United States
Environmental Protection
Agency
Robert S. Kerr Environmental
Research Laboratory
Ada OK 74820
Research and Development
EPA-600/S2-84-024 Mar. 1984
Project Summary
A Guide to the Selection of
Materials for Monitoring Well
Construction and Ground-Water
Sampling
Michael J. Barcelona, James P. Gibb, and Robin A. Miller
The project was initiated to supplement
and update existing guidance documents
for effective ground-water monitoring
efforts. The areas of primary concern
were the potential sources of errors in
chemical analyses of subsurface samples
caused by well construction and sampling
materials, techniques or procedures. A
critical review of the literature was
conducted on monitoring natural waters,
materials' performance, data and unpub-
lished information on the success of
various ground-water monitoring tech-
niques. The results of the literature
review were collected and reviewed by
a panel of experts from government
agencies, private hydrological consult-
ing firms, the manufacturing industry
and national standards organization.
The publication consists of a thorough
discussion of ground-water monitoring
strategies, requirements, and pitfalls. It
concludes with a detailed treatment of
the costs and benefits of recommended
monitoring design criteria.
The principal conclusions of the work
support the use of proven noncontami-
nating well construction and sampling
procedures employing materials' selec-
tion appropriate to the information
needs of the monitoring plan. It further
demonstrates that the use of more
sophisticated techniques and more
expensive, sturdy materials for well
construction and sampling can be cost-
effective even for short-term (5-year)
monitoring projects. The penalties
involved in sample reanalysis or gener-
ating unreliable information can be
eliminated through careful planning
and design. The second phase of the
project, in progress, consists of field
performance tests of the materials'
recommendations in the selection
guide.
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 techniques
drew little scientific attention until the
mid 1970's. Frequently, research on
subsurface processes and chemical
monitoring adopted procedures or practices
developed for surface-water monitoring
applications. The inherent difficulties in
obtaining "representative" samples of
aquifer materials or ground water have
compounded the interpretation of analyti-
cal data. Improvements in the sensitivity
and performance of analytical methods,
particularly for organic compounds
increased the demand for reliable sample
collection. In the past decade the scientific
basis for collecting reliable ground-water
data has improved and it remains an
active area of research.
Various aspects of ground-water
monitoring network design and implemen-
tation have been treated in detail in a
number of publications as well as in the
open literature. However, the biases in-
troduced into analytical data by various
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drilling or sampling techniques and the
choice of materials used in these applica-
tions have not been systematically
reviewed. Since much of the available
information was unpublished or scattered,
the project plan included the use of letter
solicitations to active researchers in
ground-water monitoring or research. A
panel of representatives from government,
industry, private enterprise and a nation-
al standards organization was assembled
to develop guidance for monitoring
personnel, regulatory agency staff and
interested scientists. The major objective
was to identify proven non-contaminat-
ing drilling, well construction, and
sampling techniques for ground-water
monitoring.
The literature review included all
English-language and selected foreign
publications in a variety of data-bases,
including: Chemical Abstracts, Selected
Water Resource Abstracts, Pollution Ab
Abstracts, Enviroline, Compendex (Engi-
neering), Metadex (Metals Abstracts/Al-
loys Index), Rapra (Rubber and Plastics
Research Association), and the National
Ground Water Center Data Base. Approxi-
mately 600 references were received in
full version for evaluation purposes. The
limited response received from the letter
solicitation proved to be fruitful in un-
covering important unpublished findings
relevant to the study.
The literature on monitoring network
design, well construction, and sampling
techniques was critically reviewed with
emphasis on techniques that cause
minimal disturbance to the subsurface
environment and permit faithful sample
collection and transfer mechanisms. A
short discussion of the nature of the
subsurface environment was included to
establish some of the demands that must
be met in order to obtain representative
water samples.
Materials' chemical compatibility data
under various types of exposures were
categorized for potential effects on the
integrity of water samples in contact with
well casing, pump parts, and transfer
tubing. Exposures were categorized in
four groups, approximating the types of
ground water or contaminated ground-
water mixtures that have been encountered
in monitoring efforts. These categories
were inorganic buffered water at pH 5,
organic-acid anion buffered water at pH
5, high dissolved solids acidic ground
water and various organic/water mixtures.
The potential for deleterious effects on
materials used for well construction or
sampling applications was scored as
unlikely, likely under some conditions, or
probable (that is, material is not recom-
mended on a three-point scale). Rigid
materials and flexible materials were
rated relative to Teflon®, which was con-
sidered the ideal material for critical
applications.
The literature data on potential materi-
als' effects on analytical data were
supplemented by documented field re-
sults for various well casing, pump, and
tubing types. Further, analytical method
performance (accuracy and precision) for
common monitoring parameters and pri-
ority pollutant determinations were com-
piled to serve as benchmarks for the poten-
tial magnitude of sample collection errors.
Costs of conducting ground-water
monitoring programs were analyzed
from the perspective of both the informa-
tion needs and the selection of rigid, well
casing materials. A sample monitoring
effort consisting of one- and five-year
operation of four well networks employ-
ing rigid PVC, Teflon® and stainless
steel casing materials with increasing
analytical detail was included. A result-
ing analysis was discussed to support
the use of recommended materials for
the specific goals of the monitoring plan.
Conclusions
Ground-water monitoring is conducted
in response to major governmental
legislation (RCRA, CERCLA, etc.) and
agency regulations. Source monitoring
may be categorized as detective or
interpretive, depending upon information
needs before or after a contaminant
release has been detected. Monitoring for
specific research into subsurface pheno-
mena and ambient monitoring for resource
evaluation also are purposes for which
sampling networks are implemented.
Regardless of the information needs,
recommended minimum planning and
design details must be considered before
network implementation. For good program
performance, the involvement of profes-
sional hydrogeologists, chemists, labora-
tory and field personnel and the director
of the monitoring effort should be
encouraged. The monitoring design
should be planned with careful consider-
ation of the hydrogeologic conditions and
analytical parameters of interest in all
subsequent decisions. Flexibility is the
most important aspect of the design. It is
necessary to maximize the usefulness of
preliminary data collection and allow for
future expansion if the goals of the
monitoring program are expanded.
Well Installation j
Well drilling and construction technol- 1
ogies are available to establish sampling
points with minimal disturbance of the
subsurface or interferences with analytical
determinations. Hollow-stem auger, air-
rotary, cable tool or inorganic mud rotary
drilling techniques are preferred. Careful
well completion methods and proper well
development procedures should be used
in conjunction with an appropriate
drilling method. The time necessary for
proper well development can save
considerable time and effort by reducing
difficulties in pumping and filtering turbid
samples. Manufactured screen materials
of proper slot sizes are recommended
over hand-sawn slits.
Sampling
Sampling gear should be selected so
that disturbance of the actual concentra-
tions of chemical constituents of interest
is reduced. Pumps or other collection
mechanisms are available which minimize
gas exchange and faithfully transfer wa-
ter samples to storage vessels. Materials'
selection for components that contact the
water in sampling operations is critical to
the elimination of bias, imprecision or
interferences in subsequent analytical
results. Simple mechanisms that reduce
the potential for human error should be m
chosen and manufacturers' claims or ™
recommendations must be carefully
evaluated for each specific application.
No-gas contact bladder pumps and
various grab-sample mechanisms are
preferred for sampling ground water for
volatile chemical constituents as well as
pH and oxygen sensitive analytes. Sampling
errors are not correctible through field
blanks, standards, or procedural standards.
Research on sampling methods and
procedures is needed.
Rigid Materials
Materials for well casing, pump and
sample transferlines must be chosen for
specific hydrogeologic conditions and the
analytes of interest. Well casing materials
must retain their structural integrity and
maintain a low analytical error rate for
long periods of time. Exposure conditions
can vary in time or by location. Compatibil-
ity with natural ground-water conditions,
as well as waste/groundwater mixtures,
should be carefully evaluated. The order
of preference for various rigid well casing
materials is shown in Table 1 with
recommendations for specific applications.
Although PVC well casing is durable and
inexpensive, the potential for interference
from leaching or adsorption of organic
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Table 1. Recommendations for Rigid Well Casing Materials
fin 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 Steel
Galvanized Steel
Carbon Steel
Recommended for most monitoring situations with detailed
organic analytical needs, particularly lor 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. Virtually an
ideal material for corrosive situations where inorganic
contaminants are of interest.
May be predisposed 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 inter-
ferences. The potential for interaction and interferences
from PVC well casing in contact with aggressive aqueous
organic mixtures is difficult to predict. PVC is not recom-
mended 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 formu-
lation 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, partic-
ularly when sulfides are present. Products of corrosion are
mainly Fe and Mn, except for galvanized steel which may
re/ease 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.
compounds makes it a less desirable
material for organic compound investiga-
tions when aqueous/organic mixtures
may be encountered. Teflon® and stainless
steel are preferred in these situations, as
well as for corrosive, high dissolved
solids' solutions. PVC also may be
expected to function well under these
conditions. The use of galvanized, low-
carbon or carbon steel is not recommended
in corrosive, acidic environments, since
these will corrode much faster than
stainless steels. Corrosion of these
materials results in the formation of
active sites for adsorptive interactions
with both organic and inorganic chemicals.
Flexible Materials
Similarly, the flexible materials for
pump components (bladders) and sample
transfer lines must be carefully chosen in
relation to the exposures expected and
the analytes of interest, because, compared
to well casing, these materials are in
close contact with the water samples
(after well purging).
Table 2 contains a list of preferred
flexible materials and recommendations
for their use. Teflon® again is the material
of choice for most situations, due to its
inertness and its freedom from nonpoly-
meric additives. Polypropylene and linear
polyethylene are recommended over
flexible polymer formulations (PVC),
since these polyolefins have better
chemical resistance and very low levels
of additives or plasticizers that will bias
detailed organic analytical procedures.
The use of the remainder of the materials
in the table should be approached
carefully, particularly for prolonged
contact with aqueous organic mixtures.
Additional controlled sorption or leach
testing is needed for these materials
using the same analytical procedures
employed for actual ground-water moni-
toring analytical work.
Cost Analysis
Analysis of the cost of implementing a
four well ground-water monitoring
network supports the cost-effective use
of appropriate well construction materials.
Because additional drilling is needed if
ground-water conditions require more
chemically-resistant, non-contaminating
monitoring wells, it makes good sense to
choose sturdy proven materials in prelim-
inary work. The cost of a single sample
reanalysis (when doubtful analytical
results are obtained) alone clearly
outweighs the choice of less expensive
materials. The cost savings in cheaper
materials actually results in greater
Table 2. Recommendations for Flexible Materials for Sampling Applications
(In 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. Docu-
mented interferences are likely with several priority pollu-
tant 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 resist-
ance as shown. Recommended only when a more suitable
material is not available for the specific use. Actual con-
trolled exposure trials may be useful in assessing the
potential for analytical bias.
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penalties as the degree of analytical
detail increases. Viable alternatives to
Teflon® or stainless steel alone in specific
monitoring applications may be the use of
either less expensive material in the
unsaturated zone, coupled to better
materials at depth or paired PVC/SS
wells to obtain high quality, unbiased
inorganic and organic analytical data,
respectively, from nested installations.
It is generally concluded that more
careful documentation of well siting,
construction, completion and sampling
procedural detail is called for. This
information is vital to unequivocal inter-
pretation of the resulting analytical data.
Complete documentation would further
facilitate the timely transfer of proven
technology and practice to various user
communities.
MichaelJ. Barcelona. JamesP. Gibb, and Robin A. Miller are with the Illinois State
Water Survey. Champaign, IL 61820.
M. Richard Scalf and Leslie G. McMillion are the EPA Project Officers (see
below).
The complete report, entitled "A Guide to the Selection of Materials for
Monitoring Well Construction and Ground-Water Sampling," (Order No. PB
84-141 779; Cost: $11.50, subject to change} will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
M. Richard Scalf can be contacted at:
Robert S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.O.Box 1198
Ada, OK 77481
Leslie G. McMillion can be contacted at:
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
P.O. Box 15027
Las Vegas, NV 89114
U S. GOVERNMENT PRINTING OFFICE; 1984 — 759-015/7638
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