United States

Environmental Protection

Agency

EPA 542-R-99-004

June 1999

clu-in.org

Multi-Phase Extraction:

State-of-the-Practice

Solid Waste and

Emergency Response

(5102G)

EPA

SOIL VAPOR

GROUNDWATER
i

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), at www.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.
ii

TABLE OF CONTENTS

Page

FOREWORD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

1 INTRODUCTION ........................................................1

2 TECHNOLOGY DESCRIPTION ...........................................2

2.1 SOIL VAPOR AND GROUNDWATER 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
TABLE OF CONTENTS

(continued)

Page

iii

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
iv

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 over time. . . . . . . . . . . . . . . . . . . . . . 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
v

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
vi

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.
1

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 conditions 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 <http://www.epareachit.org>. 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.
2

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-andtreat 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. 
3

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).
9 ’

Q = 0 gpm

DRAWDOWN = 0

2.1.1 STATIC

9 ’

Q = 1 gpm

DRAWDOWN = 9’

2.1.2 FLUID PUM PING O NLY

Q = 0 gpm 

Vac = 10’ H O2 Vac = 0’ H O2

2.1.3 O NLY VAC UUM

EFFE

2.1.4 

4

Figure 2.1. Effect of a vacuum on pumping level (Suthersan, 1997).
5

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).
STATIC FLUID LEVEL

SAND PACK

PVC SCREEN

BENTONITE

CONCRETE

PVC CAP

SUCTION LINE

CASING VACUUM GAUGE

PVC CASING

DROP TUBE

VACUUM GAUGE

LIQUID RING

 PUMP

THREADED COUPLING

LE S S TH A N 30 F T.

BORE HOLE

6

Figure 2.2. Single pump MPE well schematic (Suthersan, 1997).
-14.7 psi x 2.311 ft H O = 33.95 ft H O 1

2 2

 psi

7

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. In theory, a vacuum lift 1

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 BIOSLURPING

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 
STATIC FLUID LEVEL

SUBMERSIBLE PUMP

CEMENT GROUT

WELL SCREEN

GRAVEL PACK

SUMP

TO TREATMENT SYSTEM

SURFACE

GROUND 

CEMENT GROUT

LIQUID RING PUMP

CEMENT GROUT

BENTONITE

NATIVE FILL

8

Figure 2.3. Two-pump MPE schematic (Modified from Suthersan, 1997).
9

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.
BIOVENTING WELL

SCREEN

WATER TABLE

TO 6" HEADER

VALVE

RUBBER GASKET

TEE

VALVE

FREE PHASE PRODUCT

1" SUCTION TUBE

M ETAL PLATES

COMPRESSION SCREW S

GROUND SURFACE

2" TEE 2" VALVE

2" PVC

10

Figure 2.4. Bioslurping schematic (Kittel, et al., 1994).
11

Table 2.1. Terms referring to multi-phase extraction and their configurations.

Term Configuration Source

Dual-Phase Extraction (DPE) Non-specific MPE term 1

Drop-Tube Entrainment Extraction Single pump configuration 1

Well-Screen Entrainment Extraction Extraction of vapor and groundwater from a 1

sealed well with induced vacuum. 

Groundwater is aspirated into the vapor

stream at the well screen.

High-Vacuum Dual Phase Extraction Two pump configuration with a submersible 2

(HVDPE) pump for groundwater recovery. 

High vacuum application (18 to 26 in Hg)

Low-Vacuum Dual Phase Extraction Two pump configuration with a submersible 2

(LVDPE) pump for groundwater recovery. 

Low vacuum application (2 to 12 in Hg)

Two-Phase Extraction (TPE) Single pump configuration with high vacuum 2

application (18 to 26 in Hg)

Bioslurping Single pump configuration with drop tube set 3

at, or just below, the air-liquid interface

VE/GE (“Veggie”); Two pump configuration with a submersible 4,5

Downhole-Pump Extraction pump for groundwater recovery

Vacuum Enhanced Pumping (VEP) Non-specific MPE term 4

Vacuum Enhanced Recovery (VER) Non-specific MPE term 6

Sources:

1. EPA, 1997b

2. EPA, 1997c

3. Kittel et al, 1994

4. EPA, 1996

5. Peargin, 1995

6. Suthersan, 1997
12

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 finegrained formations in the fine sand to silty sand range (hydraulic conductivity, K = 10 to -3

10 cm/s) (EPA, 1996). Application of systems to lower conductivity (less than 10 cm/s) -5 -6

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 
13

Table 3.1. Applicability of MPE.

Parameter Applicable Range or Characteristic for MPE Source

Hydraulic Conductivity • Moderate to Low (K = 10 to 10 cm/s) 1 -3 -5

Transmissivity • Low ( 500 gpd/ft) 2

Geologic Setting • Sands to Clays 3

Vadose Zone Soil • Moderate to Low (k < 1 darcy) 3

Permeability to Air

a

Formation • Low permeability, fractured systems 1,2

Characteristics • Interbedded sand and clay stringers

• Limited saturated thickness

• Shallow water table

• Thick capillary zone (up to several feet)

• Perched NAPL or groundwater layers

Drawdown/Recovery • Conditions producing steep or high drawdown in wells 1

Rate • Low groundwater recovery rates achieved with

conventional pumping

Contaminant Location • Vadose, saturated, and capillary zones 1,3

Contaminants • Halogenated VOCs 1,3

• Aromatic VOCs and/or total petroleum hydrocarbons (TPH)

• Floating, free product (LNAPL)

Contaminant Vapor • > 1 mm Hg at 20(C 3

Pressure

Contaminant Volatility • > 0.01 at 20(C 3 b

• >2 x 10 atm m /mol at 20(C -4 3 c

 1 darcy 10 cm a -8 2

 Expressed as dimensionless Henry’s Law Constant: Concentration in gas phase/concentration in liquid phase b

 Henry’s Law Constant: Computed from (b) using method of Mills et al. (1982) as shown in Tetra Tech, 1983. c

Sources:

 1. EPA, 1996

 2. Suthersan, 1997

 3. EPA, 1997c
14

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. 
15

Table 3.2. Summary of the advantages and potential limitations of MPE.

Advantages Potential Limitations

• Effective on moderate to low permeability • Requires vacuum pump or blower (EPA,

soils (Suthersan, 1997; EPA, 1996) 1996)

• Effective source removal at low • Potentially greater treatment requirements

permeability sites where the only other as a result of NAPL emulsions and VOCviable remedial option may be excavation laden vapors (i.e., liquid-phase separation

(Suthersan, 1997) and vapor treatment) (EPA, 1996)

• Effective for simultaneous remediation of • Initial startup and adjustment periods may

dissolved, vapor, residual, and non- be longer compared to conventional

aqueous phases of contamination (EPA, pumping approaches (EPA, 1996)

1996)

• Creates potentially large radius of to conventional pumping approaches

influence and increased capture zone (EPA, 1996)

(Suthersan, 1997; EPA, 1996)

• Increase total fluids recovery, minimize configurations (EPA, 1996; EPA, 1997c)

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)

• Potentially higher capital costs compared

• Depth limitations apply to some MPE
16

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.
17

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 (<http://www.epareachit.org>). 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.
18

Table 4.1. MPE vendors listed in EPA REACH IT .1

Vendor Technology Configuration Contact Claim

Aspects of Vendor Points of Performa

# of Units

List o

Pilot

Design

Full-Scale

Billings & Associates, Inc. Subsurface • Air injection using 0 100 60 Rick Billings • Rapid www.aristotle.com Ventilation SystemTM • Vapor withdrawal • Uses air to 

Volatilization and positive pressure. Vice President installation

using negative Ph:(505) 345-1116 water treatpressure to Fx:(505)345-1756 • Able toremove volatiles. manipulate 

• Stimulation of rickbillings@aristotle.com flows and

existing microbial pressurescommunity. • Able to dir

to select aof a site.

Dames & Moore Two-phase vacuum • Recovery of 26 0 28 Joseph M. Tarsavage, • Up to 85 to www.dames.com vapor and Engineer are volatili

extraction contaminated soil P.E., Senior Chemical of contam

groundwater in stripped frsame borehole. Ph: (215)657-5000X2010 groundwat

• VOCs are Fx: (215) 657-5454 • Groundwa

stripped from extraction groundwater. phljmt@dames.com are up to 1

• Air is injected times grea

below water table. than throu

conventionpumping methods.

IT Corporation Vacuum enhanced • Passive air lift 4 16 19 John Mastroianni • Successfuwww.itcorporation.com either vacuum groundwat

pumping techniques and Project Manager used to lift

blower or pump to Ph: (713)996-4400 from depthextract fluids. Fx: (713)3299163 to 60 to 70 

jmastroianni@itcrp.com • Accelerate

bgs.remediatioprocess.
Table 4.1. MPE vendors listed in EPA REACH IT (continued).

Vendor Technology Configuration Contact Claim

Aspects of Vendor Points of Performa

# of Units

List o

Pilot

Design

Full-Scale

19

KAP & SEPA, Ltd. SVE combined with • 1⁄2-inch pipe 0 0 7 Peter Kohout • Capable owww.kap.cz extraction. No trade from 4-inch SVE (SEPA) halogenate

LNAPL vacuum extracts LNAPL (KAP) & Vladimir Kinkor treating name specified. well. nonhaloge

Czech Republic VOCPh: +4202 24313630 contaminaFx :+4202 57211255 soilspkohout@prg.kap.cz volatile.

nonhaloge

• Does not r

expensiveequipment numerouspersonnel operate.

Radian International, LLC Xerox Two-Phase • High vacuum oil 36 2 21 Joe Fitzgerald • Significant www.radian.com ExtractionTM draws vapors and convention

High Vacuum sealed pump Site Manager advantage

liquid through Ph: (315) 456-3671 dual phase extraction straw. Fx:(315) 456-6844 systems. 

joe_fitzgerald@radian.com 

Terra Vac, Inc. Dual ExtractionTM • Water table is 70 115 250 Tony Vinici • Considerawww.terravac.com ExtractionTM vacuum tube. than a P&T

Entrainment lowered by Operations Manager more effic

• Common blower Ph: (609) 371-0070 system. 

draws vacuum on Fx: (609) 371-9446 • Substantiaboth liquid and savings in vapor.
Table 4.1. MPE vendors listed in EPA REACH IT (continued).

Vendor Technology Configuration Contact Claim

Aspects of Vendor Points of Performa

# of Units

List o

Pilot

Design

Full-Scale

20

ARS Technology, Inc. Pneumatic Fracturing • High burst 36 1 11 John Liskowitz • Capital coswww.arstechnologies.com several discrete costs are

Extraction (PFE)TM injection of air at President and opera

intervals. Ph: (732)296-6620 reduced 

• Used in Fx: (732)296-6625 compared 

conjunction with otherdual phase technologiextraction and • Number of other required istechnologies. decreased

• Speeds up 

rate of maremoval.

• Reduces t

required foremediatio

Information given in this table, including aspects of configuration, number of units, points of contact, list of performance claims, and patented app

1

EPA REACH IT (<http://www.epareachit.org>) in December 1998. Information is shown as provided by technology vendors in EPA REACH IT, a

report.
21

Table 4.2. Representative MPE sites for vendors listed in EPA REACH IT .1

Site Name/ Contaminant Treated Depth Date Current 

Location Concentration Range Treated Contracted Status Media NAPL Untreated Quantity 

Contaminant Volume/

Concentration Range Treated 2

2

Billings & Associates, Inc.Subsurface Volatilization and Ventilization SystemTMConfidential Soil DNAPL Benzene: 10 ppm Benzene: 0.01 ppm 1,500 ft 40 feet March 1991 Completed - 

Groundwater LNAPL Ethylbenzene: >10 ppm Ethylbenzene: <5.0 ppm October 

Toluene: >10 ppm Toluene: <5.0 ppm 1993 Xylene: >10 ppm Xylene: <5.0 ppm 

3

Electro-Voice Site Soil Not 1,1,1 - Not Available 169,500 ft 66 feet March 1992 Ongoing Buchanan, MI Sediments reported Trichloroethane(TCA): USA Groundwater 18 ppm 

Ethylbenzene: 1,400 ppm PCE: 240 ppmToluene: 4,300 ppmTCE: 23 ppmXylene: 6,600 ppm

3

Super Valu Site Soil Not Benzene: 25 ppm Benzene: 0.01 ppm 21,600 ft 45 feet March 1992 Completed - Albuquerque, NM Sediments reported Ethylbenzene: 25 ppm Ethylbenzene: <1.0 ppm December USA Groundwater Toluene: 25 ppm Toluene: <1.0 ppm 1993 

Xylene: 25 ppm Xylene: <1.0 ppm 

3

Dames & MooreTwo-Phase Vacuum ExtractionTMIndiana Gasoline Soil LNAPL Benzene: 21 ppm Not Available 169,760 ft 10 to 20 October Ongoing Station Groundwater Ethylbenzene: 1.1 ppm feet 1992Clarkesville, IN Toluene: 14 ppmUSA Xylene: 5.8 ppm

3

Machine Shop Soil LNAPL TCA: ND-5.1 ppm TCA: ND 2,660 yd 10 feet May 1993 Ongoing Trenton, NJ Groundwater 1,1-Dichloroethane: ND 1,1-Dichloroethane: NDUSA - 2.8 ppm VOC’s: ND - 0.020 ppm

VOC’s: ND - 12.14 ppm

3

IT CorporationVacuum enhanced pumpingGasoline Service Soil LNAPL Not Available Not Available 59,850 ft 10 to 30 1992 1993 Station Groundwater feetHouston, TexasUSA

3
Table 4.2. Representative MPE sites for vendors listed in EPA REACH IT (continued). 1

Site Name/ Contaminant Treated Depth Date Current 

Location Concentration Range Treated Contracted Status Media NAPL Untreated Quantity 

Contaminant Volume/

Concentration Range Treated 2 2

22

KAP & SEPA, Ltd.Ralsko Airbase Soil LNAPL Kerosene: 0.1 - 0.4 Kerosene: 0.1 - 0.4 ppm 22,030 lbs. 26 feet March 1993 Ongoing 

PCE: 0.1 - 0.4 ppm 

PCE: 0.1 - 0.4 ppm 

RepublicRalsko, Czech Groundwater ppmRadian International LLCXerox 2-Phase High Vacuum ExtractionTMXerox Corporation Soil Not Dichloroethylene: >500 Dichloroethylene: 1.3 3,000 lbs. 25 feet NA Completed - Mississauga, Ontario Groundwater reported ppm (soil) ppm (soil) December Canada 1995 

McClellan Air Force Soil Not TCE: 7,000 ppm Not Available 6,000 lbs. 115 feet August 1994 Ongoing Base Groundwater reported Sacramento, CA USATerra Vac, Inc.TMDual Extraction, Entrainment ExtractionTMGasoline Service Soil LNAPL Benzene: free product - Benzene: ND - 0.05 ppm Approx. 25 feet September Completed - Station Sediments gasoline (soil) 500,000 ft 1990 OctoberLos Angeles, CA Groundwater 1991USA

3

Rental Car Facility Soil LNAPL BTEX: >100 ppm BTEX: ND Not Not June 1990 Completed - Los Angeles, CA Sediments TPH: >1000 ppm TPH: ND -470 ppm Available Available FebruaryUSA Groundwater 1991Tinkhams Garage Soil LNAPL PCE: .003-190 ppm NA 81,000 ft 18 feet 1989 Ongoing Londonderry, NH Sediments (soil) USA Groundwater Toluene: ND-300 ppm 

(soil) TCE: ND - 10 ppm (soil)VOC’s: ND-0.8 ppm(soil)Xylene: ND-0.3 ppm(soil)

3
Table 4.2. Representative MPE sites for vendors listed in EPA REACH IT (continued). 1

Site Name/ Contaminant Treated Depth Date Current 

Location Concentration Range Treated Contracted Status Media NAPL Untreated Quantity 

Contaminant Volume/

Concentration Range Treated 2 2

23

ARS Technology, Inc.Pneumatic Fracturing Extraction (PFE)TMElectroplating Soil DNAPL Benzene: 0.5328 Benzene: 0.00048 Approx. 9 to 17 June 1992 Completed - Industrial Site Groundwater LNAPL lbs/day lbs/day 19,000 ft feet December Somerville, NJ PCE: 0.6048 lbs/day PCE: 0.00072 lbs/day 1993 USA TCE: 0.2448 lbs/day TCE: 0.00936 lbs/day 

3

Industrial Facility Soil DNAPL TCE: 7 - 20 ppm TCE: 0.46 - 0.88 ppm 4,500 ft 3.5 to 13 August 1993 Completed - Santa Clara, CA Groundwater LNAPL feet December USA 1993 

3

Military Base Soil LNAPL Fuel Oil: 8.6 gal/day Fuel Oil: 1.2 gal/day Approx: 25 to 31 June 1993 Ongoing Oklahoma City, OK Groundwater 5,000,000 ft feet USA 

3

Petroleum Refinery Soil LNAPL BTEX: Not Available BTEX: Not Available 3,500 ft 2 to 7 feet November Completed - Marcus Hook, PA Groundwater 1991 December USA 1996 

3

Former Manufacturing Soil DNAPL TCE: 8.43 - 56.2 TCE: 0.23 - 2.40 lbs/day Approx. 10 to 17 May 1994 Ongoing Facility Groundwater LNAPL lbs/day 784,080 ft feet Highland Park, NJ USA 

3

Confidential Soil LNAPL Benzene: 2,400 - 2,500 Benzene: 10 - 13 ppm 5,400 ft 0 to 17 July 1995 Completed - Manufacturing Site Groundwater ppm feet August 1995Western NY StateUSA

3

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 contract

(<http://www.epareachit.org>) 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. lbs/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)
24

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.

Defense Supply 328 Site, Tinkhams’s Garage,

Center, Richmond, VA Santa Clara, CA Londonderry, NH

Vendor Law Engineering and HSI-GeoTrans, Inc. Terra Vac, Inc.

Environmental Services, Terra Vac, Inc.

Inc.

Technology

Configuration

Two-pump MPE Single Pump MPE with Single Pump MPE

Pneumatic Fracturing

Technology

Scale

Field demonstration Full scale Full scale

(Treatability study)

Media/Matrix

Treated

Soil and groundwater Soil and groundwater Soil (primary target

media)

Contaminants

Targeted

TCE, PCE, 1,2-DCE TCE PCE, TCE

Total VOC Mass

Removed

117 lb from soil 782 lb from soil 48 lb from soil 

28 lb from groundwater 382 lb from 5 lb from groundwater

groundwater

Period of

Operation

July 1997 - July 1998 November 1996 - November 1994-

December 1998 September 1995
25

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
26

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 (ft /d). 2
27

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 Characteristics

Geologic Setting of Source Area Upper Eastover Formation

Silty Clay, Fine Sands, Course Sands and Interlayered Gravels

0 to 25 ft bgs

Geologic Setting of Impacted Aquifer Upper Low Permeability Zone of Eastover Formation

Silty Clay, Clayey Silt, Interlayered Sand and Silty Clay

10 to 25 ft bgs

Depth to Groundwater 10 to 15 ft bgs

Hydraulic Gradient 0.001 to 0.002 ft/ft NE

Aquifer Transmissivity 374 to 504 ft /d2

Constituents of Concern Tetrachloroethylene (PCE), Trichloroethylene (TCE), 

1,2-Dichloroethylene (1,2-DCE)

Groundwater Concentrations Prior to DPE 3300 )g/L PCE; 890 )g/L TCE; 26 )g/L 1,2-DCE

Treatability Study†

Plume Area Prior to DPE Treatability Study Approximately 16,000 square feet

† Maximum detections from RI
28

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 ANP 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;
29

• 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 Time of Performance

Remedial Investigation (RI) January 1987 - November 1988

Supplemental RI September 1992 - December

1992

ROD for Soils (OU5) 1992

SVE Pilot-Test for Soil December 1992

Feasibility Study (FS) November 1994

Aquifer Test/DPE Pilot-Test for Groundwater (OU8) June - July 1995

ESD for OU5 September 1995 †

Work Task Proposal Issued for DPE July 1996

DPE System Construction Begins January 1997

Groundwater Extraction Begins June 1997

SVE and Air Injection Begins July 1997

12-Month DPE Treatability Study July 1997 - July 1998

Treatability Study Report Issued/Continued DPE Operation November 1998

† Explanation of Significant Differences (ESD) for soils at ANP site (OU5) indicated that soil contamination was below riskbased action levels. Recommendation was made to exclude OU5 from further remediation.
30

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 
31

Table 5.4. Summary of DPE system performance data at DSCR.

Parameter Value

Treatability Study Duration 384 days

DPE System Operation 7687 hours (320 days)

SVE Vacuum at Blower 42 in WC, average

SVE Air Flow Rate 314 cfm, average

Groundwater Extraction Rate 37 gpm, average

Cumulative Volume of Extracted 17,000,000 gallons

Groundwater

DPE Radius of Influence 600 to 800 ft, downgradient

Maximum Drawdown Realized 3.94 ft at 400 ft distance

Maximum Influent Total VOC 1162 )g/L (first month)

Concentrations 90 )g/L (last month)

Maximum Reduction in VOCs Constituent Initial Final % Reduction

Concentrations in Groundwater Conc. Conc.

PCE 1300 )g/L < RAO 99.6 *

TCE 290 )g/L < RAO 98.3

Soil VOC Mass Removal (Rate) 117 lb (0.37 lb/d), total

70 lb (0.22 lb/d), aromatic

47 lb (0.15 lb/d), chlorinated

Groundwater VOC Mass Removal 28 lb (0.09 lb/d), total

(Rate) 2 lb (<0.01 lb/d), aromatic

26 lb (0.08 lb/d), chlorinated

Unit notes: in WC = inches of water column; cfm = cubic feet per minute; gpm = gallons per day; )g/L = micrograms per liter;

lb = pounds; lb/d = pounds per day

* Remedial action objective (RAO) for groundwater was 5 )g/L for PCE and TCE
32

Figure 5.1. Comparison of baseline groundwater levels (Law Engineering and Environmental Services, 19

copy)
33

Table 5.5. Potentiometric surface elevations.

Well I.D.

Potentiometric

Surface Elevation

January 1997 August 1997 July 1998

DMW-23A 112.04 107.07 107.08

DMW-24A 112.05 106.04 105.86

DMW-30A 111.97 104.55 104.50

DMW-31A 111.88 105.87 104.94

MWANP-1 111.91 102.30 103.50

MWANP-2 111.62 106.88 106.43

MWANP-3 110.51 106.49 106.87

MWANP-5 NA 100.14 103.15

MWANP-6 NA 100.76 103.62

MWANP-7 111.89 101.93 103.81

MWANP-8 NA 100.14 100.40

MWANP-9 NA NA 103.00

MWANP-10 111.94 103.30 104.13

MWANP-11 111.47 106.03 106.23

USGS-2 NA 107.39 107.89

OS72-1 NA NA 108.01

OS72-1 NA NA 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 
34

Figure 5.2. Plot of VOC concentrations in SVE emissions over time (Law Engineering and Environmenta

1998). (Best copy available)
35

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

(<5 )g/L). 

Table 5.6. Summary of groundwater VOC data.

Well I.D.

Total Chlorinated

VOCs (ug/L)

January August October January April July 1998

1997 1997 1997 1998 1998

DMW-23A 0.53 3.13 2.00 2.28 0.9 2.1

DMW-24A 41.56 18.11 2.26 4.73 5.2 3.6

DMW-30A 1980.5 637.20 21.52 25.28 71.1 11.9

DMW-31A 10.43 30.39 43.71 31.81 20.2 58.6

MWANP-1 21.78 12.63 1.02 1.11 0.6 0.70

MWANP-2 116.14 83.42 28.00 16.65* 25.6 20.5

MWANP-3 2.26 9.60 14.46 43.51 158.6 141

MWANP-7 1765.9 298.95 4.50 3.89 7.7 3.5

MWANP-10 860.7 5.43 ND 0.33 0.3 0.4

MWANP-11 142.74 177.84 15.14 23.30 130.1 55.6

USGS-2 12.78 1.29 18.00 8.27 1.1 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.
36

Figure 5.3. Total VOC concentrations in groundwater (Law Engineering and Environmental Services, Inc

available copy)
37

Figure 5.4. Cumulative mass of VOCs removed by groundwater extraction (Law Engineering and Environ

1998). (Best available copy)
38

Figure 5.5. Cumulative mass of VOC’s removed by SVE (Law Engineering and Environmental Services, 

available copy)
39

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.
40

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.
41

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 
42

Figure 5.6. Map of 328 site (Zahiraleslamzadeh et al., 1998).
43

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 Characteristics

Geologic Setting of Source Area Silts and Clays, 0 to 20 feet below ground surface

Geologic Setting of Impacted Aquifers Sandy Silts, Silty Sands, and Gravelly Sands, 20 to 90 feet below

ground surface

Depth to Groundwater 8 feet below ground surface

Constituents of Concern Trichloroethylene (TCE)

Initial Concentrations 46 mg/kg in Soil; 37,000 ug/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.
44

Table 5.8. Technology summary.

Technology Mechanism

Soil Vapor Extraction Volatilization of TCE from soil matrix by extracting vadose zone air; air flow

increases volatilization processes.

Groundwater Extraction Air entrainment lifts shallow groundwater droplets with extracted vapors.

Pneumatic Fracturing 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.

Air/Water Separator Gravity separation.

Air Treatment Vapor-phase carbon removes TCE from air by adsorption.

Groundwater Treatment 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) 
45

Figure 5.7. Process flow diagram (Zahiraleslamzadeh et al., 1998).
46

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 Activities

May 1996 – August 1996 Work Plan and Design

September 1996 – November 1996 Construction and Startup

December 1996 – April 1997 Pneumatic Fracturing and 

Cluster Operations

May 1997 – May 1998 Continued Operations focused in areas of

highest impacts

June 1998 – August 1998 Shutdown and Rebound 

September 1998 – October 1998 Restart and Continued Operation

November 1998 Confirmation Soil Sampling

January 1999 Final Reports and Preparation for System

Shutdown

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.
47

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.
0.00

20.0040.0060.0080.00

100.00120.00

11/19/96 11/23/96 11/27/96 12/4/96 12/11/96 1/20/9 1 7 /24/97 2/9/97 2/13/9 2/ 721/97 3/5/9 3 7 /24/97 5/14/9 7/ 710/97 8/11/97 9/3/97 9/30/97 10/22/97 11/17/97 12/15/97 1/14/9 2 8 /12/98 3/9/98 4/6/98 5/4/98 6/5/98 9/4/9 9 8 /11/9 9/288 /9 12 8/7/98

Date

Removal Rate (pounds/day)

0.00200.00400.00600.00800.001000.001200.001400.00

Mass Removed (pounds)

Mass Removed (pounds)R em oval R ate (pounds/day)

48

Figure 5.8. VOC mass removal.
0

2,0004,0006,0008,000

10 ,00012 ,00014 ,000

A u g -9 6

D e c -9 6

M a r-9 7

Ju n -9 7

S ep -9 7

Jan -9 8

A p r-9 8

Ju l-9 8

Sample Date

Average VO C Concentrations (m icrogram s per liter)

49

Figure 5.9. Average VOC concentrations of groundwater over time.
50

Table 5.10. VOC concentrations in groundwater.

DPE Well Oct-96 Jan-97 May-97 Oct-97 May-98 Aug-98 (1) (2)

Feb-97

(3) (4) (5) (6)

DP-1 1,704 990 954 1,134

DP-2 14,000 9,900 4,700 1,000 1,477 1,039

DP-3 4,300 2,900 920 953 611

DP-4 3,700 2,200 1,500 1,100 1,510

DP-5 8,900 2,100 1,694 1,200 947 956

DP-6 2,000 1,169 770 839 367

DP-7 8,600 6,500 4,200 573

DP-8 23,000 9,300 3,200 3,200 3,400 2,214

DP-9 1,900 2,000 550 1,744

DP-10 512 330 224 237

DP-11 219 95 95 109

DP-12 1,300 2,100 640 270 199 200

DP-13 650 300 220 343

DP-14 800 130 58 41 20 131

DP-15 10,000 3,200 1,671 1,400 913 1,598

DP-16 2,200 1,700 1,294 1,154

DP-17 37,000 3,300 750 260 597 308

DP-18 8,900 4,400 5,500 1,900 1,400 369

DP-19 4,400 1,100 816 470 560 456

DP-20 6,200 1,700 1,600 906

Average 12,033 3,794 2,364 1,327 1,077 798

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
51

Table 5.11. Mass removal of VOCs from groundwater and soil vapor extraction.

Date

Run Total Mass

Time Removed Total Mass Mass Removed from GW 

(days) (lbs)1

Mass Removed During Operating Interval

Mass Removed from Soil 3 2

(lbs) (lbs/day) (lbs) (lbs/day) (lbs) (lbs/day)

1-Nov-96 0 0 0 0 0 0 00

11-Feb-97 30 603 20.0 3.3 16.7 603 100 503

16-May-97 97 810 3.1 1.3 1.8 207 87 120

22-Oct-97 213 984 1.5 0.8 0.7 174 90 84

11-May-98 386 1,139 0.9 0.5 0.4 155 87 68

21-Sep-98 432 1,164 0.5 0.4 0.2 25 18 7

12-Jan-99 544 1,221 0.5 0.3 0.2 57 38 19

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 May-98 Sep-98 (1) (2)

DP-7 20 50

DP-8 12 47

DP-18 18 11

DP-20 29 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
52

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. 
0

123456789

1 01 11 21 31 41 51 61 71 8

m e

Soil Vapor Groundwater

T i

53

Figure 5.10. VOC removal rates during operation.
54

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 16,000 yd ). 3

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. 
55

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 14 Annual Conference on Contaminated th

Soils, University of Massachusetts, Amherst, MA, October 22, 1998.
56

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
57

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 predesign 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 Derry, New Hampshire publiclyowned 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 
58

Table 5.13. Site characterization summary for Tinkham’s Garage.

Parameter Characteristics

Geologic Setting of Source Area • 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

Depth to Groundwater 5 to 6 feet bgs

Aquifer Parameters Approximate Values:

• K = 1 ft/d (overburden silts and clays)

• K = 10 ft/d (overburden sands)

• T = 900 gpd/ft (bedrock)

Constituents of Concern Tetrachloroethene (PCE) and Trichloroethene (TCE)

Pre-Remediation Concentrations Total VOCs in Soil: 652 ppm, maximum

Total VOCs in Groundwater: 42 ppm, maximum

Volume of Contaminated Media 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)
59

Table 5.14. Timeline of remedial activities at Tinkham’s Garage.

Activity Completion

Period of Performance/Date of

Remedial Investigation January 1985

Feasibility Study July 1986

Record of Decision (ROD) Signed September 30, 1986

Vapor Extraction Pilot Study December 1987 - January 1988

Pre-Design Study July 1988

ROD Amended to Include Dual Vacuum Extraction March 1989

(DVE)

Discharge Strategies Evaluated August 1990 - July 1992

Construction of Sewer Line Between Derry and August 1993

Londonderry Begins

DVE Work Plan Submitted February 1994

Excavation and Restoration of Condominium Areas March - April 1994

DVE Construction and Drilling at Tinkham’s Garage May 1994

Begins

Issuance and Approval of Industrial Discharge Permit August - October 1994

to Town of Derry POTW

DVE System Operation Begins November 22, 1994

Closure Sampling Plan Submitted July 1995

DVE System Operation Terminated September 29, 1995

Final Soil Sampling Conducted October 1995

Final Site Inspection October 25, 1995

Demobilization of DVE System November 1995

Construction of Groundwater System for Management November - December 1995

of Migration (MOM)

MOM System Operation January 1996 - Present

Source: After Terra Vac (1996).
60

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 Derry POTW pretreatment 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 sfcm 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).
61

Figure 5.11. Schematic of DVE Well and Manifold (Terra Vac, 1996).
62

Figure 5.12. Process Flow Diagram of DVE System (modified from Terra Vac, 1996).
63

Table 5.15. Summary of DVE system performance data.

Parameter Value

DVE System Operation 311 days

SVE Vacuum at Blower 5 in Hg (68 in WC), average operational

value

SVE Flow Rate 500 scfm, average operational value

Cumulative Volume of Extracted Groundwater 1,116,500 gallons

Typical DVE Well Spacing 30 ft, approximately

(Radius of Influence)

Vapor Influent - Total VOCs Concentrations 16 ppm, maximum

1.7 ppm, average

(see Figure 5.13)

Groundwater Influent - Total VOCs 446 ppb, maximum

Concentrations 81 ppb, average

(see Figure 5.14)

Soil VOC Mass Removal (Rate) 48.25 lb (0.17 lb/d), Total VOCs

Groundwater VOC Mass Removal (Rate) 5 lb (0.02 lb/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; lb = pounds; lb/d = pounds per day

Source: Terra Vac (1996)
Vapor Phase Influent

02468

1012141618

Nov-94Dec-94Jan-95Feb-95Mar-95Apr-95May-95Jun-95Jul-95Aug-95Sep-95

Date

Total VOC Concentratioin

(ppm)

Plot reproduced from data reported in Terra Vac (1996). 2

64

Figure 5.13. Time variation of vapor phase VOCs in DVE system influent.2
65

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.
Aqueous Phase Influent

0

50

100150200250300350400450

Nov-94Dec-94Jan-95Feb-95Mar-95Apr-95May-95Jun-95Jul-95Aug-95Sep-95

Date

Total VOC Concentration 

(ppb)

Plot reproduced from data reported in Terra Vac (1996). 3

66

Figure 5.14. Time variation of aqueous phase VOCs in DVE system influent.3
Cumulative VOC Removal

05

101520253035404550

Nov-94Dec-94Jan-95Feb-95Mar-95Apr-95May-95Jun-95Jul-95Aug-95Sep-95Oct-9

Date

Total Vapor Phase VOCs Recovered 

(Lbs.)

Plot reproduced from data reported in Terra Vac (1996). 4

67

Figure 5.15. Cumulative vapor phase VOC removal by DVE.4
68

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 Derry 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
69

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, MA 01844

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/R01-89/046. 

March 10, 1989.

Terra Vac, Inc. “Remedial Action Report for the Tinkham’s Garage Superfund Site,

Londonderry, New Hampshire”, March 15, 1996.
70

6 REFERENCES

American Petroleum Institute. A Guide to the Assessment and Remediation of Underground

Petroleum Releases, 3 Edition, API Publication 1628, Washington, D.C., 1996. rd

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, 1997.

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. 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, 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, S.S. Remediation Engineering: 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.
71

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 Multiphase 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

<http://www.epareachit.org>

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/R01-89/046. 

March 10, 1989.

U.S. Geological Survey. “Ground-Water Contamination and Movement at the Defense

General Supply Center”, Richmond, Virginia, U.S. Geological Survey, WaterResources 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 14 Annual Conference on Contaminated th

Soils, University of Massachusetts, Amherst, MA, October 22, 1998.