UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
September 5, 1997
l-EEC-LTR-97-011 v OFFICE OF THE ADMINISTRATOR
SCIENCE ADVISORY BOARD
Honorable Carol M. Browner
Administrator
U.S. Environmental Protection Agency
401 M Street S.W.
Washington, DC 20460
Subject: To Filter, or Not to Filter; That is the Question
Dear Ms. Browner:
In its quest to identify risks from contaminated sites that may require placing a
site on the National Priority List (NPL), the U.S. Environmental Protection Agency (EPA)
conducts preliminary assessment (PA) and site inspection (SI) to collect information for
use in its Hazard Ranking System (HRS). The HRS utilizes releases of hazardous
materials data for four pathways, including release to groundwater. Obtaining a
groundwater sample for chemical analysis requires the utmost care in order to preserve
the chemical and physical integrity of the sample. In particular, one must decide
whether or not to use filtration in the field in order to remove solids attributable to the
geological formations that may be inadvertently entrained in the sample during the
course of its collection. It is generally known that filters should not be used if the water
is to be analyzed for organic chemicals, because many organic chemicals adsorb to the
filters, thereby lowering their concentrations in the filtrate. However, whether or not to
filter groundwater samples when analyzing for metals is a much more difficult question
to answer.
Background
The Special Topics Subcommittee of the SAB's Environmental Engineering
Committee (EEC) met on April 29, 1997 to examine this question in the context of a
review of the Office of Emergency and Remedial Response's (OERR) proposed
guidance on field filtration of groundwater samples taken from monitoring wells for
metals analysis as a part of Superfund site assessment. The Subcommittee was
charged to:
a) Provide a technical review of the proposed guidance;
b) Evaluate consistency with other Agency programs; and
c) Provide comments on the appropriateness and potential impact of the
document.
U.S. Environmental Protection Agency ^
77 West Jackson Boulevard, 12th Floor
Chicago, IL 60604-3590
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The Subcommittee has developed a set of review comments focused on the
technical aspects of the guidance manual. The Subcommittee's four key points are:
proper well construction is important; filtration is not recommended under low flow
conditions; samples should be filtered when the nephelometric turbidity units (NTU)
exceeds 5 NTU; and there should be consistency on the issue across EPA.
The Agency could, as a matter of policy, decide against field filtering of
groundwater samples collected for Superfund PA and SI, but it needs to be aware of the
inherent technical limitations and uncertainties associated with such a decision. Note
that this issue of filtration of groundwater samples from Superfund sites is separate from
the issue of filtration of surface water samples from Superfund sites. The latter is a
practice that is endorsed and elaborated upon by the SAB's Ecological Processes and
Effects Committee in a separate report.
Key Findings and Recommendations
a) The Subcommittee finds that several factors could introduce errors in the
sampling and analysis of groundwater for metals. Well construction,
development, sampling, and field filtering are among the steps that could
influence the metals measured in the groundwater samples. Field filtering
is often a smaller source of variability and bias compared to these other
factors.
Therefore, the Subcommittee recommends that the Agency emphasize in
its guidance document the importance of proper well construction,
development, purging, and water pumping rates so that the field filtering
decisions can also be accurately made.
b) The Subcommittee notes that under ideal conditions, field filtered
groundwater samples should yield identical metals concentrations when
compared to unfiltered samples. However, under non-ideal conditions, the
sampling process may introduce geological materials into the sample and
would require field filtration. Under such conditions, filtering to remove the
geological artifacts has the potential of removing colloids (small particles
that may have migrated as suspended materials that are mobile in the
aquifer). Available scientific evidence indicates that field filtering should
not be necessary when: (1) wells have been properly constructed,
developed, purged; (2) when the sample has been collected without
stirring or agitating the aquifer materials; (3) and turbidity is less than 5
NTU.
Therefore, the Subcommittee agrees with OERR that for Superfund Site
Assessments the low-flow sampling technique without filtration is the
preferred sampling approach for subsequent metal analysis when well
construction, well maintenance and hydro geological conditions such as
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flow rate allow. Under such conditions, the collected "samples" should be
representative of the dissolved and particulate metals that are mobile in
groundwater systems. The Agency's proposal to rely on low flow
sampling and unfiltered samples is a conservative approach that favors
false positives over false negatives.
c) The Subcommittee is aware that when the turbidity of the sample is high,
the situation is different. It also notes that in-line filtering provides samples
which retain their chemical integrity.
Therefore, based on the available scientific knowledge, the Subcommittee
recommends that field filtering of properly collected groundwater samples
be done when turbidity in the samples is higher than 5 NTU, even after
slow pumping has been utilized to obtain the sample.
d) The Subcommittee finds that there are a number of inconsistencies-real
or apparent—that exist among Agency guidance documents dealing with
the issue of filtering; cf., OERR, Resource Conservation and Recovery Act
(RCRA), and Office of Water (OW) documents.
Therefore, the Subcommittee recommends that the Agency carefully
review its technical guidance documents on filtering to make certain that
they are consistent and that the differences (e.g., application to
groundwater vs. surface water sampling) are identified and justified.
e) With regard to the impact, the Subcommittee finds that if samples are not
filtered when they should be, then overestimation of the metals
concentrations could lead to the listing of a site on the NPL, resulting in a
misallocation of scarce resources while also presenting a major burden for
the potentially responsible parties. On the other hand, if samples are
filtered when they should not be, then the underestimation of the metals
concentrations could incorrectly result in a significant site not being listed
on the NPL.
Therefore, the Subcommittee observes that the Agency's proposal to rely
on low flow sampling and unfiltered samples for metals analysis is a
conservative approach that favors false positives over false negatives.
The Subcommittee went beyond its charge and developed the following thoughts
regarding groundwater sampling when non-aqueous phase liquids (NAPLs) are present.
f) The Subcommittee finds that potential Superfund sites often have light or
dense non-aqueous phase liquids (LNAPLs or DNAPLs, respectively)
present in their groundwater environment. The presence of these liquids
raises some important questions regarding sampling of groundwater.
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Therefore, the Subcommittee recommends that the Agency address this
issue in its revised guidance and that it conduct research to determine
whether the low flow sampling method is appropriate when LNAPLs or
DNAPLs are present.
The Subcommittee's detailed suggestions are included in the attached Appendix.
We appreciate the opportunity to review and provide comments on the draft guidance
and look forward to its completion by the Agency. While we address this report to you,
we look forward to a written response from the Assistant Administrator for the Office of
Solid Waste and Emergency Response (OSWER).
Sincerely,
Or. Genevieve M. Matanoski
Chair, SAB Executive Committee
Ishwar P. Murarka, Chair
Special Topics Subcommittee and
Environmental Engineering Committee
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APPENDIX A
Technical elaboration on points made in the EEC Report on
"To Filter, or Not to Filter; That is the Question""
An Evaluation of Superfund Proposed National Guidance on
Collection of Groundwater Samples for Metals Analysis
1. Introduction
On April 29, 1997 the Special Topics Subcommittee of the Science Advisory
Board's Environmental Engineering Committee (EEC) reviewed the Office of
Emergency and Remedial Response's (OERR's) proposed national guidance on field
filtration of groundwater samples taken for metals analysis from monitoring wells during
Superfund site assessment USEPA, 1996). Within the scope of the Superfund Hazard
Ranking System (MRS), the proposed national guidance is intended to address the
question of appropriate techniques for well water sample collection and the potential
influence of filtration on metals analysis. The results of these analyses are ultimately
used as part of the ranking exercise to determine whether or not a given site is listed on
the National Priorities List (NPL).
2. The Charge
The original charge to the Science Advisory Board (SAB) Subcommittee was to:
"provide a technical review of the proposed guidance, evaluate consistency with other
Agency programs, and provide guidance on the appropriateness and potential impact of
the document. Specific issues include: a) technical considerations, such as colloidal
mobility and transport mechanisms, phase changes, and fate and transport of inorganic
contaminants; and b) policy issues, including guidance from other federal programs,
and potential adverse impacts on other guidance or work in progress."
In this Appendix, the Subcommittee elaborates on the scientific principles that
formed the basis of their letter report.
3. Background
The Agency uses groundwater monitoring data as part of the overall evaluation
of whether or not a given site is listed on the NPL. Groundwater sampling techniques
involve invasive practices (e.g., well drilling) which have the potential to alter the
characteristics of the aquifer and the ground water. Hence, much care is required to
obtain a groundwater sample that represents the metals present in the aquifer before
the well was bored. Controversy has arisen in the technical community over the best
sampling method and whether or not the sample should be filtered prior to analysis for
metals.
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Because of differences in the way wells are installed, differences in packing
materials, and differences in the techniques used to collect groundwater samples,
considerable variability in analytical results can occur between wells and from sample to
sample. Filtering a sample is perceived by many individuals as an approach that
eliminates suspended particles and some colloids1, that contain metals (both those of
natural origin and those derived from human activities) that would not normally be in the
ground water if the soil or rock material were not disturbed during sampling. Under
these conditions, filtering of groundwater samples is likely to yield a more representative
sample and usually reduce the analytical variability between sampling events.
The literature cited by EPA indicates that colloids as large as 2 micrometers
may be mobile in porous media (Puls and Powell, 1992) and that colloid concentrations
can be as high as 1 000 times higher in fractured granitic systems (McCarthy and
Deguelde, 1993). Under these conditions, filtering is likely to yield less representative
samples. Even in the situation where non-mobile colloids were known to be present in
ground water samples, the process of filtering may remove mobile particles along with
the non-mobile particles.
Hence, the question arises as to whether or not field filtered or non-filtered
samples should be collected and whether one or the other is of greater value in judging
the concentration of mobile metal in the undisturbed ground water. Citing the literature,
the proposed guidance states that for properly constructed wells, the correct use of
"low-flow" purging and sampling techniques results in samples that more accurately
represent the mobile composition of ground waters. The low flow technique maximizes
representativeness by:
a) minimizing disturbances that may suspend geochemical materials that are
not usually mobile;
b) minimizing disturbances that may expose new reactive sites that could
result in leaching or adsorption of inorganic constituents of ground water;
c) minimizing exposure of the ground water to the atmosphere or negative
pressures, ensuring that the rate of purging and sampling doesn't remove
ground water from the well at a rate much greater than the natural ground
water influx; and
d) monitoring indicator parameters to identify when stagnant waters have
been purged and the optimum time for sample collection has been
reached.
1A colloid is defined as a particle or particles having diameters of less than 10 ,um (Puls and Powell, 1992).
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In summary, based upon the ability of the low-flow sampling technique to collect
representative samples, the Agency proposes that filtering of samples prior to metals
analysis is usually not required.
4. Guiding Principles
There are many purposes for which ground water samples may be collected, and
the specific purpose often dictates how the sample is collected, filtered, and analyzed.
Under the conservative MRS system, data are used to evaluate the potential for
contaminants to enter drinking water sources and become a potential source of human
exposure. In this context, the Subcommittee suggests the following principles. These
principles—like the proposed national guidance-may have a much broader application
than that just applied to the MRS system.
a) The purpose for which the sample is being analyzed and the goals of the
program should determine the sampling and analysis procedures.
b) Ground water samples should be collected and handled so that they are
representative of the undisturbed aquifer.
c) Ideally, the sampling technique employed should be one that does not
withdraw water at a rate that exceeds the recharge rate of the soil or rock.
This means that in most cases a "slow pump" technique is preferred.
d) Scientific investigations indicate that in most cases the analytical results
from high flow rate sampling with field filtering is similar to those obtained
from unfiltered samples collected under slow pump rate conditions.
e) In aquifers that have a very slow rate of recharge, techniques other than
slow pumping may be necessary and this may result in increased levels of
suspended particles. In these, and some other cases, it may be
necessary to filter the sample to remove solids that are introduced by the
invasive well drilling and sampling techniques and to use the results
accordingly.
fi It is inappropriate to filter ground water samples collected from aquifers
that contain naturally occurring suspended particles if they result from
transport through the aquifer due to the nature of the subsurface geology.
5. Major Recommendations
The Subcommittee agrees with OERR that for Superfund Site Assessments the
low-flow sampling technique without filtration is the preferred sampling approach for
subsequent metal analysis when well construction, well maintenance and
hydrogeological conditions such as flow rate allow. Under such conditions, the collected
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samples should represent these dissolved and particulate metals that are mobile in
groundwater systems. The Agency's proposal to rely upon low flow sampling and
unfiltered samples is a conservative approach that favors false positives over false
negatives.
The Subcommittee recommends that the revised guidance clearly state that
filtration may be required under conditions resulting in the suspension of geological or
colloidal particulates that would not otherwise be mobile. For example, sampling from
wells constructed in fine grained soils, wells with filter packs not matched to the geologic
formations, or slow recharging wells may result in the suspension of particulate
materials and associated metals that are not mobile in the groundwater system.
The Subcommittee considers that the Agency is the appropriate body to decide
whether the national guidance should require filtered or unfiitered samples for metals
analysis.
6. Elaboration of Recommendations
6.1 Purpose of the Analysis
Although the proposed guidance makes specific recommendations on handling
groundwater samples for metal analysis, these recommendations are not intended to
preclude different techniques being used to meet other project goals related to surface
waters and organic chemicals; cf., report currently being prepared by the SAB's
Ecological Processes and Effects Committee (EPEC). The Subcommittee recommends
that the revised guidance clearly provide the flexibility to match sample handling
techniques with the purpose of any study. For instance, numerous separation methods
may be required to determine what fraction of a total concentration is biologically
available.
Similarly, the Subcommittee recommends that the revised guidance indicate that
it applies equally to site samples and background samples. To the extent possible,
samples from the site and reference areas should be gathered and handled by identical
methods.
6.2 When Filtering May be Appropriate
Situations in which filtered samples might be appropriate include the following:
a) When low flow sampling is greater than the rate of qroundwater flow - This
situation arises when a well is installed in a formation where the
groundwater flow rate is much less than 0.1 liters per minute (L/min)
through the cross sectional area of the well. This situation would be
identified based on hydraulic conductivity estimates at the well (e.g., using
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baildown tests or grain size estimates) and the groundwater gradient in
the area. These are not field judgments and should be made prior to
mobilizing the sampling crew.
The linear relationship between hydraulic conductivity (K, cm/sec),
groundwater gradient (i, a dimensionless quantity), and the cross sectional
area of a well screen (A) is given by:
Flow Rate = KiA (1)
Therefore, for even a relatively high hydraulic conductivity (e.g., K = .01
cm/sec), a relatively high gradient (i = 0.01), and a typical well screen (0.5
ft diameter and 5 ft long), the calculated flow rate of 0.014 L/min is much
less than the 0.1 L/min referred to above.
A = (3.14) x (6 in x 2.5 cm/in)2 = about 700 cm2
Flow Rate = (.01 cm/sec) x (.01) x 700 cm2 x (60 sec/min) x
(1 L/1000 cc) = 0.042 L/min - which is 3x larger than the
number in the table
b) When well construction is not matched to the formation being sampled -
The well screen and filter pack are assumed to filter out the non-mobile
fraction of the formation being sampled. This may not be the case for a
well with a filter pack and slot size not matched to the formation. This can
occur at wells installed without foreknowledge of the material to be
encountered or when it is impractical to install a filter pack and slot size as
small as would be required for a fine grained formation (Nielsen, 1995).
c) When local geochemistry is important - Filtering can be important when
the geochemistry of the well environment mobilizes particulates in the
vicinity of the well, that are not mobile outside the well filter pack and
screen area. Although these situations may be much more difficult to
identify, they and the potential need for filtering under such conditions
should be recognized by the Agency in its proposed guidance.
6.3 Other Issues Affecting Samples
a) Well Construction - All wells used for sampling purposes should have
design plans or recommended installation details. These plans or
installation details should be made available to the Site Assessment
Manager (SAM) prior to the sampling event. If possible a licensed well
driller or an appropriate engineer or scientist should certify that the well
was properly designed, located, and installed, in accordance with the site
plan. This step will increase the confidence that the well was properly
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installed and capable of yielding representative groundwater samples for
analyses.
In cases where no documentation or certification of well design,
construction, and installation exists, and the well yields samples that are
turbid (>5 NTU), colored, cloudy, or contain suspended matter, the
Subcommittee recommends that the sample be field filtered.
b) Well Stabilization - The Subcommittee has identified several places where
the intended meaning of the proposed guidance is not clear in its
discussion of indicators for determining when a well has stabilized and
when sampling can occur. Specifically,
(1) The proposed guidance states that stabilization occurs when three
stable consecutive measurements are made and comply with the
acceptance criteria. Because this statement can be interpreted in
several different ways, the revised guidance should specify how the
criteria are to be applied. The table should explain what is intended
and what is feasible for field activities. Questions such as the
following arise from the current language. Do the criteria apply to
the first and the third measurement? Do the criteria apply to
consecutive pairs (the 1st to the 2nd measurement and the 2nd to the
3rd) such that a consistently increasing or decreasing trend is
acceptable as long as the trend is less than the acceptance criteria
as applied to consecutive pairs? Are the criteria applied to an
average of the three measurements and the minimum and
maximum? Are the acceptance criteria stated in terms of relative
standard deviations for the three measurements?
(2) The Agency should review the acceptance criteria and ensure that
they are appropriate over the range of measurements that can be
encountered in the variable quality ground waters that may be
sampled as part of site assessments. For example, if acceptance
criteria may change as low concentrations of an indicator such as
dissolved oxygen are measured, then separate acceptance criteria
should be included for the separate ranges. For example, + 3% is
too stringent for an indicator such as dissolved oxygen (DO)
measurements in anaerobic ground waters.
(3) The Agency should be careful in its use of terms such as
"acceptable level" when discussing NTU (for example, on page 4 of
the proposed guidance). What is meant by "acceptable levels in
nephelometric turbidity units (NTU)"? Is this a reference to the 10
NTU criteria (page 7 of guidance) which when exceeded allows use
of a 10 //m field filter? How does this criterion compare to the
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RCRA SW-846 guidance(USEPA, 1995) "Samples containing
greater than 5 NTU are only acceptable when well development is
certified by a qualified hyc'o geologist as the best obtainable"?
Does the limit of 10 NTU, (page 7 of the guidance) imply that
mobile amounts of particulates/colloids cannot equal or exceed
concentrations that yield NTUs of 5 or higher and that
nephelometric measurements this high indicate that the samples
were collected improperly? Is this true even when natural
channeling occurs in fractured bedrock? What are the implications
of such an upper limit?
Why does this section suggest use of temperature, pH and specific
conductance when a nephelometer is not available? A reference cited by
the guidance indicates that these parameters are insensitive to
stabilization (Powell and Paul, 1992). Why not suggest indicator
parameters (DO, redox potential) more sensitive to the establishment of
stabilization?
c) Vertical Heterogeneity - The traditional purging of many well volumes with
a bailer or high-speed pump prior to sampling is believed to have a side
effect of vertically mixing and possibly averaging concentrations over the
vertical water column that fell under the influence of purging. Low flow
methods have been proposed as a method of collecting a more
representative sample. When the pumping rate is less than the well
recharge rate, the zone of influence over which averaging will occur is
dramatically less and should be a function of pumping rates and ground
water flow velocities. Tom Spittler of USEPA Region I, has found that
substantial vertical VOC heterogeneity can be detected if discrete samples
are collected throughout the water column. A reference cited by the
guidance (Powell and Puls, 1993) also discusses vertical heterogeneity of
inorganic contaminants. When vertical heterogeneity exists within a well
and the rate of pumping is less than the recharge rate, the low-flow
method's smaller zone of influence has the potential to result in variable
measurements according to where the pump is located.
Therefore, assuming that the rate of pumping is less than the
recharge rate and that the low-flow/no filtration method only samples a
narrow horizontal zone, the Agency is faced with a number of questions:
(1) What is the likelihood for vertical heterogeneity to exist in a well
with a 5' or 10' screen length?
(2) What are the objectives of a Superfund assessment? Are they for
the average concentration across the entire screened length of the
well or for the highest concentration?
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(3) Where should the low-flow sampling point be placed? Middle of the
screen? Bottom?
In summary, the Subcommittee recommends that unless there is
evidence that vertical heterogeneity is not an issue, the guidance should
include a cautionary note regarding the location of the low-flow sampling
device when the pumping rate is less than the well's recharge rate.
d) LNAPLs and DNAPLs - The Subcommittee recommends that the Agency
determine whether the low flow sampling method is appropriate when light
or dense non-aqueous phase liquids (LNAPLs or DNAPLs) are present;
the revised guidance should state the Agency's position on this issue.
Region I suggests an alternate approach when LNAPL or DNAPL is
present (Cohen and Mercer, 1993; USEPA, 1993).
e) Preserving Filtered Material - The Subcommittee recommends that the
revised guidance include a paragraph that discusses disposition of the
filtered material in those cases where field filtering is found to be
necessary or preferable. For example, it may be advantageous to archive
used filter media when assessments have the potential to be contentious
or when questions remain regarding the ground water system of interest.2
Should questions arise later about the propriety of filtration, the laboratory
filter cake could be analyzed to explore the nature of the matter removed
by the filter.
6.4 Consistency with Other Guidance
The Subcommittee reviewed a limited set of examples of existing guidance
currently referenced by federal regulations and has found guidance which is not
compatible with the proposed guidance for low flow/no filtering sampling of ground
water for metals analysis. For example, Chapter 11 of SW-846 (US EPA, 1995)
a) Does not mention low flow sampling.
b) Recommends evacuation of 3 well volumes prior to sampling which is not
in agreement with the minimum disturbance of low flow sampling.
c) Lists procedures for both dissolved (filtered) and total (non-filtered) metals
and does not state a preference for either.
2 Almost all guidance recommends field filtering versus delayed filtering in the lab. One should not acid
preserve a sample prior to filtering yet the longer you wait before preserving a sample the greater the
possibility non-reversible changes will take place. However, at times samples are filtered in a lab since
the lab is nearby or because the field environment will not allow for filtering.
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Also, current Safe Drinking Water Act (SDWA) regulations (40 CFR 141.23) reference
"Methods for Chemical Analysis of Water and Wastes " (US EPA, 1979) for metals
analysis, which states "Drinking water samples containing suspended and settleable
material should be prepared using the total recoverable metal procedure" (page
METALS-5). The Agency's Contract Laboratory Program uses a similar digestion
technique while the RCRA program uses a much more aggressive digestion procedure
to determine "total" metals. RCRA Method 3005 is similar to the SDWA and the CLP
digestion procedures but is referred to as "total recoverable or dissolved". This
discrepancy in terms and sample preparation technique further complicates which
components of ground water will be considered mobile by different programs.
Until such references are changed and terminology standardized, there will not
be consistency across the different programs. Even if other existing guidance overrule
these references, their continued presence will result in a lack of consistency as ground
water sampling is applied across the various programs overseen by the Agency.
However, this lack of consistency does not preclude the Agency from basing its
decisions on sound scientific principles that are applicable to site assessments.
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REFERENCES CITED
Cohen , R.M. and J.W. Mercer. 1993. DNAPL Site Evaluation; C.K. Smoley, CRC
Press, Boca Raton, FL
McCarthy and Deguelde. 1993. Sampling and Characterization of Colloids and
Particles in Ground Water for Studying Their Role in Contaminant Transport.
Environmental Analytical and Chemistry Series. Environmental Particles,
Volume 2, Lewis Publishers, 1993, Chapters.
Nielsen. 1995. Proceedings of the Ninth Outdoor Action Conference and Exposition.
National Groundwater Association
Powell, R.M and C.J. Paul. 1992. Hazardous Waste & hazardous Materials, 9, 2,
1992pp149-162
Powell, R.M & R.W. Puls, J. 1993. Contaminant Hydrology, 12, pp51-77
Puls, R.W. and R.M. Powell. 1992. ES&T, 26, 614-621.
Spittler, T. 1993. US EPA, Region I to John Manor, Personal Communication.
US EPA. 1979. Methods for Chemical Analysis of Water & Wastes, EPA-600/4-79-
020, March 1979
US EPA. 1993. Agency document on DNAPLS, EPA-530-R-93-001
US EPA. 1995. "Test Methods for Evaluating Solid Wastes: Physical Chemical
Methods" SW-846. Third Edition, March 1995
US EPA. 1996. Proposed National Guidance on Field Filtration of Ground Water
Samples Taken for Metals Analysis from Monitoring Wells for Superfund Site
Assessment
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NOTICE
This report has been written as a part of the activities of the Science Advisory
Board, a public advisory group providing extramural scientific information and advice to
the Administrator and other officials of the Environmental Protection Agency. The
Board is structured to provide balanced expert assessment of scientific matters related
to problems faced by the Agency. This report has not been reviewed for approval by
the Agency; and hence, the contents of this report do not necessarily represent the
views and policies of the Environmental Protection Agency or other agencies in the
Federal government. Mention of trade names or commercial products does not
constitute a recommendation for use.
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U.S. Environmental Protection Agency
Science Advisory Board
Environmental Engineering Committee
Special Topics Subcommittee
April 29, 1997
CHAIR
Dr. Ishwar P. Murarka, Land & Groundwater Protection & Remediation, Environment
Group, Electric Power Research Institute, Palo Alto, CA
MEMBERS
Dr. William J. Adams, Kennecott Utah Copper Corp., Magna, UT
Dr. Stephen L. Brown, Risks of Radiation and Chemical Compounds, Oakland, CA
Dr. Linda E. Greer*, Natural Resources Defense Council, Washington, DC
Dr. Richard Kimerle, Monsanto Company (Retired), St. Louis, Ml
Dr. John P. Maney, Environmental Measurement Assessment, Hamilton, MA
Mr. Nick Molina*, P.G., Division of Hazardous Waste Management, Pennsylvania
Department of Environmental Protection, Harrisburg, PA
Dr. Thomas E. Natan*, Environmental Information Center, Washington, DC
Mr. Kenneth J. Quinn*, P.G., Montgomery Watson, Inc.,Madison, Wl
Dr. Lauren Zeise*, Reproductive and Cancer Hazard Assessment Section, California
Environmental Protection Agency, Berkeley, CA
* Greer, Natan and Zeise participated in the OECA/SFIP review only, whereas,
Molina and Quinn participated in the Filter Guidance review only.
SCIENCE ADVISORY BOARD STAFF
Kathleen W. Conway, Designated Federal Official, U.S. Environmental Protection
Agency, Science Advisory Board (1400), Washington, DC 20460
Dorothy M. Clark, Staff Secretary, U.S. Environmental Protection Agency, Science
Advisory Board (1400), Washington, DC 20460
in
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