EPA-450/2-78-027R-C
(NTIS No.^B 95-246401)^
SUPPLEMENT C
TO THE
GUIDELINE ON
AIR QUALITY MODELS (REVISED)
(Appendix W of 40 CFR Part 51)
August 1995
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
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NOTE
The following pages contained in Supplement C to the
Guideline on Air Quality Models (Revised) are to be
appropriately inserted in the Guideline. with
Supplements A and B having already been incorporated.
Noting the page numbers will indicate which pages are to
be added and which are to replace previous pages.
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4.2 Recommendations
4.2.1 Screening Techniques
Point source screening techniques are an acceptable approach
to air quality analyses. One such approach is contained in the EPA document
"Screening Procedures for Estimating the Air Quality Impact of Stationary
Sources".18 A computerized version of the screening technique, SCREEN, is
available.19'20 For the current version of SCREEN, see reference 20.
All screening procedures should be adjusted to the site and
problem at hand. Close attention should be paid to whether the area should be
classified urban or rural in accordance with Section 8.2.8. The climatology of
the area should be studied to help define the worst-case meteorological
conditions. Agreement should be reached between the model user and the
reviewing authority on the choice of the screening model for each analysis, and
on the input data as well as the ultimate use of the results.
4-2 Revised 8/95
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TABLE 4-1
Preferred Models for Selected Applications in Simple Terrain
Short Term (i.e., 1-24 hours)
Single Source
Multiple Source
Rural
Urban
Rural
Urban
Complicated Sources" Rural/Urban
Buoyant Industrial Line Sources
Long Term (i.e., monthly, seasonal or annual)
Single Source
Multiple Source
Rural
Urban
Rural
Urban
Complicated Sources'* Rural/Urban
Buoyant Industrial Line Sources
Land UseModel*
CRSTER
RAM
MPTER
RAM
ISCST***
RuralBLP
CRSTER
RAM
MPTER
COM 2.0 or RAM*™*
ISCLT*""
RuralBLP
"The models as listed here reflect the applications for which they were
originally intended. Several of these models have been adapted to contain options
which allow them to be interchanged. For example, ISCST could be substituted for
ISCLT. Similarly, for a point source application, ISCST with urban option can be
substituted for RAM. Where a substitution is convenient to the user and
equivalent estimates are assured, it may be made.
""Complicated sources are those with special problems such as aerodynamic
downwash, particle deposition, volume and area sources, etc.
***For the current version of ISC, see reference 58 and note the model
description provided in Appendix A of this document.
used.
*If only a few sources in an urban area are to be modeled, RAM should be
4-4
.Revised 8/95
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final plume rise, then the transitional (or gradual) plume rise option for
stable conditions should be selected.
The standard polar receptor grid found in the Valley
Model User's Guide may not be sufficiently dense for all analyses if only one
geographical scale factor is used. The user should choose an additional set of
receptors at appropriate downwind distances whose elevations are equal to plume
height minus 10 meters. Alternatively, the user may exercise the "Valley
equivalent" option in COMPLEX I or SCREEN and note the comments above on the
placement of receptors in complex terrain models.
When using the "Valley equivalent" option in
COMPLEX I, set the wind profile exponents (PL) to 0.0, respectively, for all
six stability classes.
5.2.1.2 CTSCREEN
CTSCREEN may be used to obtain conservative, yet
realistic, worst-case estimates for receptors located on terrain above stack
height. CTSCREEN accounts for the three-dimensional nature of plume and
terrain interaction and requires detailed terrain data representative of the
modeling domain. The model description and user's instructions are contained
in the user's guide.25 The terrain data must be digitized in the same manner as
for CTDMPLUS and a terrain processor is available.23 A discussion of the
model's performance characteristics is provided in a technical paper." CTSCREEN
is designed to execute a fixed matrix of meteorological values for wind speed
(u), standard deviation of horizontal and vertical wind speeds (av, aw) ,
vertical potential temperature gradient (d6/dz), friction velocity (u,) , Monin-
Obukhov length (L), mixing height (Zi) as a function of terrain height, and
wind directions for both neutral/stable conditions and unstable convective
conditions. Table 5-1 contains the matrix of meteorological variables that is
used for each CTSCREEN analysis. There are 96 combinations, including
exceptions, for each wind direction for the neutral/stable case, and 108
combinations for the unstable case. The specification of wind direction,
however, is handled internally, based on the source and terrain geometry. The
matrix was developed from examination of the range of meteorological variables
associated with maximum monitored concentrations from the data bases used to
evaluate the performance of CTDMPLUS. Although CTSCREEN is designed to
address a single source scenario, there are a number of options that can be
selected on a case-by-case basis to address multi-source situations. However,
the Regional Office should be consulted, and concurrence obtained, on the
protocol for modeling multiple sources with CTSCREEN to ensure that the worst
case is identified and assessed. The maximum concentration output from
CTSCREEN represents a worst-case 1-hour concentration. Time-scaling factors of
0.7 for 3-hour, 0.15 for 24-hour and 0.03 for annual concentration averages are
applied internally by CTSCREEN to the highest 1-hour concentration calculated
by the model.
5.2.1.3 COMPLEX I
If the area is rural, COMPLEX I may be used to
estimate concentrations for all averaging times. COMPLEX I is a modification
of the MPTER model that incorporates the plume impaction algorithm of the
5-2 Revised 8/95
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6.2.3 Models for Nitrogen Dioxide (Annual Average)
A tiered screening approach is recommended to obtain annual
average estimates of N02 from point sources for New Source Review analysis,
including PSD, and for SIP planning purposes. This multi-tiered approach is
conceptually shown in Figure 6-1 below:
FIGURE 6-1
Multi-tiered Screening Approach for Estimating Annual NO2
Concentrations from Point Sources
Tier 1:
Tier 2 :
Assume Total Conversion of NO to NO2
1
Multiply Annual NO, Estimate by Empirically Derived
NO2 / NO, Ratio
a) For Tier 1 (the initial screen), use an appropriate
Gaussian model from Appendix A to estimate the maximum annual average
concentration and assume a total conversion of NO to NO2. If the concentration
exceeds the NAAQS and/or PSD increments for NO2, proceed to the 2nd level
screen.
b) For Tier 2 (2nd level) screening analysis, multiply the
Tier l estimate(s) by an empirically derived NO2 / NO, value of 0.75 (annual
national default).36 An annual NO2 / NO, ratio differing from 0.75 may be used
if it can be shown that such a ratio is based on data likely to be
representative of the location(s) where maximum annual impact from the
individual source under review occurs. In the case where several sources
contribute to consumption of a PSD increment, a locally derived annual N02 / NO,
ratio should also be shown to be representative of the location where the
maximum collective impact from the new plus existing sources occurs.
In urban areas, a proportional model may be used as a
preliminary assessment to evaluate control strategies to meet the NAAQS for
multiple minor sources, i.e. minor point, area and mobile sources of NO,;
concentrations resulting from major point sources should be estimated sepa-
rately as discussed above, then added to the impact of the minor sources. An
acceptable screening technique for urban complexes is to assume that all NOX is
emitted in the form of NO2 and to use a model from Appendix A for nonreactive
pollutants to estimate NO2 concentrations. A more accurate estimate can be
obtained by: (1) calculating the annual average concentrations of NO, with an
urban model, and (2) converting these estimates to NO2 concentrations using an
empirically derived annual NO2 / NO, ratio. A value of 0.75 is recommended for
6-5 Revised 8/95
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this ratio. However, a spatially averaged annual NO2 / NO, ratio may be
determined from an existing air quality monitoring network and used in lieu of
the 0.75 value if it is determined to be representative of prevailing ratios in
the urban area by the reviewing agency. To ensure use of appropriate locally
derived annual N02 / NO, ratios, monitoring data under consideration should be
limited to those collected at monitors meeting siting criteria defined in 40
CFR 58, Appendix D as representative of "neighborhood", "urban", or "regional"
scales. Furthermore, the highest annual spatially averaged NO2 / NO, ratio from
the most recent 3 years of complete data should be used to foster conservatism
in estimated impacts.
To demonstrate compliance with N02 PSD increments in urban
areas, emissions from major and minor sources should be included in the
modeling analysis. Point and area source emissions should be modeled as
discussed above. If mobile source emissions do not contribute to localized
areas of high ambient N02 concentrations, they should be modeled as area
sources. When modeled as area sources, mobile source emissions should be
assumed uniform over the entire highway link and allocated to each area source
grid square based on the portion of highway link within each grid square. If
localized areas of high concentrations are likely, then mobile sources should
be modeled as line sources with the preferred model ISCLT.
More refined techniques to handle special circumstances may be
considered on a case-by-case basis and agreement with the reviewing authority
should be obtained. Such techniques should consider individual quantities of
NO and NO, emissions, atmospheric transport and dispersion, and atmospheric
transformation of NO to NO2. Where they are available, site-specific data on
the conversion of NO to N02 may be used. Photochemical dispersion models, if
used for other pollutants in the area, may also be applied to the NOX problem.
6-6 Revised 8/95
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transport distances are limited in detail. This limitation is a result of the
expense to perform the field studies required to verify and improve mesoscale
and long range transport models. Particularly important and sparse are
meteorological data adequate for generating three dimensional wind fields.
Application of models to complicated terrain compounds the difficulty. EPA has
completed limited evaluation of several long range transport (LRT) models
against two sets of field data. The evaluation results are discussed in the
document, "Evaluation of Short-Term Long-Range Transport Models."99-100 For the
time being, long range and mesoscale transport models must be evaluated for
regulatory use on a case-by-case basis.
There are several regulatory programs for which air pathway analysis
procedures and modeling techniques have been developed. For continuous
emission releases, ISC forms the basis of many analytical techniques. EPA is
continuing to evaluate the performance of a number of proprietary and public
domain models for intermittent and non-stack emission releases. Until EPA
completes its evaluation, it is premature to recommend specific models for air
pathway analyses of intermittent and non-stack releases in this guideline.
Regional scale models are used by EPA to develop and evaluate national
policy and assist State and local control agencies. Two such models are the
Regional Oxidant Model (ROM)l01-102-103 and the Regional Acid Deposition Model
(RADM) .l04 Due to the level of resources required to apply these models, it is
not envisioned that regional scale models will be used directly in most model
applications.
7-2 Revised 8/55
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7.2.2 Particulate Matter
The new particulate matter NAAQS, promulgated on July 1, 1987
(52 FR 24634) , includes only particles with an aerodynamic diameter less than
or equal to a nominal 10 micrometers (PM-10). EPA has also proposed regula-
tions for PSD increments measured as PM-10 in a notice published on October 5,
1989 (54 FR 41218).
Screening techniques like those identified in Section 4 are
also applicable to PM-10 and to large particles. It is recommended that
subjectively determined values for "half-life" or pollutant decay not be used
as a surrogate for particle removal. Conservative assumptions which do not
allow removal or transformation are suggested for screening. Proportional
models (rollback/forward) may not be applied for screening analysis, unless
such techniques are used in conjunction with receptor modeling.
Refined models such as those in Section 4 are recommended for
PM-10 and large particles. However, where possible, particle size, gas-to-
particle formation, and their effect on ambient concentrations may be consid-
ered. For urban-wide refined analyses CDM 2.0 or RAM should be used. CRSTER
and MPTER are recommended for point sources of small particles. For source-
specific analyses of complicated sources, the ISC model is preferred. No model
recommended for general use at this time accounts for secondary particulate
formation or other transformations in a manner suitable for
SIP control strategy demonstrations. Where possible, the use of receptor
models38-39-103'10*'107 in conjunction with dispersion models is encouraged to more
precisely characterize the emissions inventory and to validate source specific
impacts calculated by the dispersion model. A SIP development guideline,108
model reconciliation guidance,106 and an example model application109 are avail-
able to assist in PM-10 analyses and control strategy development.
Under certain conditions, recommended dispersion models are
not available or applicable. In such circumstances, the modeling approach
should, be approved by the appropriate Regional Office on a case-by-case basis.
For example, where there is no recommended air quality model and area sources
are a predominant component of PM-10, an attainment demonstration may be based
on rollback of the apportionment derived from two reconciled receptor models,
if the strategy provides a conservative demonstration of attainment. At this
time, analyses involving model calculations for distances beyond 50km and under
stagnation conditions should also be justified on a case-by-case basis (see
Sections 7.2.6 and 8.2.10).
As an aid to assessing the impact on ambient air quality of
particulate matter generated from prescribed burning activities, reference 110
is available.
7-4 Revised 8/95
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7.2.5 Good Engineering Practice Stack Height
The use of stack height credit in excess of Good Engineering
Practice (GEP) stack height or credit resulting from any other dispersion
technique is prohibited in the development of emission limitations by 40 CFR
51.118 and 40 CFR 51.164. The definitions of GEP stack height and dispersion
technique are contained in 40 CFR 51.100. Methods and procedures for making
the appropriate stack height calculations, determining stack height credits and
an example of applying those techniques are found in references 46, 47, 48, and
49.
If stacks for new or existing major sources are found to be
less than the height defined by EPA's refined formula for determining GEP
height,* then air quality impacts associated with cavity or wake effects due to
the nearby building structures should be determined. Detailed downwash
screening procedures18 for both the cavity and wake regions should be followed.
If more refined concentration estimates are required, the Industrial Source
Complex (ISC) model contains algorithms for building wake calculations and
should be used. Fluid modeling can provide a great deal of additional
information for evaluating and describing the cavity and wake effects.
"The EPA refined formula height is defined as H + 1.5L (see Reference 46).
7-7 Revised 8/95
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7.2.8 Air Pathway Analyses (Air Toxics and Hazardous Waste)
Modeling is becoming an increasingly important tool for
regulatory control agencies to assess the air quality impact of releases of
toxics and hazardous waste materials. Appropriate screening techniques"4-"5 for
calculating ambient concentrations due to various well-defined neutrally
buoyant toxic/hazardous pollutant releases are available.
Several regulatory programs within EPA have developed modeling
techniques and guidance for conducting air pathway analyses as noted in
references 116-129. ISC forms the basis of the modeling procedures for air
pathway analyses of many of these regulatory programs and, where identified, is
appropriate for obtaining refined ambient concentration estimates of neutrally
buoyant continuous air toxic releases from traditional sources. Appendix A to
this Guideline contains additional models appropriate for obtaining refined
estimates of continuous air toxic releases from traditional sources. Appendix
B contains models that may be used on a case-by-case basis for obtaining
refined estimates of denser-than-air intermittent gaseous releases, e.g.,
DEGADIS;130 guidance for the use of such models is also available.131
Many air toxics models require input of chemical properties
and/or chemical engineering variables in order to appropriately characterize
the source emissions prior to dispersion in the atmosphere; reference 132 is
one source of helpful data. In addition, EPA has numerous programs to
determine emission factors and other estimates of air toxic emissions. The
Regional Office should be consulted for guidance on appropriate emission
estimating procedures and any uncertainties that may be associated with them.
7-10 Revised 8/95
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8.2.5 Plume Rise
The plume rise methods of Briggs56'57 are incorporated in the
preferred models and are recommended for use in all modeling applications. No
provisions in these models are made for fumigation or multistack plume rise
enhancement or the handling of such special plumes as flares; these problems
should be considered on a case-by-case basis.
Since there is insufficient information to identify and
quantify dispersion during the transitional plume rise period, gradual plume
rise is not generally recommended for use. There are two exceptions where the
use of gradual plume rise is appropriate: (1) in complex terrain screening
procedures to determine close-in impacts; (2) when calculating the effects of
building wakes. The building wake algorithm in the ISC model incorporates and
automatically (i.e., internally) exercises the gradual plume rise calculations.
If the building wake is calculated to affect the plume for any hour, gradual
plume rise is also used in downwind dispersion calculations to the distance of
final plume rise, after which final plume rise is used.
Stack tip downwash generally occurs with poorly constructed
stacks and when the ratio of the stack exit velocity to wind speed is small. An
algorithm developed by Briggs (Hanna, et al.)57 is the recommended technique for
this situation and is found in the point source preferred models.
Where aerodynamic downwash occurs due to the adverse influence
of nearby structures, the algorithms included in the ISC model58 should be used.
8-7 Revised 8/95
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8.2.7 Gravitational Settling and Deposition
An "infinite half-life" should be used for estimates of
particle concentrations when Gaussian models containing only exponential decay
terms for treating settling and deposition are used.
Gravitational settling and deposition may be directly included
in a model if either is a significant factor. One preferred model (ISC)
contains a settling and deposition algorithm and is recommended for use when
particulate matter sources can be quantified and settling and deposition are
problems.
8-9 Revised 8/95
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9.3.3.2 Recommendations
Site-specific Data Collection
The document "On-Site Meteorological Program Guidance
for Regulatory Modeling Applications"66 provides recommendations on the
collection and use of on-site meteorological data. Recommendations on
characteristics, siting, and exposure of meteorological instruments and on data
recording, processing, completeness requirements, reporting, and archiving are
also included. This publication should be used as a supplement to the limited
guidance on these subjects now found in the "Ambient Monitoring Guidelines for
Prevention of Significant Deterioration".63 Detailed information on quality
assurance is provided in the "Quality Assurance Handbook for Air Pollution
Measurement Systems: Volume IV".67 As a minimum, site-specific measurements of
ambient air temperature, transport wind speed and direction, and the parameters
to determine Pasquill-Gifford (P-G) stability categories should be available in
meteorological data sets to be used in modeling. Care should be taken to
ensure that meteorological instruments are located to provide representative
characterization of pollutant transport between sources and receptors of
interest. The Regional Office will determine the appropriateness of the
measurement locations.
All site-specific data should be reduced to hourly
averages. Table 9-3 lists the wind related parameters and the averaging time
requirements.
Solar Radiation Measurements
Total solar radiation should be measured with a
reliable pyranometer, sited and operated in accordance with established on-site
meteorological guidance.66
Temperature Measurements
Temperature measurements should be made at standard
shelter height (2m) in accordance with established on-site meteorological
guidance .**
Temperature Difference Measurements
Temperature difference (AT) measurements for use in
estimating P-G stability categories using the solar radiation/delta-T (SRDT)
methodology (see Stability Categories) should be obtained using two matched
thermometers or a reliable thermocouple system to achieve adequate accuracy.
Siting, probe placement, and operation of AT systems
should be based on guidance found in Chapter 3 of reference 66, and such
guidance should be followed when obtaining vertical temperature gradient data
for use in plume rise estimates or in determining the critical dividing
streamline height.
9-16 Revised 8/95
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Wind Measurements
For refined modeling applications in simple terrain
situations, if a source has a stack below 100m, select the stack top height as
the wind measurement height for characterization of plume dilution and
transport. For sources with stacks extending above 100m, a 100m tower is
suggested unless the stack top is significantly above 100m (i.e., a200m). In
cases with stack tops a200m, remote sensing may be a feasible alternative. In
some cases, collection of stack top wind speed may be impractical or
incompatible with the input requirements of the model to be used. In such
cases, the Regional Office should be consulted to determine the appropriate
measurement height.
For refined modeling applications in complex terrain,
multiple level (typically three or more) measurements of wind speed and
direction, temperature and turbulence (wind fluctuation statistics) are
required. Such measurements should be obtained up to the representative plume
height(s) of interest (i.e., the plume height(s) under those conditions
important to the determination of the design concentration). The
representative plume height(s) of interest should be determined using an
appropriate complex terrain screening procedure (e.g., CTSCREEN) and should be
documented in the monitoring/modeling protocol. The necessary meteorological
measurements should be obtained from an appropriately sited meteorological
tower augmented by SODAR if the representative plume height(s) of interest
exceed 100m. The meteorological tower need not exceed the lesser of the
representative plume height of interest (the highest plume height if there is
more than one plume height of interest) or 100m.
In general, the wind speed used in determining plume
rise is defined as the wind speed at stack top.
Specifications for wind measuring instruments and
systems are contained in the "On-Site Meteorological Program Guidance for
Regulatory Modeling Applications".66
Stability Categories
The P-G stability categories, as originally defined,
couple near-surface measurements of wind speed with subjectively determined
insolation assessments based on hourly cloud cover and ceiling height
observations. The wind speed measurements are made at or near 10m. The
insolation rate is typically assessed using observations of cloud cover and
ceiling height based on criteria outlined by Turner.50 It is recommended that
the P-G stability category be estimated using the Turner method with site-
specific wind speed measured at or near 10m and representative cloud cover and
ceiling height. Implementation of the Turner method, as well as considerations
in determining representativeness of cloud cover and ceiling height in cases
for which site-specific cloud observations are unavailable, may be found in
Section 6 of reference 66. In the absence of requisite data to implement the
Turner method, the SRDT method or wind fluctuation statistics (i.e., the aE and
OA methods) may be used.
The SRDT method, described in Section 6.4.4.2 of
reference 66, is modified slightly from that published by Bowen et al. (1983)136
9-17 Revised 8/95
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and has been evaluated with three on-site data bases.137 The two methods of
stability classification which use wind fluctuation statistics, the aE and OA
methods, are also described in detail in Section 6.4.4 of reference 66 (note
applicable tables in Section 6). For additional information on the wind
fluctuation methods, see references 68-72.
Hours in the record having missing data should be
treated according to an established data substitution protocol and after valid
data retrieval requirements have been met. Such protocols are usually part of
the approved monitoring program plan. Data substitution guidance is provided
in Section 5.3 of reference 66.
Meteorological Data Processors
The following meteorological preprocessors are
recommended by EPA: RAMMET, PCRAMMET, STAR, PCSTAR, MPRM,135 and METPRO.24
RAMMET is the recommended meteorological preprocessor for use in applications
employing hourly NWS data. The RAMMET format is the standard data input format
used in sequential Gaussian models recommended by EPA. PCRAMMET138 is the PC
equivalent of the mainframe version (RAMMET). STAR is the recommended
preprocessor for use in applications employing joint frequency distributions
(wind direction and wind speed by stability class) based on NWS data. PCSTAR
is the PC equivalent of the mainframe version (STAR). MPRM is the recommended
preprocessor for use in applications employing on-site meteorological data.
The latest version (MPRM 1.3) has been configured to implement the SRDT method
for estimating P-G stability categories. MPRM is a general purpose
meteorological data preprocessor which supports regulatory models requiring
RAMMET formatted data and STAR formatted data. In addition to on-site data,
MPRM provides equivalent processing of NWS data. METPRO is the required
meteorological data preprocessor for use with CTDMPLUS. All of the above
mentioned data preprocessors are available for downloading from the SCRAM BBS."
9-18 Revised 8/95
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11. Fox, D.G., 1981. Judging Air Quality Model Performance. Bulletin of the
American Meteorological Society, 62(5): 599-609.
12. American Meteorological Society, 1983. Synthesis of the Rural Model
Reviews. EPA Publication No. EPA-600/3-83-108. U.S. Environmental
Protection Agency/ Research Triangle Park, NC. (NTIS No. PB 84-121037)
13. American Meteorological Society, 1984. Review of the Attributes and
Performance of Six Urban Diffusion Models. EPA Publication No.
EPA-600/S3-84-089. U.S. Environmental Protection Agency, Research
Triangle Park, NC. (NTIS No.PB 84-236850)
14. White, F.D.(Ed.), J.K.S. Ching, R.L. Dennis and W.H. Snyder, 1985.
Summary of Complex Terrain Model Evaluation. EPA Publication No.
EPA-600/3-85-060. U.S. Environmental Protection Agency, Research
Triangle Park, NC. (NTIS No. PB 85-236891)
15. Environmental Protection Agency, 1984. Interim Procedures for Evaluating
Air Quality Models (Revised). EPA Publication No. EPA-450/4-84-023.
U.S. Environmental Protection Agency, Research Triangle Park, NC.
(NTIS No. PB 85-106060)
16. Environmental Protection Agency, 1985. Interim Procedures for Evaluating
Air Quality Models: Experience with Implementation. EPA Publication No.
EPA-450/4-85-006. U.S. Environmental Protection Agency, Research
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17. Environmental Protection Agency, 1992. Protocol for Determining the Best
Performing Model. EPA Publication No. EPA-454/R-92-025. U.S. Environ-
mental Protection Agency, Research Triangle Park, NC.
18. Environmental Protection Agency,1992. Screening Procedures for
Estimating the Air Quality Impact of Stationary Sources, Revised. EPA
Publication No. EPA-454/R-92-019. U.S. Environmental Protection Agency,
Research Triangle Park, NC.
19. Environmental Protection Agency, 1989. Support Center for Regulatory Air
Models Bulletin Board System (SCRAM BBS). Source Receptor Analysis
Branch, Research Triangle Park, NC. (Docket Nos. A-88-04, II-J-4a and b)
20. Environmental Protection Agency, 1995. SCREENS User's Guide. EPA
Publication No. EPA-454/B-95-004. U.S. Environmental Protection Agency,
Research Triangle Park, NC. (NTIS No. PB 95-222766)
21. Environmental Protection Agency, 1987. EPA Complex Terrain Model
Development: Final Report. EPA Publication No. EPA-600/3-88-006. U.S.
Environmental Protection Agency, Research Triangle Park, NC. (NTIS No.
PB 88-162110)
22. Perry, S.G., D.J. Burns, L.H. Adams, R.J. Paine, M.G. Dennis, M.T. Mills,
D.J. Strimaitis, R.J. Yamartino and E.M. Insley, 1989. User's Guide to
the Complex Terrain Dispersion Model Plus Algorithms for Unstable
Situations (CTDMPLUS) Volume 1; Model Description and User Instructions.
EPA Publication No. EPA-600/8-89-041. U.S. Environmental Protection
Agency, Research Triangle Park, NC. (NTIS No. PB 89-181424)
12-2 Revised 8/95
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34. Environmental Protection Agency, 1992. Guideline for Modeling Carbon
Monoxide from Roadway Intersections. EPA Publication No. EPA-454/R-92-
005.U.S. Environmental Protection Agency, Research Triangle Park, NC.
(NTIS No. PB 93-210391)
35. Environmental Protection Agency, 1992. User's Guide for CAL3QHC
Version 2: A Modeling Methodology for Predicting Pollutant Concentrations
near Roadway Intersections. EPA Publication No. EPA-454/R-92-006. U.S.
Environmental Protection Agency, Research Triangle Park, NC. (NTIS No.
PB 93-210250)
36. Chu, S. H. and E. L. Meyer, 1991. Use of Ambient Ratios to Estimate
Impact of NOX Sources on Annual NO2 Concentrations. Proceedings, 84th
Annual Meeting & Exhibition of the Air & Waste Management Association,
Vancouver, B.C.; 16-21 June 1991. (16pp.) (Docket No. A-92-65, II-A-9)
37. U.S. Department of Housing and Urban Development, 1980. Air Quality
Considerations in Residential Planning. U.S. Superintendent of
Documents, Washington, DC. (GPO Order Nos. 023-000-00577-8,
023-000-00576-0, 023-000-00575-1)
38. Environmental Protection Agency, 1981. Receptor Model Technical Series.
Volume I: Overview of Receptor Model Application to Particulate Source
Apportionment. EPA Publication No. EPA-450/4-81-016a (NTIS No.
PB 82-139429); Volume II: Chemical Mass Balance. EPA Publication No.
EPA-450/4-81-016b (NTIS No. PB 82-187345); Volume III (Revised): CMB
User's Manual (Version 7.0). EPA Publication No. EPA-450/4-90-004 (NTIS
No. PB 90-185067); Volume IV: Technical Considerations In Source
Apportionment By Particle Identification. EPA Publication No.
EPA-450/4-83-018 (NTIS No. PB 84-103340); Volume V: Source Apportionment
Techniques and Considerations in Combining their Use. EPA Publication
No. EPA-450/4-84-020 (NTIS No. PB 85-111524); Volume VI: A Guide To The
Use of Factor Analysis and Multiple Regression (FA/MR) Techniques in
Source Apportionment. EPA Publication No. EPA-450/4-85-007 (NTIS No.
PB 86-107638) . U.S. Environmental Protection Agency, Research Triangle
Park, NC.
39. Pace, T.G., 1982. The Role of Receptor Models for Revised Particulate
Matter Standards. A Specialty Conference on: Receptor Models Applied to
Contemporary Pollution Problems. Air Pollution Control Association,
Pittsburgh, PA; pp. 18-28. (Docket No. A-80-46, II-P-10)
40. Environmental Protection Agency, 1978. Supplementary Guidelines for Lead
Implementation Plans. EPA Publication No. EPA-450/2-78-038. U.S.
Environmental Protection Agency, Research Triangle Park, NC. (NTIS No.
PB 82-232737)
41. Environmental Protection Agency, 1983. Updated Information on Approval
and Promulgation of Lead Implementation Plans (DRAFT). U.S.
Environmental Protection Agency, Research Triangle Park, NC.
(Docket No. A-80-46, II-B-38)
42. Environmental Protection Agency, 1979. Protecting Visibility: An EPA
Report to Congress. EPA Publication No. EPA-450/5-79-008. U.S.
Environmental Protection Agency, Research Triangle Park, NC.
(NTIS No. PB 80-220320)
12-4 Revised 8/95
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54. Pasquill, F., 1976. Atmospheric Dispersion Parameters in Gaussian Plume
Modeling, Part II. Possible Requirements for Change in the Turner
Workbook Values. EPA Publication No. EPA-600/4-76-030b. U.S.
Environmental Protection Agency, Research Triangle Park, NC.
(NTIS No. PB-258036/3BA)
55. Turner, D.B., 1964. A Diffusion Model for an Urban Area. Journal of
Applied Meteorology, 3(1): 83-91.
56. Briggs, G.A., 1975. Plume Rise Predictions. Chapter 3 in Lectures on
Air Pollution and Environmental Impact Analyses. American Meteorological
Society, Boston, MA; pp. 59-111.
57. Hanna, S.R., G.A. Briggs and R.P. Hosker, Jr., 1982. Plume Rise.
Chapter 2 in Handbook on Atmospheric Diffusion. Technical Information
Center, U.S. Department of Energy, Washington, DC; pp. 11-24.
DOE/TIC-11223 (DE 82002045)
58. Environmental Protection Agency, 1995. User's Guide for the Industrial
Source Complex (ISC3) Dispersion Models, Volumes 1 and 2. EPA
Publication Nos. EPA-454/B-95-003a & b. U.S. Environmental Protection
Agency, Research Triangle Park, NC. (NTIS Nos. PB 95-222741 and
PB 95-222758, respectively)
59. Irwin, J.S., 1978. Proposed Criteria for Selection of Urban Versus Rural
Dispersion Coefficients. (Draft Staff Report). Meteorology and
Assessment Division, U.S. Environmental Protection Agency, Research
Triangle Park, NC. (Docket No. A-80-46, II-B-8)
60. Auer, Jr., A.H., 1978. Correlation of Land Use and Cover with
Meteorological Anomalies. Journal of Applied Meteorology, 17(5) : 636-643.
61. Brier, G.W., 1973. Validity of the Air Quality Display Model Calibration
Procedure. EPA Publication No. EPA-R4-73-017. U.S. Environmental
Protection Agency, Research Triangle Park, NC. (NTIS No. PB-218716)
62. Environmental Protection Agency, 1985 and ff. Compilation of Air .
Pollutant Emission Factors, Volume I: Stationary Point and Area Sources
(Fourth Edition; GPO Stock No. 055-000-00251-7), and Supplements; Volume
II: Mobile Sources (NTIS PB 87-205266) and Supplement(s). EPA
Publication No. AP-42. U.S. Environmental Protection Agency,
Research Triangle Park, NC.
63. Environmental Protection Agency, 1987. Ambient Air Monitoring Guidelines
for Prevention of Significant Deterioration (PSD). EPA Publication No.
EPA-450/4-87-007. U.S. Environmental Protection Agency, Research
Triangle Park, NC. (NTIS No. PB 90-168030)
64. Landsberg, H.E. and W.C. Jacobs, 1951. Compendium of Meteorology.
American Meteorological Society, Boston, MA; pp. 976-992.
65. Burton, C.S., T.E. Stoeckenius and J.P. Nordin, 1983. The Temporal
Representativeness of Short-Term Meteorological Data Sets: Implications
for Air Quality Impact Assessments. Systems Applications, Inc., San
Rafael, CA. (Docket No. A-80-46, II-G-11)
12-6 Revised 8/55
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-------
89. Environmental Protection Agency, 1986. Emissions Trading Policy
Statement; General Principles for Creation, Banking, and Use of Emission
Reduction Credits. Federal Register. 51(233): 43814-43860.
90. Environmental Research and Technology, 1987. User's Guide to the Rough
Terrain Diffusion Model (RTDM), Rev. 3.20. ERT Document No. P-D535-585.
Environmental Research and Technology, Inc., Concord, MA. (NTIS No. PB
88-171467)
91. Burns, D.J., S.G. Perry and A.J. Cimorelli, 1991. An Advanced Screening
Model for Complex Terrain Applications. Paper presented at the 7th Joint
Conference on Applications of Air Pollution Meteorology (cosponsored by
the American Meteorological Society and the Air & Waste Management
Association), January 13-18, 1991, New Orleans, LA.
92. Perry, S.G., 1992. CTDMPLUS: A Dispersion Model for Sources near Complex
Topography. Part I: Technical Formulations. Journal of Applied
Meteorology, 31(7): 633-645.
93. Paumier, J.O., S.G. Perry and D.J. Burns, 1992. CTDMPLUS: A Dispersion
Model for Sources near Complex Topography. Part II: Performance
Characteristics. Journal of Applied Meteorology, 31(7): 646-660.
94. Environmental Protection Agency, 1986. Evaluation of Mobile Source Air
Quality Simulation Models. EPA Publication No. EPA-450/4-86-002. U.S.
Environmental Protection Agency, Research Triangle Park, NC.
(NTIS No. PB 86-167293)
95. Shannon, J.D., 1987. Mobile Source Modeling Review. A report prepared
under a cooperative agreement with the Environmental Protection Agency.
(Docket No. A-88-04, II-J-2)
96. Environmental Protection Agency, 1991. Emission Inventory Requirements
for Carbon Monoxide State Implementation Plans. EPA Publication No.
EPA-450/4-91-011. U.S. Environmental Protection Agency, Research
Triangle Park, NC. (NTIS No. PB 92-112150)
97. Environmental Protection Agency, 1992. Guideline for Regulatory
Application of the Urban Airshed Model for Areawide Carbon Monoxide. EPA
Publication No. EPA-450/4-92-Olla and b. U.S. Environmental Protection
Agency, Research Triangle Park, NC. (NTIS Nos. PB 92-213222 and
PB 92-213230)
98. Environmental Protection Agency, 1992. Technical Support Document to Aid
States with the Development of Carbon Monoxide State Implementation
Plans. EPA Publication No. EPA-452/R-92-003. U.S. Environmental
Protection Agency, Research Triangle Park, NC. {NTIS No. PB 92-233055)
99. Environmental Protection Agency, 1986. Evaluation of Short-Term Long-
Range Transport Models, Volumes I and II. EPA Publication Nos.
EPA-450/4-86-016a and b. U.S. Environmental Protection Agency, Research
Triangle Park, NC. (NTIS Nos. PB 87-142337 and PB 87-142345)
12-9 Revised 8/95
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131. Environmental Protection Agency, 1991. Guidance on the Application of
Refined Models for Air Toxics Releases. EPA Publication No.
EPA-450/4-91-007. Environmental Protection Agency, Research
Triangle Park, NC. (NTIS No. PB 91-190983)
132. Perry, R. H. and Chilton, C. H., 1973. Chemical Engineers' Handbook.
Fifth Edition, McGraw-Hill Book Company, New York, NY.
133. Environmental Protection Agency, 1988. User's Guide to SDM - A Shoreline
Dispersion Model. EPA Publication No. EPA-450/4-88-017. U.S. Environ-
mental Protection Agency, Research Triangle Park, NC. (NTIS No.
PB 89-164305)
134. Environmental Protection Agency, 1987. Analysis and Evaluation of
Statistical Coastal Fumigation Models. EPA Publication No.
EPA-450/4-87002. U.S. Environmental Protection Agency, Research
Triangle Park, NC. (NTIS No. PB 87-175519)
135. Irwin, J.S., J.O. Paumier and R.W. Erode, 1988. Meteorological Processor
for Regulatory Models (MPRM 1.2) User's Guide. EPA Publication No.
EPA-600/3-88-043R. U.S. Environmental Protection Agency, Research
Triangle Park, NC. (NTIS No. PB 89-127526)
136. Bowen, B.M., J.M. Dewart and A.I. Chen, 1983. Stability Class
Determination: A Comparison for One Site. Proceedings, Sixth Symposium
on Turbulence and Diffusion. American Meteorological Society, Boston,
MA; pp. 211-214. (Docket No. A-92-65, II-A-7)
137. Environmental Protection Agency, 1993. An Evaluation of a Solar
Radiation/Delta-T (SRDT) Method for Estimating Pasquill-Gifford (P-G)
Stability Categories. EPA Publication No. EPA-454/R-93-055. U.S.
Environmental Protection Agency, Research Triangle Park, NC. (NTIS No.
PB 94-113958)
138. Environmental Protection Agency, 1993. PCRAMMET User's Guide. EPA
Publication No. EPA-454/B-93-009. U.S. Environmental Protection Agency,
Research Triangle Park, NC.
12-13 Revised 8/95
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APPENDIX A
Table of Contents
A.O INTRODUCTION AND AVAILABILITY A-l
A.I BUOYANT LINE AND POINT SOURCE DISPERSION MODEL (BLP) . . . A-3
A. 2 CALINE3 A-7
A. 3 CLIMATOLOGICAL DISPERSION MODEL (COM 2.0) A-11
A.4 GAUSSIAN-PLUME MULTIPLE SOURCE AIR QUALITY
ALGORITHM (RAM) A-15
A. 5 INDUSTRIAL SOURCE COMPLEX MODEL (ISC3) A-21
A.6 MULTIPLE POINT GAUSSIAN DISPERSION ALGORITHM
WITH TERRAIN ADJUSTMENT (MPTER) A-25
A. 7 SINGLE SOURCE (CRSTER) MODEL A-29
A. 8 URBAN AIRSHED MODEL (UAM) A-33
A. 9 OFFSHORE AND COASTAL DISPERSION MODEL (OCD) A-39
A. 10 EMISSIONS AND DISPERSION MODEL SYSTEM (EDMS) A-43
A.11 COMPLEX TERRAIN DISPERSION MODEL PLUS ALGORITHMS
FOR UNSTABLE SITUATIONS (CTDMPLUS) A-47
A.REF REFERENCES AR-1
A-i Revised 8/95
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A.5 INDUSTRIAL SOURCE COMPLEX MODEL (ISC3)
Reference:
Environmental Protection Agency, 1995. User's Guide for the
Industrial Source Complex (ISC3) Dispersion Models, Volumes 1
and 2. EPA Publication Nos. EPA-454/B-95-003a & b. Envi-
ronmental Protection Agency, Research Triangle Park, NC.
(NTIS Nos. PB 95-222741 and PB 95-222758, respectively)
Availabilitv
The model code is available on the Support Center for Regu-
latory Air Models Bulletin Board System and also from the
National Technical Information Service (see Section A.O).
Abstract:
The ISC3 model is a steady-state Gaussian plume model which
can be used to assess pollutant concentrations from a wide
variety of sources associated with an industrial source
complex. This model can account for the following: settling
and dry deposition of particles; downwash; area, line and
volume sources; plume rise as a function of downwind dis-
tance; separation of point sources; and limited terrain
adjustment. It operates in both long-term and short-term
modes.
a. Recommendations for Regulatory Use
ISC3 is appropriate for the following applications:
0 industrial source complexes;
0 rural or urban areas;
0 flat or rolling terrain;
0 transport distances less than 50 kilometers;
0 1-hour to annual averaging times,- and
0 continuous toxic air emissions.
The following options should be selected for regulatory applications:
For short term or long term modeling, set the regulatory "default
option"; i.e., use the keyword DFAULT, which automatically selects
stack tip downwash, final plume rise, buoyancy induced dispersion
(BID), the vertical potential temperature gradient, a treatment for
calms, the appropriate wind profile exponents, the appropriate value
for pollutant half-life, and a revised building wake effects algo-
rithm; set the "rural option" (use the keyword RURAL) or "urban
option" (use the keyword URBAN) ; and set the "concentration option"
(use the keyword CONC) .
A-21
Revised 8/95
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b. Input Requirements
Source data: location, emission rate, physical stack height, stack gas
exit velocity, stack inside diameter, and stack gas temperature. Option-
al inputs include source elevation, building dimensions, particle size
distribution with corresponding settling velocities, and surface reflec-
tion coefficients.
Meteorological data: ISCST3 requires hourly surface weather data from
the preprocessor program RAMMET, which provides hourly stability
class,wind direction, wind speed, temperature, and mixing height. For
ISCLT3, input includes stability wind rose (STAR deck), average afternoon
mixing height, average morning mixing height, and average air tempera-
ture.
Receptor data: coordinates and optional ground elevation for each
receptor.
c. Output
Printed output options include:
0 program control parameters, source data, and receptor data;
0 tables of hourly meteorological data for each specified day;
o "N"-day average concentration or total deposition calculated at each
receptor for any desired source combinations;
0 concentration or deposition values calculated for any desired source
combinations at all receptors for any specified day or time period
within the day;
0 tables of highest and second highest concentration or deposition
values calculated at each receptor for each specified time period
during a(n) "N"-day period for any desired source combinations, and
tables of the maximum 50 concentration or deposition values calcu-
lated for any desired source combinations for each specified time
period.
d. Type of Model
ISC3 is a Gaussian plume model. It has been revised to perform a double
integration of the Gaussian plume kernel for area sources.
e. Pollutant Types
ISC3 may be used to model primary pollutants and continuous releases of
toxic and hazardous waste pollutants. Settling and deposition are
treated.
A-22 Revised 8/95
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f. Source-Receptor Relationships
ISC3 applies user-specified locations for point, line, area and volume
sources, and user-specified receptor locations or receptor rings.
User input topographic evaluation for each receptor is used. Elevations
above stack top are reduced to the stack top elevation, i.e., "terrain
chopping".
User input height above ground level may be used when necessary to
simulate impact at elevated or "flag pole" receptors, e.g., on buildings.
Actual separation between each source-receptor pair is used.
g. Plume Behavior
ISC3 uses Briggs (1969, 1971, 1975) plume rise equations for final rise.
Stack tip downwash equation from Briggs (1974) is used.
Revised building wake effects algorithm is used. For stacks higher than
building height plus one-half the lesser of the building height or
building width, the building wake algorithm of Huber and Snyder (1976) is
used. For lower stacks, the building wake algorithm of Schulman and
Scire (Schulman and Hanna, 1986) is used, but stack tip downwash and BID
are not used.
For rolling terrain (terrain not above stack height), plume centerline is
horizontal at height of final rise above source.
Fumigation is not treated.
h. Horizontal Winds
Constant, uniform (steady-state) wind is assumed for each hour.
Straight line plume transport is assumed to all downwind distances.
Separate wind speed profile exponents (EPA, 1980) for both rural and
urban cases are used.
An optional treatment for calm winds is included for short term modeling.
i. Vertical Wind Speed
Vertical wind speed is assumed equal to zero.
A-23 Revised 8/95
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j. Horizontal Dispersion
Rural dispersion coefficients from Turner (1969) are used, with no
adjustments for surface roughness or averaging time.
Urban dispersion coefficients from Briggs (Gifford, 1976) are used.
Buoyancy induced dispersion (Pasquill, 1976) is included.
Six stability classes are used.
k. Vertical Dispersion
Rural dispersion coefficients from Turner (1969) are used, with no
adjustments for surface roughness.
Urban dispersion coefficients from Briggs (Gifford, 1976) are used.
Buoyancy induced dispersion (Pasquill, 1976) is included.
Six stability classes are used.
Mixing height is accounted for with multiple reflections until the
vertical plume standard deviation equals 1.6 times the mixing height;
uniform vertical mixing is assumed beyond that point.
Perfect reflection is assumed at the ground.
1. Chemical Transformation
Chemical transformations are treated using exponential decay. Time
constant is input by the user.
m. Physical Removal
Dry deposition effects for particles are treated using a resistance
formulation in which the deposition velocity is the sum of the
resistances to pollutant transfer within the surface layer of the
atmosphere, plus a gravitational settling term (EPA, 1994), based on
the modified surface depletion scheme of Horst (1983).
n. Evaluation Studies
Bowers, J. F., and A. J. Anderson, 1981. An Evaluation Study for the
Industrial Source Complex (ISC) Dispersion Model, EPA Publication No.
EPA-450/4-81-002. U.S. Environmental Protection Agency, Research
Triangle Park, NC.
Bowers, J. F., A. J. Anderson, and W. R. Margraves, 1982. Tests of the
Industrial Source Complex (ISC) Dispersion Model at the Armco Middle-
town, Ohio Steel Mill, EPA Publication No. EPA-450/4-82-006. U.S.
Environmental Protection Agency, Research Triangle Park, NC.
A-24 Revised 8/95
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Environmental Protection Agency/ 1992. Comparison of a Revised Area
Source Algorithm for the Industrial Source Complex Short Term Model
and Wind Tunnel Data. EPA Publication No. EPA-454/R-92-014. U.S.
Environmental Protection Agency, Research Triangle Park, NC. (NTIS
No. PB 93-226751)
Environmental Protection Agency, 1992. Sensitivity Analysis of a Revised
Area Source Algorithm for the Industrial Source Complex Short Term
Model. EPA Publication No. EPA-454/R-92-015. U.S. Environmental
Protection Agency/ Research Triangle Park, NC. (NTIS No. PB
93-226769)
Environmental Protection Agency, 1992. Development and Evaluation of a
Revised Area Source Algorithm for the Industrial Source Complex Long
Term Model. EPA Publication No. EPA-454/R-92-016. U.S. Environ-
mental Protection Agency, Research Triangle Park, NC. (NTIS No. PB
93-226777)
Environmental Protection Agency, 1994. Development and Testing of a Dry
Deposition Algorithm (Revised). EPA Publication No. EPA-454/R-94-
015. U.S. Environmental Protection Agency, Research Triangle Park,
NC. (NTIS No. PB 94-183100)
Scire, J. S., and L. L. Schulman, 1981. Evaluation of the BLP and ISC
Models with SF6 Tracer Data and S02 Measurements at Aluminum Reduction
Plants. Air Pollution Control Association Specialty Conference on
Dispersion Modeling for Complex Sources, St. Louis, MO.
Schulman, L. L., and S. R. Hanna, 1986. Evaluation of Downwash
Modification to the Industrial Source Complex Model. Journal of the
Air Pollution Control Association, 36: 258-264.
A-24a Revised 8/95
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-------
Catalano, J. A., 1986. Addendum to the User's Manual for the Single Source
(CRSTER) Model. EPA Publication No. EPA-600/8-86-041. U.S. Environmental
Protection Agency, Research Triangle Park, NC. (NTIS No. PB 87-145843)
Gery, M. W., G. Z. Whitten and J. P. Killus, 1988. Development and Testing of
CBM-IV for Urban and Regional Modeling. EPA Publication No. EPA-600/3-88-012.
U.S. Environmental Protection Agency, Research Triangle Park, NC. (NTIS No.
PB 88-180039)
Horst, T. W., 1983. A Correction to the Gaussian Source-depletion Model. In
Precipitation Scavenging. Dry Deposition and Resuspension. H. R. Pruppacher,
R. G. Semonin, and W. G. N. Slinn, eds., Elsevier, NY.
Petersen, W. B., 1980. User's Guide for HIWAY-2 A Highway Air Pollution Model.
EPA Publication No. EPA-600/8-80-018. U.S. Environmental Protection Agency,
Research Triangle Park, NC. (NTIS PB 80-227556)
Rao, T. R. and M. T. Keenan, 1980. Suggestions for Improvement of the EPA-
HIWAY Model. Journal of the Air Pollution Control Association, 30: 247-256
(and reprinted as Appendix C in Petersen, 1980) .
Segal, H. M., 1983. Microcomputer Graphics in Atmospheric Dispersion Modeling.
Journal of the Air Pollution Control Association, 23: 598-600.
AR-3 Revised 8/95
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APPENDIX B
Table of Contents
B.O INTRODUCTION B-l
B.I AIR QUALITY DISPLAY MODEL (AQDM) B-3
B.2 AIR RESOURCES REGIONAL POLLUTION ASSESSMENT (ARRPA) MODEL . B-7
B.3 APRAC-3 B-ll
B.4 COMPTER B-15
B.5 Deleted
B.6 ERT VISIBILITY MODEL B-23
B.7 HIWAY-2 B-27
B.8 INTEGRATED MODEL FOR PLUMES AND ATMOSPHERIC CHEMISTRY
IN COMPLEX TERRAIN (IMPACT) B-31
B.9 LONGZ B-35
B.O MARYLAND POWER PLANT SITING PROGRAM (PPSP) MODEL B-39
B.ll MESOSCALE PUFF MODEL (MESOPUFF II) B-43
B.12 MESOSCALE TRANSPORT DIFFUSION AND DEPOSITION MODEL
FOR INDUSTRIAL SOURCES (MTDDIS) B-47
B.13 MODELS 3141 AND 4141 B-51
B.14 MULTIMAX B-55
B.15 Deleted
B.16 MULTI-SOURCE (SCSTER) MODEL B-63
B.17 PACIFIC GAS AND ELECTRIC PLUMES MODEL B-67
B.I8 PLMSTAR AIR QUALITY SIMULATION MODEL B-71
B.19 PLUME VISIBILITY MODEL (PLUVUE II) B-75
B.20 POINT, AREA, LINE SOURCE ALGORITHM (PAL) B-79
B.21 RANDOM WALK ADVECTION AND DISPERSION MODEL (RADM) B-83
B.22 REACTIVE PLUME MODEL (RPM-II) B-87
B-i Revised 2/93
-------
B.23 REGIONAL TRANSPORT MODEL (RTM-II) B-91
B.24 SHORTZ B-95
B.25 SIMPLE LINE-SODRCE MODEL (GMLINE) B-99
B.26 TEXAS CLIMATOLOGICAL MODEL (TCM) B-103
B.27 TEXAS EPISODIC MODEL (TEM) B-107
B.28 A.VACTA II MODEL B-lll
B.29 SHORELINE DISPERSION MODEL (SDM) B-115
B.30 WYNDvalley MODEL B-118
B.31 DENSE GAS DISPERSION MODEL (DEGADIS) B-122
B.32 HGSYSTEM B-127
B.33 SLAB B-131
B.REF REFERENCES BR-1
B-ii Revised 8/95
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B.32 HGSYSTEM: Dispersion Models for Ideal Gases and Hydrogen Fluoride
References: Post, L. (ed.), 1994. HGSYSTEM 3.0 Technical Reference
Manual. Shell Research Limited, Thornton Research Centre,
Chester, United Kingdom. (TNER 94.059)
Post, L., 1994. HGSYSTEM 3.0 User's Manual. Shell Research
Limited, Thornton Research Centre, Chester, United Kingdom.
(TNER 94.059)
Availabilitv:
Technical
Contacts:
Abstract:
The PC-DOS version of the HGSYSTEM software (HGSYSTEM:
Version 3.0, Programs for modeling the dispersion of ideal
gas and hydrogen fluoride releases, executable programs and
source code can be installed from floppy diskettes. These
diskettes and all documentation are available as a package
from API [(202) 682-8340] or NTIS (see Section B.0).
Doug N. Blewitt
AMOCO Corporation
1670 Broadway / MC 2018
Denver, CO 80201
(303) 830-5312
Howard J. Feldman
American Petroleum Institute
1220 L Street, Northwest
Washington, D.C. 20005
(202) 682-8340
HGSYSTEM is a PC-based software package consisting of
mathematical models for estimating of one or more consecutive
phases between spillage and near-field and far-field dispersion
of a pollutant. The pollutant can be either a two-phase,
multi-compound mixture of non-reactive compounds or hydrogen
fluoride (HP) with chemical reactions. The individual models
are:
Database program:
DATAPROP
generates physical properties used in other HGSYSTEM
models
Source term models:
SPILL
HFSPILL
LPOOL
transient liquid release from a pressurized vessel
SPILL version specifically for HF
evaporating multi-compound liquid pool model
Near-field dispersion models:
AEROPLDME high-momentum jet dispersion model
HFPLUME AEROPLUME version specifically for HF
HEGABOX dispersion of instantaneous heavy gas releases
Far-field dispersion models:
HEGADAS(S,T) heavy gas dispersion (steady-state and transient
version)
PGPLUME passive Gaussian dispersion
Utility programs:
HFFLASH
POSTHS/POSTHT
PROFILE
GET2COL
flashing of HF from pressurized vessel
post-processing of HEGADAS(S,T) results
post-processor for concentration contours of airborne
plumes
utility for data retrieval
The models assume flat, unobstructed terrain. HGSYSTEM can be
used to model steady-state, finite-duration, instantaneous and
time dependent releases, depending on the individual model
used. The models can be run consecutively, with relevant data
being passed on from one model to the next using link files.
The models can be run in batch mode or using an iterative
utility program.
B-127
Revised 8/95
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a. Recommendations for Regulatory Use
HGSYSTEM can be used as a refined model to estimate short-term ambient
concentrations. For toxic chemical releases {non-reactive chemicals or
hydrogen fluoride; 1-hour or less averaging times) the expected area of
exposure to concentrations above specified threshold values can be
determined. For flammable non-reactive gases it can be used to determine
the area in which the cloud may ignite.
b. Input Requirements
HFSPILL input data: reservoir data (temperature, pressure, volume, HF
mass, mass-fraction water), pipe-exit diameter and ambient pressure. .
EVAP input data: spill rate, liquid properties, and evaporation rate
(boiling pool) or ambient data (non-boiling pool).
HFPLUME and PLUME input data: reservoir characteristics, pollutant
parameters, pipe/release data, ambient conditions, surface roughness and
stability class.
HEGADAS input data: ambient conditions, pollutant parameters, pool data
or data at transition point, surface roughness, stability class and
averaging time.
PGPLUME input data: link data provided by HFPLDME and the averaging time.
c. Output
The HGSYSTEM models contain three post-processor programs which can be
used to extract modeling results for graphical display by external
software packages. GET2COL can be used to extract data from the model
output files. HSPOST can be used to develop isopleths, extract any 2
parameters for plotting and correct for finite release duration. HTPOST
can be used to produce time history plots.
HFSPILL output data: reservoir mass, spill rate, and other reservoir
variables as a function of time. For HF liquid, HFSPILL generates link
data to HFPLUME for the initial phase of choked liquid flow (flashing
jet), and link data to EVAP for the subsequent phase of unchoked liquid
flow (evaporating liquid pool).
EVAP output data: pool dimensions, pool evaporation rate, pool mass and
other pool variables for steady state conditions or as a function of
time. EVAP generates link data to the dispersion model HEGADAS (pool
dimensions and pool evaporation rate).
HFPLUME and PLUME output data: plume variables (concentration, width,
centroid height, temperature, velocity, etc.) as a function of downwind
distance.
HEGADAS output data: concentration variables and temperature as a
function of downwind distance and (for transient case) time.
PGPLUME output data: concentration as a function of downwind distance,
cross-wind distance and height.
B-128 Revised 8/95
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d. Type of Model
HGSYSTEM is made up of four types of dispersion models. HFPLDME and
PLUME simulate the near-field dispersion and PGPLDME simulates the
passive-gas dispersion downwind of a transition point. HEGADAS simulates
the ground-level heavy-gas dispersion.
e. Pollutant Types
HGSYSTEM may be used to model non-reactive chemicals or hydrogen
fluoride.
f. Source-Receptor Relationships
HGSYSTEM estimates the expected area of exposure to concentrations above
user-specified threshold values. By imposing conservation of mass,
momentum and energy the concentration, density, speed and temperature are
evaluated as a function of downwind distance.
g. Plume Behavior
HFPLUME and PLUME: (l) are steady-state models assuming a top-hat profile
with cross-section averaged plume variables; and (2) the momentum
equation is taken into account for horizontal ambient shear, gravity,
ground collision, gravity-slumping pressure forces and ground-surface
drag.
HEGADAS: assumes the heavy cloud to move with the ambient wind speed,
and adopts a power-law fit of the ambient wind speed for the velocity
profile.
PGPLUME: simulates the passive-gas dispersion downwind of a transition
point from HFPLUME or PLUME for steady-state and finite duration
releases.
h. Horizontal Winds
A power law fit of the ambient wind speed is used.
i. Vertical Wind Speed
Not treated.
j. Horizontal Dispersion
HFPLUME and PLUME: Plume dilution is caused by air entrainment resulting
from high plume speeds, trailing vortices in wake of falling plume
(before touchdown), ambient turbulence and density stratification. Plume
dispersion is assumed to be steady and momentum-dominated, and effects of
downwind diffusion and wind meander (averaging time) are not taken into
account.
B-123 Revised 8/95
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HEGADAS: This model adopts a concentration similarity profile expressed
in terms of an unknown center-line ground-level concentration and unknown
vertical/cross-wind dispersion parameters. These quantities are
determined from a number of basic equations describing gas-mass
conservation, air entrainment (empirical law describing vertical top-
entrainment in terms of global Richardson number), cross-wind gravity
spreading (initial gravity spreading followed by gravity-current
collapse) and cross-wind diffusion (Briggs formula).
PGPLDME: It assumes a Gaussian concentration profile in which the cross-
wind and vertical dispersion coefficients are determined by empirical
expressions. All unknown parameters in this profile are determined by
imposing appropriate matching criteria at the transition point.
k. Vertical Dispersion
See description above.
1. Chemical Transformation
Not treated.
m. Physical Removal
Not treated.
n. Evaluation Studies
PLUME has been validated against field data for releases of liquified
propane, and wind tunnel data for buoyant and vertically-released dense
plumes. HFPLUME and PLUME have been validated against field data for
releases of HF (Goldfish experiments) and propane releases. In addition,
the plume rise algorithms have been tested against Hoot, Meroney, and
Peterka, Ooms and Petersen databases. HEGADAS has been validated against
steady and transient releases of liquid propane and LNG over water
(Maplin Sands field data), steady and finite-duration pressurized
releases of HF (Goldfish experiments; linked with HFPLUME), instantaneous
release of Freon (Thorney Island field data; linked with the box model
HEGABOX) and wind tunnel data for steady, isothermal dispersion.
Validation studies are contained in the following references.
McFarlane, K., Prothero, A., Puttock, J.S., Roberts, P.T. and Witlox,
H.W.M., 1990. Development and validation of atmospheric dispersion
models for ideal gases and hydrogen fluoride, Part I: Technical
Reference Manual. Report TNER.90.015. Thornton Research Centre,
Shell Research, Chester, England. [EGG 1067-1151] (NTIS No.
DE 93-000953)
Witlox, H.W.M., McFarlane, K., Rees, F.J., and Puttock, J.S., 1990.
Development and validation of atmospheric dispersion models for ideal
gases and hydrogen fluoride, Part II: HGSYSTEM Program User's Manual.
Report TNER.90.016. Thornton Research Centre, Shell Research,
Chester, England. [EGG 1067-1152] (NTIS No. DE 93-000954)
B-130 Revised 8/95
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B.33 SLAB
Reference: Ennak, D.L., 1990. User's Manual for SLAB: An Atmospheric
Dispersion Model for Denser-than-Air Releases (UCRL-MA-
105607), Lawrence Livermore National Laboratory.
Availability: The computer code can be obtained from:
Energy Science and Technology Center
P.O. Box 1020
Oak Ridge, TN 37830
(615) 576-2606
The User's Manual (NTIS No. DE 91-008443) can be obtained
from:
Computer Products
National Technical Information Service
U.S. Department of Commerce
Springfield, VA 22161
(703) 487-4650
(As of this publication, the computer code is also available
on the Support Center for Regulatory Air Models Bulletin
Board System (Upload/Download Area; see Section B.O.)
Abstract: The SLAB model is a computer model, PC-based, that simulates
the atmospheric dispersion of denser-than-air releases. The
types of releases treated by the model include a ground-level
evaporating pool, an elevated horizontal jet, a stack or
elevated vertical jet and an instantaneous volume source.
All sources except the evaporating pool may be characterized
as aerosols. Only one type of release can be processed in
any individual simulation. Also, the model simulates only
one set of meteorological conditions; therefore direct
application of the model over time periods longer than one or
two hours is not recommended.
a. Recommendations for use
The SLAB model should be used as a refined model to estimate spatial and
temporal distribution of short-term ambient concentration (e.g., 1-hour
or less averaging times) and the expected area of exposure to
concentrations above specified threshold values for toxic chemical
releases where the release is suspected to be denser than the ambient
air.
B-131 Revised 8/95
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b. Input Requirements
The SLAB model is executed in the batch mode. Data are input directly
from an external input file. There are 29 input parameters required to
run each simulation. These parameters are divided into 5 categories by
the user's guide: source type, source properties, spill properties, field
properties, and meteorological parameters. The model is not designed to
accept real-time meteorological data or convert units of input values.
Chemical property data are not available within the model and must be
input by the user. Some chemical and physical property data are
available in the user's guide.
Source type is chosen as one of the following: evaporating pool release,
horizontal jet release, vertical jet or stack release, or instantaneous
or short duration evaporating pool release.
Source property data requirements are physical and chemical properties
(molecular weight, vapor heat capacity at constant pressure; boiling
point; latent heat of vaporization; liquid heat capacity; liquid density;
saturation pressure constants), and initial liquid mass fraction in the
release.
Spill properties include: source temperature, emission rate, source
dimensions, instantaneous source mass, release duration, and elevation
above ground level.
Required field properties are: desired concentration averaging time,
maximum downwind distance (to stop the calculation), and four separate
heights at which the concentration calculations are to be made.
Meteorological parameter requirements are: ambient measurement height,
ambient wind speed at designated ambient measurement height, ambient
temperature, surface roughness, relative humidity, atmospheric stability
class, and inverse Monin-Obukhov length (optional, only used as an input
parameter when stability class is unknown).
c. Output
No graphical output is generated by the current version of this program.
The output print file is automatically saved and must be sent to the
appropriate printer by the user after program execution. Printed output
includes in tabular form:
Listing of model input data;
Instantaneous spatially-averaged cloud parameters - time, downwind
distance, magnitude of peak concentration, cloud dimensions (including
length for puff-type simulations), volume (or mole) and mass fractions,
downwind velocity, vapor mass fraction, density, temperature, cloud
velocity, vapor fraction, water content, gravity flow velocities, and
entrainment velocities;
B-132 Revised 8/95
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Time-averaged cloud parameters - parameters which may be used externally
to calculate time-averaged concentrations at any location within the
simulation domain (tabulated as functions of downwind distance);
Time-averaged concentration values at plume centerline and at five off-
centerline distances (off-centerline distances are multiples of the
effective cloud half-width, which varies as a function of downwind
distance) at four user-specified heights and at the height of the plume
centerline.
d. Type of Model
As described by Ermak (1989), transport and dispersion are calculated by
solving the conservation equations for mass, species, energy, and
momentum, with the cloud being modeled as either a steady-state plume, a
transient puff, or a combination of both, depending on the duration of
the release. In the steady-state plume mode, the crosswind-averaged
conservation equations are solved and all variables depend only on the
downwind distance. In the transient puff mode, the volume-averaged
conservation equations are solved, and all variables depend only on the
downwind travel time of the puff center of mass. Time is related to
downwind distance by the height-averaged ambient wind speed. The basic
conservation equations are solved via a numerical integration scheme in
space and time.
e. Pollutant Types
Pollutants are assumed to be non-reactive and non-depositing dense gases
or liquid-vapor mixtures (aerosols). Surface heat transfer and water
vapor flux are also included in the model.
f. Source-Receptor Relationships
Only one source can be modeled at a time.
There is no limitation to the number of receptors; the downwind receptor
distances are internally-calculated by the model. The -SLAB calculation
is carried out up to the user-specified maximum downwind distance.
The model contains submodels for the source characterization of
evaporating pools, elevated vertical or horizontal jets, and
instantaneous volume sources.
g. Plume Behavior
Plume trajectory and dispersion is based on crosswind-averaged mass,
species, energy, and momentum balance equations. Surrounding terrain is
assumed to be flat and of uniform surface roughness. No obstacle or
building effects are taken into account.
h. Horizontal Winds
A power law approximation of the logarithmic velocity profile which
accounts for stability and surface roughness is used.
B-133 Revised 8/95
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i. Vertical Wind Speed
Not treated.
j. Vertical Dispersion
The crosswind dispersion parameters are calculated from formulas reported
by Morgan et al. (1983), which are based on experimental data from
several sources. The formulas account for entrainment due to atmospheric
turbulence, surface friction, thermal convection due to ground heating,
differential motion between the air and the cloud, and damping due to
stable density stratification within the cloud.
k. Horizontal Dispersion
The horizontal dispersion parameters are calculated from formulas similar
to those described for vertical dispersion, also from the work of Morgan,
et al. (1983) .
1. Chemical Transformation
The thermodynamics of the mixing of the dense gas or aerosol with ambient
air (including water vapor) are treated. The relationship between the
vapor and liquid fractions within the cloud is treated using the local
thermodynamic equilibrium approximation. Reactions of released chemicals
with water or ambient air are not treated.
m. Physical Removal
Not treated.
n. Evaluation Studies
Blewitt, D. N., J. F. Yohn, and D. L. Ermak, 1987. An Evaluation of SLAB
and DEGADIS Heavy Gas Dispersion Models Using the HF Spill Test Data,
Proceedings, AIChE International Conference on Vapor Cloud Modeling,
Boston, MA, November, pp. 56-80.
Ermak, D. L., S.T. Chan, D. L. Morgan, and L. K. Morris, 1982. A Compar-
ison of Dense Gas Dispersion Model Simulations with Burro Series LNG
Spill Test Results, J. Haz. Matls., 6: 129-160.
Zapert, J. G., R. J. Londergan, and H. Thistle, 1991. Evaluation of
Dense Gas Simulation Models. EPA Publication No. EPA-450/4-90-018.
U.S. Environmental Protection Agency, Research Triangle Park, NC.
B-134 Revised 8/95
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Whitten, G. Z., J. P. Killus, and H. Hogo, 1980. Modeling of Simulated
Photochemical Smog with Kinetic Mechanisms. Volume 1. Final Report. EPA
Publication No. EPA-600/3-80-028a. U.S. Environmental Protection Agency*
Research Triangle Park, NC.
Beals, 6. A., 1971. A Guide to Local Dispersion of Air Pollutants. Air
Weather Service Technical Report #214 (April 1971) .
Colenbrander, G. W., 1980. A Mathematical Model for the Transient Behavior of
Dense Vapor Clouds, 3rd International Symposium on Loss Prevention and Safety
Promotion in the Process Industries, Basel, Switzerland.
Green, A. E., Singhal R. P., and R. Venkateswar, 1980. Analytical Extensions
of the Gaussian Plume Model. Journal of the Air Pollution Control Association,
30: 773-776.
MacCready, P. B., Baboolal, L. B., and P. B. Lissaman, 1974. Diffusion and
Turbulence Aloft Over Complex Terrain. Preprint Volume, AMS Symposium on
Atmospheric Diffusion and Air Pollution, Santa Barbara, CA. American Meteoro-
logical Society, Boston, MA.
Slade, D. H., 1968. Meteorology and Atomic Energy. U.S. Atomic Energy Commis-
sion, 445 pp. (NTIS No. TID-24190)
Ermak, D. L., 19.89. A Description of the SLAB Model, presented at JANNAF
Safety and Environmental Protection Subcommittee Meeting, San Antonio, TX,
April, 1989.
Morgan, D. L., Jr., L. K. Morris, and D. L. Ermak, 1983. SLAB: A Time-
Dependent Computer Model for the Dispersion of Heavy Gas Released in the
Atmosphere, UCRL-53383, Lawrence Livermore National Laboratory, Livermore, CA.
BR-4 Revised 8/95
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TECHNICAL REPORT DATA
(Please read Instructions on reverse before completing)
1. REPORT NO.
EPA-450/2-78-027R-C
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Supplement C to the Guideline on Air Quality Models
(Revised)
5. REPORT DATE
August 1995
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
U.S. Environmental Protection Agency
Emissions, Monitoring, and Analysis Division (MD-14)
Office of Air Quality Planning and Standards
Research Triangle Park, NC 27711
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The Guideline (published as Appendix W to 40 CFR Part 51) serves as the basis by which air quality
models are to be used for demonstrations associated with SIP (State Implementation Plan) revisions,
AQMA (Air Quality Maintenance Area) analyses, regional classifications for episode planning, new
source review, including that pertaining to PSD (Prevention of Significant Deterioration). It is intended
for use by EPA Regional Offices in judging the adequacy of modeling analyses performed by EPA, by
State and local agencies, and by industry and its consultants. It also identifies modeling techniques and
data bases that EPA considers acceptable. The Guideline makes specific recommendations concerning
air quality models, data bases, and general requirements for making estimates.
This document is Supplement C to the Guideline. Supplement C: (1) revises the ISC model by
incorporating improved area source and dry deposition algorithms (the integrated model is renamed
ISC3); (2) adopts a solar radiation/delta-T method for estimating Pasquill-Gifford stability categories
using on-site meteorological data; (3) adopts a new screening approach for assessing annual NO2
impacts; and (4) adds SLAB and HGSYSTEM as alternative models in Appendix B.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution
Atmospheric Dispersion Modeling
Atmospheric Diffusion
Meteorology
Dispersion Modeling
Gaussian Plume Models
Clean Air Act
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (Report)
Unclassified
21. NO. OF PAGES
32
20. SECURITY CLASS (Page)
Unclassified
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION IS OBSOLETE
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