A Citizen’s Guide to

Vitrification

What is vitrification?

Vitrification is a process that permanently traps harmful chemicals in a solid block of glasslike 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.

? ? EPA uses many methods to clean up pollution at Superfund and other sites. Some, like vitrification, are considered 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.

The Citizen’s Guide Series

United States Office of Solid Waste and EPA 542-F-01-017

Environmental Protection Emergency Response December 2001

Agency (5102G) www.epa.gov/superfund/sites

www.cluin.org

ground

surface

ground

surface

hood

soil soil

electrodes

During Vitrification After Vitrification

glass-like

melted block

soil

electric

current
2

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 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 groundwater near the vitrified block to make sure that chemicals are not being released.

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 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.

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)

In general, in situ vitrification offers faster cleanup times than most methods.

Cleanup can take from weeks to months, rather than years.

How long will it take?