United States
Environmental Protection
Agency
Off ice of
Solid Waste and
Emergency Response
EPA/542/F-92/003
March 1992
v/EPA
A Citizen's Guide To
Soil Washing
Technology Innovation Office
.Technology Fact Sheet
CONTENTS
Page
What Is Soil Washing? 1
How Does Soil
Washing Work?
Why Consider
Soil Washing?
Will Soil Washing
Work At Every Site? 3
Where Is Soil Washing
Being Used? 3
For More Information
What Is Soil Washing?
Soil washing is a technology that
uses liquids (sometimes combined
with chemical additives) and a
mechanical process to scrub soils.
This scrubbing removes hazardous
contaminants and concentrates them
into a smaller volume. Hazardous
contaminants tend to bind,
chemically or physically, to silt and
clay. Silt and clay, in turn, bind to
sand and gravel particles. After the
soil washing process is completed,
the smaller volume of soil, which
contains the majority of the fine silt
and clay particles, can be further
treated by other methods (such as
incineration or bioremediation) or
disposed of according to State and
Federal regulations. The clean,
larger volume of soil is not toxic
and can be used as backfill.
How Does Soil Washing
Work?
A simplified drawing of the soil
washing process is illustrated in
Figure 1 on page 2. The process
begins by digging up the
contaminated soil and moving it to a
staging area — a place where
contaminated material is prepared
for treatment. The soil is then sifted
to remove debris and large objects,
such as rocks. The remaining
material enters a soil scrubbing unit,
in which the soil is mixed with a
washing solution and agitated. The
washing solution may be simply
water or may contain additives, like
detergent, which remove the I
contaminants from the soil. This '
process is very similar to washing
laundry. The washwater is drained
out of the soil scrubbing unit, and
Soil Washing Profile
Separates fine-grained particles (silt and clay) from coarse-grained particles (sand and gravel).
Significantly reduces the volume of contaminated soil.
Is a relatively tow-cost alternative for separating waste and minimizing volume required for subsequent
treatment. y s_ Environmental Protection Agency
.s a transportable technology that can be brought to the site. yfwTst^ackSon Boullvard, 12th Floor
Chicago, IL 60604-3590
Produced by the
Superfund Program
Printed on Recycled Paper
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the soil is rinsed with clean water.
The heavier sand and gravel particles in the processed
soil settle out and are tested for contaminants. If
clean, this material can be used on the site or taken
elsewhere for backfill. If contaminated, the material
may be run through the soil washing process again, or
collected for alternate treatment or off-site disposal.
Off-site disposal is regulated by the Resource
What is Soil Made Of?
Soil Is comprised of fine-grained (silt and clay)
and coarse-grained (sand and gravel) particles,
organic material (decayed plant and animal
matter), water, and air. Contaminants tend to
readily bind, chemically or physically, to slit,
clay, and organic material. Silt, clay, and
organic material, In turn, bind physically to sand
and gravel. When the soil contains a large
amount of clay and organic material, the
contaminants attach more easily to the soil and,
therefore, are more difficult to remove than
when a small amount of clay and organic
material Is present.
Conservation Recovery Act (RCRA) or the Toxic
Substance Control Act (TSCA) and, therefore, a
permitted RCRA or TSCA landfill must be used.
The contaminated silt and clay in the washwater settle
out and are then separated from the washwater. The
washwater, which now also contains contaminants, is
treated by wastewater treatment processes so it can be
recycled for further use. As mentioned earlier, the
washwater may contain additives, some of which may
interfere with the wastewater treatment process. If this
is the case, then the additives must be removed or
neutralized by "pretreatment" methods before the
washwater goes to wastewater treatment.
Once separated from the washwater, the silts and clays
are tested for contaminants. If clean, this material can
be used on the site or taken elsewhere for backfill. If
^contaminated, the material may be run through the soil
washing process again, or collected for alternate
treatment or off-site disposal in a permitted RCRA or
TSCA landfill.
Figure 1
Simplified Soil Washing Process Flow
Contaminated SoH
To Off-Site
W**1*wat*r
Treatment
RmkJual Material To
Other
Treatm*nt/D)*DOMl
'?m
Clean SoH
(Relumed To
Excavation)
Overtired Refect*
(Boulder*, Log*, Etc.) To
Other Tn*tm*nt/DI*po*al
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Any air emissions that may be created during the soil
washing process are collected and treated to meet
applicable regulatory standards.
Why Consider Soil Washing?
Soil washing can be used as a technology by itself but
is most likely to be used in combination with other
treatment technologies.
Soil washing reduces the volume of the contaminated
material but does not reduce the toxicity of the
contaminants. When combined with other treatment
technologies, the toxicity of the contaminants can be
reduced. The larger scale soil washing equipment
presently in use can process up to 25 tons of soil per
hour.
In general, soil washing is most effective on coarse
sand and gravel and may treat a wide range of
contaminants, such as heavy metals, gasoline and fuel
oils, and pesticides. There are several advantages to
using this technology. Soil washing:
• Provides a closed system that remains unaffected
by external conditions. This system permits
control of the conditions (such as the pH level and
temperature) which surround the soil particles
being treated.
• Allows hazardous wastes to be excavated and
treated on-site.
• Can significantly reduce the volume of the
contaminated soil that requires further treatment.
• Has the potential to remove a wide variety of
chemical contaminants from soils.
• Is cost-effective because it can be employed as a
pre-processing step in reducing the quantity of
material to be treated by another technology. It
also creates a more uniform material for
subsequent treatment technologies.
Will Soil Washing Work At Every Site?
Soil washing works best when the soil does not
contain a large amount of silt and clay. In some cases
soil washing is best applied as a technology in
combination with other treatment technologies, rather
than as a technology by itself.
Removal of contaminants can often be improved
during the soil washing process by adding chemical
additives to the washwater. However, the presence of
these additives may cause some difficulty in the
treatment of the used wastewater and the disposal of
residuals from the washing process. Costs of handling
and managing the additives have to be weighed against
the amount of improvements in the soil washing
process's performance.
S X
What Is An Innovative Treatment
Technology?
Treatment technologies are processes applied
to the treatment of hazardous waste or
contaminated materials to permanently alter
their condition through chemical, biological, or
physical means. Technologies that have been
tested, selected or used for treatment of
hazardous waste or contaminated materials but
lack well-documented cost and performance
data under a variety of operating conditions are
called Innovative treatment technologies.
Where Is Soil Washing Being Used?
Soil washing has been used at waste sites in Europe,
especially in Germany, the Netherlands, and Belgium.
In the United States, soil washing has been selected at
numerous Superfund sites. Table 1 lists some
Superfund sites where soil washing has been selected,
their location and types of facilities requiring
treatment.
U.S. Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12th Floor
Chicago, IL 60604-3590
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Table 1
Site Locations Where Soil Washing Has Been Selected *
Site Location Type of Facility
Arkwood Arkansas Wood preserving
Cabot/Koppers Florida Wood treating and pine tar distillation
Cape Fear Wood Preserving North Carolina Wood preserving
Coleman-Evans Wood Preserving Florida Wood preserving
Ewan Property New Jersey Industrial waste dumping
G.E. Wiring Devices Puerto Rico Wiring services
King of Prussia New Jersey Recycling
Koppers (Oroville Plant) California Wood preserving
Koppers/Texarkana Texas Wood preserving
Moss American Wisconsin Wood preserving
Myers Property New Jersey Pesticide manufacturing
Sand Creek Industrial Colorado Refinery, pesticide manufacturing,
and landfill
South Cavalcade Street Texas Wood preserving and coal tar distillation
United Scrap Lead Ohio Lead battery recycling
Vineland Chemical New Jersey Pesticide manufacturing
* All waste types and site conditions are not similar. Each site must be individually investigated and tested.
Engineering and scientific judgment must be used to determine if a technology is appropriate for a site.
For More Information
EPA prepared this fact sheet to provide basic information on soil washing. Additional technical reports are listed
below. The documents containing a "PB" designation are available by contacting the National Technical
Information Service (NTIS) at 1-800-336-4700. Mall orders can be sent to:
National Technical Information Service
Springfield, VA 22161
Documents containing EPA numbers can be ordered by calling (513) 569-7562 or writing to:
Center for Environmental Research Information
26 West Martin Luther King Drive
Cincinnati, OH 45268
There may be a charge for these documents.
• Handbook on In Situ Treatment of Hazardous Waste - Contaminated Soils, EPA/540/2-90/002; PB90-155607.
• Innovative Technology: Soil Washing; OSWER Directive 9200.5-250-FS, PB90-274184.
> Mobile System for Extracting Spilled Hazardous Materials from Soil (Fact Sheet available from Risk
Reduction Engineering Laboratory, Releases Control Branch, Edison, NJ 08837, (908) 321-6926.)
• Mobile Volume Reduction Unit for Washing Contaminated Soil (Fact Sheet available from Risk Reduction
Engineering Laboratory, Releases Control Branch, Edison, NJ 08837, (908) 321 -6926.)
• Overview/Soils Washing Technologies for CERCLA, RCRA, and LUST Site Remediation (available from
Risk Reduction Engineering Laboratory, Releases Control Branch, Edison, NJ 08837, (908) 321-6625.)
» Engineering Bulletin: Soil Washing Treatment, EPA/540/2-90/017.
• Field Studies of In Situ Soil Washing, EPA/600/52-87-110.
• Nunno, T.J. and J.A. Hyman, Assessment of International Technologies for Superfund Applications, EPA
540/2-88/003; PB90-106428.
• Selected Alternative and Innovative Treatment Technologies for Corrective Action and Site Remediation,
EPA/540/8-91/006.
NOTICE: This tact 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.
4 'U.S. Government Printing Office: 1992 — 648-080/60003
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