&EPA
United States
Environmental Protection
Agency
Superfund
Office of Emergency and
Remedial Response
Washington, DC 20460
Office of
Research and Development
Cincinnati, OH 45268
EPA/540/2-91/005
May 1991
Engineering Bulletin
In Situ Steam Extraction
Treatment
Purpose
Section 121 (b) of the Comprehensive Environmental Re-
sponse, Compensation, and Liability Act (CERCLA) mandates
the Environmental Protection Agency (EPA) to select remedies
that "utilize permanent solutions and alternative treatment
technologies or resource recovery technologies to the maxi-
mum extent practicable" and to prefer remedial actions in
which treatment "permanently and significantly reduces the
volume, toxicity, or mobility of hazardous substances, pollut-
ants and contaminants as a principal element." The Engi-
neering Bulletins are a series of documents that summarize
the latest information available on selected treatment and site
remediation technologies and related issues. They provide
summaries of and references for the latest information to help
remedial project managers, on-scene coordinators, contrac-
tors, and other site cleanup managers understand the type of
data and site characteristics needed to evaluate a technology
for potential applicability to their Superfund or other hazard-
ous waste site. Those documents that describe individual
treatment technologies focus on remedial investigation scoping
needs. Addenda will be issued periodically to update the
original bulletins.
Abstract
In situ steam extraction removes volatile and semivolatile
hazardous contaminants from soil and groundwater without
excavation of the hazardous waste. Waste constituents are
removed in situ by the technology and are not actually treated.
The use of steam enhances the stripping of volatile contami-
nants from soil and can be used to displace contaminated
groundwater under some conditions. The resultant con-
densed liquid contaminants can be recycled or treated prior
to disposal. The steam extraction process is applicable to
organic wastes but has not been used for removing insoluble
inorganics and metals. Steam is injected into the ground to
raise the soil temperature and drive off volatile contaminants.
Alternatively, steam can be injected to form a displacement
front by steam condensation to displace groundwater. The
contaminated liquid and steam condensate are then collected
for further treatment.
In situ steam extraction is a developing technology that
has had limited use in the United States. In situ steam
[reference number, page number]
extraction is currently being considered as a component of
the remedy for only one Superfund site, the San Fernando
Valley (Area 1), California site [1]* [2]. However, a limited
number of commercial-scale in situ steam extraction systems
are in operation. Two types of systems are discussed in this
document: the mobile system and the stationary system.
The mobile system consists of a unit that volatilizes contami-
nants in small areas in a sequential manner by injecting steam
and hot air through rotating cutter blades that pass through
the contaminated medium. The stationary system uses steam
injection as a means to volatilize and displace contaminants
from the undisturbed subsurface. Each system has specific
applications; however, the lowest cost alternative will be de-
termined by site-specific considerations. This bulletin provides
information on the technology applicability, limitations, a
description of the technology, types of residuals produced,
site requirements, the latest performance data, the status of
the technology, and sources for further information.
Technology Applicability
In situ steam extraction has been shown to be effective in
treating soil and groundwater containing such contaminants
as volatile organic compounds (VOCs) including halogenated
solvents and petroleum wastes. The technology has been
shown to be effective for extracting soluble inorganics (i.e.,
acids, bases, salts, heavy metals) on a laboratory scale [3].
The presence of semivolatile organic compounds (SVOCs)
does not interfere with extraction of the VOCs [4, p. 12]. This
process has been shown to be applicable for the removal of
VOCs including chlorinated organic solvents [4, p. 9] [5, p. i],
gasoline [6, p. 1265], and diesel [7, p. 506]. It has been
shown to be particularly effective on alkanes and alkane-
based alcohols such as octanol and butanol [8].
Steam extraction applies to less volatile compounds than
ambient vacuum extraction systems. By increasing the tem-
perature from initial conditions to the steam temperature, the
vapor pressures of most contaminants will increase, causing
them to become more volatile. Semivolatile components can
volatilize at significant rates only if the temperature is increased
[3, p. 3]. Steam extraction also may be used to remove low
boiling point VOCs more efficiently.
Printed on Recycled Paper
-------
Table 1
RCRA Codes for Wastes Applicable to Treatment
by In Situ Steam Extraction
Spent Halogenated Solvents used in Degreasing FOOT
Spent Halogenated Solvents F002
Spent Non-Halogenated Solvents F003
Spent Non-Halogenated Solvents F004
Spent Non-Halogenated Solvents F005
Table 2
Effectiveness of In Situ Steam Extraction
on General Contaminant Groups for
Soil and Groundwater
1
?»
0
1
!
Reactive
Contaminant Croups
Halogenated volatiles
Halogenated semivolatiles
Nonhalogenated volatiles
Nonhalogenated semivolatiles
PCBs
Pesticides
Dioxins/Furans
Organic cyanides
Organic corrosives
Volatile metals
Nonvolatile metals
Asbestos
Radioactive materials
norganic corrosives
norganic cyanides
Oxidizers
teducers
Effectiveness
Mobile
System
Soil
m
T
•
V
a
a
a
a
a
a
a
a
a
a
a
a
a
Groundwate
V
T
T
T
a
a
a
a
a
a
a
a
a
a
a
a
a
Stationary
System
Soil/
Groundwater
m
T
H
T
T
T
T
T
T
T
T
a
T
T
T
V
V
m Demonstrated Effectiveness: Successful treatability test at some scale
completed
V Potential Effectiveness: Expert opinion that technology will work
Q No Expected Effectiveness: Expert opinion that technology will not
work
Table 1 lists specific Resource Conservation and Recovery
Act (RCRA) wastes that are applicable to treatment by this
technology. The effectiveness of the two steam extraction
systems (mobile and stationary) on general contaminant
groups for soil and groundwater is shown in Table 2. Ex-
amples of constituents within contaminant groups are provided
in Reference 9, " Technology Screening Guide for Treatment
of CERCLA Soils and Sludges." Table 2 is based on the current
available information or professional judgment where no in-
formation was available. The proven effectiveness of the
technology for a particular site or waste does not ensure that
it will be effective at all sites or that the treatment efficiencies
achieved will be acceptable at all sites. For the ratings used
for this table, demonstrated effectiveness means that, based
on treatability studies at some scale, the technology was
effective for that particular contaminant and matrix. The
ratings of potential effectiveness or no expected effective-
ness are based upon expert judgment. Where potential
effectiveness is indicated, the technology is believed capable
of successfully treating the contaminant group in a particular
matrix. When the technology is not applicable or will prob-
ably not work for a particular combination of contaminant
group and matrix, a no-expected-effectiveness rating is given.
The table shows that the stationary system shows potential
effectiveness for inorganic and reactive contaminants. This is
only true if the compounds are soluble.
Limitations
Soil with high silt and clay content may become mal-
leable and unstable when wet, potentially causing problems
with support and mobility of the mobile steam extraction
system. Remediation of low permeability soil (high clay
content) requires longer treatment times [4, p. 8]. The soil
must be penetrable by the augers and free of underground
piping, wiring, tanks, and drums. Materials of this type must
be relocated before treatment can commence. Surface and
subsurface obstacles greater than 12 inches in diameter (e.g.,
rocks, concrete, wooden piles, trash, and metal) must be
removed to avoid damage to the equipment. Substantial
amounts of subsurface obstacles may preclude the use of a
mobile system. A climate temperature range of 20-100°F is
desirable for best operation of the mobile system [4, p. 18].
Mobile steam extraction systems can treat large con-
taminated areas but are limited by the depth of treatment.
One system that has been evaluated can treat to a depth of
30 feet.
To be effective, the stationary steam extraction system
requires a site with predominately medium- to high-perme-
ability soil. Sites with homogeneous physical soil conditions
are more amenable to the system. If impermeable lenses of
contaminated soil exist, the stationary system may not reme-
diate these areas to desired cleanup levels [5, p. 19]. How-
ever, a combination of steam injection followed by vacuum
extraction (drying) may be effective on sites with heteroge-
neous soil conditions [10]. Steam extraction may be effective
for remediation of contaminated groundwater near the source
of contamination [5, p. 14 ] [10].
There may be residual soil contamination after applica-
tion of in situ steam extraction. Study of a mobile system
showed the average removal efficiency for volatile contami-
nants was 85%; 15% of the volatile compound contamina-
tion remained in the soil [4, p. 4]. If other organic or
inorganic contamination exists, the cleaned soil may need
subsequent treatment by some other technique (i.e., stabili-
zation).
In situ steam extraction may not remove SVOCs and in-
organics effectively. The operational costs of steam extrac-
tion are greater than ambient vacuum extraction, but may
be offset by higher recovery and/or reduction in time re-
quired to remediate the site due to more efficient removal of
contaminants.
Engineering Bulletin: In Situ Steam Extraction Treatment
-------
Figure 1
Schematic of the Mobile Steam Extraction System
Kelly Bars
Shroud
Mixing
Blades
Spent
Carbon
Condensed
Organics
Collection
Tank
Cutter Blades
In situ steam extraction requires boilers to generate steam
and a sophisticated process to capture and treat extracted
steam and contaminants. Because the mobile system is me-
chanically complex its equipment may fail and shut down
frequently; however, mechanical problems may be corrected
fairly quickly. Equipment failure and shutdown are less fre-
quent for the stationary system.
The increase in soil temperature may adversely affect
other soil properties such as microbial populations, although
some microbial populations can withstand soil temperatures
up to 140°F.
Technology Description
Figure 1 is a general schematic of a mobile steam extrac-
tion system [4, p. 48]. A process tower supports and controls
a pair of cutter blades which bore vertically through the soil.
The cutter blades are rotated synchronously in opposite direc-
tions during the treatment process to break up the soil and
ensure through-flow of gases. Steam (at 400°F) and
compressed air (at 275°F) are piped to nozzles located on the
cutter blades Heat from the injected steam and hot air
volatilizes the organics. A steel shroud covers the area of soil
undergoing treatment. Suction produced by the blower
keeps the area underneath the shroud at a vacuum to pull
gases from the soil and to protect against leakage to the
outside environment. The offgases are pulled by the blower
from the shroud to the treatment train, where water and
organics are removed by condensation in coolers. The air-
stream is then treated by carbon adsorption, compressed,
and returned to the soil being treated. Water is removed
from the liquid stream with a gravity separator followed by
batch distillation and carbon adsorption and is then recycled
to a cooling tower. The condensed organics are collected
and held for romoval and transportation.
Mobile systems treat small areas of contamination until
an entire site s remediated. The action of the cutter blades
enables the process to treat low-permeability zones (high clay
content) by breaking up the soil. Current systems treat blocks
of soil measuring 7'4" x 4' by up to 30' deep.
Figure 2 is a schematic of a stationary steam extraction
system [5, p. 9]. High-quality steam is delivered through in-
dividual valves and flow meters to the injection wells from the
manifold. Gases and liquids are removed from the soil through
the recovery wells. Gases flow through a condenser and into
a separation tank where water and condensed gases are
separated from the contaminant phase. Liquid organics are
pumped from the separation tank through a meter and into a
holding tank. The water may require treatment by carbon
adsorption or another process to remove remaining contami-
nants. Noncondensible gases are passed through activated
carbon tanks where contaminants are adsorbed before the
cleaned air is vented to the atmosphere. A vacuum pump
maintains the subatmospheric pressure on the recovery well
and drives the flow of recovered gases. Contaminated liquids
are pumped out of the recovery well to a wastewater tank.
Engineering Bulletin: In Situ Steam Extraction Treatment
-------
Figure 2
Process Schematic of the Stationary Steam Extraction System
Clean Gas to
Atmosphere
Gas
Spent
Carbon
Process Residuals
At the conclusion of both processes, the contaminants
are recovered as condensed organics in the produced water
and on the spent carbon. Residual contamination will also
remain in the soil. The recovered contaminants are tempo-
rarily stored on site and may require analysis to determine the
need for further treatment before recycling, reuse, or disposal.
Separated, cleaned water is used as cooling tower
makeup water in the mobile system. Also in this system,
cleaned gas is heated and returned as hot air to the soil.
Separated water from the stationary system must be treated
to remove residual contaminants before disposal or reuse.
The cleaned gas from this system is vented to the atmosphere.
Both systems produce contaminated granular activated carbon
from the gas cleaning. The carbon must be regenerated or
disposed. There may be minor fugitive emissions of VOCs
from the soil during treatment by the steam stripping systems
and from the gas-phase carbon beds [4, p. 2].
Site Requirements
Power and telephone lines or other overhead obstacles
must be removed or rerouted to avoid conflict with the 30-
foot treatment tower on the mobile steam extraction system.
Access roads must be available for transporting the mobile
system. Sufficient land area must be available around the
identified treatment zone to maneuver the unit and to place
support equipment and trailers. The area to be treated by the
mobile steam extraction system must be capable of support-
ing the treatment rig so that it does not sink or tip. The
ground must be flat and gradable to less than 1% slope. A
minimum treatment area of approximately 0.5 acre (20,000
Gas
Liquid
Water Recovered
Liquid
Contaminants
ft2) is necessary for economical use of the mobile system.
Rectangular shaped treatment areas are most efficient. The
mobile system requires a water supply of at least 8 to 10 gpm
at 30 psig. Power for the process can be provided by on-
board diesel generators [4, p. 18].
Boilers that generate steam for the stationary steam ex-
traction system use no. 2 fuel oil or other hydrocarbon fuels.
Water and electricity must be available at the site. The site
must have sufficient room for a drilling rig to install the
injection and extraction wells and for steam generation and
waste treatment equipment to be set up, as well as room for
support equipment and trailers.
Contaminated soils or waste materials are hazardous and
their handling requires that a site safety plan be developed to
provide for personnel protection and special handling mea-
sures. Storage should be provided to hold the process prod-
uct streams until they have been tested to determine their
acceptability for disposal, reuse, or release. Depending on the
site, a method to store waste that has been prepared for
treatment may be necessary. Storage capacity will depend on
waste volume.
Onsite analytical equipment capable of determining site-
specific organic compounds for performance assessment make
the operation more efficient and provide better information
for process control.
Performance Data
Toxic Treatments (USA) Inc. used a prototype of its mo-
bile system to remediate a site in Los Angeles, California. The
site soil had been contaminated by diesel and gasoline fuel
—'^^^^^^"•^^•••^••^•^•^•^M
Engineering Bulletin: In Situ Steam Extraction Treatment
-------
Table 3
Total Petroleum Hydrocarbons Removed by
Toxic Treatments (USA) Inc. at Los Angeles, CA*
Table 4
Demonstration Test Results for Volatiles
Removed by Toxic Treatments (USA) Inc. [4]
Calculated Value
Mean
Initial
(mg/kg)
2222
Final
(mg/kg)
191
Percent Removal
91
* This information is from vendor-published literature [7]; therefore,
quality assurance has not been evaluated.
from underground storage tanks. For this application, the
steam stripping was augmented with potassium permanganate
to promote oxidation of hydrocarbons in the highly contami-
nated zones [7, p. 506]. Table 3 summarizes the results of the
treatment by steam stripping. The level of petroleum hydro-
carbons was reduced overall by an average of 91%. The
mobile system was reported to have effectively reduced the
level of petroleum hydrocarbon compounds found in the soil
at a wide range of concentrations. However, the system's
ability to remove the higher molecular weight, less volatile
components of the diesel fuel was limited.
Under the Superfund Innovative Technology Evaluation
(SITE) program, Toxic Treatments demonstrated an average
VOC removal rate of 85 percent for a test area of 12 soil
blocks [4, p. 10] as shown in Table 4. The average VOC post-
treatment concentration was 71 ppm; the cleanup level for
the site was 100 ppm. The primary VOCs were trichloroethene,
tetrachloroethene, and chlorobenzene. The test achieved a
treatment rate of 3 cu. yds./hr. in soils having high clay con-
tent and containing some high-boiling-point VOCs. Toxic
Treatments obtained similar results in tests conducted
throughout the site; baseline testing demonstrated an aver-
age post-treatment concentration of 61 ppm. The mobile
technology also demonstrated the ability to diminish the level
of SVOCs by approximately 50%, as shown in Table 5, although
the fate of these SVOCs could not be determined [4, p. 45].
These tests were conducted on contamination in the unsatur-
ated zone. A follow-up test was conducted on six soil blocks
where treatment extended into the saturated zone. Pre-
treatment data from the vendor indicated significant VOC
contamination in this area. Post-treatment results showed
that the average level of VOC contamination in the unsaturated
zone was reduced to 53 ppm. Ketones (specifically acetone,
2-methyl-4-pentanone, and 2-butanone) were found to be
the primary contaminants in the post-treatment soil. Data
from the vendor indicated that similar reduction of VOCs
occurred in the saturated zone.
The stationary steam extraction system using steam in-
jection alone decreased soil contaminant concentrations by
90 percent in a recent pilot study [5]. High concentrations of
individual contaminants were found in a low permeability
zone by use of temperature logs. The residual high contami-
nant concentrations are thought to have been caused by: 1)
retention of highly contaminated steam condensate found
ahead of the condensation front in the dry, low-permeability
zones and 2) the decreased evaporation rate of the high-
boiling-point compounds due to the high water content in
the low permeability zones [5, p. 19]. This issue is currently
under study at the University of California, Berkeley [10].
Experimental testing has shown that a combination of steam
12-Block Test Area
Pre-
Treatment
(w/g)
54
28
642
444
850
421
788*
479
1133
431
283
153
Post-
Treatment
fog/g)
14
12
29
34
82
145
61
64
104
196
60
56
Percent
Removal
73
56
96
92
90
65
92
87
91
54
79
64
Block
Number
A-25-e
A-26-e
A-27-e
A-28-e
A-29-e
A-30-e
A-31-e
A-32-e
A-33-e
A-34-e
A-35-e
A-36-e
" Only analyses from two of the three sample cores taken were available.
Table 5
Demonstration Test Results for Semivolatiles
Removed by Toxic Treatments (USA) Inc. [4]
12-Block Test Area
Block
Number
A-25-e
A-26-e
A-27-e
A-28-e
A-29-e
A-30-e
A-31-e
A-32-e
A-33-e
A-34-e
A-35-e
A-36-e
Pre-
Treatment
fag/g)
595
1117
1403
1040
1310
1073
781
994
896
698
577
336
Post-
Treatment
fcg/g)
82
172
439
576
726
818
610
49
763
163
192
314
Percent
Removal
86
85
69
45
45
24
22
95
15
77
67
7
Engineering Bulletin: In Situ Steam Extraction Treatment
-------
injection and vacuum extraction can effectively remove vola-
tile contaminants from a heterogeneous soil type [10]. Steam
injection followed by vacuum extraction produces an effec-
tive drying mechanism. The process achieves greater con-
taminant removals by enhancing the vapor flow from low- to
high-permeability regions.
Performance data may be forthcoming from full-scale
stationary system steam extraction projects being conducted
by Solvent Service, Inc. and Hydro-Fluent, Inc. Data from
laboratory-scale studies are also available [6] [3].
RCRA Land Disposal Restrictions (LDRs) that require treat-
ment of wastes to best demonstrated available technology
(BOAT) levels prior to land disposal may sometimes be deter-
mined to be applicable or relevant and appropriate require-
ments for CERCLA response actions. The in situ steam extrac-
tion technology produces liquid contaminants which may be
recyclable or may require treatment to meet treatment levels
set by BOAT. A common approach to treating liquid waste
may be to use other treatment techniques in series with in situ
steam extraction.
Technology Status
In situ extraction is being considered as a component of
the selected remedy for the San Fernando Valley (Area 1) site
in Burbank, California. The Area 1 site consists of an aquifer
contaminated with VOCs, including TCE and PCE [1, p.145].
Toxic Treatments' mobile steam extraction technology
(Detoxifier™) was used in 1986 to remediate 4,700 cu. yds.
of soil contaminated with diesel fuel at the Pacific Commerce
Center site in Los Angeles, California [7, p. 506].
In 1987, Toxic Treatments' mobile steam extraction sys-
tem was selected as the remedial action to clean up approxi-
mately 8,700 cu. yds. of soil contaminated with VOCs and
SVOCs at the GATX Annex Terminal site in San Pedro, California
[11, p. 1-1]. Treatability testing of the technology at the site
has'been underway to validate its performance prior to full
site remediation. This system also has been evaluated under
the SITE program at the site in San Pedro, California. Toxic
Treatments expects to have a second generation Detoxifier™
available soon, which will be capable of operating on grades
up to 5 percent.
For the mobile technology, the most significant factor
influencing cost is the time of treatment or treatment rate.
Treatment rate is influenced primarily by the soil type (soils
with higher clay content require longer treatment times), the
waste type, and the on-line efficiency. Cost estimates for this
technology are strongly dependent on the treatment rate and
range. A SITE demo indicated costs of $111 -317/cu. yd. (for
10 and 3 cu. yd. treatment rates, respectively). These costs
are based on a 70% on-line efficiency [4, p. 28].
Solvent Service, Inc. is using and testing its first full-scale
stationary Steam Injection Vapor Extraction (SIVE) system at
its San Jose, California, facility for remediation to a depth of
20 feet of up to 41,000 cu. yds. of soil contaminated with
numerous organic solvents [5, p. 3] [10]. Solvent Service
hopes to make the SIVE system available for other applications
in the future. The system consists of injection and extraction
wells and a gas and liquid treatment process. Equipment for
steam generation and extraction and contaminated gas/liquid
treatment are trailer mounted.
Hydro-Fluent, Inc. is designing and constructing its first
full-scale stationary steam extraction system to be used in
Huntington Beach, California for recovery of 1 35,000 gallons
of diesel fuel in soil to a depth of 40 feet at the Rainbow
Disposal, Nichols Avenue site [12]. Bench and pilot-scale
studies have been conducted.
For the stationary steam extraction system, the most
significant factor influencing cost is the number of wells re-
quired per unit area, which is related to the depth of con-
tamination and soil permeability. Shallow contamination
requires lower operating pressures to prevent soil fracturing,
and wells are placed closer together. Deeper contamination
allows higher operating pressures and greater well spacing;
therefore, fewer wells and lower capital cost. Cost estimates
for this technology range from about $50-300/cu. yd., de-
pending on site characteristics [10].
EPA Contact
Technology-specific questions regarding in situ steam
extraction may be directed to:
Michael Gruenfeld
U.S. Environmental Protection Agency
Releases Control Branch
Risk Reduction Engineering Laboratory
2890 Woodbridge Avenue
Building 10(MS-104)
Edison, N) 08837
FTS 340 6625
(908)321-6625
Acknowledgments
This bulletin was prepared for the U.S. Environmental
Protection Agency, Office of Research and Development (ORD),
Risk Reduction Engineering Laboratory (RREL), Cincinnati, Ohio,
by Science Applications International Corporation (SAIC) un-
der contract No. 68-C8-0062. Mr. Eugene Harris served as
the EPA Technical Project Monitor. Mr. Gary Baker was SAIC's
Work Assignment Manager. This bulletin was authored by
Mr. Kyle Cook of SAIC. The project team included Mr. Jim
Rawe and Mr. joe Tillman of SAIC. The author is especially
grateful to Mr. Bob Hillger and Dr. John Brugger of EPA, RREL,
who have contributed significantly by serving as technical
consultants during the development of this document.
The following other Agency and contractor personnel
have contributed their time and comments by participating in
the expert review meetings and/or peer reviewing the docu-
ment:
Mr. Clyde Dial
Mr. Vic Engleman
Mr. Trevor Jackson
Mr. Lyle Johnson
Dr. Kent Udell
SAIC
SAIC
SAIC
Western Research Institute
Udell Technologies
Engineering Bulletin: In Situ Steam Extraction Treatment
-------
/*"
REFERENCES
1. ROD Annual Report, FY 1989. EPA/540/8-90/006, U.S.
Environmental Protection Agency, 1990.
2. Personal Communications with the Regional Project
Manager, April, 1991.
3.
4.
Udell, K.S., and L.D. Stewart. Combined Steam Injection
and Vacuum Extraction for Aquifer Cleanup. Presented
at Conference of the International Association of
Hydrogeologists, Calgary, Alberta, Canada, 1990.
Applications Analysis Report—Toxic Treatments' In Situ
Steam/Hot-Air Stripping Technology, San Diego, CA.
Report to be published, U.S. Environmental Protection
Agency, 1990. (SITE Report).
Udell, Kent S., and L. D. Stewart. Field Study of In Situ
Steam Injection and Vacuum Extraction for Recovery of
Volatile Organic Solvents. University of California
Berkeley-SEEHRL Report No. 89-2, June 1989.
Udell, K. S., j. R. Hunt, and N. Sitar. Nonaqueous Phase
Liquid Transport and Cleanup 2. Experimental Studies.
Water Resources Research, 24 (8): 1259-1269, 1988.
8
La Mori, Phillip N. and M. Ridosh. In Situ Treatment
Process for Removal of Volatile Hydrocarbons from Soils:
Results of Prototype Test. EPA/600/9-87/018F, U.S.
Environmental Protection Agency, 1987.
Lord, A.E., Jr., R.M. Koerner, D.E. Hullings, and J.E.
Brugger. Laboratory Studies of Vacuum-Assisted Steam
Stripping of Organic Contaminants from Soil. Presented
at the 15th Annual Research Symposium: Remedial
Action, Treatment, and Disposal of Hazardous Waste.
EPA/600/9-90/006, U.S. Environmental Protection
Agency, 1990.
9. Technology Screening Guide for Treatment of CERCLA
Soils and Sludges. EPA/540/2-88/004, U.S. Environmen-
tal Protection Agency, 1988.
10. Udell, Kent S. Personal Communication. July 23, 1990.
11. Harding Lawson Associates, Remedial Design, Annex
Terminal Site, San Pedro, California. Prepared for GATX
Terminals Corporation, 1987.
Toxic Cleanup Going Underground. The Orange
County Register, June 25, 1990, pp. A1 and A14.
12
Engineering Bulletin: In Situ Steam Extraction Treatment
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