c/EPA
United States
Environmental Protection
Agency
EPA/540/M5-89/004
April 1989
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Demonstration Bulletin
In-Situ Soil Stabilization
International Waste Technologies
TECHNOLOGY DESCRIPTION: In in-situ
stabilization technology immobilizes organics and
inorganic compounds in wet or dry soils by using
reagents (additives) to polymerize with the soils and
sludces producing a cement-like mass. Two basic
components of this technology are the Geo-
Con/DSM Deep Soi Mixing System, a system
capaole of delivering and mixing chemicals with the
soil in-situ, and the batch mixing plant that supplies
the proprietary treatment chemicals (Figure 1).
The Geo-Con/DSM Deep Soil Mixing System,
incorporating mechanical mixing and injection,
consists of one set of cutting blades and two sets of
mixing blades attached to a vertical drive auger,
which rotate at approximately 15 rpm. Two conduits
in ths auger allow for the injection of the additive
slurry and supplemental water. Additive injection is on
the downstroke, with further mixing occurring upon
auge' withdrawal. The treated soil columns, whose
diameter is 36 inches, are positioned to provide an
overlapping pattern. In each sector, alternating
primary and secondary soil columns exist, with all
primary columns prepared before the secondary
columns are augered.
The developer states that their proprietary additive
generates a complex crystalline connective network
of inorganic polymers and that the structural bonding
in the polymer is mainly covalent. Furthermore, in the
process, there is a two-phased reaction in which the
contaminants are complexed first in a fast-acting
reaction and then in a slow-acting reaction where
the building of macromolecules continues over a long
period of time. For each type of waste, the quantity of
additives used varies and must be optimized.
WASTE APPLICABILITY: This technology can be
applied to soils, sediments, and sludge-pond
bottoms contaminated with organic compounds and
metals.
DEMONSTRATION RESULTS: The IWT stabilization
demonstration took place at a PCB-contaminated
site in Hialeah, Florida. The preliminary results of the
SITE demonstration showed that the processes
produced a solidified mass with good physical
Air
Controlled
Valves
r--J i	fOy I
Sodium
Silicate
Bin
V
SB	
I
i Purap .
| Air
j ji Compressor
• ibind j
Magnetic | r-|
Flow	i • 	
Meter	I L		
—I ^	
Air
Controlled
Valves
L-n
Reagent
Silo
V
Flow
Metpr
Pump
Pump
Valve
Water
Flow Line
Control Line
Communication Line
Figure 1.
In-situ stabilization batch mixing plant process diagram.

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Table 1. Physical Properties of Soils
Untreated	Treated

Moisture
Bulk

Permeability
Moisture
Bulk

Permeability
Sample
Content
Density
TOC
(cm/sec x
Content
Density
TOC
(cm/sec x
Designations
(%)
g/ml
mg/kg
10*2)
(%)
g/ml
mg/kg
10-7)
B-6
13.3
1.46
16000
1.4
23.1
1.77
0.43
1.84
B-7
13.3
1.74
12000
6.0
24.7
1.81

3.04
B-8
16.8
1.85
3100
0.98
19.0
1.88
0.34
27.92
properties except for resistance to freeze/thaw cycles.
Sufficient data were not available to evaluate the
performance of the system with regard to metals or
other organic compounds.
•	The demonstration took place during April 1988.
•	Based on the TCLP, PCBs did not leach from
samples of treated soil; however, in most cases
PCBs did not leach from the untreated soil.
There appears to be a trend toward
immobilization, but PCB concentration at the site
was extremely low.
•	Solidified soil was dense and exhibited
unconfined compressive strengths of 300 to 500
psi. Volume increases were small (8.5%).
•	One untreated area existed due to difficulties in
exactly locating the injection auger.
•	The mixing system achieved a homogeneous
soil/reagent blend with minimal difficulties.
FOR FURTHER INFORMATION:
EPA Project Manager:
Mary Stinson
U.S. EPA
Risk Reduction Engineering Laboratory
Woodbridge Avenue
Edison, New Jersey 08837
201-321-6683 FTS: 684-7862)
Table 2. Constituents in Soils
PCB Concentration
Four Pnonty Pollutant Metals
Sample
Designations
Untreated
Soil
(mg/kg)
Treated
Soil
(mg/kg)
Untreated
Soil TCLP
Leachate
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