&EPA
United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102G)
EPA542-R-99-004
June 1999
clu-in.org
Multi-Phase Extraction:
State-of-the-Practice
WA TER
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NOTICE
This document was prepared for the U.S. Environmental Protection Agency (EPA) under EPA
Contract Number 68-W-99-003. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
This document may be obtained from EPA's web site at www.epa.gov or at clu-in.org. A limited
number of hard copies of this document are available free-of-charge by mail from EPA's National
Service Center for Environmental Publications (NSCEP), atwww.epa.gov/ncepihom/, or at the
following address (please allow 4-6 weeks for delivery):
U.S. EPA/National Service Center for Environmental Publications
P.O. Box 42419
Cincinnati, OH 45242
Phone: (513) 489-8190 or (800) 490-9198
Fax: (513)489-8695
ACKNOWLEDGMENTS
This document was prepared for the EPA's Technology Innovation Office by Tetra Tech EM Inc.
and HSI GeoTrans, Inc. Special acknowledgment is given to Michelle Simon of EPA's Office of
Research and Development, Bill Saddington (Defense Supply Center Richmond), Zahra
Zahiraleslamzadeh (FMC Corporation), and James DiLorenzo (EPA Region 1) for their thoughtful
suggestions and support in preparing this report.
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TABLE OF CONTENTS
Page
FOREWORD vi
1 INTRODUCTION 1
2 TECHNOLOGY DESCRIPTION 2
2.1 SOIL VAPOR AND GROUND WATER EXTRACTION 2
2.2 MPE TECHNOLOGY DESCRIPTION 3
2.3 MPE AS A REMEDIATION ALTERNATIVE 5
2.4 TECHNOLOGY CONFIGURATIONS 5
2.4.1 SINGLE PUMP CONFIGURATION 5
2.4.2 TWO-PUMP CONFIGURATION 7
2.4.3 BIOSLURPING 7
2.5 MPE TERMINOLOGY 9
3 APPLICABILITY OF MPE 12
3.1 APPLICABILITY 12
3.2 ADVANTAGES AND POTENTIAL LIMITATIONS OF MPE COMPARED TO
CONVENTIONAL PUMPING 14
4 VENDORS OF MPE 17
5 CASE STUDIES 24
5.1 DEFENSE SUPPLY CENTER, RICHMOND, VA 25
5.1.1 SUMMARY INFORMATION 25
5.1.1.1 GEOLOGIC AND HYDROGEOLOGIC SETTING 26
5.1.1.2 SITE CHARACTERIZATION SUMMARY 27
5.1.1.3 REMEDIATION SUMMARY 28
5.1.2 TECHNOLOGY DESCRIPTION AND SYSTEM DESIGN 30
5.1.3 TECHNOLOGY PERFORMANCE 30
5.1.4 TECHNOLOGY COST 39
5.1.5 SUMMARY OF OBSERVATIONS AND LESSONS LEARNED 39
5.1.6 CONTACT INFORMATION 40
5.1.7 REFERENCES 40
5.2 328 SITE, SANTA CLARA, CA 41
5.2.1 SUMMARY INFORMATION 41
5.2.2 TECHNOLOGY DESCRIPTION AND SYSTEM DESIGN 43
5.2.3 TECHNOLOGY PERFORMANCE 44
5.2.3.1 VOC MASS REMOVAL 47
5.2.3.2 SHUTDOWN AND REBOUND 52
5.2.4 TECHNOLOGY COSTS 54
5.2.5 SUMMARY OF OBSERVATIONS AND LESSONS LEARNED 54
5.2.6 CONTACT INFORMATION 55
5.2.7 REFERENCES 55
11
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TABLE OF CONTENTS
(continued)
Page
5.3 TINKHAM'S GARAGE SUPERFUND SITE, LONDONDERRY, NH 56
5.3.1 SUMMARY INFORMATION 56
5.3.2 TECHNOLOGY DESCRIPTION AND SYSTEM DESIGN 57
5.3.3 TECHNOLOGY PERFORMANCE 60
5.3.4 TECHNOLOGY COST 68
5.3.5 SUMMARY OF OBSERVATIONS AND LESSONS LEARNED 68
5.3.6 CONTACT INFORMATION 69
5.3.7 REFERENCES 69
6 REFERENCES 70
in
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LIST OF FIGURES
Page
2.1 Effect of a vacuum on pumping level (Suthersan, 1997) 4
2.2 Single pump MPE well schematic (Suthersan, 1997) 6
2.3 Two-pump MPE schematic (Modified from Suthersan, 1997) 8
2.4 Bioslurping schematic (Kittel, et al., 1994) 10
5.1 Comparison of baseline groundwater levels (Law Engineering and Environmental
Services, 1998) 32
5.2 Plot of VOC concentrations in SVE emissions over time (Law Engineering
and Environmental Services, Inc., 1998) 34
5.3 Total VOC concentrations in groundwater (Law Engineering and Environmental
Services, Inc., 1998) 36
5.4 Cumulative mass of VOCs removed by groundwater extraction (Law Engineering
and Environmental Services, 1998) 37
5.5 Cumulative mass of VOC's removed by SVE (Law Engineering and Environmental
Services, 1998) 38
5.6 Map of 328 site (Zahiraleslamzadeh et al., 1998) 42
5.7 Process flow diagram (Zahiraleslamzadeh et al., 1998) 45
5.8 VOC mass removal 48
5.9 Average VOC concentrations of groundwater overtime 49
5.10 VOC removal rates during operation 53
5.11 Schematic of DVE Well and Manifold (Terra Vac, 1996) 61
5.12 Process Flow Diagram of DVE System (modified from Terra Vac, 1996) 62
5.13 Time variation of vapor phase VOCs in DVE system influent 64
5.14 Time variation of aqueous phase VOCs in DVE system influent 66
5.15 Cumulative vapor phase VOC removal by DVE 67
IV
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LIST OF TABLES
Page
2.1 Terms referring to multi-phase extraction and their configurations 11
3.1 Applicability of MPE 13
3.2 Summary of the advantages and potential limitations of MPE 15
4.1 MPE vendors listed in EPA REACH IT 18
4.2 Representative MPE sites for vendors listed in EPA REACH IT 21
5.1 Summary of identifying information for case study sites 24
5.2 DSCR-ANP site summary 27
5.3 Timeline of remedial activities at DSCR-ANP site 29
5.4 Summary of DPE system performance data at DSCR 31
5.5 Potentiometric surface elevations 33
5.6 Summary of groundwater VOC data 35
5.7 328 site setting 43
5.8 Technology summary 44
5.9 Operations timeline 46
5.10 VOC concentrations in groundwater 50
5.11 Mass removal of VOCs from groundwater and soil vapor extraction 51
5.12 VOC concentrations in extracted vapor 51
5.13 Site characterization summary for Tinkham's Garage 58
5.14 Timeline of remedial activities at Tinkham's Garage 59
5.15 Summary of DVE system performance data 63
v
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FOREWORD
This report describes the state-of-the-practice for multi-phase extraction (MPE) of
contaminated soil and groundwater, focusing primarily on the application and use of MPE at
sites with halogenated volatile organic compounds (VOCs). MPE is an innovative
technology that has the potential to be more cost-effective and to remediate sites more
quickly than with use of conventional technologies. Thousands of sites in the United States
are contaminated with VOCs, including sites under Superfund, RCRA Corrective Action,
RCRA Underground Storage Tank, Department of Defense, Department of Energy, and
civilian federal agency and state programs.
MPE technology is described in this report, including the various configurations used
for the technology, the types of site conditions to which MPE would be applicable, and the
advantages and potential limitations of using MPE at these types of sites. In addition, the
report summarizes information about vendors of MPE, including identifying sites where the
vendors have applied their technologies. Detailed case studies summarizing the cost and
performance of using MPE are provided for three sites. These sites include a military base,
an industrial manufacturing facility, and a federal Superfund site all of which were
contaminated with chlorinated VOCs in soil and groundwater.
This report is intended to assist federal and state project managers, permit writers,
technology users, and contractors that may be considering the applicability of this technology,
and in screening the feasibility of this technology early in the remedy selection process. It is
not intended to revise or update EPA policy or guidance on how to clean up sites with
contaminated soil and groundwater.
VI
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1 INTRODUCTION
EPA has estimated that more than 200,000 sites remain to be remediated in the United
States, including Superfund, RCRA Corrective Action, Underground Storage Tank,
Department of Defense (DoD), Department of Energy (DOE), civilian federal agency, and
state sites. About 70 percent of Superfund, RCRA, DoD, and DOE sites have contaminated
soil or groundwater, or both (EPA, 1997a). Volatile organic compounds (VOCs), including
chlorinated solvents, are a frequently-occurring type of contaminant at these sites.
This report provides an overview of the state-of-the-practice for multi-phase
extraction (MPE). MPE involves simultaneous extraction of soil vapor and groundwater to
remediate both types of contaminated media. MPE has seen an increase in use at Superfund
and other sites for cleanup of soil and groundwater impacted with halogenated VOCs, and
also has been used frequently for cleanup of petroleum-hydrocarbon sites. This report
focuses primarily on the applicability and use of MPE at sites with halogenated VOCs.
Section 2 of this report provides a description of MPE technology, including the
various configurations used for this technology. Section 3 describes the types of site con-
ditions to which MPE would be applicable, and discusses the advantages and disadvantages
of using MPE at these types of sites. Section 4 summarizes information about attributes of
MPE vendors and examples of sites where these vendors have applied their technologies.
Information about these vendors was obtained from EPA REACH IT, an extensive database
of information about characterization and treatment technologies. EPA REACH IT is
available on the Internet at . Detailed case studies of sites
where MPE has been used are summarized in Section 5 (for the Defense Supply Center,
Richmond, VA; 328 Site, Santa Clara, CA; and Tinkham's Garage Superfund Site,
Londonderry, NH), and referenced throughout the report. The references used during
preparation of this report are listed in Section 6, and are cited in this report using parentheses.
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2 TECHNOLOGY DESCRIPTION
Multi-phase extraction (MPE) is a generic term for technologies that extract VOCs in
soil vapor and groundwater, simultaneously (OSWER Directive No. 9335.0-68FS). This
section discusses MPE as the coupling of soil vapor extraction and groundwater pump-and-
treat by applying a vacuum on a sealed recovery well. Reasons for implementing MPE are
covered and typical configurations of MPE examined.
2.1 SOIL VAPOR AND GROUNDWATER EXTRACTION
Soil vapor extraction (SVE) is the extraction of soil vapor from the semi-saturated
subsurface, or vadose zone. SVE induces subsurface air flow by a vacuum applied to a
sealed well screened in the zone of interest. The technology is employed to facilitate mass
removal of residual and vapor phase VOCs located in the vadose zone. Volatilization, with
subsequent air advection, is the primary removal mechanism of these subsurface constituents.
SVE is beneficial for soil remediation and provides an alternative to traditional excavation
approaches for site remediation. SVE systems are useful in a variety of soil settings but are
most advantageous in low to moderate permeability formations. Subsurface air flow may be
short circuited in high permeability settings and may be inadequate in very low permeability
formations that lack secondary flow paths (Suthersan, 1997; EPA, 1997b; EPA, 1996; API,
1996).
Groundwater pump-and-treat involves the extraction of groundwater from pumping
wells and the subsequent ex-situ treatment and disposal. Groundwater flow to the well is
induced by depressing the water table surface by pumping and creating a hydraulic gradient.
Groundwater extraction seeks to reduce the mass of dissolved and non-aqueous phase
constituents and to reduce mobility of contaminant plumes by hydraulic containment. The
primary removal mechanism is groundwater advection and dissolution of constituents located
in the saturated subsurface. Groundwater extraction can be employed in a wide variety of
hydrogeologic settings ranging from high to low permeability. The effectiveness of the
technology becomes limited as permeability decreases and becomes more heterogeneous.
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Limitations manifest as low recovery rates, high drawdown, and rapid, steep gradients
providing limited capture (EPA, 1996).
2.2 MPE TECHNOLOGY DESCRIPTION
MPE is typically applied in recovery wells with some portion of the well screen
extending above the water table into the vadose zone. Groundwater recovery is achieved by
pumping at or below the water table. The applied vacuum extracts soil vapor and enhances
groundwater recovery. Liquid flow rates are increased due to the increased pressure gradient
applied on the system. In some configurations, the vacuum increases the effective drawdown
locally near the pumped well without significantly lowering the water table surface away
from the pumped well.
Figure 2.1 illustrates the effect of an applied vacuum on a pumping well. The
drawdown in a pumping well without vacuum influence will be equal to the difference in the
static water level (shown in 2.1.1) and dynamic water level in the pumping well (shown in
2.1.2). This drawdown will result in a flow rate. A well under the influence of a vacuum
only results in a water table rise equal to the applied vacuum (shown in 2.1.3). Vacuum is
negative gauge pressure (i.e., less than atmospheric) and creates a negative gradient towards
the well. In MPE the pumping and vacuum scenarios are superimposed such that the
effective drawdown is the sum of the drawdown produced by the vacuum and water table
depression (shown in 2.1.4). Because the drawdown is increased, an increase in the well
yield (extraction rate) is realized (Suthersan, 1997).
Applying a vacuum to an extraction well enhances the hydraulic gradient. The
hydraulic gradient is defined as the difference in hydraulic head between two points divided
by the length of the flow path. From Darcy's Law, it is known that the rate of flow through
the aquifer is directly proportional to the hydraulic gradient. When drawdown is maximized,
the head difference cannot be increased by lowering the water level. However, the effective
head difference can be increased by applying negative pressure (a vacuum) to the extraction
well. Thus, the hydraulic gradient is increased and a resulting increase in the rate of
groundwater extraction is realized (Suthersan, 1997).
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Figure 2.1. Effect of a vacuum on pumping level (Suthersan, 1997).
2,1,1 STATIC
2,1,2 FLUID PUMPING ONLY
2,1,3 ONLY VACUUM 2,1,4 PUMPING AND VACUUM
1
1
— J>
c
* « = o gpm
r
\
\
i
i
-~^Q -
Vac =
^
i
i
i
i
1 gpm
0'H20
,,—
1
-~N
1
->Q = 0 gpm
Vac = 10' H20
\
\
\
\
\
,
,
>Q = 2 gpm
Vac = 10'H20
9' (s')
t
t
/
DRAWDOWN = 0
DRAWDOWN = 9'
EFFECTIVE s' = Vac + s'
= 10' + 9'
= 19'
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2.3 MPE AS A REMEDIATION ALTERNATIVE
MPE addresses contamination in both the saturated and vadose zones, remediating
dissolved, vapor, residual, and non-aqueous phases of contamination. MPE affects mass
removal by volatilization, dissolution, and advective transport. In general, if both SVE and
groundwater pump-and-treat are potential applicable technologies, then MPE may be
considered as a remedial alternative. The following list highlights the capabilities of MPE
and thus the primary factors for considering MPE as a remediation alternative.
Increase in groundwater recovery rates, compared to conventional pumping
practices in equivalent settings (EPA, 1997b)
Increase in radius of influence of individual groundwater recovery wells
(Suthersan, 1997)
Recovery of shallow layer of floating, free product (EPA, 1996)
Remediation of the capillary fringe and smear zone (EPA, 1997b; EPA, 1996;
EPA, 1997c)
Remediation of volatile, residual phase contaminants located above and below
the water table (EPA, 1996; EPA, 1997c)
Simultaneous remediation of soil and groundwater
2.4 TECHNOLOGY CONFIGURATIONS
MPE can be designed and implemented in a variety of configurations. The three main
forms of MPE are the single and two pump configurations and bioslurping. The latter is
essentially a minor variation of the single pump configuration used to recover free product.
Each is described in the following sections.
2.4.1 SINGLE PUMP CONFIGURATION
In the single pump configuration, as shown in Figure 2.2, a single drop tube is
employed to extract both liquid and vapor from a single well. The vacuum and liquid suction
lift is achieved by one vacuum pump (liquid-ring pumps, jet pumps, and blowers are typical).
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Figure 2.2. Single pump MPE well schematic (Suthersan, 1997).
SUCTION LINE
VACUUM GAUGE
THREADED COUPLING
CASING VACUUM GAUGE
PVC CASING
BORE HOLE
BENTONITE
PVCSCREEN
SAND PACK
PVC CAP
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This configuration is limited to depths of about 30 feet below ground surface (bgs). A
complete vacuum would be achieved at an equal and opposite value of the atmospheric
pressure, or -14.7 psi, which equates to 34 feet of water column.1 In theory, a vacuum lift
pump can only lift water a height equal to the atmospheric pressure. As such, single pump
configurations are used for shallow (less than 30 feet) water-table remediation (Suthersan,
1997; EPA, 1996).
2.4.2 TWO-PUMP CONFIGURATION
Depth limitations can be overcome with the second configuration, the two-pump
MPE system shown in Figure 2.3. This system utilizes a submersible pump for groundwater
recovery in conjunction with a separate vacuum applied at the sealed wellhead. In this
configuration, liquid and vapor streams are separate from one another. Conductivity type
level sensors can be utilized for pump control. Level control may be necessary to prevent the
vacuum from causing the pump to lose positive suction head and cavitate. Depending on the
application, two-pump systems can utilize electric or pneumatic submersible pumps for
groundwater recovery and liquid ring pumps or blowers to induce vacuum. Applications for
the recovery of a free product, or light, non-aqueous phase liquid (LNAPL), typically employ
pneumatic submersible pumps for liquid recovery (Suthersan, 1997; EPA, 1996; Peargin,
1995).
2.4.3 BlOSLURPING
The last MPE configuration is often referred to as bioslurping (Kittel et al, 1994).
This configuration is the same as the single pump MPE scheme, however, the drop tube in a
bioslurping application is set at, or just below, the liquid-air interface. This configuration has
shown to be effective at free product recovery (Suthersan, 1997; Kittel et al, 1994) and is
primarily used for that purpose. The bioslurping system extracts water, LNAPL, and air from
a single 1-inch drop tube in a 2-inch diameter well (Kittel et al, 1994). The extraction point
alternates from recovering liquid to air, emanating a slurping sound. A secondary goal of
-14.7 psi x 2.311 ftH2O = 33.95 ft H2O
psi
7
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Figure 2.3. Two-pump MPE schematic (Modified from Suthersan, 1997).
TO TREATMENT SYSTEM
-LIQUID RING PUMP
GROUND
SURFACE ^
/
/
I-
\
V
k - -
r • ]
i
\
;
/
1 :
I
1
I * ;
=-
=-
i«««i«ff
V J
1
'" *— *fH CEMENT GROUT
f^ll
^"^•-^^^m NATIVF Fll 1
»»fiiii CEMENT GPOUT
•77"7/^'7"A
XXXx^xl
7^//4 iiiiii PFMTOMiTF
^^Xx^X/\
\
I
/ *.
1
,—mgl n R A\/ F i P A P K
/
/
• / \ A/ p | ! o p p p F M
• - - "_|-— CEMENTGROUT
, '. 1
SUBMERSIBLE PUMP
* * \
* \
",: I
i. • V
SUMP
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bioslurping is the enhancement of in-situ aerobic biodegradation of aromatic hydrocarbons as
a result of increased airflow. Figure 2.4 illustrates a typical bioslurping configuration.
2.5 MPE TERMINOLOGY
Multi-phase extraction is referred to by many other names in the literature. Table 2.1
lists some of the terms used to refer to MPE. The environmental remediation industry, as a
whole, has not become unified or consistent with MPE terminology. Some organizations
within the industry have created trademarked names. The majority of the trademarked names
will utilize one of the three main configurations presented in this section. A partial list of
trademarked names and trade names of MPE are presented in Section 4.
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Figure 2.4. Bioslurping schematic (Kittel, et al., 1994).
COMPRESSION SCREWS
METAL PLATES
2" TEE
1" SUCTION TUBE
FREE PHASE PRODUCT
VALVE
TEE
•TO 6" HEADER
VALVE
RUBBER GASKET
2"VALVE
GROUND SURFACE
2" PVC
BIOVENTING WELL
SCREEN
WATER TABLE
10
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Table 2.1. Terms referring to multi-phase extraction and their configurations.
Term
Dual-Phase Extraction (DPE)
Drop-Tube Entrainment Extraction
Well-Screen Entrainment Extraction
High-Vacuum Dual Phase Extraction
(HVDPE)
Low-Vacuum Dual Phase Extraction
(LVDPE)
Two-Phase Extraction (TPE)
Bioslurping
VE/GE ("Veggie");
Downhole-Pump Extraction
Vacuum Enhanced Pumping (VEP)
Vacuum Enhanced Recovery (VER)
Configuration
Non-specific MPE term
Single pump configuration
Extraction of vapor and groundwaterfrom a
sealed well with induced vacuum.
Groundwater is aspirated into the vapor
stream at the well screen.
Two pump configuration with a submersible
pump for groundwater recovery.
High vacuum application (18 to 26 in Hg)
Two pump configuration with a submersible
pump for groundwater recovery.
Low vacuum application (2 to 12 in Hg)
Single pump configuration with high vacuum
application (18 to 26 in Hg)
Single pump configuration with drop tube set
at, or just below, the air-liquid interface
Two pump configuration with a submersible
pump for groundwater recovery
Non-specific MPE term
Non-specific MPE term
Source
1
1
1
2
2
2
3
4,5
4
6
Sources:
1. EPA, 1997b
2. EPA, 1997c
3. Kitteletal, 1994
4. EPA, 1996
5. Peargin, 1995
6. Suthersan, 1997
11
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3 APPLICABILITY OF MPE
3.1 APPLICABILITY
The use of MPE can be highly beneficial to site remediation provided that the
technology is applied within the appropriate range of hydrogeologic settings and contaminant
properties. If applied outside of the appropriate conditions, MPE may be ineffective in
remediating the problem and may not be cost effective (Suthersan, 1997). The applicability
of MPE is governed, primarily, by media properties and, to a lesser extent, contaminant
properties. Once groundwater extraction wells have been utilized, and concentrations have
reached an asymptote (leveled off), conversion of these wells to MPE wells may be cost
effective, leading to increased contaminant mass recovery. The applicability of MPE is
summarized in Table 3.1.
Hydraulic conductivity (K) is the media parameter of greatest interest because it
characterizes the ability of a formation to transmit water. MPE is most applicable to fine-
grained formations in the fine sand to silty sand range (hydraulic conductivity, K = 10"3 to
10"5 cm/s) (EPA, 1996). Application of systems to lower conductivity (less than 10"6 cm/s)
may be possible if some secondary permeability exists (Suthersan, 1997). MPE applicability
can also be determined from the product of the saturated thickness and hydraulic
conductivity, known as the transmissivity. Low transmissivity formations of less than 500
gpd/ft (gallons per day per foot) are normally considered to be applicable to MPE (Suthersan,
1997). A typical result of pumping in low conductivity and transmissivity formations is
increased, and sometimes rapid, drawdown with steep gradients. This condition limits the
influence of the conventional pumping well. MPE overcomes this limiting factor with the
application of a vacuum (as discussed in Section 2.4).
Low permeability formations also tend to possess thick capillary zones (up to several
feet). Fluid in the capillary zone is held in the pore spaces by capillary forces at less than
atmospheric pressure. The vacuum enhancement of MPE overcomes these capillary forces
and removes the fluid from the capillary zone. This poses a particular advantage to LNAPL
recovery. LNAPL tends to accumulate in the capillary zone at the air-water interface. The
12
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Table 3.1. Applicability of MPE.
Parameter
Hydraulic Conductivity
Transmissivity
Geologic Setting
Vadose Zone Soil
Permeability to Air
Formation
Characteristics
Drawdown/Recovery
Rate
Contaminant Location
Contaminants
Contaminant Vapor
Pressure
Contaminant Volatility
Applicable Range or Characteristic for MPE
• Moderate to Low (K = 1 0"3 to 1 0"5 cm/s)
• Low (< 500 gpd/ft)
• Sands to Clays
• Moderate to Low (k < 1 darcy)3
• Low permeability, fractured systems
• Interbedded sand and clay stringers
• Limited saturated thickness
• Shallow water table
• Thick capillary zone (up to several feet)
• Perched NAPL or groundwater layers
• Conditions producing steep or high drawdown in wells
• Low groundwater recovery rates achieved with
conventional pumping
• Vadose, saturated, and capillary zones
• Halogenated VOCs
• Aromatic VOCs and/or total petroleum hydrocarbons (TPH)
• Floating, free product (LNAPL)
•> 1 mm Hg at20°C
•>0.01 at20°Cb
• >2 x 10'4 atm nf/mol at 20°CC
Source
1
2
3
3
1,2
1
1,3
1,3
3
3
'1 darcy »10-8cm2
b Expressed as dimensionless Henry's Law Constant: Concentration in gas phase/concentration in liquid phase
0 Henry's Law Constant: Computed from (b) using method of Mills et al. (1982) as shown in Tetra Tech, 1983.
Sources:
1. EPA, 1996
2. Suthersan, 1997
3. EPA, 1997c
13
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imposed vacuum of an MPE system facilitates recovery of the LNAPL by reducing the effect
of capillary and interface forces (EPA, 1996).
The applicability of MPE is also governed by the volatility or vapor pressure of the
contaminants. The primary removal mechanism of the SVE portion of MPE is volatilization
followed by advective transport to the recovery well (Peargin, 1995). Therefore, MPE is
most applicable to VOCs such as petroleum hydrocarbons (e.g., benzene, toluene,
ethylbenzene, and xylenes) and chlorinated and nonchlorinated solvents and degreasing
agents (e.g., tetrachloroethylene and trichloroethylene) (EPA, 1997b). Others state that MPE
is applicable to nonvolatile contaminants provided that the increased airflow and subsequent
introduction of oxygen stimulate biodegradation (EPA, 1997b; EPA, 1996; Kittel et al, 1994).
3.2 ADVANTAGES AND POTENTIAL LIMITATIONS OF MPE COMPARED
TO CONVENTIONAL PUMPING
MPE provides a number of advantages and benefits over conventional pumping
approaches. A summary of the advantages and potential limitations of MPE is provided in
Table 3.2. The foremost of these is the ability of MPE to effectively function in moderate to
low permeability soils (Suthersan, 1997; EPA, 1996). MPE can provide contaminant source
removal in lower permeability settings that may only be served otherwise by excavation of
the source area (Suthersan, 1997). MPE is versatile in that it can be employed to remediate
multiple phases of contamination, including the vapor, residual, dissolved, and non-aqueous
phases of contamination, while conventional pumping addresses only the latter two phases
(EPA, 1996). MPE can potentially create a large radius of influence affecting greater capture
of the contaminant plume. Conventional recovery approaches in low permeability formations
tend to realize low flow rates with steep drawdown and limited capture. This forces the use
of a greater number of recovery wells to affect mass removal and plume containment. MPE
requires significantly fewer wells due to its ability to maximize fluid recovery at the wellhead
(EPA, 1997b; Suthersan, 1997; EPA, 1996). MPE also reduces the drawdown necessary to
obtain a given flow rate. This is especially beneficial to settings requiring free product
recovery. Conventional pumping approaches tend to smear free product along the face of the
drawdown curve and have limited success in removing NAPL trapped in the capillary fringe.
14
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Table 3.2. Summary of the advantages and potential limitations of MPE.
Advantages
Potential Limitations
Effective on moderate to low permeability
soils (Suthersan, 1997; EPA, 1996)
Effective source removal at low
permeability sites where the only other
viable remedial option may be excavation
(Suthersan, 1997)
Effective for simultaneous remediation of
dissolved, vapor, residual, and non-
aqueous phases of contamination (EPA,
1996)
Creates potentially large radius of
influence and increased capture zone
(Suthersan, 1997; EPA, 1996)
Increase total fluids recovery, minimize
drawdown and free product smearing, and
maximize aquifer transmissivity at the
wellhead (EPA, 1997b; Suthersan, 1997;
EPA, 1996)
Reduces number of recovery wells
required (Suthersan, 1997)
Effective for capillary zone remediation
(EPA, 1997b;EPA, 1996)
Reduces duration of remediation
compared to conventional pumping
approaches (Suthersan, 1997; EPA, 1996)
Requires vacuum pump or blower (EPA,
1996)
Potentially greater treatment requirements
as a result of NAPL emulsions and VOC-
laden vapors (i.e., liquid-phase separation
and vapor treatment) (EPA, 1996)
Initial startup and adjustment periods may
be longer compared to conventional
pumping approaches (EPA, 1996)
Potentially higher capital costs compared
to conventional pumping approaches
(EPA, 1996)
Depth limitations apply to some MPE
configurations (EPA, 1996; EPA, 1997c)
15
-------
Smearing of free product is minimized by MPE since the aquifer transmissivity is maintained
at the well. The induced vacuum of MPE also removes NAPL from the capillary fringe by
overcoming the capillary forces (EPA, 1997b; EPA, 1996). Perhaps the most significant
advantage of MPE is its ability to expedite remediation resulting in a cost savings when
compared to conventional pumping (Suthersan, 1997; EPA, 1996).
However, compared to conventional pumping approaches, MPE has increased
equipment and appurtenance requirements that can increase costs. This includes the vacuum
pump or blower along with the various instrumentation and valving that support the vacuum
manifold. In addition, implementing MPE may result in increased treatment requirements
over conventional pumping. For example, vapor phase treatment, either by activated carbon
or thermal/catalytic destruction, may be necessary to treat the recovered soil vapor. Because
some vacuum pumps may emulsify NAPLs in the liquid stream, the emulsified product must
be separated from the liquid stream by gravimetric separation or other means to protect other
treatment processes (HSI GeoTrans, 1998). Initial startup and adjustment periods may be
longer due to the need to optimize flow rates, vacuum pressures, and drawdown throughout
the recovery network and for monitoring requirements. The most significant technical
limitation of MPE is depth for configurations, such as bioslurping, that are to be used for
LNAPL recovery. As mentioned before, vacuum lift is limited to a depth of approximately
30 feet. Other configurations, such as VE/GE or the two pump system, can be employed to
overcome depth limitations since submersible pumps are used to provide fluid lift and
recovery.
16
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4 VENDORS OF MPE
EPA's Technology Innovation Office (TIO) has an ongoing effort to update and
maintain a database of vendors of characterization and remediation technologies, known as
EPA REACH IT (). This database is used by site owners,
technology providers, and other environmental professionals to better understand the types of
technologies currently available and sites where technologies are being used.
EPA REACH IT combines information from three established EPA databases, the
Vendor Information System for Innovative Treatment Technologies (VISITT), the Vendor
Field Analytical and Characterization Technologies System (Vendor FACTS), and the
Innovative Treatment Technologies (ITT), to give users access to comprehensive information
about treatment and characterization technologies and their applications. It combines
information submitted by technology service providers about remediation and
characterization technologies with information from EPA, the U.S. Department of Defense
(DoD), the U.S. Department of Energy (DOE), and state project managers about sites at
which innovative technologies are being deployed. As of early 1999, EPA REACH IT
included information about more than 750 service providers that offer almost 1,300
remediation technologies and more than 150 characterization technologies.
A search of the EPA REACH IT database was conducted to find vendors that offer
multi-phase extraction. Table 4.1 lists the vendors and provides a summary description of the
technology they offer. The vendors also provided information on specific sites where the
technologies were applied, as shown on Table 4.2. It is important to note that information
reported in Tables 4.1 and 4.2 are claims provided by the technology vendors in EPA
REACH IT. Information was not modified or verified for this report.
Many of the vendors listed possess patents on their repsective MPE systems. Using a
patented MPE process may require the user to obtain design and/or construction services
directly from the patent holder or purchase a license to provide the technology to others.
Interested parties should contact the individual vendors to discuss licensing terms and patent
provisions.
17
-------
Table 4.1. MPE vendors listed in EPA REACH IT1.
Vendor
Billings & Associates, Inc.
www.aristotle.com
Dames & Moore
www.dames.com
IT Corporation
www.itcorporation.com
Technology
Subsurface
Volatilization and
Ventilation System™
Two-phase vacuum
extraction
Vacuum enhanced
pumping
Aspects of
Configuration
• Air injection using
positive pressure.
• Vapor withdrawal
using negative
pressure to
remove volatiles.
• Stimulation of
existing microbial
community.
• Recovery of
contaminated soil
vapor and
groundwater in
same borehole.
• VOCs are
stripped from
groundwater.
• Air is injected
below water table.
• Passive air lift
techniques and
either vacuum
blower or pump to
extract fluids.
# of Units
«
W?
£
0
26
4
c
O)
'm
0)
100
0
16
_
-------
Table 4.1. MPE vendors listed in EPA REACH IT (continued).
Vendor
KAP & SEPA, Ltd.
www.kap.cz
Radian International, LLC
www.radian.com
Terra Vac, Inc.
www.terravac.com
Technology
SVE combined with
LNAPL vacuum
extraction. No trade
name specified.
Xerox Two-Phase
High Vacuum
Extraction™
Dual Extraction™
Entrainment
Extraction™
Aspects of
Configuration
• %-inch pipe
extracts LNAPL
from 4-inch SVE
well.
• High vacuum oil
sealed pump
draws vapors and
liquid through
extraction straw.
• Water table is
lowered by
vacuum tube.
• Common blower
draws vacuum on
both liquid and
vapor.
# of Units
I
E
0
36
70
c
o>
'w
0)
Q
0
2
115
Full-Scale
7
21
250
Vendor Points of
Contact
Peter Kohout
(KAP) & Vladimir Kinkor
(SEPA)
Czech Republic
Ph: +4202 2431 3630
Fx:+4202 5721 1255
pkohout@prg.kap.cz
Joe Fitzgerald
Site Manager
Ph: (31 5) 456-3671
Fx: (31 5) 456-6844
joe_fi tzgerald@radian.com
Tony Vinici
Operations Manager
Ph: (609) 371 -0070
Fx: (609) 371 -9446
List of
Performance
Claims
• Capable of
treating
halogenated or
nonhalogenated
VOC
contaminated
soils
nonhalogenated
volatile.
• Does not require
expensive
equipment or
numerous
personnel to
operate.
• Significant
advantages over
conventional
dual phase
systems.
• Considerably
more efficient
than a P&T
system.
• Substantial
savings in cost.
Patented
Applications
Patent information
unknown.
Registered
trademark.
Patented process
by Xerox. Radian
is first full
licensee.
Non-registered
trademark.
Patented.
-------
Table 4.1. MPE vendors listed in EPA REACH IT (continued).
Vendor
ARS Technology, Inc.
www.arstechnologies.com
Technology
Pneumatic Fracturing
Extraction (PFE)™
Aspects of
Configuration
• High burst
injection of air at
several discrete
intervals.
• Used in
conjunction with
dual phase
extraction and
other
technologies.
# of Units
X
^;
E
36
c
o>
'w
0)
1
JB
(I
o
2
3
LL.
11
Vendor Points of
Contact
John Liskowitz
President
Ph: (732)296-6620
Fx: (732)296-6625
List of
Performance
Claims
• Capital costs
and operating
costs are
reduced
compared with
other
technologies.
• Number of wells
required is
decreased.
• Speeds up the
rate of mass
removal.
• Reduces time
required for
remediation.
Patented
Applications
Registered
trademark.
Patented.
to
o
Information given in this table, including aspects of configuration, number of units, points of contact, list of performance claims, and patented applications, was extracted from
EPA REACH IT () in December 1998. Information is shown as provided by technology vendors in EPA REACH IT, and was not modified for this
report.
-------
Table 4.2. Representative MPE sites for vendors listed in EPA REACH IT1.
Site Name/
Location
Media
NAPL
Contaminant
Untreated
Concentration Range2
Contaminant Treated
Concentration Range2
Volume/
Quantity
Treated
Depth
Treated
Date
Contracted
Current
Status
Project Reference
Billings & Associates, Inc.
Subsurface Volatilization and Ventilization System™
Confidential
Electro-Voice Site
Buchanan, Ml
USA
Super Valu Site
Albuquerque, NM
USA
Soil
Groundwater
Soil
Sediments
Groundwater
Soil
Sediments
Groundwater
DNAPL
LNAPL
Not
reported
Not
reported
Benzene: 10 ppm
Ethylbenzene: >10 ppm
Toluene: >10 ppm
Xylene: >10 ppm
1,1,1 -
Trichloroethane(TCA):
18 ppm
Ethylbenzene: 1 ,400
ppm
PCE: 240 ppm
Toluene: 4,300 ppm
TCE: 23 ppm
Xylene: 6,600 ppm
Benzene: 25 ppm
Ethylbenzene: 25 ppm
Toluene: 25 ppm
Xylene: 25 ppm
Benzene: 0.01 ppm
Ethylbenzene: <5.0 ppm
Toluene: <5.0 ppm
Xylene: <5.0 ppm
Not Available
Benzene: 0.01 ppm
Ethylbenzene: <1 .0 ppm
Toluene: <1.0 ppm
Xylene: <1.0 ppm
1 ,500 ft3
169,500ft3
21 ,600 ft3
40 feet
66 feet
45 feet
March 1991
March 1992
March 1992
Completed -
October
1993
Ongoing
Completed -
December
1993
James Bearzi
NMED-USTB
P.O. Box 261 10
Santa Fe, NM 87502
Tim Mayotte
Brown & Root Environmental, Inc.
4641 Willoughby Road, Hold
Michigan
Ph: (51 7) 694-6200
Keith Fox
NMED, USTB
4131 Montgomery Blvd. N.E.
Albuquerque, NM87109
(505)841-9478
Dames & Moore
Two-Phase Vacuum Extraction™
Indiana Gasoline
Station
Clarkesville, IN
USA
Machine Shop
Trenton, NJ
USA
Soil
Groundwater
Soil
Groundwater
LNAPL
LNAPL
Benzene: 21 ppm
Ethylbenzene: 1.1 ppm
Toluene: 14 ppm
Xylene: 5.8 ppm
TCA: ND-5.1 ppm
1,1-Dichloroethane: ND
- 2.8 ppm
VOC's: ND- 12. 14 ppm
Not Available
TCA: ND
1,1-Dichloroethane: ND
VOC's: ND - 0.020 ppm
169,760ft3
2,660 yd3
10 to 20
feet
10 feet
October
1992
May 1993
Ongoing
Ongoing
Not Available
Not Available
IT Corporation
Vacuum enhanced pumping
Gasoline Service
Station
Houston, Texas
USA
Soil
Groundwater
LNAPL
Not Available
Not Available
59,850 ft3
10 to 30
feet
1992
1993
Not Available
-------
Table 4.2. Representative MPE sites for vendors listed in EPA REACH IT1 (continued).
Site Name/
Location
Media
NAPL
Contaminant
Untreated
Concentration Range2
Contaminant Treated
Concentration Range2
Volume/
Quantity
Treated
Depth
Treated
Date
Contracted
Current
Status
Project Reference
KAP & SEPA, Ltd.
Ra sko Ajrbase
Ra sko, Czech
Republic
Soil
Groundwater
LNAPL
Kerosene: 0.1 - 0.4
ppm
PCE:0.1 -0.4 ppm
Kerosene: 0.1 - 0.4 ppm
PCE: 0.1 -0.4 ppm
22,030 Ibs.
26 feet
March 1993
Ongoing
Ing. Kroova, Director of
Department of Environmental
Damages
Vrsovicka 65, 1 00 1 0 Praha 1 0,
Czech Rep
+42026712078
Radian International LLC
Xerox 2-Phase High Vacuum Extraction™
Xerox Corporation
Mississauga, Ontario
Canada
McClellan Air Force
Base
Sacramento, CA
USA
Soil
Groundwater
Soil
Groundwater
Not
reported
Not
reported
Dichloroethylene: >500
ppm (soil)
TCE: 7,000 ppm
Dichloroethylene: 1.3
ppm (soil)
Not Available
3,000 Ibs.
6,000 Ibs.
25 feet
115 feet
NA
August 1994
Completed -
December
1995
Ongoing
Scott Huber
Xerox Corporation
Ontario
(716)422-0779
Kevin Wong
McClellan AFB
(916)643-0830
Terra Vac, Inc.™
Dual Extraction, Entrainment Extraction™
Gasoline Service
Station
Los Angeles, CA
USA
Rental Car Facility
Los Angeles, CA
USA
Tinkhams Garage
Londonderry, NH
USA
Soil
Sediments
Groundwater
Soil
Sediments
Groundwater
Soil
Sediments
Groundwater
LNAPL
LNAPL
LNAPL
Benzene: free product -
gasoline
BTEX:>100ppm
TPH: >1 000 ppm
PCE: .003-1 90 ppm
(soil)
Toluene: ND-300 ppm
(soil)
TCE: ND-10ppm
(soil)
VOC's: ND-0.8 ppm
(soil)
Xylene: ND-0.3 ppm
(soil)
Benzene: ND - 0.05 ppm
(soil)
BTEX: ND
TPH: ND -470 ppm
NA
Approx.
500,000 ft3
Not
Available
81 ,000 ft3
25 feet
Not
Available
18 feet
September
1990
June 1990
1989
Completed -
October
1991
Completed -
February
1991
Ongoing
Not Available
Not Available
Mike Walters
Cannons Site Group Technical
Committee
1265 Main Street
Waltham, MA 02254
-------
Table 4.2. Representative MPE sites for vendors listed in EPA REACH IT1 (continued).
Site Name/
Location
Media
NAPL
Contaminant
Untreated
Concentration Range2
Contaminant Treated
Concentration Range2
Volume/
Quantity
Treated
Depth
Treated
Date
Contracted
Current
Status
Project Reference
ARS Technology, Inc.
Pneumatic Fracturing Extraction (PFE)™
Electroplating
Industrial Site
Somerville, NJ
USA
Industrial Facility
Santa Clara, CA
USA
Military Base
Oklahoma City, OK
USA
Petroleum Refinery
Marcus Hook, PA
USA
Former Manufacturing
Facility
Highland Park, NJ
USA
Confidential
Manufacturing Site
Western NY State
USA
Soil
Groundwater
Soil
Groundwater
Soil
Groundwater
Soil
Groundwater
Soil
Groundwater
Soil
Groundwater
DNAPL
LNAPL
DNAPL
LNAPL
LNAPL
LNAPL
DNAPL
LNAPL
LNAPL
Benzene: 0.5328
Ibs/day
PCE: 0.6048 Ibs/day
TCE: 0.2448 Ibs/day
TCE: 7 - 20 ppm
Fuel Oil: 8.6 gal/day
BTEX: Not Available
TCE: 8.43 - 56.2
Ibs/day
Benzene: 2,400 - 2,500
ppm
Benzene: 0.00048
Ibs/day
PCE: 0.00072 Ibs/day
TCE: 0.00936 Ibs/day
TCE: 0.46 - 0.88 ppm
Fuel Oil: 1.2 gal/day
BTEX: Not Available
TCE: 0.23 - 2.40 Ibs/day
Benzene: 10-13 ppm
Approx.
19,000ft3
4,500 ft3
Approx:
5,000,000 ft3
3,500 ft3
Approx.
784,080 ft3
5,400 ft3
9 to 17
feet
3.5 to 13
feet
25 to 31
feet
2 to 7 feet
10to17
feet
Oto17
feet
June 1992
August 1993
June 1993
November
1991
May 1994
July 1995
Completed -
December
1993
Completed -
December
1993
Ongoing
Completed -
December
1996
Ongoing
Completed -
August 1995
Herb Skrovronek
SAIC
41 1 Hackensack Ave.
Hackensack, NJ 07652
Ph: (201) 489-5200
Trevor King
McLaren/Hart Environmental Eng.
25 Independence Blvd.
Warren, NJ 07059
Ph: (908) 647-81 1 1
Dan Hunt
TAFB
OC-ALC/EMR 7701
Second Street, Ste. 20
Midwest City, OK 731 45-91 00
John Schuring
NJIT-HSMRC
138 Warren Street
Newark, NJ 07102
Ph: (201) 596-5849
Tom Nunno
Chem Cycle Corporation
129 South Street
Boston, MA 021 11 -2820
Ph: (61 7) 451 -0922
Not Available
1 Information given in this table, including media treated, NAPL presence, untreated and treated contaminant concentrations, volume treated/quantity of contaminant extracted, depth treated, and date contracted, was extracted from EPA REACH IT
() in December 1998. Information is shown as provided by the technology vendors in EPA REACH IT, and was not modified for this report.
2 Concentration units given in mass loading rates (e.g. Ibs/day) are of the extraction system prior to and after implementing MPE. Otherwise untreated and treated media concentrations are given (e.g. ppm).
Contaminant Abbreviations: Benzene, Toluene, Ethylbenzene and Xylene (BTEX)
Total Petroleum Hydrocarbons (TPH)
Trichloroethene (TCE)
Tetrachloroethene (PCE)
-------
5 CASE STUDIES
This section summarizes three case studies of MPE technology. MPE was used at the
Defense Supply Center in Richmond, VA, the 328 Site in Santa Clara, CA, and the
Tinkham's Garage Superfund Site in Londonderry, NH. All of these case studies review the
site history, setting, contaminant source, and the performance of the MPE system employed.
A summary of identifying information for case study sites is provided in Table 5.1.
References used in preparation of the case studies are listed at the end of each case study.
Table 5.1. Summary of identifying information for case study sites.
Vendor
Technology
Configuration
Technology
Scale
Media/Matrix
Treated
Contaminants
Targeted
Total VOC Mass
Removed
Period of
Operation
Defense Supply
Center, Richmond, VA
Law Engineering and
Environmental Services,
Inc.
Two-pump MPE
Field demonstration
(Treatability study)
Soil and groundwater
TCE, PCE, 1,2-DCE
117 Ib from soil
28 Ib from groundwater
July 1997 -July 1998
328 Site,
Santa Clara, CA
HSI-GeoTrans, Inc.
Terra Vac, Inc.
Single Pump MPE with
Pneumatic Fracturing
Full scale
Soil and groundwater
TCE
782 Ib from soil
382 Ib from
groundwater
November 1996 -
December 1998
Tinkhams's Garage,
Londonderry, NH
Terra Vac, Inc.
Single Pump MPE
Full scale
Soil (primary target
media)
PCE, TCE
48 Ib from soil
5 Ib from groundwater
November 1994-
September1995
24
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5.1 DEFENSE SUPPLY CENTER, RICHMOND, VA
A treatability study using dual-phase extraction (DPE) technology was conducted at
the U.S. Defense Supply Center Richmond (DSCR) Acid Neutralization Pit (ANP) site. The
one-year treatability study (July 1997 - July 1998) focused on deriving conclusions with
respect to effectiveness of DPE and to make recommendations as to the use of this
technology for full-scale remediation. The results indicated that DPE was effective in
removing chlorinated and aromatic VOC contamination from the vadose zone and
groundwater. The preliminary results also suggested that the DPE system would likely be
adequate for groundwater remediation without additional expansion. This case study
addresses the results of the one-year treatability study and the performance of DPE
technology.
5.1.1 SUMMARY INFORMATION
The 640-acre DSCR is a military support, service, and storage facility located
approximately 11 miles south of the City of Richmond, VA and 16 miles north of the City of
Petersburg, VA. Land use in the area is predominantly residential and wooded, with the
James River located approximately one mile east of the site. Since 1942, DSCR has been
furnishing and managing general military supplies to the Armed Forces and several federal
civilian agencies. Historical and current industrial operations at the DSCR have included
repair of small equipment, engine rebuilding, and refurbishment of combat helmets and
compressed gas cylinders. Historical and current operational areas consist of indoor and
outdoor material storage areas, a motor pool facility, a National Guard training area, fire
training areas, and a wastewater treatment system.
The ANP site is located in the northern section of the DSCR in an area used for
warehouse storage and light industrial operations. Approximately one-quarter mile east and
southeast of the ANP site is an off-base residential area. The ANP site consists of two former
concrete settling basins that received wastewater from metal cleaning operations conducted at
one of the warehouse buildings. Both tanks were approximately 6.5 feet in depth with the
primary tank capacity of 14,600 gallons and a secondary tank capacity of 3,000 gallons.
Metal cleaning operations were active from 1958 into the early 1980s. The operations
25
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focused on paint and rust removal and repainting of combat helmets and compressed gas
cylinders. The cleaning process utilized inorganic acid and base baths. Spent metal cleaning
solutions were dispensed to the tanks every one to two months. Wastewater was then
discharged from the tanks to the storm sewer between 1958 and the late 1970s. After a
secondary tank was added in the late 1970s, wastewater was discharged to the sanitary sewer.
The settled solids in the tanks were periodically disposed of at a county landfill. The tanks
were closed in 1985 by cleaning the bottoms and filling with clean earth. At the time of
closing the sides of the tanks were observed to be cracked and broken. These cracks and
holes were suspected migration routes of contaminants to the surrounding soil. The
predominant contaminants detected in groundwater at the ANP site were chlorinated
solvents, notably tetrachloroethylene (PCE) and trichloroethylene (TCE). Although site
records did not indicate the use of solvents at the metal cleaning operations conducted at this
portion of the site, it has been proposed that the solvents were transported from other
locations at the DSCR and disposed of in the tanks at the ANP site.
5.1.1.1 GEOLOGIC AND HYDROGEOLOGIC SETTING
Impacted soil beneath the DSCR consists of the Eastover Formation extending from
the surface to approximately 25 feet below ground surface (bgs). Grain size diameter appears
to increase with depth in the Eastover Formation, grading from a silty clay and fine-grained
sand into a coarse-grained sand with interlayered gravel. Specifically, the layers can be
characterized as: (1) red-brown silty clay and clayey silt; (2) gray mottled, red/yellow
interlayered sand and silty clay; (3) red-yellow clayey, fine-grained sand and sandy clay; and
(4) light gray, mottled red-brown clayey, coarse-grained sand with gravel.
An unconfined water table aquifer exists in the Eastover Formation beneath the
DSCR site. The depth to the water table surface ranges from 10 to 15 feet bgs. The aquifer
found in the Eastover Formation can be separated into an upper low permeability zone and a
lower high permeability zone. The upper low permeability zone consists of the upper three
layers of the Eastover Formation, with occasional localized areas having relatively higher
permeabilities. The lower sand and gravel layer is considered the high permeability zone.
Transmissivity values for the upper aquifer range from 374 to 504 feet square per day (ft2/d).
26
-------
The hydraulic gradient is essentially flat at 0.001 ft/ft to 0.002 ft/ft with flow to the northeast
direction.
5.1.1.2 SITE CHARACTERIZATION SUMMARY
Soil and groundwater samples were collected and analyzed for the remedial
investigation (RI) in 1987 and a supplemental RI in 1992. Soil and groundwater at the ANP
site were divided into Operable Units 5 and 8, respectively. Constituents detected in soil
consisted of low levels of volatile and semi-volatile organic compounds including PCE,
phthalates, naphthalene, and phenanthrene. VOCs were detected at elevated levels in monitor
wells screened in the upper aquifer. The highest concentrations of VOCs detected
downgradient of the ANP area were 3300 micrograms per liter (//g/L) for PCE and 890 //g/L
for TCE. Chlorinated VOCs were not detected in the lower aquifer. This information
supported earlier conclusions that a clay confining interval between the upper and lower
aquifers was preventing downward migration of contaminants into the lower aquifer. Based
on the data collected during the investigations, the plume area was estimated to be 16,000
square feet. A summary of the ANP site information is provided in Table 5.2.
Table 5.2. DSCR-ANP site summary.
Parameter
Geologic Setting of Source Area
Geologic Setting of Impacted Aquifer
Depth to Groundwater
Hydraulic Gradient
Aquifer Transmissivity
Constituents of Concern
Groundwater Concentrations Prior to DPE
Treatability Study1"
Plume Area Prior to DPE Treatability Study
Characteristics
Upper Eastover Formation
Silty Clay, Fine Sands, Course Sands and Interlayered Gravels
0 to 25 ft bgs
Upper Low Permeability Zone of Eastover Formation
Silty Clay, Clayey Silt, Interlayered Sand and Silty Clay
10 to 25 ft bgs
10 to 15 ft bgs
0.001 to 0.002 ft/ft NE
374 to 504 ft2/d
Tetrachloroethylene (PCE), Trichloroethylene (TCE),
1,2-Dichloroethylene (1,2-DCE)
3300 ,ug/L PCE; 890 ^g/L TCE; 26 ^g/L 1,2-DCE
Approximately 16,000 square feet
f Maximum detections from RI
27
-------
5.1.1.3 REMEDIATION SUMMARY
The Record of Decision (ROD) for operable unit 5 (OU5) included the use of SVE to
address soil contamination. An SVE pilot test was conducted in support of the remedial
design for OU5. Results from the SVE test resulted in low air flow rates and minor recovery
of VOCs. Analysis of samples from borings installed after the SVE test showed that soil
VOC concentrations had decreased to below risk-based concentrations. An Explanation of
Significant Differences (ESD) was submitted and recommended no further remediation for
OU5.
The Feasibility Study (FS) identified dual phase extraction as a potentially viable
remediation alternative for groundwater (OU8). Aquifer tests and a DPE pilot test were
conducted to gather site-specific data including transmissivity, specific yield, groundwater
recovery rates, hydrostatic responses, vadose zone vacuum distributions, intrinsic
permeability, air extraction rates, and SVE mass removal rates. Overall the test supported the
use of DPE for VOC recovery. The test data supported the design of a larger DPE system.
The pilot test also showed the need to employ air injection to facilitate vadose zone air flow.
Several performance goals were established for remediation of groundwater by DPE
at the AMP site. The first goal was to remove contaminated groundwater from the upper
aquifer for ex-situ treatment by air stripping. In addition, DPE was to lower the groundwater
table to increase the volume of semi-saturated soil through which air flow and volatilization
of constituents would occur. Based on theory and practice, mass transfer of VOCs from the
soil will continue to occur, provided drawdown is maintained. Moreover, DPE was sought to
maintain a constant hydraulic gradient toward the DPE wells to prevent off-site migration.
The performance goals for DPE were set to evaluate its effectiveness in achieving
remedial action objectives (RAOs) for the site. The RAOs are as follows:
Reduction of the highest levels of contamination resulting in immediate risk
reduction;
Plume containment of contamination in excess of remedial goals;
28
-------
• Achievement of remedial goals (PCE < 5 //g/L, TCE < 5 //g/L), or attainment
of an asymptotic trend in contaminant of concern (COC) concentrations in
groundwater (whichever occurs first).
It was proposed that DPE would achieve these goals in a more timely manner than could be
accomplished by conventional groundwater pumping.
The purpose of the DPE treatability study at the ANP site was to evaluate the
effectiveness of a full-scale system. The treatability study also sought to collect additional
operational data that may refine system design parameters, if necessary. The study also
evaluated the effectiveness of an air injection system to facilitate air flow through soils
exposed by drawdown of the groundwater surface. Table 5.3 presents a timeline of remedial
activities related to DPE at the ANP site beginning with the remedial investigation (RI)
through the present.
Table 5.3.
Timeline of remedial activities at DSCR-ANP site.
Activity
Remedial Investigation (RI)
Supplemental RI
ROD for Soils (OU5)
SVE Pilot-Test for Soil
Feasibility Study (FS)
Aquifer Test/DPE Pilot-Test for Groundwater (OU8)
ESDfforOU5
Work Task Proposal Issued for DPE
DPE System Construction Begins
Groundwater Extraction Begins
SVE and Air Injection Begins
12-Month DPE Treatability Study
Treatability Study Report Issued/Continued DPE Operation
Time of Performance
January 1 987 - November 1 988
September 1992 - December
1992
1992
December 1992
November 1994
June- July 1995
September 1995
July 1996
January 1997
June 1997
July 1997
July 1997 -July 1998
November 1998
f Explanation of Significant Differences (ESD) for soils at ANP site (OU5) indicated that soil contamination was below risk-
based action levels. Recommendation was made to exclude OU5 from further remediation.
29
-------
5.1.2 TECHNOLOGY DESCRIPTION AND SYSTEM DESIGN
The DPE system consists of 12 dual phase extraction wells and six air injection wells
arranged in a rectangular grid. The DPE well configuration is the two pump MPE
configuration as discussed in Section 2.4.2 and shown in Figure 2.3. Each DPE well consists
of a sealed casing to maintain SVE vacuum and an electric, submersible (variable-frequency
drive) pump for groundwater extraction. The DPE wells are 6-inch diameter polyvinyl
chloride (PVC) screen and casing. Well screen was 0.020-inch factory slotted continuous for
a depth of 10 feet. A solid cased sump of 2-feet in length was provided at the base of the
well for the submersible recovery pump. The wells were installed to be fully penetrating, to
depths ranging from 22 to 28 ft bgs. Wells were developed by surging and pumping
techniques prior to use. Air injection is achieved by a low pressure rotary-lobe blower
through injection wells. The air injection, in conjunction with the SVE portion of DPE,
creates air movement through the soil to transfer VOCs. The VOC-laden vapors are
extracted by the DPE wells. SVE vacuum is induced by a blower equipped with an air-water
separator. Air extracted by the SVE blower is vented to the atmosphere. Extracted
groundwater is pumped directly to a low-profile tray type air stripper to remove VOCs. Air
stripper off-gas is released to the atmosphere. Effluent water is discharged to a storm sewer
that flows to a nearby stream. To date, an exemption from a state administered discharge
permit is active while a ROD is completed for the site.
5.1.3 TECHNOLOGY PERFORMANCE
The DPE treatability study was conducted for one year. During system operation,
operational data were routinely collected. This information served as a means of monitoring
the performance of system components. A summary of the performance data from the
treatability study is provided in Table 5.4. Figure 5.1 and Table 5.5 illustrates the
potentiometric surface of groundwater at various times of system operation. The areal extent
of drawdown in the water table (radius of influence) during the study period was estimated to
be 600 to 800 feet in a down gradient direction and 1,800 to 2,500 feet in an up gradient
direction. Drawdown in surrounding monitoring wells ranged from 3.94 feet (400 feet from
the nearest dual phase extraction well) to 10.88 feet (in a monitoring well within the
30
-------
Table 5.4. Summary of DPE system performance data at DSCR.
Parameter
Treatability Study Duration
DPE System Operation
SVE Vacuum at Blower
SVE Air Flow Rate
Groundwater Extraction Rate
Cumulative Volume of Extracted
Groundwater
DPE Radius of Influence
Maximum Drawdown Realized
Maximum Influent Total VOC
Concentrations
Maximum Reduction in VOCs
Concentrations in Groundwater
Soil VOC Mass Removal (Rate)
Groundwater VOC Mass Removal
(Rate)
Value
384 days
7687 hours (320 days)
42 in WC, average
314 cfm, average
37
gpm, average
17, 000, 000 gallons
600 to 800 ft
3.94 ft at
downgradient
400 ft distance
11 62 puQlL (first month)
90 /4J/L (last month)
Constituent Initial Final
Cone. Cone.
PCE 1300//g/L < RAO*
TCE 290 //g/L < RAO
% Reduction
99.6
98.3
1 17 Ib (0.37 Ib/d), total
70 Ib (0.22 Ib/d), aromatic
47 Ib (0.1 5 Ib/d), chlorinated
28 Ib (0.09 Ib/d), total
2 Ib (<0.01 Ib/d), aromatic
26 Ib (0.08 Ib/d), chlorinated
Unit notes: in WC = inches of water column; cfm = cubic feet per minute; gpm = gallons per day; ^g/L = micrograms per liter;
Ib = pounds; Ib/d = pounds per day
* Remedial action objective (RAO) for groundwater was 5 ^g/L for PCE and TCE
31
-------
Figure 5.1. Comparison of baseline groundwater levels (Law Engineering and Environmental Services, 1998). (Best available
copy)
to
• t ,
~'04.0
JJUL98J
T
LEGEND
* MONITORING WELL
I : RAILROAD
® DP-DUAL PHASE EXTRACTION WELL
@ Al-AIR INJECTION WELL
EXTRAPOLATED CONCENTRATION
10S.O GROUNDWATER ELEVATION
-------
Table 5.5.
Potentiometric surface elevations.
Well I.D.
DMW-23A
DMW-24A
DMW-30A
DMW-31A
MWANP-1
MWANP-2
MWANP-3
MWANP-5
MWANP-6
MWANP-7
MWANP-8
MWANP-9
MWANP-10
MWANP-1 1
USGS-2
OS72-1
OS72-1
Potentiometric
Surface Elevation
January 1997
112.04
112.05
111.97
111.88
111.91
1 1 1 .62
110.51
NA
NA
111.89
NA
NA
111.94
111.47
NA
NA
NA
August 1997
107.07
106.04
104.55
105.87
102.30
106.88
106.49
100.14
100.76
101.93
100.14
NA
103.30
106.03
107.39
NA
NA
July 1998
107.08
105.86
104.50
104.94
103.50
106.43
106.87
103.15
103.62
103.81
100.40
103.00
104.13
106.23
107.89
108.01
107.86
NA=Not Available
perimeter of the extraction wells). Groundwater was extracted at a rate between 22 to 53
gallons per minute (gpm), averaging 37 gpm for the study period.
SVE flow rates ranged from 150 to 378 cubic feet per minute (cfm) at 40 to 44 inches
of water column (in WC). The average extraction air flow rate was 314 cfm with an average
vacuum of 42 in WC. SVE emissions were routinely analyzed to support mass removal
calculations. Chlorinated VOC concentrations in the extracted vapors increased an order of
magnitude within the first 5 days of DPE system operation. This was followed by a steady
decrease over the following two weeks. A discrete peak of aromatic VOCs was observed for
one sampling event early in system operation. In general, total VOC concentrations in
extracted soil vapor remained steady over the last 10 months of the treatability study. These
static VOC levels in extracted vapor suggest that VOC removal rates through SVE
approached asymptotic levels, or steady-state. Figure 5.2 plots the time variation of VOCs in
SVE air emissions.
Groundwater samples were also analyzed at five events through the treatability study
duration plus one, initial round to establish baseline conditions. These data (shown in
33
-------
Figure 5.2. Plot of VOC concentrations in SVE emissions over time (Law Engineering and Environmental Services, Inc.,
1998). (Best copy available)
Chlorinated
0»
5.
to
O
o
"i
^^
o
Total Aromatic VOCs
%'
V
-------
Table 5.6) were used to monitor and evaluate the change in VOC concentrations in
groundwater affected by DPE. Figure 5.3 illustrates the VOC distribution in groundwater at
several stages in the study time frame. Significant reductions in groundwater VOC
concentrations were realized during DPE operation. Most notable were the reductions
observed in the plume center where total VOCs were reduced from 1766 //g/L to 3.6 //g/L at
one monitor well and from 1980 //g/L to 12 //g/L at another monitor well. Increasing
concentrations of chlorinated VOCs were observed at two wells on the outer edge of the DPE
influence. The source of this contamination is uncertain. At the conclusion of this study,
several wells possessed PCE and TCE concentrations in excess of the remedial goals
//g/L).
Table 5.6. Summary of groundwater VOC data.
Well I.D.
DMW-23A
DMW-24A
DMW-30A
DMW-31A
MWANP-1
MWANP-2
MWANP-3
MWANP-7
MWANP-10
MWANP-1 1
USGS-9
Total Chlorinated
VOCs (ug/L)
January
1997
0.53
41.56
1980.5
10.43
21.78
116.14
2.26
1765.9
860.7
142.74
19 78
August
1997
3.13
18.11
637.20
30.39
12.63
83.42
9.60
298.95
5.43
177.84
1 99
October
1997
2.00
2.26
21.52
43.71
1.02
28.00
14.46
4.50
ND
15.14
18 00
January
1998
2.28
4.73
25.28
31.81
1.11
16.65*
43.51
3.89
0.33
23.30
8 97
April
1998
0.9
5.2
71.1
20.2
0.6
25.6
158.6
7.7
0.3
130.1
1 1
July 1998
2.1
3.6
11.9
58.6
0.70
20.5
141
3.5
0.4
55.6
0 5
ND = Not Detected
'Collected in February
1998
Mass removal rates were calculated based on analytical sampling and volumetric flow
rates of SVE emissions and groundwater treatment system influent. In total, 145 pounds of
VOCs were removed by DPE. SVE accounted for approximately 117 pounds (81 percent)
and groundwater extraction for the remaining 28 pounds (19 percent). For SVE, aromatic
VOC removal rates outweighed those for chlorinated VOCs through most of the study.
Figures 5.4 and 5.5 plot the cumulative mass removal of VOCs by groundwater extraction
and SVE, respectively.
35
-------
Figure 5.3. Total VOC concentrations in groundwater (Law Engineering and Environmental Services, Inc., 1998). (Best
available copy)
OJ
ON
* MONITORING WELL
RAILROAD
DP - DUAL PHASE EXTRACTION WELL
A!-AIR INJECTION WELL
EXTRAPOLATED CONCENTRATION
105.0- _ GROUNDWATER ELEVATION
SCALE IN FEET
-------
Figure 5.4. Cumulative mass of VOCs removed by groundwater extraction (Law Engineering and Environmental Services,
1998). (Best available copy)
^i
ffi
1
"C5
&
O
O
35
30
25 -
- 2.0B-Q7
•Total CMorirsfed VOCs
—g—Tjjfgj Aj'omatie VOCs
jfe*^^s^?Tct3f VDCs
• * - • Cumulative Vc'ume
0*
-------
oo
Figure 5.5. Cumulative mass of VOC's removed by SVE (Law Engineering and Environmental Services, 1998). (Best
available copy)
u»
13
3
o
3
•a
*
D
£
IB
K
S
us
O
O
120
100
80
60-
— Ararrstic VOCs
—
• • •• - •Cumulative Volume
•O —-'•••Q-——-D——O
f
3
7.0E+07
'«
"3
E
3
O
3.0E*07
**
-------
5.1.4 TECHNOLOGY COST
The cost for pre-design investigations supporting DPE design, namely pilot and
aquifer testing, was $134,092. Engineering design of the DPE system was $73,198. System
construction costs (equipment only) were $205,743. Startup costs were $24,309 and the cost
for one year of operation and maintenance was $101,148 and includes the cost of sample
collection and analysis. Based on 17 million gallons of groundwater recovered during the
project, the total cost per unit volume of groundwater recovered and treated is $0.03 per
gallon.
5.1.5 SUMMARY OF OBSERVATIONS AND LESSONS LEARNED
The following conclusions and recommendations were identified by the Army's
contractor (Law, 1998) on the performance of the DPE system during the treatability study
period.
Site conditions are favorable for dual phase extraction to be implemented for
groundwater remediation.
The reduction in VOC concentrations in the upper aquifer of the ANP site was
affected by DPE and the existing system configuration appears to be adequate
for remediating groundwater at OU8.
Operation of the existing DPE system should be continued until remedial
goals or asymptotic levels of contaminants of concern are achieved. If
remedial goals are not achieved, then the system should be shut down to
monitor VOC rebound. Remaining contamination above remedial goals, if
present, should be evaluated and alternatives for remediation, including
continued DPE operation and natural attenuation, be considered.
Additional investigations are recommended to better define the capture zone
of the DPE system; to determine the extent of discrete, elevated levels of
contamination; and evaluate the ability of the existing DPE system to address
contamination present in that area, if necessary.
39
-------
5.1.6 CONTACT INFORMATION
Bill Saddington
DSCR Remedial Project Manager
Defense Supply Center Richmond
8000 Jefferson Davis Highway Richmond, VA 23297-5000
Tel: (804)279-3781
E-mail: bsaddington@dscr.dla.mil
Stephen Mihalko
Remedial Project Manager
Virginia Department of Environmental Quality
P.O. Box 10009
Richmond, VA 23240
Tel: (804)698-4202
Todd Richardson
U.S. EPA Region 3
1650 Arch Street (MC 3HS50)
Philadelphia, PA 19103-2029
Tel: (215)814-5264
E-mail: richardson.todd@epa.gov
Katy L. Allen, P.E.
Law Engineering and Environmental Services, Inc.
112 Town Park Drive
Kennesaw, GA 30144
Tel: (770)421-3400
5.1.7 REFERENCES
Law Engineering and Environmental Services, Inc. Fax transmission dated January 29, 1999
from Katy Allen, P.E.
Law Engineering and Environmental Services, Inc. "Final Treatability Study for Operable
Unit 8 - Acid Neutralization Pits Groundwater", Defense Supply Center Richmond,
Prepared for U.S. Army Engineering and Support Center - Huntsville, Contract No.
DACA 87-94-D-0016; D.0.17, November 1998.
Dames and Moore. "Remedial Investigation Acid Neutralization Pits, Defense Supply Center
Richmond, Virginia", Contract No. DACA 65-86-C0131, April 27, 1989.
USGS. "Ground-Water Contamination and Movement at the Defense General Supply
Center", Richmond, Virginia, U.S. Geological Survey, Water-Resources
Investigations Report 90-4113, 1990.
40
-------
5.2 328 SITE, SANTA CLARA, CA
5.2.1 SUMMARY INFORMATION
A Dual Phase Extraction (DPE) system was designed, installed, and operated to
remove VOCs from silty clay soils and shallow groundwater in a former waste storage area at
a large industrial manufacturing facility. Air flow through the soils was enhanced by
pneumatic fracturing (PF) between DPE extraction wells and by supplying continuous low
flow/low pressure air to the fractured soils. The increased air flow caused by fracturing,
within an otherwise tight clay formation, improved capture of VOCs by the vapor extraction
system. In addition, concurrent groundwater extraction removed highly impacted shallow
groundwater. Over 40 percent of the VOC mass removal occurred from the vadose zone
during the first month of operation. Groundwater extraction provided greater mass removal
rates than soil vapor extraction by the fifth month of operation. The combination of
technologies has allowed soil vapor extraction to be effective in an area that is not well suited
for in-situ remediation.
The 328 Site occupies approximately 27.1 acres in a primarily industrial and
commercial area of San Jose and Santa Clara, California, near the San Jose Airport. The 328
Site was used for manufacturing military tracked vehicles, including assembly and painting
operations, from 1963 through 1998. Manufacturing operations were discontinued in 1998
and the 328 Site is currently being remediated in anticipation of future commercial/industrial
redevelopment. This project was conducted by FMC Corporation in accordance with the
State of California San Francisco Bay Regional Water Quality Control Board Final Site
Cleanup Requirements Order Number 96-024, with HSI GeoTrans and Terra Vac as
engineer/primary contractor and subcontractor, respectively.
Figure 5.6 presents the 328 Site plan, including the source area and groundwater
containment system. Table 5.7 provides a summary of the site setting information. The
source area was a former waste handling area that is currently covered with asphalt paving.
Downgradient migration of impacted groundwater extended to the northeast past the property
boundary. A groundwater containment/treatment system was installed at the perimeter of the
property in 1993 to prevent further off-site migration of impacted groundwater. The DPE
41
-------
Figure 5.6. Map of 328 site (Zahiraleslamzadeh et al., 1998).
Groundwater Containment
System/ Extraction Wells
Extraction Trench
Coleman
istributi
Center
Existing
Groundwater
Treatment Plant
Not to Scale
Source Are
42
-------
with PF system was installed at the 0.5-acre source area in 1996 to remediate shallow soils
and groundwater.
Table 5.7. 328 site setting.
Parameter
Geologic Setting of Source Area
Geologic Setting of Impacted Aquifers
Depth to Groundwater
Constituents of Concern
Initial Concentrations
Characteristics
Silts and Clays, 0 to 20 feet below ground surface
Sandy Silts, Silty Sands, and Gravelly Sands, 20 to 90 feet
ground surface
below
8 feet below ground surface
Trichloroethylene (TCE)
46 mq/kq in Soil; 37,000 uq/L in GW
Sediments underlying the 328 Site include marine or basinal clays, coarse channel deposits,
and inter-channel silts and clays. The first extensive lithologic unit encountered at the 328
Site is a dark gray to black silty clay. This unit is immediately below ground surface to
depths of approximately 20 feet. Although groundwater is located approximately eight feet
below ground surface, the first water-bearing zone (A-level aquifer) underlies the surficial
clay, and is observed within a depth interval of approximately 20 to 50 feet below ground
surface. The second water-bearing zone (B-level aquifer) is present at depths of 50 to 90 feet
below ground surface.
VOCs, predominantly trichloroethylene (TCE), were the primary chemicals of
concern. The highest TCE concentration measured in the soil during the remedial
investigation was 46 mg/kg, and the highest concentration measured in shallow groundwater
during the remediation was 37,000 ug/L. The objective of the DPE with PF system was to
remediate shallow soil and groundwater to a depth of 20 feet below ground surface.
5.2.2 TECHNOLOGY DESCRIPTION AND SYSTEM DESIGN
Table 5.8 provides a summary of the technology used at the 328 site.
43
-------
Table 5.8. Technology summary.
Technology
Soil Vapor Extraction
Groundwater Extraction
Pneumatic Fracturing
Air/Water Separator
Air Treatment
Groundwater Treatment
Mechanism
Volatilization of TCE from soil matrix by extracting vadose zone air; airflow
increases volatilization processes.
Air entrainment lifts shallow groundwater droplets with extracted vapors.
Injecting high-pressured air for one to two minutes to create fractures within
the clay soil matrix and allow increased air flow through impacted materials.
Gravity separation.
Vapor-phase carbon removes TCE from air by adsorption.
Air strippers and vapor-phase carbon at existing downgradient groundwater
treatment plant.
Twenty dual phase, single pump extraction wells were installed at the source area
based on the results of previous SVE and PF pilot tests. Two pneumatic fracture points, at
specific depths, were installed between each pair of extraction wells - a total of 41 fracture
locations. Following initial fracturing, a low flow/low pressure compressor provided
continuous air injection into each fracture point. A process flow diagram is shown in Figure
5.7. According to the site owner and their consultant (Zahiraleslamzadeh, 1998) this system
offered the following advantages:
1. The pneumatic fracture locations specifically target the low flow regions at the
midpoints between extraction wells.
2. The low flow/low pressure air supply maintains open fractures and supplies air
to the low flow regions.
3. Air entrained extraction is cost-effective given the shallow groundwater and
clay soils.
5.2.3 TECHNOLOGY PERFORMANCE
The DPE with PF system began operating in November 1996; Table 5.9 provides an
overall operations timeline. In theory, the groundwater extraction rate would decrease as the
water table was lowered in the vicinity of each well, and additional wells could be brought
on-line; however, groundwater production was approximately five gallons per minute (gpm)
44
-------
Figure 5.7. Process flow diagram (Zahiraleslamzadeh et al., 1998).
cr
Air Supply
Pneumatic
Point
(Typ,of41)
Extraction Well
(Typ. of 20)
l-
Vapor/Liquid
Separator
•Initial Groundwater
-^
~"^
SP
4"0 Flex
Tubing (Typ.)
6"0 PVC (Typ.)
To Atmosphere
Carbon Adsorption
Vapor Treatment
-O
laaaaf
To existing on-site
groundwater treatment plant
-------
per well instead of the 0.5 to 2.0 gpm anticipated by the design. This was attributed to the
presence of high-permeability lenses in the formation that provided preferential flow paths.
Groundwater drawdown a few feet away from operating extraction wells was limited to three
to five feet, while drawdown greater than one foot was observed over 100 feet away from the
nearest operating DPE wells.
Table 5.9. Operations timeline.
Dates
May 1 996 - August 1 996
September 1 996 - November 1 996
December 1 996 - April 1 997
May 1997 -May 1998
June 1 998 - August 1 998
September 1 998 - October 1 998
November 1998
January 1999
Activities
Work Plan and Design
Construction and Startup
Pneumatic Fracturing and
Cluster Operations
Continued Operations focused in
highest impacts
areas of
Shutdown and Rebound
Restart and Continued Operation
Confirmation Soil Sampling
Final Reports and Preparation for
Shutdown
System
The DPE system extracted approximately 35 gpm of groundwater on a continuous
basis. This limited the number of extraction wells that can operate simultaneously. As such,
clusters of extraction wells were operated on a rotating basis to accommodate the unexpected
high groundwater production. Cluster operations were focused on areas of higher VOC
concentrations.
Pneumatic fracturing of the source area soils was conducted using a portable air
compressor and an air supply manifold. The manifold pressure was set at approximately 75
pounds per square inch gauge (psig) and the valve slowly opened to apply an increasing
pressure to the pneumatic fracture point. The fracture point pressures ranged from 6 to 60
psig and averaged approximately 19 psig. These fracture pressures were lower than expected
for the silty clay soils. The fracturing data also indicates that the formation likely contains
high-permeability lenses that provided preferential flow paths.
46
-------
Extraction vapor flow rates increased significantly following pneumatic fracturing.
The average vapor flow rate from the DPE wells increased from approximately 39 scfm to
over 65 scfm. In addition, numerous wells experienced order of magnitude increases in
vapor flow rate. VOC mass removal, however, remained relatively constant as VOC
concentrations were lower in extracted vapors following pneumatic fracturing.
5.2.3.1 VOC MASS REMOVAL
VOC mass removal followed a typical SVE system decline, as shown in Figure 5.8.
The VOC mass removal rate was approximately 90 pounds per day during the first four days
of operation and declined to less than 30 pounds per day by the eighth day of operation. The
DPE system removed approximately 1,220 pounds of VOCs from the source area soils and
shallow groundwater. Figure 5.8 illustrates VOC mass removal over time.
VOC concentrations in groundwater declined similar to VOC mass removal. The
average source area VOC concentration in groundwater has declined from over 12,000
micrograms per liter (ug/L) to less than 800 ug/L, during operation of the DPE system.
Groundwater monitoring results are shown in Table 5.10 and illustrated on Figure 5.9.
During initial operation, the VOC concentration in groundwater transferred from the
DPE system to the groundwater treatment plant was 380 ug/L. As such, the air entrained
extraction process strips nearly 97 percent of the VOCs from the groundwater, based on the
initial average VOC concentration in groundwater of 12,000 ug/L. Therefore, the mass of
VOCs transferred to the groundwater treatment plant is considered insignificant compared to
the mass of VOCs removed through the vapor-phase carbon treatment system.
47
-------
817
Removal Rate (pounds/day)
o
Q>
ST
I'
o
O
O
VI
VI
1
Mass Removed (pounds)
-------
Figure 5.9. Average VOC concentrations of groundwater over time.
14,000
Sample Date
-------
Table 5.10. VOC concentrations in groundwater.
DPEWell
DP-1
DP-2
DP-3
DP-4
DP-5
DP-6
DP-7
DP-8
DP-9
DP-10
DP-11
DP-1 2
DP-1 3
DP-1 4
DP-1 5
DP-1 6
DP-1 7
DP-1 8
DP-1 9
DP-20
Average
Oct-96(1)
14,000
8,900
23,000
1,300
800
10,000
37,000
8,900
4,400
12,033
Jan-97(2)
Feb-97
9,900
4,300
3,700
2,100
2,000
9,300
2,100
130
3,200
3,300
4,400
1,100
3,794
May-97(3)
1,704
4,700
2,900
2,200
1,694
1,169
8,600
3,200
1,900
512
219
640
650
58
1,671
2,200
750
5,500
816
6,200
2,364
Oct-97(4)
990
1,000
920
1,500
1,200
770
6,500
3,200
2,000
330
95
270
300
41
1,400
1,700
260
1,900
470
1,700
1,327
May-98(5)
954
1,477
953
1,100
947
839
4,200
3,400
550
224
95
199
220
20
913
1,294
597
1,400
560
1,600
1,077
Aug-98(6)
1,134
1,039
611
1,510
956
367
573
2,214
1,744
237
109
200
343
131
1,598
1,154
308
369
456
906
798
All concentrations in micrograms per liter (ug/L)
VOC=Volatile Organic Compounds
DP-# = Refers to DPE well designations on site plan
(1) Prior to implementation of dual phase extraction system
(2) Approximately one month after system startup
(3) Approximately six months after system startup
(4) Approximately one year after system startup
(5) Prior to shutdown and rebound period
(6) Following shutdown and rebound period, prior to restart
50
-------
Table 5.11. Mass removal of VOCs from groundwater and soil vapor extraction.
Date
1-Nov-96
11-Feb-97
16-May-97
22-Oct-97
11-May-98
21-Sep-98
12-Jan-99
Run
Time
(days)
0
30
97
213
386
432
544
Total Mass
Removed
(Ibs)1
0
603
810
984
1,139
1,164
1,221
Mass Removed During Operating Interval
Total Mass
(Ibs)
0
603
207
174
155
25
57
(Ibs/day)
0
20.0
3.1
1.5
0.9
0.5
0.5
Mass Removed from GW 2
(Ibs)
0
100
87
90
87
18
38
(Ibs/day)
0
3.3
1.3
0.8
0.5
0.4
0.3
Mass Removed from Soil 3
(Ibs)
0
503
120
84
68
7
19
(Ibs/day)
0
16.7
1.8
0.7
0.4
0.2
0.2
1. Based on routine monitoring data of VOC concentrations and flow rates of extracted vapor influent to the carbon treatment
units.
2. Based on average VOC concentrations in groundwater from operating DPE wells and an average groundwater extraction rate
of 35 gallons per minute.
3. Equal to the Total Mass minus the Mass Removed from Groundwater.
Table 5.12. VOC concentrations in extracted vapor.
DPE Well
DP-7
DP-8
DP-18
DP-20
May-98 (1)
20
12
18
29
Sep-98 (2)
50
47
11
69
VOC = Volatile Organic Compounds
DPE = Dual Phase Extraction
Concentrations in micrograms per liter (ug/L)
Only 4 wells operating during restart
(1) Before shutdown and rebound period
(2) After restart
51
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The mass of VOCs removed from the groundwater and the mass of VOCs removed
from soil vapor varied during system operation (see Table 5.11). Over 40 percent of the
VOC mass was removed from the vadose zone during the first month of operation. By the
fifth month of operation, however, groundwater extraction was removing more VOC mass
than soil vapor extraction. The total mass removed from groundwater is approximately 382
pounds, based on average groundwater VOC concentrations and an average extraction rate of
35 gpm. The total VOC mass removed by soil vapor extraction is approximately 782 pounds.
Figure 5.10 shows the declining removal rate over time, for both groundwater and soil vapor.
Substantial VOC mass removal by groundwater extraction is likely due to significant
groundwater production from a highly impacted area, lack of groundwater drawdown that
would create a larger vadose zone, and completion of existing vadose zone remediation.
These data illustrate the greater removal efficiency by extracting vapors from the vadose zone
rather than groundwater from the saturated zone.
5.2.3.2 SHUTDOWN AND REBOUND
The DPE system was shutdown from June 5, 1998 through August 31, 1998 to assess
any residual impacts that may provide a continuing source of VOCs after the remediation
system is removed. Increases in VOC concentrations (rebound effects) were also evaluated
to determine if remediation performance could be improved.
Concentrations of VOCs detected in groundwater from the DPE system extraction
wells declined during the shutdown and rebound period (Figure 5.12). Conversely, the VOC
concentrations detected in extracted vapor increased slightly during the shutdown and
rebound period. It is likely that VOCs volatilized from the groundwater to the vadose zone
during the shutdown period.
The VOC mass removed during the month prior to shutdown was approximately 12
pounds. After three months of shutdown, the VOC mass removed during the first month of
operation was approximately 19 pounds. Although VOC mass removal increased, it appears
that continued operation would have removed more VOC mass over the four month period
(three months shutdown plus first month of operation) than system shutdown and restart.
52
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Figure 5.10. VOC removal rates during operation.
18
17
16 -
15 -
14 -
13
12 -
11 -
10
9 -
8 -
7 _
5 -
4 -
2 -
1 -
0 -
5
se
«
DSoil Vapor
iGroundwater
c^c^
' ''
Time
-------
The relatively modest increase in VOC mass removal provides further indication that the
DPE system has achieved the remediation goals.
Groundwater monitoring well W-219A is located within the source area and screened
in the A-level aquifer. VOC concentrations in this well appeared to have stabilized above
4,000 ug/L prior to startup of the DPE system. By use of DPE, VOC concentrations have
declined from 4,000 ug/L in November 1996 to 650 ug/L in August 1998.
5.2.4 TECHNOLOGY COSTS
The cost to design and install the DPE system with pneumatic fracturing was
approximately $300,000. Approximate costs for two years of operation and maintenance
services, reporting, and analytical fees were $450,000, averaging $225,000 per year.
Approximately $100,000 was required for the disposal of spent carbon. The unit cost for the
0.5-acre source area from 0 to 20 feet bgs was on the order of $53 per cubic yard of soil (for
treatment of 16,000yd3).
5.2.5 SUMMARY OF OBSERVATIONS AND LESSONS LEARNED
A significant portion of the VOC mass was removed by soil vapor extraction during
the first month of operation, while approximately equal VOC mass removals, by soil vapor
and groundwater extraction, were achieved during continued operation. This demonstrates
the efficiency of soil vapor extraction compared to groundwater extraction, and also
demonstrates the benefits of dual phase extraction.
The system reached a steady state with respect to further remediation by the existing
DPE system. VOC concentrations in groundwater and extracted vapor remained relatively
constant over an extended shutdown period, and these concentrations are substantially less
than they were when the DPE system began operation. In addition, VOC concentrations in
the A-level aquifer have declined since the source area remediation began.
54
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5.2.6 CONTACT INFORMATION
Zahra M. Zahiraleslamzadeh
Environmental Project Manager
FMC Corporation
1125 Coleman Avenue, Gate 1 Annex
P.O. Box 58123
Santa Clara, California 95052
Tel: 408-289-3141
Fax: 408-289-0195
E-mail: zahra_zahir@udlp.com
Jeffrey C. Bensch, P.E.
HSI GeoTrans
3035 Prospect Park Drive, Suite 40
Rancho Cordova, California 95670,
Tel: 916-853-1800
Fax: 916-853-1860
E-mail: jbensch@hsigeotrans.com
5.2.7 REFERENCES
Hydro-Search, Inc., 1996, Workplan for Dual Phase Extraction System with Pneumatic
Fracturing at United Defense LP Ground Systems Division, 328 West Brokaw Road,
Santa Clara, Santa Clara County, California.
HSI GeoTrans, 1997, Implementation Report, Dual Phase extraction System with Pneumatic
Fracturing at United Defense LP, Ground Systems Division, 328 West Brokaw Road,
Santa Clara, Santa Clara County, California.
Zahiraleslamzadeh, Z.M., J.C. Bensch, and W.G. Cutler, 1998, Enhanced Soil Vapor
Extraction for Source Area Remediation Using Dual Phase Extraction with
Pneumatic Fracturing, Presented at the 14th Annual Conference on Contaminated
Soils, University of Massachusetts, Amherst, MA, October 22, 1998.
55
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5.3 TINKHAM'S GARAGE SUPERFUND SITE, LONDONDERRY, NH
A full-scale Dual Vacuum Extraction (DVE) system was designed and constructed at
the Tinkham's Garage Superfund site to simultaneously draw down the water table and
remediate approximately 9,000 cubic yards (cy) of VOC-contaminated soil by vapor
extraction. Soil cleanup goals were achieved within ten months of operation. Groundwater
cleanup goals were not met in this time, and groundwater is currently being addressed
through a pump-and-treat remedy. Remediation efforts were lead by the potentially
responsible parties (PRPs) with Terra Vac, Inc. performing the design and operation of the
DVE system and U.S. EPA Region 1 providing regulatory oversight.
5.3.1 SUMMARY INFORMATION
The Tinkham's Garage site includes 375 acres of residential and undeveloped land in
Londonderry, NH, situated in the southern portion of the state. Land use at the site includes a
400 person residential condominium complex, single-family homes, and undeveloped
wooded areas, open fields, and wetlands. The Tinkham Realty Company and Tinkham's
Garage, a large steel building, are located in the northeastern section of the site.
EPA site investigations in 1981 revealed onsite soil and groundwater contaminated
with VOCs, including PCE, TCE, and BTEX compounds. These contaminants were
determined to be the result of unauthorized surface discharges of liquids and sludge in 1978
and 1979. Three source areas were delineated. Two source areas included a soil pile behind
the condominium complex and soil overlying the condominium complex leachfield. The
third source area, of approximately one acre in size, is located behind Tinkham's Garage
("Garage Area" or "1 ppm Area") and is the focus of the remedial action summarized in this
case study.
The nature and extent of soil and groundwater contamination at the site has been
characterized by several site investigations. These investigations included a remedial
investigation in January, 1985, a feasibility study in July, 1986, a pre-design study in July,
1988, and a vapor extraction pilot test in July, 1988. These investigations found total VOCs
as high as 652 ppm in soil and 42 ppm in groundwater located in shallow, overburden and
56
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bedrock aquifers. A site characterization summary is provided in Table 5.13 and a
chronology of events in Table 5.14.
The Superfund Record of Decision (ROD) issued in September, 1986 identified the
selected remedy as excavation of approximately 10,800 cy of contaminated soil with onsite
treatment by either thermal aeration, composting, or soil washing. The local wetlands
impacted by excavation and groundwater were also to be remediated. As a result of the pre-
design and pilot studies, the ROD was amended in March, 1989 to require the treatment of
approximately 9,000 cy of onsite soil by DVE. DVE was selected to target VOCs in soil
beneath the saturated zone. This would be achieved by simultaneously lowering the shallow
water table and exposing formerly saturated soil to air flow. The rationale for using DVE for
soil remediation was based on its ability to dewater the shallow aquifer and expose the
contaminated soil to SVE. Both the original and amended RODs set cleanup goals at 1 ppm
total VOCs for soil and 5 ppb each for PCE and TCE in groundwater. The ROD also called
for long-term management of migration (MOM) through groundwater pumping of deep
bedrock wells and a shallow recovery system until cleanup standards for PCE and TCE are
obtained. Pumped groundwater was to be discharged to the Deny, New Hampshire publicly-
owned treatment works (POTW).
5.3.2 TECHNOLOGY DESCRIPTION AND SYSTEM DESIGN
Consolidation of all VOC impacted soil was determined to be the most cost-effective
means for remediation. Approximately 3,000 cy of contaminated soil from three areas near
the condominium complex was excavated and hauled to the Garage Area. The excavated soil
was then spread within the garage 1 ppm Area and compacted in place. The volume of soil
requiring remediation, including the native and excavated soil, totaled 9,000 cy.
The DVE system consisted of 33 DVE wells divided into 25 shallow DVE wells,
screened in the overburden, and 8 deep DVE wells, screened in the upper bedrock and
overburden. Five existing pilot test wells were left in place and used for vapor extraction.
The wells were distributed over three manifold lines to provide the greatest coverage over the
area of contamination. The DVE well configuration used was the two-pump system
described in Section 2.4.2, however, a central pump station consisting of two, 7.5-hp jet
57
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Table 5.13. Site characterization summary for Tinkham' s Garage.
Parameter
Geologic Setting of Source Area
Depth to Groundwater
Aquifer Parameters
Constituents of Concern
Pre-Remediation Concentrations
Volume of Contaminated Media
Characteristics
Overburden consisting of inorganic and organic silty clay
and sand grading to fine and medium-grained sand with
depth
Weathered metamorphic bedrock at approximately 14
feet bgs
5 to 6 feet bgs
Approximate Values:
K = 1 ft/d (overburden silts and clays)
K = 10 ft/d (overburden sands)
• T = 900 gpd/ft (bedrock)
Tetrachloroethene (PCE) and Trichloroethene (TCE)
Total VOCs in Soil: 652 ppm, maximum
Total VOCs in Groundwater: 42 ppm, maximum
Soil: 9,000 cubic yards
Unit Notes: bgs = below ground surface; ft/d = feet per day; gpd/ft = gallons per day per foot; ppm = parts per million
Source: U.S. EPA (1989); Terra Vac (1996), HSI GeoTrans (1999)
58
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Table 5.14. Timeline of remedial activities at Tinkham's Garage.
Activity
Remedial Investigation
Feasibility Study
Record of Decision (ROD) Signed
Vapor Extraction Pilot Study
Pre-Design Study
ROD Amended to Include Dual Vacuum Extraction
(DVE)
Discharge Strategies Evaluated
Construction of Sewer Line Between Derry and
Londonderry Begins
DVE Work Plan Submitted
Excavation and Restoration of Condominium Areas
DVE Construction and Drilling at Tinkham's Garage
Begins
Issuance and Approval of Industrial Discharge Permit
to Town of Derry POTW
DVE System Operation Begins
Closure Sampling Plan Submitted
DVE System Operation Terminated
Final Soil Sampling Conducted
Final Site Inspection
Demobilization of DVE System
Construction of Groundwater System for Management
of Migration (MOM)
MOM System Operation
Period of Performance/Date of
Completion
January 1985
July 1986
September 30, 1986
December 1987 - January 1988
July 1988
March 1989
August 1990- July 1992
August 1993
February 1994
March -April 1994
May 1994
August- October 1994
November 22, 1994
July 1995
September 29, 1995
October 1995
October 25, 1995
November 1995
November - December 1 995
January 1996 - Present
Source: After Terra Vac (1996).
59
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pumps was used for groundwater extraction instead of submersible pumps at each well. The
jet pump system was capable of a flow of 1.5 gpm per well and was regulated by a valve at
each wellhead. A schematic of a typical DVE well and wellhead manifold is provided in
Figure 5.11. Wellhead vacuum and vapor extraction was achieved by two, parallel operating
portable vacuum extraction units. Each unit included a 40-hp positive displacement blower
capable of extracting 500 scfm at a vacuum of 12 inches of mercury (in Hg). Vapor
treatment was achieved by four 1,000 pound canisters of activated carbon. Two of these four
canisters operated in series with the remaining two serving as secondary units. Two
additional canisters were kept onsite to provide immediate replacements, if necessary.
Initially, groundwater treatment by air stripping was necessary to meet the Deny POTW pre-
treatment standards. Air stripper off-gas treatment was provided using vapor phase carbon.
Figure 5.12 provides a process flow diagram of the DVE system.
5.3.3 TECHNOLOGY PERFORMANCE
Operation of the DVE system lasted 311 days from November 22, 1994 to September
29, 1995. During system operation, operational data were routinely collected to serve as a
means of monitoring system performance. A summary of the performance data from the
DVE system is provided in Table 5.15.
Vapor extraction flow rates averaged 500 sfcrn at 5 inches of Hg vacuum
(approximately 68 inches of water). Vapor extraction emissions were routinely monitored at
the blower inlet to support mass removal calculations. A plot of the variation of vapor phase
VOCs in the DVE system influent is provided in Figure 5.13. VOCs extracted in the vapor
phase were at the highest concentrations (16 ppm) at the onset of DVE system operation and
continued downward, over time, averaging 1.6 ppm for the project duration. One of the three
DVE manifolds was shut down permanently after one month of operation due to negligible
concentrations of VOCs in the vapor influent. This allowed for recovery efforts to focus on
the most contaminated regions of the source area. All remedy performance verification
samples collected at soil borings located throughout the site at the conclusion of the project
indicated that the soil had been remediated to or below the remedial action objectives for soil
(1 ppm total VOCs).
60
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Figure 5.11. Schematic of DVE Well and Manifold (Terra Vac, 1996).
1.25" ENTRAPMENT TUBE
FLOW PORT-
VACUUM GAGE-
VACUUM GAGE
SAMPLE PORT
FLOW PORT
TO MANIFOLD
-------
Figure 5.12. Process Flow Diagram of DVE System (modified from Terra Vac, 1996).
to
EXTRACTED VAPOR
FROM VE AND DVE WELLS
DVE
WELL
EXTRACTED
GROUNDWATER
FROM DVE WELLS
VAPOR PHASE
CARBON CANISTERS
WATER DISCHARGE TO
SEWER CONNECTION
DISCHARGE TO
ATMOSPHERE
1
1 9 „-
I
i
DISCHARGE TO
ATMOSPHERE
RECYCLE LINE
-------
Table 5.15. Summary of DVE system performance data.
Parameter
DVE System Operation
SVE Vacuum at Blower
SVE Flow Rate
Cumulative Volume of Extracted Groundwater
Typical DVE Well Spacing
(Radius of Influence)
Vapor Influent - Total VOCs Concentrations
Groundwater Influent - Total VOCs
Concentrations
Soil VOC Mass Removal (Rate)
Groundwater VOC Mass Removal (Rate)
Value
311 days
5 in Hg (-68 in WC), average operational
value
500 scfm, average operational value
1,1 16, 500 gallons
30 ft, approximately
16 ppm, maximum
1.7 ppm, average
(see Figure 5.13)
446 ppb, maximum
81 ppb, average
(see Figure 5.14)
48.25 Ib (0.17 Ib/d), Total VOCs
5 Ib (0.02 Ib/d), Total VOCs
Unit Notes: in Hg = inches of mercury; in WC = inches of water column; scfm = standard cubic feet per minute; ft =
feet; ppm = parts per million; ppb = parts per billion; Ib = pounds; Ib/d = pounds per day
Source: Terra Vac (1996)
63
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Figure 5.13. Time variation of vapor phase VOCs in DVE system influent.2
18
Vapor Phase Influent
s
1?
8 a
o ""
o
"re
16
14
12
10
8
6
o 4
$> <£ & $>
* ^ ^ ep ^
Date
-V
Plot reproduced from data reported in Terra Vac (1996).
-------
Groundwater concentrations in the influent increased significantly after approximately
two months of operation. The influent concentrations then generally decreased such that by
the tenth (last) month of operation they were similar to initial levels. Figure 5.14 illustrates
this observation. The maximum total VOCs detected in the influent was 446 ppb and
averaged 81 ppb for the project. The overwhelming majority of VOCs recovered were PCE
and TCE. The BTEX compounds comprised only a small portion (< 5 ppb) of the VOCs
recovered in the aqueous phase. Concentrations of VOCs in groundwater in the source area
showed notable decreases over the period of DVE operation. Of the two wells in the source
area, one showed a decrease in total VOCs concentration of over 99% and the other 64%.
However, remedial action objectives for groundwater were not obtained at the conclusion of
DVE system operation. Groundwater quality data collected since the termination of DVE
show total VOCs concentrations ranging from 29 to 237 ppb in the source area and averaging
82 ppb in five source area wells. Long-term operation of a management of migration system
(pump-and-treat) has been implemented for this area. The total volume of groundwater
recovered during DVE system operation was 1,116,500 gallons.
Mass removal rates were calculated based on analytical sampling and volumetric flow
rates of vapor emissions and groundwater. In total, approximately 53 pounds of VOCs were
removed by the DVE system. The vapor extraction portion of the system accounted for the
most significant removal at approximately 48 pounds. This figure was derived based on
measurements obtained at the inlet of the SVE blowers. It is likely that the actual removal is
greater than 48 pounds since air-bleed valves, used to balance system vacuum, diluted the
concentration of influent vapor prior to measurement at the blower inlet. A plot of VOC
removal in the vapor phase over the project duration is provided in Figure 5.15 and is based
on the blower inlet data. Vapor phase VOC removal rates were steady over the system
operation and averaged approximately 0.17 pounds per day. Approximately 5 pounds of
VOCs were recovered in the aqueous phase through groundwater extraction averaging 0.016
pounds per day over the project duration.
65
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Figure 5.14. Time variation of aqueous phase VOCs in DVE system influent.3
Aqueous Phase Influent
Oi
Oi
O
o —.
c n
o a.
O 3
O
O
5
o
450
400
350
300
250
200
150
100
Date
Plot reproduced from data reported in Terra Vac (1996).
-------
Figure 5.15. Cumulative vapor phase VOC removal by DVE.4
o
o
o>
a:
3
§7
a) .Q
w -i
re —'
o
Q.
re
re
•5
50
45
40
35
30
25
20
15
10
5
0
<
Cumulative VOC Removal
Date
Plot reproduced from data reported in Terra Vac (1996).
-------
5.3.4 TECHNOLOGY COST
The actual cost, not including permitting and oversight costs, was $170/cy ($1.5
million based on 9,000 cy treated). This figure includes an inflationary cost adjustment,
granted due to significant time delays, and design changes for system winterization measures.
The majority of the cost increase was realized during the period prior to completion of the
sewer line, as a result of performing additional field tests to evaluate interim water discharge
alternatives.
Costs for on- and off-site soil remediation alternatives were estimated prior to the
remedial design phase. These estimates, based on 1986 dollars, included on-site thermal
aeration at $288/cy, biological treatment at $133/cy, and off-site incineration at $2,400/cy.
The original estimate for DVE in the source area was $116/cy. Project delays of two years,
primarily due to the lack of availability of a groundwater discharge point (see Table 5.14) and
regulatory permitting for off-site discharge, added to the overall cost of the DVE system.
5.3.5 SUMMARY OF OBSERVATIONS AND LESSONS LEARNED
The following conclusions and recommendations were identified based on the
reported performance of the DVE system during its operational period.
According to the RPM, at this site, soil remediation was dependent upon the
ability to extract and discharge groundwater. DVE, like any groundwater
extraction and treatment technology, is highly sensitive to the existence of a
feasible discharge point. The project proceeded under the expectation that
groundwater discharge could occur. However, an acceptable discharge point
would not be made available until the sewer connection to the Deny POTW
was completed. Significant project delays (two years) and subsequent
increased costs were realized as a result of a lack of availability of an
acceptable discharge point.
Additional observations were provided by the PRP's consultant (Terra Vac, 1996).
• The site conditions were favorable for DVE to be implemented for soil and
groundwater remediation.
• DVE proved effective at remediating a significant volume (9,000 cy) of
contaminated soil to below remedial goals (1 ppm) in a relatively short period
68
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of time (10 months) with overall project costs competitive with other
applicable remedial technologies.
DVE affected some mass removal of VOCs dissolved in groundwater within
the source area. It is important to note that DVE was not intended to obtain
remediation goals for groundwater. The extraction and treatment of
groundwater was necessary to target and remediate soil contamination located
in the saturated zone. A long-term migration control remedy (pump-and-treat)
is currently operating to obtain groundwater remediation objectives.
5.3.6 CONTACT INFORMATION
James DiLorenzo
Remedial Project Manager
U.S. EPA Region 1 (MC:HBO)
One Congress Street, Suite 1100
Boston, MA 02114-2023
Tel: (617)918-1247
E-mail: dilorenzo.jim@epa.gov
Joleen Kealey
Project Manager
Terra Vac, Inc.
213 Rear Broadway
Methuen, MA01844
Tel: (978)688-5280
5.3.7 REFERENCES
HSI GeoTrans. Personal communication between Michael Montroy of HSI GeoTrans and
James DiLorenzo of U.S. EPA Region 1. March 1999.
U.S. EPA, Record of Decision (Amended), Tinkham's Garage, NH. EPA/ROD/RO1-89/046.
March 10, 1989.
Terra Vac, Inc. "Remedial Action Report for the Tinkham's Garage Superfund Site,
Londonderry, New Hampshire", March 15, 1996.
69
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6 REFERENCES
American Petroleum Institute. A Guide to the Assessment and Remediation of Underground
Petroleum Releases, 3rdEdition, API Publication 1628, Washington, D.C., 1996.
Dames and Moore. "Remedial Investigation Acid Neutralization Pits, Defense Supply Center
Richmond, Virginia", Contract No. DACA 65-86-C0131, April 27, 1989.
HSI GeoTrans. Implementation Report, Dual Phase Extraction System with Pneumatic
Fracturing at United Defense LP, Ground Systems Division, 328 West Brokaw Road,
Santa Clara, Santa Clara County, California, 1991.
HSI GeoTrans. Personal communication between Michael Montroy of HSI GeoTrans and
Don Sherhouse of North East Environmental Products. September 1998.
HSI GeoTrans. Personal communication between Michael Montroy of HSI GeoTrans and
James DiLorenzo of U.S. EPA Region 1. March 1999.
Hydro-Search, Inc. Workplanfor Dual Phase Extraction System with Pneumatic Fracturing
at United Defense LP Ground Systems Division, 328 West Brokaw Road, Santa
Clara, Santa Clara County, California, 1996.
Kittel, J.A., R.E. Hinchee, R. Hoeppel, and R. Miller. " Bioslurping -vacuum enhanced free
product recovery coupled with bioventing: A case study Petroleum Hydrocarbons and
Organic Chemicals in Groundwater: Prevention, Detection, and Remediation, 1994
NGWA/API Conference Proceedings, Houston, TX, 1994.
Law Engineering and Environmental Services, Inc. "Final Treatability Study for Operable
Unit 8 - Acid Neutralization Pits Groundwater", Defense Supply Center Richmond,
Prepared for U.S. Army Engineering and Support Center - Huntsville, Contract No.
DACA 87-94-D-0016; D.0.17, November 1998.
Law Engineering and Environmental Services, Inc. Fax transmission dated January 29, 1999
from Katy Allen, P.E.
Peargin, T. Vacuum-enhanced Recovery: Theory, Underground Tank Technology Update,
9(4):2-7, 1995.
Suthersan, $.$. Remediation Engineer ing: Design Concepts. CRC Press, Inc., 1997.
Terra Vac, Inc. "Remedial Action Report for the Tinkham's Garage Superfund Site,
Londonderry, New Hampshire", March 15, 1996.
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Tetra Tech, Inc. Water Quality Assessment: A screening procedure for toxic and
conventional pollutants in surface water. Volume 1, USEPA Center for Water
Quality Modeling, Environmental Research Laboratory, Athens, GA. September,
1983.
U.S. Army Corps of Engineers. Engineer Manual. Multi-Phase Extraction, Engineering and
Design. EM 1110-1-4010. June 1999.
U. S. Environmental Protection Agency. How to Effectively Recover Free Product at Leaking
Underground Storage Tank Sites: A Guide for State Regulators., EPA 510-R-96-001.
Washington, DC: Office of Solid Waste and Emergency Response, September, 1996.
U.S. Environmental Protection Agency. Presumptive Remedy: Supplemental Bulletin Multi-
phase Extraction (MPE) Technology for VOCs in Soil and Groundwater. EPA 540-
F-97-004. April, 1997c.
U.S. Environmental Protection Agency. EPA REACH IT database, 1998. URL
U.S. Environmental Protection Agency. Cleaning Up the Nation's Waste Sites: Markets and
Technology Trends; 1996 Edition. EPA 542-R-96-005. April, 1997a.
U.S. Environmental Protection Agency. Analysis of Selected Enhancements for Soil Vapor
Extraction. EPA-542-R-97-007. September, 1997b.
U.S. EPA, Record of Decision (Amended), Tinkham's Garage, NH. EPA/ROD/RO1-89/046.
March 10, 1989.
U.S. Geological Survey. "Ground-Water Contamination and Movement at the Defense
General Supply Center", Richmond, Virginia, U.S. Geological Survey, Water-
Resources Investigations Report 90-4113, 1990.
Zahiraleslamzadeh, Z.M., J.C. Bensch, and W.G. Cutler, 1998, Enhanced Soil Vapor
Extraction for Source Area Remediation Using Dual Phase Extraction with
Pneumatic Fracturing, Presented at the 14th Annual Conference on Contaminated
Soils, University of Massachusetts, Amherst, MA, October 22, 1998.
71
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