!PA-4 50/3-74-020
(March 1974
FOR CONSIDERING
AIR QUALITY
IN URBAN PLANNING
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Water Programs
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
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EPA-450/3-74-020
A GUIDE
FOR CONSIDERING
AIR QUALITY
IN URBAN PLANNING
by
A. H. Epstein, C. A. Leary and S. T. McCandless
with the assistance of B . J. Goldsmith, J. C. Goodrich and B. H. Willis
Environmental Research and Technology, Inc
429 Marrett Road
Lexington, Massachusetts 02173
Contract No. 68-02-0567
EPA Project Officer: John Robson
Prepared for
ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Water Programs
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
March 1974
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This report is issued by the Environmental Protection Agency to report technical
data of interest to a limited number of readers. Copies are available free of charge
to Federal employees, current contractors and grantees, and nonprofit organizations
as supplies permit - from the Air Pollution Technical Information Center, Environ-
mental Protection Agency, Research Triangle Park, North Carolina 27711, or from
the National Technical Information Service, 5285 Port Royal Road, Springfield,
Virginia 22151.
This report was furnished to the Environmental Protection Agency by Environmental
Research and Technology, Inc. , Lexington, Massachusetts, in fulfillment of
Contract No. 68-02-0567. The contents of this report are reproduced herein as
received from Environmental Research and Technology, Inc. The opinions,
findings, and conclusions expressed are those of the author and not necessarily
those of the Environmental Protection Agency. Mention of company or product,
names is not to be considered as an endorsement by the Environmental Protection
Agency.
Publication No. EPA-450/3-74-020
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TABLE OF CONTENTS
Page
LIST OF ILLUSTRATIONS V
LIST OF TABLES vii
SUMMARY 1
1. INTRODUCTION 3
1.1 Objectives 3
1.2 Overview 4
1.3 Glossary of Terms 6
2. PLAN DESIGN FACTORS 13
2.1 The National Ambient Air Quality Standards 13
2.2 Sources of Air Pollution 17
2.3 Natural Phenomena Affecting Air Quality 21
3. THE PLANNING PROCESS AS A DESIGN SYSTEM FOR AIR QUALITY 31
3.1 Factors Affecting Industrial Emissions 36
3.2 Transportation Emissions 4Q
4. RELATING POLLUTANT EMISSIONS TO AIR QUALITY 47
4.1 The Dispersion Models 47
4.2 Model Utility 49
4.3 A Simplified Urban Dispersion Model 5Q
5. RELATING ALLOWABLE EMISSION INCREASES TO SELECTION OF
INDUSTRIAL AND TRANSPORTATION LAND USES 57
5.1 Estimating Industrial Emissions 60
5.2 Estimating Transportation Emissions 62
6. ILLUSTRATIVE EXAMPLES 65
6.1 Determining Allowable Emissions 65
6.2 Constraining Industry and Transportation 68
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TABLE OF CONTENTS contd.
Page
7. THE INFLUENCE OF SOURCE CONFIGURATION 75
7.1 Industrial Sources 77
7.2 Highway Sources 89
8. AQUIP-AN EVALUATIVE TOOL FOR RANKING "FINAL" PLANS 97
9. SUMMARY AND CONCLUSIONS 99
10. REFERENCES 103
IV
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LIST OF ILLUSTRATIONS
Figure Pa&e
1 The Influence of Wind Speed on Ground Level
Pollutant Concentrations
23
2 The Influence of Wind Direction on Ground Level
Pollutant Concentrations 24
3 The Influence of Atmospheric Stability on Ground
Level Pollutant Concentrations 25
4 The Stability Wind Rose for Newark International
Airport 27
5 Nighttime Airflow into Valleys 29
6 Daytime Airflow Out of Valleys 29
7 Airflow Around and in the Wake of a Building 30
8 The Air Quality Impact-Land Use Planning Process 32
9 Step 2 in the Air Quality Impact-Land Use Planning
Process; Defining the Tolerance of the Planning Area
Toward Receiving Additional Pollution 51
10 The Relationship Between Annual Average Pollutant
Concentration and Planning Area Size 55
11 Step 3 in the Air Quality Impact-Land Use
Planning Process; Setting Constraints on
Industry and Transportation 58
12 Step 4 in the Air Quality Impact-Land Use Planning
Process; Generating Alternative Comprehensive Land
Use Plans 76
13 Annual Average Pollutant Concentrations for a Single
Area Source 80
14 Annual Average Pollutant Concentrations for Dispersed
Area Sources 81
15 Annual Average Pollutant Concentrations for a Single
Point Source 84
16 Annual Average Pollutant Concentrations for Dispersed
Point Sources 85
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LIST OF ILLUSTRATIONS contd.
Figure Page
17 Worst Case Pollutant Concentrations for a Single
Point and Area Source 87
18 Worst Case Pollutant Concentrations for a Single
Point Source and Dispersed Area Sources 88
19 The Relationship of Pollutant Concentration to
Wind Speed for a Typical Highway Configuration 90
20 The Relationship of Pollutant Concentration to
Atmospheric Stability for a Typical Highway
Configuration 92
21 The Relationship of Pollutant Concentration to
Highway Source Strength 94
22 Steps in the Air Quality Impact-Land Use Planning
Process; Evaluating the Air Quality Impact of
Final' Plans 98
VI
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LIST OF TABLES
Table Page
1 National Ambient Air Quality Standards 14
2 General Source Categories of Air Pollution 19
3 Emission Characteristics for Gasoline Powered Vehicles 42
4 Comparison of Transportation Emissions by Vehicle
and Passenger Mile of Travel 44
5 Equivalent Annual Average Air Quality Standards 53
6 General Emission Characteristics of Industries by SIC 61
7 Generalized Industrial Emission Rates 63
8 Generalized Vehicular Transportation Emission Rates 64
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SUMMARY
A Guide for Considering Air Quality in Urban Planning is intended to
provide information to the planning community that will facilitate the
incorporation of air quality considerations into the planning process.
The guide is presented in eight sections. Basic information concerning
air quality design criteria, source categories of air pollution, and natural
physical phenomena affecting the dispersion of pollutant emissions, and the
relative impact of these factors on the planning process, are discussed in
Section 2.
Section 3 presents an overview of the air quality impact-land use
planning process, including a five step procedure for its implementation.
Briefly, the individual steps are as follows:
1. Establishing air quality baseline for the planning area
2. Defining the tolerance of the planning area toward
receiving additional pollutant emissions as a
function of air quality standards, existing air
quality, and air quality maintenance policies
3. Determining acceptable industrial and transportation
activities which may be added to existing land use as
a function of the pollutant tolerance of the planning
area and generalized pollutant emission rates
4. Distributing industrial and transportation land use
within comprehensive land use plan(s) using generalized
dispersion patterns of major air pollution sources and
spatial patterns of existing air quality to locate
land use activities
5. Evaluating the air quality impact of the plan(s),
modifying land use as required by compliance eval-
uation with the air quality standards
Within this procedural framework, applications of air quality criteria
to planning decisions are defined at various levels of detail. Though this
procedure comprises a reasonable first estimate of the procedures that plan-
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ners can use to determine air quality implications of plan design decisions,
the application and interpretation of these procedures are subject to several
conditions which limit their general applicability. Some limitations are
discussed in Section 9.
Sections 4 and 5 provide the basis for translating air quality planning
parameters into preliminary plan designs in terms of industrial land use and
transportation activity. Section 4 presents a procedural scheme for defining
the tolerance of a planning area toward receiving additional pollutant
emissions. Section 5 contains procedures for determining acceptable indus-
trial and transportation activities in terms of air quality for a planning
area.
Section 6 contains examples of planning situations to clarify the pro-
cedures involved in determining allowable emissions for a planning area.
Section 7 presents information relative to the dispersion patterns of major
source configurations so that the placement of land use associated with
preliminary designs (generated as a result of determining acceptable in-
dustrial and transportation land uses) can be compatible with local air
quality considerations. Procedures relative to the distribution of those
land use activities address the relationship between existing air quality
and the siting of new land use activities. Location-sensitive analyses;
are illustrated in three case studies.
Section 8 presents a methodology which provides for the air quality
impact evaluation of comprehensive urban plans. This methodology, desig-
nated as the AQUIP system, is a completely operational computerized pro-
cedure and has been used in the evaluation of alternative land use plans
for the Hackensack Meadowlands of New Jersey.
Section 9 summarizes the documents' contents and discusses some
limitations of the applications and interpretation of the procedures
described. It is concluded that the procedures can be useful to the
planner since they provide a means of rapid estimation of the air pollution
potential of preliminary industrial/transportation land use plans, are
simple to apply and reduce the susceptibility of "final" designs to major
changes in land use required by compliance with the air quality standards.
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1. INTRODUCTION
1.1 Objectives
This document is intended to provide information to the planning com-
munity that will facilitate the incorporation of air quality considerations
into the planning process. Air pollution impacts resulting from different
land use activities are discussed, including generalized emission character-
istics of principal urban activities, associated meteorological and topo-
graphical phenomena affecting pollution diffusion, and simplified procedures
for relating pollutant emissions to ground level air pollution concentrations.
It is assumed that the primary users of the air quality planning guide
will be members of agencies responsible for the overall planning efforts of
regional and subregional areas. This guide is specifically addressed to
planners with little or no technical background in air quality analysis,
but with sufficient technical ability to follow basic procedures for quan-
tifying the relationships between land use and ambient air quality. The
current state of the art in Air Quality Impact and Land Use Planning is
reflected in this document. The technique described will probably be mod-
ified and refined as more understanding of the relationship is gained.
While the regional planner would be best suited to use the tools out-
lined in the document, the information presented may find application in
agencies with more diverse interests. Industrial councils, transportation
planners, zoning boards, and the like may find that particular areas of
the guide provide them with sufficient information to make policy decisions
which are cognizant of air quality considerations. Simplification of the
interaction between land use and air quality should enable interested cit-
izens and advocate planners, having a" minimum of background in air quality
analysis, to be aware of generalized consequences of planning decisions.
More sophisticated, detailed, and precise tools for evaluating the
impact of land use activities upon air quality are available. The technique
described in this document should not serve as a substitute for consultation
with local air pollution control experts, particularly in areas where air
pollution is or may be a significant problem.
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This document is not intended for use by air quality control agencies
and other organizations that should have sufficient professional expertise
to carry out air quality planning determinations of a much more sophisticated
nature. Neither is this guide intended to be used as a tool for environ-
mental litigants, because such litigation should depend on more specific
studies of individual air quality parameters.
Where approaches or numerical estimates are not otherwise referenced,
they are based upon the professional experience of the authors. Section 1.3
provides a glossary of terms used in the Guide and should be consulted as
necessary by the reader.
1.2 Overview
Patterns of land use and their accompanying activities have a major
impact in determining the type and amount of air pollution generated over a
region. Historically, specification of land use has been comparatively
insensitive to air quality considerations. Recent public concern for en-
vironmental quality has fostered attempts to improve air quality through
direct control of the sources of air pollution. Specifically, the current
focus of these attempts is on emissions control and more efficient fuel
utilization. However, this type of approach does not by itself address the
broad-based problems of planning for long term air quality.
The most fundamental determination of air quality levels over which
operational control can be exercised is the specification of land use.
Land use activities, including specific emission sources, can be associated
with a rate of pollution discharge. Specification of the types and amounts
of residential, commercial, industrial and transportation activity which
are consistent with air quality criteria, form the basis for generating
urban configurations which are compatible with acceptable levels of air
quality.
In order to achieve an equitable and realistic level of management of
the air resource, it is necessary to define and implement within the plan-
ning process a methodology, corresponding analytic tools, guidelines and
standards and an appropriate data base that will permit land use and trans-
portation planning that is compatible with acceptable air quality levels.
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In this way, planning for air quality will be simultaneously a constraint
and a directive for planning new development. Consideration of air quality
factors has not been a direct input into the planning process. Though air
quality considerations represent a limit on the freedom to designate amounts,
types and locations of land uses, it is expected that air quality impacts
of development will be considered simultaneously with other planning
criteria in designating future land use activities.
The air quality of an urban environment depends upon:
1. The ability of the environment to disperse, transform, and
remove pollutant loadings generated by urban land use activities.
2. Pollutant source characteristics
3. Background pollutant concentrations.
The capacity of the air basin over a region to disperse, transform and
remove atmospheric pollutants depends upon a variety of factors, including
the amount and type of pollutants emitted, and meteorological and topograph-
ical characteristics of the region.
Pollutant source characteristics include the quantity of emissions
and the physical location and configuration of sources. Sources are gener-
ally referred to as point, line and area sources. Point sources represent
major, identifiable sources within a region, such as industry or municipal
incinerators. Line sources represent emissions from motor vehicles along
principal highways and emissions from aircraft. Area sources represent
clusters of small, individual sources within a region such as emissions from
heating plants in residences and small buildings. Distinctions are also drawn
between direct and indirect sources of pollution. Direct sources are those
which emit pollutants as a result of activities inherent in their operations
(e.g., industrial facilities, housing facilities, etc.). Indirect sources
represent a major facility that spawns various emission sources, such as
transportation-related activity at an airport or shopping center.
Source emissions are in turn determined by land use category or source
type, level of activity or process rate, type and amount of fuel used, source
controls and activity schedules (see the glossary at the end of this chapter
for an explanation of these terms). These elements may be specified to
greater detail depending- on the type of land use or source type involved.
For example, for a given industry, its stack height and smoke temperature
would be specified. A source, such as a highway, may be additionally
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defined as elevated, depressed or at-grade. Each of these parameters
contributes to the determination of pollutant source characteristics.
Land use encompasses not only the type of activity intended for land areas,
but the physical interrelationship between and among various activities and
the type of ground cover on the land. Therefore, land use affects both pollu-
tant source characteristics and the ability of the environment to disperse
pollutants.
Background air pollution may be defined as that level of pollutant
concentration not directly attributable to an identifiable source or
combination of sources within the planning area. Background concentra-
tions may be relatively constant over the planning area, or they may
vary significantly within it. It is generally not possible to determine
future background pollutant levels with a high degree of accuracy.
Consequently, it is necessary to have air quality data available with
which to assess the air quality impact of planning decisions relative to
projected background air pollution.
1.3 Glossary of Terms
Activity, Activity Level
Air Quality Baseline
Air Quality Contour
Air Quality Control Region
Air Quality Criteria
Basic land use and transportation planning
units of intensity of use, e.g., vehicles per
day on a highway, acres of residential land
use, square feet of industrial plant space.
Pollutant concentration data of sufficient.
quality and quantity to satisfactorily define
existing air quality.
See reference "Isopleth."
Geographic regions (generally a state or metro-
politan area) established for the purpose of
air quality analysis under the Clean Air Act.
Factors that represent a basis for decision-
making; for example, EPA Criteria Documents
summarize effects of specified pollutants and
formed the basis for setting federal ambient
air quality standards.
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Air Quality Estimation or
Projection
Air Pollution Loading
Ambient Air
Ambient Air Quality
Ambient Air Quality Standard
Atmospheric Dispersion Model
Average Receptor Exposure
Background Air Quality
Background Emissions
The calculation of current or future air pol-
lutant concentrations at specified receptor
points resulting from the action of specified
meteorological conditions on specified emissions.
Calculation of maximum allowable emissions aver-
aged over an area as a function of emission den-
sity (regional emissions/regional area).
That portion of the atmosphere, external to
buildings, to which the general public has access.
Concentration levels in ambient air for a speci-
fied pollutant and a specified averaging time
period within a given geographic region.
A level of air quality established by federal or
state agencies which is to be achieved and main-
tained; primary standards are those judged nec-
essary, with an adequate margin of safety, to
protect the public health; secondary standards
are those judged necessary to protect the public
welfare from any known or anticipated adverse
effects of a pollutant.
An acronym for Air Quality for Urban and
Industrial Planning, a computer-based tool for
evaluating air pollution impact of land use
and transportation plans.
A mathematical procedure for calculating air
pollution concentrations that result from a
specified array of emission sources and a spec-
ified set of meteorological conditions.
A measure of the average impact of air quality
levels on a specific type of receptor; the
measure is equal to the integrated receptor
exposure divided by the total number of receptors
in the study region.
Levels of pollutant concentrations within a study
area which are the result of emissions from all
sources other than those incorporated in the
model for the study area.
The emissions inventory applicable to the back-
ground region; that is, all emission sources not
explicitly included in the model for the study
area.
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Climatology
Concentrations
Degree Days
(Heating Degree Days)
Emission Factor
Emissions
Emissions Inventory
Emissions Projection
Equivalent Ambient Air
Quality Standards
Fuel Related Sources^ Fuel
Emissions
Fuel Demand, Fuel Use
Propensity
The study of long term weather as represented by
statistical records of parameters such as winds,
temperature, cloud cover, rainfall, and humidity
which determine the characteristic climate of a
region; climatology is distinguished from meteor-
ology in that it is primarily concerned with
average, not actual, weather conditions.
A measure of the average density of pollutants
usually specified in terms of pollutant mass per
unit volume of air (typically in units of micro-
grams per cubic meter), or in terms of relative
volume of pollutant per unit volume of air
(typically in units of parts per million).
The sum of negative departures of average daily
temperature from 65°F; used to determine demand
for fuel for heating purposes.
A numerical conversion factor applied to fuel use
and process rates to determine emissions and
emission rates.
Effluents into the atmosphere, usually specified
in terms of weight per unit time for a given
pollutant from a given source.
A data set describing the location and source
strength of air pollution emissions within a
geographical region.
The quantitative estimate of emissions for a
specified source and a specified future time.
Air quality levels adopted in this study to
permit analysis of all air pollutants in terms
of annual averages; in cases where state and
federal annual standards do not exist, the
adopted levels are based on the extrapolation
of short period standards.
Fuel related sources use fuel to heat area,, or
to raise a product to a certain temperature
during an industrial process, or for cooking
in the house; they produce fuel emissions.
(See also, Non-Fuel Related Sources).
The amount of fuel needed to fulfill the total
heat requirement (space heating plus process
heating); use of a particular fuel or fuels
that determines the actual amounts of various
fuels used to satisfy the heat requirement.
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Heating Requirements
Impact Measure (or Parameter)
Influence Region for an Area
Integrated Receptor Exposure
Isopleth
Land Use Intensity
Land Use Mix
The amount of heat needed for:
Space heating - heat needed to warm an enclosed
area, such as the floor space of a school in
winter, to a desired temperature; the heat con-
tent or value of the fuel used and the outside
temperature define the space heating require-
ment.
Non-space heating, process heating - heat needed
to raise a product to a certain temperature dur-
ing an industrial process or for cooking (with
gas) in the home; it is generally not related to
outside temperature.
Percent space heating (or percent process heat-
ing) - the relative proportion of a fuel or its
heat content that is used for space heating (or
process heating).
A quantitative representation of the degree of
impact on air quality or specific receptors re-
sulting from concentrations of specified pol-
lutants.
The geographical region containing the emis-
sion sources responsible for at least 90% of
the ground level concentrations (averaged
throughout the area) of all pollutants con-
sidered. For an individual source or group
of sources, the influence region may be de-
fined as that area within which air quality
is affected by that particular source, or
group of sources.
A measure of the total impact of air quality
levels on specific receptors; the measure is
equal to the summation over all grid cells
within the study region of the number of recep-
tors times the concentration levels to which
they are exposed.
Contours of constant levels of concentration
for a specific pollutant.
The level of activity associated with a given
land use category; for example, the population
density of residential areas.
The percent of total study region area allo-
cated to specific land use categories.
Meteorology
The study of atmospheric motions and phenomena.
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Microscale Air Quality
Non-Fuel Related Sources,
Process Emissions, Separate
Process Emissions
Normalized Concentration
Process Rate
The representation of air quality in a geograph-
ical scale characterized by distances between
source and receptor ranging from a few meters to
a few hundred meters.
Sources that do not burn fuel primarily for heat-
ing purposes or do not burn fuel at all, includ-
ing transportation sources, incineration, and
certain industrial processes; emissions piroduced
by non-fuel related sources. (See also, Fuel
Related Sources).
A concentration of a pollutant that is made
independent of one or both of the dependent
variables (i.e., wind speed, or source
strength). For example, a concentration
normalized by source strength would have the
units of concentration divided by source
strength. Therefore, given a concentration
normalized by source strength for a given
configuration, an actual concentration may
be obtained simply by multiplying by the
appropriate source strength.
Process rate is a unit measure of the
productivity of a manufacturing plant.
The unit may be used to estimate or
compare industrial activity (e.g., the
process rate of a steel mill might be
expressed as tons of steel produced per
day). As used in previous studies the
term may also refer to a specific unit
of process rate.
Receptor
Receptor Point
Regional Air Quality
Schedule
A physical object which is exposed to air pol-
lution concentrations; objects may be animate or
inanimate, and may be arbitrarily defined in
terms of size, numbers, and degree of specificity
of the object.
A geographical point at which air pollution con-
centrations are measured or predicted.
The representation of air quality in a geo-
graphical scale characterized by large areas;
for example, on the order of 50 square kilom-
eters or greater.
The number of hours per year a fuel burning
activity will consume fuel; used to determine
heating requirements.
10
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Source
Source Geometry
Stability Class
Stability Wind Rose
Total Air Quality
Any stationary or mobile activity which pro-
duces air pollutant emissions.
Sources categorized for modeling purposes
as a point, line, or area source, defined
as follows:
Point source - a single major emitter located
at a point.
Line Source - a major highway link, denoted by
its end points.
Area source - a rectangular area referenced to
a grid system; includes not only area-wide
sources, such as residential emitters, but
single emitters and highway links deemed too
small to be considered individual point or line
sources.
A classification of atmospheric stability con-
ditions based on surface wind speed, cloud cover
and ceiling, supplemented by solar elevation
data (latitude, time of day, and time of year).
A 1»bulation of the joint frequency of occurrences
of wind speed and wind direction by atmospheric
stability class at a specific location.
The air quality at a receptor point resulting from
background emission sources and from emission
sources specifically within the study area.
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2. PLAN DESIGN FACTORS
In this section, basic information pertaining to the relationship be-
tween land use and air quality is presented. Specifically, three topics
are discussed:
The National Ambient Air Quality Standards
Sources of Air Pollution
Natural Phenomena Affecting Air Quality
Each of these factors are essential to a general understanding of the inter-
relationships between land use and air quality, and thus, to the formulation
of land use plans which are compatible with acceptable air quality levels.
Therefore, information contained in this section addresses background infor-
mation necessary to implement the air quality impact-land use planning
methodology which is detailed in Sections 3 through 8. Though some of the
concepts addressed are highly complex, such as meteorological phenomena
affecting air quality concentrations, these concepts have intentionally been
simplified in order to extract information that will be most instrumental
to the planner in determining the impact of land use plans relative to air
quality.
2.1 The National Ambient Air Quality Standards
Air quality standards are important to the planner because they repre-
sent not only legal mandates for air quality, but also specific design
criteria for the planning process. That is, they comprise both a set of
constraints and guidelines of which the planner must be aware in the spec-
ification of land use types and configurations. The National Ambient Air
Quality Standards (NAAQS) now in use are a direct result of the Clean Air
Act Amendments of 1970. These standards, as defined in 40 CFR Part 50, are
presented in Table 1. As shown, standards exist for six individual pollutants,
specified by concentration, averaging time and frequency. The standards spe-
cify that the maximum concentrations are not to be exceeded more than once a
year. In addition, both primary and secondary standards are indicated. Pri-
mary standards are those that are requisite to protect the public health and
13
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secondary standards, the public welfare. In some instances, individual
states have instituted air quality standards that are more stringent than
the federal standards. In these cases, the planner should design according
to the state standards because in general, state air pollution control
agencies will be responsible for the final review and approval of land use
plans relative to expected air pollution impact.
Because compliance with the standards is mandatory for each of the
time periods specified, it is important that planning decisions be based
upon air quality data reflecting these time periods. Therefore, sufficient
data should be examined to establish hourly, daily, and annual trends of
individual pollutant concentrations. A brief discussion of the individual
pollutants and their respective time frames, as addressed by the standards,
follows. The sources for each of these pollutants are discussed in Section
2.2.
Carbon Monoxide
The standards for carbon monoxide are given in terms of annual maximum
concentrations averaged over 1 and 8 hour time periods, indicating that
short duration exposures to this pollutant are most critical. Because the
prime contributor of carbon monoxide emissions is the automobile, one would
expect diurnal (daily) variations in CO levels to correlate fairly well with
variations in traffic densities. Consequently, air quality data required
for planning decisions involving vehicular transportation should be examined
for the one hour periods involving morning and evening peak hours and for
the eight hour period including the evening peak hour. Of the two, the
8-hour standard has been generally seen to be more difficult to meet; there-
fore, where limitations on data analysis exist, the planner should favor ex-
clusion of the one hour periods rather than the eight hour. Possible ex-
ceptions to this may occur in considering air quality data for areas close to
facilities having high, but intermittent traffic densities associated with
their use. In particular, sports and/or recreation complexes, industrial
parks, commuter-oriented schools and colleges, and mass transportation facil-
ities, airports, bus and train terminals, and the like, may all exhibit
traffic patterns that make considerations of the one hour period of paramount
importance in examining carbon monoxide levels relative to the standards.
15
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Hydrocarbons and Photochemical Oxidants
The standard for hydrocarbons is given as an annual maximum concen-
tration for a specific 3 hour average, i.e., 6 AM to 9 AM. ThisMnorning
time period is specified because it is during this period that meteorological
conditions are generally most favorable for initiating the formation of
photochemical oxidants. The intent here is to limit oxidant formation by
limiting hydrocarbon concentrations in the atmosphere during the time when
oxidant formation is most probably initiated.
Photochemical oxidants differ from other pollutants in that they are
not emitted directly to the atmosphere, but are produced by chemical reac-
tions among hydrocarbons and oxides of nitrogen in the presence of sunlight.
The precise nature of these reactions in the atmosphere is unknown because
there are so many variables involved. Photochemical oxidants are a regional
problem in that the contribution of the pollutant emissions from a single
facility to the concentration of photochemical oxidants in the vicinity of
that facility cannot be determined. This is due not only to the complexity
of the chemical reactions, but also to the time lag of up to several hours
between emissions of hydrocarbons and oxides of nitrogen and formation of
the photochemical oxidants. During this interval, pollutants are able to
disperse considerable distances from their sources.
The oxidant standard is given in terms of an annual maximum one hour
average concentration. Generally, oxidant concentrations are highest in the
early afternoon. In terms of the planning process, the planner should note
that a credible model for predicting oxidant concentrations has yet to be
developed. Thus, it is especially important that both oxidant and hydrocar-
bon data be available in order to empirically define the relationship be-
tween the two. A predictive model for hydrocarbons can then be employed to
estimate oxidant levels for anticipated land use.
Nitrogen Dioxide
Nitrogen dioxide has perhaps the least complex standard of all the
pollutants. The annual arithmetic mean concentration specified in the
standards makes consideration of nitrogen dioxide relatively straightforward,
because only the one number (the annual average) need be considered for this
pollutant.
16
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Sulfur Dioxide
Standards for sulfur dioxide are expressed as annual maximum concen-
trations of 3 and 24 hour averaging periods, in addition to annual arithmetic
mean concentrations. Complexity of the standards for sulfur dioxide indicate
that this pollutant has been demonstrated to have both short term as well as
long term exposure effects. Because industrial activity is, in most cases,
responsible for the majority of sulfur dioxide emissions, the planner must,
therefore, be especially careful in the specification and placement of indus-
trial land uses.
Particulate Matter
Particulate matter in the atmosphere consists of tiny solid particles
small enough to remain suspended in the air, often for hours or days, before
settling out due to their own weight, or raining out in snow or rain storms.
Industrial, transportation, and heating sources all contribute to the observed
concentration of particulates. Total suspended particulate concentrations
are regulated by an annual maximum, specified over a 24-hour period, and by
an annual geometric mean concentration. Again, the concern here is for both
long and short term exposure to the pollutant.
2.2 Sources of Air Pollution
There are only two means by which the atmosphere of a given planning
area may receive pollution:
1. Through the direct emission and consequent dispersion of
pollutants from sources within the planning area
2, Through the transport of pollutants, generated elsewhere,
into the planning area by natural atmospheric processes.
Both mechanisms of air quality degradation reflect the effects of what
should be considered as primary plan design factors influencing an area's
air quality. An area's pollutant source characteristics (quantity of emissions
and configuration of sources) may be determined from the mix of land use cat-
egories and intensity of land use activities. Background levels of pollutants
17
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as used in this Guide refer to that level of pollutant concentration not
directly attributable to an identifiable source or combination of sources
within the planning area. Therefore, pollutants both generated by and trans-
ported into the planning area may be used as criteria for defining the toler-
ance of existing air quality to additional pollutant emissions. Background
levels of pollutants may also be useful in locating both sources and receptors
of air pollution to minimize the air pollution impact of a given land use
configuration.
General Source Categories
For the purpose of defining the relationships between land use and
air quality as planning design parameters, it is most appropriate to consider
the following categorization of land use as potential sources of air pollution:
transportation, industry, and other sources. Specification of the mix, inten-
sity and locations of these three land use types, when coupled with ambient
conditions of meteorology, climatology, and topography, will determine con-
centrations and spatial patterns of all pollutants emitted in the planning
area.
The most publicized air pollution source category is transportation,
particularly motor vehicular transportation. The burning of fossil fuels
in internal combustion engines used by automobiles, trucks, and buses has
created a serious air pollution problem for highway-oriented urban areas,
Similarly, airport operations contribute heavily to air pollution, although
their impact is usually limited to the vicinity of the facility itself.
Rail transportation also contributes, although on a relatively minor scale,
to air pollution. Transportation activity as a whole is a major source of
carbon monoxide, oxides of nitrogen, hydrocarbons, and photochemical oxidants.
The second major category of air pollution sources is the general
group of industrial emitters. Industrial sources of air pollution are
responsible for emissions of S00, particulates, NOY> hydrocarbons, and to
/ A
a limited extent CO. These result both from the burning of fossil fuels
for heat and power and from the physical or chemical processes that are
indigenous to specific industrial operations. Additionally, industries
often dispose of solid wa.ste by incineration.
18
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Table 2. GENERAL SOURCE CATEGORIES OF AIR POLLUTION
I. Industrial Sources
A. Space heating of industrial buildings
B. Process heating
C. Separate process emissions
D. Solid waste disposal
II. Transportation Sources
A. Automobiles
B. Gasoline trucks and busses
C. Diesel trucks and busses
D. Diesel rail vehicles
E. Electric rail vehicles
F. Aircraft and airport operations
III. Other Pollutant Sources
A. Incineration of solid waste
B. Space heating of commercial buildings
C. Space heating of residential facilities
D. Space heating of institutions (schools and hospitals)
E. Evaporative losses from petrochemical service
operations (gas stations, fuel oil delivery, etc.)
F. Agricultural crop dusting, plowing
G. Forest fires and urban fires
19
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Finally, there is a category of other pollution sources that may have
a significant role in determining overall air quality. This group includes
residential, commercial, and institutional facilities. Their accompanying
fuel needs for space heating and public solid waste disposal facilities rep-
resent substantial contributions to an area's air pollution. In particular,
municipal incineration generates large amounts of highly visible pollutants,
primarily particulates, Except for large scale public solid waste facilities,
individual sources within this category, in comparison with industrial and
transportation sources, are relatively minor with respect to their impact
on regional air quality. Large scale solid waste facilities require indivi-
dual air quality analyses that should not be attempted by the planner.
Table 2 presents the sources of pollutant emissions by the three
general categories of urban land use discussed above. These three activity
categories are usually classified by point, line and area source configura-
tion-type to represent emissions from the different activity categories.
The relationships between industrial and transportation activities and their
emission characteristics are discussed in further detail in Section 5, where
procedures for selecting industrial and transportation plans, compatible with
acceptable air quality levels, are presented.
Background Air Pollution
Background air pollution may be defined as that level of pollutant
concentration not directly attributable to an identifiable source or
combination of sources within the planning area. Background concentrations
may be relatively constant over the planning area, or they may vary signifi-
cantly within it. It is generally not possible to determine future background
pollutant levels with a high degree of accuracy. Consequently, it is necessary
to have air quality data available with which to assess the air quality impact
of planning decisions relative to projected background air pollution.
For purposes of this and the following discussion it may be worthwhile
to clarify the intended meaning of the terms "area" and "region." In plan-
ning, "region" implies a large area, the size of a multi-county or metropolitan
area or Air Quality Control Region (AQCR); a subregion is still fairly large
(larger than a suburban political jurisdiction). An "area" on the other hand
can be of any size. It may be a few square blocks within an urban area, a
20
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town within a metropolitan region, a complete city, or a whole region. Of
course the size of the area under consideration will determine details of
the information required by and, in some cases, the basic approach to indi-
vidual planning studies. To a large degree, these will manifest themselves
as questions related to background pollution concentrations.
If the background levels of pollution are high within a planning area,
as is usually the case in urban regions, then the potential air pollution
resulting from sources within the planning area by itself may be only a small
percentage of the total air pollution. As a result, land use planning may not
be an effective means of reducing air pollution levels within the planning
region. On the other hand, where it is not possible, for whatever reason, to
prohibit growth in a region with high background levels, it may be yossible
to determine the types and amount of development that will keep regional
levels of air pollution within standards. In particular, if the spatial
variations in background concentrations are significant, then it is essential
to carefully locate land use activities relative to such concentration pat-
terns.
Low background pollutant concentrations within a planning area may
occur in two ways. First, the planning area may be located within a non-
urbanized or non-industrialized area; and secondly, the planning area
itself may encompass a sufficiently large portion of the urban region so
that the relative influence of background concentrations is low. The result,
in either case, is that the percent variation in expected pollution concen-
trations among alternative land use plans, or planning decisions, may be
relatively large. Under such circumstances, land use planning can be
effective in reducing regional pollutant concentration levels.
2.3 Natural Phenomena Affecting Air Quality
The concentration of atmospheric pollutants observed at different
locations depends on more than just the quantity of pollutants emitted at
the various sources. The atmosphere is the agent that transports and dis-
perses pollutants between sources and receptors. Consequently, the state
of the atmosphere helps to determine the concentrations of pollutants
observed at receptors. Unlike emissions sources, which can be controlled,
the state of the atmosphere is not at present susceptible to man's control.
21
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Some skill has been attained, however, in predicting the future state of the
atmosphere. Since the meteorological conditions that favor high concen-
trations of pollutants, are known, severe air pollution episodes can there-
fore be forecast.
In general, three parameters are used to describe atmospheric transport
and dispersion processes. These are wind speed, wind direction, and
atmospheric stability. For emissions at a given source, a higher wind
speed provides the pollutants with a greater air volume within which to
disperse. This causes ground level pollutant concentrations, other things
being equal, to be inversely proportional to wind speed.
Horizontally, the wind direction is the strongest factor affecting
pollutant concentrations. For a given wind direction, nearly all the
pollutant transport and dispersion will be downwind. Wind direction deter-
mines which sector of the area surrounding a source will receive pollutants
from that source. The influences of wind speed and direction on pollution
dispersion volumes and hence, on ground level concentrations are illustrated
in Figures 1 and 2.
Atmospheric stability directly affects the vertical dispersion of atmo-
spheric pollutants. Unlike wind direction and wind speed, atmospheric
stability cannot be measured directly. Atmospheric stability is a measure
of air turbulence and may be defined in terms of the atmospheric temperature
profile where ambient temperature is a function of height above ground level.
When the temperature decreases rapidly with height, vertical motions in the
atmosphere are enhanced, and the atmosphere is called unstable. An unstable
atmosphere, with its enhanced vertical motions, is more effective for
dispersing pollutants, and because of the large volume of air available for
the spread of pollutants, ground-level concentrations can be relatively low.
When the temperature does not decrease rapidly with height, vertical motions
are neither enhanced nor repressed and the stability is described as neutral.
Under these conditions, pollutants are also allowed to disperse vertically
in the atmosphere, although not as rapidly as for the unstable case.
When the temperature decreases very little, remains the same, or
increases with increasing height, the atmosphere is called stable. Under
these conditions, the atmosphere inhibits the upward spread of pollutants.
Upward-moving smoke, which rapidly assumes the temperature of the surrounding
22
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14.4
Kilometers
Height
Wind
Direction
Distance Downwind
Source of
-Air Pollution
Volume of air
containing the
pollution emitted
in one hour
Wind Speed =
4 Meters/Second
Volume of air
containing
the pollution emitted
in one hour
Wind Speed= 2 Meters/Second
Figure 1 The influence of wind speed on ground level pollutant concentrations
23
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Wind
Direction
Source
Of Air
Pollution
Wind
Direction
-Source
Of Air
Pollution
Figure 2 The influence of wind direction on ground level pollutant concentrations
24
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Inversion
The Pollutant Can Only Spread As
High As The Inversion
Mixing Layer
Temperature
s
I
When The Inversion Is Higher
The Pollutant Can Spread
Throughout A Larger Volume
Mixing Layer
Temperature
Figure 3 The influence of atmospheric stability on ground
level pollutant concentrations
25
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air, reaches a point where it is colder, and hence denser, than the air above
it, so it can rise no further. This suppression of upward motions effectively
forms a lid beneath which pollutants can disperse freely. The weaker the
temperature decrease with height, the higher is the lid. The extreme case
is an inversion, when the temperature increases with height. Often, clouds
are topped by a stable or inversion layer, which stops their vertical growth.
The well-mixed layer beneath a stable layer is called the mixing layer.
When it extends to the ground its vertical extent is known as the mixing height
or the mixing depth. Generally, turbulence is enhanced in the early morning
hours as the sun heats the ground and temperature decreases with height causing
unstable conditions. At night, as the earth cools, temperature increases with
height causing less turbulence and stable atmospheric conditions. Figure 3
illustrates the influence of atmospheric stability on ground level pollutant
concentrations.
Wind speed, wind direction, and atmospheric stability will vary greatly
with time. For a certain location, some combinations occur more frequently
than others. The planner should obtain such information about his region
so that he can take the meteorology of air pollution into account during
the planning process.
Where detailed meteorological records have been kept for a year or
more, a stability wind rose can be calculated. This wind rose is a set
of tables, one for each stability class (ranging from very stable to very un-
stable), listing the frequency of occurrence of all possible combinations of
wind speed and wind direction. Figure 4 shows a sample wind rose for Newark,
New Jersey. Such wind roses are available for many locations in the
United States from the National Climatic Center in Asheville, North
Carolina. It should be noted that topographical features such as mountains,
hills, valleys, bodies of water, buildings, and other terrain features can
change airflow patterns resulting in unexpected pollution effects.
Near a large body of water, local sea breezes influence the spread of
pollutants. Early in the morning, when the air is still or the wind is off
the land, pollutants can accumulate over their sources or downwind of them.
Later in the day, when ai local sea breeze develops, a fresh breeze blows in
the direction from the water toward land. This breeze brings with it
not only the pollutants emitted from the sources at this time of day, but
also those accumulated earlier in the day, because they are carried back
26
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LEGEND
Figure 4 The stability wind rose for Newark International Airport
aConcentric percentage circles indicate frequency of occurence
(e.g., easterly winds occur 4% of the time during the year)
27
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from water to land. Unexpectedly high pollutant concentrations can occur
near the shore when the high pollutant loading blows past. In addition to
this effect, which generally occurs close to land, the Seabreeze itself can
penetrate as far inland as 40 miles or more.
Mountains and valleys have characteristic airflow patterns, too. In
the evening, as the earth and the air close to the earth cools, the coldest
air will sink into the lowest part of the valley, as illustrated in Figure
5. This creates a stable inversion layer because lighter, warmer air stays
above the valley. In this way, pollutants are trapped in the valleys all
night. During the daytime when heating occurs, the air in the valley is
warmed and rises, permitting the pollutants to escape (Figure 6). Unfortunate-
ly, this heating and upward motion does not always occur. During periods when
high pressure settles over a region and the air is stagnant, the atmosphere
is stable all day long, and pollutants continue to accumulate in the valley.
Some of the worst episodes of air pollution have occurred in mountain chains
like the Appalacians, where industries are located in the valleys between
adjacent hills.
In cities, buildings form the topography. Where rows of tall buildings
front on narrow streets the air flows through the streets as though they were
canyons. Since ventilation is determined by building configuration, many
distortions in wind, amd hence pollution flows, take place in a city. Figure 7
shows an example. Air flows over a building and into a street downwind of it.
The lines show the direction of airflow. The building, because the air cannot
flow through it, creates an obstruction in the pattern of the smooth airflow.
Downwind of the building, an eddy, or circular movement of air at variance
with the main airflow, is formed in its wake, such as the one shown in the
figure. This eddy can trap pollutants emitted by cars in the street, and can
cause concentrations of pollutants, for example, carbon monoxide, to be as
much as three times higher on the side of the street further downwind than at
the site of pollutant origin.
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Figure 5 Nighttime airflow into valleys
Figure 6 Daytime airflow out of valleys
29
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::::::::: frC-jf" &t3Sa>
'"V% .«/'' ' ' '-^r * *"
Figure 7 Airflow around and in the wake of a building
30
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3. THE PLANNING PROCESS AS A DESIGN SYSTEM FOR
ACCEPTABLE AIR QUALITY
The objective of this section is to provide a procedural framework
for incorporating the consideration of air quality into the planning process
as a basic planning design parameter in formulating and evaluating land use
and transportation plans. The methodology presented here may be viewed as
a sifting process in which the planner avoids potential air pollution prob-
lems by applying air quality criteria to design decisions throughout the
plan's development. This effectively reduces the necessity of having to
introduce major changes involving either the mix, intensity, or location of
land uses because the "final" plan is found to be incompatible with acceptable
air quality. Specific procedures, analytical tools, and appropriate data
for applying air quality criteria to the planning process are presented in
the following sections of this document. These elements, together with the
methodology, form a design system for "building" acceptable air quality
into comprehensive planning.
Figure 8 presents the procedural outline of the air quality impact
land use planning process. As indicated, implementation of the logic flow
may be accomplished through the performance of the following five steps:
1) Establishing the air quality baseline
2) Defining the tolerance of the planning area toward receiving
additional pollution
3) Determining acceptable industrial/transportation mix(es) and
intensity(ies)
4) Distributing industrial/transportation land uses within compre-
hensive land use plan(s)
5) Evaluating the air quality impact of the plan(s)
It must be noted at this point that the procedure indicated above is
not intended as an all-encompassing determination of the optimal air quality
impact land use configuration. Rather, it is an iterative, air quality
oriented planning methodology that will help the planner arrive at a satis-
factory overall plan. Furthermore, it is not suggested that the entire
procedure be applied to every planning situation where air quality is
expected to be a factor, nor is it recommended that the planner rigorously
31
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IMPLEMENTATION
PROCEDURAL LOGIC
STEP I
Establish the Air Quality Baseline
STEPS
Define the Tolerance of the Planning
Area to Additional Pollutant Emissions
STEP 3
Set Constraints on Industry
Transportation
STEP4
Generate Comprehensive Land Use Plan
Define Pollutant Concentration Tolerance
Annual Equivalent to Standards
Existing Concentrations
Air Quality Standards
Pollutant Concentration Allowances
Define Pollutant Emission Tolerance
Simplified Dispersion Model
Air Quality Guidelines
for Simplified Disper-
sion Model Analysis
I
Emission Allowances for
Industrial 6 Transportation Sources
Develop Preliminary Design
Industrial Types fa Amounts
Transportation
Preliminary Design
STEP S
Evaluate Air Quality Impact
Comprehensive Plan
Air Quality Guidelines
for Specifying Industry
& Transportation
Develop Comprehensive Land Use Plan
Non-Industrial, Non-transportation
Land Uses
Locating M*}er Sources
Air Quality Guidelines
for Locating Major
Sources
Evaluate Air Quality Impact of Plan
Emissions Data
Meteorological Data
Air Quality Standards
Figure 8 The air quality impact-land use planning process
32
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pursue air quality goals to the exclusion of other planning concerns. The
position that air quality criteria occupies, relative to other planning
criteria, will vary depending on the priorities and needs of a specific
planning region and the capabilities of agency personnel. It is assumed
that the extent to which the air quality - land use planning methodology is
employed and the level of detail sought at each step in the process will be
tailored to the needs of individual planning regions. A brief discussion of
the individual steps follows.
1) Establishing the Air Quality Baseline
The first step in the air quality impact - land use planning process
is to define existing regional air pollutant concentrations. The purpose
of this step is to determine an air quality baseline for the planning
area. Because the entire decision-making process relative to air quality
is directly affected by this determination, it is important that the planner
use air quality data that is the most accurate, complete, and representative
information available. In most cases, state air pollution control agencies
have operational air quality monitoring systems and have been collecting
air quality data for the past few years. Where this is not the case, or
where such data are judged not to be consistent with the requirements of
planning decisions, it may be necessary to seek the services of an air
pollution specialist with air quality monitoring capabilities. In any
event, results of this data gathering should be in the form of concentra-
tion averages for the time periods specified in the standards, both averaged
over the entire area and in terns of spatial variations expressed as iso-
pleths, which are contours of constant levels of pollutant concentration.
A more detailed discussion of the individual pollutants and their respective
time frames of interest has been presented in Section 2.1.
2) Defininf the Tolerance of the Planning Area Toward Receiving
Additional Pollution
Having established the air pollution baseline, the allowable increase
in air pollutant concentrations for each pollutant within the planning area
should be determined. In addition to the improvement of air quality in
areas where NAAQS are exceeded, recent federal court decisions have inter-
33
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preted the intent of the Clean Air Act of 1970 as including the maintenance
of present air quality levels where these levels are not in violation of the
secondary air quality standards. Although regulations have been proposed
for preventing degradation of existing air quality, there are as yet no
federal policies as to what constitutes a permissible increase in concen-
tration.
Among the alternative methods proposed by the U.S. Environmental Pro-
tection Agency is a plan to prevent'significant deterioration by establishing,
for nationwide application, a maximum allowable increment in air quality above
the baseline air quality for SO- and particulates. This plan also incorpor-
ates New Source Performance Standards (Federal Register, Vol. 36, No. 247,
December 23, 1971) stipulations that all new or modified sources employ best
control technology.
Another plan proposed would indirectly prevent significant deterioration
of air quality by preventing significant increases in emissions by calculating
a ceiling emission rate based on emission density. Since these and other
alternative proposed plans to prevent significant degradation impese restric-
tions on the use of the air resource, restrictions are simultaneously
imposed on the use of land. Policies relative to nondegradation and regula-
tions for complex sources adopted by EPA will have varying land use implica-
tions for different regions, depending on the present level of air quality
in specific localities.
In any case, allowable concentration increases must be related to cor-
responding allowable increases in pollutant emissions. This relationship is
established through the use of an atmospheric dispersion model, a model based
on quantitative descriptions of the transport and dispersion of pollutants
in the atmosphere. Air pollutant dispersion models can be of use in mapping
portions of an urban area or community where an increase in emissions from
new economic activity is permissible. The models can also indicate the
amount of increase allowed for each pollutant and each time-averaging period
for which there is an air quality standard. General background information
about the types of dispersion models available and their relative utility
to the planner are presented in Section 4. A simplified dispersion model
which may be employed in this step of the process is also presented.
34
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3) Determining Acceptable Industrial/Transportation Mixes
and Intensities
The purpose of this step is to provide the planner with constraints
for the most heavily polluting land uses, i.e., industry and transportation,
based upon the tolerance of the planning area to their generalized emission
characteristics. To accomplish this objective it is necessary to relate
the increases in pollutant emissions allowed, calculated in Step 2, to
different industrial and transportation category mixes and intensities.
Examination of the possibilities relative to other planning concerns enables
the planner to postulate one or more preliminary inventory alternatives, as
indicated in Figure 8. Background information and a set of procedural
guidelines for quantifying generalized relationships between industry and
vehicular transportation activities and their emission characteristics, are
presented in Section 5.
4) Distributing Industrial/Transportation Land Uses With
Alternative Comprehensive Land Use Plan(s)
At this point in the process, the planner has defined one or more
possible industry-transportation mix alternatives for the planning area,
each of which is cognizant of acceptable levels of air quality. Individual
alternatives represent upper limits to industrial and transportation related
land use for the type of mix specified. Ideally, in defining each alterna-
tive, not only has air quality been addressed, but other pertinent planning
constraints as well. Consequently, the complete set of alternatives should
encompass the entire spectrum of what is considered to be both desirable
and feasible in terms of alternative preliminary plan designs. The planner must
now spatially distribute these industrial/transportation land use alternatives
within comprehensive land use plans. Inasmuch as this involves the place-
ment of land uses within the planning area, the spatial contours of existing
pollutant concentrations, as well as the dispersion patterns of anticipated
emissions, must be considered if local violations of the air quality stan-
dards are to be prevented. This is especially important where spatially
averaged regional pollutant concentrations are expected to be close to
standards.
35
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Generalized dispersion characteristics that may be used to locate
industrial land use and major motor vehicle corridors within the planning
area are presented in Section 7. In addition, the planner may wish to
employ a numerical simulation model to determine the specific pollutant
dispersion patterns of Important individual sources in the microscale.
Since most planning agencies do not have this type of modeling capability,
the services of an air pollution specialist should be sought to implement
these studies.
5) Evaluating the Air Quality Impact of the Plan(s)
Despite the fact that plans generated by performing the preceding four
steps have been formulated with an eye toward air quality, the planner
should recognize that an air quality impact evaluation of the plan(s) is a
mandatory final step in the process. This is primarily due to the generalized
nature of the emissions information required to make a_ priori air quality
determinations of anticipated land use and to the assumptions required by
the simplified dispersion model analysis indicated in Figure 8. However, by
specifying land uses through the performance of Step 4, the planner has
necessarily generated planning data of sufficient detail to perform a much
more extensive examination of air quality impact. In addition, spatial
variations of expected pollutant concentrations for a given plan as a
whole (which are not quantifiable to this point) must be examined if the
air quality standards are to be met everywhere within the planning area.
Section 8 presents an evaluative methodology for examining the air quality
impact of comprehensive land use alternatives. Due to the rather sophisiti-
cated nature of the indicated analyses, it is not recommended that the
planner perform these evaluations. Rather, the services of an air pollution
specialist with extensive modeling capabilities should be sought.
3.1 Factors Affecting Industrial Emissions
Industrial emission sources are quite widely varied. Although Section
5 proposes a means of estimating industrial emissions, it is important for
the planner to recognize those variables affecting emission rates from
individual industrial sources so that the capabilities and limitations of
the tools suggested here are fully realized.
36
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Generally, an industrial source may emit pollutants by any or all of
the following ways. First, most industries burn fossil fuels to provide
space heat for the physical plant, and to provide energy (either in the
form of heat or electricity) for the operation of plant components.
Secondly, individual industrial processes may have byproducts which are
vented into the atmosphere as a form of waste disposal. Finally, industries
may incinerate their own solid waste, again releasing the combustion products
into the atmosphere.
Emissions from Fuel Use
Energy requirements for industrial operations may be specified in terms
of mechanical/electrical power requirements, operational heat energy require-
ments, and space heating requirements. Operational heat and power require-
ments are generally dependent on equipment used, production rate, and activity
schedule. The amount of energy required to heat a given facility is generally
a function of the building volume (but often floor area is used since this data
is easier to obtain), local climatology, and the architectural or engineering
design of the individual building with respect to both heat retention and
heating efficiency.
Floor area of a plant will generally be related to employment and/or
production rates for a given industry. Each employee may be expected to
require a minimum amount of working area depending upon his function. A
specified production rate may require a determinable employment and equip-
ment level which in turn dictates a need for floor space. Generally,
industries are similar enough that" these space requirements are reasonably
consistent for firms manufacturing the same product.
The amount of energy required to heat a predetermined floor area is
dependent upon local climatology. Specifically, the number of degree days
of heat required per unit volume is an energy consumption parameter. A
factory in Minnesota, identical in all respects to a factory in Southern
California, will require substantially more space heating during the course
of a year. This is particularly true in winter months when outside tempera-
tures may differ as much as 40°F.
The design of a given facility will certainly be a factor in its
heating requirements. A-poorly insulated,building with high ceilings (and
37
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thus a large enclosed volume per square foot of floor area) will be much
less efficiently heated than a building with properly sealed doors, windows,
and fixtures, and with lower, insulated ceilings. In addition, inefficiencies
of heating, ventilating, and air-conditioning systems due to either poor
design, economic expediency, or poor maintenance will significantly increase
heat energy requirements for a given structure.
The nature of the heat energy source used bears greatly upon the emis-
sions from an industrial source. Current fuel supplies consist of four
major fossil fuel categories:
1) Coal
2) Residual Oil
3) Distillate Oil
4) Natural Gas
Each of these fuels is primarily a hydrocarbon compound. Whenever hydro-
carbon fuels are burned, gaseous oxidation products are formed. Optimum
combustion of these fuels results in water vapor, carbon dioxide, and nitro-
gen; all normal atmospheric constituents. If the combustion process is not
optimal, or if impurities exist in the fuel, burning may produce carbon ash,
unburned hydrocarbons, as well as sulfur and various metallic compounds.
The fuels listed above have a decreasing level of sulfur and ash content,
hence an increasing tendency to produce cleaner combustion products.
Unfortunately, the cost of heat energy from the four fuels is inverse to
their cleanliness.
Process Emissions
Industrial process emissions are related to the individual physical or
chemical processes required to manufacture a given product, and may be
quantified (as with fuel use emissions) by process rate and activity schedule.
In particular, air quality in the vicinity of a given plant may be sensitive
to differences in operational modes (i.e., high intensity - short duration
operation as opposed to low intensity - continuous operation), so that the
specification of industrial types in areas where air quality is already
a concern should involve consideration of the time frames of industrial
operations, as well as the quantity of individual pollutants, relative to
existing air quality temporal trends.
38
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Solid Waste Disposal
Solid waste disposal may, or may not be a major consideration in the
total emissions from a given industry. Many industries which produce large
volumes of solid waste may find it economically desirable to have an incinerator
on site. Since solid waste disposal is not a necessary function of any single
activity, it may cause the relative emissions of plants with similar
activities and production capacities to vary greatly.
Planners should consult local air pollution officials to ascertain
policies on incineration since local policy with respect to incinerator
operation will have effect on emissions within his region. In those areas
where solid waste disposal is tightly controlled, emissions will be lower
than those that would be estimated by using the guidelines presented in
the following section.
Regardless of the source of emissions, there are any number of emission
control devices and strategies which can be employed to minimize the impact
of industry on air quality. While the specification of industrial emission
controls is primarily an engineering and regulatory question, planners
designing new land use patterns should favor the imposition of such controls
for all new facilities. Conversely, new facilities should not be permitted
to use inferior controls with the expectation that local atmospheric disper-
sion will be adequate to ensure compliance with the air quality standards.
39
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3.2 Factors Affecting Transportation Emissions
Emissions associated with transportation sources account for a major
portion of air pollution in urban areas. Air quality characteristics of
five major categories of urban ground transportation are discussed below,
including a brief discussion of the individual categories as they affect
air quality considerations in the planning process. The five modes of
ground transportation discussed include:
1) The automobile
2) Gasoline trucks and buses
3) Diesel trucks and buses
4) Electric mass transit
5) Diesel transit
Major urban transportation systems should be examined both on an aggre-
gate and on a component basis to ensure that operational designs and the
choice of transportation modes are consistent with air quality requirements.
In most cases, major transportation projects require Environmental Impact
Statements, as outlined in the National Environmental Policy Act (NEPA) of
1969, for which air quality assessments are necessary. Nevertheless, it
may be helpful for the planner or the decision-maker to have some broad
guidelines when considering alternative transportation modes. Section 5
discusses a means of estimating emissions resulting from transportation
sources.
Potential air pollution problems associated with transportation sources,
notably the automobile mode, may be particularly accentuated in areas of:
(1) high density development, (2) pedestrian and bicycle traffic, and (3)
sensitive receptors.
Where the density of development is high, particularly where highrise
buildings are present, air quality is measurably impaired by high-density
automobile traffic. Lack of adequate street ventilation due to the obstruc-
tion of natural airflows may significantly decrease the dispersion of auto-
motive pollutants so that the same levels of emissions may result in higher
pollutant concentrations.
Although it may be obvious that automobiles are incompatible with
pedestrian and bicycle traffic on the basis of safety and efficiency of
40
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movement, planners should be aware that placing traffic volumes-iadjacent
to walkways may expose the pedestrian to pollutant concentrations above air
quality standards. This exposure is often accentuated in areas of high
density development, as previously described.
Automobile traffic may be incompatible with several land use activities
which are commonly termed "sensitive receptors." With respect to air quality,
residential areas, generally containing a large number of sensitive receptors,
should not be located adjacent to roadways with high traffic volumes.
Exposures are possible in two major areas. Dwellings near high-volume roads
may be exposed to peak hour traffic emissions in excess of hourly standards
(for CO in particular). Since residences are occupied for long periods,
residents could be exposed to 8-hour concentrations in excess of standards
as well. Medical facilities are susceptible for the same reasons as resi-
dences. Additionally, however, they often contain persons who have lower
resistance to air pollutants. Elementary schools and other similar insti-
tutional buildings are sensitive receptors since children are densely
grouped for long periods of time. Recreational facilities are often sensi-
tive receptors. They are particularly sensitive where there is heavy physical
exertion since increased respiration rates cause the intake of pollutants to
be sharply increased over a short time span.
3.2.1 Emission Characteristics by Transportation Mode
Automobiles
Travel by automobile represents the most significant mode of travel in
the United States. As such, its polluting characteristics have received a
substantial amount of study. Although the existing data on emission charac-
teristics of automobiles are far from complete, we now have a reasonable
understanding of expected emission rates for given operating conditions.
As shown in Table 3, vehicle speed, vehicle age, driving cycle characteristics
and operating temperature affect the amount of carbon monoxide, hydrocarbon
and oxides of nitrogen emissions resulting from automobile travel.
41
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Gasoline Trucks and Buses
The gasoline-powered trucks and buses exhibit emission characteristics
like those for automobiles, but at larger volumes per vehicle. They are
considered separately, however, because they serve a different transportation
need than automobiles. Buses, which exhibit emission characteristics most
like those of automobiles, are far more efficient in terms of pollutant per
passenger mile. Volumes of trucks and buses are generally quite a small
fraction of total traffic. Proposed emissions regulations, however, will
make these heavy duty gasoline-powered vehicles a more important source of
emissions in the future. While auto emission levels are to be reduced to
less than 10% of pre-emission control levels (Ref. 6, Table 3.1.2-1), heavy
duty emissions will remain at levels from 24 to 58% (Ref. 6, Table 3.1.4-3)
of pre-control levels. As a result a heavy duty truck will emit as much
NOY as 9 automobiles, as much HC as 18 automobiles and as much CO as 45
A
automobiles. These ratios indicate that each year after 1976 trucks and
buses will be the source of a larger and larger percentage of total vehicular
emissions. At some time between 1985 and 1995 the emissions from heavy
duty vehicles will be more than half of all transportation emissions,
unless control regulations are revised. Comparative analysis of emission
rates for the transportation mode categories is shown in Table 4. Gaso-
line buses are included in the comparisons.
Diesel Trucks and Buses
Since the engineering aspects of the diesel engine differ markedly
from those of the gasoline engine, there are significant differences in
the polluting natures of the two power sources. While the pollutants
produced by diesels are basically the same as those from gasoline engines,
the proportions differ. Because of the higher temperatures of combustion,
emissions of NOY from diesel engines are substantially higher than in
A.
gasoline engines. CO emissions, on the other hand, are minimal.
Unlike gasoline-powered vehicles, there are only three operating
variables that affect the exhaust output of diesels. They are engine
speed (rpm), and fuel use, which are interdependent, and vehicle age.
Diesel trucks and buses use similar engines and have similar operating
43
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Table 4. COMPARISON OF TRANSPORTATION EMISSIONS BY PASSENGER
VEHICLE AND PASSENGER MILE OF TRAVEL
EMISSIONS PER VEHICLE MILE (GRAMS)
Pollutant
CO
HC
NO,
so2
Particulates
Auto
85.00
.9.50
6.17
0.18
0.30
Gas
Bus
130.0
19.0
10.0
0.85
0.26
Diesel
Bus
20.41
3.36
33.57
2.45
1.18
Diesel
Rail
6.35
4.54
6.80
5.90
2.27
Electric Rail with
Coal
0.91
0.37
37.19
13.97
29.30
Gas
negl.
negl.
0.05
0.02
0.73
Oil
0.01
1.09
35.38
27.21
3.44
EMISSIONS PER PASSENGER MILE (GRAMS)
Pollutant
Assumed
Passenger (s)/
Vehicle
CO
HC
NO,
S02
Particulates
Auto
1.5
56.6
6.3
4.1
0.12
0.20
Gas
Bus
30.0
4.3
0.6
0.3
0.03
0.01
Diesel
Bus
30.0
0.7
0.1
1.1
0.08
0.04
Diesel
Rail
60.0
0.1
0.08
0.1
0.1
0.04
Electric Rail with
Coal
60.0
0.02
0.01
0.6
0.2
0.15
Gas
60.0
negl.
negl.
negl.
negl.
0.01
Oil
60.0
negl.
0.02
0.6
0.5
0.06
NOTE: All emission rates pertain to urban conditions for the current
National Vehicular Age Distribution Mix, 1960 and earlier to 1973
model years.
7,
An Interim Report on Motor Vehicle Emissions, Kircher and Armstrong.'
Compilation of Air Pollutant Emission Factors.
44
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characteristics. For this reason emission factors for trucks and buses
are similar and are not currently differentiated by vehicle type; all
diesel vehicles are considered to emit similar pollutant loads. Emission
characteristics for diesel buses are listed in Table 4.
Diesel Rail Vehicles
Since the diesel rail vehicles are all fairly similar in emissions
characteristics, very little individual analysis is warranted. The major
differences are the sizes of the power plants, the load capacity/efficiency
relationship (i.e., the weight of the payload being hauled versus the
engine size required to pull the load), and the operation characteristics.
Rail designs allow more work per amount of fuel consumed since the need for
acceleration and the noncruising mileage are minimized. Since operating
conditions are nearly uniform, rail engine deterioration is reduced also.
Quantitative emission comparisons, including diesel rail vehicles, are
shown in Table 4.
Electric (Rail) Transit
The nature of electric (rail) transit systems makes it impossible to
include them in a simple analysis of vehicular pollutants. For the rule-
of-thumb estimates that may be made using this document it is safe to assume
a negligible emissions burden.
Electric rail vehicles do not burn fossil fuels. Instead they use
electric power generated at a plant not necessarily in the area being
studied. The burning of fuels at a power plant to provide electric power
to transit vehicles is commonly considered an indirect or secondary impact,
but the calculation of these indirect emissions and their impact is quite
complex, and should not be attempted without the benefit of advice from
an air quality control agency.
45
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Summary of Transportation Emissions by Type
Recognizing the general polluting characteristics of the various modes
of urban transportation, the planner requires comparative values to weigh
the air pollution advantages of one mode over another. It can be readily
concluded that gasoline-powered vehicles are the major sources of both CO
and HC on a per capita basis because of their limited passenger capacities.
Similarly, it should be noted that diesel vehicles emit larger volumes
of NO , SO,,, and particulates. Lastly, it can be seen that electric rail
A £.
transit using natural gas supplied power emits almost negligible levels of
all five of the compared pollutants. In any case, all comparisons by
vehicle mile seem cuite unrealistic when comparing urban modes. Emissions
per passenger mile of urban travel probably offers ^ more viable means of
comparing transportation modes.
Table 4 points up several facts about the comparative emission rates
per passenger mile of the various transportation modes. The automobile
has the highest emission rate for each of the pollutants associated with
transportation-related land use. For CO, its emissions are a factor of
13 greater than the second worst emitter, which is the gasoline bus. It
has a rate of emitting HC that is a factor of 10 greater than that for
the gasoline bus, which is second. For NO , it is the largest unit emitter
by a factor of 7 over electric rail. For S02 and particulates, it again
has the worst emission rates with electric rail being second, depending on
the power plant supplying electric power.
Because automotive vehicular traffic is the largest contributor to
transportation-related pollutant emissions, a means of estimating these
emissions for consideration in the air quality impact-land use planning
process is contained in Section 5.
46
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4. RELATING POLLUTANT EMISSIONS TO AIR QUALITY
Thus far, typical pollutants and their principal source categories have
been discussed, including general meteorological and topographical factors
twhich affect the behavior of pollutants in the atnosphere. In addition,
emission characteristics of industrial and transportation source categories
have been discussed. Having determined existing air quality levels within
the planning area, within the context of the Air Quality Impact - Land Use
Planning methodology, the planner must now define the tolerance of the
planning area toward receiving additional pollution which would result from
new land use. To do this, it is necessary to translate pollutant emissions
into air pollution concentrations for a planning area. The relationship
of pollutant emissions to air pollution concentrations is most effectively
established through the use of an atmospheric dispersion model, a model
based on quantitative descriptions of the transport and dispersion of
pollutants in the atmosphere.
4.1 The Dispersion Models
There are many kinds of dispersion models, varying in complexity and
utility, but basically, three general types can be identified:
1) Box models
2) Gaussian plume models
3) Numerical simulation models
Each type of model is significantly different in approach from the others
and each represents a very different level of sophistication. Consequently,
results of the various model types may find application in providing dif-
ferent kinds of air quality information, of varied utility, for the planner.
The least sophisticated of the model types and that which provides
the least detail of air quality information is the box model. This type
of model is of maximum utility to the planner in making preliminary policy
and design decisions on a regional or subregional scale. Most especially,
it lends itself very well to defining the tolerance of a given area to the
more heavily polluting land use categories such as industry and transpor-
47
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tation in terms of air quality standards. The mathematical computations
required by a regional scale box model analysis are limited to simple hand
calculations.
Gaussian plume models are the next step upward in terms of level of
sophistication and can provide very detailed air quality information. This
type of model has been in operational use for a considerable period of
time, and has been, and is still being used with success where it is
appropriately applied. These models usually consider both point and area
sources. The gaussian plume model is of considerable utility to the planner
as an evaluative tool for considering alternative land use and transportation
plans in terms of their impact on the air quality of a region. On a
regional or subregional scale, a gaussian plume analysis of air quality
requires the use of a high speed digital computer along with a rather
comprehensive emissions and meteorological inventory. Use of this type of
model is therefore generally both expensive and time consuming. In
addition, because of the assumptions necessary in all models of this type,
great care must be taken in analyzing and evaluating their results. However,
gaussian plume models offer the planner the opportunity to examine in
considerable detail the air quality implications of postulated land use
and transportation configurations, individually or combined as a whole.
Numerical simulation models are the most sophisticated of the dispersion
models and are still in a relatively formative stage. They can provide very
detailed two and three dimensional pictures of the spatial patterns of
pollutant concentrations on relatively small physical scales. For this
reason, this type of model is most applicable to determining the localized
air quality impact of individual sources such as a highway or power plant,
or an emitter of other than the six typical pollutants. Invariably, numerical
simulation models require the use of a high speed digital computer. However,
because they are generally applied to individual sources they require not
nearly so much input data as the gaussian plume models. Their maximum
utility to the planner, at this point in time, is in the design and place-
ment of large individual sources of pollution. However, advances in computer
technology and numerical methods may soon make it possible to employ
numerical simulation models in the capacity presently served by gaussiem
48
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plume models. This would represent a significant increase in state of the
art of dispersion modeling because simulation models are operationally more
flexible and more tolerant of variations in source design geometry than are
the gaussian models.
4.2 Model Utility
As described in the preceding section, the planner has available three
different types of models with which to relate pollutant emissions to air
quality concentrations. Each type of model provides different kinds of
air quality information for the planner and each requires different plan-
ning information from the planner. Furthermore, the level of detail of
information available during the planning process and necessary for the
dispersion models suggests that maximum model utility may be attained by
applying each of the models to a specific procedural step of the methodology
presented in Section 3.
Box Models
Box models, the most general of the model types in terms of level
of detail, are suited for use in step 2 of the procedure, defining the
tolerance of the planning area toward receiving additional pollution.
CRefer to Figures 8 and 9). As indicated in Section 2, this step allows
for the determination of air quality constraints on land uses, based on
the determination of existing levels of air quality.
Allowable pollutant concentration increases are then transformed into
allowable increases in pollutant emissions through application of a box
model analysis. A model of this type for use in this procedure is presented
in Section 4.3.
Gaussian Plume Models
Gaussian plume models are most applicable to detailed air quality exam-
inations of comprehensive land use configurations and are therefore best
suited for use in step 5 of the procedure, the evaluation of the air quality
impact of alternative plans (refer to Figure 8). Section 9 presents an air
quality impact evaluation methodology for comprehensive land use plans
within which the use of a typical gaussian plume model is specified.
49
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Numerical Simulation Models
Because of the significance of the spatial variations of pollutant
concentrations in the microscale, and the implications these variations
have relative to the placement of air pollution sources, numerical simulation
models are most suited to be used in step 4 of the procedure, distributing
industrial/transportation land uses within comprehensive land use plans.
Examples of applications of this type of model are discussed in Section 7.
4.3 A Simplified Urban Dispersion Model
The model presented here is a meteorologically constrained simplifi-
cation of that presented by Holzworth, which has been demonstrated to
obtain good correspondence between predicted and observed mean concentra-
tions for each of several urban study areas. Although the model is an
approximation of the complex physics involved in atmospheric dispersion
processes, it is nevertheless consistent with the general nature of infor-
mation exchanged at the point of its application within the planning process.
As such, it provides a means of quantifying the relationships between
pollutant concentrations and pollutant emissions that are required by step 2
(defining the allowable increase in pollutant emissions) of the procedure
illustrated in Figure 9.
Most often, the'planner will want to use the air quality standards,
as defined in Section 3.1, as criteria in planning for acceptable air quality.
However, because violations of the 1, 3, 8, and 24 hour standards are
generally localized and occur in an area of several city blocks, and
because the level of detail of planning data at this point in the process
is, in any event, insufficient to generate meaningful air quality information
for these time frames, it is suggested that the planner use the equivalent
annual arithmetic mean air quality standards presented in Table 3. It must
be cautioned here that the concentrations cited in the table are not intended
for use as compliance criteria for the standards. Rather, they are design
values for simplifying the implementation of step 2.
50
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Equivalent Annual
Average Air
Quality Standards
State Air Quality
Control Agency
Calculate
Allowable
Increases in
'once
Existing Air
Quality Data
(From Step I)
iraiion
1 I
m J
1
1
L_
i
m
Anticipated Decrease
in Pollutant
Concentrations
»» . ^_^_ «^ M. «*« ^« -
1
1
_J
Is
Allowable
Increase
Than or Equal to
Anticipated
Increase ?
Set
Allowable
Increases
Equal to
Anticipated
Decrees
Box
Model
Analysis
Allowable
Increase in
Pollutant Emissions
Figure 9
To Step 3
Step 2 in the air quality impact-land use planning process;
defining the tolerance of the planning area to additional
pollutant emissions.
51
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Existing air quality data used in step 2 (defining tolerance of area
toward receiving additional pollution) should be in the form of annual mean
concentrations of the individual pollutants. As will be recalled from
Section 2, existing air pollutant concentrations have been compiled in this
form as a result of step 1 which established the air quality baseline.
Having defined the required inputs, implementation of step 2 proceeds
as schematically illustrated in Figure 9. The differences between pollutant
concentrations presented in Table 5 and existing pollutant concentrations are
compared with anticipated decreases in pollutant concentrations resulting
from either imposed emission controls or land use relocation, as specified
by state pollution control agencies. If these differences are equal to or
less than the anticipated decreases, they may be considered as allowable in-
creases in pollutant concentrations. If this is not the case (i.e., if
the differences are greater than anticipated decreases) the planner has
two possible courses of remedial action. He can either re-adjust the dif-
ferences (i.e., set them equal to anticipated decreases) or, where the
pressures for development are severe, he can call for the imposition of
emission controls on existing sources within the planning area. However, it
is to be noted that the implementation of a federal non-degradation policy
and accompanying standards would impose a specific mandate for increases in
pollutant emissions allowable in areas where air quality is currently at or
above the NAAQS. In all cases, the end result is a set of allowable pollutant
concentration increases which are compatible with both the Federal Ambient
Air Quality Standards and the intent of the Clean Air Act Amendments of
1970, as interpreted by the Federal Courts.
The model treats the planning area as one large continuously emitting
ground level source having a uniform average area emission rate (Q) . Spatial
variations within the area are not accounted for. Model results are presented
graphically, as shown in Figure 10, in terms of an average normalized
concentration (see Section 1.3, Glossary of Terms) in seconds/meter
i.e., a concentration (₯) in g/m averaged over the planning area and
_ 2
normalized by the area emission rate (Q) in g/m /sec), as a function of
ventilation length. The ventilation length used to determine the normalized
concentration is taken to be the longest straight line distance through the
planning area (ranging from 10 to 100 km) .
52
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Table 5. EQUIVALENT ANNUAL ARITHMETIC MEAN AIR QUALITY STANDARDS'
Pollutant
Carbon Monoxide
Hydrocarbons (non-methane)
Nitrogen Oxides (NCL)
Sulfur Oxides (SO^
Total Suspended Particulates
Standard
(pg/m3)
1425.0
160.0
100.0
60.0
60.0
*The Hackensack Meadowlands Air Pollution Study, Task 2 Report
53
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Implementation of the model requires that the planner determine, from
Figure 10, the normalized concentration for the planning area and then
apply this concentration to the following formula to obtain pollutant
emissions.
E = (C/N)A (1)
where
E = annual mean allowable increase in emission rate (griiniG/second)
C = annual mean allowable increase in pollutant concentration (grams/meter )
N = annual mean normalized concentration (second/meter), from Figure 10.
A = study area of the planning region (meter ) .
As indicated, the variables expressed in the equation are all in terms
of annual means. Meteorological parameters, specifically mixing depth and
wind speed, used to generate the curve shown in Figure 10 were specified
as estimates of annual averages and should be fairly conservative (worst
case conditions) for most areas within the contiguous United States, as is
consistent with the intended application of model results. However, given
the appropriate level of expertise, it is conceivable that the planner may
wish to calibrate this model to the specific meteorological conditions of
the region of interest, in order to obtain a more case-specific model
application. Since annua.1 average ventilation flows will, in general, not
be consistent with the longest straight line distance through the area,
model results will again be conservative.
As with other air quality considerations, implementation of the model
within the planning process is required on a pollutant by pollutant basis.
Because pollutant concentrations used in the analysis are derived from
equivalent annual mean ccncentrations of the standards (refer to Table 5) ,
the single 'curve given in Figure 10 is equally applicable to each of the
individual pollutants. Illustrative examples of model applications within
the planning process are presented in Section 6.
54
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40
36
32
o 28
0)
u
c
o
U
TO
a>
N
~o
E
o
I 12
24
20
16
0
10 20 30 40 50 60 70 80 90 100
Size of Planning Area (km)
Figure 10 The relationship between annual mean pollutant concentration
(averaged over area and normalized by emission rate) and
ventilation lengthb
.Applies to all pollutants.
Holzworth2.
55
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5. RELATING ALLOWABLE EMISSION INCREASES TO A SELECTION OF
INDUSTRIAL AND TRANSPORTATION LAND USES
Having determined the tolerance of the planning area toward receiving
additional pollution in terms of allowable emissions, industrial/transpor-
tation land use schemes appropriate to the designated allowable pollution
increase can be devised. This section describes a set of procedures for
selecting industrial/transportation plans which are consistent with basic air
quality planning goals. As indicated in Figure 8, in Section 2, this procedure
requires that the planner transform increased allowable emissions into a
preliminary inventory list of industrial/transportation land use activities.
This land use design (or several, as the case may be) must then be specified
in terms of upper limits to postulate amounts of:
1) Specific industrial land use components.
2) Motor vehicle activity.
As indicated in Figure 11 input to Step 3 consists of allowable
increases in annual mean emissions for each of the pollutants. The planner
now begins to specify types and amounts of industry which are consistent with
basic planning goals and relates them to air quality limits.
Often, future industries locating within an area as well as such
precise information as the projected number of employee-hours, will be
unknown during the initial stage of the planning process. Generally,
however, basic types of industries or characteristics of industries
that may locate in the planning area may be projected by observing existing
industries and their relationships with other industries that would tend
to locate nearby. Industry types can also be projected by noting rapid
growth industries, by studying the characteristics of the city as compared
to the needs of various industrial types, and by applying location or
economic-base theory. In addition, although most localities distinguish
only between heavy and light industry for zoning and other regulatory
purposes, many areas are contemplating performance zoning, which would
distinguish among industries by their nuisance characteristics, including
air pollution emissions. Therefore, it may be possible to prescribe
or limit by means of air pollutant emissions criteria, the types of
industries and their locations that would be allowed in order to meet air
quality standards and policies.
57
-------
Allowable Emissions
(From Step 2)
Generalized
Industrial Emission
Characteristics
Specify
Industrial
Mix &
Intensity
Industrial
Emissions
Calculate
Allowable
Transportatio
.Emissions .
Projected
Employment
Projected
Travel Area
Generalized
Transportation
Emission
Characteristics
'Calculate
Anticipated]
^Transportation,
Problems,
Are
Anticipated
Transportation
^Emissions S Allowable
Transportation
Emissions
Yes
Preliminary Design
To Step 4
Figure 11 Step 3 in the air quality impact-land use planning process;
setting constraints on industry and transportation
58
-------
Generalized emissions characteristics and a procedure for estimating
annual mean pollutant emissions for various industrial categories are
''presented in Section 5.2. For each industry specified, the planner reduces
allowable increases in emissions by the appropriate amount until the resi-
dual is estimated to approach anticipated emissions from additional trans-
portation demand. General rules of thumb for estimating this point, by
pollutant, prior to examining transportation demand are as follows based
Q
upon prior work and the professional experience of the authors:
Carbon Monoxide - reserve approximately 90 to 95% of total
allowable increases in CO emissions for transportation.
Hydrocarbons - reserve approximately 60% of total allowable
increases in HC emissions for transportation
Nitrogen Oxides (NO ) - reserve approximately 50% of total
allowable increases in NO emissions for transportation.
Total Suspended Particulates - reserve approximately 5% of
total allowable TSP emissions for transportation.
Sulfur Dioxide - since SO- is not related to transportation,
it is not necessary to reserve any portion of its allowable
emissions.
As indicated in Figure 11 the residual emissions are, in effect,
allowable transportation emissions. Having already specified an industrial
mix and its corresponding component intensities, however, these allowable
transportation emissions cannot necessarily be independently specified.
That is, an increase in industrial activity will result in an increase in
transportation demand. If this increased demand results in emissions which
exceed the residuals, the planner should either examine alternative modes of
transportation, find ways to reduce vehicle miles traveled (VMT) or readjust
industrial mix and intensity accordingly, recalculate anticipated industrial
emissions, and find the new corresponding residuals. Generalized vehicular
transportation emission rates with which to estimate transportation emissions
are presented in Section 5.4.
While the above procedure does not directly address the problem of
increased emissions from non-industrial, non-transportation sources, the
-------
generally conservative nature of the box model analysis is anticipated
to account for these sources. In addition, comprehensive evaluation of
"final" plans will conveniently point to concentrations of pollutants in
excess of the standards, so that an iterative adjustment of industry and
transportation for compliance with standards will correspondingly satisfy
the emission requirements of other land uses.
5.1 Estimating Industrial Emissions
This section provides the basis for tracing cumulative emission esti-
mates for a specified industrial mix, as required in Step 3, through a set
of industrial pollution index codes and generalized emission rates.
Table 6 is a very general guide for reference prior to hypothesizing
an industrial mix. It is intended to give the planner a qualitative estimate
of the potential to pollute for each of several major industrial categories.
Two digit Standard Industrial Classification (SIC) codes representing, the
indicated major industrial manufacturing groups are listed in ascending
order. The five columns to the right of the index column contain single
letter codes indicating the pollution potential for each of the five major
pollutants. As indicated, the letter code "A" indicates that the industrial
group is a "light industry" (i.e., an industry which pollutes very little)
with respect to the given pollutant. These industries are generally clean
and air quality need, not be a major consideration in their specification.
Conversely, letter code "B" indicates a "heavy industry" (i.e., one that
may be expected to have substantial emissions for the given pollutant).
The "B" codes indicate that some care should be taken when placing the
industry because they may not be compatible with adjacent sensitive receptors.
Likewise, clusters of more than one "B" coded industry could present signifi-
cant regional air quality problems. Code "C" indicates a "problem industry."
A "C" coded industry would be one that should be individually studied by an
air quality expert :>o that its impact on its community is both minimized
and acceptable.
The planner should be aware in his use of Table 6, that there is a
great amount of variance in polluting potential among the industries within
any set of two digit SIC coded industries. For this reason care should be
taken in the use of Table 6. It is a general guideline and should be used
as such. It should not be used as an index for making significant air
quality decisions.
60
-------
Table 6. GENERAL EMISSION CHARACTERISTIC OF INDUSTRIES BY SIC3
"A" indicates industry of the given SIC presents no air quality
problem for the pollutant considered.
Pollutant "B" indicates only a finite number of the given industry may
Classifi- be located in a given area. Care should be taken in location
cation
Code
process.u
"C" indicates a critical industry with respect to air quality
Expert advice should be solicited in choosing and locating
these sources.
Industry
Type SIC
Food Products
Textiles
Apparel
Lumber § Wood
Furniture
Paper Prod.
Printing 6
Publishing
Chemical
Petroleum
Rubber 5
Plastics
Leather Prod.
Stone, clay
§ Glass
Primary Metals
Fab. Metals
Machinery
E lee. Machinery
Transport . Equip
Prof. .Scient.
20
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
.37
38
so2
Emission
Class
B-
B+
A
A
A
C
A
B-
C
B+
B
B
B
A
B+
B+
A
A
Particulate
Emission
Class
B
A
A
A
A
B-
A
B
C
A
A
B
B
A
B+
A
A
A
CO
Emission
Class
A
A
A
A
A
A
A
B
C
A
A
A
B-
A
A
A
A
A
HC
Emission
Class
A
B
B
A
A
B
C
B
C
B+
B-
A
A
B-
B+
A
B+
A
NOX
Emission
Class
B-
B
B+
A
A
C
A
B-
C
B+
A
B
B
A
B+
A
A
B
B+
Precision made
Inst.
Misc. Manu. 39 B* A A B
O -1
Air Quality for Urban and Industrial Planning fExtensionl .Fins') Report
bB+ indicates a range closer to the "A" classification
B- indicates a range closer to the "C" classification
Note that each of these categories covers a wide range of values.
61
-------
Table 7 provides a means of estimating emissions resulting from a given
mix of industries. The table consists of estimated generalized emissions by
pollutant and letter code. From this table the planner may calculate numerical
estimates of industrial pollutants. The units are in terms of grams of
pollutant emissions per employee and per hour of plant operation. By
multiplying this unit emission by the employed intensity (employee-hour per
year), a total annual emission is estimated for each industrial source.
These estimates are applied to the selection of industrial/transportation
land use schemes in Step 3. Sample calculations for the procedure described
above are presented in Section 6.
5.2 Estimating Transportation Emissions
As indicated in Figure 11, determination of capable industrial/trans-
portation land use schemes requires that transportation demand estimates,
in the form of average daily traffic (ADT) or vehicle miles of travel (VMT)
per day, be related to annual average anticipated transportation emissions.
Table 8 provides emission rates for both urban and rural vehicular use
where 'urban' implies stop and go traffic patterns with an average route
speed under 45 mph, and 'other' implies traffic patterns with anticipated
average route speed exceeding 45 mph. It is not suggested that the table
be used to estimate emissions for specific transportation configurations
since the figures are very generalized, emission rates being representative
of typical vehicular mixes.
Annual average emission values for anticipated demand may be calculated
as follows:
E = (365)
where
E = annual average emissions (grains)
R = emission rate (from Table 8) (grams/mile)
A = estimated average daily traffic (ADT)
L = estimated vehicular miles traveled per vehicle trip per day
and the subscripts u and o define the traffic pattern (i.e., 'urban' or
'other').
Application of the emissions calculated to the Step 3 procedure is
accomplished as indicated previously. Sample calculations of the above
procedure are presented in Section 6.
62
-------
Table 7. GENERALIZED INDUSTRIAL EMISSION RATES'
(GRAMS OF POLLUTANT PER EMPLOYEE-HR.)
Industry
Type
A
B+
B
B-
C
so2
6
24
75
176
530
Particulates
5
15
86
220
660
CO
2
' 22
75
220
1320
HC
6
20
53
198
595
NOX
6
18
46
132
350
n -i
Air Quality Pollution and Industrial Planning (Extension), Final Report
These numbers are based upon fragmented data documented in the above
reference. The use of this table for significant air quality studies
and decisions is not advised at this time due to the preliminary nature
of the emissions estimates.
63
-------
Table 8. GENERALIZED VEHICULAR TRANSPORTATION EMISSION RATES
(grams/mile)
Pollutant
CO
HC
NO,
Traffic
Pattern
Urban
Other
Urban
Other
Urban
Other
1975
60
35
7.66
5.66
4.9
1980
36.5
14.2
4.1
2.0
2.8
4.2
1985
25.0
9.8
2.7
1.3
1.8
2.7
1990 5 Later
23.8
9.3
2.5
1.2
1.6
2.4
Emission rates pertain to the following vehicular mix:
90% Automobiles and light-duty vehicles
10% Heavy-duty Trucks
Current National Vehicular Age Distribution, pre-1960 and
1960 through 1973.
Source: United States, Environmental Protection Agency, Compilation of Air
Pollutant Emission Factors, Office of Air Programs, Publication No. AP-42,
February 1972; Revised, April 1973.
64
-------
6. ILLUSTRATIVE EXAMPLES
In order to clarify the procedures involved in implementing the Air
Quality Impact-Land Use Planning Proc.ess through and including the
specification of constraints to industry and transportation (step 3), the
following sections are presented to illustrate calculations required by
steps 2 and 3. The first example begins with a set of annual average
pollutant concentrations for an existing land use configuration and runs
through the procedures involved in step 2 (refer to Figure 9). The second
example takes the emissions calculated in the first example and postulates
an industrial mix, along with traffic constraints, as indicated in step 3
(refer to Figure 11). The examples are presented as illustrative matter
only and are neither intended to restrict the application of, nor limit
procedural variations to the methodology presented in Section 2.
6.1 Determining Allowable Emissions
In conjunction with the requirements of establishing an air quality
data base for a planning area, the following annual average pollutant con-
centrations have been established from data supplied by the state air
pollution control agency:
Annual Average Concentration
Pollutant CMS/"*3)
S02 48.0
NOX 5.0
CO 810.0
HC 133.0
TSP 37.0
As indicated in Figure 9, initial 'allowable1 increases in pollutant
concentrations are determined merely by subtracting the annual average
concentrations indicated above from the equivalent annual average standards
presented in Table 5.
65
-------
Initial'
Allowable Increases
so2
NO,
CO
HC
TSP
60.0 -
100.0 -
1425.0 -
160.0 -
60.0 -
48.0
5.0
810.0
133.0
37.0
Pollutant (pg/m )
12.0
95.0
615.0
27.0
23.0
From the state pollution control agency, it has been learned that
existing air quality levels are anticipated to be decreased by 1990 (the
plan design period) by the following amounts due to a uniformly applied
strategy of emission controls across the state:
Anticipated Decrease in
Pollutant Pollutant Concentrations
(Ug/m )
S02 9.0
NOY 130.0
A
CO 580.0
HC 19.0
TSP 13.0
At this point, there are two possible courses of action: add the
anticipated decreases to the initial allowable increases, or adopt the
anticipated decreases as allowable increases. In the former case the
planner would be designing up to the tolerance of the standards and,, in the
latter, designing to maintain present levels. Bearing in mind recent court
cases involving the degradation of existing air quality, the latter course
of action is taken.
66
-------
Allowable 'Final1 Increases
Pollutant (ug/m3)
S02 9.0
NOX 95.0
CO 580.0
HC 19.8
TSP 13.0
As indicated in Figure 9, a box model analysis is required to translate
these allowable concentration increases to corresponding increases in pollut-
ant emissions. It has been determined that the longest straight line distance
through the planning area is 27 kilometers. Applying this number to the
graph in Figure 10, the annual average normalized concentration is determined
to be 15.8 (seconds/meter). The study area of the planning region is 405 km
so that annual average increases in pollutant emission rates, calculated from
equation (1) are as follows:
Annual Average
Allowable Emission Rate
Increase
Pollutant (grams/second)
S02 2.31
NOX 24.35
CO 149.72
HC 5.07
TSP 3.33
In terms of total annual increases to existing emissions, increases
(multiply by 3.1536 x 10 seconds/year) are:
67
-------
Pollutant
S02
NOX
CO
HC
TSP
Annual Average Allowable
Increase in Emissions
(Grams)
7.28 x 10
76.79 x 107
469.06 x 10?
15.99 x 10?
10.50 x 10?
As indicated in Figure 9, these values represent the output of step 2.
The following section demonstrates their use in step 3.
6.2 Constraining Industry and Transportation
As a result of previous survey work, the planner has determined that the
following industries desire to locate within his planning area. These in-
dustries are for illustrative purposes only and as such are hypothetical.
Industry
1. Apex Shoes
2. Balto Furniture, Inc.
3. Cello Rubber Products
4. Diamond Lumber Co.
5. Excello Shirts
6. Franklin Petroleum
7. Gellow Steel Products
8. Halon Optical, Inc.
9. Inter Food Products
10. JEM File Cabinets
11. Kowalsky's Wooden Widgets
12. Levrett Instruments
13. Malten Moltens, Inc.
Total
SIC
31
25
30
24
23
29
33
38
20
34
24
38
33
Projected
Employment
1500
1200
6000
20
240
60
500
2000
4000
4000
300
20
300
20,140
Annual Hours
of Operation
4000
8700
6000
1800
6000
8700
7600
8700
6100
4400
4000
2000
4000
72,000
68
-------
It must now be determined which of these industries may be allowed
within the planning area without exceeding the annual average allowable
increases in emissions already defined for this example. These allowable
emissions are not to be totally allocated to industry, but must also cover
increased transportation emissions from the additional demand created by
increased Industrial activity. As indicated in Section 5, a priori estimates
of emissions from additional transportation activity may be made as follows:
Annual Average Allowable In-
crease in Emissions Reserved
Pollutant for Transportation (Grams)
S02 [ 7.28 x 107] x [0.0 ] = 0.0
NOX [ 76.79 x 107] x [ .5 ] = 38.40 x 107
CO [469.06 x 107] x [ .9 ] = 422.15 x 10?
HC [ 16.0 x 10?] x [ .6 ] = 9.59 x 10?
TSP [ 10.5 x 107] x [0.05] = .525x 10?
Subtracting these values from the total allowable emissions yields
annual average allowable industrial emissions.
Annual Average Allowable
Increase in Industrial
Emissions
Pollutant (Grams)
S02 [ 7.28 x 107] - [ 0.0] = 7.28 x 107
NOX [ 76.79 x 107] - [ 38.40 x 107] = 38.39 x 107
CO [469.06 x 10?] - [422.15 x 107] = 46.91 x 107
HC [ 15.99 x 107] - [ 9.6 x 107] = 6.40 x 1C7
TSP [ 10.50 x 107] - [ .525 x 10?] = 9.975 x 107
The process of specifying industrial mix is now initiated. Table 6 of
Section 5.2 indicates that Franklin Petroleum (Industry Number 6 above)
is coded 'C' with respect to each of the 5 pollutants. Since the planning
69
-------
area is already close to air quality limits, the planner elects to eliminate
this industry from the list of possibilities. The remaining 12 industries
are all considered to be viable choices for the planning area so that the
planner now calculates the emissions from each (using Table 7 of Section 5.2)
and consequently subtracts these emissions from allowable industrial emissions
until the residuals approach zero. It should be noted that the sequence of
these industries does not represent a "priority ranking." That is, industries
would not necessarily have to be eliminated from the bottom-up.
ANNUAL POLLUTANT EMISSIONS
(GRAMS X 10"7)
Industry
1.
2.
3.
4.
5.
7.
8.
9.
10.
11.
12.
13.
7.
-0.
6.
-0.
6.
-0.
5.
-0.
5.
-0.
5.
0.
5.
-0.
5.
-4.
1.
-CL
-0.
1.
-0.
1.
-0.
0.
so2
25
45
83
0626
73
864
874
000216
873
864
864
285
58
104
476
29
182
105
077
0072
005
00024
004
09
903
5.
-0.
5.
-0.
5.
-0.
4.
-0.
4.
-0.
4.
-0.
4.
-0.
3.
-3.
0.
-0.
0.
-0.
0.
-0.
0.
-0.
0.
NOX
1
036
064
0626
0
648
352
000216
351
02592
1748
15
313
838
16
67
105
565
0072
5578
00072
557
00552
5518
1.
-0.
1.
-0.
1.
-0.
1.
-0.
1.
-0.
1.
-0.
0.
-0.
0.
-0.
0.
-0.
0.
-0.
0.
-0.
0.
-0.
0.
CO
84
012
828
0208
808
072
736
000072
735
00288
732
836
896
0348
8612
0488
8124
352
4604
0024
458
0008
457
264
193
6
-1
5
-0
5
-0
4
-0
4
-0
4
-0
4
-0
4
-0
4
-3
0
-0
0
-0
0
-0
0
HC
.4
.18
.22
.0626
.158
.72
.438
.000216
.437
.07632
.36
.0228
.337
.104
.233
.1464
.087
.484
.603
.072
.5318
.00212
.529
.0072
.522
TSP
9.975
-0.03
9.945
-0.0522
9.893
-0.18
9.713
0.00018
9.713
0.0072
9.705
-0.3268
9.37
-0.087
9.283
-2.064
7.219
-0.088
7.131
-0.006
7.125
0.0002
7.124
-0.1032
7.02
Allowable
Projected
Residual
Projected
Residual
Proj ected
Residual
Projected
Residual
Projected
Residual
Proj ected
Residual
Projected
Residual
Projected
Residual
Projected
Residual
Projected
Residual
Projected
Residual
Projected
Residual
industrial
emissions
emissions
emissions
emissions
emissions
emissions
emissions
emissions
emissions
emissions
emissions
emissions
70
-------
Having accounted for all industries from the list of possibilities, and
aware that the CO residual is approaching zero, allowable transportation
emissions must now be compared with those calculated from projected
transportation demand estimates.
Because the residuals from allowable industrial emissions have not
gone identically to zero, the planner may add them to the allowable
transportation emissions.
Annual Average Allowable
Increase in Transportation
Emissions
Pollutant (Grams)
S02 ( 0.0) + (.903 x 107) = .903 x 10?
NOX (38.40 x 10?) + (.5518 x 10?) = 38.9518 x 10
CO (422.15 x 107) + (.193 x 107) = 422.343 x 10
HC (9.6 x 10 7) + (.522 x 107) = 10.122 x 10?
TSP (.525 x 10 7) + (7.02 x 107) = 7.545 x 10 ?
It has been estimated that the increase in industrial employment will
represent 35% of the increase in total population, so that:
Total increase in population = 20^080 a 60>00() (minus petroleum company)
-JJ
Projections by auto insurance companies and transportation planning
agencies estimate the average per capita miles travelled for work, shopping,
recreation, and secondary trips to be 7,000 miles/year.
Projected travel is anticipated to be 85% vehicular with a 1.72 persons
per vehicle occupancy rate, and 15% mass transit. Total annual vehicular
travel in miles is, therefore, estimated as follows:
Total passenger miles Passenger miles by motor vehicle
persons x person - year X Total passenger miles
Vehicle miles Vehicle miles
Passenger miles by vehicle Year
(60,000) people x (7,000) miles/person x .85 x (1/1.72) Chicles
^ ' > Person
D
-2.1 x 10 vehicle miles
per year
71
-------
Q
Of this 2.1 x 10 miles of travel, it is estimated that 80% will be
under urban (stop and go, low average speed) conditions and 20% non-urban
or expressway conditions. Applying Table 8 to equation (2) of Section 5.2
anticipated transportation emission rates are estimated as:
Pollutant
NOY
A
CO
HC
Annual Average Anticipated Transportation
Emission Rates
_ (Grams/Vehicle Mile) _
(,8)(23.8)+(.2)(9.3)
20.9
2.2
Multiplying these emission rates by the average annual VMT yields the
annual average anticipated increase in transportation emissions:
Annual Average Anticipated Net Allowable
Increase in Transportation Increase
Pollutant
Emissions
(Grams)
NOX (1.8) x (2.1 x 108) = 4.18 x 10
CO (20.9) x (2.1 x 108) = 43.89 x 10
HC (2.2) x (2.1 x 108) = 4.62 x 108
8
8
(Grams)
3.90 x 1Q
8
42.2,3 x 1Q
1.012 x 10
8
8
72
-------
Comparison of these anticipated emissions with allowable transportation
values indicates that both CO and NO may marginally exceed the non degrada-
A
tion goals set at the beginning of the problem. In fact the estimates show
that the national ambient air quality standards may be exceeded under the
proposed industrial and transportation mix. In this case the planner may
seek air quality expertise from his state or local air quality agency
to study the potential problem.
If desired the planner may also adjust his postulated industrial mix
such that NO and CO emissions will be reduced, and recalculate air quality
A
levels at a lower level of industrial activity. By this iterative process
the planner may redesign his industrial mix, incrementally eliminating
emissions, until his calculated emissions meet his air quality goals.
73
-------
-------
7. THE INFLUENCE OF SOURCE CONFIGURATION
Thus far, procedures have been outlined for establishing the air quality
baseline in a planning area (Step 1), defining allowable emission increases
(Step 2) and establishing acceptable industrial/transportation land use
designs (Spep 3). Step 4 addresses the spatial distribution of industrial/
transportation designs generated within comprehensive plans. The purpose of this
section is to demonstrate how differences in the placement and design of
major air pollution sources can be used to minimize the air quality impact
of a given mix and intensity of land uses in the implementation of Step 4
(refer to Figure 8).
As indicated in Figure 12, the input to this step consists of specified
types and amounts of industrial and transportation related land use. On
an individual basis, the effect of each major air pollution source within
these categorical sets is physically limited to a loosely defined area
surrounding the source. This area may be designated as the influenv_e
region or air pollution impact area of that source. Because pollutant
concentrations from individual and physically separated sources are
directly additive at those points where their respective influence
regions overlap, and because background pollutant concentration patterns
are further superimposed on these concentrations, the placement of major
sources relative to one another, as well as to background concentration
patterns, is critically important to the determination of local air quality
levels within the planning area. Furthermore, the locations of land uses
which are not generally associated with air quality problems but which
may be important as receptors of air pollution, are important in considering
the air quality impact of a given land use configuration.
Where sufficient engineering data for a given source exist (in terms
of stack height, flue gas rates and temperatures, etc.), or where a particu-
lar source or group of sources is anticipated to have a particularly signifi-
cant impact on air quality, the planner may wish to employ a numerical simu-
lation model (or in some cases a gaussian plume model) to explicitly define
region of influence. Where this is not the case, the information presented
in the following sections may be used as a guide for locating individual
land uses consistent with air quality requirements.
75
-------
PRELIMINARY DESIGN (S)
r .
1 Industry !
1
. Transportation .
(From Step 3)
Determini)
Influence
Region For
Important
Sources
General
Guidelines
&/or
Numerical
Simulation
Model
Spatial Variations of
Existing Pollutant
Concentrations
(From Step I)
Comprehensive Plants)
To Step 5
Figure 12 Step 4 in the air quality impact-land use planning process;
generating alternative comprehensive land use plans
n
i*.
o
76
-------
7.1 Industrial Sources
In order to evaluate the effects of land use planning on air quality
in terms of the location of pollution sources within the planning area,
several studies were undertaken that utilized a gaussian diffusion model,
MARTIK (developed by Environmental Research & Technology, Inc.), to determine
the pollutant concentration patterns for a variety of source configurations.
MARTIK is highly flexible and accepts emissions data from point (e.g.,
single stack), line (e.g., highway), and area (e.g., an industrial complex)
sources. A regional area was simulated, with a 25 by 25 grid cell system.
2
Each grid cell was 1 km on a side, so that the total area was 625 km . The
simple source configuration used for the studies together with 100 evenly
spaced receptor points were placed within this area. Contours of pollutant
concentrations were then drawn over the entire grid. This procedure allows
the pollutant concentration to be estimated at any point inside the region
by interpolation with the aid of the contour lines. Locations for sensitive
receptors can be selectively chosen from such studies, as well as the most
appropriate locations for additional sources. These points are illustrated
in the studies described in this section.
In studies concerned with the environmental impact of air pollution,
two basic types of temporal conditions are evaluated: average case and
worst case. Average case conditions simulate air quality for a given
combination of sources, emissions, and meteorological conditions, usually
specified as annual average values. They can be useful in estimating the
long-term exposure of a planning region to atmospheric pollutants.
Worst^case conditions simulate the extreme in pollutant concentrations
for a particular situation. In a study of this type, the MARTIK model
uses a single wind speed class, wind direction, and stability class. The
frequency with which these worst-case conditions occur can be estimated
from the annual average stability wind rose. Worst-case conditions are
modeled for several reasons. First, ambient air quality standards set by
government regulatory agencies are expressed as worst-case hour, three-hour,
and eight-hour averages. Estimation of worst-case conditions determines
whether a given land use plan can be expected to comply with present or
proposed air quality standards. Second, the placement of sensitive receptors
(schoolsj hospitals, etc.) depend on worst-case conditions, because such
77
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receptors contain persons who are particularly sensitive to the adverse
health effects of short-term exposure to high dosages of atmospheric pollutants.
Children, the very active, the ill, and the elderly are especially susceptible.
For the following case studies, the ground-level concentrations of
atmospheric pollutants are expressed so as to be independent of pollutant.
Emissions and concentrations are assumed to be linearly related, so that in
a given case study, doubling the emissions with all other factors held
constant would result In doubled concentrations throughout the grid. The
studies themselves are intended to be illustrative only. Although MARTIK
and the procedures described have been used extensively in operational
decision-making, the purpose here is to show the basic influence of land
use geometries on air quality.
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Case Study No. 1
The first sensitivity study is aimed at investigating the relative
effects on air quality of clustered versus dispersed area sources. In the
context of regional planning, this is related to the problem of locating
the industrialized areas of a planning region so as to minimize the adverse
effects of air pollution on the rest of the region. Figure 13 shows a
planning region within which the emissions sources are confined to a small
area in the center of the planning region, and can be treated by the disper-
sion model, MARTIK, as one area source. The contours are lines of constant
annual average pollutant concentration (isopleths). They were selected
so that, as one approaches the source, each new contour line encountered
represents a doubling of concentration. All other things being equal,
lowering the point of release of pollutant emissions results in the disper-
sion envelope, or plume, contacting the ground in a shorter downwind distance.
Since the dispersion of pollutant material is a fraction of distance down-
wind of the release point, the maximum ground level concentration resulting
from a given source will increase with decreasing stack height. The annual
wind rose for Newark International Airport was chosen as a typical wind rose.
The effects of using a particular wind rose show up as asymmetries of the
contour lines. For example, in Figure 13 the contours are elongated from
southwest to northeast because southwest winds occur more frequently at
Newark Airport than winds of other directions.
The alternative to clustering industry in a planning region is to
disperse it. In contrast to Figure 13, Figure 14 shows four area sources,
the sums of whose areas and emissions are equal to the area and emissions
of the single area source in Figure 13. The most striking difference between
the two land use configurations is the absence of the highest concentration
values in Figure 14 that appear in Figure 13. In fact, the maximum grid
point concentration (870) in the case of the dispersed sources has been reduced
by a factor of 2.4 from that in the clustered industry plan (2123). At the
same time, the minimum grid point value increases by a factor of 1.8 from the
clustered plan (80) to the dispersed plan (142). Thus, there are two main
points to be noted in this first case study:
1) Dispersion of industry decreases the highest annual mean pollutant
concentrations (those observed close to the sources) compared to
concentrating the same emissions sources.
79
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500
N
Note: Total source strength = 4000.0
Maximum concentration: 2123
Minimum concentration: 80
Figure 13 Annual average pollutant concentrations (yg/m )
for a single area source
80
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5OO
Note: Total source strength = 4000.0
Maximum concentration: 870
Minimum concentration: 142
sec
Figure 14 Annual mean pollutant concentrations (vig/m ) for dispersed area
sources
81
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2) Dispersion of industry greatly increases the lowest annual mean
pollutant concentrations (those observed away from the sources)
compared to concentrating the same emissions sources. This effect
comes about because fewer receptors can be great distances away
from any source when industry is dispersed.
The spatial analysis shown above in Figures 13 and 14 shows clear
differences between the clustered and dispersed alternatives that should be
considered in light of the other constraints and options that are available.
Several tradeoffs a.re apparent for this case study. Sensitive receptors
fare best when carefully placed within a region with clustered emission
sources. On the other hand, if annual mean concentrations predicted by a
box model are close to ambient air-quality standards, then a dispersed
configuration of msijor sources may be the only way to keep maximum concen-
trations low enough to meet standards. In addition, concentrations very
far away from a source are often sufficiently low so that even a doubling
would not cause them to approach the approximate threshold of adverse
effects for even the most sensitive receptors.
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Case Study No. 2
The second case study is aimed at investigating the relative effects
on air quality of clustered versus dispersed configurations of point sources.
This relates to the problem of deciding from an air quality standpoint
whether a region would better be served by one large incinerator or by
several smaller facilities.
Figure 15 shows contours of equal annual-average pollutant concentra-
tion resulting from a single large point source. It is interesting to note
that the concentration profiles indicated in the figure differ somewhat
from those for an area source of equal strength (refer to Figure 13).
Since the same meteorological conditions were used for both studies, the
differences are solely attributed to differences in source geometry (i.e.,
area as opposed to point source). In particular, an area source inherently
implies a dispersion of emissions over the area of the source. Consequently,
one would expect an area source to exhibit lower ground level pollutant
concentrations than a point source having the same total emissions. However,
the height at which pollutants are released has a strong effect on pollutant
dispersion in the vertical direction. Because a point source is generally
a single stack (or group of stacks), its emissions generally occur at
significant heights above ground level. Ground level pollutant concentra-
tions near the base of the stack are not always indicative of maximum values.
In most cases, maximum ground level concentrations occur immediately adjacent
to ground level sources and at some downwind distance from elevated sources.
Furthermore, for the same total emissions, an elevated source will most
often exhibit lower maximum ground level concentrations than will a ground
level source, although its impact will usually be felt over a larger area.
Figure 16 shows the concentrations resulting from four dispersed point
sources that together have the same total emission rate as the point source
in Figure 15. The effects on air quality of dispersing point sources are
identical with those of dispersing area sources so that the comments and
conclusions of the previous study are equally valid here. This represents
a steady state meteorological condition (fixed wind speed, direction and,
stability class). Depending on individual source configuration, steady
state conditions will occur within an hour, given an hour of persistent
meteorological conditions. Concentrations may be taken to be representative
of 1-hour maximum concentrations under steady state conditions.
83
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Note: Total source strength = 4000 (grams)
Figure 15 Annual mean pollutant concentrations (yg/m ) for a single
point source
84
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4OO
20O
Note: Total Source Strength = 4000.0
Figure 16 Annual mean pollutant concentrations (yg/m ) for dispersed
point sources
85
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Case Study No. 3
The third case study is aimed at investigating the relative effects on
air quality of clustered versus dispersed sources in a worst-case situation.
In this case, the wind direction chosen was southwest, with a stable atmo-
sphere. Figure 17 shows the concentrations resulting from two sources, an
area source and a point source. Southwest was chosen as the worst-case
wind direction, because the downwind effects of the two sources are super-
imposed most strongly for a southwest wind. Each contour, moving toward
a maximum, represents a doubling of pollutant concentrations. Largest
concentrations are observed somewhat downwind of the sources. With this
single wind direction, the model predicts negligible contributions to areas
outside a rather narrow downwind sector. As shown in Figure 17, the gradi-
ent of pollutant concentration is quite strong for this worst-case situation.
This sensitivity study was purposely complicated with the inclusion
of two sources, in order to illustrate the complexities of a situation
only slightly more realistic than that shown in the first two studies.
Figure 18 shows an alternate land use plan, where the area source is
dispersed into four smaller area sources. The point source remains. The
wind direction is southwest, as in Figure 17. In Figure 18, the point
source is clearly the dominant influence on the pattern of pollutant concen-
tration, as the highest grid-point value of concentration is located directly
downwind of it.
A comparison of the two land use alternatives shows that measurable
concentrations for this worst-case situation are predicted for a few more
grid points with the dispersed area sources than for the single area source.
In compensation, the maximum grid-point concentration value (16483) for the
dispersed plan is smaller by a factor of 1.4 than the maximum grid-point
concentration value (22601) for the plan with the area sources consolidated.
In practice, sensitive receptors can be positioned slightly more freely for
the case shown in Figure 17 than for the configuration shown in Figure 18.
However, when the maximum concentration of a pollutant is close to standards,
source dispersion is a useful technique for keeping worst-case concentrations
to a lower level for the same amount of emitted pollutant.
86
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2000
4000
Note: Total source strength
Point source strength
9000 r ?rams
5000 (-
^seconds'
Area source strength = 4000 f gram!> ]
.. . . T>zm seconds-1
Maximum concentration: 22601
Minimum concentration: 0
Figure 17 Worst case pollutant concentrations (ug/m ) for a single
point and area source
87
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zoqp
Wind Direction
Note: Total source strength
Point source strength
9000 ( gram;! )
seconds
5000 (-SEES*)
vseconds
Area source strength = (4x1000) = 4000 (-i£221_)
Maximum concentration: 16483
Minimum concentration.; 0
7
Figure 18 Worst case pollutant concentrations (ug/m ) for a single
point source and dispersed area sources
88
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Summary of the Three Sensitivity Studies
The above sensitivity studies have illustrated several important planning
guidelines:
1) Meteorological conditions in an area strongly affect pollutant
concentrations, for both annual mean and worst-case situations.
2) When the sources are dispersed to several smaller, more widely
spaced sources, minimum concentrations increase markedly for the
same total emissions. Thus, the most sensitive receptors in a
region might benefit from the concentration of large sources if
the receptors are located far from the sources.
3) When large sources are dispersed to several smaller, more widely
spaced sources, maximum concentrations decrease markedly for the
same total emissions. Thus, it may be useful in a planning region
to disperse large sources like industry, power generation, and
incineration, rather than to cluster them, in order to meet
ambient air-quality standards.
4) Very sensitive receptors fare best in the concentrated land use
plan, when they are placed far from the source. On the other
hand, because the maximum concentrations are higher in the clustered
case, only a limited area is available for the sensitive receptors.
For less sensitive receptors, the dispersed land use plan rates
higher for regional air quality on an annual average. The highest
concentrations are markedly reduced. When questions exist as to
whether a region will be able to meet air quality standards, dis-
person of sources should be seriously considered as a means of
reducing maximum concentrations.
7.2 Highway Sources
The dispersion patterns of pollutants emitted from highway sources
are dependent on three sets of variables: meteorological conditions, highway
geometry, and traffic characteristics. In terms of specifying highway con-
figurations which are consistent with air quality considerations, the planner
can exercise some degree of control over two of these sets (highway geometry
and traffic characteristics) and must be aware of the implications of the third.
89
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In order to quantify the relative sensitivity of air quality to each
of the three sets of variables, a numerical simulation model, EGAMA, was
put through a series of computer runs specifically designed to determine
the effect of each on the pollutant concentration field. Great care was
taken in the execution of this analysis to ensure that neither the opera-
tional capability of the model nor the myriad constraints of physical
reality were exceeded. Consequently, the sensitivity of model results to
variations of the parameters considered is consistent with observable
phys. 'al behavior.
Meteorology
Atmospheric dispersion processes are influenced to a large degree by
meteorological conditions. General comments relative to meteorological
concerns in the air quality planning process, as discussed in previous
sections, are equally valid in considering highway impact, and so will not
be repeated here. However, a graphic presentation of the effects of micro-
meteorology on pollutant dispersion may serve to illustrate the utility
of this information in locating highway and other land uses relative to one
another.
Figure 19 shows the ground level concentration profiles for a typical
at-grade, six-lane highway configuration as a function of wind speed.
Concentration values are independent of pollutant and are normalized by
the pollutant emission rate (in grams/meter-second) so that application
of the curve to determining the concentration patterns of specific highways
(of the geometry shown) may be accomplished simply by multiplying the
ordinate scale by the appropriate emission rate. It is noted that the
relationship of wind speed to the reciprocal of pollutant concentration
at a given downwind point is linear, so that the joint frequency of occur-
rence of average and worst-case wind speed and traffic conditions can be used
in conjunction with Figure 19 to perform approximate microscale evaluations
of anticipated air quality levels. Specifically, estimates of emissions
for the highway, under various assumptions of vehicular use, may be made
using Table 8. Application of these estimates to the normalized
concentrations will provide "actual" concentration profiles for the wind
speeds shown. Wind speed values considered to be representative of worst-
case and annual average conditions can then be used in adjusting these
91
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profiles to present both annual average and worst-case air pollutant concen-
trations. The planner can then determine how close to the highway various
land use categories may be specified without causing undue exposure to un-
desirable air quality levels. Conversely, where a proposed highway is to
be built through densely populated areas, these profiles can be used as
guides in routing the highway to minimize impact according to receptor
type.
It should be cautioned here that Figure 19 does not show the effects
of atmospheric stability on the concentration profiles. (The curves shown
are for the stable condition.) Where the planner has data on atmospheric
stability available, adjustments to the profiles generated from Figure 19
may be made to more accurately define worst-case as well as annual average
conditions. Concentration profiles shown in Figure 20 are normalized by
the ratio of emission rate (Q) to wind speed (U) so that 'actual' values
may be obtained by multiplying the ordinate scale by this ratio for a
specific highway. Applications of Figure 20 to the planning process are
identical with those discussed for Figure 19.
Highway Geometry
The cross sectional geometry of a highway influences pollutant disper-
sion by altering natural ventilation flows. Because highway geometry is
the only parameter which can be independently specified, it represents a
possible means of controlling very local air quality levels.
EGAMA recognizes three general highway cross sections: at-grade,
elevated, and depressed. The ground-level concentration profiles for each
will depend strongly upon the combined effects of relative location of
traffic lanes to regions of circulating flows or flow stagnation, the
depression or elevation dimensions, and meteorological parameters. Thus,
the effects of highway geometry on air quality levels cannot be simply
graphically condensed. (Indeed, this is a prime reason for use of high-
speed computer facilities for these studies.) The following generalizations
may be made, however, regarding the gross effects of highway configuration.
In the very near field of the road, concentration values for all pollutants
are predicted to be highest for the depressed geometry and lowest for the
elevated. This is consistent with the ventilation velocities (local wind
fields) associated with each geometry and is compatible with observable
93
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physical phenomena. At larger distances from the road, differences in the
ground level concentrations caused by design configuration become smaller
and air quality levels depend primarily on the basic emissions and meteoro-
logical factors. Peak ground-level concentrations for an elevated highway
section will occur at some distance downwind of the roadway. The peaks will
always be lower than those expected for either an at-grade or depressed
highway section. Measures taken to prevent noise pollution may have an
adverse effect on pollution dispersion because of noise barrier that
prevent ventilation flow.
Traffic Characteristics
Traffic characteristics are critically important to air quality pre-
dictions in the neighborhood of a highway because they determine the strength
and spatial distribution of pollutant emissions. Traffic volume, speed
distribution, and vehicle year and design mix determine source strength.
Traffic distribution by lane determines the spatial source distribution.
Source strength is the direct measure of the total amount of a given
pollutant assumed to be emitted per unit time and unit roadway length by
the vehicular traffic being modeled. As expected, the concentration values
downwind of the highway vary directly with source strength. In other words,
at a given downwind point a two-fold increase in concentration would result
from a two-fold increase in source strength. Figure 21 demonstrates this
relationship for a typical highway configuration._ The concentrations
indicated in the figure are normalized by the reciprocal of wind speed,
so that 'actual' concentration values may be obtained by dividing the
ordinate scale by the appropriate value of wind speed. Because of the
linear nature of the effect of source strength on concentration contribu-
tions, the sensitivity of model outputs to factors such as vehicle speed
can be directly deduced from the emissions factor data presented in Section
5.
Source distribution is the spatial distribution of the total source
strength within a given highway configuration. For a given total source
strength, varying the lane-by-lane source distribution will yield a sig-
nificant variation in the near road concentration values but has only a
small effect on concentrations further from the immediate roadway vicinity.
95
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Because the effect of source distribution on the concentration field is also
a function of the combined effects of highway geometry and meteorology, a
simply condensed graphical presentation of the sensitivity of local air
quality to source distribution is not possible.
Summary
1) The pollutant concentration field resulting from dispersion of
highway emissions is most strongly a function of wind speed and source
strength. Concentration levels will vary directly with source strength
and inversely with wind speed so that the characteristic profiles indicated
in Figure 21 may be used to estimate spatial patterns of highway pollutant
concentrations for both worst-case and annual average conditions. Further-
more, because source strength may be defined in terms of traffic volumes
and speed distribution, the design of individual highways will be a major
factor influencing air quality in the microscale highway environment.
2) Generally, ground level pollutant concentrations for all pollutants
are highest in those areas immediately adjacent to the highway, fall off
rapidly within about 80 meters (to approximately 30% of the maximum value),
and then decrease more gradually with downwind distance. Consequently,
highway rights-of-way should be maintained as limited-access areas wherever
possible. In particular, the practice of specifying land use adjacent to
major roadways for recreational purposes (public parks, pedestrian walkways,
bicycle paths, etc.) is especially bad air quality impact planning.
3) While highway configurations are generally postulated to satisfy
the transportation demand of a given land use configuration, there may be
several viable alternative roadway networks which can accomplish this.
The general comments addressing regional clustering versus dispersion of
pollutant sources presented in the previous section are valid for highway
sources where adjustments for emissions due to variations in speed distribu-
tion are made.
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8. AQUIP - AN EVALUATIVE TOOL FOR RANKING 'FINAL' PLANS
Having determined the desired mix and intensity of land use (step 3)
and distributed the industrial/transportation design(s) within the planning
area (step 4) wjth regard to location-sensitivity, the final step is the
evaluation of the plan(s) which have been formulated. Until quite recently,
a major constraint to the consideration of air pollution within the planning
process had been the lack of established procedures and analytical tools
which could be applied to the evaluation of land use plans.
In a study sponsored jointly by the Environmental Protection Agency
and the State of New Jersey, a methodology was developed which permits
planners to evaluate planning proposals to determine the effect on air
quality. This methodology, which has been designated as the AQUIP System
(Air Quality for Urban and Industrial Planning), is a computer-oriented set
of procedures involving the planner in an iterative cycle of plan evaluation
and modification consisting of the basic steps illustrated schematically in
Figure 22. The AQUIP System does not provide for the evaluation of plans
and revisions to plans in regard to other community planning goals and
constraints, such as population growth, future income levels, efficient
circulation systems, and so forth.
Components of the AQUIP System include techniques for projecting future
emissions based on land use and transportation planning input data, a gaussian
plume atmospheric dispersion model for projecting pollutant concentration
patterns over the planning region, data management and computation routines
for calculating quantitative measures of air pollution impact, and computer-
graphics programs for displaying land use and air quality data for plan
evaluation.
The use of a system like AQUIP is generally beyond the operational capa-
bilities of most planning agencies in terms of computer facilities and data
requirements. The AQUIP system has been fully documented elsewhere in a series
of reports and users manuals and the reader is referenced to these reports for
o
more information on the system and the methodologies.
97
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THE AQUIP SYSTEM
To Step 3
COMPREHENSIVE PLAN(S)
(From Step 4)
PLANNING DATA
CONVERT PLANNING DATA
TO
EMISSIONS DATA
EMMISIONS DATA
GAUSSIAN PLUME ATMOSPHERIC
DISPERSION MODEL
CLIMATOLOGICAL DATA
AIR QUALITY DATA, MAPS, ETC.
PLAN EVALUATION METHODOLOGY
AIR QUALITY
STANDARDS AND CRITERIA
ANALYSIS OF PLAN ADEQUACY RELATIVE
TO AIR POLLUTION CRITERIA
Figure 22 Steps in the air quality impact-land use planning process;
evaluating the air quality impact of 'final' plans
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9. SUMMARY AND CONCLUSIONS
In terms of defining an effective and meaningful policy of air resource
management, the specification of land use categories and intensities offers
the most fundamental level of air pollution control. In particular,
specification of the types and amounts of industrial and transportation
activity which are consistent with air quality criteria forms the basis for
generating urban configurations which are compatible with acceptable levels
of air quality. The methodology, analytical procedures, and generalized
emissions data presented in this document provide the planner with a set of
guidelines for incorporating the consideration of air quality into the
formulation of comprehensive land use plans.
Section 2 presented basic information regarding planning air quality
parameters and their relative impact on the planning process.
Section 3 presented an overview of the air quality impact-land use
planning process, including a 5-step procedure for its implementation.
Within the procedural framework presented, applications of air quality
criteria to planning decisions were defined at various levels of detail.
A 'final1 land use configuration which represented a synthesis of these
procedures was postulated. This design was the result of avoiding
potential air quality problems as they might occur within the sequence of
design decisions defining plan development.
Prior to developing the land use plan, those parameters and factors
influencing air quality in planning were discussed. Specifically, air
quality design criteria, source categories of air pollution, and natural
physical phenomena affecting the dispersion of pollutant emissions constitute
considerations in air quality planning in the implementation of the air
quality impact-land use planning process.
Sections 4 and 5 provided the basis for translating air quality planning
criteria to preliminary plan designs in terms of industrial land use and
transportation activity. Section 4 presented a procedural scheme for imple-
menting step 2, Section 5 for implementing step 3. Together these steps
comprised a cycle of preliminary planning decisions and air quality
evaluations to provide for a quick estimate of the compatibility of
anticipated or postulated industrial and transportation mixes and densities
99
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with acceptable air quality. Section 6 provided illustrative examples in
order to clarify the procedures involved in emissions calculations and
postulating an industrial mix, along with traffic constraints needed to
implement the air quality impact-land use planning process.
Section 7 presented information relative to the dispersion patterns of
various major source configurations so that the placement of comprehensive
land uses associated with preliminary designs generated in step 3 would not be
incompatible with local air quality considerations. Incorporation of this
information within the planning process occurred in step 4.
Finally, Section 3 discussed a methodology which provided for the air
quality impact evaluation of complete urban designs. The methodology,
designated as the AQUIP System, is completely operational and has been used
in the evaluation of alternative land use plans for the Hackensack Meadow-
lands of New Jersey. A document describing AQUIP is available from the EPA.
This guide has been designed as a resonable first estimate of the pro-
cedures planners can use to determine air quality implications of plan
design decisions. It has been based upon current data for regions pre-
viously studied; accordingly, the specific quantitative guidelines may not
translate well to certain geographic areas or long-term planning decisions.
It is expected that further studies will continue to expand upon and improve
the various data bases and specific procedures involved in the process.
In this way separate guides can be prepared for different scales of planning
decision and for varying time periods.
Limitations of Air Quality Impact - Land Use Planning Procedure
The application and interpretation of these procedures are subject to
many conditions which limit their accuracy and general applicability. A
primary limitation is due to the fact that the emissions estimation factors
presented in Sections 4 and 5 are generalized values derived from specific
current data sets, and thus cannot reasonably be expected to coincide with
assumptions involved in other regional planning situations and for long-
term future planning periods. A second limitation is that the box model
analysis presented in Section 4.3 is a very crude approximation to atmo-
sheric dispersion processes in general, and, as presented, does not allow
for regional variations in meteorological parameters. A third basic limita-
tion is that these procedures give no indication of the resultant pollutant
100
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concentration spatial patterns. A final major limitation is the accuracy
of the emission estimation factors themselves. The emission rates presented
represent averages over very broadly defined land use categories; a detailed
examination would indicate that specific emission rates for different types
of industrial developments may vary by factors ranging from 10 to 1000.
Thus, the listed emission rates for each land use category can only be
regarded as gross estimation factors.
Despite such limiting factors, these simplified procedures can be
useful to the planner since: (1) they provide a means for rapid estimation
of the air pollution potential of preliminary inventories (or lists) of
industrial/transportation land use, (2) they are relatively easy to apply,
and do not require a computer, and (3) they reduce the susceptibility of
'final1 designs to major changes in land use required by compliance with
the air quality standards.
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10. REFERENCES
1. Air Quality for Urban and Industrial Planning (Extension), Final Report,
Contract 68-02-0567, prepared by Environmental Research 5 Technology,
Inc. for the U.S. Environmental Protection Agency, Office of Air
Quality Land Use Planning Branch.
2. Holzworth, G.C., Mixing Heights, Wind Speeds and Potential for Urban Air
Pollution Throughout the Contiguous United States, U.S. Environmental
Protection Agency, Office of Air Programs, Publication No. AP-101,
January 1972.
3. Kircher, D. and Armstrong, D., An Interim Report on Motor Vehicle Emissions
Estimation, U.S. Environmental Protection Agency, Office of Air Programs,
October 1972.
4. Mahoney, J.R., Egan, B.A. and Reifenstein, E.G.; The Hackensack Meadowlands
Air Pollution Study, Task 2 Report: Development and Validation of
Air Quality Levels, prepared by Environmental Reasearch § Technology,
Inc. for the State of New Jersey, Department of Environmental Protection,
July 1973.
5. United States, Environmental Protection Agency, Compilation of AirPollutant
Emission Factors, Office of Air Programs, Publication No. AP-42,
February 1972.
6. United States, Environmental Protection Agency, Compilation of Air Pollutant
Emission Factors, Office of Air Programs, Publication No. AP-42,
April 1973.
7. Turner, D.B., Workbook of Atmospheric Dispersion Estimates, PHS Publication
No. AP-26.
8. The Hackensack Meadowlands Study Summary Report, prepared by Environmental
Research § Technology, Inc. (ERT) for the N.J. State Department of
Environmental Protection, July 1973.
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TECHNICAL REPORT DATA
(Plca.se read Instructions on the reverse before completing)
\. REPORT NO.
PA-450/3-74-020
3, RECIPIENT'S ACCESSIOf*NO.
4. TITLE AND SUBTITLE
A Guide for Considering Air Quality in Urban Planning
5. REPORT DATE
March 1974
6, PERFORMING ORGANIZATION CODE
7 AUTHORIS)
A.H. Epstein, C.A. Leary, S.T. McCandless, with the
assistance of B.J. Goldsmith, J.C. Goodrich, B.H. Willis
8. PERFORMING ORGANIZATION REPORT NO.
9 PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Research and Technology, Inc.
429 Marrett Road
Lexington, Massachusetts 02173
10. PROGRAM ELEMENT NO.
11.-CONTRACT/GRANT NO.
68-02-0567
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Protection Agency
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
Prepared in cooperation with the New Jersey Department of Environmental Protection,
Office of the Commissioner, Labor and Industry Building, Trenton, N.J. 08625
16. ABSTRACT
A Guide for Considering Air Quality in Urban Planning presents analytical
procedures and generalized emissions data needed to generate urban configurations
which are compatible with acceptable levels of air quality. Procedures are out-
lined for establishing a planning area's air quality baseline and for defining
the tolerance of a planning area toward receiving additional pollutant emissions
as a function of air quality standards, existing air quality, and air quality
maintenance policies. Methods are presented for determining acceptable industrial
and transportation activities as a function of pollutant tolerance and generalized
emission rates and for distributing land uses within comprehensive plans.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Land Use
Planning and Zoning
Local governments
County governments
State governments
Regional governments
Air Pollution Control
13. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report)
21. NO. OF PAGES
103
20 SECURITY CLASS (Thispage)
22. PRICE
EPA lr-8«Hi 1220-1 (9-73)
104
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