905R90126
United States
Environmental Protection
Agency
Office of
Solid Waste and
Emergency Response
Publication 9200.5-2161
January 1990
Superfund
Records g{
Update
FEB - 6 1990
Office of Emergency and Remedial Response
Hazardous Site Control Division OS - 220
ENVIRONMENTAL PROTECTION AGENCY
LIBRARY, REGION V
Intermittent Bulletin
Volumes Numbers
Evaluation of the
Effectiveness of
Ground-Water
Extraction Systems
The Office of Emergency and Remedial
Response (OERR) recently completed a
study that assesses the effectiveness of
ground—water extraction systems in
achieving cleanup goals. The study is
entitled, Evaluation of Ground-Water
Extraction Remedies. Data from 19 on-
going and completed ground-water ex-
traction systems were used to analyze in
detail the varbus factors that can affect
the performance of the extraction sys-
tems.
FINDINGS
The report identified several trends. They
include:
Containmentofground-waterplumes
was usually achieved, thus prevent-
ing furthermig ration of contaminants.
Significant mass removal of contami-
nants (up to 130,000 pounds over 3
years) has been achieved.
Contaminant concentrations initially
decreased significantly followed by
a leveling off. Afterthe period of rapid
decline, the continued decreases in
concentration were slower than be-
fore.
Data collected during the remedial
investigation were often insufficient
to fully assess contaminant move-
ment and system response to ex-
traction.
Four types of factors that appear to limit
the effectiveness of extraction systems
include:
• Hydrogeological factors, such as the
heterogeneity of the subsurface, the
presence of low-permeability layers,
and the presence of fractures;
Contaminant-related factors, such as
sorplion to the soil and presence of
nonaqueous phase liquids (dissolu-
tion from a separate nonaqueous
phase or partitioning of contaminants
from the residual nonaqueous phase);
• Continued leaching from source ar-
eas;
System design parameters, such as
pumping rate, screened interval, and
location of extraction wells.
COJVCLt/SIOJVS
It is expected that ground-water extrac-
tion and treatment will continue to be a
primary component of remedies address-
ing contaminated ground water. It should
be possible to return ground water to its
beneficial uses over large portions of the
area of attainment using pump and treat
systems. Limitations on the effectiveness
of ground-water extraction generally oc-
cur in the source areas where contami-
nant concentrations in the saturated soil
are high and/or nonaqueous phase liq-
uids are present. In those areas where
concentrations remain above cleanup
goals and extraction has reached a point
of limited effectiveness, enhancement
methods such as biodegradation may be
considered. Finally, containment and in-
stitutional controls should be implemented
over those portions of the ground water
that remain above levels that reflect the
beneficial uses of the ground water.
The results of this analysis also highlight
specific factors and approaches to con-
sider in developing and implementing
ground-water response actions. Recom-
mendations resulting from the study are:
initiate response action early, provide
flexibility to modify system design, and
collect applicable ground-water data.
Each of these recommendations is dis-
cussed in greater detail below.
Recommendation 1: Initiate
Response Action Early
This recommendation encourages con-
sideration of early actions to prevent
further migration of contaminants if these
measures prevent the situation from
getting worse, initiate risk reduction, and/
or provide useful information to design
the final remedy.
For early actions, an interim remedy
record of decision (ROD) may be pre-
pared with a limited evaluation of alterna-
tives. The ROD would need to discuss
how the advantages of taking an early
action outweigh the possible ramifica-
tions of waiting until the remedial investi-
gation has been completed. Evaluation
of an early action should be considered
during the project scoping and, if deter-
mined to be appropriate, implemented
while the overall RI/FS is under way.
Site managers are also advised to imple-
ment ground-water remediation systems
in a staged process at sites where data
collected during the Rl do not clearly
define the parameters necessary to opti-
mize system design. For example, this
might consist of installing an extraction
system in a highly contaminated area
and observing the response of the aqui-
fer and contaminant plume during im-
plementation of the remedy. Based on
the data gathered during this initial op-
eration, the system could be modified
Continued on p. 2
-------
continued from p. 1
and expanded as part of the remedial
action phase to address the entire plume
in the most efficient manner.
Recommendation 2: Provide
Flexibility in the Selected
Remedy to Modify the System
Based on Information Gained
During Its Operation
In many cases, it may not be possible to
determine the ultimate concentration
reductions achievable in the ground water
until the ground-water extraction system
has been implemented and monitored for
some period of time. RODs should indi-
cate the uncertainty associated with
achieving cleanup goals in the ground
water.
In general, RODs should indicate that the
goal of the remedial action is to return the
ground water to its beneficial uses, i.e.,
MCLs/health-based levels should be
achieved for ground water that is poten-
tially drinkable. In some cases, the uncer-
tainty in the ability of the remedy to achieve
this goal will be low enough that the final
remedy can be specified without a con-
tingency.
At some sites, data may indicate that it
may not be practicable to achieve the
goal over portions of the contaminated
zone, thus warranting the inclusion of
contingency measures that provide for
containment and control of areas that
prove unstable once the system has
operated for a period of time. Contin-
gency RODs should discuss the fallback
remedy in equal detail to the primary
remedial option and should provide sub-
stantive criteria by which the Agency will
decide whether or not to implement the
contingency (see Guidance on Preparing
SuperfundDecision Documents, OSWER
Directive 9355.3-02 [May 1989], pages
9-17).1 The ROD may also discuss the
possibility that an ARAR waiver will be
invoked when MCLs or other Federal or
State standards cannot practicably be
attained in the ground water; a written
waiver finding should be issued at the
time the contingency is invoked or, in
limited circumstances, can be included in
the ROD itself.2'3
For sites where there is substantial un-
certainty regarding the ability of the
remedy to return the ground water to its
beneficial uses (e.g., dense nonaqueous
phase liquids in fractured bedrock), site
managers may find it appropriate to indi-
cate that the initial action is interim with
an ultimate remedy to be determined at
some specified future date. In many of
these cases, the ability of the remedy to
achieve health-based levels can only be
determined after several years of opera-
tion. Based on data collected during the
time the remedy is operating (e.g., 5 or 10
years), a final ROD for ground water
would be prepared specifying the ulti-
matecleanupgoals, and anticipated time
frame, of the remedial action.
In all cases, although overall system
parameters must be specified in the ROD,
optimum system design is usually ad-
dressed through an iterative process of
system operation, evaluation, and modi-
fication during the construction phase.
If it is determined that some portion of the
ground water within the area of attain-
ment cannot be returned to its beneficial
uses, site managers should evaluate an
alternate goal for the ground water, en-
surethat institutional controls are in place
over ground water contaminated above
health-based levels, and continue appro-
priate containment measures.
Ground-water monitoring should continue
for 2 to 3 years after active remediation
measures have been completed to en-
sure that contaminant levels do not re-
cover. Where contaminants remain above
health-based levels, reviews to ensure
that protection is being maintained at the
site will take place at least every 5 years.
Recommendation 3: Collect Data
to Better Assess Contaminant
Movement and Likely Response
of Ground Water to Extraction
In addition to the plume characterization
data normally collect ed.thefollowingdata
are of particular importance to the design
and evaluation of ground-water reme-
dies and should be considered in scoping
ground-water RI/FSs.
More frequent coring during well
construction and analysis to assess
vertical variations in stratigraphy and
contaminant concentrations in the
soil through the saturated zone
Analysis of contaminant sorption to
soil in the saturated zone
This information can provide the basis for
estimating the time frame for reducing
contaminant concentrations to estab-
lished levels determining the most effi-
cient pump rates locating optimum depth
for well screens, and identifying the pres-
ence of nonaqueous phase liquids.
The long-term goal is to collect such
information during an Rl so that more
definitive decisions can be made at the
ROD stage. Standardized sampling and
analytical methods to support these
analyses are currently being evaluated.
Copies of the Evaluation of Ground-Water
Extraction Remedies are currently being
printed and may be obtained in February
from the Public Information Center, FTS
382-2080, (202) 382-2080, or the Center
for Environmental Research Information
FTS 684-7391 or (513) 569-7391.
For additional information, please con-
sult your Regional Ground Water Forum
member, your Regional Coordinator, or
Jennifer Haley at FTS 475-6705 in the
Hazardous Site Control Division, OERR
or Dick Scalf at the Robert S. Kerr Envi-
ronmental Research Laboratory, FTS
743-2308.
Attention; Region V
The November 1989 issue of the
ROD Update contained two incor-
rect phone numbers for your Fund-
lead Regional coordinators. The
correct phone numbers are: Trudi
Fancher FTS 475-9759{MI and Wl);
Sandra Panetta FTS 47S-9757(OH,
MN, IN, IL)
'For instance, the ROD may provide that a contingent remedy will be implemented if there is a leveling-off of contaminant concentrations despite
continued ground-water extraction over a stated period of time.
2lt may be appropriate to invoke a waiver at the time of ROD signature (a "contingent waiver") where, for example, the ROD is detailed and establishes
an objective level or situation by which the waiver would be triggered. However, the use of contingent waivers should only be considered on a case-
by-case basis after discussion with OERR/OWPE.
"Contingency remedies may be invoked through the issuance of an Explanation of Significant Differences (ESD), which does not require public comment.
The Region has the discretion, however, to obtain public comment on the ESD or to exercise the contingency remedy through the issuance of an amended
or additional ROD (which also requires public comment) if it so chooses (see Guidance on Preparing Superfund Decision Documents, July 1989, OSWER
Directive 9355.3-02, Chapters 8 and 9).
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Waiving MCLs
In the past, a number of RODs authoriz-
ing interim (nonfinal) remedies have in-
voked the CERCLA interim remedy waiver
from applicable or relevant and appropri-
ate requirements. Usually, these interim
remedy RODs have waived Safe Drink-
ing Water Act Maximum Contaminant
Levels (MCLs) as cleanup levels to be
achieved in the ground water. Typically,
these RODs have further stated that MCLs
will be achieved as a result of the final
ROD for the ground water.
Site managers should note that in-
terim (nonfinal) remedies do not need
to invoke Interim Remedy Waivers for
chemical-specific ARARs if these
ARARs are outside the scope of the
interim remedy. For interim action
RODs, the ARARs discussion should
focus only on those ARARs related to any
final disposition of waste, offsite treat-
ment or disposal, or releases caused
during implementatbn. An interim rem-
edy waiver may be necessary in some
situations. However, if an interim waiver
is needed, the final remedy must comply
with the requirement. The discussion
under "utilization of permanent solutions
and treatment to the maximum extent
practicable" should indicate that the se-
lected remedy represents the best bal-
ance of tradeoffs among alternatives with
respect to pertinent criteria, given the
limited scope of the action. The discus-
sion under the preference for treatment
section should note that the preference
will be addressed in the final decision
document for the site or operable unit.
For example, frequently the goal of an
interim ground-water remedy is to hy-
draulically contain a plume or to achieve
mass removal, not to return the ground
water to "drinkable levels.'" In these situ-
ations, MCLs are not ARARs because
they do not suit the scope of the action.
However, MCLs will be ARARs when the
final remedial action intended to restore
the aquiferto its beneficial use as a drink-
ing water source is implemented, if it is
determined in a final ROD that MCLs
cannot be achieved, a technical impracti-
cability waiver should be justified in the
ROD. Examples of RODs invoking tech-
nical impracticability waivers are shown
in the table below.
Examples of RODs Invoking Technical Impracticability Waivers
Region Site Name, State
I Sullivan's Ledge, MA
V Seymour Recyling, In
VIII Libby Ground Water, MT
Signature
Date
06/29/89
09/25/89
12/30/88
Ground-Water
Remedy
Pump & Treat
Pump & Treat
Pump & Treat
Waiver
Requirement
SWDA/MCLs
SWDA/MCLs
SWDA/MCLs
For information on documenting interim actions, see the Guidance on Preparing Superfund Decision Documents, July 1989, OSWER
Directive 9355.3-02.
FY 1982 Through Third
Quarter FT 1989 RODs
Documenting Ground-
Water Remediation
The inserted table provides a list of RODs
documenting ground-water remediation
by ground-water remedy categorization.
Provided below is a description of each
remediation category.
Complete Restoration
Extraction and treatment or natural at-
tenuation of contaminated ground water
to health-based levels (e.g., MCLs).
Partial Restoration
Extraction and treatment of drinking/sur-
face water will not attain health-based
levels (e.g., MCLs) throughout the area
of attainment. Treatment does not ad-
dress all types of contaminants (e.g., air
stripping for VOCs and metals).
Plume Containment
Slurry walls or containment barriers
(include gradient control, i.e., barrier
well systems)
• Extraction or injection wells
Dikes or containment ponds
Drains
Leachate
Collection and treatment of leachate/
ground water from the aquifer due to a
leaching waste source.
Wellhead Treatment
Treatment at the well, pumping station, or
adjacent facility prior to discharge to a
drinking water distribution system.
Other Remediation Tech-
niques
• Alternate water supplies
Institutional controls
• Deferring the ground-water remedial
investigation or cleanup goals until
the site is more fully characterized
Individual well or tap remedy (e.g.,
carbon filters)
For ideas, submissions, or questions concerning the ROD Update, please contact Sharon Frey, Hazardous Site Control
Division at FTS 475-9754. Members of the public may obtain copies by phoning or writing EPA's Public Information Cen-
ter (PM-211B), 401 M St., S.W., Washington, DC 20460. Phone (202) 382-2080.
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