United States Office of Research and EPA/600/R-00/091
Environmental Protection Development October 2000
Agency Washington, D.C. 20460
Environmental Technology
Verification Report
Groundwater Sampling
Technologies
W. L. Gore and Associates,
Inc.
GORE-SORBER® Water Quality
Monitoring
Sandia
National
ETV ETY ET
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THE ENVIRONMENTAL TECHNOLOGY VERIFICATION
PROGRAM
JLrKAlVlA
V
ET
® Sandia
National
Laboratories
ETV JOINT VERIFICATION STATEMENT
TECHNOLOGY TYPE: GROUNDWATER SAMPLING TECHNOLOGIES
APPLICATION: VOC-CONTAMINATED WATER SAMPLING
TECHNOLOGY NAME: GORE-SORBER Water Quality Monitoring
COMPANY: W. L. Gore and Associates, Inc.
ADDRESS: 100 Chesapeake Blvd. PHONE: (410)392-7600
Elkton, MD 21922-0010 FAX: (410)506-4780
WEBSITE: http://www.gore.com/corp/separations/chemical.html
EMAIL: rfenster(Sjwlgore. com
PROGRAM DESCRIPTION
The U.S. Environmental Protection Agency (EPA) has created the Environmental Technology
Verification Program (ETV) to facilitate the deployment of innovative or improved environmental
technologies through performance verification and dissemination of information. The goal of the ETV
Program is to further environmental protection by substantially accelerating the acceptance and use of
improved and cost-effective technologies. ETV seeks to achieve this goal by providing high-quality,
peer-reviewed data on technology performance to those involved in the design, distribution, financing,
permitting, purchase, and use of environmental technologies.
ETV works in partnership with recognized standards and testing organizations and stakeholder groups
consisting of regulators, buyers, and vendor organizations, with the full participation of individual
technology developers. The program evaluates the performance of innovative technologies by
developing test plans that are responsive to the needs of stakeholders, conducting field or laboratory tests
(as appropriate), collecting and analyzing data, and preparing peer-reviewed reports. All evaluations are
conducted in accordance with rigorous quality assurance protocols to ensure that data of known and
adequate quality are generated and that the results are defensible.
The Site Characterization and Monitoring Technologies Pilot, one of 12 technology areas under ETV, is
administered by EPA's National Exposure Research Laboratory. Sandia National Laboratories, a
Department of Energy laboratory, is one of the verification testing organizations within the ETV Site
Characterization and Monitoring Pilot. Sandia collaborated with personnel from the U.S. Geological
Survey to conduct a verification study of groundwater sampling technologies. This verification
statement provides a summary of the results from a verification test of GORE-SORBER Water Quality
Monitoring technology manufactured by W. L. Gore and Associates, Inc.
EPA-VS- SCM-38 The accompanying notice is an integral part of this verification statement. October 2000
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DEMONSTRATION DESCRIPTION
In August 1999, the performance of six groundwater sampling technologies was evaluated at the US
Geological Survey (USGS) Hydrological Instrumentation Facility at the National Aeronautics and Space
Administration Stennis Space Center in southwestern Mississippi. Each technology was independently
evaluated in order to assess its performance in the collection of volatile organic compound- (VOC)
contaminated water. The verification test design incorporated the use of a 5-inch diameter, 100-foot
standpipe at the USGS facility. The standpipe, serving as an "above-ground" well, was filled with tap
water spiked with various concentration levels of six target volatile organic compounds. The target
compounds (1,2-dichloroethane, 1,1-dichloroethene, trichloroethene, benzene, 1,1,2-trichloroethane, and
tetrachloroethene) were chosen to represent the range of VOC volatility likely to be encountered in
normal sampler use. Water sampling ports along the exterior of the standpipe were used to collect
reference samples over the same time interval that the passive membrane samplers were exposed to the
water inside the standpipe. Two trials were carried out at the standpipe. The first trial was a relatively
low (-20 |Jg/L) concentration level mixture of the six target VOCs. The second trial incorporated a
slowly changing concentration in the standpipe at higher (-200 |Jg/L) concentrations. The modules were
tested at five depths ranging from 17 to 53 feet.
The standpipe trials were supplemented with additional trials at groundwater monitoring wells in the
vicinity of sites with VOC-contaminated groundwater at the NASA Stennis facility. The GORE-
SORBER modules were deployed in five 2-inch and 4-inch wells, along with co-located submersible
electric gear pumps as reference samplers. The principal contaminant at the onsite monitoring wells was
trichloroethene. The onsite monitoring provided an opportunity to observe the operation of the sampling
system under typical field-use conditions.
All GORE-SORBER modules were analyzed using a gas chromatograph-mass spectrometer (GC-MS) at
the W. L. Gore and Associates, Inc. (Gore) laboratory since the sampler is sold with analysis included.
The Gore laboratory uses a modified method derived from EPA Methods SW-846 8260 and 8270. All
reference samples were analyzed by two identical field-portable GC-MS systems that were located at the
test site during the verification tests. The GC-MS analytical method used for the reference samples was
a variation of EPA Method 8260 purge-and-trap GC-MS, incorporating a headspace sampling system in
lieu of a purge and trap unit. The overall performance of the groundwater sampling technologies was
assessed by evaluating sampler precision and comparability with reference samples. Other logistical
aspects of field deployment and potential applications of the technology were also considered in the
evaluation.
Details of the demonstration, including an evaluation of the sampler's performance, may be found in the
report entitled Environmental Technology Verification Report: W. L. Gore and Associates, GORE-
SORBER Water Quality Monitoring, EPA/600/R-00/091.
TECHNOLOGY DESCRIPTION
The GORE-SORBER module consists of a water impermeable membrane surrounding an adsorbent
material that is used to collect volatile and semi-volatile compounds in water. When placed in the
screened, saturated interval of a monitoring well or piezometer, the waterproof, vapor-permeable
membrane collector housing allows for the selective movement of volatile and semi-volatile organic
compounds across the membrane onto the adsorbent. The hydrophobic nature of the membrane restricts
liquid water transfer across the membrane.
A GORE-SORBER module consists of four separate sorber packets combined into a single sampling
unit. A typical sorber packet is about 25 mm in length, 3 mm in diameter, and contains 40 mg of a
granular adsorbent material that is selected on the basis of the specific compounds to be detected.
Proprietary polymeric and carbonaceous resins are used as the sorbent material because of their affinity
EPA-VS- SCM-38 The accompanying notice is an integral part of this verification statement. October 2000
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for a broad range of VOCs and semi-VOCs. The sorber packets are sheathed in the bottom of a length of
vapor-permeable insertion and retrieval cord that includes a loop attachment. The four sorber units and
associated membrane cord are collectively termed the GORE-SORBER module. Both the retrieval cord
and sorbent container are constructed solely of inert, hydrophobic, microporous membrane. Every
module has sufficient sorbers such that there is always a minimum of two samples available in each
module for use as duplicates or backups as needed. A unique feature of the membrane is that it is
hydrophobic, excluding the transfer of liquid water across the membrane, while facilitating vapor
transfer. Thus, VOC and SVOC vapors can penetrate the sorbent module freely and collect on the
adsorbent material. Depending on the membrane characteristics, liquid water transfer across the
membrane will be limited up to a particular depth, and therefore, it is important to know the desired
depth of installation. Different membranes can be used for different installation depths, and GORE
technical support personnel can help in membrane selection. Standard (STND) and high water entry
pressure (HWEP) membranes were evaluated in this verification test.
The sampling modules are compact and completely passive. They are fastened to a string and stainless
steel weight, suspended in the well, normally at the mid-screen location, and left in place for 48 hours.
Upon retrieval they are placed in airtight containers and overnight shipped to the Gore laboratory.
Laboratory analysis options for the sorbent modules include methods for the determination of volatile
organic compounds, semi-volatile organic compounds, and polycyclic aromatic hydrocarbons. In
addition to these common suites of compounds, the samples can also be analyzed for specific groups of
compounds; i.e., fuel hydrocarbons, chlorinated organics, and others. The analyses follow modified EPA
SW846 Methods 8260 for VOCs, and 8270 for semi-VOCs. All analytical services on GORE-SORBER
modules are performed at the W.L. Gore & Associates, Inc. laboratory in Elkton, MD.
VERIFICATION OF PERFORMANCE
The following performance characteristics of the GORE-SORBER Water Quality Monitoring system
were observed:
Precision: The precision of the sampling modules, under stable concentration conditions, was
determined by the collection of replicate samples in a standpipe trial in which the target concentration
levels were about 20 ng/L at water column depths ranging from 17 to 46 feet. GORE-SORBER STND
membrane module precision, represented by the relative standard deviation, for all target VOC
compounds at 17- and 28-foot sampling depths ranged from 2 to 28% with a median value of 14%.
GORE-SORBER HWEP module relative standard deviations at 17-, 28-, 35- and 46-foot depths ranged
from 9 to 35% with a median of 21%. Reference method relative standard deviations, under similar
sampling, conditions ranged from 3 to 17% with a median value of 12%.
Comparability with a Reference: GORE-SORBER module results are reported in terms of total mass of
VOC collected in the module. In this format, the data are not directly comparable to the concentration
data derived from conventional groundwater monitoring. The first deployment of a module is usually
accompanied by the collection and analysis of a conventional groundwater sample, which enables
comparison of the two data formats. The correlation between GORE-SORBER modules data and
conventional groundwater sample data was carried out by deploying GORE-SORBER modules and
reference pump in five different wells with known TCE contamination. Trichloroethene concentration in
these 5 wells ranged from 5 to 2,000 |Jg/L. The observed correlation between GORE-SORBER module
data and reference sample data was very good. The correlation coefficients for the STND and HWEP
modules were 0.997 and 0.998 respectively.
Versatility: The versatility of the GORE-SORBER module in typical field screening and monitoring
applications for VOC compounds in groundwater is as follows: The modules have limited versatility in
terms of deployment depth since the maximum deployment for which they are rated is a water column
depth of 50 feet. The modules have wide versatility in terms of the number of compounds detected
EPA-VS- SCM-38 The accompanying notice is an integral part of this verification statement. October 2000
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since they can sample both VOCs and semi-VOCs. The modules are judged to have limited versatility in
terms of application to monitoring for regulatory compliance by virtue of their moderate (15-30%
relative standard deviation) precision.
Logistical Requirements: The sampling modules can be easily deployed and retrieved in the field by
one person. An hour of training is generally adequate to become proficient in the use of the samplers.
The samplers require a 48-hour exposure interval, and thus two trips are required to the well for
deployment and retrieval. The modules are completely passive and require no external power for
operation. Following retrieval, the samplers are shipped to the Gore analytical laboratory by overnight
mail. Refrigeration of the sample during shipment is not required. In order to estimate groundwater
concentrations, the GORE-SORBER module must be periodically accompanied by co-located
conventional groundwater sampling and analysis. Vendor recommendations are, at the onset of
sampling, to deploy the modules and conventional methods in two parallel sampling events to establish
the relationship between the two sampling methods. Thereafter, annual parallel sampling events are
suggested.
Overall Evaluation: The results of this verification test show that the GORE-SORBER Water Quality
Monitoring system can be used to monitor long-term concentration trends of VOCs in monitoring wells.
The GORE-SORBER modules are designed and are optimally suited for relatively low-cost VOC
concentration trend monitoring and screening. They are well suited for plume edge monitoring to detect
general concentration trends. The technology does require the periodic collection and analysis of co-
located reference samples in order to interpret the data from GORE-SORBER module in terms of water
concentration.
As with any technology selection, the user must determine if this technology is appropriate for the
application and the project data quality objectives. For more information on this and other verified
technologies visit the ETV web site at http://www.epa.gov/etv.
Gary J. Foley, Ph.D.
Director
National Exposure Research Laboratory
Office of Research and Development
Samuel G Varnado
Director
Energy and Critical Infrastructure Center
Sandia National Laboratories
NOTICE: EPA verifications are based on evaluations of technology performance under specific, predetermined
criteria and appropriate quality assurance procedures. The EPA and SNL make no expressed or implied
warranties as to the performance of the technology and do not certify that a technology will always operate as
verified. The end user is solely responsible for complying with any and all applicable federal, state, and local
requirements. Mention of commercial product names does not imply endorsement.
EPA-VS-SCM-38
The accompanying notice is an integral part of this verification statement.
October 2000
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EPA/600/R-00/091
October 2000
Environmental Technology
Verification Report
Groundwater Sampling
Technologies
W. L. Gore and Associates, Inc.
GORE-SORBER® Water Quality
Monitoring
by
Wayne Einfeld
Sandia National Laboratories
Albuquerque, New Mexico 87185
and
Eric N. Koglin
U.S. Environmental Protection Agency
Environmental Sciences Division
National Exposure Research Laboratory
Las Vegas, Nevada 89193-3478
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Notice
The U.S. Environmental Protection Agency (EPA), through its Office of Research and Development (ORD),
funded and managed, through Interagency Agreement No. DW66940927 with Sandia National Laboratories,
the verification effort described herein. This report has undergone peer and administrative review and has
been approved for publication as an EPA document. Mention of trade names or commercial products does
not constitute endorsement or recommendation for use of a specific product.
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Table of Contents
List of Figures iii
List of Tables iii
Acknowledgments v
List of Abbreviations and Acronyms vii
1 INTRODUCTION 1
Background 1
Demonstration Overview 1
2 TECHNOLOGY DESCRIPTION: W. L. GORE AND ASSOCIATES INC. GORE-SORBER WATER QUALITY
MONITORING 3
Module Configuration 3
Sorbent Selection 3
Shipping 3
Installation and Retrieval 4
Analytical Methods 5
Data Analysis 5
Guidelines for Use 5
Data Interpretation and Use 6
3 DEMONSTRATION PROCESS AND DESIGN 7
Introduction 7
Site Description 7
Verification Test Design Summary 9
Test Design Elements 9
Sampler Performance Parameters 10
Sample Analysis 11
Data Processing 12
Data Quality Control 12
Verification Test Plan 13
Standpipe and GW Well Sampling Matrix 13
Chronological Summary of Demonstration Activities 14
Deviations from the Verification Plan 15
4 GORE-SORBER WATER QUALITY MONITORING PERFORMANCE EVALUATION 17
Introduction 17
Standpipe Concentration Stability 17
Sampler Precision 17
Monitoring Well Results 20
Deployment Logistics 21
Sampler Versatility 21
Performance Summary 23
5 GORE-SORBER WATER QUALITY MONITORING TECHNOLOGY UPDATE AND REPRESENTATIVE
APPLICATIONS 25
Soil Gas Applications 25
Water Quality Monitoring 25
6 REFERENCES 29
APPENDICES
A: REFERENCE PUMP PERFORMANCE 31
B: QUALITY SUMMARYFOR ANALYTICAL METHOD 35
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List of Figures
1 Schematic diagram of a GORE- SORBER module 4
2 The standpipe at the USGS Hydrological Instrumentation Facility 8
3 TCE Concentration over the 48-hour exposure interval in the standpipe trial at all sampling levels 17
4 STND module precision in the standpipe trial by depth and target compound 19
5 HWEP module precision in the standpipe trial by depth and target compound 19
6 Scatter plot of STND module data vs. reference data for all GW monitoring wells 22
7 Scatter plot of HWEP module data vs. reference data for all GW monitoring wells 22
8 Statistical Comparisons between groundwater data and module data for TCE, 1,1,2,2-tetrachloro-ethane, and
carbon tetrachloride 26
A-l Percent recoveries of the reference pump by compound for the four standpipe trials 34
B-l Calibration check control chart for TCE on GC-MS #1 36
B-2 Calibration check control chart for TCE on GC-MS #2 37
B-3 Calibration check control chart for PCE on GC-MS #1 37
B-4 Calibration check control chart for PCE on GC-MS #2 38
B-5 GC-MS system check relative percent differences 38
List of Tables
1 Construction Details of Groundwater Monitoring Wells 9
2 Target VOC compounds 10
3 The GORE-SORBER Module Verification Trial at the Standpipe 13
4 GORE-SORBER Module Verification Trials at the Groundwater Monitoring Wells 14
5 STND and HWEP Module Precision Summary from the Standpipe Trial 18
6 STND and HWEP Module and Reference Results from GW Monitoring Wells 20
7 GORE-SORBER Module Performance Summary 23
8 Cost Comparison for One Round of Sampling 27
A-l Precision of Gear Pump and Reference Samples in Standpipe Trials 32
A-2 Comparability of the Gear Pump with the Reference Samples in Standpipe Trials 33
B-l Onsite GC-M S-Headspace Method Quality Control Measures 35
ill
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IV
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Acknowledgments
The authors acknowledge the support of all those who helped in the vendor solicitation, planning, field
deployment, and analysis phases of this verification test. In particular, we recognize Steve Gardner (US EPA
NERL, Las Vegas) who provided technical assistance and peer reviewed the test plan. We also acknowledge
the assistance of Eugene Hays, Bill Davies, and Ed Ford (US Geological Survey) in providing access to the
Standpipe Facility at the NASA Stennis Space Center as well as for their administrative and logistical support
during the standpipe and groundwater monitoring trials. We also thank Ronald McGee and Jenette Gordon
(NASA, Environmental Management) for their willingness to grant us access to the groundwater monitoring
wells at the NASA Stennis Space Center. Thanks also to Greg New (Foster Wheeler Environmental
Corporation) for his assistance in getting much of the site hydrological and well monitoring data into our
hands during the planning phases of this test. Finally, we thank Craig Crume and Mika Greenfield (Field
Portable Analytical) for their long hours, care, and diligence in onsite sample analysis during the field trials.
For more information on the Groundwater Sampling Technology Verification Test, contact
Eric Koglin Wayne Einfeld
Pilot Manager ETV Project Manager
Environmental Protection Agency Sandia National Laboratories
Environmental Sciences Division MS-0755 P.O. Box 5800
National Exposure Research Laboratory Albuquerque, NM 87185-0755
P. O. Box 93478 (505) 845-8314 (v)
Las Vegas, NV 89193-3478 E-mail: weinfel@sandia.gov
(702) 798-2432 (v)
E-mail: koglin.eric@epa.gov
For more information on W. L. Gore and Associates Inc., GORE-SORBER Water Quality Monitoring,
contact:
Ray Fenstermacher
W. L. Gore and Associates
100 Chesapeake Blvd. P.O. Box 10
Elkton, MD 21922-0010
410/506-4775 (v) 410/506-4780 (f)
E-mail: rfenster@wlgore.com
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VI
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List of Abbreviations and Acronyms
BFB
BNZ
BTEX
CF
DIFF
EPA
ePTFE
ETV
GC-MS
fflF
HWEP
MSL
MW
NASA
ND
NERL
PAH
PCE
PTFE
QA
QC
KEF
RSD
SCMT
SNL
SP
SSC
STND
SVOC
TCE
TWA
USGS
VGA
VOC
12DCA
11DCE
112TCA
Bromofluorobenzene
Benzene
Benzene, toluene, ethylbenzene, and xylenes
Comparison Factor
Difference
US Environmental Protection Agency
Expanded poly tetrafluoroethene
Environmental Technology Verification Program
Gas chromatograph-mass spectrometer
Hydrological Instrumentation Facility
High water entry pressure (membrane)
Mean sea level
Monitoring well
National Aeronautics and Space Administration
Not detected
National Exposure Research Laboratory
Poly cyclic aromatic hydrocarbon
Tetrachloroethene
Polytetrafluoroethylene
Quality assurance
Quality control
Reference
Relative standard deviation
Site Characterization and Monitoring Technologies Pilot
Sandia National Laboratories
Sample port
Stennis Space Center
Standard (membrane)
Semi-volatile organic compound
Trichloroethene
Time-weighted average
US Geological Survey
Volatile organics analysis
Volatile organic compound
1,2-dichloroethane
1,1 -dichloroethene
1,1,2-trichloroethane
vu
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Vlll
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Section 1 — Introduction
Background
The U.S. Environmental Protection Agency (EPA)
has created the Environmental Technology
Verification Program (ETV) to facilitate the
deployment of innovative or improved
environmental technologies through performance
verification and dissemination of information. The
goal of the ETV Program is to further
environmental protection by substantially
accelerating the acceptance and use of improved
and cost-effective technologies. ETV seeks to
achieve this goal by providing high-quality, peer-
reviewed data on technology performance to those
involved in the design, distribution, financing,
permitting, purchase, and use of environmental
technologies.
ETV works in partnership with recognized
standards and testing organizations and
stakeholder groups consisting of regulators,
buyers, and vendor organizations, with the full
participation of individual technology developers.
The program evaluates the performance of
innovative technologies by developing test plans
that are responsive to the needs of stakeholders,
conducting field or laboratory tests (as
appropriate), collecting and analyzing data, and
preparing peer-reviewed reports. All evaluations
are conducted in accordance with rigorous quality
assurance (QA) protocols to ensure that data of
known and adequate quality are generated and that
the results are defensible.
ETV is a voluntary program that seeks to provide
objective performance information to all of the
participants in the environmental marketplace and
to assist them in making informed technology
decisions. ETV does not rank technologies or
compare their performance, label or list
technologies as acceptable or unacceptable, seek
to determine "best available technology," nor
approve or disapprove technologies. The program
does not evaluate technologies at the bench or
pilot scale and does not conduct or support
research.
The program now operates 12 pilots covering a
broad range of environmental technology areas.
ETV has begun with a 5-year pilot phase (1995-
2000) to test a wide range of partner and
procedural alternatives in various pilot areas, as
well as the true market demand for and response to
such a program. In these pilots, EPA utilizes the
expertise of partner "verification organizations" to
design efficient processes for conducting
performance tests of innovative technologies.
These expert partners are both public and private
organizations, including federal laboratories,
states, industry consortia, and private sector
facilities. Verification organizations oversee and
report verification activities based on testing and
QA protocols developed with input from all major
stakeholder/customer groups associated with the
technology area. The demonstration described in
this report was administered by the Site
Characterization and Monitoring Technologies
(SCMT) Pilot. (To learn more about ETV, visit
ETV's Web site at http://www.epa.gov/etv.)
The SCMT pilot is administered by EPA's
National Exposure Research Laboratory (NERL).
Sandia National Laboratories, one of two
verification organizations associated with the
SCMT pilot, conducted a verification study of
groundwater sampling technologies during the
summer of 1999. Groundwater sampling
technologies are commonly employed at
environmental sites for site screening and
characterization, remediation assessment, and
routine environmental monitoring. Groundwater
sampling technologies generally fall into three
categories: 1) active pumping systems, 2) discrete
level grab systems, and 3) passive diffusional
systems. All three types of samplers were
evaluated during this verification study.
Demonstration Overview
In August 1999, a demonstration study was
conducted to verify the performance of six
groundwater sampling systems: Multiprobe 100
(multi-level sampler, Burge Environmental,
Tempe, AZ), SamplEase (bladder pump, Clean
Environment Equipment, Oakland, CA), Micro-
Flo (bladder pump, Geolog Inc., Medina, NY),
Well Wizard (bladder pump, QED Environmental,
Ann Arbor, MI), Kabis Sampler, (discrete-level
grab sampler, Sibak Industries, Solano Beach,
CA), and GORE-SORBER Water Quality
Monitoring (diffusional sampler, W. L. Gore and
Associates Inc., Elkton, MD). This report contains
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the evaluation of the W. L. Gore and Associates
Inc., GORE-SORBER Water Quality Monitoring
technology.
It is important to point out that the scope of this
technology demonstration was purposely limited
to sampler performance parameters such as
precision, accuracy, and where applicable,
deployment logistics. Several of the systems
tested in this study are specifically designed for
the low volume purge methods—a relatively new
approach to the collection of a representative
sample from a groundwater monitoring well. This
study was specifically intended to evaluate
sampler performance and was not an evaluation of
the merits of a low-flow purge and sampling
protocol. This protocol has been proposed,
published, and tested elsewhere [Puls and
Barcelona, 1996] and is beyond the scope of this
particular investigation.
The demonstration was conducted in August of
1999 at the National Aeronautic and Space
Administration (NASA) Stennis Space Center in
southwestern Mississippi. Sandia worked in
cooperation with the US Geological Survey, a
federal agency resident at the NASA Stennis site,
and used a 100-foot, 5-inch diameter standpipe
that is one of the testing facilities associated with
the USGS Hydrological Instrumentation Facility at
this site. The standpipe, serving as an "above-
ground" well, was filled with water spiked with
various concentration levels of six target volatile
organic compounds (VOC). Water sampling ports
along the exterior of the pipe permitted the
collection of reference samples at the same time
that groundwater sampling technologies collected
samples from the interior of the pipe.
The standpipe trials were supplemented with
additional trials at a number of groundwater
monitoring wells at sites with VOC-contaminated
groundwater at the NASA Stennis facility. The
technologies were deployed in five 2-inch wells
along with a co-located reference sampler. The
principal contaminant at the site was
trichloroethene.
With the exception of the GORE-SORBER Water
Quality Monitoring technology, all technology and
reference samples were analyzed by the same
field-portable gas chromatograph-mass
spectrometer system that was located at the test
site during the verification tests. In the case of the
GORE-SORBER modules, analysis was
performed at an offsite W.L. Gore laboratory since
purchase of the module normally includes
analysis. The overall performance of the
groundwater sampling technologies was assessed
by evaluating sampler precision as well as
comparability with reference samples collected at
the same time technology samplers were collected
during the various trials. Other aspects of field
deployment, such as logistical requirements and
potential applications of the technology are also
considered in this evaluation.
A brief outline of this report is as follows:
Section 2 contains a brief description of the
GORE-SORBER module and its capabilities.
Section 3 outlines a short description of the test
facilities and a summary of the verification test
design. Section 4 includes a technical review of
the data with an emphasis on assessing overall
sampler performance. Section 5 presents an
update of the GORE-SORBER Water Quality
Monitoring technology and provides examples of
representative applications in environmental
characterization and monitoring settings.
Appendix A includes performance data for the
reference pump, and Appendix B includes an
assessment of quality control data associated with
the analytical method used in this study.
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Section 2 — Technology Description: W. L. Gore and Associates
Inc. GORE-SORBER Water Quality Monitoring
This section provides a general description and
overview of the capabilities of the GORE-
SORBER Water Quality Monitoring technology.
The information used to prepare this section was
provided by W. L. Gore and Associates, Inc.
The GORE-SORBER module consists of an
expanded polytetrafluoroethene (ePTFE)
membrane surrounding an adsorbent material
that is used to collect volatile and semi-
volatile compounds in water. When placed in
the screened, saturated interval of a
monitoring well or piezometer, the waterproof,
vapor-permeable membrane collector housing
allows for water/air partitioning (in
accordance with Henry's Law) of dissolved-
phase organic compounds while preventing
transfer of liquid water and eliminating impact
from suspended solids on the adsorbent.
Module Configuration
A typical GORE-SORBER module consists of four
separate "sorbers" as shown in Figure 1. A typical
sorber is about 25 mm in length, 3 mm in diameter,
and contains 40 mg of a granular adsorbent material
that is selected on the basis of the specific
compounds to be detected. Typically, polymeric
and carbonaceous resins are used because of their
affinity for a broad range of VOCs and semi-VOCs
(SVOCs). The sorbers are sheathed in the bottom of
a length of vapor-permeable insertion and retrieval
cord that includes a loop attachment. The four
sorber units and associated cord are collectively
termed a GORE-SORBER® module. Both the
retrieval cord and sorbent container are constructed
solely of inert, hydrophobic, microporous
membrane. Every module has sufficient sorbers
such that there is always a minimum of two samples
available in each module (for use as duplicates or
backups, if needed).
A unique feature of the membrane is that it is
hydrophobic, excluding the transfer of liquid water
across the membrane, while facilitating vapor
transfer. Thus VOC and SVOC vapors can
penetrate the sorbent module freely and collect on
the adsorbent material. Depending on the
membrane characteristics, liquid water will be
excluded to a particular depth, therefore it is
important to know the desired depth of
installation. Different membranes can be used for
different installation depths, and GORE technical
support personnel can help in the selection of the
best membrane type. This ability to protect the
sorbent media from contact with soil and
groundwater without retarding gaseous diffusion
facilitates the application of Gore's screening
methods in both the saturated and unsaturated
zones.
Two different membrane types were evaluated in
this verification test. This first membrane type
termed standard, hereafter abbreviated STND, is
recommended for deployment in wells in which
the depth of the overlying water column does not
exceed 30 ft. A second higher density membrane
type termed high water entry pressure, hereafter
abbreviated FfWEP, can be deployed in wells with
overlying water column depths up to 50 ft.
Sorbent Selection
Sorbent selection is a critical component of any
passive sampling system. Selected sorbents must
have good sensitivity to a broad range of volatile
and semi-volatile organic compounds while
exhibiting hydrophobic properties to minimize
preferential uptake and competition from water
vapor. The sorbents used in the GORE-SORBER
modules include carbonaceous and polymeric
resins. They are designed to provide good
adsorption properties for both the VOC and SVOC
components in a mixture while at the same time
minimizing the collection of water vapor on the
sorbent.
Shipping
The modules are shipped in box containers, and
each module is shipped in a separate, pre-labeled
glass jar with a corresponding pre-labeled lid. The
numbers on the glass jar, the lid and the module
will all correspond to each other.
The shipment also contains string and stainless
steel weights to secure the module loop and to
allow the field personnel to lower the sampler into
-------
LOOP FOR
ATTACH ING STRING
TAG WITH UNIQUE
SERIAL NUMBER \
GRANULAR,
SORBENT
Figure 1. Schematic diagram of a GORE-SORBER module..
the saturated zone. A chain of custody and an
installation/retrieval form also accompany the
shipment.
Prior to deployment in a monitoring well, the
containers should be inspected to ensure that the
proper number of modules has been received, and
that the sorber units have not been damaged in
shipping.
Installation and Retrieval
Upon first use at a particular monitoring well, the
data collected by the GORE-SORBER module
must be calibrated using conventional water
sampling and analysis methods as a reference.
After at least two parallel sampling events, the
GORE-SORBER modules can be installed by
themselves (without matrix sampling), but it is
advisable to collect groundwater samples by a
reference method periodically (e.g., annually) in
order to confirm the relationship between these
two sampling methods.
Before installation of the GORE-SORBER module
into a well, it is necessary to know the depth to
water, and the screened interval of the well. The
GORE-SORBER module should be placed in the
middle of the screened interval. A length of cord
supplied with the module is tied to a clean
stainless steel weight. The GORE-SORBER
module is tied to the cord directly above the
weight. The cord is lowered into the well to the
appropriate depth and tied off to the wellhead.
After an exposure period of approximately 48
hours, the module is pulled out of the well and the
sample number is confirmed. The module is then
-------
placed into the same numbered glass vial, and
placed into the shipping container. Additional
modules are shipped as trip blank samples and are
provided to document whether the modules are
impacted during shipment. Trip blanks are
selected by the field team and noted on the
insertion/retrieval form. After module installation
is complete, the box containing the trip blanks is
transported to a secure location for temporary
storage until retrieval time. This temporary
storage area must be out of direct sunlight, well-
ventilated, and free from heat extremes as well as
any obvious ambient air contamination. Boxes
with field-exposed modules and trip blanks are
returned along with the chain-of-custody form to
Gore's laboratory in Elkton, MD usually via
overnight courier. Under these shipping
conditions, refrigeration of the sample is not
necessary.
Analytical Methods
Laboratory analysis options for the modules
include methods for the determination of volatile
organic compounds, semi-volatile organic
compounds, and poly cyclic aromatic hydrocarbons
(PAHs). In addition to these common suites of
compounds, the samples can also be analyzed for
specific groups of compounds; i.e., fuel
hydrocarbons, pesticides, explosives, and chemical
agents, among others. The analyses follow
modified EPA Methods SW846 8260 for VOCs,
and 8270 for SVOCs. All analytical services on
GORE-SORBER modules are performed at the
W.L. Gore & Associates, Inc. laboratory in Elkton,
MD.
Following module receipt and logging at the
laboratory, they are removed from the shipping
containers and prepared for the analytical process.
The sorber packets are removed, inspected, and
placed into an automatic thermal desorption unit.
During analysis, a heat pulse in the thermal
desorption unit is used to volatilize the collected
VOCs. The desorbed compounds are then
transported via a carrier gas flow into the inlet of a
gas chromatograph-mass spectrometer (GC-MS).
The compounds are identified and quantified in
the GC-MS. When the analyses are complete, an
analytical chemist verifies the data and a draft data
table is prepared.
Data Analysis
Absolute levels of detected ions in the GC-MS are
determined by the ionization efficiency of the
target compound. These efficiencies vary by a
factor of twenty for typical target analytes, and
make inter-compound comparison of ion count
data difficult or impossible. Furthermore, detected
ion levels can change as MS tuning adjustments
are made. They are also dependent on such
variables as the cleanliness of the MS source, and
the age of the GC column or desorption unit cold
trap. For this reason, GORE always includes
analyses of sorbers injected with reference
standard solution, and reports target data as a mass
of analyte, in micrograms (|Jg) per sorbent
module.
Typically, data from groundwater samples are
compared against the data from the GORE-
SORBER modules, and the relationship is
evaluated between concentration in groundwater
and mass sorbed on the collector. This
relationship is then confirmed in at least one, and
preferably two, parallel, sampling events. After
two sampling events, the GORE-SORBER
modules may be used alone, with periodic (annual)
parallel sampling to confirm and enhance the
relationship between these sets of data.
Vapor pressure, water solubility, molecular weight,
and the Henry's Law partitioning coefficient are
important chemical parameters to consider when
interpreting analysis data. The Henry's Law
coefficient reflects a compound's behavior when
partitioned into air and water, which aids in
understanding an organic chemical's likely state in
the subsurface.
Guidelines for Use
Outlined below are some general guidelines
for the use and installation of passive,
adsorbent-based GORE-SORBER modules in
monitoring wells as a means of qualitatively
screening water quality as part of a
groundwater monitoring program.
• GORE-SORBER modules can be used to
reduce the frequency of groundwater
purging and sampling for petroleum and
chlorinated organic chemicals, including
poly cyclic aromatic hydrocarbons.
• An initial round of testing consisting of
water sampling and testing by
conventional means along with
simultaneous sampling with GORE-
SORBER modules is recommended. The
deployment and retrieval of the GORE-
SORBER modules should occur prior to
-------
any purging/sampling of the well for
matrix testing purposes. This comparison
is done in order to establish a baseline
relationship at a particular well between
the water concentration data and the
sorber mass data. The results are then
plotted on a scatter diagram or color
contour maps to show the site-specific
relationship between groundwater
concentration and mass on the GORE-
SORBER module.
Subsequent testing may be performed only
using GORE-SORBER modules to
monitor trends in water quality at a
specific well over time.
Conventional well purging and
groundwater sampling, concurrent with
the use of GORE-SORBER modules, is
recommended every four to six sampling
events. To ensure comparability of the
data, these periodic matrix samples must
be collected and analyzed in a consistent
manner.
GORE-SORBER modules should be
placed within the screened interval in the
monitoring well, and not in the headspace
of the well or outside the screened
interval. Placement of the module in the
screened interval where water flow is
occurring will avoid stagnation effects that
are likely to occur if the module is placed
in a section of the well that is not
screened.
Modules should not be placed in direct
contact with free product (that is, liquid
hydrocarbons or solvents).
A two-day exposure period is
recommended for modules deployed
directly in the groundwater. This
exposure period has been derived
experimentally as part of Gore's product
validation efforts.
GORE-SORBER modules can be used to
test for benzene, toluene, ethylbenzene
and xylenes (BTEX), petroleum
hydrocarbons, chlorinated solvents and
many semi-volatile organic compounds,
such as poly cyclic aromatic hydrocarbons
(PAHs). Application for ethers, alcohols,
ketones or most other highly water-soluble
compounds has not been validated at this
time.
• Information relative to the site, the well
construction, as well as water sampling
and testing procedures being used, will be
useful for data interpretation purposes.
Data Interpretation and Use
The data collected from a GORE-SORBER Water
Quality Monitoring event along with
interpretations are provided in a final report, which
contains the following information:
• Chain-of-custody documentation
• A summary of the laboratory procedures used
in the analysis of the GORE-SORBER
modules
• A tabulation of the data from each module
(with accompanying groundwater
concentration data (if available) and color
contour maps, as necessary)
• Scatter diagrams comparing data from the
GORE-SORBER modules with groundwater
concentration data (if available)
GORE-SORBER Water Quality Monitoring
technology is designed for well screening
programs to detect order-of-magnitude changes in
groundwater concentrations over time; or, for
"sentry" monitoring programs at the leading edge
of a migrating plume. Ideally, this technology can
be used to compliment an existing water quality
monitoring program, thereby reducing the number
of aqueous groundwater samples that need to be
collected and analyzed. Such an approach can
result in considerable cost savings.
Additional information on potential applications of
this technology for environmental characterization
and monitoring can be found in Section 5-
Technology Updates and Applications.
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Section 3 — Demonstration Process and Design
Introduction
The principal objective of this demonstration was
to conduct an independent evaluation of the
capabilities of several groundwater-sampling
technologies for VOC-contaminated water. A
number of key performance parameters were
chosen to evaluate overall sampler performance.
In order to ensure data integrity and authenticity of
results, data quality control measures were also
incorporated into the study design. Personnel at
Sandia National Laboratories developed the design
with concurrence from the various technology
vendors participating in the study. EPA personnel
with professional expertise in the area of
groundwater sampling also provided technical
review of the study design. A complete
demonstration plan has previously been published
[Sandia, 1999].
Site Description
The John C. Stennis Space Center (SSC) in
southwest Mississippi is one often NASA field
centers in the United States. It is NASA's primary
center for testing and flight certifying rocket
propulsion systems for the Space Shuttle and future
generations of space vehicles. Over the years, SSC
has evolved into a multi-agency, multi-disciplinary
center for federal, state, academic and private
organizations engaged in space, oceans,
environmental programs, and national defense. The
USGS is a one of the resident agencies at the
NASA-Stennis complex and operates a number of
testing facilities as a part of its Hydrologic
Instrumentation Facility (HIF). This facility
supports USGS agency-wide hydrologic data-
collection activities through the identification of
agency needs, development of technical
specifications, and testing and evaluation.
Standpipe Facility - One of the HIF test centers is
known as the Standpipe Facility. The facility was
designed by Doreen Tai, an HIF chemical
engineer, and is housed in a Saturn V rocket
storage building at the Stennis complex. A
schematic diagram of the Standpipe and
accessories is shown in Figure 2. The Standpipe is
an above-ground, 100-foot long, 5-inch diameter,
stainless steel pipe with numerous external
sampling ports along its length. Two large tanks
at the top of the Standpipe are used to prepare
solutions which can then be drained into the
Standpipe. The tanks are equipped with motor-
driven mixing propellers and floating lids to
minimize loss of volatile compounds during
solution mixing and transfer. An external
Standpipe fill line at the bottom of the pipe enables
the pipe to be filled from the bottom up, thereby
minimizing flow turbulence and VOC losses in the
prepared solutions. The external access ports
allow reference samples to be taken
simultaneously with the collection of technology
samples inside the pipe. As shown in Figure 2, the
indoor facility has six levels of access, including
the ground floor, and a freight elevator services all
levels. In this demonstration, the Standpipe was
used in a series of controlled water sampling trials.
Technology vendors sampled VOC-contaminated
water solutions from the Standpipe while reference
samples were simultaneously taken from the
external ports.
Site Hydrogeology - The second phase of this
technology demonstration involved the collection
of groundwater samples from five onsite wells at
SSC. The site has about 200 wells that have been
used for subsurface plume characterization and
routine groundwater monitoring. The shallow,
near-surface geology where most of the
contaminant plumes are located can be
summarized as follows [Foster Wheeler, 1998]:
The geology generally consists of a thin veneer of
clayey sediments known as Upper Clay, which are
found at elevations ranging from 10 to 30 feet
above mean sea level (MSL). These overlay a
sandy unit named the Upper Sand (at 5 to 15 feet
MSL). The Upper Sand is underlain by a second
clayey unit named the Lower Clay and a second
sandy unit called the Lower Sand (at -35 to 5 feet
MSL). Below the Lower Sand another clayey unit
is present which represents an unnamed or
undifferentiated Pleistocene deposit. This deposit
is underlain by a thick zone of interbedded sand
and clay deposits that form the Citronelle
Formation (at -100 to -40 feet MSL). The VOC
contamination is present in the Upper Sand and
Lower Sand water bearing zones; and most of the
wells selected for use in this test were screened in
these zones. Typical sampling depths for the wells
selected for study ranged from about 15 to 85 feet
below ground level.
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5 IN. DIA.-
SP14 fi
5P13
SP12
SPii
SP10
SP9
SPS
SP?
SPS
5P3
SP2
SPt
HOLDINS TftNKS
FLOAT IN8 IOP
LEVEL 5
-I IN. DIA. FIIL/DRA1M LlhE
LEVEL 4
LEVEL 3
5P - SAMPLINS PORT
SP DISTANCE FROM TO1 MATER LEVEL
SPI3 17.5 ft.
SPS 54 ft.
3P7 m ft.
SP4 82 ft,
SP2 92 Ft,
LEVEL 2
/EXIT LINE
Figure 2. The standpipe at the USGS Hydrological Instrumentation Facility.
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Groundwater Monitoring Wells—Construction
information for the five wells selected for use in
this study is given in Table 1. The wells were
constructed with 2-inch-diameter
polyvinylchloride (PVC) pipe with a 10-foot PVC
screen length. All GORE-SORBER Water
Quality Monitoring and reference pump samples
were collected at the mid-screen level. Typical
water depth above the mid-screen sampling point
in the wells selected for study ranged from about 2
to 10 feet.
Verification Test Design Summary
The verification test design for the GORE-
SORBER Water Quality monitoring system
consisted of two test events. The first was a test
conducted under carefully controlled sampling
conditions at the standpipe. This trial enabled
GORE-SORBER module precision to be
systematically evaluated. The second series of
tests were conducted a series of groundwater
monitoring wells. These field trials presented an
opportunity to observe the technology in actual
field use under conditions very similar to those
that would be encountered in routine use. The
field trials also offered an opportunity to compare
GORE-SORBER Water Quality Monitoring
results to reference sample results. Together,
these two study elements provide a data set that is
adequate for an overall performance assessment of
the GORE-SORBER Water Quality monitoring
system in applications involving the sampling of
VOC-contaminated groundwater.
Test Design Elements
Additional test design element descriptions are
given below. The six participating technologies in
this verification test were split into two categories
namely, active samplers and passive samplers,
with differing sampling trials specific to the two
sampler categories. The test design element
descriptions that follow were those used for
evaluation of the GORE-SORBER Water Quality
Monitoring system.
Target VOC Compounds—Six target compounds,
all regulated under the US EPA Clean Water Act,
were selected for testing in this study. The
compounds were 1,2-dichloroethane (12DCA),
1,1-dichloroethene (11DCE), trichloroethene
(TCE), benzene (BNZ), tetrachloroethene (PCE),
and 1,1,2-trichloroethane (112TCA). With the
exception of benzene, all of these compounds are
chlorinated and have regulatory limits of 5 |jg/L in
water as presented in the Clean Water Act. The
six compounds selected encompass a range of
volatility, a parameter that is likely to influence
sampler performance. Target compound volatility
and other relevant physical data are given in
Table 2.
Table 1. Construction Details of Groundwater Monitoring Wells
Well
No.
06-04
06-09
12-01
12-06
12-09
TOC
(ft, MSL)
28.8
13.0
28.5
28.1
28.0
Total
Depth
(ft)
39.0
18.0
18.0
17.0
18.0
Screen Elev.
(ft, MSL)
Top
-1.3
4.0
13.2
21.0
18.0
Bottom
-11.3
-6.0
8.7
11.0
8.0
Well
Dia.
(in)
2
2
2
2
2
Well
Install
Date
04/95
05/95
06/92
05/95
05/95
Depth
to
Water
(ft)
24.6
8.7
10.9
9.7
10.0
Water
Level
(ft,
MSL)
4.2
4.3
17.6
18.5
18.0
Water Depth
Above
Screen
Midpoint
(ft)
10.5
5.3
9.4
2.2
5.0
Notes: TOC = top of well column; water levels from most recent quarterly well-monitoring data.
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Table 2. Target VOC compounds
Compound
Tetrachloroethene (PCE)
1,1-Dichloroethene (11DCE)
Trichloroethene (TCE)
Benzene (BNZ)
1 ,2-Dichloroethane (12DCA)
1 ,1 ,2-Trichloroethane (1 12TCA)
Henry's Constant
(kg* bar/mole at 298 K)a
High (17.2)
High (29.4)
Mid (10.0)
Mid (6.25)
Low (1.39)
Low (0.91)
Boiling Pt.
(°C)
121
32
87
80
84
114
"Henry's constant data from NIST, 2000
Test Concentrations—Water mixtures containing
the six target VOCs in a range of concentration
levels were loaded into the standpipe during
testing. For the GORE-SORBER Water Quality
Monitoring evaluation, the target compound
concentration was low (-20 |Jg/L) and uniform
throughout the pipe. Spike solutions of all six
target compounds were prepared in methanol from
pure compounds. Normally a 5-10 mL volume of
the spiking solution was injected into the mixing
tank that was pre-filled with tap water. The
solution was covered with a floating lid, gently
mixed for 5 minutes, and drained into the
standpipe. Preliminary studies at the standpipe
revealed volatile losses of target compounds
during the process of mixing and standpipe filling.
Consequently spike concentrations were not used
as a reference value in this study. Alternatively,
the study design specified the collection of
reference samples from standpipe external
sampling ports. Reference samples were collected
at the same time that each technology sample was
collected from the standpipe.
Groundwater Well Reference Samples—The use
of five onsite monitoring wells in the second phase
required the use of a co-located reference sampler
of known performance such that a comparison of
reference and GORE-SORBER module data could
be compared. A submersible electric gear pump
(Fultz, Model SP-300) was chosen as the reference
sampling device. Verification studies on the
performance of this pump were carried out during
the standpipe phase of the experiments to provide
technical data substantiating its use as a reference
method in the field. A more complete description
of the pump along with a summary of these data is
given in Appendix A. During field sampling
events, the reference pump was co-located with
the GORE-SORBER modules at the same depth in
the well in order to provide periodic reference
samples from the well over the duration that the
modules were in the well.
Sampler Performance Parameters
Four performance parameters were evaluated in
the overall assessment of each technology. They
are briefly outlined in the following paragraphs.
Precision—Sampler precision was computed for
the range of sampling conditions included in the
test matrix by the incorporation of replicate
samples from both the standpipe and the
groundwater monitoring wells in the study design.
The relative standard deviation (RSD) was used
as the parameter to estimate precision. The percent
relative standard deviation is defined as the sample
standard deviation divided by the sample mean
times 100, as shown below:
-\
X
>100
Here, X is one observation in a set of n replicate
samples where X is the average of all
observations, and n is the number of observations
in the replicate set. Precision data from the
GORE-SORBER modules and reference samples
are not directly comparable since multiple samples
are used to derive a time-weighted average
reference concentration. In this study, precision
data from a similar test in which replicate
reference samples collected at multiple standpipe
depths, comparable to those at which the GORE-
SORBER modules were tested, are used for
10
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qualitative comparison with GORE-SORBER
module precision.
Comparability—In each standpipe and
ground-water monitoring test a series of reference
samples were collected that were used to compute
a time-weighted average concentration over the
exposure interval of the GORE-SORBER
modules. The mathematical expression used to
describe the time weighted average (TWA)
concentration is given below:
IWA=-
48
where Ct is the measured concentration in units of
Hg/L at a given time step, and Tt is the duration of
the time step in hours. (Note that for / =1 and 6, a
time step duration of 6 hours was used. For all
other values of/, a time step value of 12 hours was
used.) The GORE-SORBER module data are
reported in mass units of VOC collected and thus
are not directly comparable to the time-weighted-
average concentration determined from the
reference sampler. For the groundwater wells, the
coefficient of variation (r) as defined by Havlicek
and Grain [1988] is used to describe the degree of
correlation between the GORE-SORBER module
data and the reference data over the range of
concentration examined in this study. A value of r
that is near 1 indicates a high degree of linear
correlation in the two data sets.
Sampler Versatility—The versatility of the GORE-
SORBER Water Quality Monitoring technology
was determined by evaluation of sampler
performance over the volatility and concentration
range of the target compounds as well as the range
of sampling depths encountered in both the
standpipe and the groundwater monitoring well
trials. A sampler that is judged to be versatile
operates with acceptable precision and
comparability with reference samples over the
range of experimental conditions included in this
study. Those samplers judged to have low
versatility may not perform with acceptable
precision or comparability for some of the
compounds or at some of the sampling depths.
Field Deployment Logistics—This final category
refers to the relative ease of deployment of the
sampler under its intended scope of application.
This is also a less objective category and
incorporates field observations such as personnel
and training required for use, ancillary equipment
requirements, portability, and others.
Sample Analysis
Because the GORE-SORBER modules are only
analyzed at Gore laboratories, different analytical
methods were used for technology and reference
samples. All reference sample analyses were
conducted onsite, using analytical services
provided by Field Portable Analytical (Fremont,
CA). The GORE-SORBER modules were
analyzed by the W. L. Gore laboratory using
thermal desorption of the sorbent media followed
by GC-MS analysis using a modification of EPA
SW846 Methods 8260 and 8270 [EPA, 1996]. A
brief description of the analytical method for the
GORE-SORBER Water Quality Monitoring
technology is given in Section 2.
The onsite analytical instrumentation used for
reference sample analysis consisted of two
identical field portable GC-MS units (Inficon,
HAPSITE Syracuse, NY) equipped with the
Inficon Headspace Sampling Systems. The
analysis method used was a modified Method
8260 (purge-and-trap GC-MS) with headspace
sampling replacing the purge-and-trap portion of
the method [EPA, 1996]. Sample throughput was
on the order of 4 to 6 samples per hour per
instrument for a daily throughput of 60-70 samples
per instrument. The Inficon field-portable GC-MS
system with headspace vapor sampling accessory
has previously gone through the ETV verification
process. Results from this verification study
showed that system accuracy and precision for
VOC in water analysis was comparable with a
conventional fixed laboratory analysis using
purge-and-trap sample handling combined with
bench-top GC-MS analytical systems [EPA,
1998].
A brief summary of the analytical method follows:
Reference samples were brought to the analysis
location in 40-mL volatile organics analysis
(VOA) vials and kept at temperatures near 4 °C
until they were prepared for instrument analysis.
As a result of the relatively high sample
throughput and the use of two instruments, sample
holding times did not exceed 24 hours in most
cases. Consequently, no sample preservatives
were used in the study. Immediately prior to
analysis, the chilled VOA sample vials were
11
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uncapped and immediately transferred to a 50-mL
glass syringe. Half (20 mL) of the sample was
then transferred to a second 40-mL VOA vial and
the vial was immediately capped. A 5-|jL solution
containing internal standards and surrogate
standards was injected through the septum cap of
the vial. The vial was then placed in the
headspace sampling accessory and held at 60 °C
for 15 minutes. (The original vial was again filled
with the remainder of the sample, capped, and held
under refrigeration as a spare.) Following the
temperature equilibration time, a vapor extraction
needle was inserted through the vial's septa cap
and into the headspace. A pump in the GC-MS
then sampled a fixed volume of headspace gas
through a heated gas transfer line and into a fixed-
volume gas sampling loop in the GC-MS. Under
instrument control, the gas sample was then
injected onto the capillary column for separation
and detection. An integrated data system
processed the mass detector data and output results
for the six target analytes plus internal and
surrogate standards in concentration format. The
method used the internal standard method (as
outlined in Method 8260) for computation of
target compound concentrations. Surrogate
standard results were used as measures of
instrument data quality, along with other quality
control measures outlined below.
Data Processing
The results from chemical analysis of both GORE-
SORBER modules and reference samples were
compiled into spreadsheets and the arithmetic
mean and percent relative standard deviation (as
defined in Section 3) were computed for each set
of replicate samples from each standpipe and
monitoring well trial. All GORE-SORBER
module data for the six target compounds were
reported in units of micrograms of target VOC
collected on the sorbent. All reference data were
reported in concentration units of |Jg/L. Direct
trial-by-trial comparisons were then made between
technology and reference sample results as
outlined below. All the processed data from the
verification study have been compiled into data
notebooks and are available from the authors by
special request.
Data Quality Control
The desirability of credible data in ETV
verification tests requires that a number of data
quality measures be incorporated into the study
design. Additional details on data quality control
are provided in the following paragraphs.
Sample Management—Ml sampling activities
were documented by Sandia field technicians
using chain-of-custody forms. To save sample
handling time and minimize sample labeling errors
in the field, redundant portions of the chain-of-
custody forms and all sampling labels were pre-
printed prior to the field demonstration.
Field Logbooks—Field notes were taken by
observers during the standpipe and groundwater
well sampling trials. The notes include a written
chronology of sampling events, as well as written
observations of the performance characteristics of
the various technologies tested during the
demonstration.
Pre-demo Analytical System Audit—Prior to the
actual demonstration, a number of samples
containing the six target compounds at various
concentration levels were prepared at SNL and
sent via overnight express mail to Field Portable
Analytical for analysis. The laboratory used the
same headspace-GC-MS method intended for use
in the final field test during this pre-demo audit.
Results from this preliminary audit revealed
acceptable performance of the GC-MS system and
its accompanying method. The written analytical
method that was used during the full
demonstration was also reviewed and approved at
this time.
Reference Analytical Method—The analytical
method was an adaptation of EPA Method 8260B
and followed the data quality requirements
outlined in the method. Included in the list of data
quality measures were: 1) initial calibration
criteria in terms of instrument linearity and
compound recovery, 2) daily instrument
calibration checks at the onset and completion of
each 12-hour analysis shift, 3) blank sample
instrument performance checks, 4) internal
standard recovery criteria, and 5) surrogate
standard recovery criteria. A summary of the GC-
MS analysis quality control data for the
demonstration period is given in Appendix B.
GORE-SORBER Water Quality Monitoring
Analysis—The analytical methods employed in the
analysis of the GORE-SORBER modules were a
modified EPA SW846 Method 8260 for VOCs
and 8270 for semi-VOCs. Before each run
sequence and after every 30 samples, a sorber
12
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containing 5ug bromofluorobenzene (BFB), and a
method blank were analyzed. The BFB mass
spectra was required to meet acceptance criteria
set forth in the analytical method. System
cleanliness was verified with no detection of target
compounds in the method blanks. Standards
containing the selected target compounds at three
calibration levels of 5, 20, and 50 ug were
analyzed following the initial BFB and method
blank checks. The linear calibration curve
acceptance criterion for each target compound was
relative standard deviation less than 35% . If this
criterion was not met for any target compound,
non-linear second- or third-order standard curves
were generated, as appropriate. A second-source
reference standard, at a level of 10 ug per target
compound, was analyzed after every ten samples
and/or trip blanks and at the end of the run
sequence to ensure detectability of each target
compound throughout the analysis. All target
compounds were detected in each of the second-
source reference standards.
Verification Test Plan
The preceding information, as well as that which
follows, is summarized from the Groundwater
Sampling Technologies Verification Test Plan
[Sandia, 1999], which was prepared by SNL in
entirety and with concurrence of all participants
prior to the field demonstration. The test plan
includes a more lengthy description of the site, the
role and responsibilities of the test participants, as
well as a discussion of the experimental design
and data analysis procedures.
Standpipe and GW Well Sampling
Matrix
The sampling matrix for the standpipe sampling
phase of the demonstration is given in Table 3. In
this test, GORE-SORBER modules were deployed
at up to four depths in the pipe. Four replicates of
two types of modules-standard (STND) and high
water entry pressure (HWEP) modules-were
positioned at the depths shown in Table 3. The
test was conducted with a uniform low
concentration (10-20 |Jg/L) standpipe mixture in
the pipe. The cluster of modules at each depth
were tied to a weighted nylon cord, lowered into
the standpipe, and left in place for a 48-hour
period. Periodically, throughout the 48-hour
module exposure interval, duplicate reference
samples were collected from the adjacent sampling
ports. The first duplicate reference sample was
collected at the time of module deployment, the
last reference sample was collected when the
modules were withdrawn from the well, and the
other 4 sets of reference sample collections were
done at approximate 12-hour intervals between
module deployment and retrieval.
Table 3. The GORE-SORBER Module Verification Trial at the Standpipe
VOC Concentration Level
Low (-20 pg/L)
Standpipe
Collection
Port /Depth
SP14-17feet
SP12B-28feet
SP12-35feet
SP10B-46feet
STND
Module
Replicates
4
4
—
—
HWEP
Module
Replicates
4
4
4
4
Notes: The STND module construction is not recommended for deployment in water column depths in
excess of 30 feet. The HWEP module is rated for water column depths up to 50 feet. In each trial,
duplicate reference samples were collected from adjacent sampling ports at approximate 12-hour intervals,
starting with GORE-SORBER module deployment and ending with GORE-SORBER module retrieval.
13
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The groundwater well sampling matrix is shown in
Table 4. The groundwater well trials 1 through 5
were carried out as follows. The GORE-SORBER
modules were tied to the pump line directly above
the pump intake and within 15 cm of the pump
intake. This pump/module configuration was
lowered into the well to the mid-point of the well
screen, and left in place for 48 hours. Periodic
reference samples were collected from the well
using the submersible electric pump. Five
reference samples were collected at approximate
12-hour intervals over the duration of the 48-hour
module exposure interval, beginning with a
reference sample collection at the time of module
placement and ending with a reference sample
collection at the time of module retrieval. The
reference pump was left in place in the well during
the 48-hour module exposure interval so that the
water column was not disturbed by repeated pump
placement and withdrawal. Teflon tubing (1/4-inch
outside diameter, 3/16-inch internal diameter) was
used to transport the water sample from the pump
outlet to the collection vial at the wellhead.
During each of the five reference sample
collection events, the pump was operated at a low
(100-200 mL/min) flow rate. A pre-sampling
purge volume of about 2 liters was used to flush
the pump and tubing volume of the reference
pump to ensure that the pump was sampling from
the water zone in which the modules were
positioned. Following this initial purge, duplicate
40 mL VOA sampling vials were sequentially
filled. The results from the five reference samples
were then used to calculate a time-weighted
average concentration for comparison with the
GORE-SORBER module results.
Chronological Summary of
Demonstration Activities
The demonstration began on Monday, August 9
and concluded on Tuesday, August 17. The first
four days of the demonstration were devoted to
testing those technologies designated "active
samplers." Included in this group were Burge
Environmental (multi-level sampler) Clean
Environment Equipment (bladder pump), Geolog
(bladder pump), QED Environmental (bladder
pump), and Sibak Industries (discrete-level grab
sampler). The second half of the demonstration
interval was devoted to testing the "passive
sampler" category of which W. L. Gore and
Associates Inc. (GORE-SORBER module) was the
only participant. A short briefing was held on
Monday morning for all vendor participants to
familiarize them with the standpipe facility and the
adjacent groundwater monitoring wells. The
passive sampler category tests were begun at the
standpipe Thursday, August 12 and were
completed on Monday, August 16. The passive
samplers were also deployed at a number of onsite
monitoring wells simultaneously with standpipe
testing.
Table 4. GORE-SORBER Module Verification Trials at the Groundwater Monitoring Wells
Trial
1
2
3
4
5
Well
06-04MW
12-09MW
12-01MW
06-09MW
12-06MW
Distance from
top of well to
screen mid
point (feet)
35.1
15.0
19.9
14.0
12.1
Water Column
Depth
(feet)
9.8
5.2
6.8
5.4
2.5
Approximate
TCE Cone.
(|ig/L)
350
5
2000
50
40
No. of
Replicates per
technology
4
4
4
4
4
Notes: Reference samples were collected at 12-hour intervals from a submersible electric sampling pump collocated with the
GORE-SORBER modules. Water column depth refers to the depth of water above the sampler placement location at the well
screen mid-point. Four replicates were analyzed for each of the two GORE-SORBER modules membrane types (STND and
HWEP) that were tested. Five sets of reference samples were also collected in duplicate at 12-hour intervals throughout the
module exposure interval in each well.
14
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Reference sample analysis was carried out in a
mobile laboratory parked near the standpipe and
occurred simultaneously with field-testing. An
approximate 24-hour turn around time was
encountered between sample collection and
chemical analysis completion. As previously
noted, GORE-SORBER module analysis was
conducted at Gore laboratories and reference
sample analysis was carried out onsite. All
reference samples were analyzed on the same
instrument and usually on the same day. This
approach was taken to minimize the possible
influence of instrument variability on the analysis
results.
GORE-SORBER modules were shipped to the
W.L. Gore laboratory in Pennsylvania via
overnight mail at the conclusion of the field study
and received at the laboratory on August 18.
Laboratory analysis of all modules was carried out
between August 23 and August 27.
The demonstration technical team observed and
recorded the operation of each technology during
both standpipe and monitoring well trials to assist
in the assessment of logistical requirements and
technology ease of use. These observations also
were used to document any performance
anomalies as well as the technical skills required
for operation.
Deviations from the Verification
Plan
A listing of the deviations from the test plan
during GORE-SORBER Water Quality
Monitoring testing that are judged to be important
are summarized, along with an assessment of the
resulting impact on the verification test data set.
Data collected at other standpipe depths—GORE-
SORBER modules were deployed at depths
greater than those specified for normal module
use. Data from these tests were used only for
further product research and development by W.
L. Gore personnel.
Data outliers—Two replicate data points from the
standpipe Trial 1 data set were obvious outliers
caused by membrane leakage of liquid water and
were dropped from the data set prior to the
analysis of precision and comparability to
reference samples. Instances where this occurred
along with ramifications for typical sampler use in
the field are included in the discussion of results.
Missed 12-hour sampling event—The third
sampling event (Deployment time + 24 hours) at
well number 12-01 was missed. To make up for
this data loss, the previous (+12 hour) and
following (+36-hour) sample data were averaged
and used in place of the missing data. The impact
of this data loss is not important since the well
concentration was stable over the entire 48-hour
period.
15
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16
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Section 4 — GORE-SORBER Water Quality Monitoring
Performance Evaluation
Introduction
This section briefly discusses the results of test
data analysis and summarizes sampler
performance. Sampler precision, comparability
with reference sample data, and overall versatility
of the sampler for the characterization of VOC-
contaminated water are discussed. Only summary
data are given in this report. A complete
tabulation of all test data is available from the
authors via individual request.
Standpipe Concentration Stability
The stability of the target VOC concentrations in
the standpipe over the 48-hour exposure interval in
Trial 1 are illustrated with TCE results in Figure 3.
Reference concentrations were measured at 17-,
28-, 35-, and 46-foot depths five times (every 12
hours) over the 48-hour exposure interval.
Concentrations of the target analytes were stable
and within the analytical uncertainty of the
reference method. Little change in concentration
with depth is observed. The rightmost entry on the
graph is the time-weighted average of the five
concentration measurements. The other target
VOC data show stable concentration trends with
time that are similar to that of TCE.
Sampler Precision
The precision for the GORE-SORBER STND and
HWEP modules for the steady-state concentration
trial is given in Table 5 and Figures 4 and 5. The
steady-state concentration trial consisted of a low
(-15 |Jg/L) concentration mixture containing all
six target analytes that was essentially uniform
throughout the entire length of the standpipe, as
discussed in the previous section. GORE-
SORBER modules were positioned at 17-, 28-,
35-, and 46-foot depths and exposed for 48 hours.
Reference-sample relative standard deviation was
not calculated because only duplicate reference
samples were collected from each of the sampling
20
J
1
cj
g
•u
UJ
3
j
10
•
A
t
y
*
A
X
T+24 T+36
Time Step, hours
Figure 3. TCE Concentration over the 48-hour exposure interval in
the standpipe trial at all sampling levels.
17
-------
ports over the module exposure interval.
However, the precision results from four replicate
reference samples collected from a similar multi-
level sampling test conducted at the standpipe
during the same week are given in Table 5 for a
qualitative comparison with Gore module
precision results.
In the calculation of precision data, two outlier
data points were dropped from the data set. (One
result was dropped from the 17-foot level and the
other from the 35-foot level.) The rationale for
dropping these data was the observation of liquid
water penetration through the membrane and into
the sorbent region of the module. This was noted
during inspection of the modules prior to their
analysis at the W. L. Gore laboratory. When water
penetrates the membrane, it displaces the VOCs
adsorbed on the sorbent material. The result of
water leakage through the membrane is a
conspicuously low collection mass of the target
VOCs on the sorbent material.
Table 5. STND and HWEP Module Precision Summary from the Standpipe Trial
Compound
11DCE
12DCA
BNZ
TCE
112TCA
PCE
Minimum
Maximum
Median
Depth
17
28
35
46
17
28
35
46
17
28
35
46
17
28
35
46
17
28
35
46
17
28
35
46
Relative Standard Deviation, %
STND
4
21
2
11
13
20
10
19
8
15
17
28
2
28
14
HWEP
26B
35
9B
29
16B
9
11B
27
31B
29
11B
21
32B
21
13B
18
12B
20
11B
20
25B
23
13B
21
9
35
21
Reference*
9
9
11
17
3
6
11
16
15
11
12
13
3
17
12
AReference precision data are taken from a similar multi-level test
conducted during the same week in which quadruplicate reference
samples were collected at 17- and 35-foot depths.
BRelative standard deviation was calculated from three replicate
samples instead of the normal four replicates.
18
-------
*
* 1C
a
£
MDCE
•J_X A
D17 feet
D2Bfeet
BNZ TCE
Compound
112TCA
PCE
Figure 4. STND module precision in the standpipe trial by depth and target
compound.
;=.;.
I
1 w
i/i
?! ^
D
5
n
••
_
^
^=z
•-, n
._
D 17 feet
D 28 feet
Q 35 feet
D 46 feet
1
.
i
: —
—
=
HDCE
12DCA
BNZ TCE
Compound
112TCA
Figure 5. HWEP module precision in the standpipe trial by depth and target
compound.
19
-------
Precision for the STND module decreases with
depth for all compounds tested, as shown in Figure
4. The decrease in precision is most likely due to
contamination of the sorbent material with water.
The vendor recommends that the STND module
be deployed at depths less than 30 feet, as water
can migrate through the membrane. The relative
standard deviations at the 17-foot depth ranged
from 2 to 17% for the six test compounds whereas
the relative standard deviations at the 3 5-foot
depth ranged from 11 to 28%. The median RSD
for the STND modules is 14% when the results
from all 6 target compounds are combined. For a
comparable reference sample, the median RSD for
all 6 compounds is 12%. For depth levels in
which direct comparisons can be made between
the GORE-SORBER modules and reference
measurements, four STND module RSD values
were less than the reference method and two were
greater than the reference method. Thus, from a
qualitative perspective, GORE-SORBER STND
module and reference method precisions are
comparable.
Precision for the FfWEP module shows variability
with depth in a generally consistent trend for all
target VOCs. The best precision is observed at an
intermediate sampling depth. This trend can be
seen in Figure 5 which is a bar plot of percent
RSD at the tested depths for each of the six target
compounds. As an example, TCE has an RSD of
32% at 17 feet and 21% at 28 feet. The minimum
RSD, or best precision, is 13% at 35 feet, followed
by an RSD increase to 18% at 46 feet. Nearly all
of the six compounds tested reveal this trend,
showing the best precision in the middle (28- to
35-foot) depth range of this test. The median RSD
for the FfWEP module was 21% when results from
all 6 target compounds are combined. For a
comparable reference sample, the median RSD is
12%. A comparison of FfWEP module precision
with reference sample precision shows that in six
cases, the FfWEP module was less than or equal to
the reference method and in six cases the GORE
RSD was greater than the reference method. Thus
from a qualitative perspective, GORE-SORBER
FfWEP module and reference method precision is
comparable.
Monitoring Well Results
GORE-SORBER STND and FfWEP modules were
installed for a 48-hour exposure interval at five
different monitoring wells with TCE
concentrations ranging from 5 to 2000 |Jg/L. The
samplers were deployed at relatively shallow
depths as noted in Table 6, with the shallowest
deployment in a water column depth of 2.5 feet
and the deepest in a water column depth of 9.8
feet. Reference samples were collected at 12-hour
intervals throughout the 48-hour exposure interval
using a co-located submersible electric pump that
was left in the well over the duration of the
module exposure period. The five samples
collected with the reference pump were used to
compute a time-weighted average TCE
concentration in each well. Precision data from
the four replicate STND and FfWEP modules
deployed in each well are given in Table 6 along
with the average TCE mass collected in the four
replicate modules. The relative standard
deviations for the STND and FfWEP modules
observed in the field tests are greater than the
precision data obtained for TCE in the standpipe
tests. In the standpipe, STND module precision
ranged from 10 to 19%; whereas in the field,
precision ranged from 11 to 64%. For the FFWEP
modules, the standpipe precision for TCE ranged
from 13 to 32% in comparison with a field
precision range of 10 to 65%.
Table 6. STND and HWEP Module and Reference Results from GW Monitoring Wells
Well No.
12-09
12-06
06-09
06-04
12-01
Water Depth
Above
Module
(feet)
5.2
2.5
5.4
9.8
6.8
TCE TWA
Well Cone.
(H9/L)
3.9
42.5
47.8
327
1940
STND Module
TCE Mass
(ftj)
0.1
4.2
3.3
28
110
RSD
(%)
19
11
29
64
22
HWEP Module
TCE Mass
(eg)
0.1
4.3
3.1
37
160
RSD
(%)
27
28
33
65
10
20
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A log-log scatter plot of reference sample results
versus each of the four replicate module
measurements is shown in Figure 6 for the STND
modules and Figure 7 for the FfWEP modules.
The plotted results reveal very good linearity
across nearly three orders of magnitude in
monitoring well TCE concentrations. The
correlation coefficients for the average STND and
HWEP results versus the reference TCE
concentration at each well is greater than 0.99 in
both cases. The observed correlation coefficients
very near 1.00 indicate that variations in the well
concentration are proportionately observed in the
GORE-SORBER module results.
Deployment Logistics
The following observations were made during
testing of the GORE-SORBER modules at both
the standpipe and groundwater monitoring wells.
• Only one person is required to deploy the
GORE-SORBER modules. The collection of
reference samples for the determination of a
calibration constant at initial module
deployment would likely require more than
one field technician. Training requirements
for deployment of the samplers are minimal
with an hour of so of instruction required for a
technician to become proficient in routine
handling and use of the sampling modules.
• The modules are very compact, self contained,
and require no external power for operation.
• The modules are tied to a weighted cord and
lowered to the mid-point of the well screen.
The cord is then tied off at the wellhead. The
time required for deployment of the modules
in a well is on the order of minutes.
• Under typical use, well purging is not
required. The module is lowered into the well,
positioned at the mid-screen level, and
retrieved 48 hours later.
• Care must be taken to deploy samplers only
within the range of overlying water column
depth for which they are rated. Deployment at
depths in excess of specifications can result in
water leakage across the membrane and
erroneous results.
• The analyst must also use caution in
interpreting data from single module
deployments. During this study, outlier values
were noted from two samplers placed at depth
but within product specifications. This
observation is suggestive of a membrane
defect in those two samplers. Each module
contains duplicate sorbent packets that can be
used to verify the results. However, if
membrane leakage occurs, both sorbent
packets may be adversely affected by the
leakage. To provide additional quality
control, two separate modules could be
deployed in a sampling event; however,
deployment costs would double under such a
scheme.
Sampler Versatility
Based on test results, the following comments can
be made about the versatility of the GORE-
SORBER Water Quality Monitoring technology:
• The modules must be carefully matched to
anticipated water column depth above the
sampler. The STND module is recommended
for deployment in conditions in which the
overlying water column depth is less than 30
feet. The HWEP is recommended for
deployment in conditions where the overlying
water column depth is less than 50 feet.
• The modules collected all of the six target
analytes selected for use in this study. The
target analytes were selected to represent a
wide range of compound volatility and
solubility. Thus in this respect the modules
are judged to be versatile and can be used for a
variety of VOC contaminants in water.
• The GORE-SORBER Water Quality
Monitoring technology is probably best suited
for screening applications where precision
requirements are modest. Its use as a device
for monitoring compliance with federal or
state groundwater contamination regulations
may be limited by its moderate (15-30% RSD)
precision as reflected in these tests. In this
regard, the modules are judged to have limited
versatility.
• The system is designed for trend monitoring in
wells and must be calibrated against a
conventional sample collected with a low-flow
purging and sampling protocol or other
accepted method. The units of measurement
for the module and conventional groundwater
monitoring are not the same so that a cross-
comparison is necessary to interpret module
data in terms of conventional groundwater
VOC concentration units.
21
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n
8
A
0.01 •
10 100 1000
Reference TCE Concentration, ug/L
Figure 6.
Scatter plot of STND module data vs. reference data for all GW
monitoring wells. (Note that each symbol represents a single
measurement at each of the four concentration levels)
1000
100
10
0
-Q-
0.1
0.01
100
Reference TCE Concentration, ug/L
Figure 7. Scatter plot of HWEP module data vs. reference data for all GW
monitoring wells. (Note that each symbol represents a single
measurement at each of the four concentration levels)
22
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• Following deployment, the sampler units are
re-packaged in their original shipping vials
and mailed back to the W. L. Gore Laboratory
for analysis. The module is sold with analysis
costs included. Analysis of the modules is
only available through W. L. Gore Laboratory.
• The analytical method used by the W. L. Gore
Laboratory can provide a comprehensive
screening for both volatile and semi-volatile
organic compounds.
Performance Summary
A summary of GORE-SORBER Water Quality
Monitoring technology performance is given in
Table 7. Summary categories include precision,
accuracy, comparability with reference method,
versatility, and logistical requirements. Cost and
physical characteristics of the equipment are also
summarized in the table.
The precision results of this verification test
suggest that care must be taken to select the
correct sampler membrane type for optimum
results. The results of this study show that the
STND membrane module is optimized for
deployment in water column depths less than 30
feet whereas the HWEP membrane modules are
optimized for deployment at depths less than 50
feet.
The moderate precision (15-30% RSD) noted for
these modules suggest that they are best used for
screening purposes or for concentration trend
monitoring. They may also be well suited in
plume edge monitoring for gross changes in VOC
concentrations in groundwater. The modules are
versatile in the sense that they can be used to
collect a broad range of both VOC and semi-VOC
compounds. This makes them useful for screening
groundwater systems that may contain multiple
contaminants.
Table 7. GORE-SORBER Module Performance Summary
Performance
Parameter
Performance Summary
Precision
For 6 target compounds at a concentrations level of-20 |jg/L, and at
sampling depths shown below:
STND module (17 and 28 foot depths)
RSD range: 2 -28% Median: 14%
HWEP module (17, 28, 35 and 46 foot depths)
RSD range: 9 - 35% Median: 21%
Comparability with
Reference Samples
At 5 groundwater monitoring wells with TCE concentrations ranging from 5 to
2000 |jg/L, the correlation coefficients computed from an average of four
replicate modules versus the corresponding time-weighted-average reference
concentration over the 48-hour exposure interval was as follows:
STND Module: Correlation Coefficient = 0.997
HWEP Module: Correlation Coefficient = 0.998
Sampler versatility
Limited versatility in terms of deployment depth
Wide versatility in terms of compounds detected
Limited versatility in terms of monitoring for regulatory compliance
Limited versatility in terms of deployment at locations different from where
reference measurements are taken.
23
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Table 7. GORE-SORBER Module Performance Summary (Continued)
Performance
Parameter
Logistical requirements
Completeness
Purchase cost
Size and weight
Other
Performance Summary
Modules can be deployed and retrieved by one person.
Technician training requirements are about 1 hour.
Modules require comparison with co-located conventional groundwater
sample and analysis for data interpretation.
Modules are compact and completely passive — no power requirements.
Module use requires two trips to the well, one for installation and one for
retrieval following a 48-hour exposure interval.
Modules were successfully used to collect all of the samples prescribed in the
test plan.
Per module cost ranges from $125 to $240 depending on the number of
compounds desired in the analysis. Costs include analysis but do not include
manpower for deployment/retrieval or overnight shipping costs to the
laboratory following sampler retrieval.
Each membrane module is about 4 inches long x 0.1 inch wide and weighs
about 2 ounces.
In order to provide a basis for comparison of Gore-Sorber module data to
actual VOC concentrations in a well, a co-located groundwater well sample
and analysis by conventional means is required.
Note: Target compounds were:
tetrachloroethene.
1,1-dichloroethene, 1,2-dichloroethane, benzene, trichloroethene, 1,1,2- trichloroethane, and
24
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Section 5 — GORE-SORBER Water Quality Monitoring Technology
Update and Representative Applications
Note: The following comments were provided by
the vendor and have not been verified as a part of
this ETV test. They have been edited only for
editorial consistency with the rest of the report.
Soil Gas Applications
A similar product from W.L. Gore & Associates,
Inc. is the GORE-SORBER Screening Survey,
which uses the same principles of passive
adsorption to collect a sample of soil gas over an
exposure period of 10 - 14 days. This technology
has been validated at over 2,000 sites worldwide
since it was introduced in the early 1990's. This
technology has also been evaluated as part of a
separate ETV report entitled "Soil Gas Sampling
Technology, W.L. Gore & Associates, Inc.,
GORE-SORBER Screening Survey", and is
available in Portable Document Format (.pdf) at
http://www.epa.gov/etv/verifrpt.htnrf02.
Water Quality Monitoring
This section describes a recent application of the
GORE-SORBER Water Quality Monitoring
technology.
Site Description
The technology was applied at a military facility
located on the eastern coast of the U. S. The
facility conducted munitions testing for
approximately 30 years. Numerous wells were
installed, in several phases, as part of on-going
remedial efforts at various locations at the facility.
The site geology consists of unconsolidated
alluvial sediment and alluvial deposits of gravel,
sand, silt, and clay. Groundwater depth ranges
between 5 and 30 feet, with a flow gradient
extending from northeast to southwest.
A contaminated groundwater plume was identified
and delineated in the primary area of investigation.
Elevated concentrations of several chlorinated and
non-chlorinated compounds occur in the
groundwater. Contaminant compounds included
1,1,2,2-tetrachloroethane, trichloroethene, carbon
tetrachloride, chloroform, and toluene. Maximum
total VOC levels ranged between 4,000 and 5,000
|jg/L. Groundwater monitoring did not reveal the
presence of any dense non-aqueous phase liquids.
The hydrologic system is believed to discharge
into wetlands found farther south of the area,
although the contaminant plume has not reached
the wetlands. Monitoring well sampling occurs
quarterly.
Passive Sampling Events
To date, two passive groundwater sampling events
have been undertaken using the GORE-SORBER
Water Quality Monitoring system with concurrent
groundwater sampling. The first sampling phase
occurred in July 1997, where 28 wells were co-
sampled. A total of 33 wells were co-sampled in
December 1998. The majority of the wells
sampled during the first phase were also sampled
during the second phase. In most cases, each well
was sampled using both the GORE-SORBER
modules and traditional groundwater sampling.
However, there were a few instances of missing
concurrent data.
The collectors were lowered into each well and
positioned in the groundwater within the screened
interval. Following a two-day exposure, the
collectors were retrieved and returned to the
laboratory for analysis. Traditional groundwater
sampling (matrix sampling) was conducted
immediately following the retrieval of the
collectors during each sampling phase. Target
compounds were chlorinated compounds and
xylenes. The analytical methods used for module
analysis were a modified SW846 Methods 8260
and 8270. Analytical results were provided for
chlorinated compounds as well as petroleum-
related compounds.
Results
Target compounds reported in common between
both sets of data were examined. Scatter plots
were generated to examine the comparability of
the two sets of data for trichloroethene, 1,1,2,2-
tetrachloroethane, and carbon tetrachloride (Figure
8). The correlation coefficients range from 0.60 to
0.97, respectively.
25
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Trichloroethene y = 0.0666x + 0.9832
R2 = 0.6046
70.00 '
'oi
"TO 50.00 '
Q
o 40-°°
Q.
«
-
* ^^^^ ^
^^^-^^ 4
^^^^^
^^^^
*^"^ »
0.00 4-ii ii ii ii
0 100 200 300 400 500 600 700 800 900
Groundwater Matrix Data (ug/l)
1,1,2,2-Tetrachloroethane y = o 0416x + 0 7294
R =0.7814
5
^
• ^^
* ^^
^^
^^
^^
_f^^
^^~ •
0 500 1000 1500 2000 2500 3000 3500
Groundwater Matrix Data (ug/l)
Carbon Tetrachloride v = ° 1 597x ° 8069
R2 = 0.969
1
(
*
^^
*^*^
^^
^s*\ »
200 400 600 800 1000 1200 1400 1f
Groundwater Matrix Data (ug/l)
00
Figure 8. Statistical Comparisons between groundwater data
and module data for TCE, 1,1,2,2-tetrachloro-
ethane, and carbon tetrachloride
26
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The data from GORE-SORBER modules and the
ground-water data were also plotted as contour
maps for selected compounds for each sampling
phase (copies of these maps are available from
W.L. Gore & Associates, Inc.). The spatial
distribution of the data indicates that the GORE-
SORBER Water Quality Monitoring system is
more sensitive to lower concentration levels of
compounds in groundwater than is traditional
groundwater analysis. Furthermore, the smaller
groundwater contaminant plume footprint, based
on the matrix sampling, is likely due to higher
laboratory quantitation limits. However, the
general plume orientation and the location of "hot
spots" is consistent when comparing maps from
both sets of data. Differences between the two
contour surfaces tend to be a function of missing
data between phases.
Cost Savings
Though the data collection effort is increased in
the early stages of this application, the long-term
cost savings are realized in subsequent sampling
events when only passive samplers are used. The
cost savings comparison realized from this case
study is summarized in Table 8 for one round of
sampling. The use of GORE-SORBER Water
Quality Monitoring technology would lower the
sampling costs by approximately 72%. This
represents a significant reduction in long-term
costs associated with groundwater monitoring.
In general, there is a good correlation between the
passive sampler results and the groundwater data
results from this study. Apparent discrepancies
were a function of missing data within and
between sampling phases. The results indicate
that the GORE-SORBER modules alone are
capable of capturing the quality of the
groundwater, and can illustrate concentration
changes across an area of interest. As a result of
this study, the regulatory agency is reviewing a
proposal to perform matrix sampling on a less
frequent basis (i.e., annually) thus lowering the
project sampling costs by more than $60,000 over
the estimated 20-year life of this project.
Table 8. Cost Comparison for One Round of Sampling
Item
Units
Unit Description
Extended Cost
Conventional Sampling/ Analysis
Project Management
Field Crew
Equipment-pump
Purge water disposal
Laboratory costs
42
235
1
0
50
Hours
Hours
Lump sum
Dollars
Samples
Total
$2,145
$12,993
$1,765
0#
$7,452
$24,355
GORE-SORBER Water Quality Monitoring Survey
Project Management
Field Crew
Equipment-consumables
Laboratory costs
4
31
1
26
Hours
Hours
Lot Charge
Samples
Total
$204
$1,324
$100
$5,070
$6,698
# On-site purge water treatment was available at this site
27
-------
28
-------
Section 6 — References
EPA, 1996. "Test Methods of Evaluating Solid Waste: Physical Chemical Methods; Third Edition; Final
Update III," Report No. EPA SW-846.3-3, Government Printing Office Order No. 955-001-00000-1, Office
of Solid Waste and Emergency Response, Washington, DC.
EPA, 1998. Environmental Technology Verification Report, Field Portable GC-MS, Inficon HAPSITE;
Report Number EPA/600/R-98/142, US EPA, Office of Research and Development, Washington, DC. (also
available at http://www.epa.gov/etv/verifipt.htnrf02).
Foster Wheeler, 1998. "Final Hydrogeologic Investigation Report for the National Aeronautics and Space
Administration Stennis Space Center, Mississippi," Office of Environmental Engineering, NASA, Stennis
Space Center, Mississippi, 39529.
Havlicek, L.L, and R. D. Grain, 1988, Practical Statistics for the Physical Sciences. American Chemical
Society, Washington, DC.
NIST, 2000. National Institutes of Standards and Technology, Standard Reference Database No. 69, R.
Sander, editor, available at http://webbook.nist.gov/chemistry.
Puls, R.W., and Barcelona, M. I, 1996. Low-Flow (Minimal Drawdown) Ground-Water Sampling
Procedures, US EPA Ground Water Issue (April 1996), Publication No. EPA/540/S-95/504, US EPA Office
Solid Waste and Emergency Response, Washington, DC.
Sandia, 1999. Groundwater Sampling Technologies Verification Test Plan, Sandia National Laboratories,
Albuquerque, NM 87185 (also available at http://www.epa.gov/etv/test jlan.hta#monitoring).
29
-------
30
-------
Appendix A — Reference Pump Performance
Introduction
In addition to the sampling at the standpipe, the verification test design included the collection of vendor
samples from onsite groundwater monitoring wells. During monitoring well sampling, a reference pump was
co-located in the well with the vendor sampler. Both vendor and reference samples were collected
simultaneously to enable a comparison of the results. This appendix summarizes the reference sampler
chosen and outlines its performance and acceptability as a reference sampling technique.
System Description
The reference pump selected for use in this verification study was a submersible electric gear pump (positive
displacement, low-speed pump, Fultz, Model SP-300, Lewistown, PA). Pump construction materials are
stainless steel and polytetrafluoroethylene (PTFE), and pump dimensions are 7.5 inches in length by 1.75
inches in diameter. This pump is a positive displacement device. Water is introduced into the pump through a
60-mesh inlet screen into a stainless steel cavity. Two PTFE gears inside the pump cavity push the water to
the surface through 100 feet of 'Ainch outside diameter PTFE tubing. An electronic controller is used to
regulate the flow rate of the pump. Nominal sample collection flow rates were in the range of 100-200
mL/min.
Performance Evaluation Method
The gear pump was tested during the standpipe trials in the same manner as the other vendor pumps. Water
samples were collected from the interior of the standpipe in four separate trials with both low (-20 |Jg/L) and
high (-200 |Jg/L) target concentrations at low (17 feet) and high (91 feet) sampling depths (see Section 3 for
additional details). Reference samples were collected from external sampling ports simultaneously with the
pump samples. In each trial, five replicate pump samples and five replicate port samples were collected.
Following collection, all samples were analyzed using the same onsite GC-MS system.
Pump Precision
A summary of pump precision is given in Table A-l. The percent relative standard deviation results for each
of the six target compounds in the four standpipe trials (low concentration—shallow, low concentration—
deep, and so on) for the gear pump and the external sampling port are given in columns 4 and 5, respectively.
The relative standard deviation range for the pump was 3.2 to 16.3%, with a median value of 7.6%. The port
precision data ranged from 2.8 to 16.2%, with a median value of 10.1%. The final column in the table gives
the value ofp associated with the F-ratio test (see Section 3 for a description of this test). Values ofp less
than 0.05 may indicate that significant, nonrandom differences exist between the two estimates of precision.
Out of 24 trials, only 2 show values ofp less than 0.05. These data indicate that pump precision was not
statistically different from the precision obtained from the reference samples taken directly from the standpipe
external ports.
31
-------
Table A-l.Precision of Gear Pump and Reference Samples in Standpipe Trials
Compound
11DCE
12DCA
BNZ
TCE
112TCA
PCE
Minimum
Maximum
Median
Cone.
Level
Low
Low
High
High
Low
Low
High
High
Low
Low
High
High
Low
Low
High
High
Low
Low
High
High
Low
Low
High
High
Depth
(ft)
17
91
17
91
17
91
17
91
17
91
17
91
17
91
17
91
17
91
17
91
17
91
17
91
Gear
Pump
Precision
(%RSD)
15.7
3.5
4.0
7.6
15.4
3.2
5.1
6.0
8.1
7.6
3.7
6.1
16.3
5.9
6.4
9.6
9.4
8.4
7.6
11.0
12.9
9.0
4.5
12.7
3.2
16.3
7.6
Port
Precision
(%RSD)
14.2
14.4
8.6
9.7
12.5
13.2
9.0
10.4
11.8
12.9
8.4
9.4
10.5
12.1
2.9
8.6
16.2
15.0
3.5
6.5
9.6
11.7
2.8
8.8
2.8
16.2
10.1
F-Ratio
1.11
14.7
4.81
1.28
2.35
14.1
3.18
2.38
1.71
2.30
5.02
1.83
2.41
3.12
4.82
1.55
3.38
2.81
4.76
3.43
1.36
1.50
2.28
2.38
F-Ratio
P
0.46
0.01
0.08
0.41
0.21
0.01
0.14
0.21
0.31
0.22
0.07
0.29
0.21
0.15
0.08
0.34
0.13
0.17
0.08
0.13
0.39
0.35
0.22
0.21
Pump Comparability with Reference Samples
Gear pump comparability is expressed as the percent difference relative to the reference sample concentration
by subtracting the average reference value from the average gear pump value, dividing the result by the
average reference value, and multiplying by 100. The percent differences for each of the 24 trials are given in
Table A-2. They range from -13 to 24% with a median value of 7%. A t-test for two sample means was used
to evaluate the statistical significance of the differences between the gear pump and reference samples. The
tabulated values ofp give a quantitative measure of the significant of the observed difference in probabilistic
terms. Values of p less than 0.05 suggest that a statistically significant bias may exist for the trial. With five
exceptions, all values ofp are greater than 0.05, indicating that overall, the differences between the two
sampling methods are statistically indistinguishable.
32
-------
Table A-2. Comparability of the Gear Pump with the Reference
Samples in Standpipe Trials
Compound
11DCE
12DCA
BNZ
TCE
112TCA
PCE
Minimum
Maximum
Median
Cone.
Level3
Low
Low
High
High
Low
Low
High
High
Low
Low
High
High
Low
Low
High
High
Low
Low
High
High
Low
Low
High
High
Depth
(ft)
17
91
17
91
17
91
17
91
17
91
17
91
17
91
17
91
17
91
17
91
17
91
17
91
Difference
(%)
-4
7
-3
13
24
10
-2
12
11
13
0
14
0
16
0
11
-6
7
1
10
-13
6
-6
6
-13
24
6.5
t-Tesf
P
0.64
0.31
0.54
0.05
0.05
0.13
0.71
0.06
0.13
0.11
0.98
0.03
0.99
0.04
0.95
0.10
0.51
0.41
0.77
0.15
0.08
0.37
0.03
0.42
1 The low-level concentration was in the range of 10 to 20 ng/L for all 6 target
compounds. The high-level concentration was in the range of 175 to 250 ng/L.
The t-test was used to compare differences between the gear pump and reference
samples for each compound in each trial. Small values ofp (O.05) are shown in bold and
are suggestive of a statistically significant difference. See text for further details.
33
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The percent difference data for the gear pump are also shown graphically by target compound in Figure A-l
for each of the four standpipe trials. Fifteen of the 24 percent difference values are in the positive percent
difference range, suggesting that many of the samples collected with the gear pump contained higher
concentrations than those samples collected from the corresponding external sampling port. An exhaustive
evaluation of the data was not performed to characterize this phenomenon; however, it is possible that this
was a result of bias in the analytical method, since one would not expect sample losses to be significant in the
reference sampling procedure.
15
-5
-15
-20
~20^g/L@ 17ft
-200 ^g/L @ 91 fl
~20^g/L@17ft
O-200 ^g/L (a) 91 f<
11DCE 12DCA BNZ TCE 112TCA PCE
Compound
Figure A-l. Percent recoveries of the reference pump by compound for the four
standpipe trials.
Reference Pump Performance Summary
The test data for the reference pump reveal considerable variability for PCE and 12DCA. However, the
variability and comparability for TCE, the only compound encountered in the field trials, are acceptable. The
mean relative standard deviation for TCE at concentration levels ranging from 20 to 200 |jg/L was 9.6% and
the mean percent difference for TCE in the same concentration range was 7%. The data presented for TCE
show that the pump is equivalent to the reference sampling method in terms of both precision and accuracy
and is acceptable for use as a reference standard.
34
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Appendix B — Quality Summary for Analytical Method
Introduction
An onsite GC-MS-headspace method was chosen for analysis of all samples in this study. Two identical GC-
MS systems were operated by Field Portable Analytical (Folsom, CA) using a modified EPA Method 8260
(for a summary of the method, see Section 3). Data quality measures were incorporated into all onsite
analyses consistent with the guidelines in Method 8260. This appendix summarizes those data quality
measures, thereby demonstrating the adequacy of the method for this verification study.
Data Quality Measures
A number of data quality measures were used to verify acceptable instrument performance and the adequacy
of the final analytical results throughout the course of the study. These measures are summarized in Table
B-l. All data quality measures in this table were followed, with the exception of duplicates. Duplicates were
not routinely run since all of the samples from the field were in batches of replicates. Earlier pre-field
demonstration studies indicated that the field replicates were the same in composition so that they could be
treated as analysis duplicates.
Table B-l. Onsite GC-MS-Headspace Method Quality Control Measures
Quality Control
Check
MS tune check w/
bromofluorobenzene
(BFB)
5-Point (Minimum)
calibration
Continuing calibration
check (CCC)
End calibration
checks
Duplicates
Method blanks
Minimum
Frequency
Every 12 hours
Beginning of each day
Beginning of each day
End of each day
10% of the samples
After beginning of day
CCC
Acceptance
Criteria
Ion abundance criteria
as described in EPA
Method TO-1 4
%RSD < 30%
+ 25% difference of
the expected
concentration
for the CCC
compounds
+ 25% RPDofthe
beginning CCC
Relative percent
difference < 30%
Concentrations for all
calibrated compounds
< practical
quantification level
Corrective
Action
1) Reanalyze BFB
2) Adjust tune until
BFB meets
criteria
Rerun levels that do
not meet criteria
1) Repeat analysis
2) Prepare and run
new standard
from stock
3) Recalibrate
1) Repeat analysis
2) If end check is
out, flag data
for that day
1) Analyze a third
aliquot
2) Flag reported
data
Rerun blanks until
criteria are met
Data Quality Examples
The following data are examples of system performance throughout the course of the study. In the interest of
brevity, all quality control data are not shown in this appendix. A complete tabulation of all quality control
data is included in the GW SAMPLING DATA NOTEBOOK and is available for viewing through a request
to the ETV Site Characterization and Monitoring Technologies Pilot Manager.
35
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Method Blank Check
Method blanks were run at the beginning of each 12-hour analysis session. Concentration levels of the six
target compounds were reported as non-detectable (<5 |Jg/L) for all method blank samples.
Continuing Calibration Check
The method criterion for the continuing calibration checks run at the beginning and end of each analysis cycle
was a value within 25% of the expected value. The results of the TCE continuing calibration checks for both
of the GC-MS instruments used in the study are shown in Figures B-l and B-2. Similarly, the results of the
PCE continuing calibration check for both instruments are shown in Figures B-3 and B-4. All check
compound recoveries fall within the predefined control interval of 70 to 130%. The control interval is
specified in EPA Method SW-846, from which this method is adapted. The relative percent differences
between the pre- and post-analysis batch calibration check samples are shown in Figure B-5. In two cases,
the relative percent difference falls outside the 25% window. Data from these days were not rejected,
however, since the ±30% criteria for the calibration check was met.
GCMS (Pepe) Control Chart
TCE Check Standard
130
& 110
Upper Control Limit
Lower Control Limit
8/10/99 8/11/99 8/12/99 8/13/99 8/14/99 8/15/99 8/16/99 8/17/99
Day
Figure B-l. Calibration check control chart for TCE on GC-MS #1.
36
-------
GCMS (Taz) Control Chart
TCE Check Standard
130
120
110
100
Upper Control Limit
S
in
Lower Control Limit
8/9/99 8/10/99 8/11/99 8/12/99 8/13/99 8/14/99 8/15/99 8/16/99 8/17/99
Day
Figure B-2. Calibration check control chart for TCE on GC-MS #2.
GCMS (Pepe) Control Chart
PCE Check Standard
s?
o
8
a:
Standard
i l
1
6
RD -
Upper Control Limit
4Se
«Se
riesl
ries2
*»«,*,
D :
1 l
_* f____
Lower Control Limit
. ..A.. .
8/10/99 8/11/99 8/12/99 8/13/99 8/14/99 8/15/99 8/16/99 8/17/99
Day
Figure B-3. Calibration check control chart for PCE on GC-MS #1.
37
-------
GCMS (Taz) Control Chart
130
120
100
70
Upper Control Limit
Lower Control Limit
8/9/99 8/10/99 8/11/99 8/12/99 8/13/99 8/14/99 8/15/99 8/16/99 8/17/99
Day
Figure B-4. Calibration check control chart for PCE on GC-MS #2.
GCflMS (Pep* and Taz) System Check
Relative Percent Difference - Daily Begin/End Check
50 ,
40
JO
1
i
ml
i
~
1
1
>f
-
i
_
-
-
1
BPcpc-TCE'
DPepe-PCE
PTaZ-TCE
13 Taz -PCE
^
T-
j
~"
i
h.'ii'u ?-1 :-.",'J «'16.'aB
Anafysis Date
Figure B-5. GC-MS system check relative percent differences.
38
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