United States
        Environmental Protection
        Agency
Office of Air Quality
Planning and Standards
Research Triangle Park. NC 27711
EPA-454/R-92-024
(Revises EPA-450/4-88-009)
December 1992
        Air
& EPA
      WORKBOOK OF SCREENING
     TECHNIQUES FOR ASSESSING
             IMPACTS  OF
        TOXIC AIR POLLUTANTS
               (REVISED)

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                               EPA-454/R-92-024
 WORKBOOK OF SCREENING
TECHNIQUES FOR ASSESSING
          IMPACTS OF
   TOXIC AIR POLLUTANTS
           (REVISED)
          U.S. Environmental Protection Agency
          Region 5, Library (PL.-12J)
          77 West Jackson Boulevard, 12th Floor
          Chicago, IL 60604-3590
       Office Of Air Quality Planning And Standards
           Office Of Air And Radiation
        U. S. Environmental Protection Agency
         Research Triangle Paric, NC 27711
                       
              December 1992

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This report has been reviewed by the Office Of Air Quality Planning And Standards, U. S. Environmental
Protection Agency, and has been approved for publication.  Any mention of trade names or commercial
products is not intended to constitute endorsement or recommendation for use.
                                     EPA-454/R-92-024

                                 (Revises EPA-450/4-88-009)
                                            u

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                             PREFACE

     This document supersedes the workbook version dated September
1988.  Changes include: development of new methods for estimating
emission rates; revisions to methods for esitmating emission rates
to establish consistency with current guidance;  addition of several
new  scenarios,  especially  those  related to  Superfund/  and  the
addition of a new  screening method based on the  work of Britter and
McQuaid  to  estimate the  impact  of aerosols and denser-than-air
gases released from chemical  spills.   Ambient  concentrations  are
now  illustrated  by using  the  TSCREEN model  instead  of  hand
calculations.  Thus, users comparing the predicted maximum ground
level concentrations with those shown  in the earlier document will
now find different, and more accurate, estimates.
                               111

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                        ACKNOWLEDGEMENTS

     This report was prepared by  Pacific  Environmental Services,
Inc.,  under EPA Contract No.  68D00124,  with Mr.  Jawad S. Touma as
the Work Assignment Manager.
                                IV

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                        TABLE OF CONTENTS

PREFACE	

ACKNOWLEDGEMENTS  	  iv

1.0  INTRODUCTION	1-1

2.0  SELECTION OF SCREENING TECHNIQUES FOR TOXIC AIR
     CONTAMINANTS 	 2-1
     2.1  Release Categorization   	 2-1
     2.2  Limitations and Assumptions	2-1
     2.3  Scenario Selection  	 2-3
     2 .4  Determining Maximum Short'-Term Ground Level
          Concentration 	  2-17
          2.4.1  Dispersion Models used in TSCREEN  ....  2-17
          2.4.2  Dispersion Model Selection 	  2-17
     2.5  Considerations for Time-Varying and Time-Limited
          Releases	2-24
     2.6  Denser-Than-Air Materials 	  2-25
     2.7  Dispersion Screening Estimates for Denser-Than-Air
          Contaminants  	  2-26

3.0  SUPPORT DATA FOR SCREENING ESTIMATES .'	3-1
     3.1  Meteorological Data	3-1
          3.1.1  Wind Speed and Direction	3-1
          3.1.2  Stability and Turbulence	3-2
          3.1.3  Temperature	3-3
          3.1.4  Atmospheric Pressure ..,	3-3
     3.2  Chemical and Physical Parameters  	 3-3

4.0  SCENARIOS AND TECHNIQUES FOR RELEASE AND EMISSIONS
     ESTIMATES	4-1
     4.1  Particulate Matter Release  	 4-2
          4.1.1  Releases from Stacks, Vents  	 4-2
          4.1.2  Continuous Fugitive/Windblown Dust
                 Emissions	4-11
          4.1.3  Ducting/Connector Failures .  . -	4-17
     4.2  Gaseous Release	4-23
          4.2.1  Continuous Flared Stack Emissions -
                 Gaseous	4-23
          4.2.2  Continuous Release from Stacks, Vents,
                 Conventional Point Sources 	  4-28
          4.2.3  Continuous Gas Leaks from a Reservoir   .  .  4-34
          4.2.4  Instantaneous Gas Leaks from a Reservoir  .  4-67
          4.2.5  Continuous Gas Leaks from a Pipe Attached
                 to a Reservoir	4-69
          4.2.6  Instantaneous Gas Leaks from a Pipe
                 Attached to a Reservoir	4-87
          4.2.7  Continuous Multiple Fugitive Emissions  .  .  4-89
          4.2.8  Continuous Emissions from Land Treatment
                 Facilities	4-93
          4.2.9  Continuous Emissions from Municipal Solid
                 Waste Landfills	4-97

                                v

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          4.2.10 Continuous Emissions of Pesticides .... 4-103
          4.2.11 Instantaneous Discharges from Equipment
                 Openings	4-108
     4.3  Liquid Release	4-112
          4.3.1  Continuous Evaporation from Surface
                 Impoundments (Lagoons)  	 4-112
          4.3.2  Continuous (Two-Phase)  Release Rate
                 Estimates:   Saturated Liquid from
                 Pressurized Storage  	 4-116
          4.3.3  Instantaneous (Two-Phase)  Release Rate
                 Estimates:   Saturated Liquid from
                 Pressurized Storage  	 4-124*
          4.3.4  Continuous (Two-Phase)  Release Rate
                 Estimates':   Subcooled Liquid from
                 Pressurized Storage  	 4-126
          4.3.5  Instantaneous (Two-Phase)  Release Rate
                 Estimates:   Subcooled Liquid from
                 Pressurized Storage  	 4-134
          4.3.6  Continuous High Volatility Leaks	4-136
          4.3.7  Instantaneous High Volatility Leaks  .  .   . 4-144
          4.3.8  Continuous Low Volatility Liquids from
                 Tanks and Pipes	4-146
          4.3.9  Instantaneous Low Volatility Liquids from
                 Tanks and Pipes  :	4-155
     4.4  Superfund Releases  	 4-162
          4.4.1  Air Strippers	4-162

5.0  ATMOSPHERIC DISPERSION ESTIMATES 	 5-1
     5.1  SCREEN	5-2
          5.1.1  Point Sources  .	5-2
          5.1.2  Area Sources	5-14
     5.2  RVD	5-19
          5.2.1  Inputs	5-19
          5.2.2  Model Output	5-21
     5.3  PUFF	5-26
          5.3.1  PUFF Model Discussion	5-26
          5.3.2  Model Inputs	5-28
          5.3.4  Model Output	5-30
     5.4  Britter-McQuaid	'	5-33
          5.4.1  Method for Cold Contaminant Releases  Heat
                 Transfer Effects	".   .  5-34
          5.4.2  Method for Contaminant Aerosol Releases   .  5-34
          5.4.3  Continuous (Plume)  Releases  	  5-36
          5.4.4  Instantaneous (Puff)  Releases  	  5-41
          5.4.5  Assumptions in TSCREEN	5-45
          5.4.6  Model Inputs	5-46
          5.4.7  Model Output	5-47

REFERENCES	R-l
                                VI

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APPENDIX A       EMISSION FACTORS 	 A-l

APPENDIX B       ESTIMATING SELECTED PHYSICAL PROPERTIES OF
                 MIXTURES	B-l

APPENDIX C       SELECTED CONVERSION FACTORS  	 C-l

APPENDIX D       AVERAGING PERIOD CONCENTRATION ESTIMATES  .  . D-l
                               VII

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1.0  INTRODUCTION

     This workbook provides a logical approach to the selection
of appropriate screening techniques for estimating ambient
concentrations due to various toxic/hazardous pollutant releases.
Methods used in the workbook apply to situations where a release
can be fairly well-defined, a condition typically associated with
non-accidental toxic releases.  The format of this workbook is
built around a series of release scenarios which may be
considered typical and representative of the means by which toxic
chemicals become airborne.  This document supersedes the earlier
workbook (EPA, 1988a).

     Screening techniques are simplified calculational procedures
designed with sufficient conservatism to allow a determination of
whether a source: 1) is clearly not an air quality threat or 2)
poses a potential threat which should be examined with more
sophisticated estimation techniques or measurements.  Screening
estimates obtained using this workbqok represent maximum short-
term ground level concentration estimates from a meteorological
perspective.  If the screening estimates demonstrate that during
these conditions the ground level concentrations are not likely
to be considered objectionable,  further analysis of the source
impact would not be necessary as part of the air quality review
of the source.  However, if screening demonstrates that a source
may have an objectionable impact, more detailed analysis would be
required using refined emissions and air quality models.

     For each release scenario,  the workbook describes the
procedure to be used and provides an example illustration using
the TSCREEN model.  TSCREEN, a model for screening toxic air
pollutant concentrations, is an IBM PC-based interactive model
that implements the release scenarios and methods described in
this workbook.  TSCREEN allows the user to select a scenario,
determine an emission rate, and then apply the appropriate
dispersion model in a logical problem solving approach.  The
model consists of a front-end control program with many
interactive menus and data entry screens.   As much information as
is logically and legibly possible is assembled onto unique data
entry screens.  All requests for input are written in clear text.
Extensive help screens are provided to minimize numeric data
entry errors, and default values are provided for some
parameters.  The user is able to return to previous screens and
edit data previously entered.  A chemical look-up database and an
on-line calculator are also available.  Once the nature of the
release is determined,  the user must specify the emission rate.
For some scenarios, extensive references to EPA methods are
provided, while for others, a specific method for calculating the
emission rate is given.  Density checks for the release are
performed to determine which dispersion model is selected.  Data
necessary to execute that particular model is then requested in a
logical format.  Once the model is executed,  the concentrations
are calculated and then tabulated in a clear and legible manner,


                               1-1

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and an- easy to read graph of concentration versus distance is
provided.  The printed text and graphical output can be sent to a
variety of printers and plotters through built-in software;
minimum user interface is required.

     The front-end program in TSCREEN is written in the FoxPro
programming language, a superset of the dBASE language family
suitable for PC's running MS-DOS.   The primary purpose  of a
dBASE language is database manipulation, but is can also be used
for general purpose programming.  The reasons for using this
system are: 1) a user interface which facilitates the debugging
process, and as a result, reduces the development cost/ 2) pull-
down menus and windows which require minimal programming effort
to create,- 3) built-in functions for database manipulation, and
as a result, much less code is required to create the chemical
database in TSCREEN; 4) memory management capabilities that allow
TSCREEN to run on machines with less random access memory  (RAM);
and 5) the ability to release most of the TSCREEN front-end
program from memory before it executes the dispersion models.
The main disadvantage of th'is system is the size of the files
that a user needs to run.  The system is distributed with two
run-time libraries.  These are files that contain the
implementation of functions that are called by the program.  One
of these libraries is over 300 kilobytes (K) and the other is
close to 1 megabyte  (MB).  TSCREEN is distributed through the
EPA's Technology Transfer Network, SCRAM Bulletin Board System.

     The workbook is organized into five sections and six
supporting appendices.  Section 2 discusses selection of
screening techniques and the general approach to using the
workbook.  Users are advised to consult this section both for
releases explicitly presented in the workbook and for less
typical releases.  This section also considers assumptions,
limitations and conservatism of estimates.  Section 3 describes
the support data  (i.e., meteorological data and chemical and
physical parameters) needed for making estimates.  Section 4
presents the  inputs required for each scenario and the applicable
methods for determining release  (emission) rates.  This section
also  includes an example showing the data entry screening and
sample  calculations for each scenario as used in TSCREEN.   (Note:
the values  that TSCREEN produces may be slightly different than
the values  in the examples due to differences in rounding.)  In
this  workbook 24 release scenarios have been selected to
represent situations likely to be encountered.  Section 5
describes the dispersion models that are referenced in this
workbook and  are embedded in TSCREEN.

        Appendix A discusses currently available sources for
obtaining emission  factors that can be used for some of the
scenarios.  Appendix B provides a method for estimating selected
physical properties  for mixtures.  Appendix C provides some
useful  unit  conversion  factors applicable to the workbook.
                                1-2

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Appendix D provides some techniques for converting concentrations
calculated by the models to different averaging times.

     Methods used in this workbook should be applied with
caution.  Techniques for estimating emissions are evaluated and
revised on a continuing basis by EPA.  Thus the user should
consult with EPA on the most recent emission models and emission
factors.  Meteorological methods presented in this workbook
reflect guidance published elsewhere, and in particular the
Guideline on Air Quality Models (Revised)  (EPA,  1986) and its
supplements.  The Regional Modeling Contact should be consulted
as to the present status of guidance on air quality modeling.
                              1-3

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2.0  SELECTION OF SCREENING TECHNIQUES FOR TOXIC AIR CONTAMINANTS

     This workbook attempts to account for many of the scenarios
expected to produce toxic chemical releases to the atmosphere.

2. 1  Release Categorization

     Selection of appropriate technique for screening estimates
requires categorization of the toxic chemical release of  .
interest.  There are three overlapping categories which should be
considered when defining problems for screening:

     1) Physical State - Gaseous releases to the atmosphere can,
        in general, be simulated using techniques developed for
        criteria air pollutants unless the gas is dense, is
        highly reactive, or rapidly deposits on surfaces.
        Additional source modeling must be performed if the
        release is liquid, aerosol or multi-phased to determine
        the state of the material as it disperses in air.

     2) Process/Release Conditions - Knowledge of the
        circumstances under which chemicals are released helps to
        determine both state and dispersive characteristics.   For
        example, location of a leak in a pressurized liquefied
        gas storage tank will determine if a release is liquid or
        gas and if source modeling is required prior to
        dispersion estimates.

     3) Dispersive Characteristics - Techniques for pollutant
        dispersion estimates are categorized by terms such as
        instantaneous versus continuous, or point versus area, or
        volume releases.  To complete dispersion estimates, this
        final characterization is required at some point in
        concentration calculations.

     The primary emphasis of this workbook is to serve as an
accompanying guide to the TSCREEN program which implements
screening techniques for estimating short-term, ground level
concentrations of toxic chemicals released to the atmosphere.
However, in order to do this, the workbook also provides
assistance to the user in formulating the release conditions.


2.2  Limitations and Assumptions

     Methods included in TSCREEN are intended to provide
simplified screening estimates for situations which-may represent
extremely complex release scenarios.  As such, the methods are
limited in their applicability.  Some of these limitations are as
follows:

        Screening techniques provided are intended for use on
        small to mid-scale non-accidental releases.


                               2-1

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        All techniques assume that the toxic air contaminant is
        non- reactive and non-depositing.  Thus these screening
        methods are not applicable for reactive gases and
        particle depositions.  For two-phase flows,  all released
        liquid is assumed to travel downwind as an aerosol with
        insignificant (liquid)  rain out near the source.

        Denser-than-air contaminant behavior is a consequence not
        only of the initial (depressurized)  contaminant density
        but also of the contaminant release  rate and the ambient
        wind speed; if denser-than-air contaminant behavior is
        not expected to be important,  passive atmospheric
        dispersion modeling techniques should be applied.  In
        TSCREEN Version 3.0,  the determination of denser-than-air
        behavior is done based on the initial contaminant density
        comparison to ambient air.

        Conditions resulting in worst case concentrations cannot
        be uniquely defined where meteorological conditions
        affect source estimates.  For example,  in the case of
        evaporation, the highest emission rates are related to
        high wind speeds, which, however,  result in more dilution
        and lower ambient concentrations.

        Time dependent emissions cannot be simulated with these
        simple screening technique. Techniques provided assume
        steady releases for a specified period.

        All release calculations assume ideal conditions for gas
        and liquid flows.
                                         B              
        The influence of obstructions such as buildings and
        topography on denser-than-air releases and releases close
        to the ground are not included.

        Complicated post-release thermodynamic behavior for
        denser-than-air releases is not accounted for in these
        screening techniques.

     Because of the simplifying assumptions  inherent in these
screening methods, which are specifically aimed at decreasing the
amount of information required from the user and decreasing the
computation time and sophistication, more refined assessment
techniques should be applied to a release scenario which"is
identified by these screening procedures as  violating ambient air
quality standards or other specified levels  of concern.  Refined
techniques involve both refined release (emission) rate estimates
as well as more refined atmospheric dispersion models.   (See for
example, "Guidance on the Application of Refined Dispersion
Models for Air Toxics Releases"  (EPA, 1991a).)   As with any air
quality assessment, the screening methods described here should
be applied with due caution.
                               2-2

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2.3  Scenario Selection

     Release scenarios are grouped according to four categories:
particulate matter, gases, liquids, and releases from Superfund
sites as shown in Table 2-1.  For some of'the categories, there
are additional subcategories.   Figure 2-1 provides a graphical
illustration of each release scenario.  Descriptions on similar
release scenarios are provided to help guide the user in
selecting the correct release category.  Once the correct release
category has been selected, the user should proceed to the
relevant section where further information on the release
scenario is given.  For each release scenario,  methods for
determining emission estimates are provided and then the
appropriate dispersion model is selected to determine ambient
concentrations.
                               2-3

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                                TABLE 2-1
                            RELEASE SCENARIOS
 Initial Form of Release
                Release Type
Scenario  Modeling
 Nunber   Category*
Particulate Matter


Gases










Liquid








Continuous Particulate Release from Stack, Vents
Fugitive/Windblown Dust Emissions
Ducting/Connector Failures
Flared Stack Emissions
Continuous Releases from Stacks, Vents, Point Sources
Continuous Leaks from Reservoir
Instantaneous Leak from Reservoir
Continuous Leaks from Pipe Attached to Reservoir
Instantaneous Leak from Pipe Attached to Reservoir
Gaseous Emissions from Multiple Fugitive Sources
Gaseous Emissions from Land Treatment Facilities
Emissions from Municipal Solid Waste Landfills
Emissions from Pesticides/Herbicide Applications
Discharges from Equipment Openings
Evaporation from Surface Impoundments (Lagoons)
Continuous 2-Phase Saturated Liquid from Pressurized Storage
Instantaneous 2-Phase Saturated Liquid from Pressurized Storage
Continuous 2-Phase Subcooled Liquid from Pressurized Storage
Instantaneous 2-Phase Subcooled Liquid from Pressurized Storage
Continuous High Volatility Liquid Leaks
Instantaneous High Volatility Liquid Leaks
Continuous Lou Volatility Liquid Leaks
Instantaneous Low Volatility Liquid Leaks
1.1
1.2
1.3
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
2.10
2.11
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
CP
CA
IP
CP
CP
CP
IP
CP
IP
CA
CA
CA
CA
IP
CA
CP
IP
CP
IP
CP
IP
CA
IP
    Superfund Sites
Air Stripper
   4.1
                                                                     CP
* c - Continuous
 P - Point
 A - Area
 I - Instantaneous

     Table 2-1 shows  that,  for example,  a continuous  gaseous release
from stacks,  vents and point sources  is  given Scenario number 2.2.
Figure  2-1 provides a graphical illustration and a brief description
of this scenario.  Figure 2-2 (Section 2.4)  shows that this scenario
is discussed in detail in Section 4.2.2  and that the  SCREEN dispersion
model is selected within TSCREEN to estimate ambient  ground level
concentrations for this scenario.
                                    2-4

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         Figure 2-,l.   Schematic Illustrations of Scenarios

Continuous Releases of Particulate Matter from Stacks, Vents  -1.1
Similar Releases:   Continuous  emissions  of  particulate matter
from vertical  stacks  and pipes or conventional  point  sources and
some process vents  when  emission  flow rates and temperature are
known.  Combustion  sources  and chemical  reactors are  typical
emission  sources  that may emit such  pollutants  through stacks.
These releases may  also  be  due to a  process failure such as a
rupture disk release  or  failure of control  equipment.
        Continuous  Fugitive/Windblown Dust  Emissions  -  1.2
                                          Fugitive Dust
Similar Releases:  Any  fugitive dust  from process  losses,
generated by mechanical  action in material handling or windblown
dust.  Such emissions tend  to originate from a  surface or  a
collection of  small poorly  defined point sources.
                               2-5

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   Particulate Releases from Ducting/Connector Failures - 1.3
                  Fugitive
                  Dust  *
Similar Releases;   Instantaneous bursts of particulates due to
duct failure (e.g., pneumatic conveyor line failures), line
disconnection,  isolation joint failure, or other types of
equipment openings.
             Continuous Flared Stack Emissions - 2.1
                                Emissions
                  Flare
Similar Releases:  Flares are used as a control device for a
variety of sources.  As such flares must comply with requirements
specified in 40 CFR 60.18.
                               2-6

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       Continuous Release from Stacks,  Vents,  Conventional
                       Point Sources - 2.2
Similar Releases:  Continuous emissions of a gas from vertical
stacks and pipes or conventional point sources and some process
vents when emission flow rates and temperature are known.
Combustion sources and chemical reactors are typical emission
sources that may emit such pollutants through stacks.  These
releases may also be due to a process failure such as a rupture
disk release or failure of control equipment.
          Continuous Gaseous Leaks from Reservoir - 2.3
                                      Emissions
                   Leaking flange
Similar Releases:  Continuous release of a gas  (at constant
pressure and temperature) from a containment  (reservoir) through
a hole or opening.  Possible applications include a gas leak from
a tank, a (small) gas leak from a pipe, or gas discharge from a
pressure relief valve mounted on a tank.
                               2-7

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         Instantaneous Gaseous Leak from Reservoir -  2.4
                                  Instantaneous
                                  Gaseous Emission
                               Blown Rupture Disk
Similar Releases:   Instantaneous release of a gas  (at constant
pressure and temperature)  from a containment (reservoir) through
a hole or opening.   Possible  applications include a gas leak  from
a tank, a  (small) gas  leak from a pipe,  or gas discharge from a
pressure relief valve  mounted on a tank.


    Continuous Leaks from a Pipe Attached  to  a. Reservoir -  2.5
Similar Release:   Continuous  release of a gas
pressure and temperature}  from a containment
a long pipe.
(at constant
reservoir) through
                                2-8

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  Instantaneous Leaks from a Pipe Attached to a Reservoir  -  2.6
Similar Release: . Instantaneous release of a gas  (at  constant
pressure and temperature) from a containment  (reservoir)  through
a long pipe.
           Continuous Multiple Fugitive Emissions - 2.7

                                    Range Leaks
                   Hand Valve Stem
                     Pump Seals
Open Ditches
Similar Releases:  Releases from any continuous area or volume
source where the emissions are uniformly released over the area
or the area represents a collection of small sources poorly
defined in terms of location  (e.g., multiple vents on large
manufacturing buildings, fugitive VOC sources in refineries  or
chemical process manufacturing plants).
                               2-9

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    Continuous Emissions from Land Treatment  Facilities - 2.8
                  Emissions
                              Organic Sludge
                   SoiJ Treatment
Similar Releases:  Landfarms; ground level  application of sludge
(containing volatile organic material  in oil)  to  soil surface.


Continuous  Emissions from Municipal Solid Waste Landfills  -  2.9
                                     Emissions
Similar Releases:  None.  Emission  rates  applicable, to municipal
solid waste landfills only.
                               2-10

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  Continuous Emissions from Pesticides/Herbicide Applications
                              2.10
                  Emissions
Similar Releases:   Emissions resulting  from the volatilization of
pesticides or herbicides applied to  open  fields.


    Instantaneous  Discharges from Equipment Openings - 2.11
                                      Chemical
                                      Reactor
                                   Emissions
                Coke Oven
Similar Releases:  'Any puff or burst  type release with short
duration emissions resulting from the opening of equipment after
processing (e.g.,  coke ovens or chemical reactors), from routine
sampling of product processing or gaseous emissions from
disconnected lines.
                              2-11

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Continuous Evaporation from Surface  Impoundments (Lagoons)  - 3.1
Similar Releases ;  Waste  lagoons  and other impoundments with
emissions resulting  from  the  evaporation of volatile chemicals
from liquid mixtures with biological activity.
  Continuous 2-Phase Saturated Liquid from Pressurized Storage -
                                3.2
                                  Liquid Phase ontad in Qts Phaa

                              Emissions      /
 Similar Releases:   Continuous-release of a pressurized liquid
 stored under saturated conditions.  The release occurs (at
 constant pressure  and temperature) from the containment
 (reservoir)  through a hole or opening; a provision is made  for
 the effect of a pressure drop (piping) between the tank and the
 hole or opening.  Possible applications include a saturated
 liquid leak from a pressurized tank or a saturated liquid leak
 from a pipe.

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Instantaneous  2-Phase Saturated Liquid from Pressurized Storage
                               3.3
                          Emissions   UquM Phase canted In Gas Phase
Similar Releases;   Instantaneous release of a pressurized liquid
stored under  saturated conditions.   The release occurs  (at
constant pressure  and temperature)  from the containment
(reservoir) through a hole or opening;  a provision is made  for
the effect of a pressure drop (piping)  between the tank and the
hole or opening.   Possible applications include a saturated
liquid leak from a pressurized tank or a saturated liquid leak
from a pipe.
    Continuous Subcooled Liquid from Pressurized  Storage - 3.4
                   Relief
                   Valve
                                  Liquid Phase canted In Gas Phase

                              Emissions      /
Similar Releases:  Continuous  release of pressurized liquid
stored below its saturation  pressure.   The release occurs  (at
constant pressure and  temperature)  from a containment  (reservoir)
through a hole or opening; a provision is made for the effect of
a pressure drop  (piping)  between the tank and the hole or
opening.  Possible applications  include a subcooled liquid leak
from a pressurized tank  or a subcooled leak from a pipe.
                               2-13

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  Instantaneous Subcooled Liquid from Pressurized Storage - 1.5
                         Emissions
Similar Releases:   Instantaneous release of pressurized liquid
stored below its saturation pressure.   The release occurs (at
constant pressure and temperature)  from a containment (reservoir)
through a hole or opening; a provision is made for the effect of
a pressure drop (piping)  between the tank and the hole or
opening.  Possible applications include a subcooled liquid leak
from a pressurized tank or a subcooled leak from a pipe.
          Continuous High Volatility Liquid Leaks

                             Emissions M|f|!8,
- 3.6
                  Pipe
                             Emissions
                                           Hole
                  Tank
Similar Releases:  Continuous release of high volatility liauid
(at constant temperature and pressure)  from a containment
(reservoir)  through a hole or opening.   Possible applications
include a (high volatility)  liquid leak from a tank or a liquid
leak from a pipe (when the ratio of the hole diameter to the pipe
diameter is less than 0.2).
                              2-14

-------
         Instantaneous  High Volatility Liquid Leaks  -  3.7

                             Emissions

                                         T^ \jl QWIV
Pipe
                             Emissions
                  Tank
                                           Hole
                                     A.
Similar Releases:  Instantaneous release of high, volatility
liquid (at constant temperature and pressure) from a containment
(reservoir) through a hole or opening.  Possible applications
include a  (high volatility) liquid leak from a tank or a liquid
leak from a pipe  (when the ratio of the hole diameter to the pipe
diameter is less than 0.2).
           Continuous  Low Volatility Liquid Leaks  -  3.8
                      Tanks
                Pipe
                                 Leaking Pipe Range
Similar Releases;  Continuous release of liquid whose normal
boiling point is above ambient temperature.  A low volatility
material stored at moderate to low pressure (and where the
boiling point is above storage temperature) will typically be
released as a liquid and form a pool or puddle on the ground.
The (conservative) assumption is that the liquid evaporates at
the same rate it is spilled (except when the liquid is confined
by a bund dike from which liquid does not overflow).   Possible
applications include a (low volatility)  liquid leak from a tank
or a pipe.
                               2-15

-------
         Instantaneous Low Volatility Liquid .Leaks - 3.9
                      Tanks
Pipe
Similar Releases:  Instantaneous  release  of liquid whose normal
boiling point is above ambient  temperature.  A low volatility
material stored at moderate  to  low pressure (and where the
boiling point is above storage  temperature) will typically be
released as a liquid and  form a pool  or puddle on the ground.
The (conservative) assumption is   that  the liquid evaporates at
the same rate it is spilled  (except when-  the liquid is confined
by a bund dike from which liquid  does not overflow).   Possible
applications include a  (low  volatility) liquid leak from a tank
or a pipe.
                        4.1  Air Strippers
                                        "Clean"
                                           Air
                                    Air
                 Contaminated
                 Water
                                     Clean" Air
                            Pump
                                        Clean' Water
Similar Releases:  None.
                               2-16

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2.4  Determining Maximum Short-Term Ground Level Concentration

2.4.1  Dispersion Models used in TSCREEN

     Maximum short-term ground level concentrations in TSCREEN
are based on three current EPA screening models  (SCREEN, RVD, and
PUFF) and the Britter-McQuaid screening model.  All four models
are embedded in the TSCREEN model.  SCREEN is a Gaussian
dispersion model applicable to continuous releases of particulate
matter and non-reactive, non-dense gases that are emitted  from
point, area, and flared sources.  The SCREEN model implements
most of the single source short-term procedures contained  in the
EPA screening procedures document  (EPA, 1988c.)  This includes
providing -estimated maximum ground-level concentrations and
distances to the maximum based on a pre-selected range of
meteorological conditions.  In addition, SCREEN has the option of
incorporating the effects of building downwash.  The RVD model
 (EPA, 1989) provides short-term ambient concentration estimates
for screening pollutant sources emitting denser-than-air gases
and aerosols through vertically-directed jet releases.  The model
is based on empirical equations derived from wind tunnel tests
and estimates the maximum ground level concentration at plume
touchdown at up to 30 downwind receptor locations.  The PUFF
model (EPA, 1982) is used where the release is finite but  smaller
than the travel time (i.e., an instantaneous release.)  This
model is based on the Gaussian instantaneous puff equation and is
applicable for neutrally buoyant non-reactive toxic air releases.
The Britter-McQuaid model  (1988) provides an estimate of
dispersion of denser-than-air gases from area sources for
continuous  (plume) and instantaneous  (puff) releases.  Further
discussion on model assumptions'is given in Chapter 5.0.

2.4.2  Dispersion Model Selection

     Figure 2-2 shows which screening model is associated  with
each scenario.  In TSCREEN, ambient impacts of releases from
pressurized storage vessels (and pipes) or liquid releases are
evaluated using the following test.  The release density p2
 (kg/m3)  is  compared with ambient density,  pair (kg/m3) .  If the
release density is more than ambient density  (i.e., j02//oair  > 1),
then the release is considered denser-than-air.  For denser-than-
air releases  (both continuous and instantaneous), TSCREEN  uses
the RVD model if the release is a^ vertically-directed jet  and the
Britter-McQuaid model for all other releases.  For releases that
are considered passive  (i.e.,  p2/p3il <_ 1) ,  TSCREEN uses the SCREEN
model for a continuous release and the PUFF model for an
instantaneous release.

     If the release density is greater than ambient density
 (i.e., P2/P& > 1),  a further determination of the importance of
denser-than-air behavior based on contaminant release rate and
the ambient wind speed is made after calculating the Richardson
number  (see below).  Since for many applications  (e.g., planning

                               2-17

-------
analyses) the actual wind speed is not known, this method is not
used in TSCREEN (version 3.0).   The following shows how the user
may approach the problem.
                               2-18

-------
                Figure 2-2.  Model Selection
Paniculate Hitter
 Release Type
                       TSCREEN
 Gaseous
Release Type
  Liquid
Release Type
 Superfund
Release Type
  Stacks, Vants
     4.1.1
               PARTICULATE  MATTER
                    RELEASE  TYPE
      Fugitive/Windblown
       Oust Emissions
          4.1.2
                          SCREEN
                            Area
            Ducting/Connector
               Failures
                4.1.3
              SUPERFUND RELEASE  TYPE
                          Air Stripper
                            4.4.1
                           SCREEN
                           Point
                           2-19

-------
                   GASEOUS  RELEASE   TYPE
 Flared Stack Emissions
        4.2.1
Land Treatment Facilities
  Stacks. Vent*. Conventional
       Point Sources
           4.2.2
Multiple Fugitive Sources
        4.2.7
Pesticide/Herbicide Applications
          4.2.10
  Leaks from Reservoir
  Discharges from Equipment
         Openings
          4.2.11
                                                             Leaks from Pipe
                                                          Attached To Reservoir
                                     2-20

-------
                LIQUID  RELEASE  TYPE
2-Phase Saturated Liquid
From Pressurized Storage
Surfacs
Impoundment*
4.3.1
Z-Phase Subcooled Liquid
From Pressurized Storage


Contln- .
uous
4.3.2




Instan-
taneous
4.3.3
                                       YES
                                                         YES
                             2-21

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2.4.2.1  Continuous Release

1.   Perform buoyancy check as a first check.

     A. Calculate the density of air using the  following:
                                                           (2.4-1!
        where R = 8314  (J/kg-mole-K). The molecular weight of
        air is assumed equal to 28.9  (kg/kmol),  and atmospheric
        pressure is 101325  (Pa).

     B. If p2/Pair > !/  then the buoyancy is negative; go to  steps
        2 or 3.  Otherwise, buoyancy  is neutral  or  positive and
        the SCREEN model for a point  source  should-be used.


2.   For a vertically directed jet release,  the  release
     Richardson number, Ri, is calculated using  the following
     equation:
                Ri = g  Ui-1  Qm/u D0 p2 U20 (U./ulo)2          (2.4-2)
     where g is the acceleration of gravity  (m/s2) ,  p2 is the
     plume density  (kg/m3) ,  p^ is the ambient density  (kg/m3) ,  Qm
     is the exhaust gas mass flow rate  (kg/s), u  is  the wind
     velocity at the.top of the stack  (m/sec), D0 is the stack
     diameter (m) , u10 is the wind velocity at  10m above the
     ground, U./UIQ is the ratio of friction velocity  (m/s)  to the
     wind speed at 10m  (m/s).  In version 2.0  of  the RVD model,
     this ratio is assumed to  equal 0.06 for  all  atmospheric
     stability classes.  The value of u is calculated via the
     equation:

                          u = u,0 (hs/10)P                     (2.4-3)


     where h,  is  the stack height (m)  and p is the wind speed
     profile exponent, which varies as a function of atmospheric
     stability.  By using g =  9.81 m/s2,  u = 1 m/sec, u,/uto =
     0.06, u!0 = 1 m/s, the Richardson number  is reduced to:
                                 (p.
                      Ri = 2,725 i-1
                                                           (2.4-4!
                               2-22

-------
     U = 1 m/sec was chosen as a screening method for determining
     denser-than-air effects.  However, denser-than-air effects
     do not always correspond to largest hazard extent.

3.   For other denser-than-air releases, Britter-McQuaid
     recommend that denser-than-air effects be ignored if:


                                     <0.005                (2.4-5)
     where g is the acceleration of gravity  (m/s2) ,  E is the
     release rate in kg/s, D is the (low-momentum) horiaontal
     dimension of the source(m), Ur is  the wind speed at 10  m
     (m/s),  p2  is  the discharge (depressurized)  density of air
     (kg/m3) .   See Section 5.0  for additional explanation.

     Thus, if the wind speed during the release is known, then  it
     can be inserted in the equation and a determination  can be
     made whether a dense gas model should be used.  Selections
     are summarized in the table below:

                            TABLE 2-2
             MODEL SELECTION FOR CONTINUOUS  RELEASE
Continuous
1. Buoyancy Check
2. Vertically Directed Jet
3. Other
Criteria
Pj/Pr < 1
Pz/P- > 1
Yes - Ri > 30
Ri < 30
No - (Go to '3. Other')
Ri < (1/6)3
Ri > (1/6)3

Passive
(Go to '2. or 3.')
Dense
Nondense
Dense
Passive
Models
SCREEN
RVD
SCREEN
B-M
SCREEN
4.2.2 Instantaneous Release
1.   Perform buoyancy check as a first check.

     A. Calculate the density of air using equation 2.4-1.

     B. If PI/p^ > I/  then the buoyancy is negative;  go to step 2
        or 3.  Otherwise, buoyancy is positive and the PUFF model
        will be used.

2.   For a vertically directed jet release, calculate the release
     Richardson number as shown in equation 2.4-4.

3.   For other denser-than-air releases, Britter-McQuaid
     recommend .that denser-than-air effects be ignored if.:
                               2-23

-------
                       - Pa
       g (E,/p2)
                                      Tl/2
                                         s 0.2
                                     (2.4-7)
     where g is the acceleration of gravity (m/s2) , p2 is the
     discharge density  (kg/ra3) ,  p^ is the ambient density
     (kg/m3) ,  E, is the total amount of material released (kg) ,
     and Ur  is  the wind  speed at 10 m (m/s).

     If denser-than-air effects are determined to be  important,
     then the Britter-McQuaid model is used.   Otherwise, the
     release is considered non-dense  (passive)  and the PUFF model
     applies.  Selections are summarized  in the.table below:

                             TABLE  2-3
            MODEL SELECTION FOR INSTANTANEOUS RELEASE
   Continuous
Criteria
                                                      Models
   1. Buoyancy Check
Pl/Pr i

P2/P* >
Passive
(Go to '2. or 3.')
                                PUFF
2. Vertically Directed Jet
3. Other
Yes - Ri.> 30
Ri < 30
No - (Go to '3. Other')
BH Criteria > 0.2
BM Criteria < 0.2
Dense
Nondense
Dense
Passive
RVD
PUFF .
B-M
PUFF
2.5  Considerations for Time-Varying  and  Time-Limited Releases

     A release is considered time-varying if  the release rate
varies with time.  Typically,  this behavior might be expected
because the reservoir pressure and temperature  vary with time.
As discussed in Chapter 4, reservoir  pressure and temperature
would be expected to vary with time if  the release rate was very
large in comparison with the reservoir  volume.   For these
conditions, the release rate decreases  with time so that the
maximum release rate can be determined  from initial reservoir
 (stagnation) conditions.  Therefore,  a  screening method which
uses the initial reservoir conditions would be  expected to
overestimate the release rate; this overestimation could be quite
large depending on the situation.

     A release is considered  (only) time-limited if the release
rate is constant over the duration of the r-alease, but the
release duration is short in comparison with  other important time
scales  (e.g., the averaging time  used to  assess the toxicity, or
the cloud travel time to a downwind position  of interest).
Typically, this behavior might be expected if,  for example, an
automatic shutoff system is assumed to  stop the release after a
specified  (generally short) time  period.   The release rate for
time-limited releases can still be estimated  using the screening
                               2-24

-------
methods outlined in Chapter 4; the total amount of material
released Q could then be estimated by Qm Td where  Qm is  the
release rate and Td is the release duration.  (i.e.,  Q = Qm Td)

     Finally, a release may be both time-varying  and
time-limited.  As in the time-varying case, a screening method
which uses the initial reservoir conditions can be used to  (over)
estimate the release rate, and the total amount released Q could
again be estimated by Qm Td where  Qm is the  release rate and Td is
the release duration.  Of  course, the (estimated) total amount
released can not exceed the amount of material on hand  before the
release.
2.6  Denser-Than-Air Materials

     In this workbook, the discussion of gas leaks are for
materials stored as a gas which remains entirely in the gas phase
throughout the depressurization process.  Two-phase leaks can
result for materials which are stored under pressure and will
depressurize when released to the atmosphere.  This
depressurization will then result in the formation of two
contaminant phases  (saturated liquid and vapor).  Two-phase leaks
occur for gases which cool so that condensation occurs during the
depressurization process, and for high volatility liquids
(liquids whose normal boiling point is below the ambient
temperature) which are stored typically above ambient pressure.
For screening purposes, a release from the liquid space is
considered to form an aerosol when the liquid is stored at a
temperature above its boiling point (and ambient pressure); this
assumption becomes more unrealistic as the storage pressure
approaches ambient pressure  (or equivalently as the storage
temperature approaches its boiling point).

     A high volatility liquid is considered to be a material
whose boiling point is below the ambient temperature; a high
volatility material will be released as a liquid if the storage
pressure is near ambient pressure whereas release from high
pressure storage will result in aerosol formation;  aerosol
formation is assumed when the liquid is stored at a temperature
above its (depressurized) boiling point.  In contrast,  a low
volatility liquid is considered to be a material whose boiling
point is above the ambient temperature; a low volatility material
stored at moderate to low pressure (and where the boiling point
is above the storage temperature)  will typically be released as a
liquid and form a pool or puddle on the ground.  Releases of low
volatility materials typically do not exhibit denser-than-air
effects.  Table 2-4 summarizes this information.
                               2-25

-------
                             TABLE 2-4
       (DEPRESSURIZED) RELEASE  PHASE FOR SCREENING PURPOSES*


      Storage Phase                (Depressurized) Release Phase

      Gas                       Gas
                              Aerosol possible (when T2 < Tb)
      High Volatility Liquid           Liquid (TB > T,)
           
-------
been extensively compared to the large number of recent field
test programs aimed at studying denser-than-air contaminants;
some similarity models (e.g., DEGADIS) have been found to
reproduce the range of the field results quite well.
Unfortunately, this success comes at the (modest) cost of
preparation time and user sophistication which may not entirely
fit the mold of a screening program, but in fact, this "state-of-
the-art" implies that proven similarity models should be the next
tool applied if a screening program identifies a release scenario
as a potential problem.

3.   Correlation models are based on a dimensional analysis of
the important parameters which influence the important dependent
variables (e.g., distance to a given concentration level and area
covered by a plume or puff) and on information gathered from
field test results, laboratory results, and other mathematical
models.  The stated objective of a correlation-based model is to
fit the observed data  (on which it is based) within a certain
factor  (typically two).  Because of the nature of a simple
correlation, this approach is well suited for use in a screening
program.  The RVD and the Britter-McQuaid models are derived from
correlations based on different wind tunnel experiments.

     The screening techniques presented here are designed to
identify release scenarios which may violate safety or health
criteria.  The simplifying assumptions inherent in these
screening methods are specifically aimed at decreasing the amount
of information required from the user and decreasing the
computation time and sophistication.  More refined assessment
techniques should be applied to a release scenario which is
identified by these screening procedures as violating safety or
health criteria.  As with any hazard assessment,  these screening
techniques should be applied with due caution.

     Refined release rate estimates may involve more detailed
analysis of the specifics of the release as well as application
of more refined engineering methods (e.g.,  Lees (1980)  and Perry
et al.   (1984)).  Refined atmospheric dispersion models which
account for denser-than-air contaminant.behavior (such as
DEGADIS; Spicer and Havens (1989))  can be applied.   It should be
noted that the screening assumptions inherent in the methods
suggested by Britter and McQuaid (1989) and the RVD model (EPA,
1989)  may become less justifiable for contaminants with more
complicated thermodynamic behavior after release to the
atmosphere -- particularly ammonia (NH3) , liquefied natural gas
(LNG) ,  and hydrogen fluoride (HF) ,  more sophisticated atmospheric
dispersion models may be used to account for such circumstances.
                               2-27

-------
3.0  SUPPORT DATA FOR SCREENING ESTIMATES

     Simulations of air toxic releases require information on the
meteorological conditions at the time of release as well as
physical and chemical parameters describing the materials being
released.

3.1  Meteorological Data

     Computational procedures for estimating concentrations
require data on wind speed and direction, temperature and
atmospheric pressure.  These data are normally collected at
National Weather Service stations and some military installations
on an hourly basis.  Stability and turbulence parameters can be
estimated from cloud data as described below.  A record of these
is available from the National Climatic Data Center, Asheville,
North Carolina and also from the EPA's SCRAM BBS.  On-site
meteorological data are sometimes recorded at air quality
monitoring sites.  Use of the on-site data with proper quality
assurance procedures as described in On-site Meteorological
Program Guidance for Regulatory Modeling Applications (EPA,
1987c) is preferred.

3.1.1  Wind Speed and Direction

     Wind speed and direction data are required to estimate
short-term peak concentrations.  Wind speed is used to determine
 (1) plume dilution,  (2) plume rise and (3) mass transfer in
evaporation models.  These factors, in turn, affect the magnitude
of, and distance to, the maximum ground-level concentration.
  
      Most wind data are collected near ground level.  The wind
speed at release height can be estimated by using the following
power law equation:
                           u =
where:    u  = the wind speed  (m/s) at release height h  (m),
          ut  =    -   the wind speed at the anemometer height z
                    (m),
          p  = the stability-related exponent from Table 3-1.
                               3-1

-------
                              TABLE  3-1
   WIND PROFILE EXPONENT AS A FUNCTION OF ATMOSPHERIC  STABILITY
Stability Class
A
a
c
0
E
F
Rural Exponent
0.07
0.07
0.10
0.15
0.35
0.55
Urban Exponent
0.15
0.15
0.20
0.25
 0.30
0.30
      The wind direction is an approximation for  the direction of
transport of the plume.   The variability of the direction of
transport over a period of time is  a  major factor in estimating
ground-level concentrations averaged  over that time period.

3.1.2   Stability and  Turbulence

      Stability categories, as depicted in Tables 3-1 and 3-2,
are indicators of atmospheric turbulence.  The stability category
at any  given time depends upon thermal turbulence (caused by
heating of the air at ground level) and mechanical turbulence  (a
function of wind speed and surface  roughness). Stability is
generally estimated by a method given by Turner  (1970),  which
requires information  on solar elevation angle, cloud cover, cloud
ceiling height, and wind speed (see Table 3-2).

                              TABLE 3-2
                    KEY TO STABILITY CATEGORIES

Surface Wind *~
Speed at Height
of 10m (m/sec)


<2
2-3
3-5
5-6.
>6


Day



Incoming Solar Radiation"


Strong
A
A-B
B
C
C
(Insolation)

Moderate
A-B
B
B-C
C-0
0


Slight
B
C
C
0
D
Might"

Thinly Overcast or 
4/8 Low Cloud Cover


F
E
D
0
0


5 3/8
Cloud
Cover

F
F
E
D
D
The neutral class (D) should be assumed for all overcast conditions during day or night.

   Night is defined as the period from one hour before sunset to one hour after sunrise.

   Appropriate insolation categories may be determined through the use of sky cover and solar elevation
   information as follows:
                                 3-2

-------
Sky Cover (Opaque or Total)
4/8 or Less or Any Amount of
High Thin Clouds
5/8 to 7/8 Middle Clauds
(7000 feet to 16,000 foot
base)
Solar Elevation
Angle > 60"
Strong
Moderate
Solar Elevation
Angle < 60"
But > 35
Moderate
Slight
Solar Elevation
Angle < 35"
But > 15
Slight
Slight
 5/8 to 7/8 Low Clouds (less
 than 7000 foot base)	Slight	Slight	Slight	

     The  solar elevation angle is a function of the time of year
and the time of day,  and is  presented in charts in the
Smithsonian Meteorological Tables (List,  1968).   The hourly
weather observations of  the  National Weather Service include
cloud  cover, cloud  ceiling height,  and wind speed.  Methods for
estimating atmospheric stability categories from on-site data are
provided  in EPA modeling guidelines.

     Friction  velocity  (u.)  represents mechanical  turbulence  due
to  wind flow over the surface  and is used in calculating the
release Richardson  number.   Friction velocity is a function of
stability, decreasing with increasing stability.  An
approximation  of friction velocity under neutral stability
conditions and assuming  a roughness length of 1 cm is:

     u. = 0.0 6u

where  u is the wind speed (m/s)  at a height of  10 m.

3.1.3  Temperature

       Ambient  air temperature  must be known in  order to calculate
the amount of  rise  of a  buoyant  plume and to calculate
evaporation rates.

3.1.4  Atmospheric  Pressure

     .  Atmospheric pressure data  are used in calculating gas and
liquid release rates  from storage and process vessels and pipes.

3.2  Chemical  and Physical Parameters

     Numerous  chemical and physical properties  of contaminants
are required to perform  some of  the emission estimation
techniques presented.  TSCREEN includes  a chemical database which
contains values  that  can  be automatically returned to data entry
fields.  For information  on the  use of the Chemical  Database see
Appendix D - Running  TSCREEN.    A list of the chemical properties
from TSCREEN's  Chemical Database is shown.in Figure  3-1.
                               3-3

-------
              Figure 3-1.   TSGREEN's Chemical Database
                                Chemical Data
             Chemical Name  %  r /'   ; -  '
             Boiling Point at Ambient Pressure.
             Specific Heat of Liquid
              at Constant Pressure 	
              at Constant Volume 	
             Specific Heat of Vapor
              at Constant Pressure 	
              at Constant Volume 	
             Molecular Weight	
             Latent Heat of Vaporization 	
             Liquid Density	
             Critical Temperature 	
                       J/kg "K
                     / J/kg K

                     -"  J/kg K
                       J/kg '<
                       kg/kmol
                       J/kg
                       kg/cubic m
                  Edit
 Delete
 Exit View. Screen
The  complexity and diversity of chemical and physical behavior of
many air toxic substances make it critical  that the  correct input
parameters  are obtained. These parameters can be found in
compendiums of physical and  chemical  characteristics.  Three of
the  more comprehensive sources of information are  listed in the
reference section.

The  user should be cautioned that a characteristic "constant"
used in modeling may have different values  depending on the
reference from which the parameter was obtained.
                                   3-4

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4.0  SCENARIOS AND TECHNIQUES FOR RELEASE AND EMISSIONS ESTIMATES

     Techniques for estimating air toxics emissions must be
capable of treating a large variety of potential release
scenarios.  This section is intended to help the user identify
the applicable release scenario, determine release and emission
rates, and to guide the user through the scenario inputs into
TSCREEN.  Scenarios addressing various types of particulate,
gaseous, and liquid releases are presented in this workbook.  In
addition there are scenarios typically found at Superfund sites.
If the appropriate scenario choice is not obvious, consult the
descriptions of similar releases that accompanies the graphical
illustrations shown in Section 2.3 or the EPA Regional Modeling
Contacts.

      Since many various processes and sources have the potential
for toxic chemical releases, the scenarios do not cover all
possible release, emission, and dispersion combinations.  In all
applications, the characterization of emissions is a critical
step which is best met through a complete and accurate
measurement program.  In practical applications, measured data
are seldom available and the user is left to techniques such as
those presented in this section, data from existing inventories,
emission factors, or process specific material balance estimates.

     Some of the numerous sources of existing data are permits
and files, technical literature, and SARA Title III reporting
forms.  A new data source summarizing regulatory data is the
National Air Toxics Information Clearinghouse (NATICH) and Data
Base.  Information on NATICH is available through the EPA
Regional Air Toxics Contacts, Air/Superfund Coordinators and :'

               Pollution Assessment Branch (MD-12)
               U.S.  Environmental  Protection Agency
                 Research Triangle Park,  NC 27711
                          (919)  541-0850

     For some sources, mass balances are used to estimate
releases when conservative assumptions concerning quantities of
input and output streams are made.  The amounts entering and/or
leaving a process can be measured or estimated.  A mass balance
can then be performed on the process as a whole or on the
subprocess.  For processes where material 'reacts to form a
product or is significantly changed, use of mass balance may be
too difficult for estimating emissions and the use of emission
factors may be more appropriate.

     When measured or plant specific data are unavailable, the
user is advised to review emission factors developed for specific
processes.  Appendix A provides a description of sources of
emission factors.  Emission factors represent average conditions
and do not necessarily provide a conservative estimate of total
emission rate.


                               4-1

-------
4.1  Particulate Matter Release

     A particulate matter release is a release of any solid
material such as particulates, dust, or ash.

4.1.1  Releases from Stacks. Vents
Similar Releases:  Continuous emissions of particulate matter
from vertical stacks and pipes or conventional point sources and
some process vents when emission flow rates and temperature are
known.  Combustion sources and chemical reactors are typical
emission sources that may emit such pollutants through stacks.
These releases may also be due to a process failure such as a
rupture disk release or failure of control equipment.

Discussion:

     Emission rates from such sources can be determined through
source testing using EPA. Reference Methods  (40 CFR Part 60
Appendix A) or "Screening Methods for the Development of Air
Toxics Emission  Factors", EPA-450/4-91-021 or process
calculations.  If source-specific emissions are not available,
representative emission factors can be substituted.  Emission
factors are available for individual toxic compounds  (Appendix
A).  Otherwise,  factors determined by compiling extensive source
test results using EPA Reference Methods are reported in AP-42.

     Since the input is source specific, there is'no input
section for this scenario.   If this scenario is selected, TSCREEN
directly accesses the SCREEN model input section for a point.
source.  See Section 5.1.1 for a complete list of inputs.
                               4-2

-------
Limitations and Assumptions:

          For screening, particulate deposition  is  assumed to be
          ins igni f i cant.

Input Information:

     D    diameter at release point  (m)
     V    volumetric flow rate  (m3/s)


4.1.1.1  Procedure:.

1.   Exit Velocity.  Calculate  the exit velocity Vs (m/s) through
     a stack as follows:


                             V,  = _LY_                    (4.1.1-1)
                                 7T D2


4.1,1.2  Example:  Cadmium  emission

Discussion:

     A facility .emits 0.0029 tons per  year of cadmium through a
stack that  is 16 meters  above ground.  The stack inside diameter
is 0.1 meters, the stack exit temperature  is  298 K,  and the
volumetric  flow rate is  0.14 m3/s.   The stack is adjacent to  a
square building with height and building dimensions equal to
19 m.  The  site is classified as rural, with  complex terrain
being present.  Concentrations  at'a  receptor  located 25 meters
from the stack is required.

The following information will  be required to use the SCREEN
model  (see  Section 5.1.1):

     B,,^  building maximum  horizontal  dimension  (19 m)
     BJHU,  building minimum  horizontal  dimension  (19 m)
     D    diameter at release point  (0.1 m)
     H,   release height above  ground  (16  m)
     Hb   building height  (19 m)
     Qm   emission rate  (0.0029 tons per year is equal to 9.3x-iO"*
          g/s)
     T,   temperature of the material  released (298 K)
     Ta   ambient temperature  (298  K)
     V    volumetric flow rate  (0.14 m3/s)

Procedure;

1.   Exit Velocity.  Calculate  the  stack gas  exit velocity from
     Equation  (4.1.1-1):
                                4-3

-------
                                     4  .  0.14mVs  =17>8m/s
                                     3.14  (.l)2m2

Data  entry  in the TSCREEN  model  for  this example  is  shown below:
                   Continuous Participate Releases from Stacks, Vents - Scenario 1.1
                  Based on user input, SCREEN model has been selected.

                  SCREEN MODEL INPUTS - Page 1  of 7
                  Enter a unique title for "this data's model run:
                             '''       ......... """ ...... """" ........ '""
                  RELEASE PARAMETERS
                                             Emission Rate (Qm) -> ?,3S?-4   g/s
                                              Exit Velocity (Vs)-> If.tt     m/s
                               Release Height above Ground  14       m
                                  Diameter at Release Point (D) -> .1       m
                       Temperature of the Material Released (Ts) -> 298      K
                  AMBIENT PARAMETER
                                       Ambient Temperature (Ta) -> 298
                    Continuous Participate Releases from Stacks, Vents - Scenario  1.1

                  SCREEN MODEL  INPUTS - Page 2 of 7

                  BUILDING PARAMETERS
                        Building  Height (enter 0 if no building)  -> t9       m
                           Minimum Horizontal Building Dimension  -> 1^       m
                           Maximum Horizontal Building Dimension  -> T9       m

                  URBAN/RURAL CLASSIFICATION
                                 Enter U for Urban - R for Rural  -> B
                   FENCELINE DISTANCE
                   Enter the distance from the base of the stack
                                         to the plant fenceline ->
"'-'8aft "  tr*i f.

                   SIMPLE TERRAIN
                                 Are receptors above stack-base  T

                   SIMPLE NON-FLAT TERRAIN
                    You have terrain between stack  base and stack top.
                             Do you have receptors above ground level
                                     (i.e. Flag Pole  Receptors) (Y/N)  -> K
                          screen
                                                                 $*
                                                 4-4

-------
2.   In  this example,  there are  receptors at or below stack top,-
     therefore, "Y"  is entered for the "terrain type" question.

3.   In  this example,  there are  receptors above stack base;
     therefore, "Y"  is entered,  for the "simple terrain"
     question.

     Since "Y" was entered, proceed to step 5.
     The  question  "Do you have specific locations where you would
     like pollution  concentrations  calculated  (Y/N)" will be
     skipped at this point, but  it  will be asked after the  user
     has  finished  entering terrain  elevations  on page 4 of  7.

     In this example,  receptors  are at ground  level/ therefore,
     "N"  is entered  for the "flag pole receptor" question.

     Since "Y" was entered in Step  3,  proceed  to Step 7.

     The  prompt "You have completed simple terrain inputs.   Do
     you  want to continue with complex terrain (Y/N)" will  be
     skipped at this point but will appear later.
              Continuous Particulate Releases from Stacks, Vents - Scenario 1.1
            SCREEN MODEL INPUTS/SIMPLE TERRAIN STAIRSTEP SEARCH - Page 4 of 7

            Enter distance and terrain elevation for "stair-step search".
            Enter a blank Maximum Distance to stop input.

                      Distance (meters)
                 Minimum           Maximum        Height (meters)
100    fence
200
400
800
1200
            Last Maximum Distance will be extended to 50000 m
                                              IB,,,
                                  ^i'-^                     '
      In  this example,  the terrain  elevations  for four distance
      ranges are shown above.  After entries are  complete a  window
      will  appear with the prompt listed in Step  4.

      In  this example,  there are specific locations  of interest;
      therefore, proceed to Step 8.
                                 4-5

-------
        Continuous Particulate Releases from Stacks, Vents - Scenario 1.1-

       SCREEN MODEL INPUTS DISCRETE RECEPTORS - Page 5 of 7
       Enter a height and distance(s) from the source to terrain feature(s)
       at which a specific receptor Mill be located.
       Enter a blank after the distance to stop inputs for that height.
       Enter a blank height to stop input.
 Height (m)
 **;	:"
Distances (m)
 Height..(m)


Distances (m)

 188 
                            Height (m)
            Height (m)     Height (m)


Distances (m)  Distances (m) Distances (m)
In this example,  the specific locations  of interest are at
distances associated with  terrain heights shown in the
figure above.
  uoniinuous ranicuiaie neieases Tram abacus, vents  scenario i . i
SCREEN MODEL INPUTS COMPLEX TERRAIN - Page 7 of 7
Enter height and distance for receptor location.
Enter a blank Distance to stop input. '


Plume Height -> 18.1 m
Distance to Final Plume Rise -> 152.6 m
Height (m) Distance (m) Height (m) Distance (m)
1 IT ttJB
2 2 155
3 25 ZOO
4 4? fOQa
5
6
7
a
9 - :
10 : : -:-
11
12
13
14
15
16 
17
18
19
20 .
s^^.;i^i^^^^^^
In  this example,  terrain  height  for receptors  above  stack
top and distances  to those  heights are  shown in the  figure
above.   The  figure above  shows that final plume height  is
18.1 m and  the distance to  final  plume  rise is  152.6  m.
This information  is useful  in determining at what elevation
the plume will impact terrain and the user may wish  to  add
other receptor heights at this elevation to ensure
calculating  the maximum concentration.

After the complex terrain inputs  have been entered,  TSCREEN
                              4-6

-------
        runs  the  SCREEN  model  for a point  source.

The SCREEN model  output  is  displayed below:
  *** SCREEN-1.2 MODEL  RUM ***
  *** VERSION DATED  90XXX ***

 Participate Stack Release

 COMPLEX  TERRAIN INPUTS:
    SOURCE TYPE        =    POINT
    EMISSION RATE (G/S) =    .9300E-03
    STACK HT (M)       =    16.00
    STACK DIAMETER (M)  =      .10
    STACK VELOCITY (M/S)=    17.80
    STACK GAS TEMP (K)  =   298.00
    AMBIENT AIR TEMP (IC)=   298.00
    RECEPTOR HEIGHT (M) =      .00
    IOPT  (1=URB,2=RUR)  a     2
1
  *** SCREEN-1.2 MODEL RUN ***
  *** VERSION DATED  91/10 **

 Participate Stack Release

 SIMPLE TERRAIN INPUTS:
    SOURCE  TYPE           =    POINT
    EMISSION RATE (G/S)   -    .9300E-03
    STACK HEIGHT (M)      =    16.00
    STK INSIDE D1AM (M)   =      .10
    STK EXIT VELOCITY (M/S)=  17.8000
    STK GAS EXIT TEMP (K)  =   298.00
    AMBIENT AIR TEMP (K)   =   298.00
    RECEPTOR HEIGHT (M)   =      .00
    IOPT (1=URB,2=RUR)    =     2
    BUILDING HEIGHT (M)   =    19.00
    MIN HORIZ BLDG DIM (M) =    19.00
    MAX HORIZ BLDG DIM (M) -    19.00
      ***************************************
      *** SUMMARY OF SCREEN MODEL RESULTS ***
                                                               11-30-92
                                                               15:05:25
                                              11-30-92
                                              15:05:25
CALCULATION
PROCEDURE
SIMPLE TERRAIN
COMPLEX TERRAIN
BUILDING CAVITY- 1
BUILDING CAV1TY-2
MAX CONC
(UG/M**3)
1.396
3.204
1.717
1.717
DIST TO 1
MAX (M)
105.
100.
28.
28.
rERRAIN
HT (M)
16.
17. (24-HR CONC)
-- (DIST = CAVITY LENGTH)
-- (DIST = CAVITY LENGTH)
 ***************************************************
 ** REMEMBER  TO INCLUDE BACKGROUND CONCENTRATIONS **
 ***************************************************
 BUOY. FLUX
.00 M**4/S**3;   MOW. FLUX =     .79 M**4/S**2.
                                                 4-7

-------
FINAL STABLE PLUME HEIGHT  (N) =    T8.1
DISTANCE TO FINAL RISE  (M)    =   152.6
TERR
HT '
(M)
MAX 24* HR PLUME HT PLUME HT
DIST CONC CONC ABOVE STIC CONC ABOVE STK U10M UST
(M) (UG/M**3) (UG/M**3) BASE (M) (UG/M**3) HOT (M) SC (M/S)
17. 100. 3.204 .1377E
20. 155. .4536E-02 .4536E
25. 200. .1232E-01 .1232E
47. 1000. .1047E-01 .1047E
BUOY. FLUX = .00 M**4/S**3;
*** FULL METEOROLOGY ***
*** SCREEN AUTOMATED DISTANCES *"
*** TERRAIN HEIGHT OF 1
DIST
   STAB  (M/S)  (M/S)    (M)   HT (M)   Y (M)   Z (M)  DWASH
400. .3688
500. .3214
600. .2840
700. .2537
300. .2289
6
6
6
6
6
MAXIMUM 1-HR CONCENTRATION
400. .3688
*** SCREEN AUTOMATED
*******************<
6
1.0
1.0
1.0
1.0
1.0
AT OR
1.0
1.3
1.3
1.3
1.3
1.3
BEYOND
1.3
5000
5000
5000
5000
5000
400
5000
.0
.0
.0
.0
.0
. M:
.0
6.0
6.0
6.0
6.0
6.0

6.0
25
28
32
35
38

25
.7
.9
.0
.1
.2

.7
23
23
24
24
25

23
.3
.9
.4
.9
.4

.3
SS
SS
SS
SS
SS

SS
DISTANCES ***
 *** TERRAIN HEIGHT OF   15. M ABOVE STACK BASE USED FOR FOLLOWING DISTANCES **
                                                    4-8

-------
DIST     CONC            U10M   USTK  MIX HT   PLUME   SIGMA   SIGMA
 (M)   ++<&+++ * * *^*^^**^^ ^ ^^^^













25.4


6=F)













SS
















                                               4-9

-------
 ** TERRAIN HEIGHT OF  10. M ABOVE STACK BASE USED FOR FOLLOWING DISTANCES **

  DIST    CONC           U10M  USTK  NIX HT  PLUME  SIGMA   SIGMA
      (UG/N**3)  STAB  (M/S) (M/S)    (M)  HT (M)  Y (M)   Z (M) DUASH
111.
222.
333.
*** SCREEN
1.230
.5581
.4084
DISCRETE
4
4
6
DISTANCES
**
1
1
1
*
.0
.0
.0
***
***
1.1
1.1
1.3

320
320
5000

.0
.0
.0

'6.0
6.0
6.0

13.0
21.2
23.6

16.0
22.5
22.9

SS
SS
SS

 ** TERRAIN HEIGHT OF   16. M ABOVE STACK BASE USED FOR FOLLOWING DISTANCES **

  DIST    CONC           U10M  USTK  MIX HT  PLUME  SIGMA   SIGMA
   (M)   (UG/M**3)  STAB  (M/S)  (M/S)    (M)  HT (M)  Y (M)   Z (M) DWASH
105.
188.
299.
315.
1.396
.7250
.4471
.4353
4
4
6
6
1.0
1.0
1.0
1.0
1.1
1.1
1.3
1.3
320.0
320.0
5000.0
5000.0
.0
.0
.0
.0
12.6
18.2
22.5
23.0
15.7
20.9
22.7
22.8
SS
SS
SS
SS
 DWASH"  MEANS NO CALC MADE (CONC = 0.0)
 DUASH=NO MEANS NO BUILDING DOWNWASH USED
 DWASH-HS MEANS HUBER-SNYDER DOWNWASH USED
 DWASH-SS MEANS SCHULMAN-SC1RE DOWNUASH USED
 DWASH-NA MEANS DOWNWASH NOT APPLICABLE, X<3*IB
wmr www www www www wwwwwwwwww w www ww w w w w www wwww w
* SUMMARY OF TERRAIN HEIGHTS ENTERED FOR *
* SIMPLE ELEVATED TERRAIN PROCEDURE *
TERRAIN DISTANCE RANGE (M)
HT (M) MINIMUM MAXIMUM
1.
5.
10.
15.
10.
10.
10.
16.
16.
16.
16.
100. 200.
200. 400.
400. 800.
800. 50000.
111.
222.
333.
105.
188.
299.
315.
*** CAVITY CALCULATION - 1 *** *** CAVITY CALCULATION -
CONC (UG/M**3) =
CRIT WS 310M (M/S) =
 CRIT US a HS (M/S) =
DILUTION US (M/S) =
CAVITY HT (M) =
CAVITY LENGTH (M) -
1.717 CONC (UG/M**3) =
1.00 CRIT US 310M (M/S) =
1.10 CRIT US 3 HS (M/S) =
1.00 DILUTION WS (M/S) =
27.28 CAVITY HT (M) =
27.97 CAVITY LENGTH (M) =
ALONGUIND DIM (M) = 19.00 ALONGUIND DIM (M) =











2 ***
1.717
1.00
1.10
1.00
27.28
27.97
19.00
*** END OF SCREEN MODEL OUTPUT ***



At 25  m  from the  stack,  the receptor  is  in  the cavity region  and
the maximum concentration  is 1.72  ^g/m3.    The maximum
concentration,  however,  is  2.21 ptg/ra3  at a distance of  105 m from
the source  in  complex terrain  16 m above "stack base.
                                        4-10

-------
4.1.2
                                  ussions
                                       FugtttoDust
Similar Releases:  Any fugitive dust from process losses,
generated by mechanical action in material handling or windblown
dust.  Such emissions tend to originate from a surface or a
collection of small poorly defined point sources.

Discussion:
     These fugitive dust releases are generalized area emissions
originating from a surface or collection of small, poorly
quantified point sources.  Emissions are either user-specified or
calculated with representative emission factors.  Emission
factors for fugitive dust emissions are typically found in AP-42
and are assumed to be independent of wind speed for this
workbook.  Toxic components can be determined using the methods
described in Appendix A, item 4.  This example demonstrates
calculation of particulate emissions from storage piles and use
of particulate matter profiles to study a specific chemical.

Limitations and Assumptions:

          'Worst case emission estimates are wind speed dependent.

          For screening, particle desposition is assumed to be
          insignificant.

Input Information:
     s
     P

     w
     m
     D
percent silt content (%)
number of days per year with more than 25 mm of
precipitation  (dimensionless)
percent of time wind speed exceeds 5.4 m/s  (%)
pollutant percent of total mass  (%)
diameter of storage pile  (m)
                               4-11

-------
4.1.2.1  Procedure :

l.   Emission Rate.  Calculate emission rate for wind  blown dust
     (QJ  (g/s) :

     A.   Emission Factor.  Calculate the aggregate  storage
          emission factor for wind blown dust:
           E (kg/dy /hectare) =1.9 (s/1.5)      ~   (w/15)   (4.1.2-1)


     B.   Area.  Calculate the area  (A)  (m2)  of the storage pile:


                          A(m2) ="-2                 (4.1.2-2)
     C.   Convert.  Convert the emission factor  (E)  in
          kg/dy /hectare to g/s-m2:

             E (g/s-m2) =  E(kg/dy/hectare) 1000 (g/kg)
                        86400 (s/dy) 1000 (m2/hectare)

     D.   Emission Rate.  Calculation of emission  rate (Qm)  in
          g/s.
                  Qm (g/s) = E (g/s-m2) JJL A (m2)          (4.1.2-3)
2.   Run the SCREEN model for an area source.  For  an  explanation
     of inputs for the SCREEN model for an area  source,  see
     Section 5.1.2.

4.1.2.2  Example:  Emission from Pile of Flyash

Discussion:

     Concentration estimates at the fenceline  (100  m)  are
required for arsenic emissions resulting from wind  erosion from a
circular pile of  flyash  (3 m high, and 10 m  in diameter)  at a
secondary lead smelter blast furnace.  Since the emissions factor
is not directly applicable, conservative assumptions are made
that the silt content is 50 percent, no days have precipitation
in excess of 25 mm and that 20 percent of wind exceeds 5.4 m/s.

The following information will be  required:

     s    percent silt content  (50 %)
     p    number  of days per year  with more  than 25 mm of
          precipitation  (0)
     w    percent of time wind speed exceeds 5.4 m/s  (20 %)
     m    percent of pollutant in  total mass (.3 %)
     D    diameter of storage pile (10 m)


                               4-12

-------
Procedure ;

1.   Emission Rate.  Emissions factors for aggregate  storage are
     available in AP-42 as are particulate matter profiles
     (Appendix A) .  For this example, the profiles  indicate that
     arsenic makes up 0.3 percent of fine particles (less than
     2.5 microns) emissions mass.

     A.   Emission Factor.  Calculate the aggregate storage
          emission factor for wind blown dust from  Equation
          (4.1.2-1) :


       E (kg/dy /hectare) =1.9 (50/1.5)  (3^"0) (20/15) =131.2
                                       * O J

     B.   Area.  Calculate area  (A) (m2)  of the storage pile from
          Equation (4.1.2-2) :


                     A = 3 . 14159 \     =78.5 (m2)
     C.   Convert.  Convert emission factor  (E) in kg/dy/hectare
          to g/s-m2:

       E = 131-5 (kg/dy/hectare) 1000 (g/kg) = Q Q0015 (  /S_m2)
            86400 (s/dy) 1000 (m2/hectare)

     D.   Emission Rate.  Since 0.3 % of this mass is  arsenic,
          calculate emission rate  (Qm)  in g/s from Equation
          (4.1.2-3).


     Qm = 0.00015 (g/s-m2)    '3(%)   78.5 (m2)  = 0 .000036 (g/s)


2.   TSCREEN will run the SCREEN model for an area source.

Data entry in the TSCREEN model for this example  is  shown below:
                               4-13

-------
      Release of Fugitive/Windblown Oust Emissions -  Scenario 1.2
SOURCE PARAMETERS - Page 1 of 1

Enter a unique title for this data's model run:
                                       -!''
SOURCE TYPE
Enter S if source is a storage pile - 0 if other -> |

EMISSION RATE
  Enter the Emission Rate (Qm), if unknown enter
          the boxed variables belou to calculate -> HM18BB& g/s

Percent Silt Content (s) -> 56
Number of Days per Year the Precipitation
exceeds 25 mm (p) -> $
Percent Time Wind Speed exceeds 5.4 m/s (w) -> Z8
Percent of Pollutant in Total Mass (m) > ,3
Diameter of Storage Pile (D) -> t &!:$;? m
                                                       	
URBAN/RURAL CLASSIFICATION
                    Enter U for Urban - R for Rural -> R

FENCELINE DISTANCE
    Enter the distance from the nearest edge of the
                      source to the plant fenceline -> 138      m

FLAG POLE RECEPTORS
            Enter Receptor Height above Ground (Zr) -> 6        m

RECEPTOR LOCATIONS
Do you have specific locations where you would like
    pollutant concentrations to be calculated (Y/N> -> Y

      Edtt:     Abort-
                                4-14

-------

SCREEN MODEL INPUTS
RECEPTOR LOCATIONS:
the source at which
Enter a blank after
Distance from
source (meters)
1 100 fence
2 ft? '
3 333
4 1609
5
6
7
8
9
10 - < _
- Page 2 of 2

Enter (up to 30) distances from
concentrations should be calculated.
the last distance to stop
Distance from
source (meters)
11
12
13 ;
14
15 ;
16
17
18
19
20
input.
Distance from
source (meters)
21 "
22 .
23
24
25
26
27
28
29
30
,a>ftt -
-------
of  the SCREEN  model's data contains  only points  for  the automated
distance  array used  by the model.
Oi
i
    40

    36

    32

    28
                      Em t salons  fVom a P f I oF  F I
iFenceline
 2 24
 ^^
 X
 220

 2 16
 h
 h-
 Z
 UJ
 O
 Z  4
 O
 O
   0,00   0.50
                                    3.00   3.50   4.
4,50    5,!
                               DISTANCE (Km)
        Maximum concentration 3.677E-001 ug/cubic ra at 0,100 Km  (Automated Distances)
                              Press any key to continue
                                    4-16

-------
4.1.3  Ducting/Connector Failures
                    Fugitive
                    Dust  *
Similar Releases:  Instantaneous bursts of particulate matter  due
to duct failure  (e.g., pneumatic conveyor line failures),  line
disconnection, isolation joint failure, or other types of
equipment openings.

Discussion:

     Limited information on powder releases from duct failures is
available in the technical literature.  Crude estimates of
release amounts can be-made based on-transfer line rates and time
for equipment shutdown and equipment capacity.  If possible, the
user should attempt to estimate the initial cloud dimension
resulting from dilution due to the mechanical action of the
release.'  If initial dilution cannot be estimated by the user,
conservative concentration estimates can be obtained using an
instantaneous point source simulation with the PUFF model.  There
is no release rate input section for this scenario.  For this
scenario, TSCREEN goes directly to the PUFF model input section.
See Section 5.3 for a complete list of inputs.

Limitations and Assumptions:

          For screening, particle deposition is assumed to be
          insignificant.

Input Information^

     Q    total amount of material released  (g)
     H,    release height above ground  (m)
     0y    initial laterial dispersion  (m)
     
-------
4.1.3  Ducting/Connector Failures
                    Fugitive
                    Dust  
Similar Releases:  Instantaneous bursts of particulate matter due
to duct failure  (e.g., pneumatic conveyor line failures),  line
disconnection, isolation joint failure, or other types of
equipment openings.

Discussion:

     Limited  information on powder releases from duct failures is
available in  the technical literature.  Crude estimates  of
release amounts can be made-based on transfer line rates and time
for equipment shutdown and equipment capacity.  If possible,  the
user should attempt to estimate the initial cloud dimension
resulting from dilution due to the mechanical action of  the
release.  If  initial dilution cannot be estimated by the user,
conservative  concentration estimates can be obtained using an
instantaneous point source simulation with the PUFF model.   There
is no release rate input section for this scenario.  For this
scenario, TSCREEN goes directly to the PUFF model input  section.
See Section 5.3 for a complete list of inputs.

Limitations and Assumptions:

          For screening, particle deposition is assumed  to be
          insignificant.

Input Information:

     Q    total amount of material released  (g)
     Hs   release height above ground  (m)
     
-------
4.1.3.1  Example:  Failure of a Pneumatic Conveyor System
Discussion:

     A failure of a pneumatic conveyor system carrying 3,3-
dichlorobenzidine powder from a spray dryer lasted 5 minutes.
Estimates are required for 15-minute average concentrations at
receptors downwind at or beyond the 100 m fenceline.  The release
height is 10 m, the conveyance rate is 2 kg/s and the duct
diameter is 0.305 m.

     The example represents a class of possible releases from
various types of gas-solid conveyance systems or reactor
failures.  Common causes of this type of release are duct failure
due to abrasion or failure of flexible connectors.  Short.
duration events can be simulated as instantaneous passively
dispersing puffs  (i.e., all mass was released instantaneously
 (within a few minutes)).  The effect of this assumption is a
conservative estimate of the ambient concentration.  In general,
powders emitted by this type of release will consist of
relatively large particles  (greater than 10 /z) which would be
subject to gravitational fallout.

Procedure:

1.   The release scenario would result in an initially high rate
     of emissions which decreases rapidly as line pressure
     decreases, as in a pipeline blowdown.  A point source is
     assumed because there was no indication of initial dilution
     dimensions in the problem.  The total emissions  (Q) is:

       Q =  5(min)  60(s/min) 2(kg/s) 1000(g/kg)=  600,000(g)

2.   The release height is 10 m above ground, the initial lateral
     and vertical dispersion parameters are 0 m, and the
     fenceline distance is 100 m.

Data entry in the TSCREEN model for this example is shown below.-
                               4-18

-------
                                 Ducting/Connector  Failures - Scenario 1.3
                  Based on use input, PUFF model  has been selected.

                  PUFF MODEL INPUTS - Page 1  of 2
                  Enter a unique title for this data's model run:
                  ⁢i^iS*^sbi^BSi^:.'    s   "::./.   :
RELEASE PARAMETERS
           Total Amount of Material Released (Q)  ->
               Release Height above Ground (Hs)  ->  t(
                Initial Lateral Dispersion (.ay)  ->  ft
               Initial Vertical Dispersion (oz)  ->  $'

FENCELINE
 Enter the distance  from the nearest edge of the
                  source to the plant fenceline  ->  tf
                                                                              9
                                                                              m
                                                                              m
                                                             JJBjct Scrwan    <6E.c> fibcrt
                                 Ducting/Connector  Failures - Scenario 1.3
                   PUFF MODEL INPUTS - Page 2 of 2

                   AVERAGING TIME
                   Select Desired Averaging Time from menu below for graphic output:
                                        Instantaneous  (1 second)
                                        1 minute      (60 second)
                                        5 minutes     (300 seconds)
                                        1 hour        (&0fii seconds)

                   Selected Averaging Time: 15 minutes  (900 seconds)


                     &di     J>r*viOos Screen    F1S> (ton Model    
-------
     REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS  **
    noil  <> i>**<>i>i>i>*i> ***
 * >> ********

 ***      PUFF DISTANCES      ***
 rll>* >>*********


 THE MAXIMUM CONCENTRATION AS A FUNCTION Of DOWNWIND DISTANCE
 AND THE CONDITIONS THAT PRODUCED THE MAXIMUM AT THAT DISTANCE.
 MIXING HEIGHT  (M)   320.
 WIND SPEED (M/SEC)    1.0

 AVERAGING                       DOWNWIND DISTANCE (KM)
 TIME (MIN)  MAXIMUM CONCENTRATION (G/M**3) AT  VARIOUS DOWNWIND DISTANCES.
                STABILITY CLASS THAT PRODUCED  THE MAX. LISTED BELOW
            0.01      0.03      0.05  '    0.07       0.1       0.5
 ====3Z======r=======X==3==33S=============================================
 INST.   3.997E-I-01 3.376E+02 1.748E+02 9.261E+01 4.288E+01  1.359E+01
              U         U         U        U        U        N
 1      2.005E+00 4.531E+01 3.745E+01 2.701E+01 1.732E+01  9.327E+00
              U         U         U        U        U        N
 5      4.009E-01 9.062E+00 7.490E+00 5.403E+00 3.472E+00  2.073E+00
              U         U         U        U        U        N
15     1.336E-01 3.021E+00 2.497E+00 1.801E+00 1.157E+00  6.910E-01
              U         U         U        U        U        N
 60     3.341E-02 7.551E-01 6.242E-01 4.502E-01 2.893E-01  1.728E-01
              U         U         U        U        U        N
 AVERAGING                       DOWNWIND DISTANCE (KM)
 TIME  (MIN)   MAXIMUM CONCENTRATION (G/M**3) AT VARIOUS DOWNWIND DISTANCES.
                 STABILITY CLASS THAT  PRODUCED THE MAX. LISTED BELOW
            1.0      3.0      5.0      7.0     10.0     30.0
 =========================r====================3======3r=r==================
 INST.   3.239E+00 5.931E+00 2.976E+00  1.637E+00 8.060E-01  7.088E-02
              S        S        S        S        S        S
 1 '     2.610E+00 4.759E+00 2.709E+00  1.554E+00 7.837E-01  7.061E-02
              N        S        S        S        S        S
 5      8.487E-01 1.232E+00 9.742E-01  7.200E-01 4.701E-01  6.436E-02
              N        S        S        S        S        S
*15     2.829E-01 4.108E-01 3.248E-01  2.411E-01 1.630E-01  3.736E-02
              N        S        S       .S        S        S
 60     7.072E-02 1.027E-01 8.119E-02  6.027E-02 4.076E-02  9.529E-03
              N        S        S        S        S        S

 STABILITY CLASSES
 U = UNSTABLE
 N = NEUTRAL
 S = STABLE

 * INDICATES AVERAGING TIME THAT WAS SELECTED FOR PLOTTING

********************************
*** END OF PUFF MODEL OUTPUT ***
********************************
        The  following  is  a  graph  of  the  PUFF  model  output.   The  data
that  are  plotted  are  for the  averaging time  that the user
selected  from  the second page  of  the  PUFF  model  inputs.   These
data  are  marked with  an  asterisk   (*)  above.
                                               4-20

-------
     20
                   R 16
     u
  3
   2 12
   ^^
   X
   z18
   2  8
   t-
   Z
   U
   o
   o
      0
   Ipencaline

   I
   J
   I
   I
   1
a 00   i.i
2.00   3.00   4.00   5.00   6.1
                                            7.1
a 00   9.00  10.00
                            DISTANCE (Km)
            Maximum concentration 1.177EH306 mlcrograras/abic meter at 0.221 Km
                           Press any key to continue
This is a plot  of maximum concentration regardless of
meterological conditions.   For example close to the source
unstable conditions  produce the maximum concentrations.   Beyond 3
km stable conditions produce the maximum concentration.

     The output of  the PUFF model consists of four parts.   Part 1
summarizes  the  input parameters by the user.  These values shoud
be checked  to insure accurate entry.  Part 2 of the model output
is a table  that provides the maximum concentration and  the
distance to maximum concentration for different averaging times.
In this table the minimum distance for concentration calculations
is the fenceline.   For near surface releases, highest
concentrations  will  always occur at the fenceline.  Part  3 of the
output is an extended table showing the maximum concentration
versus downwind distance (beyond fenceline) for four averaging
times and the atmospheric stability conditions that produced the
maximum.  For a surface release, stable atmospheric conditions
produce maximum concentrations for all downwind distances and
averaging times.  With increasing puff release height the
atmospheric stability conditions which produce the maximum
surface concentrations change.  In this example, where  the
release hiehgt  is 10 m, unstable atmospheric conditions produce
                                4-21

-------
the maximum concentrations near the source.  It is the values
from this table that are used to produce the plot of maximum
concentration versus downwind distance shown in the fourth part
of the output of the PUFF model.  The plot, however, only
displays the averaging time selected by the user.   : -
                              4-22

-------
4.2  Gaseous Release

     A gaseous release is a release of any matter in vapor  form
such as sulfur dioxide, volatile organics, etc.

4.2.1  Continuous Flared Stack Emissions - Gaseous
                                Emissions
                    Flare
Similar Releases:  Flares are used as control devices for a
variety of sources.  As such, flares must comply with
requirements specified in 40 CFR 60.18.  Once emissions are
vented through the flare, a minimum 98% reduction of all
combus-tible components of the original emission must be achieved.

Discussion:

     Flare problems are done in two parts, an emission
calculation and dispersion modeling.  Toxic emissions for
permitted flares are reduced to 2% of the potential emissions
based on a required control efficiency of 98%.  Flare problems
are similar to stack examples except that there are buoyancy flux
reductions associated with radiative heat losses and a need to
account for flame length in estimating plume height.

     Flares are used as a control device for a variety of
sources.  As such, flares must comply with requirements specified
in 40 CFR 60.18  if the flare is subject to the requirements of
Part 60 (New Source Performance Standards) or Part 61  (National
Emission Standards for Hazardous Air Pollutants).  Not all flares
are subject to these requirements.  Properly designed and
operated flares  should be able to meet a 98% control requirement,
however, the actual control efficiency will depend on .whether the
flare is steam or air assisted,, whether the gases are combusted,
whether an auxiliary fuel is used for combustion of low heat
                               4-23

-------
content gases, etc.  Refer to AP-42  (EPA,  1985)  Section 11.5,
"Industrial Flares", when estimates  of  flare  emissions are
needed.  There is no release rate  input section for this
scenario.  For this scenario, TSCREEN goes immediately to the
SCREEN model  input  section for  a flare  source.   See Section 5.1.1
for a complete list of SCREEN model  inputs.


Limitations and Assumptions:

          Approximately 45% of  the total heat release is assumed
          to  be radiated as sensible heat.
Input Information:

     Hj    total heat release  rate  (J/s)
     H,    physical stack height  above  ground (m)
     Hsl   effective release height before  plume rise (m)
     M,,,   molecular weight of material released (g/g-mole)
     V    volumetric flow rate to the  flare  (m3/s)
     vol  volume fraction of  pollutant (%)
     fj    volume fraction of  each component  of  the flare  input
          gas
     Hj    net heating value of each  component  (J/g-mole)

4.2.1.1  Procedure :

1.   Emission Rate  (Qm) .  Calculate  the emission  rate  in  g/s:

                              V(mVs) Mw(g/g-mole)  0.02
     Q  (g/s)
      m
                           0.0224(m3/g-mole)
     Total Heat Release Rate  (H,)  (m) .   Calculate the total heat
     release rate from the  flare gas combustion (Lahey & Davis,
     1984) :
                                     n
                      Hr  = 44.64 V   fj  Hj             (4.2.1-2)
                                    i-l

     where the value 44.6 is  derived for air  as:
                pair(g/m3)   _  1292.
              Mw (g/g-mole)   28.97
                                   =44.6(g-mole/m3)
     and the summation is over the n  components  of  the flare
     input gas stream.

3.    Effective Release Height above Ground  (H^).  Calculate the
     effective release height by adding  the  flare height  to the
     stack height, as follows  (Beychok,  1979) :
                               4-24

-------
                  Hsl  = Hs  +  4.56xlO-3(     ..b)a478        (4.2.1-3)
     where 4.1868 is a conversion factor  (Joules  to  calories) .
     Plume rise for the combusted gas is  calculated  in the SCREEN
     model for this effective release height  (EPA, 1988c).

4.2.1.2  Example:  Flare Emission

Discussion;

     A gas is sent to an elevated flare to be burned.   For,
simplicity, it is assumed that the flare  is a permitted one.   The
gas is a mixture with one toxic component.  The gas  stream is
made up of 50% methane, 9.8% ethane, and  40% carbon  dioxide and
.2% benzene.  Maximum one-hour concentrations are required for
benzene assuming 98% reduction efficiency of the  flare.   There is
a cubical building, 19 m in height, next  to this  flare.   The
fenceline is 100 m from the flare.

The following input information will be required:

     HT    total heat release rate  (3.84xl07 J/s)
     H,    physical stack height above ground  (32  m)
     Hsl   effective release height  (m)
     M,,   molecular weight of material  (78.1 g/g-mole)
     V    volumetric flow rate  (6.58 m3/s)
     vol  volume fraction of pollutant in feed gas (0.2 %)

Procedure:

1.   Emission Rate (Qm) .  Calculate the emission  rate  in g/s.
     Determine the emission rate of benzene from  the volume
     fraction, molar volume, flow rate, and molecular  weight.
     The volume of benzene is the volume  fraction of pollutant
      (vol) times material flow rate  (V).  Mass emission rate (Qm)
     after controls is given by determining the number of moles
     in the benzene fraction and multiplying by the  molecular
     weight  (the gas is assumed to be at  standard conditions
     considering the control efficiency)  from Equation (4.2.1-1) :

Q  (g/s)  =  -002   6.58(m3/s)   78.1 (g/g-mole) -0.02  =   Q  918 (g/s)
                       0.0224(m3/g-mole)

2.   Total Heat Release Rate  (HT)  (m) .   The user calculates che
     total heat release  (Hr)  from the flare  from Equation
      (4.2.1-2).  In this example, carbon  dioxide  is  not
     combustible and is assumed not to affect flame  heat.   Total
     heat generated by the flame is determined using mole
     fractions, molar flow rate, and heats of combustion for
                               4-25

-------
      methane,  ethane,  and  benzene  (see references for physical
      constants).

      H^J/s)-    (44.64  g-mole/m3)  6.58 m3/s  [0 .5 (8 .0286xl05  J/g-
                   mole) + 0.098  (1.4288xl06 J/g-mole)  +  0.002
                   (3.2696xl06 J/g-mole)]

                         1.61 x 108  (J/s)   (or 3.84X107   (cal/s))
      Effective Release Height above  Ground  (H^).   The effective
      release height is calculated from Equation (4.2.1-3):-
                     32  + 4.56x10
                     -3     (1.61X108)-478  = 51.26  m
                          4.1868
      Dispersion calculations  for  this scenario  are  made using  the
      SCREEN model  for a  flare.

Data entry in the  TSCREEN model for  this  example is shown  below.-
              - Flared Stack Emissions - Scenario 2.1
               Based on user input, SCREEN model has been selected.

               SCREEN MODEL INPUTS - Page 1 of 7   
               Enter a unique title for this data's model run:
               * :>''v':''x'^'::              ........
RELEASE PARAMETERS
Enter the Emission Rate (Qm), if unknown enter
      the boxed variables below to calculate ->
                                                           g/s
                         Volume Fraction of Pollutant  :fJC?: %
                         Volumetric Feed Gas Flow Rate (V) -> &i.5&.;':H; cubic m/s
                         Molecular Weight of Feed Gas (Mw) -> 7g&;:W g/9 mole
                                Total Heat Release Rate -> f,{&&''? J/s
                             Release Height above Ground -> 3Z;v ' :   m
                                           ?MG>:-*lext:.Scre-
                           Flared Stack Emissions - Scenario 2.1
               SCREEN MODEL INPUTS - Page 2 of 7

               BUILDING PARAMETERS
                   Building Height (enter 0 if no building) -> 19?  r::;
                      Building Minimun Horizontal Dimension -> tSt""^-..
                      Building Maxinun Horizontal Dimension -> T5'

               URBAN/RURAL CLASSIFICATION
                          Enter U for Urban - R for Rural -> 8

               FENCELINE DISTANCE
                Enter the distance from the base of the stack
                                 to the plant fenceline -> 1:SO;::::.::,
                                             m
                                             m
                                             m
                                       4-26

-------
A summary of  the  SCREEN  model's  output for this  example  is  shown
below.
  *** SCREEN-1.2 MODEL RUN ***
  *** VERSION DATED  90XXX ***

 Release from Flare  Source

 SIMPLE TERRAIN INPUTS:
    SOURCE TYPE           =   FLARE
    EMISSION RATE (G/S)    =   .9177
    FLARE STACK HEIGHT (M) =   32.00
    TOT HEAT RLS (CAL/S)   =   .3840E+08
    RECEPTOR HEIGHT  (M)    =     .00
    IOPT (1=URB,2=RUR)     =    2
    EFF RELEASE HEIGHT *****
      *** SUMMARY OF SCREEN MODEL RESULTS ***
CALCULATION
PROCEDURE
MAX CONC
(UG/M**3)
DIST TO
MAX (M)
TERRAIN
HT (M)
 SIMPLE TERRAIN
.5505
1243.
15.
 ************************>***********
 ** REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS **
 ************i>*i>i>*i>** ><*>***
                                               4-?7

-------
4.2.2     Continuous Release from Stacks. Vents. Conventional
          Point Sources
Similar Releases:  Continuous emissions of gases  from building
vents, vertical stacks and pipes or conventional  point  sources
when emission flow rates and temperature are known.  These  "
results may also be due to a process failure such as a  rupture
disk release or failure of control equipment.  .

Discussion:

     Continuous emissions of gases from stacks are analyzed in
this scenario.  Emission factors are "available for individual
toxic compounds for some processes  (Appendix A, items 1,  2,  and
3).  In other cases, total VOC emission rates can be obtained
from AP-42.  To determine toxic components of these emissions,
see Appendix A item 4.

Limitations and Assumptions:

          Release behaves as an ideal gas
          Release is neutrally buoyant

Input Information:

     D0    diameter at release point  (m)
     M3    mean molecular weight  (g/g-mole)
     R    gas constant  (8314 Pa-m3/kg-mole-'K or
          8314 J/kg-mole-K)
     Qm   total material emission rate  (g/s)
     Ta  .  ambient temperature  (K)
     T,    temperature of material released  (K)
     V    volumetric flow rate  (m3/s)
     H,    release height above ground  (m)
                                                     

                               4-28

-------
4.2.2.1  Procedure;

1.   Density Check.  The user should choose to perform  a  density
     check if the release material is thought to be denser-than-
     air.  TSCREEN will help the user determine if the  release is
     buoyant  (passive gas) or denser-than-air.  If the  release is
     thought to be buoyant (e.g., a very hot plume from an
     incinerator, power plant, furnace, etc.), then a density
     check need not be performed.  To perform a density check,
     proceed to step 2.  Otherwise, proceed to step 4.

2.   Buoyancy Check.

     A.   Mean Molecular Weight  (M,) .   Determine  the mean
          molecular weight of the gas stream using the  method
          described in Appendix B:
                         M
                              i-1
                                        -1
(4.2.2-1)
          where:    n^ =  mass  fraction of each component
                    Mj =  molecular weight of each component
                     (g/g-mole)

     B.   Discharge Density.  Calculate  the discharge  density p2
           (g/m3)  using the ideal gas law:
                                                         (4.2.2-2)
          where P, is the ambient pressure (assumed to equal
          101325Pa) .

     C.   Density of Air .  Calculate  the density of  air pair
           (kg/m3)  using the ideal gas law:
          where  P, is the ambient pressure (assumed to equal
          101325Pa) ,  and Ma is the molecular weight of air
           (assumed  to equal  28.9  kg/kg-mole) .
     D.   Perform Buoyancy Check
           If  -Li
              Pr
                               4-29

-------
          buoyancy is negative and the release is denser-than-
          air.  If buoyancy is negative proceed to step 3.
          Otherwise, buoyancy is positive and the release is
          assumed to be passive  (i.e., not denser-than-air).  If
          buoyancy is positive proceed to step 4.

3.   Richardson Number.  Perform release Richardson number  (Ri)
     check:
                      Ri = 2725 I, "  - 1 -              (4.2.2-4)
                                 1000 -D
                                       0
     where 1000 is used to convert the densities from kg/m3 to
     g/m3.   Emission rates (Qm) must be calculated  from process
     parameters or determined from representative emission
     factors.  If there are emission factors, then convert to
     emission rate by multiplying by production rate:


        AP-42     f   Ib   ]   production f 1000ft2] _ emission/ lb\
   emission factor 1000 ft2       rate    [  5r   J~   rate  \hr/

   emission rate (g/s) = emission rate (Ib/hr)   conversion factor

     See Section 2.4 for a discussion of the Richardson number.
     If Ri is a 30 then the release is passive.  Otherwise, the
     release is dense.

     Exit Velocity.  Determine stack gas exit velocity (Vs)
     (m/s) -.


                                                         (4.2.2-5)
     where: V = volumetric flow rate  (mVs)

5.   If the release is passive, then TSCREEN runs the SCREEN
     model for a point source.  If the release is dense, use
     Scenario 2.3 - Continuous Gaseous Leaks from Holes in Tanks,
     Pipes, Relief Valves.

4.2.2.2  Example: Hydrogen Cyanide  (HCN) release

Discussion:

     Hydrogen Cyanide  (HCN) is released from a vent stack at a
rate of 0.2 tons/day.  The stack is 16 meters above ground, has
an inside diameter of 0.1 meter, the stack exit temperature is
298 K and the volumetric flow rate is 0.14 m3/s.   The stack is
adjacent to a square building with height and width dimensions


                               4-30

-------
equal to 19 m.  The site is classified as rural',  non-complex
terrain.  Hourly maximum concentration estimates  are  required.
This example represents a continuous release of a gas with a
specified emission rate through a stack with possible building
downwash due to the influence of an adjacent building.   The
fenceline is 100 meters form the vent stack.

The following input information will be required:

     D    diameter at release point  (0.1 m)
     1^   building height  (19 m)
          building minimum horizontal dimension  (19 m)        -
          building maximum horizontal dimension  (19 m)
     M,   mean molecular weight  (kg/kg-mole)
     Qm   total material emission rate  (2.13 g/s)
     R    gas constant  (8314 Pa-mVkg-mole- K or
          8314 J/kg-mole-K)
     Tt   ambient temperature  (298 K)
     T,   temperature of material released  (298 K)
     V    volumetric flow rate of material released  (0.14  m3/s)

Procedure :

1.   Density Check.  A density check will be performed for this
     example, therefore, proceed to step 2.

2 .   Buoyancy Check .

     A.   Mean Molecular Weight  (M,) .   Stack tests show that HCN
          (molecular weight 27) is the primary constituent (13%)
          besides air in the gas stream.  Mean density is
          calculated as follows using Equation  (4.2.2-1):


                 Ms = -  i - _ =28.7 kg/kg-mole
                      . o /    . -L-i
                     28 .9   ~2~T

     B.   Discharge Density.  Calculate the discharge density p2
          (kg/m3)  using  Equation (4.2.2-2):


                                                        ' H. 2.2-2,
     C.   Density of Air  .  Calculate  the density  of  air
           (kg/m3)  using Equation (4.2.2-3):
     D.   Perform Buoyancy Check.   Since discharge  density is
          less  than air density  ( 1.17 (kg/m3) /1. 18 (kg/m3) < 1) ,
          the release  is positively buoyant .   Proceed to step 4

                               4-31

-------
4.     Exit Velocity.   Calculate  stack gas exit velocity  (Vs)   (m/s)
       using  Equation  (4.2.2-5):

                               =   4    0.14   = 17>8m/s
                             '    3.14 (.I)2

5.     Since  the release is passive,   dispersion calculations  for
       this  scenario  are made  using the SCREEN  model  for a point
       source.
Data  entry in the TSCREEN model for  this example is shown below:

             	Continuous Releases from Stacks, Vents, Point Sources - Scenario 2.2 	1

                SOURCE PARAMETERS - Page 1 of 2

                Enter a unique title fijr this data's model  run:
                GAS DENSITY
                BUOYANCY CHECK
Do you want to check for release
            gas density (Y/N) -> |

        Discharge Density (|?) -> 1.173638 kg/cubic m
                        Temperature of Material Released (Ts)  -> 98     "K
                           Exhaust Gas Molecular Weight (Mw)  -> 2S7    kg/kg-mole
                                  '  Density of Air (fair)  -> 1.181817 kg/cubic m
                                  Ambient Temperature (Ta)  > J98(;::i*i K
                Buoyancy is Positive
                 F2,fefit   <&>> Previous Sfrrsen
                           Steam*    -.-f3iwv.; 
                Continuous Releases from Stacks, Vents, Point Sources - Scenario 2.2
                Based on user input, SCREEN model has been selected.

                SCREEN MODEL INPUTS - Page 1 of 6
                RELEASE PARAMETERS
                                      Emission Rate (Om) -> 213;'';: : g/s
                                          Exit Velocity -> 17,8    m/s
                                 Diameter at Release Point -> .1   ;   m
                               Release Height above Ground -> 16   ;   m

                BUILDING PARAMETERS
                     Building Height (enter 0 if no building) -> T9      m
                       Building Minimum Horizontal Dimension -> 19      m
                       Building Maximum Horizontal Dimension -> 1$   -  m

                URBAN/RURAL CLASSIFICATION
                            Enter U for Urban - R for Rural -> 8

                FENCELINE DISTANCE
                 Enter the distance from the base of the stack
                                   to the plant fenceline -> 100   .  m
                                                                    ftfaort
A summary  of  the SCREEN  model's output  for this  example  is  shown
below.
                                         4-32

-------
  *** SUMMARY OF  SCREEN MODEL RESULTS
CALCULATION
PROCEDURE
SIMPLE TERRAIN
BUILDING CAVITY- 1
BUILDING CAVITY-2
>*
MAX CONC
(UG/M**3)
.8543
1.717
1.717
**
DIST TO
MAX (M)
100.
28.
28.
TERRAIN
HT (M)
0.
" (
" (
                                              (DIST a CAVITY LENGTH)
                                                   = CAVITY LENGTH)
REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS **
                             4-33

-------
                             \
4.2.3  Continuous Gas-Leaks from a Reservoir

4.2.3.1  Release Rate Estimates':  Gas Leaks from a Reservoir
                                       Emissions

                   Leaking flange
Similar Releases;  A gas leak from a tank, a  (small) gas leak
from a pipe, or gas discharge from a pressure relief valve
mounted on a .tank.

Discussion:

     This procedure applies to a continuous release of a gas  (at
constant pressure and temperature) from a containment  (reservoir)
through a hole or opening.

Limitations and Assumptions:

     The hole or opening size must be sufficiently small,
otherwise the reservoir temperature and pressure may no longer be
constant.  For the case of a leak from a tank, the assumption of
constant reservoir temperature and pressure may be violated if a
significant percentage of the tank contents is released.  For the
case of a leak from a pipe, the assumption of constant
temperature and pressure may be violated if /? > 0.2
(approximately) with  as defined below,- if  > 0.2, the scenario
described in Section 4.2.5 may be appropriate.  If the reservoir
temperature and pressure are not constant, the release race mav
vary with time, but the maximum release rate is generally
obtained for the initial reservoir temperature and pressure
(Spicer, 1992).

    _The released material must be an ideal gas at the reservoir
conditions, during the depressurization process, and after
depressurization to the atmosphere.  For the case of a tank


                               4-34

-------
                     \
containing vapor .and liquid,  the hole must be in the vapor .space
of the tank.

Input Information:

     AQ    area of reservoir hole or opening (ra2)
     AI ,  flow area  representing reservoir conditions  (m2)  (In
          case of a  leak from a tank,  Aj -   (and /3  =  0) ;  in the
          case of a  leak from a pipe,  Aj is the  cross-sectional
          area of the pipe.)
     Cp    gas  (contaminant) heat capacity at Tt  (J/kg-K)  (For
          contaminant mixtures,  see Appendix B)
     D0    (equivalent)  diameter of hole or opening  (D0 =
          2-^Ao/ir )  (m)
     ^   gas  (contaminant) molecular weight (kg/kg-mole)  (For
          contaminant mixtures,  see Appendix B)
     Pv    vapor pressure as a function of temperature  (Pa)  -
     Pt    ambient pressure  (Pa)
     P!    reservoir  pressure  (Pa)
     R    gas constant  (83*14  J/kg-mole-K or 8314
          Pa -mVkg-mole  K)
     Tb    contaminant normal  boiling point (K)
     Tc    critical temperature (for contaminant mixtures, see
          Appendix B)
     T!    reservoir  temperature (K)
     j8    y/Ao/Aj   (dimensionless)
     7    (Cp/C,,) - 1/(1 - R/(CpM)) at Tt (dimensionless)
     \    heat of vaporization at the normal boiling point  (J/kg)
     P!    contaminant density at reservoir conditions  (Tt and pv)
          (kg/m3)

Procedure:

1.   Choked Flow Pressure.  Estimate the choked flow pressure P,
     to determine if the flow is choked from Perry et al.  (1984):

                          P.   /   2  \ T'fr'1)
                          -1  =  i_             '         (4.2.3-1)
                          PI   IT * I/

     If P. * P,, then the flow is choked;  go to step 2.  If P. <
     P.,  then the flow is subcritical  (not choked) ;  go to step 3 .

2.   Choked Flow.  For  choked flow,  estimate the gas temperature
     T,  when the pressure is  P.,  the emission rate Qm/  and the
     discharge temperature  T2.

     A.   Estimate T*.   Estimate T* as follows:

                            T.
                                 ,^,                   (4.2.3-2)
                             Li
                               4-35

-------
     This estimate of T, must be checked to see if Equation
     (4.2.3-2) applies.  If T. is greater than the (pseudo)
     critical temperature Tc,  Equation (4.2.3-2)  applies; if
     not, the following procedure is  suggested.   For  single
     component contaminants, evaluate the  contaminant vapor
     pressure at T, (PV(T.))  using the Clausius-Clapeyron
     equation:
                            IN    r         *i i

                            TT   ?  ~ T-
                             R   1T   T- J J

     If PV(T.) s P,  then contaminant  condensation occurs
     during the process of depressurization,  and  this
     approach is not valid; this release should be
     considered a two-phase release.  If the  release  is  two-
     phase go to step 5  (Section 4.2.3.2).

B.   Estimate Emission Rate.  Estimate the emission rate Qm
     (kg/s) as follows from Perry et  al.  (1984):
                                                    (4.2.3-3)


     where C = 0.75  (when P, = P,; when P. > Pa/ C can be
     higher).

     Estimate Discharge Temperature.  Estimate the  discharge
     temperature T2 (after depressurization).   (T2 is
     estimated assuming the expansion from reservoir
     conditions to choked conditions occurs adiabatically
     and reversibly; the expansion from  choked conditions to
     atmospheric pressure is  assumed to  occur adiabatically
     but not reversibly.  After Lewitt  (1953), assume  this
     adiabatical  (irreversible) expansion  is  85% efficient.)
     T2 is  estimated using:
                                / ..  i \ \
                                                    (4.2.3-4)
      (Note that T2 > T,.)  Proceed to Step  4.

Subcritical Flow.   For  subcritical  (not  choked)  flow,
estimate the emission rate Qm and the discharge  temperature
T2.

A.   Estimate Emission  Hate.  Estimate the emission rate Qm
      (kg/s) as follows  from Perry et al.  (1984)':


              Qm = KYA0[2Pl-  (Pj-P. I]'"          (4.2.3-5)
     where

                     K - C / ^ 1 -04


                          4-36

-------
                                                 \

                          IP _ p 1
                         _L	!_  (0.41 H- 0.35 04)   ,
                           PI 7  J

          where C = 0.62.   (Although C  can be-larger  for Reynolds
          numbers less than 104,  typical Reynolds numbers for
          these applications are larger than 104.)

     B.    Estimate Discharge Temperature.  Estimate the  discharge
          temperature T2  (after depressurization).   T2 is
          estimated from energy balance considerations (Lees,
          1980):


                   T2 = 2 T! / [ 1 + ( 1 + 4 a T! ) 1/2 ]          (4.2.3-6)
          where

                       ~  2-v c1  I "P"  MA"
                           ' S>  ^ e    mv **0 J


          The estimate of T2 must be checked.   If T2 is greater
          than the (pseudo) critical temperature Tc,  the equation
          used to estimate T2 applies;  if not,  the following
          procedure is suggested.  For  single component
          contaminants, evaluate the contaminant vapor pressure
          at T2 (PV(T2)) using the Glausius-Clapeyron equation:
                 Pv = 101325 exp
                                I     I  b

          If PV(T2) si P.,  then contaminant condensation occurs
          during the process of depressurization, and this
          approach is not valid; this release should  be
          considered a two-phase release.  If the release is two
          phase go to step 6  (Section 4.2.3.2).

4.   Discharge Density.  Estimate the discharge density  p2 from
     the discharge temperature T2 using the ideal gas law: p2 =
     P,MW/RT2 where R * 8314 (Pa-mVkg-mole- K) .   (Note that
     correct application of a dispersion model may  require that
     the diameter of the hole or opening be modified  to
     D0(P.T2/(P.T,))1/2 for choked flow and D0(p1/p2)1/2 for subcritical
     flow if the model accounts for intial air dilution  due to
     jetting or momentum effects using an  initial velocity
     estimate; if this modification is not applied, the  initial
     gas velocity is incorrectly over estimated.  This correction
     is not needed in TSGREEN).  Go to step 7  (Section 4.2.3.3).
     to select the appropriate dispersion model.

     If the screening procedure above indicates that  partial
condensation of the released gas occurs, the following section
should be used.
                               4-37

-------
4.2.3.2   Continuous  (Two-Phase) Release Rate Estimate:  Gas
          Storage which Partially Condenses on Depressurizat ion.

Similar Releases;  A gas leak from a tank, a gas leak from a
pipe, or gas discharge from a pressure relief valve mounted on a
tank.

Discussion:

     Materials which are stored under pressure will depressurize
when released to the atmosphere.  This depressurization can
result in the formation of two contaminant phases  (saturated
liquid and vapor) for: gases which cool so that condensation
occurs during the depressurization process/ and high volatility
liquids  (liquids whose normal boiling point is below the ambient
temperature) which are stored at above ambient pressure
(typically).  (See Section 4.3.2 for more discussion on two-phase
releases.)  This scenario considers the release from a tank  (or
reservoir) and includes a provision for the effect of a pressure
drop  (piping) between the tank and the hole or opening.

     This procedure applies to a continuous release of a gas
which partially condenses during depressurization; the screening
procedure for this scenario should only be applied if the
screening procedure above indicated that partial condensation of
the released gas occured.  The release occurs  (constant pressure
and temperature) from a containment (reservoir) through a hole or
opening; a provision is made for the effect of a pressure drop
(piping) between the tank and the hole or opening.

Limitations and Assumptions:

     The pressure and temperature of the tank  (or reservoir)
contents are essentially constant.  The hole or opening size must
be sufficiently small, otherwise the reservoir temperature and
pressure may no longer be constant.  For the case of a leak from
a tank, the assumption of constant reservoir temperature and
pressure may be violated if a significant percentage of the tank
contents is released. -If the reservoir temperature and pressure
are not constant, the release rate may vary with time, but the
maximum release rate is generally obtained for"the initial
reservoir temperature and pressure.

     For the case of a leak from a pipe when /3 > 0.2  (as define'd
below), the assumption of constant temperature and pressure in
Che pipe may be violated; for such a case, the reservoir
conditions should be taken from an upstream location  (tank or
reservoir) where the temperature and pressure will be
(approximately)  constant.  For the case of a leak from a pipe
when j3 s 0.2, the assumption of constant temperature and pressure
in the pipe is reasonable, and the reservoir conditions should be
taken to be the conditions within the pipe.
                               4-38

-------
     The vapor phase of the released material  must be an ideal
gas at the reservoir conditions, during  the  depressurization
process, and after depressurization to the atmosphere;  for the
case of a tank containing vapor  and liquid,  the hole must be in
the vapor space of the tank.  For  two phase  flows,  all  released
liquid is assumed to travel downwind as  an aerosol with little
rain out of liquid near the source (Spicer,  1992) .

Input Information:

     AO    area of reservoir hole or opening  (m2)
     A!    flow area representing reservoir conditions (m2)  (In
          case of a leak from a  tank, At -  (and 0 = 0) ;  in  the
          case of a leak from a  pipe, Aj is the cross -sectional
          area of the pipe . )
     Cp    gas  (contaminant) heat capacity at Tt  (J/kg-mole- K)
           (For contaminant mixtures, see Appendix B)
     D0     (equivalent) diameter  of hole  or opening (D0 =
     Dp   pipe diameter  (as appropriate)  (m)
     Lp   pipe length  (as  appropriate)  (m)
     M,   gas  (contaminant) molecular weight  (g/g-mole)  (For
          contaminant mixtures,  see Appendix  B)
     P;   ambient pressure (Pa)
     Pv   vapor pressure as a  function  of  temperature (Pa)
     PI   reservoir pressure  (Pa)
     R    gas constant  (8314 J/kg-mole- K  or  8314
          Pa  mVkg-mole  K)
     Tb   contaminant normal boiling point (K)
     Tc   critical temperature (K)  (For contaminant .mixtures,
          see Appendix B)
     Tj   reservoir temperature  (K)
     j8    ^A0/A1   (dimensionless)
     7     (Cp/CJ = 1/(1  -  R/(CpM)) at Tt (dimensionless)  where R =
          8314  ( J/kg-mole  K)
     \    heat of vaporization at the normal  boiling point
           (cal/g-mole)
     P!   contaminant density  at not normal boiling point (kg/m3)
Procedure :
     Two-Phase Choked Flow.   Estimate the choked flow pressure P,
     to determine  if  the  flow is  choked using the procedure
     described in  Section 4.2.3.1.   If the flow is not choked,
     proceed  to  Step  6.   For choked flow,  estimate the discharge
     temperature T2, discharge density 02,  and the emission rate
     Qm.

     A.   Estimate T..  For pure components, estimate  T, (the
          temperature which corresponds to P.)  from the vapor
          pressure (Clausius-Clapeyron)  equation:
                               4-39

-------
           P. =101325  - exp        -  -             (4.2.3-7)
                                   Tb
     which can be rewritten as:

                              1
              T. =
                              in I   P'
                   Tb   AI^,      101325
B.   Estimate Properties at Choked Flow  Conditions.   Based
     on assumed isentropic behavior,  estimate  the vapor
     fraction at choked flow conditions  X, as follows:
                                                    (4.2.3-8)
     Using X, from Equation (4.2.3-8),  estimate the enthalpy
     change  (Ht-H*) and the density p, as follows:

             H! - H. = Cp  (T! - T.) + X (1  - X.)         (4.2.3-9)
     Note that values for individual  enthalpies  Ht and H. are
     not required.

C.   Estimate Emission Rate.  Extending  the  ideas  suggested
     by Lees  (1950), estimate the emission rate  Qm  (kg/s)  as
     follows:

                           [f    H - H     1 "I1/2
                    2'-85[l*4fL;/D,jJ       (4.2.3-11,

     where 0.85 is  included to  account for irreversibilities
     in the flow based on Lewitt  (1953)  and  the  term 4fLp/Dp
     accounts for  (piping) pressure drop between the
     reservoir and  the hole or  opening;  as a  preliminary
     estimate, use  f=0.0045 (since  typical Reynolds  numbers
     for these applications are larger than  105)  .

D.   Estimate Discharge Temperature and  Density.  Estimate
     the discharge  temperature  T: (after depressuri-aticn) .
     If a condensed phase is present, T2 will be given by
     the Clausius Clapeyron equation:


            P. = 101325 exp \^L [ * - 1 |]        (4.2.3-12)
                             R    Tb   T2
                          4-40

-------
         \
     which can be rewritten as:
                              In
                   Tb     M        101324
     Using this estimate of T2,  estimate the vapor fraction
     X, as:

                                                   (4.2.3-13)
                  X, - X.  * Cp(T.  - T2)/X

     When X2  (estimated from Equation (4.2.3-13))  satisfies
     1 * %2 z  0,  the  estimate of T2 is valid, and  the  density
     of the discharged material is given by:
                                   -*,
                                  PL
                                         -i
                                                   (4.2.3-14]
     (Note that for choked flow conditions, correct
     application of a dispersion model may require that  the
     diameter of the hole or opening be modified to
     D0(p,/p2)1/2 if the model accounts for initial air
     dilution due to jetting or momentum effects; if  this
     modification is not applied, the initial aerosol
     velocity is incorrectly overestimated.  This correction
     is not needed for TSCREEN.)

     However, if Xj <  0  or X2 > 1, the contaminant condensed
     phase which was present at P. and T. is no longer
     present, and the released contaminant is a gas  (without
     any condensed phase) ; the discharge temperature  and
     density are estimated as follows:

                  T2 = T. + X(l - X.)/Cp             (4.2.3-15)

                        A,-          '             (4.2.3-16)
     X2 = 0.

E.   Go to step 7  (Section 4.2.3.3) to select  the  dispersion
     model .

Two-Phase Subcritical  (Nonchoked) Flow.  For subcritical
flow, estimate the gas/liquid discharge temperature  T2,
discharge density p2,  and the emission rate Qm.

A.   Estimate  T2.   For pure components,  estimate T2  from the
     Glaus ius-Clapeyron equation:
                          4-41

-------
                     101325 exp           -             (4.2.3-17)
                                  R    Tb   T2
          which can be rewritten as:

                                  1
                    T
                    1
                         Tb   AT^     [101325
     B.   Estimate Properties at Discharge Conditions.   Based on
          assumed isentropic behavior, estimate  the vapor
          fraction at discharge flow conditions  X2 as :
                       T.
                        2
                     fT
             M.C.ln U  -Rln _1       (4.2.3-18)


          Using X2 from Equation (4.2.3-18),  estimate the
          enthalpy change  (Hj - 1^) and the density  p2 as :
                  H, - Hj = C  (Tt - T2) + X (1 - Xj)           (2.3-19)
                                       -x,
                                       PL
                                               -i
                                                          (2.3-20)
          Note that values for the individual enthalpies  are not
          required.

          Estimate Emission Rate.  Extending the  ideas  suggested
          be Lees (1950), estimate the emission rate  Qm as:
Qm = AO p2  2-0.85
                                     HI -H,
                                                Tl/2
                                      4 f Lp / Dp
                                                          (2.3-21)
          where 0.85 is included to account  for  irrevesibilities
          in the flow based on Lewitt  (1953)  and the  term 4fLp/Dp
          accounts for the pressure drop  (piping) between the
          reservoir and the hole or opening  (as  appropriate); as
          a preliminary estimate, use  f = 0.0045 (since  typical
          Reynolds numbers for these applications are larger than
          105) .

     D.   Go to step 7 to select the dispersion  model.

4.2.3.3  Dispersion Model Selection

     See Section 2.4 for a complete discussion of the model
selection.
                               4-42

-------
Input Information;

     Tt    ambient temperature (K)
     Q    total amount of material released  (kg)

Procedure :

7.   Buoyancy Check.  Evaluate release buoyancy as a first check.


     A.    Calculate the density of air using the following:

                                 P M
                                 ^jr                   (4.2.3-22)


          where- M, is  the  molecular weight  of air  (assumed to
          equal 28.9 kg/kmole) .

     B.    If p2/Pir > I/  then the buoyancy is negative.   For
          negative buoyancy, the RYD model should be used if  the
          release is from a vertically directed jet; otherwise,
          the Britter-McQuaid model should be used/ go to step  8.
          If the buoyancy is neutral or positive,  the SCREEN
          model for a point source should be used.   (See Section
          2.4 for more information on model  selection.)

     Release Duration.  The release duration is used as an input
     into the RVD and Britter-McQuaid models .  The release
     duration is used to determine if the release should be
     modeled as continuous or instantaneous  (see Section 2.5) .
     Calculate the release duration- Td using the equation below-.
                 Td (min) = _ -  .        ,  . .  .         (4.2.3-23)
                           Qm (kg/s)   60 (s/min)


4.2.3.4  Examples

4.2.3.4.1  Example 1:  Air Leak from Reservoir - Choked
     
Discussion :

     In this example, 400 kg of a chemical with the same
properties of  (dry) air stored at 1.101x10* Pa  and 293.15 K is
released from a tank through a 5.25 cm hole on the side of  the
tank.  The nearest distance to the fenceline is 100 meters.
Maximum 15 -minute average concentration is needed.  This  example
demonstrates the procedure when the flow is choked.

The following information will be required:

     AO   area of reservoir hole or opening


                               4-43

-------
          (TrD02/4 = 0.002165 m2)
     At    flow area representing  reservoir conditions (At  -  m2)
     Cp    gas (contaminant) heat  capacity at Tt  (1004 J/kg-K)
     D0    diameter of hole or opening (D0 =  0.0525 m)
     MW    gas (contaminant) molecular weight (29 kg/kmole)
     P,    ambient pressure  (101325  Pa)
     Tb    boiling point temperature (79  K)
     P!    reservoir pressure  (1.101x10* Pa)
     R    gas constant  (8314 J/kg-mole-K or 8314
          Pa-m3/kg-mole-K)
     Q    total amount of material  released (400 kg)
     T,    ambient temperature  (293.15 K)
     Tc    critical temperature  (132 K)
     Tt    reservoir temperature  (293.15  K)
     0    ^Ag/Aj   (0.0)
     7    (Cp/C,)  1/(1 - R/(CpMj)  at T!  (1.40)
     Pi    reservoir density  (at Tj and Pt)  (pt =  P^/ (RTt)  =
          (l.lOlxlO6) (29)/((8314)  (293.15)) = 13.10kg/m3)

With this information, the procedure discussed above is used to
determine the release rate, the discharge temperature,  and the
discharge density.  For dispersion  calculations, 15-minute
average concentrations at a fenceline of 100 m are desired.

Procedure:

1.   Choked Pressure.  Estimate the choked pressure P.  to
     determine if the flow  is choked.  From Equation (4.2.3-1):

               /    -}   \ 1.40/U.40-1)
          P. =	         l.lOlxlO6 =  5.82xl05 (Pa)
               \ -L  fz w ** X /

     Since P > Pa, the flow is  choked;  go to step 2.

2.   Choked Flow.  For choked flow,  estimate the gas temperature
     T.  when the pressure is P., the emission rate is Qm/ and the
     discharge temperature  is T2.

     A.   Estimate T..   Estimate T  using Equation (4.2.3-2) with
          7 = 1.40 and Tt,= 293.15  K:
                          2
                       1.40 -*- 1
                                  293.15 = 244 K
          This estimate of T. must be checked  to  see if Equation
           (4.2.3-2)  applies.   If T is greater than the (pseudo)
          critical  temperature Tc for air, Equation (4.2.3-2)
          applies.   (The pseudo critical temperature of air is Tc
          =  0.79(126.2)  + 0.21(154.6)  = 132K where the assumed
          composition (mole fraction)  of air is 79% N2 and 21% 02,
          and the critical temperatures of N2  and 02 are 126.2  K
          and 154.6 K,  respectively.)
                               4-44

-------
     B.    Estimate Emission Rate.  Estimate the emission  rate  Qm
          using Equation (4.2.3-3) with C = 0.75:
     Qm = C-0.002165
L.101xl06-13.10-1.40
                                         1.40
                          Qm. =  4 .22  kg/s
     C.   Estimate Discharge Temperature.  Estimate the discharge
          (after depressurization) temperature T2 with Equation
          (4.2.3-4):
T2 = 293.15
                         1 - 0.85
              1.40 - 1
              1.40 + 1
252 K
          Note that T2 > T,, so equations used were appropriate.
          Since flow is choked, proceed to Step 4.

4.   Discharge Density.  Estimate the discharge density p2 from
     the discharge temperature T2 using the ideal  gas law:

               (101325) (29)/(8314) (252)  =  1.40 kg/m3

     (For these choked  flow conditions, correct application  of  a
     dispersion model may require that the diameter  of the hole
     or opening be modified to D0(P.T2/P,T.) l/2 = 0.0525  [(5.82xl05)
     (252) /(101325) (244)] 1/2 =  0.128  m if  the  model accounts  for
     initial air dilution due to jetting or momentum effects.)
     Since no partial condensation was indicated  by  screening
     calculations, proceed to Step 7.

7.   Perform Buoyancy Check.

     A.   Calculate density of air using Equation (4.2.3-22) :

                      101325 -28.9   -
                  -   8314   293.15     -
                
     B-   P2/P& >  1 therefore,  buoyancy is negative.
                  /
8.   Release Duration.  Calculate the  release duration Td using
     Equation  (4.2.3-23) as  follows:


                                             =1.58 min
                     A ^ ,          ,  .  . ,
                     4.22 (kg/s)    60  (s/min)

     After this calculation run the Britter-McQuaid model  since
     the release is not from a vertically directed jet.   (See
     Section 5.4 for more information on  the Britter-McQuaid
     model . )

Data entry in the TSCREEN model for this  example  is shown  below


                               4-45

-------
            Continuous Leaks from Reservoir  -  Scenario 2.3
SOURCE PARAMETERS - Page 1  of 4

Enter; a unique.vtitle; for..jtj^s_djita/s_mdel._run:
SOURCE OF LEAK
                Area (Ao) of Hole or Opening  -> Zl^JS    cm*
               Enter P for Pipe - T  for  tank  -> t
FLOW CHARACTERISTIC
Critical Pressure (P*) -> 581698.9 Pa
Gas Heat Capacity (Cp) -> TffiJft
Reservoir Pressure (P1) -> f>.i3fE&
Molecular Weight (Mw) -> 23
J/kg K
Pa
kg/kmol
Flow Characteristic -> Choked
Ambient Pressure (Pa) -> 1S132S
Pa
            Continuous Leaks from Reservoir  -  Scenario 2.3
SOURCE PARAMETERS - Page 2 of 4

TEMPERATURES
     Gas Temperature (T*) at Critical  Pressure  > 244.3249 K
                    Reservoir Temperature  (T1)  -> 208.fj   K
                     Critical  Temperature  (Tc)  -> T2KJ   '   K
      SHt    *&>?rtm9U8 $cr*en   *f11)> t
            Continuous Leaks from Reservoir  - Scenario 2.3
SOURCE PARAMETERS - Page 3 of 4

EMISSION RATE
                            Emission  Rate  (dm)  -> 4222.151  g/s
          Density at Reservoir Conditions  (f1)  -> 13..18' .  kg/cubic m
DISCHARGE CHARACTERISTICS
                    Discharge Temperature  (T2) -> 251.6487 K
                        Discharge Density  (f2) -> 1.404462 kg/cubic m


                         Density of Air  (fair) -> 1.201474  kg/cubic m
                      Ambient  Temperature  (Ta)  -> 293.15'    K
Buoyancy is Negative
                               4-46

-------
SOURCE PARAMETERS - Page
VERTICALLY DIRECTED JET
Does the release
1
riME
Total Amount of
4 of 4
result in a vertically
directed jet (Y/M) -> f
Release Duration (Td) -> 1.578974 min
Material Released (0) -> 40$ kg

**"!*fc V*ft*t;ftfM ;^^**'WMK tst>AtoWt

Based on user input, the Britter-McQuaid model has been selected.
BRITTER-McQUAID MODEL INPUTS - Page 1 of 3
MODEL PARAMETERS
Relative Humidity (Rh) -> 58 ,, X
Desired Averaging Time for the Calculation
of Concentrations -> 1$ -. min

Pollutant Boiling
Point Temperature (Tb) -> 79 K
<(& idH f$v j*B*v? Sera*w s ^Ftl^ xt $wr <6$$* Abort
                :	Continuous Leaks from Reservoir - Scenario 2.3 

                 BRITTER-McQUAID MODEL INPUTS - Page 2 of 3

                 FENCELINE DISTANCE
                  Enter the distance from the base of the stack
                                       to the plant fenceline -> tGU;     m

                 RECEPTOR LOCATIONS
                 Do you have specific locations where you would
                 like pollutant concentrations calculated (Y/N) -> H
F$>:
           .- Screen:
                                                          Rt* Kocte-fc    xs Abort
The  Britter-McQuaid model's output  is  displayed  below:
  *** B4M MODEL  RUN ***

 Air Leak from Reservoir

 INPUTS:
   AMBIENT PRESSURE (ATM)
   AMBIENT TEMP (K)
   AVERAGING TIME (MIN)
   BOILING PT TEMP (K)
   DURATION (S)
   EMISSION RATE (KG/S)
   EXIT TEMP (K)
   MASS (KG)
                                                             11-19-92
                                                              13:34:04
1.000
293.1
15.00
79.00
94.74
4.222
251.6
400.0
                                              4-47

-------
    MOL. WEIGHT (G/G-MOLE)    -    29.00
    RELATIVE HUMIDITY (%)     =    50.00
    VAPOR FRACTION            -    1.000
      ***   SUMMARY OF B&M MODEL RESULTS  ***
MAX CONC
(UG/M**3)
MAX CONC
(PPM)
DIST TO
MAX (M)
WIND SPEED
(M/S)
    .7978E+08    .6617E+05
100.
 ** REMEMBER TO INCLUDE BACKGROUNDCONCENTRATIONS **
 *********************************
 ***************************
 ***        B&M DISTANCES      ***
 I*********************************
DIST
(M)
100.
200.
300.
400.
500.
600.
700.
300.
900.
1000.
1100.
1200.
1300.
1400.
1500.
1600.
1700.
1900.
2100.
2300.
2500.
2700.
2900.
3100.
3300.
3600.
3900.
4200.
4500.
5000.
CONC
(UG/M**3>
.7978E+08
.1323E+08
.7453E+07
.3704E+07
.2371E+07
.1821E+07
.2115E+07
.2861E+07
.2132E+07
.1638E+07
.1291E+07
.1039E+07
.8502E+06
.7064E+06
.5945E+06
.5059E+06
.4348E+06
.3292E+06
.2564E+06
.2042E-CQ6
.1658E*06
.1368E+06
.1144E+06
-9683E+05
-8282E+05
.66635+05
.5455E+05
.4532E+05
.3814E+05
.2931E+05
CONC
(PPM)
.6617E+05
.1098E+05
6182.
3072.
1966.
1510.
1754.
2373.
1768.
1359.
1071.
861.4
705.2
585.9
493.1
419.6
360.6
273.1
212.6
169.4
137.5
113.4
94.88
80.31
68.69
55.26
45.24
37.59
31.63
24.31
WIND SPEED
(M/S)
i.
2.
2.
2.
3.
3.
2.
4.
4.
4.
4.
4.
4.
4.
4.
4.
4.
4.
4.
4.
4.
4.
4.
4.
4.
4.
4.
4.
4.
4.
 CALCULATED VALUES:
    DENSITY OF DEPRESSURIZED CONTAMINANT (KG/M*
    DENSITY OF AMBIENT AIR (KG/M**3)
    MOLE FRACTION
    MIN OIST INST (M)
    MAX DIST CNST (M)
                        1.405
                        1.199
                        1.000
                        3158.
                        757.9
       NOTES & DEFINITIONS
(a) "inst" refers to an instantaneous release (Section 3.6 of B-M Workbook)
(b) "enst" refers to a continuous release (Section 3.6 of B-M Workbook)
                                                   4-48

-------
(c) "MIN D1ST INST" is the mininun distance downwind at which the release
  may be treated as instantaneous
(d) "MAX OIST CNST" is the maximum distance downwind at which the release
  may be treated as continuous
      END OF B&M OUTPUT
4.2.3.4.2  Example 2:  Air  Leak from Reservoir  -  Subcritical  (Not
           Choked)

Discussion:

      In  this example,  (dry)  air stored at 1.82xl05 and 293.15 K
is released, from a tank  through a 5.25 cm hole in the tank;  this
example  is the same as the previous example  except for the
reservoir  pressure.  This  example demonstrates the procedure when
the flow is not choked.

The following information  will be required:

      AO    area of reservoir hole or opening
           (7rD02/4  0.002165 tn2)
      A!    flow area representing reservoir conditions  (Aj -*  m2)
      Cp    gas (contaminant)  heat capacity at
           T!  (6.959  cal/g-mole  K)
      D0    diameter of hole or opening  (D0 = 0.0525 m)
      M    gas (contaminant)  molecular weight (29 kg/kmole)
      Pt    ambient pressure (101325 Pa)
      Pt    reservoir pressure -(1.82xl05 Pa)
      R    gas constant  (8314 J/kg-mole-K or 8314
           Pa-iirVkg-inole-0K)
      Q    total amount of  material released  (400 kg)
      T,    ambient temperature (293.15  K)
      T=    critical temperature (132 K)
      TI    reservoir temperature (293.15  K)
      13    VV^  (0.0)
      7    (Cp/CJ = 1/(1  *  R/MCpMJ) at  T, (1.40)
      Pi    reservoir density (at Tt and Pt)  (pl  =  P1MW/(RT1)  =
           (1.82X103) (29)/( (8314) (293.15) ) = 2.17  kg/m3)

With  this  information, the procedure discussed above  is  used to
determine  the release rate, the discharge-temperature, and  the
discharge  density.

Procedure:

1.    Choked Pressure.  Estimate the choked pressure P. to
      determine if the flow is choked.  From  Equation  (4.2.3-1):
                                 4-49

-------
                         ..
                	*             1.82x10* = 9..61X104 (P.)


     Since P. < Pt, the flow is not  choked; go to step 3.

3.   Subcritical Flow.  For subcritical  (not choked)  flow,
     estimate  the emission rate Qm  and the discharge  temperature
     T2.

     A.   Estimate Emission Rate,   Estimate  the emission rate Qm
          using Equation  (4.2.3-5):


     Qm = K-Y-.002165[ 2-2.17(1.82xl05 - 101325  ) ]^ = 0.691  kg/s

          where
          K = 0.62 / V 1 - 0  O4  =0.62
       Y = 1  -  [ 1.82x10' -101325 ] (Q ^ + Q>35 .  Q4) . Q
               [  1.82xl05  1.40  J

     B.   Estimate  Discharge Temperature.   Estimate the discharge
          (after depressurization)  temperature T2.  From  Equation
          (4.2.3-6):


       T2 = 2  293.15 / [ 1 + (1 + 4 - a  293 .15 )1/2 ] = 265 K

          where

            a = _i_ (     -691 ' 8314    Y = 4.06x10-"
                2-Cp\  101325-29-0.002165 /

          where

Cp/(J/kg<'K)=6.95889(cal/g-mole "K?  100Q (g/k,g) / 4 '184 (J/cal) =1004 (J/kgK)
                                         29(g/g-mole)

          Since T2 > Tc,  proceed  to Step 4.

4.   Discharge Density.   Estimate  the  discharge  density p2 from
     the discharge  temperature T2 using  the ideal gas  law:

               (101325) (29)/(8314)  (265)  = 1.33 kg/m3

     (Correct application of a dispersion  model  may require that
     the diameter of the hole  or opening be modified to D0(p,/,o~)1/2
     = 0.0525 m  (2.17/1.33)1'2 = 0.0671 m if the model  accounts "
     for initial air dilution  due  to  jetting or  momentun effects/
     if this modification is not applied,  the initial gas
     velocity is incorrectly overestimated.)   Since no
     condensation is predicted from the above calculations,
     proceed to Step 7.
                               4-50

-------
      Perform Buoyancy Check.

      A.    Calculate density of  air using Equation  (4.2.3-22):

                       .  101325 -28.9
      B.
P^lPm
  8314   293.15  ' >~M **'*

therefore, buoyancy is negative.
      Release Duration.   Calculate the  release duration Td using
      Equation  (4.2.3-23)  as follows:
            T,  (min) =
                                 400 (kg)
                        0.691  (kg/s)    60 (a/rain)
                                         =9.65 min
      After  this  calculation run the Britter-McQuaid model  since
      the release is not  from a  vertically directed  jet.   (See
      Section 5.4 for more information  on the  Britter-McQuaid
      model.)

Data entry  in the TSCREEN model for this example is shown  below:
                      Continuous Leaks from Reservoir - Scenario 2.3
             SOURCE PARAMETERS - Page 1 of 4

             Enter a unique title for this data's model run:
             Sub^lef&rAfr&sic	'
             SOURCEof LEA*           ' '  "
                        Area (Ao) of Hole or Opening -> 21 .iS ''  cm1
                        Enter P for Pipe - T for tank -> f
             FLOW CHARACTERISTIC
                             Critical Pressure (P*) -> 96157.31 Pa
                 Gas Heat Capacity (Cp) -> TBS&
                Reservoir Pressure (P1) ->
                  Molecular Weight (Mw) -> 29
                                                     J/kg "K
                                                     Pa
                                                     kg/kmol
                               Flow Characteristic -> Subcritical
                             Ambient Pressure (Pa) -> tO$525p. Pa
                                   4-51

-------
            Continuous Leaks from Reservoir - Scenario 2.3
SOURCE PARAMETERS - Page 2 of  4

EMISSION RATE
                            Emission Rate  (Qn -> 691.131  g/s
                        Reservoir Density  (f1) -> 1**^ '  kg/cubic m
DISCHARGE TEMPERATURE
                    Discharge Temperature  (T2) -> 264.6861 K
                    Reservoir Temperature   ^||5jp K
      Sift      1&i;!fe|: "K
DISCHARGE DENSITY
                        Discharge Density ((2)  ->  1.335283 kg/cubic m

                         Density of Air (fair)  ->  1.201474 kg/cubic m
                      Ambient Temperature (Ta)  -> %j$3$%,  K
Buoyancy is Negative
      edit    *t9* Previous $nra*n    f t0> *t Ser*n
            Continuous Leaks from Reservoir -  Scenario 2.3
SOURCE PARAMETERS - Page 4 of 4

VERTICALLY DIRECTED JET
       Does the release result in a vertically
                            directed jet (Y/N) ->  H

TIME
                         Release Duration (Td) ->  9.646025 min
         Total Amount of Material Released (Q)  ->  4(&t?3z.  kg
                                4-52

-------
                        Continuous Leaks from Reservoir - Scenario 2.3
               Based on user input, the Britter-McQuaid model has been selected.

               BRITTER-McQUAID MODEL INPUTS - Page 1 of 3

               MODEL PARAMETERS
                                 Relative Humidity (Rh) -> 56     X

                  Desired Averaging Time for the Calculation
                                     of Concentrations -> 1$     nrin

                   Pollutant Boiling Point Temperature (Tb) -> 79     K
                        Continuous Leaks from Reservoir - Scenario 2.3
BRITTER-McQUAID MODEL INPUTS - Page 2 of 3

FENCELINE DISTANCE
 Enter the distance from the base of the stack
                  'to the plant fenceline ->
                                                         j  m
               RECEPTOR LOCATIONS
               Do you have specific locations where you would
               like pollutant concentrations calculated (Y/N) -> lit
                 Eetf tf   F9> Previous $   F1S> Run od*L   
                          .3102E+08    .2573E+5
                                100.
1.
                       ** REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS **
                       *************************
4.2.3.4.3   Example  3:   Chlorine Gas Leak  - Choked

Discussion:

       In  the  example, chlorine  gas  stored  at  6.7999  atm  and 320  K
is released  through a  2.8  cm hole.   This  example  demonstrates  the
procedure  when  the  flow is  choked.

The  following information  will be  required:

       AO    area  of reservoir hole or opening  (7rD02/4  = 0.0006158
             m2)
       A!    flow  area representing reservoir conditions  (Aj -  oo m2)
       Cp  ' gas  ('contaminant)  heat capacity at Tj (489  J/kg-K)
                                       4-53

-------
     D0    diameter of hole or opening  (D0 = 0.028 m)
     1^    gas (contaminant) molecular weight  (70.9  kg/kmole)
     P,    ambient pressure  (101325 Pa)
     Pt    reservoir pressure  (6.89xl05 Pa)
     R    gas constant  (8314 J/kg-mole-K  or  8314
     Q    total amount of material released  (400  kg)
     Ta    ambient ' temperature  (293 K)
     Tc    critical temperature  (417.15  K)
     Tr    reservoir temperature  (320  K)
     j8    ^V^"  (0.0)
     7    (Cp/CJ - 1/(1 - R/fCpMj) at T\  (1.32)
          heat of vaporization at normal  boiling  point
          '(2.879X105 J/kg)
     P!    contaminant liquid density  at the  normal  boiling point
          (18.36 kg/m3)

With this information, the procedure  discussed above  determines
the release rate, the discharge  temperature,  and  the  discharge
density.

Procedure :

1.   Choked Pressure.  Estimate  the choked pressure P, to
     determine if the flow is choked.   From  Equation  (4.2.3-1):
                          ..
                 ! 32 + i)        ' 6-89xl5 " 3.74X105 P.

     Since P. > P., the flow is choked; go  to step  2.

     Choked Flow.  For choked flow, estimate the gas temperature
     T,  when the pressure is P.,  the emission rate  Qm, and  the
     discharge temperature T2.

     A.    Estimate T..   Estimate T. using  Equation  (4.2.3-2)  with
          7 = 1.32 and Tt = 320  K:

                   T- =           ' 32C  276 K
          The Clausius-Clapeyron equation  can be  conveniently
          used to estimate the vapor pressure at  T. as follows :
   P. - 10132S exp


          Since PV(T.) > P.,  no condensation occurs.

     B.    Estimate Emission Rate.  Estimate  the  emission rate Q
          using Equation  (4.2.3-3) with C  =  0.75:
                               4-54

-------
     Qm = C-0.0006158
                       '\

                                                           1/2
       S.89xl05-18.36-1.32
                                         .1.32 + 1

                          Qm  =  1.10  kg/s
     C.   Estimate Discharge Temperature.  Estimate the emission
          discharge (after depressurization) temperature T2 with
          Equation (4.2.3-4):
T2 = 320
                                           = 283 K
          Since flow is choked, proceed to Step 4.

4.   Discharge Density.  Estimate the discharge density p2 from
     the discharge temperature T2 using the ideal  gas law:

              (101325) (70.9)7(8314) (283) =  3.05 kg/m3

     (For these choked flow conditions, correct application  of  a
     dispersion model may require that the diameter  of the hole
     or opening be modified to D0(P./P.)1/2 * 0.028 m (3.69/l)1/2 =
     0.0538 m if the model accounts for the initial  air dilution
     due to jetting or momentum effects.  Since flow is one-
     phase, proceed to Step 7.

7 .   Perform Buoyancy Check .

     A.   Calculate density of air use Equation (4.2.3-22) as
          follows :
     B-   PI/P& > 1 therefore,  buoyancy is negative.

8.   Release Duration.  Calculate the release duration  Td using
     Equation  (4.2.3-23) as follows:
                     . ,n ,v        n  ,     i    '
                     1.10 (kg/s)   60  (s/min)

     After this calculation run the Britter-McQuaid model  since
     the release is not from a  vertically directed jet.   (See
     Section 5.4 for more information on the Britter-McQuaid
     model . )

Data entry in  the TSCREEN model for this example  is shown  below:
                               4-55

-------
            Continuous Leaks from Reservoir - Scenario 2.3
SOURCE PARAMETERS - Page 1 of 4

Enter a unique title for this data's model run:
1Si&jiKm'W&'-'WiW1i&	   ,
SOURCE OF LEAK
                Area (Ao) of Hole or Opening -> 6-1*58'    cm2
               Enter P for Pipe - T for tank -> I"

FLOW CHARACTERISTIC
Critical Pressure (P*)
Gas Heat Capacity (Cp)
Reservoir Pressure (P1)
Molecular Weight (Mu)
Flow Characteristic
Ambient Pressure (Pa)

-> 374093.4
-> 49* *
-> &SB&
-> Choked
-> t8&$&&

Pa
J/kg "K
Pa
kg/kmol

Pa

  Edit     Previous Screen     Next Screen     Abort
            Continuous Leaks from Reservoir - Scenario 2.3
SOURCE PARAMETERS - Page 2 of 4

TEMPERATURES
     Gas Temperature (T*) at Critical Pressure -> 276.4043 K
                    Reservoir Temperature (T1) -> 58$f,::L.:::;,''' "K
                     Critical Temperature (Tc) -> 417.15   "K
VAPOR PRESSURE
        Vapor Pressure (Pv) at Gas Temperature -> 405986   Pa
      Latent Heat of Vaporization (Lvap) at Tb -> Zia75!I  J/kg
                Boiling Point Temperature (Tb) -> 2$5&9j|::r K
 F<> &*lt     Previous 4#ew^C:'*?T^^
            Continuous Leaks from Reservoir - Scenario 2.3
SOURCE PARAMETERS - Page 3 of 4

EMISSION RATE
                            Emission Rate (Qm) -> 11006.45  g/s
          Density at Reservoir Conditions (f1) -> 1&Jf&y< kg/cubic m
DISCHARGE CHARACTERISTICS
                    Discharge Temperature (T2) -> 282.9437 "K
                        Discharge Density (f2) -> 3.053886 kg/cubic m
                         Density of Air (fair) -> 1.20209  kg/cubic m
                      Ambient Temperature (Ta) -> 2J>S|;:}T:f <
Buoyancy is Negative
                   Prepays
                                4-56

-------
                             Continuous Leaks from Reservoir - Scenario 2.3
                  SOURCE PARAMETERS   Page 4 of 4

                  VERTICALLY DIRECTED  JET
                        Does the release result in a vertically
                                            directed jet (Y/N) ->
                  TIME
                                         Release Duration '(Id) -> 0.6055085 min
                          Total Amount of Material Released (Q) ->
fitft " '" s
                         Stfeen
                                        UeXt:
                                                                          Jffiort '
                             Continuous  Leaks from Reservoir - Scenario 2.3
                  Based on user input,  the Britter-McQuaid model has been selected.

                  BRITTER-McQUAID MODEL INPUTS - Page 1  of 3

                  MODEL PARAMETERS
                                        Relative Humidity (Rh) -> SO      X

                      Desired Averaging Time for the Calculation
                                             of Concentrations -> t$      min
- SeMt
                                    Previous Scrserr-    Next Screes
                             Continuous  Leaks from Reservoir - Scenario 2.3
                  BRITTER-MCQUAID MODEL INPUTS - Page 2 of 3

                  FENCELINE DISTANCE
                   Enter the distance from the base of the stack
                                         to the plant fenceline ->
                  RECEPTOR  LOCATIONS
                  Do you have specific locations where you would
                  like pollutant concentrations calculated (Y/N) -> 8
. <{|2>- Beilr    
-------
4.2.3.4.4  Example  4:   Saturated Vapor Chlorine Leak

Discussion:

     In this example,  saturated chlorine vapor is discharged
through a pressure  relief  valve (10.16 cm diameter) designed to
open at 2.586xl06P4  (375 psia);  the chlorine vapor temperature is
estimated to be  349.2  K using  the Clausius-Clapeyron equation
and the normal boiling point  of chlorine (239.05 K) .
Condensation will be present  in this release (at the choked flow
conditions).  This  example demonstrates the procedure when the
flow is choked.

The following information  will  be required:

     AQ   area of reservoir hole or opening
           (irD02/4 =  0.008107 m2)
     AI   flow area representing reservoir conditions (At - o> m2)
     Cp   gas  (contaminant) heat capacity at Tt  (489 J/kg-K)
     D0   diameter  of  hole or opening (D0 = 0.1016  m)
     1^   gas  (contaminant) molecular weight (70.9 kg/kmol)
     P.   ambient pressure (101325 Pa)
     Pj   reservoir pressure  (2.586xl06  Pa)
     R    gas constant (8314  J/kg-mole-K or 8314
          Pa-m3/kg-mole-K)
     Q    total  amount of  material released (400 kg)
     Ta   ambient temperature (293 K)
     Tb   contaminant  normal  boiling temperature (239.05  K)
     Tc   critical  temperature  (417.15 K)
     Tx   reservoir temperature (349.2 K)
     0    y/Ao/Ai   (0.0)
     7     (Cp/CJ =  1/(1 -  R/tCpMJ) at T, (1.32)
     X    heat of vaporization  at the normal boiling point
           (2.879x10* J/kg)
     P!   contaminant  liquid  density at the normal boiling point
           (1574  kg/m3)

With this information,  the procedure discussed above determines
the release rate, the  discharge temperature, and the discharge
density.                  ,

Procedure:

1.   Choked Flow Pressure. Estimate the choked flow pressure P*
     to determine if the  flow is choked.  From Ecruation  (4.2.3-
     1) :

               /    <>    \ 1.32/(1.32-t)
          P. = _~\         2.586xl06 = 1.40xl06 (Pa)


     Since P. > Pa,  the flow is  choked; go to step 2.
                               4-58

-------
   Choked Plow.   For choked flow,  estimate the gas temperature
   T, when the pressure is P.,  the emission rate Qm,  and the
   discharge temperature  T2.

   A.    Estimate T,.  Estimate T using Equation (4.2.3-2) with
         7 =  1.32 and Tt  349.2  K:

                 T'             '  349. 2 =301 oK
         This estimate of T* must be checked  to  see  if  Equation
         (4.2.3-2)  applies.   T. is not greater than  the (pseudo)
         critical temperature Tc  (417.15 K) ; therefore,  the
         contaminant vapor pressure at T.  (PV(T.)) must  be
         calculated using the Clausius-Clapeyron equation:
  P, . 10132S exp


         The chlorine vapor pressure at 301 K is less than P,/
         so,  condensation was predicted; proceed to step 5.

    Two- Phase Choked Flow.  For choked flow,  estimate the
    discharge temperature T2, discharge  density  p2, and the
    emission rate Qm.

    A.    Estimate T.  Estimate T. (the temperature which
         corresponds to P.)  from  Equation  (4.2.3-7) :


     T,  = - - - = 321 K
              1           8314        In2.586xl06]
           239.05   2.879xl05-70.9     [  101325 J

    B.    Estimate Properties at Choked Flow Conditions.  Based
         on assumed isentropic behavior,  the vapor fraction at
         choked flow conditions is estimated from Equation
         (4.2.3-8):
                                                    r2.586xl06]"
  = 1  + 	.	  70.9-439 inl   - 8314 in
        2.879x102-70.9 [_            *  321  '           [l.40x!06JJ

  = .966

         Using Equation (4.2.3-9), the enthalpy change is
         estimated as:

Ht  - H. = 489  (349.2 - 321)  + 2.879xl05 (1 - .966) = 2.36xl04 (J/kg)

         The density is estimated using Equation  (4.2.3-10) :
                              4-59

-------
p.
c.
n
= 0 966
L I1
Estimate
emission
= 0.00810
8314-321 1 +
.40xl06-70.9J
/ 1 - 0.966 \ "
\ 1574 / _
-i
= 38.5
Emission Rate. Using Equation (4.2.
rate is estimated as:
7-38.5 2-0.85
kg/m3
3-11),

the
A ~\ I1'2
2-36x10* -, ....
     D.    Estimate Discharge Temperature and Density.
          Application of Equation  (4.2.3-12) gives  the  discharge
          temperature (T2)  as:


       T, = _ - - = 239.05 K
              1           8314          / 101325 \
            239.05   2.879xl05-70.9    U01325

          and Equation  (4.2.3-13) gives the vapor  fraction (X2)
          as:
           X, = .966 + 489(321 - 239 . 05) /2 . 879xl05 = 1.11

          since X2 >  1,  these estimates  are not valid.  Using
          Equation (4.2.3-15) gives T2 as :

             T2 = 321  - 2.879xl05(l - .966)/489 = 341 K

          and Equation  (4.2.3-16) gives  the discharge density
          (P2)  as:
          (For these choked flow conditions, correct  application
          of a dispersion model may require that the  diameter of
          the hole or opening be modified to D0(p*/p2)1/2 =
          0.1016(38.5/2.53)m  =  0.396  m if  the  model accounts for
          initial air dilution due to  jetting  or momentum
          effects; if this modification is not applied, the
          initial gas velocity is incorrectly  overestimated.)
          Proceed to Step 7.       -

7.    Perform Buoyancy Check.

     A.   Calculate density of air using Equation  (4.2.3-22)  as
          follows:
                               4-60

-------
      B.     p2/Piir >  ! therefore,  buoyancy is  negative.

      Release  Duration.   Calculate  the  release duration  Td using
      Equation  (4.2.3-23)  as follows:
             T,  (min)  =
                                    400 (kg)
                          62.5  (kg/s)   60 (s/min)
= 0.107 min
       Since the release  is  from a  relief valve,  run  the  RVP model
       (See  Section 5.2 for  more information on the RVD model.)

Data  entry in the TSCREEN  model for this  example is shown  below:
                        Continuous Leaks from Reservoir - Scenario 2.3
               SOURCE PARAMETERS  Page 1 of 4

               Enter a unique title for this data's model run:
               $^irt^vii^" 1.67 "  cm1
                           Enter P for Pipe - T for tank -> |

               FLOW CHARACTERISTIC
Critical
Pressure
Gas Heat Capacity
Reservoir Pressure
Molecular Weight
Flow
Ambient
(P*)

->
->
->
->
->
1404072
2.JSB6E&
7&J
Choked
mm
Pa

J/kg K
Pa
kg/kmol

Pa


                        Continuous Leaks from Reservoir - Scenario 2.3
               SOURCE PARAMETERS - Page 2 of 4

               TEMPERATURES
                   Gas Temperature (T*) at Critical Pressure -> 301.6262
                              Reservoir Temperature (T1)
                               Critical Temperature (Tc) -> 4;1^||5*;j:j, "K
               VAPOR PRESSURE
                     Vapor Pressure (Pv) at Gas Temperature -> 853262.5 Pa
                    Latent Heat of Vaporization (Lvap) at Tb ->
                           Boiling Point Temperature (Tb) ->
   J/kg
   K
               .  -Edit?-.. t.f
-------
            Continuous Leaks from Reservoir -  Scenario 2.3
SOURCE PARAMETERS - Page 3 of 4

EMISSION RATE
                            Emission Rate (Qra)  ->  62583.96 g/s
          Density at Reservoir Conditions (f1)  ->  15?     kg/cubic in
DISCHARGE CHARACTERISTICS
                    Discharge Temperature (T2)  -> 341.572   K
                        Discharge Density (|7)  -> 2.529709 kg/cubic  m
Vapor Fraction at Discharge Flow Conditions(X2)-> 1.105221

                         Density of Air (fair)  -> 1.20209   kg/cubic  m
                      Ambient Temperature (Ta)  -> 293KPC.  IC
Buoyancy is Negative
  aftt    <&> Previous serasn     t

TIME
                         Release Duration (Td) -> 0.106524 min
         Total Amount of Material Released (Q)  -> 4&Jf/?!%:;  kg
      edit    I9> Pf**$u Screen     :Afebrt
            Continuous Leaks from Reservoir -  Scenario 2.3
Based on user input, RVO model has been selected.

RVD MODEL INPUTS - Page 1 of 3

RELEASE PARAMETERS
                   Release Height above Ground ->  1ft'    :   m
                     Exhaust Gas Exit Velocity ->  TWL8?l   m/s

POLLUTANT INFORMATION
                 Pollutant Concentration (vol) ->  tOCfi -v .:; ?  %
                    Pollutant Molecular Weight ->  7?|%/1:;;.  g/g-mole

TIME
    Desired Averaging Time for the Calculation
                             of Concentrations ->  t&-: "''*-..  min
      dit     Previous Screen   '  Next Screen-     Abort
                                4-62

-------
                               Continuous Leaks from Reservoir  - Scenario 2.3
                   RVD MODEL INPUTS  - Page 2 of 3

                   URBAN/RURAL  CLASSIFICATION
                                  Enter U for Urban - R for Rural  > f

                   FENCELINE DISTANCE
                    Enter the distance from the base of the stack
                                          to the plant fenceline  ->

                   RECEPTOR LOCATIONS
                   Do you have  specific locations where you would
                   like pollutant  concentrations calculated (Y/N)  ->
                                               $erft
 The  RVD model's output  is displayed below:
Saturated Vapor Chlorine Leak    07-30-1992

                               Input Data

Pollutant emission  rate (kg/sec) =  62.58396
Exit gas velocity (m/sec)=  148.87
Exit Temperature (K)=  341.572
Stack Height  (m) =   10     Diameter (m) =  .101598
Pollutant Concentration (volune X) *  100
Exhaust Gas Density (kg/m3) =  2.523289
Exhaust Gas Molecular Weight -  70.9
Exhaust Gas Mass Flow Rate (kg/sec) =  62.58396
Pollutant Molecular Weight =  70.9
Release duration (min) =  .106524  Av. Time  (min) =  15
                      1.0    2.0    3.0   4.0    5.0
                      8.0   10.0   15.0  20.0
Distances (m) =  100   200    300    400    500    600    700
               . 800   900    1000    1100    1200    1300
                1500    1600    1700    1900   2100    2300
                2700    2900    3100    3300   3600    3900
                4500    5000
Ambient Temperature (K) =  293  293  293  293 293  293
Rural Wind Speed Profile Exponents
 Wind Speeds (m/sec) =
                                                              1400
                                                               2500
                                                               4200
 ***             SUMMARY OF RVD MODEL  RESULTS             ***
 ********************************************

.Maximum off site concentration is  582952.8  ug/m3
                or equivalent ly   201.4435  ppm
                 occurring at     112.2981  m downwind
              when wind speed is  1  m/sec
                and stability is  A
          REMEMBER TO INCLUDE BACKGROUND  CONCENTRATIONS
                                                  4-63

-------
***  RVD DISTANCES
 ***
Distance Concentration
  (m)
(ug/m3)
Stability  Wind
  Class    Speed
          (m/sec)

-------
Release Richardson Numbers
      Stability Class
Wind
Speed
1.0
2.0
3.0
4.0
5.0
8.0
10.0
15.0
20.0
A
-
729135.7
91142.0
27005.0
11392.7
5833.1
1424.1
729.1
216.0
91.1
B

729135.7
91142.0
27005.0
11392.7
5833.1
1424.1
729.1
216.0
91.1
C

729135.7
91142.0
27005.0
11392.7
5833.1
1424.1
729.1
216.0
91.1
D

729135.7
91142.0
27005.0
11392.7
5833.1
1424.1
729.1
216.0
91.1
E

729135.7
91142.0
27005.0
11392.7
5833.1
1424.1
729.1
216.0
91.1
F

729135.7
91142.0
27005.0
11392.7
5833.1
1424.1
729.1
216.0
91.1
Dense Plume Trajectory
Stability Wind Plune Touchdown
Class

A
A
A
B
B
B
B
B
C
C
C
C
C
C
C
C
C
D
D
D
D
D
D
0
0
D
E
E
E
E
F
F
F
Speed
(rn/sec)
1.0
2.0
3.0
1.0
2.0
3.0
4.0
5.0
" 1.0
2.0
3.0
4.0
5.0
8.0
10,0
15.0
20.0
1.0
2.0
3.0
4.0
5.0
8.0
10.0
15. Q
20.0
2.0
3.0
4.0
5.0
1.0
2.0
3.0
Rise Distance
(m) (m)
31.8 112.30
25.2 234.32
22.0 361.81
31.8 112.30
25.2 234.32
22.0 361.81
20.0 493.46
18.6 628.57
31.8 112.30
25.2 234.32
22.0 361.81
20.0 493.46
18.6 628.57
15.9 1050.62
14.8 1343.49
12.9 2107.74
11.7 2909.84
31.8 112.30
25.2 234.32
22.0 361.81
20.0 493.46
18.6 628.57
15.9 1050.62
14.8 1343.49
12.9 2107.74
11.7 2909.84
25.2 234.32
22.0 361.81
20.0 493.46
18.6 628.57
31.8 112.30
25.2 234.32
22.0 361.81
Touchdown
Concentration
(ug/m3)
0.58295E+06
0.42725E+06
0.35393E+06
0.58295E+06
0.42725E+06
0.35393E+06
0.30867E+06
0.27705E+06
0.58295E+06
0.42725E+06
0.35393E+06
0.30867E+06
0.27705E+06
0.21933E+06
0.19571E+06
0.15828E+06
0.13557E+06
0.58295E+06
0.42725E+06
0.35393E+06
0.30867E+06
0.27705E+06
Q.21933E+06
0.1 9571 E+06
0.15828E+06
0.13557E+06
0.42725E+06
0.35393E+06
0.30867E+06
0.27705E+06
0.58295E-MJ6
0. 42725 E+06
0.35393E+06
(ppm)
0.20144E+03
0. 14764E+03
0.12230E+03
0.20144E+03
0.14764E+03
0.12230E+03
0.10666E+03
0.95737E+02
0.20144E+03
0.14764E+03
0.12230E+03
0.10666E+03
0.957376*02
0.75791E*02
0.67630E+02
0.54696E+02
0.46846E+02
0.20144E*03
0.14764E+03
0.12230E+03
0.10666E+03
0.95737E+02
0.75791E+02
0.67630E+02
0.54696E+02
. 0.46846E*02
0.14764E+03
0.12230E+03
0.10666E+03
0.95737E+02
0.20144t'03
0.14764E+03
0.12230E+03
                                    4-65

-------
 Concentrations at Specific Receptor Distances

Stability Wind Distance Concentration
 Class  Speed

A
A
A
A
A
A
F
F
F
F
F
F
*******!
*** END
(m/see)
1.0
1.0
2.0
1.0
2.0
3.0
1.0
2.0
3.0
(m)
200.0
300.0
300.0
400.0
400.0
400.0
4500.0
4500.0
4500.0

0.40060E+06
0.30778E+06
0.36385E+06
0.25529E+06
0.30180E+06
0.33158E+06
0.18137E+05
0.28100E+05
0.35945E+05
1.0 5000.0 0.15163E+05
2.0 5000.0 0.23492E+05
3.0 5000.0 0.30050E+05
(PP">
0.1384E+03
0.1064E+03
0.1257E+03
0.3822E+02
0.1043E+03
0.1146E+03
0.6267E+01
0.9710E+01
0.1242E+02
0.5240E+01
0.8118E+01
0.1038E+02
OF RVD MODEL OUTPUT ***
4.2.3.5  Considerations for  Time-Varying and  Time-Limited
Releases

      See Section 2.5  for a discussion of considerations for time-
varying and time-limited releases.
                                   4-66

-------
4.2.4  Instantaneous Gas Leaks from a Reservoir
                                 Instantaneous
                                 Gaseous Emission
                             Blown Rupture Disk
Similar Releases:  A gas leak from a tank or a  (small) gas  leak
from a pipe.

Discussion:

     This procedure applies to an instantaneous release of  a  gas
(at constant pressure and temperature) from a containment
(reservoir) through a hole or opening.

Limitations and.Assumptions:

     Same as Scenario 4.2.3.

Input Information:

     Same as Scenario 4.2.3.

Procedure:

1-6. Same as Scenario 4.2.3

7.   Buoyancy Check.  Perform buoyancy check as a first check.

     A.   Calculate the density of air using the following:
                                  R T.
                                                         (4.2.4-1!
          where. Mt is the molecular weight of air (assumed to
                               4-67

-------
          equal 28.9 kg/kmol).

     B.   If p^/Pta > 1  then the buoyancy is negative.   For
          negative buoyancy, the RVD model should be used if the
          release is from a vertically directed jet/ otherwise,
          the Britter-McQuaid model should be used/ go to step 8.
          If the buoyancy is positive, the PUFF model for a point
          source should be used.   (See Section 2.4 for more
          information on model selection.)

8.   Same as Section 4.2.3

4.2.4.1  Examples

     See the examples in Section 4.2.3.
                               4-68

-------
4.2.5  Continuous Gas Leaks from a Pipe Attached to a Reservoir
4.2.5.1   Release Rate Estimates:  Gas Leaks from a Pipe Attached'
          to a Reservoir'
Similar Releases:  Continuous release of a gas  (at constant
pressure and temperature) from a containment through a long pipe.

Limitations and Assumptions:

     The hole or opening size must be sufficiently small,
otherwise the reservoir temperature and pressure may no longer be
constant.  For the case of a leak from a tank, the assumption of
constant reservoir temperature and pressure may be violated if a
significant percentage of the tank contents is released.   If the
reservoir temperature and pressure are not constant, the release
rate may vary with time, but the maximum release rate is
generally obtained for the initial reservoir temperature and
pressure .

     The flow through the pipe is assumed to be adiabatic  (i.e.,
the heat transfer to the gas being released is unimportant) ; this
assumption is not very restrictive (Levenspiel  (1977) ) .

     The released material must be a  (ideal) gas at the reservoir
conditions, during the depressurization process, and after
depressurization to the atmosphere, and for the case of a  tank
containing vapor and liquid, -the pipe must be attached to  the "
vapor space of the tank  (Spicer, 1992) .

Input Information:
          area of reservoir hole or opening  (m2)
           (equivalent) diameter of hole or opening  (D0 =
                               4-69

-------
                  )  (m)
     Dp    pipe diameter  (m)
     Lp    pipe length (m)
     MV    gas (contaminant) molecular weight  (g/g-mole)  (For
          contaminant mixtures, see Appendix B)
     Ne    number of pipe elbows (dimensionless)
     Pv    vapor pressure as a function of temperature  (Pa)
     P.    ambient pressure  (Pa)
     Pt    reservoir pressure  (Pa)
     R    gas constant  (8314 J/kg-mole-K or 8314
          P,-m3/kg-mole-K)
     Tc    critical temperature  (K)
     T!    reservoir temperature (K)
                 ~ 1/(1  - R/tCMJ)  at T! (dimensionless)
Procedure:

1.   Pipe Friction Loss.  Estimate the friction loss  in  the
     piping system.  After Perry et-al.  (1984), estimate the
     frictional loss N as-.

                     4 f L
                 N = _I + 0.5 +  0.75 Ne +  [0.5]         (4.2.5-1)


     In Equation (4.2.5-1), the first term  represents  the skin
     friction losses in the pipe;  f=0.0045  (the coefficient of
     skin friction) can be used as a preliminary estimate (i.e.,
     a tighter estimate of f would probably be less than 0.0045,
     and although f can be larger  for Reynolds numbers less than
     105,  typical Reynolds numbers  for these applications are
     larger than 10s) .   The second  term provides for the effect
     of friction losses in the reservoir-to-pipe connection.   The
     third term accounts  for frictional  losses in any  pipe
     elbows.  The fourth  term  (written in brackets) should only
     be included if D0/DP  s 0.2, otherwise it should be left off.

2.   Discharge for Choked Flow.  Estimate the discharge  rate  as
     if the flow is choked  (the validity of this assumption will
     be checked); in this case, the gas  approaches the speed  of
     sound at the exit.   For choked flow, the following  equations
     must be solved simultaneously for the  Mach number at the
     pipe entrance Mj and a dimertsionless parameter (at the pipe
     entrance) Y2:
        tfi
                        Y, = 1 + /JLlJL) Mj2                (4.2.5-2)
                               \   2   /

                           2Y*    1- f_l -lU7N =  0

                        *t (^ + 1)  j  1M*    j            (4.2.5-3)

     After M2  and Y2 are known, the mass  flux G is fixed  by:

                               4-70

-------
                                          ^1/2
                     G = P1M2
1TT7
                          (4.2.5-4)
     The discharge pressure must be checked to determine if the
     flow is indeed choked:
                    P, (Pa)
                          (4.2.5-5)
     If P3Pi, then the flow is not choked, and  these
     estimates for G, M^  Y2/ and P3 are not valid; proceed to
     step 3.  If P^P^P,,  then  the  flow is choked, and the
     release rate is given by Qm (kg/s) = G AO.   The  discharge
     temperature T3  is  given by 2^7(7+1) .  Proceed to step  4..

3.   Discharge for Subcritical Flow.  Estimate the discharge rate
     for subcritical flow; in this case,  the gas  pressure at the
     pipe exit approaches ambient pressure  (P3=PJ .   For
     subcritical flow,  the following eight equations must be
     solved simultaneously for the mass  flux G;  the  Mach number
     at the pipe entrance and exit M2 and M3; the  pressure at the
     pipe entrance P2 (Pa);  the temperature at the pipe entrance
     and exit T2 and T3; and the dimensionless flow parameters (at
     the pipe entrance and exit) Y2 and Y3:
Y = 1 + / T

Y, = 1 + ( T
Y3 1 J
JULi ) in f !i5l ] - f
i b** i
2 / M2 Y
^ 3 1
IM "v
__!lZ
"D T1
R J-i
M, = - [-
K.-*P
' P2 [1
P, f T,
_! = i-l
**\ 1 I-M
~ 1 \ M| (4.2.5
/
1 1 Ma2 (42^
2IV13 \-X.4.. _<
/
A-jLln-7N = 0
M M 1
^ M3 J (4.2.5
>,l/2
Y('Y'*'1)/(1" y) 1 / /i o c
2 (4 . 2 . b
J
T 11/2
ill (4.2.5-
  -)l/2
^CT (4.2.5-
MWJ
17/( 7-D
(4.2.6-
-6)
-7)


-8)

-9)

10)
11)

12)
                                                        (4.2.5-13)
     The solution to  these equations must be  checked particularly
     to ensure that M3<1,  Pi>P2,  and Tt>T2.  If these conditions
     are not met, the value of  f  is probably  too low and should
     be increased.  The release rate is  given by Qm  (kg/s)  = G
                               4-71

-------
     A,,.   Proceed to step 4.

4.   Check Discharge Temperature T3.   The estimate of T3 must be
     checked.  If T3 is greater than the (pseudo)  critical
     temperature Tc,  the equation used to estimate T3 applies;  if
     not, the following procedure is  suggested.   For single
     component contaminants, evaluate the contaminant vapor
     pressure at T3 (PV(T3)).   If PV(T3)  a Pa< then  contaminant
     condensation occurs during the process of depressurization,
     and this approach is not valid;  this release should  be
     considered a two-phase release.  If this is  a two-phase
     release proceed to step 6, otherwise proceed to step 5.

5.   Discharge Density.  Estimate the discharge density   from  the
     discharge temperature T3  using the ideal  gas  law:  p3  =
     PjMw/ (RT3) .   (Note that for choked flow conditions,  correct
     application of a dispersion model may require that the
     diameter of the hole or opening be modified  D0(P3/Pa)U2 if  the
     model accounts for initial air dilution due  to jetting or
     momentum effects;-if this modification is not applied, the
     initial gas velocity is incorrectly overestimated.)   Proceed
     to step 9.

4.2.5.2   Continuous  (Two-Phase) Release Rate Estimate:   Gas
          Storage which Partially Condenses on Depressurization

Similar Releases -.  A gas leak from a  tank, a gas  leak from a
pipe.

Discussion:

     Materials which are stored under pressure will depressurize
when released to the atmosphere.  This depressurization results
in the formation of two contaminant phases (saturated liquid and
vapor)  for: gases which cool so that  condensation occurs  during
the depressurization process; and high volatility liquids
(liquids whose normal boiling point is below the  ambient
temperature) which are stored at  (typically)  above ambient
pressure.   (See Section 4.3.2 for more discussion on two-phase
releases.)  In this scenario,  the terms gas,  saturated liquid,
and subcooled liquid all refer to the state of the tank
contents.)   This scenario considers  the release  from a tank  (or
reservoir) and includes provision for the effect  of a pressure
drop (piping) between the tank and the hole or opening.

     This procedure applies to a continuous release of a  gas
which partially condenses during depressurization; the screening
procedure for this scenario should only be applied if the
screening procedure above indicated that partial  condensation  of
the released gas occurs.  The release occurs  (at  constant
pressure and temperature) from a containment  (reservoir)  through
a hole or opening; a provision is made for the-effect of  a
pressure drop (piping) between the tank and the hole or opening.

                               4-72

-------
Limitations and Assumptions:

     The pressure and temperature of the tank  (or  reservoir)
contents are essentially constant.  The hole or opening size  must
be sufficiently small, otherwise the reservoir temperature and
pressure may no longer be constant.  For the case  of  a  leak from
a tank, the assumption of constant reservoir temperature and
pressure may be violated if a significant percentage  of the tank
contents is released.  If the reservoir temperature and pressure
are not constant, the release rate may vary with time,  but the
maximum release rate is generally obtained for the initial
reservoir temperature and pressure.

     For the case of a leak from a pipe when j8 > 0.2  (as defined
below), the assumption of constant temperature and pressure in
the pipe may be violated; for such a case, the reservoir
conditions should be taken from an upstream location  (tank or
reservoir) where the temperature and pressure will be
(approximately) constant.  For the case of a leak  from  a pipe
when |8 s 0.2,. -the assumption of constant temperature  and pressure
in the pipe is reasonable, and the reservoir conditions should be
taken  to be the conditions within the pipe.

     The vapor phase of the release material must  be  an ideal gas
at the reservoir conditions, during the depressurization process,
and after depressurization to the atmosphere; for  the case of a
tank containing vapor and liquid, the hole must be in the vapor
space  of the tank.  For two phase flows, all released liquid  is
assumed to travel downwind as an aerosol with little  rain out of
liquid near the source  (Spicer, 1992).

Input  Information:

     AQ   area of reservoir hole or opening  (m2)
     A!   flow area representing reservoir conditions (m2)  (In  
          case of a leak from a tank, At - oo (and /3 = 0) ;  in  the
          case of a leak from a pipe, At is the cross-sectional
          area of the pipe.)
     Cp   gas  (contaminant) heat capacity at T! (J/kg-K)  (For
          contaminant mixtures, see Appendix B)
     D0    (equivalent) diameter of hole or opening (D0 =
          2-^Ao/Tr ) (m)
     Dp   pipe diameter  (as appropriate)  (m)
     Lp   pipe length  (appropriate)  (m)
     Mw   gas  (contaminant) -molecular weight  (kg/kmol)  (For
          contaminant mixtures, see Appendix B)
     P.   ambient pressure  (Pa)
     Pv   vapor pressure as a function of temperature (Pa)
     P!   reservoir pressure  (Pa)
     R   gas constant  (8314 J/kg-mole-K or 8314  P.-m3/kg-
          mole-K)
     Tb   contaminant normal boiling point  (K)


                               4-73

-------
     Tc    critical temperature  (for contaminant mixtures, see
          Appendix B)
     T!    reservoir temperature  (K)
     j8    ^AQ/AJ   {dimensionless)
     7    (Cp/Cv)  1/(1  - R/tCpMJ)  at Tt  (dimensionless)
     X    heat of vaporization at the normal boiling point  (J/kg)
     P!    contaminant density at reservoir conditions (T: and PL)
          (kg/m3)

Procedure:

6.   Choked Pressure.  Estimate the choked pressure P, to
     determine if the flow  is choked from Perry et al.  (1984).

                                      'ITU
                                                        (4.2.5-14)


     If P. a P., then the flow is choked;  go to step 7.   If P. <
     P,,  then the  flow is subcritical  (not choked); go to step 8.


7.   Two-Phase Choked Flow.  For choked flow,  estimate the
     discharge temperature  T2/  discharge density  p2, and the
   .  emission rate Qm.

     A.   Estimate T..   For pure components, estimate T*  (the
          temperature which corresponds to P.)  from the Glausius-
          Clapeyron equation:


                P. = 101325 exp f-^.f i  -ill      (4.2.5-15)
                                [  R   [ Tb    T.  J J

          which can be rewritten as:

                                   1
                    T.  =
                               R    in
                         Tb   XMW      101325
     B.   Estimate Properties  at  Choked Flow Conditions.  Based
          on assumed  isentropic behavior,  estimate the vapor
          fraction at  choked flow conditions X, as  follows:

                       T   F        CTl        rDll
              X-  - 1 f T^r  M.  C. in Ui  -R m -^-   i     (4.2.5-16;
          Using X. from Equation (4.2.5-16), estimate  the
          enthalpy change  (Hj-H,) and the density p, as follows:

                  H, - H.  = Cp (Tt - T.)  + \ (1 - X.)        (4.2.5-17)


                               4-74

-------
             p. = X.  I R T'  I + I  1  " X* I             (2.5-17)


     Note that values for the individual enthalpies  H! and H*
     are not required.

C.   Estimate Emission Rate.  Extending the  ideas  suggested
     by Lees (1950),  estimate the  emission rate Qm  (kg/s)  as
     follows:
                P.  2-0.85
                                  - H
                                4 f
                                             1/2
                          (4.2.5-19)
     where 0.85 is included to account for  irrevesibilities
     in the flow based" on Lewitt  (1953) and the  term 4fLp/Dp
     accounts for the pressure drop  (piping) between the
     reservoir and the hole or opening/ as  a preliminary
     estimate, use f =0.0045  (since typical  Reynolds  numbers
     for these applications are larger than 105)  .

D.   Estimate Discharge Temperature  and Density.   Estimate
     the discharge temperature T2 (after depressurization) .
     If a condensed phase is present, T2 will be given by
     the Glaus ius-Clapeyron equation:


            P. = 101325 exp  i      *  - *  1         (4.2.5-20)
                                  Tb
     which can be rewritten as:

               m _            1
                             .  in
                    Tb    \M;     [101325 J

     Using this estimate of T2/  estimate the vapor fraction
     X2 as:

                                                   (4.2.5-21)
                  X. = X. + Cn(T.  - T2)/X
     When X2 estimated from Equation (4.2.5-21) satisfies  1
     a X, a 0,  the estimate of T2  is valid,  and the density
     of  che discharged material is given by:
                  r
T
                          2
                          *
                                   PL
                                                   (4.2.5-22)
     However,  if X2 < 0 or Xj  >  1,  the  contaminant condensed
     phase which was present  at P. and T. is no longer
                                                       

                          4-75

-------
          present, and the released contaminant  is  a gas (without
          any condensed phase); the discharge  temperature and
          density are estimated as follows:
T2 = T.
                               - X.)/C
                                                        (4.2.5-23)

                                                        (4.2.5-24)
E.
          where X, = 0 .

          Go to step  9 to select  the dispersion model.
8.   Two-Phase Subcritical  (Nonchoked)  Flow.   For subcritical
     flow, estimate the gas/liquid  discharge  temperature T2,
     discharge density ,o2/  and the emission rate Qm.

     A.   Estimate  T2.   For pure components,  estimate T2 from the
          Glausius-Clapeyron  equation:
                 Pa = 101325 exp
          X Mw
          ~R~
                                                   (4.2.5-25)
          which can be rewritten  as:

                                   1
                    T =
                    "2
                               R

                              i M.
                               In
                                  101325
     B.   Estimate Properties  at  Discharge Conditions.  Based on
          assumed isentropic behavior,  estimate the vapor
          fraction Xj at discharge flow conditions as:
               X2 = 1
                   "2

                   "Ml
        C ln      - B in   i
                            (4.2.5-26}
          Using X2 from Equation  (4^.2.5-26), estimate  the
          enthalpy change  (K^ - 1^) "and the density p2 .as:
                - H,
                           Cp (Tt - T2) f X (1 - X2)
                            R T2
                                        PL
                                               -i
                                 (4.2.5-27)

                                 (4.2.5-28)
          Estimate Emission Rate.   Extending the ideas suggested
          be Lees  (1950),  estimate the emission rate Qm (kg/s)
          as:
           Q.
                       Pi
0.85
                                      HI -
                                      4 f LP / DP
                                 (4.2.5-29)
                               4-76

-------
          where 0.85 is included to account for irrevesibilities
          in the flow based on Lewitt  (1953) and the term 4fLp/Dp
          accounts for the pressure drop  (piping) between the
          reservoir and the hole or opening (as appropriate);  as
          a preliminary estimate, use f = 0.0045 (since typical
          Reynolds numbers for these applications are larger than
          10J) .

     D.   Go to step 9 to determine the dispersion model.

4.2.5.3  Dispersion Model Determination

     See Section 2.4 for a complete discussion of the model
determination.

Input Information;

     T,   ambient temperature (K)
     Q    total amount of material released (kg)

Procedure:

9.   Buoyancy Check.  Evaluate release buoyancy as a first check.


     A.   Calculate the density of air using the following:


                                                        (4.2.5-30)
          where M is  the molecular weight  of air (assumed to
          equal 28.9 kg/kmol ) .

     B.   If p2//ir > !'  then the buoyancy is negative.  For
          negative buoyancy,  the RVD model should be  used  if  the
          release is from a vertically directed  jet;  otherwise,
          the Britter-McQuaid model should be used; go  to  step
          10. If the buoyancy is positive, the SCREEN model  for a
          point source should be used.   (See Section  2.4 for  more
          information on model selection.)
                            x
10.  Release Duration.  The release duration is  used  as an input
     into the RVD and Britter-McQuaid models .  The release
     duration can be used to  determine if the release is
     continuous or instantaneous  (see Section 2.5).   Calculate
     the release duration Td using the equation below:
                 Td (min) = ____  ,         ,  y  .  ,        (4.2.5-31)
                           Qm (kg/s)   60  (s/min)
                               4-77

-------
4.2.5.4  Examples

4.2.5.4.1  Example 1:  Air Leak  - Choked

Discussion:

     In this example  (from Perry et  al.  (1984)),  (dry)  air stored
at l.lOlxlO6 Pa and 293.15 K is released from a tank through 10
m of a 5.25 cm  (inside diameter) Schedule  40  steel  pipe/  there
are three elbows in the line.  The diameter of  the  opening is the
diameter of the pipe.  The fenceline is 100 m from  the  tank.
This example demonstrates the procedure when  the  flow is  choked.


The following information will be required:

     AO   area of reservoir  hole or  opening  (7rD0/4 = 0.002165 m2)
     Cp   gas  (contaminant)  heat capacity  at  TI (1004 J/kg  K)
     D0   diameter of hole or opening (D0 = 0.0525 m)
     Lp   pipe length  (10 m)
     MV   gas  (contaminant)  molecular weight  (29  kg/kmol)
     Ne   number of pipe elbows  (3)
     Pa   ambient pressure  (101325 Pa)
     P!   reservoir pressure (l.lOlxlO6 Pa)
     R    gas constant  (8314 J/kg-mole- K)
     Tb   normal boiling point  (79 K)
     Q    total amount of material released  (400  kg)
    . Ta   ambient temperature  (293 K)
     Te   critical temperature  (154.6 K)
     TI   reservoir temperature  (293.15  K)
                                   at Tt (1.40)
With this  information,  the  procedure discussed above determines
the release  rate,  the  discharge temperature,  and the discharge
density.

1.   Pipe  Friction Loss.  Estimate the friction loss in the
     piping  system.   In Equation (4.2.5-1),  the first term is
     4 (0.0045) (10) /(O. 0525)  =  3.43;  the second term is 0.5; the
     third term is 0 .76 (3) =2 .25; and the fourth term is not
     included:

                   N = 3.43  + 0.5 +  2.25 = 6.18

2.   Discharge  for Choked Flow.  Estimate the discharge rate as
     if  the  flow is choked  (the validity of  this assumption will
     be  checked).   For choked  flow,  Equations (4.2.5-2] and
      (4.2.5-3)  are solved simultaneously for Mj  and  Y2/- computer
     solution gives Mj = 0.283  and Y2 = 1.016.  With R, and  Y2
     known,  the mass  flux G is given by Equation (4.2.5-4)  as:
                               4-78

-------
   G = l.lOlxlO6   0.283 / 2^232 'is  1.016<1;40*l>'<1-1-40>)1/2 = 1210 kg/m2s


     The discharge pressure P3 is given by Equation (4.2.5-5) as:
      P3 (Pa)  =1210 [** ; ^( ^0%-JJ  =2.71x10* Pa


     Since P3 a  P,, the flow is choked, and release rate  is  given
     by Qm=(1210)  (0.002165)  =2.62 kg/s.  (Note that the
     estimated release rate for the same reservoir conditions is
     reduced from 4220 g/s to 2620 g/s if the piping pressure
     drop is included.)  The discharge temperature T3 is given by
     2Tj/(7+l);  T3 = 244 K/  Go to Step 4.

4.   Check Discharge Temperature T3.   The estimate of T3  must be
     checked.  For this example, T3 =  244 K,  and the pseudo
     critical temperature of air is 154.6 K, so no  condensation
     .occurs for these conditions.

5.   Discharge Density.  Estimate the discharge density  p3  from
     the discharge temperature T3  using the ideal gas law:

           p3 =  (101325) (29)/( (8314H244) )  = 1.45 kg/m3

      (For these choked flow conditions, correct application of a
     dispersion model may require that the diameter  of the  hole
     or opening be modified to DQ(P3/Pt)in = 0.0525 m
      (2.71x!OVl01325)1/2 = 0.0859 m if the model accounts for
     initial air dilution due to jetting or momentum effects; if
     this modification is not applied, the initial gas velocity
     is incorrectly overestimated.)  Go to step 9.

9.   Perform Buoyancy Check.

     A.   Calculate density of air.
     B.   Ps/Pur > 1 therefore, buoyancy is negative.

10.  Release Duration.  Calculate  the  release  duration Td using
     the equation below:


                                               2.54 min
                     , ^             ,      ,
                     2.62  (kg/s)   60  (s/min)

     Since the release is  not  from a  vertically directed jet, the
     Britter-McQuaid model is  used.   (See Section 5.4 for more
     information on the Britter-McQuaid model . )
                               4-79

-------
Data  entry  in the  TSCREEN model  for  this  example  is  shown  below:
                 	 Continuous Leaks from Pipe Attached to Reservoir  -  Scenario 2.5

                  SOURCE PARAMETERS  - Page 1 of 4

                  Enter a unique title for this data's model run:
                  Air Leak from Pipe Attached to a Reservoir
                   INPUT INFORMATION
                                   Area (Ao) of Hole  or Opening -> 21-65'   cm1
                                            .Pipe Diameter (Dp) -> 9.0525   m
                                               Pipe Length (Lp) -> 16      m
                                          Molecular Weight (Mw) -> Z9      kg/kmol
                                     Number of Pipe Elbows (Ne) -> 3
                                          Ambient Pressure (Pa) -> 1ST52S   Pa
                                        Reservoir Pressure (P1) -> t.ltJlEi- Pa
                                     Reservoir Temperature (T1) -> 253*15   K
                                         Gas Heat Capacity (Cp) -> 1084    J/kg K
                      Continuous Leaks from Pipe Attached to Reservoir  -  Scenario 2.5
                   SOURCE PARAMETERS - Page 2 of 4

                   CRITICAL TEMPERATURE
                                      Critical Temperature (Tc) ->
                   EMISSION CHARACTERISTICS
                                            Flow Characteristic > Choked
                                             Emission Rate (Qm) -> 2625.677 g/s
                                          Exit Temperature (T3) -> 244.3249 "K
                                         Discharge Density (f3) -> 1.446561 kg/cubic m
                                         Pipe Friction Loss (N) -> 6.178571
                                             Exit Pressure (P3) -> 271306.2 Pa
                                                  Mass Flux (G) -> 1212.783 kg/m's
                   - Previous- Street*   -Next- Seraet*. i  *Ssc> Jtoorr
                  	 Continuous Leaks  from Pipe Attached to Reservoir  - Scenario 2.5 

                   SOURCE PARAMETERS  - Page 3 of 4

                   DENSITY
                                          Density of  Air (fair) -> 1.20209  kg/cubic m
                                       Ambient Temperature (Ta) -> 293  ::T <
                   Buoyancy is negative
                                                 4-80

-------
                 	 Continuous Leaks  from Pipe Attached to Reservoir  - Scenario 2.5
                  SOURCE PARAMETERS  Page 4 of 4

                  VERTICALLY DIRECTED JET
                        Does the release result in a vertically
                                            directed  jet (Y/N) -> if
                  TIME
                                         Release Duration (Td) -> 2.539028 min
                          Total Amount of Material  Released (Q) ->
                 	 Continuous Leaks from Pipe Attached to Reservoir  - Scenario 2.5
                  Based on user input, the Britter-McQuaid model has been selected.

                  BRITTER-McQUAID MODEL INPUTS - Page 1 of 3
                         *

                  MODEL PARAMETERS
                                        Relative Humidity (Rh) -> 50       %

                      Desired Averaging Time for the Calculation
                                             of Concentrations ->&-.',    min

                        Pollutant Boiling Point Temperature (Tb) -> 79-      K
d1r
                                    Previous Screen    
                  RECEPTOR LOCATIONS
                  Do you have specific locations where you would
                  like pollutant concentrations calculated (Y/N) -> ti
                                                                              Abart
A summary  of  the  Britter-McQuaid  model's  output  is  displayed
below:
                                      SUMMARY OF B&M MODEL RESULTS
                              MAX CONC     MAX CONC    DIST TO    WIND  SPEED
                              (UG/K**3)      (PPM)      MAX (M)      (M/S)
                               .7283E+08    .6037E+05
                                 100.
2.
                              REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS
                                                4-81

-------
                                     A

4.2.5.4.2  Example 2: Air Leak  - Subcritical  (Not  Choked)


Discussion :

     In this example,  (dry) air stored  at !. 82xl05 atm and 293.15
K is released from a tank through  10 m of  a  5.25  cm (inside
diameter) Schedule 40 steel pipe; there are three  elbows in the
line.  The diameter of  the opening  is the diameter of the pipe.
The fenceline is located 100 m  from the tank.   This example
demonstrates the procedure when the flow is not choked and is
similar to the last example except  for  the  reservoir pressure.

The following information will  be required:

     AO   area of reservoir hole or opening (7rD0/4 =  0.002165 m2)
     Cp   gas-  (contaminant) heat capacity at  T:  (1004 J/kg  K)
     D0   diameter of hole or opening  (D0 = 0.0525 m)
     Lp   pipe length  (10 m)
     MT,   gas  (contaminant) molecular weight  (29 kg/kmol)
     Ne   number of pipe elbows (3)
     P.   ambient pressure  (101325  Pa)
     P!   reservoir pressure  (1.82xl05 Pa)
     R    gas constant  (8314 J/kg-mole- K)
     Tb   normal boiling point  (79  K)
     Q    total amount  of material  released (400 kg)
     T,   ambient temperature  (293  K)
     Tc   critical temperature  (154.6 K)
     T!   reservoir temperature (293.15 K)
     7     (Cp/C,) = 1/(1 - R/fCpMj)  at Tj (1.40)
With this information,  the  procedure discussed above determines
the release rate,  the  discharge  temperature,  and the discharge
density.

Procedure :

1.   Pipe Friction Loss.  Estimate the friction loss in the
     piping system.  In Equation (2.5-1),  the first term is
     4(0.0045) (10)7(0.0525)  =  3.43;  the second term is 0.5; the
     third term  is 0.76 (3) =2 .25;  and the fourth term is not
     included :

                   N = 3.43  + 0.5 + 2.25 = 6.18

2.   Discharge for Choked Flow.   Estimate the discharge rate as
     if the flow is choked  (the  validity .of  this assumption will
     be checked).   For choked  flow,  Equations (4.2.5-2)  and
      (4.2.5-3) are solved simultaneously for IV^  and Y2; computer
     solution gives Mj = 0.283 and Y2 = 1.016.  With Mj and  Y2
     known, the  mass flux G is given by Equation (4.2.5-4)  as-.
                               4-82

-------
    G = 1.82x10*   0.283        '    i.oi6<1-*'*/-1-*>   201 kg/m2s


     The discharge pressure P3 is given by Equation  (4.2.5-5)  as
           '' ' 201  29   1 40
     Since P.P2, and Tt>T2.  The release rate is  given be Qm =  (184)
     (0.002165) - 0.398 kg/s.  (Note that  the estimated release
     rate for the same reservoir conditions  is  reduced  from 693
     g/s to 398 g/s if the piping pressure drop is included.)   Go
     to step 4.

4.   Check Discharge Temperature T3.  The estimate of T3 must be
     checked.  For this example, T3  282 K, and the pseudo
     critical temperature of air is  154 . 6  K, so no condensation
     occurs for these conditions .

5.   Discharge Density.  Estimate the discharge density p3  from
     the discharge temperature T3 using the ideal gas law:

           p3 = (101325) (29)/( (8314) (282) )  = 1.25 kg/m3

     Go to step 9 .

9.   Perform Buoyancy Check.

     A.   Calculate density of air.                        /

                    _ 101325   28.9  _ .
                  *     8314 . 293

     B-   Pi/Pair >! therefore, buoyancy is negative.

10.  Release Duration.   Calculate the release duration Td using
     the equation below:


          T' (min)  
                     0.398 W40 is/mini


                               4-83

-------
       After  this  calculation  run  the Britter-McQuaid  model  since
       the  release is  not from a vertically  directed jet.    (See
       Section  5.4 for more  information on the  Britter-McQuaid
       model.)

Data entry  in the  TSCREEN  model  for this example  is  shown  below:

               	 Continuous Leaks from Pipe Attached to Reservoir - Scenario 2.5

                SOURCE  PARAMETERS - Page 1 of 4

                Enter a unique title for this data's model run:
                 INPUT INFORMATION
                                Area (Ao) of Hole or Opening -> 21.65    cm1
                                        Pipe Diameter (Dp) -> O.OS2J   m
                                          Pipe Length (Lp) -> TO  -    m
                                      Molecular Weight (Mw) -> 29      kg/kmol
                                  Number of Pipe Elbows (Ne) -> 3
                                      Ambient Pressure (Pa) -> T3T325   Pa
                                    Reservoir Pressure (P1) -> t$2&i:   Pa
                                  Reservoir Temperature (T1) -> 292S.1*   "K
                                     Gas Heat Capacity (Cp) -> TSQ4    J/kg K
 Prevfw*
                                                      e*t fcfe    <> -Abort'
                	 Continuous Leaks from Pipe Attached to Reservoir  - Scenario 2.5

                SOURCE PARAMETERS - Page 2 of 4

                CRITICAL TEMPERATURE
                                  Critical Temperature (Tc) -> T54i,f.;{: K
                EMISSION CHARACTERISTICS
                                       Flow Characteristic -> Subcritical
                                        Emission Rate (Om) -> 397.0481  g/s
                                      Exit Temperature (T3) -> 282.4518  K
                                     Discharge Density (f3) -> 1.251296  kg/cubic m
                                     Pipe Friction Loss (N) -> 6.178571
                                        Exit Pressure (P3> -> 101325.0  Pa
                                            Mass Flux (G) -> 183.3939  kg/m's
                                        Scrowt
                	 Continuous Leaks from Pipe Attached to Reservoir - Scenario 2.5 

                SOURCE PARAMETERS - Page 3 of 4

                DEMSITY
                                      Density of Air (fair) -> 1.20209  kg/cubic m
                                   Ambient Temperature (Ta) ->
                Buoyancy is Negative
                     fiflt
                       Sfefeen
                                                          5*ae    
                                           4-84

-------
                 	 Continuous  Leaks from Pipe Attached to Reservoir -  Scenario 2.5
                  SOURCE PARAMETERS - Page 4 of 4

                  VERTICALLY DIRECTED JET
                        Does the release result in a vertically
                                            directed jet (Y/N) -> H
                  TIME
                                         Release Duration (Td) -> 16.79058 min
                          Total Amount of Material Released (Q) ->
                   #>* 8lJt'  , "Pr*vf*- Screen             X

                     Desired Averaging Time for the Calculation
                                             of Concentrations -> t?      min

                       Pollutant Boiling Point Temperature (Tb) -> 79      K
                 - Continuous Leaks from Pipe Attached to Reservoir - Scenario 2.5

                  BRITTER-MCQUAID MODEL INPUTS - Page 2 of 3
                  FENCELINE DISTANCE
                   Enter the distance  from the base of the stack
                                        to the plant fenceline ->
                  RECEPTOR LOCATIONS
                  Do you have specific  locations where you would
                  like pollutant concentrations calculated (Y/N)  ->
ltodeC
                                                                             Abort
A summary  of the  Britter-McQuaid model's  output  is  displayed
below:
                                                4-85

-------
                            SUMMARY OF B&M MODEL RESULTS
                       MAX CONC    MAX CONC   DIST TO   WIND SPEED
                           (PPM)     MAX (M)    (M/S)

                       .2459E-HJ8   .2038E+05    100.      1.
                       REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS
4.2.5.5    Considerations for Time-Varying and Time-Limited
            Releases

    .  See  Section 2.5  for a  discussion  of considerations  for time-
varying and time-limited releases.
                                    4-86

-------
4.2.6     Instantaneous Gas Leaks front a Pipe Attached  to  a
          Reservoir
Similar Releases-.  Instantaneous release of a gas from  a
containment  (at constant pressure and temperature) through  a  long
pipe.

Limitations and Assumptions:

     Same as for Scenario 4.2.5.

Input Information;

     Same as for Scenario 4.2.5.

Procedure:

1-8. Same as for Scenario 4.2.5

9.   Buoyancy Check.  Evaluate release buoyancy as a  first  check.


     A.   Calculate the density of air using the  following:
                                                          x
                                 P M
                            Plit = __!                    (4.2.6-1) .
                                     &

          where M, is  the molecular weight of air (assumed to
          equal 28.9 kg/kmol).

     B.   If p2//iir > !/  then the buoyancy is negative.  For
          negative buoyancy,  the RVD model  should be  used if  the
          release is from a vertically directed jet;  otherwise,
          the Britter-McQuaid model  should  be used; go  to step
          10.  If the buoyancy is positive,  the PUFF  model  for a
                               4-87

-------
          point source should be used.  (See Section 2.4 for more
          information on model selection.)

10.  Same as Section 4.2.5

4.2.6.1  Examples

     See the examples in Section 4.2.5.
                              4-88

-------
4.2.7  Continuous  Multiple Fugitive Emissions
                                    Range Leaks
                    Hand Valve Stern
                      Pump Seals
Open Ditches
 Similar Releases:   Releases from any continuous area or volume
'source where the emissions that are uniformly released over the
 area  or the area represents a collection of small sources poorly
 defined in terms of location (e.g.,  multiple vents on large
 manufacturing buildings,  fugitive VOC sources in refineries or
 chemical process manufacturing plants).

 Discussion:

      Fugitive gaseous emissions resulting from a collection of
 small sources and gaseous area source emissions of different
 types (e.g.,  process equipment, valves,  etc.) are modeled in this
 section.  Often, areas of fugitive emissions can be specified for
 elevated releases such as manufacturing facilities where
 substantial numbers of hood and vent sources are found on the
 roof  and fugitive emissions identified in mass balances are
 suspected from ventilation sources.  In these cases, the area of
 release can be considered as a volume source using a
 characteristic height such as a building height.  Dispersion
 calculations can assume area and volume source releases.
 However, currently, the TSCREEN model does not include volume
 source releases.

    "  The use of EPA fugitive emission factors for selected
 equipment are found in the EPA report Protocol for Generating
 Unit-Specific Emission Estimates for Equipment Leaks of VOC and
 VHAP. EPA-450/3-8S-010 (Appendix A).  For selected air toxic,
 fugitive factors are also found in Appendix A  (items 1 and 3) .
                                4-89

-------
Limitations and Assumptions-.

          Dispersion calculations assume area source releases
          only.


Input Information:

     EF   emission factor from various fugitive emissions  (Mg/yr)
     Pd   production rate (kg/Mg)
     Q.m   emission rate  (g/s)


4.2.7.1  Procedure

1.^   Emission Rate.  Fugitive gaseous emissions resulting  from a
     collection of small sources and gaseous area source
     emissions of different types  (e.g., process equipment,
     valves, etc.) are modeled using a source specific emission
     rate or fugitive emission factors.  The document Protocols
     for Generating Unit-Specific Emissions Estimates for
     Equipment Leaks or VOC. and VHAP. EPA-450/3-88-010 describes
     methodologies the EPA considers appropriate for development
     of unit specific emission estimates for equipment leaks of
     organic compounds: volatile organic compounds  (VOC) and
     volatile hazardous air pollutants  (VHAP).  Estimates
     generated using this document would be specific to process
     units  (or groups of sources) for which an estimate was made.
     EPA has made provisions for extending such estimates  beyond
     the limits of that group of sources.  Five methods for
     estimating emissions from equipment leaks from a specific
     chemical processing unit are included in the protocol:
     average emission factor method; leak/no-leak emission factor
     method; three-strata emission factor method; application of
     EPA correlations; and development of new correlations.  For
     selected air toxics, factors are also found in Appendix A
     items  1 and 3.
     If the emission rate is not known it can be .calculated as
     follows:                   ,

     A.   Emission Rate in kg/yr.  Calculate emission rate in
          kg/yr.

                  Qm (kg/yr) =Pd (Mg/yr) EF (kg/Mg)          (4.2.7-1)

     B;   Emission Rate in g/s.  Convert emission rate from kg/yr
          to g/s.

                 Q (g/s) _  Qm (kg/yr) .1000 (g/kgl
                          365 (dy/yr) 86400 (s/dy)


                               4-90

-------
2.    TSCREEN will  run the SCREEN model for an area source.   See
     Section B.I.2 for a complete list of inputs.

4.2.7.2  Example:   Ethylene Bichloride Release

Discussion:

     The maximum hourly average concentration estimate  is
required for ambient  ethylene dichloride at a fenceline receptor
100 meters downwind from a production facility.  The area  of
emissions at the plant is 100 m x 100 m, and production rate is
204,000 Mg/yr  in continuous operation over the year.

     Normal production of ethylene dichloride in vinyl  chloride
plants results in  fugitive emissions from storage vents.
Specific sources of emissions cannot be specified.  As  a result,
simulations make use  of emission factors to provide average
emissions plantwide.   These emissions are then used in  a
continuous ground  level area source dispersion model.

Procedure: .

1.    Emission  Rate.  Emissions are obtained from emission  factors
     published by  EPA (1987b).   Plant-wide emissions are
     calculated from the production rate and an emission factor
     from various  fugitive sources.  'The emission factor per
     production unit  is given by:
                chIorination vent             0.0216 kg/Mg
                column vents                0.06 kg/Mg
                process storage vents           0.0003 kg/Mg
                process fugitive              0.265 kg/Mg

                Totat	0.3469 kg/Hg	


     A.    Emission Rate in kg/yr.  Total emissions  (in  kg/yr)  for
           the plant ar.e given by Equation (4.2.7-1) :

  Qm (kg/yr)  204,000  (Pflg/yr) X  0.3469  (icg/Mg). = 70,768  (kg/yr)

     B.    Emission Rate in g/s.   Convert emission rate  to g/s:

          Q  (j/g?- 70,768 (kg/yr) 1000 (g/kg)  =  2_24   / }
          Wm  y/      365 (dy/yr) 86400 (s/dy)          a

2.   Run the SCREEN model for an area source.    For a complete
     explanation  of the inputs for the SCREEN model for an area
     source,  see  Section 5.1.2.   The default release height (Hs)
     for this scenario is 0.

Data entry in the TSCREEN model for this is shown below:


                               4-91

-------
                   Gaseous Emissions from Multiple Fugitive Sources - Scenario 2.7

                   SOURCE PARAMETERS - Page 1 of 1

                   Enter a unique title for this data's model  run:
                                                                "
                                                       9/s
                   EMISSION RATE
                        Enter the Emission Rate (dm), if unknown enter
                              the boxed variables below to calculate ->
                                                Production Rate  (Pd) -> 20*09$   Mg/yr
                    Emission Factor from various fugitive sources  (EF) -> .3469    kg/Mg
id-it
                                                                           *s$>f Afeort.-:
                 	 Gaseous Emissions from Multiple  Fugitive Sources -  Scenario 2.7
                  Based on user input, SCREEN model  has been selected.
                  SCREEN MODEL INPUTS - Page 1 of 2

                  RELEASE PARAMETERS
                                    Release Height  above Ground (Hs) ->  P|i*?C n>
                                     Area of the Emitting Source (A) ->  1ieoi&C: m'

                  URBAN/RURAL CLASSIFICATION
                                     Enter U for Urban - R for Rural ->  R:

                  FENCELINE DISTANCE
                      Enter the distance from the nearest edge of the
                                       source to the  plant fenceline ->  |t98x j...'  m

                  FLAG POLE RECEPTORS
                              Enter Receptor Height  above Ground (Zr) ->  0;:;; -..:',,:-.. m

                  RECEPTOR LOCATIONS
                  Do you have specific locations where you would like
                      pollutant concentrations to be calculated (Y/N) ->  (jf
A summary  of  the  SCREEN model's  output  for this  example  is  shown
below:
                                 ***  SUMMARY OF SCREEN MODEL RESULTS ***
                                 ***************************************
                             CALCULATION
                              PROCEDURE
                       MAX CONC
                      (UG/M**3)
OlST TO
MAX (M)
TERRAIN
 HT (M)
                            SIMPLE  TERRAIN
                       1190.
                                                             100.
                                                0.
                            ***************************************************
                            ** REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS **
                                                4-92

-------
4.2.8  Continuous Emissions from Land Treatment  Facilities
                  Emissions

                             Organic Sludge
                   Soft treatment
Similar Releases:  Landfarms; ground level application  of  sludge
(volatile organic material in oil) to soil surface.

Discussion:

     The emissions equation is a  simplification of  the  Thibodeax-
Hwang model, assuming ground-level application of the waste,  more
rapid diffusion through the oil layer, and vapor-liquid
equilibrium between the oil layer and pore spaces.

Limitations and Assumptions:

          Waste is a sludge consisting of organics  in oil.

          Methods are a simplification of the Thibodeax-Hwang
          emission model  (Thibodeax and Hwang, 1982) .

          Assumes no subsurface injection, slower diffusion of
          organic component through air-filled po&e spaces  than
          through the oil layer,  and vapor-liquid equilibrium
          between the air in the  pore spaces and the^ oil  layer.

          Assumes that Raoult's Law applies.

          Effective diffusivity is assumed to be 40 % of  pure
          component diffusivity.

Input Information:

     A    release area  (m2)
     LV.P  latent heat of vaporization  (J/kmol)
     Tb    boiling point temperature  (K)
     M,,   molecular weight  (kg/kmol)


                               4-93

-------
     pptn  grams of organic component per million  grams  of  waste
          oil  (g/Mg)
     Pv   vapor pressure as a function of temperature  (Pa)
     R    gas constant  (8314 J/kg-mole- K)

4.2.8.1  Procedure

1.   Vapor Pressure.  Calculate the vapor pressure  (Pv)  in Pa.
     The vapor pressure of a pure substance  is  temperature
     dependent.  The Antoine equation could  be  used  to.  estimate
     vapor pressure; however, the Glaus ius-Clapeyron equation is
     used in TSCREEN because the required input is readily
     available for most chemicals in TSCREEN' s  chemical database
     The Claus ius-Clapeyron equation is:
                   Pv = 101325 exp2-:   -              (4.2.8-1)
     where T = liquid temperature  (K) , assumed  =  298  K.   The
     vapor pressure must be greater than 0 .

2.   Emission Rate.  Calculate Emission Rate  (Qm)  (g/s) . 'Since
     typical applications involve  applications of  volatile
     liquids such as benzene, the  Thibodeux- Hwang  emission  model
     has been simplified for screening purposes  using  default
     values .-

              Qm  K   ppm (g/Mg)  - A (m2)  (Pv)1/2 (Pa)      (4.2.8-2)

     where: K = 9 .101xlO'10(g/Pa1/2-m2-s)

3 .   Run the SCREEN model for an area source .  For an  explanation
     of inputs to the SCREEN model to an area source,  see Section
     5.1.2.


4.2.8.2  Example:  Emission from sludge containing _ benzene

Discussion:

     Sludge containing 1000 ppm benzene is applied to  a one acre
land treatment site at a rate of 1 lb/ft2 and filled to a depth
of 8 inches.  Hourly average concentrations at the fenceline of
200 m are needed.

The following input information will be required:

     A    release area (one acre or 4046.8 m2)
     ^   latent heat of vaporization  (3.9393xl05 J/kg)
     Tb    boiling point temperature of benzene (351  K)
     M,   molecular weight  (78.12 kg/kmol)
     ppm.  grams of benzene per million grams of  waste  oil  (1000 g
                                 

                               4-94

-------
             benzene/Mg  oil)
             gas  constant  (8314  J/kg-mole-K)
Procedure:

1.
Vapor  Pressure.   The  vapor pressure  is  calculated  using
Equation  (4.2.8-1)  as follows:
     P,  . Z01325 exp   3.^3x^.73.12 |_1_ .
                                                                    4 Pa
2.    Emission  Rate.   Calculate the emission  rate  (Qm)  in g/s
      using Equation  (4.2.8-2):


        Qm = S.lOlxlO'10   (1000)  -4046.8   (1.55xl04) m = 0 .46 g/s


3.    Run the SCREEN model for an area  source.

Data entry in  the TSCREEN model  for  this  example is shown  berow:

              	 Gaseous Emissions from Land Treatment Facilities - Scenario 2.8 	

               SOURCE PARAMETERS - Page 1 of 2

               Enter a unique title for this data's model run:


               EMISSIONS RATE
                   Is the Emission Rate (Qm) known (Y/N)  -> ft

               VAPOR PRESSURE
               Enter the Vapor Pressure of the Constituent  (Pv),if unknown
                     enter the variables below  to calculate -> f$$&$*9 Pa
                        Latent Heat of Vaporization (Lvap) -> 3^959365 J/kg
                           Boiling Point Temperature (Tb) -> 35-t     K
                                  Molecular Weight (Mw) -> 75.15.   kg/kmol
<$%> di-t 
                       Previous Screen-;   Next: Senew*-
                                                                Abort
              	 Gaseous Emissions from Land Treatment Facilities - Scenario 2.8

               SOURCE PARAMETERS - Page 2 of 2

               EMISSION RATE
                                     Emission Rate (Qm) -> 0.459121 g/s
                Parts of Organic Component in Waste Oil (ppm) -> 1000   g/Mg
                                      Release Area (A) -> t&<>6*&, m1
                                       4-95

-------
                 	 Gaseous Emissions from Land Treatment Facilities - Scenario  2.8
                  Based on user input, SCREEN model  has been selected.

                  SCREEN MODEL INPUTS - Page 1 of 2

                  URBAN/RURAL CLASSIFICATION
                                     Enter U for Urban - R for Rural -> B

                  FENCELINE DISTANCE
                      Enter the distance from the nearest edge of  the
                                      source to the plant fence line -> &)$.      m

                  FLAG POLE RECEPTORS
                             Enter Receptor Height  above Ground (Zr) -> ft        m

                  RECEPTOR LOCATIONS
                  Do you have specific locations where you would like
                      po.Uutant concentrations to be calculated (Y/N) -> It
                Run Jtodei.
                                                                             Abort ]
A summary  of the  SCREEN model's  output  for  this  example  is  shown
below:
                               **********************#***********
                               *** SUMMARY OF SCREEN MODEL RESULTS ***
                               *****************************
                           CALCULATION
                            PROCEDURE
 MAX CONC
(UG/M**3)
DIST TO   TERRAIN
MAX (M)    HT (M)
                          SIMPLE TERRAIN
 3464.
   100.
0.
                          * REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS **
                          #*************************************
                                               4-96

-------
4.2.9  Continuous Emissions from Municipal Solid Waste Landfills
Similar Releases:  None.  Emission rates applicable to municipal
solid waste landfills only.

Discussion:

     A New Source Performance Standard was proposed on May 30,
1991 for Municipal Solid Waste Landfills (MSWLFs).   Air emissions
from MSWLFs contribute to the formation of ambient ozone and
potentially to global warming.  The U.S. EPA estimates that
MSWLFs emit about 1% of the national stationary source volatile
organic compound  (VOC) emissions.  Also, the methane produced
from landfills is between one third and one half of the national
total.  Toxics, explosion potential, and odor nuisance are
additional problems related to air emissions from MSWLFs.

     Landfill air emissions are controlled through application of
a gas collection system and control device.  Three engineering
components comprise the collection and control system.
Extraction wells pull the gas up from the depth of the fill.  A
header system links all the wells and collects the gas by vacuum.
A control device either burns the ga"s or uses it for fuel.
                   s

     In the proposed regulation, the U.S. EPA has developed a
system to determine which landfills should be controlled.   A non-
methane organic compound (NMOC) emission rate was selected for
determining applicability under this regulation.  Each landfill
calculates its annual emissions.  If a landfill emits over a
certain amount of NMOC per year, a gas collection and control
system must be installed.

     The information in this section is taken from the background
document for proposal of air regulations for municipal solid
waste landfills (EPA, 1991b).  This document explains how
emissions can be estimated using either  (1) an equation based on


                               4-97

-------
default values or  (2) sampling data  (e.g., field measurements  of
the gas flow rate and composition) .  The equation is based  on  the
Scholl Canyon model  (EMCON Associates, 1982) and uses default  or
measured values of methane generation potential and nonmethane
organic compounds  (NMOCs) .  The total VOC emissions determined by
this procedure can be speciated using a profile as shown  in Table
4.2.9-1.  There are a number of factors contributing to the
variability in gaseous emissions from municipal solid waste
landfills (e.g., waste composition,  landfill moisture content,
age of refuse, pH and alkalinity of  landfill, amount of buried
waste, climate, and physical and operating characteristics  of  the
landfill) .  The greatest  sources of  uncertainty are the type and
amount of waste buried in a landfill.  Use of sampling data is
strongly recommended  (as  described in the EPA background  document
for proposed regulations  for municipal solid waste landfills) .
However, the use of an equation is considered appropriate as a
simple screening tool, and this approach is described below.

     Ambient concentrations resulting from municipal solid  waste
landfill emissions are determined using area source techniques in
the SCREEN model.

Limitations and Assumptions:

          Emission rates  are applicable to municipal solid  waste
          landfills only.

          An average NMOC emission rate is provided.   (To obtain
          the individual  toxic constituent emission rate, the
          individual toxic constituent percent of total emissions
          is needed.  The background document for the proposed
          regulations provides the range in the vapor phase
          concentration of toxic constituents that has been
          measured from landfills nationwide.)

          Emission 'rates  are assumed to be steady-state,  with  no
          seasonal or diurnal variation.

Output :

     MNMOC = Average annual NMOC emission rate, Mg/yr
     MNMOC (g/s) = MNMOC  (Mg/yr) X 0.0317
Input Information:
                                                 *

     L0         refuse methane generation potential  (mJ/Mg refuse)
     R         average annual waste acceptance rate  (Mg/yr)
     k         methane generation rate constant  (1/yr)
     c         year since closure (c=0 for new/active landfills)
     t         age of landfill  (yrs)
     CNMOC      concentration of NMOC  (ppmv as hexane)
     ConstPer  constituent percent of total VOC emissions  (%)
                               4-98

-------
     3.595 X 1C)'9  conversion factor
     The variables R, c, and t should be known for each landfill.
     The average annual acceptance rate, R, can be determined by
     dividing the refuse in place by the age of the landfill .   If
     site-specific values of k, L0,  or  CNMQC are unknown,  default
     values of 0.02/yr, 230 mYMg,  and  8000 ppmv as hexane may be
     used, respectively.


4.2.9.1  Procedure ;

1.   Mass Emission Rate of NMOC, Mg/yr.  Calculate the average
     annual NMOC emission rate.  The following equation is best
     suited for the purposes of the U.S. EPA to determine the
     NMOC emission rate:

          MNMOC = 2L0R(e-kc - e*)  (CNMOC) (3.595 X 10'9)         (4.2.9-1)
2.   Mass Emission Rate of NMOC, g/s.  Convert Mass Emission  Rate
     of NMOC from Mg/yr to g/s.
                MNMOC (9/s)  = MNMOC (Mg/yr)  X 0.0317       (4.2.9-2)

     Fraction of total NMOC emissions/ Qm  (g/s).

             Qm  (g/s)  = MNMOC (g/s) X ConstPer (%)/100    (4.2.9-3)
4 .    Dispersion of emissions from a landfill is simulated as  an
     area source, involving determination of dispersion
     parameters based on virtual distances before concentrations
     can be calculated at each receptor location.  The SCREEN
     model for an area source is used for this scenario.  For an
     explanation of inputs for the SCREEN model for an area
     source, see Section 5.1.2.

4.2.9.2  Example .  Municipal Solid Waste Landfill

Discussion:

     Hourly concentration estimates are required for emissions of
perchloroethene from a municipal landfill in Ohio.  The  landfill
area is 3 hectares and the distance to the nearest offsite
receptor is 100 m.

          Concentration estimates from landfills are determined
using an emissions model or site-specific measurements.   In  this
example, measurements are not available and the NMOC emission
model in Section 4.2.9.1 is used.  Once NMOC emissions are
calculated, NMOC emission profiles  (Table 4.2.9-1) are used  to
determine what fraction of the total is perchloroethene.  The
example concentrations listed are averages;  site- specif ic

                               4-99

-------
concentrations are dependent on  the  type  of  waste in the
landfill.

The following input information  will be required:

     L0   refuse methane generation  potential  (230 m3/Mg refuse)
     R    average annual waste acceptance rate  (13,000 Mg/yr)
     k    methane generation rate  constant (0.02  (1/yr))
     c    year since closure  (0)
     t    age of landfill  (10 yrs)
     CNMOC concentration of NMOC  (8000 pptnv as hexane)
           molecular weight of NMOC  (87.00 Ib/mole NMOC)
                          TABLE 4.2.9-1
                  SPECIATED VOC EMISSION PROFILE

     Air Toxic Chemical   Molecular Wt .       Concentration (ppmv)

     Benzene                   78.12                3.52
     Carbon Tetrachloride      153.81                1.49
     Chloroform                119.38                0.06
     Ethylene Bichloride       98.96                1.85
     Methylene Chloride        84.93               19.70
     Perchloroethene           165.83                6.82
     Trichloroethene           131.29                3.80
     Vinyl Chloride            62.50          '      7.04
     1, 1-Dichloroethylene      96.94                0.16

Procedure:

1.   Mass Emission Rate of NMOC, Mg/yr.   From Equation (4.2.9-1),
     emissions are calculated  as :

          MNMOC = 2(230) (13,000) (1  - e^0'02*10') (8,000) (3.595X10'9)
               =31.2 Mg/yr
2.   Mass Emission Rate of NMOC, g/s.   From  Equation (4.2.9-2
     the emissions in g/s are calculated  as:
         

          MNMOC "= 31.2 Mg/yr X 0.0317  =  .989  g/sec
                              4-100

-------
3.    Fraction of total NMOC  emissions/  Qm  (g/s).   The  fraction  of
      perchloroethylene to the total NMOC emissions can be
      calculated as  follows:

               6.82(ppmv) X   165.83(Ib/mole)    = 0.0016
               8000(ppmv)     87.00(Ib/mole NMOC)

      (ConstPer = 0.0016  x 100% =  0.16%)

      Perchloroethylene emissions  Qra can  then be calculated  as
      follows:
                  Qm = -989  (g/s)  X  .0016  = .0016 g/s

4.    TSCREEN will run the SCREEN  model  for an area source.

      Landfill area  = 3 hectares  (30,000  m2)
      Distance to nearest offsite  receptor  = 100 m

Data entry in the TSCREEN model for this example  is  shown  below:
                  Emissions from Municipal Solid Waste Landfills - Scenario 2.9
              SOURCE PARAMETERS - Page 1 of 1

              Enter a unique title for this data's model run:
                                              ""
              EMISSION RATE
              Enter the Emission Rate (Qm), if unknown
               enter the boxed variables below to calculate -> Q0015ST g/s
                      Average Annual Acceptance Rate (R) ->
                               Year since Closure (c) -> 8
                                 Age of Landfill (t) -> Iff
                    Methane Generation Rate Constant (k) -> 5.02
                  Refuse Methane Generation Potential (Lo) -> 23BS
                         Concentration of NMOC (Cnmoc) ->
                    Constituent % of Total VOC Emissions -> .
                                         Mg/yr

                                         yrs
                                         1/yr
                                         cubic m/Mg
                                         ppmv as hexane
- Next. Sew  -- Abort-
                                    4-101

-------
                	 Emissions from Municipal Solid Waste Landfills - Scenario 2.9 	
                  Based on user input, SCREEN model has been selected.
                  SCREEN MODEL INPUTS - Page 1 of  2

                  RELEASE PARAMETERS
                                    Release Height above Ground  (Hs) -> ip$fficj m
                                    Area of the  Emitting Source (A) -> $&(9^ft m'

                  URBAN/RURAL CLASSIFICATION
                                    Enter U for  Urban - R for Rural -> ft

                  FENCELINE DISTANCE
                     Enter the distance from the  nearest edge of the
                                      source to  the plant fence line -> %S;p|./| m

                  FLAG POLE RECEPTORS
                             Enter Receptor Height above Ground  (Zr) -> ^?*Q? m

                  RECEPTOR LOCATIONS
                  Do you have specific locations where you would  like
                     pollutant concentrations to  be calculated (Y/N) -> ft

                j||i||f^|fi!i^^                                                     _.";




A summary  of   SCREEN model's  output  for this  example  is  displayed
below:

                                ***************************************

                                *** S.UMHARY OF SCREEN rKOEl RESULTS ***


                             CALCULATION       MAX CONC   DIST  TO   TERRAIN
                              PROCEDURE         (UG/M**3)    MAX (M)    HT (M)

                            SIMPLE TERRAIN     5.008         100.        0.



                           ** REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS **
                           ***************************************************
                                               4-102

-------
4.2.10  Continuous Emissions of Pesticides
                   Emissions
Similar Releases:  Emissions resulting from the volatilization of
pesticides or herbicides applied to open fields.

Discussion:

     Pesticides are classified according to the targeted pest.
The most widely used pesticides, particularly in-agriculture, are
herbicides, insecticides, fungicides, and nematicides.   A
pesticide, otherwise known as the active ingredient, is combined
with inert ingredients in formulations such as sprays,  dusts,
granules, aerosols, fumigants, and microencapsulation.

     There are several factors that influence the extent and rate
of pesticide volatilization, including physical and chemical
properties of the pesticide, method of application, the type of
surface to which the pesticide is applied, and degree of
incorporation into the soil.

     Evaporative losses during application and post-application
are proportional to vapor pressure.  The vapor pressure of active
ingredients generally range from 10'3 to 10'8 millimeters of
mercury"  (mm Hg) .  Fumigants usually have higher vapor pressures.
Ethylene bromide, a common  fumigant, has a vapor pressure of 0.8
mm Hg at 20C.   Often the inert ingredient -i's an organic solvent
such as xylene,  which has a vapor pressure of 8 mm Hg.

     For pesticides applied to soils, the soil moisture content
and the depth of the tilling are important factors affecting
volatilization.  Pesticides applied to dry soils do not
                              4-103

-------
volatilize as rapidly as pesticides applied to moist soils
because of greater adsorption of pesticides on dry soil.  The
evaporation rate of pesticides incorporated into the soil is
limited primarily by pesticide movement through the soil to the
surface.  The resistance increases with mixing depth.

     Ambient concentrations resulting from the volatilization of
applied pesticides are determined by using area source techniques
in the SCREEN model.
Limitations and Assumptions
          Maximum evaporation rates of pesticides are estimated
          based on the rate of evaporation of a compound such as
          water.

          The method is based on the principle that loss of a
          pure substance into the atmosphere from an inert
          surface is proportional to the vapor pressure and the
          square root of the molecular weight of the substance.

          The water evaporation rate is adjusted for the type of
          surface and relative humidity.

References -.

          The best sources of information are technical
     literature searches and contacts with agricultural research
     stations.  Information on pesticide formulations, air
     emissions potential, and control strategies can be found in
     the Alternative Control Technology (ACT) for Application of
     Agricultural Pesticides report.  The draft report was
     released April 1992 for peer review by the Emissions
     Standards Division of the Environmental Protection Agency
     located in Research Triangle Park, North Carolina.  The
     reader may also find the following reference to be helpful .-

          Spencer, W.P. and Cliath M.M., 1973:  "Pesticide
          Volatilization as Related to Water Loss from Soil,"
          Journal of Environmental Quality.

Input Information:

     E    evaporation rate of water per acre  (inches of water
          evaporated X 226,600 pounds per inch on one acre)
          (in/day)
     aE   adjusted water evaporation rate in lb/acre; aE=0.73E,
          0.40E, and 0.70E for application to vegetated land,
          soil surfaces, and water surfaces, respectively
     RH   relative humidity  (%)
     Pw   vapor pressure of water at same temperature as PP
          (atm)
                                             

                              4-104

-------
     PP   vapor pressure of pesticide ingredient  (atm)
     Mw   molecular weight of water  (18 g/g-mole)
     Mp   molecular weight of pesticide ingredient  (g/g-mole)
     A    area of application (m2)


4.2.10.1  Procedure

1.   Evaporation Rate of Water.  Convert the evaporation rate  of
     water (E) from in/day to g/s.

      E(lb/s/acre)= E(in/day)226600(Ib/in/acre)(day/8640Qs)
                                                        (4.2.10-1)

          E  (Ib/s) =E  (Ib/s/acre)   	A (m2)	 (4.2.10-2)
                                     3910.3445  (mVacre)
                E (g/s)  *E (Ib/s)  493.593  (g/lb)       (4.2.10-3)

2.   Emission Rate Qm.   The following equation developed by
     Spencer is used ,to determine the evaporation rate  of  a
     pesticide ingredient per acre:


               ^=  [aE/(l -RH/100)]  [P, .  760   Q      (4.2.10.4)

                             Pw   760  M^'2

3.   Area source dispersion techniques are used for the emissions
     from pesticide application.  The SCREEN model for  an  area
     source is used for this scenario.  For an explanation of
     inputs to the SCREEN model  for  an area source, see Section
     5.1.2

4 .2 .10.. 2  Example:  Continuous Emissions from an Herbicide

Discussion:

     Bentazon is applied to 14.5 acres  (56,700 m2)  for
postemergence control of broadleaf weeds.  The active ingredient
is sodium bentazon at 40 percent by  weight.  The molecular weight
of sodium bentazon is 262 grams per  mole.  The vapor pressure  at
25C is approximately IxlO""' mm Hg  (1.32xlO'10 atm) .  Rate of
application is one pound of active ingredient per acre.  The
evaporation rate of water is 0.20  inches per day.  The  property
boundary is located 100 meters from  the edge of the study  field.
Maximum post-application one-hour  average concentrations are to
be estimated.  The relative humidify is 60 percent.

The following input information  will be required:


     E    evaporation rate of water  per acre  (Ib/day/acre)
           (inches of water evaporated per day X 226,600 pounds
          per inch on one acre); 0.20 in/day of water evaporated

                                     *
                              4-105

-------
      aE   adjusted  water evaporation rate  in- lb/acre/ aE=0.73E
           for application  to vegetated land
      RH   relative  humidity (60 %)
      Pw   vapor pressure of water  at same  temperature as  PP
            (.03158 atm)
      PP   vapor pressure of pesticide ingredient  (1.32xlO~10 atm)
      Mw   molecular weight of water (18 g/g-mole)
      MP
      A

Procedure:

1.
           molecular weight of  pesticide ingredient  (262 g/g-mole)
           area of application  (56,700  m2)
     Evaporation Rate of Water.   Calculate  the evaporation  rate
     of water  using Equations  (4.2.10-1),  (4.2-10.2),  and  (4.2-
     10.3):

E(Ib/s/acre)=0.20(in/day)226600(Ib/in/acre)(day/86400s)=0.52(Ib/s/acre)
     E (Itr/s)  = E  (Ib/s/acre)
                                         A (m2)
                                                        =7.6 (Ib/s)
                                  3910.3445 (m2/acre)


           E  (g/s)  = E (Ib/s)   493.593 (g/lb)  =  3440 (g/s)


2.    Emission Rate Qm.   Use  the evaporation  rate of  water  to
      estimate emissions of  sodium  beritazon  from the  field  with
      Equation (4.2.10-4):


   Q  =  t0.73-3440/(l - 60/100)]  [1. 32xlQ-10-760   2621/23  =  00oi(q/s)
                          .03158-760-181/2

3.    TSCREEN will  run the  SCREEN model for  an  area source:


Data  entry  in the  TSCREEN model for this example  is  shown  below:

             	 Emissions from Pesticide/Herbicide Applications - Scenario 2.10

             SOURCE PARAMETERS  - Page 1  of 1

             Enter a unique title for this data's model run:
             w	'+ ..'.; +	  .*.. _.   .    .   ..   .  . . .  . .   .  -,,.
             EMISSION RATE
              Enter the Emission Rate (Qm), if unknown enter
                   the boxed variables below to calculate -> ftiQODf  g/s
                         Evaporation Rate of Water  G&2? T:  in/day
              Enter V for Vegetated Land-S for Soil Surfaces
                               W for Water Surfaces -> V
                              Relative Humidity (Rh) -> 6Q     7,
                          Vapor Pressure of Water (Pw) -> fc,.83:t$i8i:. atm
                Vapor Pressure of Pesticide Ingredient (Pp) -> $i32Ei;;K> atm
               Molecular Weight of Pesticide Ingredient(Mp) -> 263:  ;  kg/kmol
                             Area of Application (A) -> 56?
-------
                 	 Emissions from Pesticide/Herbicide Applications - Scenario 2.10
                 Based on user input,  SCREEN model has been selected.

                 SCREEN MODEL INPUTS - Page 1 of 2

                 URBAN/RURAL CLASSIFICATION
                                    Enter U for Urban - R for Rural -> R

                 FENCELINE DISTANCE
                     Enter the distance from the nearest edge of the
                                     source to the plant fenceline -> 19&      m

                 FLAG POLE RECEPTORS
                            Enter Receptor Height above Ground (Zr) -> 8        m

                 RECEPTOR LOCATIONS
                 Do you have specific locations where you would like
                     pollutant concentrations to be calculated (Y/N) > ft
              Ran tet,
                   -&%> -Hilt  . "SPSS" *r*f**Sew   "
A summary of  the  SCREEN model's  output  for this  example  is
displayed below:
                               *** SUMMARY Of SCREEN MODEL RESULTS ***
                               n*************************************
                           CALCULATION       MAX CONC   DIST TO   TERRAIN
                            PROCEDURE        (UG/M**3)   MAX (M)    HT (M)
                          SIMPLE TERRAIN
.2360
100.
0.
                             REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS **
                                              4-107

-------
4.2.11  Instantaneous Discharges from Equipment Openings
                   Emissi
                                      Chemical
                                      Reactor
                                    Emissions
                   Coke Oven
Similar Releases:  Any puff or burst type release with  short
duration emissions resulting from the opening of equipment  after
processing  (e.g., coke ovens or chemical reactors), from  routine
sampling of product processing or gaseous emissions from
disconnected lines.

Discussion:

     Sources of this type are modeled as instantaneous  point-
sources of gaseous emissions due to the momentum of their
release.  Emissions can either be estimated on a source-specific
basis by the user or calculated from representative emission
factors.  Emissions estimates are available in AP-42  for  some
batch operations.  VOC profiles are also available to identify
toxic components  (Appendix A, item 4).  Simple estimates  of
emissions from failed or disconnected transfer lines  or similar
sources can be calculated from the gas volume between the break
point and nearest shutoff valve.  Ambient concentrations
resulting from instantaneous discharges are determined  by using
the PUFF model (see Section 5.3).

Limitations and Assumptions:

         Release is presumed to be neutrally buoyant.

         "There is no plume rise algorithm in the current version
          of the PUFF model.  The height of release should  be set
          to stack height.
                              4-108

-------
Input Information:

     EF   total emission times fraction associated with
          particular pollutant (g/kg)
     Pd   total production of the facility of all emissions  (kg)

4.2.11.1  Procedure

1.   Total Amount of Material Released.  Calculate the total
     amount of material released (Q)  (g).

                    Q (g)  = Pd (kg)    EF (g/kg)          (4.2.11-1)

2.   Since the release is neutrally buoyant, dispersion estimates
     are determined using the PUFF model.   For an explanation of
     inputs to the PUFF model, see Section 5.3.

4.2.11.2  Example:  Release from equipment opening

Discussion:

     A common source of emissions due to equipment openings is
found in the production of coke where the opening of the ovens at
the completion of processing results in a near instantaneous
release.  One toxic component of the emission is toluene.  A coke
oven battery produces 20,000 kg total emissions.  The oven door
is 5 m above ground.  An estimate of IS-minute average
concentration at distances beyond 50 m downwind of this source is
needed.

     Emissions from coke ovens result primarily from charging and
discharging operations and fugitive losses which occur on a
continuous basis.  The example presented is for the near
instantaneous emissions which result from discharge in the
completed coke through the oven doors.   Sample simulations are
based on the impact of a single furnace although in real
applications total emissions from a battery of ovens over time
would be more typical.  Simulations require determinations of an
emission factor for the oven and total emissions based on oven
capacity.  Dispersion estimates are made assuming that the
release is instantaneous with no initial dispersion.

The following input information will be required:

     EF   total emission times fraction associated with
          particular pollutant
     Pd   total production at the facility of all emissions
     Hs   release height above ground (5m)

Procedure:

1.   Total Amount of Material Released.  To begin, the emissions
     are estimated using emission factors (EPA, 1987b).   Assume

                              4-109

-------
      that  VOC emissions are approximately  3% of  total  coke
      pushing emissions.   (Note,  AP-42  suggests 0.2 Ib/ton).   The
      total VOC  production is:

                      0.03  X 20,000 kg = 600  kg.

      Assume that total toluene  emissions from coke production are
      0.48  Ib/ton of  VOC  (0.24 g/kg).   Coke pushing emissions are
      then  given by multiplying  the emission factor times the
      total production using Equation  (4.2.11-1):

          Q(g)  =0.24  (g/kg)    600  (kg)   =  144  (g)  toluene
2.    Because the release  is neutrally buoyant,  the cloud is
      treated as passive for this example.   TSCREEN will run  the
      PUFF model.

Data entry in  the TSCREEN model  for  this example  is shown below:
                    Discharges from Equipment Openings - Scenario 4.2.9
              SOURCE PARAMETERS - Page 1 of 1

              Enter a unique title for this data's model run:
                   ''            ................
              RELEASE MASS
               Enter Total Amount of Material Released (Q),  if unknown
               enter the boxed variables below to calculate -> 1^|:;?;c g
                  Total Production (Pd) ->
                  Emission Factor (EF) ->
                                                    Pf kg
                                                    jjj&: 9/kg
                   Discharges from Equipment Openings - Scenario 4.2.9
PUFF MODEL INPUTS - Page 1 of 2

RELEASE PARAMETER
               Release Height above Ground -> $
            Initial Lateral Dispersion (cry) -> $
           Initial Vertical Dispersion ( -> 9

FENCELINE DISTANCE
 Enter the distance from the nearest edge of the
             source to the plant fenceline -> 5&
                                                         m
                                                         m
                                                         m

                                   4-110

-------
A summary of  the  PUFF  model's  output  for this:example  is  shown
below:
                            SUMMARY OF PUFF MODEL RESULTS
                THE MAXIMUM CONCENTRATION AND THE DISTANCE TO MAXIMUM
                CONCENTRATION FOR DISTANCES BEYOND FENCELINE    .050 (KM).
                FOR NEAR SURFACE RELEASE MAXIMUM CONCENTRATION WILL OCCUR AT
                THE FENCELINE.

                    AVERAGING         MAXIMUM           DISTANCE TO        STABILITY
                    TIME (MIN)     CONCENTRATION (G/M**3)   MAX. CONC. (KM)    CLASS

                 INSTANTANEOUS            1.693E-01           .060              N
                      1                 2.107E-02           .082              N
                      5                 4.213E-03           .082              N
                *     15                1.404E-03           .082              N
                      60                3.511E-04           .082              N

                 *>* >< *
                 **  REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS  **
                                             4-111

-------
4.3  Liquid Release

     A liquid release is a release of material that may
immediately evaporate (no pooling results) ort may pool first and
then evaporate.


4.3.1  Continuous Evaporation from Surface Impoundments (Lagoons)
Similar Releases:  Waste lagoons and other impoundments with
emissions resulting from the evaporation of volatile chemicals
from liquid mixtures with biological activity.

Discussion:

     Emission rates from well-mixed aqueous waste in surface
impoundments are modeled in this scenario.  Techniques are
provided for both quiescent and aerated impoundments.  Emission
estimates account for volatilization solely,  with other removal
mechanisms assumed to be negligible.  Ambient concentrations
resulting from continuous evaporation from surface impoundments
are determined by using area source techniques in the SCREEN
model.

Limitations and Assumptions;

          Equations are simplifications of EPA methods (EPA,
          1987a)  for quiescent surface impoundments with and
          without flow and for aeration basins.

          Equations are simplified by assuming a wind speed of 5
                              4-112

-------
          m/s, a constituent diffusivity in water of 10"3 cm2/s,
          and a constituent diffusivity in air of 0.10 cm2/s.

          Assumes waste is well mixed in impoundment.

          Assumes removal entirely by volatilization, with  no
          loss due to biodegradation, seepage, or absorption.

          Assumes waste is aqueous, with no separate organic
          phase.

Input Information:

     A    area of impoundment  (m2)
     C0    initial concentration of chemical in the waste  (g/m3)

4.3.1.1  Procedure

1.   Emission Rate.  For VOC emission estimates from waste  water
     treatment systems, refer to Industrial Waste Water VOC
     Emissions -Background from BACT/LAER.  EPA-450/3-90-004,
     NTIS PB90-194754.  This document is available from the EPA
     Control Technology Center, (919) 541-0800.

     The emission rate can be calculated as follows:

                  Qm  (g/s)"  K(m/s) C^g/m3) A(m2)          (4.3.1-1)

     where:    K = 4 x 10"*(m/s) for the quiescent case
               K = 8 x 10"* (m/s)  for the aerated case

2.   Run the SCREEN dispersion model for an area source.

4.3.1.2  Example:  Emission of benzene

Discussion:

     One-hour concentration estimates of benzene are desired from
a quiescent impoundment with an area of 1500m2 and a fenceline
200 m from source.

The following input information will be required:

     A    area of impoundment  (1500 m2)
     C0    initial concentration of the chemical in the waste
           (1000 g/m3)
                              4-113

-------
Procedure:

1.
2.
Emission  Rate.    Calculate  the emission  rate  using Equation
 (4.3.1-1):

 Qm(g/s)  =  4X10-6   (m/s)     1000   (g/m3)  1500   (m2)  = 6   (g/s)

TSCREEN will run the SCREEN model  for an  area  source.
Data  entry  in  the TSCREEN model  for this example  is  shown below;

                    Evaporation from Surface Impoundments(lagoons) - Scenario 4.3.1

                SOURCE PARAMETERS - Page 1 of 1

                Enter a unique title for this data's model run:
                         ftm Surface
         IMPOUNDMENT TYPE
                 Enter Q for Quiescent - A for Aerated -> CJ

         EMISSION RATE
         Enter the Emission Rate (Qm), if unknown enter
                the boxed variables below to calculate -> &'
                                                                  g/s
                           Initial Concentration of Chemical
                                         in-the Waste (Co)  -> TW6J.";.'.  g/cubic m
                                   Area of Impoundment (A)  -> 1588::N   m2
                                                     *t Scrn    g> jsfcort
                        Evaporation from Surface Impoundments - Scenario 4.3.1
                Based on user input, SCREEN model has been selected.

                SCREEN MODEL INPUTS - Page 1 of 2

                URBAN/RURAL CLASSIFICATION
                                 Enter U for Urban -  R for Rural -> ft

                FENCELINE DISTANCE
                    Enter the distance from the nearest  edge of the
                                   source to the plant fenceline -> <& 0-

                RECEPTOR LOCATIONS
                Do you have specific locations where you would like
                    pollutant concentrations to be calculated (Y/N) > It
                                               ft
-------
A  summary  of  the SCREEN model's  output  for  this  example  is  shown
below:
                             *** SUMMARY OF SCREEN MODEL RESULTS ***
                             *t*******t******tiit***t***tt**t*t**
                         CALCULATION       MAX CONC   DIST TO  TERRAIN
                         PROCEDURE      (UG/M**3)   MAX (M)   HT  (M)


                        SIMPLE TERRAIN     .2944E+05     200.      0.
                          REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS
                                          4-115

-------
4.3.2     Continuous  (Two-Phase) Release Rate Estimates
          Saturated Liquid from Pressurized  Storage
                   Relief
                   Valve
                                 Liquid PhaM canted In Gas BUM

                              Emissions
Similar Releases:  Saturated liquid leak from a pressurized tank
(possibly through a relief valve) or a saturated  liquid  leak from
a pipe.

Digcussipr^:

     Materials which are stored under pressure will depressurize
when released to the atmosphere.  This depressurization  results
in the formation of two contaminant phases  (saturated  liquid and
vapor) for: gases which cool so that condensation occurs during
the depressurization process; and high volatility liquids
(liquids whose normal boiling point is below the  ambient
temperature) which are typically stored at  above  ambient
pressure.   (So called saturated liquids are liquids stored  at a
pressure equal to their vapor pressure for  the storage
temperature; subcooled liquids are liquids  stored at a pressure
above their vapor pressure for the storage  temperature,-  and
superheated liquids are liquids stored at a pressure below  their
vapor pressure for the storage temperature.  For  a preliminary
estimate, the temperature of superheated liquid releases should
be set to the saturation temperature.)  In  this scenario, the
terms gas, saturated liquid, and subcooled  liquid all  refer to
the state of the tank contents.   The scenario considers the
release from a tank  (or reservoir) and includes a provision for
the effect of a pressure drop  (piping) between the tank  and the
hole or opening.

     This procedure applies to a continuous release of
pressurized liquid stored under saturated conditions.  The
release occurs from  (constant pressure and  temperature)
contaminant (reservoir) through a hole or opening,- a provision is
made for the effect of a pressure drop  (piping) between  the tank
and the hole or opening. -
                              4-116

-------
Limitations and Assumptions:

     The hole or opening size must be sufficiently  small,
otherwise the reservoir temperature and pressure may no  longer be
constant.'  For the case of a leak from a tank, the  assumption of
constant reservoir temperature and pressure may be  violated if a
significant percentage of the tank contents is released.   If the
reservoir temperature and pressure are not constant, the release
rate may vary with time, but the maximum release rate  is
generally obtained from the initial reservoir temperature and
pressure.  For the case of a leak from a pipeline,  the initial
pipeline conditions can be used to estimate the release  rate,  but
this may greatly overpredict the actual release rate as  the hole
size approaches the pipe diameter.

     The vapor phase of the released material must  be  an ideal
gas at the reservoir conditions, during the depressurization
process, and after depressurization to the atmosphere,- for the
case of a tank containing vapor and liquid, the hole must be in
the liquid space of the tank  (Spicer, 1992) .

Input Information;

     Ag    area of reservoir hole or opening  (m2)
     Cp    gas  (contaminant) heat capacity .at Tt (J/kg-K)  (For
          contaminant mixtures, see Appendix B)
     Cp,   liquid  (contaminant) heat capacity at Tt  (J/kg-K)  (For
          contaminant mixtures, see Appendix B)
     D0    (equivalent) diameter of hole or opening
          (m)
     Dp    pipe diameter  (as appropriate)  (m)
     Lp    pipe length  (appropriate)  (m)
     1^   gas  (contaminant) molecular weight  (kg/kmol)  (For
          contaminant mixtures, see Appendix B)
     Pa    ambient pressure  (Pa)
     Pt    reservoir pressure  (Pa)
     Q    total amount of material released  (kg)
     T,    ambient temperature  (K)
     Tb    contaminant normal boiling point (K)
     Tt    reservoir temperature  (K)
     X    heat of vaporization at the normal boiling point (J/kg)
     Pi    contaminant liquid density at the normal  boiling point
          (kg/m3)
     R    gas constant  (8314 J/kg-moleK or 3314 Pa.mVkg-
          mole.K)
                              4-117

-------
4.3.2.1  Procedure:

1.   Estimate Discharge Temperature.   For pure  components,
     estimate the discharge temperature T2 from the vapor
     pressure (Clausius-Clapeyron)  equation:
P. = 101325 exp
                                            1
                                           T
                                            X
           (4.3.2-1)
     which can be rewritten as:
                          T-TV-H1
                          Tb   X Mw     [MWJ
     Vapor Fraction after Depressurization.  Estimate the vapor
     mass fraction (or quality)  after depressurization X2 as:
                       X, = Cpl ( T, - T2 ) / X
           (4.3.2-2;
     If 1 > Xj >  0,  then this estimate is valid/ go to step 3.
     If X2 s 0 then the  release  should be modeled like a high
     volatility liquid release;  the case of X2 a 1 is unlikely on
     physical grounds.

     Release Rate.  As recommended by Pauske and Epstein (1987),
     estimate the emission rate Qm (kg/s) depending on the pipe
     length Lp as follows:   If Lp/Le s 1  (where Le=0.1  m) ,
     where
                N =
 (kg/s)
R
'A,
X Mw Pt
R Tf
f TI
INC,
(XMWP,)2
                                             1/2
                                                        (4.3.2-3)
                    2 (Pl - P.) Pl C2  (RT,)
           (4.3.2-4)
     where C is the discharge coefficient (here,  C =0.6).   (Note
     that if Lp/Le = 0, Equations (4.3.2-3)  and (4.3.2-4)  reduce
     to the standard orifice equation for incompressible flow.)
     If
                   Qm  (kg/s) = AO F
                                  XM  p
                                    R T?
11/2
            (4.3.2-5)
     where F represents the effect of friction in the pipe (here,
     F2 = I/(l+4fLp/Dp) /  for a  Reynold's number typical of  liquid
     flow, f=0.0015 can be used as an estimate).
                              4-118

-------
4.   Discharge Density..  Estimate the density after
     depressurization p2 as:


                 ft ftj/W - [, ) * [115] J'        (4.3.2-6)


5.   Buoyancy Check.  Estimate release buoyancy as a first  check.


     A.   Calculate the density of air using the following:


                                                         (4.3.2-7)
          where M, is  the  molecular weight  of  air (assumed to
          equal 28.9 kg/kmol).

     B.   If p2/Pr > !/  then the buoyancy is negative.  For
          negative buoyancy, the RVD model should be  used  if  the
          release is from a vertically directed  jet;  otherwise,
          the Britter-McQuaid model should be used; go to  step  6.
          If the buoyancy is zero or positive, the SCREEN  model
          for a point source should be used.   (See Section 2.4
          for more information on model selection.)

6.   Release Duration.  The release duration is  used  as an input
     into the RVD and Britter-McQuaid models.  The release
     duration can be used to determine if the release is
     continuous or instantaneous  (see Section 2.5).   Calculate
     the release duration Td using the  equation below-.


                 Td (min) =  -  ,., ? (kfj! ,  , . .         (4.3.2-8)
                            Qm (kg/s)  60 (s/min)

4.3.2.2  Example; Saturated Liquid  Chlorine Leak

Discussion:

     In this example, saturated chlorine liquid  is discharged
from a heated pressurized tank through a 10.16 cm diameter hole
well below the liquid level in the  tank  (the pressure and
temperature were chosen to  illustrate that the release rates  from
the vapor space are generally much  smaller than  release rates
from the liquid space); the chlorine vapor temperature is  that  of
the tank, 349.2 K.  The fenceline  is 100 m from the  tank

The following information will be required:

     AQ   area of reservoir hole or opening (0.008107 m2)
     Cp,   liquid  (contaminant) heat capacity at  1l (920 J/kg-K)
     D0   diameter of hole  or opening  (0.1016 m)


                              4-119

-------
     MV   gas (contaminant) molecular weight  (70.9  kg/kmol)
     Pt    ambient pressure  (101325 Pa)
     Pt    reservoir pressure  (2.586x10* Pa)
     Q    total amount of material released  (50,000 kg)
     Tt    ambient temperature  (293 K)
     Tb    contaminant normal boiling point  (239.05  K)
     Tt    reservoir temperature  (349.2  K)
     X    heat of vaporization at the normal boiling point
          (2.870X103 J/kg)
     P!    contaminant density at reservoir conditions (1574
          kg/m3)

Procedure:

1.   Estimate Discharge Temperature.  Estimate  the  discharge
     temperature T2 from Equation (4.3.2-1):


       T, =	 = 239.05 K
        2      1           8314        ,J101325\
            239.05   2.879xl05-70.9    U01325/

     (This temperature is also the normal boiling point  since Pa
     = 101325 Pa).

2.   Vapor Fraction after Depressurization.  Estimate  the vapor
     fraction after depressurization X2 from Equation  (4.3.2-2)

           Xj = 920 (  349.2 - 239.05 )  /  2.879xl05 = 0.352

     Since 1 > X2 > 0,  then  this  estimate is valid;  go to step 3.

3.   Release Rate.  Since Lp/Le s 1  (where Lp = 0 and Le =  0.1  m) ,
     estimate the release rate from Equation  (4.3.2-3):


     Qm (kg/s) =0.008107 [2-879x10*.70.9-2.586x10*] /	349.2
      m                [   (8314)    (349.2)2    j \0.365   920

                          Qm = 430 kg/s

     where N is calculated from Equation  (4.3.2-4) -.

N = 	8314 (2.879x10*   2.586xl06)2	 +0/1 = 0 365
    2 (2.586xl06 - 101325)  1574   0. 62 (8314 349.2)3 920

     (Note that at this rate a "ton" container would be  emptied
     in 2 to 3 seconds.)

4.   Discharge Density.  Estimate  the  density  after
    .depressurization p2 from Equation (4.3.2-6):
                              4-120

-------
      (kg/m3)
3)  = fo.
352
/8314   239. 05
\101325 .  70. 9
                          I - 0.187\
                             1574   /
= 10.23  kg/m3
5.    Buoyancy Check.  Estimate  release buoyancy as  a first check.
      A.    Calculate the  density of air using the following:


                    '*'^-229839'^*^

            where  28.9 kg/kmol is the molecular weight of  air.

      B.    P2/PT >:L  therefore,  buoyancy  is negative.

      Release Duration.   Calculate the  release duration Td using
      the equation below:
             Td (min) =
                               50,000 (kg)
                         430 (kg/s)    60 (s/min)
                                  =1.94 min
      After this  calculation run the Britter-McQuaid model since
      the  release is assumed not to be  vertically directed jet.
      (See Section 5.4 for more  information on the  Britter-McQuaid
      model.)

Data entry in the TSCREEN model for this example is shown below:

             Continuous 2-Phase Saturated Liquid from Pressurized Storage - 3.2 	

             SOURCE PARAMETERS - Page 1 of 4

             Enter a unique title for this data's model run:
             Saturated tkfujd efclarfn* leak
             SOURCE OF LEAK
                        Area (Ao) of Hole or Opening -> 8-1,87'!'  cm2
                        Enter P for Pipe - T for Tank -> ?
             DISCHARGE TEMPERATURE
                          Discharge Temperature (T2) -> 239.05
                                   K
            Ambient Pressure (Pa) ->
      Boiling Point Temperature (Tb) >
   Latent Heat of Vaporization (Lvap) ->
            Molecular Weight CHw) ->
                                                     Pa
                                                     K
                                                     J/kg
                                                     kg/kmol
idit/- ' #9>- Pteyiaus. Street*,;
                                                          Abort
                                   4-121

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 Continuous 2-Phase Saturated Liquid from Pressurized  Storage  - 3.2

 SOURCE PARAMETERS - Page 2 of 4

 VAPOR FRACTION AFTER DEPRESSURIZATION
   Vapor Fraction after Depressurization (X2)  ->  0.352
                    Liquid Heat Capacity (Cp)  -> 92&      J/kg  K
                   Reservoir Temperature (T1)  -> 54^.2.    K
 EMISSION RATE
                           Emission Rate (Qm)  -> 430193.2  g/s
                      Reservoir Pressure (P1)  -> i*S&6&t Pa
             Liquid Heat Capacity at T1  (Cpl)  -> 92fl      J/kg  K
              Contaminant Liquid Density (fD  -> 1?4     kg/cubic m
       fidft
 Continuous 2-Phase Saturated Liquid from Pressurized  Storage  - 3.2

 SOURCE PARAMETERS - Page 3 of 4

 DISCHARGE DENSITY
                          Discharge Density (f2)  ->  10.23  kg/cubic m

 DENSITY OF AIR
                        Density of Air (fair)  ->  1.20209  kg/cubic m
                     Ambient Temperature (Ta)  -> 2S<3;f?|:  K
 Buoyancy is Negative
   &JU    f$>- Prevfcocfc Sfcre*n     Meat
   Continuous 2-Phase Saturated Liquid from Pressurized  Storage  - 3.2
 SOURCE PARAMETERS - Page 4 of 4

 VERTICALLY DIRECTED JET
        Does the release result in a vertically
                             directed jet  (Y/M) -> H

 TIME
                          Release Duration (Td) -> 1.937114 min
          Total Amount of Material  Released (Q)  ->
                                4-122

-------
                Continuous 2-Phase Saturated Liquid from Pressurized Storage  3.2
                Based on user input, the Britter-McQuaid model has been selected.

                BRITTER-McQUAID MODEL INPUTS - Page 1 of 3

                MODEL PARAMETERS
                                    Relative Humidity (Rh) -> 5ft>"   '  X
                                                             ff <

                   Desired Averaging Time for the Calculation
                                        of Concentrations -> 18-      min
                Continuous 2 -Phase Saturated Liquid from Pressurized Storage - 3.2

                BRITTER-McQUAID MODEL INPUTS - Page 2 of 3

                FENCELINE DISTANCE
                 Enter the distance from the nearest edge of the
                              source to the plant fenceline -> t<):     m

                RECEPTOR LOCATIONS
                Do you have specific locations where you would
                like pollutant concentrations calculated (Y/N) -> X
Bdift
  Screw*
                                                     ttan Itotel.   
A  summary of  the  Britter-McQuaid  model's  output  is  displayed
below:
                            **   SUMMARY OF B&M MODEL RESULTS  **
                                                ll>*lHHt1
                          MAX CONC
                          
MAX CONC
 (PPM)
                          DIST TO
                          MAX (M)
WIND SPEED
  (M/S)
                           .3535E+09   .1199E+06
            200.
                                       1.
                                                >**********
                          REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS
                        ************
                                                       **************
4.3.2.3    Considerations  for Time-Varying and  Time-Limited
              Releases

       See  Section  2.5 for  a  discussion  of  considerations  for  time-
varying and  time-limited  releases.
                                          4-123

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4.3.3     Instantaneous  (Two-Phase) Release Rate Estimates
          Saturated Liquid from Pressurized Storage
                         Emissions
                                          din Gas Phase
Similar Releases:  Saturated liquid'leak from a pressurized  tank
or a saturated liquid leak from a pipe.

Discussion:

     This procedure applies to an instantaneous release of
pressurized liquid stored under saturated conditions.  The
release occurs (at constant pressure and temperature) from a
containment (reservoir) through a hole or opening,- a provision  is
made for the effect of a pressure drop  (piping) between the  tank
and the hole or opening.  See Section 4.3.2 for further
discussion.

Limitations and Assumptions:

     Same as Section 4.3.2.

Input Information:

     Same as Section 4.3.2.

4.3.3.1  Procedure:

1-4. Same as Section 4.3.2.
                              4-124

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5.   Buoyancy Check.  Perform buoyancy check as a first check.

     A.   Calculate the density of air using the following:


                            'TX                   <*-3-*-

          where M,  is the molecular weight of air  (assumed  to
          equal 28.9 g/g-mole).

     B.   If Pj/Pair  > 1,  then the  buoyancy  is negative.   For
          negative buoyancy, the RVD model should be used if the
          release is' from a vertically directed jet; otherwise,
          the Britter-McQuaid model should be used; go to step 6.
          If the buoyancy is positive, the PUFF model for a point
          source should be used.   (See Section 2.4 for more
          information on model selection.)

6.   Same as Section 4.3.2.

4.3.3.2  Examples

     See the examples in Section 4.3.2.
                              4-125

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4.3.4     Continuous  (Two-Phase) Release Rate Estimates
          Subcooled Liquid from Pressurized Storage
                  Relief
                  Valve
                                 Uquld PtaM canted In Gas Phaaa

                              Emissions
Similar Releases.-  Subcooled liquid leak from a pressurized  tank
(possibly through a relief valve) or a subcooled liquid  leak from
a pipe.

Discussion:
     Materials which are stored under pressure will depressurize
when released to the atmosphere.  This depressurization results
in the formation of two contaminant phases  (saturated liquid  and
vapor) for: gases which cool so that condensation occurs during
the depressurization process; and high volatility liquids
(liquids whose normal boiling point is below the ambient
temperature) which are typically stored at  above ambient
pressure.   (So called saturated liquids are liquids stored at a
pressure equal to their vapor pressure for  the storage
temperature; subcooled liquids are liquids  stored at a pressure
above their vapor pressure for the storage  temperature; and
superheated liquids are liquids stored at a pressure below their
vapor pressure for the storage temperature.  For a preliminary
estimate, the temperature of superheated liquid releases should
be set to the saturation temperature.)  In  this scenario,  the
terms gas, saturated liquid, and subcooled  liquid all refer to
the state of the tank contents.   The scenario considers the
release from a tank (or reservoir) and includes provision  for the
effect of a pressure drop  (piping) between  the tank and the hole
or opening.

     This procedure applies to a continuous release of a
pressurized liquid stored above its saturation pressure.   This
release occurs (at constant pressure and temperature) from a
containment (reservoir) through a hole or opening; a provision is
made for the effect of pressure drop  (piping) between the  tank
and the hole or opening.


                              4-126

-------
Limitations and Assumptions:

     The hole or opening size must be sufficiently  small,
otherwise the reservoir temperature and pressure may  no  longer be
constant.  For the case of a leak from a tank, the  assumption of
constant reservoir temperature and pressure may be  violated if a
significant percentage of the tank contents is released.   If the
reservoir temperature and pressure are not constant,  the release
rate may vary with time, but the maximum release rate is
generally obtained from the initial reservoir temperature and
pressure.  For the case of a leak from a pipeline,  the initial
pipeline .conditions can be used to estimate the release  rate,  but
this may greatly overpredict the actual release rate  as  the hole
size approaches the pipe diameter.

     The vapor phase of the released material must  be an ideal
gas at the reservoir conditions, during the depressurization
process, and after depressurization to the atmosphere; for the
case of a tank containing vapor and liquid, the hole  must be in.
the liquid space of the tank (Spicer, 1992).

Input Information:

     AO    area of reservoir hole or opening  (m2)
     Cp    gas  (contaminant) heat capacity at Tt (J/kg-K)  (For
          contaminant mixtures, see Appendix B)
     Cpj   liquid  (contaminant)  heat capacity at T!  (J/kg-K)  (For
          contaminant mixtures, see Appendix B)
     D0    (equivalent) diameter of hole or opening  (D0=2-yA0/7r )
          (m)
     Dp    pipe diameter  (as appropriate)  (m)
     Lp    pipe length  (appropriate)  (m)
     Mw   gas  (contaminant) molecular weight  (kg/kmol)  (For
          contaminant mixtures, see Appendix B)
     P,    ambient pressure  (Pa)
     PI    reservoir pressure (Pa)
     R    gas constant  (8314 J/kg-mole-K or 8314
          Pa-m3/kg-mole-K)
     Q    total amount of material released  (kg)
     Tt    ambient temperature  (K)
     Tb    contaminant normal boiling point  (K)
     Tt    reservoir temperature  (K)
     X    heat of vaporization at the normal boiling  point (J/kg)
     pl    contaminant density at the normal boiling point (kg/m3)
                              4-127

-------
4.3.4.1  Procedure:

1.   Estimate Discharge Temperature.  For pure components,
     estimate the discharge temperature T2 from the Clausius-
     Clapeyron equation:
                 P. = 101325 exp     -  -1 - *            (4.3.4-1)
                                   K   M-b   i2
     which can be rewritten as:
                         Tb    XM,     [101325 J


     Vapor Fraction after Depressurization.  Estimate  the  vapor
     mass fraction  (or quality) after depressurization X2 as:

                       X, = Cpl ( Tt - T2 )  / X               (4.3.4-2)

     If 1 > X2 > 0,  then this estimate is valid,- go to step 3.
     If X2 s  0 then the release should be modeled like a high
     volatility liquid release; the case of  X2 a 1 is unlikely on
     physical grounds.

     Release Rate.  As recommended by Fauske and  Epstein  (1987),
     estimate the emission rate Qm  (kg/s) as follows:

                                                     1/2
                                         T72  f X M P- I2
                         2 C2 (P -P ) n +  e       v
                         * *-   1*1 *V Pi* r<  rp |	pTrT-
                                              K11
                                                         (4.3.4-3)
     where
                lv
                  (Pa)  = 101325 exp \l   . -  _i         (4.3.4-4)
     where C is the discharge coefficient  (here, C =0.6)  and F
     represents the effect of friction in  the pipe  (here,  F2 =
     l/(l+4fLp/Dp) ; for a Reynold's number  typical 'of  liquid flow,
     f=0.00l5 can be used as an estimate) .

     Discharge Density.  Estimate the density after
     depressurization p2 as :
(kg/m3
                                                         (4.3.4-5)
                            L'lp-N   I  >>  J
5.   Buoyancy Check.  Perform buoyancy check as a  first  check.

     A.   Calculate the density of air using the following:

                              4-128

-------
                                                         (4.3.4-6)


          where M,  is  the molecular weight of air (assumed to
          equal 28.9 kg/kmol) .

     B.   If Pa/Pa*  > 1,  then the buoyancy is negative.  For
          negative buoyancy, the RVD model should be  used  if  the
          release is from a vertically directed  jet;  otherwise,
          the Britter-McQuaid model should be used; go 'to  step  6.
          If the buoyancy is positive, the SCREEN model for a
          point source should be used.   (See Section  2.4 for  more
          information on model selection.)

     Release Duration.  The release duration is  used  as an input
     into the RYD and Britter-McQuaid models.  The release
     duration can be used to determine if the release is
     continuous or instantaneous (see Section 2.5).   Calculate
     the release duration Td using  the equation below:


                 T' ""in) 
                           Q. (fcg/s)    o is/mini           -'

4.3.4.2  Example: Subcooled Liquid Chlorine Leak

Discussion:

     In this example, subcooled chlorine liquid is discharged
through a 10.16 cm diameter hole in a tank  (the pressure  and
temperature were chosen to illustrate that the release  rates from
the vapor space are generally much smaller than release rates
from the liquid space) ; the chlorine vapor temperature  is
estimated to be 349.2 K using the Clausius-Clapeyron equation
and the normal boiling point of chlorine (239.05  K) .   The
fenceline is 100 m from the tank.

The following information will be required:

     AO   area of reservoir hole or opening  (0.008107 m2)
     Cp   gas (contaminant) heat capacity at Tt (489 J/kg-K)
     Cp,   liquid  (contaminant) heat capacity at TI (920  J/kg-K)
     D0   diameter of hole or opening  (0.1016 m)
     Mw   gas (contaminant) molecular weight  (70.9 kg/kmol)
     P,   ambient pressure  (101325 Pa)
     Pj   reservoir pressure  (2.586xl06 Pa)
     Q    total amount of material released  (50,000  kg)
     Tt   ambient temperature  (293 K)
     Tb   contaminant normal boiling point  (239.05  K)
     Tj   reservoir temperature  (298.15 K)
     \    heat of vaporization at the normal boiling point
           (2.879xl05 J/kg)
     Pi   contaminant density at reservoir conditions  (1574

                              4-129

-------
          kg/m3)

Procedure:

1.   Estimate Discharge Temperature.  Estimate  the discharge
     temperature T2 from Equation (4.3.4-1):


       T, - 		 = 239.05 K
        2       1    _      8314      .  ,J101325\
                             J	-ml.
                             3-70. 9    \
            239.05   2.879xl03-70.9     U01325/

     (This temperature is also the normal boiling point since Pa
     = 101325 Pa).

     Vapor Fraction after Depressurization.   Estimate the vapor
     fraction after depressurization X2 from Equation  (4.3.4-2)

          Xj = 920 ( 298.15 - 239.05 )  /.2.879xl05 = 0.1888

     Since 1 > X2 > 0,  then this estimate is valid; go  to  step  3.

     Release Rate.  Using Lp=0 (and F = 1)  ,  estimate the  release
     rate from Equation  (4.3.4-3):
Qm(kg/s)=.008107
                 2C2(2.586xl06-Plv)1574
                                       p2|2.879xlQ5-70.9-2 .586xl06
                                                8314 298.15
                                               920-298.15

                      Qm (kg/s)  = 493 (kg/s)

     where C = 0.6 and
                                     239.05    298.15
                                                        = 7.76xl05 Pa
Plv (Pa)  = 101325 exp  2.879x10^70.9  (


4.   Discharge Density.  Estimate the density after
     depressurization p2 from Equation (4.3.4-5):



  p,  (Kg/.-, - [0.1.8. (;%35^) * (i-^) }' = 18'9S k3/I"3

5.   Buoyancy Check.  Perform buoyancy check as  a first  check.

     A.    Calculate the density of  air using the following:
     B-   P2/Pr > I/ therefore, buoyancy is negative
                                              

                               4-130

-------
6.    Release Duration.   Calculate the release duration Td using
      the equation below:
              TV, (min)
                                 50,000 (kg)
                          493  (kg/s)    60  (s/min)
= 1.69 min
      After  this  calculation run the  Britter-McQuaid model  since
      the release is not from a  vertically directed jet.    (See
      Section 5.4 for more  information on  the  Britter-McQuaid
      model.)

Data entry  in the TSCREEN  model for  this  example  is shown  below:
                Continuous 2-Phase Subcooled Liquid from Pressurized Storage - 3.4
              SOURCE PARAMETERS  Page 1 of 4

              Enter a unique title for this data's model run:
              Sobc^B^'tiqiM'Btitdi^ie^Ba^''	i'
              SOURCE OF LEAK
                          Area (Ao) of Hole or Opening -> S-1.67"  cm'
                         Enter P for Pipe - T for Tank -> t
              DISCHARGE TEMPERATURE
                           Discharge Temperature (T2) -> 239.05
                               Ambient Pressure (Pa) -> t&faSJ  Pa
                        Boiling Point Temperature (Tb) -> 23$,-8  "K
                     Latent Heat of Vaporization (Lvap) -> Z.879ES J/kg
                               Molecular Weight (MM) -> ?&.?   kg/kmol
	 continuous i-pnase suocooiea Liquid Trom Pt
SOURCE PARAMETERS - Page 2 of 4
VAPOR FRACTION AFTER DEPRESSURIZATION
Vapor Fraction after Depressurization (X2)
Vapor Heat Capacity (Cp)
Reservoir Temperature (T1)
EM I SSI OH RATE
Emission Rate (dm)
Reservoir Pressure (P1)
Liquid Heat Capacity at T1 (Cpl)
Contaminant Liquid Density (f1)
essurized si
-> 0.1888
-> 485
-> 493423.2
-> 2.5S6E6
rorage - 5.4 	
J/kg K
"K
9/s
Pa
J/kg K
kg/cubic m

ll^^'lii&i^^
                                     4-131

-------
 Continuous 2-Phase Subcooled Liquid from Pressurized Storage - 3.4

 SOURCE PARAMETERS - Page 3 of  4

 DISCHARGE DENSITY
                       Discharge Density  (f2)  -> 18.96 kg/cubic m
 DENSITY OF AIR
                        Density of  Air  (fair)  -> 1.20209  kg/cubic m
                     Ambient Temperature  (Ta)  -> 295
 Buoyancy is Negative
  rfffrwt
 Continuous 2-Phase Subcooled Liquid from Pressurized Storage - 3.4
 SOURCE PARAMETERS - Page 4 of 4

 VERTICALLY DIRECTED JET
        Does the release result in a vertically
                             directed jet  (Y/N)  -> tl

 TIME
                          Release Duration (Td)  -> 1.688882 min
          Total Amount of Material  Released  (Q)  -> Sj&DCp" kg
 Continuous 2-Phase Subcooled Liquid from Pressurized Storage - 3.4
 Based on user input, the Britter-HcQuaid model has been selected.

 BRITTER-McQUAID MODEL INPUTS - Page 1 of 3

 MODEL PARAMETERS
                         Relative Humidity  (Rh) -> 5&?  J: :  %

     Desired Averaging Time for the Calculation
                              of Concentrations > 15       min
           ;'^
   Continuous 2-Phase Subcooled Liquid from Pressurized Storage - 3.4
 BRITTER-McQUAID MODEL INPUTS -  Page 2  of 3

 FENCELINE DISTANCE
  Enter the distance from the nearest edge of  the source
                         to the  plant fenceline -> 1SQ

 RECEPTOR LOCATIONS
 Do you have specific locations  where you Mould
 like pollutant concentrations calculated (Y/N) -> 
        Edit    F9> frftWidtlS Stl*e*&   
-------
A  summary of the Britter-McQuaid model's output  is displayed
below:
                        ***  SUMMARY OF B&M MODEL RESULTS
                        m>i>> *
                       MAX COHC     MAX CONC   DIST TO   WIND SPEED
                       l***l>l>ll>>* ** **

                     ** REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS **
4.3.4.3    Considerations  for Tinie-Varying and Time-Limited
            Releases

      See  Section 2.5  for  a discussion of considerations for  time-
varying and time-limited  releases.
                                    4-133

-------
4.3.5     Instantaneous  (Two-Phase) Release Rate  Estimates
          Subcooled Licmid from Pressurized Storacre
                         Emissions
                                 UquU RUM canted In Gas Ptww
Similar Releases:  Subcooled liquid leak  from a pressurized tank
or a subcooled liquid leak from a pipe.

Discussion:

     This procedure applies to an instantaneous release  of a
pressurized liquid stored above its saturation pressure.   This
release occurs  (at constant pressure and  temperature)  from a
containment  (reservoir) through a hole or opening;  a  provision is
made for the effect of pressure drop  (piping)  between the tank
and the hole or opening.  See Section 4.3.4  for further
discussion.

Limitations and Assumptions.-

     Same as Section 4.3.4.

Input Information:

     Same as Section 4.3.4.

4.3.5.1  Procedure .

1-4. Same as Section'4.3.4
       
5.   Buoyancy Check.  Perform buoyancy check as a  first  check.

     A.   Calculate the density of air using the following:

                                 P, M,
                            0.--                        (4.3.5-1)
                              4-134

-------
          where Ma  is  the molecular weight of  air  (assumed to
          equal 28.9 kg/kmol).

     B.   If p^/Pta  > I/  then the buoyancy is negative.   For
          negative buoyancy, the RVD model should be used if the
          release is from a vertically directed jet; otherwise,
          the Britter-McQuaid model should be used; go to step 8.
          If the buoyancy is positive, the PUFF model for a point
          source should be used.  (See Section 2.4 for more
          information on model selection.)

6.   Same as Section 4.3.4.

4.3.5.2  Examples

     See the examples in Section 5.4.4.
                              4-135

-------
4.3.6  Continuous High Volatility Leaks


                             Emissions
                  Pipe
                                           Crack
                             Emissions
                  Tank
Similar Releases:  High-volatility liquid leak from a tank or a
high volatility liquid leak from a pipe (when the ratio of the
hole diameter to the pipe diameter is less than 0.2).

Discussion:

     A high-volatility liquid is considered to be a material
 (liquid) whose normal boiling point is below the ambient
temperature; a high-volatility material will be released as a
liquid if the storage pressure is near ambient pressure whereas
release from high pressure storage will result in aerosol
formation.  The following considers the problem of estimating the
release rate of a high-volatility liquid when the diameter of the
hole or opening is less than the diameter of the containment
 (e.g., a pipe or a reservoir).   (When considering hole sizes
which approach the pipe diameter, the release rate should be
taken as the maximum, of the pipe flow rate and the estimated
release rate.)  For high-volatility liquid releases, the
 (conservative) assumption is that the liquid boils off
instantaneously so that the liquid release rate is equal to the
 (gas) evolution rate.

     This procedure applies to a continuous release of a high
volatility liquid  (at constant temperature and pressure) from a
containment  (reservoir) through a hole or opening.
                              4-136

-------
Limitations and Assumptions:

     For this screening procedure, the  following assumptions are
applied:

          The pressure and temperature  of  the  liquid in the
          reservoir are essentially constant.

          The hole or opening is located in  the  liquid space (as
          opposed to the vapor space).

          The gas evolution rate is assumed  to be equal to the
          liquid release rate  (i.e.,  vaporization is
          instantaneous).

     The hole or opening size must be sufficiently small,
otherwise considerations other than those  outlined below may
determine the release rate.  For the  case  of a leak from a. pipe,
/3  (defined below) should be less than 0.2; if  j8>0.2,  the release
rate should be taken to be the normal flow rate  in the pipe.  In
either case, the gas evolution rate is  assumed to be equal to the
liquid release rate  (i.e., vaporization is instantaneous).  If
the reservoir temperature, pressure,  and liquid  level are not
constant, the release rate may vary with time, but the maximum
release rate is generally obtained for  the initial reservoir'
conditions  (Spicer, 1992).

Input Information:

     AO    area of hole or opening  (m2)
     AI    flow area representing reservoir conditions (m2)  (In
          the case of a leak from a tank,  A!-* (and j3=0) ;  in  the
          case of a leak from a pipe, At is the cross-sectional
          area of the pipe.)
     D0     (equivalent) diameter of hole or opening (D0=2 -^AQ/TT )
           (m)
     g    acceleration due  to gravity (9.81  m2/s)
     HL   distance between  the hole or  opening and the top of the
          liquid level  (m)  (In the case of a leak from a pipe,
          Hr0.)
     M   contaminant molecular weight  (kg/kmol)
     P,    ambient pressure  (Pa)
     Pv    vapor pressure as a function  of  temperature (Pa)
     Pt    reservoir pressure  (Pa)
     R    gas constant  (8314 J/kg-mole-K  or 8314
          Pa-m3/kg-mole-K)
     Q    total amount of material released  (kg)
     Ta    ambient temperature  (K)
     Tb    contaminant normal boiling  point (K)
     T!    reservoir temperature  (K)
     /3    ^/AO/AJ   (dimensionless)
     7    heat of vaporization at the normal boiling point  (J/kg)

                              4-137

-------
     P!    contaminant  (liquid) density at reservoir  conditions
          (Tt and Pt)  (kg/m3)

4.3.6.1  Procedure:

1.   Pressure at the Hole or Opening.  Estimate  the  liquid
     pressure at the hole or opening P, as:

                      P.  = max(Pt< Pt)  + pt g HL             (4.3.6-1)

     where P^P,,^)  which is estimated using-the Clausius-
     Clapeyron Equation:

                 Pv  = 101325 exp \^L f * -  *  |]        (4.3.6-2)
                                [   R   [ Tb   T!  J J

2.   Emission Rate.  Estimate  the  emission  rate  Qm  (kg/s)  as
     follows from Perry  et al.  (1984):
                                r              11/2
                 Qm (kq/s)  = KAgf 2 Pl(P. - P. )  J          (4.3.6-3)

     where
                          K = C /   1 - /34

     where C = 0.65  (although C can be  larger if  j8>0.2)

     Discharge Density.   Calculate  the  discharge  density as
     follows:
                                 P M
                               _     w
                                 K ^              '       (4.3.6-4)

     Buoyancy Check.   Perform buoyancy check as  a first check.

     A.   Calculate the  density  of  air using the following:

                                  P  M,
                             P. = iV                    (4.3.6-5)
                                    1

          where M, is  the molecular weight of air  (assumed to
          equal 28.9 kg/kmol).

     B.   If PI/P& > 1, then the buoyancy is negative.   For
          negative buoyancy,  the RVD model  should be used if the
          release is from a  vertically directed  jet; otherwise,
          the Britter-McQuaid model should  be used;  go to step 5.
          If the buoyancy is positive,  the  SCREEN model for  a
          point source should be used.   (See Section 2.4 for more
          information  on model selection.)

     Release Duration.   The  release duration is  used as an input
     into the RVD and  Britter-McQuaid  models.  The release


                              4-138

-------
     duration can be used to determine  if  the  release is
     continuous or instantaneous  (see Section  2.5).   Calculate
     the release duration Td using the equation below:


                 T  (min) '
                  <         Q.   gs     o  
-------
Procedure .

1.   Pressure at the Hole or Opening.  Estimate the liquid
     pressure. P, at the hole or opening from Equation (4.3.6-1) .
     In this case, liquid chlorine is being released as a
     saturated liquid at ambient pressure, so Pa=P1=101325 Pa,  and
     P,  is  estimated as:

     P.  =max(101325, 101325) + 1574  9.81   0.4  = 1.075xl05 Pa

     which is greater than Pv calculated from Equation (4.3.6-2) :
  P, . 10X325 exp   -'           -            "25 Pa
2.   Emission Rate.  Estimate the emission rate Qm from Equation
     (4.3.6-3) as follows:

                   f         /                  \ \m
    Qm = K 0.0005067 [ 2   1574 ( 1.075xl05 - 101325 ) j  = 1.45 kg/s
     where
                    K = 0.65 / J 1 - 0 . 04  = 0.65
     At this  (maximum) rate, the tank will be emptied in 436  s;
     the actual time would be longer since Qm will decrease with
     time  (because HL decreases with time) .   (Note that this
     situation can be compared to the earlier two-phase chlorine
     .examples if the hole diameter is changed to agree with the.
     earlier examples; if the hole diameter is changed to 10.16
     cm, the emission rate' for this case would be 23.2 kg/s.
     This liquid release rate is even smaller than the example
     pressurized vapor release rate of Section 2.3.)

3.   Discharge Density.  Calculate the discharge density using
     Equation (4.3.6-4) as follows:

                  .  _ 101325 -70.9  _ , -n v/n,3
                  P> " 8314  239.05  ~ 3'61 kg/m

4.   Buoyancy Check.  Perform buoyancy check as a first check.

     A.   Calculate the density of air using Equation  (4.3.6-5):
          where 28.9 kg/kmol is the molecular weight of air.

     B.   Since p2/ ' p& > 1,  the  buoyancy is negative.
                              4-140

-------
      Release Duration.    Calculate  the  release duration Td  using
      the  equation  below:
              TV,  (min)
                                      200  (kg)
                            1.45  (kg/s)    60  (s/minT
                                           =2.30 min
      After  this calculation  run the Britter-McQuaid model since
      the  release is not  from a  vertically directed jet.   (See
      Section 5.4 for  more information  on  the Britter-McQuaid
      model.)

Data entry  in  the  TSCREEN model for this  example is shown below:

              	 Continuous High Volatility Liquid Leaks - 3.6 	
               SOURCE PARAMETERS - Page 1 of 4

               Enter a'unique title for this data's model run:
                               CMorin* Lea*..  '
               SOURCE OF LEAK
                            Area (Ao) of Hole or Opening ->
                           Enter P for Pipe - T for Tank -> |
                                            cm
               VAPOR PRESSURE
                                   Vapor Pressure (Pv) -> 101325   Pa
                       Latent Heat of Vaporization (Lvap} -> Z.879E5  J/kg
                          Boiling Point Temperature  -> 3&JB&  "K
                             Reservoir Temperature (T1) -> 2$M  K
                                 Molecular Weight (Mw) -> 78*9<    kg/kmol
Sdit
                                 Mext S6re
                                                                  Jttwft
                          Continuous High Volatility Liquid Leaks - 3.6
               SOURCE PARAMETERS - Page 2 of 4

               PRESSURE
                       Liquid Pressure at Hole or Opening (P*)  -> 107501.4 Pa
                                     Ambient Pressure (Pa) -> 101325  Pa
                                    Reservoir Pressure (P1) -> 101325  Pa
                Contaminant Density (f1) at Reservoir Conditions -> |574;;v.5.;::::; kg/cubic m
                          Distance between the Hole or Opening
                                and Top of Liquid Level (Hi) -> fti%,7%.  m
               EMISSION
                                        Emission Rate (Qm) -> 1453.136 g/s
 d1t    Abort
                                        4-141

-------
             Continuous High Volatility Liquid Leaks  -  3.6
SOURCE PARAMETERS - Page 3 of 4

DISCHARGE DENSITY
                      Discharge Density ((7)  ->  3.614632 kg/cubic m
DENSITY OF AIR
                       Density of Air (fair)  -> 1.20209  kg/cubic  m
                    Ambient Temperature (Ta)  ->  295
Buoyancy is Negative
             Continuous High Volatility Liquid
SOURCE PARAMETERS - Page 4 of 4

VERTICALLY DIRECTED JET
       Does the release result in a vertically
                            directed jet (Y/N) ->  

TIME
                         Release Duration (Td) ->  2.293889 min
         Total Amount of Material Released (Q)  ->  200".%"  kg

             Continuous High Volatility Liquid Leaks  -  3.6
Based on user input, the Britter-McQuaid model  has  been selected.

BRITTER-McQUAID MODEL INPUTS - Page 1  of 3

MODEL PARAMETERS
                        Relative Humidity (Rh)  -> 58- /I:..-  %

    Desired Averaging Time for the Calculation
                             of Concentrations  -> 15    '    min
 -dit ...  <*9> Previous Screen  .  &1Q* Hejtt Seret=. .  ;*$&<& <8rt
             Continuous High Volatility Liquid Leaks  -  3.6
BRITTER-McQUAID MODEL INPUTS - Page 2 of 3

FENCELINE DISTANCE
 Enter the distance from the nearest edge of  the source
                        to the plant fenceline -> HXJ'  '

RECEPTOR LOCATIONS
Do you have specific locations where you would
like pollutant concentrations calculated (Y/N) -> H
 xl*?*:*^
                               4-142

-------
A summary of the Britter-McQuaid model's results  is displayed
below:
                       ***  SUMMARY OF B&M MODEL RESULTS ***
                      MAX CONC    MAX CONC   OIST TO   WIND SPEED
                      (UG/M**3)    (PPM)    MAX (M)    (M/S)

                      .2865E+08  9716.       100.      3.
                      REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS **
4.3.6.3  Considerations for Time-Varying and Time-Limited Releases

      See Section  2.5 for  a discussion of  considerations  for time-
varying and time-limited  releases.
                                  4-143

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4.3.7  Instantaneous High Volatility Leaks
                             Emissions
                  Pipe
                             Emissions
                                           Hole
                  Tank
Similar Releases:  (High volatility)  liquid leak from a tank or a
liquid leak from a pipe (when the ratio of the hole diameter to
the pipe diameter is less than 0.2).

Discussion:

     This procedure applies to an instantaneous release of a high
volatility liquid'(at constant temperature and pressure)  from a
ment (reservoir) through a hole or opening.  See Section 4.3.6
for further discussion.

Limitations and Assumptions:

     Same as Section 4.3.6.

Input Information:

     Same as Section 4.3.6.

4.3.7.1  Procedure:

1-3. Same as Section 4.3.6

4.   Buoyancy Check.   Perform buoyancy check as a first check.

     A.   Calculate the density of air using the following:

                                 P. M.
                            Pair =
                                 ~R~T
(4.3.7-1)
                              4-144

-------
          where Ma is the molecular weight of air  (assumed to
          equal 28.9 k/kmol).

     B.   If PI/Pat > !/  then the buoyancy is negative.   For
          negative buoyancy,  the RVD model should be used if the
          release is from a vertically directed jet; otherwise,
          the Britter-McQuaid model should be used; go to step 8.
          If the buoyancy is positive, the PUFF model for a point
          source should be used.  (See Section 2.4 for more
          information on model selection.)

5.    Same as Section 4.3.6.

4.3.7.2  Examples

     See the examples in Section 4.3.6.
                              4-145

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4.3.8  Continuous Low Volatility Liquids from Tanks and  Pipes
                      Tanks
Pipe
                                 Leaking Pipe Range
Similar Releases:  Possible applications include a  (low
volatility) liquid leak from a. tank or a pipe.

Discussion:

     Low volatility liquid is considered to be a material  whose
normal boiling point is above the ambient temperature,- a low
volatility material stored at moderate to low pressure  (and  so
that the boiling point is above the storage temperature) will
typically be released as a liquid and form a pool or puddle  on
the ground.  For low-volatility liquid releases, the
(conservative) assumption is that the liquid evaporates at the
same rate it is spilled  (except when the puddle is  confined  by a
bund or dike from which liquid does not overflow).

Limitations and Assumptions:

          The liquid level, pressure, and temperature in the
          reservoir are essentially constant.  If these
          parameters are not constant, the release  rate may  vary
          with time, but-the maximum release rate is generally
          obtained for the initial reservoir conditions.
          The hole or opening is located in the liquid space (as
          opposed to the vapor space).
          The gas evolution  (evaporation) rate is assumed  to be
          equal to the liquid release rate  (except  when the
          puddle is confined by a dike or bund from which  liquid
          does not overflow).  See Spicer, 1992.

Input Information:

     AQ    area of hole or opening  (m2)
     Ap    puddle area  (m2)  (For unbounded puddles,  \ is to be
          determined; for releases within dikes or  bunds,  Ap is
          the dike or bund area from which liquid would
                              4-146

-------
          evaporate.)
     At    flow area representing reservoir conditions  (m2)  (In
          the case of a leak  from a tank,  Aj-wn  (and  /3=0) ;  in the
          case of a leak  from a  pipe,  Aj is the cross-sectional
          area of the pipe.)
     D0    (equivalent) diameter  of hole or opening  (D0=2-,/AO/TT  )
          (m)
     g    acceleration due  to gravity (9.81 m2/s)
     HL    distance between  the hole or opening and the top of  the
          liquid level  (where the pressure is PJ  (m)  (In the
          case of a leak  from a  pipe,  HL=0.)
     M,    contaminant molecular  weight (kg/kmol)
     P,    ambient pressure  (Pa)
     Pv    vapor pressure  as a function of  temperature  (Pa)
     P!    reservoir pressure  (Pa)
     R    gas constant  (8314  J/kg-mole-K  or 8314
          Pa-m3/kg-mole- K)
     Q    total amount of material released (kg)
     T.    ambient temperature (K)
     Tb    contaminant'normal  boiling point (K)
     Tt    liquid storage  temperature (K)
     Ur    ambient windspeed (typically considered to be at 10  m
          elevation)  (m/s)
     /3    Y/AQ/A!  (dimensionless)
     X    heat of vaporization at the normal boiling point  (J/kg)
     P!    contaminant density at reservoir conditions  (Tt and Pj)
          (kg/m3)

4.3.8.1  Procedure:

1.   Pressure at the Hole or  Opening.   Estimate the liquid
     pressure at the hole or  opening P. as:

                      P.  = max(P4, Pt) + Pl g HL              (4.3.8-1)

2.   Emission Rate.  Estimate the emission rate Qm  (kg/s) as
     follows from Perry et  al. (1984):
     
                                 r     ,        > il/2
                 Qm (kg/s) = K Ao[2 Pl ( P. - P, ) j           (4.3.8-2)
     where                K = C / \l 1 - P*

     where C =  0.65  (although C can be  larger if j3>0.2)

     Puddle Area.  For unconfined puddles,  estimate the puddle
     area Ap required for the emission rate Qm as follows  from
     Clewell  (1983) -.


         Qm (kg/s) =6 . 94xl(T7(l+0 . 0043[T2-273 . ls]'2)tf-7


                               4-147

-------
                                                         (4.3.8-3)

     where T3 =  maxCT^T,)  and [T2-273.15]* is taken to be zero if
     T2  -  273.15 <  0;  Pv  (in  Pa) is evaluated at T2 using the
     Clausius-Cl apeyr on Equation:
                 Pv = 101325 exp  _= hi- -            (4.3.8-4)
     where Pvh is the vapor pressure  (in Pa) of hydrazine
     evaluated at T2 as follows :


      Pvh = exp I 76. 8580 -  7245'2  - 8.22 ln(T2) + 0.0061557 T2 J
              I             T*                              J

     For  (potentially)  confined puddles where Ap is known a
     priori. Equation  (4.3.8-3) must be solved for Qm using the
     known value to Ap. -If Qm  from Equation (4.3.8-3)  is  less
     than Qm from Equation (4.3.8-2), the estimate of Qm from
     Equation (4.3.8-3) and the a priori value of Ap best
     represent the release conditions.  However if Qm from
     Equation (4.3.8-3) is greater than Qm from Equation  (4.3.8-
     2), the estimate  of Qm from Equation (4.3.8-2) and Ap
     estimated from Equation (4.3.8-3) best represent the release
     conditions.    (Ap is so estimated in this  case because the
     puddle size from  Equation (4.3.8-3) is smaller than  the
     confining area for the release conditions . )

4.   Discharge Density.  Calculate the discharge density  as
     follows :

                                 P M
                                 1 W
                                 R T
                                    2                     (4.3.8-5)
5.   Buoyancy Check.  Perform buoyancy check as a first  check.

     A.   Calculate the density of air using the following:
                                                         (4.3.8-6)


          where M,  is  the  molecular weight  of  air (assumed to
          equal 28.9 kg/kmol).

     B.   If PI/Pfr  > 1,  then the buoyancy is negative.  For
          negative buoyancy, the Britter-McQuaid model should be
          used; go to step 6. If the buoyancy is positive,  the
          SCREEN model for an area source should be used.   (See
          Section 2.4 for more information on model selection.)
                              4-148

-------
6.   Release Duration.  The release duration is  used as an input
     into the Britter-McQuaid model.  Calculate  the release
     duration Td using the equation below:


                 T, (min)  = 	 9 (kg)  '               (4.3.8-7)
                  d        Qm (kg/s)   60  "(s/min)
4.3.8.2   Example:  Continuous Leak of Liquid Unsymmetrical
          Dimethlhydrazine  (UDMH)

Discussion:

     For this example, consider  a  liquid UDMH (101325 Pa and 283
K) leak from a 3.2 cm diameter  hole  in a  tank;  the hole is 1.0 m
below the liquid surface.  The tank is located in a bund with a
floor area of 2500 m2.  The distance to the fenceline is  100 m.

The following information will be  required:

     AO   area of hole or opening  (-jfD0V4 = 0.0008042 m2)
     Ap    (maximum) puddle area  (2500 m2)
     A!   flow area representing reservoir conditions (A!-* m2)
     D0    (equivalent) diameter  of hole or opening (0.032 m)
     g    acceleration due to gravity (9.81 m2/s)
     HL   distance between the hole or opening and the top of the
          liquid level  (where the  pressure is PJ  (1.0 m)
     N^   contaminant molecular  weight  (60.1  kg/kmol)
     P,   ambient pressure  (101325 Pa)
     Pv   vapor pressure as a function of  temperature (Pa)
     P!   reservoir pressure  (101325  Pa)
     R    gas constant  (8314 J/kg-mole-K  or  8314
          Pa-m3/kg-mole- K)
     Q    total amount of material released (500 kg)
     T,   ambient temperature  (283 K)
     Tb   contaminant normal boiling  point (335.5 K)
     T,   liquid storage temperature  (283  K)
     Ur   ambient windspeed  (typically considered to be at a 10 m
          elevation)  (2.0 m/s)
     j8    J5J&T  (0.0)
     X    heat of vaporization at  the normal  boiling point
           (5.44X105 J/kg)
     pl   contaminant density at reservoir conditions (Tt and Pt)
           (800 kg/m3)

With this information, the procedure  discussed 'above determines
the release  rate and  puddle area.

Procedure:

1.   Pressure at the  Bole  or Opening.  Estimate the liquid
     pressure P* at the hole or opening using  Equation  (4.3.8-1) .

                              4-149   :

-------
     In this case,  the UDMH is  released as a liquid at the  -
     ambient pressure and temperature,   so P.=P1=101325 Pa:

       P. = max(101325, 101325)  + 800-9.81-1.0 = 1.09xl05 Pa

2.   Emission Rate.  Estimate the emission rate Qm using Equation
     (4.3.8-2) with C =  0.65 as follows:

                         f       /                  \ 11/2
  Qm(kg/s)  = K-0.0008042-[ 2-800-( 1.09xl05 - 101325 )]  =1.83  kg/s

     where
                    K = 0.65 / ^1 - O.O4 =0.65

3.   Puddle Area.   Since  this puddle could be bounded, use the
     known Ap = 2500 m2  in Equation (4.3.8-3)  to determine Qm as
     follows:

   Qm = 6. 94xlO'7 (l +' 0.0043 [283  - 273 . 15 f) 2 . 0-75- 2500  60 . 1  Pv/Pvb

                           Qm = 3.9  kg/s


     where T2 = min(283 K,283 K)  = 283 K and Pv (in Pa) is
     evaluated  at T2 using the Glaus ius-Clapeyron  Equation
     (4.3.8-4) :
     - ,0X3,5 exp    -                     -        - I.15xl0. Pa
     where Pvh is the vapor pressure (in Pa)  of hydrazine
     evaluated at T2 as follows:


Pvh = exp ( 76.8580 -  7245'2 - 8.22    ln(2S3) + 0.0061557 -  283 \ = 730 Pa
         \            283                                    /

     So Qm (3.9 kg/s) from Equation (4.3.8-3)  is  greater than Qm
     (1.83 kg/s) from Equation (4.3.8-2),  and the estimate of Qm
     (1.83 kg/s) from Equation (4.3.8-2)  is accepted.  Using  1.83
     kg/s in Equation  (4.3.8-3) A^  is calculated  as  follows-.

    A =	 1.83   730	
     p
        6.94xlQ-7 (l + 0.0043[283  - 273 .15 ])2 . 0'75   60.1   i.iSxlO4

                           Ap = 1170 m2

4.   Discharge Density.   Calculate the discharge density using
     Equation  (4.3.8-5)  as follows:
                               4-150

-------
5.
                *-iJ^i-**/*

  Buoyancy Check.   Perform buoyancy check as a  first check.
  A.    Calculate  the density of air using Equation (4.3.8-6)
6.
        where 28.9  kg/kmol  is  the molecular weight o air.

  B.    Since p2/'p&  >  1.02,  then the buoyancy is negative.

  Release Duration.  Calculate the release duration Td using
  the  equation  below:
            Td (min)  =
                               500  (kg)
                       1.83  (kg/s)    60 (s/min)
                                              = 4 .55 min
     After this  calculation run the  Britter-McQuaid model.    (See
     Section 5.4 for more  information on the Britter-McQuaid
     model.)

Data entry in  the TSCREEN  model for  this example is shown below:

   	 Continuous Low Volatility Liquid Leaks - 3.8 	
   SOURCE PARAMETERS - Page 1 of 4

   Enter a unique title for this data's model run:
   SOURCE OF LEAK
   TEMPERATURE
           Area (Ao) of Hole or Opening ->
          Enter P for Pipe - T for Tank -> f
               Discharge Temperature (T2) -> 283
                                         cm2
                 Storage Temperature (T1) -> 28$  ..;.  K
                 Ambient Temperature (Ta) -> ZfcSrv^:.. ..:"; K
PUDDLE AREA
    Is Maximum Puddle Area (Ap) Known (Y/N) ->
             Maximum Puddle Area (Ap) ->
                                         tn>
         i;:;:g^
                                 4-151

-------
             Continuous Low Volatility Liquid Leaks  - 3.8
SOURCE PARAMETERS - Page 2 of 4

PRESSURE
                        Liquid Pressure  109173    Pa
                       Ambient Pressure (Pa)  -> 161325   Pa
                     Reservoir Pressure CP1)  -> 101325   Pa
             Contaminant Liquid Density (f1)  -> tt&   -  kg/cubic m
            Distance between Hole or Opening
            and Top of the Liquid Level (HI)  -> 1        m
VAPOR PRESSURE
                         Vapor Pressure (Pv) -> 11518.01  Pa
                       Molecular Weight (Mw) -> 60,1      kg/kmol
          Latent Heat of Vaporization (Lvap) -> 5*45:   J/kg
              Boiling Point Temperature (Tb) -> 335?    "K
      idtt    &* PfevfcKW. SKtt&ft     ftttKX Ste*ft
             Continuous Low Volatility Liquid Leaks -  3.8
SOURCE PARAMETERS - Page 3 of 4

EMISSION RATE
                          Emission Rate (Qm) -> 1851.863 g/s
                             Uind Speed (Ur) -> 2        m/s
AREA
                                        Area -> 1180.678 m

DISCHARGE DENSITY
                      Discharge Density (|7) -> 2.588181 kg/cubic  m

DENSITY OF AIR
                       Density of Air (fair) -> 1.244566 kg/cubic  m

Buoyancy is Negative
      Edit     Previous Screen    *PtO> M*t ScreaB'    <6So>-Afaor
             Continuous Lou Volatility Liquid Leaks - 3.8
SOURCE PARAMETERS - Page 4- of 4

TIME
                         Release Duration (Td) -> 4.499973 min
         Total Amount of Material Released (Q) -> 50$      kg
      Edit     Jlext Screen     Abort
                                             4-152

-------
             Continuous Low Volatility Liquid Leaks - 3.8
   Based on user input, the Britter-McQuaid model has been selected.

   BRITTER-McQUAID MODEL INPUTS - Page 1 of 3

   MODEL PARAMETERS
                    Relative Humidity (Rh) -> 56     %

      Desired Averaging Time for the Calculation
                        of Concentrations -> 1$     min
                                                 Afeart
             Continuous Low Volatility Liquid Leaks - 3.8
    BRITTER-McQUAID MODEL INPUTS - Page 2 of 3

    FENCELINE DISTANCE
    Enter the distance from the nearest edge of the source
                     to the plant fenceline -> Ij^S^'

    RECEPTOR LOCATIONS
    Do you have specific locations where you would
    like pollutant concentrations calculated (Y/N) -> M
A  summary of the Britter-McQuaid model's output is displayed
below:
                            SUMMARY OF B&M MODEL RESULTS
MAX CONC

-------
     A release is considered  (only) time limited if the liquid
release rate is constant over the duration of the release, but,
the release duration is short in comparison with other important
time scales (e.g., the averaging, time used to assess the
toxicity, the cloud travel time to a downwind position of
interest, or the time required to evaporate the released liquid
puddle).   For liquid releases of short duration.(including
instantaneous liquid releases),  the procedure outlined above can
be used to estimate the vapor evolution rate Qm if the puddle
area for screening purposes, the puddle area can be estimated if
a liquid depth of, say 1 cm is assumed.  (While an equilibrium
depth, of 1 cm may be justified strictly on the grounds it is a
reasonable estimate for screening purposes, more extensive
modeling efforts have used a 1 cm equilibrium depth to fit
experimental data e.g., Moorehouse and Carpenter  (1986) and
Webber and Jones  (1987).)  With this assumption, an unconfined
puddle size can be determined.  Finally, the (vapor) release
duration Td can be calculated  as Td = Q/Qm where Q is the total
mass of liquid released.  (Note that Td may be  sufficiently large
enough to consider the vapor release as being continuous even for
an instantaneous liquid release.)
                              4-154

-------
4.3.9  Instantaneous Low Volatility Liquids from Tanks and  Pines
                      Tanks
Pipe
                                 Leaking Pfpa Range
Similar Releases:  Possible applications include a  (low-
volatility) liquid leak from a tank or a pipe.

Discussion:

     Low-volatility liquid is considered to be a material whose
normal boiling point is above the ambient temperature; a. low-
volatility material stored at moderate to low pressure  (and  so
that the boiling point is above the storage temperature) will
typically be released as a liquid and form a pool or puddle  on
the ground.  For low-volatility liquid releases, the
(conservative) assumption is that the liquid evaporates at the
same rate it is spilled  (except when the puddle is  confined  by a
bund or dike from which liquid does not overflow).  Possible
applications include a  (low-volatility) liquid leak from a tank
or a pipe.

     In contrast to scenario 4.3.8, pressure at the hole or
opening is not applicable to an instantaneous liquid release.
Although determination of the liquid release rate is not
applicable to an instantaneous liquid release, determination of
whether the liquid puddle will be confined or not is necessary to
know how to proceed.

Limitations and Assumptions-.

          The liquid level, pressure, and temperature in the
          reservoir are essentially constant.  If these
          parameters are not constant, the release  rate may  vary
          with time, but the maximum release rate is generally
          obtained for the initial reservoir conditions.

          The hole or opening is located in the liquid space (as
          opposed to the vapor space).
                              4-155

-------
          The gas evolution  (evaporation) rate  is  assumed to be
          equal to the liquid release rate  (except when the
          puddle is confined by a dike or bund  from which liquid
          does not overflow).  See Spicer,  1992.

Input Information:

     Ap    puddle area  (m2)  (For unbounded puddles,  Ap is to be
          determined; for releases within dikes or bunds,  Ap  is
          the dike or bund area from which  liquid  would
          evaporate.)
     Mw   contaminant molecular weight  (kg/kmol)
     R    gas constant  (8314 J/kg-mole-K or  8314
          Pa -mYkg-mole  K)
     Q    total amount of material released (kg)
     T.    ambient temperature  (K)
     Tb    contaminant normal boiling point  (K)
     T!    liquid storage temperature  (K)
     Ur    ambient windspeed  (typically considered  to be at 10 m
          elevation)  (m/s)
     V    volume of liquid spilled  (m3)
     X    heat of vaporization at the normal  boiling point (J/kg)
     pl    contaminant density at reservoir  conditions (T{  and PJ
          (kg/m3)

4.3.9.1  Procedure:

1.   Puddle Area.  Calculate the area of liquid spilled based on
     volume of liquid spilled assuming a 1  cm puddle depth.
                         T       0.01 (m)

     If the area from Equation  (4.3.9-1)  is  smaller than the bund
     area  (which is the maximum possible  puddle area),  then the
     area  from Equation  (4.3.9-1)  is  used as the puddle area
     (Ap).   Otherwise,  if the bund size is smaller than  the  area
     calculated in Equation  (4.3.9-1),  then  the bund area is used
     as the puddle size
2.   Emission Rate.  The puddle  area  is  used'to calculate the
     emission rate Qm  (kg/s)'as  follows:
         Qm = 6.94xlO'7 (l + 0.0043 [T2 - 273.15J*2) Ur-75ApMwPv/P.
                                       vh
                                         4.3 .9-2)
     where T2 = max(Tt,Tt)  and [T2-273.15]* is taken to be zero  if
     T2 - 273.15 < 0; Pv  (in  atm)  is  evaluated at T2 using  the
     Clausius-Clapeyron Equation:
                                                         (4.3.9-3)
Pv = 101325 exp
                               4-156

-------
     where Pvh is the vapor pressure  {in Pa) of hydrazine
     evaluated at T2 as  follows:
      Pvh = exp  76.8580 -    ,'   - 8.22 ln(T2) + 0.0061557 T
                                                          2
3.   Discharge Density.  Calculate the discharge density as
     follows:
                            P2 =  
                                   2                     (4.3.9-4)

4.   Buoyancy Check.  Perform buoyancy check as a first  check.

     A.   Calculate the density of air using the following:

                                 P. M.
                            '-TTT:                    (4.3.9-5)


          where M, is  the  molecular weight  of  air  (assumed to
          equal 28.9 kg/kmol).

     B.   If p2/pair > 1,  then the buoyancy is negative.  For
          negative buoyancy, the Britter-McQuaid model should be
          used.   If the buoyancy is positive, the PUFF should be
          used.   (See Section 2.4 for more information on model
          selection.)

5.   Release Duration.  The release duration is used  as  an  input
     into the PUFF and Britter-McQuaid models.  Calculate the
     release duration Td using  the equation below:

                     _	^_^__
                  d 	'   Qm (kg/s)   60 (s/min)

4 . 3.. 9 . 2  Example:  Instantaneous Liquid UDMH Leak

Discussion:

     For this example, consider an instantaneous spill of 20 m3
liquid UDMH from  storage  at 1 atm and 283  K.  The spill occurs
in a bund with a  floor area of 2500 m2.   The fenceline is 100 m
away.

The following information will be required:

     Ap   maximum puddle  area  (2500 m2)
     M^   contaminant molecular weight  (60.1 g/g-mole)
     R    gas constant
     Q    total amount of material released  (16,000 kg)
     T,   ambient temperature  (283 K)


                              4-157

-------
     Tb    contaminant normal boiling point  (335.5  K)
     T!    liquid storage temperature  (283  K)
     Ur    ambient windspeed  (typically  considered  to be at 10 m
          elevation)  (2.0 m/s)
     V    volume of liquid spilled  (20  m3)
     X    heat of vaporization at the normal  boiling point
          (5.44x105 J/kg)
     Pi    contaminant density at reservoir  conditions (Tt  and Pt)
          (800 kg/m3)

Procedure:

1.   Puddle Axea.  Calculate-the area of liquid spilled based on
     the volume of liquid spilled assuming  a  1  cm  puddle depth
     from Equation  (4.3.9-1) as follows:
                     a  (m2) =  20 m3  = 2000 m2
                      f       n ni m
                              0.01 m

     The area from Equation  (4.3.9-1)  is  smaller than the bund
     area  (which is the maximum possible  puddle area) ,-  therefore,
     the- area from Equation  (4.3.9-1)  is  used as the puddle area
     (A,).

     Emission Rate.  The puddle area  is used to calculate the
     emission rate  (Qm) from Equation  (4.3.9-2)  as  follows:


     Qm=6 . 94xlO'7(l+0 . 0043 [283-273 . 15 ]2) 2 . 0-75  2000  60 . 1  Pv/Pvh

                          Qm = 3.13  kg/s

     where T2 =  min(283 K,283 K)  = 283 K and  Pv (in atm)  is
     evaluated at T2 using the Glaus ius-Clapeyron Equation
     (4.3.9-3) :
      P, = 101325 exp  -          -       -         1-lSxlo<
     where Pvh is the vapor pressure  (in  Pa)  of  hydrazine
     evaluated at T2 as follows:
                                                                  

Pvh = exp ( 76.8580 -  7245'2 - 8.22 ln(283) + 0.0061557   283 ) = 730 Pa
        \            283                                  /
3.   Discharge Density.  Calculate  the  discharge density using
     Equation  (4.3.9-4) as  follows:

                  n -  101325  -60.1   n  c
                  P2 "   8314  283    = 2'5
                              4-158

-------
4.    Buoyancy Check.   Perform buoyancy check  as a  first check.

      A.    Calculate the density of  air using  Equation  (4.3.9-:
      where 28.9 kg/kmol is  the molecular  weight of air.

B.    Since p2/p& >  1,  the buoyancy is  negative.

Release  Duration.   Calculate the release  duration  Td  using
the equation below:


        Td  (min)  =
                                  16,000  (kg)
                           3.13  (kg/s)    60 (s/min)
                                                        = 85 min
      After  this  calculation run the  Britter-McQuaid.   (See
      Section 5.4  for  more  information on  the  Britter-McQuaid
      model.)

Data entry  in the TSCREEN  model for  this  example  is shown below:

             	 Instantaneous Low Volatility Liquid Leaks - 3.9 	
              SOURCE PARAMETERS.- Page 1 of 4

              Enter a unique title for this data's model run:



                          Volume of Liquid Spilled (V) -> 20:...f: :..- cubic m


                           Discharge Temperature (T2) -> 283    "K
        VOLUME


        TEMPERATURE
                             Storage Temperature (T1) ->
                             Ambient Temperature (Ta) ->
                                                 "K
              PUDDLE AREA
                  Is Maximum Puddle Area (Ap) Known (Y/N) -> T
                             Maximum Puddle Area (Ap) ->
               F2> Edit  ~"&9>e Prevlbua Screen; . ' "
                                                  *: 11518.01 Pa
                               Molecular Weight (Mw) ->
                      Latent Heat of Vaporization (Lvap) ->
                         Boiling Point Temperature (Tb) ->
                                                :  kg/kmol
                                                  J/kg

                                     4-159

-------
            Instantaneous Low Volatility Liquid Leaks  - 3.9
SOURCE PARAMETERS - Page 3 of 4

EMISSION RATE
                          Emission Rate (dm)  -> 3136.949  g/s
                             Wind Speed (Ur)  -> 2       m/s
AREA
                                        Area ->  2000     m'

DISCHARGE DENSITY
                      Discharge Density (f2) ->  2.588181 kg/cubic m

DENSITY OF AIR
                       Density of Air (fair) ->  1.244566 kg/cubic m

Buoyancy is Negative
      8dit     85.00829 min
         Total Amount of Material Released (Q)  ->  16000:    kg

            Instantaneous Low Volatility Liquid Leaks  - 3.9
Based on user input, the Britter-McQuaid model  has  been  selected.

BRlTTER-McQUAID MODEL INPUTS - Page 1  of 3

MODEL PARAMETERS
                        Relative Humidity (Rh)  -> 56  .!   %

    Desired Averaging Time for the Calculation
                             of Concentrations  -> 15-      min
                                                                Afcort
            Instantaneous Lou Volatility Liquid Leaks  - 3.9
BRITTER-McQUAID MODEL INPUTS - Page 2 of 3

FENCELINE DISTANCE
 Enter the distance from the nearest edge of  the source
                        to the plant fenceline  -> 100

RECEPTOR LOCATIONS
Do you have specific locations where you would
like pollutant concentrations calculated (Y/N)  -> H
                             Sewer*    
-------
A  summary of the  Britter-McQuaid model's  output is  displayed
below:
                        <>>>* >*
                        ***   SUNMARY OF BM MODEL RESULTS ***
                          >*>
                       MAX COHC    MAX CONC   DIST TO  WIND SPEED
                       (Ua/M**3>     (PPM)     MAX (M)    (M/S)

                       .4904E+08   .1895E+05    100.      4.
                     ** REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS **
                     <*> >>tm >
4.3.9.3    Considerations  for Time-Varying and  Time  Limited
            Releases

      See Section 4.3.8.3  for a  discussion of considerations  of
time-varying and time-limited releases.
                                     4-161

-------
4.4  Superfund Releases

4.4.1  Air Strippers
                  Contaminated
                  Wafer
                                       "Clean" i
                                          Air
                                   Air
Discussion:

     Air stripping  is  a widely used technique for removing
volatile organic  compounds  (VOC)  from contaminated water.
Procedures are given to evaluate  the effect of the concentration
of contaminants in  water  and the  effect of  the stripping rate on
the emission rates  and on the ambient air concentrations at
distances from, the  air stripper'.

Limitations and Assumptions L

     None.

References:
     For  further  information see:   Air/Superfund National
Technical Guidance  Study Series  -  Air Stripper Design Manual.
EPA-450/1-90-003, U.S.   Environmental Protection Agency,  Research
Triangle  Park, NC,  May  1990,  NTIS  PB91-125997,  pp 51-52.

Input  Information:

     In addition  to the SCREEN model input (see Secicn 5.1.1).
the  following  is  needed-.

     C   concentration of contaminant (mg/L)
     Q   incoming  water flow rate (L/'min)

4.4.1.1   Procedure
                               4-162

-------
1.   Emission Rate.  Calculate emission rate  (Qm) (g/s) using the
     concentration of the contaminant  (C) and the incoming water
     flow rate (Q).  VOC concentrations in ground water typically
     range from 0.1 to 1 ppmw.  Typical values for an  air
     stripper are shown in Table 4.4.1-1.

             Qm(g/s)  = C(mg/L)  Q(L/minute)   1.67xKT5    (4.4.1-1)

                          TABLE 4.4.1-1
               TYPICAL VALUES FOR AN AIR STRIPPER
Parameter
Incoming Water Flow
Stack Height
Stack Diameter
Structure Dimensions
Exit Gas Velocity
Exit Gas Temperature
Ambient Temperature
Units
L/min
m
m
m
m/sec
K
K
Small
570
7.6
0.31
7.6x1.2x1.2
6.4
293
293
Typical Value
Medium
2840
9
0.61
9x3.6x3.6
8.0
293
293
Large
5700
14
0.91
13x3.6x3.6
7.3
293
293
2.    TSCREEN will run the SCREEN model for a point source.

4.4.1.2  Example:  Air stripper example

Discussion:

     This example uses the default values provided by TSCREEN for
a large air stripper.  The fenceline is 100 m from the  air
stripper.

The following input information will be required:
     C
     Q

Procedure;

1.
     concentration of contaminant 0.5 (mg/L)
     incoming water flow (L/min) 4700 (default)
Emission Rate.  Calculate emission rate  (Qm)  (g/s) using
Equation (4.4.1-1):
            =  -5 (mg/L)  5700 (L/minute)  l.SVxlO'5 =  0.048 (g/s)
     TSCREEN will run  the SCREEN model for a point  source .   For
     an explanation of inputs- for the SCREEN model  see  Section
     5.1.1.
                              4-163

-------
Data  entry  in  the  TSCREEN  model  for this  example  is  shown  below:
                                   Air Strippers - Scenario 4.4.1
                 SOURCE PARAMETERS * Page 1 of 1

                 Enter a unique title for this data's model run:
                 EMISSION RATE
                  Enter the Emission Rate (Qm),  if unknown enter
                         the boxed variables below to calculate -> IM&?5$$ g/s
                              Concentration of Contaminate (C) -> ,5      mg/L
                                       Incoming Water Flow (Q) -> 5-TfflJ    L/min
sdft.
                                      p^:p$^^
                                   Air  Strippers - Scenario 4.4.1
                 Based on user input, SCREEN model has been selected.

                 SCREEN MODEL INPUTS - Page 1 of 7



                 RELEASE PARAMETERS

                                              Exit Velocity -> 7*3
                                  Release Height above Ground -> 14
                                    Diameter at Release Point -> .91
                          Temperature of the Material Released -> 293
                 AMBIENT PARAMETER
                                         Ambient Temperature -> 293
                                               m/s
                                               m
                                               m
                                               "K
                                                                         > Abort
                                   Air  Strippers - Scenario 4.4.1
                 SCREEN MODEL INPUTS - Page 2 of 7

                 BUILDING PARAMETERS
                      Building Height (enter 0 if no building) ->  13   ;   m
                         Building Minimum Horizontal Dimension ->  &$  ;*,};. m
                         Building Maximum Horizontal Dimension ->  &&}.;.:/' m

                 URBAN/RURAL CLASSIFICATION
                               Enter U for Urban - R for Rural ->  ft

                 FENCELINE DISTANCE
                  Enter the distance from the base of the stack
                                      to the plant fenceline ->  100 '   : m
                      idtt    *f9*: f*rtt .w.t,$fen,:. ;,,,,.
-------
     It*************************************
     *** SUMMARY OF SCREEN MODEL RESULTS ***
CALCULATION
PROCEDURE
MAX CONC
(UG/M**3)
DIST TO
MAX (M)
TERRAIN
HT (M)
SIMPLE TERRAIN      7.276

BUILDING CAVITY-1   678.0
BUILDING CAVITY-2   678.0
104.

 12.
 12.
0.
   (DIST
   (DIST
 CAVITY LENGTH)
'.CAVITY LENGTH)
it**************************************************
** REMEMBER TO INCLUDE BACKGROUND  CONCENTRATIONS **
 ***************************************************
                                4-165

-------
5.0  ATMOSPHERIC DISPERSION ESTIMATES

     Maximum short-term ground level concentrations in TSCREEN
are based on current EPA screening models (SCREEN, RVD, and PUFF)
which are embedded in the TSCREEN model.  In addition, TSCREEN
implements the Britter-McQuaid method for estimating maximum
concentration from denser-than-air continuous  (plume) and
instantaneous (puff) releases.  This section lists the TSCREEN
model inputs needed.  Sources of additional information about the
models are referenced, where appropriate.
                               5-1

-------
5.1  SCREEN

     The  SCREEN model  implements most of  the single source,  short
term procedures contained in the revised  EPA screening  procedure
document  (EPA,  1988c).   This includes providing estimated maximum
ground-level concentrations and distances to the maximum based on
a pre-selected range of  meteorological  conditions.  SCREEN is a
Gaussian  dispersion model applicable to continuous releases of
particulate matter and non-reactive, non-dense gases that are
emitted from point, area,  and flared sources.   In addition,
SCREEN has the option  of incorporating  the effects of building
downwash,  as described in the Industrial  Source Complex (ISC2)
model user's guide  (EPA,  1992) .   Refer  to the document  referenced
above for more information about the implementation of  the SCREEN
model.

5.1.1  Point Sources

5.1.1.1 Model Inputs

     This section contains a complete listing of the inputs
TSCREEN will request for the SCREEN point source.  Some of these
inputs may have already  been entered from the scenario  input
section.
                          SCENARIO NAME & NUMBER
            Based on user input, SCREEN model has been selected.

            SCREEN MODEL INPUTS - Page 1 of 7
            Enter a unique title for this data's model run:
            RELEASE PARAMETERS
                              Emission Rate (Qm) ->
                             Exit Velocity (Exitv)->
                     Release Height above Ground (Hs) ->
                       Diameter at Release Point (0) ->
                Temperature of the Material Released (Ts) ->
            AMBIENT PARAMETER
                          Ambient Temperature (Ta) -> 293
g/s
m/s
m
m
              Help    Calculator     Previous Screen    Abort
RELEASE PARAMETERS

-   Emission Rate  (Om)  (g/s)  -
    Enter the source  specific emission  rate.   EPA recommends that
    emission rates from sources be determined through  source
    testing using EPA References Methods  (40  CFR Part  60  Appendix
    A)  or process calculations. If source specific emissions are
    not available, representative emission factors can be
    substituted.  Emission factors are  available for individual
    toxic compounds.   For some sources  of applicable emissions
                                 5-2

-------
     factors  for individual  toxic  compounds see  Appendix A items
     1-4 of this workbook.

2    Exit Velocity  (Exitv)  (m/s)  -
     This value can  be calculated  from the following equation:

                            Exitv =  4 V/(7rD2)

     where:
           D  = inside diameter of  stack  (m)
           V  = volumetric  flow rate  (m3/s)

3    Release  Height  above  Ground  (H;)  (m)  -
     Enter the height of the stack or of  the release point above
     the ground.

4    Diameter at Release Point (D)  (m) -
     Enter the inside diameter of  the stack or release  point  in
     meters.

5    Temperature of  the Material Released (T.)  (K) -
     Enter the temperature of the  material  released in  degrees
     Kelvin.

AMBIENT PARAMETER

6    Ambient  Temperature  (Tj  (K)  -
     The default if  293 K.
                            SCENARIO NAME & NUMBER
             SCREEN MODEL INPUTS - Page 2 of 7

             BUILDING PARAMETERS
                 Building Height (enter 0 if no building) ->  :  ; .  m
                   Building Minimum Horizontal Dimension ->       m
                   Building Maximum Horizontal Dimension ->       m

             URBAN/RURAL CLASSIFICATION
                       Enter U for Urban - R for Rural ->

             FENCELINE DISTANCE
              Enter the distance from the base of the stack
                              to the plant fenceline ->    . ;  m
               Help   -Calculator     Previous Screen   Abort
                                   5-3

-------
BUILDING PARAMETERS

7   Building Height (m)  -
    Enter the buildings maximum height above ground in meters.
    Building parameters are needed for calculating downwash for a
    stack due to a "nearby" building.  "Nearby" includes
    structures within a distance of five times the lesser of the
    height or width of the structure, but not greater than 0.8 km
    (0.5 mile).   If more than one building is involved, each
    building/stack configuration must be modeled separately.  -For
    information about complex structures, refer to the Guideline
    for Determination of Good Engineering Practice Stack Height
    (Technical Support Document for Stack Height Regulations).
    Revised. EPA 450/4-80-023R.  For these complex
    configurations, a refined model such as the Industrial Source
    Complex  (ISC) model is recommended.  Wake effects are
    included.  Cavity calculations are made for two building
    dimensions alongwind.  The cavity calculations are summarized
    in the SCREEN model output at the distance-dependent
    calculations.  Building downwash effects are not considered
    in the SCREEN model in either the VALLEY or simple terrain
    component of the complex terrain screening procedures (see
    description Terrain Type below),  even if the building
    downwash option is selected by entering a building height.

    *     If the building height is 0 the next two parameters are
          not requested and the user will proceed to step 10.

8   Building Minimum Horizontal Dimension (m) -
    Enter the alongwind minimum .horizontal dimension of the
    "nearby" structure in meters.  A simple rectangular building
    is assumed.   (See the description of Building Height above.)

9   Building Maximum Horizontal Dimension (m) -
    Enter the alongwind maximum horizontal dimension of the
    "nearby" structure in meters.  A simple rectangular building
    is assumed.   (See the description of Building Height.)

URBAN/RURAL  CLASSIFICATION

10  Enter U  for Urban - R for Rural -
    The classification of a site as urban or rural is based on
    the procedures described in Section 8.2.8 of the Guideline on
    Air Quality Models (Revised). EPA-450/2-78-027R.

FENCELINE DISTANCE

11  Enter the distance from the base of the stack to the plant
    fenceline (m) -
    Enter the distance from the base of the stack to the plant
    fenceline in meters.  SCREEN calculates the maximum
    concentrations across a range of meteorological conditions
    for the  minimum distance given (> 1 m) and then for each

                                5-4

-------
    distance in a built-in array of  distances.   Thus,  the user
    can input the minimum fenceline  distance as  the minimum
    distance for calculation and obtain a concentration at the
    site boundary and beyond.  Distances less than the fenceline
    are ignored.  Receptors beyond the fenceline are defined as
    ambient  air.
                           SCENARIO NAME & NUMBER
            SCREEN MODEL INPUTS - Page 3 of 7

            TERRAIN TYPE
              Is this a FLAT or SIMPLE TERRAIN evaluation (Y/N) ->

            SIMPLE TERRAIN
                      Are receptors above stack-base (Y/N) ->

            SIMPLE FLAT TERRAIN
            Do you have specific locations where you would like 
               pollutant concentrations to be calculated (Y/N) ->

                   Do you have receptors above ground level
                         (i.e. Flag Pole Receptors) (Y/N) ->
              You have completed simple terrain inputs. Do you
                  want to continue with complex terrain (Y/N) ->
              Help    Calculator    Previous Screen   Abort
TERRAIN  TYPE

12  Is this a FLAT or  SIMPLE TERRAIN elevation  (Y/N)  -
    Terrain type is determined according to whether it is above
    or below stack-top.   Simple terrain is an area where terrain
    features are all lower in elevation than the  top of the  stack
    of the  source.  Complex terrain  is defined  as terrain
    exceeding the height  of the stack being modeled.   In TSCREEN,
    the  user is given  the option of  modeling simple elevated
    terrain heights where terrain heights exceed  stack base  but
    are  below stack height, or simple flat terrain,  where terrain
    heights are assumed not to exceed stack base  elevation.
    Answer  "N" if there are no flat  or simple terrain receptors;
  -  a "N" answer will  bring up the COMPLEX TERRAIN screen.
    Answer  "Y" if one  or  more receptors are located in terrain
    which is below stack-top.  Answer "Y" if your evaluation
    involves both simple  and complex terrain receptors.  You will
    have another opportunity following completion of the simple
    terrain inputs to  evaluate the complex terrain receptor.   In
    summary:

                "Y" selects FLAT or SIMPLE TERRAIN
                "N" selects COMPLEX TERRAIN

    *     If  "Y"  was entered above,  TSCREEN proceeds  to step  13.
                                 5-5

-------
    +     If "N"  was entered above,  TSCREEN proceeds to step 15.

SIMPLE TERRAIN

13  Are receptors above stack-base (Y/N)  -
    Simple terrain is an area where terrain features are all
    lower in elevation than the top of the stack of the source.
    Answer "Y" if one or more receptors are located in simple
    terrain.  "N" if all receptors are in FLAT terrain.  In
    summary:

          "Y"  selects SIMPLE TERRAIN
          "N"  selects FLAT TERRAIN

    +     If "Y"  was entered,  TSCREEN proceeds to step 15.
                                  
    *     If "N"  was entered,  TSCREEN proceeds to step 14.

SIMPLE FLAT TERRAIN

14  Do you have specific locations where you would like pollutant
    concentrations to be calculated (Y/N)  -
    The entry of "Y" will allow the user to input any number of
    specific distances (>1 m)  and the maximum concentration for
    each distance will be calculated.   Note that SCREEN has an
    automated distance array which calculates maximum
    concentrations at a pre-selected array of 50 distances
    ranging from 100 m to 50 km.   Increments of 100 m are used
    out to 3 km,  increments of 500 m are used from 3 km to 10 km,
    increments of 5 km from 10 km to 30 km, and increments of 10
    km are used out to 50 km.   For example, a specific_location
    of interest may be a school 117 m from the source.

15  Do you have receptors above ground level (i.e. Flag Pole
    Receptors) (Y/N) -
    A flag pole receptor is any receptor which is located above
    local ground level,  e.g.,  on the roof of a building.   Flag
    pole receptors are useful for estimating concentrations on
    rooftops or similar exposed locations and are most often used
    in urban modeling evaluations.  Note,  flag pole receptors
    should NOT be used to evaluate impacts on hilltops or on
    other exposed terrain features; the latter should be
    evaluated using the TSCREEN options for simple or complex
    terrain.  Answer "Y" if you want to use flag pole receptors.
    A "Y" response will invoke a request for the receptor  (i.e.,
    flag pole) height.  Answer "N" if you do not want to use flag
    pole receptors.  The receptor height defaults to zero for a
    "N" response.
                               5-6

-------
16
*     If there is Simple  terrain  (response of "Y"  at step 13)
      then,  TSCREEN proceeds to step  17.

>     If there is no Simple or Flat terrain (response of "N"
      at step 12) then, TSCREEN assumes  that there is Complex
      terrain and proceeds to step 19.'

*     If there is Flat  terrain and specific locations of
      interest (response  of "N" at step  13 and response of
      "Y"  at step 14) then, TSCREEN proceeds to step 18.

*     If there is Flat  terrain but no specific locations of
      interest (response  of "N" at step  13 and response of
      "N"  at step 14) then, TSCREEN proceeds to step 16.

You have  completed simple terrain inputs.  Do you  want to
continue  with complex terrain  (Y/N)  -
Complex terrain  is terrain exceeding  the height of the stack
being modeled.   Enter  "Y". to model complex terrain.   SCREEN
has no  automated distance array for  Complex Terrain.
Distances  must be specified by the user.

*     If  "Y" was entered,  TSCREEN proceeds to step 19.

+     If  "N" was entered,  TSCREEN runs the SCREEN  model.
                          SCENARIO NAME & NUMBER
            SCREEN MODEL INPUTS/SIMPLE TERRAIN STAIRSTEP SEARCH-- Page 4 of 7

            Enter distance and terrain elevation for "stair-step'search".
            Enter a blank Maximum Distance to stop input.

                      Distance (meters)
                 Minimum           Maximum        Height (meters)
                 100    fence
                 200
                 400
                 800
                 1200
            Last Maximum Distance will be extended to 50000 m
              Help
                   Calculator
 Previous Screen
                                               Abort
SIMPLE TERRAIN STAIR-STEP SEARCH

17  Enter  distance and  terrain elevation for "stair-step search"-
    The SCREEN model assumes that terrain elevation  either
    remains  the same or increases with  distance from the source,
    i.e.,  incremental steps, as in an ascending staircase or on  a
                                 5-7

-------
    terraced hillside.   "Stair-step  search" describes how the
    SCREEN model searches for the maximum concentration in  simple
    terrain.   The user  should enter  the distance  to and the
    elevation (above stack-base) of  each stair-tread or terrace.
    SCREEN assumes that the first stair-tread begins at the ;
    fenceline.  Thus, the user must  begin by entering the
    elevation and the distance to the  end of the  first stair-
    tread.   This is repeated for each  succeeding  stair-tread.
    The distance to the end of the last stair-tread defaults  to
    50 km.

    After  finishing inputs for this  section, TSCREEN will ask if
    there  are specific  locations of  interest (See step 13).

    *      If  "Y",  TSCREEN proceeds to  step 18.

    >      If  "N",  TSCREEN will ask the. if there is  Complex
           terrain (See  step 16).

    *      If  there is Complex terrain,  TSCREEN proceeds to  step
           19.

    *      If  there is no  Complex terrain,  TSCREEN runs the  SCREEN
           model.
                           SCENARIO NAME & NUMBER
            SCREEN MODEL INPUTS DISCRETE RECEPTORS - Page 5 of 7
            Enter a height and distance(s) from the source to terrain feature(s)
            at which a specific receptor will be located.
            Enter a blank after the distance to stop inputs for that height.
            Enter a blank height to stop input.
           Height (m)
Height (m)
Height (m)
Height (m)
Height (m)
          Distances (m)  Distances (m)  Distances (m)  Distances (m) Distances (m)
              Help
  Calculator
    Previous Screen    Abort
DISCRETE  RECEPTORS

18  Enter a height and distance(s)  from the source  to terrain
    feature(s)  at which a specific  receptor will  be located  -
    The program will  calculate concentrations at  receptors for a
    specified distance from their release.  In the  case of simple
    terrain,  a terrain height can be  specified from these
    receptors.   This  height must be s the stack height.   For the
    case  of flat terrain, a terrain height is not requested.
                                 5-8

-------
    *     If  5  heights are  entered,  TSCREEN will  ask if the user
          wants to enter  more discrete receptors.   If the
          response is "Y"   a Page 6  of 7,  which  looks the  same as
          Page  5 of 7, will appear.

    After finishing inputs  for DISCRETE RECEPTOR section,  TSCREEN
    will ask  if the user  wants to proceed with complex terrain
    (See step 17).

    *     If  response is  "Y" then TSCREEN proceeds to step 19.

    +     If" response in  "N" then, TSCREEN runs  the SCREEN model.
                           SCENARIO NAME & NUMBER
            SCREEN MODEL INPUTS COMPLEX TERRAIN - Page 7 of 7
            Enter height and distance for receptor location.
            Enter a blank Distance to stop input.
                                          Plume Height ->    m
                               Distance to Final Plume Rise ->    m
                Height (m) Distance (m)
                2
                3
                4
                5
                6
                7
                8
                9
                 Height (m)  Distance (m)

                11          ""';..
                12  :' ""-,    '- . ;':V
                13 ;:/:'-?:-,.:;.   ::;4 ;' ''

                15 -v>. :."-"i.   /":S-"v
                16 .   -*,:;   .--. .  "-
                17  'fi.:""   .-. :
                18  "^ .:-.   ;  -. ';-

                20 ...'':'::... '   ':-."'. ""'
              Help
 Calculator
                                    Previous Screen
                              Abort
COMPLEX  TERRAIN

19  Enter height and  distance  from receptor  locations  -
    Enter the terrain height and  distance  in meters for  the
    receptor of interest.  The terrain height must be  greater
    than the stack  height.

    >      After finishing inputs  for this  section,  TSCREEN runs
           the SCREEN  model.

5.1.1.2   Model Output

    For  a complete  example of  the SCREEN model for a point
source,  see Section 4.1.1.    See Appendix E - Running TSCREEN  fcr
output options after  model is  run.' The following shows  the
format of the output  file that SCREEN would  generate for a point
source if the user  has chosen  to show the  maximum concentration
in parts per million  (PPM)  in  addition to  ^g/m3 and shows  the
maximum  concentration for additional averaging times.
                                  5-9

-------
1                                                                   02-05-92
                                                                    09:50:06
  *** SCREEN-1.2 MODEL RUN ***
  *** VERSIOH DATED  90XXX ***

 Paniculate Stack Release

 COMPLEX TERRAIN INPUTS:
    SOURCE TYPE         =    POINT
    EMISSION RATE (G/S) =
    STACK HT (M)        -
    STACK DIAMETER (M)  -
    STACK VELOCITY (M/S)=
    STACK GAS TEMP (K)  =
    AMBIENT AIR TEMP (K)=
    RECEPTOR HEIGHT (M) =
    IOPT (1=URB,2=RUR)  =

1                                                             '      02-05-92
                                                                    09:50:06
*  *** SCREEN-1.2 MODEL RUN ***
  *** VERSION DATED  91/10 **
 SIMPLE TERRAIN INPUTS:
    SOURCE TYPE            =    POINT
    EMISSION RATE (G/S)    =
    STACK HEIGHT (M)       =
    STK INSIDE DIAM (M)    =
    STK EXIT VELOCITY (M/S)=
    STK GAS EXIT TEMP (K)  =
    AMBIENT AIR TEMP (K)   =
    RECEPTOR HEIGHT (M)    =
    IOPT (1=URB,2=RUR)     =
    BUILDING HEIGHT (M)    -
    MIN HORIZ BLDG DIM (M) =
    MAX HORIZ BLDG DIM (M) =
                       IF*********************
          SUMMARY OF SCREEN MODEL RESULTS *
CALCULATION
PROCEDURE
MAX CONC
(UG/M**3)
MAX CONC
(PPM)
DIST TO
MAX (M)
TERRAIN
HT (M)
 SIMPLE TERRAIN

 COMPLEX TERRAIN                                   (24-HR CONC)

 BUILDING CAVITY-1                             --  (DIST = CAVITY LENGTH)
 BUILDING CAVITY-2                             --  (DIST = CAVITY LENGTH)
 ** REMEMBER TO  INCLUDE BACKGROUND CONCENTRATIONS **
 *** *
 BUOY. FLUX =         M*4/S*3;  MOM. FLUX =         M*4/S**2.
  FINAL STABLE PLUME HEIGHT (M) =
  DISTANCE TO FINAL RISE (M)    =

                          VALLEY 24-HR CALCS*   "SIMPLE TERRAIN 24-HR CALCS**
  TERR         MAX 24 -HR              PLUME HT             PLUME HT
   HT    DIST    CONC        CONC    ABOVE STK    CONC    ABOVE STK    U10M UST


                                                   5-10

-------
  (M)     (M)    (UG/M**3)    (UG/M**3)   BASE CM)   (UG/M**2)   HGT  (M)   SC
 BUOY.  FLUX =         M**4/S**3;   MOM.  FLUX =         M**4/S**2.

 *** FULL METEOROLOGY ***
 ******************1
 *** SCREEN AUTOMATED DISTANCES ***
 **********************************                               

 *** TERRAIN HEIGHT OF       M ABOVE STACK BASE USED FOR FOLLOWING DISTANCES  **

   DIST     CONC             U10M   USTK  MIX HT   PLUME   SIGMA   SIGMA
    (M)   (UG/M**3)   STAB  (M/S)  (M/S)    (M)   HT (M)   Y CM)   Z (M)   DWASH

    100.
    200.

MAXIMUM 1-HR CONCENTRATION AT OR BEYOND        M:
             ************
 *** SCREEN AUTOMATED DISTANCES ***
 **********************************

 *** TERRAIN HEIGHT OF       M ABOVE STACK BASE USED FOR FOLLOWING DISTANCES **

   DIST     CONC             U10M   USTK  MIX HT,   PLUME   SIGMA   SIGMA
    (M)   (UG/M**3)   STAB  (M/S)  (M/S)    (M)   HT (M)   Y (M)   Z (M)  DUASH

    200.
    300.
    400.

 MAXIMUM 1-HR CONCENTRATION AT OR BEYOND        M:
 **********************************
 *** SCREEN AUTOMATED DISTANCES ***
 **********************************

 *** TERRAIN HEIGHT OF       M ABOVE STACK BASE USED FOR FOLLOWING DISTANCES **

   DIST     CONC             U10M   USTK  MIX HT   PLUME   SIGMA   SIGMA
    (M)   (UG/M*3)   STAB  (M/S)  (M/S)    (M)   HT (M)   Y (M)   Z (M)   DWASH
 MAXIMUM 1-HR CONCENTRATION AT OR BEYOND        M:



 *** SCREEN AUTOMATED DISTANCES **
 **********************************

 *** TERRAIN HEIGHT OF       M ABOVE STACK BASE USED FOR FOLLOWING DISTANCES **

   DIST     CONC             U10M   USTK  MIX HT   PLUME   SIGMA   SIGMA
  "  (M)   (UG/M**3)   STAB  (M/S)  (M/S)    (M)   HT (M)   Y (M)   Z (M)  OWASH

    900.                                                                          1000.


                                                   5-11

-------
  1100.
  1200.
  1300.
  1400.
  1500.
  1600.
  1700.
  1800.
  1900.
  2000.
  2100.
  2200.
  2300.
  2400.
  2500.
  2600.
  2700.
  2800.
  2900.
  3000.
  3500.
  4000.
  4500.
  5000.
  5500.
  6000.
  6500.
  7000.
  7500.
  8000.
  8500.
  9000.
'  9500.
 10000.
 15000.
 20000.
 25000.
 30000.
 40000.
 50000.

MAXIMUM 1-HR CONCENTRATION AT OR BEYOND
 OIST    = DISTANCE FROM THE SOURCE
 CONC    = MAXIMUM GROUND LEVEL CONCENTRATION
 STAB    = ATMOSPHERIC STABILITY CLASS (1=A, 2=8, 3=C, 4=0,  5=E,  6=F)
 U10M    = WIND SPEED AT THE 10-M LEVEL
 USTK    = WIND SPEED AT STACK HEIGHT
 MIX HT  = MIXING HEIGHT
 PLUME HT= PLUME CENTERLINE HEIGHT
 SIGMA Y = LATERAL DISPERSION PARAMETER
 SIGMA Z = VERTICAL DISPERSION PARAMETER
 OWASH   = BUILDING DOUNWASH:
           DUASH=   MEANS NO CALC MADE (CONC = 0.0)
           DUASH=NO MEANS NO BUILDING DOUNWASH USED
           DUASH=HS MEANS HUBER-SNYDER OOUNUASH USED
           DWASH=SS MEANS SCHULMAN-SCIRE DOUNUASH USED
           DWASH=NA MEANS DOUNUASH NOT APPLICABLE, X<3*LB
*** SCREEN DISCRETE DISTANCES **
*********************************
 * TERRAIN HEIGHT OF       M ABOVE STACK BASE USED FOR FOLLOWING DISTANCES **

  DIST     CONC             U10M   USTK  MIX HT   PLUME   SIGMA   SIGMA
   (M)   (UG/M**3)   STAB  (M/S)  (M/S)    (M)   HT (M)   Y (M)   Z (M)  DUASH
                                                  5-12

-------
 *** SCREEN DISCRETE DISTANCES **
 n>*i ***<"******
     TERRAIN HEIGHT OF
           N ABOVE STACK BASE USED FOR FOLLOWING DISTANCES
   DIST     CONC             U10M   USTK  NIX HT   PLUME   SIGMA   SIGMA
    (M)   (UG/M*J)   STAB  (M/S)  (M/S)    (M)   HT (M)   Y I>IIII> ****
  *  SUMMARY OF TERRAIN HEIGHTS ENTERED FOR  *
  *    SIMPLE ELEVATED TERRAIN PROCEDURE     *
  **<>IH>lr**************<><>*****
       TERRAIN        DISTANCE RANGE (M)
        HT (M)       MINIMUM     MAXIMUM
  *** CAVITY CALCULATION
   CONC (UG/M**3)     =
   CRIT US 310M (M/S) =
   CRIT US 3 HS (M/S) =
   DILUTION US (M/S)  =
   CAVITY HT (M)      =
   CAVITY LENGTH (M)  =
   ALONGUIND DIM (M)  =
                     *** CAVITY CALCULATION - 2
                      CONC (UG/M**3)     =
                      CRIT US aiOM (M/S) =
                      CRIT US 3 HS (M/S) =
                      DILUTION US (M/S)  =
                      CAVITY HT (M)
                      CAVITY LENGTH (M)  =
                      ALONGUIND DIM (M)  =
                    ******************
*** USER SPECIFIED AVERAGING TIMES ***
         *****************************
ESTIMATED MAXIMUM
         UG/M**3

ESTIMATED MAXIMUM
         UG/M**3
CONCENTRATION FOR 15 MIN AVERAGING TIME:
              PPM

CONCENTRATION FOR 30 MIN AVERAGING TIME:
              PPM
ESTIMATED MAXIMUM
      (*/-      )
CONCENTRATION FOR 3 HR AVERAGING TIME:
UG/M**3       (+/-      ) PPM
ESTIMATED MAXIMUM CONCENTRATION FOR 8 HR AVERAGING TIME:
      (+/-      ) UG/M**3       (+/-      ) PPM

ESTIMATED MAXIMUM CONCENTRATION FOR 24 HR AVERAGING TIME:
      (+/-      ) UG/M**3      . (/-      ) PPM
                                                   5-13

-------
*>>>l ***** * ****

*** END OF SCREEN MODEL OUTPUT ***
*>* I>><<**
5.1.2  Area Sources

5.1.2.1   Inputs
     This  section  contains a  listing  of the  inputs TSCREEN will
request that are  unique for  the SCREEN area source.   Some of
these inputs may  have  already been entered from the  scenario
input section.
                             SCENARIO NAME & NUMBER
             Based on user input, SCREEN model has been selected.
             SCREEN MODEL INPUTS - Page 1 of 2
             RELEASE PARAMETERS
                           Release Height above Ground (Hs) ->
                           Area of the Emitting Source (A) ->
m
m*
             URBAN/RURAL CLASSIFICATION
                           Enter U for Urban - R for Rural ->

             FENCELINE DISTANCE
                Enter the distance from the nearest edge of the
                             source to the plant fencetine ->

             FLAG POLE RECEPTORS
                      Enter Receptor Height above Ground (Zr> -> <^;-V':;- m

             RECEPTOR LOCATIONS
             Do you have specific locations where you would like
                pollutant concentrations to be calculated (Y/N) -> :

                Help    Calculator    Previous Screen    Abort
RELEASE PARAMETERS

1    Release Height above Ground  (H.)  -
     Enter  the height of  the release  area  above  the ground in
     meters.   If  the height is  < 10 m,  then  the  model  assumes a
     ground level  release.   If  the height  is > 10  m, the release
     are is probably a volume source  and SCREEN  cannot  handle this
     case.
                                                    f
2    Area of the  Emitting Source  (A)  -
     Enter  the release area in  square meters.

URBAN/RURAL CLASSIFICATION

3    Enter  U for  Urban -  R for  Rural  -
     The classification of a site as  urban or rural is  based on
     the procedures described in Section 8.2.8 of  the  Guideline on
     Air Quality  Models  (Revised). EPA-450/2-78-027R.
                                    5-14

-------
FENCELINE DISTANCE

4   Enter the distance from the nearest edge of the source to the
    plant fenceline -
    Enter the distance from the base of the stack to the plant
    fenceline in meters.  SCREEN calculates the maximum
    concentrations across a range of meteorological conditions
    for the minimum distance given (> 1 m)  and then for each
    distance in the array.  Thus, the user can input the minimum
    fenceline distance as the minimum distance for calculation
    and obtain a concentration at the site boundary and beyond.
    Distances less than the fenceline distance are ignored.
    Receptors beyond the fenceline are defined as ambient air.

FLAG POLE RECEPTORS

5  " Enter Receptor Height above Ground (Zr)  -
    Flag pole receptors are receptors at heights (meters) above
    local terrain elevation, e.g., on the roof of a building.
    Enter 0 if receptor heights are at ground level.   Flag pole
    receptors are useful for estimating concentrations on
    rooftops or similar exposed locations and are most often used
    in urban modeling evaluations.  The default is 0.

RECEPTOR LOCATIONS

    Since area sources are ground level releases,  there is no
impact on "complex terrain"; only receptors classified as "simple
terrain."

6   Do you have specific locations where you would like pollutant
    concentrations to be calculated (Y/N)  -
    The entry of "Y" will allow the user to input any number of
    specific distances (>1 m)  and the maximum concentration for
    each distance will be calculated.   Note that SCREEN has an
    automated distance array which calculates maximum
    concentrations at a pre-selected array of 50 distances
    ranging from 100 m to 50 km.   For example,  a specific
    location of interest may be a school 117 m from the source.

    With the automated distance array,  the  SCREEN model uses an
    iteration routine to determine the maximum value  and
    associated distance to the nearest meter.   Note:  SCREEN
    assumes that the overall maximum concentration occurs for the
    same stability class that is associated with the  maximum
    concentration from the automated distance array,  and begins
    iterating from that value,  examining a  range of wind speeds
    for that stability.

    *      If response  is  "Y"  then TSCREEN proceeds  to  step 7.

          If response  is  "N"  then TSCREEN runs -the  SCREEN model.
                              5-15

-------
SCREEN MODEL INPUTS
RECEPTOR LOCATIONS:
the source at which
Enter a blank after
Distance from
source (meters)
 awcnnitiw nfwic tt nunDCK ~~~
- Page 2 of 2
Enter (up to 30) distances

from
concentrations should be calculated.
the last distance to stop input.
Distance from
source (meters)
1 fence 11 " -'
2 V" :
3
4
5
6
7
8
9
10
 Help 
12
13 !
14
15
16 ,
17
18
19
20
Calculator  Previous
Distance from
source (meters)
21
22
23
24
25 ,
26 :
27
28
29
30 ;
Screen  Abort
DISCRETE  RECEPTORS

7   Enter (up to 30) distances from  the  source at which
    concentrations should be calculated  -
    Enter the Distance  in meters from  the release for calculating
    the maximum ground  level concentrations.

    >     After all of  the  desired distances have been entered,
          TSCREEN will  run  the SCREEN model  for an area source.

5.1.2.2   Model Output

    For a complete example  of the SCREEN model for a area source,
see Section  4.1.2.  (See Appendix E-Running TSCREEN  for output
options after the model is run.) The following shows the format
of the output file that SCREEN would generate for a  area source
if the user has chosen  to show the maximum concentration in  part
per million  (PPM) in addition to /zg/m3.
    SCREEN-1.2 MODEL RUN
    VERSION DATED 90XXX
                                            03-03-92
                                            10:04:59
 SIMPLE TERRAIN INPUTS:
   SOURCE TYPE
   EMISSION RATE (G/S)
   SOURCE HEIGHT (M)
   LENGTH OF SIDE (M)
   RECEPTOR HEIGHT (M)
   IOPT (1=URB,2=RUR)
AREA
      SUMMARY OF SCREEN MODEL RESULTS
                                 5-16

-------
 > * W1
CALCULATION MAX CONC
PROCEDURE 
MAX CONC
(PPM)
DIST TO
MAX (M)
TERRAIN
HT (M>
SIMPLE TERRAIN
*in>*>iiin**********
** REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS **
*> **** ******* 
BUOY. FLUX =          M**4/S**3;  MOM. FLUX a         M**4/S**2.

*** FULL METEOROLOGY ***
*** SCREEN AUTOMATED DISTANCES ***
*******

*** TERRAIN HEIGHT OF    0. M ABOVE STACK BASE USED FOR  FOLLOWING DISTANCES **

  DIST     CONC             U10M   USTK  MIX HT   PLUME   SIGMA   SIGMA
   (M)   (UG/M**3)   STAB  (M/S)  (M/S)      DUASH

   100.
   200.
   300.
   400.
   500.
   600.
   700.
   800.
   900.
  1000.
  1100.
  1200.
  1300.
  1400.
  1500.
  1600,
  1700.
  1800.
  1900.
  2000.
  2100.
  2200.
  2300.
  2400.
  2500.
  2600.
  2700.
  2800.
  2900.
  3000.
  3500.
  4000.
  4500.
  5000.
  5500.
  6000.
  6500.
  7000.
  7500.
  8000.
  8500.
  9000.
  9500.
 10000.
 15000.


                                                  5-17

-------
  20000.
  25000.
  30000.
  40000.
  50000.

 MAXIMUM 1-HR CONCENTRATION AT OR BEYOND        M:
  OIST    - DISTANCE FROM THE SOURCE
  CONC    - MAXIMUM GROUND LEVEL CONCENTRATION
  STAB    = ATMOSPHERIC STABILITY CLASS (1=A,  2=8,  3=C,  4=0,  5=,  6=F)
  U10M    * WIND SPEED AT THE 10-M LEVEL
  USTK    = WIND SPEED AT STACK HEIGHT
  MIX HT  = MIXING HEIGHT
  PLUME HT= PLUME CENTERLINE HEIGHT
  SIGMA Y = LATERAL DISPERSION PARAMETER
  SIGMA Z = VERTICAL DISPERSION PARAMETER
  DUASH   = BUILDING DOWNUASH:
            OUASH=   MEANS NO CALC MADE (CONC  = 0.0)
            DUASH=NO MEANS NO BUILDING OOWNWASH USED
            DWASH=HS MEANS HUBER-SNYDER DOUNUASH USED
            DWASH=SS MEANS SCHULMAN-SCIRE DOUNUASH  USED
            DUASH=NA MEANS DOUNUASH NOT APPLICABLE, X<3*LB
 **************<
     SCREEN DISCRETE DISTANCES
  ** TERRAIN HEIGHT OF    0. M ABOVE STACK BASE USED FOR FOLLOU1NG DISTANCES  **

   DIST     CONC             U10M   USTK  MIX HT   PLUME   SIGMA   SIGMA
    (M)   (UG/M**3)   STAB  (M/S)  (M/S)    (M)   HT (M)   Y  (M)   Z  (M)   DUASH
  QUASH-   MEANS NO CALC MADE (CONC =0.0)
  DUASH=NO MEANS NO BUILDING OOUNUASH USED
  OUASH-HS MEANS HUBER-SNYDER DOUNUASH USED
  DUASH=SS MEANS SCHULMAN-SCIRE DOUNUASH USED
  DUASH-NA MEANS DOUNUASH NOT APPLICABLE, X<3*LB
      ***********
*** END OF SCREEN MODEL OUTPUT
***********************'
                                                   5-18

-------
5.2   RVD

    The RVD model provides short-term ambient concentration
estimates for  screening pollutant sources  emitting denser-than-
air gases and  aerosols  through vertically-directed releases.
The model is based on empirical  equations  derived  from wind
tunnel  tests and estimates the maximum ground level concentration
at plume touchdown at downwind receptor  locations.   For more
information refer to User's Guide for RVD2.0J A Relief Valve
Discharge Screening Model EPA-450/4-88-024.

5.2.1  Inputs
                           SCENARIO NAME & NUMBER
             Based on user input, RVD model has been selected.

             RVD MODEL INPUTS - Page 1 of 3

             RELEASE PARAMETERS
                          Release Height above Ground -> ':';%..'':
                           Exhaust Gas Exit Velocity -> 4..;.'^
             POLLUTANT INFORMATION
                        Pollutant Concentration (vol) ->
                          Pollutant Molecular Weight -> .
             TIME
               Desired Averaging Time for the Calculation
                                of Concentrations ->
                     ' v?',:' x
                     ':';. '."' g/g-mole
                        min
              Help     Calculator
         Previous Screen   Abort
RELEASE PARAMETERS

1   Release Height above  Ground  (m)  -
    Enter the height of the stack  or of the  release point above
    the ground  in meters.

2   Exhaust Gas  Exit Velocity  (m/s)  -
    The exit velocity  (m/s)  for a  two-phase  mixture may be
    calculated  from the equation:
                     Exitv(m/s)  =
                                        Q(g/s)
                                    A(m2)  /o,(g/m3)
    where:
                A
                Pi
emission rate  (g/s)
area  (trr)
liquid  density of released material
(g/m3)
                                  5-19

-------
POLLUTANT INFORMATION

3   Pollutant Concentration (%) -
    Enter the volume  percent of the pollutant in  the release
    material.

4   Pollutant Molecular Weight  (g/q-mole)  -
    This  is the individual pollutant's molecular  weight, not  the
    molecular weight  of the exhaust material.
TIME
    Desired Averaging  Time for the Calculation of  Concentration
     (min)  -
    Enter  the desired  time span for  calculating concentrations in
    minutes.  If the release duration is less than the averaging
    time of interest,  or if the averaging time of  interest  is
    less than 60 minutes,  a correction factor is calculated
    within RVD.
                           SCENARIO NAME & NUMBER
            RVD MODEL INPUTS - Page 2 of 3

            URBAN/RURAL CLASSIFICATION
                      Enter U for Urban - R for Rural ->

            FENCELINE DISTANCE
             Enter the distance from the base of the stack
                            to the plant fenceline ->

            RECEPTOR LOCATIONS
            Do you have specific locations where you would
            like pollutant concentrations calculated (Y/N) ->
              Help    Calculator    Previous Screen   Abort
URBAN/RURAL CLASSIFICATION

6   Enter  U for Urban  -  R for Rural  -
    The  classification of a site as  urban or rural  is based on
    the  procedures described in Section 8.2.8 of  the Guideline on
    Air  Quality Models (Revised). EPA-450/2-78-927R.

FENCELINE  DISTANCE

7   Enter  the distance from the base of the stack to the giant
    fenceline (m) -
    Enter  the distance from the closest edge of the source to  the
    fenceline in meters.   The model  calculates concentrations
    only at receptors  beyond the fenceline in ambient air.
                                 5-20

-------
RECEPTOR LOCATIONS

8   Do vou have specific location where you would like pollutant
    concentrations calculated (Y/N) -
    The entry of SPECIFIC LOCATIONS allows for calculating the
    maximum ground level concentrations.at discrete,
    user-specified distances from the release.  TSCREEN will
    automatically give you maximum ground level concentrations at
    30 distances starting at the fenceline.  The first 16
    distances are in 100 m increments.  The next 8 distances are
    in 200 m increments, and the remaining 5 distances are in 300
    m increments.

    +     If "Y" is entered, proceed to step 9.

    +     If "N" is entered, TSCREEN runs the RVD model.
RVD MODEL INPUTS -
RECEPTOR LOCATIONS:
the source at which
Enter a blank after
Distance from
source (meters)
Page 3 of 3
Enter (up to 30) distances

from
concentrations should be calculated.
the last distance to stop input.
Distance from
source (meters)
1 fence 11 "-""^ -t
2 ir :V::ci.U
3 <::-V-x,:.;
4 -.'" '" '
5 "-.- '-.
6 v.:.:;;>:x;:
7 ." ""*: '"-
8 'rf *:*...
9 *; '-.;. '
10 ,,..:......'.
 Help 
12 ;>:.:,. "'*'
13 ;.'..:-:V:U-
14
15 ."-- ., .'
16 .;:jf '". ' :
17 ; :=:.-
18 . ''"<'*' '
19 ': : '"
20 ;,;. ,.-;:,:.
Calculator  Previous
Distance from
source (meters)
21 ' '.-. "' "
22 v'v .-'
23 .":::->-
24 "..'; '-,-.
25 ::
26 . 
27 ""'.-.,
28 :- ;V- /
29 : .
30 , ^v_ ' -
Screen  Abort
RECEPTOR LOCATIONS

9   Enter (up to 30) distances from the source at which
    concentrations should be calculated -
    Enter the distance in meters from the rel'ease for calculating
    the maximum ground level concentrations.

    *     After the user finishes entering distances, TSCREEN
          runs the RVD model.

5.2.2  Model Output

    For a complete example of the RVD model, see Section 4.2.3.
(See Appendix E - Running TSCREEN for output options after model
is run.) The following shows the format of the output file that
RVD would generate.  The output begins with a listing of model
inputs.  The second portion of the output identifies the maximum
                               5-21

-------
concentration  and the distance  at which it  occurred,  and  the
meteorological conditions  associated with the maximum
concentration.   The  next section lists the  maximum concentration
at  each  of the distances along  with  the meteorological
conditions.  The next portion of the output identifies those
cases in which the model is applicable.  In this section,  a "0"
indicates that the release is passive and the model  is
inapplicable,  a "1"  indicates that the gas  is influenced  by
gravitational  effects and  a "2"  indicates that  the meteorological
condition identified is not. likely to occur.  The determination
of  whether the gas is affected  by  gravitational effects  is based
initially on the Richardson number for which a  table  is
presented.  Next,  the model results  are presented in  two  forms,
a table  showing plume rise, touchdown distance,  and  touchdown
concentration  for each meteorological condition and  a table of
concentrations at specified receptors.
                       Input Data

Pollutant emission rate (kg/sec) =
Exit gas velocity (m/sec)=
Exit Temperature (K)=
Stack Height Cm) =     Diameter (m) =
Pollutant Concentration (volume X) =
Exhaust Gas Density (kg/m3) =
Exhaust Gas Molecular Weight =
Exhaust Gas Mass Flow Rate (kg/sec) =
Pollutant Molecular Weight =
Release duration (min) =    Av. Time (min) =
Wind Speeds (in/see) = 1.0   2.0  3.0   4.0   5.0
                8.0   10.0  15.0   20.0
Distances (m) - 100   200   300   400   500   600   700
            800   900   1000   1100  1200   1300   1400
            1500   1600   1800   2000   2200   2400   2600
            2800   3000   3200   3500   3800   4100   4400
            4700   5000
Ambient Temperature (K) =
Rural Wind Speed Profile Exponents
***          SUMMARY OF RVD MODEL RESULTS         ***
*************************************************************

Maximum offsite concentration is           ug/m3
            or equivalently         ppm
            occurring at          m downwind
          when wind speed is   m/sec
            and stability is


***     REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS   *
***********************

***  RVD DISTANCES ***
***********************
Distance Concentration Stability  Wind
                   Class   Speed
                                    5-22

-------
  (m)      (ug/m3)                 (m/sec)       (ppm)

  100.0
  200.0
  300.0
  400.0
  500.0
  600.0
  700.0
  800.0
  900.0
 1000.0
 1100.0
 1200.0
 1300.0
 1400.0
 1500.0
 1600.0
 1800.0
 2000.0
 2200.0
 2400.0
 2600.0
 2800.0
 3000.0
 3200.0
 3500.0
 3800.0
 4100.0
 4400.0
 4700.0
 5000.0
          Dense Gas Behavior

           Stability  Class

 Wind    A   B   C   D   E   F
Speed
  1.0
  2.0
  3.0
  4.0
  5.0
  8.0
 10.0
 15.0
 20.0

(0=Non-Dense Behavior   1=0ense  Gas  Behavior
     2=Combinations that cannot  occur)

             Release Richardson  Numbers

                   Stability Class

   Wind       A         B        C         D
   Speed
   1.0
   2.0
   3.0
   4.0
   5.0
   8.0
  10.0
  15.0
  20.0
                                                  5-23

-------
             Dense Plume Trajectocy

Stability  Wind Plume Touchdown        Touchdown
  Class   Speed  Rise  Distance      Concentration
         (rn/sec)  (m)     (m)      (ug/m3)     (ppm)

    A
    A
    A

    B
    B
    B
    B
    B

    C
    C
    C
    C
    C
    C
    C

    D
    D
    D
    D
    D
    D
    D

    E
    E
    E
    E

    F
    F
    F
 Concentrations at Specific Receptor Distances

Stability  Wind Distance  Concentration
  Class   Speed
         (m/sec)   (m)      (ug/m3)      (ppm)
                                                  5-24

-------
END OF RVD MODEL OUTPUT ***
                                        5-25

-------
5.3  PUFF

    The PUFF dispersion model provides an estimate of peak
downwind concentrations for the case where the release  time  is
finite but smaller than the travel time  (i.e., an instantaneous
release) .  The PUFF model is based on the Gaussian instantaneous
puff equation and is applicable for neutrally buoyant non-
reactive releases.  For more information on PUFF refer  to
(Petersen, W. ,  1982: Estimating Concentrations Downwind from an
Instantaneous Puff Release EPA 600/3-82-078) .  The following is
brief summary of the model assumptions.

5.3.1  PUFF Model Discussion

The generalized puff equation is given as :
                                                           (5.3-1)

Following the puff, and assuming <7X = ayl the puff equation  can be.
written as follows:
                                                           (5.3-2)

The peak concentration at distances beyond the point where  crz is
greater than 0.8L  (mixing height) can be expressed as:


                    Xu.o.o.0) = ^T-  f or az >0 . 8L             (5.3-3)
TKe concentration at the ground from an elevated release  at  a
radical distance y from the puff center is given by Equation
5.3-4:
Equations 5.3-3 and 5.3-4 account for reflection from the  top of
the mixed depth layer and are appropriate for surface level


                               5-26

-------
releases during neutral and unstable  conditions.   However,  if the
effective release height  is small  compared  to  the  mixing height,
Equations 5.3-3 and 5.3-4 are  still good  approximations.

    Frequently, instantaneous  releases are  large enough  in  the
horizontal and vertical dimensions that the initial  size cannot
be ignored in the concentration estimates.   One approach to
assessing the impact of the initial size  on downwind
concentrations is to introduce an  initial horizontal dispersion
parameter,  ay ,  and an initial vertical  dispersion  parameter,

 az .   For a ground level release,   ay  can be approximated by

dividing the total initial width (W)  of the puff by  4.3,   CTV
                                                            >o
W/4.3.  The second parameter,  az ,  can be approximated by

dividing the initial vertical  extent  of the puff  (h)  by  2.15,
 az  = h/2.15.  For an elevated release,  ay  can be approximated

by dividing the total initial  diameter  (D)  of  the  puff by 4.3,
 ay  =  az   =  D/4.3.   The  total horizontal and vertical
dispersion parameters are then given  by:
                         ay = (a2 * a/)1'2                    (5.3-5)
                          Jf    J    Ja
                         a  =  (az2 + az2)I/2                    (5.3-6)
Stability Parameters
    The stability parameters used in the instantaneous puff model
are those recommended by Slade  (1968).  Slade classified  the  data
according to the broad categories of unstable, neutral, and very
stable.  A review of the data reveals two pertinent points:  (I)
There was very little data upon which to base the  azs  during
unstable conditions; (2) Much of the dispersion data during
stable conditions lie closer to the Pasquill-Gifford F curve  than-
to the curve recommended by Slade.

Model Applicability

    Estimating concentrations at point locations is very
difficult because of the deficiencies in determining the
trajectory of the puff. Puff trajectory is most important  if
concentration estimates are to be made at specific points.
However, the .modeling effort is significantly simplified  if the
magnitudes of the concentrations are needed without regard to
exactly where the concentrations will occur.  Releases are seldom
point sources, but are more typically small area sources.  Small
area source releases can be modeled to some extent by using
initial dispersion parameters.  The initial horizontal dispersion


                               5-27

-------
is typically calculated  by dividing the  initial horizontal
dimension of the area source by 4.3.  This  method will  give
reasonable concentration estimates at downwind distances  greater
than about five times the horizontal dimension of the source.
The initial vertical dispersion parameter is typically  evaluated
by dividing the initial  vertical extent  of  the surface  release by
2.15.

    Many  sources are not  truly instantaneous.   However, if the
travel  time is long compared to- the release time, then  the puff
model can be used to estimate concentrations.   If the travel time
to a receptor is on the  same order or smaller than the  release
time, the Gaussian plume model can be used  (see Turner, 1970) .
For the case where the release time is finite but smaller than
the travel time, the instantaneous puff  model will provide a
worst-case estimate of peak concentrations  for the same total
release.   It is difficult to evaluate the effect on average
concentrations over a given sampling time for a finite  release
using simple models, since the puff is distorted in the downwind
direction.  Finally, the modeling procedures are simple
approaches to very complex problems.  In general, these
techniques will yield worst-case concentration estimates.  The
proper  modeling of any sudden release requires the skills of an
air.quality specialist and a thorough understanding of  the
physical  and chemical properties of the  release.

5.3.2   Model Inputs

    This  section contains a complete listing of the inputs
TSCREEN will request to  run the PUFF model.
                           SCENARIO NAME & NUMBER
            Based on use input, PUFF model has been selected.

            PUFF MODEL INPUTS - Page 1 of 2
            Enter a unique title for this data's model run:
            RELEASE PARAMETERS
                   Total Amount of Material Released (Q) ->      g
                      Release Height above Ground (Hs) ->      m
                       Initial Lateral Dispersion (ay) -> S^vV;.;.,;::.; m
                      Initial Vertical Dispersion in) -> 0*j ':':,:.?:. "

            FENCELINE
             Enter the distance from the nearest edge of the
                         source to the plant fenceline -> ":""{: '':.: m
              Help
 Calculator    Previous Screen    Abort
RELEASE PARAMETERS

1   Total Amount of Material Released  (0)  (a)  -
    Calculate total amount of material  released during  the
    duration of the release.  If limited  information is available
                                 5-28

-------
    in the technical literature. Conservative estimates of
    release amounts can be made based on transfer line rates and
    time from equipment shutdown and equipment capacity.  A point
    source is assumed because no indication of initial dilution
    dimensions are provided in the problem.

    Release Height above Ground (H.)  (m)
    Enter the height of the stack for the release point above the
    ground in meters.  If the puff has positive buoyancy the
    effective height of release is release height plus the rise
    of the puff due to buoyancy.  Screening methods are not
    available for estimating plume rise for a PUFF release.

    Initial Lateral Dispersion  (jy)   (m)  -
    Frequently, instantaneous releases are large enough in the
    horizontal dimension that the initial size cannot be ignored-
    in the concentration estimates.  One approach is to introduce
    the impact of the initial horizontal dispersion parameter,
    ay.  For  a  ground  level  release,  ay can be approximated by
    dividing the total initial width (W) of the'puff by 4.3, ay  =
    W/4.3.  For an elevated release, ay  can be approximated by
    dividing the total initial diameter (D) of the puff by 4.3,
    ay  = D/4.3.    The  default  in TSCREEN is 0 m.

    Initial Vertical Dispersion (aT]   (m) -
    Frequently, instantaneous releases are large enough in the
    vertical dimension that the initial size cannot be ignored in
    the concentration estimates.  One approach is to introduce
    the impact of the initial vertical dispersion parameter, az.
    For a ground level release, az  can be approximated by
    dividing the total initial vertical extent of the puff  (h) by
    2.15,  az -  h/2.15.  For an  elevated  release,  az can be
    approximated by dividing the total initial diameter (D) of
    the puff by  4.3, az = D/4.3.   The default in TSCREEN is 0 m.
FENCELINE
    Enter the distance from the nearest edge of the source to the
    plant fenceline (m)  -
    Enter the Distance from the edge of the source to the plant
    fenceline in meters.   The fenceline distance is used only to
    set the minimum distance for concentration calculations.
                               5-29

-------
                          SCENARIO NAME & NUMBER
            PUFF MODEL INPUTS - Page 2 of 2

            AVERAGING TIME
            Select Desired Averaging Time from menu below:
                          iftstantawous. ft s*cnd?
                          1 minute   ''(60 seconds)  
                          5 minutes   (300 seconds)
                          15 minutes   (900 seconds)
                          1 hour     (3600 seconds)
            Selected Averaging Time: Instantaneous (1 second)
              Help    Calculator    Previous Screen    Abort
AVERAGING TIME

6.  Select  Desired Averaging Time  from menu below:
                   Instantaneous(1  second)
                   1 minute     (60 seconds)
                   5 minutes    (300 seconds)
                   15 minutes   (900 seconds)
                   1 hour       (3600  seconds)
    The PUFF  model will calculate  averaging times according, to
    the procedure described in Appendix D.  The PUFF  model will
    calculate concentrations at  all  five averaging  times,  but
    only the  concentrations at the selected averaging time will
    be plotted if the user chooses to graph the data  (See
    Appendix  E -  RUNNING TSCREEN).   The averaging time would
    normally  be based on some health related standards.   See
    Appendix  D in the Technical  Guidance for Hazards  Analysis.
    Emergency Planning for Extremely Hazardous Substances  as an
    example.   From this document,  threshold limiting  values
    (TLV's) for averaging times  and  concentrations  can be
    obtained  for  certain chemicals.   The user can then use the
    model output  to locate the distance or the distance range
    where this TLV occurs.

    >     After the user makes this  selection, TSCREEN runs the
          PUFF model.

5.3.4  Model  Output

    For a complece example of che  PUFF model, see Section  4.1.3.
(Also see Appendix E - Running TSCREEN for output options  after
model is run).  The following shows  the format of the output file
that PUFF would generate.  This  output is useful in determining:
1) sensitivity of the concentrations to the averaging time; and
2) distances  to important concentrations  (e.g., TLV's).   The PUFF
model uses  three  stability categories: labeled U for  unstable, N
for neutral,  and S for stable.   Unstable corresponds  to stability
                                5-30

-------
categories  1  through  3  (for stabilities  A  -  C)   used by  the  SCREEN
model,  neutral  corresponds  to 4  (for  D),  and  stable corresponds
to  5  and  6   (for  E  and F).
    TOTAL AMOUNT OF  MATERIAL RELEASED (G):
         RELEASE HEIGHT ABOVE GROUND (M):
 INITIAL LATERAL DISPERSION (SIGMA Y) (M):
INITIAL VERTICAL DISPERSION (SIGMA Z) (M):
        
 a*************************************** *****

 ***        SUMMARY OF PUFF MODEL RESULTS         ***
 ***********1>|>>>I>**<>**>*****>I>1><>*


THE MAXIMUM CONCENTRATION AND THE DISTANCE TO MAXIMUM
CONCENTRATION FOR DISTANCES BEYOND FENCELINE        (KM).
FOR -NEAR SURFACE RELEASE MAXIMUM CONCENTRATION WILL OCCUR AT
THE FENCELINE.
    AVERAGING
    TIME (MIN)

INSTANTANEOUS
       1
       5
       15
       60
     MAXIMUM
CONCENTRATION (G/M**3)
                             DISTANCE TO
                             MAX. CONC. (KM)
                                                           STABILITY
                                                           CLASS
 ********************************
 **   REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS  **
 ***************************************** *************
 *********************************
 ***     PUFF DISTANCES       ***
 *********************************

 THE MAXIMUM CONCENTRATION AS A FUNCTION OF DOWNWIND DISTANCE
 AND THE CONDITIONS  THAT PRODUCED THE MAXIMUM AT THAT DISTANCE.
 MIXING HEIGHT (M)
 WIND  SPEED (M/SEC)
                    DOWNWIND DISTANCE (KM)
 MAXIMUM CONCENTRATION (G/M*3) AT VARIOUS DOWNWIND DISTANCES.
     STABILITY CLASS THAT PRODUCED THE MAX. LISTED BELOW
0.01      0.03     0.05      0.07       0.1       0.5
 AVERAGING
 TIME  (MIN)
*INST.

 1

 5

 15

 60
 AVERAGING                       DOWNWIND DISTANCE (KM)
 TIME  (MIN)   MAXIMUM CONCENTRATION (G/M**3) AT VARIOUS DOWNWIND DISTANCES.
                 STABILITY CLASS THAT PRODUCED THE MAX. LISTED BELOW
            1.0      3.0      5.0       7.0      10.0     30.0
                                               5-31

-------
INST.

 1

 5

 15

 60
 STABILITY CLASSES
 U = UNSTABLE
 N = NEUTRAL
 S = STABLE

 * INDICATES AVERAGING TIME  THAT WAS SELECTED FOR PLOTTING

>I>IHI1>* !*
*** END OF PUFF MODEL OUTPUT ***
                                                  5-32

-------
5.4  Britter-McQuaid

    Britter and McQuaid (1988) report work which provides a
correlation for estimating the dispersion of denser-than-air
gases from area sources for continuous  (plume) and instantaneous
(puff) release.  The objective was to produce correlations which
predicted the dependent variables  (distance to a given
concentration level and area covered by a plume or puff) to
within a factor of two.  The analysis identified the dominant
independent variables as: volumetric rate  (or total) contaminant
released; density of released material; windspeed at a standard
height (taken to be 10 m); and a characteristic source dimension.
Based (at least in part) on the fact that presently available
field-test data for denser-than-air gases do not clearly indicate
such, independent variables of lesser- importance were identified
as: surface roughness; atmospheric stability; atmospheric
turbulence; and exact source dimension.  Other effects not
included in Britter and McQuaid's analysis are: source momentum;
condensation of ambient humidity; and non-ideal gas behavior.
(It should be. noted that the e'ffects which were not indluded may
be of crucial importance for contaminants whose molecular weight
is less than air including, for example, liquefied natural gas
(LNG), ammonia, and hydrogen fluoride; some similarity models
(such as DEGADIS)  can take these effects into account.)

    For screening purposes, the original procedure set forth by
Britter and McQuaid will be simplified in two important ways:

          Other established (passive) screening methods are
          recommended if the release is determined to be passive
          from the source  (i.e., the denser-than-air effects are
          not expected to be important).

          The influence of buildings, topography,  and releases
          not close to the ground are not included.

In addition, the effect of initial dilution due to jetting is
beyond the scope of this effort.  At present,  the RVD model  (U.S.
EPA,  1989)  is used for such cases as pressure relief valve
discharge where source jetting will bring about air entrainment
(and resulting dilution) for the hypothesized release.  For cases
where the jet orientation is unknown or is not directed
vertically upward,  the most conservative assumption (i.e.,  the
assumption which results in the maximum downwind distance to a
given concentration level under otherwise identical
circumstances) is'to discount the initial dilution due to
]etcing;  the correlations of Britter and McQuaid do noc include
the effects of source jetting.
                               5-33

-------
5.4.1     Method for Cold Contaminant Releases  Heat Transfer -
          Effects

    Heat transfer effects are not included in Britter and
McQuaid's correlation; two ways suggested at looking at the
limiting effects associated with heat transfer:

          Assume that heat transfer is unimportant and perform
          the calculations using the originally estimated
          temperature and density  (T2  and p2, respectively).

          Assume that the heat transfer is important and  (for  the
          sake of maximizing its importance) assume that all of
          the heat transfer occurs at the source.

The  (real) effect of heat transfer should lie somewhere between
these two extremes (limiting cases).  So, an estimate of the
downwind distance to the desired concentration level should be
made for each of the limiting cases, and the greatest of the two
estimates of x (distance to a given concentration level) should
be reported.  For the first case, the input parameters will be
the same as calculated in the earlier sections.  For the second
case though, the initial density and temperature are modified  as
follows:


                         - i>2 "- P2 (T2/Ta)                    (5.4-la)
                              T2-Ta                       (5.4-lb)


where the A represents the "adjusted" initial values; for this
case then, these "adjusted" values should be used whenever p2 and
T2  are  required.

5.4.2  Method for Contaminant Aerosol Releases

    Since Britter and McQuaid' s correlations are based on the
analysis of dispersing gases, the complex thermodynamic effects
of an aerosol must be considered using an ad hoc argument that,
near the source, sufficient air will be entrained to evaporate
all of the condensed aerosol phase and raise the temperature of
the air/contaminant  (gas) mixture to a temperature where the
contaminant vapor pressure is eqaal to the ambient pressure  (for
an aerosol release, T;) .   For such a  process,  the resulting Ticle
fractions of contaminant and air are:
                                  (T-T)                   (5.4-2a)
                                  ^ J-a L2'
                               5-34

-------
                             Za = 1-ZC                      (5.4-2b)

where  (as discussed above)  the effects of humidity have been
ignored.  This air entrainment process will also change the
temperature and density of  the air/contaminant mixture.
Furthermore, since for  most release scenarios, T2 5* Ta, the effect
of heat transfer may  also be important.  Therefore, two cases are
considered:

Case 1; Air dilution  neglecting heat transfer.  The initial
density is modified as  follows:


                        P2- Ji (ZCMW + zaMa)                  (5.4-3)
                            K12

where  as before the * represents  the "adjusted" initial values-;
Ma is the  molecular weight of air  (28.96 kg/kmol).   In addition,
the.  initial volume of the release is modified.  For continuous
releases, Qm is modified as:


                    Qm-Q 
-------
5.4.3  Continuous  (Plume) Releases

    To estimate the importance of denser-than-air- effects on
continuous releases, Britter and McQuaid recommend that  denser-
than-air effects be ignored if:
                                             >6             (5.4-7)


where D is the  (low-momentum) horizontal dimension of the  source
(m) ,  Qm is the release rate (kg/s),  Ur is the windspeed  at  10  m
(m/s) ,  pa  is  the ambient air density (kg/m3) .  If the value of D
is not otherwise known  (such as the diameter of a liquid pool), a
(screening) estimate of D can be made assuming that the ratio of
the vertical source dimension to the horizontal source  dimension
is approximately 1/2 and the momentum of the release is
inconsequential.  Using this assumption,
                      .   D = v/2 (Qm/p2)  /Ur                   (5.4-8)

(Note that D is not necessarily the same as the hole or opening
diameter and may be much larger.)  If denser-than-air effects  are
determined to be unimportant, standard passive atmospheric
dispersion techniques should be applied.  Finally, note that
Equation 5.4-7 can be rewritten as:

                                       < 1/63
where the left-hand side is a Richardson number; therefore,  the
criteria in Equation 5.4-7 is comparable to other Richardson
number-based criteria suggested, for example, by Spicer and
Havens (1989) and that Ur/U. = 20 to 30 for typical atmospheric
flow fields  (where U.  is  the  friction velocity.)

    However, if denser-than-air effects are determined to be
important, the method of Britter and McQuaid can be used to
determine the downwind extent of a given concentration level
(Cm/C0) by use of Figure  5.4-1.  For  simplicity, the abscissa and
ordinate are given as:
                            ur5
                               5-36

-------
in
i
ui
                                                               Range of full-scale data
                                                                                                                                          n>

                                                                                                                                          U1
                                                                                                                                           i
                                                                                                                                          H
                                                                                                                                          W
                                                                                                                                          H
                                                                                                                                          H-
                                                                                                                                          ft
                                                                                                                                          ft
                                                                                                                                          0>
                                                                                                                                          H

                                                                                                                                       4

                                                                                                                                       it
                                                                                                                                        P>
                                                                                                                                        0
                                                                                                                                          H
                                                                                                                                          0
                                                                                                                                          ft
                                                                                                                                          H-

                                                                                                                                          

                                                                                                                                          M>
                                                                                                                                          O
                                                                                                                                          O
                                                                                                                                          O
                                                                                                                                          p
                                                                                                                                          ft
                                                                                                                                          H-

                                                                                                                                          8
                                                                                                                                          O

-------
                                 X2
respectively where x is the estimated downwind distance  to the
concentration level Cm/C0.  The  choice of  Cm should  reflect the
source temperature correction and the averaging time  effect
discussed below.  Once Cm/C0 is  set,  Figure 5.4-1  can be  used to
determine the downwind distance to that ratio; interpolation for
intermediate values of Cm/C0 should be done using  log-log
interpolation (at a fixed fc) .   For  fc > 3, c  should be
determined by (linear) extrapolation on the log-log plot in the
absence of other information since no field test  data exists for
fc  >  c.   If  the  desired Cm/C0 < 0.002, the following equation can
be used:


                                  [C  1-1/2  .
                                 -\   Ic'"2                (5.4-10)
                                  *-o J

(based on extrapolation and fitting of Britter and  McQuaid's
Figure 9) .   If the desired Cm/C0 < 0.002 and 1  a c  a  0.2,  no data
exists for this region so Britter and McQuaid make  no
recommendation.   .However, the following equation  can  be  used:
                          = 22.6   -     $;                  (5.4-11)
based on simply forcing Equation  (5-10) to agree with the passive
limit .

    Once the distance x is determined, the release duration Td
should be checked to see if steady-state conditions are  expected
at this distance.  If UrTd/x > 2.5, then the estimate based on a
continuous release is valid as recommended by Britter and
McQuaid.  If 0.6 < UrTd/x < 2.5, then an estimate assuming the
release to be instantaneous should also be made, and the greatest
estimate for x should be reported.  If UrTd/x < 0.6, then the
release should be assumed to be instantaneous .
                                                  

    The effect of averaging time should be taken into account
before using Figure 5.4-1 if the desired averaging time  is not:  a
long-term average (taken to be 10 minutes) .  Britter and McQuaid
mention that shorter averaging times will produce larger
concentrations with factors ranging from 1.4  (based on field-
scale data) to 1 . 6 (based on laboratory data) over the long time-
averaged concentrations.  If the ratio of 1.4 is used along with
a short averaging time of about one second, the following


                               5-38

-------
(approximate) power-law relationship would hold:

                     C,(10minn  F iOminj-0.05
                       C.(tJ   J  I   tw  J

where Cm(10 min)  would represent the value of Cm to be used in
Figure 5.4-1, and Cm(tav)  is the value of Cm based on the desired
averaging time t^ (Britter, 1992).

    The effect of temperature should be taken into account before
using Figure 5.4-1 if the discharge  (depressurized) contaminant
temperature is different from ambient; Britter and McQuaid
recommend using a value for Cm which reflects the nonisothermal
effects as follows:


                       C" ^  C  + T fl-C ) /T                (5.4-13)
                            uni * xa ^  Sii' ' i2
where C^ is the nonisothermal concentration  (mole fraction), Ta
is the ambient temperature  (K) , and T2 is the discharge
(depressurized) contaminant temperature  (K).

    In summary, the following procedure should be used  for
continuous  (plume) releases:

    A.    For aerosol releases, two cases must be considered for
          each release as outlined in Section 5.4.2.   Initial
          conditions for the dispersion calculation for each case
          are based on Equations 5.4-2 through 5.4-6.   Go to Step
          C.

    B.    For cold gas releases, two cases must be considered  for
          each release as outlined in Section 5.4.1.  Original
          initial conditions based on release calculations and
          modified initial conditions from Equation 5.4-1 are
          used in the dispersion calculation for each case.

    C.    For each continuous release case:

          a.   Check to see if denser-than-air effects  are
               important with Equation 5.4-7.  If denser-than-air
               effects are unimportant, use a passive atmospheric
               dispersion model.
          b.   .Modify the desired concentration Cm for  averaging
               time using Equation 5.4.11.
          c.   Modify Gm from  (b) for source cemperacure erfeons
               using Equation 5.4-12.
          d.   With Cm from (c), determine the downwind distance
               x using Figure 5.4-1 or Equation 5.4-10.
          e.   Determine whether the release duration is of
               sufficient length to establish a steady-state
               plume at the distance x.  As discussed earlier,


                               5-39

-------
               depending on UrTd/x, a dispersion  calculation for
               an instantaneous release may also be required.


Example: Chlorine Gas Leak

    Consider the example chlorine gas leak  discussed in Section
4.2.3.  Based on the earlier example, the gas  evolution rate Qm
was 1.10 kg/s and discharged at a temperature  T2 of  282.5K;  the
discharge density p2 was 3.059 kg/m3.  For a release in 2 m/s
winds  (at 10 m), determine the downwind distance to 1 ppm based
on a 15-minute time average.  The ambient temperature and
pressure are 293.15K and 101325 Pa, respectively.

    A.    Since this is not an aerosol release,  Step A is
          ignored.

    B.    The discharge temperature T2 is >2825K, so heat
          transfer is probably unimportant  since T,  - T2 is not
          large.  For the sake of illustration,  though,* consider
          two cases:  (1) p2 and T2 unchanged/ and(2)  ^2   =  3.059
          kg/m3 (282.5/293.15 = 2.948 kg/m3  and  T2   = 293.15K.

    C.    For case 1  (p2 = 3.059 kg/m3 and T2 = 282.5K) :

          a.   The left side of Equation 5.4-7 is 0.959 (with pa
               = 1.204 kg/m3/ D = 0.600 m,  using Equation  5.4-8)
               so denser-than-air effects are  expected to  be
               important.
          b.   Using tw = 15 min in Equation 5.4-11, C^ =  1.020
                (1 ppm) = 1 ppm.
          c.   Using C^ = 1 ppm = 1 x 10"6 mole fraction in
               Equation 5.4-12, C,,, = 1 ppm.
          d.   Since C^/C,, =  1  x 10"6   0.002,  Equation 5.4-10 is
               used to determine x = 8710 m c = 1.21;  fc =
               20540) .
          e.   For this release to be considered as a steady-
               state release, UrT,pc > 2.5,- so,  if Td  > 10900  s
                (182 min) then the release is a continuous  plume.

    C.    For case 2  (p2 = 2.948 kg/m3 and T2 = 293.15K) :

          a.   The left side of Equation 5.4-7 is 1.04 (with D =
               0.611 m, using Equation 5.4-8)  so denser-than-air
               effects are expected to be important.
          b.   As in case 1, using t^ = 15  min in Equation 5.4-
               11, Qa = 1.020  (1 ppm) = 1 ppm.
          c.   Also in case  1, using C* = 1 ppm  =  1  x 10"6  mole
               fraction in Equation 5.4-12,  C,,, = 1 ppm.
          d.   Since C^/C,, =  1  x 10"*   0.002,  Equation 5.4-10 is


                               5-40

-------
               used to determine x = 8950 m  (c = 1.19;  c =
               20720).
          e.   For this release to be considered as a steady-
               state release, UrTd/x > 2.5; so, if Td >  11200 s
               (186 min), then the release is a continuous  plume.

Therefore, the reported distance to the 15 minute averaged
chlorine concentration is 8950 m (provided the release  is of
sufficient duration.)

5.4.4  Instantaneous  (Puff) Releases

    To estimate the importance of denser-than-air effects on
instantaneous releases, Britter and McQuaid recommend that
denser-than-air effects be ignored if:


                     g"' f*-P.lP/ S0.2           (5.4.14)
where Q is the total amount of material released, Ur is  the
windspeed at 10 m, p2 is the discharge (depressurized)  density,
and pa  is  the  ambient air density.   If denser-than-air effects
are determined to be unimportant, standard passive atmospheric
dispersion techniques should be applied.

    However,  if denser-than-air effects are determined to be
important, the method of Britter and McQuaid can be used to
determine the downwind extent of a given concentration level
(Cm/C0) by use of  Figure  5.4-2.   For simplicity,  the  abscissa  and
ordinate are given as:-


                         g  ,/, [P2-P,,               (5_4_i5a)
                             ur-

and

                          tfi = x/(Q/p2)"3                  (5.4-15b)

respectively where x is the estimated downwind distance  to the
concentration level Cm/C0.  The effect of temperature  should  be
taken into account before using Figure 5.4-2 if the discharge
(depressurized)  contaminant temperature is different  from ambient:
using Equation 5.4-12.  Because Figure 5.4-2 uses concenLranicn
data based on (ensemble) short-term averaged concentrations,
taking longer averaging times into account would simply  shorten
predicted distances to a given concentration level; in the
absence' of further information, the predicted concentrations will
be assumed to apply regardless of averaging time  (which,- for
screening purposes, is a conservative assumption).  Once the

                                                    
                               5-41

-------
ratio Cm/C0  is  set,  Figure 5.4-2  can be used to determine the
downwind distance to that  ratio; interpolation for  intermediate
values of Cm/C0 should  be done using log-log interpolation (at a
fixed i) .   For s > 10, ^  should be assigned the value  of
j(i=10) .   If the desired Cm/C0 < 0.001, the following equation
can be used:
 r cj
k
                                    -o.4
                                                          (5.4-16)
 (based on extrapolation and fitting of Britter  and  McQuaid's
Figure 12) ; note that for  ,  > 10,  a value of ; = 10 should  be
used in Equation 5.4-16.   If  the desired  Cm/C0 < 0.001 and l a
i * 0.2, no data exists for  this  region  so  Britter and McQuaid
make no recommendation.  However,  the following equation can be
used:
                                      -0.4
                                                          (5.4-17)
based on simply forcing Equation  (5-16) to agree with the passive
limit.
                               5-42

-------
Figure 5.4-2.
Britter and McQuaid  (1989)  Correlation
Instantaneous (Puff)  Releases
                               - o
            5-43

-------
    In summary,  the following procedure should be used'for :
instantaneous (puff) releases:

    A.    For aerosol releases, two cases must be considered for
          each release as outlined in Section 5.4.2.  Initial
          conditions for the dispersion calculation for each case
          are based on Equations 5.4-2 through 5.4-6.  Go to Step
          C.

    B.    For cold gas releases, two cases must be considered for
          each release as outlined in Section 5.4.1.  Original
          initial conditions based on release calculations and
          modified initial conditions from Equation 5.4-1 are
          used in the dispersion calculation for each case.

    C.    For each, instantaneous release case:

          a.   Check to see if denser-than-air effects are
               important with Equation 5.4-13.  If denser-than-
               air effects are unimportant, use a passive
               atmospheric dispersion model.
          b.   Modify Cm for source temperature effects using
               Equation 5.4-12.
          c.   With Cm from (b) , determine the downwind distance
               x using Figure 5.4-2 or Equation 5.4-15.

Example:   Saturated Liquid Chlorine Leak(Reservoir Pressure of
          2.586 x 106 Pa.-  10.16  cm  hole)

    Consider the example chlorine leak discussed in Section 3.2.
Based on the earlier example, the evolution rate Qm was 430 kg/s
and the discharge temperature T2 was  239.05K;  the  discharge
density pz was  19.13 kg/m3.  For this example, assume the release
came from a "ton" cylinder which was initially half full
(approximately 500 kg); in this case, the release duration Td
would be small and the release can be assumed to occur
instantaneously  (with Q = 500 kg).   For a release in 2 m/s winds
(at 10 m), determine the downwind distance to 1 ppm based on a
15-minute time average.  The ambient temperature and pressure are
293.15K and 101325 Pa, respectively. 

    A.    Because this is an aerosol release, an initial amount
          if air is assumed to mix with the contaminant aerosol
          so that the liquid phase is evaporated and the mixture
          temperature is raised to the contaminant vapor pressure
           (239.05K in this case).   First, zc and za are estimated
          using Equation 5.4-2 as 0.188 and 0.812, respectively
           (using Cpa = 1006 J/kgK) .   Two cases must be
          considered:  (1)  
                               5-44

-------
           P2 =  (101325)  (36.8) / ((8314) (239.05))  =1.876kg/m3  7  and


           Q = (500)  (36.8)  / ( (0.188)  (70^9) )  = 1380 kg; and  (2)
           P2 =  (101325)  (36.8) / ((8314) (239..15))  =1.530kg/m3  ;  and

           T2 = 293.15K.     Q  will be the same for both


          cases.  Go to  Step  C.

    C.    For case 1  (p2 = 1.876 kg/m3;  T2 = 239.05K; Q = 1380
          kg) :

          a.   The left  side  of Equation 5.4-13  is 3.52  (with pa
               = 1.204 kg/m3)  so denser-than-air effects are
               expected  to be important.
          b.   Using C^  = 1 ppm = 1 x 10"* mole fraction in
               Equation  5.4-12, Cm = 1 ppm.
          c.   Since Cm/C0   1 x KrVo.188 =  5 x  lO"6 < 0.001,
               Equation  5.4-15  is used  to determine x =  6480 m
                (i  = 3.52;  *i = 717) .

    C.    For case 2  (p2 = 1:530 kg/m3;  T2 = 293.15K; Q = 1380
          kg) :

          a.   The left  side  of Equation 5.4-13  is 2.53,  so
               denser-than-air  effects  are expected to be
               important.
          b.   As in case  1,  using Cni =  1 ppm =  1  x 10"6 mole
               fraction  in Equation 5.4-12,  Cm =  1 ppm.
          c.   Since Cm/C0 =  1 x IQ^/O.ISS =  5 x  10"6 < 0.001,
               Equation  5.4-15  is used  to determine x =  7550 m
                (i  = 2.97;  ; = 781) .

Therefore, the reported  distance to the  15-minute averaged
chlorine concentration is  7550 m.

5.4.5  Assumptions in TSCREEN

    In the implementation of  the Britter-McQuaid model used in
TSCREEN, the model calculates concentrations for an array of 9
windspeeds,  for the D stability class,  at each distance.  Then,
the model output displays  the maximum concentration for  each
distance and the windspeed at which that concentration occurred.
                               5-45

-------
5.4.6  Model  Inputs
                              SCENARIO NAME & NUMBER
              Based on user input, the Britter-McQuaid model has been selected.

              BRITTER-MCQUAID MODEL INPUTS - Page 1  of'3

              MODEL PARAMETERS
                               Relative Humidity (Rh) ->  "     X
                Desired Averaging Time for the Calculation
                                  of Concentrations ->

                  Pollutant Boiling Point Temperature (Tb) ->
mm
                Help    Calculator    Previous Screen    Abort
MODEL PARAMETERS

1    Relative Humidity (Rh)  -
     Enter the  relative humidity  (%) .

2    Desired Averaging Time for the Calculation of Concentration
     (min)  -
     The  averaging "time is  used by the Britter and McQuaid  model
     to correct for  averaging times different from 10 min.
     Pgllutant  Boiling Point Temperature  (Tfr)  -
     Enter the  boiling point temperature.   This value  can be
     obtained from TSCREEN's chemical  database.
                               SCENARIO NAME & NUMBER
              BRITTER-McOUAID MODEL INPUTS - Page 2 of 3

              FENCELINE DISTANCE
               Enter the distance from the base of the stack
                               to the plant fenceline ->

              RECEPTOR LOCATIONS
              Do you have specific locations where you would
              like pollutant concentrations calculated (Y/N) -> ;J
                 Help    Calculator    Previous Screen    Abort
 FENCELINE DISTANCE

 4    Enter the distance  from the base of the stack to  the plant
     fenceline (m)  -
     Enter the distance  from the closest edge of  the source to the
     fenceline in meters.   The  model  calculates concentrations
     only at  receptors beyond the fenceline in ambient air.
                                     5-46

-------
RECEPTOR LOCATIONS
    Do you have specific location where you would like pollutant
    concentrations calculated (Y/N) -
    The entry of SPECIFIC LOCATIONS allows for calculating the
    maximum ground level concentrations at discrete,
    user-specified distances from the release.  TSCREEN will
    automatically give you maximum ground level concentrations at
    30 distances starting at the fenceline.  The first 16
    distances are in 100 m increments.  The next 8 distances are
    in 200 m increments, and the remaining 5 distances are in 300
    m increments.

    >     If "Y" is entered, proceed to step 8
    *     If "N" is entered, TSCREEN runs the Britter-McQuaid
          model.
BRITTER-McQUAID MODEL INPUTS - Page 3 of 3
RECEPTOR LOCATIONS:
the source at which
Enter a blank after
Distance from
source (meters)
1 fence
2
3
4
5
6
7
8
9
10 ,
 Help 
Enter (up to 30) distances from
concentrations should be
the last distance to stop
Distance from
source (meters)
11
12
13
14 '
15
16
17
18
19
20
calculated.
input.
Distance from
source (meters)
21
22
23
24 '
25
26
27
28
29
30
Calculator  Previous Screen  Abort
RECEPTOR LOCATIONS
               *
6   Enter  (UP to 30) distances from the source at which
    concentrations should be calculated -
    Enter the distance in meters from the release for calculating
    the maximum ground level concentrations.

    >     After the user finishes entering distances, TSCREEN
          runs the Britter-McQuaid model.

5.4.7  Model Output

    For a complete example of the Britter-McQuaid model ,see
Section  4.2.3. (See Appendix E-Running TSCREEN for output
options after the model is run.) The following shows the format
of the output file that Britter-McQuaid would generate.
                               5-47

-------
                                                                    -  -92

 *** B&M MODEL RUN ***
INPUTS:
   AMBIENT PRESSURE (ATM)
   AMBIENT TEMP (K)
   AVERAGING TIME (MIN)
   BOILING PT TEMP (K)
   DURATION (S)
   EMISSION RATE (KG/S)
   EXIT TEMP (K)
   MASS (KG)
   MOL. WEIGHT (G/G-MOLE)
   RELATIVE HUMIDITY (X)
   VAPOR FRACTION
                            i 
     ***   SUMMARY OF B&M MODEL RESULTS  ***
MAX CONC
(UG/M**3)
MAX CONC
(PPM)
DIST TO
MAX (M)
WIND SPEED
(M/S)
I***************************************************
** REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS **
***************************
**********************************
***        B&M DISTANCES      ***
****
   DIST        CONC            CONC        WIND SPEED
    (M)      (UG/M**3)         (PPM)         (M/S)
   100.
   200.
   300.
   400.
   500.
   600.
   700.
   800.
   900.
  1000. .
  1100.
  1200.
  1300.
  1400.
  1500.
  1600.
  1700.
  1900.
  2100.
  2300.
  2500.
  2700.
  2900.
  3100.
  3300.
  3600.
  3900.
  4200.
                                                  5-48

-------
   4500.
   5000.
 CALCULATED VALUES:
    DENSITY OF DEPRESSURIZED CONTAMINANT (KG/M**3) =
    DENSITY OF AMBIENT AIR (KG/M**3)               =
    MOLE FRACTION                                  =
 '   MIN DIST INST (M)                              =
    MAX DIST CNST (M)                              a
       NOTES & DEFINITIONS
(a) "inst" refers to an instantaneous release (Section 3.6 of  B-M Workbook)
(b) "cost" refers to a continuous release (Section 3.6 of  B-M  Workbook)
(c) "MIN DIST INST" is the minimum distance downwind at which  the release
    may be treated as instantaneous
(d) "MAX DIST CNST1" is the maximum distance downwind at which  the release
    may be treated as continuous
         END OF B&M OUTPUT
                                                  5-49

-------
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                                  R-2

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                                  R-3

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U.S. Environmental Protection Agency, 1990: User's Guide to
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U.S. Environmental Protection Agency, 1991b: Air Emissions from
     Municipal Solid Waste Landfills - Background.Information  for
     Proposed Standards and Guidelines, EPA-450/3-90-lla.  U.S.
     Environmental Protection Agency, Research Triangle Park,  NC.

U.S. Environmental Protection Agency, 1992: User's Guide for the
     Industrial Source Complex  (ISC2) Dispersion Models, Volume
     II - Description of Algorithms, EPA-450/4-92-008b.  U.S.
     Environmental Protection Agency,tResearch Triangle Park,  NC.
                                         
Van Ulden, A. 1974: On Spreading of a Heavy Gas Released Near  the
     Ground, 1st International Loss Prevention Symposium, The
     Hague/Delft.

Verschueren, K., 1983: Handbook of Environmental Dataon Organic
     Chemicals.  Van Nostrand Reinhold Company, New York.

Wallis, G. 1969: One Dimensj-Qnal Two-Phase Flow. McGraw-Hill,  New
     York.

Webber, D.M., and S.J. Jones, 1987-. A Model of Spreading
     Vaporising Pools, in International Conference on Vapor Cloud
     Modeling. John Woodward, ed., American Institute of Chemical
     Engineers, New York.
                                  R-4

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   APPENDIX A
EMISSION FACTORS

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                         APPENDIX A
                      EMISSION FACTORS

     One alternative for estimating air toxic emissions from
sources is through the use of emission factors.  Emission
factors have been developed for a number of processes and
pollutants.  Emission factors provide an estimate of
emissions as a function of source activity such as process
rate or some other operating parameter.  Emission factors
are intended to been used for making preliminary estimates
of toxic air emissions.  As such, they represent generic
factors whose applicability to a specific source may be
questionable.  These factors will not likely provide exact
estimates of emissions from any particular source.  The
source of an emission factor must be carefully evaluated to
determine whether it is applicable to a particular facility.
Emission factors are available for both area and point
sources.  Some sources of emission factors applicable to air
toxics emissions are presented below.
     1}   U.S. Environmental Protection Agency.  Locating
          and Estimating Air Emissions from  (or of)  (Source
          Category or Substance).   EPA 450/4-84-007a-q.  EPA
          450/4-88-004, 450/2-89-001, 450/2-89-002, 
          450/2-89-006, 450/2-89-013, 450/2-89-021,
          450/2-90-009, 450/4-91-029.  .

     EPA has underway a program to compile and publish
emission factors for various air toxics.  To date,
twenty-four reports have been published as part of this
program.  The substances covered by this series include:
acrylonitrile, carbon tetrachloride, chloroform, ethylene
dichloride, formaldehyde (revised), nickel, chromium,
manganese, phosgene, epichlorohydrin, vinylidene chloride,
ethylene oxide, chlorobenzenes,  PCBs, POM, benzene, organic
liquid storage tanks, coal and oil combustion sources,
municipal waste combustors, perchloroethylene and
trichloroethylene, 1,3-batadiene,  and sewage sludge
incinerators and styrene.

     2)   U.S. Environmental Protection Agency.  Survey of
           (Substance) Emission Sources.

     A second series of reports on specific air toxics has
been developed by EPA as part of the National Emissions
Standards for Hazardous Air Pollutants  (NESHAPS) program.
The substances covered by this series include:
trichloroethylene (EPA 450/3-85-021), perchloroethylene  (EPA
450/3-85-017), ethylene oxide (EPA 450/3-014), chloroform
(EPA 450/3-85-026),  ethylene dichloride (EPA 450/3-84-018),
methylene -chloride  ^EPA 450/3-85-015) , and -carbon
tetrachloride  (EPA 450/3-85-018).


                            A-l

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     3)   U.S. Environmental Protection Agency.
          XATEF-Crosswalk/Air Toxic Emission Factors
          Database.

     The database is available from the EPA Office of Air
Quality Planning and Standards, Technology Transfer Network
(TTN).   Files may be downloaded by dialing (919) 541-5742.
[There is no charge for access.]   This database management
system presents emission factors of air toxic pollutants for
a variety of sources with varying activity levels.  , This
database management system is updated and expanded
periodically.  The factors are associated with pollutant
names and CAS numbers, process descriptions and SIC codes,
emission source descriptions and SCC codes, notes on the
derivation of the factors and on control measures associated
with the factors, and references.  The emission factors can
be used to obtain.quick, rough estimates of air toxic
emissions.  More detailed data on the emission sources can
be obtained from the Notes and References Sections listed in
the emission factors tables.  The primary limitation of
using just the emissions factors listed in this compilation
is that their accuracy in application to a given source is
not known.  More accurate emissions estimates may require
evaluation of the application of available test data to
specific s.ource characteristics.   Otherwise,  factors
determined by compiling extensive source test results using
EPA Reference Methods are reported in AP-42.   Toxic
components of emissions can be determined using SPECIATE
database management system  (see above).

     4)   U.S. Environmental Protection Agency.  Compilation
          of Air Pollutant Emission Factors.  Fourth Edition.
          AP-42,  September 1985.   And Supplement A 1986,
          Supplement B 1988; Supplement C, 1990; Supplement
          D, 1991.

     Another tool for estimating air toxic emissions
involves the use of VOC/PM factors presented in AP-42 and
species profiles in SPECIATE database management system.
AP-42 contains emission factors for total VOC and PM rather
than for a single chemical compound.  These factors can be
used with profiles contained in SPECIATE to estimate the
releases of specific toxic compounds based on the total
amount of VOC or PM released from a source.  SPECIATE shows
the percent by weight and percent by volume of specific
chemicals in emissions from specific chemicals in emissions
from specific processes.  "Speciation factors are used to
estimate emissions of air toxics from emission factors or
estimates of total VOC or PM.  Both volumes are similarly
organized with speciation data presented by source  category
and by Source Classification Codes  (SCO .   Species  profiles
for VOCs and PM are for generic sources and -may not be
representative of emissions from an individual facility.  .


                             A-2

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SPECIATE is updated periodically.

     5)   U.S. Environmental Protection Agency.  Fugitive
          Emission Sources of Organic Compounds - Additional
          Information on Emissions. Emission Reductions, and
          Costs.  EPA-450/3-82-010, 1982.

     This document contains the data and methodologies which
EPA believes most accurately characterize average synthetic,
organic chemical manufacturing industry equipment leak
emission rates of VOC, effectiveness of.control techniques,
and control costs for selected equipment used in the
processing of organic chemicals.  The emission factors  (on
Page 1-4) can be used tb estimate VOC emissions from any
industrial plant which has the selected equipment and
handles organic chemicals.
                            A-3

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                     APPENDIX B
ESTIMATING SELECTED PHYSICAL PROPERTIES OF MIXTURES

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                         APPENDIX B
     ESTIMATING SELECTED PHYSICAL PROPERTIES OF MIXTURES

      This appendix describes methods to estimate selected
physical properties of mixtures using pure component
physical properties.  These mixture properties  include:

     Cp   gas  (contaminant) heat capacity  (J/kg K)
     Cp,   liquid  (contaminant) heat capacity  (J/kg  K)
     M    contaminant molecular weight  (g/g-mole)
     T.c   pseudo-critical .temperature (K)
     X    contaminant latent heat of vaporization  (J/kg)

For each of these mixture fluid properties, the
corresponding fluid property for each of the mixture
constituents is required.  In addition,  the mixture
composition is required; for some calculations,  the mixture
composition expressed as mole fractions is required, while
for other calculations, the mixture composition expressed as
mass fractions is required.  Because the mixture molecular
weight is required when converting from mass to mole
fractions, this calculation is outlined first.   The
calculation of mixture heat capacity and latent  heat of
vaporization is discussed together because these
calculations all require that the mixture composition be
specified as mass fractions.

Mixture Molecular Weight

     The mixture molecular weight M (g/g-mole)  is calculated
using mixture mass fractions as:
                                                        (B-l)
where ^  is  the mass  fraction  of  species  i, M, is the
molecular weight of species i  (g/g-mole)  , and the summation
is over all C components.

Using mixture mole fractions, the equation for mixture
molecular weight is:
                               Z-, M,                     (B-2)
where z( is the mole  fraction of species  i .   Conversions
between mass and mole fractions can be made using:
                                                        (B-3)
                             B-l

-------
for each of the i components.  So, if mass fractions are  .
known and mole fractions are desired, Equation  (B-l) can  be
used to calculate the molecular weight, and Equation  (B-3)
can be used to calculate the mole fractions for each
component.  And, if mole fractions are known and mass
fractions desired, Equation  (B-2) can be used to calculate
the molecular weight, and Equation (B-3) can be used to
calculate the mass fractions for each component.

Pseudo-Critical Temperature
Tc  is:
     The equation-to determine pseudo-critical temperature
                            (?
                               ZiTA                     (B-4!
where Zj  is  the mole  fraction of  species  i  and  TCii is the
temperature of species i.

Mixture Heat Capacity and Latent Heat of Vaporization

     The equations to determine mixture  (gas and  liquid)
heat capacities  (Cp and Cp,)  and latent heat of  vaporization
(X) are based on a mass-fraction weighted  contribution  of
each pure component property.  So, the equation to  determine
the (mixture) gas-phase contaminant heat capacity Cp is:
                        C  = IXc* Cj                     (B-5)
                           (-
                             \c
where 
-------
        APPENDIX  C
SELECTED CONVERSION FACTORS

-------
                               APPENDIX C
                       SELECTED CONVERSION FACTORS
  Area

       1 m2
      1 ft2
  1 hectare
    1  acre
          =  104 cm2
          =  0.0929 m2
          =  104 m2
          -  4046.86 m2
                           IN  =  1 kg   m/sec2
                                =  105 dynes
                                -  0.2248 lbf
                        1  dyne  =  1 g  cm/sec2
                                =  10'5 N
                                =  2.248 x  ID"6 lbp
                          1 lbf    4.448 N
                                =  4.448 x  10s dynes
  Concentration

  conversions  with ppm by volume:
                                  Gas Constant
     mg
     mg
        24.04
                =ppm by vol  (20C)
        0.8347 x 10-*= ppm by wt
    ^1  62.43 x 10-9= lbm 1 ft3
  m
  mg
  m~
  for  ideal  gases
vol
     vol % x  10
  fraction x 106
    = ppm by vol
    = ppm by vol
Energy or Work

     1 J  =  N
          =  107
          =  107
          =  0
          =  0
    m
    ergs
    dyne
                          cm
                 23891 g-cal
                 7373 ft-lbf
             = 9.486 x ID"4 BTU
   ft-lbf  =
1 cal(g)
   1 BTU
0.0012861 BTU
1.3562 J
1.3562 x 107 ergs
0.32396 g-cal
3.9685 x
1.0543 x 1010 ergs
1054 Joules (N-m)
10'3 BTU
Flow

   1 m3/h  =  3600 m3/s


Force
                            PV
                           Mwair
                    8314.0
                       0.08314
                       0.08206
                       0.08206
                      62.36
                       0.7302
                      10.73
                       =  nRT
                       *  29(79% N2/  21% 02)
                       m3-Pa/kg-mole- K
                       barliters/g-moleK
                       m3- atm/kg-mole  K
                       liter-atm/g-moleK
                       1-mm Hg/g-mole-K
                       ft3-atm/lb-mole- R
                       ft3-psia/lb-mole-R
              8.314  x 10-3J/kg-mole-K
              8.314      J/g-mole-K
              1.987      cal/g-mole-K
              1.987      BTU/lb-mole-0R
              5.467      gal-atm/lb-mole R

            1 gmole  gas occupies 22.41 at
            0C
            1 Ib-mole gas  occupies 359 ft3
            at 0C
            1 Ib-mole gas  occupies 380 ft3
            at 60F
                                     Heat Rate

                                      1 cal/s    1.102 x ID"6 BTU/h



                                     Length

                                          1m  =  100  ^m
                                               =  1000 mm
                                               =  39.37 in
                                               =  3.2808 ft
                                               =  1.0936 yards
                                               =  0.0006214 mils
                                               =  106 microns  (jn)
                                               =  1010  angstroms (A)
                                   C-l

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      1 ft
      1 in
12 -in
% yd
0.3048 ra
30.48 cm
2.540 cm
  F + 460
C + 273.6
R
K
  Mass
       1kg  =  lOOOg
            =  0.001 metric tons
            =  2.20462  Ibm
            =  35.27392 oz

      .llbm  =  16  oz
            =  5 x 1Q-4  tons
            =  453.593  g
            =  .453593  kg
  Mass Release Rate
     i g/s  =
    1 t/yr  =
    1 t/dy  =
7.9367 Ib/hr
3.16'x ID'2 g/s
11.57 g/s
  Power

       1 w  =  l  J/sec
            =  14.34  g-cal/min
            -  1.341  x  10"3  hp
            =  0.7376 ft-lbf/sec

  Pressure

     1 atm  =  1.1325 x 10s N/M2
            =  1.01325  x 105 Pa
            =  1.01325  x bars
            =  1.01325  dynes/cm2
            =  760 mm Hg
            =  29.9212  in Hg
            =  10.33  m  H20
            =  33.9 ft  H20
            =  14.696 psi
1 millibar  =  1000 dynes/cm2
   1 mm Hg  =  1333.224 dynes/cm2
   1  Ib/irr  =  58,947.6 dynes/cm2
   1 in Hg  =  33,863.9 dynes/cm2
  1 Pascal  =  10 dynes/cm2
  Volume

      1 m3
                         1 ft3
     1 bbl  =

   1 liter  =
  1 gallon  =
1000 liters
106 cm3
106 m 1
35.3145 ft2
61, 023 in3
220.8 imperial  gal
264.17 gallons
1056.68 quarts
1728 in3
0.028317 m3
28.317 liters
28,317 cm3
7.4805 gallons
42 gallons
158.99 liters
103 cm3
3.785 cm3
  Temperature

9/5C +32  -  F
                                  C-2

-------
Conversion Calculations

1.      To convert  from  ^g/m3 to parts per million  (ppm),  use the
        following:

                                                 IT 1
                                                 -  0.0245/MW  (C-l)
                                                  aJ

        where:
          TO  = 273.15 (K)
          Ta  = ambient temperature (K)
          MV = molecular weight  (g/g-mole)

        Equation  (C-l) is  simplified in TSCREEN by assuming T0/Ta=l.


2.      To convert  J/kg  to cal/g-mole use the following:

                     J/kg (1^/4184) = cal/g-mole                (C-2)
                                 C-3

-------
               APPENDIX D
AVERAGING PERIOD CONCENTRATION ESTIMATES

-------
                             APPENDIX D
              AVERAGING PERIOD CONCENTRATION ESTIMATES

     The purpose of this appendix is to provide some simplified
techniques for converting concentrations calculated by the models
to different averaging times.  Methods presented are applicable  to
ground-level and elevated emissions of passive gases and
particulate matter.

          Instantaneous Estimates

     For computing ground level concentrations from an
instantaneous surface release for a given stability class and
sampling time, the average concentration over sampling time  r can
be expressed as some fraction of the-peak concentration.

                             Xr = Xf * F                   '      (D-l)

where:    XT   is tne average concentration for a given sampling
               time T,
          T    is the sampling time, i.e. 5 min., 1 hour etc.,
               (expressed in seconds)
          Xp   is the instantaneous peak concentration.
          F    is the correction factor for sampling time, which
               always has a value less than or equal to one.

The correction factor F can be computed using the procedure given
by Petersen, 1982 for the averaging times not provided in TSCREEN.

     The concentration at a given receptor location ranges from
zero to a peak value as the puff moves towards trie receptor. The
peak instantaneous concentration is always assumed to occur at time
t when the center of the puff is at the receptor location. If the
growth of the puff is small as the puff passes over the receptor,
then the peak average concentration for sampling time T at a
particular location occurs during the time period t - r/2 to t +
T/2.

          Continuous Estimates
                               
     To obtain the estimate of the maximum concentration for a
longer averaging time, multiply the 1-hour maximum concentration by
the given factor:

           Averaging Time             Multiplying Factor
              3 hours                      0.9  (0.1)
              8 hours                      0.7  (0.2)
              24 hours                     0.4  (0.2)
              annual                       0.08  (0.2)


The numbers in parentheses are recommended limits to which one may
diverge form the multiplying factors representing the general case.

                                D-l

-------
For example, if aerodynamic downwash or terrain is a problem at the
facility, or if the release height is very low, it may be
appropriate to increase the factors up to the limits specified in
parentheses.  Conversely, if the stack is relatively tall and there
are no terrain or downwash problems, it may be appropriate to
decrease the factors .  For averaging times in between the values
listed above, use the multiplying factor for the shorter averaging
time.  For example, if a 4 -hour average concentration is needed,
use the multiplying factor for the 3 -hour averaging time (0.9) .

     To obtain the estimated maximum concentration for a shorter
averaging times between 30 and 60 minutes, use the 1-hour maximum
concentration.  For averaging times less than 30 minutes use the
following equation:
                                                               (D-2)
where:  t s 30 minutes
TSCREEN will present a menu containing these averaging times and
the 15 and 30 minute averaging times after the SCREEN model has
been run.  The user may select one or more of these maximum
concentrations calculated by the model.  The new concentrations
will appear at the end of the SCREEN model output.
                                 D-2

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  APPENDIX  E
RUNNING TSCREEN

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                            APPENDIX E
                         RUNNING TSCREEN
E.1  Introduction
     To correctly analyze toxic emissions and their subsequent
dispersion from one of many different types of possible releases,
the computer program TSCREEN, A Model for Screening Toxic Air
Pollutant Concentrations, should be used in conjunction with this
workbook.  With the use of these tools one can determine the type
of release and the steps to followed to simulate the release via
an applicable computer model.  Then, the dispersion
characteristics and pollutant concentrations of the resulting
plume can be calculated.  The air toxics dispersion screening
models imbedded in TSCREEN that are used for the various
scenarios are SCREEN, RVD, PUFF, and the Britter-McQuaid model.
Using TSCREEN, a particular release scenario is selected via
input parameters, and TSCREEN automatically selects and executes
the appropriate dispersion model to simulate that scenario.  The
model to be used and the worst case meteorological conditions are
automatically selected based on criteria given in those in this
workbook.  TSCREEN has a front-end control program to the models
that also provides, by use of interactive menus and data entry
screen, the same steps as the workbook.  The correct release
scenario and associated characteristics of a toxic emissions
release are selected with the help of on-screen text and graphics
and data input is performed in a full-screen edit mode.  TSCREEN
saves the input data for each release scenario to a file that can
be retrieved and later edited or executed.  TSCREEN also provided
a. method of easily viewing and saving the modeling results for
each modeled scenario.

E.2  Getting Started

Hardware Requirements

     TSCREEN is an IBM PC-based software application written and
compiled in FoxPro,  a  software application development  system,
and Microsoft C Version 5.1.   The  program requires  500
kilobytes (KB) of free Random Access Memory  (RAM).   Although
TSGREEN may operate with certain memory resident programs
installed, no attempt has been made to test its operation against
all memory resident programs available today.  If problems occur
while TSCREEN and memory resident programs are running
simultaneously, try removing the memory resident programs from
memory and re-executing TSCREEN.  The TSCREEN program files
occupy about 2.2 megabytes (MB) of disk space.  As data from
scenario runs are saved, the hard disk space needed will
increase.  To install TSCREEN on hard disk systems, make sure
there is at least 2.5 MB of free disk space available to load and
execute the program.  The time required to run the dispersion
models will be greatly reduced if the computer has a math co-
processor.

                               E-l

-------
The computer running TSCREEN must be booted with the CONFIG.SYS
file in the root directory of the boot up disk containing the
following parameters:

Files  30
Buffers = 22

If the CONFIG.SYS file already has these statements with higher
values assigned, then no modification is necessary, otherwise
either add -the needed statements or increase their value to that
of the example and reboot the computer.


Software requirements

The files required to run TSCREEN are as follows:

BMTS.EXE - The Britter & McQuaid model
CHEMBASE.DBF - The chemical database
CHEMBASE.IDX - The chemical database index-file
DISPLAY.DBF - File used to display file lists
ERHANDLE.EXE - The error handling program
ERMSG.DAT - Error message file
FOXSWAP.COM - FoxPro memory management program
FOXUSER.DBF - FoxPro database
FOXPRO.ESL - FoxPro run-time library
FOXPRO.ESO - FoxPro run-time library
FOXUSER.FPT - FoxPro database
GRAPH.EXE - The graphics generation program
PIPERES.EXE - Program-that performs calculations for the
scenarios involving gas leaks from a pipe attached to a reservoir
PUFFTS.EXE - The PUFF model
OLDRUNS.DBF - Database that contains previously entered data
OUTPUT.DBF - File used to display model output
RVDTS.EXE - The RVD model
SCREENTS.EXE - The SCREEN model
TSCREEN.EXE - The main program
TSHELP.DBF - The help database
TSHELP.FPT - File containing help text
VFONT101.FNT - The graph font file
TSMACRO.FKY - FoxPro macro file
First Time Installation

Installing TSCREEN



Because of the size of the TSCREEN program, TSCREEN is separated
into four separate zipped (compressed) files:
                               E-2

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File            Size(K)

TSCREEN1.ZIP    568
TSCREEN2.ZIP    193
TSCREEN3.ZIP    344
TSCREEN4.ZIP    227

TSCREEN1.ZIP contains the FoxPro runtime program, FOXPRO.ESO, and
TSCREEN2.ZIP contains the FoxPro runtime program, FOXPRO.ESL, and
the FoxPro memory manager FOXSWAP.COM. If you already have these
files for TSCREEN version 3.0, July 1992, then you do not need to
download TSCREEN1.ZIP and TSCREEN2.ZIP. Make sure though to
include these files in the same sub-directory of the updated
TSCREEN version 3.0, November 1992, before running the updated
program.

To unzip (decompress)  the files, you will need to have a copy of
PKUNZIP.EXE file. PKUNZIP.EXE is availible on most Bulletin Board
Systems (BBS).

Please refer to your DOS manual for the relevant commands for
creating sub-directories and copying files if the following
instructions are unclear.

TSCREEN must be installed on a hard disk in order to run.  To
install TSCREEN on a hard disk, check the available disk space
by running the DOS program CHKDSK.  To check to see if the DOS
programs are accessible from the PATH setting simply type:

PATH

If the DOS sub-directory or sub-directories containing the DOS
files is listed the type:

CHKDSK

at the hard disk prompt where TSCREEN is to be installed.  If
not, read your DOS manual to understand what you have to do to
run CHKDSK.  Check to make sure there is at least 2.5 MB of
available disk space.   Ifm there is enough free disk space, then
create a /TSCREEN sub-directory -from the root directory of the
hard drive on which TSCREEN will be installed.  The command to
create a TSCREEN sub-directory off the main or root directory is:

CD\
MD TSCREEN

Once the sub-directory is created, insert the first TSCREEN
diskette in the high-density drive of the computer (usually the A
drive on IBM AT-type machines) and copy the files from the

diskette to the sub-directory by typing the command:
                               E-3

-------
COPY A:*.* X:\TSCREEN

where  X is the letter designation of the  drive which TSCREEN is
to be  installed  (where the  sub-directory  was created).   Repeat
the command above  for the other diskettes.  Also, copy the
PKUNZIP.EXE file to your TSCREEN sub-directory. While in the
TSCREEN sub-directory,decompress the TSCREEN zip files  by typing
following command:

PKUNZIP TSCREEN1.ZIP

Repeat the command for the  other three TSCREEN zip  files
replacing TSCREEN1.ZIP with the other file  names: TSCREEN2.ZIP,
TSCREEN3.ZIP, TSCREEN4.ZIP.  Once the files  are unzipped
(decompessed), the installation is complete. Type the following
command :

TSCREEN

to start the program.


E.3  Example Scenario

     An example  TSCREEN  session is  demonstrated in  this section.
For more information on  the scenarios  in TSCREEN,  see  Sections  4
and 5  of this workbook.
Title  Screen

     Upon starting  the program a title screen will  appear as shown
in Figure E-l.

                      Figure E-l.   Title Screen
                              TSCREEN

                 A"ModeI for Screening Air Toxic Pollutant Concentrations

                     Version 3.0 (Dated 92182)       August 1992
               for Questions Contact:
        Developed by:
            Jawad S. Touna, Project Officer
            US EPA, OAQPS, TSO CMO - 14)
            Source Receptor Analysis Branch
            Research Triangle Park, NC 27711
            (919) 541-5381
Pacific Environmental Services, Inc
5001 So. Miami 3lvd, Suite 300
P.O. Box 12077
Research Triangle Park, NC 27709
(919) 941-0333
                                  E-4

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Selection Windows

     After the  reference  pages, the  main menu  bar appears across
the top of the  screen, and a list available keys appears across
the bottom of the screen  as shown in Figure E-2.  From  this menu
the user can select:

         File -  to retrieve previously entered  data,  previously
         saved model printed output,  or previously saved  model
         graphic output

         Initial Form of Release - to select a  form of release and
         enter a new scenario

         Chemical  Database - to view  or edit the  Chemical Database

         Quit -  to exit TSCREEN.

                        Figure E-2.   Main Menu
                  Initial Form of Release
                    Chemical Database   Quit
           Help   <1>/Scroll Vertical Menus    <->/<-.>ScrolI Horizontal Menu
           /Letter=Select Menu Item  Exit Current Menu  Exit All Menus
      Menu selections in  TSCREEN can be made by clicking a mouse,
by moving the  highlight  bar with  the arrow keys and pressing
,  or by pressing  the letter  of a menu  item that  is a
different color.   To enter data for this scenario, select
'Initial Form  of  Release'  from the  menu bar.   The pull-down menu
shown in Figure E-3 will appear.

                Figure E-3.   Initial Form of Release
             File
  Jnitfal
	 Initial Form of Release 	
Pwilcutatfii'Hatter Bet ess* Typ<*
Gaseous Release Type
Liquid Release Type
Superfund Release Type
                                     Chemical Database
Quit
           Help   /Scroll Vertical Menus   <-->/<->ScroU Horizontal Menu
           /Letter=Select Menu Item  Exit Current Menu  EXit All Menus
      TSCREEN  has help  available at  each point  in the  system,
activated by  pressing  the  key.   Even the  selection windows
have  help pages associated with them.   An example of  pressing  the
  key from the first  menu item  in the 'Initial Form of
                                  E-5

-------
Release'  menu  is shown  in Figure E-4.    (See Section E.7  for  a
detailed  discussion on  the use of  the help system.)

                         Figure  E-4.   Help Window
File   tn*ti*t ftw:-fl*
                                       Chemical Database   Quit
             Topics  

          " <  Next  >

            < Previous >

            < Look Up  >
          I Paniculate Natter Release Type I
          A Particulate Matter type release is a release of any solid
          material such as particulates, dust, or ash.
                       See Also: Release Definition
           Help   /Scroll Vertical Menus   <*->/<->ScrolI Horizontal Menu
           /Letter=Select Menu Item  Exit Current Menu   Exit All Menus
      Next select  'Particulate  Matter Release Type'  from  the
'Initial  Form of  Release'  menu.   Then the menu in  Figure E-5  will
appear.

         Figure E-5.   Particulate Matter  Release Type Menu
           File
     Irtit1[*l;fwin:<>ftRelease    Chemical Database   Quit
        Initial Form of Release
                           Part(cutate Matter Release Type 	
                                           Workbook Scenario
                     Fugitive/Windblown Dust Emissions - 4.1.2
                     Ducting/Connector Failures      - 4.1.3
           Help   /<4>ScrolI Vertical Menus    <-->/<->ScrolI Horizontal Menu
           /Letter=Select Menu Item  Exit Current Menu  Exit All Menus
      The  second menu of  release types that appears  lists only the
scenarios specific  to the Initial  Form of Release selected from
the  first selection menu (See  Section E.4 for  a complete list of
the  scenario  selection menus).   The  user  can return to previous
menus or  data entry windows by pressing the  key.  Pressing
 from a  menu item or from the data entry  windows that follow
will cause the user to return  to the main menu bar.
                                     E-6

-------
Data Entry  Screens

      Once the scenario has been  selected,  unique data  entry
screens  will appear  for  that  scenario.   These  screens  will  guide
the user through calculations that will select the  appropriate
dispersion  model based on the data entered.   For example, some  of
the screens calculate gas densities and others help calculate
emission rates.   Data entry screens for this example are shown  in
Figures  E-6 through  E-8.   Note that in this example there is no
scenario input  section since  the  scenario  has  already  been
determined.   Thus, the user is taken  directly  to the model  input
section.
                      Figure E-6.  Data  Entry Screen
              Continuous Participate Matter Releases from Stacks - Scenario 4.1.1-
              Based on user input, SCREEN model has been selected.

              SCREEN MODEL INPUTS - Page 1 of 7
              Enter a unique title for this data's model run:
                                 ................................
                       g/s
                       m/s
                       m
                       m
                       "K

                                 Exit Velocity (ExitV)->
                         Release Height above Ground (Hs) -> 1&d
                           Diameter at Release Point (0) -> ;.1S: :
                  Temperature of the Material Released (Ts) -> J9 2Mt,;
iSftreefti:
                  Sa:ilx':". \
                      Figure E-7.  Data  Entry Screen

              Continuous Particulate Matter Releases from Stacks - Scenario 4.1.1

              SCREEN MODEL INPUTS - Page 2 of 7

              BUILDING PARAMETERS
                  Building Height (enter 0 if no building) -> 19      m
                     Building Minimum Horizontal Dimension -> 19-   :   m
                     Building Maximum Horizontal Dimension -> 1?" .!. :  m

              URBAN/RURAL CLASSIFICATION
                         Enter U for Urban - R for Rural -> R

              FENCELINE DISTANCE
               Enter the distance from the base of the stack
                                to the plant fenceline -> 1 Help    Calculator    previous Screen    Abort
                                      E-7

-------
                   Figure E-8.   Data Entry Screen
             Continuous Participate Natter Releases from Stacks - Scenario 4.1.1
            SCREEN MODEL INPUTS - Page 3 of 7

            TERRAIN TYPE
              Is this a FLAT or SIMPLE TERRAIN evaluation (Y/N) -> V.

            SIMPLE TERRAIN
                      Are receptors above stack-base (Y/N) -> jf

            FLAT TERRAIN
            Do you have specific locations where you would like
               pollutant concentrations to be calculated (Y/N) -> T

                    Oo you have receptors above ground level
                         (i.e. Flag Pole Receptors) (Y/N) -> H
edit?
                                             6f-
      Based on user input,  the SCREEN model has  been selected with
Flat  terrain only.  Note  that the program automatically
calculates concentrations for many  receptors.   If the  user
selects "Y" to  enter discrete receptors, pressing  will
advance TSCREEN to the next page  (see Figure  E-9) and  allow the
user  to enter specified distances of interest that will be added
to the  automatic receptors.

If the  user enters "N" for discrete receptors,   SCREEN is
executed with only the automatic number of receptors.

      Figure E-9.   Data Entry Screen for Discrete Receptors
	 toniinuous parrici
SCREEN MODEL INPUTS
RECEPTOR LOCATIONS:
the source at which
Enter a blank after
Distance from
source (meters)
1 100 fenci
2 " ' .
3 <..^,.:
4 >^:;rt
5 " - ":?1 .
6 ft;>$^
7 ::;%;.<*><
8 ;:-.. '"'"> :
9 '":"'>-..: '
10 ' "H*'":X
.  Edit. ... *F9>
jiaie natter Releases iron
- Page 4 of 7
Enter (up to 30) distant
concentrations should be
the last distance to sto|
Distance from
source (meters)
5 11
12 :.!' 
13 .: '.":?*
14 .:.'?%.;,:
15 ::";'-: - :''
16 '-:; *i
17 .k,;.*' .:-H
is .;::::v-s ::;
19 :>, "i
. 20 :-x::':/; H-
ffevfous Screen. 
> siacics - scenario <.i.i 	
:es from
calculated.
> input.
Distance from
source (meters)
21
22
23
24
 25
26
27
28
29
30
Ran ftodel:.: :  will execute the SCREEN model.  As the program
                                  E-8

-------
executes  the user  is shown what  percent of  the program  is
complete.

Parts  Per Million

     After the SCREEN model has  run,  the data entry window in
Figure E-10 appears.   The user can choose to  have the maximum
concentrations displayed in parts per million (ppm) in  addition
to /zg/m3.   "N"  is entered in this example.   If "Y"  had been
entered the user would then be required to  enter the appropriate
molecular weight and the concentration in ppm would be  calculated
using  the following formula:
        concentration (ppm)   =  concent rat ion (pig/m3)  '	'
                                                         1 '\v
where:  Mw  = molecular  weight  (g/g-mole)

                  Figure E-10.  Parts Per Million
                 Do you want maximum concentrations
                   in parts per million (ppm) (Y/N) -> It
                 Help Up  <;>Down  Exit/No ppm calculation
Averaging Times

      The default  averaging time  in the'SCREEN model is  1  hour.
If the  SCREEN model  is used, the maximum concentration  can be
calculated for additional averaging times  selected from the menu
shown in Figure E-ll.   Since we  are only interested in  1-hour
averages for this example, we will not select any of the
additional averaging periods.

                    Figure E-ll.   Averaging  Times
                              Averaging Time
                        The default averaging time is 1 hour
                        select one or more from below. .  .
                               30 Minutes
                               3 Hours
                               8 Hours
                               24 Hours
                               Annual
                               Up 0own
                         / Mark/Unmark Time
                            Select Marked Times
                           Abort Without Selection
                                  E-9

-------
     Averaging times can be selected by pressing the  key
or the Space bar to mark the averaging time with an asterisk.
After all of the desired averaging times have been selected,
press  to proceed.  If additional averaging times were
selected, the estimated concentrations for the new averaging
times would appear at the end of the model output.

Model Output

     When the model has completed execution, the output will be
presented on the screen.  A portion of the model's output as it
would appear on the screen is shown in Figure E-12.  A complete
listing of the model's output is shown in Figure E-13.  The user
can scroll through the output with the / or /
keys.  A complete list of the SCREEN model output -is shown in
Figure E-13.  The user can scroll through the output using the
various keys shown.  The user can also graph, print or save the
entire output to a file.  The instructions for the keys used in
viewing the model output are explained in Section E.6 of this
appendix.

     The SCREEN model output begins with the time and date that
the model was run.  Next, there is the model name and version
number.  Following the model name is the run's title and the user
input.  Next, the output contains a summary of results showing
the maximum concentration and the distance to the maximum.  Next,
there is a list of concentrations for SCREEN's automated
distances.  Finally, there is a listing of the cavity
concentrations since the effects of building downwash are being
considered.  If additional averaging times had been selected,
these results would at the end of the model output.
                               E-10

-------
                  Figure  E-12.    Model Output on  the Screen
                   Continuous Particulate Hatter Releases from Stacks  - Scenario 4.1.1
                 ***  SCREEN-1.2 MODEL  RUN ***
                 ***  VERSION DATED  91/10 ***

                Particulate Stack Release

                SIMPLE TERRAIN INPUTS:
                   SOURCE TYPE           =    POINT
                   EMISSION RATE (G/S)    =    .9300E-03
                   STACK HEIGHT (M)       =    16.00
                   STK INSIDE DIAM (M)    =      .10
                   STIC EXIT VELOCITY  Graph
                                       Alt,
                                     

Print , , , Save to File Exit Figure E-13. Complete Model Output *** SCREEN-1.2 MODEL RUN *** *** VERSION DATED 91/10 *** Particulate Stack Release SIMPLE TERRAIN INPUTS: SOURCE TYPE = POINT EMISSION RATE (G/S) = .9300E-03 STACK HEIGHT (M) = 16.00 STK INSIDE DIAM (M) = .10 STK EXIT VELOCITY (M/S)= 17.8000 STK GAS EXIT TEMP (K) = 298.00 AMBIENT AIR TEMP (K) = 298.00 RECEPTOR HEIGHT (M) = .00 IOPT (1=URB,2=RUR) = 2 BUILDING HEIGHT (M) . = 19.00 MIN HORIZ BLDG DIM (M) = 19.00 MAX HORIZ BLDG DIM (M) = 19.00 05-02-92 13:16:50 ********************************** * SUMMARY OF SCREEN MODEL RESULTS CALCULATION PROCEDURE MAX CONC (UG/M**3) DIST TO MAX (M) TERRAIN HT (M) SIMPLE TERRAIN .8543 BUILDING CAVITY-1 1.717 BUILDING CAVITY-2 1.717 100. 28. 28. 0. (DIST (DIST CAVITY LENGTH) CAVITY LENGTH) r*W************W REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS ** E-ll


-------
BUOY. FLUX =     .00 M**4/S**3;  MOM.  FLUX =     .79 M**4/S**2.



*** FULL METEOROLOGY ***
*** SCREEN AUTOMATED DISTANCES ***
*** TERRAIN HEIGHT OF 0. M ABOVE STACK BASE USED FOR
DIST COHC U10M USTK MIX HT PLUME
(M) (UG/M**3) STAB (M/S) (M/S) (M) HT (M)
100.
200.
300.
400.
500.
600.
700.
800.
900.
1000.
1100.
1200.
1300.
1400.
1500.
1600.
1700.
1800.
1900.
2000.
2100.
2200.
2300.
2400.
2500.
2600.
2700.
2800.
2900.
3000.
3500.
4000.
4500.
5000.
5500.
6000.
6500.
7000.
7500.
8000.
8500.
9000.
9500.
10000.
15000.
20000.
25000.
30000.
40000.
50000.
MAXIMUM
100.
.8543 3
.4906 4
.3483 6
.3011 6
.2648 6
.2360 6
.2125 6
.1930 6
.1766 6
.1626 6
.1505 6
. 1420 6
.1327 6
.1245 6
.1172 6
.1107 6
.1048 6
.9939E-01 6
.9450E-01 6
.9003E-01 6
.8592E-01 6
.8214E-01 6
.7865E-01 6
.7542E-01 6
.7242E-01 6
.6963E-01 6
.6702E-01 6
.6458E-01 6
.6230E-01 6
.6015E-01 6
.5115E-01 6
.4429E-01 6
.3891E-01 6
.3458E-01 6
.3151E-01 6
.2857E-01 6
-2609E-01 6
.2397E-01 6
.22;4E-01 6
.2054E-01 6
.1914E-01 6
.1790E-01 6
.1679E-01 6
.1581E-01 6
.9929E-02 6
.7119E-02 6
.5491E-02 6
.4461E-02 6
.3229E-02 6
.2512E-02 6
1-HR CONCENTRATION AT
.8543 3
1.0 1.0 320.
1.0 1.1 320.
1.0 1.3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
t.O 1.3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
I.O 1.3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
1.0 1 .3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
1.0 1.3 5000.
I.O 1.3 5000.
1.0 1.3 5000.
I.O 1.3 5000.
1.0 1.3 5000.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
I.O 1.3 5000.0
1.0 1.3 5000.
1.0 1.3 5000.
.0 1.3 5000.
.0 1.3 5000.
.0 1.3 .5000.
.0 1.3 5000.
.0 1.3 5000.
.0 1.3 5000.
.0 1.3 5000.
.0 1.3 5000.
.0 1.3 5000.
.0 1.3 5000.
.0 1.3 5000.
.0 1.3 5000.
.0 1,3 5000.
.0 1.3 5000.
.0 1.3 5000.
OR BEYOND 100.
.0 1.0 320.
0
0
0
0
0
0 
0
0
0
0
0
0
0
0
0
0
0
N:
0
16.1
16.0
16.
16
16


16.
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
.
.
.

.
.

B
B
.
.
.
m
,
m
.

m
f
f
m

m
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
16.0
16
16
16
.
,

0
0
0
16.0
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16

16
f
.
,
B
.
,

m
.
a
.
.
.
.
B


.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

1
FOLLOUING DISTANCES **
SIGMA SIGMA
Y (M) Z (M) DUASH
12.5
19.6
22
25
28
32
35
38
41
44
47
50
53
56
59

.




a

B

^
.
m
5
7
9
0
1
2
2
2
2
2
2
1
0
61.9
64
67
70
73
76
79
81
84
87
90
93
95
98
101
114
m
n
m
.
,
m
9
m
.
m
f
m
0
B
B
8
7
5
4
2
1
9
7
5
2
0
8
5
3
8
128.2
141
154
167
180
192
205
218
230
242
254

m
m
^
m
m
m
m
B
B
5
5
5
3
9
5
0
4
7
9
267.0
279
396
508
617
722
927
1124

12
.
.
1
2
.4
B
.
B


a
0
7
0
0

5
15.3
21.9
22.8
23.3
23.9
24.4
24.9
25.4
26.0
26.5 
27.0
26.8
27.3
27.7
28.1
28.5
28.9
29.2
29.6
30.0
30.4
30.7
31.1
31.4
31 .8
32.1
32.5
32.8
33.1
33.5
35.0
36.6
38.0
39.4
40.0
41.1
42.3
43.3
44.4
45.4
46.4
47.3
48.2
49.1
55.8
61.0
65.5
69.0
74.6
79.3

15.3
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS

SS
 OIST
- DISTANCE FROM THE SOURCE
                                                E-12

-------
  CONC
  STAB
  U10N
  USTK
  NIX HT
  PLUME HT
  SIGMA Y
  SIGMA Z
  QUASH
MAXIMUM GROUND LEVEL CONCENTRATION
ATMOSPHERIC STABILITY CLASS (1=A, 2=8, 3=C, 4=0, 5=E, 6=F)
WIND SPEED AT THE 10-M LEVEL
WIND SPEED AT STACK HEIGHT
MIXING HEIGHT
PLUME CENTERLINE HEIGHT
LATERAL DISPERSION PARAMETER
VERTICAL DISPERSION PARAMETER
BUILDING DOUNUASH:
DWASH=   MEANS NO CALC MADE (CONC =0.0)
DWASH=NO MEANS NO BUILDING DOUNUASH USED
DWASH=HS MEANS HUBER-SNYDER DOUNUASH USED
DUASH=SS MEANS SCHULMAN-SCIRE DOUNUASH USED
DUASH=NA MEANS DOUNUASH NOT APPLICABLE, X<3*LB
 *** CAVITY CALCULATION - 1 ***
  CONC (UG/M**3)        1.717
  CRIT US 310M (M/S)     1.00
  CRIT US 3 HS (M/S)     1.10
  DILUTION US (M/S)      1.00
  CAVITY HT (M)        27.28
  CAVITY LENGTH (M)      27.97
  ALONGUIND DIM (M)      19.00

!> ***
*** END OF SCREEN MODEL OUTPUT **
                    *** CAVITY CALCULATION - 2 ***
                    CONC (UG/M**3)    =   1.717
                    CRIT US 31OM (M/S) =    1.00
                    CRIT US 3 HS (M/S) =    1.10
                    DILUTION US (M/S) =    1.00
                    CAVITY HT (M)    =   27.28
                    CAVITY LENGTH (M) =   27.97
                    ALONGUIND DIM (M) =   19.00
Save to  File

      If  the  'Save  to  File'  option is  selected,  the  user will be
asked to enter a  file name  of no more than eight characters  in
the  data entry window shown in  Figure E-13.    To view previously
saved model output at a later time, select 'File' from  the main
menu bar.   Then select 'Access  Model  Printer  Output'  and a list
of files containing previously  saved  model output will  appear as
shown in Figure E-14.   The.  menu in Figure  E-14  also contains
'Access  Data  from  Previous  Scenario'  which allows the user to
retrieve data from previously run scenarios by  selecting the
scenario's title  from a list.   The other menu item  is 'Access
Model Graphic Output'  which allows the user the retrieve a graph
from a list of files  containing previously saved graphs.
                                     E-13

-------
                         Figure E-13.   Save  to File

1
*** SCREEN- 1.2 MODEL RUN
*** VERSION DATED 91/10
Particulate Stack Release
03-04-9
15:47:0
***
**
SIN
Enter a unique file name for this model output -> .RPT
 Exit/ No Save
STK & EXIT tEWMK>
AMBIENT AIR TEMP ( 1C )
RECEPTOR HEIGHT (M)
I OPT "(1=URB,2=RUR)
BUILDING HEIGHT (M)
*s 298*80
= 298.00
.00
= 2
* 19.00
:-x "'
:'3$.
.}:;:.
?.'

, , ->, <->, Alt, Alt, , , , 
 Graph 

Print Save to File Exit Figure E-14. Retrieve Model Output Initial Form of Release File Chemical Database Quit Access Data from Previous Scenario . Accei'"" ""'"""'""''""'""" ''"'""''' ''''"'"Hode"l""Printed Output RVD4S RPT S411ALL RPT SCRNALL RPT Select Highlighted Run Exit/No Select Up Down Up One Screen Down One Screen Bottom <0el> Delete File Press any other key to find a file beginning with that character Graph If the 'Graph' option in Figure E-12 is selected, a plot of the concentrations vs distances will be drawn. The following window will appear first as shown in Figure E-15. E-14


-------
                  Figure E-15.   Distance  for Graph

                    	 Graphics - Distance 	
                     Enter Maxinun Distance for Graph > 5   Km

                        Graph is for Simple terrain only.


                               Use 50.00 Km
      In this example 5 km has been  selected.  JIf the  key
had been pressed,  the graph would be  plotted  from 100 m  to 50.00
km downwind.   Once a distance has been specified,  the following
menu  will appear as shown in Figure E-16 from which you  can
select an output device  for the graph'.

                 Figure  E-16.   Graphic Output Menu
                            Graphics - Main Menu
                            *: :-.::.  :-:  :  .>:; . : * :::. _  .:: :
                                   .      .
                       EPSOM FX, MX-Draft Quality
                       EPSON FX, MX  - High Quality
                       EPSON LQ     - Draft Quality
                       EPSON LQ     - High Quality
                       NEC Pinuriter - Draft Quality
                       NEC Pinwriter - High Quality
                       OKIDATA     - Draft Quality
                       OKIDATA     - High Quality
                       HP LaserJet/DeskJet - Draft Quality
                       HP LaserJet/DeskJet - High Quality
                       Hewlett-Packard plotter
                       Houston Instruments plotter
                       Change Distance for Graph
                       Save Graph to File
                              Exit Graphics
      From this  menu the output device  is selected.
example,  the user should  select 'Screen'.
For this
      Note that  if your computer does  not have  the ability to
display graphics,  the option 'Screen'  will not  be on this menu.
If a  printer  is selected  then the output device is assumed to be
LPT1.   If a plotter if selected then  the output device  is assumed
to be COM1.    For more information on  redirection of output,  the
user  should consult the DOS manual.   Before printing the  graph,
be sure that  the printer  is connected and on-line.   After
exiting from  che Graphics menu the user is returned no  che model
output.   Consult your printer's user's manual  to determine which
of the above  printers is  compatible with your  printer.

If 'Save Graph  to File' is chosen from the bottom of the  menu
shown in Figure E-16, then the data entry window in Figure E-17
will  appear.  Enter a filename of not more than eight characters.
                                  E-15

-------
If you choose to  save  the graph's .data, then the graph  can be -
generated at a  later time.   To view a previously saved  graph at a
later time, select  'File'  from the main menu bar.  Then select
'Access Model Graphic  Output'  and a list of previously  saved
graphs will appear  as  shown in Figure E-18.

                     Figure E-17.   Save Graph

             	 Graphics - Save 	
             Enter a unique file name for this graphic output ->
.GRF
                            Exit/ No Save
                   Figure E-18.  Retrieve  Graph
ili Initial Form of Release Chemical Database Quit
"''"'' cue 	 - 	   - ,
Access Data from Previous Scenario
Access Model Printer Output
fe*ES*?wtei;?^fi1:itir:::QtitpiJt


          noae i urapnic uuipui    ^ 
si*^r:rG*i
PUFFT GRF
SCRNP1 GRF
SCRNP6 GRF
 Select Highlighted Run  Exit/No Select
 Up  Down  Up One Screen  Down One Screen
 Top  Bottom <0el> Delete File
Press any other key to find a file beginning with that character



      If you  are using a plotter,  the DOS MODE command  should be
used  to configure your computer's communications port  to
correctly  match the communications settings of the plotter.
Otherwise, you will probably not get any output from the plotter.

      For example,  the Hewlett-Packard 7475A plotter has  a set of
switches located"on the back of the plotter which allows you to
set the communications parameters.  A common setting for these
switches is  shown in Figure E-19.

                Figure  E-19.   Switch Configuration

                         S2 S1 Y US A3 B4 B3 82 81

                                          1
                                          0
                                E-16

-------
The DOS MODE command which should be used to correspond to these
settings is:

     MODE COM1:96,E,7,1

This command sets  serial port 1 (COM1) to 9600 baud with even
parity, seven data bits,  and I stop bit.

     Each plotter  has unique methods of setting the
communications parameters.   You should use the plotter's manual
for the plotter  configuration in conjunction with your DOS
manual's explanation on the use of the MODE command to be certain
that your computer and plotter are configured correctly.

An example of the  graph whose descriptive title was saved as
"Particulate Stack Release" in the Data Entry Screen  depicted in
Figure E-6 is shown in Figure E-20.

        Figure E-20.. Graphic  of Concentration vs Distance
                      Part f cu 1 ate Stack Re t ease
                             DISTANCE (Km)
             Moxinun concentration 1.240E+000 ug/cubic r at 0.100 Km (Automated Distances)
                            Press any key to continue
Exiting TSCREEN

     After exiting  the  graph,  the user returns to the model
output viewing window shown in Figure E-13.  After pressing  
from this window  the  user 'will return to the main menu bar shown
in Figure E-2.  At  this point  the user can exit TSCREEN by
                               E-17

-------
selecting  'Quit' from the  main menu bar  as shown in Figure .E-21

                        Figure E-21.   Quit  Menu
          File  Initial Form of Release   Chemical Database
r                                                " "Quit TSCREEN ? -,
                                                  ,  ; **
                                                      *      h
          Help   /Scroll Vertical Menus   <->/<->ScrolI Horizontal Menu
           /Letter=Select Menu Item  Exit Current Menu  Exit All Menus
E.4   Scenario Selection

       Twenty-four  of most  prevalent release scenarios  were
selected for TSCREEN and are grouped according  to four
categories:'particulate matter, gases,  liquids,  and releases  from
Superfund  sites.

      To select a scenario  in TSCREEN, first select 'Initial Form
of Release'  from the menu  bar across the  top of the screen.   The
'Initial Form of Release'  Menu as  shown in Figure E-22 will then
appear.

             Figure E-22.   Initial Form of Release Menu
           File   5n:lt;i:at/fi(5FW:^|RHelp  /ScroU Vertical Menus    <<->/<->Scroll Horizontal Menu
           /letter=Select Menu Item  Exit Current Menu  Exit All Menus
      If the release is any solid  material such  as particulates,
dust,  of  ash, then 'Particulate Matter  Release  Type'  should  be
selected.   The menu in Figure E-23 will appear  listing
particulate scenarios.
                                   E-18

-------
        Figure E-23.   Particulate Matter Release Type Menu
          File  I&ttfet FftOft Of RtJi    Chemical Database
                  Initial Form of Release
Quit
                       Particuiate Matter Release Type
                                      Workbook Scenario

                 Fugitive/Windblown Dust Emissions - 4.1.2
                 Ducting/Connector Failures      - 4.1.3
          Help   /ScrolI Vertical Henus    <-->/<->Scroll Horizontal Menu
          /Letter=Select Menu Item  Exit Current Menu  Exit All Menus
      If the release is any matter in vapor from  such as  sulfur
dioxide,  volatile organics,  etc, then  the user should select
'Gaseous Release  Type'.  The menu in Figure E-24 will appear
listing gaseous scenarios.   Two scenario numbers for one  menu
choice  indicates  that there is both a  continuous (first  number)
and  instantaneous (second  number) scenario.

              Figure E-24.   Gaseous Release Type  Menu
File intf
Pai
Gat
Li
Su
Help
/Lei
t-1at:.form::o;f-; Release Chemical Database
- Initial Form of Release 	 .
ticulate Matter Release Type :f
M^:';R>l'8e--'Typ*'-.,7-...''- ..?''} "'--..

Stack's, 'Vents, Conventional Point Sources'
Leaks from Reservoir
Leaks from a Pipe Attached to Reservoir
Multiple Fugitive Sources
Land Treatment Facilities
Municipal Solid \/Scroll Vertical Menus <<->/<-*>ScroU Horizontal Menu
tter=Select Menu Item Exit Current Menu Exit All Menus
      If  the release is material that may immediately evaporate
(no pooling results)  or may  pool first  and then evaporate,  then
the user should  select 'Liquid Release  Type'.  The  menu in  Figure
S-25  will appear listing liquid scenarios.   Two scenario numoers
for one  menu choice indicates  that there is both  a  continuous
(first number) and instantaneous (second number)  scenario.
                                 E-19

-------
                  Figure  E-25.   Liquid Release Type
            File
                 .Tv.*:*^^"*:^:-:^*:-:*?:*:*?: ~" .1:7:7: ~
               i - Initial Form of Release
               Participate Matter Release
               Gaseous Release Type
                   Chemical Database   Quit
               ease	\
              ease Type  ';

              - '  "  '   -
               *<-.  <-v_'
                                  ,  , , ,,
                                 Liquid Release Type
                                                 Workbook Scenario
                  v "-:->."v:-:;:-XvT-.T5EvT.^':-.TT::".vrv:.-7 :*7:~.~.'''^**               2*"   u
                  2-Phase Saturated Liquid from Pressurized Storage - 3.2,3.3
                  2-Phase Subcooled Liquid from Pressurized Storage - 3.4,3.5
                  High Volatility Liquid Leaks               - 3.6,3.7
                  Lou Volatility Liquid Leaks                - 3.8,3.9
           Help   /Scroll Vertical Menus    <<->/<->Scroll Horizontal Menu
           /LetterSelect Menu Item  Exit Current Menu  Exit All Menus
      If  'Superfund Release Type'  is  selected then  the menu in
Figure E-26 will  appear  listing Superfund scenarios.

                 Figure E-26.   Superfund Release  Type
           File
                   Chemical Database
r initial Form of Release
Particulate Matter Release Type
Gaseous Release Type
Liquid Release Type
Quit
                        Superfund Release type
                              Workbook Scenario
           Help   /Scroll Vertical Menus    <-->/<-.>ScroU Horizontal Menu
           /Uetter=Select Menu Item  Exit Current Menu   Exit All Menus
E.5   Determining  Maximum Short-Term Ground Level Concentration

      Maximum short-term  ground  level  concentrations in TSCREEN
are  based  on three current EPA  screening models  (SCREEN,  RVD,  and
PUFF)  that are imbedded  in the  TSCREEN model  and an
implementation of the Britter-McQuaid model.   SCREEN is  a
Gaussian dispersion model applicable  to continuous  releases of
particulate matter and non-reactive,  non-dense gases that are
emitted from point,  area,  and  flared  sources.   The  SCREEN model
implements all of the single source short-term procedures
contained  in the  EPA screening  procedures document  (EPA,  1988a).
This includes providing  estimated maximum ground-level
concentrations and distances to the maximum based on a pre-
selected range of meteorological conditions.   In addition,  SCREEN
has  the option of incorporating the effects of building  downwash.
The  RVD model  (EPA,  1989)  provides short-term ambient
concentration estimates  for screening pollutant sources  emitting
                                   E-20

-------
denser-than-air gases and  aerosols through vertically-directed
releases.   The model is based on empirical equations derived  from
wind tunnel tests and estimates the maximum  ground level
concentration at plume touchdown at up to 30 downwind receptor
locations.   The PUFF model (Petersen, 1982)  is  used where the
release  finite but smaller than the travel time (i.e., an
instantaneous release.)  This model is based on the Gaussian
instantaneous puff equation and is applicable for neutrally
buoyant  non-reactive toxic air releases.  The Britter-McQuaid
model  is used for continuous and instantaneous  denser-than-air
scenarios.

E.6  Enter/Edit Scenario Data

     This  section provides a description of  the use of the
various  keys and data entry procedures.

Data Fields

     Data  for each scenario is entered in two sections.  There is
the scenario input section which contains a  unique set of inputs
for each scenario.  The user enters this section first and inputs
data.  Based-on user data,  one of the four models is selected by
TSCREEN, and the user proceeds to the model  input section.  The
inputs for this section are unique for each  model although they
are not  unique for each scenario.  For certain  scenarios there is
no unique  scenario input section, and the user  proceeds directly
to the model input section.   Each input section starts with 'Page
1 of.  .  .  '.  A typical data entry window for a scenario input
section  is shown in Figure E-27.

              Figure E-27.   Typical Data Entry Window
            	 Flared Stack Emissions - Scenario 2.1
            Based on user input, SCREEN model has been selected.

            SCREEN MODEL INPUTS - Page 1 of 7
            Enter a unique title for this data's model run:
            RELEASE PARAMETERS
            Enter the Emission Rate (Qm), if unknown enter
                 the boxed variables below to calculate ->
Volume Fraction of Pollutant (Vol) -> ;
Material Flow Rate (V) ->
Molecular Weight of Material Released (Mw) ->
ip X
; : cubic m/s
: g/g-mole
                        Total Heat Release Rate (Hr) >
                     Release Heignt above Ground (Us) ->
,,,?;' g/s
ip *
; : cubic m/s
: g/g-mole


              Help     Calculator
 Previous Screen   Abort
Commands active while editing  data fields include:

 - Help  on current field

                                E-21

-------
 - Calculator
 - Return to previous screen
 - Abort entry and return to the main menu bar

The keys that can be used for editing while in the highlighted
data entry fields are as follows:

 or  - toggle insert/overwrite mode  (cursor changes
size)
 or  - delete character at cursor position
<*-> (left arrow) - move cursor left one character
<- (right arrow) - move cursor right one character
<*-> (Control key and left arrow) - move cursor left one
word
<-*> (Control key and right arrow) - move cursor right one
word
 - move cursor back one character and delete character
 - move cursor to 'beginning of data in field
 - move cursor to end of data in field

Valid entry into numeric fields are numbers, minus signs(-), plus
signs(+),  a decimal(.), and the letter E or e to stand for
scientific notation (6.02E026 = 6.02e026 = 6.02E+26 = 6.02e+26 =
6.02 x 1026) .

Titles

   .  An important data field in TSCREEN for rerunning old
scenarios is the Scenario Title field.  This field should contain
a unique title for each run.  Several ways to make the title
unique are to give the facility name or add example 1, example 2,
etc,  or the date and time to the title.  This is helpful when the
user wants to retrieve data from a previously entered scenario
run by selecting 'File' from the main menu bar then selecting
'Access Data from Previous Scenario'.  The selection window will
appear allowing the user to view the titles of all previously run
scenarios.  A previous scenario may be selected to either run
again or update the data for another run.  This window is shown
in Figure E-28.  The last scenario entered appears at the bottom
of the list.
                               E-22

-------
Figure E-28.   Previously  Entered Scenarios
 Initial Form of Release
	 File	1
                                   Chemical Database
Quit
          Acce
          Acce
                             Previous Scenario
              Johnson WJdset Cowpany RanOOt
              Oust E ject i oh Number 21720/92
              Cont. Part. Stack Release-Power Plant-1/20/92
              Particulate Stack Release
                  Select Highlighted Run   Exit/Mo Select
               Up  <1> Down   Up One Screen   Down One Screen
                     Top   Bottom  <0el> Delete Run
              Press any other key to find a title beginning with that character
      From this window a previous  scenario's data  can be reloaded
 by highlighting  that scenario's title and pressing  the 
 key or clicking  with the mouse.   The 'Initial Form  of Release'
 menu will appear with the highlighted bar on the  form of release
 of the selected  scenario.  By selecting the highlighted bar on
 the preselected  release type, a second menu will  appear with the
 appropriate scenario name and number highlighted.   By selecting
 this scenario, the  data entry windows of the scenario are
 displayed with the  data fields filled with the loaded scenario's
 data.   Menu selections can be changed at any point,  but changing
 the selections will cause the loaded data to be lost,  and the
 user will have to retrieve that scenario's data again from the
 menu in Figure E-28.

 Calculated Fields

      Some of the data entry screens  have fields that can be input
 directly or calculated automatically from certain other
 parameters.  The alternative parameters will be located inside a
 box directly below  the unknown parameter.   In Figure E-29,  the
 user did not know the emission rate;  therefore, the data fields
 in the box were  entered.  Once all of the boxed variables were
 entered, the emission rate was calculated and displayed.  If the
 screen is reedited  and the calculated field is changed then the
 other parameter  fields making up  the calculated value will be
 blanked out.  If the emission rate is known it can  be entered
 directly and the program will automatically skip  over the
 parameter fields in the box.
                                 E-23

-------
            Figure E-29.   Calculated Field Illustration
            - Flared Stack Emissions  Scenario 2.1
             Based on user input, SCREEN model has been selected.

             SCREEN MODEL INPUTS - Page 1 of 7
             Enter a unique title for this data's model run: .
                                    ' -
             RELEASE PARAMETERS
             Enter the Emission Rate (dm), if unknown enter
                  the boxed variables below to calculate -> &v0t}3S?5 g/s
                     Volume Fraction of Pollutant (Vol) -> .2  "  X
                             Material Flow Rate (V) -> 4*58 "  cubic m/s
               Molecular Weight of Material Released (Mw> -> 78,1   g/g mole
F2>- ?dft
                         Total Heat Release Rate (Hr) -> 3.346?  cal/s
                      Release Height above Ground (Hs) -> 32    m
                               Streert   A&ort
End  of Screen Action

      Once data entry  on the screen has  been completed,  the
program presents the  user with  a chance to visually review the
data entered  on the current screen as shown in  Figure E-29. The
only active keyboard  commands are highlighted at  the bottom of
the  screen:

        -  Edit the current screen
        -  Return to previous screen
       -  Proceed  to next screen
       -  Abort current scenario and return  to main  menu bar

Field Sensitive Help

      The help facility (see Section E.7.)  can be  accessed by
pressing the   key from any  of the selection menus or data
entry fields.   After  pressing the   key a window with help
text will appear to further define or clarify the current data
entry field.   The user can then scroll  up or down through the
help text or  view help for other data fields using the  buttons on
the  left side of the  help window.  An example of  a help screen is
shown in Figure E-30.
                                  E-24

-------
                    Figure E-30.  Sample  Help  Screen
               Evaporation from Surface Impoundments (Lagoons) - Scenario 3.1

                      T  Emission Rate  Scenarioi 3.1j
              Topics 
              Next  >

             Previous >

             Look Up >
             See Also
    Emission rates from well-mixed aqueous waste in surface
    impoundments are described in section 4.3.1 in the
    workbook. The following is a simplified screening emission
    rate estimate based on parameters described in the
    workbook:

      E = KCoA
      where:
        E * emission rate
        Co - initial concentration of
            waste (g/cubic m)
        A = area of impoundment (m1 )
        K - equilibrium constant
                                                the chemical in the
                Help   Calculator    Previous Screen    Abort
Chemical  Look-up Database

      The  chemical  look-up database  is a  table  of chemicals and
their associated parameters that are applicable to  TSCREEN.
TSCREEN is initially distributed with only two chemicals.   Any
desired chemical and its  associated parameters may  be added  to
suite the specific  needs  of the user.  The chemical database  can
be  accessed in two  ways.   First, the chemical  database can
selecting 'Chemical Database'  from  the main menu bar.  If  this
selection is made  the menu shown in Figure E-31 will appear.

                 Figure  E-31.   Chemical  Database Menu
            File
Initial Form of Release
Chemical totafas8   Quit
  I	 Chemical Database 	
  Ssrct> ttw Database
  Add a Chemical to Database
           Help   /Scroll Vertical Menus    <-->/<->Scrol I Horizontal Menu
            /Letter=Select Menu Item  Exit Current Menu  Exit All Menus
      To  search the  chemical database for  a specific  chemical,
select  'Search the  Database' and a  scrollable  window appears  with
a list of  the  available  chemical names as shown in Figure E-32.
                                    E-25

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                  Figure E-32.   Chemical Name List
                               Chemical Name
               CHLORINE
                 Select Highlighted Chemical  Exit/No Select
                Up  Down  Up One Screen  Down One Screen
                           Top   Bottom
                Press key to find a chemical beginning with that character
      The chemical names  contained  in the database will be
displayed in  alphabetic  order.  The highlighted bar  can be moved
directly to first chemical name starting with a certain letter
just  by pressing that  letter key.   The 'Chemical Name'  window
will  size itself proportionally to the number of chemical names
contained in  the database up to the number  of chemical names  that
can fit on the  screen.   After a chemical is selected,  the
chemical parameters will be displayed.

      If 'Search Chemical Database'  was selected from the menu in
Figure E-31,  the Chemical Database parameter window  in Figure E-
33 will appear.   If  is pressed,  the user can edit the data
in any of the fields except the Chemical Name.   If  is
pressed,  the  user can  delete the chemical that is currently in
the window.   If   is pressed,  the user  will return to the
chemical list.

             Figure  E-33.   Chemical Database Parameters
                               Chemical Data
            Chemical Name 86K2ENE
            Boiling Point at Ambient Pressure	 351    K
            Specific Heat of Liquid
              at Constant Pressure	  '":::: ''V' J/kg "K
              at Constant Volume 	     . i J/kg K
            Specific Heat of Vapor
              at Constant Pressure 	      ; j/kg K
              at Constant Volume 	       J/kg "K
            Molecular Weight 	 7B..1H^"'; kg/kmol
            Latent Heat of Vaporization 	 5.93865? J/kg
            Liquid Density 	 J5787E-5 g cubic m
            Critical Temperature	 SS&ifSH K
                 Edit
<0el> Delete
 Exit View Screen
      If 'Add a  Chemical  to Database'  was selected from the menu
in Figure E-31,  the Chemical Data  window in  Figure E-33 will
appear.   A chemical list will not  appear.  A chemical  name must
be entered before any of the other parameters can be entered.   If
 is pressed,  TSCREEN will ask if the new chemical is to  be
saved.   Then the user will return  to  the menu in Figure E-35.
                                  E-26

-------
       Figure E-35.   Chemical Database  Parameters for  Adding
                                Chemical Data
             Chemical Name "  .   ..  '
             Boiling Point at Ambient Pressure.
             Specific Heat of Liquid
              at Constant Pressure	
              at Constant Volume 	
             Specific Heat of Vapor
              at Constant Pressure 	
              at Constant Volume 	
             Molecular Weight 	
             Latent Heat of Vaporization 	
             Liquid Density 	
             Critical Temperature	
J/kg "K
J/kg "1C

J/kg "K
J/kg K
kg/kmol
J/kg
g cubic m
"K
                     Up
                              Down
                                        Exit Add Screen
      The second way to enter the  chemical database  is by
accessing  help for a data entry  field  that is  a chemical
parameter.   If the user  enters the chemical database  from  a data
entry field,  a value from the database can be  returned to  that
field..  A  pointer  '*' will appear beside the value  that will be
returned.   For example,  if the user, were in a  molecular weight
input field,  the user could press ,  and help for  that  field
would appear.   After pressing  to exit the help  window,  the
chemical list shown in Figure E-32 would appear.  The menu shown
in Figure  E-31 does not  appear if the  chemical database is 
accessed through a data  entry field.   After the user  chooses the
desired chemical,  the chemical look-up screen  would appear as in
Figure E-33.   The  ,  ,  and  keys work as described
above when 'Search Chemical Database'  was selected  from the menu
in Figure  E-31.  Pressing  will exit the chemical database
and  return the marked value to the data entry  field.

  Figure  E-36.   Chemical Database Accessed  from  Data Entry Field
                                Chemical Data
             Chemical Name BENZENE
             Boiling Point at Ambient Pressure	 JSt,   : K
             Specific Heat of Liquid
              at Constant Pressure	  ::   :: J/kg "1C
              at Constant Volume	     J/kg "1C
             Specific Heat of Vapor
              at Constant Pressure 	    -: :L- J/kg K
              at Constant Volume 	  : ""  : J/kg K
             Molecular Weight 	 78*12  kg/kmol
             Latent Heat of Vaporization 	 3953ES J/kg
             Liquid Density 	 .SToTE-S g cubic m
             Critical Temperature 	 562..Q9  "K
             Edit <0el>0elete Exit/Select Data  Exit/No Select
                                   E-27

-------
Calculator
     When entering data,  a calculator is available on-line to
perform any heeded calculations. The calculator is accessed by
pressing the   key from any data entry  field.   The results of
a calculation can be passed directly from  the  calculator to the
entry field by pressing the equals <=> key.  While in the
calculator a  help screen on the calculator's functions can be
accessed by pressing the  key.  The calculator has several
built-in functions that include memory clear,  memory store,
memory recall,  square,  square root and it.  An  example of the
calculator is shown below in Figure E-37.

                     Figure  E-37.   Calculator
            Evaporation from Surface Impouncknents (Lagoons) - Scenario 3.1

            SOURCE PARAMET5

            Enter a unique
            IMPOUNDMENT TYP
                  Enter

            EMISSION RATE
            Enter the Emiss
                 the box
                    In
              Help


F1
HELP

F2
MC

F3
MS

Ft,
MR

"



7

4

1

0

F5
SO



8

5

2



F6
SR



9

6

3

S


F7
PI



+

-

*

/

E


g/s
g/cubic m
ra

n:::  Ahnrr
Model Output

     Upon  completing the last screen of data  entry for the
scenario,  the   command is 'Run Model' and  not 'Next Screen'
When the  key is pressed, the entered data is saved.  The
dispersion model  then executes.  For computers  without math co-
processors, the SCREEN model will execute for 3 to 10 minutes,
the RVD model  for 1 to 5 minutes and the PUFF model for 1 to 5
minutes depending on the data and the computer  setup on which
TSCREEN is running.  The model output will appear on the screen
in a window as shown in Figure E-38.
                                E-28

-------
                     Figure E-38.   Output Window

              Continuous Paniculate Matter Releases from Stacks - Scenario 4.1.1
                                                        03-04-9
                                                        15:47:0
             ** SCREEM-1.2 MODEL RUM ***
             *** VERSION DATED 91/10 ***

            Continuous Participate Stack Release from Power Plant

            SIMPLE TERRAIN INPUTS:
              SOURCE TYPE        =  POINT
              EMISSION RATE (G/S)   =  1200.
              STACK HEIGHT (M)     =  20.00
              STK INSIDE DIAM (M)   =   1.50
              STIC EXIT VELOCITY (M/S)=   5.00
              STK GAS EXIT TEMP (K) =  400.00
              AMBIENT AIR TEMP (K)  =  293.00
              RECEPTOR HEIGHT (M)   =    .00
              IOPT (1=URB,2=RUR)   =   2
              BUILDING HEIGHT (M)   =  25.00
              MIN HORIZ BLDG DIM (M) =  20.00
              MAX HORIZ BLDG DIM (M) =  45.00
  Alt,

Print Graph , , , Save to File Exit The model output can be scrolled line by line up or down by pressing the up or down arrow keys. The output can be put into a continuous scroll up or down by pressing the Alt - up or down arrow key combinations and stopped by pressing any key. The output can be scrolled a full screen at a time by pressing the or keys. By pressing the key the output display will show the top of .the output listing and by pressing the key the display will show the end of the output listing. To get a listing of the output on a printer press the

key. To avoid some common printing problems, before selecting printed output, make sure that a printer is connected to the computer, that the printer's power is on, that the printer is on- line and that there is plenty of paper loaded in the printer. To save the output data to a file press the key and give a filename for the output. To get a graph of the concentrations vs distances press the key. E.7 Help System The help system included with TSCREEN is field sensitive. As a result, when the key is pressed from a data entry field or from a menu item, help for that field or menu item will appear in a help window like the one shown in Figure E-39. E-29


-------
                 Figure E-39.  Example Help  Window
                         Liquid Release Type
                    A Liquid type release is a release of material that may
                    immediately evaporate (no pooling results) or may pool
                    first and then evaporate.
                    See Also: Release Definition, Pool Definition, Evaporation
                    Definition
     After  the  entering the help system,  the user can access  help
for any data  entry field or menu item  in  TSCREEN pressing  the
"buttons" on  the panel on the left side of  the help window.
These buttons can be pressed in three  ways:

        The user can click on the button  with a mouse.

        The user can highlight a button and  then press   to
        select  that  button.  To highlight a  button,  press  the
         key to first highlight the     Topics    button.
        Press   again to move to each succeeding active
        button  on the panel.  If a button is not active, its
        feature will not be available, and it will be a different
        color than the other buttons.

        Each  button has a letter that  is  a different color (i.e.,
        a "hot-key").  Press that key  to  select that button.

     Each button's function is described  below:

 Topics  

     If this  button is pressed, the  table of contents of the  help
     system will appear in the help  window.   A portion  of  the
     table  of contents is shown in Figure E-40 as it would appear
     if    Topics    where pressed from the help window  in
     Figure E-39.  From the table of contents, the user can
     scroll to  and select any definition  in the help system.   The
     table  of contents is organized  as follows: 1) help for the
     menu  items 2) help for the model  inputs  (SCREEN, PUFF, RVD,
     and Britter-McQuaid) 3) help for the scenario inputs  in  the
     order  they appear in the workbook and 4) a Glossary of
     terms.

     Once  the topic of interest has  been  highlighted, press
                                E-30

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       or select the  HELP   button by the methods listed
     above.

           Figure E-40.  Help System Table of Contents
            File
            Access Data From Previous Scenario
            Access Model Print Output
            Access Model Graphic Output
            Quit

            Initial Form of Release .
            Particulate Matter Release Type
            Gaseous Release Type
                 Release type '
                               Help 
   Next
     If this  button is pressed, the  next help definition as
     listed in the table of contents will appear.
< Previous >
     If this  button is pressed, the  previous help definition as
     listed in the table of contents will appear.
< Look Up >
     This button is not active when  the help window first
     appears.   To make this button active,  mark  (i.e.,  highlight)
     a portion of text in the'help window.  Text can be  marked by
     holding  the mouse button and dragging the mouse or by
     holding  down the  key and moving the arrow  keys.
     Once text has been marked, press this button to bring up
     help if  the marked text is an item in the table of contents.
     If the marked text is not in the table of contents, another -
     window appears as shown in Figure E-41 that contains  a list
     of the topics in the table of contents.  In this example
     "Retrieve"  was marked and  <  Look Up  > was pressed.   Since
     this was  not found in the table of contents, a second window
     opens and 'Richardson Number Definition' is highlighted
     because  it  is the closest topic alphabetically to
     "Retrieve".
                                E-31

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      Figure E-41.   Look Up Window when Topic Is Not Found
4
:?
i <
s
.V ^
X;
1 <
;::
:
'-.
&
t ropics 
E Next >
: Previous >
: Look Up >
See Also


No help found for Retrieve
Available Help Topics:
Molecular Weight Definition
Neutral Definition
Passive Release Definition
Pool Definition
Reactive Definition
Release Definition
tffiMi*}&Mifiii&miffi&ffi&
i
 Select 
< Cancel >
Slumping Definition 
Temperature of Release Mater|
Two-phase Release Definition!

                                                    Scenario
     This button  is  only active  if there is  a "See Also"  list of
topics  in the help window.  If this button  is active and  is
pressed a window  will appear as  shown in Figure E-42 that lists
the topics to cross-reference.   Making a selection from this menu
will bring up the help definition for the selected item.

                   Figure  E-42.   See Also Example
            Topi cs 

           <  Next  >

           < Previous >

           < Look Up >
     Liquid Release Type
A Liquid type release is a release of material that may
immediately evaporate (no pooling results) or may pool
first and then-evaporate.
             Release
             Pool' Definition"
             Evaporation Definition
        lease Definition, Pool Definition, Evaporation :
      When a topic is selected from the See  Also menu  and help  for
that  topic appears in the help window, the  first item of the new
topic's See Also  menu contains a reference  to the topic from
which the new  topic was called.   Using the  See Also menu from  the
new topic, the user can then return to the  original topic.  For
example,  if "Release Definition" was selected from the menu in
Figure E-42, the  help definition in Figure  E-43 will  appear.   The
                                 E-32

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first  item in the See  Also menu for  "Release" is  "Liquid Release
Type"  which the user can select to return to the  help  definition
for  "Liquid Release Type".

              Figure E-43.  Cross-Referenced Help Item

                                Kelp                      *

          ::j  Topics   |        Release
          *-";:
          i; <  Next  >
          :* < PrCVIOUS >

          ? < Look Up >
Chemicals or pollutants leaving containment, stacks, or
vents.
E.8  Error Handling

     If  an error occurs  while TSCREEN  is  running a window like
the one  shown in Figure  E-44 will appear.   This window contains
an error message, the  FoxPro  error number, the  procedure  in
which  the error occurred,  and the line number in the  code at
which  the error occurred.

                 Figure E-44.  Error Message Window
                WARNING:
                            Error Number
                            In Procedure
                            At line number
                  The error information above are saved in: ERROR.OUT

                  Please save this file for use in error diagnosis.

               Press any key to continue ...
      If  an error occurs,  data entered up  to the point  at  which
the error  occur will be  saved.   The data  can be retrieved by
selecting  'File' from  the main menu bar then selecting ''Access
Data  from  Previous Scenario'.   The data will be the last  item on
the list with appears.   In addition, the  error information from
the window in Figure E-44 will be saved in the file "ERROR.OUT".
This  file  should be saved for error diagnosis.   After  the user
exits the  window shown in Figure E-44, the user will exit
                                E-33

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TSCREEN.

     If an error occurs while a Model is running, the ERROR.OUT
file will contain the data that was sent to the Model and the
error message which will appear in the error window that is
displayed.  After the user exits the error window that is
displayed when an error in a model occurs, the user will return
to the main menu bar.
E.9  Backing Up Data

     The file BACKUP.COM that comes with DOS must be in the DOS
PATH as explained in 2.0 GETTING STARTED.  To backup the data
enter the command:

     BACKUP X:\TSCREEN\*.* A: /S

where X is the drive letter where the TSCREEN system resides.
Note that it is important .to back up every time data is edited or
added in case of a hard disk failure.

     The number of backup disks needed depends upon the amount of
data entered into the system.  As more data is entered, more
backup disks will be required to store the data.  These disks
must be formatted prior to backing up the data files.  Backup
disks should be labeled accordingly and stored in a safe place.

     To ward off data corruption, rotating back up disks is
recommended.  Rotating backup diskettes consists of 2 or 3 sets
of backup diskettes that are rotated when the backup procedure is
called. " In using a rotating backup procedure you can minimize
the possibility of backing up bad data and having corrupt files
on the system and on the backup disks.

     The BACKUP.COM program fits as much data on one disk as it
is'physically capable of storing.  If the program is in the
middle of backing up a file it will split it and store the
remaining part of the file on another disk(s).   These backed up
files are not DOS compatible files, DO NOT copy them to another
disk, especially NOT to the hard disk.  The only way these files
can be used is to first restore them with the DOS RESTORE.COM
program (discussed below).  These diskettes are created for
backup purposes only and are to be restored only when the data
files on the hard disk have become damaged beyond repair.

     The command to restore the data files is:

     RESTORE A: X: /S

where X is the drive letter where the TSCREEN system resides.
Note that the RESTORE.COM file must be in the DOS PATH in order
to execute this program from any prompt.   This command should be


                               E-34

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 used only when there has  been damage  done  to the data files on
 the  hard disk!

 E.10  Notes  on Compiling  the Source Code

 The  procedure  described on this  page  is  only for those who wish
 to make  changes in the  source code  and recompile it.   Only
 someone  with experience using computers  and preferably with
 compilers should attempt  this procedure.

 TSCREEN  is written in and compiled  with  FoxPro Version 2  and
 Microsoft C Version 5.1.  One C library was used: INGRAF
 Version  2.10 by Sutrasoft.   The  program  source  code  is available
 from  the SCRAM Bulletin  Board phone  (919)  541-5742.   Technical
 questions should be directed to  Jawad S. Touma;  Office of  Air
 Quality  Planning and Standards;  Technical  Support Division/
 Source Receptor Analysis  Branch  (MD-14)/ Research Triangle Park,
 NC   27711, phone (919)  541-5381.

 FoxPro Version 2.0 or later, C Version 5.1 or later, and
 INGRAF Version 2.10 or later are necessary to compile the
 source code.   All of the  .PRG (FoxPro)  files and .C  (C) files
 should be on a hard disk  with the following files:

      C
 CL.EXE
 LINK.EXE
 MLIBCE.LIB
 SLIBCE.LIB
 [STRING.H]
 [STDIO.H]
-[STDLIB.H]
 [PROCESS.H]
 [MATH. H]
 [DOS.H]
 [10.H]
         The  files in brackets are included with the  Microsoft C
 compiler

      INGRAF
 INGRAF.LIB
 IGEXTERN.H

 Note that you  may have  to change the  path  specifications in these
 files as well  as in the C files.    The compilation process will
 create:  TSCREEN.EXE,  GRAPH.EXE
                               E-35

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                                    TECHNICAL REPORT DATA
                  (Please read  Instructions on  reverse before completing)
1. REPORT NO.
   EPA-454/R-92-024
                                                             3. RECIPIENT'S ACCESSION MO.
4. TITLE AND SUBTITLE
             5. REPORT DATE
               December 1992
   Workbook of Screening Techniques  for Assessing
   Impacts of Toxic Air Pollutants
             6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
                                                             . PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
                                                              10. PROGRAM ELEMENT NO.
   Pacific Environmental Services
   5001  South Miami  Blvd.
   Research Triangle Park, NC 27709-2077
                                                              11. CONTRACT/GRANT NO.
                                                                 EPA Contract No. 68-D00124
12. SPONSORING AGENCY NAME AND ADDRESS
                                                              13. TYPE OF REPORT AND PERIOD COVERED
   U.S.  Environmental Protection  Agency
   Office of Air Quality Planning and Standards,  TSD
   Research Triangle  Park, NC  27711
                                                                 Final Report
             14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
   This  document  revises EPA-450/4-88-009
   Technical Representative:  Jawad S. Touma
16. ABSTRACT
      This workbook  provides a logical approach  to the selection of appropriate
screening techniques  for estimating ambient concentrations  due to various
toxic/hazardous pollutant releases.  Methods used in the workbook apply  to  situations
where a release can be fairly well-defined, a condition typically associated with non-
accidental toxic  releases.  The  format of this  workbook is  built around  a series of
release scenarios which may be considered typical and representative of  the means by
which toxic chemicals become airborne.  For each release scenario, the workbook
describes the procedure to be used and provides an example  illustration  using the
TSCREEN model.  TSCREEN, a model for screening  toxic air pollutant concentrations is an
IBM  PC-based interactive model,  that provides screening techniques for estimating
impact from various air pollutant releases.  TSCREEN allows the user to  select a
scenario, determine an emission  rate, and then  apply the appropriate dispersion model
in a logical problem  solving approach.
                                     KEY WORDS AND DOCUMENT ANALYSIS
                  DESCRIPTORS
                                             b. IDENTIFIERS/OPEN ENDED TERMS
                                                                               c. COSATI Field/GrouD
    Air Pollution
    Hazardous Waste  Assessment
    Toxic Air Pollutants
    Dense Gas
    Air Quality Dispersion Model
    TSCREEN Model
Dispersion Modeling
Meteorology
Air Pollution Control
                                                                                    123
18. DISTRIBUTION STATEMENT

   Release Unlimited
                                             1*. SECURITY CLASS IKtport I
                                                  Unclassified
                               21. NO. OF PAGES
                                  315
                                             20. SECURITY CLASS IPig*)
                                                  Unclassified
1PA form 22ZO-1 (Rwr. 4-77)
                      PREVIOUS EDITIOH IS OBSOLETE

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