-------
Results
Summary of Findings from
Ground-Water Data
Most useful indicator is maximum
percentage solubility of DNAPL
chemicals detected in ground water.
Based on ground-water concentration
data, ~60% have medium to very high
probability of DNAPL.
Results
Comparison of Ranking
Factors
A. Site History Rank
B. Ground-Water
Contamination Rank
Percent 30
of
SUcs
Combining the Site History &
Ground-Water Contamination Ranks
Results
Site Hist
Rank
6
5
4
3
2
1
Ground-Water Contam Rank
65432 1
Hi
Hi
Hi
Hi
Hi
Hi
Hi
Hi
Hi
Hi
Hi
Hi
Hi
Hi
Med
Med
Med
Med
Med
Med
Med
Med
Med
Med
Med
Med
Lo
Lo
Lo
Lo
Med
Lo
Lo
Lo
Lo
Lo
1-13
-------
Results
Summary of Combined Ranks
Likelihood
of Subsurface
DNAPL
Definite
High
Medium
Low
^
Number
of Sites
40
109
66
95
Percent
of Sites
13%-
3596
21%
31%
_X
Results
Relationship of Hydrogeological Setting
to Likelihood of Subsurface DNAPL
A. Site History Rank B. Ground-Water
Contamination Rank
as* tfxx rmx wcr WAU
tfsa ctot tKai not Acer WAU
HyiiroieoloiJciI SttflJU
Results
Relationship of Site Use to
Likelihood of Subsurface DNAPL
A. Site History Rank
B. Ground-Water
Contamination Rank
L
f
[-,
[1
nfl
ow 6
uk
5
4
3
2
1
1
£j
J-f
O* Mm MM V PN| v»«4 IM«V KM Otb
1-14
-------
Effect of Results
Hydrogeological Setting
No distinguishable difference in
DNAPL likelihood based on
geological setting
Implication: if DNAPLs are suspected
based on site history, their presence
should be investigated in all cases,
regardless of geological setting
(Heath)
Site Use Findings
Uses with a higher
likelihood of subsurface
DNAPL:
Wood treatment
Organic chemical production
General manufacturing
Industrial waste disposal
Results
r,.. TT T-" -i- Results
Site Use Findings (continued)
Uses with a lower likelihood
of subsurface DNAPL:
Combination landfills
Primary metals mdustty/mming
Inorganic chemical production
1-15
-------
f*. TT 1-" J-
Site Use Findings
> Uses for which site use
relationship is not clear from
our study:
Federal facilities (high based on
site history and low based on
ground water data)
Results
Relationship of Contaminant Type to
Likelihood of Subsurface DNAPL
A. Site History Rank
tnsr MKmv ojoty FCBOLV t*
GmUm&uitf Tyyt
B. Ground-Water
Contamination Rank
ireT MXKXV CUOLV KKOLV OfflO OAR OTHER
Distribution of
Contaminant Type
Results
Percent
M.V CUOLV 7CBIQLV OLIO CTAR
Contaminant Type
1-16
-------
Summary for Site Results
Contaminant Type
Creosote, Coal Tar, and PCB Sites:
Small proportion of sites in Superfund
Easily linked with specific site uses
High likelihood of subsurface DNAPL
Relatively small impact in terms of
volume of subsurface contaminated
Summary for Site Results
Contaminant Type (continued)
Chlorinated Solvent & Mixed
Solvent Sites:
B Majority of sites in Superfund
Associated with wide range of site uses
Range in likelihood of subsurface DNAPL
Relatively large impact hi terms of
volume of subsurface contaminated
Results
Average Plume Dimensions
by Contaminant Type
C Mixed N.
Solvents /
L = 4,500 ft
W = 1,500 ft
D = 92 ft
L = 2,800 ft
W = 1,000 ft
D = 70 ft
1-17
-------
Results
Average Plume Dimensions
by Contaminant Type (continued)
L = 1,500 ft
W= 1,200 ft
D = 26 ft
L = 600 ft
W = 250ft
D = 20 ft
Regional Distribution Results
of DNAPL Probability
Average
Rank
Region
Results
Estimated Scope of the
DNAPL Problem
Extrapolation to 712 NPL sites in Regions 1,
3, 5, 6, & 9.
Known DNAPL sites 5% >^
High (very likely)
Medium (warrant further
investigation
Low DNAPL likelihood
No organics in ground
water
35%
20%
30%
10%
40%
1-18
-------
Conclusions
Potential for subsurface DNAPL
will be consideration at majority
of Superfund sites.
May have underestimated
DNAPL potential because data
not specific to DNAPLs.
Conclusions
(Continued)
> Future research efforts should
focus on chlorinated solvent
and mixed solvent sites, as
these constitute the majority of
Superfund sites and present the
greatest challenge with respect
to site characterization and
remediation.
1-19
-------
-------
Ground-Water Remediation Policy Directive and
Superfund Accelerated Cleanup Model (SACM) Discussion
Kenneth A. Lovelace
Environmental Engineer
Hazardous Site Control Division
Office of Emergency and Remedial Response
U.S. Environmental Protection Agency, Washington, DC
Kenneth A. Lovelace is an environmental engineer with Superfund's Hazardous Site Control Division.
He received a B.S. in geology from the University of California, Davis, and an M.S. in civil engineering
from Colorado State University.
Mr. Lovelace has more than 14 years of professional experience in hydrology, as a consultant and as
a senior engineer for an oil pipeline company. His primary area of responsibility at EPA is developing
national policy for characterization, cleanup, and management of ground-water contamination at
hazardous waste sites.
2-1
-------
Ground-Water
Remediation Policy
Directive and SACM
Discussion
Kenneth A. Lovelace, P.E., P.G.
Office of Emergency and Remedial Response
Ground-Water Remediation
Policy Directive
Background
Site Investigation
DNAPL Characterization
Early Actions
Remedy Design
Background
> Ground-water contamination is
present at:
85% of Superfund National Priority
List (NPL) sites
50% of permitted RCRA land
disposal fatalities
2-2
-------
Background
(Continued)
> Subsurface NAPLs, especially
DNAPLs, will significantly
impact ground-water
remediation
Are long-term sources of
contaminants
Control of sources needed to
achieve cleanup standards
Background
(Continued)
OSWER Policy Directive, May 27,
1992
"Considerations in Ground-Water
Remediation at Superfund Sites
and RCRA Facilities - Update"
Affects CERCLA Remedial Action,
RCRA Corrective Action
Site Investigation
Evaluate likelihood of NAPL
occurrence early
Use DNAPL fact sheet
Historical and existing field data
During pre-remedial work, if possible
Needed for planning site
investigation
2-3
-------
Site Investigation
(Continued)
If NAPLs likely, further
characterization should:
Suggest areas where LNAPLs or
DNAPLs might be present
Confirm NAPL presence
Estimate NAPL extent, to extent
possible
Site Investigation
(Continued)
Why is characterization
needed?
Define sources of contaminants
Estimate flow paths and
travel time
Identify possible remedial
strategies
DNAPL Characterization
Locate geologic DNAPL traps
Topographic valleys in bedrock
surface
Traps formed by geologic features
Focus efforts on DNAPL
accumulations
More likely to be found
Depends on site conditions,
exploration methods
2-4
-------
DNAPL Characterization
(Continued)
Locating DNAPL in small
discontinuities is very
difficult
Caution should be exercised
Can be combined with other
investigation efforts
Early Actions
> Actions initiated before remedial
investigation (RI) is completed.
Removal or remedial actions.
> Focus of early actions is to:
Reduce site risks
Prevent exposure to contaminants
Minimize further migration
Control sources
Early Actions
(Continued)
Directive recommends
Early plume containment
Early extraction of free-
phase NAPLs
2-5
-------
Early Actions
(Continued)
Why are these actions
important?
Protect surrounding aquifer
Protect wells or ecological resources
Free-phase is mobile fraction and is
extractable
Much more effective to remove NAPL
sources
Remedy Design
Actions should be
implemented in a phased
approach
Information gained from
earlier phases is used to
refine later phases (also
"smart approach")
Remedy Design
(Continued)
Why is phased approach useful?
Integrates data collection with site
conceptual model
Integrates investigation and remedial
activities
Integrates early actions with, long-term
actions
Provides flexibility to respond to new
information
Minimizes uncertainty between phases
2-6
-------
Remedy Design
Design should include
monitoring to:
Determine effectiveness of action
Suggest remedy improvements
Refine predicted cleanup time
Remedy Design
(Continued)
Design should allow for
modification of remedy after
implementation to:
Improve effectiveness
Reduce remediation time
Respond to new information
Ground-Water
Remediation and SACM
Key SACM elements
Long-term actions
Early actions
SACM and Policy Directive
Remedial/removal actions
2-7
-------
Key SACM Elements
Superfund Accelerated Cleanup
Model (SACM)
Regional Decision Team used to:
Integrate investigation, and assessment
activities
Coordinate Superfund program elements
Coordinate early state and community
involvement
Key SACM Elements
(Continued)
Combine early and long-term actions
Time Frame Site Response
Under 5 years +/- Early actions to expediently
reduce site risks. Integration
of early actions, with site
investigation.
Over 5 years +/-
Long-term actions for longer
or more complex remediation,
such as environmental
restoration.
Long-Term Actions
Types of action:
Restoration to cleanup
levels
Complex source control
Maintaining plume and/or
source containment
Monitoring
,2-8
-------
Early Actions
Types of action:
Preventing exposure to
contaminants
Preventing further migration
Controlling sources - soils, NAPLs
Field testing of restoration
technologies
SACM and Policy Directive
Use of early actions is a key
recommendation of Policy
Directive.
Integration of early and long-term
actions follows "phased approach"
recommended.
Early actions include CERCLA
remedial or removal actions.
Remedial/Removal Actions
Remedial actions
Sites must be on National Priorities
List (NPL)
No statutory time or cost limitation
Early actions are generally interim
actions
ARARs must be met or waived
Fund/state cost share required
2-9
-------
Remedial/Removal Actions
(Continued)
> Removal actions
Sites can be pre-NPL or NPL
Three types: emergency, time critical,
non-time critical
limited to 12 months and $2 million,
some exemptions
ARARs must be met to extent practicable
or waived
Fund/state cost share not required, but
recommended
Remedial/Removal Actions
(Continued)
Removal
(Removal) Site Evaluation
(SE)
Sampling and Analysis
Plan (SAP)*
Engineering
Evaluation/Cost
Analysis (EE/CA)*
Action Memorandum (AM)
Remedial Investigation
(Rl)
Sampling and Analysis
Plan (SAP)
Feasibility Study (FS)
Record of Decision (ROD)
" Non-Mine critical removals only.
2-10
-------
Technical Impracticability Project
Peter R. Feldman
Environmental Scientist
Hazardous Site Control Division
Office of Emergency and Remedial Response
U.S. Environmental Protection Agency, Washington, DC
Peter R. Feldman is an environmental scientist in Superfund's Hazardous Site Control Division. Mr.
Feldman received a B.A. in geology from Wesleyan University and an M.S. in hydrology from the
University of Arizona.
Prior to joining EPA in 1991, Mr. Feldman worked in the consulting field on environmental impact and
engineering studies, water-supply development projects, and hazardous waste investigations. His current
responsibilities at EPA include development of policy and guidance related to ground-water remediation
for the Superfund program in addition to site-specific consultations at various NPL sites.
3-1
-------
Technical
Impracticability
Project
Peter R. Feldman
Office of Emergency and Remedial Response
Purpose and Overview
Background and goals
Technology limitations and
role of XI
Specifics of draft guidance
Discuss issues; get feedback
Background
> Technical studies
»19 and 24 site studies
Ongoing research on pump &
treat
DNAPL site survey
3-2
-------
Background
(Continued)
Use of TI waivers discussed in:
NCP, NCP preamble
1988 OERR ground-water guidance
1989 Cannon ground-water remediation
memo
1990 OERR/OWPE ROD language memo
1992 Clay ground-water remediation
memo
NCP Expectation for
Ground-Water Cleanup
"... EPA expects to return usable
ground waters to their beneficial
uses wherever practicable,
within a timeframe that is
reasonable given the particular
circumstances of the site."
§300.430(aXD(iii)(F)
CERCLA ARAR Waivers
Interim action
Greater risk
Technical impracticability
Equivalent standard of performance
Inconsistent state application
Fund balancing
(See CERCLA 121(d)(4)(c))
3-3
-------
Existing Guidance on TI
NCP criteria:
" engineering feasibility and
reliability, with cost generally
not a major factor unless
compliance would be
inordinately costly."
Definition of "Impracticable"
Impracticable: incapable of being
performed or accomplished by the
means employed or at command.
Impractical: not wise to put into or
keep in practice or effect; not
pleasing to common sense or
prudence.
(bom Webster's 3rd International Dictionary, 1971)
Existing Guidance
(Continued)
On "reasonable time frame":
NCP Preamble: Very rapid (1 to 5
years) to extended (several
decades)
OERR Guidance (1988): "Less than
100 years"
3-4
-------
Existing Guidance
(Continued)
On "engineering feasibility," 1988
Guidance considers:
Widespread plumes/unidentified
sources
Hydrogeologic constraints (e.g.,
fractured rock, karst, low permeability)
Contaminant characteristics (e.g.,
DNAPLs)
Sorption/desorption kinetics
Past Use of TI Waivers
Waiver in ROD
Used 13 times
Contingency TI waiver in ROD
Used 24 times
Post-ROD waivers/contingencies
3 cases
Use of TI Waivers
(through 1992)
10
g
8
7
Number B
Of 5
RODS
3
2
1
0
n
ff
Si
m
I
£
^^
IP
n
8
I*'/
CI3 TI Waiver
E3 Contingent TI Waiver
B-wj
f%t
s
*s
a
if
ri
1234
WM
1
JfriTlrL
567 8 9 10
Region
3-5
-------
Reasons for TI
DNAPLs
Extent of
Contamination
Karst
LNAPLs
ARAR Lower
ThanPQJ.
Ntunber of RODs
Status of TI Guidance
Draft stage only
Regional/state review
Summer '93
Followed by EPA senior
management review, final
revisions
Goals of Guidance
Consistency across regions
and programs
Address growing volume of
H decisions
Clarify decision criteria and
data requirements
3-6
-------
Goals of Guidance
(Continued)
Encourage better site
characterization and remedy
performance monitoring
Clarify legal and
administrative issues
Develop approach for
selecting alternative remedial
strategies
Ground-Water Remedy
Decision Framework
Uncertainty in GW
Remedy Decisions
Remediation outcome
difficult to predict
NCP provides flexibility
needed to reduce
uncertainty
3-7
-------
Uncertainty in GW Remedy
Decisions (Continued)
Can resolve uncertainty through:
Thorough site characterization (NAPLs)
Phased approach to characterization
and remediation
Early and interim actions (SACM)
Monitor and analyze data
Base final cleanup decisions on more
complete knowledge
Uncertainty and Decision
_ Documents _
Available Options:
Little to no r\ ARAR-Compliant ROD or
uncertainty L/ Tl Waiver in ROD
Moderate r\ Contingent TI waiver
uncertainty |_/ in ARAR-Compliant ROD
High
uncertainty
Interim Action ROD
(no ARARs, or interim
action waiver)
Approach for
Evaluating TI
3-8
-------
71 ^Waiver AppCication
Site needs a TI waiver
because:
D It will be REALLY REALLY
expensive to clean it up, or
D It will take a REALLY long
time to clean it up
~\
Demonstrating TI:
Factors to Consider
1. Adequacy of site conceptual
model
2. Hydrogeologic constraints
3. Contamination-related
constraints
4. Degree and effectiveness of
source control
Demonstrating TI:
Factors to Consider (continued)
5. Remedial action performance
appraisal
6. Applicability of other
technologies
7. Predictions of restoration
timeframes
8. Cost estimate
3-9
-------
1. Site Conceptual Model
Develop using iterative approach
Contaminant sources, properties,
distribution
Geology and hydrology
Assumptions and hypotheses
regarding transport, fate,
remediation
Examples of Activities
Providing Data for
Model Development
3-10
-------
Site Conceptual Model
Development
> Site background
and history
PreUininary site
investigations
Identify
Sources and
Receptors
9 Model used to
scope detailed site
investigation
Site Conceptual Model
Development
Early action/
removal
Site
characterization
(RI/FS, RFI, etc.)
Removal of
subsurface
sources
DNAPL
Removal
Drum
Removal
Excavation and
Capping
Monitoring
Model used to design
pilot studies and
subsurface actions
3-11
-------
Site Conceptual Model
Development
Pilot
studies
Interim
actions
A
-/
Pilot
Studies
Interim Action
Hydraulic
Containment
Model used to:
Evaluate potential for
restoration (or TI)
Develop treatment tram
concept/design
Site Conceptual Model
Development
Full-scale
treatment
Performance
monitoring
and
evaluations
Continued
enhancement of
conceptual model
Enhancement or
augmentation of
remediation system,
if required
9 Further evaluation of
restoration potential
(or TI), if required
3-12
-------
2. Hydrogeologic
Constraints
Examples
Heterogeneity
Hydraulic conductivity
Fracturing/solution features
Depth
3. Contaminant-Related
Constraints
Phase (i.e., aqueous, nonaqueous)
Distribution
Physical properties (e.g., viscosity,
density)
Transport and fate (e.g., retardation,
biodegradability)
4. Source Control
Includes residual and free-
phase NAPLs
Removal, stabilization,
isolation
Monitoring to assess
effectiveness
3-13
-------
5. Remedy Performance
Appraisal
Suitability of technology or
design
Adequacy of monitoring
Operational history;
enhancements
Trends in ground-water
concentration
Trends in Ground-Water
Concentration
Aqueous plume
contained/reduced?
Rate of concentration decline?
Dilution or natural attenuation
responsible?
Rebound during shutdown?
6. Applicability of Other
Technologies
Use of innovative
technologies encouraged by
statute
Burden on PRP to
demonstrate none applicable
3-14
-------
7. Restoration Timeframes
»Not explicit TI decision criterion
> Predicted through modeling -
inherent uncertainty
> Deemphasize threshold value for
"reasonable" timeframe
> Useful for alternatives comparison
or to indicate possible constraints
8. Cost
Subordinate to protectiveness
Legitimate consideration in
"engineering feasibility"
ARARs may not be subject to
cost/benefit analysis
TI Evaluation Tools
Literature
Treatability studies and pilot
systems
Modeling
Remedy performance
appraisals
3-15
-------
TI Evaluation Tools
(Continued)
Other factors to consider
Accurate evaluation might
require installation of system
Restoration potential might
vary across site
Use of treatment trains might
be necessary
TI Review Process
Decisions made by Regional
Administrator
HQ. consultation at Division
Director level
Regional or ORD technical
support role critical
Possible Outcomes of
Review Process
Decision, package inadequate
Install/enhance system to reach ARARs
Install/enhance system to reach non-
ARAR standard
Maintain existing system to reach non-
ARAR standard
Use source control, institutional
controls, natural attenuation
3-16
-------
Alternative Remedial
Strategies
NCP expectations
Prevent further migration
Prevent exposure
Evaluate further risk
reduction
Alternative Remedy
Selection
Nine criteria analysis of
alternatives
Also consider:
Current and future use
Likelihood of exposure
Availability of alternate supplies
Alternative Remedial
Strategies _
Suggested Approach
1- Less strmgent ARAR
2. Waive portion of site only
3. Site-specific cleanup levels
4. Remediate to extent
practicable; focus on source
control, containment, and
exposure control
preferable
3-17
-------
CERCLA ACLs
Alternate Concentration Limits can
be used where:
Contaminated ground-water
discharges to surface water
No statistically significant
concentration increase
Can prevent exposure to
contaminated ground water
NCP Policy on ACLs
ACLs not an entitlement, but a
limitation on use of higher
limits
Remediation to ARARs must
also be impracticable (nine
criteria analysis)
Where ACLs used, TI waivers
not necessary
Summary
»Reduce uncertainty through
phased approach
(Emphasize source control
»Detailed site characterization
and performance monitoring
needed
3-18
-------
Summary
(Continued)
TI Waivers used only where
justified on engineering basis
Distinguish between poorly
designed systems and real
problems
Alternative remedial strategy
must be established
Summary
(Continued)
Assess protectiveness and
reliability
Take further action if
warranted
3-19
-------
-------
Enforcement Concerns
Matthew J. Charsky
Geologist
CERCLA Enforcement Division
Office of Waste Programs Enforcement
US. Environmental Protection Agency, Washington, DC
Matthew J. Charsky is a geologist in the Office of Waste Programs Enforcement. Mr. Charsky was
responsible for the Oversight Guidance on PRP RI/FS which was issued in 1991 and for conducting the
regional training to promote this guidance. He currently is completing a risk assessment evaluation
to determine who will conduct future Superfund risk assessments. Mr. Charsky also has participated
as the enforcement representative on numerous work groups and reviewed many guidance documents
associated with ground-water and treatment technologies, particularly on technical impracticability, multi-
source ground water, and available and potential treatment technologies for ground water.
Prior to joining EPA, Mr. Charsky worked at the Federal Energy Regulatory Commission where he
developed and reviewed Environmental Impact Statements (EISs) and Environmental Assessments (EAs)
under the National Environmental Policy Act (NEPA) for natural-gas pipeline construction projects
nationwide.
4-1
-------
Enforcement
Concerns
Matthew J. Charsky
Office of Waste Programs Enforcement
Contacts
Matt Charsky, OWPE
CERCLA Enforcement Division
(703) 603-8931
Trish Gowland, OWPE
CERCIA Enforcement Division
(703) 603-8975
Kurt Lamber, OWPE
CERCIA Enforcement Division
(703) 603-8986
Overview
1. Program Consistency
2. Categories of Uncertainty
3. Available Options
4. What's Important
5. Current Technologies
4-2
-------
Communication
Program Consistency
I. Superfund Delegation on
TI Waivers for DNAPLs
2. Fund vs. Enforcement-
Lead
3. Superfund vs. RCRA
4. OSWER vs. OE
Superfund Delegation
Proposed remedies for sites
warranting consultation concerning
TI waivers for DNAPLs in ground
water and soil is delegated at the
Division Director's level in
Headquarters
(Twenty-fourth Remedy Delegation Report -
FY 1993, February 18, 1993)
4-3
-------
Fund vs. Enforcement-Lead
More enforcement-lead known or
suspected DNAPL sites than fund-lead
More enforcement-lead RODs with
contingency language for TI than
fund-lead
Perception that ARAR waiver for TI
gives a "greater advantage" to PRPs
Superfund vs. RCRA
1. Proposed Subpart S
2. Current Projects
3. Contacts
RCRA Framework
The proposed RCRA Corrective
Action Rule "Subpart S"
Corrective Action for Solid Waste
Management Units (SWMUs) at
hazardous waste management
facilities; (proposed Subpart S
Rule 40 CFR 264.540, (a) and (b))
[FR July 27,1990, Volume 55,
Number 145]
4-4
-------
RCRA Framework
(Continued)
Currently used as guidance
Provides only the published
discussion of TI in the RCRA
program
Current Status of RCRA
Program
RED & Working on TI (technical and
OSW process issues) via OERR
work group and RCRA
subgroup
OSW Drafting a policy strategy for
Tluse
Planned completion: FY93
Contacts
Rose Lew, OWPE
RCRA Enforcement Division
(202) 260-6720
Guy Tomassoni, OSW
Permits & State Programs Division
(703) 308-8622
Dave Bartenfelder, OSW
Permits & State Programs Division
(703) 308-8629
4-5
-------
Consent Decree Language
Addressing TI Waivers
Provide guidance regarding the use
of TI language in Remedial
Design/Remedial Action (RD/RA)
consent decrees and statements of
work (SOWs) involving remediation
of ground water.
Focused Purpose
Address situations where well-
designed ground-water extraction
systems might not be able to
reduce the levels of one or more
contaminants to the required
performance standards hi a
timeframe that EPA deems
reasonable given the particular
circumstances of the site.
Current Draft -
Dated August 1992
Current Status
Sample language, not model
language
No official inference
Regional/HQ. staff input in order to
achieve all inclusive language
Work group presently disbanded
4-6
-------
Current Draft -
Dated August 1992 (continued)
Outstanding issues:
Technical requirements
Judicial review
Contact:
Mary Andrews
Attorney - Advisor
Office of Enforcement
(202) 260-3109
Relating Timeframe of
Identified/Suspected DNAPL to
Categories of Uncertainty
1. During Negotiations
2. During Site Characterization
3. At Decision Document Stage
4. Performance Data
4-7
-------
Available Options for
DNAPLs at Superfund Sites
1. Waive ARAR Due to TI in
ROD
State standard
Chemical-specific standard
Entire/portion of aquifer
Available Options (continued)
2. Contingency Language for TI
in ROD
> Aim for remediation
« Back off to another level of
protection
« No waiver of ARARs
» Delay waiver to later stage
(i.e., RD/RA)
Available Options (continued)
3. Interim Actions
4» Issue removal order to
contain as interim remedy
* Gather additional data
outside area of containment
4-8
-------
What's Important?
Build defensible data package
Contact available resources
Verify remedy performance
data
Justify which MCLs are
unachievable and the basis for
other standards
Current Technologies
Current technologies might be able
to contain DNAPL sources
Current technologies might be able
to remediate DNAPL in the aqueous
phase
Need to promote development of
innovative technologies to do a
better job than current
technologies
Summary
> The Enforcement Program's
DNAPL policy is evolving.
> The Enforcement Program
favors a cautious and
conservative approach when
DNAPLs are known or
suspected.
4-9
-------
Summary
Tlie Enforcement Program
aims to set achievable
DNAPL goals and, when
appropriate, justify the
need for an ARAR waiver
due to XL
Conservative Approach
4-10
j.S.GOVERNMENT PRINTING OFFICE: i 1993 - 750-063/60010
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