6EPA
»3 environmtrtiai rrotocuon Aatncy
Washington. DC 20460
OSWER Directive Initiation Request
1. Directive Number
9355.4-03
2. Originator Information
Name of Contact Person
John Z. Cannon
Mail Cod*
OS-100
Office
OSWER
Telephone Code
382-4610
3. Title
Considerations in Ground Water Remediation at Superfund Sites
4. Summary of Directive (include brief statement of purpose)
The purpose of this memorandum is to transmit our findings from a recently
completed study of several sites where ground water extration is being conducted
to contain or reduce levels of contaminants in the ground water. In addition,
this memorandum presents several recommendations for modifying the Superfund
approach to ground water remediation.
S. Keywords
6a. Does THIS Directive supenseae previous uirecuve^sjy
b. Does It Supplement Previous Ofrectrve(s)?
| | No [ I Yea What directive (number. We)
Yes What elective (number. We)
No
7. Draft Level
A-SIgnedbyAA/DAA [ [ B - Signed by Office Director C - For Review 4 Comment | | D - Hi Development
8.
Document to
be distributed
*-t .
to
States
by Headquarters?
Yee
n
No
This Request Meets OSWER Directives System Format Standards.
9. Signature of Lead Office Directives Coordinator
Betti VanEpps
10. Name and Title of Approving Official
John Z. Cannon ^.
Date
11-22-89
Date
11-18-89
EPA Form 1315-17 (Rev. 5-17) Previous editions are obsolete.
OSWER OSWER OSWER O
VE DIRECTIVE DIRECTIVE DIRECTIVE
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON DC 20460
OCT I 8 1989
Directive No. 9355.4-03
MEMORANDUM
SUBJECT:
FROM:
TO:
Considerations in Ground Water Remediation at Superfur.d
Sites /
Jonathan*2. cannon
Acting Assistant Administrator
Waste Management Division Directors
Regions I, IV, v, VI, vii, viii
Emergency and Remedial Response Division Director
Region II
Hazardous Waste Management Division Directors
Region III, IX
Hazardous Waste Division Director
Region X
Purpose
The purpose of this memorandum is to transmit our findings
from a recently completed study o"f several sites where ground
water extraction is being conducted to contain or reduce levels c:
contaminants in the ground water. In addition, this memorandum
presents several recommendations for modifying the Superfund
approach to ground water remediation.
Background
The most common method for restoring contaminated ground
water is extraction and treatment of contaminated ground water.
Recent research has suggested that in many cases, it may be more
difficult than is often estimated to achieve cleanup concentration
goals in ground water. In response to these findings, the Office zi
Emergency and Remedial Response (OERR) initiated a project to
assess the effectiveness of ground water extraction systems in
achieving specified goals. Nineteen case studies were developed
from among Superfund and State-lead sites, RCRA and Federal
facilities. These sites were selected primarily on the basis that
the ground water extraction systems had been operating for a period
of time sufficiently long to allow for an evaluation of the syster..
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Objective
The objective of this memorandum is to describe the findings
cf this study and to recommend the consideration of certain
factors and approaches in developing and implementing ground vater
response actions at Superfund sites.
Findings of Study
Several trends were identified from the case studies:
o The extraction systems are generally effective in
containing contaminant plumes, thus preventing further
migration of contaminants.
o Significant mass removal of contaminants (up to 130,CCC
pounds over three years) is being achieved.
o Concentrations of contaminants have generally decreased
significantly after initiation of extraction but have
tended to level off after a period of time. At the sites
examined, this leveling off usually began to occur at
concentrations above the cleanup goal concentrations
expected to have been attained at that particular point
in time.
o Data collection was usually not sufficient to fully
assess contaminant movement and system response to
extraction.
Several factors appear to be limiting the effectiveness c:
the extraction systems examined, including:
o Hydrogeological factors, such as the heterogeneity of the
subsurface, the presence of low permeability layers, and
the presence of fractures;
o Contaminant-related factors, such as sorption to the
soil, and presence of non-aqueous phase liquids
(dissolution from a separate non-aqueous phase or
partitioning of contaminants from the residual non-
aqueous phase);
o Continued leaching from source areas;
o System design parameters, such as pumping rate, screened
interval, and location of extraction wells.
The report summarizing the study and findings, entitled
Evaluation of Ground Water Extraction Remedies is attached.
Additional copies of the report are available through the Public
Information Center ((202) 382-2080) or the Center for
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Environmental Research Information (FTS 634-7391 or (513) 569-
7391) .
P.ecc-r.endat ions
The findings of the study substantiate previous research and
confirm .that ground water remediation is a very new, complex
field. Based on this study, I am recommending consideration cf
certain factors and approaches in developing and implementing
ground water response actions. The major recommendation is to
orient our thinking so that we initiate early action on a small
scale, while gathering more detailed data prior to committing to
full-scale restoration. These recommendations are consistent
with the Guidance on Remedial Actions for Contaminated Ground
Water at Superfund Sites and do not alter Superfund's primary
goal of returning ground water to its beneficial uses in a ti.-?.e
frame that is reasonable given the particular site circumstances.
The recommendations do, however, encourage the collection of data
to allow for the design of an efficient cleanup approach that
more accurately estimates the time frames required for
remediation and the practicability of achieving cleanup goals.
While standard procedures for the more refined data
collection techniques suggested below are being developed, it
will be beneficial at most sites to implement the ground water
remedy in stages. This might consist of operating an extractirr.
system on a snail scale that can be supplemented incrementally as
information on aquifer response is obtained.
These recommendations are described further below. The
attached flow chart illustrates how the recommendations fit ir.tc
the Superfund ground water response process.
Recommendation 1: Initiate Response Action Early.
The bias for action should be considered early in the site
management process. Response measures may be implemented to
prevent further migration of contaminants if they will prevent
the situation from getting worse, initiate risk reduction, and/or
the operation of such a system would provide information useful
to the design of the final remedy. Because the data needed to
design * ground water containment system are often more limited
than that needed to implement full remediation, it will in a
number of cases be possible and valuable to prevent the
contaminant plume from spreading while the investigation to
select the remediation system progresses. The determination of
whether to implement a containment system should be based on
existing information, data defining the approximate plume
boundaries, hydrologic data, contaminants present, and
approximate concentrations, and best professional judgment.
Examples of situations where this type of action will probably be
warranted include sites where ground water plumes are migrating
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rapidly (e.g., highly permeable aquifers, mobile contaminants,
potential migration thorough fractures) and sites near drir.kir.g
water wells that are potentially affected by the plume.
Decision (ROD) for an interim remedy may be
limited evaluation of alternatives that comoars
A Record of
prepared with a lx.oi'_eu «va.j.u
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the remedy nay reveal that it is technically impracticable to
achieve health-based concentrations throughout the area of
attainment, and that another remedy or a contingent remedy may be
needed.
'v'here sufficient information is available to specify an
alternative or contingent remedy at the time of remedy selection,
the ROD should discuss the contingency in equal detail to the
primary remedial option, and should provide substantive criteria
by which the Agency will decide whether or not to implement the
contingency. See Interim Final Guidance on Preparing Superfund
Decision Documents, OSWER Directive 9355.3-02 (May 1989), at page
9-17.1 The ROD may also discuss the possibility that an ARARs
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, in the ROD
itself.2
The public should be informed of the decision to invoke the
contingency (and, perhaps, the waiver) through issuance of an
Explanation of Significant Differences (ESD) which involves a
public notice. A formal public comment period is not retired
when a decision is made to invoke a contingency specified in the
ROD; however, the Region may decide to hold additional public
comment periods pursuant to NCP section 300.825(b) (proposed)
(Dec. 21, 1988, 53FR at 51516). In any event, the public may
submit comments after ROD signature on any significant new
information which "substantially support[s] the need to
significantly alter the response action" NCP Section 300.825(c)
(proposed).
There may also be situations where the Region finds that it
is impracticable to achieve the levels set out in the ROD, but no
contingency had been previously specified in the ROD. In such
cases, a ROD amendment would be necessary to document fundamental
changes that are made in the remedy based on the information
gained during implementation; an ESO would be necessary to
1 idr instance, the ROD may provide that a contingent
remedy will be implemented if there is a levelling-off of
contaminant concentrations despite continued ground water
extraction over a stated period of time.
2 It may be possible 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 at 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.
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document significant but non-fundamental changes in the remedy
based on the additional information.
For sites where there is substantial uncertainty regarding
the ability of the remedy to return the ground water to its
beneficial uses (e.g., dense non-aqueous phase liquids in
fractured bedrock) it is appropriate to indicate that the initial
action is interim with an ultimate remedy to be determined at
some specified future date. The action should be designed to
achieve the basic goal and carefully monitored over time to
determine the feasibility of achieving this goal. In many of
these cases, this can only be determined after several years of
operation. The five year review may be the most appropriate tine
to make this evaluation. When sufficient data have been
collected to specify the ultimate goal achievable at the site
(e.g., first or second five year review), a final ROD for ground
water would be prepared specifying the ultimate goal, including
anticipated time frame, of the remedial action.
Although overall system parameters must be specified in the
ROD, it is usually appropriate to design and implement the ground
water response action as a phased process. An iterative process
of system operation, evaluation, and modification during the
construction phase can result in the optimum system design.
Extraction wells might be installed incrementally and observed
for one to three months to determine their effectiveness. This
will help to identify appropriate locations for additional wells
and can assure proper sizing of the treatment systems as the
range of contaminant concentrations in extracted ground water is
confirmed.
If it is determined that some portion of the ground water
within the area of attainment cannot be returned to its
beneficial uses, an evaluation of an alternate goal for the
ground water should be made. Experience to date on this phase of
ground water remediation is extremely limited and more definitive
guidance on when to terminate ground water extraction will be
provided later. When the point at which contaminant
concentrations in'ground water level off, however, this should be
viewed a* a signal that some re-evaluation of the remedy is
warranted. In many cases, operation of the extraction system on
an intermittent basis will provide the most efficient mass
removal. This allows contaminants to desorb from the soil in the
saturated zone before ground water is extracted providing for
maximum removal of contaminant mass per volume of ground water
removed.
Ground water monitoring should continue for two to three
years after active remediation measures have been completed to
ensure that contaminant levels do not recover. For cases where
contaminants remain above health-based levels, reviews to ensure
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that protection is being maintained at the site will take place
at least every five years.
Recommendation 3: Collect Data to Better Assess Contaminant
Movement and Likely Response of Ground Water to Extraction.
In addition to the traditional plume characterization data
normally collected, the following data is of particular
importance to .the design and evaluation of ground water remedies
and should be considered in scoping ground water RI/FSs.
Assessments of contaminant movement and extraction effectiveness
can be greatly enhanced by collecting more detailed information
on vertical variations in stratigraphy and correlating this to
contaminant concentrations in the soil during the remedial
investigation. More frequent coring during construction of
monitoring wells and the use of field techniques to assess
relative contaminant concentrations in the cores are methods that
may be used to gain this information. More detailed analysis of
contaminant sorption to soil in the saturated zone can also
provide the basis for estimating the time frame for reducing
contaminant concentrations to established levels and identifying
the presence of non-aqueous phase liquids. Cores taken from
depths where relatively high concentrations of contaminants were
identified might be analyzed to assess contaminant partitioning
between the solid and aqueous phases. This might involve
measuring the organic carbon content and/or the concentration of
the contaminants themselves.
The long-term goal is to collect this information during the
RI 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.
For further information, please consult the appropriate
Regional Ground Water Forum member, Jennifer Haley at
FTS 475-6705 or Caroline Roe at FTS 475-9754 in OERR's Hazardous
Site Control Division, or Dick Scalf at the Robert S. Kerr
Environmental Research Laboratory (FTS 743-2308)
Attachment: Flow Chart
vqj Summary Report
cc: Superfund Branch Chiefs, Regions I - X
Superfund Section Chiefs, Regions I - X wo/summary report
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GROUND WATER REMEDIATION PROCESS
Phase:
Scoping ol
wRVFS
w
1 *
Site 1
Characterization
Treatability
Investigation
Ml ,.«» 1 1
Very Hiqtw
^
Interim
Action
I iisl 01 S««>nd
!> YI.-.II Huview
r
;te»| I nidi Action
Uncertainty
Associated with
Ralurning Ground
Water to its
Beneficial Uses
Actions:
ktontty d*to ootocton
neecte
ktenttypi
Inttoll gradwnl control wells
in phased process
Monrtor aqurfer response
Design and Implement ground
water extr acton system in
phased process
Monitor aquifer response
(. v.iluate data bom syslitm
operation
Determine practicable goals
Idunbfy any areas whare
long letm institutional
contiols wiH bo nucossaiy
Admlntotntlv* Contktontlons:
ROD (Early Acton)
A) ROD (Inlehm Remedy)
B). ROD (Contingency)
C) ROD (Final)
A) ROD (Final)
B) ESDorROD
amendment
Enforcement Considerations:
Negottele Rl^FS Scope:
Data collection
Earty acton
Nogohalu Consent Decree
A). Negohale Consent Owciue
B) Possible stipulation 01
amondmonl to Consent
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