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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