BPA-542- F-18-002
April 2018
Water Forum Issue Paper
nปe=ME U ited States
ฆฆ M Environmental Protec ion
W U 9 * Agency
In Situ Treatment Performance Monitoring:
Issues and Best Practices
Index
1. INTRODUCTION 1
2. ISSUES RELATED TO MONITORING WELLS 2
2.1 Biofouling of Monitoring Wells .......2
2.2 Metal Precipitation on Monitoring Well Screens ..3
2.3 Reactions with Weil Materials and Equipment ....4
3. REPRESENTATIVENESS OF MONITORING
WELLS... ..6
3.1 Displacement of Contaminants During
Amendment Injection 6
3.2 Use of Injection Wells for Monitoring 7
3.3 Preferential Accumulation of Amendment in
Monitoring Wells 8
4. POST-SAMPLING ARTIFACTS 9
4.1 Post-Sampling Transformation of Contaminants. 9
4.2 Loss of Volatiles when Sampling High-
Temperature Groundwater 10
5. REFERENCES 10
6. NOTICE AND DISCLAIMER 12
7. ACKNOWLEDGMENTS 12
APPENDIX: Quick Reference Table: In Situ
Treatment Monitoring Issues and Best Practices
for Monitoring, Prevention and Mitigation 13
1, INTRODUCTION
The utility of monitoring wells for performance or
attainment monitoring is based on the premise that
contaminant concentrations measured in the wells are
representative of aquifer conditions. However, during in
situ treatment, various biogeochemical and hydrogeolog-
ical processes and sampling and analysis procedures may
affect the representativeness of the monitoring well and
sample quality, which may not be adequately considered
in current remediation practice.
A properly designed monitoring network that anticipates
the distribution of amendments after injection would
minimize impacts to monitoring wells. However, predicting
amendment distribution prior to injection is challenging
such that impacts to monitoring wells are likely.
The purpose of this issue paper is to:
describe how in situ treatment technologies may impact
sampling and analysis results used to monitor treatment
performance; and
provide best practices to identify and mitigate issues
that may affect sampling or analysis.
This paper discusses eight potential sampling or analytical
issues associated with groundwater monitoring at sites
where in situ treatment technologies are applied. These
issues are grouped under three topic areas:
Issues related to monitoring wells (Section 2).
Representativeness of monitoring wells (Section 3).
Post-sampling artifacts (Section 4).
The paper presents issues that pertain to collecting water
samples directly from a monitoring well and does not
discuss the use of other sampling techniques, such as
passive diffusion bags or direct push groundwater sampling.
The in situ technologies addressed in this paper are listed
in Table 1.
This issue paper does not address in situ technology
selection, design or implementation, or effects resulting
from combined remedies.
A quick-reference table in the Appendix can help identify
potential sampling issues related to the six technologies
and the best practices for monitoring or preventing and
mitigating these issues.
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Table 1. In Situ Groundwater Treatment Technologies Addressed
Technology
Acronym
General Resources
Activated Carbon-Based Injectate
CBI
Remediatina Petroleum Contaminants with Activated
Carbon-Based Iniectates
Enhanced In Situ Bioremediation
EISB
CLU-IN Bioremediation Overview: ITRC Technical and
Reaulatorv Reauirements for Enhanced In Situ Bioreme-
diation of Chlorinated Solvents in Groundwater
In Situ Chemical Oxidation
ISCO
CLU-IN In Situ Oxidation Overview: ITRC Technical and
Reaulatorv Guidance for In Situ Chemical Oxidation of
Contaminated Soil and Groundwater
In Situ Chemical Reduction
ISCR
CLU-IN In Situ Chemical Reduction technoloav area
In Situ Thermal Treatment
ISTT
CLU-IN Thermal Treatment: In Situ Overview: In Situ Thermal
Treatment of Chlorinated Solvents
In Situ Solidification
ISS
CLU-IN Solidification Overview: ITRC Develooment of
Performance Soecifications for Solidification/Stabilization
2. ISSUES RELATED TO MONITORING WELLS
2.1 Biofouling of Monitoring Wells
2.1.1 Overview
Technologies Affected
EISB
ISCO
CBI
ISCR
ISTT
ISS
Mechanism The addition of nutrients and amendments
during EISB can create conditions favoring microbial
growth in the vicinity of well screens and filter packs
(ESTCP, 2005). Biofouling of groundwater monitoring
wells occurs when enough biomass forms so that water
in the well no longer represents the aquifer (Smith and
Comeskey, 2009).
Impact Biofouling of monitoring wells deposits
slimes and excretions, sometimes called a biofilm, on
well screens, which reduces groundwater flow into
monitoring wells. Biofilms may appear as foams, pastes
or gummy/slimy accumulations on well screens and
sampling equipment. Figure 1 shows how a biofilm can
form on an injection well screen.
Approximately 17 of 20 sites EISB surveyed reported
some level of biofouling in injection wells, with most
reporting at least a significant loss of injection well
efficiency (ESTCP, 2005). Blocked monitoring wells and
filter packs hinder sample collection or result in stagnant
water in a monitoring well. Biofouling of well screens
may also modify the flow of groundwater around a
monitoring well and result in samples that may not be
representative of the well screen interval. In addition,
biofilms may trap and degrade contaminants reducing
concentrations in the well (Smith and Comeskey, 2009).
Monitoring for Biofouling Monitoring changes
in well hydraulic performance, such as reduced well
production or excessive water level drawdown and
physiochemical water quality parameters (e.g., dissolved
oxygen [DO], oxidation-reduction potential [ORP] and
specific conductivity), can provide an indication of
biofouling Inspecting wells, submerged equipment and
purge water for biofouling deposits during sampling
can help diagnose biofouling. Biofouling also may be
observed directly using borehole video cameras. Review
of the well purging history after each sampling event to
identify reductions in purge rate can help identify that
biofouling is occurring. Conducting slug or pumping
tests periodically can provide a quantitative measure
of changes over time (Barcelona et al., 1985). Limiting
the potential impacts of biofouling depends on regular
monitoring for these changes and promptly mitigating
any problems that arise (Smith, 1995).
2.1.2 Prevention and Mitigation
Prevention of biofouling in wells used to monitor EISB
performance is best achieved by understanding site
hydrogeology and contaminant distribution. This site
characterization information is necessary for anticipat-
ing amendment distribution after injection and limiting
amendment volumes to meet the site-specific electron
acceptor demand (ESTCP, 2010). With this informa-
tion, monitoring wells can be selected or installed so
2 Ground Water Forum Issue Paper
In Situ Treatment Performance Monitoring
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Orgontam
POftfฃ]*l
1 Microorganisms attach to well screen via physical and chemical
interactions
2. Attached microorganisms metabolize, nutrients to synthesize and
excrete biofilm matrix
3. Attached microorganisms multiply and obstruct screen
Figure 1. Schematic of Biofilm Formation Adapted from ESTCP, 2005.
that they are not anticipated to be influenced by the
amendments or biological growth. Given that biofoul-
ing often is observed during EISB, it is recommended
that remedial plans include well monitoring and
maintenance to identify when biofouling is occurring
and have agreed-upon procedures in place for mitiga-
tion. Mitigation procedures include both physical and
chemical methods. Physical mitigation typically includes
over-pumping, surging, jetting, or by injecting air in the
casing (or vibratory methods, metal specific only). Manual
brushing of well materials, followed by well redevelop-
ment, can also remove material from the well screen and
casing. However, brushing is not effective for cleaning
filter packs (ESTCP, 2005, Smith and Comeskey, 2009).
Chemical treatment with solutions of hypochlorite,
hydrogen peroxide, chlorine and non-oxidizing biocides
can mitigate biofouling by disinfecting the well. Chemicals
are added to the well, left for varying treatment times
depending on the chemical, and then surged within the
well and pumped out (ESTCP, 2005). The use of chlorine
will increase the concentration of chloride in groundwa-
ter, which should be considered if monitoring chloride
to indicate the degradation of chlorinated compounds.
Chemical treatment can result in byproducts. While these
byproducts are not likely to affect existing contaminants,
they may be toxic and harmful and will need to be handled
carefully prior to disposal. It is important to review the
available chemical treatment options to determine which
is best suited for a specific site (Smith, 2011 and ESTCP,
2005). Bacteria usually regrow on the well materials in a
few weeks or months after well treatment. Deeper well
screens require more resources to mitigate biofouling.
Mitigation of biofouling can be a significant operation
and maintenance cost at sites using EISB.
Prevention and Mitigation
Limit amendment volumes to meet the site-spe
cific electron acceptor demand.
Apply cleaning processes.
Physical processes: Surging, over-pumping,
jetting, air injection.
Chemical processes: Hypochlorite, hydrogen
peroxide, chlorine, non-oxidizing biocides.
2.2 Metal Precipitation on Monitoring Well Screens
2.2.1 Overview
Technologies Affected
EISB
ISCO
CBI
ISCR
ISTT
ISS
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occurring. Conducting slug or pumping tests periodically
can proyide a quantitative measure of changes oyer
time (Barcelona et al., 1985). In addition, regular visual
inspection of wells, submerged equipment and purge
water is important to monitor for the presence of metal
precipitates (Smith, 1995).
2,2,2 Prevention and Mitigation
Metal precipitation, can be anticipated through the
completion of pilot-scale treatability studies (Huling
and Pivetz, 2006). Precipitation is more likely to
occur in water that is high in calcium and low in
manganese. Activities that cause redox and pH shifts
toward oxidizing and alkaline conditions may promote
precipitation of iron, manganese and carbonates
(Smith and Comeskey, 2009). Geochemical modeling
with free software (e.g., Phreeqc or Minteq) can also
predict or assess the impact of an amendment on metal
precipitation. Mitigation for metal precipitate fouling
of monitoring wells include physical and chemical
methods. The physical methods are identical to those
discussed in Section 2.1.2. In addition to the chemical
methods discussed in Section 2.1.2., treatment
with acid solutions can remove metal precipitates.
Sulfamic acid can be effective for carbamate scales,
and hydrochloric acid (HC1) for metal oxides (Smith
and Comeskey, 2009). Glycolic acid, polymaleic acid
and citric acid have also been used to rehabilitate wells
impaired by metals precipitation. Chemicals are added
to the well, left for varying treatment times depend-
ing on the chemical, and then surged or mixed within
the well and pumped out (ESTCP, 2005). They may
also be used in combination with jetting, surging or
other physical methods (Smith and Comeskey, 2009).
Prevention and Mitigation
Complete pilot-scale treatability study and
perform geochemical modeling to anticipate
metal precipitation.
Apply cleaning processes.
Physical Processes: Surging, over pumping,
jetting, air injection, sonic and vibratory
methods.
Chemical Processes: Acid cleaning.
Mitigation may require more resources as the depth
of the well screen increases. The use of chlorine will
increase the concentration of chloride in groundwater,
which should be considered if monitoring chloride to
indicate the degradation of chlorinated compounds.
Chemical treatment can result in byproducts or oxidiz-
ing conditions. While these byproducts are not likely
to affect existing contaminants, they may be toxic
and harmtul and will need to be handled carefully.
In addition, they may have special disposal require-
ments. It is important to review the available chemical
treatment options to determine which is best suited
for a specific site (Smith, 2011).
Figure 2. Well Screen Plugged with Metal Precipitates (Scherer,
2013).
2.3 Reactions with Well Materials and Equipment
2,3,1 Oven/lew
Technologies Affected
EISB
ISCO
CBI
ISCR
isrr
ISS
s
s
Mechanism - Well casing material and sampling
equipment may be incompatible with contaminants,
amendments and heat. High or low pH conditions
resulting from the injection of strong oxidants and other
reagents may corrode metal-based materials (Barcelona
etal., 1985; Llopis, 1991). Further, oxidants may deteri-
orate piping and plumbing materials unless specialized
Oxidant-resistant materials are used (Huling and Pivetz,
2006), and materials may leach, sorb or react with
contaminants (Llopis, 1991). Excessive temperatures
may deteriorate materials such as PVC.
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Table 2. Potential Reactions with Materials
Material
Potential Reactions with Materials
Teflonฎ
PFOA may leach.
Stainless Steel
Corrosion can release iron and
chromium.
May leach metals under anoxic
conditions.
May adsorb minor amounts of
trace-level organic compounds.
Low-Carbon,
Galvanized and
Carbon Steel
Corrosion can release iron, manga-
nese, zinc and cadmium.
Weathered steel may present active
adsorption sites for organics and
inorganics.
PVC
May release organic compounds
from degradation.
May release tin or antimony.
May adsorb trace-level organic
compounds.
May melt or compromise well casing
and screen.
Flexible Polymers
May adsorb chlorinated volatile
organic compounds.
May adsorb trace-level organic
compounds.
Adapted from Barcelona et at.. 1985; McCaulou, Jeweff and
Hulhg, 1995; Smith andComeskey, 2009; and Llopis, 1991.
Impact Corrosion and degradation of steel materi-
als can lead to leaching of metals (Table 2) and
increased metal concentrations in samples. Elevated
temperatures may damage materials (e.g., melt and
deform plastic, and facilitate corrosion of stainless
steel screens), which can inhibit sample collection.
Contaminant sorption to or reaction with materials can
result in a false trend of contaminant concentrations
(Barcelona et al., 1985). Fenton and related reactions
are exothermic, resulting in heat release and elevated
temperatures during in situ Fenton oxidation. Heat
accumulation near the injection well is common due
to rapid decomposition of hydrogen peroxide and the
slow dissipation of heat. Injection wells and nearby
monitoring wells constructed of PVC have melted
during in situ Fenton oxidation. Since the melting point
of PVC is 200 ฐC, this suggests that very high localized
temperatures have occurred under some conditions
(Huling and Pivetz, 2006).
Monitoring for Reactions with Well Materials
and Equipment Regular inspection of wells and
equipment for signs of corrosion, degradation or
discoloration may reveal incompatibility. Monitoring
subsurface conditions such as pH, dissolved solids,
temperature and redox potential can also help detect
conditions that might promote corrosion, and warrant
further inspection. Reduction in well production may
indicate corrosion has occurred. Review of the well
purging history after each sampling event to identify
reductions in purge rate can help identify corrosion
and degradation. Conducting slug or pumping tests
periodically can provide a quantitative measure of
changes over time (Barcelona et al., 1985). Wells can
also be checked using wellbore video cameras to ensure
that they are physically intact and capable of providing
water samples as intended. Monitoring for increases
in metals concentrations can help identify leaching
of metals.
2.3.2 Prevention and Mitigation
Select materials that are compatible with the amendments
and target contaminants (Huling & Pivetz, 2006) and
will resist changes in subsurface conditions that could
cause corrosion or degradation. Decisions about which
materials to use can be based on a number of factors,
including structural integrity, long-term durability,
minimization of the secondary effects of sorption or
leaching, and anticipated temperatures (Barcelona et al.,
1985). Cathodic protection may reduce corrosion of
steel wells (Smith and Comesky, 2009). Also, Teflonฎ-
coated well and sampling materials may be a source of
perfluorooctanoic acid (PFOA) in groundwater well
samples (Begley et al., 2005).
Choosing appropriate filter pack material can also
help mitigate well degradation. Filter pack materi-
als should be inert, such as glass or ceramic beads,
Prevention and Mitigation
Select compatible materials.
Use cathodic protection for metal wells and
equipment.
Choose inert filter pack material.
Replace, restore or line corroded components.
In Situ Treatment Performance Monitoring
Ground Water Forum Issue Paper 5
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silica sand, or gravel (preferably quartz sand) that has
been cleaned (Barcelona et al., 1985). If corrosion or
degradation occurs, wells may be restored by adding
cathodic protection, replacing the well or corroded
parts, or lining corroded parts with a more compatible
material (Smith and Comeskey, 2009) . Monitoring wells
damaged by elevated temperatures may require repair
or replacement.
3, REPRESENTATIVENESS OF MONITORING WELLS
3.1 Displacement of Contaminants During
Amendment Injection
3,1,1 Overview
Technologies Affected
EISB
ISCO
CBI
ISCR
ISTT
ISS
/
MechanismThe injection of large volumes of amendment
solution can potentially displace contaminated water to
regions outside the treatment zone (Payne ct al., 2008 and
Huling and Pivetz, 2006). Displacement of contaminants
can potentially occur when amendments are injected in
large volumes or reactions of amendments produce large
volumes of gas in the subsurface, (e.g., Fenton reagents
for ISCO). In addition, increasing subsurface temperature
during in situ Fenton oxidation will increase contaminant
mobility and cause groundwater to volatilize and expand
potentially displacing contaminants. Contaminants may
move downgradient or be displaced along preferential
pathways of groundwater flow.
Impact If contaminants are displaced away from the
injection zone they could spread or move beyond the
treatment zone (Figure 3). Displacement could spread
contamination to areas that were previously not contam-
inated. Displacement may also affect the concentration
of contaminants in monitoring wells. Changes in concen-
trations may represent the movement of contaminants
rather than treatment and lead to inaccurate evaluation
of treatment performance. The impact of displacement
would be more significant where flowpaths are narrow,
such as fractures in bedrock or thin sand lenses in a clay
formation (Simpkin et al., 2011).
Monitoring for Displacement of Contaminants -
Decreasing concentrations of contaminants in monitor-
ing wells adjacent to an injection point coupled with
Figure 3. Model of Displacement of Contamination. The pneumat-
ic pressure from injection of oxidant (blue) results in mounding and
displacement of groundwater and potential displacement of
contaminants (orange) and DNAPL (red) away from the injection
point. Adapted from Huling and Pivetz, 2006.
increasing contaminant concentration in distal wells can
indicate potential movement of contaminants outside
the treatment zone. If displacement of contaminants is
suspected, then the wells should also be monitored for
amendments. If a well is used for injection, there are
issues associated with its use to monitor performance
(See Section 3,2 Use of Injection Wells for Monitoring}),
3.1.2 Prevention and Mitigation
To assess the likelihood of displacement, the pore
volume of the permeable formation can be estimated
and compared with the injection volume. If this evalua-
tion shows that a large fraction of the pore volume will
be occupied or a large volume of liquid is being injected,
then prevention and mitigation measures may be
necessary. However, in general, significant displacement
of contaminant mass is not expected during amendment
injection (Simpkin et al., 2011 and Payne et al., 2008).
If displacement is likely, then prevention strategies
such as groundwater recirculation or outside-m delivery
should be considered. Groundwater recirculation, where
groundwater is extracted mixed with amendments
and reinjected, minimizes the potential for displac-
ing contaminants (NAVFAC, 2013 and Borden et al.,
2008). For example, the five-spot pattern consisting of
a central permanganate injection well surrounded by
four extraction wells achieved a 97% decrease in trichlo-
roethene concentrations (Lowe et al., 2002). However,
6 Ground Water Forum Issue Paper
In Situ Treatment Performance Monitoring
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Prevention and Mitigation
Consider groundwater recirculation,
Consider outside-in delivery,
Treat areas contaminated by displacement,
Technologies Affected
EISB
ISCO
CBI
ISCR
ISTT
ISS
/
Mechanism After injection, amendments will likely
remain in and near the injection well (Figure 4).
Impact Samples collected from injection wells may
not be representative of the site as a whole because
optimal treatment performance will likely occur near the
injection well (Huling and Pivetz, 2006). Contaminant
concentrations in an injection well may also be biased
due to displacement of contaminants by the injected
amendments (See Section 3.1.).
3.2.2 Prevention and Mitigation
Remedy performance monitoring is best achieved by
having a thorough understanding of site hydrogeology
and contaminant distribution. This site characterization
information is necessary for anticipating amendment
distribution after injection and determining if an
recirculation systems have limitations where they may
require an underground injection permit, have higher
capital costs, and can be subject to fouling of injection
wells (NAVFAC, 2013 and Borden et al., 2008). Using an
outside-in delivery approach for amendment injections
could minimize the impact from the lateral displacement
of contaminants within a treatment area. With this
method, injection points are located surrounding the
contaminated area and amendments are injected from
the outside (Huling and Pivetz, 2006). If monitoring
indicates that contaminants have migrated outside the
treatment zone, additional treatment and monitoring
may be needed in the newly contaminated area. Mitiga-
tion of displaced contamination may involve expanding
the treatment zone and installing additional monitoring
wells if necessary.
3.2 Use of Injection Wells for Monitoring
3.2.1 Overview
Ground Surface
Monitoring Wells
Water Table
T
Zone of
Residual NAPL
Metering Pump
Injection Wells
Groundwater Flow
Flow
Amendment
or
men! '
Monitoring Wells
Figure 4. Use of Separate Injection and Monitoring Wells Adapted
from NAVFAC, 2013.
Generalized Monitoring Well Network
Background :
Monซoring Wei Source Monlomg / Wtซ
Sentrel Montormg v
\
Pfcn* Frige U on lorn g VYtl
Extent of
Dissolved Plum*
Groundwater Flow
Pkjme Montanng
Figure 5. Generalized Monitoring Well Network (NJDEP, 2017).
adequate performance monitoring network exists
(NJDEP, 2017). Remedy performance monitoring
will require use of monitoring wells that are strategi-
cally placed to determine impacts to the contaminant
source area, contaminant plume and potential receptors
(Figure 5). Within this context, samples from injection
wells may be useful for monitoring injection constit-
uents and estimating the maximum rate of contam-
inant degradation (NJDEP, 2017). Although water
quality samples from injection wells can be useful,
they should not comprise the entire data set (Huling
and Pivetz, 2006).
Prevention and Mitigation
Use a monitoring well network to determine
impacts to the contaminant source, plume, and
receptors,
Use injection wells to monitor injection constitu
ents and estimate the maximum rate of contam
inant degradation
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3.3 Preferential Accumulation of Amendment in
Monitoring Wells
3,3,1 Overview
Technologies Affected
EISB
ISCO
CBI
ISCR
ISTT
ISS
/
Mechanism Accumulation of amendment in monitor-
ing wells may occur when they are located close to
injection wells or high-pressure injection is used in low
permeability formations (Figure 6). Under these circum-
stances, a monitoring well is more likely to intercept
injection pathways and accumulate amendments.
Kxisting preferential pathways (e.g., utility lines) between
the injection and monitoring wells can also act as
conduits leading to the accumulation of amendment
in monitoring wells.
Impact The extent of amendment distribution in
an aquifer may be overestimated when amendments
preferentially accumulate within monitoring wells.
For example, it has been suggested that high-pressure
injection of powdered CBI into low-permeability
formations creates random fractures, which may result
in amendments accumulating in nearby monitoring
wells (Figure 6). Another impact is that samples from a
monitoring well containing amendment may no longer
be representative of the aquifer because the contami-
nant will partition to or be degraded by the amendment
(See Section 4.1.). As a result, the low contaminant
concentration measured from the impacted well may
not reflect the true extent of aquifer treatment. For
example, organic contaminants are known to strongly
partition from water to carbon and can also partition to
the -vegetable oil used for I.IS 13 (Pfeiffer et al., 2005).
Another example is with in situ ozonation where ozone
channels intercept monitoring wells and treat the water
in the monitoring wells instead of in the aquifer (See
Figure 3.).
Monitoring for Amendment Distribution - Visual
inspection of samples for color, particulates or a cloudy
suspension may indicate the presence of amendments.
For example, a light pink to deep purple color may
indicate permanganate, and black particles may indicate
the presence of carbon. The emulsified oil used in
EISB can accumulate in monitoring wells where it will
be visible as a cloudy suspension or detected by total
organic carbon and dissolved organic carbon analysis
(AFCEE, 2007).
3.3.2Prevention and Mitigation
One method for minimizing amendment accumu-
lation is to exercise best practices during injection.
Controlling injection pressure, temperature, and flow
rates can help prevent uncontrolled hydraulic fracturing
(NAVFAC, 2013). The rate an aquifer can accept fluids
and the lateral migration of these fluids before reaching
structural failure is significantly influenced by the
vertical acceptance rate (LARWQCB, 2009). Maximum
injection pressure can be estimated using Equation 1
found in LARWQCB (2009) as long as the following
are known: the density of the dry soil and saturated
soil, the thickness of the vadose zone, and the height
of the saturated zone above the injection point. When
fracturing is needed in low-permeability formations,
injection points should be carefully chosen to minimize
potential impacts to monitoring wells. Additionally, it
is important to note and consider existing preferential
pathways that may impact monitoring wells.
Figure 6. Uneven Distribution of CBI in Clay and Sand Introduced
by High-Pressure Injection.
Prevention and Mitigation
Control injection pressure, temperature, and flow
rate to prevent uncontrolled hydraulic fracturing.
8 Ground Water Forum Issue Paper
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4. POST-SAMPLING ARTIFACTS
4.1 Post-Sampling Transformation of Contaminants
4.1.1 Overview
Technologies Affected
EISB
ISCO
CBI
ISCR
ISTT
ISS
Mechanism Organic contaminants and amendments
can be commingled in groundwater samples collected
from sites where amendments have been injected,
resulting in contaminants being transformed in the time
between sample collection and analysis (Ko, Huling and
Pivetz, 2012). Examples of amendments that may persist
in samples include oxidants, such as permanganate
for ISCO, or reductants such as micron or nano zero
valent iron for ISCR. In addition, microbes contained
in groundwater samples may continue to degrade
contaminants between sample collection and analysis,
particularly when amendments have been added for
EISB. Changes in ORP between the aquifer and sample
bottle may also facilitate chemical transformation.
Impact If amendment is present and abiotic or
biotic degradation is possible, and the samples are
not preserved correctly, the results may indicate lower
concentrations of contaminants than are actually present
in the groundwater (Ko, Huling and Pivetz, 2012).
Monitoring for Post-Sampling Transformations of
Contaminants Post-sampling transformation can be
monitored by checking for the presence of oxidative
or reductive amendments in the sample. Groundwater
samples can be collected and analyzed in the field specif-
ically to determine the presence of these amendments.
If the groundwater sample contains both amendments
and organic contamination, then there is a high risk of
contaminant transformation. Field tests for permanga-
nate and persulfate oxidants include colorimetry test
kits and field-based spectrophotometric analysis (Ko,
Huling and Pivetz, 2012).
4.1.2 Prevention and Mitigation
Mitigation can be done by ensuring that the correct sample
preservation and quenching procedures are used (Table 3).
For ISCO applications, proper sample handling and preser-
vation depend on the oxidant being used (Huling and
Pivetz, 2006). In the case of permanganate and persulfate,
Prevention and Mitigation
Preserve samples.
Neutralize amendments.
Cool samples.
Allow sufficient time for amendments to fully
react before taking samples for performance
monitoring.
ascorbic acid can be added to the groundwater sample in
order to neutralize the oxidant and reduce the impact of the
oxidant on sample results (Ko, Huling and Pivetz, 2012).
Recommendations for preservative amounts can be found
in references such as Ko, Huling and Pivetz, 2012. Notify-
ing the analytical laboratory that the aqueous samples
may contain residual persulfate or permanganate, and the
volume of preservative solution added to the sample will
allow the lab to correct for dilutions. Other preservatives
have been used to successfully neutralize these oxidants but
may negatively impact the quality of the sample (Huling,
Ko and Pivetz, 2011). Applications using ozone or Fenton's
reagent typically do not require preservation to prevent
post-sampling oxidative transformation because of their
short persistence. In lieu of preservation, delaying sampling
until the oxidant has been fully consumed and is no longer
detected in screening samples minimizes post-sampling
transformation. However, permanganate may persist for
long periods and, therefore, may require neutralization
prior to complete reaction (Huling and Pivetz, 2006).
Table 3. Persistence and Preservatives for
Common Oxidants
Oxidant
Persistence
Preservative
Permanganate
>3 months
Ascorbic acid
Persulfate
Hours - weeks
Ascorbic acid
Ozone
Minutes - hours
Not applicable
Fenton's reagent
Minutes - hours
Not applicable
Adapted from Huling and Pivetz, 2006 and Ko, Huling and Pivetz,
2012.
Methods for eliminating or slowing biodegradation
in samples with volatile organics include cooling to
between 0 and 6 ฐC and adjusting the pH to less than
2 (U.S. EPA, 2016). For fuel oxygenates, base may
be added to samples to prevent biodegradation and
minimize ether hydrolysis (U.S. EPA, 2003).
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Ground Water Forum Issue Paper 9
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4.2 Loss of Volatiles when Sampling High-
Temperature Groundwater
4.2.1 Overview
Technologies Affected
EISB
ISCO
CBI
ISCR
ISTT
ISS
MechanismWhere remedy application results in elevated
temperature, it may trigger a phase change from liquid to
gas for volatile contaminants. Volatile compounds may
escape from the sample, resulting in contaminant losses,
especially where groundwater samples are exposed to the
atmosphere (USACE, 1998). ISTT heats the subsurface
and increases sample temperatures, which may result in
loss of volatiles. Technologies that cause exothermic
reactions, such as ISCO and ISS, can also heat the subsur-
face and lead to a loss of volatile contaminates during
sample collection. High temperatures may also cause
contaminants to react after sampling.
Impact Volatilization and reactions of contaminants
from samples could result in an underestimate of
contaminant concentrations (USACE, 2014).
4.2.2 Prevention and Mitigation
Evaluation of contaminant volatility at elevated
temperatures can inform approaches to prevent or
mitigate potential sampling or analytical issues associ-
ated with loss of volatiles.
Mitigation can involve using dedicated sampling ports or
taps that can be accessed without opening the monitoring
well cap (USACE, 2014). Groundwater extracted from
the well should flow through a cooling coil to decrease
the groundwater temperature before the sampling point
(USACE, 2014). In addition, submerging samples in an ice
bath immediately after collection and keeping them cool
until analysis can reduce loss of volatiles (USACE, 2014).
If dedicated sampling ports are not available, then
waiting until the subsurface has cooled before sampling
may be necessary.
Prevention and Mitigation
Use dedicated sampling ports and cooling coil
to decease groundwater temperature before
sample collection.
Allow subsurface temperature to cool before
sampling for performance monitoring.
5. REFERENCES
Air Force Center for Engineering and the Environment
(AFCEE). 2007. Protocol for In Situ Bioremediation of
Chlorinated Solvents Using Edible Oil. https://clu-in.
org/download/remed/Fina.l-Edible-Oil-Protocol-Oc-
tober-2007.pdf
Barcelona, M.J., Gibb, J.P., Helfrich, J.A. and Garske,
E.E. 1985. Practical Guide for Ground-Water Sampling.
Illinois State Water Survey, ISWS Contract Report 374.
http: //www.ora.u.org/ptp /PTP%20Libra.ry/library/
epa/samplings / pra.cgw.pdf
Begley, T.H., White, K., Honigfort, P., Twaroski, M. L.,
Neches, R. and Walker., R. A. 2005. Perfluorochemicals:
Potential sources of and migration from food packaging.
Food Additives and Contaminants 22(10):10231031.
https:/ /www.ncbi.nlm.nih.gov/pubmed/16227186
Borden, R., Clayton, M., Simking, T., Lieberman M.T.
and Weispfenning, A. 2008. Development of a Design
Tool for Planning Aqueous Amendment Injection
Systems Emulsion Design Tool. ESTCP Project
ER-20062. June, https://clu-in.org/download/contam-
inantfocus / tee /ER-0626-Emulsion-design-tool.pdf
Department of Defense Environmental Security
Technology Certification Program (ESTCP). 2005.
A Review of Biofouling Controls for Enhanced In
Situ Bioremediation of Groundwater. October. Click
Download Technical Report, https://www.serdp-es-
tcp.org/Program-Areas /Environmental-Restoration /
Contammated-Groundwater/ER-200429 /ER-200429 /
(language)/eng-US)
Fox, T. and Winner, E. 2016. Lessons Learned and
Paths to Success with Activated Carbon Injections. In
ASTSWMO Workshop, Pittsburgh, PA. April, http://
astswmo.org/files /Meetings /2016 /MYM/presenta-
tions /201 6-04-28-LlJST-1030am / Winner Fox.pdf.
Huling, S.G. and B.E. Pivetz. 2006. In-Situ Chemical
Oxidation. EPA Office of Research and Develop-
ment, EPA/600/R-06/072. August, http://nepis.
epa.gov/Exe / ZvPDF.cgi/ 2000ZXNC.PDF?Dock-
ey=2000ZXNC.PDF
Huling, S.G., Ko, S. and Pivetz, B. 2011. Groundwater
Sampling at ISCO Sites: Binary Mixtures of Volatile
Organic Compounds and Persulfate. Groundwa-
10 Ground Water Forum Issue Paper
In Situ Treatment Performance Monitoring
-------
ter Monitoring & Remediation. Volume 31, Issue 2.
Pages 72-79. Spring, http://onlinelibra.ry.wiley.com/
Hoi/10.1111 /).1 745-6592.201 1.01332.x/abstract
Ko, S. Huling, S.G. and Pivetz, B. 2012. Ground Water
Sample Preservation at In-Situ Chemical Oxidation
Sites Recommended Guidelines. EPA National Risk
Management Research Laboratory. EPA/600/R-12/049.
August, https://www.epa.gov/sites/production/
files/2015-06/documents/isco gw sampling issue
pa.per.pdf
Llopis, J.L. 1991. The Effects of Well Casing Material
on Ground Water Quality. Office of Solid Waste and
Emergency Management. EPA/540/4-91/005. October.
https: / / nepis.epa.gov/Exe/ZyPDEcgi/ 40001I6P.
PDFPDockev=40001 T6PPDF
Los Angeles Regional Water Quality Control Board
(LARWQB). 2009. Technical Report: Subsurface
Injection of In Situ Remedial Reagents (ISRRs) Within
the Los Angeles Regional Water Quality Control Board
Jurisdiction, https://www.wa.terboa.rds.ca.gov/losa.nge-
les /water issues /programs /ust/guidelines /Subsur-
face injection of ISRR.pdf
Lowe, K.S., Garder, EG. and Siegrist, R.L. 2002.
Field Evaluation of In Situ Chemical Oxidation
Through Vertical Well-to-Well Recirculation of
NaMn04. Groundwater Monitoring and Remedia-
tion 22(1): 106-115. http://onlinelibrary.wiley.com/
Hoi/10.1111 /j.1 745-6592.2002.tb00659.x/full
McCaulou, D.R., Jewett, D.G. and Huling, S.G. 1995.
Nonaqueous Phase Liquids Compatibility with Materials
Used in Well Construction, Sampling, and Remediation.
EPA/540/S-95/503. July, https://www.epa.gov/sites/
production / files /2015-06 / documents / napl.pdf
Naval Facilities Engineering Command (NAVFAC).
2013. Best Practices for Injection and Distribution of
Amendments. TR-NAVFAC-EXWC-EV-1303. March.
https: / /clu-in.org/download/techfocus /chemox/
Inject-a.mend-tr-na.vfac-exwc-ev- 1303.pdf
New Jersey Department of Environmental Protection
(NJDEP). 2017. In Situ Remediation: Design Consider-
ations and Performance Monitoring Technical Guidance
Document. October, Version 1.0. http://www.nj.gov/
dep/srp/guidance/srra/in situ remedia.tion.pdf?ver-
sion 1 0
Payne, F.C., Quinnan, J.A. and Potter, S.T. 2008.
Displacement concepts. In Remediation Hydraulics,
332-336. CRC Press, https://www.crcpress.com/
Remediation-Hydraulics /Payne-Ouinnan-Potter/p /
book/9780849372490
Pfeiffer, P., Bielefeldt, A.R., Illangasekare, T. and Henry,
B. 2005. Partitioning of dissolved chlorinated ethenes
into vegetable oil. Water Research 39: 4521-4527.
Scherer, T. 2013. Care and Maintenance of Irrigation
Wells. North Dakota State University. AE-97 (Revised).
May. https://www.ag.ndsu.edu/publications/crops/
ca.re-and-ma.intenance-of-irriga.tion-wells
Simpkin, T.J., Palaia, T., Petri, B.G. and Smith, B.A..
2011. Oxidant Delivery Approaches and Contingency
Planning. In Situ Chemical Oxidation for Groundwater
Remediation, 449-480. Springer, https://link.springer.
com /chapter/1 0.1 007/978-1 -4419-7826-4 1 1
Smith, S.A. 1995. Monitoring and Remediation Wells:
Problem Prevention, Maintenance, and Rehabilitation.
CRC Press. May 4. https://www.crcpress.com/Monitor-
ing-a.nd-Remedia.tion-Wells-Problem-Prevention-Ma.in-
tena.nce-a.nd /Smith / p /book/9780873715621
Smith, S.A. and Comeskey, A.E. 2009. Sustainable
Wells: Maintenance, Problem Prevention, and Rehabil-
itation. CRC Press. November 4. https://www.crcpress.
com/Sustainable-Wells-Maintenance-Problem-Pre-
vention-and-Rehabilitation / Smith-Comeskey / p /
book/9780849375767
Smith, S.A. 2011. Primer on Microbial Problems in
Water Wells. June 27. http://www.groundwa.ters cience.
com/resources / tech-a.rticle-libra.ry/96-primer-on-mi-
crobia.l-problems-in-water-wells.html
U.S. Army Corps of Engineers (USACE). 1998. USACE
Sample Collection and Preparation Strategies for Volatile
Organic Compounds in Solids. October, https://clu-in.
org/download/stats / sa.mpling.pdf
U.S. Army Corps of Engineers (USACE). 2014.
Section 8.1.5.1 Liquid. In Design: In Situ Thermal Remedi-
ation. USACE EM 200-1-21. May 30. http: / /www.
publica.tions.usace.army.mil/Portals /76 /Publications/
EngineerMa.nua.ls/EM 200-l-21.pdf?ver=2014-05-08-
155746-393
In Situ Treatment Performance Monitoring
Ground Water Forum Issue Paper 11
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United States Environmental Protection Agency
(U.S. EPA). 2003. Underground Storage Tanks Fact
Sheet, Analytical Methodologies for Fuel Oxygenates.
EPA-510-F-03-001. April, https://nepis.epa.gov/Exe/
ZvPDF.cgi /2000D90Y.PDF?Dockey=2000D90Y.PDF
United States Environmental Protection Agency (U.S.
EPA). 2009. Industrial Stormwater Monitoring and
Sampling Guide. EPA 832-B-09-003. March, https://
www3.epa.gov/npdes/pubs/msgp monitoring guide.pdf
United States Environmental Protection Agency (U.S.
EPA). 2016. Chapter 4, The SW-846 Compendium.
https://www.epa.gov/hw-sw846/sw-846-compendium
6. NOTICE AND DISCLAIMER
This paper was prepared for the EPA Office of
Superfund Remediation and Technology Innovation
(OSRTI), Technology Innovation and Field Services
Division and the Ground Water Forum, a component
of the U.S. EPA Superfund Technical Support Project,
under EPA Contract Number EP-W-14-001. This
information has received technical EPA review and
does not necessarily reflect the views of EPA or other
participating organizations, and no official endorsement
should be inferred. The information is not intended, nor
can it be relied upon, to create any rights enforceable
by any party in litigation with the United States or any
other party. Use or mention of trade names does not
constitute an endorsement or recommendation for use.
A PDF version of Ground WaterForum Issue Paper: In Situ
Treatment Monitoring Issues and Best Practices is available
to view or download at https://www.epa.gov/remedv-
tech /technica.l-support-proj ect-clea.ning-conta.mina.t-
ed-sites-issue-papers and http:/ /www.cluin.org.
7. ACKNOWLEDGMENTS
OSRTI and the Ground Water Forum thank all the EPA
staff involved in the development of this document.
12 Ground Water Forum Issue Paper
In Situ Treatment Performance Monitoring
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APPENDIX: Quick Reference Table: In Situ Treatment Monitoring Issues and Best Practices for Monitoring,
Prevention and Mitigation
Potential Sampling Issue
Technology
Best Practices
EISB
ISCO
CBI
ISCR
ISTT
ISS
Issues Related to Monitoring Wells
Biofouling of monitoring wells
Mechanism: Enhanced
microbial activity leads to
growth of biomass on well
screen and in filter pack.
Impact: Impedes ground-
water entry to well, poten-
tially hindering sample
collection or resulting in
stagnant water in well.
Changes groundwater flow
around well and adsorption
or degradation of contami-
nants, potentially resulting in
samples not representative
of aquifer.
Y
Monitoring
Monitor changes in well hydraulic perfor-
mance, such as reduced well produc-
tion.
Inspect monitoring wells, submerged
equipment and purge water for signs of
biofouling.
Prevention and Mitigation
Limit amendment volumes to meet the
site-specific electron acceptor demand.
Apply cleaning processes followed by
well redevelopment:
- Physical processes: surging, over-pump-
ing, brushing, jetting or air injection.
- Chemical processes: cleaning
with hypochlorite, hydrogen perox-
ide, chlorine (will increase chloride
in groundwater) or non-oxidizing
biocides.
Metals precipitation on
monitoring well screens
Mechanism: Change in
groundwater chemistry due
to addition of amendments
can cause metal precip-
itation on monitoring well
screens.
Impact: Damages or fouls
well screen impeding
groundwater entry. Potential-
ly hinders sample collection
or results in stagnant water in
well that is not representative
of the aquifer.
Monitoring
Monitor changes in well hydraulic perfor-
mance, such as reduced well production.
Inspect monitoring wells, submerged
equipment and purge water during
sampling for signs of precipitates.
Prevention and Mitigation
Complete pilot-scale treatability study
and perform geochemical modeling to
anticipate metal precipitation.
Apply cleaning processes followed by
well redevelopment:
- Physical processes: surging, over-pump-
ing, jetting, air injection, sonic or vibra-
tory methods.
- Chemical processes: acid cleaning.
In Situ Treatment Performance Monitoring
Ground Water Forum Issue Paper 13
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Potential Sampling Issue
Technology
Best Practices
EISB
ISCO
CBI
ISCR
ISTT
ISS
Reactions with well materials
and equipment
Mechanism: Well casing
material and sampling
equipment incompatible
with contaminants, amend-
ments and heat may cause
corrosion or deterioration of
casing or equipment.
Impact: May hinder sample
collection or foster adsorp-
tion or desorption of contam-
inants, resulting in samples
not representative of the
aquifer.
s
Monitoring
Monitor changes in well hydraulic perfor-
mance, such as reduced well production.
Inspect monitoring wells, submerged
equipment, and purge water during
sampling for signs of corrosion or degra-
dation.
Prevention and Mitigation
Select compatible materials.
Use cathodic protection for metal wells
and equipment.
Choose inert filter pack material.
Replace, restore or line corroded compo-
nents.
Representativeness of Monitoring Wells
Displacement of
contaminants during
amendment injection
Mechanism: Injection of
large volumes of amend-
ments or reactions of
amendments that produce
large volumes of gas can
displace contaminated
groundwater.
Impact: Displaces contami-
nated groundwater, possibly
to uncontaminated areas.
Mayyield non-representative
sampling results if sampling
is limited to original area of
contamination.
s
s
s
s
Monitoring
Monitor wells adjacent to or downgra-
dient from injection wells for increasing
contaminant concentrations.
Prevention and Mitigation
Consider groundwater recirculation.
Consider outside-in delivery.
Treat areas contaminated by displace-
ment.
Use of injection wells for
performance monitoring
Mechanism: Amendments
will likely remain in and near
the injection well.
Impact: Samples collected
from injection wells may not
be representative of the site
as a whole because optimal
treatment performance will
likely occur near the injec-
tion well.
Prevention and Mitigation
Use monitoring well network to determine
impacts to contaminant source, plume
and receptors.
Use injection wells to monitor injection
constituents and estimate maximum rate
of contaminant degradation.
14 Ground Water Forum Issue Paper
In Situ Treatment Performance Monitoring
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Potential Sampling Issue
Technology
Best Practices
EISB
ISCO
CBI
ISCR
ISTT
ISS
Preferential accumulation of
amendment in monitoring
wells
Mechanism: Injection of
amendments near monitor-
ing wells or use of high-pres-
sure injection.
Impact: Causes hydrau-
lic fracturing that creates
pathways for amendment
to flow to wells. Results in
overestimate of distribu-
tion of amendments. Also,
contaminant concentra-
tions in wells no longer repre-
sent treatment zone.
s
Monitoring
Visually observe amendments in monitor-
ing wells for color, particulates or cloudy
suspension.
Analyze total organic carbon or dissolved
organic carbon for EISB amendments.
Prevention and Mitigation
Control injection pressure, temperature
and flow rate to prevent uncontrolled
hydraulic fracturing.
Post-Sampling Artifacts
Post sampling transformation
of contaminants
Mechanism: Amend-
ments and microbes are
commingled in groundwa-
ter samples.
Impact: Transforms contam-
inants after collection but
prior to analysis, resulting in
unrepresentative samples.
V
V
Monitoring
Monitor presence of amendment and/
or microbes.
Prevention and Mitigation
Preserve samples.
- Neutralize amendments.
- Cool samples.
Allow sufficient time for amendments
to fully react before taking samples for
performance monitoring.
Loss of volatiles when
sampling high-temperature
groundwater
Mechanism: Increased
temperature of groundwa-
ter samples through appli-
cation of in situ thermal or
chemical technologies that
result in elevated tempera-
tures.
Impact: Potential loss of
volatile contaminants during
sample collection, resulting
in samples not representa-
tive of aquifer.
Monitoring
Evaluate contaminant volatility.
Monitor groundwater temperature during
all stages of sample collection.
Prevention and Mitigation
Use dedicated sampling ports and a
cooling coil to decrease groundwater
temperature before sample collection.
Allow subsurface temperatures to cool
before collecting samples.
In Situ Treatment Performance Monitoring
Ground Water Forum Issue Paper 15
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