United States
Environmental Protection
Agency
Risk Reduction Engineering
Engineering Laboratory
Cincinnati OH 45268
Research and Development
EPA/540/S2-91/003 June 1991
EPA Project Summary
Soil Vapor Extraction Technology
Reference Handbook
Tom A. Pedersen and James T. Curtis
Soil vapor extraction (SVE) systems
are being used in Increasing numbers
because of the many advantages these
systems hold over other soil treatment
technologies. SVE systems appear to
bo simple in design and operation, yet
the fundamentals governing subsurface
vapor transport are quite complex.
In view of this complexity, an expert
workshop was held to discuss the state
of the art of the technology, the best
approach to optimize system applica-
tion, and the process efficiency and
limitations. As a result of the workshop,
an SVE Technology Assessment report
was produced. This report discusses
the basic science of the subsurface
environment and subsurface vapor flow,
site Investigations, SVE system design
and operation, and includes selected
papers from the expert workshop. Addi-
tional research activities being eon-
ducted include a field demonstration of
a structured SVE system design ap-
proach, a laboratory column study to
determine and characterize residuals
following vapor extraction, an assess^
ment of secondary emissions and regu-
lations governing releases from SVE
systems, cost of SVE implementation
and operation, and a survey of tech-
niques to enhance vapor removal.
This Project Summary was devel-
oped by EPA's Risk Reduction Engi-
neering Laboratory, Cincinnati, OH, to
announce key findings of the research
project that Is fully documented In a
separate report of the same title (see
Project Report ordering Information at
back).
Introduction
SVE is being used with increasing fre-
quency throughout the country for the
remediation of unsaturated zone soils that
have become contaminated with volatile
organics. SVE, also known as vacuum
extraction, in situ vaporization, or soil
venting, has many positive features that
gives it an advantage over other soil treat-
ment techniques such as excavation and
offsite treatment, soil flushing, or
biotrealment. Some of the features that
make this technology applicable to a broad
spectrum of sites are:
• SVE is an in situ technology, so there
is a minimum of site disturbance;
often, business operations at the site
need not be interrupted;
SVE can treat large volumes of soil
at reasonable costs;
• SVE is easily installed and uses
standard, readily-available equip-
ment, which allows for rapid mobili-
zation and implementation of remedial
activities;
• SVE is effective in reducing the con-
centration of volatile organic com-
pounds (VOCs) in the vadose zone,
reducing the potential for further mi-
gration; and
SVE complements groundwater
pump and treat techniques, which
may be instituted concurrently.
These features, combined with the ap-
parent simplicity of SVE system design,
implementation, and operation, have com-
bined to make SVE one of the fastest
growing remediation choices. This growth
has not necessarily been accompanied by
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a broader expansion of the knowledge base
to properly design and operate an SVE
system. Indeed, the ease with which SVE
systems can be installed and operated
belies the very complex nature of subsur-
face vapor behavior and transport.
Much of the technical information re-
garding the design, construction, and op-
eration of an extraction system is held by
the SVE technology developers and ven-
dors. Engineering practices, which are of-
ten considered proprietary by the develop-
ers may be based in large part on each
developer's experiences. This atmosphere
does not encourage rigorous objective re-
view of design or operating methods and
makes it more difficult to analyze the results
of SVE use. This lack of knowledge poses
limitations to regulatory agency personnel
and others attempting to interpret system
operating results.
The increased use of SVE systems
and the need for a greater understanding
of the principles that underlie soil vapor
behavior and other issues related to SVE
led the U.S. Environmental Protection
Agency's Office of Research and Devel-
opment, through its Risk Reduction Engi-
neering Laboratory, Releases Control
Branch (RREL-RCB) to initiate SVE re-
search efforts. The initial step in these
efforts was the convening of an expert
workshop in Edison, NJ, on June 28 and
29,1989. Workshop participants included
SVE technology vendors, petroleum in-
dustry representatives, university re-
searchers, consulting engineers, regula-
tory agency representatives, and others
who were familiar with this technology.
The workshop had dual objectives. One
was to discuss the state of the art of SVE-
related topics, such as: site characteriza-
tion, pilot systems, full scale system design
and operation, vapor treatment options,
establishing and attaining cleanup goals,
and monitoring SVE treatment progress.
Some presenters discussed actual case
studies; and others discussed a structured
framework for conducting site investigations
and system design, the use of modeling to
help design extraction systems, and other
research on SVE currently in progress.
The second objective of the workshop was
to discuss additional research needs. Panel
discussions were held with workshop at-
tendees regarding areasforfuture research
and topics needing immediate attention.
The regulatory climate was also discussed,
including suggested remediation standards
and methods to determine cleanup attain-
ment. As a result of this workshop, an SVE
Technology Reference Handbook was de-
veloped.
Reference Handbook
The main text of this document is an
assessment of the state of the art of soil
vapor extraction technology. It was written
specifically for state and local regulators,
agency staff, environmental managers, re-
medial contractors and consultants who
desire a basic understanding of SVE prin-
ciples, applicability, operation, and cost.
A general overview of the theoretical
considerations applicable to soil vapor ex-
traction is provided in Section 2. This sec-
tion includes discussions of the effect on
SVE of contaminant properties, including
vapor pressure, solubility, Henry's law
constant, boiling point, soil sorption coeffi-
cient, contaminant composition and
weathering, and soil properties such as
structure, moisture content, texture, air
permeability, and temperature. Section 2
also discusses gaseous flow in the sub-
surface environment, including the equa-
tions that govern subsurface vapor flow.
Finally, several field methods of determin-
ing the soil's air permeability are presented.
Section 3 provides an overview of site
investigation approaches that can be used
to obtain data necessary to determine if
vapor extraction is a viable remedial option
and, if so, obtain critical design information.
This section also includes references to
field techniques and equipment used to
evaluate the site-specific feasibility of va-
por extraction.
General design approaches, including
the determination of the air permeability,
well selection, and system configuration,
are described in Section 4. In addition, this
section discusses the components that
comprise an SVE system. The purpose of
this section is to provide the reader with a
qualitative analysis of the design procedure
and the individual components to aid in the
preliminary design of such a system.
Operation, maintenance, and monitor-
ing of SVE systems are discussed in Sec-
tion 5. This section also includes discus-
sions of enhanced biotreatment due to
SVE; cleanup attainment determination,
including new methods for measuring re-
siduals; and other issues related to system
operation.
Section 6 discusses emission control
methods available to treat the extracted
vapors. Discussions are included on acti-
vated carbon adsorption, thermal and
catalytic incineration, internal combustion
engines, packed bed thermal processors,
biotreatment, and direct discharge to the
atmosphere.
The costs related to SVE implemen-
tation and operation are discussed in
Section 7. This section discusses costs for
a site investigation, component-by-compo-
nent capital costs for SVE equipment, costs
for prepackaged units, and operations and
monitoring costs for these systems.
Ten appendices contain selected pa-
pers presented at the Edison, NJ, work-
shop. Papers reprinted here were selected
as representative of the wide range of
topics discussed. Appendix A is a review
of existing SVE operations by N.E. Hutzler,
B.E. Murphy, and J.S. Gierke. This section
reports on various aspects of SVE opera-
tions, including number, type, and layout
of wells, type of blower or pump used,
emission control units, and additional op-
erational information. The section provides
the reader with a sound historical basis
with which to view other sections.
In Appendix B, J. Danko discusses the
applicability and limitations of SVE opera-
tidri7This paper describes the advantages
of SVE and discusses, from an engineering
viewpoint, some practical observations and
advice.
Appendix C contains a report by H.B.
Kerfoot on the use of soil gas surveys in
the design of SVE systems. Soil gas sur-
veys are frequently used during the site
investigation phase to help delineate the
extent of contamination and determine the
types and relative concentrations of com-
pounds in the ground. With this information,
a judgment can often be rendered regard-
ing the applicability of SVE for that site.
Appendix D, by R.E. Hinchee, D.C.
Downey, and R.N. Miller, discusses the
enhancement of biodegradation that ac-
companies the use of soil vapor extraction.
P.O. Johnson, M.W. Kemblowski, J.D.
Colthart, D.L. Byers, and C.C. Stanley
contribute "A Practical Approach to the
Design, Operation, and Monitoring of In Situ
Soil Venting Systems" in Appendix E. This
report presents a structured logical ap-
proach that forms a "decision-tree" for de-
ciding if SVE is appropriate to be used
and, if so, describes the steps to be taken
during system design, operation, and
monitoring.
Appendix F contains a scientific ap-
proach to SVE design in a paper by M.C.
Marley, S.D. Richter, B.L. Cliff, and P.E.
Nangeroni. This paper describes, among
other things, the use of a computer model
to calibrate data obtained during a field air
permeability test.
L.R. Silka, H.D. Cirpili, and D.C. Jordan
discuss in Appendix G modeling of sub-
surface vapor flow and the applications of
modeling to SVE.
,D.W. DePaoli, S.E. Herbes, and M.G.
Elliot describe in Appendix H the perfor-
mance of SVE at a jet fuel spill site in Utah.
This paper contains knowledge and expe-
rience gained during SVE operation,
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operational results, and a discussion of
various aspects of SVE.
Appendix I contains actual case history
for an industrial site that has con-
ation from several volatile organic
se neutral compounds in a report by
dutch, Jr., A.N. Clarke, D.J. Wilson,
'.D. Mutch, this interim report fo-
; on the measured zone of influence
extraction well, the composition of
traded gas and its changes with
treatability of the extracted vapor
by granular activated carbon, temperature
variations that occur in the system, and
groundwater upwelling due to the induced
vacuum. The authors also describe the
use o: a mathematical model in their work.
A report by G.E. Hoag in Appendix J
comments on recent SVE research devel-
opments and research needs. These dis-
cussions follow a summary of SVE "re-
search milestones."
Appendices K and L contain responses
to a |state-by-state survey conducted in
August 1989 regarding the allowable soil
residual and air discharge criteria.
Th is book is not intended for use as a
desig i manual, but it documents all of the
latest state of the art of the soil vapor
extraction technology.
Tf e full report was submitted in fulfill-
ment of Contract No. 68-03-3409 by COM
Federal Programs Corporation under the
sponsorship of the U.S. Environmental
Protection Agency.
•&U.S. GOVERNMENT PRINTING OFFICE: 1991 - 548-028/40010
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Tom A. Pedersen and James T. Curtis are with Camp Dresser and McKee, Inc.,
Cambridge, MA 02141.
Chl-YusnFan is the EPA Project Officer (see below).
The complete report, entitled "Soil Vapor Extraction Technology Reference
Handbook,"(Order No. PB91-168476/AS; Cost: $39.00, subject to change) will
be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Edison, NJ 08837
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA PERMIT NO. G-35
Official Business
Penalty for Private Use $300
EPA/540/S2-91/003
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