United States
Environmental Protection
Agency
     Comparison of Geoprobe®
     PRT and AMS GVP Soil-Gas
     Sampling Systems with
     Dedicated Vapor Probes
     in Sandy Soils at the
     Raymark Superfund Site

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                                                            EPA/6GO/R-06/111
                                                              November 2006


          of                                and




                             in

at  the


        Dominic DiGiulio, Cynthia Paul, and Brad Scroggins
                U.S. Environmental Protection Agency
                Office of Research and Development
           National Risk Management Research Laboratory
          Ground Water and Ecosystems Restoration Division
                           Ada, OK

                Raphael Cody and Richard Willey
                U.S. Environmental Protection Agency
                           Region I
                          Boston, MA

                         Scott Clifford
                U.S. Environmental Protection Agency
             Region I, New England Regional Laboratory
                      North Cheimsford, MA

                        Ronald Mosley
                U.S. Environmental Protection Agency
                Office of Research and Development
           National Risk Management Research Laboratory
                   Research Triangle  Park, NC

              Annette Lee and Kaneen Christensen
                Xpert Design and Diagnostics, LLC
                         Stratham, NH

                          Ravi Costa
                      The Shaw Group  Inc.
                           Ada, OK

                        Project Officer
                      Dominic C. DiGiulio
                U.S. Environmental Protection Agency
                Office of Research and Development
           National Risk Management Research Laboratory
          Ground Water and Ecosystems Restoration Division
                           Ada, OK

         U.S. ENVIRONMENTAL PROTECTION AGENCY
           OFFICE OF RESEARCH AND  DEVELOPMENT
      NATIONAL RISK MANAGEMENT RESEARCH LABORATORY
                     CINCINNATI, OH

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                                           Notice
The U.S. Environmental Protection Agency (EPA) through its Office of Research and Development funded
and managed the research described here through in-house efforts and under Contract No. 68-C-02-092 to
the Dynamac Corporation. It has been subjected to the Agency's peer and administrative reviews and has
been approved for publication as an EPA document.


All data generated in this report were subjected to  an analytical Quality Assurance Plan developed  by
EPA's New England Regional Laboratory. Also, a Quality Assurance Project Plan was implemented at the
Ground Water and Ecosystems Restoration Division.  Results of field-based studies and recommendations
provided  in this document have been subjected to external and internal peer and administrative reviews.
This report provides technical recommendations,  not policy guidance.  It is not issued as an EPA Directive,
and the recommendations of this report are not binding on enforcement actions carried  out by the EPA or
by the individual States of the United States of America.  Neither the  United States Government nor the
authors accept any liability or responsibility resulting from the use of this document. Implementation of the
recommendations   of  the document and  the  interpretation  of the  results   provided  through  that
implementation are the sole responsibility of the user.

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                                          Foreword
The U.S. Environmental Protection Agency is charged by Congress with protecting the Nation's land, air,
and water resources. Under a mandate of national environmental laws, the Agency strives to formulate and
implement actions leading to a compatible balance between human activities  and the ability of natural
systems to support and nurture life. To meet these mandates, EPA's research program is providing data
and technical support for solving environmental problems today and building a science knowledge base
necessary to manage our ecological resources wisely, understand how  pollutants affect our health, and
prevent or reduce environmental risks in the future.

The  National  Risk Management Research   Laboratory is the  Agency's center for investigation  of
technological and management approaches  for reducing risks from threats to  human  health and the
environment. The focus of the Laboratory's research program is on methods for the prevention and control
of pollution  to air, land,  water, and subsurface  resources; protection  of  water  quality  in public  water
systems; remediation  of contaminated sites and ground water;  and prevention and control of indoor air
pollution.  The goal of this  research effort is to catalyze development and implementation of innovative,
cost-effective environmental technologies; develop scientific and engineering information needed by EPA
to support regulatory and policy decisions; and  provide  technical support and information transfer to ensure
effective implementation of environmental regulations and strategies.

This report describes the  results of an investigation conducted to assist EPA's  New  England Regional
Office in evaluating vapor intrusion in homes and a commercial building near the Raymark Superfund Site
in Stratford,  Connecticut.  Specifically, a study was conducted to compare results of soil-gas sampling
using dedicated vapor  probes,  a  truck-mounted direct-push  technique,  Geoprobe® Post-Run-Tubing
system, and a hand-held rotary hammer technique, AMS Gas Vapor Probe kit.  Testing revealed  some
statistically significant differences.  However, the magnitude of variation  was similar to that due to spatial
variability on the scale of testing (1 m).   Hence  for practical purposes, all three sample systems were
considered approximately equivalent.  This investigation should provide confidence that the PRT and GVP
sample systems are satisfactory for collecting soil-gas samples in sandy  soils, such as those present near
the Raymark site, to evaluate the potential for vapor intrusion.
                                                  5hen G. Schmelling, Director,
                                              Ground Water and Ecosystenfls Restoration Division
                                              National Risk Management [Research Laboratory

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                                          Abstract

A study was conducted near the Raymark Superfund Site in Stratford, Connecticut to compare results of
soil-gas sampling using dedicated vapor probes, a truck-mounted direct-push technique - the Geoprobe
Post-Run-Tubing (PRT) system, and a hand-held rotary hammer technique - the AMS Gas Vapor Probe
(GVP) kit.  A comparison of VOC concentrations using dedicated vapor probes and the GVP sampling kit
indicated  that the two  methods provided similar results.  However, at one location, VOC concentrations
were significantly higher for dedicated vapor probes indicating  potential leakage with the GVP system.
VOC concentrations using the PRT system were higher than VOC concentrations using  dedicated vapor
probes by an average factor of 1.2. This is the same magnitude observed for spatial variability on a scale
of 1 m  (median of 1.2 and average of 1.3 for 90 sample pairs).  However, this effect did not appear to be
due to spatial variability which would result in random scatter not a consistent bias as observed.  It is also
unlikely that extraction volume or sampling sequence  caused the  observed  bias given the results of
extraction volume and  sample sequence testing.  VOC  concentrations using the PRT system were also
higher than VOC concentrations using the GVP kit by an average factor of 2.4.  Similar to the comparison
between probe and PRT sampling systems, the effect did not appear  to be due to spatial variability,
extraction volume, or sequence of sampling.  Thus, utilization of the PRT system resulted  in observation of
higher concentrations of VOCs compared to the GVP kit and dedicated vapor probes. However, variation
in concentration was relatively minor when compared to spatial variability on the scale used for comparison
testing.   Hence  for practical  purposes,  all three sample systems  can be considered approximately
equivalent.
                                              IV

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                                   Table of Contents

Notice	ii
Foreword	iii
Abstract	iv
List of Abbreviations	vi
List of Figures	vii
List of Tables	xi
Acknowledgements	xiv
Executive Summary	E1
1.0   Introduction	1
2.0   Site Description	2
3.0   Methods and Materials	6
      3.1    Soil-Gas Sampling from Dedicated Vapor Probes	6
      3.2   Soil-Gas Sampling with the GeoProbe® PRT System	8
      3.3   Soil-Gas Sampling with the AMS GVP Kit	11
      3.4   On-Site Soil-Gas Analysis and Data Quality	13
      3.5   Computation of Pre-Sample Internal Volume Exchange Requirements	15
      3.6   Assessment of Extraction Volume on Sample Results	18
      3.7   Assessment of Air Extraction at One Location on Another Location	21
      3.8   Consideration of Spatial Variability on Comparison of Sampling Techniques	22
4.0   Results	26
      4.1    Results of Testing at MW302SGM	26
      4.2   Results of Testing at MW514SG	27
      4.3   Results of Testing at MW523SGS, MW523SGM, and MW523SGD	29
      4.4   Results of Testing at MW525SG	31
      4.5   Results of Testing at MW526SGS, MW526SGM, and MW526SGD	34
5.0   Discussion of Comparison Testing	38
6.0   Summary	41
References	43
Appendix A	45

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                                  List of Abbreviations
1,1,1-TCA    1,1,1 - trichloroethane
1,1-DCE      1,1 - dichloroethylene
TCE         trichloroethylene
c-1,2-DCE    cis-1,2-dichloroethylene
O2           oxygen
CO2         carbon dioxide
CH4         methane
ID           inner diameter
VOC         volatile organic chemical
PRT         post-run tubing
GVP         gas vapor probe
PVC         polyvinylchloride
SLPM        standard liter per minute
GC          gas chromatography
                                             VI

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                                      List of Figures


Figure 1      Direction of ground-water flow (large arrows) and location of the residential area of
             investigation  near the Raymark Superfund Site (modified from Tetra Tech NUS,  Inc.,
             2000)	2

Figure 2      Location of geologic cross-sections and the residential area of investigation near the
             Raymark Superfund Site (modified from Tetra Tech NUS, Inc.,2000)	3

Figure 3      Geologic cross-section G - G' (modified from Tetra Tech NUS, Inc., 2000)	3

Figure 4      Geologic cross-section H - H' (modified from Tetra Tech NUS, Inc. 2000	4

Figure 5      Results of ten shallow single-well hydraulic conductivity tests at the Raymark site
             (boundary values for sand and gravel taken from Freeze and Cherry, 1979)	4

Figure 6      Results of a sub-slab air permeability test taken from EPA (2006)	5

Figure 7      Typical construction log for dedicated vapor probes installed at the Raymark Site	6

Figure 8      Photograph of valve used to seal dedicated probes, PVC barbed fitting, and Teflon tubing
             used for sampling	7

Figure 9      Photograph of peristaltic pump, flowmeter, and landfill gas meter used during purging
             dedicated vapor probes	8

Figure 10    Photograph of peristaltic pump and one-liter Tedlar bags (duplicate sample) used for
             sampling dedicated vapor probes	8

Figure 11     Photograph of truck-mounted PRT system	9

Figure 12    Components of PRT sampling system	9

Figure 13    Photograph of an expendable point and expendable point holder	9

Figure 14    Photograph of a PRT adapter with an O-ring and associated Teflon tubing	10

Figure 15    Photograph of metal rod used to push out the expendable point	10

Figure 16    Photograph of connection of PRT adapter to expendable point holder	10

Figure 17    Creation of hole in  asphalt prior sampling with GVP kit	11

Figure 18    Photograph of Retract-A-Tip	11

Figure 19    Disassembled view of Retract-A-Tip	11
                                              VII

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                               List of Figures - continued
Figure 20     Photograph of hammering Retract-A-Tip and support pipe using a rotary hammer drill
             and the GVP extension drive adapter	12

Figure 21     Retraction of Retract-A-Tip prior to sampling	12

Figure 22     Proximity of dedicated vapor probe (metal cover surrounded by white concrete at
             base of Geoprobe unit), PRT, and GVP sampling systems	12

Figure 23     Comparison of EPA Method TO-15 with sample collection using a peristaltic pump
             and Tedlar bags with  on-site GC analysis of 1,1,1-TCA, 1,1-DCE, TCE, and
             c-1,2-DCE  (n = 91, r2 = 0.88)	14

Figure 24     Purge volume as a function of C0/Cin and Cout/Cin	16

Figure 25     Vapor concentration as a function of cumulative post-sample extraction volume up to
             5.5 liters at dedicated vapor probe MW513SG	17

Figure 26     O2, CO2, and CH4 concentration as a function of cumulative post-sample extraction at
             dedicated vapor probe MW514SG	18

Figure 27     Vapor concentration as a function of cumulative pre-sample extraction volume using
             the PRT sampling system at a depth of 0.76 m near MW525SG	19

Figure 28     Vapor concentration as a function of cumulative pre-sample extraction volume at dedicated
             vapor probe MW513SG at a depth interval of 2.1 to 2.4 m	20

Figure 29     Comparison of first and third samples at dedicated probe, PRT, and GVP sample
             locations	21

Figure 30     Coefficient of variation (%) as a function of mean vapor concentration for first, second, and
             third samples at dedicated probe, PRT, and GVP sample locations	22

Figure 31     Photograph illustrating five PRT sample locations (orange flags) near MW213	23

Figure 32     Schematic  illustrating five PRT sample locations near MW213 in plan view	23

Figure 33a   Vapor concentration at locations S1 through S5 (one sample at each location) at a
             depth of 0.76m	24

Figure 33b   Vapor concentration at locations S1 through S5 (one sample at each location) at a
             depth of 2.3 m	24

Figure 33c   Vapor concentration at locations S1 through S5 (one sample at each location) at a
             depth of 3.2 m	25
                                             VIM

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                             List of Figures - continued
Figure 34    Schematic illustrating the location of sampling systems at MW302SGM in plan view	26

Figure 35    Comparison of mean (3 samples from each sample system) vapor concentrations at
            MW302SGM at a depth of 2.3 m	27

Figure 36    Schematic illustrating the location of sampling systems at MW514SG in plan view	28

Figure 37    Comparison of mean (3 samples from each sample system) vapor concentrations at
            MW514SG at a depth of 2.3 m	28

Figure 38    Schematic illustrating the location of sampling systems at MW523SGS, MW523SGM,
            and MW523SGD in plan view	29

Figure 39    Comparison of vapor concentrations (1 sample from each sample system) at
            MW523SGM at a depth of 2.3 m	30

Figure 40    Comparison of vapor concentrations (1 sample from each sample system) at
            MW523SG Data depth of 3.4m	31

Figure 41    Schematic illustrating the location of sampling systems at MW525SG in plan view	32

Figure 42    Comparison of mean (3 samples from each sample system) vapor concentrations at
            MW525SG at a depth of 0.91 m	32

Figure 43    Comparison of mean (3 samples from each sample system) vapor concentrations at
            MW525SG at a depth of 2.3 m	33

Figure 44    Schematic illustrating the location of sampling systems at MW526SGS, MW526SGM,
            and MW526SGD in plan view	34

Figure 45    Comparison of mean (3 samples from each sample system) vapor concentrations at
            MW526SGS at a depth of 0.76 m	35

Figure 46    Comparison of mean (3 samples from each sample system) vapor concentrations at
            MW526SGM at a depth of 0.76  m	35

Figure 47    Comparison of mean (3 samples from each sample system) vapor concentrations at
            MW526SGM at a depth of 2.3 m	36

Figure 48    Comparison of mean (3 samples from each sample system) vapor concentrations at
            MW526SG Data depth of 3.2m	37

Figure 49    Comparison of probe and GVP VOC concentrations - error bars represent one
            standard deviation from three samples	38
                                            IX

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                             List of Figures - continued
Figure 50    Comparison of dedicated vapor probe and GVP VOC concentrations - error bars represent
            one standard deviation from three samples	39

Figure 51    Comparison of PRT and GVP VOC concentrations - error bars represent one
            standard deviation from three samples	40

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                                     List of Tables


Table 1      Depth of Fill Materials and Screened Intervals in Boreholes Containing Dedicated
            Vapor Probe	45

Table 2      Results of Container Blanks	45

Table 3      Results of Field Blanks	45

Table 4      Results of Probe Blanks	45

Table 5      Results of Travel Blanks	45

Table 6      Results of Replicate Samples	46

Table 7a     Computation of Internal  Volume of PRT Sampling System When Sampling
            at 0.76m Near MW525SG	46

Table 7b     Computation of Pre-Sample Extraction and Internal Exchange Volumes of PRT
            Sample System When Sampling at 0.76 m Near MW525SG	46

Table 8a     Computation of Internal  Volume Dedicated Vapor Probe MW513SG When Sampling
            at a Depth Interval of 2.1 to 2.4 m	46

Table 8b     Computation of Pre-Sample Extraction and Internal Exchange Volumes of Dedicated Vapor
            Probe MW513SG When Sampling at a Depth Interval of 2.1 to 2.4m	47

Table 9a     Computation of Internal  Volumes  Using the PRT Sampling System at Five Sample
            Locations at a Depth of 0.76 m Near MW213	47

Table 9b     Computation of Internal  Volumes  Using the PRT Sampling System at Five Sample
            Locations at a Depth of 2.3 m Near MW213	47

Table 9c     Computation of Internal  Volumes  Using the PRT Sampling System at Five Sample
            Locations at a Depth of 3.2 m Near MW213	47

Table 9d     Computation of Pre-Sample Extraction and Internal Exchange Volumes and Sample
            Results Using the PRT Sampling  System at  a Depth of 0.76 m Near MW213	48

Table 9e     Computation of Pre-Sample Extraction and Internal Exchange Volumes and Sample
            Results Using the PRT Sampling  System at  a Depth of 2.3 m Near MW213	48

Table 9f     Computation of Pre-Sample Extraction and Internal Exchange Volumes and Sample
            Results Using the PRT Sampling  System at  a Depth of 3.2 m Near MW213	48

Table 10a    Internal Volumes of Probe, PRT, and GVP Systems at 2.3 m Near MW302SGM	48
                                            XI

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                             List of Tables - continued
Table 10b    Cumulative Pre-Sample Internal Exchanges of Probe, PRT, and GVP Systems at
            2.3m Near MW302SGM	49

Table 10c    VOC and Gas Concentrations of Probe, PRT, and GVP Systems at 2.3 m Near
            MW302SGM	49

Table 11a    Internal Volumes of Probe, PRT, and GVP Systems at 2.3 m Near MW514SG	49

Table 11 b    Cumulative Pre-Sample Internal Exchanges of Probe, PRT, and GVP Systems at 2.3 m
            NearMW514SG	50

Table 11c    VOC and Gas Concentrations of Probe, PRT, and GVP Systems at 2.3 m Near
            MW514SG	50

Table 12a    Computation of Internal Volumes of Sample Systems at 0.8 m Near MW523SGS	50

Table 12b    Computation of Pre-Sample Internal Exchanges and VOC Concentrations of Sample
            Systems at 0.8 m Near MW523SGS	51

Table 13a    Computation of Internal Volumes of Sample Systems at 2.3 m Near MW523SGM	51

Table 13b    Computation of Pre-Sample Internal Exchanges and VOC Concentrations of Sample
            Systems at 2.3 m Near MW523SGM	51

Table 14a    Computation of Internal Volumes of Sample Systems at 3.4 m Near MW523SGD	51

Table 14b    Computation of Pre-Sample Internal Exchanges and VOC Concentrations of Sample
            Systems at 3.4 m Near MW523SGD	51

Table 15a    Computation of Internal Volumes of Sample Systems at 0.91 m Near MW525SG	51

Table 15b    Computation of Pre-Sample Internal Exchanges of Sample Systems at 0.91 m Near
            MW525SG	52

Table 15c    Summary of VOC Concentrations in PRT and GVP Systems at 0.91 m Near
            MW525SG	52

Table 16a    Computation of Internal Volumes of Sample Systems at 2.3 m Near MW525SG	52

Table 16b    Computation of Pre-Sample Internal Exchanges of Sample Systems at 2.3 m Near
            MW525SG	52

Table 16c    Summary of VOC and Gas Concentrations in PRT and GVP Systems at 2.3 m Near
            MW525SG	53

Table 17a    Computation of Internal Volumes of Sample Systems at 0.91 m Near MW526SGS	53
                                          XII

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                             List of Tables - continued


Table 17b    Computation of Pre-Sample Internal Exchanges of Sample Systems at 0.91 m Near
            MW526SGS	53

Table 17c    Summary of VOC and Gas Concentrations in PRT and GVP Systems at 0.91  m Near
            MW525SG	54

Table 18a    Computation of Internal Volumes of Sample Systems at 0.91 m Near MW526SGM	54

Table 18b    Computation of Pre-Sample Internal Exchanges of Sample Systems at 0.91 m Near
            MW526SGM	54

Table 18c    Summary of VOC and Gas Concentrations in PRT and GVP Systems at 0.91  m Near
            MW526SGM	55

Table 19a    Computation of Internal Volumes of Sample Systems at 2.3 m Near MW526SGM	55

Table 19b    Computation of Pre-Sample Internal Exchanges of Sample Systems at 2.3 m  Near
            MW526SGM	55

Table 19c    Summary of VOC and Gas Concentrations in Sample Systems at 2.3 m Near
            MW526SGM	56


Table 20a    Computation of Internal Volumes of Sample Systems at 3.2 m Near MW526SGD	56

Table 20b    Computation of Pre-Sample Internal Exchanges of Sample Systems at 3.2 m  Near
            MW526SGD	56

Table 20c    Summary of VOC and Gas Concentrations in Sample Systems at 3.2 m Near
            MW526SGD	57
                                          XIII

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                                  Acknowledgements


The authors would like to thank the following for their help and support in this project:  Mike Jasinski,
Ron Jennings, Matt Hoagland, Mary Sanderson,  and Don Berger of EPA Region I, and David Burden of

NRMRL, Ada, OK.


The authors would like to acknowledge the following for their formal review of this manuscript:


Dr. John E. McCray
Colorado School of Mines
Environmental Science and Engineering Division
1500 Illinois Street
Golden, CO 80401

Dr. Blayne Hartman
HP Labs
432 N. Cedros Avenue
Solano Beach, CA 92075

Dr. Jim Weaver
U.S. Environmental Protection Agency
Office of Research and Development
National Exposure Research Laboratory
Ecosystems Research Division
Athens, GA 30605-2700
                                            XIV

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                                   Executive Summary

Soil-gas sampling is widely used as a reconnaissance tool to help delineate the areal extent of ground-
water contamination and both  the  areal and vertical  extent of vadose zone contamination by volatile
organic compounds (VOCs).  Soil-gas sampling  is often followed by ground-water and/or soil sampling to
quantify contamination in these media.  Since soil-gas data is generally not used to evaluate the need for
corrective action or attainment  of remedial goals,  quality assurance and control (QA/QC)  considerations
associated with soil-gas sampling are often less  stringent compared to ground-water or soil sampling.
However,  EPA's recent draft guidance on vapor intrusion (EPA, 2002) allows the quantitative use of soil-
gas data along with empirical attenuation factors or the Johnson-Ettinger Model (1991) to directly assess
potential  exposure from vapor intrusion.  Thus, collection of representative soil-gas samples  could be
critical to this endeavor.  Representative  soil-gas data refers to collection of a sufficient number of properly
located  samples within  an area  and  depth  of  concern  subject to  adequate  QA/QC measures.
Implementation   of QA/QC  measures  ensures  that  observed  concentrations reflect   true  soil-gas
concentrations in the vicinity of a probe during sampling.

There are a number of important QA/QC issues  relevant to  soil-gas sample collection.   One issue not
addressed in the literature is the equivalence of direct-push/hammer soil-gas sampling techniques with
dedicated vapor probes.  Dedicated  probes are generally  considered a  reliable method for  soil-gas
sampling because of the use of a layer of bentonite to isolate a sand-packed screened interval. However,
direct-push/hammer  soil-gas sampling  techniques have  become common  to support vapor intrusion
investigations because  they are more convenient (ability to sample the same day as probing) and less
expensive compared  to installation of  dedicated probes.  Also, direct-push/hammer techniques  allow
collection  of soil-gas  samples close  to a building  minimizing concern  regarding  interpolation and
extrapolation of soil-gas concentrations beneath a building.

In  this investigation,  concentrations from soil-gas  samples collected  using dedicated vapor probes were
compared with samples using the Geoprobe Post-Run Tubing (PRT) system  and AMS Gas Vapor Probe
(GVP) kit.   The PRT system  is one of the most commonly  used truck-mounted  direct-push  soil-gas
sampling systems in the United  States. The PRT system can be used to collect soil-gas samples to depths
up to 20 m.  The hand-held rotary hammer GVP kit is suitable for shallow soil-gas sampling  (up to 4 m) but
allows access within 1  m of a building.  These two methods were selected for evaluation because of their
common use.
                                              E1

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Soil-gas sampling was conducted at one to three depths at several locations near the Raymark Superfund
site in Stratford, Connecticut. Surficial soils in the soil-gas sampling areas are very permeable consisting
of sand or a mixture of sand and gravel.  A peristaltic pump with Masterflex® tubing, variable-area PVC
flowmeter, and landfill gas meter were used in line to extract air, measure flow rates, and measure gas (O2,
CO2, and CH4) concentrations during purging. A peristaltic  pump and one-liter Tedlar bags were used for
sampling.  Purging and sampling occurred at a flowrate of 0.5 standard liters per minute (SLPM). On-site
gas chromatography (GC) analysis was conducted by EPA's New England Regional Laboratory using their
standard operating procedure. Air samples from each Tedlar bag were injected into two portable  GCs with
results compared to ensure consistency. Tedlar bag sampling and on-site analysis provided near real-time
data.  Detection limits for on-site analysis were 2-5 ppbv  for VOCs of concern.  Container, field, probe,
and travel blanks demonstrated that Tedlar  bags used to collect samples, coolers  used to  transport
samples, PRT and GVP sample systems used to  extract samples, and atmospheric air were not a source
of VOCs at detection limits of concern. Replicate samples indicated excellent sample precision.

A mass-balance equation was used to estimate internal volume exchanges necessary to purge dedicated
probe,  PRT, and GVP systems  prior to sample collection. Simulations indicated that if air within  a sample
system  had initially been reduced to zero concentration  because of direct exposure to atmospheric air,
extraction  of 2.2 to 3.0 internal  volumes prior to  sampling  would ensure that VOC concentrations of air
entering a sample vessel would be  90 to 95% of VOC concentrations of soil-gas  entering  a  sampling
system.  This would be the most conservative condition and  representative of PRT  and GVP sample
systems. A zero concentration would not be expected for a  dedicated vapor probe which had been sealed
for months prior to sampling.  Purge testing at a dedicated vapor probe indicated concentration stabilization
after only  one internal volume  exchange.  In this  investigation, at  least 2 internal volumes  of air  were
removed from dedicated vapor  probes prior to sample collection.  At least 3 internal volumes of air  were
removed from PRT and GVP sample systems prior to sample collection.

To allow a comparison of dedicated probe, PRT,  and GVP sampling systems, it had to be demonstrated
that the act of sample collection did not affect sample results  at the system being  sampled or at other
nearby sample locations. Increasing internal volume exchanges or pre-sample air extraction volume in
excess  of a  purging  requirement could increase the possibility   of collecting  a soil-gas sample not
representative of some integrated volume of soil  around a screened interval. If properly sampled,  VOC
concentrations should remain relatively constant unless air is drawn in from a nearby  region of lower or
higher vapor concentration.  To evaluate the impact of pre-sample internal volume exchanges on sample
results, ten soil-gas samples were collected after various (starting with zero) internal volume exchanges at
                                              E2

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one PRT and one dedicated vapor location sampling location. In the test using the PRT system, up to 9
liters of air and 74 internal volume exchanges were extracted with little impact on vapor concentration.  In
the test using the dedicated vapor probe, up to 103 liters or internal volume exchanges were extracted with
little impact on vapor concentration (1 internal exchange equaled 1 liter).  Thus, it is unlikely that pre-
sample air extraction impacted sample results at the systems being sampled.

To evaluate the potential impact of air extraction at one location on sample results at a nearby location and
depth,  three samples were taken non-sequentially from each  sampling system.  For example,  at one
location, the PRT system was sampled first,  followed by the GVP  system, followed by  sampling  at the
dedicated probe.  The sequence was then changed to sampling at the GVP system, followed by sampling
at the dedicated vapor probe, followed by sampling at the PRT system and so on until three samples had
been obtained from each system at each depth.  A comparison  of first and third VOC concentrations for
locations and depths where three samples were collected indicated that sample collection at a one location
did not impact sample results at another location.  Also, coefficients of variation for the three samples were
generally below 10% again indicating little impact.

Another potentially complicating factor in comparing vapor concentrations from dedicated probe,  PRT, and
GVP sampling systems is spatial variability.  PRT and GVP sampling locations were positioned relatively
close (usually within 1 m) to dedicated vapor probes to minimize  the effect of spatial variability on soil-gas
concentration. To assess the presence and magnitude of spatial  variability at this scale, soil-gas sampling
was conducted at three  depths at five locations separated by 0.46 m (1.5') in a cross-like pattern using the
PRT sampling system.  In general, variation in VOC concentration with location at each depth was present
but relatively minor.

Sampling systems  were compared using data from  all locations and depths.  A comparison of VOC
concentrations using dedicated vapor probes and the GVP sampling kit indicated that the two methods
provided similar results (p = 0.31  for two-tailed paired t-Test, p > 0.2 for two-tailed non-parametric Wilcoxon
Signed Rank Test).  However, at one location, O2, CO2, and VOC concentrations were noticeably different
for sampling systems indicating potential leakage with the GVP system.

VOC concentrations using the PRT system were not statistically equivalent to VOC concentrations  using
dedicated vapor  probes (p =  0.009 for two-tailed paired t-Test, p  < 0.01 for two-tailed  non-parametric
Wilcoxon Signed  Rank Test).   VOC concentrations using the PRT system were  higher than  VOC
concentrations detected using dedicated vapor probes by an average factor of 1.2.  This is the same
                                              E3

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magnitude observed for spatial variability on a scale of 1 m  (median  of 1.2 and average of 1.3 for 90
sample pairs).  However, this effect did not appear to be due to spatial variability which would result in
random scatter not a consistent bias as observed.  It is also unlikely that extraction volume or sampling
sequence caused the observed bias given results from extraction volume and sample sequence testing.

VOC concentrations using the PRT system  were  also not statistically  equivalent to VOC concentrations
using the GVP  kit (p  = 0.03 for two-tailed paired t-Test, p < 0.01 for two-tailed non-parametric Wilcoxon
Signed Rank Test).  VOC concentrations using the PRT system were higher than VOC concentrations
detected using the GVP kit by an average factor of 2.4.  Similar to the comparison between probe and PRT
sampling systems, the effect does  not  appear to be due to spatial  variability, extraction volume, or
sequence of sampling.

Thus, utilization of the PRT system resulted in observation of higher concentrations of VOCs compared to
the GVP sampling system and dedicated vapor probes. However, the magnitude of variation was relatively
minor especially when to compared  to variation on a scale of 1 m due to  spatial variability.  Hence for
practical purposes, all three sample systems can be considered approximately equivalent.

This  testing was conducted  in highly  permeable  soils where the potential  for leakage from direct-
push/hammer soil-gas sampling systems would be expected to be low  compared to less permeable soils
such as silt and clay.  Thus, the results of this investigation should not be extrapolated to other soil textures
where additional investigation  is needed.  Also, only one direct-push and one rotary hammer method  was
evaluated for comparison with  dedicated vapor probes.  Thus, the results of this  investigation should not be
extrapolated to other direct-push/hammer soil-gas sampling techniques.
                                              E4

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                                     1.0   Introduction

Soil-gas sampling is widely used as a reconnaissance tool to help delineate the areal extent of ground-
water contamination and both the  areal and vertical extent of vadose  zone contamination  by  volatile
organic compounds (VOCs). Soil-gas sampling is often followed by ground-water and/or soil sampling to
quantify contamination in these media. Since soil-gas data is generally not used to evaluate the need for
corrective action or attainment of remedial goals, quality assurance considerations associated with soil-gas
sampling are often less stringent compared to ground-water or soil sampling. However, EPA's recent draft
guidance on vapor intrusion (EPA, 2002) allows the quantitative use of soil-gas data along with empirical
attenuation factors or the Johnson-Ettinger Model (1991) to directly assess potential exposure from vapor
intrusion.   Thus, collection of representative soil-gas  samples could be  critical to  this  endeavor.
Representative soil-gas data refers to collection of a sufficient number of  properly located samples within
an area and depth of concern subject to adequate  quality assurance and control (QA/QC)  measures.
Implementation  of  QA/QC  measures ensures  that  observed  concentrations  reflect  true  soil-gas
concentrations in the vicinity of a probe during sampling.

There are a number  of important QA/QC  issues relevant to soil-gas sample collection.  One issue not
addressed  in the literature  is the equivalence of direct-push/hammer soil-gas sampling techniques with
dedicated vapor probes.   Dedicated probes are  generally  considered  a  reliable  method  for soil-gas
sampling because of the use of a layer of bentonite to isolate a sand-packed screened interval.  However,
direct-push/hammer soil-gas sampling  techniques have become common  to support vapor intrusion
investigations because they are more convenient (ability to sample the same day as probing) and less
expensive compared to installation  of  dedicated probes.  Also,  direct-push/hammer  techniques allow
collection  of  soil-gas  samples close to  a  building  minimizing  concern  regarding interpolation  and
extrapolation of soil-gas concentrations beneath a building.

In this investigation, concentrations from soil-gas samples collected  using dedicated vapor probes were
compared with samples using the Geoprobe Post-Run Tubing (PRT) system and AMS Gas Vapor Probe
(GVP) kit.  The PRT system  is one  of the most commonly  used truck-mounted direct-push soil-gas
sampling systems in the United States. The PRT system can be used to collect soil-gas samples to depths
up to 20 m. The hand-held rotary hammer GVP kit is suitable for shallow soil-gas sampling (up to 4 m) but
allows access within 1  m of a building. These two methods were selected for evaluation because of their
common use.

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                                   2.0   Site Description

The  Raymark Superfund Site consists  of 33.4  acres  of  land  previously occupied by the Raybestos-
Manhattan Company in Stratford,  Connecticut, where the company disposed of solid-waste from settling
lagoons during its  operation.  Between 1919 and 1989, the company produced asbestos and asbestos
compounds,  metals, phenol-formaldehyde  resins,  adhesives,  gasket  material,  sheet packing, clutch
facings, transmission plates, and  brake  linings.  Between 1993 and  1996,  EPA  removed fill containing
asbestos, lead, and PCBs from a number of residential properties and a middle school.  EPA placed the fill
back on the facility  property and isolated the waste beneath a cap. In 1996 and 1997, EPA demolished the
facility buildings and placed a cap  over the area previously occupied by the buildings. The property is now
occupied by commercial buildings (e.g., Wal-Mart, Home Depot).
As illustrated in Figure 1, ground water beneath the residential area of this investigation generally flows
southeast from the former facility, underneath  a large residential  community, and  discharges into the
former facility is  contaminated  with  a number of VOCs including  1,1,1-trichloroethane (1,1,1-TCA),
                                         trichloroethene (TCE),  cis-1,2-dichloroethene (c-1,2-DCE),
                                         1,1-dichloroethene (1,1-DCE), and  1,1-dichloroethane  (1,1-
                                         DCA).

                                         Figure 1. Direction of ground-water flow (large arrows)
                                         and location of the residential area of  investigation near
                                         the Raymark Superfund Site  (modified from Tetra Tech 2000).
                                         As illustrated  in Figures 2, 3,  and 4,  glaciofluvial deposits
                                         and fractured granite  bedrock  valleys  lie  beneath  the
                                         residential area of investigation. The remedial investigation
                                         (TetraTech NUS,  2000)  and subsequent studies financed by
                                         EPA indicate that ground-water flow is  heavily influenced by
                                         the location and orientation of bedrock valleys.  This results
                                         in a fairly complex contaminant distribution  profile making
                                         interpolation and  extrapolation of ground-water and soil-gas
                                         contaminant profiles difficult.

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                                              Figure 2.  Location of geologic cross-sections and the
                                              residential area of investigation near the Raymark Superfund Site
                                              (modified from Tetra Tech NUS, Inc., 2000).
                                              Surficial soils in areas of soil-gas sampling consist of sand
                                              or a mixture of  sand and gravel. The results of ten shallow
                                              single-well ground-water hydraulic conductivity tests taken
                                              from  TetraTech NUS (2000)  are illustrated  in Figure 5.
                                              Bounds for  sand  and gravel  are taken  from  Freeze and
                                              Cherry (1979).  Values for hydraulic conductivity are typical
                                              of sand and vary  from 1.0 x10"03 to  2.0 x 10"02 cm/s.  The
                                              results of a sub-slab air permeability test taken from a home
                                              (EPA, 2006) are illustrated  in  Figure 6.  Air permeability
                                              values of sub-slab materials  are  representative of native
                                              soils  since concrete was simply poured  on sandy soils in
                                              basements.  The range of radial permeability of soils tested,
                                              7.0 x 10"07 - 8.0 x 10"07 cm2 is typical of sandy soils.
               WEST
                                                                                       EAST
           100

           80

           60

           40

         8f 20-

         §  0
         r
         W -40
           -60
           -80
          -100
          -120
            I FORMER TILO IND / STRATFORD i
                                        BOB AT
                                        - 73.47'
    Sand
I	1 Bedrock
    Gravel
    BOB AT
    - 88.74'
            0_20'  0'   200'
GRAPHIC SCALE VERTICAL  HORIZONTAL
Well Screen and corresponding
groundwater elevation

End of boring with corresponding
elevation
                                                                           100
                                                                           80
                                                                           60
                                                                           40
                                                                           20
                                                                                           •0
                                                                          L on
                                                                          [-20 H
                                                                                            -40
                                                                                            -60
                                                                                            -80
                                                                                            -100
                                                                                            -120
Figure 3. Geologic cross-section G - G' (modified from Tetra Tech NUS, Inc., 2000).

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               100

                80

                60-

             _  40-
             Q  20
             5
             Z   0
             O

             I'20
             id
               -40-
                -60-

                -80-

               -100

               -120

               -140
                    WEST
                                                                                                  EAST
 FORMER TILO
IND / STRATFORD
 SQ. SHOPPING
   CENTER
                                CT. DOT   MORGAN
                               PROPERTY  FRANCIS
      RESIDENTIAL
      PROPERTIES
   (NO TOPO COVERAGE)
                                                                               to
r?JLl1 Fill
I    I Peat
I    I Till
I    I Organic silt
I    I Clay
LZZI Silt
^3 Sand
L-—I Bedrock
     Gravel
       EOBAT
       -1244.9'
                                                       EOBAT
                                                       - 69.7'
                                                Well Screen and corresponding
                                                groundwater elevation
EOB AT   End of boring with correspondin
 -100'    elevation
                                           GRAPHIC SCALE
                                     ff	20'     o;	200'
                                     •-"-•      ^3^9
                                     VERTICAL    HORIZONTAL
  100

  80

  60

  40

  20  S
      Q

  •   I
      Z

      rl
  -40 QJ

  -60

  -80

  -100

  -120

  -140
Figure 4.  Geologic cross-section H - H' (modified from Tetra Tech NUS, Inc., 2000).

          1 .OOE+02
          1 .OOE+01
          1 .OOE+00
     •o   1 .OOE-01
      o
     O
      o
     ^   1 .OOE-02
      co
          1.00E-03
                    0
                                                                                       gravel
      1
                                   6
            8
                                                                        sand
10
Figure 5.  Results of ten shallow single-well hydraulic conductivity tests at the Raymark site (boundary values for
sand and gravel taken from Freeze and Cherry, 1979).

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    50



    45-




    40-








|  30-




i  25-
Q


§  2(
(0
CO

s>  1(
Q.  •'



    10-




     5-




     0
                  0
                                      	k, = 6.69E-07 cm2, k/k, = 1.39, leakance = 3.30E-09 cm


                                      	k, = 7.12E-07 cm2, K/K = 1-22, leakance = 3.13E-09 cm


                                       •   observed pressure differential (Pa)
                                            k, = 7.90E-07 cm2, k/k, = 1.65, leakance = 3.21 E-09 cm


                                            k, = 7.20E-07 cm2, k/k, = 1.42, leakance = 3.27E-09 cm


                                            k, = 8.16E-07 cm2, k/k, = 1.65, leakance = 3.25E-09 cm
                                                                   =-==--*=-=:,
                    200
 400           600


Radial Distance (cm)
800
1000
Figure 6.  Results of a sub-slab air permeability test taken from EPA (2006).

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                                3.0    Methods and Materials
3.1     Soil-Gas Sampling from Dedicated Vapor Probes
Dedicated vapor probes used in the study were installed by Tetra-Tech for U.S. EPA, Region I.  A typical
construction log for a dedicated probe is illustrated in  Figure 7.
               RUSH MOUNT MONITORING WELL CONSTRUCTION LOC
TETRA TECH NUS INC.
PROJECT HUME: jE^y'tfevic. 64T. PROJECT NO: tl?6 -Q3Z 0
PROJECT LOCATION SfaM&eA {"•f *Ql NO: /VH.)*TZ.t SfaflA
i-IIFNT. BOBNCND: £K5"Z4.S£Aj
CONTWCTOR' A TJ'f
LOCCEQaif: D! {j\*xlifr4'
CHECKED Br-

GROUND
SAND DRAIN LAYER 	
C E N E S » I NOTE
1 Edify ol 0 CO ior (Vard Dtrttion Indicolet tlwl StfxBved C
W tajlaUt

fe
=
i Y///////Mim 1
IIRII i fp' /*.< p4 rmJ BOR)NG LOCATION:
I1AT£-
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	 1 fftSlir 	





E
—
=


s
a
=
»-
•-
*-
!
^ —
•4 —
-4 —
•*•
•*—
•4-

- 1 FNCIh RISfR PIPF BFI nw BRO qifiF (Fl | O •*?
	 1YP£ CF SURFACE SEAL ^'Aw'^S't til.
+ 	 I1U ««FAff VII UK fin ) H "
^^ n fl(1I70M T ^JJf^ SESI ,CI , f] ^ '
/1 1*
i 	 i n nf remrnwr CAM (u ) 'j
	 TYPF (IF pflmFcriuF r««: (.«« af£>oX
	 OEPTH aonou of PROTECTIVE CASING (n.) "2- 0
^ 	 pfpmflOnnunF^K.iAvrR'n) 2-<5'
. 	 USER PIPF (In.) 10.: ^ " O.D.:
	 TYPF OF BKfR PIPF f \f£.
. 	 TYPF OF (umr^i jcniiNp RKFH nvf /^ ^
	 	 0£P?H TOP OF SEAL fFI.1 3 . ^
WFnF^u t-frtfa:!* flttf
-. 	 DEPTH 80TIOM OF SEAL (Fl ) ^ft
	 nfPTH I«> OF PFBMtKK Wr.IKK (Fl ) *^-/ £>
< LHAllET?! Of BOSfHIKf (In ) H "
. 	 . IYPF nr PTIMOI is VCTIO*) jP V £•
WE OF OPENINGS ^), ; 6
3^*^ y ^~* y "^i^
	 m>E OF FILIER PACK AROUND MjtA •rtu.Jt
?EW10US SECTION •' ' ^"^ S""1"
	 Ofr.it MTTOU OF POOTUS Sf CI«« (Fl I ^' O
-• 	 DEPTH SOnCM Cf FILTER PACK fFI ) "&.0'
	 TYPE y ascKFiiL (CROUD Al IA
3EIO* Eli TO PACK
•* 	 END Of 80R1NC, tftf)'
fOufiid Qrvation J
                                                                          TINUS Form OOSa
Figure 7. Typical construction log for dedicated vapor probes installed at the Raymark Site.

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Boreholes for dedicated vapor probes were installed using a drill rig equipped with a hollow-stem auger.
The  diameter  of boreholes varied  from 8 to  13 cm  (3 to  5").  A 1.9 cm  (%") inner  diameter  (ID)
polyvinylchloride (PVC) riser pipe containing a metal valve at the  upper end and a 30 cm (1') long 3.8 cm
(1.5") ID PVC factory-slotted screen interval at the lower  end  was lowered into each borehole and set in
place with a filter pack consisting of medium-grained sand.  Dry bentonite chips were placed above each
filter pack in small  increments (e.g., 15 cm)  and hydrated to create a seal above the  sample interval.
Medium-grained sand was placed above  each bentonite seal to serve as  a drainage  layer.   A flush-
mounted iron casing was then set in place at each borehole and sealed in concrete.

Depths of fill materials and screened intervals in each borehole are summarized in Table 1 in Appendix A.
Concrete extending from the surface to sand drain  layers varied in thickness from 0.2 to 0.3 m (0.5 to 0.8').
Bentonite layers extending from the  base sand drain layers to the top of the sand filter packs were 0.2  m
thick (0.5') for probes screened 0.61 - 0.91  m  (2 to 3') below grade, 0.9 to 1.1 m thick (3.0 to 3.5') for
probes screened 2.1 to 2.4 m (7 to 8') below grade, and  2.0 to 2.1  m thick (6.5 to 7.0') for probes screened
3.0 - 3.3 m (10  to 11') below grade.
Figures 8, 9, and 10 illustrate purge and sample collection in dedicated vapor probes.  Tetra Tech (2000)
attached a valve with a metal barbed fitting to a riser pipe to seal  all  dedicated probes.  A PVC barbed
union and 0.95 cm (3/8") ID Teflon® tubing was attached to the barbed fitting during purging and sample
collection.


                                                 Figure 8.  Photograph of valve  used to seal dedicated
                                                 probes, PVC barbed fitting, and  Teflon8 tubing used for
                                                 sampling.
                                                 During purging,  a peristaltic pump with Masterflex®
                                                 tubing, variable-area PVC flowmeter, and landfill gas
                                                 meter were used in line to extract air, measure flow
                                                 rate,  and measure oxygen  (O2),  carbon  dioxide
                                                 (CO2),  and  methane  (CH4)  gas  concentrations.
                                                 Purge and sample collection occurred at a flow rate
                                                 of  0.5  standard liters per minute  (SLPM).   To
                                                 eliminate  the   potential  of  cross-contamination,
                                                 flowrate was  not measured during sampling but set
                                                 during  purging.    Teflon® and  Masterflex®  were
                                                 replaced after sampling at each depth and location.

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                                                 Figure 9. Photograph of peristaltic pump, flowmeter, and
                                                 landfill gas meter used during purging dedicated vapor
                                                 probes.
                                                 Figure 10. Photograph of peristaltic pump and one-liter
                                                 Tedlar bags (replicate sample) used for sampling
                                                 dedicated vapor probes.
3.2    Soil-Gas Sampling with the GeoProbe PRT System

A photograph of a Geoprobe PRT system mounted on a flat-bed truck is illustrated in Figure 11.  Each

sample location  was surveyed  for the presence of underground utilities prior to probing.   Figures 12

through 16 illustrate components of the PRT system.  Probe  rods were pushed vertically into the ground
until the desired depth was reached.  The probe rods were then retracted approximately 5 cm for sampling.
A metal rod was used to push out the expendable  point.  The Teflon® tubing containing the PRT and an
adapter with an O-ring was then inserted into the probe rods and turned counterclockwise to
engage the adapter threads with the expendable point holder.

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                                       Figure 11.  Photograph of truck-mounted PRT
                                       system.

                                       The  tubing  was  pulled  up  lightly  to  test
                                       engagement of the threads.   After sampling
                                       was completed, the tubing was pulled up firmly
                                       until it  released from the adapter.  The probe
                                       rods were then retracted to recover the point
                                       holder  and PRT adapter.  Teflon® tubing was
                                       replaced  at  each  sample depth  to avoid
                                       potential cross-contamination.
Probe Rod
 PRT Expendable
 Point Holder
 Expendable
 Drive Point
Figure 12. Components of PRT sampling system.

Similar to sampling at dedicated vapor probes, a peristaltic pump, flowmeter,
and landfill gas meter were used in line to extract air and measure flow rate
and O2, CO2, and CH4 concentrations  during purging. A peristaltic pump and
one-liter Tedlar bags were used for sampling.  Flowrate during purging and
sampling was 0.5 SLPM.
                         Figure 13. Photograph of an expendable point and expendable
                         point holder.

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Figure 14.  Photograph of a PRT adapter with an O-ring
and associated Teflon8 tubing.
Figure 15.  Photograph of metal rod used to push out the
expendable point.
Figure 16.  Photograph of connection of PRT adapter to
expendable point holder.
10

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3.3    Soil-Gas Sampling with the AMS GVP System
As  illustrated in Figure 17, if asphalt was  present at the probing location,  a rotary hammer drill and
concrete bit were used to cut a 3.8 cm (11/211) hole prior to sampling.
                                       Figure 17. Creation of hole in asphalt prior sampling with GVP kit.

                                       A section (30 cm longer than target depth) of 0.48 cm (3/16") ID
                                       x 0.64 cm (1/4") OD Teflon® tubing was attached to the barbed
                                       end  of an AMS Retract-A-Tip as illustrated in Figure 18.   A
                                       disassembled view of the Retract-A-Tip  is  provided  in Figure
                                       19.  The Retract-A-Tip consists of a stainless-steel tip, screen,
                                       and  housing  having  a 1.6 cm (5/8") outside diameter. The tip
                                       was  then connected to 0.91  meter (3') sections of threaded 1.6
                                       cm OD stainless-steel pipe.   The pipe was connected to an
                                       AMS extension drive adapter and hammered to a desired depth
                                       with  a rotary hammer drill as illustrated in Figure 20.
                     Figure 18. Photograph of Retract-A-Tip and Teflon® tubing.
                                   Figure 19.  Disassembled view of Retract-A-Tip.
                                                11

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Figure 20. Photograph of hammering Retract-A-Tip and support
pipe using a rotary hammer drill and the GVP extension drive
adapter.
As illustrated in Figure 21, prior to sampling, the Retract-A-
Tip and associated pipe was retracted 5 cm using a jack
provided with the GVP  kit.  After sampling, the rods were
removed from the ground using the AMS retrieval jack.  The
Retract-A-Tip was then cleaned prior to sampling at the next
depth.

Again,  similar to sampling  at  dedicated vapor probes, a
peristaltic pump, flowmeter, and landfill gas meter were used
in line to extract air and  measure flow rate and O2, CO2, and
CH4 concentrations  during purging.   A  peristaltic pump and
one-liter Tedlar bags were used for sampling.  Purging and
sampling occurred at a flowrate of 0.5 SLPM.

Figure 21. Retraction of Retract-A-Tip prior to sampling.
As illustrated in Figure 22, dedicated vapor probe, PRT, and
GVP sampling systems were generally located within 1 m of
each other to minimize the effect of spatial variability on data
interpretation.
Figure 22. Proximity of dedicated vapor probe (metal cover
surrounded by white concrete at base of Geoprobe unit), PRT, and
GVP sampling systems.
      12

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3.4    On-Site Soil-Gas Analysis and Data Quality

On-site gas chromatography (GC) analysis was conducted by EPA's New England Regional Laboratory
using their standard  operating procedure (USEPA, 2002b).   Air samples  from  each Tedlar bag were
injected into two portable GCs with results compared for consistency. The first GC was a Shimadzu 14A
equipped with a  30 m, 0.53 mm megabore capillary column, a photoionization  detector  (PID), and an
electron capture detector.  The second GC was a Photovac 10A10 equipped with a 1.2 m (4'), 0.32 cm
(1/8") SE-30 column and a PID. A Hamilton 250 ul steel barrel syringe with a 2.5 cm 25-gauge needle was
used to directly inject  200 ul of sample into both GCs.  Single concentration standards were prepared from
readily available commercial methanol stock solutions and diluted in VOC-free water in Class A volumetric
glassware to a concentration of 10 ug/l. After preparation, standards were immediately transferred into 40
ml VOA vials and stored in an ice bath (0 - 1°C).   Prior to air sample analysis,  10 ml of standard was
withdrawn from  a 40 ml VOA vial to create a headspace above the liquid standard.  Field GCs were
calibrated for target compounds using the headspace above the 10 ug/l standard.

On-site GC analysis for 1,1,1-TCA, 1,1-DCE, TCE, and c-1,2-DCE was identical to that used for sub-slab
sampling at the Raymark site (EPA, 2006). Sub-slab air samples collected using EPA Method TO-15
(EPA,  1999) were compared with  sub-slab air samples collected using  a peristaltic pump and one-liter
Tedlar bags.  As  illustrated in Figure 23, there was good agreement between this  sampling and analytical
method and EPA Method TO-15.

Sample container blanks were collected to ensure that VOCs of concern  were not present in Tedlar bags
prior to sample  collection.   Four one-liter Tedlar bags (one  from each  batch  received) were filled with
laboratory-grade nitrogen gas and analyzed.  The results of testing are summarized in Table 2 in Appendix
A. Analysis of container blanks indicated that Tedlar bags used for sampling were not a source of VOCs of
concern above detection limits of 2 to 4 ppbv.

Field blanks were collected to assess potential breakthrough of VOCs of concern from atmospheric air  into
Tedlar bags during sampling.  Outdoor air samples were collected each of the three days of soil-gas
sampling. The  results of testing are summarized  in Table  3 in Appendix A.  Analysis of field blanks
indicated that there was little potential for atmospheric air to impact soil-gas sample results of VOCs of
concern above detection limits of 2 to 4 ppbv.
                                              13

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                                  I  I I  I I
                                  TT7TT
                                  I  I I  I I
                                  FTTTT
                                  I  I I  I I
                                  I  I I  I I
                                  I  I I  I I
                                  ETUI
                                  -JalJ
                                  L1_ML
                                  I  I I  I I
                                            L111L
                                            I  I I  I I
                                                                              I  I I  I I
                                                   n = n = c m 31 n
                                                                              i  i i  i i
                                                                              FTTTF
                                                      I* I
FTTTT
                                                                              I  I I  I I
                                         EPA Method TO-15 (ppbv)

Figure 23.  Comparison of EPA Method TO-15 with sample collection using a peristaltic pump and Tedlar bags with
on-site GC analysis of 1,1,1 -TCA, 1,1 -DCE, TCE, and c-1,2-DCE (n = 91,  r2 = 0.88).
Probe  blanks were collected  to  ensure  that components of the PRT and GVP  sample systems  and
associated tubing were not the source of VOCs of concern. Atmospheric air was passed through the probe
and tubing of GVP and PRT sampling systems several times and collected into one-liter Tedlar bags.  The
results of testing are summarized in Table 4 in Appendix A.  Analysis of probe blanks indicated that neither
GVP nor PRT sample systems and associated tubing were sources of VOCs of concern above detection
limits of 2 to 5 ppbv.  Tubing for both systems was discarded after sampling at each location and depth to
avoid potential cross-contamination.

Travel blanks were collected to ensure that storage of Tedlar bags in a cooler (not chilled) prior to analysis
did not impart an analytical bias (e.g., VOC transport from one Tedlar bag to another or presence of VOCs
in the cooler). A one-liter Tedlar bag was filled with laboratory-grade nitrogen and placed in a cooler used
to  transport (hand carry to mobile  laboratory)  samples  each  day.   The results of travel blanks  are
summarized in Table 5  in Appendix A.  Analysis  of travel  blanks for VOCs  of concern  indicated  that
transport of the Tedlar bags did not impact sample results at detection limits above 2 to 4 ppbv.
                                               14

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Replicate samples, which consisted of two samples from the same air stream, were collected to assess the
precision of the entire sample and analysis procedure. Figure 10 illustrates collection of replicate samples
from a dedicated vapor probe.  The results of replicate sampling are summarized in Table 6 in Appendix A.
The  relative percent difference (RPD) of 15 replicate  analytical pairs (from 5  samples) with detectable
concentrations varied from 0.0 to 9.1% (9 out of 15 sample pairs were 0.0%). By comparison, EPA Method
TO-15 (EPA, 1999) requires replicate precision less than or equal to 25%. RPD is defined as:
                                                   X
where: X= sample mean and X1 and X2 are values for samples 1 and 2, respectively.

3.5    Computation of Pre-Sample Internal Volume Exchange Requirements

The internal volume of dedicated vapor probes consisted of a 3.8 cm (1.5") ID, 30.5 cm (1') long slotted
PVC pipe used as a screened  interval, a 1.9 cm (0.75") ID PVC riser pipe to the surface, and 0.95 cm
(3/8")  ID Teflon® tubing used between valves and one-liter Tedlar sample bags. The internal volume of the
valve  at the top of the riser pipe was insignificant compared to other internal volume components. The
internal volume of the PRT sample  system consisted of an open 2.5 cm (1") diameter by  5 cm (2") long
cylindrical hole created during riser pipe retraction and tubing used for connection to one-liter Tedlar bags.
The internal volume of the retractable point holder and PRT adapter were similar to the Teflon® tubing and
were incorporated into the computation of the internal volume of tubing.  The internal volume of the GVP
sample system consisted of a 0.64 cm (1/4")  ID 5 cm (2") long stainless-steel screen  and 0.48 cm (3/16")
ID Teflon® tubing.

Tubing used to sample dedicated vapor probes and direct-push/hammer soil-gas sampling systems should
be purged prior to sampling.  Air inside tubing will initially have direct contact with and  be representative of
outdoor air. The relatively small screened interval of PRT and GVP sample systems should also be purged
prior to sampling because outside air may be drawn into the screened interval during  riser pipe retraction.
However, the screened interval and riser pipe of a sealed dedicated vapor probe should be more reflective,
although not necessarily the same, as nearby soil-gas concentrations if the probe was installed some time
(e.g., days or weeks) prior to sampling. Thus, less internal volume exchanges or purge volumes may be
necessary prior to sampling dedicated vapor probes compared to PRT and GVP  sample systems. Internal
volumes and pre-sample internal volume exchanges were calculated for each sample system at each
depth  and location and are presented in tables throughout Appendix A.
                                              15

-------
Calculation of a minimum purge volume prior to sampling can be estimated using a mass balance
equation:
                                               Q
where Cout is  a well-mixed  vapor concentration  within and exiting the sample system, Cin  = constant
concentration  entering the system from surrounding soil-gas, Q = flow rate entering and exiting sample
system, t = time, and V = internal volume of sampled system. When subject  to an initial condition, C0
(vapor concentration at time  zero), purge volume (tQ/V) can be expressed as a function of Cin and Cout by:
                                         tQ   ,
                                         — = ln
                                         V
                     cin-c0
                                                  in    out
Purge volumes as a function of C0/Cin and Cout/Cin are illustrated in Figure 24.
            4 -
         cS  3
         CD
         &
         3  o
         0.  *
                                      	  Cout/Cln =0.99
                                      	  Cout/Cin =0.95
                                               Cout/Cin =0.90
                                      	  Cout/Cin =0.85
                                      	Cout/Cin =0.80
              0.0
0.2
0.4             0.6
      C0/Cin
0.8
1.0
Figure 24. Purge volume as a function of C0/Cin and Cout/Cin.
                                                16

-------
The  ideal condition is that Cout/Cin =1.  However, extraction of 2.2 to 3 purge volumes ensures that the
exiting vapor concentration is approximately 90 to  95% of the entering concentration even when vapor
concentration inside the sample system has been reduced to Cout/Cin = 0.  This would be the condition most
representative of  PRT and GVP sample systems.  However,  as previously discussed, it is unlikely that
C0/Cin would equal zero for dedicated vapor probes.  If for instance C0/Cin = 0.4, then extraction of 1.8 to 2.5
purge  volumes results  in the  exiting  concentration being approximately  90 to 95% of the entering
concentration. Figure 25 illustrates vapor concentration  as a function of cumulative post-sample extraction
volume at dedicated vapor probe MW513SG.  Sample volume was 0.5 liters.
IOUU-
id.no-


f 1200-
Q.
c 1 UUU
o
ts

§ °°°
c
o
600-
0
Q.
>Af\f\ -
4UU
200-
n -

~K^ *
•-11-
-^TCF
-^c-1,








DPF
1-TCA
2-DCE



— i


                         0.5    1    1.5    2   2.5    3   3.5    4    4.5    5
                                  Cumulative Post-Sample Extraction Volume (L)
5.5
Figure 25. Vapor concentration as a function of cumulative post-sample extraction volume up to 5.5 liters at
dedicated vapor probe MW513SG.

One internal exchange or purge volume was calculated to be one liter. Cumulative post-sample extraction
volume  represents the  summation  of  air extracted during and  prior to sample  collection.   Thus, air
extraction did not occur prior to the first sample and five liters of air were extracted prior to the fifth sample.
Only the first 5 samples are shown in Figure 25.  To evaluate the effect of extraction volume on sample
concentration, a total of  10 samples were collected at MW513SG up to a cumulative post-sample volume
of 103 liters.  These results will  be discussed in Section  3.6.  There appears to be a slight increase in
concentration for all four VOCs analyzed after the first sample.  Thus, at least in this case,  a purge volume
of one liter or 1 internal  air exchange would  have been sufficient to stabilize concentrations in  dedicated
                                               17

-------
vapor probes.   Stabilization of O2,  CO2,  and CH4 concentrations is sometimes used as an indicator of
sufficient purging.  Sequential sampling indicated stable O2,  CO2, and CH4 concentrations at virtually all
locations as evidenced in Appendix  A.  For example, Figure 26 illustrates a stable gas concentration after
extraction of two liters of air at dedicated vapor probe MW514SG.  Similar to MW513SG, sample volume
was 0.5 liters while one internal exchange volume was calculated to be one liter.
              18
              16--
              14
          —  12
          .g
          |  10
           03
           O
           o
          O
          o
                 01234567
                                 Cumulative Post-Sample Extraction Volume (L)
Figure 26. O2, CO2, and CH4 concentration as a function of cumulative post-sample extraction at dedicated vapor
probe MW514SG.

In this investigation, at least 2 internal volumes were exchanged prior to sampling dedicated vapor probes.
Because of the relatively small internal volumes of PRT and GVP soil-gas systems, at least 3 internal
volumes were exchanged prior to sampling.

3.6    Assessment of  Extraction Volume on Sample Results

To allow a comparison of dedicated probe, PRT, and GVP sampling systems, the act  of sample collection
should neither affect sample results from the system being sampled nor at other sample systems nearby.
The potential for sample collection affecting sampling results from the system being sampled is discussed
in this section.  The  potential for sample collection affecting  sampling  results  at other sample systems
nearby is discussed in  Section 3.7.  Increasing pre-sample air extraction volume in excess of a purging
requirement could  increase the possibility of  collecting a soil-gas sample which is not representative of
                                               18

-------
some integrated volume of soil around a screened interval.  The most direct way to evaluate the impact of
a pre-sample  air extraction  volume  on sample results is  to  collect a  number of  soil-gas  samples
sequentially and observe vapor concentration as a function of extraction volume. During sample collection,
VOC concentrations should remain relatively constant unless air is drawn in from a nearby region of lower
or higher vapor concentration.  Extraction volume testing was performed at one  location using  the PRT
sampling system and at another location using a dedicated vapor probe.

The computation of the internal volume of a PRT sampling system when sampling at a depth of 0.76 m
(2.5')  near MW 525SG is summarized  in Table 7a  in Appendix A. The computation of cumulative post-
sample extraction volumes and pre-sample internal  exchanges is summarized in Table 7b in Appendix A.
Since the internal volume of the  PRT sampling system was only 0.122  liters, pre-sample internal volume
exchanges were relatively high  during testing at this  location (up to 73.6).  Vapor concentration as a
function of cumulative post-sample extraction volume is presented in  Figure 27 which demonstrates little
or no effect of extraction volume on sample concentration of 1,1,1-TCA, 1,1-DCE, TCE, and c-1,2-DCE.
            600
        s
        a.
        g
            500
            400
        |   30°
        o
        O
        o
        I
            200
            100
••-1,1 -DCE
••-1,1,1-TCA
   TCE
-»-c-1,2-DCE
                             2468
                              Cumulative Post-Sample Extraction Volume (L)
             10
Figure 27.  Vapor concentration as a function of cumulative pre-sample extraction volume using the PRT sampling
system at a depth of 0.76 m near MW525SG.
                                              19

-------
Vapor concentration as a function of cumulative post-sample extraction volume at dedicated vapor probe
MW513SG is illustrated in Figure 28.  The internal volume of MW513SG having a screened interval 2.1  m
(6.9') to 2.4 m (7.9') below grade was 1 liter.  The computation is summarized in Table 8a in Appendix A.
The computation  of cumulative post-sample extraction volumes  and pre-sample internal exchanges  is
summarized in Table 8b in Appendix A.  A total of 10 samples and 103 liters of air were extracted during
this test.  Since the internal volume  of MW513SG was one liter, pre-sample internal exchanges  were
equivalent to pre-sample air extraction volumes.  Thus, 102.5 liters of air or 102.5 internal exchanges
occurred prior to collecting the tenth sample. With the  exception of sample results for 1,1,1-TCA which are
somewhat erratic, it is apparent after the first one or two internal volume exchanges, sample concentration
remained relatively constant even after extraction of  over 100 liters air.  With  the exception of explicit
extraction testing, the most air extracted during  any sampling event was 8 liters (for deep dedicated vapor
probes).  This indicates that it is unlikely that the act of sample  collection impacted sample results at any
sample system at any depth in this study.
              1600
              1400
           3
           Q.
              1200
           c  1000
           o
           g   80°
           o
           O   600

               400
               200 -I
                 0
1,1-DCE
1,1 ,1-TCA
                                                                       -*-c-1,2-DCE
                             20         40         60        80        100
                                Cumulative Post-Sample Extraction Volume (L)
         120
Figure 28. Vapor concentration as a function of cumulative post-sample extraction volume at dedicated vapor probe
MW513SG at a depth interval of 2.1 to 2.4 m.
                                               20

-------
3.7     Assessment of Impact of Air Extraction at One Location on Another Location

At least conceivably, excessive air extraction volume at one probe could impact vapor concentration at a
nearby probe.  To evaluate the potential impact of pre-sample extraction volume at one location on sample
results at a nearby location and depth, three samples were taken from each sampling system at most test
locations.  For example,  at MW523SGS, the PRT system  was sampled first followed by the GVP system
followed by sampling at the dedicated probe.  The sequence was then changed to sampling  at the GVP
system followed by sampling at the dedicated vapor probe  followed by sampling at the PRT system and so
on.  A comparison of first and third vapor concentrations for locations and depths where three  samples
were  collected is presented in  Figure 29.  A 1:1  correlation between samples indicates that sample
collection at one location  did not impact sample results at another location.
            1000
         Q.
         Q.
         CD

         §
         §
         CD
         O
         Q.
             100
  GVP (0.8 m)
A GVP (2.3 m)
n PRT (0.8 m)
A PRT (2.3 m)
• PRT (3.2 m)
                                                                   n Probe (0.6 - 0.9 m)
                                                                   A Probe (2.1 -2.4m)
                                                                   • Probe (3.0 - 3.4 m)
                                                             100
                                      Initial Vapor Concentration (ppbv)
                1000
Figure 29.  Comparison of first and third samples at dedicated probe, PRT, and GVP sample locations.

Figure 30 illustrates coefficients of variation (100 x standard deviation/mean) for all locations where three
samples were collected for each sample system at each depth. Coefficients of variation were low except
when approaching detection limits around 5-10 ppbv again indicating  that sample collection at  one
location did not impact sample results at another location.
                                              21

-------
OK .
Z.O
g
c on .
.2 20
OB
1
M— -1 K -
o 10
0)
|g
*= ln .
0 \\J
8
-






































».


<





t
;

»•








' '





A






A




•
>• 1




•
A,




%
^




L




i
J
*





»
1




•
i't;





*
..A


+ GVP
• PRT
A Probe




^





i



















^
•
                                        10                    100
                                      Mean Vapor Concentration (ppbv)
1000
Figure 30.  Coefficient of variation (%) as a function of mean vapor concentration for first, second, and third samples
at dedicated probe, PRT, and GVP sample locations.

3.8    Consideration of Spatial Variability on Comparison of Sampling Techniques

PRT and GVP sampling locations were positioned relatively close (usually within 1  m) to dedicated vapor
probes to  minimize the effect of spatial variability in comparing soil-gas sampling techniques. To assess
the presence and magnitude of spatial variability on this scale, soil-gas sampling  was conducted at five
locations and three depths near MW213 using the PRT sampling system. Figures 31 and 32 illustrate the
scale and  locations of testing.

The computation of internal volumes using the PRT sampling system at five locations at depths of 0.76 m
(2.5'), 2.3  m (7.5'), and 3.2 m (10.5')  are summarized in Tables 9a through  9c in Appendix A.  Sample
results and computation of pre-sample internal exchanges at these depths are summarized in Tables 9d
through 9f in Appendix A. As these tables indicate, there were 2 to 3 internal exchanges prior to sampling.
Pre-sample O2 and CO2 concentrations were similar with depth and location.  Figures 33a, 33b, and 33c
illustrate variation in concentration  with depth and location. Concentration varied by a factor of 1.0 to 2.8.
However,  variation in  most measurements  was relatively minor as evidenced by a median of 1.2 and
average of 1.3 for 90 sample pairs.
                                               22

-------
Figure 31.  Photograph illustrating five PRT sample locations (orange flags) near MW213.




                    SIDEWALK
                      GRASS
!l.5'
                                                          1J-W
                                                    1.5'
                   ASPHALT (street)
         MW213
Figure 32.  Schematic illustrating five PRT sample locations near MW213 in plan view.
                                               23

-------
                                        S2            S3            S4
                                      Sample Location at a Depth of 0.76 m
S5
Figure 33a. Vapor concentration at S1 through S5 (one sample at each location) at a depth of 0.76 m.
                                       S2            S3            S4
                                      Sample Location at a Depth of 2.3 m
S5
Figure 33b. Vapor concentration at S1 through S5 (one sample at each location) at a depth of 2.3 m.
                                                 24

-------
                                       S2            S3            S4
                                       Sample Location at a Depth of 3.2 m
S5
Figure 33c. Vapor concentration at S1 through S5 (one sample at each location) at a depth of 3.2 m.
                                                 25

-------
                                      4.0    Results

The results of testing at and near each dedicated vapor probe are summarized in this section.  These
results will be combined and discussed in further detail in Section 5.

4.1    Results of Testing at MW302SGM

A schematic illustrating the  location of the  dedicated probe MW302SGM and nearby PRT and GVP
sampling locations systems is illustrated in Figure 34. The screened interval of MW302SGM is 2.1 - 2.4 m
(7 - 8') below ground surface. Soil-gas samples were collected using the PRT and GVP systems at 2.3 m
(7.5') below ground surface. Samples were collected from each system three times.
                                                    GRASS
                    MW302M
MW302S
MW302D
                          4.9'
                            (§)*—._ 2.0*
                        Geoprobe —  7.5'
                            below grade
                                                    ASPHALT
                                              3.3'
                                              MW302SGM
    1.8'

      AMS -  7.5'
    A)  below  grade
Figure 34. Schematic illustrating the location of sampling systems at MW302SGM in plan view.

The computation of internal  volumes and cumulative pre-sample  internal exchanges is summarized in
Tables 10a and 10b in Appendix A.  Pre-sample internal exchanges for GVP,  PRT, and probe systems
varied from 6.7 - 33.6, 2.9 -  14.3, and 2.5 - 6.5 respectively.  VOC and gas concentrations  detected from
sample systems at MW514SG are illustrated in Figure 35 and summarized in Table 10c in Appendix A.
VOC concentrations of 1,1-DCE, 1,1,1-TCA, and TCE were slightly lower at the dedicated probe compared
to PRT and GVP sample systems by a factor up to 1.3.
                                             26

-------
           250
Figure 35. Comparison of mean (3 samples from each sample system) vapor concentrations at MW302SGM at a
depth of 2.3 m.

4.2   Results of Testing at MW514SG

A schematic of the location of dedicated probe MW514SG and nearby PRT and GVP sampling systems is
illustrated in Figure 36.  The screened interval of MW514SG  is 2.1 - 2.4 m (6.9 - 7.9') below ground
surface.  PRT and GVP were sampled at 2.3 m (7.5') below ground surface.  Samples were collected from
each system three times.

The computation of internal volumes and cumulative pre-sample internal exchanges  is summarized  in
Tables 11a and 11b in Appendix A.  Pre-sample internal exchanges for GVP, PRT, and probe systems
varyed from 8.1 - 40.4, 2.8 - 13.9, and 2.5 - 6.5 respectively. VOC and gas concentrations detected from
sample systems at MW514SG  are illustrated in Figure 37 and summarized in Table 11c in Appendix A.
O2 and CO2 concentrations were very similar in all three sample systems.  VOC concentrations of 1,1-DCE,
1,1,1-TCA, TCE, and c-1,2-DCE were similar for the GVP and PRT sample systems but higher than VOC
concentrations detected using the dedicated vapor probe by a factor of up to 1.9.
                                             27

-------
MW514A
                 48
                                        MW514SG
                                         x
                                                            43"
MW5UB
                                3s;x
                                x
                            X
           AMS - 7.5'®
           below  grade
                                31
                                              36'
                                     Geoprobe  -  7.5'
                                   G) below grade
Figure 36. Schematic illustrating the location of sampling systems at MW514SG in plan view.
Figure 37. Comparison of mean (3 samples from each sample system) vapor concentrations at MW514SG at a
depth of 2.3 m.
                                          28

-------
4.3    Results of Testing at MW523SGS, MW523SGM, and MW523SGD

A schematic of the location of dedicated probes MW523SGS MW523SGM, and MW523SGD and nearby
PRT and GVP sampling locations is illustrated in Figure 38. The separation of shallow, medium, and deep
dedicated vapor probes made it difficult to locate associated PRT and GVP sample systems nearby. While
PRT and  GVP systems are  within 0.91 m (3') of each  other, both sample systems were more than 1 m
away from dedicated vapor probes used for comparison.
MW523S             MW523SG5              MW523SGM
           37"         ^           42"
       Q-
         \
                                                                45"
                                                                         MW523SGD
                                                                      r*
                             \



                                          / /
                                       s    I
                                               ~r
                                                            ASPHALT  (street)
                                                                    GRASS
           Geoprobe  —
           2.5',  7.5',  10.5
           below grade
                                                                                 17"
                                                                                 47"
                                   AMS  -
                                   2.5', 7.5*
                                   below grade
Figure 38.  Schematic illustrating the location of sampling systems at MW523SGS, MW523SGM, and MW523SGD in
plan view.

The screened interval of MW523SGS is 0.6 - 0.9 m (2 - 3') below ground surface.  PRT and GVP were
sampled at 0.8 meters (2.5 feet) below ground surface. Computation of internal volumes at MW523SGS is
summarized in Table 12a in Appendix A.  Computation  of pre-sample internal exchanges and VOC and
gas concentrations detected from sample systems at MW523SGS is summarized in Table 12b in Appendix
A. Pre-sample internal exchanges for GVP, PRT, and probe systems were 4.1, 1.8, and 3.5 respectively.
The high CH4 concentration  detected  in MW523SGS was caused by a natural gas leak in the area.
Interference  by  CH4 caused an increase  in  detection  limits  for 1,1-DCE  and c-1,2-DCE.   VOC
concentrations were too low to discern any differences between sampling systems.
                                            29

-------
The screened interval of MW523SGM is 2.1 - 2.4 m (7 - 8') below ground surface.  PRT and GVP were
sampled at 2.3 m  (7.5') below ground surface.  Computation of internal volumes at MW523SGM  is
summarized in Table 13a in Appendix A.  Computation of pre-sample internal exchanges and VOC and
gas concentrations detected from  sample systems  at MW523SGM  is summarized in  Table 13b  in
Appendix A.  VOC concentrations are illustrated  in Figure 39. Pre-sample internal exchanges  for GVP,
PRT, and  probe  systems were 5.8, 2.5, and 2.5 respectively. Again, interference  by CH4 caused an
increase in detection limits for 1,1-DCE and c-1,2-DCE.  VOC concentrations of 1,1,1-TCA and TCE were
slightly higher for the dedicated probe and PRT system compared to the GVP system (by a factor of up to
1.9).
             14
Figure 39. Comparison of vapor concentrations (1 sample from each sample system) at MW523SGM at a depth of
2.3m.
The screened interval of MW523SGD is 3.2 - 3.5 m (10.5 - 11.5') below ground surface.  The PRT system
was sampled at 3.4 m  (11') below ground surface. Sampling at this depth with the GVP system proved
difficult (resistance to  penetration with rotary hammer  drill).   Computation of internal  volumes  at
MW523SGD is summarized in Table 14a in Appendix A. Computation of pre-sample internal exchanges
and VOC and gas concentrations detected from sample systems at MW523SGM is summarized in Table
14b in Appendix A. Vapor concentrations are illustrated in Figure 40.  Pre-sample internal exchanges for
                                             30

-------
PRT and probe systems were 1.8 and 2.0 respectively.  The CH4 gas concentration was not as high as the
shallower depths but still interfered with detection of 1,1 -DCE and c-1,2-DCE.  VOC concentrations for
1,1,1-TCA and TCE were slightly higher for the PRT system compared to the dedicated vapor probe (factor
up to 1.7).
£U
-\ Q .
To
•1C.
S 1C
S- 14-
Q. 14
C
o 10 .
I u
"P m.
c iu
8
C Q.
o o-
O
« R-
O O
Q.
45
"> A.
"^ *l
2.

0.
^












MW523SGD (3.4 m)



































|— 
-------
computation of pre-sample internal exchanges is summarized in Table 15b in Appendix A while VOC and

gas concentrations are summarized in Table 15c in Appendix A. Pre-sample internal exchanges for GVP

and PRT systems were 8.7 - 60.9 and 1.9 - 13.4  respectively.  Vapor concentrations are  illustrated in

Figure 42.  Mean VOC concentrations of 1.1-DCE, 1,1,1-TCA, and TCE using the PRT system appear to

be slightly higher (up to a factor of 1.7) compared to sampling with the GVP kit.


                                                                GRASS

AMS -©
3.0', 7.5*
below grade

ASPHALT (sireet)
^ ,^
s "----^^
\ "" "~ -3-\, MW525SG
2.4\ ";:^--_ 2.7'
                         Geoprobe -
                       3.0, 7.5', 11.0
                        below  grade
     	(G)
  Purge Test Location
     Geoprobe  - 3.0*
       below  grade
Figure 41. Schematic illustrating the location of sampling systems at MW525SG in plan view.
          £
          a.
          o


          1

          I
          o
          O
          t_
          o
          Q.


          I
          CO
          CD
                                                                   MW525SG (0.91 m)
                                                       Q_

                                                       O
                                                       LLJ
                                                       O
0*
Q.

LLJ
O
Q.

O
LLJ
O
Q
cvi
                                                                        o
CL
LLJ
O
Q
C\l_

6
Figure 42. Comparison of mean (3 samples from each sample system) vapor concentrations at MW525SG at a
depth of 0.91 m.
                                              32

-------
Soil-gas samples were also collected at a depth of 2.3 m (7.5') at nearby PRT and GVP locations. The
computation of internal volumes and pre-sample internal exchanges is summarized in Tables 16a and 16b
in Appendix A. Pre-sample internal exchanges for GVP, PRT, and dedicated probe sample systems were
6.0 - 30.1, 2.9 - 14.7, and 2.6 - 6.8 respectively. VOC concentrations are illustrated in Figure 43 and
summarized in Table 16c in Appendix A. O2 concentration appeared higher and CO2 concentration lower
using the GVP kit compared to PRT and dedicated probe sample systems.  Mean CO2 concentrations in
the PRT and dedicated vapor probe sample systems were approximately six times higher than the mean
CO2  concentration detected using the GVP kit.  Mean VOC concentrations of  1,1-DCE, 1,1,1-TCA, and
TCE  using the GVP  kit appeared lower by a factor  of 8  to 9 compared to mean VOC concentrations
detected using the PRT and dedicated probe sample systems. Given the relatively small distance between
the GVP kit and PRT (0.73 m)  and  dedicated probe sample systems  (1.1 m), it is  unlikely that these
differences in  concentration were due entirely to spatial  variability.  It appears likely that  recharge from
atmospheric air or leakage occurred during sampling with the GVP  kit at this location.
          ^
          Q.
          g
          O
          O
          8
          o
          o
ouu •
450
Af\C\ -
4UO
ocn -
ooO
onn -
oUO

4 en -
TOO
•4 nn -
1UO
en .
OO
n









g
CL
O
LLJ
O
Q










CL
LJJ
O
Q















i — i





 E -g > E -g
0 CL 2 o Q. 2
LJJ UJ "V UJ LiJ "V
Q O HI O O HI
F I- 0 Q Q 0
H ri, (N Q
                                                                      O
                                                                            O
                                                                                  u
Figure 43. Comparison of mean (3 samples from each sample system) vapor concentrations at MW525SG at a
depth of 2.3 m.
                                             33

-------
4.5   Results of Testing at MW526SGS, MW526SGM, and MW526SGD

A  schematic illustrating the location of the  dedicated vapor probes MW526SGS,  MW526SGM,  and
MW526SGD and nearby PRT and GVP sampling locations  systems is illustrated in Figure 44.   The
relatively large distance between shallow, medium, and deep dedicated vapor probes necessitated the use
of  multiple PRT and GVP sampling locations.
   Geoprobe - 2.5', 10.5'
       below grade
             30"
            4*
  ^ ^   AMS - 2.5'
\ 22" ""(A) below grade
  \    1
  34" \   ^24"

      \»
        MW526SGD
                     37"
                     J7
         4-
      Geoprobe - 7.5'
    /g\ below grade
     [X 20"          Geoprobe - 2.5'
  21'I  ^^W528SGM  belowgrade
       MW526SGS
                           77"
     I   s
    /TT U"
-7.5'VA-L
V
         36"
                        —-CGJ
                                                   below grade   v
                                                                 31" '
                                                               AMS - 2.5'
                                                               below grade

Figure 44. Schematic illustrating the location of sampling systems at MW526SGS, MW526SGM, and MW526SGD in
plan view.
MW526SGS is screened over a depth of 0.61 to 0.91 m (2 to 3') while soil-gas samples were collected at a
depth of 0.76 m  (2.5 ft) at nearby PRT and GVP locations. The computation of internal volumes and pre-
sample internal  exchanges  is summarized in Tables  17a and 17b in Appendix A.  Pre-sample internal
exchanges for GVP, PRT, and dedicated probe sample systems were 8.7 - 60.9, 2.0 - 13.8, and 3.5 - 9.6
respectively. VOC concentrations are illustrated in Figure 45 and summarized in Table 17c in Appendix
A. Mean O2 and CO2 concentrations were similar for all three sample systems.  There did not appear to be
any  clear  trends in  1,1-DCE,  1,1,1-TCA,  and TCE  concentrations with the three sample  systems.
However, the concentration  of 1,1-DCE in the dedicated probe was 5.8 times greater than that in the PRT
system whereas concentrations of 1,1,1 -TCA were nearly equivalent.

Soil-gas samples were also collected at a depth of 0.76 m (2.5')  using PRT and GVP sampling systems
near MW526SGM.  The computation  of  internal volumes and pre-sample internal exchanges for  these
sampling systems is summarized in Tables 18a and 18b in Appendix A.  Pre-sample internal exchanges
for GVP and PRT sample systems were 4.5 - 31.3 and 2.0 - 14.2 respectively. VOC concentrations are
illustrated in Figure 46 and  summarized in Table 18c in Appendix A.  Mean VOC concentrations for 1,1-
                                             34

-------
DCE, 1,1,1-TCA, and TCE using the PRT system appeared to be slightly higher than those using the GVP

system by a factor up to 3.3.

             80-
         £
         Q.
         Q.
          g

         '«
         £

          I
          o
          c

          (D
Figure 45.  Comparison of mean (3 samples from each sample system) vapor concentrations at MW526SGS at a
depth of 0.76 m.
              60

          1

          &  50
           c
           o
           (D
           O

           O
          O
           L_
           O
           Q.



          f
           CO
           (D
              40
30
20
10
                                                 MW526SGM (0.76 m)
                       Q_

                       C5
                       LLJ
                       O
                       Q
                    DC
                    Q.

                    LLJ
                    O
                    Q
D_

9
LLJ
O
Q.

LLJ
O
Figure 46.  Comparison of mean (3 samples from each sample system) vapor concentrations at MW526SGM at a
depth of 0.76 m.
                                               35

-------
MW526SGM is screened over a depth of 2.1 to 2.4 m (7 to 8'). Soil-gas samples were collected at a depth
of 2.3 m (7.5')  at nearby PRT and GVP locations.  The computation of internal volumes and pre-sample
internal exchanges is summarized in Tables 19a and 19b in Appendix A.  Pre-sample internal exchanges
for GVP,  PRT, and dedicated vapor probe sample systems were 7.4 - 37.2,  3.0 - 14.9, and 2.5 - 6.5
respectively. VOC concentrations are summarized in Figure 47 and in Table 19c in Appendix A.  VOC
concentrations  of 1,1-DCE, 1,1,1-TCA, TCE,  and c-1,2-DCE using GVP  and dedicated vapor systems
appeared similar but lower than VOC concentrations detected using the PRT sampling system by a factor
of up to 1.4 which is within the range expected  for spatial variability on the scale of 1 m.
             100
Q.
&.

O

1
I
O
O
h_
o
Q.
          i
              80
              60- -f
              40--
              20--
               0
                                                                 MW526SGM (2.3 m)
                   0     O    LlJ     O
                                               0     Q-
                                     <    O
                                                                                 
-------
concentrations are illustrated  in Figure 48.  Mean  O2 and CO2 concentrations were similar for  both
sampling systems.  Mean VOC concentrations of 1,1-DCE, 1,1,1-TCA, TCE, and c-1,2-DCE were higher
using the PRT system compared to dedicated vapor probes by a factor up to 1.4 which is within the range
expected for spatial variability on the scale of 1 m.
             140
          £
          Q.
          O
          1

          I
          O
          O
          O
          Q.
          CO
          CD
             120
             100
Figure 48.  Comparison of mean (3 samples from each sample system) vapor concentrations at MW526SGD at a
depth of 3.2 m.
                                              37

-------
                      5.0   Discussion of Comparison Testing


A comparison of dedicated vapor probes and the GVP sampling kit is illustrated in Figure 49.  The vapor

probes were screened at depths of 0.61 - 0.91 and 2.1 - 2.4 m while soil-gas samples were collected at

depths of 0.76 and 2.3 m.  With the exception of sampling at MW525SG at a depth of 2.3 m, there was no

apparent bias in sample  collection method.  As previously discussed, at this location and  depth, O2

concentration was higher and CO2 concentration lower (by a factor of 6) using the GVP kit compared to the

PRT system and dedicated vapor probe indicating likely leakage with the GVP kit.  However, use of all

sample data reveals no statistical difference in sampling methods (p = 0.31 for two-tailed t-Test,  p > 0.2 for

two-tailed Wilcoxon Signed Rank Test). Random scatter about the 1:1 line is likely due at least in part to

spatial variability.
         1000
          100-
       g
§
8
0.
CD
           10
                    GVP (0.76 m)
                    GVP (2.3 m)
             itt
             Id
             -H4
   -4--I-M-H4
     I   I  I  I  I I  I
     I   I  I  I  I I I
     I   I  I  I  I I I
.-U--1-I-I4-II4
                                                  *S
                                         w:
                               izzmz
               	-r---r--M-t-r-H
              I I I
              I I I
                         I   I   I I
                         I   I   I I
                                  :zlz±zlzizlld
                                  .--I---I--I-I-I-H-I
                                   -4--I--I-I-I-H-I
                                     1   1JJJ1LJ
                                     I     I  I   I  I I I  I
                                          I  I   I  I I I  I
                        T
                        T
                        +
                                                T~l~l~ITn
                                                T~l~l~ITn
                                                + -I-H + H
                                                 I  I   I  I I I  I
                                                                             UI4J-I
                                                                             I-I4W
                                                                             UJM
                                                                             I  I I  I I
                                                                             I  I I  I I
                                                          MW525SG
                                                                T~r

                                                         	h-H--|-
                                                                 I   I
                                                         	
                                     10                     100

                                      Probe Concentration (ppbv)
                                                              1000
Figure 49. Comparison of probe and GVP VOC concentrations - error bars represent one standard deviation from
three samples.



A comparison of dedicated vapor probes and PRT sampling systems is illustrated in Figure 50.  The vapor

probes were screened at  depths of 0.61 -  0.91, 2.1  - 2.4, and 3.0 - 3.4 m while soil-gas samples were
                                            38

-------
collected at depths of 0.76, 2.3, and 3.2 m using the Geoprobe® PRT system.  Both visually and statistically
(p = 0.009 for two-tailed t-Test, p < 0.01 for two-tailed Wilcoxon Signed Rank Test), VOC concentrations in
the  PRT system were  higher than corresponding VOC concentrations in dedicated vapor probes.  VOC
concentrations using the PRT system were higher than VOC concentrations detected  using dedicated
vapor probes by an average factor of 1.2.  The effect does not appear to be due to spatial variability which
would result in random scatter of data.  It is unlikely that extraction volume or sampling sequence caused
the observed bias given results discussed in Sections 3.6 and 3.7.  Also, it is unlikely that a difference in
screen length (5 cm  for PRT and GVP system and 30 cm for dedicated vapor probes) resulted in  elevated
PRT concentrations  relative to dedicated vapor probes since concentrations should be equivalent for vapor
concentration increasing uniformly with depth.  A non-uniform increase in concentration with depth  (e.g.,
exponential function) would result in lower PRT concentrations relative to dedicated vapor probes.

          1000
100-
        O

        1
        §
                     PRT (0.76 m)
                     PRT (2.3 m)
                     PRT (3.2 m)
                        --HHH-H
                            -I-I-I-IM
                 =!=H±H
                 -I-I-I-H-I
                 -i-i-i-m
                 -I-I-ITI-I
                 -I-U-LI4
                        I
                          tt
I-M-I-M
I-M-I-H
i-M-I-M
l-UUl-U
i  i
i  i
M-l-1-1
I-U4-I
                                                        l=l=tJd
                                                        a It El
                                                        H-m
                                                        PITH


            10-
                                                                  i-H-mH
                                                                  rrnn
                                                                  rrnn
                                                                  i   i  i 111
                                                                  	
                                      10                      100
                                        Probe Concentration (ppbv)
                                                                          1000
Figure 50.  Comparison of dedicated vapor probe and GVP VOC concentrations - error bars represent one standard
deviation from three samples.

A comparison of PRT and GVP sampling systems is illustrated in Figure 51.  Both systems were sampled
at  depths  of 0.76 and 2.3 m.  Again, bias at location MW525SG at a depth of 2.3  m indicated leakage
during sampling with the GVP system.  Both visually and statistically (p = 0.03 for two-tailed t-Test, p <
                                              39

-------
0.01 for two-tailed Wilcoxon Signed Rank Test), VOC concentrations in the PRT system were higher than
corresponding VOC concentrations using the GVP system.  VOC concentrations using the  PRT system
were higher than VOC concentrations detected using the GVP kit by an average factor of 2.4.  Similar to
the comparison between probe and PRT sampling systems, the effect does not appear to be due to spatial
variability, extraction volume, or sequence of sampling.
         1000
      £
       Q.
      .g
       8
       o
      O
      0_
      (3
100-
                    GVP (0.76 m)
                    GVP (2.3 m)
                      t)±t:
                      H-r-h
                      QIC:
  = tit=t=t±tt
(--(--r-r-r-r-H
                     L__L_I_I_U_LL
                              I  I  I I I
                     r-T-rrn-rrt
                              i  i  i 1 1
                                    _ L _L J _L .LLL
                                             I  I I I
                = = =F = =F=FFR=FF:
                                                                  FFI3E
                                                                      IH-t-
                                                                   :rq:
                                                                     JlL
                                                r4^ =
                                            I--I-4-M-I-I4
                              I  I  I I I
                              I  I  I I I
                                             i  i 11
                                  h-h-r-r-r-r-H
                                             I  I 11
                                                           100
                                                                        1000
                                       PRT Concentration (ppbv)
Figure 51. Comparison of PRT and GVP VOC concentrations - error bars represent one standard deviation from
three samples.
Thus, utilization of the PRT system resulted in observation of higher concentrations of VOCs compared to
the GVP sampling system and dedicated vapor probes.  However, the magnitude of variation was relatively
minor when compared to variation on a scale of 1 m due to spatial variability (median of 1.2 and average of
1.3 for 90 sample pairs).
                                            40

-------
                                      6.0   Summary

A study was conducted near the Raymark Superfund Site in Stratford, Connecticut to compare results of
soil-gas sampling using dedicated vapor probes, a truck-mounted direct-push technique - Geoprobe® Post-
Run-Tubing (PRT) system, and a hand-held rotary hammer technique - AMS Gas Vapor Probe (GVP) kit.

A comparison of VOC concentrations using dedicated vapor probes and the GVP sampling kit indicated
that the two methods provided similar results. However, at one location, O2, CO2, and VOC concentrations
were noticeably different for sampling systems indicating potential leakage with the GVP system.

VOC concentrations using the  PRT  system were not statistically equivalent to VOC concentrations using
dedicated vapor probes. VOC concentrations using the PRT system were higher than VOC concentrations
detected using dedicated vapor probes by an average factor of 1.2.  This is the same magnitude observed
for spatial variability on a scale of 1  m (median of 1.2 and average of  1.3 for 90 sample pairs).  However,
this effect did  not  appear to be due to  spatial variability which  would  result  in random scatter not a
consistent bias as observed.  It is also unlikely that extraction volume or sampling sequence caused the
observed bias given results from extraction volume and sample sequence testing.

VOC concentrations using the PRT system were also not statistically equivalent to VOC concentrations
using the GVP  kit.  VOC concentrations using  the PRT system were higher than  VOC concentrations
detected using the GVP kit by an average factor of 2.4. Similar to the comparison between probe and PRT
sampling systems, the effect  does not appear to be due  to spatial variability, extraction volume, or
sequence of sampling.

Thus, utilization of the PRT system resulted in observation of higher concentrations of VOCs compared to
the GVP sampling system and dedicated vapor probes. However, the magnitude of variation was relatively
minor when compared to variation  on  a scale of  1  m  due to spatial  variability.  Hence for practical
purposes, all three sample systems can be considered approximately equivalent.

This  testing was conducted  in  highly permeable  soils  where the  potential for  leakage from direct-
push/hammer soil-gas sampling systems would be expected to be low compared to  less permeable soils
such as silt and clay.  Thus, the results of this investigation should not be extrapolated to other soil textures
where additional  investigation is needed.  Also, only one direct-push and  one rotary hammer method was
                                              41

-------
evaluated for comparison with dedicated vapor probes. Thus, the results of this investigation should not be
extrapolated to other direct-push/hammer soil-gas sampling techniques.
                                               42

-------
                                        References

Freeze, R. A. and J.A. Cherry. 1979. Groundwater. Prentice-Hall, Inc., Englewood Cliffs, NJ.

Johnson, P.C. and R. A. Ettinger. 1991. Heuristic model for the intrusion rate of contaminant vapors into
buildings. Environmental Science and Technology, 25(8): 14445-1452.

TetraTech NUS, Inc. 2000. Draft final remedial investigation, Raymark- OU - Groundwater, Stratford, CT,
Response action contract (RAC), Region I, EPA contract No. 68-W6-0045, EPA work assignment no. 029-
RICO-01H3.

U.S. Environmental Protection Agency. 1999. Compendium of methods for determination of toxic organic
compounds in ambient air, Determination  of  volatile  organic compounds  (VOCs) in air collected  in
specially-prepared  canisters  and analyzed  by  gas   chromatography/mass  spectrometry  (GC/MS).
http://www.epa.gov/ttn/amtic/files/ambient/airtox/to-15r.pdf. EPA/625/R-96/010b. Office  of Research  and
Development, National Risk Management Research Laboratory, Cincinnati, OH.

U.S. Environmental Protection Agency. 2002a. Draft guidance for evaluating the vapor intrusion to indoor
air  pathway  from groundwater  and  soils (subsurface  vapor intrusion guidance),  http://www.epa.gov/
correctiveaction/eis/vapor.htm. Office of Solid Waste and Emergency Response, Washington, D.C.

U.S. Environmental Protection Agency. 2002b. Air sample analysis for volatile organic compounds. Internal
report, Feb. 12, 2002. USEPA New England Regional Laboratory, Lexington, MA.

U.S. Environmental Protection Agency. 2006. Assessment of vapor intrusion in homes near the Raymark
superfund site  using  basement  and sub-slab air samples, http://www.epa.gov/ada/download/reports/
600R05147/600R05147.pdf. Office of Research and Development,  National Risk Management Research
Laboratory, Cincinnati, OH.
                                              43

-------

-------
                                         Appendix A
Table 1. Depth of Fill Materials and Screened Intervals in Boreholes Containing Dedicated Vapor Probes
Depth (m) 302SG 513SG 514SG 523SGS 523SGM 523SGD 525SG 526SGS 526SGM
Bottom of concrete seal 0.2 0.2
Bottom of sand drain layer 0.8 0.9
Bottom of bentonite 1.8 1 .8
Top of screen 2.1 2.1
Bottom of screen 2.4 2.4
Bottom of sand filter 2.4 2.4
Table 2. Results of Container Blanks
Sample 1,1-DCE 1,1,1-TCA TCE
Identification (ppbv) (ppbv) (ppbv)
SSEB-01 ND(4.0) ND(3.0) ND(3.0)
SSEB-02 ND(4.0) ND(3.0) ND(3.0)
SSEB-03 ND(4.0) ND(3.0) ND(3.0)
SSEB-04 ND(4.0) ND(3.0) ND(3.0)
ND() = not detected (detection limit)
Table 3. Results of Field Blanks
Sample 1,1-DCE 1,1,1-TCA TCE
Identification (ppbv) (ppbv) (ppbv)
Ambient 1 ND(2.0) ND(3.0) ND(3.0)
Ambient 2 ND(2.0) ND(3.0) ND(2.0)
Ambient 3 ND(3.0) ND(3.0) ND(2.0)
ND() = not detected (detection limit)
Table 4. Results of Probe Blanks
Sample Sample 1,1-DCE 1,1,1-TCA
System Identification (ppbv) (ppbv)
GVP SM-A-525 ND(2.0) ND(3.0)
PRT SM-G-525 ND(2.0) ND(3.0)
PRT SM-526-G ND(2.0) ND(3.0)
GVP SM-526-A ND(3.0) ND(3.0)
PRT SM-526-G2 ND(3.0) ND(3.0)
ND() = not detected (detection limit)
Table 5. Results of Travel Blanks
Sample 1,1-DCE 1,1,1-TCA TCE
Identification (ppbv) (ppbv) (ppbv)
ST-5-5-03 ND(2.0) ND(3.0) ND(3.0)
ST-5-6-03 ND(2.0) ND(3.0) ND(2.0)
ST-5-7-03 ND(3.0) ND(3.0) ND(2.0)
0.2 0.2 0.3 0.3 0.2 0.2 0.3
0.9 0.3 0.9 0.9 0.9 0.3 0.9
2.0 0.5 2.0 3.0 2.0 0.5 2.0
2.1 0.6 2.1 3.2 2.1 0.6 2.1
2.4 0.9 2.4 3.5 2.4 0.9 2.4
2.4 1.0 2.4 3.5 2.4 1.0 2.4
c-1,2-DCE
(PPbv)
ND(4.0)
ND(4.0)
ND(4.0)
ND(4.0)
c-1,2-DCE
(PPbv)
ND(2.0)
ND(2.0)
ND(4.0)
TCE c-1,2-DCE
(ppbv) (ppbv)
ND(3.0) ND(2.0)
ND(3.0) ND(3.0)
ND(2.0) ND(2.0)
ND(2.0) ND(4.0)
ND(5.0) ND(4.0)
c-1,2-DCE
(PPbv)
ND(2.0)
ND(2.0)
ND(4.0)
526SGD
0.2
0.9
2.9
3.0
3.4
3.4

ND() = not detected (detection limit)
                                               45

-------
Table 6.  Results of Replicate Samples
Sample
Identification
523-8-G1
523-8-G1(rep)
526-3-A2R
526-3-A2R(rep)
526-3-A3
526-3-A3(rep)
526-8-G3
526-8-G3(rep)
302SG-1
302SG-1 (rep)
1,1-DCE
(ppbv)
ND(30)
ND(30)
6.4
6.4
6.7
6.7
82
82
77
77
1,1,1-TCA
(ppbv)
8.7
8.9
28
26
64
65
102
105
157
157
TCE
(ppbv)
11
11
8.1
8.1
21
23
33
33
31
30
c-1,2-DCE
(ppbv)
ND(25)
ND(25)
ND(3.0)
ND(3.0)
ND(4.0)
ND(4.0)
12
12
ND(6.0)
ND(6.0)
 ND() = not detected (detection limit)

Table 7a. Computation of Internal Volume of PRT Sampling System When Sampling at 0.76 m Near MW 525SG
Sample
Method
 PRT
Screen  Screen   Screen   Riser  Riser     Riser   Tubing  Tubing   Tubing   Internal
ID     Length   Volume   ID    Length   Volume  ID      Length   Volume   Volume
(cm)    (cm)     (cm3)    (cm)   (cm)     (cm3)   (cm)    (cm)     (cm3)    (L)
         2.54
                5.1
                         26
                                 NR
                                       NR
                                                NR
                                                       0.64
                                                               305
                                                                       96.5
                                                                               0.122
 NR = not relevant
Table 7b. Computation of Pre-Sample Extraction and Internal Exchange Volumes of PRT Sample System When
Sampling at 0.76 m Near MW525SG
Sample
Identification


525-3-PRT1
525-3-PRT2
525-3-PRT3
525-3-PRT4
525-3-PRT5
525-3-PRT6
525-3-PRT7
525-3-PRT8
525-3-PRT9
525-3-PRT10
Pre-Sample
Purge
Volume
(L)
0.0
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
Cumulative
Pre-Sample
Extraction
Volume (L)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
Cumulative
Pre-Sample
Internal
Exchanges (-)
0.0
8.2
16.4
24.5
32.7
40.9
49.1
57.3
65.5
73.6
Sample
Volume
(L)

0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
Cumulative
Post-Sample
Extraction
Volume (L)
0.5
1.5
2.5
3.5
4.5
5.5
6.5
7.5
8.5
9.5
1,1-DCE
(ppbv)


204
248
229
254
229
221
230
234
224
226
1,1,1-TCA
(ppbv)


436
484
458
466
474
462
475
473
443
447
TCE
(ppbv)


115
126
119
126
118
118
128
126
121
123
c-1,2-DCE
(ppbv)


20
22
20
26
20
19
22
21
20
22
Table 8a. Computation of Internal Volume Dedicated Vapor Probe MW513SG When Sampling at a Depth Interval of
2.1 to 2.4m
Sample
Method

Probe
Screen  Screen  Screen  Riser  Riser   Riser    Tubing  Tubing  Tubing    Internal
ID     Length  Volume  ID    Length Volume  ID     Length  Volume   Volume
(cm)    (cm)    (cm3)    (cm)  (cm)   (cm3)    (cm)   (cm)    (cm3)     (L)
         3.81
                 30.5
                        347
                                1.9
                                      213
                                             608
                                                     0.95
                                                             61
                                                                    43.4
                                                                             0.999
                                                    46

-------
Table 8b. Computation of Pre-Sample Extraction and Internal Exchange Volumes of Dedicated Vapor Probe
MW513SG When Sampling at a Depth Interval of 2.1 to 2.4 m
Sample
Identification


513SG-1
51 3SG-2
513SG-3
513SG-4
513SG-5
513SG-6
513SG-7
513SG-8
513SG-9
513SG-10
Pre-Sample
Purge
Volume
(L)
0.0
0.0
0.5
0.5
2.0
5.0
10.0
15.0
25.0
40.0
Cumulative
Pre-Sample
Extraction
Volume (L)
0.0
0.5
1.5
2.5
5.0
10.5
21.0
36.5
62.0
102.5
Cumulative
Pre-Sample
Internal
Exchanges (-)
0.0
0.5
1.5
2.5
5.0
10.5
21.0
36.5
62.0
102.5
Sample
Volume
(L)

0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
Cumulative
Post-Sample
Extraction
Volume (L)
0.5
1.0
2.0
3.0
5.5
11.0
21.5
37.0
62.5
103.0
1,1-DCE
(ppbv)


579
616
603
611
611
609
629
637
619
646
1,1,1-TCA
(ppbv)


1306
1402
1402
1363
1389
1478
1490
1446
1414
1459
TCE
(ppbv)


186
239
218
224
228
255
265
281
261
293
c-1,2-DCE
(ppbv)


79
93
84
84
85
90
96
96
92
101
Table 9a. Computation of Internal Volumes Using the PRT Sampling System at Five Sample Locations at a Depth of
0.76m Near MW213
Sample
Identification

213-3-S1
213-3-S2
213-3-S3
213-3-S4
213-3-S5
Screen
ID
(cm)
2.54
2.54
2.54
2.54
2.54
Screen
Length
(cm)
5.1
5.1
5.1
5.1
5.1
Screen
Volume
(cm3)
26
26
26
26
26
Riser
ID
(cm)
NR
NR
NR
NR
NR
Riser
Length
(cm)
152
152
152
152
152
Riser
Volume
(cm3)
NR
NR
NR
NR
NR
Tubing
ID
(cm)
0.64
0.64
0.64
0.64
0.64
Tubing
Length
(cm)
332
335
293
274
305
Tubing
Volume
(cm3)
105.2
106.1
92.6
86.8
96.5
Internal
Volume
(L)
0.131
0.132
0.118
0.113
0.122
NR = not relevant
Table 9b. Computation of Internal Volumes Using the PRT Sampling System at Five Sample Locations at a Depth of
2.3mNearMW213
Sample
Identification

213-8-S1
213-8-S2
213-8-S3
213-8-S4
213-8-S5
Screen
ID
(cm)
2.54
2.54
2.54
2.54
2.54
Screen
Length
(cm)
5.1
5.1
5.1
5.1
5.1
Screen
Volume
(cm3)
26
26
26
26
26
Riser
ID
(cm)
NR
NR
NR
NR
NR
Riser
Length
(cm)
152
152
152
152
152
Riser
Volume
(cm3)
NR
NR
NR
NR
NR
Tubing
ID
(cm)
0.64
0.64
0.64
0.64
0.64
Tubing
Length
(cm)
418
439
457
497
430
Tubing
Volume
(cm3)
132.2
138.9
144.7
157.3
136.0
Internal
Volume
(L)
0.158
0.165
0.170
0.183
0.162
NR = not relevant
Table 9c. Computation of Internal Volumes Using the PRT Sampling System at Five Sample Locations at a Depth of
3.2mNearMW213
Sample
Identification

213-11-S1
213-11-S2
21 3-11 -S3
213-11-S4
213-11-S5
Screen
ID
(cm)
2.54
2.54
2.54
2.54
2.54
Screen
Length
(cm)
5.1
5.1
5.1
5.1
5.1
Screen
Volume
(cm3)
26
26
26
26
26
Riser
ID
(cm)
NR
NR
NR
NR
NR
Riser
Length
(cm)
152
152
152
152
152
Riser
Volume
(cm3)
NR
NR
NR
NR
NR
Tubing
ID
(cm)
0.64
0.64
0.64
0.64
0.64
Tubing
Length
(cm)
671
610
616
655
622
Tubing
Volume
(cm3)
212.3
193.0
194.9
207.4
196.8
Internal
Volume
(L)
0.238
0.219
0.221
0.233
0.223
NR = not relevant
                                                 47

-------
Table 9d.  Computation of Pre-Sample Extraction and Internal Exchange Volumes and Sample Results Using the
PRT Sampling System at a Depth of 0.76 m Near MW213
Sample
Sequence

213-3-S1
21 3-3-S2
213-3-S3
213-3-S4
213-3-S5
Pre-Sample
Purge
Volume (L)
0.25
0.25
0.25
0.25
0.25
Pre-Sample
Internal
Exchange (-)
1.9
1.9
2.1
2.2
2.0
Sample
Volume
(L)
0.50
0.50
0.50
0.50
0.50
Post-Sample
Extraction
Volume (L)
0.75
0.75
0.75
0.75
0.75
1,1 -DCE
(ppbv)

3.4
2.8
2.1
5.3
2.3
1,1,1-TCA
(ppbv)

25
24
20
36
13
TCE
(ppbv)

19
19
16
24
12
c-1,2-DCE
(ppbv)

ND(4.0)
ND(4.0)
ND(4.0)
ND(4.0)
ND(4.0)
02
(%)

20.5
20
20.2
20.2
NA
CO2
(%)

0.3
0.4
0.3
0.3
NA
CH4
(%)

0.0
0.0
0.0
0.0
NA
 NA = not analyzed
ND() = not detected
Table 9e. Computation of Pre-Sample Extraction and Internal Exchange Volumes and Sample Results Using the
PRT Sampling System at a Depth of 2.3 m Near MW213
Sample
Identification

213-8-S1
21 3-8-S2
213-8-S3
21 3-8-S4
21 3-8-S5
Pre-Sample
Purge
Volume (L)
0.50
0.50
0.50
0.50
0.50
Pre-Sample
Internal
Exchange (-)
3.2
3.0
2.9
2.7
3.1
Sample
Volume
(L)
0.50
0.50
0.50
0.50
0.50
Post-Sample
Extraction
Volume (L)
1.00
1.00
1.00
1.00
1.00
1,1 -DCE
(ppbv)

12
9.3
10
10
9.1
1,1,1-TCA
(ppbv)

46
41
42
44
37
TCE
(ppbv)

28
28
32
30
25
c-1,2-DCE
(ppbv)

ND(4.0)
ND(4.0)
ND(4.0)
ND(4.0)
ND(4.0)
02
(%)

20.4
20.3
20.0
20.3
NA
CO2
(%)

0.3
0.3
0.4
0.3
NA
CH4
(%)

0.0
0.0
0.0
0.0
NA
 NA = not analyzed
  ND() = not detected
Table 9f. Computation of Pre-Sample Extraction and Internal Exchange Volumes and Sample Results Using the PRT
Sampling System at a Depth of 3.2 m Near MW213
Sample
Identification
213-11-S1
213-11-S2
21 3-11 -S3
213-11-S4
213-11-S5
Pre-Sample
Purge
Volume (L)
0.50
0.50
0.50
0.50
0.50
Pre-Sample
Internal
Exchange (-)
2.1
2.3
2.3
2.1
2.2
Sample
Volume
(L)
0.50
0.50
0.50
0.50
0.50
Post-Sample
Extraction
Volume (L)
1.00
1.00
1.00
1.00
1.00
1,1 -DCE
(ppbv)
16
13
12
14
10
1,1,1-TCA
(ppbv)
50
48
49
54
40
TCE
(ppbv)
37
35
30
33
25
c-1,2-DCE
(ppbv)
ND(4.0)
ND(4.0)
ND(4.0)
ND(4.0)
ND(4.0)
02
(%)
20.3
20.2
20.0
19.9
NA
CO2
(%)
0.4
0.3
0.4
0.4
NA
CH4
(%)
0.0
0.0
0.0
0.0
NA
 NA = not analyzed
 ND() = not detected
Table 10a.  Internal Volumes of Probe, PRT, and GVP Systems at 2.3 m Near MW302SGM
Sample  Screen  Screen  Screen   Riser  Riser   Riser    Tubing  Tubing   Tubing   Internal
Method  ID     Length  Volume  ID    Length  Volume  ID      Length   Volume   Volume
        (cm)   (cm)    (cm3)    (cm)   (cm)   (cm3)    (cm)    (cm)     (cm3)     (L)
GVP
PRT
Probe
0.64
2.54
3.81
5.1
5.1
30.5
1.6
26
347
NR
NR
1.9
274
305
213
NR
NR
608
0.48
0.64
0.95
408
469
61
72.7
149
43.4
0.074
0.174
0.999
 NR = not relevant
                                                   48

-------
Table 10b. Cumulative Pre-Sample Internal Exchanges of Probe, PRT, and GVP Systems at 2.3 m Near
MW302SGM
Sample
Method


PRT
GVP
Probe
GVP
Probe
PRT
Probe
PRT
GVP
Sample
Identification


302-8-G1
302-8-A1
302SG-1
302-8-A2
302SG-2
302-8-G2
302SG-3
302-8-G3
302-8-A3
Pre-Sample
Purge
Volume
(L)
0.5
0.5
2.5
0.5
1.5
0.5
1.5
0.5
0.5
Cumulative
Pre-Sample
Extraction
Volume (L)
0.5
0.5
2.5
1.5
4.5
1.5
6.5
2.5
2.5
Cumulative
Pre-Sample
Internal
Exchanges (-)
2.9
6.7
2.5
20.2
4.5
8.6
6.5
14.3
33.6
Sample
Volume
(L)

0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
Cumulative
Post-Sample
Extraction
Volume (L)
1.0
1.0
3.0
2.0
5.0
2.0
7.0
3.0
3.0
Table 10c. VOC and Gas Concentrations in Probe, PRT, and GVP Systems at 2.3 m Near MW302SGM
Sample
Identification
GVP
302-8-A1
302-8-A2
302-8-A3
mean 302-8-A
stdev 302-8-A
PRT
302-8-G1
302-8-G2
302-8-G3
mean 302-8-G
stdev 302-8-G
Probe
302SG-1
302SG-2
302SG-3
mean 302SG
stdev 302SG
1,1 -DCE
(ppbv)

84
90
84
86
3.5

80
79
83
80.7
2.1

77
83
79
80
3.1
1,1,1-TCA
(ppbv)

187
187
181
185
3.5

193
192
190
192
1.5

157
156
157
157
0.6
TCE
(ppbv)

40
41
40
40
0.6

37
37
39
38
1.2

31
30
30
30
0.6
c-1,2-DCE
(ppbv)

ND(6.0)
ND(6.0)
ND(6.0)
ND(6.0)
IND

ND(6.0)
ND(6.0)
ND(6.0)
ND(6.0)
IND

ND(6.0)
ND(6.0)
ND(6.0)
ND(3.0)
IND
02
(%)

19.7
19.6
NA
19.7
0.1

19.1
NA
NA
IND
IND

20.1
NA
NA
IND
IND
CO2
(%)

1.3
1.3
NA
1.3
0.0

1.2
NA
NA
IND
IND

1.3
NA
NA
IND
IND
CH4
(%)

0.0
0.0
NA
0.0
0.0

0.0
NA
NA
IND
IND

0.0
NA
NA
IND
IND
ND( )-not detected
IND = indeterminate
Table 11 a. Internal Volumes of Probe, PRT, and GVP Systems at 2.3 m Near MW514SG
Sample
Method
GVP
PRT
Probe
Screen
ID
(cm)
0.64
2.54
3.81
Screen
Length
(cm)
5.1
5.1
30.5
Screen
Volume
(cm3)
1.6
26
347
Riser
ID
(cm)
NR
NR
1.9
Riser
Length
(cm)
274
305
213
Riser
Volume
(cm3)
NR
NR
608
Tubing
ID
(cm)
0.48
0.64
0.95
Tubing
Length
(cm)
338
488
61
Tubing
Volume
(cm3)
60.2
154
43.4
Internal
Volume
(L)
0.062
0.180
0.999
NR = not relevant
                                                49

-------
Table 11 b. Cumulative Pre-Sample Internal Exchanges of Probe, PRT, and GVP Systems at 2.3 m Near MW514SG
Sample
Method


PRT
GVP
Probe
GVP
Probe
PRT
Probe
PRT
GVP
Sample
Identification


514-8-G1
514-8-A1
514SG-1
514-8-A2
514SG-2
514-8-G2
514SG-3
514-8-G3
514-8-A3
Pre-Sample
Purge
Volume
(L)
0.5
0.5
2.5
0.5
1.5
0.5
1.5
0.5
0.5
Cumulative
Pre-Sample
Extraction
Volume (L)
0.5
0.5
2.5
1.5
4.5
1.5
6.5
2.5
2.5
Cumulative
Pre-Sample
Internal
Exchanges (-)
2.8
8.1
2.5
24.3
4.5
8.3
6.5
13.9
40.4
Sample
Volume
(L)

0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
Cumulative
Post-Sample
Extraction
Volume (L)
1.0
1.0
3.0
2.0
5.0
2.0
7.0
3.0
3.0
Table 11c. VOC and Gas Concentrations of Probe, PRT, and GVP Systems at 2.3 m Near MW514SG
Sample
Identification
GVP
514-8-A1
514-8-A2
514-8-A3
mean 514-8-A
stdev514-8-A
PRT
514-8-G1
514-8-G2
514-8-G3
mean 514-8-G
stdev514-8-G
Probe
514SG-1
514SG-2
514SG-3
mean 514SG
stdev514SG
1,1 -DCE
(ppbv)

122
120
125
122
2.5

124
127
109
120
9.6

101
103
103
102
1.2
1,1,1-TCA
(ppbv)

825
917
883
875
46.5

881
911
904
899
15.7

728
804
795
776
41.5
TCE
(ppbv)

256
291
279
275
17.8

266
283
268
272
9.3

255
247
243
248
6.1
c-1,2-DCE
(ppbv)

58
65
65
63
4.0

65
66
62
64
2.1

36
34
33
34
1.5
02
(%)

15.6
15.6
15.6
15.6
0.0

15.5
15.4
15.5
15.5
0.1

15.2
15.3
15.3
15.3
0.1
CO2
(%)

4.7
4.8
4.6
4.7
0.1

4.7
4.8
4.8
4.8
0.1

4.9
5.0
5.0
5.0
0.1
CH4
(%)

0.0
0.0
0.0
0.0
0.0

0.0
0.0
0.0
0.0
0.0

0.0
0.0
0.0
0.0
0.0
Table 12a. Computation of Internal Volumes of Sample Systems at 0.8 m Near MW523SGS

Sample  Screen   Screen   Screen  Riser   Riser    Riser    Tubing Tubing  Tubing  Internal
Method  ID      Length   Volume  ID     Length  Volume  ID     Length  Volume  Volume
        (cm)     (cm)     (cm3)    (cm)   (cm)    (cm3)    (cm)   (cm)    (cm3)    (L)
GVP
PRT
Probe
0.64
2.54
3.81
5.1
5.1
30.5
1.6
26
347
NR
NR
1.9
91
152
61
NR
NR
174
0.48
0.64
0.95
335
351
61
59.7
111.0
43.4
0.061
0.137
0.564
 NR = not relevant
                                                  50

-------
Table 12b. Computation of Pre-Sample Internal Exchanges and VOC Concentrations of Sample Systems at 0.8 m
Near MW523SGS
Sample
Method
PRT
GVP
Probe
NA = not a
Table 13
Sample
Method
GVP
PRT
Probe
NR = not r
Table 13
Near MV\
Sample
Method
PRT
GVP
Probe
ND() = not
Table 14
Sample
Method
PRT
Probe
Table 14
Near MV\
Sample
Method
PRT
Probe
ND() = nor
Table 15
Sample
Method
GVP
PRT
Sample Pre-Sample Pre-Sample Sample Post-Sample 1,1-DCE 1,1,1-TCA TCE
Identification Purge Internal Volume Extraction (ppbv) (ppbv) (ppbv)
Volume (L) Exchange (-) (L) Volume (L)
523-3-G1 0.25 1.8 0.50 0.75 ND(30) ND(2.0) ND(4.0)
523-3-A1 0.25 4.1 0.50 0.75 ND(30) 7.0 ND(5.0)
523SGS-1 2.0 3.5 0.50 2.5 ND(15) ND(3.0) 5.8
nalyzed
a. Computation of Internal Volumes of Sample Systems at 2.3 m Near MW523SGM
Screen Screen Screen Riser Riser Riser Tubing Tubing Tubing Internal
ID Length Volume ID Length Volume ID Length Volume Volume
(cm) (cm) (cm3) (cm) (cm) (cm3) (cm) (cm) (cm3) (L)
c-1,2-DCE O2 CO2 CH4
(ppbv) (%) (%) (%)
ND(25) NA NA NA
ND(25) NA NA NA
ND(25) 0.0 10.8 55.5

0.64 5.1 1.6 NR 274 NR 0.48 479 85.2 0.087
2.54 5.1 26 NR 305 NR 0.64 561 177.5 0.203
3.81 30.5 347 1.9 213 608 0.95 61 43.4 0.999
elevant
b. Computation of Pre-Sample Internal Exchanges and VOC Concentrations of Sample Systems at 2.3 m
/523SGM
Sample Pre-Sample Pre-Sample Sample Post-Sample 1,1-DCE 1,1,1-TCA TCE c-1,2-DCE O2 CO2 CH4
Identification Purge Internal Volume Extraction (ppbv) (ppbv) (ppbv) (ppbv) (%) (%) (%)
Volume (L) Exchange (-) (L) Volume (L)
523-8-G1 0.5 2.5 0.50 1.0 ND(30) 8.7 11
523-8-A1 0.5 5.8 0.50 1.0 ND(30) 4.4 7.2
523SGM-1 2.5 2.5 0.50 3.0 ND(30) 6.2 13
detected NA = not analyzed
a. Computation of Internal Volumes of Sample Systems at 3.4 m Near MW523SGD
Screen Screen Screen Riser Riser Riser Tubing Tubing Tubing Internal
ID Length Volume ID Length Volume ID Length Volume Volume
(cm) (cm) (cm3) (cm) (cm) (cm3) (cm) (cm) (cm3) (L)
2.54 5.1 26 NR 457 NR 0.64 796 252 0.278
3.81 30.5 347 1.9 305 868 0.95 61 43.4 1.259
ND(25) NA NA NA
ND(25) NA NA NA
ND(25) 0.0 11.2 26.4

b. Computation of Pre-Sample Internal Exchanges and VOC Concentrations of Sample Systems at 3.4 m
/523SGD
Sample Pre-Sample Pre-Sample Sample Post-Sample 1,1-DCE 1,1,1-TCA TCE c-1,2-DCE O2 CO2 CH4
Identification Purge Internal Volume Extraction (ppbv) (ppbv) (ppbv) (ppbv) (%) (%) (%)
Volume (L) Exchange (-) (L) Volume (L)
523-1 1-G1 0.5 1.8 0.5 1.0 ND(30) 19 15
523SGD-1 2.5 2.0 0.5 3.0 ND(30) 11 13
i-detect NA = not analyzed
a. Computation of Internal Volumes of Sample Systems at 0.91 m Near MW525SG
Screen Screen Screen Riser Riser Riser Tubing Tubing Tubing Internal
ID Length Volume ID Length Volume ID Length Volume Volume
(cm) (cm) (cm3) (cm) (cm) (cm3) (cm) (cm) (cm3) (L)
ND(25) NA NA NA
ND(25) 0.0 12.2 9.6

0.64 5.1 1.6 NA 91 NR 0.48 152 27.1 0.029
2.54 5.1 26 NA 152 NR 0.64 332 105.2 0.131
NR = not relevant
                                                51

-------
Table 15b. Computation of Pre-Sample Internal Exchanges of Sample Systems at 0.91 m Near MW525SG
Sample
Method


PRT
GVP
PRT
GVP
PRT
GVP
Sample
Identification


526-3-G1
525-3-A1
525-3-G2
525-3-A2
525-3-G3
525-3-A3
Pre-Sample
Purge
Volume
(L)
0.25
0.25
0.25
0.25
0.25
0.25
Cumulative
Pre-Sample
Extraction
Volume (L)
0.25
0.25
1.00
1.00
1.75
1.75
Cumulative
Pre-Sample
Internal
Exchanges (-)
1.9
8.7
7.6
34.8
13.4
60.9
Sample
Volume
(L)

0.50
0.50
0.50
0.50
0.50
0.50
Cumulative
Post-Sample
Extraction
Volume (L)
0.75
0.75
1.50
1.50
2.25
2.25
Table 15c. Summary of VOC Concentrations in PRT and GVP Systems at 0.91 m near MW525SG
Sample
Identification
GVP
525-3-A1
525-3-A2
525-3-A3
mean 525-3-A
stdev 525-3-A
PRT
525-3-G1
525-3-G2
525-3-G3
mean 525-3-G
stdev 525-3-G
1,1 -DCE
(ppbv)

148
151
151
150
1.7

222
221
219
221
1.5
1,1,1-TCA
(ppbv)

303
312
289
301
11.6

452
444
449
448
4.0
TCE
(ppbv)

52
58
58
56
3.5

93
97
95
95
2.0
c-1,2-DCE
(ppbv)

8.0
8.5
8.5
8.3
0.3

17
17
17
17
0.0
02
(%)

NA
NA
NA
NA
NA

18.2
NA
18.2
18.2
0.0
C02
(%)

NA
NA
NA
NA
NA

2.0
NA
1.8
1.9
0.1
CH4
(%)

NA
NA
NA
NA
NA

0.0
NA
0.0
0.0
0.0
NA = not analyzed




Table 16a. Computation of Internal Volumes of Sample Systems at 2.3 m Near MW525SG
Sample
Method
GVP
PRT
Probe
Screen
ID
(cm)
0.64
2.54
3.81
Screen
Length
(cm)
5.1
5.1
30.5
Screen
Volume
(cm3)
1.6
26
347
Riser
ID
(cm)
NA
NA
1.9
Riser
Length
(cm)
274
305
213
Riser
Volume
(cm3)
NR
NR
608
Tubing
ID
(cm)
0.48
0.64
0.95
Tubing
Length
(cm)
457
457
61
Tubing
Volume
(cm3)
81.4
145
0.0
Internal
Volume
(L)
0.083
0.170
0.955
NR = not relevant
Table 16b. Computation of Pre-Sample Internal Exchanges of Sample Systems at 2.3 m Near MW525SG
Sample
Method


PRT
GVP
Probe
GVP
Probe
PRT
Probe
PRT
GVP
Sample
Identification


525-8-G1
525-8-A1
525SG-1
525-8-A2
525SG-2
525-8-G2
525SG-3
525-8-G3
525-8-A3
Pre-Sample
Purge
Volume
(L)
0.5
0.5
2.5
0.5
1.5
0.5
1.5
0.5
0.5
Cumulative
Pre-Sample
Extraction
Volume (L)
0.5
0.5
2.5
1.5
4.5
1.5
6.5
2.5
2.5
Cumulative
Pre-Sample
Internal
Exchanges (-)
2.9
6.0
2.6
18.1
4.7
8.8
6.8
14.7
30.1
Sample
Volume
(L)

0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
Cumulative
Post-Sample
Extraction
Volume (L)
1.0
1.0
3.0
2.0
5.0
2.0
7.0
3.0
3.0
                                               52

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Table 16c. Summary of VOC and Gas Concentrations in PRT and GVP Systems at 2.3 m Near MW525SG
Sample
Identification
GVP
525-8-A1
525-8-A2
525-8-A3
mean 525-8-A
stdev 525-8-A
PRT
525-8-G1
525-8-G2
525-8-G3
mean 525-8-G
stdev 525-8-G
Probe
525SG-1
525SG-2
525SG-3
mean 525SG
stdev 525SG
1,1-DCE
(ppbv)

33
25
35
31
5.3

256
254
254
255
1.2

267
272
275
271
4.0
1,1,1-TCA
(ppbv)

55
41
55
50
8.1

450
451
452
451
1.0

389
389
400
393
6.4
TCE
(ppbv)

12
8.1
12
11
2.3

101
101
100
101
0.6

85
85
92
87
4.0
c-1,2-DCE
(ppbv)

ND(5.0)
ND(5.0)
ND(5.0)
ND(5.0)
IND

22
22
22
22
0.0

21
22
23
22
1.0
02
(%)

19.9
20.1
20.0
20.0
0.1

18.2
18.2
18.4
18.3
0.1

18.4
18.4
18.4
18.4
0.0
CO2
(%)

0.3
0.2
0.3
0.3
0.1

1.9
1.9
2.0
1.9
0.1

1.8
1.8
1.8
1.8
0.0
CH4
(%)

0.0
0.0
0.0
0.0
0.0

0.0
0.0
0.0
0.0
0.0

0.0
0.0
0.0
0.0
0.0
Table 17a. Computation of Internal Volumes of Sample Systems at 0.91 m Near MW526SGS
Sample
Method
GVP
PRT
Probe
Screen
ID
(cm)
0.64
2.54
3.81
Screen
Length
(cm)
5.1
5.1
30.5
Screen
Volume
(cm3)
1.6
26
347
Riser
ID
(cm)
NA
NA
1.9
Riser
Length
(cm)
91
152
61
Riser
Volume
(cm3)
NA
NA
174
Tubing
ID
(cm)
0.48
0.64
0.95
Tubing
Length
(cm)
152
320
61
Tubing
Volume
(cm3)
27.1
101.3
43.4
Internal
Volume
(L)
0.029
0.127
0.564
NR = not relevant
Table 17b. Computation of Pre-Sample Internal Exchanges of Sample Systems at 0.91 m Near MW526SGS
Sample
Method


PRT
GVP
Probe
GVP
Probe
PRT
Probe
PRT
GVP
Sample
Identification


526-3-G1
526-3-A1
526SGS-1
526-3-A2
526SGS-2
526-3-G2
526SGS-3
526-3-G3
526-3-A3
Pre-Sample
Purge
Volume
(L)
0.25
0.25
2.0
0.25
1.2
0.25
1.2
0.25
0.25
Cumulative
Pre-Sample
Extraction
Volume (L)
0.25
0.25
2.0
1.00
3.7
1.00
5.4
1.75
1.75
Cumulative
Pre-Sample
Internal
Exchanges (-)
2.0
8.7
3.5
34.8
6.6
7.9
9.6
13.8
60.9
Sample
Volume
(L)

0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
Cumulative
Post-Sample
Extraction
Volume (L)
0.75
0.75
2.5
1.50
4.2
1.50
5.9
2.25
2.25
                                               53

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Table 17c. Summary of VOC and Gas Concentrations in PRT and GVP Systems at 0.91 m Near MW526SG
Sample
Identification
GVP
526-3-A1
526-3-A2
526-3-A3
mean 526-3-A
stdev 526-3-A
PRT
526-3-G1
526-3-G2
526-3-G3
mean 526-3-G
stdev 526-3-G
Probe
526SGS-1
526SGS-2
526SGS-3
mean 526SGS
stdev 526SGS
1,1 -DCE
(ppbv)

11
10
6.7
9.2
2.3

6.2
3.9
2.8
4.3
1.7

25
25
25
25
0.0
1,1,1-TCA
(ppbv)

72
69
64
68
4.0

55
55
55
55
0.0

55
54
55
55
0.6
TCE
(ppbv)

22
23
21
22
1.0

12
12
12
12
0.0

21
22
22
22
0.6
c-1,2-DCE
(ppbv)

ND(4.0)
ND(4.0)
ND(4.0)
ND(4.0)
IND

ND(4.0)
ND(4.0)
ND(4.0)
ND(4.0)
IND

ND(3.0)
ND(3.0)
ND(3.0)
ND(3.0)
IND
02
(%)

18.2
18.5
18.4
18.4
0.2

18.7
18.7
18.9
18.8
0.1

19.0
18.8
18.8
18.9
0.1
CO2
(%)

1.3
1.2
1.2
1.2
0.1

1.1
1.1
1.1
1.1
0.0

1.0
1.0
1.0
1.0
0.0
CH4
(%)

0.0
0.0
0.0
0.0
0.0

0.0
0.0
0.0
0.0
0.0

0.0
0.0
0.0
0.0
0.0
ND() =not detected
IND = indeterminate
Table 18a. Computation of Internal Volumes of Sample Systems at 0.91 m Near MW526SGM
Sample
Method

GVP
PRT
Screen
ID
(cm)
0.64
2.54
Screen
Length
(cm)
5.1
5.1
Screen
Volume
(cm3)
1.6
26
Riser
ID
(cm)
NR
NR
Riser
Length
(cm)
91
152
Riser
Volume
(cm3)
NA
NA
Tubing
ID
(cm)
0.48
0.64
Tubing
Length
(cm)
305
308
Tubing
Volume
(cm3)
54.3
97.4
Internal
Volume
(L)
0.056
0.123
NR = not relevant
Table 18b. Computation of Pre-Sample Internal Exchanges of Sample Systems at 0.91 m Near MW526SGM
Sample
Method


GVP
PRT
GVP
PRT
GVP
PRT
Sample
Identification


526-3-A1 R
526-3-G1 R
526-3-A2R
526-3-G2R
526-3-A3R
526-3-G3R
Pre-Sample
Purge
Volume
(L)
0.25
0.25
0.25
0.25
0.25
0.25
Cumulative
Pre-Sample
Extraction
Volume (L)
0.25
0.25
1.00
1.00
1.75
1.75
Cumulative
Pre-Sample
Internal
Exchanges (-)
4.5
2.0
17.9
8.1
31.3
14.2
Sample
Volume
(L)

0.5
0.5
0.5
0.5
0.5
0.5
Cumulative
Post-Sample
Extraction
Volume (L)
0.75
0.75
1.50
1.50
2.25
2.25
                                                54

-------
Table 18c.  Summary of VOC and Gas Concentrations in PRT and GVP Systems at 0.91 m Near MW526SGM
Sample
Identification
GVP
526-3-A1 R
526-3-A2R
526-3-A3R
mean 525-3-AR
stdev 525-3-AR
PRT
526-3-G1R
526-3-G2R
526-3-G3R
mean 526-3-GR
stdev 526-3-GR
1,1 -DCE
(ppbv)

6.4
6.4
8.6
7.1
1.3

10
11
12
11
1.0
ND( )-not detected






1,1,1-TCA
(ppbv)

29
28
28
28
0.6

49
50
50
50
0.6
TCE
(ppbv)

8.1
8.1
8.1
8.1
0.0

26
27
28
27
1.0
c-1,2-DCE
02
CO2
CH4

(ppbv) (%) (%) (%)

ND(3
ND(3
ND(3
ND(4
IND

ND(4
ND(4
ND(4
ND(4
IND

0)
0)
0)
0)

0)
0)
0)
0)
NM - not measured
Table 19a. Computation of Internal Volumes ol
Sample
Method
GVP
PRT
Probe
Screen Screen
D Length
(cm) (cm)
0.64 5.1
2.54 5.1
3.81 30.5
NR = not relevant




Screen
Volume
(cm3)
1.6
26
347

Riser
ID
(cm)
NR
NR
1.9

Table 19b. Computation of Pre-Sample
Sample
Method
PRT
GVP
Probe
GVP
Probe
PRT
Probe
PRT
GVP
Sample
Identification
526-8-G1
526-8-A1
526SGM-1
526-8-A2
526SGM-2
526-8-G2
526SGM-3
526-8-G3
526-8-A3
Pre-Sample
Purge
Volume
(L)
0
0
2
0
1
0
1
0
0
5
5
5
5
5
5
5
5
5
Riser
Length
(cm)
274
305
213


NM
NM
NM
NM
NM

NM
NM
NM
NM
NM
IND

NM
NM
NM
NM
NM

NM
NM
NM
NM
NM

NM
NM
NM
NM
NM

NM
NM
NM
NM
NM



- indeterminate
Sample Systems at 2.3
Riser
Volume
(cm3)
NA
NA
608





Tubing Tubing
ID Length
(cm) (cm)
0.48
0.64
0.95

Internal Exchanges of
Cumulative
Pre-Sample
Extraction
Volume (L)
0.5
0.5
2.5
1.5
4.5
1.5
6.5
2.5
2.5









Cumulative
Pre-Sample
Internal
Exchanges (-)
3.0
7.4
2.5
22.3
4.5
9.0
6.5
14.9
37.2


















369
448
61

m Near MW526SGM
Tubing Internal
Volume Volume
(cm3) (L)
65.7 0.067
142 0.168
43.4 0.999

Sample Systems at 2.3 m Near MW526SGM
Sample
Volume
(L)
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
Cumulative
Post-Sample
Extraction
Volume (L)
1.0
1.0
3.0
2.0
5.0
2.0
7.0
3.0
3.0
                                             55

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Table 19c. Summary of VOC and Gas Concentrations in Sample Systems at 2.3 m Near MW526SGM
Sample
Identification
GVP
526-8-A1
526-8-A2
526-8-A3
mean 526-8-A
stdev 526-8-A
PRT
526-8-G1
526-8-G2
526-8-G3
mean 526-8-G
stdev 526-8-G
Probe
526SGM-1
526SGM-2
526SGM-3
mean 526SGM
stdev 526SGM
1,1-DCE
(ppbv)

62
61
61
61
0.6

74
80
82
79
4.2

56
56
57
56
0.6
1,1,1-TCA
(ppbv)

80
79
77
79
1.5

101
104
102
102
1.5

72
73
72
72
0.6
TCE
(ppbv)

27
27
26
27
0.6

32
34
33
33
1.0

26
26
23
25
1.7
c-1,2-DCE
(ppbv)

7.9
7.8
7.9
7.9
0.1

11
12
12
12
0.6

8.7
8.2
8.4
8.4
0.3
02
(%)

19.3
19.2
19.3
19.3
0.1

19.3
19.2
19.3
19.3
0.1

19.3
19.3
19.3
19.3
0.0
CO2
(%)

0.8
0.8
0.8
0.8
0.0

0.7
0.7
0.7
0.7
0.0

0.9
0.9
0.9
0.9
0.0
CH4
(%)

0.0
0.0
0.0
0.0
0.0

0.0
0.0
0.0
0.0
0.0

0.0
0.0
0.0
0.0
0.0
Table 20a. Computation of Internal Volumes of Sample Systems at 3.2 m Near MW526SGD
Sample
Method

PRT
Probe
Screen
ID
(cm)
2.54
3.81
Screen
Length
(cm)
5.1
30.5
Screen
Volume
(cm3)
26
347
Riser
ID
(cm)
NR
1.9
Riser
Length
(cm)
457
305
Riser
Volume
(cm3)
NR
868
Tubing
ID
(cm)
0.64
0.95
Tubing
Length
(cm)
610
61
Tubing
Volume
(cm3)
193
43.4
Internal
Volume
(L)
0.219
1.259
NR = not relevant
Table 20b. Computation of Pre-Sample Internal Exchanges of Sample Systems at 3.2 m Near MW526SGD
Sample
Method


PRT
Probe
PRT
Probe
PRT
Probe
Sample
Identification


526-11-G1
526SGD-1
526-11-G2
526SGD-2
526D-11-G3
526SGD-3
Pre-Sample
Purge
Volume
(L)
0.75
3.0
0.5
1.8
0.5
1.8
Cumulative
Pre-Sample
Extraction
Volume (L)
0.75
3.0
1.75
5.3
2.8
7.6
Cumulative
Pre-Sample
Internal
Exchanges (-)
3.4
2.4
8.0
4.2
12.6
6.0
Sample
Volume
(L)

0.5
0.5
0.5
0.5
0.5
0.5
Cumulative
Post-Sample
Extraction
Volume (L)
1.3
3.5
2.3
5.8
3.3
8.1
                                               56

-------
Table 20c.  Summary of VOC and Gas Concentrations in Sample Systems at 3.2 m Near MW526SGD
Sample
Identification
PRT
526-1 1-G1
526-1 1-G2
526-1 1-G3
mean 526-1 1-G
stdev 526-1 1-G
Probe
526SGD-1
526SGD-2
526SGD-3
mean 526SGD
stdev 526SGD
1,1 -DCE
(ppbv)

85
85
92
87
4.0

68
68
66
67
1.2
1,1,1-TCA
(ppbv)

120
121
124
122
2.1

87
87
87
87
0.0
TCE
(ppbv)

38
40
45
41
3.6

32
32
33
32
0.6
c-1,2-DCE
(ppbv)

16
18
19
18
1.5

14
14
14
14
0.0
02
(%)

18.9
19.0
19.1
19.0
0.1

19.2
19.2
19.2
19.2
0.0
CO2
(%)

0.8
0.8
0.9
0.8
0.1

0.9
0.9
0.9
0.9
0.0
CH4
(%)

0.0
0.0
0.0
0.0
0.0

0.0
0.0
0.0
0.0
0.0
                                             57

-------

-------
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