United States
                        Environmental Protection
                             Office of
                             Solid Waste and
                             Emergency Response
                                                    March 1992
A  Citizen's  Guide  To
In  Situ  Soil   Flushing
Technology Innovation Office
                                               .Technology Fact Sheet
 What Is In Situ Sol!
 Flushing?             1
 How Does It Work?
 Why Consider In Situ
 Soil Flushing?
 Will It Work At Every
 Wh«re Is In Sttu Soil
 Flushing Being
 For More Information
       What Is In Situ Soil

       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
 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
                                              Printed on Recycled Paper

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

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

    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)
                                                  Elutriate Goes tor Treatment
                                                                                             (Further Treatment />rt-
                                                                                               or Disposal)
  'This figure shows one type of soil flushing done when saturated soil conditions exist.

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

  • Heavy metals (lead,
    copper, zinc)
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

There are additional limitations of this technology. For

    •   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

    •   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

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

    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
                                                              U.S. Environmental  Frctaction Agency
                                                              Region  5, Library (PL-12J)
                                                              H West Jackson Boulevard,  12th Floor
                                                             Chicago, IL  60604-3590

                                                 Table 1
                      Site Locations Where In Situ Soil Flushing Has Been Selected
    Byron Barrel & Drum
    Goose Farm
    Lipari Landfill
    Vineland Chemical
    L.A. Clarke & Sons
    U.S. Titanium
    Ninth Avenue Dump
    U.S. Aviex
    South Cavalcade Street
    United Chrome Products
New York
New Jersey
New Jersey
New Jersey
North Carolina
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-
        •   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