United States
Environmental Protection
Agency
Solid Waste And
Emergency Response
(OS-420) WF
EPA510-R-93-001
January 1993
Hyperventilate Users Manual
(v1.01 and v2.0)
A Software Guidance System
Created For Vapor Extraction
Applications
Vapor Treatment
Unit
Pump
lllllll
Ground Surface
Wcll
Contaminated
Soil
IBM
EPA
510
R
93
001
c.2
Printed on Recycled Paper
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-------
Hyperventilate
Users Manual
A Software Guidance System Created for Vapor Extraction Applications
A Practical Approach to tht
Design, Operation, and
Monitoring of In-Situ Soil
Venting Systems
Eoooomld
Crur<4 >r
Pnl C. Jokuo», Pk.D.
SbcO Development
WtJthoDo v Rexuch C«n*r
About Thfc StMfc
Go to Ftrsl C«rd
Fteld TtStl
V
System Desica
'(-—— —— J liVewtacPMsftk? T
•^ Si* laveitfcttioa V ^ *••
Yipor f f
TVettment
Uatt_
•••
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
For sale by the U.S. Government Printing Office
Superintendent of Document*, Mail Stop: SSOP, Washington, DC 20402-9328
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- H^rVentilate Users Manual Addendwn-
Addendum for Microsoft Windows/Spinnaker PLUS Version 2.0
Summary
Hyperventilate - the software guidance system created for vapor extraction applications is now
available for IBM-compatible computers. In general, this new version (vi.O) appears and
functions like the original Apple Macintosh HyperCard version. Due to differences in the
computer platform and operating environment, however, there are some minor modifications.
This addendum to the original users manual identifies those modifications.
Hyperventilate v2.0is a product of collaboration between Shell Oil Company and U.S. EPA, and
is still under evaluation. Should you encounter problems that you think are "bugs", please write
to the author identifying the problem.
Modifications
• software platform
The original Hyperventilate program was developed and operated under the Apple
Macintosh HyperCard software environment, and initially there were no plans to develop
an IBM-compatible version. Due to popular demand; however, the author relented and
used the least painful method of adaption to the new platform. This was accomplished
through the use of Spinnaker PLUS, a HyperCard-like program that can utilize pre-v2.0
HyperCard stacks and functions on both Macintosh and IBM-compatible platforms. The
Microsoft Windows/Spinnaker PLUS version requires the user to have both Microsoft
Windows and a "run-time" version of Spinnaker PLUS (Windows 3.0 version). Infor-
mation on Spinnaker PLUS can be obtained from:
Spinnaker Software
201 Broadway
Cambridge, MA 02139
(617)494-1200
• stack names
As listed on p4, of the original users manual, Hyperventilate for the Apple Macintosh
consists of eight files. The Spinnaker PLUS version contains only seven files. The names
are:
HyperCard Version Name
Soil Venting Stack
Soil Venting Help Stack
System Design
Air Permeability Test
Aquifer Characterization
Compound list Update
HypeVent
f77.rl
Spinnaker PLUS Versdon Name
SVS. sta
SVHS.sta
SD.sta
APT.sta
AQ.sta
CLU.sta
HYPEVENT.exe
none
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installation
all files must be copied into the PLUS directory on your hard disk.
starting Hyperventilate v2.0b
To startHyperVentilate v2.0b, open the Windows 'Tile Manager", navigate to within the
PLUS directory, then open (double-click on) the tile SVS.sta.
printing cards
You may experience difficulties with some of the "Print" buttons in the program. Read
your PLUS manual to overcome these difficulties.
appearance of cards
Generally, the cards appear as they are printed in the manual. Due to platform differences,
however, some text will appear different This problem is unavoidable with Windows-
based systems, as different users will have their computers configured with different
screen fonts.
tab keys
Some cards utilize spreadsheets. In die HyperCard version the "tab" key is used to
navigate through these tables. In the PLUS version the"tab"keyisnot active and you must
use the "arrow" keys.
speed
Due to platform differences, the PLUS version does not operate as smoothly, or quickly,
as the HyperCard version. The user will notice that with time the execution speed of the
program will slow; therefore, it is recommended that you periodically exit from Windows
and restart the system.
On some machines, when Hyperventilate accesses the external compiled code
HYPEVENTEXE after clicking on the "Generate Predictions" button on card 16 of the
SVS.sta stack, there will be a long pause (as long as a few minutes) as PLUS Windows,
andHYPER\T^^'£XEfightove^availablemeInory. Typicallycard 17 will eventually
be displayed with a shaded rectangle along a portion of its lower base while this battle is
occurring. Be patient and wait for the screen to blank out and display die message "HANG
ON..." indicating that HYPEVENT.EXE is running. If you have limited memory
(<4MG), or too many applications open, this message will not be displayed, and you will
be returned to card 17 as if the program had run. The user needs to be aware that this may
occur.
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- Hyperventilate
Adndum-
Software Installation Procedure
A discussion on how to load both Spinnaker PLUS and Hyperventilate
* Loading Spinnaker PLUS
* Creating the Spinnaker PLUS Icon and Opening Spinnaker PLUS
• Loading Hyperventilate
• Installing Spinnaker PLUS "Run-Time" Version with Hyperventilate
These directions presume that the user has a working knowledge of Microsoft Windows. The
operation of Spinnaker PLUS, and therefore the IBM-compatible version of Hyperventilate
requires Microsoft Windows Version 3.0 or higher. If you arc using a version of Hyperventilate
with a "run time" version of SpinnakerPLUS, skip to the "Loading Hyperventilate" instructions.
Loading Spinnaker PLUS
The Spinnaker PLUS package contains three 3.5-inch and three 5.25-inch diskettes from which
to install the program. Use these steps to install the program:
1 . Enter Windows.
2. Double-click on the "Main" window icon (if this window is not already open).
3. Double-click on the "File Manager" icon; this will display the "Directory Tree" window.
4. Insert Disk 1 into the appropriate drive (A or B).
5. In the upper left corner of the "Directory Tree" window you will see symbols representing
the drives on your system. Click on the drive (A or B) where you just inserted Disk 1.
6. A listing of the files on Disk 1 will appear, double click on the file "plssetup.exe".
7. Awindowcalled"SpinnakerPLUS Setup" will appear. Change the path of theinstallation
from"C:NPLUS" to "C:\WINDOWS\PLUS" (Note: "C"is a standard drive specification;
you should use the letter that designates where Windows is installed on your system).
Click on "Continue." The program will start copying files from Disk 1 . Follow the rest
of the instructions and prompts on the screen.
8. When the installation has been completed, exit the 'Tile Manager" and exit Windows.
.. .l7?JtfJi?A-i r.ffflfACfl f, .w. • .
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~ Hyperventilate Users Manual Addendum-
Creating the Spinnaker PLUS Icon and Opening Spinnaker PLUS
1. Re-enter Windows. (Note: exiting and re-entering Windows is a step recommended by
the manufacturer of Spinnaker PLUS).
2. Close all windows so that the "Program Manager" window is the only one displayed on
your screen.
3. At the bottom of the window, there will be program icons displayed for "Main,"
"Accessories," and others. Is there a program icon named "Windows Applications?" If
yes, double-click on it and go to Step 4. If no, continue with Steps 3a-c to create one.
3a. dick on "File" and drag down to "New." A window called "New Program Object" will
appear.
3b. Check to make sure "Program Group" is selected; click on "OK." A window called
"Program Group Properties" will appear.
3c. The cursor will be located at the description field. Type in the words "Windows
Applications" and click on "OK." An empty window will appear called "Windows
Applications."
4. Withthiswindowopen,clickon"File"anddragdownto"New." Awindowcalled"New
Program Object" will appear.
5. Check to make sure "Program Item" is selected; click on "OK." A window called
"Program Item Properties" will appear.
6. Click on "Browse." A window called "Browse" will appear.
7. Under "Directories," double-click on "plus."
8. Under "File Name," double-click on the "plus.exe" file. This will bring you back to the
"Program Item Properties" window.
9. Click on "Change Icon," click on the icon for "Plus," and click on "OK."
10. You will now be back at the "Program Item Properties" window. Click on "OK."
11. You will now be back to the "Windows Applications" window displaying your "Plus"
icon.
12. Double-click on the "Plus" icon to run Spinnaker PLUS.
Addendum 4
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Loading Hyperventilate
The Hyperventilate package contains one 3.5-inch diskette from which to install the program.
Theprogramcan be installed fromeitherthe DOS promptorfrom within Windows. The folio wing
procedures are used for both types of installations (Note: For these installation procedures, the
3.5-inch drive from which you will be installing the program is assumed to be the B drive).
DOS Installation
1. Insert the Hyperventilate disk into the appropriate drive.
2. From the C:N> prompt in DOS, type "COPY B:\*.* C:\WINDOWSPLUS".
Windows Installation
1. Follows Steps 1 -5 of the "Loading Spinnaker Plus."
2. Click on the B:\folder icon so that it is highlighted and/or a dotted line appears around it
3. Ch"ckon"File"anddragdowntothe"Copy" command. The"Copy"windowwillappear.
4. The curser will be located at the "To" path. Type in "C:\WINDOWS\PLUS"; click on
"OK."
5. When the installation is complete, exit from the "File Manager."
Opening Hyperventilate
1. Enter Windows.
2. Double-click on the "Windows Applications" icon (if this window is not already open).
3. Double-click on the "Plus" icon.
4. Close the "Home" window.
5. Click on "File" and drag down to "Open." The window "Open Stack" will appear.
6. Either double-click on the "SVS.STA" file or click on "SVS.STA" and then click on
"Open." The user is now in Hyperventilate.
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- Hyperventilate Users Mamuil Addenditm-
Ihstalling Spinnaker PLUS "Run-Time" Version with Hyperventilate
1. Create a subdirectory on the hard disk for Hyperventilate and Spinnaker PLUS "Run
Time." For example, from the C:\> prompt, type "MD WINDOWSNPLUS".
2. Copy all die files from both the Spinnaker PLUS "Run Time" diskette and the
Hyperventilate diskette to the subdirectory. For example, from the C:\> prompt, type
"COPY B:*.* C:\WINDOWS\PLUS".
3. Follow directions in "Creating the Spinnaker PLUS Icon and Opening Spinnaker PLUS"
with die following exception: substitute "plusrtexe" for "plus.exe" in Step 8.
4. Follow directions for "Opening Hyperventilate" to run die program.
.Addendum.^..
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- Hyperventilate Users Manual •
Disclaimer
The Hyperventilate software package was completed under a Federal Technology Transfer Act
Cooperative Research and Development Agreement between EPA and Shell CHI 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 isrecognized as an effective remediation alternative
for many underground storage tank sites.
Hyperventilate is based on the document titled, "A Practical Approach to die 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.
EPAwillnotprovideinstatlationservicesortechnicalsupportinconnectionwiththeHyperVen^
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.
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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
Room EC-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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-Hyperventilate Users Manual -
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, HX, 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 Hyper Ventilate
- General Features of Cards
- Sample Problem Exercise
- Navigating Through Hyperventilate
- Is Venting Appropriate?
- Field Permeability Test
-System Design
References
i
ii
2
4
4
4
5
5
7
8
8
12
22
26
35
36
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 of In Situ
Soil Venting Systems
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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 -
Pressure
Gauge
Vapor
Flow
Air Bleed
Line
I Vacuum
f Pump
Flow
Meter
Vapor Well
Vapor Treatment
Unit
Flow
Meter
Contaminated
Soil
Vapor
Flow
Groundwater Table
flume
Figure 1. Schematic of a typical vapor extraction operation.
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- Hyperventilate UsersManual-
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 Hyper Ventilate 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 them 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
"tf" 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 a 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 comer, 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
XI
A Practical Approach to the
Design, Operation, and
Monitoring of In-Situ Soil
Venting Systems
wsioa 1.01
«19«1 AH Rifttt fiwtmi
Economics
t HyjuCwi Buck Cnttti >y:
PavlC. Johnson, Ph-D.
Amy J. Strttntm
Shell Development
WwthoDo v R«j«»reh Center
About This Stack
Go to First Card
4 SyMMnMontorinc
^
Field Tests
System Design
4 Sit Investigation
-f About Soil Venting
Is Venting Feasible?
Vapor
FlDV
\
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 10 rust
card in Venting Stack
Goe next cam
Oo t> Help card
text field
(Calculate) Perform »C«Jculatkm
When curious, dick on Symbols,
or
Fields
Fields may contain information, or they may be
a place for you to input numbers.
Scrolling Field:
dick on tiro vs to move
*xt up or do va
Bond Data Field:
When you see MI I-beam
conor tppeu in a boxed
field, click the mouse in The
box «> set Hie cursor. Then
you m»y enter dtte..
A bunon vlll ten usu»Dy
be pushed to perform en
ection or cekuktion.
Click on the wrovs , or
move the box up or dovn
vlthihe mouse.
In this *n*. TOU can
Try this example:
Enter Number in Box
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 UsersMamal-
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) Airow 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).
^^^^^^^^m^^^^^^^^^^^^^*^^^^^*mt^^^^^^^^^^^^m^*mmm^^^^^^^^^^^^^f^^^m
In-Situ Soil Venting System Design Process
Ton ran click on «ny block in ftis di*cnm * get more information about (hut pwticukr >*p. Or jou
era begin »t the start of die pieces* by ctjckine °n either the "LetX or Spill Discovered" box, or fee
urov M the bonom of (his card.
(Let* or Spffl Discovered}
"Clean-
Sits
Figure 4. Card 3 of the "Soil Venting Stack" stack.
V
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•Hyperventilate Users Manual -
Number of Venting Wells...
The procedure forestimatinc fee required
number of extraction vclb is similar to the
process used previously to determine if
venting Is appropriate at a given site.
As illustrated at the right, vt vill estimate
single vertical veil flovrates, calculate the
minimum vapor flov required, determine
fee anal extent of influence, and then
factor in any site-specific limitations. This
information tten determines the necessuy
number of extraction veDs.
Jost proceed «foDo v the steps dictated on [
tie foDovinj cards—>
Flovrate
Eattmatlon
Maximum Removal
Rate
Volume
Requirement
Slw- Specific
Limiwions
Area of Influence
Requirement
Figure 5. Card SD1 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: Tit'e 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).
-------
Step 3: 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 title card of the "Soil Venting Stack" (Figure 2).
Step 4: Location: Tide 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 (8t
hold button dovn) to see costs
associated vith that item.
ft
Figure 6. Card 27 of the "Soil Venting Stack" stack.
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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 night
be applied to remediate a given site. The organization and logic of this stack
follovs the paper:
*A Practical Approach to the Design, Operation,
and Monitoring of In-Situ Soil Venting Systems*
Uy:
P. C. Jobason, C. C. Stuley, M, W. Kemllovskl, J. D. ColHuit, & D. L. Byes*
published in Ground Water Monitoring Reviev, Spring 1990, p. 159-178
If M tikis toiat yom to aot feel comforatla witk ttt* vst of Qt» tanois,
click oic« on '?• for note iifo on the neckamics of tkis slack...
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 should feel comfortable navigating around in Hyperventilate.
10
-------
r
About Soil Veatiag...
Soil Venting (a.k.a. "in-situ soil
venting", "vacuum extraction", &
"in-situ vapor extraction") is
rapidly becoming one of the most
practiced soil remediation processes
for permeable soils contaminated
vith relatively volatile
hydrocarbons.
The underlying phenomena that
influence the success of any soil
venting operation are easily
understood. By applying a vacuum
Vepor
Treatment Unit
Vacuum
B lover
Figure 8. Card 2 of the "Soil Venting Stack" stack.
Help: About Soil Venting
More information about sofl venting cut be found in the foDo Vine articles:
M. C. Mtrky and O. I. Hoeg, Induced Soil Venting for (be RecoveryfRes*>r»tion of Gasoline
Hydrocarbons in tbe Vados* Zone, NWWA/API Conference on Petroleum Hydrocarbons and
Organic Chemicals in Orotindvewr, Houston, TX, 1984.
P. C. Johnson, M. W Kembfcvstt, and J. D. Colftart, Practical Screening Models for Sofl
Venting Applications, NWWA/API Conference on Petroleum Hydrocarbons and Organic Chemicals
in Groundvurr, Houston, TX, 1988.
N. J. HuttJer, B. E. Mtnphy, tad J. S. Oierte, S*» of Technology Reviev: Sofl Vapor Extraction
Sysfcms, U.S.H.P.A, CR-814319-OM, 1988.
D. J. Wilson, A. N. Claike, and J. H. Claike, Sofl Clean-tip byin-Jttu Aeration.!. Mathematical
Modelling, Sep. Science Tech., 23:991-1037,1988.
H2
Return
[Print References]
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 fV.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.
North
South
10'
20 _
§
j
30,
50 —
60—I
•
M» «
•
H
•
.m* *
*
•1
•
^^p>
•
-0.3
1
•0.2- -
j
"0.02
-0.0
.0.0
I
*OT -
I
-0.0
• 1.7
1
-24 i
,73
l
L9.5 '
k V Tank
Sandy V Backfill
Clay V
-------
-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).
IB Venting Appropriate?
Read This
i
FlOVIMB
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.
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- Hyperventilate Users Manual-
Flowrate Estimation:
O Medium Sand
® Fine Sand
OSiltySand
O Clayey Silts
O Input Your Ovn Permeability Range
Permeability Range (darcy)
1) Choott Sou Type, or
Optional- Enter your
2) Enter W«n Rid to (in)
3) Enter Rtdtw of Influent* (fO *, Intern! Thickness*1
4) Optional - Enter your ova v»U vacuum (406* - max)
5) Click button t> eilcuk* Predicted Plovnte Ranees
I 1 I toT 10 I
Veil Radius
Radius of Influence
in
ft
Interval Thickness* I 66 Ift
[ —>Calculate Flovrate Ranges*— ]
* tUcloui of >cnu«i iattrvil, or
Predicted Flovrate Ranges
WeU
Vacuum
P.
(torijO)
Fk)Vi»te
(SCFM)
.1.0.
20
Q.33
1.30
Figure 12. Card 8 of the "Soil Venting Slack" 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.
-------
-HyperventilateUsers[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
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
•iiftYHovDo I M««su» » Distribution?]
Figure 13. Card 10 of the "Soil Venting Stack" stack.
Help: Compound List
| Viev Only Mode |
* Compound Name
Mass
Fraction
Molecular
Weight (c)
Vapor
1
2
3
4
5
6
7
8
9
10
propane
isobutane
o-butane
trans-2-butene
cis-2-butene
3-methyl-l-butene
isopentane
1-pentene
2-methyl-l-butene
2-melhyl- 1, 3-butadiene
0.00
0.00
0
0
0
0
0.0069
0.0005
0.0008
0.0000
44.1
58.1
58.1
56.1
56.1
70.1
72.2
70.1
70.1
68.1
8. 04673 K>
2.75865 n
1.97431 if
1.84196 Ii!
1.67019 II
0.88399 11
0.73146 11
0.64989 m
0.62093 if
0.60914 K>
I 0.99628
Sum of Mass Fwctons
(ihoxild b« .1)
Hov Do I Mewuie a Dlstribution?^« Rttum te Vapor Cone. Estimation Card
Figure 14. Card H16 of the "Soil Venting Help Stack" stack.
15
-------
-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
-------
-Hyperventilate Users Manual -
Maximum Remo val
Rate Estimate*
select your unit preference beta v
OUcg/m
Ho*:
These are "maximum
removal rates", and should
only be used as screening
estimates to determine if
venting is even feasible at a
given site. Continue on to
the next card to assess if
These rales an acceptable...
Temperature (*C)
Soil Type
Sofl Permeability Range (darcy)
Well Radius (in)
Radius of Influence (ft)
Contaminant Type
Permeable Zone Thickness (ft)
Pv - Well Plovrate Estimates Max. Removal Rate Estimates
Vacuum [SCFM] [»'*J
(inHjO) (single veil) (single veil)
™.5.._.
...IQ ..
20
40
120
200
.... 0,66 ....
} 30_
2.54
....JLZ..L....
... 6,83
1007
to
to
to
to
to
to
to
....112...
6.5$,
13...Q2._
25.38
68.27™
100.66
6
. .....12
25
52
._.....&0_
178_
364
to
to
to
to
to
to
to
....._.6.2
__12L_
2.5J
517
7.o,9_
1778
3636
Figure 15. Card 12 of the "Soil Venting Stack" stack.
I* Soil Veatiog 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
®kg
Estimated Spill Massl 4000] Q ib
(2J Enter Desired i—Tgj
Remediation Time '
vAx ^ ->Press to get Rates<- J
Single Vertical Well Results
days
Desired Removal Rate:
Gauge Vacuum (in H20):
Min Flovrate @ 200 in H2O
Max Ftovrate @ 200 inH2O
Max. Est Removal Rate:
(lover estimate) • per veil j^
(upper estimate) - per veil [~
200
ID. 07
100.66
(inHZOJ
[SCFM]
[SCFM)
164.892
IfcMJ
Figure 16. Card 13 of the "Soil Venting Stack" stack.
17
-------
- HyperVentUate 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 Figure 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.
-------
- Hyperventilate Users Manual -
Model Predict/oat
To the rightist summary of the
data you havt input Ifyouvishto
change a»y of the tafo, then click
on the parameter name, and redo
the calculations on the cud you vill
be taken to. Press the blinking
'Return' button to come back
The model returns output that
tllovs you lo deterniine
iwidual unounts of
compounds falling vithin 5
boOinc point IUICM. Type in
your OVA nnces, or choose
the default values.
lllHI
Son Type
Sofl PenwibflHy Rant e (daicy)
Well Radius (in)
Radius of InOoence (ft)
Comuoinut Type
Penneable Zone Thickness (ft)
[ —> get Default BP Ranges <—
.*!..
Boilinsf Point Ranee
-=5DL
..11.1...... Jo,
144
tp
?0
£..
...IQ.......UOJ.JIU..C
£.
c
H4
250
Generate Predictions
til me more about BP runes.
Figure 17. Card 16 of the "Soil Venting Stack" stack.
—> Import Oata<— ^ S«nmttd Vapor
0.20S3H*03
FIRST PRESS TOE IMPORT
n ATA R T TTIt iM I
These an the results for the
contaminant type that you have
QtfM(O)
L-airt
f-residual
.00
.24
.57
.98
1.49
2.11
2.87
381
Vapor
Cone.
[» Initial]
100.000
75.062
58.631
48.078
39.390
31.941
25.916
21 ISO
Residual
Level
[98 Initial]
100.000
95.000
90.022
65.034
60.034
75.035
70.035
65037
£ Mia Yalnn* ID Benum
ImlflAl t>»*M«uil
1
ijii Temperature (*C):
ry Contaminant Type:
BP«1
Residual
[96 total]
.690
.123
.000
.000
.000
.000
.000
.000
BP*2
Residual
[96 total]
11.650
9.263
6.755
4.512
2.632
1.222
.385
068
BP*3
Residual
[96 total]
24.010
23.982
23.474
22.403
20.771
18.503
15.556
12.053
128 48 |L~^
l-
If 0.10 | MJM!,,!!
18 |
Weatheiei Gasolla*
BP*4
Residual
[96 total]
22.140
23.000
23.820
24.577
25.246
25.766
26.031
25.919
BPttS
Residual
[96 total]
41.510
43.632
45.950
48.509
51.350
54.509
58.028
61.959^
^>
'B
?£
m
m
IHUl
h«j
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 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 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: Card 18 of the "Soil Venting Stack" stack.
Action: Click on the right-pointing arrow button to advance to can! 19.
Result: 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.
I^^^^^^^^M^MW^^^^^H^^^BM^^^^^^^^HMWiV^^^^^^B^^MP^^^^H^^^^M^^^^^^B
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 [*C]:
ConttainBAtTyp*: ^_
Soil Type: [^
Well Radius [in]:
Eat. Radius of Influence [ft]:
Penmetble Zone Thickness [ft]:
Flown* per Well (120" Vtc) [SCFMJ
ZTovn* per Well (120" Vtc) [SCFM]
Min. VoL of Air [Uf-iesidukl]:
Estimated SpflJ Mtsj:
Desired RemediatJon Time [dtyi]:
18
Wmtk«ra< GuolfB*
6.6
6.83
68.27
128.48
4000
180
OB Tour Inpwt Parameters
Figure 19. Card 18 of the "Soil Venting Stack" stack.
21
-------
- Hyperventilate Users 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 API 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 AP3 of the "Air Permeability Test" stack.
Step 3: Location: Card AP3 of the "Air Permeability Test" stack.
-------
-Hyperventilate[Users Manual -
Action:
Step 4:
Step 5:
Result:
Location:
Action:
Result:
Location:
Action:
Result:
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
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.
Card APS of the "Air Permeability Test" stack.
Click on the "Return" button to return to card API of the "Air
Permeability Test" stack. Then click on the "Data Analysis" button.
You are now at card APS of the "Air Permeability Test" stack.
Card APS of the "Air Permeability Test" stack.
Read the text, then step through cards AP6 and AP7, until you reach
card APS of the "Air Permeability Test" stack.
You are now at card APS of the "Air Permeability Test" stack.
Air Permeability Test - Instructions
1)
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 i™,
to seal annular borehole region).
[ shov me sample data
FOR Volwne EstiiMtioa:
Enter
1) Soil Layer Thickness {ft]:
2) Estimated Radius of Influence [ft]:
3} Air Perm. Tesi Flovrue {CFM J:
6.6
50
15
( -> Calculate <
Pore Volume:
Time to Extract a Pore Volume:
APS
Figure 21. Card APS of the "Air Permeability Test" stack.
23
-------
-Hyperventilate Users Manual -
Step 6:
Location:
Action:
Card AP8 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 Gauge Vacuum
[mini fin H?O1
9 0.1
11 0.2
15 0.2
23 0.4
30 0.7
40 1.3
100 2.8
flowrate
screened interval thickness
Time
fmin]
4
7
9
12
16
24
30
39
52
77
99
110
121
141
= 15
= 6.6
Gauge Vacuum
[in H?O1
1.2
3.0
4.3
5.5
6.9
9.9
11
13
16
20
21
23
24.5
25.5
SCFM
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 "~>Calculate<~"
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.
24
-------
-Hyperventilate Users Manual -
Air Permeability Tett - Data Analysis (cont.)
Eater radial
2) distances of
monitoring poino
Enter measured —<
2) times and gauge
vacuums
^3) Enter (optional):
a)ftovra*
L 15 1(SCFM)
b) screened interval
thickness
6.6 I (ft)
53
(min) (inH20)
r= j 32.4 |(0)
(nun) (in H20)
9
11
15
23
30
40
100
O.I
0.2
0.2
0.4
0.7
1.3
2.8
o
"
,
4
7
9
12
16
24
30
39
52
7V
1.2
3
4.3
5.5
6.9
9.9
11
13
16
20
-6
J
&
is
..
<>
Figure 22. Card APS of the "Air Permeability Test" stack.
Air Permeability Test - Data Analysis (cont.)
On the previous Card (AP8), the da» you input vere fit to the Approximate expression given on Card
AP6. It v*s analyzed using both methods described on card AP7, if you input values for the
extraction veB ftovrate (Q) and the stratum thickness (in). Belov each column of data, the tvo
calculated permeability values aic denoted by:
darcy(A) - refers to calculation method 1 (see Card AP7)
- refers to calculation method 2 (see Card AP7)
During the regression analyses, the data expressed w
pairsof points (ln(t),P') are fit to a tine The
"correlation coefficient", r, is a measure of hov veil
the date conform to the theoretical curve. As i-->l, the
data points all fall on the theoretical curve. At the right
are given the correlation coefficient values for the three
data sets For more info on the meaning of r, consult
any introductory Statistics book.
Correlation Coef.
(r)
data set tl |0.941158 |
data set t2 I 0.98602
data set 13 I NoDat*
Figure 23. Card AP9 of the "Air Permeability Test" stack.
V
-------
- Hyperventilate Users Manual -
System Design
Slulr/*
T««ffl» riUf fa* O«>*
-------
-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 ID provide a
generic recipe for vacuum extraction system
design; instead v» suggest the lollo vine •» »
structured thought process. As you shall see,
even in a structured thought process, intuition
tnd experience play importat roles. Then la
no substitute for a food fundamental
understanding of vapor flov processes,
transport phenomena, tad groundvater flov!
O Number of Extraction Wells
OWell Location
O Veil Construction
O Surf ace Seals
O Groundvater Pumping System
O Vapor Treatment
* 33*
Figure 25. Card 24 of the "Soil Venting Stack" stack.
Number of Venting Wellt . . .
The procedure for estimating the required
number of extraction veils to stanfltr tt the
venting a appropriate at a given st*.
As fllustt»fcd at ft* right, v» vill eitlmaie
single vertical veil flovrates, calculate the
minimum vapor flov required, determine
ine anal enent of influence, and then
factor in any site-specific limitations. This
information then determines the necessary
number of extraction veils.
Jut proceed to folio v the steps dictated on
the foDoving cards — >
FJovrate
Estimation
Maximum Removal
Rate
Minimum Volume
Requirement
Site- Specific
Limitations
Ana of Influence
Reauinment
N\_ Hunter
(i . °'
A-^ Sxtnctlom
sy Wells
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
subsurface interval (ft BGS)
description of contaminant
radial extent of contamination (ft)
interval thickness (ft)
average contaminant concentration
Medium Sand
10-30
gasoline
20
20
100
Soil Zone
Clavev 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 H2O)
WeU 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. . .
(soilstiaticraphy fc containinant characteristics)
Please enter the required information for etch distinct soil
layer, click on (he "Upde* " button, and then proceed to
the neit cud (i.e. cUck on rijht irrov at bottom).
f the »b kev can be used to me ve betveen cells)
Select the totrt mas
tinit* that you prefer
C Clear All Entries J
OPb]
Description of
SoU Unit
J.
JLltaL
4
DepthBOS*
30
«L A
... _»,.
_».,
3SL
.*...
to
SB-
Description of
Contamination
Contaminant
Distribution
ntiu
[A]
JO.
20
[ftl
JO.
—JUKU-
1000
CeJe.
To«l
Mess
DC]
J2IL2.
0.0
•Maw Grauf Bwfut
Figure 27. Card SD2 of the "System Design" stack.
Design Input Parameters...
Please envr the nguixed infoimation for
eech distinct soil layer, and then proceed
to the next card.
No*: - click on an; (able headinc to
tet more info
- use tab key to move
betveen cells
O MtUva, Su*
On&i'oi
O Billy Bui
Extraction Wefl
Construction
• Ewtr or ckMf• (nm Ust «t to) rjgil
Figure 28. Card SD3 of the "System Design" stack.
V
-------
- 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).
Step 8: 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 Rangeso-" 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.
-------
-HyperventilateUsersManual-
Critical Volume Calculation...
typically observed In venting
operations.
The results an plotted in this vay t>
emphasize that Ac degree of
remediation that can be achieved by
venting depends mainly on the
volume of vapor extracted divided
by the initial mail of residual
hydrocarbon. For the example
pictured at the right, approximately
100 liters of air must be vitbdravn
from the subsurface In order to
remove about 90O of a single gram
QC/QC(UO)
1
% Removed
100
Return to Design
Weathered Gasoline
T-20*C
10% moisture content
C(t=0)« 222 mgrt
Figure 29. Card SD5 of the "System Design" stack.
Critical Volume
Predictions...
Simply enter the temperature at
the right, and then specify the
composition of your contaminant.
If you are unsure about this, elicit
on the "About Composition..."
button located at the low right
The model returns output that
alia vs you to determine
residual amount! of
compounds falling; vithin 5
boiling point ranges. Type in
your ovn ranges, or choose
the default values.
tell me more about BP ranges.
Contaminant
Composition
(choose one)
J~
1
L_
;> Enter Distribution
D "Fresh" Gasoline
i) "Weathered" Gasoline
( Viev Distributions J
( ~> get Default BP Ranges <— )
.M!i.ngP.oint.Bange....»3..
M!.i.Gg.P.oint.RaBge..*4.
Boilinp Point Ranfe
-------
- Hyperventilate Users Manual -
Step 10: Location:
Action:
Result:
Step 1 1 : Location:
Action:
Result:
Step 12:
Step 13:
Step 14:
Location:
Action:
Result:
Location:
Action:
Result:
Location:
Action:
Result:
Card SD7 of the "System Design" stack.
Read the instructions, then click on the "-->Import Data<~" button.
Your screen should look like Figure 3 1 . 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.
Card SD7 of the "System Design" stack.
Click on the "Return to System Design" button
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**11 column for the medium sand soil unit.
Card SD3 of the "System Design" stack.
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
Card SD3 should now resemble Figure 28.
Card SD3 of the "System Design" stack.
Click on the right-pointing arrow at the bottom of the page to
advance to Card SD4 of the "System Design" stack.
Card SD4 of the "System Design" stack should appear on your
screen.
Card SD4 of the "System Design" stack.
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.
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.
-------
'Hyperventilate Users Manual -
To read about these, click on the "Number of Wells" column
heading. Your card SD4 should resemble Figure 32.
// is importani 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 1,P.T. Kostecki and E. J. Calabrese, editors,
Lewis Publishers, p.253 - 281, 1991.
33
-------
- Hyperventilate Users Manual -
—> Import Data <--J Saturated Taper
n
0'
rm»/r i
In*'L1
FIRST PRESS THE IMPORT
DATA BUTTON!
These are the results for the
contaminant type that you have
L-ato
g-iesidual
.00
.24
.57
.98
1.49
2.11
2.87
3.81
Vapor
Cone.
I» Initial]
100.000
75.062
58.631
48.078
39.390
31.941
25.916
^1.150
Residual
Lewi
[* Initial]
100.000
95.000
90.022
85.034
80.034
75.035
70.035
65.037
£ Min Volwott to 1
^ >90» of Initial
IJji Temperatui
$ Contamlnai
BPI1
Residual
[96 total)
.690
.123
.000
.000
.000
.000
.000
.000
BP*2
Residual
[96 total]
11.650
9.263
6.755
4.512
2.632
1.222
.385
.068
EtolDDV*
Resliwl
e(*O:
« Type:
BPI3
Residual
[SB total]
24.010
23.982
23.474
22.403
20.771
18.503
15.556
12.053
128.48 | JrJShlSi
18 |
Wettheiet Gasoline
BP»4
Residual
[96 total]
22.140
23.000
23.820
24.577
25.248
25.766
26.031
25.919
BPtS
Residual
41.510 O
43.632 ~
45.950 fl
48.509 I!
51.350 |
54.509
56.028 ||
61.959 O
Return to System Design
Figure 31. Card SD7 of the "System Design" stack.
Design Input Parameter*..
Pleasa enter (1) the desired time period for
remediation, (2) the design gauge vacuum, and
then (3) click the "update" button.
No*: - click on any table heading to get more info
- we tab key to move berveen cells
Minimum Number of Wells
Description of
Soil Unit
Tune for
Clean-up
Mays|
Design
Vacuum
-------
- Hyperventilate Users Manual -
References
Hutzler, N. J,, Murphy, B. E., 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. D., 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 Huh, 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. Sci. Health, A17(l), 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.
-------
-------
- Hyperventilate Users Manual -
Appendix A: "Soil Venting Stack" stack cards.
-------
'Soil Venting Stack" Cards
A1
p
I
A Practical A
t»tb*
Uooitoruc of lB-Sita Soil
V«
m»IJI
•mi AaH0uai
DdoaCMia
•1C. JU
A»TJ. i
tf
n.o.
M«l1M>«tak
ff
OttoOMClf*
I«Tn
•*T
Tbi» HypaOrt Stact v» u «*d to halp guuto mnu unmulit icantott
through tt» ttttvte frocM Mcavjary to doada if ant bov (oil wntug migM
1» appliad IP ra
foUowitbapana
i »gT»i «» Tl» orgunboo and lope ef UMJ rack
ckto
•i UoKtoruc of I»-Sit» Soil Votuf
C. C. >h»by, M. W. Lnumtt. J. D. Cdtel. * D. L. *)
nd Wnv UaBitoni«Rnwv, Spring 1990, p. 159-178
Soti Vtnhag (».»«. 'u
wring*, •^icuantanetwo*, Ic
in-ntu Tipef mutUmi") n
npdl; taconiag «o> rf Ot mod
f« pnmiil* Kib
taflunot Iha weeaa) ef anf toil
ivtiag ofMnboci •• MBly
uudaritoid. By^^7ii«iiKui
ID tl» follow* canto v» vflt wun
U* • latk or 9ill l» tan ilaeomd,
No» wt vill Off Ormifb » l»gdl
to (
art dupUp da flovdvt tte if tto
uferttBthn«btpncm. Clickint
viUu B7 [IDCMI box viD Mfei f»u to
tW «q»ct «f ttt ttougU
Soil Venting System Design Process
Invwtifilioa
• nil
im»Higaii)u n conducud to
BOOB Of Mil VBd
* ............ * ........... ' ......
Tte
mttct on pntrtial human and
rawMan. and it conductad in a
nlatnalrihoitpriodor, on*
•qlon Ite (*Mtaiit7 of «D traM
Otnammtioo
(«*, q«d, fnittiBf pnttan
ta wtrtfatad. m ttao 0» fin!
Soil Vwung it mod liWy to bt
HBOMBM vtaB foilt «• mtdjmA t
QlD-SituBtortinJalioo
O^ftiMififrtii^rttiliKmi
OSolw* ExtndiaaSoil Voting
M ite pou* «• vill prooMd Urougb a
0*104*. proc«i to (tacidt if Mil
At
telonltM I
-------
'Soil Venting Stack* Cards
A2
O top* Y«* O»o Pwmdility Rang*
Til inrtilitj lti»t«
I I Itol Ifl I
Vdl Radn I 2 I in
Ratal of laftam I 40 lit
I 6.6 in
rate oecw* vbmmr Om npon
ronowl by anting w '
or in tqvilitniaa vilh (be
IntheraacardyouviUutuBMa
of JOW O
tfai uMnctMtt in tte i^frv krfl
oocnr of th0 uul cvd.
Vapor CMMHUMMM 1
Typ« in Tonponhn (*C) (tit )
Calculation
20
J
Click to EiMr Contortion of Coolan»nM* O Enter Diitnbuaon
! or O 'FrBh' Gasoline
Cboon one of tht Drfwlt DirtnbUiOM ® • Wnttond" Gawlme
T) Click to Vwv DiUhbuboB, (optiond)
T) Click to Parfonn CalniMxM
C VJOT Dutnbuuopi 3
O P«fonn CalcublKW
Remov*! R*te Estintmtes
Tht
nmowi rate occm vl
Ua Kport ronowd by wntmg
or in
equilibnun nth U»
Th> 'RonMil Rate' if amply
OB prodict of )!• flovnto
tim« te npor caocartntooo.
R«to
Vipor z V»por
ConcntratioB Flovrat*
ean
mf
5
10
20
•4
60
120
2on
0.33
0.66
1.30
?-5L
J.71
6. S3
1007
to
to
to
to
In
to
to
3.32
6.S9
>3.tt?
2S.3S
37.09
6127
10066
6
12
25
52
SO
17S
3M
121
2SI
517
799
1778
3636
At Ihu potnt, you coopv* the
with you- diond ran»*il rate.
If OB
do« not (End yo«r dwnd
iwoml rate, ttm soil wring
» ootltMy to OBM TOtr andi,
Dndi UMJIV rwlifttc.
Imhaanitanb. T»villr«ru»
CD Enter Ownd
Remediation Tins
O
«««t
• Uf*tRW»<—
Sugte Venial
taHZO):
pan
9200
_UJ
IOt.66
MM)
|hK20;
|1CFH|
[:
«^->-»-*«» rjfrr
Ml
MM)
W)
oriy• • Ibiteaf, ad
**^*|M te raRmd if ^cfting is
TypioUy doing toil untinft
tbtz
(vbntetottl *por fiovrate
• W
of not1
[QC(tXQC(UQ)],«bilttni
*..-j|'--_ TJlllI ,—I*. —
UUffUBUUM "UUI II
tott votinte of i
.1
.01
.001
.0001
-------
•Soil Venting Stack' Cards
A3
Is Veatiaf Appropriate*
IK Wa (120- Y«J [tCPM]
NotolW MM.Tci*A*(m-wil.lt
of wtUf if
Clidt on (to tah» to OB rij* to
System Design
System Desifa...
-------
"Soil Venting Stack* Cards
A4
System Dcsira...
Economics...
System SJbat Down
•Click' OB 107 item telov (t
hold button don) to M cocte
vitk that item.
TrgKiotl clMD-up Ineti
HOOK - J250K for tta wting
on
•idnbmdootbBiftumM
pomtiil iapKt flat «7
randtal m»y bm on «r
clMo-up tiini, ptrmiaing
Kd tfci typt of
O £>lncti«B V«U V ^or C
O EHr«tioa V«U Vtpor Compontto*
*too to ralKMi to nf*tr
Tte tvo mjor COM ••
Titb Uv
OSoil Borin* EMa
Acknowledgements.
-------
-------
r
'Hyperventilate Users Manual -
Appendix B: "Soil Venting Help Stack" stack cards.
-------
•Soil Venting Help Slack' Cards
B1
Help: Stack Information
Buttons
Biraom have been placed in each
curd. Clicking on any button will
perform in action. tuA ac
When curiaiu, click an Symbol*,
Picmet or Tea.
Fields
Field! my contain information, or they my be
i place for yon to input nimben.
Scrolling Fi«M:
Help: About Soil Venting
Un» afonpuo. Awl (oil wumi OB te rood t> *» followiit
Orp
V
Onmtwua. tfaUM, TX. I
Or|>Ke
N.I.Itaotot. B.E. Mun*».l»U S OMB. SUB orTuhDotoiy SCVBW: Soil Vapor Eincioe I
SyiMHl. UJB^jk, CRJU319-01-1. 1«M. |
D.I. Wilaoa. A. N. OKto. «d J. H.d«*». Soil r>M->p by ffl*tu Acnao^ I
ISM,
Help: In-Situ Soil Venting System Design Process
Help: Preliminary Site Investigation
Thi* if the deciiion prooeM iha one nuut follow to:
I) decide if toil vetoing it tpplioble it a given cite
&
Z) design in effective toil venting iyttem
ll ii tn tbridged vention of Rfure 2 in M Practical Approach to tte Duif*.
Opmtiat, A Mont/WMf ofln-Siut Soil V,HIM, Syntmt". by P. C. Johnon.
C. C Stanley. M. W. Kcmbtowiki, 1. D. Colthvt, Kid D. L Bycn.
Mow infonniiion about rile invcmimoon and rcmedution can be found in the
following nuclei:
API Publication 1C28
"A Guide to the Aseunxnt and Remediation of Underground Petroleum
American Petroleum Innitulc, 1230 L Street Nonhwen, Waihington DC, 20005
Help: Thermal Desorption
Pntm Dtteriptiea
in i thermal dexirptii
proccaa, aoik conuuninaicd with
voUnlc/iemi-voUUJe orfanic* ire
heated, and the volatilized
contaminUM are nripped with air,
•team, or combuation producu
(burner flue (ate*) at relatively
nodeat tonptnmn* comparad wiih
incinentica (200-500'C >
1000-1200'CX Ihedcaortaed
organic oonuunuumu are
Help: Incineration
FnctH Dticriflio*
Incinenuon, or the thermal
douwcuon of waoea, it a complete
dcatruction technology that can be
uaed to treat aoila contaminated with
a wide range of hazardous organic
•ea. Contaminated aoila.
tludgea, or liquid waitca are added
to a high-Umpenturc combuition
(rotary kiln, fixed hearth, multiple
heanh. nuidixed bed, liquid
Pncfti Dtterifdam
Compoatrat a an above-ground soil
mmatonent lechniqiie in which
amended toil, containing organic
waittt, it placed in large pile* and
aerated. The tendon enhances
microbial dejradation by providing
oxygen to Hie toil/wane. Wife
time, the deoompofed wane i§
reduced in weight and volume, and
Ite proceaa produce, a ttabifoed.
enriched. humu»-like maurial.
Pratfii Dncripllau
"Landfmrming" icfen to the
practice of tprcading organic
over an are* of land, then relying
on natural microbial action to
degrade the wine. It in widely
accepted and con-effective practice
for Ihe treatment of petroleum
hydrocarbon*, chlorinated
compound!, and peadcidea. Inthu
procew aoil-uMciated
roieroorganiBn§ (bacteria and
-------
•Soil Venting Help Stack* Cards
B2
Help: In-Situ Biostimulation
Help: Solidification / Stabilization
Dttcrtfttfm
Pnattt DttcrifUf*
Treatment of groundwter Hid toil
comanunaiion below the water able
("utiiriied zone") by in-«ini
bioctimulaiian involve, flic addition
of nutrienn and/or O2 (uwally ai
H2O2 or liquid O2) 10 m aquifer in
order to enhance the degradation of
the hydrocarboni by indigenoua uil
microbe*. The nutriena mi
oxygenate added above (mind to
Stabilisation and | ir Em]
UK
Taa eqaMioa totow • ia>
Help: Unit Conversion (k and K)
I > am nlae tf kydnuMe andxb>riiy m fenaMUiir n be cnvuvd
DCaoOKaaaalcaiai
O cmk
O ftM
• on1
O darcy
Compwud Nimt
uobuiane
n-buune
truw-2-bulene
cia-2-bulene
3-methyl-1-buune
1-pcniene
2-meihyl-l.buUnc
2-methyl- IJ-buladiene
Man MaUcalar Prm.r<
Fr.di.. Wri.lt (.)
0.00
0.00
0
0
0
0
0.0069
0.0005
0.0001
1.0000
.1
5..1
58.1
56.1
56.1
70.1
72.2
70.1
70.1
68.1
0.94
0.7S
0.7
047
04S
-------
'Soil Venting Help Stack" Cards
B3
Summary Card: Site Characterization
Compound List Default Data
Acomplete tile tttrumemmuat determine tie following:
Svburracc Characterbliei
Caatamin*M Dcltaeatloa
• enmiofri
Help: Data for Fortran Program
Help: How Do I Measure a Distribution?
Ml* V*cr
» Compound Na
MdtoilirCQ
W«H. 01
(«-)
(AOD) SohiMlitr Du.
9T» CodT
20-C
cu-2-bbBB»
3-oxrtyl-l
ITt-l
t^JBW-1.
44.1
St.l
51.1
56.1
56.1
70.1
72.2
70.1
70.1
«l.l
»J
i.n
2.11
1.J7
1.7J
0.96
0.71
0.7
0*7
OJ55
62
»9
61
430
430
130
4«
141
113
6*2
73
537
946
20*
204
701
l«3
710
52)
323
0.00
OJM>
0
0
0
0
O.OOW
0.0009
O.OOM
o.oo«o
Help: Calculate a Distribution
Help: About Calculation
In dm eniimtion of equilibrium
(•Hinted) vipor conocmnlioni.
we mume ttut the conuminim
coocenmtiom in fral enough
(>200 m|At TTH) flat it U
dilthbuled between vipor,
locfeed. ditiolved-in-ioil-
moimre, A fiee-phuct. In thii
cue, the oqutlion u the right
•pjttia Oook for -JUouH'i UW
* Ae Idoil Gw LJW-in my
IpUiiMxiynuiuoi tcxioook fof
RferenoEt). We do correct for
• nal v^gr nManm
Help: 6a) Dilution Effects [Bypassing]
Help: 6b) Liquid Layers
SM< View
Vi*w
Tbefnure ibove depicuihe cue where ume npan "liypMi* taum of
conmiintion. nd flmdbre the npon removed from the unction well
npretem t mixture of the vcpon obninod from both contmintted md elan
vipor nowpMhi. One am roughly judge the tmounl of byp«nn» by the weU
placement, fcncning, md conuunirmu diflhbutioa Genenlly, otnerved
la Figure fib, rapor flowi pnllel to, but not through, the tone of
iorutr^trieugn^icmtiniwtnniterreiiiunceiiviDorphuc
diffuriaa. ThU would be the cue for • Uyer of liquid hydrocarbon rening on
top of m irrfxnnemble Brali or the witer table. ThU problem wu studied by
lohntan «t «109M. NWWVAP1 Pcmtoim Hydroorbont Conference) for
-------
"Soil Venting Help Stack" Cards
H25
B4
Help: 6c) Low Permeability Lenses
Help: 6c) Low Permeability Lenses - Equations
i
HI
In the situation depicted above, vipor flow I put, rather than through the
contaminated toil zone, nich as might be the cue for • contaminated clay lent
surrounded by sandy aoili. In this case vapor diffusion through the clay to the
flowing vapor limit* the removal rale (the removal rale actually become*
Lars Da • Calculation
c l=j/d|
Undine of •oricd-oW UK \m\
o • pmu [•)
cudndnl MM)
i* a) |BS/kfj
UDC Id]
Derivations for that
equations arc given in
Johnson, « al - "A Practical
Approach u the Design,
Operation and Monitoring
of In Situ Soil Venting
System** • 1990.
These Equations are valid
for single-component
Help: Default Boiling Point Ranges
Help: Boundary Layer Equations
The Fonnn program HYPEVENT will report residual levels of compounds
filling between user specified boiling point ranges. The default values have
been chosen so that residual levels of compounds with boiling points between
the following compounds are grouped together:
Propane • Isopemane (-50 to 28 C)
bopenunc - Benzene (21 to 80 C)
Benzene - Toluene (80 - 111 C)
Toluene- Xylenes(111 - 144C)
Xylenes - Methylnapihalene (144-250 C)
The equation above
estimates the removal
rale from a layer of
liquid product by a
•ingle well, baaed on a
Boundary Layer Theory
approach to the
problem. It it not
directly applicable to
mixtures, because it
aaaaaaaaaaaaaaavaal
left Do • Calculation
1» - P,)]
R«t * fHinmnrt rnacvd rue
T| * efficMicy lelim* ti
p* * «*Toc«** BDil verpor (haTuHoa eocffiocBt toa^/kj
jt s vucoHCy at ui j» IJ, i ]0-4 f/bB-«
^ « ami penneibilicy BO vtipor flow |c»2j
Rj > ndtu* tf nnuEBDB of ycBhnf weU [em)
1^. => voui&f iMdl ndta* [cm|
PAM > kbMttt.* atobamt pcwtoc - 1 X)l« x 106 t/an-*a
P, "itadufcpreMP
B,-cr the
nearest minute should be sufficient-
Samplc devices are Rolen watches,
hour glasses, sun dials, and timers.
-------
•Soil Venting Help Stack' Cards
85
Vapor Flow Rates...
Pressure/Vacuum Readings.
Vipor flow rates from each
extraction well «nd into any injection
wellt should be monitored.
Sample meuurint devices include
pilot tubet, oriface plates and
rotameters. It ii important to hive
calibrated these device* at the field
operating prcaauroi and temperatures
n
Pla»
Pressuref/Vacuums ihoukl be
manured at each extraction and
injection well. In addition, subsurface
pressure distributions (measured with
loae tone inullaiioni) are uaeful
for deia mining the zone of influence
and vapor flow patha.
Typical preuure/vacuum measuring
devieea include manometer! and
differential prcaaurc (augea.
Vapor Concentrations & Composition...
Temperature...
The vapor concentration and
coR^Maition liutii each extraction
well ahould be analyzed pehodicatly.
This data ia multiplied by the
extraction well flowrate u> calculate
the removal rate (i.e. Ib/day). and
cumulative amount of cotvaTunant
removed.
By itself, vapor concentration dan
doe» not give a complete picture of
the system* performance. Dcucam
The aoil and ambi
4, 4,
nt lemptratiirea
can have a significant effect on the
performance of aoil venting system*.
The aoil temperature affectt the
contaminant vapor concentration!,
while the ambient temperature
controli whether or not condensation.
or even freezing will be aigiuficani.
Por future reference, therefore, it ii
aseJul to record the ambient and aoil
temperatures.
Water Table
Soil Gas Concentration & Composition...
Whenever the contaminated lone lie»
near the groundwater table (within 3
to 5 ft), it ia important to monitor the
water table level tt> ensure that
contaminated soil! remain fnpiTifd to
vapor flow. Measuring the water
table level during venting ia not a
trivial talk becaiue the monitoring
well muat remain scaled. Uncapping
the well releaaea the vacuum and any
effect that it hat on the water table
level.
WuehaBWan
Theac ahould be measured
periodically at different radial
distance* from the vapor extraction
weUXi). Data from aoil gaa sampling
ii valuable for three reasons:
(1) by comparing extraction well
concemrauona with aoil gas
ooneentrationa, it is possible to
catimaie the fraction of vapor that ia
flowing through the contaminated
ic (i.e. the 'efficiency'' of
Cumulative Amount Removed.
Extraction Well Vapor Concentration.
CUMULATIVE AMOUNT
REMOVED
it determined by integrating the
measured removal rates (flowrate x |
concentration) wWt time. While
this value indicates how much
contaminant ha* been removed, it • |
usually not very useful tar
determining when to lake
confirmation borings unless the
original spill mass ia known very
accurately, la most cases that
CW6)
Tua>(daya)
EXTRACTION WELL VAPOR
CONCENTRATION
the vapor concemraiiona are good
indication! of how effectively the
venting rynem is working, but
in vapor extraction well
concentrations are not strong
evidence that aoil concentration!
may also
be due to other phenomena such aa
water table level increases,
mass transfer resistance
(mart)
-------
•Soil Venting Help Stack" Cards
B6
Extraction Weil Vapor Composition...
Soil Gas Data...
EXTRACTION WELL VAPOR
COMPOSITION
when combined with vipof
concentration* Out dm fivei more
in»i|htinu>theeffeaivGneMofihc
•yaem. If the local vtpor
change in campotition. it»
probably due to increaaed raw
transfer micanrr (wafer able
ipwellinj. drying-out of low
penncability lonta, etc.), and ii net
SOU. GAS DATA
Ihif d*u ii the mo* meful becniie
it yiddi infonmlion about the
midual oompocilioa nd enatt of
Soil Gu Monilorlng
IniUlUtlan KctulU
Vq
am
(•*«
Vipof ooncsimtMM mi notf in
ftnenJ, be luod ID dcurmine the
rartkul lord, euept in the limit of |
v«9 lowrakkwl kwli (when
propooiocul to »oil rc«
-------
-------
-Hyperventilate Users Manual-
Appendix C: "Air Permeability Test" stack cards.
-------
•Air Permeability Stack' Cards
C1
Air Permeability Tests...
The purpoee of in air permeability lot if
to obtain lite-cpecific data thai will be
Calculate <- ]
Air Permeability Test - Sample Data
Pictured at the rifht are the
MU vacumu nMawBDBnti
from an air penneability
inanity
TV cpecific opentini
in *A Practical Approach u>
te DenfA Operation, and
Momtoriai of In Situ Soil
Vom*t| Synem", by P. C
Air PermeaMlity Test * Data Analyrfs
The expecttd decnaie in labeurface preacure (incrmae in |au|e vacuum) P if
predicted by: <«»MfMi«iltl**0|«>*n*aB«a>
Air Permeability Test - Data Analysis (cont.)
For (r* C|iH k P** t) < 0.1, the |overniii| equation cm be approximated by the
exfroaiaa:
TUf Equation praScif that a plot of P* -vt- ln(t) ihould be a Mrai|ht line wiQi slope
A and y-imeraept B equal to:
Air Permeability Test - Data Analysis (cont.)
The permeability, k. can dm be calculated by on* of two mothodc
ft-. The fim if applicable when both Qtflowraic) and n> (well acre
^•^ known accurately. The caJcnlamd tlope A U uaed:
© The Kcond appmeh if uaed whenever Q or m am not known wiA confidence.
Jn thif caw, both the tlopc, A. and Wercept, B, m uaed:
Air Permeability Test - Data Analysis (cont.)
-------
•Air Permeability Stack" Cards
C2
Mr Permeability Test - Data Analysis (cont.)
1» ^ JUIIIM. rmi Cfilt). te Hit 1 in i
M«. II nil •hail njij >irt •>mli i
i lii m tin muiimm inpnajw i«m
i« mil nrt. if mil ni|iiil » ijim fw TW
KncCMAIT)
-------
-------
- Hyperventilate Users Manual -
Appendix D: "Aquifer Characterization" stack cards.
-------
•Aquifer Characterization" Stack Cards
D1
Aquifer Characterization:
To achieve efficient «««*«. the
to expand ID air flow, ttaerafon, in
moat caaea where the reaidual toil
conlaminatian liet clow to, or below,
the Mined nil
lilili). ii milll ••Mill In
Aquifer Characterization:
Shu* mo* vantiai fjMam are tamltod •bow "phreaUc aquifere" (iquitei with
MrfWii), ID* two prinvy njuif• pmmno* needed for oetign
K • HyilTBIIllIT OOBOuOUVIly
S • •fltoiv* porouty {or fpedrw yield)
Itofim
tedion of ihe fundvncnul
Aquifer Characterization:
Th«« penmeun (K and S) cen be eclkMUd uinf Iht nnlu of e modwd
(rouadwaier pump ten with i comua punrii« nu. The mutu tra UMD oampend
igiiact nandord type eurvei* for ^wafic aquifer titmiiam (i.e. leaky, unconfined
aquifers, stt).
pump MM*, md data analyst*.
" bunon below far more alfeiraatioa on ftuf Ml*, bill taata.
Aquifer Characterization - References
). Bev. -Hyonulici of OnoadwaW. McGnw-Hilt. 1979. ISBN CMTT-OW170-9.
p.4«3.490.
R. A. fnei* and I. A. Cherry. "Groundw.ier-, Premiee-Hall. 1979. ISBN
0-13-MS312-*. p. «9 - Ml
-------
- Hyperventilate Users Manual -
Appendix E: "System Design" stack cards.
-------
'System Design* Stack Cards
E1
Number of Venting Well*
ml oBMm tar ««* *ttaa ml
try*, dkk cm die TptaB* tana, mt tat pnncd •>
te Mil end (it. dick » n|M
H fvllB^
C Cl«ir All EHrin J
prom mat pcvioojty ID iaamam t
vaumj at ^^tafoat it • ftWB «•.
A> lUmmanl ic <• li^tt, »• oil
ingle MTBMI »«U downrt, rolfnlut
V.DOJ flew mpn*
fee ml UMU of isflaoBO.
fetor 11 ray iK-ipcafictuxu
Design Input
(DfediucdBmcpcralfor
ten 0) dick ibe "upd**'
Maumim Nmber of Welli
Volume
Predictions..,
Critical Volume Calculation...
O Enur Oinribuiian
Q -Frah" Gasoline
® "Wottwrcd' Gisolme
If »« « mom ikav itaw. die*
• fe 'About
bana tocttd u Ibe law ri|bL
-> Stt DcfuH BP R»|«
nwml mm. wMb to
100 200
Q«An(t»0) (1/j)
Generate Crtdlctlon«
Removal Efficiency...
Tta nibivfiB • difficult to
) S.UrmUJ Vapor
Mi* V.l.m. to Kcmo*«
>*** «T Uilicl Rt.id««l I
Ttcv me 4« MttlBfor Ac
me atamet m "A Pnoial Appraxt» die
DB^K. OJWMOB, ud Moniwmj of Ii Sim Soil
Low Permobiliiy Laim
Ground W»tcr Upoclling
R«mm to Symm IX»igi
-------
•System Design* Slack Cards
E2
Help: Well Parameters
Help: Minimum Number of Wells
No. tar rf Wen." * akvbM >> to n»
•WtU Rjdin.-. kpunliiilkiterasiMaflkt
i*>lisafSl»ilta*jarasiMaflk*MU I
*-— *-** >— -*-| H-| —--•:- ,
mpierirf •• p. •niii. *• <» «oii
fen-Mi. —I
liaaniltflh* ~| T
tap— —.
J 1
Tta
•roica'aa •«». »>•» fle gage |IIM«M»
im
Tte
Contaminant Composition
Vkw
Compoand Num
Wtiakt (t)
1
2
3
4
S
6
7
S
9
10
propane
isobutane
n-butane
tnns-2-butene
cj**2"butcne
3 -methyl- 1-buiene
mpoicuic
l-pentene
2-methyl- 1 -buteoe
2-methyl- 1 >buudieoe
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
1.00000
44.1
51.1
SS.1
56.1
56.1
70.1
72.2
70.1
70.1
61. 1
8.5 O
2.93
111 |
1.97 li
1.79 1
0.96 *
0.7S 1
0.7 t
0.67 !
0.65 O
• lomof Mi«fW*oa>
How Do I Measure a Distribution?
Determining the exact composition of
complex mixtures
(such as gasoline) requires specialized
analytical techniques. For the purpose of
estimating the response to venting, however,
an approximaie composition can be used with
very food results.
To determine an approximate distribution,
one must analyze the mixture by gas
chromaiofraphic analyses. Prior u> the
analyses, choose about 6-10 marker
compounds whose properties are well known.
Calculate a Distribution
taftlKlOCnMrV*
K4m4lpMB»»iM>
• Bill
fc.TAfao.ih.oist.
Tsca. Click CMcaUat.
OjOO
OM
0.00
1111
t>M
OM
OM
OM
OM
0.00
0.00000
1.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
Well Location
To be able to fuccestflilry locale
extraction wells, pauivc well*,
and nir&oc seal* one must have *
good understanding of vapor flow
behavior. Wells location* should
be chosen to maximize vapor flow
through the contaminated zone,
while mintmizint vapor flow
through other tone*.
If one mil is sufficient, il should
almost always be placed in the
geometric center of the
Return to Design
Well Construction
Surface Seals
Welk should be screened only
through the zone of contamination,
unless the permeability to vapor
flow is so low that removal rate*
would be greater if flow were
induced in an adjacent soil layer.
Removal rate estimates for various
mass-transfer limited scenario* are
discussed elsewhere in this stack.
Based on predictive equations, the
flowrace is nprrtal to mmtssf by
15* when the exttmction well
PVCPtpe
Surface seals, such s*
polymer-based linen and asphalt,
concrete, or clay caps, are
sometime* used to control the
vapor flow pains. Figure 12
Ulusttmies the effect thai a surface
seal will have on vapor flow
panerns. For shallow treatment
zones (<5 m) the surface seal will
have a significsni effect on the
vapor flow paths, and seals can be
added or removed u achieve me
desired vapor flowpath. For
tl'OpCB'MllHIlfalX
-------
-System Design' Stack Cards
E3
Bp««l»( (*»»-*>) of tta
Cranadwaur Ubto wiU ootw
S^apor Treatment Systems
CttraXly UMK I four nun
pnwem mifcbte
-------
Hyperventilate Users Manual-
Appendix F: "Compound List Update" stack cards.
-------
"Compound List Update* Stack Cards
F1
Compound List Update
Thit card it provided at • utility to let you add, or deklc compound! from Die
Compound Lid Data BMC Ihit th* program utet. You may not deloe or change the
propeniea of the bate 62 compound*, tince ihete are needed for the two deftuh
fatoline cue calculation (i.e. the "Frah" and "Weathered" gatolinet). If you wish
to change any of ihc properbe* of the added chemical!. Tint delete them, then
reinsert them into the Compound lift Du* Bate. Follow the direction below:
T} Qaafc OK of Ac foOowil«:
®ia»rl clumul
QttltU ekciniul
[T) Iqw «e pnacwi u *K nabi
r» or \em)
CWmieal ___
M«l*t»iar Wciiht (j/mot.)
Viper Preunre *}2*C [•in-1
Boiliaa Pool «>1 aim 1C]
Expound NOODOB Not A«n|icdl
-------
- Hyperventilate Users Manual -
Appendix G: Reprint of:
"A Practical Approach to the Design, Operation, and
Monitoring of In Situ Soil Venting Systems"
-------
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, C.C. Stanley, M.W. Kemblowski, D.L. Byers, andJ.D. Colthan
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
trivia!. 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 al. 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-
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terize and delineate the zone of soil and 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 she 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/hydrogeological 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 Extraction Well
Vapor
Flow
Contaminated
Soil
Vapor
Flow
Free-Liquid
Hydrocarbon
Groundwater Table
Sotubk
Plume
Figtm 1. "Basic" in situ soil-venting system.
Process
Output
Syaetn Shut-On
FffHre 2. In stta soil-venting system design process.
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ble 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
0.0
T(°C)
b
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 (he., 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)
where:
Ces, = estimate of contaminant vapor concentration
[mg/L]
Xj = mole fraction of component i in liquid-phase
residual (Xj = 1 for single compound)
Pi" = pure component vapor pressure at tempera-
ture T [atm]
MW,J = molecular weight of component i [mg/mole]
R = gas constant = 0.0821 l-atm/tnole-0K
T - absolute temperature of residual [°K].
Table 1 presents data for some chemicals and mix-
TABLE 1
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
tetraethyllead
gasoline1
weathered gasoline2
Mw
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tures 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 residual concentration (but still depend
on composition), and Equation 1 is applicable (Johnson
et ai. 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 will decline with time due to changes in composi-
tion, residual levels, or increased diffusionat resistances.
These topics will be discussed in more detail.
Under Ideal Vapor Flow Conditions ~. ) - conctnmoon in medune-equviknl pom (wl/vol.) unio
*•"
Ffeu* 4. !• sft»
rat*)
i nte tad vtpor concentration.
complete the cleanup within eight months, then Raccepu-
We = 6.3 kg/d. Based on Figure 4, therefore, Cen would
have to average >1.5 mg/L (2400 ppmou) for Q=2800
l/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.
listica
lly
What Range of Vapor How Rates Can Re
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 /s], can be used for this purpose:
k [l-(PA,m/Pw)2]
(5)
where:
k «
u, =
Pw =
pA
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This equation is derived from the simplistic steady-
s :ate 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" Rt. Values ranging from 9m (30 ft)
to 30m (100 ft) are reported in the literature (Hutzler
et al. 1988) for a variety of soil conditions, but fortun-
ately Equation 5 is not sensitive to large changes in Rj.
for estimation purposes, therefore, a value of Rt=12m
(40 ft) can be used without a significant loss of accuracy.
Typical vacuum well pressures range from 0.95 - 0.90
atm (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/PAtm) for a 5.1cm radius (4-in diameter) extrac-
tion well, and a wide range of soil permeabilities and
applied vacuums. Here H denotes the thickness of the
screened interval, which is often chosen to be equal to
the thickness of the zone of soil contamination (this
minimizes removing and treating any excess "clean"
air). For other conditions the Q*/H values in Figure 5
can be multiplied by the following factors:
Rw a 5.1cm (2 in) R, = 7.6m (25 ft) - multiply Q*/H
by 1.09
Rw = 5.1cm (2 in) R, = 23m (75 ft) - multiply Q*/H
by 0.90
Rw * 7.6cm (3 in) R, - 12m (40 ft) - multiply Q*/H
by 1.08
Rw = 10cm (4 in) R, = 12m (40 ft) - multiply Q*/H
by 1.15
Rw = 10cm (4 in) R, = 7.6m (25 ft) - multiply Q*/H
by 1.27
As indicated by the preceding multipliers given,
changing the radius of influence from 12m (40 ft) to
23 m (75 ft) only decreases the predicted flow rate by
10 percent. The largest uncertainty in flow rate calcula-
i ions will be due to the air permeability value k, which
can vary by one to three orders of magnitude across a
site and can realistically only be estimated from boring
log data within an order of magnitude. It is prudent,
therefore, to choose a range of k values during this
phase of the decision process. For example, if boring
logs indicate fine sandy soils are present, then flow rates
should be calculated for k values in the range of
0.1ntaminant vapors. For this "best" case the estimated
removal rate is given by Equation 2:
noo
(m vm-min)
Vapor
Flowme
(scfm/ft)
.0001
- o.ot i
0.001!
.i i 10 too ton
Soil Permeabilty (dajcy)
vacuum uprated a equivalent water column heiihu
Figure 5. Predicted steady-state flow rates (per unit well
screen thickness) for a range of soil permeabilities and applied
vapor flow
/
SMfeVKW
b)
liquid e
c)
Figure 6. Scenarios for removal rate estimates.
R«, = Ccsl 0 (2)
Changes in- Cest are still being neglected with time
due to composition changes. Other less optimal condi-
tions are often encountered in practice and it is useful
to be able to quantify how much lower the removal rate
will be from the value predicted by Equation 2. We will
consider the three cases illustrated in Figures 6a, b, and c.
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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^Ml-'WQCes, (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:
Cesl
JM
(eDu/k)"2 (ln(RI/Rw)/(PAlm - PJ]"2
where:
T) = efficiency relative to maximum
removal rate
D = effective soil-vapor diffusion coeffici-
ent [cnvVs]
p. = viscosity of air = 1.8 x 10* g/cm-s
k = soil permeability to vapor flow [cmz]
H = thickness of screened interval [cm]
R{ = radius of influence of venting well
[cm]
Rw - venting well radius [cm]
PAIID = absolute ambient pressure = 1.016 x
10* g/cm-sj
Pw = absolute pressure at the venting well
(g/cm-s2]
R! < r < R2 = defines region in which contamina-
tion is present.
Note that the efficiency T\ is inversely proportional
to the screened interval thickness H because a larger
interval will, in this geometry, pull 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 €?:
D = D°
where eA and eA are related by:
(8)
(9)
Here pb and 6M are the soil bulk density [g/cma] 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=0.90 atm (0.91 x 10* g/cm-s1), and the contamination
extends from the region Rt = Rw = 5.1cm to R2 = 9m
(30 ft). The well is screened over a 3m (10 ft) interval.
Assuming that:
Pb = 1.6 g/cm5
6M = 0.10
D" » 0.087 cm'/s
eT = 0.30
RI = 12 m
then the venting efficiency relative to the maximum
removal rate (Equation 2), calculated from Equations 7
through 9 is:
•n = 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
clay 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 tow permeability will exist
with a thickness 5. An estimate of the removal rate R«,
from a contaminated zone extending from R] to R2 is:
= IE
(10)
where D is the effective porous media vapor diffusion
coefficient (as calculated previously from Equations 8
and 9) and Ces, is the estimated equilibrium vapor con-
centration (Equation 1). With time 8(t) will grow larger.
In the case of a single component system the dry zone
thickness can be calculated from the mass balance:
(H)
where C, 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:
(12)
As an example, consider the case where benzene (Q, =
3.19 x 10* 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), pt
= 1.6 g/cms, D° = 0.087 cmVs, and eT = eA = 0.30. Figure
7 presents the predicted removal rates and "dry" zone
thickness 8(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
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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
rat ;s 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
rerioved 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
Hcag (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,
bu: 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
foi 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
(kg/d)
100.
10
i
benzene (20 C)
R, »S.l cm
R2»900cm
200
"Dry" Zone
Thickness
6
(cm)
100
0 100 200 300 400 500
Time (d)
Figure 7. Estimated maximum removal rates for a venting
operation Untiled by diffusion.
a)
% removed
.0001
100 200
Qi/m(t=0) (I/g)
b)
QC/QC(t=0)
.01
.001
.0001
Weathered Gasoline
T-20°C
10% moisture content
dinted front 4.ph>K » C0=0) = 270 mgfl
Approximate Composition
100
80
% removed
"60
•40
20
300
0 100 200
Qt/m(l=0) (1/g)
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 rale 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.
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TABLE 2
Composition
Compound
Name
propane
isobutane
ii-butane
trans-2-butene
cis-2-butene
3-methyi-l-butene
isopentane
1-pentene
2-methyl-l-butene
2-methyl-t,3-buladiene
iwpentane
trans-2-pentene
2-methyl-2-butene
2-methyl- 1 ,2-butadiene
3,3-dimethyI-l -buiene
cyclopentane
3-methyl-l-pentene
2,3-dimethylbutane
2-methylpentane
3-methylpentane
n-hexane
methylcyclopentane
2.2-dimethylpentane
benzene
cyclohexane
2.3-dimethylpentane
3-methylhexane
3-ethylpentane
n-heptane
2,2,4- 1 rime thy 1 pe n t a ne
methylcyclohexane
2,2-dimethylhexane
toluene
2,3,4- trimethylpentane
3-me thy (heptane
2-methylheptane
n-octane
2,4,4-trimethylhexane
2,2-dimethylheptane
e thy (benzene
p-xylene
m-xytene
3,3,4-trimeihylhexane
o-xy!ene
2,2,4- trimethylheptane
n-noname
3,3,5-trimethylheptane
n-propylbenzene
2,3,4-trimelhylheptane
1,3,5-trimethylbenzene
1 ,2-4-(rimeihylbenzene
n-decane
methylpropylbenzene
di methy le thy (benzene
n-undecane
1 ,2,4,5-tetramethylbenzene
1 ,23,4-tetramethylbenzene
1 ,2,4-trimethyl-5-ethylbenzene
n-dodecane
napthalene
n-hexylbenzene
meihylnapthalene
Total
(Mass Fractions) off Fresh and Weathered Gasolines
Mw
(8>
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
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
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
0.0343
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
mode]. The necessary minimum average vapor flow rate
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
Off-Silt
Passive Air Injection Well
or
Perimeter Gnxmdwtier Moniiorirtf Well
b)
Wiier Table Upwellinj
Caused by Vicinal)
Figure 9. (i) Use of passive vapor wells to prevent migration
of off-rite 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
-------
Preuurc V«po» Rownwtcr
Pressure Swiping Probes
Fipre 10. Air-pernMtMltty lest 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:
(13)
For (r2 eji/4kPAUnt)<0.1 Equation 13 can be approxi-
mated by:
P' =
Here
P'
4jon(k/u)
-0.5772 - In
Alm
(14)
= "gauge" pressure measured at distance r
and time t
= stratum thickness
= radial distance from vapor extraction well
= soil permeability to air flow
= viscosity of air = 1.8 x 10^ g/cm-s
= air-filled soil void fraction
= time
= volumetric vapor flow rate from extraction
well
= ambient atmospheric pressure = 1.0 atm =
1.013 x 10» g/cm-s2.
Equation 14 predicts a plot of p'-vs- In(t) should be a
straight line with slope A and y-intercept B equal to:
m
r
k
ix
e
t
Q
A =
B =
4*m(k/u)
Q
4nm(k/iO
-0.5772 - In
Aim
(15)
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:
4Aiun
The second approach must be used whenever Q or m
is not known. In this case the values A and B are both
used:
+ 0.5772)
(17)
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 rp for one pore volume to be
removed is:
TP = Vp/Q = €A irR2 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
mj /min (20 ft3 /mm). Then Tp=475 m V0.57 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 = 4irT S(r,t)/W(u) (19)
where: W(u) is the well function (Bear 1979) of u = Sr2/
-------
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 weils 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 Res, 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 Nwens required to achieve the
acceptable removal rate is:
- Raeceptable/Resl
(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 soil
zone. If our spill mass is 1500kg (=500 gal), then a mini-
mum of 1.5 x 10" 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 m3 /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 residual soil contamina-
tion are removed from the entire zone of contamination
Nmin- This is simply equal to the ratio of the area of
contamination Acon,.™,,^,,,,, to the area of influence of
a single venting well irR]2:
Acontl
(21)
This requires an estimate of RI, which defines the zone
in which vapor flow is induced. In general, RI 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). P. [! +
-------
a)
welh
I)
b)
viporflcw .
line*
injection
well
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 welt with time). A passive well is simply
a well that is open to the atmosphere; in many cases
ground water monitoring welts 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 lie 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-
"opra" mil tuifice
b>
impermeable K»l
Fignie 12. Effect of surface seal on vapor flow path.
cement cip
S)
Figure 13. (a) Extraction well construction, and (b) air-tight
groMd water level meawuiag system.
terns. For shallow treatment zones (
-------
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 unhs: 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 ppmv. More con-
centrated vapors can cause catalyst bed temperature
excursions and meltdown.
• Carbon beds: Carbon can be used to 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 welts: 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:
• Soil-gas vapor concentrations and compositions:
These should be measured periodically at different
radial distances from the extraction well. Figure 14
-------
1/8" OD Teflon Tubinf
Ground Surface
Box ConMiimif Vipor Sunpliiii
Pom AThomooaupia
Jang
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 4>=Cex,r«,jon
weii/Cjoi, g». 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 confir-
mation borings unless the original spill mass is known
accurately. In most cases 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
zone; 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 CVCOa 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 t>r 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 wells 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.
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) and 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.
JO-
J.
1
i--
1
w-
Vapor
?
— *
»
=«
\
WWiM SMHliH
mo_ \ J *«"
•"r v. r
, (Kkllll
\ *
\
Fine to
CtmStM
Silly CUjr
*
Otyey Silt
Medium Swd
• 03 /
Ml
.«
' WT7
•151
J»7
Dill
1.1
' MaiifoM
a.X' °w?Si2r*
t
A
. D j
.u
, 214 .
•1
ant •
• 0)1
•0.1'
•M
. 1-J
1J
»f
HB-17
SuUcOmnd
wwrlttk
KB
7HB-5
HB25
IV.pt.
HB3
HB-21 ««»«yWdll
Rtcovnj Wdl]
Figure 15. Initial tout hydrocartwn 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 b 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:
Ceit = 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 R(K!eept.bie- Assum-
ing M$pm = 4000kg and T = 180 d, then:
R.ccept.We = 22 kg/d
Using Equation 2, Ceit = 240 mg/L, and Q = 28001/
min (100 cfm):
Re« = 970 kg/d
which is greater than R»cccpl.bie-
• 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 m3/m-min Rw = 5.1cm, RI = 12m
0.43 < Q < 43 ftVft-min Rw = 2.0 in, R, = 40 ft.
The thickness of this zone and probable screen thick-
ness of an extraction well is about 2m (6.6 ft). The total
flow rate per well through this zone is estimated to be
0.08l«.m)
0 HB-14D(t=9.8cn)
+ HB-IO (r*7.6m)
n1^
a
-^
D -f^o0
f .*v°
dP
H
f + +
a ° ^s*0 °
T O t x *
1 10
*o
£*°
A
k A A
100 1000
Time (min)
FIfwe 16. Air permeability test results: (a) vapor extraction
lest; (b) air injection test [In HjO] denote vacuums expressed
a* equivalent water column heights.
determine the permeability to vapor flow. The k values
ranged from 2 to 280 darcys, with the median being ~8
darcys.
System Design
• Number of vapor extraction wells:
Based on the 8 darcys permeability, and assuming
a 15cm diameter (6 in) venting well, a 2m screened
section, Pw = 0-90 atm (41 in H2O vacuum) and R|=12m,
then Equation 5 predicts:
Q = 0.7 mVmin = 25 cfm
Based on the preceding discussion, a minimum aver-
age flow rate of 1.5 mj/min is needed to reduce the
residual to 1000 ppm in six months. The number of wells
required is then 1.5/0.7 = 2, assuming that 100 percent
of the vapor flows through contaminated soils. It is not
likely that this will occur, and a more conservative esti-
mate of 50 percent vapor flowing through contaminated
soils would require that twice as many wells (four) be
installed.
A single vapor extraction well (HB-25) was installed
in this soil layer with the knowledge that more wells
were likely to be required. Its location and screened
interval are shown in Figure 15. Other wells were installed
in the day layer and upper sandy zone, but in this paper
only results from treatment of the lower contaminated
-------
isone 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 IS.
{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
idjacent to the aquifer. The vapor flow rate from HB-
25 and vapor concentrations were measured frequently,
ind the vapor composition was determined by GC-F1D
analysis. In addition, the water level in the ground water
monitoring wells was measured with the system pictured
n 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 aim (20 in H2O vacuum), and
:he flow rate was initially 12 scfm. It gradually decreased
:o 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
How. 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
i he total concentration of known and unknown com-
]x>unds 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
Ihere 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 =
:i 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
HB-25 100
Vacuum
(in HO) M
120
100
80
to
40
0.
4
1?
— •-- HMK
\' "''",.'
i * •
**, /''
V i'
^
'15
10
•5
Ftowraie
(SCFM)
20 40 60 10 100 120
Time (d)
E vMaynu ttpmwt u equivalent wuer eohnui height*
b)
0 20 40 60 80 100 120
Time (d)
Figure 17. Soil-venting retails: (*) vacuum/flow rate data,
(b) concentration/composition data.
a)
Removal «
Rale
(kg/d) so
400
200
too
Cumulative
Recovered
(gal)
20 40 60 *0 100 120
Time (d)
b)
ftH.O
2 0.3-
0.0
I 10
Time (min)
(ft HO) denote vtcuums expressed is equivalent water column heights
Figure 18. 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 upweiling *as monitored.
Figure 18b presents the results. Note that the water
table rise paralleled the vacuum increase, although the
water table did not 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 4> 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 residual 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,
1.0
0.8
C(t)/C(t=0)
0.6
CftVC(l=«) predicted
C(lVC(l=0) measured
weathered gasoline
m(t=0)-4000kg
0.4
0.2
0123456789 10
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 of NWWA/AP1 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/API
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. 1988. 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 (Westhollotv 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 environmental risk
-------
assessments.
Curtis C. Stanley received Ms degree in geology with
an engineering minor from North Carolina State Uni-
versity in 1979, He is currently a senior hydrogeologist
for Shell Oil 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
ami 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
Shtil Development Co. (Westhollow Research Center,
Houston, TX 77082) where he has worked since 1985.
He obtained his M.S. degree in civil engineering from
tht Technical University of Warsaw, Poland, in 1973
andhisPh.D. 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
Mtxico 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 t'he 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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