United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268 ' r \
Research and Development
EPA-600/S2-83-088 Dec. 1983
SERA Project Summary
Feasibility of In Situ
Solidification/Stabilization of
Landfilled Hazardous Wastes
J. Bruce Truett, Richard L Holberger, and Kris W. Barrett
A study was made of the feasibility of
solidifying or stabilizing hazardous
industrial wastes that are already in
place at a landfill. Solidification and
stabilization methods were examined
for their applicability to specific condi-
tions at the LaBounty waste disposal
site at Charles City, Iowa. None of the
methods appears suitable for in situ
application as a principal means of
pollution control at this site because of
large variations in the permeability of
the fill material and the diverse chemical
composition of the wastes.
This Project Summary was developed
by EPA's Municipal Environmental
Research Laboratory. Cincinnati, OH.
to announce key findings of the research
project that is fully documented in a
separate report of the same title fsee
Project Report ordering information at
back).
Introduction
This study investigated the feasibility of
solidifying or stabilizing hazardous
industrial wastes that are already in
place at a landfill. Solidification methods
considered included (1) incorporating the
waste in solid masses formed by cement,
lime, lime plus siliceous materials,
organic polymers, or thermoplastic
materials such as bitumens; (2) fusing the
waste with soil to form a vitreous solid;
and (3) isolating the waste by enclosing it
in impermeable, inert envelopes (surface
encapsulation) or smaller capsules
(microencapsulation), or by constructing
an impermeable barrier of grout or other
material that completely surrounds the
entire mass of landfilled waste. The study
also considered other waste stabilization
methods that do not involve solidification,
such as neutralizing or destroying
hazardous constituents through chemical
reactions, or immobilizing toxic ions by
ion-exchange mechanisms. The neutraliz-
ing or immobilizing agents can be applied
most effectively by injection into the fill or
surrounding soils.
None of the solidification methods
appears generally applicable to large
landfills containing mixed industrial
wastes, but two methods, injection of
reactive chemical agents and vitrification,
appear promising for some specific
applications.
The more promising methods were
examined for possible application at a
specific landfill—the 8.5-acre LaBounty
site at Charles City, Iowa. This fill poses
several problems for in situ remedial
actions, including diverse chemical
constituents that are partially below the
water table and are in contact with
highly-fractured bedrock containing an
important aquifer system.
General Feasibility of
In Situ Solidification and
Stabilization
A number of methods are available for
effectively solidifying or otherwise
stabilizing a great variety of hazardous
wastes—particularly inorganic wastes,
but also an increasing number of organics.
Some of these methods have been
demonstrated and are commercially
available for large-scale applications. All
of the demonstrated methods require
thorough mixing of the waste and
solidification or stabilization agents.
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The effective use of existing solidifica-
tion methods for in situ application to
wastes buried in landfills is technically
infeasible at the current state of technolo-
gy with one possible exception—vitrifica-
tion by electrical energy But this method
is economically infeasible for large-scale
use with most industrial hazardous
wastes.
On the other hand, existing stabilization
methods that do not involve solidification
are feasible for in situ application to
landfilled wastes under certain conditions
where simple neutralization and/or
oxidation-reduction reactions are possible.
No actual examples of large-scale applica-
tions of in situ solidification or stabilization
in the United States were identified
during the present study.
Two commonly encountered characte-
ristics of industrial landfills that militate
against the in situ application of solidifica-
tion or stabilization technology are.
• Large variations in the permeability
of the landfilled wastes (and inter-
mixed soils) from one part of the fill
to another, and
• Diversity in the chemical constitu-
ents of the wastes and variations in
their concentration from one part of
the fill to another.
Chemical components of some wastes
may interfere with the desired action of
certain solidification or stabilization
agents, whether they are applied before
deposition of wastes in a landfill, in situ,
or after the wastes have been moved No
generally available base of quantitative
data exists on how various concentrations
of specific interfering substances affect
the performance of specific solidification
or stabilization agents.
Feasibility of In Situ
Solidification and Stabilization
at the LaBounty Site
Identified solidification and stabilization
methods are not feasible for in situ
application at the LaBounty landfill,
principally because of four conditions at
this site'
1. Large variations in permeability of
the chemical fill and soils from one
part of the fill to another;
2. The diverse chemical composition
of the landfilled wastes and their
heterogeneous distribution within
the fill;
3. The lack of suitability of the principal
hazardous constituents of the site
to currently available in situ methods;
and
4. The highly-fractured condition of
the bedrock underlying the site.
The full report was submitted in
fulfillment of Contract No. 68-02-3665 by
The Mitre Corporation under the sponsor-
ship of the U.S. Environmental Protection
Agency.
J. Bruce Truett, Richard L. Holberger. and Kris W. Barrett are with the Mitre Corpora-
tion, McLean, VA22102.
Wendy Davis-Hoover and Donald E. Banning are the EPA Project Officers (see
below).
The complete report, entitled "Feasibility of In Situ Solidification/Stabilization of
Landfilled Hazardous Wastes," {Order No. PB 83-261099; Cost: $11.50, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
(
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