United States
Environmental Protection
Agency
Office of Solid Waste and
Emergency Response
(5102G)
&EPA A Citizen's Guide to
Vitrification
EPA 542-F-01-017
December 2001
www.epa.gov/superfund/sites
www.cluin.org
Tlhe Citizen's Guide Series
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EPA uses many methods to clean up pollution at Superfund and other sites. Some, like vitrification, are; consid-
ered new or innovative. Such methods can be quicker and cheaper than more common methods. 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.
What Is vitrification?
Vitrification is a process that permanently traps harmful chemicals in a solid block of glass-
like material. This keeps them from leaving the site. Vitrification can be done either in
place or above ground.
How does It work?
Vitrification uses electric power to create the heat needed to melt soil. Four rods, called
electrodes, are drilled in the polluted area. An electric current is passed between the
electrodes, melting the soil between them. Melting starts near the ground surface and
moves down. As the soil melts, the electrodes sink further into the ground causing deeper
soil to melt. When the power is turned off, the melted soil cools and vitrifies, which
means it turns into a solid block of glass-like material. The electrodes become part of the
block. When vitrified, the original volume of soil shrinks. This causes the ground surface in
the area to sink slightly. To level it, the sunken area is filled with clean soil.
electrodes
hood
ground
surface
electric
current
ground
surface
During Vitrification
After Vitrification
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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/
supcrfund/sites.
The heat used to melt the soil can also destroy some of the harmful chemicals and cause
others to evaporate. The evaporated chemicals rise through the melted soil to the ground
surface. Here, a hood, which covers the heated area, collects the chemicals. These chemicals
are sent to a treatment system where they are cleaned up.
Any harmful chemicals that remain underground become trapped in the vitrified block, which
is left in place. This prevents rainfall, groundwater flow, and wind from transporting the
chemicals offsite.
Is vitrification safe?
When used properly, vitrification can be quite safe. The gas hood must be large enough to
cover the polluted area so it can capture all the chemicals released from the soil. Any wet soil
must be dried first to prevent steam from forming. The release of steam can splash hot, melted
soil above ground. The hood further prevents site workers from being splashed.
The vitrified block that is left in place is permanent and not harmful to people. However, EPA
may limit construction on the land to avoid damage to it. EPA also tests the soil and ground-
water near the vitrified block to make sure that chemicals are not being released.
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How long will it take?
The time it takes for in situ vitrification to clean up a site depends on
several factors:
• size and depth of the polluted area
• types and amounts of chemicals present
• how wet the soil is (wet soil must be dried, which takes more time)
hi general, in situ vitrification offers faster cleanup times than most methods.
Cleanup can take from weeks to months, rather than years.
Why use vitrification?
Vitrification has been used at sites across the country, including one Superfund site. It can
clean up several types of chemicals and soils. By cleaning up soil in place, it avoids the
expense of digging up soil or trucking it to a landfill for disposal. Vitrification also tends to be
faster than other methods.
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 parly 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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