EPA
500
G  ,
B
92
001
  4
           United States
           Environmental Protection
           Agency
                        Solid Waste And
                        Emergency Response
                        (OS-420) WF
EPA500-C-B-92-001
March 1992
vxEPA    Hyperventilate Users Manual

           A Software Guidance System
           Created For Vapor Extraction
           Applications
             Ground Surface
                          Pump

                           I

                           oi.
                         Well
                        Contaminated
                        	
                                ubte
                               Flame
                                    Vapor Treatment
                                       Unit
                                       I
                                    Printed on Recycled Paper

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                                                         *
                                                        j
SOFTWARE heW by Library  I
Database Coordinator,
please inquire at Circulation Desk

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Hyperventilate
Users Manual
  A Software Guidance System Created for Vapor Extraction Applications
       A Practical Approach to the
         Design, Operation, and
        Monitoring of In-Situ Soil
            Venting Systems
                wnioa 1.01
           » Hyj»rC«* Stick Cnitii ly:

           Panic. Johnson, Pfc.D.
             AmyJ. SUbeaan

              Shen Development
           WesthoDov Research Center
        About This Stack
                     Go to First Card
  Economics   \_
System Monitoring

  Field Teats •
                System Design
-
                                                  Vapor   f f
                                                 Treatment I
                                                         Vapor
                                                         Ptov
                                  by

                          Paul C Johnson, Ph.D.
                            Shell Development
                        Westhollow Research Center
                           Environmental R&D
                             P. O. Box 1380
                           Houston, TX 77251
                     Apple® Macintosh™ HyperCard™
                          compatible version 1.01

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C'
JJ
Disclaimer

The Hyperventilate software package was completed under a Federal Technology Transfer
Act Cooperative Research and Development Agreement between EPA arid Shell Oil
Company, signed in 1990.

EPA is facilitating the distribution of Hyperventilate because the Agency has found the
software and manual to be helpful tools, especially in teaching users about in situ soil
venting and in  guiding them through a structured thought process to evaluate the
applicability of soil venting at a particular site.  EPA's Office of Underground Storage
Tanks advocates the use of innovative cleanup technologies, and in situ soil venting is
recognized as an effective remediation alternative for many underground storage tank sites.

Hyperventilate is based on the document titled, "A Practical Approach to the Design,
Operation, and Monitoring of Soil Venting Systems" by P. C. Johnson, C. C. Stanley, M.
W. Kemblowski, J. D. Colthart, and D. L. Byers, published 1990 by Shell Oil Company.
The program asks a series of questions and forms a "decision tree" in an attempt to identify
the limitations of in situ soil venting for soils contaminated with gasoline, solvents or other
relatively volatile compounds.

EPA and Shell Oil Company make no warranties,  either express or implied, regarding the
Hyperventilate computer software package, its  merchantability, or its fitness for any
particular purpose.  EPA and Shell Oil Company do not warrant that this software will be
error free or operate without interruption. EPA and Shell Oil Company do encourage
testing of this product.

EPA will not provide installation services or technical support in connection with the
Hyperventilate computer software package. Neither will EPA provide testing, updating or
debugging services in connection with the enclosed computer software package.

The Hyperventilate computer software package and this manual are not copyrighted.
                                      For sale by the U.S. Government Printing Office
                               Superintendent of Documents, Mail Stop: SSOP, Washington, DC 20402-9328
  OQ
  UJ
  U-
                                         HEADQUARTERS LIBRARY
                                         ENVIRONMENTAL PROTECTION AGENCY
                                         WASHINGTON, O.C. 20460

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                        -Hyperventilate Users Manual -
Disclaimer

Shell Oil Co. makes no  warranties, either express or implied, regarding the
enclosed  computer software package, its merchantability,  or its fitness for
any  particular purpose.  Shell Oil Co.  does not warrant  that  this software
will  be error free or operate without interruption.   The exclusion of implied
warranties is not permitted by some states.   The above  exclusion may not
apply to you.  This warranty provides you  with specific legal rights.   There
may be other rights that you may have which  vary from state to state.
Apple is a registered trademark of Apple Computer, Inc.

Macintosh and HyperCard are trademarks of Apple Computer, Inc.

f77.rl is a product of Absoft Corp
Comments/Suggestions?

Comments and/or suggestions about the usefulness of this program can be mailed to:

                              Paul C. Johnson
                              Shell Development
                         Westhollow Research Center
                               P.O. Box 1380
                               RoomEC-649
                          Houston, TX-77251-1380

Please do not  call the author and/or Shell with questions about the  use  or
interpretation of results from  this program.

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Foreword

Hyperventilate is a software  guidance system for vapor extraction (soil venting)
applications. Initial development of this program occured under the Apple Macintosh
HyperCard environment, due to its programming simplicity, ability to incorporate text and
graphics, and interfacing with other Macintosh programs (such as FORTRAN codes, etc.).
The objective was to create a user-friendly software package that could be both educational
for the novice environmental professional, and functional for more experienced users.

Hyperventilate will not completely design your vapor extraction system, tell you exactly
how many days it should be operated, or predict the future. It will guide you through a
structured thought process to: (a) identify and characterize required site-specific data, (b)
decide if soil venting is appropriate at your site, (c) evaluate air permeability test results, (d)
calculate the minimum number of vapor extraction wells, and (e) quantify how results at
your site might differ from the ideal case.

Hyperventilate is based on the article "A Practical Approach to the Design, Operation,
and Monitoring of Soil Venting Systems" by P. C. Johnson, C.  C. Stanley, M. W.
Kemblowski, J. D. Colthart, and D. L. Byers [Ground Water Monitoring Review, Spring
1990, p.159 -178]. The software performs all necessary calculations and contains "help
cards"  that define the equations used,  perform unit conversions, and provide
supplementary information on related topics. In addition, a 62-compound user-updatable
library (to a maximum of 400 compounds) is also included.

Hyperventilate version 1.01  for the Apple Macintosh requires an  Apple Macintosh
(Plus, SE, SE/30, II, IDC, or portable) computer equipped with at least 1 MB RAM (2 MB
preferred) and the Apple HyperCard Software Program (v.2.0 or greater)

This manual is not intended to be a primer on soil venting (although the software is) and it
is assumed that the user is familiar with the use of an Apple Macintosh personal computer.

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                       -Hyperventilate Users Manual-
Table of Contents
            Title
Page


I
II ,
in
IV
V
V.I
V.2
V.3
V.3.1
V.3.2
V.3.3
V.3.4
VI
Appendices
A
B
C
D
E
F
G

Disclaimer
Foreword
. Introduction
Definition of Some Terms Appearing in this Manual
Software/Hardware Requirements
Loading Hyperventilate Software
Using Hyperventilate ,
- Starting Hyperventilate,
- General Features of Cards
- Sample Problem Exercise
- Navigating Through Hyperventilate .
- Is Venting Appropriate?
- Field Permeability Test
-System Design
References
' "3
Soil Venting Stack Cards
Soil Venting Help Stack Cards
Air Permeability Test Cards
Aquifer Characterization Cards
System Design Cards
Compound List Update Cards
A Practical Approach to the Design, Operation, and Monitoring
Soil Venting Svstems
i
ii
2
4
4
4
5
5
7
8
8
12
22
26'
35
36






of In Situ


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                         - Hyperventilate Users Manual -
I. Introduction

In situ vapor extraction, or soil venting is recognized as an attractive remediation alternative
for "permeable" soils contaminated with "volatile" compounds.  As Figure 1 illustrates,
vapors are removed from extraction wells, thereby creating a vacuum and vapor flow
through the subsurface.  Until the residual contamination is depleted, contaminants will
volatilize and be swept by the vapor flow to extraction wells.  While its use has been
demonstrated at service stations, Superfund sites, and manufacturing locations (see Hutzler
et al. [1988] for case study reviews), vapor extraction systems are currently designed more
by intuition than logic. In fact, many systems are installed at sites where the technology is
not appropriate.

"A Practical Approach to the Design, Operation, and Monitoring of In Situ Soil Venting
Systems" [Johnson et al. 1990a - see Appendix G] is a first attempt at creating a logical
thought process for soil venting applications.  The article, which is based on earlier results
of Thornton and Wootan [1982], Marley and  Hoag [1984], Johnson et al. [1990], and
discussions with several of these authors, describes a series of calculations for determining:
(a) if soil venting is appropriate at a given site, (b) limitations of soil venting, and (c)
system design parameters, such as minimum number of extraction wells and potential
operating conditions.

Hyperventilate is a software  guidance  system based  on the  Johnson et al. [1990a]
article. The software performs all necessary calculations and contains  "help cards" that
define the equations used, perform  unit conversions, and provide supplementary
information on related topics. In  addition, a 62-compound updatable chemical library (to a
maximum of 400 compounds) is included.                             ,

Initial development of this program occured  under the Apple Macintosh HyperCard
environment, due to its programming simplicity, ability to incorporate text and graphics,
and interfacing with other Macintosh programs (such as FORTRAN codes, etc.).  The
objective was to create a user-friendly software package that could be both educational for
the novice environmental professional,  and a functional tool for more experienced users.
The OASIS [1990] system  created at  Rice University for groundwater  contamination
problems is another excellent example of the use of HyperCard as a technology transfer
tool.

This document is a users manual for Hyper Ventilate. It contains sections describing the
installation and operation of the  software.  During the development of Hyperventilate,
the goal was to create  a guidance system that could be used with little or  no instruction.
Experienced Apple Macintosh users, therefore, can load and explore the capabilities of this
program after glancing at the "Loading Hyperventilate Software" section. Those users that
are less comfortable about exploring software  without a  manual are encouraged to read
through it once, and work through the sample problem.  It is intentionally brief, and a
beginner should be able to navigate through the system in less than a couple hours.  It is
assumed that the user has  some previous Macintosh experience.  If not,  consult a
Macintosh users manual for a quick tutorial.

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                          -Hyperventilate Users Manual -
                             Air Bleed
                                                          Vapor Treatment
                                                                Unit
 Vapor
 Flow

Pressure ^,
Gauge
J
_n





;
:


?
j
LJ




5
S
1
m
I Vacuum vvX*»X
?[| * S...S

— . | I O I IHIIIIB * ^^^ ' "
Flow f
Meter Flow
Meter
-*- Vapor Well
Contaminated -^ —
Soil — Vapor
Flow
                                                  Ground water Table
Figure 1. Schematic of a typical vapor extraction operation.
                                                                               3

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II. Definition of Some Terms Appearing  in this  Manual

button      -  an object on a "card" that causes some action to be performed when
              "clicked" on
card       -  an individual screen that you view on your monitor
click       -  refers to the pressing and releasing of the button on your mouse
drag       -  refers to holding down the mouse button while moving the mouse
field       -  a text entry location on a "card"
HyperCard -  a programming environment created by Apple Computer, Inc.
mouse      -  the device used to move the cursor within your monitor
select      - 'refers to "dragging" the cursor across a "field"
stack       -  a group, or file, of "cards"
III. Software/Hardware  Requirements

Apple  Macintosh HyperVentilate  version 1.01  requires an Apple Macintosh  (or
equivalent) computer equipped with at least 1 MB RAM (2 MB preferable), a hard disk,
and the Apple HyperCard Software Program (v 2.0).  Check to make sure that your
system software is compatible with your version of HyperCard.
IV.  Loading  HyperVentilate  Software

Hyperventilate is supplied on an 800 kB double-sided, double density 3.5" diskette.
Follow the instructions listed below to insure proper operation of the software.

1)     Insert  the HyperVentilate disk into  your computer's floppy drive.   The
       HyperVentilate disk should contain the files:

             - "Soil Venting Stack"
             - "Soil Venting Help Stack"
             - "System Design"
             - "Air Permeability Test"
             - "Aquifer Characterization"
             - "Compound List Update"
             - "HypeVent"
             - "f77.rl"

2)     Copy these files onto your hard disk.  They must be copied into the folder
       that contains the "HyperCard" program, or else the software will not
       operate  properly.

3)     Eject the HyperVentilate disk

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                          - Hyperventilate Users Manual -
V. Using  Hyperventilate

The authors of Hyperventilate intend it to be an application that requires little pre-
training for the user.  It is mouse-driven and instructions are included on each card, so
please take the time to read diem when you first use Hyperventilate.

This section of the users manual is divided into three subsections. Start-up instructions are
given in the first, basic features of the cards are described in the second, and a sample
exercise is presented in the third. For reference, copies of all cards, as well as more details
on each are given in Appendices A through F.
V.I. Starting Hyperventilate

1)     Those users with color monitors should use the "Control Panel" (pull down the
       "ll" menu and select "Control Panel", then click on the "Monitors" icon) to set their
       monitors to black and white, and two shades of grey.

2)     To avoid unnecessary "card-flipping", set the "Text Arrows" option in your
       "Home" stack "User Preferences" card to on. You can get to this card from within
       any HyperCard application by selecting "Home" under the "Go" menu. This will
       take you to the first card in the "Home" stack.  At this point click on the left-
       pointing arrow and the "User Preferences" card will appear on your screen. Then
       click on the square to the left of "Text Arrows" until an "X" appears in the square.

3)     Hyperventilate is started by double-clicking on the "Soil Venting Stack" file icon
     '  from the Finder (or Desktop), or by choosing "Open" under the "File" menu  (Note
       that using d more advanced version of HyperCard than the one under which this
       system was developed (v 2.0) may require you to first "convert" each of the seven
       HyperCard stacks contained in Hyperventilate).

4)     Your monitor should display the card shown in Figure 2.  Note that there are a
       number of buttons on this card; there are two at the lower left corner, and then each
       file folder tab is also a button (some cards may contain less obvious "hidden"
       buttons; try clicking on the authors name on the title card for example). Clicking on
       any of these will take you to another card.  For example, clicking on the "About
       This Stack" button will take you to the card shown in Figure 3, which gives a brief
       description about the use of buttons and fields. Read this card well.

5)     Explore for a few minutes. Try.to see where various buttons will  take you, try
       entering numbers in fields, or play with calculations: Again, just remember to read
       instructions given on the cards.

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                              -Hyperventilate Users Manual -
                                                                Buttons
          A Practical Approach to the
            Design, Operation, and
           Monitoring of In-Situ Soil
                Venting Systems
                     vtnioa 1.01
                91991 AnBffVf Butnftl
                   Bfell On Com)uy
        Economics
               k Hyj«rCw4 BUrft Ciutrf »y:

              Paul C. Johnson, PlLD.
                 Amy 3. Strtenan

                  Shell Development
              Wwthoflo v Research Center
           About This Stack
                           Go to First Card
System Monitoring

   Field Tests

 Site Investigation

About SOU Venting
                         Sy'»m Sh«-Doim
                          System Design
                        Is Venting Feasible?
                             ^
                                                                          Vapor
                                                                          Flov
                  \
                    Buttons

Figure 2. First Card of the "Soil Venting Stack" stack.
         Help: Stack Information
         Buttons
         Buttons have been placed in each
         card.  Clicking on any button vill
         perform an action, such as:
                   Go Home to first
                   «rt In Venting Stack

                   Oo to next card

                   Oo to Help cud

                   Ptintcartor
                   text field
          Calculate)  Perform«Calculation
         When curious, click on Symbols,
         Pictures or Text
Fields
Fields may contain information, or they may be
a place for you to input numbers.
Scrolling Field:

Click on arrow to move
text up or do vn

Boxed Data Field:

 When you see an I-beam
cursor appear in a boxed
field, click the mouse in the
box to set the cursor. Then
you may enter data.
 A button vffl then usually
be pushed to perform an
action or calculation.
Click on the arro vs , or
move the box up or do vn
vith the mouse.
In (his are*, you can
O
il
ilia;
                  Try this example:

                  Enter Number in B ox
                 I        11 inches
                  (Click for calculation)

                       2.54  centimeters
Figure 3. Card HI of the "Soil Venting Help Stack" stack.

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                           - Hyperventilate Users Manual -
V.2.  General Features of Cards

Figures 4 and 5 are examples of cards from the "Soil Venting Stack" stack and "System
Design" stack.  There are a few general features, of these cards that users  should
understand:

a)     Each card (with the exception of the first card of the "Soil Venting Stack" stack) has
       been numbered for easy reference with the printouts given in Appendices A through
       F. In the "Soil Venting Stack" these numbers appear in the bottom center of each
       card (i.e. number "3" in Figure 4). In other stacks these numbers appear at either
       the top or bottom corners of the card (i.e. "SD1" in Figure 5).

b)     Arrow buttons are included at the bottom of some cards. Clicking on right-pointing
       arrow will advance you to .the next card in the stack; clicking on the left-pointing
       arrow will take you in the opposite direction.

c)     The identifying card numbers in the "Soil Venting Stack" stack are also fields into
       which text can be typed.  You can skip  to other parts of the "Soil Venting Stack"
       stack by selecting this field, typing in the card number of your destination (within
       the "Soil Venting Stack"), and then hitting the "return" key.

d)     Many cards have a house button in the lower left corner. Clicking on this button
       will take you to the first card of the "Soil Venting Stack" stack, which is the card
       displayed at start-up (see Figure 2).
            •••••i^^^^^^^^H^^^^^^HMWIIBBB^IBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBllMillMH^^^^^^^^^^^^H^^^RMHM^^^^^^^^^^^^H
            In-Situ Soil Venting System Design Process
        You can click on any block in this diagram to jet more information about that particular step. Or yau
        can begin at the start of (he process by ctkking on either the "Leak or SpOl Discovered" box, or the '
        right-directed arrov at the bottom of this card.
                                                                 Clean"
                                                                  Sits
Figure 4. Card 3 of the "Soil Venting Stack" stack.

V

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                           -HyperventilateUsers Manual -
         Number of Venting Wells...
         The procedure for estimating the required
         number of extraction velb is similar tj (he
         process used previously to determine if
         venting is appropriate at a given site.

         As fflusinteft at the right, ve vffl estimate
         single vertical veil flffwiates, calculi* the
         minimum vapor flov required, determine
         Ow area! extent of influence, and then,
         factor in any site-specific limitetiou. This
         information then determines the necessary
         number of extraction veils.

         Just proceed to' foliov the steps dictated on
         the foOoving cards—>
   Plovrate
Maximum Removal
     Rate	
  Requirement
  Site-Specific
   Limitations

 Area of Influence
  Requirement
Figures.  CardSDl of the "System Design" stack.
V.3.  Sample Problem Exercise

 In the following a sample problem is executed in excruciating detail. Those not wishing to
work along with the example are encouraged to utilize Appendices A through F as
references for more details on the less obvious functions of some cards.

This "Sample Problem Exercise" is divided into to four subsections that address: navigating
through Hyperventilate (§V.3.1), screening sites to see if soil venting is an appropriate
technology (§V.3.2), interpreting air permeability test data (§V.3.3), and guidance for
designing soil venting systems (§V.3.4).

V.3.1 Navigating  Through  Hyperventilate

Step 1:     Location:  The "Desktop" or Finder.
           Action:    Start-up Hyperventilate by double-clicking on the "Soil Venting
                     Stack" icon, or click once on this icon and then choose "Open" from
                     the "File" menu.
           Result:    Hyperventilate will start-up and display the title card (Figure 2).

Step 2:     Location:  Tide Card of the "Soil Venting Stack" stack.
           Action:    Click on the "About This Stack" button.
           Result:    You are now at card HI of the "Soil Venting Help Stack" stack
                     (Figure 3).

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                           -Hyperventilate Users Manual -
StepS:    Location:  Card HI of the "Soil Venting Help Stack" stack.
          Action:    Play with the buttons and scrolling field.  Practice entering a number
                     in the field in front of "inches". Place the cursor in the box. It will
       ;             change from a hand to an "I-bar" as it enters the field. Hold down
                     the mouse button and drag the I-bar across the entry, which will
                     become hilited. Now type in another number, or hit the delete key.
                     Practice until you feel comfortable selecting text and entering
                     numbers.  Then click on the "Click for Calculation" button. When
                     you are done practicing, click on the "Return" button.
          Result:    Return to the tide card of the "Soil Venting Stack" (Figure 2).

Step 4:    Location:  Title Card of the "Soil Venting Stack" stack.
          Action:    Click on the  "Economics" file folder tab.     ?
          Result:.    You are now at card 27  of the "Soil Venting Stack" stack. Take a
                     quick glance at this card, which is displayed in Figure 6. *

Step 5:    Location:  Card 27 of the "Soil Venting Stack" stack.
          Action:    Click on the  "House" button in the lower left corner.
          Result:    You are back at the title card (Figure 2).    •  •

Step 6:    Location:  Title card of the "Soil Venting Stack" stack.
          Action:    Click on the "Go to First Card" button.
          Result:    You are now at card 1 of the "Soil Venting Stack" stack.(Figure 7).
         Economics...
        For typical service station sites,
        clean-up costs can range from
        $100K - $250K for the venting
        operation alone, depending on
        the complexity of the site, clean-
        up time, permitting
        requirements, and the type of
        vapor treatment system used.  .

        The tvo major costs are
        generally associated vith the
        vapor treatment unit and
"Click" on any item belov (&
hold button dovn) to see costs
   associated vita that item.
Figure 6. Card 27 of the "Soil Venting Stack" stack.

V

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                           -Hyperventilate Users Manual -
           This HyperCard Stack vas created to help guide environmental scientists
           through the thought process necessary to decide if and hov soil venting might
           be applied to remediate a given site. The organization and logic of this stack
           follow the paper:

                    'A Practical Approach to the Design, Operation,
                    and Monitoring of In-Situ Soil Venting Systems"

                                         Uy:
          P. C. Jonason, C. C. Stanley. M. W, KemtlovsH, J. D. Colttait, ft D. L. flyers

             published in Ground Water Monitoring Reviev, Spring 1990, p. 159-178
            If at ttis yoiai yo« to not feel comfortable vitk the use of the buttons, please
            click once on *?" for moie info on the mechanics of this stack...
Figure 7.  Card 1 of the "Soil Venting Stack" stack.

Step 7:     Location:  Card 1 of the "Soil Venting Stack" stack.
           Action:    Click on the right-pointing arrow.
           Result:    You are now at Card 2 of the "Soil Venting Stack" stack (Figure 8).

Step 8:     Location:  Card 2 of the "Soil Venting Stack" stack.
           Action:    Read the text, and click on the "down" and "up" arrows on the
                     displayed text field  under "About Soil Venting..." to make the
                     field scroll. Then click on the left-pointing arrow at the card bottom.
           Result:    You are now back at card 1 of the "Soil Venting Stack" (Figure 7).

Step 9:     Location:  Card 1 of the "Soil Venting Stack" stack.
           Action:    Click on the right pointing arrow.
           Result:    You are again at card 2 of the "Soil Venting Stack" stack (Figure 8).
                     By now you should feel comfortable using the left-  and right-
                     pointing arrows to travel through the stack.

Step 10:   Location:  Card 2 of the "Soil Venting Stack" stack.
           Action:    Click on the "?" button in the lower right corner of the card. This
                     button indicates that there  is a "Help" card containing additional
                     information.
           Result:    You are now at card H2 of the "Soil Venting Help Stack" stack
                     (Figure 9). Scroll through the list of references, then click  on the
                     "Return" button to return to card 2 of the "Soil Venting Stack" stack.

At this point you shpuld feel comfortable navigating around in Ilyperyentjlate.	
10

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                               - Hyperventilate Users Manual -
             About Soil Venting...
            Soil Venting (a.k.a. "in-situsoil
            venting", "vacuum extraction", &
            "in-situ vapor extraction") is
            rapidly becoming one of the most
            practiced soil remediation processes
            for permeable soils contaminated
            vilh relatively volatile
            hydrocarbons.

            The underlying phenomena that
            influence the success of any soil
            venting operation are easily
            understood. By applying a vacuum
               Vapor
            Treatment Unit
Vicwim
Blover
Figure 8. Card 2 of the "Soil Venting Stack" stack.
         Help: About Soil Venting
         Mow information about sou venting can be found in the foBovmg articles:
         M. C. Marie; and G. E. Hoaj, Induced Soil Venting for fee Recovery/Restoration of Gasoline
         Hydrocarbons in the Vadoie Zone. NWWA/API Conference on Petroleum Hydrocarbons and
         Organic Chemicals inOroundvater, Houston, TX, 1984.

         P. C. Johnson, M. W. Kemblovsld, and J. D. Colthan, Practical Screening Models for Sofl
         Venting Applications, NWWA/API Conference on Petroleum Hydrocarbons and Organic Chemicals
         in Ground vater, Houston, TX, 1988.

         H. J. Hutzler, B. E. Murphy, and J. S. Gierke, State of Technology Reviev: Sofl Vapor Extraction
         System], U.S.E.P.A, CR-814319-OM, 1988.

         D. J. Wilson, A. N. Clarke, and J. H. Clarke, Sofl Clean-up byin-situ Aeration. I. Mathematical
         ModelKr*, Sep. Science Tech., 23:991-1037,1988.
Figure 9. Card H2 of the "Soil Venting Help Stack" stack.
                                                                                              11

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                          -Hyperventilate Users Manual -
V.3.2 Sample  Problem Exercise  - Is Venting Appropriate?

In §V.3.2. you will work through an example problem to illustrate how one might decide if
venting is appropriate at any given site.  For the purpose of this example we will use the
example site information given in Figure 10.
   10'
   20,
   30,
 I 40_
     ~*
   50,
   60'
           North
South
m
•^ •
•
•
•
— - <•
•
P
•

HE
i
-0.3
1
•0.2- -
j
•0.02
• 0.0
.0.0
i
-02- -
i
• 0.0
• 1.7
1
-24 ,
. 73

1
• 9.5
M7
, Vv*: . Tank
Sandy V;«:
•
Fine to
Coarse Sand
m
i
Silty Clay
&
Clayey Silt
f
•
>
Medium Sand

HI
•Ply
^L7y — — •
-512
-5.4
-8577 .
•341- — — •
•653
•3267
. 1237
• 23831
•
.3319
.1.7
MO H
- 0.8 -
^4.6- — — — .
.•0.3 -
. 8.2
. 214
--31— — — — •
.967
- 971
^28679
•
. 23167 .


3-5 H
- 0.31
-1.2-
" 0.44
- 0.17
• 8.8
.-0.63
. 1.5
- 0.86
• 23
-1.6'
- 3.2_ T


3-3
     Static Ground
      Water Table
                                                             SCALE (fl)

                                                        \	1	1
                                                                 10
                                                                         20
Contamination Type:  Weathered Gasoline
Figure 10.   Sample site data (Johnson et al. [1990a]). Total petroleum hydrocarbons
            (TPH) [mg/kg] values are noted for each boring.
12

-------
                           -Hyperventilate Users' Manual -
Using your newly developed navigational skills and the right pointing arrow located at the
bottom of each card, slowly step your way through the stack until you reach card 7 of the
"Soil Venting Stack" stack (Figure 11). Take your time to read the text and "Help" cards
associated with each card along the, way.

Step 1:     Location:  Card 7 of the "Soil Venting Stack" stack.
           Action:    Read this card.  It explains the process that you will use to decide if
                     venting is appropriate. Then advance to card 8 of the "Soil Venting
                     Stack" stack.
           Result:    You are now at card 8  of the "Soil Venting Help Stack" stack
                     (Figure 12).                   .

Step 2:     Location:  Card 8 of the "Soil Venting Help Stack" stack.
           Action:    Read the instructions on this  card.  Take the time to read the
                     information on the two "Help" cards: "Info about Calculation" and
                     "About Soils (& Unit  Conversions)".

                     Now we will evaluate the efficacy of applying in situ soil venting to
                     the lower soil zone (45 -  50 ft below ground surface) in Figure 10,
                     which is composed of fine to medium sands.  It also is the zone of
                     highest hydrocarbon residual levels (>20000 mg/kg TPH in some
                     areas).
           It Venting Appropriate?

                   Read This
                      i
   Ptovmte
   Estimation
          At this point ve vill proceed through a
          simple thought process to decide if soil
          venting is a feasible alternative.  As
          mentioned earlier, the three main factors that
          govern the success of a venting operation are:

           - vapor flovrate
           - vapor concentrations
           - subsurface stratigraphy (or the location of
            contaminants relative to the vapor
            flovpath)
 Maximum Vapor
  Concentration
     ±
Maximum Removal
     Ratt
Figure 11.  Card 7 of the "Soil Venting Stack" stack.
                                                                                 13
    324-235 O - 92 - 2 QL 3

-------
                            -Hyperventilate'
Flowrate Estimation:
 O Medium Sand
 ® Fine Sand
 O Silly Sand
 O Clayey Silts
 O Input Your Ovn Permeability Range
    Permeability Range (darcy)
              to
                                      1) Choose Soil Type, or
                                        Optional - Enter your oim permeability values (daicy)
                                      2) EnterWellRadto(Ia)
                                      3) Enter Radios of Influence (ft) & Interval TTucknew*
                                      4) Optional- Enter your ovn veil vacuum (406 " = max)
                                      5) Click button ID calculate Predicted Flovrate Ranees
             L- i   itor  10   i
                                    Jin
 Well Radius
 Radius of Influence  	
 Interval Thickness*  L 6.6|ft

 [  —>Calculate Flovrate Ranges-*— J
 * tiickua of cenu«4 ixttrvtX ar
             Ataut Soib (ft UrutConvopioM
                                                  Predicted Flovrate Ranges
Well Flovrate
Vacuum (SCPM)
Pw (single veil)
(inH20)
5
1QL
20
4Q
JiH
J2Q.
-2HQ.
0.33
0.66
1,30
2.54
3.71
6.83
1007
to
to
to
to
to
to
to
_ 3.32

13-02.
25.38
37.09
68.27
100.66
                                                Info about Calculation
Figure 12. Card 8 of the "Soil Venting Stack" stack.
Step 3:     Location:  Card 8 of the "Soil Venting Stack" stack.
           Action:    Choose the "Fine Sand" soil type, and enter:
                            well radius =            2 in
                            radius of influence =     40 ft
                            interval thickness =      6.6 ft
                            user input vacuum =     200 in H2O
                     into the appropriate fields, then click on the
                     "~>Calculate Flowrate Ranges<~" button.
           Result:    The flowrate ranges are calculated and displayed.  Your screen
                     should now look like Figure 12. The calculated values are estimates
                     of the flowrate to a single vertical well (and are only valid estimates
                     when your conditions are consistent with the assumptions built into
                     the calculation - see Johnson et al. [1990a, b] for more details).

Step 4:     Location:  Card 8 of the "Soil Venting Stack" stack.
           Action:    Click on the right pointing arrow to advance to card 9.  Read the
                     information on this card, then advance to card  10
           Result:    You are now at card 10 of the "Soil Venting Stack" stack (see Figure
                     13).

Step 5:     Location:  Card 10 of the "Soil Venting Stack" stack.
           Action:    Assume that the soil temperature at our sample site is 18° C.  Enter
                     this value in the appropriate field, then hit the "return" key.  This
                     action clears all values from the other fields.
14

-------
                            - Hyperventilate Users Manual -
                 Vapor Concentration Estimation - Calculation
         T") Type in Temperature (*C) (hit )

              Click to Enter Composition of Contaminant
         T) or
              Choose one of the Default Distributions
          v                ,             '
         T) Click to Viev Distributions, (optional)

         T) Click to Perform Calculations
             18
      O Enter Distribution
      O "Fresh" Gasoline
      ® "Weathered" Gasoline

      C Viev Distributions'")

      {§) Perform Calculations
                            Sum of Mass Fractions
            Results:       Calc. Vapor Pressure
                            Calc. Vapor Concentration
          iMLHovDo I Measure a Dutnwrton? 1

        [About Calculation!
Figure 13. Card 10 of the "Soil Venting Stack" stack.
        Help:  Compound  List
        [  Viev Only Mode   \
            t  Compound Name
 Mass
Fraction
             Vapor
Molecular Preaanre (atm)
1
2
3
4
5
6
7
8
9
10
propane
isobutane , .
n-butane
trans-2-butene
cis-2-butene
3-methyl- 1-butene
isopentane
1-pentene
2-methyl- 1-butene
2-methyl- 1, 3-butadiene
0.00
0.00
0
0
0
0
0.0069
0.0005
0.0008
0.0000
44. .
58.
58.
56.
56.
70.
72.2
70.1
70.1
68.1
8.04673
2.75865
1.97431
1.84196
1.67019
0.88399
0.73146
0.64989
0.62093
0.60914
<5

iS
,i!l,!i
i

•%'
c-
a.
iii.fi
M-
'JLL
O
                                           I D.99628  1= SuinofMeajFnctions
                                                       (should be -1)
        Hov Do I Meaarne « Dfrmhntton?JHi Return to Vapor COM. Estimation Cart
Figure 14. Card H16 of the "Soil Venting Help Stack" stack.
                                                                                  ~\5

-------
                          •Hyperventilate Users Manual -
                    At this site the residual hydrocarbon is a "weathered" gasoline, so
                    choose this selection from the three composition options listed. The
                    "Fresh" and "Weathered" gasoline selections correspond to pre-
                    programmed compositions that are useful for estimation purposes. >
                    If you knew the composition of your residual, then you could enter
                    it by selecting the "Enter Distribution" option. Click on the "View
                    Distributions" button to take a look at the compound library and the
                    pre-specified composition of "weathered" gasoline.     -.
          Result:    You are now at card HI6 of the "Soil Venting Help Stack" stack
                    (see Figure 14).

Step 6:    Location:  Card H16 of the "Soil Venting Help Stack" stack.
          Action:    View the library and pre-specified composition;   If you are
                    interested, explore some of the help cards. Then click on the
                    "Return to Vapor Cone. Estimation Card" button to return to card 10
                    of the "Soil Venting Stack" stack.
          Result:    You are now at card 10 of the "Soil Venting Stack" stack  (Figure
                    13).

Step 7:    Location:  Card 10 of the "Soil Venting Stack" stack.
          Action:    Click on the "Perform Calculations" button.
          Result:    Hyperventilate  calculates  the maximum  possible vapor
                    concentration  corresponding to the specified composition and
                    temperature.  The results are displayed in Card  10 of the "Soil
                    Venting Stack" stack, which  should now look like Figure 13.

Step 8:    Location:  Card 10 of the "Soil Venting Stack" stack.
          Action:    Using the right-pointing arrow button, advance to card 11 of the
                    "Soil Venting Stack" stack. Take the time to read the text, then click
                    on the "Calculate Estimates" button
          Result:    You are at card 12 of the "Soil Venting Stack" stack. The calculated
                    flowrates and maximum possible removal rates are displayed along
                    with an updated list of the input parameters that you have entered.
                    Your screen should look like Figure 15, if you have chosen the
                    "Ib/d" units.

Step 9:    Location:  Card 12 of the "Soil Venting Stack" stack.
          Action:    Click on the right-pointing arrow button.  You are now at card 13 of
                    the "Soil Venting Stack" stack. Read the text, then enter:
                    estimated spill mass          = 4000 kg
                    desired remediation time      = 180 d
                    Now click on the "~>Press to Get Rates<—" button
16

-------
                              -Hyperventilate Users Manual -
 Maximum Removal
 Rate Estimates

select your unit preference belov
      <§> Ub/d]
      O
                                      Temperature CQ
                                       °
         Note:

         These an "maximum
         removal rates", and should
         only be used as screening
         estimates to determine if
         venting is even feasible at a
         given site. Continue on ID
         the next card to assess if
         these rates BIB acceptable...
                                      WeU Radius (in)
                                      Radius of Influence (fQ
                                      Contaminant Type
                                      Permeable Zone Thickness (ft)
Pv-Well FtoTOLte Estimates Max. Removal Rate Estimates
Vacuum [SCFM] [IWdJ
(inH20) • (single veil) (single veil)
. 5_
..10
2J_
..IP
...6..P
120
2QQ_
p 33 	
0.66
1.30 .
.... ___
.. 6,8.3 ....
10.07

to
to
to
to
to
to
to
3.32
6.59
13.02
25.38
......3LP8.
.....68.27.
100.66

	 12.,....,.
....2.5
52
~J78 "I
364

to
to
to
to
to
to
to
62
}24
251
517
799
J778
- 3636

Figure 15.  Card 12 of the "Soil Venting Stack!' stack.
          I* Soil  Venting Appropriate?    Enter
          At this point, you compare the
          maximum possible removal rate
          vith your desired removal rate.

          If the maximum removal rate •
          does not exceed your desired
          removal rate, then soil venting
          is not likely to meet your needs,
          and you should consider another
          treatment technology, or make
          your needs more realistic.

          In the next cards, ve vill refine
          the removal rate estimates, in
                                     .D Estimated Spill Mass)   4DOO| Q |b

                                                               180|  days
£j Enter Desired
    Remediation Time
                                                  toeetRates<~
                                     Single Vertical Veil Results
                                Desired Removal Rate:
                                Gauge Vacuum (in H2O):
                                Mia Flo-mate @ 200 inH2O
                                Max Fbiraate @ 200 inH2O
                                Max. Eat Removal Rate:
                                (lover estimate) - pei veil
                                (upper estimate) - per veH
                               Ekc'd]
                               [inHZO]
                               ISCFM]
                               JSCFM]
Figure 16.  Card 13 of the "Soil Venting Stack" stack.
                                                                                         17

-------
                          -Hyperventilate Users Manual -
          Result:    Your screen should now look like Figure 16. Note that your desired
                    removal rate (=22 kg/d) is less than the estimated maximum removal
                    rates for a single vertical well (=165 to 1650 kg/d). At this point in
                    the screening exercise, therefore, soil venting still appears to be a
                    viable option.

Step 10:   Location:  Card 13 of the "Soil Venting Stack" stack.
          Action:    Click on the right-pointing arrow button to advance to card 14 of the
                    "Soil Venting Stack" stack.  Read the text, then advance to card 15
                    of the "Soil Venting Stack" by clicking on the right-pointing arrow
                    button. Again, take the time to read the text, then advance to card 16
                    of the "Soil Venting Stack"  stack.  The focus of these cards is the
                    prediction of vapor concentrations and removal rates as they change
                    with time due to composition changes.  It is important to try to
                    understand the concepts introduced in these cards.
          Result:    You are at card 16 of the "Soil Venting Stack" stack (see Rgure 17).

Step 11:   Location:  Card 16 of the "Soil Venting Stack" stack.
          Action:    This card is used to finalize your input data prior to calculating vapor
                    concentration and residual soil contamination composition changes
                    with time. Read the instructions in the order that they are numbered.
                    Note that the summary table in the upper right corner of the card
                    contains all the parameter values that you have input thus far. The
                    instructions describe how to change these values, but at this point
                    we will retain the displayed values.  Because it is difficult to present
                    the behavior of each compound in a mixture composed  of an
                    arbitrary number of compounds, the output is  simplified by
                    reporting the behavior in terms of "boiling point" ranges. This
                    simply represents a summation of all compounds whose boiling
                    points fall between pre-specified values.  Presented in this fashion,
                    the model results can be interpreted much more quickly. Click on
                    the "tell me more about BP ranges..." button, read the help card,
                    then return to card 16 of the "Soil Venting Stack" stack. Click on
                    the "~>Set Default BP Ranges<~" button.  Your screen should now
                    look like Figure 17. Click on the "Generate Predictions" button
          Result:    The message  "Sit Back and Relax..." will appear on your screen,
                    followed by a screen on which the following appears:
                    "Copyright © Absoft Corp 1988
                    Copyright © Shell Oil Co 1990
                    HANG ON	YOU WILL BE RETURNED TO HYPERCARD...
                    # OF COMPOUNDS IN LIBRARY = 62"
                    Then card 17 of the "Soil Venting Stack" stack will appear.
18

-------
            Motfel Predictions
           To flit right fa a summary of the
           data you hav« input If you Irish *
           choice any of the info, men. clfck
           on the parameter name, and redo
           the calculations oathe card you vffl
           be taken to. Press to Winking
           •Return' button to come tack
           The model returns output that
           allo vs you to determine
           residual amounts of
           compounds faffing viihin 5
           toiling point ranees. Type in
           your ovn ranges, or choose
           the default values.
Temperature
Son Type
Soil Permeability Ranee (darcy)
Well Radius (in)
Radius of Influence (ft)
Contaminant Type
Permeable Zone Thickness (ft)
        "* Set DefM* BP Ranges
Boiling Point Range *2
BoUingP.omtB.aage.«.
.Boiling.P.oint_gaagB*i
Boiling Point Range *5
                                                                  -5Q
-28...
 80
                        111
                       J44_
                              to
                              to
to
Jo
                                   2?
     80
JJLL ...C.
-ill. ...£.
 250   C
           Generate Predictions
                tell me more about BP ranges.
 Figure 17. Card 16 of the "Soil Venting Stack" stack.
                                                                                 [mcO.]
FIRST PRESS THE IMPORT
DATA. BUTTON!
These are the results (or the
contaminant type mat you have
Q«M(0)
L-airf
g-iesidual
.00
.24
.57
.98
1.49
2.11
2.87
3,81
Vapor
Cone.'
!» Initial]
100.000
75.062
58.631
48.078
39.390
31.941
25.916
21.150
Residual
Level
[» Initial]
100.000
95.000
90.022
85.034
80.034
75.035
70.035
65.037
Sm Hl& T* tfil'H'Bfr^ ^Q
p, >9D» of Initial
III Temperana
^ Contunina]
BP«1
Residual
[* total]
.690
.123
.000
.000
.000
.000
.000
,000
BPI2
Residual
[« total]
11.650
9.263
6.755
4.512
2.632
1.222
.385
.068
Remove
Residual
«(*C):
MType:
BP*3
Residual
[* total]
24.010
23.982
23.474
22.403
20.771
18.503
15.556
12.053

128.48 | £„!£

18 |

We&thered Gasoline
BP84
Residual
[« total]
22.140
23.000
23.820
24.577
25.248
25.766
26.031
25.919
BPttS
Residual
[» total]
41.510
43.632
45.950
48.509
51.350
54.509
58.028
61.959
lal]
o
iiiin
Ittr'i!
>|l|l|l
Figure 18.  Card 17 of the "Soil Venting Stack" stack.

V

-------
                          -Hyperventilate Users Manual -
Step 12:   Location:  Card 17 of the "Soil Venting Stack" stack.
          Action:    Read the instructions, then click on the "—>Import Data<—" button.
          Result:    Your screen should look like Figure 18.  The table in the lower part
                    of the card lists model predictions: vapor concentration and residual
                    soil concentration (expressed as a percentage of their initial values),
                    as well as the composition of the residual (expressed as a percentage
                    of the total for each boiling point range) as a function of the amount
                    of air drawn through the contaminated soil. Note that as the volume
                    of air drawn through the soil increases, the vapor concentration and
                    residual soil levels decrease, and the composition of the residual
                    becomes richer in the less volatile compounds (BP Range #5).  In
                    the upper right corner  of the card are displayed the saturated, or
                    initial, vapor concentration and the minimum amount of air that must
                    be drawn through the soil per gram of initial contaminant to achieve
                    at least a 90% reduction in the  initial residual level.  This value is
                    used in future calculations as a design parameter.

Step 13:   Location:  Card 17 of the "Soil Venting Stack" stack.
          Action:    Click on the right-pointing arrow to advance to card 18 of the "Soil
                    Venting Stack" stack.
          Result:    You are at card 18  of the "Soil Venting Stack" stack, which should
                    resemble Figure 19. Read the text. A summary of your input
                    parameters appears on  the right side of this card. At the bottom
                    appears two calculated values representing the range of the minimum
                    number of wells  required to achieve a 90% reduction in the initial
                    residual level in the desired  remediation time. These values
                    correspond to idealized conditions, however, they can be used to
                    gauge the efficacy of soil venting at your site. For example, in this
                    case the minimum number of wells ranges between 0.7 - 7, which is
                    not an unreasonable number for a site the size of a service station. If
                    the range had been 100 - 1000, then it  might be wise to consider
                    other remediation options.

                    It is important to recognize that model predictions are intended to
                    serve  as guidelines,  and are limited in their ability to describe
                    behavior that might be observed at any given site. One should use
                    all  the  information  available, in addition to idealized  model
                    predictions to make rational decisions about the applicability of soil
                    venting.

-------
                            -Hyperventilate Users Manual -
Step 14: .  Location:
           Action:
           Result:
Card 18 of the "Soil Venting Stack" stack.
Click on the right-pointing arrow button to advance to card 19.
You are now at card 19 of the "Soil Venting Stack" stack. This card
lists several phenomena that can cause one to achieve less than ideal
removal rates. Take the time to explore each of these options, then
return to card 19 of the "Soil Venting Stack", stack.
         Is  Venting Appropriate?
         This is a complete summary
         of the data and results.
         Based upon these numbers, a
         "minimum number of veils"
         has been calculated, vhich
         should give you some
         indication of hov
         appropriate venting is for
         your application.  Note that
         this is the number of veils if
         circumstances are ideal,
               Temperature fC ]: •       	|    18. ~
               Contaminant Type:      [Weathered Gasolim
               Soil Type:                |   Fine Sand"
               Well Radius [in]:                	Z
               Est. Radius of Influence [ft]:            40
               Permeatle Zone Thickness [ft]:         6.6
               ROTO* perWeE(120" V«> [SCFM]    6.83
               Flovn* per Well (120" Vac) [SCFM]    68.27
               Min. Vol. of Air [U|-residtial]:        128-48
               Estimated SpfflMa»:                4DOO
               Desired Remediation Time [dayj]: •  I   180
                              	     Minimum t of Wells
                              I   0-72   K        Based       <|
                                           on Tour Input Parameters
                                                7.23
Figure 19. Card 18 of the "Soil Venting Stack" stack.
                                                                                   21

-------
                        -HyperventilateUsers[Manual-
                   Field  Tests
Figure 20.  Card 20 of the "Soil Venting Stack" stack.

V.3.3 Sample Problem Exercise -  Field Permeability Test.

Note:       It is recommended that you always plot and visually inspect your data prior
            to attempting to fit it to any theory.

In this example, we use Hyperventilate to analyze air permeability test data from the site
pictured in Figure 10. We will focus on results from the lower fine to medium sand zone
(45 - 50 ft below ground surface). Advance to card 20 (Figure 20) of the "Soil Venting
Stack" stack to begin.

Step 1:     Location:  Card 20 of the "Soil Venting Stack" stack.
          Action:    Using the right-pointing  arrow, advance to card 21 of the "Soil
                   Venting Stack" stack.  Read the text, then  click on the "Air
                   Permeability Test" button.
          Result:    You are at card AP1 of the "Air Permeability Test" stack.

Step 2:     Location:  Card API of the "Air Permeability Test" stack
          Action:    Read the instructions, then click on the "Show Me Set-up" button.
                   Take a look at the figure, then click the "Return" button to return to
                   card API of the "Air Permeability Test" stack. Now click on the
                   "Test Instructions" button.
          Result:    You are at card APS of the "Air Permeability Test" stack.
Step 3:   Location:  Card APS of the "Air Permeability Test" stack.
22

-------
                           -Hyperventilate Users Manual -
           Action:
Read the text, look at the sample data (click on the "show me sample
data" button) then enter the following values for this example:
                     soil layer thickness
                     estimated radius of influence
                     air permeability test flowrate
                                     = 6.6 ft
                                     = 50 ft
                                     = 15CFM
           Result:
Click on the "~>Calculate<-" button to estimate how long the air
permeability test should be conducted.
Your results should match those displayed below in Figure 21.
Step 4:     Location:  Card AP3 of the "Air Permeability Test" stack.
           Action:    Click on  the "Return" button to return to card API  of the "Air
                     Permeability Test" stack.  Then click on the "Data Analysis" button.
           Result:    You are now at card APS of the "Air Permeability Test" stack.

Step 5:     Location:  Card APS of the "Air Permeability Test" stack.
           Action:    Read the text, then step through cards AP6 and AP7, until you reach
                     card APS of the "Air Permeability Test" stack.
           Result:    You are now at card APS of the "Air Permeability Test" stack.
         Air Permeability Test - Instructions
         i)
         Identify soil zones to be treated

         2)
         Install vapor extraction vell(s) in this
         zone(s). Existing monitoring veils
         may be used, vhen the screen interval
         extends only into the zone to be treated. |
         Note the extraction veil radius and
         borehole size.  Insure that the veil is
         not "connected" to other soil zones
         through the borehole (use cement/grout [
         to seal annular borehole region).
                            [  shov me sample data
                        FOR Volume Estimation

                        Enter
                        1) Soil Layer Thfctaess [ft]:
                        2) Estimated Radius of Influence [ft]:
                        3) Air Perm. Test Ftovn* [CFM]:
6.6
50
15
                             \J—> Calculate

                       Pan Volume:
                       Time t> Extract * Pore Volume:
Figure 21.  Card AP3 of the "Air Permeability Test" stack.
                                                                                 23

-------
                          -Hyperventilate Users Manual -
Step 6:
Location:
Action:
Card APS of the "Air Permeability Test" stack.
Read the text, click the "clear" buttons to clear any entries from
columns, then enter the following data:
                         r = 53 ft
                                              r = 32.4 ft
Time
[mini
9
11
15
23
30
40
100







flowrate
screened
Gauge Vacuum
fin H^.Ol
0.1
0.2 .
0.2
0.4
0.7
1.3
2.8







Time
[min]
4
7
9
12
16
24
30
39
' 52
77
99
110
121
141
Gauge Vacuum
fin H?O1
1.2
3.0
4.3
5.5
6.9
9.9
11
13
16
20
21
23
24.5
25.5
= 15 SCFM
interval thickness
= 6.6 ft

Step 7:
          While entering the data it is convenient to place the curser in the time
          column, type in the time value, then use the "tab" key to advance to
          the vacuum reading column.  Enter the corresponding vacuum
          value, then hit the "tab key again.  As  you see, this advances the
          curser to the time column again.  Now click the "~>CaIculate<—"
          button.
Result:    Your results should match those displayed in Figure 22.  Soil
          permeability values have been calculated by fitting the field data to
          the theoretical model described in cards APS - AP7 of the "Air
          Permeability Test" stack.

Location:  Card APS of the "Air Permeability Test"  stack.
Action:    Review the results, then click on the "Explanation & Statistics"
          button.. This advances you to card AP9 of the "Air Permeability
          Test" stack, which lists correlation coefficients for the data fitting
          process.  These values give an indication of how well the model
          describes the behavior observed in the field. Values approaching
          unity indicate a good fit.  Your results should match those given in
          Figure 23.

-------
                                - Hyperventilate Users Manual -
          Air Permeability Test - Data Analytic (coat.)
             Eater radial   	
          T) distances of
             monitorine points

             Inter measured—.
          ?) tines and gauge
             Vacuums

          3) Eater (optional):
          ajflovrate
             I  15  USCFM)
          b) screened interval
             thickness
               6.6  J(TO
r- I   53   IffO
(nsin)  (inH2O)
           P-l  32.4  IffO
           (mm)  (inH20)
P=l        1(«
(min)  (inH2O)
     9
    11
    15
    23
    30
    40
   100
 0.1
 0.2
'0.2
 0.4
 0.7
 1.3
 2.8
4
7
9
12
16
24
30
39
52
77
1.2
3
4.3
5.5
6.9
9.9
11
13
16
20
Q

!!

it
..;....
1
'!PF
li
o
Figure 22.  Card APS of the "Air Permeability Test" stack.
          Air Permeability Test - Data Analysis (cont.)
          On the previous Card (APS), the data, you input vere fit to the approximate exptession given on Caid
          AP6. Ifvas analyzed \»»( both methods described on caid AP7, if you input values for the
          eitraction veil flovrate (Q) and the stratum thkkneas (m). Betov each column, of data, the tvo
          calculated penneabflity values an denoted by:

          darcy(A) - refers to calculation method 1 (see Caid APT)
          darey(B) - refers to calculation method 2 (see Card APT)
          During the regression analyses, (he data expressed as
          pain of points (ln(t), P') an fit to a BM. The '
          "correlation coefficient", r, is a measure of bov veU
          fee data conform to the theoretical curve. Asr-->l,the
          data point* an fall on the theoretical curve. A.t the rif lit
          ate jiven 0» correlation coefficient values for the three
          data. sets. For more info on the mewnine of r, consult
          any introductory Statistics book.
                                                                       Correlation Coef.
                                  data set tl [0-941158 |
                                  data set 12 I 0-98602
                                  da* set M I  Ho Data |
Figure 23.  Card AP9 of the "Air Permeability Test" stack.
v

-------
                       - Hyperventilate Users Manual -
              System Design
Figure 24. Card 22 of the "Soil Venting Stack" stack.


V.3.4   Sample  Problem Exercise -  System Design

In this example we illustrate the use of Hyperventilate for system design guidance. As in
§V.3.2 and §V.3.3, we use the sample site presented in Figure 10. At this site gasoline
was detected in three distinct soil strata: a  fine to coarse zone located 10 - 30 ft below
ground surface (BGS), a silty clay/clayey silt zone located 30 to 42 ft BGS, and a fine to
medium sand zone that extends from 42 ft  BGS to the deepest soil boring (60 ft BGS).
Groundwater is detected in monitoring wells at about 50 ft BGS.

Advance to card 22 of the "Soil Venting Stack" stack to begin (Figure 24).

Step 1:   Location:  Card 22 of the "Soil Venting Stack" stack.
         Action:   Use the right-pointing arrow to advance to card 23 of the "Soil
                  Venting Stack" stack. Read the text, then advance to card 24 of the
                  "Soil Venting Stack" stack.
         Result:   Card 24 of the "Soil Venting Stack" stack, which appears in Figure
                  25, should be displayed.

Step 2:   Location:  Card 24 of the "Soil Venting Stack" stack.
         Action:   Read the text, explore using some of the options. You will find that
                  the options: "Well Location", "Well Construction", "Surface Seals",
                  "Groundwater Pumping System", and "Vapor Treatment" provide
                  some useful guidance information on aspects and components of a
                  soil venting system. Return to card 24.
         Result:   Card 24 of the "Soil Venting Stack" stack should be displayed.
26

-------
                             - Hyperventilate Users Manual -
          System Design...

         At the right is a list of the components
         of a venting system design.  Click on
         each to conduct the indicated phase of
         the design process
         Remember: It is not our intention to provide a
         generic recipe for vacuum extraction system
         design; Instead v* suggest the folio vine « *
         structured thought process.  As you shall see,
         even in a structured thought process, intuition
         and experience play important roles. There is
         no substitute for a good fundamental
         understanding of vapor flov processes,
         transport phenomena, and ground vater ftovl
O Number of Extraction Wells

O Veil Location

O Veil Construction

O Surface Seals

O Ground vater Pumping System

O Vapor Treatment
                                        t«i mm
Figure 25. Card 24 of the "Soil Venting Stack" stack.
Number of Venting Wells...
The procedure for estimating the required
number of extraction veils is similar to the
process used previously to determine if
venting is appropriate at a given site.
As illustrated at the right, ve vill estimate
single vertical •veil flovrates, calculate the
minimum vapor ftov required , determine
the anal extent of influence, and fiun
factor in any site-specific Imitations. This
information then determines tile necessary
number of extraction veils.
Just proceed to folio v tile steps dictated on
the foDovng caids — >
<>
I
|
I
O


Ftovrate
Estimation

Maximum Removal
Rate

Minimum Volume
Regainment

Site-Specific
Limitations

Ana of Influence
Red uin ment

>A_ K«nft«r
l) • of
)>-J Brtractlon
j/y Wells
:Tkiiiliirr'tr Return ^r^^P^t*i"»«t,:aii^^^ gpi
Figure 26. Card SD1 of the "System Design" stack.

V

-------
                          -Hyperventilate Users Manual -
Step 3:    Location:  Card 24 of the "Soil Venting Stack" stack.
          Action:    Select "Number of Extraction Wells" from the list of options.
          Result:    Card SD1 of the "System Design" stack should be displayed, as
                    pictured in Figure 26.

Step 4:    Location:  Card SD1 of the "System Design" stack.
          Action:    Read the text, then use the right-pointing arrow to advance to card
                    SD2.
          Result:    Card SD2 of the "System Design" stack should be displayed.

Step 5:    Location:  Card SD2 of the "System Design" stack.
          Action:    Read the instructions on the card, enter the following values into the
                    table, then click on the "Update" button:
Parameter Medium Sand
subsurface interval (ft BGS)
description of contaminant
radial extent of contamination (ft)
interval thickness (ft)
average contaminant concentration
10-30
gasoline
20
20
100
Soil Zone
Clayey Silt
30-43
gasoline
20
13
1000
Fine Sand
43-50
gasoline
20
7"'
10000
          Result:    Card SD2 should now resemble Figure 27.

Step 6:    Location:  Card SD2 of the "System Design" stack.
          Action:    Use the right-pointing arrow to advance to card SD3 of the "System
                    Design" stack.
          Result:    Card SD3 of the "System Design" stack should be displayed.

Step 7:    Location:  Card SD3 of the "System Design" stack.
          Action:    Read the text. Note that "clicking" on many of the table headings
                    will take you to "help" cards.  Take a few minutes to explore the
                    use of these, then enter the following information:
Parameter
permeability (darcy)
design vacuum (in HiO)
Well Construction:
Radius of Influence (ft)
Extraction Well Radius (in)
Extraction Well Screen Thickness (ft)
Medium
10-100
40
40
2
10
Soil Zone
Sand Clayey Silt
0.01 - 0.1
40 ,
40
2
5
Fine Sand
1-10
40
40
2
5

-------
                                -Hyperventilate Users Manual -
Design Input Parameters...
(soil stratigraphy & contaminant characteristics)
Please enter the required information for each distinct soil
layer, click on the "Update* button, and then proceed to
the neit card (i.e. click on right ano v at bottom).
fthe tab key can be used to mow between celta)
Description of
Soil Unit
._L
JL
3
4
5
*
7
a
Medium Sand ..

FtoeSand 	

-



Depth BOS*
[ft]
10
3,0. 	
43





to.
to
to
to
to
to
to
30
•s. 	
50






Description of
Contamination
easoUne
JCSffilto
easoline



"



• BdevGnwdftufiH
^_
Sebct the total mass
units that yon prefer
C Cleai All Entries i

Contaminant
Distribution
n&u
20
^ 	 2jp
20


•I


fciirwl
takkatis
mi
20
ti
7





kvtni*
coke.
100
Iflflfl.
10000





ow
Cak.
Tottl
Mass
J20,?.
-29§ Q.
4232:3
0.0
0.0
_ 	 P.O.
0.0
r o.o
(Update)
rafl-gi'W 111 ^ 	 ;;s •! 'mB + M-J-\>WM + jjaiT^Wi S-:;B?S;
 Figure 27. Card SD2 of the ."System Design" stack.   .
   Design Input Parameters . . .
   Please enter the muted information for
   each distinct soil layer, and then proceed
   to the next card.
                                 Note: - click on any febfe heading «
                                       jet more Mo
                                      - use tab key to move
                                       betveen cells
                                     O Bitty *»*
     Description of
       Soil Unit
    1
Medium Sand
Permeability* .
   [darcyj
                     .DJ21
                             Design
                             Vacuum
                             (inH20)
100
                               Jft
                  40
                                .JQ.
                                 40.
                                              Extraction Wen
                                               Cons traction
            ntou
              .....2
                                                  lent*
                                                   fftl
10
                                                        rUmof
                                                    mi
40
           Critical
          Volume of
            Air**
            [L/gl
128.48
                                     ...1.21
            Efficiency
              (96)
.159.
                                                      ..1.09.
                                               128 	100
      * Eatir or CAMM from BJ( it to) rijV
         •B^B^BaBBBBVB^BlB^
          Clear All Entries
                                     •mm vohmi oCv&jorrtfvinlta ukicvt rutLtlutioa.
                                     •^BBBBBBBBH
                                   Return
 Figure 28. Card SD3 of the "System Design" stack.

JJ7	.    	:	

    324-235 O  -  92  - 3  QL 3
                                                                                        29

-------
                         - Hyperventilate Users Manual -
                    The "Critical Volume of Air" is calculated by the same procedure
                    used previously in §V.3.2  (steps  10 -13).   To  initiate this
                    calculation, "click" on the "Critical Volume of Air**" heading.
          Result:    Card SD5 of the "System Design" stack appears on your screen
                    (Figure 29).

StepS:    Location:  Card SD5 of the "System Design" stack.
          Action:    Read the text carefully.  The focus of this card is the prediction of
                    vapor concentrations and removal rates as they change with time due
                    to composition changes. It is important to try to understand the
                    concepts introduced in this card.  For more information, read the
                    reference article contained in the appendix.  Click on the "Do a
                    Calculation" button to advance to card SD6 of the "System Design"
                    stack (Figure 30).
          Result:    Card SD6 of the "System Design" stack appears on your screen.

Step 9:    Location:  Card SD6 of the "System Design" stack.
          Action:    This card is used to finalize your input data prior to calculating vapor
                    concentration and residual soil contamination composition changes
                    with time.  Read the instructions in the order that they are numbered,
                    then enter "18" for the temperature and select "weathered gasoline"
                    from the three composition options. Because it is difficult to present
                    the  behavior of each compound in  a mixture composed  of  an
                    arbitrary number of compounds, the output is simplified by
                    reporting the behavior in terms of "boiling point" ranges.  This
                    simply represents a summation of all compounds whose boiling
                    points fall between pre-specified values. Presented in this fashion,
                    the model results can be interpreted much more quickly: Click on
                    the "tell me more about BP ranges..." button, read the help card,
                    then return to card SD6 of the "System Design" stack.  Click on the
                    "~>Set Default  BP Ranges<~" button. Your screen should now
                    look like Figure 30.  Click on the "Generate Predictions" button
          Result:    The message "Sit Back and Relax..." will appear on  your screen,
                    followed by a screen on which the following appears:
                    "Copyright © Absoft Corp 1988
                    Copyright © Shell Oil Co 1990
                    HANG ON	YOU WILL BE RETURNED TO HYPERCARD...
                    # OF COMPOUNDS IN LIBRARY = 62"
                    Then card SD7 of the "System Design" stack will appear as shown
              :      in Figure 31.
30

-------
                               -Hyperventilate Users Manual -
           Critical Volume Calculation...
            typically observed In venting
            operations.

            The results an plotted in this vay to
            emphasize that the degree of
            remediation that can be achieved by
            venting depends mainly on **
            volume of vapor extracted divided
            by the initial mass of residual
            hydrocarbon.  For the example
            pictured at the right, approximately
            100 liters of air must be vilMravn
            from the subsurface in older to
            remove about 90% of a single gram
QC/QC(t=0)
    1
                               % Removed
                                       100
                    Weathered Gasoline
                    T-20"C
                    10* moisture content
                    C(t=0) ~ 222
                          Return to Design
Figure 29. Card SD5 of the "System Design" stack.
              100        200
              Qtfm(t=0) (1/g)
            Do a Calculation
                                      300
          Critical  Volume
          Predictions...
          Simply ewer the temperature at
          the iigh.t;*,and then specify'die
          composition of your contaminant
          If you an unsure about Has, click
          on the 'About Composition... *
          button located at the loirer right
          The model returns output that
          allovs you to determine
          residual amounts of
          compounds falling •within 5
          boiling point ranges.  Type in
          your ovn ranges, or choose
          fee default values.
 Temperature (*C)
Contaminant
Composition
(choose one)
                         18
                     O Enter Distribution
                     O "Fresh" Gasoline,
                     ® "Weathered" Gasoline
                      ( VievDistributions)
[.—> Set Default BP Ranges <—J
Boilincr Point Ranse Jfl
Boiling Point Range 92
Boiling Point Range *3
Boiling Point Range *4
Boilincr Point Ranro *5
-5fl
?X
80
111
144
t?
to
to
to
to
_2?
??n
in
_m^
250
S
C
c
JL
c
   1
       Generate Predictions
               ten me more about B P
                                nnges

                    About Composition...
Figure 30. Card SD6 of the "System Design" stack.

V
                                                                                             31

-------
                          -Hyperventilate Users Manual -
Step 10:   Location:  Card SD7 of the "System Design" stack.
          Action:    Read the instructions, then click on the "~>Import Data<—" button.
          Result:    Your screen should look like Figure 31. The table in the lower part
                    of the card lists model predictions: vapor concentration and residual
                    soil concentration (expressed as a percentage of their initial values),
                    as well as the composition of the residual (expressed as a percentage
                    of the total for each boiling point range) as a function of the amount
                    of air drawn through the contaminated soil.  Note that as the volume
                    of air drawn through the soil increases, the vapor concentration and
                    residual soil levels decrease, and the composition of the residual
                    becomes richer in the less volatile compounds (BP Range #5).  In
                    the  upper right comer of  the card are displayed the saturated, or
                    initial, vapor concentration and the minimum amount of air that must
                    be drawn through the soil per gram of initial contaminant to achieve
                    at least a 90% reduction in the initial residual level. This value is
                    used in future calculations as a design parameter.

Step 11:   Location:  Card SD7 of the "System Design" stack.
          Action:    Click on the "Return to System Design" button
          Result:    A dialog box will appear asking: "Transfer Critical Volume Value?".
                    Click on the "Yes" button. You will now be prompted by another
                    dialog box asking: "What  soil unit # is this value for?". Enter "1"
                    into the appropriate place then click on the "OK" button.  You will
                    now be transferred back to card SD3 of the "System Design" stack.
                    Note that the value "128.48" has been entered into the  "Critical
                    Volume of Air**" column for the medium sand soil unit.

Step 12:   Location:  Card SD3 of the "System Design" stack.
          Action:    Enter "128" into the "Critical Volume of Air**"  column for the
                    clayey silt and fine sand soil units. For this example problem enter
                    "100" for the efficiency in all three soil units
          Result:    Card SD3 should now resemble Figure 28.
                                                                $
Step 13:   Location:  Card SD3 of the "System Design" stack.
          Action:    Click on the right-pointing arrow at the  bottom of the page to
                    advance to Card SD4 of the "System Design" stack.
          Result:    Card SD4 of the "System Design" stack  should appear on your
                    screen.

Step 14:   Location:  Card SD4 of the "System Design" stack.
          Action:    Assume that you wish to  remediate this site  in 180 days.  Enter
                    "180" in the "Time for Clean-up" column for each  soil unit. Click
                    on the "Update" button.
          Result:    Hyperventilate calculates a range of flowrates to a single vertical
                    well, then uses this value and other input parameters to determine
                    the  minimum number of wells required based on two approaches.
32

-------
      -Hyperventilate Users Manual -
To read about these, click on the  "Number of Wells" column
heading. Your card SIM should resemble Figure 32.

It is important to recognize that model predictions are intended to
serve as guidelines,  and are limited in their ability to describe
behavior that might be observed at any given site. One should use
all the information  available, in addition  to idealized model
predictions to make rational, decisions about the applicability of soil
venting.       ;

You can read about the effect of venting at this site in the article:
"Soil  Venting at  a California Site:  Field Data Reconciled with
Theory", by P. C: Johnson, C. C. Stanley,  D. L.  Byers, D. A.
Benson, and M. A. Acton, in Hydrocarbon Contaminated Soils and
Groundwater: Analysis, Fate, Environmental Health Effects, and
Remediation Volume  7, P. T. Kostecki and E. J. Calabrese, editors,
Lewis Publishers, p.253 - 281,1991. .

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                               'Hyperventilate Users Manual -
                                         Saturated Vapor         lo 20S3E*03 I  fmefl.1
                                         Cow:«itiatlcm«tlme=a  I0'2053"*03 I  |m*'L1
FIRST PRESS THE IMPORT
DATABUTTON1
These an the results for the
contaminant type that you have
QtfM(0>
L-airf
g-RSidual
.00
.24
.57
.98
1.49
2.11
2.87
3.81
Vapor
Cone.
[» Initial]
100.000
75*062
58.631
48.078
39.390
31.941
25.916
21.150
Residual
Level
[» Initial]
100.000
95.000
90.022
85.034
80.034
75.035
70.035
65.037
H Hin Volume ID Bemove
>4)fm nf Tnftful B»«ttiMl
jjjjj Temperatun (*C):
O , Contaminant Type:
BP«1
Residual
[» total]
.690
.123
.000
.000
.000
.000
.000
.000
BPI2
Residual
[96 total]
11.650
9.263
6.755
4.512
2.632
1.222
.385
.068
BP«3
Residual
[» total]
24.010
23.982
23.474
22.403
20.771
18.503
15.556
12.053

128 48 ^"m>
g-
IfO.tO | mnHr.11

18 |

Weathered Gasoline
BPS4
Residual
[% total]
22.140
23.000
23.820
24.577
25.248
25.766
26.03t
25.919
BPS5
Residual
[» total]
41.510
43.632
45.950
48.509
51.350
54.509
58.028
61.959




&

'.

!¥!*)
III!)!
Hll)
o
              Launch Excel
             Return to System Desij
Figure 31. Card SD7 of the "System Design" stack.
          Design Input Parameters.
          Please enter (1) the desired time period for
          remediation, (2) the design gauge vacuum, and
          then (3) click the •update" button.
                      Note: - click on any table heading to get mote info
                          - use tab key to mon betveen cells
                                     @ (  Update  J
                                                                Minimum Number of Wells
            Description of
              Son Unit
Time for
Clean-up
 [days]
 Design
 Vacuum

-------
                        'Hyperventilate Users Manual -
References
      Hutzler, N. J., Murphy, B. EM and Gierke, J. S., State of Technology Review:
      Soil Vapor Extraction Systems, U.S.E.P.A, EPA/600/2-89/024, June 1989.

      Johnson, P. C., Kemblowski, M.  W., and Colthart, J. DM  Practical Screening
      Models for Soil Venting Applications, NWWA/API Conference on Petroleum
      Hydrocarbons and Organic Chemicals in Groundwater, Houston, TX, 1988.

      Johnson, P. C., Stanley,  C.  C., Kemblowski, M., W.,  Byers, D. L., and
      Colthart, J. D., A Practical Approach to the Design, Operation, and Monitoring of
      In Situ Soil Venting Systems,  to appear in Ground Water Monitoring Review,
      Spring 1990.

      Marley,  M.   C.,  and  Hoag,   G.  E., Induced  Soil  Venting  for  the
      Recovery/Restoration of Gasoline Hydrocarbons in the Vadose Zone, NWWA/API
      Conference on Petroleum Hydrocarbons and Organic Chemicals in Groundwater,
      Houston, TX, 1984.

      Marley, M. C., Baehr, A. L., and Hull, M. F., Evaluation of Air-Permeability in
      the Unsaturated Zone using Pneumatic Pump Tests: 1. Theoretical Considerations,
      in review, 1990.

      Thornton, J. S. and Wootan, W. L., Venting for the Removal of Hydrocarbon
      Vapors from Gasoline Contaminated Soil, J. Environ. Scl Health, A 17(1), 31-44,
      1982.

      Newell, C. J.,  Haasbeek, J. F., and Bedient, P. B., OASIS: A Graphical Decision
      Support System for Ground-Water Contaminant Modeling, Ground Water, 28 (2),
      224 - 234, March - April 1990.
                                                                         35

-------

-------
            -Hyperventilate Users Manual -
Appendix A: "Soil Venting  Stack" stack cards.

-------

-------
                                                  'Soil  Venting Stack' Cards
                                                                                                         A1
A Practical Approach to the
  Design, Operrioa, ml
 Uomtoring of In-Sita Soil
      Venting Systems
This HyperCard Slack
through the thought p
                                                         created to help guide environmental nentists
                                                                 y to decide if and bov toil renting might
ha applied to
foUomthe
                                                         TBnstte. Tha organization ml logic of this stack
                                                                         P. C. miMM.C. C. twain,*- W. SLnUonU, J. ». CoMut. * D. L. Bjra

                                                                            published in Ground Water Monitoring Reviev, Spring 1990. p. 159-178
                                                                            In-Sitn Soil Venting System Design Process
AtoatSoilV*
                                                                                                                                      Oijtra
                                                                        en ta|B> M «• «n «« «• puna tycttcUif a ate «• tMk a Spffl Dbowm*- fcu. or «•
                                                                                          ' -   "•   '
Soil Venting («.k.a. "uxinisoil
*ia-silu vapor mncbon') is
raptdJy bamming on of U» mo«t
influent* tbefueeen of toy »oil
wnUngopa
undentood.
                                    Pralimiitmfy Site InvwHigation
        orSfrll DucowumJ...
 In U» foUoviagcardf vi vill aaumt
 lhat * leak or ipill tea bam discovered,
 andUeappropriataeiaErgencrreioni
                                            B Tflfl i Tti'ffliaiytfK'H pr?i7iftfn tf fiftlff^lftTf
                                   or (utpKtal, a, site invesngatton is conducted to
                                   characterize and delineate Ua zone of soil and
                                   groundviter contaminatioo. In general, tb> site
 HOVVB will ctep through « logical
 thought procanto dead* if »U Mtfiag
 iiBppropriakiatthiia*). The preview
 card display 00 flovcnnt that it tfae
 basis (of tix) tbot^tt prouu. Clicking
 vilhin any prootsf box via take you to
 that action of the «»aci dealing vith
 that aspect of d» tbougbt proaa.
                                      uDnvdiaBi inyact on poutiilial huiuauaod
                                     virocnnBBb) mton. and is conducted in a
                                    nlatMy ihort period of hm{dayi).  A dstailad
                                   alia elm aHm uation than follow.  Itspurpoa, like
                                   tteanergencyrespomgxnl abatement phase, is to
                                   dulHiuunv potoBbial nttgratioo pattivays and
                                                                                      til impact associated vith prennt
                                                                          b Venting Appropriate?
 Screen Treatment AltematiTes
 With any oontanuntednki, one should
 BinlorettafBanbilityofantreanM
 procnns. After oompilm,} • list 01
                                    At this pout m vill p
O IncinBranon
O Composting

O Land Farming
Oln-Situ
 impte thought process to decide if soil
 venting is a (eeahleallBmaliw. As
 mentiotBd earlier, the three main factors thai
 govern the succesi of a venting operation are:
 be eKaUished, and than tna final
 choices)
 - vapor flovnte
 - vapor *^""""*>
 - subiurAcB Miaiig^&pby (or tfa§ loution of
QSolidifialionfilabilizalMD
OSohent ExtnctionSoil Washing
 Soil Venting it meat likely tote
 cuccBsdld VDB&joilf aremly and Ite


-------
                                                 •Soil  Venting Stack*  Cards
                                                                                                                                         A2
Fknrnf* KHuamtaam:
                            1) Canon loBT)n, or
 O Medium Sand
 9 Fin Sod
 OSiltySana
 O Clayey Silt.
 O Input Your Ovn Permeability Range
   Permeability Range
     i   i   i u> i  in   i
 WellRaditB
 Radios of Inftatoc*
                                                                       Vapor Concentration Estimate
                                                                       Tba
                                                                       rate secure vlnumur tha vapon
                                                                       renjpvBd by venting vs "saturated*
                                                                       or in equilibrium vilh the
                                                                       In the ani card you villc

                                                                       ofyoureofBanuanl. JurtfoUov
                                                                       fl> in-tructioni in tt» upper left
                                                                       eoner of the not cent.
        Vapor Concentration Estimation -

T) Type to Temperature (*C) (hit )      [~
     Click to Enter Composition of C<
[2J or
     ChMM one of the Default DiHributioni

(T) Click to Viev Dirtritaitionj, (optional)

[T) Click to PBrfonnCalculationi
                                       O Enter Dirthbution
                                       O "Fresh* Gasolin
                                       ( VievDirthbulioDi 1

                                       OPafonDCakadaliooi
                                                                                   Removal Rate Estimates
                                                                      J.UIDOV81 T***V OCCWS VDfiUf
Un vapon removed by venting j
   'saturated' or in
equilibrium vith the
                           Extimztod
Removal  -     Vapor    z  Vapor
  Rate      Concentration   Flovnte
                  Sum of Man Fraction
                  Calc. Vapor PTCBUT*
Tha 'Reoxmt Rate' i* (imply
the product «f tba Oovrate
tum IhB *ffltl"l' f^.HM.BBfrlrt17B
The TClu* yon iapiA on Cardf
(fclOvillaauMlto
                                                                      vith jow dennd removal rata.
                                                                                                        Enter Deand
                                                                                                        RamdiatioB Time
                                                                                                                                   ays
                                                                      don not mad your danrad
                                                                      removal rate, then Mil venting
                                                                      if DM likely to matt your medi, I
                                                                      and you ifaoukl oonnder another |
                                                                             technology^ or Bosks
                                                                                                     Singto Vntieal Will KmoOU
                                                                      In the npl cards, ve vill refine \
                                                                                                  *.[£•*
          VeatiqgAfptoprimti? - &*fiaeJfrtim*ttt
 The pnc8diQff cftuDstu m
 useful only •> a •{Snteut*. and
 should be refined if venting it
 itill a potentially taribto
 option.

 Typically during foil venting.
 tot metrured vapor
 toe plot on the rigjtf
 (vhen th> tote] vapor flovrate
 ii relatively conttmi).
                                                                      Man P**iMC*lcat*tx>a*
                                                                       Pictml fltlbs r^gfaiw
                                                                       resuHt of mnpifl ™r<**a*
                                                                       predictionf,for«
                                                                                                , OOCjC(t-0)
                                                                       Tn§ wuual ans nplttanni
                                                                                  •d
                                                                                  [C(tyC(t-0)l
                                                                       or nonnaliad removal rates
                                                                       total vdurnt of vapor
                                                                                                                                 300

-------
                               •Soil Venting Stack" Cards
                                                                      A3
Is Vejitiag Appropriate?
                           Other fltinridnntiba*
of to data and rente.
Based upon than number*, a
should g™ yousomt
                           Ilk]:
                        (uo* T«> i«cmi
appropriate wrtuig ii for
yourapplialion. Note that
Qas it tl» nmnter of valli if
Mia Vol alAfe |U|-mUMl|:
                                                                    Lov Permeability Lenses
                                                     1b tan Aon •*. click

        Field  Tests
                           /•Mt/STfc
Prior to tba design or ai
obtaiii m&n rafiDBd ost
potential vapor flovrab
rft"**>¥>"'*f'> vapor cone
1 IB BtU toil Q
irabtoto
jnatejoftto
ability.
«, and
sntnttioDs. In
tyiluiu nffi1* te uBtaUod, tben
aquifer doracteristia nut also be
determund. -
Click on the button to OB rigB to
tarn about tlnse lasts, or to analyze
data that you hme already collected. O
                                                                   . Air Pannaahility Tait

                                                                    Aquifar Characterizatioa
     System Design

-------
                                            "Soil Venting Stack"  Cards
                                                                                                  A4
System Design...

AttharijtttifaltstoraBCMnpoamti
«f a venting fyjtamdaagn. Click on
t*ett to coaSiEt tte jwtimtiiii
   OKwnftar of Ettnetira Wall*

   O Wall
                             O

                             Q


                             O Vapor Treatment
                                     System Monitoring..
                                     Tto fttffotiDMDCB of •
                                       luzu DQUA bo iQDQikWBd ilk onlsr
                                     to mutt flfficiflEi ojMnEbon, and
                                     to bBtp dfitenoiDB vbm to chut off
                                                                                                 Tio
                                                                                        O Vapor Flow RUM
                                     At t miiMiEua, tba itemt Ibtad to
                                     UB ri^rt tbould be nwwimL
                                     •Click' on My oaB to get mon
                         O Vapor ConcantralioBf k Compoatiom

                         OTonpamlun

                         OVatar TmblB Lmd

                         O Soil Gta Concutntion fc Coopoation
 System Shut Down...
Target »c«I dasn-uj) tonb an
often nt on a ow-iy-ntB batii,
mdanbasadontteeftiniated
potential imp«rt that any
raniltal may bam on air
   lity, ^oundvahr quality, or
otharhB«mutai>danJt.
O CmaHatiw Amaont Ramomd

O EaJr«Uon WaU Vapor Coocramiion

O EatraetioB Watt Vapor CompontioD

OSoilGaiData

QSoU Boring Data
                                     Economics...
For typic&l ttrvm station sites,

HOOK - J250K for the wrting
oporvboD BOOB, dflpeoding on
UB oocnphrpty of Ibo sits,
dtMtHB) tine, pBnnitting
          and Ite typn of
                                  •Click- oo any itam belov (aV
                                  hold boUoDdovn) long costi
                                    •ncocirtad vitb that item.
 Acknowledgements...
                                                                                                                                       I
                                                                                                                                       I*

-------
               -Hyperventilate Users Manual -
Appendix B:  "Soil  Venting Help Stack" stack cards.

-------

-------
                                                  "Soil Venting "Help Stack* Cards
                                                                                                                   B1
Help:  Stack Information
                                             Help:  About Soil Venting
ate iofanaiuii ataat ton vcnina on te fool m the fdooiaa sttMeK
             in Oramiwuei, HOMEU, TX, 1984.

P. C lahoMB, M. W. Kcmblmnki. «ui I. D. CoUhul, Raaicii
VMI
ia O
                                                                          N. J. Hacdn, 8. E. Mmpby. md J. S. Okrtt. Slue of Tcdmoloiy Rcvvw: Soil Vipoi Einraos
                                                                                                     , IMt.     "
                                             D. J. Wilion, A. N. Oatte, mA J. R date. Soil Oun-up by mom
                                             MafeUnf. Sep. Socnce Toct. 23591-1037. 19U.
Buttons
Biuuni have been placed in each
card. Clicking on any button will
pcitunu an action, neb as:
         OoHomnGnl
         cninVeBiiiaSw*
When curious, click on Symbols,
Picture or Text.
Fields
Reids may contain information, or they may be
a place for you 10 input munben.
Scrolling Field:
didc a smsi • aw
  XcEcB lae sown, H
mow tm to» up or daw
win UK mouse.

  Inihi»atM.TOiicm  _
                             Boxed DaU Field:
                     Try this example:
                     Bpttr Number is Baa
                     I        II inches
Help: fa-Situ Soil Venting System Design Process
                                             Help: Preliminary Site Investigation
 This i> the decision process that one must follow to:

 1) decide if toil venting is applicable at a given rite

 &

 2) deaign an effective aoil venting system

 It ia an abridged version of Figure 2 In M Practical Approach to rA* Duign,
 OptnUUM. 
-------
                                              "Soil Venting  Help Stack" Cards
                                                                B2
Help: In-Situ  Biostimulation
Help: Solidification / Stabilization
 Fnctit Dtterifttoit
 Pnctit Diteriptio*
 Treatment of groundwtter tad toil
 contamination below the water able

 (•saturated zone*) by iwitu
 bioeumulition involves the iddition
 of nutrients and/or O2 (usually aa
 H2OZ or liquid O2) to to aquifer in
 order to enJitnce the de0adstion of
 die hydrocarbons by indigenous toil
 microbes. The nutrient! tud
 oxygen trc added tbove (round to
 Stabilization ind solidification «re
 Ubauiient processes designed lo
 either improve waste handling and
 physics! chjuacterisQcs, decrease
 surface am scrota which potlutanU
 an teach, or limit the solubility of
 hazardous comuratati. When
 discussing thiJ technology, the
 following definition.!
 Solidification.

Help: Solvent Extraction / Soil Washing
  Proctti D€fcriptton
  "Solvent 010*0100" it the process
  by wnicn contaminants aits nnweu
  from toil* or sludges by mixing
  them with a solvent into which the
  contaminants preferentially
  partition.  Which solvent is used for
  any particular treatment it very
  dependent upon the type of
  contaminant present in the coil.
  Ihe solvent ihould have * high
  affinity for the contanuntm(t) of

Help: Soil Permeability
 NaB fttfk den.*,
 onta. while K
 coqducivuy'. The Mo «• nttmt fcy:
Help: Decision Matrix
 (1) - Offcrouconpouadi trill »aiy m
 fteir«ssMtf
Help: Vapor Flowrate per Unit Well Thickness
                                                                                                     veil li/aa-if] a (ami
                                                                                                    t jOl a lO*»Aan» n-1 «n
Help: Unit Conversion (k and K)

       Bad miai - <** for «dl olcaluioo!)
     Convert Rcm

     O cnvk
     O Wd
     ® cm2

     O darcy
 Help: Compound List
   Vkw Only Mode  I
        ConuMnnd Name
                                                                                                      Friction  WcifM
                                                                                                                          V.BW
1
2
3
4
J
6
7
8
9
10
propane
isotelane
it-butane
tnni-2^>utcnc
cis-2-butene
3-mwhyl-l-butene
isopentane
1-pentene
2Hnethyl-l-butene
2-methyJ- 1 J-buiadiene
0.00
0.00
0
0
0
0
0.0069
0.0005
0.0008
0.0000
f "1.00660 1
44.1
58.1
58.1
56.1
56.1
70.1
72.2
70.1
70.1
6S.1
IJ A
2JJ
2.11 I
\yi 1
I.W I
OM i
0.71 I
"•' 1
Oil 1
045 C
» torn «f Mist PrtcDoo.
                                                                                                                (.bouUte-1)

-------
                                              "Soil Venting  Help Stack" Cards
                                                                                                                B3
Summary Card: Site Characterization
                                               Compound List Default Data
                     mult determine Ihe following:
 SttbivrFacc Characteristics
                                 Contaminant Delineation
                                 • emt rf heftfoaK aydraibn
  duncaaMiaof etsoaa nl kyot
  teenwtiliiy «ejiii
Help: Data for Fortran Program
                                               Help: How Do I Measure a Distribution?
                                 V*nr
 *  Compound Name
     i<'Q  (Ana) SolulaSly DuL
Wat* 01  @T.
 (em)  An  20'C
                                             Cocff   Din.
   BHB-I^ume
   2-mabyi.l
 44.1
 31.1
 58.1
 5«.l
 36.1
 70.1
 74£
 70.1
 70.1
 M.I
8J
2.93
2.11
1.97
1.79
0.96
0.71
0.7
OJS7
OJS3
62
49
61
430
430
130
41
141
155
M2
73
537
944
204
204
708
1(62
710
923
323
OJ)0
OjOO
0
0
0
0
0.00«9
0.0005
0.000*
0.0000
                                                                      ieriet cdtmibs clMin iltm (n-kuuB, n-penoa:.
Help: Calculate a Distribution
                                               rlelp: About Calculation
                                                                     In this estimation of equilibrium
                                                                       mnted) vipor concenntioni,
                                                                     we attume that the con&uninmu
    Buerte*
                           1000
                           5000
                           7000
                                                VOtt
                                                OM
                                                OM
                        0.00000
                        0.07C92
                        0.3*4«2
                        OJ3844
                        0.00000
                        0.00000
                        0.00000
                        0.00000
                        0.00000
                        0.00000
                               (>200 aiffeg TPH) DIM it is
                               distributed between vapor,
                               loitacd, diiiolved-in-wil-
                               moiraire, A fice-phasei. In thii
                               cue. the equation at the light
                               applia Oook for 'Raouli'f Uw*
                               A the "Ideal Cat UW in any
                               ttennodynamici textbook for
                                                                                                                         i[unij
                                                                            M.
                                                                            K
                                                                            T
                                                                                               RT
Help: 6a) Dilution Effects [Bypassing]
                                               Help; 6b) Liquid Layers
 vqwrflow
                            flow
             SU* View
                                                View
  Tlie figure above depict* tile ate where aome vapora  bypaia* zone* of
   anwmination, and Ihcrcfore the vtpon removed from Ihe euraction well
  repreaeni a routrarc of 0ie vapon obtained from both contanunated and clean
  vapor flowpuhf. One can roughly judge the amount of bypatnni by Ihe well
  placement, icreoiing, t«i cocBaniinanJ diitribulion. Cenenlly, obterad
                                                In Figure 6b, vapor flows parallel to, but not through, the zone of
                                                contamination, and the significant maw transfer resistance i* vapor phase
                                                        This would be Ihe case for a layer of liquid hydrocarbon rating on
                                                        mpcnneable strati or the water table. This problem was
                                                                 NWW,

                                                                          ihotu Me Eauvllont
                                                                                                  Return
                                                                                                              left DO • Calculation

-------
                                               "Soil Venting  Help Stack*  Cards
                                                                                                                                         B4
                                                                      Help: 6c) Low Permeability Lenses - Equations
Help: 6c) Low Permeability Lenses
                                                                                                                 Derivnuona for these
                                                                                                                 cqu>Uon> ire given in
                                                                                                                 Johnson, et al • "A Practical
                                                                                                                 Approach to the Design.
                                                                                                                 Operation and Monitoring
                                                                                                                 of In Situ Soil Venting
                                                                                                                 Systems" - 1990.
 In the situation depicted above, vapor flows past, rather than through the
 contaminated soil zone, such M might be the cue for a contaminated city ten
 surrounded by sandy soils. In this cue vapor diffusion through the clay to the
 flowinRVaoor limits the removal rate fthc removal rate actually become!
                                                                                                                These Equations are valid
                                           test's Do sj Calculation
Help: Default Boiling Point Ranges
                                                                      Help: Boundary Layer Equations
   The Fonnn program HYPEVEKT will report residual levels of compound!
   Ailing between user specified boiling point ranges. The default value* have
   been chosen  10-4 s>cm«
* nil pnBB«bil]iy n v^por flew [cm2]
a dacsm of smcacd ouov.1 [cm]
'= ndius of mnuracc of wnui well |cm)
     |VcUn4iiiB(aBl
               •an -1J161106 j/an-«Z
           > il Itae VCBB>( «r<41 [fjcm42]
     • ie(ioo m wluch c
 Help:  Boundary Layer Equations - Calculation
                                                                       Help: Low Permeability Lenses  - Calculation
                                                                                                            3] C    -> Calculate <--    J
 T)Soll Tjtpt (choose one)
 QSiHySjml
 Q Input You Ova tamubi£9 Bmie

 ;   ;   I to I   10   I  Idarcjrsl
 T) ProccM Variables)
                                      Jun enter valua into the
                                      approprUtc field*, then click on
                                      the "calculate" button.
                                     The "Relative Efficiency" U the
                                     ratio of the predicted removal
                                     rate to the removal rale that
                                     would be obtained if the euncied
                                     vapon wen saturated, or in
                                     equilibrium with the liquid
                                   Relative Efficiency
                                          (*)

Ground Water Table Upwelling
                                                                        Date and Time...
  During venting, the pressure
  within the radius of influence of
  the vapor extraction well is
  lowered, due to fee applied
  vacuum. This lowering of the
  pnsnire affects the groundwater
  level in this zone, and an
  "upwclling", or local rise in the
  water table will occur.

  The local water table rise can be
  u great as the gauge vacuum
  applied at the extraction well
                                                                        Generally, the DATE and TIME
                                                                        Should be recanted along with any
                                                                          uuremeni that is made.  Given the
                                                                        time scale for vcnting-relsted
                                                                        processes, recording the time to the
                                                                        nearest minute should be sufficient.

                                                                        Sample devices are Rokex watches,
                                                                        hour glasses, sun dials, and timers.



-------
                                                 -Soil Venting Help Stack* Cards
                                                                                           B5
Vapor Flow  Rates...
                       Pressure/Vacuum  Readings.
 Vipor flow rates from ctdi
 ounelion well and into my injection
 welUihould be monitored.

 Simple measuring device* include
 pitol tubes, oriface plates and  4
 rotameten. it "a important to have
 cilibnted these devioet M Ibc field
 operating prciiiini Mid temperature*
                        Pftsnu is/Vacuums should be
                        measured it each extraction and
                        injection mil. In addition. subsurfaee|
                        pressure distributions (measured with
                        vsdose zone installations) are useful
                        for determining the zone of influence
                        aid vapor flow pathi.
Vapor Concentrations & Composition...
                       Temperature...
 The vapor concentration and
 composition from each extraction
 well should be analyzed periodically.
 Thit data is multiplied by the
 extraction well flownte to calculate
 the removal nte (i.e. IWdiy), and
 cumulative amount of contaminant
 removed.

 By iuelf, vapor eoncentniion data
 doe* not give a complete picture of
 the system's performance. Decreaiei
                                                           TeJnBif
                        The soil and ambient tempcraoirei
                        can have a significant effect on the
                        performance of soil venting system!
                        The soil temperature affects the
                        contaminant vapor concentrations,
                        while the ambient temperature
                        contrail whether or not condensation,
                        or even freezing will be significant.
                        For future reference, therefore, it is
                        useful to record UK ambient and soil
                        tempefaoires.
                                                                                                                             


-------
                                                 •Soil Venting Help Stack* Cards
                                                                      B6
Extraction Well Vapor Composition...
Soil  Gas Data...
 EXTRACTION WELL VAPOR
 COMPOSITION

 when combined with vipor
 concentrations ihif da* gives more
 insight into the effectiveness of die
 system. If the lout vipor
 concentration dfrmiei without •
 change in composition* it is
 probably due to increased m«s
 transfer retuuncc (water table
 upwelling, drying-out of low
 permeability looet, etc.). and is not
 SOIL GAS DATA

 this data 'a the most useful because
 it yields information about the
 residual composition snd extent of
 Vspor concentntian can not, in
 genera), be used to determine the
 residual levd, except in the limit of
 very low residual levels (when
 vapor concentrations are
 proportional to soil residual levels).
Soil Cat Monitoring
 Installation Results
                                                             r.Sft
 SOIL BORING DATA
 Generally confirmation (oil barings
 are taken once a system is turned
 off, and these sie often analyzed for
 TPH (total petroleum
 hydrocarbons) and volatile
 residuals.

 One should keep in mind (hit TPH
 results can often be misleading.
 since they reveal nothing about the
 composition of the residual or its
Bont
Bcfm
B-l
B-2
B-3
Ate
B-4
B-i
BJS
TPH
fmsAtl
1200
14OOO
S600

20
120
5
BTBX
(ni/ktl
20
120
400

ND
O.I
ND

-------
              -HyperVentilate Users Manual -
Appendix  C: "Air  Permeability Test"  stack  cards.

-------

-------
                                                "Air Permeability Stack" Cards
                                                                                                                                         C1
Air   Permeability   Tests...
The purpose of an air permeability lest it
to obtain siie-spocific data Oat will be
used in the final system design. It is a
way to verify thai venting is an
appropriate remediation technique for
your site.

In particular, one typically tries to get a
better estimate of the soil permeability of
each distinct soil layer to be mated, and
a bcoer estimate of contaminant vapor
concenlrations
                                      (   Show Me Set-Upj
                                      [   Test Instructions
                                                                                           Calculate <- J
                                   •Hoc nEina a Pn> Volume:
                                                             fr"3
     Air  Permeability  Test  -  Sample  Data
                                  • ,               ,
                                                                      Pictured at file right are the
                                                                      soil vacuum measurements
                                                                      from an air permeability
                                                                      tat conducted in a silly
The specific operating
conditions and site
characteristics arc described
in "A Practical Approach to
the Design, Operation, and
Monitoring of In Situ Soil '
Venting Systems-, by P. C
                                                                                                                     Time(nun)
 Air Permeability Test - Data Analysis

 The expected decrease in subsurface pressure (increase in gauge vacuum) P* is
 predicted by: <*eJota«.B«l(l990)forcta1».»D>
              F(r,t) =
                       4itm(k/|i)
                                 f     *•
                                J *.r
                                                                      Air Permeability Test -  Data Analysis (cont.)

                                                                      For (r* cuH k Pi»» I) < 0.1, the governing equation can be approximated by the
                                                                      expression:
                         .[ -0.5772 - I
                                                                                                                     ln(t)J
                                                                       This Equation predicts that a plot of P1 -vs- ln(t) should be a straight line with slope
                                                                       A and y-tntercept B equal to:
 Air Permeability Test - Data Analysis (cont.)

The permeability, k, can men be calculated by one of two mohodi;

/yv The first is applicable when both Q (flowrate) and m (well icreen interval) are
^ known accurately. The calculated slope A is used:
    The second approadi is used whenever Q or m are not known wilh confidence.
    In ihiJ case. both, the slope, A, and intercept, B, are used:
                  t •.«* 0,5772 + £.)]
                                                                      Air Permeability Test - Data Analysis (cont.)

-------
                                           "Air  Permeability Stack"  Cards
C2
Air Permeability Test -  Data Analysis (cont.)
                   4tf»jMil>pt>enliI»llBTOnaim»
-------
                -Hyperventilate Users Manual -
Appendix D: "Aquifer Characterization" stack cards.

-------

-------
                                         'Aquifer  Characterization"  Stack  Cards
                                                                 D1
Aquifer  Characterization:
To achieve efficient venting, the
hydrocarbon-contaminated ml must
be exposed to air flow, therefore, in
most case* where the residual nil
contamination lies close to, or below,
the unrated toil zone (grouadwster
able), it will be necectaiy to
incoipontte a groundwater punping
system in the vapor cunoioo system
design*

A« mentioned previously, one mut
always be aware of the troundwater
Aquifer  Characterization:
Since mod venting systems are installed tbove "phreatic squifen" (aquifen with
unconfraed upper tarlmctt), the two primary aquifer parameters needed for daign
                  K » hydraulic conductivity
                  S - effective porwity (or tpecifie yield)

The fint parameter repreienti a convenient combination of the fundamental
parameter*: permeability, deraity, and vitcoiity:
where;
Aquifer   Characterization:
These parameters (K and S) can be estimated iving the result* of • nmoud traoiicnt
groundwaur pump ten with a connant punning me. The resuiu arc then compared
igainn nandard "type curve** for specific aquifer lituations (i.e. leaky, unconfmcd
iquifen, etc.).
Presa the "Reference!" button below for more information on dug tests, bail tens,
pump teat, and data analysis.


                             1 to Main Stack ]
Aquifer  Characterization  -  References
}. Bear. "Hydraulics of Groundwater", McGraw-Hill, 1979. ISBN 0-07-004170-9,
p. 463-490.

R. A. freeze and I. A. Cherry, "Groundw.ter-. Premice-Hali, 1979. ISBN
0-13-365312-9, p. 339 - 35Z

-------

-------
           - Hyperventilate Users Maraud -
Appendix E: "System Design" stack cards.

-------

-------
                                                                             "System Design* Stack Cards
                                                                                                                                                    E1
h   '
\j
                         Number  of Venting  Wells...
                         lumber of ettacBOB well* ia inaSar ID Of
                                ea'fanfxxialjilodctniBB
                                ipf«o"naa> « • •*•» "»»•
                                                                                    m Ot *Ufib»' btutoo. tad Ota poacd •>
                                                                                    i (i». dick  Stl 0«t»»lt BP
                                                                                                        Boilim Faint Raiwe »5
                                                                                                                              -5.0...
                                                                                                                             ...at...
                                                                                                                              .8ft...
                                                                                                                              .UL.
                              ...2ft..;
                              ........
                              ...Ul..
                                                                            Removal   Efficiency...

                                                                            IBB mbuface ia difficiill n cbanocriae, aid
                                                                            lanly oanf onaa to oar ttodan of a "auHlbta".
                                                                            Tbaw an tme amend damoa of Btouicoa But
                                                                            will caaac mliif nmtnal «Ea • BB baiBtaD
                                                                            BMo pnotcM tat 
-------
                                                •System Design' Stack Cards
                                                                                               E2
Help: Well Parameters
                           Help: Minimum Number of Wells
                                                                                 a Nomber of Won.- ii c*lcBB«l by a» mv BKlbodi dimmed bdo«r
                                                                        to pan* «r flaw dmmsk to ammamm* ne MYOB hm
                                                                                      MtenailamgrcoBiMiaMio^
                                                                                      teflBBM* if « aBKtiai «dl, few
                                                                                       Ri1
 Contaminant Composition
   Vttw only Mod«
        CorapoiDd Nimc
                                    Man
                                  Fraclira
Molccibr
Wrijhl d)  Ol  II  TC
I
2
3
4
S
6
7
8
9
10
propane
isobutftjK
n-buuae
tnin-Z-butcnc
c«-2-buteoe
3-methyl-l-buune
uopodine
1-pentene
2-nmhyl-l-buiene
2^n«hyl-l J-butadiene
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
44.1
58.1
58.1
S6.1
S6.1
70.1
72.2
70.1
70.1
68.1
" 2
193
111
1.97
1.79
0.96
0.78 |
0.7
0.67
0.65 C
                            Flow Do I Measure a Distribution?
Detamining ihe ejuet oompoeuoo of
u>iiykn mixtures
(nich u guoline) requtrei ipeciftlized
•nalytUal technique*. For the purpose of
cnimaimg the roponsc to vouing, however,
   ipproximuc compoiitiaa on be tiled widi
voy good result*.


one mu*t unftyze the mixture by gu
        nphic «n*ly»o.  Prior to the
Butyia. ehoOK about 6-10 muter
 ompoundt who«t proptrue* «ie wdl known.
Calculate a Distribution
          aGCoatyica
                                                  0X10
                                                  OJOO
                                                  111)
                                                  OJOO
                                                  OM
                                                  OJDO
                                                  OM
                                                  OXK)
                                                  DM
              0.00000
              0.00000

              1.00000
              0.00000
              0.00000

              0.00000
              0.00000
              0.00000
To be able to nicceafuUy locate  i
attraction well*, passive wells,
and surface seals one must have a
good undemanding of vapor flow
behavior. Wells locations should
be chosen to maximize vapor flow
through the contaminated zone,
while minimizing vapor flow
through other zones.

If one well is sufficient, it should
almost always be placed in the
geometric center of the
I
Well Construction
                            Surface Seals
 Wells should be screened only

 unless the permeability to vapor
 flow is so low thst removal rates
 would be greater if flow were
 induced in an adjacent soil layer.
 Removal rate estimates for various
 msss-tzaosfer limited scenarios m
 discussed elsewhere in this suck.

 Based on predictive equations, the
 dowrate is expected to increase by
 15* what the extraction well
            rvCFipe
Surface mil, such as
polymer-based linen and asphalt,
concrete, or clay ops, are
sometimes used to control the
vapor flow paths. Figure 12
illustrates the effect thai a surface
seal will have on vapor flow
patterns.  For shallow ^*ffi^trrf
zones <
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                                                "System Design" Stack Cards
                                                                  E3

Groundwater Pumping Systems
 In cue* wheie oonaminated toil*
 lie jun above or below die water
 table, (rouadwMcr pumping
 ijrstena will be required to insure
 tint contaminated aoila remain
 espoied. In designing a
 groundwiter system it u
 irapomm to be awue itat
 upwelling (draw-up) of the
 groundwiter table will occur
 when • vKuum it »ppUed it die
 attraction weU
 (tee the figure ai the right).
Vapor Treatment Systems
 Currently there * four main
   itmoit aroaeut* available:
 VAPOR COMBUSTION UNITS:
 Vapors are incinerated «nd
 denrucuon efficiencies «re
 typically >9S*. A supplenwnial
 fuel, such u propane, it added
 before combustion unlen
 extraction well vapor
 concentntions are on Ibe order of

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              -Hyperventilate Users Manual -
Appendix F: "Compound List Update" stack  cards.

-------

-------
                                            'Compound List Update' Stack Cards
F1
Compound List Update
Thi« cvd U provided u i utility Co let you »dd, or delete compound! from the
Compound Lift Du* B«e thit thii program uicx. You miy not delete or ohmge Ibc
properties of (he bnw <2 compounds, fince ttoe vc needed for the two definite
guoline cue odcuUtion (U. the "Frcih" and "Weathered* guolinet). If you wish
to chinge toy of the propertei of the idded chemicals, firet delete them, then
reiraert them into the Con^oand Lilt DtuBtte.  Follow the direction below:
          egftefbOmim:
                                           (meanly 30
                         Ckcminl N»inc;lNe»Comg
                                                         otlcn)
                         Molcutor Wdikl [l/mot«]
                         Vmpor Pm»n «2IC J.titi)
                         8«Uli« Pei.l 01 aim (C|

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               -HyperventilateUsers Manual-
              Appendix  G: Reprint of:

"A Practical Approach to the  Design,  Operation,  and
    Monitoring  of In  Situ Soil Venting Systems"

-------

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                      Reprinted from the Spring  1990 Issue of
                          Ground Water Monitoring Review

            A  Practical  Approach to  the  Design,

            Operation,  and  Monitoring  of In  Situ

                            Soil-Venting  Systems

        by P.C. Johnson, CC. Stanley, M.W. Kemblowski, D.L.  Byers, and J.D. Colthart

 Abstract
    When operated properly, in situ soil venting or vapor extraction can be one of the most cost-effective remediation
 processes for soils contaminated with gasoline, solvents, or other relatively .volatile compounds. The components of
 soil-venting systems are typically off-the-shelf items, and the installation of wells and trenches can be done by
 reputable  environmental firms. However, the design, operation, and monitoring of soil-venting systems are not
 trivial. In fact, choosing whether or not venting should be applied at a given site is a difficult decision in itself. If
 one decides to utilize venting, design criteria involving the number of wells, well spacing, well location, well construc-
 tion, and vapor treatment systems must be addressed. A series of questions must be addressed to decide if venting
 is appropriate at a given site and to design cost-effective in situ soil-venting systems. This series of steps and questions
 forms a "decision tree" process. The development of this approach is an attempt to identify the limitations of in
 situ soil venting, and subjects or behavior that are currently difficult to quantify and for which  future study is needed.
 Introduction
    When operated properly, in situ soil venting or vapor
 extraction can be a cost-effective remediation process
 for soils contaminated with gasoline, solvents, or other
 relatively volatile compounds. A "basic" system, such
 as the one shown in Figure 1, couples vapor extraction
 (recovery) wells with blowers or vacuum pumps to
 remove vapors from the vadose zone and thereby reduce
 residual levels of soil contaminants. More complex sys-
 tems, incorporate trenches, air injection wells, passive-
 wells, and surface seals. Above-ground treatment sys-
 tems condense, adsorb, or incinerate vapors; in some
 cases vapors are simply emitted to the atmosphere
 through diffuser stacks. In situ soil venting is an espe-
 cially attractive  treatment  option because the soil is
 treated in place, sophisticated equipment  is not
 required, and the cost is typically lower than other
 options.
   The basic phenomena governing the performance of
 soil-venting systems are easily understood. By applying
 a vacuum and removing vapors from extraction wells,
 vapor flow through the unsaturated soil zone is induced.
 Contaminants volatilize from the soil  matrix and are
 swept by the carrier gas flow (primarily air) to the extrac-
 tion wells or trenches. Many complex processes occur
 on the microscale, however, the three main factors that
 control the performance of a venting operation are the
 chemical composition of the contaminant, vapor  flow
 rates through the unsaturated zone, and the flow path
of carrier vapors relative to the location of the contamin-
ants.
   The components of soil-venting systems are typically
off-the-shelf items,  and the installation of wells and
trenches can be done by reputable environmental firms.
However, the design, operation, and monitoring of soil-
venting systems is not trivial. In fact, choosing whether
or not venting should be applied at a given site is a
difficult question in itself. If one decides to utilize vent-
ing, design criteria involving the number of wells, well
spacing, well location, well construction, and  vapor
treatment systems must be addressed. It is the current
state-of-the-art that  such questions are answered more
by experience than by rigorous logic. This is evidenced
by published soil venting "success stories" (see Hutzler
et at. 1988  for a good review), which rarely include
insight into  the design process.
   In this paper, a series of questions are presented that
must be addressed to:
   •  Decide if venting is appropriate  at a given site.
   •  Design cost-effective in situ soil-venting systems.
This series  of steps and questions forms a "decision
tree"  process. The development of this approach is an
attempt to identify the limitations of in situ soil venting,
and subjects or behavior that are currently difficult to
quantify and for which future study is needed.
The "Practical Approach"
   Figure 2 presents a flow chart of the process dis-
cussed in this paper.  Each step of the flow chart will be
discussed  in detail, and where appropriate, examples
are given.

The Site Characterization
   Whenever a soil contamination problem is detected
or suspected, a site investigation is conducted to charac-

-------
 terize and delineate the zone of soil arid ground water
 contamination. In general, the  site characterization  is
 conducted in two stages. The emergency response and
 abatement phase  assesses the  immediate  impact on
 potential human and environmental receptors, and  is
 conducted in a relatively short period of time (days). A
 detailed site characterization then follows. Its purpose,
 like the emergency response and abatement  phase,  is
 to determine potential migration  pathways  and assess
 the environmental impact associated with present condi-
 tions and future migration of the  contaminants. Often
 the  sequence of steps following  initial  response and
 abatement is as follows:
 •  Background review: Involves assembling historical
   records, plot plans, engineering drawings (showing
   utility lines), and interviewing  site personnel.  This
   information is used to help identify the contaminant,
   probable source of release, zone of contamination,
   and potentially impacted areas  (neighbors, drinking
   water supplies, etc.).
•  Preliminary site screening:  Preliminary  screening
   tools such as soil-gas surveys and cone penetrometers
   are used to roughly define the zone of contamination
   and the site geology. Knowledge  of site  geology is
   essential to determine probable migration of conta-
   minants through the unsaturated zone.
•  Detailed site characterization: Soil borings are drilled
   and monitoring wells are installed.
•  Contaminant characterization: Soil and ground water
  samples are analyzed to determine contaminant con-
  centrations and compositions.
   Costs associated with site investigations can be rela-
tively high depending on the complexity of the site and
size  of the spill or leak.  For large spills and complex
site geological/hydrogeologica! conditions, site investi-
gation costs may begin to approach remediation costs.
In addition, the choice and design  of  a remediation
system is based on the data obtained  during the site
investigation. For these reasons it is important to ensure
that specific information is collected, and to validate the
quality of the data.
   If it is presumed that in situ soil venting will be  a
candidate for treatment, then the following information
needs to be obtained during the preliminary site investi-
gation:
• Subsurface characteristics — site  geology: This
  includes the determination of soil stratigraphy (va-
  dose and saturated zone) and characteristics of dis-
  tinct soil layers (i.e., soil type, permeability estimates).
  While they are not essential, the moisture  content,
  total organic carbon, and permeability of each distinct
  soil layer also provides useful information that can
  be used to choose and design a  remediation system.
* Subsurface characteristics —  site  hydrogeology:
  Depth to ground water, and the ground water gradi-
  ent must be known, as well as estimates of the aquifer
  hydraulic conductivity.
• Contaminant delineation: The  distribution of con-
  taminants  in the saturated and  vadose zones needs
  to be assessed. This includes  the extent of the free-
  phase  hydrocarbon, residual hydrocarbon, and solu-
                                    Vapor Treatment
                                        Unit
Vapor
Flow
                          - Vapor Extraction Weil
Contaminated
    Soil
                  Vapor
                   Flow
                                             Free-Liquid
                                             Hydrocarbon
    Groundwater Table
                                Soluble
                                Plume
Figure. 1. "Basic" in silu soil-venling system.
         Process
           Output
                                Background Review

                                Sifp rhararfpi-Kfirs:

                                Sutmirfacf Cbaracfmitkft

                                * charactentnct of Aicinc! tod laycn
                                (pcrmeabiliiy estimates, icil typci)
                                • depth to groundwater
                                • {Toiindwaicx gradient

                                * aquifer permeability (estimate) '
                                • lutttilrface & ittaVc-gr-

j 	 T7 — ~ — h

1
| Ground water Pump Test | 	 *
^ 	 -^
- removal rale alimxlc* 1
• vapof fiowrate euunatea I
* final Riidual fcvel* A. composition ]

- air pcnpcvtilitjr of difiinct 101) Mycn
• radius of influence of vapor wcljj
• initial vapor conc«rtntf ion»

• tadtux of influence ]
* pumping r»e decenninaiion |
                               number of vapor extraction w
                               vapor *d( ccfuituction
                               vapor well fpaaiy
                                  maunoM tysem
                                   (vieuuin) ipcdficaioni
                               |roundw*ia pumping lytiem ipecifici
                               v«iti«t iwovery mei
                        System Shut-Off

Figure 2. In situ soil-venting system design process.

-------
 hie hydrocarbon. Soil samples should be analyzed to
 determine which contaminants are present at what
 levels (contaminant composition). Specific analytical
 methods should be used to identify target compounds
 (i.e., benzene, toluene, or xylenes) and total hydrocar-
 bons present. For soil analyses these methods are:
 EPA  8240. 8020, 8010 -  volatile organic chemicals
  (VOCs)
 EPA 8270 - semivolatile organic chemicals
 EPA 418.1 - total petroleum hydrocarbons (TPH).

 The corresponding methods for water samples are:
 EPA  8240, 8020, 8010  - volatile organic chemicals
  {VOCs)
 EPA 8270 - semivolatile organic chemicals
 EPA 418.1   - total  petroleum hydrocarbons (TPH).
    With the current high cost of chemical analyses it
 is important to intelligently select which analyses
 should be performed and which  samples should be
 sent to a certified laboratory. Local regulations usu-
 ally require that a minimum number of soil borings
 be performed, and  target compounds must be ana-
 lyzed based on the suspected composition of the con-
 tamination. Costs can be  minimized and more data
 obtained by utilizing field screening tools,  such  as
 hand-held vapor meters or portable field gas chroma-
 tographs (GCs). These  instruments can be  used  to
 measure both residual soil contamination levels and
 headspace vapors above  contaminated soils. At a
 minimum, soil samples corresponding to lithology
 changes or obvious changes in residual levels (based
 on visual observations or odor) should be analyzed.
    For complex contamination mixtures, such as gas-
 oline,  diesel fuel, and solvent mixtures, it is not prac-
 tical or necessary to identify and quantify each com-
 pound present. In such cases it is recommended that
 a "boiling point" distribution be measured for a
 representative sample of the residual contamination.
 Boiling point distribution curves, such as shown  in
 Figure 3 for "fresh" and "weathered" gasoline samples,
 can be constructed from GC analyses of the residual
 soil contamination (or free product) and  knowledge  of
 the GC elution behavior of a known series of compounds
 (such as straight-chain alkanes). Compounds generally
 elute from a GC packed column in the order of increas-
 ing boiling point, so a boiling point distribution curve
 is constructed by grouping all unknowns that elute
 between two known  peaks (i.e., between n-hexane and
 n-heptane). Then they are assigned an average boiling
 point,  molecular weight, and vapor pressure. Use of
 these data will be explained later.
   The cone penetrometer, which is essentially an
 instrumented steel rod that is driven into the soil,  is
 becoming a popular tool for preliminary site screening
 investigations. By measuring the  shear and normal
 forces  on the leading end of the  rod, soil structure
 can be defined and permeability or hydraulic conduc-
tivity can be estimated. Some cone penetrometers are
also constructed to  allow the collection of vapor or
ground water samples. This tool has several advan-
           1.0

Cumulative
  Weight    og;
 Fraction
           0.6
        .  ' 0.4
           0.2
           O.O.-
  Figure 3. Boiling point distribution curves for samples of
  "fresh" and "weathered" gasolines.

    tages over conventional soil boring techniques (as a
    preliminary site characterization tool): (1) the subsur-
    face soil structure can be defined better; (2) no soil
    cuttings are generated; and (3) more analyses can be
    performed per day.
  • Temperature (both above and below ground surface)
    Contaminant vapor concentrations are dependent on
    temperature,  and therefore, removal  rates are
    strongly  influenced  by subsurface temperatures.
    Above-ground temperatures will influence the  selec-
    tion  of materials and  construction of the above-
    ground vapor treatment system.
     Results from the preliminary  site investigation
  should be summarized in contour plots, fence diagrams,
  and tables in preparation for deciding whether venting
  is appropriate, and for the final design of the system.

  Deciding if Venting Is Appropriate
     As previously stated, the three main factors govern-
  ing the  behavior of any in situ soil-venting operation
  are the vapor flow rate, contaminant vapor concentra-
  tions, and the vapor flow path relative to the contamin-
  ant location. In an article by Johnson et al. (1988), simple
  mathematical equations were presented to help quantify
  each of these factors. Following it is illustrated how to
  use these ."screening models"and the information col-
  lected during the preliminary site investigation to help
  determine if in situ soil venting is appropriate at a  given
  site. In making this decision the following questions will
  be answered:
     1. What contaminant vapor concentrations are  likely
  to be obtained?
    2. Under ideal vapor flow conditions (i.e., 100 -1000
  scfm  vapor flow rates), is  this concentration  great
  enough to yield acceptable removal  rates?
    3. What range of .vapor flow  rates  can  realistically
  be achieved?
    4. Will the contaminant concentrations and realistic
  vapor flow rates produce acceptable removal rates?
    5. What residual, if any, will be left in the soil? What

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vapor composition and concentration changes will occur
with time? How do these values relate to the regulatory
requirements?
   6. Are there likely to be any negative effects of soil
venting?
   Negative answers to questions 2 or 4 will  rule out
in situ soil venting as a practical treatment method.

What Contaminant Vapor Concentrations Are Likely
to Be Obtained?
   Question 1 can be answered based on the results of
soil-vapor surveys, analyses of headspace vapors above
contaminated soil samples, or equilibrium vapor models
(Johnson et al. 1988). In some cases just knowing which
compounds are present is sufficient to estimate if venting
is feasible. In the absence of  soil-vapor survey data,
contaminant vapor concentrations can be  estimated.
The  maximum vapor concentration  of any  compound
(mixture) in extracted vapors is its equilibrium or "satur-
ated" vapor concentration, which  is easily calculated
from knowledge of the compound's (mixture's) molecu-
lar weight, vapor pressure at the soil temperature, resid-
ual soil contaminant composition, and the ideal gas law:
                                               (1)
             RT
where:
   CC5l  = estimate of contaminant vapor concentration
[mg/L]
   Xi  = mole fraction of component i in liquid-phase
residual (x, = 1 for single compound)
   P;v = pure component vapor pressure at tempera-
ture T [atm]
Mw-i =  molecular weight of component i [mg/mole]
R    =  gas constant = 0.0821 l-atm/mole-°K
T   = absolute temperature of residual [°K].
Table 1 presents data for some chemicals and mix-
                                                TABLE1
            Selected Compounds and Their Chemical Properties (Johnson et al. 1988)
Compound
n-pentane
n-hexane
trichloroethane
benzene
cyclohexane
trichloroethylene
n-heptane
toluene
tetrachloroethylene
n-octane
chlorobenzene
p-xylene
ethylbenzene
m-xylene
o-xylene
styrene
n-nonane
n-propylbenzene
1,2,4 trimethylbenzene
n-decane
DBCP
n-undecane
n-dodecane
napthalene
tetraethyilead
gasoline1
weathered gasoline2
Mw
(g/mole)
72.2
86.2
133.4
78.1
84.2
131.5
100.2
92.1
166
114.2
113
106.2
106.2
106.2
106.2
104.1
128.3
120.2
120.2
142.3
263
156.3
170.3
128.2
323
95
111
Tb (1 atm)
(C)
36
69
75
80
81
87
98
111
121
126
132
138
138
139
144
145
151
159
169
173
196
196
216
218
dec.@200C
-
-
PV-20C
(atm)
0.57
0.16
0.132
0.10
0.10
0.026
0.046
0.029
0.018
0.014
0.012
0.0086
0.0092
0.0080'
0.0066
0.0066
0.0042
0.0033
0.0019
0.0013
0.0011
0.0006
0.00015
0.00014
0.0002
0.34
0.049
ces,
(mg/L)
. 1700
560
720
320
340
140
190
110
130
65
55
37
40
35
29
28
22.0
16
9.3
7.6
11
3.8
1.1
0.73
2.6
1300
220
'Corresponds to "fresh" gasoline defined in Table 2 with boiling point distribution shown in Figure 3.
'Corresponds to "weathered" gasoline defined in Table 2 with boiling point distribution shown in Figure 3.
Tb (1 aim) • compound boiling point at 1 aim absolute pressure.
Mw - molecular weight.
Ce« - equilibrium vapor concentration (see Equation 1).
Pv° (20 C), - vapor pressure measured at 20 C.

-------
 lures accidentally released to the environment. There
 are more sophisticated equations for predicting vapor
 concentrations in soil systems based on equilibrium par-
 titioning arguments, but these  require more detailed
 information (organic carbon content, soil moisture) than
 is normally available. If a site is chosen for remediation,
 the residual total hydrocarbons in soil typically exceed
 500 mg/kg. In this residual concentration range most of
 the hydrocarbons will be present as a separate or "free"
 phase, the  contaminant vapor concentrations become
 independent of residua! concentration (but still depend
 on composition), and Equation 1 is applicable (Johnson
 et al. 1988). In any case, it should be noted  that these
 are estimates only for vapor concentrations at the start
 of venting, which is when the removal rates are generally
 greatest. Contaminant concentrations in the extracted
 vapors wiH decline with time due to changes in composi-
 tion, residual levels, or increased diffusional resistances.
 These topics will be discussed in more detail.

 Under Ideal Vapor Flow Conditions (i.e., 100 - 1000
 scfm Vapor Flow Rates), Is This Concentration Great
 Enough to Yield Acceptable Removal Rates?
    Question 2 is answered by multiplying the concentra-
 tion estimate Ccsl, by a range of reasonable flow rates,
 O:
    R«« = Cest Q                                (2)

    Here Res, denotes the estimated removal rate, and
 Cesi and Q  must be  expressed in consistent units. For
 reference, documented venting operations at service sta-
 tion sites typically report vapor flow rates in the 10 -
 100 scfm range (Hutzler et al.  1988), although 100 -
 1000 scfm flow rates are achievable  for sandy soils or
 large numbers of extraction weHs. At this point in the
 decision process what is still being neglected is that
 vapor concentrations decrease during venting due to
 compositional changes and mass transfer  resistances.
 Figure 4 presents calculated removal rates Rcsl [kg/d]
 for a range of Qj, and Q values. Ces, values are  presented
 in [mg/L] and [ppmCH-»] units, where [ppmcH4] represents
 methane-equivalent  parts-per-million volume/volume
 (ppmv) units. The [ppmow] units are used because field
 analytical tools that report [ppmv] values are often cali-
 brated with methane. The [mg/L] and [ppmcm] units are
 related by:
         [ppmcH4J * 16000 mg-CH4/mole-CH4 * 10'*
 [mg/L]=	
                                                                                    (ppm.
                -13.3
                                                       153000
             (0.0821 l-atm/°K-mole) * (298 K)
(3)
For field instruments calibrated with other compounds
(i.e., butane, propane), [ppmv] values are converted to
[mg/L] by replacing the molecular weight of CH4 in
Equation  3 by the molecular weight [mg/mole] of the
calibration compound.
   Acceptable or desirable removal rates Raccepiabic>can
be determined by dividing the estimated spill mass Mspiii.
by the maximum acceptable cleanup time T:

   Racccpiable = Mspin/T                           (4)
   For example, if 1500kg (•*• 500 gal) of gasoline had
been spilled at a service station and it was wished to
         Removal
          Rate
          (kg/d)
                   (ppm,.
                      t
                   .1          1         10
                     Vapor Concentration (mg/1)

                I ) * concentration in methftne-equivmlent ppm (vo) Aol.) units
                                                         100
 Figure 4 In situ soil-venting removal rate dependence on
 vapor extraction rate and vapor concentration.

 complete the cleanup within eight months, then Raccepta-
 b(e = 6.3 kg/d. Based on Figure 4, therefore, Cesl would
 have  to average >1.5 mg/L (2400 ppmCH«) for 6=2800
 1/min (100 cfm) if venting is to be an acceptable option.
 Generally, removal rates <1 kg/d will be unacceptable
 for most releases, so soils contaminated with compounds
 (mixtures) having saturated vapor concentrations less
 than 0.3 mg/L (450 ppmCH4) will not be good candidates
 for venting, unless vapor flow rates exceed 100 scfm.
Judging from the compounds listed in Table 1 , this corre-
 sponds to compounds with boiling points (Tb)>150  C,
or pure component vapor pressures <0.0001 atm evalu-
ated at the subsurface temperature.

What Range of Vapor Flow Rates Can Realistically
Be Achieved?
   Question 3 requires that realistic vapor flow 'rates for
the site-specific conditions be estimated. Equation  5,
which predicts the flow rate per unit thickness of well
screen Q/H [cm3 Is], can be used for this purpose:
                                                                    [ 1 - (PA,n,/Pw)2]
                                                        (5)
        where:
        k     = soil permeability to air flow [cm2 ] or [darcy]
        p.     = viscosity of air = 1.8 x 10* g/cm-s or 0.018 cp
        Pw    = absolute pressure at extraction well [g/cm-s2]
               or [atm]
        PAIOI  = absolute ambient pressure °» 1.01 x 10* g/cm-s2
               or 1 atm
        Rw •   = radius of vapor extraction well [cm]
        RI    = radius of influence of vapor extraction well
               [cm].

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   This equation is derived from the simplistic steady-
state radial flow solution for compressible flow (Johnson
ct al. 1988),  but should  provide reasonable estimates
for vapor flow rates. If k can be measured or estimated,
then the only unknown parameter is the empirical "ra-
dius of influence" Rj. Values ranging from 9m (30 ft)
to 30m (100  ft) are reported in  the literature (Hutzler
et ai. 1988) for a variety of soil  conditions, but fortun-
ately Equation 5 is not sensitive to large changes in R|.
For estimation purposes, therefore, a value of R|=12m
(40 ft) can be used without a significant loss of accuracy.
Typical vacuum well  pressures range from 0.95 - 0.90
aim (20 - 40 in H2O vacuum).  Figure 5 presents pre-
dicted flow rates per unit  well  screen thickness Q/H,
expressed in  "standard"  volumetric units Q*/H (= Q/
H(Pw/PA
-------
    In Figure 6a a fraction <}> of the vapor flows through
 uncontaminated soil. The fraction can be roughly esti-
 mated by assessing the location of the well relative to
 the contaminant distribution. In Figure 6a for example,
 it appears .that roughly 25 percent of the vapor  flows
 through uncontaminated soil. The maximum removal
 rate  for this case is then:
    R«. = (1-*)QC«                           (6)
    In Figure 6b, vapor flows parallel to, but not through,
 the zone of contamination, and  the significant  mass
 transfer resistance is vapor phase diffusion. This would
 be the case for a layer of liquid hydrocarbon resting on
 top of an impermeable strata or. the water table. This
 problem was studied by Johnson et al (1988)  for the
 case  of a single component. The solution is:
    Rest = *\Q Ces,
n = --
    jtt

where:
tj
                 [ln(R,/Rw)/{PAlm -
              = efficiency relative to maximum
                removal rate
 D            = effective soil-vapor diffusion coeffici-
                ent [cnf/s]
 ft            = viscosity of air = 1.8 x 10 4 g/crn-s
 k            = soil permeability to vapor flow [cm3]
 H            = thickness of screened interval [cm]
 RI         '   = radius of influence of venting well
                [cm]
 Rw           ~ venting' well radius [cm]
 PAI™         = absolute ambient pressure = 1.016 x
                10* g/cm-s2
 PW            = absolute pressure at the venting well
                [g/cm-s2]
 RI  < r < R2   = defines region in which contamina-
                tion is present.
    Note that the efficiency ^ is inversely proportional
 to the screened interval thickness H because  a larger
 interval will, in  this geometry, puil in  unsaturated air
 that has passed above the liquid-phase contamination.
 D is calculated by the Millington-Quirk  (Millington and
 Quirk 1961) expression, which utilizes the  molecular
 diffusion coefficient in air D", the vapor-filled soil poros-
 ity  eA, and the total soil porosity eT:
   = D°
where eA and eA are related by:
                                               (8)
                                                (9)
   Here pb and 9M are the soil bulk density [g/cm'] and
soil moisture content [g-H2O/g-soil].
   As an example, consider removing a layer of contam-
ination'bounded by sandy soil (k=l darcy). A 5.1cm (4
in) radius vapor extraction well is being" operated at
Pw=0.90atm (6.91 x 10* g/cm'-s'), and the contamination
extends from the region R! = Rw =?  5.1cm to R2 = 9m
(30 ft). The well is screened over a 3m'(10 ft)'interval.
 Assuming that:                               •
    •pb  =   1.6g/cnV
    6M  =  0.10                               .
    D°  = 0.087  cm'/s
    eT  = 0.30
    RI   =  12m   '         •    "
 then the venting efficiency relative to the maximum
 removal rate (Equation 2), calculated from  Equations 7
 through 9.is: .
    T,   = 0.09-9%., .
    Figure 6c depicts  the situation in which vapor flows
 primarily past, rather than through the contaminated
 soil zone, such as might be the case for a contaminated
 day lens surrounded  by sandy soils. In this case vapor-
 phase diffusion through the clay to the flowing vapor
 limits the removal rate. The maximum removal rate in
 this case occurs when the vapor flow is fast enough to
 maintain a  low vapor concentration at the permeable/
 impermeable soil interface. At any time t a contaminant-
 free or "dried out" zone of low permeability will exist
 with a thickness 6. An estimate of the removal rate  Rcs,
 from a contaminated zone extending from  RI to R2 is:
                                                            = n(R22~Rf)Ces,D/8(t)
                                               (10)
                                                        where D is the effective porous media vapor diffusion
                                                        coefficient (as calculated previously from Equations 8
                                                        and 9) and Ce^t is the estimated equilibrium vapor con-
                                                        centration (Equation 1). With time 5(t) wiil grow larger.
                                                        In the case  of a single component system the dry zone
                                                        thickness can be calculated from the mass balance:
                                                             d5
                                                        pb Cs — = Cesl D/8(t)                          (11)
                                                             at
                                                        where Cs is the residual level of contamination in the
                                                        low permeability zone [g-contamination/g-soil]," and all
                                                        other  variables have been  defined. The solution to
                                                        Equations 10 and 11 yields the following equation that
                                                        predicts the change in removal rate with time:
8(0 =
2 Ces, D t
  pbcs
                                                                                                      (12)
As an example, consider the case where benzene (Cy =
3.19 x ]0~* g/cm3 @20 C) is being-removed from a zone
extending from RI = 5.1cm to R2 = 9m. The initial
residual level is 10,000 ppm (0.01 g-benzene/g-soil), pb
= 1.6 g/cm', D" = 0.087 cmVs, and eT = eA = 0.30. Figure
7 presents the predicted removal rates and "dry" zone
thickness 5(t) as a function of time. Note that it would
take approximately one year to clean a layer 1.5m (5
ft) thick, for a compound as volatile as benzene. Equa-
tion 12 predicts high initial removal rates; in practice,
however, the removal rate will be limited initially by
the vapor-phase diffusion behavior described previously
for Figure 6b.
   Mixture removal rates for the situations depicted in
Figures  6b and 6c are difficult to estimate  because

-------
changes in composition and liquid-phase diffusion affect
the behavior. Currently there are no simple analytical
solutions for these situations, but it can be postulated
that they should be less than the rates predicted previ-
ously for pure components.
   The use of equilibrium-based  models  to predict
required removal rates will be discussed under the next
question.
What Residual, If Any, Will Be Left in the Soil?
What Vapor Composition and Concentration
Changes Will Occur With Time? How Do These
Values Relate to the Regulatory Requirements?
   As contaminants  are removed during venting, the
residual soil contamination level decreases and mixture
compositions become richer in the less volatile com-
pounds.  Both of these processes result in decreased
vapor concentrations, and  hence, decreased removal
rates with time. At low residual soil contamination levels
(<500.ppm) Equation 1 becomes less valid as sorption
and dissolution phenomena begin to affect the soil resid-
ual - vapor equilibrium.  In the limit of low residual
contamination  levels, contaminant equilibrium vapor
concentrations are expected to become proportional to
the residual soil contaminant concentrations. As venting
continues and residual soil levels decrease, therefore, it
becomes more difficult to remove the residual contami-
nation. It is important to realize that, even with soil
venting, there are practical limitations on the final soil
contamination levels  that can be achieved. Knowledge
of these limits is necessary to realistically set cleanup
criteria and design effective venting systems.
   The maximum efficiency of a venting operation is
limited by the equilibrium partitioning of contaminants
between the soil matrix and vapor phases.  The maxi-
mum removal rate is achieved when  the vapor being
removed from an extraction well is in equilibrium with
the contaminated soil. Models for predicting this maxi-
mum removal rate have been presented by Marley and
Hoag (1984) and Johnson et al. (1988). The former con-
sidered only compositions in a residual free-phase, while
the latter also considered the effects  of sorption and
dissolution processes. A complete discussion  of the
development of these models is not appropriate here,
but we will discuss the use of the predictions.
   The change in composition, vapor concentration,
removal rate, and residual soil contamination level with
time are functions of the initial residual  composition,
vapor extraction well flow rate, and initial soil contami-
nation level. It is not necessary to generate predictions
for every combination of variables, however, because
with appropriate scaling  all results will form a single
curve for a given initial mixture composition. Figure 8a
presents the results computed with the  model presented
by Johnson et al. (1988) for the "weathered" gasoline
mixture whose composition is given  by Table 2. The
important variable that determines residual soil levels,
vapor concentrations, and removal rates is the ratio Qt/
M(t=0), which represents the volume of air drawn
through the contaminated zone per unit mass of conta-
                                                               1000,
        10-
           benzene (20 C'
  200
  "Dry" Zone
  Thickness

      5
    (cm)
  100
          0     100    200    300     400    500
                        Time (d)
 Figure 7. Estimated maximum removal rales for a venting
 operation limited by diffusion.
                             Weathered Gasoline
                             T = 20°C
                             10% moisture content

                 cta^dta.*.,***»  C<(=0) = 222 me/1
                   3 phuc tywoft
        .0001
                                           100
 •80
   % removed
                                           60
                                           40
                                           20
                     100        ZOO
                      Qt/m(t=0) >ucK  C(l=0) = 270 mg/t
  S(*M«.!
             Approximate Composition
                                          100
•BO
 % removed
 60


 40
                     100       200
                     Qt/m(i=0) (1/g)
                                        300
 Figure 8. Maximum predicted removal rates for a weathered .
 gasoline: (a) full composition (b) approximate composition.

 minant. In Figure 8, the scaled removal rate (or equiva-
 lently the vapor concentration) decreases with time as
 the mixture becomes richer in the less volatile com-
 pounds.
    While a detailed compositional analysis was availa-
 ble for this gasoline sample, an approximate composi-
 tion based on a boiling point distribution curve predicts
 similar results. Figure 8b presents the results for the
 approximate mixture composition also given in Table 2.
    Model predictions, such as those shown in Figure 8
 for the gasoline sample defined by Table 2, can be used
 to estimate removal rates (if the vapor flow rate is speci-
 fied), or alternatively the predictions  can be  used to
 estimate vapor flow rate requirements (if the desired
 removal rate is specified). For example, if we wanted
 to reduce the initial contamination level by 90 percent,

-------
TABLE 2
Composition
Compound
Name
propane
isobuiane
n-butaoe
trans-2-butene
cis-2-butene
3-methyl-l-butene
isopentane
1 -pentene
2-methyl-l-butene
2-methyl-l ,3-butadiene
n-pentane
trans-2-pentene
2-methyl-2-butene
2-methyl- 1 .2-butadiene
3,3-dimethyl-l-butene
cyclopentane
3-methyl-l -pentene
2.3-dimethylbutane
2-methylpentane
3-methylpentane
n-hexane
methykyclopentane
2.2-dimethylpentane
benzene
cyclohexane
2,3-dimethylpentane
3-methylhexane
3-ethylpentane
n-heptane
2,2.4-trimethyIpentane
methylcyclohexane
2,2-dimethylhexane
toluene .
2,3,4-trimethyipentane
3-melhylheptane
2-methylheptane
n-octane
2,4,4-trimethylhexane
2,2-dimethylheptane
ethylbenzene
p-xylene
m-xylene
3,3,4-trimethylhexane
o-xylene
2,2,4-trimethylheptane
n-noname
3,3,5-trimethylheptane
n-propylbenzene
2,3,4-trimethylheptane
1 ,3,5-trimethyIbenzene
1 ,2-4-trimethy Ibenzene
n-decane
methylpropylbenzene
dimethylethylbenzene
n-undecane
1 ,2,4,5-tetramethylbenzene
1 ,2,3,4-tetramethylbenzene
1 ,2,4-trimethyl-5-ethylbenzene
n-dodecane
napthalene ' • • •
n-hexylbenzene . .
methylnapthalene
Total
(Mass Fractions)
Mw

44.1
58.1
58.1
56.1
56.1
70.1
72.2
70.1
70.1
68.1
72.2
70.1
70.1
68.1
84.2
70.1
84.2
86.2
86.2
86.2
86.2
84.2
100.2
78.1
84.2
100.2
100.2
100.2
100.2
114.2
98.2
114.2
92.1
. 114.2
114.2
114.2
114.2
128.3
128.3
106.2
106.2
106.2
' 128.3
106.2
142.3 -
128.3
142.3
120.2
142.3
120.2
120.2
142.3
134.2
134.2
156.3
134.2
134.2
148.2
170.3
128.2
162.3
142.2

of Fresh and
Fresh
Gasoline
0.0001
0.0122
0.0629
0.0007
0.0000
0.0006
0.1049
0.0000
0.0000
0.0000
0.0586
0.0000
0.0044
0.0000
0.0049
0.0000
0.0000
0.0730
0.0273
0.0000
0.0283
0.0083
0.0076
0.0076
0.0000
0.0390
0.0000
0.0000
0.0063
0.0121
0.0000
0.0055
0.0550
0.0121
0.0000
0.0155
0.0013
0.0087
0.0000
0.0000
0.0957
0.0000
0.0281
0.0000
0.0105
0.0000
0.0000
0.0841
0.0000
0.0411
0.0213
0.0000
0.0351
0.0307
0.0000
0.0133
0.0129
0.0405
0.0230
0.0045
0.0000
0.0023
1.0000
Weathered Gasolines
Weathered
Gasoline
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0069
0.0005
0.0008
0.0000
0.0095
' 0.0017
0.0021
0.0010
0.0000
0.0046
0.0000
0.0044
. 0.0207
0.0186
0.0207
0.0234
0.0064
0.0021
0.0137
0.0000 .
0.0355
0.0000
0.0447
0.0503
0.0393
0.0207
0.0359
0.0000
6.0343
0.0324
0.3000
0.0034
0.0226
0.0130
0.0151
0.0376
0.0056
0.0274
0.0012
0.0382
0.0000
0.0117
0.0000
0.0493
0.0707
0.0140
0.0170
0.0289
0.0075
0.0056
0.0704
0.0651
0.0000
0.0076
0.0147
0.0134
1.0000

Approximate
Composition
0.
0
0
0
0
0
0.0177
0
0
0
0
0
0
0
0
0.0738
0
0
0
0
0
0
0
0
0.1761
0
0
0
0
0
0
0
0.1926
0
0
0
0
0
0
0
0
0.1641
0
0
0
0
0
0.1455 -
0
0
0
0
0
0.0534
0
0
0.1411
0
0
0
0.0357
0
1.00000

-------
then Figure 8 predicts that •* 100 1-air/g-gasoline will
be  required. This is the  minimum  amount of vapor
required, because it is based on an  equilibrium-based
model. The necessary minimum average vapor flow rale
is then equal to the spill mass times the minimum
required vapor  flow/mass gasoline divided  by the
desired duration of venting. Use of this approach  is
illustrated  in the service station site  example provided
at the end of this paper.
    Figure 8 also illustrates that there is a practical limit
to the amount of residual contaminant  that  can be
removed by venting alone. For example, it will take a
minimum of 1001-vapor/g-gasoline to remove 90 percent
of the weathered gasoline defined in Table 2, while  it
will take about  200 1-air/g-gasoline to  remove the
remaining  10 percent. In  the case of gasoline, by the
time 90 percent of the initial residual has been removed,
the residual consists of relatively insoluble and non-
volatile compounds. It is important to recognize this
limitation of venting, and when setting realistic cleanup
target levels, they should be based on the potential envi-
ronmental impact of the residual rather than any specific
total residual  hydrocarbon levels. Because  mandated
cleanup levels are generally independent of the remedia-
tion method, this also indicates that soil  venting will
often be one of many processes used during a given site
remediation. It is not difficult to envision that in the
future soil venting may be followed or coupled with
enhanced  biodegradation to  achieve lower cleanup
levels.
   It is appropriate  to mention at this point that the.
mathematical models presented in this paper are being
used as "tools" to help plan and design venting system.
As with any models, they are mathematical descriptions
of processes that at best approximate real phenomena,
and care should be taken not to misapply or misinterpret
the results.
Are There Likely to Be Any Negative Effects of Soil
Venting?
   It is possible that venting will  induce the migration
of off-site  contaminant vapors toward the extraction
wells. This may occur at a  service station, which  is often
in close proximity to other service stations. If this occurs,
one could spend a lot of time and money to unknowingly
clean up someone else's  problem. The solution is to
establish a "vapor barrier" at the  perimeter of the con-
taminated  zone. This can  be accomplished by allowing
vapor flow into any perimeter ground water monitoring
wells (which often have screened intervals extending
above the saturated zone), which then act as passive air
supply wells. In other cases it may be necessary to install
passive air injection  wells, or trenches, as illustrated in
Figure 9a.
    As pointed out by Johnson et al. (1988), the applica-
tion of a vacuum to extraction wells can  also cause a
water table rise.  In many cases contaminated soils lie
just above the water table and they become water satur-
ated, as  illustrated in Figure  9b. The  maximum  rise
occurs at, or below the vapor extraction well, where the
water table rise will be equal to the vacuum at that point
  a)
   Vapot Extraction
      Well
     C
                                         Off-She
                                       Contamination
                       Passive Air Injection Well
                             or
                   Perimeter Grouitdwaier Monitoring Well
  b)
   L'nsaturated
   Soil Zone
                            Vapor Extraction
                               Well
                     Water Table Upweltmg
                      Caused by Vacuum
Figure 9. (a) Use of passive vapor wells to prevent migration
of off-site contaminant vapors, (b) Water table rise caused by
the applied vacuum.

 expressed as an equivalent water column height (i.e.. in
 ft H2O). The recommended solution to this problem is
 to install a dewatering system, with ground water pump-
 ing wells located as close to vapor extraction wells as
 possible.  The dewatering system must be  designed to
 ensure that contaminated soils remain exposed to vapor
 flow. Other considerations not directly related to vent-
 ing system design, such as soluble plume migration con-
 trol and free-liquid product yield, will also be factors in
 the design of the ground water pumping system.
 Design Information
    If venting is still a remediation option after answer-
 ing the questions above, then more accurate information
 must be collected.  Specifically, the soil permeability to
 vapor flow, vapor  concentrations, and aquifer charac-
 teristics need to be determined. These are obtained by
 two  field experiments: air permeability and ground
 water pumping tests, described briefly next.
 Air Permeability Tests
    Figure 10 depicts the setup of an  air permeability
 test. The object of  this experiment is to remove vapors
 at a constant rate from an extraction well, while monitor-
 ing with time the transient subsurface pressure distribu-
 tion at fixed points. Effluent vapor concentrations are
 also monitored. It is important that the test be conducted
 properly to obtain accurate design information. The
 extraction well should be screened through the soil zone
 that will be vented during the actual operation. In many
 cases existing ground water monitoring wells are suffici-
 ent, if their screened sections extend above  the water
 table. Subsurface pressure  monitoring probes can be

-------
Pressure   Vapor flowmeter
Gauge
                               Vapor Treatment
      Vapor Sampling
         Pod
    Vapor
     Flow"
                      Pressure Sampling Probes
 Figure 10. Air-permeability test system.

 driven soil-vapor sampling probes (for <20 ft deep con-
 tamination problems) or more permanent installations.
    Flow rate and  transient pressure distribution data
 are used to estimate the soil permeability to vapor flow.
 The expected change in the subsurface pressure distribu-
 tion with time P'(r,t) is predicted (Johnson et al.) by:
 P' —
         Q
     4jtm(k/u)
     /"V

        *
dx
                                                (13)
For (r e|a./4kPAlmt)<0.r Equation 13 can be approxi-
mated by:
 P1 =
     4jcm(k/n)  I
    [-0.5772 - in 1-^- } + ln(t)l   (14)
    I            UkPAtm /       J
Here:
 P'     = "gauge" pressure measured at distance r
          and time t
 m     = stratum thickness
 r      = radial distance from vapor extraction well
 k      = soil permeability to air flow
 |x      = viscosity of air = 1.8 x 104 g/cm-s
 «      = air-filled soil void fraction
 t      = time
 Q     = volumetric vapor flow rate from extraction
          well
 PAI™   = ambient atmospheric  pressure = 1.0 atm =
          1.013x 10"g/cm-s:.
Equation 14 predicts a  plot of p'-vs- In(t) should be a
straight line with slope  A and y-intercept B equal to:
 A =
 B =
     4jtm(k/u.)
-0.5772-In
                          / r en
               \4kPy
                               Atm
                                    (IS)
The permeability to vapor flow can then be calculated
from the data by one of two methods. The first is applica-
ble when Q and m are known. The calculated slope A
                                                        is used:
                                              k =
                                       4A,m         .                            <16)
                                   The second approach must be used whenever Q or m
                                   is not known. In this case the values A and B are both
                                   used:
                                                             reu.      -B
                                                         k = - -  exp(- + 0.5772)
                                                                     HV
                                                            4P
                                                                                            (17)
                                                   AUB
                                            Equation 13 can also be used to choose the locations
                                         of subsurface pressure monitoring points before con-
                                         ducting the air permeability test, given an estimation of
                                         k and the flow rate to be used.
                                            Vapor samples should be taken at the beginning and
                                         end of the air permeability test, which should be con-
                                         ducted for a long enough time to extract at least one
                                         "pore volume" VP of vapor from the contaminated soil
                                         zone. This ensures that all vapors existing in the forma-
                                         tion prior to venting are removed. The vapor concentra-
                                         tion-at the start of the test is representative of the equi-
                                         librium vapor concentration, while  the concentration
                                         measured  after one pore volume has been extracted
                                         gives, an indication of realistic removal rates and the
                                         mixing or diffusional limitations discussed in association
                                         with Figure 6. The time Vp for one pore  volume to be
                                         removed is:
                                      TP = Vp/Q = €A
                                                                   H/Q
                                                                                       .(18)
                                   where R, H. eA, and Q are the radius of the zone of
                                   contamination, vertical thickness of the zone of contami-
                                   nation, air-filled void fraction, and  volumetric vapor
                                   flow rate from the extraction well. For example, consider
                                   the case where R=12 m, H=3 m. eA=0.35, and Q=0.57
                                   m3 /min (20 ft' /min). Then rp=475 m 70.57 m' /min=833
                                   min=14 h.

                                   Ground Water Pumping Tests
                                     To achieve efficient venting, the  hydrocarbon-con-
                                   taminated soil .has to be exposed to  air flow, which in
                                   turn requires that the water table be lowered to counter-
                                   act the water upwelling effect caused by the decreased
                                   vapor pressure in the vicinity of a venting well (Johnson
                                   et al. 1988) and to possibly expose contaminated soil
                                   below the water table. Thus the ground water pumping
                                   system has to  have a sufficient pumping rate and be
                                   operated  for a long enough time period  to obtain  the.
                                   required drawdowns. Because most venting systems are
                                   installed above phreatic aquifers, two aquifer parame-
                                   ters are needed for the design: average transmissivity T'
                                   and storage coefficient S. These parameters can be esti-
                                   mated using the results of the standard transient ground
                                   water pumping test with a constant pumping rate (Bear
                                   1979). Using the estimated values, the required pumping'
                                   rate may  be calculated as follows:
                                                Q .= 4-nT S(r,t)/W(u)
                                                                                 (19)
                                             where: W(u) is the well function (Bear 1979) of u = Sr/

-------
 4Tt, and s(r,t) is the required drawdown at distance r
 and pumping time equal to t.

 System Design
    In this section the questions that must be answered
 in order to design an in situ soil-venting system will be
 discussed. It is not the authors' intention to provide  a
 generic "recipe" for soil-venting system design; instead,
 a structured thought process to guide in choosing the
 number of extraction wells, well spacing, well construc-
 tion, etc.  is suggested.  Even in a structured  thought
 process, intuition, and experience play important roles.
 There  is no substitute for a good fundamental under-
 standing of vapor flow processes, transport phenomena,
 and ground water flow.
Choosing the Number of Vapor Extraction Wells
   Three methods for choosing the number of vapor
extraction wells are outlined in the following text. The
greatest number of wells from these three methods is
then the value that should be used. The objective is to
satisfy removal rate requirements and achieve vapor
removal from the entire zone of contamination.
   For the first estimate residual contaminant composi-
tion and vapor concentration changes with time are neg-
lected. The acceptable removal rate  Raccepiabie is calcu-
lated from Equation 4, while the estimated removal rate
from  a single well Rest is estimated from a choice of
Equations 2,6,7, or 12 depending on whether the speci-
fic site conditions are most like Figure 6a, 6b, or 6c.
The number of wells Nwcns required to achieve the
acceptable removal rate is:
         - Racceplable'Rest
(20)
Equations 2,6, and 7 require vapor flow estimates, which
can be calculated from Equation 5 using the measured
soil permeability and chosen extraction well vacuum Pw.
At  this point one must determine what blowers and
vacuum pumps are available because the characteristics
of these units will limit the range of feasible (PW,Q)
values. For example, a blower that can pump 100 scfm
at 2 in. H2O vacuum may only be able to pump 10 scfm
at 100 in. H2O vacuum.
   The second method, which accounts for composition
changes with  time, utilizes model predictions, such as
those illustrated in Figure 8. Recall that equilibrium-
based models are used to calculate the minimum vapor
flow to achieve a given  degree of remediation. For exam-
ple, if we wish to obtain a 90 percent reduction in resid-
ual gasoline levels, Figure 8 indicates that ==1001-vapor/
g-gasoline must pass  through the contaminated soi!
zone. If our spill mass is 1500kg (=500 gal), then a mini-
mum of 1.5 x 10s 1-vapor must pass through the conta-
minated soil zone. If  the target  cleanup period is six
months, this corresponds to a minimum average vapor
flow rate of 0.57 m* /min (=20 cfm). The minimum num-
ber of extraction wells is then equal to the required
minimum average flow rate/flow  rate-per-well.
   The third  method  for determining the number of
          wells ensures that vapors and residua) soil contamina-
          tion are removed from the entire zone of contamination
          Nmin- This is simply equal to the ratio of the area of
          contamination Aconlamina,i0ni to the area of influence of
          a single venting well irR|2:
          Nmin =
                  ^contamination
                    KR
                                               (21)
          This requires an estimate of RI, which defines the zone
          in which vapor flow is induced. In general, R[ depends
          on soil properties of the vented zone, properties of sur-
          rounding soil layers, the depth  at which the well is
          screened, and the presence of any impermeable bound-
          aries (water table, clay  layers, surface seal, building
          basement, etc.). At this point it is useful to have some
          understanding of vapor flow patterns because, except
          for certain ideal cases (Wilson et  al. 1988), one cannot
          accurately predict vapor flow paths without numerically
          solving vapor-flow equations. An estimate for RI can
          be  obtained by fitting radial pressure distribution data
          from the air permeability test to the steady-state radial
          pressure distribution equation (Johnson et al. 1988):
P(r) = Pw [l + (i _ (  *!E
                                     lp(r/R-> 11/2
                                     ln(Rw/R,)J
(22)
where P(r), PAlm, Pw, and Rw are the absolute pressure
measured at a distance r from the venting well, absolute
ambient pressure, absolute pressure applied at the vapor
extraction well, and extraction well radius, respectively.
Given that these tests are usually conducted for less
than a day, the results will generally underestimate RP
If no site-specific data are available, one can conserva-
tively estimate R( based on the published reports from
in situ soil-venting operations. Reported RI values for
permeable soils (sandy soils) at  depths greater than
20 feet below ground surface, or shallower soils beneath
good surface seals,  are usually 10m - 40m (Hutzler et
al. 1988). For less permeable soils (silts, clays), or more
shallow zones R| is usually less.

Choosing Well  Location, Spacing, Passive Wells, and
Surface Seals
   To be able  to successfully locate extraction wells,
passive wells, and surface seals one must have a good
understanding of vapor flow  behavior. Well locations
should be chosen to ensure adequate vapor flow through
the  contaminated zone, while minimizing  vapor flow
through other zones.
   If one well is sufficient, it should almost always be
placed in the geometric center of the contaminated soil
zone, unless it is expected that vapor flow channeling
along a preferred direction will occur. In that case the
well should be placed so as to maximize air flow through
the  contaminated zone.
   When multiple wells are used it is important to con-
sider the effect that each well has on the vapor flow to
all other wells.  For example, if three extraction wells
are  required at a given  site, and they are  installed in
the triplate design shown in Figure lla, this would result

-------
 a>
                                                              a)
  b)
         vapor flow f
           lines
         injection
          well
  _ . extraction
"" ,' wells
   c)
 Figure 11. Venting well configurations
 in a "stagnant" region in the middle of the wells where
 air flow  would be small in  comparison  to the  flow
 induced outside the triplate  pattern  boundaries.  This
 problem can be alleviated by  the use of "passive wells"
 or "forced injection" wells as illustrated in Figure lib
 (it can also.be  minimized by changing  the vapor  flow
 rates from each well with time). A passive well is simply
 a well that is open to the atmosphere; in many cases
 ground water monitoring wells are suitable. If a passive
 or forced injection well is to have any positive effect, it
 must be  located within the extraction  well's zone  of
 influence. Forced injection wells are simply vapor wells
 into which  air  is pumped rather  than  removed.  One
 must be careful in choosing the locations of forced injec-
 tion wells so that contaminant vapors are  captured  by
 the extraction wells, rather than forced off-site. To  date
 there have  not been any detailed reports of venting
 operations designed to study  the advantages/disadvan-
 tages of using forced injection wells. Figure 1 Ic presents
 another possible extraction/injection well combination.
 As illustrated in Figure 9, passive wells can  also be  used
 as vapor  barriers to prevent  on-site migration of off-
 site contamination problems.
  For shallow  contamination  problems (<4m  below
 ground surface) vapor extraction trenches combined
 with surface seals may be more effective than vertical
 wells. Trenches are usually limited to shallow soil zones
 because the difficulty of installation increases with
 depth.
   Surface  seals, such  as polymer-based liners  and
asphalt, concrete, or clay caps, are sometimes used  to
control the  vapor-flow paths. Figure 12  illustrates the
effect that a surface seal will have on vapor-flow  pat-
                                                                       "open" soil fuif
                                                            b)
                                   impermeable sol
                                                            Figure 12. Effect of surface seal on vapor flow path.
                                                             a)
                                                                         cement cap
                                                                        stoned pipe
                     b)
                        air-Tight monitoring well
                       cap/water sensor assembly
                                                                                          coarse packing
                                                                                          "*" material
                                                      pressure gauge
                                                       connection
wire lo i
   double ictton
  inner scpu ical

 well cap
                                                       i
                    Figure 13. (») Extraction well construction, and (b) air-tight
                    ground water level measuring system.	
                    terns.  For shallow treatment zones (<5m) the surface
                    seal will have a significant effect on the vapor flow paths,
                    and seals can be added or  removed to achieve the
                    desired vapor flow path. For wells screened below 8m
                    the influence of surface seals becomes less significant.

                    Well Screening and Construction              .   .
                        Wells should be screened only through the zone of
                    contamination, unless the permeability to vapor flow is
                    so low that removal rates would be greater if flow were
                    induced in an adjacent soil layer (see Figure 6). Removal
                    rate estimates for various  mass-transfer  limited sce-
                    narios can be calculated from Equations 7 and 12.
                        Based on Equation 5, the flow rate is expected to

-------
 increase by 15 percent when the extraction well diameter
 is increased from 10cm (4 in) to 20cm (8 in). This implies
 that well diameters should be as large as is practically
 possible.
    A typical well as shown in Figure 13a is constructed
 from slotted pipe (usually PVC). The slot size and num-
 ber of slots per inch should be chosen to maximize the
 open area of the pipe. A filter packing, such as sand or
 gravel, is placed in the annulus between the borehole
 and pipe. Vapor extraction wells are similar to ground
 water  monitoring wells in construction but there is no
 need to filter vapors before they enter  the  well. The
 filter packing, therefore, should be as coarse as possible.
 Any dust carried by the vapor flow can be removed by
 an above-ground filter. Bentonite pellets and a cement
 grout are placed above the filter packing. It is important
 that these be properly installed to prevent a vapor flow
 "short-circuiting." Any ground water monitoring wells
 installed near the extraction wells must also be installed
 with good seals.

 Vapor Treatment
    Currently, there a four main  treatment processes
 available:
 *  Vapor combustion units: Vapors are incinerated and
   destruction efficiencies are  typically >95 percent. A
   supplemental fuel, such  as propane, is added before
   combustion unless extraction well vapor concentra-
   tions are on the order of a few percent by volume.
   This process becomes less economical as vapor con-
   centrations decrease below  «• 10,000 ppmv.
 •  Catalytic oxidation units: Vapor streams are heated
   and  then passed over a catalyst bed. Destruction effi-
   ciencies are typically  >95 percent. These units are
   used for vapor concentrations <8000 ppnv More con-
   centrated vapors can cause catalyst bed temperature
   excursions  and meltdown.
•  Carbon beds: Carbon can be used 10  treat almost any
   vapor streams, but is  only economical for  very low
   emission  rates (<100 g/d)
•  Diffuser stacks: These do not treat  vapors, but are
   the most economical solution for areas in which they
   are permitted. They  must be carefully designed to
   minimize health risks and maximize safety.

 Ground Water Pumping System
   In cases where contaminated soils lie just above or
 below  the water table, ground water pumping systems
 will be required to ensure that  contaminated  soils
 remain exposed. In designing a ground water pumping
 system it is important to be aware that upwelling (draw-
 up) of the ground water table will occur when a vacuum
 is applied at the extraction well (see Figure 9b). Because
 the upwelling will be greatest at the  extraction wells,
 ground water pumping wells should be located within
 or as close to the  extraction  wells as possible. Their
 surface seals must be airtight to prevent  unwanted short-
 circuiting of airflow down  the ground water wells.

 System Integration
   System components  (pumps, wells, vapor treating
 units, etc.) should be combined to allow maximum flexi-
 bility of operation. The review by Hutzler et al. (1988)
 provides descriptions of many reported systems. Specific
 requirements are:
 • Separate valves, flow meters, and pressure gauges for
   each extraction and injection well.
 • Air  filter to remove particulates from vapors
   upstream of the pump and flow meter.
 • Knock-out pot to remove any liquid  from vapor
   stream upstream of the pump and flow  meter.

 Monitoring
   The performance of a soil-venting system must be
 monitored in order to ensure efficient operation, and
 to help determine when to shut off the system. At a
 minimum the following should be measured:
 •  Date and time of measurement.
 •  Vapor flow rates from extraction wells and into injec-
   tion wells: These can be measured by a variety of
   flow meters including pilot tubes, orifice plates and
   rotameters. It is important to have calibrated these
   devices at the field operating pressures and tempera-
   tures.
 •  Pressure readings at each  extraction and injection
   well can be measured with manometers or magnahelic
   gauges.
 •  Vapor concentrations and compositions from extrac-
   tion wells: total hydrocarbon concentration can be
   measured by an on-line total hydrocarbon analyzer
   calibrated to a specific hydrocarbon. This information
   is  combined with vapor flow rate data to calculate
   removal rates and the cumulative amount of contam-
   inant removed. In addition, for mixtures the vapor
   composition  should be  periodically  checked. It is
   impossible to assess if vapor concentration decreases
   with time are due to compositional changes or some
   other phenomena (mass transfer resistance, water
   table  upwelling, pore blockage, etc.) without this
   information. Vapor samples can be collected in evacu-
   ated gas sampling cylinders, stored, and later ana-
  lyzed.
• Temperature: ambient and soil.
• Water table level (for contaminated soils located near
  the water table): It is important to monitor the water
  table level to ensure that contaminated soils remain
  exposed to vapor flow.  Measuring the water table
  level during venting is not a trivial task because the
  monitoring well must remain sealed. Uncapping the
  well releases the vacuum and any effect  that it  has
  on the water table level. Figure 13b illustrates a moni-
  toring well cap (constructed by Applied Geosciences
  Inc., Tustin, California) that allows one to simulta-
  neously measure the water table level and vacuum in
  a monitoring well. It is constructed from  a commer-
  cially available  monitoring well cap and utilizes an
  electronic water level sensor.
Other valuable, but optional measurements are:
t Soil-gas vapor concentrations and  compositions:
  These should be measured periodically at different
  radial distances from the extraction well. Figure 14

-------
   1/g" OD Teflon Tubing
                                     Ground Surface
                          ^>sx<^ Bo* Containing Vapor Sampling
                             ^"Ss.   Ports ^Thermocouples
                             PPVCPipe
                                coarse packing
                                ceriient/behtonite
Figure 14. Vadose zone monitoring well installation.


   shows the construction of a  permanent  monitoring
   installation that can be used for vapor sampling and
   subsurface temperature measurements. Another
   alternative for shallow contamination zones is the use
   of soil-gas survey probes. Data from soil-gas probes
   are valuable for two reasons: (1) by comparing extrac-
   tion well concentrations with soil-gas concentrations
   it is possible  to estimate the fraction of vapor that is
   flowing through the contaminated zone <)>=Cextrac,iori
   weii/Qoii gas* and (2)  it is possible to determine if the
   zone of contamination is shrinking toward the extrac-
   tion well, as it should with time. Three measuring
   points are probably sufficient if one is located near
   the  extraction well,  one  is placed near  the  original
   edge of the zone of contamination, and the third is
   placed somewhere in between.
    These monitoring installations  can also be useful for
monitoring subsurface  vapors after venting has ceased.

Determining When to Turn  Off the System
    Target soil cleanup levels are often set on a site-by-
site basis, and  are based on the  estimated potential
impact that any residual may have on air quality, ground
water quality, or other health standards. They may also
be related to safety considerations (explosive limits).
Generally, confirmation soil borings, and  sometimes
soil-vapor surveys are required before  closure is
granted. Because these analyses can be expensive and
often disrupt the normal business  of a site, it would be
valuable to be  able  to determine when confirmation
borings should  be taken. If the monitoring is done as
suggested previously, then the.following criteria can be
used:            '    ,        •
•  Cumulative amount removed: Determined by inte-
   grating the measured removal rates (flow rate x con-
   centration) with time. While this value indicates how
   much contaminant has been removed, it is usually
  •not very useful for determining when to  take confix
   mation borings unless the original spill mass is known
   accurately. In mostcases that information is not avail-
   able and cannot be calculated accurately from soil-
   boring data.
*  Extraction well vapor concentrations: The vapor con-
   centrations are good  indications of how effectively
   the venting system is working, but decreases in vapor
   extraction well concentrations are not strong evidence
   that soil .concentrations have decreased. Decreases
   may also be due to other phenomena such as water
   table level increases, increased  mass transfer resist-
   ance due to drying, or leaks in the extraction system.
 • Extraction well vapor composition: When combined
   with vapor  concentrations  these data  offer more
   insight into the effectiveness of the system. If the total
   vapor concentration decreases without a change in
   composition, it is probably due to one  of the phe-
   nomena mentioned previously, and is not an indica-
   tion that the residual contamination has been signific-
   antly reduced. If a decrease in vapor  concentration
   is accompanied by a shift in composition toward less
   volatile compounds, on the other hand, it is most
   likely due to a change in  the residual contaminant
   concentration.  For residual gasoline cleanup, for
   example, one might operate a venting system until
   benzene, toluene, and xylenes were  not  detected in
   the vapors. The remaining residual  would  then be
   composed of larger molecules, and it can be argued
   that these do not pose a health threat through volatili-
   zation or leaching pathways.
 • Soil-gas contaminant concentration and composition:
   These data are the most useful because it yields infor-
   mation about the residual composition and extent of
   contamination. Vapor concentrations cannot, in gen-
   eral, be used to determine the residual level, except
   in the limit of low residual levels (note that Equation 1
   is independent of residual concentration). It is important
   to consider the effect of continued soil-venting system
   operation on soil-gas sampling results. Results taken
 • during operation, or immediately after shutdown, can
   be used to assess the spatial extent of contamination
   and composition of the vapors.  After  the system is
   shut  down, vapors  will begin to migrate  away from
   the source and equilibrate on a larger  scale. True soil-
   vapor concentrations can be measured once equilib-
   rium concentrations are attained in the sampling
   /one; at least two sampling times will be required to
 ,  determine that equilibration has occurred. Due to the
   diffusion of vapors, samples taken after shutdown are
   not good indicators of the spatial extent of the conta-
   minated zone:

Other Factors
Increased Biodegradation
   It is often postulated that because the air supply to
the vadose zone is increased, the natural aerobic micro-
biological activity is increased during venting. While the
argument is plausible  and some. laboratory data  are
available (Salanitro et al.  1989), conclusive'evidence
supporting this theory has. yet to be .presented. This is
due in  part to  the difficulty in making  such  a mea-
surement. A mass balance approach is not likely to be
useful because' the initial spill mass is generally not
known  with sufficient accuracy. An indirect method
would be to measure CO2 levels in the  extraction well

-------
vapors, but this in itself does not rule out the possibility
that O2 is converted  to CO2 before the vapors pass
through the contaminated soil zone. The best approach
is to measure the O2/CO2 concentrations in the vapors
at the edge of the contaminated zone, and in  the vapor
extraction wells. If the CO2/O2  concentration ratio
increases as the vapors pass through the contaminated
soil, one can surmise that a transformation is occurring,
although other possible mechanisms (inorganic reac-
tions) must be considered. An increase in aerobic mic-
robial populations would be additional supporting evid-
ence.
In Situ Heating/Venting
   The main  property of a compound that determines
whether or not it can be removed by venting is its vapor
pressure, which increases with increasing temperature.
Compounds that are considered non-volatile, therefore,
can be removed by venting if the contaminated soil is
heated to the proper temperature. In situ heating/vent-
ing systems utilizing radio-frequency heating and con-
duction heating  are currently under study (Dev et al.
1988). An alternative  is to reinject heated vapors from
catalytic  oxidation or combustion units into the con-
taminated soil zone.
Air Sparging
   Due to seasonal ground water level fluctuations, con-
taminants sometimes become trapped below  the water
table. In some cases ground water pumping can lower
the water table enough to expose this zone, but in other
cases this is not practical. One  possible solution is to
install air sparging welts and then inject air below the
water table. Vapor extraction wells would then capture
the vapors that bubbled up through the ground  water.
To date, success of this approach has yet to be demon-
strated. This  could have a negative effect if foaming,
formation plugging, or downward migration of the resid-
ual occurred.
                          i"     '   i" '
Application of the Design  Approach
to a Service Station Remediation.        :,
   In the following, the use of the approach  discussed
previously and outlined in Figure 2, is demonstrated for
a service station remediation.

Preliminary Site Investigation
   Prior to sampling it was estimated that 2000 gallons
of gasoline had leaked from a product line at this operat-
ing service station site. Several soil borings were drilled
and the soil samples were analyzed for total petroleum
hydrocarbons (TPH) arid  other  specific compounds
(benzene, toluene, xylenes)  by a heated-headspace
method utilizing a field GC-FID. Figure 15 summarizes
some of the  results for one transect at this site. The
following relevant information was collected:
• Based on boring logs there are four distinct soil layers
  between 0 - 18m (0 - 60 ft) below ground surface
  (BGS). Figure 15 indicates the soil type and location
  of each of  these layers.
• Depth to ground water was 15m, with fine to medium
  sand soils.
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• J.2 "

HB-10y HB-5 HB-3
/ BB-23
fVvnr
                         HB-21
                       [Ground Wucr
                      . Recovery WcllJ
                               Recovery Well]
Figure 15. Initial total hydrocarbon distribution [mg/kg-soil]
and location of lower zone vent welL

•  The  largest concentrations of hydrocarbons  were
   detected in the sandy and silty clay layers adjacent
   to the water table. Some residual was detected below
   the water table. Based on the data presented in Figure
   15  it is estimated that = 4000kg of hydrocarbons are
   present in the lower two soil zones.
•  Initially there was some free-liquid gasoline floating
   on the water  table: this was subsequently removed
 •.  by  pumping. A sample of  this product was analyzed
   and its approximate composition (=20 percent of the
   compounds could  not be identified) is listed in
   Table 2 as the "weathered gasoline." The corre-
   sponding boiling point distribution curve for this mix-
   ture has been  presented in Figure 3.
•  Vadose zone monitoring installations similar to the
   one pictured in Figure 14  were installed during the
   preliminary site investigation.

Deciding if Venting Is Appropriate
   For the remainder of the  analysis the contaminated
soils located just above the water table will be the focus.
•  What contaminant vapor concentrations are likely to
   be  obtained?
   Based on the composition given in Table 2, and using
Equation 1, the predicted saturated TPH vapor concen-
tration for this gasoline is:
   Cest  = 220 mg/L
   Using the "approximate" composition listed in Table
2 yields a value of 270 mg/L. The measured soil-vapor
concentration obtained from the vadose zone monitoring
well was 240 mg/L. Due to composition changes with time,
this will be the maximum concentration obtained during
venting.
•  Under ideal flow conditions is this concentration great
   enough to yield acceptable removal rates?

-------
   Equation 4 was used to calculate Racceptabie- Assum-
ing Mspm = 4000kg and T = 180 d, then:
   Racccpubie = 22 kg/d
   Using Equation 2, CCSI = 240 mg/L, and Q = 2800 V
min (100 cfm):
   Res, = 970 kg/d
which is greater than Raccepubie-
• What range of vapor flow rates can realistically be
  achieved?
   Based on boring logs, the contaminated zone just
above the water table is composed of fine to medium
sands, which have an estimated permeability 1< k < 10
darcy. Using Figure 5, or Equation 5, the predicted flow
rates for an extraction well vacuum Pw = 0.90 atm are:
   0.04 < Q < 0.4 m'/m-min    Rw = 5.1cm, R! = 12m
   0.43 < Q < 4.3 ftVft-min   Rw - 2.0 in, RI =  40 ft.
   The thickness of this zone and probable screen thickr
ness of an extraction well is about 2m (6.6 ft). The total
flow rate per well through this zone is estimated to be
0.08
-------
 zone will be discussed. A ground water pumping well was
 installed to maintain a 2m drawdown below the static water
 level. Its location is also shown in Figure 15.

 System Monitoring
    Three vadose monitoring wells similar in construc-
 tion to the one pictured in Figure 14 were installed so
 that the soil temperature, soil-gas concentrations, and
 subsurface pressure distribution could be  monitored at
 three depths. One sampling port is located in the zone
 adjacent to the aquifer. The vapor flow rate from HB-
 25 and vapor concentrations were measured frequently,
 and the vapor composition was determined by GC-FID
 analysis. In addition, the water level in the ground water
 monitoring wells was measured with the system pictured
 in Figure 13b. The results from the first four months of
 operation are discussed in following text
    In Figure 17a the extraction well vacuum and corre-
 sponding vapor flow rate are presented.  The vacuum
 was maintained at  0.95 atm (20 in H2O vacuum), and
 the flow rate was initially 12 scfm. It gradually decreased
 to about 6 scfm over 80 d. For comparison, Equation 5
 predicts that Q=12 cfm for k=8 darcys. Increasing the
 applied vacuum to  0.70 atm (120 in H2O vacuum) had
 little effect on the  flow rate. This could be explained
 by increased water table upwelling, which would act to
 decrease the vertical  cross section available for vapor
 flow. The scatter in the flow rate measurements is prob-
 ably due to inconsistent operation of the ground water
 pumping operation, which frequently failed to perform
 properly.
    Figure 17b presents the change in vapor concentra-
 tion with time.  Fifteen specific compounds were identi-
 fied during the GC-FID vapor analyses; in this figure
 the total concentration of known and unknown com-
 pounds detected between five boiling point ranges are
 presented:
    methane - isopentane (<28 C)
    isopentane - benzene (28 - 80 C)
    benzene - toluene (80 - 111 C)
    toluene - xylenes (111 - 144 C)
    >xylenes (>144 C).
   There was a shift in composition toward less volatile
 compounds  in  the first 20 days, but after that period
 the composition remained relatively constant. Note that
 there is still a significant fraction of volatile compounds
 present. Within the first two days the vapor concentra-
 tion decreased by 50 percent, which corresponds to the
 time period for the removal of the first pore volume of
 air. Comparing the subsequent vapor concentrations
with the concentrations measured in the.vadose zone
 monitoring wells indicates that  only (80 mg/L)/(240 mg/
 L)* 100=33% of the vapors are flowing through contamin-
 ated soil.
   Figure 18a presents calculated removal rates (flow
rate x concentration)  and cumulative amount (1 gal =
3 kg) removed during the first four months. The
decrease in removal rate with time is due to a combina-
tion of decreases in flow rate  and hydrocarbon vapor
concentrations. After  the first four months approxi-
 mately one-fourth of the estimated residual has been
a)
HB-25
Vacuum
(in H O)
140 - ' - 	 -
120
100
80
60-
40
6.
f 1^ v— ,
. 1—- n».
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V


„;•/>
V V'
^
Flowratc
(SCFM)
•10 '
•5
                   20    40-60   80   100   120
                          Time (d)
         (in H.O| denote vacuums expressed as equivalent water column height]
    b)
                   20   40   60   80   100   120
                        Time (d)
 Figure 17. Soil-venting results: (a) vacuum/flow rate data,
 (b) concentration/composition data.
    a)
     Removal
      Rate
      (kg/d)  30-|

            20

            10-1

             0
                                          400.
200
   Cumulative
   Recovered
     (gal)
100
                  20   40    60   80  •' 100   120
                         Time (d)
  b)
      ftH.,0
                         Time (min)
         1ft HO] denote vacuums expressed as equivalent water column heights

Figure IS. Soil-venting results: (a) removal rate/cumulative
recovered, (b) water table, rise.
 removed from this lower zone.
    On day 80 the vacuum was increased from 20 - 120
 in H2O vacuum and the'subsequent increase in subsur-

-------
face vacuum and water table upwelling was monitored.
Figure 18b presents the results. Note that the water
table rise paralleled the vacuum increase, although the
water table did hot rise the same amount that  the
vacuum did.
   Figure 19 compares the reduced measured TPH
vapor concentration C(t)/C(t=0) with model predic-
tions. C(t=0) was taken to be the vapor concentration
after one pore volume of air had passed through the
contaminated zone (=80 mg/L),  m(t=0) is equal to the
estimated spill mass (=4000 kg), and V(t)  is the total
volume of air that has passed through the contaminated
zone. This quantity is obtained by integrating the total
vapor flow rate with time,  then multiplying it by the
fraction of vapors passing  through the contaminated
zone <|> (=0.33). As discussed, the quantity   was esti-
mated by comparing soil-gas concentrations from the
vadose zone monitoring installations with vapor concen-
trations in  the extraction well vapors. There is good
quantitative agreement between  the measured and pre-
dicted values.
   Based on the data presented in Figures 15 through
19 and the model predictions in Figure 8, it appears that
more extraction wells (= 10 more) are needed to reme-
diate the site within a reasonable amount of time (< 2
years).

Conclusions
   A structured, technically based approach has been
presented  for the design, construction, and operation
of venting systems. While an attempt has been made to
explain the process in detail for those not familiar with
venting  operations or the  underlying governing phe-
nomena, the most effective  and efficient systems  can
only be designed and operated by personnel with a good
understanding of the fundamental processes involved.
The service station spill example  presented supports the
validity and usefulness of this approach.
   There are still many technical issues that need to be
resolved in the future. The usefulness of forced or pas-
sive vapor injection wells is often debated, as well as
other means of controlling vapor flow paths (impermea-
ble surface covers, for example). A well-documented
demonstration of the effectiveness of soil  venting for
the removal of contaminants from low-permeability
soils is also needed. It is clear from the simplistic model-
ing results presented in this paper that venting will be
less effective in such situations.  Without a comparison
with other viable  treatment alternatives, however, it is
difficult to determine if soil  venting would still be the
preferred option in such cases. Other topics for future
study include: enhanced aerobic  biodegradation by soil
venting, the possibility of decreasing residua! contami-
nant levels in water-saturated zones by  air sparging/
vapor extraction, and optimal operation schemes for
multiple vapor extraction well systems.

References
Bear, J.1979. Hydraulics of Groundwater, McGraw-Hill.
Dev, H., G.C. Sresty, I.E.  Bridges, and D. Downey,
                                 weathered gasoline
                                 m(t=0)-4000kg
          0.0
             01234567*9   JO
                      V(t)/m(t=0) (1/g) .,

•Figure 19. Comparison of model predictions and measured
response.

   1988. Field test of the radio frequency in situ soil
   decontamination process. In Superfund '88: Proceed-
   ings of the 9th National Conference, HMCRI, Novem-
   ber 1988.
 Hutzler, N. J., B.E. Murphy, and J.S. Gierke. 1988. State
   of Technology Review:  Soil Vapor Extraction Sys-
   tems, U.S EPA, CR-814319-01-1.
 Johnson, P.C., M.W. Kemblowski, and  J.D. Colthart.
   1988. Practical screening  models for soil venting
   applications.. In Proceedings ofNWWA/API Confer-
   ence on Petroleum Hydrocarbons and Organic Chem-
   icals in  Ground Water, Houston, Texas.
 Marley, M.C, and G.E. Hoag. 1984 Induced soil venting
   for the recovery/restoration of gasoline hydrocarbons
   in the vadose zone. In Proceedings of NWWA/APl
   Conference on Petroleum Hydrocarbons and Organic
   Chemicals in Ground Water, Houston, Texas.
 Millington, R.J. and J.M. Quirk.  1961. Permeability of
   Porous  Solids, Trans. Faraday Soc., 57:1200-1207.
 Salanitro, J. P., M.M. Western, and M.W. Kemblowski.
   1989. Biodegradation  of aromatic hydrocarbons in
   unsaturated soil microcosms. Poster paper presented
   at the Fourth National Conference  on Petroleum
   Contaminated Soils, University  of Massachusetts,
   Amherst, September 25-28.
 Wilson, D. J., A.N. Clarke, and J.H. Clarke. 198& Soil
   Clean-up by in situ aeration. I. Mathematical Modell-
   ing, Sep. Science Tech., voj. 23 pp. 991-1037.

 Biographical  Sketches
       Paul C. Johnson,  Ph.D., joined Shell
 Development Co.'s  (Westhollow Research Center,
 Room EC-649, P.O. Box 1380, Houston, TX 77251-
 1380) Environmental Science Department in 1987 after
 earning his B.S. in chemical engineering from the Uni-
 versity of California, Davis, and his Ph.D. in chemical
 engineering from Princeton University. His current
 areas of research include the development and evalua-
 tion of soil treatment processes, modeling and measur-
 ing  transport phenomena  in porous media, and the
 development of transport models for predicting emis-
 sions and exposures used in envvironmental risk

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 assessments.
  •  Curtis C. Stanley received his degree in geology with
 an engineering minor from North Carolina State Uni-
 versity in 1979. He is currently a senior hydrpgeologist
 for Shell O.il Co. (Westhollow Research Center, 2236
 Two Shell Plaza, Houston, TX 77082) and is responsi-
 ble for hydrogeologic response at Shell's retail facilities.
 Stanley is a Certified Professional Geological Scientist
 and also a Certified Ground Water Professional with
 the NWWA's Association of Ground Water Scientists
 and Engineers. He is also a member of API's Ground
 Water Technology Taskforce and  is an EPA Peer
 Reviewer.
    Marian W. Kemblowski, Ph.D., is a senior research
 engineer in the Environmental Science Department at
 Shell Development Co. (Westhollow Research Center,
 Houston,  TX 77082) where he has worked since 1985.
 He obtained his  M.S. degree in civil engineering from
 the Technical University of Warsaw, Poland, in 1973
 andhisPLD. in ground water hydrology from the Insti-
 tute for Land Reclamation in Warsaw, Poland, in 1978.
 In 1980 - 1981 he was a visiting hydrologist in the New
 Mexico School of Mining and Technology. From 1981
 to 1985 he worked as an assistant scientist at the Uni-
 versity of Kansas. His principal research interests are
 in the areas of numerical analysis, transport in porous
 media, and ground water monitoring systems.
   Dallas L. Byers is a technical associate in the Envi-
ronmental Science Department at Shell Development.
After receiving his B.S. degree in zoology from the Uni-
versity of Nevada, Las Vegas, he was employed by the
Texas Water Quality Board as a quality control chemist
for 3'/2 years. In 1977  he joined Shell (Westhollow
Research Center, Houston, TX  77082)  where he  cur-
rently is providing technical assistance and support for
research in  the fate of chemicals in soil and gorund
water.
   James D. Colthart, Ph.D., has been in a variety of
R&D and technical planning positions since joining
Shell (Westhollow Research Center, Houston, TX
77082)  in 1966. He has a B.E.  from Yale University
and a Ph.D. from Rice  University, both in chemical
engineering. Currently he is the research manager of
Shell Development Co. Air, Waste,  and Groundwater
Group.
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