f j •§ UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
OCT101990
OFFICE OF
SOLID WASTE AND EMERGENCY RESPONSE
OSWER Directive 9283.1-03
MEMORANDUM
SUBJECT: Suggested ROD Language for Various Ground Water
Remediation Options
FROM: Henry L. Longest II, Director /s/
Office of Emergency and Remedial Response
Bruce M. Diamond, Director /s/
Office of Waste Programs Enforcement
TO: Director, Waste Management Division
Regions I, IV, V, VII, VIII
Director, Emergency and Remedial Response Division
Region II
Director, Hazardous Waste Management Division
Regions III, VI, IX
Director, Hazardous Waste Division, Region X
Regional Counsels, Region I - X
Purpose
The purpose of this memorandum is to provide
supplemental guidance to the October 18, 1989, OSWER Directive
9355.4-03, entitled "Considerations in Ground Water Remediation at
Superfund Sites," which examines the role of ground water
remediation in Superfund cleanups and recommends modifications to
the current approach.
Background
A recent study conducted by the Office of Emergency and
Remedial Response (OERR) assessed the effectiveness of nineteen
operating ground water extractions systems in achieving specified
goals. The study found that ground water extraction was effective
in containing contaminant plumes and achieving significant mass
removal of contaminants. However, in many cases, contaminant
concentrations did not decrease linearly over time to reach desired
remediation goals. After significant initial decreases,
concentrations typically leveled off, often at concentrations
higher than the cleanup levels. Factors
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which may explain this phenomenon include the extent of source
removal, hydrogeological characteristics of the aquifer, the
physico-chemical nature of the contaminants, and extraction system
design parameters.
Based on these findings, OSWER recommended consideration of
the following approaches to planning and implementing ground water
remediation: 1) initiation of early or interim response measures
designed to prevent further migration of contaminants during the
remedial investigation, and/or until sufficient information about
system response has been obtained to allow final remedy selection;
2) provision for changes in the remedy during implementation in the
Record of Decision, either by specifying a contingency remedy or by
selecting an interim remedy and goal; and 3) collection of
additional or supplemental information with which to better assess
contaminant mobility and system effectiveness, such as data related
to vertical changes in hydraulic conductivity, contaminant
partitioning between soil and ground water, and the presence of
non-aqueous phase liquids.
Objective
The objective of this memorandum is to provide suggested
language for Records of Decision corresponding to recommendations 1
and 2 from the OSWER Directive.
Recommended Language
Study findings indicate that it is often difficult to predict
the ultimate concentration to which contaminants in ground water
may be reduced until an extraction system has been operating for
some period of time. Records of Decision should reflect the amount
of relative uncertainty believed to be associated with achieving
remediation goals in ground water at a particular site.
Corresponding to recommendations 1 and 2 from OSWER Directive
9355.4-03, RODs may be structured in several ways to reflect
purpose of a selected remedy: 1) as final actions, intended to
restore ground water quality; 2) as final actions, with a provision
for establishing contingency goals; or 3) as interim actions,
intended to promote plume containment and generate additional
performance data, to be followed by final decisions. The following
standard language may be employed, when appropriate, to correspond
to site-specific remediation scenarios.
1. FINAL ACTION (low uncertainty, restoration actions)
In some cases, there may be little uncertainty that the remedy
will be able to achieve the remediation goals specified in
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the ROD throughout the area of attainment. Under these
circumstances, a final remedy, designed to restore the aquifer, may
be specified without a contingency. The following type of statement
should appear in the Selected Remedy section of the ROD:
A
The goal of this remedial action is to restore ground
water to its beneficial use, which is, at this site, (specify
whether this is a potential or actual drinking water source,
or used for (non-domestic purposes). Based on information
obtained during the remedial investigation and on a careful
analysis of all remedial alternatives, EPA < (optional) and
the State/Commonwealth of > believe that the selected
remedy will achieve this goal. It may become apparent, during
implementation or operation of the ground water extraction
system and its modifications, that contaminant levels have
ceased to decline and are remaining constant at levels higher
than the remediation goal over some portion of the
contaminated plume. In such a case, the system performance
standards and/or the remedy may be reevaluated.
The selected remedy will include ground water extraction for
an estimated period of years, during which the systems
performance will be carefully monitored on a regular basis and
adjusted as warranted by the performance data collected during
operation. Modifications may include any or all of the
following:
a) at individual wells where cleanup goals have been
attained, pumping may be discontinued;
b) alternating pumping at wells to eliminate stagnation
points;
c) pulse pumping to allow aquifer equilibration and to
allow adsorbed contaminants to partition into ground
water; and
d) installation of additional extraction wells to
facilitate or accelerate cleanup of the contaminant
plume.
To ensure that cleanup goals continue to be maintained, the
aquifer will be monitored at those wells where pumping has
ceased on an occurrence of every years following
discontinuation of ground water extraction.
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If it is determined that drinking water is not the beneficial
use of the aquifer, as in a Class III aquifer, then the preceding
language should be modified to reflect alternative uses and
remediation goals.
2. CONTINGENCY MEASURES/GOALS (high to moderate uncertainty,
potential ARARs waiver, potential containment goal)
In many cases, information may emerge during implementation
and monitoring of the recovery system which strongly suggests that
it is technically impracticable to restore the aquifer, or achieve
remediation goals throughout the area of attainment (e.g., in the
entire ground water plume; or, if waste is left in place, the area
of the plume excluding the waste management unit). If it is likely
that such information will emerge, the Region has the option of
anticipating future changes in the Record of Decision by providing
for contingency measures. The ROD should explain those measures in
sufficient detail (i.e., in the Comparative Analysis of
Alternatives and Selected Remedy sections), so that the public has
ample opportunity to review and comment on the contingency as well
as the selected remedy. The Selected Remedy section should also
specify the criteria under which the contingency measures would be
implemented.
A. Suggested Language for the Selected Remedy Section of the ROD
The following type of language should appear in the Selected
Remedy portion of the ROD, corresponding to situations in which it
is anticipated that it may be technically impracticable to reach
MCLs/MCLGs or other goals as discussed in the ROD. An ARARs waiver
will be invoked, accompanied by an Explanation of Significant
Difference (ESD), if it is determined, on the basis of the stated
criteria, that MCLs/MCLGs or other ARARs cannot be achieved within
all portions of the area of attainment.
The goal of this remedial action is to restore the ground
water to its beneficial use, which is, at this site, (specify
whether this is a drinking water aquifer or used for
non-domestic purposes). Based on information obtained during
the remedial investigation, and the analysis of all remedial
alternatives, EPA < (optional) and the State/Commonwealth of
> believe that the selected remedy may be able to
achieve this goal. Ground water contamination may be
especially persistent in the immediate vicinity of the
contaminants' source, where concentrations are relatively
high. The ability to achieve cleanup goals at all points
throughout the area of attainment, or plume, cannot be
determined until the extraction system has been implemented,
modified as necessary, and plume
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response monitored over time. If the selected remedy cannot
meet the specified remediation goals, at any or all of the
monitoring points during implementation, the contingency
measures and goals described in this section may replace the
selected remedy and goals for these portions of the plume.
Such contingency measures will, at a minimum, prevent further
migration of the plume and include a combination of
containment technologies < typically, ground water extraction
and treatment > and institutional controls. These measures are
considered to be protective of human health and the
environment, and are technically practicable under the
corresponding circumstances.
The selected remedy will include ground water extraction
for an estimated period of years, during which time
the system's performance will be carefully monitored on a
regular basis and adjusted as warranted by the performance
data collected during operation. Modifications may include any
or all of the following:
a) at individual wells where cleanup goals have been
attained, pumping may be discontinued;
b) alternating pumping at wells to eliminate stagnation
points;
c) pulse pumping to allow aquifer equilibration and
encourage adsorbed contaminants to partition into
ground water; and
d) installation of additional extraction wells to
facilitate or accelerate cleanup of the contaminant
plume.
To ensure that cleanup goals continue to be maintained,
the aquifer will be monitored at those wells where pumping has
ceased on an occurrence of every years following
discontinuation of ground water extraction.
If, in EPA's judgment, implementation of the selected remedy
clearly demonstrates, in corroboration with strong hydrogeological
and chemical evidence, that it will be technically impracticable to
achieve and maintain remediation goals in the plume or a portion of
the plume, a contingency will be implemented. For example, a
contingency may be invoked when it has been demonstrated that
contaminant levels have ceased to
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decline over time, and have remained constant for a specified
period of time at some statistically significant level above
remediation goals, as verified by multiple monitoring wells. Where
such a contingency situation arises, ground water extraction and
treatment would typically continue as necessary to achieve mass
reduction and remediation goals throughout the rest of the area of
attainment. The following suggested language describes the
recommended contingency measures:
If it is determined, on the basis of the preceding
criteria and the system performance data, that certain
portions of the aquifer cannot be restored to their beneficial
use, all of the following measures involving long-term
management may occur, for an indefinite period of time, as a
modification of the existing system:
a) engineering controls such as physical barriers, or
long-term gradient control provided by low level
pumping, as containment measures;
b) chemical-specific ARARs will be waived for the
cleanup of those portions of the aquifer based on
the technical impracticability of achieving further
contaminant reductions;
c) institutional controls will be provided/maintained
to restrict access to those portions of the aquifer
which remain above remediation goals;
d) continued monitoring of specified wells; and
e) periodic reevaluation of remedial technologies for
ground water restoration.
The decision to invoke any or all of these measures may
be made during a periodic review of the remedial action, which
will occur at year intervals < at least, every five
years, in accordance with CERCLA section 121 (c) >.
Where the contingency implemented differs significantly from
that described in the ROD, an Explanation of Significant
Differences will be issued or it may be necessary to do a ROD
amendment. Even where the contingency implemented does not differ
significantly from that described in the ROD, it would be advisable
to issue an ESD to inform the public of these actions.
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Where RODs have been issued prior to this guidance, and
information emerges during the implementation and operation of the
ground water extraction system which indicates that restoration of
the aquifer will not be practicable, these RODs may in some cases
have to be amended to accommodate the changes in goals and remedy
design suggested by this document.
B. Supporting Language
If a contingency remedy is presented in the ROD, the preceding
language should be accompanied by supporting language in the
Comparative Analysis of Alternatives section of the ROD, which
indicates:
a. that both the primary remedy and the contingency
measures provide overall protection of human health and
the environment, either by reducing contaminants to
MCLs/MCLGs or other remediation goals, or through a
combination of mass reduction, institutional and/or
engineering controls;
b. that chemical-specific ARARs will either be attained
or waived.
The Statutory Determinations section should establish that
both the selected remedy and the contingency measures fulfill
CERCLA section 121 requirements. In addition, any ARARs waiver must
be justified under the Compliance with ARARs determination.
3. INTERIM ACTIONS (moderate to substantial uncertainty, or early
action containment measures)
Interim actions may be specified under two scenarios: 1) to
prevent further plume migration and initiate cleanup while RI/FS
and post-RI/FS activities are being completed; and 2) to obtain
information about the response of the aquifer to remediation
measures in order to define final cleanup goals that are
practicable for the site. Where there is substantial uncertainty
regarding the ability of a remedy to restore ground water to
drinking water quality (i.e., MCLs/MCLGs) or other beneficial uses,
which could be reduced by further information obtained during
implementation of a remedial action, it will often be appropriate
to select an interim remedial action to prevent further plume
migration and initiate ground water restoration.
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A. Interim Actions
The purpose of the interim action, as discussed in the Scope
and Role of the Operable Unit section, may be to initiate
restoration while additional information is collected to better
assess the practicability of aquifer restoration prior to the
determination of final cleanup levels. Preliminary cleanup levels
may be identified, but this section should emphasize that while the
purpose of the action is to work toward the goal of restoration, it
does not constitute a final action for the ground water. All
interim action RODs should specify, to the extent possible, the
period of operation that will occur before a final decision is made
regarding the practicability of aquifer restoration. At the end of
this time, a final action ROD should be prepared which specifies
the final remedy goals and timeframe, for the contaminated ground
water at the site.
An interim action ROD should include the following type of
language in the Selected Remedy section.
This alternative calls for the design and implementation
of an interim remedial action to protect human health and the
environment. The goal(s) of this remedial action is(are) to
(specify interim goals, e.g., halt the spread of a contaminant
plume, remove contaminant mass, etc.) and to collect data on
aquifer and contaminant response to remediation measures. The
ultimate goal of remediation will be determined in a final
remedial action for this site. This remedial action will be
monitored carefully to determine the feasibility of achieving
this goal with this method and to ensure that hydraulic
control of the method and plume is maintained. After the
period of time necessary, in EPA's judgment, to arrive at a
final decision for the site, a final ROD for ground water,
which specifies the ultimate goal, remedy and anticipated
remediation timeframe, will be prepared. Upon completion of
the RI/FS, this interim system may be incorporated into the
design of the site remedy specified in the final action ROD.
B. Early Interim Actions
As discussed in the National Contingency Plan (NCP) (55 FR
8846, March 8, 1990), EPA is encouraged to initiate interim actions
early in the process, i.e., during the RI/FS. An early interim
action may be used to restrict plume migration until an RI/FS for a
final remedial action is completed. Information collected during
implementation will also be used to evaluate aquifer response to
remediation. This purpose should be discussed In the Scope and Role
of the Operable Unit section.
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Early interim action RODs should not specify final cleanup levels
because such goals are beyond the limited scope of the action.
These will be addressed by the final remedial action ROD.
Both the Early Interim Action and Interim Action options
should be supported by language in the Comparative Analysis of
Alternatives section which indicates that these actions may not
achieve final cleanup levels for the ground water at the site,
although it is effective in the short term in preventing further
degradation and initiating reduction in toxicity, mobility or
volume. MCLs/MCLGs or state cleanup standards will not be ARARs for
these actions because they are beyond the scope of the interim
action. The nine-criteria evaluation should focus on those criteria
most pertinent to short-term effectiveness and reduction of
toxicity, mobility or volume, consistent with the scope and purpose
of the interim action. In addition, the Statutory Determinations
section should discuss the ways in which the interim action
satisfies the CERCLA section 121 requirements within the scope of
the action (i.e., protectiveness of the remedy).
Action Requested
Language like that provided in this memorandum should be
incorporated, where appropriate, in Records of Decision which
address contaminated ground water. For additional guidance on
preparing Records of Decision for Superfund sites, please refer to
OSWER Directive 9355.3-02, "Guidance on Preparing Superfund
Decision Documents" (October, 1989) .
If you have any questions about this material, please contact
your OERR or OWPE Regional Coordinator, Alison Barry at FTS
398-8366 or (703) 308-8366, or Jennifer Haley at FTS 398-8363 or
(703) 308-8363, in OERR's Hazardous Site Control Division.
cc: Superfund Branch Chiefs, Regions I - X
Superfund Section Chiefs, Regions I - X
NOTICE: The policies set out in this memorandum are intended
solely as guidance. They are not intended, nor can they be relied
upon, to create any right enforceable by any party in litigation
with the United States. EPA officials may decide to follow the
guidance provided in this memorandum, or to act at variance with
the guidance, based on an analysis of specific site circumstances.
The Agency also reserves the right to change this guidance at any
time without public notice.
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