United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102G)
EPA 542-F-96-008
April 1996
vvEPA
A Citizen's Guide to
Soil Vapor Extraction
and Air Sparging
Technology Innovation Office
Technology Fact Sheet
What is soil vapor extraction?
Soil vapor extraction, known as SVE, is the most
frequently selected innovative treatment at Super-
fund sites. It is a relatively simple process that
physically separates contaminants from soil. As the
name suggests, SVE extracts contaminants from the
soil in vapor form. Therefore, SVE systems are de-
signed to remove contaminants that have a tendency'
to volatilize or evaporate easily. SVE removes vola-
tile organic compounds (VOCs) and some semi-
volatile organic compounds (SVOCs) from soil
beneath the ground surface in the unsaturated
zone—that part of the subsurface located above the
water table. By applying a vacuum through a system
of underground wells, contaminants are pulled to the
surface as vapor or gas. Often, in addition to
vacuum extraction wells, air injection wells are in-
stalled to increase the air flow and improve the re-
moval rate of the contaminant. An added benefit of
introducing air into the soil is that it can stimulate
bioremediation of some contaminants.
SVE is sometimes called in situ volatilization,
enhanced volatilization, in situ soil venting,
forced soil venting, in situ air stripping, or soil
vacuum extraction.
What is air sparging?
Used alone, soil vapor extraction cannot remove.
contaminants in the saturated zone of the subsur-
face, the water-soaked soil that lies below the water
table. At sites where contamination is in the saturat-
ed zone, a process called air sparging may be used
along with the SVE system. Air sparging means
pumping air into the saturated zone to help flush
(bubble) the contaminants up into the unsaturated
zone where the SVE extraction wells can remove
them (Figure 1).
For air sparging to be successful, the soil in the
saturated zone must be loose enough to allow the
injected air to readily escape up into the unsaturated
zone. Air sparging, therefore, will work fastest at
sites with coarse-grained soil, like sand and gravel.
A Quick Look at Soil Vapor Extraction
Pulls contaminants from soil in vapor form.
Provides an oxygen source which may stimulate bioremediation of some contaminants.
Most frequently used innovative treatment technology.
A Quick Look at Air Sparging
Extends the effectiveness of soit vapor extraction to include contaminants that exist in ground water.
Can accelerate cleanup at pump-and-treat sites.
Provides an oxygen source which may stimulate bioremediation of some contaminants.
Printed on Recycled Paper
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Figure 1
A Combined Soil Vapor Extraction/Air Sparging System
Air Sparging
Air Well
Vent
0 o o n o \
w
Water f
Unsaturated
Zone
Saturated
Zone
As with SVE, an added benefit of air sparging is that
it provides an oxygen source that helps stimulate the
bioremediation of some contaminants. Bioremedia-
tion is an innovative treatment technology that uses
microorganisms, such as bacteria, that live in the soil
or groundwater to break down contaminants into
harmless substances. (Bioremediation is explained in
detail in another Citizen's Guide. See the "For More
Information" box on page 4.) Air sparging also can
be a quick and effective treatment for VOCs in
groundwater.
How does an SVE system work?
The first step to constructing an SVE system is to in-
stall vapor extraction wells and injection wells (or
air vents) in the contaminated area. Air injection
wells use air compressors to force air into the
ground. Air vents serve the same function as air in-
jection wells, but are passive—instead of pumping
air they just provide a passage for air to be drawn
into the ground. When incoming air passes through
the soil on its way to the extraction wells, contam-
inants evaporate out of the spaces between the
soil particles and are pulled by the air to the wells
and removed.
Vapor extraction wells can be placed either verti-
cally or horizontally. Typically, they are placed
vertically and are designed to penetrate the lower
portion of the unsaturated zone.
Vapors extracted by the SVE process are typically
treated using carbon adsorption, incineration, cata-
lytic oxidation, or condensation. Other methods,
such as biological treatment and ultraviolet oxida-
tion, also have been used with SVE systems. The
type of treatment chosen depends on which contami-
nants are present and their concentrations.
Carbon adsorption is the most commonly used treat-
ment for contaminated vapors and is adaptable to a
wide range of volatile organic compounds.
When properly designed and operated, SVE is a
safe, low maintenance process. Explosion-proof
equipment is available to handle the potentially ex-
plosive mixtures of extracted gas that may be en-
countered on some landfill or gasoline spill sites.
SVE with thermal enhancement. SVE performance
can be enhanced or improved by injecting heated air
or steam into the contaminated soil through the in-
jection wells. The heated air or steam helps to
"loosen" some less volatile compounds from the
soil. Researchers have done large-scale demonstra-
tions of SVE with steam injection at several sites. In
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addition to heated air or steam, another enhancement of
SVE is the use of radio-frequency (RF) heating to bet-
ter vaporize or volatilize compounds in clay and silt-
type soils. Demonstrations of RF heating are
underway.
Dual phase extraction. Dual phase extraction is a
treatment system similar to SVE, but the extraction
wells are sunk more deeply into the ground—below
the water table into the saturated zone. Strong vacu-
um is applied through the extraction wells to simul-
taneously remove groundwater and vapors from the
subsurface. Once above ground, the extracted vapors
and groundwater are separated and treated. Dual
phase extraction is more effective than SVE at sites
with dense, clayey soil. When dual-phase extraction
is combined with bioremediation, air sparging or
bioventing, it can shorten cleanup times.
Why consider SVE or air sparging?
SVE is very effective at removing VOCs from the
unsatufated zone". With the" addition of an air
sparging system, contaminants can be removed from
the saturated zone as well. Neither technique
requires excavation of the contaminated soil.
(Excavation is undesirable because it is expensive,
creates dust, and allows volatile contaminants to
escape untreated into the atmosphere.) The extracted
vapors usually require treatment, but costs for
treating extracted vapors and liquids are low
compared to the costs of technologies requiring
excavation. The technologies are relatively simple to
install, can be used effectively in combination with
other treatment technologies, and are effective under
a variety of site conditions.
WiH SVE or air sparging work at every
site?
SVE and air sparging may be good choices at sites
contaminated with solvents and other volatile organ-
ic compounds (such as trichloroethane, trichloroeth-
ylene, benzene, toluene, ethylbenzene, and xylene)
and fuels. Because properties of the soil have such
an important effect on the movement of soil vapors,
the performance and design of SVE and air sparging
systems depend greatly on the properties of the soil.
SVE is best used at sites with loose unsaturated soil,
such as sand, gravel, and coarse silt or fractured bed-
rock. However, it has been applied to sites with
denser soils, although treatment may take longer.
Also, the higher the moisture content of the soil, the
slower SVE works.
Where are SVE and air sparging being
used?
SVE has been used at many Superfund and other
hazardous waste sites. The Verona Well Field in
Michigan is a Superfund site at which SVE was used
to treat a one-half acre area to a depth of 20 feet con-
taminated with trichloroethene, tetrachloroethylene,
and "BTEX," a mixture of benzene, toluene, ethyl-
benzene, and xylene. The SVE system removed and
treated a total of 45,000 pounds of contaminants
from the treatment area. EPA set target cleanup
levels for 19 different contaminants at the site and
the SVE system successfully met the goals for all the
contaminants. Table 1 on page 4 lists other Super-
fund sites at which SVE, air sparging, and dual-
phase extraction are planned or have been used.
Whatjs An Innovative Treatment
Technology?
Treatment technologies are processes ap-
plied to hazardous waste or contaminated
materials to permanently alter their condition
through chemical, biological, or physical
means. Treatment technologies are able to
alter, by destroying or changing, contami-
nated materials so they are less hazardous
or are no longer hazardous. This may be
done by reducing the amount of contami-
nated material, by recovering or removing a
component that gives the material its haz-
ardous properties or by immobilizing the
waste. Innovative treatment technologies
are technologies that have been tested, se-
lected or used for treatment of hazardous
waste or contaminated materials but still
lack well-documented cost and performance
data under a variety of operating conditions.
Some innovative treatment technologies,
such as SVE and thermal desorption, are so
widely used that the term "innovative" may
seem inappropriate. However, innovative
variations on these technologies are still be-
ing developed and EPA still is not able to
predict with certainty the time and cost re-
quired to clean up a site using them. For
these reasons, EPA continues to track these
technologies and collect data about them.
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Table 1
Examples of Superfund Sites Using Soil Vapor Extraction (SVE), Air Sparging (AS),
or Dual Phase Extraction (DPE)*
Name of Site Technology Status**
Fairchild Semiconductor (San Jose), CA SVE Completed
Garden State Cleaners, NJ SVE Completed
Defense General Supply Center, VA SVE Completed
Hollingsworth Solderless, FL SVE Completed
Rocky Mountain Arsenal, CO SVE Completed
Lindsay Manufacturing, NE SVE Operational
Applied Environmental Services, NY SVE/AS Operational
Wayne Reclamation and Recycling, IN SVE/AS Operational
Sand Creek Industrial, CO SVE/DPE Predesign
Unemaster Switch Corporation, CT SVE/DPE In design
Rochester Property, SC AS Operational
Fairchild Air Force Base, WA AS Operational
Contaminants
Volatile organic compounds (VOCs),
benzene, toluene, ethylbenzene & xylene
(BTEX)
VOCs
VOCs
VOCs
VOCs
VOCs
BTEX, VOCs, semi-volatile organic
compounds (SVOCs), polyaromatic
hydrocarbons (PAHs)
VOCs, BTEX
VOCs, PAHs, BTEX
VOCs
VOCs
VOCs, BTEX
For a listing of Superfund sites at which innovative treatment technologies have been used or selected for use,
contact NCEPI at the address in the box below for a copy of the document entitled Innovative Treatment
Technologies: Annual Status Report (7th Ed.), EPA 542-R-95-008. Additional information about the sites listed
in the Annual Status Report is available in database format. The database can be downloaded free of charge from
EPA's Cleanup Information bulletin board (CLU-IN). Call CLU-IN at 301-589-8366 (modem). CLU-IN's help line is
301-589-8368. The database also is available for purchase on diskettes. Contact NCEPI for details.
* Not aff waste types and site conditions are comparable. Each site must be individually investigated and tested.
EngtoaBring and scientific judgment must be used to determine if a technology is appropriate fora site.
"As of August 1995
For More Information
The publications listed below can be ordered free of charge by calling NCEPI at 513-489-8190 or faxing your request to
513-489-8695. If NCEPI is out of stock of a document, you may be directed to other sources. Write to NCEPI at:
National Center for Environmental Publications and Information (NCEPI)
P.O. Box 42419
Cincinnati, OH 45242
• Selected Alternative and Innovative Treatment Technologies for Corrective Action and Site Remediation: A
Bibliography of EPA Resources, January 1995, EPA 542-B-95-001. A bibliography of EPA publications about
innovative treatment technologies.
• Soil Vapor Extraction Treatment Technology Resource Guide, September 1994, EPA 542-B-94-007. A bibliography
of publications and other sources of information about SVE, air sparging and other innovative treatment
technologies.
• In Situ Remediation Technology Status Report: Thermal Enhancements, April 1995, EPA 542-K-94-009.
• Technology Assessment of Soil Vapor Extraction and Air Sparging, September 1992, EPA 600-R-92-173.
• Superfund Innovative Technology Evaluation Program: Technology Profiles (7th Ed.), EPA 540-R-94-526.
• A Citizen's Guide to Bioremediation, EPA 542-F-96-007.
• WASTECH® Monograph on Vacuum Vapor Extraction, ISBN #1-883767-08-3. Available for $49.95 from the American
Academy of Environmental Engineers, 130 Holiday Court, Annapolis, MD 21401. Telephone 410-266-3311.
NOTICE: Th!s fact sheet is intended solely as general guidance and information. It Is not intended, nor can it be relied upon, to create any rights enforceable by any
party in litigation with the United States. The Agency also reserves the right to change this guidance at any time without public notice.
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