United States
Environmental Protection
Agency
Office of
Solid Waste and
Emergency Response
EPA/542/F-92/007
March 1992
&EPA
A Citizen's Guide To
In Situ Soil Flushing
Technology Innovation Office
.Technology Fact Sheet
CONTENTS
Page
What Is In Situ Sol!
Flushing? 1
How Does It Work?
Why Consider In Situ
Soil Flushing?
Will It Work At Every
Stte?
Wh«re Is In Sttu Soil
Flushing Being
Selected?
For More Information
What Is In Situ Soil
Flushing?
In situ soil flushing is an innovative
treatment technology that floods
contaminated soils beneath the ground
surface with a solution that will flush
out the contaminants to an area where
they will be extracted. In situ
meaning in place refers to treating
the contaminated soil without
excavating and removing it.
The contaminants in the soil determine
the type of flushing solution needed in
the treatment process. The flushing
solution is typically one of three types
of fluids: 1) water only, 2) water plus
additives such as acids (low pH), bases
(high pH) or surfactants (like
detergents); or 3) organic solvents.
contaminants, such as those typically
found in battery recycling or industrial
chrome plating processes. For example,
zinc contamination which can result
from plating operations would be
treated with an acidic solution.
A basic solution is a mixture of water
and a base, such as sodium hydroxide.
An example of a base commonly used
in households is ammonia. Basic
solutions are used to treat phenols and
certain metal species.
A surfactant is a detergent or
emulsifier. Emulsifiers can join
substances together which normally do
not mix such as oil and water.
Surfactant solutions are effective at
removing contaminants, such as oil.
Organic solvents are substances that
usually dissolve the contaminants water
cannot dissolve. Common household
products that contain organic solvents
are paint strippers and nail polish
removers.
Water is used to treat contaminants that
dissolve easily in water. An acidic
solution is a mixture of water and an
acid, such as nitric acid or hydrochloric
acid. Acidic solutions are used to
remove metals and organic
U.S. Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12th Floor
Chicago, IL 60604-3590
In Situ Soil Flushing Profile
Injects a washing solution Into unexcavated soils to flush out contaminants.
Is most affective on soils that contain low slit or clay content.
Requires the drilling of injection and extraction wells on-site.
Is a transportable technology that can be brought to the site after the wells have been Installed.
Produced by the
Supcrfund Program
1
Printed on Recycled Paper
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How Does It Work?
Figure 1 on page 2 provides an illustration of one type of an
in situ soil flushing process. The process begins by drilling
injection wells and extraction wells into the subsurface
where the contamination exists. The number, location, and
depth of the injection and extraction wells depends on many
geological factors and engineering considerations. Wells
may be installed either vertically or horizontally. After the
wells are in place, the soil flushing equipment andv
typically, a wastewater treatment system, are transported to
or built on the site.
The soil flushing equipment pumps the selected flushing
solution into the injection wells. The solution percolates
through the soils, picking up contaminants along its way.
The natural flow of this percolation moves the solution
toward the extraction wells. The extraction wells collect the
subsequent elutriate the flushing solution mixed with the
contaminants.
From the extraction wells, the elutriate is pumped to the
ground surface. Here, the elutriate is typically treated by a
wastewater treatment system to remove the contaminants.
What is An innovative Treatment
Technology?
Treatment technologies are processes applied
to the treatment of hazardous waste or
contaminated material* 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 *wov»tfv» treatment technologies.
The contaminants are subjected to further treatment or
disposal, and the treated water can either be recycled for use
in the flushing solution, reinjected into the ground, or
discharged in another acceptable manner. It is because of
this circular process that in situ soil flushing systems are
often referred to as injection/recirculation systems.
In situ soil flushing systems are designed to operate without
air emissions. However, volatile air emissions could occur
Figure 1
In Situ Soil Flushing* (Using Vertical Wells)
Treated Water
(either recycled for UM In washing eolation, relnjected Into
i ground, or discharged In another acceptable manner)
Treated
Emissions
Elutriate Goes tor Treatment
(Further Treatment />rt-
or Disposal)
Injection
Well
Extraction
Well
'This figure shows one type of soil flushing done when saturated soil conditions exist.
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during wastewater treatment If necessary, air emissions
will be controlled by collecting and treating the air prior to it
being released.
Why Consider In Situ Soil Flushing?
In situ soil flushing is tailored to treat specific contaminants.
By adding certain cleaning agents to the flushing solution,
for example, the solution can be adjusted to mix more easily
with certain soil contaminants. These contaminants, in turn,
are carried away with the elutriate. Since in situ soil
flushing is tailored to treat specific contaminants, this
technology is not highly effective with soils contaminated
with a variety of hazardous substances. It would be difficult
to prepare a flushing solution that would effectively remove
different types of contaminants.
In addition, since soil flushing is conducted in situ, no
excavation is required. This reduces the need for
excavation, handling, or transportation of the hazardous
substances. The process has been most effective in
removing the contaminants such as those identified in
Figure 2 below. Some of the industries where these
contaminants are found are also listed.
Figure 2
Contaminants Considered for Treatment
by In Situ Soil Flushing
Contaminants
Heavy metals (lead,
copper, zinc)
Industries
Where Found*
Battery Recycling,
Metal Plating
Halogenated solvents Drycleaning,
(TCE, trichtoroethane) Electronics Assembly
Aromatics (benzene, Wood Treating
toluene, cresol, phenol)
Gasoline and fuel oils Petroleum, Automobile
PCBs and chlorinated Pesticide, Herbicide,
phenols Electric Power
* All waste types and site conditions ore 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.
Will It Work At Every Site?
In situ soil flushing works best with soils that contain very
little silt or clay. If the soil has a high percentage of silt or
clay, the flushing solution can not easily move through the
soil. This limits the overall effectiveness of the soil flushing
process. In addition, some flushing fluids contain additives
or cleaning agents which may create some ground water
contamination since all of it may not be completely
removed.
There are additional limitations of this technology. For
example:
Ground water flow must be well-defined in order
to design the well system for a given site. Defining
the ground water flow can require extensive field
investigations.
In some cases, the chemical reactions of the soil
with the flushing solution may decrease the ease
with which the contaminants are carried away with
the elutriate. To illustrate this, suppose a given site
contains soil that is basic and is contaminated with
metals. The most appropriate flushing fluid for this
site would be an acid solution. The basic soil,
however, may neutralize the acid solution,
therefore inhibiting the transport of the metals.
Where Is In Situ Soil Flushing Being
Selected?
Table 1, on page 4, lists some Superfund sites where in situ
soil flushing has been selected as a treatment method. The
table shows the sites, their location, and the types of
facilities requiring treatment.
How Is Soil Flushing Different From Soil
Washing?
With soil flushing, the soil Is treated In place
using an Injectlon/recirculatton process. Soil
washing Involves excavating the contaminated
soil and treating It at the surface in a soil
washer.
U.S. Environmental Frctaction Agency
Region 5, Library (PL-12J)
H West Jackson Boulevard, 12th Floor
Chicago, IL 60604-3590
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Table 1
Site Locations Where In Situ Soil Flushing Has Been Selected
Site
Byron Barrel & Drum
Goose Farm
Lipari Landfill
Vineland Chemical
L.A. Clarke & Sons
U.S. Titanium
Jadco-Hughes
Ninth Avenue Dump
U.S. Aviex
South Cavalcade Street
Poly-Garb
United Chrome Products
Location
New York
New Jersey
New Jersey
New Jersey
Virginia
Virginia
North Carolina
Indiana
Michigan
Texas
Nevada
Oregon
Facility Description*
Uncontrolled dump site and landfill
Uncontrolled dump site
Commercial dump site
Pesticide manufacturing
Wood preserving
Titanium dioxide plant
Solvent recovery and storage
Commercial dump site
Chemical packaging
Wood preserving and coal tar distillation
Inactive waste management
Chrome Plating
* A/I 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 fn situ soil flushing. Additional technical
reports are listed below. The documents containing a "PB" designation are available by contacting the
National Technical Information Service (NT1S) at 1-800-336-4700. Mail orders can be sent to:
National Technical Information Service
Springfield, VA 22161
The additional document may be obtained 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.
Mobile Treatment Technologies for Superfund Wastes, EPA/540/2-86/003; PB89-135859.
A Compendium of Technologies Used In the Treatment of Hazardous Wastes, EPA/625/8-87/014.
NOTICE: This 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.
U.S. Government Printing Office: 1992 648-080/60007
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