&EPA
United States
Environmental Protection
Agency
Office of Research and
Development
Washington, DC 20460
EPA/600/R-93/028
February 1993
Decision-Support
Software for
Soil Vapor Extraction
Technology Application:
Hyperventilate
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EPA/600/R-93/028
February T993
DECISION-SUPPORT SOFTWARE FOR SOIL VAPOR EXTRACTION
TECHNOLOGY APPLICATION: Hyperventilate
by
Curtis A. Kruger
Midwest Research Institute
Falls Church, VA 22041
and
John G. Morse
IT Corporation
Knoxville, TN 37923
Contract No. 68-C2-0108 »
Project Officer
Chi-Yuan Fan
Superfund Technology Demonstration Division
Risk Reduction Engineering Laboratory
Edison, New Jersey 08837
RISK REDUCTION ENGINEERING LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
Printed on Recycled Paper
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DISCLAIMER NOTICE
The information in this document has been funded by the U.S. Environmental
Protection Agency (EPA) under Contract No. 68-C2-0108 to International Technology
Corporation and its subcontractor Midwest Research Institute. It has been subjected to the
Agency's peer and administrative review, and has been approved for publication. Mention of
trade names or commercial products does not Constitute endorsement or recommendation for
use.
11
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FOREWORD
Today's rapidly developing and changing technologies and industrial products and
practices frequently carry with them the increased generation of materials that, if improperly
dealt with, may threaten both human health and the environment The U.S. Environmental
Protection Agency (EPA) is charged by Congress with protecting the Nation's land, air, and
water resources. Under a mandate of national environmental laws, the Agency strives to
formulate and implement actions leading to a compatible balance between human activities
and the ability of natural resources to support and nurture life. These laws direct the EPA to
perform research to define our environmental problems, measure the impacts, and search for
solutions.
The Risk Reduction Engineering Laboratory is responsible for planning, implementing
and managing research, development, and demonstration programs to provide an authoritative,
defensible engineering basis in support of the policies, programs, and regulations of the EPA
with respect to drinking water, toxic substances, solid and hazardous wastes, and other
environmental programs. This publication presents information on a corrective action
technology tool and provides a vital communication link between the researcher and the user
community.
An area of major concern to the Risk Reduction Engineering Laboratory is the
selection and use of appropriate and cost-effective corrective action technologies for cleanup
of petroleum hydrocarbon releases from leaking underground storage tanks. This document
presents an approach for evaluating the feasibility of a specific corrective action technology,
soil vapor extraction, through the use of decision-support software developed by EPA and the
Shell Oil Company.
E. Timothy Oppelt, Director
Risk Reduction Engineering Laboratory
m
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ABSTRACT
The U.S. Environmental Protection Agency (EPA) estimates that 15 to 20% of the
approximately 1.7 million underground storage tank (UST) systems containing petroleum
products are either leaking or will leak in the near future. These UST systems could pose a
serious threat to public health and the environment. Selection of appropriate corrective action
technologies that can be rapidly implemented, and that are efficient and cost-effective is
essential to minimize the impact of UST releases on the environment and public health. Soil
vapor extraction (SVE) is a proven, in situ corrective action technology that can remove
volatile organic compounds (VOC) and selected residual petroleum hydrocarbons from
unsaturated soils. To assist regulators, investigators, and UST owners in evaluating whether
SVE is an appropriate cleanup technology for use at UST sites, decision-support software
entitled Hyperventilate has been developed by EPA and Shell Oil Company under a 1990
Cooperative Research and Development Agreement under the Federal Technology Act.
Hyperventilate is an interactive, software guidance system for evaluating the
feasibility of using SVE at a specific site based on site and contaminant characteristics.
Hyperventilate is designed to (1) identify the level of site data required to evaluate SVE
systems, (2) evaluate soil permeability test results, (3) approximate the minimum number of
extraction wells likely to be needed, and (4) provide a rough approximation of the system's
desired and maximum removal rates.
This document provides guidance in evaluating the use of the IBM-compatible version
of Hyperventilate that requires a computer equipped minimum with 80386 processor, 4 MB
RAM, DOS 3.1, Microsoft Windows 3x, and Spinnaker PLUS 2,5. An overview of SVE
principles and procedures is presented along with the basic model principles and a sensitivity
analysis of Hyperventilate. A sample application of the software is also presented using data
from an actual UST site. The case study demonstrates how to estimate and determine input
parameters, goes through the steps involved in deriving estimates to evaluate if SVE is
appropriate, and discusses interpretation of the case study results.
This report was submitted in fulfillment of Contract No. 68-C2-0108 by International
Technology Corporation, under the sponsorship of the U.S. Environmental Protection Agency.
This report covers a period from 15 April 1992 to 15 December 1992.
IV
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CONTENTS
Section
Foreword .......................... , ......... . . ................... ijj
Abstract .... ..... ........... . . ........ . ................. .......... iv
Figures . . ...... .... ..... . . . ........... ....... ...... ... ............ vi
Tables ..... .............................. .......... . ........ ^ vji
List of Abbreviations and Symbols . . ........... . ....... . ....... . ......... ix
Acknowledgements ..... .......... .............. ... ...... ...... xi
1. introduction . .......... .......................... . ........... 1
Background ....................... , ..... ...... ........ .t t \
Soil Vapor Extraction Technology ......... . ......... ..... ..... 3
2. Hyperventilate .............. ............ . . . ................. 24
Basic Model Principles . . ............ ........... .......... . 24
Computer Software Structure .................... ........... . 28
3. Model Application Case Study ..................... . . ............ 46
Background , ........ ....... ...... .........>. ............ 46
Initial Estimates - Is Soil Venting Appropriate? . . ..... . ........ ... 47
Refined Estimates - How Appropriate is Soil Venting? ........ ...... 57
4. Model Analysis ............................... t . ............ 68
Parameter Response Test ............. .......... .... ...... 68
Sensitivity Analysis ............................ ........... 84
References ...... ............. .............. ........... ; ...... , gg
Appendices
A. Software Installation Procedures .................................. 91
B. User's Manual ............. .............. . . ........ ......... 96
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FIGURES
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Page
Unsaturated zone contaminant phase • • • 6
Typical soil vapor extraction system schematic 14
Zone of contamination at the Roseville, MN site 48
Cross section A-A': 49
Cross section A-B': 50
Cross section C-C': • 51
Shallow vapor extraction well schematic 53
Deep vapor extraction well schematic 54
Vapor extraction system layout 55
System design card 2 ,. • 63
System design card 3 64
Systemudesign card 4 > . ... , . ..... ..... .- 65
The relationship between permeability and flow rate 70
The relationship between well radius and flow rate 71
The relationship between radius of influence and flow rate 72
The relationship between interval thickness and flow rate 73
The relationship between well vacuum and flow rate 75
VI
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TABLES
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Chemical Properties of Hydrocarbon Constituents 8
Variations in Gasoline Composition and Aqueous-Phase
Concentrations of Fuel Components in Gasoline 10
Summary Matrix of Models 20
Hyperventilate Input Parameter Limitations 33
Practical Range and Relative Importance of Input Parameters 34
Boiling Point Distribution List of Compounds 43
Stratigraphy , 47
Air Permeability Test Data 60
Minimum Number of Wells Based on Critical Volume of
Air Scenarios •.'..... 62
"Is Venting Appropriate?" Response to Temperature Changes 74
"Is Venting Appropriate?" Response to Contaminant Composition
Changes 76
"Low Permeability Lenses" Response to Contaminant Molecular
Weight Changes .......... , 80
"Low Permeability Lenses" Response to Temperature
Changes , . . . , go
"Air Permeability Test" Response to Soil Layer Thickness
Changes ....... ; ! 81
vu
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TABLES
(Continued)
Vi ' '• * •
15 "System Design" Response to Contaminant Radius Changes 83
Vlll
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ABBREVIATIONS
LIST OF ABBREVIATIONS AND SYMBOLS
°C
op
ACFM
API
atm
BCF
BTEX
CFR
cm
cm2
cm
CRTC
dim.
DOS
e.g.
est.
EPA
GAC
GC
HSWA
ICE
i.e.
in.
JP-4
K
KB
kg
KO
L
lb
m
degree Celsius
degree Fahrenheit
actual cubic feet per minute
American Petroleum Institute
atmosphere
Block Centered Flow
benzene, toluene, ethyl benzene, and xylenes
Code of Federal Regulations
centimeters
centimeters squared
cubic centimeter
Chevron Research and Technology Company
dimensionless
disk operating system
example
estimate
Environmental Protection Agency
granular activated carbon
gas chromatography
Hazardous and Solid Waste Amendments
internal combustion engine
explanation
inches
jet petroleum grade 4
Kelvin
kilobytes
soil sorption coefficient
Henry's law constant
kilogram
octanol-water coefficient
liter
pound
meter
IX
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nr
MB
mg
min
mm
MPCA
NAPL
OUST
PC
ppmv
PVC
RAM
RCRA
RF
RIR
s
SCFM
SVE
T
TPH
USGS
UST
VOCs
vs.
LIST OF ABBREVIATIONS AND SYMBOLS
(Continued)
cubic meter
megabytes ....„•
milligrams • \
minutes
millimeters .
Minnesota Pollution Control Agency
nonaqueous phase liquid
Office of Underground Storage Tanks
personal computer
parts per million volume
polyvinyl chloride
random access memory
Resource Conservation and Recovery Act
radio frequency ,
remedial investigation report .
.seconds
standard cubic feet per minute
soil vapor extraction
temperature
total petroleum hydrocarbons
U.S. Geological Survey
underground storage tank
volatile organic compounds
versus
SYMBOLS
H20
Hg
71
water
mercury
"Pi" = 3.1415927
greater than
percent
approximately
equals
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ACKNOWLEDGEMENTS
This document was prepared for the U.S. Environmental Protection Agency (EPA)
Office of Research and Development Risk Reduction Engineering Laboratory (RREL) under
Contract No. 68-C2-0108 by IT Corporation.
IT acknowledges the guidance and assistance provided by Mr. Anthony Tafuri, RREL's
Project Officer, and Mr. Chi-Yuan Fan, RREL's Technical Project Manager for this Work
Assignment. Technical support was provided by Dr. Paul Johnson of Shell Development
Corporation, and the technical review was provided by Dr. James Stumbar and Mr. Thomas
Douglas of Foster Wheeler Corporation.
This document was produced under the direction of Mr. Robert Amick, IT's Program
Director. Mr. Roy Chaudet served as the Work Assignment Manager. Mr. Curtis Kruger
from Midwest Research Institute and Mr. John Morse from IT Corporation are the principal
authors. Ms. Linda McConnell and Mr. Jerry Day provided editorial support. Ms. Karen
Price and Ms. Joanna Engle prepared the manuscript.
XI
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SECTION 1
INTRODUCTION
BACKGROUND
Hundreds of thousands of underground storage tanks (USTs) containing petroleum
products and hazardous chemicals have been installed in the past 30 to 40 years. Many of
these tanks have either been abandoned or exceeded their useful life. In addition, many are
leaking and thereby pose a serious threat to the Nation's surface and groundwater supplies
and to public health. In response to this threat, the Hazardous and Solid Waste Amendments
(HSWA) of 1984 (PL98-616) were enacted to add Subtitle I, Regulation of Underground
Storage Tanks, to the Resource Conservation and Recovery Act (RCRA). These amendments
required the U.S. Environmental Protection Agency (EPA) to develop and implement a
regulatory program to deal with USTs containing petroleum products and hazardous substanc-
es. After the passage of HSWA, EPA established the Office of Underground Storage Tanks
(OUST) to promulgate final rules (40 Code of Federal Regulations [CFR] 280) in 1988 under
Subtitle I to prevent, detect, and remediate UST releases to the environment.
EPA estimates that as many as 15 to 20% of the approximately 1.8 million regulated
UST systems nationwide either are leaking or are expected to leak in the near future (EPA,
1991a). Approximately 90 to 95% of the regulated facilities contain motor fuels and petro-
leum products. The environmental threat from leaking tank- systems has a direct impact on
public health because approximately half of the Nation's drinking water supply comes from
groundwater. Small quantities of gasoline released from UST systems can contaminate
millions of gallons of potable groundwater and surface water with suspected carcinogens such
as benzene. In addition, the components of petroleum products released in the subsurface can
preferentially migrate through underground utility trenches to the basements of homes and
businesses and accumulate to explosive levels.
In the first several years following promulgation of the Federal UST regulations, EPA
focused on evaluating, developing, and implementing effective release detection techniques.
This effort has resulted in the rapid identification of a significant number of past and ongoing
releases. By December 1991, 137,000 confirmed releases had been identified; however, less
than 40,000 of these releases have been remediated (EPA, 199 Ib). Effective and efficient
corrective action technologies have not been developed, evaluated, or implemented quickly
enough to address the increasing number of releases identified and confirmed. EPA has been
1
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working with the regulatory community to implement new, modified, or innovative corrective
action technologies more rapidly. One of the methods that is proving to be very effective is
soil vapor extraction (SVE).
SVE is a proven in situ technology used to remove volatile organic compounds
(VOCs) and selected residual hydrocarbons from soils. SVE has gained popularity over the
last 5 years because it can be rapidly implemented, it has a potentially high removal rate of
VOCs from the subsurface, and it generally costs less than other treatment alternatives. To
ensure effective and. efficient cleanup, however, many site and contaminant characteristics
must be evaluated before SVE can be selected.
A practical approach has been developed for evaluating the selection, design,
operation, and monitoring of SVE systems (Johnson et. al., 1990a). Based on this approach,
Dr. Paul Johnson and Ms. Amy Stabenau of Shell Development Corporation developed
decision-support software entitled Hyperventilate in 1991. Hyperventilate was originally .-
developed for use on Apple Macintosh computers, but it is now available in an IBM-
compatible version for use on IBM and IBM-compatible personal computers (PC). This
decision-support software was designed to enable regulators, consultants, and owners of UST
systems to evaluate site characteristics and determine whether SVE technology is a viable
option for remediation of volatile petroleum hydrocarbons.
Since promulgation of the Federal regulations, the number of leaking UST systems
being discovered has rapidly outpaced the capabilities and resources of both industry and
regulatory agencies to implement and complete corrective actions at these sites. Because the
number of unaddressed sites is increasing, decision-support software such as Hyperventilate
can be a valuable tool for expediting the process of selecting and implementing effective
corrective actions.
The objective of Hyperventilate is to help the user engage in a systematic, iterative
evaluation of the feasibility of SVE as a remedial alternative at a given site. The software
utilizes data provided by the user to develop a rough approximation of the system's desired
and maximum removal rates. At no point does the software give a definitive "yes" or "no"
response to the question of feasibility. The software can provide two estimates of the
minimum number of vapor extraction wells needed to achieve remediation. The first estimate
is developed by simply comparing the anticipated extraction well radius of influence with the
radial area of contamination. The second estimate is based on a calculation of the volume of
air that needs to be extracted from the soil in order to remove residual contamination. The
user is ultimately responsible for deciding if the estimates generated by the software are
technically and economically practical for a particular site. Hyperventilate is primarily a
software tool for evaluating SVE as a remediation alternative; it is not intended to be a
detailed SVE modeling or design tool.
The purpose of this document is to provide technical assistance in evaluating the
practical use of the IBM-compatible version of Hyperventilate for examining design and
operational parameters in the screening of SVE as an option for site remediation. This
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document presents practical information on the capabilities and uses of Hyperventilate as a '
decision-support tool for evaluating SVE as a remedial option. Section 1 provides an
overview of the SVE technology, including a brief discussion of the behavior'of petroleum
contaminants in the subsurface, the SVE process, and SVE system modeling. Section 2
describes the basic model principles and structure of the software application of HyperVenti-
late. Section 3 describes how actual site data can be used to apply the software to a case
study. Section 4 provides an analysis of the sensitivity of the software and a test of the
response of different input parameters. Appendices to this document include procedures for
installing the IBM-compatible version of Hyperventilate and a copy of the User's Manual
developed for the Apple Macintosh version.
SOIL VAPOR EXTRACTION TECHNOLOGY
SVE is a proven, cost-effective technique for removing VOCs and motor fuels from
contaminated soil in the unsaturated or vadose zone. This technology is also referred to as
vacuum extraction, soil venting, aeration, in situ volatilization, and enhanced volatilization.
SVE is the term selected for use in this document. ,•••••• ,
The following advantages of SVE systems make this technology applicable to a broad
spectrum of sites: :
• This in situ technology can be implemented with only minor site disturbance.
Normal business operations often can be continued throughout the cleanup .;,' • *
period.
••--• Large volumes of soil can be treated at reasonable costs, compared with other
available technologies.
• The systems are relatively easy to install, and their use of standard, readily avail-
able equipment enables rapid, cost-effective mobilization and implementation of
remedial activities.
• VOC concentration in the vadose zone is effectively reduced. This, in turn,
^ reduces the potential for further transport of contaminants as a result of vapor
r migration and infiltrating precipitation.
• SVE can be an essential element of a complete remedial program, which may
include groundwater extraction and treatment.
• Discharge vapor treatment options allow the design flexibility necessary to
comply with site-specific air emission regulations.
To determine if SVE is applicable for a particular site as well as the key design and
operational limitations, an understanding is needed of the behavior of petroleum hydrocarbons
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in the vadose zone, the SVE process, and modeling tools that are used to evaluate the
effectiveness of an SVE system.
This section provides an overview of the factors that influence contaminant fate and
vapor-phase transport in the vadose zone. The basic principles that govern vapor behavior
and transport in soils are identified to provide a sound basis for decision making with regard
to site investigations; pilot testing; and system design, operation, and monitoring. Specifically
addressed are the behavior of hydrocarbon contaminants and the characteristics of soil in the
vadose zone, the SVE process, and the SVE system modeling.
Principles of Contaminant Behavior in the Vadose Zone
A fundamental understanding of how hydrocarbon contaminants behave in the vadose
zone is necessary to properly interpret the results from Hyperventilate in determining if SVE
is an appropriate and effective corrective action technology. The behavior of hydrocarbon
contaminants in the vadose zone is determined by the quantity of contaminant released, the
time since the release occurred, the physical and chemical properties of the contaminant, and
the characteristics of the soils through which these contaminants migrate. SVE can be used
to remove volatile constituents present in soil gas as well as free and residual liquid product
in the vadose or unsaturated zone. SVE also can treat contaminants dissolved in immobile
soil water in the unsaturated zone. Theoretical opinions and field studies indicate that SVE
cannot effectively remove constituents trapped in the interior of the soil matrix, however.
Because the quantity of such constituents may exceed surface contamination by one to two
orders of magnitude (Travis and Macinnis, 1992), SVE cannot be used to return long-
contaminated locations to original pristine conditions. This section discusses the physical
properties of typical hydrocarbon contaminants and the characteristics of soils in the vadose
zone that influence the effectiveness of SVE.
Soil Characteristics--
In this document, soil in the vadose or unsaturated zone is defined as unconsolidated
mineral and organic material that extends from the ground surface to the top of the capillary
fringe and contains soil vapor and a lesser amount of soil water in the pore space between or
on soil solids (API, 1992). The textural classes of soil range from clays to silts to sands.
The actual soil types present at any particular site are frequently limited. Fill material is
often present in vadose zone soils that are contaminated by petroleum hydrocarbons (API,
1992). Fill materials commonly consist of soil, sand, gravel, or crushed rock. Also present
in vadose zone soils are biota and manmade structures. An understanding of the interactions
between these naturally occurring and manmade features and the movement of petroleum
hydrocarbons is necessary for an effective evaluation of SVE as a remedial option.
Critical to the application of SVE technology is the ability to achieve adequate vapor
flow through the contaminated soil Vapor flow rates in the vadose zone depend in part upon
soil characteristics such as air permeability, water content, and the heterogeneity of these
properties among different soil types. These properties are briefly discussed below.
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Air Permeability—Air permeability is the measure of a porous medium's ability to
transmit fluids based on laboratory or field airflow tests. The density and viscosity of vapors
combined with the permeability of the porous medium significantly influence the ability of
the vapor to flow through the soil. Permeability of soil is perhaps the single most important
soil parameter to be considered in the successful application of SVE. It is a key parameter
not only in deciding if SVE is a feasible remedial option, but also for establishing SVE
system design criteria (Johnson et al., 1990b). The permeability of the soil or vadose zone is
determined from literature values and laboratory or field testing. Permeability is expressed in
terms of "darcys" or cm2 and has the units of length squared. The literature and laboratory
tests usually provide values of intrinsic permeability, which is generally the permeability of
the dry soil matrix. Field tests usually yield "pneumatic" permeability, which is the perme-
ability of the soil matrix with soil moisture taking up sonic of the soil pore space. "Pneumat-
ic" permeability is less than intrinsic but approaches the intrinsic permeability as the soil dries
out. This can be important in evaluating and designing SVE systems because the site
pneumatic permeability can be expected to increase somewhat as the soil dries out during
SVE operation. This, in turn, can increase the flow rate and removal rate.
Soil Heterogeneity—The structure, stratification, type, and size of soil particles that
influence contaminant migration are often heterogeneous in vadose zone soils. Soil heteroge-
neity accounts for differences in permeability in or between different soil layers or horizons.
Coarsely textured, highly permeable soils are best suited for SVE. Heterogeneous soils that
contain low-permeability layers or lenses require a careful evaluation in the selection and
design of SVE systems. SVE has been successfully used to remediate volatile hydrocarbons
from clays and silts in interbedded permeable layers and in secondary structures such as joint
systems or macropores, which include fractures or expressions of bedrock faults.
Water Content-Soil water content (the percentage of soil pore spaces filled with
water) affects the air-filled porosity of a soil and the permeability as discussed previously. A
higher water content in the soil generally limits the effectiveness of SVE by reducing air-
filled porosity, which decreases the size of the connected pores through which air can flow.
SVE is well suited for soils with lower water content because a greater percentage of the pore
space is air filled and available for vapor transport and therefore can result in a greater
induced airflow for a particular vacuum. If the water content is very low, however, sorption
of contaminants to soil increases and competes with the volatilization of constituents into the
soil gas (Reible, 1989). A range of 94 to 98.5% relative humidity in soil gas appears to be
optimal for SVE (Davies, 1989).
Contaminant Characteristics--
Petroleum hydrocarbons are complex mixtures of many different compounds. The
composition of specific petroleum products (e.g., gasoline, diesel fuel) differs widely and
therefore behaves differently in the subsurface. Petroleum hydrocarbons are released in the
subsurface partition in four phases: (1) nonaqueous phase liquid (NAPL), (2) dissolved phase
in water, (3) sorbed phase to soil particles and colloids, and (4) vapor phase. Figure 1
graphically depicts each of these hydrocarbon phases in the subsurface environment.
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SAND
PARTICLES
SILT
CLAY
ORGANIC
MATTER
PETROLEUM
PRODUCT
VAPORS
IN PORE
SPACE
SORBED TO
SOIL
PARTICLE
©
PETROLEUM
PRODUCT
DISSOLVED
IN SOIL
MOISTURE
CLEAN
SOIL
SOIL CONTAMINATED BY
PETROLEUM HYDROCARBONS
RELEASE
Figure 1. Unsaturated zone contaminant phase.
Source: EPA. 1991c
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Petroleum hydrocarbons released in the subsurface are partitioned among the four
phases depending on the chemical and physical characteristics of the product, the degree of
product weathering that has occurred, and the characteristics of the vadose zone soil. The
movement and fate of petroleum products in unsaturated soils are influenced by the following
primary physical and chemical properties: vapor pressure, Henry's law constant, solubility,
soil sorption coefficient, and chemical composition. Each of these properties is discussed as
follows. ,
Vapor Pressure—The degree to which a constituent transforms from the liquid to the
vapor phase is controlled by the vapor pressure according to Raoult's law. Vapor pressure is
directly related to the vapor of the chemical constituent in equilibrium with its pure liquid
product. For "fresh" or unweathered gasoline releases, the high vapor pressure, lower
molecular weight constituents (e.g., butane or pentane) typically account for 75 to 85% of the
hydrocarbons in the vapor phase in equilibrium with the gasoline liquid. These constituents
can be readily removed by SVE (see Table 1). Temperature has a strong influence on the
vapor pressure of a constituent, with the vapor pressure increasing exponentially as tempera-
ture increases (three to four times for each 10 °C). Vapor pressure must always be reported
at a specified temperature at which the pressure was measured. Table 1 lists vapor pressures
at a temperature of 20 °C.
There is also an important relationship between a compound's boiling point and vapor
pressure. At a compound's boiling point, its vapor pressure equals the vapor pressure of the
atmosphere. At sea level the pressure exerted by the atmosphere is 760 millimeters mercury
(mm Hg). A decrease in atmospheric pressure results in a reduction in the boiling point. At
a pressure of 451 mm Hg, for example, water boils at a temperature of 86 °C, significantly
less than the boiling point at sea level (100 °C). Inducing a vacuum in the soil reduces the
air pressure in the soil pore space. This causes the boiling point to decrease and cause more
of the liquid compound to transfer into the vapor phase. The depression of the boiling point
due to the induced vacuum is not always a major factor in the volatilization of compounds;
however, understanding this phenomenon provides an appreciation of the factors that might
influence SVE operation.
Henry's Law—Henry's law constant (Kh) governs the volatilization of a contaminant
in aqueous solution, rather than a pure product. Henry's law is an appropriate partitioning
constant for evaluating the partitioning of NAPL into the vapor phase, where the contaminant
is likely to exist in solution with soil pore water (Stephanatos, 1988). Table 1 lists the
Henry's law constant (Kh) for several hydrocarbon constituents. Constituents with Henry's
law constants (K^) greater than 0.01 (dimensionless) will have significant volatility and are
amenable to removal by SVE (Danko, 1989; Hutzler et al., 1988). Gasoline is particularly
well suited to SVE because of its high composite volatility (for fresh gasoline, Kh = 32).
Other petroleum products, such as fuel oil No. 6, are less amenable than gasoline to removal
by SVE because of their lower volatility. Researchers have reported, however, successful
removal of petroleum products other than gasoline with SVE. For example, DePaoli et al.
(1989) reports the successful removal of jet petroleum grade 4 (JP-4) from a site in Utah.
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Henry's law constant is highly temperature dependent and increases with an increase in
temperature (1.6 times increase for each 10 °C).
Water Solubility—Solubility controls the degree to which a constituent dissolves into
groundwater and soil pore water in the vadose zone. Constituents present in petroleum
products have widely varying solubilities. As shown in Table 1, pure constituents such as
phenols and simple aromatic hydrocarbons (benzene and toluene) are highly soluble compared
with the alkane constituents. The solubilities of constituents in a hydrocarbon blend or
mixture, however, are different than those for the pure constituents. Differences or large
variations in the composition of the hydrocarbon blend can result in a large variation of
dissolved constituent concentrations in water. For example, the range of aromatic hydrocar-
bon concentration dissolved in water can vary over one order of magnitude depending on the
composition of the gasoline (Cline et al., 1991). The range in concentrations of aromatic
constituents in water, shown in Table 2, reflects the range of equilibrium concentrations that
may be found in water saturated with gasoline. Soluble constituents in hydrocarbon blends
that are in unsaturated soils are likely to dissolve in widely varying concentrations when
precipitation infiltrates through the soil and becomes part of the soil pore water or migrates
into the groundwater.
Soil Sorption Coefficient-Sorption of contaminant liquids to soil particles and organic
matter controls the distribution of released products in the soil and strongly affects product
movement through the vadose zone. A significant portion of the released product often may
be sorbed onto the soil. The sorption of a liquid product to soil and organic matter can be
described by the contaminant's soil sorption coefficient, Kd. Because values for Kd are not
always readily available, the more common octanol-water coefficient, K^, is often used as a
surrogate for the soil sorption coefficient. Table 1 lists the octanol-water coefficients for
common hydrocarbon constituents. This table shows the strong relationship between the
number of carbon atoms and the octanol-water coefficient; the larger molecules have a much
greater tendency to sorb (i.e., KQC is a larger value). This explains in part why compounds
such as No. 6 fuel oil, which are high in these "heavy fractions," are very immobile in the
subsurface (viscosity is also an important factor).
Contaminant Composition-Petroleum hydrocarbons are the most common products
stored in USTs (EPA, 1988) and constitute the majority of confirmed releases. Petroleum
fuels are composed of a complex mixture of constituents. Each type of fuel has a different
composition and will behave differently in the vadose zone. Contaminants that have a greater
amount of lighter, more volatile fractions (e.g., gasoline) are more applicable to rapid SVE
removal than those with heavier, less volatile fractions (e.g., diesel or heating oils). Hydro-
carbons released into the vadose zone will change composition with time because the more
volatile constituents will partition into the vapor phase and the more soluble constituents will
preferentially dissolve, thereby leaving the less volatile and less soluble constituents in the
soil. The concept of weathering applies to the effectiveness of SVE for removing contami-
nants and the effect on the residual contaminant. Volatile constituents are first removed at
the startup of the SVE system; however, after the system has been operating, the extracted
vapor will be depleted in the lighter-end fractions and enriched with heavier-end constituents.
-------
TABLE 2. VARIATIONS IN GASOLINE COMPOSITION AND
AQUEOUS-PHASE CONCENTRATIONS OF FUEL COMPONENTS IN GASOLINE8
Constituent
Benzene
Toluene
Ethyl benzene
m-.p-Xylene
o-Xylene
n-Propyl benzene
3-,4-Ethyl toluene
1,2,3-Trirnethyl benzene
Gasoline Composition
Weight %
Avg.b
1.73
9.51
1.61
5.95
2.33
0.57
2.20
0.8
(Mln.-Max.)c
(0.7 - 3.8)
(4.5-21.0)
(0.7 - 2.8)
(3.7 - 14.5)
(1.1-3.7)
(0.13-0.85)
(1.5-3.2)
(0.6-1.1)
SDd
0.68
3.59
0.48
2.07
0.72
0.14
0.40
0.12
Aqueous-Phase
Concentration, mg/L
Avg.b
42.6
69.4
3.2
11.4
5.6
0.4
1.7
0.7
(Min.-Max.)c
(12.3 - 130)
(23 - 185)
(1.3-5.7)
(2.6 - 22.9)
(2.6 - 9.7)
(0.1-3)
(0.8 - 3.8)
(0.2 - 2)
SDd
18.9
25.4
0.8
3.8
1.8 '
0.1
0.3
0.2
aAfter Cline et al., 1991
bAvg.= average
°Min. =s minimum; Max. = maximum
dSD - standard deviation
10
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As SYE progresses and volatile fractions are removed, isolated liquid globules may form in
soil pores and prove difficult to remove by SVE alone. Depending on a number of operation-
al factors such as flow rate and total treatment time, less volatile constituents may remain in
the soil as residuals. Conventional SVE techniques may not remove these residual constitu-
ents to an acceptable cleanup level.
Vaoor Transport
The flow of vapor through soils can be described by application of Darcy's law. The
applied gradients in the soil will dominate the natural gradients under vacuum conditions.
Thus, this law can be simplified as follows:
^Pa Equation 1
where qa = airflow per unit area (cm/s)
k = permeability of soil (cm2)
H = air viscosity (g/cm-s)
v Pa = pressure gradient from applied vacuum ([g/cm-s2]/cm>
The permeability of the soils determines the radius of influence and air discharge rate
for a given wellhead vacuum. The soil permeability depends on various soil characteristics
such as porosity, structure, grain size distribution, water content, and preferred flow paths.
Therefore, SVE applicability is primarily a function of the permeability and the viscosity and
density of the air flowing through the soil.
Under ambient conditions, vapor transport can occur by diffusion in response to
concentration gradients, density differences in pore gases, meteorological changes in tempera-
ture, barometric pressure, and wind speed; infiltration of rainfall; and a fluctuating water
table. When a vacuum is applied to the vadose zone, these transport mechanisms are
dominated by pressure gradients induced by the vacuum well system. For soils with
sufficient permeability, advective flow in response to the applied vacuum is far greater than
diffusive flow. For soil layers or lenses with low permeability, the vapor flow is limited by
diffusion transport.
Vacuum applied to a well will cause a negative pressure in the zone in the immediate
proximity of that well. This zone extends radially from the well and is known as the radius
of influence. Within the radius of influence, the vacuum and pressure gradients are strongest
at the well and decrease with increasing distance from the well. Wells placed in different soil
layers containing distinct permeabilities require applicable vacuum rates, flow rates, and time
frames to maintain a similar radius of influence. The interrelationship of these design
parameters will be discussed further in Section 4.
11
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Soil Vapor Extraction Process
SVE system equipment consists of commonly used and widely available devices such
as polyvinyl chloride (PVC) piping, valves, and pumps. SVE therefore has an advantage over
other techniques that require more complex designs or single-purpose equipment. A thorough
knowledge of site conditions and SVE processes is still required, however, to achieve
maximum system efficiency and contaminant removal.
Site Evaluation--
A detailed site characterization should be performed to obtain data needed for SVE
system design. Data obtained from soil borings, soil vapor surveys, and monitoring wells
during the site evaluation include soil type and structure, moisture content, air permeability,
depth to groundwater, and the source, volume, and type of contaminant. As discussed earlier,
permeability of soil is perhaps the single most important soil parameter with respect to the
success of SVE. Permeability incorporates the effects of several soil and vapor characteris-
tics. Among the important soil characteristics to be considered are soil type and structure,
air-filled porosity, particle size distribution, water content, and the presence or absence of
macropores or preferred flow paths. Important contaminant characteristics include contami-
nant composition, vapor viscosity, and vapor density.
Pilot testing performed along with the evaluation enables specific soil and contami-
nant properties to be determined for use in the full-scale system design. Although SVE is
often implemented without the aid of pilot studies, data obtained through field piloting are
invaluable in defining contaminant levels and in developing full system design. In a pilot
test, a vacuum (or positive pressure) is applied to a vapor extraction well that is screened in
the vadose zone. A pressure distribution is created in the subsurface as a result of the
vacuum. Soil pressure measured in probes, or monitoring wells located at various horizontal
and vertical distances from the extraction well, is analyzed to measure pressure distribution.
Data on soil pressure and extraction well pressure are then used to calculate the soil perme-
ability, radius of influence, and vapor flow rate at different wellhead vacuums. In addition,
effluent air samples provide data on expected initial discharge concentrations.
SVE applicability and design can be evaluated from pilot test data using a soil
permeability test developed by Johnson et al. (1990a,b). In this test, which is similar to the
oil field drawdown gas permeability test, the drawdown (or vacuum pressure) is measured at a
monitoring point at a known distance from the vapor extraction well while vapors are
regularly extracted. Field data are used to graphically estimate soil permeability. Calcula-
tions are made of the slope of the regression line that relates gauge pressure (measured at a
sample probe well) to the natural logarithm of the time from which vapor extraction began.
The slope of the line is then used to calculate permeability using the known airflow rate and
viscosity.
The method developed by Johnson et al. (1990a,b) to determine soil permeability
assumes that the time from initiation of SVE increases along with the vacuum pressure in the
subsurface (i.e., the absolute pressure becomes more negative). Permeability should be
12
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measured over a long enough period to extract at least one pore volume of air, yet at the
same time, the time interval should be short enough so as not to be limited by variations in
atmospheric pressure. Effective porosity changes can occur after rainfall and when soil-air
moisture condenses and evaporates during diurnal temperature changes. A constant vapor
extraction rate is often difficult to maintain during SVE operation. Therefore, variations in
the vapor extraction rate should be recorded and used when data are evaluated. The sensitivi-
ty of the permeability measurement will be reduced as the variations in the vapor extraction
rate increase. Permeability should be measured at a number of depths and locations around
the vapor extraction well to provide a reasonable estimate of its variability.
System Design
The objective of the design process is to develop an SVE system that removes the
contaminant efficiently, in a timely manner, and cost-effectively. This design requires a
knowledge of system effectiveness including contaminant composition and characteristics
vapor flow path and flow rate, and contaminant location with respect to the vapor flow paths
(Johnson et al., 1990a,b). In situ SVE systems are designed to increase airflow through the
contamination zone. Vertical wells or trenches also are used as extraction points. Wells are
used for deep contamination, and trenches are more useful when the water table is close to
the surface. .
Basic equipment used in SVE systems (see Figure 2) includes pumps or blowers to
produce the applied vacuum; piping, valves, and instrumentation to transfer air from the wells
through the system and to calculate contaminant concentration and total airflow vapor
pretreatment to remove soil particles and water from the vapors treated; and an emission
control device to concentrate or destroy vapor-phase contaminants.
The radius of influence defines the area farthest from the vapor extraction well at
which air pressure effects can be measured. The radius of influence is usually estimated as
?"V d£ta,nce fr°m me vaP°r extraction well where the air pressure reduction or vacuum is 1 0
inch H20. The radius is determined by a site-specific pilot test or is estimated based on
permeability. This radius depends mainly on the permeability of the soil, but it is partly
dependent on the applied vacuum. The radius of influence can also be controlled by the
depth to water, the location of the extraction wells relative to the surface, low-permeability
lenses, or an impermeable surface seal. Air inlet or injection wells also affect the radius of
influence. Inlet wells enable air to enter the subsurface at specific points, and injection wells
iorce air into the soil.
• u Wdl ,systems mav be used at sites in which lower permeability soils are
interbedded with higher permeability soils. The higher permeability soils help increase the
radius of influence and move vapors from the lower permeability soils. Wells in soil layers
with lower air permeability (such as 2- to 3-feet thick clays and silts) should be screened
across the entire stratigraphic sequence of the targeted contaminated soil zone. Hydrocarbon
vapors will tend to diffuse out of the silt-clay layers and into the interfered sands or
gravels The vapors will then migrate to the extraction well or trench. Remediation of low-
permeability soil layers or lenses requires more time because vapor transport is limited by the
13
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u
o
n.
u
'S.
14
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diffusion of hydrocarbon vapors through low-permeability soils. For thicker clay-silt soil
lenses, separate layers with individual wells may be targeted to permit a higher wellhead
vacuum and closer well spacings in the lower permeability layers.
The type of blower or vacuum pump selected for use on an SVE system depends on
site and contaminant characteristics. The appropriate blower or vacuum pump can be selected
after the desired wellhead vacuum and resulting total system flow rate are estimated. In
general order of increased vacuum and flow rate, the equipment used includes regenerative
blowers, rotary positive blowers, turbo exhausters, multistage centrifuge pumps, and liquid
ring vacuum pumps. An air-water separator (condensate-collection tank) often is used on the
blower to collect most of the soil moisture condensation. Some condensation also may
collect in the extraction piping. Because this air is continually in contact with hydrocarbon
vapors, it may contain significant concentrations of dissolved hydrocarbons. Special handling
and disposal procedures may also be required. Appropriate equipment is selected based on
performance characteristics, mechanical reliability, and cost.
SVE can be operated and controlled automatically via microprocessors, or it can be
manually operated. Volume flow rate and vapor concentration are monitored to assess
cleanup progress. These data can then be converted to a mass flow rate. Vapor extraction is
operated in a continuous or "pulsed" (i.e., intermittent) mode. Pulsed venting is generally
more energy efficient.
Vapor treatment can easily double the cost of implementing and operating an SVE
system. Hydrocarbons from extracted vapor streams can be removed or destroyed by granular
activated carbon (GAC) adsorption, incineration, catalytic oxidation, and internal combustion
engines (ICEs). GAC is commonly used to treat vapors because of its ease of implementation
and operation, its ability to regenerate spent carbon, and its applicability to a wide range of
contaminants, concentrations, and flow rates. Because of the increased costs of carbon
regeneration or replacement, GAC generally may not be the most cost-effective option when
hydrocarbon concentrations/mass removal rates are high. Incineration, which uses very high
temperatures (760 °C/1400 °F or higher) to destroy vapor-phase contaminants, is well suited
for streams with high concentrations because it can become self-sustaining at vapor concentra-
tions greater than approximately 10,000 parts per million volume (ppmv); below this level,
however, supplemental fuel must be used. Catalytic oxidation employs a precious metal
formulation as a catalyst to allow the reaction to occur at temperatures of 427 °C (800 °F),
thereby resulting in reduced fuel costs. The incoming vapor stream concentration is limited
to approximately 3,000 ppmv because the heat of combustion will destroy the catalyst at
higher concentrations. Results of ICE system tests show that the units reduce hydrocarbon
concentrations (>99%); however,- a supplemental fuel source is usually required.
Biofilters is another option that is gaining acceptance for treating extracted contami-
nant vapor. Contaminant vapors from extraction wells are introduced into a sealed soil
mound that serves as the medium for microbial degradation. Vapor emissions from these
biofilters do not require further treatment.
15
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SVE systems may not require vapor treatment if emission rates are below levels
defined by the state or local regulatory agency. This exemption generally occurs when
airflow rates or contaminant concentrations in soil are low.
System Performance Monitoring--
Monitoring is performed to determine the amount and movement of pollutants in the
subsurface environment before, during, and after remediation (Fan and Tafuri, 1992). An
effective monitoring program includes the design of a reliable well network to determine and
assess site conditions. The following should be considered in setting up an effective
monitoring network:
• At least one well should be placed upgradient or outside the contamination
zone so that accurate background levels can be monitored.
• Sufficient downgradient wells should be available to adequately monitor the
horizontal and vertical extent of contamination, especially in complex stratig-
raphy or fluctuating groundwater table areas.
• Wells should be screened in the contamination zone. Special attention should
be given to the design of the length of well screens. Longer screens are more
likely to intercept the contaminant plume, but may result in diluted soil gas or
groundwater samples. Shorter screens provide better concentration estimates,
but require more accurate placement to ensure the plume is intercepted.
• Well screen length in the capillary zone must be longer than the total depth of
groundwater fluctuations in order to adequately monitor floating NAPL.
• All pathways for potential contaminant migration should be monitored in
multiple stratigraphies and aquifers.
The overall objectives of a monitoring program are to: (1) assess site conditions to
determine a remediation approach, including the feasibility and requirement of a "no-action"
decision; (2) evaluate the progress of in situ treatment; and (3) determine site conditions
following treatment.
A field monitoring program should be conducted to select and design the final
corrective action approach. Field sampling will be included in the monitoring program to
verify soil and site characteristics and to confirm previous assumptions regarding the
subsurface. The monitoring well network must be properly designed and operated to
determine contaminant movement and to examine passive biodegradation potential. (Natural-
ly occurring biodegradation may be a feasible option for attaining site remediation. To assess
this "no-action" alternative and to evaluate decision criteria, the monitoring network should be
designed in conjunction with site-specific vapor and groundwater transport modeling.)
16
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After a technology has been selected, designed, and installed, the treatment system
performance must be continually evaluated to ensure its effective operation. Remediation of
petroleum product releases is often a long process. A treatment technology is usually
designed to remove one or more specific constituents to a specified level that conforms to
regulatory standards. Performance is then evaluated by measuring the concentrations of each
contaminant of concern and comparing those levels to cleanup goals.
SVE performance monitoring of airflow rates and vapor-phase concentrations and
composition in extracted vapors directly measures the rate of volatile hydrocarbon removal by
the system. Monitoring data typically show that removal rates decrease as the cleanup
progresses and the most volatile compounds are removed. Airflow rates and hydrocarbon
vapor concentration and composition are monitored at periodic intervals determined by site
conditions and SVE system design. Monitoring results can be used to optimize SVE
operation and minimize the time and cost of cleanup. Once a sufficiently low rate of
hydrocarbon mass removal has been reached, the practical performance limits of the SVE
system may have been achieved.
Two basic types of SVE performance categories have been defined by Chevron
Research and Technology Company (CRTC) based on soil and site conditions controlling
hydrocarbon mass removal rates (CRTC, 1991). These categories are advection and diffu-
sion-limited sites. The rate of hydrocarbon removal at sites where soil subsurface vapor
transport is predominantly by advection is primarily a function of hydrocarbon volatilization
and airflow rates. Consequently, hydrocarbon removal rates decline toward a near zero
asymptote. Once near-zero asymptotic removal rates have been achieved for advection-
dominated sites, soil sampling can begin prior to site closure.
Diffusion-limited sites typically contain heterogeneous soils consisting of layers of
different air permeabilities in which vapor flows along preferential pathways in soils with
higher air permeability. Soils in the airflow pathways are remediated early during SVE
operation, whereas hydrocarbon mass transfer from lower permeability soils is controlled by
the rate of diffusion of hydrocarbon vapors into the airflow pathways. For these sites,
hydrocarbon mass removal rates decrease to a nonzero, diffusion-limited asymptotic value.
Diffusion-limited sites may require significantly longer SVE operation to adequately reduce
hydrocarbon concentrations in lower permeability soils.
Site remediation is complete once the cleanup goals and cleanup criteria have been
met and maintained or when the limits of the corrective action technology have been reached
and the remaining contaminants pose no threat to human health or safety. Remediation
should not be suspended only because the cleanup criteria have been met. Site monitoring
should continue after cleanup because contamination levels can.increase even after treatment
stops. The following are some of the causes of increased site contamination levels:
17
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• Adsorbed contaminants or contaminants in low-permeability zones can persist in
the subsurface but may not be detected at monitoring wells during system
operation. These contaminants will tend to disperse after shutdown, increasing
contamination levels in soil gas or groundwater.
• Soil gas or groundwater flow patterns created by extraction wells can dilute
samples. After pumping stops, normal flow patterns return and concentration
levels may increase.
The decision to discontinue monitoring should therefore be made jointly with
regulatory officials and experienced professionals to ensure that remediation is actually
complete.
Trends in SVE Application
SVE has found widespread application for remediation of soils impacted through the
release of gasoline and other petroleum products from USTs. The performance of SVE
applications has recently led to improved treatment approaches through use in combination
with in situ air sparging (the introduction of air into the subsurface to facilitate volatilization
of organic compounds) and in situ bioremediation (referred to as bioventing). SVE has also
been used in stockpiled soil mounds to augment bioremediation. SVE systems will find wider
application to complex subsurface conditions once a better understanding is gained of vapor
flow physics and contaminant fate. Models for predicting subsurface vapor flows will
continue to become more sophisticated and provide the required tools to enable an under-
standing of soil/vapor/contaminant systems. Advances in analytical and field investigation
approaches will enable a more accurate assessment of contaminant transport. In addition, a
cleanup evaluation will be attained through the use of innovative statistical techniques.
Application of SVE to more restrictive subsurface conditions will be expanded
through use of horizontal well systems and high-vacuum techniques. Vacuum-enhanced
pumping systems that remove air and groundwater simultaneously are proving very effective
for some sites. Subsurface pneumatic fracturing and bioaugmentation will also be used with
SVE at future sites. More types of contaminants will be amenable to removal by SVE
through steam injection, subsurface radio frequency, or other radiation sources that increase
volatilization and use gases other than ambient air. Advances in discharge air treatment
technologies will allow SVE to be used in areas where regulatory discharge limitations
previously restricted these technologies.
The overall trend in SVE is toward increased sophistication in the assessment of
subsurface conditions, simplification of system design, coupling of treatment technologies,
and application to increasingly complex sites. Decision-support tools are being developed to
assist in selecting and evaluating the design of SVE systems in integrated treatment systems.
18
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Soil Vapor Extraction System Modeling
Models are physically or mathematically constructed to simulate or approximate the
behavior of an actual physical process. Models are used as an aid for understanding
processes or portions of processes with a high degree of complexity or that cannot be readily
understood by direct observation. Models are particularly valuable in evaluating the perfor-
mance of a soil-vapor-groundwater system prior to construction of a remediation system.
Such models also can be used to determine the applicability and effectiveness of a particular
corrective action technology and can lower the cost associated with trial-and-error system
design and operation.
Effective SVE process modeling has many practical implications. For example,
efficient modeling leads to a better examination of process feasibility, a more accurate
prediction of potential performance, and the development of system engineering design
criteria prior to SVE implementation. This section presents a short summary of the applica-
tion of microcomputer models for demonstrating how an SVE system influences the soil
vapor transport. This section also presents an evaluation of the feasibility of using SVE for
site remediation. Table 3 is a summary matrix of general types of models.
The effective design of an SVE system requires an understanding of the mechanisms
that control the fate and transport processes and the site characteristics that affect them. SVE
is affected by the following major processes: advection, diffusion, dispersion, partitioning,
and abiotic and biological transformations.
The results of laboratory SVE column experiments and the results from field-scale
implementation of SVE have been analyzed and developed into mathematical models.
Subsurface vapor transport models (a larger group of models) were examined to determine
their use in evaluating SVE systems. The seven model types within this group include
models developed to simulate laboratory column studies, models developed to simulate
laboratory pilot (sandbox) studies, SVE screening models, models developed to simulate the
field-scale effect of SVE, subsurface flow models for calculating vapor flow rates and
pressure distributions, and groundwater flow models modified to approximate vapor flow.
Although each of these types of models has an important application in subsurface
vapor transport, only those models that can simulate SVE systems on a personal computer
will be discussed.
Column Models--
Column models have been developed to simulate laboratory column studies and to
determine the effectiveness of various fate and transport processes under simplified and
controlled column conditions. Column studies incorporating computer modeling have been
conducted as part of the SVE treatability study and research.
Wilson (1991) developed an SVE column model to simulate one-dimensional flow in
laboratory column studies. This model was used to determine the local equilibrium between
19
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the vapor phase, aqueous phase, adsorbed state, and nonaqueous liquid phase. The model
considered the effect of advection and diffusion/dispersion in the vapor and aqueous phases.
Biological degradation was also modeled as a first-order process in the aqueous phase. In
addition, sorption parameters can be determined based on the test results obtained by use of
the Freundlich, Langmuir, and BET adsorption isotherm characteristics.
Screening Models--
SVE screening models are primarily used to semiquantitatively estimate the feasibility
of SVE for application at a specific site. These models also may provide estimates of design
parameters used to size an SVE system. Johnson et al. (1990a,b) presented a useful screening
approach for determining the feasibility of SVE at a particular site. This practical approach
makes use of equations that estimate VOC removal rates and pressure distributions for various
SVE design parameters. The two models that were developed based on this approach are
VENTING and Hyperventilate.
VENTING can be used to estimate the rate of VOC removal from the vadose zone
under SVE conditions. This model assumes a steady gas flow, equilibrium partitioning
between the free product and vapor phases, and complete mixing of free product and vapor in
order to reduce the mass of each contaminant component during the extraction time. The
mass balance only considers partitioning from the free-product phase into the vapor phase. It
also assumes that the aqueous and adsorbed phases make negligible contributions to the vapor
phase. The volumetric gas flow rate is the key parameter that determines the VENTING
modeling results. The flow rate may either be input directly based on field measurements or
may be estimated based on the permeability of the contaminated soil and the vent pressure.
VENTING also provides a method of estimating permeability by use of permeability test data.
Hyperventilate was developed independently from venting and is designed to be used
as an instructional tool to identify required site data, decide if SVE is appropriate at a site,
evaluate air permeability tests, and estimate the minimum number of wells needed. It is not
intended to be a detailed SVE predictive modeling or design tool. The basic model principles
and computer software structure are discussed further in Section 2.
Subsurface Vapor Flow Models--
Subsurface vapor transport models calculate the two- or three-dimensional flow of
soil vapor through a porous medium as a result of the pressure gradient created by an
extraction well. These models do not consider the contaminant concentrations in the soil
vapor, but do simulate vapor compressibility. An example of this type model is CSUGAS, a
three-dimensional finite difference model that numerically simulates the flow field of a
compressible gas in a porous medium as a result of the influence of an SVE system. The
finite differences method is used to numerically approximate a solution to the system of
equations. This method also allows for use of a heterogeneous and isotropic porous medium
with gaseous flow under steady-state or transient conditions. Model applications include
selecting design parameters, determining the feasibility of SVE at a particular site, and
evaluating proposed modifications to existing SVE systems.
21
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Airflow is a two-dimensional finite element radial-symmetric model that simulates the
flow of vapors in the unsaturated zone. It computes vapor pressure distribution resulting from
a vapor extraction well at steady state for an ideal, compressible gas in vertical section.
Different vapor characteristics can be simulated by using different gas constants, molecular
mass, viscosities and temperatures. The model can simulate heterogeneous and anisotropic
permeability zones. A variety of boundary conditions can also be imposed.
Airiest is a two-dimensional analytical radial-symmetric model that can be used to
estimate permeabilities from test data and/or estimate pressure distribution and flow in soil.
The program is currently being tested and documentation is being developed. The program
can be run in either interactive or batch mode.
Groundwater Flow Models—
Groundwater flow models are another approach for predicting the pressure distribu-
tion and flow of an SVE system for design purposes. Because equations used to describe
vapor and groundwater flow in a porous medium are similar, groundwater flow models can be
used to approximate the pressure field and flow of a given system design. Use of groundwa-
ter models is advantageous because they are readily available, well documented, previously
validated, and may already be familiar.
A commonly used groundwater flow model is MODFLOW. The U.S. Geological
Survey (USGS) developed this three-dimensional finite difference groundwater flow model to
simulate many hydrologic systems (McDonald and Harbaugh, 1985). Several optional
features of this model, however, are not applicable for simulating airflow. The model is
divided into packages that represent a hydrologic or computational feature. The packages are
further divided into module subroutines designed for use in a particular package. The two
packages that are the most pertinent for SVE applications are the Block Centered Flow (BCF)
Package, which simulates flow within a porous media, and the Basic Package. The Basic
Package includes definitions of the number of rows, columns, and layers in the finite
difference grid, analysis timing, initial pressures (head for groundwater), boundary conditions,
output timing and format, and volumetric balance.
Recent SVE system designs for removing VOCs have mostly been empirically based
because of the simplicity of the process and the lack of analytical tools capable of aiding
system design. Many numerical models have practical applications in actual field situations
that can evaluate the effectiveness of SVE in removing organic vapors. Sensitivity analyses
can be used to determine the role of soil moisture, temperature, soil heterogeneity, and other
factors in controlling the migration of volatile constituents through the unsaturated zone. The
process of contaminant desorption from soil particles involves three consecutive mass
transport steps. This process can be used to determine final cleanup efficiency. It also can
result in significant differences in removal rates for the various types of soils and volatile
organic components.
22
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The focus of this document is on evaluating the practical use of the IBM-compatible
version of Hyperventilate as a screening model The principles, structure, and analyses of
Hyperventilate are discussed in detail in Sections 2 and 4 of this document. An application
using site data is presented in Section 3.
23
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SECTION 2
Hyperventilate
BASIC MODEL PRINCIPLES
Hyperventilate, an interactive, software guidance system, is a useful tool for
evaluating the feasibility of using SVE at a specific site. Hyperventilate was designed for
use as a guide to achieve the following: (1) to identify the level of site data needed to
evaluate SVE systems, (2) to determine if soil venting is appropriate at a site, (3) to evaluate
soil permeability test results, and (4) to approximate the minimum number of extraction wells
likely to be needed. The basic model principles presented in this part of the document are
based on information presented by EPA, 1991, and Johnson et. al, 1990.
Software Characteristics
Hyperventilate Version 1.01 was originally developed for the Apple Macintosh (Plus,
SE, Classic, LC, n, Portable, or Powerbook) computer with 2 MB RAM and the Apple
HyperCard Software Program (Version 2.0 or higher). Hyperventilate Version 2.0 is now
available for IBM compatible PCs equipped with an 80386 processor, 4 MB RAM minimum,
VGA or 8514, DOS 3.1 or higher, Microsoft Windows 3.x and Spinnaker PLUS 2.5 or
higher. The version of Hyperventilate that will be available through the EPA will have a
"run time" version of Spinnaker PLUS sufficient to run only Hyperventilate.
Hyperventilate is composed of a system of multiple stacks of cards in which each
computer screen view is called a card. Related cards that follow in sequential order are
organized into card stacks, and the main card stack is the soil venting stack. To obtain
further explanation of individual cards within this stack, secondary card sets can be accessed
through the soil venting help stack. Other supporting stacks include the air permeability test
stack, the aquifer characterization stack, the system design stack, and the compound list
update stack. The multiple card file system has the flexibility to allow the user to access part
of the software without having to work through the entire program.
The Hyperventilate software system uses these stacks to provide card sets with
information and calculations on nine major topics associated with implementing SVE. The
following sets of cards are used:
24
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• "Is Venting Appropriate?";
• Field Tests;
• System Design;
• About Soil Venting;
• Site Investigation;
• System Monitoring;
• Economics;
• System Shutdown; and
• The "Practical Approach."
The first three card sets listed allow the user to perform calculations related to SVE
feasibility, field tests, and design. The other six sets provide technical information on SVE
concepts, techniques, and procedures. The following subsections provide information on the
basic principles and calculations used in these Hyperventilate stacks.
Venting Applicability
A preliminary estimate of SVE applicability is calculated in the "Is Venting Appropri-
ate?" card set and is based on projected estimates of contaminant characteristics and soil
permeability. The first set of calculations is an estimate of ranges of extraction well vapor
flows. These ranges are based on input values of the air permeability associated with a given
soil type, the radius of the extraction well, the estimated vapor extraction well radius of
influence, and the thickness of the subsurface over which vapor extraction is Implemented.
The following equation is used to estimate the actual horizontal flow rate:
Qwell kp -[
=7C—"\Af
H 1 w
Equation 2
where
H
k
w
3
atm
R
RT
W
= actual airflow rate at extraction well (cm3/s)
= vapor extraction interval thickness (cm)
= soil permeability (cm2)
= viscosity of air (1.8 x 10"4 g/cm-s)
= absolute pressure at extraction well (g/cm-s2)
= absolute ambient pressure (1.013 x 106 g/cm-s2)
= radius of vapor extraction well (cm)
= radius of influence of vapor extraction well (cm)
The units shown in parentheses illustrate that the use of this equation requires a
dimensionally consistent set of metric or English units. The flow rate (Qweu) obtained from
Equation 2 is the flow rate that would be measured under the given wellhead vacuum and soil
permeability conditions. To convert Qwell to standard volumetric units (Qg), QweU is
multiplied by the ratio of Pw/Patm as follows:
25
-------
x
aim
Equation 3
Qg is expressed in standard cubic feet per minute (SCFM) in the Hyperventilate program,
and Qwen is in actual cubic feet per minute (ACFM).
The "Is Venting Appropriate?" section of the software calculates flow rates in SCFM
for five extraction well vacuums ranging from 5 to 120 inches H2O. Users can also input one
vacuum pressure of their choice. In the "System Design" section, the flow rate in SCFM is
calculated for the user specified wellhead vacuum.
The second set of calculations in the "Is Venting Appropriate?" card set estimates
constituent vapor pressure and vapor concentration. A data base supplied by Hyperventilate
is used to determine these vapor estimates for application to gasoline and weathered gasoline.
This data base defines the chemical composition of gasoline and the vapor pressures for 62 of
the chemical constituents identified in gasoline. The program enables the user to enter mass
fractions for these constituents into the data base. The method of estimating vapor concentra-
tion is described in Johnson et al., 1990a. The equilibrium or "saturated" vapor concentra-
tion is the maximum vapor concentration of any mixture of volatile constituents in extracted
vapors. This concentration is easily calculated based on the molecular weight and vapor
pressure at the soil temperature for each constituent in the contaminant mixture, the residual
soil contaminant composition, and the ideal gas law using Equation 4:
'est
-E-
/
>;"/W,
w,i
Equation 4
RT
'est
xi
where C»cf = estimate of contaminant vapor concentration (mg/L)
mole fraction of component i in liquid-phase residual (xj = 1) for
single compound
pure component vapor pressure at temperature T (atm)
molecular weight of component i (mg/mole)
gas constant = 0.0821 1-atm/mole-K
T = absolute temperature of residual (K)
The software adjusts the vapor pressure and concentration estimates to allow for soil tempera-
ture changes.
The third calculation estimates maximum removal rates as a function of the maximum
vapor concentration and the estimated vapor flow rate:
26
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= C
est
Equation 5
where Rest = estimated removal rate (kg/day or Ib/day)
QweU = flow rate from soil venting operations (ACFM)
Maximum removal rates are estimated based on the range of extraction well flow
rates (Qweu) previously estimated in Equation 2. A preliminary assessment of SVE feasibility
can then be made by comparing the desired removal rate with the estimated range of removal
rates. The desired removal rate is calculated by dividing the estimated spill mass (Ms m) by
the desired remediation time. SVE is considered to be feasible at this point in the evaluation.
If the desired removal rate is less than the maximum removal rate at the desired extraction
well vapor pressure.
After the desired and estimated removal rates are evaluated, the minimum volume of
air required to remove 90% of the residual gasoline in the soil is estimated as „ Vcritical. The
estimate along with previously estimated parameters, is used to determine the number of
vapor extraction wells required for site remediation. Johnson et al., 1988, developed a
correlation between the gasoline vapor concentration versus the air volume extracted over
time. This correlation is used to derive the air volume required to remove a given percentage
of residual hydrocarbons in soil. The Hyperventilate software calculates vapor concentration
and residual concentrations in 5% increments to estimate Vcritical. The following equation is
used to estimate the number of vapor extraction wells required based on
^^
Nwells = (Vertical x Mspi^(^well x e x Av) Equation 6
where additional parameters are:
critical
Mspill
Qwell
e
AT
minimum volume of air required to remove
90% of residual gasoline
mass of spill
flow rate from extraction well
efficiency of removal
desired remediation time
When Equation 6 is used to provide a preliminary estimate of SVE feasibility, it is
assumed that the well efficiency is 1.0 (100%) for initial estimation purposes. In the design
stack, the program calculates the number of wells based on Vcritical using Equation 6 and on
area using Equation 7 as follows:
N
wells =
Equation 7
27
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where Rc = radius of contamination
Rj = estimated radius of influence
The number of vapor extraction wells initially required is best estimated prior to field
data collection. This estimate can be used to guide field data collection activities and to
approximate the feasibility of implementing SVE at a given site.
Field Test Evaluation
The section of Hyperventilate dealing with air permeability field data evaluations can
be found in the Field Tests set of cards. Air permeability tests use airflow and transient air
pressure measurements taken from a field SVE test to estimate the permeability of the
unsaturated soil matrix. The permeability estimation process follows methodology presented
in Johnson et aL, 1990a. The resulting permeability measurements can be compared with the
values previously estimated for the various soil types found at the site. The permeability
calculations in Hyperventilate are independent of the other portions of the software. The
user, therefore, can choose the calculated permeability values from this part of the program or
the permeability values estimated from the soil type.
System Design
The SVE system design stack of Hyperventilate discusses the number and location of
extraction wells needed, well construction, surface seals, groundwater pumping systems, and
vapor treatment. The section on the number of extraction wells required is the only section
that provides calculation spreadsheets. These spreadsheets or cards essentially repeat the
calculation steps (i.e., Equations 2, 4, 5, 6, and 7) used in the "Is Venting Appropriate?"
stack. The multiple soil units are evaluated with respect to the total mass of contaminants,
critical volume of air needed to remediate 90% of the residual petroleum hydrocarbons,
estimated flow rate per vapor extraction well, and minimum number of vapor extraction wells
required. In addition, the regional efficiency is provided and the number of extraction wells
is estimated. Hyperventilate provides methods for estimating efficiency in two different
subsurface cases: (1) vapor flowing past liquid layers floating on the water table and (2)
diffusion of vapors from contaminated low-permeability lenses.
COMPUTER SOFTWARE STRUCTURE
Hyperventilate is interactive software with a dual nature. On one level, it is tutorial,
intended to help the user understand the nature and distribution of hydrocarbons in the
subsurface and to determine if SVE is an appropriate remedial technology at a given site. On
another level, it is computational, allowing the user to work through several sequences of
operations to determine if SVE is appropriate for use under specific site conditions.
28
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Hyperventilate Multiple Stack Cards
Hyperventilate comprises 100 cards made up of six stacks that provide calculations
and information on nine topics as listed on pages 22 and 23. Each topic is handled with a set
of cards. The first three sets ("Is Venting Appropriate?," Field Tests, and System Design)
take the user through the systematic decision process and evaluation of SVE. The other six
sets provide Help cards or technical information on SVE concepts, techniques, and economics.
In this subsection, the cards used in the SVE decision process will be discussed sequentially.
Entering HyperVentilate--
Upon opening the Hyperventilate icon, the user finds two disclaimer cards. Clicking
on the "NOPE" button will exit Hyperventilate and return the user to the Windows menu.
The user must "click" on the "OK" buttons on both cards to proceed into the software. The
next card is the main menu or home card that can be used to directly access different stacks.
If the user is familiar with the software and wants to access a specific card or stack, the user
can click on any of the folder tabs on the right side of the screen. The user should proceed
to the next card if unfamiliar with the software. The next card is the equivalent of the
software's cover page and table of contents. The fourth card, Card 1 of the soil venting
stack, provides an introduction to the software. Cards 2 through 6 and subordinate cards that
can be accessed from these cards introduce the user to soil venting and the soil venting
system design process.
"Is Venting Appropriate?"--
Cards 8 through 13 contain the first set of cards with computations designed to obtain
a rough approximation of SVE feasibility at a specific site. The user should be able to obtain
or estimate the required input parameters for these cards from data obtained from a prelimi-
nary site investigation. These computations allow the user to estimate the desired system
contaminant removal rate. Card 13 has a range of values for the maximum estimated
contaminant removal rate. The following scenarios are used to interpret the results and to
determine whether to use SVE:
• If the desired removal rate is less than the lower estimate for the removal rate,
soil venting is probably a viable remedial technology.
• If the desired removal rate falls between the upper and lower estimates for the
removal rate, application of soil venting may not be successful.
• If the desired removal rate exceeds the upper estimate for the removal rate, soil
venting is not likely to be appropriate and other treatment alternatives should be
considered.
The calculations on Cards 14 through 18 allow the user to refine this initial estimate,
taking into consideration anticipated compositional changes in the contaminant mass over the
course of remediation. The calculations estimate the minimum number of wells likely to be
required to achieve remediation within the specified time. These two initial approximations
29
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consider ideal circumstances in which the vadose zone containing contaminants is essentially
homogeneous and contaminants are distributed uniformly.
Other Considerations-
Card 19 provides the user with information and equations for four special cases that
can affect vapor extraction well efficiency. The cards used to access the four special cases
are the "Dilution Effects" or "Ground Water Upwelling" buttons, which are strictly tutorial;
the "Liquid Layers" button, which provides an explanation of how the contaminant removal
efficiency can be calculated when an NAPL layer is present; and the "Low Permeability
Lenses" button, which lets the user access cards that explain how to calculate the removal rate
of contaminants in a lens of low-permeability material.
Field Tests--
Cards 20 and 21 deal with field tests that should be performed in support of a soil
venting system design. Clicking on the "Aquifer Characterization" button on Card 20 opens a
support stack that identifies the circumstances that warrant aquifer characterization, provides a
brief description of aquifer characteristics, and identifies useful references on aquifer testing.
Clicking on the "Air Permeability Test" button on Card 21 opens a support stack that
describes how to conduct and evaluate an air permeability test.
System Design--
Cards 22 through 24 provide a thorough overview of all aspects of the vapor extrac-
tion system design. On Card 24, several buttons access cards in the system design support
stack. All of these buttons, except "Number of Extraction Wells," open up tutorial cards.
The "Number of Extraction Wells" button opens up a sequence of cards (System Design
Cards, SD1-4) that allow the user to refine the estimate of the number of extraction wells
likely needed to achieve remediation through SVE at the defined site. System Design Cards
SD2-4 contain tables that allow the user to subdivide the unsaturated zone interval slated for
remediation into eight units, based on stratigraphy and contaminant characteristics. Each of
the units identified by the user generates the following: (1) range of flow rates per vapor
extraction well, (2) minimum number of wells based on a comparison of the radius of
influence with the radial area of contamination, and (3) range for the minimum number of
wells based on the estimated volume of soil vapor (in liters) that must be removed to recover
each gram of residual contamination.
Tutorial Cards-
Cards 25, 26, and 27 contain tutorial material concerning appropriate system monitor-
ing parameters, system shutdown criteria, and soil vapor extraction economics, respectively.
The final card, Card 28, identifies the original intent of the software and acknowledges the
contributions of people who have participated in the software's development.
Software Inputs and Outputs
The following input information is required for use of the Hyperventilate software:
30
-------
• Soil types or permeability range;
• Vapor extraction well radius;
• Estimated radius of influence of the vapor extraction well;
• Thickness of subsurface interval over which vapor extraction occurs;
• Estimated vacuum pressure at extraction wells;
• Contaminant type: gasoline, "weathered" gasoline, or other chemical constituent
(molecular weight and vapor pressure at 20 °C and boiling point at 1 atm needed
if a constituent is not in the data base);
• Average subsurface soil temperature;
• Estimated spill mass;
• Desired remediation time;
• Screened interval of vapor extraction well;
• Stratigraphy of contaminated layers: soil types and depth intervals;
• Radius of contaminant layers
• Contaminant distribution thickness;
• Average contaminant concentration;
• Information on air permeability test analysis including:
- Vapor pressure versus time measurements at vapor monitoring wells based on
short-term permeability tests;
- Distance of vapor monitoring wells from vapor extraction well;
- Vapor extraction flow rate and vacuum pressure applied during permeability
test.
Note: The radius of influence depends on soil permeability, extraction well vacuum, and
boundary effects and must be estimated for program input. The equations used in HyperVen-
tilate are not very sensitive to the radius-of-influence parameter; a value of 12 meters or 40
feet is often used for estimating purposes.
31
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Hyperventilate guidance software provides the following output information:
• Estimated range of potential flow rates from a single vapor extraction well;
• Composite contaminant vapor pressure and concentration at a given temperature;
• Desired contaminant mass removal rate;
• Estimated maximum mass removal rate;
• Minimum air volume required to remove 90% of the initial contaminant residual;
• Number of extraction wells required at different measurements of inches of
wellhead vacuum pressure;
• Contaminant removal efficiency;
• Permeability based on air permeability site tests;
• Contaminant mass based on average contaminant concentration and extent of
contamination;
• Estimated minimum number of extraction wells required with the design vacuum
pressure.
Input Parameter Requirements. Data Sources., and Software Constraints
In this section, each input parameter is presented in the order in which it appears on
the Hyperventilate cards. When the software calls for a given input parameter, both the
source of that parameter and the software constraints on the use of that parameter are
addressed. The software constraints are also summarized in Table 4. As indicated earlier,
Hyperventilate is available (with minor differences) for both Apple Macintosh and IBM-
compatible systems. This evaluation will focus on the IBM-compatible version, but differ-
ences between the two versions will be identified. Table 5 presents a summary of the relative
importance, effects, and realistic range of values of the different input parameters presented in
this section.
Permeability (k)~ ...
Permeability, expressed in darcys, is first required on Card 8 (Flow Rate Estimation).
As mentioned earlier, Cards 8 through 18 ("Is Venting Appropriate?" stack) represent a
cursory evaluation of SVE feasibility based on data acquired early in the site-investigation
process. As such, permeability ranges entered on Card 8 (Flow Rate Estimation) are expected
to be determined based on soil type identified from descriptions of soil boring logs or tank
excavation sidewalls.
32
-------
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33
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34
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The software provides four default permeability ranges on Card 8 (Flow Rate Estima-
tion). Each range is one order-pf-magnitude in size. Given the lateral and vertical heteroge-
neity common to many sites, these ranges may often be too conservative. The user can enter
alternative permeability ranges if the available default permeability ranges seem either too
broad or too narrow for the site in question, or the soil type is not applicable to these default
ranges. If the user's estimated permeability or hydraulic conductivity values are expressed in
other units, the nomograph oh Card H13 (Help: Soil Permeability) or the computational
routine on Card H15 (Help: Unit Conversion [k and K]) can automatically convert the units
and/or convert from saturated hydraulic conductivity values to corresponding permeability
(intrinsic) values.
When large permeability values outside of the practical range are entered, the resulting
flow rate values may exceed the size of the display field provided for them on the card. In
these instances, the last digit(s) in the flow rate display are displaced to the next lower line,
thereby disrupting the flow rate table. In the Apple Macintosh version, permeability values in
the gravel range (^lO4 darcys) can result in flow rate values larger than the available flow
rate field. In the IBM-compatible version, the flow rate display field is larger, and this
problem does not occur until the user enters a permeability value of 10? darcys. Because this
is an unrealistic value, the problem should not occur for the majority of site permeability
values.
The next opportunity to enter permeability values is on Card H29 (Help: Boundary
Layer Equations - Calculation). This is the computational card for the "Help 6b, Liquid
Layer" special condition (Card 19). At this point in the program, it is likely the user has
refined estimates for unsaturated zone permeability. These refined estimates may come from
additional drilling, field air permeability testing, or laboratory permeability testing. Although
the software automatically defaults to the value range last entered on Card 8 (Flow Rate
Estimation), the user can change these values to reflect new permeability estimates. Card
H29 computes the relative efficiency of the vapor extraction system in the presence of a
liquid hydrocarbon layer. Relative efficiency of the SVE system decreases with increasing
permeability. In both versions of the software, the following fairly routine parameter values
are entered on this card: (screened thickness = 10 feet, radius of influence = 50 feet, venting
well radius = 4 inches, applied vacuum = 120 inches H2O, and radial width of contaminated
zone = 100 feet). The computations will provide unique relative efficiencies for permeability
values ranging from 10"2 to 104 darcys.
The final location for entering permeability values is in the system design stack on
Card SD3 (Design Input). Ideally, the values for k entered on this card have been derived
from either field or laboratory permeability tests (discussed on Card 21 - Field Tests). The
user can input a unique range of k values for each of the defined stratigraphic or contaminant
layers that will provide the system designer with a more accurate projection of the number of
wells needed to remediate each layer.
35
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Well Radius (Rw)»
As with permeability, the venting well radius is first entered on Card 8 (Flow Rate
Estimation) and carried through Card 18 ("Is Venting Appropriate?"). Most vapor extraction
wells tend to be constructed of 2- to 4-inch inside-diameter PVC. 'Because the permeability
of the sand- or gravel-packed annular space around the screened interval tends to be signifi-
cantly more permeable than the formation material, the effective well radius can be consi-
dered equal to the borehole radius. This would include the well and sand- or gravel-packed
annular space. '
As a result, the Rw values that the user should enter on Card 8 (Flow Rate Estima-
tion) will depend on the anticipated design diameter of the well and the drilling method to be
used to install the venting well. Boreholes resulting from rotary drilling techniques usually
have diameters that closely match the diameter of the drill bit. However, particularly in
coarser materials, augered boreholes may have a diameter more than 2 inches larger than the
outside diameter of the auger flight. Because the system design process has riot begun at this
point in the program, the user may use a range of values between 3 and 6 inches on Card 8
(Flow Rate Estimation).
Card H29 (Help: Boundary Layer Equations - Calculation) presents the next opportu-
nity to enter a value for Rw. The software defaults to the value on Card 8 (Flow Rate
Estimation); however, because system design may have progressed at this point, the user may
have a better idea of the planned venting well radius.
The value Rw is also used in the "Help: Low Permeability Lenses - Calculation"
special condition (Card H30). The user must enter the desired value. This card computes the
diffusion-limited removal rate for contaminants from a low-permeability layer and the
thickness of the low-permeability layer that is "dried out" or depleted of contaminants at
various times, up to 1,080 days. Rw has no significant impact on this latter output parameter.
Rw is also entered on Card SD3 (Design Input) of the system design stack. The user
can assign a unique venting well radius for each of the defined stratigraphic or contaminant
layers and can use these tables to try a variety of venting well radii in each interval to quickly
determine optimum well sizes. Conditions discussed regarding Cards 8 (Flow Rate Estima-
tion) and H30 (Help: Low Permeability Lenses - Calculation) continue on Card SD3 (Design
Input).
Radius of Influence (Rj)~
The radius of influence, as with permeability and the well radius, is initially required
on Card 8 (Flow Rate Estimation). The radius of influence value entered on this card is
carried through Card 18 ("Is Venting Appropriate?").
The radius of influence is defined in theoretical calculations as the radial distance
from a vapor extraction well, where the gauge pressure measured in the soil during an air
permeability test is approximately zero. This is generally identified as the radial distance at
which the measurable vacuum is 1 inch H2O or less. It should be noted that air pressure
36
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readings showing a measurable vacuum are no assurance of vapor flow or migration. The
radius of influence is a dependent variable that is directly related to soil permeability, applied
wellhead vacuum, and boundary conditions such as vertical airflow from the surface and
preferential flow paths. Reported Rj values for permeable soils have generally been in the
40- to 120-foot range; tighter soils with lower permeability will cause Rj results to be in the
10-foot or lower range. Because soil vapor extraction pilot tests are rarely performed early in
the investigation of a site, the user should experiment with the full range of typical values for
this initial evaluation.
The radius of influence is subsequently used in Card AP3 (Air Permeability Test -
Instructions) of the air permeability test stack. This card is reached by first clicking on the
"Air Permeability Test" button on Card 21 (Field Tests) and then clicking on the "Test
Instruction" button on Card API (Air Permeability Tests). Card APS is intended to help the
user estimate the duration of an air permeability test. First, the user must enter the estimated
radius of influence. The card then calculates one pore volume of soil vapor within the radius
of influence and the time required to extract one pore volume. The pore volume output box
will only display five significant figures. As a result, large input values for Rj (>100 feet) for
"Soil Layer Thickness" and "Air Permeability Test Flow Rate" will cause Pore Volume values
to exceed the display field, and digits at the end of the value for Pore Volume will not be
completely displayed. The user can check for significant figures outside of the display by
deleting larger digits from the display box.
Card SD3 (Design Input) is the final location for entering a value for Rj. The user
can enter a unique Rj for each of the defined stratigraphic or contaminant layers. For the
system design, the user should have air permeability test data from each of these layers.
Interval Thickness (H)-- .
Interval thickness, as in the preceding input parameters, is first required on Card 8
(Flow Rate Estimation), and the value entered on this card is carried through to Card 18 ("Is
Venting Appropriate?"). As used in the software, interval thickness refers to the smaller of
either the length of the screened interval or the thickness of the permeable zone in question.
Under ideal circumstances, these values will be the same. Typically, values for H will fall in
die 5- to 20-foot range. Flow rates vary in direct proportion to changes in interval thickness.
Interval thickness can next be entered on Card H29 (Help: Boundary Layer Equa-
tions - Calculation). The software will use the value entered on Card 8 (Flow Rate Estima-
tion) as a default value, or the user can enter a new value. The upper boundary of the
relative efficiency output reaches 100% at a minimum interval thickness of 0.1 foot in
medium sand and about 1 foot in clayey silt.
Interval thickness is entered separately for each contaminant or stratigraphic layer on
Cards SD2 and SD3, respectively. On Card SD2 (Design Input), the user enters a value for H
in the "Interval Thickness" column under "Contaminant Distribution" for each defined
contaminant or stratigraphic layer. This interval thickness should correspond to the "Depth
BGS" interval on the same card. On Card SD3 (Design Input), a value for H is entered in the
37
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"Screen Thickness" column under "Extraction Well Construction" for each defined layer. The
values for H entered on these cards should be the same for each layer in order to match the
screened interval with the interval of concern. Based on the critical volume measurement
(volume of air required to remove 1 gram of contaminant mass), a contaminant interval
thickness larger than the screened interval increases the minimum number of wells required.
With this design, the remediation of the contaminant interval not intersected by the well
screen will depend on contaminant diffusion into the vapor flow path. Based on critical
volume, use of a screened interval larger than the contaminant interval thickness will result in
a smaller minimum number of wells because of an increased flow rate per vapor extraction
well. The user should reduce the well "Efficiency" value entered on Card SD2 (Design
Input), however, to accommodate the extraction of uncontaminated vapors with this design.
As long as the two H values are changed together, the minimum number of wells based on
critical volume will remain constant for any H value because changes in the "Calculated Total
Contaminant Mass" are offset by corresponding changes in the "Mow Rate per Vapor
Extraction Well." If the two H values (interval and screen thickness) are varied together, the
"How Rate per Vapor Extraction Well" range is the only output parameter that is sensitive to
change.
Well Vacuum (Pw)»
Well vacuum is the last input parameter to be entered on Card 8 (Flow Rate Estima-
tion). The software provides six default well vacuums. In addition, the user can define a
well vacuum that may be more appropriate in the field at the bottom of the column. The user
should select a value such that 0 < Pw < 406 inches H2O. This maximum Pw corresponds to
absolute ambient pressure (Patm) or one atmosphere of pressure. All well vacuums appearing
on Card 8 are carried to Card 12 (Maximum Removal Rate Estimates). On Card 13 ("Is Soil
Venting Appropriate?"), the largest well vacuum from Card 8 (Flow Rate Estimation) is
displayed, and the corresponding flow rates and maximum removal rates are used to deter-
mine the first estimate of soil venting. On Card 18 ("Is Venting Appropriate?"), however, the
software uses a default Pw value of 120 inches H2O, the associated range of flow rates, and
maximum removal rates for determining the first estimate of the minimum number of wells
required.
Well vacuum is used next on Card H29 (Help: Boundary Layer Equations - Calcula-
tion) to calculate well efficiency in the special liquid-layer condition. The user must enter the
appropriate value for well vacuum.
In the system design stack, well vacuum is entered on Card SD2 (Design Input) and
automatically displayed on Card SD3 (Design Input). Values for the minimum number of
wells, based on critical volume, decrease with increasing well vacuum to reflect greater flow
rates and estimated contaminant removal rates.
Temperature (T)~
Temperature, in degrees Celsius, is entered for the first time on Card 10 (Vapor
Concentration Estimation - Calculation). The value for temperature entered on this card will
be carried through Card 18 ("Is Venting Appropriate?"). This input parameter is defined as
38
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the temperature of the vapor in the subsurface, As shown in Equation 2 and on Card H22
(Help: About Calculation)'* while the user enters the temperature value in degrees Celsius, the
software converts the entered value to degrees Kelvin for the calculations. On Card 10
(Vapor Concentration Estimation - Calculation), the calculated output parameters, the
"Calculated Vapor Pressure," and the "Calculated Vapor Concentration" are affected by the
value of T; the "Sum of Mass Fractions," however, is Unaffected by the value for T used.
Temperature is also used in the "Help: Low Permeability Lenses - Calculation" special
condition (Card H30). Process variables are input in Step 1 of Card H30. In Step 2 of Card
H30, the user should input the values defined and computed on Card 10 (Vapor Concentration
Estimation - Calculation).
Contaminant Cbmposition-
Card 10 (Vapor Concentration Estimation - Calculation) provides four ways in which
a user can define the composition of a contaminant mass at a given site:
• Default composition for fresh gasoline product,
• Default composition for weathered gasoline product,
• Results of boiling point distribution analysis, and
• Results of detailed gas chromatograph (GC) analysis.
The software provides default compositions for use with fresh and weathered gasoline
products. These compositions are based on an analysis of two gasoline samples of 62
representative volatile and semivolatile compounds. The default fresh gasoline distribution is
based on a sample of regular unleaded gasoline taken directly from a retail pump. The
default weathered gasoline distribution is based on a sample of product recovered from the
water table at a site in California. If the user is confident of the age of a site release, the
default distributions can be an appropriate means of developing preliminary estimates of
recovery rates. Once a site reaches the design stage, however, the user would be advised to
revisit Card 10 with site-specific analytical data prior to using the system design stack. Based
on these data, Card 10 (Vapor Concentration Estimation - Calculation) should be run by using
one of the two approaches on the "Help: Compound List" card, which is accessed through the
"Enter Distribution" button.
One approach is to conduct a boiling point distribution analysis. In this approach, a
normal GC analysis is run on one or more samples. Rather than calculate the concentration
represented by each peak on the GC scan, marker compounds are selected and peaks around
these marker compounds are summed and reported as the marker compound. This results in a
comparatively inexpensive, reasonably complete generalized profile of vapor composition.
Once the laboratory results are available, the user clicks on the "How Do I Measure a
Distribution" button located on the bottom left corner of Card 10 (Vapor Concentration
Estimation - Calculation) to move to the "Help: How Do I Measure a Distribution?" card.
The user then clicks on the "Calculate a Distribution" button located in the bottom right
corner of this card. This moves the user to the "Help: Calculate a Distribution" card. The
concentrations or areas associated with each of these marker compounds are then entered on
39
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this card, and the user clicks on the "Calculate" button. When the calculations are complete,
the user clicks on the "Transfer Data to Distribution Card" button. This transfers the user and
data to the "Help: Compound List" card. The user checks to ensure the sum of mass fractions
equals or is close to one, and clicks on the "Return to Vapor Concentration Estimation Card"
button to return to Card 10. Finally, the user clicks on the "Perform Calculations" button to
obtain vapor pressure and vapor concentration values.
The second approach is to run a normal GC analysis on one or more samples, and
input the analytical results by clicking on the "Enter Distribution" button on Card 10 (Vapor
Concentration Estimation - Calculation). This transfers the user to the "Help: Compound
List" card, where the user enters the mass fraction of each of the compounds in the analytical
results. The user should always click on the "Sum" button to ensure that the sum of mass
fractions comes close to equaling one. The user then clicks on the "Return to Vapor
Concentration Estimation Card" button to return to Card 10 (Vapor Concentration Estima-
tion - Calculation), and finally clicks on the "Perform Calculations" button.
If the GC analysis contains compounds that do not appear on this card, the user must
quit the Hyperventilate file and click on the "Compound List Update" file icon. When the
"Compound List Update" card shows on the screen, the user enters the chemical name,
molecular weight, vapor pressure at 20 °C (in atm), and boiling point at 1 atm (in °C) for the
new compound(s) and clicks on the "Insert Compound" button. When all new compounds
have been added, the user quits the "Compound List Update" file and returns to the "Help:
Compound List" card in the Hyperventilate file to enter the remaining mass fractions.
At a fixed temperature, higher proportions of lower boiling point compounds result in
higher calculated vapor pressures and vapor concentrations (with the reverse being true for
higher proportions of higher boiling point compounds). Neither extreme will affect the output
displays on Cards 10 through 18.
Estimated Spill Mass (MSpiU)~
The user needs to enter the estimated spill mass on Card 13 ("Is Soil Venting Appro-
priate?") to calculate a desired removal rate. This input can be one of the most difficult
parameters to determine. Under ideal circumstances, the user will know the specific volume
of the release and make a simple conversion to either kilograms or pounds. If the contami-
nant volume is not known, however, other methods are available for estimating the residual
spill mass in the unsaturated zone.
The simplest method, at least within the framework of Hyperventilate, is to skip
forward to the system design stack. Before clicking on the "Update" button, the user simply
enters a radial area of contamination, contaminated interval thickness, and average contami-
nant concentration within the defined soil volume. The software computes the total residual
contaminant mass in either pounds or kilograms; the equation V = Ttr^h is used to determine
soil volume and soil density in lb/ft3. The user then enters this calculated value on Card 13.
40
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Another method for estimating the residual spill mass is to use a software routine,
such as SPILLGAD. SPILLCAD is a PC-based program designed to calculate the volume (as
NAPLs) of hydrocarbons occurring both in the unsaturated zone and on the water table.
Desired Remediation Time—
The user enters the desired remediation time on Card 13 ("Is Soil Venting Appro-
priate?"). The value selected for this highly subjective input parameter can be driven by such
factors as perceived potential impact of contaminant migration on downgradient receptors,
demand for action from surrounding property owners, responsible party's and consul-
tant/contractor's relationships with regulator, and responsible party's plans for the site,
A review of the output parameters (desired removal rate versus the range of maximum
estimated removal rates) displayed on Card 13 ("Is Soil Venting Appropriate?") often leads to
an obvious conclusion of S VE feasibility. The potential flexibility of the desired remediation
time comes into play in the gray area when the "Desired Removal Rate" falls between the
upper and lower estimates of the "Maximum Estimated Removal Rate." The desired
remediation time often can be extended to increase the viability of SVE as a remedial alterna-
tive. If the desired remediation time cannot be changed because of external circumstances,
the design variable's well radius or well vacuum on Card 8 (Flow Rate Estimation) may be
manipulated to achieve the same end. This alteration, however, may require upgrading vapor
effluent treatment capabilities. Inasmuch as this card represents the initial evaluation of
SVE's potential effectiveness as a remedial technology at the subject site, there is still room
for considerable flexibility in the selection of design criteria.
Although the desired remediation time is not entered on Card H30 (Help: Low
Permeability Lenses - Calculation), it is useful to compare the projected time frame for
remediation to the table displayed on this card. If the target of a site remediation is a low-
permeability layer of known thickness, this table can be used to quickly confirm if the entire
thickness of the target unit will be "dried out" and, if not, what the anticipated contaminant
removal rate will be at that time.
In the system design stack, the desired remediation time is entered on Card SD4
(Design Input). This input parameter will have no bearing on either the "Flow Rate per
Vapor Extraction Well" or the "Minimum Number of Wells Based on Area." Changes to the
"Time for Clean-up" will have a direct, proportional impact on the estimated "Minimum
Number of Wells Based on Critical Volume."
Boiling Point Ranges—
The author of the Hyperventilate users manual (Appendix B, pages 30 and 32), Dr.
Paul Johnson, encourages the use of a boiling point distribution analysis as a means of
acquiring a comparatively economical profile of the distribution of compounds in the initial
subsurface contaminant mass. The software takes the same approach in estimating the
residual distribution of compounds over the course of vapor extraction. The initial contami-
nant distribution is reduced to five boiling point ranges. The following default ranges can be
found on Cards 16 (Model Predictions) and H27 (Help: Default Boiling Point Ranges):
41
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(1) Propane to isopentane
(2) Isopentane to benzene
(3) Benzene to toluene
(4) Toluene to xylenes
(5) Xylenes to methylnaphthalene
-50 to 28 °C
28 to 80 °C
80 to 111 °C
111 to 144 °C
144 to 250 °C.
The boiling points of all 62 compounds on the software's compound list are included
in Table 6. This table shows that Boiling Point Ranges 1 and 2 contain only light-end alipha-
tics. Because state regulators and remedial contractors are particularly interested in benzene,
toluene, ethyl benzene, and xylenes (BTEX) constituents, they have been highlighted with
boldface type in the table. Benzene and toluene are among the compounds in Boiling Point
Range 3, and Boiling Point Range 4 contains ethyl benzene, p-xylene, and m-xylene. Finally,
Boiling Point Range 5 contains o-xylene and other compounds not easily recoverable through
SYE. After the boiling point ranges have been established, the user clicks on the "Generate
Predictions" button. When the screen displays Card 17, the user clicks on the "Import Data"
button. This fills the "Saturated Vapor Concentration at time=0" and the "Min Volume to
Remove >90% of Initial Residual" boxes and the table.
The default boiling point distribution ranges are effective under normal circumstances.
The user may want to adjust those ranges, however, under certain circumstances. For
instance, if the regulations in a given locality are tied to residual benzene concentrations, the
user can alter the ranges so that the first range extends from -50 to 75 °C, the second range
extends to 85 °C, and the rest are left unchanged. This change places benzene in the second
boiling point range in which the critical volume of air is determined for benzene removal.
After clicking on the "General Predictions Button" and the "Important Data Button," the user
could scan the columns to 0, and obtain the volume of air moved per gram of residual
contamination needed to achieve that goal from the first column. This volume of air may be
as little as one-tenth the volume of air cited for removing >90% of the initial residual. If this
value is inserted into the "Min Vol..." box on Card 17, an equal or greater reduction in the
minimum number of wells required will result on Card 18 ("Is Venting Appropriate?"),
thereby making SVE a far more attractive proposition for all concerned. The impact is the
same in the system design stack.
Radial Width of Contaminated Zone- ,
The radial width of the contaminated zone is first required on Card H29 (Help:
Boundary Layer Equations - Calculations) to calculate the effect of a liquid layer of petro-
leum hydrocarbons on recovery well efficiency. At this juncture, the distribution of contami-
nants at a site should be well delineated either through the use of a soil vapor survey or the
drilling and installation of a plethora of borings and monitoring wells. Calculated well
efficiencies increase with the radial width of the contaminated zone. Under conventional
circumstances (15-foot screened interval, 40-foot radius of influence, 4-inch effective well
radius, and a well vacuum of 120 inches H2O), the upper boundary of relative efficiency
reaches 100% in medium sand at a radial width of 1,067 feet.
42
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TABLE 6. BOILING POINT DISTRIBUTION LIST OF COMPOUNDS
B.P. Range
1
2
Compound
)ropane
sobutane
n-butane
rans 2-butene
cis-2-butene
3-methyl-1 -butene
isopentane
1-pentene
2-methyl-1 -butene
2-methyI-1 ,3-butadiene
n-pentane
pans-2-pentene
2-methyl-2-butene
,
3
4
3-methyl-1 ,2-butadiene ,
3,3-dimethyl-1 -butene
cyclopentane
3-methyl-1-pentene
2,3-dimethylbutane
2-methylpentane
3-methylpentane
n-hexane
methylcyclopentane
2,2-dimethylpentane
benzene
cyclohexane
2,3-dimethylpentane . .
3-methylhexane
3-ethylpentane
2,2,4-trimethylpentane
n-heptane
methylcyclohexane
2,2-dimethylhexane
toluene
2,3,4-trimethylpentane
2-methylheptane
3-methylheptane
n-octane
2,4,4-trimethylhexane
2,2-dimethylheptane
ethyl benzene
p-xylene
m-xylene
3,3,4-trimethylhexane
Boiling Point
-42.07
-11.40
-0.50
0.88 ,
3.70
20.00
27.85
29.97
31.16
34.00
36.07
36.35
38.57
40.00
41.20
49.26
51.14
58.00
60.27
63.28
68.95
71.80
79.20
80.10
80.74
89.80
92.00
93.50
99.24
98.42
100.90
106.84
110.60
113.47
117.70
118.00
125.66
126.00*
127.00*
136.20
138.35
139.10 .-
141.00*
(continued)
43
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TABLE 6. (continued)
B.P. Range
Compound
Boiling Point
o-xylene
2,2,4-trimethylheptane
n-nonane
3,3,5-trimethylheptane
n-propylbenzene
2,3,4-trimethylheptane
1,3,5-trimethylbenzene
1,2,4-trimethylbenzene
n-decane
methylpropylbenzene
dimethylethylbenzene
n-undecane
1,2,4,5-tetramethylbenzene
1,2,3,4-tetramethylbenzene
1,2,4-trimethyl-5-ethylbenzene
n-dodecane
naphthalene
n-hexylbenzene
methylnapthalene
144.40
147.00*
150.80
152.00*
159.20
159.00*
164.70
169.35
174.10
185.00
189.75
195.90
196.80
205.00
208.10
216.30
218.00
230.00*
241.05
*ThIs Is an approximate value.
44
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In the system design stack, the radial width of the contaminated zone is entered on
Card SD2 (Design Input) as one of the values needed to calculate the total contaminant mass.
Because the software uses the equation V = ra^h to determine the volume of contaminated
soil, the "Calculated Total Mass" increases by the square of any increase in the "Contaminant
Distribution Radius."
45
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SECTION 3
MODEL APPLICATION CASE STUDY
This section presents a sample application of Hyperventilate based on data obtained
from a site in Minnesota. It provides examples of how to estimate and determine input
parameters from data provided in a remedial investigation report (RIR), defines the steps
involved in determining appropriate SVE estimates, and describes how to interpret results.
This section also demonstrates the utility of Hyperventilate as an iterative analysis of SVE
design in addition to its use as an instructional tool.
BACKGROUND
The Roseville Case Study (Kruger and Carson, 1991) was originally prepared as a
demonstration of Hyperventilate for use by the Minnesota Pollution Control Agency (MPCA),
Tank and Spill Section. The site was chosen for the study because it is generally representa-
tive of the gasoline-station-release scenario commonly faced by the MPCA staff. In this
exercise, site data from MPCA files were used to illustrate the value of the software as both
an SVE tutorial and an interactive screening tool to help MPCA case managers make better
decisions about contractor proposals. The Roseville case also will be more instructive
because an operating system at the site has yielded performance data that can be viewed in
comparison to the SVE scenarios suggested by Hyperventilate.
This case study demonstrates the process of reviewing a remedial investigation/cor-
rective action plan in order to determine input parameters for Hyperventilate. Initially, the
software will help to examine the site from a very basic point of view; the view includes a
number of simplistic, but important assumptions about subsurface conditions and contaminant
behavior that are explained within the software. Because data needs for this part of the
analysis are not rigorous, an iterative approach is encouraged. The software subsequently will
be used to revise the initial assumptions, develop better input data, and refine the use of SVE
at the site. Users should follow along with this discussion using their own Hyperventilate
program and then enter the appropriate data in sequence. Similarly, the user should also read
the software text in sequence for further clarification and understanding. Please note that
many program inputs are presented in English units for ease of use. The user has a choice of
using metric or English units for the outputs.
46
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INITIAL ESTIMATES - IS SOIL VENTING APPROPRIATE?
The user should first review the RIR submitted by the contractor. As part of this
review, the user should study the data necessary to run Hyperventilate from the RIR. Two
key items needed from the RIR for this study are (1) a site plan showing the locations of
wells and vapor monitoring probes as well as the extent of soil contamination (Figure 3) and
(2) one or more good representative geologic cross sections with profiles of the distribution of
soil contamination (Figures 4, 5, and 6). If! the latter are not provided, they should be
constructed from the raw data available.
Flow Rates
To begin the first interactive portion of the software program involving Flow Rate
Estimation (Card 8), the following are needed:
• Air permeability data (in darcys) or a gross grain size estimate based on soil
types that match one of four default categories (medium sand, fine sand, silty
sand, or clayey silt) provided in the software, '.._
• Well radius (the borehole radius is used because the packing material around the
well is typically much more permeable than the soil formation),
• An estimate of the radius of influence of, the extraction well,
• A measurement of the thickness of the screened interval (ideally, this will be the
thickness of the contaminated zone), and
• If available, the anticipated well vacuum pressure.
As depicted in Table 7, the contractor has divided the soil profile into four units The
water table is located approximately 65 feet (19.8 m) below grade, below the silt layer.
Hydraulic conductivity /values from rising water level test data are also provided. Although
not ideal, these data can be converted to equivalent permeability values in lieu of air per-
meability test data; however, they should only be considered representative of Unit 4, if at all.
L' TABLET. STRATIGRAPHY
Unit No.
Unitl
Unit 2
Units
Unit 4
Thickness
(ft)
3-8
45-50
3-5
15+
Lithology
Surface Fill
Fine to Coarse Sand
Silt
Fine to Coarse Sand (similar to Unit 2)
Estimated Permeability (k)
(darcy)
•
0.3 - 0.6
47
-------
!§•
5"
s Mi
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I rii
« * O. ~*
II
II
i
Q
8 i
en
cc
01 K
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LU UJ
2 u.
OJ
H < i
8 -
cc
O
UJ
OO =
111
S cc tu
S e M
zee
ie
i|
u. «
O "J o «J Q '
CO
UJ
\
48
-------
ELEVATION m METERS
I
y.
a
=
CO
g §
49
-------
ELEVATION IN METERS
CQ
.2
4—»
•8
GO
en
§
JG3J Nl NOUVA7I3
50
-------
ELEVATION IN METERS
§ IS
<
N
o
en
5
§
ea
133 d Nl NOU.VA313
51
-------
The geologic cross sections show that the majority of soil contamination is within Unit
2. Therefore, this unit will be the limiting zone and will be the focus of further interest.
Hyperventilate can be used to determine a range of permeability values for Unit 2. The fine
sand default value (1 to 10 darcys) will be used.
The contractor proposes the installation of both shallow and deep extraction wells
screened within the upper and lower portions, respectively, of Unit 2. Combined, the
screened depth intervals of the wells span most of Unit 2. The following additional Hyper-
Ventilate input data are provided by the contractor's design plans including well schematics
(Figures 7 and 8) and a proposed system layout (Figure 9):
• The borehole (well) radii are ~3.5 inches (8.9 cm).
• A minimum radius of influence of 20 feet (6 m) is implied by the proposed well
spacing.
• The screened interval for both the shallow and deep wells combined is 35 feet
(11 m).
• An anticipated well vacuum pressure is not specified.
Based on these data, Hyperventilate calculates Predicted Flow Rate Ranges of 2.3 to
469.3 SCFM for various well vacuum pressures (5 to 120 inches H2O).
Vapor Concentration
The next step in the exercise is to calculate a "Vapor Concentration Estimation" (Card
10). Two new input parameters are needed:
\
• Soil vapor temperature in °C, and
• Contaminant composition or distribution.
Although neither of these parameters was specifically provided in the RIR, approxi-
mations can be made based on general knowledge of soil conditions and petroleum contami-
nant behavior. In addition, Hyperventilate provides two default contaminant distributions--
"fresh" and "weathered" gasoline—just in case actual site-specific data are not initially
available. Therefore, one can make the following generalizations:
» Ground temperature at depths below subsoil in midlatitude regions such as
Minnesota is approximately 10 °C.
• Laboratory analytical results reported in the RIR showed that whenever BTEX
was detected in soil (3 out of 14 samples), toluene and xylene concentrations
greatly exceeded benzene concentrations. This relationship is more typical of a
"weathered" gasoline than a "fresh" gasoline.
52
-------
.1
4' CLEA
TOS
_L
nz_ •— i I
RANGE
EAL
r
8'
BENTONITE/
CEMENT SEAL
•^|r
t
151 SC
SECT
0.020"
>
i
REEN
[ION
SLOT
f
—
^- 2-PVCAIRMANIFOL
t=>
*—
X
<>w
61 - 8' O.D.
SLOPE TO CONDENSATE
TRAP -1/8" /FT.
.. — 2" PVC RISER
(UNSLOTTED)
s- GRAVEL PACK
/ #10-#20SAND
NOT TO SCALE
Figure 7. Shallow vapor extraction well schematic.
53
-------
TOTAL DEPTH = 60'
(DO NOT DRILL INTO/
THROUGH CLAY LAYER
PRESENT AT 50'-60')
1
4' CLEA
TOS
>
i
21
BENTC
CEMEN
>
i
20' SC
SEC1
0.020"
>
M J I" 1 1
RANGE
EAL
r
k
)NITE/
TSEAL
r
i
REEN
RON
SLOT
r
—
—
—
2" PVCAIR MANIFOLD
X
[=>
*-
X
V-B'O.D.
SLOPE TO CONDENSATE
TRAP -1/8" /FT.
2" PVC RISER
(UNSLOTTED)
,- GRAVEL PACK
/ #10-#20SAND
'
NOT TO SCALE
Figure 8. Deep vapor extraction well schematic.
54
-------
EXISTING
PARKING GARAGE
FENCE
NOTE: PVC VAPOR EXTRACTION LINES
WILL SLOPE TO CONDENSATE
TRAP FROM EACH WELL
1/8- / FT. Ml'NIMUM
N
LEGEND:
• SHALLOW VENT WELL
• DEEP SOIL VENT WELL
Figure 9. Vapor extraction system layout.
55
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Performing the calculations using these parameters results in a "Calculated Vapor
Pressure" of 0.04 atm and a "Calculated Vapor Concentration" of 142.7 mg/L. This estimate
is constrained, however, by a lack of detailed information about the contaminant composition.
The contaminant may, in fact, be a mixture of gasoline and other petroleum products or an
older, more "weathered" product These and other compositional factors can affect vapor
concentration significantly.
Calculated Removal Rate
The predicted flow rate ranges and the calculated vapor concentration can now be used
to calculate a "Removal Rate Estimation" (Card 12) for the idealized situation. The estimates
suggest that a single well with a 35-foot (11-m) screened interval in Unit 2 would have a
"Maximum Removal Rate" of 30 to 8,552 Ib/day (13 to 3,874 kg/day) depending upon the
vacuum applied (5 to 120 inches H2O).
Desired Removal Rate
At this point in the exercise, one can begin to ask the question "Is Soil Venting
Appropriate?" (Card 13). This is a very rough cut evaluation that depends not only on the
"best-case," idealized estimates of contaminant removal rates, but also on two additional and
very important input parameters:
• An estimate of the total contaminant or spill mass, and
• The amount of time available for cleanup.
In many situations, it can be very difficult to approximate or anticipate these figures
with any reasonable accuracy. Neither of these parameters is provided in the RIR.
It is suggested that 1 year can be picked as an initial timeframe to begin the evaluation
of the appropriateness of SVE. A revision of this figure may be warranted if subsequent
analyses suggest that this timeframe is overly optimistic. A spill mass is calculated based on
available information. Using the site plan (Figure 3) and cross sections (Figures 4, 5, and 6),
one can estimate the radius and thickness of the contaminated zone as well as the average
contaminant concentration in the zone. Hyperventilate can be used to calculate a total spill
mass (Card SD2) based on the following input estimates:
• The maximum (96.5 feet [29.4 m]) and minimum (76.8 feet [23.4 m]) radial
dimensions of the irregularly shaped contaminated area were averaged to give an
estimated radius of 43.49 feet (13.26 m).
i
• The bulk of the contaminant mass is within Soil Units 1, 2, and 3 with a total
combined interval thickness of ~58 feet (18 m).
56
-------
• The average of all laboratory analytical results indicating detectable concentra-
tions of total hydrocarbons as gasoline in soil within the contaminated zone is
542 mg/kg.
From these input parameters, one calculates a total spill mass of 19,840 Ib (8,987 kg).
Note that this is an estimate of the contaminant mass throughout the entire contaminated
zone, not just the screened intervals of the proposed wells.
On the basis of the above inputs, one then calculates (Card 13) a "Desired Removal
Rate" of 54.3 Ib/day (24.6 kg/day). This value can be compared with the maximum removal
rate range (at 120 inches H2O well vacuum) and/or the calculated removal rate range at a
design-specified well vacuum. If the desired rate is greater than the maximum or design rate,
then one surmises that vapor extraction is probably not an appropriate remediation alternative.
In the Roseville case, however, the desired rate is well within the calculated maximum range.
Therefore, the application of SVE at this site should be further examined.
REFINED ESTIMATES - HOW APPROPRIATE IS SOIL VENTING?
The next sequence of calculations refines the estimates to determine vapor extraction
feasibility. The first interactive portion of this sequence, "Model Predictions" (Card 16),
allows a look at changes in residual contaminant composition that occur as a result of vapor
recovery. The results provide more details on each progressive stage of the venting process
as well as the amount of air that must be moved to accomplish each stage. Ultimately,
Hyperventilate will determine a first approximation of the minimum number of wells needed
to move the requisite air volume based on previously calculated flow rate ranges.
Critical Volume of Air
No new input parameters initially are needed for the "Model Predictions" (Card 16).
The default boiling point ranges can be adjusted (Card H27), however, to include all BTEX
constituents within Boiling Point Ranges 3 and 4. This adjustment will make it easier to
estimate the point at which all BTEX is removed from the residual. Clicking on the
"Generate Predictions" button starts the Hyperventilate computations. Results are then
displayed (Card 17); the "saturated vapor concentration at time = 0 is 147.7 mg/L and the
"minimum volume of air" estimated as necessary to remove 90% of 1 gram of the initial
residual spill mass is 221 L-air/g-residual.
A comparison of Columns 1 and 3 in the table on Card 17 shows that the 221 L-air/g-
residual value is more accurately described as the estimate for removing 94.3% of the original
spill mass. A rough interpolation shows that only about 165 L-air/g-residual are needed to
remove 90% of the original spill mass. By entering 165 L-air/g-residual in the minimum
volume box, the user can evaluate a more optimistic estimate for achieving the >90% goal.
Alternatively, if the objective were to remove all BTEX components, the user needs to find
the minimum volume at which all of the Boiling Point Range 4 residual was removed. In
57
-------
this case, an even more optimistic value (56 L-air/g-residual) is required to remove those
constituents.
Finally, a complete summary of the data and results is displayed (Card 18) and the
user asks again, "Is Venting Appropriate?". The basis for the evaluation, as provided by
Hyperventilate, is an estimate of the number of wells needed to achieve a >90% reduction of
the total spill mass in the time desired. Note that this estimate is based on the most ideal
circumstances. Nevertheless, it does give a qualitative sense of the feasibility of using vapor
extraction at the site. On the basis of the default value of 221 L-air/g-residual (-94%
removal), Hyperventilate estimates that 0.2 to 2 vapor extraction wells will be needed to
complete remediation in 1 year. Remember that the range in the number of wells reported
reflects the range in air permeability values at the default well vacuum of 120 inches E^O.
Alternatively, on the basis of the extrapolated value of 165 L-air/g-residual (-90% removal),
Hyperventilate estimates that 0.15 to 1.5 vapor extraction wells are needed to accomplish
remediation. If 100% BTEX removal is required and the user inputs 56 L-air/g-residual, an
estimated 0.05 to 0.5 vapor extraction wells may only be needed to accomplish remediation in
1 year.
In all of these potential scenarios, the calculated results must be compared with
practical considerations such as cost of equipment, available space, etc. In the Roseville case,
the results look promising and SVE appears to be a viable option. If these calculated values
do not seem practical or realistic, however, vapor extraction may not be an appropriate
technology. Alternatively, the user can reevaluate SVE feasibility by revising the expecta-
tions of system performance and then recalculate the results. This iterative type of analysis is
the key to using Hyperventilate effectively. The program can help the user to explore fully
the limitations imposed by both site conditions and vapor extraction technology. "Other
Considerations" suggested by the program continue that theme and help to evaluate special
cases.
Special Case
The Roseville site exhibits characteristics of the contaminants within Soil Unit 3 under
the special case for "Low Permeability Lenses." In this case, Hyperventilate allows an
evaluation of the diffusion-limited vapor transport through a soil matrix. To perform the
calculations for this case (Card H30), the following parameters must be recalled:
• Borehole (well) radius (3.5 inches [8.9 cm]),
• Radius of the contaminated zone (43.5 feet [13.3 m]), and
• Average concentration of residual contamination in soil (542 mg/kg).
In addition, values for contaminant molecular weight (81.3 g/mole), contaminant vapor
pressure (31 mm Hg), and temperature (10 °C) can be directly imported from previous inputs
(Card 10). Hyperventilate can then calculate estimates of gradual reductions in the rate of
contaminant removal from the low-permeability lens and estimates of the thickness of low-
permeability material that is gradually "dried" or stripped of contamination. The program
58
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estimates that the removal rate at Roseville will decline from 53.4 to -1.6 kg/day over a
period of 365 days, with contamination removed from =14.1 feet [4.3 m] of low-permeability
material. The full 5-foot (2-m) thickness of Unit 3 could be stripped of contaminants after
=55 days. Thus, a gross estimate is provided of how removal rates in the low-permeability
lens resulting from airflow in the overlying unit might compare with rates estimated for the
overlying unit itself. Alternatively, a comparison could be made of removal rates from an
imaginary well screened within the low-permeability lens.
Air Permeability Testing
Field tests to determine the soil's permeability to airflow are yet another step in the
analysis of site condition's and the accuracy of the program input parameters (Cards AP2
through 4). Hyperventilate allows the user to evaluate air permeability test data easily and
quickly (Card APS). The program calculates permeability values using two methods. These
methods are based on a governing equation that predicts a straight line for the logarithmic
plot of subsurface pressure versus time. Method A relies on the premise that permeability is
proportional to the slope A of the line. Method B relies on the premise that permeability is
proportional to the y-intercept B (Cards APS through 7). The following parameters must be
determined for both methods:
• Airflow rate of the test,
• Screened interval thickness for the test extraction well,
• Radial distances from the subsurface pressure monitoring locations to the
extraction well, and
• Air pressure at each monitoring location at various times throughout the test.
Method B can be used when either the airflow rate or screened interval thickness is
uncertain.
Actual Test Data
Air permeability tests at the Roseville site were conducted with groundwater monitor-
ing well MW-1 as the extraction well. Monitoring locations included groundwater monitoring
wells MW-2 and MW-3 and soil vapor monitoring points VMP-1, VMP-2, and VMP-3 (see
Figure 3). Actual test data are provided in Table 8. Unfortunately, the screened intervals for
these monitoring locations were not all equivalent. The three soil vapor monitoring points
were all screened in Unit 2. Therefore, airflow between MW-1 and these vapor monitoring
points had to pass through Unit 3, the low-permeability lens. As a result, permeability
estimates based on data from the soil vapor monitoring points cannot be considered represen-
tative of any one unit. Alternatively, all three groundwater wells were screened within soil
Unit 4. Data from these monitoring locations can be considered representative of Unit 4;
however, Unit 2 is the unit of interest. As a compromise, one can assume that because the
59
-------
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60
-------
lithologic descriptions of Units 2 and 4 are essentially the same, the Unit 4 permeability
values can be used for Unit 2.
It is important to run field tests long enough to obtain air permeability values for all
types of soils at the site. The extraction of one complete pore volume from the zone of
interest generally is sufficient. Hyperventilate conveniently allows the user to calculate the
approximate time needed (Card AP3). The user needs the following information to perform
the calculation:
(1) Thickness of the soil layer of interest or the extraction well screened interval
(10 feet [3 m]),
(2) Estimated radius of influence of the extraction well (~20 feet [6 m]), and
(3) Air permeability test flow rate (57 SCFM).
As a result, one obtains a "pore volume" of 3,768 ft3 and a "time to extract a pore
volume" of 0.05 day (72 minutes). Test data provided show that only one test, No. 2, was
run for a sufficient amount of time (170 minutes).
Air Permeability Calculations
After the data are examined to determine any potential problems in its collection, the
user is now prepared to calculate air permeability values for Unit 4 (Card AP8). These values
are determined from Table 8 data, Items 1 through 3 previously listed, and the following
calculations:
(4) Radial distance from MW-1 to MW-2 (109.44 feet [33.36 m]),
(5) Radial distance from MW-1 to MW-3 (86.16 feet [26.26 m]), and
(6) Subsurface pressure versus time data (Table 8).
The resulting air permeability values calculated by Method A are «237 darcys and 149
darcys for MW-2 and MW-3, respectively. Results calculated by Method B are 55 darcys
and 31 darcys, respectively. These data result in a 0.98 coefficient of correlation with the
theoretical pressure drawdown curve (Card AP9). An average range of these values, 193 to
43 darcys, will be used in further calculations.
System Design - Number of Extraction Wells
This final interactive sequence of Hyperventilate provides an overview of all aspects
of vapor extraction system design and allows further refinement of the estimated "Number of
Extraction Wells" (Card SD1) that are likely to be needed to achieve the specified remedi-
ation goals. Inputs and best estimates of critical design parameters for each soil unit can be
organized in a series of descriptive tables (Cards SD2 through 4). Up to this point, only Unit
2 has been considered; therefore, the steps previously described for the other soil units must
61
-------
be repeated. This iteration will require that the calculated spill mass be proportioned accord-
ing to the thickness and average radius of the contaminated zone within each specific soil
unit. In addition, because the contractor has proposed both shallow and deep extraction wells
within Unit 2, that distinction will be made for the final tabulations. Figures 10, 11, and 12
present the appropriate data inputs for each of the soil units. Note that the total calculated
spill mass of 12,224 Ib (5,539 kg) is now substantially less than the initial estimate used in
Card 13. This discrepancy highlights again the need for sufficient data concerning the
distribution of residual contaminants.
The user is now ready to calculate final estimates of the minimum number of
extraction wells. For illustration purposes, separate runs are made with each of the critical air
volumes (221, 165, and 56 L-air/g-residual) previously calculated (Card 17). A 50%
efficiency value is assumed in all cases. The results of each of these trial runs are shown in
Table 9.
TABLE 9. MINIMUM NUMBER OF WELLS BASED ON CRITICAL VOLUME OF AIR SCENARIOS
Critical
Volume of
Air (L/g)
221
165
56
Well Vacu-
um
(In. H2O)
5
5
5
Lithologic Unit
Upper Unit 2
Lower Unit 2
Upper Unit 2
Lower Unit 2
Upper Unit 2
Lower Unit 2
Flow Rate
(SCFM)
30-134
30-134
30 - 134
30-134
30-134
30 - 134
Number of Wells Based
on Critical Volume
0.2 - 0.8
0.6-2.6
0.1-0.6
0.4-1.9
0.0-0.2
0.1 - 0.7
The net result is an estimation, based on the critical volume of air constraint, that at least 1 to
3 extraction wells would be necessary to remediate the site effectively in 1 year. As depicted
in Figure 9, the contractor proposed four wells, arranged in two pairs of deep and shallow
wells. The HyperVentilate-derived minimum number of wells indicates that this approach
could be successful; however, the user should consider that one to three wells is a "best-case"
estimate and that more than 1 year may be required for the proposed design to achieve
complete removal of all but the most volatile fraction of the contaminant mixture.
System Performance
The MPCA eventually approved the construction and operation of a vapor extraction
system at the Roseville site with only minor modifications to the proposed design. MPCA
personnel have provided system performance data that presents an interesting and instructive
critique of the Hyperventilate site review process described. These data covered the first 11
62
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Design Input Parameters
(soil stratigraphy St contaminant characteristics)
Please enter the required information £oreach distinct soil layer. Please
enter the required information {or each distinct soil layer, clicli on the
"Update" button, and then proceed to the next card (i.e. clicli on right
arrow at bottom 1
Description oE
Contamination
Description of
Soil Unit
Figure 10. System design card 2
63
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Design Input Parameters...
Fleas* enter the required information for each
distinct foil layer, and thenproceed to the next card.
getmoreinfo
- use arrow key to mow
between cells
Medium Sand
(_) line Sand
Q S'Ky Smi
O Clayey Silts
Description o£ .
Soil Unit
Pemeab lit/
[darcyj
Design
Vacuum
(inH20J
fKtraction Hell Construction
well
radius
[in]
thickness
™
radius o(
influence
[ftl
Critical
Volume oE
Air"
Efficiency
2
LJL
(in
C to
fine-coarse sand
to
192.5
3.5
IK
221.5
50
i"m«-coarse sand
JO.
192.5
3.5
siUt.osil«j^Mnd_
fJ3Sic-9aC5«1J.ind_
J1<
221.5
50
• Inter or Aoese item list * top tigtrt
•• minimum volume of vapor required to aeWeve remediation
SD3
Figure 11. System design card 3
64
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Design Input Parameters...
Please enter (1) the desired time period Eor remediation. (2)
Hote: • click on any table heading to get more info
- use arrowkey to move between cells
the design gauge vacuum, and then (3) click the "update"
button.
0 @
Description of
Soil Unit
1
4
.....5..
7
8
fill
silt to silty sand
Time Eor
Clean-up
[days]
C
365
365
' C
0
Design
Vacuum
(rnE20)
C
C
C
0
Flowrate per Vapor
Extraction Well
[SCFM]
. . KA
29.92
_39.90
HA
HA
HA
to
..to..
to
_»_.
.to..
to
to
to
HA
133.97
.. 178.62
MA
HA
MA
HA
HA
© 1
' Update ])
Minimum Number of Hells
i»ed on Ar<
HA
. 0,
0:
HA
HA
.._. MA
HA
HA
a Based on Critical
Volume"
HA
J0.2
HA
HA
HA
HA
HA
to
.to..
.Jo...
to
.Jo...
JESL
to
to
HA|
—2
HA
MA
M.A
HA
HA
HA • not oougli input data — minimum volume of vapor requited to achieve remediation
Cigar All Ei^trif s
Return
SD4
Figure 12. System design card 4
65
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months of system operation, ending December 20, 1991. As of September 1992, the system
was still operating. During the reporting period, the system flow rate was maintained at 140
to 190 SCFM, which was somewhat higher than the range used in the Hyperventilate
estimate. The removal rate, however, declined from 469 to 5.9 Ib/day. Based on the
Hyperventilate analyses, a removal rate of at least 30 Ib/day was necessary to achieve full <
remediation within the 1 year desired. Actual system removal rates decreased below this
desired level after only 17 days of operation. This illustrates the importance of viewing
Hyperventilate estimates as "best-case" scenarios.
As of the final available monitoring report, a total of 7,369 Ib of hydrocarbons
(gasoline) had been recovered. Spill mass estimates between 12,225 and 19,840 Ib were used
in the Hyperventilate analyses. System performance results indicated that between 37 and
60% of the calculated spill mass was removed in 11 months. Once again, this points out the
importance of sufficient and good quality data for estimating spill mass prior to initiation of
vapor extraction system planning. Otherwise, it is difficult to design the system appropriately
and measure success as remediation progresses.
At the start of .system operation, the effluent benzene concentrations were reported to
be 180 ppmv. The concentrations had decreased to 1 ppmv, however, by the end of the
reporting period. The Hyperventilate Model Predictions (Card 17) apparently show that
virtually all of the first two Boiling Point Range compounds (propane to benzene) had been
removed by that point. Hyperventilate indicates that contaminant removal will be less
efficient as system operation continues. The MPCA depicted this phenomenon in a graphical
plot of total hydrocarbon removal as a function of time. The plot is very steep in slope
during the first 20 days of system operation and then becomes fairly gently sloped, averaging
about 330 Ib/month for the remainder of the reporting period.
These monitoring data generally indicate that actual system performance is lagging
behind the "best-case" scenarios suggested by the Hyperventilate analysis despite operation at
significantly higher flow rates than those .used in the software calculations. Working back
through the software with this hindsight might point to design changes and or operational
changes that could be made to improve performance or increase efficiency. For instance,
after removal of the initial vapor-phase contaminant concentrations in the unsaturated zone,
flow rates could have been slowed down because they apparently greatly exceeded the ability
of residual contaminants in the vadose zone to re-establish equilibrium conditions. Similarly,
Hyperventilate hindsight can suggest areas where important details may have been over-
looked in the system planning and design stages or where information was insufficient to
adequately anticipate system performance. For instance, the residual contaminant mass at the
Roseville site may have been significantly more degraded or "weathered" than the "weath-
ered" gasoline used by default in the software (i.e., volatiles comprised a lesser fraction of the
contaminant mixture at the outset). Therefore, a more qualitative and quantitative analysis of
the contaminant mixture probably should have been obtained as part of the contractor's
feasibility analysis.
66
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In general, Hyperventilate can be an instructive, functional tool in the critical analysis
of a proposed vapor extraction system design. Not only are the important concepts, approach-
es, processes, and equipment described in an overview along with the tutorial sequences of
the program, but the interactive sequences .help to direct and, expedite a focused iterative
review process. Further, the program identifies specific data needs that are critical to good
planning and appropriate design and operation. Once a system is deployed, Hyperventilate
can continue to be used to troubleshoot performance relative to a standard of what is possible
under ideal circumstances. Most importantly, it can provide a useful frame of reference for
contractor/site manager discussions and perhaps, as a result, increase their system knowledge.
67
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SECTION 4
MODEL ANALYSIS
A modeling analysis of Hyperventilate was conducted to address two considerations:
(1) variations in output parameters were identified over a range of input parameter values, and
(2) the sensitivity of each output parameter to changes in input parameter values was
addressed. The purpose of this analysis was to identify those site conditions and system
design considerations that most strongly affect the potential success of a vapor extraction
system at a given site and to identify those parameters over which a system designer can
exert some measure of control. This section presents a discussion of these two modeling
analyses.
PARAMETER RESPONSE TEST
The parameter response test was conducted to ensure that accurate solutions are
generated for all of the equations used in the software. For each parameter analysis, the
target input parameter was varied over a sufficient range of values to allow an observable
trend in the output parameters. All other input parameters were held constant. The results
presented in the tables and text are rounded off. The value for the minimum number of wells
was set at the next whole integer.
In this exercise, the following baseline input parameter values were selected to reflect
"average" site conditions:
• Permeability
• Venting Well Radius
• Radius of Influence
• Interval Thickness
• Extraction Well Vacuum
• Temperature
• Contaminant Composition
• Estimated Spill Mass
• Desired Remediation Time
• Radius of Contamination
• Average Contaminant Concentration (in soil)
• Contaminant Molecular Weight
10 darcys
4 inches
40 feet
10 feet
120 inches
20 °C
"Fresh" Gasoline
10,000 kg
100 days
60 feet
1,000 mg/kg
65 g/mole
68
-------
• Contaminant Vapor Pressure
• Air Permeability Test Flow Rate
• Monitoring Point Distance
• Critical Volume of Air
• Efficiency
"Is Venting Appropriate?" (Cards 8 through 18)
366 mm Hg/0.482 atm
120 SCFM
50 feet
37 L/g
50%
Permeability--
Permeability was the first parameter tested. As shown in Figure 13, there is
essentially a one-to-one correspondence between changes in permeability and changes in flow
rate and maximum removal rate. This relationship is expected based on Equation 2. There is
an inverse relationship between permeability and the minimum number of wells estimated on
Card 18 ("Is Venting Appropriate?"): the number of wells required is reduced by a factor of
10 with every order-of-magnitude increase in permeability. The relationship between
permeability and these output parameters is intuitive. Increased permeability allows for
greater flow rates, thereby resulting in higher removal rates and the need for fewer wells to
achieve the desired result in a fixed amount of time. Subsurface permeabilities at a UST site
are generally not applicable to other situations.
Well Radius--
Following permeability testing, the venting well radius was varied. As shown in
Figure 14, over an input parameter of 0.25 to 16 inches, flow rate increases by an average
factor of 1.16 for every doubling of the venting well radius. Over the range of input
parameters used, this factor increases from 1.16 to 1.26 as a natural logarithmic function (see
Rw in Equation 2). Based on the range of well radius values used, the minimum number of
extraction wells required remains at one. An increase in the radius of the extraction well will
result in a slight increase in the flow rate, thus decreasing the time required for remediation.
This may result in considerable savings in operation and maintenance costs, depending on the
time required to complete remediation.
Radius of Influence--
Radius of influence was the next input parameter tested. Results are shown in Figure
15. Over the range of 10 to 160 feet, flow rate decreased by an average factor of 0.84 for
every doubling in the estimated radius of influence. The minimum number of wells required
remained at one. The radius of influence is dependent on the air permeability of the site
subsurface and, to a lesser extent, the vacuum applied to the vapor extraction well. Larger
radii of influence reduce flow rates by distributing the applied well vacuum over a larger
volume of material. Although additional wells may be required for sufficient coverage,
practitioners may wish to constrain the radius of influence at a site through the use of air inlet
wells in order to enhance well efficiency.
Interval Thickness—
The final input parameter tested on Card 8 (Flow Rate Estimation) was interval
thickness. As shown in Figure 16, flow rate doubles with each doubling of the interval
69
-------
1000
0.01
0.001
0.01 0.1 1
Permeability darcys
10
Permeability
(darcys)
0.001
0.01
0.1
1.0
10.0
Flow Rate
(SCFM)
0.012
0.12
1.2
11.8
118
Min. No.
of Wells
6348
529
54
5
0.5
Figure 13. Relationship between permeability and flow rate.
70
-------
170
110
100
10J2
Well Radius, cm
20.3
40.6
6 8 10
Well Radius, in.
14
16
Well Radius
cm in.
5.1 2.0
10.2 4.0
20.3 8.0
40.6 , 16.0
Flow Rate
(SCFM)
103
118
138
166.7
Figure 14. Relationship between well radius and flow rate.
71
-------
Radius of Influence, m
12.2 24.4
48.8
174
162 —
90
20 40 60 80 100 120 140 160
Radius of Influence, ft
Change m
m
3.0
6.0
12.2
24.4
48.8
Radius of Influence
ft
10
20
40
80
160
Change in
Flow Rate (SCFM)
167
138
118
103
92
Figure 15. Relatonship between the radius of influence and flow rate.
72
-------
Interval Thickness, m
o.e
12.2
Figure 16. Relationship between interval thickness and flow rate.
24.4
O.4 1.5 3.1
900 —
750-
600 -
450 ~
300 ~
150 -
I
J 0.
— • — Flow Rate
X
D 1
S
0 2(
/
D 3(
/
D 4(
/
S
) 5
/
0 6
/
^
D 70 8C
Interval thickness, ft
Interval Thickness
m ft
Flow Rate Min. No.
(SCFM) of Wells
0.4 1.25 15 5
0.8 2.5 30 3
1.5 5 59 2
3.0 10 118 1
6.1 20 237 1
12.2 40 474 1
24.4 80 947 1
73
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thickness from 1.25 to 80 feet. As was the case with permeability, this relationship is
expected on the basis of Equation 2. Because this equation generates solutions in terms of
the flow rate per unit thickness (Q/H), it assumes uniform distribution of the flow rate over
the entire screened interval. In practice, with large screen intervals, flow rates are likely to be
variable over the length of the screen, resulting in reduced vapor flow and removal along the
length of the screened interval. As a result, the greatest vapor extraction well efficiency is
likely to be realized through the use of small screened intervals. Smaller screened intervals,
however, may require the installation of additional extraction wells, screened to varying
depths, to intersect the entire zone of contamination effectively.
Well (Gauge) Vacuum--
In Card 8 (Flow Rate Estimation), the flow rate is calculated over a range of six
vacuum values ranging between 5 and 120 inches H2O. Users have the option of selecting an
alternate well vacuum. With this matrix, users can estimate the flow rate if they knows the
optimal well vacuum of the blower or vacuum pump that the contractor normally uses.
Alternatively, users can easily determine the well vacuum required to achieve the desired flow
rate if they know the capacity of the vapor treatment units or the desired removal rate.
The flow rate increases with increasing well vacuums over a 5- to 360-inch H2O
range, as is shown in Figure 17. The relationship between well vacuum and flow rate is less
straightforward than for the previous input parameters. At low well vacuums (<100 inches
H^O), there is a one-to-one correlation between changes in well vacuum and flow rate. As
well vacuums are further increased, however, the increase in flow rate lags behind the well
vacuum increase. This is due to the larger pressure reduction and resulting difference
between actual flow rate (ACFM) in Equation 2 and "standard" flow rate (SCFM) in Equation
3. •' ' "• .•"" •' ' : ' ; ' / •'.""'" •'
Temperature— ^ ........
Temperature was the first input parameter varied on Card 10 (Vapor Concentration
Estimation - Calculation). Table 10 shows that the number of output parameters affected by
temperature is much larger than for previous input parameters.
TABLE 10. "IS VENTING APPROPRIATE?" RESPONSE TO TEMPERATURE CHANGES
Temp.
<°C)
0
5
10
15
20
30
Calc. Vapor
Pressure
(aim)
0.23
0.28
0.34
0.41
0.48
0.67
Calc. Vapor Cone.
(mg/L)
632
766
922
1,102
1,312
1,828
Sat. Vapor Cone, at
Tlme=0 (mg/L)
679
807
954
1,122
1,312
1,767
Min. Vol. to Remove
>90% Initial Residual
(L-alr/g-resldual)
199
141
101
73
. 37
21
Min. No. of
Wells
3
,3
2
2
1
1
74
-------
280
240
200
160
120
80
40
1016.0 Well Vacuum, mm H_O
508.0
254.0
,S7i' 152f'9 ^y-9 , • a*?'7 9143.6
-
-
-
-
-
-
-
^
/
\ I 1 1 1
0 E
/
^
1 1 M
0 11
Flowf
X
^
1 1 1 1
X> 1E
j
"iaie .;
>x
^
I I 1 1
0 20
x"
1 1 1 1
0 2E
^
Mil
50 3C
^
i i i i
ro 35
1 1 1 1
iO 4CK
Well Vacuum, in H O
Well
mm HO
127.0
254.0
508.0
1016.0
1523.9
3047.9
6095.7
9143.6
Vacuum
in. H20
5
-. . 10
20
40
60
120
240
360
Flow Rate
(SCFM)
6
11 -
23
44
64
, 118
196
232
Figure 17. Relationship between well vacuum and flow rate.
75
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Although temperature was entered in terms of °C, it is used in Equation 2 in Kelvin*
Incremental temperature increases from 5 to 30 °C (278 to 303 K) resulted in increases in
vapor pressure and saturated vapor concentration. At the same time, decreases resulted in the
minimum volume required to remove >90% of the initial residual spill mass, the minimum
number of wells, the minimum volume value, and the minimum number of wells; thus,
temperature changes have a tremendous impact on the effectiveness of system operations.
Contaminant Composition--
This is the last input parameter that impacts multiple output parameters in this stack.
As discussed previously in Section 2 under "Input Parameter Requirements, Data Sources, and
Software Constraints," the user has three options for testing this parameter. Users may use
one of the two default compositions provided in the software, or they may enter a unique
distribution based on laboratory analysis of samples taken from a specific site. Table 11 was
developed to provide the user with a snapshot of how the various output parameters are
affected by contaminant composition. One of the following compounds was selected to
represent each of the boiling point ranges used in the software: n-butane, n-hexane, n-
heptane, n-octane, and n-nonane.
TABLE 11. "IS VENTING APPROPRIATE?" RESPONSE TO
CONTAMINANT COMPOSITION CHANGES
B.P. Range
1, n-butane
2, n-hexane
3, n-heptane
4, n-octane
5, n-nonane
Calc. Vapor
Pressure
(atm)
2.11
0.16
0.046
0.014
0.0042
Calc. Vapor
Cone.
(mg/L)
5,096
; 537
192
67
22
Min. Vol. to Remove >90%
Initial Residual
(L-air/g-residual)
0.18
1.57
4.96
13.54
40.18
As shown in the table, a change from a lower to a higher boiling point contaminant
results in a decrease in vapor pressure and vapor concentration. There is also a corresponding
increase in the minimum volume of ah- required to remove greater than 90% of the initial
mass of contamination.
Estimated Spill Mass--
The desired removal rate is the only output parameter affected by estimated spill mass.
Both parameters are shown on Card 13 ("Is Soil Venting Appropriate?"). When the desired
remediation time is held constant, the desired removal rate increases by the same magnitude
as any increase in the estimated spill mass. The realistic range of the spill mass is from 1 to
107kgorlb.
76
-------
Desired Remediation Time--
As with the Estimated Spill Mass, the only output parameter this input parameter
affects is the desired removal rate. Both parameters are shown on Card 13 ("Is Soil Venting
Appropriate?"). When the estimated spill mass is held constant, the desired removal rate
decreases by the same magnitude as any increase in the desired remediation time. A
reasonable range for remediation time is from 30 to 720 days.
"Other Considerations/Liquid Layers" (Cards 19 and H29)
The cards address the situation in which a layer of liquid hydrocarbons rests either on
an impermeable strata or on the water table. Under both of these conditions, the effectiveness
of a vapor extraction system depends on the rate at which vapor-phase constituents diffuse out
of the liquid hydrocarbon layer. Vapof-phase diffusion will be constrained by the mass
transfer resistance between the liquid layer and the unsaturated zone. This mass transfer
resistance is best overcome by imposing sufficient airflow rates to ensure that disequilibrium
conditions are maintained for vapor-phase constituents between the unsaturated zone and the
liquid layer.
/ - '
Permeability--
This was the first parameter manipulated on Card H29 (Help: Boundary Layer
Equations - Calculations). Changing permeability from 0.01 to 100 darcys resulted in a
corresponding change in relative efficiency from 100 to 2.2%. Generally there is a 32%
decrease in relative well efficiency for every order-of-magnitude increase in permeability.
This is a direct result of the position of permeability in Equation 8, which is used to calculate
well efficiency. At all permeabilities lower than 0.05 darcy, the program sets the relative
well efficiency at 100%.
Equation 8
where t\
D
k
H
PW
Rj
-------
which resulted in a change in relative efficiency from 55 to 1.8%. Each increase in screened
interval thickness is matched by a corresponding decrease in relative well efficiency. This
relationship is shown in Equation 8.
Venting Well Radius of Influence-
The computations on Card H29 (Help: Boundary Layer Equations - Calculations)
showed that the relative well efficiency increased in proportion to increases in the venting
well radius of influence. The radius of influence was varied from 10 to 160 feet, and the
relative efficiency changed from 5.8 to 7.8%. The increase in well efficiency diminishes with
progressively larger values of the ventine well radius of influence. This characteristic results
from the In (Rj/Rw) component of Equation 8.
Venting Well Radius—
The relationship between venting well radius and radius of influence in Equation 8 is
again apparent when this input parameter was varied on Card H29 (Help: Boundary Layer ;
Equations - Calculations). The well radius was changed from 2.0 to 16.0 inches and the
relative efficiency from 7.4 to 5.8%. Relative well efficiency decreases with a larger venting
well radius, and the'decline in the well efficiency accelerates with progressively larger values*
of the venting well radius.
Applied Well Vacuum--
Increases in the vacuum applied to a well on Card H29 (Help: Boundary Layer
Equations - Calculations) reduce the relative well efficiency. The wellhead vacuum was
varied from 10 to 360 inches I^O, and the relative efficiency decreased from 24 to 4%.
Radial Width of Contaminated Zone-
Based on calculations determined using Card H29 (Help: Boundary Layer Equations -
Calculations), the user found that when the radial width of the contaminated zone was
increased, the relative well efficiency experienced a corresponding increase of equal
magnitude. Radial width was varied from 5 to 240 feet, and the corresponding relative
efficiency changed from 0.6 to 27.6%.
"Other Considerations/Low Permeability Lenses" (Cards 19 and H30) >• n
These cards address the situation in which residual hydrocarbons are contained in a
lens of material that possesses a lower permeability to air than does overlying or underlying
materials. This lower permeability layer could be silt within a sand unit, or a fine sand in a
gravel. In this situation, vapor flow, resulting from the vacuum on an extraction well, will
preferentially pass above and/or below the layer of lower permeability material rather than
through the unit. As a result, the removal effectiveness of the vapor extraction system will be
limited by the rate at which vapor-phase constituents diffuse out of the lower permeability
material. Maintaining disequilibrium conditions for vapor-phase constituents between the
lower permeability material and the rest of the unsaturated zone will accelerate vapor-phase
diffusion.
78
-------
On Card H30, process variables employed earlier in the software instructions can be
used or adjusted to reflect new information or to test various design options. In contrast,
temperature and constituent properties (molecular weight and vapor pressure) are inextricably
linked together. As a result of these relationships, the impact of changes in constituent
properties on removal rates and the thickness of the "dried-out" layer was not tested by
varying one parameter at a time while the other two parameters were held constant. Instead,
constituent vapor pressure was allowed to act as a dependent variable while constituent
molecular weight was varied. Both constituent molecular weight and constituent vapor
pressure were allowed to act as dependent variables while temperature was varied. To
accomplish this, contaminant molecular weight and temperature were varied on Card 10 and
the calculated outputs from this card were imported to Card H30.
Venting Well Radius-
Increasing the venting well radius on Card H30 (Help: Low Permeability Lenses -
Calculations) had no impact on the calculations of the thickness of the "dried-out" layer over
time. Incremental increases in the venting well radius from 2.0 to 36.0 inches marginally
decreased the Day 1 removal rate from 418.8 to 417.7 kg/day. A similar minuscule reduction
in the removal rate is recorded for the Day 1080 removal rate.
Radial Width of Contaminated Zone-
The computations on Card H30 (Help: Low Permeability Lenses - Calculations)
showed that increases in the radial width of the contaminated zone had no impact on the
thickness of the "dried-out" layer over time. Each doubling in the well radial width of the
contaminated zone from 5 to 240 feet resulted in an increase in the Day 1 removal rate from
3 to 6,700 kg/day and an increase in the Day 1080 removal rate from 0.09 to 203 kg/day.
When the radial width of the contaminated zone is much larger than the venting well radius,
the estimated removal rates will increase by the square of the increase in the radial width of
the contaminated zone.
Residual Contaminant Level--
This was the final process variable to be varied on Card H30 (Help: Low Permeability
Lenses - Calculations). Each tenfold increase in the residual contaminant level increased the
removal rates by a factor of 3. The thickness of the "dried-out" layer at any time becomes
smaller by the same factor. Varying the residual contamination level from 1 to 100,000
mg/kg produced the following results:
Removal Rate Day 1: 13 to 4,189 kg/day
Removal Rate Day 1080: 0.4 to 127 kg/day
Thickness of Dried-Out Layer Day 1: 16 to 0.05 foot
Thickness of Dried-Out Layer Day 1080: 518 to 1.6 feet.
Contaminant Molecular Weight and Vapor Pressure-
This was the only contaminant property variable changed on Card H30 (Help: Low
Permeability Lenses - Calculations). As shown in Table 12, increases in contaminant
79
-------
molecular weight, imported from Card 10, result in decreased contaminant vapor pressure,
removal rates, and thickness of the "dried-out" layer.
TABLE 12. "LOW PERMEABILITY LENSES" RESPONSE TO
CONTAMINANT MOLECULAR WEIGHT CHANGES
Contaminant
Molecular
Weight
(g/mole)
58.10
65.43
86.2
95.0
100.2
114.2
Contaminant
Vapor Pressure
(mm Hg)
1603
366.6
121.6
47.9
35.0
10.6
Removal
Rate on
Day1
(kg/day)
825
418.8
276.9
172.3
160.0
94.3
Removal Rate on
Day 1080
(kg/day)
25
12.7
8.4
5.3
4.8
2.9
Thickness of
"Dried-Out"
Layer on
Day1
(feet)
0.98
0.5
0.3
0.21
0.19
0.11
Thickness
of "Dried-
Out" Layer
on Day 1080
(feet)
32
16.4
10.8
6.8
6.3
3.7
Changes in contaminant vapor pressure in response to changes in contaminant molecular
weight are the product of Henry's law, the ideal gas law, and Raoult's law. For single-
component contaminants, vapor pressure declines exponentially with increases in molecular
weight. The mixing effect of multiple components results in a vapor pressure for "fresh"
gasoline (molecular weight at 20 °C = 65.43) and "weathered" gasoline (molecular weight at
20 °C = 84.97) that is somewhat lower than would be anticipated from their respective
molecular weights. Removal rates, the thickness of the "dried-out" layer, and the contaminant
molecular weight all vary by the same amount.
Temperature—
As stated previously, this input parameter directly affects both contaminant properties
on Card H30 (Help: Low Permeability Lenses - Calculations). Temperature- variations and the
resulting calculations imported from Card 10 for use in the Card HBO calculations in Table 13
show that each increase in temperature causes a corresponding increase in the contaminant
properties, removal rates, and thickness of the "dried-out" layer.
TABLE 13. "LOW PERMEABILITY LENSES" RESPONSE TO TEMPERATURE CHANGES
Temperature
(°C)
0
5
Contaminant
Molecular Weight
(g/mole)
60.4
61.7
Contaminant
Vapor Pressure
(mm Hg)
178
215
Removal Rate
on
Day1
(kg/day)
290
320
Removal
Rate on
Day 1080
(kg/day)
8.9
9.7
Thickness of
"Dried-out"
Layer on
Day)
(feet)
0.35
0.38
Thickness of
"Dried- Out-
Layer on Day
1080 (feet)
11.4
12.5
80
-------
Temperature
<°C)
10
15
20
30
Contaminant
Molecular Weight
(g/mole)
62.9
64.2
65.4
67.0
Contaminant
Vapor Pressure
(mm Hg)
259
309
367
508
Removal Rate
on
Day1
(kg/day)
351
384
418
494
Removal
Rate on
Day 1080
(kg/day)
10.7
11.7
12.7
15.0
Thickness of
"Dried-out"
Layer on
Day1
(feet)
0.42
0.46
0.5
0.6
Thickness of
"Dried- Out"
Layer on Day
1080 (feet)
13.7
15.0
16.4
19,3
The increase in contaminant molecular weight is the only response that seems abnormal. This
result is a function of the manner in which the software performs the computations associated
with Equation 2. Through the summation process, this equation treats a complex mixture of
compounds as a single component in order to calculate an average molecular weight for the
mixture. With each temperature change, the vapor pressures of the individual constituents in
the mixture do not change equally. As a result, increases in temperature result in a greater
contribution from the higher molecular weight compounds in the calculation of the average
molecular weight of the mixture.
Air Permeability Test Stack (Cards 21. AP3. and APS)
Only one of the tables in Card APS (Air Permeability Test - Data Analysis [cont.])
was used to evaluate the input parameters in this stack. The hypothetical field data readings
used in Table 14 were: 0.1 inch H2O at 9 minutes, 0.2 inch H2O at 11 minutes, 0.2 inch H2O
at 15 minutes, 0.4 inch H2O at 23 minutes, 0.7 inch H2O at 30 minutes, 1.3 inches H2Q at 40
minutes, and 2.8 inches H2O at 100 minutes. Thi3 set of data was used in the following
parameter response analyses.
TABLE 14. "AIR PERMEABILITY TEST' RESPONSE TO SOIL LAYER THICKNESS CHANGES
Soil Layer Thickness
(feet)
2.5
5.0
10.0
20.0
40.0
Pore Volume
(ft3)
3,768
7,536
15,072
30,144
60,288
Time to Extract a
Pore Volume (days)
0.02
0.04
0.09
0.17
0.35
Air Permeability by
Method A (darcys)
395
197
99
49
25
Soil Layer (Interval) Thickness--
This was the first input variable to be manipulated on Card AP3 (Air Permeability
Test - Instructions). As shown in Table 14, changes in soil layer thickness result in equal
81
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changes in the calculated pore volume and calculated time needed to extract a pore volume.
Changes in soil layer thickness also have a (direct, inverse impact on air permeability
calculated by test analysis Method A on Card AP8 (Air Permeability Test - Data Analysis
[cont.]). Soil layer thickness did not affect the air permeability measurements calculated bv
MethodB.
Estimated Radius of Influence-
This input parameter was used only on Card APS (Air Permeability Test - ;
Instructions) to compute the pore volume and the amount of time needed to extract a pore
volume. It had no bearing on the results of the air permeability test data analysis. Varying
the radius of influence from 10 to 80 feet caused the pore volume to change from 942 to
60,288 ft3 and the time needed to extract a pore volume from 0.1 to 0.35 day. This variation
is a direct result of the standard volumetric calculation.
Air Permeability Test Flow Rate-
This was the final input variable to be changed on Card APS (Air Permeability Test -
Instructions). Changes in the test flow rate have no impact on the calculated pore volume.
Any change in the test flow rate did have the expected equal, inverse effect oh the calculated
time required to extract a pore volume. Changes in the test flow rate were matched by equal
changes in air permeability calculated by test analysis Method A on Card APS (Air
Permeability Test - Data Analysis [cont]). The test flow rate does not affect the air
permeability results calculated by Method B.
Radial Distance of Monitoring Point-
This input variable is unique to Card APS (Air Permeability Test - Data Analysis
[cont.]). Changes in this parameter had no impact on the air permeability measurements ''••
calculated by Method A. Changes in the radial distance of a monitoring point resulted in a
change in air permeability calculated by test analysis Method B that is equal to the square of
the change in the monitoring point distance.
System Design Stack (Cards 24 and SD2 through 4)
Contaminant Radius- „ i; m
This is the first Contaminant Distribution input variable on Card SD2 (Design Input)."'
As shown in Table 15, changes in the contaminant radius result in changes in the calculated
total mass equal to the square of the change in the contaminant radius. The average
contaminant concentration (Average Cone. mg/kg...Card SD2) used for these calculations was
1,000 mg/kg.
82
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TABLE 15. "SYSTEM DESIGN" RESPONSE TO CONTAMINANT RADIUS CHANGES
Contaminant
Radius
(feet)
10
20
40
60
120
Calculated
Total Mass
(kg)
151
604
2,418
5,441
21,766
Flow Rate per
Extraction Well
(SCFM)
118
118
118
118
118
Minimum No. of
Wells Based
on Area
1
1
1
3
9
Minimum No. of
Wells Based on
Critical Volume
' -'.1'.- • ' '
1
1
1
3
, ; Changes in the contaminant radius had no impact on the flow rate of the extraction
wells. The relationship between contaminant radius and total mass is simply the standard
volumetric calculation.
';?.,".; ... - - s ... , "' . , " ' •' • ?
Changes in the number of wells based on area and contaminant radius are expressed in
Equation 5. When the contaminant radius is smaller than the radius of influence, the ;
minimum number of wells will be one. As the value of the contaminant radius becomes
increasingly larger, the increase in the minimum number of wells will approach the square of
the increase in me contaminant radius. In Equation 4, the relationship between the
contaminant radius and the minimum number of wells based on critical volume is tied to the
calculated total mass (Mspill). When Mspill is very small (<10 kg) relative to the flow rate
(Q^ell), the minimum number of wells will be one. As larger contaminant radius values are
Used* me minimum number of wells will increase significantly.
Contaminant Interval Thickness—
This is the second of three input variables on Card SD2 (Design Input) for computing
total contaminant mass. Changes in the contaminant interval thickness result in equal changes
in the calculated total mass. The relationship between contaminant interval and calculated
tot;al fnass stems from the remainder of the standard volumetric calculation that pertains to the
radius;, Changes in the contaminant interval thickness have no impact on either the flow rate
per extraction well or the minimum,number of wells based on area. The relationship between
qhanges in the contaminant interval thickness and the minimum number of wells based on
critical volume is again tied to the mass of contaminant.
Average Contaminant Concentration—
This is the final contaminant distribution input variable on Card SD2 (Design Input).
Changes in the average contaminant concentration result in equal changes in the calculated
total mass. Average contaminant concentration represents a scaling factor applied to the
standard volumetric calculation discussed previously. Changes in the average contaminant
concentration have no impact on either the flow rate per extraction well or the minimum
83
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number of wells based on area. A very small average contaminant concentration (<100
mg/kg) results in a spill mass relative to the flow rate (QweU), and the calculated minimum
number of wells based on critical volume will be one. As larger average contaminant
concentration values are used, the minimum number of wells (based on critical volume) will
increase at the same rate as the mass of contamination spilled.
Critical Volume of Air~
Although this input parameter on Card SD3 (Design Input) is not a true independent
variable, it is displayed on Card 17 as a result of the "more detailed" calculations using
temperature and contaminant composition that were performed on Card 16 (Model
Predictions). As such, this parameter is used to depict changes in flow rate and the minimum
number of wells in the system design stack resulting from changes in temperature and/or
contaminant composition. The range of values utilized here is designed to encompass the
previously calculated range of values for determining the critical volume of air. Increases in
the critical volume of air cause corresponding equal increases in the minimum number of
wells. Varying the critical volume of air from 0.1 to 450 L/g results in a change in the
minimal number of wells from 1 to 8.
Efficiency--
This is the final input parameter on Card SD3 (Design Input). Although not a true
independent variable, efficiency is derived based on an evaluation of special cases utilizing
Card 19 (Other Considerations). As such, this parameter is used to adjust the expected
effectiveness of the extraction wells as a result of dilution effects, the presence of liquid
layers or low-permeability layers, and the potential for groundwater upwelling. Increases in
the well efficiency cause corresponding equal and inverse decreases in the minimum number
of wells based on the critical volume of air. The minimum number of wells based on area is
not affected by changes in well efficiency. A change in the relative efficiency from 1 to 30%
resulted in a change in the minimum number of wells from 25 to 1.
Time for Cleanup—
This is the only input parameter on Card SD4 (Design Input) and the final input
parameter for the system design stack. Increases in the time allotted for cleanup result in
corresponding equal and inverse decreases in the minimum number of wells based on the
critical volume of air, which can be an important economic consideration. Neither the flow
rate per extraction well nor the minimum number of wells based on area is affected by
changes in cleanup time. Varying the cleanup time from 30 to 360 days resulted in a' change
in the minimum number of wells from 2 to 1.
SENSITIVITY ANALYSIS
The purpose of this section is to focus the user's attention on the sensitivity of each
output parameter as it pertains to the final estimate of the minimum number of extraction
wells required. This evaluation will also indicate the feasibility of using an SVE system.
This section identifies the extent to which each site and system design characteristics affect
the feasibility of a vapor extraction system and identifies those parameters over which a
84
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system designer can exert some measure of control. Each of the input parameters in the
system design stack is addressed with a brief discussion on how to control that parameter's
value.
Contaminant Radius™
The minimum number of wells calculated on the basis of area (NA) and critical
volume (Ncv) will both increase by the square of the increase in the radius of contamination.
The only control that can be exerted on the radius of contamination is the
determination as to what constitutes the limits of contamination. The radius of contamination
will have one value if it is defined as the point at which no detectable contamination is found.
It will have another value, however, if the radius of contamination is defined as X mg/kg total
petroleum hydrocarbons (TPH). This definition could have important economic ramifications
on the selection of SVE.
Contaminant Interval Thickness—
Although the number of wells required should not be affected by interval thickness,
the flow rate and possibly the wellhead vacuum will be. Once again, the only control that
can be exerted over the contaminant interval thickness is the determination as to what
constitutes the limits of contamination.
Average Contaminant Concentration--
Essentially, Ncv will increase or decrease in direct proportion to changes in the
average contaminant concentration (Cave). The relationship between Cave and Ncv is tied to
the spill mass Ms_jU. Here again, the user can only exert the defined level of control. In this
case, the average contaminant concentration will differ only for changes in TPH, total BTEX,
benzene, or some other range of constituents.
Permeability--
As shown in the preceding section, the minimum number of wells required at a site,
based on the critical volume of air (Ncv), is decreased by an amount equal to the increase in
permeability. That is, if the permeability value is doubled, N^v will be halved. In Section 1,
it was indicated that permeability could vary by as much as several orders of magnitude
across a site. Because the appropriate distribution of extraction wells will be strongly
influenced by lateral variations in permeability, it is important to know the distribution of
these permeability changes.
Design Vacuum--
Design vacuum (Pw) and Ncv are joined through flow rate (Qweu). At low Pw
values, an increase in the design vacuum results in a decrease in Ncv by approximately an
equal magnitude. The result of the "compressibility effect" (discussed earlier in "Is Venting
Appropriate?" (Cards 8 through 18: Well [Gauge] Vacuum) is to progressively accelerate the
decrease in Ncv as Pw values approach atmospheric pressure (406 inches H2O).
85
-------
Because Ncv is so closely tied to the extraction well vacuum, it can be a sure means
of minimizing the number of wells used at a site. A system's design vacuum initially will be
constrained by the capacity of a side waste stream treatment unit for handling the early
contaminant vapor concentrations. If extraction well construction can be made suitable to
prevent surface breakthrough, the well vacuum probably can be increased gradually to
maximize system removal efficiency.
Extraction Well Radius--
The extraction well radius (R\y) is also tied to Ncv through Qweu. Increasing the
well radius results in decreased Ncv values. As a result of this natural log function, the well
radius has no impact on the minimum number of wells based on area. Because price
differentials between well construction materials of different diameters are minimal, the
system designer should consider using larger borehole and pipe diameters as an economical
means to possibly maximize vapor-phase recovery and minimize the number of extraction
wells required.
Extraction Well Screen Thickness-
The extraction screen thickness (Hs) is also tied to Ncv through Qweu. Increases in
Hs result in equivalent increases in the extraction well flow rate. This would cause an equal
decrease in Ncv. As the software indicates on Card 19 (Other Considerations) and Card H23
(Help: 6a, Dilution Effects [Bypassing]), however, if the thickness of the screened interval is
greater than the thickness of the contaminated soil thickness or is not matched to the
contaminated interval, then fewer vapors will flow to that part of the screen outside the zone
of contamination than will be saturated in vapor-phase contaminants. This effectively reduces
the well's efficiency to the percentage of the screened interval in the zone of contamination.
Because extraction vapor concentrations tend to run at 10 to 50% of saturation, every effort
must be made to accurately match the screened interval to the zone of contamination in order
to maximize extraction well efficiency. Screen thickness has no impact on the minimum
number of wells based on area.
Critical Volume of Air— ~,
As identified during the system design stack discussion, the critical volume of air r
required to remove 1 gram of initial residual contamination (Vcritical) is a synthesis of the
temperature and contaminant composition input parameters entered on Card 10 (Vapor
Concentration Estimation - Calculation). Ncv will vary in direct response to and by the same
magnitude as changes in Vcritjcai An increase in temperature resulted in a decrease in
^critical* Even at ^ow temperatures (0 to 10 °C), a 5-degree temperature increase resulted in a
30% reduction in Vcriticaj, which translates into an equal reduction in Ncv. In contrast,
^critical' an^ as a KS[dt NCV' increases with changes in contaminant composition toward
higher boiling point (and higher molecular weight) compounds.
Although designers of vapor extraction systems cannot control contaminant
composition, they can control subsurface vapor temperatures or adjust system operations to
take into account the impact of temperature. When state regulations permit, one fairly
economical means of increasing subsurface vapor temperatures is through the reinjection of
86
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vapor extraction system effluent air that has passed through a thermal treatment unit.
Alternatively, Sresty et al. (1992) has recently demonstrated the effectiveness of in situ radio
frequency (RF) heating in increasing soil temperatures to the 150 to 200 °C range in order to
remove polycyclic aromatic hydrocarbons and phenols. This method is still developmental,
however, and it is likely to be several years before it is an economically feasible approach to
the use of hydrocarbons. Also, the removal rates of contaminant constituents are dependent
on their boiling points. As a result, as vapor extraction proceeds at a site, the residual
subsurface contaminant composition becomes increasingly dominated by higher boiling point
(less volatile) constituents.
Efficiency--
As mentioned previously in the extraction well screened thickness discussion, factors
that can affect well efficiency are addressed on Card 19 (Other Considerations) of the
software. Changes that increase well efficiency cause corresponding equal decreases in NCy.
Changes to the expected extraction well efficiency have no impact on NA.
System designers can exert a large degree of control over well efficiencies. In
reference to Card 19, designers of vapor extraction systems need to ensure that both
horizontal and vertical placement of extraction wells maximizes the percentage of extracted
vapors that contain volatile contaminants. Also, in situations where the target zone of
contamination is close to the water table, the designers need to consider the potential for ;
groundwater upwelling in response to the extraction well vacuums, and they need to be 7
prepared to offset upwelling with groundwater pumping wells.
Time for Cleanup— •
The time allocated for cleanup through SVE affects Nev. Any increase in the
allocated time decreases N^y by the same magnitude, with the opposite true for .decreases in
time. Remediation time has no bearing on NAt , ;
As discussed in the "Desired Remediation Time" portion of Section 1, the time
allocated for site cleanup may or may not be within the control of the system designer/The
time frame selected is often driven by the actual or perceived potential impact of contaminant
migration to downgradient receptors; demands for action from surrounding property owners;
the level of trust between responsible parties, consultant/contractors and regulators; or a '
responsible party's plans for the site. Few parameters, however, can have as great an impact!
on the determination of the economic or technical viability of using vapor extraction at the
time of cleanup.
87
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REFERENCES
American Petroleum Institute (API). 1992. A Draft Guide for Assessing and Remediating
Petroleum Hydrocarbons in Soils, API Publication No. 1629, API marketing department,
Washington, D.C., April.
Chevron Research and Technology Company (CRTC). 1991. Vapor Extraction System
Perforfnance Study. Chevron Research and Technology Company internal document, written
for Chevron USA marketing department
Cline, P. V., J. J. Delfino, and P. S. Rao. 1991. "Partitioning of Aromatic Constituents intp
Water from Gasoline and Other Complex Solvent Mixtures." Environmental Science and
Technology, 26(5):914-920.
Danko, J. "Applicability and Limitations of Soil Vapor Extraction." 1989. Presented at the
Soil Vapor Extraction Technology Workshop, Office of Research and Development, Edison,
New Jersey, June 28-29.
Davies, S. H. 1989. "The Influence of Soil Characteristics on the Sorption of Organic
Vapors." Presented at the Workshop on Soil Vacuum Extraction, R. S. Kerr Environmental
Research Laboratory, Ada, Oklahoma, April 27-2.
DePaoli, D. W., S. E. Herbes, and M. G. Elliott. 1989. "Performance of In-situ Soil Venting
System at Jet Fuel Spill Site." Presented at the Soil Vapor Extraction Technology Workshop,
Office of Research and Development, Edison, New Jersey, June 28-29. f
Hutzler, N. J., B. E. Murphy, and J. S. Gierke. 1988. State of Technology Review: Soil
Vapor Extraction Systems. U.S. EPA, CR-814319-01-1.
Johnson, P. C., C. C. Stanley, M. W. Kemblowski, D. L. Byers, and J. D. Colthart. 1990a.
"A Practical Approach to the Design, Operation, and Monitoring of In Situ Soil-Venting
Systems." Ground Water Monitoring Review, pp. 159-178.
Johnson, P. C., M. W. Kemblowski, and J. D. Colthart. 1990b. "Quantitative Analysis for
the Cleanup of Hydrocarbon Contaminated Soils by In Situ Soil Venting," Ground Water,
28(3):413.
-------
Kruger, C. A., and T. Carson. 1991. "Roseville Site," Vapor Extraction Systems Course
Notebook, Final Report, EPA Contract No. 68-WO-0015, WA 04, February.
f
McDonald, M. G. and A. W. Harbaugh. 1988. A Modular Three Dimensional Finite
Difference Ground Water Flow Model, U.S. Geological Society Book 6.
/
Reible, D. D. 1989. "Introduction to Physico-Chemical Processes Influencing Enhanced
Volatilization." Presented at the Workshop on Soil Vacuum Extraction, R. S. Kerr Environ-
mental Research Laboratory, Ada, Oklahoma, April 27-28.
Sabadell, G. P., J. J. Eisenbeis, and D. K. Sunada. 1989. "The 3-D Model CSUGAS: A
Management Tool for the Design and Operation of Soil Venting Systems." In: Proceedings
of the 9th Annual Conference on Hazardous Waste and Hazardous Material, New Orleans,
Louisiana, pp. 177-182.
Sresty, Guggilam, H. Dev, and J. Change. 1992. In Situ Treatment of Soil Contaminated
with PAH's and Phenols. Abstract Proceedings of the Eighteenth Annual Risk Reduction
Engineering Laboratory Research Symposium, U.S. Environmental Protection Agency, EPA-
600/R-92/028, April.
Stephanatos, B. N. 1988. "Modeling the Transport of Gasoline Vapors by an Advective
Diffusive Unsaturated Zone Model." In: Proceedings of the Conference on Petroleum
Hydrocarbons and Organic Chemicals in Ground Water: Prevention, Detection, and Restora-
tion, Houston, Texas, November 9-11, pp. 591-611.
Travis, C. C. and Macinnis, J. M. 1992. Environmental Science and Technology,
26(10):1885-1887.
U.S. Environmental Protection Agency (EPA). 1991a. Strategic Tracking and Results
System, 1st Quarter, Fiscal Year 1992.
U.S. Environmental Protection Agency (EPA). 1991b. "Superfund, RCRA, and UST: The
Clean-up Threesome," EPA Journal, 17(3): 14.
U.S. Environmental Protection Agency (EPA). 1991c. Soil Vapor Extraction Technology
Reference Handbook, EPA-540/2-91/011.
U.S. Environmental Protection Agency (EPA). 1990. "Assessing UST Corrective Action
Technologies: Site Assessment and Selection of Unsaturated Zone Treatment Technologies."
EPA-600/2-90/011.
U.S. Environmental Protection Agency (EPA). 1988. "Underground Storage Tanks:
Technical Requirements," Federal Register 53, No. 185, 23 September 1988, 37082-37212.
89
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Wilson, O. J. 1991. "Movement of a Volatile Organic Compound in a Soil Vapor Extraction
Column," (unpublished paper).
90
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APPENDIX A
SOFTWARE INSTALLATION PROCEDURE
91
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SOFTWARE INSTALLATION PROCEDURE
the
This appendix provides a discussion on how to load both Spinnaker PLUS and
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 are
using a version of Hyperventilate with a "run time" version of Spinnaker PLUS, skip to i
"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 A window called "Spinnaker PLUS Setup" will appear. Change the path of the
installation from "C:\PLUS" 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
92
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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 "File Manager" and exit
Windows.
Creating the Spinnaker PLUS Icon and Opening Spinnaker PUTS
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. Click 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. With this window open, click on "File" and drag down to "New." A window
called "New Program Object" will appear.
5. Check to make sure "Program Item" is selected; click on "OK." A window
1 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."
93
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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.
Loading HvperVentilate
The Hyperventilate package contains one 3.5-inch diskette from which to install the ,;
program. The program can be installed from either the DOS prompt or from within
Windows. The following 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:\WINDOWS\PLUS".
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. Click on "File" and drag down to the "Copy" command. The "Copy" window
will appear.
4. The curser will be located at the "To" path. Type in "CWINDOWSNPLUS";
click on "OK."
5. When the installation is complete, exit from the "File Manager."
Opening HvoerVentilate
1. Enter Windows.
2. Double-click on the "Windows Applications" icon (if this window is not
already open).
94
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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 "SYS.STA" file or click on "SVS.STA" and then
click on "Open." The user is now in Hyperventilate.
Installing Spinnaker PLUS "Run Time" Version with Hyperventilate
1. Create a subdirectory on the hard disk for Hyperventilate and Spinnaker PLUS
"RunTime." For example, from the C:\> prompt, type
"MDWINDOWSNPLUS".
2. Copy all the 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 the following exception: substitute "plusrt.exe" for
"plus.exe" in Step 8.
4. Follow directions for "Opening Hyperventilate" to run the program.
95
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APPENDIX B
USER'S MANUAL
96
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Hyperventilate
Users Manual
A Software Guidance System Created for Vapor Extraction Applications
A Practical Approach to the
Design, Operation, and
Monitoring of In-Situ Soil
Venting Systems
vtrsion 1.01
91991 AUHigUs Rtstrnl
Shell Oil Comf toy
Economics
* HyjerCwi Suck CreUttd ty.
Paul c. Johnson, Pk.D.
Amy J. Stabenan
Shell Development
Westhollov Research Center
About This Stack
Go to First Card
System Monitoring ^ System Shut-Do vn
-\J' System Design V
Field Tests
Site investigation Vj**^*****^,
AtoutSoilVenting fo "PracticalApproach^
Vapor A 4
Treatment Ivvv
by
Paul C. Johnson, Ph.D.
Apple® Macintosh™ HyperCard™
compatible version 1.01
JBM® PC-compatible
Microsoft® Windows™ version 3.x
Spinnaker PLUS® version 2.5
Copyright© 1991 by Shell Oil Company. All rights reserved. No part of this work covered by the
copyrights herein may be reproduced or used in any form or by any means - graphic, electronic, or
mechanical, including photocopying, recording, taping, or information storage and retrieval system -
without permission of Shell Oil Company. Permission to use the software contained in this package may
be obtained from Shell Oil Company, Patents & Licensing, P.O. Box 2463, Houston, TX 77252-2463.
97
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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 Oil
Company, signed in 1990.
EPA is facilitating the distribution of Hyperventilate because the Agency has found the
software and manual to be helpful tools, especially in teaching users about in situ soil
venting and in guiding them through a structured thought process to evaluate the
applicability of soil venting at a particular site. EPA's Office of Underground Storage
Tanks advocates the use of innovative cleanup technologies, and in situ soil venting is
recognized as an effective remediation alternative for many underground storage tank sites.
Hyperventilate is based on the document titled, "A Practical Approach to the Design,
Operation, and Monitoring of Soil Venting Systems" by P. C. Johnson, C. C. Stanley, M.
W. Kemblowski, J. D. Colthart, and D. L. Byers, published 1990 by Shell Oil Company.
The program asks a series of questions and forms a "decision tree" in an attempt to identify
the limitations of in situ soil venting for soils contaminated with gasoline, solvents or other
relatively volatile compounds.
EPA and Shell Oil Co. 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 Co. do not warrant that this software will be error
free or operate without interruption. EPA and Shell Oil Company do encourage testing of
this product.
EPA will not provide installation services or technical support in connection with the
HyperVenAlate computer software package. Neither will EPA provide testing, updating or
debugging services in connection with the enclosed computer software package.
98
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Notes
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, EX, or portable) computer equipped with at least \ MB RAM (2 MB
preferred) and the Apple HyperCard Software Program (v.2.0 or greater).
Hyperventilate version 2.0 for the IBM-compatible PC requires a personal computer
equipped with a 80386 processor and an 80387 co-processor, 4 MB RAM minimum, VGA
or 8514 monitor, DOS 3.1 or higher, Microsoft Windows 3.x and Spinnaker PLUS 2.5 or
higher.
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 or IBM personal
computer.
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
99
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IBM is a registered trademark of International Business Machines Corporation
Microsoft is a registered trademark of Microsoft Corporation
Windows is a trademark of Microsoft Corporation
Spinnaker PLUS is a registered trademark of Spinnaker Software Corporation
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.
100
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Hyperventilate
Users Manual
Addendum for Microsoft Windows/Spinnaker PLUS Version
Summary
Hyperventilate - the software guidance system created for vapor extraction applications is
now available for IBM-compatible personal computers. In general, this new version (v2.0)
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 v2.0 is a product of collaboration between Shell Oil Company and U.S.
E.P.A., 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 adaptation 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). Information 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
Spinnaker PLUS Version Name
SVS.sta
SVHS.sta
SD.sta
101
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Air Permeability Test
Aquifer Characterization
Compound List Update
HypeVent
f77.rl
APT.sta
AQ.sta
CLU.sta
HYPEVENT.exe
none
installation
All files must be copied into the PLUS directory on your hard disk.
starting Hyperventilate v2.Ob
To start Hyperventilate v2.0b, open the Windows "File Manager", navigate to
within the PLUS directory, then open (double-click on) the file 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 the HyperCard version the "tab" key is used to
navigate through these tables. In the PLUS version the "tab" key is not 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
HYPEVENT.EXE 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, and HYPEVENT.EXE fight over available memory. Typically card 17
will eventually be displayed with a shaded rectangle along a portion of it slower
base while this battle is occuring. Be patient and wait for the screen to blank out
and display the message "HANG ON...." indicating that HYPEVENT.EXE is
running. If you have limited memory (<4 MB), 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.
102
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- Hyperventilate Users Manual -
Table of Contents
Title
Page
Disclaimer
Notes
Addendum
Table of Contents
I Introduction
II Definition of Some Terms Appearing in this Manual
in Software/Hardware Requirements
IV Loading Hyper Ventilate Software
V Using Hyperventilate
V.I - Starting Hyperventilate
V.2 - General Features of Cards
V.3 -Sample Problem Exercise
V.3.1 - Navigating Through Hyperventilate
V.3.2 - Is Venting Appropriate?
V.3.3 -Field Permeability Test
V.3.4 -System Design
VI References
Appendices
A Soil Venting Stack Cards
B Soil Venting Help Stack Cards
C Air Permeability Test Cards
D Aquifer Characterization Cards
E System Design Cards
F Compound List Update Cards
98
99
101
103
104
106
106
106
107
107
109
110
110
114
124
128
137
138
143
150
153
155
159
103
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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
104
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- Hyperventilate'Users' Manual -
assumed that the user has some previous Macintosh experience. If not, consult a
Macintosh users manual for a quick tutorial.
Vapor
Flow
\
Air Bleed
Line
Vacuum
Pump
Pressure ^/7s *
Gauge Vf/
Flow
Meter
Vapor Well
Vapor Treatment
Unit
Flow
Meter
Contaminated:
Groundwater Table
Figure 1. Schematic of a typical vapor extraction operation.
105
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II. Definition of Some Terms Appearing in this Manual
button - an object on a "card" that causes some action to be performed when
"clicked" on
card - an individual screen that you view on your monitor
click - refers to the pressing and releasing of the button on your mouse
drag - refers to holding down the mouse button while moving the mouse
field - a text entry location on a "card"
HyperCard - a programming environment created by Apple Computer, Inc.
mouse - the device used to move the cursor within your monitor
select - refers to "dragging" the cursor across a "field"
stack - a group, or file, of "cards"
IDC. Software/Hardware Requirements
Apple Macintosh Hyperventilate version 1.01 requires an Apple Macintosh (or
equivalent) computer equipped with at least 1 MB RAM (2 MB preferable), a hard disk,
and the Apple HyperCard Software Program (v 2.0). Check to make sure that your
system software is compatible with your version of HyperCard.
IV. Loading Hyperventilate Software
Hyperventilate is supplied on an 800 kB double-sided, double density 3.5" diskette.
Follow the instructions listed below to insure proper operation of the software.
1) Insert the Hyperventilate disk into your computer's floppy drive. The
Hyperventilate disk should contain the files:
-"Soil Venting Stack"
- "Soil Venting Help Stack"
-"System Design"
- "Air Permeability Test"
- "Aquifer Characterization"
- "Compound List Update"
- "HypeVent"
- "f77.rl"
2) Copy these files onto your hard disk. They must be copied into the folder
that contains the "HyperCard" program, or else the software will not
operate properly.
3) Eject the Hyperventilate disk
106
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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
"<" 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 sn. 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 corner, and then each
file folder tab is also a button (some cards may contain less obvious "hidden"
buttons; try clicking on the authors name on the title card for example). Clicking on
any of these will take you to another card. For example, clicking on the "About
This Stack" button will take you to the card shown in Figure 3, which gives a brief
description about the use of buttons and fields. Read this card well.
5) Explore for a few minutes. Try to see where various buttons will take you, try
entering numbers in fields, or play with calculations. Again, just remember to read
instructions given on the cards.
107
-------
Buttons
i
A Practical Approach to the
Design, Operation, and
Monitoring of In-Situ Soil
Venting Systems
vtttion 1.01
® 1991 AH Mjfc* Hwtral
81*11 Oil Comjmy
ik HyierCwt St«rk Citrttl )y:
Paul C. Johnson, Ph_D.
AmyJ. Stabenaxi
Shell Development
Westhollo v Research Center
About This Stack!
Go -to First Card
Economics
System Monitoring "T
PfeM Tests
SystemDesn
Site Instigation
1" Voting F^lDle?
About Soil Venting
"*
Vapor
Treatment
Urdu
ft
Yapor
Flov
\
Buttons
Figure 2. Fkst Card of the "Soil Venting Stack" stack.
Help: Stack Information
Buttons
Buttons have been placed in each
card. Clicking on any button vill
perform an action, such as:
Go Home to first
card Inventing Stack
Go to next card
Go to Help card
Print cart or
text field
Perform a Calculation
When curious, click on Symbols,
Pictures or Text.
Fields
Fields may contain information, or they may be
a place for you to input numbers.
Scrolling Field:
Click on arrovs to move
•toxtupordotrn
Boxed Data Field:
When you see an I-beam
cursor appear in a boxed
field, click the mouse in the
box to set the cursor. Then
you may enter data.
A button vill then usually
be pushed to perform an
action or calculation.
Click on the anows, or
move the box tip or ilo-vn
vith the mouse.
In this area, yon can
O
<>
Try this example:
Enter Number in Box
| 1"1 inches
(Click for calculation)
2.54 centimeters
Figure 3. Card HI of the "Soil Venting Help Stack" stack.
108
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-Hyperventilate Users Manual -
V.2. General Features of Cards
Figures 4 and 5 are examples of cards from the "Soil Venting Stack" stack and "System
Design" stack. There are a few general features of these cards that users should
understand:
a) Each card (with the exception of the first card of the "Soil Venting Stack" stack) has
been numbered for easy reference with the printouts given in Appendices A through
F. In the "Soil Venting Stack" these numbers appear in the bottom center of each
card (i.e. number "3" in Figure 4). in other stacks these numbers appear at either
the top or bottom corners of the card (i.e. "SD1" in Figure 5).
b) Arrow buttons are included at the bottom of some cards. Clicking on right-pointing
arrow will advance you to the next card in the stack; clicking on the left-pointing
arrow will take you in the opposite direction.
c) The identifying card numbers in the "Soil Venting Stack" stack are also fields into
which text can be typed. You can skip to other parts of the "Soil Venting Stack"
stack by selecting this field, typing in the card number of your destination (within
the "Soil Venting Stack"), and then hitting the "return" key.
d) Many cards have a house button in the lower left corner. Clicking on this button
will take you to the first card of the "Soil Venting Stack" stack, which is the card
displayed at start-up (see Figure 2).
s^gmamemiHm^msimllSm^ESaai^mmi^mmSm^mmi^^^^^^a^^M^si^^^^^^^^^S^^^^^^^^^^^
In-Situ Soil Venting System Design Process
You can click on any block in this diagram to get more information about that particular step Or 5011
can begin at fee start of the process by clicking on either the "Leak or Spill Discovered" box' or the
right-directed arro-v at flue bottom of this card ./*«•=
Spffl Discovered)
No
Yes
No
"Clean"
Site
No
CTumOff
Yes
System
Shut-Off
[Print Flov Diagram!
Figure 4. Card 3 of the "Soil Venting Stack" stack.
109
-------
Number of Venting Wells...
The procedure for estimating the required
number of extraction veils is similar to the
process used previously to determine if
venting is appropriate at a given site.
Aa illustrated at the light, ve trill estimate
single vertical •vellfloviates, calculate the
minimum vapor flo-v required, determine
the are&l extent of influence, and then
factor in any site-specific limitations. This
information then determines the necessary
number of extraction veils.
Just proceed to foDov the steps dictated on
the foUoving cards-->
PITT
Flovrate
Estimation
Maximum Removal
Rate
Minimum Volume
Requirement
Site-Specific
Limitations
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: Title 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
(Figure3).
110
-------
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,
cleanr-up costs can range from
$100K - $250K for the venting
operation alone, depending on
the complexity of the site, clean-
up time, permitting
requirements, and the type of
vapor treatment system used.
The tvo major costs are
generally associated vith the
vapor treatment unit and
"Click" on any item belov (&
hold button dovn) to see costs
associated vith that item.
Figure 6. Card 27 of the "Soil Venting Stack" stack.
Ill
-------
This HyperCard Stack vas created to help guide environmental scientists
through the thought process necessary to decide if and hov soil venting might
be applied to remediate a given site. The organization and logic of this stack
follovs the paper:
"A Practical Approach to the Design, Operation,
and Monitoring of In-Situ Soil Venting Systems"
P. C. Joliason, C. C. Stanley, M. W. Kenftbrvski, J. D. Colthait, & D. L.
published in Ground Water Monitoring Reviev, Spring 1990, p. 159-178
If M *»»« joint yom to not feel comfortable -witk the we of fte TrattoBS, f lease
click o»ce on "?" for JBOIC iafo on the neckaucs of tkis stack...
Figure 7. Card 1 of the "Soil Venting Stack" stack.
Step 7: Location: Card 1 of the "Soil Venting Stack" stack.
Action: Click on the right-pointing arrow.
Result: You are now at Card 2 of the "Soil Venting Stack" stack (Figure 8).
Step 8: Location: Card 2 of the "Soil Venting Stack" stack.
Action: Read the text, and click on the "down" and "up" arrows on the
displayed text field under "About Soil Venting..." to make the
field scroll. Then click on the left-pointing arrow at the card bottom.
Result: You are now back at card 1 of the "Soil Venting Stack" (Figure 7).
Step 9: Location: Card 1 of the "Soil Venting Stack" stack.
Action: Click on the right pointing arrow.
Result: You are again at card 2 of the "Soil Venting Stack" stack (Figure 8).
By now you should feel comfortable using the left- and right-
pointing arrows to travel through the stack.
Step 10: Location: Card 2 of the "Soil Venting Stack" stack.
Action: Click on the "?" button in the lower right corner of the card. This
button indicates that there is a "Help" card containing additional
information.
Result: You are now at card H2 of the "Soil Venting Help .Stack" stack
(Figure 9). Scroll through the list of references, then click on the
"Return" button to return to card 2 of the "Soil Venting Stack" stack.
is,^
112
-------
.^Hyperventilate Users Manual -
About Soil Veal/op...
Soil Venting (a.k.a. "in-situsoil
venting", "vacuum extraction", &
"in-situ vapor extraction") is
rapidly becoming one of the most
practiced soil remediation processes
for permeable soils contaminated
vith relatively volatile
hydrocarbons.
The underlying phenomena that
influence the success of any soil
venting operation are easily
understood. By applying a vacuum
M!
Vapor
Treatment Unit
Vacuum
B lover
Figure 8. Card 2 of the "Soil Venting Stack" stack.
Help: About Soil VentL
More information about soil venting can be found in the folio ving articles:
M. C. Marley and G. E. Hoag, Indeed Soil Venting for the Recovery/Restoration of Gasoline
Hydrocarbons in the Vadose Zone, NWWA/AH Conference on Petroleum Hydrocarbons and
Organic Chemicals in Groundi/ater, Houston, TX, 1984.
P. C. Johnson, M. W. Kembloiraki, and J. D. CoWiart, Practical Screening Models for Sofl
Venting Applications, NWWA/API Conference on Petroleum Hydrocarbons and Organic Chemicals
in Ground-water, Houston, TX, 1988.
N. J. Hutzler, B. E. Murphy, and J. S. Gierke, State of Technology Reviev: Sofl Vapor Extraction
Systems, U.S.E.P.A, CR-814319-01-1,1988.
D. J. Wilson, A. N. Clarke, and J. H. Clarke, Soil Clean-up by in-situ Aeration. I. Mathematical
Modelling, Sep. Science Tech., 23391-1037,1988.
H2
[Print References]
Figure 9. Card H2 of the "Soil Venting Help Stack" stack.
113
-------
V.3.2 Sample Problem Exercise - Is Venting Appropriate? .. '
;-. s» ' i ' . ' .•'. •'
In §V.3.2. you will work through an example problem to illustrate how'one might decide if
venting is appropriate at any given site. For the purpose of this example we will use the
example site information given in Figure 10.
10'
20.
30,
I40-
PQ
SO—.
60 —
North
South
•
— «i
•
•
•
— v
•
•
•
HI
i
-0.3
1
-0.2- -
j
•0.02
.0.0
.0.0
1
-02- -
J
-0.0
"1.7
"24
.«
-9.5
3-17
\ • Tank
Sandy \ BackfiU
Clay \i (former tank
f ' \ location) '
\
•
Fine to
Coarse Sand
Silty Clay
&
Clayey Silt
r
•
•
i
Medium Sand
•
r
HI
"0.5 /
• 1.7-/ — — -
.512
.5.4 .
.8577
•341- — — •
-653 «
"3267
.1237 ' .
• 23831
•
.3319
.1.7
3-10 H
• 0.8
. 0.3 -
. 8.2
.214
.967
-.971 ',
B_2867_9 ':'_ "•_ _^
. 23167
3-5 - H
- 0.31
— 1.2-
• 0.44
- 0.17
• 8.8
•-0.63
.'1.5
- 0.86
• 23
• 1.6
- 3.2
B-3
Static Ground
Water Table
SCALEtft)
I——f-——I
0
10
20
Contamination Type: Weathered Gasoline
Figure 10. Sample site data (Johnson et al. [1990a]). Total petroleum hydrocarbons
(TPH) [mg/kg] values are noted for each boring.
114
-------
-Hyperventilate[UsersManual -
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).
I !• Venting Appropriate?
Read This
I
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)
Flovrate
. Estimation
Maximum Vapor
Concentration
Maximum Removal
. Rate
Figure II;' Card 7 of the "Soil Venting Stack" stack.
115
-------
Flowrate Estimation:
O Medium Sand
® Fine Sand
OSiltySand
O Clayey Silts
O Input Your Ovn Permeability R
Permeability Range (darcy
1 1 Itol 10 1
Well Radius 1 2
Radius of Influence 1 40
Interval Thickness* 1 66 1
1) Choose Soil Type, or
Optional- Enter your oim permeability values (darcy)
2) Enter Wen Radius (m)
3) Enter Radios of Influence (ft) & Interval Thickness*
4) Optional- Enter your ovnureU vacuum (406 " = max)
5) Click button to calculate Predicted Flovxate Runges
Predicted Flovrate Raioges
ange
)
in
ft
ft
[ — >Calculate Flovrate Ranges<— }
* Oiekuii of icntxl iattml, or Q]
^irmtaMi zoat fvMetavtris s&Jklltrl.
WeU Flovxate
Vacuum (SCFM)
Pw (single -veil)
(JnH20)
_ 5_
IK
40
6.0
120
2QIL
n 33
_JLSL
J.30__.;...
S?!
6.8?
10 07
to
to
to
to
to
to
to
659
iMa.
•-••|-^
100.66
,;,aa About Soils ( & Unit Conversions) @K_1 8 •"^••"•r Info TiTmin r*r1-"1^*rfl ^^^
Figure 12. Card 8 of the "Soil Venting Stack" stack.
Step 3: Location: Card 8 of the "Soil Venting Stack" stack.
Action: Choose the "Fine Sand" soil type, and enter:
well radius = 2 in
radius of influence = 40ft
interval thickness = 6.6 ft,
user input vacuum = 200 in E^O
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.
116
-------
Vapor Concentration Estimation - Calculation
T) Type in Temperature (*C) (hit )
18
J
Click to Enter Composition of Contaminant O Enter Distribution
IT) or O "Fresh" Gasoline
Choose one of the Default Distributions <§> "Weathered" Gasoline
Click to Yiev Distributions, (optional)
Click to Perform Calculations
C Viev Distributions )
<§> Perform Calculations
Sum of Mass Fractions
Results: Calc. Vapor Pressure
; Calc. Vapor Concentration
Hov Do I Measure &. Distribution? 1
Figure 13. Card 10 of the "Soil Venting Stack" stack.
Help: Compound List
I Viev Only Mode j
t Compound Name
Yayor
Haas Molecular Pleasure
Fraction Weight (g) , e I 18
1
2
3
4
5
6
7
8
9
10
propane
isobutane
n-butane
trans-2-butene
cis-2-butene
3-methyl- 1-butene
isopentane
1-pentene
2-methyl-l-butene
2-methyl- 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
2.75865
1.97431
1.84196
1.67019
0.88399
0.73146
0.64989
0.62093
0.60914
•6
Zl
Will
!Wl'
'
ill
HUH
1
1
ililili
O
0.99628
Sum of Mass Fractions
(should t>««
Hov Do I Measure a Distribution?jil|iRetum to Vapor Cone. Estimation Card
Figure 14. Card H16 of the "Soil Venting Help Stack" stack.
117
-------
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 HI 6 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?: 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 131
StepS: 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 =180d
Now click on the "—>Press to Get Rates<~" button
118
-------
-HyperVentilateUsers Manuul-
Afstxinauu Removal
Estimates
select your unit preference belov
® [Ib/dl
Note:
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 rates are acceptable...
Temperature (°C)
Son Type
Sofl Permeability Range (darcy)
WeU Radius (in)
Radius of Influence (ft)
Contaminant Type
Permeable Zone Thickness (ft)
P^-Well Flovrate Estimates Max. Removal Rate Estimates
Vacuum [SCFM] [ttld]
(inHgO) (single -well) (single veil)
.5.
_.10._
_2JL_
_io_
60
120
200
... Q,3..3_
,._q,66_....
._l.3Q_....
._2,54 ....
3J.L.....
... 6,8.3 ....
10.07
to
to
to
to
to
to
to
L3..2...
6J5i.._
.......13,Q2_
,._.25,38
.3Z..0.9.
68,27
100.66
it
. ...J.Q
178
364
to
to
to
to
to
to
to
.62.
]24 ......
251
....._li.7_
..... Z9.9 ......
1778
3636
Figure 15. Card 12 of the "Soil Venting Stack" stack.
Soil Venting Appropriate?
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
Enter
Estimated Spill Mass[
Enter Desired
Remediation Time
—>Press to get Rates<— J
Single Vertical Well Results
Desired Removal Rate:
Gauge Vacuum (in H2O):
Min Flovrate @ 200 inH2O
Max Flovrate @ 200 inH2O
Max. Est Removal Rate:
(lover estimate) - per veil
(upper estimate) - per veil
[kg/d]
[inHZO]
[SCFM]
[SCFM]
Figure 16. Card 13 of the "Soil Venting Stack" stack.
119
-------
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 a? 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.
120
-------
-Hyperventilate(UsersManual-
Motfel Predictions
To the right is a summary of the
data you have input If you visit to
change any of the info, then click
on the parameter name, and redo
the calculations on the card you vill
be taken to. Press the blinking
'Return1 button to come back
The model returns output that
allo vs you to determine
residual amounts of
compounds falling vithin 5
boiling point ranges. Type in
your own ranges, or choose
the default values.
tula tell me more about BP ranges.
Temperature (°C)
SoflType
Soil Permeability Range (darcy)
WeU Radius (in)
Radius of Influence (ft)
Contaminant Type
Permeable Zone Thickness (ft)
[ —•> Set Default BP Ranges <— )
.ioilir»g.Point.Rai}gg..£3.
MU.Ug.PpintRfflagg..|4..
Boilinj? Point Ranee #5
-50
28
..80....
JJLL
144
SSL
Jo
to,
to
to
,.J?.§....
..J.1U
.._].
250
...G...
..£.
c
4SL.JL
Generate Predictions
mmm
Figure 17. Card 16 of the "Soil Venting Stack" stack.
C
DC — > Import Data <— ) Satan
FIRST PRESS THE IMPORT
DATA.BUTTON!
These are the result! for the
contaminant type that you have
Qt/M(0)
L-wcl
g-residual
.00
.24
.57
.98
1.49
2.11
2.87
3 81
Yapor
Cone;
[» Initial]
100.000
75.062
58.631
48.078
39.390
31.941
25.916
21.150
Residual
Level
[96 Initial]
100.000
95.000
90.022
85.034
80.034
75.035
70.035
65.037
PH HiiiV
>90«
III
o
BPttl
Residual
[96 total]
.690
.123
.000
.000
.000
.000
.000
.000
ited Vapor
ntration at
olume to 1
of Initial
Temperatur
Contaminai
BP#2
Residual
[96 total]
11.650
9.263
6.755
4.512
2.632
1.222
.385
.068
ttime=0
iemoT«
Residual
e(«C):
rtType:
BP#3
Residual
[96 total]
24.010
23.982
23.474
22.403
20.771
18.503
15.556
12.053
0.2053E+03 | [mg/L]
.9ttait 1 [L-air
128.48 | „,,,,,„
18 |
Weathered Gasoline
BP«4
Residual
[96 total]
22.140
23.000
23.820
24.577
25.248
25.766
26.031
25.919
BPS5
Residual
[» total]
41.510
43.632
45.950
48.509
51.350
54.509
58.028
61.959
g-
alj
o
II
«w5*s!53*ir m Hi *
Figure 18. Card 17 of the "Soil Venting Stack" stack.
121
-------
Stepl2: Location: Card 17 of the "Soil Venting Stack" stack.
Action: Read the instructions, then click on the "~>Import Data<~" button.
Result: Your screen should look like Figure 18. The table in the lower part
of the card lists model predictions: vapor concentration and residual
soil concentration (expressed as a percentage of their initial values),
as well as the composition of the residual (expressed as a percentage
of the total for each boiling point range) as a function of the amount
of air drawn through the contaminated soil. Note that as the volume
of air drawn through the soil increases, the vapor concentration and
residual soil levels decrease, and the composition of the residual
becomes richer in the less volatile compounds (BP Range #5). In
the upper right corner of the card are displayed the saturated, or
initial, vapor concentration and the minimum amount of air that must
be drawn through the soil per gram of initial contaminant to achieve
at least a 90% reduction in the initial residual level. This value is
used in future calculations as a design parameter.
Step 13: Location: Card 17 of the "Soil Venting Stack" stack.
Action: Click on the right-pointing arrow to advance to card 18 of the "Soil
Venting Stack" stack.
Result: You are at card 18 of the "Soil Venting Stack" stack, which should
resemble Figure 19. Read the text. A summary of your input
parameters appears on the right side of this card. At the bottom
appears two calculated values representing the range of the minimum
number of wells required to achieve a 90% reduction in the initial
residual level in the desired remediation time. These values
correspond to idealized conditions, however, they can be used to
gauge the efficacy of soil venting at your site. For example, in this
case the rninimuin 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.
122
-------
Stepl4: Location: Card 18 of the "Soil Venting Stack" stack.
Action: Click on the right-pointing arrow button to advance to card 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.
Ventjjag 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.
18
Weathered Gasoline
Temperature pCJ:
Contaminant Type:
Soil Type: | Fiae Saad"
Well Radius [in]:
Eat. Radius of Influence [ft]:
Permeable Zone Thickness [ft]:
Floimte per Well (120" Yac) [SCFM]
Flovrate per Well (120" Vac) [SCFM]
Min. Vol. of Air [Ug-residual]:
Estimated Spill Mass:
Desired Remediation Time [days]:
Minimum • of Wells
Based
on Tour Inpvt Parameters
Figure 19. Card 18 of the "Soil Venting Stack" stack.
123
-------
- 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 APS of the "Air Permeability Test" stack.
124
-------
-Hyperventilate Users' Manual-
Step 3:
Step 4:
Step 5:
Location:
Action:
Result:
Location:
Action:
Result:
Location:
Action:
Result:
Card APS of the "Air Permeability Test" stack.
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
i)
Identify soil zones to be treated
2)
Install vapor extraction vell(s) in this
zone(s). Existing monitoring veils
may be used, vhen the screen interval
extends only into the zone to be treated.
Note the extraction veil radius and
borehole size. Insure that the veil is
not "connected" to other soil zones
through the borehole (use cement/grout
to seal annular borehole region^.
O
[ shov me sample data
Pole Volume Estimatiom:
Enter
1) Soil Layer Thickness [ft]:
2) Estimated Radius of Influence [ft]:
3) Air Perm. TestFloviate [CFM]:
6.6
50
15
( -> Calculate <
Pore Volume:
Time to Extract a Pore Volume:
Return
APS
Figure 21. Card APS of the "Air Permeability Test" stack.
125
-------
-Hyperventilate Users' Manual -
Step 6: Location: Card APS of the "Air Permeability Test" stack.
Action: Read the text, click the "clear" buttons to clear any entries from
columns, then enter the following data:
r = 32.4 ft
Time Gauge Vacuum
fain! FinKbOl
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
["mini
4
7
9
12
16
24
30
39
52
77
99
110
121
141
= 15
Gauge Vacuum
FinlfrOl
1.2
3.0
. 4.3
5.5
6.9
9.9
11
13
16
20
21
23
24.5
25,5
SCFM
= 6.6 ft
Result:
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.
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.
126
-------
Air Permeability Test - Data. Analysis (coat.)
Enter radial __
3) distances of
monitoring points
Enter measured — *
2) times and gauge
vacuums
T) Enter (optional):
a)flovrate
I 15 I(SCPM)
b) screened interval
thickness
r- I 53 |(ft)
(min) (inH2O)
9
11
15
23
30
40
100
0.1
0.2
0.2
0.4
0.7
1.3
2.8
O
inn
in
32.4 I (ft)
(min) (inH2O)
(ft)
(inH2O)
Figure 22. Card APS of the "Air Permeability Test" stack.
11 ' "^^^^^^^^^^^^^^^^^^^^^^^mmm^^mmmmmi^^^^^^mm^^^^^mimi^mmfmm
Air Permeability Test - Data Analysis (cont.)
On the previous Card (APS), the data you input vere fit to the approximate expression given on Card
AP6. It vas analyzed using both methods described on card APT, if you input values for the
extraction-veil flovrate (Q) and the stratum thickness (m). Belov each column of data, the two
calculated permeability values are denoted by:
darcy(A) - refers to calculation method 1 (see Card APT)
darcy(B) - refers to calculation method 2 (see Card APT)
During the regression analyses, the data expressed as
pain of points (ln(t), P1) are fit to a line. The
"correlation coefficient", r, is a measure of hov veil
fte data conform to the theoretical curve. Asr->l,the
data points all fall on the theoretical curve. At the right
are given the correlation coefficient values for the three
data sett. For more info on the meaning of r, consult
any introductory Statistics took.
Correlation Coef.
(r)
data set tl 10.941158 |
data set #2 I 0.98602
data set *3 | No Data |
127
-------
Figure 23. Card AP9 of the "Air Permeability Test" stack
System Design
Figure 24 Card 22 of the "Soil Venting Stack" stack.
V.3.4 Sample Problem Exercise - System Design
In this example we illustrate the use of Hyperventilate for system design guidance. As in
§V.3.2 and §V.3.3, we use the sample site presented in Figure 10. At this site gasoline
was detected in three distinct soil strata: a fine to coarse zone located 10 - 30 ft below
ground surface (BGS), a silty clay/clayey silt zone located 30 to 42 ft BGS, and a fine to
medium sand zone that extends from 42 ft BGS to the deepest soil boring (60 ft BGS).
Groundwater is detected in monitoring wells at about 50 ft BGS.
Advance to card 22 of the "Soil Venting Stack" stack to begin (Figure 24).
Step 1: Location: Card 22 of the "Soil Venting Stack" stack.
Action: Use the right-pointing arrow to advance to card 23 of the "Soil
Venting Stack" stack. Read the text, then advance to card 24 of the
"Soil Venting Stack" stack.
Result: Card 24 of the "Soil Venting Stack" stack, which appears in Figure
25, should be displayed.
Step 2: Location: Card 24 of the "Soil Venting Stack" stack.
Action: Read the text, explore using some of the options. You will find that
the options: "Well Location", "Well Construction", "Surface Seals",
"Groundwater Pumping System", and "Vapor Treatment" provide
some useful guidance information on aspects and components of a
soil venting system. Return to card 24.
128
-------
Result: Card 24 of the "Soil Venting Stack" stack should be displayed.
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
O Number of Extraction Wells
Location
Remember: It is not our intention to provide a
generic recipe for vacuum extraction system
design; instead ire suggest the following as a
structured thought process. As you shall see,
even in a structured thought process, intuition
and experience play important roles. There is
no substitute for a good fundamental
understanding of vapor flov processes,
transport phenomena, and ground vater flovi
O Veil Construction
O Surface Seals
O Ground vater Pumping System
O Vapor Treatment
Figure 25. Card 24 of the "Soil Venting Stack" stack.
Number of Venting Wells..
The procedure for estimating the required
number of extraction veils is similar to the
process used previously to determine if
venting is appropriate at a given site.
As illustrated at the right, ire -will estimate
single vertical veil flovrates, calculate the
minimum vapor flovrequired, determine
the area! extent of influence, and then
factor in any site-specific limitations. This
information then determines the necessary
number of extraction veils.
Just proceed to folio v the steps dictated on
the folioving cards—>
Flovrate
Estimation
Maximum Removal
Rate
Minimum Volume
v Requirement
Site-Specific
Limitations
Area of Influence
Reouiiement
129
-------
Figure 26. Card SDl of the^'System Design" stack.
Step 3: Location: Card 24 of the "Soil Venting Stack" stack.
Action: Select "Number of Extraction Wells" from the list of options.
Result: Card SD1 of the "System Design" stack should be displayed, as
pictured in Figure 26.
Step 4: Location: Card SD1 of the "System Design" stack.
Action: Read the text, then use the right-pointing arrow to advance to card
SD2.
Result: Card SD2 of the "System Design" stack should be displayed.
Step 5: Location: Card SD2 of the "System Design" stack.
Action: Read the instructions on the card, enter the following values into the
table, then click on the "Update" button:
Parameter Medium Sand
subsurface interval (ft BGS)
description of contaminant
radial extent of contamination (ft)
interval thickness (ft)
average contaminant concentration
10-30
gasoline
20
20
100
Soil Zone
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)
Well Construction:
Radius of Influence (ft)
Extraction Well Radius (in)
Extraction Well Screen Thickness (ft)
Medium
10-100
40
40
2
10
Soil Zone
Sand Clavev Silt
0.01 - 0.1
40
40
2
5
Fine Sand
1-10
40
40
2
5
130
-------
Design Input Parameters...
(soil stratigraphy & contaminant characteristics)
Please enter the required information for each distinct soil
layer, click on the "Update" button, and then proceed to
the next card (i. e. click on right anoir at bottom).
(the tab key can be used to move between cells)
Select the total mass
units that you prefer
C Clear AU Entries )
Q
Description of
Contamination
Figure 27. Card SD2 of the "System Design" stack.
Design Input Parameters...
Note: - click on any table heading to
get more info
- use tab key to move
betveen cells
Please entente required information for
each distinct soil layer, and then proceed
to the next card.
Extraction Well
Construction
Design
Vacuum
(in HBO)
Description of
Soil Unit
Permeability*
[darcy]
._Jfl.O.
_JDDL
100
* Eitcr or choose from list it to; riffit
** mm^mn. volume of v»jor rejiurel to wiieve rencJution
Figure 28. Card SD3 of the "System Design" stack.
131
-------
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 Ranges<~" button. Your screen should now
look like Figure 30. Click on the "Generate Predictions" button
Result: The message "Sit Back and Relax..." will appear on your screen,
followed by a screen on which the following appears:
"Copyright © Absoft Corp 1988
Copyright © Shell Oil Co 1990
HANG ON YOU WILL BE RETURNED TO HYPERCARD...
# OF COMPOUNDS IN LIBRARY = 62"
Then card SD7 of the "System Design" stack will appear as shown
in Figure 31.
132
-------
Critical Volume Calculation...
typically observed in venting
operations.
The results are plotted in this my to
emphasize that the degree of
remediation that can be achieved by
venting depends mainly on the
volume of vapor extracted divided
by the initial mass of residual
hydrocarbon. For the example
pictured at the right, approximately
100 liters of air must be •withdrawn
from the subsurface in order to
remove about 90% of a single gram
QC/QC(t=0)
1
% Removed
•100
Weathered Gasoline
T-20"C
1096 moisture content
C(t=0) = 222 mgll
100 200
Qt/m(t=0) (1/g)
80
60
40
Return to Design
Do a Calculation
JLEL
Figure 29. Card SD5 of the "System Design" stack.
Critical Volume
Prediction*...
Simply enter the temperature at
Set Default BP Ranges <—
*3
Boiling.Point.RajBgB..*4.
Boiling Point Range #5
80
111
144
to.
80...
JJLL
250
c.
...c.
c.
c.
c
41 Generate Predictions
Figure 30. Card SD6 of the "System Design" stack.
133
-------
Step 10: Location: Card SD7 of the "System Design" stack.
Action: Read the instructions, then click on the "~>Import Data<~" button.
Result: Your screen should look like Figure 31. The table in the lower part
of the card lists model predictions: vapor concentration and residual
soil concentration (expressed as a percentage of their initial values),
as well as the composition of the residual (expressed as a percentage
of the total for each boiling point range) as a function of the amount
of air drawn through the contaminated soil. Note that as the volume
of air drawn through the soil increases, the vapor concentration and
residual soil levels decrease, and the composition of the residual
becomes richer in the less volatile compounds (BP Range #5). In
the upper right corner of the card are displayed the saturated, or
initial, vapor concentration and the minimum amount of air that must
be drawn through the soil per gram of initial contaminant to achieve
at least a 90% reduction in the initial residual level. This value is
used in future calculations as a design parameter.
Step 11: Location: Card SD7 of the "System Design" stack.
Action: Click on the "Return to System Design" button
Result: A dialog box will appear asking: "Transfer Critical Volume Value?".
Click on the "Yes" button. You will now be prompted by another
dialog box asking: "What soil unit # is this value for?". Enter "1"
into the appropriate place then click on the "OK" button. You will
now be transferred back to card SD3 of the "System Design" stack.
Note that the value "128.48" has been entered into the "Critical
Volume of Air**" column for the medium sand soil unit.
Step 12: Location: Card SD3 of the "System Design" stack.
Action: Enter "128" into the "Critical Volume of Air**" column for the
clayey silt and fine sand soil units. For this example problem enter
" 100" for the efficiency in all three soil units
Result: Card SD3 should now resemble Figure 28.
Step 13: Location: Card SD3 of the "System Design" stack.
Action: Click on the right-pointing arrow at the bottom of the page to
advance to Card SD4 of the "System Design" stack.
Result: Card SD4 of the "System Design" stack should appear on your
screen.
Step 14: Location: Card SD4 of the "System Design" stack.
Action: Assume that you wish to remediate this site in 180 days. Enter
"180" in the "Time for Clean-up" column for each soil unit. Click
on the "Update" button.
Result: Hyperventilate calculates a range of flowrates to a single vertical
well, then uses this value and other input parameters to determine
134
-------
se™Manual -
the minimum number of wells required based on two approaches.
To read about these, click on the "Number of Wells" column
heading. Your card SD4 should resemble Figure 32.
It is important to recognize that model predictions are intended to
serve as guidelines, and are limited in their ability to describe
behavior that might be observed at any given site. One should use
all the information available, in addition to idealized model
predictions to make rational decisions about the applicability of soil
venting. ,
You can read about the effect of venting at this site in the article:
"Soil Venting at a California Site: Field Data Reconciled with
Theory", by P.'C. Johnson, C. C. Stanley, D. L. Byers, D. A.
Benson, and M. A. Acton, in Hydrocarbon Contaminated Soils and
Ground-water: Analysis, Fate, Environmental Health Effects, and
Remediation Volume 1, P. T. Kostecki and E. J. Calabrese, editors,
Lewis Publishers, p.253 - 281, 1991.
135
-------
(,
\j ^ — > impon uaia < —
FIRST PRESS THE IMPORT
DATA. BUTTON '
These are the results for the
contaminant type that you have
QtfM(0)
L-airf
t-resJdual
.00
.24
.57
.98
1.49
2.11
2.87
3.81
Vapor
Cone.
[96 Initial]
100.000
75.062
58.631
48.078
39.390
31.941
25.916
21.150
•vUL Launch Excel "
Residual
Level
[» Initial]
100.000
95.000
90.022
85.034
80.034
75.035
70.035
65,037
i saturated vapor
... , Concentration at thne=O
y"v
2i Min Volume to Eemore
^.Qfl ContamliiantType:
BP#1
Residual
[56 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
0.2053E+03 | [mg/L]
ITfl /IR 1L~*U
te-
128.48 | TMHla1j
18 |
Weatherei Gasoline
BP#4
Residual
[95 total]
22.140
23.000
23.820
24.577
25.248
25.766
26.031
25.919
BP«5
Residual
[96 total]
41.510
43.632
45.950
48.509
51.350
54.509
58.028
61.959
<>
:
tflflf
i!!!(i
f'iW
O
SJE3ST Return to System Design HSBf Print Card jf SD7
Figure 31. Card SD7 of the "System Design" stack.
Design Input Parameters...
Please enter (1) the desired time period for
remediation, (2) the design gauge vacuum, and
then (3) click the "update" button.
Note: - click on any table beading to get more Info
- use tab key 10 move between cell!
Fkrviate per Vapor
Extraction Well
[SCFM]
HA - not ooiiffli i»jv* bu
^^^^^^^^mmmmam
Clear All Entries
** minimum volume of vnjornjuirslto wldtvc rm«ii»JIJoii
MMl
SD4
Figure 32. Card SD4 of the "System Design" stack.
136
-------
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 Hult, M. P., 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. P., and Bedient, P. B., OASIS: A Graphical Decision
Support System for Ground-Water Contaminant Modeling, Ground Water, 28 (2),
224 - 234, March - April 1990.
137
-------
Appendix A: "Soil Venting Stack" stack cards.
138
-------
"Soil Venting Stack" Cards
A Practical Approach to the
Design, Operation, and
Uonitoring of In-Sita Soil
Venting System*
Tat HyperCard Stack vas created to help guide environmental scientists
through ttg thought process necessary to decide if and hay soil venung might
be applied to remediate a given site. The organization and logic of this stack
follovs the paper:
"A Practical Approach to tfan Design, Operation,
aad Uomtoring of In-Sitn Soil Venting System*
P. C. JoaMB. C. C. Stukty. M. W. EntklonU. }. D. Coldun. ft D. L. Bjt
published in Ground Water Monitoring Reviav, Spring 1990, p. 159-178
In-Sita Soil Venting System Design Process
About Soff Veotuy...
SoU Venting (a.k.a. 'in-atusoil
venting*, 'vanun extraction*, &
'in-situ vapor extraction*) it
rapidly becoming ore of tie raxt
practiced soil remediation processes
for jmnfttrihlft soils contaninated
vith relatively volatile
bydrocarboni.
Tbfi uoderlying pheooooBxia tbal
innuence the succets of any soil
wotting operation an eaoly
understood. By applying a ncuum
Le*t air Spill DttcommJ...
In tbe folloving cards ve Till assume
tbat a leak or spill has been discovered,
aod the appropriate emergency response
and »h»ti»Tr»oT« hate taken place.
Nov ve vill step through a logical
thought process to daode if toil venting
u appropriate at ttusitg. Tbepnmous
card display! the flovcharl that a tbe
baas for the thought process. Clicking
villnn any process box vill take you to
that section of the stack rtnahng vith
thai aspect of the thought process.
Preliminary Site hmstigatioa.
Whensver a soil contamination problem is detected
or suspected, a site investigation ii conducted to
characterize and delineate the zone of soil and
groundvater contaminalioa In general, the ate
characterization is conducted in tvo stages. The
emer^ncy response and *h*toimtt phase •*g*»fim
the immediate import on potential human and
environmental racepton, andaconluctedina
relatively short period of time (days). A detailed
nte characterization then follovs. Its purpose, like
the emergency response and «*»«*«»nffnt phase, is to
determme potential migration pathvays and assasr
the environmental impact —«~-.-t~| vith present
danctemtton
1 —
Screen Treatment Alternati
With any contsmualBd site, one should
explore the feanbtlity of all treenmm
procsssei. Afterconvdingalistof
alternatives, selection criteria
(cost, speed, permitting problems) should |
be established, and then the final
choics(j) made.
SoU Venting is most likely to be
successful vben soils are sandy and the
containment a volatile.
Other options are available, hovevar.
O Thermal Dasorpuon
O Incineration
OCompocung
O Land Farming
O In-Situ BioRunulaUon
O Soudificaaon/Statalization
O Solvent Extraction/Soil Wasting
ReadTliii
i
At tins point v» vill proceed through a
sunple thought process to decide if soil
venting u a faecibl* alternative. As
mentioned earlier, the three man factors that I
govern the success of a venting operation are: |
- vapor flovma
- vapor concentration-
- subturfaca stratigraphy (or tbe location of
contamuaols relative to tfae vapor
flovpeth)
IMlTrninrnBenonl I
Rt»
139
-------
"Soil Venting Stack" Cards
A2
Flown!* EitimaUioa:
OMxliumStcd
OSiltySeod
Predicted Flovrraia' Reagan
Your OvnPennsebOity Range
permeability Rang*
I I Itol 16 I
Veil Kadis I 2 lin
Radit* of InfltMua I 4D Ifl
klcrnl •nickMii* I 66 m
(SCTM)
10
0.33 to 3.32
0.66
1.30
2.54
6.59
13.02
25.38
Vapor Coaeemtntioa Rili tin lion:
The maximum acbieveble removal
rate ocon vbenever tie vapors
removed by noting are 'saturated*
or in equilibrium -nth Uie
toil matrix.
In the next card you vill estimate
the iy>«iTM»w vapor concentration
of your contaminant. juctfollov
the instruction in tin upper left
corner of tin nxt card.
Vapor Coacratxalion Estimation - Calculation
TTP»nTi!H)era«urtrC)(bit)
I
20
CUclc to EnitrConsionlionof Conuminmi O Enter Distribution
) or O 'Fresh* Gasoline
CbooH oot of Ua Dtfwlt DiitntnUionc ® 'Weathered' Gasolim
Click to Vuv Dutribuboa, (optiooal)
Click to Perform
C Visv Di5tributiont~)
O Perform Calculation
Removal Rate Estimates
7te ojexiEaum achievable
removal rale occurs vhrnever
thf vapors removed bj venting
are "saturated* or in
equilibrium nth the
contaminacs/soil matrix.
Tba 'Removal Rate* is simply
the product of the flovrate
tim to vapor concentration.
The values you input on Cards
8 IclO vill be used to generate
Removal - Vapor
Rat* Concentration
Estimated
x Vapor
Flovrate
It, ma mir te but eratfkmt (max npm &
Sum of Man Fraction
Calc. Vapor Pnoun
Calc. Vapor Cotesntraaoa
At this point, you compare the
iiMi»iiiuui> possible removal rats
vith your danred removal rate.
(7> Enter Desired
Remediation Time
_180| days
\2j [ ->Pan P ctt Rite-c-
Singfji Vertical Well Reralts
If the '"••'"•u" removal rate
doa> not exceed your desired
removal rale, then soil venting
is not likely to meet your needs,
eod you should consider another
Ueatiignt technology, or make
your mods more realistic.
Ma.
ODWT atlmMi) • ptr «*n
In thB naxt casxls, ve Till refine
It Soil Veatiof AffTopri*lo? - EeflasJ Ettiamie*
The preceding esumBac an
utafut ody as I 'fimcuf, sod
should be refined if venting is
riU a potentially feasible
option.
Typically during soil venting,
the measured vapor
eooaarrahoo and removal net
dcptotax* on time recsembte
the plot on the right
(vbea (be total vapor HovnH
u relatively contact).
ViiorOoec,
•!*•»<•)
Mm DtttmileJ Cflmlmtion*
Pictured at the right are the
results of sample model
prediction, for**rae)herad
gaeolina ssopl*.
3 OC/QC(UO)
1
The vertical axis represents
eithsr normalized
concentration [C(tyC(t-0)l
or normalized removal rates
[C}C(iyCJC(t-0)lvhuethB
horoootal axis reprasents the
total Toimne of vapor
100 200
Qt/m(l-0)(l/g)
140
-------
"Soil Venting Stack" Cards
duct tny of *» iaa>, t«m dfck
M,iad»&)
&• cvii jom vBL
» Ufa>k»
•Benny name came t«c>
PnmMbk Zmx Ttdcfcm (rg
TtemxUl
•Dow jom o
0 [ generate Predlclloni ]
Veatiaff Appropriate?
Tbif if a complete summary
of the data and results.
Based upon **"»•» n»mimi t^ a
has been calculated, vbich
should give you some
indication of hov
appropriate venting is for
your application. Note that
this is the ram^ar of veils if
k •* Pncttal Anpnck n «• D*ECB,
Ofnukm, mi Mmiutac
-------
"Soil Venting Stack" Cards
A4
System Design...
At the right is a list of Its components
of a VBBGKg system dengn. Clickon
each to conduct the indicated pben of
ubet Mctflp proem
O Hnmber of Extraction l^iUi
OWill Location
O Veil CocatmetioB
O GroandvmUr Pnmpjng STitem
O Vapor Tr^dmuit
Tho perfonnro of a foil miling
system murt be monitored in ordar
to euue efficispt operatioD, 3Dd
to help detBrmu» vtan to ihut off
At ft miiimm, the itenx listed to
the list* ttould be meennd.
'Click* on «7 one to ggt own
inf OTOBtlOIL . .
QDela and Tim
O Vapor FIov IUI«f
O Pren^are/Vacanm Readings
O Vapor Concantrations Ic Compositions
O Temperature
O VatBi- Table Unl
OSoil Gm Cobeentratioa fc Competition
System Shot Dowa...
Tirgtttoil clMD-up lercls an
oAtn s*t on a ate-bj>-til» bods,
tod ere bmd on tie ntumad
potanlul impart thai any
ntuluil mey has* oa au1
quality, jroucdTttKT quality, or I
othff bxllh Usndards, Tbiy
mty tbo be rtlaad to nfttf
coocdeitionc (>>)cattm e feenra
ixMnv at -Hjrmxr ijr*mt •
• u«u>«i«. «« rym'a tajt
142
-------
Appendix B: "Soil Venting Help Stack" stack cards.
143
-------
"Soil Venting Help Stack" Cards
81
Heln: Stack Information
Bunons
Buttons h»ve been plsced fa e»eh
card. Clicking on my bunco will
perform in scuon, such IK
GoHonctorot
hrta=aCiIc«lsac«
When cunous, click oo Symbols.
Picture* of Ten.
Fields
Fields may contain information. or they nay be
a place for you to input numbers.
Scrolling Field:
Qick oa «row» to mow
Kit op or dawn
Boxed Data Field:
Wbea you tec an I-btan
cunor^pesrraaboiod
IWd, click fee BOMB in the
bm Bid UK eunor. Tben
Try this example:
Eater Number in Baz
! inches
bepuahod to perform ai
- of f-^fiiT.rinn.
(Click for calculition)
centimeter
Help: About Soil Venting
M. C Mariey tad G. E. Hc«a, Induced Soil Venting for the RfODvery/RjeiunDoo of Gvoliac !
Hydrocat>xvmtfaeViabKZaiK,NWWA/AFICoiifcniiceoiiFElciinHydn>carbouBd |
Orgnac f^*««^u in Orooadwucr. Hoomn. TX, 19S4. t
P. CJohMOB.M.W.Kemblowtki.indJ.D. Coluwn. Prteoeal Soeenaif ModeU for Soil |
Vmmi Apphouioin. NWWA/API Ctrnfooxx on PcmJ.:um Hydioclrbau Kd djmc Chcmioli I
inOroimiwtler. Hoojua.TX 1988. [
I
N J Hutzler B. E. Mmphy, «ul J. S. Gierte, Stale of Technology Rrview: Soil V«|>or Exuuoon | '
Syinu. UJ£J>Jk, CRJ14319-01-1, 19J8. '
D. 3. Wilm, A. N. Oirke, Kd J. H. a«ta, Sail Oem-up by in-iitu Aeruon. I. Mubemuul
Mofclinj. Sep. Sdaice Tech.. 23:991-1037,1988.
-L
Hel: In-Situ Soil Venting System Design Process
Ths< t> the decision ptoccu that one mun follow to:
I) decide if soil venting U applicable at a given site
&
2) design an effective soil venting system
h is an abridged version of Figure 2 in "A Praatcal Approach to iht Outfit.
Ofiraaat. & Uanaorutt ofln-Sau Soil V,iautt Sysitia'. by P. C. Johnson,
C C Stanley. M. W. Kemblowski. J. D. Colihan, and D, L. Byers.
Help: Preliminary Site Investigation
More information about site investigation and remediation can be found in the
following articles:
API Publication 1628
'A Guide to the Assessment and Remediation of Underground Petroleum
Releases9.
American Petroleum Institute, 1220 L Street Northwest, Washington DC, 20005
Help: Thermal Desorption
Proem Dtteriptiom
in a thermal desorpuon treatment
process, soils contaminated with
votiojcfcemi-volsule orgimcs are
heated, and the volsulued
contaminants are stripped with air.
iteam. or combustion products
(burner flue gsses) at relatively
modest tcmpennirej compared with
incineration (200-SOO'C versus
1000-1200'C). Tnedesorbed
organic comanunsnia are
Help: Composting
TVoail Screw Dnorpooo Unu
Help: Incineration
Proettt Description
Incineration, or the thermal
destruction of wastes, is a complete
destruction technology that can be
used to treat soils contaminated with
a wide range of hazardous organic
wastes. Contaminated soils.
sludges, or liquid wastes are added
to a high-temperature combustion
chamber
(rotary kiln, fixed hearth, multiple
hearth, fluidized bed, liquid
Soiidl Hindi™, Rollry jgjn
Syttem J~ '
frtcilt Dtieriftie*
Composang u an above-ground soil
management technique in which
amended toil, containing organic
wastes, is placed in large piles and
aerated. The aeration enhances
mloobial degradation by providing
oxygen to the soil/waste. With
lime, the decomposed waste is
reduced in weight and volume, and
the process produces a stabilized.
enriched, humus-like material.
Spray ImpnoB
ndftrahsr
Help: Land Fanning
Praun Dncriplio*
"Landfamung'* refers to the
practice of spreading organic wastes
over an area of land, then relying
on natural microbial action to
degrade the waste. It is a widely
accepted and cost-effective practice
for the treatment of petroleum
hydrocarbons, chlorinated
compounds, and pesticides. In this
process soil-associated
microorganisms (bacteria and
Solid + W»u m Top 6' • 12'
144
-------
"Soil Venting Help Stack" Cards
B2
Help: In-Situ Biostimulation
Process Description
Treatment of groundwtter and soil
contamination below the water table
C'saturated zone") by in-situ
biostimulation involves the addition
of nutrients and/or O2 (usually as
H2O2 or liquid O2) to an aquifer in
order to enhance the degradation of
the hydrocarbon! by indigenous soil
microbes. The nutrients and
oxygen are added above ground to
ffiumealj
Help: Solidification / Stabilization
Procett Detcriptiom
Stabilization and solidification are §
treatment processes designed to
either improve waste handling and
physical characteristics, decrease
surface area across which pollutants
can leach, or limit the solubility of
hazardous constituents. When
discussing this technology, the
following definitions are common:
Solidification.
Help: Solvent Extraction / Soil Washing
Process Description
"Solvent extraction" is the process
by which contaminants are removed
from soils or sludges by mixing
them with a solvent into which the
contaminants preferentially
partition. Which solvent is used for
any particular treatment is very
dependent upon the type of
contaminant present in the soil.
The solvent should have a high
affinity for the contaminants) of
Help: Decision Matrix
€> -applicable
O - poBnaiUy applicable,
but aot conduavdy demontrued
(1) - Different compound* will vary m
ebeir dcfiBc of biodep.uUb.lity.
Lucer canpatiadt typically have
•lower dcpmdarion rut*.
(2) - ftee-liquid pumpmj is only
applicable wbco tike imdual
conanunaooo level is M hifM that
<•>
&J:
$
|
Help: Soil Permeability
NOB thai k denote* the "pcnneabihty" of a porou*
media, while K rcpre»en» ibe tydimuiic
conducavity'. Tbe two sre related by:
C -
)iui -
Pu " innnrof
«• e nanr (960 c
|0.01 f/ca»-»|
-10'
- 10
-1
10 '
,o2
h18'
Lio4
-10-
-1C7
-10'
-10'
-1C1
-10°
•-I0
K
(OD/I)
r'°J
- 10
-1
-ID'1
-IO2
-Id'
-IO4
-IO5
- IO4
- 10
Help: Vapor Flowrate per Unit Well Thickness
,iowJOulonl)ayemi:illcj. Ue
•mplmic, u tomlly pnnndc. (ood cnmuu for vipor flownlu. la toancy u. of count, tailed
by tic «eajncyo( the v«Juc«ycuinput. Innmculir. Ihe ficjim imrm.mty,. ,,,»iiy ._^,.,rt
widt ttic iol pcnoeabiliry, wfaidi can vary by aevenl orckn of .magDitude over null Hi«.r,~t
H * ln(Rv/R,)
c aenl permeability ro airflow [cm2) or [darcy]
x 10 4/cm-a or 0.018 cp
diw of v^jor extncaoo \«U [cm]
u of mHuaioE of vapor euncooo well [cml
11 »CTeqi maavd, or pgmeable tod zope (cboo>e anaHcaty«)ue)
Return
Help: Unit Conversion (k and K)
I) later value of bydrMihccooducnvity or pcrtncabdity •> tat
2) Qiooate tniaal unio
3} Qiooae fiiMl unm - (dick for e«di calculaiiooJ)
Conv
O OTA
O ft/d
® cm2
O darcy
a 10 cm»
Convert To
S> cmA
O ft/d
O cm2
O darcy
Vtew Only Mode |
Compound Name
Vapor
Moil Molecular Preiuirc
"C
1
2
}
4
5
6
7
g
9
10
propane
isobutane
n-butanc
trans-2-butenc
cis-2-butene
3-methyl-l-bulene
isopentane
1-pentene
2-methyl-l-butene
2-methyl- IJ-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
8J 0
2.93
2.11 ™
1.97
1.79
0.96
0.78
0.7
0.67
i SumofMajatPrmcoonj
(ibouldbe-1)
VaporCooc. F«J™I«BH« '
145
-------
"Soil Venting Help Stack" Cards
B3
Summary Card: Site Characterization
A complete site assessment must determine the following:
Subsurface Characteristics Contaminant Delineation
• aalanetnciv
• efcarauunta oTdiieaa lod Uytn
• dtfta to i
• inuadw
• •uionil w*KrtiBlefl&c&iaQoQt
• iqiifcr rcnnf«.Mvly <<«om«e)
• futaafftce A abovo'frouDd fcanpenene
• exEeol of ftce-phaK bydnxaitxm
• ducnbuoonof conanuMaravidoaszone
• ex Kot of iOluWe ooonsssnt pluoao
• foil vipjr cuuo.tjjK.ooB (opaoul)
Compound List Default Data
# Compound Name
Bourns Vapor New Vapor
Molecular (-Q (Ann) (Am)
Wast* & \ @T^IO @T=
(jm) An 'C
Man Fraction Data
AD 'Froth' "Wellhead-
to Guctae Guolme
n-buome
tnni-2-buaae
oij-2-bul:De
wopentane
1-pCCEOB
2-mcayl-l >bumjjme
58.1
58.1
56.1
56.1
70.1
7Z2
70.1
70.1
68.1
8.S
2.93
2.11
1.97
1.79
0.96
0.78
0.7
0.67
0.65
8.5
2.93
2.11
1.97
1.79
0.96
0.78
0.7
047
0.65
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0001
0.0122
0.0629
0.0007
0.0000
0.0006
0.1049
0.0000
0.0000
0.0000
0.00
0.00
0
0
0
0
0.0069
0.0005
0.0008
0.0000
Help: Data for Fortran Program
« Compound Name
Baibni Vapor Oiiaac
Poou Preuurc C>boB Mau
7 (Ana) Solubility Due. Prac&on
Waiht 91 @TM Coeff Dm.
(En) Ad 20 'C
uopcBtux
44.1
58.1
38.1
56.1
56.1
70.1
7i2
70.1
70.1
68.1
-42
8.5
2.93
2.11
1.97
1.79
0.96
0.78
0.7
047
62
49
61
130
430
130
148
155
642
73
537
946
204
204
708
1862
710
525
323
0.00
0.00
0
0
0
0
0.0069
0.0005
0.0008
0.0000
Help: How Do I Measure a Distribution?
f^ enfnpg«lftqn of f*rnfSTH BUXQIICt)
(nch u faadme) require* ipccUliKd intlyaaJ
vcntmf , bov*svcr, «ia^jprojum»iecocipo.naoncin be
lued with very food remits.
To drarmiy MI Mnmuaatc dittnbuDDQ, one ciuft
•udyae Gbe miznue by gu datauiognfbic culyic*.
compouodi wboac properoe* aie vwll known. Of en a
KDCI of Kmihicbua alkine* (n-buOnc, n-pcnome,
n-bexxoe, etc.) u dioaoi. Then the unknown miinue in
•ittyjcd. Bd the mtm o/ aB peaks ehttmf between the
mmoi of two knows peak* uc wmmed md
M one of tfag hj»mi»B T^T^IT. M UltHOUsd on 'N*
D-bexane •
D-beptuv- -
Rejpoojc
Help: Calculate a Distribution
rtrfonatOCuulyiu
Rcaoott amok be eoTMen
t&e Xsowv coBjpouaiii.
EaEf t&eirouor
eooosalrmaou m the
Coopouad
Coocsotnaaa Notmthjod
crAica Dumbuooo
&e Tafel* oa UK aifeb
Tbca,QidcCiIailue.
Oil* ae Tmufor
\ DUJL.* tuooo tad your
' Atfmbvcoa win be coped
B DC CoapoNtoB Tifcie.
1
2
3
10
propne
Q^UOOC
B{XSQUK
a.tezue
o^roaaB
a-ooue
B.DOIUBK
*Jffm*f
Q^iadecaDe
a^oouaae
0.00
1000
5000
7000
0X10
0.00
0^0
OJ30
OJDO
OJM
0.00000 O
0.07692
0.3S462
053844
0.00000
0.00000
000000
0.00000
0.00000
0,00000
x>
(£°SJf
rXcntra i
» Ceoc. Calc. CrdJ
Return
flelp: About Calculation
In this esumauon of equilibrium
(utunied) vapor concentrations.
we auume that the contaminant
conceniniions are great enough
(>200 mg/kg TPH) that it U
distributed between vapor,
•orbed, diuplved-in-soil-
moisnire. & free-phase*. In this
care. the equation at the right
applies (look for "Raoult's Law"
A. the "Ideal Gas Law" in any
thermodynamics textbook for
references). We do correct for
C "
RT
Cv * total vapor conoeamDon [cag/l]
i = mole ftac&on of component i
Pv = vnpor picMure of componeott (ana)
MW » molecular weight of component i (msAnole)
R a Unvenal Ga* Connuit * OJXil 1-amyK-molc
T * abflolute fctnpeniure (K) « T(C) •»• 273
Help: 6a) Dilution Effects [Bypassing]
Help: 6b) Liquid Layers
vapor Row
v^orflow
Vhw
Vk>
The fiture above depicu the cue where tome vtpon 'bypau' zonea of
conumimiion, tnd therefore ihe vapon removed from ihe utncuon well
represent a mixmrc of the vapors obtained from both contaminated and clean
vipor flowpuhi. One can rotifhly judge the amount of bypauint by the well
pliccmcnu screening, tnd contaminant dismbuuon. Gonenlly, observed
„.-«. «^^.^.>^ti~.. ~- ~,,.i.i« in . tna. nr.>., ,*-.! ..mr.n-rf
vapor flow
In Figure 6b. vapor flows parallel to, but not through, the zone of
contamination, and the significant mass transfer resistance ix 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 - NWWA/API Petroleum Hydrocarbons Conference) for
146
-------
"Soil Venting Help Stack" Cards
H25
B4
Help: 6c) Low Permeability Lenses
viporflow
d jsaoc
\,
In the situitioii depicted above, vapor flows put, rather thin through the
contaminated coil zone, such as might be the case for a contaminated clay lens
surrounded by sandy soils. In this cue vapor diffusion through the clay to the
flowing vapor limits the removal rate (the removal rate actually becomes
Help: 6c) Low Permeability Lenses - Equations
«D*C«
2t
R«M » ramnainrl icmoval me
f *Uiictaie» of •dried-ota* zoDe(m]
RI * defuca repon m which coommiooB it proem [ml
Ht * tlrfiTfa ic^mi in which ctntimiiiitton M pnaent [D]
CM a r «i HUMNI Mnmrd vapor OHHgBUanen fcaiAo3)
r/« * effective aod vapor dimiain caemdctt |m2Al]
CMfl = mitial nidaal level of coaDuiuualiiiioil[mf/ki]
6-
eld)
Denvations for these
equations are given in
Johnson, et al - "A Practical
Approach to the Design,
Operation and Monitoring
of In Situ Soil Venting
Systems'. 1990.
These Equations are valid
for single-component
Help: Default Boiling Point Ranges
The Fortran program HYPEVENT will report residual levels of compounds
falling 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 - Isopentane (-SO to 28 C)
Isopentane - Benzene (28 to 80 C)
Benzene - Toluene (80 - 111 C)
Toluene • Xylcnes (111 - 144 C)
Xylenes - Methylnapthalene (144-230 C)
Help: Boundary Layer Equations
The equation above
estimates the removal
rate from a layer of
liquid product by i
single well, based on a
Boundary Layer Theory
approach to the
problem. It is not
directly applicable to
mixtures, because it
1
D-
u
It
H
HI
R,
s ~»"nitrfl removtl rue
= effioBQcy leliove lo maxiam renovil nK
* effecave ami vipor difluaoo cocffiaent (an2/il
svucoBlyaf ur < 1 J z 10-4|/cm-i
s ml penneabuity to vapor flow {as2]
3 ndiua of iaAucDcc of \enDoi weU [cml
3 vcatuis well ntiiu* (on]
3 abuluB «ntaen[ pranre - 1 .016 z 106 |/an-«2
= Hxaliic ficmiK it Hie vaum( weU |ltenj2)
H deftau resioo m wtudi caQUmoudoe is p
Help: Boundary Layer Equations - Calculation
(T) Soil Type (choose one)
O lifedium Sod ' O Q»y:y SilB
O Silry Stud © Hue Sind
O Iqnu Your Own Permeability Ruae
I 1 I to I 16 I (darcyi)
(T) Process Variables:
mickm of icrccned DEml |ft|
ndiiH of mftucncc of veoojis well {fi|
vcDODs well ndiiu [ml
^ «ppbed vacuiin u wcl) [ui H2OJ
40 I radial «t(U of
©
Just enter values mto the u
appropriaLe fields/then click on
the "calculate** button.
The "Relative Efficiency" is the
rauo of the predicted removal
rate to the removal rate that
would be obtained if Ihe extracted
vapors were saturated, or in
equilibrium with the liquid
Help: Low Permeability Lenses - Calculation
(T) Process Variables:
(input v«lue»)
vtnanx «vll tadiu fia]
nMful width of onuounuedzcoe {
IQOOO I rawtaal cDDnmnuBtkwl (mjA<]
CDC
--> Calculate <—
ConUminant Properties:
-242g| con
I43.95R4I ocnl
O UK value* alTCadympizCrora Card 10
JUM enter valuta m
dtckontbc'Calcul
D ifac ippiopnma; field*, then O
ur" button.
O
Removal
Time Rate
-------
"Soil Venting Help Stack" Cards
B5
Vapor Flow Rates...
Vapor flow rate* from e»ch
extraeuon well and into toy injection
wclll ihauld be monitored.
Sample measuring devices include
pilot lubes, orifice plates ind
niunaen. It 'a important to hive
calibrated these device* -
TeQon Tubing
PVCPipe
Boa Conutani Vapor
SampliDi Pom &
Thermocouple Lead*
t|—BB |- PVCPipe
*—13 Cosie Padoni
Cumulative Amount Removed...
CUMULATIVE AMOUNT
REMOVED
U deunmned by tmegraung the
matured removal rates (flowrate x
concdurauon) with time. While
this value indicates how much
eonnminant hat been removed, it is
usually not very useful for
determining when to take
confirmation borags unices the
original rpiU mass is known very
accwaiely. In most cases that
Tool Removed
(JlllODl)
Time (days)
Extraction Well Vapor Concentration...
EXTRACTION WELL VAPOR
CONCENTRATION
the vapor concentrations are good
indications of how effectively the
venting system is working, but
reases 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 resistance
Time(diYi)
148
-------
"Soil Venting Help Stack" Cards
B6
Extraction Well Vapor Composition...
EXTRACTION WELL VAPOR
COMPOSITION
when combined with vipor
concentrations this din gives more
insight into the effectiveness of the
system. If the toul vipor
concentntion decrease* without a
change in composition, it is
probably due to increased mass
transfer resistance (water table
upwelling, drying-out of low
permeability zones, etc.). and is not
Soil Gas Data...
SOIL GAS DATA
this data is the most useful because
it yields information about the
residual composition and extent of
contamination.
Vapor concentrations can not, in
general, be used to determine the
residual level, except in the limit of
very low residual levels (when
vapor concentrations are
proportional to soil residual levels), tin
Soil Gas Monitoring
Installation Results
V.pcr
Concenanaon
(mayi)
SOIL BORING DATA
Generally confirmation soil borings
are taken once a system is turned
off, and these are often analyzed for
TPH (total petroleum
hydrocarbons) and volatile
residuals.
One should keep in mind that TPH
results can often be misleading,
since they reveal nothing about the
composition of the residual or its
Bonat
UxanoD
Bctae
B-l
B-2
B-3
Afer
B-4
B-5
B-«
TPH
[mi/ktl
*
1200
14000
8600
20
120
5
BTEX
[metal
20
120
400
ND
0.1
ND
149
-------
Appendix C: "Air Permeability Test" stack cards.
150
-------
"Air Permeability Stack" Cards
Air Permeability Tests...
The purpose of in tir permeability test it
to obtain site-specific data that will be
used in the final system design. It is a
way to verify that venting is an
appropriate remediation technique for
your site.
In particular, one typically tries to get a
better estimate of the soil permeability of
each distinct soil layer to be treated, and
a better estimate of conuuninani vapor
concentrations
Sh
low Me Stl-Up ]
Test Instructions J
Data Analysis j
Air Permeability
Test Set-up
V^oc
Row
• Preaure Sampliii Probei
Return
Air Permeability Test - Instructions
i)
Identify soil zones to be treated
2)
Install vapor extraction wcll(l) in this
zone(s). Existing monitoring wells
may be used, when the screen interval
extends only into the zone to be
treated. Note the extraction well
radius and borehole size. Insure that
the well is not "connected" to other soil
zones through the borehole (use
cement/gout to seal annular borehole
show me sample data ]
Pore Volum. E.timtUoi;
Earr:
1) Sol Uycx Tbldam [fit
2) EiomiKd (Udjiu of Influence (ft]:!
3)AjjPeim.Te«tFlowme[CPM]: j
-> Calculate <-•
Time K> Ex Old > Pore Volume:
day.
Air Permeability Test - Sample Data
Pictured at the right are the
soil vacuum measurements
from an air permeability
ten conducted in a silty
sand.
The specific operating
conditions and site
characteristics are described
in "A Practical Approach to
the Design, Operation, and
Monitoring of In Situ Soil
Venting Systems", by P, C
Preawre •*
Change
<"«,«> -I
Timc(niin)
Air Permeability Test - Data Analysis
The expected decrease in subsurface pressure {increase in gauge vacuum) P is
predicted by: <«e Jobnno ct al (1990] for den*«ocm)
P'(r,t) =
k « KM) pennemtehty
(i • urvucaaury « 0.011 aenDpoiae
* * .u-rtlled vad fncaae
i .uw
Q • wamcmc Howru: fnxo
ancaae well
Air Permeability Test - Data Analysis (cont.)
For (r* c n/4 k P^. t) < 0. 1, the governing equation can be approximated by the
expression:
This Equation predicts that a plot of P1 -vs- ln(t) should be a straight line with slope
A and y-intercept B equal to:
Air Permeability Test - Data Analysis (cont.)
The permeability, k. can then be calculated by one of two methods:
Q-\ The firn u applicable when both Q (flowrate) and m tweil screen interval) are
^"^ known accurately. The calculated slope A is used.
t.
CD The second approach is used whenever Q or m arc not known with confide
In this case, both the slope. A, and intercept. B. arc ued:
-arf 0.5772
Air PermeabUity Test - Data Analysis (cont.)
"' " '"" "' "•* '"
mcGiionnipomii (mm) (mH2O)
•)Do
-------
"Air Permeability Stack" Cards
C2
Air Permeability Test - Data Analysis (cont.)
Oa fie prcncxa Cud (APS), te dttiyea mpnt woo fit to tte ^jproiunUE aprcmoa given on Cvd
AN. ltwumjlyBe4uuif botfi BK^odiducnted on card AFT, if you input viluo for tbs*
*cil flowrUB (Q) Bd ibctfftcum thidoacM(mX Below e*chcolunm of dua,[be two
vilon «e dxocd by:
refco e ok^jooa aeibod 1 (ice Cird APT)
djrcyjnaf tbc nptaaoM Kilytei, tbe diu expcciKd u
«fpouaOa<0,f^irefkB*liBe. Tbe
"eomlioott coeffiermr*,r, 1* t innapin dbow well
i*aCKfanalatboitedc&ctlcurve. Air->l,tbe
dm pmtii iB fifl a 6e «»moU owe. At ibe ntht
ConeUooa Coef.
diUKtfl |0.941I3B|
daaiKtf2 I 0.98602]
dim«f3 1 No Dm |
152
-------
Appendix D: "Aquifer Characterization" stack cards.
153
-------
"Aquifer Characterization' Stack Cards
D1
Aquifer Characterization:
To achieve efficient venting, the
hydrocubon-coiuiralnittd toil must
be exposed to air flow, therefore, in
mon cud where the residual soil
coniaminiUon Uet clou to, or below,
the sacursted toil zone (groundwsur
table), U will be neceuuy to
incorporate i froundwaicr pumping
sysum in Ihe vapor extraction system
design.
Ai rocnUoned previously, one rnut
always be aware of fre poundwiier
Aquifer Characterization:
Since mod venting lyittmj ire iniulled above "phrenic aquifers" (aquifers wilh
unconfmed upper surfaces), the two primary aquifer parameters needed for design
are:
K » hydraulic conductivity
S * effective porosity (or specific yield)
The first parameter represents a convenient combination of the fundamental
parameters: permeability, density, and viscosity:
where:
k * pGODcability
p • fluid deuily
gm icceknlioB due no gravity
Aquifer Characterization:
These parameters (K and S) can be estimated using the results of a standard transient
groundwater pump test with a constant pumping rate. The results are then compared
against sundxrd "type curves* for specific aquifer situations (i.e. leaky, unconfmed
aquifers, etc.).
Press the •References* button below for more information on slug tests, bail tests,
pump tests, and diu analysis.
Aquifer Characterization - References
J. Bear. "Hydraulics of Croundwater", McGraw-Hill, 1979, ISBN 0-07-004170-9,
p. 463 - 490.
R. A. Freeze and J. A. Cherry, "Groundwater", Prentice-Hall, 1979, ISBN
0-13-365312-9. p. 339 - 352.
ri D r*htrtJT, "A
Ei^ll* nf ,h» Uvnrrl*
154
-------
Appendix E: "System Design" stack cards.
155
-------
"System Design" Stack Cards
E1
Number of Venting Wells...
To« proee*™ for MmiUf ••
ftoaber of ancaoa. w»Ba ifl monitor n tbe
DRUM moi pcnoiuly «o de
u appropnalB u • p«» toe.
iMwiBcosmuac
*atl9 vtmcmJ wdj flownea, alaalw
BU-umxM wper flow r-aqwrc.i. deiHiainB
fioot la try aHMpcaficlmiianraM. Tbti
ia
Ksabor«fcilaatai»c!U.
2oat proceed t> fellow tfee
6«folJowmtcanl*->
Design Input
(1) tix ^tued time pehod for
HOB: - dxk on toy nbie bndmt
tetraocemfo
UK tab key U mow
benraea cells
NQK: - dick oa my able beadios TO (el more info
ub key n move bet\*«a oeUi
HOWTUB per Vapor
Exncioo Well
ISCFM1
Critical Volume
Predictions...
I " 1
O Enter Dinribution
O "Fresh" Cuolinc
© "Weathered* Gasoline
Critical Volume Calculation...
Compcwnon
(chooa: one
Soapy cn-er me lempenniB ai
(be nfhi, aod ttacacpeofy tbe
componooo of your contaminant;
If you are uoaun abotM tin*, didc
OB the 'About Compoairiop—'
bOkntocuedailla-elovwTnihl.
pk tMdel p-edieamBi, (or
Weamaed CMohae
T*20*C
10% mouaire cnueei
( -> Set Default BP R»n«et <- J
Tte model -eomia ooffiol that
•Uo-M yoo to deternooe
limdaatamooDB(-f
emnpouada falhm| wimm 5
bodmg poou raofea. Typem
your owe range*, or dioose
ifaedefaultvaluea.
mB«nrs] MS, tad %rta>0*e4
tfae beJumor &M
«> Import DalK" J SaUiratt.-! Vaa-or It 2t53E*«3l
—•^ Ca«aalratMa ai Urn***! I*'**JJ& WJ|
FO-^rn-^SS THE IMPORT ^
DATABUITONI
tte
QtAW)
75,041
31 U I
100IXX)
H.OOO
90.O2
15.034
10.034
73.035
70.035
Mia Vvlnrnc t» R«ma-*<
>H% of Uitul Bawl•«!
Tcrapamae ("C*
ilType:
J ™S
W« lit red Gasolia*
*»»11
.12}
J»0
oca
jxa
JOOO
£00
J2S5L
I* Boll
11.650
9JW3
6.755
4J12
24.010
ZJ.474
22.4O3
M.771
1IJW3
15J54
15.051
BP M BP §3
22.140
23.000
23.120
24.577
1SJ4S
25.766
26.031
15.919
!*«»!]
4IJ10
45.950
41.509
51J50
54^09
5IJOI
Removal Efficiency...
The aufeMface la dtfitcult to diaraaenae, aod
rarely cae/on-oa ID oar aoaoe of a *aaodboB*.
Tbers an mne acoetml daw* of attuaaaoe mat
viU C4BMD VCDOBJ removal raiDB ID be kaa man
•tu-a-optnhcKdforibeidealcaae. Eachoftbcae
are dMCiwaed m "A Practical Approadt la On
r***»yy OpennoD, and Mounrmf of la Situ Soil
Vesdof SytMcaM*. You caakuamoaB about
eac-k by ctadcmt on fee buna ID the niliL
la atUitiaa, wfaea oooammants are located doac
ID (rovDd waa. me c-ffocx of tbe vacuum on the
water able level cae • paficantiy enpacs a venom
cyMea'a porformaDoe. To learn about ihia, dick
OB me •Orocad Wa«-T Upwelhat' bunco.
Dilution Effect*
Liquid Ljyen
]
Low Permeability Lenta ]
Ground Waier Upwelling )
156
-------
"System Design" Stack Cards
E2
Help: Well Parameters
Help: Minimum Number of Wells
"Soeen TladcneH*
m ton* »fll be te ndiu* of the well
typically BKMB permeable th« the *ad
u the leniifa of the aloral interval of the
wefl. or die thictoxw of the permeable
zone, whichever u mailer.
The •Wmnum Number of Wen*" i* calculated by the two method* i*\mttt4 below:
a)B»edonAna-
m thi* approach we uoauue the mammon number of well* required
to provide atr flow through the coUMmnjCcd zone a* you have
defined it. If Re denote* the radial emt of oontummnoo, md Ri
dreou the "radiDi of inflaeace" of m exaacaon well, (hen:
Ria
b) BMBd OB Critical Vohtme tf V^or -
u the radial duMmr? away from the ,. pjQjTVO
eitracaoa wcQ, where the (auieprDuure I \_
meawied in OB nil is ^ipronmucty zero. I ^^ND
^X^-
The pndichoofl are sot very aenMDve to tbu
of well* reqmrod to
anct file cnooal votume of vapor 6no the eonuoiuMUDd ml zone
Vcnncal« cnnoJ votmne of v^or fUj-e»di»l]
M^dl .^nllm*«(|-rc«du*J]
Qwefl « votumeoic flownc from Bifle well [Ud]
= efficiency of exmoxm pioceM
x tune for deao-up [d] ' *
Contaminant Composition
View only Mode |
Compound Name
M.i.
Fractioi
V.por
Prettar*
ia| ;» re
1
2
3
4
5
6
7
8
9
10
propane
isobuiane
n-buune
tnm-2-buunc
ci*>2-butene
3-methyl-l
-------
"System Design' Stack Cards
E3
Groundwater Pumping Systems
la cuo where oonianiniied nils
lie jua above or below the water
table, poundwater pumpinj
syiurai will be required to iniure
that conuminited tolls remain
expoicd. Indefignmgi
(roundwiier lynem it ii
imporjuitlo be >wve Uut
upweUlnj (cfrtw-up) of the
trouiidwueruble will occur
when * viaium a ipplled u the
exnaionwell
(ice the EIUIC it the rijhl).
Vapor Treatment Systems
Currently there a four main
treatment prooeuei available
VAPOR COMBUSTION UNITS:
Vapors are incinerated and
dominion eSictenciet are
typically >95*. A fupplemental
fuel, sich w propane, is added
before cornbunion unlcM
extraction well vapor
ooncentrationi are on the order of
158
-------
Appendix F: "Compound List Update" stack cards.
159
-------
"Compound List Update" Stack Cards
F1
Compound List Update
This card ii provided u a utility to let you add, or delete compounds from the
Compound Lin Data Base thit thii program out. You may not delete or change the
properties of the bate 62 compounds, since these are needed for the two default
gauline cue calculations fie. the "Rah" and "Weathered' gasolines). If you wish
to change any of the properties of the added chemicals, first delete them, then
rctntot them into the Compound List Data Base. Follow the directions below:
ckimkal
Ctlmiol N.miHffcwComp
Molct.br Weiial [|/molt]
V.p.r Prai.rt <92IC [>lin|
Pol.l «1 ilm 1C]
160
irU.S. GOVERNMENT PRINTING OFFICE: 1993-751-808
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