UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
Directive No. 9283.1-06
MAY 27 1992
OFFICE OF
SOLID WASTE AND EMERGENCY RESPONSE
MEMORANDUM
SUBJECT:
FROM:
To:
Considerations in Ground-Water Remediation at Superfund
Sites and RCRA Facilities — Update
Don R.
Assistant Administra
Waste Management Division Directors
Regions I, IV, V, VII
Emergency and Remedial Response Division Director
Region II
Air and Waste Management Division Director
Region II
Hazardous Waste Management Division Directors
Regions III, VI, VIII, IX
Hazardous Waste Division Director
Region X
Environmental Services Division Directors
Regions I, VI, VII
Purpose
This updated Directive clarifies and expands OSWER's general
policy concerning remediation of contaminated ground water,
especially with regard to nonaqueous phase liquid (NAPL)
contaminants. This document promotes a consistent and sound
approach to ground-water remediation at both Superfund sites and
RCRA facilities and reinforces OSWER's commitment to cleanup
ground-water contamination at these sites to the fullest extent
possible.
Background
This Directive does not supersede or replace previous
Superfund or RCRA Directives regarding ground-water remediation
policy. The 1989 and 1990 Directives address Superfund sites
only and should continue to be consulted with regard to Superfund
policy and Record of Decision (ROD) language. This updated
U.S. EPA. Considerations in Ground-Water Remediation at Superfund Sites. Directive 9355.4-03,
Office of Solid Waste and Emergency Response(OSWER), October 18, 1989.
U.S. EPA. Suggested ROD Language for Various Ground-Water Remediation Options. Directive 9283.1-03,
OSWER, October 10, 1990.
Printed on Recycled Paper
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Directive reiterates and clarifies technical recommendations from
prior Directives and expands upon them to address remediation
problems associated with NAPLs. Also, this Directive is
consistent with the principles of the 1991 EPA Ground-Water
Protection Strategy , but does not specifically address how
ground-water remedial activities are to be prioritized.
Ground-water contamination is one of the most prevalent and
challenging problems at hazardous waste sites in both the
Superfund and RCRA Corrective Action programs. Ground-water
contamination is present at more than 70% of the sites on the
National Priorities List and almost 50% of the permitted RCRA
land disposal facilities. The Office of Emergency and Remedial
Response (OERR) completed a study in 1989 which evaluated the
performance of ground-water extraction systems operating at 19
sites. Recently, an update and expansion of this study has been
completed for 17 of the original and five additional sites .
These evaluations identified hydrogeologic and contaminant
characteristics as well as system design factors that may impede
the ability of extraction systems to achieve appropriate cleanup
levels over the entire area of contamination. These
characteristics, listed below, are probably more common at
hazardous waste sites than previously realized and should be
considered during site characterization and conceptual model
development.
1. Hydrogeologic factors: such as significant subsurface
heterogeneity, numerous low permeability layers, fractured
or karst aquifers, or other hydrogeologic complexities.
2. Contaminant factors: such as continued leaching of
contaminants from source areas, partitioning of contaminants
between ground water and aquifer solids, or presence of NAPL
in the subsurface.
3. System design factors: such as poorly designed or
improperly located extraction wells, or inefficient pumping
schemes.
In particular, this Directive addresses EPA's approach at
sites involving nonaqueous phase liquid (NAPL) contamination.
Virtually all NAPLs are organic compounds (or mixtures of
compounds) that are immiscible (resistant to mixing) with
U.S. EPA. Protecting the Nation's Ground Water: EPA's Strategy for the 1990's, Final Report of the
EPA Ground-Water Task Force. Publication 21Z-1020, Office of the Administrator, July 1991.
U.S. EPA. Evaluation of Ground-Water Extraction Remedies. Publication EPA/540/2-89/054, OERR,
September 1989.
U.S. EPA. Evaluation of Ground-Water Extraction Remedies: Phase II, Pre-print. Publication 9355.4-
05 and 05A, OERR.
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water. The distinct interface resulting from the water-NAPL
contact does allow some NAPL to dissolve, with the degree of
aqueous solubility varying dramatically among NAPL compounds«
The term NAPL refers to the undissolved liquid phase of a
compound, such as Trichloroethylene (TCE), and not to the aqueous
phase dissolved in water. NAPL usually enters the subsurface as
a separate liquid phase, and may penetrate to significant depths.
As NAPL moves through the subsurface, a portion becomes trapped
in soil pore spaces (or rock fractures) and a portion may
continue to migrate. "Free-phase NAPL" is the migrating portion,
which can flow into a well. "Residual NAPL" is that portion
trapped in pore spaces by capillary forces, which can not
generally flow into a well or migrate as a separate phase.
In the unsaturated zone (subsurface zone above the water
table), NAPLs may release vapor phase organic contaminants to
soil pore spaces and dissolved contaminants to infiltrating
waters. In the saturated zone, NAPLs that are less dense than
water (light NAPLs or LNAPLs) will tend to float on the water
table while those more dense than water (DNAPLs) sink downward,
through ground water. DNAPLs may exhibit varying behavior
depending on local geologic conditions. For example, DNAPLs can
move downslope along the upper surfaces of low permeability
layers or along fractures, can form pools in stratigraphic or
structural depressions, and can sometimes penetrate low
permeability layers via fractures. Since DNAPLs are driven by
gravity, they may move across or in the opposite direction from
ground-water flow. LNAPLs tend to migrate along the water table
surface. Both residual and free-phase NAPLs dissolve slowly,
supplying potentially significant concentrations of contaminants
to ground water over very long time periods. Therefore,, the
presence of H&PLs uili have a significant influence on the time
frame required or likelihood of achieving cleanup standardsp and
should be evaluated ??hen selecting appropriate remedial actions.
Cleanup standards for contaminated ground water are
generally based on protection of human health and the
environment. For Superfund sites, site-specific ground-water
cleanup standards are established based on applicable or relevant
and appropriate requirements (ARARs) for the use classification
of the ground water and/or acceptable human health and
environmental risk levels for current and future pathways of
exposure. (ARARs include standards established under the Safe
Drinking Water Act, Clean Water Act, or applicable State
standards.) Under RCRA, facility-specific "media cleanup
standards" for ground water are established for Corrective Action
U.S. EPA. Ground Water Issue: Dense Nonaqueous Phase Liquids. Publication EPA/540/4-91-002, Office
of Research and Development(ORD)/OSWER, March 1991.
' U.S. EPA. Dense Nonaqueous Phase Liquids -- A Workshop Summary. Publication EPA/600/R-92/030, ORD,
February 1992.
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facilities using applicable human health and environmental
standards and/or acceptable health/environmental risk levels. In
this Directive the term "cleanup standards" will be used in
reference to appropriate cleanup levels for both the Superfund
and RCRA programs.
Objective
Recommendations are provided for investigation and
remediation of contaminated ground water for both Superfund sites
and RCRA Corrective Action facilities. This recommended guidance
is presented for each response stage, including investigation,
early or interim action and remedy implementation. Actions at
each site should be tailored to the specific conditions and
applicable requirements at that site.
In addition to data collected during site investigation,
data obtained during response actions (interim and final) should
be considered for use in: 1) further characterizing the site and
refining the conceptual model for site contamination; and 2)
evaluating the design and operation of remedial actions for the
site.
Implementation
I. OSWER GROUND-WATER POLICY
A. Investigation
The following recommended activities focus on identifying
the nature and extent of ground-water contamination; contaminant
sources; the conceptual model for contaminant migration and fate;
potentially appropriate early response actions; and site factors
that may affect the time frame or likelihood of achieving cleanup
standards. These activities should generally be performed at
Superfund sites or RCRA facilities by EPA, potentially
responsible parties, owner operators or other entity responsible
for such activities.
1. The likelihood of subsurface NAPL contamination should be
evaluated as a part of all site investigations. The potential
presence or absence of LNAPL or DNAPL should influence the
methods chosen for site characterization and remediation,
particularly in the case of DNAPL. Certain site factors (such as
the types of chemicals released, types of industrial processes,
chemical storage and waste disposal practices at the site) can
indicate the potential likelihood of NAPL occurrence. These
factors should be evaluated (see EPA Fact Sheet) from site
U.S. EPA. Fact Sheet: Estimating Potential for Occurrence of DNAPL at Superfund Sites. Publication
9355.4-07FS, OSWER/R.S. Kerr Environmental Research Laboratory (RSKERL), January 1992.
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historical information and other data prior to initiating field
investigatory work.
2. If NAPL contamination is likely, characterization of tbe
potential nature and extent of such contamination is recommended
to determine appropriate remedial actions. For these sites, a
review of existing data and collection of subsurface information
should be performed to:
a) suggest areas where LNAPL and/or DNAPL may be present;
b) to confirm the presence or absence of NAPL in these
areas, to the extent practicable; and
c) if NAPLs are present, to estimate their extent.
Such information could include delineation of NAPL source
areas; delineation of the types of subsurface features that could
act as DNAPL conduits or traps (in order to determine where it
may have accumulated); measurement of vertical variation in
aqueous contaminant concentration, especially above low
permeability layers; and inspection of soil samples (or rock
cores) for NAPL, both above and below the water table. For DNAPL
contamination, the subsurface stratigraphy and structural geology
can play a more important role than ground-water flow in
controlling gravity-driven DNAPL transport. If planned from the
beginning, collection of this information can be combined with
other efforts such that investigation costs and time frames
should not be greater than current levels, for most sites.
The degree of effort expended in locating DNAPL
accumulations should be based on the degree of characterization
necessary for remedy selection. Locating DNAPL in small
stratigraphic or structural discontinuities is generally not
possible. However, efforts should be made to identify subsurface
geologic environments where DNAPL accumulations may be present,
such as topographic valleys in the bedrock surface or other
potential traps formed by soil layers, by (lithologic or
structural) geologic boundaries or by other features. It is
recommended that characterizing efforts focus on those locations
where DNAPL accumulations are more likely to be present and which
are more likely to be found using applicable exploration methods
(conventional or innovative). Characterizing the potential
nature and extent of DNAPL contamination will provide a better
understanding of the sources of contaminants to ground water and
of contaminant flow paths from these sources. Also,
characteristics that influence travel times for aqueous
contaminants, such as partitioning between soil and ground water,
should generally be estimated. This additional information can
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recommended investigation strategy is to drill in expected DNAPL
zones after subsurface conditions have been characterized by
drilling in surrounding DNAPL-free areas (the "outside-in"
strategy) . In DNAPL zones, drilling should generally be
minimized and should be suspended when a potential trapping layer
is first encountered. Drilling through DNAPL zones into deeper
stratigraphic units should be avoided. Also non-invasive
methods, such as geophysical or geochemical surveys, can be
useful at some sites to roughly define subsurface geologic or
contaminant conditions .
B. Early or Interim Action
The following recommended activities focus on
preventing/minimizing further migration of contaminants as early
as possible, preferably before a final remedy is selected. These
activities should generally be performed at Superfund sites or
RCRA facilities by EPA, potentially responsible parties, owner
operators or other entity responsible for such activities.
1. Contain the pltsme early.. Aqueous phase contaminant plumes
should generally be contained early, while determining what
further remedial action is needed. A containment system, such as
pumping to control hydraulic gradients or other method, should be
implemented expeditiously in order to prevent/minimize migration
of contaminants. Early containment may limit the area over which
future restoration is required and is especially important at
sites where the plume is migrating rapidly or may contaminate
water supply wells or environmental resources. The system should
be monitored to determine the effectiveness of containment and
changes in contaminant concentrations. Monitoring data can
provide information useful for further site characterization and
also for remedial design. In addition to containment, extraction
systems can be used to remove dissolved contaminants in zones of
high concentration or "hot spots", although this may not be
effective in zones containing NAPL. Treatment of ground water
extracted for plume containment may be required, if contaminant
concentrations are above standards appropriate for the type of
discharge selected, such as NPDES permit requirements.
U.S. EPA. Fact Sheet: Information Required to Evaluate Remedial Activities for DNAPL at Superfund
Sites. In preparation, by OSUER/RSKERL.
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2. Extract free-phase 8J&PL early„ where possible., Free-phase
NAPL should generally be removed from the subsurface as an early
action to minimize further migration and to remove sources of
further contaminants to ground water. Free-phase NAPL can be very
mobile in the subsurface environment. Where free-phase DNAPL is
encountered in routine excavations or boreholes, it should be
removed expeditiously by pumping or other direct extraction
methods. Where accumulations of free-phase DNAPL are confirmed,
additional efforts should generally be undertaken to estimate
their extent and to implement removal. Knowledge of structural
geologic features which trap or limit DNAPL migration can be
useful for design of removal methods. LNAPLs are somewhat easier
to locate and remediate than DNAPLs because they tend to float on
the water table. Expeditious removal of free-phase LNAPL is also
recommended.
For Superfund sites where NAPL contamination is suspected,
EPA should include a free-phase NAPL removal provision in the
Remedial Investigation/Feasibility Study (RI/FS) Statement of
Work for Fund-lead sites, or in the Work to be Performed section
of the RI/FS consent order for Enforcement-lead sites. At sites
with ongoing RI/FS work, this would require modifying the
existing consent order or Statement of Work. Another option
available at Enforcement-lead sites is for EPA to issue a
separate removal order (consent or unilateral) requiring a PRP to
extract free-phase NAPL expeditiously after discovery. At all
sites, the on-site contractor should be required to notify the
EPA Remedial Project Manager within 24 hours after the initial
discovery of free-phase NAPL. For RCRA Corrective Action
facilities where NAPLs are suspected, EPA should include a free-
phase NAPL removal provision either in the Corrective Action
Permit, or in the Interim Measures portions of the RCRA Facility
Investigation/Corrective Measures Study (RFI/CMS) Order, and/or
require that NAPLs be addressed expeditiously in the context of
Additional Work Provisions in the order, throughout corrective
measures implementation. If a permitted facility will not address
free-phase NAPL removal voluntarily, a permit modification may be
necessary.
3. Initiation of early actions should tak© plae© as soon as
possible after a problem is identified that either requires an
expeditious response or for which an early action is appropriate,
Early refers to the timing of the action with respect to other
site response actions. For Superfund sites, early actions may
include removal actions, interim actions, or early final actions.
Superfund interim actions are remedial responses that are
initiated prior to final remedy selection, which should be
consistent with and not preclude implementation of the final
remedy. For RCRA Corrective Action facilities, interim measures
can be used as early actions. RCRA interim measures are those
required to mitigate or eliminate releases, or to prevent
"further degradation of the medium which may occur if remedial
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action is not initiated expeditiously" . More frequent use of
interim measures has been recommended by the recently adopted
RCRA Stabilization Effort . Stabilization includes mitigating
releases and preventing the further spread of contamination as
the first phase of RCRA corrective action. For both programs,
early actions should be coordinated with final remedies such that
they are the first phase of the overall remedial action.
Determination of whether and when to implement the early
response actions recommended above should be based on existing
information concerning the location of contaminant sources,
location of and risk to human health or environmental resources,
rate of plume expansion, stage of plume or NAPL characterization,
nature and location of free-phase NAPLs, potential for inducing
undesired movement of dissolved or NAPL contaminants, subsurface
geologic conditions, feasibility of the action, and best
professional judgement. Caution should be exercised to prevent
drilling or pumping operations from inducing further migration of
free-phase DNAPL. Care is especially important in fractured or
karst media because DNAPL can penetrate fine fractures or
solution channels.
4. Early or interim actions should be appropriately documented.
For Superfund sites, the need and rationale for selecting a
removal action should be documented in an Action Memorandum. The
need and rationale for selecting actions under remedial authority
(interim actions, early interim actions, or early final actions)
should be documented in a Record of Decision. For RCRA
facilities, interim measure decisions should be documented in the
enforcement order, in the negotiations section of the facility's
Administrative Record and in the Statement of Basis. Some
interim measures (as determined by EPA) at RCRA facilities may
require an approved interim measures work plan under the
enforcement order, a permit modification, or an additional order.
For both RCRA and Superfund actions, a brief summary of site data
collected during field investigations should be sufficient to
document a problem in need of an expeditious response. In
addition, a concise description and comparative analysis of the
alternatives considered should be prepared in accordance with
existing guidance.
Corrective Action for Solid Waste Management Units (SWMUs) at hazardous waste management facilities;
(proposed Subpart S Rule 40 CFR 264.540, (a) and (b)).
U.S. EPA. Memorandum: Lowrance (Office of Solid Waste) and Diamond (Office of Waste Programs
Enforcement) to Regions t-X Waste Management Division Directors, "Managing the Corrective Action Program for
Environmental Results: The RCRA Facility Stabilization Effort," October 25, 1991.
U.S. EPA. Fact Sheet: Guide to Developing Superfund No Action, Interim Action, and Contingency
Remedy RODs. Publication 9355.3-02FS-3, OSWER, April 1991.
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C. Remedy Implementation
While early response actions should focus on
preventing/minimizing further contaminant migration, the
following recommendations focus on restoring ground-water
quality, to the extent practicable, after a final remedy is
selected.
1. Remedial actions/measures for contaminated ground water
should generally be implemented in a phased approach. In a phased
remedial approach, actions are modified or are succeeded by
different (but compatible) or more comprehensive actions in
subsequent phases. This approach can improve the effectiveness
and efficiency of cleanup. The first phase could include
containment or source removal actions and should be implemented
as early as possible in the site response process, preferably as
an early response action. A phased approach is especially useful
where uncertainty exists regarding the ability of the selected
remedy to meet cleanup standards, such as in areas of complex
hydrogeology or contaminant distribution, or where DNAPL has been
confirmed or is strongly suspected.
2. Ground-water remedial actions should be designed to include
careful monitoring and provisions for modifying them over time to
improve their effectiveness and efficiency. For ground-water
extraction (or gravity drainage) systems, performance monitoring
data should be collected to define changes in aqueous
concentrations within and outside the general plume area, as well
as responses in the potentiometric surface. For extraction
systems, concentration data should be obtained from non-pumping
wells, and potentiometric data from both pumping and non-pumping
wells. Monitoring data should be periodically assessed and
should generally be used to suggest system modifications which
provide more effective or efficient attainment of cleanup
standards. (For these evaluations, ground-water flow and
contaminant transport models can be very useful.) Such
modifications may include: increasing or decreasing the
extraction rate, initiating a pulsed pumping schedule, installing
additional extraction wells (or drains), or ceasing extraction at
wells where the aquifer has been restored. Monitoring should be
used to assess the effectiveness of the modifications implemented
and can be used to re-assess the time frame required to achieve
cleanup standards. Such changes may need to be reflected in
appropriate decision documents, depending on the specific
requirements of each program.
U.S. EPA. General Methods for Remedial Operation Performance Evaluations, Pre-print Draft. RSKERL.
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3. After a ground-water remedy is implemented, modification of
remedial action objectives may be warranted where cleanup
standards cannot be achieved, due to technical impracticability
from an engineering perspective. There are three overall
requirements for such modification:
a) demonstration of technical impracticability to the
satisfaction of EPA (or other entity responsible for making
decisions at the site);
b) EPA issuance of a technical impracticability waiver (40
CFR 300.430 (f) (1) (ii) (C) (3)) for Superfund sites, or a
permit or order modification for RCRA facilities (Proposed
40 CFR 264.525 (d)(2) (iii) and 264.531) ; and
c) EPA determination of alternative remedial action
objectives.
Also for Superfund sites, an Explanation of Significant
Differences (BSD) or Record of Decision (ROD) Amendment will be
required to document the changed remedial action objectives. A
ROD Amendment is required if the remedy used to meet the
alternative remedial action objectives is fundamentally different
from either the remedy selected or the contingent remedy defined
in the ROD. It is highly recommended that the public be given an
opportunity to comment if an BSD is used for this type of change.
4. EPA will make its determination on whether or not aquifer
restoration to cleanup standards is technically impracticable for
a given site based upon EPA approved data, supporting analysis
and site characterization which justifies such a determination.
This information should include some or all of the following:
contaminant characteristics; hydrogeological conditions;
contaminant distribution and potential subsurface migration;
performance of aquifer restoration or other response actions
attempted; availability of alternative technologies; an estimate
of the degree of restoration that will be achievable at the site,
where applicable; and additional information deemed necessary by
EPA.5
Although not final, most of the proposed Subpart S Rule, including these sections, may be used as
guidance. The specific requirements must generally be imposed in the permit or order and justified on a
case-by-case basis. (See: U.S. EPA Memo, "Use of Proposed Subpart S Corrective Action Rule as Guidance
Pending Promulgation of the Final Rule," Friedman (Office of General Counsel) to Regional Counsel RCRA
Branch Chiefs, March 27,1991.)
Further guidance concerning technical and administrative requirements and other issues related to
technical impracticability of ground-water restoration is currently under development by an OSUER workgroup.
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In characterizing site hydrogeology and contamination, EPA
will consider both aqueous and nonaqueous phase contaminants, as
discussed in Section I.A.2., above. Evaluation of the
performance of aquifer restoration or other response actions
should generally include a description of each implemented
restoration, source control, or other action; arid a discussion of
results achieved and modifications made to improve the
effectiveness of the action, as discussed in Section I.C.2. In
evaluating the availability of other technologies (which may
include field testing if required by EPA), EPA will consider new
conventional and/or innovative technologies which could
practicably achieve compliance with cleanup standardso
Estimation of the degree of restoration achievable, when
applicable, should be based on the results of aquifer restoration
efforts over a sufficiently long time frame to allow meaningful
predictions for that particular site.
5. If a determination of technical impracticability is made,
EP& will also determine alternative remedial action objectives
which protect human health and the environment and are
appropriatei based on site conditionso EPA will require that
exposure to contaminated ground water be prevented, and to the
extent practicable, that further contaminant migration be
prevented. Where applicable and to the extent practicable, EPA
will generally also require reduction of the areal extent of the
dissolved contaminant plume and removal of subsurface NAPLs.
Alternative remedial actions that prevent exposure to
contaminated ground water and those which prevent contaminant
migration will be required to continue for as long as contaminant
concentrations remain above cleanup standards. Operation and
maintenance of these systems may be required for very long or
indefinite time frames. Exposure prevention actions may include
alternative water supplies or institutional controls. Migration
prevention actions may include hydraulic gradient control by
pumping or physical containment measures, which should address
both aqueous and nonaqueous contaminants. Containment systems
must also be monitored to demonstrate their effectiveness. New
conventional and/or innovative containment technologies should be
considered where they have the potential to provide long term
cost savings and effectiveness.
Where applicable and to the extent practicable (as
determined by EPA), reduction of the areal extent of the
dissolved contaminant plume should be an alternative remedial
action objective. Evidence from operating systems indicates that
ground-water extraction systems can substantially reduce the
areal extent of dissolved contaminant plumes. Thus, restoration
(to cleanup standards) over portions of the contaminated aquifer
can be achieved, even if restoration of the entire aquifer is not
possible. Shrinking the plume will reduce the area over which
health/environmental protection is dependent on the maintenance
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of engineered systems and institutional controls. This will
increase the reliability of the remedy and decrease long term
operating costs. Monitoring will be required in order to
demonstrate the extent of plume reduction achieved.
Where applicable and to the extent practicable (as
determined by EPA), removal of subsurface NAPLs should be an
alternative remedial action objective. NAPLs dissolve slowly,
supplying potentially significant concentrations of contaminants
to ground water over very long time periods. Removal of these
sources, from both the unsaturated and saturated zones, will
abate continued aquifer contamination. In some cases, remedial
actions to remove these sources will be more economical than long
term extraction and treatment of the contaminated ground water.
Source removal could include excavation, in-situ soil treatment,
extraction of free-phase NAPL, or enhanced recovery of residual
NAPL. Accumulations of free-phase LNAPL and DNAPL, which were
not removed as an early action, should generally be removed
during the final remedy, to the extent practicable. Furthermore,
because the mass proportion and spatial extent of residual NAPL
is usually much greater than that of the free-phase, new
conventional and/or innovative technologies should be considered
for enhanced recovery of residual LNAPL and DNAPL from the
subsurface.
II. ON-GOING PROJECTS
Through the Technical Support Program, the Office of Solid
Waste and Emergency Response (OSWER) is supporting a long-term
research effort by the Robert S. Kerr Environmental Research
Laboratory (RSKERL) to evaluate innovative technologies that will
improve our ability to remediate contaminated ground water. This
will include technologies with potential for removing NAPL from
the subsurface. OSWER will also be working closely with RSKERL
to develop fact sheets and guidance on site characterization,
remediation, and performance monitoring for DNAPL-cohtaminated
sites. Additionally, the Office of Emergency and Remedial
Response (OERR) has initiated a survey to determine the potential
number of existing Superfund sites where DNAPL contamination is
likely. This year-long survey will help to assess the
significance of this problem for the Superfund program. OERR is
also supporting a National Research Council (NRC) study,
"Alternatives for Reducing Risk from Existing Ground-Water
Contamination" that will assess the current state-of the-science
concerning ground-water remediation and look at alternative
approaches for addressing ground-water contamination. The NRC
study is scheduled for completion by September 1993.
A technical workgroup has recently been established within
OSWER to develop further guidance concerning waivers due to
technical impracticability for ground water. Participants
include OERR, Office of Solid Waste (OSW), Office of Waste
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Programs Enforcement (OWPE) and the Ground Water Forum. One or
more guidance documents are planned for development in 1992.
Another workgroup, led by the Office of Enforcement, is
developing model consent decree language addressing a technical
impracticability waiver process for implemented pump and treat
remedies at Superfund sites.
Finally, OSWER will continue to learn from program
experience. Many ground-water remediation systems are now in
either the design or the construction phase, so our data base
will grow significantly over the next few years. We will be
monitoring these systems closely and will continue to improve
EPA's approach to assessing and remediating contaminated ground
water.
If you would like additional information please contact Ken
Lovelace (Hazardous Site Control Division/OERR) at FTS 678-8362,
Dave Bartenfelder (Permits and State Programs Division/OSW) at
FTS 260-9828 or Matt Charsky (CERCLA Enforcement Division/OWPE)
at FTS 260-9805.
NOTICE: The policies and procedures set out in this document are intended solely for the guidance of
response personnel. They are not intended, nor can they be relied upon, to create any rights, substantive
or procedural, enforceable by any party in litigation with the United States. EPA officials may decide to
follow this guidance, or to act at variance with these policies and procedures based on an analysis of
specific site circumstances, and to change them at any time without public notice.
•U.S. Government Printing Office: 1993— 760-071/60232
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