categories E and F) Apply the I
following equation to estimate plume rise (Ah) as a function of wind
speed. Apply the equation for both stable categories (E and F) . Refer |
to Steps 1 and 3 on pages 4-7 and 4-8 for definition of terms in that
equation:
I
*The stability wind rose is a joint frequency distribution of wind speed,
wind direction and atmospheric stability for a given locality. Stability
wind roses for many locations are available from the National Climatic I
Center, Asheville, North Carolina.
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_
*
r
Ah = 2.4 a
M
AZ
1/3
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Step 3. Compute plume rise (Ah) for each stability-wind speed
category in Table 4-4 by (1) substituting the corresponding wind speed
for u in the appropriate equation from Step 1 or 2 above and (2) solving
the equation for Ah. The wind speeds listed in Table 4-4 are derived
I from the wind speed intervals used by the National Climatic Center
(Table 4-5) in specifying stability-wind roses.
Step 4. Compute plume height (H) for each stability-wind speed
I
of the plume rise values computed in Step 3:
category in Table 4-4 by adding the physical stack height (h ) to each
H = hs + Ah
Step 5. Estimate the contribution to the annual average concen-
tration at the specified location for each of the stability-wind speed
categories in Table 4-4. First, determine the vertical dispersion
coefficient (a ) for each stability class for the downwind distance (x)
I between the source and the specified location, using Figure 4-5. (Note:
For urban F stability cases, use the a for stability E.) Next, deter-
^^ 2
| mine the mixing height (L) applicable to each stability class. For
stabilities A to D, use the average afternoon mixing height for the area
(Figure 4-16). For urban stabilities E and F, use the average morning
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Table 4-4. STABILITY-WIND SPEED COMBINATIONS THAT ARE
CONSIDERED IN ESTIMATING ANNUAL AVERAGE CONCENTRATIONS
Atmospheric
Stability Categories
A
B
C
D
E
F
Wind Speed (m/sec)
1.5
*
*
*
*
*
*
2.5
*
*
*
*
*
*
4.5
*
*
*
*
7
*
*
9.5
*
*
12.5
*
*It is only necessary to consider the stability-wind speed conditions
marked with an asterisk.
Table 4-5. WIND SPEED INTERVALS USED BY THE NATIONAL CLIMATIC CENTER
FOR JOINT FREQUENCY DISTRIBUTIONS OF WIND SPEED,
WIND DIRECTION AND STABILITY
Class
1
2
3
4
5
6
Speed Interval ,
0 to 1.8
1.8 to 3.3
3.3 to 5.4
5.4 to 8.5
8.5 to 11.0
>n.o
m/sec (knots)
(0 to 3)
(4 to 6)
(7 to 10)
(11 to 16)
(17 to 21)
(>21)
Representative Wind
m/sec
1.5
2.5
4.5
7.0
9.5
12.5
Speed
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mixing height (Figure 4-17). For rural stabilities E and F, mixing
height is not applicable. Then, use that information as follows: For
all stability-wind conditions when the plume height (H) is greater than
(L), assume a zero contribution to the annual average concentration at
the specified location. For each condition when a < 0.8L, and for all
z
rural stability E and F cases, apply the following equation to estimate
o
the contribution C (g/m ):
c = 2.03 Q f
a U X
exp
1
2
For each condition during which a > 0.8L, the following equation is
applied:
r 2.55 Q f
L " L u x
In those equations:
Q = pollutant emission rate (g/sec)
u = wind speed (m/sec)
f = frequency of occurrence of the particular wind speed-stability
combination (obtained from the stability-wind rose) for the
wind direction of concern. Only consider the wind speed-
stability combinations for the wind direction that will bring
the plume closest to the specified location.
Step 6. Sum the contributions (C) computed in Step 5 to estimate
the annual average concentration at the specified location.
4.4.2 Maximum Annual Average Concentration
To estimate the overall maximum annual average concentration (the
maximum concentration regardless of location) follow the procedure for
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the annual average concentration at a specified location, repeating I
the procedure for each of several receptor distances, and for all
directions. Because of the large number of calculations required, it I
is recommended that a computer model such as the COM (Climatological
Dispersion Model) be used. The COM is a part of the UNAMAP series,
which is discussed in Appendix A. I
4.5 Special Topics
4.5.1 Concentrations at Receptors on Elevated Terrain |
Dispersion models developed for estimating maximum ground-level _
concentrations in complex terrain have not been adequately evaluated.
However, there is growing acceptance of the hypothesis that greater I
concentrations can occur on elevated than on flat terrain in the
vicinity of an elevated source.* That is particularly true when |
the terrain extends well above the plume centerline (plume height). «
A procedure is presented here to (1) determine whether or not
an elevated plume may intercept terrain and, (2) if terrain is likely I
to be intercepted, estimate the maximum 24-hour concentration. The
procedure is based largely upon the 24-hour mode of the EPA Valley |
Model . A concentration estimate obtained through the procedure will _
likely be somewhat greater than provided by the Valley Model, primarily
due to the relatively conservative plume height that is used in Step 1: B
*An exception may be certain flat terrain situations where aerodynamic I
downwash is a problem. (See Procedure 4(f) on page 4-18).
I
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1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Step 1. Determine if the plume is likely to intercept terrain in
the vicinity of the source:
(1) Compute one-half the plume rise (Ah/2) that can be expected
during F stability and a wind speed (u) of 2.5 m/sec. (The reason for
using only one-half the normally computed plume rise is to provide a
margin of safety in determining (1) if the plume may intercept terrain
and (2) the resulting ground-level concentration.):
Ah/2 = 1.2
"FT I1/3
a
uq
_
Refer to Steps 1 and 3 on pages 4-7 and 4-8 for definition of terms.
(2) Compute a conservative plume height (H ) by adding the
physical stack height (h )
to Ah/2:
HC = hs + Ah/2
(3) Determine if any terrain features in the vicinity of the
source are as high as H . If so, proceed with Step 2. If that is
not the case, the plume is not likely to intercept terrain, and Step 2
is not applicable.*
*Even if the plume is not
concentration averaging ti
to Account for terrain if
procedure for doing so is
all stabilities) by the el
location of the receptor(s
can then be used in conjur
procedures described earl i
likely to intercept terrain (and for all
mes of concern) the user should attempt
the terrain features are significant. A
to reduce the computed plume height H (for
evation difference between stack base and
;) in question. The adjusted plume heights
iction with the "flat-terrain" modeling
er .
.-:...
-------
I
Step 2. Estimate the maximum 24-hour ground-level concentration on I
elevated terrain in the vicinity of the source:
(1) Using a topographic map, determine the distance from the
source to the nearest ground-level location at the height H .
(2) Using Figure 4-18 and the distance determined in (a), estimate
a 24-hour x/Q value. I
(3) Multiply the (x/Q)24 value by the emission rate Q (g/sec) to
estimate the maximum 24-hour concentration XOA due to plume interception
of terrain:
x24 = (x/Q)24 (Q)
I
4.5.2 Contributions from Other Sources
To assess the significance of the air quality impact of a proposed
source, the impact of nearby sources and "background" must be specifically
determined. (Background includes those concentrations due to natural
sources and distant, unspecified man-made sources.) Then the impact of I
the proposed source can be separately estimated, applying the techniques
presented elsewhere in Section 4, and superimposed upon the impact of
the nearby sources and background to determine total concentrations in
the vicinity of the proposed source.
This section addresses the estimation of concentrations due to nearby
sources and background. Three situations are considered:
A. A proposed source relatively isolated from other sources.
B. A proposed source in the vicinity of a few other sources.
C. A proposed source in the vicinity of an urban area or other
large number of sources. _
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It must be noted that in all references to air quality monitoring
in the following discussion, it is assumed that the source in question
is not yet operating. If the source is emitting pollutants during the
period of air quality data collection, care must be taken not to use
monitoring data influenced by the impact of the source.
A. Relatively Isolated Proposed Source
A proposed source may be considered to be isolated if it is expected
that background will be the only other significant contributor to ambient
pollutant concentrations in its vicinity. In that case, it is recommended
that air quality data from monitors in the vicinity of the proposed
source be used to estimate the background concentrations. If monitoring
data are not available from the vicinity of the source, use data from a
"regional" site; i.e., a site that characterizes air quality across a
broad area, including that in which the source is located.
Annual average concentrations should be relatively easy to determine
from available air quality data. For averaging times of about 24 hours or
less, meteorology must be accounted for; i.e., it is necessary to ensure
that background concentration estimates are based on data collected during
the same meteorological situations as those during which the source is
expected to have its greatest impact on air quality.
B. Proposed Source in the Vicinity of a Few Other Sources
If there already are a few sources in the vicinity of the proposed
facility, the air quality impact of these sources should be accounted for.
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As long as the number of nearby sources is relatively small, the recom-
mended procedure is to use (1) air quality monitoring data to estimate
background concentrations and (2) dispersion modeling to estimate con-
centrations due to the nearby sources. Then superimpose those estimates
to determine total concentrations in the vicinity of the proposed source.
To estimate background concentrations, follow the same basic pro-
cedure as in the case of an isolated source. In this case, however,
there is one added complication. Wind direction must be accounted for
in order to single out the air quality data that represent background
only (i.e., data that are not affected by contributions from nearby
sources). I
Concentrations due to the nearby sources will normally be best
determined through dispersion modeling. The modeling techniques presented
in this guideline may be used. If the user has access to UNAMAP (see
Appendix A and references to UNAMAP in Section 4), the modeling effort
can be considerably simplified. If UNAMAP can not be used, the user
should model each source separately to estimate concentrations due to
each source during various meteorological conditions and at an array of
receptor locations (e.g., see Sections 4.3 and 4.4.1) where interactions
between the effluents of the proposed source and the nearby sources can
occur. Significant locations include (1) the area of expected maximum I
impact of the proposed source, (2) the area of maximum impact of the
nearby sources, and (3) the area where all sources will combine to cause
maximum impact. It may be necessary to identify those locations through
a trial and error analysis.
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C. Proposed Source in the Vicinity of an Urban Area or Other Large
fl Number of Sources
For more than a very small number of nearby sources, it may be
impractical to model each source separately. Two possible alternatives
for estimating ambient concentrations are to use air quality monitor
data or a multi-source dispersion model.
If data from a comprehensive air monitoring network are available,
it may be possible to rely entirely on the measured data. The data
should be adequate to permit a reliable assessment of maximum concentra-
tions, particularly in (1) the area of expected maximum impact of the
proposed source, (2) the area of maximum impact of the existing sources
and (3) the area where all sources will combine to cause maximum impact.
In some cases, the available air quality monitor data will only be
adequate to estimate general area-wide background concentrations. In
such cases, there is no choice but to use dispersion modeling to estimate
concentrations due to the nearby sources. If possible, a multi-source
dispersion model should be used. If the user has access to UNAMAP (see
Appendix A and references to UNAMAP in Section 4) the Climatological
I Dispersion Model (COM) can be applied for long-term concentration estimates
and the PTMTP model for short-term estimates (PTMTP can handle up to 25
point sources).
If it is not feasible to apply a multi-source model, and there is a
considerable number of nearby sources, a rough estimate of maximum
concentrations due to those sources can be made by arbitrarily grouping
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the sources into an area source through the following equation . (The
4-37
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estimate is primarily applicable to receptor locations near the center I
of the area source, defined below, although it may be considered a
reasonable first-approximation for any location within the area.):
C = 18 4 (4X)1/4 I
where:
I
C = maximum contribution to ground-level
concentrations (g/m3) m
Q = average emission rate (g/m2/sec) within the area
defined by Ax _
u = assumed average wind speed (m/sec) for the averaging
time of concern
Ax = length (m) of one side of the smallest square area that
will contain the nearby sources, ignoring relatively
small outlying sources or any source that is considerably
I
removed from the other sources.
The best results will be obtained with the above equation when emissions
are uniformly distributed over the defined area. Any large point sources
in the vicinity should be modeled separately, and the estimated concen-
trations manually superimposed upon that computed for the area source.
I
4.5.3 Long Range Transport
In certain instances it will be necessary to estimate the air
quality impact of a proposed source at locations beyond its vicinity
(beyond roughly 30-50 kilometers). To estimate seasonal or annual
average concentrations (out to about 100 kilometers) the procedures
of Section 4.4 will provide a rough estimate. Those procedures should
not be applied beyond 100 kilometers.
4-38
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1
For short-term estimates (concentration averaging times up to about
24 hours)
downwind,
beyond the vicinity of the source and out to 100 kilometers
the following procedure is recommended. The procedure accounts
for the meteorological situations likely to result in the highest concen-
1
1
1
1
trations
at large distances; viz., limited mixing conditions (Steps 1-
5) and stable conditions (Steps 6-9):
Step
1. Estimate the normalized plume rise (uAh) applicable to
neutral and unstable atmospheric conditions. Use the procedure
described
Step
Step
downwind
Step
using the
in Step 1 on page 4-7.
2. Compute plume height (H):
H - h + UAh
H ' hs 7.5
3. Using Figure 4-19, obtain a xu/Q value for the desired
distance (D stability case).
4. Compute the maximum 1-hour D stability concentration Y ,
max
xu/Q value obtained in Step 3:
xmax = 0- [xU/Q]
For Q, substitute the source emission rate (g/sec). The value 7.5 is
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1
the recommended wind speed (m/sec) for computations of x =, at large
IT)a X
distances
Step
under limited mixing conditions.
5. Estimate the plume rise (Ah) applicable to stable condi-
tions (stability class E), using the procedure described in Step 3 on
page 4-8.
Assume a wind speed equal to 4 m/sec.
4-39
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Step 6. Compute plume height (H):
H = hs + Ah *
Step 7. From Figure 4-20, obtain a xu/Q value for the same distance
considered in Step 3 above.
Step 8. Compute the maximum 1-hour E stability concentration x
a
I
ulaX
using the xu/Q value obtained in Step 7:
*max = 4 [xU/Q]
where 4 is the assumed wind speed (m/sec).
Step 9. Select the higher of the \ values computed in Steps 4
max
and 8. The selected value represents the highest 1-hour concentration
likely to occur at the specified distance.
M
Step 10. To estimate concentrations for averaging times up to
24 hours, multiply the 1-hour value by the factors presented in Step 5
on page 4-20.
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tfl
w
0)
c
o
r-t
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O
§
C
O
3
X
6
E
H
X
OS
C
o
(U E
u
C
01
a
c
o
u
e
H
X
to
a
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cfl
4-1
03
H
C!
rl
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CM
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oo
00
rl
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0)
a
H
n)
-------
0.1
10
-6
1Q-5 2 5
MAXIMUM Xu/Q, m'2
10-4
Figure 4-3. Downwind distance to maximum concentration and maximum xu/Q
as a function of s
are on the curves.
1 32
as a function of stability class for urban terrain. ' Plume heights (m)
4-42
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10,000
5,000
2,000
1,000
«, 200
o
100
.
10
0.1 0.2
s /
/ '' '
XXX
XXX
k x x
/ / XX
S ' ' s S
XX X x X
n
x x
S ' '
X x X
' '
' '
// / /
' '
' '
' X
' X
S
X
0.5 1 2 5 10 20
DOWNWIND DISTANCE, km
50 100
Figure 4-4. Horizontal dispersion parameter (ay) as a function of downwind distance and
stability class; rural terrainJ 7
-------
2,000
1,000
500
200
| 100
50
20
10
0.1 0.2
0.5 1 2 5 10
DOWNWIND DISTANCE, km
20
50 100
Figure 4-5. Vertical dispersion parameter (az) as a function of downwind distance and
stability class; rural terrain. 17
4-44
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0.1 0.2
0.5
12 5 10
DOWNWIND DISTANCE, km
20
50 100
Figure 4-6. Stability class A; rural terrain xu/Q versus distance for various
plume heights (H), assuming very restrictive mixing heights (L): L = 50 m
for H < 50 m; L = H for H > 50 m.
4-45
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10
0.2
0.5
12 5 10
DOWNWIND DISTANCE, km
20
50
100
Figure 4-7. Stability class B; rural terrain xu/Q versus distance for various
plume heights (H), assuming very restrictive mixing heights (L): L = 50 m
for H < 50 m; L = H for H > 50 m.
4-46
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10
iinWNWINU DISTANCE, km
Figuio48. ']l;ibility cl.iss C, nit.il leir.nn Ku/O vorsus distance (or various
plume liL'icjhts < 11), issuinin'i vn >/ ti'stic live 'nixuio h(.'i(|hts (I.): I r
(or H --50m. L H tor H 00 «n
ni
-------
0.1
0.2
0.5
12 5 10
DOWNWIND DISTANCE, km
20
50
100
Figure 4-9. Stability class D; rural terrain xu/Q. versus distance for various
plume heights (H), assuming very restrictive mixing heights (L): L = 50 m
for H < 50 m; L = H for H > 50 m.
4-48
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10
0.1
0.2
0.5
20
50
12 5 10
DOWNWIND DISTANCE, km
Figure 4-10. Stability class E; rural terrain \u/Q versus distance for various plume
heights (H), assuming very restrictive mixing heights (L): L = 50 m for H < 50 m,
L= H for H> 50m.
4-49
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10-2
12 5 10
DOWNWIND DISTANCE, km
20
50
100
Figure 4-11. Stability class F; rural terrain xu/Q versus distance for various
plume heights (H), assuming very restrictive mixing heights (L): L = 50 m
for H < 50 m; L = H for H > 50 m.
4-50
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0.1
0.5
2 5 10
DOWNWIND DISTANCE, km
20
50
100
Figure 4-12. Stability classes A and B; urban terrain \uiQ versus distance for various plume
heights (H), assuming very restrictive mixing heights (L): L = 50 m for H < 50 m; L = H
for H > 50 m.32
4-51
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10
0.2
0.5
20
50
12 5 10
DOWNWIND DISTANCE, km
Figure 4-13. Stability class C; urban terrain %u/Q versus distance for various plume heights (H),
assuming very restrictive mixing heights (L): L = 50 m for H < 50 m; L = H for H > 50 m.32
4-52
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0.5
12 5 10
DOWNWIND DISTANCE, km
20
50
100
Figure 4-14. Stability class D; urban terrain xu/Q versus distance for various plume heights
(H), assuming very restrictive mixing heights (L): L = 50 m for H < 50 m; L = H for
H>50m.32
4-53
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DOWNWIND DISTANCE, km
Figure 4-15. Stability class E; urban terrain xu/Q versus distance for various plume heights
(H), assuming very restrictive mixing heights (L): L = 50 m for H < 50 m; L = H for
H>50m.3Z
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0.1
0.2
2 5
DOWNWIND DISTANCE, km
10
20
50
100
Figure 4-18. 24-hour x/Q versus downwind distance, obtained from the Valley Modeled.
Assumptions include stability class F, a wind speed of 2.5 m/sec, and plume height 10
meters above terrain.
4-57
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10
20 SO
DOWNWIND DISTANCE, km
Figure 4-19. Maximum xu/Q as a function of downwind distance and plume
height (H), assuming a mixing height of 500 meters; D stability.
4-58
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10
Figure 4-20. Maximum
height (H); E stability.
20 50 100
DOWNWIND DISTANCE, km
as a function of downwind distance and plume
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5. REFLRENCES
1. U. S. Environmental Protection Agency, September 1974. Guidelines
for Air Quality Maintenance Planning and Analysis, Volume 10:
Reviewing New Stationary Sources. EPA-450/4-74-011 (OAQPS Number
1.2-029), Research Triangle Park, N. C. 27711.
2. U. S. Environmental Protection Agency, 1977. Interim Guideline on Air
Quality Models. Research Triangle Park, N. C. 27711.
3. U.S. Congress, August 1977. Clean Air Act Amendments of 1977 -
Public Law 95-95, Section 302 (j).
4. U. S. Environmental Protection Agency, 1973. Guide for Compiling
a Comprehensive Emission Inventory. Revised. Publication No.
APTD-1135, Research Triangle Park, N. C. 27711.
5. U. S. Environmental Protection Agency, 1975. Compilation of Air
Pollution Emission Factors. Second Edition, Publication No. AP-42,
Research Triangle Park, N. C. 27711.
6. Vatavuk, W. M., July 1973; National Emissions Data System Control
Device Workbook; Pub. No. APTD-1570; Research Triangle Park, N. C.
27711.
7. Danielson, J. A., Editor, 1973. Air Pollution Engineering Manual.
Second Edition. AP-40. U. S. Environmental Protection Agency,
Research Triangle Park, N. C. 27711.
8. Lund, H. F., Editor-in-Chief, 1971. Industrial Pollution Control
Handbook. McGraw-Hill Book Company, New York, N. Y.
9. Stern, A. C., Editor, 1968. Air Pollution, Second Edition, Volume
III. Academic Press, Inc., Ill Fifth Avenue, New York, N. Y. 10003.
10. U. S. DHEW, January 1969. Control Techniques for Particulate Air
Pollutants. AP-51, U. S. Government Printing Office, Washington,
D. C. 20402.
11. U. S. DHEW, January 1969. Control Techniques for Sulfur Oxide Air
Pollutants. AP-52; U. S. Government Printing Office, Washington,
D. C. 20402
12. U. S. DHEW, March 1970. Control Techniques for Carbon Monoxide
Emissions from Stationary Sources. AP-65; U. S. Government Printing
Office, Washington, D. C. 20402.
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13. U. S. DHEW, March 1970. Control Techniques for Nitrogen Oxide
Emissions from Stationary Sources. AP-67; U. S. Government
Printing Office, Washington, D. C. 20402.
U. S. DHEW, March 1970. Control Techniques for Hydrocarbon and
Organic Solvent Emissions from Stationary Sources. AP-68, U. S. |
Government Printing Office, Washington, D. C. 20402.
15. U. S. Environmental Protection Agency, 1971. Background for
Proposed New-Source Performance Standards: Steam Generators,
Incinerators, Portland Cement Plants, Nitric Acid Plants, Sulfuric
Acid Plants; APTD-0711; Research Triangle Park, N. C. 27711.
16. U. S. Environmental Protection Agency, 1973. Background Informa-
tion for Proposed New Source Performance Standards: Asphalt
Concrete Plants, Petroleum Refineries, Storage Vessels, Secondary |
Fuel Smelters and Refineries, Brass or Bronze Ingot Production
Plants, Iron and Steel Plants, Sewage Treatment Plants. Volume 1,
Main Text. Publication No. APTD-1352a, Research Triangle Park,
N. C. 27711.
17. Turner, D. B., 1970. Workbook of Atmospheric Dispersion Estimates.
Revised, Sixth printing, Jan. 1973. Office of Air Programs Publi-
cation No. AP-26. U. S. Environmental Protection Agency. U. S.
Government Printing Office, Washington, D. C. 20402.
18. List, R. J., 1951. Smithsonian Meteorological Tables. Sixth Revised
Edition. Smithsonian Institution, Washington, D. C. _
19. Holzworth, G. C., 1972. Mixing Heights, Wind Speeds, and Potential
for Urban Air Pollution Throughout the Contiguous United States.
Office of Air Programs Publication No. AP-101, U. S. Environmental
Protection Agency. U. S. Government Printing Office, Washington,
D. C. 20402.
20. Turner, D. B. and Martinez, E. L., 1973. A Simple Screening Technique |
for Estimating the Impact of a Point Source of Air Pollution Relative
to the Air Quality Standards. (NOAA manuscript) U. S. Environmental _
Protection Agency, Research Triangle Park, N. C. 27711.
21. Briggs, G. A., 1969. Plume Rise. USAEC Critical Review Series
TID-25075, National Technical Information Service, Springfield,
VA 22151.
22. Briggs, G. A., 1971. Some Recent Analyses of Plume Rise Observation. M
Pages 1029-1032 of the Proceedings of the Second International Clean |
Air Congress, edited by H. M Englund and W. T. Berry. Academic
Press, N. Y.
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23. Briggs, G. A., July 1972. Discussion on Chimney Plumes in Neutral
and Stable Surroundings. Atmospheric Environment, 10, 507-510.
24. U. S. Environmental Protection Agency, 1971. Exhaust Gases from
Combustion and Industrial Sources, APTD-0805. Pub. No. PB204-861,
NTIS, Springfield, Virginia 22151.
25. Lyons, W. A., and H. S. Cole, 1973. Fumigation and Plume Trapping
on the Shores of Lake Michigan During Stable Onshore Flow. J. of
Applied Meteorology, 12, pp. 494-510.
26. Snyder, W. H., and R. E. Lawson, Jr., 1976. Determination of a
Necessary Height for a Stack Close to a BuildingA Wind Tunnel
Study. Atmospheric Environment, 10, 683-691.
27. Smith, M., Editor, 1973. Recommended Guide for the Prediction of
the Dispersion of Airborne Effluents. Second Edition. The American
Society of Mechanical Engineers, New York, N. Y.
28. Huber, A. H., and W. H. Snyder, October 1976. Building Wake Effects
on Short Stack Effluents. Preprint volume: Third Symposium on
Atmospheric Turbulence, Diffusion and Air Quality. Published by
American Meteorological Society, Boston, Massachusetts, pp. 235-242.
29. Huber, A. H., 1977. Incorporating Building/Terrain Wake Effects on
Stack Effluents. Preprint volume: AMS-APCA Joint Conference on
Applications of Air Pollution Meteorology, November 29-December 2,
1977, Salt Lake City, Utah.
30. Burt, E. W., September 1977. Valley Model User's Guide. EPA-450/2-
77-018. U. S. Environmental Protection Agency, Research Triangle
Park, N. C. 27711.
31. Hanna, S. R., 1971. A Simple Method of Calculating Dispersion from
Urban Area Sources. Journal of the Air Pollution Control Association,
12, 774-777.
32. McElroy, J. L. and Pooler, F., December 1968. St. Louis Dispersion
Study, Volume II - Analyses. AP-53. National Air Pollution Control
Administration, Arlington, Virginia 22203.
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" APPENDIX A
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UNAMAP DISPERSION MODELS
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Since May 1973 the Meteorology and Assessment Division, Environ-
mental Protection Agency, Research Triangle Park, North Carolina, has
made six air quality simulation models available to those wanting to
make dispersion estimates. These six models are collectively referred
to as UNAMAP (Users' Network for Applied Modeling of Air Pollution).
Brief abstracts of the six models are enclosed. Publications related to
these models are listed on the enclosed UNAMAP Reference sheet. Most of
these publications are available from NTIS.
In addition to making these models available to EPA users on the
UNIVAC 1110 in Research Triangle Park, the UNAMAP models are available
in two ways:
(1) The UNAMAP models can be executed on Computer Science Cor-
poration's INFONET. Users must establish accounts with CSC and are
charged according to the services provided. Users are linked to the
computer via telephone lines. Users interested in access to UNAMAP by
this method should contact the INFONET Customer Service Representative
at the nearest Computer Sciences Corporation Office. The principal
advantage of accessing UNAMAP in this way is relatively rapid access to
changes or additions to UNAMAP. CSC is making some changes to the
operation of UNAMAP on INFONET in order to ensure that updates reach
each customer quickly.
(2) The UNAMAP models are available on magnetic tape from NTIS.
The tape record mode is 9 track, 800 bits per inch, EBCDIC code, odd
parity. Physical records each contain 10 logical records in card image
format (that is, 80 byte logical records; 800 byte block size). As an
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option NTIS can copy the tape to 7 track (556 or 800 bpi) BCD format. _
The price per tape is $175.00 ($219.00 - foreign orders). When ordering,
specify the desired format as mentioned above. The tape identification
should be specified as follows:
NTIS Accession No. PB 229-771, Users Network for Applied I
Modeling of Air Pollution (UNAMAP)
Until January 1975, the first version of this tape containing
interactive versions of the six UNAMAP models was sold. In January
1975, this original tape was replaced with version 2 of this tape. The
new tape contains batch versions and test data for all six models and
interactive versions of PTMAX, PTDIS, PTMTP, and HIWAY. The principal
reason for the change was the availability of a new version of HIWAY.
Persons ordering PB 229-771 after about February 1, 1975, should have
received version 2. If your tape is version 2 you will have version
74333 in your HIWAY program source listing. For purchasers of the
version 1 tape, a 'Change Tape for UNAMAP1, PB 240-273 is available for
$97.50 ($122.50-foreign orders). A list of purchasers of the tape that I
fill in the registration form accompanying the tape is maintained,
so that additional information can be furnished to them.
UNAMAP MODEL ABSTRACTS
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APRAC Stanford Research Institute's urban carbon monoxide model. _
Computes hourly averages for any urban location. Requires
an extensive traffic inventory for the city of interest.
Requirements and technical details are documented in "User's
Manual for the APRAC-1A Urban Diffusion Model Computer Program"
which is available from NTIS (accession number PB 213-091,
$5.25).
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HIWAY An interactive program which computes the hourly concentra-
tions of non-reactive pollutants downwind of roadways. It
is applicable for uniform wind conditions and level terrain.
Although best suited for at-grade highways, it can also be
applied to depressed highways (cut sections). The "User's
Guide for HIWAY: A Highway Air Pollution Model," is available
from EPA as EPA-650/4-74-008 and from NTIS (accession number
PB 239-944/AS, $4.25).
COM The Climatological Dispersion Model determines long term
(seasonal or annual) quasi-stable pollutant concentrations
at any ground level receptor using average emission rates
from point and area sources and a joint frequency distribution
of wind direction, wind speed, and stability for the same
period. The "User's Guide for the Climatological Dispersion
Model" is available from EPA as EPA-R4-73-024 and from NTIS
(accession number PB 227-346-AS, $4.75).
Three Point Source Models - The three following point source models
use Briggs plume rise methods and Pasquill-Gifford dispersion
methods as given in EPA's AP-26, "Workbook of Atmospheric
Dispersion Estimates," to estimate hourly concentrations for
stable pollutants. A draft users' guide for these three models
is available from the Environmental Applications Branch,
Meteorology and Assessment Division, Mail Drop 80, EPA,
Research Triangle Park, N.C. 27711.
PTMAX An interactive program that performs an analysis of the maximum
short term concentrations from a single point source as a
function of stability and wind speed. The final plume height
is used for each computation.
PTDIS An interactive program that estimates short-term concentrations
directly downwind of a point source at distances specified
by the user. The effect of limiting vertical dispersion by
a mixing height can be included and gradual plume rise to the
point of final rise is also considered. An option allows the
calculation of isopleth half-widths for specific concentrations
at each downwind distance.
PTMTP An interactive program that estimates for a number of arbitra-
rily located receptor points at or above ground-level, the
concentration from a number of point sources. Plume rise is
determined for each source. Downwind and crosswind distances
are determined for each source-receptor pair. Concentrations
at a receptor from various sources are assumed additive.
Hourly meteorological data are used; both hourly concentrations
and averages over any averaging time from one to 24 hours can
be obtained.
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UNAMAP MODEL REFERENCES
APRAC User's Manual for the APRAC-1A Urban Diffusion Model Computer
Program (available from NTIS, accession number PB 213-091.
$5.25 per paper copy, $2.25 for microfiche.) [Additional
information is available on APRAC from:
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A Practical, Multipurpose Urban Diffusion Model for Carbon I
Monoxide (NTIS accession number PB 196-003) *
Field Study for Initial Evaluation of an Urban Diffusion I
Model for Carbon Monoxide (NTIS ar-cession number PB 203-469)
Evaluation of the APRAC-1A Urban Diffusion Model for Carbon
Monoxide (NTIS accession number PB 210-813)]
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Dabberdt, Walter F.; Ludwig, F.L.; and Johnson, Warren B., Jr., _
1973: Validation and Applications of an Urban Diffusion Model
for Vehicular Pollutants, Atmos. Environ., ]_, 603-618.
Johnson, W.B.; Ludwig, F.L.; Dabberdt, W.F.; and Allen, R.J.,
1973: An Urban Diffusion Simulation Model for Carbon Monoxide.
J. Air Poll. Control Assoc. 23, 6, 490-498.
COM Busse, A.D., and Zimmerman, J.R., 1973: User's Guide for the |
Climatological Dispersion Model. U.S. Environmental Protection
Agency. Research Triangle Park, N.C. Environmental Monitoring _
Series, EPA-R4-73-024, 131 p. (NTIS accession number PB 227-346/AS,
$4.75 paper copy).
HIWAY Zimmerman, J.R.; and Thompson, R.S., 1975: User's Guide for
HIWAY: A Highway Air Pollution Model. U.S. Environmental
Protection Agency, Research Triangle Park, N.C. Environmental
Monitoring Series, EPA-650/4-74-008, 59 p. (NTIS accession
number PB 239-944/AS, $4.25 paper copy). |
PTMAX, PTDIS, and PTMPT - Turner, D.B.; and Busse, A.D., 1973: User's -
Guides to the Interactive Versions of Three Point Source
Dispersion Programs: PTMAX, PTDIS, and PTMTP Preliminary
Draft, Meteorology Laboratory, U.S. Environmental Protection
Agency, Research Triangle Park, N.C. 27711.
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NTIS - National Technical Information Service
U.S. Department of Commerce
Springfield, VA 22161
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 REPORT NO.
EPA-450/4-77-001
4. TITLE AND SUBTITLE
Guidelines for Air Quality Maintenance Planning and
AnalysisVolume 10 (Revised): Procedures for Evaluati
Air Quality Impact of New Stationary Sources
3 RECIPIENT'S ACCESSIOf*NO.
5. REPORT DATE
October 1977
..PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
Laurence J. Budney
OAQPS No. 1.2-029 R
9. PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, Nf ?7711
10. PROGRAM ELEMENT NO.
2AF 643
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13, TYPE OF REPORT AND PERIOD COVERED
OAQPS/AQMPA Guideline
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
This is a revision of the original Volume 10 of the Air Quality Maintenance Planning
and Analysis Series, published in September 1974.
16. ABSTRACT
This document is a revision of the original Volume 10 (EPA-450/4-74-011:
"Reviewing New Stationary Sources") of the EPA Guidelines for Air Quality Maintenance
Planning and Analysis. It provides basic modeling techniques for estimating the air
quality impact of new (proposed) stationary sources. The revision is in a more
readily useable format and incorporates changes and additions to the technical
approach. Also, a simple screening procedure has been added. The techniques are
applicable to chemically stable, gaseous or fine particulate pollutants. An impor-
tant advantage of the technique is that a sophisticated computer is not required. A
pocket or desk calculator will generally suffice.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Air Pollution
Airborne Wastes
Meteorology
Micrometeorology
Atmospheric Diffusion
Atmospheric Models
b.IDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group
New Source Review
Air Quality Maintenance
Point Sources
Emissions
Stack Design
IB. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (This Report)
None
21. NO OF PAGES
20. SECURITY CLASS (This page)
None
22. PRICE
I EPA Form 2220-1 (9-73)
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