United States
                    Environmental Protection
                    Agency
                    Research and Development
Robert S. Kerr Environmental
Research Laboratory
Ada OK 74820
EPA/600/S2 85/104 Feb. 1986
SER&         Project  Summary

                    Practical  Guide for
                    Ground-Water  Sampling
                    Michael J. Barcelona, James P. Gibb, John A. Helfrich, and Edward E. Garske
                      This work was initiated as the second
                    phase of an investigation of the reliabil-
                    ity of monitoring well construction and
                    ground-water sampling techniques. The
                    project also included both laboratory
                    and field testing of sampling materials
                    and sampling mechanisms with  an
                    emphasis on minimizing error, particu-
                    larly for volatile  organic compound
                    sampling and analysis. The Guide is a
                    companion volume  to the Phase 1
                    report,  "A Guide to the Selection of
                    Materials for Monitoring Well Construc-
                    tion  and  Ground-Water Sampling,"
                    (EPA/600/2-83/024).
                      The full report explains the need to
                    address the quality control and quality
                    assurance considerations of a ground-
                    water monitoring program at the outset
                    of planning. The sampling and analytical
                    protocols for specific monitoring instal-
                    lations should be integrated into a well
                    conceived design for the collection of
                    high quality hydrologic and chemical
                    data. Though accuracy and precision
                    data provide measures of data quality, it
                    is equally important to collect samples
                    that are representative of in situ condi-
                    tions. These goals can be achieved if the
                    essential elements of a ground-water
                    sampling program are addressed in the
                    preliminary and implementation phases
                    of monitoring program development.
                      The essential elements of effective
                    ground-water sampling include:

                    • Evaluation of the hydrogeologic set-
                       ting and program information needs,
                    • Proper placement and construction
                       of the well,
                    • Evaluation of performance of the
                       well  and purging strategies, and
                    • The design and execution of sampling
                       and analytical protocols which entail
   appropriate selection of sampling
   mechanisms and materials as well as
   sample collection,  handling and
   analysis procedures.

  Detailed discussions  of the advan-
tages and disadvantages of various
approaches to selecting appropriate
methods and materials for specific
monitoring purposes are provided in the
Guide. The emphasis is  on straightfor-
ward techniques which  minimize both
the disturbance of the subsurface envi-
ronment and the potential sources of
error for routine sampling applications.
Further, specific recommendations are
made  for step-by-step sampling proto-
cols which should be applied in sampling
for volatile organic compounds which
are among the most difficult chemical
constituents to sample effectively. The
recommendations are  supported by
extensive references, where  the litera-
ture permits, and it should prove useful
to the planning and execution of regula-
tory and research activities which
demand high quality  ground-water
quality data.
  This Project Summary  was developed
by EPA's Robert S. Kerr Environmental
Research Laboratory, Ada, OK, and the
Environmental Monitoring Systems
Laboratory, Las Vegas, NV, to announce
key findings of the research project that
is fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
  Ground-water monitoring is conducted
for a variety of purposes, though detective
and assessment compliance monitoring
efforts are most common. The absence of
proven recommendations for effective

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monitoring network designs and reliable
sampling protocols has  resulted in the
collection  of ground-water  quality data
with questionable value. When this type
of data is used as a basis for assessment
or remedial action activities, the success
of these actions may be very limited.
  Recent research has demonstrated that
the details of well construction, choice of
sampling mechanisms and materials and
sampling protocols can introduce errors
into analytical results which exceed those
involved in the analytical  procedures.
Analytical operations have been the major
focus of quality assurance and quality
control  (QA/AC)  recommendations  for
monitoring programs. Sampling QA/AC
is equally  important to the development
of high quality data which is representa-
tive of the site under investigation. Re-
quiring that water samples be represen-
tative of the in situ condition is insufficient
to ensure a high level of confidence in the
monitoring results. The  hydraulic per-
formance of the well (i.e., sampling point)
and the integrity of the sampling protocol
must be established before samples are
collected, if representative data are to  be
generated. Then the characteristics of a
representative sample can be established
for  the specific goals of the program.
  The Guide provides a thorough discus-
sion of the essential elements of well
construction and sampling protocols for
the collection of  high quality ground-
water quality data. Representative water
samples are generally defined by being
minimally disturbed samples which satis-
fy  charge balance considerations  and
permit the determination of trace organic
compounds at their limits of quantitation
within acceptable accuracy and precision
limits.  Each  element of the  sampling
protocol for a particular investigation can
be evaluated for its contribution to error
in the final results.
  The  available literature supports the
approach that a representative sampling
protocol for volatile or reactive chemical
constituents can satisfy the most demand-
ing data quality requirements applied to
routine monitoring efforts. Sampling and
analytical  protocol development must  be
tailored to the actual  hydrogeologic con-
ditions  of the site under  investigation.
Careful attention to the elements of the
sampling protocol will permit the refine-
ment of routine procedures as the moni-
toring activity develops. The emphasis of
the recommendations is on the simplest
sampling  procedures  possible which
provide data of known quality over the
duration of the monitoring effort.
Hydrogeologic Setting and
Information Requirements
  The hydrogeologic conditions at each
site (e.g., background and regulated unit)
must be evaluated for the potential  im-
pacts the setting may have on the devel-
opment of the monitoring program and
the quality of the resulting data. The types
and distribution of geologic materials, the
occurrence  and  movement of ground
water through those materials, the loca-
tion of the site in the regional ground-
water flow system,  the  relative perme-
ability of the materials and the potential
interactions between the mineral and
biological constituents of the formations
of interest, and the chemical constituents
of interest must  all  be considered. Both
the direction and the  rate  of ground-
water movement are important. Piezo-
metric surface data  or water level infor-
mation on each  geologic formation at
properly selected locations will provide
the basis for determining horizontal and
vertical ground-water flow paths at the
site. There  are  significant  differences
between the hydrogeology of arid and
humid climatic regions,  as well as sea-
sonal variations  which should be taken
into account. The rate  of ground-water
travel can be used to calculate optimum
sampling frequencies, should additional
detail beyond that provided in quarterly
sampling become necessary.
  Additional site and waste information
needs arise when tailoring the sampling
and analytical protocols to the specific
needs of the program. A minimum data
set for ground-water monitoring should
include general water quality parameters,
hydrologic parameters and pollutant indi-
cator parameters. A suggested list of
basic measurements is provided below:

         Chemical Parameters
pH, CT\ TOC, TOX
Alkalinity, CL , NO3 , SO/, PO« , silicate
Na*, K+, Ca++, Mg++,  Fe and Mn

         Hydrologic Parameters
Water Level, hydraulic conductivity
  The  pollutant indicator parameters
noted above [i.e., pH, Q~1, (specific con-
ductance), TOC andTOX] provide minimal
capability to ensure the detection of target
chemical constituents in ground water.
The pH  and conductance parameters
should be measured with care in the field.
TOC and TOX determinations should be
made after collection in headspace-free
glass vials with Teflon®* septa to preserve
the volatile organic fraction of the dis-
solved organic  matter  The pollutant
indicator parameters should also be sup-
plemented with determinations of specific
chemical constituents which are likely to
be mobile and persistent in the subsur-
face.

Well Placement and
Construction Procedures
  The  placement  and construction of
monitoring wells are among the most
difficult tasks involved  in developing an
effective monitoring program. The prelim-
inary locations and depths of monitoring
wells should be selected on the basis of
the best available pre-drilling information.
Then, as the  installation of these wells
progresses, new geologic and hydroiogic
data should  be incorporated into  the
overall monitoring plan to ensure that the
wells will perform the tasks for which
they are designed. It is advisableto select
initially a minimum array of monitoring
wells for the collection of geologic and
hydrologic data. Additional wells can be
positioned later at monitoring points likely
to intercept contaminant flow paths.
  Well construction should be accom-
plished with minimal disturbance of the
subsurface. The selection and cleaning of
both drilling  equipment  and well con-
struction materials should be performed
with the aim of minimizing the intro-
duction of foreign materials into  the
subsurface environment. Given the rela-
tively shallow depths of interest in many
ground-water monitoring efforts, hollow-
stem auger drilling techniques are pre-
ferred because they are mobile, fast, and
inexpensive.  Also, disturbance of  the
subsurface can  be effectively minimized.
To properly  define  the  movement of
pollutants, in both vertical and horizontal
directions, it is essential to collect depth
discrete water level data. Well completion
depth will depend on the location of the
uppermost permeable,  saturated zone
(i.e., "water-table") in unconfined forma-
tions or the piezometric surface of the
most shallow permeable zone in confined
formations. Vertically nested wells pro-
vide information on the vertical direction
of ground-water movement  and their
placement will be a function of the hydro-
geologic setting, particularly the relative
horizontal and vertical  permeabilities of
the formations beneath the site. Screen
size, grouts,  seals  and sampling point
•Mention of trade names or commercral products
 does not constitute endorsement or recommenda-
 tion for use

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documentation are also important aspects
of monitoring well  construction which
should  be addressed in the monitoring
program.

Evaluation of Well  Performance
  The effectiveness of a ground-water
monitoring program may be judged on the
attention  which  has been  paid  to the
evaluation of the hydraulic performance
of the monitoring well network. Each well
should be properly developed after con-
struction and periodically redeveloped to
ensure  that it provides useful hydraulic
data. Development also reduces the time
and effort necessary to collect representa-
tive ground-water quality information. A
variety of proven well development tech-
niques are amenable to the development
of shallow 2"  o.d.  monitoring  wells.
Accurate water level measurements pro-
vide the primary data for the evaluation of
well performance. Steel tapes(graduated
to the nearest hundredth of a foot with
raised lettering and  divisions), electrical
drop lines and sensitive pressure trans-
ducers are useful tools in this regard.
  Field  hydraulic conductivity testing of
the monitoring wells will avoid the un-
resolved issues which attend the inter-
pretation of laboratory conductivity test
results. Slug or bail tests,  repeated at
least threetimes, should provide accurate
hydraulic  conductivity determinations
with a  precision of  ±20%. In  general,
multiple pump tests are too expensive to
consider  for evaluating the hydraulic
performance of all monitoring wells with-
in a site network. The results of conduc-
tivity tests provide a basic  measure of
well hydraulic well performance which is
useful for judging the  significance of
water level excursions and long-term well
performance.  The testing  procedures
should  be repeated  at least every five
years and after each redevelopment effort
is performed. Well performance evalua-
tion also provides a basis for determining
an appropriate well purging strategy prior
to sampling. No single number of purge
volumes to be pumped prior to sampling
can be expected to suit all situations. A
well  conceived purging strategy that
includes  pumping rates and volumes
calculated on the basis of well perform-
ance and the transmissivity of the forma-
tion  of  interest  is essential to  effective
ground-water sampling efforts.

Sampling Protocol
  The hydraulic  performance  of the
sampling  points permits the design and
execution of effective water sampling and
analytical  protocols.  These  protocols
should be planned for collecting verif iably
high quality water  chemistry  results in
order to distinguish natural variability in
the geochemistry of the subsurface from
those  caused  by site  operations. The
sampling protocol  should incorporate
sampling mechanismsand materialsthat
are appropriate for the information needs
of the program. Since contaminant
migration may be detected at trace (e.g.,
ppb) levels of  individual  constituents,
sampling mechanisms and  materials
must be very carefully chosen to avoid
biases caused by contamination or sorp-
tion. The materials  of well construction,
samplers and sample transfer tubing are
as important as sample storage vessels
and analytical  performance in  this re-
spect.  Recommended materials for well
construction and sampling devices  are
shown in  Tables 1 and  2. Materials'
selections should be made with the long-
term use of the sampling points in mind.
                 Sampling mechanisms are devices for
               the collection of water samples. They are
               not, of themselves, sampling methods.
               This should be clear from inspection of
               Figure 1. The steps in the  sampling
               protocol in the first column of the figure
               are common to all ground-water monitor-
               ing efforts. Though the details of indi-
               vidual monitoring  efforts may vary, the
               steps  in  Figure 1 provide  a  guide  for
               effective  planning. The performance  of
               the sampling  point,  materials selected
               and the chemical constituents of interest
               will dictate the choice  of  appropriate
               sampling devices. Figure  2 contains
               recommendations for sampling mecha-
               nisms according to the specific demands
               of the monitoring effort.

               Conclusions
                 The development of reliable sampling
               protocols for ground-water quality moni-
               toring is a complex, programmatic process
               that must be designed to meet the specific
Table 1.
           Recommendations for Rigid Materials in Sampling Applications (In Decreasing
           Order of Preference)
          Material
                                              Recommendations
Teflon®
(flush threaded)
Stainless Steel 316
(flush threaded)


Stainless Steel 304
(flush threaded)

PVC
(flush threaded)
other noncemented
connections, only NSF*
approved materials for
well casing or potable
water applications
Low-Carbon Steet

Galvanized Steel

Carbon Steel
Recommended for most monitoring situations with detailed
organic analytical needs, particularly for aggressive,  organic
leachate impacted hydrogeologic conditions. Virtually an ideal
material for corrosive situations where inorganic contaminants
are of interest.
Recommended for most monitoring situations with detailed
organic analytical needs, particularly for aggressive,  organic
leachate impacted hydrogeologic conditions.
May be prone to slow pitting corrosion in contact with acidic high
total dissolved solids aqueous solutions. Corrosion products
limited mainly to Fe and possibly Cr and Ni.

Recommended for limited monitoring situations where inorganic
contaminants are of interest and it is known that aggressive
organic leachate mixtures will not be contacted. Cemented
installations have caused documented interferences.
The potential for interaction and interferences from PVC well
casing in contact with aggressive aqueous organic mixtures is
difficult to predict. PVC is not recommended for detailed organic
analytical schemes.
Recommended for monitoring inorganic contaminants in
corrosive, acidic inorganic situations. May release Sn or Sb
compounds from the original heat stabilizers in the formulation
after long exposures.
May be superior to PVC for exposures to aggressive aqueous
organic mixtures. These materials must be very carefully cleaned
to remove oily manufacturing residues. Corrosion is likely in high
dissolved solids, acidic environments, and particularly when
sulfides are present. Products of corrosion are mainly Fe andMn,
except for galvanized steel which may release Zn and Cd.
Weathered steel surfaces present very active adsorption sites for
trace organic and inorganic chemical species.
®Trademark of DuPont, Inc.
* National Sanitation Foundation approved materials carry the NSF logo indicative of the product's
 certification of meeting industry standards for performance and formulation purity.

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Table 2.    Recommendations for Flexible Materials in Sampling Applications fin Decreasing
           Order of Preference)
          Materials
                   Recommendations
Teflon®




Polypropylene

Polyethylene (linear)

PVC (flexible)




Viton®

Silicone
(medical grade only)

Neoprene
Recommended for most monitoring work, particularly for detailed
organic analytical schemes. The material least likely to introduce
significant sampling bias or imprecision. The easiest material to
clean in order to prevent cross-contamination.
Strongly recommended for corrosive high dissolved solids
solutions. Less likely to introduce significant bias into analytical
results than polymer formulations (PVC) or other flexible
materials with the exception of Teflon®.
Not recommended for detailed organic analytical schemes.
Plasticizers and stabilizers make up a sizable percentage of the
material by weight as long as it remains flexible. Documented
interferences are likely with several priority pollutant classes.

Flexible elastomeric materials for gaskets, O-rings, bladder and
tubing applications. Performance expected to be a function of
exposure  type and the order of chemical resistance as shown.
Recommended only when a more  suitable material is not
available for the specific use.  Actual controlled exposure trials
may be useful in assessing the potential for analytical bias.
®Trademark of DuPont, Inc.
goals of the monitoring effort in question.
The long-term  goals and  information
needs of the monitoring  program must
first be  thoroughly understood. Once
these considerations have been identified,
the  many  factors  that can affect  the
results can be addressed.
  In formulating the  sampling protocol,
the emphasis should be to collect hydro-
logic and chemical data that accurately
represent in situ hydrologic and chemical
conditions. With good quality assurance
guidelines and quality control measures,
the protocol  should provide the  needed
data for successful management of the
monitoring program  at a high  level of
confidence. Straightforward techniques
that  minimize the disturbance  of  the
subsurface and the samples at each step
in the sampling effort should be given
priority.
  The planning  of a monitoring program
should be a staged  effort designed to
collect information during the exploratory
or initial stages  of the program. Informa-
tion gained throughout the development
of the program should be used for refining
the preliminary  program  design. During
all  phases of protocol development, the
long-term costs  of collecting the required
hydrologic and chemical  data should be
kept in mind. These long-term costs may
be  several  orders  of magnitude larger
than the combined costs of planning, well
construction, purchase of sampling  and
support  equipment, and  data collection
start-up. It also  should be  remembered
that high quality data cannot be obtained
               from a poorly conceived and implemented
               monitoring  program, regardless of the
               added care and  costs  of sophisticated
               sampling and analytical procedures.
                 Finally, the ultimate costs of defending
               poor quality data in court or in compliance
               to regulatory requirements should not be
               overlooked. Due to the lack of documented
               standard techniques for developing moni-
               toring programs, constructing monitoring
               wells,  and  collecting  samples, quality
               control  measures must  be tailored for
               each individual site to be monitored. They
               should be designed  to ensure that dis-
               turbances  to  both  the hydrogeologic
               system  and the sample are  minimized.
               The care exercised in the well placement
               and construction, and sample collection
               and analysis can pay real dividends in the
               control  of  systematic  errors. Repeated
               sampling and field  measurements will
               further define the magnitude of random
               errors induced by field  conditions and
               human error. The burden of assuring the
               success of a program relies on careful
               documentation and  the performance of
               quality assurance audit procedures.

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Step
                                                Procedure
                                                                Essential Elements
Well Inspection

Well Purging
Sample Collection
Filtration*
Field
Determinations**
Preservation
Field Blanks
Standards
                Hydrologic Measurements
                            \
                Removal or Isolation of
                Stagnant Water
                            \
                Determination of Well-Purging
                Parameters (pH, Eh.  T, fT1)**
       Unfiltered
                                Volatile Organics, TOX

                                Dissolved Gases. TOO

                                Large Volume Samples for
                                Organic Compound
                                Determinations
Assorted Sensitive
Inorganic Species
NOi, NH<\ Fe (II)
                                (as needed for good
                                QA/QCI
     Field Filtered*
                                                                Alkalinity/A cidity*
Trace Metal Samples
                                                                S°, Sensitive
                                                                Inorganics
                                Major Cation and
                                Anions
Storage
Transport
Water-level Measurements

Representative Water Access


Verification of Representa-
tive Water Sample Access

Sample Collection by
Appropriate Mechanism

Minimal Sample Handling

Head-Space Free Samples

Head-Space Free Samples

Minimal Aeration or
Depressurization
Minimal Air Contact,
Field Determination

Adequate Rinsing Against
Contamination
                                                                Minimal Air Contact,
                                                                Preservation
                                                                Minimal Loss of Sample
                                                                Integrity Prior to Analysis
'Denotes samples that should be filtered in order to determine dissolved constituents. Filtration should be accomplished preferably with in-line filters
  and pump pressure or by /Vz pressure methods. Samples for dissolved gases or volatile organics should not be filtered. In instances where well
  development procedures do not allow for turbidity-free samples and may bias analytical results, split samples should be spiked with standards before
  filtration. Both spiked samples and regular samples should be analyzed to determine recoveries from both types of handling.

**Denotes analytical determinations which should be made in the field.
Figure 1.     Generalized flow diagram of ground- water sampling steps.

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Type of
Constituent
Volatile
Organic
Compounds
Organometallics
Dissolved Gases
Well-Purging
Parameters
Trace Inorganic
Metal Species
Reduced Species
Major Cations
& Anions
Example of
Constituent
Chloroform
TOX
CHaHg

Oa. C02
PH. rr1
Eh
Fe, Cu
NOi. S"
Na\ 1C. Ca"
Mg"
cr, so**
Positive
Displacement
Bladder Pumps



Sample Sensitivit
Increasing ,'



Superior
Performance for
Most Applications

Superior
Performance for
Most Applications
Superior
Performance for
Most Applications
Superior
Performance for
Most Applications
Thief, in situ or
Dual Check Valve
Bailers


May be adequate if
well purging is
assured

May be adequate if
we II purging is
assured
May be adequate if
well purging is
assured
Adequate
May be adequate if
we/I purging is
aec//r^/V
Mechanical Positive
Displacement Pumps
Gas-Drive
Devices
Suction
Mechanisms
'eliability of Sampling Mechanisms
May be adequate if
design and operation
are controlled

May be adequate if
design and operation
are controlled
Adequate
Adequate
Not
recommended

Not
recommended
May be
adequate
Adequate
Not
recommended

Not
recommended
May be ade-
quate if
materials
are approp-
riate
Adequate
Figure 2.    Matrix of sensitive chemical constituents and various sampling mechanisms.
                                                                                       . S. GOVERNMENT PRINTING OFFICE:] 986/646-116/20770

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                                           Michael J. Barcelona, James P. Gibb, John A. Helfrich. and Edward E. Garskeare
                                             with the Illinois State Water Survey. Champaign, IL 61820.
                                           Marion R. Scalf is the EPA Project Officer (see below).
                                           The complete report, entitled "Practical Guide for Ground-Water Sampling,"
                                             (Order  No. PB  86-137 304/AS;  Cost: $16.95, subject to change) will be
                                             available only from:
                                                  National  Technical Information Service
                                                  5285 Port Royal Road
                                                  Springfield, VA22161
                                                  Telephone: 703-487-4650
                                           The EPA Project Officer can be contacted at:
                                                  Robert S. Kerr Environmental Research Laboratory
                                                  U.S. Environmental Protection Agency
                                                  P.O.Box  1198
                                                  Ada, OK 74820
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
All
Official Business
Penalty for Private Use S300

EPA/600/S2.-85/104
          0000329   PS
                                         4GENCT
          230  S  DEARBORN  STREET
          CHICAGO               it    60604

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