EPA-453/--94-
056A
United States
Enviroamental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park, NC 27711
EPA-4^3/R-94-058A
July 1994
AIR
SV EPA Toxic Modeling System Short-Term (TOXST)
User's Guide: Volume I
PROTECTION
AGENCY
DAttAS, TEXAS
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TOXIC MODELING SYSTEM SHORT-TERM (TOXST)
USER'S GUIDE
VOLUME I
July 30, 1994
'\
Prepared for:
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Research Triangle Park, NC 27711
o
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DISCLAIMER
This document has been reviewed by the Office of Air Quality Planning and Standards, U.S. Environmental Protection
Agency, and approved for publication. Approval does not signify that the contents necessarily reflect the view and
policies of the U.S. Environmental Protection Agency, nor does mention of trade names or commercial products
constitute endorsement or recommendation for use.
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ACKNOWLEDGMENTS
This document was originally based on the document, Integrated Toxic Expected Exceedance (INTOXX) Model
User's Guide, written by T. E. Stoeckenius and J. R. Pehling of Systems Applications International, San Rafael,
California. That work was funded by the U. S. Environmental Protection Agency (EPA) under Contract 68D90006.
A revision was performed in 1992 by J.S. Dunn of Research Triangle Institute, Research Triangle Park, NC, which
was also funded by the EPA under Contract 2D1482NALX. During the revision made by Research Triangle Institute
the INTOXX model was renamed TOXST. Subsequent modifications have been the result of efforts in 1993 by T.
Grosch, D. Hlinka, and D. Sullivan of Sullivan Environmental Consulting, Alexandria, VA under EPA contract
68D20189. The development of this modeling system has been supervised by Dr. David E. Guinnup of the EPA.
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Table of Contents
1. INTRODUCTION
1.1 Background 1
1.2 Overview of TOXST 2
1.3 Manual Scope and Organization 3
2. TOXST ALGORITHMS
2.1 Overview 5
2.2 ISCST2 Algorithms 7
2.3 TOXX Algorithms - 7
2.3.1 The Emissions Algorithm 7
2.3.2 Expected Exceedances Calculations . . . 8
2.3.3 Multiple Sources 9
2.3.4 Modeling Multiple Pollutants 11
2.3.5 Screening Procedures 13
2.3.6 Mutual Exclusion Option 13
2.3.7 Batch Operations Option 14
2.3.8 Non-batch Operations Option 15
2.3.8 Multiple Hourly Averaging 15
2.4 TOXST Limitations 15
2.5 Summary of TOXST Inputs and Outputs 16
3. PREPARING TOXST INPUT FILES 19
3.1 Preparation of ISCST2 Input Files 19
3.1.1 ISCST2 Modeling Restrictions 22
3.2 Preparation of TOXX Input Parameter File 22
4. EXECUTING TOXST 61
4.1 System Requirements 61
4.2 Execution Procedure 62
in
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5. TOXST OUTPUT 65
5.1 General Output 65
5.2 ISCST2 Printout File 65
5.3 TOXST Printout File 65
6. EXAMPLE TOXST APPLICATIONS 67
References : 79
VOLUME 2:
*
APPENDIX A: Case Study / Example Applications A-l
APPENDIX B: TOXX Source Model Code B-l
IV
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1. INTRODUCTION
1.1 BACKGROUND
The Toxic Modeling System Short-Term (TOXST) addresses the problem of estimating expected
exceedances of specified short-term health effects thresholds in the vicinity of continuous and
intermittent toxic releases.
Certain industrial facilities emit airborne toxic chemicals known to be harmful when their
concentrations exceed a specified health effect threshold value for a specified length of time.
However, releases of such chemicals often occur intermittently. This random emission pattern
makes it difficult to predict the frequency with which ambient concentrations will exceed the
health effect threshold (exceedance rate) in the vicinity of a source, since the particular
atmospheric dispersion conditions coinciding with each release period cannot be known in
advance. An analysis in which worst-case dispersion conditions are assumed to coincide with
each release would tend overestimate the exceedance frequency, since a certain proportion of
releases is likely to occur under more favorable dispersion conditions. On the other hand,
assuming that each release occurs in conjunction with some more favorable dispersion condition,
or that the source operates continuously at some long-term average emission rate, would likely
underestimate the exceedance rate.
TOXST attempts to avoid the problems of underestimation and overestimation of exceedance
rates resulting from random emission patterns by using the Monte Carlo simulation of source
emissions of user-specified durations and rates at randomly selected points in time over a
(simulated) long period of time. In addition, TOXST maintains the capability of simulating
continuous emission sources along with intermittent emissions, thereby providing a more
realistic simulation of actual industrial operations.
With the promulgation of "A Tiered Modeling Approach for Assessing the Risks Due to Sources
of Hazardous Air Pollutants" (Guinnup, 1992) and the release of new versions of the United
States Environmental Protection Agency's (EPA) Industrial Source Complex (ISC2) Dispersion
Models in March of 1992 (EPA, 1992), it became necessary to revise the former Integrated
Toxic Expected Exceedance (INTOXX) Model (Stoeckenius and Pehling, 1990), which was
based on the superceded version of the Industrial Source Complex (Short-Term) {ISCST) model
(EPA, 1988). This document describes that revision to TOXST and subsequent enhancements.
It draws heavily upon the previous INTOXX documentation and programs.
TOXST allows for Monte Carlo post-processing of output from the EPA model ISCST2 to
account for the variability in emissions. The previous versions of TOXST were simplified to
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treat sources as "on" or "off." The Chemical Manufacturer's Association (CMA) sponsored two
previous studies that were undertaken to improve the flexibility and accuracy of modeling peak
releases (CMA, 1992; Whitmyre, et al., 1992). This work has been utilized in the
development of the current version of TOXST. As a result, the flexibility of this model has
been expanded to allow for emissions distributions (both daytime and nighttime), batch
operations, mutually-exclusive source groups, and multiple hourly averaging.
1.2 OVERVIEW OF TOXST
This manual describes a system of computer programs known as TOXST (TOXic modeling
system S_hort-Term). TOXST is an interactive, PC-based system designed to assist users in
analyzing the air quality impacts of intermittent releases of toxic materials from industrial
sources. TOXST consists of three programs:
RUNTOXST, a control program that assists users in setting up and executing
ISCST2 and TOXX runs,
ISCST2, a widely-used EPA dispersion model which is used to predict
ambient concentrations resulting from each source included in the simulation,
and
TOXX, a post-processor which comprises the Toxic Expected Exceedances
model that carries out the exceedance calculations.
RUNTOXST prompts users to enter the names .of appropriate, previously created ISCST2 and
TOXX input files; it then sets up and executes first ISCST2 and then TOXX using these files.
Transfer of data from ISCST2 to TOXX is handled automatically by TOXST using the
TOXXFILE option; no user intervention is required. Options allow delayed model execution
(for example, model runs can be set up during the day and execution delayed until evening) and
allow only ISCST2 or only TOXX to be executed (in the latter case, using the output of a
previous ISCST2 run). . .
The ISCST2 program generates screened ambient concentration values resulting from each toxic
pollutant source included in the TOXST simulation. All sources are modeled in ISCST2 as if
they were continuous and operating at a unit emission rate (1 g/s); the intermittency of these
sources is subsequently accounted for in the TOXX post-processor. Concentration predictions
are passed from ISCST2 to the TOXX post-processor using the TOXXFILE option in ISCST2.
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It is in TOXX that concentrations are scaled to account for the stochastic variability in emission
rates.
The TOXX post-processor utilizes the ISCST2 results in the TOXXFILE for random,
intermittent sources to calculate the real-time concentration impacts of the simulated facility,
either on a source-by-source basis or for all sources combined. Each ambient (1-hour)
concentration impact is then compared to a user-specified threshold to determine if an
"exceedance" of that threshold occurs. Exceedances are subsequently tracked at each receptor
during each hour of the year to obtain annual exceedance rates, and these rates are reported in
the program output. In addition to the calculation of single pollutant threshold exceedance
rates, the TOXX post-processor can also calculate multiple-pollutant "exceedance" rates, using
an additive, hazard index approach. The current version of TOXST allows the investigation of
exceedance rates for concentrations over longer averaging times. In addition, the multiple-
pollutant impacts are calculated using a composite emission rate approach (see section 2.3.4).
TOXST requires several ISCST2 and TOXX model input files. ISCST2 model input files used
with TOXST are described in the ISC2 user's manual, Vol. I. (EPA, 1992). These files
contain information on physical source parameters (e.g., location, stack height) and
meteorological conditions. TOXX input files contain information on the species of toxic
pollutants being emitted by the source(s) under study, the distribution of emission probabilities
and emissions rates and batch operation characteristics, health effect thresholds, and background
concentrations (if any) for each species.
1.3 MANUAL SCOPE AND ORGANIZATION
This manual presents information needed to develop inputs for and execute TOXST on an IBM
PC-compatible computer.1 It also describes algorithms used in the TOXX model contained
within TOXST, TOXX input parameters, formats of TOXX input files, and the output produced
by the TOXX model.
We assume that users are familiar with the preparation of input files for, and the interpretation
of output from, the ISCST2 dispersion model as described in the ISC2 manuals (EPA, 1992).
Thus this information will not be repeated in detail here although an example is given and items
pertinent to TOXST are noted.
1 Although TOXST will run on most PC-compatible machines running some version of the PC- or
MS-DOS, the minimum recommended system requirements for acceptable performance are: 80386- or
80486-based PC-compatible with monochrome monitor, math coprocessor, 40MB hard disk and DOS 3.2
or higher.
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The manual consists of six chapters. Chapter 1 constitutes a general introduction to TOXST.
Chapter 2 describes the principal TOXST applications, concepts, and algorithms. Chapter 3
contains an example ISCST2 input file with brief description and a detailed description of the
content and format of the TOXST input files. Chapter 4 provides information needed to
execute TOXST on an IBM-PC or compatible machine. Chapter 5 describes the output
produced by TOXST. Chapter 6 presents some sample applications with input and output file
listings.
Volume II contains Appendices A and B. Appendix A provides all of the example model run
input and output files as referenced in Section 6. Appendix B contains the TOXX source code.
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2. TOXST ALGORITHMS
2.1 OVERVIEW
In this chapter, we briefly describe the algorithms used in TOXST, focusing in particular on the
algorithms used in the TOXX model itself. An overview of the TOXST modeling system is
shown in Figure 2-1. TOXST consists of three programs:
The ISCST2 model,
the TOXX model, and
RUNTOXST, an interactive control program.
The flow of information between the three programs is depicted in Figure 2-1, including a
description of each of the input and output files associated with their execution.
Prior to using TOXST, it is necessary to prepare all of the ISGST2 input files and the
input parameter files shown in Figure 2-1. Information needed to prepare the TOXX input
parameter files is presented in Chapter 3. Information needed to prepare the ISCST2 input files
(i.e., the preprocessed meteorological data file and the ISCST2 input parameter file) is provided
in the ISC2 user's guide Volume I (EPA, 1992). Additional information on the proper
specification of ISCST2 model options and source emission rates is presented in Section 3.1.
Once all input files have been prepared, the TOXST control program is invoked. Using input
file names specified by the user, this program creates batch input files and MS-DOS batch files
that run first ISCST2 and then TOXX. By specifying multiple sets of ISCST2 input files, each
corresponding to a different year of meteorological data, multiple ISCST2 runs can be
performed, producing a set of binary output files for a multi-year period; these files are then
used as input to the TOXX model.
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TOXST Control Program.
Preproces«ed
oat. data file
ISCST2 input
parameter fila
ISCST2 |
dispersion model
ISCST2 output
file (printable)
Screened normalized
concentrations for ona calendar year
(TOXXFILE)
TOXX input
parameter file
Temporary paging file
(binary format)
FIGURE 2-1. Overview of the TOXST system.
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2.2 ISCST2 ALGORITHMS
Algorithms used in the ISCST2 dispersion model are described in detail in the ISC2 user's
manual Volume II (EPA, 1992). It is assumed here that readers are already familiar with
ISCST2. A procedure referred to as the TOX^EILE--oriUonJias been incorporatedJnto ISCST2
which creates a "screened" binary concentration output file, that contains only those
concentrations for each hour at each receptor whose concentration exceeds a user-defined
threshold value for TOXX averaging periods of 1 hour duration. The purpose of the
TOXXFILE option is to reduce the size of the binary output file. Guidance on the selection of
an appropriate threshold value is given in Section 3.1.
In multiple-source applications, the concentration attributed to each individual source for a given
receptor-hour is compared to the screening threshold value. If the contribution of any single
source exceeds the threshold, all source contributions for the receptor-hour are written to the
binary output file. This procedure insures that multiple- source exceedance calculations will be
carried out properly in the TOXX model.
2.3 TOXX ALGORITHMS
In this section we briefly describe the algorithms used in TOXX to calculate expected
exceedances of health effects threshold concentrations. TOXX contains ajeaturejhat allows
multiglejhourly averaging for all averaging periods that can b.fijsvenLy d,iyidedjntp_24, i.e. 2, 3,
4, 6, 8, 12, and 24-hour periods, which is consistent with the resolution available through
ISCST2. This feature allows computations to match the different averaging periods required in
different state programs (Whitmyre, Baker and Sullivan, 1992). Based on Whitmyre, Baker, and
Sullivan, 1992, there are two cases where this range of averaging periods would not meet
potential data needs, i.e., averaging periods of 30-minutes or less as required for North Carolina
and Texas. For these special case applications, which would require site-specific analysis, the
user would need to seek specific modeling guidance from their respective states.
2.3.1 The Emissions Algorithms
The current version of TOXX contains several approaches to treat emission rates. As in earlier
versions, this version includes the ability to treat emissions from a source as "on" or "off"
during each hour, with a fixed duration for each "on" period, and with a constant emission rate.
The user sets the probability of the source turning on during any given hour and the duration of
the release.
Since many industrial operations have a range of emission events, each with different average
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emission rates, and some with a different probability of turning "on" on a daytime and nighttime
basis, the current version of TOXX also allows the user the option of inputting a distribution of
emission rates as a function of daytime and nighttime periods. With this option, the user can
assign probabilities to each emission rate on a daytime and nighttime basis. This approach
provides substantially greater flexibility than earlier versions to model complex sources.
Section 3.2 contains an example of assigning emissions distributions to a hypothetical source.
Sections 2.3.6 and 2.3.7 describe the mutual exclusion and batch operation options, respectively,
which further enhance the utility of using TOXST to represent a wide range of industrial
applications.
Appropriate specification of p^ (probability of a source turning on when off) for TOXST
simulations can be achieved by following several simple rules. (1) For each continuous
emission source, p^ should be specified as 1.0. The specified duration of these releases is
subsequently irrelevant to the calculation, but a specification of 8760 is recommended (this
results in a slight reduction of run time). (2) For each unconstrained intermittent source, p^ is
equal to the average number of releases per year divided by 8760 (the number of hours in a
non-leap year). The specified duration of these releases should be equal to the nearest integer
hour which is not less than the actual average release duration. (3) For each intermittent source
whose hours of possible operation are constrained to a portion of the day, month or year, pOT
should be specified as the average number of releases per year divided by the total number of
hours in the year during which its operation is possible. The duration should be specified as in
rule (2) above. For sources that have different emissions probabilities on a nighttime and
daytime basis, a comparable approach is used to assign probabilities for the daytime and
nighttime periods.
2.3.2 Expected Exceedances Calculations
Calculations of the expected number of exceedances at each receptor for a particular pollutant
species and threshold concentration combination are dependent on a Monte Carlo procedure.
Simply put, for an analysis of a single TOXX source group, a one-year sequence of emission
rates is randomly generated for each of a series of trials or "sample years." The randomly
generated emission rate for each hour is multiplied by the corresponding normalized dispersion
model result (x/q value). If the resulting product is greater than or equal to the health effect
threshold concentration (less background concentration, if any), an exceedance is recorded, and
the total number of such exceedances in each sample year is noted. For the analysis of multiple
TOXX source groups, a comparable approach is used to generate emission rates for each hour
for each source group, and the incremental concentrations are summed across all TOXX source
groups to determine if an exceedance has occurred.
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This process is repeated for a large number of sample years using a new set of randomly
generated emission rates each year. The average number of exceedances per year over all trials
is then taken as an estimate of the expected exceedance rate.
In some cases, it is useful to display the distribution of concentrations rather than simply
displaying the number of exceedances. A distribution of concentrations provides a more
complete data set for a subsequent risk assessment. TOXX now can provide a distribution of
concentrations for single pollutant runs, and also for multiple pollutant runs if the emissions
pre-processing shown in Section 2.3.4 is performed.
In TOXX, the term "health effect threshold" is used to denote the concentration that defines an
exceedance.
2.3.3 Multiple Sources
Emissions of toxic compounds from a complex of multiple sources can be modeled with
TOXX. Two release scenarios are available to the TOXX user:
Independently varying sources in which the emissions during any hour at one source
are not in any way related to emissions during the same hour at any other source, and
Covarying sources in which all sources in a source group are either emitting or not
emitting during any particular hour.
Coyarying sources are typically found in industrial facilities where a single batch process results
in simultaneous releases of pollutants from multiple locations. Independently varying sources
may occur in large facilities where several processes are being carried out independent of one
another^ resulting in releases that are not correlated from one source to the next.
TOXX is designed to handle combinations of covarying and independently varying sources in a
single application. Sources that are covarying must be assigned to the same TOXX source
group when creating the TOXX input parameter file described in Section 3.2. Sources with
independently varying emissions must be assigned to different source groups. Each source
identified in the TOXX input parameter file must be associated with its own set of dispersion
model results in the binary ISCST2 dispersion model results file. The TOXX user may then
choose to group some or all of these sources, depending on which sources are to have
covarying emissions. These TOXX source groups should not be confused with the "source
groups" defined in the ISCST2 input parameter file. Throughout this User's Guide, the term
"source group" is used to refer to TOXX source groups unless otherwise stated. A single set
of normalized dispersion estimates (x/q values) will appear in the ISCST2 binary dispersion
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result file for each ISCST2 source group defined in the ISCST2 input parameter file.
Therefore, each individual source identified in the TOXX input parameter file must correspond
to an ISCST2 source group consisting of one or more actual sources as defined in the ISCST2
input parameter file. This relationship is illustrated in Figure 2-2. The current version of
TOXST limits the total number of TOXX source groups to 20.
Source A
Source B
Source C -
c«,,».^^ n
Source D -
IS§JoUp°££Ce
Source #1
Source #2
TOXX Source
Group #1
ISCST Source rr,r>vv
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ThejcurrenLversioBuof.TOXST i^stmctutedjojtnpdel only^ gn^£pHutant_ger_modeij[un.
NJultiple species model applications, however, can still be made by assuming additive impacts
apply. Using the pre-processing that is shown in Section 2.3.4, it is possible to combine the
species based on relative thresholds to create a so-called composite emission rate. On this
basis, one reference pollutant is modeled to simulate the impacts of all pollutants, and the full
features of TOXST can be applied to the analysis. Additional information concerning the
TOXX input parameter file is presented in Section 3.2.
23.4 Modeling Multiple Pollutants
There are some simplifying steps that are recommended when there is a need to model the
impacts of multiple pollutants from the same source(s). Guidance is provided below for two
cases: (1) the interactive mode, and (2) the independent mode.
Interactive Mode - In the interactive mode, pollutant impacts are assessed using the
assumption that impacts are additive. This approach may be useful for groups of similar non-
carcinogens where the target organ for the adverse effect is the same. To use this approach, a
composite emission rate for each source included in the analysis is developed prior to the
simulation.
When simulating non-cancer impacts for multiple pollutants, the following procedure can be
used to develop one composite emission rate for each source included in the simulation which is
based on consideration of the emission rate and threshold for each species:
where:
EM; = Composite emission rate for source i normalized to the threshold
concentration for the selected reference pollutant;
= Emission rate for pollutant p;
n = Number of pollutants;
Tj = Threshold concentration for the reference pollutant; and
Tp = Threshold concentration for pollutant p
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Composite emission rates are developed as above for all sources. Choice of reference pollutant
is arbitrary.
If any background concentrations are to be included in the analysis, a composite background
should be calculated as follows:
where:
Bc = Composite background concentration normalized to the threshold
concentration for the selected reference pollutant;
Bp = Background concentration for pollutant p;
n = Number of pollutants;
Tj = Threshold concentration for the reference pollutant; and
Tp = Threshold concentration for pollutant p
It should be noted that, even though multiple pollutant impacts are being assessed with this
procedure, the TOXX model (in its current version) is operated as if only one pollutant is
included in the analysis. In this manner, impacts summed across all pollutants can be modeled
in a single model run, and a frequency distribution of combined concentrations can be displayed
based on scaling by relative thresholds. Any exceedances flagged by the output are interpreted
as hazard index values exceeding one. If it is desirable to assess the individual impacts after
performing the multiple pollutant simulation, the independent mode can be used, as described
below.
Independent Mode - Since this version of TOXST does not allow the simulation of impacts
explicitly for more than one pollutant at a time, separate TOXX runs will be required to
determine the impacts from each pollutant. It should be noted, however, that only one ISCST2
simulation may be required to develop the concentration input file for all the individual TOXX
simulations. Actual emission rates, not composite emission rates, should be used in the
individual independent mode runs.
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2.3.5 Screening Procedures
In the TOXX post-processor, a screening procedure is used to eliminate from consideration any
concentration values so small that they result in a negligibly small probability of exceedance.
This saves computing time since the vast majority of concentration values are typically less than
the screening level and are thus eliminated from subsequent calculations. The procedure in
TOXX has been designed to eliminate concentration values so small that even with all sources
emitting at their maximum emission rate no exceedance would result. The TOXX screening
procedure is designed to determine the proper screening level.
The screening procedure within TOXX should not be confused with the preliminary screening
performed by ISCST2 in the creation of the TOXXFILE binary concentration output file (see
Section 2.2). The ISCST2 screening is a coarse screen designed to limit the size of the binary
X/q files. The TOXX screening is performed on only those x/q passing through the ISCST2
screen and is designed to reduce the computational burden of the TOXX exceedance
calculations. This screening procedure is tailored to the specific input parameters of each
TOXX run. If the screening value calculated by TOXX is less than the screening value input to
ISCST2. the TOXX results will be incorrect. In such cases, a warning message will be output.
It is important, therefore, to select an ISCST2 screening level that is at least as small as the
smallest screening level likely to be used in any subsequent applications of TOXX to the
ISCST2 results. However, the use of an excessively small ISCST2 screening level may result
in unmanageably large ISCST2 x/q output files. On the other hand, the ISCST2 screening
level is used as the default concentration in TOXX for multiple hour averaging. Therefore,
with the use of a smaller screening level, a lower number of exceedances may result because
the default is used for hours with no concentration sent by ISCST2 to the TOXXFILE.
If a user is interested in displaying a distribution of concentrations for a pollutant, using up to
six concentration ranges, (e.g., thresholds) care should be used when selecting the ISCST2
screening threshold values. Unlike the case where the only output of interest is the number of
exceedances of a threshold, a lower threshold generally would be appropriate when a
distribution of concentrations will be displayed.
2.3.6 Mutual Exclusion Option
The mutual exclusion option provides the flexibility to allow only one TOXX source group to
be operational ("on") while all other TOXX source groups are not operational (not "on").3
It is important to distinguish between a TOXX source group being "on" and
its emission rate. A source group is "on" in the mutual exclusion treatment if
it is in operation at a given time. While in operation, it is still possible
that randomly extracted emission rate for any given hour could be zero.
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The probability that a source group will turn on (if it is off) is still treated as an input parameter
(i.e., probOn) in the input file.
In the current version of TOXST, the mutual exclusion feature applies to all sources included in
the simulation. If one source is "on", all others are "off1. Future refinements to TOXST could
provide the flexibility to identify only a subset of sources for the mutual exclusion treatment.
2.3.7 Batch Operations Option
The option for batch processes permits a more realistic representation of industrial processes
which intermittently emit pollutants in a fixed temporal pattern. Rather then applying a single
emission rate for the entire time the process is "on", TOXX now permits the specification of
emission rates for up to ten sequential time periods, thereby allowing emissions for a particular
process to sequentially ramp up or down, depending upon the specific characteristics of the
process. Figure 2-3 illustrates how the current version of TOXST can simulate a batch process
whose emission rates ramp up and down over the course of a ten hour time period, comparing
that emission profile with that which would have been simulated using the previous version of
TOXST to achieve the same average emission rate. The individual emission rates and their
durations must be specified in the input file. Section 3.2 contains an example input file
representing a set of emission rates for the batch operations option.
Figure 2-3
Constant/Batch Emissions Comparison
Emission rate
3atch Option
Approach V
Constan' emissions
j Approach
5 s 7 a s 10
Time (hrs)
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2.3.8 Non-Batch Operations Option
To simulate industrial processes whose emissions are intermittent but which do not vary in a
fixed temporal pattern with time, a "non-batch" option is incorporated. This option will trigger
intermittent emissions of constant rate and duration, just as in earlier versions of TOXST. In
addition, this version is capable of changing emission rates during any hour of an "on" period
based on whether that hour is during the daytime or during the nighttime. Plus, for the case
where several different emission levels are possible for the same emission point, up to ten
different emission rates (each with their respective probabilities of occurrence) may be selected
from once a specific emission point is deemed to be "on". An example of the non-batch
operations option appears in section 3.2.
2.3.9 Multiple Hourly Averaging
Multiple hourly averaging computations are performed in TOXST by maintaining a cumulative
concentration for each receptor for each TOXX source group during the specified averaging
time. Concentrations for hours that do not exceed the cutoff (i.e., missing concentration
values) are defaulted to the cutoff value. This provides a conservative estimate of time-
averaged concentrations. When it is determined that an averaging period has been completed,
the average concentration is calculated by dividing the cumulative concentration by the number
of hours in the averaging period. The average concentration is subsequently compared to the
relevant health threshold to determine if an exceedance has occurred.
2.4 TOXST LIMITATIONS
Since TOXST uses the Monte-Carlo simulation procedure, users should be aware that the
accurate calculation of expected exceedances requires a sufficiently large number of
simulations. If computing resources severely limit the number of simulations that can be
performed, large errors may result. The number of simulations performed is set by a
parameter in the TOXX input parameter file (see Section 3.2). A minimum of 200 simulations
is recommended for most applications, and more may be desirable for complex simulations.
The recent enhancements to TOXST greatly increase the flexibility of the model to more
realistically represent a wide range of industrial operations. Through the use of the new
features such as emissions distributions, batch operations, mutual exclusion, daytime/nighttime
options, and multiple hourly averaging, the characteristics of release features can be more
accurately represented. In spite of these refinements, in some cases analysts will need to
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simplify complex operations by making conservative assumptions, and possibly make a series of
runs to reasonably represent the annual cycle of operations. The following presents three
example situations where special considerations may be needed to represent complex sources:
Seasonal Operations - Some operations may have seasonal cycles to their operations,
. in either production rates or the generation of specific products. Monte Carlo
extraction of emission rates from one emissions distribution may not adequately
represent all seasons. In this case, seasonal model runs can be with TOXST, using
appropriate emissions distributions for each season. Then, the annual exceedances
could be summed across all four seasons. In extreme cases, monthly resolution in
emissions distributions may be warranted. The user may alternately want to combine
the temporal variability options in ISCST2 with the TOXX intermittent release options
to achieve the desired emissions profiles. In any event, by refining the temporal
resolution in the emissions data, it is possible to reasonably represent such differences
in production rates or product generation.
Sources that are Neither Fully Independent nor Fully Co-Varying - TOXST was not
designed to specifically model this situation. As a conservative simplification,
however, such sources could be modeled in the same TOXX source group as co-
varying sources.
Non-Independence of Emissions as a Function of Time - In some cases, there may be
cycles to an operation that result in trends, which also contain stochastic variability.
For 1-hour averaging, this problem is less of an issue than for multiple hourly
averaging. One approach to this situation would be to consider using diurnal factors
through the daytime/nighttime feature of TOXST. This could account for some trends
caused by differences in shift operations. Alternately, trends for specific emission
events that are covered in the emissions distribution can be conservatively represented
by selecting upper end values to represent a range of emission rates for duration equal
to a greater than the average period of interest, if possible. Finally, combining the
long-term temporal variability options in ISCST2 with the shorter-term variability
options in TOXX may provide the capability of simulating the desired emission
trends.
2.5 DISCUSSION OF TOXST INPUTS AND OUTPUTS
As illustrated in Figure 2-1, TOXST applications involve the execution of the ISCST2 Gaussian
dispersion model followed by execution of the TOXX post-processor. The ISCST2 model used
16
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with TOXST reads the meteorological data file and input parameter file described in the ISC2
user's guide, Vol I (EPA, 1992). As noted in Section 3.1, certain options must be specified in
the ISCST2 input parameter file to assure compatibility with TOXST. These options instruct
the program to prepare the binary file of dispersion estimates required by the TOXX model
(TOXXFILE).
In most TOXST applications, a unit source emission rate of 1.0 g/s is specified in the ISCST2
input parameter file to produce "normalized" dispersion results for subsequent processing by
the TOXX^post-processor. In such cases, actual emission rates are provided as "emission rate
multiplier" inputs in the TOXX input file. In other TOXST applications, however, it may be
desirable to use actual average emission rates as inputs in ISCST2, and provide emission rate
scalars in the TOXX input file to account for emission variability. In the latter approach, the
ISCST2 model output is more directly useful for examining maximum concentration impacts.
Either approach is possible as long as the user takes care to insure that the product of the
appropriate ISCST2 emission rate times the corresponding TOXX emission rate sealer result in
the desired emission rate for each modeled source. Additional information concerning the
proper specification of emission rates is provided in Section 2.3.4.
TOXX requires as input the binary dispersion,file (TOXXFILE) produced by ISCST2 and an
input parameter file. The following points should be noted:
• Parameters required as input to TOXX to describe the emissions distribution are: (1)
the probability of a release beginning during a given hour, (2) the number (maximum
of 10) of emission categories for each source (3) the duration of the release in hours
for each emission distribution category, (4) the probability each emission distribution
category is valid for, and (5) the AM and PM emission rates for each emission
distribution during a release.
• Since TOXX uses a Monte-Carlo simulation, the desired number of sample-years must
be input.
• Up to six threshold concentrations may be entered along with a single background
concentration. For multiple-pollutant applications, preprocessing of emissions and
background concentrations is required, so that one reference pollutant is modeled. In
this case, composite emission rates and background concentrations are computed prior
to model execution, based on preprocessing described in Section 2.3.4.
Outputs produced by TOXST include the standard ISCST2 printout as described in the ISC2
user's guide Vol. I (EPA, 1992), and the TOXX model printout as described in Section 5.3.
17
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The latter file includes a listing of all TOXX input parameters and the results of the expected
exceedance calculations for each receptor site.
Section 3.2 contains example TOXX input and output files displaying examples of the output
options, including: concentration distributions, threshold exceedance displays, summary
statistics (to facilitate intersite comparisons), and polar / rectangular displays. Appendix A
contains a TOXX output file displaying a boundary receptor display. Outputs are formatted to
produce report quality tables that include titles and table numbers.
18
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3. PREPARING TOXST INPUT FILES
In the previous chapter we presented an overview of TOXST and the associated input and
output files. In this chapter we provide a detailed description of the contents and formats of the
input files. Output files are described in Chapter 5.
3.1 PREPARATION OF ISCST2 INPUT FILES
The ISCST2 meteorological data input file and the ISCST2 input parameter file used in TOXST
are identical in content and format to, respectively, the binary meteorological data file and the
"card image input file" used with the ISCST2 model dated 92273, as described in the ISC2
user's guide, Vol. I (EPA, 1992). Certain options must be specified in the input parameter file
so that ISCST2 will produce the desired binary dispersion estimate output file. Specifically, the
ISCST2 OUtput pathway option to produce TOXXFILE output must be set, as must the option
to perform only one-hour averaging (AVERTIME = 1 in the COntrol pathway).
The concentration cutoff value, or threshold, provided to ISCST2 should be small enough so
that all "significant" concentration values are included in the TOXXFILE, but not so small as to
render that file unmanageable. One reasonable approach to follow is:
1. For a simulation involving N pollutants (Note: N is always set to 1 in the current
version of TOXST) and J ISCST2 source groups, select the lowest health effects
concentration threshold to be included in the analysis. Call it L.
2. Select a cutoff concentration value which is no larger than X, where
X = L / (N * J), which would be simplified to:
X = L/J
A listing of an example ISCST2 input file is shown in Table 3-1. Items of particular interest to
TOXST users are flagged with ««. (Do not include the « markings in an actual input file;
an error will result, terminating the ISCST2 run.)
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TABLE 3-1 Example input parameter file for the ISCST2 model
CO STARTING
CO TITLEONE CASE STUDY / NORMALIZED EMISSIONS -1984
CO MODELOPT CONC RURAL
CO AVERTIME 1 ««—1 hour averaging time
CO POLLUTID COMPOSITE
CO TERRHGTS FLAT
CO RUNORNOT RUN
CO FINISHED
SO STARTING ««—source locations and parameters
SO LOCATION SRC1 VOLUME 375675
SO LOCATION SRC2 VOLUME 375675
SO LOCATION SRC3 VOLUME 375675
SO LOCATION SRC4 VOLUME 375675
SO LOCATION SRC13 VOLUME 465750
SO LOCATION SRC14 VOLUME 465760
SO LOCATION SRC15 VOLUME 465770
SO LOCATION SRC16 AREA 465 750
SO LOCATION SRC17 AREA 465 750
SO SRCPARAM SRC1 1.00 5.33 4.96 14.24
SO SRCPARAM SRC2 1.00 5.33 4.96 14.24
SO SRCPARAM SRC3 1.00 5.33 4.96 14.24
SO SRCPARAM SRC4 1.00 5.33 4.96 14.24
SO SRCPARAM SRC13 1.00 6.40 5.95 6.98
SO SRCPARAM SRC14 1.00 6.40 5.95 6.98
SO SRCPARAM SRC15 1.00 6.40 5.95 6.98
SO SRCPARAM SRC16 1.20 1.00 0.91
SO SRCPARAM SRC17 0.43 1.00 1.52
** SOURCE GROUPS <««—9 source groups
SO SRCGROUP SRC1 SRC1
SO SRCGROUP SRC2 SRC2
SO SRCGROUP SRC3 SRC3
SO SRCGROUP SRC4 SRC4
SO SRCGROUP SRC13 SRC13
SO SRCGROUP SRC14 SRC14
SO SRCGROUP SRC15 SRC15
SO SRCGROUP SRC16 SRC16
SO SRCGROUP SRC17 SRC17
SO FINISHED
RE STARTING «<«—starting of boundary grid
RE BOUNDARY SRC1 1910
RE BOUNDARY SRC1 2000
RE BOUNDARY SRC1 2180
20
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RE BOUNDARY SRC1 1880
RE BOUNDARY SRC1 1340
RE BOUNDARY SRC1 1085
RE BOUNDARY SRC1 930
RE BOUNDARY SRC1 825
RE BOUNDARY SRC1 780
RE BOUNDARY SRC1 750
RE BOUNDARY SRC1 750
RE BOUNDARY SRC1 780
RE BOUNDARY SRC1 825
RE BOUNDARY SRC1 690
RE BOUNDARY SRC1 480
RE BOUNDARY SRC1 380
RE BOUNDARY SRC1 310
RE BOUNDARY SRC1 260
RE BOUNDARY SRC1 250
RE BOUNDARY SRC1 240
RE BOUNDARY SRC1 225
RE BOUNDARY SRC1 230
RE BOUNDARY SRC1 250
RE BOUNDARY SRC1 270
RE BOUNDARY SRC1 300
RE BOUNDARY SRC1 350
RE BOUNDARY SRC1 460
RE BOUNDARY SRC1 575
RE BOUNDARY SRC1 575
RE BOUNDARY SRC1 580
RE BOUNDARY SRC1 610
RE BOUNDARY SRC1 660
RE BOUNDARY SRC1 770
RE BOUNDARY SRC1 935
RE BOUNDARY SRC1 1230
RE BOUNDARY SRC1 1870
RE FINISHED
ME STARTING <««—meteorological information
ME INPUTFIL CMA84.BIN UNFORM
ME ANEMHGHT 6.1 METERS
ME SURFDATA 13000 1984
ME UAIRDATA 03000 1984
ME FINISHED
OU STARTING <««— ISCST2 output tables and TOXX flle identification
OU RECTABLE 1 FIRST
OU TOXXFILE 1 2.07E-6 ISC1H84.TOX
OU FINISHED
(end of table)
21
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3.1.1 ISCST2 Modeling Restrictions
In order for TOXX to be able to use the TOXXFILE created by ISCST2 correctly, there are a
few guidelines that must be followed:
1. Only one grid system can be modeled. That is, if a grid system is desired, onj^_one
receptor grid type (rectangular, polar, or boundary) may be used during a single run.
2. If discrete receptors are desired in addition to a receptor grid, they must be specified in
the input file after the receptor grid.
3. No more than 125 receptors may be modeled in any one run.
3.2 PREPARATION OF TOXX INPUT PARAMETER FILES
An example TOXX input parameter file is shown in Table 3-2. Free format is used throughout,
with the exception of the parameters title, hName, pName, ISCOuFn, and sName which are
character strings. The title can be typed in alphanumeric characters anywhere in the first 80
spaces of record 1; hName and pName, respectively, can be typed anywhere in the first 20
spaces of record types 4 and 5, ISCOuFn can be typed anywhere in the first 30 spaces of
record 9, and sName can be typed anywhere in the first 20 spaces of record type 10. A
description of the individual records follows:
Record 1
title -- Title of the TOXX run (may be up to 80 characters long)
Record 2
nHET — Number of health effect thresholds. A maximum of six different
thresholds may be specified.
hET -- List of nHET health effect threshold concentrations («g/m3).
Record 3
nPol -- Number of pollutant species to be modeled. Only a 1 will be accepted
here for current version of TOXST.
bkgd ~ Background concentration for pollutant
22
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The following record type is repeated once for each health effect threshold concentration
specified in record 2. Thus there are nHET records of this type:
Record Type 4
hName — Health effect threshold name used in identifying the threshold on
output pages (maximum of 20 characters).
Record Type 5
pName ~ Name of pollutant species (maximum of 20 characters).
The following records appear only once; they are not repeated.
Record Type 6
nSim -- Number of sample years for the Monte-Carlo simulation (may be
between 1 and 1999, but values of at least 200 are recommended for most
situations). A minimum of 100 can be used for applications where all
sources emit near maximum emission rates for at least 25 percent of the year
(refer to Section A.7 in Appendix A for a discussion of the sensitivity of
TOXST to the number of simulations).
nSrc -- Number of TOXX emission sources described in this input file (must
be between 1 and 20).
iAvPer — Averaging period (hours). Restricted to 1, 2, 3, 4, 6, 8, 12, and 24
hour periods.
nBat ~ Number of "batch" emission sources (must be between 1 and 20, this
value has no effect on the results of TOXX).
Record Type 7
mRecPr — Number of receptors to be printed across top of output table
(maximum of 20). It is a good idea to first run a few short simulations (e.g.,
use a value of nSim = 1) and examine output tables before proceeding with a
23
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with a run that will execute for a long time. In this way, the user can
preview the output and make adjustments as necessary in the output format.
lYrly—Yearly output flag. Controls option to print expected exceedances for
individual meteorological years (i.e., individual years of dispersion model
results) in addition to printing one set of results averaged over all
meteorological years: lYrly = 0, do not print yearly output; lYrly = 1,
print yearly output.
MEEm — Flag whether emission sources are mutually exclusive or not.
MEEm = 0: emission sources are not mutually
exclusive
MEEm = 1: emission sources are mutually
exclusive.
iGP - Switch to determine if the user wants only source group combined
output (1 = YES, 0 = NO). If no, separate outputs will reflect the impacts
of each source. If yes, outputs will only reflect the total impact of all
sources combined.
Record Type 8
nYear — Number of meteorological years (i.e., years of dispersion model
results; maximum of 6).
iYear — List of the years of dispersion model results. All four digits of the
year must be entered (i.e., 1965, 1966, 1967).
Record Type 9
ISCOuFn -- Name of the ISCST2 output file that was created during the
execution of ISCST2. If more than one year was modeled resulting in
multiple ISCST2 output files, only one output file name needs to be entered
in the first 30 characters. This file is used to retrieve receptor location
data.
The next five record types are repeated for each source when more than one source is being
considered:
24
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Record Type 10
sName — Source name (20 characters maximum)
Record Type 11
iSrc - The ISCST2 source group number as assigned by ISCST2. ISCST2
source groups should not be confused with TOXX source groups; see Section
2.3. If the dispersion model was exercised for ISCST2 source groups
numbered 10, 11 and 13, and parameters for the second of these three source
groups are being entered, iSrc would be set equal to 11. Not all ISCST2
source groups included in the dispersion model output need be included in a
TOXX run; impacts from ISCST2 source groups with group numbers not
assigned to iSrc will be ignored by TOXX. For most applications, however.
the most convenient approach is to have the same source groups in ISCST2
and TOXX.
iGrp - TOXX source group number. Each source is assigned to a TOXX
source group such that all sources with covarying emissions are assigned to
the same group and sources with independently varying emissions are
assigned to different groups (see Section 2.3). TOXX source group numbers
should be assigned consecutively, beginning with group number 1. A
maximum of 20 groups may be specified.
The values of the following parameters must be identical for all sources
belonging to the same TOXX source group. Thus, some information is
repeated if a group consists of more than a single source. For more
information, see Sections 2.2 and 2.3. Again, for most applications it is
more convenient to have the same source groups in ISCST2 and TOXX.
which simplifies these inputs and removes the need for identical parameters
in these inputs.
probOn — Probability of source switching on (must be a value between 0
and 1; see Section 2.3.1).
Batch - Identifies the source type (1 = BATCH, 0 = NON-BATCH).
iMax — Number of emission categories for this source.
25
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Record Type 12
PrbOn - probability of using the corresponding emission rate for each
emission category. The sum of these probabilities must equal 1.0 for non-
batch sources. This variable is only used for a non-batch process but a value
must be present for all TOXX runs. For batch sources, a placeholder value
of 1.0 is suggested.
Record Type 13
BatOn — The number of hours for which the corresponding emission
category is valid.
Record Type 14
BatRate - The corresponding emission rates for each category. There are
two sets of emission rates. Emission rates for AM periods are read in first,
and then all the PM emission rates are read in. This variable is used to input
emission rates for both batch and non-batch operations. In either case, it is
possible to enter different emissions data for daytime and nighttime periods.
For batch operations, however, it would be very unusual if the daytime and
nighttime characteristics were not the same. Non-batch operations, on the
other hand, would be expected to more frequently have different operational
characteristics on a diurnal basis.
26
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TABLE 3-2. Example TOXX input parameter file.
Line
(Record) Record Example of Actual
Number Type* Input Parameter Names
1 1 title
2 2 nHET, hET(l), hET(2)
3 3 nPol, bkgd(l)
4 4 hName(l)
5 4 " hName(2)
6 5 pName
7 6 nSim, nSrc, iAvPer, nBat
8 7 mRecPr, lYrly, MEEm, iGP
9 8 nYear, iYear(l)...iYear(n)
10 9 ISCOuFn
11 10 sName(l)
12 11 iSrc, iGrp, probOn, Batch, iMax*
13 12 PrbOn(l), PrbOn(2)...PrbOn(N)
14 13 BatOn(l), BatOn(2)...BatOn(N)
15 14 BatRate(l)...BatRate(N) AM
16 14 BatRate(l)...BatRate(N) PM
17 10 sName(2)
18 11 iSrc, iGrp, probOn, Batch, iMax*
19 12 PrbOn(l), PrbOn(2)...PrbOn(N)
20 13 BatOn(l), BatOn(2)...BatOn(N)
21 14 BatRate(l)...BatRate(N) AM
22 14 BatRate(l)...BatRate(N) PM
23 10 sName(N)
24 11 iSrc, iGrp, probOn, Batch, iMax*
25 12 PrbOn(l), PrbOn(2)...PrbOn(N)
26 13 BatOn(l), BatOn(2)...BatOn(N)
27 14 BatRate(l)...BatRate(N) AM
28 14 BatRate(l)...BatRate(N) PM
Corresponds to record types described in text.
iMax = N: number of emission distributions for source group
27
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The following is an input file with clarifying statements preceded by a "»" and ">". The bold
lines are what actually goes into the input file.
CASE STUDY OPERATIONS - 1-HOUR - 1984-1989 Dist.
» The above line is the title line. The first 80 characters
> will be echoed in the TOXX output file.
6, 385., 550., 900., 1350., 1800., 2700.
» The 6 in the above line indicates that six health effect
> thresholds (HET's) follow. The HET's are in /*g/m3. A
> maximum of six HET's may be specified.
1,0.
» The 1 indicates that one pollutant is modeled, whether it
> is a single species or a composite of multiple pollutants.
> Only the number 1 is valid as the number on this line.
» The value that follows is the background concentration for
> the pollutant in /Jg/m3.
THRESHOLD #1
THRESHOLD #2
THRESHOLD #3
THRESHOLD #4
THRESHOLD #5
THRESHOLD #6
» The above 6 lines are the names of each of the 6 HET's.
> Enter one name per line for each HET in the first 20
> characters.
COMPOSITE
» The above line is the name of the pollutant. In this
> case, the pollutant was a composite of multiple pollutants.
200, 9, 1, 8 NOTE: This bold comment can be included in file.
» 200 indicates the number of simulated years TOXX will
> execute for. A maximum of 1999 is allowed.
» The 9 indicates the actual number of emission sources in
> this TOXX run.
» The 1 indicates that TOXX will calculate exceedances based
> on one hour averaging.
» The 8 indicates that 8 of the 9 emission sources are
> batch sources. The value entered here is for cosmetic
> purposes only in the output file and does not effect the
> results of the run.
28
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» The NOTE:... in the above line can be included on any line
> other than lines with character variables such as source
> name, pollutant name, and title (unless it is after the
> character variable declared space). The program will
> know not to read it The user can include notes here
> to help clarify input parameters. See the next line for
> another example.
20, 0, 0, 0 MRECPR, LYRLY, MEEm, IGP
» The 20 instructs the program to print output tables with a
> maximum of 20 X-coordinates across the page. The user has
> the option to display up to 20 X-coordinates across a page.
> The user can vary the amount according to the size of
> the modeling domain. It is suggested that the user
> make a test run with minimal simulations to determine if
> the number selected is appropriate for a portrait layout
> or a- landscape layout during print out.
» The first 0 indicates that the user does not want output
> results from every year modeled. In other words, results
> for each individual year modeled (in this case 1984 through
> 1989) will not be printed out, only the average over all
> years. A "1" in this position would instruct the program
> to provide printed data for each individual year and all
> years combined.
» The second 0 instructs the program not to treat emission
> sources as mutually exclusive. All sources can operate
> at the same time. A "1" in this place would allow only one
> emission source to operate at a time (i.e. mutually
> exclusive option).
» The last 0 indicates that the user wants printed output
> for each source group for each HET and for all source
> groups combined. A 1 in this place would instruct the
> program to provide output for all sources combined only
> for each HET.
» The "MRECPR, LYRLY, MEEm, IGP" is a note to the user to
> help him recall what the values stand for on this line.
> This information is not read in by the program.
5, 1984, 1985, 1987, 1988, 1989
» The 5 indicates that 5 years are to be modeled, each year
> simulated 200 times as indicated above.
» The five values following the 5 are the years that were
29
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> modeled.
ISC1H84.OUT
» The above line contains the name of the ISCST2 output
> file (TOXXF1LE). Only one output file name is needed even
> if more than one year was modeled. It does not matter what
> year the file is for since this file will only be used to
> retrieve receptor location data and grid type.
SOURCE 1
» The above line, and the lines that follow contain emission
> source data. This particular line is the name of the first
> source. It can have as many as 20 characters beginning in
> the first column.
1, 1, 1.000, 1, 2
» The first 1 in the above line indicates that this is the
> ISCST2 source group number one. The results in the ISCST2
> TOXXFILE that was created during the execution of ISCST2
> for the first ISCST2 source group will correspond to this
> source.
» The second 1 indicates the this TOXX source belongs to the
> first TOXX source group.
> The third 1 (i.e. 1.000) is the probability that this
> source will turn on if it is off. A 1.000 in this case
> indicates that the source is always on.
» The fourth 1 indicates that the source is a batch process.
> Once the source turns on, it will emit at a particular
> emission rate for a specified amount of time (as indicated
> in the next few lines) and continue onto the next emission
> category and emit at that rate for another specified
> period of time, until there are no more emission
> categories remaining. If the 1 representing the source
> is a batch process was a 0, the source would be a non-
> batch process and randomly select an emission category
> based on the associated probabilities (see next input
> line), emit at that rate for the specified amount of time
> for that category, and then turn off.
» The last value in the line above, 2, indicates that this
> particular source has two emission distribution categories,
> each category having a probability of being selected if it
> is a non-batch process and has a duration in hours that
> the emission category is valid for and two sets of
30
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> emission rates, one for AM (daylight hours) and one for PM
> hours (nighttime hours). This value can be a maximum of
> 10 (i.e. maximum of 10 emission distributions).
1.0, 1.0
» The two 1.0 numbers serve only as placeholders for batch
> processes, not probabilities of occurrence.
» For a non-batch process, the probabilities must add up to
> 100%. For example, see the inputs for "SOURCE 13" below.
2184, 736
» The above two numbers represent the duration of each
> emission category (in hours). Since this source is a batch
> (or sequential) process, once it turns on it will operate
> at the emission rate in the first emission category for
> 2184 hours. Once 2184 hours have elapsed, it will proceed
> to emit at the rate in the second emission category for 736
> hours. If there are more emission categories, each one
> will be used sequentially until there are no more emission
> categories. In this case, after using the emission rates
> and durations for 2 categories, the source will turn off.
> However, this particular source has a 100% probability of
> being on so during the next hour it will turn back on and
> start the cycle over.
0.189, 0.000
» The above two numbers are the daytime emission rates for
> each of the 2 emission categories for this source. The
> first emission rate will be effective during the daytime
> hours (7 AM through 6 PM) of the 2184 hour duration of this
> emission process and the second emission rate will be
> effective for the daytime hours of the next 736 hours.
> Notice that the second emission rate is 0.000 g/s. This
> is the same as saying that the source is off for 736
> consecutive daytime hours every 2184 hours since the
> probability of this source being on is 100%.
0.189, 0.000
» The above line represents nighttime emission rates (7 PM
> through 6 AM) and has an explanation similar to the
> previous input line.
» The above line ends the source data for the first emission
> source.
SOURCE 2
31
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» The line above represents the name of the second emission
> source.
» Explanations for the following will not be repeated
> unless a parameter warrants additional explanation.
2, 2, 1.000, 1, 2
1.0, 1.0
2184, 736
0.018, 0.000
0.018, 0.000
SOURCE 3
3, 3, 0.0034, 1, 1
» Notice that the last value on the above line is a 1
> indicating that there is only one value in the emission
> distribution. In this case it does not matter if the
> source is declared as a batch or non-batch process. If it
> is a batch process, it will start and end with the one
> value in the one and only emission distribution category.
> If it is a non-batch process, there is only one emission
> category to randomly select (remember to make the
> probability 1.0 in this case since it is the only emission
> category), giving the same result.
1.0
144
0.761
0.761
SOURCE 4
4, 4, 0.0039, 1, 1
1.0
144
0.088
0.088
SOURCE 13
5, 5 , 0.0005, 0, 6
» Notice the 0 in the above line. This indicates that this
> source is a non-batch process. Once it is deemed to have
> turned "on", the emission rate will be randomly selected
> from six emission categories.
.10, .143, .313, .148, .148, .148
» Since this is a non-batch process, the probabilities of
> each emission category being selected must add up
32
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> to 1.0.
3, 48, 12, 1, 1, 1
0.238, 0.004, 0.060, 0.109, 0.870, 0.109
0.238, 0.000, 0.060, 0.109, 0.870, 0.109
» Each time SOURCE 13 turns on, its emission rate is
> selected from one of the six emission categories. That
> emission rate is held constant throughout its corresponding
> duration (except that emission rates may change between
> daytime and nighttime), after which the source turns off.
> The next time the source turns on, another emission rate is
> randomly selected. This feature allows for substantial
> flexibility in the specification of emission rates for
> sources which are both intermittent and variable in nature.
> It should be noted that this feature also allows the
> simulation of continuous sources which have variable
> emissions such as sulfur dioxide emissions from coal
> combustion. These continuous emissions, which are known to
> have a log-normal variability, may be simulated by .
> specifying a release probability of 1.0 and providing a
> discrete emission distribution with appropriate
> probabilities to approximate the log-normal emission
> distribution for the coal being combusted.
SOURCE 14
6, 6 , 0.0005, 1, 6
1.0, 1.0, 1.0, 1.0, 1.0, 1.0
3, 48, 12, 1, 1, 1
0.238, 0.004, 0.060, 0.109, 0.870, 0.109
0.238, 0.000, 0.060, 0.109, 0.870, 0.109
SOURCE 15
7, 7 , 0.0005, 1, 6
1.0, 1.0, 1.0, 1.0, 1.0, 1.0
3, 48, 12, 1, 1, 1
0.238, 0.004, 0.060, 0.109, 0.870, 0.109
0.238, 0.000, 0.060, 0.109, 0.870, 0.109
SOURCE 16
8, 8 , .0002283, 1, 2
1.0, 1.0
1, 1
1.5531, 0.5177
1.5531, 0.5177
33
-------
SOURCE 17
9, 9 , .0001142, 1,
1.0, 1.0
1, 1
3.1062, 1.0354
3.1062, 1.0354
(end of table)
34
-------
The following are examples of two TOXX input and output files.
NOTE: The bold text following the « is not part of the input file.
**************** EXAMPLE 1 Input File ****************
toxxl.inp: Pollutant_A - Example Plant « TITLE OF RUN
4, 410., 600., 700., 1000. « # OF THRESHOLDS AND EACH THRESHOLD
1, 0. « # OF POLLUTANTS (MUST BE 1) AND BACKGROUND CONC.
THRESHOLD #1 « THRESHOLD #1 NAME
THRESHOLD #2 « THRESHOLD #2 NAME
THRESHOLD #3 « THRESHOLD #3 NAME
THRESHOLD #4 « THRESHOLD #4 NAME
Pollutant_A « POLLUTANT NAME
200, 1, 1, 0 « NSIM, NSRC, IAVPER, NBAT
20, 1, 0, 0 « MRECPR, LYRLY, MEEM, IGP
1, 1964 « # OF YEARS MODELED AND THE YEAR(S)
TEST1.OUT « NAME OF THE ISCST2 OUTPUT FILE
SOURCE 1 « NAME OF THE FIRST SOURCE
1, 1, .427, 0, 1 « ISRC, IGRP, PRBON, BATCH (NON-BATCH = 0), IMAX
1.00 « PROBABILITY EMISS. CAT. WILL TURN ON
1 « # OF HOURS DURATION THIS EMISSION CAT.
1.00 « AM EMISSION RATE (G/S) FOR THIS EMISS. CAT.
1.00 « PM EMISSION RATE (G/S) FOR THIS EMISS. CAT.
35
-------
EXAMPLE 1 Output File ****************
********************************** TOXST, TOXICS EXPECTED EXCEEDANCES SYSTEM, SHORT-TERM *************************************
TOXX, September 1993 Version
(IBM PC Compatible Version)
Sullivan Environmental Consulting, Inc.
**********************************************************************************************************************************
Date and time of run: 10- 6-1993 14:50
User Input Information
Title of run
# simulations per meteorological year
if emission sources
# receptors printed per row
Averaging period (hours)
Number of source group batch operations
Only source groups combined output Yes = 1
Emissions mutually exclusive? Yes = 1
Representative ISCST2 output file name
Metyears of requested dispersion results
toxxl.inp: Pollutant A - Example Plant
200
1
20
1
0
0
0
TEST1.0UT
1964
Output expected exceedances yearly and averaged over all meteorological years.
Find expected exceedances of multiple thresholds.
Pollutant and Threshold Information:
Poll. Id #:
1
Pollutant Data
Pollutant Name:
Pollutant A
Background (ug/m3):
.00
Thrs. Id #:
1
2
3
4
•- neann trrec
Health Effec
THRESHOLD #1
THRESHOLD #2
THRESHOLD #3
THRESHOLD #4
Threshold (ug/m3):
410.00
600.00
700.00
1000.00
Emission Sources Information:
Source* Group*
1 1
Dist Prob: >
Dist Valid (hrs):
AM Emiss Rate:
PM Emiss Rate:
Source Name
SOURCE 1
1.00000
> 1
1.000
1.000
Release Max Release
Probability Duration (hr)
.42700000 1
Pollutant Name
Pollutant A
Max Emiss
Rate (g/s)
1.000
Batch Number
Yes = 1 Em Cats
0 1
Dispersion Model Results Data Information
Datafile Headers:
Title of dispersion model result data
Year modeled
# sources
# receptors
# averaging periods modeled in ISCST2
Exex output by recptr? (0=no,1=pol,2=rect)
Pollutant_A - Example Plant
1964
1
32
8784
1
36
-------
# radials (polar) or rows (rect) : 8
Cut-off value used in ISCST2 (g/m3) : 1.5000E-06
1
Messages from Subroutine Setup (may be blank)
Dispersion Model Results (DMR) Read/Screened
.DMR File* Year Modeled Total # Data in File # Saved for Calculation
1 1964 3369 864
Totals: 3369 864
Lowest value any chi/q may take and still cause exceedance of a threshold is (X/Q)min = 4.100000E-04 s/m3.
37
-------
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u
X
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«*
s
r-Coordii
o
3
in
o
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0
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§
00
Q.
<1> »• J3
E X O CO
•O 01 t- O) Q.
O ID O) 01
v- 41 4) U
O — t> > 0)
> O <-
ra 4-> o -O
ra ja ra L.
(0 01
f CO.
<-• c ~
«• -t- .^- cfl
•O 3 01 01
•*• CO U U
u (i) 01 C C
Q.
OJ
01 01
U U
10 U 01 X X
0) oi u 01 01
I- u X
to O 01 Ol
u am
— m — ' >
i- z H- < <
-------
TABLE 5
Number of exceedances within each NET category.
All sources combined
(Year: 1964)
Rec #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
X-Coord
70.71
141.42
282.84
565.69
100.00
200.00
400.00
800.00
70.71
141.42
282.84
565.69
.00
.00
.00
.00
-70.71
-141.42
-282.84
-565.69
-100.00
-200.00
-400.00
-800.00
-70.71
-141.42
-282.84
-565.69
.00
.00
.00
.00
Y-Coord
70.71
141.42
282.84
565.69
.00
.00
.00
.00
-70.71
-141.42
-282.84
•565.69
-100.00
-200.00
-400.00
-800.00
-70.71
-141.42
-282.84
-565.69
.00
.00
.00
.00
70.71
141.42
282.84
565.69
100.00
200.00
400.00
800.00
(ug/m"3)
0.0-
410.0
8767.33
8770.67
8781 .82
8784.00
8716.48
8744.62
8775.50
8783.57
8772.38
8777.28
8783.17
8784.00
8769.69
8776.63
8781.53
8783.19
8769.04
8771.00
8782.08
8784.00
8746.87
8758.54
8781.11
8783.65
8756.88
8765.61
8782.31
8784.00
8769.80
8772.33
8779.33
8783.64
410.0-
600.0
1.69
5.55
1.68
.00
9.37
11.19
5.41
.44
.43
3.81
.83
.00
1.28
1.65
.87
.81
.00
3.73
1.10
.00
2.60
7.32
1.64
.35
3.07
6.47
1.69
.00
1.64
2.52
2.15
.36
600.0-
700.0
.92
1.33
.50
.00
3.17
4.28
1.78
.00
.38
.74
.00
.00
1.74
.00
.80
.00
2.27
1.29
.00
.00
2.53
4.22
.90
.00
1.28
3.05
.00
.00
.93
.00
.43
.00
700.0-
1000.0
1.64
5.10
.00
.00
13.02
14.93
.87
.00
4.11
1.72
.00
.00
2.13
2.05
.00
.00
.86
3.79
.83
.00
7.07
8.89
.00
.00
3.54
4.96
.00
.00
1.24
5.09
1.74
.00
>1000.0
12.41
1.36
.00
.00
41.96
8.98
.44
.00
6.71
.46
.00
.00
9.16
3.67
.81
.00
11.84
4.20
.00
.00
24.94
5.04
.35
.00
19.22
3.92
.00
.00
10.39
4.07
.36
.00
Date and time of end: 10- 6-1993 14:56
42
-------
**************** EXAMPLE 2 Input File ****************
toxx2.inp: Pollutant A - Example Plant « TITLE OF RUN
4, 410., 600., TOO., TOOO. « f OF THRESHOLDS AND EACH THRESHOLD
« f OF POLLUTANTS (MUST BE 1) AND BACKGROUND CONC.
« THRESHOLD fl NAME
« THRESHOLD *2 NAME
« THRESHOLD « NAME
« THRESHOLD ft NAME
« POLLUTANT NAME
« NSIN. NSRC, IAVPER, NBAT
« NRECPR, LTRLY, NEEM. IGP
« f OF YEARS MODELED AND THE YEAR(S)
« NAME OF THE ISCST2 OUTPUT FILE
« NAME OF THE FIRST SOURCE
« ISRC, IGRP, PRBON, BATCH (NON-BATCH = 0), IMAX
« PROBABILITY EMISS. CAT. UILL TURN ON
« * HOURS DURATION FOR EACH EMISS. CAT.
« AM EMISSION RATE (G/S) FOR EACH EMISS. CAT.
« PM EMISSION RATE (G/S) FOR EACH EMISS. CAT.
« NAME OF SECOND SOURCE
« ISRC. IGRP. PRBON, BATCH (BATCH = 1), IMAX
« PROBABILITY EMISS. CAT. UILL TURN ON
« * HOURS DURATION FOR EACH EMISS. CAT.
« AN EMISSION RATE (G/S) FOR EACH EMISS. CAT.
« PM EMISSION RATE (G/S) FOR EACH EMISS. CAT.
« NAME OF THIRD SOURCE
« ISRC, IGRP, PRBON, BATCH (BATCH = 1), IMAX
« PROBABILITY EMISS. CAT. UILL TURN ON
« * HOURS DURATION FOR EACH EMISS. CAT.
« AN EMISSION RATE (G/S) FOR EACH EMISS. CAT.
« PM EMISSION RATE (G/S) FOR EACH EMISS. CAT.
1, 0.
THRESHOLD #1
THRESHOLD #2
THRESHOLD #3
THRESHOLD #4
Pollutant A
290, 3, 17 1
20, 0, 0, 0
1, 1964
TEST.OUT
SOURCE 1
1, 1. .427, 1, 3
1.00, 1.00, 1
6, 2,
1.11, 5.13, 5.98
1.04, 4.34, 5.93
SOURCE 2
2, 2, .427, 0, 2
0.34, .66
24
19.7
19.7
.00
2
5,
10.0,
10.0,
SOURCE 3
3, 3, .427, 1, 2
1.00 1.00
3, 1
7.66, 9.44
6.56, 9.21
43
-------
**************** EXAMPLE 2 Output File ****************
*************** TOXST, TOXICS EXPECTED EXCEEDANCES SYSTEM, SHORT-TERM ***************************
TOXX September 1993 Version
(IBM PC Compatible Version)
Date and time of run: 1-29-1994 4:39
User Input Information
Title of run
# simulations per meteorological year *
# emission sources
# receptors printed per row
Averaging period (hours)
Number of source group batch operations
Output only source groups combined? Yes =
Emissions mutually exclusive? Yes = 1
Representative ISCST2 output file name
Metyears of requested dispersion results
toxxZ.inp: Pollutant A - Example Plant
200
3
20
1
1
0
0
TEST-ST2.0UT
1964
Output only expected exceedances averaged over all meteorological years.
Find expected exceedances of multiple thresholds.
Pollutant and Threshold Information:
Poll. Id #:
1
Pollutant Data
Pollutant Name:
Pollutant A
Background (ug/m3):
.00
Thrs. Id #:
1
2
3
4
Health Effect Threshold Data
Health Effect Name: Threshold (ug/m3):
THRESHOLD #1
THRESHOLD #2
THRESHOLD #3
THRESHOLD #4
410.00
600.00
700.00
1000.00
Emission Sources Information:
Source* Group*
1 1
Dist Prob: >
Dist Valid (hrs):
AM Emiss Rate:
PM Emiss Rate:
2 2
Dist Prob: >
Dist Valid (hrs):
AM Emiss Rate:
PM Emiss Rate:
3 3
Dist Prob: >
Dist Valid (hrs):
AM Emiss Rate:
PM Emiss Rate:
Source Name
SOURCE 1
1.00000 1
> 6
1.110
1.040
SOURCE 2
.34000
> 5
10.000
10.000
SOURCE 3
1.00000 1
> 3
7.660
6.560
.00000
2
5.130
4.340
.66000
24
19.700
19.700
.00000
1
9.440
9.210
Release Max Release
Probability Duration (hr)
.42700000 10
1.00000
2
5.980
5.930
.42700000 29
.42700000
Pollutant Name
Pollutant A
Pollutant A
Pollutant A
Max Emiss
Rate (g/s)
5.980
19.700
9.440
Batch Number
Yes = 1 Em Cats
1 3
44
-------
Dispersion Modal Results Data Information
Datafile Headers:
Title of dispersion model result data
Year modeled
# sources
# receptors
if averaging periods modeled in ISCST2
Exex output by recptr? (0»no,1*polf2=rect)
# radials (polar) or rows (rect)
Cut-off value used in ISCST2 (g/m3)
Pollutant A - Example Plant
1964
3
41
8784
0
4
1.5000E-06
Messages from Subroutine Setup (may be blank)
Dispersion Model Results (DMR) Read/Screened
DMR File #
1
Year Modeled
1964
Total it Data in File
15684
it Saved for Calculation
13842
Totals: 15684 13842
Lowest value any chi/q may take and still cause exceedance of a threshold is (X/Q)min = 1.167426E-05 s/m3.
45
-------
TABLE 1
Average Exceedances of Pollutant: Pollutant A
Above threshold number 1 ( > 410.00 ug/m3)~
For source group: SOURCE 1
Year: 1964
Y-Coordinate (m)
X-Coordinate (m)
500.0
250.0
-250.0
-500.0
-500.0
8.9
15.8
4.9
4.8
-400.0
11.6
21.0
7.1
6.7
•200.0
14.9
32.3
14.1
7.4
-100.0
13.7
44.7
14.8
9.4
100.0
17.9
37.7
19.6
7.7
200.0
13.8
26.9
13.9
5.9
400.0
6.9
56.8
6.2
4.8
500.0
8.9
51.2
5.0
3.4
Total area of grid: 1.00000 sq. km.
Number receptors with at least one exceedance: 32
Total exceedances in above grid: 518.64000
Average exceedance in above grid: 518.64000 per sq. km.
Average exceedances per receptor in above grid: 16.20750 exceedances per receptor.
TABLE 2
Average Exceedances of Pollutant: Pollutant A
Above threshold number 2 ( > 600.00 ug/m3)~
For source group: SOURCE 1
Year: 1964
Y-Coordinate (in)
X-Coordinate (m)
500.0
250.0
-250.0
-500.0
-500.0
4.5
7.9
1.6
2.2
-400.0
7.8
13.0
5.2
3.5
-200.0
9.4
25.0
10.8
4.5
-100.0
10.4
34.2
10.5
6.1
100.0
13.2
33.9
11.5
6.5
200.0
8.2
20.2
11.1
3.8
400.0
5.2
39.4
4.1
3.0
500.0
5.9
32.4
2.3
2.3
Total area of grid: 1.00000 sq. km.
Number receptors with at least one exceedance: 32
Total exceedances in above grid: 359.96000
Average exceedance in above grid: 359.96000 per sq. km.
Average exceedances per receptor in above grid: 11.24875 exceedances per receptor.
46
-------
TABLE 3
Average Exceedances of Pollutant: Pollutant A
Above threshold number 3 ( > 700.00 ug/m3)
For source group: SOURCE 1
Year: 1964
Y-Coordinate (m)
X-Coordinate (m)
500
250
-250
-500
.0
.0
.0
.0
•500
3
5
1
1
.0
.7
.8
.4
.8
-400.0
5.4
10.4
3.8
2.9
-200.0
7.6
22.6
9.4
3.3
-100
9
31
9
5
.0
.3
.0
.0
.0
100.0
11.9
31.8
10.2
6.3
200.0
7.6
19.6
9.2
3.2
400.0
4.2
35.4
3.5
2.4
500.0
5.0
27.8
1.8
2.0
Total area of grid: 1.00000 sq. km.
Number receptors with at least one exceedance: 32
Total exceedances in above grid: 314.28490
Average exceedance in above grid: 314.28490 per sq. km.
Average exceedances per receptor in above grid: 9.82140 exceedances per receptor.
TABLE 4
Average Exceedances of Pollutant: Pollutant A
Above threshold number 4 ( > 1000.00 ug/m3)~
For source group: SOURCE 1
Year: 1964
Y-Coordinate (m)
X-Coordinate (m)
500
250
-250
-500
.0
.0
.0
.0
•500
2
3
1
1
.0
.3
.2
.1
.3
-400.0
3.1
5.4
1.4
1.4
-200.0
4.3
15.4
6.5
2.1
-100
5
21
6
3
.0
.7
.0
.8
.4
100.0
9.1
27.8
7.4
3.4
200.0
5.0
15.8
5.7
1.4
400.0
2.2
27.1
2.8
1.6
500.0
3.8
19.5
1.0
1.0
Total area of grid: 1.00000 sq. km.
Number receptors with at least one exceedance: 31
Total exceedances in above grid: 218.84500
Average exceedance in above grid: 218.84500 per sq. km.
Average exceedances per receptor in above grid: 6.83891 exceedances per receptor.
47
-------
TABLE 5
Number of exceedances within each NET category. (Year: 1964)
Source: SOURCE 1
Rec #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
X-Coord
Y-Coord
500.00
400.00
200.00
100.00
100.00
200.00
400.00
500.00
500.00
400.00
200.00
100.00
100.00
200.00
400.00
500.00
500.00
400.00
200.00
100.00
100.00
200.00
400.00
500.00
500.00
•400.00
200.00
•100.00
100.00
200.00
400.00
500.00
-500.00
-500.00
-500.00
-500.00
-500.00
-500.00
-500.00
-500.00
-250.00
-250.00
-250.00
-250.00
-250.00
-250.00
-250.00
-250.00
250.00
250.00
250.00
250.00
250.00
250.00
250.00
250.00
500.00
500.00
500.00
500.00
500.00
500.00
500.00
500.00
(ug/nT3)
0.0-
410.0
8779.22
8777.29
8776.60
8774.64
8776.29
8778.08
8779.16
8780.62
8779.14
8776.94
8769.90
8769.19
8764.38
8770.09
8777.84
8779.00
8768.25
8762.95
8751.71
8739.34
8746.35
8757.05
8727.24
8732.79
8775.11
8772.39
8769.09
8770.28
8766.11
8770.17
8777.06
8775.10
410.0-
600.0
2.61
3.19
2.90
3.30
1.21
2.10
1.82
1.03
3.30
1.85
3.26
4.26
8.16
2.82
2.05
2.66
7.80
8.01
7.24
10.44
3.73
6.70
17.36
18.75
4.44
3.77
5.54
3.35
4.68
5.64
1.78
2.95
600.0-
700.0
.34
.60
1.18
1.03
.23
.63
.65
.35
.13
1.38
1.43
1.54
1.26
1.88
.63
.55
2.16
2.61
2.41
3.24
2.14
.61
3.97
4.64
.79
2.48
1.76
1.12
1.35
.63
.96
.99
700.0-
1000.0
.48
1.54
1.22
1.67
2.91
1.79
.78
.98
.34
2.44
2.94
2.17
2.77
3.48
.65
.83
2.63
5.05
7.22
10.02
3.97
3.84
8.31
8.31
1.38
2.27
3.32
3.58
2.81
2.61
2.01
1.12
>1000.0
1.35
1.38
2.10
3.37
3.36
1.41
1.59
1.02
1.09
1.39
6.46
6.83
7.43
5.74
2.83
.97
3.16
5.39
15.41
20.96
27.80
15.80
27.12
19.50
2.29
3.10
4.29
5.68
9.07
4.97
2.19
3.84
48
-------
TABLE 6
Average Exceedances of Pollutant: Pollutant A
Above threshold number 1 ( > 410.00 ug/m3)~
For source group: SOURCE 2
Year: 1964
Y-Coordinate (m)
X-Coordinate (m)
500
250
-250
-500
.0
.0
.0
.0
-500
76
95
39
31
.0
.5
.7
.2
.2
-400.0
80.8
100.4
39.0
31.9
-200.0
80.2
108.9
40.0
32.5
-100
73
114
43
33
.0
.5
.9
.7
.7
100.0
62.5
118.2
42.4
37.4
200.0
53.6
43.5
44.9
37.5
400.0
47.5
215.7
35.8
31.4
500.0
62.3
209.3
31.2
29.2
Total area of grid: 1.00000 sq. km.
Number receptors with at least one exceedance: 32
Total exceedances in above grid: 2124.46000
Average exceedance in above grid: 2124.46000 per sq. km.
Average exceedances per receptor in above grid: 66.38938 exceedances per receptor.
TABLE 7
Average Exceedances of Pollutant: Pollutant_A
Above threshold number 2 ( > 600.00 ug/m3)~
For source group: SOURCE 2
Year: 1964
Y-Coordinate (m)
X-Coordinate (m)
500
250
-250
-500
.0
.0
.0
.0
-500.0
66.8
82.1
37.8
29.1
-400.0
71.2
93.7
34.5
29.8
-200.0
71.0
104.8
36.6
29.2
-100.0
67.9
106.2
39.2
30.1
100
56
112
40
33
.0
.2
.6
.3
.1
200.0
52.3
42.5
41.4
34.3
400
41
209
35
29
.0
.4
.2
.5
.3
500.0
59.4
203.7
29.3
27.2
Total area of grid: 1.00000 sq. km.
Number receptors with at least one exceedance: 32
Total exceedances in above grid: 1977.59000
Average exceedance in above grid: 1977.59000 per sq. km.
Average exceedances per receptor in above grid: 61.79968 exceedances per receptor.
49
-------
TABLE 8
Average Exceedances of Pollutant: PollutantJV
Above threshold number 3 < > 700.00 ug/m3)~
For source group: SOURCE 2
Year: 1964
Y-Coordinate (m)
X-Coordinate (m)
500.
250.
-250.
-500.
0
0
0
0
-500
64
80
34
27
.0
.1
.9
.8
.9
-400.0
65.5
90.9
32.3
28.8
-200.0
69.7
100.5
34.8
28.1
-100
67
104
39
28
.0
.8
.3
.0
.9
100.0
55.1
111.7
40.2
32.1
200.0
52.3
42.4
40.5
34.2
400.0
41.4
207.2
34.5
29.0
500.0
55.5
201.8
29.3
26.3
Total area of grid: 1.00000 sq. km.
Number receptors with at least one exceedance: 32
Total exceedances in above grid: 1931.43500
Average exceedance in above grid: 1931.43500 per sq. km.
Average exceedances per receptor in above grid: 60.35735 exceedances per receptor.
TABLE 9
Average Exceedances of Pollutant: Pollutant_A
Above threshold number 4 ( > 1000.00 ug/m3)~
For source group: SOURCE 2
Year: 1964
Y-Coordinate (m)
X-Coordinate (m)
500
250
-250
-500
.0
.0
.0
.0
-500
52
71
27
25
.0
.5
.8
.7
.7
-400.0
56.8
78.9
28.6
24.3
-200.0
60.0
95.3
32.7
24.4
-100
63
99
36
25
.0
.2
.3
.2
.3
100.0
53.4
109.5
38.2
29.6
200.0
47.8
40.4
38.4
27.8
400.0
38.4
198.4
29.3
24.3
500.0
49.1
194.9
26.2
23.3
Total area of grid: 1.00000 sq. km.
Number receptors with at least one exceedance: 32
Total exceedances in above grid: 1771.42500
Average exceedance in above grid: 1771.42500 per sq. km.
Average exceedances per receptor in above grid: 55.35703 exceedances per receptor.
50
-------
TABLE 10
Number of exceedances within each NET category.
Source: SOURCE 2
(Year: 1964)
Rec #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
X-Coord
-500.00
-400.00
-200.00
-100.00
100.00
200.00
400.00
500.00
-500.00
-400.00
-200.00
-100.00
100.00
200.00
400.00
500.00
-500.00
-400.00
•200.00
-100.00
100.00
200.00
400.00
500.00
-500.00
-400.00
-200.00
-100.00
100.00
200.00
400.00
500.00
Y-Coord
-500.00
-500.00
-500.00
-500.00
-500.00
-500.00
-500.00
-500.00
-250.00
-250.00
•250.00
-250.00
-250.00
-250.00
-250.00
-250.00
250.00
250.00
250.00
250.00
250.00
250.00
250.00
250.00
500.00
500.00
500.00
500.00
500.00
500.00
500.00
500.00
0.0-
410.0
8752.84
8752.13
8751.46
8750.28
8746.58
8746.49
8752.64
8754.83
8744.77
8744.95
8744.03
8740.29
8741 .60
8739.11
8748.25
8752.76
8688.34
8683.55
8675.13
8669.08
8665.78
8740.54
8568.33
8574.66
8707.46
8703.24
8703.80
8710.47
8721.53
8730.40
8736.53
8721.66
410.0-
600.0
2.10
2.06
3.33
3.64
4.34
3.20
2.03
1.98
1.48
4.51
3.38
4.52
2.14
3.47
.26
1.90
13.56
6.72
4.09
8.68
5.63
.96
6.51
5.67
9.72
9.57
9.22
5.59
6.28
1.29
6.09
2.94
600.0-
700.0
1.13
1.01
1.11
1.18
.97
.16
.33
.93
2.96
2.27
1.75
.23
.09
.95
.96
.00
1.22
2.86
4.28
1.91
.92
.11
1.96
1.90
2.69
5.72
1.32
.18
1.11
.00
.00
3.93
700.0-
1000.0
2.21
4.53
3.74
3.65
2.45
6.36
4.74
2.96
7.11
3.67
2.18
2.76
1.92
2.09
5.25
3.14
9.12
11.95
5.24
4.99
2.22
1.98
8.77
6.86
11.61
8.70
9.66
4.58
1.65
4.48
3.02
6.41
>1000.0
25.72
24.27
24.36
25.25
29.65
27.80
24.25
23.30
27.67
28.59
32.65
36.20
38.24
38.38
29.27
26.19
71.76
78.92
95.25
99.34
109.46
40.40
198.43
194.91
52.52
56.76
60.01
63.17
53.43
47.83
38.36
49.06
51
-------
TABLE 11
Average Exceedances of Pollutant: Pollutant_A
Above threshold number 1 ( > 410.00 ug/m3>~
For source group: SOURCE 3
Year: 1964
Y-Coordinate (m)
X-Coordinate (m)
500
250
-250
-500
.0
.0
.0
.0
-500.0
52.1
58.9
23.1
22.2
-400.0
54.0
62.6
23.6
22.3
-200
63
69
27
21
.0
.0
.1
.0
.0
-100.0
72.0
74.6
29.0
22.1
100.0
62.0
75.3
26.4
24.9
200
53
69
30
24
.0
.7
.5
.6
.8
400.0
34.9
72.7
28.6
25.8
500.0
60.0
120.7
25.8
21.9
Total area of grid: 1.00000 sq. km.
Number receptors with at least one exceedance: 32
Total exceedances in above grid: 1454.13500
Average exceedance in above grid: 1454.13500 per sq. km.
Average exceedances per receptor in above grid: 45.44172 exceedances per receptor.
TABLE 12
Average Exceedances of Pollutant: Pollutant A
Above threshold number 2 ( > 600.00 ug/m3)~
For source group: SOURCE 3
Year: 1964
Y-Coordinate (m)
X-Coordinate (m)
500
250
-250
-500
.0
.0
.0
.0
-500
44
53
17
18
.0
.3
.2
.9
.8
-400.0
46.3
57.8
19.0
18.5
-200.0
59.3
64.9
24.9
17.7
-100
66
69
25
20
.0
.5
.2
.8
.0
100.0
59.2
74.1
25.1
20.1
200.0
47.2
66.2
29.4
21.8
400.0
31.1
70.4
27.5
22.2
500.0
51.2
116.3
23.8
19.4
Total area of grid: 1.00000 sq. km.
Number receptors with at least one exceedance: 32
Total exceedances in above grid: 1329.27500
Average exceedance in above grid: 1329.27500 per sq. km.
Average exceedances per receptor in above grid: 41.53985 exceedances per receptor.
52
-------
TABLE 13
Average Exceedances of Pollutant: Pollutant_A
Above threshold number 3 < > 700.00 ug/m3)
For source group: SOURCE 3
Year: 1964
Y-Coordinate (m)
X-Coordinate (m)
500
250
-250
-500
.0
.0
.0
.0
-500.
42.
49.
16.
17.
0
0
7
1
8
-400.0
42.6
55.6
17.3
17.5
-200.0
58.5
63.3
23.7
16.8
-100.0
63.6
67.4
24.3
19.8
100.0
57.2
71.8
23.7
19.7
200
46
64
28
21
.0
.4
.6
.8
.0
400.0
29.9
70.2
26.9
18.8
500.0
48.9
113.7
22.5
16.4
Total area of grid: 1.00000 sq. km.
Number receptors with at least one exceedance: 32
Total exceedances in above grid: 1276.76000
Average exceedance in above grid: 1276.76000 per sq. km.
Average exceedances per receptor in above grid: 39.89875 exceedances per receptor.
TABLE 14
Average Exceedances of Pollutant: Pollutant A
Above threshold number 4 ( > 1000.00 ug/m3)~
For source group: SOURCE 3
Year: 1964
Y-Coordinate (m)
X-Coordinate (m)
500.0
250.0
-250.0
-500.0
-500.0
33.0
41.4
13.6
12.8
-400.0
37.9
46.4
15.1
14.2
-200.0
49.3
60.5
20.7
12.7
-100.0
52.9
63.4
20.2
17.0
100.0
53.0
68.7
19.5
15.5
200.0
43.6
. 61.4
25.8
16.7
400.0
27.1
65.2
25.5
13.7
500.0
44.7
'108.4
20.6
11.7
Total area of grid: 1.00000 sq. km.
Number receptors with at least one exceedance: 32
Total exceedances in above grid: 1132.08500
Average exceedance in above grid: 1132.08500 per sq. km. :. '.-
Average exceedances per receptor in above grid: 35.37766 exceedances per receptor.
53
-------
TABLE 15
Number of exceedances within each MET category. (Year: 1964)
Source: SOURCE 3
Rec #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
X-Coord
Y-Coord
500.00
400.00
200.00
100.00
100.00
200.00
400.00
500.00
500.00
400.00
200.00
100.00
100.00
200.00
400.00
500.00
500.00
•400.00
200.00
•100.00
100.00
200.00
400.00
500.00
•500.00
•400.00
•200.00
•100.00
100.00
200.00
400.00
500.00
-500.00
-500.00
-500.00
-500.00
-500.00
-500.00
-500.00
-500.00
-250.00
-250.00
-250.00
-250.00
-250.00
-250.00
-250.00
-250.00
250.00
250.00
250.00
250.00
250.00
250.00
250.00
250.00
500.00
500.00
500.00
500.00
500.00
500.00
500.00
500.00
0.0-
410.0
8761.79
8761.75
8763.01
8761.87
8759.13
8759.20
8758.24
8762.13
8760.86
8760.43
8756.97
8754.98
8757.56
8753.42
8755.38
8758.20
8725.09
8721.35
8714.91
8709.42
8708.74
8714.47
8711.28
8663.29
8731.89
8729.98
8721.03
8712.03
8722.04
8730.30
8749.12
8724.03
410.0-
600.0
• 3.40
3.75
3.26
2.12
4.81
3.02
3.52
2.46
5.22
4.53
2.12
3.17
1.33
1.16
1.14
2.03
5.70
4.80
4.16
5.34
1.15
3.33
2.37
4.44
7.81
7.68
3.69
5.51
2.81
6.51
3.76
8.77
600.0-
700.0
.96
1.00
.94
.17
.40
.76
3.48
2.96
.85
.71
.20
.55
.38
.57
.58
1.33
3.50
2.20
1.60
1.82
2.30
1.60
.19
2.56
2.29
3.76
.76
2.83
1.99
.76
1.20
2.32
700.0-
1000.0
5.01
3.29
4.13
2.85
4.16
4.36
5.05
4.77
2.43
2.22
3.03
4.13 •
4.22
3.03
1.42
1.87
8.31
9.23
2.85
4.05
3.11
3.22
4.99
5.31
8.98
4.72
9.23
10.73
4.18
2.83
2.83
4.16.
>1000.0
12.84
14.22
12.67
17.00
15.50
16.66
13.70
11.68
13.64
15.11
20.68
20.17
19.52
25.82
25.47
20.58
41.40
46.42
60.49
63.37
68.71
61.38
65.18
108.40
33.03
37.87
49.28
52.91
52.98
43.60
27.11
44.73
54
-------
TABLE 16
Average Exceedances of Pollutant: Pollutant A
Above threshold number 1 ( > 410.00 ug/m3)~
All source groups combined.
Year: 1964
Y-Coordinate (m)
X-Coordinate (m)
500
250
-250
-500
.0
.0
.0
.0
-500.
98.
113.
44.
37.
0
3
1
4
8
-400.0
104.0
121.0
46.7
37.4
-200.0
112.2
144.5
43.7
38.1
-100.0
118.2
171.0
48.3
39.3
100.
107.
211.
55.
46.
0
7
7
7
2
200.0
96.8
131.9
61.7
47.7
400.0
58.4
277.6
52.7
42.4
500.0
81.6
267.8
46.3
37.7
Total area of grid: 1.00000 sq. km.
Number receptors with at least one exceedance: 32
Total exceedances in above grid: 2941.91900
Average exceedance in above grid: 2941.91900 per sq. km.
Average exceedances per receptor in above grid: 91.93498 exceedances per receptor.
TABLE 17
Average Exceedances of Pollutant: Pollutant_A
Above threshold number 2 ( > 600.00 ug/m3)~
All source groups combined.
Year: 1964
Y-Coordinate (m)
X-Coordinate (m)
500.
250.
-250.
-500.
0
0
0
0
-500
86
103
42
33
.0
.5
.7
.3
.9
-400
94
113
40
34
.0
.3
.6
.5
.0
-200.0
106.0
136.9
41.7
35.0
-100.0
111.5
159.9
45.6
36.8
100.0
104.6
204.7
52.4
41.6
200.0
91.2
124.4
58.5
44.9
400.0
53.2
271.5
49.4
39.6
500.0
76.3
260.5
43.4
34.3
Total area of grid: 1.00000 sq. km.
Number receptors with at least one exceedance: 32
Total exceedances in above grid: 2772.88900
Average exceedance in above grid: 2772.88900 per sq. km.
Average exceedances per receptor in above grid: 86.65278 exceedances per receptor.
55
-------
TABLE 18
Average Exceedances of Pollutant: Pollutant A
Above threshold number 3 ( > 700.00 ug/n£)~
All source groups combined.
Year: 1964
Y-Coordinate (m)
X-Coordinate (m)
500
250
-250
-500
.0
.0
.0
.0
-500
82
100
40
31
.0
.4
.3
.0
.8
-400.0
90.4
111.0
39.0
33.3
-200.0
104.6
133.8
40.5
33.3
-100
108
155
45
34
.0
.1
.8
.1
.1
100.0
102.4
200.8
50.2
39.0
200.0
90.3
122.2
56.1
42.6
400.0
50.9
270.3
48.4
39.2
500.0
73.2
258.4
41.3
33.5
Total area of grid: 1.00000 sq. km.
Number receptors with at least one exceedance: 32
Total exceedances in above grid: 2702.44100
Average exceedance in above grid: 2702.44100 per sq. km.
Average exceedances per receptor in above grid: 84.45129 exceedances per receptor.
TABLE 19
Average Exceedances of Pollutant: Pollutant A
Above threshold number 4 ( > 1000.00 ug/m3)~
All source groups combined.
Year: 1964
Y-Coordinate (m)
X-Coordinate (m)
500
250
-250
-500
.0
.0
.0
.0
-500
72
91
36
29
.0
.7
.3
.5
.8
-400.0
80.8
101.4
33.9
30.3
-200.0
96.2
127.2
36.8
29.2
-100
98
144
41
31
.0
.1
.8
.0
.1
100.0
97.1
192.6
46.4
36.2
200.0
86.4
113.6
53.0
37.4
400.0
47.6
262.3
44.5
36.2
500.0
64.0
252.6
39.1
31.0
Total area of grid: 1.00000 sq. km.
Number receptors with at least one exceedance: 32
Total exceedances in above grid: 2521.18600
Average exceedance in above grid: 2521.18600 per sq. km.
Average exceedances per receptor in above grid: 78.78706 exceedances per receptor.
56
-------
TABLE 20
Number of exceedances within each NET category. (Year: 1964)
All sources combined
Rec #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
X-Coord
-500.00
-400.00
-200.00
-100.00
100.00
200.00
400.00
500.00
-500.00
-400.00
-200.00
-100.00
100.00
200.00
400.00
500.00
-500.00
-400.00
-200.00
-100.00
100.00
200.00
400.00
500.00
-500.00
-400.00
-200.00
-100.00
100.00
200.00
400.00
500.00
Y-Coord
-500.00
-500.00
-500.00
-500.00
-500.00
-500.00
-500.00
-500.00
-250.00
-250.00
-250.00
-250.00
-250.00
-250.00
-250.00
-250.00
250.00
250.00
250.00
250.00
250.00
250.00
250.00
250.00
500.00
500.00
500.00
500.00
500.00
500.00
500.00
500.00
(ug/nTS)
0.0-
410.0
8746.17
8746.58
8745.93
8744.65
8737.77
8736.29
8741.61
8746.32
8739.55
8737.32
8740.28
8735.67
8728.33
8722.26
8731.32
8737.69
8670.92
8663.00
8639.52
8613.03
8572.26
8652.07
8506.44
8516.19
8685.73
8679.99
8671.83
8665.80
8676.29
8687.20
8725.64
8702.44
410.0-
600.0
3.89
3.41
3.12
2.54
4.62
2.85
2.82
3.35
2.12
6.18
2.01
2.69
3.28
3.22
3.25
2.90
9.36
7.42
7.53
11.08
7.06
7.53
6.07
7.26
11.76
9.68
6.20
6.70
3.10
5.59
5.17
5.30
600.0-
700.0
2.19
.74
1.64
2.69
2.63
2.24
.36
.79
2.32
1.54
1.25
.50
2.22
2.44
1.02
2.08
3.41
2.61
3.16
4.08
3.85
2.20
1.16
2.13
4.07
3.97
1.36
3.43
2.18
.88
2.25
3.05
700.0-
1000.0
1.92
3.02
4.07
3.00
2.73
5.18
3.01
2.52
3.54
5.09
3.68
4.16
3.77
3.07
3.87
2.19
9.01
9.60
6.57 '
11.03
8.25
8.56
8.04
5.84
9.73
9.60
8.43
9.99
5.32
3.90
3.35
9.22
>1000.0
29.83
30.26
29.24
31.12
36.25
37.44
36.20
31.02
36.47
33.87
36.78
40.98
46.40
53.02
44.54
39.14
91 .-31
101.37
127.21
144.79
192.59
113.64
262.29
252.57
72.71
80.76
96.18
98.07
97.12
86.43
47.60
63.99
57
-------
TABLE 21
Expected Exceedances for discrete receptors above thresholds:
Source: SOURCE 1
Year: 1964
Rec #
33
34
35
36
37
38
39
40
41
X-Coord
50.00
100.00
200.00
300.00
-200.00
-400.00
100.00
400.00
-500.00
Y-Coord
50.00
100.00
250.00
250.00
-250.00
-500.00
-250.00
500.00
-250.00
> 410.0 > 600.0 > 700.0 >1000.0
39.05
.00
26.94
48.82
14.10
6.71
19.62
6.94
4.86
38.10
.00
20.25
35.72
10.84
3.52
11.46
5.16
1.56
37.73
.00
19.64
30.24
9.40
2.92
10.19
4.20
1.43
34.47
.00
15.80
21.01
6.46
1.38
7.43
2.19
1.09
TABLE 22
Expected Exceedances for discrete receptors above thresholds:
Source: SOURCE 2
Year: 1964
Rec #
33
34
35
36
37
38
39
40
41
X-Coord
50.00
100.00
200.00
300.00
-200.00
-400.00
100.00
400.00
-500.00
Y-Coord
50.00
100.00
250.00
250.00
-250.00
-500.00
-250.00
500.00
-250.00
> 410.0 > 600.0 > 700.0 >1000.0
52.55
56.77
43.45
177.66
39.97
31.88
42.40
47.47
39.23
50.74
54.25
42.49
170.76
36.59
29.82
40.25
41.38
37.75
50.42
52.54
42.38
168.70
34.84
28.81
40.16
41.38
34.78
49.12
50.81
40.40
160.96
32.65
24.27
38.24
38.36
27.67
58
-------
TABLE 23
Expected Exceedances for discrete receptors above thresholds:
Source: SOURCE 3
Year: 1964
Rec #
33
34
35
36
37
38
39
40
41
X-Coord
50.00
100.00
200.00
300.00
-200.00
-400.00
100.00
400.00
-500.00
Y-Coord
50.00
100.00
250.00
250.00
-250.00
-500.00
-250.00
500.00
-250.00
> 410.0 > 600.0 > 700.0 >1000.0
34.56
38.86
69.53
28.99
27.03
22.26
26.44
34.89
23.14
31.14
35.90
66.19
28.99
24.91
18.51
25.12
31.13
17.92
30.93
34.37
64.60
28.99
23.72
17.50
23.74
29.94
16.08
30.15
31.14
61.38
28.23
20.68
14.22
19.52
27.11
13.64
TABLE 24
Expected Exceedances for discrete receptors above thresholds:
All sources combined:
Year: 1964
Rec #
33
34
35
36
37
38
39
40
41
X-Coord
50.00
100.00
200.00
300.00
-200.00
-400.00
100.00
400.00
-500.00
Y-Coord
50.00
100.00
250.00
250.00
-250.00
-500.00
-250.00
500.00
-250.00
> 410.0 > 600.0 > 700.0 >1000.0 >
59.46
60.90
131.93
213.93
43.72
37.42
55.67
58.36
44.45
55.88
58.60
124.40
207.27
41.71
34.02
52.39
53.20
42.33
55.11
56.75
122.20
204.64
40.46
33.27
50.17
50.95
40.01
54.18
53.48
113.64
194.45
36.78
30.26
46.40
47.60
36.47
Date and time of end: 1-29-1994 4:54
59
-------
60
-------
4. EXECUTING TOXST
4.1 SYSTEM REQUIREMENTS
TOXST was designed to be executed on personal computers. While the TOXST system has
been tested fully on only Zeos 80386 and 80486-based PC-compatibles, the executable version
available on the EPA SCRAM bulletin board should run on any PC-compatible, with or without
a math coprocessor. Faster machines are recommended for higher performance (e.g. 80486-
66), but are not necessarily required. MS DOS 5.0 and 6.0 were used in developing and
testing TOXST, but some other versions of DOS may serve as well. To insure acceptable
performance, the minimum recommended system configuration is a 386-based PC-compatible
with a 40 MB hard-disk drive monochrome monitor and DOS 5.0 or higher. TOXST disk
storage requirements are largely a function of the complexity of the dispersion modeling
scenario; the volume of output produced by TOXX is negligible in comparison to that produced
by ISCST2. Typical disk storage requirements are as follows:
TOXST executable program code 525Kb
ISCST2 input data 500Kb
ISCST2 binary output 12.6 Mb
ISCST2 printable output negligible
TOXX input data negligible
TOXX temporary paging file variable4
TOXX output negligible
Approximate Total (excluding TOXX paging file) 14 Mb
The size of the ISCST2 binary output file is determined by the number of receptors and source
groups specified and, most important, by the value of the screening cutoff concentration
specified hi the ISCST2 input file OUput pathway (see Section 3.1). The file size indicated
above is based on a rough estimate of the maximum disk storage required for one year of
dispersion data for a network of 125 receptors, assuming that all the hourly x/q values pass the
ISCST2 prescreening. This would output 24 hours/day * 365 days * 125 receptors =1.1
* Minimum size is 32 Kb, maximum size is size of ISCST2 binary output less 32 Kb. Actual size
depends on how many x/q values have the potential to produce exceedances when all sources are "on"
(see Section 2.3.5).
61
-------
million receptor-hours of x/q values. Each such receptor-hour would require approximately 8
bytes disk space, so that the entire binary x/q output file would occupy 8.8 Mb. Of course,
this is a "worst case" one-year scenario. With a suitable choice for the ISCST2 prescreening
cutoff, the size of the binary x/q file may be reduced by 90% or more. In estimating overall
storage requirements, it is necessary to consider the size of the ISCST2 output produced for
each year modeled.
There are three include files for the FORTRAN programs: RUNTOXST.VIN,
RUNTOXST.FIN, and TOXX.INS. In addition, there is an MS-DOS batch file, TOXST.Bat,
which is used to invoke the TOXST system.
The FORTRAN programs in TOXST were developed using the Microsoft FORTRAN
Optimizing Compiler Version 5.1.
43 EXECUTION PROCEDURE
For proper execution, it is required that all executable TOXST code (the batch control file
TOXST.Bat and the executable versions of RUNTOXST, ISCST2, and TOXX) must be located
in the same directory on the user's hard disk. Input files for ISCST2 and TOXX may reside in
other directories, and must be set up in advance of running TOXST.5 After downloading the
executable files from the bulletin board into a directory on the hard disk, the user enters the
command TOXST to begin execution. The program is operated through a series of menu
screens. The main menu is shown in Figure 4-1.
After selecting one of the options on this menu, additional menus appear and the user is
requested to enter the number of ISCST2 and TOXX runs to be set up along with the
appropriate filespecs (i.e., extended DOS file identifiers including; optionally, drive, path
name, file name, and file extension) for the required ISCST2 and/or TOXX input and output
files.
If filespecs are entered without drive/path specifiers, files must be located in the directory from
5 The executable versions of TOXST programs available on the SCRAM bulletin board may be
downloaded and executed "as is" by following the directions hi the README.TXT file available on the
bulletin board. Source code versions of TOXST obtained from SCRAM must be compiled with the
aforementioned compiler and linked with one or both of the aforementioned libraries. For further
information on compiling TOXST source code, consult the README.TXT file.
62
-------
: « TOXST Main Menu »
: CX) create batch files to run ISCST2 or TQXX.
: {2} Queue created batch files for post-TOXST execution,
(3) Exit TOXST program.
Please select one of the above by number.
FIGURE 4-1. TOXST main menu screen.
which TOXST was invoked. TOXST restricts the length of ISCST2 filespecs to 80 characters
and that of TOXX filespecs to 64 characters. The system uses these filespecs to construct DOS
batch files to run ISCST2 and/or TOXX. By selecting the appropriate menu options, these
batch jobs may be executed automatically upon termination of TOXST, or stored for later
execution. Under the latter option, it is necessary to remember that the following filenames are
used: The standard batch file that carries out ISCST2 runs configured with TOXST is
GoISCST2.Bat; that for TOXX runs is GoTOXX.Bat. These batch files, as well as any
temporary files created by ISCST2 or TOXX, are stored in the directory from which the
TOXST system was invoked.
A TOXST session proceeds in a sequence of steps. The first step creates ISCST2 and TOXX
batch files (choice (1) from the main menu, Figure 4-1). It is here that the user enters the
number of executions of each program to be performed, and the names of input and output files
for each such execution.6 At each stage, TOXST checks to be sure that the specified input
files exist. If a required file is not present, the user is prompted to enter a new filespec.
Required input files include the ISCST2 or TOXX parameter input files and the ISCST2
meteorological input file. If a TOXX batch file is created without first creating a ISCST2 batch
file, one or more binary x/q files created by ISCST2 are also required.
After creating batch files for either or both ISCST2 and TOXX, the user may queue either or
both batch files for automatic execution on termination of the TOXST session (choice (2) on the
main menu, Figure 4-1). This step only requires the selection of the program (ISCST2 or
TOXX) for which a batch file is to be queued. If both a ISCST2 and a TOXX.run are to be
performed, the ISCST2 run must be queued first.
Once these steps have been carried out, the user exits from TOXST. If ISCST2 and/or TOXX
* Note that the "log" output files referred to in the program prompts are actually the "printable
output" or "printout" files referred to in the text and shown in Figure 2-1. -
63
-------
batch files have been queued for automatic execution, they will begin running, with the ISCST2
runs always occurring first. If no batch files have been queued, the user may carry out the
ISCST2 and/or TOXX runs that have been set up by running the GoISCST2.Bat and
GoTOXX.Bat batch files at any convenient tune. Two example TOXST model runs are
described in detail in Appendix A, based on a case study at a chemical manufacturing facility.
64
-------
5. TOXST OUTPUT
5.1 GENERAL OUTPUT
As shown in Figure 2-1, the principal output of TOXST is the TOXX printout file, which
contains the results of the expected exceedance calculations. In addition to this file, most users
also will want to examine the ISCST2 printout file to verify the proper operation of the ISCST2
model. Neither the binary normalized concentration file produced by ISCST2 nor the TOXX
temporary paging file (which is automatically erased after the TOXX model has been
successfully run) are printable files. These files are not normally examined by TOXST users
and, therefore, are not described in this manual.
52 ISCST2 PRINTOUT FILE
Output produced by the ISCST2 model is described in the ISC2 user's guide, Vol. I. Users
needing additional information about this file should refer to the user's guide. The file is
formatted using FORTRAN carriage control characters in column one.
5.3 TOXX PRINTOUT FILE
TOXX produces a single printout file that is formatted using FORTRAN carriage control
characters in column one. Examples of typical TOXX output files can be found in Section 3.1
and in Appendix A.l.
The first page of the TOXX printout repeats information specified by the user in the input
parameter file for verification. The second page describes information contained in the
normalized dispersion model output (x/q) file or files used in the TOXX run. The third page
contains any warning messages output by the TOXX subroutine setup. The fourth page
summarizes the results of the TOXX screening procedure, which is designed to eliminate x/q
values not large enough to potentially result in exceedances. Additional information on the
screening procedure and interpretation of this page of the output can be found in Section 2.3.5.
The remaining pages of the TOXX printout show the results of the expected exceedance
calculations. Results are shown for each receptor. Results for individual meteorological years
are output only if the "output by years" option (input parameter lYrly = 1) has been specified.
Otherwise, only the expected exceedances averaged over all years are output.
65
-------
66
-------
6. EXAMPLE TOXST APPLICATIONS
Appendix A presents example TOXST model runs based on a case study of an actual chemical
manufacturing facility. The use of TOXST is described for the actual operating scenario as
well as selected hypothetical examples that demonstrate additional features of TOXST.
The case study was conducted to demonstrate the application of the TOXST model at a
representative chemical manufacturing facility (Sullivan, Grosch and Hlinka, 1993). The
process area was one small part of a major organic chemical manufacturing facility located in
the United States.
The selected process area represents a typical industrial application of TOXST. This operation
is comprised of two major units: (1) a dedicated unit that produces intermediate products that
supply the main production unit, and (2) a production unit that is used to produce a variety of
products on a campaign basis. Figure 6-1 shows a simplified sketch of the two units relative to
the entire plant and the plant boundaries.
FIGURE »-1
LOCATION Of PROCESS UNITS AND MOOS.
RECEPTORS ALONG PLANT gOUNOART
T
3
z.a
t
l.S
i
;
0.5
0
0
Direction (Km) ~*~
/
/
/
* «E
Nt
"***
f f
fun mmi
^•-
WW
^^Mf.
»
•
/
"\
/
(-1
u
0.5 1 1.5 2
x Direction (Km)
67
-------
This figure also shows the locations of the 36 boundary receptors that were used in the
modeling analysis.
Both units are typically operated on a three-month on and one-month off cycle7, with nearly
continuous emissions for some sources; batch emissions are also associated with both units.
The dedicated unit (Unit 1) that supplies the intermediate products always produces the same
intermediates for use in Unit 2. The operation of the production unit (Unit 2), on the other
hand, is varied to produce the range of chemical products that are manufactured by this process
area.
The operation of this process area produces emissions from the following major categories: (1)
production equipment vents, (2) breathing and working loss from chemical storage tanks, (3)
emissions during cleaning of tanks (since many tanks are not dedicated to the storage of only
one chemical), and (4) infrequent chemical spills during transfer operations. Each of the four
source categories is described in Appendix A.
In particular, it was desired to investigate the impacts of four hazardous air pollutants from this
facility. This required the development of composite emission rates for the sources involved.
For the composite chemical model runs, it was assumed that the health effects were interactive
(which is consistent with the eye and respiratory irritation effects for each of these four
chemicals). The emissions for each pollutant were pre-processed to show emissions relative to
the chosen reference pollutant, consistent with Section 2.3.4. In particular, the composite
annual (tons/year) emission rates relative to the reference pollutant emissions were calculated
first, based on the procedure described in Section 2.3.4 of the text8. The annual pollutant
emission rates for each source were factored by the appropriate 8-hour and 1-hour acceptable
threshold ratios shown in Table A-l, and then were factored to represent each emission
category (start-up, routine operation, and tank cleaning).
For simplicity, it was assumed that the continuous sources in Unit
1 operate three months on and one month off, and that intermittent
sources could "turn on" at any time. For a regulatory
application, however, the modeling could be refined by doing four
separate model runs, i.e. one model run to represent each three
month period for the continuous sources, and one to represent the
intermittent sources. The results of each model run could then be
merged during post processing to estimate exceedances.
For the interactive mode, the procedure to develop a composite
emission rate is based on consideration of the emission rate and
the threshold for each species (See Section 2.3.4 of TOXST User's
Guide). A frequency distribution of combined concentrations then
can be displayed, since multiple thresholds can be used in TOXX if
the emissions are preprocessed in this manner.
68 -
-------
The resulting composite emission rates presented in Tables 6-1 and 6-2 were used for the
modeling runs of the composite chemicals. The processed emission rates are substantially
higher for the 8-hour averaging period, as shown hi Table 6-2, since there were more
chemicals with 8-hr threshold values than those with applicable 1-hour threshold values.
69
-------
TABLE 6-1
Hours of Operation and Emission Rates
For Sources of 1-Hour Composite Emissions
Source
Number
of Times
Source On
Per Year
Hour* of
Operation
Each Cycle
Startup
Emission
Rate (G/S)
Routine
Emission
Rate (G/S)
Tank
Cleaning
Emission
Rate (G/S)
Yeariy
Emission
Rate(T/Y)
PROCESS UNIT 1
SRC 1
SRC 2
SRC 3
SRC 4
3
3
30
34
2184
2184
144
144
0.1890
0.0180
0.7610
0.0880
0.1890
0.0180
0.7610
0.0880
N/A.
N/A
N/A
N/A
4.860
0.450
13.042
1.714
PROCESS UNIT 2
SRC 5
SRC 6
SRC 7
SRC 8
SRC 9
SRC 10
SRC 11
SRC 12
3
27
21
24
12
2
12
12
2184
195
264
267
267
120
264
264
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
N/A '
0.000
N/A
0.000
0.000
N/A
N/A
N/A
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
UNIT 2 STORAGE AREA
SRC 13
SRC 14
SRC 15
SRC 16
(5 Gallon)
SRC 17
(10 Gallon)
4
4
4
2
1
66
66
66
2
2
0.238
0.238
0.238
SPILLS
N/A
N/A
0.004
0.004
0.004
1.5531
3.1062
0.870
0.870
0.870
N/A
N/A
0.040
0.040
0.040
0.016
0.016
N/A = Not Applicable
70
-------
TABLE 6-2
Hours of Operation and Emission Rates
For Sources of 8-Hour Composite Emissions
Somee
Number
of Times
Source On
Per Year
Hour* of
Operation
Each Cycle
StartUp
Emission
Rate(G/S)
Routine
Emission
Rate(G/S)
Tank
Cleaning
Emission
Rate(G/S)
Yearly
Emission
RatefT/Y)
PROCESS UNIT 1
SRC 1
SRC 2
SRC 3
SRC 4
3
3.
30
34
2184
2184
144
144
0.3040
0.0270
0.9550
0.1030
0.3040
0.0270
0.9550
0.1030
N/A
N/A
N/A
N/A
7.808
0.707
16.366
2.000
PROCESS UNIT 2
SRC 5
SRC 6
SRC 7
SRC 8
SRC 9
SRC 10
SRC 11
SRC 12
3
27
21
24
12
2
12
12
2184
195
264
267
267
120
264
264
0.0010
0.1 WO
0.0011
0.0044
0.3560
0.3340
0.0810
0.0100
0.0010
0.0920
0.0010
0.0040
0.2850
0.3340
0.0780
0.0090
N/A
0.7620
N/A
0.4310
0.4310
N/A
N/A
N/A
0.035
1.993
0.012
0.146
3.610
0.318
0.976
0.113
UNIT 2 STORAGE AREA
SRC 13
SRC 14
SRC 15
4
4
4
66
66
66
SRC 16
(5 Gallon)
SRC 17
(10 Gallon)
2
1
2
2
2.5550
2.5550
2.5550
SPILLS
N/A
N/A
0.0170
0.0170
0.0170
9.3560
9.3560
9.3560
•0.434
0.434
0.434
1.5531
3.1062
N/A
N/A
0.016
0.016
N/A = Not Applicable
71
-------
The input files used for the ISCST2 and TOXST model runs are shown below. A total of 17
source groups were modeled in both ISCST2 and TOXST. Five years of hourly meteorological
data (1984-1985 and 1987-1989) were used to support the analysis, however, the TOXX input
file and excerpt from the output are base on 1984 and 1985 meteorological years.
**************** Example TOXST Incut File ****************
CASE STUDY OPERATIONS - 8-HOUR - 1984-1985 DIST
6, 385., 550., 900., 1350., 1800., 2700.
1,0.
THRESHOLD #1
THRESHOLD #2
THRESHOLD #3
THRESHOLD #4
THRESHOLD #5
THRESHOLD #6
COMPOSITE
200, 17, 8, 17
18, 0, 0, 1
2, 1984, 1985
ISC8H84.OUT
SOURCE 1
1, 1, 1.0000, 1, 2
1.0, 1.0
2184, 736
0.304, 0.000
0.304, 0.000
SOURCE 2
2, 2, 1.0000, 1, 2
1.0, 1.0
2184, 736
0.027, 0.000
0.027, 0.000
SOURCE 3
3,3,0.0034, 1, 1
1.0
144
0.955
0.955
SOURCE 4
4,4,0.0039, 1, 1
1.0
144
0.103
0.103
SOURCE 5
72
-------
5, 5, 1.0000, 1, 2
1.0, 1.0
2184, 736
0.001, 0.000
0.001, 0.000
SOURCE 6
6,6,0.0031, 1, 5
1.0, 1.0, 1.0, 1.0, 1.0
2 j
-------
13, 13,0.0050, 1, 6
1.0, 1.0, 1.0, 1.0, 1.0, 1.0
3, 48, 12, 1, 1, 1
2.555, 0.034, 0.645, 1.170, 9.356, 1.170
2.555, 0.000, 0.645, 1.170, 9.356, 1.170
SOURCE 14
14, 14,0.0050, 1, 6
1.0, 1.0, 1.0, 1.0, 1.0, 1.0
3, 48, 12, 1, 1, 1
2.555, 0.034, 0.645, 1.170, 9.356, 1.170
2.555, 0.000, 0.645, 1.170, 9.356, 1.170
SOURCE 15
15, 15,0.0050, 1, 6
1.0, 1.0, 1.0, 1.0, 1.0, 1.0
3, 48, 12, 1, 1, 1
2.555, 0.034, 0.645, 1.170, 9.356, 1.170
2.555, 0.000, 0.645, 1.170, 9.356, 1.170
SOURCE 16
16, 16, .0002283, 1, 2
1.0, 1.0
1, 1
1.5531, 0.5177
1.5531, 0.5177
SOURCE 17
17, 17, .0001142, 1, 2
1.0, 1.0
1, 1
3.1062, 1.0354
3.1062, 1.0354
The results in this section are shown for the four chemical (composite) screening-level and
TOXST model runs. Table 6-3 is an actual table created by TOXX based on assuming additive
effects for the four chemicals, using pre-processing of emission rates as shown in Section 2.3.4
of the text. Only the TOXX table for the first threshold is presented here for all sources
combined. Appendix A contains a complete output file.
74
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References
Guinnup, D. E. 1992. "A Tiered Modeling Approach for Assessing the Risks Due To Sources
of Hazardous Air Pollutants." U.S. Environmental Protection Agency (EPA-450/4-92-001).
EPA. 1988. "Industrial Source Complex (ISC) Dispersion Model user's guide-Second Edition
(Revised). Volume 1." U.S. Environmental Protection Agency (EPA-450/4-88-002A).
EPA. 1992. "User's Guide for the Industrial Source (ISC2) Dispersion Models." (EPA-
450/4-92-008a, b, and c):
Volume I User Instructions
Volume II Dispersion Algorithms
Volume III Guide to Programmers
Stoeckenius, T. E., and J. R. Pehling. 1990. "Toxic Expected Exceedance TOXX Model
user's guide." Systems Applications, Inc., San Rafael, California (SYSAPP-90/000).
Whitmyre, G. K., S. R. Baker, and D. A. Sullivan. 1992 "Evaluation of State Regulatory
Initiatives for Assessing Peak Exposures to Air Toxics." Presented at the AWMA 85th Annual
Meeting in Kansas City, Missouri, June 1992.
Sullivan, D.A., T.G. Grosch, and D.J. Hlinka, "Case Study of TOXST Application," prepared
for the Chemical Manufacturer's Association by Sullivan Environmental, June 1993.
79
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80
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TECHNICAL REPORT DATA
(Please read Instructions on reverse before completing)
1. REPORT NO.
EPA-453/R-94-058A
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Toxic Modeling System Short-Term (TOXST) User's Guide:
Volume I
5. REPORT DATE
July 1994
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Sullivan Environmental Consulting, Inc.
1900 Elkin St, Suite 200
Alexandria, VA 22308
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68D20189
II SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Emission Standards Division
Research Triangle Park, NC 27711
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
EPA project manager: David E. Guinnup
16. ABSTRACT
This document describes the Toxic Modeling System Short-Term (TOXST) and provides instructions
on its implementation. TOXST is a personal-computer-based model that has been developed in
conjunction with the release of the EPA's Industrial Source Complex Dispersion Model (EPA, 1992) and
the publication of the EPA's "A Tiered Modeling Approach for Assessing the Risks Due to Sources of
Hazardous Air Pollution," (EPA-450/4-92-001). The purpose of TOXST is to assist in the evaluation of
acute health hazards that may result from short-term exposure to air pollutants. This document represents
a revision of the earlier version of TOXST which incorporates additional options for simulating complex
intermittent sources of industrial pollution.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution
Atmospheric Dispersion Modeling
Air Toxics
Risk Assessment
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (Report)
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (Page)
Unclassified
22. PRICE
EPA Form 222H (Rev. 4-T7) PREVIOUS EDITION IS OBSOLETE
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