United States
Environmental Protection
Agency
Office of Solid Waste and
Emergency Response
(5102G)
EPA 542-F-01-006
April 2001
www.epa.gov/superfund/sites
www.cluin.org
&EPA A Citizen's Guide to Soil Vapor
Extraction and Air Sparging
The Citizen's Guide Series
EPA uses many methods to clean up pollution at Superfund and other sites. If you live, work, or go to school
near a Superfund site, you may want to learn more about cleanup methods. Perhaps they are being used or are
proposed for use at your site. How do they work? Are they safe? This Citizen's Guide is one in a series to help
answer your questions.
is the
The water table is the level of groundwater below
the ground surface.
What are soil vapor extraction and air sparging?
Soil vapor extraction or SVE removes harmful chemicals, in the form of vapors, from the soil
above the water table. Vapors are the gases that form when chemicals evaporate. The vapors
are extracted (removed) from the ground by applying a vacuum
to pull the vapors out.
Air sparging uses air to help remove harmful vapors from polluted
soil and groundwater below the water table. When air is pumped
underground, the chemicals evaporate faster, which makes them
easier to remove. Like SVE, a vacuum then extracts the vapors. Certain chemicals—like solvents
and fuel—evaporate easily. SVE and air sparging work best on these types of chemicals. SVE
and air sparging are often used at the same time to clean up both soil and groundwater.
How do they work?
SVE requires drilling extraction wells within the polluted area. These wells are drilled into
the soil, but not the groundwater. Attached to the wells is equipment that creates a vacuum,
which pulls air and vapors through the soil and up to the surface.
Air injection wells can be drilled to help the cleanup. Air injection wells pump air into the
ground. The air causes the pollution to evaporate faster. Sometimes air vents are used instead
of air injection wells. Air vents don't pump air, but provide a passage for fresh air to enter the
ground. The number of air injection and extraction wells can range from one to hundreds,
depending on the size of the polluted area.
Once the extraction wells pull the air and vapors out of the ground, special air pollution
control equipment collects them. The equipment separates the harmful vapors from the clean
air. Then, the vapors sorb or stick to solid materials. Or they are condensed to liquids. These
polluted solids and liquids are disposed of safely.
Air sparging works very much like SVE. However, the wells that pump air into the ground
are drilled into water-soaked soil below the water table. Air pumped into the wells disturbs
the groundwater. This helps the pollution change into vapors. The vapors rise into the drier
soil above the groundwater and are pulled out of the ground by extraction wells. The harmful
vapors are removed in the same way as SVE.
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For more
information
write the Technology
Innovation Office at:
U.S.EPA(5102G)
1200 Pennsylvania Ave.,
NW
Washington, DC 20460
or call them at
(703) 603-9910.
Further information also
can be obtained at
www.cluin.org or
www.epa.gov/
superfund/sites.
The air used in S VE and air sparging also helps clean up pollution by encouraging the growth of
microbes. These tiny bugs are found naturally in soil and can use pollution for food. When
microbes completely digest pollution, they can change it into water and harmless vapors. (A
Citizen's Guide to Bioremediation [EPA 542-F-01-001] describes how microbes work.)
Are soil vapor extraction and air sparging safe?
When properly designed and operated, SVE and air sparging are safe cleanup methods. No one
has to dig up the pollution, and no chemicals—just air—are added to the ground.
EPA makes sure that harmful vapors are collected and disposed of properly.
- How long will It ?
Cleaning up a site using S VE and air sparging can take years. The
time depends on several factors:
• size and depth of the polluted area
• type of soil and conditions present (wet or dense soil can slow the proces;
• type and amounts of harmful chemicals present
The air injected into the ground can be heated to speed up the process. The heated soil
helps evaporate the chemicals faster. Also, other sources of heat, like steam or hot water
can be pumped into the injection wells to heat up the soil. (See A Citizen's Guide to In
Situ Thermal Treatment [EPA 542-F-01-012].)
Why use soil vapor extraction and air sparging?
S VE and air sparging are quicker than cleanup methods that rely on natural processes to do the
work. In general, the wells and equipment are simple to install and maintain. And they can reach
greater depths than methods that involve digging up soil. S VE and air sparging are effective at
removing many types of pollution that can evaporate. B oth methods can be used with other methods to
clean up other types of pollution as well. Both methods work best in loose soils—like sand and gravel.
But they both work well under many types of conditions.
S VE and air sparging are often chosen to clean up Superfund sites. EPA has selected S VE for
use at approximately 196 sites and air sparging for use at roughly 48 sites.
NOTE: This fact sheet is intended solely as general guidance and information to the public. It is not intended, nor can it be relied
upon, to create any rights enforceable by any party in litigation with the United States, or to endorse the use of products or services
provided by specific vendors. The Agency also reserves the right to change this fact sheet at any time without public notice.
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