vvEPA
United States
Environmental Protection
Agency
EPA/540/S5-89/004
June 1989
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Technology Demonstration
Summary
International Waste
Technologies In Situ
Stabilization/Solidification,
Hialeah, Florida
A demonstration of the Inter-
national Waste Technologies (IWT)
process, utilizing the Geo-Con, Inc.,
deep-soil-mixing equipment has been
performed under the Superfund
Innovative Technology Evaluation
(SITE) Program. This was the first
field demonstration of an in situ
stabilization/solidification process.
The demonstration occurred in April
1988 at the site of a General Electric
Company electric service shop in
Hialeah, FL, where the soil contained
polychlorinated biphenyls (PCBs) and
localized concentrations of volatile
organics and heavy metal contam-
inants. The demonstrated process
mixed in situ the contaminated soil
with a mixture of a proprietary
additive, called HWT-20, and water.
The technical criteria used to
evaluate the effectiveness of the IWT
process were contaminant mobility,
based on leaching and permeability
tests; and the potential integrity of
solidified soils, based on measure-
ments of physical and micro-
structural properties. Performance of
the Geo-Con deep-soil-mixing equip-
ment was also evaluated.
The process did appear to
immobilize PCEis. However, because
of the very low PCB concentrations in
the leachates, caused in part by the
low concentrations of PCBs in the
soils, absolute confirmation of PCB
immobilization was not possible.
Physical properties were satisfactory
except for the freeze/thaw weathering
tests, where considerable degrada-
tion of the test specimens occurred.
The microstructural analyses showed
that the process produced a dense,
homogeneous mass with low
porosity.
The Geo-Con deep-soil-mixing
equipment performed well, with only
minor difficulties encountered, which
can be easily corrected. The HWT-20
additive was well dispersed into the
soil, as evidenced by the relatively
uniform change in chemical and
physical characteristics of treated
soil versus untreated soil.
The estimated remediation cost
with operation of the 1-auger
machine used for the demonstration
is $194/ton ($150/yd3). For larger
applications, using Gee-Con's 4-
auger machine, costs would be
lower.
This Summary was developed by
EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to
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announce key findings of the SITE
program demonstration that is fully
documented In two separate reports.
(see ordering Information at back).
Introduction
In response to the Superfund
Amendments and Reauthorization Act of
1986 (SARA), the U.S. Environmental
Protection Agency's Office of Research
and Development (ORD) and Office of
Solid Waste and Emergency Response
(OSWER) have established a formal
program to accelerate the development,
demonstration, and use of new or
innovative technologies as alternatives to
current containment systems for
hazardous wastes. This new program is
called Superfund Innovative Technology
Evaluation, or SITE.
The major objectives of the SITE
Program are to develop reliable cost and
performance information. One process,
which was demonstrated in April 1988 at
a General Electric (GE) electric service
shop in Hialeah. FL, as part of the SITE
Program, was the International Waste
Technologies (IWT) in situ stabili-
zation/solidification process, using the
Geo-Con, Inc., deep-soil-mixing equip-
ment. This was the first field demon-
stration of an in situ stabilization/
solidification process. In this demon-
stration, both the IWT and Geo-Con
technologies were evaluated. The test
was performed to meet the goals of the
SITE Program along with those of GE.
GE's goals, which were developed
independently of the SITE Program, were
to fulfill the requirements of the
Metropolitan Dade County Environmental
Resources Management (MDCERM) to
demonstrate, prior to the full site
remediation, that this treatment method
would immobilize PCBs. The SITE
project, proposed to determine the
technological and economic viability of
the IWT process and the Geo-Con deep-
soil-mixing technology, involved a more
expansive testing program than that
required by GE to meet their obligations
to MDCERM. This expanded effort
included three different leaching pro-
cedures, physical and microstructural
tests, and analyses of leachates for
volatile organic compounds (VOCs) and
metals if these contaminants were
detected in the untreated soil.
IWT, the stabilization/solidification tech-
nology developer, and Geo-Con, Inc.,
provider of the specialized drilling and
mixing equipment, were participants in
both the SITE and GE programs. Under
the latter program, IWT and Geo-Con
served as contractors to GE for the
mandated test before the site
remediation. In addition, under a
cooperative agreement with EPA, IWT
was designated as the SITE technology
developer for the demonstration, and
Geo-Con verbally agreed that its in situ
procedures were to be evaluated.
The IWT process involved the in situ
mixing of the service shop soil (which
was contaminated with polychlorinated
biphenyls), with a cement-organo clay
mix referred to as HWT-20. Two 10x20-ft
test sectors (designated B and C) were
treated to a depth of 18 ft in Sector B and
14 ft in Sector C. These depths were
defined by GE to treat all the soil
containing at least 1.0 mg/kg of PCBs.
Each sector was treated by creating
thirty-six 3-ft-diameter columns of treated
soil. The two sectors were designated by
GE because they were expected to be
high in PCBs. The developer claimed the
wastes would be immobilized and bound
into a hardened, leach-resistant, con-
crete-like solidified mass.
The major objectives of this SITE
project were to determine the following:
1. Ability of the stabilization/solidification
technology to immobilize PCBs. (If
VOCs and heavy metals were detected
in the untreated soil, their immobi-
lization would need to be measured.)
2.Effectiveness, performance, and
reliability of Geo-Con deep-soil-mixing
equipment used for the in situ
solidification (including continuity of
operation, uniformity of mixing, and
accuracy of column overlap).
3. Degree of soil consolidation (solidi-
fication) caused by the chemical
additives.
4. Probable long-term stability and in-
tegrity of the solidified soil.
5. Costs for commercial-scale applica-
tions.
The following technical criteria were
used to evaluate the effectiveness of in
situ stabilization/solidification:
1. Mobility of the contaminants—Areas of
high PCBs and VOCs were sampled,
with the analytical emphasis on
leaching characteristics. Three leach-
ability tests were performed: the
Toxicity Characteristic Leaching
Procedure (TCLP) and two leach tests
that evaluate solidified conditions,
MCC-1P and ANS 16.1. Only the
effectiveness with PCBs was evaluated,
as the additive HWT-20 was not
designed to immobilize VOCs or other
contaminants. Permeabilities also were
measured before and after soil
treatment. These values indicate the
degree to which the solidified material
permits or prohibits the passage of
water through the soil mass, and thus
the degree of water contact with the
contaminants.
2. Durability of the solidified soil mass —
Core sections from the solidified mass
were analyzed to determine uniformity
and long-term endurance potential.
However, if a chemical bond forms
between HWT-20 and the PCBs, as
claimed by IWT, then meiintaining
durability of the solidified mass to
prevent the mobility of the contaminant
becomes less important. The analyses
obtained information on the following:
• Integrity of the remediated soil
columns at their interfaces with each
other.
• Unconfined compressive strength
results as an indication of long-term
durability.
• Microstructural characteristics as a
source of information on treated soil
porosity, crystalline structure, and
degree of mixing. These indicate the
potential for long-term durability of
the hardened mass.
• Wet/dry and freeze/thaw weathering
tests as information on weight loss.
Permeability and unconfined
compressive strength of the weath-
ered samples also were performed,
providing additional indications of
short-term durability.
Procedure
The demonstration, utilizing IWT's
HWT-20 additive with Geo-Con's deep-
soil-mixing equipment, was performed on
two 10x20-ft test sectors.
The Geo-Con/DSM deep-soil-mixing
system of mechanical mixing and
injection consisted of one set of cutting
blades and two sets of mixing blades
attached to a vertical drive auger, which
rotated at approximately 15 rpm. Two
conduits in the auger allowed for the
injection of the additive slurry and
supplemental water. HWT-20 additive
was injected on the downstroke, with
further mixing occurring on auger
withdrawal. The treated 36-in. diameter
soil columns were positioned in an
overlapping pattern to cover the entire
area.
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A batch mixing system processed the
feed additives. HWT-20 was conveyed by
air from a supply truck to a storage silo.
To treat three or four soil columns, a
measured amount of water was fed to a
1,000-gal mixing tank. The HWT-20 was
fed to the tank at a weight ratio to water
of 4:3. A screw-type positive-displace-
ment pump moved the slurry to the auger
at an average rate of 0.18 Ib of HWT-
20/lb of dry soil. Water was fed
separately to the drill rig on a ratio basis
to the additive slurry. Sufficient water was
provided to produce a final soil product
containing 1.6-1.7 Ib of water/lb of HWT-
20.
Sampling and Analysis Program
Soil sampling, provided by EPA, was
performed two weeks before, and five
weeks after, the remediation of the test
sectors. Samples were taken at soil
column centers, at column interfaces, and
at five locations around one anticipated
hot spot in each sector. Samples were
taken at three or four depths, from the
top layer of unconsolidated sand, the
limestone layer, and the lower
unconsolidated sand layer. In Sector B,
where the HWT-20 was injected to a
depth of 18 ft, a sample at a fourth depth
was also collected.
Samples of untreated and treated soil
were collected for the following physical
property measurements:
• Moisture content
• Bulk density
• Permeability
• pH (untreated soil only)
• Unconfined compressive strength
(treated soil samples)
• Oil and grease and total organic carbon
(untreated soil only)
• Weathering—wet/dry and freeze/thaw—
(treated soil only).
Chemical analyses were performed to
identify and quantify soil contaminants in
both the untreated and treated soil. In
addition, three different leaching tests
were performed:
• TCLP —a commonly accepted
procedure for measuring leachability of
both organics and inorganics.
• ANS 16.1 —This test simulates leaching
from the intact solidified core by
modeling a condition of percolating
water flow that is sufficiently rapid to
prevent it from becoming saturated.
• MCC-1P—simulates leaching from the
intact, solidified core into relatively
stagnant groundwater.
These latter two tests were drawn from
the nuclear industry and modified to suit
hazardous waste analysis.
In order to obtain information on
potential long-term integrity, micro-
structural studies were performed on the
untreated and treated soils. These
analyses included:
« X-ray diffractometry—to identify
crystalline structures.
• Microscopy—use of scanning electron
microscopy and optical microscopy to
characterize porosity, hydration
products, and fractures.
Results and Discussion
The following results were obtained
and are summarized in Tables 1 and 2:
• The chemical analyses of the untreated
soils showed the highest PCB
concentrations (Aroclor 1260) in Sector
B, up to 950 mg/kg, with the maximum
concentration in Sector C being 150
mg/kg. The maximum concentration of
PCBs in the treated soil was 170
mg/kg, with all other values 110 mg/kg
or less. The untreated soil at sample
locations B-6, B-7, and B-8 also
contained large quantities of VOCs
(xylenes, chlorobenzene, and
ethylbenzene)—from 160 to 1,485
mg/kg total—and some heavy metals
(lead, copper, chromium, and zinc)—up
to 5,000 mg/kg total metals. In the
treated soil, the total VOCs ranged
from 2 to 41 mg/kg, and the total
metals, 80 to 279 mg/kg. These
reductions may have been produced
by the mixing action of the auger,
which blended soils with both low and
high concentrations of contaminants.
• The untreated-soil TCLP leachates
showed PCB concentrations (Aroclor
1260) up to 13 ug/L. Leachates of all
untreated soil samples below 63 mg/kg
of PCBs were below the PCB detection
limit of 1.0 yg/L, and all soil samples
with PCB concentrations above 300
mg/kg showed detectable PCB
concentrations in the leachate. For the
soil samples with PCB concentrations
between 63 and 300 mg/kg, some
leachate samples had detectable
quantities, but others did not. All
leachates of treated soil samples were
below 1.0 pg/L PCBs, the detection
limit used for all samples. Seven
treated soil leachates were analyzed a
second time with the detection limit
reduced to 0.1 yg/L, and four of the
samples were below this detection
limit. Thus, the IWT process appears to
immobilize PCBs, but because of the
very low values being measured, it
cannot be confirmed by this project.
«The VOC concentrations in the
untreated soil TCLP leachates ranged
from 2,490 to 7,890 yg/L. The VOC
concentrations in the treated soil
leachates ranged from 325 to 605 yg/L.
This reduction in VOC concentrations
was likely due to a combination of
factors. The largest one was probably
the Geo-Con mixing operations, which
blended high and low concentration
soils.
• The total heavy-metal concentrations in
the TCLP leachates ranged for the
untreated soil from 320 to 2,650 yg/L
and for the treated soil from 120 to 210
yg/L. As with the VOCs, this leachate
reduction may have been a result of
the reduction in metals concentrations
in the soil caused by the Geo-Con
mixing operation.
• In the special leach tests, ANS 16.1
and MCC-1P, performed on treated soil
samples, PCBs and VOCs were not
detected in any of the leachates.
• The oil and grease and total organic
carbon contents of the untreated soil
were both approximately 0.1% by wt.,
except at sample locations B-6, B-7,
and B-8, where values up to 1.5% by
wt. were measured. These values were
too low to interfere with the cement
hydration reactions
•The average permeability of the
untreated soils was 1.8 x 10-2 cm/s,
and ranged from 0.1 x 10-2 to 12 x 10-2
cm/s. Results obtained for the treated
soil were 10-6 to 10-7 cm/s. These
values essentially meet the EPA
guideline of 10-7 cm/s for the maximum
allowable value for hazardous-waste
landfill liners. Because of the large
decrease in permeability after soil
treatment, groundwater will flow
around, not through, the treated soil.
• The unconfined compressive strength
(DCS) measured in both sectors was
quite satisfactory, easily meeting the
EPA guideline minimum of 50 psi. In
Sector B values ranged from 75 to 579
psi. In Sector C, the range was from
247 to 866 psi. Sector C samples had
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Table 1. Chemical Properties
PCB Concentrations
Untreated Soil Treated Soil
Sample Untreated Soil, TCLP Leachate, Treated Soil, TCLP
Designation' mglkg pg/L mglkg Leachate, iig/L
8-6 650 12.0(15.0) 49 < 1.0 (0.1 5)
8-7 460 400.0(250) 82 < 1.0 (0.1 2)
B-8 220 <1.0 9.6 <1.0
B-11 950 7.2(0.33) 170 < 1.0 (< 0.10)
B-12 140 1.1 16 <1.0
B-13 250 <1.0
B-16 300 3.7(0.50) 100 <1.0(<0.1)
8-77 495 3.0(1.0) 100 < 1.0 (0.20)
8-27 -- -- 60 <1.0
8-22 -- -- 114 <1.0
C~1 98 <1.0 20 <1.0
C-3 94 <1.0 57 <1.0
C-7 750 <1.0 22 <1.0
C-TO 86 <7,0 80 <1.0(<0.10)
* Selected locations of highest PCB concentrations.
() Repeat teachate analysis of existing TCLP leachate analyzed to a detection limit of 0. 1 ftg/L
Tablo 2. Average Physical Properties
Sector 8 Sector C
Untreated Treated Untreated Treated
Moisture content. % 11.8 19.0 13.2 77.3
Bulk density, g/mL 7.57 7.85 7.56 1.94
Permeability, c/n/s i.46xio~2 s.sxw7 3.5x70-2 2.7xio-f
Unconfined compressive - 290 -- 536
strength, psl
Weathering tests
wet/dry, wt % lost -- 0.39" -- 0.34"
freeze/tfiaw, wt % lost -- 7.2" - 6.0"
pH 8.1 - 8.5
Oil and grease, % 0.3 - 0.1
JOC,mg:kg 4,380 - 2,300
* These values represent the weight loss of the test specimens. The wet/dry weight losses of the
controls were approximately 0.7% less. For the freeze/thaw controls the absolute weight
losses were In the range of 0.3% to 0.4%.
an average UCS of 536 psi higher than losses of test specimens to controls
Sector B, with an average of 288 psi. A were very small, averaging about 0.1%.
factor that may have contributed to this The UCS values of the wet/dry test and
difference was the higher additive control specimens after 12 cycles of
injection rate in Sector C compared to weathering were equal and the same
Sector B. as for the unweathered samples.
• The wet/dry weathering test results • The freeze/thaw tests showed large
were satisfactory. They showed very losses, up to 30.7% by wt. The weight
low weight losses, 0.25% to 0.50% for loss of the controls was 0.25% to
the 12-cycle tests. The relative weight 0.70%. For the freeze/thaw specimens
where weight losses exceeded 3%, the
UCS values decreased dramatically,
approaching zero for some samples.
Permeabilities performed on eight
weathered samples with low-to-
moderate weight losses were
equivalent to unweathered samples.
• The microstructural analysis,
performed on each sample collected,
showed that the IWT process produced
a dense, homogeneous mass with low
porosity. It also showed that variation of
properties in the vertical and horizontal
direction of the treated soil was absent,
which indicated that mixing was quite
satisfactory.
• The bulk density of the soil increased
21 % after treatment, which equated to
a volume increase of 8.5%. This is
equivalent to a ground rise of
approximately 18.4 in. in Sector B and
14.3 in. in Sector C, which agrees with
the general observations made by the
test observers. Although this volume
increase is modest, it may still cause
land contour problems in some small
restricted areas.
• Total additive, water, and sodium
silicate addition increased the treated
soil weight compared to the untreated
soil by an average of 32%. The
average additive addition was 0.171
Ib/lb of dry soil in Sector B, and 0.193
Ib/lb of dry soil in Sector C, compared
to values targeted by the developer of
0.131 Ib in Sector B and 0.150 Ib in
Sector C, respectively. In Sector B, the
dosage of additive for secondary
columns (drilled after the primary
columns were completed) was reduced
by almost 30% compared to the
primary columns.
• The demonstration operations lasted
six days— three days on each sector.
Operations were well organized and ran
smoothly, although some minor
difficulties were encountered, including
the following:
—The locations of the soil columns
deviated from the planned points,
and therefore some untreated areas
exist between columns. Neverthe-
less, because Geo-Con has since
indicated that their auger actually
creates a column slightly greater in
diameter than 36 in., the untreated
areas would be proportionally
smaller.
—Automatic feed control could not be
maintained, resulting in lean and rich
injection areas. Manual control was
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the predominant technique used.
This difficulty was caused in part by
trying to adapt a system designed
for the larger 4-auger commercial
unit to the 1-auger unit used in the
demonstration.
—A major water leak occurred at the
drill head, precluding the use of
supplemental water for the last 21
columns. To save time, Geo-Con was
instructed by GE to continue without
repairing the leak.
With the experience gained by Geo-
Con, these minor difficulties should be
readily eliminated for a commercial
operation.
Conclusions
A demonstration on the IWT in situ
stabilization/solidification process,
utilizing the Geo-Con deep-soil-mixing
equipment, was performed on a narrow
range of hazardous wastes, with low-to-
moderate concentrations of PCBs and
one localized area containing VOCs and
heavy metals. Two test sectors,10 x 20 ft,
were remediated to a depth of 18 ft in
one sector and 14 ft in the other.
Samples of untreated and treated soil
were taken from the same locations in
each test sector, and laboratory analyses
were performed to obtain a comparison
of physical properties and contaminant
mobilities before and after soil treatment.
Highlights of the results were as follows:
Based on TCLP analyses, the PCBs
appear to be immobilized. However.
due to the very low PCB concen-
trations measured in the soil and
leachates, it cannot be confirmed by
this project.
The physical test results were
satisfactory (except for the freeze/thaw
tests) indicating a potential for long-
term durability of the hardened mass
These results were as follows:
— High unconfined compressive
strength (average about 410 psi).
— Soil permeability was improved by
treatment four orders of magnitude,
to an average of 4x10-7 cm/s.
—Wet/dry weathered samples showed
satisfactorily low weight losses.
—Volume increased with treatment by
8.5%.
—Freeze/thaw weathered samples
showed unsatisfactorily large weight
losses.
—Microstructural studies showed the
treated soil to have a dense.
homogeneous structure of low
porosity, which might give long-term
durability.
—Operations were well organized and
ran smoothly; the difficulties
experienced should be readily
correctable.
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The EPA Project Manager, Mary Stinson, is with the Risk Reduction Engineering
Laboratory, Edison, NJ 08837 (see below).
The complete report, entitled "Technology Evaluation Report: SITE Program
Demonstration Test, International Waste Technologies In Situ
Stabilization/Solidification, Hialeah, Florida," consists of two volumes:
'Volume I" (Order No. PB 89-194 161/AS; Cost: $21.95. subject to change)
discusses the results of the SITE demonstration.
'Volume II" (Order No. PB 89-194 1791 AS; Cost: $85.95, subject to change)
contains the technical operating data logs, the sampling and analytical
data, and the quality assurance data.
Both volumes of this report will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
A related report, entitled "SITE Program Applications Analysis Report: Assess-
ment of Superfund Applications for International Waste Technologies In Situ
Stabilization/Solidification," which discusses application and costs, is under
development.
The EPA Project Manager can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Edison, NJ 08837
United States
Environmental Protection
Agency
Risk Reduction Engineering
Laboratory
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
Official Business
Penalty for Private Use $300
EPA/540/S5-89/004
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