SEPA
United States
Environmental Protection
Agency
EPA/540/S5-89/004a
January 1991
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Technology Demonstration
Summary
International Waste
Technologies/Geo-Con In Situ
Stabilization/Solidification
Update Report
In April 1988, the U.S. Environ-
mental Protection Agency (EPA),
under the Superfund Innovative Tech-
nology Evaluation (SITE) Program,
evaluated the effectiveness of the
International Waste Technologies
(IWT)/Geo-Con combined tech-
nologies for immobilizing poly-
chlorinated biphenyls (PCBs) in soil.
At a former electric service shop in
Hialeah, FL, IWTs soil additive was
mixed with contaminated soil with the
use of the Geo-Con deep-soil-mixing
system. Physical and chemical
analyses of the soil were performed
on samples collected before the
demonstration and at 2 wk and 1 yr
after the treatment.
The report concludes that, after 1
yr, PCB mobility remained unchanged
and that long-term durability of the
treated soil appears greater than
originally estimated.
This Summary was developed by
EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to
announce the key findings of this SITE
demonstration. These findings are
fully documented in five separate
reports (see ordering information at
back).
Introduction
In 1986, the U.S. Environmental
Protection Agency (EPA) established the
Superfund Innovative Technology
Evaluation (SITE) Program to promote
the development and use of innovative
technologies to cleanup Superfund sites.
This update report summary highlights
the results obtained 1 yr after the SITE
demonstration of the International Waste
Technologies (IWT)/Geo-Con in situ
stabilization/solidification technology and
compares them with data contained in
the earlier, related technology evaluation
report and applications analysis report.
The most extensive testing of the
combined technologies was performed
during the SITE demonstration, which
occurred at a General Electric Co. (GE)
electric service shop in Hialeah, FL, in
April 1988. The process involved the in
situ injection and mixing of the IWT
additive HWT-20 (a pozzolanic-based
material containing treated clay
adsorbents) with the contaminated soil.
The demonstration was performed on two
areas, each 200 ft2, that were relatively
high in PCBs (a maximum of 950 mg/kg
in the untreated soil), the primary
contaminant. The major objectives of the
entire SITE project were to evaluate the
,A) Printed on Recycled Paper
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IWT/Geo-Con in situ stabilization/solidifi-
cation technology for:
1. Immobilization of RGBs and, if
detected, immobilization of volatile
organic compounds (VOCs) and
heavy metals.
2. Effectiveness and reliability of the in
situ operation of the Geo-Con deep-
soil-mixing equipment.
3. Degree of soil solidification caused
by the IWT chemical additive HWT-
20.
4. Comparative effectiveness of the
stabilization/solidification for
unconsolidated sand and limestone;
comparative effectiveness above and
below the water table.
5. Cost for commercial-scale
applications.
6. Viability of the technology for use at
other sites.
7. Continuing, long-term stability and
integrity of the solidified soil over a
5-yr period.
The 12-mo sampling and analysis
work respond to the last objective.
Samples were collected 1 yr after the
demonstration. The test results were
compared with those from samples
collected 1 mo after (posttreatment) and
2 wk before (pretreatment) the
demonstration.
The following technical criteria were
used to evaluate the effectiveness of the
in situ stabilization/solidification process:
Mobility of the contaminants as
measured by leaching and
permeability tests.
Durability of the solidified soil mass
based upon information obtained
from weathering tests (wet/dry and
freeze/thaw), measurements of
unconfined compressive strength,
and analysis of microstructurai
characteristics (porosity, degree of
mixing and crystalline structure).
Procedure
The demonstration of the IWT/Geo-
Con technology was performed on two
10- x 20-ft test sectors. One sector was
treated to a depth of 18 ft (sector B) and
the other to a depth of 14 ft (sector C).
The local regulatory authority
Metropolitan Dade County Environmental
Resources Management (MDCERM)
required GE to remediate the site for
PCBs, with the two sectors to be tested
before full site cleanup began. The
objectives of the SITE project, however,
were broader than GE's. Thus, three
different leaching tests, microstructurai
analyses, and measurements for VOCs
and heavy metals were performed (if the
latter two were detected).
The Geo-Con's deep-soil mechanical-
mixing and injection machine consisted
of one set of cutting blades and two sets
of mixing blades (each set, 3 ft in
diameter) attached to a vertical drive
auger, which rotated at approximately 15
rpm. Two conduits in the auger allowed
low-pressure injection of the additive
slurry and supplemental water. The
additive and water were injected on the
downstroke and mixed into the soil with
additional mixing on the upstroke.
A batch-mixing system processed the
feed additives. The HWT-20 was air-
conveyed from the supply truck to a
storage silo. It was then slurried with
water at a solids to water ratio of 4:3 in a
1000-gal mixing tank. The tank held
enough slurry sufficient for three or four
columns of soil treatment. The slurry and
supplemental water were then pumped to
the drill rig at a dry solids rate of 0.18 Ib
of HWT-20/lb of dry soil.
The deep-soil-mixmg machine was
tracked into position and the horizontal
and vertical alignments checked. The
elevation measurements were made by
using a small tracking wheel attached to
a digital tachometer. Machine locations
were verified by the use of a stationary
laser.
Soil samples in the treated sectors
were taken 2 wk before the
demonstration and approximately 1 mo
after the demonstration. The latter
samples were collected from points at the
same locations as the pretreatment
samples. The 12-mo samples were
collected from points very close to the
posttreatment sample locations so that
the impact of the technology could be
evaluated from predemonstration through
long-term monitoring.
Sampling and Analysis Program
Fewer locations were selected for
sampling during the 12-mo monitoring
than were selected during the
demonstration. The 12-mo sample points
were at areas of high PCB concentration,
where VOCs were measured, and at
points of soil treatment column overlap.
Seven samples were collected from
sector B and six from sector C.
The sampling depths for the collected
samples were as follows:
Samples
Sampling depth,
ft below grade
B-6, B-6 duplicate, 1 -2
B-21, C-15
B-7, B-22, C-1, 7-8
C-3, C-7, C-16
B-8, C-17 11-12
B-9 16-17
The water table depth is 5 to 7 ft below
grade.
The 12-mo samples were collected for
the following analyses:
Toxicity characteristic leach
procedure (TCLP) for PCBs (also
VOCs and heavy metals, where
applicable)
Permeability
Acid neutralization capacity (not
performed during the demonstration)
Unconfined compressive strength
(DCS)
Moisture
Bulk density
Specific gravity (not performed
during the demonstration) to allow
the calculation of porosity
Wet/dry weathering test
Freeze/thaw weathering test
Post weathering tests
- TCLP for PCBs (not performed on
the posttreatment samples)
- UCS
- Permeability
Tolal PCBs in soil
Tolal VOCs in soil (B-6,7,8 only)
Metals in soil (B-6,7,8 only)
Microstructurai, X-ray diffraction,
microscopy
Results and Discussion
The chemical test results are
highlighted in Table 1 and summarizec
as follows:
1. After 1 yr, the treated soi
compositions for PCBs ranged frorr
less than 1.0 to 180 mg/kg anc
agreed favorably with treated soi
samples obtained during the
demonstration. The PCB concen-
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trations in the TCLP leachates for the
12-mo samples were usually below
the detection limit of 0.1 iig/L. The
results appear to agree with those
measured from postdemonstration
samples. (Only a few samples were
measured to a detection limit of 0.1
ng/L with the remainder to 1.0 ng/L.)
TCLP leach tests performed after the
weathering tests on the 12-mo
samples also measured PCB
concentrations at or below detection
limits. Thus, at the concentration
levels existing at the site, the
mobility of the PCBs in pretreatment,
posttreatment, 12-mo, and weathered
12-mo samples were all at or below
the detection limits. Therefore, a
determination about the immobili-
zation of PCBs could not be made.
2. The total VOC concentrations
(chlorobenzene, ethylbenzene, and
total xylenes) in samples collected at
locations B-6, B-7, and B-8 were
equivalent to the postdemonstration
results for each component and for the
total concentration. They ranged from
a total of 10.4 to 44.6 mg/kg. This
indicates that VOCs were not being
lost from the treated soil.
The TCLP leachate concentrations for
each component of the 12-mo
samples appear to be considerably
greater-by a factor greater than 2 on
the average-than the postdemon-
stration samples. Since the VOC
concentrations in the treated soil are
only a small fraction of those in the
untreated soil (less than 10 wt%),
concentration comparisons in the
leachates between treated and
untreated soil samples are not
practical. In addition, conclusions on
the ability of the IWT additive to treat
VOCs should not be made, since IWT
indicated that its formulation was
designed for treating only PCBs.
3. The soil and TCLP leachate values for
the heavy metals (chromium, copper,
lead, and zinc) were approximately the
same for the 12-mo samples as for the
posttreatment samples. The total
metals in the 12-mo TCLP leachates
ranged from 0.1 to 0.2 mg/L for soil
concentrations ranging from 122 to
592 mg/kg.
4. The acid neutralization capacity test
was performed only on the 12-mo
samples. The results showed a high
alkalinity in the treated soil; this
usually reduces heavy metals
teachability.
The physical test results are
highlighted in Table 2 and summarized
as follows:
1. The moisture content and bulk density
of the 12-mo samples were the same
as those for the postdemonstration
samples, with values of approximately
18 wt% and 1.9 g/mL, respectively.
The constant moisture content
indicates that curing was essentially
complete when the posttreatment
samples were analyzed.
2. The specific gravity of the 12-mo
samples was 2.53 g/mL. From specific
gravity and bulk density, porosity can
be calculated. It averaged 0.37, which
is relatively good compared with a
typical value for concrete of 0.20. The
lower the value, the less porous the
sample.
3. The permeability of the thirteen 12-mo
samples was very low, averaging
1.4x10-7 cm/s; this is approximately
one-half the average permeability
value obtained for the postdemon-
stration samples. Many of the values
for the 12-mo samples were close to
1x10-8 cm/s.
4. The UCS values ranged from 521 psi
for sample location B-22 to 1,703 psi
at C-1 and averaged 980 psi. This is a
150% increase over the postdemon-
stration samples, which indicates
curing (although not seen in the free
moisture values) continued between
sample collection periods.
5. Freeze/thaw and wet/dry weathering
tests performed on the 12-mo samples
showed the following results:
The relative and absolute weight
losses for the wet/dry samples
remained unchanged. The relative
weight loss (difference of test
specimen and control) was 0.1
wt%.
The freeze/thaw weight losses of
the test specimens were large,
averaging 4.1%. This is
comparable to the posttreatment
samples, average value of 6.6
wt%. The weight loss of the
controls in both instances
averaged 0.3%.
TCLP leach test results for PCBs
on weathered samples were
usually below detection limits,
which is equivalent to those on
the unweathered samples.
The results of the UCS and
permeability tests on the
postweathering 12-mo samples
were equivalent to those on the
postdemonstration samples.
Microstructural analyses of the 12-mo
samples appear substantially similar to
those of the postdemonstration samples,
and deterioration of the solid mass was
not observed.
Overall, the physical test results on the
12-mo samples for UCS, permeability,
and weathering have improved indicating
that the durability of the two solidified
masses at the Hialeah site appears to be
greater than expected, based upon the
posttreatment results from the
demonstration.
Obtaining further data on Geo-Con in
situ operations was not applicable to the
12-mo sampling program.
Conclusions
The following conclusions were drawn
from comparing the 12-mo monitoring
data with the pretreatment and
posttreatment results:
1. PCB mobility did not increase
between the posttreatment and 12-mo
samples. The TCLP leachate
concentrations for 12-mo, post-
treatment, and pretreatment samples
were at or below the detection limits.
Thus PCB immobilization still could
not be confirmed.
2. The physical properties of the treated
soil-UCS, permeability, and wet/dry
and freeze/thaw weathering-greatly
improved after 1 yr of curing. The
freeze/thaw test specimen weight
losses, however, were still
unsatisfactorily high. Permeability and
TCLP leaching tests performed after
the weathering tests provided results
equivalent to those performed on
unweathered samples.
3. The microstructural analyses
confirmed that the 12-mo durability of
the treated soil is probably
satisfactory. The structure of the 12-
mo samples appeared unchanged
from those of the postdemonstration
samples.
The overall conclusions drawn from
the 12-mo monitoring results are that
PCB mobility after 1 yr in the field is
unchanged and that the potential long-
term durability appears to be greater than
estimated, based on the postdemon-
stration samples.
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Table 1. PCS Concentrations in Soils and Leachates
Soil Samples 12-Mo Posttreatmenf
Soil Samples 1-Mo Posttreatmenfr
TCLP Leachate, ygIL
Sample
Designation
B-6
B-6 Dupl.
B-7
B-8
8-9
8-27
8-22
C-7
C-3
C-7
C-rs
C-76
C-r 7
Soil, mg/kg
99
82
89
20
<1.0
80
180
17
45
24
16
3.8
0.84
Unweathered*
<0.10
0.12
<0.10
0.13
<0.10
0.13
0.16
<0.10
<0.10
<0.10
0.16
<0.10
<0.10
Freeze/Thaw
Freeze/ThawtS Controls Wet/DrytS
<0.10 - <0.10
0.77
<0.70 0.72
-
<0.70
0.36
0.47 0.28
<0.70
<0.70
0.72 -- 0.72
<0.70
<0.70
<7.0 <0.70
Treated
Soil,
mg/kg
35
63
82
9.6
<1.0
60
130
20
110
16
17
6.0
<1.0
Treated Soil, TCLP Untreated
Leachate, yg/L Soil, mg/kg
<1.0 650
0.15
0.12 460
<1.0 220
<1.0 16
<1.0
<1.0
<1.0 98
<1.0 96
<1.0 150
<1.0 80
<1.0 13
<1.0 <1.0
Untreated
Soil, TCLP
Leachate, jig/L
75
-
250
<7.0
<7.0
-
-
<7.0
<7.0
<7.0
<7.0
<7.0
<7.0
* PCS detection limits for soils is 1.0 mgikg and for leachates is 0.10 uglL. The untreated TCLP leachates and many of the treated soil leachates had detection limits of 1.0
1 TCLP leachate analyses following freeze/thaw and wet/dry tests were not performed during the demonstration.
fLeacnate result from same unweathered sample as used for soil analysis.
S These TCLP results were obtained after the completion of the 12-cycle accelerated weathering tests. The controls cycle on a 24-hr basis between soaking in water and
being in an ambient temperature humidification chamber. The control is in the humidification chamber when the test specimen is in the freezer. Both the test specimen and
control are soaking in water at the same time, also for 24 hr.
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Table 2. Physical Test Results
Weathering - wt% Loss
Unconfirmed Compressive
Strength, psi Permeability, cm/s x I07t
Sample
Designation
B-6
B-6 Dupl.
S-7
e-s
e-9
B-21
B-22
C-1
C-3
C-7
C-15
C-16
C-7 7
12-Mo"
647
620
841
649
786
7,555
527
7,703
7,747
7,077
850
7,220
7,785
Demo"
114
115
173
303
470
479
428
866
482
343
247
435
521
12-Mo
2.4
5.6
0.07
0.5
7.8
0.05
0.73
0.06
2.7
2.8
0.06
0.73
2.5
"72-mo" represents the 12-mo results and "Demo" represents
fThe actual results are shown
tWeight loss values
multipled by 107.
Demo
4.2
-
5.9
-
--
8.3
4.1
0.24
-
4.1
-
4.6
2.5
Wet/Dryf
12-Mo
0.43
0.48
0.35
0.26
3.19
0.64
0.40
0.30
0.26
0.30
0.30
0.25
0.23
Freeze/Thawf
Demo
0.43
0.49
--
0.34
0.39
0.39
0.39
0.35
0.27
0.31
0.33
0.30
0.29
12-Mo
1.19
0.88
2.86
13.88
24.79
1.47
2.71
0.60
1.41
0.74
0.73
1.81
0.75
Demo
2.17
1.52
1.52
27.92
29.53
1.34
4.64
2.06
3.94
0.30
0.30
0.28
0.78
12-Mo Freeze/Thaw^
TCLP, itg/L PCBs
Weathered
<0.70
0.77
<0.70
-
<0.70
--
0.47
<0.70
<0.70
0.72
<0.70
<0.70
<0.70
Unweathered
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The EPA Project Manager, Mary Stinson, is with the Risk Reduction Engineering
Laboratory, Edison, NJ 08837 (see below).
The complete update report, entitled "Technology Evaluation Report: International
Waste Technologies/Geo-Con In Situ Stabilization/Solidification," consists of two
volumes:
"Volume III" (Order No. PB 90-269 069/AS; Cost: $17.00, subject to change)
discusses the results of the 12-mo monitoring tests and how they compare with the
results of the demonstration.
"Volume IV" (Order No. PB 90-269 0771 AS; Cost: $31.00, subject to change) contains
the technical operating data-logs, laboratory analyses, and microstructural analyses.
Both volumes of this report will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
Three related reports discuss the demonstration and the applications:
"Technology Evaluation Report: SITE Program Demonstration Test, International Waste
Technologies In Situ Stabilization/Solidification, Hialeah, Florida, Volumes I and II"
(EPAI540/5-89/004a and b dated June 1989), and "SITE Program Applications
Analysis Report, International Waste Technologies/Geo-Con In Situ
Stabilization/Solidification" (EPA/540/A5-89/004 dated August 1990).
The EPA Project Manager can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Edison, NJ 08837
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