EPA/540/AR-93/509
July 1993
ACCUTECH PNEUMATIC FRACTURING EXTRACTION
AND HOT GAS INJECTION, PHASE I
Applications Analysis Report
RISK REDUCTION ENGINEERING LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OH 45268
Printed on Recycled Paper
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Notice
The information in this document has been funded by the U.S. Environmental Protection
Agency under the auspices of the Superfund Innovative Technology Evaluation (SITE)
Program under Contract No. 68-CO-0048 to Science Applications International
Corporation. It has been subjected to the Agency's peer and administrative review, and
it has been approved for publication as an EPA document. Mention of trade names or
commercial products does not constitute an endorsement or recommendation for use.
11
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Foreword
The Superfund Innovative Technology Evaluation (SITE) Program was authorized in
the 1986 Superfund Amendments. The Program is a joint effort between EPA's Office
of Research and Development and Office of Solid Waste and Emergency Response.
The purpose of the program is to assist the development of hazardous waste treatment
technologies necessary to implement new cleanup standards with greater reliance on
permanent remedies. This is accomplished through technology demonstrations designed
to provide engineering and cost data on selected innovative technologies.
This project consists of a demonstration of the removal of chlorinated volatile organics
from vadose zones of low permeability using the Accutech Remedial Systems'
Pneumatic Fracturing Extraction(SM) process. The project also evaluated the effects, in
terms of heat transfer and VOC mass removal, of hot gas injection into the formation.
The study was carried out at an industrial park in Somerville, New Jersey where
removal of VOC contamination is necessary to comply with New Jersey's
Environmental Cleanup Responsibility Act (ECRA).
The goals of the study, summarized in this Applications Analysis Report and described
in more detail in the companion Technology Evaluation Report, were to evaluate the
pneumatic fracturing and vapor extraction process in terms of VOC mass removal rate
and economics and to assess, qualitatively, the effects of hot gas injection. The study
also considered the potential applicability of the process to other wastes and/or
Superfund and hazardous waste sites.
Additional copies of this report may be obtained at no charge from EPA's Center for
Environmental Research Information, 26 West Martin Luther King Drive, Cincinnati,
Ohio 45268, using the EPA document number on the report's front cover. Once this
supply is exhausted, copies can be purchased from the National Technical Information
Service, Ravensworth Building, Springfield, VA, 22161, 703-487-4600. Reference
copies will be available at EPA libraries in their Hazardous Waste Collection. To
obtain information regarding the SITE Program and other SITE projects, call 513-569-
7696 in Cincinnati, OH. To inquire about the availability of other SITE project reports,
call the Office of Research and Development (ORD) Publications in Cincinnati, OH at
513-569-7562.
E. Timothy Oppelt, Director
Risk Reduction Engineering Laboratory
111
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Abstract
This document summarizes and analyzes the results of a 4-wk evaluation of the
Accutech Remedial Systems, Inc. (ARS) Pneumatic Fracturing Extraction(SM) (PFE)(SM)
process for increasing the removal of volatile organic contaminants from the vadose
zone, particularly where the ground formation is relatively impermeable to air flow.
Based on the Superfund Innovative Technology Evaluation (SITE) Program
demonstration at an industrial park in Somerville, New Jersey and data from other
Accutech investigations, conclusions are presented concerning the technological
effectiveness and the economics of the process, and its potential utility for other sites.
During the SITE demonstration, operations were carefully monitored to establish a
database against which the vendor's claims for the technology could be evaluated
reliably. These claims were that PFE would increase extracted air flow rates from the
formation by at least 100% and the mass removal rate for the key contaminant,
trichloroethene (TCE), by at least 50%. In addition, although no claim was made,
evaluation of hot gas injection was also an objective.
It was found that Pneumatic Fracturing Extraction (PFE) does increase extracted air
flow rates by considerably more than 100% and TCE removal rate by much more than
the claimed 50% at this site. Specifically, based on comparison of 4-hr test results
before and after fracturing, air flow rates were increased >600%, and TCE mass
removal rates increased ~675%. The increase in TCE mass removal rate appears to be
due primarily to the increased air flow since TCE concentrations in the extracted air
remained in the 50 to 60 ppmv range. In addition, the extracted air contained
significantly higher concentrations of other VOCs after fracturing. The radius of
influence for vapor extraction also was greatly enlarged by fracturing. Average
extracted air flow rates from peripheral monitoring wells increased by approximately
700% to 1,000% in wells 10 ft away, and 200% to 900% in wells 20 ft away.
With surrounding wells open as passive air inlets, the extracted air flow rate increase
after fracturing was even higher, -19,500%, and the TCE removal rate increased
-2,300%.
These results suggest that PFE can make low-permeable formations, such as the bedrock
at this site, suitable for vapor extraction. Fewer extraction wells would be required, or
remediation could be completed more quickly with PFE, thereby reducing remediation
cost.
IV
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With PFE, the cost for full-scale remediation of the site was estimated at $307/kg
($140/lb) of TCE removed based on the SITE demonstration experience and information
provided by the developer. Major cost factors were labor (29%), capital equipment
(22%), VOC emission control (19%), site preparation (11%), and residuals management
(10%). The nature of the formation, the nature and concentration of the contaminants,
and other factors, including site preparations, need for post-treatment, etc., may affect
total cost and operating efficiency. The cost estimate should be used with caution.
Based on the results of two experiments, the effects of hot gas injection remain unclear.
In one test (90-hr), temperatures in surrounding monitoring wells increased, but TCE
mass removal decreased when compared with a pretest without hot gas injection. In
a second test (24-hr), TCE mass removal rates increased, primarily due to increased air
flow rates, but temperatures did not increase.
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Contents
Notice . • »
Foreword »i
Abstract iv
Figures viii
Tables • • ix
Abbreviations and Symbols • x
Conversion Factors • • x|
Acknowledgements • • • • xii
1. Executive Summary • • • 1
Introduction 1
Conclusions 1
Discussion of Conclusions :...... 2
2. Introduction 4
The SITE Program • 4
SITE Program Reports I ..... 5
Purpose of the Applications Analysis Report 5
Key Contacts • 5
3. Technology Applications Analysis • 6
Introduction .• 6
Conclusions , 6
Discussion of Conclusions • 7
Applicable Wastes 10
Site Characteristics • 1°
Environmental Regulation Requirements 11
Materials Handling Requirements 12
Personnel Issues 12
Testing Issues • •• 12
4. Economic Analysis 14
Introduction • • 14
Conclusions 14
Issues and Assumptions . . • • • • 15
Basis for Economic Analysis 17
Results 21
5. Bibliography • 22
VI
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Appendices
A. 'Process Description 23
Introduction 23
Process Description , 23
B. Vendor's Claims for the Technology 27
Technology Overview 27
Theoretical Discussion of Pneumatic Fracturing Extraction 27
Hot Gas Injection ; '....; 29
Applicability 30
Integrated Systems 30
C. SITE Demonstration Results 32
Introduction 32.
Field Activities 34
Test Procedures 34
Results -..'...' 34
Air Flow Impact of Fracturing - Monitoring Wells Capped . ... .... 34
Trichloroethene Removal Before and After Fracturing •. 34
Physical Impact of Fracturing on the Formation 35
Passive Air Inlet Tests 37
Effect of Hot Gas Injection 37
GC/MS Analysis of Gas Samples 38
Quality Assurance 39
D. Case Studies
1. Soil Vat Tests . 40
2. Test Site - Newark, NJ . 41
3. Former Tank Farm - Richmond, Va 43
4. Industrial Site - Newark, NJ 44
Vll
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Figures
1. Conceptual Schematic of Pneumatic Fracturing 7
2. Site Plan with Pre-Existing Wells 8
3. Comparison of 4-hr TCE Mass Removal Rates 8
A-l. HQ Injector , 24
A-2. Wellhead Design 24
A-3. Wellhead Assemblies 24
A-4. Vapor Extraction System 25
A-5. Well Location Diagram , 26
B-l. Prefecture Vacuum Radius of Influence 28
B-2. Postfracture Vacuum Radius of Influence 28
B-3. Types of Soil and Rock Treatable ' 30
C-l. Site Plan 32
C-2. Comparison of 4-hr Air Flow Rates 35
C-3. Comparison of 4-hr TCE Mass Removal 35
C-4. Tiltmeter Contour Plots 36
C-5. Air Flow and TCE Mass Removal Rates • • • •; 37
C-6. Temperature in Wells, 90-hr HGI Test 38
C-7. TCE Mass Removal Rates, 24-hr HGI Test 38
D-l. Air Permeability Log, 9-11 ft Fracture Zone. 42
D-2. Air Permeability Log, 15-17 ft Fracture Zone 42
D-3. Effect of Fracturing, Richmond, VA Site 43
Vlll
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Tables
1. Effects of Fracturing, 4-hr Tests 2
2. Monitoring Well Extraction Tests 8
3. VOCs in Extracted Air, Before and After Fracturing 9
4. Passive Air Inlet Tests 9
5. Estimated Annual Costs for Large Scale Cleanup . 21
C-l. Analysis of Wells on Demonstration Site 33
C-2. Effects of Fracturing, 4-hr Tests 34
C-3. Maximum Pressure During Fracturing Events 35
C-4. Monitoring Well Extraction Tests 37
C-5. Passive Air Inlet Tests 37
C-6. Hot Gas Injection Test, 90-hr , 37
C-7. Hot Gas Injection Test, 24-hr 38
C-8. GC/MS Analysis of VOCs in Extracted Air 39
D-l Vat Tests of Pneumatic Fracturing 40
IX
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Abbreviations and Symbols
acfm actual cubic feet per minute
bis below land surface
BOD biochemical oxygen demand (mg oxygen/liter)
BTEX benzene, toluene, ethyl benzene, and xylenes
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act of 1980
cfm cubic feet per minute
COD chemical oxygen demand (mg oxygen/liter)
ECRA Environmental Cleanup Responsibility Act
GC/MS gas chromatograph/mass spectrometer
gpm gallons per minute
HSWA Hazardous and Solid Waste Amendments to RCRA - 1984
kwh kilowatt-hour
Mgd million gallons per day
mg/L milligrams per liter
NJDEPE New Jersey Dept. of Environmental Protection and Energy
NAPL Non-aqueous phase liquid
NPL National Priorities List
NPDES National Pollutant Discharge Elimination System
ORD Office of Research and Development
OSHA Occupational Safety and Health Administration or Act
OSWER Office of Solid Waste and Emergency Response
PEL Permissible Exposure Limit
POTW publicly owned treatment works
ppb parts per billion
ppm parts per million
ppmv parts per million by volume
psi pounds per square inch pressure
psia pounds per square inch pressure, absolute
psig pounds per square inch, gauge pressure
QA/QC quality assurance/quality control
RCRA Resource Conservation and Recovery Act of 1976
RREL Risk Reduction Engineering Laboratory
SAIC Science Applications International Corporation
SARA Superfund Amendments and Reauthorization Act of 1986
scfh standard cubic feet per hour
scfm standard cubic feet per minute
SITE Superfund Innovative Technology Evaluation
TCE trichloroethene or trichloroethylene
TSDF treatment, storage, and disposal facility
VOC volatile organic carbon (mg/liter)
X
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Conversion Factors
English (US) x
Factor
Metric
Area:
Flow Rate:
Length:
Mass:
Volume:
1ft2
lin2
1 cfin
1 gal/min
1 gal/min
1 Mgal/d
1 Mgal/d
1 Mgal/d
1 ft
1 in
1 yd
1 Ib
1 Ib
1 ft3
Iff3
1 gal
1 gal
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
9.29 x lO'2
6.45
2.83 x 10-2
6.31 x ID'5
6.31 x 10'2
43.81
3.78 x 103
4.3? x 10-2
0.30
2.54
0.91
4.54 x 102
0.454
28.32
2.832 x lO'2
3.785
3.785 x 10-3
m2
cm2
mVmin
m3/s
L/s.
L/s
m3/d
mVs
m
cm
m
g
kg
L
m3
L
m3
Pressure:
1 psia
51.71
cm Hg
ft = foot, ft2 = square foot, ft3 = cubic foot
in = inch, hi2 = square inch
Ib = pound
gal = gallon
gal/min (or gpm) = gallons per minute
m = meter, m2 = square meter, m3 = cubic meter
cm = centimeter, cm2 = square centimeter
L = liter
g = gram
kg = kilogram
cfin = cubic feet per minute
L/s = liters/sec
m3/d = cubic meters per day
XI
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Acknowledgements
This project was directed and coordinated by Mr. Uwe Frank, EPA SITE Technical Project
Manager in the Risk Reduction Engineering Laboratory - Cincinnati, Ohio.
This report was prepared for EPA's Superfund Innovative Technology Evaluation (SITE)
Program under the leadership of Herbert S. Skovronek of Science Applications International
Corporation for the U.S. Environmental Protection Agency under Contract No. 68-CO-0048.
Major contributors to the program were Susan Christians, Paul Feinberg, Omer Kitaplioglu, and
Rita Schmon-Stasik.
The cooperation and participation of John J. Liskowitz of Accutech Remedial Systems, Inc.,
Professor John Schuring the Hazardous Substance Management Research Center at the New
Jersey Institute of Technology throughout the course of the project and in review of this report
are gratefully acknowledged. Special thanks are offered to the staff of McLaren/Hart
Environmental Engineers, Inc.
Pat LaFomara and Carolyn Esposito ofUSEPA's Risk Reduction Engineering Laboratory
provided invaluable reviews of the draft reports.
Xll
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Section 1
Executive Summary
Introduction
Accutech Remedial Systems, Inc.'s Pneumatic
Fracturing Extraction(SM) (PFE)(SM) process has been
evaluated as a means of remediating a trichloroethene-
contaminated vadose zone over a contaminated
groundwater zone at an industrial park in central New
Jersey. Cleanup of the site is required under New Jersey's
Environmental Cleanup Responsibility Act (ECRA) before
new construction may be started. Operational and cost
data collected in this investigation serve as a basis, for an
evaluation of the utility of this technology for remediation
of this and other VOC-contaminated sites across the nation.
Supporting data from other studies of the process at other
sites are discussed hi Appendix D.
Conclusions
Based on the results of the SITE demonstration project
in Somerville, NJ and other information provided by the
developers, Accutech Remedial Systems, Inc. (ARS) and
the Hazardous Substance Management Research Center
(HSMRC) at the New Jersey Institute of Technology
(NJIT), several conclusions were reached.
Pneumatic fracturing does introduce additional
fractures into this shale formation and/or enlarges and
extends existing fractures, thereby extending the
vacuum radius of influence significantly. Extracted air
flow through the formation is increased considerably
more than the 100% claimed by the developer.
Largely as a result of the increased extracted air flow
rate, and perhaps due to accessibility of new pockets
of VOCs, the mass removal rate for trichloroethene
also is increased far hi excess of the 50% claimed by
the developer.
• Specifically, based on 4-hr extraction tests, prefracture
air flows of O.017 mVmin (<0.6 scfm) increased to
0.112 to 0.168 mVmin (4.0 to 6.0 scfm) or an average
increase of >600%. Trichloroethene (TCE) mass
removal rates increased from <4.9 mg/min (<11 x W6
Ib/min) to 38 mg/min (84 x 10'6 Ib/min), an average
increase of over 675%.
Access to and removal of other VOCs also appears to
be improved, since elevated concentrations (and
masses) not found hi the prefracture extraction test were
found hi the extracted air after fracturing.
Based on extraction tests from the peripheral
monitoring wells, average ah- flow rates were increased
from 700% to 1,000% hi wells at a 10 ft distance, and
even 200% to 900% hi wells 20 ft from the fracture
well.
The spatial uniformity of fracturing may be affected by
geological and man-made heterogeneities hi the
formation. Fracturing effects may be unpredictable hi
a heterogeneous formation; man-made structures, e.g.,
building foundations, sewer and utility lines, etc., may
affect the extent, direction, or effectiveness of
fracturing.
Water hi the formation may have removed additional
TCE (and other volatiles), but may also have adversely
affected the air flow and, hi the hot gas injection
experiments, heat transfer.
With radially placed wells open as passive ah- inlets,
significantly higher extracted ah flow rates (19,500%
increase) were obtained after fracturing and the TCE
mass removal rates also were increased (2,300%).
The total cost for Pneumatic Fracturing Extraction is
estimated at $307/kg or $140/lb of TCE removed based
on the demonstration. Major cost factors were: labor
(29%), capital equipment (22%), VOC emission control
(19%), site preparation (11%), and residues
management (10%). Several assumptions were made hi
developing this cost estimate.
The major advantages of Pneumatic Fracturing
Extraction are (a) the increase in air flow and VOC
removal achievable in "tight" rock formations; (b) the
reduction hi the number of wells that should be needed
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to remediate a specific site, i.e., greatly extended
radius of influence for a given number of wells; (c)
decreased time required to remediate a given area to a
certain level; and (d) elimination of the need to.
excavate and treat large volumes of soil.
The equipment needed to support this process is
considerably less than that which would be needed for
aboveground treatment systems such as incineration or
soil washing. Compared to conventional soil vapor
extraction, if that can be used cost-effectively, the only
additional equipment needed is a packer system and a
source of compressed gas for fracturing. Aboveground
treatment of the VOC vapors would require similar
equipment, such as carbon adsorption, incineration, or
catalytic destruction for either extraction process.
With proper selection and characterization of a site,
Pneumatic Fracturing Extraction should be well suited
to the treatment of vadose zones of low permeability
containing a wide range of VOC pollutants.
The measurable effects of hot gas injection remain
unclear. In one experiment of 90-hr duration,
extraction and monitoring well temperatures did
increase, but TCE mass removal rates decreased. In a
second experiment (24-hr), increased air flow rates
resulted in increased TCE mass removal rates, but no
temperature increase was observed.
Discussion of Conclusions
A mobile PFE system consisting of a source of
compressed air, a means of injecting the pressurized air
into the ground, and a conventional vapor extraction
system was evaluated under the Superfund Innovative
Technology Evaluation (SITE) program. Extensive data
were collected over about a 4-wk period (a) to compare the
ability of the extraction system to remove TCE and other
VOCs from the vadose zone before and after pneumatic
fracturing; (b) to identify the operational requirements of
the system; and (c) to establish bases for estimating the
cost of operation. In addition, two experiments, one of 90-
hr duration and one of 24-hr duration, were carried out to
evaluate hot gas injection. The data from these tests serve
as the primary basis for the foregoing conclusions.
Additional information from other field studies was
provided by Accutech and HSMRC.
An extensive Quality Assurance (QA) program was
conducted by SAIC in conjunction with EPA's QA
program, including audits and data review along with
corrective action procedures to correct specific problems.
This program assured the quality of the data derived from
the SITE project. Discussion of the QA program and the
results of audits, data reviews, corrective actions, etc. can
be found in the Technology Evaluation Report.
Well placement was designed so that the extracted air
flow rates in all directions and TCE concentrations could
be assessed before and after fracturing. The primary
evaluation consisted of 4-hr tests before and after
fracturing. Shorter tests and visual examination by
borehole camera were used to measure the effectiveness of
fracturing and to provide evidence of connections due to
fractures. Extensive data were collected on air flow rates,
pressures, and TCE concentrations. All results are
corrected to standard conditions (1 arm, 60°F).
The results of the SITE project demonstrated that PFE
created and/or enlarged fractures in the formation,
increased connections between wells, and made increased
removal of TCE possible (Table 1). Unexpected perched
water in the vadose zone appeared to interfere with air
movement between wells, but VOC-laden air still could be
extracted after fracturing at rates far above that claimed by
the developer.
Table 1. Effects of Fracturing, 4-hr Tests
Prefracture
Parameter
Prefracture
Restart Postfracture
Pressure, psia
Air flow, scfrn
TCE mass removal,
10-6lb/min
11.1
<0.6*
<10.9
11.1
<0.6*
<11.0
11.4
4.2±0.6
83.9±31
* HSMRC data indicate air flow <0.6 scfrn.
Based on the demonstration, there are several factors
that could be critical to cost-effective PFE operation at
other sites. First among these is the geological character
of the vadose zone formation, particularly its permeability,
i.e., how easily and effectively conventional soil vapor
extraction could be applied. Second is the spatial
uniformity of the formation. Natural fractures or ease of
fracturing may affect the extent and direction of fracturing
and, consequently, the number and placement of wells
needed for remediation. The presence of water in the
vadose zone and the solubility of contaminants in the water
will also be factors. Finally, any preferential pathways
such as buried sewers, pipelines, building foundations, etc.
may influence the direction, extent, and possibly the safety
of pneumatic fracturing. Another factor to consider when
comparing remediation options would be the concentration
of key pollutants that would reach the aboveground air
treatment system. Low concentrations may be more
appropriately adsorbed on carbon while higher
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concentrations (e.g., >50 ppm) may be more economically
incinerated or destroyed by catalytic systems,
Hot Gas Injection (HGI) experiments were carried out
to provide data on the transfer of heat to the formation and
TCE removal rate. In the first (90-hr) experiment,
increases in extraction and thermal monitoring well
temperatures were observed, but accompanied by a
decrease in TCE mass removal rate when compared with
a baseline experiment without hot gas injection. A second
experiment (24-hr) was conducted using new wells in an
area where successful horizontal fracturing had occurred
and where higher TCE concentrations were anticipated. In
this case, increased TCE mass removal rates, corresponding
to increased air flow rates, were observed, but with no
temperature increases.
Several factors may contribute to the anomalous results
in these HGI experiments, including the nature of the
baseline experiments used for comparison and the variable
presence of water in the zone. It remains unclear from the
experimental results whether injection of hot ah- can
increase VOC mass removal rate. Permeability of the
formation, water content, heat capacity of the formation,
etc. all may affect heat transfer. Even where good
connection exists between injection and extraction wells,
removal of VOC contaminants may be limited by diffusion
or desorption rate rather than dependent on the increased
volatilization induced by any heat transferred to the
formation.
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Section 2
Introduction
The SITE Program
The EPA's Office of Solid Waste and Emergency
Response (OSWER) and the Office of Research and
Development (ORD) established the Superfund Innovative
Technology Evaluation (SITE) Program in 1986 to promote
the development and use of innovative technologies to
clean up Superfund sites across the country. Now in its
eighth year, the SITE Program is helping to provide the
treatment technologies necessary to implement new federal
and state cleanup standards aimed at permanent remedies,
rather than quick fixes. The SITE Program is composed of
four elements: the Demonstration Program, the Emerging
Technologies Program, the Monitoring and Measurement
Technologies Program, and the Technology Transfer
Program.
The major focus has been on the Demonstration
Program, which is designed to provide engineering and
cost data on selected innovative technologies that are in an
advanced stage of development. To date, the
demonstration projects have not involved funding to
technology developers. EPA and the developers
participating in the program share the cost of the
demonstration. Developers are responsible for
demonstrating their innovative systems at chosen sites,
usually Superfund sites, although in this case a NJ ECRA
site was selected. EPA is responsible for developing a
mutually acceptable evaluation protocol, sampling and
analyzing specified streams, and evaluating all test results.
The result is an independent assessment of the
technology's performance, reliability, and cost. This
information will be used in conjunction with other data to
select the most appropriate technologies for the cleanup of
Superfund sites and other sites contaminated with
hazardous wastes.
Developers of innovative technologies apply to the
Demonstration Program by responding to EPA's annual
solicitation. To qualify for the program, a new technology
must have a pilot- or full-scale unit and must offer some
expected advantage over existing technologies. Mobile and
in situ technologies are of particular interest to EPA.
Once EPA has accepted a proposal, the Agency and the
developer work with the EPA Regional offices and state
agencies to identify a site containing wastes suitable for
testing the capabilities of the technology. EPA designs a
detailed sampling and analysis plan to evaluate the
technology thoroughly and to ensure that the resulting data
are reliable. The duration of a demonstration varies from
a few days to several months, depending on the type of
process and the quantity of waste needed to assess the
technology. Although it may be possible to obtain
meaningful results in a demonstration lasting one week for
an incineration process where contaminants are destroyed
in a matter of seconds, other technologies where
contaminant variability, system acclimation, and system
stability must be examined may require an extended period
of time. For Pneumatic Fracturing Extraction, it was
determined that approximately two weeks of operation,
with key tests lasting several hours before and after
fracturing, would be indicative of the effectiveness and
utility of the process. To evaluate the effects of Hot Gas
Injection, a test lasting several days was desirable.
After completing the demonstration, EPA prepares two
reports which are explained in more detail below.
Ultimately, the Demonstration Program leads to an analysis
of the technology's overall applicability to Superfund
problems.
The second principal element of the SITE Program is
the Emerging Technologies Program, which fosters the
investigation and development of treatment technologies
that are still at the laboratory scale. Successful validation
of these technologies can lead to the development of
systems to a stage ready for field demonstration. The third
component of the SITE Program, the Measurement and
Monitoring Technologies Program, provides assistance in
the development and demonstration of innovative
technologies to more efficiently characterize Superfund
sites. As part of the Technology Transfer Program, a
Technology Evaluation Report and an Applications
Analysis Report are published at the conclusion of each
demonstration. Research reports on emerging technology
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projects are also produced. Results and status updates are
distributed to the user community, including EPA Regions,
state agencies, remediation contractors, and responsible
parties, through many media and activities.
SITE Program Reports
The results of the SITE Demonstration Program are
incorporated hi two basic documents, the Technology
Evaluation Report and the Applications Analysis Report.
The former provides a comprehensive description of the
demonstration and its results. The anticipated audience
will be industrial and governmental engineers responsible
for detailed evaluation of technologies for other sites and
contaminant situations. These technical evaluators will
want to understand thoroughly the performance of the
technology during the demonstration and the advantages,
risks, and costs of the technology for the given application.
The Applications Analysis Report is directed to
decision-makers responsible for selecting and implementing
specific remedial actions. This report provides sufficient
information to determine if the technology merits further
consideration as an option in cleaning up specific sites. If
the candidate technology described in the Applications
Analysis Report appears to meet the needs of a site, a more
thorough analysis of the technology will be made based on
the Technology Evaluation Report and other information
such as previous remedial investigations for the specific
site. In summary, the Applications Analysis Report will
assist in determining whether the specific technology
should be considered further as an option for a particular
cleanup situation.
Purpose of the Applications Analysis Report
Each SITE demonstration will evaluate the
performance of a technology while treating the particular
waste found at the demonstration site. Additional data
from other projects also will be presented where available
to assist in evaluation of the applicability.
Usually the waste at other sites being considered for
remediation will differ in some way from the waste tested.
Waste and site characteristics could affect treatability, cost,
and the advisability of using the demonstrated technology
at other sites. Thus, successful demonstration of a
technology at one site does not assure that a technology
will work equally well at other sites. The operating range
over which the technology performs satisfactorily can only
be determined by examining a broad range of wastes and
sites. The Applications Analysis Report provides an
indication of the applicability of the demonstrated
technology, Pneumatic Fracturing Extraction in this case,
by examining not only the demonstration test data, but also
data available from other field applications of the
technology.
To encourage the general use of demonstrated
innovative technologies, EPA evaluates the probable
applicability of each technology to sites and wastes in
addition to those tested, and studies the technology's likely
costs in these applications. The results of these analyses
are summarized and distributed to potentially interested
parties through the Applications Analysis Report.
Key Contacts
For more information on the demonstration of the
Accutech Pneumatic Fracturing Extraction and Hot Gas
Injection processes for decontamination of low permeability
vadose zones, please contact:
1. Vendor concerning the process:
Harry Moscatello, President
John J. Liskowitz, Development Engineer
Accutech Remedial Systems, Inc.
Cass Road at Route 35
Keyport, New Jersey 07735
908-739-6444
and
Prof. John Semiring, Ph.D.
Hazardous Substance Management Research Center
New Jersey Institute of Technology
Newark, New Jersey 07102
201-596-5849
2. EPA Technical Project Manager concerning the SITE
Demonstration:
Mr. Uwe Frank
U.S. EPA - ORD
Releases Control Branch (MS-106)
2890 Woodbridge Avenue
Edison, NJ 08837-3679
908-321-6626
3. Contact concerning the site:
Mr. James Mack
McLaren/Hart Environmental Engineers, Inc.
25 Independence Boulevard
Warren, New Jersey 07059
908-647-8111
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Section 3
Technology Applications Analysis
Introduction
This section of the report addresses the potential
applicability of the Accutech Pneumatic Fracturing
Extraction (PFE) process to various other -contaminants,
formations, and Superfund site situations where volatile
organic pollutants are of primary interest. The
demonstration provided an extensive database for this
process and serves as a foundation for conclusions on the
effectiveness and the applicability for cleanup of other
sites. Supporting information provided by the developer is
also referred to when considering the applicability of the
technology to other situations.
The following subsections summarize conclusions and
observations drawn from the current study and supporting
information. Included are factors such as contaminant
types, site characteristics and constraints, applicability and
impact of state and federal environmental regulations,
unique handling or operating requirements, and personnel
requirements. Additional information on the ARS
technology, including a process description, vendor claims,
a summary of the Demonstration test results, and Case
Studies of other investigations is provided in the
Appendices.
Conclusions
Based on the results of the demonstration study and
other information provided by the developer, the vendor's
claims are substantiated.
The Pneumatic Fracturing Extraction process can
increase ah* flow through relatively non-permeable vadose
zone formations by 400 to 700%, averaging 600% at this
site. The increase may not be uniform in all directions nor
at all depths, depending on the character of the formation
and other influences.
With the increase hi extracted ah- flow, the removal of
VOCs, in terms of mass oftrichloroethene (TCE) removed
per unit time, is also increased, approximating 675%, based
on the comparison of results of 4-hr tests before and after
fracturing. Fracturing of the vadose zone also appears to
have increased the accessibility and removal of other
chlorinated hydrocarbons and benzene which had not been
detected during vapor extraction before fracturing.
Based on short duration (10-min) extraction tests at the
monitoring wells, PFE increased the permeability of the
formation, in terms of average extracted air flow rate,
between 700% and 1,000% in wells at 10 ft and 200% and
900% hi wells 20 ft from the fracture well.
Allowing air to enter at four wells (passive air inlet)
while extracting from the fracture well produced even
larger increases hi air flow and TCE mass removal rates,
approximately 19,500% and 2,300%, respectively. When
compared to the postfracture extraction with wells capped,
TCE mass removal rate was increased 38%.
The costs for the PFE .process are estimated on the
basis of the pilot plant and other data provided by
Accutech and HSMRC. For a surface area of 15,000 ft2
and a vadose zone depth of 20 ft, a predicted fracturing
radius of 25 ft with 15% to 20% overlap, 15
fracture/extraction wells would have to be installed to
cover the area. On this basis, the estimated cost for a 1-yr
cleanup effort is $307/kg, or $140/lb of TCE removed.
Labor is the major cost factor, accounting for 29%; capital
equipment accounts for 22%; and collection and disposal
of VOC emissions accounts for another 19% of the costs.
Site preparation and residuals disposal account'for 11% and
10%, respectively.
The PFE process provides a means of carrying out
vapor extraction of volatile contaminants from low
permeability formations such as bedrock, where poor
permeability and poor connection between extraction well
and a source of air would normally preclude such a
process. This may provide an attractive 'alternative to
costly excavation and ex-situ treatment.
The system is simple to operate and requires a
minimum of operator attention or maintenance once
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fracturing has been accomplished. The pneumatic
fracturing is a rapid operation that can be applied over an
extended area at relatively low cost. Vapor extraction also
is a relatively low cost operation, although treatment of the
extracted vapors can affect economics.
The impacts of hot gas injection into the fractured
formation,, in terms of heat transfer, air flow, and TCE
mass removal, were unclear and remain open to
interpretation. In one experiment, increases were observed
in well temperature (to ~656F to 85°F), but TCE mass
removal decreased. A second, shorter experiment provided
contradictory results: increased TCE mass removal rates at
increased injected (and extracted) air flow rates, but no
elevated temperatures in the extraction wells.
to make an informed decision concerning a more extensive
Phase II study of the PFE technology, catalytic oxidation
(Catox), and Hot Gas Injection (HGI).
The SITE Program demonstration in Somerville, New
Jersey clearly indicated that fracturing was an attractive
means of increasing the removal of volatiles from a low-
permeable vadose zone with minimum disturbance of the
formation or the surface. Figure 1 conceptually describes
a bedrock formation before and after fracturing. Figure 2
indicates the location of the wells used in this investigation
of Pneumatic Fracturing Extraction, including monitoring
wells that could be used as injection or extraction wells in
a more extensive test or remediation (see next pages).
Discussion of Conclusions
The developer originally had proposed an extensive
program integrating PFE with catalytic oxidation of
extracted chlorinated volatile organics and injection of the
exhaust gas from the catalytic oxidation unit. Sufficient
information was not available for this site at the outset of
this demonstration to justify such an expenditure of time
and resources by all parties. Consequently, a Phase I study
consisting of short term tests was considered a practical
and cost-effective means of obtaining a reliable evaluation
of the primary technology, PFE. EPA would then be able
Air Flow Increase with Fracturing
Based on pressure and ah- flow measurements at the
fracture well and at monitoring wells before and after
fracturing, it is concluded that the connectivity between
wells can be considerably increased by fracturing but may
vary with direction, distance, and the nature of the
formation between two wells. Surprisingly, the existing
strike and dip direption did not have an impact on the
fracturing pattern and preferential ah- flow was not
observed. The results in Table 2 were obtained during 10-
miri extraction tests at each monitoring well before and
after fracturing.
Norm«l "Tight" Formation . uflpof Eurasian
^ —
^*f
f
E
X
t
r
c
t
1
0
W
i
i
. '
^^
~
A
A
1
r
1
n
i
t
1
n
Mlnln
—_ _^__ Mlnln
^"*"*
' NAPL
Slow,
Muttl|
NAPL Pockets Remain
Slow, Incomplete Removal
Multiple Wells Required
Pneumatic Fracturing
Increased Air Flow
Multiple Fractures
Created/Enlarged
More Rapid VOC Removal
NAPL Pockets Accessed
Minimal Number of Wells
Figure 1. Conceptual Schematic of Pneumatic Fracturing.
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Building
MW-2
Concrete Foundation
(of former building)
Tree Line
Figure 2. Site plan with pre-existing wells.
I
o>
Tabta 2. Monitoring
Dtstanco Welt
(torn FW, No.
ft
7.5d' FMW 6
10 s FMW 1
10 ols FMW 2
10 d FMW 3
10s FMW 4
20 s FMW 5
20 d FMW 7
A prefecture air flows
* $ - strike; d - dip ;
Well Extraction Tests
Air flow rate,
scfm avg
pre-fracfure post-fracture
<.89A 6.1
<.63 5.6
<.74 6.1
<.63 7.2
<.63 6.9
<.63 6.5
<.63 2.0
based on HSMRC data.
o|s - off strike and dip
Increase,
% avg
>580
>790
>720
>1040
>990
>930
>220
170
ISO
ISO
140
= 130
E mass flow rate, 10* Ib/n
SSSSSSsS
o *
H 30
20
10
n
-
\ poatfracture
prefracture restart
. prefracture , , ,
Increase in Trlcltloroethene Removal with Fracturing
Field analyses before and after fracturing indicated that
the mass of TCE removed over the course of the 4-hr test
period paralleled the increase in air flow. On the basis of
these results (Table 1, earlier), the developer's claim that
the mass removal rate for TCE from the formation could
be increased by 50% or more was clearly validated and
considerably exceeded. Figure 3 graphically presents the
increase in TCE mass removal achieved by fracturing in
the 4-hr tests.
0 20 40 60 00 100 120 140 160 ISO 200 220 24O
Elapsed time, mln
Figure 3. Comparison of 4-hr TCE mass removal rates.
The experiments examined the relatively short term (4-
hr) benefits of fracturing; extrapolation to long term
benefits, e.g., total VOC removed or the final
concentrations in the formation, should be done with
extreme caution. For example, the data clearly show larger
TCE mass removal rates during the first 30 min of testing,
particularly during the postfracture test.
-------
Analysis of samples by gas chromatography/mass
spectrometry (GC/MS) confirmed TCE as a major
contaminant before fracturing and confirmed the field GC
indications of significantly higher concentrations for
several other contaminants after fracturing, including other
chlorinated hydrocarbons and benzene (Table 3).
Fracturing may have provided access to pockets of these
NAPLs (non-aqueous phase liquids). Considering the very
large increases in air flow after fracturing, removal of such
other contaminants becomes very significant.
Table 3. VOCs in Extracted Air, Before and After Fracturing
Contaminant
Concentration, ppmv
Prefracture Postfracture
Melhylene chloride
Chloroform
c- 1 ,2-dichloroethene
Trichloroethene
Benzene
Tetrachloroethene
Toluene
Xylene, m/p-
Xylene, o-
1.4
3.5
U(<3)
59.4
5.4
3.3
U (<3.3)
U (<2.8)
U (<2.8)
26.0
108.5
U (<12.5)
113.4
412.7
220.4
5.2J
U (<11.4)
U (<11.4)
U = below detection limit
J — estimated, below quantitation limit
Additional tests were carried out by extracting from
the fracture well while up to 4 of the monitoring wells
were left uncapped to allow for passive ah- inlet. Under
these conditions, the extracted ah- flow and TCE mass
removal rates after fracturing increased even more
dramatically when compared with the prefracture results
(Table 4), although air flow rate increased more than TCE
mass removal rate.
Table 4. Passive Air Inlet Tests
Parameter Prefracture Postfracture
Increase, %
Pressure, psia
Air flow, scfm
10.8
0.39+.04
14.6
76.4+4.8
....
19,500
TCE mass removal,
10-6lb/min
4.79±1.4
116.0±91
2,270
Operational Reliability/Stability
The extraction system proved to be quite stable and
required a minimum of attention over the course of the 4-
wk study. Unexpected water hi the vadose zone did
present a problem, and it was found necessary to pump the
wells daily, prior to each day's tests, to assure that the
needed open zone (from the 8 ft deep casing to the -20 ft
well bottom) was available for testing. Obviously, some
TCE was removed hi this water as well, but, because of the
nature of the test program, this removal route was
considered outside the scope of the study. Although this
contribution to TCE mass removal was not routinely
measured, analyses for disposal indicated TCE
concentration to be -100 ppb. Other than this pumping,
which might or might not be needed at other sites, little
attention to the system was necessary once the fracturing
was completed and the extraction system had been
stabilized. The exhaust vapors were passed through a
granular activated carbon adsorption tram to remove the
VOCs and the exhaust was checked daily by OVA for total
VOCs to assure that contaminant breakthrough into the
atmosphere was not occurring.
Similarly, during Hot Gas Injection a minimum of,
attention was required once compressor pressure and air
flow had been adjusted to maintain a constant injection
temperature (~200°F to 250°F). In a fully integrated
system, where hot gas (~1000°F) would be generated as a
by-product of catalytic oxidation of VOCs, some additional
attention may be needed to maintain temperature balance
as the concentration of VOCs in the extracted gas and the
amount of heat resulting from VOC decomposition
decreases.
Costs
Cost data were developed for a hypothetical 40 hp (500
cfin) extraction unit on the basis of experience during the
SITE demonstration, assuming that wells would be spaced
in accordance with the fracture/extraction radius observed
hi the demonstration. The major cost factors for PFE were
found to be the labor required during fracturing and to
oversee the ongoing vapor extraction (29%); the amortized
cost of capital equipment (22%); collection of VOCs on
activated carbon (19%); site preparation (11%); and
management of residuals (10%). In the absence of a
catalytic oxidizer for the TCE (and other volatiles) in the
extracted gas, use of carbon adsorption for emission control
would be continued and, as noted, contributed significantly
to overall cost.
For this cost estimate, it was assumed that water would
be present in the vadose zone, as at the demonstration site.
In the demonstration, this water was accumulated in a
tanker truck and disposed of off-site at a cost of about
$ I/gallon as hazardous waste. A more realistic alternative
for a larger scale remediation would be to air strip this
perched water on-site together with the groundwater and
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adsorb the volatiles on carbon until a catalytic oxidation
unit is available. The cost for the carbon canisters used for
emission control in the demonstration, including carbon
disposal and replacement, was $1120/drum, or about $4/lb
of carbon. Combining the water streams, air stripping, and
carbon adsorption was selected as the most realistic option
for the hypothetical cost model; no incremental cost for
stripping or the carbon used for the VOCs from the
perched water was included.
It would not be meaningful to estimate the cost
parameters for Hot Gas Injection on the basis of this
demonstration. Production of hot air, as done hi the
demonstration by compression of air, is not the intended
approach in a remediation; hot gas production cost would
be a derivative of the catalytic destruction cost and was not
considered in this analysis.
Applicable Wastes
Although this study of the Accutech Pneumatic
Fracturing Extraction system was directed to
trichloroethene, which was expected to be the predominant
contaminant in the vadose zone at the site, the technology
should be equally well suited to other volatiles, both
chlorinated and non-chlorinated, as suggested by the
removal of other volatiles (BTX) during the postfracture
segment of this demonstration and in results provided by
the vendor for other sites. These may be present as
adsorbed material, dissolved in water, or as pockets of
"NAPLs", non-aqueous phase liquids. Such NAPLs can be
lighter than or heavier than water. The design of the
system is such that even elevated concentrations of
contaminants in the vadose zone should not affect
operation, except in determining the length of time the
system may be needed at a particular site to achieve a
specified removal or final concentration. In addition, the
choice of final treatment for the extracted volatiles (e.g.,
stripping, incineration, or carbon) and the scaling of that
treatment system would also be dependent on the nature of
the VOCs and their concentrations, as in any vapor
extraction.
Ground temperatures, water in the vadose zone,
solubility of the VOCs in water, volatilization rates, and
the vapor pressure of the VOCs also could affect the
operation and cost of the PFE process, but were not studied
in the demonstration.
Other pollutants in the vadose zone should not
adversely affect the operation of the system except that, if
extracted into the air stream, their removal would have to
be addressed. And, if Hot Gas Injection were used to
accelerate VOC removal from a site, transfer of
semivolatiles into the gas stream may increase
simultaneously. As noted, however, the demonstration
results did not consistently indicate increased TCE removal
rates from the injection of hot ah- (200°F to 250°F).
Site Characteristics
Vapor extraction is an appropriate innovative removal
approach for VOCs from unsaturated ground formations
where sufficient air flow for extraction can be achieved.
PFE would offer an attractive alternative for formations
which have insufficient air permeability for conventional
vapor extraction. This could include shales such as the
Brunswick formation, found widely across the northern part
of New Jersey, as well as silts and clays of low
permeability. Such geological characteristics may be found
elsewhere in Superfund and RCRA sites. Other studies by
HSMRC have shown that the benefits of fracturing, in
terms of increased permeability, are inversely related to soil
particle size, and that the technique can improve vapor
extraction effectiveness, even in more permeable soils,
although not to as great an extent. Appendix D presents
summaries of such evaluations.
Since the fracturing wells are best left uncased to allow
fracturing hi several narrow intervals, the formation must
have enough integral strength not to collapse or recompress
during well drilling, fracturing, or vapor extraction.
Although some settling of fractures with time may be
tolerable, ideally the voids created or enlarged during
fracturing must remain open for air flow or re-fracturing
may be required. Finally, the nature of the formation must
be such that preferential horizontal fracturing occurs, rather
than vertical fracturing, particularly where the water table
is close to the zone being fractured and. could be
contaminated further by vertical movement of
contaminants.
Extensive three-dimensional characterization of the
formation (including water levels, natural fractures, strike
and dip orientation, etc.) would be helpful in planning the
well field and anticipating the radius of influence of each
fracturing effort at a particular site. Obstacles such as
building foundations, underground utilities, and sources of
"short circuiting" such as pipelines, permeable soil lenses,
etc., need to be identified and, if possible, avoided or at
least factored into the cleanup plan. For example, during
fracturing at the demonstration site, an unexpected escape
of air and vapors occurred at an abandoned and unmarked
borehole about 30 ft from the fracture well.
To date, PFE has been applied to the decontamination
of the unsaturated. zone. However, in some situations it
may also be used cost-effectively to treat NAPLs in
10
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saturated zones, where the water table can be lowered by
pumping or natural drying (e.g., seasonal), leaving the
NAPLs absorbed in the dewatered formation. Presumably,
any water pumped from such a site would require some
treatment to remove and treat the dissolved or dispersed
organics in the water. Research at HSMRC has also
developed evidence that fracturing can be carried out in a
saturated zone without dewatering and subsequent VOC
removal by a combination of stripping and vapor extraction
is enhanced.
The mobile extraction system and the staging area for
the compressed air source used in the demonstration
program required only a level work area of approximately
50 ft by 50 ft. Electrical power for the extraction unit and
for pumping of well water was provided by temporary
service to the site, but a diesel generator could be used just
as effectively. Obviously, the site must be sufficiently
accessibie to allow a drill rig to be positioned for the
installation of the necessary wells.
Depending on local, state, and federal requirements,
extracted VOCs may be emitted into the atmosphere
(unlikely), adsorbed from the extracted air on carbon as
was done during the demonstration, or destroyed by
incineration or the proposed catalytic oxidation. Water
pumped from the formation would presumably contain the
contaminants (both volatiles and others) present in the zone
and could require treatment to meet discharge or
reinjection requirements. Since vapor concentrations
suitable for PFE are equivalent to significantly lower
concentrations in the water phase, any wastewater may be
acceptable for discharge to surface water or to a POTW
without pretreatment.
Environmental Regulation Requirements
A first concern would be state or local well-drilling
requirements, including permits and management of well
cuttings. In some cases, as at the demonstration site, there
may be concern about penetration of the wells into the
underlying groundwater. This was originally expressed in
DEPE's review comments concerning the ECRA Cleanup
Plan, where well depth was limited to 25 ft.
Water removed during well drilling or subsequently
must be disposed in accordance with federal and/or state
regulations, as a hazardous waste if it contains sufficiently
high concentrations of VOCs or other contaminants
(organic and inorganic). Treatment (e.g., air stripping)
may be required before the water can be discharged to
surface water or introduced into a POTW as non-
hazardous. Such ancillary activities may require a NPDES
Permit or a RCRA Part B permit as a TSD facility. And,
depending on the volume, rate of production, and
characteristics of the water, any tanks used for storage or
to provide equalization may themselves need regulatory
attention (permits, design, etc.), depending on their size and
placement.
The removal, treatment, and disposal of groundwater
was not part of this project but is addressed for this site in
the ECRA Cleanup Plan. State or federal permitting would
be required for treatment and discharge of any such
groundwater at other sites, as well.
Under the Comprehensive Environmental Response,
Compensation, and Liability Act of 1980 (CERCLA) and
the Superfund Amendments and Reauthorization Act of
1986 (SARA), EPA is responsible for determining the
methods and criteria for the extent of removal of hazardous
contaminants from Superfund sites. The utility and cost
effectiveness of the PFE system would, at such sites, be at
least partially dependent on the final level deemed
appropriate and necessary at a particular site. However,
since the use of remedial actions by treatment that
"...permanently and significantly reduces the volume,
toxicity, or mobility of hazardous substances" is strongly
recommended (Section 121 of SARA), the PFE system
coupled with appropriate aboveground treatment would
appear to be an attractive remedy for a site where the
vadose zone is contaminated with hazardous VOCs.
SARA also requires consideration of potential
contamination of the ambient air and general criteria
requiring remedies that protect human health and the
environment. Any vapor extraction process such as PFE
would probably require further treatment of emissions, such
as catalytic oxidation or carbon adsorption (and disposal of
carbon) to assure that hazardous VOCs are not emitted to
the ambient ah-. Depending on the location of a site, this
might be addressed as part of an air emissions or a
hazardous waste permit. The overall impact of the Clean
Ah- Act of 1990 is not yet clear, but a permit may be
required if certain VOCs are present or the quantity of
emissions is large.
At the demonstration site, fugitive VOC emissions
occurred during the initial stages of Hot Gas Injection.
From both a worker safety and an environmental point of
view, it would be necessary to assure, to the maximum
extent possible, that such "short circuiting" through vertical
fractures, sewer lines, etc., did not occur during a site
remediation. Although OSHA does not issue permits, it
would be an operator's responsibility to monitor and
document that emitted concentrations of VOCs were below
allowable airborne concentrations. For example, the
current Permissible Exposure Limit (PEL) for TCE is 100
11
-------
ppmv; a new standard, currently in litigation, would reduce
this exposure limit to 50 ppmv.
Chlorinated ethenes and ethanes in groundwater
occasionally have been found to produce vinyl chloride,
probably by anaerobic biodegradation. Although none was
found at the New Jersey site, characterization of other sites
should probably include measurement for vinyl chloride
and dichloroethenes and additional controls if these species
are present in significant concentrations. The PEL for
vinyl chloride is 1.0 ppmv; it will not change with the new
OSHA standards.
The use of Hot Gas Injection could raise several
additional regulatory issues. Accutech has proposed that
the hot exhaust gases from catalytic oxidation of the VOCs
be injected directly. Since these gases may be
contaminated, as with HC1 from the destruction of
halogcnated VOCs, direct injection may not be acceptable
unless it can be demonstrated that such contaminants do
not adversely affect the formation or leach into
groundwater at the site. For example, acid gases could
solubilizc metals in the soil. Such situations could be
avoided by scrubbing the gas prior to injection or by using
a heat exchanger.
Materials Handling Requirements
The materials handling requirements for the Pneumatic
Fracturing Extraction process are quite limited since the
process is carried out "in situ", at least relative to
excavation. The site must be able to support a well
drilling rig capable of drilling through shale or other
relatively impermeable formations.
Full-scale remediation of a site using PFE must be
designed with appropriate air treatment to remove the
extracted VOCs (and semivolatiles) from the air stream
before it is exhausted to the environment. Carbon
adsorption may be the most appropriate method for low
concentrations (and masses) of contaminants, but alternate
means, such as the catalytic oxidation proposed for Phase
II study by Accutech, may be more cost-effective at higher
(>SQ ppmv) concentrations. Similarly, any water removed
from the formation before, during, or after fracturing or
vapor extraction would also require treatment prior to
discharge. This can be accomplished by stripping and
carbon treatment or, as suggested by Accutech for Phase II
study, by stripping and catalytic oxidation of the vapors.
Although the matter was not investigated as part of
this Phase I demonstration, it may be necessary to use high
temperature grout when installing well casings that will be
exposed to extreme heat during Hot Gas Injection from
catalytic destruction. Some products exist to meet this
need.
Personnel Issues
Well drilling also would be a labor-intensive phase of
the Pneumatic Fracturing Extraction process. Although a
certain number of wells covering the area being remediated
can be installed at the outset, additional wells may be
needed as the actual radius of influence resulting from each
fracturing well is determined.
Except during the well drilling and the actual fracturing,
installation and operation of the PFE system requires little
attention. Although a number of personnel were needed
during the demonstration to observe and record data at the
several wells and other tasks, vapor extraction normally
operates unattended once steady state operation is achieved.
If the water table must be suppressed or perched water
must be pumped out to provide an unsaturated zone for
fracturing and extraction, then the labor requirements could
increase somewhat. Less labor-intensive operation could
be achieved with automatic level-activated pumps.
Treatment of extracted vapors (and pumped water) may
also increase manpower requirements slightly but, again,
these operations can usually be unattended once a steady
state is established.
Testing Issues
Probably the most important testing for the use of
Accutech's Pneumatic Fracturing Extraction process takes
place during site characterization and includes profiling the
formation and determining the nature and concentrations of
contaminants in the strata. This makes it possible to plan
the most efficient well field and fracturing protocols for the
site with minimal risk of groundwater contamination or
short circuiting to the surface. Such a testing program
would entail groundwater flow measurements, air
permeability tests, geological characterization, contaminant
characterization, documentation of all underground utilities,
and where possible, soil gas or other vapor phase analysis
of VOCs in the vadose zone.
Pressure and ah- flow measurements can be indicators
of extraction efficiency, but pollutant-sp'ecific analysis
ultimately is necessary. Because of the rapid changes hi
VOC concentrations expected during the .demonstration,
on-site monitoring of the extracted air by gas
chromatography of Tedlar bag samples was selected as the
most cost-effective methodology. It was found that the
number of analyses that could be carried out within
12
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Method 18 specified Tedlar bag holding time (2 hr) was
limited, particularly when numerous volatile constituents
were present in the extracted gas. During remediation of
larger sites, this should not be a problem since such an
extensive evaluation of the offgases should not be
necessary. If variable concentrations or compositions are
anticipated, or if significant concentrations ofsemivolatiles
are expected as well, more complete GC/MS analyses may
be desirable. In those cases, collection of air samples in
Summa canisters or on adsorbents may be necessary to
allow for the more tune-consuming analyses, using EPA
standard methods, unless an on-site GC/MS is available.
Once characterization has been completed, routine semi-
quantitative monitoring by instruments such as the OVM
may be sufficient. Portable organic vapor analyzers should
also be in use at the site to monitor VOC levels during
drilling and to detect any unexpected vertical fracturing
leading to short-circuiting to the surface, as was
encountered during Hot Gas Injection at the demonstration
.site. This will provide protection for workers and the
ambient air. The portable vapor analyzers, coupled with
quantitative and pollutant-specific analysis by GC or
GC/MS, also may be needed to fulfill air permit
requirements.
13
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Section 4
Economic Analysis
Introduction
The primary purpose of this economic analysis is to
estimate costs for commercial-scale remediation using the
Accutech PFE system based on the experience gained
during the demonstration. With realistic costs and a
knowledge of the bases for then- determination, it should be
possible to estimate the economics for operating similar-
sized systems as well as larger systems at other sites
utilizing various scale-up approaches and cleanup
scenarios.
Cost and efficiency for vapor extraction are dependent
on the concentration present, the areal extent of
contamination, the distribution of contaminants among
different matrices, and soil characteristics, e.g., air
permeability, etc. One key factor that may not be
accurately predictable without a pilot test is the radius of
influence and, consequently, the number of wells needed to
remediate a particular site. The cost of conducting such a
pilot study is not included here.
Although the cost of remediation is often presented in
terms of dollars to achieve a final cleanup level on the site,
that approach could not be applied in this situation because
no final cleanup criteria for the air or soil had been
established. Instead, costs in twelve categories for an
assumed 1-yr cleanup time were estimated. As in the SITE
demonstration, the primary contaminant of interest was
assumed to be trichloroethene (TCE). The sum of these
costs was then divided by the total mass of TCE that could
be removed in the same 1-yr time period, assuming that the
performance of a commercial-scale remediation would be
comparable to that demonstrated under the SITE program
and would remain constant for the entire year.
As expected, even in a 4-hr test, the TCE mass
removal rate was higher at the start than at the end. It is
difficult to extrapolate performance over a 1-yr time period
based on 4 hr and it must be expected that airborne
concentrations and removal rates will gradually decrease
over the year. Therefore, the reader is cautioned that the
TCE mass removal rate used for this economic analysis is
optimistic hi assuming that it remained constant at the 4-hr
rate over a 1-yr tune period. In addition, the cost to
remove a unit mass of TCE is considerably lower at the
beginning of treatment than at the end when concentrations
are lower and the distribution of the contamination among
matrices may be different. Cost estimates also are
provided for the subsequent aboveground removal of TCE
from the extracted gas stream, although this cost varies
with the concentration, scale of remediation, and method.
Costs and assumptions were based on information
provided by Accutech and HSMRC, and on results and
observations gained from this SITE demonstration,
particularly the 4-hr postfracture extraction test. Certain
actual or potential costs were omitted because site-specific
engineering aspects beyond the scope of this SITE project
would be required or the item was assumed to be the
obligation of the responsible parties or site owner. Cost
figures provided here are "order-of-magnitude" estimates,
generally +50% to -30%, and are representative of charges
typically assessed to a client by the vendor.
The developer has indicated that process operation may
be altered from that which was demonstrated to enhance
contaminant removal, especially hi the latter stages of
remediation. Among these changes may be:
• repeat fracturing
• passive air inlet
• intermittent operation or pulsing
• forced hot gas injection, and
• air stripping of VOCs contained in the perched
and/or groundwater, and subsequent treatment with
the extracted soil vapor air stream.
The impact that these changes would have on costs has not
been taken into account here.
Conclusions
• The cost to extract 1 Ib of VOC measured as TCE with
the Pneumatic Fracturing Extraction process assuming
14
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that the 4-hr postfracture extraction rate was
maintained for 1 yr, was $140 ($307/kg). A
comparison with conventional vapor extraction really
should not be made since the formation is so
impermeable that vapor extraction would not be
practical.
For full-scale remediation using PFE with a 500 cfm,
40 hp mobile extraction unit operating at 300 cfin, the
largest cost component is labor (29%), followed by
capital equipment (22%), emission treatment and
disposal (19%), site preparation (11%), and
residuals/waste shipping and handling (10%). The
remaining five cost categories combined accounted for
the remaining 9%.
Operational process changes to minimize residuals and
waste, as suggested by the developer, may reduce costs
further. These improvements were not considered.
No cost analysis or evaluation was carried out for Hot
Gas Injection since the intended source, a catalytic
oxidation unit, was not employed.
Issues and Assumptions
This section summarizes the major issues and
assumptions used to evaluate the cost of Accutech's
Pneumatic Fracturing Extraction system. In general,
assumptions are based on information provided by
Accutech and observations during the demonstration
project. Certain assumptions were made to account for
variable site and waste parameters and would, undoubtedly,
have to be modified to reflect specific conditions at other
sites.
Waste Volumes and Site Size
Neither the extent of the formation to be remediated at
the demonstration site nor the remediation objectives under
the New Jersey Environmental Cleanup Responsibility Act
(ECRA) have yet been fully determined. A pump-and-treat
system probably will be used to stop the groundwater
plume from migrating, but this will be inadequate or take
excessively long to eliminate the ongoing contamination of
the groundwater as additional contaminants seep in from
the vadose zone. Conventional vapor extraction would
remove the vadose zone source of the contamination, but
does not appear viable for this relatively impermeable
formation. Hence, PFE was considered a viable
remediation alternative.
For purposes of this cost estimate, an area measuring
150 ft x 100 ft (15,000 ft2) bordered by a fence and trees
at the site was assumed to delineate the cleanup zone.
System Design and Performance Factors
A properly designed, installed, and operated vapor
extraction system can remove a large amount of
contamination from a site in an efficient, timely, and cost-
effective manner. The three main determinants of system
effectiveness are:
• the composition and characteristics of the
contaminants;
• the vapor flow path and flow rate; and
• the location of the contamination with respect to the
vapor flow paths.
A correctly designed and installed vapor extraction
system will maximize the intersection of the vapor flow
path with the contaminated zone. A correctly operated
system will maximize the efficiency of the contaminant
removal and reduce costs.
The number and location of extraction wells required
for remediation are highly site-specific and depend on
many factors, including the extent of the zone of
contamination, the physicochemical properties of the
contaminants, the soil type and characteristics (especially
the ah- permeability), the depth of contamination, and
discontinuities in the subsurface. The effective radius of
influence is the primary design variable and incorporates
many of the above parameters.
The effective radius of influence is defined arbitrarily
by Accutech as the furthest extent from an extraction well
at which a vacuum of 10 in. of mercury can be detected.
Obviously, this definition depends on how much vacuum
can be produced at the extraction well and this hi turn
depends on the soil characteristics. For this site, a vacuum
pressure at the extraction well of 9.8 psia was assumed.
Using this definition and the postfracture test results from
the fracture monitoring wells, an effective radius of
influence of at least 20 ft was demonstrated. For the
purposes of this cost estimate, an effective radius of
influence of 25 ft (area = 1964 ft2) was assumed for the
full-scale remediation. To insure that all contaminated
areas are treated, the effective radius of influence of each
well would have to overlap by 15 to 20%. Thus, each well
would account for cleaning up roughly half of its 1964 ft2
area or 982 ft2. Therefore, to clean up the entire 15,000 ft2
area of contamination, approximately 15 wells (15,000
ft2/982 rrVwell) would be required.
15
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Figure A-4 in Appendix A shows a simplified
flowsheet of Accutech's PFE system. A commercial-scale
unit would be similar in design and performance to that
demonstrated under the SITE program, but would include
a larger extraction system and possibly a different well
configuration.
During the SITE demonstration, average contaminant
concentrations in the extracted air remained essentially the
same (50 ppmv to 58 ppmv) before and after fracturing.
Contaminant mass removal was enhanced by virtue of the
increased air flow rate after fracturing as compared with
prefracture conditions. The contaminant mass removal rate
is expected to decrease with time as the site is remediated,
but it was not possible to extrapolate long-term removal
rates (1-yr), from short-term data (4-hr). For purposes of
this economic analysis, the contaminant removal rate was
assumed to be constant at a 4-hr postfracture average rate
of 722 x 10"6 Ib/min (33 mg/min) for one well operating
at an air flow rate of 4.2 scfrn, with all other wells capped.
Similarly, where the radius of influence of adjacent wells
overlap, the contaminant removal rate may be less than that
observed here. For purposes of this analysis, it was
assumed to be the same as that during the SITE
demonstration.
As stated earlier, increasing air flow rate is the
predominant way to extract gas phase contaminants from
soils. The air flow rate is, in turn, determined by the
vacuum pressure that can be developed at the well head,
and the vacuum pressure is limited by the air permeability
of the soil. For the demonstration study, a 7.7 hp blower
capable of delivering a vacuum pressure of 11 psia was
used, corresponding to an air flow rate up to 12 scfrn after
fracturing, with all other wells capped. Higher air flow
rates through the formation may have been achievable if it
were not for the perched water. Fluctuating perched water
levels were observed to block and, after dewatering, to
expose fractures. Dewatering would effectively increase
the soil permeability and hence, the amount of air that
could flow through the formation. In the field, it was
observed that this perched water became less of a problem
with time. Over the course of a 1-yr cleanup, it is
reasonable to anticipate that higher flow rates could be
achieved, especially with a larger blower in use.
Another way that air flow rates through the formation
could be increased is by using some of the wells as passive
air inlets. Limited testing during this demonstration
showed that this was possible; however, the corresponding
TCE concentration decreased due to dilution. The net
result still was an increase in the TCE mass removal rate,
although not as great as the increase in the air flow rate.
This is a parameter that the developer may be able to
adjust to suit a particular site to achieve optimum
performance, but a larger blower would be required. For
purposes of this economic analysis, an air flow rate of 20
scfrn per well with all other wells capped was assumed.
Hence, the total extraction rate for 15 wells would be 300
scfrn, corresponding to a 30 hp blower.
The source of compressed air for fracturing would
continue to be a bank of cylinders manifolded together and
mounted on a mobile trailer along with a compressor that
would serve to recharge the cylinder bank between fracture
injections.
As mentioned earlier, perched water was an
unanticipated problem encountered during the
demonstration. A make-shift pumping system was installed
hi the field. Since similar problems may be encountered
during an actual remediation, the cost of properly designing
and installing a low yield pumping system was included in
this economic analysis. During the SITE demonstration,
the collected water was stored and shipped off-site for
disposal. Recognizing that this would be very costly for a
long-term, full-scale remediation, on-site treatment, of the
perched water along with the groundwater using an air
stripper was assumed. The amount of perched water
relative to the amount of groundwater is assumed to be so
small that it would not add a substantial amount to the
operating or capital costs of the groundwater remediation
system.
The contaminants that are air stripped from the perched
water can be treated with the air stream extracted from the
wells. Again, this would not add substantially to the cost
of the aboveground treatment of the extracted VOC vapors,
which was assumed to be accomplished by carbon
adsorption. Accutech has suggested that catalytic
oxidation, particularly during the early periods when
concentrations of stripped VOCs would be highest, would
be more cost-effective. Since this approach was' not
evaluated during the Phase I study, it is not included in this
cost analysis.
The cost estimate does not include provisions for
pumping, collection, and treatment of groundwater from the
saturated zone beneath the water table. Those needs are
expected to be relatively constant regardless of the
approach to vadose zone remediation. The duration of
operation for a pump-and-treat system will be reduced by
eliminating the source of contamination in the vadose zone;
however, it is not possible to estimate the benefits
quantitatively.
16
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System Operating Requirements
The pilot-scale extraction unit, consisting of
compressor/blower, associated piping, valving and gauges,
and water knock-out vessel, was designed for the
demonstration project. The compressor/blower with a
capacity of 100 cfin was electrically operated and required
approximately 30 amp/240V service. Air flow rate and
pressure can be adjusted up to the maximum by throttling
a valve. The high pressure air (up to 500 psig) for
fracturing is provided by a bank of 12 cylinders. Larger
fracturing and extraction systems could be designed
similarly except that the compressor/blower(s) could be
operated by a diesel engine or a diesel generator. Capacity
would be dependent on the size of the compressor/blower
selected.
Although the Pneumatic Fracturing Extraction tests
were of limited duration, partially to avoid depletion of the
VOCs hi the formation, it can be assumed that the
extraction unit would operate continuously during a full-
scale remediation. Vapors would be extracted from all
wells at the same time. As noted earlier, optimistic
estimates were made for long term (1-yr) removal rate for
VOCs based on the short term (4-hr) tests. One operator
making daily visits to the site would normally be adequate
to identify and correct any problems, to adjust flow rates,
and, occasionally, to obtain samples from which progress
could be monitored.
Utilization Rates and Maintenance Schedules
Cost for installation of wells has been separately
identified at an approximate rate of $2000/well on the basis
of experience at the demonstration site. This will,
obviously, be dependent on the number of wells, the depth
and diameter of each, and the nature of the formation.
The pneumatic fracturing portion of the process would
be done at the beginning of the project and would take no
more than 2 wk for all 15 wells. Again, no downtime for
repairs was assumed since a back-up packer/injector would
be available on-site. A 25% annual utilization rate was
assumed by Accutech in estimating the capital costs for the
pneumatic injection equipment.
The extraction equipment was assumed to run 24
hr/day, 350 day/yr. Since this is a continuous, steady state
operation with very few moving parts after fracturing,
utilization rates should be quite high once operating
parameters have been established. A 90% on-line stream
factor was assumed. One week for mobilization and
training and 2 wk for demobilization were included in the
1 yr on-site tune.
Routine maintenance for all of the equipment would be
rather straightforward and could be done while in
operation.
Financial Assumptions
For the purpose of this analysis, capital equipment costs
include profit, overhead, and maintenance and were
amortized by the developer over a 2-yr period with no
salvage value. Insurance and tax are assumed to be fixed
costs listed under "Startup" and are calculated as 10% of
annual capital equipment costs.
Basis for Economic Analysis
In order to compare the cost-effectiveness of
technologies in the SITE program, EPA breaks down costs
into 12 categories using the assumptions already described.
The assumptions used for each cost factor are described in
more detail below.
Site Preparation Costs
The amount of preliminary preparation will depend on
the site and should be minimal when compared to other
remediation approaches. Site preparation responsibilities
include site design and layout, surveys and site logistics,
legal searches, access rights and roads, and preparations for
support facilities, decontamination facilities, utility
connections, and auxiliary buildings.
Drilling and preparation (purging, casing, caps, etc.) of
fracture/extraction wells are assumed to be performed by a
contractor and are a necessary part of the technology.
Although the total of these costs are highly site-specific,
they are included at a rate of $2000/well. For 15 wells, the
total for drilling would be $30,000. The costs of other
wells, such as those for site characterization and SITE
project monitoring of the process, are not included.
Additional costs incurred under the SITE program that
would also be included hi a full-scale remediation would
be:
Fencing
Electric Service Connection Charge
Electric Panels and Outlets
Cleaning Debris, Putting Gravel on
Permeable Fabric
SITE Full-Scale
=$1000 $2000
=$2000 $2000
=$3000 $3000
=$2000 $5000
17
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Permitting and Regulatory Costs
These costs may include actual permit costs, system
health/safety monitoring, and analytical protocols.
Permitting and regulatory costs can vary greatly because
they are very site- and waste-specific. For example, in the
case of the demonstration site, the bulk of the permitting
efforts are part of the more extensive ECRA Cleanup Plan,
an effort that has been ongoing for some time and which
addresses many aspects beyond remediation of the vadose
zone. New Jersey did, however, require a Permit to
Construct and Operate an air emission source ($1,000) and
permits for each well (SSO/well x 15 wells = $750). No
other permitting costs are included in this analysis;
however, depending on the site, this could be a significant
factor since permitting can be a very expensive and time-
consuming activity. The total for Permitting and
Regulatory Costs would be $1,750.
Equipment Costs
Capital equipment costs' were apportioned into vapor
extraction and pneumatic fracturing components. The
vapor extraction equipment cost of $l,090/wk was
provided by Accutech Remedial Systems, Inc. and included
a mobile trailer equipped with a 40 hp vacuum blower,
associated plumbing, controls and instrumentation, and a
water knock-out vessel. Capital equipment costs for the
same sized unit from several independent sources averaged
about $50,000, instead of the $113,360 estimated for
Accutech's proprietary equipment. The developer has,
however, decided to amortize these costs in a relatively
short time period (2 yr) and to include profit, overhead,
and maintenance, which translates into a capital equipment
cost of $113,360.
The pneumatic injection equipment cost of $7,131/wk
'was provided by HSMRC and included a mobile trailer
equipped with a bank of 12 cylinders manifolded together,
and maintained at a pressure of 2,500 psig with a 12 hp,
5,000 psig compressor to recharge the cylinder bank in 45
min between fracture injections, two packer/injector
assemblies (one for standby), and associated plumbing,
instrumentation and controls. An additional $6,656/wk is
included for a monitoring and analytical package, including
an on-site gas chromatograph and associated power
supplies, data acquisition, computer, software and
peripheral support. The pneumatic fracturing equipment
portion of the cost would then add up to $13,787/wk.
For a 1-yr remediation, the total equipment cost can be
calculated as:
Vapor Extraction: $l,090/wk x 50 wk = $54,500
Pneumatic Fracturing: $13,787/wk x 2 wk = 27.574
$82,074
Since no attempt was made in this project to estimate
the total VOC's in the vadose zone, it is not possible to
estimate the long term capital cost contribution to overall
cost. Instead, for planning purposes, it is assumed that the
TCE removal rate remains constant for a 1-yr period during
which time the site is remediated to a level (TCE residual
concentration in ah-, soil gas, or soil) acceptable to the New
Jersey DEPE. The reader is cautioned to use these
numbers with great care due to the assumptions made.
Startup
The mobile unit is designed to be moved from site to
site. Transportation costs are only charged to the client for
one direction of travel and are usually included with
mobilization rather than demobilization. Transportation
costs are not expected to be a major factor; they are
variable and dependent on site location and size/weight
load limits, which vary from state to state.
The amount of on-site assembly required for the mobile
unit (or a permanent installation) is minimal, consisting of
unloading equipment from trucks and trailers used for
transportation; joining piping to well caps, the extraction
blower, and the carbon adsorption system;, and assuring
that all joints are leak-free. Mobilization and minimal
training are estimated to take one person about 1 wk; this
time is included in the total time on-site (1 yr).
It is anticipated that installation of wells would be done
before and during the mobilization of the
fracturing/extraction system, based on careful review of
existing site characterization data. This also would be the
basis for selecting PFE as the preferred remediation
technology. Well installation would be carried out by a
drilling contractor, but it would presumably require
oversight by one person. Assuming one well could be
drilled and cased per day, this could add an additional 2
wk of effort to install 15 fracture/extraction wells.
Fracturing also would be integrated into the drilling tune
frame.
Depending on the site and the contaminants, local
authorities may impose specific guidelines for health and
safety monitoring programs. The stringency and frequency
of monitoring required may impact on project costs, for
example, if Level C protection is required during well
drilling or during fracturing to protect against inadvertent
emissions resulting from vertical fractures.
18
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Fixed costs, such as insurance and taxes are also
included here. The total of all startup costs was assumed
to be 10% of the annual capital equipment costs, or $8,200.
worn as a precaution. Nevertheless, since the manpower
requirements for operating the system are small, the cost
for health and safety gear will be minimal.
Labor
Operating labor costs were also divided into vapor
extraction and pneumatic fracturing components. Accutech
Remedial Systems, Inc. assumed that one engineer at a
salary of $65/hr would devote 24 hr/wk for 49 wk/yr to
vapor extraction, for a total of $76,440. During
mobilization and demobilization, Accutech assumed that
two engineers would work 40 hr/wk (1 wk for
mobilization, 2 wk for demobilization), for an additional
cost of $15,600. HSMRC assumed three engineers at a
salary of $65/hr would work 40 hr/wk for 2 wk/yr on
pneumatic fracturing for an additional cost of $15,600. No
labor cost has been included for site characterization or
system design.
The hourly rate includes salary, benefits, and profit but
excludes administration and overhead costs. Travel, per
diem, or car rental have not been included hi these figures
and can easily have a major impact if the duties cannot be
assumed by an on-site employee. The total cost of labor
for a 1-yr remediation is then $107,640.
Consumables and Supplies
Compressed air is the major consumable used by the
PFE process. For the demonstration, it was furnished by
a bank of compressed air cylinders. For a full-scale
remediation requiring numerous fracturings, an on-site
compressor was deemed to be more economical, even
though it is used only to repressurize a bank of cylinders.
These costs have already been discussed under "Equipment
Costs".
Some lubricants are required to maintain the blowers
but the cost would be negligible. No chemicals are used
in the process.
Where carbon adsorption is used to collect the VOCs
removed from the extracted gas, the cost of this material,
together with disposal cost, must be included. For this
estimate, that cost is included under "Emission Treatment
and Disposal".
Two other items that should be considered are health
and safety gear, estimated at $1000/yr, and maintenance
supplies (spare parts, oils, and lubricants, etc.), estimated
at $3000/yr by ARS. This may be somewhat higher during
well installation when events of elevated VOC levels hi the
air may be encountered and for which protection should be
Utilities
The total electrical demand for operation of the system
is estimated to be about 30 hp, primarily to operate the
vacuum blower. Assuming continuous operation, electrical
cost of $0.06/kwh would equate to about $11,750 per year.
The cost of bringing power to the site (approximately
$2000 at the demonstration site) has been included under
"Site Preparation." It is assumed that the cost for diesel
fuel for larger, diesel operated compressors would be
comparable.
A small additional cost could be included for lighting
of the system • during the nights, if only for security
purposes. Including on-site telephone and facsimile
service, the total annual utility costs would be about
$17,000/yr.
Emission Treatment and Disposal
The extracted VOCs from the Pneumatic Fracturing
Extraction will require collection and treatment. Although
Accutech has proposed catalytic destruction, particularly
where VOC concentrations in the extracted ah- are above
^approximately 50 ppmv, carbon adsorption was used for
control of these emissions during the demonstration.
For the full-scale remediation, it was assumed that the
TCE concentration remains at 50 ppmv for the full 1 yr
duration at an air flow rate of 300 scfrn. Thus, 1210 kg or
2660 Ib of TCE would be removed. If it is conservatively
estimated that 10 Ib of carbon are required for each pound
of VOC extracted, then 26,600 Ib of carbon would be
necessary for treatment over the year.
Rental of a stainless steel vessel with 1800 Ib of vapor
phase reactivated carbon would cost about $4,500/unit,
including spent carbon handling and off-site reactivation.
The unit would have to be replaced 15 times over the
course of a year. Additionally, there would be a one time
RCRA carbon acceptance fee of $2,500 to sample the spent
carbon to ensure safe reactivation. Therefore, it would cost
about $70,000/yr for emission treatment and disposal.
Residuals Storage, Handling, and Transport Costs
At the demonstration site, the ECRA Cleanup Plan calls
for pump-and-treat of the contaminated groundwater at the
site. Costs for this activity are not included in the
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estimate. At other sites, such pump-and-treat operations
may be necessary or desirable as a means of suppressing
the groundwater table to create an "artificial" vadose zone
or to remove dissolved contaminants before the PFE
process is applied. In those cases, an additional cost factor
may need to be included. Further, although the Cleanup
Plan calls for carbon treatment of the contaminated
groundwater at the demonstration site, air stripping of
contaminated water and catalytic destruction of the stripped
VOCs along with the VOCs removed by vapor extraction
may be a preferred alternative at other sites.
The perched water found at the demonstration site
presented an unanticipated process and disposal problem
and a makeshift pumping system was installed to remove
water from the well bores. A similar perched water
problem may be encountered at other sites. Hence, the
cost of designing, buying, installing, and operating a
comparable system was included. It was assumed that a
low yield (3 gpm) pneumatic pump, would be installed at
each of the 15 wells. The cost, including the associated
controls, plumbing, and compressor, was estimated to be
520,000.
During the demonstration, ~4000 gal of water pumped
from the vadose zone was stored hi 55 gal drums,
transferred to a 5000 gal tanker truck, analyzed, and
disposed of as hazardous waste. Rental of a 5,000 gal
tanker truck was Sl,200/mo. Sampling, analysis, and
disposal cost an additional $3,400. It was unclear whether
the water required disposal as a hazardous waste. For a
full-scale remediation, it would be cost-effective to airstrip
contaminants from the perched water together with the
groundwater and treat the contaminated ah- stream, with
carbon. The treated water would then be disposed of to a
POTW or surface water. Since, as noted earlier, the
incremental cost for air stripping of the perched water is
expected to be minimal, no additional cost for storing or
disposing of the perched water was included.
During the SITE demonstration, 18 drums of well
cuttings from 14 wells (8 FMWs, 2 injection wells, and 4
TMWs) were generated. The cost to manifest, transport,
handle, and dispose of these was estimated at $500/drum.
Since a full-scale remediation will involve about the same
number of wells, it was assumed that 20 drums of well
cuttings would be produced. The cost to dispose of these
was then estimated to be approximately $10,000.
Two drums of health and safety gear were produced
during the SITE demonstration and the cost to manifest,
transport, handle, and dispose of these was estimated at
S600/dmm. For a full-scale remediation, it was assumed
that I drum of personal protective equipment would be
generated every month. Therefore, the annual cost to
dispose of 12 drums would be $7,200 (12 drums x
$600/drum).
Therefore, the total yearly cost of Residuals/Waste
Storage, Handling, and Shipping are itemized as follows:
Dewatering System: $ 20,000
Well Cuttings: 10,000
Personal Protective Equipment: 7.200
TOTAL $ 37,200
Analytical Services
Standard operating procedures for Accutech do not
require planned sampling and analytical activities; in
practice, routine monitoring of extracted VOCs might be
carried out using portable instruments such as the HNu or
OVA, with less frequent but more complete laboratory
analyses by GC or GC/MS for confirmation and/or to meet
regulatory requirements. Short term rental of a portable
unit (OVA or HNu) is approximately $250/month and is
assumed to be included in "Capital Equipment" costs. No
costs have been included for pre-disposal testing of wastes.
Facility Modification, Repair, and Replacement
As stated earlier, site preparation activities for the
demonstration were carried out by EPA under the SITE
contract. Likewise, any modifications to the site for a
more extensive remediation, such as leveling, excavation,
removal of pipelines, sealing of pre-existing wells, etc.,
were assumed to be done by the responsible party (or site
owner), but such activities might be carried out by a
contractor such as Accutech and have already been
included under Site Preparation.
Demobilization
It is estimated that demobilization would take about 2
wk. Site cleanup and restoration is limited to the removal
of all equipment, facilities, and wastes from the site.
Requirements for grading or recompaction of the soil will
vary depending on the future use of the site and is assumed
to be the obligation of the responsible party or site owner.
Demobilization of wells is a requirement of -New Jersey
well drilling permits. It consists of removing aboveground
casing, plugging the full length of each well with grout or
cement, and surveying each well.
Since the wells at the demonstration site may be used
in the coming years as part..of the remediation,
responsibility for ultimate demobilization (abandonment)
was transferred from EPA to McLaren/Hart, the site
20
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owner's environmental consultant. The cost for well
closure was estimated at $100/well or $1,500 for 15 wells.
Results
Table 5 shows a breakdown of the costs for one
possible configuration of a full-scale .remediation of a
given portion of this site using the PFE process. The
largest cost category is Labor (29%), followed by Capital
Equipment (22%), Emissions Control (19%), Site
Preparation (11%), and Residuals/Waste Shipping,
Handling and Storage (10%). The remaining five cost
categories account for the remaining 9%. The reader is
cautioned to view the figures carefully when applying them
to other sites.
Table 5. Estimated Annual Costs for Large Scale Cleanup
Cost Category Total Cost Percent of
Total
Site Preparation (leveling, wells)
Permitting and Regulatory Requirements
Capital Equipment (amortized over 2 yr)
Startup
Labor • Salary
Consumables & Supplies
Utilities-Electricity, Telephone, Fax)
Emission Treatment and Disposal
Residuals Storing, Handling, and Transport
Analytical Services
Facility Repair, Replacement & Modification
Demobilization
TOTAL
$ 42,000
1,750
82,074
8,200
107,640
4,000
17,000
70,000
37,200
N/A
N/A
1,500
$371,364
11.3
0.5
22.1
2.2
29.0
1.1
4.6
18.8
10.0
....
0.4
100.0
Assuming the contaminant removal rate to be constant
at the 4-hr postfracture extraction rate of 122 x 10"6 Ib/min
for the entire 1-yr period, the average unit cost of TCE
removal will be $371,364 for 1,210 kg (2,660 Ib) of TCE,
or $307/kg ($140/lb) of TCE. It is felt that this is a valid,
but not necessarily realistic, number, considering the
optimistic assumptions regarding TCE removal rate.
Other operating scenarios are obviously possible. For
example, a more realistic approach could be to assume that
the TCE removal rate decreases linearly over the year by
90%, rather than remaining constant. The average removal
rate then would be 55% of that used in the above estimate.
Examining the 12 cost categories, however, only VOC
control cost would be impacted. Consequently, the total
cost for a 1-yr cleanup would be $339,864. Since only 665
kg (1460 Ib) of TCE would be removed, the unit cost
would increase to $51 I/kg or $232/lb of TCE removed.
Similarly, if the original hypothetical mass of TCE,
1210 kg, were removed over a 2-yr cleanup, the total cost
would increase to about $534,164 and the unit cost would
be $443/kg or $201/lb of TCE removed. These figures
assume increases of $56,680 hi capital, $5,670 in startup
costs, $81,120 in labor, $4,000 in consumables, and
$17,000 in utilities .for the second year of operation.
21
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Section 5
Bibliography
K. G. Angell, Bass, D. H., and Herman, C., "Air Sparging: An
Innovative Technique for Site Remediation," Proceedings for the
18lh Environmental Symposium and Exhibition, American
Defense Preparedness Association, Alexandria, VA, February 24-
27d, 1992, p. 57-63.
Anon, "Pneumatic Fracturing Unlocks Trapped Soil Contaminants,
Enables In Situ Remediation," Chemical Engineering Progress,
Oct.. 25-26 (1992).
Anon, "Soil Cleanup Method Being Developed," Chem. & Eng.
News, Sept. 21. 17 (1992).
O. Cunha-Leite, "Incineration of Liquid Halogenated
Hydrocarbons," The National Environmental J., Sept/Oct. 38-42
(1992).
R. R. Dupont and Reineman, J. A., "Evaluation of Volatilization
of Hazardous Constituents at Hazardous Waste Land Treatment
Sites," U. S. Environmental Protection Agency, Ada, OK,
EPA/600/2-86/07 August 1986.
N. J. Fcndingcr, Glotfelty, D. E., and Freeman, H. P.,
"Comparison of T%vo Experimental Techniques for Determining
AfrAVater Henry's Law Constants," Environ. Sci. & Tech., 23
£12, 1528 (1989).
C. Y. Jcng, Chen, D. H., and Yaws, C. L., "Data Compilation for
Soil Sorption Coefficient," Pollution Engineering, June 15. 54-60
(1992).
P. Kroopnicfc, "Modeling the In Situ Venting of Hydrocarbon
Contaminated Soil," Proceedings for the 18th Environmental
Symposium and Exhibition, American Defense Preparedness
Association, Alexandria, VA, February 24-27, 1992, p. 410-419.
McLaren/Hart Environmental Engineering Corp., "Cleanup Plan
for Groundwater - Derelco Properties - Hillsborough, New
Jersey," October, 1990.
McLaren/Hart Environmental Engineering Corp., "Groundwater
Sampling Plan Results Report - Derelco Property, Hillsborough,
New Jersey," October, 1990.
McLaren/Hart Environmental Engineering Corp., "Interim Pre-
Design Report: Groundwater Cleanup - National Diagnostics and
Derelco Property - Somerville, New Jersey," December, 1991.
J. R. Schuring and Chan, P. C., "Removal of Contaminants from
the Vadose Zone by Pneumatic Fracturing," U. S. Geological
Survey, Dept. of Interior, Award 14-08-0001-G1739, January
1992.
J. R. Schuring, et al, U. S. Patent 5,032,042, "Method and
Apparatus for Eliminating Non-naturally Occurring Subsurface,
Liquid Toxic Contaminants from Soil," July 16, 1991.
C. C. Travis and MaCinnis, J. M., "Vapor Extraction from
Subsurface Soils. Is it Effective?" Environ. Sci. & Tech., 26. #10,
1885-1887 (1992).
U. S. Environmental Protection Agency, "Guidance on Remedial
Actions for Contaminated Ground Water at Superfund Sites," U.
S. Environmental Protection Agency, Washington, D.C.,
EPA/540/G-88/003, December 1988.
U. S. Environmental Protection Agency, "Technology Evaluation
Report: SITE Program Demonstration Test; Terra Vac In Situ
Vacuum Extraction System - Groveland, Massachusetts," U. S.
Environmental Protection Agency, Cincinnati, OH, EPA/540/5-
89/003a, April 1989.
U. S. Environmental Protection Agency, "Guide for Conducting
Treatability Studies Under CERCLA: Soil Vapor Extraction -
Interim Guidance," U. S. Environmental Protection Agency,
Cincinnati, OH, EPA/540/2-91/019A, September 1991.
U. S. Environmental Protection Agency, "Seminar Publication:
Site Characterization for Subsurface Remediation," U. S.
Environmental Protection Agency, Cincinnati, OH, EPA/625/4-
91/026, November 1991.
U. S. Environmental Protection Agency, "PROJECT SUMMARY:
A Technology Assessment of Soil Vapor Extraction and Air
Sparging," U. S. Environmental Protection Agency, Cincinnati,
OH, EPA/600/SR-92/173, September 1992.
22
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Appendix A
Process Description
Introduction
Vapor extraction is becoming a widely accepted
technique for the removal of volatile organic compounds
from unsaturated ground formations. As an "hi situ"
technology, at least to the extent that excavation is not
required, it offers considerable cost savings over soil
excavation and aboveground treatment or off-site disposal.
The primary limitation to the technology is that the vadose
zone formation must be sufficiently permeable for air to
flow and vaporize the volatile contaminants into the air
stream.
This section of the report presents a concise
description of the Pneumatic Fracturing Extraction (PFE)
and Hot Gas Injection (HGI) processes as they were carried
out at the demonstration site in New Jersey. Pre-
demonstration factors involved hi site selection are
presented to assist engineers and scientists in evaluating the
suitability of the process for their own needs at Superfund
and other hazardous waste sites. Results of the
demonstration, including a summary of analytical data, are
presented in Appendix C. More comprehensive
descriptions of the process and the demonstration study are
contained in the Technology Evaluation Report.
Vapor extraction can be carried out hi one of several
modes, including:
a. vacuum extraction from a central well (or wells) with
air injection into surrounding wells;
b. vacuum extraction from a central well (or wells) with
surrounding wells open to the atmosphere (passive
inlet);
c. vacuum extraction from a central well (or wells) with
no surrounding wells or with surrounding wells sealed;
d. air injection into a central well with vacuum extraction
from surrounding wells; and
e. combinations of the above.
Varying combinations of the above modes were examined
during this demonstration.
Process Description
To facilitate the cleanup of soil and rock formations
with poor ah- permeability, such as shales and clay,
Accutech and the Hazardous Substance Management
Research Center (HSMRC) at the New Jersey Institute of
Technology have devised a means of increasing the
permeability of such tight formations. This method, the
subject of this investigation, involves injecting short bursts
(<1 min) of compressed air (up to 500 psig) into the
formation, causing the formation to fracture at weak points.
These fractures, which are found to occur predominantly in
the horizontal direction in formations such as clay and
shale, enlarge and extend existing fissures and/or generate
new fissures. Where these fractures connect an extraction
well with an ah- injection well or other source of air, they
allow increased flow of air through the formation and, hi
effect, increase the permeability of the formation. The
increased flow of ah- then allows increased masses of
trapped/adsorbed/absorbed organics to be removed by
volatilization. In addition, the generation or extension of
fractures can provide access to areas of the formation that
were simply not accessible to extraction before fracturing.
See Figure 1, shown earlier, for a conceptual representation
of the effect of fracturing on a formation of low
permeability.
For maximum control, the fracturing is carried out hi
narrow depth intervals using a proprietary lance (HQ
Injector) equipped with rubber "packers" which, are
expanded by pressurization with ah- to isolate each interval
of the wellbore from those above and below it. This tends
to concentrate the effect of the pressure pulse and may also
help minimize the formation or propagation of vertical
fractures by providing resistance above and below. The
injector and packer are shown schematically hi Figure A-l.
23
-------
f ~ Pneumatic Pressure Source
»• T 2-tt.
>• Fracti
~- -fc. J_ Intervi
Fracture
Interval
Figure A-l. HQ Injector.
Once fracturing has been successfully achieved in
several intervals, the permeability of the formation is
significantly increased and the radius of influence for vapor
extraction is expanded. In situ removal of VOCs then can
bo accomplished.
By enlarging the radius of influence, fracturing allows
vapor extraction with a minimal number of wells and/or
increased effectiveness. At the demonstration site, the
radial distribution of fractures was relatively uniform, but
fracturing is influenced by the geological character of the
formation and the presence of easy paths, such as
pipelines, obstacles, perched water, or building foundations.
Consequently, the actual radial impact may not be uniform.
Even heavy loads on the surface may prevent or reduce
fracturing in particular directions, a phenomenon used to
advantage when oil wells are hydraulically fractured at
much greater formation depths. By carefully monitoring
the direction and distance (radius) of fracturing using
measurements of surface heave and connectivity between
wells, an entire formation can be remediated more
efficiently, with a minimum number of wells, and in a
shorter time period.
Accutech also has proposed that hot gas injection into
bedrock can accelerate VOC removal by vapor extraction,
particularly when integrated with PFE. Hot Gas Injection
was an outgrowth of plans (not yet implemented) to
destroy extracted chlorinated VOCs with a catalytic
oxidation unit and inject the hot exhaust gases from the
catalytic oxidation unit. For the current Phase I
demonstration, hot gas production was simulated by
compression of ah-, albeit at a significantly lower
temperature (~200°F to 250°F) than expected from the
catalytic oxidizer (~1000°F). In addition to providing a
preliminary evaluation of the, technique, these data are
being used by HSMRC in developing and calibrating a
thermal model for hot gas flow and heat transfer in
different formations.
Several experiments were devised to evaluate the PFE
technology and its applicability to this site. A series of 6-
in. diameter monitoring wells surrounding a central
fracturing well of 3 in. diameter were installed, each
limited to a depth of about 20 ft below land surface (bis)
to assure that the water table was not penetrated. Each
well, originally drilled out to 10 to 12 in. in diameter to a
depth of about 8 ft, was cased to about 8 ft bis with a 6
in. OD steel casing threaded at the top. The remaining
length of each well was left uncased and unscreened to
assure maximum connection with the formation. Each well
casing was fitted with a threaded iron cap with two 2-in.
ports (Figure A-2) where the extraction hose, a gauge,
manifold, injection, or extraction equipment could be
installed (Figure A-3).
2 in. Nipples -
Outside NPT Threads
6 in. Carbon Steel Cap
Female NPT Threads
Figure A-2. Wellhead design.
Extraction Wall Assembly
Flow Measurement
/xa
Manometer o'
to Tedlar Bags
to Flexible Hose
Thermocouple
Figure A-3. Wellhead assemblies.
24
-------
The vacuum extraction system used in this
demonstration consisted of a single trailer (8 ft by 15 ft) on
which the compressors, manifold (with valves and gauges),
water knock-out vessel, and compressor/vacuum blowers
were installed (Figure A-4). Two granular activated carbon
adsorption drums (55 gal) were installed in series to
remove the VOCs from the extracted air before it was
exhausted to the atmosphere. The pneumatic injection
system consisted of the HQ Injector connected to a bank of
compressed air cylinders through a manifold and an
electrical solenoid valve that allowed a high, controlled
pressure (up to 500 psig) to be introduced into the interval
when activated. Once fracturing was completed
successfully in all intervals, as indicated by pressure/flow
measurements at the fracture well indicative of connection
between wells, and surface heave measurements by
electronic tiltmeters and other instruments, the system was
ready to operate as a conventional vapor extraction unit.
For the primary tests of the demonstration, the central or
fracture well became the extraction well while air was
drawn in from the surrounding formation, with all
monitoring wells capped, or by opening one or more
monitoring wells to allow passive air inlet. Well
placement for the demonstration is shown in Figure A-5.
VAPOR EXTRACTION SYSTEM
WATER
KNOCK-OUT
POT
DISCHARGE TO
ATMOSPHERE
VAPOR
PHASE
CARBON
VAPOR
EXTRACTION
WELL
VACUUM
BLOWER
-». WATER
A level area about 50 x 50 ft is needed to support the
extraction trailer, the compressed air source, and auxiliary
facilities. The capacity of the compressor used in the
demonstration was about 100 cfm at a maximum extraction
vacuum of about 10 psia.
For the demonstration ofPFE, the series of experiments
included:
a.
Measurement of pressure, air flow rate, and TCE
concentrations in 4-hr tests before fracturing, after a 24-
hr dormant period, and after fracturing, using the
fracture well as a central extraction well with all other
wells capped;
b. Measurement of pressure, air flow rate, and TCE
concentration at the central fracture/extraction well
before and after fracturing, with some monitoring wells
open for passive air inlet;
c.
d.
Figure A-4. Vapor extraction system.
Measurement of air flow rate and pressures while
extracting at individual monitoring wells with all other
wells capped, both before and after fracturing;
Measurement of pressure, air flow rate, and TCE
concentrations before and after each 2-ft interval was
fractured to establish whether fracturing of that interval
had been successful.
During the Hot Gas Injection tests, compressor exhaust
air (~200°F to 250°F) was injected at between 15 and 24
psia and 75 scfin into one well while temperature was
monitored in all wells and the extracted air flow rate and
TCE concentration were measured in the extraction stream
manifold. Extraction tests were also conducted prior to the
start of the HGI experiments for comparison purposes.
25
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STRIKE
Building
Foundation
DIP
FMW5 (20')
FMW4 (10')
FMW3(10')
O O ©
FMW7 (20') TMW4 (5')
FW FMW6(7.5') IW2(18') FMW8 (28')
FMW2(10')
FMW1 (10')
LEGEND:
• FW = Fracture Well
-------
Appendix B
Vendor's Claims for the Technology
Technology Overview
Conventional in situ soil vapor extraction (SVE) is a
remediation treatment technology that is finding
widespread use for the removal of volatile organic
compounds (VOCs) in the vadose zone. By simply
extracting and treating contaminated air from the
subsurface, a formation can be cleaned up relatively
quickly and efficiently. However, a major obstacle to this
form of remediation is formation permeability. Low
permeability formations, such as fractured shales, silts, and
clays, usually do not allow sufficient subsurface air flow
for conventional vapor extraction to be effective. Thus
entire pockets of VOCs may remain unaffected by remedial
attempts while continuing to slowly contaminate ground-
water. Pneumatic Fracturing ExtractionSM (PFE)SM,
however, is a treatment process developed by Accutech
Remedial Systems, Inc. to overcome the difficulties of low
permeability formations and to allow thorough and
effective in situ remediation.
An integral component of the PFE technology is a
patented (U.S. Patent # 5,032,042) process called
Pneumatic Fracturing, which was developed by the
Hazardous Substance Management Research Center
(HSMRC) located at the New Jersey Institute of
Technology. Accutech is a technology development
partner with the Center and is currently the only company
permitted to apply this patented innovative technology in
the United States. Accutech's integration of the pneumatic
fracturing technique with other in situ treatment methods
allows for cost effective treatment of a wide range of
contaminant compounds in complex geologic matrices.
With the PFE process, the difficulties posed by low
permeability formations are overcome. During the SITE
Demonstration, increases in permeability were tabulated by
measuring the increase in air extraction flow rate obtained
from the formation. Demonstration results indicated
extraction flow rate increases of up to 19,500% and TCE
mass removal rate increases of about 2,300%. In other
types of formations, even greater increases have been
recorded.
The increase in extraction air flow rate provided by
PFE is significant hi that it means that a greater amount of
ah" is moving through the formation at a given tune. Better
subsurface air flow will allow contaminants to volatilize
and be removed faster than with conventional technology.
The formation permeability increase created by PFE
also allows for a much greater vacuum radius of influence
to be induced from an extraction well. During all
Demonstration postfracture extraction tests, communication
between the monitoring wells and the fracture well had
vastly improved due to the PFE.
The most graphic way to quantify the overall effect is
through a vacuum radius of influence contour profile.
Figures B-l and B-2 represent the effective areas of
influence for the prefracture and postfracture conditions,
respectively. By selecting the 13 in. (of water) vacuum as
the outer boundary of influence, the effective radius of
influence was increased from 557 ft2 to 1488 ft2, almost a
three-fold increase. It should be noted that the postfracture
value was extrapolated beyond monitoring well FMW5
because this well represented the most distant monitoring
point. As supported by the very high vacuum gradient
measured at FMW5, the area under effective vacuum
influence may have been significantly greater but could not
be measured.
Since the spacing between extraction wells is
significantly increased, the total number of wells needed to
remediate a site is reduced. As a result, contaminants are
extracted faster and from a larger subsurface volume than
was initially possible, at a substantial cost savings to the
client.
Theoretical Discussion of Pneumatic
Fracturing Extraction
Fracture orientation is an important consideration hi the
application of Pneumatic Fracturing Extraction for full-
scale remediation projects. Both horizontal and vertical
effects were studied carefully during the Demonstration.
27
-------
FMWJ5
Figure B-l. Prefracture vacuum radius of influence.
SIKIKL iS Nt
Figure B-2. Postfracture vacuum radius of influence.
Fracture Orientation-Horizontal Effects
Several independent field observations confirmed that
the direction of fracture propagation at this site was
predominantly horizontal. This was expected since the
nearly horizontal bedding joints in the bedrock provided
preferential planes of weakness. Another factor which
probably affected fracture orientation was the
overconsolidated condition of the bedrock formation.
Horizontal fractures are favored hi overconsolidated
formations since the direction of the least principal stress
is vertical and the formation separates in a sheet-like
fashion when subjected to injection pressures. Although
no measurement of in situ stresses was made at this site,
regional geologic data suggest that this formation is
typically overconsolidated at shallow depths.
Direct evidence of horizontal fracture orientation was
provided by electronic tiltmeters, which showed circular or
elliptical patterns of surface heave extending 25 ft and
more from the injection point. Based on general
experience in the petroleum industry with hydraulic
fracturing, this pattern of surface deformation is consistent
with a horizontal fracture plane. In contrast, the surface
heave pattern for a vertical fracture plane would have been
"saddle shaped", which was not observed during any of the
injections. Additional evidence of horizontal fracturing
was provided by the strong air communication observed
between the fracture well and the seven outlying
monitoring wells. All of the monitoring wells, which
ranged from 7.5 to 20 ft from the fracture well, showed
positive pressure surges during injection which could only
have been caused by horizontal fractures intersecting the
wells.
Fracture Orientation-Vertical Effects
It is believed that vertical fracturing at this site v/as
minimal, since a formation does not yield along two
perpendicular planes simultaneously. Some dilation of
existing vertical fractures above the injection zone probably
occurred as rock blocks shifted during injection. While it
is difficult to determine whether or not any new downward
vertical fractures were caused by the pneumatic injections,
the continued presence of perched water in the treatment
zone throughout the demonstration suggests that downward
vertical fractures did not form. If they had, the perched
water would have drained after completion of the fracturing
operation.
Fracture Control and Uniformity
The geologic structure of the site can influence the
propagation of pneumatic fractures. As a result, fracture
patterns (when viewed in plan) are not always circular, but
may exhibit some directional preference. In sedimentary
rock formations, for example, pneumatic fractures will
typically propagate along the bedding planes. In tilted
sedimentary beds, the dip and strike may also be
significant, since in situ stresses and secondary jointing
systems usually align relative to these directions.
Directional fracture preferences at sites are identified
during pilot testing and are incorporated into the design of
the production fracturing operation.
PFE injections are typically accomplished using a
proprietary HQ injector which evenly distributes the air in
28
-------
all directions simultaneously. A modification of this
injector can encourage fracture propagation towards a
particular direction. Steering of fractures can also be
accomplished by positioning a surface load adjacent to the
injection hole, which is a technique used in the hydraulic
fracturing industry.
The Self-Propping Phenomenon
Following pneumatic injections, the formation settles
and the fracture network constricts. Field data indicate that
the closure of fractures is only partial, however, as residual
surface heave was recorded by both tiltmeters and optical
levels at the SITE Demonstration. The formation clearly
exhibited the phenomenon known as "self-propping". This
behavior is attributed to the asperities present along the
fracture planes, as well as the rock block shifting which
takes place during injection. -Self-propping is accentuated
hi brittle geologic materials like the siltstone present hi the
fracture zone at this site.
Once formed, the open, self-propped fractures resulting
from the pneumatic injections are capable of transmitting
significant amounts of fluid flow. The high flow potential
for even small fractures may be explained by the "cubic
law", which states that flow rate hi planar fractures is
proportional to the cube of the aperture. Numerous
hydrogeologic studies have confirmed the cubic law
prevails hi fractured bedrock formations, and this is the
principal reason why dramatic permeability increases are
observed hi pneumatically fractured formations.
Diffusion and Flow Channelization
Once a fracture network is established hi a low
permeability formation, aqueous and residual products in
the vicinity of the fracture are easily accessed, and hi the
case of PFE, they are removed rapidly through
volatilization. It is expected that the fracture distribution
in a formation will not be totally uniform, since certain
geologic conditions will possess preferential directions. In
sedimentary rock formations, for example, pneumatic
fractures will typically propagate along the bedding planes.
In tilted sedimentary beds, the dip and strike may also be
significant, since hi situ stresses and secondary jointing
systems usually align relative to these directions.
Directional fracture preferences at sites are identified
during pilot testing, and are incorporated into the design of
the production fracturing operation.
It is noted that highest contaminant concentrations
usually occur within and adjacent to existing structural
discontinuities in the formation (e.g. joints, cracks, bedding
planes). Since pneumatic fracturing dilates and
interconnects existing discontinuities, direct access is
provided to a majority of the contaminant mass. In these
situations, the diffusive processes in the matrix blocks
become less important, and it may be possible to meet
target concentrations without cleaning the blocks
completely.
In a pneumatically fractured formation, it is probable
that ah- flow will be proportional to fracture size, i.e., the
largest flows will occur hi the largest fractures. This flow
channelization will not preclude at least some flow hi the
smaller fractures, however, as long as suitable vacuum
levels are applied to the formation. Even small ah" flows
through the smaller fracture network are capable of
volatilizing and removing contaminant, thereby causing an
outward diffusive gradient of the contaminant from the
matrix block to the smaller fractures.
Hot Gas Injection
Hot Gas Injection technology consists of utilizing the
energy generated during process operation to aid the
remediation effort. Conceptually, by injecting a hot gas
into the contaminated subsurface fracture network, the
thermal energy of the gas would be transferred to the
subsurface rock material surface and any contaminant
contained thereon. The resulting rise hi contaminant
temperature would substantially increase its vapor pressure,
which results hi directly increasing the mass transport rate
of the material to any gas flow through the region. Since
the vapor pressure is exponentially dependent on the
temperature, a modest temperature increase can achieve
significant mass transport rate changes (e.g., 20°F increase
will double the vapor pressure and mass transport rate of
typical hydrocarbons, another 20°F will re-double, etc.).
hi the application of hot gas injection technology to
geologic formations, the low heat capacity of air is the
major factor. This can be offset by utilizing one or both of
the following approaches: 1) Injecting ah- at very high
temperatures; or 2) Injecting very large volumes of hot ah".
The first approach, maintaining very high temperatures,
is cost prohibited due to the excessive energy requirements.
The second approach may also be difficult, since large air
volumes cannot be forced through a porous media unless
the formation possesses a naturally high permeability.
As a result, utilization of conventional hot gas injection
technology is unpractical hi the remediation of most
geologic formations due to the inability of the process to
develop subsurface thermal effects.
29
-------
By integrating PFE with Accutech's HGI technology,
the limitation of formation permeability can be overcome
since the subsurface air flow in a pneumatically fractured
formation will follow the "Cubic Law", substantially higher
air flow rates can be developed than in a standard porous
media. -An additional benefit of the PFE/HGI integration
can be realized in formations that contain naturally
occurring fractures such as the siltstone present at the
Demonstration site.
Since the natural fractures serve as the primary
pathway of entry for the contamination into the formation,
the largest contaminant mass will be logically in and
adjacent to these natural fractures. After these fractures
become dilated as a result of the PFE injection, the
subsequently injected heated air will volatilize the
contaminants in the vicinity of the fractures and it will not
be necessary to heat the entire rock mass to access a
majority of the contaminants.
The baseline subsurface temperature observed during
both the pre-Demonstration and Demonstration activities
ranged from 53°F to 60°F. The middle of this range is
consistent with expected subsurface temperatures based
upon standard geothermal gradients for these depths. The
minor variations hi the baseline are likely due to site
activities including air extraction, which causes a slight
heating effect, (extracted air ultimately comes from the
atmosphere), and cooling effects induced from extraction
of perched ground water.
During the Demonstration 90-hr HGI test wherein the
injection temperatures ranged from 150°F to 200°F air into
the formation, thermal gradients as high as 77°F were
observed as much as seven and one half feet away from
the injection well.
Full-scale remedial application of Hot Gas Injection
technology, whether operated as a "pulsing" mode or as an
active inlet well source, provides the potential to
accelerate the recovery of volatile organics and to offer a
method to recover semi-volatile compounds with low vapor
pressures.
Applicability
Pneumatic Fracturing Extraction is applicable for
removal of volatile and semi-volatile chemicals hi low
permeable formations. It has been demonstrated to
enhance contaminant removal rates from soil formations
consisting of silts and clays and moderately fractured
sedimentary rock formations such as shale. Figure B-3
provides approximate guidelines for PFE application. As
indicated, PFE can generally improve air flow in geologic
formations whose natural air conductivity is less than 10"5
cm/sec through the creation of a fracture network. In
formations with higher concentrations, PFE is most useful
for rapid aeration and making subsurface flow paths
uniform. Since no two sites exhibit the same
environmental characteristics, geology, or contaminants,
Accutech readily integrates the PFE process with other
complementary technologies to address each site's unique
remedial requirements. The following are examples of
technologies that PFE has been integrated with.
Types of Soil and Rock Treatable
Natural Air Conductivity (col/sec)
^
1
Soil Type
Sedimen
(Sandstone, S
Apply Pneu
•2
n 1
Sand
-4
P '
Fine
tary Rock
iltstone, Shale)
natlc Fracturing
F
1
Sand
p-
Silt
•Mghly
actured
•a
P
Fractured
Slightly
Apply Pneumatic Fracturing
For Rapid Aeration (Aerates Pores)
To Improve Air Permeability
(Creates Fractures)
Figure B-3. Types of soil and rock treatable.
Integrated Systems
In situ Bioremediation
In situ bioremediation, is a treatment technology which
utilizes naturally occurring biological processes to degrade
hazardous compounds. For degradation to occur, however,
certain substrates such as oxygen and nutrients must be
available to the soil microorganisms. Low formation
permeability limits the ability for these substrates to move
through the subsurface and thus can retard or prevent the
desired microbial activity from occurring.
By integrating the PFE process with bioremediation
techniques, the limitations of formation permeability are
overcome, which allows for uniform oxygen distribution
within the subsurface. Nutrients and any other necessary
substrates are then injected into the formation through a
process called Pneumatic Bio-injection. Thus, biological
activity can be stimulated hi the contaminated sections of
30
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the formation, with the hazardous compounds being
degraded into harmless minerals.
PFE Saturated Zone Applications
While the EPA SITE Demonstration was focused upon
vadose zone source removal, situations are encountered
where the source of the contamination is located in the
saturated zone. In formations where contamination is
adversely affecting groundwater quality, Accutech
integrates both its PFE and/or HGI processes to
groundwater recovery and treatment applications.
Application of the PFE process has been demonstrated
to improve recovery rates of contaminated groundwater in
both soil and rock formations. In situations where free
product is present hi low permeability formations, PFE
offers the ability to enhance the operation of product
recovery systems. Because PFE increases the formation
permeability, integration of the technology with any liquid
removal system will enhance the treatment effectiveness
versus technologies applied in unfractured media.
PFE Sparging
Conventional air sparging combined with SVE is an
emerging treatment technology for the removal of volatile
organics from soil and groundwater. The air sparging
technology consists of injecting air into the saturated zone
at the depth of the contaminant plume. Bubbles of air then
volatilize dissolved or adsorbed phase contaminants in the
groundwater. Volatilized compounds are then carried to
the vadose zone by the air bubbles, where they are
removed through an SVE type system. As with other hi
situ technologies, this remedial technology can be limited
by formation permeability. Even if the permeability issues
can be overcome, over-pressurization can lead to
uncontrolled dispersion of contamination.
Pneumatically enhanced sparging allows for the
effective treatment of a larger portion of the contaminant
plume more effectively. However, since radius of fracture
influence is a function of PFE application parameters, the
extent of higher permeability can be controlled. Therefore,
the potential for over-pressurization is limited and the risk
of undesirable dispersion is reduced. By substituting Hot
Gas for atmospheric air for injection into the saturated
zone, contaminant volatilization will be greater.
31
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Appendix C
SITE Demonstration Results
Introduction
The objectives of this demonstration project were to:
(1) study the effectiveness of the Pneumatic Fracturing
Extraction (PFE) process as a means of increasing airflow
rate and the. radius of influence and, consequently,
increasing the removal of volatiles, specifically
trichloroethene, from a low permeability bedrock
formation; (2) demonstrate that fracturing had increased the
permeability or the connectivity of the formation between
wells; and (3) provide preliminary data on the effects of
Hot Gas Injection (HG1) in terms of heat transfer and VOC
removal from such formations.
The site had been used by industrial firms until a fire
destroyed the building in 1985. During cleanup after the
fire, the groundwater was found to be contaminated with
halogenated volatile organics, primarily trichloroethene.
The site was selected for evaluation of this technology on
the basis of extensive soil and groundwater evaluations
carried out by McLaren/Hart Environmental Engineers (and
others) as part of a New Jersey Environmental Cleanup
Responsibility Act (ECRA) Cleanup Plan for the site.
Under New Jersey's ECRA regulations, the site may not be
redeveloped until it has been decontaminated. Although
this site is not a Superfund site by other definitions, it is
representative of contamination and ground character
encountered at Superfund sites. Figure C-l presents the
general layout of the facility and the location of existing
wells that were used to assess the suitability for the SITE
demonstration project.
Based on analyses from these test wells (Table C-l) and
others, it was concluded that the unsaturated or vadose
zone was also contaminated with trichloroethene, and that
the sump area near the foundation of the destroyed building
was probably the source. In addition, the data suggested
that the groundwater plume was moving to the northeast
Concrete Foundation
(of former building)
Tree Line
Figure C-l. Site plan.
32
-------
while the vapors were moving northwest. The bedrock
was characterized as part of the Brunswick formation, a
highly fractured shale. From the existing studies, it was
clear that TCE was present hi both the groundwater and the
vadose zone, with concentrations of TCE hi the soil gas
perhaps reaching several hundred ppmv, and concentrations
in the groundwater hi the <100 ppm range.
Table C-l. Analysis of Wells on Demonstration Site
Well No. Depth, ft TCE DCE
PCE
Groundwater analyses, ppm (mg/L)
MW-1S
MW-ID1
MW-2
Soil Gas Analyses, comv
VG-3
VG-3
18-50
57-80
20-50
5-7
15-17
52-70
.032-045
8.4
35
126
6.9-0.2
ND-.003
0.26
2.5-3.0
ND-.003
0.059
4.6J
5.6J
J = below quantitation limit.
Considerable TCE contamination remained after the
surface layer of soil (~2 to 3 ft deep) had been removed
from the sump area. The fractured shale character of the
exposed bedrock would make further excavation both slow
and costly, even though the area is relatively small.
Without removal of the source of contamination hi the
vadose zone, the underlying groundwater (water table at
approximately 25 ft below land surface) would continue to
be contaminated and would make the planned pump-and-
treat remediation of the groundwater slow and inefficient.
The PFE process appeared to be well suited to remediation
of the vadose zone at this site, and would remove at least
one significant source of groundwater contamination.
Pneumatic Fracturing Extraction
The tests were carried out hi an area near but not
directly hi the sump area (see Figure A-5 for well
placement). The .primary experiment consisted of a
comparison of 4-hr extraction tests before and after
fracturing, hi terms of both ah1 flow rate and TCE mass
removal rates. Half-hour composite samples of the
extracted gas were collected at a constant rate (3 L/30 min)
hi Tedlar bags (EPA Method 18) and analyzed by an on-
site GC within 2 hr.
A "recharge" effect often is observed when vapor
extraction is stopped and then restarted, with contaminant
concentrations peaking again on startup. Since a delay was
necessary and planned while the central well was fractured,
a second prefracture test was carried out after the system
was dormant for 22 hr and the data from this test (ah- flow
rate, TCE concentration, etc.) were used for comparison
with the postfracture test.
A series of tests also were carried out before and after
fracturing to evaluate the effective radius of extraction.
This was done by extracting from each of the fracture
monitoring wells (FMWs) while all other wells remained
capped. Pressure and ah- flow rate were monitored for
each 10-min test.
hi addition, passive ah- inlet tests were carried out
before and after fracturing by allowing ah- to enter one or
more monitoring wells while ah- was extracted from the
fracture well. Pressure, air flow rate, and TCE
concentration were monitored at the extraction well.
Brief tests also were carried out before and after
fracturing of each interval to learn whether significant
vertical connections were initially present or were created
by fracturing. This was accomplished by extracting from
each fracture interval while the packer assembly was still
in place and monitoring pressure, ah- flow rate, and TCE
concentration.
Hot Gas Injection
hi anticipation of future investigation of catalytic
oxidation of TCE in the extracted air stream and injection
of the hot exhaust gas into the formation (possible Phase
II study), two experiments were carried out to evaluate the
effects of HGI. These tests provided data for HSMRC to
use hi their development of a model for transient heat
transfer hi a fractured formation, and also provided data on
TCE removal.
In the first HGI experiment, the existing field of wells
was expanded by installing four thermal monitoring wells
at about 5 and 7 ft distances from the fracture/injection
well, as shown in Figure A-5. Pressures, temperatures at
varying depths hi each monitoring well, and TCE removal
rates from the extraction well were measured over the
course of a 90-hr test while hot air (~200°F to 250°F, 15 to
24 psia, and 65 to 75 scfrn) produced by compressidn
heating was injected into the fracture well.
hi the second test, two additional 4-in. wells (IW2 and
FMWS in Figure A-5) which intersected a more
contaminated zone were installed. Wells number FMW6
and FMWS (new) were manifolded together and used as
extraction wells while hot air was injected into well IW2.
This experiment was carried out for 24 hr while
temperature, air flow rate, and pressure were monitored and
1-hr composite samples were collected hi Tedlar bags for
33
-------
immediate analysis by GC. No additional fracturing was
carried out.
Field Activities
Accutech and HSMRC were responsible for the
specifications and locations for the wells, which were
drilled under the direction of SAIC's Field
Manager/Geologist. Accutech and HSMRC were
responsible for fracturing the central well and for operating
the extraction system. SAIC obtained and recorded the
bulk of the pressure, flow, and temperature data, but
HSMRC also recorded comparable data in most instances
using other equipment. Tedlar bag samples were collected
by SAIC's subcontractor, IEA Laboratories, and analyzed
on-site by gas chromatography. A limited number of
Tedlar bag samples also were collected during the course
of the project for more complete analysis by GC/MS using
CLP Methods at DEA's Connecticut laboratory.
Although it had been anticipated that the vadose zone
would be relatively free of water, considerable water was
present and gradually filled all the wells. All parties
collaborated on daily pumping of the wells before each
experiment in an attempt to maintain the most constant
depth of open hole in all wells. Over the course of the 4-
\vk investigation, there were indications that the water
recharge rate was decreasing, but the water problem
persisted throughout the study. Presumably, some TCE
was being removed in this water, but the volume of water
and the TCE concentration were not measured during the
study. Even if such data were obtained, it would not have
been possible to attribute the values to any particular
experiment. (A single analysis of the water by EPA
Method 8010 indicated 0.130 ppm of TCE; a sample taken
later in preparation for disposal indicated a very low
concentration, 0.044 ppm, of TCE, and no other
contaminants.)
Test Procedures
After considering several alternatives, a modified EPA
Method 18 sampling procedure was chosen to collect
samples of the extracted air. Duplicate samples of the
extracted air were collected in evacuated 3-L Tedlar bags
at uniform rates over 0.5 hr intervals during most of the
study. For certain experiments, the sampling time was
increased to 1 hr and for others it was only 10 min. A
small impinger was included in the Method 18 sampling
train to collect any entrained water for TCE determination
by Method 8010 so that its mass could be added to the
amount measured in the gas. Surprisingly, although
considerable water accumulated upstream in the knockout
trap on the extraction trailer and water certainly was
present in the vadose zone, no water was found in the
impinger during any experiment. ...
An in-line Organic Vapor Monitor (OVM, Foxboro
Model 580B) was also installed ,in a "T" off the manifold
so that total volatile hydrocarbons could be correlated with
the TCE measured by GC. Unfortunately, the OVM and
substitute HNu instruments repeatedly failed, making this
data collection effort incomplete.
Air in the exhaust stack after the carbon adsorber was
monitored daily using an OVA or HNu calibrated against
isobutylene and occasionally cross-checking these results
with GC analysis of Tedlar bag samples. This assured that
the final exhaust from the system met the air monitoring
requirements imposed by the New Jersey DEPE. Ambient
air quality was also monitored for VOCs by OVA (or
HNu) during all test activities, particularly the beginning of
the HGI test when odors detected along the perimeter of
the foundation raised concern about worker safety.
Results
Air Flow Impact of Fracturing - Monitoring Wells
Capped
Based on a comparison of the air flow extracted from
the fracture/extraction well during the 4-hr prefracture
(restart) test with that after fracturing, the air flow rate
(corrected to standard conditions of 1 atmosphere and 60°F)
increased about 600% (Table C-2). Figure C-2 graphically
presents the air flow data before and after fracturing.
Table C-2. Effects of Fracturing, 4-hr Tests
Parameter Pre- Prefracture Post- Increase,
. fracture Restart fracture %
Pressure, psia
Air flow, scfin
TCE mass removal,
10-6lb/min
11.1
0.6s
<10.9
11.1
<0.6*
<11.0
11.4
4.2±0.6
83.9±31
600
675
* increase = 100 X (postfracture-restart)/restart.
# HSMRC data indicate air flow <0.6 scfin.
Trichloroethene Removal Before and After Fracturing
Although the concentrations of TCE in the extracted air
did not increase much as a result of fracturing (prefracture
average: 50 ppmv; postfracture average: 58 ppmv), the
TCE mass removal rate during the 4 hr increased about
675%, largely as a result of the large increase (600%) in
34
-------
air flow rate. -These results are also summarized in Table
•C-2 and in Figure C-3. A significant change in TCE mass
removal rate , was not observed when extraction was
restarted after the 22-hr dormant period, suggesting that
recharging while fracturing was carried out was not a
significant contributor to the increased TCE mass removal
rate observed in the postfracture test.
concentration increased further (5.0 scfm and 70 ppmv,
respectively). The calculated increase in TCE mass
removal rate after fracturing, based on the 6 hr of
operation, was 800%. Removal of perched water from the
well bores between the two segments of the postfracture
test also may have contributed to increased air flow rate
and/or exposure of new pockets of contamination and,
consequently, to increased TCE removal.
postfracture
prefracture
prefracture restart
0 20 40 60 80 100 120 140 ISO 180 200 220 24O
Elapsed time, min
Figure C-2. Comparison of 4-hr air flow rates.
ISO
170
wo
ISO
140
130
120
«°
WO
60
i so
g «
I- 30
20
K>
postfracture
prefracture restart
prefracture
0 20 4O 60 80 100 120 140 ISO 180 20O 220 240
Elapsed time, min
Figure C-3. Comparison of 4-hr TCE mass removal rates.
The postfracture test was also extended 2 hr so that
additional data could be accumulated. During the added 2
hr, after again dewatering the wells, both air flow and TCE
Physical Impact of Fracturing on the Formation
Analysis of tilrmeter data collected by HSMRC
personnel during the fracturing events indicated that
measurable surface heave was detected as much as 20 ft
away from the fracturing well and appeared to favor the
strike direction to a small extent. Computer-derived
contour maps of the fracturing events were developed by
HSMRC; the series of these maps for one fracturing
interval showing the change with time are presented in
Figure C-4.
A profile of maximum pressures hi all the monitoring
wells during the actual fracturing events (Table C-3) also
suggests that fracturing direction is relatively uniform, and
that more distant wells are less affected. Although
considerable pressure is transmitted to monitoring wells
even 20 ft from the fracturing well, uncertainty about water
levels in one or more wells makes more detailed use of
these results questionable.
Table C-3. Maximum Pressure During Fracture
Events
Monitor
Well
No.
FMW1
FMW2
FMW3
FMW4
FMW5
FMW6
FMW7
Distance
toFW,
ft
10
10
10
10
20
. 7.5
20
Maximum Pressure, psig
in Interval, ft bis
9-11.1 11.1-13.3 13.1-15.3
16
14
15
18
14
19
12
18
18
17
18
14
20
15
23
23
22
23
15
22
15
14.5-16.4
23
21
19
22
11
25
11
Direct examination of the effects of pneumatic
fracturing on the formation was made with a borehole
camera. Comparison of prefracture and postfracture videos
revealed a widening of existing discontinuities and the
appearance of some new fractures. When the camera was
operated during vacuum extraction, the pulsing of water
into the borehole from certain fractures was very evident.
35
-------
8 19 29 30 48 GO 60 70 B8 98 16
IMP
98
63
78
68
£ 68
*" «
39
29
19
a
.
•
*
• N
:f
. hEAVE UNITi
FRACTLRE ICL
\
//\\
0 ':
^**
INO-ES
0. COORDINATESl (60,60)
1IA
90
80
70
60
60
40
30
2O
10
0
X (FT)
TIME = 1 SEC
E
**
>•
tea
98
89
78
69
«•
•(9
38
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192939406060709090
100
N
t
(B0.60)
00
90
80
70
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GO
•40
30
20
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102833496068709093
X (FT)
TIME = 15 SEC
188
ea
79
8 18 23 30 49
60 70 80 90
38
28
19
100
100
(S0.60,
90
80
TO
60
GO
4O
30
20
to
18 28 3O
O 58 60 70 60 9O 1E
X (FT)
100
90
80
70
60
SO
•4O
30
20
10
0 10 20 30 40 60 60 70 80 90 1C
0
HEAVE UNIT: INOES
FRACTURE KU. CCX3RDINATES: (60.60)
100
90
80
70
60
EO
40
30
20
10
100
90
80
70
60
: 50
40
30
20
10
0 10 20 30 40 60 60 7O 80 90
X (FT)
TIME = 9 SEC
.0 10 20 30 40 50 60 70 80 90
HEAVE UNIT: INCHES
FRACTURE tELL COORDINATES. (60,583
90
en
70
60
60
•40
30
20
10
10 20 30 40 50 60 70 80 90
X (FT)
TIME = 19.5 SEC
.01
THIRD FRACTURE INJECTION
DEPTH: 13.1 TO 15.3 FT
DURATION: 21 SECONDS DATE: 8/21/92
TIME = 100 SEC
Figure C-4. Tiltmeter contour plots.
36
-------
Similarly, measurements, of pressure and air flow rates
during short term (10 to 15 min) extraction tests at
individual monitoring wells before and after fracturing
suggest (a) that a connection probably existed between the
fracture well and monitoring well FMW6 before fracturing
and (b) that there was a considerable increase in
permeability or connection in all directions after fracturing
(Table C-4). These observations must be considered
cautiously since perched water may have interfered with
valid data from one or more wells.
Table C-4. Monitoring Well Extraction Tests
Distance
from FW,
ft
7.5d*
10s
10o/s
10 d
10s
20s
20 d
Well
No.
FMW6
FMW1
FMW2
FMW3
FMW4
FMW 5
FMW7
Air flow rate,
scfm avg
pre-fracture post-fracture
<.89A
<.63
<.72
<.63
<.63
<.63
<.63
6.1
5.6
6.1
7.2
6.9
6.5.
2.0
Increase,
% avg
>580
>790
>720
> 1040
>1000
>930
>220
~ these results are based partially on HSMRC data.
* s - strike; d - dip; ofs - off strike -and dip.
Passive Air Inlet Tests
Extraction tests before and after fracturing with one or
more wells open to the air (passive inlet mode) indicated
a very large increase in air flow rate and consequently, in
TCE mass removal rate (Table C-5). Using this mode, the
TCE mass removal rate after fracturing was about 40%
greater than that observed during extraction with all the
monitoring wells capped. Although the SAIC pressure
gauges used to calculate ah- flow rates remained essentially
at "0", rotameters used by HSMRC indicated values
ranging from 0.3 to 0.6 scfm in the prefracture test.
Table C-5. Passive Air Inlet Tests
Parameter
Prefracture
Postfracture Increase, %
Pressure,
psia avg
Air flow,
scfin avg
TCE mass removal
rate, lO^lb/min
10.8
0.39+.04
4.8±1.4
14.6
76.4+4.8
116.0±91
—
19,500
2,300
Effect of Hot Gas Injection
In the first HGI experiment, lasting 90-hr, temperature
increases were observed hi wells at different distances and
different depths, usually at an 8 ft depth. These increases
were greater at the monitoring wells closer to the hot air
injection well, and may have reached a maximum before
the first readings were taken at the 8 ft depth, after 20 hr.
Unfortunately, the thermocouples were at the 14 ft bis
depth during the first 20 hr and may have been submerged
hi water at that depth. In addition, extraction was taking
place only from FMW5 during the initial 20 hr. Because
very low TCE concentrations were observed, Accutech
manifolded three other wells (FMW1, 3, and 6) together
with FMW5 at that tune, resulting in increased extracted
ah- flow rates subsequently. When compared with a 4-hr
baseline test during which air was extracted from the same
FMW5 well, but no air was injected into the central
fracture/injection well, it was apparent that HGI did not
substantially increase the TCE mass removal rate hi the
extracted air, even when multiple wells were manifolded to
the extraction system. Table C-6 and Figure C-5
summarize the air flow and TCE mass removal results, and
Figure C-6 graphically describes the temperatures observed
hi the different capped wells.
Table C-6. Hot Gas Injection Test, 90 hr
Parameter Pre-HGI-1 HGI-1* Increase, %
Extraction pressure,
psia avg
Air flpw rate,
scfm avg
TCE mass removal
rate, 10'6lb/min
10.9
11.6±1.5
172±18
13.4
82.6±7.1
31.2+10.3
-~
612
-82
* Results shown are for 22-90 hr period; 4 extraction
wells on manifold.
Extraction air flow rats
0 I 20 I «
TO 3O
60 | 80 I
70 90
Elapsed time, hr
Figure C-5. Air flow and TCE mass removal rates.
37
-------
10 ft radius
ill walla capped
40
Elipiad lime, hr
Figure C-6. Temperature in wells, 90-hr HGI test.
Interestingly, when HGI was discontinued, the
temperature in'some of the wells continued to increase for
some time. This may be due to the air flow convectively
cooling the thermocouples during hot gas injection and
extraction but not during the post test when the air was
shut off.
Because one explanation considered for the low TCE
removal was that the TCE in this area had been exhausted,
a brief (3-hr) follow-up extraction test was carried out as
a comparison with the original postfiracture extraction test.
The results of this test, with extraction from the same
FMW5 with all other wells capped, indicated that TCE still
could be removed by vapor extraction at a TCE mass
removal rate of 82 x 10"6 Ib/min. Similarly, when a 1-hr
post-HGI extraction test was carried out from the fracture
well (FW), as in the original PFE tests, the formation again
yielded a TCE mass removal rate of 95.1 x 10"6 Ib/min. It
could, however, be argued that during HGI different
pockets of the bedrock were being accessed.
A second HGI experiment was carried out in an area
believed to be more heavily contaminated and where
connection between wells had been observed during the
original fracturing event. NO ADDITIONAL
FRACTURING WAS CARRIED OUT. Hot air was
injected into a central well (IW2) and extracted from two
outer wells (FMW6 and FMW8), each -10 ft distant.
When these results were compared to a baseline in which
no hot air was injected, the TCE mass removal rate
extracted increased about 53%, significantly less than the
150% increase observed in the air flow rate. In this case,
however, no increase in temperature was observed in the
extraction wells, which may be due to the short duration of
the test. These results are summarized in Table C-7 and
presented graphically in Figure C-7.
Table C-7. Hot Gas Injection Test, 24-hr
Parameter Pre-HGI-2 .HGI-2
Increase, %
Extraction pressure,
psia avg
Air flow rate,
scfm avg
TCE mass removal
rate, lO^lb/min
11.0
3.7±1.8
63±27
11.8
9.2±4.7
97±33
—
150
54 •' •/
160
ISO
HO
130
f M °°
If"
i!
70
60
SO
4O -
30 -
20 -
U
0
I 12 I 16
» 14
20
2 6
Elapsed time, hr
Figure C-7. TCE mass removal rates, 24-hr HGI
24
22
test.
Several explanations have been considered for the
anomalous results from the two experiments, including: no
available TCE in the formation or short-circuiting, water at
higher and variable depths in some wells, unsuitable
control experiment, solar heating of the air in the extraction
wells, cooling effect of moving air, etc.
GC/MS Analysis of Gas Samples
Concentrations of the various volatiles in the extracted
air samples were somewhat surprising. Although TCE was
a prominent contaminant, it was not always the
predominant one. Particularly in the postfracture
extraction, it was clear from the complexity of, the VOC
scan hi the field-GC analyses,that many other constituents
were now being extracted. This was confirmed by GC/MS.
analyses (Table C-8). Similar constituents, but at lower
concentrations, were also found in the ' air samples
examined during HGI. It is unclear what caused the
increase of other classes of compounds in the postfracture
38
-------
sample, but it may be speculated that pockets of absorbed
or NAPL organics were accessed.
Table C-8. GCfMS Analysis of VQCs in Extracted Air
Contaminant PFE Tests HGI Tests
Prefecture Postfracture PreHGI-1 HGI-1 HGI-2
Concentration, ppmv
methylene chloride
chloroform
c-1,2-dichloroethene
trichloroethene
benzene
tetrachloroethene
toluene
xylene, m/p-
xylene, o-
1.4
3.5
U«3.)
59.4
5.4
3.3
U«3.3)
U«2.8)
U«2.8)
26.0
108.5
U«12.5)
113.4
412.7
220.4
5.2J
U«11.4)
U«11.4)
11.9
40.2
21.8
49.4
107.8
92.8
1.8J
5.0
3.2
0.93 3.6
3.2 1.5
1.2 2.2
10.2 18.6
7.1 3.4
4.3 7.5
U«.6) U«.5)
0,25 U«.5)
0.2J U«.5)
U - below detection Jimit
J - no definition available, probably below quantitation limit
Although these VOCs were measured in an essentially
closed system, the presence of elevated concentrations of
benzene must serve as a warning that careful monitoring
and personal protection must be employed during well
installation, during fracturing, and at any other times when
unexpected exposure could occur.
Quality Assurance
The critical analysis of trichloroethene (TCE) was
performed on-site using capillary column gas chromato-
graphy and a flame ionization detector. Samples were
collected in Tedlar bags and analyzed in accordance with
EPA Method 18. Extensive QA/QC procedures were
specified and followed, including initial and continuing
calibration protocols, blank analyses, second-source
standards, audit gas analyses, replicate injections, and
duplicate sample analyses. Accuracy was evaluated
through the analysis of second-source standards and audit
gases; these analyses generally met specified criteria
(±10%), although some low concentration standards were
outside the limits. The potential bias in TGE
concentrations reported at values near the detection limit of
1.0 ppmv has limited impact on project objectives since
these results were not from critical tests. Precision, as
assessed by duplicate sample analyses, was generally
excellent with most RPD values less than 10% for sample
pairs with TCE concentrations above the detection limit.
Critical process determinations included flow rate,
temperature, and pressure. There exists a slight potential
for a maximum 20% error in some reported pressure
values; some pressure measurements may not have been
corrected as required, based on parity plots of the
calibrated gauge, when the specific gauge used was not
documented.
In general, data generated for this project were
determined to be of sufficient quality to provide for the
proper evaluation of test objectives.
39
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Appendix D-l
Soil Vat Tests
Basic evidence for the benefits of pneumatic fracturing
were first obtained by laboratory tests carried out at
HSMRC.
A series of plexiglass vats were filled with soils
containing a surrogate contaminant. The vats were
equipped with a central nozzle connected to laboratory
compressed air (60 psig) for fracturing. Extraction rubes
were located in the four corners of the vats. Vacuum
extraction tests could be carried out using vacuum, positive
pressure, or a combination of both.
Two different soil types were tested, a silty sand
(United Classification "SM") and a silty clay (United
Classification "CL"). The surrogate contaminant was
alcohol in water, which avoided any problems with
disposal.
Test results with these systems and soils indicated
increases in contaminant removal by 100% to 360% after
fracturing, compared to vacuum extraction or ah- injection
of unfractured soil, respectively.
Table D-1. Vat tests of Pneumatic Fracturing
Test
no.
PF-3
PF4
PF-5
PF-6
PF-7
PF-8
PF-9
PF-10
PF-11
Soil
type
SM
SM
SM
CL
CL
CL
CL
CL
CL
Extract Surrogate Soil density
mode cone, before after
% Ib/cf
Al*
Al
VE/AI
Al
Al
VE
VE
VE
Al
14.7
13.8
15.8
10.6
14.8
14.0
14.0
15.9
15.7
101.1
102.1
100.2
100.2
112.0
111.4
121.5
99.3
100.7
88.6
91.8
92.3
84.7
98.5
103.5
108.5
93.5
92.1
Increase
in removal,
%
320
170
100
230
183
14Ei
140
180
360
Al - air inject, VE - vacuum extraction
Conclusions
1. Pneumatic fracturing consistently increased contaminant
removal, by rates ranging from 100% to 360% greater
than in unfractured extraction.
2. The increases in contaminant removal are primarily
attributable to increases in air flow in the fractured soil.
3. Soil type affects the benefits of fracturing. • Finer
grained soils exhibit more gradual contaminant loss,
which is consistent with their lower permeability.
40
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Appendix D-2
Test Site - Newark, NJ
Background
A series of pneumatic fracturing tests were performed
at a clean site located on the NJIT campus in Newark, NJ.
The purpose was to evaluate the effects of fracturing on
sedimentary bedrock using ground surface heave and
formation permeability. All tests were conducted in the
vadose zone, and were continued over a period of 8 mo to
examine the effects of fracture longevity in rock. The site
was located hi an active parking lot which was subjected
to car and truck traffic throughout the study period.
The site is underlain by the Brunswick Formation
which consists of fractured siltstones and sandstones. A
single 28 ft deep well was drilled to serve both as a
fracture well and an extraction well. It was cased to a
depth of 4 ft, below which the well remained uncased with
a 3-in. bore. The water table fluctuated between 21 and 25
ft deep throughout the study period.
Test Procedure and Results
Baseline air permeability was measured by extracting
through a double packer system in 2-ft intervals over the
depth range of 7 to 19 ft. Total well behavior was also
measured by extracting from the entire well. All ah- flows
were measured at a standard vacuum of 20 in. H2O.
Fracture injections were then made at two discrete depth
intervals: 9 to 11 ft and 15 to 17 ft. The profile of air
permeability was measured again to evaluate the changes
hi ah- flow caused by the fracturing. Ground surface heave
was monitored during fracturing with a reference beam
system.
The permeability tests showed that the air flows hi the
fracture zones increased 9 to 14 tunes as result of
fracturing. The air flow hi the 9 to 11 ft zone increased
from 2.1 scfrn to >10.5 scfhi, and the ah- flow hi the 15 to
17 ft zone increased from 0.5 scfrn to 7.2 scfrn. The
effects of the fracture injection on the 9 to 11 ft zone is
summarized hi Figure D-l, which also depicts the visual
log for the rock core.
Air flow measurements were repeated over a period of
8 mo during which the area was subjected to car and truck
traffic. The fractures remained viable throughout the study
period and no significant fluctuations hi ah- flow were
observed. The long .term flow behavior of the 15 to 17 ft
fracture zone is shown hi Figure D-2.
Ground surface heave measurements made during
injection indicated that the fractures propagated at least 10
ft hi all directions. Maximum ground surface heave for
the 9 to 11 ft zone was 0.16 hi., and 0.13 in. at the 15 to
17 ft zone. No discernible effects were observed on the
asphalt pavement which covered the test site.
Conclusions
Pneumatic fracturing successfully enhanced the
permeability of sedimentary rock from 5 to 14 tunes.
Long term studies showed that fractures remained viable hi
rock for at least 8 months. Measurement of downhole
fracture injection pressures suggested that the principal
mechanism of permeability enhancement is dilation of
existing rock discontinuities. Ground surface heave
measurements showed that fracture radii exceeded 10 ft.
41
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NEW JERSEY INSTITUTE OF TECHNOLOGY
AIR PERMEABILITY LOG
MOJECT. HSHHC SITE 21 PNEUMATIC FrUCTURmO QATC 3/8/91
LOCATION- *TC PARKINS LOT, NEWARK. H.J. ~2L~
iwcxcone
LOU
'Z 3 4 S 6 7 8 9 10 II 12 £
AlrFlo»(CF.MJot20"rUO v«W,« 'S _7l
IO.S »
"(ZIExtrap.)
,—Shan Parting*
NOTES
L Zont bitwun 9' to II1 wa* pniumatlcally fraeturtd. J2
. Flow volui in fractur* zone wot txtraDalatid tlniarlv
from 10 to 20" H»0 vacuum. y
Mwnancal Una* During Coring'
I/a" To 1/4" Fraquint POOH Voidt
I 0!«eontinuily
Urunanrad on Pnviow 5' Run
Flow Gtfor* Fractur*
Additional Flaw Afttr Fractura
Figure D-l. Air permeability log, 9-11 ft fracture zone.
NEW.JERSEY INSTITUTE OF TECHNOLOGY
'AIR PERMEABILITY LOG
PHOJECT HSHRC SITE 21 PHEUHATIC FRACTURING DATE 4/5/91
LOCATIOm ATC PAHKIHO LOT. NEWARK, H.J.
<— Shall Parting
NOTES
I. Zona b«twi«n 19* to 17* was pniumatically.
fraeturid.
LEGEND
,!___ Mtenarical 8m> During Camg
. • • 1/8" To 1/4" Fraquint Poelt Votdi
• »°
—— EiMIng Dlicanlinuily
Unraegnnd on Pmioui 5* Run
Flow Bifort Fractun
Additional Flow Afttr Fracrura
Figure D-2. Air permeability log, 15-17 ft fracture zone.
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Appendix D-3
Former Tank Farm - Richmond VA
Background
An abandoned section of a tank farm in Richmond,
Virginia was the location of this demonstration of
Pneumatic Fracturing Extraction. The formation at this site
consisted of highly overconsolidated stiff clay, (United
Classification CH-MH) which was overlain by a clayey silt
' and hi some sections by a concrete slab. All fracture
injections were made between 5 to 10 ft below grade in the
stiff clay layer. ,
The aboveground tank at this site had been removed
with only the concrete slab remaining. Soil samples taken
from the vadose zone indicated that methylene chloride
(CHzCl.,) and trichloroethane (TCA) were the principal
contaminants of concern. An adjacent sump seemed to be
the source of contamination.
concentration of CH2C12 leveled off to about 200 ppm,
which was still far above the concentrations that were
detected before application of the PFE process.
Pra-Fracture Mass Removal Concentrations
10 16 20 26
Results
Baseline conditions were established for both air
extraction flow rate and contaminant mass removal. These
tests confirmed the extremely low formation permeability,
as the flow rates were less than 0.00071 scfm, which was
the lower limit of the flow measurement system. The
removal rate for both contaminants peaked at about 23
ppm, and neared a non-detect level after 35 minutes.
Contaminant concentrations were measured using a gas
chromatograph.
During pneumatic injection events, surface heave was
measured to be over 1 in. in some spots. Although the
concrete pad did deflect some of the injection influence,
fractures were detected below the concrete pad.
Following pneumatic injections, the formation
permeability greatly unproved as indicated by the 4,900%
increase in air extraction flow rates. Contaminant
extraction concentrations peaked at 8,677 ppm for CH2C12
and 4,050 ppm for TCA as shown hi Figure D-3. The
Post Fracture Mass Removal Concentrations
30 40
Tfiw (minutM)
70
Figure D-3. Effect of fracturing, Richmond, VA site.
Conclusions
PFE increased both the extraction air flow rate and the
concentration of contaminants in the extraction stream. It
was also demonstrated that the injections from this process
created fractures below the existing concrete slab.
43
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Appendix D-4
Industrial Site - Newark, NJ
Background
A pilot test of Pneumatic Fracturing Extraction (PFE)
was performed at an industrial site in Newark, NJ. The
test was conducted in a clean portion of the site in order to
demonstrate an increase in formation permeability.
Fracturing on this site occurred both in the vadose zone
and in the saturated zone.
The geology of the site consisted of an approximately
6-in. to 12-in. concrete cap over 18 in. of gravel. This was
followed by an unconsolidated zone consisting of urban fill
overlying natural sediments of silts, clays, and sands. At
the outset of the test, the depth to groundwater was
measured at 5.1 ft below grade. A single 4-in. fracture
well (3-in. open-bore) was installed in the selected clean
section of the site. This well was surrounded by four
monitoring wells at distances ranging from 7.5 to 18 ft
from the fracture point.
Results
Baseline conditions were established for both
extraction flow rate and vacuum radius of influence. Total
well extraction with monitoring wells sealed yielded an
effluent flow rate of 4.7 serin. Vacuum influence
measurements taken during this test ranged from 2 to 12.5
in. (of water) at the monitoring wells. Operating the
extraction system utilizing the monitoring wells as passive
inlet wells increased the extraction flow rate to 6 scfrn.
The PFE technology was applied to two intervals. The
first fracture interval (4.0 to 6.2 ft below grade), intersected
the water table, which was at 5.1 ft. A second fracture
interval (5.0 to 1.2 ft), was located completely in the
saturated zone.
The surface heave observed during the pneumatic
injections ranged from 0.16 to 0.19 in. After all PFE
injections had been completed, the air extraction flow rates
increased to 15.26 scfrn. All monitoring wells measured an
increase in vacuum pressure, which ranged from 8 to 30 in.
of water. Operating with passive inlet wells, extraction
flow rate increased to 17.5 scfrn.
Conclusions
PFE was effective in increasing the extraction ah- flow
rate at this site almost 400%. The process was also
effective in increasing the effective vacuum radius of
influence. Calculations showed that the area under
remedial influence increased from 143 sq ft to 380 sq ft
due to the PFE process.
44
.S. GOVERNMENT PRINTING OFFICE: 1993-752-987
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